In-Situ Tools Used in Vanadium Redox Flow Battery Research—Review

Abstract

Progress in renewable energy production has directed interest in advanced developments of energy storage systems. The all-vanadium redox flow battery (VRFB) is one of the attractive technologies for large scale energy storage due to its design versatility and scalability, longevity, good round-trip efficiencies, stable capacity and safety. Despite these advantages, the deployment of the vanadium battery has been limited due to vanadium and cell material costs, as well as supply issues. Improving stack power density can lower the cost per kW power output and therefore, intensive research and development is currently ongoing to improve cell performance by increasing electrode activity, reducing cell resistance, improving membrane selectivity and ionic conductivity, etc. In order to evaluate the cell performance arising from this intensive R&D, numerous physical, electrochemical and chemical techniques are employed, which are mostly carried out ex situ, particularly on cell characterizations. However, this approach is unable to provide in-depth insights into the changes within the cell during operation. Therefore, in situ diagnostic tools have been developed to acquire information relating to the design, operating parameters and cell materials during VRFB operation. This paper reviews in situ diagnostic tools used to realize an in-depth insight into the VRFBs. A systematic review of the previous research in the field is presented with the advantages and limitations of each technique being discussed, along with the recommendations to guide researchers to identify the most appropriate technique for specific investigations.

High-Capacity Retention Thermally Reinforced Pore-Filled Anion Exchange Membrane for All-Vanadium Flow Batteries

“…Under identical experimental conditions, the peak power density of Nafion 117 was 300 mW cm –2 at a limiting current density of 350 mA cm –2 . The good ionic conductivity and low thickness of the PFAEM minimized the ohmic losses, which dominate the linear part of the polarization curve . The measured self-discharge time for the PFAEM was close to ∼7 h (Figure b) with an open circuit potential of 1.44 V. The overall standard cell potential of a VRFB system is 1.26 V at 25 °C.…”

On the challenges of materials and electrochemical characterization of concentrated electrolytes for redox flow batteries

“…[29][30][31] Thus, quantifying electrolyte properties at different SOCs and supporting salt concentrations presents an additional handle to tune the electrolyte structure and evince essential chemical and electrochemical features; for example, these quantitative relationships have previously been used to monitor operando SOCs using in-line density and viscosity measurements in vanadium RFBs. 32,33 2.2. Future approaches Methods for investigating rheological and transport phenomena are relatively mature, as they are integral to a range of disciplines (e.g., uid mechanics, so matter physics, electroanalytical chemistry); as such, the tools discussed here are likely to be sufficient for the characterization of modern electrolyte formulations.…”

“…29–31 Thus, quantifying electrolyte properties at different SOCs and supporting salt concentrations presents an additional handle to tune the electrolyte structure and evince essential chemical and electrochemical features; for example, these quantitative relationships have previously been used to monitor operando SOCs using in-line density and viscosity measurements in vanadium RFBs. 32,33…”

Redox flow battery time‐varying parameter estimation based on high‐order sliding mode differentiators

“…4 Among ESS, redox flow batteries (RFB) are one of the technologies that are receiving a great deal of attention for large-scale energy storage in stationary applications. 5,6 Regarding the most important features of RFB it can be mentioned their high efficiency ($80%), simple and safe operation, rapid response time, independence between power output and capacity, long service life, and suitability for long-term storage with very little self-discharge. 7 In addition, they require low maintenance and, if necessary, can be quickly refuelled by renewing the tanks content.…”