N-doped ZnC composites with gelatin coating as enhanced lithium-storage anode materials

Abstract

Zeolitic imidazolate framework-8 (ZIF-8) is composed of Zn2+ ions chelated with four imidazolate rings, and its derivatives are actively investigated as promising anode materials for lithium-ion batteries (LIBs). Herein, ZIF-8 with a decahedral structure was coated with gelatin matrix possessing abundant carbon and nitrogen atoms (so-called ZIF-8@gelatin). The calcined ZIF-8 (N-ZnC) and ZIF-8@gelatin (N-ZnC@gelatin) at 700 degrees C under N-2 flow exhibited the characteristic diffraction patterns of nitrogen-doped graphitic carbons. A simple gelatin coating improved the electrochemical performance of ZIF-8-based anode materials. When compared with gelatin-free analogue (N-ZnC), N-ZnC@gelatin exhibited the enhanced thermal stability, high surface area, and improved electrical conductivity. At a current density of 0.1 Ag-1 after 100 cycles, N-ZnC@gelatin delivered a high reversible capacity of 600 mAhg(-1), whereas N-ZnC exhibited a relatively low capacity of 450 mAhg(-1). At a high current density of 1.0 Ag-1, N-ZnC@gelatin maintained a high reversible capacity of 400 mAhg(-1) even after 450 cycles, because of the enhanced structural stability and electrochemical properties that were attributed to incorporation of gelatin matrix.