Unraveling Cu²⁺ Ion Intercalation-Based V₃O₇·H₂O Cathode to Drive Ultrahigh-Rate Aqueous Zinc-Ion Batteries

Abstract

Vanadium-based cathode materials have attracted significant interest owing to their high theoretical capacities (>300 mA h g^-1), versatile electrochemical ion insertions, and high valence states. However, their poor electrical conductivities and dissolution in electrolytes have hindered the development of grid energy storage systems. To address these issues, Cu²⁺ ion-doped V₃O₇·H₂O (CuVO-2) cathode materials prepared via a one-step hydrothermal method were used to solve the aforementioned problems. The as-prepared CuVO-2 offered ample space for rapid ion transport, enabling a high reversible capacity of 444.8 mA h g^-1 at 0.1 A g^-1, excellent rechargeability of up to 5000 cycles at 5 A g^-1 with a Coulombic efficiency (CE) of 84.4%, and an acceptable energy density of 302.65 W h kg^-1. To better understand the storage mechanism of CuVO-2, several characterizations were conducted, including ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which helped elucidate the intercalation mechanism of the developed cathode materials. These findings offer valuable insights into the design of stable V-based cathode materials for next-generation aqueous zinc-ion batteries (AZIBs).