Li–B–O–N electrolytes for all-solid-state thin film batteries

We report for the first time new Li+ ion conducting thin film solid electrolytes based on Li–B–O–N system. Substitution of oxygen in xLi2O–B2O3 (x = 1, 3, 5) by nitrogen was successfully achieved by reactive sputtering under nitrogen plasma. FTIR and XPS analyses indicated that N atom was incorporated in the Li–B–O matrix film, and an increase in the composition of Li2O together with N-substitution caused the structural conversion from ring-type borate to open structured one, where more free space and ionic bonding characteristic are offered for higher mobility of Li+ ions. A high ionic conductivity of ca. 2.3 × 10−6 S cm−1 at room temperature was obtained from the thin film electrolyte of Li3.09BO2.53N0.52 glass that was prepared using 3Li2O–B2O3 target. Electrochemical analyses suggest the high Li+ ion conductivity is induced by the reduced activation energy through the control of the composition and the structure.