JP2011108538A - Laminate battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate battery which can ensure safety by preferentially opening a prescribed portion, when an inner pressure abnormally is increase, and exhibits proper storage properties. <P>SOLUTION: The laminate battery includes an electrode body having sheet positive electrodes, sheet negative electrodes, and separators housed in an outer package formed of metal laminate films each having at least a laminated metal layer and thermally fused resin layer; a heat seal part in a peripheral edge part of the outer package includes a part passing from one side to the other side of the metal layer, included in the one metal laminate film out of the laminated metal laminate films; and the passed part serves as a vent part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laminated battery having good safety when an internal pressure abnormally increases.

  In recent years, as the use of batteries has expanded, development aimed at improving battery characteristics such as higher capacity, higher energy density, and higher output has been actively conducted. In particular, the application of a battery to an application requiring high output and high capacity such as an automobile application has been required. For example, application of a lithium ion secondary battery has been studied.

  In many cases, a laminate film exterior body composed of a metal laminate film is used as an exterior body of a battery applied to such applications because of its advantage of being highly lightweight and lightweight.

  By the way, in a battery having a cylindrical or rectangular metal container (battery can) as an exterior body, for example, a part of the metal container is thinned to ensure safety when the battery internal pressure rises abnormally. In general, a vent portion is provided.

  On the other hand, the laminate type battery using the laminate film outer package has a smaller strength than the cylindrical or square metal container (battery can) and the heat fusion resin of the metal laminate film. Is sealed by heat sealing, so that the pressure resistance is lower than that of a battery having a metal container, and the battery expands or opens with a slight increase in internal pressure. For this reason, there has been an idea that in a laminated battery, it is not necessary to install a vent part.

  However, in recent devices, in order to manage charge and discharge and to ensure safety, there are increasing opportunities to install precise circuits near the battery, and if the electrolyte inside the battery adheres to these circuits or substrates, Corrosion may lead to equipment malfunction or fire. For this reason, even in laminated batteries, it is necessary to provide a vent so that even if liquid leaks or gas leaks from the inside, a circuit or substrate placed in the vicinity of the battery does not exist. It has become. Particularly in recent batteries, the amount of each power generation element has been increased with the increase in capacity, and in order to cope with applications requiring high load characteristics, the liquid electrolyte solution is not gelled. The need for venting is increasing because it is also being used.

  Conventionally, many techniques for providing a vent in a laminated battery have been proposed. For example, a method of punching or notching a part of a heat seal portion of a laminate film outer package (for example, Patent Document 1), a laminate film, and the like. The strength of a part of the heat-sealed part can be obtained by placing a thin piece or lithium fluoride between the heat-sealing resin layers of the upper and lower metal laminate films that make up the exterior body, or by thinning part of the heat-fusion resin layer. There are known methods for lowering (for example, Patent Documents 2 to 4).

JP 2006-351431 A JP 2001-250526 A Japanese Patent No. 4178436 Japanese Patent No. 3638765

  By the way, considering the durability of the laminated battery, it is required to have a function of maintaining the battery contents (power generation element) in a good state when the battery is stored for a long time. However, when a part of the heat seal portion related to the laminate film outer package is punched out or cut out as in the above technique, a narrow portion is formed in the heat seal portion. When the vent function is provided by lowering the strength of a part of the heat seal portion related to the film exterior body, the reliability of the heat seal portion may be impaired. Therefore, in laminated batteries obtained by these technologies, the permeability of moisture and solvent in the heat seal part of the laminate film outer package becomes high, moisture penetrates from the outside, and the internal electrolyte solvent evaporates. In some cases, the storability may decrease.

  For this reason, in the laminated battery, it is necessary to develop a technology that can open only a specific portion when the internal pressure of the battery rises abnormally while suppressing the deterioration of storage stability as much as possible. .

  The present invention has been made in view of the above circumstances, and a purpose of the present invention is to provide a laminated battery that can ensure safety by preferentially opening a specific portion when the internal pressure rises abnormally and has good storage properties. Is to provide.

  The laminated battery of the present invention that can achieve the above object has a metal laminate film in which at least a metal layer and a heat-sealing resin layer are laminated as an exterior body, and a positive external terminal is connected to the interior of the exterior body. A laminated battery containing an electrode body having a sheet-like negative electrode connected to a sheet-like positive electrode and a negative electrode external terminal and a separator, wherein the exterior body is composed of two metal laminate films, or 1 The metal laminate film is folded in half, and the outer periphery of the exterior body is heat-sealed in a state where the positive electrode external terminal and the negative electrode external terminal are drawn to the outside. In the heat seal part at the periphery, the metal layer of one of the laminated metal laminate films has the other side from one side. And the portion which passes through is provided to, and is characterized in that a portion of the through and vent.

  According to the present invention, when the internal pressure rises abnormally, a specific portion is preferentially opened to ensure safety, and a laminated battery having good storage properties can be provided.

It is a top view which represents typically an example of the laminated battery of this invention. It is a principal part enlarged view of the AA line cross section of FIG.

  1 and 2 schematically show an example of a laminated battery of the present invention. FIG. 1 is a plan view of a laminated battery 1, and FIG. 2 is an enlarged view of a main part of the cross section taken along the line AA of FIG. In FIG. 2, the positive electrode mixture layer and the current collector of the sheet-like positive electrode and the negative electrode mixture layer and the current collector of the sheet-like negative electrode are not distinguished in order to avoid complication of the drawing.

  In the laminated battery 1, a laminated electrode body in which a plurality of sheet-like positive electrodes 6 and a plurality of sheet-like negative electrodes 7 are laminated via separators 8, and an electrolytic solution (not shown) are rectangular outer bodies 2 in plan view. Is housed inside. A positive external terminal 3 and a negative external terminal 4 are drawn from the exterior body 2. The positive electrode external terminal 3 and the negative electrode external terminal 4 are both planar, and are connected to the sheet-like positive electrode 6 and the sheet-like negative electrode 7 directly or via a lead body or the like in the exterior body 2, respectively. 1 shows an example in which the positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn from the same side of the outer package 2, but in the battery of the present invention, the positive electrode external terminal, the negative electrode external terminal, May be drawn from different sides of the exterior body.

  The exterior body 2 is configured by a metal laminate film 20 having a heat-sealing resin layer on the surface that becomes the inside of the battery. More specifically, the metal laminate film 20 according to the exterior body 2 is configured by laminating an exterior resin layer 21, a metal layer 22, and a heat-sealing resin layer 23 in order from the outside of the battery. (Left side in FIG. 2), the heat-sealing resin layer 23 according to the upper metal laminate film 20 and the heat-sealing resin layer 23 according to the lower metal laminate film 20 are heat-sealed and integrated, Thus, the inside of the exterior body 2 is sealed.

  In the battery shown in FIGS. 1 and 2, one of the metal laminate films 20, 20 superimposed on the heat seal portion at the peripheral edge of the outer package 2 (the upper side in FIGS. 1 and 2). The metal layer 22 of the metal laminate film 20) is provided with a portion 5 penetrating from one surface to the other surface, and this portion serves as a vent portion.

  That is, the strength of the metal layer 22 portion is smaller in the portion where the penetrating portion 5 is formed in the heat seal portion of the exterior body 2 than in other portions. Therefore, when the internal pressure of the laminated battery abnormally rises, the low-strength heat-sealing resin layer is broken and the internal pressure is released at the location where the penetrating portion 5 is formed. Functions as a vent part.

  Moreover, in the battery of the present invention, unlike the case where, for example, a part of the heat seal portion related to the exterior body is cut out or punched out, a narrow portion is formed in the heat seal portion. Absent. Therefore, in the battery of the present invention, it is possible to suppress as much as possible an increase in the permeability of moisture and electrolyte solvent in the heat seal part due to the formation of the vent part.

  In addition, although there is a possibility of moisture intrusion through the penetrating portion 5 and evaporation of the electrolyte solvent, the entire film is placed at a place where it is planned to be a heat seal portion of the metal laminate film constituting the exterior body. By forming a penetrating part in advance and manufacturing a laminated battery using this metal laminate film, as shown in FIG. 2, a part of the heat-sealing resin melted at the time of heat sealing of the outer package 2 is obtained. It is thought that it penetrate | invades and by this, the opening of the said penetration part 5 is blocked, and the penetration | invasion of a water | moisture content and evaporation of electrolyte solution solvent are suppressed.

  Further, at the place where the penetrating portion 5 is formed, the other metal laminate film 20 (a metal laminate film 20 different from the metal laminate film 20 on which the penetrating portion 5 is formed) penetrates the metal layer 22. The part is not formed. Therefore, the strength reduction in the portion where the penetrating portion 5 is formed in the heat seal portion can be suppressed as much as possible.

  In the battery of the present invention, when the internal pressure is abnormally increased, the specific portion is preferentially opened by the above-described actions, so that safety can be ensured and storage property can be improved.

  In the heat seal portion of the exterior body, there is no particular limitation on the shape of the portion penetrating from one side to the other side formed in the metal layer according to one metal laminate film, for example, in a plan view, linear, curved, Any of a combination of a straight line and a curved line may be used. More specifically, for example, straight stripes, grooves, circles, ellipses, and the like are listed in plan view. When the shape of the penetrating portion is linear in plan view, it is preferable that the penetrating portion is substantially perpendicular (including vertical) to the width direction of the exterior body (the length direction a in FIG. 2).

  The penetrating portion is preferably formed at a location 1 mm or more outside from the inner end of the heat seal portion of the exterior body, and more preferably 2 mm or more. That is, in FIG. 2, the length of a is preferably 1 mm or more, and more preferably 2 mm or more. If the formation portion of the penetrating portion is too close to the inner end of the heat seal portion of the exterior body, the function of preventing the permeation of moisture and electrolyte solvent may be reduced, and it depends on the battery life (life). However, the reliability (storability) improvement effect may be reduced.

  1 and 2 show an example in which one penetration portion is provided, the battery of the present invention has a plurality of penetration portions (for example, two, three, four, etc.). It may be. However, considering the productivity of the battery, the number of the penetrating portions is preferably small, and more preferably one.

  The total length of the penetrating portion in plan view (when there are a plurality of penetrating portions, the total length thereof; the same applies to the total length of the penetrating portion in plan view). From the viewpoint of more effectively exerting the action, it is preferably 3 mm or more, and more preferably 5 mm or more. However, if the total length of the penetrating portion in plan view is too long, the effect of improving the reliability of the battery may be reduced. Therefore, the total length in plan view of the penetrating portion is preferably 50 mm or less, and more preferably 30 mm or less.

  Further, since the width of the penetrating portion (the length of b in FIG. 2) is too large, the effect of improving the reliability of the battery may be reduced. Therefore, the width is preferably 3 mm or less. It is more preferable that On the other hand, the lower limit value of the width of the penetrating portion is not particularly limited, and may be any width that can be formed. Specifically, for example, as in the case of only cutting with a cutter or the like, It may be 0 mm.

  In the battery of the present invention, an adhesive layer containing the same kind of resin as the heat fusion resin contained in the heat fusion resin layer is provided between the positive electrode external terminal or the negative electrode external terminal and the heat fusion resin layer of the outer package. The positive electrode external terminal or the negative electrode external terminal and the outer package (its heat-sealing resin layer) can be bonded via the adhesive layer. The side from which the positive external terminal or the negative external terminal is drawn usually tends to reduce the strength of the heat seal part, but the heat seal part of the side from which the positive external terminal or negative external terminal is drawn by such a method is used. Strength can be increased.

  The width of the heat seal portion at the peripheral edge of the outer package is preferably 5 to 20 mm.

  In the sheet-like positive electrode constituting the laminate battery, for example, a layer made of a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder (positive electrode mixture layer) is formed on one side or both sides of the current collector. Things can be used.

As the positive electrode active material, for example, when the laminate type battery of the present invention is a lithium ion secondary battery, an active material capable of inserting and extracting lithium ions is used. As a specific example of such a positive electrode active material, for example, a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Lithium-containing transition metal oxide, LiMn ₂ O ₄ and spinel-structured lithium manganese oxide obtained by substituting some of its elements with other elements, LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.) Type compounds. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ and LiNi _1-x Co _xy Al _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _{3 / 5} Mn _1/5 Co _1/5 O ₂ etc.).

  As the current collector for the positive electrode, an aluminum foil or an aluminum alloy foil is suitable. The thickness of the current collector is preferably 0.01 to 0.02 mm, for example, although it depends on the size and capacity of the battery.

  In producing the positive electrode, the positive electrode active material, a conductive additive such as graphite, acetylene black, carbon black, and fibrous carbon, and a positive electrode mixture containing a binder such as polyvinylidene fluoride (PVDF), N -A paste-like or slurry-like composition uniformly dispersed using a solvent such as methyl-2-pyrrolidone (NMP) is prepared (the binder may be dissolved in the solvent), and this composition is used as the positive electrode A method of applying to the current collector and drying, and adjusting the thickness and density of the positive electrode mixture layer by pressing as necessary can be employed. However, the manufacturing method of the positive electrode according to the present invention is not limited to the above method, and other methods may be adopted.

  The thickness of the positive electrode mixture layer in the sheet-like positive electrode is preferably 30 to 100 μm per side. Moreover, it is preferable that content of each structural component in a positive mix layer shall be positive electrode active material: 90-98 mass%, conductive support agent: 1-5 mass%, and binder: 1-5 mass%.

  The positive electrode external terminal is preferably made of aluminum or an aluminum alloy from the viewpoint of ease of connection with the equipment used. The thickness of the positive external terminal is preferably 50 to 300 μm. That is, by setting the thickness of the positive external terminal to 50 μm or more, it is possible to prevent cutting during welding of the positive external terminal and to prevent tearing due to pulling and bending. Further, by setting the thickness of the positive external terminal to 300 μm or less, it is possible to prevent a gap in the thickness direction from being generated in the heat seal portion of the exterior body. In addition, as described above, an adhesive layer may be interposed between the exterior body and the positive electrode external terminal in order to increase the strength of the heat seal portion at the side where the positive electrode external terminal is drawn out of the peripheral portion of the exterior body. However, the adhesive layer may be provided in advance at a place where the positive electrode external terminal is expected to be located at the heat seal portion.

  The sheet-like positive electrode and the positive electrode external terminal may be connected by directly connecting the sheet-like positive electrode current collector and the positive electrode external terminal. For example, the sheet-like positive electrode collector may be connected via an aluminum lead body. It can also be performed by connecting the electric body and the positive external terminal. The thickness of the aluminum lead body is preferably 50 to 300 μm, like the positive external terminal. Such a lead body is preferably used when the aluminum foil as the positive electrode current collector is particularly thin and the strength is insufficient for direct connection with the positive electrode external terminal.

  Examples of the method of connecting the current collector in the sheet-like positive electrode or the aluminum lead connected to the current collector and the positive external terminal include, for example, resistance welding, ultrasonic welding, laser welding, caulking, and conductive adhesive Various methods can be employed, such as the method by, but ultrasonic welding is particularly suitable.

As the sheet-like negative electrode constituting the laminated battery, for example, when the laminated battery of the present invention is a lithium ion secondary battery, one containing an active material capable of inserting and extracting lithium ions is used. Examples of such negative electrode active materials include graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, mesocarbon microbeads (MCMB), and carbon fibers. One or a mixture of two or more releasable carbon-based materials is used. In addition, elements such as Si, Sn, Ge, Bi, Sb, In and their alloys, lithium-containing nitrides, or compounds that can be charged and discharged at a low voltage close to lithium metals such as oxides (such as LiTi ₅ O ₁₂ ), or Lithium metal or lithium / aluminum alloy can also be used as the negative electrode active material. These negative electrode active materials include conductive assistants (carbon materials exemplified as conductive assistants related to positive electrodes) and binders (mixed binders of rubber binders such as PVDF and styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC). Etc.] or the like, and a finished product (negative electrode mixture layer) using the current collector as a core material, or the above-mentioned various alloys and lithium metal foils are laminated on the surface of the current collector And the like are used as a sheet-like negative electrode.

  For example, in the case of a sheet-like negative electrode having a negative electrode mixture layer, a negative electrode mixture containing the negative electrode active material, the binder, and a conductive auxiliary agent such as graphite, acetylene black, and carbon black, if necessary, A paste-like or slurry-like composition uniformly dispersed using a solvent such as NMP is prepared (the binder may be dissolved in the solvent), and this composition is applied onto the negative electrode current collector. The method of drying and adjusting the thickness and density of a negative mix layer layer by press processing as needed can be employ | adopted. However, the method for producing the sheet-like negative electrode according to the present invention is not limited to the above method, and other methods may be adopted.

  As the current collector for the negative electrode, a copper foil is suitable. The thickness of the current collector is preferably 0.05 to 0.02 mm, for example, although it depends on the size and capacity of the battery.

  The thickness of the negative electrode mixture layer in the sheet-like negative electrode is preferably 30 to 100 μm per side. Moreover, it is preferable that content of each structural component in a negative mix layer shall be negative electrode active material: 90-98 mass%, binder: 1-5 mass%. Moreover, when using a conductive support agent for a negative electrode, it is preferable that content of the conductive support agent in a negative mix layer shall be 1-5 mass%.

  For the negative electrode external terminal, a metal foil or ribbon such as nickel, nickel-plated copper, or nickel-copper clad is preferable. Further, the thickness of the negative electrode external terminal is preferably 50 to 300 μm similarly to the positive electrode external terminal. That is, by setting the thickness of the negative electrode external terminal to 50 μm or more, it is possible to prevent cutting during welding of the negative electrode external terminal and to prevent tearing due to pulling and bending. Further, by setting the thickness of the negative electrode external terminal to 300 μm or less, it is possible to prevent a gap in the thickness direction from being generated in the heat seal portion of the exterior body. In addition, as described above, an adhesive layer may be interposed between the exterior body and the negative electrode external terminal in order to increase the strength of the heat seal portion at the side where the negative electrode external terminal is drawn out of the peripheral portion of the exterior body. However, the adhesive layer may be provided in advance at a place where the negative electrode external terminal is expected to be located in the heat seal portion.

  The sheet-like negative electrode and the negative electrode external terminal may be connected by directly connecting the sheet-like negative electrode current collector and the negative electrode external terminal. For example, the sheet-like negative electrode current collector may be connected via a copper lead. It can also be performed by connecting the body and the negative electrode external terminal. The thickness of the copper lead body is preferably 50 to 300 μm, similarly to the negative electrode external terminal. Such a lead body is preferably used when the copper foil as the negative electrode current collector is particularly thin and the strength is insufficient for direct connection with the negative electrode external terminal.

  Examples of the method of connecting the current collector in the sheet-like negative electrode or the copper lead connected to the current collector include various methods such as resistance welding, ultrasonic welding, laser welding, caulking, and a method using a conductive adhesive. Although methods can be employed, ultrasonic welding is particularly suitable.

  In the laminated battery of the present invention, the sheet-like positive electrode and the sheet-like negative electrode are laminated with a separator interposed therebetween, or a winding wound in a spiral shape after being overlapped with a separator. It can be used as an electrode body. In the laminated electrode body and the wound electrode body, a plurality of sheet-like positive electrodes and sheet-like negative electrodes can be used as necessary. In the case of a wound electrode body, the cross section may be shaped to be flat as necessary.

  Examples of the separator relating to the laminated battery include a porous film and a nonwoven fabric made of polyethylene, polypropylene, a fusion of polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate, and the like. The thickness of the separator is preferably 10 to 50 μm, and the porosity is preferably 30 to 70%. Moreover, the effect which prevents a short circuit can be improved and the reliability of a battery can be improved more by using several separators, such as overlapping a porous film and a nonwoven fabric.

As an electrolyte solution for a laminate type battery, when the laminate type battery of the present invention is a lithium ion secondary battery, for example, a high dielectric constant such as ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (BL), etc. A solution in which a solute such as LiPF ₆ or LiBF ₄ is dissolved in a solvent or an organic solvent such as a linear solvent such as a low viscosity solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), or methyl ethyl carbonate (EMC) ( Non-aqueous electrolyte). In addition, it is more preferable to use the mixed solvent of the said high dielectric constant solvent and a low-viscosity solvent as an electrolyte solution solvent. PVDF, rubber-based material, alicyclic epoxy, oxetane-based material having a three-dimensional cross-linked structure, and the like may be mixed and solidified into the above solution to form a polymer electrolyte.

  The outer package of the laminated battery is composed of a metal laminate film. The metal laminate film only needs to have at least a metal layer and a heat-sealing resin layer, and has only these layers. Although a two-layer structure may be used, a three-layer metal laminate film composed of an exterior resin layer / a metal layer / a heat-sealing resin layer as shown in FIG. 2 is more preferably used.

  In addition, in the metal laminate film, the penetrating portion only has to penetrate only the metal layer from one side to the other side. For example, when a metal laminate film having a three-layer structure having an exterior resin layer is used, the production is Since it becomes easy, also in the exterior resin layer, a portion penetrating from one surface to the other surface may be provided at a position corresponding to the penetrating portion formed in the metal layer.

  Examples of the metal layer in the metal laminate film include an aluminum film and a stainless steel film, and examples of the heat fusion resin layer include a modified polyolefin film (such as a modified polyolefin ionomer film). When the metal laminate film has an exterior resin layer, examples of the exterior resin layer include a nylon film (such as nylon 66 film) and a polyester film (such as PET film).

  In the metal laminate film, the thickness of the metal layer is preferably 10 to 150 μm, and the thickness of the heat-sealing resin layer is preferably 20 to 100 μm. When the metal laminate film has an exterior resin layer, the thickness is preferably 20 to 100 μm,

  The shape of the exterior body is not particularly limited. For example, the shape of the exterior body may be a polygon such as a triangle, a quadrangle, a pentagon, a hexagon, a heptagon, and an octagon in plan view. A square (rectangular or square) is common.

  In the laminated battery of the present invention, an exterior body formed by folding a single metal laminate film may be used, or an exterior body configured by stacking two metal laminate films may be used. Good.

  The laminated battery of the present invention is a conventionally known laminated battery (especially a laminated battery) such as a power supply for various electronic devices, including applications requiring high output and high capacity batteries such as automobile applications. It can be used for the same applications as various applications in which lithium ion secondary batteries) are used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
LiCoO ₂ : 96 parts by mass, acetylene black: 2 parts by mass, and PVDF: 2 parts by mass were mixed, and NMP was further added to prepare a positive electrode mixture-containing paste. The obtained positive electrode mixture-containing paste was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and then subjected to a press treatment to form a positive electrode mixture layer, whereby a sheet-like positive electrode was obtained. The thickness of the positive electrode mixture layer of the obtained sheet-like positive electrode was 60 μm per one side of the current collector. Thereafter, the obtained sheet-like positive electrode was cut into a shape in which a portion where the positive electrode mixture layer was formed had a width of 105 mm and a length of 200 mm, and also included an exposed portion of a positive electrode current collector serving as a current collecting tab.

<Production of negative electrode>
Graphite: 98% by mass, SBR: 1.5% by mass and CMC: 0.5% by mass were added and mixed, and further water was added to prepare a negative electrode mixture-containing paste. The obtained negative electrode mixture-containing paste was applied to both sides of a current collector made of a copper foil having a thickness of 10 μm, dried, and then subjected to a press treatment to form a negative electrode mixture layer, whereby a sheet-like negative electrode was obtained. The thickness of the negative electrode mixture layer of the obtained sheet-like negative electrode was 60 μm per one side of the current collector. Thereafter, the obtained sheet-like negative electrode was cut into a shape in which a portion where the negative electrode mixture layer was formed had a width of 110 mm and a length of 205 mm, and also included an exposed portion of the negative electrode current collector that became a current collecting tab.

<Battery assembly>
10 sheets of the sheet-like positive electrode and 11 sheets of the sheet-like negative electrode were laminated via a separator (a polyolefin microporous film having a thickness of 25 μm) to obtain a laminated electrode body. In addition, it laminated | stacked so that both ends of a laminated electrode body might become a negative electrode. Next, the current collecting tabs of each sheet-like positive electrode according to the laminated electrode body are ultrasonically welded to the positive electrode external terminal made of aluminum, and the current collecting tabs of each sheet-like negative electrode are ultrasonically welded to the negative electrode external terminal made of copper. did. The positive electrode external terminal and the negative electrode external terminal are made of the same modified polyolefin as the resin constituting the heat-sealing resin layer of the exterior body on both surfaces where the heat seal portion of the exterior body is expected to be located. An adhesive layer was placed.

  A 150-μm thick three-layered metal laminate film (rectangular, size 130 mm × 230 mm) made of polyester film / aluminum film / modified polyolefin film was prepared. Then, the laminated electrode body is placed on the modified polyolefin film layer in the metal laminate film so that a part of the positive electrode external terminal and the negative electrode external terminal protrude from the same side of the metal laminate film as shown in FIG. The metal laminate film was folded in half so as to wrap the electrode body. The metal laminate film penetrates from one side to the other side of the aluminum film (aluminum film and polyester film) of the metal laminate film located on the upper side of the portion corresponding to the portion 5 that penetrates the metal layer in FIG. The part to be formed was previously formed. The penetrating portion is a straight groove shape having a width (length b in FIG. 2) of 1 mm and a length in plan view of 10 mm, and the formation position and direction thereof is the inner end of the heat seal portion of the outer package. To 3 mm (the length of a in FIG. 2 is 3 mm) and the direction perpendicular to the width direction of the heat seal portion.

Thereafter, the side from which the positive electrode external terminal and the negative electrode external terminal were drawn, the two vertical sides on the right side in FIG. 1, and the side having the folded end were heat sealed to form an exterior body, which was vacuum dried at 70 ° C. for 15 hours. Thereafter, a non-aqueous electrolyte was injected from the left vertical side in FIG. 1, and the vertical side was heat-sealed and sealed under reduced pressure. Note that the nonaqueous electrolytic solution, a solution was used in which a LiPF ₆ in a solvent mixture to 1: 3 to EC and DEC at a volume ratio at a concentration 1.0 mol / l. Moreover, the heat seal width | variety of the exterior body was all 10 mm.

  The sealed outer body (outer body containing the laminated electrode body and the non-aqueous electrolyte solution) is aged for 24 hours, and then charged for 1 hour at a current value of 0.1 C, followed by a total charging time of 4 Laminate type lithium ion which performs chemical conversion treatment by carrying out constant current-constant voltage charge (constant current charge: 0.5 C, constant voltage charge: 4.2 V), and uses the penetrating part as a vent part. A secondary battery was obtained.

Example 2
The shape of the portion through which the aluminum film (and the polyester film) penetrates in the upper metal laminate film constituting the outer package was the same as in Example 1 except that the shape was a straight line with a length of 10 mm in plan view. Thus, a laminated lithium ion secondary battery was produced.

Example 3
Laminated lithium in the same manner as in Example 1 except that the shape of the portion through which the aluminum film (and polyester film) penetrates in the upper metal laminate film constituting the outer package was a circle having a diameter of 5 mm in plan view. An ion secondary battery was produced.

Comparative Example 1
A laminated lithium ion secondary battery was produced in the same manner as in Example 1 except that the penetrating portion was not formed in the aluminum film (and the polyester film) in the upper metal laminate film constituting the outer package.

Comparative Example 2
From the one side to the other side of the aluminum film (and polyester film) in the upper metal laminate film and the lower metal laminate constituting the exterior body at a position corresponding to the formation portion of the penetrating portion in the battery of Example 1. A laminated lithium ion secondary battery was produced in the same manner as in Example 1 except that the penetrating part was formed in the same shape as the penetrating part in the battery of Example 1.

  The following evaluations were performed on the laminated lithium ion secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2. These results are shown in Table 1 together with the shape of the penetrating portion.

<Measurement of working pressure at vent part>
For the batteries of Examples 1 to 3 and Comparative Examples 1 and 2 (battery before heat-sealing the side where the non-aqueous electrolyte was injected), compressed air was allowed to flow from the side where the non-aqueous electrolyte was injected. A pressure was applied to the case and the pressure when the outer package was opened was measured.

<Storage test>
After measuring the internal resistance values of the batteries of Examples 1 to 3 and Comparative Examples 1 and 2, each battery was left in an atmosphere of 60 ° C. and 90% relative humidity for 20 days, and then the internal resistance value was measured. Then, the internal resistance value before storage was subtracted from the internal resistance value after storage, and the value was divided by the internal resistance value before storage, and expressed as a percentage, which was defined as “internal resistance increase”.

  As is clear from Table 1, the laminated lithium ion secondary batteries of Examples 1 to 3 in which the penetrating part was formed had a relatively low opening pressure when measuring the working pressure of the vent part, and the penetrating part. The part which penetrated functioned well as a vent part. In addition, the batteries of Examples 1 to 3 have a relatively low increase in internal resistance due to a storage test, and also have good storage characteristics. Furthermore, the batteries of Examples 1 to 3 were also examined for discharge characteristics, and all of them were confirmed to have good capacity, load characteristics, and charge / discharge cycle characteristics.

  On the other hand, the battery of Comparative Example 1 in which the penetrating part is not formed has a high opening pressure at the time of measuring the operating pressure of the vent part, and the exterior body does not open at a certain location. Furthermore, the battery of Comparative Example 2 in which the penetrating portion was formed not only in the upper metal laminate film of the outer package but also in the lower metal laminate film had a large increase in internal resistance due to a storage test and was inferior in storage characteristics. Yes.

DESCRIPTION OF SYMBOLS 1 Laminated battery 2 Exterior body 5 The part which penetrates from one side to the other side of the metal layer which concerns on a metal laminate film 6 Sheet-like positive electrode 7 Sheet-like negative electrode 8 Separator 20 Metal laminate film 21 Exterior resin layer 22 Metal layer 23 Heat-fusion resin layer

Claims (6)

A metal laminate film in which at least a metal layer and a heat-sealing resin layer are laminated is used as an outer package, and a sheet-like positive electrode connected to a positive electrode external terminal and a sheet-like negative electrode connected to a negative electrode external terminal inside the outer package; A laminated battery containing an electrode body having a separator,
The exterior body is composed of two metal laminate films or is formed by folding one metal laminate film in half,
In a state where the positive electrode external terminal and the negative electrode external terminal are drawn out to the outside, a peripheral edge portion of the exterior body is heat-sealed,
In the heat seal portion at the peripheral edge of the exterior body, a portion that penetrates from one side to the other side is provided in the metal layer of any one of the laminated metal laminate films, and the portion that penetrates A laminated battery characterized by having a bent part as a vent.   2. The laminated battery according to claim 1, wherein a shape of a portion penetrating from one side to the other side of the metal layer of the metal laminate film is a straight line, a curved line, or a combination of a straight line and a curved line in plan view. .   The laminate type battery according to claim 1 or 2, wherein a total length in a plan view of a portion penetrating from one side to the other side in the metal layer of the metal laminate film is 3 to 50 mm.   In the metal layer of the metal laminate film, a portion penetrating from one surface to the other surface is linear in a plan view, and is formed in a direction substantially perpendicular to the width direction of the heat seal portion of the exterior body. 4. The laminated battery according to any one of 3 above.   The laminate-type battery according to any one of claims 1 to 3, wherein a shape of a portion penetrating from one side to the other side of the metal layer of the metal laminate film is a circle or an ellipse in a plan view.   The laminated battery according to any one of claims 1 to 5, wherein a portion of the metal layer of the metal laminate film that penetrates from one side to the other side is formed 1 mm or more outside from the inner end of the heat seal portion.

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