Enhanced electrochemical performances and thermal stability of LiNi 1/3 Co 1/3 Mn 1/3 O 2 by surface modification with YF 3

Abstract Layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were prepared using a sol-gel method and subsequently surface-modified with YF 3 layer by a wet chemical process. In comparison with pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 @YF 3 exhibited higher rate capability, better cyclability and better thermal stability. After 100 cycles at 5 C and 25 °C, LiNi 1/3 Co 1/3 Mn 1/3 O 2 @YF 3 showed 93% capacity retention compared with 74% for pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Electrochemical measurements demonstrated that the improved electrochemical performances of YF 3 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 might be attributed to smaller charge-transfer resistance, higher lithium diffusion rate, more stable electrolyte/electrode interfacial structure, and lower activation energy. Kelvin probe force microscopy measurements revealed that the LiNi 1/3 Co 1/3 Mn 1/3 O 2 @YF 3 cathode possessed a lower surface potential and work function than those of the pristine one, which help to facilitate electron transport and suppress reactions between the electrolyte and cathode during the charge/discharge processes. In a certain way, the reported results clarified the possible mechanism of the enhanced performances of cathode materials with surface modification in terms of interfacial effect.