HQ-doped redox-active gelatin hydrogel membrane electrolytes synthesized by chemical crosslinking of gelatin with glyoxal and glutaraldehyde for solid-state EDLCs
摘要
Hydrogels are widely used as quasi-solid electrolytes in electric double-layer capacitors (EDLCs), a kind of energy storage system. In order to synthesize gelatin hydrogel membrane electrolytes (GTHMEs), gelatin (GT) has been chemically crosslinked with glyoxal (GLY) and glutaraldehyde (GU) separately in an aqueous medium. Hydroquinone (HQ) was employed as a redox dopant in gelatin-based hydrogel membrane electrolytes crosslinked with GLY (GLY-GTHME-HQ) and GU (GU-GTHME-HQ), achieving ionic conductivities of 8.6 × 10−4 and 8.2 × 10−4 S cm−1, respectively. The low HQ concentration (0.1 M) was optimized to prevent crystallization observed at higher concentrations in previous studies. EDLCs employing Black Pearls carbon (BPC) as electrode and quasi-solid electrolytes GLY-GTHME-HQ (BPC//GLY-GTHME-HQ//BPC) as well as GU-GTHME-HQ (BPC//GU-GTHME-HQ//BPC) were assembled. Specific capacitances of 11.16 and 15.02 F g−1, respectively, have been observed in BPC//GLY-GTHME-HQ//BPC and BPC//GU-GTHME-HQ//BPC at 5 mVs−1, which is closely in agreement with specific capacitance calculated from GCD at 1 mAcm−2, i.e., 9.27 and 12.24 F g−1 for BPC//GLY-GTHME-HQ//BPC and BPC//GU-GTHME-HQ//BPC, respectively. Cell resistances of 1.22 and 0.86 Ω have been observed in BPC//GLY-GTHME-HQ//BPC and BPC//GU-GTHME-HQ//BPC, respectively. Energy densities of 1.28 and 1.7 Whkg−1 have been observed for BPC//GLY-GTHME-HQ//BPC and BPC//GU-GTHME-HQ//BPC, respectively. BPC//GLY-GTHME-HQ//BPC and BPC//GU-GTHME-HQ//BPC have demonstrated 4000 and 7000 charge–discharge cycles, respectively, in cycle life tests conducted at 1 mA cm−2. A 1-V LED bulb has been powered for 50 s using a prototype device made up of five numbers of BPC//GU-GTHME-HQ//BPC coupled in series.
Graphical Abstract