JP2005100926A - Electrochemical cell laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical cell laminate with improved reliability. <P>SOLUTION: On the electrochemical cell laminate formed by laminating a plurality of electrochemical cell units, composed of sheet-shaped separators, a pair of positive and negative sheet-shaped electrodes impregnated with electrolyte, a pair of positive and negative current collectors arranged through the pair of positive and negative electrodes, and a gasket surrounding an outer periphery of the electrodes for sealing the pair of electrodes, a sheet-shaped conductive material is arranged between the units so that an outer periphery of the contact face with the unit almost fits with an inner periphery of the gasket of the unit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrochemical cell laminate in which electrochemical cell units having a separator, an electrode, a current collector, and a gasket are laminated in series.

  An electrochemical cell having a structure including a pair of positive and negative electrodes arranged via a separator is used for an electric double layer capacitor or a secondary battery. Such electrochemical cells include a small cell called a coin cell and a wound cell that can obtain a relatively large capacity.

  FIG. 5 shows a cross section of a unit of an electrochemical cell which forms a basic structural unit of a coin-type electric double layer capacitor. In FIG. 5, 2 is a polarizable electrode on the positive electrode side, 3 is a polarizable electrode on the negative electrode side, 4 is a current collector on the positive electrode side, 5 is a current collector on the negative electrode side, 6 is an annular gasket, and 7 is a separator. is there.

  As shown in FIG. 5, in the electric double layer capacitor, positive and negative polarizable electrodes 2 and 3 formed by binding a carbonaceous material powder or the like with a binder through a separator 7 made of a porous polymer sheet; The positive and negative current collectors 4 and 5 made of a conductive sheet are laminated in this order, and the positive and negative polarizable electrodes 2 and 3 are impregnated with an electrolytic solution, and then sealed with a gasket 6 made of a rubber-based material. , Constituting unit 1.

  Such a unit may be used as an electrochemical cell as it is, but in order to obtain a required output, a plurality of units may be stacked and electrically connected in series to be used as an electrochemical cell stack. is there. Problems that arise when a plurality of units are used in a stacked manner include a reduction in contact resistance between the units, a reduction in internal resistance in the units, and suppression of variations in the electrochemical reaction between the units.

  An example in which a plurality of units are stacked and used is described in JP-A-6-215794 (Patent Document 1). Patent Document 1 discloses a technique for obtaining a thin sealed lead-acid battery that can extend the life by reducing the difference in decrease in electrolyte in each unit. Specifically, a metal plate having an area larger than the unit laminate surface is interposed between adjacent units of the laminate, and the laminate surface is pressurized by a case that houses the laminate. is there.

  FIG. 7 is a cross-sectional view schematically showing an example of an electrochemical cell laminate according to the technique disclosed in Patent Document 1. In FIG. 7, 1 is an electrochemical cell unit, 8c is a conducting material, and 9 is a pressure plate. As shown in FIG. 7, the conductive material 8 c has a larger area than the laminated surface of the unit 1.

  In Patent Document 1, by adopting such a configuration, the metal plate (corresponding to the conductive material 8c in FIG. 7) and the unit can be satisfactorily adhered, and there is a difference in decrease in the electrolyte due to moisture permeation. It is described that it becomes less.

  However, in the technique disclosed in Patent Document 1, since the metal plate interposed between the units has a larger area than the laminated surface of the units, the gasket is mainly subjected to pressure, and is sufficient for the electrode portion. No pressure is applied to the. Among the above-mentioned problems, from the viewpoint of reducing internal resistance in the unit and suppressing variation between units of electrochemical reaction in the electrode, by sufficiently pressurizing the electrode part, the contact between the electrode and the electrolyte is more uniform and It may be performed sufficiently and an improvement effect may be obtained.

  For this reason, in the technique of Patent Document 1, a certain degree of effect can be obtained in terms of suppressing variation in decrease in the electrolyte contained in the unit. However, the internal resistance is reduced in the unit and the electrochemical reaction in the electrode varies between units. In terms of suppression, almost no effect can be expected.

On the other hand, in Japanese Patent Application Laid-Open No. 10-189056 (Patent Document 2), a pressure mat having a structure that can be filled with a fluid such as gas is installed in the center of an electrode laminate housed in a rectangular metal case. In addition, a technique is disclosed in which an equal pressure is applied to all regions of all electrodes of the electrode stack to maintain a constant electrode interval and to equalize electrochemical reactions. However, this technique pressurizes the electrode laminate from the inside of the electrochemical cell and cannot be applied to an electrochemical cell unit sealed with a gasket having the structure shown in FIG.
JP-A-6-215794 Japanese Patent Laid-Open No. 10-189056

  An object of the present invention is to provide an electrochemical cell laminate having improved reliability, which is formed by laminating a unit of an electrochemical cell having a separator, an electrode, a current collector, and a gasket.

  In order to achieve the above-mentioned object, the present invention has been made as a result of studying a configuration when stacking electrochemical cell units.

  The present invention includes embodiments described in the following items 1 to 7.

(1) A sheet-like separator, a pair of positive and negative sheet-like electrodes disposed opposite to each other via the separator and impregnated with an electrolytic solution, and a pair of positive and negative current collectors respectively arranged via the pair of positive and negative electrodes And an electrochemical cell laminate in which a plurality of electrochemical cell units having a gasket surrounding the outer periphery of the body and the electrode for sealing the pair of electrodes are laminated,
Between the units of the laminate, having a sheet-like conductive material,
The sheet-like conductive material is an electrochemical cell laminate in which an outer periphery of a contact surface with the unit is arranged so as to substantially overlap an inner periphery of a gasket of the unit.

(2) A sheet-like separator, a pair of positive and negative sheet-like electrodes disposed opposite to each other via the separator and impregnated with an electrolytic solution, and a pair of positive and negative current collectors respectively arranged via the pair of positive and negative electrodes And an electrochemical cell laminate in which a plurality of electrochemical cell units having a gasket surrounding the outer periphery of the body and the electrode for sealing the pair of electrodes are laminated,
Between the units of the laminate, having a sheet-like conductive material,
The sheet-like conductive material is arranged so that the outer periphery of the contact surface with the unit has a planar shape corresponding to the inner periphery of the gasket of the unit, and the outer periphery is located inside the inner periphery of the gasket of the unit. Electrochemical cell stack.

  (3) The electrochemical cell laminate according to item 1 or 2, wherein the gasket has an annular shape, and the sheet-like conductive material has a circular shape corresponding to the inner periphery of the gasket.

  (4) The electrochemical cell laminate according to item 1, 2 or 3, wherein the sheet-like conductive material has a protrusion extending to the outer periphery of the gasket at the center in the thickness direction.

  (5) The unit of the electrochemical cell contains a positive electrode containing a proton conductive compound as an electrode active material, a negative electrode containing a proton conductive compound as an electrode active material, and an electrolyte containing a proton source. The electrochemical cell laminate according to any one of items 1 to 4.

  (6) The electrochemical cell laminate according to any one of items 1 to 5, wherein the unit of the electrochemical cell has an electrode and a current collector separately formed and laminated.

  (7) A power storage device using the electrochemical cell laminate according to any one of items 1 to 6.

  According to the present invention, since the planar shape of the sheet-like conductive material interposed between the units is a shape corresponding to the inner periphery of the gasket, the sheet-like conductive material applies equal and sufficient pressure to the electrodes of the unit. Can do. Accordingly, as a first action, the contact resistance between the units and the variation in the contact resistance are reduced, and accordingly, the voltage applied to each unit can be equalized. In addition, as a second function, the contact between the electrode and the electrolytic solution or the contact between the electrode and the current collector is made more uniform and sufficient, the internal resistance of the unit is reduced, and the electrochemical reaction within the unit is performed between the units. Can be reduced. And the electrochemical cell laminated body which was excellent in the voltage balance and improved the reliability by the synergistic effect of these effect | actions can be provided.

  In addition, by providing the sheet-like conductive material with a protrusion that extends to the outer periphery of the gasket, it is easy to align the unit and the sheet-shaped conductive material when stacked, and productivity is improved.

  Next, an embodiment of the present invention will be described taking a secondary battery as an example.

  The unit of the electrochemical cell used in the present invention can basically be one having a conventional structure, and this part will be described with reference to FIG. The unit 1 shown in FIG. 5 includes a positive electrode 2 composed of a positive electrode active material, a conductive auxiliary agent, and a binder, a negative electrode active material, a conductive auxiliary agent, and a negative electrode composed of a binder. A separator 7 disposed between the side electrode 3, the positive electrode 2 and the negative electrode 3, which is ion-permeable and insulating, and a positive-side current collector 4 disposed on the upper and lower surfaces in FIG. It consists of a current collector 5 on the negative electrode side and a gasket 6 arranged around these electrodes and separator. In consideration of the volume change of the electrode accompanying the reaction, the electrode and the current collector can be separately shaped and laminated.

  FIG. 1 is a cross-sectional view schematically showing an example of the electrochemical cell laminate of the present invention. Here, as shown in FIG. 1, a plurality of units 1 are stacked via the conductive material 8 a, and the pressure plates 9 are disposed at both ends in the stacking direction. As the conductive material interposed between the units, a conductor such as a metal sheet, a graphite sheet such as a graph foil can be used. As shown in FIG. 1, the conductive material 8a has an outer peripheral shape that corresponds to the inner periphery of the gasket 6, typically has the same shape, and abuts only on the positive / negative electrode arrangement region of the current collector. Therefore, the electrode can be uniformly and sufficiently pressurized by the pressure from the pressure plate 9. From the same point of view, it is preferable that the outer peripheral shape of the pressure plates 9 arranged on both sides of the laminate corresponds to the inner periphery of the gasket 6 and typically has the same shape.

  It is preferable that the area of the surface in contact with the unit of the conductive material or the pressure plate is the same as or smaller than the area of the inner periphery on the lamination plane of the gasket of the unit, and 90% or more with respect to the area of the gasket inner periphery It is preferable that it is 95% or more.

  When the gasket has an annular structure, a circular plate having an outer diameter that is the same as or smaller than the inner diameter of the gasket can be used as the conductive material or the pressure plate. Moreover, it is preferable that the outer diameter of this circular plate is substantially the same as the outer diameter of the said electrode so that the whole arrangement | positioning area | region of the electrode arrange | positioned inside a gasket can be pressurized.

  The annular gasket and the circular plate can be arranged so as to be aligned such that their centers are located on the same axis.

  FIG. 2 is a cross-sectional view schematically showing another example of the electrochemical cell laminate of the present invention. Here, a conductive material 8b having a shape having a protrusion extending to the outer peripheral portion of the gasket at the center in the thickness direction is used. By providing such a protrusion on the conductive material, the positioning of the unit and the conductive material becomes extremely easy, and the assembly work efficiency can be improved.

  FIG. 3 shows an example of a conductive material having a protrusion, FIG. 3 (a) and FIG. 3 (c) are perspective views, and FIG. 3 (b) is a cross-sectional view. In FIG. 3, 10a is a protrusion provided on the entire outer periphery of the conductive material, and 10b is a protrusion provided on a part of the outer periphery of the conductive material. As described above, since the protrusion is used for alignment in the assembly work, it may be provided on the entire outer periphery of the conductive material as shown in FIG. 3A, or as shown in FIG. 3C. It may be partially provided on the outer periphery.

  FIG. 4 is a diagram showing a state in which the unit 1 and the conductive material 8b are stacked using the conductive material protrusion 10a. As shown in FIG. 4, the projection 10a of the unit 1 and the conductive material 8a has an outer shape with substantially the same outer diameter, and therefore, by using a positioning member (not shown) that contacts at least three points on the outer peripheral portion. , Positioning becomes easy.

  As an electrochemical cell in which the effects of the present invention can be obtained more remarkably, a cell that can operate so that only protons act as charge carriers in the oxidation-reduction reaction in both electrodes accompanying charging and discharging, more specifically, a proton source is used. The electrolyte concentration and operating voltage of the electrolyte are controlled so that only the proton adsorption / desorption of the electrode active material can be involved in the electron transfer accompanying the oxidation-reduction reaction at both electrodes accompanying charging and discharging. What is done is preferable.

The following reaction formula shows the reaction of polyindole, which is one of proton conducting compounds. The first stage reaction shows a reaction by doping. X ⁻ in the formula represents a dopant ion, for example, a sulfate ion, a halide ion or the like, which is doped with a proton conductive compound to impart electrochemical activity. The reaction in the second stage shows an electrochemical reaction (electrode reaction) involving adsorption and desorption of protons of the doped compound. In an electrochemical cell that causes such an electrode reaction, only the adsorption and desorption of protons is involved in the electron exchange associated with the oxidation-reduction reaction, so that the only mobile substance during charge and discharge is protons. The volume change is small, the cycle characteristics are excellent, and the proton mobility is high and the reaction is fast, so that the high rate characteristics are excellent, that is, the rapid charge / discharge characteristics are excellent.

  As described above, a proton-conducting compound is used as the electrode active material in the present invention, and this proton-conducting compound is an organic compound (polymer) that can accumulate electrochemical energy by an oxidation-reduction reaction with an ion of an electrolyte. Included).

  As such proton-conducting compounds, conventionally known compounds can be used. For example, polyaniline, polythiophene, polypyrrole, polyacetylene, poly-p-phenylene, polyphenylene vinylene, polyperiphthalene, polyfuran, polyflurane, polythienylene, polythienylene. Π-conjugated polymers such as pyridinediyl, polyisothianaphthene, polyquinoxaline, polypyridine, polypyrimidine, polyindole, polyaminoanthraquinone, polyimidazole and their derivatives, indole π-conjugated compounds such as indole trimer compounds, benzoquinone Quinone compounds such as naphthoquinone and anthraquinone, quinone polymers such as polyanthraquinone, polynaphthoquinone and polybenzoquinone (quinone oxygen becomes a hydroxyl group by conjugation) And a proton-conducting polymer obtained by copolymerization of two or more monomers that give the polymer. By doping these compounds, a redox pair is formed and conductivity is exhibited. These compounds are selectively used as a positive electrode and a negative electrode active material by appropriately adjusting the difference in oxidation-reduction potential.

  As the proton-conducting compound, a π-conjugated compound or π-conjugated polymer having a nitrogen atom, a quinone compound or a quinone polymer can be preferably used.

  An inorganic acid or an organic acid can be used as a proton source of an electrolyte containing a proton source (which can give a proton). For example, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, tetrafluoroboric acid, hexafluoroboric acid can be used as the inorganic acid. Examples of the organic acid include saturated monocarboxylic acid, aliphatic carboxylic acid, oxycarboxylic acid, p-toluenesulfonic acid, polyvinylsulfonic acid, and lauric acid. Among the electrolytes containing these proton sources, an acid-containing aqueous solution is preferable, and a sulfuric acid aqueous solution is particularly preferable.

The proton concentration in the electrolyte solution containing the proton source is preferably 10 ⁻³ mol / l or more, more preferably 10 ⁻¹ mol / l or more, from the viewpoint of the reactivity of the electrode material. 18 mol / l or less is preferable from the point of prevention of 7 mol / l or less.

  Next, the present invention will be described in more detail based on specific examples. In addition, since the unit of an electrochemical cell can use what has a conventional structure fundamentally, the structure of a unit is demonstrated with reference to FIG.

(Example 1)
A polyindole having a unit represented by the following formula, which is an electrode active material on the positive electrode side, contains 20% by weight of carbon by vapor deposition as a conductive auxiliary agent with respect to the electrode active material and an average molecular weight of 1100 as a binder. 8% by weight of polyvinylidene fluoride was added to the electrode active material, and the mixture was stirred and mixed using a blender. The obtained mixture was hot press molded to obtain a positive electrode 2 (outer diameter: 13.2 mm).

  Next, to the polyphenylquinoxaline represented by the following formula, which is an electrode active material on the negative electrode side, 25% by weight of carbon by a vapor phase growth method is added as a conductive additive to the electrode active material, and a blender is used. Stir and mix. The obtained mixture was hot press molded to obtain a negative electrode 3 (outer diameter: 13.2 mm).

  Next, the positive and negative electrodes were impregnated with the electrolytic solution. Here, an aqueous sulfuric acid solution having a concentration of 20% by weight was used as the electrolytic solution. As the separator, porous polypropylene having a thickness of 150 μm was used, and positive and negative electrodes were laminated with the polypropylene interposed therebetween.

  Next, the obtained laminate, positive and negative current collectors 4 and 5 made of conductive rubber, and gasket 6 made of a rubber-based material were combined, and the current collector and an annular gasket (outer diameter: 16.2 mm, inner diameter) : 14.2 mm) was vulcanized and bonded to produce unit 1 of an electrochemical cell. Here, vulcanization adhesion is used, but the method is not particularly limited as long as a stable adhesion state is obtained.

  Six units 1 were laminated through a circular stainless steel plate (outer diameter: 14.0 mm) having a planar shape substantially the same as the inner peripheral shape of the gasket and a thickness of 200 μm. Further, circular pressure plates were arranged on both sides of the laminate, and an electrochemical cell laminate having a structure similar to the cross-sectional structure shown in FIG. 1 was obtained except for the number of units laminated.

(Example 2)
An electrochemical cell laminate was prepared in the same manner as in Example 1 except that a stainless plate having a thickness of 100 μm was used as the conductive material.

(Example 3)
An electrochemical cell laminate was produced in the same manner as in Example 1 except that a conductive material having a thickness of 200 μm and having a protrusion at the center in the thickness direction was used. The cross-sectional shape of this electrochemical cell laminate is the same as that shown in FIG. 2 except for the number of units laminated.

Example 4
An electrochemical cell laminate was prepared in the same manner as in Example 1 except that the number of units 1 laminated was three.

(Comparative Example 1)
An electrochemical cell laminate was produced in the same manner as in Example 1 except that no conducting material was interposed. The cross-sectional shape of this electrochemical cell stack is the same as that shown in FIG. 6 except for the number of stacked units.

(Comparative Example 2)
An electrochemical cell laminate was produced in the same manner as in Comparative Example 1 except that the number of units was three.

(Comparative Example 3)
An electrochemical cell laminate was produced in the same manner as in Example 1 except that six units were laminated with a conductive material made of a stainless steel plate having a larger outer diameter than the gasket and a thickness of 200 μm interposed. The cross-sectional shape of this electrochemical cell laminate is the same as that shown in FIG. 7 except for the number of units laminated. That is, this electrochemical cell laminate corresponds to the laminate of Patent Document 1.

  About the electrochemical cell laminated body demonstrated above, the constant voltage application test was implemented at 45 degreeC. The measurement item is equivalent series resistance (hereinafter referred to as ESR). Table 1 summarizes the results. The numerical value of ESR in Table 1 is a relative value calculated by setting ESR before the constant voltage application test of Comparative Example 1 as 100.

  According to the results of Table 1, it is clear that the ESR change before and after the constant voltage application test is much less than that of Comparative Example 1 in any of the electrochemical cell laminates of Examples 1 to 4. In other words, regardless of the thickness, the presence or absence of protrusions, and the number of stacked units, it is understood that the inclusion of the conductive material contributed to the reduction in variation in contact resistance and the equalization of the voltage applied to each unit.

  On the other hand, the ESR change rates before and after the constant voltage application test in Comparative Example 1 and Comparative Example 2 are about 2.6 times and 1.7 times, respectively, and due to variations in contact resistance between the units, It is understood that the balance of the voltage applied to each unit is reduced, leading to an increase in ESR change. Moreover, it is thought that the comparative example 2 had a smaller ESR change rate because the number of units stacked was small, and the influence of variations in contact resistance among the units was small.

  Moreover, in Comparative Example 3, although the conducting material was interposed, the ESR change rate was larger than that of any of the examples, but this is because the outer diameter of the conducting material is larger than that of the gasket. As a result, the gasket part receives pressure, and it is understood that sufficient pressure is not applied to the electrode part that needs to be pressurized.

  In the above description, the secondary battery has been described as an example, but the same effect can be expected when applied to another power storage device such as an electric double layer capacitor.

Sectional drawing which showed the example of the electrochemical cell laminated body of this invention typically. Sectional drawing which showed the example of the electrochemical cell laminated body of this invention typically. The figure which shows the example of the conduction | electrical_connection material which has protrusion in this invention. The figure which shows the state which laminates | stacks the electrically conductive material with a protrusion in the electrochemical cell laminated body of this invention. Sectional drawing of the unit of the electrochemical cell which makes the basic structural unit of the conventional coin type electric double layer capacitor. Sectional drawing of an example of the electrochemical cell laminated body which does not use the conventional electrically conductive material. Sectional drawing which showed the example of the conventional electrochemical cell laminated body which concerns on patent document 1 typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 (Electrochemical cell) unit 2 Positive electrode 3 Negative electrode 4 Current collector 5 Negative current collector 6 Gasket 7 Separator 8a, 8b, 8c Conductive material 9 Pressure plate 10a, 10b Protrusion

Claims (7)

A sheet-like separator, a pair of positive and negative sheet-like electrodes disposed opposite to each other via the separator and impregnated with an electrolyte, and a pair of positive and negative current collectors respectively arranged via the pair of positive and negative electrodes; An electrochemical cell laminate in which a plurality of electrochemical cell units having a gasket surrounding the outer periphery of the electrode for sealing the pair of electrodes is laminated,
Between the units of the laminate, having a sheet-like conductive material,
The sheet-like conductive material is an electrochemical cell laminate in which an outer periphery of a contact surface with the unit is arranged so as to substantially overlap an inner periphery of a gasket of the unit. A sheet-like separator, a pair of positive and negative sheet-like electrodes disposed opposite to each other via the separator and impregnated with an electrolyte, and a pair of positive and negative current collectors respectively arranged via the pair of positive and negative electrodes; An electrochemical cell laminate in which a plurality of electrochemical cell units having a gasket surrounding the outer periphery of the electrode for sealing the pair of electrodes is laminated,
Between the units of the laminate, having a sheet-like conductive material,
The sheet-like conductive material is arranged so that the outer periphery of the contact surface with the unit has a planar shape corresponding to the inner periphery of the gasket of the unit, and the outer periphery is located inside the inner periphery of the gasket of the unit. Electrochemical cell stack.   The electrochemical cell laminate according to claim 1, wherein the gasket has an annular shape, and the sheet-like conductive material has a circular shape corresponding to an inner periphery of the gasket.   4. The electrochemical cell laminate according to claim 1, wherein the sheet-like conductive material has a protruding portion extending to the outer peripheral portion of the gasket at a central portion in the thickness direction.   The unit of the electrochemical cell contains a positive electrode containing a proton conductive compound as an electrode active material, a negative electrode containing a proton conductive compound as an electrode active material, and an electrolyte containing a proton source. The electrochemical cell laminated body in any one of 1-4.   The electrochemical cell laminate according to any one of claims 1 to 5, wherein in the electrochemical cell unit, an electrode and a current collector are separately shaped and laminated.   The electrical storage apparatus using the electrochemical cell laminated body in any one of Claims 1-6.

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