Nanoporous Carbon/Cobalt Composite Derived from End-of-Life Lithium Cobalt Oxide-Type Lithium-Ion Batteries for Supercapacitor Applications

A simple, effective, and environment-friendly recycling process has been designed to recover cobalt as a nanoporous carbon/cobalt (NPC@Co) composite from the electrode black powder of spent lithium cobalt oxide-type (LiCoO2 cathode-based) lithium-ion batteries (LIBs). In this process, citric acid is used as a lixiviant to leach the cobalt and lithium into the aqueous solution. Furthermore, the dissolved cobalt was precipitated as a cobalt-based metal-organic framework (ZIF-67) at room temperature. Finally, as-recovered ZIF-67 was annealed at 700 degrees C for 8 h under a nitrogen atmosphere to synthesize the NPC@Co composite. The electrochemical behavior of the NPC@Co composite was also investigated in the 1 M H2SO4 electrolyte. This composite electrode delivers a specific capacitance of 160 F g-1 at a current density of 1 A g-1 within a potential window of 0-1 V. The NPC@ Co composite also showed good stability and retained approximately 83.76% of its initial capacity after 5000 continuous charge- discharge cycles.