Enhanced cyclability and safety performance of LiNi0.6Co0.2Mn0.2O2 at elevated temperature by AlPO4 modification

As attractive materials for the power sources with high energy density, high-nickel electrode materials are limited by cyclability and safety problems for extensive applications. In order to improve the performance of LiNi0.6Co0.2Mn0.2O2 (NCM622), aluminium phosphate (AlPO4) modification was adopted via a facile approach. AlPO4 improves the cyclability and lowers the strain at high temperature despite of an initial discharge capacity decrease of the pristine NCM622 at 0.1 C. NCM622 with 0.3 wt% of AlPO4 shows the best comprehensive performance, and after 50 cycles at 1 C at 40 °C and 60 °C, the retention ratios of discharge capacity are respectively 86.20% and 85.44%, much higher than that of the corresponding values of 78.31% and 71.32% of the pristine NCM622. 0.3 wt% of AlPO4 decreases the stress of NCM622 from 2.6 to 1.1 MPa at 40 °C, and from 5.1 to 2.9 MPa at 60 °C, respectively. XRD and XPS results suggest that the crystal structure of NCM622 has no obvious change by AlPO4, and LiAlO2 and Li3PO4 co-exist on the surface. Density Functional Theory (DFT) calculation was utilized to analyse the interface. The morphology and elemental distribution were evaluated by FESEM and EDS. The enhanced mechanisms of NCM622 by AlPO4 were discussed with various techniques. The facile method using AlPO4 modification may be adoptable to improve the performance of other energy materials.