Investigation On Characters Of Chromium Battery And The Mechanism Of Its Electrode Reaction

Redox flow battery is a new-style and environmentally friendly energy storage battery that has many characteristics such as instant recharge /discharged at large current density, really fully discharged(100%), increasing storage capacity easily, a theoretically unlimited life, simple operation and maintenance. Therefore, it is undergoing an exciting development. However, few people researched all chromium flow battery previously.In this paper, the battery reaction system and mechanism of the electrode reaction have been investigated. Chromium electrolyte has been prepared by confecting CrO3 liquor and Cr2(SO4)3 liquor, then a simple laboratory battery was tested as battery system. We studied trivalence chromium ion electrode reaction on three different surface state by cyclic voltammetry, discussed electrode activation influence on electrode reaction, and analysed the mechanism of electrode reaction. We discussed current efficiency during the first charge process and charge/discharge cycle performance by invariable current charge method.Cyclic voltammetry indicated that there were Cr(Ⅲ)→Cr(Ⅳ), Cr(Ⅲ) →Cr(Ⅵ) oxidation reaction on anode, while there were Cr(Ⅵ)→Cr(Ⅴ), Cr(Ⅴ)→Cr(Ⅳ), Cr(Ⅲ) →Cr(Ⅱ) deoxidization reaction on cathode. The graphite electrodes treated by acid and heating could enhance the reversibility and kinetic of the electrode reaction. The nature graphite electrodes had been eroded during charge/discharge process, while the graphite electrodes by activation could avoide corroding by hexad chromium ion. The reversibility and kinetic of the electrode reaction of chromium ion on activation electrode had been increased, so which indicated that graphite surface augment oxygenous function corps which could increase electrode hydrophile capability. Invariable current charge method discussed current efficiency during the first charge process, experiment result indicated that current efficiency was low. There were many causes, such as the initial chromium electrolyte had not been activated easily, battery septum had bad ion selectivity, which resulted in different ion in cathode and anode chamber mixed by septum, which made battery local action, two electrode distance was too long which brought the high resistance. Invariable current charge /discharge experiment indicated that Cr(NO3)3.9H2O electrolyte could produce high battery capacity, but the reversibility was too bad, Cr2(SO4)3.6H2O electrolyte could bring morecalm charge/discharge flats ,what's more two charge flats and two discharge flats.electrolyte could bring more calm charge/discharge flats, what's more two charge flats and two discharge flats.Experiment indicated that the battery capacity of all chromium redox flow was more higher than that of the tradition Fe-Cr system battery.