| Redox flow battery is a new-style energy storage battery that has been attracting many researches. In redox flow battery, active component is flowing electrolyte, which is different from other usual batteries. This kind of battery has many characteristics, and the most distinct one is that it can be used to store electricity on a large scale. Therefore, it is undergoing an exciting development and commercialization. However, there are still some questions to be solved before its general application.In this paper, all chromium redox flow battery has been researched. In order to choose the appropriate electrode for the battery, several kinds of electrode have been taken into experiment, such as graphite rod electrode, graphite powder-carbon composite electrode, graphite powder-carbon microelectrode, the electrode filled with graphite powder-carbon and graphite felt electrode. Furthermore, the CV tests indicate that graphite felt is excellent material used as electrode. Since graphite felt has nicer conductivity, physical stability, electrochemistry activity and corrosion resistance, it is appropriate to be used in all chromium redox flow battery. So all the experiments are taken with graphite felt electrodes treated in three ways: untreated, heat-treated, oil of vitriol & heat-treaded. According to SEM, different surface state of the three kinds of graphite felt is observed. On the surface of treated graphite felt, impurity and contamination, which may affect electrochemistry reaction, has been gotten rid of. As a result, clean, smooth and improved surface has been gained. EIS experiment indicates that the resistance of treated electrode is decreased clearly, which confirms that the characteristics of graphite felt can be improved after activating treatment. For example, surface state was improved, resistance was decreased, and electrochemistry reaction activity was enhanced.It can be learned by CV experiment that the electrode reactions are very intricate. In the beginning, there is Cr(Ⅲ)→Cr(Ⅵ) oxidation reaction on anode, then there are Cr(Ⅵ)→Cr(Ⅴ),Cr(Ⅴ)→Cr(Ⅲ), Cr(Ⅲ)→Cr(Ⅱ) deoxidization reaction on cathode. After several cycles, there is Cr(Ⅱ)→Cr(Ⅲ) oxidation reaction besides Cr(Ⅲ)→Cr(Ⅵ) oxidation reaction on anode. Cr(Ⅲ)→Cr(Ⅵ) oxidation reaction and Cr(Ⅴ)→Cr(Ⅲ) deoxidization reaction are also more clear when concentration of chromium electrolyte is increased. The graphite felt electrode treated by oil of vitriol & heat and heat can enhance the reversibility and kinetic of the electrode reaction. The reversibility of electrode reaction falls with the increase of potential scan rate.During the first charge process, we can learn that the activation of chromium electrolyte is difficult and takes long time. What's more, it goes with oxygen evolution reaction. During the charge/discharge process, there are three charge flats and two discharge flats. The battery capacity is up to 0.45mAh/ml. And it is added when concentration of chromium electrolyte is increased. Otherwise, logical charge/discharge condition is important. The high E limit should be higher and the low E limit should be lower when charge/discharge current is large, however, it is opposite when the current is tiny.In the paper, demonstration of the successful application of lab-level chromium battery is given, which is the powerful experimental evidence for theoretical research and development of all chromium redox flow battery.
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