Preparation of sulfonated polyimide/polyvinyl alcohol composite membrane for vanadium redox flow battery applications

An Ultra-Low Self-Discharge Aqueous|Organic Membraneless Battery with Minimized Br2 Cross-Over

Batteries dissolving active materials in liquids possess safety and size advantages compared to solid-based batteries, yet the intrinsic liquid properties lead to material cross-over induced self-discharge both during cycling and idle when the electrolytes are in contact, thus highly efficient and cost-effective solutions to minimize cross-over are in high demand. An ultra-low self-discharge aqueous|organic membraneless battery using dichloromethane (CH2 Cl2 ) and tetrabutylammonium bromide (TBABr) added to a zinc bromide (ZnBr2 ) solution as the electrolyte is demonstrated. The polybromide is confined in the organic phase, and bromine (Br2 ) diffusion-induced self-discharge is minimized. At 90% state of charge (SOC), the membraneless ZnBr2 |TBABr (Z|T) battery shows an open circuit voltage (OCV) drop of only 42 mV after 120 days, 152 times longer than the ZnBr2  battery, and superior to 102 previous reports from all types of liquid active material batteries. The 120-day capacity retention of 95.5% is higher than commercial zinc-nickel (Zn-Ni) batteries and vanadium redox flow batteries (VRFB, electrolytes stored separately) and close to lithium-ion (Li-ion) batteries. Z|T achieves >500 cycles (2670 h, 0.5 m electrolyte, 250 folds of membraneless ZnBr2  battery) with ≈100% Coulombic efficiency (CE). The simple and cost-effective design of Z|T provides a conceptual inspiration to regulate material cross-over in liquid-based batteries to realize extended operation.

Sulfonated poly (arylene ether sulfone)-graft-sulfonated poly (vinyl alcohol) proton exchange membranes: Improved proton selectivity

Aldehyde terminated sulfonated poly (arylene ether sulfone) (SPAES-CHO) is prepared by a series of nucleophilic substitution reaction based on SPAES in this paper. Novel SPAES-graft-SPVA (SPAES-g-SPVA) membranes are fabricated by acetal reaction between SPAES-CHO and different amounts of sulfonated poly (vinyl alcohol) (SPVA). The 1H-NMR and FTIR indicate the successful preparation of SPAES-CHO and SPAES-g-SPVA membranes. With the introduction of SPVA, the SPAES-g-SPVA membranes have much lower methanol permeability than pure SPAES membrane and Nafion117 membrane. The methanol permeability coefficients of the SPAES-g-SPVA membranes decrease from 3.41 × 10−7 cm2 s−1 to 1.67 × 10−7 cm2 s−1 with the increase of SPVA content. And the proton conductivity of all the membranes is higher than 15 mS cm−1 at 25°C. Moreover, SPAES-g-SPVA membranes exhibit high proton selectivity. Especially, SPAES-g-SPVA-30% membrane has the highest proton selectivity, which is nearly five times higher than Nafion117.