Synthesis of Metal Organic Frameworks-Derived CoxNi3-x-S Electrode Materials from Recycled Spent Batteries and Their Application in Supercapacitors

Adjusting the composition and microstructure of multiphase nanocomposites is a promising way to increase the storage capacity of the electrode. In this work, cobalt ion leachate is recovered from the cathode material of spent lithium cobalt oxide batteries through molten salt-assisted calcination and water leaching process. Using the cobalt ion leachate as the precursor, spherical Co x Ni 3-x -MOF precursors are synthesized via a solvothermal method and subsequently carbonized and sulfurized in an Ar 2 atmosphere, yielding spherical core-shell structured Co x Ni 3-x -S bimetallic sulfides. Electrochemical tests indicate that this material exhibits excellent specific capacitance (1285 F/g) at a current density of 1 A/g, significantly outperforming traditional cobalt-nickel-based materials (such as NiCo 2 O 4 with ∼800 F/g). The enhanced performance is attributed to the increased specific surface area and active sites of the spherical core-shell structure, as well as the optimized electron transfer and redox reaction kinetics facilitated by the Co/Ni bimetallic synergy. The sulfidation treatment further improves conductivity and structural stability. Additionally, an asymmetric supercapacitor using Co x Ni 3-x -S as the cathode and corn-straw-derived activated carbon (CAC) as the anode achieves an energy density of 38.6 Wh/kg at a power density of 800 W/kg, demonstrating good cycling stability with 71% capacitance retention after 3000 cycles. These improvements are the result of the synergistic effects between the metal sulfides and the bimetallic cobalt-nickel components, as evidenced by electrochemical performance testing and Transmission Electron Microscopy (TEM). This highlights the potential of the spherical Co x Ni 3-x -S core-shell structured materials for use in high-performance supercapacitors.