A ‘poly(ions–water ligand) network’ electrolyte enables high-voltage high-conductivity aqueous metal-ion chemistries?

Journal of Materials Chemistry A Pub Date: 2022-09-23 DOI: 10.1039/D2TA05705K

Abstract

Aqueous electrolytes are essential for ensuring safe and environmentally friendly energy storage devices. Low-concentration aqueous electrolytes exhibit narrow electrochemical stability windows (ESWs) of 1.23 V, but they have high ionic conductivities (～125 mS cm?1). Contemporary methods use ultrahigh salt concentrations of 21–63 mol kg?1 (m), which can widen the ESWs (up to ～3 V); however, they result in low ionic conductivities (10 mS cm?1). Achieving low-concentration aqueous electrolytes with wide ESWs and high ionic conductivities is challenging. Herein, we report a low-concentration aqueous electrolyte with a dual-network structure (2.11 m), a wide ESW of 4.6 V, and an ionic conductivity of 110 mS cm?1 at 25 °C. As a proof of concept, a ‘poly(ion-water ligand) network’ is designed to regulate the water properties of an ‘ion/H2O-rich hydrogen-bond network’ (low-concentration aqueous electrolyte). Supercapacitors as well as zinc-ion capacitors exhibit excellent cycling stabilities and high energy densities (～29 W h kg?1 and ～128 W h kg?1, respectively) within the operating voltage window (0–2.5 V).

Graphical abstract: A ‘poly(ions–water ligand) network’ electrolyte enables high-voltage high-conductivity aqueous metal-ion chemistries
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