Membrane-less hybrid flow battery based on low-cost elements

Abstract

The capital cost of conventional redox flow batteries is relatively high (> USD$ 200 /kWh) due to the use of expensive active materials and ion-exchange membranes. This paper presents a membrane-less hybrid organic-inorganic flow battery based on the low-cost elements zinc (< USD$ 3 Kg -1 ) and para-benzoquinone (< USD$ 8 Kg -1 ). Redox potential and voltammetric studies show that the open-circuit voltage of the battery is 1.17 -1.59 V over a wide range of pH. Half-cell charge-discharge and dissolution experiments indicate that the negative electrode reaction is limiting due to the presence of chemical side reactions on the electrode surface. The positive electrode redox reactions are not affected and exhibit (half-cell) coulombic efficiencies of > 92.7 % with the use of carbon felt electrodes. In the presence of a fully oxidized active species close to its solubility limit, dissolution of the deposited anode is relatively slow (< 2.37 g h -1 cm -2 ) with an equivalent corrosion current density of < 1.9 mA cm -2 . In a parallel plate flow configuration, the resulting battery was charge-discharge cycled at 30 mA cm -2 with average coulombic and energy efficiencies of c.a. 71.8 and c.a. 42.0 % over 20 cycles, respectively.

A Membrane‐Free Redox Flow Battery with Two Immiscible Redox Electrolytes

“…[18,19] Regardless of the chemical nature of the electroactive species and the type of electrolytes, most RFBs rely on ion-selective membranes to separate the two redox electrolytes and to prevent the crossover of active compounds while allowing the migration of charge carriers. It is worth mentioning that membranes are not employed in some hybrid RFBs in which one of the active species is a solid, such as Zn, [20,21] Cd, [22] lithium, [23] or graphite. [24] However, in this hybrid RFB technology is not possible to fully decouple power and energy, this decoupling however is probably the most important advantage of redox flow batteries over conventional ones.…”

Recent developments in organic redox flow batteries: A critical review

“…The first membrane-less organic-inorganic redox flow battery was introduced by Leung and co-workers [42,152]. The operating concept makes use of the slow dissolution of the deposited metal in the presence of the soluble active species in the common electrolytes, which has been used in previous inorganic systems [88,155].…”

“…These compounds are based on common elements, such as carbon, hydrogen, oxygen and sulfur. Even in the early stages of development, the electrolyte cost of some organic-based flow batteries has been demonstrated to be lower than USD$ 35 (kW h) -1 (based on half-cell estimates) [39][40][41][42]. With advances in synthetic chemistry, the properties of these organic molecules can be further tailored to provide fast kinetics and high solubility, and to yield high cell voltages in batteries [43][44][45][46][47].…”

Rechargeable organic–air redox flow batteries

“…USD$ 25 Kg -1 ) and fluorinated ionexchange membranes (Nafion ® 117: c.a. USD$ 250 m -2 ); in previous cost models [4], they are estimated to be more than 30 % and 40 % of the overall capital cost, respectively. In order to meet the US Department of Energy (DoE) cost target of USD$ 100 -150 / kWh, it is perhaps necessary to use lower-cost alternative materials rather than rely on (possible) economies of scale [5].…”