Research On Determining Methods Of SOC In The Vanadium Redox Flow Battery

With low pollution, all vanadium redox flow battery has been received considerable attention on energy storage areas. It is very important to monitor the remaining battery capacity by monitoring the State of Charge.In this paper, the anolyte of vanadium redox flow battery was produced by oxidate reduction method in oxalic acid, however the concentration of sulfuric and vanadium ion in the anolyte could not be controlled and was not suitable for the researched electrolyte.The analysis of the equation of ln(1/ SOC-1)- ORP in Blank anode electrolyte showed that ORP- SOC has a good linear equation and can be realized in situ monitoring of the state of charge(SOC) at room temperature.The effect of different additives,such as potassium sulfate, sodium sulfate, zinc sulfate, urea, citric acid, sodium citrate, Trisodium citrate and EDTA were investigated,the mechanisms of anode elctrolyte with different additives were also discussed. The result showed that the stability of 1% potassium sulfate, sodium sulfate was better than that of zinc sulfate and the open circuit voltage of anode electrolyte substantially unchanged. The stability will be improved by adding 1% urea and the open circuit voltage dropped a small margin. Due to the reduction of additions, such as citric acid,sodium citrate, Trisodium citrate and EDTA, the V(V)ion is oxidated to V(IV)ion,which leaded the open circuit voltage drop a large margin, and V( IV)ion could not precipitate at high temperature, thereby increasing the stability of anode electrolyte. It was showed that the error between the ORP- SOC equation of anolyte which added potassium sulfate,urea, citric acid, EDTA and the linear fit equation are ± 2.5 %,± 7.5 %,± 7.5 %,± 3.0% by comparing the linear fit equation and ORP- SOC equation and Added four additives to the anolyte does not change electrochemical property of anolyte.