Preparation Of Vanadium Oxide-based Zinc Ion Color-changing Battery Electrode Material And Research On Its Performance

Zinc-ion batteries have gradually become a new and most promising secondary energy storage system due to the advantages of high content,good safety,and low price,and have received extensive attention in recent years.Due to the similar device structure and working principle of the electrochromic device and the zinc ion battery,the two can be integrated to produce a color changing zinc ion battery,real-time monitoring of battery capacity through color changes.In the working process of zinc-ion batteries and electrochromic devices,electrode materials play a decisive role in the performance of the two,so the research on electrode materials is very important.The large pore crystal structure of vanadium oxide can provide a fast path for ion transmission.The multivalent state of vanadium can inhibit the polarization phenomenon in the embedding and extraction of the material,and has good electrochemical performance.In this paper,a one-dimensional tubular structure of vanadium oxide is prepared,which relies on the stress of the tubular structure to maintain its structural stability during the cycle.At the same time,the tubular structure increases the contact area with the electrolyte and makes the ion transmission rate faster.The material is applied to the electrode material of the zinc ion battery,and the color change is combined with energy storage to obtain the color change zinc ion battery that realizes the visual monitoring of the battery capacity through the color change and prevents safety problems caused by overcharging or overdischarging.The specific research content is as follows:（1）In this paper,V₂O₅ uniaxial nanotubes were prepared due to the self-curling phenomenon of the layered vanadium pentoxide material under high pressure conditions through solvothermal reaction.Through the experimental variable method,different experiments were designed,and the best experimental conditions for material preparation were as follows:the volume ratio of ethanol to water was 1:1,the molar mass of hexadecylamine and V₂O₅ was 1:1,and the reaction was 96 h.The formation mechanism of nanotubes was deeply explored,and the formation process of the original material was first intercalated into a sheet-like material,then rolled into a tubular material and finally fused into a uniaxial nanotube.Comparing the morphology and electrochemical performance of V₂O₅ films at different annealing temperatures,the 300℃is the best annealing temperature.The discoloration and battery performance of the sample obtained under the best conditions were studied,and it was found that at a current density of 2 A g^-1,the average discharge capacity after 500 cycles was 164.8 m Ah g^-1,and the capacity retention rate after cycling was 67%.The electrochromic performance test of the material shows that the maximum transmittance is about 47%,the fading response time is 1.97 s,and the coloring response time is 19.2 s.It can be observed that the electrode color gradually changes from yellow to dark green.After500 cycles,the retention rate of the optical modulation range reached 88%.This result preliminarily proved the feasibility of the constructed zinc ion color-changing battery.（2）Using the above process conditions for preparing the V₂O₅ nanotube film,and according to the mechanism of aniline polymerization,a design experiment is to combine V₂O₅ nanotubes and polyaniline under acidic conditions to prepare a core-shell structured composite nanotube material.Control the experimental variables,design different experimental conditions,and summarize the best experimental conditions as follows:solution p H=2,reaction time is 2 h.The morphology and electrochemical performance of the V₂O₅@PANI film obtained at different reaction times were explored through testing.The best electrochemical performance of the composite material was obtained after the reaction for 2 h.The cycle performance test of the composite material with the best electrochemical performance shows that the capacity can reach 240 m Ah g^-1 at a current density of 2 A g^-1,and the capacity retention rate can reach 95%after 500 cycles.The electrochromic performance test shows that the maximum optical modulation range is about 60%,the fade response time is 9.5 s,and the color response time is 3.1 s.The electrode color can change from purple→blue→green→colorless.Compared with a single V₂O₅ material,there are more types of color changes.Compared with a single V₂O₅ material,there are more types of color changes.After 500 cycles,the retention rate of the optical modulation range is 90%,the curve is stable as a whole,and the active material does not fall off significantly after the cycle,which proves that the outer layer of polyaniline polymerization has played the role of a"protective layer",reflecting V₂O₅@PANI Excellent electrochromic properties of the film.The zinc-ion color-changing battery constructed with composite materials as the electrode initially realized the visual monitoring of the battery charge and discharge capacity.