JP2005116474A - Film-shaped battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-shaped battery with high safety having a safety valve operating with high precision. <P>SOLUTION: The film-shaped battery provided with a safety valve 40 having a valve body made of resin with a low melting point, formed apart from lead members 21, 22, and heat conduction members 50 connected to the safety valve 40, capable of directly conducting heat generated at a power generating element 10 to the safety valve 40. Namely, heat from the outside of the battery is quickly conducted since the safety valve is arranged at a sealing part of a film-shaped envelope. Further, heat generated at the inside of the power generating element also is quickly conducted to the safety valve by newly arranging heat conduction members effectively conducting the heat generated from the power generating element. As a result, the safety valve can be quickly operated with good precision regardless of whether an abnormal heat source is located inside or outside of the battery. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a film type battery employing a laminate film or the like as an exterior body, and particularly to a highly safe film type battery.

  2. Description of the Related Art A film type battery that employs a film such as a laminate film as a battery outer body for the purpose of improving the energy density of a secondary battery or the like is known. By the way, when some abnormality occurs inside the battery and the temperature inside the battery rises, the pressure rises due to gas generation inside the battery. The film outer package composed of a film is hermetically sealed by sealing the opening of the film, and when the internal pressure of the battery rises, the sealed portion opens in an unpredictable state. It has been conventionally proposed to provide a safety valve for removing (Patent Documents 1 and 2, etc.).

These safety valves are equipped with a valve body made of a low melting point resin. When the temperature inside the battery becomes high, the low melting point resin melts and is caused by opening ahead of other sealing parts. Gas can be safely discharged outside the battery to reduce the internal pressure.
JP 2001-93489 A JP 2001-283800 A

  By the way, the cause of the abnormality of the battery temperature may be not only the case where the battery is heated by an external heat source but also the heat generation (short circuit, overcharge, etc.) from the power generation element of the battery. In that case, it is preferable that the timing at which the safety valve operates is stabilized also depending on the position of the heat source for heating the battery. In particular, since gas generation from the inside of the battery has a high correlation with the temperature inside the battery, it is considered that the safety of the battery can be improved by more accurately controlling the battery temperature at which the safety valve opens.

  This invention is made | formed in view of the said situation, and makes it the subject which should be solved to provide a safer film type battery by operating a safety valve accurately.

  In order to solve the above problems, the present inventors have conducted intensive research. As a result, in the safety valve provided in the sealing portion of the film outer package as disclosed in Patent Documents 1 and 2, the power generation element inside the battery It has been found that there is a difference in the timing at which the safety valve operates between the heat transmitted and the heat transmitted from the outside, and the following invention has been conceived in order to reduce the difference in timing at which the safety valve operates.

That is, the film type battery of the present invention includes a power generation element, a film exterior body for storing the power generation element, a safety valve having a valve body made of a low melting point resin provided at a welded portion of the film exterior body, A lead member that is electrically connected to an element and transmits and receives electric power inside and outside the film outer package,
The safety valve is spaced apart from the lead member;
A heat transfer member connected to the safety valve and capable of directly transferring heat generated from the power generation element to the safety valve is provided.

  That is, since the safety valve is disposed at the sealing portion of the film exterior body, heat from the outside of the battery is quickly transferred. Furthermore, by newly providing a heat transfer member that effectively transfers heat generated from the power generation element inside the battery to the safety valve, heat generated from the inside of the battery is also quickly transferred to the safety valve. As a result, the safety valve can be quickly operated with high accuracy regardless of whether the abnormal heating source is located inside or outside the battery.

  It is also conceivable to employ the lead member as it is as the heat transfer member. However, by disposing the safety valve away from the lead member without contacting the lead member, gas discharge in the battery accompanying the opening of the valve body of the safety valve becomes possible without affecting the lead member, and the safety of the battery is further improved. Get higher. By stabilizing the lead member even when the safety valve is in operation, it is possible to effectively prevent inconveniences such as the occurrence of a secondary short circuit due to the movement of the lead member.

  In addition, it is conceivable that the safety valve is disposed other than the sealing part, but the structure can be simplified by arranging the safety valve in the sealing part, so that the reliability and safety of the battery can be improved and the manufacturing can be easily performed. There is. Therefore, the safety valve is disposed in the sealing portion in a state of being separated from the power generation element and the lead member. In the present specification, “the safety valve is in a state of being separated from the lead member” means that at least a portion of the valve body of the safety valve that opens is not overlapped with a portion of the lead member held by the film exterior body. Means that.

  The heat transfer member can conduct heat to the safety valve via the lead member. By adopting a member that connects between the lead member and the safety valve as the heat transfer member, a battery having a simple structure that can achieve the above effect can be provided. Since the connection between the lead member and the heat transfer member can be performed after the power generation element is completed, the thermal connection between the power generation element and the heat transfer member is easier than when the heat transfer member is connected to other parts of the power generation element. Can be achieved. Both can be easily connected by resistance welding, ultrasonic welding or the like after the power generation element is completed. Power generation elements in film batteries often have a structure in which striped positive and negative electrodes are wound and laminated, or a plurality of plate-like positive and negative electrodes are stacked. In many cases, it is easier to connect a heat transfer member or a safety valve to a lead member after completion of the power generation element than to connect the heat transfer member. In this case, the heat transfer member is preferably made of the same material as the lead member. Since the lead member employs a good conductor, it has excellent heat conductivity, and the heat transfer member is made of the same material as the lead member, thereby preventing electrical corrosion due to contact of different materials.

  Moreover, it is preferable that the temperature increase rate of the valve body due to heat generation from the power generation element is larger than the temperature increase rate of the portion of the lead member that contacts the film exterior body. The rate of temperature rise of the valve body due to heat generation from the power generation element is larger than the rate of temperature rise of the valve body when it is assumed that the lead member is disposed in a portion that contacts the film exterior body. preferable. By adopting a heat transfer member with a fast heating rate of the valve body, it is possible to respond quickly to an abnormality. It should be noted that the slow rate of the temperature rise rate can be controlled by changing the position of the safety valve, changing the length and cross-sectional area of the heat transfer member, changing the material of the heat transfer member, and the like. Regarding the safety valve, the actual slowing rate of the temperature rise rate can be easily confirmed by actually measuring the film type battery or comparing the position of the safety valve with that of the lead member.

  The film type battery of the present invention will be described in detail based on the following embodiments. The film type battery of this embodiment includes a power generation element, a film outer package, a safety valve, and a lead member. Furthermore, other members can be provided as necessary. A plurality of the batteries may be provided for each member. In particular, there may be a plurality of sets of safety valves and heat transfer members even in a general mode.

  Examples of the power generation element include a member for a secondary battery in which a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material are formed to face each other with an electrolyte interposed therebetween. The power generation element can be disposed by alternately laminating a plurality of plate-like positive and negative electrodes via separators, or by winding and winding band-like positive and negative electrodes via band-like separators. The power generation element includes an electrolyte. The electrolyte may be in any form such as liquid or gel. Even if the electrolyte itself is a liquid substance, it is often used with an appropriate solvent. Furthermore, as a power generation element, a member for an electric double layer capacitor having an electrode in which an electrode mixture containing activated carbon having a large specific surface area as an active material is formed on the surface of a current collector can be applied. Therefore, in this specification, “battery” includes the meaning of “electric double layer capacitor”.

  The film exterior body is a member that partitions the inside and outside of the film-type battery in order to store the power generation element. The film outer body regulates the movement of substances between inside and outside the battery. The film outer package forms a sealed portion in which the opening is sealed after the power generation element is wrapped with the film. The width of the sealing portion of the film outer package and the sealing method are not particularly limited, but the sealing is performed with such a strength and width that the sealing portion does not peel off when a normal battery is used. The film can be sealed by heat sealing or bonding with an adhesive. The film constituting the film outer package is desired to be chemically and physically stable in the atmosphere in the film type battery and to have low permeability of the electrolyte contained in the power generation element and the solvent that dissolves the electrolyte. Furthermore, it is preferable that it is excellent in mechanical strength.

  As a preferable film, a laminate film can be adopted. A laminate film is a film in which thin films made of a plurality of types of materials are laminated and integrated. The thin film which comprises a laminate film is selected according to the characteristic requested | required of a film. For example, a metal thin film such as aluminum having a low material permeability is sandwiched by a resin thin film having excellent heat sealability, chemical stability, and mechanical strength. As the resin constituting the resin thin film, a polyolefin resin such as polypropylene (PP) or polyethylene (PE), a polyester resin such as PET, a polyamide resin, an alloy thereof, a copolymer, or the like is used alone or in combination. be able to. In addition, for the purpose of improving heat sealability, a material (modified olefin or the like) modified as necessary may be employed.

  The safety valve has a valve body made of a low melting point resin. The valve body is a member that is provided in a sealing portion of the film exterior body and communicates so that the inside and outside of the film exterior body can be ventilated by opening the valve body. The low melting point resin is a resin that melts at a lower melting point than the material constituting the film outer package. In particular, when the sealing portion of the film outer package is heat-sealed, the resin has a melting point lower than that of the heat-sealed resin. The melting point of the low melting point resin is preferably about 80 ° C to 130 ° C. For example, when PP is adopted as the resin that ensures the heat sealability of the film outer package, PE can be adopted as the low melting point resin. Since this low melting point resin directly contacts the atmosphere inside the film type battery, it is desired that the physical and chemical stability in the atmosphere inside the battery is high.

  All the safety valves are made of a low melting point resin and only the valve body is configured, and a structure in which the valve body is held by a support body that supports the valve body may be employed. As the valve body, a film-like member having a certain area can be adopted. A safety valve can be configured by sandwiching the membrane-like valve body alone or together with the support body in the sealing portion of the film exterior body. When the battery is overheated, gas is generated from the inside, and the valve body is heated to the melting point or higher, the valve body is melted, so the valve body portion of the safety valve is opened by the internal pressure of the battery. The length of the safety valve in the direction in which the sealing portion of the film exterior body divides the inside and outside of the film exterior body is the same as or slightly longer than the width of the sealing portion of the film exterior body and narrows to the sealing portion. It is preferable to make it exposed to the inside and outside of the sealing portion when held.

  The lead member is a member for transferring power to the power generation element from the outside of the film outer package. The lead member is electrically connected to the power generation element, and a part thereof is exposed to the outside of the film exterior body. The lead member is separated from the aforementioned safety valve. The lead member is preferably formed from a metal such as copper or aluminum. The lead member can also be integrated with the power generation element. When the power generation element has a current collector made of metal foil, the current collector can be cut out in the shape of the lead member. The lead member can also be joined to the power generation element by welding or the like. When the lead member is exposed from the sealing portion of the film outer package, the lead member is preferably formed from a foil-like or plate-like member in order to reduce stress concentration on the sealing portion. For example, it may be a strip-shaped member having a cross-sectional area that allows sufficient power transfer.

  The heat transfer member is a member that transfers heat generated from the power generation element to the valve body of the safety valve. The heat transfer member contacts the safety valve. The heat transfer member can also be brought into direct contact with the valve body. The heat transfer member can be in direct contact with the power generation element. Further, the heat transfer member can be connected in the middle of the lead member. In any case, heat generated from the power generation element can be transferred to the safety valve. When directly connecting to the power generation element, it is welded and fixed to a current collector or the like constituting the power generation element, as in the case of the lead member, or is closely attached to the power generation element. When the heat transfer member is connected to the lead member, the heat transfer member can be fixed by welding or brought into close contact. It is preferable to fix the heat transfer member by welding or the like. The heat transfer member is preferably made of the same material as the lead member. The length with which the heat transfer member contacts the safety valve is about 30% to 60%, preferably about 40%, based on the length of the portion where the safety valve is held by the sealing portion. Further, it is about 40% to 70%, preferably about 60%, based on the total length of the safety valve.

  The member that can be provided as necessary is not particularly limited, but is a cylindrical member connected to the outside of the film outer body of the valve body of the safety valve, and the gas discharged from the valve body of the safety valve is supplied to a safe part. Examples of such ducts are as follows.

(Test 1)
-Preparation of test battery A lithium ion secondary battery was adopted as a test battery. 85 parts by mass of lithium nickelate as a positive electrode active material, 10 parts by mass of carbon black as a conductive material, 5 parts by mass of polyvinylidene fluoride (PVDF) as a binder, and mixed in N-pyrrolidone A composite paste was prepared, applied to both surfaces of an aluminum current collector (thickness 15 μm), and dried to form a positive electrode mixture layer having a thickness of 30 μm. After application of the composite paste, the positive electrode sheet provided with a 30 mm × 40 mm rectangle and a protruding portion having a width of 8 mm and a length of 5 mm provided at the end of the short side of the rectangle was formed.

  92.5 parts by mass of graphite as the negative electrode active material, 7.5 parts by mass of PVDF as the binder, and N-pyrrolidone were mixed to prepare a negative electrode mixture paste to obtain a copper current collector (thickness 20 μm) ) On both sides and dried to form a negative electrode mixture layer having a thickness of 40 μm. After application of the composite paste, cutting was performed to form a negative electrode sheet having a 32 mm × 42 mm rectangle and a protruding portion having a width of 8 mm and a length of 5 mm provided at the end of the short side of the rectangle.

  The protrusions of the positive and negative electrode sheets peeled the applied positive and negative electrode mixture layer. Seven of these positive electrode sheets and eight of the negative electrode sheets became negative electrode sheets at both ends, and were stacked alternately so that the respective protrusions overlapped at the same position to obtain a power generation element. A separator made of a PE porous film having a thickness of 25 μm and 34 mm × 44 mm was sandwiched between the positive and negative electrode sheets.

  A positive electrode lead member (5 mm × 40 mm made of aluminum having a thickness of 20 μm) is joined to the protrusions (7 sheets) of the positive electrode sheet of the power generation element by ultrasonic welding, and the negative electrode leads are connected to the protrusions (8 sheets) of the negative electrode sheet. Members (made of copper with a thickness of 30 μm and 5 mm × 40 mm) were joined by resistance welding.

Two laminated films (PET having a thickness of 30 μm) constituting the film outer package so that the tip of the positive and negative electrode lead members protrude 27.5 mm each from the sealing portion of the film outer package. A sheet, a laminate of 40 μm thick aluminum foil, and a 30 μm thick PP sheet; 40 mm × 62 mm) and heat-sealed (applying pressure 0.1 MPa, temperature 190 ° C., 10 seconds) with a width of 5 mm. The film exterior body was sealed by forming a sealing portion. The inside of the film outer package was filled with an electrolytic solution (1 mol / L LiPF ₆ in ethylene carbonate / diethyl carbonate = 3/7 (volume ratio) solution).

  Test batteries 1, 3, and 4 were formed by holding safety valves at various positions of the sealing portion. The safety valve was a 50 μm thick film having a three-layer structure of PP-PE-PP, and was cut into a size of 8 mm × 8 mm. PE also corresponds to a valve body, and PP holding the PE corresponds to a support body. That is, the PP films are bonded by PE, but the PE portion melts and the battery internal pressure rises, so that the PP portion is peeled off and opened. The melting point of PE used here is about 105 ° C to 115 ° C. This safety valve was held in a predetermined position shown in FIG. 1 with one side aligned with the outer edge of the sealing portion of the film outer package. FIG. 1 shows a state in which a part of the film outer package 30 of each test battery is cut away so that the inside can be easily grasped. In addition, the figure in a present Example is a schematic diagram, and the scale of each component, the structure of details, etc. may not be exact. Moreover, in each figure, the same code | symbol is attached | subjected to the related component.

  In the test battery 1, the test battery 1 was disposed on the side of the negative lead member 22 (FIG. 1A). The heat transfer member 50 (30 μm thick copper foil, 5 mm × 15 mm) formed from the same material as the lead member 22 was thermally connected to the negative lead member 22. The heat transfer member 50 and the lead member 22 were formed by resistance welding. The heat transfer member 50 and the safety valve 40 were stacked with a width of 5 mm from the inside of the battery of the safety valve 40. Therefore, the safety valve 40 and the heat transfer member 50 are overlapped by 2 mm at the portion overlapping the sealing portion 31, and the safety valve 40 and the heat transfer member 50 are overlapped by 3 mm at the portion removed from the sealing portion 31 (the safety valve is attached to the sealing portion). 40% based on the length of the sandwiched portion and 62.5% based on the length of the entire safety valve).

The test battery 2 was not provided with a safety valve (FIG. 1 (b)). In the test battery 3, the safety valve 40 is disposed at a substantially central portion of the portion where the positive and negative electrode lead members 21 and 22 are sandwiched by the sealing portion 31 (FIG. 1C). In the test battery 4, the safety valve 40 was disposed so as to overlap the negative electrode lead member 22 and to be sandwiched between the sealing portions 31 (FIG. 1D). Five test batteries were prepared.
Test For each test battery, an overcharge test (SOC was started from 100% and charged continuously with a current of 1A (equivalent to 3C)) and a heating test (in a state where the SOC was 100%, The heating was performed from the starting ambient temperature of 160 ° C. at a temperature rising rate of 5 ° C./min). Each test was performed until the safety valve of the test battery was opened or the sealing part was opened and the gas inside was released, and the temperature of the test battery (near the center of the power generation element) in that case was measured. The test results show the minimum and maximum values for five of each test battery.
-Result: Overcharge test In the test battery 1, the safety valve was activated 330 to 370 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 102 ° C to 110 ° C. The test battery 2 released the internal gas from the unexpected sealing portion in 992 to 1214 seconds after the start of the overcharge test. The temperature of the test battery was 165 ° C to 1750 ° C.

In the test battery 3, the safety valve was activated 621 seconds to 653 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 140 ° C to 145 ° C. In the test battery 4, the safety valve was activated 424 seconds to 448 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 125 ° C to 131 ° C.
Result: Heat test The test battery 1 provided with a heat transfer member that separates the safety valve from the lead member and directly conducts heat generated from the power generation element to the safety valve is 16 minutes 30 seconds to 17 minutes 5 seconds after the start of the heat test. The safety valve was activated and the internal gas was released. The temperature of the test battery was 90 ° C to 93 ° C. The test battery 2 having no safety valve released the internal gas from the unexpected sealing portion at 22 minutes 15 seconds to 23 minutes 20 seconds after the start of the heating test. The temperature of the test battery was 160 ° C.

  Although the safety valve is separated from the lead member, the test battery 3 having no heat transfer member that directly conducts heat generated from the power generation element to the safety valve is 16 minutes 10 seconds to 16 minutes 55 seconds after the start of the heating test. The safety valve was activated and the internal gas was released. The temperature of the test battery was 91 ° C to 93 ° C. In the test battery 4 that conducts heat generated from the power generation element directly to the safety valve through the lead member after the safety valve is brought into contact with the lead member, the safety valve operates 16 minutes 40 seconds to 16 minutes 50 seconds after the start of the heating test. The gas inside was released. The temperature of the test battery was 91 ° C to 93 ° C.

  The following results were found from the results of both tests. The test battery 1 was able to quickly release the internal gas as soon as the safety valve opened in both tests. The temperature of the test battery when the safety valve was opened was also low.

  Test battery 2 took the longest time to release the gas in both tests. This is probably because a safety valve was not provided. In addition, there is a disadvantage that the opening portion of the sealing portion cannot be predicted in advance. Furthermore, in the overcharge test, there was also a test battery that ignited a non-aqueous solvent constituting the electrolytic solution by internal overheating.

  The test batteries 3 and 4 were able to open the safety valve at the test battery temperature and the test battery temperature approximately the same as the test battery 1 in the heating test. This suggests that heat transfer from the outside does not have a significant effect depending on the presence or absence of a heat transfer member. However, in the overcharge test, it takes a longer time than the test battery 1 to open the safety valve, and the test battery temperature when the valve is opened is also high. In the overcharge test, the time until the safety valve of the test battery 3 was opened was longer than that of the test battery 4. Further, the test battery 3 had a higher battery temperature when the valve was opened than the test battery 4. It is considered that this is because the test battery 4 is provided with a safety valve so as to be in contact with the negative lead member, and heat generated from the power generation element due to overcharging is more directly transmitted to the safety valve.

  In the test battery 4, there was a battery in which the lead member of the negative electrode was dropped when a part of the safety valve was opened. The dropout of the lead member in the test battery 4 is considered to be caused by mechanical stress caused by arranging the lead member and the safety valve in an overlapping manner. When the lead member falls off, an unnecessary force is applied to the lead member, and an unnecessary force is applied to the power generation element.

Therefore, it was found that among the test batteries 1 to 4, the test battery 1 can safely release the gas generated inside the battery most quickly in an emergency such as an overcharged state or an overheated state.
(Test 2)
-Preparation of test battery The test battery of this test is almost the same as the test battery 1 except that the amount of overlap between the test battery 1 of test 1 shown in FIG. 2A and the safety valve and the heat transfer member is changed. The test batteries 5 and 6 produced as described above were used. As shown in FIG. 2B, the test battery 5 was obtained by stacking the heat transfer member 50 and the safety valve 40 with a width of 7 mm from the battery inner side of the safety valve 40. Therefore, in the sealing part 31, the safety valve 40 and the heat transfer member 50 are overlapped by 4 mm, and the sealing part 31 is removed and the safety valve 40 and the heat transfer member 50 are overlapped by 3 mm (a part where the safety valve is sandwiched by the sealing part) 80% based on the length of 87.5% based on the length of the entire safety valve). As shown in FIG. 2C, the test battery 6 was obtained by stacking the heat transfer member 50 and the safety valve 40 with a width of 2 mm from the inside of the battery of the safety valve 40. Therefore, there is no portion where the safety valve 40 and the heat transfer member 50 overlap in the sealing portion 31, and the safety valve 40 and the heat transfer member 50 overlap each other by 2 mm after removing the sealing portion 31 (from the end of the sealing portion 31. The end of the thermal member 50 was 1 mm apart; 0% based on the length of the part where the safety valve is held between the sealing parts, and 25% based on the total length of the safety valve).
Test and Results For each test battery, an overcharge test was performed in the same manner as in Test 1. Each test was performed until the safety valve of the test battery was opened or the sealing part was opened, and the temperature of the test battery (near the center of the power generation element) in that case was measured. The test results show the minimum and maximum values for five of each test battery.

  In the test battery 1, the safety valve was activated 330 to 370 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 102 ° C to 110 ° C. In the test battery 5, the safety valve was activated 450 to 475 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 128 ° C to 135 ° C. In the test battery 5, there was a test battery in which the periphery of the safety valve was broken at the same time as the safety valve was opened. A large force was also applied to the negative lead member to which the heat transfer member was connected because the periphery of the safety valve was torn. In the test battery 6, the safety valve was activated 633 to 648 seconds after the start of the overcharge test, and the internal gas was released. The temperature of the test battery was 143 ° C to 146 ° C.

  The following results were found from the test results. Test battery 1 was able to quickly release the internal gas as soon as the safety valve opened. The temperature of the test battery when the safety valve was opened was also low. The test battery 5 took longer than the test battery 1 to reach internal gas release. Therefore, it has been found that there is an appropriate value for the contact area between the safety valve and the heat transfer member, and the quick opening of the safety valve does not proceed even if the contact area is too large. That is, if the contact area is large, the temperature rise rate of the safety valve is slowed down due to heat transfer by the heat transfer member, and the time to reach the melting point of the low melting point resin constituting the valve body becomes longer. In the test battery 1, since the area of the overlapping portion is appropriate, it is considered that the safety valve overlapping with the heat transfer member first melts and the safety valve partially peels off, so that the opening of the safety valve proceeds promptly. This is supported by the fact that, in Test 1, the opening time of the safety valve of the test battery 4 (the lead member passes through the safety valve) is longer than that of the test battery 1. Therefore, it is preferable that the heat transfer member does not penetrate the safety valve and protrude outside the film exterior body. Further, in the test battery 5, as the safety valve was opened, as in the test battery 4, the heat transfer member and the lead member were applied with the tearing around the safety valve.

  In the test battery 6, there are few overlapping portions between the heat transfer member and the safety valve, so that heat generated from the power generation element cannot be quickly conducted to the safety valve, and the time until the valve opens is slower than that of the test electricity 1 and 5. Conceivable. Since the valve opening time is delayed, the temperature of the test battery when the safety valve is opened is also the highest.

  Therefore, it was found that among the test batteries 1, 5 and 6, the test battery 1 can safely release the gas generated inside the battery most quickly in an emergency such as an overcharged state or an overheated state. Furthermore, it has been found that the valve opening timing can be adjusted by adjusting the amount of overlap between the safety valve and the heat transfer member. That is, an appropriate valve opening behavior can be realized by changing the overlapping portion of the safety valve and the heat transfer member.

It is a schematic partial cross section figure of the test battery used in the Example. It is the partially expanded view which showed typically the relationship between the safety valve and heat-transfer member of the test battery used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power generation element 21 ... Positive electrode lead member 22 ... Negative electrode lead member 30 ... Film exterior body 31 ... Sealing part 40 ... Safety valve 50 ... Heat-transfer member

Claims (5)

A power generation element, a film exterior body for storing the power generation element, a safety valve having a valve body made of a low melting point resin provided in a sealing portion of the film exterior body, and electrically connected to the power generation element A film-type battery comprising a lead member for transmitting and receiving electric power inside and outside the film outer package,
The safety valve is spaced apart from the lead member;
A film type battery comprising a heat transfer member connected to the safety valve and capable of directly transferring heat generated from the power generation element to the safety valve.   The film type battery according to claim 1, wherein the heat transfer member conducts heat to the safety valve through the lead member.   The film type battery according to claim 1, wherein the heat transfer member is formed of the same material as the lead member.   The film type battery according to any one of claims 1 to 3, wherein a temperature increase rate of the valve body due to heat generation from the power generation element is larger than a temperature increase rate of a portion of the lead member that contacts the film exterior body.   The heating rate of the valve body due to heat generation from the power generation element is larger than the heating rate of the valve body when it is assumed that the lead member is disposed in a portion in contact with the film exterior body. 4. The film type battery according to any one of 3 above.

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