| As fossil fuels continue to be depleted,the use of electrochemical energy storage devices to enable the storage of renewable energy is important.The high safety and economic characteristics of aqueous zinc ion batteries make them promise for stationary storage devices such as grids or mini-grids and other applications where weight-tovolume is less of a concern,such as home batteries or other distributed power sources.Vanadium oxide is an important anode material for aqueous zinc ion batteries and has many advantages in terms of abundance and high specific capacity,however,it also has many problems during cycling,such as strong interactions between the zinc ions and the main lattice of the material,causing the battery to exhibit poor cycling stability and multiplier performance.Another advantage of aqueous zinc ion battery is the use of zinc metal directly as the negative electrode.Zinc metal negative electrodes are gaining more and more attention due to their non-toxicity,low price,low redox potential(-0.76 V vs.standard hydrogen electrode)and high theoretical specific capacity(820 m Ah·g-1).However,there are still some problems in the application of zinc anode,such as the tendency of zinc metal to corrode in aqueous electrolytes and the uncontrollable growth of dendrites during the cycle.These problems can cause short-circuiting,failure or reduction of Coulomb efficiency in zinc ion batteries,which in turn seriously affects the practical application of zinc ion batteries.This thesis proposes modification strategies for both positive and negative electrodes from the working principle of the battery,aiming to develop electrode materials with high performance and low cost for zinc ion batteries.1.Monovalent cationic Pre-inserted vanadium oxide cathode materials were prepared by stirring impregnation method and the mechanism of their transformation was investigated.A comparative test of the reaction of the V2O5 precursor in different salt solutions was designed.Through the study of the experimental phenomena during the reaction and the composition,morphology and structure of the final product,it was demonstrated that the radius of the cationic hydration ion and the enthalpy of hydration are the key factors in the preparation of cationic pre-embedded vanadium oxide materials by this method.It is shown that the reaction is a solvation recrystallisation process and that the reaction rate decreases with increasing cation hydration ion radius.The zinc storage performance of different cationic pre-embedded vanadium oxide cathode materials was also investigated,and it was demonstrated that the NVO sample with the largest layer spacing had the best electrochemical performance.Based on the above study,an innovative strategy for the preparation of cationic Pre-inserted vanadium oxide cathode materials by simulating seawater as a reaction solution was proposed to exploit the large difference in reaction rates between Na+,K+,Mg2+ and Ca2+ cations and vanadium pentoxide in seawater to achieve the preparation of sodium/potassium cationic pre-embedded vanadium oxide materials.The strategy proposed in this experiment for the preparation of cationic Pre-inserted vanadium oxide cathode materials by simulated seawater impregnation is universal,low cost and simple,and provides insight into the preparation of future low-cost zinc ion batteries.2.A polypyrrole intercalated vanadium oxide cathode material was prepared using a hydrothermal method.Polypyrrole intercalated vanadium oxide has a wider interlayer spacing than hydrated vanadium oxide,which facilitates the diffusion of zinc ions within its lattice.In addition,polypyrrole improves the electrical conductivity of V2O5 and enhances the electron transfer capability during the electrochemical reaction,which in turn enhances the electrode cycling stability.Zinc ion batteries assembled from polypyrrole intercalated vanadium oxide cathodes exhibit high specific capacity(404m Ah·g-1 at 0.2 A·g-1)and excellent durability(nearly 98% capacity retention after 2000cycles).The energy storage mechanism of the polypyrrole-intercalated vanadium oxide electrode was investigated by a series of electrochemical and non-in-situ test means,and its Zn2+/H+ co-intercalation mechanism was demonstrated.3.Organic-inorganic(PANI-V2O5,PVO)hybrid materials with adjustable layer spacing were synthesised using simultaneous oxidative polymerisation using vanadate and aniline as precursors.PVO has a unique flower cluster structure,which facilitates the entry of electrolyte into the material and can effectively shorten the ion transport path.Electrochemical tests and density flooding theory calculations also confirm the better electrical conductivity and electrochemical stability of the PVO composite.The results show that zinc ion batteries assembled from PVO-60 electrodes exhibit a specific capacity of 391.1 m Ah·g-1 at a current density of 0.2 A·g-1.The self-charging phenomenon of PVO electrodes in air was also investigated.The results show that O2 can oxidise the PVO electrode material in the reduced state,resulting in an increase in electrode potential,which provides a promising research direction for the design of next-generation selfpowered systems.4.A hybrid interface of metallic tin and zinc fluoride is constructed on the negative surface of zinc metal using a substitution reaction.The interface effectively protects the zinc metal from corrosion by aqueous electrolytes while inducing dendrite free zinc deposition.The protection mechanism of this artificial interface was investigated by various characterization methods.The results show that the tin in the artificial interface layer of the Sn/Zn F2 electrode has zinc-friendly properties and can induce uniform zinc metal deposition,while the zinc fluoride can reduce the electrical conductivity of the surface,prevent tip discharge and inhibit the occurrence of hydrogen precipitation reactions.The electrochemical performance of the zinc ion battery assembled with Sn/Zn F2-5 and potassium vanadate cathode was tested,and a discharge specific capacity of 213.8 m Ah·g-1 could be retained after 1500 cycles,with a capacity retention rate of80.9%,significantly higher than that of the full battery with bare zinc electrode at 57.4%.This hybrid interfacial protective layer preparation strategy can induce uniform zinc deposition while suppressing interfacial side reactions,which can effectively enhance the performance of the full cell. |
PDF Full Text Request