A comparative study of crystalline and amorphous Li0.5La0.5TiO3 as surface coating layers to enhance the electrochemical performance of LiNi0.815Co0.15Al0.035O2 cathode

Abstract Surface coating is an effective strategy to boost the application of LiNi0.815Co0.15Al0.035O2 in the lithium ion batteries. The crystalline state of the coating layer is crucial for the transportation of lithium ions, the suppression of involved side reaction and the improvement of electrode structure stability, which ultimately determine the electrochemical performance. Here, the effects of crystalline state of Li0.5La0.5TiO3 on the electrochemical performance of LiNi0.815Co0.15Al0.035O2 are comparatively investigated. The Li0.5La0.5TiO3 coating layer with a thickness of about 2 nm is introduced on the surface of LiNi0.815Co0.15Al0.035O2, and the crystalline state (crystalline or amorphous) of coating layer is successfully controlled by tuning post-annealing temperature. The structure stability, dynamics performance, reaction activity and electrochemical performance of the coated and pristine samples are investigated. Compared with the pristine sample, the coated materials both demonstrate superior electrochemical performance. And the crystalline Li0.5La0.5TiO3 coated sample shows a better capacity retention (94.5%) than the amorphous Li0.5La0.5TiO3 coated sample (88.0%). The improved electrochemical performance of crystalline Li0.5La0.5TiO3 coated sample could be ascribed to a better interface between the electrolyte and active material, which facilitates intercalation/extraction of lithium ions during the charge/discharge processes.