Tungsten-doped polypyrrole/activated carbon asymmetric supercapacitor: design, fabrication, and performance evaluation

In this work, polypyrrole (PPy) electrodes with varying tungsten (W) doping levels were synthesized, and the energy storage performance of a W/PPy//AC asymmetric supercapacitor constructed by combining the optimal W/PPy electrode with an activated carbon (AC) electrode was systematically examined. All electrochemical measurements were carried out in 1 M Na₂SO₄ electrolyte, using a potential window of − 1 to 1 V for the three-electrode configuration and 0 to 1 V for the asymmetric device. The electrodes were thoroughly characterized to assess their structural and surface properties. Electrochemical testing showed that the 5% W-doped PPy electrode delivered the highest specific capacity of 1252.2 mF cm⁻². The corresponding W/PPy//AC asymmetric supercapacitor achieved a specific capacity of 104.4 mF cm⁻², with energy and power densities of 0.385 Wh kg⁻¹/0.0145 mWh cm − 2 and 6.77 W kg⁻¹/0.255 mW cm⁻², respectively. Remarkably, at a current density of 5 mA cm⁻², the device retained 98.0% of its initial capacitance after 20,000 GCD cycles, along with a Coulombic efficiency of 94.2%. The high cycling stability suggests that tungsten incorporation may help mitigate structural degradation during repeated charge–discharge processes.