JP2006196217A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance volume efficiency by simplifying a battery pack structure, and prevent thermal runaway and short circuit when abnormal heat is generated. <P>SOLUTION: In a polymer battery using a gelatinous electrolyte, after a battery element peripheral part is sealed by pinching the battery element by a soft laminate 11b in which a soft metal is used in a metal layer and a hard laminate 11a in which a hard metal is used in the metal layer, it is molded in the battery pack shape and the hard laminate is also used as a battery pack cabinet in common. Furthermore, by making a heat capacity of the hard metal used for the metal layer of the hard laminate 0.019 J/K cm<SP>2</SP>or more, the laminate absorbs heat in the abnormal heat generation and prevents the thermal runaway. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery pack applied to, for example, a lithium ion polymer secondary battery.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Videotape recorder), a mobile phone, or a laptop computer have appeared, and their size and weight have been reduced. Along with this, the demand for batteries used as power sources for portable electronic devices is growing rapidly, and the battery packs connected to the devices are lighter and thinner in order to reduce the size and weight of the devices. There is a need to use the storage space efficiently. As a battery satisfying such requirements, a lithium ion battery having a large energy density and output density is most suitable.

  Since the conventional battery pack stores the unit cell in an outer case made of plastic or the like, the battery capacity per volume is not very efficient. Therefore, in order to solve such a problem, a battery pack having a simple structure has been devised.

  For example, a battery pack having a shape in which a lithium ion battery using a rectangular can is used, a protective circuit is mounted on the battery lid surface, and is solidified with a resin, and the entire side surface is covered with a label. Since this metal can itself has a pack housing, this battery does not require the use of an outer case, and has a configuration with good volume efficiency.

  However, when the above-described configuration is used, once the liquid leaks from the battery, the device itself on which the battery pack is mounted may be easily attacked by the electrolytic solution.

Therefore, as a countermeasure against liquid leakage, which is a problem when using a liquid electrolyte, a battery prepared by adding a substance having an adhesive action to the electrolyte or a so-called polymer battery using a gel electrolyte using a polymer Is widely used. In these batteries, the electrode and the electrolyte are in close contact with each other, and the contact state can be maintained. With such a configuration, liquid leakage can be prevented, and a thin battery using a film-shaped exterior material such as an aluminum laminate film can be manufactured.
Japanese Laid-Open Patent Publication No. 2002-8606

  However, when the laminate film is used as the outermost package, the strength of the laminate film itself is weak and easily damaged. For this reason, it is necessary to store the battery pack in an outer case made of plastic or the like in the same manner as a battery pack using a conventional single battery. In the case of such a conventional battery pack, the thickness of the outer case is about 0.3 to 0.4 mm, and the thickness of the cell is 0.8 to 1.0 mm in consideration of the double-sided tape for fixing and the tolerance. The thickness was increased. In addition, a shape for ultrasonic welding of the upper and lower mold cases is required also in the outer peripheral direction, and therefore, a thickness of about 0.7 mm is required. As a result, the increase in the volume of the battery pack is 1.3 to 1.4 times the volume of the cell, and the battery capacity per volume is not very efficient.

  In addition, if the battery element is covered with an insulator in multiple layers, the heat dissipation becomes worse, and the battery is likely to cause thermal runaway in the event of abnormal heat generation. For example, when a nail or the like is pierced and short-circuited inside the battery, heat is generated, and this can serve as an initiating agent to cause a decomposition reaction within the battery, resulting in dangerous heat generation.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a battery pack having a high volumetric efficiency of battery capacity and high safety and exterior strength.

In order to solve the above problems, a first aspect of the present invention is a battery pack having a battery element of a polymer battery covered with a laminate film in which a metal layer is sandwiched between an outer resin layer and an inner resin layer. A battery element is accommodated between a hard laminate film using a hard metal for the layer and a soft laminate film using a soft metal for the metal layer, sealing the peripheral part of the battery element, and forming the hard laminate film into a battery element shape. A battery cell that is curved along the edge of the hard laminate film and sealed together, a circuit board provided with a protective circuit joined to an electrode terminal derived from the battery element, and an opening end of the battery cell. and a resin cover for sealing, and wherein the heat capacity of the hard metal used for the metal layer of the rigid laminated film is 0.019J / K · cm ² or more That is a battery pack.

  According to a second aspect of the present invention, in a battery pack having a battery element of a polymer battery covered with a laminate film in which a metal layer is sandwiched between an outer resin layer and an inner resin layer, a hard metal is used for the metal layer. The battery element is housed between the hard laminate film and the soft laminate film using a soft metal in the metal layer, sealing the periphery of the battery element, bending the hard laminate film along the battery element shape, A battery cell in which the ends of the laminate film are sealed together, a circuit board provided with a protection circuit joined to an electrode terminal derived from the battery element, and a resinous cover for sealing the open end of the battery cell The electrode terminal lead-out part of the battery cell has a metal heater head arranged on the hard laminate film side and a metal arranged on the soft laminate film side Heat-sealed with the Taheddo a battery pack only metal heater head disposed flexible laminated film side and having a groove notch corresponding to the shape of the electrode terminal.

  According to this invention, since a battery pack can be produced without using an exterior case, the battery capacity per volume can be increased. Further, since a laminate material using a metal layer having a large heat capacity is used, heat is absorbed during heat generation, and safety is high. Furthermore, since a hard laminate material is used as an exterior material, a battery pack with high mechanical strength can be produced.

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

  FIG. 1 shows a configuration of a battery pack of a lithium ion polymer secondary battery to which the present invention is applied. In this battery pack, the battery cell 10 is produced by covering the battery element with a hard laminate material indicated by reference numeral 11a and a soft laminate material indicated by reference numeral 11b sandwiching the upper and lower sides of the battery element. A positive electrode terminal 2a connected to the positive electrode and a negative electrode terminal 2b connected to the negative electrode are led out from a battery element (not shown), and a hard laminate material 11a and a soft laminate material are provided on both surfaces of the positive electrode terminal 2a and the negative electrode terminal 2b. In order to improve the adhesiveness to 11b, resin pieces (hereinafter referred to as sealants) 3a and 3b are coated.

  The derived positive electrode terminal 2a and negative electrode terminal 2b are joined to the protection circuit by a method such as resistance welding or ultrasonic welding. The circuit board 4 on which the protection circuit bonded to the battery element is mounted is inserted between the top covers 5, and the positive terminal 2 a, the negative terminal 2 b, and the circuit board 4 are housed in the battery pack as the top cover 5 is welded. Configure as follows. The protection circuit of the circuit board 4 has a temperature protection element such as a PTC (Positive Temperature Coefficient) and a thermistor, and cuts off the current path when the inside of the battery pack becomes high temperature. Note that one end face from which the positive electrode terminal and the negative electrode terminal are derived is appropriately referred to as a top side, and the other end portion is appropriately referred to as a bottom side.

  FIG. 2 shows main structures of the hard laminate material 11a and the soft laminate material 11b. The hard laminate material 11a and the soft laminate material 11b have a three-layer structure in which the metal layer indicated by reference numeral 12 is sandwiched between the outer resin layer 13 and the inner resin layer 14, and are multilayers having moisture resistance and insulation properties. It is a film. The metal layer 12 plays the most important role of protecting the contents by preventing the ingress of moisture, oxygen and light, and aluminum (Al) is most often used because of its lightness, extensibility, cost and ease of processing. Nylon (Ny), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN) is used for the outer resin layer 13 because of its beautiful appearance, toughness, and flexibility. The inner resin layer 14 is a portion that melts and fuses with heat or ultrasonic waves, and unstretched polypropylene (CPP) or polyethylene (PE) is often used.

  The metal layer 12 and the outer resin layer 13 are bonded together by providing an adhesive layer 15. On the other hand, the metal layer 12 and the inner resin layer 14 are not only the method of providing the adhesive layer 16, but also the method of heating and melting CPP or PE and bonding it to the metal layer 12, or the method of bonding the CPP film or PE film with a heat roller or the like. Various methods can be used.

  Al, copper (Cu), iron, nickel (Ni), stainless steel (SUS), titanium, or the like can be used for the metal layer of the hard laminate 11a. When Al is used for the metal layer, in addition to 3003H, 3004H, and 1100H according to JIS standards, hard aluminum materials of 2000 series, 5000 series, and 6000 series can be used.

  The main structure of the hard laminate 11a is composed of Al for the metal layer, Ny for the outer resin layer, and CPP for the inner resin layer. The structure of the thickness is Ny / adhesive layer / Al / (adhesive layer) / CPP = 15 ± 5/3 ± 1/100 ± 20/2 ± 1/30 ± 5 [μm], and the total thickness of the hard laminate material 11a Is 150 ± 32 [μm].

This time, in order to produce a highly safe battery pack even when the battery element generates heat, a hard laminate material having a heat capacity per square centimeter of the metal layer of 0.019 J / K · cm ² or more is used. Use. In addition, the battery pack in this case shall have a battery capacity of 500 to 900 mAh which is generally used. Since the heat capacity of the metal layer is large, the metal layer absorbs heat even when the battery element generates heat, and the battery element can be prevented from being overheated and short-circuited.

  Further, for the metal layer of the soft laminating material 11b, in addition to 8079O and 8021O according to JIS standards, 8000 series general soft aluminum materials can be used.

  The main structure of the soft laminate material 11b is the same as the hard laminate material 11a, the metal layer is made of Al, the outer resin layer is made of Ny, the inner resin layer is made of CPP, and the thickness is made of Ny / adhesive layer / Al / ( Adhesive layer) / CPP = 20 ± 5/3 ± 1/35 ± 10/2 ± 1/30 ± 5 [μm]. For this reason, the total thickness of the hard laminate material 11a is 90 ± 22 [μm]. In the present invention, a soft laminate material having a total thickness of about 85 μm with Ny / adhesive layer / Al / (adhesive layer) / CPP = 15/3/35/2/30 [μm] was used.

  A battery cell is produced using such a hard laminate material 11a and a soft laminate material 11b. First, a method for manufacturing the battery element 1 will be described.

  FIG. 3 shows an example of a battery element constituting a battery pack to which the present invention is applied. This battery element is formed by laminating a strip-like positive electrode 21, a separator 23a, a strip-like negative electrode 22 disposed opposite to the positive electrode 21, and a separator 23b and winding them in the longitudinal direction. Gel electrolyte 24 is applied to both surfaces of 22. The positive electrode terminal 2a and the negative electrode terminal 2b are connected to the positive electrode 21 and the negative electrode 22, respectively.

[Positive electrode]
The positive electrode has a positive electrode active material layer containing a positive electrode active material formed on both surfaces of the positive electrode current collector. The positive electrode current collector is made of a metal foil such as an Al foil, Ni foil, or SUS foil.

  The positive electrode active material layer includes, for example, a positive electrode active material, a conductive agent, and a binder. These are uniformly mixed to form a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent to form a slurry. Next, the slurry is uniformly applied on the positive electrode current collector by a doctor blade method or the like, dried at a high temperature, and the solvent is removed. Here, the positive electrode active material, the conductive agent, the binder, and the solvent only have to be uniformly dispersed, and the mixing ratio is not limited.

As the positive electrode active material, mainly Li _x MO ₂ (wherein M represents one or more transition metals, x is different depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less). A composite oxide of lithium and a transition metal is used. _{Specifically, LiCoO 2, LiNiO 2, LiMn} 2 O 4, LiNi y Co 1-y O 2 (0 <y <1) , and the like. A solid solution in which a part of the transition metal element is substituted with another element can also be used. Examples thereof include LiNi _0.5 Co _0.5 O ₂ and LiNi _0.8 Co _0.2 O ₂ . These lithium composite oxides can generate a high voltage and have an excellent energy density. _{Furthermore, TiS 2, MoS 2, NbSe} 2, V 2 O no lithium metal sulfides such as ₅ or may be used an oxide as the positive electrode active material.

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

  The positive electrode 21 has a positive electrode terminal 2a connected to one end of the electrode by spot welding or ultrasonic welding. The positive electrode terminal is preferably a metal foil or a mesh-like one, but there is no problem even if it is not a metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material for the positive electrode terminal include Al.

[Negative electrode]
The negative electrode is formed by forming a negative electrode active material layer containing a negative electrode active material on both surfaces of a negative electrode current collector. The negative electrode current collector is made of, for example, a metal foil such as a Cu foil, a Ni foil, or a SUS foil.

  The negative electrode active material layer includes, for example, a negative electrode active material, a conductive agent if necessary, and a binder. These are uniformly mixed to form a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent to form a slurry. Next, this slurry is uniformly applied on the negative electrode current collector by a doctor blade method or the like, dried at a high temperature, and the solvent is blown off. Here, the negative electrode active material, the conductive agent, the binder, and the solvent only have to be uniformly dispersed, and the mixing ratio is not limited.

  As the negative electrode active material, lithium metal, a lithium alloy, a carbon material that can be doped / undoped with lithium, or a composite material of a metal material and a carbon material is used. Specific examples include graphite, non-graphitizable carbon, and graphitizable carbon. As the graphite, artificial graphite such as mesophase carbon microbeads, carbon fiber, coke, and natural graphite can be used. Various types of metals can be used as materials capable of alloying lithium, but tin (Sn), cobalt (Co), indium (In), Al, silicon (Si) and alloys thereof are often used. It is done. When metal lithium is used, it is not always necessary to use powder as a coating film with a binder, and a rolled Li metal plate may be used.

  As the binder, for example, polyvinylidene fluoride, styrene butadiene rubber or the like is used. Moreover, as a solvent, N-methylpyrrolidone, methyl ethyl ketone, etc. are used, for example.

  Similarly to the positive electrode, the negative electrode also has a negative electrode terminal 2b connected to one end of the electrode by spot welding or ultrasonic welding. The negative electrode terminal is preferably a metal foil or a mesh-like one, but there is no problem even if it is not a metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material for the negative electrode terminal include Cu and Ni.

  In addition, although it is preferable that the positive electrode terminal and the negative electrode terminal are derived | led-out from the same direction, there is no problem even if it derive | leads out from which direction as long as a short circuit etc. do not occur and there is no problem in battery performance. Moreover, the connection place of a positive electrode terminal and a negative electrode terminal will not be restricted to said example, if the electrical contact has taken place and the attachment method.

[Electrolytes]
As the electrolyte, an electrolyte salt and a non-aqueous solvent that are generally used in lithium ion batteries can be used. Specific examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ethylpropyl carbonate, or hydrogen of these carbonic acid esters to halogen. Examples include substituted solvents. One of these solvents may be used alone, or a plurality of these solvents may be mixed with a predetermined composition.

As electrolyte salt, what melt | dissolves in the said nonaqueous solvent can be used. For example _{LiPF 6, LiBF 4, LiN (} CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiClO 4 and the like. The electrolyte salt concentration is not a problem as long as it can be dissolved in the above solvent, but the lithium ion concentration is in the range of 0.4 mol / kg or more and 2.0 mol / kg or less with respect to the non-aqueous solvent. Is preferred.

  A gel electrolyte is obtained by gelling an electrolytic solution obtained by mixing the above-described electrolyte and electrolytic salt with a matrix polymer. The matrix polymer is not particularly limited as long as it is compatible with a non-aqueous electrolyte obtained by dissolving the electrolyte salt in the non-aqueous solvent and can be gelled. Examples of such a matrix polymer include a polymer containing polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile, and polymethacrylonitrile in repeating units. Such a polymer may be used individually by 1 type, and may mix and use 2 or more types.

  The battery element 1 produced as described above is packaged with a hard laminate material 11a and a soft laminate material 11b and molded to produce a battery cell 10.

  FIG. 4 shows the configuration of the battery cell 10. The battery cell 10 is produced by arranging a hard laminate material 11a and a soft laminate material 11b on the upper and lower sides of the battery element indicated by reference numeral 1, heat-welding, and then molding the hard laminate material 11a to be an exterior. . The soft laminate material 11b is provided with a recess for arranging the battery element 1, and the recess is formed by deep drawing from the CPP layer side which is the inner resin layer.

  The battery element 1 is accommodated in the above-described recess, and the hard laminate material 11a covers the opening of the recess. Each of the hard laminate material 11a and the soft laminate material 11b is arranged so that the CPP layers (or PE layers) thereof face each other.

  Next, the four sides around the battery element 1 are heat-sealed under reduced pressure and sealed. Generally, when sealing the laminate sheathing by taking out the electrode terminal from the sealing portion interface, an elastic body such as rubber is lined on the surface or the upper and lower heaters are used to absorb the thickness of the electrode terminal. Notches are provided on the head surface (the surface in contact with the laminate film). When a flat metal head is used, a large pressure is applied to the electrode terminal part during heat sealing, preventing the electrode terminal from being cut, or preventing the metal head from hitting the part that does not sandwich the electrode terminal, resulting in poor sealing performance. Because.

  When sealing the battery cell this time, since a thick laminate sheathing material is used, it is expected that a large amount of heat is taken away by the electrode terminals and the laminate sheathing material. As a means of efficiently heating and sealing the electrode terminal portion of the battery cell using such a laminate material, it is effective to heat-seal using a wide heater head, but the dead space is large. Loss of capacity. Considering the moisture barrier property of the material, it is desirable that the sealing width be in the range of 1.0 to 3.0 mm in order to achieve both reliability and battery capacity. In this case, since the heater head using an elastic body cannot be sufficiently sealed, it is effective to seal using a metal heater head provided with a notch.

  However, since the laminate material using a hard metal film is not flexible like this time, it is difficult to deform and seal it along the notch groove and the terminal cross-sectional shape, and sealing was possible. However, a seal mark as shown by the hatched portion in FIG. 5 remains, which is extremely inappropriate as a pack appearance.

  Therefore, as shown in FIG. 6, when sealing the electrode terminal lead-out portion, a metal head without a notch groove is used as the heater head on the hard laminate material side, and the notch is used as the heater head on the soft laminate material side. By using a metal head provided with a groove, a battery cell free from defects such as seal marks and terminal cutting can be obtained. 6A shows a state before heat fusion, and FIG. 6B shows a state after heat fusion.

  However, if the width of the notch groove provided in the heater head is too narrow, the electrode terminal is sandwiched, resulting in cutting of the terminal and insufficient sealing near the electrode terminal. On the other hand, if it is too wide, the sealing property around the electrode terminal is deteriorated, and moisture easily enters. Therefore, by providing the notch groove so that the width of the notch groove is 2.0 to 6.0 mm wider than the width of the electrode terminal, a margin of 1.0 to 3.0 mm can be provided on each of the left and right sides of the electrode terminal. Sealing can be performed. It should be noted that the inner resin layer is melted and bonded even if it is a portion where the heater head does not contact during heat fusion, and therefore, if there is a margin of about 1.0 to 3.0 mm, sealing is possible without any problem.

  Further, if the metal layer of the hard laminate is too thick, it cannot be bent later when it is molded, and if it is too thin, a seal mark at the time of heat-sealing remains. Therefore, by using a hard laminate material having a metal layer thickness of 80 to 120 [μm], molding becomes possible, and no seal marks remain, so that a good pack appearance can be realized.

  Further, as shown in FIG. 7, when the electrode terminal lead-out portion is sealed with the heater head, the laminate exterior material is bonded, and the heater head avoids the laminate material end portion from which the electrode terminal is led, Heat to heat-seal. A portion indicated by a hatched portion in FIG. 7 is a portion pressed and heated by the heater head.

  When heat sealing is performed by stepping on the end of the laminate material, the cut burr generated when the laminate exterior material is trimmed to an appropriate size may be short-circuited with the electrode terminals, or the metal layer of the heater head and laminate exterior material may be This is because a short circuit may occur due to contact. The heater head avoids the end portion of the laminate material and heat-bonds the electrode terminal lead-out portion, so that the end portion of the laminate material where the cut burr is generated is not sandwiched between the heater heads and pressed, and the heater head and the metal layer are There is no contact.

  The battery element 1 after heat sealing is put in a mold, the hard laminate material 11a and the soft laminate material 11b are curved along the shape of the battery element, and are molded so as to have an elliptical cross section as shown in FIG. Thus, the hard laminate material 11a is used as the outermost case to protect the battery element 1.

  As shown by the dotted line portion in FIG. 8, a seam is formed at a portion where the film end portions of the hard laminate material 11a and the soft laminate material 11b are combined. This part is enlarged and shown in FIG. Since the hard laminate material 11a and the soft laminate material 11b are shifted and overlapped, the seam of the hard laminate material 11a and the soft laminate material 11b are formed so that the seams of the hard laminate material 11a and the soft laminate material 11b are displaced. The CPP layers 14b of the material 11b are heat-sealed and sealed without a gap.

  At this time, an adhesive sheet is disposed outside the bottom surface of the recess provided in the soft laminate 11b. The pressure-sensitive adhesive sheet is an auxiliary member used for bonding the Ny layers of the soft laminate 11b, the PET layers, or the PEN layers at a high temperature. In addition, in the case of the battery pack to which the present invention is applied, since the soft laminate is not visible to the outside, the outer resin layer is made the same CPP layer or PE layer as the inner resin layer without using an adhesive sheet. The laminate material inside the battery pack can be bonded.

  Next, a protection circuit is joined to the positive electrode terminal 2a and the negative electrode terminal 2b led out from the battery cell 10 molded into a predetermined shape. The protection circuit is mounted in advance on the circuit board 4, and the circuit board connected to the battery element 1 is inserted into a pre-molded top cover 5.

  Furthermore, as shown in FIG. 10, the top cover 5 and the rear cover 6 are joined to the produced battery cell 10. The top cover 5 integrated with the circuit board and the rear cover 6 molded in the same manner as the top cover 5 are joined to the battery cell 10 by heat welding or a method of pouring a warmed resin material (hot melt agent). In addition, without forming the top cover 5 and the rear cover 6 in advance, the battery cell is set in the top cover or the mold of the rear cover shape, and a warmed resin material is poured into the battery cell 10 while molding the top cover or the rear cover. It is also possible to use a method of performing bonding. In addition, when pouring warmed resin, it is necessary to comprise so that a circuit board may not be deform | transformed or damaged with a heat | fever.

  Finally, a decorative label is attached around the hard laminate material to complete a battery pack as a product. In addition, although a decorative label may be affixed so that a battery pack may be made 1 round, and may be affixed only on a battery pack single side | surface, it is more preferable to affix on only one side, considering heat dissipation.

  As described above, a battery pack in which the hard laminate material also serves as an exterior can be manufactured without using a resin exterior case.

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

[Production of positive electrode]
92% by weight of lithium cobaltate (LiCoO ₂ ), 3% by weight of powdered polyvinylidene fluoride, and 5% by weight of powdered graphite were uniformly mixed and dispersed in N-methylpyrrolidone to form a slurry-like positive electrode composite. An agent was prepared. This positive electrode mixture was uniformly applied to both surfaces of an Al foil serving as a positive electrode current collector, and dried under reduced pressure at 100 ° C. for 24 hours to form a positive electrode active material layer.

  Subsequently, this was pressure-formed with a roll press to obtain a positive electrode, and an Al ribbon positive electrode terminal was welded to an uncoated portion of the positive electrode active material. Further, a portion of the positive electrode terminal sandwiched between the aluminum laminate films was bonded to both sides with a polypropylene resin piece to form a sealant.

[Production of negative electrode]
Artificial graphite (91% by weight) and powdery polyvinylidene fluoride (9% by weight) were uniformly mixed and dispersed in N-methylpyrrolidone to prepare a slurry-like negative electrode mixture. Next, this negative electrode mixture was uniformly applied to both surfaces of a copper foil serving as a negative electrode current collector, and dried under reduced pressure at 120 ° C. for 24 hours to form a negative electrode active material layer.

  Next, this was subjected to pressure molding with a roll press to obtain a negative electrode, and a negative electrode terminal of a Ni ribbon was welded to an uncoated portion of the negative electrode active material. In addition, a piece of polypropylene was bonded to both sides of the negative electrode terminal sandwiched between the aluminum laminate films.

[Preparation of gel electrolyte]
A polyvinylidene fluoride copolymerized with 6.9% of hexafluoropropylene, a non-aqueous electrolyte, and dimethyl carbonate (DMC) as a diluting solvent are mixed, stirred and dissolved to obtain a sol electrolyte solution. Obtained. The electrolyte was prepared by mixing ethylene carbonate and propylene carbonate in a weight ratio of 6: 4 and dissolving 0.8 mol / kg LiPF ₆ and 0.2 mol / kg LiBF ₄ . The mixing ratio was a weight ratio of polyvinylidene fluoride: electrolyte: DMC = 1: 6: 12. Next, the obtained sol-form electrolyte solution was uniformly applied to both surfaces of the positive electrode and the negative electrode. Then, it was made to dry at 50 degreeC for 3 minute (s), the solvent was removed, and the gel electrolyte layer was formed on both surfaces of the positive electrode and the negative electrode.

[Production of test battery]
A belt-like positive electrode having a gel electrolyte layer formed on both sides and a belt-like negative electrode having a gel electrolyte layer formed on both sides, produced as described above, are wound in a longitudinal direction via a separator. Thus, a battery element was obtained. As the separator, a porous polyethylene film having a thickness of 10 μm and a porosity of 33% was used.

<Example 1> Nail penetration test The battery element described above was sandwiched between a hard laminate material and a soft laminate material, and the periphery was heat-sealed. Then, a circuit board was connected, and a pre-molded top cover and rear cover were heat-sealed. A battery pack was prepared. In Example 1, a hard laminate was prepared with Ny as the outer resin layer of 15 μm, CPP as the inner resin layer of 30 μm, the adhesive layer between the Ny layer and the metal layer as 3 μm, and the adhesive layer between the CPP layer and the metal layer as 2 μm. Further, as the soft laminate material, a laminate material having a total thickness of 85 μm using a 35 μm thick aluminum alloy 8079O as a metal layer was used.

  Further, as the hard laminate material, a hard laminate material having metal layers having different materials and thicknesses was used. Since the materials and thicknesses of the metal layers are different, the heat capacity per unit area and the exterior strength of each example and comparative example are different.

  The produced batteries of Examples 1-1 to 1-8 and Comparative examples 1-1 and 1-2 were charged at a constant current of 0.1 C and charged until the voltage reached 4.4V. After completion of charging, a nail was passed through the center of the wide surface of the battery pack, and the presence or absence of heat generation due to thermal runaway was examined.

The materials, thicknesses, heat capacities, and test results of the hard laminate films of each Example and Comparative Example are as follows.

  From the above results, safety in the nail penetration test can be ensured if the thickness of the metal layer is 80 μm or more. In order to enhance heat dissipation, it is desirable that the total thickness of the outer packaging material that wraps the battery element is within 660 μm. A battery with high safety and high battery capacity can be provided. The soft laminate material is 85 μm, the pressure-sensitive adhesive sheet for adhering the soft laminate materials is 50 μm, the decorative label is 50 μm, and the total thickness of the exterior material that wraps the battery element is 610 μm when the decorative label is attached to one side, This is because the thickness is 660 μm when both sides or one round is attached.

  Note that, for example, when soft aluminum alloy 8079O or the like is used for the exterior, since a hole is easily formed when a nail is pierced, heat generation is likely to occur. In addition to the nail penetration, the soft laminate material has low mechanical strength and may be crushed by external pressure. For this reason, the soft laminate material is not suitable for the outermost package from the viewpoint of safety.

Example 2 Sealing Test The above battery element was sandwiched between a hard laminate material having a total thickness of 150 μm using an aluminum alloy 3003H as a metal layer and a soft laminate material having a total thickness of 90 μm using an aluminum alloy 1100O as a metal layer. The electrode terminal lead-out portion was heat-sealed with a metal heater head and sealed. At this time, the positive electrode terminal and the negative electrode terminal derived from the battery element had a width of 4 mm and a thickness of 70 μm, and heat fusion was performed by changing the depth and width of the notch groove provided in the heater head. Thereafter, sealing defects such as appearance defects due to cutting of electrode terminals and seal marks were examined.

  The materials, thicknesses, heat capacities, and test results of the hard laminate films of each Example and Comparative Example are as follows.

  From the above results, there is no problem in sealing performance when the notch groove is not provided in the heater head on the hard laminate material side and the width of the notch groove on the soft laminate material side is 6 to 10 mm. That is, when the width of the electrode terminal is 2 to 6 mm wider, it can be seen that the sealing performance is good.

  On the other hand, when notched grooves are provided in both heater heads as in Comparative Example 2-1, seal marks remain even when the notched groove width is within an appropriate range of 8 mm, resulting in poor appearance. In addition, when the notch groove width is narrower than the lead width as in Comparative Example 2-2, the heater head pressurizes the lead and the lead may be cut or short-circuited. The fusion in the vicinity of the electrode terminal becomes insufficiently sealed. Furthermore, when the notch groove width is wide as in Comparative Example 2-3, sealing near the electrode terminal is insufficient, and external air and moisture enter and exit from the leak path due to the unfused portion.

<Example 3> Capacity comparison Battery pack capacity comparison is performed by changing the thermal fusion width of the electrode terminal lead-out portion. The battery element is sandwiched between a hard laminate and a deep-drawn soft laminate, the battery element peripheral part is heat-sealed and molded so that the cross section becomes an elliptical shape, and then the electrode terminal and the protection circuit are connected to form a battery. After forming the cell, the top cover and the rear cover are joined to form a battery pack. The battery cell is produced by changing the thermal fusion width of the electrode terminal lead-out portion by 0.5 mm in a range of 0.5 to 3.5 mm. At this time, when the cell height is 50 mm, when the thermal fusion width is 0.5 mm, the height of the battery element is 45.5 mm, and when the thermal fusion width is 1.0 mm, the height of the battery element is 45. By reducing the height of the battery element by 0 mm and the increase in the thermal fusion width, the dimensions of the battery pack are kept unchanged.

  The battery capacity is determined by the height of the element, that is, the length from the bottom part of the battery cell to the heat welded part. In Example 3, since the dimensions of the battery pack are constant, the smaller the width of the heat-sealed portion, the higher the battery element height and the battery capacity is improved.

  In Example 3, an aluminum alloy 3003H having a thickness of 100 μm is used as the metal layer of the hard laminate material, PET is 12 μm as the outer resin layer, CPP is 30 μm as the inner resin layer, and an adhesive layer between the PET layer and the metal layer is 3 μm. A hard laminate was prepared with an adhesive layer of 2 μm between the metal layer and the metal layer. As the soft laminate material, a laminate material having a total thickness of 85 μm using an aluminum alloy 8087O as a metal layer was used.

Since the conventional battery pack of the same size has a battery capacity of 800 mAh, the battery capacity of 800 mAh or more was accepted. Table 3 below shows the heat-sealing width of each example and comparative example, the thickness of the metal layer of the hard laminate material used, the battery capacity of the produced battery pack, and the presence or absence of defects in the battery pack.

From the above results, it can be seen that when the thermal fusion width is 1.0 to 3.0 mm, a battery having a high battery capacity can be obtained. When the thermal fusion width is 3.5 mm as in Comparative Example 3-1, the battery capacity is reduced, which is not suitable for practical use as compared with the conventional battery pack. Also, the thermal fusion width is 0.5mm
In this case, the sealing property is poor, and moisture cannot enter the battery.

<Example 4> Rigidity comparison of exterior The thickness of the aluminum alloy material and the metal layer used for the metal layer of the hard laminate material used as the exterior of the battery pack is changed, and the hard laminate material side has a not-grooved heater head and soft laminate. On the material side, the electrode terminal lead-out portion was sealed using a heater head with a notch groove. After sealing, it was confirmed whether or not a seal mark by the heater remained on the appearance and whether there was an appropriate bending workability.

  In Example 4, 3003H and 3004H were mainly used as the metal layer of the hard laminate material. For comparison, rigidity was also compared using soft 8079O. The metal layer used in each example and comparative example was 12 μm PET as the outer resin layer, 30 μm CPP as the inner resin layer, 3 μm adhesive layer between the PET layer and the metal layer, and 2 μm adhesive layer between the CPP layer and the metal layer. A hard laminate material was prepared. Further, as the soft laminate material, a laminate material having a total thickness of 85 μm using an aluminum alloy 8079O as a metal layer was used.

  Table 4 below shows the type of aluminum alloy used for the metal layer, the thickness and seal marks of the metal layer, and the results of confirmation of bending workability.

  From the above results, it is understood that when hard 3003H and 3004H are used for the metal layer of the hard laminate material, the seal mark is not left and the bending workability is good by setting the thickness to 80 to 120 μm.

  On the other hand, when soft 8079O is used as in Comparative Example 4-1, a seal mark remains even if the thickness is 120 μm, and there is a defect in appearance. Further, as in Comparative Example 4-2 and Comparative Example 4-4, even when hard 3003H and 3004H are used, if the thickness is as thin as 70 μm, seal marks remain as in Comparative Example 4-1. .

  Further, as in Comparative Example 4-3 and Comparative Example 4-5, when hard 3003H and 3004H are used and the thickness of the metal layer is increased to 130 μm, bending becomes impossible, and there remains a problem in bending workability.

  From the results of the above examples, by using a hard laminate material having a metal layer of 80 to 120 μm for the outermost package, a battery pack having a high mechanical strength and safety of the package and a high battery capacity per volume is produced. be able to.

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

  For example, the numerical values and materials mentioned in the above-described embodiment are merely examples, and different numerical values and materials may be used as necessary.

It is a schematic diagram which shows the structure of the battery pack of the lithium ion polymer secondary battery to which this invention is applied. It is sectional drawing which shows the structure of the laminate material used for preparation of a battery cell. It is a schematic diagram which shows an example of the battery element which comprises the battery pack to which this invention is applied. 1 is a schematic diagram showing a configuration of a battery cell 10. It is a schematic diagram which shows a mode that a seal | sticker trace remains with the heater head which has a notch groove. It is a schematic diagram which shows the mode of the heat welding of the electrode terminal derivation | leading-out part to which this invention is applied. It is a schematic diagram which shows a mode that a heater head presses and heats avoiding a laminated material edge part. It is sectional drawing which shows the structure of a battery cell. It is a schematic diagram which shows the mode of the joint of a hard laminate material and a soft laminate material. It is a schematic diagram which shows the external appearance of the battery pack to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery element 2a ... Positive electrode terminal 2b ... Negative electrode terminal 3a, 3b ... Sealant 4 ... Circuit board 5 ... Top cover 6 ... Rear cover 10 ... Battery cell 11a .... Hard laminate material 11b ... Soft laminate material 12 ... Metal layer 13 ... Outer resin layer 14 ... Inner resin layer 15, 16 ... Adhesive layer 21 ... Positive electrode 22 ... Negative electrode 23a, 23b ... separator 24 ... gel electrolyte

Claims (10)

In a battery pack having a battery element of a polymer battery covered with a laminate film in which a metal layer is sandwiched between an outer resin layer and an inner resin layer,
The battery element is accommodated between a hard laminate film using a hard metal for the metal layer and a soft laminate film using a soft metal for the metal layer, and the peripheral portion of the battery element is sealed. A battery cell that is curved along the battery element shape and sealed by aligning the ends of the hard laminate film;
A circuit board provided with a protection circuit joined to an electrode terminal derived from the battery element;
A resinous cover for sealing the open end of the battery cell;
A battery pack, wherein a heat capacity of the hard metal used for the metal layer of the hard laminate film is 0.019 J / K · cm ² or more.   The battery pack according to claim 1, wherein the battery cell has a battery capacity of 500 to 900 mAh.   The battery pack according to claim 1, wherein the hard metal used for the metal layer of the hard laminate film is any one of aluminum, copper, iron, nickel, stainless steel, and titanium.   The battery pack according to claim 3, wherein the aluminum is either 3003H or 3004H.   The battery pack according to claim 3, wherein the aluminum has a thickness of 80 to 120 μm.   The battery pack according to claim 1, wherein the outer surface resin layer of the hard laminate film is any one of nylon, polyethylene, and polyethylene naphthalate.   The battery pack according to claim 1, wherein the inner surface resin layer of the hard laminate film is one of polyethylene and polypropylene. In a battery pack having a battery element of a polymer battery covered with a laminate film in which a metal layer is sandwiched between an outer resin layer and an inner resin layer,
The battery element is accommodated between a hard laminate film using a hard metal for the metal layer and a soft laminate film using a soft metal for the metal layer, and the peripheral portion of the battery element is sealed. A battery cell that is curved along the battery element shape and sealed by aligning the ends of the hard laminate film;
A circuit board provided with a protection circuit joined to an electrode terminal derived from the battery element;
A resinous cover for sealing the open end of the battery cell;
The electrode terminal lead-out part of the battery cell is heat-sealed with a metal heater head arranged on the hard laminate film side and a metal heater head arranged on the soft laminate film side,
A battery pack, wherein only the metal heater head disposed on the soft laminate film side has a cutout groove in accordance with the shape of the electrode terminal.   The width of the metal heater head arranged on the hard laminate film side and the width of the metal heater head arranged on the soft laminate film side are 1.0 to 3.0 mm. Battery pack. 9. The battery pack according to claim 8, wherein the width of the notch groove is 2.0 to 6.0 mm wider than the width of the electrode terminal.

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