JPH10162805A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance safety of a battery by connecting current collecting terminals of one polarity and external terminals of one polarity in a plurality in series to each other, and connecting them through PTC elements having a positive temperature characteristic arranged in a place where calking pressure is not applied at battery manufacturing time in a lithium secondary battery. SOLUTION: One surface where PTC elements 1 are superposed by two sheets and are electrically connected in series to each other and a positive electrode current collecting terminal 2 derived from a positive electrode current collecting body, are electrically contacted with each other, and another one surface of the PTC elements 1 and a positive electrode external terminal 4 are electrically contacted with each other. At this time, the PTC elements 1 are arranged between a positive electrode cap 5, the positive electrode external terminal 4 and a power generation element 3, and pressure by a calking process at battery sealing time is avoided, and a hindrance to expansion at high temperature time is prevented. Therefore, a resistance characteristic to cope with characteristic dispersion of the PTC elements and a high temperature at discharging a battery is compensated, and reduction in safety of the battery can be restrained without impairing a function of breaking an electric current and of restraining an electric current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a battery in which a C element functions as a current interrupting mechanism or a current suppressing mechanism.

[0002]

2. Description of the Related Art PTC (Positive Temperature Coeffici)
ent) A typical example of a battery having an element is a lithium secondary battery. This type of battery has a battery container 7 as disclosed in JP-A-6-187970 for the purpose of improving safety.
A PTC element is installed in a positive electrode cap 5 that seals the PTC. The positive electrode current collecting terminal and the positive electrode external terminal 4 (a member referred to as a positive electrode terminal from the appearance of the battery) derived from the power generating element are:
They are electrically connected via PTC elements (FIG. 3).
A PTC element is a type of thermistor whose electric resistance increases with a rise in temperature. In the above lithium secondary battery,
A PTC element in which a resin molded product studded with a conductive material such as carbon is sandwiched between metal foils is usually used.
This type of PTC element expands due to self-heating when a large current flows, and reduces the contact area between the conductive materials, thereby increasing its electrical resistance. Therefore, with the configuration of FIG. 3, when the battery temperature rises, the current is cut off or the current is limited, and the battery can be prevented from being charged or discharged with a current larger than a predetermined value.

[0003]

SUMMARY OF THE INVENTION However, PTC
A first problem in using the element is that the PTC element itself has large variations in characteristics. When a PTC element deviating from predetermined characteristics is incorporated in a battery, the electric resistance of the PTC element does not increase even if the battery temperature increases, and the safety of the battery cannot be maintained. The second problem is that when a PTC element of a resin molded body studded with a conductive agent is installed in the positive electrode cap 5 as in the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-187970, the PTC element is not sealed during battery sealing (caulking). (During the process). When the resin molded body studded with the conductive agent is pressed, even if the temperature rises, it does not self-expand, the electrical resistance does not increase, and the original function cannot be exhibited when the battery is used. In particular, lithium secondary batteries use organic electrolytes with low ionic conductivity, so they tend to generate heat when charged or discharged at a large current density,
To cut off or limit the current at that time, PTC
The element is currently considered an indispensable member. Therefore, at present, it can be said that the battery has the above-described problems most. A first problem to be solved by the present invention is to suppress a decrease in the safety of a battery even if it has the first problem, that is, a problem that the characteristics of the PTC element vary.
The second problem to be solved by the present invention is to solve the first problem, and to solve the second problem, that is, the battery molded by pressing the resin molded body PTC element studded with the conductive agent. The purpose is to suppress a decrease in safety.

[0004]

In order to solve the above-mentioned first problem, a battery according to the present invention comprises a current collecting terminal having one polarity derived from a power generating element 3 and an external terminal having the one polarity connected to a P terminal.
The PTC element 1 is electrically connected via the TC element 1, and two or more PTC elements 1 are electrically connected in series. Alternatively, each of the positive and negative current collecting terminals derived from the power generating element 3 and each of the positive and negative external terminals are P
It is characterized by being electrically connected via the TC element 1. The PTC element 1 may be in a state of being connected in series to two or more polarities of one polarity. By adopting the above configuration, even when one PTC element deviates from a predetermined characteristic, another PTC element can be expected to function.

In order to solve the second problem, in addition to the above-described structure, in a sealed battery employing caulking as a sealing means, the PTC element 1 is placed in the battery container 7 and at a location which is not subjected to pressure during caulking. To exist. The portion that is not subjected to pressure during crimping is, for example, a portion other than the inside of the positive electrode cap 5 in FIG. As shown in FIG. 3, the positive electrode cap 5 is fixed by caulking the upper edge of the battery container 7,
A member that seals the battery container 7. In the caulking process, the gasket 6 is interposed between the upper edge of the battery container 7 and the periphery of the positive electrode cap 5.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention is a lithium secondary battery.
This will be described below with reference to the drawings using a secondary battery as an example. FIG.
FIG. 1 is a sectional view of a main part of a battery according to an example of the present invention. Battery case 7
Inside, LiCoO _TwoMade of positive electrode, lithium electrochemical
An anode composed of a carbon material that can be stored and released
An electric element 3 is provided. Organic electrolyte is propylene
Carbonate, dimethyl carbonate and diethyl carbonate
Are mixed at a predetermined ratio, and a concentration of 1 mol / l
With LiPF₆Are dissolved. From the positive electrode current collector
The derived positive electrode current collector terminal 2 has a flat cylindrical shape shown in FIG.
PTC element 1 (manufactured by Raychem Corporation, trade name: PTC device)
ISIS, Model PSR-22992)
In electrical contact with one side of the
And the other surface of the PTC element 1 and the positive terminal 4
And are in electrical contact. Gasket 6 is made of polypropylene
And a positive electrode cap through the opening of the battery container 7
The battery is hermetically sealed by caulking the battery. Used in this example
The PTC element 1 used is made of resin studded with carbon.
It is a shape. This is 3.3A at 0 ° C and 20 ° C
2.7A, 1.6A current at 60 ° C
And begin to limit the current. Derived from power generation element 3
The positive electrode current collecting terminal 2 and the positive electrode external terminal 4
In a battery electrically connected via
As described above, two PTC elements 1 are electrically connected in series.
A continuous state can be realized.

In the configuration shown in FIG. 1, the PTC element 1 is disposed inside the battery container 7 and other than inside the positive electrode cap 5. Specifically, the PTC element 1 is disposed between the positive electrode cap 5 and the positive electrode external terminal 4 and the power generation element 3. As a result, pressure of the PTC element 1 during the caulking step for sealing the battery can be avoided, and when a large current flows through the PTC element, the PTC element expands due to self-heating, and the contact area between the conductive materials decreases. It is possible to maintain the function of increasing the electric resistance and suppressing the transient current from flowing into the battery (charging and discharging with a large current). Therefore, it is possible to suppress a decrease in the safety of the battery.

In this example, the battery has an organic electrolyte and the PT
Since the C element 1 is a resin studded with a conductive agent, it is desirable that the resin is resistant to an electrolytic solution. If the organic electrolyte dissolves the resin, P
The conductive material constituting the TC element 1 may enter the power generating element 3 and short-circuit the battery. In addition, the resin dissolved in the organic electrolytic solution may decrease the ionic conductivity of the electrolytic solution, and may deteriorate battery performance. PTC element 1
When it is difficult to make the resin constituting the electrolyte resistant,
It is also an effective means to coat the PTC element 1 with an electrolyte-resistant material while maintaining the electrical connection between the positive electrode current collecting terminal 2, the PTC element 1, and the positive electrode external terminal 4. In this example, the side surface (peripheral surface) of the PTC element is covered by means such as injection molding of a material such as polypropylene that does not dissolve in the electrolytic solution having the above-described composition (not shown), and the positive current collecting terminal 2 and the positive external terminal 4 are formed. PTC element 1 electrically connected to PTC element 1
The surface was covered with a metal foil or the like. An oxidation resistant material such as aluminum can be suitably used for the metal foil. In this example, the plane portion of the PTC element 1 is covered with an aluminum foil. Means for coating the aluminum foil include vapor deposition and pressure bonding.

Contact, pressure welding, welding, and the like can be suitably selected as means for electrically connecting the positive electrode current collecting terminal 2, the PTC element 1, and the positive electrode external terminal 4. When welding is selected, it is considered preferable to arrange a metal foil or the like on the surface of the PTC element 1 in order to improve welding strength. In addition, contact or the like can be suitably used as an electrical connection means between the PTC elements 1. As an example of the means for maintaining the contact, mechanical holding means or the like, such as covering the side surface of the PTC element 1 by injection molding of a material such as polypropylene as described above, can be considered.

In this embodiment, a flat cylindrical insulating member (insulator 8) made of polypropylene is used as the power generating element 3.
And the positive electrode current collecting terminal 2. Insulator 8
Has a function of avoiding contact between the positive current collecting terminal 2 and the negative electrode in the power generating element 3, and by adjusting the thickness thereof, the positive current collecting terminal 2, the PTC element 1, the positive external terminal 4, and the PT
There is a function to improve the electrical contact between the C elements. In this example, by adjusting the thickness of the insulator 8, the positive electrode current collecting terminal 2, the PTC element 1, the positive electrode external terminal 4, and the electrical connection between the PTC elements were realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lithium secondary battery (Example) shown in FIG. 1 and the lithium secondary battery manufactured under the same conditions as those of the Example except that the conventional structure shown in FIG. Each of the 10 secondary batteries was manufactured, and 2
C was subjected to a continuous overcharge test. Ambient temperature is 20 ℃ ± 5
° C. Table 1 shows the number of explosions of the battery after one hour of the overcharge test.

[0012]

[Table 1]

As is apparent from Table 1, the PTC element did not operate properly in the conventional battery and the battery sometimes exploded. On the other hand, in the battery of the embodiment, two PTC elements were used. Therefore, even if one PTC element does not operate normally, the other PTC element operates normally,
It is probable that the battery did not explode.

In this embodiment, a lithium secondary battery is used. However, the present invention can be applied to other battery systems such as an alkaline storage battery and a dry battery. In this embodiment, the members electrically connected to the PTC element are the positive current collecting terminal and the positive external terminal, but may be the negative current collecting terminal and the negative external terminal. Also,
The present invention may be applied to each of the positive and negative current collecting terminals and each of the positive and negative external terminals. When applied to each of the positive / negative current collecting terminals and the positive / negative external terminals, two or more PTC elements may be connected in series for at least one polarity. In this embodiment, the PTC element is made of resin in which carbon is studded, but it goes without saying that the same effect can be obtained by using another PTC element.

[0015]

According to the present invention, even if there is a problem that the characteristics of the PTC element vary, the reduction in the safety of the battery is suppressed, and further, a resin molded article PTC studded with a conductive agent is provided.
It was possible to suppress a decrease in the safety of the battery due to the compression of the element.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a battery according to an example of the present invention.

FIG. 2 is a perspective view of an example of a PTC element according to the present invention.

FIG. 3 is a cross-sectional view of a conventional battery.

[Explanation of symbols]

 1. 1. PTC element 2. Positive electrode collecting terminal Power generation element 4. Positive external terminal 5. Positive electrode cap 6. Gasket 7. Battery container 8. Insulator

Claims (7)

[Claims] 1. A battery in which a current collecting terminal of at least one polarity derived from a power generating element and an external terminal of the same polarity are electrically connected via a PTC element, wherein the number of the PTC elements is two or more. A battery characterized by being electrically connected in series. 2. A battery, wherein each of positive and negative current collecting terminals derived from a power generating element and each of positive and negative external terminals are electrically connected via a PTC element. 3. The battery according to claim 2, wherein two or more PTC elements for at least one polarity are connected in series. 4. The battery according to claim 1, wherein the battery is a lithium secondary battery having an organic electrolyte. 5. The battery according to claim 4, wherein the PTC element is obtained by mixing a conductive material into a resin. 6. A battery according to claim 5, wherein the PTC element is located at a place where the pressure is not applied during caulking in a sealed battery employing caulking as a means for sealing the battery container. 7. The battery according to claim 5, wherein the PTC element is configured not to contact the organic electrolyte.