High-performance solid-state bendable supercapacitors based on PEGBEM-g-PAEMA graft copolymer electrolyte

We report a solid electrolyte comprising poly(ethylene glycol) behenyl ether methacrylate-g-poly((2-acetoacetoxy)ethyl methacrylate) (PEGBEM-g-PAEMA) graft copolymer for application to solid-state bendable supercapacitors. The graft copolymer was synthesized via free-radical polymerization, and the electrolytes were fabricated by adding 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄). Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, small-angle X-ray scattering, and transmission electron microscopy were employed to investigate the chemical, structural, thermal, and morphological properties of the fabricated electrolytes and the compatibility of the two components. The graft copolymer interacted with EMIMBF₄ (the two materials were compatible with each other), and the intruded ionic liquid was well-dispersed through the entire region of the polymer matrix. The fabricated electrolyte maintained its flexible solid film state for EMIMBF₄ content up to 200% without leakage problems. The capacitors were manufactured with porous carbon electrodes and a PEGBEM-g-PAEMA/EMIMBF₄ electrolyte. The capacitors exhibited a capacitance of 55.5F/g, a power density of 900 W/kg, and an energy density of 25 Wh/kg at 1.0 A/g. The capacitors were measured at various bending angles and exhibited good performance without specific encapsulation. According to the results, the newly synthesized PEGBEM-g-PAEMA graft copolymer is a good candidate for a polymer matrix for electrolytes in all-solid-state bendable/flexible supercapacitors.