Ultrahigh-Ni Cathode with Superior Structure Stability Enabled by a Covalent Bonding Strategy

Abstract

Ultrahigh-nickel layered oxide cathodes are the most promising cathode materials for high-energy lithium-ion batteries. However, the rapid structural degradation during cycling charge-discharge process limits its commercial application. Herein, we report a covalent pinning strategy to enhance structure stability of ultrahigh-Ni cathode LiNi_0.9Co_0.06Mn_0.04O₂ (NCM90). Zr is gradient diffused into the lattice of NCM90 and forms Zr−O bonds during the sintering process, which can effectively alleviate the lattice distortion like introducing pinning centers due to the stronger bond energy, enhancing its structure stability during charge-discharge process. In the meanwhile, the Zr−O on the surface of NCM90 powder forms Li_xZr_yO_z coating layer due to the reaction with lithium residue, which prevents from the edge reconstruction and mitigates the occurrence of side reactions, as well as ensuring a fast Li⁺ diffusion pathway crossing the interface. As a result, the Zr−O modified NCM90 (Zr-NCM) achieves 88.8 % remarkable capacity retention at 1 C after 200 cycles over 2.8–4.3 V, which is superior to the pristine NCM90 with 71.2 % retention. This work demonstrates that the Zr−O bonding can provide an effective structure pinning for the ultrahigh-Ni cathode, which will largely guide the development of high-performance lithium-ion battery cathode materials.