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In this work the metallic cobalt was electrodeposited on 430 steel in order to obtain a low electrical resistance film made to Co 3 O 4 . Pure cobalt was obtained by acidic dissolution of lithium cobalt oxide (LiCoO 2 ) present in exhausted Li-ion battery cathode. The electrodeposition was performed with a 96% efficiency at a potential of 1.50 V versus Ag/AgCl. The electrodeposited cobalt showed the face-centered cubic (23%) and hexagonal centered (77%) phases. After oxidation at 850°C for 1000 h in air, the cobalt layer was transformed into the Co 3 O 4 phase. On the other hand, a sample without cobalt showed the usual Cr 2 O 3 and FeCr 2 O 4 phases. After 1000 h at 850°C, in air the area specific resistance of the sample with the cobalt oxide layer was 0.038 X cm -2 , while it was 1.30 X cm -2 for the bare sample.

The supercapacitive behavior of the metallic cobalt recycled from Li-ion batteries has been studied in this work. The reversibility of both redox process (Co II /Co III ) and (Co III /Co IV ) in KOH 6 mol L -1 is very high and promising for capacitive applications in electrochemical devices. The specific capacitances calculated from cyclic voltammetry and electrochemical impedance spectroscopy show a good agreement, giving the value of 625 Fg -1 . The electrode morphology presents a high porosity, thus an electrical equivalent circuit composed of two parallel resistance and capacitance elements in series was proposed. The specific capacitance values calculated from charge/discharge curves at 0.23 and 2.3 mA/cm 2 are 601 and 384 Fg -1 , respectively. Thereby, it was observed that metallic cobalt recycled from ion-Li batteries is compatible with other supercapacitive materials. This shows that cobalt recycling from Li-ion batteries is economically and environmentally viable for application in supercapacitor devices.

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This paper aims to present the mechanism study of methylene blue (MB) discoloration using spent Li-ion battery cathode tape and hydrogen peroxide. The recycled cathode used in this work is composed of 72% of LiCoO 2 , 18% of carbon, and 10% of Al. The value found for surface area is 8.9 m 2 /g and the ZCP value occurs in pH = 2.95. Different from what is proposed in the literature, the most likely mechanism of methylene blue discoloration is the oxidation/delitiation of LiCoO 2 and the reduction of H 2 O 2 forming OH• . Thus, in this paper, an important and promising alternative for discoloration of textile industry dyes using spent Li-ion battery cathode is presented.