Revealing the Correlation between Structural Evolution and Reversible Phase Transition of Single-Crystalline Ni-Rich Cathode.

Abstract

Single-crystal nickel-rich cathodes are widely used in electric vehicles. However, the irreversible phase transition of H2-H3 during cycling leads to severe lattice distortion and disruption of the crystal structure, which seriously hinders their practical application. Herein, we formed an atomic rearrangement structure with a superlattice phenomenon on the surface of the material by lattice engineering to achieve the reversible phase transition of H2-H3 and obtained structurally stable cathode materials. Benefiting from the synergistic effect of anionic and cationic codoping, the orderly occupation of transition metal ions with lithium ions stabilizes the long-range layered plate and realizes the reversible phase transition of H2-H3 in the highly charged state. Interestingly, the atomic rearrangement of the surface structure enhanced the mechanical modulus and suppressed particle cracks caused by compressive stress concentration. In addition, the stable electrode-electrolyte interface shielded the interfacial side reactions and mitigated the escape of lattice oxygen and the leaching of transition metals. As a result, the designed Zr/F-NCM||graphite pouch battery maintained 92.4% capacity after 1000 cycles, which provides a prospective guideline for improving the durability of layered oxide cathode materials.