Improved electrochemical performance of LiNi0.8Co0.15Al0.05O2 with ultrathin and thickness-controlled TiO2 shell via atomic layer deposition technology

Abstract

Atomic layer deposition (ALD) technology is used to deposit TiO₂ coating on the nickel-rich material LiNi_0.8Co_0.15Al_0.05O₂. The ultrathin and thickness-controlled coating shell serves as a physical barrier which protects the structure of the core and thereby enhances the electrochemical performance of the coated material. Coating shells of TiO₂ with different thicknesses corresponding to different ALD cycles are obtained and detected via transmission electron microscope (TEM) analysis. A TiO₂-coated sample with 138 ALD cycles reveals optimal electrochemical performance in the voltage range of 2.8–4.5 V. After 100 cycles, discharge capacities of 171.36 and 154.69 mA h g⁻¹ at room (25 °C) and elevated (55 °C) temperatures are observed, with higher cycle-ability of 90.21% and 73.21%, in comparison with those of 50.13% and 43.97% for pristine samples at the same temperatures. The improvements in electrochemical characterizations are ascribed to the stable structure and interface modified by the high-quality dense, ultrathin and amorphous ALD TiO₂ coating layer, which can protect the cathode particles from hydrofluoric acid attack.