Electrical insulation properties of RF-sputtered LiPON layers towards electrochemical stability of lithium batteries. (3rd November 2016) - Vieira, E M F
Abstract: Electrochemical stability, moderate ionic conductivity and low electronic conductivity make the lithium phosphorous oxynitride (LiPON) electrolyte suitable for micro and nanoscale lithium batteries. The electrical and electrochemical properties of thin-film electrolytes can seriously compromise full battery performance. Here, radio-frequency (RF)-sputtered LiPON thin films were fabricated in nitrogen plasma under different working pressure conditions. With a slight decrease in the deposition pressure from 6 to 1 × 10 −3 mbar, the 600 nm thick LiPON film reveals an electric resistivity increase from 10 8 to 10 10 Ω · cm, respectively. UV– micro-Raman spectroscopy confirms the nitrogen incorporation on the Li3 PO4 material, while scanning electron microscopy, Rutherford backscattering spectrometry and nuclear reaction analysis show a well-defined compact structure with a composition of Li2.2 PO2.2 N0.6 for the higher electrical-resistivity film. An ionic conductivity close to 3 × 10 −7 S cm −1 at room temperature (22 °C) was measured by AC impedance spectroscopy. Thermal properties were investigated through the differential scanning calorimetry technique. LiPON films reveal high optical transmission (>75%) in the UV–vis range, which could be interesting for transparent electronic devices.