Facile Magnetite Coating for Stable High‐Voltage Cycling of Nickel‐Rich Cathodes in Conventional Liquid and All‐Solid‐State Lithium‐Ion Batteries

Abstract

The instability of Nickel (Ni)‐rich cathodes at high voltage is a critical bottleneck toward developing superior lithium‐ion batteries. This instability is driven by cathode‐electrolyte side reactions, causing rapid degradation, and compromising the overall cycle life. In this study, a protective coating using dispersed “magnetite (FeO.Fe2O3)” nanoparticles is used to uniformly decorate the surface of LiNi0.8Co0.1Mn0.1O2 (NMC 811) microparticles. The modified cathode delivers significant improvement in electrochemical performance at high voltage (≈4.6 V) by suppressing deleterious electrode–electrolyte interactions. A notably higher cycle stability, rate performance, and overall energy density is realized for the coated cathode in a conventional liquid electrolyte battery. When deployed in pellet‐stacked solid‐state cells with Li6PS5Cl as the electrolyte, the magnetite‐coated NMC 811 showed strikingly superior cycling stability than its uncoated counterpart, proving the versatility of the chemistry. The facile surfactant‐assisted coating process developed in this work, in conjunction with the affordability, abundance, and nontoxic nature of magnetite makes this a promising approach to realize commercially viable high voltage Ni‐rich cathodes that exhibit stable performance in liquid as well as solid‐state lithium‐ion batteries.