Electrospun fibrous electrodes with tunable microstructure made of polyaniline/multi-walled carbon nanotube suspension for all-solid-state supercapacitors

Highlights: • Electrospun PANI/MWCNT fibrous electrodes for supercapacitor were prepared. • Microstructure of electrodes is tunable by changing the electrospin parameters. • Fiber-diameter dependence of the electrode performance was observed. • High performance and good stability of electrospun electrodes were obtained. - Abstract: Electrospinning technique was used to prepare high performance fibrous electrodes with tunable microstructure for all-solid-state electrochemical supercapacitor. Symmetrically sandwiched supercapacitors consisting of flexible electrospun polyaniline (PANI)/multi-walled carbon nanotube (MWCNT) electrodes and polyvinyl alcohol (PVA)/sulfuric acid (H₂SO₄) gel electrolyte were assembled. Tunable microstructure of the fibrous electrode was obtained by changing the electrospinning parameters including the collector–needle distance (CND) and the suspension flow rate (SFR). Results show that, higher CND combining with lower SFR can result in a smaller average diameter of the electrospun fibers and hence improve the electrode performance. When the CND changes from 80 to 140 mm, the average fiber diameter will decrease from 2.89 to 1.21 μm, and the specific surface area of the electrode can increase from 57 to 83 m²·g⁻¹. The corresponding specific capacitance of the electrospun electrode will therefore increase from 129.5 to 180 F·g⁻¹, leading to a synchronous improvement of the energy density of the supercapacitor from 18 to 25 Wh·kg⁻¹. On the other hand, the supercapacitors using fibrous electrodes in this work also show good rate capability and cycling stability. Using the electrode with an average fiber diameter of 1.21 μm, the specific capacitances can maintain 131 F·g⁻¹ at a current density of 4 A·g⁻¹, which is 73% of the specific capacitance of the same sample at a current density of 0.5 A·g⁻¹. And the specific capacitance of the electrode can retain 89% after 1500 charge/discharge cycles.