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.