Robust Ultrafine-Graphite-Sheet/Si@Carbon Microsphere with Double Protective Layers as High-Performance Lithium-Ion Battery Anode

Abstract

The anchored Si on the graphite as anode has attracted enormous attention as a promising alternative to graphite in the high-performance lithium-ion batteries (LIBs). However, the limited Si load, huge volume expansion and structural instability seriously restrict the performance of LIBs. In this work, the robust Si-based microspheres with double protective layers of ultrafine graphite sheet (UGS) and carbon layer are fabricated in a large scale and low-cost. The Si loads up to 44.7 wt% in the abundant 3D interconnected nano-porous channels. Both of UGS and UGS/nano-Si display excellent fast discharge/charge properties, compared with bulk flake graphite (FG) and FG/nano-Si. UGS/nano-Si@C exhibits an excellent electrochemical behavior. The initial capacity is up high to 1431.1 mAh g-1 at 0.1 A g-1 and the capacity retention can be maintained at 82.5% after 300 cycles. The excellent electrochemical properties are mainly ascribed to the robust composite structure and 3D interconnected nano-porous channels, which are beneficial for the fast electron/lithium-ion transfer and the reduced volume change. The ultrafine graphite sheet also shortens the lithium-ion diffusion path. The feasible strategy of the enhancement of Si load, the improvement of electronic conductivity and structural stability of Si-C composites will be significant for the next-generation electrode fabrication of high-capacity LIBs.

Keywords: Si anode, ultrafine graphite sheet, high Si loading, 3D interconnected nano-porous channels, fast diffusion and de-intercalation