JP2017028274A - Electrochemical cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical cell having high reliability, in which conductivity and capacitance density can be increased.SOLUTION: The electrochemical cell includes at least a base container, a cell element, a plurality of cell leads as an extension of the cell element, a pad film made of a valve metal formed on an inner bottom of the base container, a base internal wiring connected to the pad film, and a lid for air-tightly closing the base container. The cell element includes a positive electrode and a negative electrode disposed to interpose a separator and contains a non-aqueous electrolyte. At least one of the positive electrode and the negative electrode comprises an aluminum collector and a carbon material layer fixed by a compound of aluminum and carbon on the aluminum collector. The non-aqueous electrolyte has a composition comprising 13 to 43 mass% of a supporting electrolyte and a balance solvent; and the solvent comprises 60 to 90 mass% of sulfolane and 10 to 40 mass% of ethylmethylsulfone.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a highly reliable electrochemical cell capable of reflow soldering.

There are known electrochemical cells such as an electric double layer capacitor that is used for data writing support to a memory at the time of a momentary power failure or for smoothing a circuit voltage and has a low resistance by winding or stacking. Conventionally, a laminate type package is known as a package of these electrochemical cells.
In this type of electrochemical cell package, there has been proposed a ceramic package that is excellent in sealing performance, improves long-term reliability, and is compatible with reflow soldering (see Patent Document 1).
As an electrode of this type of electrochemical cell, various electrode sheet configurations are known in addition to an electrode sheet obtained by applying a slurry containing an active material to a current collector made of aluminum foil or the like. For example, the electrode described in Patent Document 2 below employs a structure that can improve the adhesion between the active material and the current collector and suppress the surface resistance value.

JP 2013-30750 A JP 2006-1000047 A

Conventionally, in a ceramic package used for this type of electrochemical cell, a constant container wall thickness has been required from the viewpoint of manufacturing and durability. Furthermore, since the lead of the element connected to the pad film of the container has a certain thickness, there is a problem that the size of the element that can be accommodated in the container is further restricted.
For this reason, in order to arrange an electrochemical cell having a ceramic package in the same mounting space that is used for the same application as the conventional laminate type, it is necessary to increase the conductivity and capacity density compared to the conventional configuration. It was.
Furthermore, in order to reduce the mounting space, it is necessary to provide an element that is required to be used in a single cell with improved heat resistance and withstand voltage.
In addition, in an electrochemical cell using a ceramic package, when reflow soldering is performed, there is a problem that the internal resistance increases due to the heat of the solder, and there is a problem that characteristics of the electrochemical cell deteriorate due to the reflow soldering process. It was.

  The present invention has been made in view of the conventional circumstances, and provides an electrochemical cell that increases conductivity and capacity density, is highly reliable even in a small element shape, and has little characteristic deterioration due to reflow soldering. Objective.

In order to solve the above-mentioned problems, the present invention is formed on a base container, a cell element housed in the base container, a plurality of cell leads which are extensions of the cell element, and an inner bottom surface of the base container. An electrochemical cell having at least a pad film made of a valve metal, a base wiring connected to the pad film and formed from an inner bottom surface to a lower surface of the base container, and a lid for hermetically closing the base container In the cell element, a positive electrode and a negative electrode are disposed with a separator interposed therebetween, and further, a non-aqueous electrolyte is contained. At least one of the positive electrode and the negative electrode is an aluminum current collector, and the aluminum current collector is disposed on the aluminum current collector. Including a layer of a carbon material fixed by a compound of aluminum and carbon, and the non-aqueous electrolyte is a supporting salt: 13 to 43% by mass, the remaining solvent, and the remaining solvent In an amount ratio of sulfolane: 60 to 90 wt%, ethyl methyl sulfone and having a composition of 10 to 40 wt%.
The cell element and electrolyte are contained in an airtight base container, and the supporting salt, sulfolane, and ethylmethylsulfone are used in an appropriate ratio, so the supporting salt is highly soluble and receives the heat of reflow soldering. However, it is possible to provide an electrochemical cell having a low rate of increase in internal resistance and improved heat resistance with little decrease in capacity.
In addition, since the interface between the carbon material layer and the aluminum current collector is fixed with a compound of aluminum and carbon, the adhesion of carbon particles on the surface of the aluminum current collector is unlikely to deteriorate even when subjected to the heat of reflow soldering. Therefore, an electrochemical cell having high heat resistance can be obtained.

In the present invention, an intermediate layer containing the compound of aluminum and carbon is formed on the surface portion of the aluminum current collector, and a second surface portion extending outward from the intermediate layer is formed. A structure in which a layer of the carbon material having a conductive layer in which a plurality of carbon particles are fixed can be employed on the surface portion.
By adopting a structure having a conductive layer in which a plurality of carbon particles are fixed to a second surface portion extending from an intervening layer containing an aluminum and carbon compound formed on the surface portion of the aluminum current collector, Even if it receives, it can be set as the electrode structure which a carbon particle does not isolate | separate from an aluminum electrical power collector. For this reason, since the adhesion of the carbon particles on the surface of the aluminum current collector is unlikely to deteriorate even when subjected to the heat of the reflow solder, an electrochemical cell having high heat resistance can be provided.
In the present invention, a configuration in which the conductive layer includes an active material can be employed.
By including an active material in the conductive layer, the capacity of the cell can be increased.

In the present invention, a configuration in which the supporting salt is a quaternary ammonium salt or a quaternary phosphonium salt can be employed.
If these supporting salts are used, a high solubility of the supporting salt in the electrolytic solution can be obtained, and a solvent having high electrical conductivity can be obtained.
In the present invention, a configuration in which the nonaqueous electrolyte is impregnated around the positive electrode, the negative electrode, and the separator of the cell element accommodated in the base container can be employed.
When impregnating the non-aqueous electrolyte around the positive electrode, negative electrode and separator of the cell element, the size was reduced by using an electrolyte composed of a solvent containing sulfolane and ethylmethylsulfone in the above composition ratio and a supporting salt in the above composition ratio. An electrochemical cell in which the cell element is sufficiently impregnated with the electrolyte can be provided.

Since the electrochemical cell of the present invention includes an electrode having a structure in which a carbon material layer is fixed by an aluminum and carbon compound on an aluminum current collector of a cell element, the aluminum current collector and the carbon material layer It has good adhesion and can suppress an increase in interface resistance between the aluminum current collector and the carbon material layer. Therefore, it is possible to provide an electrochemical cell having higher conductivity and capacity density than an electrochemical cell having a conventional structure in which a slurry containing an active material, a conductive additive, and a binder is directly coated on an aluminum current collector. In addition, since the good adhesion between the aluminum current collector and the carbon material layer is less likely to decrease even when subjected to the heat of reflow solder, the cell element is accommodated in the base container and the base container has wiring. Thus, an electrochemical cell capable of highly reliable reflow soldering even with a small element shape can be provided.
The electrochemical cell of the present invention has sulfolane: 60 to 90% by mass and ethylmethylsulfone: 10 to 40% by mass as a solvent in addition to the supporting salt of 13 to 43% by mass. Therefore, it is possible to provide an electrochemical cell having high charge characteristics and excellent charge characteristics. Also, when the base container containing the cell element is sealed with a lid, the heat of welding for sealing is transferred to the non-aqueous electrolyte, so that the non-aqueous electrolyte is difficult to evaporate, and the non-aqueous electrolyte is altered. Thus, it is possible to provide an electrochemical cell in which resistance increase due to the occurrence of resistance is difficult.

The electrochemical cell of 1st Embodiment which concerns on this invention is shown, (a) is a perspective view, (b) is a fragmentary sectional view. The relationship between the pad film, via wiring, and connection terminal of the electrochemical cell is shown, (a) is a view from the pad film side, and (b) is a view from the connection terminal side. The cell lead of the same electrochemical cell and the connection state of a pad film | membrane are shown, (a) is a top view of a connection part, (b) is sectional drawing which shows an example of the state welded with the chip | tip for welding. The cell element accommodated in the same electrochemical cell is shown, (a) is the block diagram of a cell element, (b) is the elements on larger scale of a collector and a conductive layer. The block diagram which shows the electrochemical cell of 2nd Embodiment which concerns on this invention. The block diagram which shows the electrochemical cell of 3rd Embodiment which concerns on this invention. The electrochemical cell of 4th Embodiment which concerns on this invention is shown, (a) is a perspective view of a base container, (b) is sectional drawing of the electrochemical cell provided with the said base container, (c) is other Sectional drawing which shows the electrochemical cell of an example. The graph which shows the internal resistance before and behind the reflow solder test about the electrochemical cell of Examples 1 and 2 and the electrochemical cell of Comparative Example 1. The graph which shows the discharge time before and after the reflow solder test about the electrochemical cell of Examples 1 and 2 and the electrochemical cell of Comparative Example 1. The internal resistance before and after the reflow solder test was obtained for the electrochemical cell of Comparative Example 2 obtained by changing the solvent to the electrochemical cell of Example 1, and compared with the measurement result of the internal resistance of the electrochemical cell of Example 1 Graph showing. The graph which shows the discharge time before and behind the reflow solder test about the electrochemical cell of Example 1 and the electrochemical cell of Comparative Example 2. The graph which shows the capacity | capacitance maintenance factor according to the elapsed days at the time of setting to 60 degreeC and the charge voltage 3.0V about the electrochemical cell of Example 1 and the electrochemical cell of the comparative example 2. FIG. The graph which shows the internal resistance increase rate according to the elapsed days at the time of setting to 60 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 1, and the electrochemical cell of the comparative example 2. FIG. The graph which shows the capacity | capacitance maintenance factor according to the elapsed days at the time of setting to 85 degreeC and the charge voltage 3.0V about the electrochemical cell of Example 1, and the electrochemical cell of the comparative example 2. FIG. The graph which shows the internal resistance raise rate according to the elapsed days at the time of setting 85 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 1, and the electrochemical cell of the comparative example 2. FIG. The graph which shows the internal resistance before and behind the reflow solder test about the electrochemical cell of Examples 3 and 4 and the electrochemical cell of Comparative Examples 3 and 4. The graph which shows the discharge time before and behind the reflow solder test about the electrochemical cell of Examples 3 and 4 and the electrochemical cell of Comparative Examples 3 and 4. The graph which shows the capacity | capacitance maintenance factor according to the storage days at the time of setting to 70 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 3, 4 and the electrochemical cell of Comparative Example 3, 4. The graph which shows the internal resistance raise rate according to the preservation | save day at the time of setting to 70 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 3, 4 and the electrochemical cell of Comparative Example 3, 4. The graph which shows the capacity | capacitance maintenance factor according to the storage days at the time of setting to 85 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 3, 4 and the electrochemical cell of Comparative Example 3, 4. The graph which shows the internal resistance raise rate according to the preservation days at the time of setting 85 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 3, 4 and the electrochemical cell of Comparative Example 3, 4. The graph which shows the internal resistance before and behind the reflow solder test about the electrochemical cell of Examples 5, 6, and 7 and the electrochemical cell of Comparative Examples 5 and 6. The graph which shows the discharge time before and behind the reflow solder test about the electrochemical cell of Examples 5, 6, and 7 and the electrochemical cell of Comparative Examples 5 and 6. The graph which shows the capacity | capacitance maintenance factor according to the preservation days at the time of setting to 70 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 5, and the electrochemical cell of Comparative Examples 5 and 6. FIG. The graph which shows the internal resistance raise rate according to the preservation | save day at the time of setting to 70 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 5, and the electrochemical cell of Comparative Examples 5 and 6. FIG. The graph which shows the capacity | capacitance maintenance factor according to the storage days at the time of setting to 85 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 5, and the electrochemical cell of Comparative Examples 5 and 6. FIG. The graph which shows the internal resistance raise rate according to the preservation days at the time of setting to 85 degreeC and the charging voltage 2.5V about the electrochemical cell of Example 5, and the electrochemical cell of Comparative Examples 5 and 6. FIG.

Hereinafter, an electrochemical cell according to a first embodiment of the present invention will be described with reference to the drawings.
The electrochemical cell 1 of the first embodiment is mainly used by being mounted on a substrate inside a personal computer or a small portable device.
(Electrochemical cell 1)
Fig.1 (a) is an external view (perspective view) of the electrochemical cell 1 of this embodiment.
As shown in FIG. 1, the electrochemical cell 1 is shown as a rectangular parallelepiped shape as an example, but may be a track shape or a cylindrical shape. The electrochemical cell 1 of the present embodiment includes a base container 2 that functions as a container that houses a cell element 6 that is a power generation element, and a lid (lid) 10 that functions as a sealing plate for hermetically closing the opening. Are provided as exterior parts. The exterior container of the electrochemical cell 1 is composed of the base container 2 and a lid 10 that seals the opening of the base container 2.

  FIG.1 (b) is sectional drawing which follows the AA line of Fig.1 (a). The cell element 6 is accommodated in the concave base container 2, and further filled with the electrolytic solution 7, and the base is formed by the lid 10 pressed against the seal ring 9 provided so as to go around the upper surface of the opening of the base container 2. The container 2 is hermetically sealed. A pad film 5, which is a pair of current collector metal films, is juxtaposed on the base inner bottom surface 2 c of the base container 2. Also, a plurality of via wirings 3 are formed on the bottom surface side of the pad film 5 so as to penetrate the base container bottom wall from the base inner bottom surface 2c to the base lower surface 2d. These via wirings 3 electrically connect the pad film 5 and the connection terminals 4 formed on the base lower surface 2d.

  On the other hand, the cell element 6 is accommodated in the base container 2. The cell element 6 is formed by a winding method or a laminating method in which a pair of electrode sheets made of a current collector of a metal sheet carrying a layer of carbon material such as carbon particles is inserted with an insulating separator. It is. A cell lead 8 made of a metal plate is connected to each end of the positive and negative current collectors. The cell leads 8 of the positive electrode and the negative electrode are fixed to the pair of pad films 5 by welding, for example. The positive electrode and the negative electrode of the cell element 6 are electrically connected to the mounting pattern of the substrate mounted by the connection terminal 4.

(Base container 2)
The base container 2 is a container made of a box-shaped ceramic with an opening at the top, and has a rectangular base bottom 2a and a rectangular frame-shaped base peripheral wall 2b erected on the outer edge of the base bottom 2a. doing. The size of the base container 2 can be about 5 to 20 mm on a side and about 1 to 3 mm in height. 2A and 2B are views showing the base inner bottom surface 2c and the base lower surface 2d of the base container 2, respectively. A pair of pad films 5 made of a conductive material are disposed on the base inner bottom surface 2c shown in FIG. Four via wirings 3 indicated by broken lines are provided adjacent to each other on the lower surface of the pad film 5, and these via wirings 3 are respectively connected to connection terminals 4 (also indicated by broken lines) arranged on the lower surface 2d of the base. ing.

The constituent material of the base container 2 includes a ceramic containing at least one selected from the group consisting of alumina, silicon nitride, zirconia, silicon carbide, aluminum nitride, mullite, and composite materials thereof. Is not limited to this. Soda lime glass and heat-resistant glass can also be used. Since a long glass can be used as a material, in the case of a small package, a large number of pieces can be set for one glass, and cost reduction of the base member can be expected.
In the base container 2 of the present embodiment, for example, a ceramic green sheet corresponding to the base bottom portion 2a punched into a rectangular shape is bonded to a ceramic green sheet corresponding to the base peripheral wall portion 2b punched into a rectangular frame shape. It is formed by firing. A through hole can be formed by punching a ceramic green sheet corresponding to the base bottom 2b in advance by punching, and the via wiring 3 can be formed using the through hole.

(Via wiring 3)
The via wiring 3 is a wiring formed from the base inner bottom surface 2 c of the base container 2 to the base lower surface 2 d. In the via wiring 3, first, a through hole for connecting the base inner bottom surface 2 c and the base lower surface 2 d through substantially perpendicularly is provided in the base bottom portion 2 a, and the through hole is filled with a metal wiring paste such as tungsten. Is formed. Further, by forming the via wiring 3, the airtightness of the through hole is satisfied.
As the conductive paste used for the via wiring 3, a paste in which carbon and a resin are mixed, or a paste in which tungsten, molybdenum, nickel, gold, or a composite material of these metals and a resin are mixed can be used.

The paste filled in the through hole becomes the via wiring 3 by firing together with the ceramic green sheet to be the base container 2.
As described above, when the base container 2 is formed of a glass material such as soda lime glass or heat-resistant glass, means for forming recesses and through-holes in these glasses include chemical etching and sandblasting. The concave portion and the through hole can be formed simultaneously using a mold in a physical method or in a high temperature atmosphere. Then, after forming an aluminum film on the inner surface of the through hole, the via hole 3 is filled with a glass paste having a matching thermal expansion coefficient, and is subjected to binder removal and firing, thereby forming an airtight and conductive via wiring 3. Can be formed. In such a case, there is no concern that the via wiring 3 is dissolved by the electrolyte solution 7 described later. The film forming the inner surface of the via wiring 3 is not limited to aluminum, and may be a film containing other valve metal such as titanium.

(Connection terminal 4)
A pair of connection terminals 4 are provided on the base lower surface 2 d shown in FIG. 2B so as to face the pad film 5. The connection terminal 4 is fixed to the substrate by cream solder or the like provided on the pattern of the mounting substrate by reflow processing or the like.
In this embodiment, the connection terminal 4 can be formed by printing the electrode pattern by tungsten beforehand on the ceramic green sheet used as the base container 2, and baking the said ceramic green sheet. Moreover, it is preferable that the connection terminal 4 is provided with a plating film made of nickel and gold on a tungsten pattern formed by a printing method. Furthermore, tungsten and these plating materials are also patterned in the concave portion of the base side surface 2e, and these function as a part of the connection terminal.

(Pad film 5)
The pad film 5 is a substantially rectangular film made of a conductive material disposed at two locations on the base inner bottom surface 2c. The pad film 5 has a welded portion for preventing direct contact between the upper end portion of the via wiring 3 and the electrolytic solution 7 and connecting the cell lead 8 by welding.
In addition, although the pad film | membrane 5 of this embodiment is juxtaposed in the longitudinal direction of the base container 2, it can also be juxtaposed in a short side direction, and can be arranged in the diagonal direction of a longitudinal direction.
The pad film 5 is a film made of a chemically stable valve metal such as aluminum or titanium, and is made of a material that is difficult to dissolve in the electrolytic solution 7. These films can be provided by a known film forming method such as vapor deposition, ion plating, or sputtering. In the case of these methods, first, a metal such as tungsten is filled and fired in a through hole by a printing method or the like, and the airtight via wiring 3 is finished and then formed. When forming a film in a vacuum, for example, preparing a mask made of metal or the like patterned so as to have two openings spatially separated from each other so as to constitute the positive and negative electrode pad films 5, respectively. After being housed in the chamber of the film formation apparatus and evacuated to a predetermined degree of vacuum by a vacuum exhaust system, the valve metal material is deposited or the target made of the valve metal material is physically hit with ions to remove the valve metal material. Then, a film is formed on the bottom surface 2c in the base. In these film forming methods, since the film forming conditions are easily controlled, a high-density film having a low resistivity and a low liquid penetration property can be formed.

  The aluminum film can also be formed by screen printing. A technique has been developed that can form a wiring pattern at a temperature of 150 ° C. or lower even for aluminum that is easily oxidized at a high temperature. Since this method is a printing method, a thicker film can be formed and a thick film of several tens of μm can be easily obtained as compared with a thin film forming technique such as a vapor deposition method. Further, the aluminum film can be produced by electroplating. A film formed with a film thickness of about 40 μm using a plating solution comprising dimethylsulfone and aluminum chloride can provide a film having a smooth surface and a uniform film interior.

Subsequently, the film thickness of the pad film 5 is desirably 5 μm or more and 100 μm or less. Preferably, the range of 10 μm or more and 30 μm or less is more desirable. When the film thickness is thin, fine porous existing inside the film is connected, and the electrolytic solution 7 easily penetrates into the tungsten via wiring 3 under the pad film and easily causes electrolytic corrosion of tungsten. When the cell lead 8 is connected by welding, the welding conditions are extremely limited, and it is difficult to realize reliable joining. Here, after forming an aluminum film having a thickness of 5 μm as a pad film 5 on a soda-lime glass plate having a thickness of about 1.3 mm by an ion plating method, an experiment in which a thin plate of aluminum having a thickness of 80 μm is welded by ultrasonic welding. Carried out.
As a result, it was confirmed that a minute crack was generated in the glass plate in one sample out of five cell leads. Therefore, it can be estimated that 5 μm is a practical lower limit for the thickness of the pad film 5. Practically, it is desirable that the thickness of the pad film 5 be 10 μm or more.

(Cell element 6)
Next, the cell element 6 will be described. The cell element 6 is formed by winding a pair of positive and negative electrode sheets having an aluminum foil having a thickness of 5 μm to 100 μm as a current collector and a carbon material layer containing an active material on the surface, with a separator made of an insulator interposed therebetween. It is a power generation element that is integrated by techniques such as stacking and folding.
In the cell element 6 of the present embodiment, as will be described later, an intervening layer containing an aluminum and carbon compound is formed on the surface portion of the aluminum current collector, and the second surface portion extends outward from the intervening layer. The electrode sheet is provided with a special structure having a conductive layer in which a plurality of carbon particles are fixed in a carbon material layer. The electrode sheet preferably has an active material layer formed on the conductive layer. Furthermore, the conductive layer may contain an active material. When the conductive layer includes an active material, it is preferable to include activated carbon. By forming an electrode sheet having a conductive layer containing an active material, the capacity of the electrochemical cell can be increased. Even in this case, since the adhesion of the carbon particles on the surface of the aluminum current collector is unlikely to be lowered even when receiving heat from the reflow solder, an electrochemical cell having high heat resistance can be obtained.
This electrode sheet can be manufactured with reference to, for example, WO2004 / 089784. Specifically, it can be obtained by applying carbon particles to the surface of the aluminum foil and then heating to about 300 to 650 ° C. in a hydrocarbon atmosphere.
By this heat treatment, a compound of aluminum and carbon can be generated on the surface of the aluminum foil, and the carbon particles can be fixed on the surface of the aluminum foil by the compound of aluminum and carbon. More specifically, Toyal Carbo (registered trademark) manufactured by Toyo Aluminum Co., Ltd. can be used. The aluminum and carbon compound is particularly preferably aluminum carbide (Al ₄ C ₃ ).

FIG. 4 shows a schematic structure of an example in which the cell element 6 is wound.
As shown in FIG. 4A, the cell element 6 includes a film-like positive electrode (positive electrode) 32 composed of a conductive layer 30 containing an aggregate of carbon particles and a positive electrode current collector 31 of an aluminum foil, and an aggregate of carbon particles. A film-like negative electrode body (negative electrode) 42 composed of a conductive layer 40 including a body and a negative electrode current collector 41 of aluminum foil, and a film-like separator 35 provided between the positive electrode body 32 and the negative electrode body 42 are laminated. Has a laminated structure. That is, the cell element 6 has a spiral structure in which a film-like positive electrode body 32 and a negative electrode body 42 are overlapped with each other with a separator 35 therebetween, and this laminate-like laminate is wound in the same direction. ing.
In addition, the positive electrode cell lead 8 is bonded to a part of the positive electrode current collector 31, and the negative electrode cell lead 8 is bonded to a part of the negative electrode current collector 41, and these are drawn to the outside of the spiral structure. The cell element 6 shown in 4 (a) is configured.

  Aluminum used as the aluminum foil is not particularly limited, and pure aluminum or an aluminum alloy can be widely used. Aluminum used in the present embodiment has a composition of lead (Pb), silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc ( Zn alloy, titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), and aluminum alloy to which at least one alloy element is added within the necessary range, or an inevitable impurity element Including aluminum containing selenium.

The thickness of the aluminum foil is not particularly limited, but can be in the range of 5 μm to 100 μm, for example, in the range of 5 μm to 20 μm.
The thickness of the carbon material layer can be in the range of 0.01 μm to 200 μm, for example, in the range of 0.3 μm to 50 μm.
The relationship between the positive electrode current collector 31 and the conductive layer 30 has an enlarged structure shown in FIG. That is, the conductive layer 30 including an aggregate of carbon particles is formed on the surface portion of the positive electrode current collector 31, and the intervening layer 33 is formed between the positive electrode current collector 31 and the conductive layer 30. The intervening layer 33 constitutes a first surface portion containing a compound of aluminum and carbon formed in at least a partial region of the surface of the positive electrode current collector 31 made of aluminum. Conductive layer 30 includes a second surface portion 34 including an aluminum and carbon compound extending outwardly from the aluminum and carbon compound of intervening layer 33. A plurality of carbon particles 36 are fixed to the second surface portion 34 to form the conductive layer 30. The conductive layer 30 may be formed on one surface of the positive electrode current collector 31 as shown in FIG. 4A, or may be formed on both surfaces.
Moreover, in this embodiment, it is preferable that the active material layer which consists of activated carbon, a conductive support agent, and a binder is formed in the required thickness (for example, about 30 micrometers) on the conductive layer 30 which formed the carbon particle 36 on the surface.
Similarly, the relationship between the negative electrode current collector 41 and the conductive layer 40 is such that an intervening layer (first surface portion) 33 is formed on the surface of the negative electrode current collector 41 and a second surface portion 34 is formed thereon. A plurality of carbon particles 36 are fixed to the second surface portion 34 to form the conductive layer 40. It is preferable that an active material layer made of activated carbon, a conductive auxiliary agent, and a binder is formed on the conductive layer 40 to a necessary thickness (for example, about 30 μm). The conductive layer 40 may be formed on one surface of the negative electrode current collector 41 as shown in FIG. 4A, or may be formed on both surfaces.

The separator 35 regulates direct contact between the positive electrode body 32 and the negative electrode body 42, and an insulating film having a large ion permeability and a predetermined mechanical strength is used. For example, in an environment where heat resistance is required, resins such as polytetrafluoroethylene, polyphenylene sulfide, polyethylene terephthalate, polyamide, and polyimide can be used in addition to glass fibers. The pore diameter and thickness of the separator are not particularly limited, but are determined based on the current value of the equipment used and the internal resistance of the electrochemical cell 1. It is also possible to use a porous ceramic body as a separator.
The configuration of the cell element 6 shown in FIG. 4A is a general example of a wound cell element, but the cell element may adopt any configuration such as a stacked type and a folded type.

(Electrolytic solution 7)
As the electrolytic solution 7, it is preferable to use a mixed electrolytic solution in which a supporting salt is dissolved in a mixed solvent containing sulfolane (SL) and ethyl methyl sulfone (EMS).
Sulfolane (SL) is one of cyclic sulfones, and has a high dielectric constant. By dissolving a large amount of the supporting salt, it is possible to obtain an electrolyte with good conductivity. Since this SL has a high boiling point and strong oxidation resistance, it can be used as the main solvent of the electrolyte solution of the electrochemical cell. Ethyl methyl sulfone (EMS) is one of chain sulfones. By mixing this EMS with sulfolane (SL) having a high melting point and using it as a solvent for the electrolyte, the viscosity can be lowered as compared with a solvent containing only sulfolane (SL).
Examples of the supporting salt include quaternary ammonium salts and quaternary phosphonium salts. More specifically, examples of the compound having only a fatty chain in the quaternary ammonium salt include triethylmethylammonium (TEMA) salt and tetraethylammonium (TEA) salt. Examples of the spiro compound include 5-azonia spiro [4,4] nonanetetrafluoroborate (spiro- (1,1 ′)-bipyrrolidinium: SBP-BF4), 6-azoniaspiro [5,5] undecanetetrafluoroborate, 3 -Azonia spiro [2, 6] nonane tetrafluoroborate, 4-azonia spiro [3, 5] nonane tetrafluoroborate, etc. are mentioned. Examples of the quaternary phosphonium salt include 5-phosphonyl spiro [4,4] nonanetetrafluoroborate.
As the supporting salt, a quaternary ammonium salt is preferable, a spiro compound is more preferable, and 5-azonia spiro [4,4] nonanetetrafluoroborate is more preferable. Since the quaternary ammonium salt spiro compound has high electrical conductivity, the discharge capacity can be increased.

The electrolyte solution 7 is, for example, a supporting salt of 13 to 43% by mass and the composition of the remaining solvent. In the remaining solvent mass ratio, sulfolane (SL): 60 to 90% by mass, ethyl methyl sulfone (EMS): 10 to 40% by mass. It is preferable that it is an electrolyte solution which has a composition of%. In the present embodiment, when the upper and lower limits of mass% are expressed as 13 to 43 mass%, unless otherwise noted, the upper and lower limits are included. Therefore, 13-43 mass% means 13 mass% or more and 43 mass% or less.
For example, it is possible to use an electrolytic solution in which the supporting salt is 25% by mass and SL: EMS = 80% by mass: 20% by mass in a mass ratio (%) with respect to the total mass of the electrolytic solution.
The mass of the supporting salt is more preferably in the range of 20 to 30% by mass, and still more preferably in the range of 22 to 27% by mass with respect to the total mass of the electrolytic solution.
Moreover, about mass ratio of each component with respect to the whole solvent, the range of SL: 75-85 mass% and EMS: 15-25 mass% is more preferable.

(Cell Lead 8)
The cell lead 8 is a terminal for taking out electric power from the cell element 6. The cell lead 8 may be an extension part obtained by thinly extending the current collector itself, or an extension part formed by mechanically connecting another thin thin plate or a wire-like lead. The cell lead 8 of the present embodiment is preferably an extension of the current collector itself, and a welding region 8a which is a part of the cell lead 8 is fixed to the welding portion 5a of the pad film 5 by welding.
As shown in FIGS. 3A and 3B, the cell lead 8 of the present embodiment is long enough to place the cell 6 outside the base container 2, and is welded to the pad film 5. It is desirable that the length of the welding tip 20 does not hinder the movement of the welding tip 20. This is because an excessively long internal resistance increases. The cell element 6 is housed in the base container 2 after the cell lead 8 and the pad film 5 are welded. At this time, the cell lead 8 is folded inside the base container 2. Further, when the cell lead 8 is folded, care must be taken so that the cell lead 8 does not come into contact with the seal ring 9 in order to avoid short circuit of the cell element 6.

(Seal ring 9)
As shown in FIG. 1, the seal ring 9 has a square frame-like cross section that matches the shape of the upper end surface of the base wall 2b of the base container 2, and brazing material is applied to the upper end surface of the base wall 2b. Are joined through. The seal ring 9 can be made of a material having a thermal expansion coefficient close to that of ceramic, for example, Kovar (trade name of Westinghouse), which is an iron / cobalt / nickel alloy. The brazing material is made of an Ag—Cu alloy, an Au—Cu alloy, or the like.

(Lid 10)
As shown in FIG. 1, the lid 10 is joined to the upper surface of the seal ring 9 and seals the base container 2. The lid 10 is made of a nickel-plated alloy such as Kovar or 42 alloy whose thermal expansion coefficient is close to that of ceramic. Specifically, Kovar is a thin plate having a thickness of about 0.1 mm to 0.2 mm, and the surface thereof is subjected to electrolytic nickel plating or electroless nickel plating with a thickness of about 2 μm to 4 μm. The lid 10 using such a material can be welded to the seal ring 9 by, for example, resistance seam welding, laser seam welding, and the like, and the airtightness inside the base container 2 in a closed state is improved.

In resistance seam welding used as a method of welding the lid 10 and the seal ring 9, the lid 10 is brought into contact with the seal ring 9, and then the trapezoidal shape opposed to two points at the approximate center on the long side of the lid 10. The roller electrode is arranged and a low voltage and large current is allowed to flow for a short time, and the temporary welding (spot welding) of the lid 10 is performed. In this way, the lid 10 is temporarily fixed and the position does not shift due to vibration or the like during the welding operation.
Subsequently, for example, the base container 2 and the lid 10 are moved and welded so that the long side is traced by the roller electrode from the end of the long side. Next, the base container 2 and the lid 10 are rotated 90 degrees, and the short sides are similarly welded. In this way, welding is performed over the entire circumference of the lid 10. In both the above-described temporary fixing and the resistance seam welding, gold and nickel are diffused at the interface between the lid 10 and the seal ring 9, and an airtight and strong diffusion bonding layer is formed. Thereby, the lid 10 seals the base container 2 with high airtightness.

The lid 10 and the seal ring 9 can be welded using laser scanning irradiation. After carrying out the temporary welding in the same manner as described above, the laser is scanned and irradiated so as to go around the lid 10 once. As a result, a diffusion bonding layer is formed at the interface between the lid 10 and the seal ring 9. In this case, it is possible to lower the melting temperature to the temperature of the brazing material by sticking a brazing material sheet made of silver and copper on the surface of the lid 10 on the joining side.
In addition, when the electrolytic solution 7 is made of a liquid solvent or a supporting salt at room temperature and the step of filling the electrolytic solution 7 before sealing the lid 10 is adopted, the liquid is at the interface between the lid 10 and the seal ring 9. There can be a place to exist. Even in such a case, joining using seam welding is possible.
Seam welding may be performed using a roller electrode or using laser scanning irradiation.
The reason why airtight welding is possible even if liquid exists at the interface is considered to be that the liquid present at the interface evaporates and scatters because the temperature in the vicinity of the liquid increases rapidly during welding. Note that the upper end surface of the base container 2 and the lid 10 may be joined via a brazing material without using the seal ring 9.

  The electrochemical cell 1 configured as described above includes a positive electrode including conductive layers 30 and 40 in which carbon particles are fixed by a compound of aluminum and carbon on current collectors 31 and 41 made of aluminum constituting the cell element 6. Since the body 32 and the negative electrode body 42 are provided, the aluminum current collectors 31 and 41 and the conductive layers 30 and 40 of the carbon material layer have good adhesion, and the aluminum current collectors 31 and 41 and An increase in interface resistance between the carbon material layer and the conductive layers 30 and 40 can be suppressed. For this reason, the electrochemical cell 1 has higher conductivity and capacity density than the conventional electrochemical cell in which a slurry containing an active material, a conductive additive, a binder and the like is directly coated on an aluminum current collector. Can provide. In addition, since the good adhesion between the aluminum current collectors 31 and 41 and the conductive layers 30 and 40 of the carbon material layer is less likely to be lowered by the heat of the reflow solder, the cell element 6 is attached to the base container 2. It is possible to provide an electrochemical cell 1 that can be reflow soldered with high reliability even if it is housed in a small container and has a small element shape having wiring in the base container 2.

The electrochemical cell of this embodiment has a composition of 13 to 43% by mass of the supporting salt and the remaining solvent, and the composition of sulfolane: 60 to 90% by mass and ethylmethylsulfone: 10 to 40% by mass in the remaining solvent mass ratio. Since the electrolytic solution 7 is provided, the electrochemical cell 1 having high conductivity and capacity density and excellent charging characteristics can be provided. The electrolytic solution having the above composition is desirable as an electrolytic solution for achieving a 2.5V withstand voltage, and has characteristics of withstanding a higher voltage charge and excellent long-term storage stability. About long-term storage stability, it has the characteristic which is excellent also in high temperature stability of 70 degreeC or 85 degreeC.
When the base container 2 containing the cell element 6 is sealed with a lid 10 by a method such as laser welding, seam welding or brazing, even if heat for sealing is transferred to the non-aqueous electrolyte near the lid, It is possible to provide the electrochemical cell 1 in which the non-aqueous electrolyte is difficult to evaporate and resistance is not easily increased due to alteration of the non-aqueous electrolyte.
Moreover, if it is the said electrolyte solution, since 3V withstand voltage can be ensured, it replaces with the usage which uses the conventional electrochemical cell of 2.5V withstand voltage two in series, and uses a booster circuit and is single. It becomes possible to make a cell. Thereby, there is an effect that the mounting space can be reduced.

A second embodiment of the electrochemical cell according to the present invention will be described with reference to FIG.
In the electrochemical cell 15 shown in FIG. 5, the via wiring 3 is not directly penetrated from the base inner bottom surface 2c to the base lower surface 2d, but the via wiring 3 is a base first plate which is two plates constituting the base bottom portion 2a. The structure is stopped at the interface between the bottom 2f and the base second bottom 2g. A wiring pattern 18 is provided at this interface. The wiring pattern 18 is connected to the via wiring 3, extends horizontally, is exposed on the outer surface, and is further connected to the connection terminal 4.
The pad film 5 is made of an aluminum film having a thickness of 5 μm to 100 μm, as in the first embodiment. A pair of cell leads 8 connected to the cell element 6 is connected to the pad film 5 by welding. Further, after the electrolytic solution 7 is filled, the base container 2 is hermetically sealed by the lid 10 to constitute an outer container.

The other configuration of the electrochemical cell 15 shown in FIG. 5 is the same as that of the electrochemical cell 1 of the first embodiment.
Also in the electrochemical cell 15 having the configuration shown in FIG. 5, as in the previous electrochemical cell 1, it is possible to provide the electrochemical cell 15 having high conductivity and high capacity density and high reliability even in a small element shape. Further, it is possible to provide the electrochemical cell 15 having high conductivity and capacity density, excellent charging characteristics, and hardly causing an increase in resistance due to alteration of the non-aqueous electrolyte even with a hermetically sealed structure. Furthermore, it is possible to provide an electrochemical cell that can withstand high voltage charging and has excellent long-term storage stability.

A third embodiment of the electrochemical cell according to the present invention will be described with reference to FIG.
In the electrochemical cell 16 shown in FIG. 6, an outer container is constituted by a base container 2 made of only a ceramic flat plate and a metal cavity lid 10 a having a concave shape, and FIG. 6 shows the electrochemical cell 16. The cross section of is shown. As in the previous embodiment, the cell element 6, the pair of cell leads 8, and the electrolytic solution 7 are accommodated in the exterior container, and the cell leads 8 and the pad film 5 formed on the base container 2 are welded. Connected by.

As shown in FIG. 6, the cavity lid 10 a is welded so that its opening is in contact with a seal ring 9 provided around the base container 2 so as to cover the cell element 6 and the like. For this welding, laser seam welding is preferred. When performing seam welding, laser irradiation is performed from the direction of the arrow in FIG. In resistance seam welding using a roller electrode, the roller electrode is likely to come into contact with the step of the cavity-type lid 10a, and it becomes difficult to properly bring the roller electrode into contact with the joint.
In the cavity-type lid 10a, a small hole is provided in the bottom surface portion (the upper end portion in the drawing) of the cavity-type lid 10a. This is intended so that after the base container 2 and the cavity type lid 10a are welded, the electrolyte solution 7 is filled from the small holes, and then sealed airtightly using the sealing plug 10b.
Thereby, the efficiency fall of the sealing work by the electrolyte solution 7 existing between the sealing ring 9 and the joining surface of the cavity type lid 10a can be prevented. The material and the range of the thickness of the pad film 5 formed on the inner surface of the base container 2, the structure and number of the via wirings 3, and the bonding means between the cell leads 8 and the pad film 5 are the same as described above. Omitted.

The other configuration of the electrochemical cell 16 shown in FIG. 6 is the same as that of the electrochemical cell 1 of the first embodiment.
Also in the electrochemical cell 16 having the configuration shown in FIG. 6, like the previous electrochemical cell 1, it is possible to provide the electrochemical cell 16 having high conductivity and high capacity density and high reliability even in a small element shape. Further, it is possible to provide the electrochemical cell 16 that has high conductivity and high capacity density, excellent charging characteristics, and is less likely to increase in resistance due to alteration of the non-aqueous electrolyte even with a hermetic sealing structure. Further, it is possible to provide the electrochemical cell 16 that has high conductivity and high capacity density, excellent charging characteristics, and is less likely to increase in resistance due to alteration of the non-aqueous electrolyte even with a hermetic sealing structure. Furthermore, it is possible to provide an electrochemical cell 16 that can withstand high voltage charging and has excellent long-term storage stability.

A fourth embodiment of the electrochemical cell according to the present invention will be described with reference to FIG.
FIG. 7A shows the base container 2 used in the fourth embodiment. In this embodiment, the base container 2 is composed of a ceramic flat plate and a metal cylindrical metal side wall 12 joined to the flat plate, thereby forming a concave container. A via wiring 3 that directly penetrates the base bottom portion 2a is provided on the base inner bottom surface 2c of the base container 2, and a pair of pad films 5 are disposed thereon. The metal metal side wall 12 is selected so that the coefficient of thermal expansion matches that of the base container 2 and is joined to the flat plate with a brazing material.
On the other hand, the opening on the opposite side of the base container 2 forms a joint surface of the lid 10. In the present modification, the seal ring 9 of the first embodiment for sealing the lid 10 is not necessary, and the metal side wall 12 itself also serves as the seal ring 9. Therefore, at least a surface of the metal side wall 12 to be joined to the lid 10 is provided with a nickel and gold plating film. The lid 10 is in contact with the plating surface, and resistance seam welding or laser seam welding is used. It is comprised so that joining is possible.

FIG. 7B shows a cross-sectional view of the electrochemical cell 17 using the flat base container 2. A pair of cell leads 8 connected to the cell element 6 are connected to the pad film 5 by welding means, and connected to the connection terminal 4 by the via wiring 3. The exterior container is filled with the electrolytic solution 7 and hermetically sealed with the lid 10. The material and thickness of the pad film are the same as described above. Since the metal side wall 12 is made of metal, it can be processed into various shapes. As the shape, a corner, a track shape, an ellipse, a circle, or the like can be selected. In particular, when a standard hollow pipe is cut to an arbitrary length and used, the height of the electrochemical cell 17 can be freely determined and the manufacturing cost can be reduced.
In the electrochemical cell 17 shown in FIG. 7C, the metal side wall 12 is used as in FIG. 7B, but the pad film 5 is formed only on the positive electrode side. The positive electrode cell lead 8 b is connected to the pad film 5 by ultrasonic welding, while the negative electrode cell lead 8 c is connected to the inside of the metal side wall 12 by welding. Since the metal side wall 12 is made of metal and the path through which current flows is large, the wiring resistance value on the negative electrode side can be kept low. Therefore, the electrochemical cell 17 of the present embodiment can discharge a large current.

The other configuration of the electrochemical cell 17 shown in FIG. 7 is the same as that of the electrochemical cell 1 of the first embodiment.
Also in the electrochemical cell 17 having the configuration shown in FIG. 7, as in the previous electrochemical cell 1, the electrochemical property has high conductivity and capacity density, and can perform reflow soldering with high reliability even in a small element shape. A cell 17 can be provided. Further, it is possible to provide the electrochemical cell 17 that has high conductivity and high capacity density, excellent charging characteristics, and is less likely to increase in resistance due to alteration of the nonaqueous electrolytic solution even with a hermetic sealing structure. Furthermore, it is possible to provide an electrochemical cell 17 that can withstand high voltage charging and has excellent long-term storage stability.

A concave base container 2 and a lid 10 shown in FIGS. 1A and 1B were prepared. The base container 2 was a box-shaped container made of alumina having a long side of 10 mm, a short side of 8 mm, a height of 1.8 mm, and a bottom wall thickness of 0.38 mm.
The base container 2 was formed by laminating a ceramic green sheet corresponding to the wall 2b punched out in a rectangular frame shape on the ceramic green sheet and firing it at about 1500 ° C. Four via wirings 3 having an outer diameter of 0.2 mm were provided on each of the positive electrode side and the negative electrode side so as to directly penetrate the base inner bottom surface 2c and the base lower surface 2d. The surface of the via wiring 3 was plated with nickel and gold. A pair of connection terminals 4 are arranged on the base lower surface 2 d and connected to the via wiring 3. The connection terminal 4 was subjected to gold plating with nickel as a base.

Next, a pair of pad films 5 made of an aluminum vapor deposition film was formed on the base inner bottom surface 2c. The pad film 5 has a short side of 2.4 mm, a long side of 3 mm, and a thickness of about 15 μm. On the other hand, for the lid 10, a Kovar plate having a long side of 9 mm, a short side of 7 mm, and a thickness of 0.125 mm was prepared, and the surface was subjected to electrolytic nickel plating.
Subsequently, the cell element 6 is prepared.
In Example 1, Toyo Carbo (registered trademark) manufactured by Toyo Aluminum Co., Ltd., in which carbon particles were fixed with aluminum carbide (Al ₄ C ₃ ) on the surface of a current collector made of an aluminum foil having a thickness of 20 μm, was used for the surface layer. An active material layer with a thickness of 30 μm consisting of 85% by mass of activated carbon having a particle size of 6 μm, a conductive additive (Ketjen black, 8% by mass), a binder (polytetrafluoroethylene, 7% by mass) and a thickener is coated on one side. A sheet electrode was prepared. In Example 2, an electrode sheet in which an active material layer having a thickness of 10 μm including activated carbon having a particle diameter of 6 μm made of aluminum carbide (Al ₄ C ₃ ) on a current collector made of an aluminum foil having a thickness of 20 μm was prepared on one side. .
After cutting these sheet electrodes to an appropriate length, a cell lead 8 was obtained by attaching an aluminum thin plate having a thickness of 80 μm, a width of 1.5 mm, and a length of 4 mm to one end thereof by ultrasonic welding. PTFE / glass / PPA / nylon / PEEK / PBT (PTFE: polytetrafluoroethylene, PPA: polyphthalamide, PEEK: polyetheretherketone, PBT: poly) After sandwiching a separator having a laminated structure of (butylene terephthalate), a core was inserted and wound into a track shape. Thereafter, the winding core was taken out and the gap was lightly crushed to form a wound type cell element 6.

  Subsequently, ultrasonic welding is performed. The cell leads 8 were brought into close contact with the surface of the pad film 5 of the base container 2 prepared previously and positioned. Ultrasonic welding performed the cell leads 8 one by one. The oscillation frequency of the ultrasonic melter was 40 kHz. The welding horn is made of iron, and the ultrasonic welding tip 20 made of the same material is integrally provided at the tip of the horn. On the surface of the ultrasonic welding tip 20, a staggered concavo-convex pattern (Nar) having a pitch of 0.2 mm was provided in an area of 2.0 × 1.5 mm. The difference between the height of the mountain and the bottom of the valley is 0.2 mm. The welding mode was a mode for controlling the energy supplied to the cell lead 8 during welding, the welding energy set value was in the range of 0.5 to 100 J, and the welding time was in the range of 50 to 2000 msec. After the ultrasonic welding tip 20 is lowered to the surface of the cell lead 8 made of aluminum by the air mechanism, the ultrasonic welding tip 20 bites into the surface of the cell lead 8 and vibrates between the interface of the cell lead 8 and the pad film 5 to perform welding. .

After the ultrasonic welding was completed, the cell element 6 was stored in the base container 2 so that the cell lead 8 was folded. At this time, care was taken so that the cell lead 8 did not contact the seal ring 9. This is to avoid a short circuit of the electrochemical cell.
Next, the base container 2 in which the cell element 6 was accommodated was immersed in a liquid electrolyte solution 7 and vacuum degassed for 1 minute. Here, SBP · BF4 (5-azoniaspiro [4.4] nonane tetrafluholoborate) is used as the supporting salt of the electrolytic solution 7, and a mixed solution of sulfolane (SL) and ethyl methyl sulfone (EMS) as a non-aqueous solvent. Were prepared at the following ratio and used as a mixed electrolyte. The ratio of mixing is 25% by mass of the supporting salt in the mass ratio with respect to the total mass of the electrolytic solution and the composition of the remaining solvent, and the electrolyte contains SL: 80% by mass and EMS: 20% by mass in the solvent Yes.

Subsequently, after returning to atmospheric pressure and taking out the base container 2 containing the cell elements 6 from the electrolyte 7, the lid 10 is brought into contact with the seal ring 9 in a nitrogen atmosphere, and two points on the long side are contacted. Temporary welding was performed, and subsequently, the long side and the short side were successively subjected to resistance seam welding in this order, and the base container 2 was hermetically sealed. In this way, the electrochemical cell of this example was produced.
The electrical characteristics of the produced electrochemical cell were tested.

For comparison, when a sheet electrode is manufactured in the manufacturing process, 85% by mass of activated carbon having a particle diameter of 6 μm and a conductive assistant on the surface of a current collector made of aluminum having a thickness of 20 μm are used. A sheet electrode for comparison, in which an active material layer having a thickness of 30 μm composed of an agent (Ketjen Black, 8% by mass), a binder (polytetrafluoroethylene, 7% by mass) and a thickener is applied on one side, An electrochemical cell of Comparative Example 1 was produced that was accommodated in the base container 2 in the same manner as described above and sealed with the lid 10.
In order to evaluate the resistance to reflow soldering for each obtained electrochemical cell, a reflow soldering test was performed by holding the whole at 260 ° C. for 5 seconds, and the internal resistance (Ω) before and after the reflow soldering test was measured. The rate of change (rate of change before and after reflow) was calculated.
The internal resistance was determined by measuring the impedance at an alternating current of 1 kHz (the same applies to the measurement of the internal resistance described below). The results are shown in Table 1 below and FIG.

As is apparent from the results shown in Table 1 and FIG. 8, an electrochemical cell (electric double layer capacitor) having a sheet electrode having a structure in which a layer of a carbon material is supported by aluminum carbide (Al ₄ C ₃ ) according to the present invention. Even when exposed to the reflow soldering heating environment, it was found that the increase in internal resistance was small compared to the conventional structure shown in Comparative Example 1, and the deterioration was extremely small. Therefore, it can be seen that the electrochemical cell according to the present invention can withstand the process of reflow soldering and can suppress an increase in internal resistance as an electrochemical cell.

  Next, the electrochemical cell having the same structure as that of Example 1 and Example 2 and the electrochemical cell having the same structure as that of Comparative Example 1 were charged at a charging voltage of 3.0 V / a charging current of 10 mA for 10 minutes, and then discharged. The discharge time (sec) was measured under the condition of 1 mA and a discharge end voltage of 2.0V. Moreover, the reflow solder test equivalent to the previous example was implemented, the discharge time (sec) before and after the reflow solder test was measured, and the rate of change before and after (reflow rate before and after reflow) was calculated. The results are shown in Table 2 below and FIG.

  As is apparent from the results shown in Table 2 and FIG. 9, even when the electrochemical cell having the sheet electrode of the present invention structure is exposed to the reflow soldering heating environment, the discharge time is reduced little and the capacity is reduced little. It has been found. For this reason, it can be seen that the electrochemical cell according to the present invention can withstand the process of reflow soldering and can suppress a decrease in capacity as an electrochemical cell.

Next, for comparison, the supporting salt is 25% by mass, the remaining solvent is the mass ratio in the solvent, PC (propylene carbonate): EC (ethylene carbonate): DMC (dimethyl carbonate) = 39% by mass: 32% by mass: Comparative Example 2 was prepared in the same manner as in Example 1 except that the electrolytic solution mixed at a ratio of 29% by mass was used.
For each electrochemical cell having the same structure as Example 1 and Comparative Example 2 described above, the reflow solder test equivalent to the previous example was performed, the internal resistance (Ω) before and after the reflow solder test was measured, and the change before and after that The rate (rate of change before and after reflow) was evaluated. Further, the discharge time (sec) before and after the reflow solder test and the rate of change before and after (reflow rate before and after reflow) were evaluated. These results are shown in the following Table 3, Table 4, FIG. 10, and FIG.

  From the results shown in Table 3 and FIG. 10, regarding the rate of change in internal resistance before and after the reflow solder test (rate of change before and after reflow), Example 1 in which SL is the main solvent is Comparative Example 2 in which PC and EC are the main solvents. Although the internal resistance was higher than that, the rate of change before and after reflow was slightly smaller. Further, from the results shown in Table 4 and FIG. 11, Example 1 using an SL-based electrolyte with high voltage resistance with respect to the change rate of the discharge time before and after the reflow solder test at 3.0 to 2.0 V. Then, the fall of the discharge time by reflow was smaller than the comparative example 2. Thus, it was found that the initial electrical characteristics (internal resistance, capacity) are excellent particularly in the high voltage band when the SL electrolyte is used.

<Evaluation of storage characteristics>
Next, when an electrochemical cell having the same structure as in Example 1 and Comparative Example 2 is used, the charging voltage is set to 3.0 V at 60 ° C., and the charging voltage is set to 2.5 V at 85 ° C. The capacity maintenance rate (capacity maintenance rate at HTV (storage characteristics)) according to the number of days is shown in Table 5, Table 7, FIG. 12, and FIG. 14, and the internal resistance increase rate (internal resistance increase rate at HTV (storage characteristics)) ) Are shown in Table 6, Table 8, FIG. 13, and FIG. These tests correspond to floating tests in which voltage is applied under high temperature storage.

In the electrochemical cell of Comparative Example 2, the internal resistance greatly increases with the passage of storage days, and the capacity retention rate significantly decreases. On the other hand, the electrochemical cell of Example 1 has a small internal resistance increase rate in both the storage temperature of 60 ° C./charge voltage of 3.0 V and the storage temperature of 85 ° C./charge voltage of 2.5 V, and the capacity is maintained. There is almost no decrease in rate.
For this reason, it can be seen that the electrochemical cell of Example 1 has a low internal resistance increase rate even when the number of days elapses, and a high capacity maintenance rate even when the days elapse.
From the above results, the cell element is provided with a sheet electrode having a structure in which a carbon material layer is supported by aluminum carbide (Al ₄ C ₃ ), and a mixed solvent of sulfolane (SL) and ethyl methyl sulfone (EMS) in a desired ratio. The electrochemical cell using the electrolytic solution using clarified advantages over the conventional electrochemical cell equipped with a coating electrode, and the electrochemical cell using a mixed solvent of propylene carbonate, ethylene carbonate and dimethyl carbonate became. That is, the electrochemical cells of Examples 3 and 4 can be charged at 3 V, have excellent voltage resistance, high capacity, and excellent heat resistance.
In addition, an electrochemical cell equipped with a sheet electrode having a structure in which a carbon material layer is supported by aluminum carbide (Al ₄ C ₃ ) has an internal structure compared to a coating type conventional electrode structure even when exposed to a reflow soldering heating environment. It was found that the increase in resistance was small.

<Supported salt ratio change test>
Next, when producing the electrochemical cell of Example 1, the electrochemical cell of Example 3 using an electrolytic solution set to 15% by mass with respect to the mass ratio of the supporting salt in the applied electrolytic solution, and 40% by mass. The electrochemical cell of Example 4 using the electrolyte set to%, the electrochemical cell of Comparative Example 3 using the electrolyte set to 10% by mass, and the comparison using the electrolyte set to 45% by mass The electrochemical cell of Example 4 was prepared and subjected to the following impedance measurement test.
The impedance measurement test takes into account the resistance to reflow soldering, performs a reflow soldering test in which the entire electrochemical cell is held at 260 ° C. for 5 seconds, measures the internal resistance before and after the reflow soldering test, and the rate of change of the internal resistance before and after the reflow soldering test. It calculated about (change rate before and after reflow). The results are shown in Table 9 below and FIG.

As is apparent from the results shown in Table 9 and FIG. 16, the electrochemical cell having the electrolytic solution in which the mass ratio of the supporting salt was set in the range of 13 to 43% by mass exhibited a low internal resistance even after the reflow soldering.
In the electrochemical cell of Comparative Example 3 in which the mass ratio of the supporting salt was less than the desirable range of the present invention (13 to 43 mass%), the conductivity decreased and the internal resistance increased. In the electrochemical cell of Comparative Example 4 in which the mass ratio of the supporting salt is excessively larger than the above range, the influence of decomposition and deterioration of the solvent due to heating increases due to the small ratio of the solvent to the supporting salt, and the reflow soldering is performed. This increased the internal resistance.

Using an electrochemical cell having the same structure as in Examples 3 and 4 and Comparative Examples 3 and 4 described above, the reflow solder test equivalent to the previous example was performed, and the discharge time (sec) after the reflow solder test was measured. The rate of change before and after that (rate of change before and after reflow) was evaluated. The results are shown in Table 10 below and FIG.
As charging conditions, the electrochemical cells of Examples 3 and 4 and Comparative Examples 3 and 4 were set with a charging voltage of 3.0 V, a charging current of 10 mA, and a charging time of 10 minutes. As discharge conditions, the discharge current was set to 1 mA and the discharge end voltage was set to 2.0V.

  From the results shown in Table 10 and FIG. 17, the supporting salt (SBP · BF4) is exposed to the reflow soldering heating environment by setting the range of 13 mass% to 43 mass% in which the increase in internal resistance due to the reflow solder is small. Even so, it can be seen that an electrochemical cell can be provided in which the decrease in discharge time is small and the capacity is reduced little.

<Supported salt ratio change storage characteristics evaluation>
Using an electrochemical cell having the same structure as in Examples 3 and 4 and Comparative Examples 3 and 4, tests for evaluating storage characteristics were performed.

The capacity maintenance ratio (capacity maintenance ratio in HTV (storage characteristics)) according to the elapsed (storage) days when the charging voltage is set to 2.5 V at 70 ° C. is shown in Table 11 and FIG. The rate (internal resistance increase rate in HTV (storage characteristics)) is shown in Table 12 below and FIG.
The capacity retention rate (capacity retention rate in HTV (storage characteristics)) according to the elapsed (storage) days when the charging voltage is set to 2.5 V at 85 ° C. is shown in Table 13 and FIG. The rate (internal resistance increase rate in HTV (storage characteristics)) is shown in Table 14 below and FIG.

In the above results, from the data at 70 ° C. in Tables 11 and 12, Comparative Example 3 in which the content of the supporting salt was decreased showed a large decrease in capacity retention rate as compared with Examples 3 and 4. This is because by reducing the content of the supporting salt, the ratio of the solvent to the supporting salt is increased, and the influence of decomposition and deterioration of the supporting salt due to heating is increased. On the other hand, in Comparative Example 4 in which the content of the supporting salt was increased, the increase in internal resistance was larger than those in Examples 3 and 4. This is because the amount of the supporting salt is too large and the solvent ratio in the electrolytic solution is small, and the influence of the decomposition and deterioration of the solvent is increased. From this, the electrochemical cell having the electrolytic solution in which the mass ratio of the supporting salt is set in the range of 13 to 43% by mass has an internal resistance even when the number of days elapses with a voltage of 2.5 V applied at a temperature of 70 ° C. It can be seen that the increase and the capacity retention rate decrease are suppressed, and the storage characteristics are excellent.
Further, from the data at 85 ° C. in Tables 13 and 14, Comparative Example 3 in which the content of the supporting salt was reduced showed a greater decrease in the capacity retention rate than Examples 3 and 4. In Comparative Example 4 in which the content of the supporting salt was increased, the increase in internal resistance was larger than that in Examples 3 and 4. From this result, the electrochemical cell having the electrolytic solution in which the mass ratio of the supporting salt is set in the range of 13 to 43% by mass has an internal resistance even when the number of days elapses with a voltage of 2.5 V applied at a temperature of 85 ° C. It can be seen that the increase and the capacity retention rate decrease are suppressed, and the storage characteristics are excellent.

<Solvent ratio change test>
When the electrochemical cell having the above-described structure is prepared, 25% by mass of SBP · BF4 (5-azoniaspiro [4.4] nonane tetrafluoroborate) is used as a supporting salt, and sulfolane (SL) and ethyl are used as nonaqueous solvents. A mixed solution of methylsulfone (EMS) was prepared at the following ratio and used as a mixed electrolyte. Other structures are the same as those of the first embodiment.
A mixture ratio of SL and EMS used as a solvent was set to SL: EMS = 80 mass%: 20 mass% in Example 5, and SL: EMS = 88 mass%: 12 mass% in Example 6, SL: EMS = 64% by mass: 36% by mass Example 7 SL: EMS = 93% by mass: 7% by mass Comparative Example 5, SL: EMS = 53% by mass: 47% by mass Was used as Comparative Example 6.

  Similarly to the evaluation performed previously for the electrochemical cells having the same structure as in Examples 5 to 7 and Comparative Examples 5 and 6, the internal resistance was compared with the rate of change before and after (reflow rate before and after reflow). The results are shown in Table 15 below and FIG.

  As shown in Table 15 and FIG. 22, in Comparative Example 5 with a small amount of EMS, the viscosity was increased, and the internal resistance was considered to be increased due to the deterioration of the impregnation property of the electrolyte when the cell element was produced. On the contrary, it is considered that Comparative Example 6 with a lot of EMS has reduced viscosity and reduced internal resistance.

Using an electrochemical cell having the same structure as that of Examples 5 to 7 and Comparative Examples 5 and 6, the discharge time (sec) after the reflow solder test and the rate of change before and after (reflow rate before and after reflow) were measured. The results are shown in Table 16 below and FIG.
As the charging conditions, the electrochemical cells of the examples and comparative examples were set with a charging voltage of 3.0 V, a charging current of 10 mA, and a charging time of 10 minutes. Further, as discharge conditions, the discharge current was set to 1 mA and the end voltage was set to 2.0V.

  As shown in Table 16 and FIG. 23, in Comparative Example 6 with a large amount of EMS and a small amount of SL, the capacitance was a small value. This is because the dielectric constant of the electrolyte decreased due to the small amount of SL. On the other hand, the electrochemical cells of Examples 5 to 7 and Comparative Example 5 showed a high capacity even after reflow.

<EMS ratio change storage characteristics evaluation>
Using an electrochemical cell having the same structure as in Example 5 and Comparative Examples 5 and 6, a test for evaluating the storage characteristics was performed.
The capacity retention rate (capacity retention rate in HTV (storage characteristics)) according to the elapsed (storage) days when the charging voltage is set to 2.5 V at 70 ° C. is shown in Table 17 and FIG. The rate (internal resistance increase rate in HTV (storage characteristics)) is shown in Table 18 below and FIG.
The capacity retention rate (capacity retention rate in HTV (storage characteristics)) according to the elapsed (storage) days when the charging voltage is set to 2.5 V at 85 ° C. is shown in Table 19 and FIG. The rate (internal resistance increase rate in HTV (storage characteristics)) is shown in Table 20 below and FIG.

As shown in Tables 17 and 18 and FIGS. 24 and 25, both the comparative example 5 in which the EMS is less than the preferred range of the present application (10 to 40% by mass) and the comparative example 6 in which the EMS is greater than the preferred range of the present application are maintained. The rate decreased and the internal resistance increased. This is because in Comparative Example 5 with a small amount of EMS, since the viscosity of the cell element is large and the impregnation property of the electrolyte solution is poor, the electrolyte solution not impregnated when sealing the cell during assembly overflows to the outside of the cell. This is because the electrolyte solution tends to deteriorate over time due to the lack of the electrolyte solution inside. On the contrary, Comparative Example 6 with a large number of EMSs was because the withstand voltage was lowered due to a decrease in SL.
In addition, as shown in Tables 19 and 20 and FIGS. 26 and 27, in Comparative Example 5 with less EMS and with Comparative Example 6 with more EMS than the preferred range of the present application, the capacity retention rate decreased and the internal resistance increased. It was seen.
As shown in the above Tables 15 to 20, by using a solvent mixed in the range of SL: 60 to 90% by mass and EMS: 10 to 40% by mass, a cell having excellent storage characteristics can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Electrochemical cell, 2 ... Base container, 2a ... Base bottom part, 2b ... Base wall part, 2c ... Base bottom face, 2d ... Base bottom face, 2e ... Base side face, 2f ... Base 1st bottom part, 2g ... Base 2nd Bottom part, 3 ... via wiring, 4 ... connecting terminal, 5 ... pad film, 5a ... welded part, 6 ... cell element, 7 ... electrolyte, 8 ... cell lead, 8a ... welded region, 8b ... positive electrode cell lead, 8c ... negative electrode cell lead , 9 ... Seal ring, 10 ... Lid, 10a ... Cavity-type lid, 10b ... Seal plug, 15, 16, 17 ... Electrochemical cell, 18 ... Wiring pattern, 20 ... Ultrasonic tip, 20a ... Tip tip, 30 ... Conductive layer, 31 ... positive electrode current collector, 32 ... positive electrode body (positive electrode), 33 ... intervening layer (first surface portion), 34 ... second surface portion, 35 ... separator, 36 ... carbon particles, 40 ... conductive Layer, 41 ... collection of negative electrodes Body, 42 ... negative electrode body (negative electrode).

Claims (6)

A base container; a cell element housed in the base container; a plurality of cell leads which are extensions of the cell element; a pad film made of a valve metal formed on the inner bottom surface of the base container; and the pad An electrochemical cell having at least a base internal wiring connected to a membrane and formed from an inner bottom surface to a lower surface of the base container, and a lid for hermetically closing the base container;
In the cell element, a positive electrode and a negative electrode are disposed with a separator interposed therebetween, and further, a non-aqueous electrolyte is contained, at least one of the positive electrode and the negative electrode is an aluminum current collector, and aluminum is disposed on the aluminum current collector. A layer of carbon material fixed by a compound of carbon,
The non-aqueous electrolyte is a supporting salt: 13 to 43% by mass and the remaining solvent, and the remaining solvent ratio has a composition of sulfolane: 60 to 90% by mass and ethyl methyl sulfone: 10 to 40% by mass. And electrochemical cell.   The electrochemical cell according to claim 1, wherein the lid is welded to the base container.   An intervening layer containing the aluminum and carbon compound is formed on the surface portion of the aluminum current collector, a second surface portion extending outward from the intervening layer is formed, and the second surface portion The electrochemical cell according to claim 1 or 2, wherein a layer of the carbon material having a conductive layer to which a plurality of carbon particles are fixed is formed.   The electrochemical cell according to claim 3, wherein the conductive layer contains an active material.   The electrochemical cell according to any one of claims 1 to 4, wherein the supporting salt is a quaternary ammonium salt or a quaternary phosphonium salt.   The electrochemical cell according to any one of claims 1 to 5, wherein the non-aqueous electrolyte is impregnated around a positive electrode, a negative electrode, and a separator of a cell element housed in the base container. .

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