Li4Ti5O12 and LiMn2O4 thin-film electrodes on transparent conducting oxides for all-solid-state and electrochromic applications

Transparent Li4Ti5O12 and LiMn2O4 thin films were prepared on transparent conducting oxide substrates via sol-gel dip coating technique. The resulting films were highly uniform and transparent after annealing at 600 °C and 400 °C for Li4Ti5O12 and LiMn2O4, respectively. Different film thicknesses ranging from 50 nm to about 800 nm were attained and the films were characterized by scanning electron microscopy (SEM) for surface morphology and X-ray diffraction (XRD) for evaluating the crystallization of the active materials. Ellipsometric porosimetry was used to measure the porosity of the anode material. Furthermore, electrochemical techniques such as cyclovoltametry and galvanostatic charging/discharging confirm the successful synthesis of electrochemically active LiMn2O4 and Li4Ti5O12 films. Single-layer electrodes show stable capacities at discharge rates up to 100C indicating the high rate capability and therefore and therefore are classified as materials for power. Furthermore, the electrochromic effects were observed for both thin-film systems and evaluated in preliminary tests.