Modification Of Doping And Compounding For Vanadium-based Film Electrodes And Research Of Electrochemical Properties

Sodium-ion batteries（SIBs）are considered as the most suitable options to substitute lithium-ion batteries（LIBs）,and their related research has been in full swing worldwide.Various electrode materials have emerged one after another since the rise of research about SIBs.Nevertheless,SIBs are not mature enough in practical application compared with LIBs,their energy,power density and electrochemical stability are needed to improve to adapt actual production.The performance of batteries mainly relies on electrode materials,so the challenges of SIBs focus on the development and selection of materials.So far,vanadium-based electrode materials have been widely used as the cathodes of SIBs.To further improve the performance,this paper was based on a representative vanadium bronze material to modify.Doping and compounding had been chosen to modify,and the differences in structure,morphology and electrochemical performance of the materials after modification were summarized and elaborated.The main research are as follows.（1）V₂O₅/Ca_0.17V₂O₅composite films were synthesized on indium-doped tin oxide（ITO）conductive glasses by a low-temperature liquid-phase deposition method and subsequent thermal treatment.The electrochemical performance of the V₂O₅/Ca_0.17V₂O₅films was excellent.The capacity of the V₂O₅/Ca_0.17V₂O₅film was larger than the pure V₂O₅film.The V₂O₅/Ca_0.17V₂O₅delivered a discharge capacity of 148.465 m A h m^–2at 1C rate,while the capacity of the pure V₂O₅was 100.086 m A h m^–2.The conductivity of the composite film electrodes was better.The charge transfer resistance of the pure V₂O₅was168.5Ω,and the charge transfer resistance of the V₂O₅/Ca_0.17V₂O₅was 116.5Ω,indicating electrochemical reactions were easier to proceed.In addition,the cyclic performance of the V₂O₅/Ca_0.17V₂O₅film was excellent,the capacity retention at 1C rate was 90.11%,and the capacity retention at 2C rate was 103.91%after 100 cycles.The Ca_0.17V₂O₅supported the stability of the structure,the other V₂O₅phase acted as a host material for ions insertion/extraction.Therefore,the synergistic effect of the Ca_0.17V₂O₅and V₂O₅was what made the electrochemical performance so well.（2）The Ca-doped NaV₆O₁₅films were also prepared on ITO conductive glasses via a low-temperature liquid-phase deposition method,the Ca²⁺together with Na⁺between V-O layers to support the stability.The Ca²⁺had been chosen because their radius was close to Na⁺and more electronegative than Na⁺,the electrostatic interaction between Ca²⁺and V-O layers was stronger.The Ca²⁺could distinctly enhance the electrochemical performance.In terms of ions diffusion,the diffusion coefficient of Na⁺in the Ca-doped NaV₆O₁₅film was larger than the pure NaV₆O₁₅.In terms of capacity,the Ca-doped NaV₆O₁₅film delivered a capacity of 237.476 m A h m^-2,while NaV₆O₁₅delivered a capacity of 96.719 m A h m^-2at1C rate.In terms of cyclic stability,the first discharge capacity of the Ca-doped NaV₆O₁₅film at 0.5C rate was 271.361 m A h m^-2,which retained 229.906 m A h m^-2after 100 cycles.The capacity retention was 84.72%,indicating the stability of the doped film was excellent.（3）The Cu-doped NaV₆O₁₅films were prepared on ITO conductive glasses using a low-temperature liquid-phase deposition method,and effects of doping amount on films were explored.The results showed that the film with the largest amount of Cu would decrease the spacing between V-O layers,and aggregate in morphology,which was not favorable to electrolyte penetration and ions diffusion.The film with the least amount of Cu without aggregation in morphology,which was uniformly dispersed and had a pore structure,that was favorable to electrolyte penetration and ions diffusion.The electrochemical properties changed with the amount of Cu.The film with the least amount of Cu had the largest current and the best conductivity,which displayed the best performance.The discharge capacity of the film at 1.5C rate was 130.162 m A h m^-2,the capacity retention was 71.16%after 100 cycles.The discharge capacity at 3C rate was115.331 m A h m^-2,and the capacity retention was 83.23%after 150 cycles,indicating that the film electrodes possessed excellent cyclic stability.Figure[44]table[10]reference[147]...