Abstract: he next generation of space products put forward higher demand for energy storage system, and the surface modification method is proposed to improve the cyclic stability of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material in lithium ion batteries. By using phosphoric acid (H3PO4) to treat the NCA cathode materials, H3PO4 reacts with the lithiumcontaining alkaline substances on the surface of NCA, so as to generate a stable and conductive Li3PO4 interface layer on the surface of NCA particles. As a result, the H3PO4modified NCA shows better capacity retention (170.5mA·h/g,94%) and lower impedance after 50 cycles than the bare one, which is attributed to the presence of the Li3PO4based coating layer. H3PO4 surface modification method has positive effects on the electrochemical performance and structural integrity of the NCA electrode materials.

Key words: Liion battery, cathode, LiNi0.8Co0.15Al0.05O2, surface modification, electrochemical performances, space energy storage system