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

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/Zn²⁺), 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-O₂ reaction, delivering the promising application of ion intercalation and metal–air hybrid battery.