JP2010244865A - Laminated battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated type battery securing safety by preferentially opening a prescribed portion, when the internal pressure of the battery is abnormally increased and enhancing reliability. <P>SOLUTION: The laminated battery is formed, in such a way that an electrode body having a sheet-like positive electrode, a sheet-like negative electrode, and a separator housed in a laminated film outer packaging which is a polygon, as viewed from above; a positive electrode outer terminal connected to the sheet-like positive electrode; and a negative electrode outer terminal connected to the sheet-like negative electrode are drawn out to the outside, and in this state, the periphery of the laminate film outer packaging is heat-sealed, and a venting section is formed in the periphery of the laminated film outer packaging. A heat-seal part on the sides other than a side from which the positive electrode outer terminal and the negative electrode outer terminal are drawn out in the laminated film outer packaging has a portion folded upward of the inside of the battery, as viewed from above, and a portion which is not folded, and the portion where is not folded of the heat-seal part is used as the venting section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laminated battery having good safety when the internal pressure of the battery 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.

  In a laminate type battery using a laminate film outer package, the heat sealing resin of the metal laminate film is sealed by heat sealing, so that the strength of such a sealing portion (heat seal portion) is small. There is a problem, and it is required to increase the strength of the sealing portion as the battery is required to have higher functionality.

  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.

  In contrast, a laminated battery using a laminate film outer package has a lower strength than the cylindrical or square metal container, and the heat fusion resin of the metal laminate film is thermally fused. Since it is sealed with a heat seal, the pressure resistance is lower than that of a battery having a metal container, and it expands or opens with a slight increase in internal pressure. For this reason, there has been an idea that in the laminated battery, it is not particularly necessary to install a vent portion.

  However, when a battery is mounted on a device, the terminal and the protection circuit are often installed near the battery, and even when there is an abnormality, the terminal and the protection circuit are corroded by leakage of the contents from the inside of the battery. Or generating heat may cause secondary problems. For this reason, even in laminated batteries, when the internal pressure of the battery rises abnormally, only a specific location is opened, and leakage of contents is required to be suppressed only from the opened location. It was.

  For example, there is also a proposal of a technique for providing a vent portion in a laminated battery by disposing thin pieces between heat-sealing resin layers of upper and lower metal laminate films constituting a laminate film exterior body (Patent Document 1). According to the above-described technique, the adhesive strength between the heat-sealing resin layers of the metal laminate film (the strength of the heat seal portion) decreases in the portion where the thin piece is disposed, so the portion where the thin piece is disposed functions as a vent portion. To do.

  However, since the decrease in the adhesive strength between the heat-sealing resin layers of the metal laminate film due to the flakes is relatively large, the heat-sealing resin layers at the locations where the flakes are disposed are favorably adhered during battery manufacture and use. There is also a possibility that it cannot be maintained.

  For this reason, there is a need for development of a technique that can open only a specific portion when the battery internal pressure rises abnormally without damaging the strength of the heat seal portion of the laminate film outer package as much as possible.

JP 2001-250526 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly reliable laminate that can secure safety by preferentially opening a specific portion when the internal pressure of the battery abnormally increases. The object is to provide a battery.

  In the laminated battery of the present invention that can achieve the above object, an electrode body having a sheet-like positive electrode, a sheet-like negative electrode, and a separator is accommodated in a polygonal laminate film outer package in a plan view, and the sheet-like battery In the state where the positive electrode external terminal connected to the positive electrode and the negative electrode external terminal connected to the sheet-like negative electrode are drawn to the outside, the outer periphery of the laminate film exterior body is heat sealed, and the laminate film exterior A laminated battery having a vent portion on the outer periphery of the body, wherein the heat seal portion of the laminate film exterior body other than the side from which the positive electrode external terminal and the negative electrode external terminal are drawn out is in plan view. A heat folded portion having a portion folded toward the inner side of the battery and a portion not folded; The width of the part and the width of the heat seal part in the unfolded part of the heat seal part are substantially the same, and the part of the heat seal part not folded is used as a vent part. is there.

  ADVANTAGE OF THE INVENTION According to this invention, when the internal pressure of a battery rises abnormally, a specific location is opened preferentially and the laminated battery which can ensure safety | security and has high reliability can be provided.

It is a top view which represents typically an example of the laminated battery of this invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG.

  1 to 3 schematically show an example of a laminated battery of the present invention. 1 is a plan view of a laminated battery 1, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. In FIGS. 2 and 3, the layers of the metal laminate film constituting the laminate film exterior body are not distinguished in order to avoid the complexity of the drawings.

  In the laminated battery 1, a laminated electrode body in which a plurality of sheet-like positive electrodes 5 and a plurality of sheet-like negative electrodes 6 are laminated via separators 7 and an electrolyte solution (not shown) are rectangular laminate film exteriors in a plan view. It is housed in the body 2. A positive electrode external terminal 3 and a negative electrode external terminal 4 are drawn out from the laminate film 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 5 and the sheet-like negative electrode 6 directly or via a lead body in the laminate film outer package 2 ( Figure 2). FIG. 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 laminate film outer package 2, but in the battery of the present invention, the positive electrode external terminal and the negative electrode external terminal are shown. Each terminal may be drawn from a different side of the laminate film outer package.

  The laminated battery 1 is hermetically sealed by heat sealing the outer periphery of the laminate film outer package 2. And among the heat seal portions around the outer periphery of the laminate film outer package 2, heat seals on the sides (two vertical sides and the lower side in FIG. 1) other than the sides from which the positive external terminal 3 and the negative external terminal 4 are drawn. The part is a folded part 21a. As shown in FIG. 3, in the folding part 21a, the heat seal part is folded toward the inside of the battery in a plan view. Thus, the intensity | strength of a heat seal part can be raised by making the heat seal part of the outer periphery of the laminate film exterior body 2 into the folding part 21a.

  In the folding part 21a in the laminate film outer package 2, as shown in FIG. 3, the heat seal part may be folded only once, but it may be folded a plurality of times (two times, three times, four times, etc.). As the number increases, the strength of the heat seal portion can be increased. However, if the number of times of folding of the folding part is increased, the mass of the laminate film outer package, that is, the mass of the laminated battery is increased, and the production of the laminated battery becomes complicated. Therefore, the number of times of folding in the folding portion is preferably about 1 to 3 times.

  In addition, since the heat seal part in the sides other than the side from which the positive electrode external terminal and the negative electrode external terminal are drawn out is folded as described above, the width of the heat seal part (for example, the length of a in FIG. 2) Is preferably a length that can be folded at least in two (that is, a length that can be folded at least once).

  Further, the heat seal portion of the laminate film exterior body may be further bent so that the end portion (folded end) faces the battery upper side (upper side in FIG. 2) or the battery lower side (lower side in FIG. 2).

  Further, in the laminated battery 1, the heat seal part on the side other than the side from which the positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn out is used as the folding part 21 a, and a part thereof is left without being folded. And

  As described above, since the strength of the portion is improved by using the heat seal portion as the folding portion, the strength of the portion of the heat seal portion left unfolded is smaller than that of the folding portion. For this reason, when the internal pressure of the laminated battery abnormally increases, the portion of the heat seal portion that is left unfolded can be preferentially opened, and this can be used as a vent portion. That is, in the laminated battery of the present invention, the heat seal strength of the portion that becomes the vent portion is not lowered, but the portion other than the vent portion of the heat seal portion of the laminate film exterior body is folded as described above to increase the strength. On the other hand, if the part to be the vent part is only heat-sealed, there is a difference between the strength of the vent part and the strength of the other part, and when the internal pressure of the battery rises abnormally, The vent part can be opened preferentially. Therefore, in the battery of the present invention, the heat seal strength of the vent portion can be made comparable to the heat seal strength of the laminate film outer package in the conventional laminate type battery. For example, when manufacturing a battery or using a normal battery In this case, it is possible to satisfactorily prevent the problem that the portion that becomes the vent portion is opened.

  In the laminated film outer package, the width of the heat seal portion of the unfolded portion (width of the heat seal portion of the portion serving as the vent portion) on the side other than the side from which the positive electrode external terminal and the negative electrode external terminal are drawn out Is not necessarily the same as the width of the heat-sealed part of the folded part, but if the part that is not folded is trimmed for the length that protrudes from the folded part, the sealing performance will decrease. As a result, moisture outside the battery can easily enter the exterior body, and the electrolyte solvent in the battery can easily be scattered outside the battery. Therefore, in the laminate film exterior body according to the battery of the present invention, the width of the heat-sealed portion of the unfolded portion is substantially the same as the width of the heat-sealed portion of the folded portion (the heat of the folded portion). It is preferable to secure it at approximately 80% or more of the width of the seal portion. Thereby, the movement of moisture and electrolyte solution solvent inside and outside the battery can be satisfactorily suppressed, and a highly reliable battery can be obtained.

  Although the suitable width (length of a in FIG. 2) of the heat seal part of a laminate film exterior body may change with the size of a laminate film exterior body, it is preferable to set it as 3-15 mm, for example.

  In the laminated battery 1, the position of the vent portion 21 b has an adverse effect on the terminal of the device that houses the laminated battery 1 due to, for example, an electrolyte solution that leaks from the location when the vent portion 21 b operates. In order to avoid this, it is preferable that the laminated film exterior body 1 be located as far as possible from the location where the positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn. For example, as shown in FIG. 1, when the positive external terminal 3 and the negative external terminal 4 are drawn from the same side of the rectangular laminate film outer package 2 in plan view, the positive external terminal 3 and the negative external terminal 4 are It is preferable to provide the vent part 21b on the side opposite to the drawn side.

  Although FIG. 1 shows an example in which one vent portion 21b is provided, the laminated battery may have a plurality of vent portions (two, three, four, etc.). However, if the number of vent parts is increased, there are problems such as complicated battery manufacture. Therefore, the number of vent parts is preferably 1 to 2.

  The width of the vent portion 21b (lateral length in FIG. 1) is preferably 2 mm or more, more preferably 5 mm or more, and preferably 20 mm or less, and 10 mm or less. Is more preferable.

  In addition, in the outer periphery of the laminate film outer package 2, the heat seal portion cannot be folded at the side where the positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn out, so the internal pressure of the laminate battery 1 rises abnormally. In this case, it is preferable to increase the strength of the heat seal portion so that the side portion does not open.

  As a method for increasing the strength of the heat seal portion at the side where the positive electrode external terminal or the negative electrode external terminal is drawn out, for example, the width of the heat seal portion is set to other than the side where the positive electrode external terminal or the negative electrode external terminal is drawn out. The method of making it wider than the width | variety of the heat seal part in a edge | side is mentioned. More specifically, for example, from the viewpoint of improving the strength of the heat seal portion in the side where the positive electrode external terminal and the negative electrode external terminal are drawn out more favorably, in the side where the positive electrode external terminal and the negative electrode external terminal are drawn out The width of the heat seal portion is preferably 1.2 times or more the width of the heat seal portion on a side other than the side from which the positive electrode external terminal or the negative electrode external terminal is drawn. However, if the width of the heat seal part on the side where the positive electrode external terminal or the negative electrode external terminal is drawn out is too long, it is necessary to lengthen the positive electrode external terminal or the negative electrode external terminal, and the resistance value of these external terminals increases. Or a laminate battery becomes too large. Therefore, the width of the heat seal part in the side where the positive electrode external terminal or the negative electrode external terminal is drawn out is not more than twice the width of the heat seal part in the side other than the side where the positive electrode external terminal or the negative electrode external terminal is drawn out. It is preferable to do.

  Further, as will be described in detail later, the metal laminate film constituting the laminate film outer package has a heat fusion resin layer on the inner surface of the battery. An adhesive layer (8 in FIGS. 1 and 2) containing a resin of the same type as the heat-sealing resin contained in the adhesive resin layer is used in advance, and a positive external terminal and a negative electrode are provided via this adhesive layer. Also by bonding the external terminal and the laminate film outer package (its heat-sealing resin layer), the strength of the heat seal portion on the side where the positive electrode external terminal and the negative electrode external terminal are drawn can be increased.

  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. In addition, 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 laminate film exterior body. As described above, an adhesive layer is provided between the laminate film exterior body and the positive electrode external terminal in order to increase the strength of the heat seal portion on the side where the positive electrode external terminal is drawn out of the outer periphery of the laminate film exterior body. Although it can interpose, you may provide the said contact bonding layer previously in the location planned to be located in the heat seal part in a positive electrode external terminal.

  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. In addition, 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 laminate film exterior body. In addition, as described above, an adhesive layer is provided between the laminate film exterior body and the negative electrode external terminal in order to increase the strength of the heat seal portion on the side where the negative electrode external terminal is drawn out of the outer periphery of the laminate film exterior body. Although it can interpose, you may provide the said adhesive layer previously in the location planned to be located in the heat seal part in a negative electrode external terminal.

  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 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 laminate film outer package of the laminate type battery is composed of a metal laminate film, and examples thereof include a three-layer metal laminate film composed of an outer resin layer / a metal layer / a heat-sealing resin layer. Nylon film (such as nylon 66 film), polyester film (such as PET film), etc. as the exterior resin layer in the metal laminate film, aluminum film, stainless steel film, etc. as the metal layer, modified as the heat sealing resin layer Polyolefin film (modified polyolefin ionomer film etc.) etc. are mentioned.

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

  In addition, if the laminate film exterior body is a polygon in plan view, the shape is not particularly limited, and if necessary, in a plan view, a triangle, a tetragon, a pentagon, a hexagon, a heptagon, Various shapes such as an octagon can be taken, but a quadrangle (rectangle or square) is common in plan view.

  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 62 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. In addition, the positive electrode external terminal and the negative electrode external terminal are modified in the same manner as the resin constituting the heat-welding resin layer of the laminate film exterior body on both sides of the location that is expected to be located in the heat seal portion of the laminate film exterior body. An adhesive layer made of polyolefin was disposed.

Two sheets of a 150-μm thick three-layered metal laminate film (rectangular, size 130 mm × 230 mm) made of polyester film / aluminum film / modified polyolefin film were prepared. Then, the laminated electrode body is placed on the modified polyolefin film layer of one metal laminate film so that a part of the positive electrode external terminal and a part of the negative electrode external terminal protrude from the same side of the metal laminate film as shown in FIG. The other metal laminate film was placed on top of it, and three sides were heat-sealed to form a laminate film outer package, which was vacuum dried at 70 ° C. for 15 hours. Thereafter, a non-aqueous electrolyte was injected from one side of the laminate film outer package that was not sealed, and the one side was heat-sealed in a reduced pressure state to obtain a laminated lithium ion secondary battery. Note that the nonaqueous electrolytic solution, a solution was used in which a LiPF ₆ in a solvent mixture to 1: 2 of EC and DEC at a volume ratio at a concentration 1.0 mol / l. The width of the heat seal of the laminate film outer package was 10 mm.

  The laminated lithium ion secondary battery was aged for 24 hours, then charged for 1 hour at a current value of 0.1 C, then charged for 4 hours at a current value of 0.5 C, and further fixed at 4.2 V. Chemical conversion treatment was performed by voltage charging. And about 3 sides other than the side which pulled out the positive electrode external terminal and negative electrode external terminal in the outer periphery of a laminate film exterior body, the heat seal part of the laminate film exterior body was folded in the place of 3 mm from the end. However, in the heat seal portion on the side opposite to the side from which the positive electrode external terminal and the negative electrode external terminal were drawn, as shown in FIG. 1, a portion having a length of 10 mm from one end was left unfolded to form a vent portion. Note that the thickness of the laminated lithium ion secondary battery of Example 1 was 4.5 mm.

Example 2
The bent portion is formed at the outer periphery of the laminate film outer body by folding the both ends of the heat seal portion opposite to the side from which the positive electrode external terminal and the negative electrode external terminal are pulled out (each 5 mm long from the end). A laminated lithium ion secondary battery was produced in the same manner as in Example 1 except that the vent portion was left.

Comparative Example 1
The laminated lithium ion secondary is the same as in Example 1 except that all the portions of the heat seal portion on the three sides other than the side from which the positive electrode external terminal and the negative electrode external terminal are pulled out in the outer periphery of the laminate film outer package are not folded. A battery was produced.

Comparative Example 2
All the parts of the heat seal part on the three sides other than the side from which the positive electrode external terminal and the negative electrode external terminal were pulled out in the outer periphery of the laminate film exterior body were folded at 3 mm from the end, and the vent part was not provided. A laminated lithium ion secondary battery was produced in the same manner as in Example 1.

Comparative Example 3
In the heat seal part of the side opposite to the side from which the positive electrode external terminal and the negative electrode external terminal were drawn out in the laminate film outer package, a part with a length of 10 mm from one end was left unfolded as in Example 1, and the remaining part A laminated lithium ion secondary battery was produced in the same manner as in Example 1 except that the width was aligned with the width of the folded portion. That is, in the laminated lithium ion secondary battery of Comparative Example 3, the width of the heat seal portion at the folded portion is 10 mm, and the width of the heat seal portion left without being folded is 7 mm.

  The batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to the following high-temperature storage test and internal resistance measurement. These results are shown in Table 1.

<High temperature storage test>
Each battery was evaluated for opening pressure and opening position of the laminate film outer package when stored at 130 ° C. for 1 hour. In addition, the pressure at the time of opening of the laminated film exterior body of each battery was substituted with the thickness of the battery at the time of opening (maximum thickness of the battery). That is, if the pressure resistance of the battery laminate film exterior is large, it will not be opened even if the swelling increases, but if the pressure resistance is low, it will be opened when the swelling is small. It can be said that the pressure (internal pressure) is large.

<Internal resistance measurement>
AC impedance measurement of internal resistance after storing each battery (battery different from that used for high-temperature storage test) for 100 days in an environment of 60 ° C. and 90% relative humidity, and internal resistance before storage (1 kHz). And the internal resistance of the battery after storage was evaluated by the ratio (internal resistance increase) when the internal resistance of the battery before storage was 100%.

  In addition, “terminal part” and “terminal part etc.” described in “open position” of “high temperature storage test” in Table 1 indicate that the laminate film exterior body by the high temperature storage test is “positive electrode external terminal and negative electrode external terminal”, respectively. Means that it has been opened at “side portion drawn out”, “side portion where the positive electrode external terminal and negative electrode external terminal are drawn and other side portions”.

  As is clear from Table 1, in the laminated batteries of Examples 1 and 2, the laminate film outer package was opened only at the vent portion after storage at 130 ° C. for 1 hour. On the other hand, in the batteries of Comparative Examples 1 and 2 in which the bent portion was not formed by providing the folded portion and the non-foldable portion in the heat seal portion around the outer periphery of the laminate film outer package, the positive external terminal and the negative external Opening of the laminate film outer package occurs at the side portion from which the terminal is pulled out and the other side portion.

  Moreover, in the battery of Comparative Example 3 in which the width of the heat seal portion serving as the vent portion is aligned with the width of the adjacent folded portion, the internal resistance after storage for 100 days is increased. This is because the width of the heat seal part used as the vent part is shorter than the width of the other heat seal parts, so that moisture and electrolyte solvent move inside and outside the battery in the vent part during storage. It is thought that the internal resistance of the battery increased. On the other hand, in the batteries of Examples 1 and 2 in which the portion of the heat seal part as the vent part was left without being cut, an increase in internal resistance was not observed after 100 days storage, The movement of the electrolyte solvent can be satisfactorily suppressed and has high reliability.

DESCRIPTION OF SYMBOLS 1 Laminated battery 2 Laminate film exterior body 21a Folding part 21b vent part in the heat seal part of a laminate film exterior body

Claims (3)

An electrode body having a sheet-like positive electrode, a sheet-like negative electrode, and a separator is accommodated in a polygonal laminate film outer package in a plan view, and connected to the positive electrode external terminal connected to the sheet-like positive electrode and the sheet-like negative electrode A laminated battery in which the outer periphery of the laminate film exterior body is heat-sealed in a state where the negative electrode external terminal is pulled out, and has a vent portion on the outer periphery of the laminate film exterior body, ,
The heat seal part of the side other than the side from which the positive electrode external terminal and the negative electrode external terminal are drawn out of the laminate film exterior body is a part folded toward the inside of the battery in a plan view and a part not folded And
The width of the heat seal portion in the folded portion of the heat seal portion and the width of the heat seal portion in the unfolded portion of the heat seal portion are substantially the same,
A laminate type battery characterized in that the unfolded portion of the heat seal portion is a vent portion.   2. The laminated battery according to claim 1, wherein the width of the heat seal portion on a side of the laminate film exterior body other than the side from which the positive electrode external terminal and the negative electrode external terminal are drawn is a length that can be folded in at least two. The width of the heat seal part in the side where the positive electrode external terminal and the negative electrode external terminal are drawn out of the laminate film outer package is larger than the width of the heat seal part in the side other than the side where the positive electrode external terminal and the negative electrode external terminal are drawn out. The laminate type battery according to claim 1 or 2, which is wider.

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