Advanced Membranes Boost the Industrialization of Flow Battery

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Flow battery (FB) is nowadays one of the most suited energy storage technologies for large-scale stationary energy storage, which plays a vital role in accelerating the wide deployment of renewable energies. FBs achieve the energy conversion by reversible redox reactions of flowing active species at the positive and negative sides. An ion conducting membrane (ICM) is necessary to separate the anolyte and catholyte, while conducting chargebalanced ions to form a complete electric circuit simultaneously. However, the commonly used commercial perfluorinated sulfonated ion exchange membranes suffer from low selectivity and high cost. The widely studied nonfluorinated ion exchange membranes have poor chemical stability. Most importantly, these membranes are confronted with a trade-off between selectivity and conductivity. That has motivated researchers to explore novel membrane materials with innovative design. Among them, porous membranes based on the "ion sieving conducting" mechanism instead of the "ion exchange conducting" mechanism from traditional ion exchange membranes were put forward, upon which very impressive progress has been achieved in recent years. Different from ion exchange membranes, the porous ICMs can separate active species from charge-balanced ions by pore size exclusion. As a result, by controlling the pore structures, porous membranes can break up the selectivity and conductivity trade-off. However, the initial performance of the first reported porous ICM is not high enough to afford the industrialization of FBs. As a group striving for the integration of basic, applied and translational research, we have devoted substantial efforts to optimizing the current membrane fabrication methods, developing novel fabrication techniques, exploring novel membrane materials and increasing the membrane performance for over a decade. Based on these efforts, the preliminary industrial applications of ICMs in FBs have been realized. In this Account, we summarize and discuss the development process of ICMs in various FB systems, mainly including vanadium FBs and zinc-based FBs. We begin the discussion from the brief description of FBs and their ICMs. Then we will illustrate the "ion sieving conducting" mechanism of ICMs deeply and elaborately. This account will focus on our contributions to accelerating the industrial applications of ICMs in FB energy storage systems, upon which the modification strategies on ICMs will be illustrated thoroughly, including the regulation of formation parameters, the introduction of functional materials or functional separation layers and the implementation of post-treatment steps. We also discuss the current challenges of ICMs and propose prospects on their future development.

Bioinspired 2D nanofluidic membranes for energy applications

“…Redox flow batteries (RFBs) are promising in the field of large-scale energy storage due to their scalable energy and power densities, long discharge duration at rated power, high power output, long operational life, low maintenance required, and non-flammability in aqueous electrolytes. 255–259 However, the key limitation for its further development lies in finding low-cost, high-performance separators. The most basic requirements for RFB separators are high ionic conductivity and low cost with minimal cross-over.…”

Electrochemical Deposition of Bismuth on Graphite Felt Electrodes: Influence on Negative Half-Cell Reactions in Vanadium Redox Flow Batteries

“…The capacity and power of the battery can be adjusted flexibly according to the needs, and the electrolyte is easy to recycle to restore the battery capacity and prolong the lifetime of the VRFB [4][5][6]. In particular, VRFBs have been widely studied as a new type of efficient, economical and environmentally friendly secondary batteries due to the wide standard reduction potentials of vanadium redox couples [7][8][9].…”

Modified Membranes for Redox Flow Batteries—A Review

“…We recently published a comprehensive review paper [ 15 ], that covered both theoretical models and experimental evidence on the transport of ions and active substances through the membranes, as well as the correlation between different membrane characteristics and cell performance. As discussed, porous membranes are often associated with high levels of active species crossover, while dense ion-exchange membranes currently utilized in RFBs have not been initially designed for this purpose and therefore exhibit low selectivity and efficiency [ 16 ].…”