JP2007018746A - Film-coated lithium cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-coated lithium cell which benefits from use of a film coating material, while improving the heat dissipation. <P>SOLUTION: A film coating type lithium cell 1 includes a cell capacity of 3Ah or more (typically 3 to 10Ah). This lithium cell 1 incorporates a low-profile lithium cell element 2, wherein a flattened electrode unit 30 with positive and negative electrodes is accommodated in a film coating material 10, as well as heat sinks 42 and 44 both attached in contact with the outside of the flattened surface on the lithium cell element 2. The electrode unit 30 is ≤3mm thick, while the heat sinks 42 and 44 are respectively 0.05 to 1mm thick. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film-clad lithium battery, and more particularly to a film-clad lithium battery having a film-clad lithium battery element as a constituent element.

  A structure in which an electrode unit including a positive electrode and a negative electrode is housed and sealed inside a film outer package (for example, a bag-like container formed by bonding sealing films such as a laminate film by heat fusion or the like). So-called film-clad batteries are known. Such a film-clad battery has an advantage that it can be easily reduced in size and weight as compared with a battery provided with a hard exterior body (such as a metal can) made of metal or the like. Patent document 1 is mentioned as a prior art document regarding a film-clad battery. Moreover, patent document 2 is mentioned as a prior art document regarding a battery.

JP 2004-355915 A JP 2000-106214 A

By the way, the battery may cause an internal short circuit due to overcharge or excessive external pressure. If locally generated heat is accumulated (retained) at such a short-circuited location, the entire battery may be overheated, causing rapid thermal decomposition of the positive electrode active material or the electrolyte.
Patent Document 1 describes a battery that includes a restraining member that restrains a side surface of a power generation element from both sides, and the power generation element and the restraining member are collectively sealed with a laminate film. This Patent Document 1 also describes providing a metal heat dissipating part in a part of the restraining member. In the battery having such a configuration, since the restraining member is housed inside the film exterior body, the compactness that is one of the advantages of the film exterior battery is impaired.
Patent Document 2 describes a technique for ensuring the heat dissipation of a battery by defining the surface area of a battery case (for example, a metal can formed by processing a stainless steel plate) with respect to the energy capacity when the battery is fully charged. Has been. However, in general, a sealing film constituting a film outer package has a smaller heat capacity than a metal can or the like. For this reason, when the technique described in Patent Document 2 is applied to a film-clad battery, the ability to disperse local heat generated by a short circuit tends to be insufficient. Moreover, since the method of adjusting the surface area by providing irregularities on the surface of the battery case is difficult to apply to the film outer package, it is difficult to properly balance the battery capacity and the surface area.

  Therefore, the present invention has an object to provide a film-covered lithium battery having improved heat dissipation (for example, the ability to disperse heat generated locally by a short circuit or the like) while taking advantage of using a film-covered body. And

A film-clad lithium battery provided by the present invention includes a flat-shaped lithium battery element in which a flat-shaped electrode unit including a positive electrode and a negative electrode is accommodated in a film-clad body, and the outside of the flat surface of the battery element. And a heat sink provided in contact with the outer surface of the film exterior body. The battery capacity of this lithium battery can be about 3 Ah or more (typically 3 to 10 Ah). The electrode unit may have a thickness of about 3 mm or less (typically 1 to 3 mm). The heat sink may have a thickness of about 0.05 to 1 mm.
According to the battery having such a configuration, even when heat is locally generated due to a short circuit or the like, the heat can be appropriately dispersed by the heat radiating plate provided outside the flat surface of the battery element. As a result, it is possible to avoid a phenomenon in which the local heat is accumulated and the entire battery is overheated. Since the said heat sink is provided in the exterior of the film exterior body, the volume of a film exterior body does not become large by installation of this heat sink. Therefore, according to the battery of this invention, favorable heat dissipation can be implement | achieved, making use of the advantage (for example, size reduction being easy) by using a film exterior body.

  In one preferable aspect of the battery disclosed herein, the heat radiating plate extends outward from the outer edge of the electrode unit as viewed from the flat surface side of the battery element. By setting the installation range of the heat sink within the above range, better heat dissipation can be realized.

  In another preferable aspect of the battery disclosed herein, the heat radiating plate is provided in a range on the inner side of the outer edge of the exterior body as viewed from the flat surface side. By setting it as this installation range, a heat sink can be installed, without expanding the external shape of a battery in a surface direction. Therefore, good heat dissipation can be realized while taking advantage of the use of the film outer package (for example, easy miniaturization). Limiting the installation range of the heat sink in this way is also preferable from the viewpoint of reducing the weight of the battery.

  In another preferable aspect of the battery disclosed herein, the lithium battery element is sandwiched between two heat radiating plates from both outer sides of the flat surface, and the battery element is interposed between the two heat radiating plates. Open to the outside. Thus, the heat dissipation more favorable can be exhibited by setting it as the structure by which the battery element was pinched | interposed between the two heat sinks. Moreover, it is advantageous from a viewpoint of size reduction and weight reduction of a battery that the lithium battery element is open | released outside between these two heat sinks.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that technical matters other than the contents particularly mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the technical contents disclosed in the present specification and the common general technical knowledge in the field.

  The present invention relates to a relatively large capacity lithium battery (typically a lithium ion secondary battery) having a battery capacity of about 3 Ah or more (typically about 3 Ah to 10 Ah, for example, about 3 Ah to 7 Ah). Here, the battery capacity of the lithium battery refers to, for example, a discharge capacity when the battery is fully charged at a rated charge voltage and then discharged to a rated discharge voltage (end voltage) at a discharge rate of 1C. Note that the discharge rate 1C means discharging with a discharge current [A] that takes 1 hour to reach the rated discharge voltage.

The electrode unit constituting the lithium battery disclosed herein includes a positive electrode and a negative electrode, and typically further includes a separator that separates the positive electrode and the negative electrode. The electrode unit has a flat shape, and its thickness (that is, the distance between the flat surfaces) is about 3 mm or less. If the thickness of the electrode unit exceeds about 3 mm, it becomes difficult to transfer heat generated by an internal short circuit or the like at the center in the thickness direction to the heat sink. For this reason, the heat radiation improvement effect by providing a heat sink tends to decrease. On the other hand, from the viewpoint of heat dissipation, it is advantageous to reduce the thickness of the electrode unit. However, when the electrode unit is thinned, the flat area required to secure a desired battery capacity tends to increase. Therefore, if the electrode unit is made too thin, the internal resistance of the battery tends to increase. Taking these circumstances into consideration, it is usually preferable to set the thickness of the electrode unit to about 1 to 3 mm. Further, it is preferably in the range of approximately 130～1500Cm ² about an area viewed electrode unit from the flat surface (e.g. 138~1390cm ^2). The more preferable range of the area when the electrode unit is viewed from the flat surface side may vary depending on the battery capacity of the lithium battery including the electrode unit. For example, in the case of a battery with a battery capacity of about 3 Ah, good heat dissipation can be realized by setting the area to a range of about 130 to 450 cm ² (for example, 139 to 417 cm ² ). If the battery of the battery capacity is generally about 7Ah, good heat dissipation by the range of the area to approximately 300～1000Cm ² about (e.g. 324~974cm ²⁾ it can be realized. If the battery capacity is about 10 Ah, good heat dissipation can be realized by setting the area to about 450 to 1500 cm ² (for example, 463 to 1390 cm ² ).
Further, when the shape of the electrode unit viewed from the flat plane side is substantially rectangular, the length of one side of the rectangle is 1, and the length of the side adjacent to the side is about 0.2 to 1 (more preferably , Preferably in the range of about 0.3 to 1).

  The film-clad lithium battery disclosed herein includes a lithium battery element having a configuration in which the electrode unit as described above is accommodated in a film-clad body. The lithium battery element having such a configuration can function as a lithium battery by itself (the element alone, that is, a structure having no heat dissipation plate). The film exterior body can be formed, for example, by joining the inner surfaces of a sealing film (exterior film) such as a laminate film. From the viewpoint of reducing the size of the battery and improving the heat dissipation, the electrode unit is accommodated in the film outer package so that the flat surface thereof is close to the inner surface of the film outer package (typically substantially in close contact). It is preferable. In one exemplary embodiment of the battery disclosed herein, an electrolytic solution containing an electrolyte (typically a lithium salt) is accommodated inside the film outer package, and the electrode unit is impregnated with the electrolytic solution. Has been. A positive electrode terminal and a negative electrode terminal are connected to the positive electrode and the negative electrode constituting the electrode unit, respectively. These electrode terminals are pulled out to the outside of the film exterior body through, for example, a joint (joint portion) of the exterior film.

  On the outer side of the flat surface of the lithium battery element, at least one heat radiating plate is provided in contact with the outer surface of the film outer package. By adopting a configuration in which a heat sink is provided on at least one flat surface of the battery element, a lithium battery exhibiting better heat dissipation than a lithium battery having no heat sink can be obtained. Since a higher heat dissipation effect can be exhibited, the battery element has a heat dissipation plate on both one and the other flat surfaces (that is, a structure in which both sides in the thickness direction of the battery element are sandwiched between heat dissipation plates). A lithium battery is preferred.

As a material constituting such a heat sink, from the viewpoint of thermal conductivity, various metals (for example, aluminum (Al), iron (Fe), copper (Cu), silver (Ag)) or any of these metals are used. An alloy having such a main component can be preferably employed. From the viewpoint of weight reduction of the battery, a heat sink made of a light metal such as aluminum or an alloy containing the light metal as a main component is preferable.
The thickness of the heat radiating plate may be about 0.05 to 1 mm (for example, about 0.1 to 1 mm, preferably about 0.1 to 0.5 mm). If the heat radiating plate is too thin, the heat capacity of the heat radiating plate is small, so that the effect of improving the heat dissipation is reduced. On the other hand, it is not preferable to make the heat sink excessively thick because the entire physique (particularly the thickness) of the battery is increased and the mass of the entire battery is increased.
As a typical shape of the heat sink, a flat plate shape can be exemplified. Irregularities may be provided on the surface of the flat plate (for example, the outer surface). As a result, the effect of improving heat dissipation can be realized. From the viewpoint of manufacturing cost, a simple flat heat sink can usually be suitably employed.

The heat radiating plate is preferably installed so as to cover an area of at least about 80% (more preferably about 90% or more) of the electrode unit as viewed from the flat surface side of the battery element. It is more preferable that the heat radiating plate is provided so as to cover almost the entire electrode unit, and it is more preferable that the outer periphery of the heat radiating plate is extended to the outside of the outer edge of the electrode unit. By setting it as such an installation range, good heat dissipation is obtained.
Moreover, it is preferable that the heat sink is provided in a range on the inner side of the outer edge of the film exterior body as seen from the flat surface side of the battery element. By setting it as this installation range, a heat sink can be installed, without enlarging the external shape of a battery in a surface direction. Therefore, good heat dissipation can be realized while taking advantage of the use of the film outer package (for example, easy miniaturization). The installation range is preferable from the viewpoint of reducing the weight of the battery.

  In general, as the battery capacity required for a lithium battery increases, the volume of an electrode unit required to realize the battery capacity increases. In the battery of the present invention, since the shape of the electrode unit is defined as a flat shape having a thickness of 3 mm or less, the area of the flat surface (wide surface) of the electrode unit tends to increase as the battery capacity of the battery increases. is there. Therefore, by providing a heat sink on such a flat surface, it is possible to efficiently dissipate the heat generated locally due to a short circuit of the battery by the heat sink while avoiding the outer shape of the battery from increasing in the surface direction. It becomes possible. Note that if the area of the flat surface of the electrode unit becomes too large, the internal resistance of the battery tends to increase. Therefore, the present invention is preferably applied to a battery having a battery capacity up to about 10 Ah (typically about 3 Ah to 10 Ah), and a battery capacity up to about 7 Ah (typically about 3 Ah to 7 Ah). It is more preferably applied to a battery.

  The said heat sink should just be installed so that this heat sink may be hold | maintained on the outer surface of a film exterior body, The installation method is not specifically limited. For example, the method of joining the outer surface of the film exterior body which covers the flat surface of an electrode unit, and the inner surface (surface on the side which faces a lithium battery element) of a heat sink is employable. Such bonding methods include heat-fusible resins (ethylene vinyl acetate copolymer resins, olefin resins, etc.) and adhesives (hot-melt adhesives, moisture-curing adhesives, pressure-sensitive adhesives, etc.) A method of bonding using a bonding agent can be exemplified. Therefore, a configuration in which such a bonding agent is interposed between the heat radiating plate and the film outer package can also be included in an example of a configuration in which the heat radiating plate is provided in contact with the outer surface of the film outer package. Moreover, it is good also as a structure by which the constituent material of the film exterior body and the heat sink were heat-welded. Alternatively, a battery element may be sandwiched between two heat radiating plates, and the two heat radiating plates may be connected (restrained) with an appropriate jig.

  As long as the effects of the present invention described above can be exhibited, the composition and configuration of the electrodes (positive electrode and negative electrode) constituting the lithium battery according to the present invention, the shape of the electrode unit, the connection method between the electrode unit and the external circuit, and the nonaqueous electrolyte The composition may be the same as that of a conventionally known lithium battery (typically a lithium secondary battery) and is not particularly limited.

For example, the positive electrode is preferably a sheet-like positive electrode having a structure in which a positive electrode mixture mainly composed of a positive electrode active material is held in layers on one or both sides of a sheet-like conductive member (positive electrode current collector). Can be used. As the positive electrode current collector, for example, a foil-like body made of any metal selected from aluminum (Al), nickel (Ni), titanium (Ti), or the like, or an alloy mainly containing any of these metals. Can be used. It is particularly preferable to use an aluminum foil as the positive electrode current collector. As the positive electrode active material, any material that can dope and dedope lithium ions can be used without particular limitation. As a positive electrode active material preferable for the present invention, a lithium transition metal composite oxide can be exemplified. For example, a positive electrode active material mainly composed of lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide and a mixture thereof is preferable.
Here, the “lithium nickel oxide” is an oxide having lithium (Li) and nickel (Ni) as constituent metal elements and the main (first) transition metal element is Ni. In addition to Li and Ni, an oxide having a composition containing at least one other metal element (that is, a transition metal element other than Li and Ni and / or a typical metal element) in a smaller proportion (atomic ratio) than Ni is also included. It means to include. The metal element is selected from the group consisting of, for example, Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. Can be one type or two or more types. The same applies to lithium cobalt oxides and lithium manganese oxides.

  Examples of components other than the positive electrode active material that can be included in the positive electrode mixture include a conductive material and a binder. As the conductive material, for example, a carbon material such as carbon black (acetylene black or the like), a conductive metal powder such as nickel powder, or the like can be used. Examples of the binder include celluloses such as methyl cellulose (MC), carboxymethyl cellulose (CMC), and ethyl cellulose (EC); polyvinyl alcohol; polyacrylate; polyalkylene oxide (for example, polyethylene oxide); polyvinylidene fluoride (PVDF), Fluorine polymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP); organic polymers such as styrene butadiene block copolymer (SBR) can be used.

  As the negative electrode, a sheet-like negative electrode having a configuration in which a negative electrode mixture mainly composed of a negative electrode active material is held in layers on one or both sides of a sheet-like conductive member (negative electrode current collector) is preferably used. Can do. As the negative electrode current collector, for example, a foil-like body made of any metal selected from copper (Cu), nickel (Ni), titanium (Ti), or the like, or an alloy mainly containing any of these metals. Can be used. It is particularly preferable to use a copper foil as the negative electrode current collector. As the negative electrode active material, any material that can dope and dedope lithium ions can be used without particular limitation. One or more active materials used for negative electrodes of general lithium secondary batteries, such as natural graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon, and metallic lithium Can be preferably used. Alternatively, a negative electrode active material such as tin oxide or silicon oxide may be used. Preferred negative electrode active materials for the present invention include amorphous and / or graphite-structured carbon materials. Examples of components other than the negative electrode active material that can be included in the negative electrode mixture include a conductive material and a binder. As the conductive material, the same materials as those for the positive electrode mixture can be used, and the same applies to the binder.

In one preferable aspect of the battery disclosed herein, the battery includes an electrode unit having a configuration in which a sheet-like positive electrode and a sheet-like negative electrode are laminated via a separator. For example, the present invention can be preferably applied to a lithium battery including an electrode unit in which a sheet-like positive electrode and a sheet-like negative electrode are laminated via a separator and the laminated body is wound (that is, a wound type). Further, the present invention provides an electrode unit having a configuration in which one or more sheet-like positive electrodes and one or more sheet-like negative electrodes are alternately laminated via separators (ie, a laminated type). It can be preferably applied to a lithium battery provided.
As the separator constituting the electrode unit of such an embodiment, for example, a porous film made of a polyolefin-based (for example, polyethylene, polypropylene) resin can be preferably used. Or you may use the woven fabric or nonwoven fabric which consists of inorganic fiber, such as organic fiber, such as polyolefin type and a cellulose type (for example, methylcellulose), or glass fiber.

The non-aqueous electrolyte provided in the battery disclosed herein may be a liquid electrolyte (non-aqueous electrolyte) containing a so-called non-aqueous organic solvent as a main component, or may be a gel-like or solid electrolyte. Good. As the nonaqueous electrolytic solution, a nonaqueous electrolytic solution used in a conventional lithium battery can be used without any particular limitation. For example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, methyl formate LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF An electrolytic solution having a composition in which one or two or more lithium salts (supporting salts) such as ₃ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) ₃ are dissolved can be used. The concentration of the lithium salt in this electrolyte is not particularly limited, but it is usually suitable to be in the range of about 0.5 to 2 mol / L.

  As the sealing film constituting the film outer package (that is, the outer film), any film can be used without particular limitation as long as it can constitute the outer package of this type of film outer battery. For example, a so-called laminate film conventionally used as an exterior film constituting an exterior body such as a lithium secondary battery can be used. The laminate film preferably used includes a barrier layer (a layer that blocks gas and moisture) made of metal foil (for example, aluminum and steel), and an outer surface layer provided on one side of the barrier layer. An outer surface (protective) layer composed of a melting point resin (for example, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyamide-based resin) and an adhesive layer provided on the other surface side of the barrier layer. It is mainly composed of three layers including an adhesive layer composed of a fusible resin (a thermoplastic resin having a relatively low melting point, such as ethylene vinyl acetate copolymer resin (EVA), or an olefin resin such as polyethylene and polypropylene)). The laminated film comprised can be illustrated. Such a laminate film having a three-layer structure can be easily bonded (fused) to each other by using an appropriate thermocompression bonding means (for example, a heat press machine).

  Although the lithium battery provided by the present invention is a battery having a relatively large capacity of about 3 Ah or more, the electrode unit has a very slim thickness of about 3 mm or less. This lithium battery has good heat dissipation due to the heat sink provided outside the flat surface of the battery element. In other words, the lithium battery prevents the occurrence of such an event that the entire battery is overheated due to local heat generation due to an internal short circuit, causing rapid thermal decomposition of the positive electrode active material or the electrolyte. Alternatively, a suppression means is provided. Further, since the lithium battery is a film exterior type, it is excellent in small size and light weight. The lithium battery of the present invention (typically, a lithium ion secondary battery) having such features is useful as a battery mounted on, for example, a hybrid electric vehicle.

  Specific examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Example 1>
FIG. 1 is a plan view (corresponding to a view seen from the flat surface side) of the lithium secondary battery according to the present embodiment, and FIG. 2 is a view taken in the direction of arrow II. However, in FIG. 1, the heat radiating plate 42 is indicated by imaginary lines in order to make the drawing easier to see. As shown in these drawings, the lithium secondary battery 1 roughly includes a flat battery element 2 and two heat radiation plates 42 and 44 sandwiching the battery element 2 from both sides in the thickness direction. Prepare. The battery element 2 includes a film outer package 10, a wound electrode unit 30 accommodated in the outer package 10, and a positive electrode terminal 3 and a negative electrode terminal 5 connected to the electrode unit 30. As shown in FIG. 2, the electrode unit 30 is wound into a flat shape having a thickness T of 1.7 mm. The shape of the electrode unit 30 viewed from the flat surface side is a rectangular shape (see FIG. 1), and the length L1 in the winding axis direction is 130 mm and the winding width L2 is 452 mm. The lithium secondary battery 1 has a rated charging voltage of 4.1 V, and is fully charged at the rated charging voltage and then discharged at a constant current of 1 C to 3 V (the discharge end voltage of the battery) (that is, the battery capacity). ) Is designed to be approximately 5.4 Ah.

The film exterior body 10 is constituted by two rectangular exterior films 12 and 14 arranged to face each other, as in this type of general film exterior battery. These exterior films 12 and 14 are constructed using a conventional general three-layer laminated film. Specifically, for example, an outer surface layer (protective layer) made of polyethylene terephthalate resin, a barrier layer made of aluminum foil, and an adhesive layer made of polypropylene resin are laminated in this order. As shown in FIG. 1 and FIG. 2, the exterior films 12, 14 project in a substantially rectangular shape on the flat surface side and the opposite side thereof at the central portion viewed from the flat surface side (thickness direction) of the film exterior body 10. An electrode unit housing portion 102 is formed. The electrode unit 30 and an electrolyte (not shown) are accommodated in the internal space of the accommodating portion 102. In this example, a lithium salt (such as LiPF ₆ ) is used as a supporting salt in a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) (such as a mixed solvent in which the mass ratio of DEC: EC is 7: 3). A nonaqueous electrolytic solution dissolved at a concentration of about 1 mol / L was used.

  On the other hand, a flange portion 104 is formed on the outer edge (outer periphery) of the film outer package 10 surrounding the electrode unit housing portion 102 by the outer edges of the outer films 12 and 14. The flange portion 104 extends outward from each side of the outer periphery (rectangular shape when viewed from the plane side) of the housing portion 102. In the flange portion 104, as shown in FIG. 2, the inner surfaces of the exterior films 12 and 14 constituting the flange portion 104 are heat-bonded to each other. Thereby, the sealing property of the electrode unit accommodation space is ensured.

The electrode unit 30 accommodated in the internal space of the electrode unit accommodating portion 102 includes a positive electrode sheet having a layer containing a positive electrode active material (positive electrode active material layer) on the surface of the positive electrode current collector and a negative electrode active material on the surface of the negative electrode current collector. A negative electrode sheet having a material layer is superposed via a separator sheet, and these sheets are rolled flat. In this example, a long (band-shaped) aluminum foil having a thickness of about 15 μm, a width of 108.5 mm, and a length of 3840 mm was used as the positive electrode current collector. On the surface of the positive electrode current collector, lithium nickelate (LiNiO ₂ ), carbon black (CB), and polytetrafluoroethylene (PTFE) as positive electrode active materials in a mass ratio of LiNiO ₂ : CB: PTFE = 87: 10 : The positive electrode composition containing in the ratio of 3 was apply | coated, and it pressed after drying, and produced the positive electrode sheet. Further, as the negative electrode current collector, a long (band-shaped) copper foil having a thickness of about 10 μm, a width of 108.5 mm, and a length of 3990 mm was used. A negative electrode composition comprising carbon (graphite powder), carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) in a mass ratio of carbon: CMC: SBR = 98: 1: 1 on the surface of the negative electrode current collector. Was applied to a negative electrode current collector, dried and pressed to prepare a negative electrode sheet. As the separator sheet, a 25 μm-thick polypropylene porous sheet was used. An electrode unit 30 having a thickness of 1.7 mm was manufactured by rolling the stacked sheets of the sheet flatly for 4.2 turns.

  One end of the positive electrode terminal 3 is connected to the positive electrode current collector constituting the electrode unit 30, and one end of the negative electrode terminal 4 is connected to the negative electrode current collector. In this example, an aluminum plate was used as the positive electrode terminal 3 and a copper plate was used as the negative electrode terminal 4. The other ends of the positive electrode terminal 3 and the negative electrode terminal 4 are drawn in opposite directions from both ends of the electrode unit 30 in the winding axis direction through the joints (flange portions 104) of the exterior films 12 and 14. The lithium battery element 2 having such a configuration can itself function as a flat lithium secondary battery of a film exterior type.

  On the outside of the flat surface of the lithium battery element 2, aluminum radiator plates 42 and 44 are provided in contact with the outer surfaces of the exterior films 12 and 14, respectively. Each of these heat sinks 42 and 44 is a flat plate having a thickness of 0.1 mm, and its planar shape (the shape seen from the flat surface side) is a rectangular shape. As shown well in FIG. 1, the outer edges of the heat sinks 42 and 44 are located between the outer edge of the electrode unit 30 and the outer edge of the film outer package 10 (that is, the outer edge of the flange portion 104) over the entire circumference. Yes. In other words, when viewed from the flat surface side of the battery element 2, the heat dissipation plates 42 and 44 are provided in a range that covers the entire electrode unit 30 and does not protrude from the film outer package 10. The center part (the part covering the electrode unit housing part 102) on the side facing the lithium battery element 2 of the heat sinks 42 and 44 is an adhesive (not shown) (here, an EVA-based hot-melt adhesive is used). It is joined to the outer surface of the exterior films 12 and 14 in a plane. As well shown in FIG. 2, the outer edge portions of the heat radiation plates 42 and 44 (portions that cover the electrode unit housing portion 102) are not joined to the exterior films 12 and 14. And between the heat sinks 42 and 44, the battery element 2 is open | released outside.

  The lithium nail battery having such a configuration was subjected to the following nail penetration test to observe the battery behavior (surface temperature profile). That is, the lithium secondary battery was adjusted to 80% of SOC (State of Charge). A nail having a diameter of 2.5 mm was pierced and penetrated at a speed of 350 mm / second in the approximate center of the flat surface of the battery. The battery was kept in a state where the nail was stuck as it was, and the transition of the surface temperature was measured. This surface temperature was detected by a thermocouple attached to the side surface of the film outer package 15 mm away from the nail. As a result, the maximum temperature reached on the surface of the film exterior body of the lithium secondary battery according to this example (the maximum temperature reached immediately after nail penetration until the completion of discharge) was 41 ° C.

<Example 2>
The lithium secondary battery 1 according to the present embodiment includes a lithium battery element 2 configured substantially in the same manner as in the first embodiment except that the thickness T and the winding width L2 of the electrode unit 30 are different (FIGS. 1 and 3). 2). Specifically, in this embodiment, the thickness T of the electrode unit 30 is 2.0 mm, and the winding width L2 is 384 mm. The value of the winding width L2 is set so that the same battery capacity (that is, 5.4 Ah) as that in Example 1 is realized when the thickness T of the electrode unit 30 is 2.0 mm. In order to adjust the thickness T of the electrode unit 30 to 2.0 mm, in the present embodiment, the number of times of stacking the positive and negative electrode sheets and the separator sheet is set to 5.0 turns. The lithium secondary battery 1 according to the present embodiment includes heat radiation plates 42 and 44 having the same material and thickness as those of the first embodiment outside the both flat surfaces of the lithium battery element 2 having the above-described configuration. However, by making the length of the heat radiation plates 42 and 44 in the L2 direction (winding width direction of the electrode unit) shorter than that in the first embodiment, the outer edges of the heat radiation plates 42 and 44 are electrodes as in the first embodiment. The sizes of the heat sinks 42 and 44 are adjusted so as to be positioned between the outer edge of the unit 30 and the outer edge of the film outer package 10.
Using this lithium secondary battery, the same nail penetration test as in Example 1 was performed. As a result, the maximum temperature reached on the surface of the film outer package of this battery was 46 ° C.

<Example 3>
The lithium secondary battery 1 according to the present example is a lithium battery element configured substantially in the same manner as in Example 1 except that the thickness T of the electrode unit 30 is 2.3 mm and the winding width L2 is 334 mm. 2 is provided. The value of the winding width L2 is set so that the same battery capacity as in Example 1 is realized when the thickness T of the electrode unit 30 is 2.3 mm. In order to adjust the thickness T to 2.3 mm, in this embodiment, the number of wrinkles of the superimposed positive and negative electrode sheets and separator sheets is set to 5.7 turns. The lithium secondary battery 1 of the present embodiment is provided with heat sinks 42 and 44 having the same material and thickness as those of the first embodiment. The sizes of the heat sinks 42 and 44 are such that the outer edges of the heat sinks 42 and 44 are electrodes. It is adjusted so as to be positioned between the outer edge of the unit 30 and the outer edge of the film outer package 10.
Using this lithium secondary battery, the same nail penetration test as in Example 1 was performed. As a result, the maximum temperature reached on the surface of the film outer package of this battery was 45 ° C.

  Table 1 summarizes the shapes of lithium secondary batteries according to Examples 1 to 3 (sizes of electrode units constituting the battery) and nail penetration test results of the batteries. In the nail penetration test of these lithium secondary batteries, no phenomenon that the whole battery was overheated was observed.

<Comparative Examples 1-5>
The lithium secondary batteries according to Comparative Examples 1 to 5 are wound so that the thickness T of the electrode unit is a value shown in Table 2, and the same battery capacity as that of Example 1 is realized according to each thickness T. The configuration is substantially the same as in the first embodiment except that the width value is set. The lithium secondary batteries according to these comparative examples are provided with heat sinks of the same material and thickness as in Example 1, and the sizes of the heat sinks are such that the outer edges of the heat sinks are the outer edges of the electrode unit and the film outer package. It is adjusted to be located between the outer edges.
Table 2 shows the results of the same nail penetration test as in Example 1 using these lithium secondary batteries, together with the sizes of the electrode units constituting the batteries. As can be seen from this table, the maximum temperature reached markedly increased as the thickness of the electrode unit increased. In the batteries of Comparative Examples 2 to 5, there was a phenomenon that the whole battery was overheated.

  In addition, when the said nail penetration test was implemented about the lithium battery element which comprises the lithium secondary battery of the comparative example 1, the highest ultimate temperature exceeded 150 degreeC and the phenomenon by which the whole battery was overheated was seen. Moreover, when the said nail penetration test was implemented about the lithium battery element which comprises the lithium secondary battery of Example 3, the highest attained temperature rose to about 100 degreeC. From these results, it was confirmed that the effect of defining the thickness T of the electrode unit and the effect of improving the heat dissipation by providing a heat sink on the outside of the flat surface of the battery element were confirmed.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Moreover, the technique illustrated in this specification or the drawings achieves a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

It is a top view of the lithium secondary battery which concerns on an Example. It is an II directional arrow line view of FIG.

Explanation of symbols

1: Lithium secondary battery (film-encased lithium battery)
2: Battery element (lithium battery element)
3: Positive electrode terminal 4: Negative electrode terminal 10: Film exterior body 12, 14: Exterior film 30: Electrode unit 42, 44: Heat radiation plate 102: Electrode unit housing portion 104: Flange portion

Claims (4)

A flat lithium battery element in which a flat electrode unit including a positive electrode and a negative electrode is housed in a film outer package;
A heat sink provided on the outside of the flat surface of the battery element in contact with the outer surface of the film outer package;
A film exterior type lithium battery comprising:
The battery capacity of the battery is 3 Ah or more,
The film-covered lithium battery, wherein the electrode unit has a thickness of 3 mm or less, and the heat sink has a thickness of 0.05 to 1 mm.   2. The battery according to claim 1, wherein the heat radiating plate extends outward from an outer edge of the electrode unit as viewed from a flat surface side of the battery element.   The battery according to claim 2, wherein the heat radiating plate is provided in a range inside the outer edge of the exterior body as viewed from the flat surface side.   The lithium battery element is sandwiched between two heat radiating plates from both outer sides of the flat surface, and the battery element is open to the outside between the two heat radiating plates. The battery according to one item.

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