Electrochemical properties of LiCoO2 thin film surface modified by lithium tantalate and lithium niobate coatings

Amorphous lithium tantalate (LTaO)- and lithium niobate (LNbO)-coated LiCoO2 (LCO) thin film electrodes were fabricated by pulsed laser deposition (PLD). The LTaO- and LNbO-coated LCOs showed lower interfacial resistances and high-rate charge-discharge properties as compared with a bare LCO. The contribution of the LTaO and LNbO coatings to the electrochemical properties was considered using lithium diffusion and surface analysis. Tracer lithium diffusion coefficients (DLi⁎) of the LTaO and LNbO thin films were determined by secondary ion mass spectroscopy (SIMS) using 6Li and 7Li isotopes. Surface analysis of the LTaO- and LNbO-coated LCOs before and after electrochemical measurement was performed using X-ray photoemission spectroscopy (XPS). The LTaO and LNbO thin films indicated fast lithium-ion diffusion; moreover, no degradation of the surface of the LNbO-coated LCO was observed during the electrochemical measurements. Therefore, LNbO is considered an excellent coating material for decreasing interfacial resistance.