Additives for fluorenone/fluorenol based aqueous redox flow batteries

Patent metadata

Field	Value
Publication number	US-12555809-B2
Application number	US-202217748699-A
Country	US
Kind code	B2
Filing date	May 19, 2022
Priority date	Jun 9, 2021
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

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.

First claim

We claim:

1 . An aqueous composition, comprising:
an aqueous anolyte comprising
(i) a fluorenone/fluorenol derivative or a salt thereof having a structure according to any one of formulas I-III

where Q 1 -Q 4 independently are CH, C(R 1 ) or N, wherein 0, 1, or 2 of Q 1 -Q 4 are N, Q 5 -Q 8 independently are CH, C(R 2 ), or N, wherein 0, 1, or 2 of Q 5 -Q 8 are N, Y is C═O or C(H) OH,
each R 1 and R 2 independently is an electron withdrawing group,
n is an integer >1, and
x and y independently are 0, 1, 2, 3, or 4, where if none of Q 1 -Q 8 is N, then x and y are not 0, and
(a) R 1 and R 2 are different electron withdrawing groups, or
(b) the compound comprises two different R 1 or two different R 2 groups, or
(c) both (a) and (b);

(ii) an additive, wherein the additive is an organic compound including one or more proton acceptor groups;
(iii) an alkali metal hydroxide; and
(iv) water.

2 . The aqueous composition of claim 1 , wherein:
(i) the additive comprises two or more proton acceptor groups; or (ii) wherein the additive has a pKa of from 9 to 17; or (iii) both (i) and (ii).

3 . The aqueous composition of claim 1 , wherein the proton acceptor groups comprise —OH, —N(R A )R B , —O − Z, or any combination thereof, where Z is a counterion with a +1 charge, and R A and R B independently are H, unsubstituted C 1 -C 6 alkyl, or substituted C 1 -C 6 alkyl.

4 . The aqueous composition of claim 1 , wherein the additive comprises an oligosaccharide, a sugar alcohol, a glycol, guanidinium chloride, an amine, or any combination thereof.

5 . The aqueous composition of claim 1 , wherein the additive comprises a cyclodextrin, D-sorbitol, diglycol, guanidinium chloride, or any combination thereof.

6 . The aqueous composition of claim 1 , wherein:
(i) the additive is present in the anolyte at a concentration of from 0.05 M to 2 M; or (ii) the additive is present in the anolyte at a concentration of from 1.5 N to 2 N with respect to proton acceptor groups; or (iii) both (i) and (ii).

7 . The aqueous composition of claim 1 , wherein the additive comprises β-cyclodextrin.

8 . The aqueous composition of claim 7 , wherein the anolyte comprises 0.07 M to 0.1 M β-cyclodextrin.

9 . The aqueous composition of claim 1 , wherein each R 1 and R 2 independently is —SO 3 Z, —CO 2 Z, —CF 3 , —NO 2 , —CN, or —OH, wherein each Z independently is a counterion with a +1 charge.

10 . The aqueous composition of claim 1 , wherein the fluorenone/fluorenol derivative has a structure according to any one of formulas IA-IC, IIA-IIB, or IIIA-IIIC:

11 . The aqueous composition of claim 1 , wherein the fluorenone/fluorenol derivative comprises

or any combination thereof, where Y is C═O or C(H)OH, and each Z independently is a counterion with a +1 charge.

12 . The aqueous composition of claim 11 , wherein the additive comprises a cyclodextrin, D-sorbitol, diglycol, guanidinium chloride-, diglyme, or any combination thereof.

13 . The aqueous composition of claim 12 , wherein the additive comprises β-cyclodextrin.

14 . The aqueous composition of claim 1 , wherein:
(i) the fluorenone/fluorenol derivative is present in the anolyte at a concentration of 0.5 M to 1.5 M; or (ii) the additive is present in the anolyte at a concentration of from 1.5 N to 2 N with respect to proton acceptor groups; or (iii) the alkali metal hydroxide is present in the anolyte at a concentration of from 0.1 M to 6 M; or (iv) any combination of two or more of (i), (ii), and (iii).

15 . The aqueous composition of claim 1 , consisting essentially of:
the fluorenone/fluorenol derivative; the additive; the alkali metal hydroxide; and water.

16 . An aqueous electrolyte system for a redox flow battery system, comprising:
an aqueous anolyte comprising an aqueous composition according to claim 1 ; and an aqueous catholyte comprising water and an electrochemically active material.

17 . The aqueous electrolyte system of claim 16 , wherein the aqueous catholyte comprises:
K 4 Fe(CN) 6 , K 3 Fe(CN) 6 , or a combination thereof; and water.

18 . The aqueous electrolyte system of claim 16 , wherein the additive comprises a cyclodextrin, D-sorbitol, diglycol, guanidinium chloride-, diglyme, or any combination thereof.

19 . The aqueous electrolyte system of claim 16 , wherein:
(i) the fluorenone/fluorenol derivative comprises

or any combination thereof, where Y is C═O or C(H)OH, and each Z independently is a counterion with a +1 charge; or
(ii) the additive comprises a cyclodextrin; or
(iii) both (i) and (ii).

20 . A redox flow battery system, comprising:
the aqueous electrolyte system of claim 16 ; an anode; a cathode; and a separator.

Assignees

• Battelle Memorial Institute

Inventors

• Feng Ruozhu
• Wang Wei
• Zhang Xin
• Liang Yangang
• Hollas Aaron M
• Shao Yuyan
• Murugesan Vijayakumar
• Chen Ying

Classifications

• H01M8/188 Primary

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• H01M8/08 Primary

  Fuel cells with aqueous electrolytes · CPC title

• H01M2300/0002

  Aqueous electrolytes · CPC title

• Y02E60/50

  Fuel cells · CPC title