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.

suffer from safety problems arising from lithium anode and fast capacity fading due to the insulating nature of sulfur, the dissolution-induced polysulfide shuttle reaction, and large volume changes. [4][5][6] To address these issues, carbonaceous material [7,8] and conducting polymers [9] have been used to trap the high-order polysulfides in the cathodes; protective layers and electrolyte additives are employed for protection of metallic-lithium anodes from reactions with polysulfide. [10,11] However, the shuttle reaction still exists, and the safety issue induced by lithium dendrite is still a great challenge.All-solid-state Li-S batteries can completely inhibit the dissolution of polysulfide, eliminate the polysulfide shuttle, and avoid lithium dendrite formation. [12][13][14][15][16][17][18][19] However, the use of rigid solid electrolytes in all-solid-state Li-S batteries also increases the stress/strain and interface resistance and reduce the reaction kinetics. [20][21][22] The key challenge is to minimize stress/strain and to construct a robust electronic and ionic pathway in the sulfur cathode, due to the electronic/ionic insulting nature of sulfur. For enhancing the electronic conductivity and reducing the electronic contact resistance, Kobayashi et al. synthesized a sulfur and acetylene black (AB) nanocomposite cathode using a gas-phase mixing method, and reported a reversible capacity of 900 mA h g −1 at a current density of 0.013 mA cm −2 in all-solid-state batteries. [23] The sulfur and carbon-nanofibers composite cathode also shows a high capacity in the all-solid-state Li-S batteries. [24] To ensure high ionic conduction in the sulfur cathode, Lin et al. synthesized core-shell structured lithium-sulfide nanoparticles with an Li 3 PS 4 electrolyte as shell, showing six orders of magnitude higher in ionic conductivity than that of bulk lithiumsulfide. Excellent cyclic performance was demonstrated for allsolid-state Li-S batteries at 60 °C. [13] By incorporation of five sulfur atoms in the Li 3 PS 4 electrolyte, the Li 3 PS 4+5 cathode with loading density of 0.25-0.6 mg cm −2 exhibits excellent cycling stability for all-solid-state Li-S batteries. [14] These studies demonstrate that a close contact of the nanosulfur, either to carbon or to electrolytes, and uniformly distributing these composites into an ionic/electronic conducting matrix, can significantly improve the electrochemical performances of solid-state Li-S cell because the nano-sulfur contacts both the highly ionic and Safety and the polysulfide shuttle reaction are two major challenges for liquid electrolyte lithium-sulfur (Li-S) batteries. Although use of solid-state electrolytes can overcome these two challenges, it also brings new challenges by increasing the interface resistance and stress/strain. In this work, the interface resistance and stress/strain of sulfur cathodes are significantly reduced by conformal coating ≈2 nm sulfur (S) onto reduced graphene oxide (rGO). An Li-S full cell consisting of an rGO@S-Li 10 GeP 2 S 12 -acetyle...

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An ultrathin solid polymer electrolyte (SPE) consisting of modified polyethylene (PE) as the host and poly(ethylene glycol) methyl ether acrylate and lithium salts as fillers is presented. The porous poly(methyl methacrylate)–polystyrene interface layers closely attached on both sides of the PE effectively improve the interface compatibility among electrolytes and electrodes. The resultant 10 μm‐thick SPEs possess an ultrahigh ionic conductance of 34.84 mS at room temperature and excellent mechanical properties of 103.0 MPa with elongation up to 142.3%. The Li//Li symmetric cell employing an optimized solid electrolyte can stably cycle more than 1500 h at 60 °C. Moreover, the LiFePO4//Li pouch cell can stably cycle over 1000 cycles at 1 C rate and with a capacity retention of 76.4% from 148.9 to 113.7 mAh g−1 at 60 °C. The LiCoO2//Li pouch cell can stably operate at 0.1 and 0.2 C rate for each 100 cycles. Furthermore, the LiFePO4//Li pouch cell can work stably after curling and folding, which proves its excellent flexibility and safety simultaneously. This work offers a promising strategy to realize ultrathinness, excellent compatibility, high strength, as well as safe solid electrolytes for all‐solid‐state lithium‐metal batteries.

High energy and power densities are the greatest challenge for all-solid-state lithium batteries due to the poor interfacial compatibility between electrodes and electrolytes as well as low lithium ion transfer kinetics in solid materials. Intimate contact at the cathode-solid electrolyte interface and high ionic conductivity of solid electrolyte are crucial to realizing high-performance all-solid-state lithium batteries. Here, we report a general interfacial architecture, i.e., LiPS electrolyte particles anchored on cobalt sulfide nanosheets, by an in situ liquid-phase approach. The anchored LiPS electrolyte particle size is around 10 nm, which is the smallest sulfide electrolyte particles reported to date, leading to an increased contact area and intimate contact interface between electrolyte and active materials. The neat LiPS electrolyte synthesized by the same liquid-phase approach exhibits a very high ionic conductivity of 1.5 × 10 S cm with a particle size of 0.4-1.0 μm. All-solid-state lithium batteries employing cobalt sulfide-LiPS nanocomposites in combination with the neat LiPS electrolyte and Super P as the cathode and lithium metal as the anode exhibit excellent rate capability and cycling stability, showing reversible discharge capacity of 421 mAh g at 1.27 mA cm after 1000 cycles. Moreover, the obtained all-solid-state lithium batteries possesses very high energy and power densities, exhibiting 360 Wh kg and 3823 W kg at current densities of 0.13 and 12.73 mA cm, respectively. This contribution demonstrates a new interfacial design for all-solid-state battery with high performance.

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An ingenious interface re-engineering strategy was applied to in situ prepare a manipulated LiHPO protective layer on the surface of Li anode for circumventing the intrinsic chemical stability issues of LiGePS (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 within ±0.05 V. The optimized ASSLiB of LiCoO (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 at the initial cycle and 113.7 mAh g 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.

A simple and scalable method is developed to synthesize TiO(2)/graphene nanostructured composites as high-performance anode materials for Li-ion batteries using hydroxyl titanium oxalate (HTO) as the intermediate for TiO(2). With assistance of a surfactant, amorphous HTO can condense as a flower-like nanostructure on graphene oxide (GO) sheets. By calcination, the HTO/GO nanocomposite can be converted to TiO(2)/graphene nanocomposite with well preserved flower-like nanostructure. In the composite, TiO(2) nanoparticles with an ultrasmall size of several nanometers construct the porous flower-like nanostructure which strongly attached onto conductive graphene nanosheets. The TiO(2)/graphene nanocomposite is able to deliver a capacity of 230 mA h g(-1) at 0.1 C (corresponding to a current density of 17 mA g(-1)), and demonstrates superior high-rate charge-discharge capability and cycling stability at charge/discharge rates up to 50 C in a half cell configuration. Full cell measurement using the TiO(2)/graphene as the anode material and spinel LiMnO(2) as the cathode material exhibit good high-rate performance and cycling stability, indicating that the TiO(2)/graphene nanocomposite has a practical application potential in advanced Li-ion batteries.