A study of the electrochemical behaviour of electrodes in operating solid-state supercapacitors

The electrochemical behaviour of electrodes and of complete solid-state supercapacitors has been studied by cyclic voltammetry (CV) andgalvanostatic charge/discharge (CD) measurements using two independent electrochemical equipments. The first one controlled the execution ofthe test and recorded the voltage and current values of the complete supercapacitor while the other one recorded the potential changes of the singleelectrodes. In this work, two different types of capacitors were studied: (a) a symmetric supercapacitor using carbon electrodes, and (b) a hybrid(asymmetric) supercapacitor with ruthenium oxide/carbon in the positive electrode and carbon in the negative electrode. The studies evidenced thatin the symmetric capacitors the positive electrode controlled the capacitive performance and an optimal mass ratio from 1.2:1 to 1.3:1 between thepositive and the negative electrodeswas found in the investigated conditions. For the hybrid supercapacitor itwas observed that the ruthenium-basedpositive electrode influenced the capacitive performance of carbon-based negative electrode and that an accurate balance of carbon loading in thenegative electrode was necessary.