Here, we report a type of rechargeable battery whose novelty lies in the use of halogen anions as charge carrier, a metal-organic framework (MOF) [2] as a solo redox-active material, pure ionic liquid as electrolyte, and films of carbon nanotubes as binder-free electrodes. A cell combines microcrystals of a MOF composed of trinuclear copper and triazole immobilized in a flexible film of carbon nanotubes (MOF@CNT), and an imidazolium ionic liquid with Cl or Br, e.g. 1-Methyl-3-octylimidazolium chloride (OMIM-Cl), 1-Methyl-3-octylimidazolium bromide (OMIM-Br), or 1-Hexyl-3-methylimidazolium chloride (HMIM-Cl). It is a halogenion battery in which halogen anions (Cl -or Br -) shuttle reversibly between the MOF@CNT cathode and a pure CNT anode upon cyclic charging and discharging. Halogen as anionic charge carriers were previously utilized in metal-halide batteries whose cathodes are typically metal halides . Despite advantages associated with the properties of halogen anions, such as high theoretical energy densities, low manufacturing costs, and dendrite-free cycling, metal-halide batteries suffer cyclic instability due to large volume changes of the metal halides. MOFs' permanent nanoscsale open porosity allows ionic species to reach every single redox-active site in the framework without causing permanent lattice deformation. Spectroelectrochemistry elucidates two redox states of the MOF responsible for the energy storage in the battery cell which operates through halogenation of the µ3-oxo bridged trinuclear copper. This working principle is well distinguished from those of other existing types of secondary batteries that utilize cation transport (e.g. lithium-ion battery) or anion transport (e.g. metal-halogen battery ), as well as from dual ion and dual carbon batteries .