Degradation of High Nickel Li‐Ion Cathode Materials Induced by Exposure to Fully‐Charged State and Its Mitigation

Abstract Ni‐rich layered oxides are strong candidates for next–generation high‐energy batteries. Unlike batteries in typical laboratory settings, batteries in practical applications are generally not discharged immediately upon reaching a fully charged state, but instead, remain there for varying periods of time before usage. Such a state places immense electrochemical stress on the cathode as much of the Ni‐rich layered oxide degradation mechanisms occur at the highly charged/delithiated state. Differentiating between lab and practical use cases, it is shown for Li[Ni_0.90Co_0.05Mn_0.05]O₂ that even the introduction of a short dwell period at the highly charged state leads to substantial differences in cycling performance (capacity retention of 89.4% vs 37.5% at the 100^th cycle with or without dwelling, respectively). To overcome the rapid deterioration at high voltage, antimony is used as a dopant to reduce the lattice instability of the high Ni layer structure, especially at the grain boundaries regions, where degradation concentrates at the cathode‐electrolyte interfaces. The resulting Li[Ni_0.895Co_0.05Mn_0.05Sb_0.05]O₂ cathode material not only maintains stability during extended dwelling periods at the charged state, but also accommodates superior fast‐charge capabilities.