LiNi${}_{0.8}$Co${}_{0.15}$Al${}_{0.05}$O${}_2$ coated by chromium oxide as a cathode material for lithium-ion batteries

LiNi${}_{0.8}$Co${}_{0.15}$Al${}_{0.05}$O${}_2$ (NCA) material was decorated with different contents of Cr${}_2$O${}_3$ (0.01–2 wt%) via a precipitation technique followed by calcination at 600 °C. The existence of the coating on the NCA particles was confirmed by SEM and elemental EDS mapping. XRD analysis showed that the addition of Cr${}_2$O${}_3$ did not change the crystalline structure of NCA. The electrochemical performance of samples was evaluated by cyclability, cyclic voltammetry, electrochemical impedance spectroscopy, and rate capability tests. Electrochemical evaluations revealed that the addition of 0.25–0.5 wt% Cr${}_2$O${}_3$ not only enhanced the electrochemical reversibility of NCA but also improved its rate capability. The capacity retention of 92.1% after 50 cycles at the 0.5C rate was obtained for the optimized material, while the bare NCA retained a capacity of 69%. At a rate of 2C, the specific discharge capacity of the optimized material was 162.2 mAh g${}^{-1}$, while it was 149.7 mAh g${}^{-1}$ for the bare one. These enhancements may be attributed to the stability of the surface film on the NCA, reduction of the SEI layer thickness, and reduction of charge-transfer resistance of the electrode due to the Cr${}_2$O${}_3$ protection layer on the cathode material, which reduced the side reactions of the cathode material with the electrolyte.