NH₄V₄O₁₀/rGO Heterostructure with Enlarged (001) Plane Spacing for Aqueous Zinc-Ion Batteries with High Zinc Storage and Highly Reversible Zn²⁺ Insertion/Extraction

The scarcity of suitable cathode materials for aqueous zinc-ion batteries (ZIBs) is primarily attributed to the strong Coulombic force between Zn 2+ and host materials. In this regard, the double two-dimensional flake structures of ammonium vanadate nanosheet and reduced graphene oxide (rGO) tend to form a heterogeneous structure, resulting in reduced interaction, improved electrical conductivity, and zinc storage. Consequently, the NH 4 V 4 O 10 /rGO cathode with heterostructures that accomplish high specific capacity and rapid charge transfer kinetics was synthesized via microwave-assisted chemical deposition. Through the formation of a conductive network, the rGO-covered and connected NH 4 V 4 O 10 nanosheets facilitated fast ion/electron transport kinetics. Furthermore, the interlayer spacing of NH 4 V 4 O 10 increased by combining rGO, thereby weakening the electrostatic interaction between Zn 2+ ions and the NH 4 V 4 O 10 crystal structure. The NH 4 V 4 O 10 /rGO composite exhibited a high capacity of 551 mAh g –1 at 0.1 A g –1 as well as a long cycle life (capacity retention rate of 130.6% after 2000 cycles) as a cathode for ZIBs. The increase in the layer spacing of NH 4 V 4 O 10 resulting from the lattice mismatch between rGO and NH 4 V 4 O 10 was verified by first-principles calculations, which also demonstrated the beneficial role of the NH 4 V 4 O 10 /rGO heterostructure in improving conductivity and zinc storage.