Tailoring Pure Inorganic Electrolyte for Aqueous Sodium‐Ion Batteries Operating at −60 °C

Abstract Aqueous sodium‐ion batteries (ASIBs) have attracted increasing attention for next‐generation energy storage technologies due to their abundant resources and environmentally‐safe, while their application scenarios are severely limited by the high freezing point of conventional aqueous electrolytes. To overcome the aforementioned issues of ASIBs, a novel hybrid 3.5 m Mg(ClO₄)₂+0.5 m NaClO₄ electrolyte (m: mol kg⁻¹) with an ultra‐low freezing point (<−80 °C) is proposed. The exceptional anti‐freezing feature is mainly attributed to the higher ionic potential of Mg²⁺, greatly affecting the chemical environment of water molecules and inhibiting ice formation under subzero conditions. Benefiting from the superiority of ionic conductivity (4.86 mS cm⁻¹) for the hybrid electrolyte at −60 °C, the full cell of active carbon||NaTi₂(PO₄)₃@C delivers an ultra‐long lifespan of 10000 cycles under 8 C (1 C=133 mA g⁻¹) at −60 °C. More importantly, some representative devices in daily life including smartphone and motor can be powered by ASIBs at −60 °C. Therefore, this work provides a rational and effective strategy for design and application of ASIBs with excellent electrochemical performance that can work in extremely cold environments.