Sublimation-Induced Gas-Reacting Process for High-Energy-Density Ni-Rich Electrode Materials

Abstract

Ni-rich layered electrode materials have attracted great attention as a promising cathode candidate for high-energy-density lithium-ion batteries because of their high capacity and relatively low cost. However, they have been suffering from severe capacity fading for cycles, which can originate from several factors such as the phase transition at the end of charge and disintegration of the particles. Herein, a simple and novel sublimation-induced gas-reacting (SIGR) process has been developed by using elemental sulfur to conformally coat Ni-rich layered materials. The sublimated gas-phase S can react with detrimental residual Li compounds on the surface of the particles. As a result, the reacted layer of LixSyOz phases forms on the outside of the secondary particles and simultaneously in the boundaries between primary particles inside the secondary particles. Compared to other reported surface modification processes, the SIGR-treated Ni-rich materials show substantially increased capacity retention and superior voltage retention by protecting the surface from the electrolyte and mitigating disintegration of the secondary particles. The SIGR process is a simple and scalable solid-state reaction at low temperature to improve the cycling stability of high-capacity Ni-rich electrode materials.