In-situ construction of dual-coated silicon/carbon composite anode for fast-charging Li-ion batteries

Silicon (Si) is regarded as a promising candidate anode for next-generation high-energy-density batteries due to its ultrahigh theoretical capacity of 4200 mAh g(-1). However, silicon anodes face tremendous challenges during cycling, including huge volume expansion, highly unstable interfaces and inherently low conductivity. In this study, the dual-coated silicon/carbon composite anode (Si@SiOx@C) with high silicon content of 85 % is obtained by high-energy ball milling and combined with phenolic resin-assisted encapsulation. The amorphous SiOx layer (similar to 3 nm) facilitates the rapid Li+ transport and mitigates the volume expansion, while the hard carbon layer (similar to 3 nm) improves the electronic conductivity and helps to protect against silicon oxide layer erosion from electrolyte, synergistically contributing to the fast-charging performance. With the synergistic effect of dual coating, the Si@SiOx@C anode shows a high initial Coulombic efficiency of 91 % and maintains a high capacity of 1250 mAh g(-1) even after 500 cycles at a high rate of 4 A/g. Moreover, the volume expansion of silicon anode during cycling is significantly reduced. This work provides a novel strategy for high silicon content anode in developing fast-charging batteries through dual-coating regulation.