Thick vacuum deposited silicon films suitable for the anode of Li-ion battery

Vacuum deposited silicon film on a Ni foil substrate showed very stable Li charge/discharge performance in PC containing 1 M LiClO4. The performance, however, became poorer rapidly with the increase in the film thickness. In an attempt to attain long cycleability with large capacity for the vacuum deposited thicker silicon film, surface morphology of the depositing substrate metal was examined. Filing with a sand paper was quite effective for providing longer cycleability as compared to the pristine Ni foil. Etching with aqueous solution of FeCl3 resulted in giving the surface roughened to a great extent. A 1.1 μm thick silicon film deposited on the well-etched substrate maintained the specific capacity over 1500 mAh g−1 even after 400 cycles with 1 C rate constant current charge/discharge. The most roughened surface could be obtained by depositing electrolytically on a copper foil. The surface revealed a jammed group of tiny pyramid like steeple-crowned caps. A 3.6 μm thick silicon film deposited on the copper substrate thus obtained maintained constantly around 2000 mAh g−1 during 50 cycles.