Electrolytes with Micelle-Assisted Formation of Directional Ion Transport Channels for Aqueous Rechargeable Batteries with Impressive Performance

Abstract

Low-cost and ecofriendly electrolytes with suppressed water reactivity and raised ionic conductivity are desirable for aqueous rechargeable batteries because it is a dilemma to decrease the water reactivity and increase the ionic conductivity at the same time. In this paper, Li2SO4–Na2SO4–sodium dodecyl sulfate (LN-SDS)-based aqueous electrolytes are designed, where: (i) Na+ ions dissociated from SDS increase the charge carrier concentration, (ii) DS−/SO42− anions and Li+/Na+ cations are capable of trapping water molecules through hydrogen bonding and/or hydration, resulting in a lowered melting point, (iii) Li+ ions reduce the Krafft temperature of LN-SDS, (iv) Na+ and SO42− ions increase the low-temperature electrolyte ionic conductivity, and (v) SDS micelle clusters are orderly aggregated to form directional ion transport channels, enabling the formation of quasi-continuous ion flows without (r.t.) and with (≤0 °C) applying voltage. The screened LN-SDS is featured with suppressed water reactivity and high ionic conductivity at temperatures ranging from room temperature to −15 °C. Additionally, NaTi2(PO4)3‖LiMn2O4 batteries operating with LN-SDS manifest impressive electrochemical performance at both room temperature and −15 °C, especially the cycling stability and low-temperature performance.