Fig. 1. Single-wire resistances and line widths under different powers and scanning speeds. (a) Single-wire resistance; (b) line width

Fig. 2. Determination of sweeping line clearance. (a) SEM image of carbonized surface by single-line scanning; (b) SEM image of carbonized side by single-line scanning; (c) schematic of resistance measurement of carbide electrode; (d) structural diagram of interdigital electrode

Fig. 3. Preparation of LIG and LIG/RuO₂ electrodes. (a) Schematic of preparation of LIG electrode; (b) schematic of preparation of LIG/RuO₂ electrode; (c) PI film fixed on glass slide; (d) PI film with RuCl₃ sprayed on its surface; (e) interdigital electrode array; (f) formed interdigital electrode

Fig. 4. Micro-nano structure of electrode and EDS characterization. (a) SEM image of LIG/RuO₂ electrode surface; (b) porous structure inside LIG electrode; (c) micro-nano structure of LIG/RuO₂ electrode surface; (d) micro-nano structure inside LIG/RuO₂ electrode; (e) flocculent structure of LIG/RuO₂ electrode surface; (f) element content in flocculent structure

Fig. 5. EDS scanning results of LIG/RuO₂ electrode surface. (a) C element distribution; (b) N element distribution; (c) O element distribution; (d) Cl element distribution; (e) Ru element distribution; (f) atomic fraction of each element

Fig. 6. Raman and XPS characterization of electrodes. (a) Raman spectrum of LIG electrode; (b) XPS peak splitting curves of LIG/RuO₂ electrode

Fig. 7. Cyclic voltammetric curves of electrodes with different interdigital spacings at voltage sweeping speed of 10 mV/s. (a) Cyclic voltammetric curves of LIG electrodes; (b) cyclic voltammetric curves of LIG/RuO₂ electrodes

Fig. 8. Capacitance comparison of LIG electrode and LIG/RuO₂ electrode at voltage sweeping speed of 10 mV/s. (a) Capacitance comparison under different interdigital spacings; (b) comparison of cyclic voltammetric curves under 20 μm interdigital spacing

Fig. 9. Rate performance comparison of LIG electrode and LIG/RuO₂ electrode. (a) LIG electrode; (b) LIG/RuO₂ electrode

Fig. 10. Constant current charge-discharge curves and impedance spectrum of LIG/RuO₂ electrode. (a) Constant current charge-　discharge curves of LIG/RuO₂ electrode under different current densities; (b) impedance spectrum of LIG/RuO₂ electrode