Solvent‐Free Synthesis of Thin,Flexible, Nonflammable Garnet‐Based Composite Solid Electrolyte for All‐Solid‐State Lithium Batteries

Thin solid‐state electrolytes with nonflammability, high ionic conductivity, low interfacial resistance, and good processability are urgently required for next‐generation safe, high energy density lithium metal batteries. Here, a 3D Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZTO) self‐supporting framework interconnected by polytetrafluoroethylene (PTFE) binder is prepared through a simple grinding method without any solvent. Subsequently, a garnet‐based composite electrolyte is achieved through filling the flexible 3D LLZTO framework with a succinonitrile solid electrolyte. Due to the high content of garnet ceramic (80.4 wt%) and high heat‐resistance of the PTFE binder, such a composite electrolyte film with nonflammability and high processability exhibits a wide electrochemical window of 4.8 V versus Li/Li⁺ and high ionic transference number of 0.53. The continuous Li⁺ transfer channels between interconnected LLZTO particles and succinonitrile, and the soft electrolyte/electrode interface jointly contribute to a high ambient‐temperature ionic conductivity of 1.2 × 10^?4 S cm^?1 and excellent long‐term stability of the Li symmetric battery (stable at a current density of 0.1 mA cm^?2 for over 500 h). Furthermore, as‐prepared LiFePO₄|Li and LiNi_0.5Mn_0.3Co_0.2O₂|Li batteries based on the thin composite electrolyte exhibit high discharge specific capacities of 153 and 158 mAh g^?1 respectively, and desirable cyclic stabilities at room temperature.     

Incorporating Solvate and Solid Electrolytes for All‐Solid‐State Li2S Batteries with High Capacity and Long Cycle Life

The development of all‐solid‐state lithium–sulfur batteries is hindered by the poor interfacial properties at solid electrolyte (SE)/electrode interfaces. The interface is modified by employing the highly concentrated solvate electrolyte, (MeCN)₂?LiTFSI:TTE, as an interlayer material at the electrolyte/electrode interfaces. The incorporation of an interlayer significantly improves the cycling performance of solid‐state Li₂S batteries compared to the bare counterpart, exhibiting a specific capacity of 760 mAh g^?1 at cycle 100 (330 mAh g^?1 for the bare cell). Electrochemical impedance spectroscopy shows that the interfacial resistance of the interlayer‐modified cell gradually decreases as a function of cycle number, while the impedance of the bare cell remains almost constant. Cross‐section scanning electron microscopy (SEM)/ energy dispersive X‐ray spectroscopy (EDS) measurements on the interlayer‐modified cell confirm the permeation of solvate into the cathode and the SE with electrochemical cycling, which is related to the decrease in cell impedance. In order to mimic the full permeation of the solvate across the entire cell, the solvate is directly mixed with the SE to form a “solvSEM” electrolyte. The hybrid Li₂S cell using a solvSEM electrolyte exhibits superior cycling performance compared to the solid‐state cells, in terms of Li₂S loading, Li₂S utilization, and cycling stability. The improved performance is due to the favorable ionic contact at the battery interfaces.     

Perovskite Membranes with Vertically Aligned Microchannels for All‐Solid‐State Lithium Batteries

Perovskite‐type solid‐state electrolytes exhibit great potential for the development of all‐solid‐state lithium batteries due to their high Li‐ion conductivity (approaching 10^?3 S cm^?1), wide potential window, and excellent thermal/chemical stability. However, the large solid–solid interfacial resistance between perovskite electrolytes and electrode materials is still a great challenge that hinders the development of high‐performance all‐solid‐state lithium batteries. In this work, a perovskite‐type Li_0.34La_0.51TiO₃ (LLTO) membrane with vertically aligned microchannels is constructed by a phase‐inversion method. The 3D vertically aligned microchannel framework membrane enables more effective Li‐ion transport between the cathode and solid‐state electrolyte than a planar LLTO membrane. A significant decrease in the perovskite/cathode interfacial resistance, from 853 to 133 Ω cm², is observed. It is also demonstrated that full cells utilizing LLTO with vertically aligned microchannels as the electrolyte exhibit a high specific capacity and improved rate performance.     

A Lithium Amide‐Borohydride Solid‐State Electrolyte with Lithium‐Ion Conductivities Comparable to Liquid Electrolytes

High ionic conductivity of up to 6.4 × 10^?3 S cm^?1 near room temperature (40 °C) in lithium amide‐borohydrides is reported, comparable to values of liquid organic electrolytes commonly employed in lithium‐ion batteries. Density functional theory is applied coupled with X‐ray diffraction, calorimetry, and nuclear magnetic resonance experiments to shed light on the conduction mechanism. A Li₄Ti₅O₁₂ half‐cell battery incorporating the lithium amide‐borohydride electrolyte exhibits good rate performance up to 3.5 mA cm^?2 (5 C) and stable cycling over 400 cycles at 1 C at 40 °C, indicating high bulk and interfacial stability. The results demonstrate the potential of lithium amide‐borohydrides as solid‐state electrolytes for high‐power lithium‐ion batteries.     

Rational Design of Hierarchical “Ceramic‐in‐Polymer” and “Polymer‐in‐Ceramic” Electrolytes for Dendrite‐Free Solid‐State Batteries

Solid polymer electrolytes as one of the promising solid‐state electrolytes have received extensive attention due to their excellent flexibility. However, the issues of lithium (Li) dendrite growth still hinder their practical applications in solid‐state batteries (SSBs). Herein, composite electrolytes from “ceramic‐in‐polymer” (CIP) to “polymer‐in‐ceramic” (PIC) with different sizes of garnet particles are investigated for their effectiveness in dendrite suppression. While the CIP electrolyte with 20 vol% 200 nm Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) particles (CIP‐200 nm) exhibits the highest ionic conductivity of 1.6 × 10^?4 S cm^?1 at 30 °C and excellent flexibility, the PIC electrolyte with 80 vol% 5 µm LLZTO (PIC‐5 µm) shows the highest tensile strength of 12.7 MPa. A sandwich‐type composite electrolyte (SCE) with hierarchical garnet particles (a PIC‐5 µm interlayer sandwiched between two CIP‐200 nm thin layers) is constructed to simultaneously achieve dendrite suppression and excellent interfacial contact with Li metal. The SCE enables highly stable Li plating/stripping cycling for over 400 h at 0.2 mA cm^?2 at 30 °C. The LiFePO₄/SCE/Li cells also demonstrate excellent cycle performance at room temperature. Fabricating sandwich‐type composite electrolytes with hierarchical filler designs can be an effective strategy to achieve dendrite‐free SSBs with high performance and high safety at room temperature.     

Germanium Thin Film Protected Lithium Aluminum Germanium Phosphate for Solid‐State Li Batteries

Solid‐state Li batteries using Na⁺ superionic conductor type solid electrolyte attracts wide interest because of its safety and high theoretical energy density. The NASCION type solid electrolyte LAGP (Li_1.5Al_0.5Ge_0.5P₃O₁₂) shows favorable conductivity as well as good mechanical strength to prevent Li dendrite penetration. However, the instability of LAGP with Li metal remains a great challenge. In this work, an amorphous Ge thin film is sputtered on an LAGP surface, which can not only suppress the reduction reaction of Ge⁴⁺ and Li, but also produces intimate contact between the Li metal and the LAGP solid electrolyte. The symmetric cell with the Ge‐coated LAGP solid electrolyte shows superior stability and cycle performance for 100 cycles at 0.1 mA cm^?2. A quasi‐solid‐state Li–air battery has also been assembled to further demonstrate this advantage. A stable cycling performance of 30 cycles in ambient air can be obtained. This work helps to achieve a stable and ionic conducting interface in solid‐state Li batteries.     

Ultrathin,Flexible Polymer Electrolyte for Cost‐Effective Fabrication of All‐Solid‐State Lithium Metal Batteries

All‐solid‐state batteries are promising candidates for the next‐generation safer batteries. However, a number of obstacles have limited the practical application of all‐solid‐state Li batteries (ASSLBs), such as moderate ionic conductivity at room temperature. Here, unlike most of the previous approaches, superior performances of ASSLBs are achieved by greatly reducing the thickness of the solid‐state electrolyte (SSE), where ionic conductivity is no longer a limiting factor. The ultrathin SSE (7.5 µm) is developed by integrating the low‐cost polyethylene separator with polyethylene oxide (PEO)/Li‐salt (PPL). The ultrathin PPL shortens Li⁺ diffusion time and distance within the electrolyte, and provides sufficient Li⁺ conductance for batteries to operate at room temperature. The robust yet flexible polyethylene offers mechanical support for the soft PEO/Li‐salt, effectively preventing short‐circuits even under mechanical deformation. Various ASSLBs with PPL electrolyte show superior electrochemical performance. An initial capacity of 135 mAh g^?1 at room temperature and the high‐rate capacity up to 10 C at 60 °C can be achieved in LiFePO₄/PPL/Li batteries. The high‐energy‐density sulfur cathode and MoS₂ anode employing PPL electrolyte also realize remarkable performance. Moreover, the ASSLB can be assembled by a facile process, which can be easily scaled up to mass production.     

A Metal Organic Framework Derived Solid Electrolyte for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are currently considered as promising candidates for next‐generation energy storage technologies. However, their practical application is hindered by the critical issue of the polysulfide‐shuttle. Herein, a metal organic framework (MOF)‐derived solid electrolyte is presented to address it. The MOF solid electrolyte is developed based on a Universitetet i Oslo (UIO) structure. By grafting a lithium sulfonate (‐SO₃Li) group to the UIO ligand, both the ionic conductivity and the polysulfide‐suppression capability of the resulting ‐SO₃Li grafted UIO (UIOSLi) solid electrolyte are greatly improved. After integrating a Li‐based ionic liquid (Li‐IL), lithium bis(trifluoromethanesulfonyl)imide in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide, the resulting Li‐IL/UIOSLi solid electrolyte exhibits an ionic conductivity of 3.3 × 10^?4 S cm^?1 at room temperature. Based on its unique structure, the Li‐IL/UIOSLi solid electrolyte effectively restrains the polysulfide shuttle and suppresses lithium dendritic growth. Lithium–sulfur cells with the Li‐IL/UIOSLi solid electrolyte and a Li₂S₆ catholyte show stable cycling performance that preserves 84% of the initial capacity after 250 cycles with a capacity‐fade rate of 0.06% per cycle.     

A Flexible Solid Electrolyte with Multilayer Structure for Sodium Metal Batteries

Solid electrolytes (SEs) can potentially address the inherent safety problems of conventional organic liquid electrolytes. However, their low ionic conductivity and large interfacial resistance limit the practical applications of SEs. Here, a flexible solid electrolyte with a multilayer structure is fabricated by the UV curing of an interpenetrating network of poly(ether‐acrylate) (ipn‐PEA) in the Na₃Zr₂Si₂PO₁₂/poly(vinylidene fluoride‐hexafluoropropylene) porous skeleton (NZSP/PVDF‐HFP), exhibiting a high Na⁺ transference number of 0.63 and a suitable ionic conductivity of above 10^?4 S cm^?1 at 60 °C. In addition, due to the unique structure of the internal rigidity and external flexibility, the composite solid electrolyte can effectively mitigate interfacial ion transfer issues while guaranteeing a certain mechanical strength, and largely inhibiting the formation of dendrite and dead sodium. The solid sodium metal batteries using Na₃V₂(PO₄)₃ (NVP) as a cathode possess a discharge capacity of 85 mA h g^?1 after 100 cycles at 0.5 C, and achieve above 90% of capacity retention rate during 100 cycles at 0.1 C for Na_2/3Ni_1/3Mn_1/3Ti_1/3O₂ (NTMO) at 60 °C. The flexible solid electrolyte with multilayer structure shows a great advantage for managing the ionic conductivity and interface resistance problem, suggesting a promise as a practical sodium metal battery.     

Correlating Macro and Atomic Structure with Elastic Properties and Ionic Transport of Glassy Li2S‐P2S5 (LPS) Solid Electrolyte for Solid‐State Li Metal Batteries

A combination of high ionic conductivity and facile processing suggest that sulfide‐based materials are promising solid electrolytes that have the potential to enable Li metal batteries. Although the Li₂S‐P₂S₅ (LPS) family of compounds exhibit desirable characteristics, it is known that Li metal preferentially propagates through microstructural defects, such as particle boundaries and/or pores. Herein, it is demonstrated that a near theoretical density (98% relative density) LPS 75‐25 glassy electrolyte exhibiting high ionic conductivity can be achieved by optimizing the molding pressure and temperature. The optimal molding pressure reduces porosity and particle boundaries while preserving the preferred amorphous structure. Moreover, molecular rearrangements and favorable Li coordination environments for conduction are attained. Consequently, the Young's Modulus approximately doubles (30 GPa) and the ionic conductivity increases by a factor of five (1.1 mS cm^?1) compared to conventional room temperature molding conditions. It is believed that this study can provide mechanistic insight into processing‐structure‐property relationships that can be used as a guide to tune microstructural defects/properties that have been identified to have an effect on the maximum charging current that a solid electrolyte can withstand during cycling without short‐circuiting.     

Viscoelastic and Nonflammable Interface Design–Enabled Dendrite‐Free and Safe Solid Lithium Metal Batteries

Herein, a composite polymer electrolyte with a viscoelastic and nonflammable interface is designed to handle the contact issue and preclude Li dendrite formation. The composite polymer electrolyte (cellulose acetate/polyethylene glycol/Li_1.4Al_0.4Ti_1.6P₃O₁₂) exhibits a wide electrochemical window of 5 V (vs Li⁺/Li), a high Li⁺ transference number of 0.61, and an excellent ionic conductivity of above 10^?4 S cm^?1 at 60 °C. In particular, the intimate contact, low interfacial impedance, and fast ion‐transport process between the electrodes and solid electrolytes can be simultaneously achieved by the viscoelastic and nonflammable layer. Benefiting from this novel design, solid lithium metal batteries with either LiFePO₄ or LiCoO₂ as cathode exhibit superior cyclability and rate capability, such as a discharge capacity of 157 mA h g^?1 after 100 cycles at C/2 and 97 mA h g^?1 at 5C for LiFePO₄ cathode. Moreover, the smooth and uniform Li surface after long‐term cycling confirms the successful suppression of dendrite formation. The viscoelastic and nonflammable interface modification of solid electrolytes provides a promising and general strategy to handle the interfacial issues and improves the operative safety of solid lithium metal batteries.     

Suppressing Li Dendrite Formation in Li2S‐P2S5 Solid Electrolyte by LiI Incorporation

Solid electrolytes have been considered as a promising approach for Li dendrite prevention because of their high mechanical strength and high Li transference number. However, recent reports indicate that Li dendrites also form in Li₂S‐P₂S₅ based sulfide electrolytes at current densities much lower than that in the conventional liquid electrolytes. The methods of suppressing dendrite formation in sulfide electrolytes have rarely been reported because the mechanism for the “unexpected” dendrite formation is unclear, limiting the successful utilization of high‐energy Li anode with these electrolytes. Herein, the authors demonstrate that the Li dendrite formation in Li₂S‐P₂S₅ glass can be effectively suppressed by tuning the composition of the solid electrolyte interphase (SEI) at the Li/electrolyte interface through incorporating LiI into the electrolyte. This approach introduces high ionic conductivity but electronic insulation of LiI in the SEI, and more importantly, improves the mobility of Li atoms, promoting the Li depositon at the interface and thus suppresses dendrite growth. It is shown that the critical current density is improved significantly after incorporating LiI into Li₂S‐P₂S₅ glass, reaching 3.90 mA cm^?2 at 100 °C after adding 30 mol% LiI. Stable cycling of the Li‐Li cells for 200 h is also achieved at 1.50 mA cm^?2 at 100 °C.     

Interface‐Engineered All‐Solid‐State Li‐Ion Batteries Based on Garnet‐Type Fast Li+ Conductors

All‐solid‐state Li‐ion batteries based on Li₇La₃Zr₂O₁₂ (LLZO) garnet structures require novel electrode assembly strategies to guarantee a proper Li⁺ transfer at the electrode–electrolyte interfaces. Here, first stable cell performances are reported for Li‐garnet, c‐Li_6.25Al_0.25La₃Zr₂O₁₂, all‐solid‐state batteries running safely with a full ceramics setup, exemplified with the anode material Li₄Ti₅O₁₂. Novel strategies to design an enhanced Li⁺ transfer at the electrode–electrolyte interface using an interface‐engineered all‐solid‐state battery cell based on a porous garnet electrolyte interface structure, in which the electrode material is intimately embedded, are presented. The results presented here show for the first time that all‐solid‐state Li‐ion batteries with LLZO electrolytes can be reversibly charge–discharge cycled also in the low potential ranges (≈1.5 V) for combinations with a ceramic anode material. Through a model experiment, the interface between the electrode and electrolyte constituents is systematically modified revealing that the interface engineering helps to improve delivered capacities and cycling properties of the all‐solid‐state Li‐ion batteries based on garnet‐type cubic LLZO structures.     

In Situ Generated Fireproof Gel Polymer Electrolyte with Li6.4Ga0.2La3Zr2O12 As Initiator and Ion‐Conductive Filler

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) based gel polymer electrolyte is regarded as a promising candidate to settle the safety issues of liquid electrolytes. However, the currently reported gel polymer electrolytes are still not safe enough owing to high amount of flammable liquid solvents contained in them. Herein, a fireproof PVDF‐HFP based gel polymer electrolyte is designed and synthesized through an in situ crosslinking method, with Li_6.4Ga_0.2La₃Zr₂O₁₂ as initiator and ion‐conductive filler. The obtained gel polymer electrolyte demonstrates superior fire resisting properties. The optimized gel polymer electrolyte exhibits an ionic conductivity as high as 1.84 × 10^?3 S cm^?1 at 20 °C with an electrochemical window up to 4.75 V at room temperature. Moreover, the obtained gel polymer electrolyte shows excellent compatibility with lithium anodes. Therefore, the lithium anode is well protected. Lithium batteries assembled with the gel polymer electrolyte possess superb safety properties in cutting and burning tests. Furthermore, the batteries also show a discharge retention rate as high as 94.08% (in comparison with the initial discharge capacity) after cycling at 0.5 C for 360 cycles with an average columbic efficiency higher than 98%. The purpose of this report is to show the great potential of applying fire‐retardant gel polymer electrolyte to achieve high safety lithium batteries.     

Flexible,Scalable, and Highly Conductive Garnet‐Polymer Solid Electrolyte Templated by Bacterial Cellulose

Solid‐state electrolytes are a promising candidate for the next‐generation lithium‐ion battery, as they have the advantages of eliminating the leakage hazard of liquid solvent and elevating stability. However, inherent limitations such as the low ionic conductivity of solid polymer electrolytes and the high brittleness of inorganic ceramic electrolytes severally impede their practical application. Here, an inexpensive, facile, and scalable strategy to fabricate a hybrid Li₇La₃Zr₂O₁₂ (LLZO) and poly(ethylene oxide)‐based electrolyte by exploiting bacterial cellulose as a template is reported. The well‐organized LLZO network significantly enhances the ionic conductivity by extending long transport pathways for Li ions, exhibiting an elevated conductivity of 1.12 × 10^?4 S cm^?1. In addition, the hybrid electrolyte presents a structural flexibility, with minor impedance increase after bending. The facile and applicable approach establishes new principles for the strategy of designing scalable and flexible hybrid polymer electrolytes that can be utilized for high‐energy‐density batteries.     

Polysulfide‐Shuttle Control in Lithium‐Sulfur Batteries with a Chemically/Electrochemically Compatible NaSICON‐Type Solid Electrolyte

A NaSICON‐type Li⁺‐ion conductive membrane with a formula of Li_{1+ x} Y _x Zr_{2? x} (PO₄)₃ (LYZP) (x = 0–0.15) has been explored as a solid‐electrolyte/separator to suppress polysulfide‐crossover in lithium‐sulfur (Li‐S) batteries. The LYZP membrane with a reasonable Li⁺‐ion conductivity shows both favorable chemical compatibility with the lithium polysulfide species and exhibits good electrochemical stability under the operating conditions of the Li‐S batteries. Through an integration of the LYZP solid electrolyte with the liquid electrolyte, the hybrid Li‐S batteries show greatly enhanced cyclability in contrast to the conventional Li‐S batteries with the porous polymer (e.g., Celgard) separator. At a rate of C/5, the hybrid Li ||LYZP|| Li₂S₆ batteries developed in this study (with a Li‐metal anode, a liquid/LYZP hybrid electrolyte, and a dissolved lithium polysulfide cathode) delivers an initial discharge capacity of ≈1000 mA h g^?1 (based on the active sulfur material) and retains ≈90% of the initial capacity after 150 cycles with a low capacity fade‐rate of <0.07% per cycle.     

Building Lithiophilic Ion‐Conduction Highways on Garnet‐Type Solid‐State Li+ Conductors

The integration of highly conductive solid‐state electrolytes (SSEs) into solid‐state cells is still a challenge mainly due to the high impedance existing at the electrolyte/electrode interface. Although solid‐state garnet‐based batteries have been successfully assembled with the assistance of an intermediate layer between the garnet and the Li metal anode, the slow discharging/charging rates of the batteries inhibits practical applications, which require much higher power densities. Here, a crystalline sulfonated‐covalent organic framework (COF) thin layer is grown on the garnet surface via a simple solution process. It not only significantly improves the lithiophilicity of garnet electrolytes via the lithiation of the COF layer with molten Li, but also creates effective Li⁺ diffusion “highways” between the garnet and the Li metal anode. As a result, the interfacial impedance of symmetric solid‐state Li cells is significantly decreased and the cells can be operated at high current densities up to 3 mA cm^?2, which is difficult to achieve with current interfacial modification technologies for SSEs. The solid‐state Li‐ion batteries using LiFePO₄ cathodes, Li anodes, and COF‐modified garnet electrolytes thus exhibit a significantly improved rate capability.     

The Fast Charge Transfer Kinetics of the Lithium Metal Anode on the Garnet‐Type Solid Electrolyte Li6.25Al0.25La3Zr2O12

The charge transfer kinetics between a lithium metal electrode and an inorganic solid electrolyte is of key interest to assess the rate capability of future lithium metal solid state batteries. In an in situ microelectrode study run in a scanning electron microscope, it is demonstrated that—contrary to the prevailing opinion—the intrinsic charge transfer resistance of the Li|Li_6.25Al_0.25La₃Zr₂O₁₂ (LLZO) interface is in the order of 10^?1 Ω cm² and thus negligibly small. The corresponding high exchange current density in combination with the single ion transport mechanism (t⁺ ≈ 1) of the inorganic solid electrolyte enables extremely fast plating kinetics without the occurrence of transport limitations. Local plating rates in the range of several A cm^?2 are demonstrated at defect free and chemically clean Li|LLZO interfaces. Practically achievable current densities are limited by lateral growth of lithium along the surface as well as electro‐chemo‐mechanical‐induced fracture of the solid electrolyte. In combination with the lithium vacancy diffusion limitation during electrodissolution, these morphological instabilities are identified as the key fundamental limitations of the lithium metal electrode for solid‐state batteries with inorganic solid electrolytes.     

Sodium Plating from Na‐β″‐Alumina Ceramics at Room Temperature,Paving the Way for Fast‐Charging All‐Solid‐State Batteries

All‐solid‐state batteries with an alkali metal anode have the potential to achieve high energy density. However, the onset of dendrite formation limits the maximum plating current density across the solid electrolyte and prevents fast charging. It is shown that the maximum plating current density is related to the interfacial resistance between the solid electrolyte and the metal anode. Due to their high ionic conductivity, low electronic conductivity, and stability against sodium metal, Na‐β″‐alumina ceramics are excellent candidates as electrolytes for room‐temperature all‐solid‐state batteries. Here, it is demonstrated that a heat treatment of Na‐β″‐alumina ceramics in argon atmosphere enables an interfacial resistance <10 Ω cm² and current densities up to 12 mA cm^?2 at room temperature. The current density obtained for Na‐β″‐alumina is ten times higher than that measured on a garnet‐type Li₇La₃Zr₂O₁₂ electrolyte under equivalent conditions. X‐ray photoelectron spectroscopy shows that eliminating hydroxyl groups and carbon contaminations at the interface between Na‐β″‐alumina and sodium metal is key to reach such values. By comparing the temperature‐dependent stripping/plating behavior of Na‐β″‐alumina and Li₇La₃Zr₂O₁₂, the role of the alkali metal in governing interface kinetics is discussed. This study provides new insights into dendrite formation and paves the way for fast‐charging all‐solid‐state batteries.     

A Lithium Oxythioborosilicate Solid Electrolyte Glass with Superionic Conductivity

As potential next‐generation energy storage devices, solid‐state lithium batteries require highly functional solid state electrolytes. Recent research is primarily focused on crystalline materials, while amorphous materials offer advantages by eliminating problematic grain boundaries that can limit ion transport and trigger dendritic growth at the Li anode. However, simultaneously achieving high conductivity and stability in glasses is a challenge. New quaternary superionic lithium oxythioborate glasses are reported that exhibit high ion conductivity up to 2 mS cm^?1 despite relatively high oxygen: sulfur ratios of more than 1:2, that exhibit greatly reduced H₂S evolution upon exposure to air compared to Li₇P₃S₁₁. These monolithic glasses are prepared from vitreous melts without ball‐milling and exhibit no discernable XRD pattern. Solid‐state NMR studies elucidate the structural entities that comprise the local glass structure which dictates fast ion conduction. Stripping/plating onto lithium metal results in very low polarization at a current density of 0.1 mA cm^?2 over repeated cycling. Evaluation of the optimal glass composition as an electrolyte in an all‐solid‐state battery shows it exhibits excellent cycling stability and maintains near theoretical capacity for over 130 cycles at room temperature with Coulombic efficiency close to 99.9%, opening up new avenues of exploration for these quaternary compositions.