Vertically aligned Si@reduced graphene oxide frameworks for binder-free high-areal-capacity Li-ion battery anodes

In this study, lamellar-structured, vertically aligned silicon@reduced graphene oxide frameworks (VA-Si@rGO) are developed for binder-free, high-areal-capacity lithium ion battery (LiB) anodes. First, SiO₂/rGO frameworks with unidirectional pores are constructed via the gelation of SiO₂/graphene oxide sol and subsequent freeze-casting. Afterwards, the sturdy constructed frameworks are maintained during a series of processes, namely magnesiothermic reduction, acid etching, and thermal carbon coating, which result in carbon-coated VA-Si@rGO. The electrode exhibits a high specific capacity, reversibility, and cycle stability, which are attributed to its unique inner porous structure, high Si yield, and uniform carbon layers. A high areal capacity of approximately 9 mAh cm⁻² could be achieved by increasing the initial sol concentration up to 23.5 wt%. Furthermore, even at a high current density of 3 mA cm⁻², the electrode delivered a high areal capacity of approximately 6 mAh cm⁻² and exhibited excellent stability with a high capacity retention of 68% after the 150th cycle.