Li0.33La0.56TiO3, a novel coating to improve the electrochemical properties and safety of NCM523 cathode materials for Li-ion batteries

Abstract

There is an increasing demand for high energy density lithium-ion battery cathodes such as LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523); however, severe capacity fading, and structural instability have limited their widespread application. In this study, the effect of surface modification with Li_0.33La_0.56TiO₃ (LLTO) and its crystallinity on the electrochemical performance of NCM523 cathode materials was investigated. Scanning and transmission electron microscopy observation showed a uniform distribution of 3 and 5 wt% LLTO coating, but agglomeration was observed in a higher coating content. According to the electrochemical tests, the amorphous LLTO coating improved the cycling performance and rate capability of the NCM523 cathode. The 5 wt% amorphous LLTO-coated cathode showed the highest discharge capacity after 30 cycles at 0.1 C and after 100 cycles at 0.5 C (136.3 and 104.6 mA h g⁻¹); significantly higher than that of the pristine NCM523 cathode (98.5 and 62.5 mA h g⁻¹). The discharge capacity of this coated sample at 5 C was also much higher than that of the pristine cathode (106.8 compared to 78.5 mA h g⁻¹). In addition, 5 wt% of the amorphous LLTO coating shifted the exothermic peak of the NCM523 electrode from 249 to 281 °C, indicating enhanced safety after the coating process. Compared to the crystalline LLTO-coated NCM523, the cathode with amorphous coating delivered a higher discharge capacity over cycling and at different C-rates. In light of the results, it is evident that surface modification with an amorphous LLTO coating could be a promising approach for industrial application of NCM523 cathode materials.