A Cobalt Enrichment Strategy for Suppressing the 4.2 V Adverse Phase Transition in Ni-Rich Layered Materials

Abstract

In this study, a Co-rich Ni-rich layered material with a core–shell structure is designed, in which LiNi0.82Co0.12Mn0.06O2 (NCM-Ni82) is used as the core wrapped in the shell by doping Al into LiNi0.735Co0.15Mn0.1Al0.015O2 to form the hybrid particle LiNi0.795Co0.13Mn0.07Al0.005O2 (NCM-HA). NCM-HA is divided modularly into the core part NCM-Ni82 and the single hybrid part without doped Al (NCM-HS), and then all modules were compared with the pristine LiNi0.8Co0.1Mn0.1O2 via various characterization methods to reveal the superiority of the design. The core–shell structure, which prevents the diffusion of microcracks caused by the lattice shrinkage of a high content of cobalt, is used to improve the morphological strength of the material so that the cathode material is capable of fully playing the excellent stable cycling performance brought by the remarkable cationic order degree of Co-rich treatment. The excellent cathode material NCM-HA still has a capacity retention rate of 83.35% after 200 cycles, while the pristine material has a rate of 55.42%. Moreover, NCM-HA successfully inhibits the unsteady phase transition of layered materials at 4.2 V and reduces the degree of polarization during the cycling process. This study provides a new strategy for the modification of Cobalt-enriched Ni-rich layered materials.