Al-doped nitrogen-doped carbon-loaded vanadium nitride vanadium trioxide heterojunctions composites as cathode material for high-performance aqueous zinc ion battery

Aqueous zinc-ion batteries (AZIBs) have gained considerable attention due to their high energy density and safety. However, the drawbacks of poor cycle stability and low electrical conductivity of today's widely used vanadium-based materials limit their further application. In this study, heterojunction composites of nitrogen-doped carbon nanosheets loaded with aluminium-doped vanadium/vanadium trioxide nanoparticles (Al-VN/V₂O₃/NC) are designed and prepared. Structural characterisation reveals that the composites consisted of VN and V₂O₃ with different crystalline surfaces, forming a non-homogeneous interfacial network. This network effectively reduces ion transfer resistance and improves cycling stability, while the introduction of Al further enhances these effects by reducing resistance and improving stability. As a result, the prepared electrode material exhibits excellent performance by delivering a specific capacity of 363.8 mAh g^-¹ at 1 A g^-¹, a high specific capacity of 187 mAh g^-¹ at 10 A g^-¹ and a capacity retention of 83.2% for 2000 cycles. Furthermore, the energy storage mechanism over the Al-VN/V₂O₃/NC during cycling is further explored and elucidated via ex-situ XRD, XPS, and in situ Raman techniques. This work provides a reference for the construction of heterostructures in vanadium-based cathode materials for AZIBs.