Nano-Silicon Encased in a S, N Co-doped Carbon Shells Anode Delivers High Lithium-Ion Storage Performance

Nano-silicon (Si) integrating carbonous material has been recognized as a viable approach for restraining the intrinsic serious volume change and enhancing poor conductivity, finally resulting in improved electrochemical properties, including capacity, rate performance, and cycling life-span. Nevertheless, it remains a huge challenge via a straightforward strategy to obtain the homogeneous Si@C composite with an exceptional Li⁺ storage performance. Herein, novel Si integrating a S, N co-doped carbon shell and a graphite composite material (Si@C/SN@Graphite) have been prepared through combining in situ carbon coating with a liquid-phase ball milling method, in which thiourea was used as dopant, poly(ethylene glycols) were used as carbon coating precursor, and graphite was utilized as carbon matrix. The combined effect of the S and N co-doping carbon coating layer and graphite sheet is sufficient to efficiently restrain the serious volume expansion, enhance electronic conductivity, and provide numerous Li⁺ storage rooms for Si anode. Furthermore, the theoretical simulation and electrochemical testing have been carried out to further demonstrate the superiority of the S, N co-doped carbon coating layer. As a result, the as-prepared Si@C/SN anode delivers a notable initial Coulombic efficiency (ICE) of 91%, high reversible capacity of 1213 mAh/g at 2 A/g within 0-1.0 V coupled with 92.8% capacity retention rate for 400 cycles. Moreover, the Si@C/SN@Graphite anode exhibits outstanding reversible capacities of 690 and 379 mAh/g at 0.05 and 1 A/g within 0-2 V along with a 90% capacity retention rate for 500 cycles. Additionally, the full cell assembled by using Si@C/SN@Graphite as anode and LiFePO₄ as cathode presents reversible capacities of 176.5 and 137.9 mAh/g at 0.2 and 3 C, respectively, and considerable ICE of 92% as well as 90% capacity retention for 200 cycles. This work provides a facile and cost-effective strategy for obtaining Si@C composites with exceptional Li-ion storage capabilities in LIBs.