The application of solid-state batteries is constrained by the difficulty of solid-solid interface ion transport.Coating modification of cathode materials is an improvement method.The LiNi0.8Co0.1Mn0.1O2(NCM811)/Li3Zr2Si2PO12(LZSP)composite cathode materials are prepared by ball milling and sintering.The structure of the material and the electrochemical performance of the prepared batteries are analyzed by SEM,energy dispersive X-ray spectroscopy(EDS),XRD,resistivity testing and electrochemical impedance spectroscopy(EIS)tests.LZSP forms a uniform and continuous coating layer on the surface of NCM particles,the coating does not change the crystal structure of the NCM material.Compared with the unmodified NCM material,the NCM/LZSP-5 composite cathode with a LZSP coating mass fraction of 5％exhibits the lowest electrode resistivity,which is 12.31 Ω·cm at 30 MPa.The interfacial impedance,charge transfer impedance and diffusion impedance of the batteries prepared with the NCM/LZSP cathode are all lower than those prepared with pure NCM.The battery prepared with the NCM/LZSP-5 composite cathode exhibits the best electrochemical performance.When charged-discharged in 2.7-4.3 V,the coin cell delivers an initial charge specific capacity as high as 141.49 mAh/g at 0.1 C,an initial discharge specific capacity of 140.61 mAh/g,an initial Coulombic efficiency of 99.4％.The coin cell and pouch battery achieve maximum 0.2 C cycle lives of 95 cycles and 36 cycles,respectively.