Thin film lithium ion conducting LiBSO solid electrolyte

Thin films of 1–2 μm amorphous solid electrolytes, (1−x)LiBO2–xLi2SO4 (LiBSO), were fabricated by RF magnetron sputtering with a wide range of compositions, i.e. x=0.4–0.8, which are beyond the glass-forming region by conventional melt quenching method. The ionic conductivity of the electrolyte at room temperature increased with x and showed a maximum at x=0.7, about 2.5×10−6 S/cm. For higher x, (x>0.7), the conductivity began to decrease due to the partial crystallization. In addition, the electrolyte was stable up to 5.8 V vs. Li/Li+. LiBSO thin film electrolyte was incorporated into Li/TiS2 microbattery, showing a good cycling performance.