A silicon/carbon/reduced-graphene composite of honeycomb structure for high-performance lithium-ion batteries

The high theoretical capacity of silicon (Si) makes it an attractive anode for lithium-ion batteries (LIBs). However, the poor cycle performance due to the volumetric expansion of Si during the charging-discharging process hinders its practical applications. A composite of graphene and silicon can buffer effectively the volumetric expansion of Si during the charging and discharging process of the battery. Herewith we describe a honeycomb structure constructed with Si nanoparticles (NPs), acetylene black (ACET), and reduced graphene (rGO). In this 3D structure, ACET and Si formed a Si/C composite by mechanical ball milling and it was then encapsulated in a graphene oxide (GO) suspension. After reduction with hydrazine hydrate (N2H4·H2O) to create rGO, a stable composite Si/C/rGO was obtained. As an anode for LIB, the Si/C/rGO composite exhibited excellent cycle and rate performance. Firstly, the initial coulombic efficiency (ICE) of the battery is very high, exceeding 85%. Secondly, the reversible capacity was retained at 1004 mAh/g after 270 cycles at a current density of 1 A/g. The composite maintained good cycling stability even at current densities of 2 and 3 A/g. Finally, in the rate cycle test, the reversible capacity was up to 450 mAh/g at 5 A/g.