Recovery of cobalt as CoS from spent Li-ion batteries and investigation of its use as an electrode material for supercapacitors

Abstract

It is a reality that the world's growing energy resource consumption will increase the demand for materials made through recycling. The present study focuses on the production of new materials by recycling. The cathode of a discarded commercial Li-ion battery (LiCoO₂) was used to produce a CoS-based supercapacitor electrode material. The leaching of LiCoO₂ was done using 0.1 M H₂SO₄ aided by 1.0 M H₂O₂ at room temperature. After leaching, CoS was precipitated by the addition of Na₂S. For the first time, the precipitation of Co²⁺ ions leached from the cathode material was accomplished utilizing Na₂S as a sulfur source at room temperature and CoS was then used as an electrode material in a coin cell-type supercapacitor. The morphology and properties of the produced CoS were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and Mastersizer analyses. The electrode used in the supercapacitor was formed by combining CoS, carbon black, and polyvinylidene fluoride (PVDF) as the binder in varying compositions. The active materials were coated on the graphite foil and an asymmetric-type supercapacitor device was produced using 2 M KOH as the electrolyte. Using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques, the electrochemical performances of supercapacitors were evaluated. In cyclic voltammetric analyses, the maximum potential range for supercapacitors was determined as −1.0 V to 1.0 V. The cycling performance of the supercapacitors was measured by CV analyses for 1000 cycles at 200 mV s⁻¹. The highest specific capacitance was obtained from the C80 electrode as 70.5 F g⁻¹ at a 1 A g⁻¹ charge/discharge current density.