Preparation of electric double layer capacitors (EDLCs) from two types of electrospun lignin fibers

Electrodes has been prepared for application in an electric double layer capacitor (EDLC) based on polyethylene glycol lignin (PEGL) and soda lignin (SL) derived from cedar wood. Fibers with a diameter of 23 mu m were prepared by direct melt electrospinning of PEGL. Much finer fibers of 3.6 mu m diameter were obtained by dry electrospinning of 70% PEGL in a dimethyl formamide (DMF) solution at 145 degrees C. The dry electrospinning of SL alone in an alkaline aqueous solution was not achievable, but this was possible of a mixture of SL and polyethylene glycol (M-w = 500 000) at a ratio of 99/1, which resulted in thin SL fibers with a diameter of 0.85 mu m. These fibers were converted into activated carbon fibers (ACFs) by thermostabilization, carbonization, and steam activation. The specific Brunauer, Emmett and Teller (BET) surface areas of the resulting PEGL-ACFs and SL-ACFs were 1880 m(2) g(-1) and 1411 m(2) g(-1), respectively. PEGL-ACFs electrodes with an organic electrolyte exhibited an impedance of 1.6 Omega and a specific capacitance of 92.6 F g(-1) at a scan rate of 1 A g(-1), and the SL-ACFs electrodes had an impedance and specific capacitance of 4.5 Omega and 55.6 F g(-1), respectively.