Cu-hierarchical porous carbon anodes derived from metal-organic frameworks for long-lasting and high-energy lithium storage

Abstract

To tackle the challenges encountered by metal–organic frameworks (MOFs) used as lithium-ion battery anodes, like structural stability of the electrodes, low electrical conductivity and low tight stacking density. A hierarchical porous carbon with uniform Cu nanoclusters (Cu-HPC) was synthesized through high-temperature molten salt pyrolysis. The effects of the molten salt amount and pyrolysis temperature on the properties of Cu-HPC were investigated. It was discovered that Cu-HPC demonstrated optimal characteristics at 730 °C, including a high specific surface area (607.78 m2/g), a large pore volume (0.50 cm3 g−1), high conductivity Cu-C walls and an open interconnected hierarchical porous structure. These unique structural parameters of Cu-HPC not only enhance Li+ diffusion and electron transport, but also effectively alleviate the bulk stress during cycling to improve the structural stability of the electrode. The Cu-HPC 730 electrode exhibited an outstanding reversible lithium storage capacity of 1499.7 mAh/g at 0.2 A/g, excellent rate capacity and satisfactory long cycle stability (retaining 1427.4 mAh/g after 1000 cycles at 3.0 A/g). Furthermore, when assembled with a LiFePO4 cathode, the reversible specific capacity of the full cell can reach 150.1 mAh/g after 150 cycles at 0.1C. The capacity enhancement mechanism and lithium storage mechanism of Cu-HPC materials were elucidated through the analysis of density functional theory calculations (DFT) and electrochemical kinetic behavior. This study contributes to the design and development of advanced MOF anode materials for LIBs, thereby paving the way for their practical application.