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_1.8S@C and Cu_2‐xSe@C. The materials exhibit excellent electrochemical performance with high specific capacities (504 mAh g^–1 for Cu_1.8S@C and 317 mAh g^–1 for Cu_2‐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 Cu_2‐xSe@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‐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 Cu_2‐xSe@C) after 1800 cycles at 2 A g^–1 and enabling high specific energy and power.