Necklace-like NiCo2O4@carbon composite nanofibers derived from metal–organic framework compounds for high-rate lithium storage

Abstract

In this study, a necklace-like NiCo₂O₄@carbon composite nanofiber (NCO@CNF) anode composed of a metal–organic framework, featuring low volume expansion and high rate properties, was prepared as an anode for lithium-ion batteries. By tuning the ratio of the ZIF-67 precursor and growth time, unique necklace-like NCO@CNFs were synthesized for the first time. The novel necklace-like NCO@CNFs presented an interconnected architecture with a large specific surface area (194.2 m² g⁻¹), robust pore structures and superior mechanical strength. Benefiting from the abovementioned excellent physical properties, the issue of volume expansion derived from Li⁺ insertion/extraction during cycling was effectively mitigated by improved ionic transportation kinetics when the prepared NCO@CNFs were applied as an anode in a lithium-ion battery. Through a series of electrochemical measurements, the NCO@CNF electrode exhibited a high specific capacity of 1953 mA h g⁻¹ at the current density of 0.3 A g⁻¹, prolonged cycling stability with a reversible capacity of 1388 mA h g⁻¹ after 500 cycles and good rate capability with a reversible capacity of 652 mA h g⁻¹ at a high current density of 2 A g⁻¹. Moreover, its excellent stability was revealed by the sustained integrity of its necklace structure, similar to that of the fresh electrode, without significant volume expansion or pulverization even after 500 cycles.