Electrical insulation properties of RF-sputtered LiPON layers towards electrochemical stability of lithium batteries

Electrochemical stability, moderate ionic conductivity and low electronic conductivity make \nthe lithium phosphorous oxynitride (LiPON) electrolyte suitable for micro and nanoscale \nlithium batteries. The electrical and electrochemical properties of thin-film electrolytes can \nseriously compromise full battery performance. Here, radio-frequency (RF)-sputtered LiPON \nthin films were fabricated in nitrogen plasma under different working pressure conditions. \nWith a slight decrease in the deposition pressure from 6 to 1 × 10−3 \n mbar, the 600 nm thick \nLiPON film reveals an electric resistivity increase from 108 \n to 1010 Ω · cm, respectively. UV– \nmicro-Raman spectroscopy confirms the nitrogen incorporation on the Li3PO4 material, while \nscanning electron microscopy, Rutherford backscattering spectrometry and nuclear reaction \nanalysis show a well-defined compact structure with a composition of Li2.2PO2.2N0.6 for the \nhigher electrical-resistivity film. An ionic conductivity close to 3 × 10−7 \n S cm−1 \n at room \ntemperature (22 °C) was measured by AC impedance spectroscopy. Thermal properties were \ninvestigated through the differential scanning calorimetry technique. LiPON films reveal high \noptical transmission (>75%) in the UV–vis range, which could be interesting for transparent \nelectronic devices.