Unlocking Vanadium Diboride As High-Performance Cathodes for Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) are increasingly valued for safe, large-scale and green energy storage applications. However, conventional Mn-based and V-based cathode materials suffer from inferior structure stability and poor conductivity-induced unsatisfactory electrochemical performance. This work proposes structure-reorganized vanadium diboride (VB2) materials to realize advanced high-capacity and stable cathodes for ZIBs. Layer-structured VB2 material possesses metal-like electrical conductivity, whereas it presents poor ion-storage capability such as a low capacity of 29 mAh/g in ZIBs since its high crystallinity coupling with the small interlayer spacing restricts the Zn2+ diffusion-storage. A constant-voltage electrochemical activation induces the transformation of the VB2 into an amorphous-nanocrystalline heterostructure with abundant defects, not only guaranteeing high electric conductivity but also allowing ions easily diffuse to the active sites, i.e., triangular bipyramids constructed by V-B atoms, thereby realizing a large reversible capacity of 398 mAh/g, impressive rate performance and excellent cycling stability with 99% capacity retention over 3500 cycles. A Zn2+/H+ co-storage mechanism, which is dominated by Zn2+ storage, is elucidated for the structure reorganized VB2 cathode. This work provides a green methodology and theoretical foundation for exploring diborides as a new family of advanced cathode materials for ZIBs.