JP2007184138A - Current control mechanism and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current control mechanism which can be miniaturized into a foil. <P>SOLUTION: Connecting plates 9a and 9b are arranged opposite to each other. In the gap between the opposite connecting plates, an insulating sheet 8a made of an insulating material is arranged at the inner circumferential side, and an insulating sheet 8b is arranged at the outer circumferential side. Solder 7 serving as a conductive member melting at a given temperature is arranged to be sandwiched between the insulating sheets 8a and 8b in the gap between the opposite connecting plates. The solder 7 is made of a material that can hardly be alloyed with a conductive member contained in at least either of the connecting plates 9a and 9b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a current control mechanism that controls a current when a battery generates abnormal heat, and a battery including the current control mechanism.

  In recent years, portable electronic devices such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistants) have become widespread, and lithium ion batteries having advantages such as high voltage, high energy density, and light weight have been widely used as power sources.

  Further, as a countermeasure against liquid leakage that becomes a problem when using a liquid electrolyte, for example, an electrolyte that uses a gel polymer film in which a polymer is impregnated with a non-aqueous electrolyte, or an all-solid electrolyte A lithium ion polymer secondary battery using an electrolyte has been put into practical use.

  Lithium ion batteries and lithium ion polymer secondary batteries may rupture or ignite due to abnormal heat generation of the battery. Therefore, these batteries are provided with a current control mechanism for reducing the current load when the battery abnormally generates heat in order to prevent bursting and ignition. The battery current control mechanism is normally a PTC element (Positive Temperature Coefficient). When the battery temperature rises higher than the set temperature, the electrical resistance increases rapidly, and the current flowing through the battery is reduced. Substantially cut off.

  However, since the PTC element itself has a large resistance even when the temperature is lower than the set temperature, the battery characteristics are deteriorated. As a method for solving this problem, during normal use, the resistance value is lower than that of the PTC element, and when the battery temperature exceeds a predetermined temperature, the low melting point alloy provided in the current path is melted to cause the current to flow. A current interrupting mechanism for interrupting is described in Patent Document 1 below.

Japanese Patent Laid-Open No. 10-233233

  However, the current interrupt mechanism described above controls the current by fusing like a fuse when an excessive current flows, and the shape and dimensions are determined according to the allowable amount of current. However, there is a problem that the shape and dimensions cannot be determined freely, for example, it is made thin like a foil shape, and there are restrictions on the location and space in the battery.

  Accordingly, an object of the present invention is to provide a current control mechanism and a battery that can be miniaturized like a foil shape, regardless of the shape, size, space, and location of the battery.

  In order to solve the above-described problems, the first invention includes a first connection plate and a second connection plate, and a first connection plate and a second connection plate, which are made of a conductive material arranged to face each other. And an insulating member made of an insulating material and disposed so as to be sandwiched between insulating materials in the opposing gap and melted at a predetermined temperature. The current control mechanism is characterized in that at least one of the first connection plate and the second connection plate is difficult to alloy with the conductive member.

  Further, the second invention is a battery having a battery element housed in a battery can and a current control mechanism, wherein the current control mechanism has an opening in the central portion and is disposed to face each other, at least one of which is The first connecting plate and the second connecting plate made of a conductive material that are difficult to be alloyed, and the inner and outer peripheral sides of the opposing gaps of the first connecting plate and the second connecting plate are insulated. A battery comprising: an insulating member made of a conductive material; and a conductive member that is disposed so as to be sandwiched between insulating materials in a facing gap and melts at a predetermined temperature. Here, “difficult” for alloying means that the alloy is practically hardly alloyed. Specifically, in the alloy phase diagram with solder materials such as tin, lead, copper, indium and bismuth, there is no phase / region alloying in a region exceeding 1%.

  As described above, in the first and second inventions, the conductive member that melts at a predetermined temperature is disposed in the opposing gap between the first connection plate and the second connection plate, and the first connection plate Since at least one of the second connecting plate and the second connecting plate is difficult to be alloyed with the conductive member, the contact area between the connecting plate and the conductive member decreases due to the surface tension of the conductive member during heat generation. The resistance value between them can be increased.

  In this invention, since the current control mechanism is manufactured using a thin-film material, the size and size of the foil can be reduced without being restricted by the shape and size of the battery, the space, and the location in the battery. There is an effect that can be done.

  An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a lithium ion secondary battery to which the present invention is applied. This secondary battery is a so-called cylindrical type, and a strip-like positive electrode 11 and a negative electrode 12 are wound inside a substantially hollow cylindrical battery can 1 via a separator 15 (15a, 15b). The battery element 10 is included. The battery can 1 is made of, for example, iron plated with nickel, and has one end closed and the other end open. Inside the battery can 1, a pair of insulating plates 2 a and 2 b are arranged perpendicular to the winding peripheral surface so as to sandwich the battery element 10.

  Examples of the material of the battery can 1 include iron (Fe), nickel (Ni), stainless steel (SUS), aluminum (Al), titanium (Ti), and the like. The battery can 1 may be plated in order to prevent corrosion due to the electrochemical non-aqueous electrolyte accompanying charging / discharging of the battery. A positive terminal plate 3 and a safety valve mechanism 4 and a current control mechanism 5 provided inside the positive terminal plate 3 are attached to the open end of the battery can 1 by caulking through an insulating sealing gasket 6. It has been.

  The positive electrode terminal plate 3 is made of, for example, the same material as that of the battery can 1. The safety valve mechanism 4 is electrically connected to the positive electrode terminal plate 3 via the current control mechanism 5, and the positive electrode terminal plate 3 and the battery element 10 are electrically connected. When the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating, the disk plate 4a is reversed to disconnect the electrical connection between the positive electrode terminal plate 3 and the battery element 10. . When the temperature rises, the current control mechanism 5 limits the current by increasing the resistance value and prevents abnormal heat generation due to an excessive current. The insulating sealing gasket 6 is made of, for example, an insulating material, and the surface is coated with asphalt.

  The battery element 10 is wound around the center pin 16. A positive electrode terminal 13 is connected to the positive electrode 11 of the battery element 10, and a negative electrode terminal 14 is connected to the negative electrode 12. The positive electrode terminal 13 is electrically connected to the positive electrode terminal plate 3 by being welded to the safety valve mechanism 4, and the negative electrode terminal 14 is welded and electrically connected to the battery can 1.

  Hereinafter, the configuration of the battery element 10 accommodated in the battery can 1 will be described.

[Positive electrode]
In the positive electrode 11, a positive electrode active material layer 11 a containing a positive electrode active material is formed on both surfaces of a positive electrode current collector 11 b. The positive electrode current collector 11b is made of, for example, a metal foil such as an aluminum (Al) foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 11a includes, for example, a positive electrode active material, a conductive agent, and a binder. The positive electrode active material, the conductive agent, the binder, and the solvent only need to be uniformly dispersed, and the mixing ratio is not limited.

As the positive electrode active material, a known positive electrode active material that can be doped / dedoped with lithium ions can be used. Depending on the type of the target battery, a metal oxide, a metal sulfide, or a specific polymer can be used. Can be used. For example, metal sulfides or metal oxides not containing lithium, such as TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ , Li _x MO ₂ or Li _x M ₂ O ₄ (wherein M is one or more types) X is different depending on the charge / discharge state of the battery, and is generally 0.05 ≦ x ≦ 1.10.) A lithium composite oxide or an intercalation compound containing lithium is mainly used. As a transition metal constituting these, at least one selected from cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), aluminum (Al), vanadium (V), and titanium (Ti) is selected. Is done.

Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiNi _y Co _1-y O ₂ (where x and y vary depending on the charge / discharge state of the battery, and generally 0 <x ≦ 1. 2, 0.7 <z <1.02.) Or LiMn ₂ O ₄ or the like. Such a lithium composite oxide is a particularly preferable material because it can generate a high voltage when used as a positive electrode active material and has an excellent energy density.

Li _a MX _b (wherein, M is one selected from the above transition metals, X is selected from S, Se, and PO ₄ , and a and b are integers) can also be used. .

  Note that, as the positive electrode active material, a plurality of the above-described positive electrode active materials can be mixed and used.

  The conductive agent is not particularly limited as long as an appropriate amount can be mixed with the positive electrode active material to impart conductivity, and for example, a carbon material such as carbon black or graphite is used. As the binder, a known binder that is usually used in a positive electrode mixture of this type of battery can be used, and preferably polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, etc. A fluorine resin is used. The solvent is not particularly limited as long as it is inert to the electrode material and can dissolve the binder, and any of inorganic solvents and organic solvents can be used. Methyl-2-pyrrolidone (NMP) or the like is used.

  The above-mentioned positive electrode active material, binder, and conductive agent are uniformly mixed to form a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent and, if necessary, in a slurry state by a ball mill, a sand mill, a twin-screw kneader, etc. To. Next, this slurry is uniformly applied to both surfaces of the positive electrode current collector by a doctor blade method or the like. Furthermore, the positive electrode active material layer is formed by drying at a high temperature and removing the solvent.

  The coating apparatus is not particularly limited, and slide coating, extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, micro gravure, rod coater, blade coater and the like can be used. Also, the drying method is not particularly limited, but standing drying, blower dryer, hot air dryer, infrared heater, far infrared heater, and the like can be used.

  One positive electrode terminal 13 connected by spot welding or ultrasonic welding is welded to one end of the positive electrode 11. The positive electrode terminal 13 is preferably a metal foil or mesh-like one, but there is no problem even if it is not a metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material of the positive electrode terminal 13 include Al. The positive electrode terminal 13 is welded to the exposed portion of the positive electrode current collector provided at the end of the positive electrode 11.

[Negative electrode]
The negative electrode 12 is obtained by forming a negative electrode active material layer 12a containing a negative electrode active material on both surfaces of a negative electrode current collector 12b. The negative electrode current collector 12b is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 12a includes, for example, a negative electrode active material, a conductive agent if necessary, and a binder. The mixing ratio of the negative electrode active material, the conductive agent, the binder, and the solvent is not limited as in the positive electrode active material.

  As the negative electrode active material, a carbon material, crystalline, or amorphous metal oxide that can be doped / undoped with lithium is used. Specifically, examples of the carbon material that can be doped / dedoped with lithium include graphite, non-graphitizable carbon material, graphitizable carbon material, and highly crystalline carbon material with a developed crystal structure. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature. Baked and carbonized), carbon materials such as carbon fiber and activated carbon, polymers such as polyacetylene, and the like can be used.

As another negative electrode active material, a metal capable of forming an alloy with lithium, or an alloy compound of such a metal can be given. Specifically, the alloy compound referred to here is M _p M ′ _q Li _r (where M ′ is 1 other than the Li element and the M element), where M is a metal element capable of forming an alloy with lithium. And p is a value greater than 0, and q and r are values greater than or equal to 0). Further, in the present invention, elements such as B, Si, As and the like, which are semiconductor elements, are also included in the metal element, specifically, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga). , Indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn) , Hafnium (Hf), zirconium (Zr), yttrium (Y) and their alloy compounds, for example, Li-Al, Li-Al-M (where M is a group 2A, 3B, 4B) It consists of one or more transition metal elements.), AlSb, CuMgSb and the like.

Among the elements described above, it is preferable to use a group 3B typical element as an element capable of forming an alloy with lithium. Among them, it is preferable to use an element such as Si or Sn or an alloy thereof, and Si or Si alloy is particularly preferable. Specifically, the Si alloy or the Sn alloy is a compound represented by M _x Si, M _x Sn (wherein M is one or more metal elements excluding Si or Sn), specifically, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi _{2 and the} like.

Furthermore, a 4B group compound excluding carbon containing one or more nonmetallic elements can also be used as the negative electrode material of the present invention. Two or more types of 4B group elements may be contained in the negative electrode material. Moreover, metal elements other than the 4B group containing lithium may be contained. For example, SiC, Si ₃ N ₄ , Si ₂ N ₂ O, Ge ₂ N ₂ O, SiO _x (0 <x ≦ 2), SNO _x (0 <x ≦ 2), LiSiO, LiSNO, and the like.

  As the binder, for example, polyvinylidene fluoride, styrene butadiene rubber or the like is used. Examples of the solvent include N-methyl-2-pyrrolidone and methyl ethyl ketone.

  The above-described negative electrode active material, binder, and conductive agent are uniformly mixed to form a negative electrode mixture, which is dispersed in a solvent to form a slurry. At this time, a ball mill, a sand mill, a biaxial kneader or the like may be used as in the case of the positive electrode mixture. Next, this slurry is uniformly applied to both surfaces of the negative electrode current collector by a doctor blade method or the like. Furthermore, the negative electrode active material layer is formed by drying at a high temperature and removing the solvent.

  One end of the negative electrode 12 has one negative terminal 14 connected by spot welding or ultrasonic welding. The negative electrode terminal 14 is electrochemically and chemically stable, and there is no problem even if it is not a metal as long as it can conduct electricity. Examples of the material of the negative electrode terminal 14 include copper and nickel. Similarly to the positive electrode terminal welded portion, the negative electrode terminal 14 is welded to the exposed portion of the negative electrode current collector provided at the end of the negative electrode 12.

[Electrolytes]
As the electrolyte, any of a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, a solid electrolyte containing an electrolyte salt, and a gel electrolyte in which an organic polymer is impregnated with a nonaqueous solvent and an electrolyte salt are used. Can do.

  The nonaqueous electrolytic solution is prepared by appropriately combining a nonaqueous solvent and an electrolyte salt, and any organic solvent can be used as long as it is a material generally used for this type of battery. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, acetic acid ester, tangled acid ester or propionic acid ester are preferred. Among these, Any one kind or a mixture of two or more kinds can be used.

As the electrolyte salt, one that dissolves in the non-aqueous solvent is used, and a combination of a cation and an anion is used. Alkali metals and alkaline earth metals are used as cations, and Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ^{− and the} like are used as anions. It is done. Specifically, for example, LiCl, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, N (CnF _{2n + 1} SO ₂ ) ₂ Li and the like, and any one of these or a mixture of two or more thereof is used. Among them, it is preferable to mainly use LiPF ₆ . The electrolyte salt concentration is not a problem as long as it can be dissolved in the non-aqueous solvent, but the lithium ion concentration is 0.4 mol / kg or more and 2.0 mol / kg or less with respect to the non-aqueous solvent. A range is preferable.

  As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Specifically, examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The solid polymer electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. Examples of the polymer compound include ether polymers such as poly (ethylene oxide) and the same cross-linked products, poly (methacrylate) esters, and acrylates. A system or the like is used alone or copolymerized or mixed in the molecule.

  As the matrix polymer of the gel electrolyte, various polymers can be used as long as they can be gelled by absorbing the non-aqueous electrolyte described above. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products thereof, and poly (acrylonitrile) Can be used. In particular, it is desirable to use a fluoropolymer from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

  Alternatively, a polymer solid electrolyte containing a simple substance or a mixture of conductive polymer compounds or a gel electrolyte containing a swelling solvent may be used. The conductive polymer compound contained in the polymer solid electrolyte or the gel electrolyte is compatible with the electrolytic solution, specifically silicon gel, acrylic gel, acrylonitrile gel, polyphosphazene modified polymer, polyethylene oxide, Polypropylene oxide, fluorine-based polymers, composite polymers, cross-linked polymers, modified polymers, and the like thereof can be used. Examples of the fluorine-based polymer include poly (vinylidene fluoride), poly (vinylidene fluoride-co-hexafluoropropylene), poly (vinylidene fluoride-co-trifluoroethylene), or poly (vinylidene fluoride-co-tetra). Polymer materials such as fluoroethylene) and mixtures thereof are used.

[Separator]
The separator is made of, for example, a porous film made of a polyolefin-based material such as polypropylene (PP) or polyethylene (PE), or a porous film made of an inorganic material such as a ceramic nonwoven fabric. A structure in which a porous film is laminated may be used. Among these, polyethylene and polypropylene porous films are the most effective.

  In general, the thickness of the separator is preferably 5 to 50 μm, more preferably 7 to 30 μm. If the separator is too thick, the amount of the active material filled decreases, the battery capacity decreases, and the ionic conductivity decreases and the current characteristics deteriorate. On the other hand, if the film is too thin, the mechanical strength of the film decreases.

[Production of battery element]
The positive electrode 11 and the negative electrode 12 as described above are stacked in the order of the positive electrode 11, the separator 15 a, the negative electrode 12, and the separator 15 b, and wound to form the battery element 10. At this time, the positive electrode 11 and the negative electrode 12 are stacked so as to provide current collector facing surfaces facing the current collector exposed portions, and the battery elements are collected at the outermost peripheral portion, innermost peripheral portion, and intermediate layer portion. The electric body facing surface is configured to have one or more rounds. In the case of using a solid or gel electrolyte, the electrolyte solution is uniformly applied to the surfaces of the positive electrode 11 and the negative electrode 12, dried at room temperature or high temperature atmosphere, and the solvent is vaporized and removed to form an electrolyte layer. Thereafter, it is laminated with a separator and wound to obtain a battery element.

  Next, the battery element 10 described above is accommodated in the battery can 1. At this time, the negative electrode terminal lead-out side of the winding surface of the battery element 10 is accommodated so as to be covered with the insulating plate 2a made of an insulating resin. Thereafter, one electrode rod is inserted from the battery element winding center portion, the other electrode rod is disposed outside the bottom surface of the battery can and resistance welding is performed, and the negative electrode terminal is welded to the battery can.

  After the negative electrode terminal 14 and the battery can 1 are welded, the center pin 16 is inserted, and the insulating plate 2b is also disposed on the winding surface portion located at the open end of the battery can to inject the electrolyte. Further, the positive electrode terminal 13 is connected to the positive electrode terminal plate 3 provided with the safety valve mechanism 4 and the current control mechanism 5 on the inner side, and the positive electrode terminal plate 3 is attached by being caulked through the insulating sealing gasket 6. The inside of 1 is sealed.

  In addition, it is necessary to use a positive electrode terminal having a certain length in the manufacturing process. This is because the open end of the battery can is sealed after the positive electrode terminal 13 is connected to the safety valve mechanism 4 provided on the positive electrode terminal plate 3 in advance. The shorter the positive electrode terminal 13 is, the positive electrode terminal 13 and the positive electrode terminal plate are. 3 connection becomes difficult. For this reason, the positive electrode terminal 13 is bent and accommodated in a substantially U shape inside the battery.

  Next, the configuration of an example of a current control mechanism according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is an exploded perspective view showing the layer structure of the current control mechanism 5 according to the embodiment of the present invention. FIG. 3 is a sectional view in the axial direction of the current control mechanism 5 according to the embodiment of the present invention. The current control mechanism 5 includes solder 7 that is a conductive member, insulating sheets 8a and 8b that are insulating members, a connection plate 9a, and a connection plate 9b.

  The connection plate 9a and the connection plate 9b are made of a conductive material such as metal, and at least one of the connection plate 9a and the connection plate 9b is made of a material that is difficult to be alloyed with the solder 7, such as an aluminum foil. . The connection plate 9a is disposed so as to contact the positive electrode terminal plate 3, and the connection plate 9a and the positive electrode terminal plate 3 are electrically connected. Further, the connection plate 9b is disposed so as to contact the safety valve mechanism 4, and the connection plate 9b and the safety valve mechanism 4 are electrically connected.

  The insulating sheet 8a and the insulating sheet 8b are made of an insulating material, and for example, a nonwoven fabric or a resin member can be used. More specifically, for example, aramid nonwoven fabric or PP (polypropylene) is used as the resin member. The insulating sheet 8a is disposed between the connection plates 9a and 9b so as to be sandwiched between the connection plates 9a and 9b. Moreover, the insulating sheet 8b is arrange | positioned at the outer peripheral side between both connection plates.

  The solder 7 is made of a conductive material that melts at a predetermined temperature and forms an alloy with another metal. For example, the solder 7 is generated by mixing materials such as Sn, Pb, and Bi. The solder 7 is disposed so as to be sandwiched between the insulating sheet 8a and the insulating sheet 8b disposed between the connection plate 9a and the connection plate 9b.

  Next, a manufacturing process of the current control mechanism 5 will be described. The current control mechanisms 5 stacked as shown in FIG. 3 are heated at a predetermined temperature in a state where a predetermined pressure is applied from the outer surfaces of the connection plate 9a and the connection plate 9b. The predetermined temperature is a temperature at which the solder 7 is not completely dissolved, for example, a temperature of about 200 ° C. At this time, the solder 7 is heated to be softened, and the aluminum foil of the connecting plate and the solder 7 are partially fused. By doing so, the connection plate and the solder are electrically connected.

  Note that the connection plate 9a and the connection plate 9b do not necessarily need to be made of aluminum foil. It is sufficient that at least one of the connection plate 9a and the connection plate 9b is made of an aluminum foil. That is, when the solder 7 is melted, one of the connection plates may be made of a metal that is difficult to be alloyed.

  Thus, since the current control mechanism 5 is manufactured using a thin-film material, the size can be reduced, and the shape, size, and arrangement of the current control mechanism 5 can be selected according to the shape, size, and space of the battery. Place etc. can be decided freely.

  Next, the operation of limiting the current in the current control mechanism according to the embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows an enlarged view of a portion where the connection plate 9b and the solder 7 are in contact with each other. Usually, the aluminum foil of the connecting plate 9b has fine irregularities, and as shown in FIG. 4A, during normal use, the solder 7 is partially in contact with the irregularities of the aluminum foil and fused, The connection plate 9b and the solder 7 are electrically connected.

  When heat is generated by the excessive current flowing, the solder 7 is heated and melted. Since the melted solder 7 is difficult to be alloyed with the aluminum foil, as shown in FIG. 4B, a part of the portion that has been in contact with the connection plate 9b is separated by the surface tension of the solder 7, and the connection plate 9b The contact area with is reduced. Therefore, the resistance value between both connection plates increases, and the current flowing from the battery element 10 to the positive electrode terminal plate 3 via the current control mechanism 5 is limited. Note that the contact area between the connecting plate 9a and the solder 7 is also reduced by the surface tension of the solder 7 as described above.

  Thus, during heat generation, the contact area between the two connection plates and the solder 7 decreases due to the surface tension of the melted solder 7, so that the resistance value between the two connection plates increases.

  In the above-described embodiment, the cylindrical battery has been described. However, the present invention is not limited to this, and the present invention can be applied to batteries having various shapes such as a square, a coin, and a button.

  The shape of the current control mechanism is not limited to the ring shape described above, and may be a disk shape, for example. FIG. 5 shows an example of the layer configuration of the current control mechanism 5 ′ having a disk shape. In the current control mechanism 5 ′, a hollow disk-shaped insulating sheet 8 is disposed on the outer peripheral side on a disk-shaped connection plate 9 b ′, and a disk-shaped tape-shaped solder 7 is disposed in a hollow portion of the insulating sheet 8. To do. Then, the disk-shaped connection plate 9 a ′ is disposed so as to be laminated on the insulating sheet 8 and the solder 7. In this way, a disc-shaped current control mechanism 5 'may be formed.

  Furthermore, the shape of the current control mechanism 5 ′ is not limited to a disk shape. It arrange | positions so that the circumference | surroundings of the solder 7 which is an electroconductive member arrange | positioned between both connection plates may be enclosed with the insulating sheet 8 which is an insulating member, and the solder 7 melt | dissolved at the time of a heating does not flow out of the electric current control mechanism 5 '. Any configuration can be used as long as it is a simple configuration.

  Hereinafter, the current control mechanism according to the embodiment of the present invention will be specifically described with reference to examples.

Example 1
As shown in FIG. 5, a hollow circular insulating sheet 8 is disposed on a circular connecting plate 9 b ′, and a circular and tape-shaped solder 7 is disposed in a hollow portion of the insulating sheet 8. Furthermore, a circular connection plate 9 a ′ was disposed so as to be laminated on the insulating sheet 8 and the solder 7, thereby producing a current control mechanism 5 ′.

  A circular aluminum foil having a diameter of 16 mm and a thickness of 0.1 mm was used for the connection plate 9a 'and the connection plate 9b'. A hollow circular aramid nonwoven fabric having a diameter of 17 mm, a thickness of 0.1 mm, and a hole having a diameter of 5 mm in the center was used for the insulating sheet 8 as an insulating member. Further, the solder 7 which is a conductive member is a circular shape having a diameter of 5 mm and a thickness of 0.1 mm, in which Bi is mixed at a ratio of 50%, Pb of 30% and Sn of 20%. It was used.

Comparative Example 1
Comparative Example 1 was produced in the same manner as Example 1 except that an aluminum foil having the same shape was used instead of the solder 7 used as the conductive member.

Comparative Example 2
Comparative Example 2 was produced in the same manner as Example 1 except that nickel foil was used instead of the aluminum foil used as the material of connection plate 9a ′ and connection plate 9b ′.

  FIG. 6 shows a cross-sectional view of an example configuration for measuring the resistance value between both connection plates of the current control mechanism 5 according to the embodiment of the present invention. In contrast to the current control mechanisms produced in Example 1, Comparative Example 1 and Comparative Example 2 described above, the metal tabs 21a and 21b for resistance measurement are placed on the outer surfaces of the connection plate 9a ′ and the connection plate 9b ′. The current control mechanism and the tabs 21a and 21b were placed on the heating hot plate 22, and the weight 23 was placed on the upper portion of the tab 21a and heated to 200 ° C. while applying pressure. After heating, this current control mechanism is once cooled to a normal use temperature and placed on the hot plate 22 again so that the hot plate temperature becomes 23 ° C, 45 ° C, 60 ° C, 80 ° C, 100 ° C and 120 ° C. Were sequentially heated and the set temperature was maintained for about 10 minutes, and then the resistance values between the tabs 21a and 21b were confirmed.

  Table 1 below shows the measurement results.

  As a result of the measurement, in Example 1, when the temperature was 60 ° C. or lower, the resistance value was “0.04Ω”, and there was no change. In the state heated to 80 ° C., the resistance value was “0.08Ω”, and an increase in the resistance value was confirmed. In the state of overheating to 100 ° C. and 120 ° C., the resistance values were “0.18Ω” and “0.22Ω”, respectively, and it was confirmed that the resistance value increased as the temperature increased. This is presumably because the solder 7 melts and the surface tension increases, and the contact area between the aluminum foil of the connecting plate and the solder 7 decreases.

  In Comparative Example 1, even when heated from 23 ° C. to 120 ° C., the resistance value was always “0.04Ω”, and it was confirmed that there was no change in the resistance value. This is considered to be because the aluminum foil used instead of the solder 7 does not change even when heated, and the contact area between the connection plate and the aluminum foil hardly changes.

  In Comparative Example 2, in the state heated from 23 ° C. to 60 ° C., the resistance value was “0.04Ω”, and it was confirmed that there was no change in the resistance value. Moreover, in the state heated from 80 degreeC to 12 degreeC, resistance value became "0.03 (ohm)", and it has confirmed that resistance value decreased compared with the normal temperature. This is because the nickel foil used instead of the aluminum foil of the connection plate and the solder 7 melted by heating were fused, and the contact area between the connection plate and the solder 7 was increased. Conceivable.

  From this result, it was confirmed that the current can be limited as the temperature increases by using an aluminum foil, which is difficult to be alloyed with solder, for the connection plate.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the embodiment of the present invention described above, and various modifications and applications can be made without departing from the gist of the present invention. Is possible. For example, in the above-described embodiment, the secondary battery has been described as an example. However, the present invention is not limited to this and can be applied to other batteries such as a primary battery. Further, for example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary.

  In the above embodiment, the lithium ion battery has been described as an example. However, the present invention is not limited to this example, and can be applied to a battery using various positive and negative electrode materials.

It is sectional drawing which shows the structure of an example of the secondary battery by one Embodiment of this invention. It is a basic diagram which shows an example of the laminated constitution of the electric current control mechanism by one Embodiment of this invention. It is sectional drawing which shows the structure of an example of the current control mechanism by one Embodiment of this invention. It is the basic diagram which expanded the contact part of the connection board and solder of the current control mechanism by one Embodiment of this invention. It is an approximate line figure showing an example of layer composition of current control mechanism 5 'whose shape is circular. FIG. 3 is a schematic diagram illustrating an example of a current control mechanism according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2a, 2b Insulation board 3 Positive electrode terminal board 4 Safety valve mechanism 4a Disk board 5 Current control mechanism 6 Insulation sealing gasket 7 Solder 8, 8a, 8b Insulation sheet 9a, 9a ', 9b, 9b' Connection board 10 Battery element 11 Positive electrode 11a Positive electrode active material layer 11b Positive electrode current collector 12 Negative electrode 12a Negative electrode active material layer 12b Negative electrode current collector 13 Positive electrode terminal 14 Negative electrode terminals 15a, 15b Separator 16 Center pin 21 Tab 22 Hot plate 23 Weight

Claims (6)

A first connection plate and a second connection plate made of a conductive material disposed opposite to each other;
An insulating member disposed on an inner peripheral side and an outer peripheral side of a facing gap between the first connecting plate and the second connecting plate, and made of an insulating material;
A conductive member disposed so as to be sandwiched between the insulating materials in the opposed gap, and melted at a predetermined temperature;
A current control mechanism, wherein at least one of the first connection plate and the second connection plate is difficult to alloy with the conductive member. The current control mechanism according to claim 1,
At least one of the first connection plate and the second connection plate is made of an aluminum foil. The current control mechanism according to claim 1,
The current control mechanism, wherein the first connection plate and the second connection plate are formed in a ring shape. In the battery element housed in the exterior body and the battery having a current control mechanism,
The current control mechanism is
A first connection plate and a second connection plate made of a conductive material disposed opposite to each other;
An insulating member disposed on an inner peripheral side and an outer peripheral side of a facing gap between the first connecting plate and the second connecting plate, and made of an insulating material;
A conductive member disposed so as to be sandwiched between the insulating materials in the opposed gap, and melted at a predetermined temperature;
A battery, wherein at least one of the first connection plate and the second connection plate is difficult to alloy with the conductive member. The battery according to claim 4.
The battery according to claim 1, wherein the first connection plate and the second connection plate are formed in a ring shape. The battery according to claim 4.
The battery according to claim 1, wherein the outer package is a metal can.

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