物理化学学报 >> 2019, Vol. 35 >> Issue (12): 1372-1381.doi: 10.3866/PKU.WHXB201905011

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基于磷钨酸功能化纳米纤维的超高质子/钒选择性的聚苯并咪唑膜在全钒液流电池中的应用

杨晓兵,赵磊,隋旭磊,孟令辉*(),王振波*()   

  • 收稿日期:2019-05-02 录用日期:2019-06-05 发布日期:2019-06-13
  • 通讯作者: 孟令辉,王振波 E-mail:menglinh@hit.edu.cn;wangzhb@hit.edu.cn
  • 基金资助:
    国家自然科学基金(21273058);国家自然科学基金(21673064);国家自然科学基金(51802059);国家自然科学基金(21503059);中国博士后科学基金(2018M631938);中国博士后科学基金(2018T110307);中国博士后科学基金(2017M621284);黑龙江博士后基金(LBH-Z17074);中央高校基础研究基金(HIT. NSRIF. 2019040);中央高校基础研究基金(HIT. NSRIF. 2019041)

Ultra-High Proton/Vanadium Selectivity of Polybenzimidazole Membrane by Incorporating Phosphotungstic Acid Functionalized Nanofibers for Vanadium Redox Flow Battery

Xiaobing YANG,Lei ZHAO,Xulei SUI,Linghui MENG*(),Zhenbo WANG*()   

  • Received:2019-05-02 Accepted:2019-06-05 Published:2019-06-13
  • Contact: Linghui MENG,Zhenbo WANG E-mail:menglinh@hit.edu.cn;wangzhb@hit.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21273058);the National Natural Science Foundation of China(21673064);the National Natural Science Foundation of China(51802059);the National Natural Science Foundation of China(21503059);China Postdoctoral Science Foundation(2018M631938);China Postdoctoral Science Foundation(2018T110307);China Postdoctoral Science Foundation(2017M621284);Heilongjiang Postdoctoral Fund, China(LBH-Z17074);Fundamental Research Funds for the Central Universities, China(HIT. NSRIF. 2019040);Fundamental Research Funds for the Central Universities, China(HIT. NSRIF. 2019041)

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摘要：

质子交换膜是全钒液流电池的关键组件，其质子/钒选择性对于单电池的性能发挥至关重要。商用的全氟磺酸(Nafion)膜具有优异的质子传导率和化学耐受性，但是过于严重的钒离子渗透率阻碍了其工业化应用。本文中，以稠密的碳氢聚合物聚苯并咪唑(PBI)为基体材料，通过磷钨酸(PWA)的掺杂赋予其适当的质子传导能力，而其本征的高阻钒性则有助于高质子/选择性的获得。考虑到PWA水溶性较强易于从水中流失的缺陷，选用了有机的聚合物纳米凯夫拉纤维(NKFs)作为PWA的锚定剂，实现了良好的锚定效果，同时也解决了无机锚定剂与聚合物基体相容性差的问题。利用扫描电镜(SEM)、傅里叶变换红外(FT-IR)光谱表征了PWA功能化NKFs的形成，紫外-可见光(UV-Vis)光谱评估了NKFs对PWA的锚定稳定性，并对复合膜进行了吸水率(WU)、溶胀比(SR)、离子交换容量(IEC)、质子传导率、钒离子渗透率及选择性等测试表征了其基本性能。同时，在40-100 mA∙cm-2下对以复合膜及重铸全氟磺酸(recast Nafion)膜组装的单电池进行了充放电、自放电及循环性能测试。结果表明，制备的复合膜体现出远超recast Nafion膜的质子/钒选择性，且以复合膜组装的单电池表现出更高的库仑效率和显著下降的自放电速率。

关键词: 全钒液流电池, 聚苯并咪唑, 磷钨酸, 质子交换膜, 高质子/钒选择性

Abstract:

Proton exchange membrane (PEM) is a key component of vanadium redox flow battery (VRB), and its proton/vanadium selectivity plays an important role in the performance of a VRB single cell. Commercially available perfluorosulfonic acid (Nafion) membranes have been widely used due to their excellent proton conductivity and favorable chemical resistance. However, the large pore size micelle channels formed by the pendant sulfonic acid groups lead to the excessive penetration of vanadium ions, which seriously affects the coulombic efficiency (CE) of the single cell and accelerates the self-discharge rate of the battery. Additionally, the expensive cost of Nafion is also an important reason to limit its large-scale application. In this paper, the dense and low-cost hydrocarbon polymer polybenzimidazole (PBI) is used as the matrix material of the PEM, which is doped with phosphotungstic acid (PWA) to acquire excellent proton conductivity, and the intrinsic high resistance of PBI for vanadium ions is helpful to obtain high proton/vanadium selectivity. Considering the enormous water solubility of PWA and its easy leaching from membrane, organic polymer nano-Kevlar fibers (NKFs) are utilized as the anchoring agent of PWA, which achieves good anchoring effect and solves the problem of the poor compatibility between inorganic anchoring agent and the polymer matrix. The formation of PWA functionalized NKFs was characterized by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy. The anchoring stability of NKFs for PWA was evaluated by UV-Vis spectroscopy. The characterizations including water uptake, swelling ratio, ion exchange capacity, proton conductivity, vanadium ion permeability and ion selectivity were performed to evaluate the basic properties of the membranes. At the same time, the charge-discharge, self-discharge and cycle performance of single cell assembled with the composite membrane and recast Nafion were tested at various current densities from 40 to 100 mA∙cm-2. Simple tuning for the filling amount of NKFs@PWA gives the composite membrane superior ion selectivity including an optimal value of 3.26 × 105 S∙min∙cm-3, which is 8.5 times higher than that of recast Nafion (0.34 × 105 S∙min∙cm-3). As a result, the VRB single cell assembled with the composite membrane exhibits higher CE and significantly lower self-discharge rate compared with recast Nafion. Typically, the CE of the VRB based on PBI-(NKFs@PWA)-22.5% membrane is 97.31% at 100 mA∙cm-2 while the value of recast Nafion is only 90.28%. The open circuit voltage (VOC) holding time above 0.8 V of the single cell assembled with the composite membrane is 95 h, which is about 2.4 times as long as that of recast Nafion-based VRB. The utilization of PBI as a separator for VRB can effectively suppress the penetration of vanadium ions, achieve higher proton/vanadium selectivity and superior battery performance as well as reduce the cost of the PEM, which will play an active role in the promotion of VRB applications.

Key words: Vanadium redox flow battery, Polybenzimidazole, Phosphotungstic acid, Proton exchange membrane, High proton/vanadium selectivity

MSC2000: 

  • O646