Fabrication of a PPy composite with EMD nanorods recovered from Li-ion batteries for supercapacitor

Abstract

Polypyrrole/electrolytic manganese dioxide (PPy/EMD) composite is fabricated electrochemically on a stainless-steel mesh (SSM) surface in acetonitrile containing EMD nanorods and pyrrole monomer as a supercapacitor anode electrode material. EMD is recovered with an efficiency of 96.2% from a methanesulfonic acid leached solution of spent Li-ion batteries using an iridium-tantalum-coated titanium anode. The composite-coated electrode is characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) by comparison with those of its components: the electrode with a mass loading of 10 mg.cm^-2 has the highest specific capacitance (72 F g^-1) and pseudocapacitive contribution (95% at 50 mV s^-1) and the lowest resistance (1.85 Ω cm²). Spectroscopic studies of the composite coating are carried out using energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), while the morphological and structural analyses are performed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). EMD nanoparticles with ε-MnO₂ and oxygen-deficient structure are homogeneously distributed in the composite at 8.4 wt% and encapsulated within the growing PPy clusters. Thus, due to the pseudocapacitive behavior, EMD recovered from batteries contributes significantly to the capacitance of the composite. PPy/EMD- and C- coated electrodes are combined in polyvinyl alcohol/Li₂SO₄ gel electrolyte to construct an asymmetric supercapacitor cell: it has a 23.2 Wh.kg^-1 energy density and a 0.31 kW.kg^-1 power density at 0.50 A.g^-1 from the galvanostatic charge-discharge (GCD) test. After 5000 cycles, cycle life is 74.0% with a coulombic efficiency of 77.7%.