Porous carbon thin films for electrochemical capacitors

• Published in: Carbon (New York) 2013-11, Vol.64, p.456-463
• Main Authors: Laušević, Zoran, Apel, Pavel Yu, Krstić, Jugoslav B., Blonskaya, Irina V.
• Format: Article
• Language: English
• Subjects: Activation; Capacitance; Carbon; Finishes; Polyimide resins; Solvents; Surface layer; Texture; Thin films
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2013.07.098

Activation effects on carbon films, derived from commercial aromatic polyimide films (Kapton, DuPont), in CO2 atmosphere at 1203K on capacitance properties were studied. Two thicknesses of polyimide films were used: 7 and 25μm. Pore formation during the activation process progresses in two steps due to the existence of a denser surface layer and a more porous core material. In the first step micropores are opening in the dense surface region of the material with average pore diameter smaller than 1nm. During the second step, mesopores start opening, while micropore volume remains constant with the average micropore diameter of over 1nm, producing bimodal texture. The first step finishes after 30min for the thinner samples while for the thicker samples it finishes after 60min of activation. As a consequence of such textural changes during activation, the thicker sample has a maximum areal capacitance of 0.35F/cm2. The thinner sample activated for 30min has a maximum volumetric capacitance of 220F/cm3 and achieves a maximum gravimetric capacitance of 240F/g when the texture becomes bimodal after 240min of activation. These results confirm that activation of carbonized Kapton films gives promising electrode materials for supercapacitors.