“…In order to further improve the energy densities of SSLBs, high specific capacities and high-voltage cathodes (e.g., LiNi 1‑x‑y Co x Mn y O 2 , LiNi 0.5 Mn 1.5 O 4 ) have been widely utilized, which require the SPEs to be compatible with both high-voltage cathodes and low-voltage Li metal anodes. , However, low-voltage stable SPE (such as polyether) is easy to be oxidized and decomposed at high voltage, while SPE with good antioxidation capability (such as polyester) is easy to be reduced in contact with a Li metal anode, resulting in battery failure. , The compatibilities of SPEs with cathodes and anodes are decided by either their electrochemical windows or whether a stable SEI and cathode–electrolyte interphase (CEI) can be formed (Figure a). , When the highest occupied molecular orbital (HOMO) of SPE is lower than the cathode potential (μ C ) or a stable CEI is formed, the SPE has the capability to restrain oxidative decomposition and is stable with a cathode. Similarly, for the low-voltage anode, the lowest unoccupied molecular orbital (LUMO) should be higher than the anode potential (μ A ) or form a stable SEI. , However, it is extremely difficult for one electrolyte to satisfy both of these conditions at the same time (Figure b, c).…”