Synergistic Stabilization of Zinc Anode by Additives and In Situ Gel Electrolyte for High‐Performance Zinc‐Ion Capacitors

Featured by inherent advantages of low cost and high safety, zinc‐ion energy storage devices have emerged as a pivotal focus in the field of energy storage research. However, their large‐scale application is hindered by critical challenges: the instability of zinc anodes, which are plagued by dendritic growth and severe detrimental interfacial side reactions. In this study, by utilizing the inherent reducibility of the Zn anode and adding sodium carboxymethyl cellulose (CMC‐Na) as an electrolyte additive, we have prepared in situ cross‐linked CMC‐Na/polyacrylamide (PAM) hydrogel electrolytes to improve the stability of the Zn anode. The proposed synergistic optimization strategy effectively suppresses interfacial side reactions triggered by active water molecules. Moreover, this dual‐strategy intervention mitigates anode corrosion and dendrite growth through cooperative regulatory mechanisms. Consequently, the symmetric cells assembled with the in situ‐formed hydrogel electrolyte deliver stable cycling performance for 1000 h at a current density of 1 mA cm −2 . For the hybrid capacitor integrated with the CMC‐Na/PAM hydrogel electrolyte, it maintains efficient operation over 10,000 cycles even at a high current density of 10 mA cm −2 . This study demonstrates the superior efficacy of the integrated dual optimization strategies, offering a practical pathway for the advancement of high‐performance zinc‐ion hybrid capacitors.