Co₃ZnC@NC Material Derived from ZIF-8 for Lithium-Ion Capacitors

Abstract

Metal-organic framework (MOF)-derived carbon materials were widely reported as the anodes of lithium-ion capacitors (LICs). However, tunning the structure and electrochemical performance of the MOF-derived carbon materials is still challenging. Herein, metal carbide materials of Co₃ZnC@NC-8:2 were obtained by the pyrolysis of the MOF materials of Co_0.2Zn_0.8ZIF-8 (Zn/Co ratio of 8:2). A half-cell assembled with the Co₃ZnC@NC-8:2 electrode exhibits a discharge capacity of the electrode material of 598 mAh g^-1 at a current density of 0.1 A g^-1. After 100 cycles, the retention rate of discharge specific capacity is about 90%. The high performance of Co₃ZnC@NC-8:2 is ascribed to its high crystalline degree and well-defined structure, which facilitates the intercalation/deintercalation of lithium ions and buffers the volume change during the charge/discharge process. The high capacitance contribution ratio calculated by cyclic voltammetry (CV) curves at different scanning rates indicates the pseudocapacitance storage mechanism. LICs constructed from the Co₃ZnC@NC-8:2 material have a rectangular CV curve, while the charge-discharge curve has a symmetrical triangular shape. This study indicates that MOF-derived carbon is one of the promising materials for high-performance LICs.