High‐Performance Aqueous Na–Zn Hybrid Ion Battery Boosted by “Water‐In‐Gel” Electrolyte

Abstract Aqueous hybrid Na–Zn ion batteries (ASZIBs) are promising for large‐scale energy storage due to their low cost and potential for high output voltage. However, most ASZIBs show limited discharge voltage (<2.0 V) and capacity (<100 mAh g –1 ) due to inefficient usage of the dual ions. In this study, a novel large‐electrochemical‐window “water‐in‐gel” electrolyte based CuHCF‐CNT/Zn Na–Zn hybrid battery is proposed, which achieves a high extraction voltage of Na ion (2.1 V vs Zn/Zn 2+ ), together with a large discharge specific capacity (260 mAh g –1 ) thanks to the Zn‐ion insertion, delivering a superior energy density of 440 Wh kg –1 . The hybrid battery also shows a high capacity retention of 96.8% after 450 cycles. Moreover, an ultrahigh discharge capacity of 1250 mAh g –1 is achieved when further coupled with the Zn‐O 2 reaction, delivering the promising application of ion intercalation and metal–air hybrid battery.