A robust carbon coating strategy toward Ni-rich lithium cathodes

Abstract The surface coating strategy provide a facile and effective means of improving the electrochemical behavior of lithium-ion batteries (LiBs) since it can prevent cathodes/anodes from contacting moisture and improve the thermal stability and cyclability of LiBs. However, to date, few studies have focused on carbon coating Ni-rich cathodes due to the moisture sensitivity of cathode materials. Herein, poly (vinylidene fluoride)/n-vinyl-2-pyrrolidinone (PVDF/NMP) solution was employed as the carbon source to coat LiNi0.8Mn0.1Co0.1O2 (NMC811) spheres for the first time. The coating process mainly includes two steps under moisture-free conditions: (1) wetting NMC811 using PVDF/NMP solution and (2) heat treatment of NMC811/PVDF under inert circumstances. The thickness of the obtained carbon layer can be controlled easily by adjusting the solution concentration. A 2.5 wt% PVDF containing solution can coat a carbon layer of ~4 nm on NMC811 spheres, which significantly improved the integral Li+ storage performance. The discharge capacity of the resulting carbon-coated NMC811 showed only a 1.26% decrease after 100 cycles at a 0.2 C rate, while pristine NMC811 lost 6.85% of its initial reversible capacity. This work highlights that carbon coating offers a facile yet effective approach to achieve high-performance cathodes materials for LIBs.