Improving the Cycling Stability of Ni-Rich Layered Cathode Material By Introducing Redox Shuttle Electrolyte Additives

A systematic post-mortem analysis on a batch of power-optimized commercial LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) electrodes with different aging conditions was conducted. This aging study provides direct evidence that the intrinsic surface heterogeneity, resulting in locally overcharge reactions, plays a critical role in the degradation of NCA electrodes. Accordingly, we propose a counter measure, adding redox shuttle electrolyte additive (RSA), to improve the cycling stability of Ni-rich layered cathode materials. The RSA can effectively balance the inhomogeneously distributed state-of-charge by shuttling excess charges between overcharged particles and normal charged particles. The unfavorably local overcharging reactions are thus inhibited. As indicated in the experimental results, with a small amount (0.025 M) of RSA 1,4-di-tert-Butyl-2,5-bis(2,2,2-trifluoroethoxy)benzene, the cycling performance of the commercial Nickel-rich cathode materials is improved about 30% in practical utilizing conditions as shown in the figure. There is a great potential for exploiting this approach in all kinds of commercial lithium-ion battery systems containing a liquid electrolyte. Furthermore, the remarkable effectiveness of the RSA approach further justifies the crucial role that the surface inhomogeneity plays in the cycling aging. Therefore, this issue deserves more attention in future aging studies of lithium-ion batteries. Figure 1