All-solid-state Batteries Research Articles

LiTaO3 mixing effects to suppress side reactions at the LiNi0.8Co0.1Mn0.1O2 cathode and Li5.3PS4.3Cl1.7 solid electrolyte of all-solid-state lithium batteries

Suppressing the side reactions at the solid electrolyte-electrode interface in all-solid-state battery (ASSB) is very important aspect of improving battery performance. Coating an electrochemically stable material on the surface of cathode has been used to suppress the side reactions occurring at interface between solid electrolyte and cathode. However, to achieve effective suppression, the thickness of the coating film must be thin and uniform. Moreover, an expensive ethoxide series typically must be used as a starting material. In this study, LiTaO3 coating material was simply mixed with the solid electrolyte to measure the effect of suppressing side reactions. To synthesize the solid electrolyte Li5.3PS4.3Cl1.7 and the mixing material LiTaO3, high-energy ball milling and wet milling methods were used, respectively. The structural characteristics of the prepared solid electrolytes were studied by powder X-ray diffraction. The LiTaO3 mixed solid electrolyte based ASSB showed a high discharge capacity of 177.3 mAh/g in the initial cycle, whereas the bare solid electrolyte (Li5.3PS4.3Cl1.7) based ASSB showed a discharge capacity of 159.1 mAh/g. To understand the side reactions, electrochemical impedance spectroscopy (EIS) analysis was performed after galvanostatic charge-discharge cycles. The EIS analysis confirmed that the side reaction between a solid electrolyte and a cathode was effectively suppressed in LiTaO3 mixed solid electrolyte based ASSBs.

ZnO Substitution in Argyrodite Li5.5+3xZnxP1‐xOxS4.5‐xBr1.5 Electrolyte with Enhanced Interface Performance for All‐Solid‐State Battery

AbstractArgyrodite sulfide solid electrolytes (SSEs) have been attracting more concentration in ionic conductivity, crystal structure, and mechanical properties. Nevertheless, shortcomings of SSEs like poor air‐vapor stability and interface reactions limit the wider application in batteries. Herein, a double‐element ZnO substitution strategy is applied to enhancing Li5.5PS4.5Br1.5 Argyrodite electrolyte structure stability and property, Li5.5PS4.5Br1.5 electrolyte with a small amount of ZnO substitution to P and S. Li5.5+3xZnxP1‐xOxS4.5‐xBr1.5 solid electrolytes have achieved improved performance, interface composition also has changed, and crystal structure is becoming more stable. Specifically, LPSBr1.5‐4 %ZnO exhibits the most promising comprehensive properties, more expanded lithium pathway and crystal cell size, 2.25 mS cm−1 ionic conductivity at 25 °C, 65 % electronic conductivity decline, and air stability enhancement. Moreover, LPSBr1.5‐4 %ZnO show decent lithium compatibility and dendrite suppression capability, LPSBr1.5‐4 %ZnO can continue cycling for more than 800 h at 0.1 mA cm−2 in Li symmetric cell, and critical current density has reached 1.4 mA cm−2. More importantly, an all‐solid‐state battery (ASSB) with LPSBr1.5‐4 %ZnO electrolyte can cycle with 130 mAh g−1 capacity and more than 120 cycles in LiCoO2|SSE|In‐Li cell. Our work might provide a strategy to promote structure stability and electrochemical durability, and how element substitution affects ionic transport pathway and crystal structure.

Halide Superionic Conductors for All-Solid-State Batteries: Effects of Synthesis and Composition on Lithium-Ion Conductivity.

Owing to their high-voltage stabilities, halide superionic conductors such as Li3YCl6 recently emerged as promising solid electrolyte (SE) materials for all-solid-state batteries (ASSBs). It has been shown that by either introducing off-stoichiometry in solid-state (SS) synthesis or using a mechanochemical (MC) synthesis method the ionic conductivities of Li3-3xY1+xCl6 can increase up to an order of magnitude. The underlying mechanism, however, is unclear. In the present study, we adopt a hopping frequency analysis method of impedance spectra to reveal the correlations in stoichiometry, crystal structure, synthesis conditions, Li+ carrier concentrations, hopping migration barriers, and ionic conductivity. We show that unlike the conventional Li3YCl6 made by SS synthesis, mobile Li+ carriers in the defect-containing SS-Li3-3xY1+xCl6 (0 < x < 0.17) and MC-Li3-3xY1+xCl6 are generated with an activation energy and their concentration is dependent on temperature. Higher ionic conductivities in these samples arise from a combination of a higher Li+ carrier concentration and lower migration energy barriers. A new off-stoichiometric halide (Li2.61Y1.13Cl6) with the highest ionic conductivity (0.47 mS cm-1) in the series is discovered, which delivers exceptional cycling performance (∼90% capacity retention after 1000 cycles) in ASSB cells equipped with an uncoated high-energy LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. This work sheds light on the thermal activation process that releases trapped Li+ ions in defect-containing halides and provides guidance for the future development of superionic conductors for all-solid-state batteries.

In-Situ Construction of Electronically Insulating and Air-Stable Ionic Conductor Layer on Electrolyte Surface and Grain Boundary to Enable High-Performance Garnet-Type Solid-State Batteries.

Lithophobic Li2CO3/LiOH contaminants and high-resistance lithium-deficient phases produced from the exposure of garnet electrolyte to air leads to a decrease in electrolyte ion transfer ability. Additionally, garnet electrolyte grain boundaries (GBs) with narrow bandgap and high electron conductivity are potential channels for current leakage, which accelerate Li dendrites generation, ultimately leading to short-circuiting of all-solid-state batteries (ASSBs). Herein, a stably lithiophilic Li2ZO3 is in situ constructed at garnet electrolyte surface and GBs by interfacial modification with ZrO2 and Li2CO3 (Z+C) co-sintering to eliminate the detrimental contaminants and lithium-deficient phases. The Li2ZO3 formed on the modified electrolyte (LLZTO-(Z+C)) surface effectively improves the interfacial compatibility and air stability of the electrolyte. Li2ZO3 formed at GBs broadens the energy bandgaps of LLZTO-(Z+C) and significantly inhibits lithium dendrite generation. More Li+ transport paths found in LLZTO-Z+C by first-principles calculations increase Li+ conductivity from 1.04×10-4 to 7.45×10-4Scm-1. Eventually, the Li|LLZTO-(Z+C)|Li symmetric cell maintains stable cycling for over 2000h at 0.8mAcm-2. The capacity retention of LiFePO4|LLZTO-(Z+C)|Li battery retains 70.5% after 5800 ultralong cycles at 4C. This work provides a potential solution to simultaneously enhance the air stability and modulate chemical characteristics of the garnet electrolyte surface and GBs for ASSBs.

Processing-structure-property relationships in practical thin solid-electrolyte separators for all-solid-state batteries

Scalable processing of thin and robust solid-electrolyte (SE) separators is key for the commercialization of high-energy all-solid-state batteries (ASSBs). Herein, we report the preparation of Li6PS5Cl-based thin SE separators incorporating suitable binders for potential use in ASSBs by two scalable wet processing techniques: tape-casting with nitrile-butadiene rubber (NBR) and calendering with carboxylated nitrile butadiene rubber (XNBR). By means of tensile testing and electrochemical impedance spectroscopy, the influence of processing on the mechanical as well as the electrochemical properties of the resulting thin SE separators is investigated. A trade-off between the mechanical and electrochemical properties is observed, which is due to the inextricably linked microstructures (particle size, binder content and distribution, and porosity) induced by the two different processes. Thin SE separators prepared using the tape-casting method with the more well-distributed binder network demonstrate superior tensile mechanical properties compared to the ones prepared by the calendering method. The results provide insights into the processing-structure-property relationships of the thin SE separators, which will contribute to advancing the application of practical thin solid electrolytes in ASSBs.

Improved ionic conductivity and Li7P3S11 solid electrolyte based all-solid state batteries for practical applications

Improved ionic conductivity and Li7P3S11 solid electrolyte based all-solid state batteries for practical applications

Designing Reliable Cathode System for High-Performance Inorganic Solid-State Pouch Cells.

All-solid-state batteries (ASSBs) based on inorganic solid electrolytes fascinate a large body of researchers in terms of overcoming the inferior energy density and safety issues of existing lithium-ion batteries. To date, the cathode designs in the ASSBs achieve remarkable achievements, adding the urgency of scaling up the battery system toward inorganic solid-state pouch cell configuration for the application market. Herein, the recent developments of cathode materials and the design considerations for their application in the pouch cell format are reviewed to straighten out the roadmap of ASSBs. Specifically, the intercalation compounds and the conversion materials with conversion chemistries are highlighted and discussed as two potentially valuable material types. This review focuses on the basic electrochemical mechanisms, mechanical contact issues, and sheet-type structure in inorganic solid-state pouch cells with corresponding perspectives, thus guiding the future research direction. Finally, the benchmarks for manufacturing inorganic solid-state pouch cells to meet practical high energy density targets are provided in this review for the development of commercially viable products.

Crack‐Free Single‐Crystalline LiNiO2 for High Energy Density All‐Solid‐State Batteries

AbstractSingle‐crystalline layered oxide (LiNi1‐x‐yMnxCoyO2) cathodes have been found to exhibit exceptional electrochemical properties when coupled with various inorganic solid electrolytes (ISEs) in all‐solid‐state batteries (ASSBs). Their advantages stem from the robust morphological integrity with the absence of grain boundaries and the high electrochemical oxidative stability. Here, ASSBs featuring single‐crystalline LiNiO2 (LNO) with the highest Ni content are reported, offering a high theoretical specific capacity of 275 mAh g‐1 alongside a high average discharge voltage (3.7 V vs Li+/Li). Through a careful investigation, it is demonstrated that micron‐sized single‐crystalline LNO (µSC‐LNO) composite cathodes with a halide ISE exhibit a high initial discharge capacity of 205 mAh g‐1 with an outstanding cycle performance over 200 cycles in room‐temperature ASSBs. The significance of engineering parameters is emphasized, such as particle size and specific density, in promoting a homogeneous and fast Li+ transport within the composite cathodes. Furthermore, the formation of undesirable interphase between the halide ISE in the cathode and sulfide ISE separator is elucidated, which may be a critical factor impeding long‐term cyclability of ASSBs. This work provides insights into the design of composite cathodes for high‐energy‐density ASSBs.

Two in one: The use of hexagonal copper sulfide (CuS) nanoparticles as a bifunctional high-performance cathode and as a reinforced electrolyte additive for an all-solid-state lithium battery

All Solid-State Batteries (ASSBs) based on solid polymer electrolytes (SPEs) have improved safety, energy, and power densities than conventional liquid electrolyte-based Lithium-ion batteries (LIBs). However, two significant obstacles still need to be addressed, including the low ionic conductivities and the low interfacial contact between ASSB components. This study involves the fabrication of hexagonal CuS nanoparticles by a one-step hydrothermal method and uses them for both cathode and solid electrolyte formulation functions. The reasonable ionic conductivity of 4.68 × 10−4 S.cm−1 at 60℃ and the instant transport number of 0.86 of the designed CuS filler-incorporated solid electrolyte offered great promise for ASSBs applications. In particular, the CuS filler-incorporated solid electrolyte exhibited ceaseless and prompt Li-ion transportation kinetics and delivered a dendrite resistance capability over 200 cycles of stripping/plating of Li. In addition, the Li metal solid-state battery is also verified using CuS as the cathode and SPE electrolyte (PEO/LiTFSI/CuS SPE) system. It offers an initial discharge capacity of up to 695 mAh/g and keeps an average capacity of ∼ 365 mAh/g after 50 cycles at a current density of 0.5C. Thus, this study introduced a simple but effective solution to mitigate the dendrite problems associated with solid polymer electrolytes by using CuS as a durable inactive filler.

In-situ cathode coating for all-solid-state batteries by freeze-drying technology

All solid-state batteries (ASSBs) are considered in the next generation of energy storage, but their active material ratio is low and cathode interface reactions are severe.To overcome these two challenges, a layer of fast ion conductor Li3InCl6 is in-situ synthesized to realize uniform coating on LiCoO2 surface by freeze drying technology, which effectively improves active material proportions/ion transportation capability in the cathode, and prevents interfacial degradation between sulfide solid electrolyte and LiCoO2. The resultant Li-anode ASSBs show excellent electrochemical performances, including 7000 cycles at 20 C (9.4 mA/cm2), unprecedented current rates of 70 C and high loading of 15 mAh/cm2 (110 mg/cm2). The ASSB achieved an energy density of 340 Wh/kg. These encouraging results make future practical applications of high-energy-density ASSB with high cathode loadings and fast-charging capabilities possible.

Unveiling the dynamic change in the ionic conductivity of a solid-state binary mixture comprising an organic ionic plastic crystal and LiBF4

The binary composites of organic ionic plastic crystals (OIPCs) and lithium salts are a promising new class of solid electrolytes for all-solid-state batteries (ASSBs). One of the primary areas of research to enable their application into battery devices is to understand their complex physicochemical features, in particular their phase behaviors in response to changing compositions and the ensuing correlation with ionic conductivities. Herein, the phase behaviors and transport properties of binary OIPC–lithium-salt composites are reported over the full compositional window using N-ethyl-N-methylpyrrolidinium tetrafluoroborate ([C2mpyr][BF4]) and lithium tetrafluoroborate (LiBF4). The phase diagram of the Lix[C2mpyr]1–x[BF4] electrolyte was constructed and used to not only provide valuable insights into the key composition–property relationships but also guide the selection of Li+ concentrations in OIPC composites for Li+-based ASSBs. Differential scanning calorimetry and 19F nuclear magnetic resonance (NMR) spectroscopy revealed the emergence of intermediate secondary phases as the composition was varied. Significant and sudden variations in ionic conductivity at or near the Li+-concentration-driven phase transitions were attributed to the presence of these intermediate phases which ultimately provide the dominant contribution to the ionic conductivity of the Lix[C2mpyr]1–x[BF4] electrolyte.

Enabling High Performance Bismuth Trifluoride Cathode by Engineering the Cathode/Electrolyte Interface in Sulfide‐Based All Solid State Batteries

AbstractMetal fluorides are conversion‐type cathodes that have the potential to boost the energy densities of next generation lithium‐ion batteries (LIBs). However, the study of non‐transitional metal fluorides (NTMFs) such as bismuth trifluoride (BiF3) is limited due to the challenges on the construction of a stable electrochemical reaction interfaces with liquid electrolyte, although it shows advantages on high electrochemical potential, moderately high theoretical capacity and low voltage hysteresis. Moreover, the performance of BiF3 in all solid state batteries (ASSBs) has not been explored. In this contribution, the micro‐sized commercial BiF3 is successfully coated with a cyclic polyacrylonitrile (cPAN) and refined its size to nanoscale. The refined nano‐sized BiF3@cPAN uniformly disperses in the solid electrode and delivers an initial discharge capacity of 330 and 200 mAh g−1 after 250 cycles in sulfide electrolyte based ASSBs. Furthermore, the voltage hysteresis of the ASSBs reaches a record low value of 180 mV. Postmortem analysis shows that the elastic coating hindered the undesirable interface side reaction and rendered the BiF3 with excellent cycle reversibility. This work demonstrates the crucial role of stable interfaces for BiF3 in preventing electrolyte decomposition, which promotes the practical adoption of BiF3 cathode with higher specific energy for LIBs.

Rate-limiting mechanism of all-solid-state battery unravelled by low-temperature test-analysis flow

All-solid-state batteries (ASSBs) with potentially improved energy density and safety have been recognized as the next-generation energy storage technology. However, their performances at subzero temperatures are rarely investigated, with rate-limiting process/mechanisms unidentified. Herein, the rate-limiting process/mechanisms for -40℃ ASSBs are accurately identified/analyzed by developing a standard test-analysis flow model. We reveal that the rate-limiting processes of LiCoO2 (LCO)+sulfide solid electrolyte (SE) composite cathode are the sluggish ion transport across unfavorable interfacial reaction layer and charge transfer at damaged LCO cathode surface. After inserting Li2ZrO3 (LZO) coating layer to suppress interfacial reactions, the rate-limiting process of LCO@LZO+sulfide SE composite cathode turns into the arduous ion transport across the interphase composed of the self-decomposition products of sulfide SE. Interestingly, by replacing sulfide SE with halide SE, LCO+halide SE composite cathode delivers fast charge transfer and the ion conduction through the thick SE separator becomes the rate-limiting process, thus enabling a superior capacity retention rate (41.4 %) at -40℃. Furthermore, the capacity retention of ASSB coupling LCO+halide SE composite cathode with Si anode can be boosted from 28.9 % to 38.6 % at -40℃ by employing superionic conductor with low activation energy. These successful identifications/modulations on rate-limiting process/mechanism and improvements on low-temperature performance demonstrate the significant role of this test-analysis flow in propelling the development of low-temperature ASSBs.

On the Origin of Anode and Cathode Contributions to the Impedance of All‐Solid‐State Batteries

AbstractAll‐solid‐state‐batteries (ASSBs) are considered as promising next‐generation batteries in order to achieve improvements in both energy density and safety. The complex electrochemical processes in ASSBs taking place on different time scales can be probed by means of electrochemical impedance spectroscopy. However, the separation of anode and cathode contributions to the impedance and the understanding of the underlying electrochemical processes in both electrodes is a challenging task. Here, we compare the impedance spectrum of a prototypical full ASSB to those of symmetric cells anode | separator | anode and cathode | separator | cathode. We use Ni‐rich polycrystalline LiNi0.85Co0.10Mn0.05O2 particles as active material inside the composite cathode and an indium‐lithium alloy as anode. Based on the comparison, we show that the charge transfer process inside the cathode is remarkably fast, i. e., even faster than observed for cathodes of batteries with liquid electrolyte. Our results give indication that the differences in the time scales of cathode and anode processes are related to the distinct transport properties of interphases inside the cathode and at the anode | separator interface, respectively.

Superior Low-Temperature All-Solid-State Battery Enabled by High-Ionic-Conductivity and Low-Energy-Barrier Interface.

All-solid-state batteries (ASSBs) working at room and mild temperature have demonstrated inspiring performances over recent years. However, the kinetic attributes of the interface applicable to the subzero temperatures are still unidentified, restricting the low-temperature interface design and operation. Herein, a host of cathode interfaces are constructed and investigated to unlock the critical interface features required for cryogenic temperatures. The unstable interface between LiNi0.90Co0.05Mn0.05O2 (Ni90) and Li6PS5Cl (LPSC) sulfide solid electrolyte (SE) results in unfavorable cathode-electrolyte interphase (CEI) and sluggish lithium-ion transport across the CEI. After inserting a Li2ZrO3 (LZO) coating layer, the activation energy of the Ni90@LZO/sulfide SE interface can be reduced from 60.19 kJ mol-1 to 41.39 kJ mol-1 owing to the suppressed interfacial reactions. Through replacing the LPSC SE and LZO coating layer by the Li3InCl6 (LIC) halide SE, both a highly stable interface and low activation energy (25.79 kJ mol-1) can be achieved, thus realizing an improved capacity retention (26.9%) at -30 °C for the Ni90/LIC/LPSC/Li-In ASSB. Moreover, theoretical evaluation clarifies that cathode/SE interfaces with high ionic conductivity and low energy barrier are favorable to the Li+ conduction through the interphase and the Li+ transfer across the cathode/interphase interface. These critical understandings may provide guidance for low-temperature interface design in ASSBs.

A High‐Voltage Solid State Electrolyte Based on Spinel‐Like Chloride Made of Low‐Cost and Abundant Resources

AbstractRecently, halide solid state electrolytes (SSEs) have received great attention owing to their fast ionic conductivity, high oxidation potential, and good chemical and electrochemical compatibility with high voltage cathode materials. However, most of reported halide SSEs contain rather rare and expensive elements, which hinders their sustainable utilizations in practical batteries. Here in this work, under the guidance of systematic modelling based on the density functional theory (DFT), a low‐cost alternative is developed through optimizing the lattice chemistry in a recently identified spinel‐like chloride Li2CrCl4 into Li5/3Cr1/3Zr1/3Cl4 for remarkably enhanced ionic conductivity and stable electrochemical window with respect to the Li‐anode. This new phase has then been synthesized successfully, delivering an ionic conductivity over 1200 times of that of the pristine phase Li2CrCl4, in addition to a high oxidation potential (up to 4.1 V vs Li/Li+) to enable outstanding interfacial compatibility with high voltage cathodes. Such a high‐voltage and fast Li‐ion conducting solid‐state electrolyte is expected to provide a highly desirable basis toward developing high energy‐density all solid‐state batteries (ASSBs) using economical and Earth‐rich elements.

Surface Reconditioning of Lithium Metal Electrodes by Laser Treatment for the Industrial Production of Enhanced Lithium Metal Batteries

AbstractIncorporating lithium metal anodes in next‐generation batteries promises enhanced energy densities. However, lithium's reactivity results in the formation of a native surface film, affecting battery performance. Therefore, precisely controlling the chemical and morphological surface condition of lithium metal anodes is imperative for producing high‐performance lithium metal batteries. This study demonstrates the efficacy of laser treatment for removing superficial contaminants from lithium metal substrates. To this end, picosecond‐pulsed laser radiation is proposed for modifying the surface of lithium metal substrates. Scanning electron microscopy (SEM) revealed that different laser process regimes can be exploited to achieve a wide spectrum of surface morphologies. Energy‐dispersive X‐ray spectroscopy (EDX) confirmed substantial reductions of ≈80% in oxidic and carbonaceous surface species. The contamination layer removal translated into interfacial resistance reductions of 35% and 44% when testing laser‐cleaned lithium metal anodes in symmetric all‐solid‐state batteries (ASSBs) with lithium phosphorus sulfur chloride (LPSCl) and lithium lanthanum zirconium oxide (LLZO) solid electrolytes, respectively. Finally, a framework for integrating laser cleaning into industrial battery production is suggested, evidencing the industrial feasibility of the approach. In summary, this work advances the understanding of lithium metal surface treatments and serves as proof of principle for its industrial applicability.

Size-controlled wet-chemical synthesis of sulfide superionic conductors for high-performance all-solid-state batteries

The escalating concerns surrounding the safety issues tied to the flammability of organic liquid electrolytes in conventional lithium-ion batteries have catalyzed the evolution and advancement of all-solid-state batteries (ASSBs) integrated with solid electrolytes (SEs). Among various SE materials, sulfide-based lithium argyrodite has risen to prominence owing to its high ionic conductivity and ease of processability. Despite the wet-chemical processing method being considered advantageous for the synthesis of sulfide SEs, due to its inherent simplicity, potential scalability, and cost-effectiveness, certain challenges persist. These primarily pertain to achieving high ionic conductivity and mitigating interfacial resistance between the electrode and the SEs. Addressing these challenges, this study presents a novel, scalable, and cost-efficient wet synthesis approach to produce superionic conductive sulfide-based SEs. This method involves careful regulation of the nucleation rate and strategic substitution of elements to control particle size and enhance ionic conductivity. The resultant Li5.5PS4.5Cl1.5 SEs synthesized show a uniform size distribution (average particle diameter = 7 μm), coupled with a high ionic conductivity of 4.98 mS cm−1. This level of ionic conductivity is either comparable to or exceeds those produced through dry processes. The ability to control particle size optimizes the contact interface between the electrode and the electrolyte, reducing interfacial resistance and increasing discharge capacity. Consequently, this method paves the way for mass production of high-quality sulfide SEs. The findings of this study serve to further the development of high-performing ASSBs, making them suitable for implementation in high output power and long cruising distance electric vehicles, pushing the envelope for battery-powered transportation solutions.

Bottom Deposition Enables Stable All-Solid-State Batteries with Ultrathin Lithium Metal Anode.

Modern strides in energy storage underscore the significance of all-solid-state batteries (ASSBs) predicated on solid electrolytes and lithium (Li) metal anodes in response to the demand for safer batteries. Nonetheless, ASSBs are often beleaguered by non-uniform Li deposition during cycling, leading to compromised cell performance from internal short circuits and hindered charge transfer. In this study, the concept of "bottom deposition" is introduced to stabilize metal deposition based on the lithiophilic current collector and a protective layer composed of a polymeric binder and carbon black. The bottom deposition, wherein Li plating ensues between the protective layer and the current collector, circumvents internal short circuits and facilitates uniform volumetric changes of Li. The prepared functional binder for the protective layer presents outstanding mechanical robustness and adhesive properties, which can withstand the volume expansion caused by metal growth. Furthermore, its excellent ion transfer properties promote uniform Li bottom deposition even under a current density of 6 mA·cm-2. Also, scanning electron microscopy analysis reveals a consistent plating/stripping morphology of Li after cycling. Consequently, the proposed system exhibits enhanced electrochemical performance when assessed within the ASSB framework, operating under a configuration marked by a high Li utilization rate reliant on an ultrathin Li.

Boosting the Interfacial Stability of the Li6PS5Cl Electrolyte with a Li Anode via In Situ Formation of a LiF-Rich SEI Layer and a Ductile Sulfide Composite Solid Electrolyte.

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li6PS5Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.