Characteristics of a new type of solid-state electrolyte with a LiPON interlayer for Li-ion thin film batteries

In this study, the feasibility of applying lithium phosphorous tungsten oxynitride (Li–P–W–O–N) thin films as solid-state electrolytes in solid-state ionic energy systems such as thin film batteries and super-capacitors was evaluated. The Li–P–W–O–N thin film electrolyte was prepared by radio frequency (RF) magnetron sputtering under various working pressures of nitrogen (N2) reactive gas. We propose that the LiPON/Li–P–W–O–N/LiPON structure makes it possible to use a Li–P–W–O–N thin film as a thin film solid electrolyte because of the potential short circuiting of the Li–P–W–O–N thin film. To prepare the structure, a LiPON thin film was also deposited by RF magnetron sputtering onto Steel Us Stainless (SUS)/SiO2/Si. When a LiPON thin film interlayer was deposited on the sandwich structure of the Li–P–W–O–N thin film electrolyte, the current was less than 1 μA. For the final cell structure of SUS/LiPON/Li–P–W–O–N/LiPON/SUS/SiO2/Si, impedance measurements conducted at room temperature revealed ionic conductivities in the range of 1.5–1.2 × 10−7 Scm−1 for the various deposition conditions of the Li–P–W–O–N thin films. This result suggests that the LiPON/Li–P–W–O–N/LiPON structured thin film electrolyte has potential as a solid oxide thin film electrolyte in solid-state ionic devices.