JP2017028275A - 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 and reflow soldering can be performed.SOLUTION: The electrochemical cell includes a base container, a cell element stored in the base container, 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 formed in an area from the inner bottom to a lower surface of 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 conductive particle layer having a total thickness of 1 to 15 μm and comprising conductive particles fixed by a compound of aluminum and carbon on the aluminum collector. The non-aqueous electrolyte has a composition comprising 8 to 43 mass% of a supporting electrolyte and a balance solvent; and the balance solvent comprises, on a mass ratio basis, 26 to 57 mass% of PC, 0 to 43 mass% of EC and 16 to 48 mass% of DMC.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, a structure in which the adhesion between the active material and the current collector is improved and the surface resistance value is suppressed is known (see Patent Document 2).

JP 2013-30750 A International Publication No. 2010/109783

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.
In addition, in this type of electrochemical cell, when it is necessary to rapidly pressurize the cell (with a short charging time), the conventional activated carbon coated electrode has a problem that it takes time to fill due to an excessive capacity. Furthermore, if the amount of electrodes (the size of the current collector) is reduced to reduce the charging time, there arises a problem that the resistance increases.
Further, in this type of electrochemical cell, when reflow soldering is performed, there is a problem that the internal resistance is increased due to the heat of the solder, and there is a problem that the characteristics of the electrochemical cell deteriorate due to the reflow soldering process. For example, in an electrochemical cell using a ceramic package, when the package is sealed, the heat of welding may be transmitted around the sealed portion. Therefore, depending on the composition of the electrolyte, the electrolyte that receives the heat partially evaporates. However, the characteristics may be deteriorated.

  The present invention has been made in view of the conventional situation, and adopts a structure that can withstand reflow soldering, to increase conductivity and capacity density, and to provide a highly reliable electrochemical cell even in a small element shape. With the goal.

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. A conductive particle layer having a total thickness of 1 to 15 μm including conductive particles fixed by a compound of aluminum and carbon, and the non-aqueous electrolyte is 8 to 43 mass of the supporting salt. A remainder solvent, in the balance solvent weight ratio of propylene carbonate: 26 to 57 wt%, ethylene carbonate: 0-43 wt%, dimethyl carbonate: characterized by having a composition of 16 to 48 wt%.
Since the cell element and the electrolyte solution are contained in an airtight base container, and the support salt, propylene carbonate, ethylene carbonate, and dimethyl carbonate are used in an appropriate ratio, the support salt has high solubility and the heat of the reflow soldering Even if it receives, the increase rate of internal resistance is low, and the electrochemical cell which improved heat resistance with little capacity degradation can be provided.
In addition, since the interface between the conductive particle layer having an appropriate thickness of 1 to 15 μm and the aluminum current collector is fixed using a compound of aluminum and carbon, the conductive particle layer and the current collector in the positive electrode or the negative electrode Therefore, an electrochemical cell having excellent characteristics during charging can be obtained.

In the present invention, a structure in which the lid is welded to the base container can be employed.
When the lid is welded to the base container by a welding method such as seam welding, heat during welding is transmitted to a part of the electrolyte contained in the base container. However, if it is a solvent having the above composition ratio, propylene carbonate, ethylene carbonate, and dimethyl carbonate are used as an appropriate ratio, so that the influence of evaporation of some components of the electrolyte is small even when receiving heat during welding. Therefore, it is possible to provide an electrochemical cell that is easy to obtain the desired high capacity, has low resistance, and has little characteristic deterioration even when subjected to the heat of reflow soldering.

In the present invention, the conductive particle layer may include a valve metal oxide conductive particle fixed by a compound of aluminum and carbon.
In the present invention, a configuration in which the conductive particle layer is a layer of titanium oxide particles can be employed.
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. By adopting a structure in which a plurality of conductive particles are fixed to the surface portion, an electrode structure in which the conductive particles are not separated from the aluminum current collector even when subjected to heat can be obtained. For this reason, even if it receives the heat of reflow solder, since the adhesiveness of the conductive particles on the surface of the aluminum current collector is hardly lowered, an electrochemical cell having high heat resistance can be provided.
In the present invention, a configuration in which an active material containing activated carbon is fixed to the second surface portion can be adopted.
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.

  The electrochemical cell of the present invention includes an electrode having a structure in which an interface between an aluminum current collector of a cell element and a conductive particle layer having a desired thickness is fixed by a compound of aluminum and carbon. It has good adhesion to the particle layer and can suppress an increase in interface resistance between the aluminum current collector and the conductive particle layer. For this reason, the conductivity and capacity density are increased and the quick chargeability is superior to the electrochemical cell of the conventional structure in which the slurry containing the active material, the conductive additive, and the binder is directly coated on the aluminum current collector. An electrochemical cell can be provided. In addition, since the good adhesion between the aluminum current collector and the conductive particles 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 is provided with wiring. An electrochemical cell capable of highly reliable reflow soldering even in the element shape can be provided.

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 structure of the cell element accommodated in the same electrochemical cell is shown, (a) is a block diagram, (b) is the elements on larger scale of a collector and an electroconductive particle 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 after a reflow solder test about the electrochemical cell of Examples 2, 3, and 4 and the electrochemical cell of Comparative Examples 2 and 3. FIG. The graph which shows the discharge time after a reflow solder test about the electrochemical cell of Examples 2, 3, and 4 and Comparative Examples 2 and 3. FIG. The graph which shows the charge time after a reflow solder test about the electrochemical cell of Examples 2, 3, and 4 and Comparative Examples 2 and 3. FIG. The graph which shows the internal resistance after the reflow soldering test about the electrochemical cell of Examples 5-8 and the comparative example 4. FIG. The graph which shows the discharge time after a reflow solder test about the electrochemical cell of Examples 5-8 and Comparative Example 4. FIG. The graph which shows the charge time after a reflow solder test about the electrochemical cell of Examples 5-8 and the comparative example 4. FIG. The graph which shows the internal resistance after a reflow solder test about the electrochemical cell of Examples 9-12 and Comparative Examples 5 and 6. FIG. The graph which shows the discharge time after a reflow solder test about the electrochemical cell of Examples 9-12 and Comparative Examples 5 and 6. FIG. The graph which shows the charge time after a reflow solder test about the electrochemical cell of Examples 9-12 and Comparative Examples 5 and 6. FIG. The graph which shows the internal resistance before and behind the reflow solder test about the electrochemical cell of Examples 1, 13, and 14 and Comparative Examples 7 and 8. FIG. The graph which shows the discharge time before and behind the reflow solder test about the electrochemical cell of Examples 1, 13, and 14 and Comparative Examples 7 and 8. FIG. The graph which shows the charge time before and behind the reflow solder test about the electrochemical cell of Examples 1, 13, and 14 and Comparative Examples 7 and 8. FIG. The graph which shows the result of having measured the change of the discharge time by the difference in charge time about the electrochemical cell of Examples 1, 13, and 14 and Comparative Examples 7 and 8. FIG. The graph which shows the discharge time when the time of 10000 sec charge is set to 100 about the electrochemical cell of Examples 1, 13, and 14 and Comparative Examples 7 and 8. 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 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 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 winding or laminating a set of electrode sheets made of a current collector of a metal sheet to which a conductive particle layer made of an oxide of a valve metal is fixed, with an insulating separator interposed therebetween. , And so on. 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 base container 2 can have a side of about 5 to 20 mm and a height of about 1 to 3 mm. 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. In the case of film formation in a vacuum, for example, a mask made of metal or the like patterned so as to have two openings spatially separated from each other is prepared to form the positive and negative pad films 5, respectively. After being stored in the chamber of the device 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 fly the valve metal material. Then, a film is formed on the base inner bottom surface 2c. 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 made of an aluminum foil having a thickness of 5 μm to 100 μm as a current collector, and a pair of electrode sheets of a positive electrode and a negative electrode provided with a conductive particle layer on the surface thereof are wound and laminated with a separator made of an insulator interposed therebetween, It is a power generation element that is integrated by a method such as 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 having a special structure in which a conductive particle layer having a total thickness of 1 to 15 μm including a plurality of conductive particles fixed to the second surface portion is formed. The total thickness of the conductive particle layer is the thickness of the conductive particle layer when the conductive particle layer is formed only on one side of the aluminum foil, and the both sides when the conductive particle layer is formed on both sides of the aluminum foil. It means the total thickness of the formed conductive particle layers. Further, the conductive particle layer in the present invention may contain an active material. When the active material is contained, the thickness including the thickness of the active material layer is referred to as the total thickness.

This electrode sheet can be manufactured with reference to, for example, WO2007 / 051211, etc. Specifically, it can be obtained by applying conductive particles such as valve metal oxide particles on 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 conductive particles made of the valve metal oxide can be fixed to the surface of the aluminum foil by the compound of aluminum and carbon. The aluminum and carbon compound is particularly preferably aluminum carbide (Al ₄ C ₃ ). The conductive particles are not limited to oxides of valve metals, and may be conductive particles made of a carbon material such as carbon particles.
More specifically, TOYAL Titanium (registered trademark) manufactured by Toyo Aluminum Co., Ltd. using a titanium oxide particle layer which is a valve metal can be used.
Moreover, in the said embodiment, the capacity | capacitance of an electrochemical cell can be enlarged by forming the electrode sheet which fixed the active material containing activated carbon with the compound of aluminum and carbon in the 2nd surface part. Even in this case, since the adhesion of the conductive 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.

FIG. 4 shows a schematic structure of an example in which the cell element 6 is wound.
As shown in FIG. 4 (a), the cell element 6 includes a conductive particle layer 30 including an assembly of conductive particles made of valve group oxide particles or particles of a carbon material, and an aluminum foil positive electrode current collector 31. A film comprising a film-like positive electrode body (positive electrode) 32, a conductive particle layer 40 including an aggregate of conductive particles made of valve group oxide particles or carbon material, and an aluminum foil negative electrode current collector 41 A negative electrode body (negative electrode) 42 and a film-like separator 35 provided between the positive electrode body 32 and the negative electrode body 42 are laminated. 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.
The conductive particle layers 30 and 40 provided in the cell element 6 each have a total thickness of 1 to 15 μm. If the total thickness of the conductive particle layers 30 and 40 is within this range, the capacity is more than necessary. The charging time can be shortened without increasing the charging time. If the total thickness of the conductive particle layers 30 and 40 is less than 1 μm, the layer thickness is insufficient, so that the resistance may increase due to the heat of the reflow solder. If the thickness exceeds 15 μm, the electrochemical cell will increase as the capacity increases. The charging time will be longer.
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 relationship between the positive electrode current collector 31 and the conductive particle layer 30 has a structure shown in an enlarged manner in FIG. That is, a conductive particle layer 30 including an aggregate of conductive particles made of a valve metal oxide or the like is formed on the surface portion of the positive electrode current collector 31, and an intermediate layer is interposed between the positive electrode current collector 31 and the conductive particle layer 30. 33 is formed. 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 particle layer 30 includes a second surface portion 34 of an aluminum and carbon compound that extends outwardly from the aluminum and carbon compound of intervening layer 33. Conductive particles 36 such as titanium oxide particles or carbon particles are fixed to the second surface portion 34 to form a conductive particle layer 30 containing the conductive particles. As shown in FIG. 4A, the conductive particle layer 30 may be formed on one surface of the positive electrode current collector 31, or may be formed on both surfaces.
Moreover, in this embodiment, the active material layer which consists of activated carbon, a conductive support agent, and a binder may be further formed in the range of total thickness on the conductive particle 36 in the conductive particle layer.
Similarly, the relationship between the negative electrode current collector 41 and the conductive particle 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 the second surface portion 34 is formed thereon. In addition, a plurality of conductive particles 36 such as titanium oxide particles are fixed to the second surface portion 34 to form a conductive particle layer 40 including the conductive particles. An active material layer made of activated carbon, a conductive additive, and a binder may be formed within the total thickness within the conductive particle layer 40. The conductive particle 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)
The electrolytic solution 7 is preferably a mixed electrolytic solution in which a supporting salt is dissolved in a mixed solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC). However, ethylene carbonate (EC) may not be included in the mixed solvent.
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, the composition of the supporting salt 8 to 43% by mass and the remaining solvent, and in the remaining solvent ratio, propylene carbonate: 26 to 57% by mass, ethylene carbonate: 0 to 43% by mass, dimethyl carbonate: 16 to An electrolytic solution having a composition of 48% by mass is preferable. In the present embodiment, when the upper and lower limits of mass% are expressed as 16 to 48 mass%, unless otherwise noted, the upper and lower limits are included. Therefore, 16 to 48 mass% means 16 mass% or more and 48 mass% or less.
For example, the support salt is 25% by mass in the mass ratio (%) with respect to the total mass of the electrolyte, and the remaining solvent is PC: EC: DMC = 39% by mass: 32% by mass: 29% by mass in the solvent ratio. The electrolytic solution can be used.
Further, the mass of the supporting salt is more preferably in the range of 22 to 27 mass% with respect to the mass of the entire electrolyte solution.
Moreover, about mass ratio of each component with respect to the whole solvent, the range of PC = 33-42 mass%, EC = 27-36 mass%, DMC = 28-32 mass% is still more preferable, PC = 37-40 mass%, The ranges of EC = 31 to 33% by mass and DMC = 28 to 31% by mass are most preferable.

  When the lid 10 is welded to the base container 2 by a welding method such as seam welding, heat at the time of welding is transmitted to a part of the electrolytic solution 7 accommodated in the base container 2. However, if the electrolyte solution 7 has a solvent having the above composition ratio, the electrolyte solution 7 has a suitable ratio of propylene carbonate, ethylene carbonate, and dimethyl carbonate. The electrochemical cell 1 is less likely to evaporate dimethyl carbonate, which has the lowest boiling point among the three components, for example, easily obtains the desired high capacity, and has low resistance and low characteristic deterioration even when subjected to the heat of reflow soldering. Can be provided.

(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 stored 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 a 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 42alloy that has a thermal expansion coefficient close to that of ceramic. More specifically, a thin plate made of Kovar having a thickness of about 0.1 mm to 0.2 mm and having a surface subjected to electrolytic nickel plating or electroless nickel plating with a thickness of about 2 μm to 4 μm is used. 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 can be improved. The base 10 is hermetically closed by the lid 10.

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 has a conductive property such as valve metal oxide particles (titanium oxide particles) or carbon particles fixed on aluminum current collectors 31 and 41 constituting the cell element 6. Since the positive electrode body 32 and the negative electrode body 42 including the conductive particle layers 30 and 40 including particles are provided, the aluminum current collectors 31 and 41 and the conductive particle layers 30 and 40 have good adhesion. An increase in interface resistance between the aluminum current collectors 31 and 41 and the conductive particle 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 particle layers 30 and 40 is less likely to deteriorate even when subjected to the heat of the reflow solder, the cell element 6 is accommodated in the base container 2. And the electrochemical cell 1 which can perform the reflow soldering with high reliability even if it is a small element shape which has wiring in the base container 2 can be provided.

The electrochemical cell 1 of the present embodiment has a composition of a supporting salt of 8 to 43% by mass and a remaining solvent, and in the remaining solvent mass ratio, propylene carbonate: 26 to 57% by mass, ethylene carbonate: 0 to 43% by mass, dimethyl Since the nonaqueous electrolytic solution 7 having a composition of carbonate: 16 to 48% by mass is provided, the electrochemical cell 1 having high conductivity and high capacity density and excellent charging characteristics can be provided.
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, heat for sealing is transferred to the non-aqueous electrolyte 7 near the lid. However, it is possible to provide the electrochemical cell 1 in which the nonaqueous electrolytic solution 7 having the above-described composition is difficult to evaporate and resistance is not easily increased due to alteration of the nonaqueous electrolytic solution 7.

  Further, the surface of the aluminum current collectors 31 and 41 is provided with conductive particle layers 30 and 40 having a suitable thickness of 1 to 15 μm in total, and the conductive particle layer containing oxide particles or carbon particles of the valve metal When the thickness is within the range, low resistance is exhibited and excellent quick chargeability can be provided.

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 base first bottom portion 2f and the base which are two plates constituting the base bottom portion 2a. The via wiring 3 is stopped at the interface with the 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, the electrochemical property is high in conductivity and capacity density, and can be reflow soldered with high reliability even in a small element shape. A cell 15 can be provided. Further, it is possible to provide the electrochemical cell 15 having high conductivity and capacity density, excellent charging characteristics, and hardly causing resistance deterioration due to alteration of the non-aqueous electrolyte even in an airtight sealed structure.

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 only of a ceramic flat plate and a metal cavity lid 10a having a concave shape, and FIG. 6 shows a sectional structure. ing. 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, 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 16 can be provided. Further, it is possible to provide the electrochemical cell 16 having high conductivity and capacity density, excellent charging characteristics, and hardly causing resistance deterioration due to alteration of the nonaqueous electrolytic solution even in a hermetic sealing structure.

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 structure 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 hardly undergoes resistance deterioration due to alteration of the nonaqueous electrolytic solution even in a hermetically sealed structure.

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 2c punched into 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.
As an example of an electrode body, a conductive particle layer having a thickness of 6 μm per side made of titanium oxide particles is supported on both surfaces of a current collector surface made of an aluminum foil having a thickness of 20 μm with aluminum carbide (Al ₄ C ₃ ). A sheet electrode having a structure (Toyal Titanium (registered trademark) manufactured by Toyo Aluminum Co., Ltd.) was used.

  After this sheet electrode was cut to an appropriate length, an aluminum thin plate having a thickness of 80 μm, a width of 1.5 mm, and a length of 4 mm was attached to one end thereof by ultrasonic welding to form a cell lead 8. 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 a pair of positive and negative electrodes were wound in 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. One of the above-described two types of cell leads 8 was brought into close contact with the surface of any one of the pad films 5 of the plurality of base containers 2 prepared in advance. Ultrasonic welding performed the cell leads 8 one by one. The oscillation frequency of the ultrasonic welder 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. The ultrasonic welding tip 20 was lowered onto the surface of the cell lead 8 made of aluminum by an air mechanism, and then was cut into the surface of the cell lead 8 and welded by vibrating between the interface of the cell lead 8 and the pad film 5.

After the ultrasonic welding, the cell elements 6 were accommodated in the base container 2 so that the respective cell leads 8 were folded. At this time, care was taken so that the cell lead 8 did not contact the seal ring 9. This is to avoid an internal short circuit of the electrochemical cell.
Next, the plurality of base containers 2 in which the respective cell elements 6 were accommodated were immersed in a liquid electrolyte solution 7 and vacuum degassed for 1 minute. Here, SBP · BF4 (5-azoniaspiro [4.4] nonane tetrafluoroborate) is used as the supporting salt of the electrolytic solution 7, and propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC) are used as solvents. ) Was mixed at the following ratio and used as a mixed electrolyte. The mixing ratio is the composition of the supporting salt and the remaining solvent of 25% by mass with respect to the total mass of the electrolyte solution 7, and the solvent is mixed at a ratio of PC: EC: DMC = 39% by mass: 32% by mass: 29% by mass. As a solvent.
Subsequently, after returning to atmospheric pressure and taking out the base container 2 containing the cell elements 6 from the electrolyte solution 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 temporarily welded. Subsequently, resistance seam welding was continuously performed on the long side and the short side in this order, and the base container 2 was hermetically sealed. Thus, the electrochemical cell of Example 1 was produced.
The electrical characteristics test described later was performed on the fabricated electrochemical cell of the first example.

<Supported salt ratio change test>
When producing the electrochemical cell of Example 1, the mass ratio of the supporting salt in the applied electrolyte is set to 40% by mass with the electrochemical cell of Example 2 using the electrolyte set to 15% by mass. Of the electrochemical cell of Example 3 using the electrolytic solution prepared, the electrochemical cell of Example 4 using the electrolytic solution set to 10% by mass, and Comparative Example 2 using the electrolytic solution set to 45% by mass An electrochemical cell and an electrochemical cell of Comparative Example 3 set to 5% by mass were produced.
In order to evaluate the resistance against reflow soldering for each of the produced electrochemical cells, a reflow solder test was performed by holding the entire electrochemical cell at 260 ° C. for 5 seconds, and the internal resistance (Ω) after the reflow solder test was measured. 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, the electrochemical cell having the electrolytic solution in which the mass ratio of the supporting salt was set in the range of 8 to 43 mass% showed low 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 (8 to 43 mass%), the conductivity of the electrolyte decreased and the resistance increased. Further, the electrochemical cell of Comparative Example 2 in which the mass ratio of the supporting salt was larger than the above range was greatly affected by solvent decomposition due to heating, and the resistance after reflow soldering was increased.

Using an electrochemical cell having the same structure as in Examples 2 to 4 and Comparative Examples 2 and 3, the discharge time (sec) after the reflow solder test was measured. The results are shown in Table 2 below and FIG.
The electrochemical cell of each example and comparative example was charged for 10 minutes at a charging voltage of 2.5 V / charging current of 10 mA, and then discharged after a reflow solder test under the conditions of a discharging current of 1 mA and a discharge end voltage of 1.4 V (sec). Was measured.

  From the results shown in Table 2 and FIG. 9, it was found that the change in discharge time (capacity) due to the change in the weight ratio of the supporting salt (SBP · BF4) was small in each Example and Comparative Example. Accordingly, if the content of the supporting salt is within a preferable range (8 to 43% by mass) of the present application that can keep the resistance of the electrochemical cell low, the capacity of the supporting salt can be reduced even when exposed to the reflow soldering environment. A large electrochemical cell can be provided.

  Using an electrochemical cell having the same structure as each example and comparative example, the charging time until reaching 2.5 V was measured. The case where the charging current was set to 100 μA was tested. The results are shown in Table 3 below, and FIG. 10 shows the results when the charging current is set to 100 μA.

From the results shown in Table 3 and FIG. 10, it was found that the change in time required for charging due to the change in the weight ratio of the supporting salt (SBP · BF4) was small in each Example and Comparative Example. Thereby, if the content of the supporting salt is within the preferred range (8 to 43% by mass) of the present application that can keep the resistance of the electrochemical cell low, rapid charging is possible.
As described above, from Tables 1 to 3 and FIGS. 8 to 10, it is possible to provide an electrochemical cell having a small internal resistance by setting the content of the supporting salt within a preferable range (8 to 43 mass%) of the present application. it can.

<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 propylene carbonate (PC) is used as a nonaqueous solvent. A mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) was mixed at the following ratio and used as a mixed electrolyte.
The mixing ratio is the composition of the supporting salt of 25% by mass and the remaining solvent with respect to the total mass of the electrolyte solution 7. The solvent is PC: EC: DMC = 47% by mass: 20% by mass: 23% by mass. An electrochemical cell using the prepared solvent was used as Example 5.
An electrochemical cell using a solvent in which the supporting salt was mixed in the same composition ratio as a solvent in the ratio of PC: EC: DMC = 31 mass%: 40 mass%: 29 mass% was used as Example 6.
An electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and in the ratio of PC: EC: DMC = 53 mass%: 0 mass%: 47 mass% was used as Example 7.
An electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and in the ratio of PC: EC: DMC = 55% by mass: 16% by mass: 29% by mass was used as Example 8.
As Comparative Example 4, an electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and the solvent was PC: EC: DMC = 25 mass%: 45 mass%: 30 mass% was used.

  The internal resistance (Ω) after reflow soldering was measured for the electrochemical cells of each Example and Comparative Example. The results are shown in Table 4 below and FIG.

  As shown in Table 4 and FIG. 11, by including EC within the preferred range (0 to 43% by mass) of the present application, an electrochemical cell having a low internal resistance is provided even when exposed to a reflow soldering heating environment. be able to. On the other hand, in Comparative Example 4 having a large EC, the internal resistance increased due to the increase in the viscosity of the mixed electrolyte.

Using an electrochemical cell having the same structure as each example and comparative example, the discharge time (sec) after the reflow solder test was measured. The results are shown in Table 5 below and FIG.
As charging conditions, the electrochemical cells of each Example and Comparative Example were charged after charging for 10 minutes at a charging voltage of 2.5 V / charging current of 10 mA, and then discharged after a reflow solder test under the conditions of a discharging current of 1 mA and a discharge end voltage of 1.4 V. Time (sec) was measured.

  As shown in Table 5 and FIG. 12, in each of the examples and comparative examples, as the content of ethylene carbonate increased, the capacity tended to increase due to the increase in dielectric constant. However, within the preferable range (0 to 43% by mass) of the present application, an electrochemical cell having a structure equivalent to any of the examples had a capacity suitable for practical use.

  Using an electrochemical cell having the same structure as each example and comparative example, the charging time until reaching 2.5 V was measured. The case where the charging current was set to 100 μA was tested. The results are shown in Table 6 below, and FIG. 13 shows the results when the charging current is set to 100 μA.

From the results shown in Table 6 and FIG. 13, it can be seen that by setting ethylene carbonate in the range of 0% by mass to 43% by mass, the quick charge characteristics are excellent. On the other hand, in Comparative Example 4 having a large ethylene carbonate content, the time required for charging increased as the capacity increased due to an increase in the dielectric constant.
As described above, from the results shown in Tables 4 to 6 and FIGS. 11 to 13, by setting the content of ethylene carbonate to a preferred range (0 to 43 mass%) of the present application, the internal resistance is small and the charging time is It can be seen that a short electrochemical cell can be provided.

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 propylene carbonate (PC) is used as a nonaqueous solvent. A mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) was mixed at the following ratio and used as a mixed electrolyte.
The mixing ratio is the composition of the supporting salt of 25% by mass and the remaining solvent with respect to the total mass of the electrolyte solution 7. The solvent is PC: EC: DMC = 39% by mass: 32% by mass: 29% by mass. An electrochemical cell using the prepared solvent was used as Example 9.
An electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and PC: EC: DMC = 32 mass%: 23 mass%: 45 mass% as a solvent was used as Example 10.
An electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and in the ratio of PC: EC: DMC = 44% by mass: 36% by mass: 20% by mass was used as Example 11.
An electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and in the ratio of PC: EC: DMC = 34% by mass: 28% by mass: 38% by mass was used as Example 12.
As Comparative Example 5, an electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and the solvent was PC: EC: DMC = 47% by mass: 43% by mass: 10% by mass was used.
As Comparative Example 6, an electrochemical cell using a solvent in which the supporting salt was mixed at the same composition ratio and the solvent was PC: EC: DMC = 29 mass%: 21 mass%: 50 mass% was used.

  The internal resistance (Ω) after reflow soldering was measured for the electrochemical cells of each Example and Comparative Example. The results are shown in Table 7 below and FIG.

  As shown in Table 7 and FIG. 14, in Comparative Example 5 having less dimethyl carbonate than the preferred range (16 to 48% by mass) of the present application, the viscosity increased and the resistance increased. Further, in Comparative Example 6 having a large amount of dimethyl carbonate, the internal resistance was a large value. This is because when the lid 10 is seam welded, the influence of solvent evaporation due to welding heat is large.

Using an electrochemical cell having the same structure as each example and comparative example, the discharge time (sec) after the reflow solder test was measured. The results are shown in Table 8 below and FIG.
As charging conditions, the electrochemical cells of each Example and Comparative Example were charged after charging for 10 minutes at a charging voltage of 2.5 V / charging current of 10 mA, and then discharged after a reflow solder test under the conditions of a discharging current of 1 mA and a discharge end voltage of 1.4 V. Time (sec) was measured.

  As shown in Table 8 and FIG. 15, when the content of dimethyl carbonate was within the preferred range of the present application (16 to 48% by mass), an electrochemical cell with little change in capacity was obtained. On the other hand, Comparative Example 6 with a large amount of dimethyl carbonate had a smaller capacity as the dielectric constant of the electrolyte decreased.

  Using an electrochemical cell having the same structure as each example and comparative example, the charging time until reaching 2.5 V was measured. The case where the charging current was set to 100 μA was tested. The results are shown in Table 9 below and FIG.

From the results shown in Table 9 and FIG. 16, if the content of dimethyl carbonate is within the preferred range of the present application (16 to 48% by mass), the charging time is equivalent to that of the other examples, and the rapid charging characteristics are excellent. I understand. In Comparative Example 6 having a high dimethyl carbonate content, the time required for charging decreased as shown in Table 9 as the capacity decreased as shown in Table 8.
As described above, from Tables 7 to 9 and FIGS. 14 to 16, it is possible to provide an electrochemical cell having a small internal resistance by setting the content of dimethyl carbonate within the preferable range (16 to 48% by mass) of the present application. it can.

<Contrast with conventional coated electrode>
As another example of the sheet electrode, in Example 13, activated carbon particles having a particle diameter of 6 μm made of aluminum carbide (Al ₄ C ₃ ) are formed on the surface of a current collector made of an aluminum foil having a thickness of 20 μm on only one side. Thus, a sheet electrode having a structure fixed in layers was used. In Example 14 and Comparative Example 7, a conductive particle layer having a thickness of 1 μm per side made of carbon particles with aluminum carbide (Al ₄ C ₃ ) is supported on both surfaces on a current collector surface made of an aluminum foil having a thickness of 20 μm. The sheet electrode (Toyaru Carbo (registered trademark) manufactured by Toyo Aluminum Co., Ltd.) having the above structure is used as a current collector, 85% by mass of activated carbon having a particle diameter of 6 μm, a conductive additive (Ketjen Black, 8% by mass), and a binder (polytetraflur) An active material layer made of (ethylene, 7% by mass) was applied on only one side so as to be 10 μm (Example 14) and 30 μm (Comparative Example 7).
For comparison, 85 mass% activated carbon having a particle diameter of 6 μm, a conductive auxiliary agent (Ketjen black, 8 mass%) and a binder (polytetrafluoroethylene, A conventional electrode coated with an active material having a thickness of 30 μm was used (Comparative Example 8). Electrochemical cells equipped with the sheet electrodes of these examples and comparative examples were prepared and subjected to the following tests.

For the electrochemical cells of each Example and Comparative Example, the reflow solder test was performed by holding the entire electrochemical cell at 260 ° C. for 5 seconds in consideration of the resistance to reflow solder, and the internal resistance (Ω) was measured after the reflow solder test. . The internal resistance was determined by measuring the impedance (resistance) at an alternating current of 1 kHz.
In addition, the electrochemical cell of each Example and Comparative Example was subjected to a reflow solder test equivalent to the previous example, and after charging for 10 minutes at a charging voltage of 2.5 V / charging current of 10 mA, a discharging current of 1 mA and a discharging end voltage of 1. The discharge time (sec) after the reflow solder test was measured under the condition of 4V.
Furthermore, about the electrochemical cell of each Example and the comparative example, the reflow soldering test equivalent to the previous example was done, and the charging time until it reached 2.5V with a charging current of 100 μA was measured.
These results are shown in Tables 10 to 12 and FIGS.

From the results shown in Table 10 and FIG. 17, by using the electrodes and electrolytes as shown in Examples 1, 13, 14 and Comparative Example 7, the resistance after reflowing was compared with the conventional electrode shown in Comparative Example 8. The rise can be suppressed. That is, an electrochemical cell having a sheet electrode having a structure in which these titanium oxide particle layers are fixed or a sheet electrode having a structure in which a carbon material is fixed with aluminum carbide (Al ₄ C ₃ ) is exposed to a heating environment by reflow soldering. Even so, the increase in internal resistance is small compared to the conventional coated electrode shown in Comparative Example 8.

Further, from the results shown in Table 11 and FIG. 18, by using the electrodes and electrolytes as shown in Examples 1, 13, 14 and Comparative Example 7, the conventional electrode shown in Comparative Example 8 was reflowed. A decrease in discharge time (capacity) can be suppressed. That is, an electrochemical cell having a sheet electrode having a structure in which these titanium oxide particle layers are fixed or a sheet electrode having a structure in which a carbon material is fixed with aluminum carbide (Al ₄ C ₃ ) is exposed to a reflow soldering heating environment. Even so, the decrease in discharge time is small and the capacity degradation is small.

  Furthermore, from the results shown in Table 12 and FIG. 19, the electrodes and electrolytes shown in Examples 1, 13, and 14 and Comparative Example 7 were used, so that the conventional electrode shown in Comparative Example 8 was reflowed. A decrease in charging time can be suppressed.

  On the other hand, as shown in Example 1, an electrochemical cell including a sheet electrode having a structure in which a titanium oxide particle layer is fixed is an electrochemical cell including a sheet electrode having a structure in which a carbon material is fixed (Example 13, Implementation). The pressure is increased in a shorter time than in Example 14 and Comparative Example 7). Moreover, as shown in Example 13, Example 14, and Comparative Example 7, the electrochemical cell is boosted in a shorter time as the thickness of the active material layer formed in the conductive particle layer is smaller. The

Next, in the electrochemical cells of Examples 1, 13, 14 and Comparative Examples 7 and 8, the change in discharge time due to the difference in charge voltage (difference in charge time) was measured. In this measurement, the discharge current was 1 mA and the final voltage was 1.4V. The results are shown in Table 13 and FIG.
In addition, in the electrochemical cells of Examples 1, 13, 14 and Comparative Examples 7 and 8, when the discharge time of each electrochemical cell when the charge time is 10,000 sec is 100, the discharge time of each electrochemical cell is The relative values are shown in Table 14 below and FIG.

From the results shown in Table 13, Table 14, FIG. 20, and FIG. 21, as shown in Example 1, the electrochemical cell including the sheet electrode having a structure in which the titanium oxide particle layer is fixed has a discharge capacity even in a short-time charge. Can be kept large.
This is because, in addition to using an active material made of titanium oxide particles having a smaller capacity density than that of activated carbon, the thickness of the active material layer and the like can be controlled to be smaller than in the past. Thereby, it turns out that it can be set as the electrochemical cell excellent in the quick charge characteristic by employ | adopting the structure of Example 1. FIG.
On the other hand, as shown in Examples 13 and 14, even in the case of a sheet electrode in which the conductive particle layer is made of a carbon material, the discharge capacity is maintained large even during short-time charging by reducing the total thickness of the conductive particle layer. be able to.
Thereby, an electrochemical cell excellent in rapid charge characteristics can be provided even by using a sheet electrode in which the total thickness of the conductive particle layer is 15 μm or less, more preferably 10 μm or less, which is the preferred range of the present application.

  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, 4b ... extension part, 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, 20 ... Ultrasonic tip, 20a ... Tip tip, 30 ... conductive particle layer, 31 ... positive electrode current collector, 33 ... intervening layer (first surface portion), 34 ... second surface portion, 32 ... positive electrode body (positive electrode), 35 ... separator, 36 ... conductive particles, 40 ... conductive particle layer, 41 ... negative electrode Collector, 42 ... negative electrode body (negative electrode).

Claims (7)

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. Including a conductive particle layer having a total thickness of 1 to 15 μm including conductive particles fixed by a carbon compound;
The non-aqueous electrolyte is a supporting salt of 8 to 43% by mass and the remaining solvent, and in the remaining solvent mass ratio, propylene carbonate: 26 to 57% by mass, ethylene carbonate: 0 to 43% by mass, dimethyl carbonate: 16 to 48%. An electrochemical cell having a composition by mass.   The electrochemical cell according to claim 1, wherein the lid is welded to the base container.   3. The electrochemical cell according to claim 1, wherein the conductive particle layer includes conductive particles of valve metal oxide fixed by the compound of aluminum and carbon. 4.   The electrochemical cell according to claim 3, wherein the conductive particle layer is a layer of titanium oxide particles.   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 any one of claims 1 to 4, wherein the conductive particle layer including a plurality of fixed conductive particles is formed.   The electrochemical cell according to claim 5, wherein an active material containing activated carbon is fixed to the second surface portion.   The electrochemical cell according to any one of claims 1 to 6, wherein the supporting salt is a quaternary ammonium salt or a quaternary phosphonium salt.

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