Direct Growth Of Vanadium-based Materials On Substrates And Their Applications In Aqueous Zinc-ion Batteries

Lithium-ion batteries（LIBs）have developed rapidly and swept the portable electronic products and electric vehicle market since the commercialization of LIBs.However,the limited abundance of lithium increases the potential cost.Aqueous solution zinc batteries（ZIBs）are a promising alternative to LIBs,and have become the focus of energy research.But traditional electrode preparation process requires uniformly mixed of the conductive additives,polymer binder and active substances to a slurry,and the slurry rely on the binder to adhere to the collector.Neither conductive additives or binders used in this process are electrochemical activity,which becomes the obstacle to the transmission of metal ion and the diffusion of electrolyte,resulting in low rate performance and reversible capacity.In addition,the active material can be easily separated from the collector because the binder cannot form a strong chemical bond with the substrate.This also affects the reversibility of metal ion intercalation and removal.Direct in-situ growth of active materials on the collector can overcome the above problems.This will enhance the adhesiveness between the collector and the active material,and improve the conductivity,which can prevent the caking of the active material in the long cycle process.Vanadium based materials have been widely studied because of their safety,diverse crystal structure,abundant resources,low cost and high theoretical capacity.Specific contents are as follows:（1）Based on hydrothermal synthesis technology,various vanadium based materials,including calcium vanadate nanobelts(Ca_0.24（V₂O₅）（H₂O）),potassium vanadate(K_0.23V₂O₅)nanobelts,hydrated vanadium pentoxide（V₂O₅·1.6H₂O）and ion intercalated vanadium pentoxide(Ca²⁺,Cu²⁺)were grown on carbon cloth in situ.The phase and morphology of as-synthesized materials were characterized and analyzed in details,the results indicate that the as-synthesized active materials have high load on carbon cloth.（2）The zinc storage performance and mechanism of Ca_0.24（V₂O₅）（H₂O）as ZIBs cathode have been studied.Results show that the specific discharge capacity of as-prepared CVO@CC at 0.5 A g^-1 was reach to 167.4 m Ah g^-1 and 95.6 m Ah g^-1 of discharge capacity was obtained after 530 cycles at a current density of 1.0 A g^-1.Ca²⁺seems to be involved in the charge and discharge process of the battery.（3）The insertion and detachment of Zn²⁺in K_0.23V₂O₅ nanoribbons were confirmed by in situ measurements.The specific discharge capacity of 236.6 m Ah g^-1 can be obtained at 0.1 A g^-1 of current density.（4）The energy storage mechanism and electrochemical kinetics of V₂O₅·1.6H₂O and its intercalated oxides were studied in detail.The results show that the electrochemical performance of Cu²⁺or Ca²⁺intercalated active materials is better than that of pure V₂O₅·1.6H₂O.Especially when the current density is 0.1 A g^-1,the Ca VOH intercalated by Ca²⁺is more stable,which the specific capacity of 248.7 m Ah g^-1 was obtained.Based on the reaction kinetics of the material,the best electrochemical performance of Ca VOH was studied,which was attributed to the large crystal plane spacing,the minimum charge transfer impedance and the highest pseudo capacitance contribution.