Olivine LiFePO4 as an additive into LiCoO2 electrodes for LIBs to improve high-voltage performances

Abstract

Abstract The structural stability of LiCoO2 at high voltage is a crucial concern of LiCoO2 electrode. The experiment in this work have proved that mixed LiCoO2 and LiFePO4 electrode can stabilize the layered structure of LiCoO2 and improve their cycle stability significantly. The SEM images show that a protective thin film was gradually formed on the surface of LiCoO2 particles during charging and discharging. With the amount of mixed LiFePO4 increasing, the film increases, which inhibits the broken of the LiCoO2 particles and the formation of Co3O4; The battery built using the mixed LiCoO2 and LiFePO4 electrodes shows the best cycle stability when the content of LiFePO4 is 12 wt%, with the initial discharge specific capacity of 177.9 mA h g−1 and the capacity retention of 77.2% after 200 cycles between 3.0 and 4.5 V at 0.2 C.