A novel conductive network surface coated anode material Si/SA-CNTs for lithium ion batteries

Silicon (Si) material is considered the most promising ideal anode material due to its highest theoretical specific capacity of 4200 mAh g−1. However, the large volume changes during the lithiation-delithiation process lead to electrode structure collapsed failure and hinder silicon anode application. To inhibit the volume expansion of silicon anode materials, this paper focuses on the surface modification of silicon-based thin film anode materials. Through the combination of plasma enhanced chemical vapor deposition technology (PECVD) and surface coating modification technology, sodium alginate (SA) coating is introduced on the surface of amorphous Si thin film to obtain Si/SA composite with good cycle performance. Furthermore, by constructing carbon nanotubes on the SA coating layer, Si/SA-CNTs composite was successfully prepared. The initially discharge specific capacity of Si/SA-CNTs is 3716 mAh g−1, and the discharge specific capacity is 2028 mAh g−1 after 200 cycles at 0.5C (1C = 4.2 A g−1). It increased by 1413 mAh g−1 compared with pure Si thin film. At the same time, its discharge specific capacity at 10C is 1726 mAh g−1, showing excellent rate performance. This surface coating modification helps relieve the stress and strain during the charge/discharge process. Meanwhile, the conductive structure enhances the transport of electrons and ions, which effectively improves the electrochemical performance of the Si thin film.