Scientists in India fabricated a redox flow battery based on zinc and iron that showed strong storage characteristics and no signs of degradation over 30 charge-discharge cycles. The battery also showed no signs of dendrite formation, overcoming one of the key hurdles for redox-flow batteries based on these low-cost, abundant materials.
Redox flow batteries present an attractive alternative to lithium-ion in the stationary storage segment, thanks to potentially longer lifetimes and capability for daily 100% discharge without loss of performance.
Many commercial projects featuring different types of flow batteries are already underway for both large-scale and residential energy storage. However, questions are being raised about the materials used in some of the batteries, with the toxicity of vanadium used in most of the large-scale projects a particular sticking point.
Zinc-based flow batteries present a less toxic option, and a zinc-bromine chemistry has already seen some commercial development. Zinc-iron (Zn-Fe) is another option widely explored by researchers, with the abundance of iron making it a particularly attractive option. However, dendrite growth and the related performance loss and short-circuiting, have held this chemistry back so far.
Scientists led by the University of Calicut in India fabricated a zinc-iron redox flow battery that demonstrated discharge voltage of approximately 1.34 V at 25 mA cm−2, with a coulombic efficiency (CE) of 92%, voltage efficiency (VE) of 85% and energy efficiency (EE) of ~78% for 30 charge-discharge cycles. Most importantly, the battery showed no performance degradation over those initial 30 cycles, and zero dendrite growth. The battery is described in full in the paper A dendrite free Zn-Fe hybrid redox flow battery for renewable energy storage.
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