Achieving high-performance parameters in NASICON-polymer composite electrolyte-based solid-state supercapacitors by interface modification†

The present study reveals a strategy to enhance the performance of solid-state supercapacitors based on activated carbon electrodes and a Na₃Zr₂Si₂PO₁₂ (NZSP) dispersed fast ionic solid polymer electrolyte membrane. The electrode–electrolyte interface is optimized using a novel ‘solvent layer’ approach to enhance supercapacitor performance. By adding a small amount of acetonitrile organic solvent (a few μL cm⁻²) at the electrode–electrolyte interface and utilizing high surface area (1800 m² g⁻¹) activated carbon, significant improvements in specific capacitance, specific energy, specific power, and cycling stability are achieved. Device performance at various operating voltages and discharge currents reveals interesting results. A specific capacitance of approximately 260 F g⁻¹ and a high specific power of 4780 W kg⁻¹ is achieved at 3 V/5 mA. Moreover, after 10 000 galvanostatic charge–discharge cycles (1 V/1 mA), the supercapacitor exhibits ∼99% stable coulombic efficiency along with appreciably high capacitance retention (∼90%). A stack of five such cells can power an 8 V LED circuit for more than 30 minutes. Applying such a solvent layer enables effective use of the surface area of the activated carbon. Results suggest that solvent incorporation enables a local ‘gel-like’ layer formation that couples the electrode with a solid polymer electrolyte and facilitates faster charge movement across the electrode–electrolyte interface.