Vertically-Aligned Card-House Structure for Composite Solid Polymer Electrolyte with Fast and Stable Ion Transport Channels

All-solid-state lithium batteries (ASSLBs) are highly promising as next-generation energy storage devices owing to their potential for great safety and high energy density. This work demonstrates that composite solid polymer electrolyte with vertically-aligned card-house structure can simultaneously improve the high rate and long-term cycling performance of ASSLBs. The vertical alignment of laponite nanosheets creates fast and uniform Li+ ion transport channels at the nanosheets/polymer interphase, resulting in high ionic conductivity of 8.9 × 10-4 S cm-1 and Li+ transference number of 0.32 at 60 °C, as well as uniformly distributed solid electrolyte interphase. Such electrolyte is characterized by high mechanical strength, low flammability, excellent structural stability and stable ion transport channels. In addition, the ASSLB cell with the electrolyte and LiFePO4 cathode delivers a high discharge specific capacity of 124.8 mAh g-1 , which accounts for 85.6% of its initial capacity after 500 cycles at 1C. The reasonable design through structural control strategy by interconnecting the vertically-aligned nanosheets open a way to fabricate high performance composite solid polymer electrolytes.

A Dynamically Stable Sulfide Electrolyte Architecture for High-Performance All-Solid-State Lithium Metal Batteries

All-solid-state batteries employing sulfide solid electrolyte and Li metal anode are promising because of their high safety and energy densities. However, the interface between Li metal and sulfides suffers from catastrophic instability which stems the practical use. Here, a dynamically stable sulfide electrolyte architecture to construct the hierarchy of interface stability is reported. By rationally designing the multilayer structures of sulfide electrolytes, the dynamic decomposing-alloying process from MS4 (M = Ge or Sn) unit in sulfide interlayer can significantly prohibit Li dendrite penetration is revealed. The abundance of highly electronic insulating decompositions, such as Li2 S, at the sulfide interlayer interface helps to well constrain the dynamic decomposition process and preserve the long-term polarization stability is also highlighted. By using Li6 PS5 Cl||Li10 SnP2 S12 ||Li6 PS5 Cl electrolyte architecture, Li metal anode shows an unprecedented critical current density over 3 mA cm-2 and achieves the steady over-potential for ≈900 hours. Based upon the merits, the Li||LiNi0.8 Co0.1 Mn0.1 O2 battery delivers a remarkable 75.3% retention even after 600 cycles at 1 C (1C-0.95 mA cm-2 ) under a low stack pressure of 15 MPa.

Solid Polymer Electrolytes with Dual Anion Synergy and Twofold Reinforcement Effect for All-Solid-State Lithium Batteries

Solid polymer electrolytes (SPEs) have emerged as a viable alternative to traditional organic liquid-based electrolytes for high energy density and safer lithium batteries. Poly(ethylene oxide) (PEO)-based SPEs are considered one of the mainstream SPE materials with excellent dissociation ability of lithium salts. However, the inferior ionic conductivity at room temperature and poor dimensional stability at high temperature limit their utilization. In this work, a semi-interpenetrating polymer network (semi-IPN) forming a precursor based on an ionic liquid (IL) monomer and linear PEO chains were introduced into an electrospun poly(acrylonitrile) (PAN) fibrous mat with subsequent thermal-initiated cross-linking. 1,4-Diazabicyclo [2.2.2] octane (DABCO) and 4-(chloromethyl) styrene were used to synthesize the styrenic-DABCO-based IL monomer with bis(trifluoromethane sulfonyl)imide (TFSI-) or bis(fluoromethane sulfonyl)imide (FSI-) as the anion, named as SDTFSI and SDFSI, respectively. Together, the FSI- and TFSI- anions demonstrate a synergistic effect in providing ion-conductive LiF and Li3N-rich inorganic SEI layer with enhanced lithium dendrite suppression ability. The twofold reinforcement effect is achieved collectively from the semi-IPN structure and the three-dimensional (3D) PAN network that help to construct highly efficient and uniform ion transport channels with excellent flexibility, further suppressing the lithium dendrite growth. The SPEs were dimensionally stable even at elevated temperatures of 150 °C. Moreover, the SPEs show an ionic conductivity of 4.4 × 10-4 S cm-1 at 25 °C and 1.81 × 10-3 S cm-1 at 55 °C and a lithium-ion transference number of 0.56. The favorable electrochemical performance of the SPEs was verified by operating LiFePO4/Li and NMC/Li cells.

Stack Pressure Dependence of Li Stripping/Plating Performance in All-Solid-State Li Metal Cells Containing Sulfide Glass Electrolytes

Sulfide-based all-solid-state Li/S batteries have attracted considerable attention as next-generation batteries with high energy density. However, their practical applications are limited by short-circuiting due to Li dendrite growth. One of the possible reasons for this phenomenon is the contact failure caused by void formation at the Li/solid electrolyte interface during Li stripping. Herein, we studied the operating conditions, such as stack pressure, operating temperature, and electrode composition, that could potentially suppress the formation of voids. Furthermore, we investigated the effects of these operating conditions on the Li stripping/plating performance of all-solid-state Li symmetric cells containing glass sulfide electrolytes with a reduction tolerance. As a result, symmetric cells with Li-Mg alloy electrodes instead of Li metal electrodes exhibited high cycling stability at current densities above 2.0 mA cm^-2, a temperature of 60 °C, and stack pressures of 3-10 MPa. In addition, an all-solid-state Li/S cell with a Li-Mg alloy negative electrode operated stably for 50 cycles at a current density of 2.0 mA cm^-2, stack pressure of 5 MPa, and temperature of 60 °C, while its measured capacity was close to a theoretical value. The obtained results provide guidelines for the construction of all-solid-state Li/S batteries that can reversibly operate at high current densities.

Slurry-Coated LiNi0.8Co0.1Mn0.1O2-Li3InCl6 Composite Cathode with Enhanced Interfacial Stability for Sulfide-Based All-Solid-State Batteries

The implementation of all-solid-state lithium batteries (ASSLBs) is regarded as an important step toward the next-generation energy storage systems. The sulfide solid-state electrolyte (SSE) is a promising candidate for ASSLBs due to its high ionic conductivity and easy processability. However, the interface stability of sulfide SSEs toward high-capacity cathodes like nickel-rich layered cathodes is limited by the interfacial side reaction and narrow electrochemical window of the electrolyte. Herein, we propose introducing the halide SSE Li₃InCl₆ (LIC) with high (electro)chemical stability and superior Li⁺ conductivity to act as an ionic conductive additive in the Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) cathode mixture through a slurry coating, aiming to build a stable cathode-electrolyte interface. This work demonstrates that the sulfide SSE Li_5.5PS_4.5Cl_1.5 (LPSCl) is chemically incompatible with the NCM cathode, and the indispensable role of the substitution of LPSCl with LIC in enhancing the interfacial compatibility and oxidation stability of the electrolyte is highlighted. Accordingly, this new configuration shows superior electrochemical performance at room temperature. It shows a high initial discharge capacity (136.3 mA h g^-1 at 0.1C), cycling performance (77.4% capacity retention at the 100th cycle), and rate capability (79.3 mA h g^-1 at 0.5C). This work paves the way for investigating interfacial challenges regarding high-voltage cathodes and provides new insights into possible interface engineering strategies.

In Situ Nano-SiO2 Electrospun Polyethylene-Oxide-Based Nano-Fiber Composite Solid Polymer Electrolyte for High-Performance Lithium-Ion Batteries

Polyethylene oxide (PEO)-based composite polymer electrolytes (CPEs) containing in situ SiO₂ fillers are prepared using an electrostatic spinning method at room temperature. Through the in situ hydrolysis of tetraethyl silicate (TEOS), the generated SiO₂ nanospheres are uniformly dispersed in the PEO matrix to form a 3D ceramic network, which enhances the mechanical properties of the electrolyte as a reinforcing phase. The interaction between SiO₂ nanospheres and PEO chains results in chemical bonding with a decrease in the crystallinity of the PEO matrix, as well as the complexation strength of PEO chains with lithium ions during the hydrolysis process. Meanwhile, the addition of SiO₂ nanospheres can disturb the orderliness of PEO chain segments and further suppress the crystallization of the PEO matrix. Therefore, improved mechanical/electrochemical properties can be obtained in the as-spun electrolyte with the unique one-dimensional high-speed ion channels. The electrospun CPE with in situ SiO₂ (10 wt%, ca. 45 nm) has a higher ionic conductivity of 1.03 × 10^-3 S cm^-1 than that of the mechanical blending one. Meanwhile, the upper limit of the electrochemical stability window is up to 5.5 V versus Li⁺/Li, and a lithium-ion migration number can be of up to 0.282 at room temperature. In addition, in situ SiO₂ electrospun CPE achieves a tensile strength of 1.12 MPa, elongation at the break of 488.1%, and it has an excellent plasticity. All in all, it is expected that the electrospun CPE prepared in this study is a promising one for application in an all-solid-state lithium-ion battery (LIB) with a high energy density, long life cycle, and high safety.

Engineering a High-Voltage Durable Cathode/Electrolyte Interface for All-Solid-State Lithium Metal Batteries via In Situ Electropolymerization

Poly(ethylene oxide) (PEO)-based polymer electrolytes have been widely studied as a result of their flexibility, excellent interface contact, and high compatibility with a lithium metal anode. Owing to the poor oxidation resistance of ethers, however, the PEO-based electrolytes are only compatible with low-voltage cathodes, which limits their energy density. Here, a high-voltage stable solid-state interface layer based on polyfluoroalkyl acrylate was constructed via in situ solvent-free bulk electropolymerization between the LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathode and the PEO-based solid polymer electrolyte. The electrochemical oxidation window of the as-synthesized electrolyte was therefore expanded from 4.3 V for the PEO-based matrix electrolyte to 5.1 V, and the ionic conductivity was improved to 1.02 × 10^-4 S cm^-1 at ambient temperature and 4.72 × 10^-4 S cm^-1 at 60 °C as a result of the improved Li⁺ migration. This fabrication process for the interface buffer layer by an in situ electrochemical process provides an innovative and universal interface engineering strategy for high-performance and high-energy-density solid-state batteries, which has not been explicitly discussed before, paving the way toward the large-scale production of the next generation of solid-state lithium batteries.

Drastic Reduction of the Solid Electrolyte-Electrode Interface Resistance via Annealing in Battery Form

The origin of electrical resistance at the interface between the positive electrode and solid electrolyte of an all-solid-state Li battery has not been fully determined. It is well known that the interface resistance increases when the electrode surface is exposed to air. However, an effective method of reducing this resistance has not been developed. This report demonstrates that drastic reduction of the resistance is achievable by annealing the entire battery cell. Exposing the LiCoO₂ positive electrode surface to H₂O vapor increases the resistance by more than 10 times (to greater than 136 Ω cm²). The magnitude can be reduced to the initial value (10.3 Ω cm²) by annealing the sample in a battery form. First-principles calculations reveal that the protons incorporated into the LiCoO₂ structure are spontaneously deintercalated during annealing to restore the low-resistance interface. These results provide fundamental insights into the fabrication of high-performance all-solid-state Li batteries.

High Performance Single-Crystal Ni-Rich Cathode Modification via Crystalline LLTO Nanocoating for All-Solid-State Lithium Batteries

Sulfide-based all-solid-state lithium batteries (ASSLBs) assembled with Ni-rich layered cathodes are currently promising candidates for achieving high-energy-density and high-safety energy storage systems. However, the interfacial challenges between sulfide electrolyte and Ni-rich layered cathode, such as space charge layer, side reaction, and poor physical contact, greatly limit the practicality of all-solid-state batteries. In this work, an optimal crystalline Li_0.35La_0.55TiO₃ (LLTO) surface coating with a thickness of roughly 6 nm and a high Li ion conductivity of 0.3 mS cm^-1 was adopted to enhance the structural stability of the single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ (S-NCM622) cathode in ASSLBs. Furthermore, due to the high ionic conductivity and chemical stability of the LLTO coating layer, the interfacial problems, involving interfacial reaction and a space charge layer, in sulfide-based all-solid-state batteries have been effectively solved. As a result, the assembled ASSLBs with the S-NCM622@LLTO cathode exhibit high initial capacity (179.7 mAh g^-1) at 0.05 C and excellent cycling performance with 84.5% capacity retention after 100 cycles at 0.1 C at room temperature. This work proposes an effective strategy to enhance the performance of Ni-rich layered cathodes for next-generation high-energy-density sulfide-based lithium batteries.

Preparing Two-Dimensional Ordered Li0.33 La0.557 TiO3 Crystal in Interlayer Channel of Thin Laminar Inorganic Solid-State Electrolyte towards Ultrafast Li+ Transfer

Inorganic superionic conductor holds great promise for high-performance all-solid-state lithium batteries. However, the ionic conductivity of traditional inorganic solid electrolytes (ISEs) is always unsatisfactory owing to the grain boundary resistance and large thickness. Here, a 13 μm-thick laminar framework with ≈1.3 nm interlayer channels is fabricated by self-assembling rigid, hydrophilic vermiculite (Vr) nanosheets. Then, Li_0.33 La_0.557 TiO₃ (LLTO) precursors are impregnated in interlayer channels and afterwards in situ sintered to large-size, oriented, and defect-free LLTO crystal. We demonstrate that the confinement effect permits ordered arrangement of LLTO crystal along the c-axis (the fastest Li⁺ transfer direction), permitting the resultant 15 μm-thick Vr-LLTO electrolyte an ionic conductivity of 8.22×10^-5  S cm^-1 and conductance of 87.2 mS at 30 °C. These values are several times' higher than that of traditional LLTO-based electrolytes. Moreover, Vr-LLTO electrolyte has a compressive modulus of 1.24 GPa. Excellent cycling performance is demonstrated with all-solid-state Li/LiFePO₄ battery.

Understanding LiI-LiBr Catalyst Activity for Solid State Li2S/S Reactions in an All-Solid-State Lithium Battery

Li||MoS₂ solid-state batteries have higher volumetric energy density and power density than Li||Li₂S batteries. However, they suffer from energy and power decay due to the formation of lithium sulfide that has low ionic/electronic conductivity and a strong Li-S bond. Herein, we overcome these challenges by incorporating the catalytic LiI-LiBr compound and carbon black into MoS₂. The comprehensive simulations, characterizations, and electrochemical evaluations demonstrated that LiI-LiBr significantly reduces Li⁺/S^2- interaction and increases the ionic conductivity of Li₂S, thus enhancing the reaction kinetics and Li₂S/S redox reversibility. MoS₂@LiI-LiBr@C||Li cells with an areal capacity of 0.87 mAh cm^-2 provide a reversible capacity of 816.2 mAh g^-1 at 200 mA g^-1 and maintain 604.8 mAh g^-1 (based on the mass of MoS₂) for 100 cycles. At a high areal capacity of 2 mAh cm^-2, the battery still delivers reversible capacity of 498 mAh g^-1. LiI-LiBr-carbon additive can be broadly applied for all transition-metal sulfide cathodes to enhance the cyclic and rate performance.

Robust Li6PS5I Interlayer to Stabilize the Tailored Electrolyte Li9.95SnP2S11.95F0.05/Li Metal Interface

All-solid-state lithium-metal batteries (ASSLMBs) with sulfide electrolytes have attracted attention owing to their superior safety and high energy density. However, interfacial instability of sulfide electrolytes against Li metal still hinders their applications. Herein, F-doping is adopted to optimize the structure of Li₁₀SnP₂S₁₂. It is demonstrated that the Li_9.95SnP₂S_11.95F_0.05 (LSPSF) electrolyte exhibits a high ionic conductivity of 6.4 mS cm^-1 because of F-doping, which can reduce the impurity Li₂SnS₃ and generate Li⁺ vacancies. In addition, the Li₆PS₅I (LPSI) glass-ceramic interlayer is employed to enhance the interfacial stability between the sulfide electrolyte and Li metal by restraining the reduction of Sn⁴⁺ cations, as indicated by X-ray photoelectron spectroscopy (XPS). As a result, the assembled ASSLMBs with the LPSI interlayer deliver high initial discharge capacity and remarkable cycling stability. This work provides a new design route for manufacturing high-performance ASSLMBs.

Visualization and Control of Chemically Induced Crack Formation in All-Solid-State Lithium-Metal Batteries with Sulfide Electrolyte

The application of lithium metal as a negative electrode in all-solid-state batteries shows promise for optimizing battery safety and energy density. However, further development relies on a detailed understanding of the chemo-mechanical issues at the interface between the lithium metal and solid electrolyte (SE). In this study, crack formation inside the sulfide SE (Li₃PS₄: LPS) layers during battery operation was visualized using in situ X-ray computed tomography (X-ray CT). Moreover, the degradation mechanism that causes short-circuiting was proposed based on a combination of the X-ray CT results and scanning electron microscopy images after short-circuiting. The primary cause of short-circuiting was a chemical reaction in which LPS was reduced at the lithium interface. The LPS expanded during decomposition, thereby forming small cracks. Lithium penetrated the small cracks to form new interfaces with fresh LPS on the interior of the LPS layers. This combination of reduction-expansion-cracking of LPS was repeated at these new interfaces. Lithium clusters eventually formed, thereby generating large cracks due to stress concentration. Lithium penetrated these large cracks easily, finally causing short-circuiting. Therefore, preventing the reduction reaction at the interface between the SE and lithium metal is effective in suppressing degradation. In fact, LPS-LiI electrolytes, which are highly stable to reduction, were demonstrated to prevent the repeated degradation mechanism. These findings will promote all-solid-state lithium-metal battery development by providing valuable insight into the design of the interface between SEs and lithium, where the selection of a suitable SE is vital.

Improved Ionic Conductivity and Li Dendrite Suppression Capability toward Li7P3S11-Based Solid Electrolytes Triggered by Nb and O Cosubstitution

It is still a big challenge to simultaneously enhance the ionic conductivity, dendrite suppression capability, and interfacial compatibility of sulfide solid electrolytes. In this work, a novel Li₇P_2.88Nb_0.12S_10.7O_0.3 solid electrolyte is prepared via Nb and O cosubstitution of glass-ceramic Li₇P₃S₁₁. This sulfide-based electrolyte possesses a high ionic conductivity (3.59 mS cm^-1) at 298 K, improved critical current density (1.16 mA cm^-2), and excellent interfacial compatibility between the sulfide electrolyte and Li₂S active material. The improved electrochemical stability of the sulfide solid electrolyte against metallic lithium is attributed to the formation of Nb and Li₂O at the interface, which can induce uniform Li deposition and prevent further side reaction. The all-solid-state Li/Li₂S batteries based on this electrolyte exhibit remarkably enhanced cycling stability and rate performance.

Densified Li6PS5Cl Nanorods with High Ionic Conductivity and Improved Critical Current Density for All-Solid-State Lithium Batteries

Solid electrolytes are receiving great interest owing to their good mechanical properties and high lithium-ion transference number, which could potentially suppress lithium dendrites. However, lithium dendrites can still penetrate solid electrolytes even at low current densities. In this work, a flat-surface Li₆PS₅Cl nanorod pellet with high density is achieved, which exhibits an ionic conductivity as high as 6.11 mS cm^-1 at 25 °C. The flat surface of the pellet is beneficial for the homogeneous lithium deposition, and the dense pellet microstructure can suppress the growth of lithium dendrites along the grain boundaries, leading to a significantly improved critical current density of 1.05 mA cm^-2 at 25 °C. The resultant dense Li₆PS₅Cl pellet is further employed in a LiCoO₂/Li₆PS₅Cl/Li all-solid-state lithium battery, showing an initial discharge capacity of 115.3 mAh g^-1 at 1C (0.35 mA cm^-2, 25 °C) with a capacity retention of 80.3% after 100 cycles.

Sulfide Electrolyte Suppressing Side Reactions in Composite Positive Electrodes for All-Solid-State Lithium Batteries

Long-lasting all-solid-state batteries can be achieved by preventing side reactions in the composite electrodes comprising electrode active materials and solid electrolytes. Typically, the battery performance can be enhanced through the use of robust solid electrolytes that are resistant to oxidation and decomposition. In this study, the thermal stability of sulfide solid electrolytes Li₃PS₄ and Li₄SnS₄ toward oxide positive electrode active materials was estimated by investigating the occurrence of side reactions at the electrolyte-electrode interfaces when the composite electrodes are heated in an accelerated aging test: Li₄SnS₄ showed higher thermal stability because of the suppression of the substitution reaction between S and O. Moreover, thermally stable sulfide solid electrolytes are amenable to an improved cell construction process. The sintering (pelletizing and subsequent heating) of the composite electrodes with Li₄SnS₄ as the solid electrolyte allowed the manufacture of dense electrodes that exhibited increased ionic conductivity, thereby enhancing the battery performance.

Novel Research Approach Combined with Dielectric Spectrum Testing for Dual-Doped Li7P3S11 Glass-Ceramic Electrolytes

Owing to the expanding function of Li-ion transmission channels, it is important to explore the doping effects of different compounds into sulfide solid electrolytes to improve their electrochemical performances. However, it is hard to characterize the doping behaviors within sulfide solid electrolytes with low crystallinity and poor stability just by conventional crystallography analytical methods. In this work, the dielectric spectrum testing combined with other analytical methods, such as ⁷Li solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy, and the electrochemical method, have been applied to investigate the dual-doping behaviors of WS₂ and LiBr within Li₇P₃S₁₁ glass-ceramic electrolytes. This research method can not only evaluate the internal acting effect between the skeleton of sulfide solid electrolytes and the migrating kinetics of Li ions but also explore the capacitance at the interfaces of LiCoO₂/sulfide solid electrolytes. The experimental results show that the number of Li ions with fast transport velocity within Li₂S-P₂S₅-based solid electrolytes has been increased. Meanwhile, the interfacial capacitances between Li₂S-P₂S₅-based solid electrolytes and the LiCoO₂ cathode have decreased after dual-doping of WS₂ and LiBr, indicating a synergetic effect for the doped Li₇P₃S₁₁ glass-ceramic electrolytes in terms of the ionic conductivities and interfacial compatibilities. This work may provide a novel analytical approach to explore both the diffusion kinetics and interfacial behaviors for the solid electrolytes of lithium batteries.

LiI-Doped Sulfide Solid Electrolyte: Enabling a High-Capacity Slurry-Cast Electrode by Low-Temperature Post-Sintering for Practical All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) based on sulfide solid electrolytes (SEs) have received great attention because of the high ionic conductivity of the SEs, intrinsic thermal safety, and higher energy density achievable with a Li metal anode. However, studies on practical slurry-cast composite electrodes show an extremely limited battery performance than the binder-free pelletized electrodes because of the poor interfacial robustness between the active materials and SEs by the presence of a polymeric binder. Here, we employ a low-temperature post-sintering process for the slurry-cast composite electrodes in order to overcome the binder-induced detrimental effects on the electrochemical performance. The LiI-doped Li₃PS₄ SEs are chosen because the addition of iodine not only improves the Li-ion conductivity and Li metal compatibility but also lowers the glass-transition and crystallization temperatures. Low-temperature post-sintering of composite cathodes consisting of a LiNi_0.6Co_0.2Mn_0.2O₂-active material, LiI-doped Li₃PS₄ SE, polymeric binder, and conducting agent shows a significantly improved electrochemical performance as compared to a conventional slurry-cast electrode containing pre-annealed SEs. Detailed analyses by electrochemical impedance spectroscopy and galvanostatic intermittent titration technique confirm that post-sintering effectively reduces the interfacial resistance and enhances the chemomechanical robustness at solid-solid interfaces, which enables the development of practical slurry-cast ASSLBs with sulfide SEs.

Interface Re-Engineering of Li10GeP2S12 Electrolyte and Lithium anode for All-Solid-State Lithium Batteries with Ultralong Cycle Life

An ingenious interface re-engineering strategy was applied to in situ prepare a manipulated LiH₂PO₄ protective layer on the surface of Li anode for circumventing the intrinsic chemical stability issues of Li₁₀GeP₂S₁₂ (LGPS) to Li metal, specifically the migration of mixed ionic-electronic reactants to the inner of LGPS, and the kinetically sluggish reactions in the interface. As consequence, the stability of LGPS with Li metal increased substantially and the cycling of symmetric Li/Li cell showed that the polarization voltage could keep relative stable for over 950 h at 0.1 mA cm^-2 within ±0.05 V. The optimized ASSLiB of LiCoO₂ (LCO)/LGPS/Li with interface-engineered structure was able to deliver long cycle life and high capacity, i.e., a reversible discharge capacity of 131.1 mAh g^-1 at the initial cycle and 113.7 mAh g^-1 at the 500th cycle under 0.1 C with a retention of 86.7%. In addition, the factors effected on the interphases formation of the LGPS/Li interface were analyzed, and the mechanism of the stability between LGPS and Li anode with protective layer was further investigated. Moreover, the probable causes of battery degradation were also explored. Above all, this work would give an alternative strategy for the modification of Li anode in high energy density solid-state lithium metal batteries.

Suppression of Lithium Dendrite Formation by Using LAGP-PEO (LiTFSI) Composite Solid Electrolyte and Lithium Metal Anode Modified by PEO (LiTFSI) in All-Solid-State Lithium Batteries

The formation of lithium dendrites is suppressed using a Li_1.5Al_0.5Ge_1.5(PO₄)₃-poly(ethylene oxide) (LAGP-PEO) composite solid electrolyte and a PEO (lithium bis(trifluoromethane)sulfonimide) [PEO (LiTFSI)]-modified lithium metal anode in all-solid-state lithium batteries. The effects on the anode performance based on the PEO content in the composite solid electrolyte and the molecular weight of PEO used to modify the Li anode are studied. The structure, surface morphology, and stability of the composite solid electrolyte are examined by X-ray diffraction spectroscopy, scanning electron microscopy, and electrochemical tests. Results show that the presence of a PEO-500000(LiTFSI) film on a Li anode results in good mechanical properties and satisfactory interface contact features. The film can also prevent Li from reacting with LAGP. Furthermore, the formation of lithium dendrites can be effectively inhibited as the composite solid electrolyte is combined with the PEO film on the Li anode. The ratio of PEO in the composite solid electrolyte can be reduced to a low level of 1 wt %. PEO remains stable even at a high potential of 5.12 V (vs Li/Li⁺). The assembled Li-PEO (LiTFSI)/LAGP-PEO/LiMn_0.8Fe_0.2PO₄ all-solid-state cell can deliver an initial discharge capacity of 160.8 mAh g^-1 and exhibit good cycling stability and rate performance at 50 °C.