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 (LiNi0.8Co0.15Al0.05O2, NCA) as an example, herein, a nondestructive 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 LiNixCoyMn1-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.