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

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 SiN_x 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 SiN_x thin film are confirmed by X-ray photoelectron spectroscopy analysis. The SiN_0.85 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 SiN_0.85 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, respectively. These results demonstrate that the SiN_0.85 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.