Mitigating the Surface Reconstruction of Ni-Rich Cathode via P2-Type Mn-Rich Oxide Coating for Durable Lithium Ion...

Ni-rich materials have received widespread attention as one of the mainstream cathodes in high-energy-density lithium-ion batteries for electric vehicles. However, Ni-rich cathodes suffer from severe surface reconstruction in a high delithiation state, constraining their rate capabilities and life span. Herein, a novel P2-type NaNi_0.33Mn_0.67O₂ (NNMO) is rationally selected as the surficial modification layer for LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode, which undergoes a spontaneous Na⁺-Li⁺ exchange reaction to form an O2-type LiNi_0.33Mn_0.67O₂ (LNMO) layer revealed by combining X-ray diffraction and solid-state nuclear magnetic resonance techniques. Owing to the specific oxygen stacking sequence, O2-type LNMO significantly prevents the initial layered structure of NCM811 from transforming to the spinel or rock-salt phases during cycling, thus effectively maintaining the integral surficial structure and the Li⁺ diffusion channels of NCM811. Eventually, the NNMO@NCM811 electrode yields enhanced thermal stability, outstanding rate performance, and long cycling stability with 80% capacity retention after 294 cycles at 200 mA g^-1, and its life span is further extended to 531 cycles while enhancing the mechanical stability of the bulk material.