Separation membrane for redox flow secondary battery and redox flow secondary battery comprising the same

1. A redox flow secondary battery comprising an electrolytic cell, the electrolytic cell comprising:

a positive electrode cell,

a negative electrode cell, and

a separation membrane that separates the positive electrode cell and the negative electrode cell,

wherein:

the separation membrane comprises a microporous membrane and an ion-exchange resin layer contacting the microporous membrane, and an air resistance of the separation membrane per thickness of 200 μm is 50000 sec/100 cc or more,

the microporous membrane comprises a polyolefin resin or a vinylidene fluoride resin and an inorganic filler, and

a smoothness of at least a surface of the microporous membrane contacting the ion-exchange resin layer is 16000 seconds or less.

2. The redox flow secondary battery according to claim 1 , wherein a tensile modulus of the microporous membrane is 200 N/cm or less.

3. The redox flow secondary battery according to claim 2 , wherein the redox flow secondary battery is a vanadium redox flow secondary battery, in which an electrolytic solution comprising vanadium is used as a positive electrolytic solution and a negative electrolytic solution.

4. The redox flow secondary battery according to claim 2 , wherein the ion-exchange resin layer comprises an ion-exchange resin composition comprising, as a main component, a fluorine-based polyelectrolyte polymer having a structure represented by the following formula (1):

[CF 2 CX 1 X 2 ] a —[CF 2 —CF((—O—CF 2 —CF(CF 2 X 3 )) b —O c —(CFR 1 ) d —(CFR 2 ) e —(CF 2 ) f —X 4 )] g —  (1)

wherein:

X 1 , X 2 and X 3 each independently represent one or more selected from the group consisting of a halogen atom and a perfluoroalkyl group having 1 to 3 carbon atoms;

X 4 represents COOZ, SO 3 Z, PO 3 Z 2 or PO 3 HZ;

Z represents a hydrogen atom, an alkaline metal atom, an alkaline-earth metal atom, or an amine selected from the group consisting of NH 4 , NH 3 R 1 , NH 2 R 1 R 2 , NHR 1 R 2 R 3 and NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 and R 4 each independently represent any one or more selected from the group consisting of an alkyl group and an arene group, and when X 4 is PO 3 Z 2 , Z may be identical to or different from one another;

R 1 and R 2 each independently represent one or more selected from the group consisting of a halogen atom, a perfluoroalkyl group and a fluorochloroalkyl group having 1 to 10 carbon atoms;

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

b represents an integer of 0 to 8;

c represents 0 or 1; and

d, e and f each independently represent an integer of 0 to 6 provided that d, e and f do not simultaneously represent 0.

5. The redox flow secondary battery according to claim 2 , wherein the ion-exchange resin layer comprises, as a fluorine-based polyelectrolyte polymer, a perfluorocarbon sulfonic acid resin (PFSA resin) having a structure represented by the following formula (2):

[CF 2 CF 2 ] a —[CF 2 —CF((—O—(CF 2 ) m —X 4 )] g —  (2)

wherein:

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

m represents an integer of 1 to 6; and

X 4 represents SO 3 H.

6. The redox flow secondary battery according to claim 2 ,

wherein:

the ion-exchange resin layer comprises a fluorine-based polyelectrolyte polymer having an equivalent weight EW (dry mass grams per equivalent of ion exchange groups) of 300 to 1300 g/eq, and

an equilibrium water content of the ion-exchange resin layer is 5% to 80% by mass.

7. A separation membrane for redox flow secondary battery, comprising:

a microporous membrane comprising a polyolefin resin or a vinylidene fluoride resin and an inorganic filler; and

an ion-exchange resin layer contacting the microporous membrane,

wherein:

an air resistance of the separation membrane per thickness of 200 μm is 50000 sec/100 cc or more, and

a smoothness of at least a surface of the microporous membrane contacting the ion-exchange resin layer is 16000 seconds or less.

8. The separation membrane for redox flow secondary battery according to claim 7 , wherein a tensile modulus of the microporous membrane is 200 N/cm or less.

9. The separation membrane for redox flow secondary battery according to claim 8 , wherein the ion-exchange resin layer comprises an ion-exchange resin composition comprising, as a main component, a fluorine-based polyelectrolyte polymer having a structure represented by the following formula (1):

[CF 2 CX 1 X 2 ] a —[CF 2 —CF((—O—CF 2 —CF(CF 2 X 3 )) b —O c —(CFR 1 ) d —(CFR 2 ) e —(CF 2 ) f —X 4 )] g —  (1)

wherein:

X 1 , X 2 and X 3 each independently represent one or more selected from the group consisting of a halogen atom and a perfluoroalkyl group having 1 to 3 carbon atoms;

X 4 represents COOZ, SO 3 Z, PO 3 Z 2 or PO 3 HZ;

Z represents a hydrogen atom, an alkaline metal atom, an alkaline-earth metal atom, or an amine selected from the group of consisting of NH 4 , NH 3 R 1 , NH 2 R 1 R 2 , NHR 1 R 2 R 3 and NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 and R 4 each independently represent any one or more selected from the group consisting of an alkyl group and an arene group, and when X 4 is PO 3 Z 2 , Z may be identical to or different from one another;

R 1 and R 2 each independently represent one or more selected from the group consisting of a halogen atom, a perfluoroalkyl group and a fluorochloroalkyl group having 1 to 10 carbon atoms;

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

b represents an integer of 0 to 8;

c represents 0 or 1; and

d, e and f each independently represent an integer of 0 to 6, provided that d, e and f do not simultaneously represent 0.

10. The separation membrane for redox flow secondary battery according to claim 8 ,

wherein the ion-exchange resin layer comprises, as a fluorine-based polyelectrolyte polymer, a perfluorocarbon sulfonic acid resin (PFSA resin) having a structure represented by the following formula (2):

[CF 2 CF 2 ] a —[CF 2 —CF((—O—(CF 2 ) m —X 4 )] g —  (2)

wherein:

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

m represents an integer of 1 to 6; and

X 4 represents SO 3 H.

11. The separation membrane for redox flow secondary battery according to claim 8 ,

wherein:

the ion-exchange resin layer comprises a fluorine-based polyelectrolyte polymer having an equivalent weight EW (dry mass grams per equivalent of ion exchange groups) of 300 to 1300 g/eq, and

an equilibrium water content of the ion-exchange resin layer is 5% to 80% by mass.

12. The redox flow secondary battery according to claim 1 , wherein the redox flow secondary battery is a vanadium redox flow secondary battery, in which an electrolytic solution comprising vanadium is used as a positive electrolytic solution and a negative electrolytic solution.

13. The redox flow secondary battery according to claim 1 , wherein the ion-exchange resin layer comprises an ion-exchange resin composition comprising, as a main component, a fluorine-based polyelectrolyte polymer having a structure represented by the following formula (1):

[CF 2 CX 1 X 2 ] a —[CF 2 —CF((—O—CF 2 —CF(CF 2 X 3 )) b —O c —(CFR 1 ) d —(CFR 2 ) e —(CF 2 ) f —X 4 )] g —  (1)

X 1 , X 2 and X 3 each independently represent one or more selected from the group consisting of a halogen atom and a perfluoroalkyl group having 1 to 3 carbon atoms;

X 4 represents COOZ, SO 3 Z, PO 3 Z 2 or PO 3 HZ;

Z represents a hydrogen atom, an alkaline metal atom, an alkaline-earth metal atom, or an amine selected from the group consisting of NH 4 , NH 3 R 1 , NH 2 R 1 R 2 , NHR 1 R 2 R 3 and NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 and R 4 each independently represent any one or more selected from the group consisting of an alkyl group and an arene group, and when X 4 is PO 3 Z 2 , Z may be identical to or different from one another;

R 1 and R 2 each independently represent one or more selected from the group consisting of a halogen atom, a perfluoroalkyl group and a fluorochloroalkyl group having 1 to 10 carbon atoms;

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

b represents an integer of 0 to 8;

c represents 0 or 1; and

d, e and f each independently represent an integer of 0 to 6, provided that d, e and f do not simultaneously represent 0.

14. The redox flow secondary battery according to claim 1 , wherein the ion-exchange resin layer comprises, as a fluorine-based polyelectrolyte polymer, a perfluorocarbon sulfonic acid resin (PFSA resin) having a structure represented by the following formula (2):

[CF 2 CF 2 ] a —[CF 2 —CF((—O—(CF 2 ) m —X 4 )] g —  (2)

wherein:

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

m represents an integer of 1 to 6; and

X 4 represents SO 3 H.

15. The redox flow secondary battery according to claim 1 ,

wherein:

the ion-exchange resin layer comprises a fluorine-based polyelectrolyte polymer having an equivalent weight EW (dry mass grams per equivalent of ion exchange groups) of 300 to 1300 g/eq, and

an equilibrium water content of the ion-exchange resin layer is 5% to 80% by mass.

16. The separation membrane for redox flow secondary battery according to claim 7 , wherein the ion-exchange resin layer comprises an ion-exchange resin composition comprising, as a main component, a fluorine-based polyelectrolyte polymer having a structure represented by the following formula (1):

[CF 2 CX 1 X 2 ] a —[CF 2 —CF((—O—CF 2 —CF(CF 2 X 3 )) b —O c —(CFR 1 ) d —(CFR 2 ) e —(CF 2 ) f —X 4 )] g —  (1)

wherein:

X 1 , X 2 and X 3 each independently represent one or more selected from the group consisting of a halogen atom and a perfluoroalkyl group having 1 to 3 carbon atoms;

X 4 represents COOZ, SO 3 Z, PO 3 Z 2 or PO 3 HZ;

Z represents a hydrogen atom, an alkaline metal atom, an alkaline-earth metal atom, or an amine selected from the group consisting of NH 4 , NH 3 R 1 , NH 2 R 1 R 2 , NHR 1 R 2 R 3 and NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 and R 4 each independently represent any one or more selected from the group consisting of an alkyl group and an arene group, and when X 4 is PO 3 Z 2 , Z may be identical to or different from one another;

R 1 and R 2 each independently represent one or more selected from the group consisting of a halogen atom, a perfluoroalkyl group and a fluorochloroalkyl group having 1 to 10 carbon atoms;

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

b represents an integer of 0 to 8;

c represents 0 or 1; and

d, e and f each independently represent an integer of 0 to 6, provided that d, e and f do not simultaneously represent 0.

17. The separation membrane for redox flow secondary battery according to claim 7 ,

wherein the ion-exchange resin layer comprises, as a fluorine-based polyelectrolyte polymer, a perfluorocarbon sulfonic acid resin (PFSA resin) having a structure represented by the following formula (2):

[CF 2 CF 2 ] a —[CF 2 —CF((—O—(CF 2 ) m —X 4 )] g —  (2)

wherein:

a and g each represent a number satisfying 0≦a<1, 0<g≦1, and a+g=1;

m represents an integer of 1 to 6; and

X 4 represents SO 3 H.

18. The separation membrane for redox flow secondary battery according to claim 7 ,

wherein:

the ion-exchange resin layer comprises a fluorine-based polyelectrolyte polymer having an equivalent weight EW (dry mass grams per equivalent of ion exchange groups) of 300 to 1300 g/eq, and

an equilibrium water content of the ion-exchange resin layer is 5% to 80% by mass.