Copper/cobalt metal-organic framework composites for advanced anode material of lithium-ion battery

In this paper, two new types of metal-organic frameworks (MOFs) materials, namely Cu-IM and Co-MOF, have been successfully applied to the anode of lithium-ion batteries with LiPF6 (EC: DMC = 1:1, volume) electrolyte additive. Cu-IM and Co-MOF employed imidazole (IM) and 2-methylimidazole (2-MeIM) as organic ligands, respectively. The results revealed the synthesized MOFs exhibited high initial discharge specific capacities (Cu-IM: 1964.5 mAh g−1, Co-MOF: 1423.3 mAh g−1) as well as low internal resistances (Cu-IM: 146 Ω; Co-MOF: 236 Ω). To alleviate the issue of capacity decay in single MOFs, we attempted the dual-MOFs materials through the rational design of interfacial/surface properties and microstructure. Compared to Cu-IM, the prepared Cu-IM/Co-MOF composites have a higher specific surface area and pore volume. Furthermore, the charge transfer resistance of Cu-IM/Co-MOF composites (141 Ω) was lower than that of Cu-IM and Co-MOF respectively. After a heat treatment to Cu-IM/Co-MOF composites, the electrochemical performance of obtained Cu-IM/Co-MOF 250 dual-MOFs composites have been significantly improved. The Cu-IM/Co-MOF 250 dual-MOFs composites demonstrated excellent cycling stability and high discharge specific capacities at various current densities. The composites displayed stable discharge specific capacity retention of 834 mAh g−1 (50 mA g−1, 75 cycles), 710.5 mAh g−1 (200 mA g−1, 50 cycles), and 392.5 mAh g−1 (500 mA g−1, 50 cycles), highlighting their promising performance for energy storage applications. The synthesized Cu-IM/Co-MOF 250 dual-MOFs composites demonstrates exceptional cycling performance and rate capability, implying that it has the promising prospects as anode material for lithium-ion batteries.