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

Abstract 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 Cu 1.8 S@C and Cu 2‐ x Se@C. The materials exhibit excellent electrochemical performance with high specific capacities (504 mAh g –1 for Cu 1.8 S@C and 317 mAh g –1 for Cu 2‐ x Se@C at 0.1 A g –1 ) and long‐term cycling stability when used as anode materials in cells employing carbon‐coated Na 3 V 2 (PO 4 ) 3 (NVP/C) positive electrodes. The Cu 2‐ x Se@C||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 ≈99.9%. Moreover, the Cu 2‐ x Se@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 Cu 2‐ x Se@C) after 1800 cycles at 2 A g –1 and enabling high specific energy and power.