A systematic investigation on the existence of chloroiodates formed by reaction of Cl with I Cl , apart from the well-known [ICl ] , namely [I Cl ] and [I Cl ] , was undertaken by employing theoretical as well as experimental methods. The thermodynamic stability in terms of the complexation enthalpies and Gibbs energies, and also the decomposition of the iodine(III) polyinterhalogen anions through dichlorine elimination to form iodine (I) compounds, was studied by means of DFT and ab initio quantum-chemical calculations up to an extrapolated CCSD(T)/A'QZ level. On the experimental side, mixtures of [HMIM]Cl ([HMIM] =1-hexyl-3-methylimidazolium), [BMP]Cl ([BMP] =1-butyl-1-methylpyrrolidinium chloride) and [NEt ]Cl with 0.5, 1.0, and 1.5 equivalents of I Cl were investigated by single-crystal XRD, ion chromatography, NMR- and Raman spectroscopy. The reactions with 0.5 equivalents of I Cl resulted in the compounds [HMIM][ICl ], [BMP][ICl ], and [NEt ][ICl ], of which crystal structures were determined. The mixtures with 1.0 or 1.5 equivalents of I Cl yielded dark red liquids or suspensions of a dark red liquid with an orange solid, respectively. Both mixtures were studied by NMR-spectroscopy for the organic cation part and ion chromatography and Raman spectroscopy for the polyinterhalogen anions. The discussion of the experimental Raman spectra is supplemented with computed spectra based on the structures obtained from RI-MP2/def2-TZVPP structure optimisations. Overall [I Cl ] appears to be the predominating anionic species in mixtures with 1.0 equivalents I Cl , while mixtures with 1.5 equivalents of I Cl are suspensions of I Cl in a liquid phase containing mixed anionic interhalogen complexes.

We present first investigations towards the feasibility of an Al/Br2 battery based on ionic liquids (ILs). The charged battery consisted of an Al anode, a bromoaluminate IL as the anolyte, an ion‐exchange membrane, a polybromide IL as the catholyte, and an inert cathode. The open‐circuit voltage (OCV) of the battery was strongly dependent on the molar ratio of AlBr3 in the anolyte with values of 1.9 V when using a Lewis basic anolyte and 1.1 V when using a Lewis neutral anolyte. NMR studies with different organic cations in both electrolytes revealed the migration of organic cations as major charge‐balancing ions, which leads to a reduced theoretical energy density of 33 Wh L−1 (as opposed to 166 Wh L−1 for an anion mechanism). The battery could be discharged with high discharge resistance values of up to 3 kΩ cm2, and preliminary charging attempts revealed high overpotentials. Hitherto, an Al/Br2 cell with a Lewis basic anolyte could be used as primary battery with an OCV of 1.9 V.

The importance of electrical energystorage systems (EES), for a successful integration of intermittent renewable energy sources into the electrical grid is beyond dispute. [1][2][3][4] For mobile applications, lithium ion batteries (LIBs) with high energy density prevail. [2,5,6] Although many efforts focus on alternative chemical systems (e.g., multivalent Al, Mg, and Ca), it is hard to imagine that LIBs will disappear in the near future. [4,7] Yet, for large scale stationary EES, there is no such prevailing technology. Although other alternatives, like pumped hydro or fuel cells are available, batteries are amongst the most promising technologies for this purpose. [1,3,8] With the energy density being slightly less relevant, other redox active materials could be employed in large scale EES, i.e., redox-flow batteries (RFBs) with their very long cycle life and decoupled capacity, power and energy output. [2,9,10] Their benchmark is the allvanadium redox-flow battery (VRFB) with V II /V III and V IV / V V redox couples, [2] as well as a 15 000-20 000 charge/discharge cycles lifetime and an acceptable energy density of 25-35 Wh L −1 installed in up to 60 MWh capacity EES. [2,6] However, probably due to the high cost, a commercial breakthrough still has to come. [2,6,9] Considering abundancy and cost, few elements are suitable as redox active material in sustainable batteries. [4,11] Manganese is one of them and, therefore, finds application in LIB-cathode active materials (e.g., LiMn 2 O 4 or Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 ) or in cathode materials of primary batteries (MnO 2 ). [5,12] However, to the best of our knowledge, only one battery system exclusively using manganese compounds at both electrodes is described, [13] i.e., Mn(acac) 3 acetonitrile (MeCN) solutions with the Mn II /Mn III couple at the negative and the Mn III /Mn IV couple at the positive electrode. Yet, with E cell of 1.1 V the system does not exploit the large potential range advantage of a non-aqueous electrolyte. Already the aqueous standard potential difference ΔE 0 of Mn 0 /Mn II and Mn II /Mn III redox couples amounts to an impressive 2.69 V. In addition, the Mn volumetric specific capacity is 7034.7 Ah L −1 (two-electron-process). It clearly exceeds that of zinc (5853.8 Ah L −1 ), which in the zinc A new all-Manganese flow battery (all-MFB) as a non-aqueous hybrid redox-flow battery is reported. The discharged active material [Cat] 2 [Mn II Cl 4 ] (Cat = organic cation) utilized in both half-cells supports a long cycle life. The reversible oxidation of [Mn II Cl 4 ] 2− to [Mn III Cl 5 ] 2− at the positive electrode and manganese metal deposition from [Mn II Cl 4 ] 2− at the negative electrode give a cell voltage of 2.59 V. Suitable electrolytes are prepared and optimized, followed by a characterization in static battery cells and in a pumped flow-cell. Several electrode materials, solvents, and membranes are tested for their feasibility in the all-MFB. An electrolyte consisting of [EMP] 2 [MnCl 4 ] and some solvent γ-butyrolactone is cycle...