High performance electrospun Li + -functionalized sulfonated poly(ether ether ketone)/PVA based nanocomposite gel polymer electrolyte for solid-state electric double layer capacitors.

The synthesis of a nanocomposite gel polymer electrolytes (NGPEs) using Li ⁺ -functionalized SPEEK (SPEEK(Li)) nanofiber membrane as a matrix, cross-linked PVA as a gelled agent and LiClO ₄ as an electrolytic salt for electric double layer capacitors (EDLCs) were reported in this work. Compared with conventional PVA based gel electrolyte, the "SO ₃ ^- Li ⁺ " functional groups and the pores structure of the SPEEK(Li) nanofiber membrane improves the ionic conductivity as well as mechanical stability, which made the prepared NGPEs exhibited a high ionic conductivity of 8.9 × 10 ^-3  S cm ^-1 at ambient temperature and a large voltage stability window range from 0 to 2.0 V. The fabricated symmetric EDLCs showed a specific capacitance of 146.96 F g ^-1 at a current density of 0.5 A g ^-1 , with a maximum energy density of 18.26 W h kg ^-1 . Meanwhile, the EDLCs showed outstanding cyclical stability of 98% specific capacitance retention after 3000 cycles GCD testing, all of these results indicated that the NGPEs should be appropriate to EDLCs and next-generation energy storage systems.
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