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

Abstract

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 (N 2) 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)/SiO 2/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/SiO 2/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.