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

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^-/SO₄^2- 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 SO₄^2- 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.