JP4017376B2 - Lithium secondary battery - Google Patents

Description

【００６７】
表１から明らかなように、フッ素系の樹脂からなる基材と、天然ゴム、イソブチルゴム、スチレンブタジエンゴムから選ばれた少なくとも一種からなる粘着剤と、フタロシアニンを成分とする有機物、チタン及びアルミニウムの金属粉や酸化物から選ばれた一種からなる顔料から構成される粘着テープにて、正極リードを被覆することにより、正極活物質との反応による金属還元体の生成を抑制することができ、充放電サイクルや高温保存をしても、微小ショートによる電圧不良や電池容量の低下を引き起こさないリチウム二次電池が得られることがわかった。
【００６８】
そして、粘着テープを正極板の活物質層と接触しないように正極リードを被覆することにより、さらに充放電サイクルや高温保存特性に優れたリチウム二次電池が得られることがわかった。
【００６９】
【発明の効果】
以上の説明の通り本発明による粘着テープを正極板の活物質層と接触しないように正極リードを被覆することにより、正極活物質との反応による金属還元体の生成を抑制することができ、充放電サイクルや高温保存をしても、微小ショートによる電圧不良や電池容量の低下を引き起こさないリチウム二次電池が得られる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る（ａ）は正極板、（ｂ）は負極板の平面図
【図２】本発明の実施形態に係る電池の断面図
【図３】本発明の別の実施形態に係る（ａ）は正極板、（ｂ）は負極板の平面図
【図４】従来例に係る（ａ）は正極板、（ｂ）は負極板の平面図
【符号の説明】
１ 正極板
２ 正極リード
３ 負極板
４ 負極リード
５ セパレータ
６ 上部絶縁板
７ 下部絶縁板
８ 電池ケース
９ ガスケット
１０ 封口板
１１ 正極活物質無地部
１２ 正極粘着テープ
１３ 負極活物質無地部
１４ 負極粘着テープ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium secondary battery using a non-aqueous electrolyte, and more particularly to an adhesive tape for covering a positive electrode lead.
[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 the semiconductor elements and electronic circuits that are mounted, but also the chargeable / dischargeable secondary batteries. It is desired to realize light weight and compactness simultaneously with the increase in battery capacity. As a secondary battery that meets these demands, a nickel-metal hydride storage battery having an energy density about twice that of a nickel cadmium storage battery has been developed, and then a lithium secondary battery exceeding this has been developed and is in the limelight.
[0003]
In this lithium secondary battery, a positive electrode and a negative electrode are disposed in a non-aqueous electrolyte, and a positive electrode active material is bound to the surface of the current collector or a negative electrode active material is formed on the surface of the current collector. It has a structure in which substances are bound. A battery electrode plate used in this battery generally collects a paste mixture obtained by kneading and dispersing an active material (positive electrode active material or negative electrode active material), a conductive material, a binder (binder), etc. in a solvent. It is produced by applying a material to one or both sides of the body, drying it, rolling it to a predetermined thickness, and cutting it into a predetermined shape.
[0004]
The positive electrode plate and the negative electrode plate are accommodated in a case with a group of electrode plates wound in a spiral shape through a separator, and after pouring a non-aqueous electrolyte, the positive electrode plate and the negative electrode plate are sealed with a sealing plate, thereby lithium. A secondary battery is manufactured. Therefore, in order to avoid an increase in the diameter of the electrode group due to a decrease in the group pressure until the electrode group is accommodated in the case, and thereby preventing the electrode group from being accommodated in the case, the winding end portion of the electrode group is adhered to A method of fixing the group by sticking with a tape is employed.
[0005]
Further, as shown in FIG. 4A, the positive electrode plate of the lithium secondary battery has one end side of the positive electrode lead 2 connected to the positive electrode active material plain portion 11 of the positive electrode plate 1 and the other end side connected to the positive electrode terminal. In the negative electrode plate, as shown in FIG. 4B, one end side of the negative electrode lead 4 is connected to the negative electrode active material plain portion 13 of the negative electrode plate 3, and the other end side is connected to the negative electrode terminal. A positive electrode adhesive tape 12 and a negative electrode adhesive tape 14 are attached to the positive electrode lead 2 and the negative electrode lead 4, respectively.
[0006]
[Problems to be solved by the invention]
Since the pressure-sensitive adhesive tape attached to the electrode plate group and the lead terminal is stored in the case as it is, it is immersed in the non-aqueous electrolyte. When this adhesive tape is immersed in the non-aqueous electrolyte for a long period of time, the base material and / or the adhesive of the adhesive tape will elute into the non-aqueous electrolyte, reducing the ionic conductivity of the non-aqueous electrolyte and reducing the battery capacity. There was a problem of causing a decrease. The cause of this problem is due to both the base material of the adhesive tape and / or the material used when the adhesive is likely to elute into the organic solvent in the non-aqueous electrolyte and the inappropriate organic solvent. If you want to. Therefore, a method using a polyimide or polyolefin as a main component of the adhesive tape, an acrylic adhesive as the adhesive, and a specific organic solvent is disclosed in JP-A-7-142089 and JP-A-10-12277. A method using a pressure-sensitive adhesive having a specific degree of unsaturation is proposed in Japanese Patent Laid-Open No. 10-247489.
[0007]
However, there is no problem when an adhesive tape using these base materials and / or adhesives is attached to the electrode plate group and the negative electrode lead, but when the adhesive tape is attached to the positive electrode lead, the positive electrode active material, the adhesive The potential difference between the positive electrode plate and the adhesive tape occurs at the part where the tape and separator come into contact, and the reaction between the adhesive tape and the positive electrode active material elutes metal reductants such as cobalt contained in the positive electrode active material. The separator is clogged and a voltage failure due to a micro short circuit occurs.
[0008]
The reason why the potential difference occurs between the positive electrode plate and the adhesive tape is that the amount of lithium remains as an irreversible capacity in the negative electrode active material region facing the positive electrode active material region that releases lithium ions, whereas the positive electrode uncoated region This is because the negative electrode active material region opposite to the positive electrode active material region from which lithium ions are released is about 0.1 V lower than the lithium redox potential.
[0009]
In particular, when the packing density of the positive electrode active material is increased to increase the capacity of the battery and the binding rate of the electrode plate group is increased, this becomes more conspicuous. It was a problem to inhibit.
[0010]
In view of the above problems, an object of the present invention is to provide a lithium secondary battery that does not cause a voltage failure or a decrease in battery capacity due to a micro short-circuit even when it is charged and discharged or stored at a high temperature.
[0011]
[Means for Solving the Problems]
  In order to solve these problems, the present invention provides a positive electrode lead of the positive electrode plate in a battery in which a positive electrode plate and a negative electrode plate are housed in a case in which a positive electrode plate and a negative electrode plate are spirally wound via a separator. Is coated with a pressure-sensitive adhesive tape, and the pressure-sensitive adhesive tape is made of a fluorine-based resin, and a pressure-sensitive adhesive made of at least one selected from natural rubber, isobutyl rubber, and styrene-butadiene rubber.And a pigment composed of one kind selected from organic materials containing phthalocyanine, titanium and aluminum metal powders and oxidesThe lithium secondary battery is characterized in that the adhesive tape covers the positive electrode lead so as not to contact the active material layer of the positive electrode plate,The pigment is a metal powder or oxide of titanium and aluminum, and the average particle diameter is 0.5 μm to 5 μm.It is preferable. It is more preferable that the negative electrode lead of the negative electrode plate and / or the winding terminal portion of the electrode plate group is also covered with the adhesive tape.
[0012]
A base material made of a fluororesin, an adhesive made of at least one selected from natural rubber, isobutyl rubber and styrene butadiene rubber, an organic substance containing phthalocyanine as a component, and metal powders and oxides of titanium and aluminum. By using an adhesive tape colored with a pigment, which is a kind of pigment, even if it is used for a positive electrode lead of a positive electrode plate having a potential difference, a component such as a halogen or an azo group is contained in the adhesive tape substrate, adhesive and pigment components. Since there is no functional group having a heavy bond, generation of a metal reductant due to reaction with the positive electrode active material can be suppressed.
[0013]
Titanium and aluminum metal powders and oxides have electrical conductivity, but titanium shows stable behavior even when the potential is scanned to a lithium redox potential of 4.5 V, and aluminum forms a passive film and stabilizes. Therefore, it is suitable for use as a pigment.
[0014]
Then, by sticking the adhesive tape for covering the positive electrode lead welded to the plain part without the positive electrode active material of the positive electrode plate so as not to come into contact with the positive electrode active material layer, the base material of the adhesive tape and the component of the adhesive It is possible to further suppress the formation of a metal reductant due to the reaction between the cathode and the positive electrode active material. Therefore, even if charging / discharging cycles or high-temperature storage of a battery with a higher capacity of the battery by increasing the packing density of the positive electrode active material layer or the tightness ratio of the electrode plate group, the voltage failure or battery capacity due to micro short-circuiting A lithium secondary battery that does not cause a decrease is obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
FIG. 2 is a cross-sectional view of a cylindrical lithium secondary battery.
[0017]
A positive electrode plate 1 is housed in a bottomed battery case 8 having an open top and is wound in a spiral shape with the positive electrode plate 1 and the negative electrode plate 3 insulated via a separator 5. The other end of the positive electrode lead 2 connected to the battery is connected to a sealing plate that seals the opening of the battery case 8 via a gasket 9, and the other end of the negative electrode lead 4 connected to the negative electrode plate is connected to the battery case. 8, insulating plates 6 and 7 are disposed on the upper and lower parts of the electrode plate group, respectively.
[0018]
A plan view of the positive electrode plate 1 is shown in FIG.
[0019]
A positive electrode active material and a binder, and if necessary, a conductive agent and a thickener are kneaded in a solvent on one or both sides of a current collector made of aluminum foil, lath processed or etched foil having a thickness of 10 μm to 60 μm The dispersed paste is applied, dried, and rolled to produce an active material layer, a solid portion is provided on the active material layer, and a positive electrode lead is welded.
[0020]
Although it does not specifically limit as a positive electrode active material, For example, the lithium containing transition metal compound which can accept a lithium ion as a guest is used. For example, a composite metal oxide of at least one metal selected from cobalt, manganese, nickel, chromium, iron and vanadium and lithium, LiCoO₂LiMnO₂, LiNiO₂LiCo_xNi_(1-x)O₂(0 <x <1), LiCrO₂, ΑLiFeO₂, LiVO₂Etc. are preferred.
[0021]
The binder is not particularly limited as long as it can be kneaded and dispersed in a solvent. For example, a fluorine binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR), acrylic heavy A polymer, a vinyl polymer or the like can be used alone or as a mixture or copolymer of two or more. As the fluorine-based binder, for example, polyvinylidene fluoride, a copolymer of vinylidene fluoride and propylene hexafluoride, and a dispersion of polytetrafluoroethylene resin are preferable.
[0022]
A conductive agent and a thickener can be added as necessary. As the conductive agent, acetylene black, graphite, carbon fiber, etc. are used alone or as a mixture of two or more kinds. As the thickener, ethylene-vinyl alcohol is used. A polymer, carboxymethylcellulose, methylcellulose and the like are preferable.
[0023]
As the solvent, a solvent capable of dissolving the binder is suitable. In the case of an organic binder, N-methyl-2-pyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide, hexamethyl Organic solvents such as sulforamide, tetramethylurea, acetone, and methyl ethyl ketone are preferably used alone or as a mixed solvent thereof. In the case of an aqueous binder, water or warm water is preferred.
[0024]
By the way, the method of preparing a paste-like mixture by kneading and dispersing an active material, a binder, and a conductive agent added as necessary in a solvent in the present invention is not particularly limited. For example, a planetary mixer, A homomixer, a pin mixer, a kneader, a homogenizer, or the like can be used. These can be used alone or in combination.
[0025]
In addition, various dispersants, surfactants, stabilizers, and the like can be added as needed during the kneading and dispersing of the paste mixture.
[0026]
The coating and drying is not particularly limited, and the paste-like mixture kneaded and dispersed as described above, for example, slit die coater, reverse roll coater, lip coater, blade coater, knife coater, gravure coater, It can be easily applied using a dip coater or the like, and drying close to natural drying is preferable. However, considering productivity, it is preferable to dry at a temperature of 70 ° C. to 300 ° C. for 5 hours to 1 minute.
[0027]
The rolling is preferably performed several times at a linear pressure of 1000 to 2000 kg / cm, or by changing the linear pressure until a predetermined thickness is reached by a roll press.
[0028]
As shown in FIG. 1 (a), a positive electrode active material plain portion 11 from which the positive electrode active material layer has been peeled and removed is formed at the position where the positive electrode lead 2 of the positive electrode plate 1 is connected. From the viewpoint of weldability such as spot welding or resistance welding, the dimension in the width direction is preferably 5 mm to the full width and the dimension in the longitudinal direction is 2 mm to 3 mm wider than the width dimension of the positive electrode lead 2. One end side of the positive electrode lead 2 is welded, and the positive electrode adhesive tape 12 is attached so as to cover the positive electrode lead 2 and not to contact the positive electrode active material layer 18.
[0029]
The positive electrode adhesive tape 12 is composed of a base material, an adhesive layer, and a pigment for coloring. The base material is polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), four Fluorine resin such as fluorinated ethylene / perfluoroalkoxyethylene copolymer (PFA), the adhesive layer is an adhesive layer made of at least one selected from natural rubber, isobutyl rubber and styrene butadiene rubber, and the pigment is phthalocyanine. Coloring is performed using an organic pigment of phthalocyanine blue (copper phthalocyanine complex) as a component, and a kind of pigment selected from metal powders and oxides of titanium and aluminum. The particle diameters of titanium and aluminum metal powders and oxides are not particularly limited, but are preferably in the range of 0.5 μm to 5 μm. By using the positive electrode pressure-sensitive adhesive tape 12 having such a structure, even if it is used for the positive electrode lead 2 of the positive electrode plate 1 having a potential difference, the base material of the positive electrode pressure-sensitive adhesive tape 12 and the components of the pressure-sensitive adhesive include two components such as halogen or azo group. Since there is no functional group having a heavy bond, generation of a metal reductant due to reaction with the positive electrode active material can be suppressed.
[0030]
The dimensions of the positive electrode adhesive tape 12 for covering the positive electrode lead 2 welded to the plain portion 11 without the positive electrode active material of the positive electrode plate 1 are the same width as the positive electrode lead 2 to 1 mm to 2 mm narrower than the plain portion 11, By using an adhesive tape having a thickness of 20 μm to 60 μm and an adhesive thickness of 20 μm to 80 μm, which is thinner than the thickness of the active material layer, the insulation covering property and adhesive strength of the positive electrode lead 2 are ensured, and the positive electrode active material Since it can stick so that it may not contact a layer, while being able to further suppress generation of a metal reductant by reaction with a base material of a positive electrode adhesive tape 12, an ingredient of an adhesive, and a positive electrode active material, it is uniform. A wound electrode group is obtained. Therefore, even if the packing density of the positive electrode active material layer or the tightness ratio of the electrode plate group is increased to increase the capacity of the battery, a lithium secondary battery that does not cause a voltage failure or a decrease in battery capacity due to a micro short circuit can be obtained. .
[0031]
The negative electrode plate 3 is coated on one surface of a current collector with a negative electrode active material, a binder, and, if necessary, a paste-like mixture in which a conductive additive is kneaded and dispersed in an organic solvent, and then dried. The other surface is coated, dried and then rolled.
[0032]
The negative electrode current collector is made of a copper foil, a lathed foil, or an etched foil, and the thickness is preferably in the range of 10 μm to 50 μm.
[0033]
Although it does not specifically limit as a negative electrode active material, For example, it obtains by baking the carbon material obtained by baking organic polymer compounds (Phenol resin, polyacrylonitrile, cellulose, etc.), coke, and pitch. As the shape of the carbon material to be obtained, or artificial graphite, natural graphite or the like, a spherical shape, a scale shape or a lump shape can be used.
[0034]
As the binder and the thickener that can be added as necessary, the same binder as that of the positive electrode plate can be used.
[0035]
As the separator 5, a microporous polyolefin resin such as a polyethylene resin or a polypropylene resin having a thickness of 15 μm to 30 μm is preferable.
[0036]
In order to produce the electrode plate group by winding the positive electrode plate 1 and the negative electrode plate 3 thus obtained in a spiral manner via the separator 5, the positive electrode lead 2 while maintaining a constant tension in the electrode plate hoop. After attaching and adhering the adhesive tape, it is wound in a spiral shape so that the position of the positive electrode lead 2 of the positive electrode plate 1 is disposed in the negative electrode active material layer region of the negative electrode plate 3 facing it. The positive electrode plate 1 and the negative electrode plate 3 are simultaneously wound so that the negative electrode lead 4 welded and attached to the active material plain portion 13 of the negative electrode plate 3 is disposed outside the region of the positive electrode active material layer 19. By disposing the negative electrode lead 4 at the end of winding of the group, or by first winding the negative electrode plate 3 and disposing the negative electrode lead 4 at the winding start portion of the electrode plate group, The winding state of the electrode plate group becomes uniform, and there is no risk of peeling of the positive electrode adhesive tape 12 Even if the charge-discharge cycle and high-temperature storage, does not occur a lowering of the voltage failure and battery capacity due to micro-short circuit.
[0037]
Since there is no risk that the negative electrode adhesive tape 14 covering the negative electrode lead 4 reacts with the negative electrode active material, the negative electrode adhesive tape 14 may contact the negative electrode active material layer. Contact with the layer is not preferable because the thickness of the portion increases and the electrode plate group becomes non-uniform.
[0038]
Further, a non-aqueous electrolyte is injected into the battery case 8, and then a sealing plate 10 provided with a safety mechanism caulks the peripheral edge of the opening of the battery case 8 through the insulating packing 9. It is hermetically sealed.
[0039]
The electrolyte is adjusted by dissolving the electrolyte in a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-dichloroethane, 1,3-dimethoxypropane, 4- Methyl-2-pentanone, 1,4-dioxane, acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, sulfolane, 3-methyl-sulfolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylformamide, dimethylsulfoxide, dimethylformamide, Trimethyl phosphate, triethyl phosphate and the like can be used, and these nonaqueous solvents can be used alone or as a mixed solvent of two or more kinds.
[0040]
As the electrolyte contained in the non-aqueous electrolyte, for example, a lithium salt having a strong electron withdrawing property is used, for example, LiPF.₆, LiBF_FourLiClO_Four, LiAsF₆, LiCF_ThreeSO_Three, LiN (SO₂CF_Three)₂, LiN (SO₂C₂F_Five)₂, LiC (SO₂CF_Three)_ThreeEtc. These electrolytes may be used alone or in combination of two or more. These electrolytes are preferably dissolved at a concentration of 0.5 to 1.5 M in the non-aqueous solvent.
[0041]
【Example】
The present invention will be described in detail using examples and comparative examples, but these do not limit the present invention in any way.
[0042]
Example 1
First, a manufacturing method of the positive electrode plate 1 whose plan view is shown in FIG.
[0043]
100 parts by weight of lithium cobaltate as a positive electrode active material, 3 parts by weight of acetylene black as a conductive agent, 4 parts by weight of polytetrafluoroethylene (PTFE) resin as a binder and 0.8 parts by weight of carboxymethyl cellulose And kneaded and dispersed with water as a solvent to prepare a paste. The paste is continuously applied intermittently to a current collector made of a strip-shaped aluminum foil having a thickness of 20 μm and dried, followed by heat treatment at 250 ° C. for 10 hours to produce a positive electrode plate having a thickness of 290 μm. The positive electrode plate was rolled to 180 μm by rolling three times at 1000 kg / cm.
[0044]
As shown in FIG. 1 (a), the solid state part 11 for welding the positive electrode lead 2 to the central part of the positive electrode plate 1 is peeled off by using an active material peeling apparatus having an ultrasonic horn, The positive electrode active material was removed with a brass rotating brush to produce a width of 7.0 mm and a length of 38.0 mm.
This plain part 11 is made of aluminum and is 4.5 mm wide and 38.0 mm long by spot welding, and the base material is made of fluororesin made of PTFE. The thickness is 30 μm, and the adhesive is styrene butadiene rubber (SBR). The positive electrode lead 2 is covered with a positive electrode adhesive tape 12 having a thickness of 30 μm, a pigment made of phthalocyanine blue pigment, a width of 5.5 mm, and a length of 34.0 mm. It stuck so that it might not contact.
[0045]
Next, a manufacturing method of the negative electrode plate 3 whose plan view is shown in FIG.
[0046]
100 parts by weight of scaly graphite capable of occluding and releasing lithium as a negative electrode active material, 4 parts by weight of a water-soluble dispersion of styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose as a thickener 0.8 parts by weight of water as a solvent was added and kneaded and dispersed to prepare a paste mixture.
[0047]
The paste was continuously applied intermittently to a current collector made of a strip-shaped copper foil having a thickness of 14 μm and dried, followed by heat treatment at 110 ° C. for 10 hours to produce a negative electrode plate having a thickness of 300 μm, The negative electrode plate thickness was rolled to 196 μm by rolling three times at a pressure of 110 kg / cm.
[0048]
As shown in FIG. 1B, the plain portion 13 for welding the negative electrode lead 4 to the right end portion of the negative electrode plate 3 has a width of 6.0 mm and a length of 38.0 mm in the same manner as the positive electrode plate 1. It was produced in.
[0049]
A negative electrode lead 4 made of nickel, having a width of 4.0 mm and a length of 38 mm, is spot-welded to the plain portion 13, and the base material is a fluororesin made of PTFE with a thickness of 30 μm, and the adhesive is isobutyl rubber and the thickness is 30 μm. The negative electrode adhesive tape 14 having a width of 5.0 mm and a length of 34.0 mm is coated with the negative electrode lead 4, and the negative electrode active material layer 19 and the pigment are made of titanium dioxide powder having an average particle diameter of 3.0 μm. It stuck so that it might not contact.
[0050]
The positive electrode plate 1 as shown in FIG. 1 (a) and the negative electrode plate 3 as shown in FIG. 1 (b) thus produced are interposed via a separator 5 made of a microporous polyethylene resin having a thickness of 25 μm. The positive electrode active material of the positive electrode plate 1 which is insulated and is disposed in the negative electrode active material layer region of the negative electrode plate 3 where the position of the positive electrode lead 2 of the positive electrode plate 1 faces and the position of the negative electrode lead 4 of the negative electrode plate 3 faces. As shown in FIG. 2, after the winding terminal portion of the electrode group wound in a spiral shape so as to be disposed outside the layer region is fixed with the positive electrode adhesive tape 12 used in the positive electrode plate 1. The other end of the positive electrode lead 2 connected to the positive electrode plate 1 is connected to the sealing plate 10 and the negative electrode lead 4 connected to the negative electrode plate 3. The other end of the battery was connected to the bottom of the battery case 8.
[0051]
An upper insulating plate 6 and a lower insulating plate 7 are arranged above and below the electrode plate group, respectively.
[0052]
Furthermore, lithium hexafluorophosphate (LiPF) is used as an electrolyte in a mixed solvent of ethylene carbonate and ethyl methyl carbonate.₆After a predetermined amount of an electrolytic solution in which 1.3 moles of an electrolyte is dissolved, the battery case 8 is sealed with a sealing plate 10 through a gasket 9 made of polypropylene resin, and the battery capacity is ICR17500 size described in JIS C8711. Produced a battery of 800 mAh to obtain a battery of Example 1.
[0053]
(Example 2)
The positive electrode pressure-sensitive adhesive tape 12 used in the positive electrode plate 1 of Example 1 was used. The dimensions were 8.0 mm in width and 34.0 mm in length, the positive electrode lead 2 was covered, and the width in contact with the positive electrode active material layer was 1. A battery was produced in the same manner as in Example 1 except that the thickness was 0 mm, so that a battery of Example 2 was obtained.
[0054]
(Example 3)
Implemented except that the base material is a fluororesin made of FEP, the thickness is 40 μm, the pressure-sensitive adhesive is made of natural rubber, the thickness is 20 μm, and the pigment is made of titanium dioxide powder with an average particle size of 2.5 μm. 3B produced in the same manner as in Example 1, except that the position of the positive electrode plate 1 and the negative electrode lead 4 as shown in FIG. The negative electrode plate 3 as shown in the drawing is wound around the separator 5 made of a microporous polypropylene resin having a thickness of 20 μm, and the negative electrode lead 4 is disposed at the winding start portion of the electrode plate group. A battery was fabricated in the same manner as in Example 1, except that the positive electrode lead 2 of the positive electrode plate 1 was wound in a spiral shape so that the positive electrode lead 2 was disposed in the negative electrode active material layer region of the negative electrode plate 3. Thus, a battery of Example 3 was obtained.
[0055]
Example 4
The positive electrode adhesive tape 12 used in the positive electrode plate 1 of Example 3 was used. The dimensions were 8.0 mm in width and 34.0 mm in length, the positive electrode lead 2 was covered, and the width in contact with the positive electrode active material layer was 1. A battery was produced in the same manner as in Example 3 except that the thickness was 0 mm, so that a battery of Example 4 was obtained.
[0056]
(Example 5)
A negative electrode adhesive tape 14 having a base material made of polypropylene resin and a thickness of 30 μm, an adhesive made of an acrylic resin mainly composed of butyl acrylate, a thickness of 30 μm, and a pigment made of disazo yellow, having a width of 8. Example 4 is the same as Example 4 except that the negative electrode plate 3 was used which was 0 mm in length and 34.0 mm in length, covered with the negative electrode lead 4 and pasted so that the width in contact with the negative electrode active material layer was 2.0 mm. In the same manner, a battery was produced in the same manner as in Example 1, except that a group of electrode plates was prepared and the winding end portion of this group was group-fixed with the positive electrode adhesive tape 12 used in the positive electrode plate 1. 5 batteries were obtained.
[0057]
(Example 6)
A battery was produced in the same manner as in Example 2 except that the negative electrode adhesive tape 14 used in the negative electrode plate 3 of Example 5 was used.
[0058]
(Example 7)
A negative electrode used in the negative electrode plate 3 of Example 5 using a positive electrode adhesive tape 15 having a thickness of 30 μm as a base material made of PFA, an adhesive made of isobutyl rubber, a thickness of 30 μm, and a pigment made of phthalocyanine blue. A battery was prepared in the same manner as in Example 5 except that the adhesive tape 14 was used, and the battery of Example 7 was obtained.
[0059]
(Comparative Example 1)
A battery was fabricated in the same manner as in Example 1, except that the positive electrode adhesive tape 12 was used which was made of polyimide resin and had a thickness of 30 μm, the adhesive was made of silicon resin and had a thickness of 30 μm, and the pigment was made of phthalocyanine blue. Thus, a battery of Comparative Example 1 was obtained.
[0060]
(Comparative Example 2)
Example 1 except that the substrate was made of polypropylene resin and had a thickness of 30 μm, the pressure-sensitive adhesive was made of an acrylic resin mainly composed of butyl acrylate, the thickness was 30 μm, and the positive electrode pressure-sensitive adhesive tape 12 was made of phthalocyanine blue. A battery was produced in the same manner as described above to obtain a battery of Comparative Example 2.
[0061]
(Comparative Example 3)
A battery was produced in the same manner as in Example 1 except that disazo yellow was used as the pigment of the positive electrode adhesive tape 12 to obtain a battery of Comparative Example 3.
[0062]
(Comparative Example 4)
A battery was produced in the same manner as in Example 1 except that the positive electrode adhesive tape 12 made of silicon resin and having a thickness of 30 μm was used.
[0063]
For the batteries of Examples 1 to 7 and Comparative Examples 1 to 4 thus produced, 20 samples were prepared and subjected to a charge / discharge cycle test and a high temperature storage test.
[0064]
In the charge / discharge cycle test, charging was performed at 4.2 V for 2 hours with constant current-constant voltage charging. Until the battery voltage reaches 4.2V, the battery is charged with a constant current of 800mA (1CmA). After that, the battery is charged until the current value decreases to 40mA (0.05CmA), and then the constant current of 800mA is 3.0V. Table 1 shows the results of the average values obtained for the capacity retention rate of the 500th cycle when the charge / discharge cycle for discharging to the final discharge voltage is repeated 500 cycles in an environment of 20 ° C. and the third cycle is taken as 100%. Show.
[0065]
The high-temperature storage characteristic is that after repeating this charge / discharge cycle for 3 cycles, the battery is charged under the above charging conditions, left in an environment of 80 ° C. for 168 hours, then cooled to 20 ° C. Repeated. Table 1 shows the results of average values obtained by determining the capacity ratio before and after storage at 60 ° C as the capacity recovery rate after storage at high temperature.
[0066]
[Table 1]

[0067]
  As is clear from Table 1, a base material made of a fluorine-based resin, and an adhesive comprising at least one selected from natural rubber, isobutyl rubber, and styrene butadiene rubberAnd a pigment composed of one kind selected from organic materials containing phthalocyanine, titanium and aluminum metal powders and oxidesBy covering the positive electrode lead with the adhesive tape composed of, it is possible to suppress the formation of a metal reductant due to the reaction with the positive electrode active material, and even with charge / discharge cycles and high temperature storage, It was found that a lithium secondary battery that does not cause voltage failure or battery capacity reduction can be obtained.
[0068]
  Cover the positive lead so that the adhesive tape does not come into contact with the active material layer of the positive plate.YouAs a result, it was found that a lithium secondary battery excellent in charge / discharge cycle and high-temperature storage characteristics can be obtained..
[0069]
【The invention's effect】
As described above, by covering the positive electrode lead so that the pressure-sensitive adhesive tape according to the present invention does not come into contact with the active material layer of the positive electrode plate, the formation of a metal reductant due to the reaction with the positive electrode active material can be suppressed. A lithium secondary battery that does not cause a voltage failure or a reduction in battery capacity due to a short-circuit even if it is discharged or stored at a high temperature can be obtained.
[Brief description of the drawings]
1A is a plan view of a positive electrode plate, and FIG. 1B is a plan view of a negative electrode plate according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a battery according to an embodiment of the present invention.
3A is a plan view of a positive electrode plate, and FIG. 3B is a plan view of a negative electrode plate according to another embodiment of the present invention.
4A is a plan view of a positive electrode plate, and FIG. 4B is a plan view of a negative electrode plate according to a conventional example.
[Explanation of symbols]
1 Positive electrode plate
2 Positive lead
3 Negative electrode plate
4 Negative lead
5 Separator
6 Upper insulation plate
7 Lower insulation plate
8 Battery case
9 Gasket
10 Sealing plate
11 Positive active material plain part
12 Positive electrode adhesive tape
13 Negative electrode active material plain part
14 Negative electrode adhesive tape

Claims (4)

In a battery in which an electrode plate group in which a positive electrode plate and a negative electrode plate are spirally wound via a separator is housed in a case, the positive electrode lead of the positive electrode plate is covered with an adhesive tape. Selected from a base material made of a fluorine-based resin, an adhesive composed of at least one selected from natural rubber, isobutyl rubber and styrene butadiene rubber , an organic substance containing phthalocyanine, titanium and aluminum metal powders and oxides A lithium secondary battery comprising a kind of pigment . The lithium secondary battery according to claim 1, wherein the adhesive tape covers the positive electrode lead so as not to contact the active material layer of the positive electrode plate. Wherein the pigment is a metal powder or oxides of titanium and aluminum, a lithium secondary battery according to claim 1 or claim 2, characterized in that the average particle diameter of 0.5 m to 5 m. The lithium secondary battery, wherein the negative electrode lead of the negative electrode plate and / or the winding end portion of the electrode plate group is covered with the adhesive tape according to any one of claims 1 to 3.

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