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

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