UV-crosslinked glyoxal-methacrylate electrolytes for quasi-solid electric double layer capacitors

Abstract

In this paper, the difunctional oligomer bisphenol A ethoxylate dimethacrylate (BEMA), known for readily undergo UV-induced polymerisation, is employed to produce a highly crosslinked polymer network, in combination with poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) as a reactive diluent. The methacrylate-based membranes are soaked with a low-volatile glyoxal-based electrolyte, namely 1 M sodium bis(trifluoromethanesulfonil)imide (NaTFSI) in a 3:7 mixture of tetraethoxyglyoxal (TEG) and propylene carbonate (PC), respectively. The resulting gel polymer electrolytes are successfully employed for the fabrication of laboratory-scale quasi-solid electric double layer capacitors (EDLCs), showing sufficient thermal stability, high ionic conductivity at different temperatures, suitable electrochemical stability window and stable prolonged constant-current cycling (high capacitance up to 21 F g⁻¹ at 0.2 A g⁻¹ with excellent efficiency for thousands of cycles and >85 % of capacitance retention after a rate capability test and 9500 reversible cycles), thus paving the way for further detailed studies and optimizations.