Stabilizing surface chemical and structural Ni-rich cathode via a non-destructive surface reinforcement strategy

Surface chemistry and micro/nano-structure of precursors greatly determine the characteristics and performances of precursor-derived Ni-rich cathodes. Some progress has been achieved in pre-treating precursors via classical wet-chemical methods, nevertheless, it is still inevitable that the surface chemical components or structures of precursors will be changed. Thus, exploring the non-destructive surface reinforcement strategy is of vital importance. Taking the typical Ni-rich cathodes (LiNi_0.8Co_0.15Al_0.05O₂, NCA) as an example, herein, a non-destructive surface reinforcement strategy to tailor surface characteristics of the precursor through plasma treatment technique has been proposed. Impressively, spectroscopic analysis and atomic-level imaging reveal that the plasma treatment of precursor is beneficial for both promoting the conversion of Ni²⁺ to Ni³⁺ and the formation of a porous surface without crystal defects. As a result, the annealed high-crystallinity NCA cathode, without NiO-type rock salt phase on the surface, displays enhanced cycling stability (81.2% capacity retention at 1C over 200 cycles) and increased rate performances (161.1 mA h g⁻¹ at 5C). The feasibility of extending this strategy to other electrode materials (such as LiNi_xCo_yMn_1-x-yO₂, LiNiO₂, etc.) by sintering precursors further promises a bright future. This work provides guidance to rational modify the Ni-based cathode materials and hold great potential of reviving the next generation high-energy-density Li-ion batteries.