JP2008027607A - Electric power storage device, cell for electric power storage device, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell for an electric power storage device, which has no effect of heat and pressure on the inside of the cell; and to provide the manufacturing method of the cell. <P>SOLUTION: In the cell for the electric power storage device, a gasket 7 made of non-conductive rubber surrounding the outer peripheral surfaces of a pair of electrodes arranged through a separator and the bonding part of the electrodes and a current collector made of conductive rubber covering the upper and lower surfaces of the gasket 7 are cured, and the gasket other than the bonding part and the current collector are not cured. The manufacturing method contains a process of surrounding the outer peripheral surfaces of the pair of electrodes arranged through the separator with the gasket 7 made of the non-conductive rubber and covering the electrodes and the upper and lower surfaces of the gasket 7 with the current collector made of the conductive rubber; a process of pouring an electrolyte into the cell; and a process heating and pressing with a curing jig having a projecting pressing part in a contact part between the gasket 7 and the current collector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power storage device, for example, a battery such as a proton polymer battery, or an electric double layer capacitor cell, and a method for manufacturing the same, in which the cell is sealed by vulcanizing and bonding unvulcanized rubber.

  In recent years, as power storage devices, large-scale products such as batteries and electric double layer capacitors are used as automobile batteries, and the market is expected to expand rapidly. As small products, with the advent of the ubiquitous era, new mobile electronic devices and cordless devices used indoors will increase, and advanced functions will increase due to technological advances. As the demand for electric double layer capacitors increases, the demand for improved energy density and miniaturization has become very strong.

  In backup power supply applications, coin size batteries and coin-type electric double layer capacitors are becoming important issues for development due to the downsizing of devices, and the energy gained by improving the performance and utilization of electrode materials. Improvements in density, cell sealing technology, and improvement in exterior efficiency are required.

  Conventionally, when the electrolytic solution is an alkaline solution or an organic solvent, the outer packaging of the cell is generally a conductive or liquid barrier as disclosed in Patent Document 1 as an outer packaging material for batteries and capacitors. Metal materials that are very good in terms of properties are used. However, when the electrolytic solution is an acid solution, the metal material corrodes except for some noble metals, and thus cannot be used as an exterior material. Therefore, when an acid solution is used as the electrolytic solution, a conductive rubber in which carbon powder (carbon filler or the like) is dispersed in a carbon material or a rubber material is used. When conductive rubber is used for the exterior material, a method using an adhesive is also conceivable as an exterior assembly method (adhesion method), but vulcanization adhesion is superior in terms of ease of assembly.

  In the production method in which an acid solution is used as an electrolyte solution in a cell and a conductive rubber is used as an exterior material to adhere by vulcanization, as disclosed in Patent Document 2, the electrolyte solution is held in advance on an electrode or a separator and sealed. And a method of injecting an electrolytic solution after vulcanization adhesion by forming a needle for injecting an electrolytic solution as disclosed in Patent Document 3.

In the method in which the electrolytic solution is held in advance on an electrode or a separator and sealed, it is necessary to apply a pressure of several kgf / cm ² and heat the rubber for vulcanization at several tens of degrees Celsius for several tens of minutes. The influence of heating on the cell is a particular problem. The expansion or boiling of the electrolyte occurs due to heat, and the electrolyte oozes out to the rubber vulcanization interface, resulting in insufficient vulcanization, reducing the reliability of the exterior material, and causing the electrolyte to permeate outside the cell, resulting in vulcanization. The amount of electrolyte in the subsequent cell is insufficient. In the method of forming the hole for injecting the electrolyte, the hole is an obstacle particularly when the hole is made smaller and thinner.

JP 2000-348777 A JP-A-5-217803 JP 2002-358949 A

  In order to satisfy the improvement in cell sealing technology and exterior efficiency, it is required to make members such as current collectors and gaskets as thin as possible. However, thinning the exterior has required reduction in cell sealing due to deterioration in gas permeability, influence on the cell in the manufacturing process as described above, establishment of a manufacturing method for small products, and the like.

Conductive rubber covering the upper and lower surfaces of a gasket made of non-conductive rubber that surrounds the outer peripheral surfaces of a pair of electrodes containing positive electrode and negative electrode active materials, conductive assistants, and binders arranged via a separator When a cell including a current collector made of is prepared, an electrolytic solution is injected into the cell, and then conductive rubber and non-conductive rubber are bonded by vulcanization to seal the cell. Vulcanization for sealing usually requires heating at a few tens of degrees centigrade for several tens of degrees by applying a pressure of several kgf / cm ² , during which time the electrodes, separators, and electrolytes inside the cell Since the load due to heat and pressure is applied, the reliability of the exterior material is lowered, and the amount of the electrolyte in the cell after vulcanization is reduced.

  Under such circumstances, an object of the present invention is to provide a small and thin cell for a power storage device that is not affected by heat and pressure inside the cell, a method for manufacturing the same, and a power storage device.

  In order to solve the above-described problems, a cell for a power storage device according to the present invention includes a gasket made of non-conductive rubber surrounding a side outer peripheral surface of a pair of electrodes disposed via a separator, an electrode, and upper and lower surfaces of the gasket. The contact portion of the current collector made of the conductive rubber to be covered is vulcanized, and the current collector excluding the contact portion is not vulcanized.

  In the method for producing a cell for a power storage device of the present invention, the outer peripheral surfaces of a pair of electrodes arranged via a separator are surrounded by a gasket made of non-conductive rubber, and the electrodes and the upper and lower surfaces of the gasket are electrically conductive. A step of producing a cell covered with a current collector made of rubber, a step of injecting an electrolyte into the cell, and a vulcanizing treatment having a convex pressure portion at a contact portion between the gasket and the current collector. The method includes a step of heating and pressurizing using a tool.

  The step of cooling the cell once after heating and pressurizing using the vulcanizing jig may be repeated at least twice. Moreover, it is good to include the process of heating only the one side of the said cell for the said jig | tool for vulcanization | cure. Moreover, the heating temperature of the said cell is good in it being 160-190 degreeC. In addition, the power storage device may be configured such that the power storage device cell is placed in a metal case, the surface of the metal case is heated, and the current collector made of the conductive rubber is vulcanized and bonded to the metal case.

  According to the present invention, a conductive rubber that is a current collector and a non-conductive rubber that is a gasket are used in which the pressing portion of the vulcanizing jig is processed into a convex shape in accordance with the shape of the bonded portion. By applying heat and pressure only to the contact area of the battery, the load due to heat and pressure inside the cell can be minimized, and the cell for the power storage device that has a small size and a thin profile with good characteristics and The manufacturing method and the power storage device are obtained.

  In general, rubber vulcanization can shorten the time by raising the temperature, so considering the heat effect on the cell, sandwiching the cell with a vulcanizing jig heated only on one side, the cell side by side, By vulcanizing repeatedly and intermittently in a short time at a temperature higher than the conditions for long-term vulcanization on both sides, the effect of temperature and pressure on the inside of the cell is minimized and the vulcanization time is reduced. Can be shortened.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 is a plan view of a vulcanizing jig, FIG. 2 is a cross-sectional view of the vulcanizing jig of FIG. 1 along the line AA, FIG. 3 is a cross-sectional view of a coin-type proton polymer battery, and FIG. It is sectional drawing which shows the structure of the battery cell.

  As an example of a power storage device, an embodiment of the present invention will be described for a coin-type proton polymer battery. As shown in FIG. 3, the coin-type proton polymer battery is arranged in a state where a plurality of cells 8 having a power storage function are singly or stacked in series, and serves as a can 11 and an upper lid through an insulating packing 9. It is obtained by mechanical caulking with the cap 10.

  For example, as shown in FIG. 4, the structure of the cell 8 is such that the positive electrode 3 and the negative electrode 4 are arranged to face each other with a separator 5 interposed therebetween, and an electrolyte solution that is an aqueous solution or non-aqueous solution containing a proton source is in each electrode and the separator 5. Exists inside. As the electrode active material contained in each electrode, a proton-conducting polymer that is appropriately selected in combination with a difference in redox potential capable of expressing the target electromotive force is used. And the circumference | surroundings are sealed with the collector 6 and the gasket 7, and the collector 6 has a function which takes the electrical contact with the positive / negative electrodes 3 and 4 and the exterior.

  The electrolytic solution is roughly classified into an organic solvent system and an aqueous solution system. In the proton polymer battery, since an aqueous solution containing a proton source has a particularly high capacity, an acidic aqueous solution is exclusively used. Therefore, a material having acid resistance is used for the current collector 6, the gasket 7, and the separator 5. For example, butyl rubber or elastomer to which conductivity is imparted by adding carbon or the like to the current collector 6, and soft plastics such as butyl rubber or thermoplastic elastomer are generally used for the gasket 7.

  After assembling a predetermined number of cells 8, for example 25, as described above (see FIG. 4), the vulcanizing jig 2 shown in FIGS. 1 and 2 is heated to bond the gasket 7 and the current collector 6 together. Is vulcanized by pressurizing. At that time, the convex pressurizing portion of the vulcanizing jig is set so as to correspond to the position of the gasket 7 of the cell 8.

  The electric double layer capacitor basically has the same structure as the proton polymer battery described above, and uses activated carbon as the electrode active material contained in the positive electrode 3 and the negative electrode 4, and includes a separator, gasket, current collector Using the body is similar.

  The indole trimer, which is a positive electrode active material, is mixed with 20% by weight of vapor-grown carbon (hereinafter referred to as wt%) as a conductive material by a powder blender, and the mixture contains 10% by weight of polytetrafluoroethylene (hereinafter referred to as PTFE) particles. 60% PTFE dispersion was added as described above, mixed with a stirring deaerator, and then dried. 100 wt% of water was added to the obtained mixture and kneaded in a mortar. Thereafter, the kneaded product was rolled with a roll molding machine to obtain a sheet-like electrode having a thickness of 0.2 mm. The obtained sheet-like positive electrode was punched out with a diameter of 2.3 mm to obtain a thin disc-like positive electrode.

  25 wt% of ketjen black EC600JD (manufactured by Lion Corporation) as a conductive material was added to polyphenylquinoxaline as a negative electrode active material with respect to the negative electrode active material and mixed with a powder blender. 100 wt% of m-cresol was added to the obtained mixed powder with respect to the total weight of the negative electrode active material and the conductive material, and kneaded with a kneader for 1 hour. M-Cresol was further added to the obtained kneaded material and mixed for 30 minutes with a homogenizer so that the viscosity of the mixed slurry was 1000 mPa · s to obtain a slurry.

  The obtained electrode slurry was applied onto polyethylene terephthalate (hereinafter referred to as PET), dried, and then the PET was peeled off to obtain a negative electrode sheet. The obtained sheet-like negative electrode was punched out with a diameter of 2.3 mm to obtain a thin disc-shaped negative electrode.

  The separator is made of PTFE, thickness 50 μm (manufactured by Gore-Tex), the conductive rubber is carbon-added conductive unvulcanized butyl rubber, the thickness is 70 μm (manufactured by Fujikura Rubber Industries), and the non-conductive rubber is not yet Vulcanized butyl rubber, thickness 280 μm (manufactured by Fujikura Rubber Industry Co., Ltd.), and 20% sulfuric acid was used as the electrolyte.

  On a conductive unvulcanized butyl rubber of size 90 mm x 90 mm, a total of 25 holes of φ2.5 mm for electrode placement in a 90 mm x 90 mm size are arranged in 5 rows each in a 15 mm pitch. Was placed as a gasket, pressure-bonded using the adhesiveness of rubber, and the positive electrode was inserted into the hole for electrode placement to obtain a positive electrode insertion sheet. Further, a negative electrode was inserted into the same sheet and a separator having a diameter of 2.8 mm was pressure-bonded thereon to obtain a negative electrode insertion sheet. An electrolyte solution was poured into each electrode insertion sheet and bonded in a vacuum.

As shown in FIGS. 1 and 2, the obtained sheet is sandwiched from both sides with a vulcanizing jig 2 having a convex pressure part 1 so that the pressure part and the gasket part correspond to each other, and vulcanization conditions, temperature Conductive unvulcanized butyl rubber and unvulcanized butyl rubber at an outer diameter of φ5.0 mm and an inner diameter of φ2.5 mm on the concentric circle of the hole into which the electrode is inserted at 120 ° C. for 30 minutes and a pressure of 10 kgf / cm ² The cell portion where the electrode, separator, and electrolytic solution were present was sealed by vulcanizing and bonding the contact portion. This sheet was punched out with a diameter of 3.5 mm on the concentric circle of the hole into which the electrode was inserted, whereby a cell as shown in FIG. 4 was obtained. 25 cells are obtained from one sheet.

  The two cells thus obtained are arranged in series, integrated into an outer container composed of a stainless steel cap and a stainless steel case via a PPS insulating packing, and then caulked and sealed. A coin-type proton polymer battery as shown in 3 was obtained.

In addition, in order to evaluate the adhesive strength by vulcanization, two vulcanized butyl rubbers having a thickness of 280 μm were vulcanized having a convex pressure part at a temperature of 120 ° C. for 30 minutes and a pressure of 10 kgf / cm ² under the same conditions as described above. Table 1 shows the average value of the peel strength of the vulcanized portion corresponding to one cell, which was vulcanized with a jig for use and measured with a peel tester.

  In addition, in order to evaluate the decrease amount of the electrolytic solution due to vulcanization, the inner diameter of the gasket is 15 mm in diameter, and the average weight of 100 positive cells, negative electrodes, separators and 100 completely empty cells not containing the electrolytic solution is obtained. A cell in which only 50 μL of electrolyte solution was injected without a separator was added, and an approximate value of the weight of electrolyte solution remaining inside the cell after vulcanization was obtained by subtracting the average weight value of empty cells from the weight. Asked. The difference between this value and the weight of the electrolytic solution 50 μL was defined as the amount of decrease in the electrolytic solution due to vulcanization. Moreover, the internal resistance at 1 kHz of the cell was measured.

The positive electrode and negative electrode insertion integrated sheet is vulcanized under vulcanization conditions, temperature 160 ° C., time 30 seconds, pressure 10 kgf / cm ² , cooled once, vulcanized again under the same conditions, and cooled. Except for repeating this vulcanization and cooling five times, the adhesive strength, the amount of decrease in the electrolyte solution, and the internal resistance at 1 kHz were evaluated in the same manner as in Example 1.

When vulcanizing, only one of the vulcanizing jigs is heated, and the positive and negative electrode insertion integrated sheet is vulcanized from one side direction under vulcanization conditions, temperature 160 ° C., time 30 seconds, pressure 10 kgf / cm ^2. Then, it is cooled once, the sheet is turned over, vulcanized again from the surface opposite to the vulcanized surface under the same conditions, and then cooled. While repeating vulcanization, cooling, and reversal of the heating surface, vulcanization was promoted on each side. The adhesive strength, the amount of decrease in electrolytic solution, and the internal resistance at 1 kHz were evaluated in the same manner as in Example 1 except that this was performed three times on one side.

  Vulcanization was carried out in the same manner as in Example 3 except that the number of times of vulcanization on one side was changed to 5, and adhesive strength, amount of decrease in electrolytic solution, and internal resistance at 1 kHz were evaluated in the same manner as in Example 1.

  Vulcanization was carried out in the same manner as in Example 4 except that the temperature of the vulcanization condition was 180 ° C. and the time was 25 seconds, and the adhesive strength, the amount of decrease in electrolytic solution, and the internal resistance at 1 kHz were evaluated in the same manner as in Example 1. Went. Moreover, the change in internal resistance at 1 kHz when lead-free reflow was performed under conditions of preheating 160 ° C., 120 seconds, peak 260 ° C., and 5 seconds was measured.

Activated carbon having a specific surface area of 1500 m ² / g is used as the electrode active material, carbon black is mixed as a conductive material with a 20% by weight powder blender with respect to the activated carbon, and 60% PTFE dispersion is added to the mixture so that the PTFE particles become 10 wt%. Was added, mixed with a stirring deaerator, and then dried. 180 wt% of water was added to the obtained mixture and kneaded in a mortar. Thereafter, the kneaded product was rolled with a roll molding machine to obtain a sheet-like electrode having a thickness of 0.2 mm. The obtained sheet-like activated carbon electrode was punched out with a diameter of 2.3 mm to obtain a thin disk-like activated carbon electrode. The vulcanization method was performed in the same manner as in Example 5 to obtain an electric double layer capacitor cell, and the internal resistance at 1 kHz was measured.

(Comparative Example 1)
Vulcanization was performed in the same manner as in Example 1 except that the positive electrode and negative electrode insertion integrated sheet was sandwiched between stainless steel plates and the sheet was pressed and heated in a furnace at 120 ° C. for 40 minutes. In this method, the adhesive strength, the amount of decrease in the electrolytic solution, and the internal resistance at 1 kHz were evaluated.

(Comparative Example 2)
Vulcanization was performed by sandwiching the positive and negative electrode-inserted integrated sheet between stainless steel plates and putting the sheet in a pressurized state, and heating it in a furnace at 120 ° C. for 40 minutes. The internal resistance at 1 kHz was measured in the same manner as in Example 6 except for the vulcanization method.

  Table 1 shows average values of peel strengths of Examples 1 to 5 and Comparative Example 1.

  As can be seen from Table 1, Examples 1 to 5 vulcanized by the method according to the present invention have the same adhesive strength compared to Comparative Example 1 vulcanized by the conventional method. Regarding Example 5, the result exceeded that of Comparative Example 1.

  Table 2 shows the approximate electrolyte solution weight reduction rate by vulcanization obtained from the measurements and calculations of Examples 1 to 5 and Comparative Example 1, respectively.

  This result shows how much the heat to the inside of the cell affects the amount of the electrolyte solution. In Comparative Example 1 vulcanized by the conventional method, the electrolyte solution was reduced by 15 wt% by vulcanization. On the other hand, in Examples 1-5, it is 5 wt% or less, especially about Examples 3-5, it is 1 wt% or less, and the influence of heat is suppressed significantly.

  Table 3 shows the average value of internal resistance at 1 kHz in Examples 1 to 6, Comparative Example 1, and Comparative Example 2.

  The main reason for the high internal resistance is that the amount of electrolyte in the cell decreases. This result is consistent with the result of the decrease in the amount of the electrolyte solution described above, and Comparative Example 1 vulcanized by the conventional method is the highest, followed by Example 1. In Comparative Example 1 and Example 1, the temperature was low during vulcanization, but since heat was applied for a long time, the time for the electrolyte to permeate outside the cell became longer, the amount of the electrolyte decreased, It is considered that the internal resistance is increased because the current collector is deformed and the contact property between the current collector and the electrode is lowered due to the pressure of the electrode being high for a long time.

  The internal resistance of Examples 3 to 5 is lower than that of Example 2, but this is because the influence of heat on the inside of the cell and the like is suppressed by applying heat to one side instead of both sides and vulcanizing. This is probably because the permeation of the electrolyte solution decreased. Similar results were obtained when Example 6 and Comparative Example 2 were compared.

  Table 4 shows the internal resistance at 1 kHz after the cells obtained in Example 5 and Comparative Example 1 were subjected to a reflow test under the lead-free conditions.

  In Comparative Example 1 vulcanized by the conventional method, the internal resistance increased to about 50% compared to the values in Table 3, whereas in Example 1, the increase was about 15%. This increase is one of the causes that the coin case bulges due to an increase in internal pressure when reflowed, and the contact between the butyl rubber as the current collector, the coin case, and the electrode is deteriorated, and the difference is between Example 5 and Comparative Example 1. It is thought that this is the difference. In the cell obtained in Example 5, since the portion other than the portion bonded to the current collector butyl rubber gasket was unvulcanized before reflow, this unvulcanized portion was vulcanized by the heat of reflow. It is considered that the increase in internal resistance was suppressed as compared with Comparative Example 1 by bonding with a coin case and an electrode. When the coin case and the cell after reflow are actually disassembled, the coin case, the electrode, and the butyl rubber which is the current collector of the internal cell are firmly bonded.

  From the results of the examples, by using the vulcanization method of the present invention, the adhesive strength is almost the same as that of the conventional method, the thermal effect on the inside of the cell is small, the vulcanization time can be shortened, and the reflow resistance is good. A vulcanization method for obtaining a simple cell can be provided. In the examples, the heating temperature was set to 160 ° C. However, if the heating temperature is higher than 190 ° C., the electrolyte solution may be decreased, which is not preferable. Moreover, although it was set as the example repeated 3 to 5 times about the heating of a cell and cooling after pressurization, an effect is acquired even twice.

The top view of the jig | tool for vulcanization | cure. The AA sectional view taken on the line of the vulcanizing jig of FIG. Sectional drawing of a coin-type proton polymer battery. Sectional drawing which shows the structure of the cell for proton polymer batteries.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Convex pressure part 2 Vulcanizing jig 3 Positive electrode 4 Negative electrode 5 Separator 6 Current collector 7 Gasket 8 Cell 9 Insulation packing 10 Cap 11 Can

Claims (6)

  A gasket made of non-conductive rubber that surrounds a pair of electrode side portion outer peripheral surfaces disposed via a separator, and upper and lower surfaces of the gasket of a current collector made of conductive rubber that covers the upper and lower surfaces of the electrode and the gasket A cell for a power storage device, characterized in that a close contact portion is vulcanized and a current collector excluding the close contact portion is not vulcanized.   A step of enclosing the outer peripheral surfaces of a pair of electrodes disposed via a separator with a gasket made of non-conductive rubber, and covering the electrodes and the upper and lower surfaces of the gasket with a current collector made of conductive rubber; and A step of injecting an electrolyte into the cell, and a step of heating and pressurizing using a vulcanizing jig having a convex pressurizing portion at a contact portion between the gasket and the current collector, A method for manufacturing a cell for a power storage device.   3. The method of manufacturing a cell for a power storage device according to claim 2, wherein the step of cooling the cell once after heating and pressurizing using the vulcanizing jig is repeated at least twice.   The method for manufacturing a cell for a power storage device according to claim 2, further comprising a step of heating the vulcanizing jig only on one side of the cell.   5. The method for manufacturing a cell for a power storage device according to claim 2, wherein the heating temperature of the cell is 160 to 190 ° C. 6.   The power storage device cell obtained by the method for manufacturing a power storage device cell according to any one of claims 2 to 5 is placed in a metal case, the surface of the metal case is heated, and the conductive rubber is used. A power storage device in which a current collector is vulcanized and bonded to a metal case.

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