Stabilizing the Interphase in Cobalt‐Free, Ultrahigh‐Nickel Cathodes for Lithium‐Ion Batteries

Abstract

AbstractHigh‐nickel layered oxide cathodes, such as LiNi1‐x‐yMnxCoyO2 (NMC) and LiNi1‐x‐yCoxAlyO2 (NCA), are at the forefront for implementation in high‐energy‐density lithium‐ion batteries. The presence of cobalt in both cathode chemistries, however, largely deters their application due to fiscal and humanitarian issues affiliated with cobalt sourcing. Increasing the Ni content drives down the Co content, but introduces additional structural and electrochemical problems attributed to high‐Ni cathodes. Herein a dually modified cobalt‐free ultrahigh‐nickel cathode 0.02B‐LiNi0.99Mg0.01O2 (NBM) is presented with 1 mol% Mg and 2 mol% B that exhibits a high initial 1C discharge capacity of 210 mA h g−1 with a 20% capacity retention improvement over 500 cycles when benchmarked against LiNiO2 (LNO) in pouch full cell configurations with graphite anode. Postmortem analyses reveal the enhanced performance stems from reduced active lithium inventory loss and localized surface reactivity in the NBM cathode. The stabilized cathode‐electrolyte interphase subsequently reduces transition‐metal dissolution and ensuing chemical crossover to the graphite anode, which prevents further catalyzed parasitic reactions that harmfully passivate the anode surface. Altogether, this study aims to highlight the importance of electrode characterization and analysis from an interphasial viewpoint and to push the ongoing research to stabilize cobalt‐free ultrahigh‐Ni cathodes for industrial feasibility.