A halogen-ion battery made with a metal-organic framework

The global renewable energy industry awaits new battery technologies that power the future. Here we conceptualize and fabricate a halogen-ion battery that is charged up via halogenation of a water-stable metal-organic framework (MOF) made of trinuclear copper and triazole. A battery cell uses a pure imidazolium ionic liquid electrolyte, and binder-free carbon nanotube electrodes, one of which accommodates microcrystals of the MOF. It offers redox potentials greater than 0.6 V, energy densities and specific capacitances as high as 7 Wh/kg and 10 mAh/g, respectively, with an excellent cyclic stability over 100 cycles, that are sufficient for practical applications. Spectroelectrochemistry reveals the redox states responsible for the energy storage. This rechargeable battery is non-flammable and moisture resistant, as well as all elements used are abundant, hence it is a promising alternative to some of the existing batteries.