ZnZrF ₆ ‐Based Electrolytes are Used in High‐Stability Zinc‐Ion Capacitors

ABSTRACT This research proposes a low‐cost and efficient interfacial regulation strategy by introducing ZnZrF ₆ as an electrolyte additive in a ZnSO ₄ system to enhance aqueous zinc‐ion capacitor performance. During cycling, Zr ⁴⁺ participates in interfacial reactions on the Zn anode, forming a stable composite SEI layer rich in ZnF ₂ , which promotes uniform Zn ²⁺ deposition and suppresses dendrite growth. Meanwhile, F ⁻ reduces side reactions, inhibiting corrosion and hydrogen evolution, thus improving stability. The Zn symmetric cell operates stably over 2700 h, while Zn||Cu cells maintain over 99.9% coulombic efficiency. The assembled capacitors exhibit excellent cycling stability over 50 000 cycles, demonstrating high performance and practical potential.