An organic additive strategy for high-performance and durable alkaline zinc/ferricyanide flow batteries

Abstract

Alkaline zinc/ferricyanide flow batteries (AZFFBs) offer high safety, high energy density, and lower cost, but their long-term reliability is hindered by zinc dendrite growth and parasitic reactions on the anode. Here we show that monosodium glutamate (MSG) acts as a multifunctional electrolyte additive that modulates the coordination environment of zincate species, promotes more uniform zinc deposition, and suppresses the electrochemical hydrogen–evolution response. These effects are consistent with MSG–induced changes in zincate solvation and interfacial reaction kinetics. A Zn||Zn symmetric cell with baseline electrolyte (BE) fails in less than 220 h at 100 mA cm −2 , whereas the MSG-containing cell operates stably for over 800 h. An AZFFB with MSG in the anolyte operated for approximately 14,000 cycles at 100 mA cm −2 , with an average Coulombic efficiency exceeding 99.9% and an average energy efficiency of 83.5%. Over the common 14,000 - cycle test at 100 mA cm −2 , the average and final-cycle capacity retentions were 77.0% and 70.2% for the MSG-containing cell, compared with 58.4% and 43.2% for the BE cell, respectively. Stable low-temperature operation (−10 °C) is also demonstrated for over 3700 cycles. This work demonstrates a simple and readily implementable electrolyte−additive strategy for improving the durability of alkaline zinc-based flow batteries.