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.