Optimized Anion Exchange Membranes for Vanadium Redox Flow Batteries

In order to understand the properties of low vanadium permeability anion exchange membranes for vanadium redox flow batteries (VRFBs), quaternary ammonium functionalized Radel (QA-Radel) membranes with three ion exchange capacities (IECs) from 1.7 to 2.4 mequiv g^–1 were synthesized and 55–60 μm thick membrane samples were evaluated for their transport properties and in-cell battery performance. The ionic conductivity and vanadium permeability of the membranes were investigated and correlated to the battery performance through measurements of Coulombic efficiency, voltage efficiency and energy efficiency in single cell tests, and capacity fade during cycling. Increasing the IEC of the QA-Radel membranes increased both the ionic conductivity and VO²⁺ permeability. The 1.7 mequiv g^–1 IEC QA-Radel had the highest Coulombic efficiency and best cycling capacity maintenance in the VRFB, while the cell’s voltage efficiency was limited by the membrane’s low ionic conductivity. Increasing the IEC resulted in higher voltage efficiency for the 2.0 and 2.4 mequiv g^–1 samples, but the cells with these membranes displayed reduced Coulombic efficiency and faster capacity fade. The QA-Radel with an IEC of 2.0 mequiv g^–1 had the best balance of ionic conductivity and VO²⁺ permeability, achieving a maximum power density of 218 mW cm^–2 which was higher than the maximum power density of a VRFB assembled with a Nafion N212 membrane in our system. While anion exchange membranes are under study for a variety of VRFB applications, this work demonstrates that the material parameters must be optimized to obtain the maximum cell performance

Toward High-Performance Nonaqueous Redox Flow Batteries through Electrolyte Design

Redox flow batteries (RFBs) have emerged as a promising solution for large-scale stationary energy storage. However, nonaqueous flow batteries, despite having promising potential, are lagging behind aqueous flow batteries due to the lack of suitable redox pairs that can deliver high energy density and long cycle life. In this study, we implemented a counterion modification strategy to greatly enhance the solubility of both catholyte and anolyte active materials. Specifically, we increased the solubility of anthraquinone-2-sulfonic acid sodium salt (AQS) by three orders of magnitude in acetonitrile by replacing a sodium countercation with tetra-n-butylammonium. We present the first report of the flow cell cycling of all anionic active materials with a tetra-n-butyl countercation in supporting-salt-free conditions. We investigated the electrochemical behavior of each individual active material in a symmetric flow cell and then paired the AQS anolyte with the bio-inspired catholyte, tetra-n-butylammonium vanadium-bis-hydroxyiminodiacetate (TBA2VBH), in a full cell. The significant crossover observed in a full cell was mitigated by using a compositionally symmetric, mixed electrolyte as both the catholyte and anolyte. Additionally, because AQS and VBH coexist stably in the mixed electrolyte, even at high concentrations, we demonstrate that the cell capacity can be fully restored by rebalancing the electrolyte leading to long cycle life. This strategy, which has been employed in aqueous, acidic, all-vanadium flow battery systems, could be a promising pathway toward robust, high-performance nonaqueous flow batteries

Toward High-Performance Nonaqueous Redox Flow Batteries through Electrolyte Design

Redox flow batteries (RFBs) have emerged as a promising solution for large-scale stationary energy storage. However, nonaqueous flow batteries, despite having promising potential, are lagging behind aqueous flow batteries due to the lack of suitable redox pairs that can deliver high energy density and long cycle life. In this study, we implemented a counterion modification strategy to greatly enhance the solubility of both catholyte and anolyte active materials. Specifically, we increased the solubility of anthraquinone-2-sulfonic acid sodium salt (AQS) by three orders of magnitude in acetonitrile by replacing a sodium countercation with tetra-n-butylammonium. We present the first report of the flow cell cycling of all anionic active materials with a tetra-n-butyl countercation in supporting-salt-free conditions. We investigated the electrochemical behavior of each individual active material in a symmetric flow cell and then paired the AQS anolyte with the bio-inspired catholyte, tetra-n-butylammonium vanadium-bis-hydroxyiminodiacetate (TBA2VBH), in a full cell. The significant crossover observed in a full cell was mitigated by using a compositionally symmetric, mixed electrolyte as both the catholyte and anolyte. Additionally, because AQS and VBH coexist stably in the mixed electrolyte, even at high concentrations, we demonstrate that the cell capacity can be fully restored by rebalancing the electrolyte leading to long cycle life. This strategy, which has been employed in aqueous, acidic, all-vanadium flow battery systems, could be a promising pathway toward robust, high-performance nonaqueous flow batteries

Toward High-Performance Nonaqueous Redox Flow Batteries through Electrolyte Design

Redox flow batteries (RFBs) have emerged as a promising solution for large-scale stationary energy storage. However, nonaqueous flow batteries, despite having promising potential, are lagging behind aqueous flow batteries due to the lack of suitable redox pairs that can deliver high energy density and long cycle life. In this study, we implemented a counterion modification strategy to greatly enhance the solubility of both catholyte and anolyte active materials. Specifically, we increased the solubility of anthraquinone-2-sulfonic acid sodium salt (AQS) by three orders of magnitude in acetonitrile by replacing a sodium countercation with tetra-n-butylammonium. We present the first report of the flow cell cycling of all anionic active materials with a tetra-n-butyl countercation in supporting-salt-free conditions. We investigated the electrochemical behavior of each individual active material in a symmetric flow cell and then paired the AQS anolyte with the bio-inspired catholyte, tetra-n-butylammonium vanadium-bis-hydroxyiminodiacetate (TBA2VBH), in a full cell. The significant crossover observed in a full cell was mitigated by using a compositionally symmetric, mixed electrolyte as both the catholyte and anolyte. Additionally, because AQS and VBH coexist stably in the mixed electrolyte, even at high concentrations, we demonstrate that the cell capacity can be fully restored by rebalancing the electrolyte leading to long cycle life. This strategy, which has been employed in aqueous, acidic, all-vanadium flow battery systems, could be a promising pathway toward robust, high-performance nonaqueous flow batteries

Table1_The viability of implementing hydrogen in the Commonwealth of Massachusetts.docx

In recent years, there has been an increased interest in hydrogen energy due to a desire to reduce greenhouse gas emissions by utilizing hydrogen for numerous applications. Some countries (e.g., Japan, Iceland, and parts of Europe) have made great strides in the advancement of hydrogen generation and utilization. However, in the United States, there remains significant reservation and public uncertainty on the use and integration of hydrogen into the energy ecosystem. Massachusetts, similar to many other states and small countries, faces technical, infrastructure, policy, safety, and acceptance challenges with regards to hydrogen production and utilization. A hydrogen economy has the potential to provide economic benefits, a reduction in greenhouse gas emissions, and sector coupling to provide a resilient energy grid. In this paper, the issues associated with integrating hydrogen into Massachusetts and other similar states or regions are studied to determine which hydrogen applications have the most potential, understand the technical and integration challenges, and identify how a hydrogen energy economy may be beneficial. Additionally, hydrogen’s safety concerns and possible contribution to greenhouse gas emissions are also reviewed. Ultimately, a set of eight recommendations is made to guide the Commonwealth’s consideration of hydrogen as a key component of its policies on carbon emissions and energy.</p