A flexible polyelectrolyte-based gel polymer electrolyte for high-performance all-solid-state supercapacitor application

Abstract

A simple polymerization process assisted with UV light for preparing a novel flexible polyelectrolyte-based gel polymer electrolyte (PGPE) is reported. Due to the existence of charged groups in the polyelectrolyte matrix, the PGPE exhibits favorable mechanical strength and excellent ionic conductivity (66.8 mS cm^-1 at 25 °C). In addition, the all-solid-state supercapacitor fabricated with a PGPE membrane and activated carbon electrodes shows outstanding electrochemical performance. The specific capacitance of the PGPE supercapacitor is 64.92 F g^-1 at 1 A g^-1, and the device shows a maximum energy density of 13.26 W h kg^-1 and a maximum power density of 2.26 kW kg^-1. After 10 000 cycles at a current density of 2 A g^-1, the all-solid-state supercapacitor with PGPE reveals a capacitance retention of 94.63%. Furthermore, the specific capacitance and charge-discharge behaviors of the flexible PGPE device hardly change with the bending states.

Scheme 1. Synthesis of the PGPE matrix.

Fig. 1. (a) FT-IR spectra of the reactants (DMAEMA and C₃H₇Br) and the product C₃(Br)DMAEMA. (b) ¹³C NMR spectrum of the product C₃(Br)DMAEMA. Characters 1–11 represent the C atom with different chemical shifts. (c) ¹H NMR spectrum of the product C₃(Br)DMAEMA. Characters (a–j) represent the H atom with different chemical shifts.

Fig. 2. (a) Photograph image of the PGPE with a thickness of about 500 μm. Typical SEM image of (b–d) PGPE matrix with various magnification, (e) interface between the AC electrode and PGPE, and (f) the electrode-PDPA interface. (g) Element mapping image of the surface of the PGPE.

Fig. 3. (a) FT-IR spectra of the monomers (PEGMA and C₃(Br)DMAEMA) and the PGPE matrix. (b) XRD patterns of PGPE matrix and PGPE film. (c) TGA thermograms of PDPA matrix, PDPA, PGPE, PGPE matrix and 1 M Li₂SO₄/H₂O solution. (d) Typical stress–stain curves of GPE with different monomer ratios (immersing in 1 M Li₂SO₄/H₂O solution).

Fig. 4. (a) Nyquist plots of PGPE and PDPA (inset shows the high-frequency region of the Nyquist plot) at 25 °C. (b) Temperature impendence of the ionic conductivity (ln σ vs. 1000/T) of PGPE and PDPA. Solid lines represent fitting results.

Fig. 5. (a) CV curves of PGPE supercapacitor at different scan rates from 10 to 200 mV s⁻¹, (b) GCD curves at different current densities from 0.5 to 10 A g⁻¹ in the voltage range of 0–1.2 V. Comparison of CV measurement for PGPE and PDPA supercapacitors at the scan rates of (c) 20 and (d) 200 mV s⁻¹.

Fig. 6. Comparison of electrochemical performance of supercapacitors: (a) Nyquist plots of supercapacitors with a frequency range of 1 Hz to 1 MHz (inset shows the high-frequency region of the Nyquist plot), (b) GCD curves at 1 A g⁻¹, (c) IR drop at different current densities from 0.5 to 10 A g⁻¹, (d) specific capacitance of supercapacitors at different current densities, (e) Ragone plots and (f) capacitance retention at a current density of 2 A g⁻¹.

Fig. 7. (a) CV and (b) GCD curves of the flexible PGPE supercapacitors at a scan rate of 20 mV s⁻¹ and a current density of 1 A g⁻¹ under various flexible deformation states, (c) photograph image of a LED powered by a 2.4 V device (two 1.2 V PGPE supercapacitor devices connected in series), (d) photographs of the flexible PGPE device at different bending states.