Flow battery is a promising energy storage technology for facilitating utilization of renewable resources. While new types of flow batteries have been explored toward high energy density, hampering the power density due to high electrolyte viscosity and sluggish reaction kinetics. Discovery of an aqueous electrolyte with multi-electron transfer reaction is thus favorable for both high energy and power densities due to its multiple charge stored at the same concentration. Both criteria are crucial to improve the flexibility of cell design and widen the application potential. Herein, bismuth is pioneered as negative electrolyte (negolyte) for hybrid flow battery owing to its three-electron reaction and the significantly increased solubility in methanesulfonic acid. In conjunction with cerium electrolyte, a volumetric energy density of 90 Wh L −1 is achieved and simultaneously a high power density of 295 mW cm −2 at 90% state-of-charge is demonstrated using low-cost carbon electrode. Furthermore, a high volumetric capacity of 120 Ah L −1 is reached via adopting graphite felt, which is 100% of the theoretical specific capacity of 1.5 M bismuth negolyte.
Yufei Wang,Shuanjin Wang,Min Xiao,Shuqin Song,Dongmei Han,Michael A. Hickner,Yuezhong Meng
Novel sulfonated poly (fluorenyl ether ketone) with pendant quaternary ammonium groups (SPFEKA) was successfully synthesized by one-pot copolymerization of bis(4-fluoro-3-sulfophenyl)sulfone disodium salt, 4,4′-difluorobenzophenone, bisphenol fluorene and 2,2′-dimethylaminemethylene-9,9′-bis(4-hydroxyphenyl) fluorene (DABPF). The chemical structures were confirmed by FT-IR, and 1 H NMR. The thermal properties were fully investigated by TGA . The synthesized copolymers SPFEKAs are soluble in aprotic solvents, and can be cast into membranes on a glass plate from their N,N′-dimethylacetamide (DMAc) solution. A new kind of amphoteric ion exchange membrane (AIEM) was obtained by immersed SPFEKA into 1 M sulfuric acid. The proton conductivities of these membranes are comparable to the most reported sulfonated polymers under the same conditions. The permeability of vanadium ions in vanadium redox flow battery (VRB) was effectively suppressed by introducing quaternary ammonium groups for Donnan exclusion effect . AIEM-20% possess a only 4.4% vanadium ion permeability of Nafion 115. Cell performance tests showed that the VRB assembled with AIEM-20% shows the highest coulombic efficiency (CE) at the current density of 50 mA/cm 2 , because of its lowest VO 2+ permeability. In conclusion, these ionomers could be promising candidates for ion-exchange membranes for VRB applications.
High-molecular-weight bulky-block poly(fluorenyl ether thioether ketone)s were successfully synthesized by a two steps one-pot protocol using N,N′ -dimethy- S -carbamate masked dithiols for vanadium redox flow battery (VRB) application. The followed sulfonation procedure gave birth to novel sulfonated block poly(fluorenyl ether thioether ketone)s (SPFETKs) with controlled ionic exchange capacities (IEC). Membranes with proton conductivities higher than (IEC > 1.66 mequiv. g −1 ) or comparable to (IEC < 1.66 mequiv. g −1 ) that of Nafion117 membrane were achieved. The VO 2+ permeabilities of SPFETKs membranes were much lower than that of Nafion117 membrane. The thermal properties, mechanical properties, oxidative stability , water uptake, proton conductivity, VO 2+ permeability and cell performance were investigated in detail.
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