Biodegradable poly-ε-caprolactone based porous polymer electrolytes for high performance supercapacitors with carbon electrodes

Herein, we report porous polymers electrolytes (PPEs), composed of a biodegradable polymer poly-epsilon-capro-lactone (PCL), activated with organic liquid electrolyte (ethylene carbonate (EC)/propylene carbonate (PC)/ NaClO4) and an ionic liquid (IL)-incorporated electrolyte (1-ethyl-3-methylimidazolium trifluoromethane-sulfonate (EMITf)/Na-trifluoromethane sulfonate (NaTf). The porous polymeric membranes are prepared via a simple, one step immersion precipitation method, which provide channels for ionic transport. Morphological/ structural, thermal and electrochemical studies on PPEs exhibit excellent flexibility, good porosity (-80%), high (-90%) liquid electrolyte uptake and high room temperature ionic conductivity (1.8-1.9 x 10-3 Scm- 1) with wide electrochemical stability window (>5.0 V). Quasi-solid-state carbon supercapacitors/electrical double layer capacitors (EDLCs) are fabricated from symmetrical activated carbon (AC) electrodes (derived from a waste -biomass, sugarcane bagasse), separated by PPE-films. The supercapacitor based on IL-incorporated PPE ex-hibits higher specific capacitance (-170 F g-1) and specific energy (-34 Wh kg -1) compared to the device based on organic solvents-based PPEs (-130 F g-1 and-24 Wh kg -1, respectively). Substantial energy storage in supercapacitor is evident from the glow of LED (35-50 mW) for longer duration. The device demonstrates stable performance up to-10,000 charge-discharge cycles with-15% initial capacitance fading and-100% Coulombic efficiency.