Foldable chromium vanadate cathodes for high-performance aqueous zinc ion batteries

Abstract

Aqueous zinc ion batteries (AZIBs), featuring intrinsic high safety, low cost, and environmental benignity, are one promising candidate for scalable energy storage. Vanadium-based materials show great potential as cathodes for AZIBs. However, either low electronic conductivity or structural collapse limits their practical applications. Herein, we report a novel CrV_2.7O_4.36·2.85H₂O (CVO) nanoflower, carbon nanotube (CNT), and reduced graphene oxide (rGO) composite (CVO/CNT-rGO) cathode. The rGO and CNT framework can improve electronic conductivity and inhibit structural collapse, and the introduced Cr³⁺ can also stabilize the lattice structure. As a result, the CVO/CNT-rGO exhibits a high capacity (397 mA h g⁻¹ at 0.2 A g⁻¹), high rate performance (252 mA h g⁻¹ at 5 A g⁻¹), and long cyclability (87% capacity retention after 1000 cycles). It also shows a Zn²⁺/H⁺ insertion/extraction mechanism. Additionally, the high conductivity and flexibility of CVO/CNT-rGO endow the CVO/CNT-rGO//Zn pouch cell with satisfactory cyclability at various folding states.