High Cycling Rate‐Induced Irreversible TMO6 Slabs Glide in Co‐Free High‐Ni Layered Cathode Materials

Abstract

AbstractCo‐free high‐Ni layered transition metal oxide is a promising cost‐effective cathode material for high‐energy Li‐ion batteries, but it suffers from undesirable rate performance and rapid capacity decay upon high‐rate cycling. The underlying structural changes under fast electrochemical processes remain unclear to date. In this study, atomic scale structural evolutions of Co‐free high‐Ni layered cathode at different cycling rates are revealed by advanced TEM characterization. It is found that the phase transition after high‐rate cycling is much different from that after low‐rate cycling. The low‐rate cycled sample shows a typical layer‐to‐rock salt transition. However, O1‐type stacking faults are uncovered in the high‐rate cycled sample owing to irreversible TMO6 slabs glide, which induces severe lattice distortion and structural dislocations. These findings deepen the understanding of the rate‐dependent structural degradation mechanism of Co‐free high‐Ni layered cathodes, and have significant implications for improving current materials to withstand high‐rate applications.