In Situ X-ray Near-Edge Absorption Spectroscopy Investigation of the State of Charge of All-Vanadium Redox Flow Batteries
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- 作者：Chuankun Jia ; Qi Liu ; Cheng-Jun Sun ; Fan Yang ; Yang Ren ; Steve M. Heald ; Yadong Liu ; Zhe-Fei Li ; Wenquan Lu ; Jian Xie
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2014
- 出版时间：October 22, 2014
- 年：2014
- 卷：6
- 期：20
- 页码：17920-17925
- 全文大小：347K
- ISSN：1944-8252
文摘
Synchrotron-based in situ X-ray near-edge absorption spectroscopy (XANES) has been used to study the valence state evolution of the vanadium ion for both the catholyte and anolyte in all-vanadium redox flow batteries (VRB) under realistic cycling conditions. The results indicate that, when using the widely used charge鈥揹ischarge profile during the first charge process (charging the VRB cell to 1.65 V under a constant current mode), the vanadium ion valence did not reach V(V) in the catholyte and did not reach V(II) in the anolyte. Consequently, the state of charge (SOC) for the VRB cell was only 82%, far below the desired 100% SOC. Thus, such incompletely charged mix electrolytes results in not only wasting the electrolytes but also decreasing the cell performance in the following cycles. On the basis of our study, we proposed a new charge鈥揹ischarge profile (first charged at a constant current mode up to 1.65 V and then continuously charged at a constant voltage mode until the capacity was close to the theoretical value) for the first charge process that achieved 100% SOC after the initial charge process. Utilizing this new charge鈥揹ischarge profile, the theoretical charge capacity and the full utilization of electrolytes has been achieved, thus having a significant impact on the cost reduction of the electrolytes in VRB.