Coordination compounds having redox non-innocent ligands and flow batteries containing the same
View Patent ↗Electrolyte solutions for flow batteries and other electrochemical systems can contain an active material capable of transferring more than one electron per oxidation-reduction cycle. Such active materials can include coordination compounds containing a metal center and at least one redox non-innocent ligand. Accordingly, flow batteries can include a first half-cell having a first electrolyte solution therein, where the first electrolyte solution contains a coordination compound having at least one redox non-innocent ligand coordinated to a metal center. Particular redox non-innocent ligands can include those bearing a quinone functional group, such as substituted catecholates bearing a quinone functional group. Some active materials can include compositions containing a coordination compound having at least one redox non-innocent ligand coordinated to a metal center, where the at least one redox non-innocent ligand is a substituted catecholate or a salt thereof bearing a quinone functional group.
1. A flow battery comprising:
a first half-cell having a first electrolyte solution therein, the first electrolyte solution comprising a coordination compound having at least one redox non-innocent ligand coordinated to a metal center,
wherein the at least one redox non-innocent ligand bears a quinone functional group,
wherein the quinone functional group is part of an aromatic ring bearing a catechol group, fused to the aromatic ring bearing the catechol group, or tethered via a linker to the aromatic ring bearing the catechol group.
2. The flow battery of claim 1 , wherein the at least one redox non-innocent ligand comprises a salt of a substituted catecholate bearing the quinone functional group.
3. The flow battery of claim 1 , wherein the at least one redox non-innocent ligand is selected from the group consisting of
4. The flow battery of claim 1 , wherein the coordination compound has a formula of
D g M(L 1 )(L 2 )(L 3 );
wherein M is a transition metal; D is ammonium, tetraalkylammonium, or an alkali metal ion; g ranges between 0 and 6; and L 1 , L 2 and L 3 are ligands, at least one of L 1 , L 2 and L 3 being the at least one redox non-innocent ligand.
5. The flow battery of claim 4 , wherein the transition metal comprises titanium.
6. The flow battery of claim 1 , wherein the metal center comprises a transition metal.
7. The flow battery of claim 6 , wherein the transition metal comprises titanium.
8. The flow battery of claim 1 , further comprising:
a second half-cell having a second electrolyte solution therein, the second electrolyte solution comprising an iron hexacyanide complex.
9. A composition comprising:
a coordination compound having at least one redox non-innocent ligand coordinated to a metal center;
wherein the at least one redox non-innocent ligand comprises a substituted catecholate or a salt thereof bearing a quinone functional group;
wherein the quinone functional group is part of an aromatic ring bearing a catechol group, fused to the aromatic ring bearing the catechol group, or tethered via a linker to the aromatic ring bearing the catechol group.
10. The composition of claim 9 , wherein the metal center comprises a transition metal.
11. The composition of claim 10 , wherein the metal center comprises a transition metal.
12. The composition of claim 9 , wherein the coordination compound has a formula of
D g M(L 1 )(L 2 )(L 3 );
wherein M is a transition metal; D is ammonium, tetraalkylammonium, or an alkali metal ion; g ranges between 0 and 6; and L 1 , L 2 and L 3 are ligands, at least one of L 1 , L 2 and L 3 being the at least one redox non-innocent ligand.
13. The composition of claim 9 , wherein the at least one redox non-innocent ligand is selected from the group consisting of
14. The composition of claim 9 , further comprising:
an aqueous solution in which the coordination compound is disposed.
15. The composition of claim 14 , wherein the aqueous solution has an alkaline pH.