A Functional Air-Stable Li9.8GeP1.7Sb0.3S11.8I0.2 Superionic Conductor for High-Performance All-Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) based on sulfides have become a subject of great interest due to their superior Li-ion conductivity, low grain boundary resistance, and adequate mechanical strength. However, they grapple with chemical instability toward moisture hypersensitivity, which decreases their ionic conductivity, leading to more processing requirements. Herein, a Li9.8GeP1.7Sb0.3S11.8I0.2 (LGPSSI) superionic conductor is designed with a Li+ conductivity of 6.6 mS cm-1 and superior air stability based on hard and soft acids and bases (HSAB) theory. The introduction of optimal antimony (Sb) and iodine (I) into the Li10GeP2S12 (LGPS) structure facilitates fast Li-ion migration with low activation energy (Ea) of 20.33 kJ mol-1. The higher air stability of LGPSSI is credited to the strategic substitution of soft acid Sb into (Ge/P)S4 tetrahedral sites, examined by Raman and X-ray photoelectron spectroscopy techniques. Relatively lower acidity of Sb compared to phosphorus (P) realizes a stronger Sb-S bond, minimizing the evolution of toxic H2S (0.1728 cm3 g-1), which is ∼3 times lower than pristine LGPS when LGPSSI is exposed to moist air for 120 min. The NCA//Li-In full cell with a LGPSSI superionic conductor delivered the first discharge capacity of 209.1 mAh g-1 with 86.94% Coulombic efficiency at 0.1 mA cm-2. Furthermore, operating at a current density of 0.3 mA cm-2, LiNbO3@NCA/LGPSSI/Li-In cell demonstrated an exceptional reversible capacity of 117.70 mAh g-1, retaining 92.64% of its original capacity over 100 cycles.

Status and Prospect of Two-Dimensional Materials in Electrolytes for All-Solid-State Lithium Batteries

Replacing liquid electrolytes and separators in conventional lithium-ion batteries with solid-state electrolytes (SSEs) is an important strategy to ensure both high energy density and high safety. Searching for fast ionic conductors with high electrochemical and chemical stability has been the core of SSE research and applications over the past decades. Based on the atomic-level thickness and infinitely expandable planar structure, numerous two-dimensional materials (2DMs) have been exploited and applied to address the most critical issues of low ionic conductivity of SSEs and lithium dendrite growth in all-solid-state lithium batteries. This review introduces the research process of 2DMs in SSEs, then summarizes the mechanisms and strategies of inert and active 2DMs toward Li+ transport to improve the ionic conductivity and enhance the electrode/SSE interfacial compatibility. More importantly, the main challenges and future directions for the application of 2DMs in SSEs are considered, including the importance of exploring the relationship between the anisotropic structure of 2DMs and Li+ diffusion behavior, the exploitation of more 2DMs, and the significance of in situ characterizations in elucidating the mechanisms of Li+ transport and interfacial reactions. This review aims to provide a comprehensive understanding to facilitate the application of 2DMs in SSEs.

Low-cost BPO4 In Situ Synthetic Li3 PO4 Coating and B/P-Doping to Boost 4.8 V Cyclability for Sulfide-Based All-Solid-State Lithium Batteries

Structural damage of Ni-rich layered oxide cathodes such as LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) and serious interfacial side reactions and physical contact failures with sulfide electrolytes (SEs) are the main obstacles restricting ≥4.6 V high-voltage cyclability of all-solid-state lithium batteries (ASSLBs). To tackle this constraint, here, a modified NCM811 with Li3 PO4 coating and B/P co-doping using inexpensive BPO4 as raw materials via the one-step in situ synthesis process is presented. Phosphates have good electrochemical stability and contain the same anion (O2- ) and cation (P5+ ) as in cathode and SEs, respectively, thus Li3 PO4 coating precludes interfacial anion exchange, lessening side reactivity. Based on the high bond energy of B─O and P─O, the lattice O and crystal texture of NCM811 can be stabilized by B3+ /P5+ co-doping, thereby suppressing microcracks during high-voltage cycling. Therefore, when tested in combination with Li─In anode and Li6 PS5 Cl solid electrolytes (LPSCl), the modified NCM811 exhibits extraordinary performance, with 200.36 mAh g-1 initial discharge capacity (4.6 V), cycling 2300 cycles with decay rate as low as 0.01% per cycle (1C), and 208.26 mAh g-1 initial discharge capacity (4.8 V), cycling 1986 cycles with 0.02% per cycle decay rate. Simultaneously, it also has remarkable electrochemical abilities at both -20 °C and 60 °C.

Critical Factors to Understanding the Electrochemical Performance of All-Solid-State Batteries: Solid Interfaces and Non-Zero Lattice Strain

All-solid-state lithium batteries have been developed to secure safety by substituting a flammable liquid electrolyte with a non-flammable solid electrolyte. However, owing to the nature of solids, interfacial issues between cathode materials and solid electrolytes, including chemical incompatibility, electrochemo-mechanical behavior, and physical contact, pose significant challenges for commercialization. Herein, critical factors for understanding the performance of all-solid-state batteries in terms of solid interfaces and non-zero lattice strains are identified through a strategic approach. The initial battery capacity can be increased via surface coating and electrode-fabrication methods; however, the increased lattice strain causes significant stress to the solid interface, which degrades the battery cycle life. However, this seesaw effect can be alleviated using a more compacted electrode microstructure between the solid electrolyte and oxide cathode materials. The compact solid interfaces contribute to low charge-transfer resistance and a homogeneous reaction between particles, thereby leading to improved electrochemical performance. These findings demonstrate, for the first time, a correlation between the uniformity of the electrode microstructure and electrochemical performance through the investigation of the reaction homogeneity among particles. Additionally, this study furthers the understanding of the relationship between electrochemical performance, non-zero lattice strain, and solid interfaces.

Dual-Coordination-Induced Poly(vinylidene fluoride)/Li6.4Ga0.2La3Zr2O12/Succinonitrile Composite Solid Electrolytes Toward Enhanced Rate Performance in All-Solid-State Lithium Batteries

Pursuing high energy and power density in all-solid-state lithium batteries (ASSLBs) has been the focus of attention. However, due to their inferior ion transport, their rate performance is limited compared to traditional lithium-ion batteries. Herein, a dual-coordination mechanism is first proposed to construct a high-performance poly(vinylidene fluoride)/Li6.4Ga0.2La3Zr2O12/succinonitrile (PVDF/LLZO/SN) composite solid electrolyte. The dual-coordination interactions of SN with both LLZO and Li+ in lithium salts allow SN to act like a branched chain of PVDF, realizing an increase in the free volume of the composite electrolyte. Meanwhile, SN molecules are immobilized within the electrolyte membrane by coordinating with LLZO, ensuring good interfacial stability. Profiting from the dual-coordination mechanism, the PVDF/LLZO/SN composite solid electrolyte combines enhanced electrochemical performance and interfacial compatibility. When applied to ASSLBs, the composite solid electrolyte enables the battery to operate at rates up to 6 C. The LiFePO4/Li batteries operated at 4 C can still deliver a high capacity retention rate of 96.4% after 50 cycles. Notably, these batteries also exhibit good long-cycle stability. After 500 cycles at 0.5 C, the discharge capacity was maintained at 145.9 mAh g-1.

Fluorinated Li10 GeP2 S12 Enables Stable All-Solid-State Lithium Batteries

The instability of Li₁₀ GeP₂ S₁₂ toward moisture and that toward lithium metal are two challenges for the application in all-solid-state lithium batteries. In this work, Li₁₀ GeP₂ S₁₂ is fluorinated to form a LiF-coated core-shell solid electrolyte LiF@Li₁₀ GeP₂ S₁₂ . Density-functional theory calculations confirm the hydrolysis mechanism of Li₁₀ GeP₂ S₁₂ solid electrolyte, including H₂ O adsorption on Li atoms of Li₁₀ GeP₂ S₁₂ and the subsequent PS₄ ^3- dissociation affected by hydrogen bond. The hydrophobic LiF shell can reduce the adsorption site, thus resulting in superior moisture stability when exposing in 30% relative humidity air. Moreover, with LiF shell, Li₁₀ GeP₂ S₁₂ shows one order lower electronic conductivity, which can significantly suppress lithium dendrite growth and reduce the side reaction between Li₁₀ GeP₂ S₁₂ and lithium, realizing three times higher critical current density to 3 mA cm^-2 . The assembled LiNbO₃ @LiCoO₂ /LiF@Li₁₀ GeP₂ S₁₂ /Li battery exhibits an initial discharge capacity of 101.0 mAh g^-1 with a capacity retention of 94.8% after 1000 cycles at 1 C.

An Ion-Channel-Restructured Zwitterionic Covalent Organic Framework Solid Electrolyte for All-Solid-State Lithium-Metal Batteries

Organic solid electrolytes offer an effective route for safe and high-energy-density all-solid-state Li metal batteries. However, it remains a challenge to devise a new strategy to promote the dissociation of strong ion pairs and the transport of ionic components in organic solid electrolytes. Herein, a zwitterionic covalent organic framework (Zwitt-COF) with well-defined chemical and pore structures is prepared as a solid electrolyte capable of accelerating the dissociation and transport of Li ions. The Zwitt-COF solid electrolyte exhibits a high room-temperature ionic conductivity of 1.65 × 10^-4  S cm^-1 with a wide electrochemical stability window. Besides, the Zwitt-COF solid electrolyte displays stable Li plating/stripping behavior via effective inhibition of the formation of Li dendrites and dead Li, leading to superior long-term cycle performance with retention of 99% discharge capacity and 98% Coulombic efficiency in an all-solid-state Li-metal battery. Theoretical simulations reveal that the incorporation of zwitterionic groups into COF can facilitate the dissociation of strong ion pairs and reconstruct the AA-stacking configuration by dissociative adsorption of Li⁺ ions on Zwitt-COF producing linear hexagonal ion channels in the Zwitt-COF solid electrolyte. This strategy based on Zwitt-COF can provide an alternative way to construct various solid-state Li batteries.

Enhanced Moisture Stability of Lithium-Rich Antiperovskites for Sustainable All-Solid-State Lithium Batteries

Lithium-rich antiperovskites (LiRAPs) solid electrolytes have attracted extensive interest due to their advantages of structural tunability, mechanical flexibility, and low cost. However, LiRAPs are instinctively hygroscopic and suffer from decomposition in air, which not only diversifies their electrochemical performances in present reports but also hinders their application in all-solid-state lithium batteries (ASSLBs). Herein, the origin of the hygroscopicity, and also the effect of the hygroscopicity on the electrochemical performances of Li_3-x (OH_x )Cl are systematically investigated. Li_3-x (OH_x )Cl is demonstrated to be unstable in the air and prone to decompose into LiOH and LiCl. Nevertheless, with fluorine doping on chlorine sites, the hygroscopicity of LiRAPs is suppressed by weakening the intermolecular hydrogen bond between LiRAPs and H₂ O, forming a moisture-resistive Li_3-x (OH_x )Cl_0.9 F_0.1 . Taking advantage of its low melting point (274 °C), two prototypes of ASSLBs are assembled in the ambient air by means of co-coating sintering and melt-infiltration. With LiRAPs as the solder, low-temperature sintering of the ASSLBs with low interfacial resistance is demonstrated as feasible. The understanding of the hygroscopic behavior of LiRAPs and the integration of the moisture-resistive LiRAPs with ASSLBs provide an effective way toward the fabrication of the ASSLBs.

Practical Application of Li-Rich Materials in Halide All-Solid-State Batteries and Interfacial Reactions between Cathodes and Electrolytes

Benefiting from the advanced solid-state electrolytes (SSEs), conventional cathodes have been widely applied in all-solid-state lithium batteries (ASSLBs). However, Li-rich Mn-based (LRM) cathodes, which possess enhanced discharge capacities beyond 250 mA h g^-1, have not yet been studied in ASSLBs. In this work, the practical application of LRM cathodes in ASSLBs using a high-voltage-stability halide SSE (Li₃InCl₆, LIC) is reported for the first time. Furthermore, we decipher that the active oxygen released from LRM cathodes at a high operation voltage seriously oxidizes the LIC electrolytes, thus resulting in the large interfacial resistance between cathodes and electrolytes and hindering their industrialized application in ASSLBs. Therefore, surface chemistry engineering of LRM cathodes with an ionic conductive coating material of LiNbO₃ (LNO) is employed to stabilize the LRM/LIC interface. Consequently, the LRM-based ASSLBs deliver a high specific capacity of 221 mA h g^-1 at 0.1 C and a decent cycle life of 100 cycles. This contribution gives insights into studying the interfacial issues between LRM cathodes and halide electrolytes and sheds light on the application of LRM cathode materials in ASSLBs.

Excellent Stability of Ga-Doped Garnet Electrolyte against Li Metal Anode via Eliminating LiGaO2 Precipitates for Advanced All-Solid-State Batteries

Ga-doped garnet-type Li₇La₃Zr₂O₁₂ (Ga-LLZO) ceramics have long been recognized as ideal electrolyte candidates for all-solid-state lithium batteries (ASSLBs). However, in this study, it is shown that Ga-LLZO easily and promptly cracks in contact with molten lithium during the ASSLB assembly. This can be mainly ascribed to two aspects: (i) lithium captures O atoms and reduces Ga ions of the Ga-LLZO matrix, leading to a band-gap closure from >5 to <2 eV and a structural collapse from cubic to tetrahedral; and (ii) the in situ-formed LiGaO₂ impurity phase has severe side reactions with lithium, resulting in huge stress release along the grain boundaries. It is also revealed that, while the former process consumes hours to take effect, the latter one is immediate and accounts for the crack propagation of Ga-LLZO electrolytes. A minute SiO₂ is preadded during the synthesis of Ga-LLZO and found effective in eliminating the LiGaO₂ impurity phase. The SiO₂-modified Ga-LLZO solid electrolytes display excellent thermomechanical and electrochemical stabilities against lithium metals and well-reserved ionic conductivities, which was further confirmed by half-cells and full batteries. This study contributes to the understanding of the stability of garnet electrolytes and promotes their potential commercial applications in ASSLBs.

Toluene Tolerated Li9.88GeP1.96Sb0.04S11.88Cl0.12 Solid Electrolyte toward Ultrathin Membranes for All-Solid-State Lithium Batteries

Sulfide solid electrolyte membranes employed in all-solid-state lithium batteries generally show high thickness and poor chemical stability, which limit the cell-level energy density and cycle life. In this work, Li_9.88GeP_1.96Sb_0.04S_11.88Cl_0.12 solid electrolyte is synthesized with Sb, Cl partial substitution of P, S, possessing excellent toluene tolerance and stability to lithium. The formed SbS₄^3- group in Li_9.88GeP_1.96Sb_0.04S_11.88Cl_0.12 exhibits low adsorption energy and reactivity for toluene molecules, confirmed by first-principles density functional theory calculation. Using toluene as the solvent, ultrathin Li_9.88GeP_1.96Sb_0.04S_11.88Cl_0.12 membranes with adjustable thicknesses can be well prepared by the wet coating method, and an 8 μm thick membrane exhibits an ionic conductivity of 1.9 mS cm^-1 with ultrahigh ionic conductance of 1860 mS and ultralow areal resistance of 0.68 Ω cm^-2 at 25 °C. The obtained LiCoO₂|Li_9.88GeP_1.96Sb_0.04S_11.88Cl_0.12 membrane|Li all-solid-state lithium battery shows an initial reversible capacity of 125.6 mAh g^-1 with a capacity retention of 86.3% after 250 cycles at 0.1 C under 60 °C.

Effects of Li+ conduction on the capacity utilization of cathodes in all-solid-state lithium batteries

Li⁺ conduction in all-solid-state lithium batteries is limited compared with that in lithium-ion batteries based on liquid electrolytes because of the lack of an infiltrative network for Li⁺ transportation. Especially for the cathode, the practically available capacity is constrained due to the limited Li⁺ diffusivity. In this study, all-solid-state thin-film lithium batteries based on LiCoO₂ thin films with varying thicknesses were fabricated and tested. To guide the cathode material development and cell design of all-solid-state lithium batteries, a one-dimensional model was utilized to explore the characteristic size for a cathode with varying Li⁺ diffusivity that would not constrain the available capacity. The results indicated that the available capacity of cathode materials was only 65.6% of the expected value when the area capacity was as high as 1.2 mAh/cm2. The uneven Li distribution in cathode thin films owing to the restricted Li+ diffusivity was revealed. The characteristic size for a cathode with varying Li⁺ diffusivity that would not constrain the available capacity was explored to guide the cathode material development and cell design of all-solid-state lithium batteries.

In-Operando Lithium-Ion Transport Tracking in an All-Solid-State Battery

An all-solid-state battery is a secondary battery that is charged and discharged by the transport of lithium ions between positive and negative electrodes. To fully realize the significant benefits of this battery technology, for example, higher energy densities, faster charging times, and safer operation, it is essential to understand how lithium ions are transported and distributed in the battery during operation. However, as the third lightest element, methods for quantitatively analyzing lithium during operation of an all-solid-state device are limited such that real-time tracking of lithium transport has not yet been demonstrated. Here, the authors report that the transport of lithium ions in an all-solid-state battery is quantitatively tracked in near real time by utilizing a high-intensity thermal neutron source and lithium-6 as a tracer in a thermal neutron-induced nuclear reaction. Furthermore, the authors show that the lithium-ion migration mechanism and pathway through the solid electrolyte can be determined by in-operando tracking. From these results, the authors suggest that the development of all-solid-state batteries has entered a phase where further advances can be carried out while understanding the transport of lithium ions in the batteries.

Priority and Prospect of Sulfide-Based Solid-Electrolyte Membrane

All-solid-state lithium batteries (ASSLBs) employing sulfide solid electrolytes (SEs) promise sustainable energy storage systems with energy-dense integration and critical intrinsic safety, yet they still require cost-effective manufacturing and the integration of thin membrane-based SE separators into large-format cells to achieve scalable deployment. This review, based on an overview of sulfide SE materials, is expounded on why implementing a thin membrane-based separator is the priority for mass production of ASSLBs and critical criteria for capturing a high-quality thin sulfide SE membrane are identified. Moreover, from the aspects of material availability, membrane processing, and cell integration, the major challenges and associated strategies are described to meet these criteria throughout the whole manufacturing chain to provide a realistic assessment of the current status of sulfide SE membranes. Finally, future directions and prospects for scalable and manufacturable sulfide SE membranes for ASSLBs are presented.

Ultrafast Sintering for Ceramic-Based All-Solid-State Lithium-Metal Batteries

Long processing time and high temperatures are often required in sintering ceramic electrolytes, which lead to volatile element loss and high cost. Here, an ultrafast sintering method of microwave-induced carbothermal shock to fabricate various ceramic electrolytes in seconds is reported. Furthermore, it is also possible to integrate the electrode and electrolyte in one step by simultaneous co-sintering. Based on this ultrafast co-sintering technique, an all-solid-state lithium-metal battery with a high areal capacity is successfully achieved, realizing a promising electrochemical performance at room temperature. This method can extend to other various ceramic multilayer-based solid devices.

Lithium Bromide-Induced Organic-Rich Cathode/Electrolyte Interphase for High-Voltage and Flame-Retardant All-Solid-State Lithium Batteries

Poly(ethylene oxide) (PEO)-based solid electrolyte suffers from limited anodic stability and an intrinsic flammable issue, hindering the achievement of high energy density and safe all-solid-state lithium batteries. Herein, we surprisingly found out that a bromine-rich additive, decabromodiphenyl ethane (DBDPE), could be preferably oxidized at an elevated voltage and decompose to lithium bromide at an elevated potential followed by inducing an organic-rich cathode/electrolyte interphase (CEI) on NCM811 surface, enabling both high-voltage resistance (up to 4.5 V) and flame-retardancy for the PEO-based electrolyte. On the basis of this novel solid electrolyte, all-solid-state Li/NCM811 batteries deliver an average reversible capacity of 151.4 mAh g^-1 over the first 150 cycles with high capacity retention (83.0%) and high average Coulombic efficiency (99.7%) even at a 4.5 V cutoff voltage with a unprecedented flame-retardant properties. In view of these exploration, our studies revealed the critical role of LiBr in inducing an organic-rich thin and uniform CEI passivating layer with enhanced lithium ion surface diffusion and high-voltage resistant properties, which provides a new protocol for the further design of a high-voltage PEO-based all-solid-state electrolyte.

Amorphous Titanium Polysulfide Composites with Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries

All-solid-state lithium/sulfide batteries are considered as next-generation high-energy-density batteries with unrivaled safety. However, sulfide cathodes generally suffer from insulating properties and huge volume expansion in all-solid-state lithium batteries. Based on amorphous TiS₄ (a-TiS₄), a certain proportion of Super P is introduced to suppress the volume expansion and increase the electronic conductivity. Meanwhile, a Li₇P₃S₁₁ solid electrolyte is in situ coated on the surface of 20% Super P/a-TiS₄, and the close interfacial contact between the active material and the solid electrolyte constructs a favorable ionic conduction path. As a result, a Li/75% Li₂S-24% P₂S₅-1% P₂O₅/Li₁₀GeP₂S₁₂/20% Super P/a-TiS₄@Li₇P₃S₁₁ battery shows a high reversible capacity of 507.4 mAh g^-1 after 100 cycles at 0.1 A g^-1. Even the current density increases to 1.0 A g^-1, and it can also provide a reversible capacity of 349.8 mAh g^-1 after 200 cycles. These results demonstrate a promising 20% Super P/a-TiS₄@Li₇P₃S₁₁ cathode material with electronic/ionic conduction networks for all-solid-state lithium batteries.

2D Materials for All-Solid-State Lithium Batteries

Although one of the most mature battery technologies, lithium-ion batteries still have many aspects that have not reached the desired requirements, such as energy density, current density, safety, environmental compatibility, and price. To solve these problems, all-solid-state lithium batteries (ASSLB) based on lithium metal anodes with high energy density and safety have been proposed and become a research hotpot in recent years. Due to the advanced electrochemical properties of 2D materials (2DM), they have been applied to mitigate some of the current problems of ASSLBs, such as high interface impedance and low electrolyte ionic conductivity. In this work, the background and fabrication method of 2DMs are reviewed initially. The improvement strategies of 2DMs are categorized based on their application in the three main components of ASSLBs: The anode, cathode, and electrolyte. Finally, to elucidate the mechanisms of 2DMs in ASSLBs, the role of in situ characterization, synchrotron X-ray techniques, and other advanced characterization are discussed.

Nonstoichiometric Molybdenum Trioxide Adjustable Energy Barrier Enabling Ultralong-Life All-Solid-State Lithium Batteries

The performance of lithium batteries is largely dependent on the ionic conductivity within robust solid electrolytes. Poly(ethylene oxide) (PEO)-based electrolytes, however, have a low lithium ionic conductivity, which limits the hop of Li⁺. Herein, a novel PEO-based composite electrolyte is prepared that contains nonstoichiometric transition molybdenum trioxide (MoO_3-x) nanosheets as fillers to improve the ionic conductivity. The MoO_3-x nanosheets containing many oxygen vacancies can cross-link with PEO chains to reduce the energy barrier of Li⁺ migration and the matrix crystallinity, leading to an increase in the lithium-ion transference number (up to 0.56) and a high ionic conductivity (up to 6 × 10^-4 S cm^-1) at 60 °C. Meanwhile, the incorporation of MoO_3-x nanosheets alleviates the decomposition of the electrolyte, enhancing the tensile strength by ∼4 times compared to PEO. As a result, a LiFePO₄/Li cell with PEO/LiTFSI/MoO_3-x (PLM3-x) delivers an excellent rate capability, high capacity, and lifespan during high rates (2 C, ≥10 000 cycles), which demonstrates a facile yet effective strategy toward high-performance lithium batteries.

Single-Crystal-Layered Ni-Rich Oxide Modified by Phosphate Coating Boosting Interfacial Stability of Li10 SnP2 S12 -Based All-Solid-State Li Batteries

All-solid-state lithium batteries (ASSLBs) adopting sulfide electrolytes and high-voltage layered oxide cathodes have moved into the mainstream owing to their superior safety and immense potential in high energy density. However, the poor electrochemical compatibility between oxide cathodes and sulfide electrolytes remains a challenge for high-performance ASSLBs. In this study, a nanoscale Li_1.4 Al_0.4 Ti_1.6 (PO₄ )₃ (LATP) phosphate coating is reasonably constructed on the surface of single-crystal LiNi_0.6 Co_0.2 Mn_0.2 O₂ particles to achieve cathode/electrolyte interfacial stability. The conformal LATP layer with inherent high-voltage stability can effectively suppress the oxidation decomposition of the electrolyte and demonstrate chemical inertness to both the oxide cathode and Li₁₀ SnP₂ S₁₂ electrolyte. ASSLBs with an LATP-modified cathode exhibited a high initial discharge capacity (152.1 mAh g^-1 ), acceptable rate capability, and superior cycling performance with a capacity retention of 87.6% after 100 cycles at 0.1 C. Interfacial modification is an effective approach for achieving high-performance sulfide-based ASSLBs with superior interfacial stability.

Wet-Milling Synthesis of Superionic Lithium Argyrodite Electrolytes with Different Concentrations of Lithium Vacancy

The ionic conductivities of argyrodite electrolytes are significantly affected by the concentrations of lithium vacancy. Herein, a facile and rapid synthesis route is proposed to systematically investigate Li_6-xPS_5-xCl_1+x (0 ≤ x ≤ 0.8) with different lithium vacancies by adjusting ratios of S/Cl. The highest ionic conductivity of the wet-milling synthesized Li_5.4PS_4.4Cl_1.6 is 6.18 mS cm^-1, which is attributed to higher lithium vacancy concentration and lower electrostatic interaction for ion migration. The Li/Li_5.4PS_4.4Cl_1.6/Li symmetric cell cycles stably for 2000 h at 0.1 mA cm^-2, showing excellent dendrite suppression capability. Moreover, the initial discharge capacity of LiCoO₂/Li_5.4PS_4.4Cl_1.6/Li all-solid-state battery is 126.0 mAh g^-1 at 0.1C and the capacity retention is 83% after 50 cycles. The wet-milling method provides the possibility for rapid exploration and preparation of other argyrodite electrolytes in the future.

Unprecedented Self-Healing Effect of Li6 PS5 Cl-Based All-Solid-State Lithium Battery

Argyrodite Li₆ PS₅ Cl with high Li⁺ conductivity is a promising material for solid-state electrolytes (SSEs) in all-solid-state lithium batteries (ASSLBs). However, the narrow electrochemical window of Li₆ PS₅ Cl limits its applications in ASSLBs with high energy densities, and those that consist of high-voltage cathode materials and metallic lithium anodes. Unstable lithium deposition and stripping at interfaces is also a factor that restricts its industrialization. Herein, the authors investigated the electrochemical stability of Li₆ PS₅ Cl using it as both the cathode and electrolyte. The Li₆ PS₅ Cl-C/Li₆ PS₅ Cl/Li cell and symmetric Li/Li₆ PS₅ Cl/Li cells failed after a certain number of cycles, and subsequently healed electrochemically. This failure/healing phenomenon recurred during the cycling process. The self-healing behavior is closely related to the electrochemical window, which suggests that it can be controlled by the charge-discharge voltage range. In-depth X-ray photoelectron spectroscopy, in situ Raman spectroscopy, and in situ electrochemical impedance spectroscopy revealed the reversible Li₆ PS₅ Cl decomposition and metallic lithium growth inside the electrolyte during the cycling process. This self-healing behavior is mainly attributed to the reciprocating lithium growth and reversible redox reaction of the Li₆ PS₅ Cl decomposition. The proposed self-healing mechanism is a key aspect for sulfide-based SSEs, guiding the interface modification, and material design of ASSLBs.

Flexible Sulfide Electrolyte Thin Membrane with Ultrahigh Ionic Conductivity for All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) employing Li-metal anode, sulfide solid electrolyte (SE) can deliver high energy density with high safety. The thick SE separator and its low ionic conductivity are two major challenges. Herein, a 30 μm sulfide SE membrane with ultrahigh room temperature conductivity of 8.4 mS cm^-1 is realized by mechanized manufacturing technologies using highly conductive Li_5.4PS_4.4Cl_1.6 SE powder. Moreover, a 400 nm magnetron sputtered Al₂O₃ interlayer is introduced into the SE/Li interface to improve the anodic stability, which suppresses the short circuit in Li/Li symmetric cells. Combining these merits, ASSLBs with LiNi_0.5Co_0.2Mn_0.3O₂ as the cathode exhibit a stable cyclic performance, delivering a discharge specific capacity of 135.3 mAh g^-1 (1.4 mAh cm^-2) with a retention of 80.2% after 150 cycles and an average Coulombic efficiency over 99.5%. The high ionic conductivity SE membrane and interface design principle show promising feasible strategies for practical high performance ASSLBs.

Lithium/Sulfide All-Solid-State Batteries using Sulfide Electrolytes

All-solid-state lithium batteries (ASSLBs) are considered as the next generation electrochemical energy storage devices because of their high safety and energy density, simple packaging, and wide operable temperature range. The critical component in ASSLBs is the solid-state electrolyte. Among all solid-state electrolytes, the sulfide electrolytes have the highest ionic conductivity and favorable interface compatibility with sulfur-based cathodes. The ionic conductivity of sulfide electrolytes is comparable with or even higher than that of the commercial organic liquid electrolytes. However, several critical challenges for sulfide electrolytes still remain to be solved, including their narrow electrochemical stability window, the unstable interface between the electrolyte and the electrodes, as well as lithium dendrite formation in the electrolytes. Herein, the emerging sulfide electrolytes and preparation methods are reviewed. In particular, the required properties of the sulfide electrolytes, such as the electrochemical stabilities of the electrolytes and the compatible electrode/electrolyte interfaces are highlighted. The opportunities for sulfide-based ASSLBs are also discussed.

Rational Design of an Electron/Ion Dual-Conductive Cathode Framework for High-Performance All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) have been paid increasing attention because of the better security compared with conventional lithium-ion batteries with flammable organic electrolytes. However, the poor ion transport between the cathode materials greatly hinders the capacity performance of ASSLBs. Herein, an electron/ion dual-conductive electrode framework is proposed for superior performance ASSLBs. Highly electronic conductive reduced graphene oxide and carbon nanotubes interconnect with active materials in the cathodes, constructing a three-dimensional continuous electron transport network. The composite electrolyte penetrates into the porous structure of the electrode, forming a consecutive ionic conductive framework. Furthermore, the thin electrolyte film formed on the surface of the cathode effectively lowers the interfacial resistance with the electrolyte membrane. Highly electron/ion conductive electrodes, combined with the polyethylene oxide-Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (PEO-LLZTO) composite electrolyte, show excellent capacity performance for both LiFePO₄ and sulfur (lithium-sulfur battery) active materials. In addition, the LiFePO₄ cathode demonstrates superior capacity performance and rate capability at room temperature. Furthermore, the relationship between the low Coulombic efficiency and Li dendrite growth has been revealed in this work. An effective layer is formed on the surface of Li metal by the simple modification of cupric fluoride (CuF₂), which can stabilize the electrolyte/anode interface. Finally, high-performance ASSLBs with high Coulombic efficiency can be achieved.

In Situ Coating of Li7P3S11 Electrolyte on CuCo2S4/Graphene Nanocomposite as a High-Performance Cathode for All-Solid-State Lithium Batteries

A cathode material, CuCo₂S₄/graphene@10%Li₇P₃S₁₁, is reported for all-solid-state lithium batteries with high performance. The electrical conductivity of CuCo₂S₄ is improved by compounding with graphene. Meanwhile, Li₇P₃S₁₁ electrolyte is coated on the surface of CuCo₂S₄/graphene nanosheets to build an intimate contact interface between the solid electrolyte and the electrode effectively, facilitating lithium-ion conduction. Benefitting from the balanced and efficient electronic and ionic conductions, all-solid-state lithium batteries using CuCo₂S₄/graphene@10%Li₇P₃S₁₁ composite as cathode materials demonstrate superior cycling stability and rate capabilities, exhibiting an initial discharge specific capacity of 1102.25 mAh g^-1 at 50 mA g^-1 and reversible capacity of 556.41 mAh g^-1 at a high current density of 500 mA g^-1 after 100 cycles. These results demonstrate that the CuCo₂S₄/graphene@10%Li₇P₃S₁₁ nanocomposite is a promising active material for all-solid-state lithium batteries with superior performances.

Electrochemical and Structural Analysis in All-Solid-State Lithium Batteries by Analytical Electron Microscopy: Progress and Perspectives

Advanced scanning transmission electron microscopy (STEM) and its associated instruments have made significant contributions to the characterization of all-solid-state (ASS) Li batteries, as these tools provide localized information on the structure, morphology, chemistry, and electronic state of electrodes, electrolytes, and their interfaces at the nano- and atomic scale. Furthermore, the rapid development of in situ techniques has enabled a deep understanding of interfacial dynamic behavior and heterogeneous characteristics during the cycling process. However, due to the beam-sensitive nature of light elements in the interphases, e.g., Li and O, thorough and reliable studies of the interfacial structure and chemistry at an ultrahigh spatial resolution without beam damage is still a formidable challenge. Herein, the following points are discussed: (1) the recent contributions of advanced STEM to the study of ASS Li batteries; (2) current challenges associated with using this method; and (3) potential opportunities for combining cryo-electron microscopy and the STEM phase contrast imaging techniques.

Composition Modulation and Structure Design of Inorganic-in-Polymer Composite Solid Electrolytes for Advanced Lithium Batteries

Owing to their safety, high energy density, and long cycling life, all-solid-state lithium batteries (ASSLBs) have been identified as promising systems to power portable electronic devices and electric vehicles. Developing high-performance solid-state electrolytes is vital for the successful commercialization of ASSLBs. In particular, polymer-based composite solid electrolytes (PCSEs), derived from the incorporation of inorganic fillers into polymer solid electrolytes, have emerged as one of the most promising electrolyte candidates for ASSLBs because they can synergistically integrate many merits from their components. The development of PCSEs is summarized. Their major components, including typical polymer matrices and diverse inorganic fillers, are reviewed in detail. The effects of fillers on their ionic conductivity, mechanical strength, thermal/interfacial stability and possible Li⁺ -conductive mechanisms are discussed. Recent progress in a number of rationally constructed PCSEs by compositional and structural modulation based on different design concepts is introduced. Successful applications of PCSEs in various lithium-battery systems including lithium-sulfur and lithium-gas batteries are evaluated. Finally, the challenges and future perspectives for developing high-performance PCSEs are proposed.

Co3S4@Li7P3S11 Hexagonal Platelets as Cathodes with Superior Interfacial Contact for All-Solid-State Lithium Batteries

Poor solid-solid contact between an electrode and solid electrolyte is a great challenge for all-solid-state lithium batteries (ASSLBs) which results in limited ion transport and eventually leads to rapid capacity fading. Two-dimensional (2D) materials have incomparable advantage in the construction of the desired interface because of their flat surface and large specific surface area. In order to realize intimate interfacial contact and superior ion transport, monodisperse 2D Co₃S₄ hexagonal platelets as cathodes for all ASSLBs are synthesized through a series of topological reactions followed with in situ coating of tiny Li₇P₃S₁₁ using a liquid-phase method. The unique 2D hexagonal platelets are favorable for in situ solid electrolyte coating. Moreover, the well-designed interfacial structure can make the electrode materials contact with solid electrolytes more closely, contributing to a remarkable improvement on electrochemical performance. ASSLBs employing the Co₃S₄@Li₇P₃S₁₁ composite platelets as a cathode deliver a large reversible capacity of 685.9 mA h g^-1 at 0.5 A g^-1 for 50 cycles. Even at a high current density of 1 A g^-1, the Co₃S₄@Li₇P₃S₁₁ composite cathode still exhibits a high capacity of 457.3 mA h g^-1 after 100 cycles. This work provides a simple strategy to design the composite electrode with intimate contact and superior ion transport via morphology controlling.

Construction of 3D Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries

High and balanced electronic and ionic transportation networks with nanoscale distribution in solid-state cathodes are crucial to realize high-performance all-solid-state lithium batteries. Using Cu₂ SnS₃ as a model active material, such a kind of solid-state Cu₂ SnS₃ @graphene-Li₇ P₃ S₁₁ nanocomposite cathodes are synthesized, where 5-10 nm Cu₂ SnS₃ nanoparticles homogenously anchor on the graphene nanosheets, while the Li₇ P₃ S₁₁ electrolytes uniformly coat on the surface of Cu₂ SnS₃ @graphene composite forming nanoscaled electron/ion transportation networks. The large amount of nanoscaled triple-phase boundary in cathode ensures high power density due to high ionic/electronic conductions and long cycle life due to uniform and reduced volume change of nano-Cu₂ SnS_3. The Cu₂ SnS₃ @graphene-Li₇ P₃ S₁₁ cathode layer with 2.0 mg cm^-2 loading in all-solid-state lithium batteries demonstrates a high reversible discharge specific capacity of 813.2 mAh g^-1 at 100 mA g^-1 and retains 732.0 mAh g^-1 after 60 cycles, corresponding to a high energy density of 410.4 Wh kg^-1 based on the total mass of Cu₂ SnS₃ @graphene-Li₇ P₃ S₁₁ composite based cathode. Moreover, it exhibits excellent rate capability and high-rate cycling stability, showing reversible capacity of 363.5 mAh g^-1 at 500 mA g^-1 after 200 cycles. The study provides a new insight into constructing both electronic and ionic conduction networks for all-solid-state lithium batteries.

Promises, Challenges, and Recent Progress of Inorganic Solid-State Electrolytes for All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) have the potential to revolutionize battery systems for electric vehicles due to their benefits in safety, energy density, packaging, and operable temperature range. As the key component in ASSLBs, inorganic lithium-ion-based solid-state electrolytes (SSEs) have attracted great interest, and advances in SSEs are vital to deliver the promise of ASSLBs. Herein, a survey of emerging SSEs is presented, and ion-transport mechanisms are briefly discussed. Techniques for increasing the ionic conductivity of SSEs, including substitution and mechanical strain treatment, are highlighted. Recent advances in various classes of SSEs enabled by different preparation methods are described. Then, the issues of chemical stabilities, electrochemical compatibility, and the interfaces between electrodes and SSEs are focused on. A variety of research addressing these issues is outlined accordingly. Given their importance for next-generation battery systems and transportation style, a perspective on the current challenges and opportunities is provided, and suggestions for future research directions for SSEs and ASSLBs are suggested.

Highly Crystalline Layered VS2 Nanosheets for All-Solid-State Lithium Batteries with Enhanced Electrochemical Performances

All-solid-state lithium batteries employing inorganic solid electrolytes have been regarded as an ultimate solution to safety issues because of their features of no leakage as well as incombustibility and they are expected to achieve higher energy densities owing to their simplified structure. Two-dimensional transition-metal dichalcogenides exhibit a great potential in energy storage devices because of their unique physical and chemical characteristics. In this work, 50 nm thick highly crystalline layered VS₂ (hc-VS₂) nanosheets are prepared by a solvothermal method, and their electrochemical performances are evaluated in Li/75% Li₂S-24% P₂S₅-1% P₂O₅/Li₁₀GeP₂S₁₂/hc-VS₂ all-solid-state lithium batteries. At 50 mA g^-1, hc-VS₂ nanosheets show a high reversible capacity of 532.2 mAh g^-1 after 30 cycles. Moreover, stable discharge capacities are maintained at 436.8 and 270.4 mAh g^-1 at 100 and 500 mA g^-1 after 100 cycles, respectively. The superior rate capability and cycling stability are ascribed to the better electronic conductivity and well-developed layered structure. In addition, the electrochemical reaction kinetics and capacity contributions were analyzed via cyclic voltammetry measurements at different scan rates.

Garnet-Type Fast Li-Ion Conductors with High Ionic Conductivities for All-Solid-State Batteries

All-solid-state Li-ion batteries with metallic Li anodes and solid electrolytes could offer superior energy density and safety over conventional Li-ion batteries. However, compared with organic liquid electrolytes, the low conductivity of solid electrolytes and large electrolyte/electrode interfacial resistance impede their practical application. Garnet-type Li-ion conducting oxides are among the most promising electrolytes for all-solid-state Li-ion batteries. In this work, the large-radius Rb is doped at the La site of cubic Li_6.10Ga_0.30La₃Zr₂O₁₂ to enhance the Li-ion conductivity for the first time. The Li_6.20Ga_0.30La_2.95Rb_0.05Zr₂O₁₂ electrolyte exhibits a Li-ion conductivity of 1.62 mS cm^-1 at room temperature, which is the highest conductivity reported until now. All-solid-state Li-ion batteries are constructed from the electrolyte, metallic Li anode, and LiFePO₄ active cathode. The addition of Li(CF₃SO₂)₂N electrolytic salt in the cathode effectively reduces the interfacial resistance, allowing for a high initial discharge capacity of 152 mAh g^-1 and good cycling stability with 110 mAh g^-1 retained after 20 cycles at a charge/discharge rate of 0.05 C at 60 °C.

Dual Cation- and Anion-Based Redox Process in Lithium Titanium Oxysulfide Thin Film Cathodes for All-Solid-State Lithium-Ion Batteries

A dual redox process involving Ti³⁺/Ti⁴⁺ cation species and S^2-/(S₂)^2- anion species is highlighted in oxygenated lithium titanium sulfide thin film electrodes during lithium (de)insertion, leading to a high specific capacity. These cathodes for all-solid-state lithium-ion microbatteries are synthesized by sputtering of LiTiS₂ targets prepared by different means. The limited oxygenation of the films that is induced during the sputtering process favors the occurrence of the S^2-/(S₂)^2- redox process at the expense of the Ti³⁺/Ti⁴⁺ one during the battery operation, and influences its voltage profile. Finally, a perfect reversibility of both electrochemical processes is observed, whatever the initial film composition. All-solid-state lithium microbatteries using these amorphous lithiated titanium disulfide thin films and operated between 1.5 and 3.0 V/Li⁺/Li deliver a greater capacity (210-270 mAh g^-1) than LiCoO₂, with a perfect capacity retention (-0.0015% cycle^-1).