With the advantages of low cost, safety and environment-friendly, aqueous zinc ion batteries (AZIBs) show promising in the field of large scale energy storage and smart wearables. In addition, with the expansion of the field of flexible electronics, the huge demand potential of wearable smart electronic devices is increasingly highlighted, which puts forward higher requirements for the structural stability and electrochemical stability of energy storage devices and device safety in the process of physical deformation. AZIBs based on aqueous electrolytes are prone to interface separation during bending, which affects battery stability and makes it difficult to achieve further practical applications of flexible electronics. Compared to aqueous electrolytes, hydrogel electrolyte is flexible and foldable, guaranteeing the structural and performance stability of flexible energy storage devices under the action of external forces. In particular, polyacrylamide-based (PAM) hydrogel is preferred materials for preparing hydrogel electrolytes because of the advantages of better ionic conductivity, strain and stability. In this work, montmorillonite-polyacrylamide hydrogel (MMT-PAM) electrolytes with the three-dimensional network structure were synthesized by a two-step process using two-dimensional layered montmorillonite and acrylamide monomer. The addition of montmorillonite provides adsorption sites for in-situ polymerization of acrylamide monomer to improve the mechanical properties of the hydrogel, and facilitates the rapid transport of Zn2+ through the abundant negative charge on the surface of MMT, increasing its ionic conductivity (34 mS·cm-1 at room temperature is much higher than the 17 mS·cm-1 of PAM hydrogel electrolyte) to give MMT-PAM hydrogel electrolytes better electrochemical properties. Zn-MnO2 batteries based on MMT-PAM hydrogel electrolytes provided a specific capacity of 289 mAh·g-1 at the current density of 0.2 A·g-1 and could be stably cycled for 2000 cycles, while Zn-MnO2 batteries prepared based on PAM hydrogel electrolytes only cycled for hundreds of cycles at the same current density before short circuiting, thus exhibiting the long battery cycle life of the Zn-MnO2 batteries prepared by MMT-PAM hydrogel electrolytes. It maintained a high specific capacity even at a high current density of 4 A·g-1. Furthermore, the flexible batteries prepared using MMT-PAM hydrogel as electrolytes could still work properly under different external conditions of impact such as cutting and piercing. The prepared flexible batteries were folded and immersed in aqueous solution to provide stable voltage and excellent water resistance, exhibiting its application feasibility in the field of flexible electronics. Therefore, it is reasonable to believe that this work promotes the possibility of further application of hydrogel electrolytes in aqueous Zn-MnO2 batteries, and promotes the further development of flexible energy storage devices based on hydrogel electrolytes.
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