P doping in NCMA cathode improves electronic and cationic conductivity to enable higher capacity retention and better rate performance

Abstract

In previous reports, P doping was regarded as an effective approach to endow layered NCA cathode material with a better electrochemical performance via suppressing polarization or promoting Li migration. In this work, P doping enables higher capacity retention and better rate performance of NCMA cathode due to the dually improved electronic and cationic conductivity. DFT calculation reveals that P doping reduces the bandgap of NCMA, which inhibits the increase of internal resistance during cycling and thereafter improves capacity retention. Furthermore, P doping also expands the thickness of the Li slab within the NCMA lattice, which facilitates lithium ion diffusion and significantly enhances rate capability. Under a current of 0.5 C, P-doped NCMA exhibits a high initial capacity of 198.4 mAh·g−1 with an exceptional capacity retention of 93.7% after 100 cycles. Even at a high rate of 5 C, it still delivers a discharge capacity of 162.2 mAh·g−1. These promoted performances indicate the high potential of P-doped NCMA as a candidate cathode material for high-energy-density battery systems.