Building the Stable Oxygen Framework in High-Ni Layered Oxide Cathode for High-Energy-Density Li-Ion Batteries

[摘要] High-Ni layered oxide cathodes hold a great promise for fabricating high-energy lithium-ion batteries. However, the oxygen evolution during cycling is a crucial factor in the structure deterioration, potential change, and capacity decay of cathodes, limiting the commercial application of high-Ni (Ni > 0.9) layered oxides in batteries. Herein, we demonstrate a feasible approach to enhance the stability of oxygen framework, through the surface oxygen immobilization with yttrium and bulk oxygen stabilization with aluminum in high-Ni layered oxides. As expected, benefiting from the oxygen-stabilized framework, the bulk structure deterioration, and interfacial parasitic reaction are mitigated obviously during battery operation, along with the improved thermal stability of cathode. Correspondingly, the as-prepared high-Ni oxide delivers high reversible capacity, impressive cycle ability, and low potential polarization upon cycling. Such significant improvement on the electrochemical performance is primarily attributed to the strong oxygen affinities of both yttrium at the surface layer and aluminum in the bulk, which synergistically stabilizes the oxygen framework of high-Ni oxide via raising the energy barrier for oxygen evolution. Therefore, building the stable oxygen framework is critical for enhancing the energy density output, cycle operation, and thermal stability of high-Ni oxide cathodes.

[关键词] Li-ion batteries;cathode;high-Ni oxide;oxygen evolution;structure stability