Metal-Organic Framework Derived Copper Chalcogenides-Carbon Composites as High-Rate and Stable Storage Materials for Na Ions

Transition metal chalcogenides have been regarded as promising storage materials for sodium ions owing to their high theoretical capacity. Herein, copper-based metal-organic frameworks (Cu-BTC) are reported as precursors to fabrica copper chalcogenides-carbon composites, namely Cu1.8S@C and Cu2-xSe@C. The materials exhibit excellent electrochemical performance with high specific capacities (504 mAh g(-1) for Cu1.8S@C and 317 mAh g(-1) for Cu2-xSe@C at 0.1 A g(-1)) and long-term cycling stability when used as anode materials in cells employing carbon-coated Na3V2(PO4)(3) (NVP/C) positive electrodes. The Cu2-xSe@C parallel to NVP/C cell delivers a specific capacity of 73 mAh g(-1) at 1.2 A g(-1) (based on cathode mass) and excellent cycling stability (capacity retention of 85% after 500 cycles at 0.12 A g(-1)) with Coulombic efficiency of approximate to 99.9%. Moreover, the Cu2-xSe@C composite performs well as positive electrode storage material in a sodium-metal cell, offering a high reversible capacity of 216 mAh (per gram of Cu2-xSe@C) after 1800 cycles at 2 A g(-1) and enabling high specific energy and power.

Automated summary

Copper-based metal-organic frameworks are used as precursors to fabricate copper chalcogenides-carbon composites. These composites exhibit excellent electrochemical performance and long-term cycling stability when used as anode materials in cells with carbon-coated positive electrodes. They also show promising results as positive electrode storage materials in sodium-metal cells.