JP2004179073A - Protective element for secondary battery, and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective element for a secondary battery, and a secondary battery with a temperature element built in, wherein a current is broken when overcharged and unnecessary breaking of the current is not caused when discharged. <P>SOLUTION: In the protective element 30, a conductive plate 31 and a conductive plate 32 consisting of a nickel plate are joined to the temperature element 33, and these are fixed by a resin mold 34. A negative pole terminal of an elementary battery and a terminal board 26 for discharging are conducted through the conductive plate 31. Power is supplied to an external load from the elementary battery via the conductive plate 31 not via the temperature element 33 when discharging. The negative pole terminal and a terminal board 27 for charging are connected through the temperature element 33 and the conductive plates 31, 32, and power is supplied via the temperature element 33 when charging. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
The present invention relates to a secondary battery having a built-in temperature element such as a PTC, a bimetal, and a thermal fuse.
[0002]
[Prior art]
A secondary battery represented by a lithium ion battery is widely used as a power source for personal computers, digital cameras, and the like. The secondary battery includes a rechargeable power generating element and an external terminal. When the power generating element is charged from the outside or discharged from the power generating element to the outside, the operation is performed through the external terminal. ing.
[0003]
In the case of a lithium-ion battery, if it is overcharged, the temperature inside the battery becomes abnormally high and may rupture or ignite. Therefore, in general, a temperature-sensitive temperature element (temperature A fuse, a PTC, or the like) is inserted between the power generating element and the external terminal. For example, Patent Literature 1 describes a battery pack having a built-in protection element.
[0004]
When the temperature becomes higher than a set temperature, the thermal fuse is blown and cuts off the current path. When the temperature of the PTC also becomes high, the electric resistance sharply increases, so that the current path is substantially cut off.
Therefore, by incorporating such a temperature element in the lithium ion battery, the battery is prevented from being ruptured or ignited due to overcharging.
[0005]
[Patent Document 1]
JP 2000-243362 A
[Problems to be solved by the invention]
However, in the secondary battery including the temperature element as described above, the temperature element operates as the temperature inside the battery becomes high even though the discharge current at the time of discharging is within the originally allowable range. Current path may be interrupted. For example, in the graph shown in FIG. 5, although the battery temperature gradually rises as the lithium ion battery is continuously discharged, the battery temperature becomes as high as about 90 ° C. due to a temporary increase in load current. In such a case, the temperature element may operate to stop the discharge. In general, when the load current temporarily increases due to a load fluctuation or the like, as shown by the broken line in FIG. 5, after the load is reduced, the terminal voltage of the battery is restored, and the power supplied to the load remains. However, there is a problem in that if the temperature element operates when the temperature rises, the connection with the load is cut off at that point and power cannot be supplied.
[0007]
In particular, when the battery is frequently discharged under a high load, such as a personal computer or a digital camera, such a problem is likely to occur because the temperature inside the battery is likely to be high and the self-heating of the temperature element is large.
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a secondary battery having a built-in temperature element, in which current is interrupted at the time of overcharging and unnecessary current interruption is not caused at the time of discharging.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a chargeable power generation element, a protection element incorporated in a secondary battery including a charging external terminal for charging the power generation element and a discharge external terminal for discharging. A power generating element side terminal connected to the power generating element, a charging side terminal connected to the charging external terminal, a discharging side terminal connected to the discharging external terminal, a power generating element side terminal and a charging side terminal. Between the power generation element side terminal and the discharge side terminal, which is made of a conductive material, and is kept in a conductive state at the first temperature and cuts off the current at a second temperature higher than the first temperature. And a conductive portion to be provided.
[0009]
In the secondary battery incorporating the protection element of the present invention, the current interrupting unit keeps the conductive state between the power generating element side terminal and the charging side terminal at the first temperature and the current at the higher second temperature. Cut off. Therefore, at the time of normal charging, the unit cell can be charged from the outside via the external terminal for charging and the temperature element unit, and at the time of overcharging when the temperature inside the battery becomes high, the charging of the unit cell can be stopped. Therefore, the battery is prevented from being ruptured or ignited by overcharging.
[0010]
On the other hand, at the time of discharging, the unit cell is discharged to the outside via the conducting portion and the external discharging terminal without passing through the current interrupting portion.
Here, since the conductive portion is formed of a conductive material, power loss in the protection element during discharge is small, and the protection element hardly generates heat by the discharge current. Therefore, at the time of discharging, even if the temperature inside the battery rises, the current interrupting unit is hard to operate, so that the current is not unnecessarily interrupted at the time of discharging unlike the conventional protection element.
[0011]
Further, the protection element of the present invention includes a power-generating element-side terminal connected to the power-generating element, a charging-side terminal connected to the external terminal for charging, and a discharge-side terminal connected to the external terminal for discharging. Therefore, the unit cell can be easily connected to the external charging terminal and the external discharging terminal via this protective element without using other members.
[0012]
In the above protection element, the conductive part, the power generating element side terminal part, and the discharge side terminal part are formed by one conductive plate, and the current interrupting element and the conductive material are fixed with a resin or the like, thereby simplifying the configuration. And a slim shape. Further, the protection element can be easily manufactured.
In the secondary battery provided with the protection element, if the charging external terminal and the discharging external terminal are provided on a holder attached to the power generation element, and the protection element is housed between the holder and the power generation element, the battery The whole can be made compact and the battery can be easily assembled.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view of the lithium secondary battery 1. The secondary battery 1 is a rectangular sealed type and includes a unit cell 10, a terminal holder 20, a protection element 30, and the like. A plurality of the secondary batteries 1 are connected in series or in parallel and housed in an outer case, are incorporated in a portable personal computer, supply power for driving an arithmetic unit and a display unit including a CPU, and It is charged through a built-in charger. In addition, the secondary battery 1 of the present invention can be used not only for a personal computer but also for a device such as a digital camera, and one or more rechargeable batteries can be used.
[0014]
(Configuration of Cell 10)
The unit cell 10 is configured such that a spirally wound electrode body (not shown) is accommodated inside a bottomed rectangular cylindrical outer can 11, and an opening of the outer can 11 is sealed with a sealing lid 12.
The sealing lid 12 has a rectangular shape, and a rib 13 is formed along a peripheral edge thereof. Inside the rib 13, a concave portion 13a serving as a space for accommodating the protection element 30 is formed.
[0015]
The exterior can 11 and the sealing lid 12 are manufactured by pressing an aluminum or aluminum alloy plate by pressing.
The opening edge of the outer can 11 and the rib 13 of the sealing lid 12 are hermetically sealed by laser welding.
A negative electrode terminal 14 is attached to the center of the sealing lid 12, and a safety valve 15 is mounted beside the negative electrode terminal 14.
[0016]
The negative electrode terminal 14 is fixed to the sealing lid 12 via an insulating packing. Thereby, the negative electrode terminal 14 is insulated from the sealing lid 12 and the sealing lid 12 is hermetically sealed.
The safety valve 15 is configured by hermetically closing a hole formed in the sealing lid 12 with a thin film. When the internal pressure of the battery becomes higher than a set pressure, the thin film is broken and gas in the battery is released to the outside.
[0017]
The size and the battery capacity of the unit cell 10 are, for example, 50 mm in height, 34 mm in width, 10 mm in thickness, and 1700 mAh.
(Configuration of terminal holder 20 and terminal plate)
The terminal holder 20 is mounted on the sealing lid 12 of the unit cell 10 and holds terminal plates 26 and 27 as external connection terminals.
[0018]
The terminal holder 20 is a plate-like member having the same size as the sealing lid 12, and is formed of an insulating material (specifically, plastic such as polycarbonate). The terminal plates 26 and 27 are mounted on the upper surface of the terminal holder 20. The terminal plate 26 is a terminal plate for discharging, and the terminal plate 27 is a terminal plate for charging.
The terminal plates 26 and 27 are made of a conductive metal plate, and are arranged side by side in the width direction. The terminal plates 26 and 27 extend in the longitudinal direction of the terminal holder 20.
[0019]
FIG. 2 is a diagram of the terminal holder 20 on which the terminal plates 26 and 27 are mounted as viewed from the lower surface side (back surface side).
On the lower surface side (rear surface side) of the terminal holder 20, a rib 22 protruding downward along the outer peripheral portion is provided. A concave portion 22 a serving as a space for accommodating the protection element 30 is formed inside the rib 22.
[0020]
Further, a window 23 is opened in the center of the terminal holder 20, and windows 24 and 25 are opened near the end of the terminal holder 20.
The window 23 is for connecting a lead terminal 35 of the protection element 30 described later to the negative terminal 14. The windows 24 and 25 are for connecting the lead terminals 36 and 37 of the protection element 30 to the terminal plates 26 and 27, and the back surfaces of the terminal plates 26 and 27 are connected to the windows 24 and 25. I'm coming.
[0021]
The terminal holder 20 on which the terminal plates 26 and 27 are mounted can be efficiently manufactured by using the insert molding technique.
(Configuration and connection of protection element 30)
As shown in FIG. 2, the appearance of the protection element 30 is such that a lead terminal portion 35 connected to the negative electrode terminal 14 of the unit cell 10 extends from one side of the resin mold portion 34 and extends from the other side of the resin mold portion 34. A lead terminal portion 36 connected to the discharging terminal plate 26 and a lead terminal portion 37 connected to the charging terminal plate 27 extend side by side. The interval between the lead terminals 36 and 37 is set in accordance with the interval between the windows 24 and 25.
[0022]
The internal structure of the protection element 30 is as shown in FIG. 3, in which a conductive plate 31 and a conductive plate 32 made of a conductive metal plate (for example, a Ni plate) are joined to a temperature element 33, and these are joined to a resin mold section. 34 and is fixed.
More specifically, the conductive plate 31 has a branch portion 31 a formed in a resin mold portion 34. The branch portion 31 a is connected to one terminal of the temperature element 33, and the conductive plate 32 is connected to the temperature element 33. Connected to other terminals.
[0023]
The temperature element 33 is embedded in the resin mold part 34, but the conductive plate 31 penetrates the resin mold part 34, and both ends thereof extend out from the resin mold part 34 to form the lead terminal part. 35 and 36 are formed. The conductive plate 32 extends out of the resin mold part 34 to form the lead terminal part 37.
[0024]
The temperature element 33 has a function of interrupting the current when the temperature reaches a certain temperature (for example, about 90 ° C.) in a state where the normal charging current is flowing. May be. As the non-return type, a thermal fuse can be used, and as the return type, PTC or bimetal can be used.
In the case of a thermal fuse, when the temperature becomes high, the fuse is blown and the current is cut off. In the case of a bimetal, the contact is separated and the current is cut off when the temperature becomes high. In the case of PTC, when the temperature becomes high, the electric resistance increases rapidly, and the current is substantially cut off.
[0025]
As shown in FIG. 3, in the protection element 30, since the conductive plates 31 and 32 and the temperature element 33 are arranged on substantially one plane, the whole has a slim shape.
The protection element 30 having the above-described configuration can be easily manufactured by joining the conductive plates 31 and 32 and the temperature element 33 to each other, and insert-molding with a molding resin to form the resin mold portion 34.
[0026]
As shown in FIG. 1, the protection element 30 having the above configuration is stored in a storage space between the unit cell 10 and the terminal holder 20, and as shown in FIG. Are connected to terminal plates 26 and 27 through windows 24 and 25 from below. The lead terminal 35 is connected to the negative terminal 14 of the unit cell 10.
[0027]
FIG. 4 is a diagram showing an electrical connection form inside the secondary battery 1.
The negative electrode terminal 14 of the unit cell 10 and the discharge terminal plate 26 are electrically connected by the conductive plate 31. On the other hand, the negative electrode terminal 14 and the charging terminal plate 27 are connected via the temperature element 33 and the conductive plates 31 and 32.
(Assembly of battery 1)
The protection element 30 is temporarily fixed to the storage space on the back side of the terminal holder 20, and the lead terminal portions 36 and 37 are spot-welded to the terminal plates 26 and 27 through the windows 24 and 25.
[0028]
Then, the terminal holder 20 to which the protection element 30 is mounted is placed on the sealing lid 12, an electrode rod for spot welding is inserted from the window 23, and the lead terminal 35 is spot-welded to the negative electrode terminal 14.
Then, as shown in FIG. 1, the battery 1 is manufactured by fixing the terminal holder 20 to the unit cell 10 with the adhesive film 28.
[0029]
The order of the welding may be reversed, and the lead terminal portions 35 and 37 may be welded to the negative electrode terminal 14 and then the lead terminal portions 36 and 37 may be welded to the terminal plates 26 and 27.
Further, the temperature element 33 may be bonded to the surface of the sealing lid 12 with an adhesive.
Further, the terminal holder 20 and the unit cell 10 may be fixed by a film such as a heat shrink film.
[0030]
(Operation and Effect of Secondary Battery 1)
The charging and discharging of the secondary battery 1 is performed from the personal computer body.
When charging the secondary battery 1, the negative electrode and the positive electrode of the charger are connected to the charging terminal plate 27 and the outer can 11, and the unit cell 10 is charged from the charger.
At the time of charging, power is supplied via the temperature element 33, but at the time of normal charging, the battery is charged with a relatively small current (for example, about 1.5 A), so that the temperature inside the battery does not become very high. During overcharge, the temperature inside the battery becomes high. On the other hand, when the temperature reaches a certain temperature (about 90 ° C.), the temperature element 33 operates, so that charging of the unit cell 10 is stopped.
[0031]
When discharging from the secondary battery 1, the negative electrode and the positive electrode of an external load (an operation unit and a display unit of the personal computer) are connected to the discharge terminal plate 26 and the outer can 11, and the unit cell 10 discharges to the external load. At this time, electric power is supplied from the unit cell 10 to the external load via the conductive plate 31 without passing through the temperature element 33.
FIG. 5 is an example showing changes in temperature, current, and terminal voltage when a lithium secondary battery is discharged.
[0032]
At the time of discharging, the battery is often discharged with a larger current than at the time of charging. When discharging from the secondary battery 1 for a long time, the temperature inside the secondary battery 1 rises as shown in FIG. Further, when the arithmetic unit is operated under a high load, the secondary battery 1 may be discharged with a large current (for example, about 7 A).
Here, if the battery is discharged via the temperature element at the time of discharge as in a conventional general ion battery, the temperature of the battery becomes high, and the self-heating of the temperature element is accompanied by the self-heating of the temperature element at the time of high current discharge. The current is interrupted before reaching. On the other hand, in the secondary battery 1 according to the present embodiment, since the discharge is performed via the conductive plate 31 having good conductivity without passing through the temperature element 33, the protection element 30 is self-discharged by the discharge current. Does not generate heat. Therefore, even when the temperature inside the battery 1 reaches the above-mentioned constant temperature during discharging, the current path is not interrupted.
[0033]
Therefore, in the secondary battery 1, the current path is interrupted at the time of overcharging, and unnecessary current interruption at the time of discharging is avoided.
Furthermore, the secondary battery 1 has the following structural and manufacturing effects.
Since the protection element 30 is slim as a whole, it is stored in a storage space between the back surface of the terminal holder 20 and the sealing lid 12. Therefore, the overall shape of the secondary battery 1 can be made compact.
[0034]
Further, since the protection element 30 is mounted near the terminal plates 26 and 27 of the terminal holder 20, the length of the lead terminal portions 36 and 37 can be reduced, and the lead terminal portions 36 and 37 and the terminal plates 26 and 27 It is also easy to connect.
In addition, since the conductive element 31 and the temperature element 33 are incorporated in the protection element 30 and are fixed by the resin mold part 34, the protection element 30 is mounted between the unit cell 10 and the terminal holder 20, and the protection element 30 The electric connection in the battery 1 is completed only by welding the three lead terminal portions 35, 36, 37 to the negative electrode terminal 14 and the terminal plates 26, 27.
[0035]
That is, as shown in FIG. 4, in order to electrically connect the negative electrode terminal 14 and the terminal plate 26 and connect the negative electrode terminal 14 and the terminal plate 27 via the temperature element 33, wiring is performed using a printed board or the like. Although it is conceivable to use a method of arranging a lead wire or the like, a battery can be easily assembled by using the protective element 30 as in the present embodiment.
[0036]
(Modifications, etc.)
In the above embodiment, the unit cell 10 is rectangular, but the same can be applied to a cylindrical unit.
In the above-described embodiment, an example is shown in which the protection element 30 is interposed between the negative electrode terminal 14 of the unit cell 10 and the external terminal plates 26 and 27 of the negative electrode. The same can be achieved by interposing a protection element between the side.
[0037]
In the above embodiment, the case where the unit cell 10 is a lithium ion battery has been described as an example. However, the unit cell 10 is not necessarily a lithium ion battery, and may be a chargeable / dischargeable secondary battery such as a nickel metal hydride battery. The present invention is applicable.
In the case where a temperature element that operates at a higher temperature than the temperature element 33 is interposed between the lead terminal section 35 and the lead terminal section 37 in the protection element 30, similarly, unnecessary current during discharge can be obtained. Although the occurrence of interruption can be avoided, it is preferable to connect only the conductive material between the lead terminal portion 35 and the lead terminal portion 37 as in the above-described embodiment, since the power loss during discharging can be reduced.
[0038]
【The invention's effect】
The present invention relates to a power generation element connected to a power generation element, and a protection element built in a secondary battery including a chargeable power generation element, a charging external terminal for charging the power generation element, and a discharge external terminal for discharging. An element-side terminal portion, a charging-side terminal portion connected to a charging external terminal, a discharging-side terminal portion connected to a discharging external terminal, and a power-generating element-side terminal and a charging-side terminal interposed therebetween. A current interrupting portion that maintains a conductive state at one temperature and interrupts current at a second temperature higher than the first temperature, and a conductive portion that is made of a conductive material and connects between the power generation element side terminal and the discharge side terminal is provided. Thus, the current is interrupted at the time of overcharging, and unnecessary current interruption is not generated at the time of discharging. In addition, the unit cell can be easily connected to the external charging terminal and the external discharging terminal via the protection element.
[0039]
In the above protection element, if the conductive part, the power generation element side terminal part, and the discharge side terminal part are formed by one conductive plate, and the current interrupting element and the conductive material are fixed with resin or the like, the configuration is simplified and slim. The protection element can be easily manufactured.
Further, in a secondary battery provided with the protection element, the charging external terminal and the discharging external terminal are provided on a holder attached to the power generation element, and the protection element is housed between the holder and the power generation element. The whole battery can be made compact and the battery can be easily assembled.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a lithium secondary battery according to an embodiment.
FIG. 2 is a view of a terminal holder used for the lithium secondary battery as viewed from a lower surface side.
FIG. 3 is a diagram showing an internal structure of a protection element used for the lithium secondary battery.
FIG. 4 is a diagram showing an electrical connection mode inside the secondary battery.
FIG. 5 is a diagram showing changes in temperature, current, and terminal voltage when discharging a lithium secondary battery.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lithium secondary battery 10 Unit cell 11 Outer can 12 Sealing lid 14 Negative terminal 20 Terminal holder 22, 23 Terminal plate 23, 24, 25 Window 26 Discharge terminal plate 27 Charging terminal plate 30 Protective element 31, 32 Conductive plate 33 Temperature element 34 Resin molded parts 35, 36, 37 Lead terminal part

Claims (4)

A chargeable power generating element, a protection element built in a secondary battery including a charging external terminal for charging the power generating element and a discharging external terminal for discharging,
A power generation element side terminal portion connected to the power generation element,
A charging-side terminal connected to the external terminal for charging;
A discharge-side terminal connected to the discharge external terminal;
A current interrupting unit interposed between the power generating element side terminal and the charging side terminal, maintaining a conductive state at a first temperature, and interrupting a current at a second temperature higher than the first temperature;
A protection element comprising: a conductive part made of a conductive material and connecting between the power generation element side terminal and the discharge side terminal. The conductive portion, the power generating element side terminal portion and the discharge side terminal portion are formed by one conductive plate,
The current interrupting portion and the conductive plate,
The protection element according to claim 1, wherein the protection element is fixed to each other. The protection element according to claim 1 is built in,
A power generation element to which the power generation element side terminal is connected,
An external terminal for charging to which the charging side terminal is connected,
A secondary battery comprising: a discharge external terminal to which the discharge side terminal is connected. The charging external terminal and the discharging external terminal,
Held by a holder attached to the power generating element,
The protection element,
The secondary battery according to claim 3, wherein the secondary battery is housed between the holder and the power generation element.

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