Carboxymethyl chitosan doped hydrogel electrolyte with wide temperature domain for high performance flexible supercapacitor

The flexible energy storage devices are more challenging because they not only need to perform well in terms of electrochemical properties, but also need to exhibit wide temperature domain and good mechanical properties. Herein, we prepare a novel wide temperature flexible polyacrylamide (PAM)/carboxymethyl chitosan (CMCS)/polyethylene glycol (PEG)‑sulfuric acid (H2SO4) hydrogel electrolyte (PAM/CMCS/PEG-H2SO4) by one-step free radical polymerization method using PAM as the polymer matrix, CMCS as blend material and PEG as functional additive. Among them, CMCS contains numerous -OH and -NH2 groups, which can cross-link PAM and PEG to form network and bond with water molecules, making the hydrogel has excellent performance. The optimized PAM/CMCS/PEG-H2SO4 hydrogel has a tensile strain about 800 % and high conductivity in the temperature ranges from −10 to 90 °C. The flexible supercapacitor assembled with commercial AC as electrode, PAM/CMCS/PEG-H2SO4 hydrogel as electrolyte exhibits good cycle life with capacitance retention rate of 83.3 % after 5000 charge/discharge cycles. In addition, the device exhibits excellent electrochemical performance under wide temperature domain and various bending angles. •A novel wide temperature gel electrolyte is prepared by one-s`tep free radical polymerization.•The gel exhibits 800 % tensile strain and high conductivity in temperature range from −10 to 90 °C.•A flexible supercapacitor device assembled with the gel has high capacitance and energy density.•The device has 83.3 % capacitance retention rate after 5000 charge/discharge cycles.•The device possesses 90 % excellent capacitance retention when bending in the range of 0° ~ 180°.