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Page 4 of 17 Zhang et al. Soft Sci. 2026, 6, 16

Figure 1. Schematic diagram of the fabrication process of anodized SS flexible electrodes coated with ECR carbon film. SS: Stainless steel;
ECR: electron cyclotron resonance; EG: ethylene glycol; DC: direct current.

The gel electrolyte was used to assemble the all-solid-state flexible supercapacitor. A total of 2.1324 g of AM
and 0.0040 g of MBA were uniformly dispersed in 10 mL of DI water, followed by the addition of 0.0400 g of
KPS with continuous stirring. The mixture was shaped in a mold and then placed in an oven (Kaile
DZF6020, China) at 60 °C for 6 h to obtain the PAM gel. The as-fabricated gel was subsequently immersed in
1 M Na SO for 24 h to produce the PAM/Na SO gel electrolyte.
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Physicochemical characterization
A scanning electron microscope (SEM, Zeiss GeminiSEM 300, Germany), a transmission electron
microscope (TEM, Thermo Fisher Talos F200S G2, USA), and an energy dispersive X-ray spectrometer
(EDS, Zeiss GeminiSEM 300, Germany) were used to observe the surface morphology and element
distribution of the carbon film-coated nanoporous structure. X-ray diffraction (XRD, PANalytical
Empyrean, Netherlands) was employed to determine the crystal phases of the anodized SS sample under
Cu-Kα irradiation over a scan range of 20°-70°. The elemental compositions were analyzed using X-ray
photoelectron spectroscopy (XPS, Thermo Fisher K-Alpha, USA).

To avoid the influence of the SS substrate, a series of carbon films on silica wafer samples were deposited,
and their thicknesses were measured by a stylus profiler (Bruker DektakXT, USA), followed by the resistivity
obtained via a four-probe method (4Probes Tech RTS-8, China). The Raman spectra (Horiba LabRAM HR
Evolution, Japan) were analyzed under a 532 nm wavelength laser ranging from 1,000 to 3,500 cm .
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Electrochemical measurements
The electrochemical characterizations, including cyclic voltammetry (CV), galvanostatic charge-discharge
(GCD), electrochemical impedance spectroscopy (EIS), and cycling test, were performed on an
electrochemical workstation (Zahner IM6, Germany). The intrinsic capacitance of the electrode was studied
using a three-electrode system, where the as-fabricated electrodes served as the working electrode, a
platinum mesh as the counter electrode, a standard Ag/AgCl electrode as the reference electrode and 1 M
Na SO as the electrolyte. The electrochemical performance of the flexible supercapacitor was evaluated in a
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two-electrode system mentioned above. The specific capacitance (C), energy density (E), and power density
(P) were calculated using :
[19]
×
= (1)
Δ ×
1000 2
= × × Δ (2)
2 × 3600