Multi-functional modification of nickel-rich lithium cathode materials using Na2PO3F

Abstract

Surface side reactions and microstructural defects are detrimental to the electrochemical properties of nickel-rich cathode materials in lithium-ion batteries. In this work, Na₂PO₃F was used to rationally improve the properties of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) materials due to its many multi-functional effects using a one-step sintering modification method. The results demonstrate that a Li₃PO₄ layer is in situ formed on the surface of the secondary particles. The Li₃PO₄ layer can effectively protect the material from reacting with the liquid electrolyte at a high charged voltage and reduce residual Li compounds on the surface. Additionally, Na/F could suppress Li/Ni cation mixing due to the increased Li-ion layer distance. Therefore, the as-prepared material shows alleviated structure collapse and relatively low TM migration and dissolution, enhancing its cycling stability. As a result, the modified NCM delivers superior cycling stability and rate performance, with a charge/discharge capacity retention of >85% after 400 cycles and >70% at a high-rate density of 10C.