Preparation And Zinc Storage Properties Modification Research Of Structural Water Pre-intercalated Vanadium Oxide

Zinc metal batteries,directly use zinc metal as anode,with the characteristics of low cost,high safety,and environmental friendliness,have great application prospects in the field of large-scale energy storage.Vanadium-based materials are one of the most commonly used cathode materials due to their rich variety,diverse structures and high theoretical capacity.Among the vanadium-based materials reported so far,the vanadium-based materials containing structural water exhibit excellent electrochemical performance.However,the presence of structured water also aggravates the dissolution of vanadium-based materials in aqueous electrolyte.Therefore,how to maintain the good cycle performance of high-capacity structured water-containing vanadium-based materials is a huge challenge for Zn-V metal batteries in future practical applications.In this paper,structured water pre-intercalated vanadium pentoxide（V₂O₅·n H₂O）was first prepared.From the perspective of structure control of electrode materials and electrolyte optimization,the electrochemical performance of vanadium oxide pre-intercalated with structured water was optimized.The main research results and conclusions are as follows:（1）Structural water pre-intercalated vanadium pentoxide（V₂O₅·n H₂O,HVO）and sodium vanadate(HNa V₆O₁₆·4H₂O,HNVO)were synthesized by hydrothermal method,and their zinc storage properties were studied.The HVO cathode exhibited high specific capacity,400 m A h g^-1 at a current density of 0.1 A g^-1,but has poor cycling stability in conventional aqueous electrolytes.The results show that the method of pre-intercalation of sodium ions and structural water can greatly improve the structural stability of layered V₂O₅.Aiming at HNVO cathode,1 M Zn SO₄+1 M Na₂SO₄ electrolyte was further selected,making it a better cycling stability,with a capacity of 195 m A h g^-1 at a current density of 2 A g^-1,and the capacity retention rate is 85%after1000 cycles.（2）PEG 400 was introduced as a co-solvent in the conventional aqueous electrolytes,and a low-concentration 1 m Zn（CF₃SO₃）₂-H₂O-60%PEG hybrid electrolyte was developed,which improved the cycling stability of Zn/HVO batteries.The experimental results show that on the one hand the hybrid electrolyte inhibits the HVO cathode dissolution under electrochemical conditions,and on the other hand reduces the problems of negative by-products and zinc dendrites.Based on the hybrid electrolyte,the HVO battery has a high specific capacity of 372 m A h g^-1at a low current density of 0.1 A g^-1,and the capacity retention is as high as 96%after 50 cycles.In particular,it also exhibits excellent cycling stability under intermittent electrochemical tests.