Dual conductive network-enabled graphene/Si-C composite anode with high areal capacity for lithium-ion batteries

Silicon has been regarded as one of the most promising alternatives to the current commercial graphite anode for Li-ion batteries due to its high theoretical capacity and abundance. Although high gravimetric capacity (mAh/g) of Si-based materials can be achieved, areal capacity (mAh/cm²), an indication of the energy stored at the electrode level, has rarely been discussed. Herein, a novel micro-sized graphene/Si-C composite (G/Si-C) is reported, in which micro-sized Si-C particles are wrapped by graphene sheets. Owing to dual conductive networks both within single particles formed by carbon and between different particles formed by graphene, low electrical resistance can be maintained at high mass loading, which enables a high degree of material utilization. Areal capacity thus increases almost linearly with mass loading. As a result, G/Si-C exhibits a high areal capacity of 3.2mAh/cm² after 100 cycles with high coulombic efficiency (average 99.51% from 2nd to 100th cycle), comparable to that of commercial anodes. The current findings demonstrate the importance of building a conductive network at the electrode level to ensure high material utilization at high mass loading and may shed light on future designs of Si-based anodes with high areal capacity.