Electric Double Layer Capacitance Device

• US 20080180881A1
• Filed: 11/15/2007
• Published: 07/31/2008
• Est. Priority Date: 11/15/2006
• Status: Active Grant

• Current Assignee: BASF SE, University of Washington
• Original Assignee: EnerG2, Inc. (BASF SE)
• Inventors: Cao, Guozhong, Feaver, Aaron M.
• Granted Patent: US 7,835,136 B2
• Time in Patent Office: Days
• US Class Current: 361/502
• CPC Class Codes: C01B 32/30 Active carbon
• CPC Class Codes: C01B 32/318 characterised by the starting materials
• CPC Class Codes: H01G 11/24 characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
• CPC Class Codes: H01G 11/26 characterised by their structure, e.g. multi-layered, porosity or surface features
• CPC Class Codes: H01G 11/30 characterised by their material
• CPC Class Codes: H01G 11/32 Carbon-based
• CPC Class Codes: H01G 11/34 characterised by carbonisation or activation of carbon
• CPC Class Codes: H01G 11/84 Processes for the manufacture of hybrid or EDL capacitors, or components thereof
• CPC Class Codes: H01G 11/86 specially adapted for electrodes carbonisation or activation of carbon for the manufacture of electrodes H01G11/34
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors
• CPC Class Codes: Y02P 20/133 Renewable energy sources, e.g. sunlight
• CPC Class Codes: Y10T 428/249978 Voids specified as micro
• CPC Class Codes: Y10T 428/24998 Composite has more than two layers

Abstract

The present application is directed to electric double layer capacitance (EDLC) devices. In one aspect, the present application is directed to an electrode comprising an activated carbon cryogel having a tunable pore structure wherein: the surface area is at least 1500 m2/g as determined by nitrogen sorption at 77K and BET analysis; and the pore structure comprises a pore volume ranging from about 0.01 cc/g to about 0.25 cc/g for pores having a pore diameter of 0.6 to 1.0 nm. In another aspect, the present application is directed to an Electric Double Layer Capacitor (EDLC) device comprising an activated cryogel.

Claims

1. An electrode comprising an activated carbon cryogel having a tunable pore structure wherein:

the surface area is at least 1500 m²/g as determined by nitrogen sorption at 77K and BET analysis

and the pore structure comprises a pore volume ranging from about 0.01 cc/g to about 0.25 cc/g for pores having a pore diameter of 0.6 to 1.0 nm.

2. The electrode of claim 1 wherein the specific capacitance of the electrode is at least 75 F/g and the specific power of the electrode is at least 10 W/g when each of the specific capacitance and specific power is measured in an electric double layer capacitor device comprising an electrolyte comprising equal volumes of propylene carbonate and dimethylcarbonate and further comprising about 1.0 M tetraethylammonium-tetrafluoroborate.

3. The electrode of claim 1 wherein the electrode is a component in a supercapacitor, an ultracapacitor, an electric double layer capacitor or a pseudo capacitor.

4. An Electric Double Layer Capacitor (EDLC) device comprising:

a) a positive electrode and a negative electrode wherein each of the positive and the negative electrodes comprise an activated carbon cryogel having a tunable pore structure;

b) an inert porous separator;

c) an electrolyte;

wherein the positive electrode and the negative electrode are separated by the inert porous separator; and

the specific capacitance of each of the positive and negative electrodes is independently at least 75 F/g and the specific power of each of the positive and negative electrodes is independently at least 10 W/g.

5. The EDLC device of claim 4 wherein each of the specific capacitance and the specific power is determined in a device wherein the electrolyte comprises propylene carbonate.

6. The EDLC device of claim 5 wherein the specific capacitance of each of the positive and negative electrodes independently ranges from about 75 F/g to about 150 F/g.

7. The EDLC device of claim 6 wherein the specific capacitance of each of the positive and negative electrodes independently ranges from about 90 F/g to about 130 F/g.

8. The EDLC device of claim 7 wherein the specific power of each of the positive and negative electrodes independently ranges from about 25 W/g to about 35 W/g.

9. The EDLC device of claim 4 where the specific energy of each of the positive and negative electrodes is independently at least about 25 J/g.

10. The EDLC device of claim 9 where the specific energy of each of the positive and negative electrodes independently ranges from about 38 J/g to about 45 J/g.

11. The EDLC device of claim 4 wherein the activated carbon cryogel has surface area greater than about 1500 m²/g as determined by nitrogen sorption at 77K and BET analysis.

12. The EDLC device of claim 11 wherein the activated carbon cryogel has surface area greater than about 2000 m²/g as determined by nitrogen sorption at 77K and BET analysis.

13. The EDLC device of claim 12 wherein the activated carbon cryogel has surface area greater than about 2750 m²/g as determined by nitrogen sorption at 77K and BET analysis.

14. The EDLC device of claim 4 wherein the electrolyte comprises equal volumes of propylene carbonate and dimethylcarbonate and further comprises about 1.0 M tetraethylammonium-tetrafluoroborate.

15. The EDLC device of claim 4 wherein the activated carbon cryogel is prepared according to a method comprising:

a) combining in a first solvent a catalyst with a first monomeric polymer ingredient and a second monomeric polymer ingredient to yield a sol;

b) gelling the sol by heating at a gelling temperature sufficient to yield a tunable synthetic polymer precursor material;

c) freeze-drying the tunable synthetic polymer precursor material to yield a dried cryogel;

d) heating the dried cryogel in the presence of an inert gas or in a vacuum at a carbonization dwell temperature sufficient to carbonize the dried cryogel; and

e) heating the carbonized cryogel at an activation dwell temperature sufficient to activate the carbonized cryogel.

16. The EDLC device of claim 15 wherein step e) comprises any one of:

i) heating the carbonized cryogel at an activation dwell temperature in the presence of carbon dioxide;

ii) heating the carbonized cryogel at an activation dwell temperature in the presence of steam; and

iii) heating the carbonized cryogel at an activation dwell temperature in the presence of an activating aid.

17. The EDLC device of claim 15 wherein the tunable pore structure of the activated carbon cryogel is tuned by any one of:

i) changing the catalyst;

ii) changing the amount of catalyst;

iii) changing the solvent used in step (a);

iv) changing the amount of solvent;

v) changing the first and/or second monomeric polymer ingredients;

vi) changing the relative amount of the first and/or second monomeric polymer ingredients.

vii) changing the length of time of the freeze drying;

viii) changing the pressure of the freeze drying;

ix) changing the temperature of the freeze drying.

18. The EDLC device of claim 15 wherein the tunable pore structure of the activated carbon cryogel is tuned by any one of:

i) changing the dwell temperature at which the dried cryogel is carbonized;

ii) changing the rate of heating to the carbonization dwell temperature;

iii) changing the amount of time the dried cryogel is held at the carbonization dwell temperature;

iv) using a different flow rate of gas during carbonization;

v) using a different pressure of gas during carbonization;

vi) using a different gas during carbonization;

vii) using a vacuum during carbonization;

viii) changing the dwell temperature at which the carbonized cryogel is activated;

ix) changing the rate of heating to the activation dwell temperature;

x) changing the amount of time the dried cryogel is held at the activation dwell temperature;

xi) using a different flow rate of gas during activation;

xii) using a different pressure of gas during activation; and

xiii) using a different gas during activation.

19. The EDLC device of any claim 4 where the tunable pore structure has a pore volume ranging from about 0.01 cc/g to about 0.25 cc/g for pores having a diameter between about 0.6 nm and about 1.0 nm.

20. The EDLC device of claim 4 where the tunable pore structure has a pore volume ranging from about 0.30 cc/g to about 0.70 cc/g for pores having diameter between about 1.0 nm and about 2.0 nm.

21. The EDLC device of claim 4 where the tunable pore structure has a pore volume ranging from about 0.15 cc/g to about 0.70 cc/g for pores having diameter between about 2.0 nm and about 4.0 nm.

22. The EDLC device of claim 4 where the tunable pore structure has:

a pore volume ranging from about 0.01 cc/g to about 0.15 cc/g for pores having a diameter less than about 0.6 nm;

a pore volume ranging from about 0.01 cc/g to about 0.25 cc/g for pores having a diameter between about 0.6 nm and about 1.0 nm;

a pore volume ranging from about 0.30 cc/g to about 0.70 cc/g for pores having diameter between about 1.0 nm and about 2.0 nm;

a pore volume ranging from about 0.15 cc/g to about 0.70 cc/g for pores having diameter between about 2.0 nm and about 4.0 nm;

a pore volume ranging from about 0.06 cc/g to about 0.50 cc/g for pores having diameter between about 4.0 nm and about 6.0 nm; and

a pore volume ranging from about 0.01 cc/g to about 0.30 cc/g for pores having diameter between about 6.0 nm and about 8.0 nm.

23. The EDLC device of claim 4 wherein the tunable pore structure comprises micropores having an effective length of less than about 5 nm as determined by TEM measurements.

24. The EDLC device of claim 4 wherein the tunable pore structure comprises mesopores having a diameter ranging from about 2.0 to about 10.0 nm as determined from N₂ sorption derived DFT.

25. The EDLC device of claim 24 wherein the tunable pore structure comprises mesopores having a diameter ranging from about 2.0 to about 4.0 nm as determined from N₂ sorption derived DFT.

26. The EDLC device of claim 4 wherein the tunable pore structure comprises micropores having a diameter ranging from about 0.3 nm to about 2.0 nm as determined from CO₂ sorption derived DFT.

27. The EDLC device of claim 26 wherein the tunable pore structure comprises micropores having a diameter ranging from about 0.6 to about 1.0 nm as determined from CO₂ sorption derived DFT.

28. An electric double layer capacitor (EDLC) device comprising:

a) a positive electrode and a negative electrode wherein each of the positive and second electrode comprises an activated carbon cryogel and polytetrafluoroethylene;

b) an inert porous separator comprising polypropylene or polyethylene;

c) a first and a second current collector each comprising a non-corrosive metal;

d) an electrolyte comprising equal volumes of propylene carbonate and dimethylcarbonate and further comprising about 1.0 M tetraethylammonium-tetrafluoroborate;

wherein the positive and negative electrodes are separated by the porous separator and each is in contact with one current collector;

the specific capacitance of each of the positive and negative electrodes as measured in the device is independently at least 75 F/g and the specific power of each of the positive and negative electrodes as measured in the device is independently at least 10 W/g.

29. The EDLC device of claim 28 wherein the activated carbon cryogel is prepared according to a method comprising:

a) combining in a solvent a catalyst with resorcinol and formaldehyde to yield a sol;

b) gelling the sol by heating at a gelling temperature sufficient to yield a sol gel;

c) freeze-drying the sol gel to yield a dried cryogel;

d) heating the dried cryogel in the presence of an inert gas at a carbonization dwell temperature sufficient to carbonize the dried cryogel; and

e) heating the carbonized cryogel at an activation dwell temperature sufficient to activate the carbonized cryogel.

30. The EDLC device of claim 29 wherein the specific capacitance of each of the positive and negative electrodes independently ranges from about 75 F/g to about 150 F/g.

31. The EDLC device of claim 29 wherein the specific power for the each of the positive and negative electrode independently ranges from about 25 to about 35 W/g.

32. The EDLC device of claim 29 wherein the specific energy for the each of the positive and negative electrode independently ranges from about 38 to about 45 J/g.

33. The EDLC device of claim 29 wherein the activated carbon cryogel has surface area greater than about 1500 m²/g as determined by nitrogen sorption at 77K and BET analysis.

34. The EDLC device of claim 33 wherein the activated carbon cryogel has surface area greater than about 2000 m²/g as determined by nitrogen sorption at 77K and BET analysis.

35. The EDLC device of claim 34 wherein the activated carbon cryogel has surface area greater than about 2750 m²/g as determined by nitrogen sorption at 77K and BET analysis.