Joint Center for Energy Storage Research , Argonne , Illinois 60439 , United States.
Department of Chemical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
ACS Appl Mater Interfaces. 2018 Dec 26;10(51):44430-44442. doi: 10.1021/acsami.8b15793. Epub 2018 Dec 12.
Sluggish vanadium reaction rates on the porous carbon electrodes typically used in redox flow batteries have prompted research into pretreatment strategies, most notably thermal oxidation, to improve performance. While effective, these approaches have nuanced and complex effects on electrode characteristics hampering the development of explicit structure-function relations that enable quantitative correlation between specific properties and overall electrochemical performance. Here, we seek to resolve these relationships through rigorous analysis of thermally pretreated SGL 29AA carbon paper electrodes using a suite of electrochemical, microscopic, and spectroscopic techniques and culminating in full cell testing. We systematically vary pretreatment temperature, from 400 to 500 °C, while holding pretreatment time constant at 30 h, and evaluate changes in the physical, chemical, and electrochemical properties of the electrodes. We find that several different parameters contribute to observed performance, including hydrophilicity, microstructure, electrochemical surface area, and surface chemistry, and it is important to note that not all of these properties improve with increasing pretreatment temperature. Consequently, while the best overall performance is achieved with a 475 °C pretreatment, this enhancement is achieved from a balance, rather than a maximization, of critical properties. A deeper understanding of the role each property plays in battery performance is the first step toward developing targeted pretreatment strategies that may enable transformative performance improvements.
在氧化还原液流电池中常用的多孔碳电极上，钒的反应速率缓慢，这促使人们研究预处理策略，尤其是热氧化，以提高性能。虽然这些方法有效，但它们对电极特性有细微而复杂的影响，阻碍了明确的结构-功能关系的发展，而这种关系可以使特定性质与整体电化学性能之间实现定量相关。在这里，我们通过使用一系列电化学、显微镜和光谱技术对经过热预处理的 SGL 29AA 碳纸电极进行严格分析，并最终进行全电池测试，试图解决这些关系。我们系统地改变预处理温度，从 400°C 到 500°C，同时将预处理时间保持在 30 小时不变，并评估电极的物理、化学和电化学性质的变化。我们发现，观察到的性能与几个不同的参数有关，包括亲水性、微观结构、电化学表面积和表面化学，需要注意的是，并非所有这些性质都随预处理温度的升高而改善。因此，虽然 475°C 预处理可获得最佳的整体性能，但这种增强是通过关键性质的平衡而不是最大化来实现的。深入了解每种性质在电池性能中的作用是开发有针对性的预处理策略的第一步，这种策略可能会实现具有变革性的性能提升。
