JP2004273201A - Flat battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat battery reducing breakage of an electrode plate and failure caused by coming off of an active material layer in housing a flat electrode group in a battery case and enhancing discharge rate characteristics by increasing impregnation of a nonaqueous electrolyte into the flat electrode group in the flat battery in which a lower bottom surface and the side surface of the vicinity of the bottom surface of a flat electrode group comprising almost the straight line part and a curvature part in which a positive plate and a negative plate are insulated through a separator are insulated with an insulating tape and housed in a battery case with a bottom in which the upper part is opened, and the opening part of the battery case is sealed. <P>SOLUTION: The side surface in the vicinity of at least the bottom surface of at least the straight line part of the flat electrode group is covered with an insulating tape obtained by sticking an adhesive mass on a base material. Covering of 1/10 to 8/10 of almost the straight line part is preferable. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００６５】
表１から明らかなように、正極板と負極板とがセパレーターを介して絶縁されている略直線部と曲率部からなる扁平電極群の少なくとも略直線部の下部底面近傍の両側面を基材に粘着材を貼付してなる絶縁テープで被覆してなる実施例の場合、電池ケース内に収納する際の極板の破損や活物質層の脱落による不良を低減すると同時に、扁平電極群への非水電解液の含浸性を向上させることにより放電率特性にも優れた扁平形電池が得られるが、比較例の場合、粘着材が基材全面に貼付されている為、扁平電極群と電池ケースの４隅の空隙部に注入された非水電解液が、扁平電極群底面の曲率部から扁平電極群内部の正負極板及びセパレータ中に含浸させるのが困難な為に、電池ケースの底面に非水電解液が残存し、２Ｃの放電率特性が低下することがわかった。
【００６６】
また、実施例２より、基材に粘着材を貼付してなる寸法が略直線部の下部底面近傍の側面の１／１０未満の場合には、扁平電極群と絶縁テープとの密着性が悪く、電池ケースに収納する際に、位置ずれ等が発生し、活物質層が脱落する不良率が０．１％発生した。
【００６７】
逆に、実施例５より、基材に粘着材を貼付してなる寸法が略直線部の下部底面近傍の側面の８／１０を超える場合には、２０セル中１セル電池ケースの底面に数滴の非水電解液が残存するものがあり、粘着材２３が貼付されている位置の寸法バラツキによって曲率部１５ｂに粘着材が貼付されていた為に、非水電解液の扁平電極群への含浸性が低下したと思われる。
【００６８】
さらに、実施例７より、扁平電極群の略直線部の下部底面およびこの底面近傍の両側面を基材に粘着材を貼付してなる絶縁テープで被覆した場合、注入された非水電解液が電池ケースの底面に残存することはなかったが、扁平電極群内部の正負極板及びセパレータ中に均一に含浸できていない為に、２Ｃの放電率特性が僅かに低下したと思われる。
【００６９】
【発明の効果】
以上説明したように本発明の扁平形電池によれば、扁平電極群を電池ケース内に収納する際の扁平電極群の破損や活物質層の脱落による不良を大幅に抑制できる。さらに、非水電解液の注入時に扁平電極群と電池ケースとの４隅の空隙部に流れ込んだ電解液は、扁平電極群底面曲率部と基材に粘着材が貼付されていない絶縁テープとの界面から扁平電極群内の正負極板及びセパレータに含浸させることができ高率放電特性にも優れた扁平形電池を提供することができる。
【図面の簡単な説明】
【図１】本願の扁平電極群の外観形状を示す斜視図
【図２】（ａ）本願の絶縁テープの平面図
（ｂ）本願の絶縁テープの断面図
【図３】本願の絶縁テープを扁平電極群に貼付した状態を示す斜視図
【図４】扁平電極群を電池ケースに収納した場合の断面図
【図５】（ａ）従来の絶縁テープの平面図
（ｂ）従来の絶縁テープの断面図
（ｃ）従来の別の絶縁テープの平面図
【符号の説明】
１１ 扁平電極群
１２ 正極集電体
１３ セパレータ
１４ 群固定テープ
１５ 扁平電極群の底面
１５ａ 略直線部
１５ｂ 曲率部部
１６ 正極リード
１７ 正極リードテープ
１８ 負極リード
１９ 負極リードテープ
２１ 絶縁テープ
２１ａ 扁平電極群の略直線部に相対する部分
２１ｂ 扁平電極群の曲率部に相対する部分
２１ｃ 扁平電極群の曲率部の外側に相対する部分
２１ｄ 扁平電極群の底面に相対する部分
２１ｅ 扁平電極群の底面近傍の側面に相対する部分
２２ 基材
２３ 粘着材
２４ 絶縁テープに設けた穴
３１ 電池ケース
３２ａ、３２ｂ、３２ｃ、３２ｄ 電池ケースと扁平電極群との空隙部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention suppresses the breakage of the flat electrode group and the falling off of the active material layer when the flat electrode group is housed in the battery case, and also allows the non-aqueous electrolyte to be injected into the flat electrode group housed in the battery case. The present invention relates to a flat battery having excellent characteristics.
[0002]
[Prior art]
In recent years, the performance of portable electronic devices such as mobile phones and personal digital assistants largely depends on the performance of not only semiconductor elements and electronic circuits to be mounted, but also the performance of chargeable and dischargeable sealed secondary batteries. It is desired that the capacity of the sealed secondary battery be increased and the weight and size be reduced at the same time. As a sealed secondary battery that meets these demands, a nickel-metal hydride storage battery with an energy density about twice that of a nickel-cadmium storage battery has been developed, and then a lithium-ion battery that exceeds this has been developed. It is used properly.
[0003]
These sealed secondary batteries house a positive electrode plate and a negative electrode plate spirally wound or laminated via a separator in a cylindrical or flat prismatic battery case with a power generation element consisting of an electrode group and an electrolyte. It is formed by caulking or laser sealing, and among other things, a thin flat battery from the viewpoint of effective use of space, especially a lithium ion battery using a flat aluminum case that also satisfies the demand for weight reduction, is in the spotlight. Is taking a bath.
[0004]
In this flat battery, a flat electrode group including a substantially linear portion and a curved portion in which a positive electrode plate and a negative electrode plate are insulated via a separator is housed in a bottomed battery case having an open top. After the water electrolyte is injected and impregnated, the opening of the battery case is sealed to produce a flat battery.
[0005]
When the flat electrode group consisting of the substantially straight part and the curvature part as described above is housed in the bottomed battery case, the active material is filled at a high density, so there is no room for the space between the battery case and the battery case. If the degree of parallelism between the inner surface of the battery case and the substantially straight portion of the flat electrode group is not obtained, it becomes difficult to store the flat electrode group in the battery case, and when the pressure for housing is increased, the outermost periphery of the flat electrode group is reduced. In some cases, the side and bottom surfaces were damaged, the active material layer was dropped, and the dropped active material was short-circuited.
[0006]
In order to suppress the occurrence of such inconveniences, the outermost terminal portion of the flat electrode group or the entire circumference of the flat electrode group is fixed with an insulating tape, thereby preventing the flat electrode group from bulging due to loose winding. In addition, the displacement of the electrode plate when housed in the battery case and the falling off of the active material layer are suppressed (for example, see Patent Document 1).
[0007]
However, in such a configuration, the insulating tape only prevents swelling due to loose winding of the flat electrode group, and when the flat electrode group is stored in the battery case, the bottom surface of the flat electrode group contacts the battery case. However, the effect of suppressing damage to the flat electrode group and falling off of the active material layer cannot be expected.
[0008]
Further, in the case of a method in which a sheet material is projected from the entire outermost periphery of the flat electrode group and lower than the lower end of the flat electrode group into a battery case (for example, see Patent Document 2), the lower end of the flat electrode group is used. In some cases, the sheet material projecting downward may be curved outward and cannot be stored in the battery case.
[0009]
Since the bending of the sheet material accommodated in the battery case is not constant, the height of the flat electrode group is not constant, and the impregnating property of the injected electrolyte into the flat electrode group is poor.
[0010]
In view of this, there has been proposed a method in which an insulating tape having a width wider than the width of the bottom surface is attached to the bottom surface located on the storage side of the flat electrode group and stored in the battery case (for example, see Patent Document 3). Since the bottom surface of the electrode group and the side surface near the bottom surface are covered, the end surface of the flat electrode group comes into contact with the battery case, and the active material layer is prevented from falling off.
[0011]
However, since the entire bottom surface of the flat electrode group and the side surface near the bottom surface are covered, after the flat electrode group is stored in the battery case, in the step of injecting the electrolyte, the entire bottom surface of the insulating tape and the flat electrode group and Since the side surface near the bottom surface is in close contact, it is difficult to impregnate the flat electrode group with the electrolyte injected between the flat electrode group and the battery case. In particular, the above phenomenon is remarkable in an electrode group that is filled with an active material at a high density or wound with a high binding force.
[0012]
A method of covering the bottom surface of the flat electrode group and the side surface near the bottom surface with an insulating tape provided with a plurality of holes (for example, see Patent Document 4) has also been proposed, but the effect of impregnating the flat electrode group with the electrolyte is not so much. There is no.
[0013]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 07-142089 [Patent Document 2]
JP 2002-124293 A [Patent Document 3]
Japanese Utility Model Publication No. 06-0554208 [Patent Document 4]
JP-A-2001-273931
[Problems to be solved by the invention]
The present invention, in order to solve the above problems, while suppressing the flat electrode group damage and fall of the active material layer when storing the flat electrode group in the battery case, and to the flat electrode group housed in the battery case A main object of the present invention is to provide a flat battery having excellent non-aqueous electrolyte injectability.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the flat battery according to the present invention has a lower bottom surface and a side surface near the bottom surface of a flat electrode group including a substantially linear portion and a curvature portion in which a positive electrode plate and a negative electrode plate are insulated via a separator. A flat battery, which is covered with an insulating tape, is housed in a bottomed battery case having an open top, and hermetically seals the opening of the battery case, wherein at least the substantially straight portion is A flat battery, wherein a side surface near a bottom surface is covered with an insulating tape obtained by attaching an adhesive material to a base material, wherein 1/10 to 8/10 of the substantially straight line portion is applied to the base material. It is preferably covered with an insulating tape to which an adhesive material is attached.
[0016]
According to the present invention, there is no breakage of the flat electrode group or dropout of the active material layer when the flat electrode group including the substantially straight portion and the curved portion is housed in the battery case, and the flat electrode group is flat when the nonaqueous electrolyte is injected. The non-aqueous electrolyte injected into the gaps at the four corners of the electrode group and the battery case should be impregnated into the flat electrode group from the curvature of the insulating tape where the adhesive is not attached to the base material on the bottom of the flat electrode group. Can be.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the present invention will be described with reference to the drawings.
[0018]
1 is a perspective view of a flat electrode group, FIG. 2A is a plan view of an insulating tape, FIG. 2B is a cross-sectional view of the insulating tape, and FIG. 3 is a perspective view of a flat electrode group to which the insulating tape is attached. FIG. 4 is a sectional view when the flat electrode group is housed in a battery case.
[0019]
In FIG. 1, a flat electrode group 11 is wound in a state where a positive electrode plate and a negative electrode plate are insulated with a separator 13 interposed therebetween, and a positive electrode current collector 12 is exposed on the outermost periphery. A positive electrode lead 16 covered with a tape 17 is attached, and the outermost end is fixed with a group fixing tape 14.
[0020]
The bottom surface 15 of the flat electrode group composed of the substantially straight portion 15a and the curvature portion 15b and the side surface near this bottom surface are covered with the insulating tape 21 shown in FIG. 2 as shown in FIG. The battery is a flat battery that is housed in the inside of the battery case 31, infused with a non-aqueous electrolyte, and sealed the upper opening of the battery case 31 and the sealing plate.
[0021]
More specifically, as shown in FIG. 2, the insulating tape 21 includes a base material 22 and an adhesive 23, and the base material 22 has a flat portion 21a facing the substantially straight portion 15a of the flat electrode group, and a flat portion 21a. A portion 21b opposed to the curvature portion 15b of the electrode group and a portion 21c opposed to the outside of the curvature portion 21b of the flat electrode group are provided, and a portion 21d opposed to the bottom surface 15 of the flat electrode group and a side surface near the bottom surface of the flat electrode group. This is the opposing portion 21e.
[0022]
The adhesive material 23 is provided at least at a portion surrounded by a portion 21a facing the substantially straight portion 15a of the flat electrode group and a portion 21e facing the side surface near the bottom surface of the flat electrode group, and has a dimension of 2 mm from the bottom surface. The range of ８8 mm is preferable from the viewpoint of storability in the battery case 31 and discharge rate characteristics.
[0023]
In addition, the portion surrounded by 21a and 21d may or may not have an adhesive, but it is more preferable that there is no adhesive in this portion because of the impregnation of the nonaqueous electrolyte into the flat electrode group. . And it is preferable to stick the adhesive material 23 to a portion corresponding to 1/10 to 8/10 of the substantially straight portion 15a.
[0024]
If the ratio is less than 1/10, the adhesion between the flat electrode group 11 and the insulating tape 21 is poor, and when the flat electrode group 11 is stored in the battery case 31, a displacement or the like occurs. In some cases, dropout cannot be prevented. On the other hand, if it exceeds 8/10, the adhesive is attached to the curvature portion due to dimensional variations at the position where the adhesive 23 is attached, and the impregnation of the nonaqueous electrolyte into the flat electrode group is performed. May decrease.
[0025]
After the insulating tape 21 is attached to the bottom surface 15 of the flat electrode group so as to have such a positional relationship, the insulating tape 21 is housed in the bottomed battery case 31 having an open upper portion, so that the flat electrode group may be damaged or the active material may be damaged. The layer can be prevented from falling off.
[0026]
Next, when the non-aqueous electrolyte is injected, the non-aqueous electrolyte flows between the flat electrode group 11 and the battery case 31, but the gap between the battery case 31 and the flat electrode group 11 is large as shown in FIG. A non-aqueous electrolyte exists on the bottom surface of the voids at the four corners indicated by 32a to 32d.
[0027]
The nonaqueous electrolyte can be impregnated into the positive / negative electrode plate and the separator in the flat electrode group from the interface between the flat electrode group bottom surface curvature portion 15b and the insulating tape on which the adhesive is not attached to the base material.
[0028]
The material of the base material 22 is not particularly limited, and a polyimide resin, a polyphenylene sulfide resin, a fluororesin, a silicone resin, a polyolefin resin such as a polyethylene resin or a polypropylene resin, or a blended product can be used. The thickness is preferably in the range of 15 μm to 40 μm from the viewpoint of strength.
[0029]
The material of the adhesive is not particularly limited, but is preferably isobutyl rubber, styrene butadiene rubber, silicone resin, or acrylic resin, and the thickness of the adhesive layer is a side surface near the bottom of the substantially linear portion of the flat electrode group. From the viewpoint of adhesiveness, the range of 15 μm to 70 μm is preferable.
[0030]
Next, the components of the flat electrode group of the present invention and the configuration of the non-aqueous electrolyte will be described in detail.
[0031]
This positive electrode plate, for example, on one or both sides of a positive electrode current collector having a thickness of 10 μm to 60 μm that has been subjected to foil or lath processing or etching processing made of aluminum or an aluminum alloy, applying a positive electrode paste, drying and rolling. It is manufactured by forming a positive electrode active material layer. The positive electrode paste is prepared by dispersing a positive electrode active material, a binder, a conductive agent, and, if necessary, a thickener in a dispersion medium. The positive electrode is provided with a solid portion having no active material layer, and a positive electrode lead is welded to the uncoated portion.
[0032]
The positive electrode active material is not particularly limited, but a lithium-containing transition metal compound that can accept lithium ions as a guest can be used. For example, a composite metal oxide of lithium and at least one transition metal selected from cobalt, manganese, nickel, chromium, iron and vanadium is used. Of these _{Li x CoO 2, Li x MnO} 2, Li x NiO 2, LiCrO 2, αLiFeO 2, LiVO 2, Li x Co y Ni 1-y O 2, Li x Co y M 1-y O z, Li x _{Ni 1-y M y O z} , Li x Mn 2 O 4, Li x Mn 2-y M y O 4 ( where, M = Na, Mg, Sc , Y, Mn, Fe, Co, Ni, Cu, At least one selected from the group consisting of Zn, Al, Cr, Pb, Sb and B, x = 0 to 1.2, y = 0 to 0.9, z = 2.0 to 2.3), transition metal Preference is given to chalcogenides, lithiated vanadium oxides, lithiated niobium oxides and the like. These may be used alone or in combination of two or more. In addition, the above-mentioned x value increases and decreases by charging and discharging. The average particle size of the positive electrode active material is preferably 1 μm to 30 μm.
[0033]
As the binder, the conductive agent, and the thickener that can be added as needed, the same materials as those used in the related art can be used for the positive electrode paste.
[0034]
The binder is not particularly limited as long as it can be dissolved or dispersed in the dispersion medium of the paste. For example, a fluorine-based binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR) , An acrylic polymer, a vinyl polymer, and the like. These may be used alone or in combination of two or more. As the fluorine-based binder, for example, polyvinylidene fluoride, a copolymer of vinylidene fluoride and propylene hexafluoride, polytetrafluoroethylene, and the like are preferable, and these can be used as a dispersion.
[0035]
As the conductive agent, acetylene black, graphite, carbon fiber, or the like can be used. These may be used alone or in combination of two or more.
[0036]
As the thickener, ethylene-vinyl alcohol copolymer, carboxymethylcellulose, methylcellulose and the like are preferable.
[0037]
As the dispersion medium, those in which the binder can be dissolved are suitable. When an organic binder is used, N-methyl-2-pyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide, hexamethylsulfonamide, tetramethylurea, acetone, methylethylketone or the like may be used alone or It is preferable to use a mixture. In the case where an aqueous binder is used, water or warm water is preferred.
[0038]
The method for preparing the positive electrode paste by dispersing the positive electrode active material, the binder, the conductive agent, and the thickener to be added as necessary in a dispersion medium is not particularly limited. For example, a planetary mixer, a homogenizer, and the like. A mixer, pin mixer, kneader, homogenizer and the like can be used. These may be used alone or in combination of two or more. Further, at the time of kneading and dispersing the positive electrode paste, various dispersants, surfactants, stabilizers and the like can be added as necessary.
[0039]
The positive electrode paste can be easily applied to the positive electrode current collector using, for example, a slit die coater, a reverse roll coater, a lip coater, a blade coater, a knife coater, a gravure coater, a dip coater, or the like. The positive electrode paste applied to the positive electrode current collector is preferably dried close to natural drying, but is preferably dried at a temperature of 70 ° C to 200 ° C for 10 minutes to 5 hours in consideration of productivity.
[0040]
Rolling is preferably performed several times at a linear pressure of 1000 to 2000 kg / cm or by changing the linear pressure until the positive electrode plate has a predetermined thickness of 130 μm to 200 μm using a roll press machine.
[0041]
The negative electrode is coated with a negative electrode paste on one or both sides of a negative electrode current collector having a thickness of 10 μm to 50 μm made of, for example, ordinary copper foil or lath-processed or etched copper foil, dried, and rolled to form a negative electrode. It is manufactured by forming an active material layer. The negative electrode paste is prepared by dispersing a negative electrode active material, a binder, and if necessary, a conductive agent and a thickener in a dispersion medium. The negative electrode is provided with a solid portion having no active material layer, to which a negative electrode lead is welded.
[0042]
The negative electrode active material is not particularly limited, but a carbon material that can release and occlude lithium ions by charging and discharging can be used. For example, carbon materials obtained by firing organic polymer compounds (phenol resin, polyacrylonitrile, cellulose, etc.), carbon materials obtained by firing coke and pitch, artificial graphite, natural graphite, pitch-based carbon fibers, PAN-based carbon fibers and the like are preferable, and the shape is preferably fibrous, spherical, scale-like, or lump-like.
[0043]
As the binder, the conductive agent and the thickener used as needed, the same binder, conductive agent and thickener as those used for the positive electrode plate can be used.
[0044]
Examples of the separator 13 include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyether (polyethylene oxide and polypropylene oxide), A microporous film composed of a polymer such as cellulose (carboxymethylcellulose or hydroxypropylcellulose), poly (meth) acrylic acid, or poly (meth) acrylate is preferably used. Further, a multilayer film in which these microporous films are overlapped is also used. Among them, a microporous film made of polyethylene, polypropylene, polyvinylidene fluoride or the like is preferable, and the thickness is preferably 15 μm to 30 μm.
[0045]
The battery case 31 is a flat rectangular battery case with a bottom that has an open top. The material is made of an aluminum alloy. From the viewpoint of pressure resistance, manganese and an aluminum alloy containing a small amount of a metal such as copper are preferable. Alloy No. A 3000 series aluminum alloy is preferred.
[0046]
The non-aqueous electrolyte contains a non-aqueous solvent and a solute, and the non-aqueous solvent contains a cyclic carbonate and a chain carbonate as main components. The cyclic carbonate is preferably at least one selected from ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). In addition, the chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and the like.
[0047]
As the solute, for example, a lithium salt having a strong electron-withdrawing property is used. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C) _{2 F 5) 2, LiC (} SO 2 CF 3) 3 and the like. These electrolytes may be used alone or in combination of two or more. These solutes are preferably dissolved in the non-aqueous solvent at a concentration of 0.5 to 1.5M.
[0048]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but these do not limit the present invention at all.
[0049]
(Example 1)
50 parts by mass of lithium cobalt oxide (LiCoO ₂ ) powder as a positive electrode active material, 1.5 parts by mass of acetylene black as a conductive agent, 7 parts by mass of a 50% by mass polyfluoroethylene (PTFE) dispersion aqueous solution as a binder, and thickening As an agent, 41.5 parts by mass of a 1% by mass aqueous solution of ammonium salt of carboxymethyl cellulose was added, kneaded and dispersed to prepare a paste for a positive electrode. This positive electrode paste was applied to both surfaces of a positive electrode current collector 12 made of aluminum foil having a thickness of 20 μm using a die coater so as to have a thickness of 0.35 mm, dried, and then heated to 200 ° C. to obtain a binder. Of PTFE particles were sintered. When the flat electrode group is formed, a portion corresponding to the outermost periphery has a configuration in which the positive electrode current collector is exposed. Thereafter, the positive electrode plate was rolled to a thickness of 0.15 mm, and cut into predetermined dimensions of 42 mm in width and 466 mm in length to obtain a belt-shaped positive electrode plate. An aluminum lead 16 was welded to the positive electrode current collector 12, and a positive electrode lead covering tape 17 was attached thereon to cover the lead 16.
[0050]
On the other hand, as a negative electrode active material, 5 parts by mass of a binder solution comprising a styrene-butadiene copolymer was added to 100 parts by mass of graphite powder, kneaded and dispersed to prepare a paste for a negative electrode. This negative electrode paste is applied to both surfaces of a negative electrode current collector made of copper foil having a thickness of 10 μm using a die coater, dried, and then rolled to a thickness of 0.15 mm, and a predetermined width of 44 mm and a length of 447 mm is obtained. It was cut into dimensions to obtain a strip-shaped negative electrode plate. A lead 18 made of nickel was welded to the negative electrode current collector, and a negative electrode lead covering tape 19 was adhered thereon to cover. As the separator 13, a microporous film made of polyethylene resin cut into a width of 46 mm and a thickness of 27 μm was used.
[0051]
Next, one end of the separator is sandwiched between slits of a core jig having an elliptical cross section, and the core jig is rotated, and one positive electrode plate is provided on the outer periphery of the core jig via the separator. And a negative electrode plate were wound to form a flat electrode group having an elliptical cross section. The outermost positive electrode current collector 12 of the flat electrode group was fixed with a group fixing tape 14 having a width of 40 mm and a length of 16 mm with a base made of polypropylene resin.
[0052]
Then, the flat electrode group is extracted from the core jig, and the flat electrode group is pressed and deformed at a pressure of 5 MPa while being sandwiched between a pair of flat plates parallel to the long axis of the flat electrode group, and is flattened. The electrode group 11 was configured.
[0053]
Furthermore, as shown in FIG. 2, a portion surrounded by a portion 21 a facing the substantially straight portion 15 a of the flat electrode group 11 and a portion 21 e facing the side surface near the bottom surface of the flat electrode group 11 having a major axis of 38 mm and a minor axis of 16 mm as shown in FIG. Among them, an adhesive 23 is formed at a central portion of the 21a so as to have a size of 12 mm corresponding to a size of 5/10 of a substantially straight portion, and there is no adhesive at other portions, and only the base 22 is used. The insulating tape 21 is attached to one side near the bottom of the central portion of the 21a at a size of 5 mm from the bottom, bent at the dotted line, and the bottom located on the storage side in the aluminum alloy battery case 31 is removed. 5 mm from the bottom surface on the opposite side surface near the bottom surface.
[0054]
The insulating tape 21 used had a base material 22 made of a polypropylene resin and had a thickness of 30 μm, and the adhesive material 23 formed on the base material had a silicon resin thickness of 30 μm.
[0055]
Thereafter, the flat electrode group 11 is housed in a battery case 31 made of an aluminum alloy, and then the positive electrode lead 16 is electrically connected to a sealing plate with the negative electrode lead 18 through an insulating gasket in a mounting hole at the center of the sealing plate. Each washer was laser-welded to a washer attached in an insulated state. This sealing plate was fitted into a predetermined position of the opening of the battery case 31, and the periphery thereof was fixed to the inner peripheral surface of the battery case by laser welding. Thereafter, 3.4 g of the non-aqueous electrolyte is injected into and impregnated into the battery case 31 from the liquid injection hole of the sealing plate, and then the plugging member is stored in the liquid injection hole of the sealing plate. The flat battery of Example 1 having a width of 34 mm, a thickness of 6 mm, and a height of 50 mm and a capacity of 950 mAh was produced by laser welding the plate and the sealing plate.
[0056]
The non-aqueous electrolyte used was a mixture of ethylene carbonate and ethyl methyl carbonate in an equal amount of lithium hexafluorophosphate (LiPF ₆ ) having a concentration of 1.0 mol / l as an electrolyte.
[0057]
(Examples 2 to 5)
Insulating tape so that the size of the adhesive material attached to both sides near the bottom surface of the substantially straight portion 15a of the flat electrode group is 1/20, 1/10, 8/10, and 10/10 of the substantially straight portion. Was affixed to the center of the substantially linear portion, and flat batteries of Examples 2 to 5 were produced in the same manner as in Example 1.
[0058]
(Example 6)
On both sides near the bottom surface of the substantially linear portion 15a of the flat electrode group, an insulating tape whose adhesive material is attached is 3/10 of the substantially linear portion, and the total is 6/10, and the substantially linear portion is divided into five equal parts. A flat battery of Example 6 was produced in the same manner as in Example 1, except that the flat battery was affixed to the central portions corresponding to the second and fourth positions.
[0059]
(Example 7)
A substantially straight portion is formed at the center of a portion surrounded by a portion 21a facing the substantially straight portion of the flat electrode group, a portion 21e facing the side surface near the bottom surface of the flat electrode group, and a portion 21d facing the bottom surface of the flat electrode group. An adhesive material 23 is formed so as to have a size of 12 mm corresponding to the size of 5/10, and an insulating tape 21 consisting of only the base material 22 is provided with no adhesive material in other places, and a bottom surface of the central portion of the 21a is formed. Affixed to one side in the vicinity at a dimension of 5 mm from the bottom, bent at the dotted line, and sized 5 mm from the bottom on the side near the bottom opposite to the bottom positioned on the storage side in the aluminum alloy battery case 31. A flat battery of Example 7 was made in the same manner as Example 1 except that the battery was adhered.
[0060]
(Comparative Example 1)
As shown in FIGS. 5 (a) and 5 (b), Example 1 was the same as Example 1 except that the entire bottom surface of the flat electrode group and the side surface in the vicinity thereof were covered using an insulating tape to which an adhesive was applied over the entire surface of the base material. Similarly, a flat battery of Comparative Example 1 was manufactured.
[0061]
(Comparative Example 2)
As shown in FIGS. 5 (b) and 5 (c), an adhesive is stuck on the entire surface of the base material, and the bottom surface of the flat electrode group and the side surface in the vicinity thereof are covered with an insulating tape having a hole of 1.0 mm in diameter. Then, a flat battery of Comparative Example 2 was produced in the same manner as in Example 1 except that 9/10 of the whole was covered.
[0062]
For each of the thus obtained flat batteries of Examples 1 to 7 and Comparative Examples 1 and 2, the battery was disassembled, the flat electrode group was removed from the battery case, and the battery was placed on the bottom surface of the battery case. Measure the mass of the remaining non-aqueous electrolyte and visually inspect and compare the defect rate due to electrode plate breakage, peeling of the active material layer, and falling off after storing the flat electrode group in the battery case for each 1000 cells. The results are shown in Table 1.
[0063]
Table 1 shows the results obtained by calculating the discharge rate of 2C at 20 ° C. as follows for each of the 20 flat batteries. Charging is performed at 4.2 V for 2 hours with constant current-constant voltage charging, and until the battery voltage reaches 4.2 V, constant current charging of 950 mA (1 ItA) is performed. Then, the battery was discharged to a discharge termination voltage of 3.0 V at a constant current of 190 mA (0.2 ItA). Next, after charging as described above, the battery was discharged at a constant current of 1900 mA (2 ItA) to a discharge end voltage of 3.0 V, and the discharge rate of 2 C was calculated as (capacity at 2 ItA discharge) / (0.2 ItA discharge at the time of discharge). Capacity).
[0064]
[Table 1]

[0065]
As is clear from Table 1, both sides near the lower bottom surface of at least the substantially linear portion of the flat electrode group including the substantially linear portion and the curved portion where the positive electrode plate and the negative electrode plate are insulated via the separator are used as the base material. In the case of the embodiment in which the electrode is covered with an insulating tape to which an adhesive material is adhered, failure due to breakage of the electrode plate and falling off of the active material layer when housed in the battery case is reduced, and at the same time, non-contact to the flat electrode group is reduced. By improving the impregnation of the water electrolyte, a flat battery having excellent discharge rate characteristics can be obtained, but in the case of the comparative example, since the adhesive is adhered to the entire surface of the base material, the flat electrode group and the battery case are formed. It is difficult for the nonaqueous electrolyte injected into the voids at the four corners of the flat electrode group to impregnate the positive and negative electrode plates and the separator inside the flat electrode group from the curvature section of the flat electrode group bottom face. Non-aqueous electrolyte remains and 2C discharge rate characteristics decrease It was found.
[0066]
Further, according to Example 2, when the dimension obtained by attaching the adhesive to the base material is less than 1/10 of the side surface near the lower bottom surface of the substantially straight portion, the adhesion between the flat electrode group and the insulating tape is poor. When the battery was housed in the battery case, misregistration occurred and the active material layer fell off, resulting in a 0.1% defective rate.
[0067]
Conversely, according to Example 5, when the size of the adhesive material adhered to the base material exceeds 8/10 of the side surface near the lower bottom surface of the substantially straight portion, the number of cells on the bottom surface of the 1-cell battery case out of 20 cells increases. Some of the non-aqueous electrolyte remains as drops, and the adhesive is attached to the curvature portion 15b due to dimensional variation at the position where the adhesive 23 is attached. It is thought that the impregnation property was reduced.
[0068]
Further, from Example 7, when the lower bottom surface of the substantially linear portion of the flat electrode group and both side surfaces near this bottom surface were covered with an insulating tape formed by attaching an adhesive to a base material, the injected non-aqueous electrolyte was Although it did not remain on the bottom surface of the battery case, it was considered that the discharge rate characteristics of 2C were slightly lowered because the positive and negative electrode plates and the separator inside the flat electrode group were not uniformly impregnated.
[0069]
【The invention's effect】
As described above, according to the flat battery of the present invention, when the flat electrode group is housed in the battery case, failure due to breakage of the flat electrode group or falling off of the active material layer can be significantly suppressed. Further, the electrolyte flowing into the gaps at the four corners of the flat electrode group and the battery case during the injection of the non-aqueous electrolyte is formed by the flat electrode group bottom surface curvature portion and the insulating tape on which the adhesive is not attached to the base material. It is possible to provide a flat battery that can be impregnated from the interface into the positive and negative electrode plates and the separator in the flat electrode group and has excellent high-rate discharge characteristics.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external shape of a flat electrode group of the present application. FIG. 2 (a) is a plan view of an insulating tape of the present application. FIG. 1 (b) is a sectional view of the insulating tape of the present application. FIG. 4 is a perspective view showing a state where the flat electrode group is attached to a battery case. FIG. 5 (a) is a plan view of a conventional insulating tape. FIG. 5 (b) is a cross-sectional view of a conventional insulating tape. Figure (c) Plan view of another conventional insulating tape
DESCRIPTION OF SYMBOLS 11 Flat electrode group 12 Positive electrode collector 13 Separator 14 Group fixing tape 15 Bottom surface 15a of flat electrode group Substantially linear portion 15b Curvature portion 16 Positive electrode lead 17 Positive electrode lead tape 18 Negative lead 19 Negative electrode lead tape 21 Insulating tape 21a Flat electrode group A portion 21b facing the curved portion of the flat electrode group 21c a portion facing the outside of the curved portion of the flat electrode group 21d a portion facing the bottom surface of the flat electrode group 21e a portion near the bottom surface of the flat electrode group Portion 22 facing the side surface Base material 23 Adhesive material 24 Hole 31 provided in insulating tape Battery case 32a, 32b, 32c, 32d Gap between battery case and flat electrode group

Claims (2)

The lower and lower sides of the flat electrode group consisting of a substantially linear portion and a curved portion in which the positive electrode plate and the negative electrode plate are insulated via a separator and the side near this bottom surface are covered with insulating tape, and the upper portion is opened. A flat battery that is housed in a bottomed battery case and has an opening in the battery case sealed, and at least a side surface near the bottom surface of the substantially linear portion is formed by attaching an adhesive to a base material. A flat battery characterized by being covered with an insulating tape. The flat battery according to claim 1, wherein 1/10 to 8/10 of the substantially straight portion is covered with an insulating tape obtained by attaching an adhesive to a base material.

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