Abstract: Lithiumrich layered cathode material Li_1.18Ni_0.15Co_0.15Mn_0.52O₂ was synthesized by the solgel method, then surface coated using Cu₃(PO₄)₂. The surface morphology of the samples was measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy, and the samples were tested by constant current chargedischarge and electrochemical impedance spectroscopy. The results show that Cu₃(PO₄)₂ distributes uniformly on the surface of the material. Cu₃(PO₄)₂ exists in amorphous form and the ordered arrangement of Li⁺ in transition metal layer is destroyed after modification. The initial Coulomb efficiency of the material is increased from 77% to 94% after surface modification. The initial discharge capacity of the all materials is 244 mA·h/g, the specific discharge capacity of the Cu₃(PO₄)₂ modified material is 203 mA·h/g after 100 cycles, and  the capacity retention is 83%. 
A pair of redox peaks appear at 30, 27 V while the charge/discharge curve appear a new platform after surface modification. The impedance of surface modified lithiumrich layered cathode material is obviously reduced.

Key words: lithiumion battery, cathode material, Lirich material, surface modification, copper phosphate