Si–Al thin film anode material with superior cycle performance and rate capability for lithium ion batteries

To improve the electrochemical performance of Si thin film, we have investigated the effect of the addition of Al in the film. The Si–Al thin film were prepared by co-deposition from Si target embedded with Al rods on Cu foil. The atomic ratio of Al in the film is 18.69% estimated by energy-dispersive spectroscopy. The XRD and TEM analysis revealed that the Si–Al thin film was a complete amorphous structure. The electrochemical performance of the Si–Al thin film as anode material for lithium ion battery was investigated by the cyclic voltammetry and charge/discharge tests. The Si–Al thin film delivered a high reversible capacity of 2257.8 mAh g−1 and an initial Coulombic efficiency of 85.9% at 0.05C rates. Compared with pure Si thin film with the same thickness, Si–Al thin film showed superior rate capability and cycle performance. And the Li+ diffusion coefficient of Si–Al thin film is much higher than that of Si thin film.