Si-C nanocomposites supported on vertical graphene sheets grown on graphite for fast-charging lithium ion batteries

Abstract

Silicon/carbon (Si/C) anodes have been successfully used in commercial lithium-ion batteries because of their high capacity and excellent safety. Nevertheless, their cycling stability and fast-charging capability are still unsatisfactory due to large volume expansion and slow charge transport capability under industrial electrode conditions. Here, we fabricate a Si/C anode via homogeneously depositing amorphous SiC nanolayers on graphite armored with N-doped porous flexible vertical graphene sheets (VGSs) (named as Si-C/VGSs/graphite). SiC nanolayers consist of homogeneously dispersed sub-nanometer Si particles in 3D carbon skeleton, which effectively alleviate the volume change of Si, and hugely accelerate electron and Li-ion transport. The N-doped VGSs possess porous structure, good flexibility, numerous exposed edges, and directional ion transport channels, which provide rational space for accommodating volume change of Si, buffer the stress caused by the volume change, increase the electrical contact points between Si-C/VGSs/graphite, and accelerate Li-ion transport, respectively. Consequently, Si-C/VGSs/graphite delivers superior rate capacity and long cycle life under industrial electrode conditions. When matched with the cathode of Li[Ni0.8Co0.1Mn0.1]O2, the full cell demonstrates a predominant fast-charging capability (180.8 Wh kg−1, charging for 8.2 min, 5C) accompanied by long cycle life.