JP2006324049A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery which is superior in battery characteristics such to have a small deterioration of capacity at high rate discharge and a high charge and discharge voltage, and which is improved in vibration resistant property by preventing fracture of a negative electrode terminal. <P>SOLUTION: One piece of positive electrode terminal is connected to the nearly central part in longitudinal direction of a positive electrode of belt-shape in which a positive electrode active material is formed, and respectively each one piece, total two pieces, of negative electrode terminals are connected to the both end parts of a negative electrode of belt-shape in which a negative electrode active material is formed. A battery element is formed by using these positive electrode and negative electrode, and stored in a battery can, then, the negative electrode terminals are connected to the battery can. At this time, the negative electrode terminal which is led out from inner peripheral part of the battery element is bent to the outer periphery side of the battery element, and connected to the battery can together with another one piece of negative electrode terminal which is bent to the inner periphery side of the battery element, led out from the outer periphery side of the battery element, and again bent to the inner periphery side of the battery element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte secondary battery covered with a metal can.

  In recent years, electronic devices such as mobile phones and notebook computers have become cordless and portable, and thin, small, and lightweight portable electronic devices have been developed one after another. In addition, the amount of power used is increasing due to diversification of devices and functions, and there is an increasing demand for higher capacities of batteries that are energy sources of these electronic devices.

  Conventionally, primary batteries such as alkaline manganese batteries, secondary batteries such as lead livestock batteries, nickel-cadmium (Ni-Cd) batteries, nickel-metal hydride (Ni-MH) batteries have been used as portable power sources for these electronic devices. It was.

  However, due to the downsizing, thinning, and multi-functionality of electronic devices, a portable power source that is lightweight and compact but has high energy density is required. Of course, the secondary battery as described above, which has a low discharge voltage, is difficult to improve energy density, and is difficult to reduce in weight, has not sufficiently satisfied the requirements.

Under these circumstances, for example, a positive electrode comprising a positive active material with LiCoO ₂ and LiNiO lithium composite oxides such as _2, a carbonaceous material such as lithium doping / possible dedoping as graphite or non-graphitizable carbon material A non-aqueous electrolyte secondary battery using a negative electrode made of the negative electrode active material used has been proposed.

  The non-aqueous electrolyte secondary battery described above has a strip-shaped positive electrode in which a positive electrode active material layer is formed on both sides and a positive electrode terminal is welded, and a strip-shaped positive electrode in which a negative electrode active material layer is formed on both surfaces and a negative electrode terminal is welded. A negative electrode is stacked and wound via a separator to form a battery element, which is housed in, for example, an outer packaging material such as a battery can, and then injected with a non-aqueous electrolyte, and a positive electrode terminal plate (battery cover) is caulked. Use batteries. Such a non-aqueous electrolyte secondary battery has a number of advantages such as a high charge / discharge voltage and a high energy density.

Patent Document 1 below describes a secondary battery using a lithium composite oxide as a positive electrode active material and a carbon-based material as a negative electrode active material.
JP 2001-110453 A

  In the secondary battery of Patent Document 1, in order to obtain a secondary battery that has a small capacity drop during high-rate discharge and excellent output characteristics, a positive electrode collector in which the positive electrode active material 1b shown in FIG. 1A is formed as an example. Two negative terminals 4a and 4b (hereinafter referred to as specific negative terminals) are formed on the positive electrode 1 in which the positive electrode terminal 3 is welded on the electric body 1a and the negative electrode current collector 2a in which the negative electrode active material 2b shown in FIG. 1B is formed. In this case, the negative electrode 2 is used. The positive electrode 1 and the negative electrode 2 are laminated via a separator and wound to form a battery element, which is accommodated in a metal battery can. At this time, the negative electrode is wound from the negative electrode terminal 4a side, the negative electrode terminal 4a is derived from the battery element inner periphery, the negative electrode terminal 4b is derived from the battery element outer periphery, and the negative electrodes 4a and 4b are connected to the bottom surface of the battery can. Connected.

  As described above, by reducing the distance between the positive electrode terminal 3 and the negative electrode terminal 4, the battery has a high charge / discharge voltage, and the internal resistance of the battery is reduced, so that loss of discharge capacity can be suppressed.

  By the way, in the battery having the above structure, for example, as shown in FIG. 2, the battery element is accommodated in the battery can 5 in a state where the derived two negative terminals 4 a and 4 b are bent inward toward the center of the battery. The negative terminals 4a and 4b and the battery can 5 are connected at the center of the bottom surface of the battery can. The negative terminals 4a and 4b are connected to the negative current collector 2a. However, for convenience, the negative terminal 4a and the negative current collector 2a or the negative terminal 4b and the negative current collector 2a are integrated in FIG. As shown.

  However, in the secondary battery with this structure, the negative electrode terminal 4a on the inner peripheral side may be broken when the battery is repeatedly vibrated. This is because even if the distance from the portion where the negative electrode terminal 4a on the inner peripheral side is led out from the battery element to the portion connected to the battery can is very short and the battery element vibrates slightly, the negative electrode terminal 4a This is because a large load is applied to the negative electrode terminal 4a as a result. On the other hand, the negative electrode terminal 4b on the outer peripheral side is not as burdened as the negative electrode terminal 4a on the inner peripheral side because the distance from the portion led out from the battery element to the connection portion with the battery can is long.

  Therefore, in view of the above problems, an object of the present invention is to provide a non-aqueous electrolyte secondary battery that prevents breakage of the negative electrode terminal and has excellent vibration resistance.

  In order to solve the above problems, in the nonaqueous electrolyte secondary battery according to the present invention, a belt-like positive electrode provided with one positive electrode terminal, and a belt-like negative electrode provided with one negative electrode terminal at each of both ends of the negative electrode, In the secondary battery in which the battery element is housed in a battery can, the negative electrode terminal on the inner peripheral side is once bent toward the outer peripheral side of the battery element and further bent toward the inner peripheral side of the battery element. Thus, a length up to the connection portion with the battery can is provided so that the negative electrode terminal can follow when the battery element vibrates.

  Specifically, when a battery can having a diameter A [mm] is used, the negative electrode terminal on the inner peripheral side is led out from the battery element, and bent from the portion bent toward the outer peripheral side of the battery element toward the inner peripheral side of the battery element. The distance to the part is 1 mm or more and (A / 2) mm or less.

  According to the present invention, it is possible to significantly reduce the burden on the negative electrode terminal derived from the battery element inner periphery when the battery element vibrates. For this reason, the breakage of the negative electrode terminal can be prevented, and the vibration resistance of the nonaqueous electrolyte secondary battery is improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 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 21 and a negative electrode 22 are wound inside a substantially hollow cylindrical battery can 11 via a separator 25 (25a, 25b). The battery element 20 is included. The battery can 11 is made of, for example, iron plated with nickel, and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 a and 12 b are respectively disposed perpendicular to the winding peripheral surface so as to sandwich the battery element 20.

  A positive terminal plate 13 and a safety valve mechanism 14 and a PTC element 15 provided inside the positive terminal plate 13 are attached to the open end portion of the battery can 11 by caulking through an insulating sealing gasket 16. ing. The positive electrode terminal plate 13 is made of the same material as the battery can 11, for example. The safety valve mechanism 14 is electrically connected to the positive electrode terminal plate 13 via the PTC element 15, and the disk plate 14a is reversed when the internal pressure of the battery exceeds a certain level due to internal short circuit or external heating. Thus, the electrical connection between the positive terminal plate 13 and the battery element 20 is cut off. When the temperature rises, the PTC element 15 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. For example, the PTC element 15 is made of barium titanate semiconductor ceramics. The insulating sealing gasket 16 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The battery element 20 is wound around the center pin 26. A positive electrode terminal 23 is connected to the positive electrode 21 of the battery element 20, and two negative electrode terminals 24 a and 24 b are connected to the negative electrode 22. The positive electrode terminal 23 is electrically connected to the positive electrode terminal plate 13 by being welded to the safety valve mechanism 14, and the negative electrode terminal is welded and electrically connected to the battery can 11.

  Hereinafter, the configuration of the battery element 20 accommodated in the battery can 11 will be described.

[Positive electrode]
The positive electrode 21 is obtained by forming positive electrode active material layers 21b containing a positive electrode active material on both surfaces of the positive electrode current collector 21a. The positive electrode current collector 21a is made of a metal foil such as an aluminum (Al) foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21b 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 metal oxide, a metal sulfide, or a specific polymer can be used depending on the type of the target battery. For example, in the case of constituting a lithium ion secondary battery, a composite oxide of lithium and transition metal, or an intercalation compound containing lithium, mainly composed of LiMO ₂ (wherein M represents one or more transition metals) is used. 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.

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. .

Alternatively, a lithium composite oxide represented by Li _y MIO ₂ or Li _y MII ₂ O ₄ can be used as the positive electrode active material. 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. In these composition formulas, MI represents one or more transition metal elements, and specifically, preferably contains at least one of cobalt and nickel. MII represents one or more transition metal elements, and specifically, manganese (Mn) is preferable. The value of y varies depending on the charge / discharge state of the battery, and is usually in the range of 0.05 to 1.10. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiNi _z Co _1-z O ₂ (where 0 <z <1), LiMn ₂ O _{4, and the} like.

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. As the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride, or the like is used. Moreover, as a solvent, N-methyl-2-pyrrolidone (NMP) etc. are used, for example.

  The above-described 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 to form a slurry. 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.

  Moreover, the positive electrode 21 has one positive electrode terminal 23 connected by spot welding or ultrasonic welding to a substantially central portion in the longitudinal direction of the positive electrode current collector. The positive electrode terminal 23 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 23 include Al. Moreover, the positive electrode terminal welding part on the positive electrode collector 21a is good also as a positive electrode collector exposed part which does not form the positive electrode active material layer 21b. In this case, the positive electrode terminal 23 can be easily welded, and the active material layer may be damaged due to heat and vibration generated during the positive electrode terminal welding, and the active material layer may fall off, which can be prevented. .

[Negative electrode]
The negative electrode 22 is obtained by forming a negative electrode active material layer 22b containing a negative electrode active material on both surfaces of a negative electrode current collector 22a. The negative electrode current collector 22a 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 22b 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 that can be doped / undoped with lithium, a crystalline material, and an amorphous metal oxide are used. Specifically, examples of the carbon material that can be doped / undoped 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. Carbon materials such as those obtained by firing and carbonization), carbon fibers, activated carbon, 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 Li element and M element), where M is a metal element capable of forming an alloy with lithium. And p is a numerical value greater than 0, and q and r are numerical 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, Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb. , Bi, Cd, Ag, Zn, Hf, Zr, Y and their alloy compounds, that is, for example, Li-Al, Li-Al-M (wherein M is a 2A group, 3B group, 4B group transition) 1 or more of metal elements), AlSb, CuMgSb, and the like.

Among the elements described above, it is preferable to use elements such as Si and Sn or alloys thereof in addition to the group 3B typical elements, and Si or Si alloys are particularly preferable. Specifically, Si or Si 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.

  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. 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.

  The negative electrode 22 has two negative terminals 24a and 24b connected to both ends of the current collector by spot welding or ultrasonic welding. The negative terminals 24a and 24b are electrochemically and chemically stable, and there is no problem even if they are not made of metal as long as they can be electrically connected. Examples of the material of the negative terminals 24a and 24b include copper and nickel. Similarly to the positive electrode terminal welded portion, the negative electrode terminal welded portion may be a negative electrode current collector exposed portion, thereby preventing the active material from dropping off during the negative electrode terminal welding.

[Electrolyte]
The electrolytic solution is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and materials generally used for lithium ion batteries can be used. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-dimethoxyethane, 1,3-dioxolane, 4-methyl-1,3-dioxolane. , Diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, and the like are preferable, and any one of these or a mixture of two or more thereof 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 + 1SO 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.

  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 composed 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 21 and the negative electrode 22 as described above are laminated in the order of the positive electrode 21, the separator 25 a, the negative electrode 22, and the separator 25 b, and wound with the separator 25 b inside to form the battery element 20. When a solid or gel electrolyte is used, the electrolyte solution is uniformly applied to the surfaces of the positive electrode 21 and the negative electrode 22, dried in a normal 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.

  From the electronic element 20 described above, a negative electrode terminal (hereinafter referred to as an inner peripheral negative electrode terminal) 24a derived from the battery element inner peripheral portion and a negative electrode terminal (hereinafter referred to as an outer peripheral negative electrode terminal) derived from the battery element outer peripheral side. 24b are derived respectively. The inner peripheral side negative terminal 24a is bent from the portion led out from the battery element 20 to the outer periphery side of the battery element, and is further folded back to the inner peripheral side of the battery element to have a substantially U-shaped or substantially V-shaped cross section. The outer peripheral side negative terminal 24b is bent from the derived battery element outer peripheral side toward the battery element inner peripheral side.

  The bending state of the inner peripheral negative electrode terminal 24a and the outer peripheral negative electrode terminal 24b at this time will be described in detail with reference to FIGS. 4A, 4B, 5A, 5B, and 6. FIG. 4A and 5A are schematic views showing the internal configuration when viewed from the front of the non-aqueous electrolyte secondary battery to which the present invention is applied, and FIGS. 4B and 5B are housed in the non-aqueous electrolyte secondary battery. It is the schematic diagram which showed the mode of the bottom face part of the battery element made. 4A and 4B are appropriately referred to as FIG. 4, and when FIGS. 5A and 5B are not specified, they are appropriately referred to as FIG.

  4A and 5A, the gaps between the bottom surface of the battery can 11 and the battery element 20 are provided to explain the configuration of the negative terminals 24a and 24b. This is a detailed explanation of the present invention. This is to make it easier. Actually, the battery element 20 is inserted to the bottom of the battery can 11 and is not configured to have a gap.

  As shown in FIG. 4, when the lead-out portion of the inner peripheral negative electrode terminal 24a and the lead-out portion of the outer peripheral negative electrode terminal 24b are located on the radius of the battery element with the center pin insertion portion as the center, the inner peripheral negative electrode terminal 24a Is bent to the outer peripheral side and bent again toward the inside. Further, the outer peripheral negative electrode terminal 24b is bent so as to overlap the inner peripheral negative electrode terminal 24a.

  At this time, a length L from the portion where the inner peripheral negative electrode terminal 24a is led out from the battery element and bent toward the outer peripheral side of the battery element to the portion bent again toward the inner peripheral side of the battery element is the inner peripheral side. Assuming that the negative electrode terminal 24a is folded back and the diameter of the battery can used is A [mm], the inner circumferential negative electrode terminal 24a is folded back to a length of 1 [mm] or more and A / 2 [mm] or less. To do. Specifically, if the battery system has a diameter of 26 mm, the folding amount of the inner circumferential negative electrode terminal 24 a is 1 mm or more and 13 mm or less, and if the battery system has a diameter of 18 mm, the folding amount of the inner circumferential negative electrode terminal 24 a is 1 mm or more and 9 mm or less. And it is sufficient.

  When the amount of folding is less than 1 mm, the inner circumferential negative electrode terminal 24a cannot follow the movement of the battery element 20 during vibration, and the inner circumferential negative electrode terminal 24a may be broken. Further, when the folding amount is larger than 13 mm, the inner circumferential negative electrode terminal 24a is distorted and easily comes into contact with the electrode, so that a short circuit is likely to occur.

  Further, as shown in FIG. 5, the lead-out portion of the inner peripheral negative electrode terminal 24 a and the lead-out portion of the outer peripheral negative electrode terminal 24 b are located on opposite sides of the center pin insertion portion, and each is on the diameter of the battery element 20. 6, for example, as shown in FIG. 6, the lead-out portion of the inner peripheral negative electrode terminal 24 a and the lead-out portion of the outer peripheral negative electrode terminal 24 b are at an angle of 90 ° with the center pin insertion portion as the center. A case other than the state shown in FIG. 4 is conceivable.

  Also in this case, the inner peripheral negative electrode terminal 24a is bent in a substantially U shape or a substantially V shape, and the outer peripheral negative electrode terminal 24b is bent toward the inner peripheral side of the battery element. Since the outer peripheral side negative electrode terminal 24b overlaps at the center of the bottom surface of the battery can, the overlapped portion and the battery can are connected by resistance welding. When the diameter of the battery can is A [mm] at the folded portion of the inner peripheral negative electrode terminal 24a as in FIG. 4, the folded amount of the inner peripheral negative electrode terminal 24a is 1 [mm] or more and A / 2 [mm]. The length should be as follows.

  Next, the battery element 20 described above is accommodated in the battery can 11. At this time, the negative electrode terminal lead-out side of the winding surface of the battery element 20 is accommodated so as to be covered with an insulating plate 12a 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 the inner peripheral negative electrode terminal 24a and the outer peripheral negative electrode terminal 24b are overlapped. Resistance welding is performed.

  After the two negative terminals 24a and 24b are welded to the battery can 11, the center pin 26 is inserted, and the insulating plate 12b is also disposed on the winding surface portion located at the open end of the battery can to inject the electrolyte. To do. At this time, when a solid or gel electrolyte is used, the electrolyte solution is not injected. Further, the positive terminal 23 is connected to the positive terminal plate 13 provided with the safety valve mechanism 14 and the PTC element 15 on the inner side, and the positive terminal plate 13 is attached by caulking through an insulating sealing gasket 16, so that the battery can 11 The inside of 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 23 is connected to the safety valve mechanism 14 provided on the positive electrode terminal plate 13 in advance. The shorter the positive electrode terminal 23 is, the positive electrode terminal 23 and the positive electrode terminal plate are. 13 connections become difficult. By using such a structure, the positive terminal 23 is bent and accommodated in a substantially U shape inside the battery.

  As described above, a nonaqueous electrolyte secondary battery to which the present invention is applied is manufactured.

  Further, in the battery element 20 accommodated in the non-aqueous electrolyte secondary battery, the positive electrode current collector exposed portion where no positive electrode mixture is applied to the winding end portion of the positive electrode current collector 21a, and the negative electrode current collector 22a are wound. It is good also as a structure which provided the negative electrode electrical power collector exposure part which does not apply | coat a negative mix to a turn termination | terminus part, respectively. At this time, the battery element 20 after winding is disposed so that the positive electrode current collector exposed portion and the negative electrode current collector exposed portion face each other, and the facing portion between the positive electrode current collector exposed portion and the negative electrode current collector exposed portion is By having a structure that covers the outermost periphery of the battery element 20 more than one round, when a large load is applied from the outside of the battery can and the battery is crushed or a nail or the like is pierced, a short-circuit with low resistance can be instantaneously generated. , Can prevent sudden heat generation.

  Hereinafter, the present invention will be specifically described by way of examples.

<Example 1>
[Production of positive electrode]
A positive electrode is produced using a composite material of LiNiO ₂ and LiMn ₂ O ₄ as a positive electrode active material. First, LiNiO ₂ and LiMn ₂ O ₄ are mixed at a ratio of 6: 4 and fired to obtain a lithium composite material. 94 parts by weight of this lithium composite material, 3 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were prepared and further dispersed in N-methyl-2-pyrrolidone. A slurry-like positive electrode mixture was prepared.

  Next, this slurry-like positive electrode mixture was uniformly applied to both surfaces of a 20 μm-thick strip-shaped aluminum foil as a positive electrode current collector with a thickness of 120 μm. Next, after a drying process, compression molding was performed with a roll press to obtain a positive electrode. Further, one aluminum positive electrode terminal was connected to the substantially central portion of the positive electrode.

[Production of negative electrode]
90 parts by weight of the pulverized artificial graphite powder and 10 parts by weight of polyvinylidene fluoride as a binder were prepared and further dispersed in N-methyl-2-pyrrolidone to obtain a slurry-like negative electrode mixture. .

  Next, this slurry-like negative electrode mixture was uniformly applied to both surfaces of a 20 μm-thick strip-shaped copper foil as a negative electrode current collector with a thickness of 150 μm. Then, after passing through a drying process, it was compression molded with a roll press to obtain a negative electrode. Moreover, the negative electrode terminal made from nickel was connected to the both ends of a negative electrode, respectively, and two negative electrode terminals were derived | led-out.

[Electrolyte]
50 parts by weight of ethylene carbonate (EC) and 50 parts by weight of propylene carbonate (PC) were mixed, and 0.7 mol / kg of LiPF ₆ was dissolved as an electrolyte salt to prepare an electrolytic solution.

[Production of test battery]
The positive electrode and the negative electrode produced as described above are laminated in the order of the positive electrode, the separator, the negative electrode, and the separator, and wound to obtain a battery element. Next, this battery element is accommodated in a battery can, bent by setting the folding amount of the inner peripheral negative electrode terminal to 1 mm, and connected to the battery can together with the outer negative terminal, and then on the positive terminal plate provided with the safety valve mechanism and the PTC element on the inner side. A positive electrode terminal was connected, and the positive electrode terminal plate was attached to a battery can to obtain a test battery having a diameter of 26 mm and a height of 650 mm. Five test batteries were produced.

<Example 2>
Five test batteries were produced in the same manner as in Example 1 except that the amount of folding of the inner peripheral negative electrode terminal was 5 mm.

<Example 3>
Five test batteries were produced in the same manner as in Example 1 except that the amount of folding of the inner peripheral negative electrode terminal was 13 mm.

<Comparative Example 1>
Five test batteries were produced in the same manner as in Example 1 except that the amount of folding of the inner peripheral negative electrode terminal was 0 mm.

<Comparative Example 2>
Five test batteries were produced in the same manner as in Example 1 except that the amount of folding of the inner peripheral negative electrode terminal was 0.5 mm.

<Comparative Example 3>
Five test batteries were produced in the same manner as in Example 1 except that the amount of folding of the inner peripheral negative electrode terminal was 14 mm.

  About each battery for a test produced as mentioned above, constant current constant voltage charge of 2.5A and 4.2V was performed for 2.5 hours.

  After charging, a vibration test was performed. The vibration test was carried out based on the “safety test standard” defined in “Lithium Secondary Battery Safety Evaluation Standard Guidelines” (SBA G1101-1997) according to the guidelines of the Battery Industry Association.

  After the vibration test, a constant current discharge at 2.5 A was performed, and when the battery voltage reached 2.5 V, the process was terminated, and the battery capacity at this time was measured. Moreover, the presence or absence of a short circuit was confirmed after discharge, and each test battery was disassembled to confirm the state of the inner peripheral negative electrode terminal 24a being cut.

  Table 1 below shows the measurement results.

  As can be seen from Table 1, in the case of a battery having a diameter of 26 mm, when the folding amount of the inner peripheral negative electrode terminal is 1 mm or more and 13 mm or less, the battery capacity after the vibration test has a high capacity of 2500 mAh or more, It can be seen that the inner peripheral negative terminal is not cut or short-circuited and has excellent vibration resistance.

  On the other hand, in the test batteries of Comparative Example 1 and Comparative Example 2 in which the amount of folding back to the outside of the inner peripheral negative electrode terminal is less than 1 mm, the battery capacity decreased to 0 mAh, and the inner peripheral side The negative electrode terminal was also cut off. This is considered to be because the inner peripheral negative terminal was damaged by repeated vibration and the inner peripheral negative terminal was broken.

  Moreover, when the amount of folding outward of the inner peripheral negative electrode terminal was 14 mm, which was larger than the radius of the battery can as in Comparative Example 3, the inner peripheral negative electrode terminal did not break, but a short circuit occurred. This is considered to be because the distortion generated in the inner peripheral negative electrode terminal inside the battery was in contact with the electrode.

  Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  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-described embodiment, the cylindrical non-aqueous electrolyte secondary battery using the lithium composite oxide as the positive electrode active material has been described. However, not only the lithium ion secondary battery but also a battery using other materials. Is also applicable. Furthermore, it is applicable not only to a cylindrical battery but also to a square battery.

2 is a schematic diagram showing the structure of a positive electrode and a negative electrode in a battery of Patent Document 1. 2 is a cross-sectional view showing a battery configuration in a battery of Patent Document 1. FIG. It is sectional drawing which shows an example of the battery structure of the nonaqueous electrolyte secondary battery to which this invention is applied. It is a schematic diagram which shows an example of the battery structure of the nonaqueous electrolyte secondary battery to which this invention is applied. It is a schematic diagram which shows an example of the battery structure of the nonaqueous electrolyte secondary battery to which this invention is applied. It is a schematic diagram which shows an example of the battery structure of the nonaqueous electrolyte secondary battery to which this invention is applied.

Explanation of symbols

1, 21 ... Positive electrode 1a, 21a ... Positive electrode current collector 1b, 21b ... Positive electrode active material layer 2, 22 ... Negative electrode 2a, 22a ... Negative electrode current collector 2b, 22b ... Negative electrode active material layers 3, 23 ... Positive electrode terminals 4, 4a, 4b ... Negative electrode terminals 5, 11 ... Battery cans 12a, 12b ... Insulating plate 13 ... Positive electrode terminal plate 14 ... Safety valve Mechanism 14a ... Disk plate 15 ... PTC element 16 ... Insulation sealing gasket 20 ... Battery element 24a ... Inner peripheral negative electrode terminal 24a
24b ... Outer peripheral side negative terminal 24b
25, 25a, 25b ... separator 26 ... center pin

Claims (3)

A negative electrode active material layer is formed on the negative electrode current collector, and a strip-shaped negative electrode in which the first negative electrode terminal and the second negative electrode terminal are connected to both ends of the negative electrode current collector, and the positive electrode current collector A battery element is formed from a strip-like positive electrode in which a positive electrode active material layer is formed and a positive electrode terminal is connected to a portion facing the substantially central portion of the first negative electrode terminal and the second negative electrode terminal. Is a non-aqueous electrolyte secondary battery housed in a battery can having a diameter of Amm,
Derived from the inner periphery of the battery element, bent toward the outer periphery of the battery element, and further bent toward the inner periphery of the battery element, and derived from the outer periphery of the battery element, The second negative electrode terminal bent to the peripheral side is connected to the bottom of the battery can,
A non-aqueous electrolyte secondary battery, wherein the amount of bending of the first negative electrode terminal toward the outer periphery of the battery element is 1 mm or more (A / 2) mm or less.   2. The nonaqueous electrolyte secondary battery according to claim 1, further comprising a battery can having a diameter of 26 mm, wherein an amount of bending of the first negative electrode terminal to the outside of the battery element is 1 mm or more and 13 mm or less.   2. The nonaqueous electrolyte secondary battery according to claim 1, further comprising a battery can having a diameter of 18 mm, wherein an amount of bending of the first negative electrode terminal to the outside of the battery element is 1 mm or more and 9 mm or less.

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