Lithium-ion batteries (LIBs) have been used in various fields and have significantly changed people's lives in the past few decades. [1] However, the unprecedented demand for energy storage presents the development goals of high safety and high energy density. Compared to conventional LIBs, lithium-metal SSBs are considered to be the most promising candidates for advanced high-energy storage systems due to their nonleakage, wide electrochemical window, and many other merits. [2] SEs are critical to developing advanced SSBs.In recent years, various SEs including inorganic SEs, polymer SEs, and composites SEs have been intensively studied. [3] Among them, inorganic SEs mainly include oxides and sulfides. [4] Typical oxide SEs such as garnet-type, [5] NASICONtype, [6] perovskite-type, [7] and antiperovskite-type [8] electrolytes have high ionic conductivity (>10 À4 S cm À1 ) and relatively stable structure. [3,5b,9] However, oxide SEs have high synthesis temperatures, high fabrication cost, high rigidity, and poor interfacial contact with the cathode and anode. [4,5] . Currently, the more studied sulfide SEs are Li 10 GeP 2 S 12 , [10] Li 2 S-P 2 S 5 , [11] and Li 6 PS 5 X (X = Cl, Br, I). [12] Compared with oxide SEs, sulfide SEs have higher ionic conductivity, lower synthesis temperature, and better flexibility. [13] However, sulfide SEs are susceptible to reduction at lower voltages and have poor electrochemical stability. [14] Tremendous efforts such as elemental doping, [15] optimization of preparation methods, [16] interfacial modification, [17] and exploitation of novel electrolyte systems have been made to optimize inorganic SE systems, and the development of inorganic SEs has made breakthrough progress. However, the interface issues between inorganic SEs with electrodes still severely limit their practical applications. [18] Fortunately, polymer-based SEs with good electrode contact stability and excellent processing properties offer great promise for practical applications of SSBs. [19] The main polymer SEs that have been reported include polyethylene oxide (PEO), [20] polyacrylonitrile (PAN), [21] poly(vinylidene fluoride) (PVDF), [22] poly (methyl methacrylate) (PMMA), [23] and poly(propylene carbonate) (PPC). [24] However, the inherent issues such as low roomtemperature ionic conductivity, poor mechanical properties, and poor interfacial stability of polymeric SEs have greatly limited their further development. [25] Therefore, the modification of polymer SEs is mainly focused on improving the ionic