Amorphous silicon thin film anodes for lithium-ion batteries

Due to its order of magnitude higher theoretical capacity, silicon has been widely proposed as a potential next-generation anode material to replace conventional carbon based lithium-ion battery anodes. In this study, the properties of amorphous 250 nm and 1 mum silicon films deposited by R.F. magnetron sputtering on copper foil are investigated using x-ray diffraction, electron microscopy, and electrochemical methods. Battery tests have shown that the 250 nm Si thin films exhibit an excellent reversible specific capacity of nearly 3500 mAh/g when tested for 30 cycles. The high reversible capacity and excellent cyclability of the 250 nm sputtered silicon thin films suggest excellent adhesion between Si and Cu leading to high capacity retention. SEM analysis conducted on the 250 nm Si films after the 30(th) charge suggests the good adhesion of the similar to 2 mum diameter "plates" of silicon to the copper substrate.