Transparent SiNx thin-film anode for thin-film batteries by reactive sputtering at room temperature

Abstract

Silicon is extensively researched as an substitute for carbon as the anode material in Li-ion batteries. However, the cycle life of Si is very short because of its high volume expansion. Herein, we propose SiNx deposited by radio frequency reactive sputtering at room temperature as an anode material. Sputtering presents the advantage of being easily applicable to fabricate all-solid-state thin film batteries. In this study, we use a Si target and explore the deposition conditions, and the compositions of the SiNx thin film are confirmed by X-ray photoelectron spectroscopy analysis. The SiN0.85 thin film shows an initial discharge capacity of 1018 mAh g(-1) and capacity retention of 95.4% after 100 cycles, thus exhibiting stable performance. In addition, the transmittance of the SiN0.85 thin film on the glass substrate is 88% in the visible region (400-800 nm). Meanwhile, on the transparent conducting electrode, the transmittance before and after lithiation is 80% and 55% in the visible region, re-spectively. These results demonstrate that the SiN0.85 thin film, which can be used as the anode of transparent thin-film batteries, can be fabricated using reactive RF magnetron sputtering at room temperature.