Silicon-based Lithium-ion Batteries Research Articles

Microporous Binder for the Silicon-Based Lithium-Ion Battery Anode with Exceptional Rate Capability and Improved Cyclic Performance.

Silicon anodes have attracted much attention owing to their high theoretical capacity. Nonetheless, an inevitable and enormous volumetric expansion of silicon in the lithiated state restrained the development of the silicon anode for lithium-ion batteries. Fortunately, the utilization of the high-performance binder is a promising and effective way to overcome such obstacles. Herein, a polymer of intrinsic microporosity (PIM) is applied as the binder for the silicon anode, which is composed of a rigid polymer backbone, an intrinsic porous structure, and active carboxyl groups (PIM-COOH). Compared to the traditional binder, both the long-term stability and rate performance of the electrode using PIM-COOH as the binder are significantly improved. The mechanism responsible for the enhanced performance is investigated. The PIM-COOH binder provides stronger adhesion toward the current collector than the conventional binders. The unique rigid polymer backbone and porous structure of the PIM-COOH binder enable a good capability to withstand the volume change and external stress generated by the Si anode. The porous structure of the PIM-COOH binder enhances lithium-ion transportation compared to the SA binder, which improves rate performance of the silicon anode. This work provides a unique insight into design, synthesis, and utilization of the binders for lithium-ion batteries.

Poly(4-vinylbenzoic acid): A Re-Engineered Binder for Improved Performance from Water-Free Slurry Processing for Silicon Graphite Composite Electrodes

In silicon-based lithium-ion batteries, polymeric binders play the crucial role of “gluing” the electrode matrix together, providing strong adhesion between the active silicon (Si) and conductive c...

Nanoscale silicon-based actuators with extremely large actuation strain and extremely low driving voltage

The coupling between lithiation reaction of silicon and the considerable volume change has been widely recognized as an adverse effect which hinders the practical application of silicon-based lithium-ion batteries. Here we theoretically demonstrate a novel class of nanoscale electrochemically-driven silicon actuators, in virtue of the “unfavorable” gigantic volume expansion engendered by lithiation. Two representative design prototypes are reported, namely, a nano-sized flat-film silicon actuator and a nanowire silicon actuator. Our thermodynamic analysis establishes the operation condition of the actuators by identifying the electrochemical driving force and mechanical resistance due to lithiation-induced stress. We show that the nano-actuator exhibits an extremely low driving voltage about 1 V and an extremely high strain of actuation up to 300%, which goes far beyond the features of most common actuator materials. Given a mechanical load, the flat-film silicon actuator features a constant actuation strain and the nanowire actuator can provide tunable actuation strain. The results from the study offer quantitative guidance to the design of the novel silicon-based nano-actuators.

Conducting polyaniline/poly (acrylic acid)/phytic acid multifunctional binders for Si anodes in lithium ion batteries

The poor cycling stability is a tricky problem in the silicon-based lithium-ion batteries. Herein, we fabricate a three-dimension polyaniline/poly (acrylic acid)/phytic acid compound binder for the silicon anodes. In this binder, polyaniline-doped and gelated by phytic acid functions as a continuous electrically conductive network structure for the silicon anodes. Meanwhile, a high density of carboxyl groups provided by poly (acrylic acid) enhance the stability of the silicon electrodes by supplying strong binding ability with current collectors and silicon particles. Using this multifunctional binder in silicon anode, we succeed in manufacturing very long cycle life of larger than 1000 cycles at a current density of 4.2 A g−1.

3D-structured multi-walled carbon nanotubes/copper nanowires composite as a porous current collector for the enhanced silicon-based anode

In this study, multi-walled carbon nanotubes/Cu nanowires-coated on the copper foil used as a three-dimensional porous current collector for Si electrode has been developed to tackle the problems of silicon-based lithium-ion batteries. The highly conductive Cu nanowires cooperated with robust multi-walled carbon nanotubes not only improve the inferior electric conductivity of the Si anode but also strengthen the total frame stability. Furthermore, the three-dimensional structure creates numerous voids on the surface of Cu foils. Such porous structure of the modified current collector offers the flexible volume expansion during lithiation/delithiation process. Meanwhile, the core-shell structure of multi-walled carbon nanotubes/Si and Cu nanowires/Si minimizes the deformation strain and greatly improves the long-term cycling performance in a real battery. As a result, a high specific capacity of 1845 mAh g−1 in a half cell at a current density of 3.5 A g−1 after 180 cycles with a capacity retention of 85.1% has been achieved without any conductive additives or binder. The demonstrated three-dimensional current collector coupled with Si anode might inspire new material development on high-performance of lithium-ion batteries.

Experimental Methods to Study Environmental Sustainability of Silicon-based Lithium Ion Battery Manufacturing

Abstract Next-generation lithium ion batteries (LIBs) are under rapid development using various nano-structured materials. Among them, silicon nanowires (SiNWs) and silicon nanotubes (SiNTs) are two promising anode materials due to their high specific capacities. However, fabrication processes of SiNWs and SiNTs involve a large amount of toxic chemicals and generate significant potential impacts on the environment. In this study, both in-situ and ex-situ measurements were proposed for investigating the process emissions, including gas, aerosol nanoparticle, and aqueous nanoparticle emissions, from chemical etching processes for producing SiNWs and SiNTs for use as anode materials for LIBs. The feasibilities of the measurements were verified by the preliminary results of the emissions from the SiNTs synthesis process. This study provides insight into experimental measurements of and supports the gathering of process data on emissions from synthesis processes for SiNWs and SiNTs as anode materials for LIBs, which can be useful for future assessment of the sustainability performance of silicon-based LIB technology.

Waterborne polyurethane as a carbon coating for micrometre-sized silicon-based lithium-ion battery anode material.

Waterborne polyurethane (WPU) is first used as a carbon-coating source for micrometre-sized silicon. The remaining nitrogen (N) and oxygen (O) heteroatoms during pyrolysis of the WPU interact with the surface oxide on the silicon (Si) particles via hydrogen bonding (Si–OH⋯N and Si–OH⋯O). The N and O atoms involved in the carbon network can interact with the lithium ions, which is conducive to lithium-ion insertion. A satisfactory performance of the Si@N, O-doped carbon (Si@CNO) anode is gained at 25 and 55°C. The Si@CNO anode shows stable cycling performance (capacity retention of 70.0% over 100 cycles at 25°C and 60.3% over 90 cycles at 55°C with a current density of 500 mA g−1) and a superior rate capacity of 864.1 mA h g−1 at 1000 mA g−1 (25°C). The improved electrochemical performance of the Si@CNO electrode is attributed to the enhanced electrical conductivity and structural stability.

A 1D Mathematical Model to Study the Effects of Adhesive Strength on the Electrochemical Performance of Silicon Electrodes for Advanced Lithium Ion Batteries

In recent times, commercially available lithium ion batteries (LIBs) employ graphite, with a theoretical capacity of 372 mAh g-1, as their anode material. To enhance the energy density of LIBs, alternative anode materials with higher capacities, such as Li metal, Si, and various alloys, have been extensively exploited. With its advantages of a higher theoretical capacity (4200 mAh g-1), environmental friendliness, and terrestrial abundance, Si is particularly well-suited as an anode material for this purpose. Nevertheless, Si suffers from large volume variations (up to 300%) during lithiation/delithiation processes, leading to pulverization, low cycling efficiency, unstable solid electrolyte interphases (SEI), and permanent capacity losses. There have been several scientific investigations and strategies to solve the issues related to the large volume changes in Si. Relevant breakthroughs have been made with the help of advanced nanotechnologies in terms of enhancing the cycle life and improving the cycle rate performance. Notable among them is the use of binding materials with improved adhesive properties, such as copolyimide, alginate, poly(acrylic acid) (PAA), carboxymethyl cellulose, polyamide-imide, polyimide, and polymers that form cross-linked networks. Moreover, enhancing the adhesive strength between the Si composite electrode and Cu current collector by coating the latter’s surface with a very thin polymeric layer has significantly enhanced the electrochemical performance of Si anodes. However, the mechanism underlying this improvement in performance was not clearly addressed. In this presentation, a coupled chemo-mechanical model which considers the contact resistance as well as the influence of the attractive forces inside the contact area between the electrode and current collector was developed to study the effects of the adhesive strength of a binding material on the electrochemical performance of silicon-based lithium-ion batteries. The model predictions were validated with experimental data from coin-type half-cells composed of Li metal, Si electrodes, and Cu current collectors coated with binding materials with different adhesive strengths. The proposed model was used to investigate the effects of the adhesive strength and various cell design parameters on the specific capacity of the Si-based Li-ion cells.

A coupled chemo-mechanical model to study the effects of adhesive strength on the electrochemical performance of silicon electrodes for advanced lithium ion batteries

A coupled chemo-mechanical model which considers the contact resistance as well as the influence of the attractive forces inside the contact area between the electrode and current collector was developed to evaluate the effects of the adhesive strength of a binding material on the electrochemical performance of silicon-based lithium-ion batteries. The increase in contact resistance between the electrode and current collector was introduced as a factor that reduces the electrochemical performance of the cell. The model predictions were validated with experimental data from coin-type half-cells composed of Li metal, Si electrodes, and Cu current collectors coated with binding materials with different adhesive strengths. The contact resistance increased with an increasing number of cyclic current rate. The adhesive strength decreased with cyclic current rate. The proposed model was used to investigate the effects of adhesive strength and various cell design parameters on the specific capacity of the Si-based Li-ion cells.

All gas-phase synthesis of graphene: Characterization and its utilization for silicon-based lithium-ion batteries

We report on a gas-phase synthesis method for the preparation of free-standing few-layer graphene in a microwave plasma reactor using pure ethanol as precursor. This scalable synthesis route produces gas-phase graphene (GPG) with lab-scale production rates up to a few hundred mg/h. The physico-chemical properties of the resulting GPG were characterized by XRD, FTIR-, and Raman spectroscopy, electrical conductivity measurements, XPS, and HRTEM in combination with EELS. The materials' properties were compared with those of reduced graphene oxide (rGO) made by the established Hummers' method. The results indicate that the gas-phase synthesis method provides highly-ordered few-layer graphene with extraordinary high purity, very low oxygen content of less than 1 at.%, and high specific conductivity. Both graphene materials were processed in combination with gas-phase synthesized silicon nanoparticles towards silicon-graphene nanocomposites for Li-ion battery anodes. Subsequent electrochemical testing revealed that the gas-phase graphene significantly enhances the long-term stability and Coulomb efficiency of the composite compared to pristine silicon and outperforms the composite fabricated from reduced graphene oxide.

Evolving affinity between Coulombic reversibility and hysteretic phase transformations in nano-structured silicon-based lithium-ion batteries

Nano-structured silicon is an attractive alternative anode material to conventional graphite in lithium-ion batteries. However, the anode designs with higher silicon concentrations remain to be commercialized despite recent remarkable progress. One of the most critical issues is the fundamental understanding of the lithium–silicon Coulombic efficiency. Particularly, this is the key to resolve subtle yet accumulatively significant alterations of Coulombic efficiency by various paths of lithium–silicon processes over cycles. Here, we provide quantitative and qualitative insight into how the irreversible behaviors are altered by the processes under amorphous volume changes and hysteretic amorphous–crystalline phase transformations. Repeated latter transformations over cycles, typically featured as a degradation factor, can govern the reversibility behaviors, improving the irreversibility and eventually minimizing cumulative irreversible lithium consumption. This is clearly different from repeated amorphous volume changes with different lithiation depths. The mechanism behind the correlations is elucidated by electrochemical and structural probing.

Novel approach for improving the performance of Si-based anodes in lithium-ion batteries

Herein, we report successful deposition of aluminum oxide films on the silicon nanowires (SiNWs) to realize core–shell silicon-based lithium-ion battery anodes. By means of reactive ion etching, it has been possible to form an ultra-thin layer of Al2O3 on SiNWs through hydrogen plasma. This deposition technique leads to the formation of tiny holes on the surface of the Al2O3 layer while introducing the pore sites into the inner silicon material without damaging the whole structure. SiNW@Al2O3 core–shell nanostructures were used as the effective anode materials and showed a superior electrochemical performance compared to conventional SiNWs. Our electrode exhibited the high first cycle specific discharge capacity of 3936 mAh g−1 at a rate of C/16 as well as high rate capability. Furthermore, this anode electrode showed less than 6% degradation of specific capacity over 120 cycles at high rate density of 2C and it delivers high reversible capacity of 965 mAh g−1. The improvement in the electrochemical properties of our electrode is achieved due to both a high specific capacity of Si core and the effect of aluminum oxide shell on active material cycling stability.

Investigation of the Conductivity Effect on Silicon Anode Performance for Lithium Ion Batteries

The early development on rechargeable lithium battery began with lithium (Li) metal and Sony put into the market the first lithium ion batteries in 1991. Since that date the graphite has been used as commercial anode with the practiable capacity of 250 mAh/g and it has been yet reached the 290 mAh/g in 2015 [1]. In the development of high capacity anode materials for lithium ion batteries, silicon is apparently very promising as anode material due to its high theoretical capacity ~4200 mAh/g. However, the huge volume change (~300%) occurs during the cycling and it results breakdown of the conductive network of the composite electrode. This causes the electrical contact problem between conductive agent and the current collector, resulting low Coulombic efficiency and poor capacity retention for silicon-based lithium ion batteries (LIBs). Polypyrene (Ppr) polymer has much concern recently not only the conductivity and other electrical properties but also thermal stability and mechanical properties. In this study, the aim is to enhance the conductivity of Si electrode which is crucial for charge-discharge rate of a battery. The high conductivity provides fast charge-discharge and that is very important for consumer electronics and electric vehicle applications. For this purpose, the conductive Ppr was synthesized through the free-radical polymerization of the acrylate backbone in the presence of an initiator. It was used as a conductive polymer for silicon anode in LIBs. The conductivity of anode was also studied with different carbonecous additives (carbon black, super p and carbon nanotube). The cells were fabricated as half and full cell. Li was used as the counter electrode for half-cell and NCA was used as the cathode for full cell. Table 1. Experimental results for the conductivity study of Si anode Experiment No Composition Ratio Active Material Binder Conductive additive 1 90:10 Si Ppr - 2 85:15 Si Ppr - 3 85:10:5 Si Ppr CB 4 85:10:5 Si Ppr SP 5 85:10:5 Si Ppr CNT 6 85:10:5 Si PVDF CB

Advanced Characterization of a Stabilized Solid Electrolyte Interphase on Silicon Anodes for Lithium-Ion Batteries By in-Situ Electrochemical Surfaces Forces Apparatus

The unsatisfactory behaviour of the solid electrolyte interphase (SEI) on silicon-based anodes still prevents the commercial introduction of silicon in lithium-ion batteries – a milestone which would be a huge leap forward towards a sustainable energy use.[1] Our group has recently developed an electrolyte mixture improving the cycling performance of a silicon-based lithium-ion battery. For understanding the stabilizing effect of this novel electrolyte on the SEI, advanced characterization techniques had to be employed, such as a modified Surface Forces Apparatus (SFA) and synchrotron-based Hard X-ray Photoelectron Spectroscopy (HAXPES). So far, the SFA was used to research fundamental biologic and solution based interfacial processes.[2] Here we present a detailed investigation of the SEI on a silicon anode by designing a battery SFA cell for in-situ electrochemical measurements. This enabled us to monitor the SEI thickness during the different stages of the SEI formation on both silicon and graphite surfaces. Additionally, we report the mechanical properties of the SEI for different electrolytes which can also be addressed by the SFA setup. HAXPES data collected on a modified SEI on silicon based anodes reveal a complex nanostructure and provide an additional insight into the stabilization mechanism of the electrolyte mixture. Coin-cell testing confirm the stabilizing effect of the novel electrolyte mixture on the battery performance. The electrochemical battery SFA will be an important tool for evaluating novel electrolyte compositions and their effect on the mechanical properties and growth mechanism of the interfacial SEI. The introduction of this in-situ battery test cell for SFA opens the way for both fundamental interfacial insights as well as applied material studies in battery research. REFERENCES 1. E.C. Evarts, To the limits of lithium, Nature, 2015, 526, 593-595.2. J. Israelachvili et al., Recent advances in the surface forces apparatus (SFA) technique, Rep. Prog. Phys., 2010, 73, 1-16. Figure 1

Understanding the Roles of Electrolyte Additives on the Surface Modification Mechanism of Silicon-Based Anodes in Lithium-Ion Batteries

Silicon is considered as a promising candidate of the anode material for the next generation lithium-ion batteries, due to its substantially higher gravimetric and volumetric capacity compared to conventionally used graphite. Electrolyte additives, fluoroethylene carbonate (FEC) and vinylene carbonate (VC) particularly, are usually applied for silicon-based lithium-ion batteries to tackle the problems such as poor capacity retention and low coulombic efficiency.1-3 In the present work, the decomposition mechanism of FEC as well as the surface modification of Si electrodes were investigated.4 It was observed that the FEC additive degrades at a higher reduction potential prior to the other carbonate solvents. A conformal solid electrolyte interphase (SEI), which consists of the decomposition products of FEC, is instantaneously formed on the silicon electrode as a result. This stable SEI layer sufficiently limits the emergence of cracks and suppresses the additional SEI formation from the decomposition of other electrolyte components. Both of these effects lead to a slower increase in polarization, thus a slower capacity fading, for the FEC containing cell. The differences in the SEI layer, formed with or without the presence of FEC, are schematically demonstrated in Fig 1. Besides, it was also observed that the LiPF6 decomposition can be influenced with the presence of FEC, and this was further studied with a combination of X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (NMR) techniques. We also demonstrated that by forming an effective SEI layer with the FEC and VC electrolyte additives, the silicon electrodes can be equally well functioning with a novel lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI)-based electrolyte as with the state-of-art LiPF6-based electrolyte.5 Figure 1

One-step solid-state in-situ thermal polymerization of silicon-PEDOT nanocomposites for the application in lithium-ion battery anodes

Abstract The current study presents a one-step solid-state in-situ thermal polymerization approach to prepare silicon nanoparticles-polyethylenedioxythiophene (SiNPs-PEDOT) nanocomposites. The structure-related electrochemical performance of the in-situ polymerized 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) with SiNPs has been studied for the first time in application to silicon-based lithium-ion battery anodes. Thermal polymerization applied to a solution containing DBEDOT in acetonitrile with suspended silicon nanoparticles resulted in an in-situ formed SiNPs-PEDOT nanocomposite. The structure, morphology, and the corresponding electrochemical performance of the in-situ SiNPs-PEDOT nanocomposites was studied in comparison to a pure PEDOT as well as to the ex-situ polymerized SiNPs-PEDOT nanocomposites using XRD, FTIR, TGA, SEM, TEM, cyclic voltammetry, impedance spectroscopy, and constant current charge-discharge cycles. The XRD, FTIR, and TGA analysis reveal that the in-situ polymerization of monomer is not impeded by the presence of the silicon nanoparticles. The SEMand TEM studies reveal a uniform dispersion of SiNPs within in-situ polymerized PEDOT matrix compared to ex-situ formed SiNPs-PEDOT nanocomposite. In the lithium-ion battery anode, the in-situ polymerized SiNPs-PEDOT nanocomposite demonstrates the enhanced lithiation-delithiation kinetics, conductivity, and rate capability in comparison to the ex-situ SiNPs-PEDOT nanocomposite.

Phase Field Modeling of Lithium-Ion Diffusion and Crack Formation in the Solid Electrolyte Interphase of Silicon-Based Lithium-Ion Battery

Lithium-ion batteries (LIBs) play a key role in portable equipment, electric vehicles, and other energy storage modules. Solid electrolyte interface (SEI) layer cause a significant degradation for lithium-ion batteries’ electrochemical performance. Recently, silicon or Si-based anodes becomes an attractive candidate for the electrode of LIBs due to the low cost and high theoretical specific capacity. However, the mechanism of lithium-ion transport through the SEI layer is not fully understood as well as the crack formation of SEI layer due to silicon severe volume change. A phase field model is employed and developed to simulate the SEI structure and lithium-ion diffusion inside SEI layer including the thermodynamic chemical potential and elastic energy. SEI layer is believed to have multilayered structure; And SEI formation can be regarded as a solidification process. The phase field model is a powerful tool to investigate solidification problems without explicitly tracking the interfaces between the SEI species and electrolyte solution. Two sets of phase field variables are used to describe the microstructure of SEI layer and Lithium-ion transport in SEI layer. One is associated with the volume fraction of the interface. And the other is associated with the concentrations of SEI species. Lithium-ion transport will cause the elastic energy change. Therefore, elastic field needs to be considered in the developed model. And the elastic energy can be applied to investigate the crack initiation and propagation. Most importantly, the present developed model has great potential to be extended to three dimensional spaces for SEI layer spatial growth investigation.

Tailoring the Desired Surface Chemistry in Silicon-Based Lithium-Ion Batteries with Electrolyte Additives

The design of safe, high-energy batteries exhibiting prolonged lifetime greatly depends on understanding the surface reactions occurring on the electrode surfaces and the role of the solid electrolyte interphase (SEI) film. Most of the naturally forming SEI films demonstrate undesirable characteristics, such as instability and continuous surface reaction that decrease the capacity of Si-based Li-ion batteries (LIBs). An effective and economic way to modify the surface chemistry in LIBs rather than the Si architecture is by electrolyte additives. The objective of the present study is the examination of the concentration dependence of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) additives on the long-term electrochemical performance of LIBs, as well as the dependence of the SEI formation mechanism on the concentration of the VC and FEC additives. A significant improvement in the cycling performance of Si electrodes can be achieved under operation conditions of optimum VC and FEC concentration. To better understand the additive concentration effect, the reduction mechanisms of VC and FEC were investigated for both Si nanoparticle and Si(100) single crystal working electrodes. Ex-situ ATR-FTIR spectra of Si electrodes for 5% VC additive show a broad peak at a higher wavenumber (1831 cm–1) compared to the EC residual electrolyte (1799 and 1769 cm–1) (Fig. 1). Based on synthesized poly-VC standard spectra, the VC additive reduction compound is assigned to poly-VC or its oligomer, which is consistent with previous reports. However, for Si electrode and FEC additive, the original C=O stretch (1829 and 1802 cm–1) disappears or shifts to a lower wavenumber. The exact reduction product of FEC degradation has not been confirmed yet due to the lack of significant features other than the residual electrolyte. However, it is clear that FEC follows a different reduction path than VC. The reduction path of VC is polymerization with the reduction product remaining a “ring” structure (the C=O peak shifts to a higher wavenumber), whereas the reduction path of FEC is similar to that of ethylene carbonate (EC), leading to a reduction product of open “ring” structure, similar to that produced from EC reduction. More experiments are underway to confirm the different reduction paths of VC and FEC stated above. Acknowledgement This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Freedom CAR and Vehicle Technologies of the U.S. Department of Energy under contract No. DE-AC02-OSCH11231. Figure 1

Understanding the Effect of Different Polymeric Surfactants on Enhancing the Silicon/Reduced Graphene Oxide Anode Performance

Silicon-based lithium-ion battery anodes have brought encouraging results to the current state-of-the-art battery technologies due to their high theoretical capacity, but their large-scale application has been hampered by a large volume change (>300%) of silicon upon lithium insertion and extraction, which leads to severe electrode pulverization and capacity degradation. Polymeric surfactants directing the combination of silicon nanoparticles and reduced graphene oxide have attracted great interest as promising choices for accommodating the huge volume variation of silicon. However, the influence of different polymeric surfactants on improving the electrochemical performance of silicon/reduced graphene oxide (Si/RGO) anodes remains unclear because of the different structural configurations of polymeric surfactants. Here, we systematically study the effect of different polymeric surfactants on enhancing the Si/RGO anode performance. Three of the most well-known polymeric surfactants, poly(sodium 4-styrenesulfonate) (PSS), poly(diallydimethylammonium chloride) (PDDA), and polyvinylpyrrolidone (PVP), were used to direct the combination of silicon nanoparticles and RGO through van der Waals interaction. The Si/RGO anodes made from these composites act as ideal models to investigate and compare how the van der Waals forces between polymeric surfactants and GO affect the final silicon anode performance from both experimental observations and theoretical simulations. We found that the capability of these three surfactants in enhancing long-term cycling stability and high-rate performance of the Si/RGO anodes decreased in the order of PVP > PDDA > PSS.

Novel design of silicon-based lithium-ion battery anode for highly stable cycling at elevated temperature

We demonstrate a facile method for synthesizing silicon particles with a double coating layer consisting of aluminum trifluoride and amorphous carbon to use as an anode material for high-performance lithium-ion batteries at elevated temperatures.