JP2013021340A - Electrochemical cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical cell that can be efficiently disposed on a substrate since it has no projection such as a terminal.SOLUTION: A lidded vessel is formed from a bottomed prismatic vessel, a metal ring positioned along the upper end fringe of the vessel, and a lid located in the upper part of the metal ring, and two positive and negative connection terminals are taken out from the lidded vessel. One end of one connection terminal is connected to the metal ring, and the other end thereof is positioned on the lower face of the bottom plate of the bottomed prismatic vessel. One end of the other connection terminal is positioned in the inside of the bottom plate of the vessel, and the other end thereof is positioned on the lower face of the bottom plate of the bottomed prismatic vessel. The connection terminal positioned in the inside of the bottom plate of the vessel can be electrically connected to the inside of the lidded vessel. A positive electrode active material, a negative electrode active material, an electrolyte, and a separator for separating the positive electrode active material from the negative electrode active material is housed in the inside of the vessel.

Description

  The present invention relates to electrochemical cells such as non-aqueous electrolyte batteries and electric double layer capacitors.

The electrochemical cell is used as a backup power source for a clock function, a backup power source for a semiconductor memory, a spare power source for an electronic device such as a microcomputer or an IC memory, a battery for a solar clock, a power source for driving a motor, and the like.
Disk-shaped button-type electrochemical cells are often used, but button-type electrochemical cells need to be pre-welded to the case in order to perform reflow soldering, increasing the number of parts and manufacturing man-hours. The cost was increased in terms of increase. Further, it is necessary to provide a space for connecting terminals on the substrate, and there is a limit to downsizing.
Furthermore, the electrochemical cell is required to have improved heat resistance. This is because the electrochemical cell is mounted on the substrate by reflow soldering. With reflow soldering, solder cream or the like is applied to the part to be soldered on the printed circuit board in advance, and a part is placed on that part, or solder spheres (solder bumps) are soldered after placing the part. The solder is melted by passing the printed board on which the parts are mounted in a furnace in a high-temperature atmosphere set so that the soldered part is higher than the melting point of the solder, for example, 200 to 260 ° C. This is a method of soldering.

In order to solve these problems, an electrochemical cell using a heat-resistant container as an exterior body for housing an electrode and an electrolyte and having a terminal has been studied (for example, see Patent Document 1).
JP 2001-216952 (2nd to 3rd terms, Fig. 1)

The problem to be solved by the present invention is to provide an electrochemical cell in which dissolution of the positive electrode current collector of the electrochemical cell is prevented.
A cross-sectional view of a conventional electrochemical cell is shown in FIG.
When the material of the container 101 is made of ceramics, the container 101 is made of ceramics such as alumina, and is produced by printing a high melting point metal such as tungsten on a green sheet and firing it.
A positive electrode active material 106 is disposed on the bottom side of the container 101, and the positive electrode active material 106 is bonded to the positive electrode current collector 103 using a conductive adhesive 1111. The container 101 is sealed with a lid 102, and the container 101 and the lid 102 are joined via a metal ring 109. Further, the negative electrode active material 107 is bonded to the lid 102 using a conductive adhesive 1112.

The positive electrode active material 106 and the negative electrode active material 107 are separated by the separator 105. In addition, a connection terminal A1041 and a connection terminal B1042 are provided to connect the electrodes to an external circuit.
However, when the conventional electrochemical cell is used at a relatively high voltage, for example, around 3 V, there is a problem that the positive electrode current collector 103 in contact with the positive electrode active material is dissolved.
This is presumably because the potential on the positive electrode side rises when the electrochemical cell is charged and reaches a voltage at which the positive electrode current collector 103 is dissolved.
In view of the above, an object of the present invention is to provide an electrochemical cell that is easy to manufacture and that can be used at a high voltage by preventing dissolution of the positive electrode current collector.

  The electrochemical cell of the present invention comprises a bottomed rectangular tube-shaped container, a metal ring positioned along the upper edge of the bottomed rectangular tube-shaped container, and a lid positioned above the metal ring. The container with lid is provided with two positive and negative connection terminals, one of the connection terminals is connected to a metal ring at one end, and the other end is positioned on the bottom surface of the bottom plate of the bottomed rectangular tube-shaped container The other connection terminal is positioned at one end inside the bottom plate of the bottomed rectangular tube-shaped container, and the other end is positioned on the bottom surface of the bottom plate of the bottomed rectangular tube-shaped container, and the bottomed square tube And electrically connecting the connection terminal positioned inside the bottom plate of the container and the inside of the lidded container, and inside the lidded container, a positive electrode active material, a negative electrode active material, an electrolyte solution, A separator for separating the positive electrode active material and the negative electrode active material; That.

In the electrochemical cell, tungsten may be used for the positive electrode current collector.
The valve metal of the covering portion in the positive electrode current collector may be any one of aluminum, tantalum, niobium, titanium, hafnium, and zirconium.
Furthermore, in the electrochemical cell of the present invention, a part of the positive electrode current collector is embedded in the container, and a part of the positive electrode current collector that is not embedded is covered with a covering portion.
Preferably, in the electrochemical cell of the present invention, the covering portion and the positive electrode active material are bonded or connected by a conductive adhesive.
More preferably, in the electrochemical cell of the present invention, the application area of the conductive adhesive to the positive electrode active material is larger than the area of the covering portion.

  An electrochemical cell in which the container is ceramic is also preferable.

The dissolution of the positive electrode active material can be prevented, and the electrochemical cell can be used at a high voltage. Further, by using a heat resistant material for the container, the heat resistance is improved, and the characteristics of the electrochemical cell are not deteriorated even if reflow soldering is performed, and the reliability is improved.
Since the electrochemical cell of the present invention has a square design, there is no protrusion of terminals and the like, so that it can be efficiently arranged on the substrate.

A cross-sectional view of an electrochemical cell according to a reference example of the present invention is shown in FIG. A positive electrode active material 106 is disposed on the bottom surface side of the container 101. A coating portion 112 using valve metal or carbon is formed on the surface of the positive electrode current collector 103, and the positive electrode active material 106 is bonded to the coating portion 112 using a conductive adhesive 1111. The positive electrode current collector 103 and the positive electrode active material 106 are electrically connected through the conductive adhesive 1111 and the covering portion 112.
A metal ring 109 is provided on the outer wall of the container, and a bonding material is disposed on the surface of the metal ring 109. A bonding material is also disposed on the surface of the lid 102. The container 101 and the lid 102 are sealed by melting the bonding material. A negative electrode active material 107 is attached to the lid 102 with a conductive adhesive 1112. The lid 102 has conductivity and functions as a negative electrode current collector.

In addition, the positive electrode active material 106 and the negative electrode active material 107 are separated by the separator 105. Further, another metal may be present between the positive electrode current collector and the covering portion 112, and the positive electrode current collector may be covered with a covering portion after being plated with gold or nickel. The container 101 is filled with the electrolytic solution 108.
Next, FIG. 2 shows a cross-sectional view of the electrochemical cell according to the present invention. When the container 101 of the present invention is made of alumina, a square alumina green sheet serving as a bottom surface is provided, and a tungsten print is applied to the surface thereof, and the positive electrode current collector 103 and a part of the wiring of the connection terminal A1041 and the connection terminal B1042 Apply.

  Moreover, depending on the production | generation conditions of a coating | coated part, a defect may arise in a coating | coated part. In particular, the covering portion near the side wall of the container 101 is likely to be defective. An example of the generated film defect is shown in FIG. A part of the positive electrode current collector 103 may be exposed as shown in A of FIG. 8 or may be in contact with the metal ring 109 as shown in B. If a part of the positive electrode current collector 103 is exposed as shown in FIG. 8A, a part of the positive electrode current collector 103 may be dissolved by applying a voltage to the electrochemical cell. Further, the film formed as shown in FIG. 8B comes into contact with the metal ring 109, causing the electrochemical cell to short-circuit and not function. In order to prevent this, the positive electrode current collector in the vicinity of the side wall of the container was embedded in the container, and the portion where the positive electrode current collector was not embedded was covered with a covering portion. A second square alumina green sheet having a circular hole in the center is disposed. Thereby, the area of a positive electrode electrical power collector can be restrict | limited. A part of the positive electrode current collector 103 is embedded in the container 101, and the remaining part of the positive electrode current collector is exposed.

Further, an alumina green sheet serving as the outer wall of the container 101 is disposed. When this state is viewed from the top of the container 101, it becomes as shown in FIG. 4, and the exposed area of the positive electrode current collector 103 is smaller than the area of the container bottom surface 1011. At this time, the positive electrode current collector 103 does not need to have the same shape as the hole of the second square alumina green sheet. Any shape that can be in electrical contact with the covering portion 112 disposed in a later step may be used. For example, it may be a line or a band. The positive electrode current collector 103 and the positive electrode active material 106 are electrically connected through the covering portion 112. The shape of the holes in the second square alumina green sheet need not be circular.
Next, the remaining wiring of the connection terminal A1041 and the connection terminal B1042 was disposed on the outer wall of the container 101, and then fired to obtain the container 101. A metal ring 109 was further joined to the container 101.

The covering portion 112 was disposed on the surface of the positive electrode current collector 103. FIG. 5 shows the state as seen from above. The positive electrode active material 106 is bonded with a conductive adhesive. On the positive electrode side, the covering portion 112 is smaller than the positive electrode active material 106, but the conductive adhesive 1111 is applied to approximately the same size as the positive electrode active material 106, so that the flow of electrons between the electrode active material and the current collector is obstructed. There was no deterioration in characteristics such as increasing the internal resistance of the electrochemical cell. In addition, the current collector and the positive electrode active material 106 do not need to be particularly bonded, and the conductive adhesive 1111 may be simply applied on the bottom of the container 101 and then placed on top.
The lid 102 and the negative electrode active material 107 were bonded in advance with a conductive adhesive 1112 containing carbon.

The metal ring 109 is electrically connected to the connection terminal B1042 by a tungsten layer passing through the outer wall of FIG.
The portion of the lid 102 on the container side was subjected to nickel plating as a bonding material.
The positive and negative electrodes, the separator 105, and the electrolyte solution 108 were housed inside the container, and the lid 102 was covered, and then the two opposite sides of the lid 102 were welded by a parallel seam welding machine using the principle of resistance welding. By this method, highly reliable sealing was obtained.
The covering portion 112 preferably completely covers the hole on the bottom surface of the container 101. FIG. 6 shows a view from the top of the electrochemical cell in that case, and FIG. 7 shows a cross-sectional view. By completely covering the portion where the positive electrode current collector 103 is not embedded with the covering portion 112, the positive electrode current collector 103 is not exposed due to a defect or the like when the covering portion 112 is formed. Therefore, the reliability of the electrochemical cell is greatly improved.

If the covering portion 112 is too large, the conductor adheres to the inside of the outer wall of the container 101, causing contact with the metal ring 109 or the bonding material or contact between the electrode active materials, causing an internal short circuit.
The container 101 is made of ceramics, and high strength, insulating ceramics such as alumina and zirconia can be used. As a processing method, a method in which green sheets punched into a predetermined shape are stacked and fired is also effective in forming the positive electrode current collector 103, the connection terminal A1041, and the connection terminal B1042.
The positive electrode current collector 103, the connection terminal A1041, and the connection terminal B1042 can be manufactured by wiring and wiring with a tungsten print containing tungsten powder. The positive electrode current collector 103 and the connection terminal A1041 are connected.

By using tungsten for the positive electrode current collector, the heat resistance of the positive electrode current collector is improved, and further, the tungsten positive electrode current collector can be formed at the same time as the formation of the container by using the tungsten print. Can do. This is because when a ceramic container is made by firing at a high temperature, the positive electrode current collector is also exposed to a high temperature, so that tungsten is effective because it is a heat-resistant metal. Other heat-resistant metal such as molybdenum can also be used. Tungsten is advantageous in terms of wiring reliability.
When the electrochemical cell is used at a relatively high voltage, for example, around 3 V, there is a problem that the positive electrode current collector is dissolved and the characteristics are remarkably deteriorated.

Therefore, the covering portion 112 is formed on the surface of the positive electrode current collector 103 made of tungsten to prevent dissolution of the positive electrode current collector. The covering portion 112 is made of aluminum, tantalum, niobium, titanium, hafnium, zirconium or carbon called a valve metal. In particular, aluminum is a cheap and easy-to-use material. When these materials are used, even if a potential of 4 V / vs Li or higher is applied to the covering portion 112 at the lithium counter electrode, the covering portion 112 does not dissolve.
Forming methods include plating, vapor deposition, sputtering, CVD, and thermal spraying. In the case of using aluminum, thermal spraying or plating from room temperature molten salt (butylpydium chloride bath, imidazolium chloride bath) can be used. In the present invention, since the area of the positive electrode current collector 103 is small, there are few defects when plated, and no masking is required when vapor deposition, sputtering, CVD, or thermal spraying is used, or the covering portion 112 is formed by simple masking. can do.

The metal ring 109 is preferably made of a material having a thermal expansion coefficient close to that of the container 101.
For example, when the container 101 uses alumina having a thermal expansion coefficient of 6.8 × 10 −6 / ° C., it is desirable to use Kovar having a thermal expansion coefficient of 5.2 × 10 −6 / ° C. as the metal ring.
Further, it is desirable to use the same Kovar as the metal ring in order to increase the reliability after welding for the lid 102. This is because after the welding, when it is surface-mounted on the substrate of the equipment, that is, when reflow soldering, it is heated again.
For the connection terminal A 1041 and the connection terminal B 1042, nickel, gold, tin, and solder layers may be provided on the surface for soldering to the base. It is preferable to provide a layer of nickel, gold, or the like that is compatible with the bonding material also at the edge of the container 101. Examples of the layer forming method include vapor phase methods such as plating and vapor deposition.

It is effective to provide a nickel and / or gold layer as a bonding material on the surfaces of the metal ring 109 and the lid 102 to be bonded. This is because the melting point of gold is 1063 ° C. and the melting point of nickel is 1453 ° C., but the melting point can be lowered to 1000 ° C. or less by using an alloy of gold and nickel. Examples of the layer forming method include a vapor phase method such as plating and vapor deposition, and a thick film method using printing. In particular, a thick film method using plating and printing is advantageous in terms of cost.
However, impurity elements such as P, B, S, N, and C in the bonding material layer need to be 10% or less. Care must be taken especially when plating is used. For example, in electroless plating, P is likely to enter from the reducing agent sodium hypophosphite and B from dimethylamine borane. Also, in electroplating, care must be taken because it may enter from brightener additives and anions. It is necessary to adjust the amount of reducing agent, additive, etc. to 10% or less. If it enters 10% or more, an intermetallic compound is formed on the joint surface and cracks are generated.

When nickel is used for the bonding material on the lid 102 side, gold is preferably used for the bonding agent on the container 101 side. The ratio of gold to nickel is preferably between 1: 2 and 1: 1, and the melting point of the alloy is lowered, so that the welding temperature is lowered and the bondability is improved.
The joint can be welded by seam welding using resistance welding. After the lid 102 and the container 101 are spot welded and temporarily fixed, welding is performed according to the principle of resistance welding by pressing a roller-type electrode facing two opposite sides of the lid 102 and passing an electric current. Sealing can be performed by welding the four sides of the lid 102. Since the current flows in a pulsed manner while rotating the roller electrode, it becomes a seam shape after welding. If the pulse width is not controlled so that individual weld marks by the pulses overlap, complete sealing cannot be achieved.

Seam welding using resistance welding was particularly preferred for welding batteries and capacitors containing electrolyte (liquid).
The separator to be used is preferably a heat-resistant nonwoven fabric. For example, a roll-rolled separator such as a porous film has heat resistance but shrinks in the rolling direction due to heat during seam welding using a resistance welding method. As a result, internal short circuit is likely to occur. In the case of a separator using a heat-resistant resin or glass fiber, shrinkage was good with little shrinkage. As the resin, PPS (polyphenylene sulfide) and PEEK (polyether ether ketone) were good. In particular, glass fiber was effective. A ceramic porous body can also be used.

  The shape of the electrochemical cell of the present invention is basically free. The shape of a conventional electrochemical cell by caulking is limited to a substantially circular shape. For this reason, when trying to arrange them on the same substrate as other electronic components that are almost square, dead space is inevitably wasted. Since the electrochemical cell of the present invention has a square design, there is no protrusion of terminals and the like, so that it can be efficiently arranged on the substrate.

  An electric double layer capacitor was produced using the container 101 having the shape of FIG. The dimensions of the container 101 were 3 × 5 mm and the height was 0.5 mm. The thickness of the part which becomes the outer wall of the container 101 was 0.3 mm. The positive electrode current collector 103, the connection terminal A1041, and the connection terminal B1042 were wired by tungsten printing. The positive electrode current collector 103 and the connection terminal A1041 are connected. The positive electrode current collector 103 was a circle having a diameter of 1.0 mm, and the area thereof was sufficiently smaller than the area of the container bottom surface 1011. At the upper part of the container 101, a metal ring 109 made of Kovar and having a thickness of 0.15 mm was previously joined with a metal brazing material. As a result, the height of the outer wall of the container 101 was 0.4 mm.

The exposed metal portion of the container 101 was subjected to nickel plating and then gold plating. After gold plating, the covering portion 112 was formed by thermal spraying of aluminum.
The lid 102 was a 2 × 4 mm, 0.15 mm thick Kovar plate plated with nickel.
As the positive electrode active material 106 and the negative electrode active material 107, an activated carbon sheet having a size of 2 × 4 mm and a thickness of 0.15 mm was used. The positive electrode active material 106 was bonded to the bottom of the container 101 with a conductive adhesive 1111. The negative electrode active material 107 was bonded to the lid 102 with a conductive adhesive 1112. Next, the separator 105 was placed on the positive electrode active material 106, and 5 μL of an electrolytic solution obtained by adding 1 mol / L of (C2H5) 4NBF4 to propylene carbonate (PC) was added. Cover the lid 102 to which the negative electrode active material 107 is adhered, spot weld the lid 102 and the container 101, temporarily press the roller-type electrode facing the two opposite sides of the lid 102, and pass a current to generate resistance. Seam welding was performed according to the welding principle.

As Comparative Example 1, an electric double layer capacitor in which a hole was formed in a part of the protective part and the positive electrode current collector was exposed was produced. The electrode material, electrolytic solution, sealing method, and the like were the same as those in Example 1.
The electric double layer capacitors of Example 1 and Comparative Example 1 were stored for a predetermined number of days in a state where a voltage of 3.3 ° C. was applied at 70 ° C., and changes in capacity retention and internal resistance were measured. It was investigated whether or not. The results are shown in FIG. 9 and FIG. Generally, storage at 70 ° C. for 10 days is considered to correspond to one year. In Example 1, even after storage for 40 days, the capacity retention was about 80%, the internal resistance was 1000Ω or less, and there was no problem in practical use, and a very good result was obtained. On the other hand, the capacity retention rate of Comparative Example 1 was greatly reduced, the internal resistance was increased, and deterioration occurred in the electrochemical cell. When the electric double layer capacitor of Comparative Example 1 after storage was disassembled and examined, there were portions where the current collector on the positive electrode side was dissolved. This is presumably because the positive electrode current collector was not completely covered but was partially exposed.

  Next, an example in which the covering portion is formed by a different method will be shown. Similarly to Example 1, an electric double layer capacitor was fabricated using the container 101 having the shape of FIG. The dimensions of the container 101 were 3 × 5 mm and the height was 0.5 mm. The thickness of the part which becomes the outer wall of the container 101 was 0.3 mm. The positive electrode current collector 103, the connection terminal A1041, and the connection terminal B1042 were wired by tungsten printing. The positive electrode current collector 103 was a circle having a diameter of 1.0 mm, and the area thereof was sufficiently smaller than the area of the container bottom surface 1011. At the upper part of the container 101, a metal ring 109 made of Kovar and having a thickness of 0.15 mm was previously joined with a metal brazing material. As a result, the height of the outer wall of the container 101 was 0.4 mm.

The connection terminal of the container 101 was subjected to nickel plating and then gold plating.
In forming the covering portion 112, a simple metal mask (a shape opened squarely in accordance with the container) was placed on the container 101, and aluminum deposition was performed. FIG. 11 shows a perspective view of the container 101 after aluminum deposition and removal of the metal mask. The covering portion 112 could be formed in a square shape on the bottom surface of the container 101. The aluminum vapor deposition film at this time was about 8 μm. The effective thickness of the aluminum vapor deposition film was about 8 μm. When the thickness is 3 μm or less, pinholes are generated, and it is difficult to maintain the characteristics of the capacitor. Moreover, when it is 15 μm or more, it takes time for vapor deposition, which is not preferable in terms of production cost.

  The lid 102 was a 2 × 4 mm, 0.15 mm thick Kovar plate plated with nickel. As in Example 1, the positive electrode active material 106 and the negative electrode active material 107 were activated carbon sheets having a size of 2 × 4 mm and a thickness of 0.15 mm. The positive electrode active material 106 was bonded to the bottom of the container 101 with a conductive adhesive 1111. The negative electrode active material 107 was bonded to the lid 102 with a conductive adhesive 1112. Next, the separator 105 was placed on the positive electrode active material 106, and 5 μL of an electrolytic solution obtained by adding 1 mol / L of (C2H5) 4NBF4 to propylene carbonate (PC) was added. Cover the lid 102 to which the negative electrode active material 107 is adhered, spot weld the lid 102 and the container 101, temporarily press the roller-type electrode facing the two opposite sides of the lid 102, and pass a current to generate resistance. Seam welding was performed according to the welding principle.

Similarly to Example 1, the electric double layer capacitor of Example 2 was stored for a predetermined number of days in a state where a voltage of 3.3 V was applied at 70 ° C., and changes in capacity retention rate and internal resistance were measured. It was investigated whether the double layer capacitor deteriorated. As a result, as in Example 1, there was no practical problem and a very good result was obtained.
In this example, only the electric double layer capacitor was described, but the same effect was observed in storage when applied to a non-aqueous secondary battery. In addition, the storage characteristics were improved when a voltage of 3.3 V or less was applied as compared with the conventional structure.
In the present embodiment, only the case where the covering portion 112 is aluminum is described, but the same effect can be obtained when tantalum, niobium, titanium, hafnium, or zirconium is used. Since aluminum is effective in terms of ease of formation and cost, it has been described in the examples.

  In this example, only the electric double layer capacitor was described, but the same effect was observed in storage when applied to a non-aqueous secondary battery. In addition, the storage characteristics were improved when a voltage of 3.3 V or less was applied as compared with the conventional structure.

  Since the electrochemical cell of the present invention has a square design, there is no protrusion of terminals and the like, so that it can be efficiently arranged on the substrate.

It is sectional drawing of the electrochemical cell as a reference example of this invention. It is sectional drawing of the electrochemical cell of this invention. It is sectional drawing of the conventional electrochemical cell. It is the figure which looked at the container of the electrochemical cell of this invention from the top. It is the figure which formed the coating | coated part in the container of the electrochemical cell of this invention, and was seen from the top. It is the figure which formed the coating | coated part 112 in the container 101 of this invention, and was seen from the top. It is sectional drawing at the time of forming the coating | coated part 112 in the container 101 of this invention. It is sectional drawing of the container of the conventional electrochemical cell. 6 is a graph showing changes in capacity retention ratios of Example 1 and Comparative Example 1. 6 is a graph showing changes in internal resistance of Example 1 and Comparative Example 1. It is a perspective view at the time of forming the coating | coated part 112 in the container 101 of this invention.

101 container 1011 container bottom surface 102 lid 103 positive electrode current collector 1041 connection terminal A
1042 Connection terminal B
105 Separator 106 Positive Electrode Active Material 107 Negative Electrode Active Material 108 Electrolyte 109 Metal Ring 1111 Conductive Adhesive 1112 Conductive Adhesive 112 Covering Portion

Claims (1)

A container with a lid is formed from a bottomed rectangular tube-shaped container, a metal ring positioned along the upper edge of the bottomed rectangular tube-shaped container, and a lid positioned at the top of the metal ring,
The container with lid is provided with two positive and negative connection terminals,
One connection terminal, one end is connected to the metal ring, the other end is positioned on the bottom plate bottom surface of the bottomed rectangular tube-shaped container,
One end of the other connecting terminal is positioned inside the bottom plate of the bottomed rectangular tube-shaped container, the other end is positioned on the bottom surface of the bottom plate of the bottomed rectangular tube-shaped container, and the bottomed rectangular tube-shaped Electrically connecting the connection terminal located inside the bottom plate of the container and the inside of the container with the lid,
An electrochemical cell characterized in that a positive electrode active material, a negative electrode active material, an electrolytic solution, and a separator for separating the positive electrode active material and the negative electrode active material are housed inside the lidded container.

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