The surface double-coupling on single-crystal LiNi0.8Co0.1Mn0.1O2 for inhibiting the formation of intragranular cracks and oxygen vacancies

Single-crystal LiNi0.8Co0.1Mn0.1O2 (SC-811), which prevents grain-boundary fracture and offers better cycle performance compared to the polycrystalline morphology, has gained great attention as cathode materials for lithium-ion batteries. However, the single-crystal Ni-rich LiNixCoyMnzO2 (x+y+z=1) (NCM) is suffering from oxygen vacancy, intragranular crack, and ion diffusion in large particles that hinder its electrochemical performance. Herein, a double coupling of surface La2Li0.5Al0.5O4 coating and concentration-gradient Al3+ doping is exploited on SC-811 cathode by facile sol-gel method. The synergistic impacts endow the SC-811 with excellent capacity retentions: 90.9%, after 200 cycles at 1 C. In a pouch-type full battery, the graphite/LLA modified SC-811 exhibits a capacity retention of 90.1% after 500 cycles at 1 C in the 2.8-4.25 V range at 25°C. Multiple characterizations reveal that the excellent electrochemical performance are mainly attributed to double-coupling that successfully inhibits the attenuation of H2-H3 phase, intragranular cracks, oxygen vacancies, the serious rock salt phase transition, and alleviates the growth of solid electrolyte interphase (SEI) and the side reaction of electrode/electrolyte during cycling. This work demonstrates that doping combined with coating is a critical pathway for the further development of single-crystal ternary cathode materials.