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Safer Lithium-ion Battery Anode based on Ti3C2Tz MXene with Thermal Safety Mechanistic Elucidation
Abstract
Thermal safety concerns of lithium ion batteries (LIBs) need to be solved urgently to facilitate their large-scale applications. Introducing safer anode materials can suppress the thermal runaway initiation but is usually compromising the cell performance due to their induced lower energy density. In this work, Ti3C2Tz MXene with tailored surface terminating groups is identified to be a safer LIB anode with improved capacity and lower operational potential. Calorimetric analyses demonstrate its significantly reduced heat generation (204 J g⁻¹) with electrolyte compared to conventional graphite anode (995 J g⁻¹). Detailed characterizations and thermal analyses reveal the great dependence of its thermal behavior on the lithiation states, surface morphology, and surface-terminating functional groups. Modifying the Ti3C2Tz surface functional groups via annealing can eliminate the irreversible lithium metal plating, which mitigates the parasitic exothermic reactions during thermal runaway and enhances the anode initial coulombic efficiency and cycling stability. The in-situ thermal analyses of LIB full cells demonstrate the obviously improved onset temperature of thermal runaway (195 °C) from the modified Ti3C2Tz-lithium cobalt oxide (LCO) full cell than the graphite-LCO full cell (169 °C), indicating a much safer LIB developed.
... T z and T x are the amount of titanium in the MXene structure. Data of the VPL, [34] P2, [46] DBM, [13] EPD1, [33] BMP2, [30] BMP3, [31] EPD2, [13] PLS, [47] BMP1, [32] and SLR [14] samples are taken from the cited references. Com18, [19] Com28, [20] and Com11. ...
... As far as the ratecapability and performance of the MXene electrode are considered, Figure 2a,b shows the descending order of the reported BMP methods as BMP2, [30] BMP3, [31] and BMP1. [32] Accordingly, it can be concluded that for synthesis of the pristine MAX-phase, the higher rotations-per-minute (rpm) (≈100 rpm) and time (≈24 h) of the BMP and also the lower temperature (≈1400-1450°C) and time (≈2-3 h) of the heat-treatment process should result to the better properties of the final MXene as an electrode. One may conclude that the higher entropy of the sample may result in the better properties. ...
... Comparing the samples of BMP1 [32] with each other, the normalization and ordinary diagrams in Figure 2c,d show that the annealing procedure affected on the activating the particles. Also, the annealed sample increased the active particles' fraction by increasing the rate. ...
Eliminating A element from the MAX phases, the resulted 2D structure, named MXene, can be used as the electrode material for the intercalation, namely, Li‐ion, Na‐ion, K‐ion, and Mg‐ion batteries. MXene Ti3C2, produced by etching Ti3AlC2, is a promising intercalation electrode material, which is systematically evaluated in this article by taking data from literature. The diagrams provide a manner to assess and compare the most important characterizations, i.e., rate‐capability and performance. The evaluations show that the synthesis methods of the pristine MAX phase as well as the final MXene play vital roles on the properties. The rank of synthesis methods and also commercial pristine material is recognized and reported based on the analyzed properties. Moreover, effectiveness of the additives, dopants, compositing, nanosizing, and etching is assessed precisely. Also, comparison between different types of intercalation batteries regarding the usage of MXene as the electrode is performed. This article paves the way for future studies and evaluations of this kind of electrode materials. It guides the researchers to modify, design, and engineer their manufactured electrodes to meet higher quality of the properties.
... To prevent thermal runaway, it is crucial to take precautions such as thermal management systems, safety features, system-level controls, cell design modifications, and sensors. Given the difficulty and expense of conducting large-scale experiments to study TR, lab-scale experiments and computer simulations are commonly used [12]- [15]. ...
... Self-heating ignition in LIBs is a complex phenomenon that is challenging to study due to the high costs and large spaces required for large-scale experiments. Therefore, lab-scale experiments [12][13][14][15] and the application of physical theories or heat transfer models are commonly used to study and predict selfheating ignition on a larger scale [16]. Additionally, computer simulations can also be used to study self-heating ignition in LIBs. ...
Lithium-ion batteries (LIBs) are central in numerous high-demand applications due to their high energy density and prolonged cycle life. Despite these advantages, their susceptibility to thermal runaway (TR) poses a significant safety risk, with the potential for catastrophic failures. This study focuses on the thermal behavior of prismatic lithium-ion cells, using a finite volume-based partial differential equation (PDE) solver developed in MATLAB and JULIA to model TR behavior. This solver accurately simulates transient behaviors, convection, diffusion, and source terms across various coordinate systems. By engaging in a series of increasing complex case studies, this research aims to identify the critical ambient temperatures that can induce TR in LIBs. It thoroughly investigates the decomposition kinetics of cell components and examines the impact of inter-cell contact resistance on TR progression. Furthermore, through comparative analyses with industry-standard tools like GPYRO and COMSOL Multiphysics, alongside precise experimental validations, the study confirms the consistency of its findings. These insights are crucial for enhancing large-scale energy storage systems. The outcomes of this research are instrumental in informing the development of effective cooling mechanisms, robust insulation materials, and advanced thermal management strategies. Such enhancements are vital for sustaining the safety and reliability of lithium-ion battery applications, thereby supporting their broader adoption in technology-dependent sectors. This study not only furthers our understanding of thermal processes in LIBs but also contributes significantly to the field by suggesting practical solutions to mitigate risks associated with thermal runaway.
... In one example, Nitou et al. significantly increased thermal stability by coating cathode materials with phosphates and fluorides [12]. Cai et al. developed surface-functionalized Ti3C2Tz MXene cathode materials and used annealing to modify the surface functional groups of Ti3C2Tz, eliminating irreversible lithium metal plating [13]. This strategy effectively mitigated exothermic reactions during thermal runaway, enhancing the anode's initial Coulombic efficiency and cycle stability. ...
... In one example, Nitou et al. significantly increased thermal stability by coating cathode materials with phosphates and fluorides [12]. Cai et al. developed surface-functionalized Ti 3 C 2 T z MXene cathode materials and used annealing to modify the surface functional groups of Ti 3 C 2 T z , eliminating irreversible lithium metal plating [13]. This strategy effectively mitigated exothermic reactions during thermal runaway, enhancing the anode's initial Coulombic efficiency and cycle stability. ...
Since 2014, the electric vehicle industry in China has flourished and has been accompanied by rapid growth in the power battery industry led by lithium-ion battery (LIB) development. Due to a variety of factors, LIBs have been widely used, but user abuse and battery quality issues have led to explosion accidents that have caused loss of life and property. Current strategies to address battery safety concerns mainly involve enhancing the intrinsic safety of batteries and strengthening safety controls with approaches such as early warning systems to alert users before thermal runaway and ensure user safety. In this paper, we discuss the current research status and trends in two areas, intrinsic battery safety risk control and early warning methods, with the goal of promoting the development of safe LIB solutions in new energy applications.
... Studies and experiments have demonstrated that batteries with Ti 3 C 2 T x MXene anodes significantly improve charge capacity and retention over time, suggesting longer-lasting batteries with the capability to endure more charge-discharge cycles before degradation. The potential applications of Ti 3 C 2 T x MXene extend to the development of batteries that not only offer higher energy densities but also possess the ability to sustain the rapid charge and discharge rates required by advanced technologies, such as grid storage systems and high-performance electric vehicles [14][15][16]. This opens the door for LIBs to be more effectively integrated into largescale renewable energy systems, where reliable and efficient energy storage solutions are paramount. ...
Ti3C2Tx MXene has emerged as an exceptional candidate for use as an anode material in lithium-ion batteries (LIB) due to its unique structural and electrochemical properties. Nevertheless, its full potential is often not realized due to incomplete dealumination when synthesized using conventional etching. Therefore, this study proposes an innovative approach using ultrasonic-assisted dealumination to enhance the synthesis process. Based on the result, Ti3C2Tx processed through ultrasonic (U-Mxene) exhibited significantly higher charge–discharge capacities of 216–219 mA h/g and Columbic efficiency of 98.6%. The observed improvements are likely the result of the more efficient removal of alumina by HF from the parent Ti3AlC2 phase, facilitated by ultrasonic irradiation, which disrupts the solid structure more effectively than traditional methods. The implications of this synthesis approach extend to the practical deployment of Ti3C2Tx MXene in advanced LIB systems, paving the way for more efficient, durable, and higher-capacity energy storage solutions.
Graphical Abstract
... To prevent thermal runaway, it is crucial to take precautions such as thermal management systems, safety features, system-level controls, cell design modifications, and sensors. Given the difficulty and expense of conducting large-scale experiments to study TR, lab-scale experiments and computer simulations are commonly used [12]- [15]. ...
Lithium-ion batteries (LIBs) are widely used in various applications due to their high energy density and long cycle life, but their safety is a significant concern because of the potential for thermal runaway, which can lead to catastrophic failure. The present study investigates thermal runaway (TR) for prismatic cell geometries with inter-cell contact resistances using finite volume based PDE solver implemented in MATLAB and Julia. This solver can handle transient, convection, diffusion, and linear and constant source terms in all cartesian, cylindrical, and spherical coordinates. It provides convenient postprocessing capabilities and a direct graphical interface. The results obtained from the finite volume approach are compared with two other models, GPYRO and COMSOL Multiphysics, and show good agreement between them. The study finds that the inter-cell contact resistance has a significant effect on the thermal behavior of LIBs and must be considered when designing and modeling battery systems. The FVM toolbox is demonstrated to be a reliable and efficient tool for predicting the critical conditions for thermal runaway in LIBs, providing valuable insights into the complex heat and mass transfer processes that govern thermal runaway. The study highlights the potential of the FVM toolbox for use in battery design and safety analysis, guiding the development of safer and more reliable energy storage systems. By accurately predicting the onset of thermal runaway, the FVM toolbox can identify critical design parameters and provide insights into the effects of changes in cell geometry and inter-cell contact resistance on the thermal behavior of LIBs.
... Self-heating ignition in LIBs is a complex phenomenon that is challenging to study due to the high costs and large spaces required for large-scale experiments. Therefore, lab-scale experiments [12][13][14][15] and the application of physical theories or heat transfer models are commonly used to study and predict selfheating ignition on a larger scale [16]. Additionally, computer simulations can also be used to study self-heating ignition in LIBs. ...
Lithium-ion batteries (LIBs) are quickly becoming a popular choice for powering devices, but they have several restrictions. If they are used excessively or left uncharged for a long time, LIBs might suffer from overloading. Furthermore, LIBs can experience thermal runaway, which causes them to reach an uncontrolled, self-heating condition. The rapid changes in the rates of chemical reactions and the transport of individual species inside the battery are exceptionally difficult to measure experimentally during thermal runaway. Hence, comprehensive numerical models are required to understand the complex heat and mass transfer processes dictating the thermal runaway. Due to limited understanding, the only work completed is based on mathematical modeling. The assumptions and resources required by the various modeling tools published in the literature vary, and they may produce drastically different predictions. As previous models in Fortran and Gpyro lacked convenient post-processing capabilities and a direct graphical interface, the present study concentrates on the finite volume based PDE solver in MATLAB and Julia (FVM toolbox). Here, the models can be implemented in all cartesian, cylindrical, and spherical coordinates and can be available as an open-source project for the community's convenience. Besides, FVM is supported in Julia for high performance computing. Different case studies of increasing complexity are considered, which are based on the generic scalar transport equation for transient, convection, diffusion, as well as linear and constant source terms. Results show good agreement between the FVM toolbox and the other two models, GPYRO and COMSOL Multi-physics, available in the literature. Although the assumptions and resources required by these models differ significantly, they can reliably forecast the crucial conditions for the self-heating ignition of LIBs.
... 88.6%, 79.1%, 73.1%, 62.1%, and 33.1% at a current density of 0.1 A g −1 (Fig. 22d), respectively. At the current density of 2 A g −1 , the reversible specific capacity after 1000 cycles is 144.2 mAh g −1 (Fig. 22e), which is higher than that of many reported MXenes anodes [242][243][244]. The surface morphology of two-dimensional MoB MBene electrode after electrochemical cycle is shown in Fig. 22f. ...
As a flourishing member of the two-dimensional (2D) nanomaterial family, MXenes have shown great potential in various research areas. In recent years, the continued growth of interest in MXene derivatives, 2D transition metal borides (MBenes), has contributed to the emergence of this 2D material as a latecomer. Due to the excellent electrical conductivity, mechanical properties and electrical properties, thus MBenes attract more researchers' interest. Extensive experimental and theoretical studies have shown that they have exciting energy conversion and electrochemical storage potential. However, a comprehensive and systematic review of MBenes applications has not been available so far. For this reason, we present a comprehensive summary of recent advances in MBenes research. We started by summarizing the latest fabrication routes and excellent properties of MBenes. The focus will then turn to their exciting potential for energy storage and conversion. Finally, a brief summary of the challenges and opportunities for MBenes in future practical applications is presented.
... In the aspect of transportation, electric vehicles using LIBs as the main power source are gradually taking the place of traditional fuel vehicles [2] . At the same time, in order to avoid the damage of passengers' lives and property safety, the LIB safety problems cannot be neglected, among which thermal safety needs to be paid more attention to [3] . During LIB operation, heat will be generated by electrochemical reactions inside the battery [4] . ...
Nowadays, lithium-ion batteries are widely used in electric vehicles as the power source and its safety attracts increasing attention. Particularly, the thermal runaway is a highest risk needed to be solved. In order to effectively inhibit thermal runaway propagation, an efficient and energy-saving battery thermal management system is proposed in this study, which integrates phase change cooling, nanofluid cooling and heat insulation materials. Firstly, the system model is established by integrating electrochemical model, thermal model and fluid model, and the validity of the model is analyzed. Then the cooling performance of the system under two working conditions is discussed. In the normal heat dissipation condition, Scheme 6 can effectively inhibit thermal runaway propagation and reduce the maximum battery temperature from 1013.50 K to 328.34 K. In the extreme condition, Scheme 6 can reduce the maximum battery temperature from 980.51 K to 380.34 K, and the heat in the system can be taken away in time. In addition, the effects of the volume fraction of nanoparticles and the flow rate of nanofluids on the cooling performance are studied. Finally, for purpose of further improving the cooling performance, uniform-precision rotatable central composite design is used to establish the regression equation and determine the best combination factors. Comparing with Scheme 6, the maximum battery temperature in the improved scheme is reduced by 23%, and the economic index is reduced by 22%.
... Since self-heating ignition happens more often when reactive materials are stacked in large piles, it is difficult to study via large-scale experiments due to the heavy costs and large spaces needed. Current most feasible approach is through investigating the reaction kinetics by means of lab-scale experiments [14][15][16][17] and then applying it via physical theories or heat transfer models to make large-scale predictions [18]. According to chemical kinetics, models for self-heating ignition can be divided into two categories. ...
Recent studies have shown that self-heating ignition is a possible cause of fires when Lithium-ion batteries (LIBs) are stacked in large numbers, for example, during storage. The understanding of this ignition type is limited, and most current studies are based on numerical modelling. The different modelling tools found in the literature differ in their assumptions, capabilities, and resources needed, and may provide significantly different predictions. This study presents a benchmarking between COMSOL Multiphysics, which is one of the most prevailing tools used in modelling thermal-electrochemical behaviour of LIBs, and Gpyro, which is widely used in modelling ignition of solid fuels. Four case studies are designed with increasing levels of complexity: (1) just chemical kinetics at the microscale, (2) just heat transfer at the mesoscale, (3) self-heating behaviour at the mesoscale for coupled chemical reactions and heat transfer of a single cell, and (4) four-cell ensemble for multiphysics at a larger scale. The results of scenarios #3 and #4 are also compared to experiments. The results show that although COMSOL and Gpyro have significant differences in their assumptions and resources needed, both tools can accurately predict the critical conditions for ignition for self-heating, which validates their use to study the safety of LIBs.
... In recent years, high-energy, high-capacity lithium-ion batteries (LIB) have become widely used, including in electric vehicles (EVs), ships, and new alternatives for energy storage. During the LIBs' standard operating cycle, discharge at a high current will inevitably generate heat [1]. Heat accumulation in the battery pack could significantly reduce its useful life and give rise to the thermal runaway phenomenon (TR) [2], which may cause fire and even explosions [3]. ...
The use of high thermal conductive materials for heat transfer is gaining attention as a suitable treatment for improving battery performance. Thermal runaway is a relevant issue for maintaining safety and for proficient employment of accumulators; therefore, new solutions for thermal management are mandatory. For this purpose, a hierarchical nanomaterial made of graphite nanoplatelet has been considered as an interface material. High-content graphite nanoplatelet films have very high thermal conductivity and might improve heat dissipation. This study investigates the effect of a thermally conductive material as a method for safety enhancement for a battery module. A numerical model based on the finite element method has been developed to predict the heat generation during a battery pack’s charge and discharge cycle, using the Multiphysics software Comsol. The lumped battery interface generates appropriate heat sources coupled to the Heat Transfer Interface in 3D geometry. Simulation results show that the protection of neighbouring cells from the interleaved layer is fundamental for avoiding heat propagation and an uncontrollable heating rise of the entire battery pack. The use of graphite nanocomposite sheets could effectively help to uniform the temperature and delay the TR propagation.
... Lithium-ion-batteries (LIBs) is the kind of battery which possess a moderate ability of repeatable charging which usually depends on the liberation of Li + from the accommodating electrodes through the electrochemical reactions of redox for charging and discharging process [82,104,117]. Throughout, the charging and discharging processes of Li + will move back and forth between the positive (e.g. LiCoO2) and negative electrodes, producing an ion intercalation or de-intercalation processes [100]. ...
MXene is a recently emerged two dimensional (2D) layered materials, a novel series of transition metal carbides, nitrides and carbonitrides were established by a group of scientists from Drexel University in 2011. Multi-layered MXene nanomaterials have been synthesized using different wet chemistry etching approaches. To date, around twenty different types of MXenes are synthesized using different wet chemistry etching techniques. To ensure reproducibility of the MXene, advanced characterizations in terms of morphology, structure as well as elemental compositions of the MXene flakes are conducted. MXenes nanosheets possess a significant thermo-electrical conductivity, reasonable band gap and high intrinsic carrier mobilities. The family materials of the MXenes have high potential for making energy storage devices such as batteries and supercapacitors as well as several many other implications such as electromagnetic interference shielding and capacitive desalination. MXenes are the potential candidates for hydrogen storage due to the interactive nature of hydrogen and these layered-structure materials. MXenes in biomedical applications were proven as valuable materials due to the tunable physiochemical properties into new distinct structures which is difficult to be manipulated in bulk materials. Besides, MXenes possess suitability of functionalization for tuning the various required properties for the specific properties. The many potential properties of MXene have disclosed new possibility to address the current need of higher efficiency materials for different applications.
... Battery safety is one of the key issues for lithium ion batteries. Safer lithium ion battery anode based on Ti 3 C 2 T z MXene with thermal safety has been studied [51]. ...
Although MXene is still considered as the newcomer of the 2D nanomaterials family for energy storage application, pristine MXene is unable to satisfy the capacity demand of energy storage devices like alkali-ion batteries. Here, we present a DFT based investigation with GGA-PBE exchange-correlation functional on pristine and Si-doped Ti2C system for potential application as anode materials in lithium ion batteries. This work explores the structural, electronic and adsorption behavior of pristine and Si-doped Ti2C nanosheets. All predicted Si-doped Ti2C MXenes adsorbed Li-atoms with favorable adsorption energy (Ead) without any structural deformation, exhibiting good structural stability. For three distinct adsorption sites, the Ead are calculated as −1.48 eV, −1.55 eV and −1.57 eV which indicates that Ead is higher when lithium ion is adsorbed at the titanium atomic sites. The calculated specific capacity for pristine Ti2C is 331.6 mAh/g, which is less than conventional graphite anode material. But after doping Si atoms, the specific capacity increases up to 439.4 mAh/g for Si-doped Ti2C and enhance the storage capacity up to 32% for lithium ion batteries. The predicted Voc for pristine nanosheet is 2.26 V and for the mono- and di-Si doped nanosheets 2.24 V and 2.14 V, respectively. Besides, the nanosheets remain metallic during lithiation process after doping silicon.
... Crossing the two mountains depends on the vigorous development and widespread promotion of cleaner and more renewable energy sources [1] . Lithium ion battery (LIB), due to the superiorities of strong energy storage, long useful life and low probability of self-discharge, is increasingly applied to electric vehicles (EVs) and hybrid electric vehicles (HEVs) as the energy supplying device [2] . When the vehicle is running normally, the LIBs undertake the discharge at a high current, which will inevitably generate a good deal of heat [3] . ...
Nowadays, electric vehicles attract much attention due to the advantages of low energy consumption and zero emission. As the power source of electric vehicles, the safe and stable operation of lithium ion battery is very important. However, owing to overcharge, mechanical collision, overheating or other conditions, the battery may occur thermal runaway, which can cause serious accidents such as fire or explosion. To solve this problem, an efficient and energy-saving battery thermal management system becomes a necessary choice. In this paper, a novel integrated battery thermal management system with multi-measure prevention strategy is designed and analyzed, which is mainly composed of the composite phase change material, aerogel and cooling-channel. Firstly, the electrochemical-thermal coupling mathematical model is established, and then the reliabilities of thermal runaway model, phase change cooling model and liquid cooling model are verified, respectively. Next the numerical simulation including the effect of different operating modes, extreme case and coolant flow rate on the battery thermal management system is carried out, and finally the results are discussed in detail. The results show that the battery thermal management system can not only quickly take away the accumulated heat and separate the propagation of thermal runaway, but also maintain the temperature uniformity of battery.
... However, the traditional graphitic anode exhibits low specific capacity of 372 mAh/g and poor rate performance, which limits the wide application of the lithium-ion batteries [12,13]. Therefore, it is important to develop new anode materials with high specific capacity values [14][15][16][17][18]. During the past decades, many new type anode materials were reported, including Si and Si-based materials [19,20], Sn-based materials [21], and transition metal oxides [22] and NiCo 2 O 4 materials [23]. ...
Although NiCo2O4 is considered the promising anode materials for the lithium-ion batteries due to its high specific capacity, it also suffers from poor cycling stability. This is attributed to its poor electron conductivity and huge structure collapse during the electrochemical cycles. Therefore, it is important to develop NiCo2O4-based composites, which could improve the electron conductivity and keep structural stability at the same time. Herein, we prepared NiCo2O4/carbon nanofiber (NCO/CNF) composites via facile strategy and used as anode materials in the lithium-ion batteries. The detailed structure characterization was conducted for the NCO/CNF composites. The as-prepared NCO/CNF composites exhibit high specific capacity and outstanding cycling performance. Such composite structure could not only show an ability to enhance the electron conductivity, but also buffer the volume change during the electrochemical cycles.
... Until now, the main researches are focused on improving the electrochemical performance of the lithium-sulfur batteries. At the beginning, many works are about the development of the host materials for the element sulfur in the lithium-sulfur batteries, including various carbon materials [20], metal oxides [21], metal sulfides [22], and other metal-based materials [23]. After that, the researchers put their eyes on the employment of the functional separators and interlayers in the lithium-sulfur batteries. ...
Rational design of host materials for element sulfur is critical in the lithium-sulfur batteries to stabilize the polysulfide, which could migrate from the cathode to the anode, leading to the so-called shuttle effect. Herein, we develop a method to prepare the suitable sulfur host materials for the lithium-sulfur batteries. The manganese dioxide nanospheres are successfully prepared and designed as sulfur host in the lithium-sulfur batteries. The as-prepared manganese dioxide/S composites could be formed flexible and self-supported electrode without the current collector. Due to the presence of the manganese dioxide/S composites, the lithium-sulfur batteries exhibit superior electrochemical performance, including high specific capacity, stable cycling performance, and excellent rate performance.
Hazardous inert pollutants, organic dyes, pharmaceuticals, and widespread discharge of pesticide contaminants into water sources due to population growth and global industrialization are becoming some of the world's most pressing health problems. A novel kind of carbonitride or transition metal carbide, known as two‐dimensional (2D) MXene materials, has shown promise in adsorbing several heavy pollutants, including lead, mercury, chromium, and copper. The removal of pollutants from watery environments using MXene nanocomposites is reviewed in this article. This review highlights the different synthesis methods and potential of MXene nanocomposites to improve water purification methods by offering a thorough overview of recent developments in their application for photocatalytic wastewater treatment. This review further explores existing constraints, looks at the mechanisms behind MXene‐mediated pollutant degradation, and suggests future research approaches to improve MXene nanomaterials for extensive ecological and wastewater treatment applications.
Lithium‐ion batteries (LIBs) are extensively used everywhere today due to their prominent advantages. However, the safety issues of LIBs such as fire and explosion have been a serious concern. It is important to focus on the root causes of safety accidents in LIBs and the mechanisms of their development. This will enable the reasonable control of battery risk factors and the minimization of the probability of safety accidents. Especially, the chemical crosstalk between two electrodes and the internal short circuit (ISC) generated by various triggers are the main reasons for the abnormal rise in temperature, which eventually leads to thermal runaway (TR) and safety accidents. Herein, this review paper concentrates on the advances of the mechanism of TR in two main paths: chemical crosstalk and ISC. It analyses the origin of each type of path, illustrates the evolution of TR, and then outlines the progress of safety control strategies in recent years. Moreover, the review offers a forward‐looking perspective on the evolution of safety technologies. This work aims to enhance the battery community's comprehension of TR behavior in LIBs by categorizing and examining the pathways induced by TR. This work will contribute to the effective reduction of safety accidents of LIBs.
The extraordinary mechanical capabilities of 2D self-supporting nanofilms render them highly desirable for fabricating flexible devices. These films possess unique structural properties at the nanoscale, translating into exceptional rigidity or flexibility at the macroscopic level. Their remarkable ability to maintain structural integrity and shape under stress situations empowers them to bend, fold, and twist without compromising performance. Furthermore, the excellent elasticity of film enables them to adapt to curved surfaces, facilitating their seamless integration into wearable electronics. 2D self-supporting films with outstanding superior properties surpass substrate-based films and hold tremendous promise for various applications in energy storage, sensing, membranes and biomedical devices. Achieving their full potential in multiple applications necessitates a comprehensive understanding of the mechanical flexibility of these 2D nanomaterials. Researchers can gain insights into the material's responses to applied force or deformation by analyzing its mechanical behavior, which is crucial for designing and developing. The primary objectives of this study are to provide in-depth elucidation of the mechanical characteristics of 2D nanomaterials, their formation into nanofilms, and the subsequent removal of these films from the substrate. Such a comprehensive investigation enables researchers to understand the intrinsic behavior of 2D nanomaterials and develop strategies to optimize their properties for a wide range of applications.
Hydrogen evolution technology by photocatalysts has shown broad prospects in solving the global energy crisis and environmental pollution problems. Cadmium sulfide (CdS) heterojunctions have been concerned as a promising photocatalyst...
The severe degradation of electrochemical performance for lithium-ion batteries (LIBs) at low temperatures poses a significant challenge to their practical applications. Consequently, extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li ⁺ diffusion kinetics for achieving favorable low-temperature performance of LIBs. Herein, we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials. First, we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures. Second, detailed discussions concerning the key pathways (boosting electronic conductivity, enhancing Li ⁺ diffusion kinetics, and inhibiting lithium dendrite) for improving the low-temperature performance of anode materials are presented. Third, several commonly used low-temperature anode materials are briefly introduced. Fourth, recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design, morphology control, surface & interface modifications, and multiphase materials. Finally, the challenges that remain to be solved in the field of low-temperature anode materials are discussed. This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.
The carbonate intercalated magnesium aluminum layered double hydroxide is used as an anode material for lithium-ion batteries, displaying a maximum discharge specific capacity of 814 mAh·g–1 at 200 mA·g–1 in...
Lithium-ion batteries (LIBs)—are the most demanding technology of today. LIBs show a high energy density, high voltage capability, long life span, low discharge capacity, and higher power density than other technology. With their technical advantages, lithium-based batteries have the potential to transform the photovoltaic (PV) sector and renewable energy sources. Lithium-ion batteries have a lower cost and long life cycle than other batteries. MXene is a two-dimensional (2D) layered anodic material for Lithium-ion batteries, distinguished by its unusual physical and chemical features, as well as its applicability for high-power applications. MAX phase structure is used in a battery in which ‘M’ is the transition metal; ‘A’ for the 4th group of elements and ‘X’ may be nitrogen or carbon. In this chapter, we debated the current development of lithium-ion batteries. Also, discussed what are the changes required to compete with modern techniques. How MXene energy application cause changes in LIBs. The efficiency of LIBs is enhanced when modifying the surface structure of ionic species. Gel polymers are used in LIBs for the enhancement of mechanical performance, chemical and electrochemical stability, and excellent ionic stability. The revolutionization of portable electronics by LIBs sparked a surge in academic interest over the next few years. It also explains the key parts of material science in the advancement of LIBs. After two decades of Li-ion technology marketing for portable devices, LIBs are gaining attraction for a variety of new energy or power-intensive applications for both stationary and electro-mobility. Their performance is dependent on a precise balance of transport phenomena and interfacial processes. This chapter is based on the recent developments made in the field of Lithium-ion batteries.KeywordsLIBsElectrodeSeparatorGel polymerMXene
The properties and applications of MXenes (a family of layered transition metal carbides, nitrides, and carbonitrides) have aroused enormous research interests for a decade since the successful synthesis of few‐layer transition metal carbides in 2011. Though MXenes, as the building blocks, have already been applied in various fields (such as wearable electronics) owing to the distinctive optical, mechanical and electrical properties, their thermal stability and intrinsic thermal properties were less thoroughly investigated compared to other characteristics in early reports. The pioneering theoretical prediction of the thermoelectric nature of MXenes was performed in 2013 while the first experiment‐based report concerning the degradation behavior of the 2D structure at elevated temperatures in a controlled atmosphere was published in 2015, followed by numerous discoveries regarding the thermal properties of MXenes. Herein, after a brief description of the synthesis, this Review summarized the latest insights into the thermal stability and thermophysical properties of MXenes, and further associated these unique properties with relevant applications by multiple examples. Finally, current hurdles and challenges in this field were provided along with some advices on potential research directions in the future.
Electrode alignment is one of design parameters that must be carefully controlled for reliable full cells with limited lithium ion inventory. Especially because punched disk-type cathodes and anodes are movable during assembling coin-type cells, the misalignment of electrodes cannot be completely prevented. This misalignment is not only mixed with other defects but also sometimes leads to better electrochemical characteristics. To systematically unveil this ignored but important parameter, we fabricated coin-type LiNi0.6Mn0.2Co0.2O2/graphite full cells with different electrode alignments and evaluated them to determine any noticeable changes in their electrochemical properties. As frequently reported, the misaligned cell shows lower specific discharge capacity and initial coulombic efficiency than the well-aligned one due to an irreversible Li plating on the coin cell bottom during the first charging process. However, we have now recognized the misaligned cell can exhibit a smaller low-frequency semicircle in the AC impedance spectra and lower DC-IRs at lowly charged states than those of the well-aligned cell because of the less lithiated state of the misaligned cathode. Thus, to exclude data from misaligned full cells, it is necessary to verify the electrode alignment even after the cell evaluation process.
Encapsulated phase-change materials (PCMs) have been widely studied in the field of solar thermal energy storage due to the advantages of stable shape and repeatability. In this work, a series of potatoes phase-change materials (PPMs) were conceived and synthesized via a common vacuum impregnation method, with biomass porous potatoes (PP) as substrate, polyethylene glycol (PEG) as phase change medium and MXene nanosheets as functional filler. The experimental results show that the introduction of MXene nanosheets not only significantly improve the photo-to-thermal conversion efficiency, but also help to increase the adsorption rate of PEG in PCMs. The PEG percentage of potatoes phase-change material (PPM) increases from 60.9% (PPM-0) to 82.1% (PPM-12.5), melting/freezing enthalpy values are also increases from 94.08 J/g/100.46 J/g of PPM-2.5 to 135.57 J/g/139.88 J/g of PPM-12.5, and its enthalpy efficiency λ and relative enthalpy efficiency η also increase from 57.6%/91.5% to 77.7%/98.3%. The results show that the prepared PPMs can be effectively applied to solar photo-to-thermal energy storage.
Solid state sodium-ion batteries (SSIBs) are promising energy storage devices due to the advanced safety and abundant natural sodium sources. However, the developments of SSIBs are seriously limited by the shortage of choice for both solid state electrolytes and anode materials. To cater for this problem, we provide a composite of cobalt disulfide and carbon nanotubes in suit growth on MXene and a derivative grow out of MXene during the prepared process (named as CoS2/CNTs/TiOxNy) as anode material, and PFSA-Na membranes as solid-state electrolyte for SSIBs. The as-suggested SSIBs based on CoS2/CNTs/TiOxNy and PFSA-Na membranes demonstrat promising electrochemical properties at room temperature, which is a significant improvement compared with the high-temperature running SSIBs. Furthermore, the electrochemical mechanism of CoS2/CNTs/TiOxNy in SSIBs is investigated by in-situ Raman and ex-situ XPS analysis to understand the reaction mechanism.
A composite anode material synthesized using silicon nanoparticles, micrometer sized graphite particles, and starch‐derived amorphous carbon (GCSi) offers scalability and enhanced electrochemical performance when compared to existing graphite anodes. Mechanistic elucidation of the formation steps of tailored GCSi composite are achieved with environmental transmission electron microscopy (ETEM) and thermal safety aspects of the composite anode are studied for the first time using specially designed multimode calorimetry for coin cell studies. Electrochemical analysis of the composite anode demonstrates a high initial discharge capacity (1126 mAh g⁻¹) and yields a high coulombic efficiency of 83% in the first charge cycle. Applying a current density of 500 mA g⁻¹, the anode composite retains 448 mAh g⁻¹ specific capacity after 100 cycles. Cycling stability is a result of improved interfacial binding made possible by the interconnected architecture of wheat derived amorphous carbon, enhancing the electrochemical kinetics and decreasing the inherent issues associated with volume expansion and pulverization of pristine Si electrodes. Comparing the energy released during thermal runaway, per specific capacity for the full‐cell, the GCSi composite releases less heat than the conventional graphitic anode, suggesting a synergistic effect of each ingredient of the GCSi composite, providing a safer and higher performing anode.
The currently commercialized lithium‐ion batteries have allowed for the creation of practical electric vehicles, simultaneously satisfying many stringent milestones in energy density, lifetime, safety, power, and cost requirements of the electric vehicle economy. The next wave of consumer electric vehicles is just around the corner. Although widely adopted in the vehicle market, lithium‐ion batteries still require further development to sustain their dominating roles among competitors. In this review, the authors survey the state‐of‐the‐art active electrode materials and cell chemistries for automotive batteries. The performance, production, and cost are included. The advances and challenges in the lithium‐ion battery economy from the material design to the cell and the battery packs fitting the rapid developing automotive market are discussed in detail. Also, new technologies of promising battery chemistries are comprehensively evaluated for their potential to satisfy the targets of future electric vehicles.
In recent years, the rapidly growing attention on MXenes makes the material a rising star in the 2D materials family. Although most researchers' interests are still focused on the properties of bare MXenes, little attention has been paid to the surface chemistry of MXenes and MXene‐based nanocomposites. To this end, this Review offers a comprehensive discussion on surface modified MXene‐based nanocomposites for energy conversion and storage (ECS) applications. Based on the structure and reaction mechanism, the related synthesis methods toward MXenes are briefly summarized. After the discussion of existing surface modification techniques, the surface modified MXene‐based nanocomposites and their inherent chemical principles are presented. Finally, the application of these surface modified nanocomposites for supercapacitors (SCs), lithium/sodium–ion batteries (LIBs/SIBs), and electrocatalytic water splitting is discussed. The challenges and prospects of MXene‐based nanocomposites for future ECS applications are also presented.
Pseudocapacitive energy storage in supercapacitor electrodes differs significantly from the electrical double-layer mechanism of porous carbon materials, which requires a change from conventional thinking when choosing appropriate electrolytes. Here we show how simply changing the solvent of an electrolyte system can drastically influence the pseudocapacitive charge storage of the two-dimensional titanium carbide, Ti3C2 (a representative member of the MXene family). Measurements of the charge stored by Ti3C2 in lithium-containing electrolytes with nitrile-, carbonate- and sulfoxide-based solvents show that the use of a carbonate solvent doubles the charge stored by Ti3C2 when compared with the other solvent systems. We find that the chemical nature of the electrolyte solvent has a profound effect on the arrangement of molecules/ions in Ti3C2, which correlates directly to the total charge being stored. Having nearly completely desolvated lithium ions in Ti3C2 for the carbonate-based electrolyte leads to high volumetric capacitance at high charge–discharge rates, demonstrating the importance of considering all aspects of an electrochemical system during development.
Lithium-iodine (Li-I) batteries have attracted tremendous attention due to their high energy and power densities as well as the low cost of iodine. However, the severe shuttle effect of iodine species and the uncontrollable lithium dendrite growth have strongly hindered their practical applications. Here we successfully develop a quasi-solid-state Li-I battery enabled by a MXene-based iodine cathode and a composite polymer electrolyte (CPE) containing NaNO 3 particles dispersing in a pentaerythritol-tetraacrylate-based (PETEA-based) gel polymer electrolyte. As verified by experimental characterizations and first-principle calculations, the abundant functional groups on the surface of MXene sheets provide strong chemical binding to iodine species, and therefore immobilize their shuttling. The PETEA-based polymer matrix simultaneously suppresses the diffusion of iodine species and stabilizes the Li anode/CPE interface against dendrite growth. The NaNO 3 particles act as an effective catalyst to facilitate the transformation kinetics of LiI 3 on the cathode. Owing to such synergistic optimization, the as-developed Li-I batteries deliver high energy/power density with long cycling stability and good flexibility. This work opens up a new avenue to improve the performance of Li-I batteries.
Nanocomposite polymer electrolytes (CPEs) are promising materials for all-solid-state lithium metal batteries (LMBs) due to their enhanced ionic conductivities and stabilitity to lithium anode. Mxene is a new two-dimensional, 2D, family of early transition metal carbides and nitrides, that has high aspect ratio and hydrophylic surface. Herein, using a green, facile aqueous solution blending method, we uniformly dispersed small amounts of Ti3C2Tx into poly(ethylene oxide)/LiTFSI complex (PEO20-LiTFSI), to fabricate MXene-based CPEs (MCPEs). The addition of the 2D flakes to PEO, simultaneously retards PEO crystallization, enhances its segmental motion. Compared to the 0D and 1D nanofillers, MXene shows higher efficiency in ionic conductivity enhancement and LMBs perfomance improvement. The CPE with 3.6 wt.% MXene shows the highest ionic conductivity at room temperature (2.2×10-5 S cm-1 at 28 °C). LMB using MCPE with only 1.5 wt.% MXene shows rate capability and stability comparable with the state-of-the-art CPE LMBs. We attribute the excellent performance to the 2D geometry of the filler, the good dispersion of the flakes in the polymer matrix, and, the functional group-rich surface.
Lithium-ion batteries (LIBs) are considered to be one of the most important energy storage technologies. As the energy density of batteries increases, battery safety becomes even more critical if the energy is released unintentionally. Accidents related to fires and explosions of LIBs occur frequently worldwide. Some have caused serious threats to human life and health and have led to numerous product recalls by manufacturers. These incidents are reminders that safety is a prerequisite for batteries, and serious issues need to be resolved before the future application of high-energy battery systems. This Review aims to summarize the fundamentals of the origins of LIB safety issues and highlight recent key progress in materials design to improve LIB safety. We anticipate that this Review will inspire further improvement in battery safety, especially for emerging LIBs with high-energy density.
The lithium ion battery (LIB) has proven to be a very reliably used system to store electrical energy, for either mobile or stationary applications. Among others, TiO2-based anodes are the most attractive candidates for building safe and durable lithium ion batteries with high energy density. A variety of TiO2 nanostructures has been thoroughly investigated as anodes in LIBs, e.g., nanoparticles, nanorods, nanoneedles, nanowires, and nanotubes discussed either in their pure form or in composites. In this review, we present the recent developments and breakthroughs demonstrated to synthesize safe, high power, and low cost nanostructured titania-based anodes. The reader is provided with an in-depth review of well-oriented TiO2-based nanotubes fabricated by anodic oxidation. Other strategies for modification of TiO2-based anodes with other elements or materials are also highlighted in this report.
Severe safety concerns are impeding the large-scale employment of lithium/sodium batteries. Conventional electrolytes are highly flammable and volatile, which may cause catastrophic fires or explosions. Efforts to introduce flame-retardant solvents into the electrolytes have generally resulted in compromised battery performance because those solvents do not suitably passivate carbonaceous anodes. Here we report a salt-concentrated electrolyte design to resolve this dilemma via the spontaneous formation of a robust inorganic passivation film on the anode. We demonstrate that a concentrated electrolyte using a salt and a popular flame-retardant solvent (trimethyl phosphate), without any additives or soft binders, allows stable charge–discharge cycling of both hard-carbon and graphite anodes for more than 1,000 cycles (over one year) with negligible degradation; this performance is comparable or superior to that of conventional flammable carbonate electrolytes. The unusual passivation character of the concentrated electrolyte coupled with its fire-extinguishing property contributes to developing safe and long-lasting batteries, unlocking the limit toward development of much higher energy-density batteries.
MXene-based materials are promising electrode materials for electrochemical capacitors (ECs) due to their unique two-dimensional layered structure, high surface area, remarkable chemical stability, and electrical conductivity. TiO2 nanoparticles decorated Ti3C2 MXene were synthesized through a simple in situ hydrolysis and heat-treatment process and subsequently fabricated as an electrode for ECs. The as-prepared Ti3C2, TiO2, and TiO2-Ti3C2 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that TiO2 nanoparticles with a diameter of less than 30 nm were decorated onto the Ti3C2 MXene nanosheets. The resulting composites exhibited significantly higher specific capacitance of 143 F g−1 at 5 mV s−1, which was 1.5 times that of pure Ti3C2 (93 F g−1). Moreover, TiO2-Ti3C2 showed excellent cycling stability, retaining ∼92% of its initial capacitance after 6000 cycles. These results suggest that TiO2-Ti3C2 nanocomposite has the potential as an electrode material for high-performance energy storage devices.
Two-dimensional Ti 2 CT x MXene nanosheets were prepared by the selective etching of Al layer from Ti 2 AlC MAX phase using HF treatment. The MXene sheets retained the hexagonal symmetry of the parent Ti 2 AlC MAX phase. Effect of the postetch annealing ambient (Ar, N 2 , N 2 /H 2 , and air) on the structure and electrochemical properties of the MXene nanosheets was investigated in detail. After annealing in air, the MXene sheets exhibited variations in structure, morphology, and electrochemical properties as compared to HF treated MAX phase. In contrast, samples annealed in Ar, N 2 , and N 2 /H 2 ambient retained their original morphology. However, a significant improvement in the supercapacitor performance is observed upon heat treatment in Ar, N 2 , and N 2 /H 2 ambients. When used in symmetric two-electrode configuration, the MXene sample annealed in N 2 /H 2 atmosphere exhibited the best capacitive performance with specific capacitance value (51 F/g at 1A/g) and high rate performance (86%). This improvement in the electrochemical performance of annealed samples is attributed to highest carbon content, and lowest fluorine content on the surface of the sample upon annealing, while retaining the original two-dimensional layered morphology and providing maximum access of aqueous electrolyte to the electrodes.
The low room-temperature ionic conductivity, narrow voltage window, and poor thermal stability of solid polymer electrolyte hinder the application of high energy density, safer solid-state lithium batteries (SLBs). Hence, we developed a novel composite solid polymer electrolyte (CSPE) with high room-temperature ionic conductivity (2.4×10⁻⁴ S cm⁻¹), wide voltage window (∼ 4.8 V), and excellent thermal stability (∼ 330 °C) by combining Li6.4La3Zr1.4Ta0.6O12 ceramic filler with poly(vinylidene fluoride) (PVDF) polymer and bis(trifluoromethane)sulfonimide lithium (LiTFSI) salt. Free-standing, scalable, and mechanically robust CSPE separately coupled with LiFePO4 and high-voltage LiNi1/3Co1/3Mn1/3O2 cathodes vs lithium anode demonstrated stable cycling. More importantly, we in-situ measured the thermal stable window (177 °C) with a small heat release (189 J g⁻¹) during the thermal runaway of the entire CSPE coin cell. In contrast, the liquid electrolyte cell delivered a depressing thermal stable window (157 °C) and release a significant amount of heat (812 J g⁻¹). The superior thermal safety of CSPE cell can be ascribed to the solid-state property and outstanding thermal stability of the CSPE. Most notably, this work not only proposes a promising CSPE but also highlights a reference for in-situ quantitative study on the thermal safety of entire SLBs.
To realize high-rate and long-term performance of rechargeable batteries, the most effective approach is to develop an advanced hybrid material with stable structure and more reaction active sites. Recently, 2D MXenes have become a up-and-coming electrode owing to high conductivity and large redox-active surface area. In this work, we firstly prepared the Ti3C2 MXenes through selective etching of silicon from Ti3SiC2 (MAX) using HF and oxidant for high durable lithium-ion batteries (LIBs). The interlayer distance of Ti3C2 MXenes can be controllable with the oxidizability of oxidant and etching temperature. In addition, Ti3C2@TiO2 MXene hybrids with further expanded interlayer spacing were purposefully fabricated by a simple hydrothermal method. The hierarchical N-doped Ti3C2@TiO2 MXene hybrids exhibit that the in-situ synthesized nanoscaled TiO2 particles are loaded homogeneously on the layered N-doped Ti3C2 surface. The interlayer distance of N-doped Ti3C2@TiO2 MXene can reach 12.77 Å when using HNO3 as the oxidant at room temperature. As an anode material, the N-doped Ti3C2@TiO2(HNO3-RT) hybrid displays a high reversible capacity of 302 mA h g-1 at 200 mA g-1 after 500 cycles and 154 mA h g-1 at 2000 mA g-1 after 1500 cycles, which indicates its long cycle lifetime and excellent stability in LIBs. This high durable LIB anode performance is ascribed to synergetic contributions from the high capacitive contribution, high electrical conductivity, high-capacity of in-situ formed nanoscaled TiO2 and interlayer-expanded architecture of the N-doped Ti3C2@TiO2(HNO3-RT). This study provides theoretical basis for the application of MXenes as a high capacity anode for advanced LIBs.
Electrolyte ionic diffusivity significantly affects the power density and useable energy density of a lithium ion battery. During usage, electrolyte can decompose, leading to reduced ionic diffusivity. Understanding the degradation mechanism and its effect on ionic diffusivity is important for both battery design optimization to provide superior performance with a long cycle life and for better battery management during usage to extend the battery life. In this research, the ionic diffusivity of key electrolytes and their degradation, including DMC-LiPF6, EMC-LiPF6 and DEC-LiPF6, are quantitatively predicted with classical and ReaxFF molecular dynamics simulations. The electrolyte solvent structures and reaction pathways are characterized. The effect of temperature, salt concentration and degree of thermal degradation on electrolyte ionic diffusivity are identified. A list of gas-phase, solvent-phase and solid-phase degradation products are categorized. DMC-LiPF6 shows the highest thermal stability, while DEC-LiPF6 shows the lowest thermal stability because of a large amount of –CH3CH2 group in the molecule. PF6- tends to decompose first. The decomposed product of PF5 can further lead to C–O bond breaking in solvent molecules, causing them to decompose into products composed of smaller molecules. Simulations show that the diffusion coefficients of cations and anions decrease with thermal degradation. The mechanism is found to be related to the clustering of Li⁺, R-O⁻ and (R–OCO2)⁻, which impedes ion diffusion in the electrolyte. This paper provides a quantitative understanding of electrolyte thermal degradation, revealing the underlying mechanisms and effects on electrolyte properties at the atomistic level by a systematic comparative study for the first time. The approach will provide valuable guidance to the development of lithium ion batteries.
Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have attracted significant attention due to their electronic, electrochemical, chemical, and optical properties. However, understanding of their thermal stability is still lacking. To date, MXenes are synthesized via top-down wet chemical etching, which intrinsically results in surface terminations. Here, we provide detailed insight on the surface terminations of three carbide MXenes (Ti3C2Tx, Mo2CTx and Nb2CTx) by performing thermal gravimetric with mass spectrometry analysis (TA-MS) up to 1500 ºC under He atmosphere. This specific technique enables probing surface terminations including hydroxyl, oxygen and fluoride –OH/=O/–F; intercalated species, such as salts and structural water. The MXene hydrophilicity depends on the type of etching (hydrofluoric acid concentration and/or mixed acid composition) and subsequent delamination conditions. We show that the amount of structural water in Ti3C2Tx increases with decreasing O-containing surface terminations. The thermal stability of Ti3C2Tx is improved by employing low HF concentration or using a mixture of etchant acids, such as H2SO4/HF or HCl/HF instead of only HF, due to the reduced defect density. When tetramethylammonium hydroxide (TMAOH) is used for delamination, new N-containing species appear on the MXene surface. Moreover, free-standing films produced from Ti3C2Tx etched with different HF concentrations and delaminated using TMAOH have similar TA-MS profiles, indicating that post-treatment of Ti3C2Tx controls its surface chemistry. The thermal stability of MXenes strongly depends on their chemical composition and structure; Ti3C2Tx is more thermally stable than the fewer-atomic-layered Mo2CTx or Nb2CTx and Mo2CTx is more/less thermally stable than Nb2CTx.
MXenes, as an emerging family of conductive two-dimensional materials, hold promise for late-model electrode materials in Li-ion batteries. A primary challenge hindering the development of MXenes as electrode materials is that a complete understanding of the intrinsic storage mechanism underlying the charge/discharge behavior remains elusive. This article presents two key discoveries: first, the characteristics of Ti3C2Tx structure can be modified systematically by calcination in various atmospheres, and second, that these structural changes greatly affect Li-ion storage behavior, which reveals the mechanism for lithium storage in Ti3C2Tx MXene. Specifically, via ammonization, the interlayer spacing gets dilated and uniform, giving rise to only one redox couple. In stark contrast, there are two well-recognized redox couples corresponding to two interlayer spacings in pristine Ti3C2Tx MXene, in which Li-ion (de)intercalation occurs between interlayers in a sequential manner as evidenced by ex-situ X-ray diffraction (XRD). Notably, the XRD diffraction peaks shift hardly in the whole range of charge/discharge voltage, indicating a zero-strain feature upon Li-ion (de)intercalation. Moreover, the diffusion-controlled contribution percentage to capacity inversely depends on scan rate. The understanding suggests a new design principle of MXene anode: reduced lateral size to shorten the diffusion path and dilated interlayer spacing.
Tremendous efforts are devoted to developing advanced electrode materials with superior electrochemical performance, high energy density, and high power density for energy storage and conversion. Two‐dimensional (2D) materials, owing to their unique properties, have shown great potential for energy storage. Following the discovery of graphene, a new family of 2D transition metal carbides/nitrides, MXenes, derived from MAX phase precursors, have attracted extensive attention in recent years. The superior physical and chemical properties of MXenes include high mechanical strength, excellent electrical conductivity, multiple possible surface terminations, hydrophilic features, superior specific surface area, and the ability to accommodate intercalants. When applied as electrodes in lithium‐based batteries, MXenes have demonstrated excellent performance. In this progress report, the authors summarize the recent advances of MXenes and MXene‐based composites in terms of synthesis strategies, morphology engineering, physical/chemical properties, and their applications in lithium‐ion batteries and lithium–sulfur batteries. Furthermore, challenges and perspectives for MXenes and MXene‐based composites for lithium‐based energy storage devices are also outlined.
Thermal runaway of three lithium ion cells (“A” - NCA/Graphite, “B” - LFP/Graphite, “C” - NCA/LTO) at 0%, 50%, and 100% state of charge (SOC) is studied by Accelerating Rate Calorimetry (ARC). Thermal behaviour of harvested positive and negative electrodes at three SOC (0%, 50%, and 100%) is analyzed using Differential Scanning Calorimetry (DSC). Thermal stability of recovered separators is also investigated by DSC. Harvested electrodes and separators are studied alone and in contact with a liquid electrolyte. The thermal behaviour of each component and its contribution is quantified and thoroughly discussed. A crucial negative impact of the state of charge and presence of highly flammable liquid electrolyte on the thermal instability of the investigated cells and “electrode - electrolyte” systems is clearly revealed. Among studied cells, LiFePO4/Graphite one is the safest due to intrinsic thermal stability of lithium iron phosphate LiFePO4 based cathode and despite the fact of using a microporous polyolefin separator with limited thermal stability.
The presented work compared the etching behavior between combustion synthesized Ti3AlC2 (SHS-Ti3AlC2) and pressureless synthesized Ti3AlC2 (PLS-Ti3AlC2). Because the former had a more compact structure, it was harder to be etched than PLS-Ti3AlC2 under the same conditions. When served as anode material for Li-ion batteries, SHS-Ti3C2 showed much lower capacity than PLS-Ti3C2 at 1C (52.7 and 87.4 mAh·g-1, respectively) due to the smaller d-spacing. Furthermore, Potentiostatic Intermittent Titration Technique (PITT) was used to determine the Li-ion chemical diffusion coefficient of Ti3C2 in the range of 10-10-10-9 cm2·s-1, indicating that Ti3C2 could exhibit an excellent diffusion mobility for Li-ion.
Rational design and construction of advanced hybrid electrodes would contribute to enormous development of rechargeable batteries. Herein, hierarchical accordion-like TiO2/Ti3C2 nanohybrid is purposefully synthesized by using Ti3C2 as single precursor through a scalable hydration process, and further evaluated as promising anode material both for Li-ion batteries (LIBs) and Na-ion batteries (SIBs). Physicochemical characterizations demonstrate that the unique hierarchical nanohybrid possesses a layered architecture, where the in-situ formed nanoscaled TiO2 is decorated uniformly on the Ti3C2 surface. Benefiting from synergetic contributions from interlayer-expanded architecture, high-capacity nano-TiO2 and excellent electrical conductivity of the Ti3C2, the resulted TiO2/Ti3C2 anode exhibits large reversible capacities of ∼267 and ∼101 mAh g⁻¹ for LIBs and SIBs, respectively, at a current density of 200 mA g⁻¹. Moreover, no any capacity decay over consecutive 500, and even 2000 cycles at high rates further confirms its outstanding electrochemcial stability for practical applications. More appealingly, all the results highlight that the cost-efficiency TiO2/Ti3C2 hybrid architecture would be a promising anode candidate for advanced next-generation LIBs and SIBs.
Ti3C2Tx, a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti3C2Tx directly influence its electrochemical performance, e.g., the use of a well-designed 2D Ti3C2Tx as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier/charge-transport kinetics. Some recent progresses of Ti3C2Tx MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti3C2Tx MXene including supercapacitors, lithium-ion batteries, sodium-ion batteries, and lithium–sulfur batteries. The current opportunities and future challenges of Ti3C2Tx MXene are addressed for energy-storage devices. This Review seeks to provide a rational and in-depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti3C2Tx, which will promote the further development of 2D MXenes in energy-storage applications.
For the first time, thermal runaway of charged graphite anodes for K-ion batteries is investigated, using differential scanning calorimetry (DSC) to probe the exothermic degradation reactions. Investigated parameters such as state of charge, cycle number, surface area, and binder demonstrate strong influences on the DSC profiles. Thermal runaway initiates at 100 °C owing to KxC8 – electrolyte reactions, but the K-ion graphite anode evolves significantly less heat as compared to the analogous Li-ion system (395 J g⁻¹ vs. 1048 J g⁻¹). The large volumetric expansion of graphite during potassiation cracks the SEI layer, enabling contact and reaction of KC8 – electrolyte, which diminishes with cycle number due to continuous SEI growth. High surface area graphite decreases the total heat generation, owing to thermal stability of the K-ion SEI layer. These findings illustrate the dynamic nature of K-ion thermal runaway and its many contrasts with the Li-ion graphite system, permitting possible engineering solutions for safer batteries.
Two-dimensional V2C (MXene) derived from layered V2AlC phase attracts increasing interest due to its various promising applications such as lithium-ion batteries. Yet it is a great challenge to obtain completely exfoliated V2C MXene by etching Al from V2AlC. Here, in this work, we highlight that alloying Ti can significantly enhance the exfoliation of (V1-xTix)2C MXene from (V1-xTix)2AlC based on our systematic studies of experiments and first-principles calculations. Furthermore, the exfoliated (V1-xTix)2C MXene shows better multilayered morphology characterized by X-ray diffraction and scanning electron microscopy. Meanwhile, by analyzing the exfoliation process and electron localization functions, we have demonstrated that the micro-origin of Ti enhancement effect on the exfoliation of (V1-xTix)2AlC is due to the significantly weakened interlayer bonding between the VC and Al layers in (V1-xTix)2AlC induced by alloying Ti. Finally, we have shown that the performance of (V1-xTix)2C as anode materials for Li-ion batteries is improved with the increase of Ti content. Our results provide a useful way to improve the synthesis of V-based MXenes and are beneficial to the applications as well.
The safety concern is the main obstacle that hinders the large-scale applications of lithium ion batteries in electric vehicles. With continuous improvement of lithium ion batteries in energy density, enhancing their safety is becoming increasingly urgent for the electric vehicle development. Thermal runaway is the key scientific problem in battery safety research. Therefore, this paper provides a comprehensive review on the thermal runaway mechanism of the commercial lithium ion battery for electric vehicles. Learning from typical accidents, the abuse conditions that may lead to thermal runaway have been summarized. The abuse conditions include mechanical abuse, electrical abuse, and thermal abuse. Internal short circuit is the most common feature for all the abuse conditions. The thermal runaway follows a mechanism of chain reactions, during which the decomposition reaction of the battery component materials occurs one after another. A novel energy release diagram, which can quantify the reaction kinetics for all the battery component materials, is proposed to interpret the mechanisms of the chain reactions during thermal runaway. The relationship between the internal short circuit and the thermal runaway is further clarified using the energy release diagram with two cases. Finally, a three-level protection concept is proposed to help reduce the thermal runaway hazard. The three-level protection can be fulfilled by providing passive defense and early warning before the occurrence of thermal runaway, by enhancing the intrinsic thermal stability of the materials, and by reducing the secondary hazard like thermal runaway propagation.
Sodium and potassium ion batteries hold promise for next-generation energy storage systems due to their rich abundance and low cost, but are facing great challenges in optimum electrode materials for actual applications. Here, ultrathin nanoribbons of sodium titanate (M-NTO, NaTi1.5O8.3) and potassium titanate (M-KTO, K2Ti4O9) were successfully synthesized by simultaneous oxidation and alkalization process of Ti3C2 MXene. Benefiting from the suitable interlayer spacing (0.90 nm for M-NTO, 0.93nm for M-KTO), ultrathin thickness (<11 nm), narrow widths of nanoribbons (<60 nm), and open macroporous structures for enhanced ion insertion/extraction kinetics, the resulting M-NTO exhibited a large reversible capacity of 191 mAh g-1 at 200 mA g-1 for sodium storage, higher than those of pristine Ti3C2 (178 mAh g-1) and commercial TiC derivatives (86 mAh g-1). Notably, M-KTO displayed superior reversible capacity of 151 mAh g-1 at 50 mA g-1, 88 mAh g-1 at a high rate of 300 mA g-1, and long-term stable cyclability over 900 times, which outperform other Ti-based layered materials reported to date. Moreover, this strategy is facile and highly flexible, and can be extended for preparing a large number of MXene-derived materials, from 60+ group of MAX phases, for various applications such as supercapacitors, batteries, and electrocatalysis.
Engineering electrode nanostructures is critical in developing high-capacity, fast rate-response, and safe Li-ion batteries. This study demonstrates the synthesis of orthorhombic Nb2O5@Nb4C3Tx (or @Nb2CTx) hierarchical composites via a one-step oxidation -in flowing CO2 at 850 °C -of 2D Nb4C3Tx (or Nb2CTx) MXene. The composites possess a layered architecture with orthorhombic Nb2O5 nanoparticles decorated uniformly on the surface of the MXene flakes and interconnected by disordered carbon. The composites have a capacity of 208 mAh g-1 at a rate of 50 mA g-1 (0.25 C) in 1-3 V versus Li+/Li, and retain 94% of the specific capacity with 100% Coulombic efficiency after 400 cycles. The good electrochemical performances could be attributed to three synergistic effects: (1) the high conductivity of the interior, unoxidized Nb4C3Tx layers, (2) the fast rate response and high capacity of the external Nb2O5 nanoparticles, and (3) the electron "bridge" effects of the disordered carbon. This oxidation method was successfully extended to Ti3C2Tx and Nb2CTx MXenes to prepare corresponding composites with similar hierarchical structures. Since this is an early report on producing this structure, there is much room to push the boundaries further and achieve better electrochemical performance.
Various active/inactive nanocomposites of Cu2Sb-Al2O3@C, Cu2Sb-TiC, and Cu2Sb-TiC@C have been synthesized by high energy mechanical milling and investigated by differential scanning calorimetry (DSC) to determine the lithiated phase stability and heat generation arising from these electrodes. The milling process reduces the Li3Sb phase stability, relative to the un-milled samples, to below ∼200 °C. However, the incorporation of the reinforcing, inactive phases Al2O3, TiC, and carbon black offer a slight improvement. DSC curves also show that the low-temperature heat generation in the SEI-layer reaction range is not noticeably altered by either the milling process or the addition of the inactive phases. A strong exothermic peak is observed at ∼200 °C for the 0% state of charge electrodes of Cu2Sb-Al2O3@C and Cu2Sb-TiC@C that was caused by the incorporation of carbon black into the composite. This peak was not present in the electrodes of milled Cu2Sb or Cu2Sb-TiC, suggesting that efforts to extend the cycle life of alloy anodes should avoid carbon black due to its destabilizing effects on delithiated electrodes. Fourier Transform infrared spectroscopy analysis indicates that the reaction arising from the incorporation of carbon black is tied to a low-temperature breakdown of the lithium salt LiPF6.
A new MXene phase, Ti2C, obtained by aluminum extraction from Ti2AlC and exfoliation of the reaction product, was electrochemically studied vs. Lithium. Li-ions insertion into the 2-D structure was characterized by in situ XRD measurements. Additional electrochemical kinetic characterizations of Ti2C, using a cavity micro-electrode, showed that the electrochemical reactions involve two different phenomena: one diffusion-limited, the other not. A Ti2C/activated carbon asymmetric cell was assembled to highlight the high rate performance of the MXene. The cell was cycled between 1.0 V and 3.5 V, and showed good capacity retention during 1000 galvanostatic charge/discharge cycles at rates up to 10C.
Safe and powerful energy storage devices are becoming increasingly important. Charging times of seconds to minutes, with power densities exceeding those of batteries, can in principle be provided by electrochemical capacitors—in particular, pseudocapacitors1, 2. Recent research has focused mainly on improving the gravimetric performance of the electrodes of such systems, but for portable electronics and vehicles volume is at a premium3. The best volumetric capacitances of carbon-based electrodes are around 300 farads per cubic centimetre4, 5; hydrated ruthenium oxide can reach capacitances of 1,000 to 1,500 farads per cubic centimetre with great cyclability, but only in thin films6. Recently, electrodes made of two-dimensional titanium carbide (Ti3C2, a member of the ‘MXene’ family), produced by etching aluminium from titanium aluminium carbide (Ti3AlC2, a ‘MAX’ phase) in concentrated hydrofluoric acid, have been shown to have volumetric capacitances of over 300 farads per cubic centimetre7, 8. Here we report a method of producing this material using a solution of lithium fluoride and hydrochloric acid. The resulting hydrophilic material swells in volume when hydrated, and can be shaped like clay and dried into a highly conductive solid or rolled into films tens of micrometres thick. Additive-free films of this titanium carbide ‘clay’ have volumetric capacitances of up to 900 farads per cubic centimetre, with excellent cyclability and rate performances. This capacitance is almost twice that of our previous report8, and our synthetic method also offers a much faster route to film production as well as the avoidance of handling hazardous concentrated hydrofluoric acid.
Li-ion battery (LIB) monopolizes the mobile electronic market as the power source of choice, but proper attention will be given to electrolytes developed for the so-called beyond lithium ion chemistries. Electrolytes in batteries must cater to the needs of both electrodes; hence, in principle, new battery chemistries would have incurred new electrolyte compositions. The use of mixed instead of single solvents raises complications in the effort to optimize ion conductivities. For example, in a ternary solvent mixture, thousands of electrolyte compositions might need to be experimentally prepared and measured to generate a complete conductivity contour map, which is a function of temperature, solvent composition, salt species, and concentration in a 5-D space.
Lithium-ion batteries have been long considered a promising energy storage technology for electrification of the transportation system. However, the poor safety characteristics of lithium-ion batteries is one of several technological barriers that hinder their deployment for automobile applications. Within the field of battery research and development, titanium-based anode materials have recently attracted widespread attention due to their significantly better thermal stability than the conventional graphite anode. In this chapter, the fundamental properties and promising electrochemical performance of titanium-based anode materials will be discussed for applications in hybrid electric vehicles.
Two-dimensional (2D) materials can have an excellent capability to handle
high rates of charge in ion batteries since metal ions need not diffuse in a 3D
lattice structure. However graphene, which is the most important 2D material,
is known to have no Li capacity. Herein, adsorption of Li, as well as Na, K,
and Ca on TiC, one representative MXene, is predicted by
first-principles density functional calculations. In our study, we observed
that these alkali ions exhibit different adsorption energy depending on the
coverage. The adsorption energies of Na, K and Ca decrease as coverage
increases, while Li shows little sensitivity to variance in coverage. This
observed relationship between adsorption energies and coverage of alkali ions
on TiC can be explained by their effective ionic radii. A larger
effective ionic radius increases interaction between alkali atoms, thus lower
capacity and coverage are obtained. Our calculated capacity values for Li, Na,
K and Ca on TiC are 639.5, 319.8, 191.8 and 159.9 mAh g,
respectively. Compared to materials currently used in Li ion battery anodes,
MXene shows great promise in increasing overall battery performance.
New two-dimensional niobium and vanadium carbides have been synthesized by selective etching, at room temperature, of Al from Nb2AlC and V2AlC, respectively. These new matrials are promising electrode materials for Li-ion batteries, demonstrating good capability to handle high charge-discharge rates. Reversible capacities of 170 and 260 mA·h·g(-1) at 1 C, and 110 and 125 mA·h·g(-1) at 10 C were obtained for Nb2C and V2C-based electrodes, respectively.
Carbon-coated nano-Li4Ti5O12 (LTO) anode material was prepared and evaluated with 5.5 Ah pouch cells, paired with LiNi1/3Co1/3Mn1/3O2 cathode for potential hybrid electric vehicle (HEV) application. The as-prepared LTO batteries showed excellent electrochemical performance. They delivered a peak discharge power density of ca. 2,800 W kg−1, and featured a high power (94 and 92 % of discharge and charge capacity at 20 C, respectively) and a prolonged cycle life (89 % capacity retention after 5,000 cycles at 10 C charge and discharge rate). However, the severe capacity decay was observed at elevated temperatures because of loose (worse) interfaces caused by gas generation. It was found that H2 was the dominant gas component, and the inflation rate had an Arrhenius-type correlation with storage temperature. The battery inflation, arising from side reactions between electrolyte and LTO anode, is the major technical barrier for practical application of the LTO batteries in HEV.
Herein we report on the influence of particle size, time and temperature on the kinetics – quantified by X-ray diffraction – of the selective extraction of Al from the ternary layered transition metal carbide, Ti3AlC2, when powders of the latter are immersed in hydrofluoric acid. Transmission and scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis were also used to characterize the resulting powders. Increasing the temperature and immersion times, and decreasing the Ti3AlC2 particle size, led to faster conversion of Ti3AlC2 to its 2-D Ti3C2 counterpart. Arch-shaped edges at the ends of some Ti3C2 layers resembled graphene, corroborating the single-sheet structure of exfoliated Ti3C2. The removal of water and/or OH surface groups from Ti3C2 using drying in vacuum was also attempted.
We investigate the properties of nanosized TiO2 rutile by electrochemical methods and thermal analysis. The material shows a high capacity, high rate performance and excellent cycling stability. We can clearly prove the safer character of rutile electrodes by thermal analysis. The lithiated rutile electrodes exhibit exothermic reactions with a very small energy release and they are mainly related to surface film (SEI) decomposition. The impedance spectra strongly indicate the formation of a surface film, but the semicircles of charge transfer and SEI formation cannot be resolved at any potential. In addition a new pouch cell design which is suitable for in situ measurements such as FTIR, Raman and XRD is introduced and its efficiency is proven by in situ optical microscopy.
We report an anhydrous, autogenic technique for synthesizing electronically interconnected, carbon-encapsulated, nanoparticulate anatase anode materials (TiO2–C) for lithium-ion batteries. The TiO2–C nanoparticles provide a reversible capacity of ∼200mAhg−1, which exceeds the theoretical capacity of the commercially attractive spinel anode, Li4Ti5O12 (175mAhg−1) and is competitive with the capacity reported for other TiO2 products. The processing method is extremely versatile and has implications for preparing, in a single step, a wide variety of electrochemically active compounds that are coated, in situ, with carbon.
Thermal stability of electrochemically lithiated graphite with 1 M LiPF6/EC+DMC and PVdF-binder has been investigated. DSC measurements using an airtight sample case reveal a mild heat generation started from 130 °C with a small peak at 140 °C. The mild heat generation continued until a sharp exothermic peak appeared at 280 °C. The heat evolved in the small peak at 140 °C decreased by storage of the lithiated graphite with PVdF and the electrolyte at 50 °C for 3 days before the DSC measurements. The lithiated graphite with the electrolyte without PVdF-binder did not show the small peak at 140 °C. The peak at 140 °C seems to be caused by the reaction (the Solid Electrolyte Interphase (SEI) formation) of the electrolyte and lithiated graphite, whose surface is covered by poly(vinylidene flouride) (PVdF)-binder without formation of SEI at a lower temperature. The mild heat generation from 140 to 280 °C is the reaction of the lithiated graphite and the electrolyte through SEI (SEI formation), because there was no such mild heat generation when non-lithiated graphite was used. The peak at 280 °C is probably a direct reaction of lithiated graphite and electrolyte by a breakdown of SEI.
The influence of electrolyte additives on the thermal stability of graphite anodes in a Li-ion battery has been investigated. The selected additives are: ethyltriacetoxysilane, 1,3-benzoldioxole, tetra(ethylene glycol)dimethylether and vinylene carbonate. These compounds were added in 4% to an electrolyte consisting of 1M LiBF4 ethylene carbonate (EC)/diethyl carbonate (DEC) solvent mixture. Differential scanning calorimetry (DSC) was used to investigate the thermal stability. The electrochemical performance was investigated by galvanostatic cycling and the formed solid electrolyte interphase (SEI) was characterised by photoelectron spectroscopy (PES) using AlKα and synchrotron radiation (SR). The onset temperature for the thermally activated reactions was found to increase for all electrodes cycled with additives compared to electrodes cycled without additives. The onset temperature increased in the order: no additive < tetra(ethylene glycol)dimethyl ether < 1,3-benzoldioxole < ethyl-triacetoxysilane < vinylene carbonate. Features in the PES spectra found to be associated with high onset temperatures for thermally activated reactions are: (i) no discernible graphite peak, (ii) small amount of salt species of the type LiF and LixBFyOz and (iii) larger amounts of organic compounds preferably with a high oxygen content.
An accelerating rate calorimeter (ARC) was used to measure the thermal stability of a lithiated mesocarbon microbead (MCMB)
material in electrolyte under adiabatic conditions. Measurements were carried out to determine the effects of the lithium
content and surface area of the electrode as well as the effects of the electrolyte type and the initial heating temperature
on thermal stability. MCMB electrodes with both high and low surface area were reacted electrochemically to three compositions:
,
, and
in
ethylene carbonate/diethyl carbonate (EC:DEC) (33:67) electrolyte. The low‐surface‐area MCMB samples were also lithiated
in
EC:DEC (50:50) and
EC:DEC (50:50) electrolytes The results showed that self‐heating of the MCMB samples depends on (i) the initial lithium content of the material; (ii) the electrolyte used; (iii) the surface area, and (iv) the initial heating temperature of the sample. Measurable self‐heating in the
EC:DEC (33:67) samples was detected at 80°C, at 70°C for MCMB in
EC:DEC (1:1), and at 50°C for MCMB in
EC:DEC (1:1). The initial self‐heating rate for samples containing
EC:DEC (33:67) electrolyte could be fit by an Arrhenius relation with an activation energy of 1.4 eV. The initial form of
the self‐heating rate profile was a result of the conversion of metastable solid electrolyte interface (SEI) components to
stable SEI components. © 1999 The Electrochemical Society. All rights reserved.
A C80 calorimeter was used to study the thermal behaviors of
and
in
electrolyte. C80 results show that
alone shows one exothermic peak, which is attributed to the solid electrolyte interphase (SEI) decomposition. Four exothermic
peaks were detected in
electrolyte samples. These four peaks are attributed to SEI decomposition, Li-electrolyte reaction as well as new SEI film
formation, new SEI film decomposition, and Li with PVDF/other products reactions. The apparent activation energy of
and
-electrolyte at different states of charge was calculated, and it was found that with intercalated lithium increasing, the
activation energy shows a decreasing trend.
Using an accelerating rate calorimeter, the reaction between lithium-containing carbon samples and nonaqueous electrolyte has been studied. Six different carbons, differing in morphology (fiber, spheres, flakes), heat-treatment temperature (1200 to 3000 degrees C), and surface area (0.4 to 9.2 m(2)/g) were studied. The reaction processes for all six samples were similar, showing an initial activated process, associated with decomposition of metastable components of the solid electrolyte interface, followed by reaction of intercalated lithium with electrolyte. The activation energy for the first process is about 1.4 eV for the lithium-containing carbons in LiPF6 ethylene carbonate:diethyl carbonate electrolyte. The reaction rates, however, were strongly dependent on the surface area of the graphitized samples, increasing by about two orders of magnitude from the lowest to the highest surface area sample. Surprisingly, a petroleum coke sample, heated to only near 1200 degrees C, showed reaction rates an order of magnitude lower than expected based on its surface area. These results point the way to better carbons for safer Li-ion cells. (C) 1999 The Electrochemical Society. S0013-4651(99)03-026-5. All rights reserved.
The thermal stabilities of 1 M LiPF6/EC + DEC and with electrodes were studied by calorimetry. The results show that both the electrolyte–Li0.5CoO2 and electrolyte–LixC6 system have lower decomposition onset temperatures than either the separate electrolyte or electrodes. The electrolyte is oxidized by Li0.5CoO2, while its reaction with lithiated graphite occurs because the solid electrolyte interphase (SEI) breaks down at 57 °C. The 1 M LiPF6/EC + DEC in air is less stable than in argon, but the reaction is similar.
The improvement of Li-ion batteries safety in abuse use is one of the key issues for their establishment in future hybrid or electrical vehicles. Such a challenge requires a perfect understanding of phenomena which could occur in abuse situation. A new technique for a better understanding of Li-ion cell safety has been so investigated. Reactions between electrolyte and charged electrodes (positive and negative just recovered from dismantled charged 4/5A cells) have been initiated by a laser beam, having a monitored intensity and time pulse. From such a device, a strong and controlled heating can be generated, in a very short time scale, on a defined electrode surface area. This localized heating, which is supposed to be similar to that could occur from a cell internal short-circuit, is able to initiate “self-propagation reactions” on charged negative and positive electrodes. This new technique has allowed a ranking of charged electrodes in terms of “self-propagation ability”. This range of new data has been compared to results obtained from classical thermal characterization methods (DSC, DTA) and results obtained from normalized abuse tests. Global charged negative and positive electrodes degradation mechanisms have been proposed in good agreement with the whole results. The safety of a done Li-ion cell seems mainly related to active negative and positive active materials, but also to other components of the electrodes, and especially additive carbons and aluminum collector of the positive side.
A novel Li-ion polymer battery (Li-IonPB) based on LiNi0.8Co0.2O2 as a cathode and an alternative composite anode (CA) is proposed for future application in hybrid electric vehicles (HEV). A micro-Li-ion polymer cell is prepared in situ inside the differential scanning calorimetry (DSC) sample pan, and the exothermic heat development is compared with that of the micro-lithium-solid polymer electrolyte cell. The thermal decomposition of both cells is further investigated from a qualitative point of view.
The thermal stability of fluorinated ester electrolytes with and without lithium metal and the positive electrode material at the charged state were investigated, in terms of application for electrolytes in lithium metal anode cells. The fluorinated ester electrolytes are solutions dissolving LiPF6 in carboxylic acid esters whose original carboxylic acids are partially fluorinated. The corresponding non-fluorinated ester electrolytes were also studied for comparison. According to differential scanning calorimetry (DSC) measurement, fluorinated ester electrolytes exhibited significant thermal stability when coexisting with lithium metal or Li0.5CoO2. LiPF6/methyl difluoroacetate showed the best stabilization effect, which shifted the exothermic peak of the electrolyte with lithium metal or Li0.5CoO2 to about 300°C. In addition, LiPF6/methyl difluoroacetate exhibited a good lithium anode cycling efficiency. We believe that LiPF6/methyl difluoroacetate is a very promising electrolyte for use in realizing lithium metal anode secondary cells.