Nanoporous Helium-Silicon Co-Deposition Thin Film via Plasma-Assisted Process for Lithium-Ion-Battery Anodes

In this study, silicon (Si) deposition is performed in a high-density (10(18) m(-3)) helium (He) plasma environment, and He-Si co-deposition layers, where He atoms are implanted into the Si thin film, are formed. The He-containing thin film, which has a porosity of approximate to 0.5, is composed of smaller clusters with the size of 100-200 nm including many pores with different sizes, which is advantageous for lithium-ion-battery (LIB) negative electrode. It is also shown that substrate copper (Cu) atoms are diffused into the deposition layer and Cu doping occurred naturally. The LIB performance of the He-Si co-deposited thin film (>1 mu m in thickness) is evaluated. When the substrate temperature is at 523 K during the deposition, the Si layer has amorphous structure, and the LIB discharge capacity remains 1800 mAh g(-1) after 100 cycles. In the results, it is shown that the Si-He co-deposition method can be a novel method to fabricate Cu-doped porous amorphous Si thin film for high-performance LIB application.