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Thermal stability and kinetics of delithiated LiCoO2
Abstract
The thermal stability of the materials that comprise the battery has been one of the important issues. By using temperature programmed desorption-mass spectrometry (TPD-MS) and XRD, the thermal decomposition reaction of delithiated LixCoO2 (x = 1, 0.81, 0.65) was quantitatively analyzed. Delithiated LixCoO2 samples were metastable and liberated oxygen at a temperature of above 250 °C. Liberated oxygen gas was quantified by TPD-MS. Structural changes of the samples were confirmed by XRD. We identified the stoichiometry of the thermal decomposition reaction of LixCoO2. Furthermore, to analyze the heating rate dependence of the oxygen generation, we calculated the activation energy (Ea) of the thermal decomposition reaction. The average Ea through the reaction of Li0.81CoO2 is 130 kJ mol−1, and that of Li0.65CoO2 is 97 kJ mol−1. The Li content decreased as the activation energy increased.
... Many efforts have been conducted to improve the safety of LIB in the active material processing, as well as the cell battery manufacturing and management technology [7][8][9][10][11][12]. Especially, the thermal stability of LCO has been intensively investigated compared with those of other cathode materials to predict the thermal behaviors of lithium-ion cell. ...
... Since the information is resulted from complex electrochemical reactions influenced by various factors, including electrode consisting materials such as conducting agents, binders, electrolyte solvents and salts, as well as their composition in the battery cell. To obtain the decomposition of LCO itself without other reactions involved, Furushima et al. quantified the O 2 evolution rate with chemically delithiated LCO (Li 0.65 CoO 2 and Li 0.81 CoO 2 ) by using a temperature programmed desorption-mass spectrometry (TPD-MS) and determined the activation energy of the delithiated LCO decomposition kinetics [11]. Yamaki et al. also studied on the O 2 evolution from delithiated LCO state [12]. ...
... Eurasian Chemico-Technological Journal 21 (2019) [3][4][5][6][7][8][9][10][11][12] TCD was used to determine the amount of H 2 consumption. 10 mg of the sample was loaded in the reactor and 4% H 2 /Ar was fed at a rate of 10 ml min -1 . ...
Temperature programmed reduction (TPR) method was introduced to analyze the structural change and thermal stability of LixCoO2 (LCO) cathode material. The reduction peaks of delithiated LCO clearly represented the different phases of LCO. The reduction peak at a temperature below 250 °C can be attributed to the transformation of CoO2–like to Co3O4–like phase which is similar reduction patterns of CoO2 phase resulting from delithiation of LCO structure. The 2nd reduction peak at 300~375 °C corresponds to the reduction of Co3O4–like phase to CoO–like phase. TPR results indicate the thermal instability of delithiated LCO driven by CoO2–like phase on the surface of the delithiated LCO. In the TPR kinetics, the activation energies (Ea) obtained for as-synthesized LCO were 105.6 and 82.7 kJ mol-1 for Tm_H1 and Tm_H2, respectively, whereas Ea for the delithiated LCO were 93.2, 124.1 and 216.3 kJ mol-1 for Tm_L1, Tm_L2 and Tm_L3, respectively. As a result, the TPR method enables to identify the structural changes and thermal stability of each phase and effectively characterize the distinctive thermal behavior between as-synthesized and delithiated LCO.
... Enclose or carefully insulate all wire connections. Be aware that component failure could cause high voltage to appear in unexpected places, such as heat sinks on the switching transistors.13. Use of circuit breakers as switches. ...
... The pore size distribution of the raw black mass BM-1 and FJHactivated BM-1. First principle simulations of FJH activation of black mass Supplementary Fig. 17 Energy preference towards phase segregation of partially delithiated lithium cobalt oxide.First principle calculations allowed us to demonstrate a possible route for FJH activation process of partially delithiated LixCoO2 through phase segregation to form the crystalline LiCoO2, Co3O4 and release of O2 gas:13 ...
The staggering accumulation of end-of-life lithium-ion batteries (LIBs) and the growing scarcity of battery metal sources have triggered an urgent call for an effective recycling strategy. However, it is challenging to reclaim these metals with both high efficiency and low environmental footprint. We use here a pulsed direct current flash Joule heating (FJH) strategy that heats the black mass, the combined anode and cathode, to >2100 K within seconds, leading to ~1000-fold increase in subsequent leaching kinetics. There are high recovery yields of all the battery metals, regardless of their chemistries, using even diluted acids like 0.01 M HCl, thereby lessening the secondary waste stream. The ultrafast high-temperature achieves thermal decomposition of the passivated solid-electrolyte-interphase and valance-state reduction of the hard-to-dissolve metal compounds, while mitigating diffusional loss of volatile metals. Life-cycle-analysis vs current recycling methods shows that FJH significantly reduces the environmental footprint of spent LIB processing, while turning it into an economically attractive process.
... The observed weight losses for the delithiated LCOs were in good agreement with the total amounts of liberated oxygen from Li 0.81 CoO 2 and Li 0.65 CoO 2 , respectively. 35 This suggests that the weight losses of the chemically delithiated LCOs are related to oxygen release from the layered structure, and the LCO with a higher degree of Li loss (i.e., Li 0.6 CoO 2 ) is more unstable, owing to the release of more oxygen from the layered structure at elevated temperatures. 35 Furthermore, the results confirmed that chemical compositions of the delithiated LCO samples were close to the target compositions of Li 0.8 CoO 2 and Li 0.6 CoO 2 . ...
... 35 This suggests that the weight losses of the chemically delithiated LCOs are related to oxygen release from the layered structure, and the LCO with a higher degree of Li loss (i.e., Li 0.6 CoO 2 ) is more unstable, owing to the release of more oxygen from the layered structure at elevated temperatures. 35 Furthermore, the results confirmed that chemical compositions of the delithiated LCO samples were close to the target compositions of Li 0.8 CoO 2 and Li 0.6 CoO 2 . ...
Reusing valuable cathode materials from end-of-life (EOL) Li-ion batteries can help lower dependence on mining for raw materials for cathodes while also preventing the rise in commodity prices. This work employed chemically-delithiated cathodes that are analogous to the spent cathodes but free of any impurities to fundamentally elucidate the effectiveness of cathode regeneration. Two lithium cobalt oxides (LCOs) at different degrees of delithiation were synthesized by chemical delithiation, and their material and electrochemical characteristics were systematically compared before/after hydrothermal-based cathode regeneration. The material and electrochemical characteristics were further evaluated in comparison with the pristine LCO. Both the LCOs at high and low state of health (SOH) recovered their reversible capacity and cycle performance comparable to the pristine LCO. However, the high-rate performance (2C) of the regenerated LCOs was not comparable to that of the pristine LCO. The slight increase in the cell resistance of the regenerated LCOs was attributed to the lower high-rate performance, which was identified as a key challenge of cathode regeneration. Our study provides valuable insights into the effectiveness of cathode regeneration by revealing how the disordered, lithium-deficient LCOs at different levels of SOH from EOL batteries are regenerated without losing their functional integrity.
... Though the peak from the Li 1x CoO 2y phase could be identified after chlorination at 500 o C, it was difficult to find at 550 o C. These findings can be explained by the thermal decomposition of the Li 1x CoO 2y phase, as demonstrated earlier [15]. The thermal decomposition of Li 0.65 CoO 2 and Li 0.81 CoO 2 started at 250 o C, while the fully lithiated LiCoO 2 phase was thermally stable up to 600 o C [15]. ...
... These findings can be explained by the thermal decomposition of the Li 1x CoO 2y phase, as demonstrated earlier [15]. The thermal decomposition of Li 0.65 CoO 2 and Li 0.81 CoO 2 started at 250 o C, while the fully lithiated LiCoO 2 phase was thermally stable up to 600 o C [15]. Therefore, it is theorized that thermal decomposition occurred at 550 o C via the following reaction equation: ...
The chlorination behavior of LiCoO2 (LCO) was investigated as a function of the reaction temperature (400–600 °C) and time (1–8 h) under a 190 mL/min Ar+10 mL/min Cl2 flow. Based on the results of a structural analysis, a sequential reaction mechanism was proposed for the chlorination of LCO: LiCoO2→(400–600 °C) Li1−xCoO2−y→(450–600 °C) Co3O4→ (500–600 °C) CoCl2. It was also found that thermal decomposition of the Li1−xCoO2−y phase to the LiCoO2 and Co3O4 phases occurs simultaneously in the temperature range of 550–600 °C, resulting in reduced Li removal ratios. A change in the reaction temperature caused significant changes in the reaction product in terms of the constituent phases and their ratios because each reaction step is independently affected by the reaction temperature. In consideration of the highest Li removal ratio (0.86 after 8 h of the chlorination) and potential loss of Co by sublimation of CoCl2 at elevated temperatures, the optimum suggested temperature for the chlorination of LCO is 500 °C.
... Previously, research into anode materials has focused on the development of hybrid electrode materials with different nanostructures and AC coatings. Hierarchical nanostructures reduce the charge diffusion path and enhance the active electrochemical sites, while a coating of conductive carbon offers a channeled framework for fast kinetic processes [176,177,181]. ...
... Also, the toxic nature of cobalt has limited the further widespread application of LiCoO 2 . Several efforts have been made to improve the performance of LCO, either by metal doping (doping with Zr, Mg, Mo, Sr, V, or Al) or surface modification using metal oxides such as TiO 2 , Al 2 O 3 , SiO 2 , B 2 O 3 , MgO, LiMn 2 O 4 , AlPO 4 , and LiPON polyimide [180][181][182][183][184][185][186][187]. ...
... In this particular type of LG cylindrical cell the cathode is NMC532 (Li(Ni0.5 Mn0.3 Co 0.2)O2). When comparing cathode chemistries, the thermal stability order of different cathode structures has been reported to follow the trend (at full SOC): LFP > LMO > NMC > NCA > LCO, with the latter being the least stable [32]. ...
The ubiquitous deployment of Li-ion batteries (LIBs) in more demanding applications has reinforced the need to understand root-causes of thermal runaway. Herein we perform a forensic simulation of a real-case failure scenario, using localised heating of Li(Ni0.5Mn0.3Co0.2)O2 versus graphite 18650 cylindrical cells. This study determined the localised temperatures that would lead to venting and thermal runaway of these cells, as well as correlating the gases produced as a function of degradation pathway. Catastrophic failure, involving melting (with internal cell temperatures exceeding 1085°C), deformation and ejection of cell componentry, was induced by locally applying 200 °C and 250 °C to a fully charged cell. Conversely, catastrophic failure was not observed when the same temperatures were applied to the cells at lower state of charge (SOC). This work highlights the importance of SOC, chemistry and heat in driving the thermal failure mode of Ni-rich LIB cells, allowing for a better understanding of battery safety and associated design improvements.
... In this particular type of LG cylindrical cell, the cathode is NMC532 (Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 ). When comparing the cathode chemistries, the thermal stability order of different cathode structures has been reported to follow the trend (at full SOC) LFP > LMO > NMC > NCA > LCO, with the latter being the least stable [32]. ...
The ubiquitous deployment of Li-ion batteries (LIBs) in more demanding applications has reinforced the need to understand the root causes of thermal runaway. Herein, we perform a forensic simulation of a real-case failure scenario, using localised heating of Li(Ni0.5Mn0.3Co0.2)O2 versus graphite 18650 cylindrical cells. This study determined the localised temperatures that would lead to venting and thermal runaway of these cells, as well as correlating the gases produced as a function of the degradation pathway. Catastrophic failure, involving melting (with internal cell temperatures exceeding 1085 °C), deformation and ejection of the cell componentry, was induced by locally applying 200 °C and 250 °C to a fully charged cell. Conversely, catastrophic failure was not observed when the same temperatures were applied to the cells at a lower state of charge (SOC). This work highlights the importance of SOC, chemistry and heat in driving the thermal failure mode of Ni-rich LIB cells, allowing for a better understanding of battery safety and the associated design improvements.
... The fully discharged Li-ion battery cathode materials with layered metal oxides LiCoO 2 and NMC are stable up to 900°C. 21 However, after partially charge they become unstable at about 200°C with the release of molecular oxygen and the formation of Co 3 O 4 . 22,23 A detailed discussion of Li-ion battery cathode materials degradation with the release of oxygen has been reported by Sahrifi-Asi et al. 22 M.K.H. Hsieh et al. reported on a case study of electric scooter battery detonation in Singapore. ...
Lithium-Ion batteries are highly successful high-energy-density commercial energy sources used to run consumer devices such as cellphones, E-bikes, hoverboards, laptops, tablets, and medical equipment. They are safe if produced with attention paid to the selection of materials and to the manufacturing methods used for their production and quality control processes. However, safety hazards arising from rare manufacturing defects have given them notoriety as devices to be handled with utmost care. This manuscript provides an account of the safety-related chemistry of Li-ion batteries and the processes used to manufacture and utilize them safely.
... Relatively low ΔE are observed in cathodes with nearly stochiometric composition compared to aged ones where a substantial degree of delithiation is observed. This result indicates the increased effectiveness of the thermal decomposition during the FJH activation of heavily degraded cathode particles (56,57). The microscale and nanoscale morphologies of FJH-activated black mass are shown in Fig. 4 (A and B). ...
The staggering accumulation of end-of-life lithium-ion batteries (LIBs) and the growing scarcity of battery metal sources have triggered an urgent call for an effective recycling strategy. However, it is challenging to reclaim these metals with both high efficiency and low environmental footprint. We use here a pulsed dc flash Joule heating (FJH) strategy that heats the black mass, the combined anode and cathode, to >2100 kelvin within seconds, leading to ~1000-fold increase in subsequent leaching kinetics. There are high recovery yields of all the battery metals, regardless of their chemistries, using even diluted acids like 0.01 M HCl, thereby lessening the secondary waste stream. The ultrafast high temperature achieves thermal decomposition of the passivated solid electrolyte interphase and valence state reduction of the hard-to-dissolve metal compounds while mitigating diffusional loss of volatile metals. Life cycle analysis versus present recycling methods shows that FJH significantly reduces the environmental footprint of spent LIB processing while turning it into an economically attractive process.
... One of the possible methods to obtain CTE is thermal XRD measurements. We have found only one experimental work with thermal XRD data in the range from 25 to 600 ○ C, measured for LCO, 37 but it reports only temperature dependence of the c-axis length and near constant values of the a-axis length. Since a proper calculation of CTE needs the temperature dependence of unit cell volume, we have measured the XRD patterns of the studied LCO sample in the temperature range from 25 to 450 ○ C, wide enough to define CTE. ...
Lithium cobalt oxide is a convenient model material for the vast family of cathode materials with a layered structure and still retains some commercial perspectives for microbatteries and some other applications. In this work, we have used ab initio calculations, x-ray diffraction, Raman spectroscopy, and a theoretical physical model, based on quasi-harmonic approximation with anharmonic contributions of the three-phonon and four-phonon processes, to study a temperature-induced change of Raman spectra for LiCoO2. The obtained values of shift and broadening for Eg and A1g bands can be used for quantitative characterization of temperature change, for example, due to laser-induced heating during Raman spectra measurements. The theoretical analysis of the experimental results lets us conclude that Raman spectra changes for LiCoO2 can be explained by the combination of thermal expansion of the crystal lattice and phonon damping by anharmonic coupling with comparable contributions of the three-phonon and four-phonon processes. The obtained results can be further used to develop Raman-based quality control tools.
... [40] For comparison, some literature values for the diffusion of associated elements are summarized in Table IX. The present value of activation energy falls in the range of the activation energies of oxygen diffusion through non-stoichiometric LiCoO 2 of Furushima et al. [45] This might indicate that during the early stage of the reduction, the dominant mechanism is oxygen diffusion in the LiCoO 2 during its decomposition. The period of diffusion-control was different at each reaction temperature, as shown in Table II. ...
Recycling of Li-ion battery cathode materials using carbon from the anode materials via carbothermic reduction would provide a reduction process option that could be carried out without introducing any external reactants. From this basis, this study investigated and examined the kinetics of carbothermic reduction of LiCoO2 at 700 °C to 1100 °C under inert atmosphere up to 240 minutes reaction time using an isothermal mass change analysis combined with detailed microstructure evolution observation. The overall reduction mechanism appeared to involve diffusion of oxygen in LiCoO2 during its thermal decomposition in the first stage, followed by the nucleation of cobalt in the second stage. The activation energy of the diffusion and nucleation stages were calculated to be 121 and 95 kJ/mol, respectively. The microstructure analyses showed a complex evolution of phases. At 700 °C to 900 °C, Li2CO3 and Co phases were observed as the product of the reductions; while at 1000 °C to 1100 °C, Li2O and Co phases were observed. The information and data obtained are useful when comparing different recycling methods and optimizing the carbothermic reduction parameters for recycling cathode materials from spent Li-ion batteries.
... In fact, pristine layered LiCoO 2 materials are quite stable under high temperature, e.g. 900 °C, yet charged particles with partial lithium extraction start to release oxygen above 250 °C [144]. ...
Worldwide demands for green energy have driven the ever-growing popularity of electric vehicles, resulting in demands for a million tons of lithium-ion batteries (LIBs). Such exigency will not only outstrip the current reserves of critical metals, such as Li, Co, Ni, and Mn, which are essential for LIB fabrication, but also necessitate the methods to properly, safely, and sustainably handle spent LIBs. Current LIB recycling infrastructure uses pyrometallurgical or hydrometallurgical methods and mainly focuses on cobalt recovery to maximize economic benefits. Despite being commercialized, these two methods are either energy-intensive or highly complicated, and their long-term economic feasibility is still uncertain, as the market trend is shifting towards cobalt-poor or even cobalt-free chemistry. Alternative non-destructive methods, including direct recycling and upcycling, have attracted much interest. Direct recycling, which is a non-destructive method, allows spent cathodes to be directly regenerated into new active materials for reuse, while upcycling, as an upgraded direct recycling method, transforms degraded cathode materials into materials with a better performance or applicability in other fields. This review mainly focuses on recent advances in techniques including pyro- and hydrometallurgy, direct recycling, and upcycling.Graphical abstract
... The study was further developed by Richard and Dahn [68] to establish the models for the reactions between the electrolyte and the lithiated graphite. The kinetic parameters for the various cathode material decomposition reactions have been investigated using the DSC test results through Ozawa's method and Kissinger's method [69][70][71][72]. Similarly, Chen et al. [73,74] used the DSC tests for calculating the activation energy of the reaction relating to the decomposition of SEI film in four different types of graphite anodes. ...
Lithium-ion batteries are widely considered the leading candidate energy source for powering electric vehicles due to their high energy and power densities. The thermal runaway of lithium-ion batteries is the phenomenon of chain exothermic reactions within the battery. These reactions cause a sharp rise in the internal battery temperature causing the inner structures of the battery to destabilize and degrade, which eventually leads to the failure of the battery. This paper provides a comprehensive review of the key aspects of the thermal runaway processes, which consists of thermal runaway initiation mechanisms, thermal runaway propagation, and the characterization of vented gases during the thermal runaway process. Thermal runaway is a major safety concern; therefore, the development of mathematical and numerical models to predict thermal runaway is reviewed, which provides useful data to design and develop battery packs with thermal runaway safety features. Furthermore, the development of effective battery thermal management systems is discussed, which is essential to prevent thermal runaway initiation. Finally, mitigation strategies are reviewed, which are developed to contain and minimize damages when thermal runaway occurs.
... Such high operating voltage in a lithium-ion battery offered remarkably higher energy density compared to its predecessors. Unfortunately, the Li X CoO 2 cathode can only be delithiated to x = 0.5, as further removal of lithium ions will lead to irreversible collapse of the crystal lattice, causing severe capacity deterioration and poor cycling stability [44][45][46]. To further improve the capacity of the cathode, cobalt was partially substituted with nickel (higher specific capacity) and manganese (better cycling stability), leading to the extensively studied layer-structured lithium nickel cobalt manganese oxide (NCM) materials [47][48][49]. ...
Electrical energy generation and storage have always been complementary to each other but are often disconnected in practical electrical appliances. Recently, efforts to combine both energy generation and storage into self-powered energizers have demonstrated promising power sources for wearable and implantable electronics. In line with these efforts, achieving self-rechargeability in energy storage from ambient energy is envisioned as a tertiary energy storage (3rd-ES) phenomenon. This review examines a few of the possible 3rd-ES capable of harvesting ambient energy (photo-, thermo-, piezo-, tribo-, and bio-electrochemical energizers), focusing also on the devices’ sustainability. The self-rechargeability mechanisms of these devices, which function through modifications of the energizers’ constituents, are analyzed, and designs for wearable electronics are also reviewed. The challenges for self-rechargeable energizers and avenues for further electrochemical performance enhancement are discussed. This article serves as a one-stop source of information on self-rechargeable energizers, which are anticipated to drive the revolution in 3rd-ES technologies.
... The most important aspect of this parameterization to the DSC data is the fact that while TGA shows O 2 release from Li 0.47 CoO 2 at ∼250°C, the DSC shows no significant exotherms until >300°C. 12,25 This indicates molten Li is present with O 2 but there is no reaction until the temperature in the DSC exceeds 300°C. We account for this behavior with the ( ) H T function in Eq. 13. ...
Solid-state batteries are often considered to have superior safety compared to their liquid electrolyte counterparts, but further analysis is needed, especially because the higher specific energy a of solid-state lithium metal battery results in a higher potential temperature rise from the electrical energy in the cell. We construct a model of the temperature rise during a thermal ramp test and short circuit in a large-format solid-state LCO|LLZO|Li battery based on measurements of thermal runaway reaction thermochemistry upon heating. O2 released from the metal oxide cathode starting at ~250°C reacts with molten Li metal to form Li2O in an exothermic reaction that may drive the cell temperature to ~1000°C in our model, comparable to temperature rise from high-energy Li-ion cells. Transport of O2 or Li through the solid-state separator (e.g., through cracks), and the passivation of Li metal by solid products such as Li2O, are key determinants of the peak temperature. Our work demonstrates the critical importance of the management of molten Li and O2 gas within the cell, and the importance of future modeling and experimental work to quantify the rate of the 2Li+1/2O2Li2O reaction, and others, within a large format solid-state battery.
... So far, there are numerous studies that deal with the thermal stability of LIB cathode materials [35][36][37][38][39][40]. Since these are often only concerned with safety-related or performancerelevant issues, the analyses are usually carried out in temperature ranges below 300 • C. Pyrometallurgical recycling approaches on the other hand operate at temperatures of well above 1000 • C and cannot be adequately described by observed reactions and phenomena at lower temperatures [41][42][43][44][45]. ...
Within the e-mobility sector, which represents a major driver of the development of the overall lithium-ion battery market, batteries with nickel-manganese-cobalt (NMC) cathode chemistries are currently gaining ground. This work is specifically dedicated to this NMC battery type and investigates achievable recovery rates of the valuable materials contained when applying an unconventional, pyrometallurgical reactor concept. For this purpose, the currently most prevalent NMC modifications (5-3-2, 6-2-2, and 8-1-1) with carbon addition were analyzed using thermogravimetric analysis and differential scanning calorimetry, and treated in a lab-scale application of the mentioned reactor principle. It was shown that the reactor concept achieves high recovery rates for nickel, cobalt, and manganese of well above 80%. For lithium, which is usually oxidized and slagged, the transfer coefficient into the slag phase was less than 10% in every experimental trial. Instead, it was possible to remove the vast amount of it via a gas phase, which could potentially open up new paths regarding metal recovery from spent lithium-ion batteries.
... If the heating rate is lower than 0.3 °C min −1 , selfdischarge will occur at lower temperatures due to the longer heating time [19]. As a result, Li ions in the negative electrode return to the positive electrode, and the thermal stability of the cathode material increases [45]. For this measurement, these heating rates are suitable because the voltage drop behavior below 150 °C is similar. ...
Thermal runaway of lithium-ion battery (LIB) depends not only on the chemical composition of cathode materials but also on grain boundary. However, despite many studies on thermal stability of cathode materials to date, few safety diagrams of thermal runaway in full cells have been reported. In this study, the thermal safety diagram is compared in the full cell by using single-crystal and polycrystalline particles LiNi0.8Co0.1Mn0.1O2 (NCM 811) as cathode material and natural graphite (NG) as anode material. A thermal safety diagram is made
using a differential scanning calorimetry (DSC) by using an all-inclusive cell, which consists of all LIB components. Since a thermal runaway reaction is a series of elementary reactions, it is determined using the Friedman differential isoconversional method. Thermal runaway prediction results obtained using DSC data are verified using an acceleration rate calorimeter (ARC). The prediction results nearly match the verification results of ARC measurements, and it is clarified that the full cell using single-crystal particles NCM 811 as the cathode material
has higher thermal safety than that using polycrystalline particles NCM 811.
... It is presumably associated with the decomposition of the formed cathode powders itself. According to [39] the thermal decomposition of LiCoO 2 proceeds at the temperatures of 900°C and higher and are accompanied by oxygen release. However, due to experiment atmosphere (synthetic air) releasing oxygen cannot be detected by a mass spectrometer. ...
Lithium‑cobalt oxide (LiCoO₂) is the first and still popular cathode material (LCO) used in Li-ion batteries. Its high theoretical capacity is a driving force to improve its properties in order to fully use its significant potential. In this paper the attempts of a partial substitution of Co³⁺ ions with Y³⁺ ions to synthesize yttrium-doped LiCoO2 cathode (0–15 mol% of Y) were described. The physicochemical characterization were conducted by ICP, TGA-MS, N₂ physisorption, X-ray diffraction (PXRD) and scanning electron microscopy (SEM-EDS). All the prepared cathode materials exhibit well-layered structure and high crystallinity. Unexpectedly, yttrium ions did not substituted the Co³⁺ sites and were present in the form of a separate oxide phase. Yttrium oxide act as a modifier adversely affecting the initial capacity of the LCO cathode material. However, the galvanostatic cycling revealed that the yttrium oxide addition has a beneficial effect on the cycling stability and capacity retention of the LCO material, especially for the small content of Y³⁺ (5 mol%). The cycling of this electrode (100 cycles at 1C between 3.0 and 4.4 V vs. Li/Li⁺) was stable and constant, the loss of capacity was steady and the smallest among all the tested materials.
... The high thermal stability of the CLCO cell at this temperature indicates that the in-situ formed interphase between cathode and polymer electrolyte can efficiently cut off their interfacial reactions. And the relatively small amount of heat release at~260 C for both BLCO and CLCO cells is originated from oxygen generation from the cathode and the subsequent reactions with the anode, based on previous studies about thermal behaviors of the charged cathode [32,33]. The CLCO cell shows slight heat release at this temperature, but still lower than the BLCO cell, indicating the cathode decomposition can be restrained by the in-situ CEI coating layer on cathode particles, since the cathode coating strategy was reported to enhance the thermal stability of cathode in conventional LIBs [34]. ...
All-solid-state batteries have been considered as the ultimate solution for energy storage systems with high energy density and high safety. However, the obvious solid-solid contact and the interface stability issues pose great challenges to the construction of all-solid-state batteries with practically usable performances. Here, we discover that the heat-initiated polymerization of vinylene carbonate (VC) and the simultaneous incorporation of cathode electrolyte interphase (CEI) forming additive lithium difluoro(oxalato)borate (LiDFOB) can synergistically promote the formation of a high-voltage stable and low resistant interface layer between the cathode and solid electrolyte. A poly(ethylene oxide) PEO-based all-solid-state lithium battery (ASSLB) employing the LiCoO2 cathode electrode modified through such an in-situ CEI strategy demonstrates superior 4.2 V cycle stability, with a discharge capacity retention of 71.5% after 500 cycles. Besides, the accelerating rate calorimetry (ARC) test reveals that the cell displays extraordinary safety performance with no distinct thermal runaway below 350 °C. This work demonstrates an effective interface engineering strategy that can promise the formation of electrochemically and thermally stable cathode/solid electrolyte interface which is essential for the stable and safe operation of ASSLBs. Moreover, the validation of stable cycling of PEO-based ASSLBs at high voltages may encourage the efforts on further optimizations of interface engineering processes as well as large-scale fabrication, as the improvement of the energy-densities of PEO-based ASSLBs will be of paramount significance for practical applications.
... One step global oxygen release rate equations are developed for various delithiation amounts. Furushima et al. [26] used temperature programmed desorptionmass spectrometry (TPD-MS) and observed oxygen generation after 250°C. Recently, Jung et al. [27] used temperature programmed reduction technique to identify the reaction kinetics of all three stages related with the oxygen release. ...
Characterizing propagation of a thermal runaway hazard in cell arrays and modules is critical to understanding fire hazards in energy storage systems. In this paper, the thermal runaway propagation of a pouch cell array has been examined by developing a 1D finite difference model. The results are compared with experimental data. First, the thermal runaway reactions found in the literature are reviewed. Using the insight of the literature review and premixed flame propagation theory, a global first order Arrhenius type reaction is characterized. While applying the multiple kinetic reactions, an “onset temperature” of the combustion reactions has been determined by performing an induction time analysis on ethylene. The propagation speeds are predicted with a 1D finite difference model by using both multi-reaction kinetics and one step reduced-order kinetics. These results are in a good agreement with experiments for both 10 Ah and 5 Ah cell arrays.
... It should be emphasized that they are both present into each particle of the thermally decomposed LiCoO 2 powder and not as single composition particles [40,44,45]. Their relative weights are closely related to the lithium deficiency in the non-stoichiometric Li x CoO 2 compounds according to the thermal decomposition reaction occurring in the 300-400°C temperature range, keeping stable until 800°C [40,42,44], as, ...
In the last decades, the demand for lithium-ion batteries (LIBs) has been growing fast to attend the markets of electric and hybrid vehicles and of electric portable devices. As scarce metals like cobalt and lithium are employed in their manufacturing the recycling of spent LIBs is a strategic solution for the sustainability of these minerals and also the maintenance of the LIBs production. Therefore, efforts should be driven to produce low cost, environment-friendly and industrially scalable recycling processes. In this study, a closed-loop process with these characteristics was developed to recover cobalt and lithium compounds from LiCoO2 cathodes of spent cell phone lithium-ion batteries. The process employs citric acid as green leaching agent to recover cobalt as CoC2O4.2H2O and Co3O4 and lithium as Li2CO3. Lithium compound was recovered from a proposed new and original method based on simple chemical procedures as evaporation-calcination and water dissolution. The developed process also allows the resynthesis of LiCoO2 as a stoichiometric, well crystallized and structurally ordered compound from the recovered Co and Li compounds, in a closed-loop recycling process. The obtained results indicate that the developed process has great potential to be scaled up to a recycling industrial plant of spent lithium-ion batteries.
... Dahn et al. has calculated the kinetics parameters of several exothermic reactions from the Arrhenius plots in the ARC tests, and established models for the SEI film decomposition reaction [16], the reaction between lithiated graphite and electrolyte [17], and the Li x CO 2 decomposition reaction [35][36][37]. The kinetics parameters of the decomposition reactions of several cathode materials, such as Li x CO 2 and Li x (Ni 1/3 Co 1/3 Mn 1/3 )O 2 , have been investigated based on DSC tests results using Kissinger's method and Ozawa's method [24,[38][39][40][41]. For anode materials, Chen et al. [19,42] has calculated the activation energy of the SEI film decomposition reaction in four types of graphite anodes from DSC tests results. ...
... In comparison, Gotcu et al. experimentally determined the heat capacity and thermal diffusivity of NMC cathodes and found it to be higher than LCO, subsequently resulting in an increased heat transfer and storage [50]. Analogous to Furushima et al. [51], they were able to show that this increase in thermal conductivity is more pronounced in delithiated samples, corresponding to a fully charged battery where thermal runaway is of concern. All of these aspects lead to a reduced temperature rise for NMC batteries and higher onset temperature for self-heating. ...
Numerical models for battery management systems must be computationally efficient with enough accuracy for predictive usage when the vehicle is operating. For electric vehicles (EVs), this requires accounting for capacity offset, temperature dependency, and battery aging effects. This effort provides an enhanced formulation of Peukert’s equation including temperature effects and the inclusion of an absolute capacity that is calibrated to five different cathodes (LiCoO2, LiCoNiAlO2, LiNiMnCoO2, LiMnNiO2, and LiFePO4) with two types of crystal structures (layered and olivine) from four manufacturers. After data collection using a Vencon battery analyzer and two thermistors measuring self-heating temperature swings, the results demonstrate that the model works relatively well in predicting the State of Charge curve. As expected, the capacity specific parameter is near unity when simulating low offset olivine compounds; whereas, the temperature dependent variable illustrates a wide-range of values with cobalt constituted chemistries on the higher end. Additionally, the model tends to perform better for non-spinel compounds and that manufacturer specified nominal capacities are around 95-99% of the model defined absolute capacity. Overall, the technique of separating current and temperature based phenomena and recognizing modeled patterns that align with current literature are useful steps in developing an efficient battery model.
... Finally, overcharge beyond the cut-off voltage will bring a high SOC to the battery. However, SOC has a great influence on the thermal stability of electroactive materials, where highly delithiated electroactive materials become more reactive [30,31]. This induces more intense reactions in the processing of thermal runaway, including SEI decomposition, the polymer separator shrinking, reaction between electrode materials, reaction between the electrode material and electrolyte, etc. [32,33]. ...
Numerous lithium-ion battery (LIB) fires and explosions have raised serious concerns about the safety issued associated with LIBs; some of these incidents were mainly caused by overcharging of LIBs. Therefore, to have a better understanding of the fire hazards caused by LIB overcharging, two widely used commercial LIBs, nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP), with different cut-off voltages (4.2 V, 4.5 V, 4.8 V and 5.0 V), were tested in this work. Some parameters including the surface temperature, the flame temperature, voltage, and radiative heat flux were measured and analyzed. The results indicate that the initial discharging voltage increases with the growth of charge cut-off voltage. Moreover, the higher the cut-off voltage, the longer the discharging time to reach 2.5 V. An overcharged LIB will undergo a more violent combustion process and has lower stability than a normal one, and the increasing cut-off voltage aggravates the severity. In addition, it is also revealed that the NMC fails earlier than the LFP under the same condition. The temperatures for safety vent cracking, ignition, and thermal runaway of LIBs exhibit similar values for the same condition, which demonstrates that the LIB will fail at a certain temperature. Finally, the peak heat flux, total radiative heat flux, and total radiative heat will rise with the increase in voltage.
... It can be noticed that onset temperatures of the exothermic reactions tend to decrease by increasing the state of charge. This reflects the influence of the state of charge on the thermal stability of the electrode materials, where highly delithiated electrode materials become more reactive [8]. . 2 shows a thermal mapping plot of non-degraded cells, this plot summarizes the ARC results. Non-selfheating, self-heating and thermal runaway regions are identified as a function of SOC. ...
Understanding the behavior of Li-ion cells during thermal runaway is critical to evaluate the safety of these energy storage devices under outstanding conditions. Li-ion cells possess a high energy density and are used to store and supply energy to many aerospace applications. Incidents related to the overheating or thermal runaway of these cells can cause catastrophic damages that could end up costly space missions; therefore, thermal studies of Li-ion cells are very important for ensuring safety and reliability of space missions. This work evaluates the thermal behavior of Li-ion cells before and after storage degradation at high temperature using accelerating rate calorimeter (ARC) equipment to analyze the thermal behavior of Li-ion cells under adiabatic conditions. Onset temperature points of self-heating and thermal runaway reactions are obtained. The onset points are used to identify non-self-heating, self-heating and thermal runaway regions as a function of state of charge. The results obtained can be useful to develop accurate thermo-electrochemical models of Li-ion cells.
The dynamic environment within lithium-ion batteries induces significant changes in local thermodynamic functions, hampering the accurate prediction of the stability of the cathodes during cycling. While delithiation primarily affects the surface properties of the cathode structure, there is a lack of fundamental understanding concerning the evolution of interfacial energies with varying stoichiometry. Here, we used microcalorimetry to quantify the thermodynamic changes between the stoichiometric and partially delithiated nano-LiCoO2 states for the first time. A mild delithiation from LiCoO2 to Li0.71CoO2 caused a surface energy reduction, negatively affecting the adhesion between adjacent grains by ∼0.4J/m². The introduction of lanthanum at 1.0 atom % reduced the surface energy of the stoichiometric LiCoO2 while forcing a constant surface energy state during delithiation down to Li0.57CoO2. This reduced the thermodynamic stress between grains during lithium cycling, mitigating degradation mechanisms. The lanthanum-induced surface stabilization also inhibited the coarsening and dissolution of the cathode particles. We used electron microscopy to propose an atomistic mechanism by which the lanthanum doping pins surface dissolution for improved cathode stability.
Lithium-ion batteries (LIBs) are widely recognized as advanced energy storage systems (ESSs) due to their enhanced power capacity, extensive charging–discharging efficiency, and extended lifespan. However, the chemical and electrochemical interactions resulting in the uncontrolled exothermic reaction of LIB components should be considered when numerous fire or explosive incidents occur sporadically worldwide. Due to the characteristics of these active materials, an improved understanding of their thermal instability, their thermokinetic mechanisms when an LIB powers an electric system, and especially their reactivity is required as an alternative goal of proactive loss prevention. Calorimetric tests and thermal analysis techniques are introduced to determine an LIB's electrochemical and chemical reactions, which include the interaction among active components, thermal decomposition, and short circuits. The heat accumulation of an LIB affected by its components can result in a thermal explosion. Analytical thermokinetic equations are proposed to determine LIBs' exothermic reaction and create a self-heating model. The knowledge of an LIB's complex electrochemical and chemical reactions in case of thermal runaway from the calorimetry is subjected to fires or explosions. The advanced ESS of LIBs requires a proper thermal management system and a feasible, safe design.
The ever-growing market share of electrical transportation and energy storage stations has led to a demand surge for lithium-ion batteries (LIBs). Despite their popularity in global energy storage market, an efficient, sustainable and green method that can recycle spent LIBs is also in active exploration. Currently, recycling methods that destructively extract valuables from spent cells, pyro- and hydro-metallurgy, have demonstrated their feasibility at industrial scale, yet both approaches are criticized of generation of undesired environmental concerns. Both metallurgical methods aimed at extracting valuable metals only, however, suffer from the market trend shifting towards cobalt-poor and even cobalt-free chemistry. Recently guided by circular and green economy, alternative innovative strategies are emerging in order to achieve an “closed-loop” recycling of spent LIBs. What is interesting in these strategies is a complete recovery of the pristine structure and functionality of cathode materials in non-destructive methods. Despite the great promise and advantages of the direct recovery method in terms of simplicity, low energy consumption and low stress on the environment, it is still inadequate and ineffective to process obsolete cathodes, such as LiCoO2 and NCM111, to meet the current market. In view of this, another nondestructive method, upcycling, is developed, which aims at either recycling spent cathodes with increased functionality for new applications, or regenerating cathodes with increased performance. This thesis includes fundamental development of cathode recycling strategies, and focuses on developing efficient and effective upcycling method.
This thesis starts with a literature review (Chapter 1) on necessary pretreatment process and recent advances in current four recycling methods, where their ascendancy, challenges, and perspectives are also discussed. Then, the focus of this thesis is extended to a research attempt on testing the feasibility of upcycling methods (Chapter 2). In this research, a 5% LiMn0.75Ni0.25O2 coating is manufactured on spent LiCoO2 cathode material through a modified hydrothermal treatment coupled with a short annealing. With this coating, the upcycled cathode shows a capacity of 160.23 mAh/g with a capacity retention of 91.2% after 100 cycles which are much improved comparing with pristine LiCoO2.
The chlorination behavior of Li(Ni1/3Co1/3Mn1/3)O2 (NCM) was investigated as a function of the reaction temperature (400–600 °C) and time (1–8 h) for application in a chlorination-based recycling process. Structural analysis results revealed that chlorination leads to a sequential transition from a hexagonal LiMO2 structure to a hexagonal Li1−x′MO2−y′ (observed only at 400 °C), a hexagonal Li1−xMO2−y (x≥x′, y≥y′, at 400–600 °C), and a spinel-type M3O4 phase (≥500 °C, M represents Ni,Co,Mn). It was also found that this structural transition is accelerated by an increase in the reaction temperature, except at 600 °C, where the thermal decomposition of the Li1−xMO2−y phase inhibited the formation of the M3O4 phase. Weight changes of the samples suggested that the chlorination of the transition metals begins at 500 °C and that its rate increases with an increase in the reaction temperature. It was revealed by a composition analysis that an increase in the reaction temperature (except at 600 °C) and longer times result in a higher Li removal ratio. A temperature of 550 °C was proposed as the optimum temperature for the chlorination of NCM in consideration of the findings from this work.
The need for high power density cathodes for Li‐ion batteries can be fulfilled by application of a high charging voltage above 4.5 V. As lithium cobalt oxide (LCO) remains a dominant commercial cathode material, tremendous efforts are invested to increase its charging potential toward 4.6 V. Yet, the long‐term performance of high voltage LCO cathodes still remains poor. Here, an integrated approach combining the application of an aluminum fluoride coating and the use of electrolyte solutions comprising 1:1:8 mixtures of difluoroethylene:fluoroethylene carbonate:dimethyl carbonate and 1 m LiPF6 is reported. This results in superior behavior of LCO cathodes charged at 4.6 V with high initial capacity of 223 mAh g⁻¹, excellent long‐term performance, and 78% capacity retention after 500 cycles. Impressive stability is also found at 450 °C with an initial capacity of 220 mAh g⁻¹ and around 84% capacity retention after 100 cycles. Systematic post‐mortem analysis of LCO cathodes and Li anodes after prolonged cycling reveals two main degradation routes related to changes at the surface of the cathodes and formation of passivation layers on the anodes. This study demonstrates the importance of appropriate selection of electrolyte solutions and development of effective coatings for improved performance of high voltage LCO‐based Li batteries.
Lithium-rich layered oxides (LLOs) are one of the most promising cathodes for next-generation Li-ion batteries owing to their extraordinary energy density and low cost. However, the anionic redox reactions inevitably destabilize the oxygen framework and lead to oxygen release, which incurs voltage fading and capacity decay. Although less voltage fading can be realized in the cobalt-free iron-substituted materials, they still suffer from severe transition metal (TM) dissolution and poor kinetics. Herein, to ameliorate these drawbacks, we develop a novel eutectic melting salt treatment strategy. By controlling the melt and solidification of a LiF-MgF2-CaF2 ternary salt, the robust fluoride coating layer and functional doping were synchronously conducted in a Co-free Fe-substituted Li-rich cathode Li1.2Ni0.13Fe0.13Mn0.54O2. The outer fluoride layer effectively suppresses the oxygen release and prevents TM ion dissolution, while the inner doping elements improve the Li⁺ diffusion kinetics and further stabilize the bulk crystal structure. Benefiting from these, the modified cathode exhibits significantly enhanced electrochemical performance, with negligible capacity loss from the 35th to the 120th cycles at 0.2 C, mitigated voltage fading, improved rate capability and better thermal stability as well.
Lithium-ion batteries are favored by the electric vehicle (EV) industry due to their high energy density, good cycling performance and no memory. However, with the wide application of EVs, frequent thermal runaway events have become a problem that cannot be ignored. The following is a comprehensive review of the research work on thermal runaway of lithium-ion batteries. Firstly, the functions of each part of the battery and the related flame-retardant modification are summarized. The thermal properties of the battery are improved by means of coating of cathode materials and adding anion receptors. Secondly, the thermal runaway behavior and its triggering mechanism are introduced, and the decomposition reactions of common cathode materials are analyzed. Finally, the methods of thermal runaway monitoring and thermal management are summarized to provide the reference for the safety of lithium-ion batteries.
Thermal safety is one of the major issues for lithium‐ion batteries (LIBs) used in electric vehicles. The thermal runaway mechanism and process of LIBs have been extensively studied, but the thermal problems of LIBs remain intractable due to the flammability, volatility and corrosiveness of organic liquid electrolytes. To ultimately solve the thermal problem, all‐solid‐state LIBs (ASSLIBs) are considered to be the most promising technology. However, research on the thermal stability of solid‐state electrolytes (SEs) is still in its initial stage, and the thermal safety of ASSLIBs still needs further validation. Moreover, the specified reviews summarizing the thermal stability of ASSLIBs and all types of SEs are still missing. To fill this gap, this review systematically discussed recent progress in the field of thermal properties investigation for ASSLIBs, form levels of materials and interface to the whole battery. The thermal properties of three major types of SEs, including polymer, oxide, and sulfide SEs are systematically reviewed here. This review aims to provide a comprehensive understanding of the thermal stability of SEs for the benign development of ASSLIBs and their promising application under practical operating conditions. Thermal failure is a serious issue for liquid‐electrolyte‐based lithium‐ion batteries, and substituting liquid electrolytes with solid‐state electrolytes is expected to solve this problem. This review summarizes the thermal stability of polymers, oxides, sulfides, and other solid‐state electrolytes from the level of material, interface, and battery, and points out the limitations and future of thermal stability studies in solid‐state batteries.
Electrochemical energy storage systems with high energy/power density are a key technology for the development of intelligent society, especially for portable electronics devices and electric vehicles. The most effective strategy to enhance the energy/power density of batteries is to explore for high-capacity electrode materials. Layered cathode materials with high specific capacity and high operating voltage have attracted great research interests. However, severe surface structural degradation, irreversible oxygen release and interfacial side-reactions occurring in the cycles of layered materials at high voltage, cause undesirable capacity and voltage deterioration, blocking their further development. Interface engineering, in particular constructing stable heteroepitaxial interfaces on layered cathode materials, has been recognized as an effective strategy to solve these abovementioned problems comprehensively. Here, the development history and structural characteristics of layered cathode materials are reviewed, different types of heteroepitaxial interfaces and their construction methods are discussed in detail. Particularly, the mechanism and function of constructing heteroepitaxial interface in layered materials are emphasized. However, some essential issues still remain controversial, especially with regard to understanding of the surface structure and chemistry properties related to the material composition and synthesis process, and charge transfer and ionic transport of the interfacial processes of layered cathodes. A clear understanding of these fundamental mechanisms is therefore essential to optimize the synthesis process and electrochemical performance of layered cathodes.
Increasing upper cut-off voltage is capable of achieving higher charge capacity whereas this strategy always causes a dramatic degradation of cycling and thermal stability. In this study, we first report spinel LiNi0.5Mn1.5O4-modified LiCoO2 ([email protected]) as an outstanding cathode material. [email protected] retains capacity retention of 81.4% in a full cell between 4.45 and 3.00 V after 400 cycles at 0.5 C, and is superior to 55.3% of pure LiCoO2. In situ X-ray diffraction at an upper cutoff voltage of 4.75 V in combination with differential capacity curve reveals that the promoted cycling performance is ascribed to a delay of O3→H1-3→O1 phase transitions and a suppression of cobalt dissolution-induced side reactions. Moreover, LiNi0.5Mn1.5O4 modification improves thermal stability of LiCoO2 by depressing the release of oxygen and the formation of cobalt dendrites.
A review gathering available results on the chemical kinetics in literature for the commercial 18650 lithium-ion batteries containing cathode material of LiCoO2 and related components is summarized and discussed. Most of these kinetic parameters derived from adiabatic and heat-flow calorimeter, some few of them with the fitting of electrochemical-thermal model associated with data of accelerating rate calorimeter. However, due to the complexity of solid-state reaction involving both anode and cathode as well as the difficulty to determine the reaction mechanism function by thermal analysis on the solid electrode, most of the interpretation of calorimetric data set the order to be unity for simplicity. Kinetics-based heat rates under thermal abuses encompass the decomposition of solid electrolyte interface (stage III from 85 to 120 °C), reaction of LixC6 with electrolyte (stage IV from 120 to 170 °C), reaction of LixCoO2 with electrolyte (stage V from 170 to 200 °C), decomposition of LixCoO2 (stage VI > 200 °C), decomposition of solvent (stage VI > 200 °C) induced by internal short, and auto-ignition of solvent (stage VI > 200 °C). To clearly capture the distinctive features of these kinetic behaviors, the standard deviations adopted by the American Society for Testing and Materials E2781 and International Confederation for Thermal Analysis and Calorimetry are applied to enhance the accuracy and precision of the kinetic parameters. A diagram integrating all the Ea and log A values of LiCoO2 battery and its components is depicted, in which a newly phenomenon of compensation effect has been discovered. The linear equation of log A versus Ea tells the truth that some large errors existed in the data acquisition of kinetic parameters. Taking and comparing individually the average kinetic parameters from the decomposition of SEI, reaction of LixC6 with electrolyte, reaction of LixCoO2 with electrolyte to the whole battery, it is noteworthy that the chemical kinetics of the LiCoO2 battery is next door to that of LixCoO2 with electrolyte in n-th order reactions. The autocatalytic model II in Ea versus log A diagram seems to have the biggest deviations. The paradoxical model between the n-th order and autocatalytic type regarding the reaction of LixCoO2 with electrolyte exists and has not been exactly solved. Practically, some unimaginable disagreement among parameters of Ea and logA (sec⁻¹ M¹⁻ⁿ) are as yet unsettled, which reveals that the more extensive studies are needed to resolve the existing disputes. For the near future, a breakthrough of exceedingly better technology for acquiring the accurate chemical kinetics of a LiCoO2 battery and its ingredients will be expected earnestly.
LiNi0.8Co0.15Al0.05O2 (NCA) is widely used as cathode material in commercialized high energy density lithium ion battery due to its high specific capacity. However, the structure and thermal stability of NCA after long electrochemical cycles are remained unclear. Herein, we investigate the structure and thermal stability of aged NCA at both lithiated and delithiated states using in-situ charge/discharge and high temperature X-ray diffraction and transmission electron microscopy images. The thermal stability of delithiated NCA cathode after 400 cycles at 1C is obviously inferior to the lithiated and pristine one. The particle surface of aged NCA changes from layered to spinel phase, while the bulk area maintains the layered structure. The temperature inducing structure change of aged NCA is much lower than that of pristine NCA and the delithiated state of NCA is more vulnerable at high temperature. The drastic structure transformation of aged NCA occurs at 250 °C during heating, which accompanies with oxygen loss and the formation of intergranular cracks in the NCA secondary particles. Thus, this work provides significant information of structure stability of cycled NCA at high temperature for optimizing its surface structure to achieve excellent cycling performance under extreme conditions.
The electrochemical properties and performances of lithium-ion batteries are primarily governed by their constituent electrode materials, whose intrinsic thermodynamic and kinetic properties are understood as the determining factor. As a part of complementing the intrinsic material properties, the strategy of nanosizing has been widely applied to electrodes to improve battery performance. It has been revealed that this not only improves the kinetics of the electrode materials but is also capable of regulating their thermodynamic properties, taking advantage of nanoscale phenomena regarding the changes in redox potential, solid-state solubility of the intercalation compounds, and reaction paths. In addition, the nanosizing of materials has recently enabled the discovery of new energy storage mechanisms, through which unexplored classes of electrodes could be introduced. Herein, we review the nanoscale phenomena discovered or exploited in lithium-ion battery chemistry thus far and discuss their potential implications, providing opportunities to further unveil uncharted electrode materials and chemistries. Finally, we discuss the limitations of the nanoscale phenomena presently employed in battery applications and suggest strategies to overcome these limitations.
The high cut-off voltage for delivering the high reversible capacity of LiCoO2 often causes its capacity fading and potential safety hazards. Herein, LiNi0.45Al0.05Mn0.5O2 is uniformly modified on LiCoO2 to prepare LiCoO2@LiNi0.45Al0.05Mn0.5O2 via a ball-milling method. In half-cell (or full-cell) tests, the LiCoO2@LiNi0.45Al0.05Mn0.5O2 exhibits the improved cycle stability between 3.00 V and 4.55 V (or 4.48 V). The capacity of LiCoO2@LiNi0.45Al0.05Mn0.5O2 with 1.0% modification content can be up to 161.9 mAh g⁻¹ from 133.3 mAh g⁻¹ of LiCoO2 after 150 cycles. The cyclability improvement of lithium ion batteries employing LiCoO2@LiNi0.45Al0.05Mn0.5O2 cathode is ascribed to a delay of structure collapse and a decrement of cobalt dissolution. Moreover, LiNi0.45Al0.05Mn0.5O2 on the LiCoO2 leads to an increase in the onset temperature of primary exothermic peaks, and a decrease in the maximum rising temperature of thermal shock from 500 °C to 160 °C while LiCoO2@LiNi0.45Al0.05Mn0.5O2/graphite full cell is charged to 4.48 V. The LiNi0.45Al0.05Mn0.5O2 improves thermal stability of the LiCoO2-based cathode by depressing O2 evolution and decreasing internal short dots.
The performance of lithium-ion batteries is very much affected by the temperature under which they are running due to changes in the properties of the battery components. By employing techniques of thermogravimetric analysis (TGA), X-ray diffraction (XRD) followed by Rietveld refinements, infrared spectroscopy and scanning electron microscopy (SEM), we show that the LiCoO2 cathode material of a lithium-ion battery is specially affected in their composition and structural properties when the entire cathode (cathode material +current collector) was heat-treated from room temperature till 400 °C. After 250 °C, the starting electroactive cathode material, Li0.94CoO2, decomposes thermally in the Li1CoO2, Co3O4 and O2 reaction products, with their relative masses changing with the temperatures of heat treatments. Concomitantly, the treatments promoted changes in the lattice parameters of the pristine and decomposed cobalt oxides, as well as in the Li–O and Co–O interatomic distances, in the angles between the O–Co–O and O–Li–O bonds and in the intensity of infrared absorption of Co–O vibrational modes. Very surprisingly, all these parameters presented minimum or maximum values under the thermal treatment at 350 °C. This effect is believed to be related to the rate of Li0.94CoO2 mass decomposition that reaches its maximum value at 335 °C, close to the temperature of 350 °C. The α, β and γ crystalline phases of the polyvinylidene difluoride (PVDF) binder and the agglomeration states of the cathode particles are as well affected by the thermal treatment performed.
Widespread application of Li‐ion batteries (LIBs) in large‐scale transportation and grid storage systems requires highly stable and safe performance of the batteries in prolonged and diverse service conditions. Oxygen release from oxygen‐containing positive electrode materials is one of the major structural degradations resulting in rapid capacity/voltage fading of the battery and triggering the parasitic thermal runaway events. Herein, the authors summarize the recent progress in understanding the mechanisms of the oxygen release phenomena and correlative structural degradations observed in four major groups of cathode materials: layered, spinel, olivine, and Li‐rich cathodes. In addition, the engineering and materials design approaches that improve the structural integrity of the cathode materials and minimize the detrimental O2 evolution reaction are summarized. The authors believe that this review can guide researchers on developing mitigation strategies for the design of next‐generation oxygen‐containing cathode materials where the oxygen release is no longer a major degradation issue.
LiCoO2 is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from LixCoO2 particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of LixCoO2. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O2 formation more effectively due to the strong COcathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.
In this study, we demonstrate first time the application of confinement tests under excessive heating to track the thermal responses during the thermal runaway in hard prismatic lithium-ion batteries used in smart phones. Seven hard prismatic lithium-ion batteries used in smart phones of iPhone 5, iPhone 6, Redmi 2, SAMSUNG Note 3, SAMSUNG S5, SONY C3 and SONY Z3 at full-charged state have been studied. Characteristics in relation to thermodynamics such as onset temperature, crucial temperature, maximum self-heat rate and maximum temperature are measured and assessed. SAMSUNG S5 shall carry the most unstable feature with an exothermic onset temperature as low as 117 °C. SAMSUNG Note 3 displays the worst-case scenario by possessing the maximum temperature and maximum self-heat rate reaching the extremity of 675.6 °C and 11,860.0 °C min−1.
Despite the tremendous success of Li-ion battery based upon liquid electrolytes and oxide positive electrodes,
their widespread application is limited due to the safety concerns originated from the oxygen
release. Consequently, the oxygen release causes phase transformation, which also leads to the mechanical
failure of a battery. Thus, this paper presents a detailed multiphase-field model (PFM) to predict
chemo-mechanical properties of oxide based battery electrodes. The PFM considers the chemical composition
change, the associated phase transformation and the stress generation in the bulk as well as at the
surface of the electrode. This model is applied to capture the development and evaluation of phase transformation
mechanism, which occurs at elevated temperatures in the partially delithiated Li0.45CoO2 (LCO)
material. Our results indicate that the major oxygen concentration change occurs in the narrow region
between the phases, and the compressive stress is generated inside the bulk LCO, whereas tensile stress
is observed within the LCO-gas phase interface. In addition, an important contribution of this work is the
derivation of a new set of thermodynamic and kinetic data of the oxygen release. The modeling results
allow for a direct comparison with the in-situ transmission electron microscopy (TEM) measurements
reported by Sharifi-Asl et al. [Nano Letters, 17(4), 2165, 2017]. Thus, our findings provide new qualitative
and quantitative understandings of the LCO phase transformations and the kinetics of oxygen release.
To elucidate the chemical and structural changes of sulfide solid electrolyte during heat treatment, in situ outgas (TPD-MS), Raman, and XRD analyses were applied for a 70Li2S-30P2S5 glass sample. A sulfide solid electrolyte was constructed from the PS43 − and P2S74 − anions, together with a small amount of P2S64 − anions. In the course of the structural change from glass to glass-ceramic through heat treatment, the fraction of PS43 − anion decreased and P2S74 − anion increased at 210 °C. Sulfur compounds were detected as outgas at about 240 °C, which suggests thermal decomposition of PS43 − anion to produce P2S74 − and sulfur compounds as by-product. The thermal treatment temperature should be higher than 240 °C to eliminate sulfur compounds generated as the reaction by-product. In the same temperature region, crystallization of Li7P3S11 was also detected using in situ XRD. The ionic conductivity increased from 1.0 × 10− 4 S cm− 1 to 8.4 × 10− 4 S cm− 1 after heat treatment at 270 °C. Therefore, the partial compositional change of PS43 − to P2S74 − anions and crystallization of Li7P3S11 are key factors producing higher ionic conductivity. By combining these experimental techniques implemented in this study, it is possible to detect the temperature at which the chemical and structural changes proceed. One can also ascertain the suitable heat treatment temperature for production of by-product free and high-quality sulfide-based solid electrolyte.
The recent dramatic increase in demand lithium ion batteries (LIBs) in the automotive and electronic industries makes it desirable to establish sustainable recycling technology to recover cobalt from the cathode material (LiCoO2). Although the combination of physical and hydrometallurgical processes is one option for recovery of metals, the large amount of aluminum in the cathode of spent LIBs can negatively affect the process performances. Therefore, as a means to enhance the cobalt recovery from spent LIBs, we investigated the feasibility of a physical process for separation of cobalt and aluminum by thermal treatment and wet magnetic separation. Results highlighted the efficiency of the thermal treatment for conversion of the cathode material to magnetic cobalt due to (i) the presence of the more reactive lithium-deficient LixCoO2 (x<1), (ii) the presence of reductive aluminum and graphite from electrode supports, and (iii) the generation of CO, CH4 and C2H4, which activate reduction and carbonation. Furthermore, a slow rise in temperature during heating promoted increases of the grain size of CoO and Co and prevented the pulverization of Al. As a result, 75.5% of cobalt could be recovered from spent LIBs without contamination by aluminum.
Local crystalline structures of LiCoO2 nanothin film cathodes in a lithium ion battery have been spectroscopically elucidated through confocal Raman imaging analysis at high spatial resolution of several hundred nanometers. A significant difference in the crystalline structure is found between the nanometric thin films and bulk powders. Thermally induced local decomposition of LiCoO2 into an impurity phase on the films has also been revealed along with the mechanism of the temperature-triggered decomposition process. Moreover, frequency-based Raman imaging enables us to locally probe spatial separation between stoichiometric (LiCoO2) and non-stoichiometric (Li1-xCoO2, 0 < x < 1) crystal phases on the thin films. Such local crystalline analysis is a promising approach to provide new insights into the degradation mechanism of lithium-ion batteries, which would result in improving the performance of thin film-based lithium ion batteries.
Electrochemical properties of LixCoO2 are studied as Li is deintercalated from LiCoO2. High precision voltage measurements and in situ x-ray diffraction indicate a sequence of three distinct phase transitions as x varies from 1 to 0.4. Two of the transitions are situated slightly above and below x = 1/2 and are caused by an order/disorder transition of the lithium ions. The order/disorder transition is studied as a function of temperature allowing the determination of an order/disorder phase diagram. In situ x-ray diffraction measurements facilitate a direct observation of the effects of deintercalation on the host lattice crystal structure. The other phase transition is shown to be first order (coexisting phases are observed for 0.75 less-than-or-equal-to x less-than-or-equal-to 0.93) involving a significant expansion of the c-lattice parameter of the hexagonal unit cell. We report the variation of the lattice constants of LixCoO2 with x and show that the phase transition to the lithium ordered phase near x = 1/2 is accompanied by a lattice distortion to a monoclinic unit cell with a(Mon) = 4.865 (2) angstrom, b(Mon) = 2.806 (1) angstrom, c(Mon) = 14.420 (4) angstrom and beta = 90.77 (3). Finally we report an overall phase diagram for 0.4 less-than-or-equal-to x less-than-or-equal-to 1.0 and -10-degrees-C less-than-or-equal-to T less-than-or-equal-to 60-degrees-C.
The thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal stability of fully charged and discharged LiCoO2 cathode and graphite anode in nitrogen and air atmospheres. The results showed that the weight of charged and discharged LiCoO2 cathode samples exhibited an obvious decrease between 100 and 120°C in two atmospheres. The exothermic decomposition reaction of fully charged LiCoO2 cathode occurred at 250°C in two atmospheres. A small decomposition reaction of the discharged LiCoO2 cathode occurred at 300°C. When the temperature of samples was elevated to 600°C, the weight of fully charged and discharged LiCoO2 cathode in air atmosphere did not change; while the weight of samples in nitrogen atmosphere decreased. This was because the Co3O4 as the decomposition product of the cathodes could be reduced to CoO by the carbon black above 600°C in N2 atmosphere. The solid electrolyte interphase (SEI) film of fully charged and discharged graphite anode was decomposed at 100–120°C in two atmospheres, and the weight loss of fully charged graphite anode at 100–120°C was obviously less than that of the fully discharged graphite anode. When the samples were heated to 300°C, there was no fierce exothermic reaction for the lithiated graphite anode in N2 atmosphere, whereas an exothermic reaction in air atmosphere occurred rapidly.
Thermal behavior of LixCoO2 cathode material from cells charged to different voltages has been analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mass loss appearing between 60 and 125°C in TGA and the exothermic peaks with 4.9 and 7.0Jg−1 in DSC around 75 and 85°C for the LixCoO2 cathodes of 4.20 and 4.35V cells has been explained based on solid electrolyte interface (SEI) film-break down. The SEI film-break down for the highly charged cathode at low temperature region has been attributed to the conversion of lithium fluoride into hydrofluoric acid in concomitant with the reaction, Li2CO3+2HF→2LiF+CO2+H2O. Presence of ionic carbonate in the positive electrode has been identified by ion chromatography (IC). The thermal peaks appearing in different temperature regions have been explained based on decomposition reaction of LixCoO2 cathodes and the SEI film.
The thermal stability of electrolytes with LixCoO2 cathode or lithiated carbon anode was reviewed including our recent results. From our experiments, it was found that LixCoO2, delithiated by a chemical method using H2SO4 showed two exothermic peaks, one beginning at 190°C and the other beginning at 290°C. From high-temperature XRD, it was found that the first peak, from 190°C, was the phase transition from a monoclinic (R-3m) to a spinel structure (Fd3m). The spinel structure LixCoO2 showed a very small cycling capacity. Probably, cation mixing was induced by the heat treatment. The DSC measurements of Li0.49CoO2 with 1M LiPF6/EC+DMC showed two exothermic peaks. The peak starting at 190°C probably resulted from the decomposition of solvent due to an active cathode surface, and the peak starting at 230°C was electrolyte oxidation caused by released oxygen from Li0.49CoO2. From DSC profiles of chemically delithiated Li0.49CoO2 and 1M PC electrolytes with various Li salts, it was found that the inhibition effect of the surface reaction starting at 190°C was large when LiBF4, LiPF6, and LiClO4 were used.The thermal stability of electrochemically lithiated graphite with 1M LiPF6/EC+DMC and PVdF-binder has been investigated. DSC revealed a mild heat generation starting 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 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, which surface is covered by poly(vinylidene fluoride) (PVdF)-binder without formation of SEI at a lower temperature.
Single crystals of Li0.68CoO2, Li0.48CoO2, and Li0.35CoO2 were successfully synthesized for the first time by means of electrochemical and chemical delithiation processes using LiCoO2 single crystals as a parent compound. A single-crystal X-ray diffraction study confirmed the trigonal R3¯m space group and the hexagonal lattice parameters a=2.8107(5)Å, c=14.2235(6)Å, and c/a=5.060 for Li0.68CoO2; a=2.8090(15)Å, c=14.3890(17)Å, and c/a=5.122 for Li0.48CoO2; and a=2.8070(12)Å, c=14.4359(14)Å, and c/a=5.143 for Li0.35CoO2. The crystal structures were refined to the conventional values R=1.99% and wR=1.88% for Li0.68CoO2; R=2.40% and wR=2.58% for Li0.48CoO2; and R=2.63% and wR=2.56% for Li0.35CoO2. The oxygen–oxygen contact distance in the CoO6 octahedron was determined to be shortened by the delithiation from 2.6180(9)Å in LiCoO2 to 2.5385(15)Å in Li0.35CoO2. The electron density distributions of these LixCoO2 crystals were analyzed by the maximum entropy method (MEM) using the present single-crystal X-ray diffraction data at 300K. From the results of the single-crystal MEM, strong covalent bonding was clearly visible between the Co and O atoms, while no bonding was found around the Li atoms in these compounds. The gradual decrease in the electron density at the Li site upon delithiation could be precisely analyzed.
It is well known that charged LixCoO2 (x<1) is metastable, and that oxygen evolution has been observed at temperatures above 200 degreesC. LixCoO2, delithiated by a chemical method using H2SO4, was investigated by means of differential scanning calorimetry (DSC) with/without an electrolyte (1 M LiPF6/ethylene carbonate (EQ + dimethyl carbonate (DMC). The lithium content x in the delithiated LixCoO2, was determined by atomic absorption spectroscopy. The DSC profile of Li0.49CoO2 showed two exothermic peaks, one beginning at 190 degreesC and the other beginning at 290 degreesC. From high-temperature X-ray diffraction (XRD), it was found that the first peak, from 190 degreesC, was the phase transition from a monoclinic (R (3) over barm) to a spinel structure (Fd3m). The DSC measurements of Li0.49CoO2 With the electrolyte at various mixing ratios showed two exothermic peaks, one beginning at 190 degreesC and the other at 230 degreesC. The exothermic heat of each peak was proportional to the amount of Li0.49CoO2. The peak starting at 190 degreesC probably resulted from the decomposition of solvent due to an active cathode surface, and the peak starting at 230 degreesC was electrolyte oxidation caused by released oxygen from Li0.49CoO2. The exothermic heat from 190 to 230 degreesC based on cathode weight was 420 +/- 120 J/g, and that from 230 to 300 degreesC was 1000 +/- 250 J/g.
By expanding the initial equation, it is shown that the Friedman method for estimating the activation energy of chemical reactions by using both the conversion and the rate in the thermoanalytical data has wide applicability to crystal growth from pre-existing nuclei, diffusion and other processes in which a single unit process is involved.
A new method of obtaining the kinetic parameters from thermogravimetric curves has been proposed. The method is simple and applicable to reactions which can not be analyzed by other methods. The effect of the heating rate on thermogravimetric curves has been elucidated, and the master curve of the experimental curves at different heating rates has been derived.
The applications of the method to the pyrolyses of calcium oxalate and nylon 6 have been shown ; the results are in good agreement with the reported values.
The applicability of the method to other types of thermal analyses has been discussed, and the method of the conversion of the data to other conditions of temperature change has been suggested. From these discussions, the definition of the thermal stability of materials has been criticized.
Chemical extraction of lithium from LiCoO2has been investigated with various oxidizing agents—Cl2, Br2, and I2—and with dilute sulfuric acid. A considerable amount of lithium could be extracted with both chlorine and acid to give a final lithium content (1 −x) ≈ 0.3 in Li1−xCoO2. The stronger oxidizing power of Cl2and the relative instability associated with the Li-extracted samples lead to the dissolution of a considerable amount of the sample during chlorine oxidation. A deeper lithium extraction with chlorine also leads to the occurrence of oxygen vacancies in Li1−xCoO2−δ. Lithium extraction with acid proceeds predominantly by a disproportionation of Co3+to Co2+and Co4+analogous to that in the spinel LiMn2O4with a small degree of ion exchange of Li+by H+. However, the results of both chlorine oxidation and acid treatment are strongly influenced by the nature of the initial material. An Li/Co ratio < 1 and/or a disorder between Li and Co in the initial Li1−zCo1+zO2result in a competition of Co extraction from Li planes with Li extraction as evidenced by the Li/Co ratio in the filtrate as well as the changes in the relative intensities of the (003) and (104) reflections. Extraction of Co from Li planes by this process might prove to be useful to obtain improved electrode materials for lithium batteries. The degree of lithium extraction that can be achieved with different oxidizing agents follows the trend in their oxidation potential. In addition, the literature data that Na can be extracted more easily from NaCoO2than Li from LiCoO2is explained on the basis of the relative energies of the Co3+/4+redox couple in the two compounds.
Metastable layered phases of lithium-containing cobalt oxyhydroxides Li1-x--yHyCoO2(x ≤ 0.55, x + y < 1) are obtained by acid digestion of LiCoO2 at room temperature. X-ray powder diffraction, thermal analysis, magnetic susceptibility measurements, and EPR are used to investigate the structural peculiarities of these phases. It has been shown that the layered CoO2 framework of parent LiCoO2 is retained during acid treatment. Lithium extraction from the LiO2 layers introduces Co4+ ions in the CoO2 layers, which, with progressive lithium removal, tend to segregate as demonstrated by EPR and magnetic susceptibility measurements. In addition, lithium extraction enters into competition with exchange of lithium ions with protons, depending on the acid concentration and on the dissolution degree of the samples. The simultaneous presence of Li+ and H+ in the CoO2 matrix, as well as the Co4+ clustering, provokes a certain disorder in the parent layered structure and determines the thermal instability of acid-treated LiCoO2. On heating, cation redistribution is initiated in the metastable phases, culminating above 230°C in thermal decomposition into a lithium-cobalt spinel.
LiCoO2, LiNiO2 and LiMn2O4 are all stable in air to high temperature. By contrast, LixCoO2, LixNiO2 and LixMn2O4 (x<1) are metastable and liberate oxygen when they are heated in air or in inert gas. The temperature at which oxygen evolution occurs depends on x and on the material. Using thermal gravimetric analysis and mass spectrometry, we have studied the thermal decomposition of these materials in inert gas. We find that the nickel materials are least stable, the manganese compounds are most stable, and that the cobalt compounds show intermediate behaviour. These results have important consequences for the safety of Li-ion cells, and suggest that cells using LiMn2O4 as the cathode should be safer than those using LiNiO2 or LiCoO2.
A kinetic study of the thermal decomposition of engineering polyesters has been made by means of controlled-rate thermogravimetry (CRTG), a procedure that is a part of controlled-rate thermal analysis (CRTA). Various decomposition rates were used in the constant decomposition rate control (CDRC) experiments, in order to estimate the apparent activation energy without prior knowledge of the actual mechanism. The kinetic equations governing the thermal decomposition of poly(ethylene terphthalate) (PET) and poly(butylene terphthalate) (PBT) were determined. The kinetic parameters of these polyesters were estimated from both, the CDRC curve and evolved-gas components, obtained from the simultaneous TG-MS system, and corresponding to a kinetic-model-supported random scission of the main chain and with L=2. It is concluded that analytic techniques using the thermogravimetric traces obtained from different decomposition rates at CDRC are capable of establishing unique kinetic parameters. CRTG (CRTA) offers significant advantages in this field of study when dealing with thermal decomposition of polymers.
The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E
a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.
- Y B He
- Z T Tang
- Q S Song
- H Xie
- Q Xu
- Y G Liu
- G W Ling
Y.B. He, Z.T. Tang, Q.S. Song, H. Xie, Q. Xu, Y.G. Liu, G.W. Ling, Thermochim. Acta
480 (2008) 15-21.
- A Veluchamy
- C.-H Doh
- D H Kim
- J H Lee
- H M Shin
- H S Kim
- S I Moon
A. Veluchamy, C.-H. Doh, D.H. Kim, J.H. Lee, H.M. Shin, H.S. Kim, S.I. Moon, J.
Power Sources 189 (2009) 855-858.