High power density near‐neutral pH aqueous redox flow batteries using zinc chloride and 4,5‐dihydroxy‐1,3‐benzenedisulfonate as redox couple with polyethylene glycol additive

Abstract

Summary Redox flow batteries (RFBs) using zinc chloride (ZnCl2) and 4,5‐dihydroxy‐1,3‐benzenedisulfonate (Tiron) redox couple is introduced. ZnCl2 and Tiron are used as negative and positive active materials, which are dissolved in near‐neutral pH, ammonium chloride (NH4Cl) supporting electrolyte. Cell voltage of RFB using ZnCl2 and Tiron is extremely high as 1.8 V, while two cellulose spacers are introduced to prevent the growth of zinc dendrite on the membrane. When the performances of RFBs using ZnCl2 and Tiron are measured, their charge efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are 95, 79, and 75% at 40 mA cm−2, whereas their capacity fading rate is high as 0.12 Ah L−1 per cycle. This is due to the zinc dendrite formed on the electrode of RFB that is attributed to the aggregation of zinc ions. To suppress the aggregation and to preserve active sites for the redox reaction of zinc ions during cycling, the polyethylene glycol (PEG) additive is suggested. Regarding the optimization of PEG, 5000 ppm PEG induces both high efficiencies (97, 81, and 79% of CE, VE, and EE at 40 mA cm−2) and low capacity loss rate (0.03 Ah L−1 per cycle), which are more enhanced performances than those of RFBs operated without PEG. In terms of power density of RFB using ZnCl2 and Tiron, high power density of 144 mW cm−2 is achieved under 120 mA cm−2, which is far better performance than that of other RFBs operated under near‐neutral pH electrolyte.

Freestanding V 5 O 12 · 6H 2 O‐CNTs composite films as cathode for foldable aqueous zinc‐ion batteries

“…The second charge/discharge voltage plateau (0.9-1.2 V/0.6-0.3 V) corresponds to the redox peaks at the positions of peaks 3 and 1 (0.7 V/0.4 V). 11,35,36 The area of the CV closure region represents the capacity of the cell and can be divided into a surface-controlled capacitance and diffusion-induced capacitance.…”

“…The first charge/discharge voltage plateau (0.6‐0.8 V/1‐0.84 V) corresponds to the redox peaks at the positions of peaks 2 and 4 (0.87 V/1.0 V). The second charge/discharge voltage plateau (0.9‐1.2 V/0.6‐0.3 V) corresponds to the redox peaks at the positions of peaks 3 and 1 (0.7 V/0.4 V) 11,35,36 . The area of the CV closure region represents the capacity of the cell and can be divided into a surface‐controlled capacitance and diffusion‐induced capacitance.…”

Alkaline naphthoquinone‐based redox flow batteries with a crosslinked sulfonated polyphenylsulfone membrane

“…The pH of supporting electrolytes for AORFBs can be acidic, neutral or alkaline 36‐57 . Among them, alkaline pH‐based AORFBs are the most common.…”

Stability enhancement for all‐iron aqueous redox flow battery using iron‐3‐[bis(2‐hydroxyethyl)amino]‐2‐hydroxypropanesulfonic acid complex and ferrocyanide as redox couple

“…To solve these problems, energy storage system (ESS) was suggested because this could store and stabilize such produced energies and supply them to the grid as necessary. [1][2][3][4][5][6] Typical ESSs include flywheel, pumped hydro, and batteries. [7][8][9][10] Among them, ESSs using batteries are most famous, and of them, lithium-ion batteries have been the significant ESS device so far.…”