摘要/Abstract
随着新能源技术的不断发展, 大规模储能技术受到了广泛的关注. 全钒液流电池因其容量和功率设计灵活、安全可靠、寿命长等优势成为发展较快的储能电池之一. 离子膜作为液流电池的关键部件, 对电池的能量转化效率、寿命和成本具有显著影响. 本工作以高化学稳定性的聚偏氟乙烯作为膜材料, 利用聚乙二醇和聚乙烯吡咯烷酮分别作为模板和稳定剂, 在聚偏氟乙烯膜内成功构建了具有较好H/V离子选择性的三维离子传输通道. 电池性能测试表明, 该聚偏氟乙烯(PVDF)离子膜有着出色的化学稳定性, 在100 mA•cm-2电流密度下, 具有98%以上的电流效率和83.5%的能量效率. 此外, 聚偏氟乙烯具有价格低的显著特点, 使其在全钒液流电池中有较好的应用前景.
关键词: 离子膜, 聚偏氟乙烯, 全钒液流电池, 大规模储能技术
With the increasing demand of renewable energy, large-scale energy storage technology has attracted extensive attention. Vanadium redox flow battery (VRFB), benefiting from its adjustable capacity, high safety and long life, has become one of the fastest developing batteries for large-scale energy storage. Ion exchange membrane is a key component of VRFB, which notably affects the efficiency, cost and stability of the batteries. However, as the most commonly used membrane in VRFBs, Nafion shows shortages of high vanadium permeability and high economic cost, which largely hinder the commercial application of VRFBs. In order to develop low-cost, durable and high-performance ion exchange membranes for flow batteries, in this work, dual-porous poly(vinylidene fluoride) ion exchange membranes have been developed, in which polyethylene glycol (PEG) and polyvinylidene pyrrolidone (PVP) are applied as the template and stabilizer molecules, respectively. As a result, three-dimensional ion-conducting network has been successfully built in the poly(vinylidene fluoride) (PVDF) matrix which enable fast proton conduction and ion selection. The ion-conducting channels and thereby the proton conductivity and H/V ion selectivity of the membrane can be finely controlled by simply adjusting the PEG content in the casting solution. The unique dual porous structure of the membrane is clearly observed by using a scanning electron microscope. Battery efficiency including coulombic efficiency, voltage efficiency and energy efficiency have been characterized in VRFB single cells and the results show that the prepared PVDF ion-exchange membrane possesses high coulombic efficiency exceeding 98% and energy efficiency as high as 83.5% at a current density of 100 mA•cm-2, which are comparable to that of Nafion membranes. Moreover, the prepared PVDF ion-exchange membranes illustrate excellent chemical stability after the chemical stability test lasting for 30 d. In a word, due to the very low cost of the polymer material, excellent chemical stability and good performance of the dual-porous PVDF membranes, the novel ion exchange membrane shows great prospect for the application in VRFBs.
Key words: ion-conducting membrane, poly(vinylidene fluoride), vanadium redox flow battery, large-scale energy storage technology
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