Si nanoparticles confined within a conductive 2D porous Cu-based metal–organic framework (Cu3(HITP)2) as potential anodes for high-capacity Li-ion batteries

The utility of metal–organic frameworks (MOFs) as active agents in electronic appliances is beneficial owing to their outstanding properties, particularly their high porosity, high surface area, and unique chemical stability. Herein, we report the in-situ growth of Cu3(HITP)2, a two-dimensional (2D) conductive MOF with Cu at the center, around Si nanoparticles (SiNPs) at 27 °C. Enclosing the Si nanoparticles with the Cu-MOF yielded a desired buffer against the volume expansion and also effective electron- and ion-conducting channels for the SiNPs. Accordingly, the Cu-MOF-coated Si electrode exhibited high structural stability and low electrochemical degradation during lithiation/delithiation cycles. The electrode composed of SiNPs coated with 5% Cu-MOF exhibited an extremely high initial reversible capacity of 2511 mAh g−1 at the 0.1C rate with a coulombic efficiency of 78.5% in the first cycle and a capacity of 2483 mAh g−1 after 100 cycles. The reversible capacities during rate capability were 1303, 785, and 404 mAh g−1 at the rates of 5, 10, and 20C, respectively. The Cu-MOF (5%) delivered a reversible capacity of 1039 mAh g−1, even after 1000 cycles, at the high rate of 1C. The full-cell, composed of the Cu-MOF-coated Si anode and a LiCoO2 cathode, exhibited a remarkable rate capability and cyclability at 0.1C. This full-cell supplied a reversible (discharge) capacity of 1267 and 1105 mAh g−1 at rates of 0.5C and 1C, respectively. These results demonstrate the considerable potential of the synthesized Cu-MOF-encaged Si as a competitive anode material for next-generation LIBs in the near future.