Solvent-free synthesis of zwitterionic gel electrolytes using 2-methacryloyloxyethyl phosphorylcholine for solid-state supercapacitors

We report a zwitterionic gel polymer electrolyte (GPE) synthesized via a solvent-free UV crosslinking process using 2-methacryloyloxyethyl phosphorylcholine (MPC), poly(ethylene glycol) diacrylate (PEGDA) and ionic liquid (EMIMTFSI). The incorporation of zwitterionic MPC unit into the PEGDA network enhances ionic dissociation and promotes a conformal interface with the porous carbon electrodes. This intimate electrode–electrolyte contact promotes the effective utilization of the electrode surface, leading to a higher initial capacitance. Moreover, the zwitterionic framework maintains mechanical compliance and interfacial stability during repeated cycling, thereby suppressing the growth of internal resistance and mitigating IR drop. As a result, the GPE-MPC system enables stable charge transport with minimal degradation under long-term operation. These findings highlight the potential of zwitterion-functionalized polymer electrolytes as a robust strategy for enhancing both the initial electrochemical performance and cycling stability of solid-state supercapacitors.