Sulfur anion doping and surface modification with LiNiPO4 of a LiNi0.5Mn0.3Co0.2O2 cathode

Abstract

LiNi0.5Mn0.3Co0.2O2 and LiNi0.5Mn0.3Co0.2O1.98S0.02 were prepared using a simple combustion method. Surface coating was carried out by the sol–gel method using LiNi0.5Mn0.3Co0.2O2, LiNi0.5Mn0.3Co0.2O1.98S0.02, and LiNiPO4. Physical properties of the synthesized materials were measured by XRD, SEM, and TEM. Electrochemical performance was assessed by measuring parameters such as charge and discharge capacity, cycling performance, rate capability, EIS testing, and the XANES. Sulfur-doped cathode material conferred improved cycling performance compared with LiNi0.5Mn0.3Co0.2O2 and had a low capacity decrease after 50 cycles. LiNiPO4 provided an enhancement of rate capability for discharging at 0.1–5 C. In addition, the 3 wt% LiNiPO4-coated LiNi0.5Mn0.3Co0.2O1.98S0.02 cathode material had improved cycling performance, rate capability, and EIS testing results compared with the other samples. The rate capability and cycling performance of LiNi0.5Mn0.3Co0.2O2 cathode material for lithium ion batteries have been enhanced by the stabilization of the surface of cathode with a LiNiPO4 coating and sulfur doping.