Interface Reduction Synthesis of H2V3O8 Nanobelts-Graphene for High-Rate Li-Ion Batteries

Layer-structured vanadium oxides are one of the most promising cathode intercalation materials for the next generation of lithium-ion batteries (LIBs) because of their high specific capacity, abundant sources, and low cost. Their widespread commercialization is, however, hindered by the fact that most vanadium oxides suffer from low electrical conductivity and poor cycling stability. We synthesized the sandwich composites of H2V3O8 nanobelts and reduced graphene oxide (H2V3O8-rGO) which synergistically combine the advantages of both materials for lithium ion intercalation. Further, we investigated the growth process of the H2V3O8-rGO composites and propose an adsorption-nucleation-reduction-recrystallization mechanism. In the study, graphene oxide played multiple roles: (a) reducing agent to enable the direct surface growth of H2V3O8 nanobelts, (b) providing intimate conducting pathways, and (c) structural stabilizer. A discharge capacity of 246 mAh/g was obtained for the composite at a current density of 0.05 A/g and remained at 221 mAh/g after 90 cycles. At a much higher current density of 1.0 A/g, the capacity still remains at 120 mAh/g after 400 cycles, corresponding to 87% capacity retention, which is indicative of the good cycling stability and excellent high-rate capacity of the composites.