Abstract:

A sandwich-type Si/Fe/Si film was deposited on Cu foil by magnetron sputtering. High-resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) results indicated that the sputtered film had an amorphous structure. The cross-sectional scanning electron microscope (SEM) images and the energy dispersive X-ray spectrometry (EDXS) spectra showed that the thickness of the filmwas 3.2 μm, and its volume expansion ratio was up to 265% after the prolonged electrochemical lithiation and delithiation cycles. In the potential range 1.5-0.005 V (vs Li+/Li) at the current density of 0.1 mA·cm-2, the film anode exhibited a high initial lithiation capacity around 1.85 mAh·cm-2, and reached the highest reversible delithiation capacity of 0.84 mAh·cm-2 after 70 cycles. After 200 cycles, it still retained a reversible capacity of 0.55 mAh·cm-2, which was 66%of the highest reversible capacity. The introduction of Fe to Si not only improved the conductivity of the film, which partially reduced the voltage hysteresis, but also effectively suppressed the volume expansion, which led to a prolonged cycle life.

Key words: Lithium-ion battery, Anode material, Magnetron sputtering, Sandwich-type structure, Si/Fe/Si film