An undivided zinc–cerium redox flow battery operating at room temperature (295 K)

An undivided zinc–cerium hybrid redox flow battery is proposed. High discharge cell voltage of c.a. 2.1 V at 20 mA cm− 2 and an average energy efficiency of 75% were obtained. The cerium half-cell reaction was highly reversible on a carbon felt electrode with less than a 15 mV change between charge and discharge cycles. The limiting factor for extended cycling was the zinc negative electrode, as residual zinc remained on the electrode after discharge. The battery self-discharge was evaluated by monitoring the open-circuit cell voltage, the capacity was found to last for approximately 7 h after being charged for 30 min.

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► Highest open-circuit cell voltage among other proposed flow battery chemistries.
► High energy efficiency at charge/discharge current density of 20 mA cm-2.
► Undivided configuration that simplifies cell design and reduce maintenance and cost.
► Self-discharge of the undivided Zn/Ce compares well with all-V redox flow battery.