JP2008251342A - Lithium ion battery and battery pack having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion battery and battery pack having the same lithium ion battery which are excellent in shock resistance and moldability and secures safe performance by using an external body having a constant back strength. <P>SOLUTION: A case 7 is formed by winding a lithium ion battery body 2 including a positive electrode, an negative electrode, and an electrolyte filled between the positive electrode and the negative electrode with a resin film on the side surface of the lithium ion battery 1 firmly sealed and stored by an external package body 5 with a loop stiffness of 1.5 N or more and 3.0 N or less, which is how the battery pack is produced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lithium ion battery and a battery pack.

  Battery packs are conveniently installed in electrical equipment as power sources for portable devices such as notebook computers, digital cameras, and small video cameras. However, in recent years, battery packs have become smaller and thinner as electrical devices become smaller and thinner. There is also a need to make it. In particular, a thin battery pack is strongly desired in an electric device such as a mobile phone that needs to be designed thin overall.

  Also, as a thin battery stored in a battery pack, the output voltage is higher than that of a nickel cadmium battery or a nickel metal hydride battery, and it has a high energy density, and the apparent discharge capacity decreases by repeating shallow discharge and recharging, so-called There is a tendency to use lithium ion batteries having an excellent feature that there is no memory effect.

Here, the lithium ion battery is also referred to as a lithium secondary battery, and includes a liquid, gel-like, and polymer-like electrolyte, and a cathode / negative electrode active material made of a polymer. In this lithium ion battery, the lithium atom (Li) in the lithium transition metal oxide, which is the positive electrode active material, is charged as lithium ion (Li ⁺ ) during charging and enters the carbon layer of the negative electrode (intercalation). This is a battery in which charge / discharge reaction proceeds when ions (Li ⁺ ) are desorbed (deintercalated) from the carbon layer and moved to the positive electrode to become the original lithium compound.

  In addition, the configuration of the lithium ion battery is as follows: positive electrode current collector (aluminum, nickel) / positive electrode active material layer (polymeric positive electrode material such as metal oxide, carbon black, metal sulfide, electrolytic solution, polyacrylonitrile) / electrolyte layer ( Carbonate electrolytes such as propylene carbonate, ethylene carbonate, dimethyl carbonate, ethylene methyl carbonate, inorganic solid electrolytes composed of lithium salts, gel electrolytes, etc.) / Negative electrode active material layers (lithium metals, alloys, carbon, electrolytes, polyacrylonitrile, etc.) Polymer negative electrode material) / negative electrode current collector (copper, nickel, stainless steel) and an outer package for packaging them.

  As the exterior body, a metal can that has been conventionally pressed into a cylindrical shape or a rectangular parallelepiped shape has been used. However, since the outer wall of the metal can is rigid, the shape of the battery itself is As a result, it was necessary to design the hardware side to match the battery. On the other hand, a multi-layer film composed of an outermost layer, an aluminum foil layer, and a sealant layer is particularly suitable as an outer package for a thin battery because it can be designed to be extremely thin as a whole.

  At this time, since the outer package made of the laminate forms the multilayer film into a bag shape or presses the recess, it is necessary to use a multilayer film excellent in moldability. However, the exterior body is required to have a predetermined waist strength that can withstand an external impact, and the exterior body having excellent moldability has a problem that the waist strength is generally weak and inferior in safety. For this reason, conventionally, an exterior body having low waist strength is used as the exterior body and is housed in a plastic casing to ensure impact resistance and moldability.

  However, when the double structure of the exterior body and the plastic casing is adopted, there is a problem that an excessive gap is generated between the battery and the casing, which is contrary to the downsizing and thinning of the battery pack. Therefore, in order to solve this problem, soft aluminum is used for the tray portion to be pressed, hard aluminum is used for the sheet material for closing the opening, and both ends of the hard aluminum are folded to the back side of the tray. A battery pack in which a casing is formed has been proposed (Patent Document 1).

Since the battery pack described in Patent Document 1 does not need to be stored in a plastic casing, it has excellent characteristics in terms of downsizing and thinning of the battery pack. However, since the heat seal layer of the exterior body is generally melted and recrystallized at the time of heat sealing, cracks are likely to occur when an extra load is applied. For this reason, when folding hard aluminum, it is highly possible that the heat seal part will be bent and cracks will occur in that part, and the electrolyte will contact the aluminum foil through the cracks and the output of the lithium ion battery may be reduced. was there.
JP 2005-166650 A

  Accordingly, in view of the above problems, the present invention stably secures the sealing performance of a lithium ion battery by using an exterior body having predetermined waist strength and formability as the exterior body, and between the housing and the lithium ion battery. The purpose of the present invention is to provide a battery pack having a predetermined strength and safety while ensuring the battery capacity of a lithium ion battery by reducing the gap generated in the battery.

  In order to achieve the above object, the present invention provides a lithium ion battery body comprising a positive electrode, a negative electrode, and an electrolyte filled between the positive electrode and the negative electrode, a base material layer, an aluminum foil layer, and a thermoadhesive resin layer. Is a lithium ion battery that is sealed in at least a sequentially stacked battery case and heat-sealed at the periphery of the case, wherein the outer case has a loop stiffness of 1.5 N or more and 3.0 N or less. A lithium ion battery.

  According to the present invention, in the lithium ion battery having the above-described configuration, the aluminum foil layer is an annealed aluminum having a thickness of 80 μm or more.

  Further, the present invention is characterized in that a corner portion of the outer periphery of the exterior body is cut out and the peripheral portion is bent.

  Moreover, this invention is a battery pack provided with the lithium ion battery of the said structure and the housing | casing which accommodates this lithium ion battery.

  According to the present invention, in the battery pack configured as described above, the casing is formed by winding a resin film around a side surface of the lithium ion battery.

  According to the present invention, in the battery pack configured as described above, the resin film is a stretch film.

  According to the first configuration of the present invention, a lithium ion battery is configured using an exterior body having a loop stiffness of 1.5 N or more, thereby having a predetermined waist strength and excellent impact resistance from the outside. A lithium ion battery can be provided. In addition, by using an exterior body having a loop stiffness of 3.0 N or less, a predetermined formability can be ensured, and a lithium ion battery that matches the shape of the hardware can be formed.

  Further, according to the second configuration of the present invention, the annealed aluminum is excellent in formability, and since the thickness of the aluminum is 80 μm or more, a predetermined strength can be ensured.

  Moreover, according to the 3rd structure of this invention, the volume of the whole lithium ion battery can be restrained by bending an exterior body peripheral part. Moreover, when the outer peripheral edge portion is bent by notching the corner portion, generation of wrinkles and sagging can be prevented.

  Moreover, according to the 4th structure of this invention, the battery pack comprised with the lithium ion battery provided with the said characteristic can be provided.

  Also, according to the fifth configuration of the present invention, the lithium ion battery has a predetermined waist strength and safety is ensured, and therefore needs to be stored in a plastic casing as used conventionally. There is no. Thereby, it is possible to further reduce the thickness of the battery pack. Further, by winding a resin film around the side surface of the lithium ion battery, the peripheral portion of the heat-sealed exterior body can be folded to suppress the volume ratio of the battery pack. Moreover, although the aluminum foil is exposed at the end surface of the exterior body, it is possible to prevent the hardware from being damaged by the exposed aluminum foil by folding the peripheral portion and covering it with a resin film.

  Moreover, according to the 6th structure of this invention, the manufacturing efficiency of a battery pack can be improved by using a stretch film for the side surface of a lithium ion battery.

  Hereinafter, the manufacturing method and structure of the lithium ion battery 1 and the housing 7 of the present invention will be described with reference to the drawings. FIG. 1A is a perspective view showing a state in which the lithium ion battery 1 is disassembled, and FIG. 1B is a perspective view of the lithium ion battery. As shown in FIGS. 1A and 1B, a lithium ion battery 1 is composed of a lithium ion battery body 2 and an exterior body 5, and the lithium ion battery body 2 housed in the exterior body 5 is Moisture resistance is imparted by sealing the periphery with the tab film 6 interposed between the tabs 4.

  Here, the exterior body 5 is a laminated body in which the waist strength by loop stiffness exhibits a value of 1.5N or more and 3.0N or less. Thereby, the exterior body 5 has a predetermined waist strength, ensures impact resistance, and also has a certain formability. Accordingly, when forming the pouch-type exterior body 5 shown in FIG. 1 (a) and the tray portion 5a of the embossed-type exterior body 5 shown in FIG. 5 (b), the occurrence of cracks, wrinkles and breakage is suppressed. Can do. In addition, the detailed description about each structure of an exterior body is shown below.

  The lithium ion battery body 2 includes a positive electrode made of a positive electrode active material and a positive electrode current collector, a negative electrode made of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode (both shown). ) And a tab (electrode terminal) 4 that is connected to the positive electrode and the negative electrode in the cell 3 and has a tip protruding outside the outer package 5.

  FIG. 2A shows a state before the lithium ion battery 1 is stored in the housing 7, and FIG. 2B shows a state after the lithium ion battery 1 is stored in the housing 7. As shown in FIGS. 2A and 2B, the lithium ion battery 1 is inserted and stored in a cylindrical housing 7.

  FIG. 2C is a perspective view of the battery pack according to the present invention. The battery pack connects the tab 4 of the lithium ion battery 1 to a circuit board (not shown) provided inside the casing 7, and The opening of the body 7 is configured to be closed with lid materials 8 and 9. At this time, an electronic terminal 8 a is provided on the outer surface of the lid member 8, and the electronic terminal 8 a is connected to the circuit board inside the housing 7.

  Here, the housing 7 is formed by forming a polyethylene naphthalate film (hereinafter referred to as a PEN film) into a cylindrical shape. Since the exterior body 5 has a predetermined waist strength, sufficient impact resistance can be obtained simply by housing the lithium ion battery 1 in the case 7 made of a cylindrical PEN film instead of the case of the conventional plastic case. Sex can be secured. Further, the PEN film is thinner than the thickness of the plastic resin and contributes to the thinning of the battery pack.

  Further, the casing 7 does not need to be formed into a cylindrical shape in advance, and may be formed by winding a PEN film around the lithium ion battery 1 as shown in FIG. As a result, the casing 7 can be formed along the outer shape of the lithium ion battery 1, the gap between the lithium ion battery 1 and the casing 7 is eliminated, and the battery pack is reduced in size while ensuring the battery capacity. Further, the thickness can be reduced.

  FIG. 4 is a perspective view showing the back surface of the housing 7 when the lithium ion battery 1 is accommodated by the method shown in FIG. When the adhesive is applied to the back surface of the PEN film as shown in FIG. 4A, the adhesive on the back surface is in close contact with the lithium ion battery 1 without bonding both ends of the PEN film, and the PEN film is attached to the housing 7. Serves as a function. In this case, since the lithium ion battery 1 can be accommodated in the housing 7 simply by placing the lithium ion battery 1 on the PEN film and folding it from both ends, the manufacturing efficiency is excellent.

  Further, as shown in FIG. 4B, both ends of the PEN film can be joined to fix the lithium ion battery 1 in the housing 7. At this time, it can adhere | attach by heat-sealing a junction part using what laminated | stacked the sheet | seat which has heat adhesiveness on the PEN film. Moreover, even if it is a PEN film in which the heat-adhesive sheet | seat is not laminated | stacked, it is also possible to apply | coat an adhesive agent to a junction part and to adhere | attach.

  The battery pack according to the present invention is not limited to the pouch-type lithium ion battery 1 in which the lithium ion battery main body 2 is packaged in the pillow-shaped exterior body 5 shown in FIGS. The present invention can also be applied to an embossed type lithium ion battery 1 in which a lithium ion battery main body 2 is packaged using an exterior body 5 composed of a tray part 5a and a sheet part 5b formed with an embossed part as shown.

  FIG. 6A is a perspective view showing a state before the embossed type lithium ion battery 1 is stored in the housing 7, and FIG. 6B is a perspective view showing a state after being stored in the housing 7. . The embossed type lithium ion battery 1 heat seals the peripheral edge portion 5c of the outer package 5 to seal the inside, but the peripheral edge portion 5c is folded in the direction indicated by the arrow in FIG. Store in. Moreover, the aluminum foil which comprises a laminated body is exposed to the end surface of the peripheral part 5c, and there exists a possibility of damaging hardware at the time of mounting | wearing, but this possibility is eliminated by folding and accommodating in the housing | casing 7. FIG.

  FIG. 5C is a plan view of the embossed type lithium ion battery 1, and the outer peripheral portion 5 c has a corner portion 5 d cut away. Thereby, when folding the outer periphery 5c, the generation of wrinkles and sagging can be suppressed.

  Further, in the embossed type lithium ion battery 1, the housing 7 may be configured by winding a resin film around the side surface of the lithium ion battery 1 by the method shown in FIGS. 3 and 4.

  FIG. 6C is a perspective view of a battery pack containing an embossed type lithium ion battery 1, and the battery pack is a circuit board (not shown) provided with a tab 4 of the lithium ion battery 1 inside the housing 7. ), And the two openings of the housing 7 are closed with a lid 8. At this time, the electronic terminals 8 a provided on the outer surface of the lid member 8 are connected to the circuit board inside the housing 7. Although the battery pack is housed in the housing 7 and the opening is closed with the lid 8, the outer peripheral edge 5c is folded and fixed with an adhesive tape without being housed in the housing 7. It is also possible to configure a battery pack by connecting the circuit provided in the material 8 and the tab 4.

  Next, the resin film which comprises the housing | casing 7 of this invention is demonstrated. Since the resin film is a part in direct contact with the hard, a resin layer having an insulating property is basically good. Further, heat resistance against heat generation of the lithium ion battery itself is also required. Although the PEN film is used in this embodiment, a polyethylene terephthalate film, a polyvinyl chloride film, or the like can be used in addition to the PEN film.

  When a stretch film is used as the resin film, the stretch film having an inner diameter slightly smaller than the outer diameter of the lithium ion battery 1 is stretched to wrap the lithium ion battery 1, and the lithium ion battery 1 is used by utilizing the restoring force of the film. Pack tightly. According to this method, the outer periphery 5c can be folded more compactly and the volume of the battery pack can be kept low. Further, the process of housing the lithium ion battery 1 in the housing 7 is made efficient, and the production efficiency of the battery pack is improved.

  Further, as the characteristics of the stretch film, in addition to the self-shrinkability, heat resistance against heat generation of the lithium ion battery, impact resistance as a battery pack housing, toughness, and the like are required. Moreover, when printing the product number etc. of a battery pack on a stretch film, printability is needed. Specific examples include a resin film made of a mixture of at least one of low density polyethylene and linear low density polyethylene and an ethylene-vinyl acetate copolymer, a polypropylene film, polybutadiene, a polyolefin elastomer, and an ionomer.

  Next, the material of the exterior body used for the lithium ion battery of this invention is demonstrated. As shown in FIG. 7A, the laminate 10 forming the exterior body includes at least a base material layer 11, a barrier layer 12, and an innermost layer (thermal adhesive layer) 14, and an adhesive layer 16 is provided between these layers. And laminating by a method such as a dry laminating method, a sandwich laminating method, an extrusion laminating method, or a thermal laminating method. Further, as shown in FIG. 7B, an intermediate layer 13 may be provided between the barrier layer 12 and the innermost layer 14.

  Moreover, the exterior body which concerns on this invention has the waist strength whose loop stiffness is 1.5N or more and 3.0N or less. Thereby, the impact resistance and moldability as an exterior body are ensured. The relationship between the waist strength and the formability will be described later using examples.

  The outermost layer is made of stretched polyester or nylon film, and examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. Examples of the nylon resin include polyamide resins such as nylon 6, nylon 6,6, copolymers of nylon 6,6 and nylon 6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like. It is done.

  The outermost layer needs to have a thickness of 6 μm or more in consideration of the presence of pinholes in the film alone and the occurrence of pinholes during processing, and the preferred thickness is 12 to 25 μm. .

The outermost layer can be laminated in order to improve pinhole resistance, insulation when used as a battery outer body, and deep drawability during emboss molding. When the outermost layer is laminated, the outermost layer includes at least one resin layer of two or more layers, and the thickness of each layer is 6 μm or more, preferably 12 to 25 μm. Examples of laminating the outermost layer include the following 1) to 7) although not shown.
1) Stretched polyethylene terephthalate / stretched nylon 2) Stretched nylon / stretched polyethylene terephthalate

In addition, mechanical suitability of packaging materials (stability of conveyance in packaging machines and processing machines), surface protection (heat resistance and electrolyte resistance), secondary processing and embossing type outer packaging for lithium ion batteries (See Fig. 5) For the purpose of reducing the frictional resistance between the mold and the outermost layer during embossing, the outermost layer is multilayered, and the surface of the outermost layer is valtimic acid amide, erucic acid amide, stearic acid amide, etc. It is preferable to provide a lubricant coating or a fluorine resin layer, an acrylic resin layer, a silicone resin layer, or the like. For example,
3) Fluorine resin / stretched polyethylene terephthalate (Fluorine resin is a film or formed by drying after liquid coating)
4) Silicone resin / stretched polyethylene terephthalate (silicone resin is a film or formed by drying after liquid coating)
5) Fluorine resin / stretched polyethylene terephthalate / stretched nylon 6) Silicone resin / stretched polyethylene terephthalate / stretched nylon 7) Acrylic resin / stretched nylon

  As a laminating method for forming the outer package having a laminated structure, a dry laminating method, a thermal laminating method, an extrusion laminating method, a sandwich laminating method, a coextrusion laminating method, or the like can be used.

  The barrier layer 12 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside through the exterior body 5. In addition to the annealed aluminum, the barrier layer 12 has a pinhole and a processability (pouch). In addition, a metal such as nickel having a thickness of 15 μm or more, or a film on which an inorganic compound such as silicon oxide or alumina is deposited may be used.

  Furthermore, a chemical conversion treatment layer 15 made of an oxide film is provided on the surface of the barrier layer 12. The chemical conversion treatment layer 15 prevents the corrosion and dissolution of the surface of the barrier layer 12 due to hydrogen fluoride generated by the electrolyte and moisture of the lithium ion battery, and improves the adhesion (wetting property) of the surface of the barrier layer 12 to provide a laminate. The adhesive force between the barrier layer 12, the base material layer 11, and the innermost layer 14 (or the intermediate layer 13) at the time of formation is stabilized.

  Further, the innermost layer 14 is sandwiched between the innermost layer 14 and the tab 4 when the tab 4 connected to each of the positive electrode and the negative electrode of the lithium battery main body 2 is sandwiched in a protruding state and thermally bonded. The resin type differs depending on whether or not the tab film 6 is interposed. When the tab film 6 is interposed, a film made of a propylene-based resin alone or a mixture may be used. When the tab film 6 is not interposed, a film made of an acid-modified olefin resin modified with a graph with an unsaturated carboxylic acid. May be used.

  Polypropylene is preferably used as the innermost layer 14, but a single layer or a multilayer composed of a linear low density polyethylene, a medium density polyethylene single layer or a multilayer, or a linear low density polyethylene, a medium density polyethylene blend resin. It can also be used as a film consisting of

  For each type of polypropylene, that is, random propylene, homopropylene, block propylene, and linear low density polyethylene, medium density polyethylene, low crystalline ethylene-butene copolymer, low crystalline propylene-butene copolymer, A terpolymer composed of a three-component copolymer of ethylene, butene, and propylene, silica, zeolite, an antiblocking agent (AB agent) such as acrylic resin beads, a fatty acid amide slip agent, and the like may be added.

  Further, by using an unstretched polypropylene layer having a melting point of 140 to 180 ° C., in the lithium ion battery, the temperature inside the outer package 5 rises due to overcharge or the like, the tab 4 generates heat, and the tab 4 is sandwiched. Even when the portion is melted, it is possible to prevent the tab 4 and the barrier layer 12 made of metal foil from coming into contact with each other and short-circuiting.

  In addition, the layers of the laminate 10 are appropriately subjected to corona treatment and blast treatment for the purpose of improving and stabilizing film forming properties, lamination processing, and final product secondary processing (pouching, embossing) suitability. Surface activation treatment such as oxidation treatment or ozone treatment may be performed.

  In addition, the lamination method between the layers can be specifically formed using a T-die method, an inflation method, a co-extrusion method, or the like. If necessary, the secondary film may be formed by a method such as coating, vapor deposition, ultraviolet curing, or electron beam curing. Moreover, as a bonding method, methods such as a dry laminating method, an extrusion laminating method, a coextrusion laminating method, and a thermal laminating method can be used.

  When laminating by the dry laminating method, polyester, polyethyleneimine, polyether, cyanoacrylate, urethane, organic titanium, polyetherurethane, epoxy, polyesterurethane, imide, isocyanate Various adhesives based on polyolefin, polyolefin, and silicone can be used. In addition, these adhesive layers appropriately contain at least one of silicon oxide, calcium carbonate, zinc, red lead, lead suboxide, lead oxide, lead cyanamide, zinc chromate, barium potassium chromate, and barium zinc chromate. Addition of an additive characterized by this further improves chemical resistance and organic solvent resistance. In particular, silicon oxide, calcium carbonate, zinc, red lead, lead suboxide, zinc oxide, lead cyanamide, zinc chromate, potassium barium chromate, barium zinc chromate, etc. are generated by the reaction of electrolyte with moisture Has the effect of preventing the corrosion of hydrogen fluoride on each layer, particularly the barrier layer (aluminum).

  In addition, when using the extrusion laminating method, polyester, polyether, urethane, polyetherurethane, polyesterurethane, isocyanate, and polyolefin can be used as an adhesion promotion method that stabilizes the adhesive strength between the layers to be bonded. Applying resin such as polyethyleneimine, cyanoarylate, organotitanium compound, epoxy, imide, silicone, and their modified products or mixtures, about 1μm, or surface activation treatment by ozone treatment It can be carried out. Further, by using an unsaturated carboxylic acid grafted polyolefin as a resin when bonded by an extrusion laminating method or a thermal laminating method, adhesion resistance and content resistance are improved.

  Next, the relationship between the waist strength and the formability of the exterior body according to the present invention will be described below by examples.

[Preparation of sample]
Anodized aluminum foil (Toyo Aluminum Co., Ltd., 3004-O material: 100 μm thick) was subjected to chemical conversion treatment, and one chemical conversion treated surface was biaxially stretched nylon film (thickness 25 μm) Were bonded together by a dry laminating method through a two-component curable polyurethane adhesive. Next, acid-modified polypropylene was applied and baked on the other chemical conversion treated surface by a roll coating method, and an unstretched polypropylene film (thickness 30 μm) was laminated by a thermal laminating method to obtain a sample according to the present invention. The total thickness of the sample according to the present invention is 176 μm.

  Next, a chemical conversion treatment was performed on both surfaces of an aluminum foil that was not annealed (Toyo Aluminum Co., Ltd., 3004-H material: thickness 100 μm), and a polyethylene naphthalate film (thickness) was formed on one chemical conversion treatment surface. 12 μm) was bonded by a dry laminating method through a two-component curable polyurethane adhesive. Next, an unstretched polypropylene film (thickness of 30 μm) was bonded to the other chemical conversion treated surface by a thermal lamination method to obtain a sample according to Comparative Example 2. The total thickness of the sample according to Comparative Example 2 is 145 μm.

  Next, both surfaces of the annealed aluminum foil (thickness 40 μm) are subjected to chemical conversion treatment, and a biaxially stretched nylon film (thickness 25 μm) is applied to one chemical conversion treatment surface with a two-component curable polyurethane adhesive. And bonded together by a dry laminating method. Next, acid-modified polypropylene was applied and baked on the other chemical conversion treated surface by a roll coating method, and an unstretched polypropylene film (thickness 30 μm) was laminated by a thermal laminating method to obtain a sample according to Comparative Example 3. Note that the total thickness of the sample according to Comparative Example 3 is 113 μm.

In this example, the chemical conversion treatment layer was coated with a treatment liquid comprising a phenol resin, a chromium fluoride compound, and phosphoric acid by a roll coating method, and baked under a condition where the film temperature was 90 ° C. or higher. Here, the coating amount of chromium is 10 mg / m ² (dry weight). The acid-modified polypropylene was baked under conditions where the aluminum temperature was 180 ° C. or higher, and the coating amount of the acid-modified polypropylene was 3 g / m ² (dry weight).

[Loop stiffness measurement]
Next, the sample according to the present invention and Comparative Examples 2 and 3 is cut into a size of 25 mm × 140 mm, both ends of the sample are fixed with a width of 20 mm using the apparatus shown in FIG. 8, and the sample has a circumference of 100 mm. After forming into a cylindrical shape, the force required to compress at 50 mm / min until the Z value reached 25 mm was measured from the upper side as the waist stiffness of the loop stiffness, and the results are summarized in Table 1. These measured values are values in the MD direction of each sample.

[Formability comparison test]
Next, each sample according to the present invention 1 and comparative examples 2 and 3 is cut into a size of 80 mm × 100 mm, and the sample is formed into a molding die (female die) having a diameter of 34 mm × 44 mm and a corresponding molding die. Using a mold (male), press molding was performed on 10 samples at a pressing pressure of 0.25 MPa by changing the molding depth from 0.5 mm to 0.5 mm, and the sample had 10 wrinkles and cracks. The forming depth not occurring in any of the samples was defined as the limit forming depth, and the forming depth was used as the evaluation value.

  As a result, the limit formability of the sample according to the present invention 1 is 4.5 mm, the limit formability of the sample according to Comparative Example 2 is 0 mm, and the limit formability of the sample according to Comparative Example 3 is 7.0 mm. there were.

  As described above, it is considered that an exterior body having a loop stiffness value of 3.0 N or more is remarkably inferior in formability and unsuitable for use as an exterior body from the measured loop stiffness and the moldability comparison test. Moreover, it is thought that the exterior body which is excellent in limit moldability is not suitable for use as the battery pack according to the present invention because the loop stiffness value is very small and there is no waist. Moreover, it turned out that the exterior body which concerns on this invention is excellent in both waist strength and a moldability, and is suitable for the lithium ion battery and battery pack which concern on this invention.

  By using the lithium ion battery and the battery pack according to the present invention, it is possible to further reduce the thickness of the battery pack that houses the lithium ion battery, and the lithium ion battery is suitable as a power source for portable devices such as mobile phones. Can be provided.

(A) is an exploded perspective view of a lithium ion battery (pouch type) according to the present invention, and (b) is a perspective view thereof. (A) is a perspective view which shows the state before accommodating the lithium ion battery (pouch type) which concerns on this invention in a housing | casing, (b) is a case where the lithium ion battery (pouch type) which concerns on this invention is a housing | casing It is a perspective view which shows the state after accommodating in (c), (c) is a perspective view of the battery pack which concerns on this invention. These are perspective views which show an example of the method of accommodating the lithium ion battery which concerns on this invention in a housing | casing. (A), (b) is a perspective view which shows the back surface in the state which accommodated the lithium ion battery which concerns on this invention in the housing | casing. (A) is an exploded perspective view of a lithium ion battery (embossed type), (b) is a perspective view of a lithium ion battery (embossed type), and c) is a front view of the lithium ion battery (embossed type). is there. (A) is a perspective view which shows the state before accommodating the lithium ion battery (embossed type) which concerns on this invention in a housing | casing, (b) is a lithium ion battery embossed type which concerns on this invention) on a housing | casing. It is a perspective view which shows the state after accommodating, (c) is a perspective view of the battery pack which concerns on this invention. These are sectional drawings which show the laminated structure of the exterior body of the lithium ion battery which concerns on this invention. FIG. 3 is a perspective view of an apparatus used for loop stiffness measurement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Lithium ion battery main body 3 Cell (electric storage part)
4 Tab 5 Exterior body 5a Tray part 5a
5b Sheet portion 5b
5c Peripheral part 5d Corner part 6 Adhesive film 7 Housing 8 Lid material 8a Electronic terminal 9 Lid material 10 Laminate 11 Innermost layer (heat seal layer)
12 Metal foil layer 13 Intermediate layer 14 Innermost layer (heat seal layer)
15 Chemical conversion layer (metal foil layer surface)
16 Adhesive layer

Claims (6)

A lithium ion battery body including a positive electrode, a negative electrode, and an electrolyte filled between the positive electrode and the negative electrode is formed into a battery outer package in which a base material layer, an aluminum foil layer, and a heat-adhesive resin layer are sequentially laminated. A lithium ion battery encapsulated and heat-sealed at the periphery of the exterior body,
A lithium ion battery having a loop stiffness of the outer package of 1.5N or more and 3.0N or less.   The lithium ion battery according to claim 1, wherein the aluminum foil layer is an annealed aluminum having a thickness of 80 μm or more.   3. The lithium ion battery according to claim 1, wherein a corner portion of the outer periphery of the outer package is cut out and the peripheral portion is bent.   A battery pack comprising: the lithium ion battery according to any one of claims 1 to 3; and a housing that houses the lithium ion battery.   The battery pack according to claim 4, wherein the casing is formed by winding a resin film around a side surface of the lithium ion battery.   The battery pack according to claim 5, wherein the resin film is a stretch film.

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