A zinc-iron chloride flow battery relies on mixed, equimolar electrolytes to maintain a consistent open-circuit voltage of about 1.5 V and stable performance during continuous charge-discharge. Considering the good performance relative to the low-cost materials, zinc-iron chloride flow batteries represent a promising new approach in grid-scale and other energy storage applications.

A zinc-iron chloride flow battery relies on mixed, equimolar electrolytes to maintain a consistent open-circuit voltage of about 1.5 V and stable performance during continuous charge-discharge. Considering the good performance relative to the low-cost materials, zinc-iron chloride flow batteries represent a promising new approach in grid-scale and other energy storage applications.

The present disclosure relates to a heterocyclic compound represented by formula (1), (2) or (3), or a salt thereof. The present disclosure also relates to an active material containing at least one heterocyclic compound or a salt thereof described above, an electrolytic solution containing the active material, and a redox flow battery including the electrolytic solution.

The present disclosure relates to a heterocyclic compound represented by formula (1), (2) or (3), or a salt thereof. The present disclosure also relates to an active material containing at least one heterocyclic compound or a salt thereof described above, an electrolytic solution containing the active material, and a redox flow battery including the electrolytic solution.

A redox flow battery system includes an anolyte having chromium ions in solution, wherein at least a portion of the chromium ions form a chromium complex with at least one of the following: NH.sub.3, NH.sub.4.sup.+, CO(NH.sub.2).sub.2, SCN.sup.−, or CS(NH.sub.2).sub.2; a catholyte having iron ions in solution; a first half-cell including a first electrode in contact with the anolyte; a second half-cell including a second electrode in contact with the catholyte; and a first separator separating the first half-cell from the second half-cell.

A redox flow battery system includes an anolyte having chromium ions in solution, wherein at least a portion of the chromium ions form a chromium complex with at least one of the following: NH.sub.3, NH.sub.4.sup.+, CO(NH.sub.2).sub.2, SCN.sup.−, or CS(NH.sub.2).sub.2; a catholyte having iron ions in solution; a first half-cell including a first electrode in contact with the anolyte; a second half-cell including a second electrode in contact with the catholyte; and a first separator separating the first half-cell from the second half-cell.

Aqueous anolytes for redox flow batteries are disclosed. The anolytes include a fluorenone-fluorenol derivative, an additive comprising an organic compound including one or more proton acceptor groups, an alkali metal hydroxide, and water. The additive functions as a homogeneous organocatalyst and may increase the current density of an aqueous redox flow battery including the anolyte.

Aqueous anolytes for redox flow batteries are disclosed. The anolytes include a fluorenone-fluorenol derivative, an additive comprising an organic compound including one or more proton acceptor groups, an alkali metal hydroxide, and water. The additive functions as a homogeneous organocatalyst and may increase the current density of an aqueous redox flow battery including the anolyte.

An electrical energy generating device includes an electrical energy generating element, a first container, a second container, and a liquid having positive and negative ions. The electrical energy generating element includes a first porous electrode, an eggshell membrane, and a second porous electrode stacked on each other in that order. The first container is located on a side of the first porous electrode away from the eggshell membrane. The second container is located on a side of the second porous electrode away from the eggshell membrane. The liquid is located in at least one of the first container and the second container, and the liquid is configured to penetrate from one of the first container and the second container to another through the electrical energy generating element.

A flow battery includes a positive electrode, a positive electrode electrolyte, a negative electrode, a negative electrode electrolyte, and a polymer electrolyte membrane interposed between the positive electrode and the negative electrode. The positive electrode electrolyte includes water and a first redox couple. The first redox couple includes a first organic compound which includes a first moiety in conjugation with a second moiety. The first organic compound is reduced during discharge while during charging the reduction product of the first organic compound is oxidized to the first organic compound. The negative electrode electrolyte includes water and a second redox couple. The second couple includes a second organic compound including a first moiety in conjugation with a second moiety. The reduction product of the second organic compound is oxidized to the second organic compound during discharge.