Development And Application Of New Vanadium-based Cathode Materials For Zinc-ion Batteries

The cathode material is the key factor to determine the electrochemical performance of zinc ion battery.Vanadium based materials can realize multi-electron transfer due to their changeable valence state,multi-channel and layered structure,which is expected to afford the battery high capacity.As the cathode material of zinc ion battery,vanadium based materials have always been a hot research field.However,the specific capacity,cycle and rate performance of vanadium based cathode materials reported at present are not satisfactory,and most vanadium oxides and vanadate are synthesized by hydrothermal method.The synthesis method is complicated,requires complex equipment,and is not suitable for large-scale production.Therefore,it is still of great research significance to explore vanadium based cathode materials with high performance.Herein,two new strategies were developed to prepare cathode materials for aqueous zinc ion batteries.The specific research work is as follows:The composition,structure,morphology and electrochemical properties of vanadium based oxides were adjusted by using a facile pyrolysis method.A series of vanadium based oxide cathode materials(VO-X,X represents the calcination temperature)were synthesized by using a facile pyrolysis method with NH₄VO₃ and H₂C₂O₄ as starting materials.Among them,VO-700 is composed of V₄O₇.The Zn²⁺storage performance of V₄O₇ was investigated for the first time.It is found that after100/1000 cycles at the current density of 1/5 A g^-1,the specific capacity of the electrode is 367.2/132.8 m Ah g^-1,and the capacity retention rate is about 84.9%/87%.In addition,a series of structural and electrochemical characterization were used to reveal the possible charging and discharging motor system.A vanadium-based coordination compound(VOF)was synthesized with the terpyridine ligand.With VOF as precursor,a series of cathode materials VOCl₂@OF-X(X represents the calcination temperature)for zinc ion batteries were prepared and their electrochemical performance was investigated in detail.Especially for VOCl₂@OF-400,the maximum specific capacity is up to 419.7 m Ah g^-1 at the current density of 0.5 A g^-1.After 1300 cycles,the capacity remained 356.8 m Ah g^-1.Compared with the initial capacity,its capacity retention rate is 85%.After 1200 cycles at the current density of 2 A g^-1,the capacity retention rate is about 90%.The structural characterization results of electrode materials and the related electrochemical Zn²⁺storage mechanism confirmed the good performance of VOCl₂@OF-400 can be ascribed to the following facts.On one hand,the remained organic skeleton in VOCl₂@OF-400 provides a good channel for the transmission of Zn²⁺;On the other hand,the remained channels and chloride ions in the skeleton afford the electrode with excellent conductivity.