Stable Interfacial Phase on Single-Crystalline Ni-Rich Cathode via Chemical Reaction with Phosphomolybdic Acid

Abstract Ni-rich single-crystalline cathode has been demonstrated to be a promising candidate for next-generation high energy density batteries by solving intergranular cracks occurring in its counterpart consisting of aggregated small primary particles. However, the inherently unstable surface nature of Ni-rich cathodes, such as rock-salt phase transition, reactive oxygen release, and parasitic side reactions, has not been solved, which would deteriorate the electrochemical performance of single-crystalline Ni-rich cathode. To further improve the durability, these surface issues should be urgently mitigated. Herein, we proffer a simple yet effective method to regulate the surface chemical composition and property of single-crystalline LiNi0.8Co0.1Mn0.1O2 via phosphomolybdic acid treating. This novel surface treating method successfully suppressed rock-salt phase transformation and (cathode electrolyte interphase) CEI growth during cycling. As a result, the as-obtained LiNi0.8Co0.1Mn0.1O2 cathode exhibits excellent capacity retention of 92% after 200 cycles at 0.5 C. Also, a remarkable enhancement of thermal stability was achieved. This work demonstrates the great potential of surface modification strategy for Ni-rich single-crystalline cathode and would pave the way for its implementation.