The increasing global energy demand requires the development of an infrastructure of renewable energies since fossil fuels are not disposable unlimitedly. Renewable energy sources such as solar panels and wind turbines deliver a fluctuating supply of energy. One way to store this harvested energy is in backup batteries, e.g. redox flow batteries (RFBs), which provide the energy to a given system when needed. Therefore, the present dissertation deals with the synthesis and characterization of ionic liquids based on bromostannates and polyhalides for a possible application in a new type of redox flow battery as well as expanding the spectrum of poly(inter)halides. The preparation of bromostannate(II) ([SnBr3]–) and bromostannate(IV) ([SnBr5]–) was achieved by reaction of [OMIM]Br (OMIM = 1-octyl-3-methylimidazolium) with SnBr2 and SnBr4, respectively. The liquids were subject to Raman and NMR spectroscopic characterization. Additionally, solid [OMIM][SnBr5] was analyzed by single crystal X-ray diffraction, making it the only second [SnBr5]– containing compound in the Cambridge Crystallographic Data Centre (CCDC), and the first ionic liquid with this rare anion. When employing the same cation, ionic liquids based on polybromides were obtained, namely [OMIM][Br3] and [OMIM][Br9], of which the electrical conductivity was determined. In addition, the field of polyhalides has been greatly expanded. In one project, the hexabromide dianion [Br6]2– was stabilized by a cyclic Vilsmeier cation derivative in [C5H10N2Br]2[Br6]. This L-shaped [Br6]2– was the last gap to fill in the series of polybromides between [Br3]– and [Br11]–. Moreover, the synthesis and characterization of other Vilsmeier salt derivatives [BrC(NMe2)2][Br3] and [BrC(NMe2)2]2[Br8] showed the influence of the solvent and the cation on the resulting polybromides. A comparison to the corresponding polychlorides was drawn. Lastly, the challenging synthesis of polychlorides was successfully accomplished and the hitherto unknown polychloride monoanions [Cl11]– and [Cl13]– were prepared in the compounds [AsPh4][Cl11], [PPh4][Cl11], [PNP][Cl11] · Cl2, and [PNP][Cl13] (PNP = bis(triphenylphosphine)-iminium). The octahedral structure of [Cl13]– is very uncommon in polyhalogen chemistry and represents the first and only isotridecahalide. On top of that, [NMe3Ph]2[Cl12] was prepared, consisting of the largest polychloride dianion known to date: [Cl12]2–. All compounds were thoroughly characterized by NMR and Raman spectroscopy, X-ray diffraction, and compared to molecular and periodic solid-state quantum-chemical calculations.