Protons Enhance Conductivities in Lithium Halide Hydroxide/Lithium Oxyhalide Solid Electrolytes by Forming Rotating Hydroxy Groups

Li‐halide hydroxides (Li₂OHX) and Li‐oxyhalides (Li₃OX) have emerged as new classes of low‐cost, lightweight solid state electrolytes (SSE) showing promising Li‐ion conductivities. The similarity in the lattice parameters between them, careless synthesis, and insufficient rigor in characterization often lead to erroneous interpretations of their compositions. Finally, moisture remaining in the synthesis or cell assembling environment and variability in the equivalent circuit models additionally contribute to significant errors in their properties. Thus, there remains a controversy about the real values of Li‐ion conductivities in such SSEs. Here an ultra‐fast synthesis and comprehensive material characterization is utilized to report on the ionic conductivities of contaminant‐free Li2+xOH_1?xCl (x=0‐0.7), and Li₂OHBr not exceeding 10^‐4 S cm^‐1 at 110 °C. Using powerful combination of experimental and numerical approaches, it is demonstrated that the presence of H in these SSEs yields significantly higher Li⁺ ‐ionic conductivity. Born‐Oppenheimer molecular dynamics simulations show excellent agreement with experimental results and reveal an unexpected mechanism for faster Li⁺ transport. It involves rotation of a short OH‐group in SSEs, which opens lower‐energy pathways for the formation of Frenkel defects and highly‐correlated Li⁺ jumps. These findings will reduce the existing confusions and show new avenues for tuning SSE compositions for further improved Li‐ion conductivities.     

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.     

Understanding Li‐Ion Dynamics in Lithium Hydroxychloride (Li2OHCl) Solid State Electrolyte via Addressing the Role of Protons

Low‐melting‐point solid‐state electrolytes (SSE) are critically important for low‐cost manufacturing of all‐solid‐state batteries. Lithium hydroxychloride (Li₂OHCl) is a promising material within the SSE domain due to its low melting point (mp < 300 °C), cheap ingredients (Li, H, O, and Cl), and rapid synthesis. Another unique feature of this compound is the presence of Li vacancies and rotating hydroxyl groups which promote Li‐ion diffusion, yet the role of the protons in the ion transport remains poorly understood. To examine lithium and proton dynamics, a set of solid‐state NMR experiments are conducted, such as magic‐angle spinning ⁷Li NMR, static ⁷Li and ¹H NMR, and spin‐lattice T₁(⁷Li)/T₁(¹H) relaxation experiments. It is determined that only Li⁺ contributes to long‐range ion transport, while H⁺ dynamics is constrained to an incomplete isotropic rotation of the OH group. The results uncover detailed mechanistic understanding of the ion transport in Li₂OHCl. It is shown that two distinct phases of ionic motions appear at low and elevated temperatures, and that the rotation of the OH group controls Li⁺ and H⁺ dynamics in both phases. The model based on the NMR experiments is fully consistent with crystallographic information, ionic conductivity measurements, and Born–Oppenheimer molecular dynamic simulations.     

Mesoscopic Framework Enables Facile Ionic Transport in Solid Electrolytes for Li Batteries

Li‐ion‐conducting solid electrolytes can simultaneously overcome two grand challenges for Li‐ion batteries: the severe safety concerns that limit the large‐scale application and the poor electrolyte stability that forbids the use of high‐voltage cathodes. Nevertheless, the ionic conductivity of solid electrolytes is typically low, compromising the battery performances. Precisely determining the ionic transport mechanism(s) is a prerequisite for the rational design of highly conductive solid electrolytes. For decades, the research on this subject has primarily focused on the atomic and microscopic scales, where the main features of interest are unit cells and microstructures, respectively. Here, it is shown that the largely overlooked mesoscopic scale lying between these extremes could be the key to fast ionic conduction. In a prototype system, (Li_0.33La_0.56)TiO₃, a mesoscopic framework is revealed for the first time by state‐of‐the‐art scanning transmission electron microscopy. Corroborated by theoretical calculations and impedance measurements, it is demonstrated that such a unique configuration maximizes the number of percolation directions and thus most effectively improves the ionic conductivity. This discovery reconciles the long‐standing structure–property inconsistency in (Li_0.33La_0.56)TiO₃ and also identifies mesoscopic ordering as a promising general strategy for optimizing Li⁺ conduction.     

Improvements to the Overpotential of All‐Solid‐State Lithium‐Ion Batteries during the Past Ten Years

After the research that shows that Li₁₀GeP₂S₁₂ (LGPS)‐type sulfide solid electrolytes can reach the high ionic conductivity at the room temperature, sulfide solid electrolytes have been intensively developed with regard to ionic conductivity and mechanical properties. As a result, an increasing volume of research has been conducted to employ all‐solid‐state lithium batteries in electric automobiles within the next five years. To achieve this goal, it is important to review the research over the past decade, and understand the requirements for future research necessary to realize the practical applications of all‐solid‐state lithium batteries. To date, research on all‐solid‐state lithium batteries has focused on achieving overpotential properties similar to those of conventional liquid‐lithium‐ion batteries by increasing the ionic conductivity of the solid electrolytes. However, the increase in the ionic conductivity should be accompanied by improvements of the electronic conductivity within the electrode to enable practical applications. This essay provides a critical overview of the recent progress and future research directions of the all‐solid‐state lithium batteries for practical applications.     

Computation‐Guided Design of LiTaSiO5, a New Lithium Ionic Conductor with Sphene Structure

The development of all‐solid‐state Li‐ion batteries requires solid electrolyte materials with many desired properties, such as ionic conductivity, chemical and electrochemical stability, and mechanical durability. Computation‐guided materials design techniques are advantageous in designing and identifying new solid electrolytes that can simultaneously meet these requirements. In this joint computational and experimental study, a new family of fast lithium ion conductors, namely, LiTaSiO₅ with sphene structure, are successfully identified, synthesized, and demonstrated using a novel computational design strategy. First‐principles computation predicts that Zr‐doped LiTaSiO₅ sphene materials have fast Li diffusion, good phase stability, and poor electronic conductivity, which are ideal for solid electrolytes. Experiments confirm that Zr‐doped LiTaSiO₅ sphene structure indeed exhibits encouraging ionic conductivity. The lithium diffusion mechanisms in this material are also investigated, indicating the sphene materials are 3D conductors with facile 1D diffusion along the [101] direction and additional cross‐channel migration. This study demonstrates a novel design strategy of activating fast Li ionic diffusion in lithium sphenes, a new materials family of superionic conductors.     

Unraveling the Intra and Intercycle Interfacial Evolution of Li6PS5Cl‐Based All‐Solid‐State Lithium Batteries

High‐performance rechargeable all‐solid‐state lithium metal batteries with high energy density and enhanced safety are attractive for applications like portable electronic devices and electric vehicles. Among the various solid electrolytes, argyrodite Li₆PS₅Cl with high ionic conductivity and easy processability is of great interest. However, the low interface compatibility between sulfide solid electrolytes and high capacity cathodes like nickel‐rich layered oxides requires many thorny issues to be resolved, such as the space charge layer (SCL) and interfacial reactions. In this work, in situ electrochemical impedance spectroscopy and in situ Raman spectroscopy measurements are performed to monitor the detailed interface evolutions in a LiNi_0.8Co_0.1Mn_0.1O₂ (NCM)/Li₆PS₅Cl/Li cell. Combining with ex situ characterizations including scanning electron microscopy and X‐ray photoelectron spectroscopy, the evolution of the SCL and the chemical bond vibration at NCM/Li₆PS₅Cl interface during the early cycles is elaborated. It is found that the Li⁺ ion migration, which varies with the potential change, is a very significant cause of these interface behaviors. For the long‐term cycling, the SCL, interfacial reactions, lithium dendrites, and chemo‐mechanical failure have an integrated effect on interfaces, further deteriorating the interfacial structure and electrochemical performance. This research provides a new insight on intra and intercycle interfacial evolution of solid‐state 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.     

A Versatile Sn‐Substituted Argyrodite Sulfide Electrolyte for All‐Solid‐State Li Metal Batteries

Sulfide‐based solid‐state electrolytes (SSEs) for all‐solid‐state Li metal batteries (ASSLMBs) are attracting significant attention due to their high ionic conductivity, inherently soft properties, and decent mechanical strength. However, the poor incompatibility with Li metal and air sensitivity have hindered their application. Herein, the Sn (IV) substitution for P (V) in argyrodite sulfide Li₆PS₅I (LPSI) SSEs is reported, in the preparation of novel LPSI‐xSn SSEs (where x is the Sn substitution percentage). Appropriate aliovalent element substitutions with larger atomic radius (R_<Sn> > R_<P>) provides the optimized LPSI‐20Sn electrolyte with a 125 times higher ionic conductivity compared to that of the LPSI electrolyte. The high ionic conductivity of LPSI‐20Sn enables the rich I‐containing electrolyte to serve as a stabilized interlayer against Li metal in sulfide‐based ASSLMBs with outstanding cycling stability and rate capability. Most importantly, benefiting from the strong Sn–S bonding in Sn‐substituted electrolytes, the LPSI‐20Sn electrolyte shows excellent structural stability and improved air stability after exposure to O₂ and moisture. The versatile Sn substitution in argyrodite LPSI electrolytes is believed to provide a new and effective strategy to achieve Li metal‐compatible and air‐stable sulfide‐based SSEs for large‐scale applications.     

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.     

Realizing Reversible Conversion‐Alloying of Sb(V) in Polyantimonic Acid for Fast and Durable Lithium‐ and Potassium‐Ion Storage

Finding suitable electrode materials for alkali‐metal‐ion storage is vital to the next‐generation energy‐storage technologies. Polyantimonic acid (PAA, H₂Sb₂O₆ · nH₂O), having pentavalent antimony species and an interconnected tunnel‐like pyrochlore crystal framework, is a promising high‐capacity energy‐storage material. Fabricating electrochemically reversible PAA electrode materials for alkali‐metal‐ion storage is a challenge and has never been reported due to the extremely poor intrinsic electronic conductivity of PAA associated with the highest oxidation state Sb(V). Combining nanostructure engineering with a conductive‐network construction strategy, here is reported a facile one‐pot synthesis protocol for crafting uniform internal‐void‐containing PAA nano‐octahedra in a composite with nitrogen‐doped reduced graphene oxide nanosheets (PAA?N‐RGO), and for the first time, realizing the reversible storage of both Li⁺ and K⁺ ions in PAA?N‐RGO. Such an architecture, as validated by theoretical calculations and ex/in situ experiments, not only fully takes advantage of the large‐sized tunnel transport pathways (0.37 nm²) of PAA for fast solid‐phase ionic diffusion but also leads to exponentially increased electrical conductivity (3.3 S cm^?1 in PAA?N‐RGO vs 4.8 × 10^?10 S cm^?1 in bare‐PAA) and yields an inside‐out buffer function for accommodating volume expansion. Compared to electrochemically irreversible bare‐PAA, PAA?N‐RGO manifests reversible conversion‐alloying of Sb(V) toward fast and durable Li⁺‐ and K⁺‐ion storage.     

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.     

A Tale of Two Sites: On Defining the Carrier Concentration in Garnet‐Based Ionic Conductors for Advanced Li Batteries

Solid electrolytes based on the garnet crystal structure have recently been identified as a promising material to enable advance Li battery cell chemistries because of the unprecedented combination of high ionic conductivity and electrochemical stability against metallic Li. To better understand the mechanisms that give rise to high conductivity, the goal of this work is to correlate Li site occupancy with Li‐ion transport. Toward this goal, the Li site occupancy is studied in cubic garnet as a function of Li concentration over the compositions range: Li_7?xLa₃Zr_2?xTa_xO₁₂ (x = 0.5, 0.75, and 1.5). The distribution of Li between the two interstitial sites (24d and 96h) is determined using neutron and synchrotron diffraction. The bulk conductivity is measured on >97% relative density polycrystalline specimens to correlate Li‐ion transport as a function of Li site occupancy. It is determined that the conductivity changes nonlinearly with the occupancy of the octahedral (96h) Li site. It is shown that the effective carrier concentration is dependent on the Li site occupancy and suggests that this is a consequence of significant carrier–carrier coulombic interactions. Furthermore, the observation of maximum conductivity near Li = 6.5 mol is explained.     

A Conductive Molecular Framework Derived Li2S/N,P‐Codoped Carbon Cathode for Advanced Lithium–Sulfur Batteries

Li₂S is one of the most promising cathode materials for Li‐ion batteries because of its high theoretical capacity and compatibility with Li‐metal‐free anode materials. However, the poor conductivity and electrochemical reactivity lead to low initial capacity and severe capacity decay. In this communication, a nitrogen and phosphorus codoped carbon (N,P–C) framework derived from phytic acid doped polyaniline hydrogel is designed to support Li₂S nanoparticles as a binder‐free cathode for Li–S battery. The porous 3D architecture of N and P codoped carbon provides continuous electron pathways and hierarchically porous channels for Li ion transport. Phosphorus doping can also suppress the shuttle effect through strong interaction between sulfur and the carbon framework, resulting in high Coulombic efficiency. Meanwhile, P doping in the carbon framework plays an important role in improving the reaction kinetics, as it may help catalyze the redox reactions of sulfur species to reduce electrochemical polarization, and enhance the ionic conductivity of Li₂S. As a result, the Li₂S/N,P–C composite electrode delivers a stable capacity of 700 mA h g^?1 with average Coulombic efficiency of 99.4% over 100 cycles at 0.1C and an areal capacity as high as 2 mA h cm^?2 at 0.5C.     

An Air‐Stable and Dendrite‐Free Li Anode for Highly Stable All‐Solid‐State Sulfide‐Based Li Batteries

Li metal is a promising anode material for all‐solid‐state batteries, owing to its high specific capacity and low electrochemical potential. However, direct contact of Li metal with most solid‐state electrolytes induces severe side reactions that can lead to dendrite formation and short circuits. Moreover, Li metal is unstable when exposed to air, leading to stringent processing requirements. Herein, it is reported that the Li₃PS₄/Li interface in all‐solid‐state batteries can be stabilized by an air‐stable Li_xSiS_y protection layer that is formed in situ on the surface of Li metal through a solution‐based method. Highly stable Li cycling for over 2000 h in symmetrical cells and a lifetime of over 100 cycles can be achieved for an all‐solid‐state LiCoO₂/Li₃PS₄/Li cell. Synchrotron‐based high energy X‐ray photoelectron spectroscopy in‐depth analysis demonstrates the distribution of different components within the protection layer. The in situ formation of an electronically insulating Li_xSiS_y protection layer with highly ionic conductivity provides an effective way to prevent Li dendrite formation in high‐energy all‐solid‐state Li metal batteries.     

MXene‐Based Mesoporous Nanosheets Toward Superior Lithium Ion Conductors

Although solid polymer electrolytes have some intrinsic advantages in synthesis and film processing compared with inorganic solid electrolytes, low ionic conductivities and mechanical moduli hamper their practical applications in lithium‐based batteries. Here, an efficient strategy is developed to produce a unique solid polymer electrolyte containing MXene‐based mesoporous silica nanosheets with a sandwich structure, which are fabricated via controllable hydrolysis of tetraethyl orthosilicate around the surface of MXene‐Ti₃C₂ under the direction of cationic surfactants. Such unique nanosheets not only exhibit individual, thin, and insulated features, but also possess abundant functional groups in mesopores and on the surface, which are favorable for the formation of Lewis acid–base interactions with anions in polymer electrolytes such as poly(propylene oxide) elastomer, enabling the fast Li⁺ transportation at the mesoporous nanosheets/polymer interfaces. As a consequence, a solid polymer electrolyte with high ionic conductivity of 4.6 × 10^?4 S cm^?1, high Young's modulus of 10.5 MPa, and long‐term electrochemical stability is achieved.     

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.     

Fabrication of Sub‐Micrometer‐Thick Solid Electrolyte Membranes of β‐Li3PS4 via Tiled Assembly of Nanoscale,Plate‐Like Building Blocks

Solid electrolytes represent a critical component in future batteries that provide higher energy and power densities than the current lithium‐ion batteries. The potential of using ultrathin films is among the best merits of solid electrolytes for considerably reducing the weight and volume of each battery unit, thereby significantly enhancing the energy density. However, it is challenging to fabricate ultrathin membranes of solid electrolytes using the conventional techniques. Here, a new strategy is reported for fabricating sub‐micrometer‐thick membranes of β‐Li₃PS₄ solid electrolytes via tiled assembly of shape‐controlled, nanoscale building blocks. This strategy relies on facile, low‐cost, solution‐based chemistry to create membranes with tunable thicknesses. The ultrathin membranes of β‐Li₃PS₄ show desirable ionic conductivity and necessary compatibility with metallic lithium anodes. The results of this study also highlight a viable strategy for creating ultrathin, dense solid electrolytes with high ionic conductivities for the next‐generation energy storage and conversion systems.     

Slurry‐Fabricable Li+‐Conductive Polymeric Binders for Practical All‐Solid‐State Lithium‐Ion Batteries Enabled by Solvate Ionic Liquids

For mass production of all‐solid‐state lithium‐ion batteries (ASLBs) employing highly Li⁺ conductive and mechanically sinterable sulfide solid electrolytes (SEs), the wet‐slurry process is imperative. Unfortunately, the poor chemical stability of sulfide SEs severely restrict available candidates for solvents and in turn polymeric binders. Moreover, the binders interrupt Li⁺‐ionic contacts at interfaces, resulting in the below par electrochemical performance. In this work, a new scalable slurry fabrication protocol for sheet‐type ASLB electrodes made of Li⁺‐conductive polymeric binders is reported. The use of intermediate‐polarity solvent (e.g., dibromomethane) for the slurry allows for accommodating Li₆PS₅Cl and solvate‐ionic‐liquid‐based polymeric binders (NBR‐Li(G3)TFSI, NBR: nitrile?butadiene rubber, G3: triethylene glycol dimethyl ether, LiTFSI: lithium bis(trifluoromethanesulfonyl)imide) together without suffering from undesirable side reactions or phase separation. The LiNi_0.6Co_0.2Mn_0.2O₂ and Li₄Ti₅O₁₂ electrodes employing NBR‐Li(G3)TFSI show high capacities of 174 and 160 mA h g^?1 at 30 °C, respectively, which are far superior to those using conventional NBR (144 and 76 mA h g^?1). Moreover, high areal capacity of 7.4 mA h cm^?2 is highlighted for the LiNi_0.7Co_0.15Mn_0.15O₂ electrodes with ultrahigh mass loading of 45 mg cm^?2. The facilitated Li⁺‐ionic contacts at interfaces paved by NBR‐Li(G3)TFSI are evidenced by the complementary analysis from electrochemical and ⁷Li nuclear magnetic resonance measurements.     

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.