JP2003515251A - Capacitor - Google Patents

Abstract

(57) [Summary] The present invention is directed to a supercapacitor or an ultracapacitor. The ultracapacitor includes at least one bipolar electrode plate (12), an electrolyte (14), and a separator (16). The bipolar electrode plate (12) comprises a current collector and electrode material associated with the current collector. The electrolyte (14) is located between adjacently oriented bipolar plates and includes a neutral organic solvent and a salt. The stabilizing additive, in association with the electrolyte, stabilizes the electrochemical action between the electrolyte and at least one of the current collector and the electrode material and the electrolyte. In addition, the electrolyte may further include a wetting agent that increases the wettability of the electrode.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. TECHNICAL FIELD The present invention is directed to capacitors, and in particular to super or ultra capacitors of the type utilizing bipolar electrode plates.

2. Ultracapacitors, also known as prior art supercapacitors, are well known to those skilled in the art. These ultracapacitors electrostatically store energy by polarizing a solution of electrolyte. Ultracapacitors are actually electrochemical devices, but their energy storage mechanism does not involve chemical reactions. For historical background and operating characteristics and customary construction, see "Ultracapacitors For Portable Electr.
onics ", by Xavier Andrieu, The Big Little Book of Capacitors, Chapter 15 of 521
Can be found on page ~ 547.

Ultracapacitors typically consist of an electrolyte and a separator located in the electrolyte (
It is composed of two or more bipolar electrode plates separated from each other by a polarizing plate.
These electrode plates include a current collector composed of a conductive material and an electrode material associated with the current collector. The components of the capacitor are effectively fixed and housed within the enclosure. From this housing are electrical leads for connection to the item to be subjected to the electrical utility of the capacitor.

In a conventional dielectric capacitor, energy is stored in the form of separated charges, and the larger the area where the charges are stored and the closer the separated charges are, the larger the capacitance becomes. In such capacitors, the area for accumulating charge is obtained from a plate of flat conductive material and the charged plate is separated by a dielectric material.

In ultracapacitors, the charge storage region is usually obtained from a porous carbon material. The porous structure of carbon allows a much larger rechargeable area than a flat conductor plate of a dielectric capacitor. In addition, the charge separation distance of ultracapacitors is usually determined by the size of the ions in the associated electrolyte, which are attracted to the charged electrodes. Such charge separation is substantially less than the charge separation that can be obtained with conventional dielectric materials.
Therefore, the combination of the relatively large surface area and the small charge separation results in a capacitance that is superior to conventional capacitors.

SUMMARY OF THE INVENTION The present invention is directed to capacitors, and more particularly to supercapacitors, which include at least one electrode each comprising a current collector and an electrode material associated with the current collector. Located adjacent to the plate, a neutral organic solvent, a salt, and an electrolyte comprising means for stabilizing the electrochemical action between the solvent and at least one of the current collector and / or the electrode material. And a separator that can be placed in the electrolyte to prevent physical contact between the electrode plates.

In a preferred embodiment of the invention said electrolyte further comprises means for increasing the wettability of the electrode. The wettability increasing means can be composed of a surfactant.

In these preferred embodiments, the surfactant is selected from the group consisting of nonionic fluoroalkanes.

In another preferred embodiment of the present invention, the means for stabilizing the electrochemical action comprises a reducible chemical component instead of the solvent. In such a preferred embodiment, the means for stabilizing the electrochemical action is selected from the group consisting of carbonates such as vinylene carbonate, spirolactone, anhydrides, and oligomers (low polymers).

In yet another preferred embodiment of the invention, the current collector has a low electrical resistance, a substantial impermeability to electrolyte permeation, a chemical compatibility with at least one of the electrode material and the electrolyte, and a chemical resistance. It is selected from the group of stable materials.

In one of these preferred embodiments, the current collector comprises a carbon material, and in another preferred embodiment the current collector comprises aluminum.

In yet another preferred embodiment of the present invention, the capacitor further comprises a substantially inert frame structure. In such a preferred embodiment, the frame structure comprises an end plate having a current collector associated with the frame structure.

The ultracapacitor produced as described above, particularly the carbon / graphite fiber electron active material, the non-aqueous electrolyte, and the polymer-coated aluminum bar polar current collector plate, has a capacitance of 0.95 F / cm ² . And energy as high as 1 mAh / cm ² . These capacitors are constructed using commercially available components. The materials and components are chosen in relation to known and anticipated manufacturing constraints, and to allow increased manufacturing of capacitors.

BEST MODE FOR CARRYING OUT THE INVENTION Although the present invention can be embodied in many different forms, some preferred embodiments will now be described in detail with reference to the drawings. The examples of the present invention illustrate the principles of the present invention and are not intended to limit the present invention to the illustrated examples.

FIG. 1 shows a schematic cross-sectional view of an ultra capacitor 10, which includes a bipolar electrode plate 12, an electrolyte 14, a separator (polarizing plate) 16, a case 18, and end plates 19 and 19 of the case. ', And the corresponding outlying current collector leads 20, 22 arranged through the end plates. As can be seen, these separators are located between adjacent bipolar electrode plates and in the electrolyte to prevent inadvertent contact between these bipolar electrode plates. Although FIG. 1 shows an ultracapacitor with five bipolar electrode plates, it will be readily understood by one of ordinary skill in the art that any number of desired electrode plates are contemplated in the present invention.

A bipolar electrode plate 12 of the type shown in FIG. 1 is shown in FIG. 2 as comprising a current collector 24 (FIG. 3) and an electrode material 26 (see FIG. 3) associated with this current collector. The combination of the current collector 24 and the electrode material 26 is fixed to the frame structure 28 and surrounded by this frame structure.

The frame structure 28 is constructed of a substantially inert, non-conductive material such as polyethylene and / or polypropylene. Alternatively, glass fiber filled polyethylene, which has a low temperature induced deformation and a low melting point, can be utilized. It is also conceivable to manufacture the frame structure from other materials such as low density, non-linear polyethylene and / or polypropylene. The frame structure is die cutting,
It can be manufactured by conventional techniques such as injection molding and uniform extrusion. The housing 18 (FIG. 1) can also be made from the same material as the frame structure for the bipolar electrode plate. The end plates 19, 19 'may further be manufactured from a glass sheet reinforced polyethylene sheet, the current collector of the relevant end plate being manufactured from the same material as the current collector itself, for example drawn copper mesh or aluminum. You can

The current collector 24 is made from a material that has low electrical resistance, impermeability to penetration and penetration of electrolytes, chemical compatibility, and electrochemical stability. A preferred material is polyethylene coated aluminum foil, commercially available under the trade name COER-Xal from Rexam Graphics of South Hadley, Massachusetts, USA. It has been found that the use of such materials results in several advantageous features. In particular: aluminum foil provides complete separation of the electrolyte in the bipolar electrode structure; PE coating on the aluminum foil provides additional mechanical and chemical stability to the aluminum foil; PE coating on the aluminum foil It provides the "high temperature melting" adhesive property to the current collector, which enhances the adhesion of the carbon electrode onto the current collector; and the COER-Xal provides good conductivity, a fairly thin configuration (25 μm on each side).
75μm Al with PE) is available.

As an alternative to the above, other materials such as polyethylene-carbon paper (25 μm) are conceivable, and polyethylene-carbon synthetic materials can also be used.

With respect to electrode material 26, such materials can be made from conventional types of electrode materials currently available for the production of super or ultracapacitors.
An example of an acceptable electrode material, the most frequently described, is based on the use of highly activated carbon powder in the surface area.
The surface area of carbon is generally greater than 1500 m ² / g. These carbons generally have a total pore volume of 1 ml / g and an average pore diameter of 20Å. In order to make electrode materials using these carbons, the carbon powder of choice must be mixed with a suitable "binder" (bond) and applied onto the current collector to be adhered.

A second acceptable type of carbon electrode is based on activated carbon fibers and is commonly available in the form of reticulated or non-reticed felts, fabrics, foams or webs (machine knitted fabrics). It is possible. Carbon fibers having surface areas similar to those prepared for activated carbon are commercially available. The use of carbon fiber webs eliminates the need to mix activated carbon powder with a binder, and generally eliminates the need to coat the mixed carbon powder on a current collector by a solvent coating process.
It simplifies the electrode assembly process. It is believed that the main difference between carbon powder and carbon fiber lies in the trade-off between the energy storage capacity of the carbon electrode and the ease with which the electrode can be processed.

The electrolyte 14 shown in FIG. 1 is composed of a neutral organic solvent, a salt, a stabilizer, and a surfactant. This solvent is used in Dr. Ue In J. Electrochem. Soc. 141, 11 (1994) 2989.
It can be constructed from conventional, known materials such as those described on pages 2996. By way of example only, propylene carbonate ("PC") can be used. P
Although C has been found to be a good solvent, it has a high viscosity (n = 2.5 cp) and is consequently less than optimal conductivity. Therefore, mixed solvents have also been considered and tested. Acetonitrile (n = 0.3cp) and y-bryrolacurone (n = 1.7cp)
Initially selected as a co-solvent for PC.

The salt used in forming the electrolyte is composed of tetra-ethylene-ammonium-tetra-fluoride salt. But among some other customary salts,
Other salts, such as fluoroalkylammonium can be considered for use as well.

Since the electrochemical stability of neutral organic solvents in contact with carbon powder / fibers is a concern in the capacitor industry, the present invention provides a preferentially reducible additive / chemistry instead of solvent. We respond to these concerns by utilizing the natural ingredients. For example, in a preferred example, the additive is carbonate (vinylene carbonate),
It can be composed of spirolactone, anhydrides, and oligomers (low polymers).

To increase the wettability of the carbon electrode with the electrolyte, a surfactant is added to the electrolyte solution. These surfactants are generally chosen to be nonionic fluoroalkanes. (The examples are F-142d and F177 of Dainippon Ink and FC-171 and FC-170C of 3M.)

In order to support the beneficial effects obtained from the ultracapacitors constructed according to the above, a number of analyzes were carried out and the results are graphically represented in FIGS. 4 to 24, where the additive (stabilizer , And surfactants) conventional electrode materials (ie, TSW2, TSW3 carbon fiber electrode materials commercially available from Toyobo, Japan, and satin-based electrodes commercially available from Calgon, UK). It is used in combination with. Further information on the analysis can be found in the corresponding provisional US patent application 60/165.
No. 865, filed Nov. 16, 1999, the present application is based on this patent application and is hereby incorporated by reference in its entirety. In particular, these graphs are as follows.

FIG. 4 is a graphical representation of the AC impedance measurements of the present invention based on TSW2 carbon fiber electrodes.

FIG. 5 is a graphical representation of the present invention's normalized AC impedance based on TSW2, showing the effect of viscosity between the current collector and the electroactive material. Better viscosity results in lower internal resistance.

FIG. 6 is a graph showing voltage-time characteristics of initial charge / discharge for the ultracapacitor of the present invention configured by using electrodes based on TSW2. Some difference in charge time is observed, but discharge time is almost constant for all systems. This behavior is further shown in FIG.

FIG. 7 is a graph showing the discharge voltage-time characteristics of an ultracapacitor configured by using electrodes based on TSW2.

FIG. 8 is a graphical representation of discharge capacity retention as a function of cycle number, showing the first five cycles for a capacitor constructed with electrodes based on TSW2.

FIG. 9 is a diagram in which the initial power performance of the capacitor of the present invention is expressed in a graph by the voltage-time characteristic, and is for a capacitor configured by using electrodes based on TSW2.

FIG. 10 is a graph showing the normalized voltage-time characteristics during the power test of the capacitor configured by using the electrodes based on TSW2. These results show good capacity retention for these electrodes. This is further shown in FIG.

FIG. 11 is a graphical representation of the total delivered energy during discharge at different power rates as a function of time.

FIG. 12 is a graph showing the AC impedance by comparing the TSW2 electrode material and the TSW3 electrode material, which are considered “equivalent” by the manufacturer.

FIG. 13 is a graph showing voltage-time characteristics of initial charge / discharge for the TSW2 electrode material and the TSW3 electrode material.

FIG. 14 is a graph showing the AC impedance by comparing the TSW2 and TSW3 electrode materials with the satin electrode material.

FIG. 15 is a graph showing voltage-time characteristics by comparing a capacitor made of TSW2 carbon paper with a capacitor made of satin carbon fabric.

FIG. 16 is a graph showing discharge voltage-time characteristics by comparing a capacitor made of TSW2 carbon paper with a capacitor made of satin carbon fabric.

FIG. 17 is a graph representation of the initial power performance, showing the voltage-time characteristics of an ultracapacitor made of satin carbon fabric.

FIG. 18 is a graphic representation of the normalized voltage-time characteristics during the power test of an ultracapacitor constructed using satin-based electrodes. This result is
It shows good capacity retention for these electrodes. This is further shown in FIG.
Shown in.

FIG. 19 is a graphical representation of the total delivered energy during discharge at different power rates as a function of time.

FIG. 20 is a graph showing the effect of the additive of the electrolyte on the charging behavior of the ultracapacitor. Capacitor number 110103, without an electrolyte additive, exhibits long self-decomposition behavior during initial charge, while capacitor number 102902 exhibits normal charge behavior.

[0044]   FIG. 21 is a graph showing the effect of the maximum charging voltage.

FIG. 22 is a graphical representation of the effect of an electrolyte based on a cosolvent on the total resistance of the cell for an ultracapacitor constructed using TSW3 electrode material.

FIG. 23 is a graphic representation of the effect of an electrolyte based on a cosolvent on the total resistance of the cell for an ultracapacitor constructed using satin fabric. Tests carried out with a 1: 1 mixture of propylene carbonate and acetonitrile show that the conductivity of the electrolyte is increased as expected, but the electrochemical stability of the electrolyte is reduced. This may be due, in part, to water pollution and the presence of other residual impurities.

FIG. 24 is a graph showing voltage-time characteristics of initial charge / discharge for an ultracapacitor configured by using a cosolvent based on a satin fabric and an electrolyte (No. 101501).

The above description and drawings are merely illustrative of the present invention, and the claims of the present invention may be practiced by those of ordinary skill in the art without departing from the scope of the invention upon reading the text of this specification. The above description does not limit the invention, except to the extent that it is limited to the possible modifications and variations.

[Brief description of drawings]

1 is a schematic cross-sectional view of the present invention.

FIG. 2 is a perspective view of a bipolar electrode plate of the present invention.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2, showing the current collector material and electrode material of the present invention.

FIG. 4 is a graph representation of the AC impedance of the present invention.

FIG. 5 is a graph representation of the normalized AC impedance of the present invention.

FIG. 6 is a graph showing voltage-time characteristics of initial charge and discharge for the ultracapacitor of the present invention.

FIG. 7 is a graph showing the discharge voltage-time characteristics of the ultracapacitor of the present invention.

FIG. 8 is a graphical representation of discharge capacity retention as a function of cycle number.

FIG. 9 is a graph showing the initial power performance of the capacitor of the present invention by a voltage-time characteristic.

FIG. 10 is a graph showing normalized voltage-time characteristics during the power test of the capacitor of the present invention.

FIG. 11 is a graphical representation of total delivered energy during discharge at different power rates as a function of time.

FIG. 12 is a graph showing a comparison of AC impedances.

FIG. 13 is a graph showing voltage-time characteristics of initial charge and discharge.

FIG. 14 is a graph showing a comparison of AC impedances.

FIG. 15 is a graph showing voltage-time characteristics for comparison.

FIG. 16 is a graph showing a comparison of discharge voltage-time characteristics.

FIG. 17 is a graph showing the initial power performance.

FIG. 18 is a graph showing a normalized voltage-time characteristic during a power test.

FIG. 19 is a graphical representation of total delivered energy during discharge at different power rates as a function of time.

FIG. 20 is a graph showing the effect of an electrolyte additive on the charging behavior of an ultracapacitor.

FIG. 21 is a graph showing the effect of the maximum charging voltage.

FIG. 22 is a graphical representation of the effect of cosolvent based electrolytes on total cell resistance.

FIG. 23 is a graphic representation of the effect of cosolvent based electrolytes on total cell resistance.

FIG. 24 is a graph showing voltage-time characteristics of initial charge / discharge.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), OA (BF , BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, G M, KE, LS, MW, MZ, SD, SL, SZ, TZ , UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, C H, CN, CR, CU, CZ, DE, DK, DM, EE , ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, K P, KR, KZ, LC, LK, LR, LS, LT, LU , LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, S G, SI, SK, SL, TJ, TM, TR, TT, TZ , UA, UG, US, UZ, VN, YU, ZA, ZW

Claims (11)

[Claims] 1. At least one bipolar electrode plate each comprising a current collector and an electrode material associated with the current collector; a neutral organic solvent, a salt, and the solvent and at least one of the current collector and the electrode material. A capacitor comprising an electrolyte composed of a means for stabilizing the electrochemical action between the two; and a separator. 2. The capacitor of claim 1, wherein the electrolyte further comprises means for increasing the wettability of the electrode. 3. The capacitor according to claim 2, wherein the wettability increasing means is composed of a surfactant. 4. The capacitor according to claim 3, wherein the surfactant is selected from the group consisting of nonionic fluoroalkanes. 5. The capacitor according to claim 1, wherein said electrochemical action stabilizing means comprises a reducible chemical component instead of said solvent. 6. The stabilizing means for the electrochemical action is carbonate, spirolactone,
The capacitor according to claim 5, wherein the capacitor is selected from the group consisting of anhydrides and oligomers. 7. The current collector is selected from the group of materials having low electrical resistance, substantial impermeability to electrolyte permeation, chemical compatibility with at least one of the electrode material and electrolyte, and chemical stability. The capacitor according to claim 1, which is selected. 8. The capacitor of claim 7, wherein the current collector comprises a carbon material. 9. The capacitor according to claim 7, wherein the current collector is made of aluminum. 10. The capacitor of claim 1, further comprising a substantially inert frame structure. 11. The capacitor of claim 10, wherein the frame structure comprises an end plate having a current collector lead associated with the frame structure.