Stabilization of lattice oxygen in lithium rich cathode materials via manipulating Ni content

Abstract

Li-rich layered oxides (LLOs) have been vigorously explored as promising cathodes for next generation Li-ion batteries due to their high capacity. But their adoption is hampered by poor stability and serious voltage decay during cycling due to the oxygen vacancies (V_o) existing within the active particles and the V_o sites can result in structural reconstruction of the material. Herein, we focus our research on controlling the oxygen vacancies by adjusting the Ni content in Li-rich cathodes to improve their cycling stability and suppress the voltage decay. Based on comprehensive physical characterization, electrochemical analysis, and theoretical calculations, the key factors that contribute to the improved electrochemical performance of the lithium-rich materials are: (1) a reduced number of V_o results in a more stable structure, thereby stabilizing the lattice oxygen; and (2) modulating the nickel content causes an increase of the potential for redox reactions and remarkably enhances the oxygen stability under high voltage. The designed cathode exhibits a high initial coulombic efficiency of 83%. And a specific capability of 125 mA h g⁻¹ can be reached at 5C with a capacity retention of 97% even after 200 cycles. This strategy of modulating the Ni content of LLOs has great potential for designing high-energy-density Li-ion batteries.