The Modification And Electrochemical Property Investigation On Vanadium Dioxide Cathode For Aqueous Zinc Ion Batteries

Compared to organic-based batteries,aqueous zinc-ion batteries have emerged as a promising high-efficiency energy storage solution due to their environmentally friendly,highly safe,and cost-effective advantages.Typically,vanadium-based oxides with layered or tunnel-like structures serve as positive electrode materials for aqueous zinc-ion batteries.Such structures offer effective channels for the transmission of zinc ions,while the rich valence states of vanadium enable abundant redox reacti ons and higher capacity.However,the solubility and poor conductivity of vanadium and the relatively large ionic radius of zinc ions can lead to the collapse of the positive electrode material structure,resulting in poor rate performance and cycling stab ility during repeated insertion and extraction of zinc ions during the energy storage process.Therefore,this research focuses on a typical vanadium-based oxide,vanadium dioxide,as the research subject,exploring nanomorphology regulation strategies,me tal ion pre-embedding strategies,and crystalline water molecule pre-embedding strategies to modify its morphology,structure,and electrochemical performance.The specific research objectives are as follows:（1）A monoclinic vanadium dioxide（VO₂（B））sample with a petal-shaped nano-sheet structure was prepared using a simple one-step hydrothermal method.Test results show that its unique petal-shaped,wrinkled nano-morphology can reduce structural stress during energy storage processes,provide mo re reaction sites for zinc ion transport,and enhance the pseudocapacitance contribution rate of electrode materials.This allows the material to exhibit faster kinetic behavior and better electronic conductivity.Therefore,the petal-shaped VO₂（B）nano-sheet exhibits a high specific capacity of 301.7 m Ah g^-1 at 1 A g^-1,and still has a capacity of 89.0 m Ah g^-1 at 50 A g^-1,demonstrating high-rate performance.After 2000 cycles at a current density of 10A g^-1,it achieved a high capacity retention rate of 87%.（2）By using the hydrothermal method,an appropriate amount of Na⁺was incorporated into the structure of VO₂（B）to synthesize a 0.1Na⁺-VO₂（B）sample,which did not change its crystal phase.The pre-inserted sodium ions enlarged the interplanar spacing of the（110）plane of the original VO ₂（B）sample,supporting the tunnel-like structure,and increasing the material’s conductivity.Therefore,the 0.1Na⁺-VO₂（B）sample exhibited significant improvement in the specific capacity(314.6 m Ah g^-1 at0.5 A g^-1),rate performance(163.9 m Ah g^-1 at 15 A g^-1),and long-term cycling stability(191.7 m Ah g^-1 and 83.13%capacity retention after 6000 cycles at 10 A g^-1)of VO₂（B）.Moreover,the 0.1Na⁺-VO₂（B）sample has a high pseudocapacitance contribution rate and a fast ion transport rate.（3）Crystalline water-supported VO₂·0.25H₂O nanosheets were prepared by using a solvothermal method to modify the morphology and structure of the V ₂O₅ precursor.In-situ XRD and XPS testing confirmed that the energy storage mechani sm of the sample involved the joint extraction of H⁺and Zn²⁺,and that the structure of VO₂·0.25H₂O nanosheets was supported by crystalline water during the energy storage process.Therefore,the VO₂·0.25H₂O sample still exhibited a discharge specific capacity of 223.5 m Ah g^-1 after 6000 cycles at 5 A g^-1,with a capacity retention rate of 84.3%.Moreover,the sample showed high dynamic behavior controlled by pseudocapacitance and a rapid Zn²⁺diffusion rate,resulting in high energy and power densities(300.7 Wh kg^-1 at 168.61 W kg^-1 and 233.9 Wh kg^-1 at 7317 W kg^-1).The research results show that the strategies of nano-morphology regulation,metal ion pre-embedding,and crystalline water molecule pre-embedding can effectively improve the electrochemical performance and kinetic behavior of vanadium-based oxides.Different strategies improve the conductivity and ion transfer capacity of the sample by changing different structural parameters such as the microstructure,active sites,crystal s tructure,and electronic structure of the original sample,which in turn affects its electrochemical performance and kinetic behavior.This study provides new references for the modification strategies of vanadium-based oxide positive electrode materials for aqueous zinc-ion batteries,which promotes the further application of vanadium-based oxide materials.