Towards high-performance cathode materials for lithium-ion batteries: Al 2 O 3 -coated LiNi 0.8 Co 0.15 Zn 0.05 O 2

Zn-doped LiNi 0.8 Co 0.2 O 2 exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi 0.8 Co 0.15 Zn 0.05 O 2 as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al 2 O 3 layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al 2 O 3 -coated LiNi 0.8 Co 0.15 Zn 0.05 O 2 cathode delivers a highly reversible capacity of 182 mA h g −1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi 0.8 Co 0.15 Zn 0.05 O 2 cathode. The enhanced electrochemistry performance can be attributed to the Al 2 O 3 -coated protective layer, which prevents the direct contact between the LiNi 0.8 Co 0.15 Zn 0.05 O 2 and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al 2 O 3 -coated LiNi 0.8 Co 0.15 Zn 0.05 O 2 , which rationally illuminates the protection mechanism of the Al 2 O 3 -coated layer.