In order to enable higher penetration of renewable energy sources into the electric grid, such as solar and wind, efficient and inexpensive energy storage systems are required. Zinc-bromine flow batteries are highly promising, as they rely on fast electrochemical reactions which do not require any specialized catalyst material, as well as inexpensive reactants. The anodic electrolyte (anolyte) and the cathodic electrolyte (catholyte) are circulated between the battery where power is delivered, and tank where the chemical energy is stored. During charging, ions from the anolyte are reduced into metal zinc which is deposited on the anode. Ions from the catholyte are oxidized into bromine which accumulates in the catholyte tank. During the discharge, zinc and bromine are converted to their ionic form.

Zinc deposition on the anode is limited by the volume between the anode and the membrane. Also, zinc tends to grow protrusions (dendrites) what can reach the membrane and puncture it (a). We propose to solve those problems by introducing metal particles into the anolyte flow. This way the zinc is deposited on the metal particles and returned to the anolyte tank (b). The continuous movement of the metal particles in the flow prevents dendrite growth. Also, their storage in the anolyte tank rather than in the battery itself allows storage of large amount of zinc upon charging. We have developed highly conductive fluidized bed electrodes using metal particles, leveraging the phenomena of large scale particle “vortices” which form when the electrode is sufficiently concentrated with particles. We discovered that such vortices allow for fast transport of electrons across the electrode compartment, making them ideal for use in efficient flow batteries.