Bulk Aging of Graphite-Polypropylene Current Collectors Induced by Electrochemical Cycling in the Positive Electrolyte of Vanadium Redox Flow Batteries
Bulk Aging of Graphite-Polypropylene Current Collectors Induced by Electrochemical Cycling in the Positive Electrolyte of Vanadium Redox Flow Batteries
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DOI：
10.1149/2.1261712jes
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发表时间：
2017
影响因子：
3.9
通讯作者：
Barbara Satola;L. Komsiyska;G. Wittstock
中科院分区：
文献类型：
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作者：
Barbara Satola;L. Komsiyska;G. Wittstock
碳基双极板 (BPP) 是钒氧化还原液流电池 (VRFB) 堆的重要组成部分，可保证相邻电池的导电性和物理隔离。它们通常由含有导电碳成分和聚合物粘合剂材料的结构复杂的复合材料制成。为了通过模拟电解液流动缓慢区域的重复充电/放电条件来研究它们的老化，在具有正电解液（VO 2 + /VO 2 + ）的三电极电化学电池中，使用不同的充电状态（SOC），在扩散限制条件下对市售的石墨-聚丙烯BPP进行动电处理。电流在100和-100mA/cm 2 之间扫描。老化后，使用稀释H 2 SO 4 中的循环伏安法(CV)分析BPP的双层电容和氧化还原活性的变化。通过扫描电子和共焦显微镜以及 X 射线计算机显微断层扫描对表面纹理和块体材料进行形态学研究。在高 SOC 下的正极电解液中进行 3000 次扫描循环后，BPP 显示出双层电容的增加以及更高的粗糙度以及深度达 100 μm 的开孔体积的增加。老化效应归因于表面的氧化和腐蚀。由于容量和功率的大小独立，钒氧化还原液流电池（VRFB）是一种很有前途的存储技术，适用于固定的小型到大型应用。 1-3 它基于酸性电解质中钒离子不同氧化态之间的氧化还原反应。正极（VO 2 + /VO 2 + ）和负极（V 2 + /V 3 + ）电解质存储在单独的罐中，溶液通过电池组泵送。 3,4 反应单元中的每个单池均由两个由离子交换膜隔开的电极组成。相邻电池通过双极板 (BPP) 进行电连接和离子分离。 2,5碳基复合材料广泛用作VRFB中的BPP，因为它们具有机械稳定性、足够的导电性和在恶劣的酸性电解质环境中良好的耐化学性的特点。 6,7 复合材料通常含有导电碳成分，如石墨、炭黑、碳纤维或纳米管，以及聚合物粘合剂，如聚乙烯、环氧树脂或 5,8–11 VRFB 的电解质具有较长的循环寿命和良好的可回收性。 3,4 然而，电池组组件在酸性介质和恶劣的氧化条件下会发生不可逆的老化。到 的粗糙度。在调平共焦显微镜图像后，通过 SensoScan 计算均值表面粗糙度 (Sq)。
Carbon-based bipolar plates (BPP) are essential components of the vanadium redox flow battery (VRFB) stack guaranteeing electrical conductivity and physical separation of adjacent cells. They are usually made of composite materials with complex structures containing conductive carbon components and polymer binder materials. In order to investigate their aging by simulation of repetitive charging/discharging conditions in areas with sluggish electrolyte flow, commercially available graphite-polypropylene BPPs were subjected to galvanodynamic treatment under diffusion limitation conditions in a three electrode electrochemical cell with positive electrolyte (VO 2 + /VO 2 + ) using different states of charge (SOC). The current was swept between 100 and − 100 mA/cm 2 . After aging, cyclic voltammetry (CV) in diluted H 2 SO 4 was used to analyze the change in double layer capacitance and redox activity of the BPPs. Morphological investigations of the surface texture and bulk material were performed by means of scanning electron and confocal microscopies as well as by X-ray computed microtomography. After 3000 sweeping cycles in the positive electrolyte at high SOC the BPP showed an increase in double layer capacitance as well as higher roughness and increase in open pore volume in depths up to 100 μ m. The aging effects are ascribed to oxidation and corrosion of the surface. The vanadium redox flow battery (VRFB) is a promising stor- age technology for stationary small to large scale applications due to independent sizing of capacity and power. 1–3 It is based on redox reactions between different oxidation states of vanadium ions in an acidic electrolyte. The positive (VO 2 + /VO 2 + ) and the negative (V 2 + /V 3 + ) electrolytes are stored in separate tanks and the solutions are pumped through a battery stack. 3,4 Each single cell in the reaction unit consists of two electrodes separated by an ion exchange membrane. Adjacent cells are electrically connected and ionically separated by means of bipolar plates (BPP). 2,5 Carbon-based composite materials are widely used as BPPs in VRFBs as they are characterized by a mechanical stability, sufficient electrical conductivity and good chemical resistance in the harsh acidic electrolyte environment. 6,7 The composites usually contain conductive carbon components such as graphite, car- bon black, carbon fibers or nanotubes and a polymeric binder such as polyethylene, epoxy resin or 5,8–11 In it is the electrolyte of the VRFB has a long cycle life as well as a good recyclability. 3,4 However, components of the battery stack irreversible aging the acidic media and harsh oxidative conditions. to the roughness of . was performed step The root mean surface roughness (Sq) was calculated by means of SensoScan after leveling the confocal microscopy image.