JP6308578B2 - Electrochemical cell - Google Patents

Description

  The present invention relates to a surface mountable electrochemical cell.

Electrochemical cells such as electric double layer capacitors and batteries are mounted on a printed circuit board as a backup power source for watches and semiconductor memories. Along with the miniaturization of these mounting devices, in order to cope with the miniaturization of the electrochemical cell itself and the reduction of the mounting area, instead of the conventional round coin-shaped or button-shaped electrochemical cell, it has a rectangular shape. A chip-type electrochemical cell is provided.
In the chip-type electrochemical cell, a concave container is used for the case. A concave portion (accommodating portion) of the concave container accommodates a pair of electrodes composed of a positive electrode and a negative electrode, a separator provided between both electrodes, and an electrolyte. In addition, a seal ring is provided on the upper surface of the concave container, and a plate-like lid is placed thereon, thereby forming a container.

  Patent Document 1 discloses an electrochemical cell that achieves miniaturization and high capacity. When the positive electrode current collector provided on the bottom surface of the housing portion of the concave container is used in a state of being in direct contact with the electrolyte, the surface is corroded and disconnection occurs. Therefore, in this electrochemical cell, reliability improvement is realized by covering the positive electrode current collector with a protective film made of aluminum or the like.

WO2007 / 013223

In recent years, there has been a demand for miniaturization of the electrochemical cell, but when the electrochemical cell is to be miniaturized, it is necessary to reduce the overall thickness.
On the other hand, in order to seal this electrochemical cell, it is necessary to put a lid on the seal ring and join it by resistance welding or laser welding. At this time, the ceramic container expands and contracts due to the heat applied to the container, but when the container wall is thinned, cracking occurs due to thermal stress on the long side wall or bottom peripheral surface. There are things to do.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable electrochemical cell that is resistant to heat and does not crack on the side wall even when the container is reduced in size and thickness.

(First invention)
The first invention of the present invention has a housing portion 2a inside, a concave container 2 having insulation, a seal ring 3 joined to the upper end surface of the concave container 2, and a top surface of the seal ring 3, The concave container 2 is formed of a rectangular plate-shaped bottom portion 2b and a rectangular frame- shaped wall portion 2c erected on the outer edge of the bottom portion 2b. The inner wall surface of the wall portion 2c is formed by a continuous surface, and the wiring connected to the electrode (positive electrode 8) accommodated in the concave container 2 is formed on the outer wall surface on the short side of the concave container 2 (Positive electrode external terminal 6e) can be disposed, and a notch portion (wiring connection portion 14b) that is notched toward the housing portion 2a side is provided. A flat surface portion 14a is provided. As a result, the non-planar portion 14a absorbs the distortion caused by the thermal stress and enhances heat dissipation, so that it is possible to prevent cracking on the long side due to the thermal stress when the lid portion 4 is welded to the seal ring 3. In addition, since the wall portion 2c can be thinned by preventing cracking, it is possible to provide an electrochemical cell in which the container is reduced in size and thickness.

(Second invention)
The second aspect of the present invention is characterized by the following points in addition to the characteristic points of the first aspect described above. That is, the non-planar portion 14a is a groove or a rib provided in at least one place on the outer wall surface on the long side and extending in the vertical direction .
In the present invention , for example , in the rectangular electrochemical cell 1, the bottom 2b or the wall 2c of the concave container 2 or the outer peripheral surface of the long side of the outer peripheral surfaces of both, a semicircular notch or At least one or more non-planar portions 14a made of protruding portions are provided. As a result, the non-planar portion 14a absorbs the distortion caused by the thermal stress and the surface area of the outer peripheral surface on the long side increases, so that the heat dissipation can be further improved.

(Third invention)
The third aspect of the present invention is characterized by the following points in addition to the characteristic points of the first aspect described above. The non-planar portion 14a is a dent or protrusion provided at least at one place on the outer wall surface on the long side .
In the present invention , for example , in the rectangular electrochemical cell 1, the non-planar portion formed of a hemispherical recess or protrusion on the outer peripheral surface on the long side of the outer peripheral surface of the bottom 2b or the wall 2c of the concave container 2 or both At least one 14a is provided. Thereby, the surface area of the outer peripheral surface on the long side increases, so that not only the number of strain absorption points due to thermal stress increases, but also the heat dissipation can be improved.

Since this invention is comprised as mentioned above, there exists an effect as described below.
According to the electrochemical cell of the present invention, by providing a non-planar portion on the wall portion, when the lid portion is covered during manufacturing, the seal ring and the lid portion are overlapped and joined by resistance welding, laser welding, or the like. No cracks in the wall. Therefore, a highly reliable electrochemical cell can be provided even if the container is made smaller and thinner.

1 is a vertical sectional view of an electrochemical cell according to a first embodiment of the present invention. It is (A) top view and (B) front view of the concave container of the electrochemical cell of the 1st Embodiment of this invention. It is (A) top view and (B) front view of the concave container of the electrochemical cell of the 2nd Embodiment of this invention. It is the (A) top view and (B) front view of the concave container of the electrochemical cell of the 3rd Embodiment of this invention.

(First embodiment)
The electrochemical cell 1 of the present invention has a substantially cubic appearance. As shown in FIG. 1, the electrochemical cell 1 includes a bottomed rectangular tube-like concave container 2 made of an insulating material having an accommodating portion 2 a inside, and a square frame-shaped seal ring joined to the upper end surface of the concave container 2. 3 and a quadrangular plate-like lid portion 4 that is joined to the upper surface of the seal ring 3 and closes the upper surface of the seal ring 3.
The concave container 2 is a container made of a box-shaped ceramic with the top opened, and has a rectangular bottom 2b and a rectangular frame-shaped wall 2c standing on the outer edge of the bottom 2b. As shown in FIG. 2A, four positive electrode current collectors 6 b that are electrically connected to the positive electrode 8 are formed on the bottom surface of the housing portion 2 a of the concave container 2. In addition, as shown in FIG. 1, four via wirings 6c are formed from the bottom surface of the housing portion 2a to a depth half the thickness of the bottom portion 2b. The upper surface of each via wiring 6c is exposed as the positive electrode current collector 6b on the bottom surface of the housing portion 2a. Interlayer wiring 6d is formed at an intermediate portion between the bottom surface of the accommodating portion 2a and the bottom surface of the bottom portion 2b. The interlayer wiring 6d has one end connected to the via wiring 6c and the other end exposed at the side surface of the concave container 2. A positive external terminal 6e is formed from the exposed portion of the interlayer wiring 6d to the lower surface of the bottom 2b. Further, a negative electrode external terminal 7b is formed from the upper end portion of the side surface opposite to the side surface of the concave container 2 having the positive electrode external terminal 6e, through the wall portion 2c to the lower surface of the bottom portion 2b.

The concave container 2 is made of 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. The concave container 2 can be made of a heat resistant material such as glass or glass ceramics. On the other hand, the via wiring 6c, the interlayer wiring 6d, the positive external terminal 6e and the negative external terminal 7b are made of tungsten, molybdenum, nickel, gold and a composite material thereof.
The concave container 2 is formed by bonding a ceramic green sheet corresponding to the wall 2c punched into a rectangular frame shape to a ceramic green sheet corresponding to the bottom 2b punched into a rectangular shape, and then firing it. The At this time, if an electrode pattern is printed on the ceramic green sheet in advance, the via wiring 6c, the interlayer wiring 6d, the positive external terminal 6e, and the negative external terminal 7b can be formed. Further, the via wiring 6c may be formed by filling each via hole with a paste in which carbon and resin are mixed in advance and firing together with the ceramic green sheet to be the concave container 2.

The seal ring 3 has a square frame-shaped cross section that matches the shape of the upper end surface of the wall 2c of the concave container 2, and is joined to the upper end surface of the wall 2c via a brazing material 5. The seal ring 3 may be made of Kovar having a thermal expansion coefficient close to that of ceramic. The brazing material 5 is made of an Ag—Cu alloy, an Au—Cu alloy, or the like.
Note that the upper end surface of the wall 2c and the seal ring 3 may be directly joined without using the brazing material 5.
The lid portion 4 is joined to the upper surface of the seal ring 3, and seals the accommodating portion 2a of the concave container 2. The lid 4 is made of a nickel-plated alloy such as Kovar or 42alloy whose thermal expansion coefficient is close to that of ceramic. The lid portion 4 using such a material can be welded to the seal ring 3 by, for example, resistance seam welding, laser seam welding, electron beam welding, etc., and the hermeticity of the closed accommodating portion 2a is improved. Improve. Instead of using the seal ring 3, the upper end surface of the wall 2c and the lid 4 may be directly joined with a brazing material.

Since the lid portion 4 of the present embodiment is a conductive material, the lid portion 4 itself serves as a negative electrode current collector. On the other hand, when a material such as a heat-resistant resin, glass, ceramic, or ceramic glass is used for the lid 4, it is necessary to form a negative electrode current collector on the lower surface of the lid 4. The negative electrode current collector is preferably made of tungsten, silver or gold which has excellent corrosion resistance and can be formed by a film thickness method.
The accommodating portion 2a of the concave container 2 accommodates a pair of electrodes composed of a positive electrode and a negative electrode, an electrolyte, and the like. Specifically, as shown in FIG. 1, the housing portion 2 a includes an upper surface of the positive electrode current collector 6 b and a protective film 6 a formed around the upper surface, a positive electrode 8 bonded to the protective film 6 a, and a positive electrode 8. The separator 10 is disposed above, the negative electrode 9 separated from the positive electrode 8 by the separator 10, and the adhesive portion 7 a provided between the negative electrode 9 and the lid portion 4. In addition, the inside of the accommodating portion 2a is filled with the electrolyte 11.

The protective film 6a is a conductive adhesive that bonds the positive electrode current collector 6b and the positive electrode 8, and prevents positive contact with the positive electrode current collector 6b and the electrolyte 11, thereby preventing the positive electrode current collector by charging or discharging. It is provided to suppress corrosion of the electric body 6b. The protective film 6a is made of a material mainly composed of aluminum or carbon having high corrosion resistance and conductivity. In the case of the protective film 6a made of aluminum, vapor deposition, sputtering, spraying, paste coating, etc. using pure aluminum system, Al-Cu system alloy, Al-Mn system alloy, Al-Mg system alloy specified by JIS, etc. Can be formed by a method.
Further, the adhesive portion 7a provided between the lid portion 4 and the negative electrode 9 is formed of a conductive adhesive, and for this conductive adhesive, the conductive adhesive used for the protective film 6a and Similar ones can be used.

When using the electrochemical cell as an electric double layer capacitor, the positive electrode 8 and the negative electrode 9 are obtained by press molding together with an appropriate binder, activated carbon powder obtained by activating sawdust, coconut shell, pitch, etc. Or what was rolled and rolled can be used. Also, phenol, rayon, acrylic, pitch, etc. fibers are infusibilized and carbonized to form activated carbon or activated carbon fibers, which are made into a felt, fiber, paper, or sintered body. It may be used. Polyaniline (PAN) or polyacene may also be used.
Further, when the electrochemical cell is used as a battery, the positive electrode 8 is composed of lithium-containing manganese oxide, lithium-containing cobalt oxide, lithium-containing nickel oxide, lithium-containing titanium oxide, molybdenum trioxide, niobium pentoxide, etc. A mixture of a conventionally known active material and a suitable binder and graphite as a conductive aid can be used.

In addition, when the electrochemical cell is used as a battery, the negative electrode 9 is a binder and a conductive auxiliary agent suitable for conventionally known active materials such as carbon, lithium alloys such as lithium-aluminum, silicon and silicon oxide. What mixed graphite which is can be used.
As the separator 10, an insulating film having a large ion permeability and mechanical strength can be used. Considering mounting in a furnace in reflow soldering and thermal effects due to welding with the lid 4, the separator 10 can be made of glass fiber having excellent thermal and mechanical resistance. Further, a resin such as polyphenylene sulfide, polyamide, polyimide, polytetrafluoroethylene may be used.

The electrolyte 11 is preferably a liquid or gel used for known electric double layer capacitors and non-aqueous electrolyte secondary batteries.
Organic solvents used for the liquid and gel electrolyte 11 include acetonitrile, diethyl ether, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, propylene carbonate (PC), ethylene carbonate (EC), and γ-butyrolactone (γBL).
The materials contained in the liquid and gel electrolyte 11 include (C ₂ H ₅ ) ₄ PBF ₄ , (C ₃ H ₇ ) ₄ PBF ₄ , (CH ₃ ) (C ₂ H ₅ ) ₃ NBF ₄ , ( _{C 2 H 5) 4 NBF 4} , (C 2 H 5) 4 PPF 6, (C 2 H 5) 4 PCF 3 SO 4, (C 2 H 5) 4 NPF 6, lithium perchlorate (LiClO _4), Lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ], thiocyanate, aluminum fluoride, lithium salt and the like can be used, but are not limited thereto.

The gel electrolyte 11 is obtained by impregnating a polymer gel with a liquid electrolyte. Polyethylene oxide, polymethyl methacrylate, and polyvinylidene fluoride are suitable as the polymer gel, but are not limited thereto.
Furthermore, pyridine-based, alicyclic amine-based, aliphatic amine-based or imidazolium-based ionic liquids or amidine-based room temperature molten salts may be used.
As shown in FIG. 2, the non-planar portion 14a is provided at the center of the outer peripheral surface on the long side of the wall portion 2c of the concave container 2, and is a semicircular notch in a top view. The notch is preferably formed only on the wall 2c in order to maintain the strength of the concave container 2, but can be formed continuously up to the bottom 2b.

Furthermore, the non-planar portion 14a can be formed only on the outer peripheral surface on the long side of the bottom portion 2b, or on the outer peripheral surface on the long side of the wall portion 2c and the bottom portion 2b.
The non-planar portion 14a can be formed by cutting through a ceramic green sheet. By firing this as a container shape as described above, the concave container 2 is completed.
The wiring connection portion 14b is a substantially rectangular cutout in a top view provided in the center of the side surface on the short side of the wall portion 2c of the concave container 2. The wiring connection portion 14b is formed continuously from the wall portion 2c to the bottom portion 2b so that wiring can be connected when the electrochemical cell 1 is mounted on the substrate.
The wiring forming portion 14c is a semicircular cutout in a top view provided at the corner of the side surface on the short side of the wall 2c of the concave container 2. The wiring forming portion 14c is formed continuously from the wall 2c to the bottom 2b in order to form wiring in the concave container 2.

As described above, when the electrochemical cell 1 is sealed, it is necessary to overlap the seal portion 3 on the seal ring 3 and join them by resistance welding or laser welding. At this time, the concave container 2 expands and contracts due to the applied heat. When the height of the wall 2c of the container is lowered or the thickness of the wall 2c is reduced, thermal stress is applied to the long side of the wall 2c unless the non-planar part 14a is provided. May cause cracks. Therefore, by providing the non-planar portion 14a on the long side of the wall 2c or the bottom 2b, strain caused by thermal stress is absorbed by the non-planar portion 14a, and the occurrence of cracks is reduced.
The cutout of the non-planar portion 14a may be triangular or trapezoidal in addition to a semicircular shape when viewed from above. Further, the non-planar portion 14a is not limited to the notch and may be a protruding portion having the above shape.

(Second Embodiment)
The electrochemical cell 1 according to this embodiment has the same basic structure as that of the first embodiment, but differs in the following points. That is, in the first embodiment, the non-planar portion 14a is formed only in one place on the outer peripheral surface on the long side of the wall portion 2c, whereas in the second embodiment, as shown in FIG. A total of 14 locations are formed, 7 locations per side. In addition, the non-planar part 14a is not restricted to seven places per long side like FIG. 3, What is necessary is just to form two or more.
By forming a plurality of non-planar portions 14a, heat dissipation can be further improved by increasing the surface area of the side surface in addition to the dispersion of thermal stress.

(Third embodiment)
The electrochemical cell 1 according to this embodiment has the same basic structure as that of the second embodiment, but differs in the following points. That is, in place of the semicircular notch in the second embodiment, a hemispherical recess as shown in FIG. 4 is formed at a total of 14 locations, 7 locations on the outer peripheral surface of one long side.
Similarly to the second embodiment, by forming a plurality of non-planar portions 14a, heat dissipation can be further improved by increasing the surface area of the side surface in addition to the dispersion of thermal stress. In addition, the non-planar part 14a is not restricted to seven places per long side like FIG. Further, the non-planar portion 14a is not limited to a hemispherical shape as shown in FIG. 4, and a shape that increases the surface area of the side surface is preferable because heat dissipation can be improved.

1 Electrochemical cell 2 Recessed container 2a Housing
2b Bottom 2c Wall
3 Seal ring 4 Lid 5 Brazing material
6a Protective film 6b Positive electrode current collector 6c Via wiring
6d Interlayer wiring 6e Positive external terminal
7a Bonding part 7b Negative external terminal
8 Positive electrode 9 Negative electrode 10 Separator
11 Electrolyte 14a Non-planar part 14b Wiring connection part
14c Wiring formation part

Claims (3)

A concave container having an inside as a housing part and having an insulating property;
A seal ring joined to the upper end surface of the concave container;
A lid portion joined to the upper surface of the seal ring and closing the upper surface of the seal ring;
The concave container is composed of a rectangular plate-shaped bottom portion and a rectangular frame- shaped wall portion erected on the outer edge of the bottom portion,
The inner wall surface of the wall portion is composed of a continuous surface,
On the outer side wall surface on the short side of the concave container, a wiring connected to an electrode accommodated in the concave container can be disposed, and a notch portion notched toward the accommodating portion side is provided. And
A non-planar portion is provided on an outer wall surface on the long side of the concave container . 2. The electrochemical cell according to claim 1, wherein the non-planar part is a groove or a rib provided in at least one place on the outer wall surface on the long side and extending in the vertical direction . 2. The electrochemical cell according to claim 1, wherein the non-planar portion is a recess or a protrusion provided at least at one place on the outer wall surface on the long side .