摘要:
全钒液流电池 (VRFB) 因其固有安全性和超长服役寿命, 被认为是最具应用前景的大规模电化学储能技术之一。VRFB负极电解液在充放电过程中主要发生V (Ⅲ)↔V (Ⅱ) 离子氧化/还原反应, 因V (Ⅲ) 离子还原的标准电极电位为-0.25 V (vs.NHE), 充电过程易于发生析氢副反应而严重影响VRFB性能, 负极电解液的活性和析氢行为与V (Ⅲ) 离子结构密切相关。基于Gaussian量子化学计算平台, 采用MP2理论方法和LANL2DZ基组对不同构型V (Ⅲ) 离子进行结构优化, 分析其反应活性, 并结合电解液电化学性能测试结果, 发现新制备电解液中的V (Ⅲ) 离子因存在一定程度聚合而表现出较差的电化学活性, 经过5次充放电循环后, 钒离子聚合程度减小, 表现出较好的电化学活性, 析氢副反应也得到抑制, 充放电活化的电解液室温存放40天后活性又出现明显下降, 表明VRFB负极电解液中V (Ⅲ) 离子水解聚合是自发性的。
Abstract:
All-vanadium redox flow battery（VRFB） is one of the most promising large-scale energy storage technologies,owing to its inherent safety and long service life.During the charging-discharging process,the redox reaction of V（Ⅲ）↔V（Ⅱ） with standard electrode potential of-0.25 V（vs.NHE） is the main electrochemical reaction in negative electrolyte.The side reaction of hydrogen evolution would take place with low electrochemical activity of V（Ⅲ） ion,which will degrade VRFB performance.In present work,to explore the relationship of structure and electrochemical activity of V（Ⅲ） ion,the quantum chemistry calculation and activity analysis of V（Ⅲ） ions with various structures were conducted with the MP2 theoretical method and LANL2 DZ basis using the Gaussian software.Combining to the experimental results of electrochemical activity,the low electrochemical activity of V（Ⅲ） ion in fresh prepared electrolyte was found due to their hydrolytic polymerization.,The polymerization can be reduced by 5 cycles of charge and discharge,which leads to a high electrochemical activity of V（Ⅲ） ion and inhibition of hydrogen evolution.But the electrochemical activity of activated electrolyte will obviously reduce after 40 days’ standing at room temperature,indicating that the hydrolytic polymerization of V（Ⅲ） ions in negative electrolyte may be spontaneous.
下载:
