Preparation And Electrochemical Properties Of V₂O₅-Based Cathode Materials For Aqueous Zinc-Ion Batteries

In recent years,aqueous zinc-ion batteries are considered as potential competitors of lithium-ion batteries due to their advantages of environmental protection,non-flammability,low cost and simple assembly process.The cathode material is an important part of aqueous zinc-ion battery.Vanadium-based oxides have many advantages,such as adjustable structure,high working voltage,low cost and high theoretical specific capacity,and are favored by researchers.However,some disadvantages remain,e.g.,the slow diffusion kinetics of Zn²⁺,the dissolution of transition metal ions and the low conductivity,which blocks the improvement of electrochemical performance.Thus,V₂O₅-based materials are selected.By using delicate structural design,improvement of both structural stability and diffusion dynamics in the storage process of Zn²⁺,we obtained the vanadium-based oxide cathode material with high-performance of Zn²⁺storage.The specific work is as follows:（1）Investigations on the electrochemical performance and storage behavior of amorphous/crystalline composite structures V₂O₅·1.6H₂O（VOH）cathode materials for zinc storage.In view of the structural instability of V₂O₅ electrode material during long cycle,VOH cathode materials with ordered/disordered hybrid structure was prepared by using hydrothermal method in this paper.As of the integration of an ordered layered structure（reversible ion insertion/deserted）and a disordered structure（relieving stress and volume changes）,it helps to maintain the structural stability of the electrode material,alleviate the generation and diffusion of microcracks in the electrode material.Furthermore,it greatly improves the strong electrostatic interaction between the electrode material and Zn²⁺,enhancing the diffusion dynamics of Zn²⁺.In addition,the interlayer water molecules can play the role of charge shielding and interlayer support,effectively alleviate the strong electrostatic interaction between Zn²⁺and electrode materials,expand the Zn²⁺transport channel,and promote the diffusion dynamics of Zn²⁺.The VOH cathode material has achieved a high reversible specific capacity of429.9 m Ah g^-1(0.1 A g^-1),and the better long cycle life performance,it can deliver 70%capacity retention after 2000 cycles at the current density of 2 A g^-1.（2）Investigations on electrochemical storage performance of V₂O₅/V₂C cathode material in aqueous zinc-ion batteries.Aiming at the problems of poor conductivity and low specific surface area of vanadium-based oxides,the V₂O₅/V₂C composite material were prepared by combining V₂O₅ with V₂C with large specific surface area and high conductivity.The high conductivity of V₂C makes up for the short plate with low conductivity of V₂O₅,which faciliates V₂O₅/V₂C cathode material in exhibiting faster dynamic transport of electrons/ions.In addition,V₂C has a large specific surface area and a relatively solid skeleton structure,which can maintain the structural stability of V₂O₅/V₂C cathode material during the dis/charging process and increase the contact area between the electrode material.and V₂O₅/V₂C cathode material shows discharge specific capacity of 234 m Ah g^-1 after 900 cycles at 1 A g^-1,and the coulomb efficiency is close to 100%.It also exhibits excellent electrochemical performance under high current charging and discharging,reaching a discharge specific capacity of 251.2 m Ah g^-1 at a current density of 2.0 A g^-1,and still reaching 392.7 m Ah g^-1 when returning to a low current density(0.2 A g^-1).