Realizing excellent cycling stability of LiNi0.80Co0.15Al0.05O2 cathode at high cutoff voltage by Al(PO3)3 modification

Ni-rich layered LiNi0.80Co0.15Al0.05O2 (NCA) cathode materials have attracted extensive attention in power lithium ion batteries on account of their high specific capacities and low voltage delay. However, they still suffer from inferior cycling stability, especially operating at a high cutoff voltage. In this paper, a surface modification strategy was proposed by utilizing Al(PO3)3 as a coating material to enhance the cycling performance of NCA in 2.7–4.6 V (vs. Li/Li+). The surface modification effects of Al3+ lattice doping and Al(PO3)3 coating were verified to be well achieved. In particular, besides the functions in stabilizing surface crystal structure of the NCA and isolating the erosion from electrolyte, the Al(PO3)3 coating could eliminate the residual lithium on the NCA surface to in-situ generate the Li3PO3 which was conductive to the rate performance. Accordingly, the Al(PO3)3-modified NCA cathode delivered excellent cycling performance, of which the initial discharge capacity was 235.9 mAh.g−1 at high cutoff voltage of 4.6 V, with a capacity retention of 71.6% after 100 cycles at 1 C. This work demonstrates the feasibility of surface modification on NCA via the phosphate coating with multiple functions, and provides an efficient approach to improve the cycling stability of Ni-rich layered cathode materials at higher cutoff voltage.