Aqueous electrolytes for redox flow battery systems

Patent metadata

Field	Value
Publication number	US-2016308233-A1
Application number	US-201514690224-A
Country	US
Kind code	A1
Filing date	Apr 17, 2015
Priority date	Apr 17, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

An aqueous redox flow battery system includes an aqueous catholyte and an aqueous anolyte. The aqueous catholyte may comprise (i) an optionally substituted thiourea or a nitroxyl radical compound and (ii) a catholyte aqueous supporting solution. The aqueous anolyte may comprise (i) metal cations or a viologen compound and (ii) an anolyte aqueous supporting solution. The catholyte aqueous supporting solution and the anolyte aqueous supporting solution independently may comprise (i) a proton source, (ii) a halide source, or (iii) a proton source and a halide source.

First claim

We claim:

1 . An aqueous catholyte for use in a redox flow battery system, comprising:
a catholyte aqueous supporting solution; and an electrochemically active component comprising
(i) an optionally substituted thiourea having a general formula I

wherein R 1 -R 4 independently are hydrogen, aliphatic, substituted aliphatic, alkoxy, substituted alkoxy, acyl, substituted acyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, alkylaryl, or substituted alkylaryl, the optionally substituted thiourea having a concentration sufficient to charge a redox flow battery system when the optionally substituted thiourea is oxidized, and/or

(ii) a nitroxyl radical compound having a general formula II

wherein n is 0, 1, or 2,
R 5 -R 6 and R 9 -R 14 independently are hydrogen, aliphatic, substituted aliphatic, halo, hydroxyl, carboxyl, amino, cyano, or thiol, and
each R 7 and R 8 independently is hydrogen, optionally substituted aliphatic, halo, hydroxyl, carboxyl, amino, cyano, or thiol, the nitroxyl radical compound having a concentration sufficient to charge a redox flow battery system when the nitroxyl radical compound is oxidized.

2 . The aqueous catholyte of claim 1 , wherein the optionally substituted thiourea is an alkyl-substituted thiourea.

3 . The aqueous catholyte of claim 1 , wherein the optionally substituted thiourea is monosubstituted, disubstituted, trisubstituted, or tetrasubstituted.

4 . The aqueous catholyte of claim 1 , wherein the optionally substituted thiourea is N-methyl thiourea, N,N′-dimethyl thiourea, N-ethyl thiourea, N,N′-diethyl thiourea, tetramethyl thiourea, tetraethyl thiourea, or any combination thereof.

5 . The aqueous catholyte of claim 1 , wherein:
R 5 , R 6 and R 11 -R 14 independently are hydrogen or lower alkyl; each R 7 and R 8 independently is hydrogen or lower alkyl; and at least one of R 9 and R 10 is other than hydrogen.

6 . The aqueous catholyte of claim 1 , wherein:
R 5 , R 6 , R 13 , and R 14 are independently lower alkyl; R 7 , R 8 , R 11 , and R 12 are hydrogen; and at least one of R 9 and R 10 is hydroxyl, amino, carboxyl, or cyano.

7 . The aqueous catholyte of claim 1 , wherein the nitroxyl radical compound is:

or any combination thereof.

8 . The aqueous catholyte of claim 1 , wherein the catholyte, prior to charging, has a concentration of the optionally substituted thiourea within a range of 0.05 M to 5 M and/or a concentration of the nitroxyl radical compound within a range of 1 mM to 5 M.

9 . The aqueous catholyte of claim 1 , wherein the catholyte aqueous supporting solution comprises a binary acid, an alkali metal halide, or a combination thereof.

10 . The aqueous catholyte of claim 1 , wherein the catholyte aqueous supporting solution comprises a halide (X − ) source, and [X − ]≧[electrochemically active component].

11 . The aqueous catholyte of claim 1 , wherein:
the catholyte aqueous supporting solution comprises (i) a proton source, (ii) a halide source, or (iii) a proton source and a halide source.

12 . The aqueous catholyte of claim 1 , wherein:
the electrochemically active component is an optionally substituted thiourea, and the catholyte aqueous supporting solution comprises NaCl, KCl, HCl, or a combination thereof; or the electrochemically active component is a nitroxyl radical compound, and the catholyte aqueous supporting solution comprises NaCl, KCl, or a combination thereof.

13 . The aqueous catholyte of claim 1 , wherein, prior to charging, the catholyte consists essentially of:
the optionally substituted thiourea and/or the nitroxyl radical compound; and the aqueous catholyte supporting solution, wherein the aqueous catholyte supporting solution consists essentially of (i) water and (ii) the proton source, the halide source, or both the proton source and the halide source.

14 . An aqueous electrolyte system for use in a redox flow battery system, comprising:
an aqueous catholyte according to claim 1 ; an aqueous anolyte.

15 . The aqueous electrolyte system of claim 14 , wherein the aqueous anolyte comprises:
an anolyte aqueous supporting solution; and metal cations or a viologen compound comprising cations having a general formula

wherein R 15 is aliphatic, substituted aliphatic, aryl, substituted aryl, arylalkyl, or substituted arylalkyl.

16 . The aqueous electrolyte system of claim 15 , wherein:
the anolyte comprises metal cations, and each of the anolyte aqueous supporting solution and the aqueous catholyte supporting solution independently comprises (i) a proton source, (ii) a halide source, or (iii) a proton source and a halide source; or the anolyte comprises the viologen compound, and each of the aqueous anolyte supporting solution and the aqueous catholyte supporting solution independently comprises a non-acidic halide source.

17 . A redox flow battery system, comprising:
the aqueous electrolyte system of claim 14 ; and an ion-exchange membrane or porous separator.

18 . The redox flow battery system of claim 17 , wherein when the redox flow battery system is at least partially charged:
the catholyte comprises a redox pair consisting of (i) the optionally substituted thiourea and corresponding formamidinium disulfide cations, or (ii) the nitroxyl radical compound and corresponding nitroxyl compound cations; and the anolyte comprises (a) a metal redox pair comprising the metal cations or (b) a viologen redox pair consisting of +2 and +1 viologen cations.

19 . The redox flow battery system of claim 17 , wherein when the redox flow battery system is at least partially charged, the catholyte consists essentially of:
(a) the optionally substituted thiourea and corresponding optionally substituted formamidinium disulfide cations, and the aqueous catholyte supporting solution, wherein the aqueous catholyte supporting solution consists essentially of (i) water and (ii) the proton source, the halide source, or both the proton source and the halide source; or (b) the nitroxyl radical compound and corresponding nitroxyl compound cations, and the aqueous catholyte supporting solution, wherein the aqueous catholyte supporting solution consists essentially of (i) water and (ii) the proton source, the halide source, or both the proton source and the halide source.

20 . An aqueous anolyte for use in a redox flow battery system, comprising:
a non-acidic anolyte aqueous supporting solution comprising an anolyte halide source; and a viologen compound providing viologen cations having a general formula

wherein R 15 is aliphatic, substituted aliphatic, aryl, or substituted aryl, the viologen compound having a concentration sufficient to charge a redox flow battery system when the viologen compound is reduced.

21 . The aqueous anolyte of claim 20 , wherein R 15 is lower alkyl, aryl,

Assignees

• Battelle Memorial Institute

Inventors

• Liu Tianbiao
• Li Bin
• Wei Xiaoliang
• Nie Zimin
• Wang Wei
• Liu Jun
• Sprenkle Vincent L

Classifications

• H01M8/20

  Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence) · CPC title

• H01M8/188 Primary

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

• H01M2300/0002

  Aqueous electrolytes · CPC title

• Y02E60/50

  Fuel cells · CPC title