JP2008117653A - Battery pack and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of contributing to achievement of downsizing and light weight, securement of shock resistance, and improvement in manufacturing efficiency, and its manufacturing method. <P>SOLUTION: The battery pack includes a non-aqueous electrolyte secondary battery which has a battery element 10 made by winding or laminating a positive electrode and a negative electrode through a separator and a battery element outer package member which is made of a laminated film and surrounds the battery element, and in which the battery element outer package member is sealed along the surroundings of the battery element, while leading the electrode terminal of the positive electrode and the negative electrode to the outside, a battery sheath material 18 to surround the battery element outer package member, and a protection circuit board 32 which is built in the battery sheath material and can control voltage and current of the non-aqueous electrolyte secondary battery. The battery sheath material contains a shape-keeping polymer of post-curing type and a filler, and the filler is metal oxide such as silicon, aluminum, zirconium, zinc, calcium, and magnesium, and the average particle size of the filler is 0.5-40 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery pack and a method for manufacturing the same, and more particularly to a battery pack that can be reduced in size and weight and has a desired impact resistance, and a method for manufacturing the battery pack that is excellent in manufacturing efficiency.

In recent years, a large number of portable electronic devices such as camera-integrated video tape recorders, mobile phones, and portable computers have appeared, and their size and weight have been reduced. With the reduction in size and weight of such electronic devices, battery packs used as portable power sources are also required to have high energy and be reduced in size and weight.
As a battery used for such a battery pack, there is a lithium ion secondary battery having a high capacity.

A lithium ion secondary battery includes a battery element having a positive electrode and a negative electrode that can be doped / undoped with lithium ions, and is controlled by a circuit board that is electrically connected to the battery element. Lithium ion batteries are sealed in metal cans and metal laminate films.
When encapsulated in a metal can, since the metal can formed by deep drawing is used, it is difficult to make the longitudinal direction of deep drawing long among the three sides of the rectangular parallelepiped of the can. Therefore, only the shape design of the type in which the thickness of the can is naturally large can be performed, and a large-sized battery cannot be manufactured.
In addition, since the thickness of cans formed by deep drawing is limited to 200 μm, only cans with a thickness of 200 μm or less can be applied as manufacturing suitability, and conversely, the thickness is designed to be several mm or more to increase the strength. I could not do it, and there was no design freedom.
Moreover, since only a metal excellent in formability can be input for deep drawing, the strength could not be improved. Since the battery enclosed in the metal can cannot be heat-pressed after the injection, the metal can cannot be used practically in the polymer battery.
From the above, the metal can has problems in that it has no volume energy density, size and shape freedom, and design of strength as a pack.
On the other hand, when encapsulated in a light and thin metal laminate film, there is a drawback that the strength of the battery is weak although the above-mentioned heat press, size and shape are free.

Moreover, a lithium ion secondary battery is accommodated in a storage case with a circuit board, when forming a battery pack (for example, refer patent documents 1-3).
Here, the storage case is made of a thermoplastic resin or the like in which a resin such as polyamide or polyurethane is melted and poured, and is divided into, for example, an upper case and a lower case. The storage case connects the upper case and the lower case to form a single housing having a space for storing the lithium ion secondary battery and the circuit board.
Japanese Patent No. 3556875 Japanese Patent No. 3614767 Japanese Patent No. 3643779

When forming a battery pack using such a storage case, the storage case needs to have a certain thickness in order to protect the lithium ion secondary battery and circuit board stored therein from external impacts and the like. . For this reason, the battery pack as a whole is thick and heavy.
In addition, when the storage cases divided into the upper and lower parts are joined with the double-sided tape, the thickness of the battery pack is further increased by the thickness of the double-sided tape. Furthermore, when the divided storage cases are joined together by ultrasonic welding, a certain amount of thickness is required for the ultrasonic welding portion, which increases the size of the battery pack.
Thus, in the conventional battery pack, the thickness of the storage case is inevitably increased, the overall size is increased, the weight is increased, and the application is not suitable for a portable power source.

Conventionally, a method has also been proposed in which a rectangular battery in which a battery element is sealed in a metal can is integrally molded with a molten resin, that is, a thermoplastic resin (see, for example, Patent Documents 4 and 5).
JP 2004-303625 A JP 2004-358735 A

Such a system is intended to have a structure in which the protective circuit is bonded to eliminate the gap, but the strength and dimensional accuracy of the prismatic battery sealed in the metal can and the battery sealed in the aluminum laminate film And there is a big gap in manufacturing conditions.
For example, since a battery enclosed in a metal can is already enclosed in a thick metal can, the mechanical strength is sufficient, and a resin excellent in elasticity is used as a resin for integral molding in consideration of drop impact resistance. There is a need. Therefore, a flexible rubber-like resin is injected instead of a hard resin.

  Furthermore, in a battery sealed in a metal can, it is not possible to go through a heat press process in which an electrolyte is injected and the gel polymer is heat-welded after being manufactured. Therefore, only a liquid electrolyte can be used as a battery enclosed in a metal can, and only a so-called laminate battery can use both liquid and gel polymer electrolytes.

For these known technologies, a frame is disposed so as to surround the laminated battery and the circuit board, and the battery, the circuit board, and the frame are collectively wrapped in a thin plate-like package to achieve a reduction in size and weight. A battery pack has been proposed (see, for example, Patent Document 6).
Japanese Patent Application Laid-Open No. 2005-158452

However, even in such a battery pack described in Patent Document 6, in order to obtain the necessary hardness and formability because a metal plate is used for the package, typically a thickness of about 100 to 200 μm. Further, the adhesive and the adhesive tape require a thickness of about 50 to 100 μm, and further improvement is desired.
It is also conceivable to use metal oxide ceramics for the exterior of battery packs, but metal oxide ceramics are harder than the metal itself, but are brittle, so there is a problem with the processing technology for thinly adhering to the exterior. It was.

  As described above, in the above prior art, a battery pack using a laminate film contributes to improvement of the volume energy density of the battery pack, realization of size and weight reduction, ensuring impact resistance, and improvement of manufacturing efficiency. There was no battery pack that could be used, and no method for manufacturing the battery pack.

  The present invention has been made in view of such problems of the prior art, and its purpose is to improve the volume energy density of the battery pack, to realize a small size and light weight, to ensure impact resistance, An object of the present invention is to provide a battery pack that can contribute to an improvement in manufacturing efficiency and a manufacturing method thereof.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by using a specific shape maintaining polymer and filler, and have completed the present invention.

That is, the battery pack of the present invention includes a battery element formed by winding or laminating a positive electrode and a negative electrode with a separator interposed therebetween, and a battery element exterior member that is formed of a laminate film and surrounds the battery element. A non-aqueous electrolyte secondary battery formed by sealing the battery element exterior member along the periphery of the battery element, with the electrode terminal of the negative electrode led out to the outside,
A battery exterior material surrounding the battery element exterior member;
A protection circuit board that is built in the battery exterior material and can control the voltage and current of the non-aqueous electrolyte secondary battery, and
The battery exterior material contains a shape-maintaining polymer that is a post-curing resin and a filler,
The filler is a metal oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, zinc, calcium and magnesium;
The filler has an average particle size of 0.5 to 40 μm.

The battery pack manufacturing method of the present invention includes a battery element formed by winding or laminating a positive electrode and a negative electrode with a separator interposed therebetween, and a battery element exterior member that is formed of a laminate film and surrounds the battery element. A non-aqueous electrolyte secondary battery formed by sealing the battery element exterior member along the periphery of the battery element, with the electrode terminals of the positive electrode and the negative electrode being led out to the outside,
A battery exterior material surrounding the battery element exterior member;
A protection circuit board that is built in the battery exterior material and can control the voltage and current of the non-aqueous electrolyte secondary battery, and
The battery exterior material contains a shape-maintaining polymer that is a post-curing resin and a filler,
The filler is a metal oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, zinc, calcium and magnesium;
In producing a battery pack having an average particle size of the filler of 0.5 to 40 μm,
The non-aqueous electrolyte secondary battery and the protective circuit board are disposed in a mold for molding the battery exterior material,
Next, the post-curing molding material containing the shape maintaining polymer and the filler is injected into the cavity of the molding die and cured.

  According to the present invention, since a specific shape-maintaining polymer and filler that are post-curing resins are used, the volume energy density of the battery pack is improved, the size and weight are reduced, the impact resistance is ensured, and the manufacturing efficiency is improved. It is possible to provide a battery pack that can contribute to the manufacturing process and a method for manufacturing the battery pack.

  Hereinafter, the battery pack of the present invention will be described in detail. In the present specification, “%” for concentration, content, blending amount, etc. represents mass percentage unless otherwise specified.

  As described above, the battery pack of the present invention includes a non-aqueous electrolyte secondary battery in which a wound-type or laminated-type battery element is packaged with an exterior member made of a laminate film, and a protective circuit board of the battery using a post-curing resin. Surrounded by a battery exterior material containing a predetermined shape maintaining polymer and filler, specifically, the battery exterior material is integrally molded so as to enclose the non-aqueous electrolyte secondary battery and the protective circuit board. .

Here, the shape-maintaining polymer that is a post-curing resin constituting the battery exterior material is a polymer that has affinity, compatibility, or reactivity with the filler and has high dimensional accuracy and strength. For example, urethane resin, acrylic resin, or epoxy resin can be suitably used.
In addition, as a shape maintenance polymer, the adhesiveness with the laminate film which is a battery element exterior material is favorable, and the thing excellent in dimensional stability and a moldability is preferable.

As the filler, a metal oxide containing an element related to silicon (Si), aluminum (Al), zirconium (Zr), zinc (Zn), magnesium (Mg), or a combination thereof is used.
Such a metal oxide filler fulfills the function of improving the hardness of the exterior material, and is disposed in contact with the shape maintaining polymer. For example, the metal oxide filler may be mixed in the shape maintaining polymer. In this case, it is preferable that the metal oxide filler is uniformly dispersed throughout the shape maintaining polymer.

The average particle diameter of the filler is 500 nm (0.5 μm) to 40 μm, preferably 2 to 20 μm.
When the average particle size is lowered, the hardness increases, but the filling property at the time of molding may be affected to cause a problem in productivity. When the average particle size is increased, it is difficult to obtain a desired strength, and there is a possibility that sufficient dimensional accuracy as a battery pack cannot be obtained.

As the shape of the filler, various shapes such as a spherical shape, a scale shape, a plate shape, and a needle shape can be adopted. Although not particularly limited, a spherical shape is preferable because it is easy to produce and a product having a uniform average particle diameter can be obtained at low cost. Further, those having a needle shape and a high aspect ratio are preferable because the strength is easily improved as a filler. Scale-like is preferable because the filling property can be improved when the filler content is increased.
In the present invention, fillers having different average particle diameters can be mixed and used according to applications and materials, and fillers having different shapes can be mixed and used.

The amount of the filler mixed in the shape maintaining polymer can be appropriately changed according to the type of the shape maintaining polymer, etc., and typically about 3 to 60% with respect to the mass of the shape maintaining polymer. It is preferable to do.
If it is less than 3%, the hardness of the battery outer packaging material may not be sufficiently improved. If it exceeds 60%, a problem may occur due to formability during production and brittleness of the metal oxide.

By the way, when trying to form the exterior material by the mold hot melt method, use a solid thermoplastic resin that has the property of being liquefied by heating and solidifying again when cooled, or initially in a molten state. A thermosetting resin that cures by reaction can be selected.
Thermoplastic resins have the advantage that close adhesion can be created in a few seconds in the process of wetting the surface of the adherend while it is in a high-temperature liquid state, and then cooling and solidifying.
However, in order to develop fluidity by being heated to a temperature 50 to 150 ° C. higher than the melting point or glass transition temperature of the resin, it is necessary to heat to a high temperature of about 180 ° C. to 450 ° C. In addition, if the mold thickness is to be reduced because the curing starts from the point of pouring into the mold, it will be a process of pouring a resin that will harden in a few seconds from a very narrow gap to a wide area in the vicinity of the injection port. . Even if the viscosity is lowered by increasing the temperature of the resin, the injection pressure is increased, or the number of injection holes is increased, it is not possible to produce a pack with a large area and a thickness of 250 μm or less. There was a problem that only packs with inferior volume energy density could be produced.
On the other hand, even when a thermosetting resin is used, the curing temperature of some thermosetting resins can be relatively low, but the curing temperature of some thermosetting resins excellent in strength is around 150 ° C. Since the temperature is still high and it takes time to cure, there is a disadvantage that the productivity is inferior.

Moreover, the polyethylene-based separator generally used for the non-aqueous electrolyte secondary battery is usually shut down at 120 to 140 ° C. and changed to a film that does not transmit ions.
Further, in such a battery, since the electrolytic solution is oxidized at the positive electrode and reduced at the negative electrode, there is a possibility that swelling occurs due to gas generation if the electrolyte is held at a high temperature of 60 ° C. or higher.
Furthermore, when a physical gel such as PVdF (polyvinylidene fluoride) is used in a polymer battery packaged with an aluminum laminate to prevent leakage, gel melting may occur at 80 to 90 ° C. and the battery shape may be deformed. There is.
In addition, when a pack integrally molded with a protection circuit board is used, PTC (Positive Temperature Coefficient: positive temperature coefficient “positive temperature coefficient” is incorporated into the protection circuit as a control component when an abnormal current flows. Accordingly, the battery resistance value also increases, and the positive coefficient value changes), or the thermal fuse may be damaged.
In the case of PTC, the electric resistance value returns to a value close to the previous value up to 120 ° C., but at a higher temperature, it still does not return with the electricity cut off. In the case of a substrate using a thermal fuse, depending on the type of the fuse, once the temperature exceeds 90 ° C. to 130 ° C., the fuse may not be activated or restored.

As described above, in heating, particularly in molding with a temperature of 120 ° C. or higher, there is a risk of serious temperature damage to the battery element disposed in the mold.
For this, it is conceivable to use an epoxy resin containing a metal filler and use putty without temperature control.
However, when an epoxy resin is used without heat treatment, the resulting exterior material is inferior in strength, and depending on the target strength, the reaction time (curing time) usually takes at least 15 minutes or more and usually takes more than 1 day. For this reason, production efficiency may be deteriorated.

  From the above, in the present invention, the above-mentioned urethane resin, acrylic resin, or epoxy resin is used as the shape maintaining polymer, but these resins are those that are thermally cured at 120 ° C. or less or that are cured with ultraviolet rays. It is desirable to use it.

In the present invention, such a shape maintaining polymer is mixed with the metal oxide filler as described above. However, a resin using the metal oxide as a filler is used as a dental filler from an automobile. Wide range of materials used.
Usually, as a dental filler, an extremely fine filler of about several tens of nm to 1 μm is used in order to increase wear strength and biting. On the other hand, as an automotive part, an aluminum metal filler of about 200 μm, an aluminum nitride of about 100 μm, and the like are used, and they are used industrially, such as a metallic luster obtained only by molding and no color peeling.

Thus, the metal oxide filler used for dental fillers and automobile parts is substantially different from the average particle size range intended by the present invention.
In addition, the use of metal oxide fillers generally reduces the particle size, making the material itself closer to ceramic and increasing its strength and strength, while the flowability during molding becomes difficult, and the elasticity of the resin Since parameters such as strength, impact resistance, and productivity are intertwined in a complicated manner, such as loss of mold and difficulty in molding, detailed examination is necessary for selection of filler material and control of particle size.

  The present inventors have repeatedly conducted various studies under the technical background as described above, and have found out the combined use of the shape-maintaining polymer and the filler as described above. Such mixed use is laminated as a battery element exterior member. It is extremely suitable for use as a battery exterior material in which a nonaqueous electrolyte secondary battery using a film and a protective circuit board are integrally molded and surrounded.

  As described above, the battery exterior material used in the present invention has a predetermined shape maintaining polymer and a metal oxide filler as essential constituent requirements, but can contain various additives other than this, for example, In the shape maintaining polymer, an ultraviolet absorber, a light stabilizer, a curing agent, or any mixture thereof can be added to coexist with the metal oxide filler.

Such a battery outer packaging material is thin, and the thickness of the pack portion on the maximum surface of a rectangular battery for portable equipment is, for example, 1000 μm or less.
When the thickness exceeds 1000 μm, even a battery pack manufactured using this exterior material may hardly exhibit the merit in terms of volume energy density.
More preferably, the thickness is 300 μm or less, and the thinner the better, as long as the required mechanical strength and impact resistance are satisfied.
The combined use of the shape-maintaining polymer and filler of the present invention is higher in strength and impact resistance than the combined use of conventional aluminum metal or thermoplastic resin and metal. Thus, the volume energy density can be increased. Further, if the thickness is increased, a battery pack having higher strength and higher reliability than the conventional one can be obtained. Furthermore, since the size and shape of the battery can be freely selected, it can be applied to large batteries such as bicycles, automobiles, and backup power supplies having a large size, and has a degree of freedom for designing the necessary strength for a necessary part.

As described above, the battery exterior material described above can realize a battery pack that is thinner and stronger than conventional ones, and can also be reduced in size and weight.
Moreover, it is thinner than a conventionally used metal plate by using any of an ultraviolet absorber, a light stabilizer and a curing agent together with the metal oxide filler as described above, and using either an acrylic resin or an epoxy resin. Since processing with excellent productivity can be performed, not only the energy density of the obtained battery is improved, but also a pack in which the size, shape, and required strength are freely designed according to various applications can be provided.

Next, the battery pack of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an exploded perspective view showing a nonaqueous electrolyte secondary battery before being packed with a battery exterior material in an embodiment of the battery pack of the present invention.
In this figure, the battery 20 is manufactured by covering a battery element 10 with a metal laminate film 17 which is an example of a battery element exterior member. The battery element 10 is formed with a recess 17a ( It is accommodated in the void 17a) and its periphery is sealed.
In the present embodiment, the void 17a has a rectangular plate-shaped space corresponding to the shape of the battery element 10 having a rectangular plate shape.

Next, the configuration of the battery element 10 will be described.
FIG. 2 is a perspective view showing the structure of the battery element 10 that is packaged and accommodated in the laminate film 17. In this figure, the battery element 10 is formed by sequentially laminating a strip-like positive electrode 11, a separator 13a, a strip-like negative electrode 12 arranged to face the positive electrode 11, and a separator 13b, and winding them in the longitudinal direction. The gel electrolyte 14 is applied to both surfaces of the positive electrode 11 and the negative electrode 12.

  From the battery element 10, a positive electrode terminal 15 a connected to the positive electrode 11 and a negative electrode terminal 15 b connected to the negative electrode 12 are derived (hereinafter referred to as an electrode terminal 15 when a specific terminal is not specified). 15a and negative electrode terminal 15b have sealants 16a and 16b (hereinafter referred to as specific sealants) which are resin pieces such as polypropylene anhydride (PPa) modified with maleic anhydride in order to improve adhesion to the laminate film 17 to be packaged later. Is designated as sealant 16 as appropriate).

Hereinafter, the constituent elements of the above-described battery (before packing with the battery outer packaging material) will be described in detail.
[Positive electrode]
In the positive electrode, a positive electrode active material layer containing a positive electrode active material is formed on both surfaces of a positive electrode current collector. The positive electrode current collector is made of a metal foil such as an aluminum (Al) foil.
The positive electrode active material layer includes, for example, a positive electrode active material, a conductive agent, and a binder. 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, a metal oxide, a metal sulfide, or a specific polymer can be used depending on the type of the target battery. For example, when a lithium ion battery is configured, the following formula (1) is mainly used.
Li _X MO ₂ (1)
(Wherein M represents at least one transition metal and X varies depending on the charge / discharge state of the battery, but is usually 0.05 to 1.10.) Things are used. Note that cobalt (Co), nickel (Ni), manganese (Mn), or the like is used as the transition metal (M) constituting the lithium composite oxide.

As such lithium composite oxide, _{specifically, LiCoO 2, LiNiO 2, LiMn} 2 O 4 and _{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, may be used NbSe no lithium metal sulfides such as ₂ and _V 2 _{O 5} or the oxide as a cathode active material. These positive electrode active materials may be used alone or in admixture of a plurality of types.

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. Furthermore, 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 above-described positive electrode active material, binder and conductive agent 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, and then dried at a high temperature to evaporate the solvent and press to form a positive electrode active material layer.

  The positive electrode 11 has a positive electrode terminal 15a connected to one end of the positive electrode current collector by spot welding or ultrasonic welding. The positive electrode terminal 15a is preferably a metal foil or a mesh, but there is no problem even if it is not metal as long as it is electrochemically and chemically stable and can be energized. Examples of the material of the positive electrode terminal 15a include aluminum.

[Negative electrode]
In the negative electrode, a negative electrode active material layer containing a negative electrode active material is formed on both surfaces of a negative electrode current collector. The negative electrode current collector is composed of a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer includes, for example, a negative electrode active material, a conductive agent and a binder as necessary. In addition, about a negative electrode active material, a electrically conductive agent, a binder, and a solvent, the mixing ratio is not ask | required similarly to a positive electrode active material.

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-based material and a carbon-based material is used.
Specific examples of carbon materials that can be doped / undoped with lithium include graphite, non-graphitizable carbon, and graphitizable carbon. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature. Carbon materials such as those obtained by firing and carbonization), carbon fibers, and activated carbon can be used.
Furthermore, as a material that can be doped / undoped with lithium, polymers such as polyacetylene and polypyrrole, and oxides such as SnO ₂ can be used.

  In addition, various types of metals can be used as materials capable of alloying lithium, but tin (Sn), cobalt (Co), indium (In), aluminum, silicon (Si), and alloys thereof can be used. Often used. When metal lithium is used, it is not always necessary to use powder as a coating film with a binder, and a rolled lithium metal foil may be pressure-bonded to a current collector.

  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.

  The above-described negative electrode active material, binder, and conductive agent are uniformly mixed to form a negative electrode mixture, which is dispersed in a solvent to form a slurry. Subsequently, after apply | coating uniformly on a negative electrode electrical power collector by the method similar to a positive electrode, it is made to dry at high temperature, a solvent is scattered, and a negative electrode active material layer is formed by pressing.

  Similarly to the positive electrode 11, the negative electrode 12 has a negative electrode terminal 15b connected to one end of the current collector by spot welding or ultrasonic welding, and this negative electrode terminal 15b is electrochemically and chemically stable. If it can be energized, there is no problem even if it is not metal. Examples of the material of the negative electrode terminal 15b include copper and nickel.

The positive electrode terminal 15a and the negative electrode terminal 15b are led out from the same direction, for example, from one side (usually one of the short sides) when the battery element 10 has a rectangular plate shape as shown in FIG. Although it is preferable, no short circuit or the like occurs and there is no problem in battery performance.
Moreover, the connection location of the positive electrode terminals 15a and 15b is not limited to the above example as long as electrical contact is established and the location and method of attachment are not limited.

[Electrolyte]
As the electrolytic solution, 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 and ethylpropyl carbonate, or hydrogen of these carbonic acid esters as halogen. Examples include substituted solvents. One of these solvents may be used alone, or a plurality of these solvents may be mixed and used in a predetermined composition.

Moreover, as lithium salt which is an example of electrolyte salt, it is possible to use the material used for normal battery electrolyte solution. Specifically, LiCl, LiBr, LiI, LiClO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiNO ₃ , LiN (CF ₃ SO ₂ ) 2, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl _4, LiSiF _{6, and the} like can be mentioned, but LiPF ₆ and LiBF ₄ are desirable from the viewpoint of oxidation stability. These lithium salts may be used alone or in combination of two or more.
The concentration for dissolving the lithium salt is not a problem as long as it can be dissolved in the non-aqueous solvent, but the lithium ion concentration is in the range of 0.4 mol / kg to 2.0 mol / kg with respect to the non-aqueous solvent. It is preferable that

In the case of using a gel electrolyte, the above-described electrolytic solution is gelled 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.

Among them, particularly preferable as the matrix polymer is polyvinylidene fluoride or a copolymer in which hexafluoropropylene is introduced into polyvinylidene fluoride at a ratio of 7.5% or less.
Such polymers usually have a number average molecular weight in the range of 5.0 × 10 ^{5 to} 7.0 × 10 ⁵ (500,000 to 700,000) or a weight average molecular weight of 2.1 × 10 ^{5 to} 3. It is in the range of 1 × 10 ⁵ (210,000-310,000), and the intrinsic viscosity is in the range of 1.7-2.1 dl / g.

[Separator]
The separator is composed of a porous film made of a polyolefin-based material such as polypropylene (PP) or polyethylene (PE), or a porous film made of an inorganic material such as a ceramic non-woven fabric. It is good also as a structure which laminated | stacked the porous film. Among these, polyethylene and polypropylene porous films are the most effective.

  In general, the thickness of the separator is preferably 5 to 50 μm, more preferably 7 to 30 μm. If the separator is too thick, the amount of the active material filled decreases, the battery capacity decreases, and the ionic conductivity decreases and the current characteristics deteriorate. On the other hand, if the film is too thin, the mechanical strength of the film decreases.

[Production of battery]
The gel electrolyte solution prepared as described above is uniformly applied to the positive electrode 11 and the negative electrode 12 and impregnated in the positive electrode active material layer and the negative electrode active material layer, and then stored at room temperature or subjected to a drying process. A state electrolyte layer 14 is formed.
Next, using the positive electrode 11 and the negative electrode 12 on which the gel electrolyte layer 14 is formed, the positive electrode 11, the separator 13 a, the negative electrode 12, and the separator 13 b are stacked and wound in this order to obtain the battery element 10.
Next, the battery element 10 is housed in a recess (vacant space) 17a of the laminate film 17 and packaged to obtain a gel-like nonaqueous electrolyte secondary battery.

As the laminate film 17, a conventionally known metal laminate film such as an aluminum laminate film can be used.
As such an aluminum laminate film, a film suitable for drawing and suitable for forming the recess 17a for accommodating the battery element 10 is preferable.

  In general, an aluminum laminate film has a laminated structure in which an adhesive layer and a surface protective layer are disposed on both sides of an aluminum layer, and a polypropylene layer (PP as an adhesive layer) in order from the inside, that is, the surface side of the battery element 10. Layer), an aluminum layer as a metal layer, and a nylon layer or a polyethylene terephthalate layer (PET layer) as a surface protective layer.

In this embodiment, as shown in FIGS. 1 and 2, the battery element 10 is packaged with the laminate film 17 as described above, and the periphery of the battery element 10 is welded and sealed to form the battery 20.
In addition, as described above, after the battery element 10 is accommodated and sealed in the battery element exterior material, as shown in FIGS. 3A and 3B, the concave portion in which the battery element 10 is accommodated. The portions on both sides of 17a (hereinafter referred to as side sealing portions as appropriate) 17b are bent toward the direction of the recess 17a.

The bending angle θ is preferably in the range of 80 ° to 100 °.
If the angle is less than 80 °, the side walls 17b provided on both sides of the concave portion 17a are too open, and the width of the battery 20 is widened, making it difficult to reduce the size of the battery 20 and improve the battery capacity. The upper limit of 100 ° is a value defined by the shape of the recess 17a. When the flat battery element 10 is accommodated, the limit value of the bending angle is about 100 °. In addition, the width | variety of the heat welding in the side sealing part 17b becomes like this. Preferably it is 0.5-2.5 mm, More preferably, it is 1.5-2.5 mm.

  In order to reduce the size of the battery 20 and improve the battery capacity, the folded width D of the side portion 17b is preferably set to a dimension equal to or smaller than the height h of the recess 17a or the thickness of the battery element 10. In order to reduce the size of the nonaqueous electrolyte secondary battery 20 and improve the battery capacity, the number of turns is preferably set to one.

Next, an embodiment of the battery pack manufacturing method of the present invention will be described.
As described above, in the battery pack manufacturing method of the present invention, the non-aqueous electrolyte secondary battery manufactured as described above is molded together with a protective circuit board capable of controlling the voltage and current of the battery. Placed in a predetermined position of the cavity.
Next, a melt molding material containing the shape-maintaining polymer and filler is injected into the cavity and cured, thereby obtaining a battery pack with a battery exterior material attached thereto.

  Here, for the reasons described above, the melt-molded material can be cured by exposure to ultraviolet rays or standing at a temperature of room temperature to less than 150 ° C. in order to avoid thermal damage to the battery and improve the production efficiency. preferable. In addition, the various additives described above may be added to the post-curing molding material.

In the above embodiment, the molding die to be used can be arranged in the cavity with the battery 20 packed with the aluminum laminate film 17, the protection circuit board, and a buffer material (described later) used as necessary. As long as it is not particularly limited, it usually has two or more gates for guiding the post-curing molding material to the cavity. Therefore, in the obtained battery pack, an excess of the molding material corresponding to the gate is cured and remains in any part of the battery exterior material.
In the present invention, the excess molding material is trimmed and deleted, but some resin injection marks remain.

The protection circuit is usually disposed above the positive terminal 15a and the negative terminal 15b (see FIG. 1). Moreover, when the above-described cushioning material has a rectangular plate shape like the battery 20 (when the formed battery exterior material is a rectangular plate shape), the side portions in the lead-out direction of the terminals 15a and 15b or the side portions facing the side portions. Or on both sides.
Specifically, in FIG. 1, the battery 20 having a rectangular plate shape is arranged on one short side or both short sides.
The protective circuit board and the buffer material thus arranged are molded integrally with the battery 20 by the molding material.

In addition, the said buffer material improves the impact resistance of the battery pack obtained while protecting a battery and a circuit board.
For this reason, the material used for the cushioning material is a resin such as polycarbonate, acrylonitrile-butadiene-styrene resin (ABS), polypropylene, polyethylene, etc. that has impact resistance and good dimensional accuracy, or a metal such as aluminum or stainless steel. It is preferable to use a resin material obtained by insert molding a metal material such as aluminum into a resin material.

In the present invention, since the mechanical strength of the pack material itself is excellent, various rubber-like plastics can be used for the purpose of improving the impact resistance.
Specifically, natural rubber, vulcanized synthetic rubber, such as polybutadiene, butadiene-acrylonitrile, styrene-butadiene, chloroprene, etc., ebonite, urethane rubber, silicon rubber can be used.

FIG. 4 is an explanatory plan view showing a process for producing a battery pack according to this embodiment by packing a battery with a battery outer packaging material.
First, the battery 20 is bent along the broken line in the figure (FIGS. 4A and 4B), and the protection circuit board 32 and the top cushioning material 34 are disposed on the top side, and the bottom cushioning material 33 is disposed on the bottom side. And installed in a molding die (not shown). Next, a molding material containing the shape maintaining polymer and filler is injected into a molding die and cured to obtain a battery pack 30 of the present embodiment in which the aluminum laminate film 17 is covered with the battery exterior material 18 (see FIG. 4 (C)).
FIG. 5A shows a cross-sectional view of the obtained battery pack 30 cut along the bottom portion, and FIG. 5B shows a cross-sectional view cut along the extending direction of the electrode terminals.

In the above-described embodiment, the nonaqueous electrolyte secondary battery 20 using the gel electrolyte has been described, but the present invention can also be applied to a laminated film exterior battery using an electrolytic solution. In this case, in the above-described embodiment, the step of applying the gel electrolyte to the positive electrode and the negative electrode surface is omitted, and the step of injecting the electrolytic solution in the middle of the laminate film welding step is provided.
More specifically, after welding and sealing three sides around the battery element 10 having a rectangular plate shape, an electrolytic solution is injected from the opening of the remaining one side, and then this one side is welded. And can be sealed. Thereby, the whole shape of a sealing part becomes a rectangular frame shape.

  In addition, according to this invention, the battery pack by which the above size reduction and weight reduction were achieved can be obtained. Such a battery pack is usually provided with a connection terminal for connection with a target device, but the description thereof is omitted above.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Examples 1-34, Comparative Examples 1-5)
In a battery as shown in FIG. 1, a battery 20 having a battery element exterior material (laminate film 17) in which an adhesive is applied to the inner surface side of an aluminum-deposited PET film is prepared, and a substrate that functions as a protective circuit for the laminate battery is prepared. After connecting, in some cases, a cushioning material (rubber-like part) was placed and placed in the mold.
Next, a resin containing a metal oxide filler (shape maintaining polymer) is injected and filled from three resin injection holes having a diameter of 0.5 mm at the top of the mold, and excess metal oxidation is performed from the three resin discharge holes at the bottom. When a resin containing a material filler comes out, it is left at room temperature, left in a constant temperature bath at the temperature shown in Table 1 and Table 2, or using a transparent mold and irradiated with 365 nm ultraviolet light by an ultraviolet irradiation device. The battery exterior material 18 was formed by curing the resin (see FIGS. 4 and 5). After curing, the excess branch-like resin remaining in the resin injection hole and the discharge hole was cut to complete the battery pack of each example.
Tables 1 and 2 show the specifications of the battery pack of each example.

(Performance evaluation)
For the battery pack of each example, the (Shore) durometer hardness, water absorption, rated E density, 3C load characteristics, drop test, curing time, etc. of the exterior material were measured, and the results obtained are also shown in Tables 1 and 2 did.

[Rated energy density]
First, constant current / constant voltage charging at 1 C was performed at 23 ° C. for 15 hours to an upper limit of 4.2 V, and then constant current discharging at 1 C was performed to a final voltage of 2.5 V. This charge / discharge was repeated, and the rated energy density was determined from the discharge capacity at the first cycle.
Rated energy density [Wh / l] = (average discharge voltage [V] × rated capacity [Ah]) / battery volume [l]
Note that 1C represents a current value that can discharge the theoretical capacity of the battery in one hour.

[3C load characteristics]
Moreover, constant current constant voltage charge of 1 C was performed at 23 ° C. for 15 hours to an upper limit of 4.2 V, then constant current discharge of 1 C was performed up to a final voltage of 2.5 V, and a discharge capacity by 1 C was obtained. Moreover, after performing constant current constant voltage charge on the same conditions, 3 C constant current discharge was performed to the final voltage 2.5V, and the discharge capacity by 3 C was calculated | required.
The load characteristic is the ratio of the discharge capacity by 3C to the discharge capacity by 1C,
That is, it was obtained from (ratio of discharge capacity by 3C / discharge capacity by 1C) × 100 (%).
3C represents a current value that can discharge the theoretical capacity of the battery in 1/3 hour.

[Shore durometer hardness of exterior materials]
Based on the JIS-K7215 plastic durometer hardness test method, it was measured using a type D durometer.

[Water absorption rate]
JIS-K7209 Plastic -Measured based on how to determine water absorption.

[2m drop test]
While randomly changing the surface to which the battery was dropped, it was allowed to fall freely onto the concrete floor so that all six sides of the square battery hit. A product with no abnormality in the appearance of the pack after being dropped 10 times was regarded as a good product, and a product with an abnormality in the appearance such as cracking or removal of a part was regarded as a defective product.

[Curing time]
In the case of a thermosetting resin, a urethane resin, an acrylic resin or an epoxy resin containing a metal oxide such as silicon or aluminum which is a molding material for the battery exterior material 18 is put together in a molding die, and Table 1, The time required for mold-curing while maintaining the predetermined curing temperature shown in FIG.
In the case of an ultraviolet curable resin, a urethane resin, an acrylic resin or an epoxy resin containing a metal oxide such as silicon or aluminum, which is a molding material for the battery outer packaging material 18, is put together in a transparent molding die, and an ultraviolet irradiation device Thus, the curing time was defined as the time required for molding and curing by irradiating ultraviolet rays having a wavelength of 365 nm with an irradiation intensity of 200 mW / cm ² .

The urethane resin, acrylic resin or epoxy resin containing metal oxides such as silicon and aluminum, which is a molding material for the battery 20 and the battery exterior material 18, are put together in a molding die and molded and cured, and an aluminum-deposited PET film The nonaqueous electrolyte secondary battery packs of Examples 1 to 34 in which the battery outer packaging material 18 is provided on the surface of the battery element outer packaging material (laminate film 17) coated with an adhesive on the inner surface side belong to the scope of the present invention. From Table 1 and Table 2, it can be seen that these have strength characteristics excellent in drop tests without affecting battery characteristics.
The strength was improved by making the filler needle-like and the aspect ratio was improved, and the strength could be maintained even with a thinner pack. Even when two kinds of fillers having different average particle diameters were mixed, the strength could be maintained with a thinner pack.

As mentioned above, although this invention was demonstrated by some suitable embodiment and an Example, this invention is not limited to this embodiment or an Example, A various deformation | transformation is possible within the range which does not deviate from the summary of this invention. It is.
For example, the battery pack of the present invention can be applied not only to the battery and battery element shown in FIG. 1 and the like, but also to various gel-like or polymer type non-aqueous electrolyte secondary batteries, and only the wound battery element. In addition, the present invention can be applied to a stacked battery element.

In one Embodiment of the battery pack of this invention, it is a disassembled perspective view which shows the nonaqueous electrolyte secondary battery before packing with a battery exterior material. It is a perspective view which shows the structure of the battery element packaged and accommodated in a laminate film. It is an end view which shows the side wall vicinity of the battery shown in FIG. It is plane explanatory drawing which showed the process of packing a battery with a battery exterior material, and producing a battery pack. It is sectional drawing of a battery pack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Battery element, 11 ... Positive electrode, 12 ... Negative electrode, 13a, 13b ... Separator, 14 ... Gel electrolyte, 15a ... Positive electrode terminal, 15b ... Negative electrode terminal, 16a, 16b ... Sealant, 17 ... Laminate film, 17a ... Concave ( Empty space), 17b ... side sealing part, 18 ... battery exterior material, 20 ... battery, 30 ... nonaqueous electrolyte secondary battery, 32 ... protective circuit board, 33 ... buffer material (bottom part), 34 ... buffer material ( Top part), θ ... bending angle, D ... folding width, h ... recess height

Claims (6)

A battery element formed by winding or laminating a positive electrode and a negative electrode with a separator interposed therebetween, and a battery element exterior member made of a laminate film and surrounding the battery element, wherein the electrode terminals of the positive electrode and the negative electrode are led out to the outside. The nonaqueous electrolyte secondary battery formed by sealing the battery element exterior member along the periphery of the battery element,
A battery exterior material surrounding the battery element exterior member;
A protection circuit board that is built in the battery exterior material and can control the voltage and current of the non-aqueous electrolyte secondary battery, and
The battery exterior material contains a shape maintaining polymer and a filler,
The filler is a metal oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, zinc, calcium and magnesium;
The battery pack, wherein the filler has an average particle size of 0.5 to 40 μm.   The battery pack according to claim 1, wherein the shape maintaining polymer is a urethane resin, an acrylic resin, or an epoxy resin.   The battery pack according to claim 1, wherein the battery exterior material has an injection mark of a melt of the shape maintaining polymer and filler.   The battery exterior material has a rectangular plate shape, and in the battery exterior material having the rectangular plate shape, a buffer material is incorporated in at least one of the side portion on the electrode terminal lead-out side and the opposite side portion. The battery pack according to claim 1. A battery element formed by winding or laminating a positive electrode and a negative electrode with a separator interposed therebetween, and a battery element exterior member made of a laminate film and surrounding the battery element, wherein the electrode terminals of the positive electrode and the negative electrode are led out to the outside. The nonaqueous electrolyte secondary battery formed by sealing the battery element exterior member along the periphery of the battery element,
A battery exterior material surrounding the battery element exterior member;
A protection circuit board that is built in the battery exterior material and can control the voltage and current of the non-aqueous electrolyte secondary battery, and
The battery exterior material contains a shape maintaining polymer and a filler,
The filler is a metal oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, zinc, calcium and magnesium;
In producing a battery pack having an average particle size of the filler of 0.5 to 40 μm,
The non-aqueous electrolyte secondary battery and the protective circuit board are disposed in a mold for molding the battery exterior material,
Next, a post-curing molding material containing the shape-maintaining polymer and the filler is injected into the cavity of the molding die and cured, and then the battery pack manufacturing method is characterized.   The cavity of the molding die has two or more gates, and the molding material surplus formed on the battery exterior material due to the gate is cut off after the curing. The manufacturing method of the battery pack of description.

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