Stabilizing lattice oxygen in slightly Li-enriched nickel oxide cathodes toward high-energy batteries

Lattice oxygen release (LOR), which promotes surface structural degradation and electrolyte decomposition, is a major contributor to capacity fade and thermal runaway in layered oxide cathodes. Despite decades of research, it is still a great challenge to stabilize the lattice oxygen, especially in deeply delithiated cathodes. Here, we demonstrate an Li-enrichment strategy to revive lithium nickel oxide (LNO), a high-energy cathode (>900 Wh kg−1) long plagued by poor cycle performance and thermal instability. In a slightly Li-enriched LNO (Li1.04Ni0.96O2) prepared by a specially designed molten-salt synthesis, spatially resolved (operando) characterizations reveal intralayer Ni migration upon delithiation, and this leads to the formation of vacancy clusters to trap the electrochemically oxidized oxygen in the near-surface lattice. Thus, the detrimental effects of LOR are effectively suppressed. The Li-rich LNO cathode greatly outperforms the traditional Li-deficient LNO cathodes modified by conventional approaches such as doping and surface coating. Our findings open up new opportunities for building better batteries.