<p>Vanadium-based materials are recognized as promising cathodes for high-energy-density aqueous zinc-ion batteries (AZIBs). However, their inherent low intrinsic conductivities and sluggish reaction kinetics curtail their capacity release. Here, we enhanced the electron and ion transport properties of vanadium-based cathodes through heterojunction engineering, coupled with in situ electrochemical activation, significantly enhancing an unprecedented zinc-ion storage capacity and rapid kinetic performance. A heterostructured V₂O₃/g-C₃N₄ (V₂O₃/CN) precursor was synthesized via a calcination process firstly. When employed as a cathode in AZIBs, this precursor undergoes an in situ phase transformation into Zn₃(OH)₂V₂O₇·2H₂O/C₃N₄ (ZVOH/CN) during the inaugural charging process, while retaining its heterojunction structure. Both electrochemical assessments and theoretical calculations revealed that ZVOH/CN exhibits superior zinc-ion adsorption and migration capabilities compared to conventional vanadium-based cathodes. The formation of the heterojunction amplifies the material’s electronic conductivity and ion diffusion kinetics. As a result, the optimal ZVOH/CN composite electrode showcases a remarkable capacity of 518.5&#xa0;mAh&#xa0;g⁻¹ at 0.5&#xa0;A&#xa0;g⁻¹, superior rate performance of 177.8&#xa0;mAh&#xa0;g⁻¹ at 20&#xa0;A&#xa0;g⁻¹, and impressive cycling stability. This work offers a novel design strategy for vanadium-based composite materials as high-performance AZIB cathodes.</p> Graphical abstract <p></p>