Self-deformed Si/Graphene@C anode for stress relief in lithium ion batteries

Abstract

Despite considerable efforts of carbon matrix for the superior structural integrity of Si anode of lithium-ion batteries, Si/C architectures with thick carbon layer suppress its ion kinetics. The design of Si/C architectures with thin carbon layers is promising for superior ion/charge kinetics but still arouses its deterioration in structural stability due to the agglomeration of Si nanoparticles (SiNPs). Herein, SiNPs are dispersed on large-sized graphene (Si/G@C) with robust linkings, which effectively suppresses the self-limiting effect due to the dispersed SiNPs on graphene. Finite element analysis reveals well-dispersed SiNPs in Si/G@C provide enough room for accumulating its volume variations. Even, the accumulated stress in relatively dense regions of SiNPs is relieved via self-deformed graphene. Thin carbon layers are grown on SiNPs of Si/G@C for low ion diffusion barriers, in agreement with density function theory simulation. Meanwhile, an electrical network and high electrical-field response on the interface of Si and carbon layers improve its charge transfer. Therefore, the prepared Si/G@C shows superior rate capability (1127.1 mAh/g at 4 A/g), capacity retention (∼74.56% after 303 cycles at 1A/g) and low electrode swelling (∼3.60% after 303 cycles). This design of Si/G@C sheds light on the preparation of advanced Si-based anode in lithium-ion battery.