Surface Characterization of Supercapacitor Electrodes after Long-Lasting Constant Current Tests

Abstract

TOF-SIMS, FIB-SEM, XPS and electrochemical methods have been used for the characterization of physical properties and chemical composition of microporous carbide derived carbon electrodes, prepared from TiC at 950 ºC (noted as TiC-CDC) after 40000 charge/discharge cycles. Some changes in surface chemical composition of TiC-CDC electrodes and Al current collectors has been established including partial dissolution of Al from positively charged electrode and deposition of Al onto the negatively charged TiC-CDC electrode surface. The values of gravimetric energy (taking into consideration the active TiC-CDC material weight only) calculated before and after constant current charge/discharge cycling tests at cell voltage 3.4 V were quite similar (35 and 34 W h kg-1, respectively). At starting moment the gravimetric power was practically 1.4 times higher (195 kW kg-1, 146 kW dm-3) than that calculated after 40000 charge/discharge cycles (144 kW kg-1, 104 kW dm-3). The characteristic relaxation time constant (0.94 and 1.23 s, respectively) increases somewhat in accordance with the decrease of power density during long-lasting cycling at higher cell voltage range from 0.2 to 3.4 V.