Application of additive-free, ultra-stable polyimide-derived porous carbon with controllable structure in flexible supercapacitors

Polymer-derived nitrogen-doped porous carbon networks display stable electrochemical properties and have been extensively studied as electrode materials. However, the precise control of pore morphology and size distribution remains challenging. Herein, the pore structure of polyimide membranes was initially established by controlling the coating thickness. Subsequent to carbonization, the pore morphology and surface area were further controlled. The resulting optimized porous carbon exhibits a uniform pore distribution, a large specific surface area, and appropriate heteroatom content. In a three-electrode system, it achieves a specific capacitance of 328.4 F g⁻¹ at 0.5 A g⁻¹. Additionally, the symmetric supercapacitor delivers an impressive energy density of 20.3 Wh kg⁻¹ at 350 W kg⁻¹ in a 6 M KOH electrolyte, retaining 88.5 % of its specific capacity after 5000 cycles. Notably, the specific capacitance of a flexible solid-state device is 151.6 mF cm⁻² at 2 mA cm⁻². This work introduces a simple, environmentally friendly approach for producing porous carbon from polyimide with adjustable morphology.