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.

Poly(vinylidene fluoride)‐based polymer electrolytes are being intensely investigated for solid‐state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom‐to‐up strategy is employed to design single‐phase and densified polymer electrolytes via incorporating quasi‐ionic liquid with poly(vinylidene fluoride‐co‐hexafluoropropylene). Due to strong ion/dipole–dipole interaction, the optimized polymer electrolyte delivers high room‐temperature ionic conductivity of 1.55 × 10−3 S cm−1, superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm−3 as well as desirable self‐extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm−2. In particular, lithium metal battery Li||LiNi0.6Co0.2Mn0.2O2 exhibits a room‐temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid‐flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi‐ionic liquid/polymer electrolytes in safe lithium metal batteries.

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The doped garnet-type solid electrolytes are attracting great interest due to high ionic conductivity and excellent electrochemical stability against Li metal. However, the thick electrolyte layer and rigid nature as well as poor interfacial contact are huge obstacles for its application in all-solid-state lithium batteries. Herein, an ultrathin flexible Li6.4La3Zr1.4Ta0.6O12- (LLZTO-) based solid electrolyte with 90 wt% LLZTO content is realized through solvent-free procedure. The resultant 20 μm-thick LLZTO-based film exhibits ultrahigh ionic conductance of 41.21 mS at 30°C, excellent oxidation stability of 4.6 V, superior thermal stability and nonflammability. Moreover, the corresponding Li||Li symmetric cell can stable cycle for more than 2000 h with low overpotential at 0.1 mA cm-2 under 60°C. The assembled Li||LiFePO4 pouch cell with integrated electrolyte/cathode interface exhibits excellent rate performances and cycle performances with a capacity retention of 71.4% from 153 mAh g-1 to 109.2 mAh g-1 at 0.1 C over 500 cycles under 60°C. This work provides a promising strategy towards realizing ultrathin flexible solid electrolyte for high-performance all-solid-state lithium batteries.

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Lithium sulfur (Li-S) batteries possess high theoretical capacity and energy density, holding great promise for next generation electronics and electrical vehicles. However, the Li-S batteries development is hindered by the shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs). Designing highly polar materials such as metal oxides (MOs) with moderate adsorption and effective catalytic activity is essential to overcome the above issues. To design efficient MOs catalysts, it is critical and necessary to understand the adsorption mechanism and associated catalytic processes of LiPSs. However, most reviews still lack a comprehensive investigation of the basic mechanism and always ignore their in-depth relationship. In this review, a systematic analysis toward understanding the underlying adsorption and catalytic mechanism in Li-S chemistry as well as discussion of the typical works concerning MOs electrocatalysts are provided. Moreover, to improve the sluggish "adsorption-diffusion-conversion" process caused by the low conductive nature of MOs, oxygen vacancies and heterostructure engineering are elucidated as the two most effective strategies. The challenges and prospects of MOs electrocatalysts are also provided in the last section. The authors hope this review will provide instructive guidance to design effective catalyst materials and explore practical possibilities for the commercialization of Li-S batteries.