A physically cross-linked carboxymethyl cellulose/chitosan hydrogel electrolyte with high ionic conductivity for zinc-ion hybrid supercapacitors

The growing interest in zinc-ion hybrid supercapacitors (ZHSCs) has spurred research into hydrogel polymer electrolytes with high ionic conductivity and electrochemical stability. Leveraging the advantages of natural polymers, this study presents a carboxymethyl cellulose (CMC)/chitosan (CS) PECH synthesized via the semidissolution acidification sol-gel transition (SD-A-SGT) method. The presence of -COO- and -NH3+ groups within the PECH provides ion transport channels, enabling the formation of a CMC/CS-ZnSO4 (CCZ) hydrogel electrolyte with high ionic conductivity (110 mS cm- 1) and ion transference number (0.73) upon soaking in ZnSO4 solution. This CCZ electrolyte exhibits excellent polarization stability, a wide electrochemical stability window, and low corrosion current in zinc symmetric cells. ZHSCs utilizing the CCZ electrolyte demonstrate impressive cycling stability (retaining 84.8 % capacity after 10,000 cycles at a high current density of 10.0 A g- 1) and favorable energy density (186.88 Wh kg- 1 at 1.6 kW kg- 1). Furthermore, the electrolyte maintains its electrochemical stability in flexible ZHSC devices, showcasing its potential for flexible energy storage. This research contributes to the development of high-performance, durable polyelectrolyte composite hydrogel electrolytes for flexible ZHSC devices.