Preparation And Electrochemical Performance Investigation Of Vanadium-based Cathode For Aqueous Zinc-ion Batteries

Aqueous Zinc Ion Batteries(ZIB)systems have presented impressive advantages and promising potential in the field of energy storage on account of their high security,low cost and eco-friendliness in recent years.Vanadium-based materials,especially vanadium oxides,possess a large open framework,which present the possibility to accommodate numerous Zn²⁺ions for storage.Although a high specific capacity and high energy density can be achieved due to multiple electron transfer offered by the divalent Zn²⁺ions,such Zn²⁺ions with high charge density will generate electrostatic force in the host materials,leading to an acceleration of the skeleton bending vibration and a distortion of the lattice,which will ultimately cause the structure to collapse.This serious structure degradation of vanadium oxides during the charge–discharge process,to a great extent,impedes their deeper development in this filed.The purpose of this film is to improve the rate performance,cycle stability and capacity of vanada oxide-based materials,finally to improve the overall performance of the battery by a variety of means,including optimizing the electrode integration mode and electrode microstructure,utilizing pillar effect,optimizing the material growth orientation and so on.Firstly,this article focuses on the commercial V₂O₅ bulk powder as a study subject.Through the structure characterization and performance testing,one can understand the characteristic of V₂O₅ material performance and be prepared for the subsequent vanadium base material modified steps.At the same time,by using the in situ growth method and simple suction filter method,binder-free three-dimensional flexible electrodes with efficient conductive network have been successfully developed.Based on this,the flexible zinc ion batteries were then constructed and the discharge capability was investigated.A worthy initiative was proposed that the discharge capacity of self-supported electrode can be improved under high current density without using binders that containing highly polarity atoms.At the meantime,the optimization of nanoscale morphology can also support V₂O₅ material to obtain higher capacity of 402mAh·g^-1(the current density is 0.5A·g^-1).Secondly,in view of several issues of V₂O₅ material,such as narrow interlayer spacing,unstable structure and serious capacity fading,a smart strategy is used here that introducing low molar mass guest species into vanadium-based materials as pillars to relieve the structural deterioration derived from the repeated intercalation of ions,especially multivalent ions.And for another,by introducing such pillars,the interlayer space for Zn²⁺ions occupation can be enlarged,thus leading to boosting the comprehensive electrochemical performance with more stable structures.In addition,highly(001)oriented V₂O₅ materials with long range ordered structure were prepared by means of high-temperature calcining.It is benefit to achieve high-speed migration of Zn²⁺ions in the host material thus improve the rate performance of batteries.Finally,a strategy of preparing vanadium sulfide was proposed.It aimed at the slow Zn²⁺diffusion problem due to the high charge density,which could result in the accumulation of Zn²⁺in the host lattice.Through solvent method,VS₂ with anion defect was prepared.From perspectives of both experiment and theoretical analysis,this material with vacancies was proved to be beneficial for zinc ions to anchoring on the material surface and the migration between the interlayer.Moreover,in view of the present issues of V₂O₅ material such as low discharge platform,poor cycle stability,the development of novel vanadium base material is required.For the first time,Mn₂V₂O₇ is used as zinc ion battery cathode material,and the performance is studied in detail.It has a higher discharge platform with a more stable cycle performance than normal V₂O₅ material.A possible mechanism of zinc ion storage is put forward.At the end,it is a kind of potential anode material in the field of energy storage.