Robust Solid Electrolyte Interphase Layer Research Articles

High‐Performance Na‐Storage and Sodiation Behavior Identification in Cellulose‐Derived Hard Carbon by High‐Resolution Element Mapping Microscopy

Nowadays, hard carbon is one of the most promising anode materials for sodium‐ion batteries. However, the Na‐storage performance of hard carbon varies for different precursors and synthetic processes due to disparities in the dopant content, dimensions, and categories of defects, graphitic domains, which lead to controversial explanations for the energy storage mechanism. Herein, self‐freestanding membrane of cellulose‐derived carbon fibers is presented, delivering a reversible Na‐storage capacity of 330 mAh g−1 at 50 mA g−1 due to abundant ordered graphitic zones with enlarged interlayer spacings around 0.39 ± 0.03 nm. Benefiting from a robust solid electrolyte interphase layer rich in NaF nanocrystals, the membrane also holds a superior rate capability of 100 mAh g−1 at 2 A g−1 and long‐term cycling stability with capacity retention of 82.6% at 1.5 A g−1 for 4000 cycles. A clear sodiation behavior of Na+ intercalation into enlarged carbon graphitic layers at the slope step above 0.10 V and Na cluster evolution in the micropores at the plateau step around 0.01–0.10 V is disclosed by high‐resolution element mapping microscopy, different from the accepted mechanism of Na+ intercalation into graphitic layers at the plateau step.

Modification of polypropylene separator with multifunctional layers to achieve highly stable sodium metal anode

Separator modification is an effective approach to suppress dendrite growth to realize high-energy sodium metal batteries (SMBs) in practical applications, however, its success is mainly subject to surface modification. Herein, a separator with multifunctional layers composed of N-doped mesoporous hollow carbon spheres (HCS) as the inner layer and sodium fluoride (NaF) as the outer layer on commercial polypropylene separator (PP) is proposed (PP@HCS-NaF) to achieve stable cycling in SMB. At the molecular level, the inner HCS layer with a high content of pyrrolic-N induces the uniform Na+ flux as a potential Na+ redistributor for homogenous deposition, whereas its hollow mesoporous structure offers nano-porous buffers and ion channels to regulate Na+ ion distribution and uniform deposition. The outer layer (NaF) constructs the NaF-enriched robust solid electrolyte interphase layer, significantly lowering the Na+ ions diffusion barrier. Benefiting from these merits, higher electrochemical performances are achieved with multifunctional double-layered PP@HCS-NaF separators compared with single-layered separators (i.e. PP@HCS or PP@NaF) in SMBs. The Na||Cu half-cell with PP@HCS-NaF offers stable cycling (280 cycles) with a high CE (99.6%), and Na||Na symmetric cells demonstrate extended lifespans for over 6000 h at 1 mA cm−2 with a progressively stable overpotential of 9 mV. Remarkably, in Na||NVP full-cells, the PP@HCS-NaF separator grants a stable capacity of ∼81 mA h g−1 after 3500 cycles at 1C and an impressive rate capability performance (∼70 mA h g−1 at 15C).

Air‐stable Li3.12P0.94Bi0.06S3.91I0.18 solid‐state electrolyte with high ionic conductivity and lithium anode compatibility toward high‐performance all‐solid‐state lithium metal batteries

AbstractSulfide solid‐state electrolytes (SSEs) with superior ionic conductivity and processability are highly promising candidates for constructing all‐solid‐state lithium metal batteries (ASSLMBs). However, their practical applications are limited by their intrinsic air instability and serious interfacial incompatibility. Herein, a novel glass‐ceramic electrolyte Li3.12P0.94Bi0.06S3.91I0.18 was synthesized by co‐doping Li3PS4 with Bi and I for high‐performance ASSLMBs. Owing to the strong Bi‒S bonds that are thermodynamically stable to water, increased unit cell volume and Li+ concentration caused by P5+ substitution with Bi3+, and the in situ formed robust solid electrolyte interphase layer LiI at lithium surface, the as‐prepared Li3.12P0.94Bi0.06S3.91I0.18 SSE achieved excellent air stability with a H2S concentration of only 0.205 cm3 g−1 (after 300 min of air exposure), outperforming Li3PS4 (0.632 cm3 g−1) and the most reported sulfide SSEs, together with high ionic conductivity of 4.05 mS cm−1. Furthermore, the Li3.12P0.94Bi0.06S3.91I0.18 effectively improved lithium metal stability. With this SSE, an ultralong cyclability of 700 h at 0.1 mA cm−2 was realized in a lithium symmetrical cell. Moreover, the Li3.12P0.94Bi0.06S3.91I0.18‐based ASSLMBs with LiNi0.8Mn0.1Co0.1O2 cathode achieved ultrastable capacity retention rate of 95.8% after 300 cycles at 0.1 C. This work provides reliable strategy for designing advanced sulfide SSEs for commercial applications in ASSLMBs.

High-modulus solid electrolyte interphase layer with gradient composition enables long-cycle all-solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur batteries (ASSLSBs) have become one of the most potential candidates for the next-generation high-energy systems due to their intrinsic safety and high theoretical energy density. However, PEO-based ASSLSBs face the dilemma of insufficient Coulombic efficiency and long-term stability caused by the coupling problems of dendrite growth of anode and polysulfide shuttle of cathode. In this work, 1,3,5-trioxane (TOX) is used as a functional additive to design a PEO-based composite solid-state electrolyte (denoted as TOX-CSE), which realizes the stable long-term cycle of an ASSLSB. The results show that TOX can in-situ decompose on the anode to form a composite solid electrolyte interphase (SEI) layer with rich-organic component. It yields a high average modulus of 5.0 GPa, greatly improving the mechanical stability of the SEI layer and thus inhibiting the growth of dendrites. Also, the robust SEI layer can act as a barrier to block the side reaction between polysulfides and lithium metal. As a result, a Li-Li symmetric cell assembled with a TOX-CSE exhibits prolonged cycling stability over 2000 h at 0.2 mA cm−2. The ASSLSB also shows a stable cycling performance of 500 cycles at 0.5 C. This work reveals the structure–activity relationship between the mechanical property of interface layer and the battery’s cycling stability.

1,3,6-Hexanetricarbonitrile as electrolyte additive to inhibit sodium dendrites in sodium-metal batteries

Sodium-metal batteries (SMBs) offer substantial competitiveness owing to their wide elemental distribution and high specific capacity. However, SMBs face safety issues such as unstable properties of the Solid Electrolyte Interphase (SEI) layer due to irregular sodium dendrites. In this paper, we constructed a stable and uniform SEI layer by introducing the 1,3,6-Hexanetricarbonitrile (HTCN) electrolyte additive, replacing the conventional, insoluble nitrate. HTCN facilitates the generation of substances like Na3N with high electrical conductivity on the Na anode surface. This accelerates Na+ shuttling and provides high-flux nucleation sites. Molecular dynamics simulations were employed to elucidate the solvated structure of electrolyte and radial distribution of Na+ after HTCN addition. Moreover, in-situ optical microscopy revealed a stable and robust SEI layer, effectively inhibiting the disorderly growth of sodium dendrites. The superior cycling performance of the Na3V2(PO4)3 (NVP)/Na full cell further demonstrates the addition of HTCN.

Stable operation of highly loaded pure Si-Fe anode under ambient pressure via carboxy silane-directed robust solid electrolyte interphase

Incorporation of higher content Si anode material beyond 5 wt% to Li-ion batteries (LIBs) is challenging, owing to large volume change, swelling, and solid electrolyte interphase (SEI) instability issues. Herein, a strategy of diacetoxydimethylsilane (DAMS) additive-directed SEI stabilization is proposed for a stable operation of Si-0.33FeSi2 (named as Si-Fe) anode without graphite, which provides siloxane inorganics and organics enrichment that compensate insufficient passivation of fluoroethylene carbonate (FEC) additive and reduce a dependence on FEC. Unprecedented stable cycling performance of highly loaded (3.5 mA h cm−2) pure Si-Fe anode is achieved with 2 wt% DAMS combined with 9 wt% FEC additives under ambient pressure, yielding high capacity 1270 mA h g−1 at 0.5 C and significantly improved capacity retention of 81% after 100 cycles, whereas short circuit and rapid capacity fade occur with FEC only additive. DAMS-directed robust SEI layer dramatically suppresses swelling and particles crossover through separator, and therefore prevents short circuit, demonstrating a possible operation of pure Si or Si-dominant anodes in the next-generation high-energy-density and safe LIBs.

Transforming Dye Molecules into Electrochemical Allies: Direct Red 80 as a Dual-Functional Electrolyte Additive for Dendrite-Free Aqueous Zinc-Ion Batteries.

Despite the numerous advantages of abundant zinc resources, low redox potential, and affordability, aqueous zinc-ion batteries (AZIBs) currently face limitations due to dendritic growth and side reactions. This study explores the use of low-cost and efficient anionic dyes, specifically Direct Red 80 (DR80) as dual-functional electrolyte additives to enhance the electrochemical performance of AZIBs and facilitate the reuse of dye wastewater. Experimental and theory calculation results all demonstrate that the DR80 molecules readily adsorb onto the surface of the zinc anode, creating a stable and robust solid electrolyte interphase layer. This layer acts as a protective barrier, effectively mitigating H+ attacks and reducing both hydrogen evolution and corrosion reactions. Additionally, it covers any initial protrusions on the zinc anode, preventing the occurrence of the "tip-effect" phenomenon and limiting access of water to the zinc anode, thereby minimizing water decomposition. Moreover, the sulfonic acid groups of DR80 molecules displace some water molecules in [Zn(H2O)6]2+, disrupting the original solvent sheath and reducing water decomposition. Especially, using the DR80 additive, the Zn/Zn cell reaches an impressive cycle life of 1500 h at 2 mA cm-2@1 mAh cm-2. Given the low cost and widespread availability, this additive shows great potential in the future practical implementation of AZIBs.

Unraveling New Role of Binder Functional Group as a Probe to Detect Dynamic Lithium‐Ion De‐Solvation Process toward High Electrode Performances

AbstractBinder plays a pivotal role in the development of lithium‐ion batteries as it must be used to adhere electrode materials on current collectors tightly to guarantee stability. Then, many binder molecules have been designed to enhance the adhesion capability, and conductivity, and/or form a robust solid electrolyte interphase layer for better performance. However, the binder effect on the lithium‐ion (i.e., Li+) de‐solvation on the electrode surface has never been reported before. Herein, it is reported that the binder can influence the Li+ (de‐)solvation process significantly, where its functional group can serve as a probe to detect the dynamic Li+ (de‐)solvation process. It is discovered that different binder functional groups (e.g., *─COO− versus *─F) can affect the Li+‐solvent arrangement on the electrode surface, leading to different degrees of side‐reactions, rate capabilities, and/or the tolerance against Li+‐solvent co‐insertion for the graphite anode, such as in the propylene carbonate‐based electrolyte. A molecular interfacial model related to the electrolyte component's behaviors and binder functional group is proposed to interpret the varied electrode performance. This discovery opens a new avenue for studying the interactions between the binder and electrolyte solvation structure, in turn helping to understand electrode performances underlying the micro‐structures.

Lithiophilic Mo2C Clusters‐Embedded Carbon Nanofibers for High Energy Density Lithium Metal Batteries

AbstractLithium metal anodes are widely regarded as the ideal candidate for the next generation of high‐energy‐density lithium batteries. Here, a 3D host made of lithiophilic Mo2C clusters‐embedded carbon nanofibers (Mo2C@CNF) is developed. The uniformly dispersed clusters and large specific surface areas of Mo2C@CNF provide numerous nucleation sites for lithium deposition. Mo2C clusters exhibit ultralow nucleation overpotential compared to MoO2, which is also supported by density functional theory calculations. Furthermore, the transition metal element serves as a catalyst for the formation of a stable and robust solid electrolyte interphase layer containing LiF on Mo2C@CNF, effectively mitigating the occurrence of dead lithium and enhancing the Coulombic efficiency during prolonged operation. As a result, the Mo2C@CNF composite delivers superior electrochemical performance (>1600 h) at 1 mA cm−2 and lower nucleation overpotential (13 mV) for lithium plating. The Li/Mo2C@CNF anode coupled with the commercial LiFePO4 cathode exhibits excellent cycling stability (300 cycles at 1 C) and high rate capability at low N/P ratios.

Ti3CNTx MXene/rGO scaffolds directing the formation of a robust, layered SEI toward high-rate and long-cycle lithium metal batteries

The practical usage of lithium (Li) metal anodes has been hindered by the inherent uncontrolled growth of Li dendrites during stripping/plating. Approaching regulation of uniform Li deposition and robust solid-electrolyte interphase (SEI) is of significance. Herein, we utilized the unique surface chemistry of two-dimensional titanium carbonitride (Ti3CNTx) and the three-dimensional reduced graphene oxide (rGO)-based conductive scaffold architecture, to regulate the Li nucleation and SEI. The lithiophilic functional groups on Ti3CNTx improve the charge-transfer-promoted decomposition of LiN(CF3SO2)2 and resulting in the formation of a uniform SEI layer decorated with evenly distributed LiF and ordered layered Li2O, as evidenced by cryogenic transmission electron microscopy. The Ti3CNTx-rGO-Li electrodes based full cells with LiFePO4 guarantee a superior cycling lifespan over 900 cycles with a capacity retention of 77.7% at 30 C. This work demonstrates that through surface engineering and multiscale architecture design, the suppression of Li dendrites and formation of robust SEI layer can be achieved simultaneously.

A Low‐Concentration Electrolyte for High‐Voltage Lithium‐Metal Batteries: Fluorinated Solvation Shell and Low Salt Concentration Effect

AbstractConcentration of electrolyte has significant effects on performances of rechargeable batteries. Previous studies mainly focused on concentrated electrolytes. So far, only several recipes on low‐concentration electrolytes were studied, performing enhanced performance in advanced rechargeable batteries. Here, based on common electrolyte components, a low‐concentration electrolyte composed of 0.2 M lithium hexafluorophosphate (LiPF6) solvated in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) is employed for high‐voltage Li metal battery. The synergistic working mechanisms of introducing fluorine‐containing solvent in the solvated structure and low salt concentration effect are revealed, resulting in LiF‐rich, uniform, and robust solid electrolyte interphase layer and fewer unfavorable decomposition products. As a result, this low‐concentration electrolyte significantly enhances electrochemical performances of Li||Li symmetric cells and high‐voltage LiCoO2||Li batteries.

A Low-Concentration Electrolyte for High-Voltage Lithium-Metal Batteries: Fluorinated Solvation Shell and Low Salt Concentration Effect.

Concentration of electrolyte has significant effects on performances of rechargeable batteries. Previous studies mainly focused on concentrated electrolytes. So far, only several recipes on low-concentration electrolytes were studied, performing enhanced performance in advanced rechargeable batteries. Here, based on common electrolyte components, a low-concentration electrolyte composed of 0.2 M lithium hexafluorophosphate (LiPF6 ) solvated in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) is employed for high-voltage Li metal battery. The synergistic working mechanisms of introducing fluorine-containing solvent in the solvated structure and low salt concentration effect are revealed, resulting in LiF-rich, uniform, and robust solid electrolyte interphase layer and fewer unfavorable decomposition products. As a result, this low-concentration electrolyte significantly enhances electrochemical performances of Li||Li symmetric cells and high-voltage LiCoO2 ||Li batteries.

Solid electrolyte interphase layer induced electrochemical behavior diversity of aluminum foil anode for lithium ion batteries

Metal or alloy foil anode has attracted great attention for high energy density and low-cost Lithium ion batteries (LIBs). However, the intractable challenges are still the low tolerance of volume change induced pulverization and associated solid electrolyte interphase (SEI) successive reconstruction, which leads to the fast performance degradation of LIBs. The SEI layer is supposed to play an important role in maintaining good charge transport behavior, and mechanical-electrochemical stability of the foil anode during (de) lithiation. Herein, we investigate the electrochemical behavior and corresponding structure evolution of Al foil anode, which exhibit a strong SEI dependence. The thin and robust SEI layer with much abundant LiF components and LiF/Li2CO3 heterostructures exhibits good ion transport capability. This kind of SEI layer can ease the pulverization of the Al anode during (de) lithiation at a certain extent, leading to much improved mechanical-electrochemical stability, Coulombic efficiency (CE), and depolarization phenomenon. The LIBs full-cell demonstrates a gravimetric specific capacity of 120 mAh g−1 at 1 mA cm−2 as long as 400 cycles, with a nearly 100% CE. This report offers an important compensation for systematic solution that can enable great bespoke performances of foil anode for high energy density and low-cost LIBs.

Interfacial fluoride engineering enabled robust LiF-rich solid electrolyte interphase to reduce active lithium loss in rechargeable lithium battery

Active lithium loss, which is caused by parasitic reactions due to the instability of solid electrolyte interphase (SEI) on the anodes, results in fast capacity fade of batteries. Constructing robust SEI layer is an effective way to reduce active lithium loss. Herein, we propose a AgF-coated separator (AgF-CS) to facilitate robust LiF-rich SEI on the anode during initial cycle. Electrochemical analysis and microstructure investigations confirm the formation of the LiF-rich SEI on the anode induced by the fluoride-containing coating layer. The fluoride-containing interfacial layer not only effectively enhances the reversible capacity of the SiO anode even under lean electrolyte (14 μL mAh−1) condition, but also prolongs the cycling life of lithium metal batteries by reducing the consumption of electrolyte and active lithium. The initial Coulombic efficiency (ICE) of LiFePO4||SiO full cell is increased from 43.68 % to 84.18 % with pretreatment by AgF-CS. As a result, the reversible capacity of LiFePO4||SiO full cell is increased by ∼124 % in contrast with that of the unmodified one. The strategy proposed here, benefiting from the simple manufacture, provides a feasible way to alleviate active lithium loss and elevate energy density of rechargeable lithium batteries.

Rational Design of Sulfonamide‐Based Additive Enables Stable Solid Electrolyte Interphase for Reversible Zn Metal Anode

AbstractThe solid electrolyte interphase (SEI)‐forming additives strategy is of great significance for improving the cycle stability of zinc (Zn) anodes. Although various additives have been reported, the relationship between their molecular structures and SEI chemistries is poorly understood. Herein, a molecular design principle for sulfonamide‐containing additives that endow Zn anodes with a robust SEI layer is proposed. The incorporation of the benzene ring and amino group (−NH2) leads to high adsorption energy, low lowest unoccupied molecular orbital lowest unoccupied molecular orbital (LUMO), and a small highest occupied molecular orbital‐LUMO (HOMO‐LUMO) gap, facilitating the reduction process of sulfanilamide (SA) additives. Coupled with SA/ZnSO4 electrolytes, Zn|Zn symmetric cells deliver an ultralong cycle life of 4800 h (200 days) at 2 mA cm−2 and 2 mAh cm−2. Additionally, a high cumulative plated capacity (CPC) of 6000 mAh cm−2 and 2700 mAh cm−2 is also achieved at a capacity per cycle of 10 mAh cm−2 and 30 mAh cm−2, respectively. More importantly, the versatility of SA additives is also demonstrated in Zn‐V2O5, Zn‐I2, and Zn‐MnO2 full cells at a low N/P ratio (the theoretical capacity ratio between the negative and positive electrode) of 5.3, 8.3, and 4.5, respectively. This molecular structure strategy provides a promising path to develop effective SEI‐forming additives.

Electrolyte Additive Enabled Low Temperature Lithium Metal Batteries

One of the key challenges in the development of energy storage devices is the ability to operate efficiently under extremely cold environments (i.e. below -20 °C), especially for batteries in temperature-sensitive applications such as portable electronic devices, transportation, and stationary energy storage. As reported, at low temperature, the increased internal resistance and sluggish ion diffusion in batteries lead to declined charge-delivering capability, which deteriorates cell performance and eventually terminates the power output. Although lithium (Li) metal battery (LMB) with ether electrolyte is considered promising in overcoming these issues due to the low viscosity of ether solvent and its distinctive electrode structure, the low-temperature performance of LMBs remains unsatisfactory. A series of problems are observed upon the anode-electrolyte interphase, including aggravated side reactions, abnormal Li deposition, and dramatically increased solid-electrolyte interphase (SEI) resistance. Thus, building a stable SEI layer on the Li metal anode is critical for the development of low-temperature LMBs.Here, we demonstrate a dioxolane (DOL)-based electrolyte with dimethyl sulfoxide (DMSO) as the low-temperature additive, which helps to construct a robust SEI layer that possesses uniform structure and good composition consistency even under extremely cold condition. In this electrolyte, DOL works as the primary electrolyte component that defines the basic electrochemical properties, while DMSO further tunes the SEI composition to boost the low-temperature performance. To elucidate the modified microstructure and chemical composition of the SEI film, cryogenic transmission electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy are conducted to make a comprehensive investigation. Moreover, a series of electrochemical tests are conducted under extremely cold environments, and results demonstrate that the adjusted SEI is resilient to the stripping and plating cycles of Li metal at temperatures as low as -80 °C. Full cells with lithium iron phosphate as the cathode material are assembled and good electrochemical performance is achieved at -40 °C at 0.2 C. The solvation structure of DMSO added electrolyte is also investigated to fundamentally understand how it affects the SEI formation. Our work establishes fundamental insights into the low-temperature electrolyte additives and paves the road to the further applications of LMBs in harsh environments.

Stable Dendrite-Free High-Voltage Lithium Metal Batteries Enabled by Localized High Concentration Fluoroethylene Carbonate Based Electrolytes

Lithium-metal anode has been considered as the Holy Grail anode to achieve high-energy-storage batteries. However, significant challenges still exist in developing the highly stable electrolytes for Li-metal anodes and high-voltage cathodes. In this work, a localized high-concentration electrolyte (LHCE, 1.48 M FEC/EMC/HFE-LiDFOB) is proposed to realize stable dendrite-free cycling with excellent ca. 85% capacity retention and >99.5% Coulombic efficiency (CE) in LiNi0.6Co0.2Mn0.2O2 (NCM622) batteries at 0.5 C after 150 cycles. The cycling stability is largely improved, which can be associated with the formation of the robust solid electrolyte interphase layer on Li-metal anode owing to the preferential decomposition of LiDFOB salt and fluoroethylene carbonate solvent molecules. This study greatly expands knowledge of LHCE and provides a perspective of electrolyte design to achieve high-energy-density LMBs.

Designer Cathode Additive for Stable Interphases on High-Energy Anodes.

Rechargeable lithium-based batteries built with high-energy anode materials (e.g., silicon-based and silicon-derivative materials) are considered a feasible solution to satisfy the stringent requirements imposed by emerging markets, including electric vehicles and grid storage, due to their higher energy density compared to contemporary lithium-ion batteries. The robustness of the solid electrolyte interphase (SEI) layer on high-energy anodes is critical to achieve long-term and stable cycling performances of the batteries. Herein, we propose a new type of designer cathode additive (DCA), i.e., an ultrathin coating layer of elemental sulfur on the cathode, for the in situ formation of a thin and robust SEI layer on various types of high-energy anodes. The DCA elemental sulfur undergoes simultaneous oxidation and reduction paths, forming lithium alkyl sulfate (R-OSO2OLi) and poly(ethylene oxide) (PEO)-like polymers on the anode surface. The as-formed R-OSO2OLi/PEO-modified SEI layer has good lithium cation (Li+) permeability to facilitate fast ion transportation across the interphases and superior elasticity to adapt to large volume changes, which is particularly effective for improving the cycling efficiency of high-energy anodes (e.g., ca. 14-35% increase in capacity retention for the silicon-carbon composite (SiC) or silicon-tin alloy (Si-Sn)||LiFePO4 cells). The present work opens a new avenue toward the practical deployment of high-energy rechargeable lithium-based batteries.

Undervalued Roles of Binder in Modulating Solid Electrolyte Interphase Formation of Silicon-Based Anode Materials.

The use of silicon (Si) for lithium (Li) storage has the significant merits of an ultrahigh theoretical specific capacity and a low working platform, potentially enabling a high-energy-density Li-ion battery (LIB). However, the Si itself undergoes a huge volume variation (>300%) upon the lithiation/delithiation process, which inevitably causes material pulverization and electrode cracking as well as ceaselessly repairs the solid electrolyte interphase (SEI), eventually resulting in a rapid capacity decay of the Si anode. Presently, using a robust binder has been well-recognized as an effective solution, which is generally explained by its robust mechanical properties that enable the electrode integrity of the Si anode during the repeated cycling process. Comparatively, the roles of the binder in modulating the chemical composition and the spatial distribution of the Si-based SEI layer are overlooked. This review will specifically provide an overview of the correlation between the binder species and SEI properties. The binder species have a critical role of inducing a robust SEI layer by selectively allowing the electrolyte salt and the solvent to connect the Si surface in the initial discharging process. Finally, we conclude by providing the perspective of the binder design based on interfacial chemistries and new characterization techniques.

Stable Cycle Performance of a Phosphorus Negative Electrode in Lithium-Ion Batteries Derived from Ionic Liquid Electrolytes.

Although high-capacity negative electrode materials are seen as a propitious strategy for improving the performance of lithium-ion batteries (LIBs), their advancement is curbed by issues such as pulverization during the charge/discharge process and the formation of an unstable solid electrolyte interphase (SEI). In particular, electrolytes play a vital role in determining the properties of an SEI layer. Thus, in this study, we investigate the performance of a red phosphorus/acetylene black composite (P/AB) prepared by high-energy ball milling as a negative electrode material for LIBs using organic and ionic liquid (IL) electrolytes. Galvanostatic tests performed on half cells demonstrate high discharge capacities in the 1386-1700 mAh (g-P/AB)-1 range along with high Coulombic efficiencies of 85.3-88.2% in the first cycle, irrespective of the electrolyte used. Upon cycling, the Li[FSA]-[C2C1im][FSA] (FSA- = bis(fluorosulfonyl)amide and C2C1im+ = 1-ethyl-3-methylimidazolium) IL electrolyte (2:8 in mol) demonstrates a high capacity retention of 78.8% after 350 cycles, whereas significant capacity fading is observed in the Li[PF6] and Li[FSA] organic electrolytes. Electrochemical impedance spectroscopy conducted with cycling revealed lower interfacial resistance in the IL electrolyte than in the organic electrolytes. Scanning electron microscopy and X-ray photoelectron spectroscopy after cycling in different electrolytes evinced that the IL electrolyte facilitates the formation of a robust SEI layer comprising multiple layers of sulfur species resulting from FSA- decomposition. A P/AB|LiFePO4 full cell using the IL electrolyte showed superior capacity retention than organic electrolytes and a high energy density under ambient conditions. This work not only illuminates the improved performance of a phosphorous-based negative electrode alongside ionic liquid electrolytes but also displays a viable strategy for the development of high-performance LIBs, especially for large-scale applications.