Bimetallic MOFs with tunable morphology: Synthesis and enhanced lithium storage properties

A series of isostructural bimetallic metal-organic frameworks (Co–Ni-MOF) were rationally synthesized by a facile one-step solvothermal method in the presence of varying mole ratios of Co/Ni mixed-metal ions. As the Co ion doping content decreased, the morphology of Co–Ni-MOF changed from irregular nanofragments to nanospheres. Meanwhile, doping Co ions in Ni-MOF can effectively improve the Li+ storage capacity. Attributing to the combined effect of metal ion reduction and successive lithiation of the organic ligands, the improved electrical conductivity and the synergetic advantages of Co and Ni, enhanced lithium storage properties of the prepared bimetallic MOFs have been achieved. Specifically, the Co–Ni-MOF electrode with a Co/Ni molar ratio of 1:1 displays a high reversible specific capacity of 800 ​mA ​h ​g−1 with 98% specific capacity retention after 100 cycles at 100 ​mA ​g−1, as well as good rate capability (600 ​mA ​h ​g−1 ​at 500 ​mA ​g−1 and 380 ​mA ​h ​g−1 ​at 1000 ​mA ​g−1).