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Chemical systems may be maintained far from equilibrium by sequestering otherwise reactive species into different microenvironments. It remains a significant challenge to control the amount of chemical energy stored in such systems and to utilize it on demand to perform useful work. Here, we show that redox-active molecules compartmentalized in multiphasic structured-liquid devices can be charged and discharged to power a load on an external circuit. The two liquid phases of these devices feature charge-complementary polyelectrolytes that serve a dual purpose: they generate an ionically conductive coacervate membrane at the liquid–liquid interface, providing structural support; they also mitigate active-material crossover between phases via ion pairing with the oppositely charged anolyte and catholyte active materials. Structured-liquid batteries enabled by this design were rechargeable over hundreds of hours. We envision that these devices may be integrated with soft electronics to enable functional circuits for smart textiles, medical implants, and wearables.

Electric vehicles capable of recharging in the same time it takes to refuel a gasoline-powered car require electrolytes that maximize areal ion flux to enable electrochemical reactions to proceed at the same rate that current is passed through the external circuit. While strategies for increasing ionic charge carrier concentration in electrolytes are well-established, enhancements are made at the expense of carrier mobility, placing a ceiling on areal ion flux below the requirement for fast-charge. Here, we explore locally superconcentrated electrolytes, which employ a noncoordinating diluent to reduce viscosity, for delivering an 80% change in state-of-charge in Li|NMC622 batteries in 5–15 min. We investigate the effects of concentration, viscosity, ionic conductivity, and solvation on lowering fast-charge overpotentials and extending cycle life. We identify divergent failure mechanisms that occur on different time scales when cycling the cells at different charge rates and depths of discharge, which has implications for future electrolyte designs.

The ongoing development of redox-active charge carriers for nonaqueous redox-flow batteries has led to energy-dense storage concepts and chemistries with high cell voltages. However, rarely are these candidates for flowable energy storage evaluated in tandem with cell separators compatible with organic solvent, limiting progress in the identification of suitable charge carrier–separator pairings. This is important, as the efficiency of a redox-flow battery is dictated by extent of active species crossover through a separator, dividing the two cells, and the contribution of the separator to cell resistance. Here, we report the size-dependent crossover behavior of a series of redox-active vanadium­(III) acetoacetonate, and two polyoxovanadate-alkoxide clusters, [V6O7(OR)12] (R = CH3, C5H11) through separators derived from polymers of intrinsic microporosity (PIMs). We find that highly efficacious active-material blocking requires both increasing the size of the vanadium species and restricting pore swelling of the PIMs in nonaqueous electrolyte. Notably, increasing the size of the vanadium species does not significantly affect its redox reversibility, and reducing swelling decreases the conductivity of the separator by only 50%. By pairing polyoxometalate clusters with PIM membranes in nonaqueous redox-flow batteries, more efficient systems may well be within reach.

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