JP2005044626A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of preventing overcharging or the like by constituting an external insulating plate 7 with a negative temperature characteristic member such as NTC thermistor, without externally fitting an element component of the negative temperature characteristic member outside the battery nor housing it inside a battery vessel for connection. <P>SOLUTION: A part of or the entire external insulating plate 7 for insulating a negative electrode terminal 8 from a lid plate 2 which is a positive electrode terminal, is made of the negative temperature characteristic member such as the NTC thermistor whose resistance value decreases as a temperature rises, so that at over charging, the external insulating plate 7 shorts the positive electrode terminal and the negative electrode terminal 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery that prevents a temperature rise due to overcharging or the like.

  Many chargers for secondary batteries cut off the charging current and automatically terminate charging when the terminal voltage of the secondary battery exceeds the full charge voltage. However, when charging with a charger that does not have a function to detect such full charge, when the full charge detection function of the charger is broken, or when a charger that is not for the battery is used incorrectly The secondary battery may be overcharged. If the secondary battery is overcharged in this manner, the decomposition reaction of the active material and the electrolyte may occur, and the inside of the battery may become abnormally high temperature or high pressure. Especially in the case of a non-aqueous electrolyte secondary battery, this temperature Or pressure increase may be significant.

  Therefore, conventionally, an invention has been made in which a failure due to overcharging is prevented by connecting an NTC thermistor in parallel between the terminals of the battery (see, for example, Patent Document 1). NTC thermistors are NTC (Negative Temperature Coefficient) whose resistance value decreases as temperature rises, that is, a negative temperature characteristic element made of semiconductor ceramics with negative temperature characteristics. The resistance value decreases as this temperature rises. Elements with a particularly large degree are used. Therefore, if the battery is overcharged and the temperature of the battery rises abnormally, the resistance value of the NTC thermistor connected between the terminals is reduced to bypass the charging current. Can be prevented from flowing into. Moreover, in this patent document 1, instead of the NTC thermistor, by using a negative temperature characteristic element in which conductive particles are dispersed in a heat-shrinkable resin or the like, the resistance value at the time of temperature rise is further rapidly reduced, and thereafter There has been proposed an overcharge protection invention in which the resistance value does not increase and return even when the temperature decreases.

  Semiconductor ceramics, resins, and the like that are the negative temperature characteristic elements are connected to the battery as element parts housed in a package. That is, conventionally, the case where the element part of the negative temperature characteristic element is connected to the outside of the battery as a protection circuit, and the case where the element part of the negative temperature characteristic element is stored inside the battery container of the battery and connected internally. was there.

However, in the case where the element part of the negative temperature characteristic element is connected to the outside of the battery, there is a problem that it is necessary for the user to connect the element part when the battery is mounted on the device. In addition, when this element component is connected during battery manufacture, there is a risk that it will be in the way when the battery is installed, or it may be removed carelessly. There was also a problem that it was necessary to do. On the other hand, when the element part of the negative temperature characteristic element is housed inside the battery container of the battery, the battery has a function of overcharge protection alone, so that it is easy to handle and highly versatile. However, even in this case, it is necessary to use an element component that is resistant to the electrolyte, and the capacity density is reduced in order to secure a storage space for the element component in a narrow battery container, and welding or caulking is performed. There has been a problem that the connection work such as the above becomes a fine and troublesome work. Further, when the resistance of the negative temperature characteristic element decreases and a large current flows when the temperature of the battery rises, there is a problem that the temperature of the inside of the battery further increases because this element component generates heat due to Joule heat.
JP 2002-43104 A

  In the present invention, when a negative temperature characteristic element such as an NTC thermistor is connected in parallel to the battery, the element parts such as the NTC thermistor are externally attached to the outside of the battery or are housed and connected inside the battery container. It tries to solve the problem.

  The battery according to claim 1 is characterized in that all or a part of the insulating member that insulates between the positive and negative electrodes is composed of a negative temperature characteristic member that decreases in resistance value when the temperature rises.

  According to the first aspect of the present invention, since the negative temperature characteristic element is used as the insulating member, if the battery temperature rises abnormally due to overcharging or the like, the resistance value of the negative temperature characteristic element decreases and a short circuit current flows. It becomes like this. Then, the charging current is bypassed to the negative temperature characteristic element, thereby preventing an excessive current from flowing into the battery body and causing a decomposition reaction of the active material or the electrolyte, thereby preventing the battery from becoming an abnormally high temperature or high pressure. Will be able to.

  Moreover, since the negative temperature characteristic element is all or part of the insulating member originally used for insulation between the positive and negative electrodes, there is no need to separately connect the negative temperature characteristic element to the outside of the battery. By being integrated with the battery, it is easy to handle and highly versatile. In particular, when the insulating member is an insulating sealing member that also seals between the members, since the insulating member is pressed and disposed between the positive electrode side member and the negative electrode side member, The negative temperature characteristic element can be reliably connected between the positive and negative electrodes only by exposing the portions to the positive electrode side and the negative electrode side.

  In addition, since it is not necessary to separately store and connect the element part of the negative temperature characteristic element inside the battery container, the capacity density is not reduced by the storage space of the element part, and this element part is connected. The troublesome work is no longer necessary. Furthermore, when the insulating member is disposed inside the battery container, a temperature increase inside the battery can be quickly detected and a reliable operation can be performed.

  Hereinafter, the best embodiment of the present invention will be described.

  In the present embodiment, as shown in FIG. 2, a small square nonaqueous electrolyte secondary battery will be described. This non-aqueous electrolyte secondary battery is used as a power source for a mobile phone or the like, and a lid plate 2 made of an aluminum plate is fitted into an opening of a thin box-shaped aluminum battery can 1 and sealed by welding. Thus, the battery container is configured. Inside the battery can 1, the power generation element 3 is accommodated and filled with a non-aqueous electrolyte. The power generation element 3 is obtained by winding a positive electrode 3a and a negative electrode 3b into a long cylindrical shape via a separator 3c. The power generating element 3 is formed by narrowing the width in the opposite direction so that the current collector base material of the positive electrode 3a and the negative electrode 3b wound on the outermost periphery is not overlapped with each other from both ends. Has been pulled out as a lead.

  As shown in FIGS. 1 and 2, the lid plate 2 has a positive current collector connection plate 4 connected and fixed to one end of the back surface facing the inside of the battery can 1, and an internal insulation on the other end side of the back surface. A negative electrode current collector connection plate 6 is disposed through the plate 5. The positive electrode current collector connection plate 4 is formed by bending an aluminum plate into an L-shaped cross section, and one bent piece is directly connected and fixed to the back surface of the lid plate 2 by welding. The negative electrode current collector connection plate 6 is formed by bending a copper plate into an L-shaped cross section, and one bent plate piece is disposed on the back surface of the lid plate 2 via the internal insulating plate 5. Further, as shown in FIG. 1, a negative electrode terminal 8 is disposed at the center of the surface of the lid plate 2 via an external insulating plate 7. The negative electrode terminal 8 has a connection projection 8 a protruding from the center of the back surface of a main body of a rectangular thick plate-shaped iron material that is sufficiently smaller than the cover plate 2. The negative electrode terminal 8 is caulked by passing the connection protrusion 8a through the through holes of the external insulating plate 7, the cover plate 2 and the internal insulating plate 5 and further through the through holes of the negative current collector connecting plate 6. Thus, the outer insulating plate 7, the inner insulating plate 5, and the negative electrode current collector connection plate 6 are fixed to the cover plate 2 together. However, a sleeve 5 a is projected from the surface of the inner insulating plate 5, and this sleeve 5 a is fitted into the through hole of the cover plate 2 and the outer insulating plate 7. Further, the connection protrusion 8a of the negative terminal 8 is fitted into the through hole of the sleeve 5a. Therefore, the back surface of the negative electrode terminal 8 is pressed against the surface of the external insulating plate 7, but the connection protrusion 8 a is only in contact with the inner surface of the through-hole of the sleeve 5 a of the internal insulating plate 5. 6 is connected and fixed.

  The external insulating plate 7 is formed of a rectangular plate-shaped NTC thermistor that is slightly larger than the negative electrode terminal 8. A concave portion for fitting the negative electrode terminal 8 is formed on the surface, and a through hole is formed in the central portion. . The NTC thermistor is a semiconductor ceramic made of an oxide such as nickel, cobalt, or manganese, and the external insulating plate 7 itself can be formed by forming and firing the raw material into a square plate having through holes. . The NTC thermistor of the external insulating plate 7 is a negative temperature characteristic element in which the resistance value between the front and back sides of the rectangular plate shape decreases exponentially as the temperature rises. The internal insulating plate 5 is formed by molding an insulating resin into a square plate shape, and a sleeve 5a and a through hole are formed during this molding.

  The lid plate 2 connects and fixes the positive electrode current collector connection plate 4, and insulates and fixes the negative electrode terminal 8 and the negative electrode current collector connection plate 6 via the external insulating plate 7 and the internal insulating plate 5. As shown, the aluminum foil of the positive electrode 3 a drawn out from the power generation element 3 is welded to the positive electrode current collector connection plate 4, and the copper foil of the negative electrode 3 b drawn from this power generation element 3 is welded to the negative electrode current collector connection plate 6. To do. Then, the power generation element 3 is inserted into the battery can 1 from the opening, and the lid plate 2 is fitted into the opening and the periphery is welded to seal the battery can 1. The non-aqueous electrolyte is injected from a liquid injection port (not shown) formed in the battery can 1 and the cover plate 2, and the liquid injection port is sealed after the liquid injection.

  In the non-aqueous electrolyte secondary battery having the above-described configuration, the positive electrode 3a of the power generation element 3 is connected to the cover plate 2 and the battery can 1 via the positive current collecting connection plate 4, and thus the cover plate 2 and the battery can 1 are connected to each other. It becomes the positive terminal. The negative electrode 3 b is connected to the negative electrode terminal 8 through the negative electrode current collector connection plate 6. At this time, the negative current collector connection plate 6 and the connection protrusion 8 a of the negative electrode terminal 8 are insulated from the lid plate 2 by the internal insulating plate 5. Further, since the outer insulating plate 7 is pressed against the back surface of the negative electrode terminal 8 on the front surface and the front surface of the lid plate 2 serving as the positive electrode terminal is pressed against the back surface, the negative electrode terminal 8 and the lid plate 2 serving as the positive electrode terminal It becomes the structure connected between.

  Here, if the non-aqueous electrolyte secondary battery is normally repeatedly charged and discharged, the temperature of the external insulating plate 7 in close contact with the cover plate 2 will not rise abnormally. The plate 7 functions as a high resistance insulator. However, when the temperature of the power generating element 3 or the like rises abnormally due to overcharging, the external insulating plate 7 also becomes an abnormally high temperature via the cover plate 2 or the negative electrode terminal 8. It decreases and functions as a conductor. Therefore, when overcharge occurs, the charging current flowing from the battery can 1 or the cover plate 2 that is the positive electrode terminal is short-circuited by the external insulating plate 7 and flows out from the negative electrode terminal 8. By being supplied, it is possible to prevent the inside of the battery container from becoming abnormally high temperature or high pressure. In addition, since the charging current flows as a short-circuit current in the external insulating plate 7 during this overcharge, the external insulating plate 7 also generates heat. However, since the external insulating plate 7 is disposed on the surface of the lid plate 2, that is, outside the battery container, the generated heat can be smoothly released to the outside.

  As a result, the non-aqueous electrolyte secondary battery of the present embodiment is configured such that the external insulating plate 7 for originally performing insulation between the negative electrode terminal 8 and the cover plate 2 that is the positive electrode terminal is configured by an NTC thermistor. Thus, there is no need to connect the NTC thermistor element part to the non-aqueous electrolyte secondary battery, and there is no risk that the user will not have to perform connection work or that the element part will be inadvertently removed. In addition, it is not necessary to store the nonaqueous electrolyte secondary battery in a resin package or the like together with the element parts of the NTC thermistor connected to the outside to form a battery pack. Further, since it is not necessary to house and connect the element parts of the NTC thermistor inside the battery container, the battery capacity is not reduced by being occupied by the storage space of the element parts. Thus, the troublesome work for connecting to the positive electrode 3a and the negative electrode 3b is not required.

  In the above embodiment, when the non-aqueous electrolyte secondary battery is normally charged and discharged and used, the NTC thermistor of the external insulating plate 7 functions as an insulator, and becomes abnormally hot due to overcharging. The case of functioning as a conductor is shown. However, the insulator here may be any material that has a sufficiently high resistance in practical use. For example, a current of about several μA that is always consumed by the protection circuit IC of the nonaqueous electrolyte secondary battery flows. May be. Moreover, the conductor here should just have a low resistance practically enough, for example, should just flow the electric current more than 3 times (3 ItA) of battery capacity. Furthermore, it is ideal that the state of the insulator and the state of the conductor change suddenly at a specific temperature, but actually, the resistance value decreases exponentially as the temperature rises. Only. Therefore, by using an NTC thermistor with a resistance reduction rate as large as possible, wasteful power consumption in the external insulating plate 7 is reduced when the nonaqueous electrolyte secondary battery is normal, and the external insulating plate 7 can be used as much as possible when overcharging. It is preferable that a large short-circuit current flows.

  Moreover, although the case where the external insulating plate 7 is composed of an NTC thermistor has been described in the above embodiment, any other element can be used as long as it is a negative temperature characteristic element whose resistance value decreases as the temperature rises. An example of such a negative temperature characteristic element is CTR (Critical Temperature Resistance). This CTR is a negative temperature characteristic element having an excellent characteristic that its resistance value decreases abruptly when it rises above a specific temperature. However, the CTR is not sufficiently put into practical use by the current technology.

  In addition, as the negative temperature characteristic element as described above, it is possible to use a device in which a conductive material such as a metal wire or carbon is dispersed inside a resin having heat shrinkability. In this element, the conductive material is normally separated by resin etc. to become an insulating material, but when the temperature rises abnormally, the heat shrinkable resin etc. contracts, so the internal conductive material is pressed and brought into contact with each other As a result, the entire device becomes conductive. Therefore, this element also has an excellent negative temperature characteristic in which the resistance value decreases extremely rapidly. Moreover, once the temperature rises abnormally, the conductivity is maintained even if the temperature is lowered thereafter, so that the charging current bypassed by the negative temperature characteristic element can be prevented from being supplied to the power generation element 3 again. it can.

  Furthermore, the present invention is not limited to the negative temperature characteristic element as described above, and any negative temperature characteristic member whose resistance value decreases as the temperature rises may be used. Therefore, the bimetal switch 9 having a mechanical structure as shown in FIG. 3 is used. You can also. The bimetal switch 9 is a switch that closes the circuit when the temperature rises abnormally and the bimetal 9a is displaced and reversed and the movable contact 9b is pressed against the fixed contact 9c. The conventional bimetal switch used for the overcharge protection circuit of a battery shuts off the charging current when the temperature rises abnormally and the bimetal displaces and the contact opens, so the charging current is cut off and the temperature drops. Since the contact closes again and repeats ON / OFF, the contact may be deteriorated. However, when the bimetal switch 9 as shown in FIG. 3 is used, the contacts 9b and 9c are closed and the charging current flows through the bimetal 9a, so that heat is generated, so that the short circuit state can be maintained. In such a bimetal switch 9, for example, the external insulating plate 7 can be configured by arranging the terminals such that the movable contact 9 b is connected to the cover plate 2 and the fixed contact 9 c is connected to the negative terminal 8. Further, a temperature-sensitive reed switch can be used in place of the bimetal switch 9. The temperature-sensitive reed switch is a switch that closes the contact point with a magnet by losing magnetism when the magnetic material reaches or exceeds the Curie point temperature.

  Moreover, although the case where all the external insulating plates 7 were comprised with negative temperature characteristic members, such as NTC thermistor, was shown in the said embodiment, a part of this external insulating plate 7 can also be comprised with a negative temperature characteristic member. . For example, a negative temperature characteristic member may be embedded in a part of an insulator such as resin or rubber to form the external insulating plate 7. In addition, a conductor serving as an electrode may be appropriately connected to the negative temperature characteristic member embedded in a part of the external insulating plate 7 as described above.

  Moreover, in the said embodiment, although the case where all or one part of the external insulating board 7 was comprised with negative temperature characteristic members, such as NTC thermistor, was shown, all or one part of the internal insulating board 5 is comprised with a negative temperature characteristic member. You can also Furthermore, instead of such an insulating plate, for example, all or a part of an insulating member that insulates between positive and negative electrodes, such as the separator 3c of the power generation element 3, may be configured by a negative temperature characteristic member. In particular, if a flexible sheet-like negative temperature characteristic element can be produced, it can be used for any insulating member. In addition, when used for an insulating member disposed inside the battery container, such as the internal insulating plate 5 or the separator 3c, the temperature of the negative temperature characteristic member immediately increases due to heat generated during overcharge. Detection is quick and reliable operation can be performed.

  Moreover, in the said embodiment, although the cover plate 2 became a positive electrode terminal and the non-aqueous electrolyte secondary battery of the terminal structure which attaches the negative electrode terminal 8 via the internal insulating board 5 or the external insulating board 7 here was demonstrated, this terminal The structure is arbitrary. Furthermore, in the above embodiment, the non-aqueous electrolyte secondary battery has been described. However, the present invention can also be implemented with other secondary batteries, and in order to prevent the risk of erroneous charging even in the case of a primary battery. Can be implemented as well.

  By constituting all or part of the insulating member for insulating between the positive and negative electrodes with a negative temperature characteristic member such as an NTC thermistor, the present invention can be applied to a battery that can prevent overcharge and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an assembled perspective view showing a configuration of a lid plate portion of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an assembled perspective view for illustrating a structure of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram illustrating an equivalent circuit when an NTC thermistor is used as an external insulating plate of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

Explanation of symbols

2 Lid plate 3 Power generation element 3a Positive electrode 3b Negative electrode 3c Separator 4 Positive current collector connection plate 5 Internal insulation plate 6 Negative current collection connection plate 7 External insulation plate 8 Negative electrode terminal

Claims (1)

  A battery characterized in that all or part of an insulating member that insulates between positive and negative electrodes is composed of a negative temperature characteristic member whose resistance value decreases as the temperature rises.

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