METAL-CARBON COMPOSITE ELECTRODES FROM FIBER PRECURSORS .2. ELECTROCHEMICAL CHARACTERIZATION OF STAINLESS STEEL-CARBON STRUCTURES

In this study, the capacitances of stainless steel-carbon composite electrodes in 1.0M Na2SO4 were determined as a function of stainless steel loading, sintering temperature, and sintering time (i.e., 0.1–0.5g of stainless steel fiber/1g of carbon fiber, 1323–1423 K, and 2.5–152 min, respectively). Kinetic parameters were determined for stainless steel sintering and catalytic carbon gasification by weight loss measurements and capacitance changes using ac impedance, single potential step methods, and cyclic voltammetry. Apparent activation energies for carbon gasification and sintering were found to be 80 and 200 kJ/mol, respectively. Measured reaction rates and kinetic parameters were used to verify the importance of stainless steel-carbon contacts toward overall electrode capacitance and to successfully predict a maximum capacitance of 45.3 F/g on a total electrode weight basis. This capacitance value yields energy densities of ca. 90 kJ/kg of electrode and does not require pressure for good electrical contact as do electrodes prepared from carbon powders. Capacitance and kinetic measurements demonstrate the ability to control conductivity and active surface area by adjusting: stainless steel to carbon loading, sintering temperature, and sintering time. © 1990, The Electrochemical Society, Inc. All rights reserved.