Li-rich layered oxide materials (LLOs) represent a promising pathway to ultrahigh-energy lithium-ion batteries due to their exceptional theoretical capacity exceeding 250 mAh g-1. However, conventional O3-type LLOs suffer from severe voltage fade, rapid capacity decay, and poor rate capability, primarily caused by irreversible oxygen release, detrimental transition metal migration, and consequent structural degradation into spinel phases. Herein, we demonstrate that these challenges can be effectively mitigated through structural engineering by adopting an O2-type configuration in LiLi0.125Ni0.125Co0.125Mn0.625O2 (O2-LNCMO). The unique face-sharing coordination in the O2 structure inherently suppresses the transition metal migration into lithium layers, stabilizes the anionic redox activity, and inhibits oxygen release. This inherent structural stability, synergized with expanded interlayer spacing that facilitates rapid Li+ diffusion, enables exceptional electrochemical performance in O2-LNCMO. The material achieves minimal voltage decay of only 0.1 V over 100 cycles, alongside outstanding rate capability, delivering over double the capacity of its O3-type counterpart at high current densities. This work develops promising O2-type LLOs as high-energy cathodes and provides valuable insights into structural design strategies for next-generation lithium-ion batteries.
He et al. (Tue,) studied this question.