Enhancing the ionic conductivity and mechanical properties of zwitterionic polymer electrolytes by betaine-functionalized graphene oxide for high-performance and flexible supercapacitors

In this study, we demonstrate the betaine-functionalized graphene oxide (BFGO) as roles in reinforcement filler and dissociation enhancer, enhancing the mechanical properties and ionic conductivity of zwitterionic polymers electrolytes (ZPEs). BFGO was synthesized by grafting sulfobetaine methacrylate onto the graphene oxide via oxa-michael addition reaction. Then, BFGO-ZPs were prepared by random oxidative polymerization of equimolar Positive charged monomer (TMA) and negative charged monomer(AMPS) with PEGDA in aqueous dispersions of BFGO. BFGO-ZPE was simply prepared by 1 M Na₂SO_4(aq) intake. BFGO enables a high water content of 86.4 wt% and swelling ratio of 625% in BFGO-ZPEs which also showed excellent mechanical properties, including the compressive strength of 84.4 kPa, compressive strain of 67%, compressive modulus of 14.2 kPa, and toughness of 1.16 Jm^-3. In addition, BFGO-ZPEs possess ultra-high ionic conductivity of 107 mScm⁻¹ at 25 °C. Furthermore, the electrochemical performances of electrolytes were studied using carbon-based supercapacitors which were assembled with BFGO-ZPEs (SBGZ). Since BFGO-ZPEs possessed ultra-high ionic conductivity, SBGZ possessed the remarkable high energy density of 46.2 WhKg⁻¹ and high power density of 8.2 kWKg⁻¹. Notably, SBGZ also possess 100% capacitance retention after bending to 90°, being potential application in flexible supercapacitors.