Effect of co-sputtering power on ionic transport in Li-Al-Ti-O thin-film electrolytes

Abstract

Room-temperature synthesis routes for thin-film solid-state electrolytes are critically important for advancing supercapacitors, lithium-ion batteries, electrolyte-gated thin-film transistors, and electrochromic devices. In the present study, we report, for the first time, the room-temperature deposition of Li–Al–Ti–O thin films via magnetron co-sputtering. Ionic transport properties were systematically tuned by maintaining a constant RF power of 150 W on the Li target while varying the DC power applied to the AlTi target from 60 to 140 W. XPS analyses revealed enhanced incorporation of Ti and Al into the Li–Al–Ti–O matrix, accompanied by a decrease in the fraction of bound lithium ions )62.63% to 41.51%( with increasing DC power. FESEM observations demonstrated that the higher incorporation of metals (Al, Ti) relative to Li atoms promoted smooth and homogeneous film morphologies, effectively suppressing granular structure formation. XRD results confirmed the amorphous nature of the as-deposited films. Impedance spectroscopy measurements indicated that the increased substitution of Li sites with Al and Ti introduced additional Li vacancies and lowered the activation energy from 0.76 to 0.21 eV, thereby enhancing Li-ion transport. Consequently, a maximum ionic conductivity of 7.53 × 10 −7 S cm −1 was achieved for the co-sputtered Li–Al–Ti–O films at an RF power of 150 W and a DC power of 140 W. The observed correlations among deposition parameters, structural characteristics, composition, and ionic transport provide crucial insights for the rational design of high-performance thin-film electrolytes.