Ball milling synthesis of robust sandwich-structured C/Si@SnO2 anode with porous silicon buffer layer for fast charging lithium-ion battery

Aiming at enhancing cyclic stability and fast charging performance of lithium-ion batteries (LIBs), a sandwich structured composite with a buffer layer of porous silicon (Si) between the carbon layer and SnO2 layer (C/Si@SnO2) was developed by using ball milling. The results showed that the Si layer with plenty of mesoporous and cracks was coated successfully and the introduction of Si increased the disordered structure of SnO2, including the expansion of interlayer spacing, the emergence of Sn and SiOx indicated the reaction between Si and SnO2 occurred during the ball milling process, while the generation of Si-O-Sn and Si-O-C bonds formed by Si integration connected the three components with intimate interfaces. Used as an anode for LIBs, the C/Si@SnO2 electrode performed a favorable discharge capacity (919.21 mAh·g−1 at 0.1 A·g−1), the ultra-long cyclability after 1000 and 2000 cycles, impressive rate performance (269.87 mAh·g−1 at 5 A·g−1), and fast charging capability accompanying discharge capacity of 805.57 mAh·g−1 at 0.2 A·g−1 and charge capacity of 400.55 mAh·g−1 at 2 A·g−1. In addition, the electrochemical impedance spectroscopy analysis showed that the graphitic carbon layer and porous Si layer improved the rapid Li+ diffusion and transportation, which was beneficial to fast charging in LIBs. Our work provided a facile and green ball milling method to construct porous sandwich structured metal oxide/C composites with the introduction of Si, which can effectively increase the disordered structure of composite and also open up a new scheme of Si materials as an anode in the field of fast charging for LIBs.