Shorting Effects of LiFePO<sub>4</sub> Cathode in Lithium Ion Batteries

Co3(PO4)2 or AlPO4 coating layers were formed on the surface of LiNi0.8Co0.15Al0.05O2 cathode material by in situ chemical method and calcination at 700°C to improve the electrochemical cyclability and structural stability during charge-discharge process of the cathode. The structure and electrochemical properties of the pristine LiNi0.8Co0.15Al0.05O2 cathode materials and the metal phosphate coated-cathode materials were investigated by X-ray powder diffraction, scanning electron microscopy, particle size analysis, Brunauer-Emmett-Teller method, cyclic voltammetry, and galvanostatic charge-discharge test. Co3(PO4)2-LiNi0.8Co0.15Al0.05O2 and AlPO4- LiNi0.8Co0.15Al0.05O2 cathode showed the improved reversibility compared with the pristine cathode material. It is attributed to the structural stability of metal phosphate coated LiNi0.8Co0.15Al0.05O2. In particular, Co3(PO4)2-LiNi0.8Co0.15Al0.05O2 showed a more stable rate capability than the pristine LiNi0.8Co0.15Al0.05O2 and AlPO4-LiNi0.8Co0.15Al0.05O2 at high C-rate.