JP2979963B2 - Rechargeable battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery provided with a protection circuit.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic devices such as portable radio telephones, portable personal computers, and portable video cameras, lithium ion secondary batteries having high energy density and excellent lightness have been developed. Has been put to practical use.
In a lithium ion secondary battery, for example, a LiCo-based compound is used as a positive electrode active material, and a carbon material is used as a negative electrode active material.

When a lithium ion secondary battery is overcharged to a predetermined battery voltage or more, deposition of lithium metal on the negative electrode,
Decomposition of the positive electrode active material, decomposition of the organic electrolyte, and the like occur, causing short-circuiting of the positive and negative electrodes, deterioration of battery performance, and the like. Conversely, when the lithium ion secondary battery is overdischarged below a predetermined battery voltage, the metal of the negative electrode current collector is ionized and eluted into the organic electrolytic solution, and the capacity due to the deterioration of the current collecting function and the falling off of the negative electrode active material. It causes a decline.

In order to prevent overcharge and overdischarge of a lithium ion secondary battery, Japanese Patent Application Laid-Open No. 4-33142 has been proposed.
Various protection circuits have been developed as disclosed in Japanese Patent Application Laid-Open No. 5-115129 and Japanese Patent Application Laid-Open No. 5-115129. By connecting such a protection circuit to the secondary battery, overcharge and overdischarge are prevented.

[0005]

The above-mentioned Japanese Patent Application Laid-Open No. 4-331425 discloses a battery pack in which a protection circuit and a secondary battery are housed in a molded case made of resin or the like. In this battery pack, the printed circuit board on which the protection circuit is mounted is arranged on the side of the secondary battery and housed in the mold case, and the discharge terminal, the charge terminal and the common terminal are provided in the mold case. , A protection circuit on a printed circuit board, a discharge terminal, a charge terminal, and a common terminal are connected using a plurality of tabs.

Therefore, this battery pack has a problem that the structure is complicated, the number of parts is large, and the wiring is long. In addition, since the mold case usually has a thickness of about 1.5 mm, the width and the thickness of the battery pack increase. In particular, in a miniaturized electronic device such as a portable radio telephone device, a portable personal computer, a portable video camera, and the like, a thin battery is required.

Therefore, an object of the present invention is to provide a secondary battery with a high volumetric efficiency, in which the protection circuit is compactly integrated.

[0008]

In a secondary battery according to the present invention, a secondary battery element is housed in a case serving as a first electrode, and a second electrode and a safety valve are provided in an upper opening of the case. In the secondary battery formed by fitting the provided lid, a substrate on which a first external terminal, a second external terminal, and a protection circuit are mounted and a hole is formed at a position corresponding to the safety valve is provided on the top of the lid. In addition to mounting, the first and second external terminals are connected to the case and the second electrode via a protection circuit, respectively.

Preferably, the substrate includes a flexible substrate in which a flexible resin layer and a wiring layer are laminated, and the first and second substrates are formed using the wiring layer of the flexible substrate.
Are connected to the case and the second electrode via a protection circuit.

[0010] The secondary battery element may comprise an organic electrolyte secondary battery element. Further, the case may be formed of a prismatic case.

[0011]

In the secondary battery according to the present invention, a first external terminal is provided on an upper portion of a lid fitted to a case serving as a first electrode.
Since the substrate provided with the second external terminal and the protection circuit is mounted, and the first and second external terminals are connected to the case and the second electrode through the protection circuit, respectively, the first and second terminals are connected. Since the wiring from the external terminal to the protection circuit and the wiring from the protection circuit to the first and second electrodes are connected via a wiring layer of a flexible substrate integrated at a high density, the size is reduced and the size is reduced. The provision of the protection circuit does not increase the width, thickness, or diameter of the secondary battery. Therefore, a secondary battery in which the protection circuit is integrated and which is small, compact, and high in volume efficiency can be obtained.

Further, since the hole is provided at the position of the substrate corresponding to the safety valve, even if the internal pressure rises,
The gas inside is released to the outside through the holes of the safety valve and the substrate. Moreover, since the structure is simple, manufacturing is easy and the number of parts is reduced.

[0013]

FIG. 1 is a sectional view of a lithium ion secondary battery according to one embodiment of the present invention. In FIG. 1, secondary battery elements such as a positive electrode active material, a negative electrode active material, a positive electrode current collector, a negative electrode current collector, a separator, and an organic electrolytic solution (shown in a bottomed prismatic metal case 1 made of stainless steel, for example) are shown. Is stored. In this lithium secondary battery, for example, LiCoO ₂ is used as a positive electrode active material, carbon having a graphite structure is used as a negative electrode active material, and the positive electrode active material is Al.
And the negative electrode active material is held by a negative electrode current collector made of Cu. A separator is arranged between the positive electrode active material and the negative electrode active material, and is filled with an organic electrolyte.

In the lithium ion secondary battery of FIG. 1, the metal case 1 serves as a negative electrode. A metal cover 2 having a concave cross section is fitted into the upper opening of the metal case 1. A positive electrode 4 is attached to the center of the metal lid 2 via an insulating layer 3 made of glass, ceramic, or the like. Further, a hole is formed at a predetermined position of the metal cover 2, and the safety valve 5 is mounted and integrated into the hole.

A composite board 8 composed of a printed board 6 and a flexible board 7 is mounted on the metal cover 2. On the lower surface of the printed circuit board 6, a protection circuit 9 for preventing overdischarge, overcharge, overcurrent, excessive input and overheating is mounted. On the upper surface of the flexible substrate 7, a positive external terminal 10, a negative external terminal 11, and a thermistor external terminal 12 are formed. Further, holes 13 and 14 are formed in the printed board 6 and the flexible board 7 at positions corresponding to the safety valve 5 provided on the metal lid 2.

An insulating plate 15 having external terminal holes 17, 18, and 19 formed on the composite substrate 8 at positions corresponding to the positive external terminal 10, the negative external terminal 11, and the thermistor external terminal 12, respectively. ing. On the other hand, an insulating plate 16 is also arranged on the lower surface of the metal case 1. Insulating plate 1
5. The outer surfaces of the metal case 1 and the insulating plate 16 are covered with a heat-shrinkable tube 20.

A charger or an electronic device is connected between the positive external terminal 10 and the negative external terminal 11, and the thermistor external terminal 12 is connected to a temperature detecting terminal of the charger or the electronic device.

FIG. 2 is a view showing the structure of the composite substrate 8.
(A) is a plan view, (b) is a side view, and (c) is a bottom view. As shown in FIG. 2B, a flexible board 7 is mounted on a printed board 6. As shown in FIG. 2C, an integrated circuit element 61, a polyswitch 62 (see FIG. 2B), a thermistor 63, and an FET (field effect transistor) element 64 are provided on the lower surface of the printed circuit board 6, as shown in FIG.
And a protection circuit including capacitors 65 and 66 are mounted. On the other hand, as shown in FIG. 2A, a positive electrode external terminal 10 made of Cu
The thermistor external terminal 12 and the negative electrode external terminal 11 are formed.

As shown in FIG. 2B, the flexible substrate 7 is formed by laminating a polyimide resin layer 72 on both surfaces of a wiring layer 71 made of a copper foil formed in a predetermined pattern. The thickness of the wiring layer 71 made of copper foil is 75 to 100 μm
And the thickness of the polyimide resin layer 72 is about 10 μm. A tab 71a for connecting a positive electrode extends from one end of the flexible substrate 7, and a tab 7a for connecting a negative electrode extends from the other end.
1b is extended. The holes 13 and 14 described above are formed in the printed board 6 and the flexible board 7.

FIG. 3 is a circuit diagram showing an example of the protection circuit 9. In FIG. 3, an FET element 64 including an over-discharge prevention FET 64a and an over-voltage prevention FET 64b is connected between the metal case 1 and the negative electrode external terminal 11. The thermistor external terminal 12 and the negative electrode external terminal 1
A thermistor 63 is connected between the thermistor 63 and the thermistor 63. Positive electrode 4
A polyswitch 62 is connected between the positive terminal 10 and the positive external terminal 10. When an overcurrent flows through the polyswitch 62, the resistance value increases due to heat generation, and the current is cut off. Therefore, the polyswitch 62 prevents overcurrent and overheating. The poly switch 62 returns to the conductive state when the temperature decreases.

When an overvoltage is applied between the positive electrode 4 and the metal case 1, the integrated circuit element 61 turns off the FET 64b. Thereby, overcharging is prevented. When the voltage between the positive electrode 4 and the metal case 1 becomes lower than a predetermined voltage due to overdischarge, the integrated circuit element 61
Turn off 64a. Thereby, overdischarge is prevented. Further, the integrated circuit element 61 turns off the transistor 64a when an overcurrent flows due to a short circuit between the positive external terminal 10 and the negative external terminal 11. Thereby, an overcurrent is prevented.

Referring again to FIG. 1, positive electrode connection tab 71a of flexible substrate 7 is soldered to one metal terminal 62a of polyswitch 62, and metal terminal 62a is spot welded to the upper portion of positive electrode 4. ing. The other metal terminal 62 b of the poly switch 62 is soldered to the printed circuit board 6. On the other hand, the negative electrode connection tab 71b of the flexible substrate 7 is spot-welded to the side surface of the metal case 1.

The flexible substrate 7 has flexibility, and the wiring layer 71 made of copper foil can be spot-welded to metal, so that wiring and connection are easy. Further, since the flexible substrate 7 is mounted on the printed circuit board 6, the wiring between the positive external terminal 10, the negative external terminal 11, the thermistor external terminal 12 and the protection circuit 9 is shortened, and the upper part of the metal cover 2 Since the composite board 8 is mounted on the metal case 1, the wiring between the metal case 1 and the positive electrode 4 and the protection circuit 9 is shortened. Therefore, the routing of the wiring is eliminated.

Further, since the holes 13 and 14 for the safety valve 5 are formed in the printed circuit board 6 and the flexible substrate 7, even when the pressure inside the secondary battery rises, the safety valve 5 and the holes 13 and 14 are used. The gas inside is released to the outside. Therefore, safety is ensured.

FIG. 4 is an external perspective view of the lithium ion secondary battery of FIG. As shown in FIG. 4, this lithium ion battery has a positive external terminal 10 and a negative external terminal 1 in appearance.
1 and an external terminal 12 for thermistor. As described above, since the composite substrate 8 is mounted on the upper portion of the metal lid 2 and can be entirely covered with a thin heat-shrinkable tube without using a mold case, the protection circuit is built-in. Regardless, the width W and the thickness D of the secondary battery do not increase, and lightness is maintained. As described above, a secondary battery in which the protection circuit is integrated and which is small, compact, and high in volume efficiency can be obtained.

The secondary battery elements are not limited to those of the above embodiment. The positive electrode active material may be any material capable of dedoping or doping lithium ions. In addition to lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium chromium oxide, lithium vanadium oxide, lithium molybdenum An oxide, lithium molybdenum disulfide, lithium titanium oxide, lithium titanium sulfide, or the like, or a composite compound of these can be used. In addition, as the negative electrode active material, metallic carbon, a lithium alloy, or a carbonaceous material that can be doped or dedoped with lithium ions, for example, graphite, pyrolytic carbon, pitch coke, needle coke, petroleum coke, and firing of organic polymer (A fired body such as a phenol resin, a furan resin, and polyacrylonitrile) can be used.

Further, as an electrolyte in the organic electrolyte,
Is LiClO_Four, LiAsF₆, LiPF₆, LiB
F_Four, CH_ThreeSO_ThreeLi, CF_ThreeSO_ThreeLi, (CF_Three
SO _Two)_TwoAny one of lithium salts such as NLi or
A mixture of two or more can be used. Organic electricity
As a solvent in the dissolution, for example, propylene carbohydrate
, Ethylene carbonate, dimethyl carbonate
G, diethyl carbonate, methyl ethyl carbonate
G, 1,2-dimethoxyethane, 1,2-diethoxye
Tan, γ-butyrolactone, tetrahydrofuran, 2-
Methyltetrahydrofuran, 1,3-dioxolan,
Ruphoran, methylsulfolane, acetonitrile, propyl
Onitrile, methyl formate, ethyl formate, methyl acetate, vinegar
Either one or two or more such as ethyl acid
Can be used. Polyester as a separator
Microporous membrane of polyolefin such as styrene and polypropylene
One or two or more kinds of laminated films, polyolefins,
Nonwoven fabric such as polyester, polyamide, cellulose, etc.
Use a monolayer or a laminated membrane with the above microporous membrane
Can be. Particularly preferably, a polyethylene microporous membrane is used.
Used.

In the above embodiment, the case where the present invention is applied to a prismatic secondary battery has been described. However, the present invention can be similarly applied to a cylindrical secondary battery. Further, the present invention is not limited to a lithium ion secondary battery, but can be applied to other secondary batteries.

Further, the positions, shapes, and the like of the positive electrode external terminal 10, the negative electrode external terminal 11, and the thermistor external terminal 12 are not limited to those in the above embodiment. In the above embodiment, the upper surfaces of the positive electrode external terminal 10, the negative electrode external terminal 11, and the thermistor external terminal 12 are arranged so as to be concave with respect to the surface of the insulating plate 15. The upper surfaces of 11 and 12 may be arranged so as to be convex or flush with the surface of the insulating plate 15.

[0030]

As described above, according to the present invention, the protection circuit is integrated, small, compact, and has high volumetric efficiency.
A secondary battery in which safety is ensured is provided. Moreover, since the structure is simple, manufacturing is easy and the number of parts is small.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lithium ion secondary battery according to an embodiment of the present invention.

FIG. 2 is a plan view, a side view, and a bottom view showing a structure of a composite board composed of a printed board and a flexible board.

FIG. 3 is a circuit diagram illustrating an example of a protection circuit mounted on the printed circuit board of FIG. 2;

FIG. 4 is an external perspective view of the lithium ion secondary battery of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal case 2 Metal cover 4 Positive electrode 5 Safety valve 6 Printed circuit board 7 Flexible board 8 Composite board 9 Protection circuit 10 Positive external terminal 11 Negative external terminal 13, 14 hole 71 Wiring layer 72 Polyimide resin layer Indicates the same or corresponding parts.

Continuation of the front page (56) References JP-A-7-282842 (JP, A) JP-A-7-272748 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 10 / 00-10/48

Claims (4)

(57) [Claims] 1. A secondary battery in which a secondary battery element is housed in a case serving as a first electrode, and a lid provided with a second electrode and a safety valve is fitted into an upper opening of the case. Mounting a substrate on which a first external terminal, a second external terminal, and a protection circuit are mounted and a hole is formed at a position corresponding to the safety valve, on the top of the lid;
And a second external terminal connected to the case and the second electrode via the protection circuit, respectively. 2. The substrate includes a flexible substrate in which a flexible resin layer and a wiring layer are laminated, and the first and second external terminals are connected to the protection circuit by using the wiring layer of the flexible substrate. The secondary battery according to claim 1, wherein the secondary battery is connected to the case and the second electrode via a first electrode and a second electrode, respectively. 3. The secondary battery according to claim 1, wherein the secondary battery element comprises an organic electrolyte secondary battery element. 4. The secondary battery according to claim 1, wherein the case comprises a prismatic case.