Three novel multi-ligand coordination compounds, namely [Ni(IMI)6](ClO4)2 (1), [Ni(IMI)6](NO3)2 (2), and [Ni(IMI)6](CO3)·5H2O (3) were synthesized and characterized by elemental analysis and FT-IR spectroscopy. The crystal structures were determined by X-ray single crystal diffraction. The title compounds crystallize monoclinically, rhombohedrally, and hexagonally, and belong to space groups P21/m, R3, and P63/m, respectively. The nickel(II) ions are hexacoordinated to six imidazole molecules by the nitrogen atoms. The thermal decomposition mechanisms of compounds 1 and 2 were studied by using differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. The thermal decompositions were carried out in a nitrogen atmosphere with a heating rate of 10 K·min–1 and contain one endothermic process between 350 K and 500 K and one main exothermic process between 500 K and 800 K in the DSC curves. In addition, the non-isothermal kinetical parameters were calculated by using Kissinger's and Ozawa's method, respectively. The energies of combustion and the enthalpies of formation were measured and calculated, and the results indicated that both compounds have good combustion performance. The sensitivities were also determined with standard methods. The results showed that [Ni(IMI)6](L)2 compounds have a potential application as energetic materials.