A neutral pH aqueous biphasic system applied to both static and flow membrane-free battery

Abstract

Here, we present a new aqueous biphasic system (ABS) with near neutral pH and containing highly soluble organic/organometallic active species that avoids crossover due to the thermodynamic separation of active species. This ABS become the best example of “Static” Membrane-Free Battery with the highest maximum theoretical energy density (21.7 Wh L−1), enhanced coulombic efficiency (96%) and stable performance over 250 cycles. Moreover, this work assesses the process of the self-discharge stablishing for the first time a protocol to quantify this phenomenon that results in low coulombic efficiencies in membrane-free batteries. Remarkably, a radically new membrane-free flow-reactor was specifically designed to maintain a stable liquid-liquid interphase that allows the battery to operate under flowing conditions. This resulted in flow battery with a two-fold increase of power density, high coulombic efficiencies and excellent capacity retention over 100 cycles. This work demonstrates for the first time the feasibility of this biphasic electrolyte concept in a truly Membrane-free “Flow” Battery.