Cost-Effective Membrane and Advanced Electrode for Stable Polysulfide-Ferricyanide Flow Battery

Abstract

Based on inexpensive, safe, and environmentally friendly active redox species, neutral polysulfide-ferrocyanide redox flow batteries (PFRFBs) have attracted much attention for large-scale energy storage. However, the development of PFRFBs is undermined by the expensive commercial membrane materials as well as the sluggish polysulfide redox reactions. This work attempts to solve these critical problems by combining the economical membrane with the highly catalytic electrode. In specific, K+-exchanged sulfonated polyether ether ketone (SPEEK-K) membranes have been investigated in PFRFBs to replace the costly Nafion membrane. SPEEK-K with optimized degree of sulfonation enables the PFRFB high average coulombic efficiency of 99.80% and superior energy efficiency of 90.42% at a current density of 20 mA cm-2. Meanwhile, to overcome the kinetic limitations of polysulfide redox reactions, a CuS-modified carbon felt electrode is demonstrated with excellent catalytic performance, enabling the PFRFB higher and more stable energy efficiency over cycling. The combination of the cost-effective membrane with the catalytic electrode in one cell leads to a capacity retention of 99.54% after 1180 cycles and an outstanding power density (up to 223 mW cm-2). The significant enhancements of electrochemical performance at reduced capital cost will make the PFRFB more promising for large-scale energy storage systems.

An aqueous polysulfide redox flow battery with a semi-fluorinated cation exchange membrane

“…A diffusion coefficient value of 3.95 Â 10 À9 and 6.8 Â 10 À8 cm 2 s À1 for polysulfide across Nafion-212 and the Celgard mesoporous separator respectively has been reported. 26,58 Well defined hydrophilic ion clusters present in the Nafion membranes might be the reason for the relatively fast diffusion of redox active species. 59 However, we were not able to match the outstanding polysulfide blocking ability of the charge-reinforced ion selective membrane (CRIS) developed by Li and Lu.…”

“…Recently, the Lou group reported an average CE of 99.80% and EE of 90.42% over 1051 cycles at a current density of 20 mA cm À2 for a neutral polysulfide-ferrocyanide redox flow battery with an affordable SPEEK-K membrane and a highly catalytic copper sulfide-modified carbon felt electrode. 58 A charge-reinforced ion selective membrane, i.e., a polyvinylidene fluoride (PVDF)-bound carbon layer on the Nafion membrane developed Li and Lu at the Chinese University of Hong Kong, is the best membrane reported for polysulfide-based redox flow batteries. 32 The polysulfide iodine redox flow battery with a CRIS membrane demonstrated stable cycling over 500 continuous charge/discharge cycles with no detectable capacity decay.…”

Development of Membranes and Separators to Inhibit Cross‐Shuttling of Sulfur in Polysulfide‐Based Redox Flow Batteries: A Review

“…The limitations of polysulfide redox kinetics have also been overcome using CuS-modified carbon felt, which led to a capacity retention of 99.54 %, even after 1180 cycles. [102]…”

“…The SPEEK–K membrane achieved a Coulombic efficiency of 99.80 %, energy efficiency of 90.42 %, and current density of 20 mA/cm 2 . The limitations of polysulfide redox kinetics have also been overcome using CuS‐modified carbon felt, which led to a capacity retention of 99.54 %, even after 1180 cycles [102] …”

A Highly Reversible Low-Cost Aqueous Sulfur–Manganese Redox Flow Battery

“…Herein, we demonstrate an ultra-low-cost sulfur–manganese (S–Mn) redox flow battery coupling a Mn 2+ /MnO 2 (s) posolyte and polysulfide negolyte. Polysulfide is one of the cheapest raw materials for energy storage (0.05 $/kAh) with high solubility and stability in aqueous media, − making it promising for next-generation energy storage. During charge and discharge, the nominal reaction in aqueous media is based on the conversion between S 2 2– and S 2– , as shown in eq . , normalS 2 2 − + 2 normale − ⇔ 2 normalS 2 − ⁣ E ° = prefix− 0.51 .25em normalV .25em vs .25em SHE …”