Copper Sulfide (CuxS) Nanowire-in-Carbon Composites Formed from Direct Sulfurization of the Metal-Organic Framework HKUST-1 and Their Use as Li-Ion Battery Cathodes

Li-ion batteries containing cost-effective, environmentally benign cathode materials with high specific capacities are in critical demand to deliver the energy density requirements of electric vehicles and next-generation electronic devices. Here, the phase-controlled synthesis of copper sulfide (Cu_xS) composites by the temperature-controlled sulfurization of a prototypal Cu metal-organic framework (MOF), HKUST-1 is reported. The tunable formation of different Cu_xS phases within a carbon network represents a simple method for the production of effective composite cathode materials for Li-ion batteries. A direct link between the sulfurization temperature of the MOF and the resultant Cu_xS phase formed with more Cu-rich phases favored at higher temperatures is further shown. The Cu_xS/C samples are characterized through X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDX) in addition to testing as Li-ion cathodes. It is shown that the performance is dependent on both the Cu_xS phase and the crystal morphology with the Cu_1.8S/C-500 material as a nanowire composite exhibiting the best performance, showing a specific capacity of 220 mAh g⁻¹ after 200 charge/discharge cycles.