Abstract: | High ionic conductivity at room temperature (RT) and good ion transport capability at electrode/electrolyte interface are fundamental requirements for high‐rate solid‐state lithium batteries (SSBs). In this work, we designed a poly (propylene carbonate) (PPC)‐based organic/inorganic composite solid electrolyte (CSE) membrane with high filling of tantalum‐doped lithium lanthanum zirconium oxide (LLZTO) and functionalized layers for enhancing the RT rate performance of SSB. The synergistic effect of LLZTO and interfacial functionalized layers endows the NCM622/CSE/Li battery with high‐rate and cycling performances at RT. The SSB with 20% LLZTO‐filled solid electrolyte shows the initial capacities of 162.0, 148.5 and 130.1 mAh g?1 at 1C, 2C, and 3C respectively, with retention capacities of 115.6, 104, and 100.6 mAh g?1 after 150 cycles. This strategy for an organic/inorganic CSE is of great practical significance for the development of high‐rate SSBs. |