Pseudocapacitance-dominated zinc storage enabled by nitrogen-doped carbon stabilized amorphous vanadyl phosphate

Abstract Rechargeable zinc-based batteries are attracting considerable attention for practical energy storage owing to their abundant reserves, low cost, and high safety. However, it remains a significant challenge to develop cathode materials with robust structure and high energy density. Layered VOPO4·xH2O was proposed as a cathode candidate for aqueous Zinc-ion batteries (ZIBs), but its structural stability and conductivity need to be further optimized. Herein, a novel amorphous superlattice of Vanadyl phosphate intercalated with Nitrogen-doped carbon (VOP/NC) is formed by organic molecule interlayer engineering and in-situ carbonization. The nitrogen-doped carbon as interlayer guest not only acts as a structure stabilizer to inhibit the dissolution of active materials, but also serves as capacity contributor to boost the pseudocapacitive capabilities. Based on the characteristics of stable structure and abundant active sites, the modified VOP/NC performs well in ZIBs in terms of long-term durability (1,000 cycles at 500 mA g−1) and high reversible capacity (187.9 mA h g−1 at 50 mA g−1). Furthermore, an intercalation pseudocapacitive Zn2+ storage mechanism accompanied by reversible cationic (Vn+/V(n−1)+) and anionic (N3−/N2−) redox reactions is proposed. This strategy is promising to intercalative layered materials for advanced zinc-based energy storage applications.