Retaining the reversible capacity by Lorentz forces for enhanced cyclability of aqueous zinc-bromide batteries using internal magnets

Abstract

Despite the high safety and low-cost of aqueous zinc-bromide batteries (AZBBs), their widespread application in portable and stationary energy storage systems is hindered by deleterious zinc-dendrite growth and cross-diffusion of tribromide (Br3−) ions. Here, we, for the first time demonstrate the effect of Lorentz force using internal magnets to retain the reversible capacity for mitigated cross-diffusion of Br3−, dendrite-free zinc deposition, enhanced cycle life, improved voltage efficiency and energy efficiency of AZBBs via magnetohydrodynamics. Of the magnetic field strengths investigated (0 – 70 ± 1 mT), cells incorporating 50 ± 1 mT achieved a high energy efficiency of 88.8 % (coulombic efficiency of 99.3 %) with a small decay of 7.6 % after 550 cycles. Interestingly, batteries with internal magnets resist self-discharge and exhibit an improved rate-capability (up to 3C rate) compared to batteries without magnets. Scanning electron microscopy images and energy dispersive X-ray analysis of zinc electrodes (after 100 cycles) of AZBBs containing 50 ± 1 mT revealed the suppressed amount of cross-diffused bromine and dendrite-free zinc deposits without any passivation layer. Operando UV–vis spectroscopic data of membrane electrode assembly (MEA) of AZBB confirmed the retention of Br3− ions at 50 ± 1 mT, whereas the MEA without magnets suffered severe leaching of Br3− ions into the electrolyte.