Research On Key Material For Vanadium Redox Battery

Vanadium redox flow battery（VRB） technology is a new type of large-scale and efficientenergy storage technology, with no pollution, long life, high energy efficiency, maintenancesimple and short construction period.Electrolyte and electrode material as an important part ofthe vanadium battery have a direct impact on the cost and performance of the vanadiumbattery, Preparation and Properties of vanadium battery electrolyte and electrode material wassystematic studied in this thesis,.The effect of two process parameters of the ratio of raw materials and the heatingtemperature on the preparation of V（Ⅲ）-V（Ⅳ） mixed electrolytewas studied.The resultsshowed that when the mass ratio of the raw material of V₂O₃and V₂O₅is6:1, the ratio oftrivalent and tetravalent vanadium ions is1:1in the obtained electrolyte, and the heatingtemperature is preferably about115℃. In order to improve the concentration and the Stabilityof the electrolyte, Different additives were added to V（Ⅲ）-V（Ⅳ）mixed electrolyte. It wasfound that Methanesulfonic acid and sorbitol was helpful to improve the electrolyte stability.The anodic peak current of V4+/V5+redox couple was improved by26.2%by addingmethanesulfonic acid, and the addition of sorbitol did not have great impact on the electricalconductivity of the electrolyte and the molecular structure of vanadium ions.Then graphite felt modified by different treatment was used for the preparation ofcomposite electrode. It was found that graphite felt treated at400℃for30h and concentratedsulfuric acid for8h exhibited good activity. The polarization curves showed that thepolarization resistance decreased by45.5%after heat treatment, compared to the original felt,and the polarization resistance increased by45.5%after acid treatment. Further studies showedthat the reaction resistance of the graphite felt was greater than the rest of the impedance value,which indicated that the electron transfer process is the control step of the entire electrodereaction. After heat treatment, the reaction resistance is reduced by50.8%of the original felt,thus speeding up the speed of the electrode reaction.V（Ⅲ）-V（Ⅳ） mixed electrolyte can be directly used in the vanadium battery. Thecharge-discharge resistance of battery with heat treatment graphite felt was minimum, and thecoulomb efficiency is stable at80%or more. The factors that affect battery performance weresubsequently studied. The results suggested that the reduction of the electrode spacing and theincrease in the flow velocity of the electrolyte was conducive to improve the efficiency of thebattery. With the increase of charge-discharge current, the coulombic efficiency of the cellgradually increased, the voltage efficiency was gradually reduced, and the energy efficiencyincreased at first and then decreased. At a constant current of200mA, The voltage efficiency of battery is82.8%, with a energy efficiency of73.2%, and the coulombic efficiency of88.4%.At the same time the degree of self-discharge is small.