Electrodeposited cobalt hydroxide in expanded carbon graphite electrode obtained from exhausted batteries applied as energy storage device

This paper describes the preparation and characterization of CG/Co(OH)2 electrode obtained by electrodeposition of cobalt hydroxide on expanded carbon graphite electrode (CG) for potential application as energy storage devices. The CG electrodes used in this work were obtained from exhausted batteries. Firstly, the CG electrode was submitted to an anodic polarization at 2 V in H2SO4 solution, in order to increase the active surface area at different times. Thereafter, the electrodeposition of the Co(OH)2 was carried out by applying different reduction potentials over different times in order to optimize the electrodeposition process. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy results confirmed the expansion of the bare CG and the Co(OH)2 electrodeposition. Cyclic voltammetry, galvanostatic charge/discharge curves and electrochemical impedance spectroscopy were used to evaluate the electrochemical performance of the modified electrode. It was observed that the parameters of the modification process affect the morphology of the electrodeposited cobalt hydroxide. The best performance was found for the CG/Co(OH)2 modified electrode obtained by CG expanded during 750 s, followed by the electrodeposition conditions of −1.25 V during 250 s, presenting a capacitiy of 3.4 C cm−2 in an applied current density of 1.0 mA cm−2. In addition, this modified electrode also presented a retention capacity of 91% after 1400 cycles. Keywords: Carbon graphite, Cobalt hydroxide, Energy storage device