Characterization of lithium borophosphate glass thin film electrolytes deposited by RF-magnetron sputtering for micro-batteries

Lithium ion conducting thin film electrolytes, Li2O-B2O3-P2O5 glass systems, were prepared with a wide range of chemical composition by co-sputtering method with multi-targets. The maximum ionic conductivity at room temperature was 1.22×10−6S/cm and the activation energy of this specimen was 0.54eV when enhanced by the mixed former effect and the high network modifier content. The increased ion conductivity of the films appeared to be associated with the formation of stable tetrahedral borate at high lithium concentration and this structural change facilitated faster ion migrations. The relationship between the glass structure and electrical performance of the mixed former glasses was investigated by the infrared spectra analysis of borate networks. The conductivity of the mixed former electrolytes increased gradually with increasing the RF power on Li2O target, and the maximum conductivity was obtained at 100W. The structural role of the network modifier in xLi2O-(1-x)(B2O3-P2O5) glasses was analyzed by the O1s spectra of X-ray Photoelectron Spectroscopy. A quantitative deconvolution of O1s spectra suggests that the increased conductivity with increasing lithium content is due to the formation of non-bridging oxygen. ► Lithium borophosphate glass electrolytes for the all-solid-state thin film batteries. ► The enhancement of ionic conductivity by mixed former effect of boron and phosphorous. ► The electrolytes with high lithium-ion contents by co-sputtering with Li2O target. ► The maximum conductivity of 1.22×10−6S/cm, which is close to that of LiPON electrolytes.