Sustainable Clay Electrolytes for Aqueous Batteries: All-Temperature Single-Ion Conductor with Nanoconfined Hydration...

Ion transport property and water structure of electrolytes are two of the most important issues for aqueous batteries, especially when operated at extreme temperatures. To this end, a sepiolite-based clay electrolyte (SCYE) with nanoconfined channels as single-ion conductor is proposed. The inner Zn²⁺ and anions solvation shells exhibit fascinating hydration-shell reconfiguration behavior compared to the conventional Zn(ClO₄)₂ aqueous electrolytes. The bond-orientational order of the Zn²⁺ and anions is broken and highly developed, respectively, thus improving the Zn²⁺ transference number to 0.97. Moreover, free water molecules are dramatically reduced in the SCYE, contributing to improved anti-freezing ability and thermal stability. The single-ion transport property of the SCYE endows the PANI||Zn full cells with excellent rate performances, with an ≈84% capacity retention from 1 to 20 A g^-1. Besides, full cells with the SCYE achieve 17,000 cycles under -40 °C with a specific capacity of 130 mAh g^-1 at 1 A g^-1 and considerable performances even at -60 °C, while they can operate over 3000 cycles at 60 °C with 87% capacity retention. This attracting effect can be expanded to several other clay materials, all presenting improved ion transport capability, which paves a road for future aqueous batteries across extreme temperatures.