Enhancement in electrochemical properties of sodium-doped LiNi0.815Co0.15Al0.035O2 cathode

Abstract

Lithium-ion batteries (LIBs) as energy storage devices have been booming recently to fill the demand for energy requirements. High‑nickel ternary cathode material LiNi0.815Co0.15Al0.035O2 (NCA), extremely possible to be the next generation of cathode materials for applications due to its high energy density, low cost, and environmental friendliness. However, the rate capability and cycling stability of this cathode material is mediocre. In this work, NCA-based cathode materials have been modified by sodium (Na+) doping through a high-temperature solid-state reaction, the results show that Na+-doping can effectively improve the electrochemical performance of NCA. Electrochemical test results show that Na+-doping improves Li+ diffusion coefficient, inhibits NCA polarization, and reduces the charge transfer impedance. As-prepared 2%Na-NCA at the current density of 1.0C shows a discharge-specific capacity of 149.16 mAh/g and a retention rate of 96.49% after 100 cycles, but the retention rate of the Pure-NCA was (84.47%). Furthermore, 2% Na-NCA shows 121.07 mAh/g at 5.0C, with an increase of 27.05 mAh/g over the Pure-NCA (94.02 mAh/g). The results of the study showed that doping with sodium ions can effectively improve the rate capabilities and cycling stability of NCA.