No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Polymeric ionic liquid as binder: A promising strategy for enhancing Li-S battery performance
Abstract
The development of the most promising next-generation Lisingle bondS batteries with an improved cyclability is one of the greatest challenges nowadays. In this sense, here, a novel imidazolium-based polymeric ionic liquid (PVI10Cl) was successfully synthesized and integrated into a high-performing sulfur cathode. The lithium polysulfide trapping ability of PVI10Cl was confirmed, which helps to accelerate conversion kinetics. This synergetic effect leads to enhanced C-rate response, improving the discharge capacities and reducing the overpotentials even at 1C in comparison with conventional PVdF binder. These features also allow cells to be operated for 100 cycles with excellent capacity retention. All in one, while conventional binders are viewed only as a “glue” to hold the active material together, it has been shown that PVI10Cl binder has additional functions and plays an active role during Lisingle bondS battery operation.
... This cationic polyelectrolyte binder promotes lithium ion transport via a reconfigurable anion transport network and restricts polysulfide diffusion from the mesoporous carbon host through anion decomposition [125]. For example, the integration of a novel imidazole-based PIL (PVI 10 Cl) into a highperformance sulfur cathode can capture polysulfide lithium and help accelerate the conversion kinetics (Fig. 10c) [127]. Using PVI 10 Cl as a binder is superior to traditional PVDF binder, especially regarding rate capability and recyclability. ...
... Layered graphene platelets have the possibility of high tortuosity [23], but they tend to curl and form large pockets in which sulfur is impregnated and unfortunately from which any soluble sulfides can easily migrate [17,24,25]. Ionic liquid polymer binders that attract polysulfides may also act as trapping means and may be used in meso-and microporous cathode coatings to prevent the migration of polysulfides [26,27]. Alternatively, 1T-MoS 2 is another conductive 2D material the nanoplatelets of which might also curl [28,29] but can also form layered, large, conductive platelets [30][31][32][33] that can reduce the migration of soluble sulfides via the high tortuosity and high adsorption energy of the 1T-MoS 2 which also acts as an excellent electrocatalyst in the electrochemical reactions of Li-S batteries [31]. ...
The aim of this study is to investigate new materials that can be employed as cathode hosts in Li-S batteries, which would be able to overcome the effect of the shuttling of soluble polysulfides and maximize the battery capacity and energy density. Density functional theory (DFT) simulations are used to determine the adsorption energy of lithium sulfides in two types of cathode hosts: lithiated 1T-MoS2 (1T-LixMoS2) and hybrid 1T-LixMoS2/graphene. Initial simulations of lithiated 1T-MoS2 structures led to the selection of an optimized 1T-Li0.75MoS2 structure, which was utilized for the formation of an optimized 1T-Li0.75MoS2 bilayer and a hybrid 1T-Li0.75MoS2/graphene bilayer structure. It was found that all sulfides exhibited super-high adsorption energies in the interlayer inside the 1T-Li0.75MoS2 bilayer and very good adsorption energy values in the interlayer inside the hybrid 1T-Li0.75MoS2/graphene bilayer. The placement of sulfides outside each type of bilayer, over the 1T-Li0.75MoS2 surface, yielded good adsorption energies in the range of −2 to −3.8 eV, which are higher than those over a 1T-MoS2 substrate.
The design of binders for lithium-ion batteries is highlighted, with an emphasis on key parameters affecting device performance and failure mechanisms. These issues are discussed in detail using the example of a silicon anode and a sulfur cathode.
The growing requirements for electrified applications entail exploring alternative battery systems. Lithium‐sulfur batteries (LSBs) have emerged as a promising, cost‐effective, and sustainable solution; however, their practical commercialization is impeded by several intrinsic challenges. With the aim of surpassing these challenges, the implementation of a holistic LSB concept is proposed. To this end, the effectiveness of coupling a high‐performing 2D graphene‐based sulfur cathode with a well‐suited sparingly solvating electrolyte (SSE) is reported. The incorporation of bis(fluorosulfonyl)imide (LiFSI) salt to tune sulfolane and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropylether based SSE enables the formation of a robust and compact lithium fluoride‐rich solid electrolyte interphase. Consequently, the lithium compatibility is improved, achieving a high Coulombic efficiency (CE) of 98.8% in the Li||Cu cells and enabling thin and dense lithium depositions. When combined with a high‐performing 2D graphene‐based sulfur cathode, a symbiotic effect is shown, leading to high discharge capacities, remarkable rate capability (2.5 mAh cm⁻² at C/2), enhanced cell stability, and wide temperature applicability. Furthermore, the scalability of this strategy is successfully demonstrated by assembling high‐performing monolayer prototype cells with a total capacity of 93 mAh, notable capacity retention of 70% after 100 cycles, and a high average CE of 99%.
Lithium‐sulfur batteries (LSBs) are one of the most promising and potential modern‐day energy storage devices due to the low‐cost sulfur‐based cathode and remarkably high energy density (∼2600 Wh kg⁻¹). However, the detrimental shuttle effect of lithium polysulfide (LiPS) and the sluggish electrochemical redox kinetics of lithium sulfide (Li2S) formation restrict its commercial viability. Herein, we design a novel transition metal‐rare earth high entropy oxide (TM‐RE HEO) Co0.08Mn0.08Ni0.08Fe1.96Mg0.08Nd0.01Gd0.01Sm0.01Pr0.01O4 as a polysulfide adsorbent and catalyst for the redox reactions of sulfur species in Li−S battery. TM‐RE HEO interlayer exhibits an excellent discharge capacity of 1146 mAh g⁻¹ at 0.1 C rate, high rate capability, and reasonable long‐term cycling stability at 0.5 C rate with a low capacity decay of 0.08 % per cycle after 300 cycles. High degree of chemical confinement of soluble polysulfides, as demonstrated by the strong bonding between TM‐RE HEO and Li2S6, and expedited catalytic conversion to insoluble Li2S, result from strong polar catalytically active multiple metal sites and abundant oxygen vacancies. This work demonstrates the potential of high entropy oxide in developing high‐efficiency LSB technology.
Gel polymer electrolytes (GPEs) are emerging as suitable candidates for high-performing lithium-sulfur batteries (LSBs) due to their excellent performance and improved safety. Within them, poly(vinylidene difluoride) (PVdF) and its derivatives have been widely used as polymer hosts due to their ideal mechanical and electrochemical properties. However, their poor stability with lithium metal (Li⁰) anode has been identified as their main drawback. Here, the stability of two PVdF-based GPEs with Li⁰ and their application in LSBs is studied. PVdF-based GPEs undergo a dehydrofluorination process upon contact with the Li⁰. This process results in the formation of a LiF-rich solid electrolyte interphase that provides high stability during galvanostatic cycling. Nevertheless, despite their outstanding initial discharge, both GPEs show an unsuitable battery performance characterized by a capacity drop, ascribed to the loss of the lithium polysulfides and their interaction with the dehydrofluorinated polymer host. Through the introduction of an intriguing lithium salt (lithium nitrate) in the electrolyte, a significant improvement is achieved delivering higher capacity retention. Apart from providing a detailed study of the hitherto poorly characterized interaction process between PVdF-based GPEs and the Li⁰, this study demonstrates the need for an anode protection process to use this type of electrolytes in LSBs.
The Li-S chemistry is thermodynamically promising for high-density energy storage but kinetically challenging. Over the past few years, many catalyst materials have been developed to improve the performance of Li-S batteries and their catalytic role has been increasingly accepted. However, the classic catalytic behavior, i.e., reduction of reaction barrier, has not been clearly observed. Crucial mechanistic questions, including what specific step is limiting the reaction rate, whether/how it can be catalyzed, and how the catalysis is sustained after the catalyst surface is covered by solid products, remain unanswered. Herein, we report the first identification of the potential-limiting step of Li-S batteries operating under lean electrolyte conditions and its catalysis that conforms to classic catalysis principles, where the catalyst lowers the kinetic barrier of the potential-limiting step and accelerates the reaction without affecting the product composition. After carefully examining the electrochemistry under lean electrolyte conditions, we update the pathway of the Li-S battery reaction: S8 solid is first reduced to Li2S8 and Li2S4 molecular species sequentially; the following reduction of Li2S4 to a Li2S2-Li2S solid with an almost constant ratio of 1:4 is the potential-limiting step; the previously believed Li2S2-to-Li2S solid-solid conversion does not occur; and the recharging reaction is relatively fast. We further demonstrate that supported cobalt phthalocyanine molecules can effectively catalyze the potential-limiting step. After Li2S2/Li2S buries the active sites, it can self-catalyze the reaction and continue driving the discharging process.
The increasing demand for electrical energy storage makes it essential to explore alternative battery chemistries that overcome the energy-density limitations of the current state-of-the-art lithium-ion batteries. In this scenario, lithium-sulfur batteries (LSBs) stand out due to the low cost, high theoretical capacity, and sustainability of sulfur. However, this battery technology presents several intrinsic limitations that need to be addressed in order to definitively achieve its commercialization. Herein, we report the fruitfulness of three different formulations using well-selected functional carbonaceous additives for sulfur cathode development, an in-house synthesized graphene-based porous carbon (ResFArGO), and a mixture of commercially available conductive carbons (CAs), as a facile and scalable strategy for the development of high-performing LSBs. The additives clearly improve the electrochemical properties of the sulfur electrodes due to an electronic conductivity enhancement, leading to an outstanding C-rate response with a remarkable capacity of 2 mA h cm-2 at 1C and superb capacities of 4.3, 4.0, and 3.6 mA h cm-2 at C/10 for ResFArGO10, ResFArGO5, and CAs, respectively. Moreover, in the case of ResFArGO, the presence of oxygen functional groups enables the development of compact high sulfur loading cathodes (>4 mgS cm-2) with a great ability to trap the soluble lithium polysulfides. Notably, the scalability of our system was further demonstrated by the assembly of prototype pouch cells delivering excellent capacities of 90 mA h (ResFArGO10 cell) and 70 mA h (ResFArGO5 and CAs cell) at C/10.
Lithium-sulfur (Li-S) battery is recognized as one of the promising candidates to break through the specific energy limitations of commercial lithium-ion batteries given the high theoretical specific energy, environmental friendliness, and low cost. Over the past decade, tremendous progress have been achieved in improving the electrochemical performance especially the lifespan by various strategies mainly concentrated on the sulfur cathodes. In this review, the fundamental electrochemistry of sulfur cathode and lithium anode is revealed to understand the current dilemmas. And the advances achieved through diverse strategies are comprehensively summarized, which involves lithium polysulfides (LiPSs) limitation, sulfur redox reaction regulation and electrocatalysis in sulfur cathode and artificial solid electrolyte interface (SEI), electrolyte design, and structured anode in lithium anode. Additionally, the differences between laboratory level coin cells and actual pouch cells need to be addressed that only few reports on practical Li-S pouch cell are available due to the unexpected problems on both sulfur cathode and lithium anode which are masked at lithium and electrolyte excess. Lastly, the challenges and perspective toward the practical Li-S batteries are also offered.
Lithium-sulfur batteries with high theoretical specific capacity and high energy density are considered to be one of the most promising energy storage devices. However, the “shuttle effect” caused by the soluble polysulphide intermediates migrating back and forth between the positive and negative electrodes significantly reduces the active substance content of the battery and hinders the commercial applications of lithium–sulfur batteries. The separator being far from the electrochemical reaction interface and in close contact with the electrode poses an important barrier to polysulfide shuttle. Therefore, the electrochemical performance including coulombic efficiency and cycle stability of lithium–sulfur batteries can be effectively improved by rationally designing the separator. In this paper, the research progress of the modification of lithium–sulfur battery separators is reviewed from the perspectives of adsorption effect, electrostatic effect, and steric hindrance effect , and a novel modification of the lithium–sulfur battery separator is prospected.
The increasing demand for electrical energy storage requires the exploration of alternative battery chemistries that overcome the limitations of the current state‐of‐the‐art lithium‐ion batteries. In this scenario, lithium‐sulfur batteries stand out for their high theoretical energy density. However, several inherent limitations still hinder their commercialization. In this work, we report the synthesis and study of two high‐performance activated carbon‐based materials that allow to overcome the most challenging limitations of sulfur electrodes, i. e., low electronic conductivity and the polysulfide shuttle effect. The two tailored nanomaterials are based on porous carbon structures mixed with conductive reduced graphene oxide, one derived from an organic waste and the other from an organic synthetic route. These structures not only feature excellent individual properties, but also present excellent performance when implemented in batteries, related to their superior conductivity and polysulfide trapping ability, allowing to obtain improved rate capacity and high sulfur loading cycling. Additionally, we demonstrate the scalability of the best performing material by the assembly of high‐performance pouch cells.
Abstract Lithium–sulfur (Li–S) batteries, although a promising candidate of next‐generation energy storage devices, are hindered by some bottlenecks in their roadmap toward commercialization. The key challenges include solving the issues such as low utilization of active materials, poor cyclic stability, poor rate performance, and unsatisfactory Coulombic efficiency due to the inherent poor electrical and ionic conductivity of sulfur and its discharged products (e.g., Li2S2 and Li2S), dissolution and migration of polysulfide ions in the electrolyte, unstable solid electrolyte interphase and dendritic growth on anodes, and volume change in both cathodes and anodes. Owing to the high specific surface area, pore volume, low density, good chemical stability, and particularly multimodal pore sizes, hierarchical porous carbon (HPC) materials have received considerable attention for circumventing the above problems in Li–S batteries. Herein, recent progress made in the synthetic methods and deployment of HPC materials for various components including sulfur cathodes, separators and interlayers, and lithium anodes in Li–S batteries is presented and summarized. More importantly, the correlation between the structures (pore volume, specific surface area, degree of pores, and heteroatom‐doping) of HPC and the electrochemical performances of Li–S batteries is elaborated. Finally, a discussion on the challenges and future perspectives associated with HPCs for Li–S batteries is provided.
Li-S batteries, as the most promising post Li-ion technology, have been intensively investigated for more than a decade. Although most previous studies have focused on liquid systems, solid electrolytes, particularly all-solid-state polymer electrolytes (ASSPEs) and quasi-solid-state polymer electrolyte (QSSPEs), are appealing for Li-S cells due to their excellent flexibility and mechanical stability. Such Li-S batteries not only provide significantly improved safety but are also expected to augment the all-inclusive energy density compared to liquid systems. Therefore, this perspective briefly summarizes the recent progress on polymer-based solid-state Li-S batteries, with a special focus on electrolytes, including ASSPEs and QSSPEs. Furthermore, future work is proposed based on the existing development and current challenges.
This work provides a comprehensive review on the incorporation of ionic liquid (ILs) into polymer blends and their utilization as proton exchanges membranes (PEM). Various conventional polymers that incorporate ILs are discussed, such as Nafion, poly (vinylidene fluoride), polyben-zimidazole, sulfonated poly (ether ether ketone), and sulfonated polyimide. The methods of synthesis of IL/polymer composite membranes are summarized and the role of ionic liquids as electrolytes and structure directing agents in PEM fuel cells (PEMFCs) is presented. In addition, the obstacles that are reported to impede the development of commercial polymerized IL membranes are highlighted in this work. The paper concludes that the presence of certain ILs can increase the conductivity of the PEM, and consequently, enhance the performance of PEMFCs. Nevertheless, the leakage of ILs from composite membranes as well as the limited long-term thermal and mechanical stability are considered as the main challenges that limit the employment of IL/polymer composite membranes in PEMFCs, especially for high-temperature applications.
Since the investigation of the properties of ionic liquids, there has been an increasing interest in these materials in the field of sensors area due to their unique properties. The electrochemical and radiolytic stability of ionic liquids are prerequisites for using ionic liquids. In addition, a large number of ionic liquids can be synthesized with the combination of different anions and cations. Therefore, they are preferred to fabricate the electrochemical, optical sensors, and biosensors or used in electrolyte solutions as they promise a facile and low-cost way to examine the analytes due to their properties such as increasing the conductivity, optical properties, and stability, lowering the detection limit, facilitating the electron transfer and increasing the effective surface area of the electrode and sensor platform. All of those properties are powered with the use of nanomaterials in the modification of the sensors. In this review, general information about the properties of ionic liquids were given. Moreover, the recent developments in electrochemical and optical sensor applications in the last five years were summarized. Finally, the utilization of ionic liquids and nanomaterials in the modification of the sensor platform and the advances of the proposed sensors for the analyses taking place in different molecules were discussed.
The serious shuttle effect, sluggish reduction kinetics of polysulfides and the difficult oxidation reaction of Li2S have hindered LiS battery practical application. Herein, a 3D hierarchical structure composed of NiMoO4 nanosheets in situ anchored on NS doped carbon clothes (NiMoO4@NSCC) as the free‐standing host is creatively designed and constructed for LiS battery. Dual transitional metal oxide (NiMoO4) increases the electrons density near the Fermi level due to the contribution of the incorporating molybdenum (Mo), leading to the smaller bandgap, and thus stronger metallic properties compared with NiO. Furthermore, as a bidirectional catalyst, NiMoO4 is proposed to facilitate reductions of polysulfides through lengthening the SS bond distance of Li2S4 and reducing the free energy of polysulfides conversion, meanwhile promote critical oxidation of insulative discharge product (Li2S) via lengthening LiS bond distance of Li2S and decreasing Li2S decomposition barrier. Therefore, after loading sulfur (2 mg cm−2), NiMoO4@NSCC/S as the self‐supporting cathode for the LiS battery exhibits impressive long cycle stability. This study proposes a concept of a bidirectional catalyst with dual metal oxides, which would supply a novel vision to construct the high‐performance LiS battery. NiMoO4 nanosheets anchored on NS doped carbon clothes (NiMoO4@NSCC) as a bidirectional catalyst for LiS battery can facilitate polysulfides reduction through lengthening the SS bond distance of Li2S4 and reducing the free energy of LiPSs conversion, meanwhile promote critical oxidation of Li2S via lengthening its LiS bond distance and decreasing its decomposition barrier. Therefore, LiPSs redox kinetics can be simultaneously elevated.
Electrification is progressing significantly within the present and future vehicle sectors such as large commercial vehicles (e.g., trucks and buses), high-altitude long endurance (HALE), high-altitude pseudosatellites (HAPS), and electric vertical take-off and landing (eVTOL). The battery systems’ performance requirements differ across these applications in terms of power, cycle life, system cost, etc. However, the need for high gravimetric energy density, 400 Wh/kg and beyond, is common across them all, as it enables vehicles to achieve extended range, a longer mission duration, lighter weight, or increased payload. The system-level requirements of these emerging applications are broken down into the component-level developments required to integrate Li–S technology as the power system of choice. To adapt batteries’ properties, such as energy and power density, to the respective application, the academic research community has a key role to play in component-level development. However, materials and component research must be conducted within the context of a viable Li–S cell system. Herein, the key performance benefits, limitations, modeling, and recent progress of the Li–S battery technology and its adaption toward real-world application are discussed.
Lithium–sulfur (Li–S) batteries are recognized as promising candidates for next‐generation electrochemical energy storage systems owing to their high energy density and cost‐effective raw materials. However, the sluggish multielectron sulfur redox reactions are the root cause of most of the issues for Li–S batteries. Herein, a high‐efficiency CoSe electrocatalyst with hierarchical porous nanopolyhedron architecture (CS@HPP) derived from a metal–organic framework is presented as the sulfur host for Li–S batteries. The CS@HPP with high crystal quality and abundant reaction active sites can catalytically accelerate capture/diffusion of polysulfides and precipitation/decomposition of Li2S. Thus, the CS@HPP sulfur cathode exhibits an excellent capacity of 1634.9 mAh g⁻¹, high rate performance, and a long cycle life with a low capacity decay of 0.04% per cycle over 1200 cycles. CoSe nanopolyhedrons are further fabricated on a carbon cloth framework (CC@CS@HPP) to unfold the electrocatalytic activity by its high electrical conductivity and large surface area. A freestanding CC@CS@HPP sulfur cathode with sulfur loading of 8.1 mg cm⁻² delivers a high areal capacity of 8.1 mAh cm⁻² under a lean electrolyte. This work will enlighten the rational design of structure–catalysis engineering of transition‐metal‐based nanomaterials for diverse applications.
Lithium-sulfur (Li-S) batteries have the advantages of high theoretical capacity and energy density, which are considered as promising future energy storage. Besides, the high gravimetric energy density makes Li-S batteries more suitable as power sources for apparatus such as high-altitude drones and space vehicles. For these applications, the batteries should have a low self-discharge and a wide temperature range. Here, we introduce carbon nanofibers with MnS sulfiphilic sites as a flexible interlayer into Li-S batteries, reducing shuttle effect and accelerating reaction kinetics through physical inhibition, chemical adsorption and conversion promote synergy. The self-discharge of the cell is significantly weakened. The voltage is maintained at 2.37 V during 150 hours resting after 20 cycles. For sulfur loading of 2 mg cm-2, the capacity is as high as 714 mAh g-1 after 400 cycles at 1 C at room temperature. Besides, the operating temperature of the cell is broadened. At 55 °C and 0 oC, the capacity can be stabilized at 894 mAh g-1 and 853 mAh g-1 after 100 cycles at 0.5 C, respectively. This work can arouse wide research interests of lithium-sulfur batteries for applications in extreme environment.
Lithium–sulfur batteries (LSBs) are regarded as a new kind of energy storage device due to their remarkable theoretical energy density. However, some issues, such as the low conductivity and the large volume variation of sulfur, as well as the formation of polysulfides during cycling, are yet to be addressed before LSBs can become an actual reality. Here, presented is a comprehensive overview illustrating the techniques capable of mitigating these undesirable problems together with the electrochemical performances associated to the different proposed solutions. In particular, the analysis is organized by separately addressing cathode, anode, separator, and electrolyte. Furthermore, to better understand the chemistry and failure mechanisms of LSBs, important characterization techniques applied to energy storage systems are reviewed. Similarly, considerations on the theoretical approaches used in the energy storage field are provided, as they can become the key tool for the design of the next generation LSBs. Afterward, the state of the art of LSBs technology is presented from a geopolitical perspective by comparing the results achieved in this field by the main world actors, namely Asia, North America, and Europe. Finally, this review is concluded with the application status of LSBs technology, and its prospects are offered.
A collection of different polymeric ionic liquids (PILs) were explored as cathode binders in lithium-sulfur batteries. The PIL molecular structure, polymer backbone, and polymer architecture were found to influence cell capacity, cyclability, and the morphology of the cathode itself. PILs with styrene backbones performed better than vinyl-based polymer, while crosslinked PILs imparted further improved capacities, cyclability, and reduced over-potentials. Unlike PVdF, PIL binders mixed with the sulfide species, resulting in more uniformly distributed sulfides in the cathode and better sulfide transport. These features helped to mitigate volume change-induced degradation that typically plagues Li-S batteries. The uptake of polysulfides by PILs also constrains the polysulfide shuttle during battery cycling, leading to better cycling stability. While traditionally binders are viewed only as a “glue” to hold active material together, PIL binders have additional functions and play an active role during Li-S working operation.
Polymer binders in battery electrodes may be either active or passive. This distinction depends on whether the polymer influences charge or mass transport in the electrode. Although it is desirable to understand how to tailor the macromolecular design of a polymer to play a passive or active role, design rules are still lacking, as is a framework to assess the divergence in such behaviors. Here, we reveal the molecular-level underpinnings that distinguish an active polyelectrolyte binder designed for lithium-sulfur batteries from a passive alternative. The binder, a cationic polyelectrolyte, is shown to both facilitate lithium-ion transport through its reconfigurable network of mobile anions and restrict polysulfide diffusion from mesoporous carbon hosts by anion metathesis, which we show is selective for higher oligomers. These attributes allow cells to be operated for >100 cycles with excellent rate capability using cathodes with areal sulfur loadings up to 8.1 mg cm-2.
Lithium polysulfides sequestration by polymeric binders in lithium-sulfur battery cathodes is investigated in this study. We prove polycations can effectively adsorb lithium polysulfides via coulombic attraction between the positively charged backbone and the polysulfide anions. For the first time, we measure the simultaneous mass change of the sulfur cathodes using poly(diallyldimethyl ammonium triflate) (PDAT) and polyvinylpyrrolidone (PVP) binders during lithiation-delithiation with electrochemical quartz crystal microbalance (EQCM). The EQCM results demonstrate significantly higher mass gain with PDAT binder under identical conditions, providing the direct evidence that PDAT is a superior binder. The advantage of polycation binders is also proved by charge-discharge cycling combined with UV-Vis spectroscopy and X-ray photoelectron spectroscopy. With the PDAT binder and minimized electrolyte/sulfur weight ratio, we further demonstrate electrodes with high sulfur loading achieving 4.2 mAh cm-2 areal capacity.
The role of binders is crucial to achieve high performance and long cycle lifes in next-generation electrodes for lithium batteries. Currently used binders in electrode configurations, such as poly(vinylidene difluoride) (PVDF) are inactive polymers that do not transport lithium ions themselves, causing restrictions for high-power applications. Thus, developing innovative binders with an affinity towards lithium mobility is important for both lithium-ion and lithium-air batteries. In this work, we present for the first time the use of PDADMA poly(ionic liquid)s with fluorinated anions (FSI, TFSI, BETI, and CFSO) as cathode binders in Li-ion and Li-air batteries. The high-voltage NMC 532 cathodes with fluorinated PDADMA binders showed improved cells performances as: capacity values, rate performance, and cycling stability in accelerating aging conditions dedicated for more environmental-friendly mobility applications. Especially, PDADMA-CFSO binder in cathodes shows a cell capacity increase of 26% at 5C (12 min charge), when compared to PVDF one. Moreover, the fluorinated PDADMA binders in cathode improve the discharge capacities in Li–O2 cells, both with liquid and solid gel polymer electrolytes. Impressively, the Coulombic efficiency improves by 146% and the cycling capacity by 70% in solid-state Li–O2 cells using PDADMA-CFSO binder in the cathode, instead of common lithiated Nafion. All in all, the proposed fluorinated PDADMA Poly(ionic liquid)s can be a highly competitive alternative to conventional binders used nowadays in Li-ion and Li-air batteries.
Lithium-sulfur (Li-S) batteries are disclosed as prospective alternatives for next-generation energy storage technologies, due to their high theoretical energy density and cost-effectiveness. However, the shuttle effect and sluggish conversion reaction of polysulfide (LiPS) inhibit them from commercial application. To overcome these challenges, we anticipated a novel strategy to rational design a hollow titanium oxide nanosphere that is decorated with vanadium phosphide nanosheets (h-TiO2@VP) as an efficient sulfur host. The combination of strong chemical adsorption ability of hollow TiO2 nanospheres and excellent LiPS conversion catalyst of VP nanosheets which help to suppress the shuttling effect. The theoretical calculation showed that the h-TiO2@VP-50 (ratio of 5:5) could deliver higher conductivity and better adsorption ability toward LiPS. In particular, the composite of h-TiO2@VP and sulfur (h-TiO2@VP/S) cathode reveals a high specific capacity of ∼1430 mAh g⁻¹ at 0.1 C, and an excellent rate capacity of ∼521 mAh g⁻¹ at 5 C. Even at a high sulfur loading of ∼7.5 mg cm⁻², the h-TiO2@VP/S cathode-based Li-S battery delivers an exceptional areal capacity of ∼7.13 mAh cm⁻². This study opens a new door for designing the highly efficient Li-S battery cathode which can be a promising alternation for the state-of-the-art Li-ion cell.
Lithium-sulfur (Li-S) battery are regarded as a strong candidate for the next generation of high-performance battery due to its ultra-high capacity and low cost. However, severe shuttle effect of polysulfides (LiPSs) and the random deposition of lithium sulfide (Li2S) are vital challenges that impede the popularization of Li-S chemistry. Herein, inspired by charge-coordination interaction, a novel lithiophilic and sulfiphilic bifunctional polymer (LSBP) synthesized by in situ dynamic cross-linked is proposed to anchor LiPSs and enable controllable deposition of Li2S. The LSBP binder significantly improves the conversion reaction activity of LiPSs while the co-existence of lithiophilic (-COO⁻, -SO3⁻) and sulfiphilic (-NH2) sites effectively suppresses the shuttle of LiPSs, which is confirmed by in-situ time-resolved ultraviolet-visible (UV-vis) measurement. As a result, a high-loading (3.5 mgcm⁻²) and crack-free sulfur-based cathode with LSBP binder is achieved. Besides its stable cycling performance, the cathode exhibits an outstanding rate capacity under a high rate of 2.5 C. This work proposes a scalable strategy to obtain practicable Li-S battery through the improvement in binder, which is inherently low-cost and environmentally friendly.
Lithium−sulfur (Li–S) batteries have become the most promising candidates for next-generation power storage technologies owing to their ultrahigh energy density and low cost. However, the practical Li–S batteries, operated under...
The lithium-sulfur (Li-S) battery is considered one of the most promising technologies for next-generation energy storage. To realise its practical applications, electrodes with high areal sulfur loading, low-cost raw materials, and easily accessible fabrication processes are essential. Herein, we demonstrated the effectiveness of a commercially available black pigment, titanium black (TiB), as a multi-functional additive for sulfur electrodes. Benefiting from the amphipathic nature of TiB, it was easy to obtain a homogenous coating on a current collector (>4 mg cm⁻²) by applying a traditional slurry containing aqueous carboxymethyl cellulose/styrene-butadiene rubber as a binder. Contact angle measurements revealed much better electrolyte wettability for the electrode with the addition of TiB. Combined with a sparingly solvating electrolyte based on sulfolane and Li[N(SO2CF3)2], the electrode showed excellent cycling performance and high coulombic efficiency at a relatively high current density. Finally, pouch cells were fabricated with a low electrolyte/sulfur (E/S) ratio of 3.2 μL mg⁻¹, and a high energy density of 280 W h kg⁻¹was achieved. Subsequent investigation of the gassing behaviour revealed that swelling of the charged cells at 60 °C was suppressed for half a month. This study may pave the way for designing Li-S batteries with practical utility.
Lithium-sulfur (Li-S) technology was identified as a promising candidate to overcome energy density limitations of common lithium-ion batteries given the world-wide abundance of sulfur as a low-cost alternative to state-of-the-art active materials, such as Ni and Co. Li-S cells have received tremendous recognition in recent years, both from a scientific and industrial perspective. However, only few data on adequate multilayer-pouch cell characterization are available so far, and transparent calculations on components require more consideration. Because of the gap of lab cell characterization and prototype cell development, misinterpretations and false expectations are frequently reported, mostly resulting from lithium and electrolyte excess. For the commercialization of the Li-S technology, rapid transfer of new concepts on the prototype cell level is essential. Furthermore, fundamental studies should concentrate on fundamental scientific questions related to the main bottlenecks of Li-S cells: understanding anode and electrolyte degradation phenomena and realistic evaluation of stabilizing interfaces.
The development of most promising next generation Li-S batteries with a high utilization of sulfur while retaining the high capacity is one of the great challenge of the 21st century. Here we report a sandwich polyoxometalate [WZn3(H2O)2(ZnW9O34)2]¹²⁻ (ZnPOM) over a poly(1-vinyl-3(2-(2-methoxyethoxy)ethyl)imida¬zolium) cation (PVIMo) matrix as a binder free cathode catalyst for a high capacity LiS battery with a high areal loading of 7.68 mg/cm² and high areal capacity of 11.14 mAh/cm² (70% sulfur). The synergistic effect between PVIMo and ZnPOM shown to exhibit an outstanding initial discharge capacity of 1450 mAh/g at 0.5C with a high capacity retention of 97% and coulombic efficiency (>98%) with a electrolyte sulfur ratio of 10 µL(E)/mg(S) and a capacity fading of only 0.02% per cycle. The cationic polymer PVIMo hold the negatively charged polysulfide ions at the cathode and the ZnPOM facilitate the conversion of polysulfides to sulfur. Quantitative estimation by EQCM, UV-Vis analysis and potentiometric titration demonstrate a negligible loss of sulfur even after 120 cycles of charge-discharge process.
The market share in electric vehicles (EV) is increasing. This trend is likely to continue due to the increased interest in reducing CO2 emissions. The electric vehicle market evolution depends principally on the evolution of batteries capacity. As a consequence, automobile manufacturers focus their efforts on launching in the market EVs capable to compete with internal combustion engine vehicles (ICEV) in both performance and economic aspects. Although EVs are suitable for the day-to-day needs of the typical urban driver, their range is still lower than ICEV, because batteries are not able to store and supply enough energy to the vehicle and provide the same autonomy as ICEV.
EV use mostly Lithium-ion (Li-ion) batteries but this technology is reaching its theoretical limit (200-250 Wh/kg). Although the research to improve Li-ion batteries is very active, other researches began to investigate alternative electrochemical energy storage systems with higher energy density. At present, the most promising technology is the Lithium-Sulphur (Li-S) battery.
This paper presents a review of the state of art of Li-Sulphur battery on EVs compared to Li-ion ones, considering technical, modelling, environmental and economic aspects with the aim of depicting the challenges this technology has to overcome to substitute Li-ion in the near future. This study shows how the main drawbacks for Li-S concern are durability, self-discharge and battery modelling. However, from an environmental and economic point of view, Li-S technology presents many advantages over Li-ion.
With a remarkably higher theoretical energy density compared to lithium-ion batteries (LIBs) and abundance of elemental sulfur, lithium sulfur (Li-S) batteries have emerged as one of the most promising alternatives among all the post LIB technologies. In particular, the coupling of solid polymer electrolytes (SPEs) with the cell chemistry of Li-S batteries enables a safe and high-capacity electrochemical energy storage system, due to the better process-ability and less flammability of SPEs compared to liquid electrolytes. However, the practical deployment of all solid-state Li-S batteries (ASSLSBs) containing SPEs is largely hindered by the low accessibility of active materials and side reactions of soluble polysulfide species, resulting in a poor specific capacity and cyclability. In the present work, an ultrahigh performance of ASSLSBs is obtained via an anomalous synergistic effect between (fluorosul-fonyl)(trifluoromethanesulfonyl)imide anions inherited from the design of lithium salts in SPEs and the polysulfide species formed during the cycling. The corresponding Li-S cells deliver high specific/areal capacity (1394 mAh gsulfur–1, 1.2 mAh cm−2), good coulombic efficiency, and superior rate capability (~800 mAh gsulfur–1 after 60 cycles). These results imply the importance of the molecular structure of lithium salts in ASSLSBs and pave a way for future development of safe and cost-effective Li-S batteries.
Lithium-sulfur batteries are on the run to become the next generation energy storage technology. First of all due to its high theoretical energy density but also for its sustainability and low cost. However, there are still several challenges to take into account such as reducing the shuttle effect, decreasing the amount of conductive carbon to increase the energy density or enhancing the sulfur utilization. Herein, redox-active binders based on polyimide-polyether copolymers have been proposed as a solution to those drawbacks. These multiblock copolymers combine the ability of poly (ethylene oxide) to act as polysulfide trap and the properties of the imide groups to redox mediate the charge-discharge of sulfur. Thus, poly (ethylene oxide) block helps with the shuttle effect and mass transport in the electrode whereas the polyimide part enhances the charge transfer promoting the sulfur utilization. Sulfur cathodes containing pyromellitic, naphthalene or perylene polyimide-polyether binders featured improved cell performance in comparison with pure PEO binder. Among them, the electrode with naphthalene polyimide-PEO binder showed the best results with an initial capacity of 1300 mA h g⁻¹ at C/5, low polarization and 70% capacity retention after 30 cycles. Reducing the amount of carbon black in the cathode to 5 wt%, the cell with the redox-active binder was able to deliver 500 mA h g⁻¹ at C/5 with 78% capacity retention after 20 cycles. Our results demonstrate the possibility to reduce the amount of carbon by introducing polyimide-polyether copolymers as redox-active binders, increasing the sulfur utilization, redox kinetics and stability of the cell.
Solid imidazolium-based polyionic liquids (PILs; a class of polyelectrolyte) were synthesized for the absorption of n-butanol and other inhibitory biosynthesis products from dilute aqueous solutions. Conventional hydrogels prepared by cross-linking water-soluble PILs demonstrated biocompatibility with Saccharomyces cerevisiae¬, successfully eliminating cytotoxicity concerns associated with the IL monomers. However, the cross-linked PILs’ solute absorption capacity and selectivity for butanol relative to water were below the levels likely needed for a viable extractive fermentation process. Uncross-linked PILs bearing long-chain aliphatic substituents also proved to be biocompatible by virtue of their insolubility in water, and delivered significantly improved absorptive performance. Among biocompatible absorbents, these PILs demonstrated some of the highest absorption of n-butanol and other hydrophilic fermentation products reported to date, with n-butanol partition coefficient (PC) values up to 7.6 and butanol/water selectivity (αb/w) values up to 78. The influence of linear N-alkyl side chain length (C8 to C16) and counter anions (Clˉ, Brˉ, Iˉ, BF4ˉ, co-SSˉ) on solute partition coefficient, selectivity and physical properties are detailed and discussed. In all, this work demonstrates that polymerization of cytotoxic ILs can successfully yield biocompatible absorbents with excellent absorptive performance for the recovery of hydrophilic bioproducts.
During the operation of a Lithium-Sulfur (Li-S) cell, structural changes take place within both positive and negative electrodes. During discharge, the sulfur cathode expands as solid products (mainly Li2S or Li2S/Li2S2) are precipitated on its surface, whereas metallic Li anode contracts due to Li oxidation/stripping. The opposite processes occur during charge, where Li anode tends to expand due to lithium plating and solid precipitates from the cathode side are removed, causing its thickness to decrease. Most research literature describe these processes as they occur within single electrode cell constructions. Since a large format Li-S pouch cell is composed of multiple layers of electrodes stacked together, and antagonistic effects (i.e. expansion and shrinkage) occur simultaneously during both charge and discharge, it is important to investigate the volumetric changes of a complete cell. Herein, we report for the first time the thickness variation of a Li-S pouch cell prototype. In these studies we used a laser gauge for monitoring the cell thickness variation under operation. The effects of different voltage windows as well as discharge regimes are explored. It was found that the thickness evolution of a complete pouch cell is mostly governed by Li anodes volume changes, which mask the response of the sulfur cathodes. Interesting findings on cell swelling when cycled at slow currents and full voltage windows are presented. A correlation between capacity retention and cell thickness variation is demonstrated, which could be potentially incorporated into Battery Management System (BMS) design for Li-S batteries.
Solid polymer electrolytes (SPEs) comprising lithium bis(fluorosulfonyl)imide (Li[N(SO2F)2], LiFSI) and poly(ethylene oxide) (PEO) have been studied as electrolyte material and binder for the Li-S polymer cell. The LiFSI-based Li-S all solid polymer cell can deliver high specific discharge capacity of 800 mAh gsulfur−1 (i.e., 320 mAh gcathode−1), high areal capacity of 0.5 mAh cm–2 and relatively good rate capability. The cycling performances of Li-S polymer cell with LiFSI are significantly improved compared to with those with conventional LiTFSI (Li[N(SO2CF3)2]) salt in the polymer membrane, due to the improved stability of the Li anode/electrolyte interphases formed in the LiFSI-based SPEs. These results suggest that the LiFSI-based SPEs are attractive electrolyte materials for solid-state Li-S batteries.
For the Lithium-Sulfur (Li-S) battery to be competitive in commercialization, it is requested that the sulfur electrode must have deliverable areal capacity > 8 mAh cm⁻², which corresponds to a sulfur loading > 6 mg cm⁻². At this relatively high sulfur loading, we evaluated the impact of binder and carbon type on the mechanical integrity and the electrochemical properties of sulfur electrodes. We identified hydroxypropyl cellulose (HPC) as a new binder for the sulfur electrode because it offers better adhesion between the electrode and the aluminum current collector than the commonly used polyvinylidene fluoride (PVDF) binder. In combination with the binder study, multiple types of carbon with high specific surface area were evaluated as sulfur hosts for high loading sulfur electrodes. A commercial microporous carbon derived from wood with high pore volume showed the best performance. An electrode with sulfur loading up to 10 mg cm⁻² was achieved with the optimized recipe. Based on systematic electrochemical studies, the soluble polysulfide to insoluble Li2S2/Li2S conversion was identified to be the major barrier for high loading sulfur electrodes to achieve high sulfur utilization.
Die Einführung von Festkörper-Polymerelektrolyten in Lithiumbatterien vor über vierzig Jahren basierte auf der Fähigkeit von Polyethylenoxid (PEO), bestimmte Lithiumsalze zu lösen. Seitdem wurden viele Varianten dieses Systems vorgeschlagen und getestet, unter anderem die Zugabe von herkömmlichen carbonatbasierten Elektrolyten, niedermolekularen Polymeren sowie keramischen Füllstoffen. Dieser Aufsatz gibt einen Überblick über den aktuellen Stand der Forschung zu ternären Polymerelektrolyten, also ionenleitenden Systemen aus einem Polymer und zwei Salzen, eines mit Lithiumkation, das andere mit zusätzlichen Anionen, die das Polymer plastifizieren. Weiterhin werden Grundlagen zu den Wechselwirkungen in Polymerelektrolyten diskutiert, um Überlegungen zu den Herausforderungen und Möglichkeiten von Lithiummetallbatterien anzuregen.
Rechargeable lithium-sulfur batteries have attracted great interest in recent years because of their high theoretical specific energy, which is several times that of current lithium-ion batteries. Compared to sulfur, fully-lithiated Li2S represents a more attractive cathode material because it enables pairing with safer, lithium metal-free anodes. Here, we demonstrate stable and high-performance Li2S cathodes by using ab initio simulations to guide our rational selection of poly(vinylpyrrolidone) binder which exhibits strong affinity with both Li2S and lithium polysulfides. A high discharge capacity of 760 mA h g−1 of Li2S (1090 mA h g−1 of S) was achieved at 0.2 C with stable cycling over prolonged 500 charge/discharge cycles.
Cholinium-based ionic liquid methacrylic monomers having halide, lactate and acetate counter-anions were synthesized and polymerized by using conventional free radical polymerization. The polymer properties were characterized by NMR, SEC/GPC, TGA, and DSC and compared among eight different cationic polymethacrylic analogs. Polycations with different methacrylic alkylammonium backbones having lactate anion displayed comparatively better thermal stability than those having the acetate counter-anions and they also exhibited lower glass transition temperatures than their counterparts having acetate and halide counteranions. As an application, cholinium lactate methacrylate ionic liquid monomer was used to prepare ion gels by photopolymerization. Interestingly, these are the first examples of ion gels which are fully composed of low toxicity and biocompatible cholinium ionic liquids. Furthermore, the same ionic liquid monomer, cholinium lactate methacrylate, showed the ability to dissolve cellulose. This facilitated the preparation of transparent poly(ionic liquid)/cellulose composite coatings by photopolymerization.
Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li-air (O(2)) and Li-S. The energy that can be stored in Li-air (based on aqueous or non-aqueous electrolytes) and Li-S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li-air and Li-S justify the continued research effort that will be needed.