Long-Term Structural and Chemical Stability of Carbon Electrodes in Vanadium Redox Flow Battery

Abstract

Predicting the performance decay in carbon electrodes is critical to maximizing the longevity of redox flow battery (RFB) systems. This study investigates the effect of long-term cycling (over 8000 cycles) on the structural and chemical evolution of carbon electrodes. We find that the microstructural aspects such as graphitic stacking order and interlayer spacing along with overall morphological construct remain largely unchanged even after the prolonged cycling process. Conversely, significant changes in surface chemistry such as the evolution of functional groups and point defects are evident from our combined multimodal spectroscopic and computational analysis. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis reveal chemical absorption of chloride counter anions at point defects within the graphitic surface. Additionally, our results suggest that vanadium cation plays an important role in counter anion–carbon surface interaction and subsequently the surface chemistry evolutions. Our findings provide insights about surface chemical evolution that is critical for predicting electrode performance and longevity of RFB.

Taurine Electrografting onto Porous Electrodes Improves Redox Flow Battery Performance

“…Next to these performance metrics, the stability of electrode interfaces under the aggressive electrochemical environment plays a critical role. If the interaction between the anchored functionality and the substrate is not strong enough (e.g., weak interactions as opposed to a covalent bond), the electrode functionality can be lost or negatively impacted over a lifetime. , Thus, it is critical to assess the stability of the electrodes for prolonged operation. We performed preliminary electrode stability measurements using the single-electrolyte flow cell configuration under open-circuit potential (OCV) and applied voltage conditions (see the Supporting Information Stability tests ).…”

“…For example, the hydrophobic properties of carbon fiber-based porous electrodes challenge the operation of aqueous systems as capillary forces prevent full wetting of the electrode . Furthermore, the relative inertness of the carbon surface toward aqueous metal redox couples (V 2+/3+ and Fe 2+/3+ ) is another drawback of pristine carbonaceous materials, limiting electrochemical kinetics and resulting in cell overpotentials. , Large charging potentials and prolonged cycling can modify the surface chemistry of the carbon electrode, resulting in decreased cell performance. , Thus, engineering electrode interfaces to sustain the stringent requirements of liquid phase electrochemistry is a powerful strategy to reduce stack costs.…”

“…12,13 Large charging potentials and prolonged cycling can modify the surface chemistry of the carbon electrode, resulting in decreased cell performance. 14,15 Thus, engineering electrode interfaces to sustain the stringent requirements of liquid phase electrochemistry is a powerful strategy to reduce stack costs.…”

Comprehensive Analysis of Critical Issues in All-Vanadium Redox Flow Battery

“…Figure. shows a classification of electrode materials of VRFBs and analyzes the characteristics of three different electrode materials. , …”

“…Figure . 5 shows a classification of electrode materials of VRFBs and analyzes the characteristics of three different electrode materials. 55,56 In recent years, the research of electrodes mainly focuses on the stabilities of electrode materials, catalytic activities, porosities, resistances, side reactions, and costs and has achieved remarkable results. It is worth noting that electrode compression is also an effective way to improve the performances of VRFBs.…”