Synthesis of V2O5 Nanoribbon–Reduced Graphene Oxide Hybrids as Stable Aqueous Zinc-Ion Battery Cathodes via Divalent Transition Metal Cation-Mediated Coprecipitation

Aqueous zinc-ion batteries (AZIBs) are an emerging sustainable and safer technology for large-scale electrical energy storage. Here, we report the synthesis of hybrid materials consisting of V2O5 nanoribbons (NRs) and reduced graphene oxide (rGO) nanosheets as AZIB cathode materials by divalent metal cation-mediated coprecipitation. The divalent metal ions M2+ (Zn2+ and Mn2+) effectively neutralize the negative charges on the surface of microwave-exfoliated crystalline V2O5 NRs and graphene oxide (GO) nanosheets to form a strongly bound assembly. After thermal annealing in a nitrogen atmosphere, GO is converted into rGO with higher electrical conductivity while the layers in V2O5 NRs are expanded by M2+ intercalation. When only Zn2+ ions are used during coprecipitation, the produced Zn-V2O5 NR/rGO hybrid shows a very high reversible specific capacity of ∼395 mAh g–1 at 0.50 A g–1 but suffers from poor stability. This is improved by mixing Mn2+ with Zn2+ ions during coprecipitation. The (Mn + Zn)-V2O5 NR/rGO hybrid shows a slightly lower specific capacity of ∼291 mAh g–1 at 0.5 A g–1 but a substantially improved long-cycling stability and better rate performance due to the stronger binding of Mn atoms in the V2O5 host that serve as stable pillars to support the expanded V2O5 layers.