JP2006147392A - battery - Google Patents

Abstract

A positive electrode plate coated with a positive electrode mixture containing a positive electrode active material on a positive electrode current collector and a negative electrode plate coated with a negative electrode mixture containing a negative electrode active material on a negative electrode current collector are wound through a separator. In the battery in which the electrode plate group formed in the case is stored in the case, the electrode plate group can be smoothly inserted into the limited battery case, the damage to the separator is eliminated, no internal leak occurs, and Provide a battery with sufficient capacity.
An insulating tape is attached to a coating end of a positive electrode mixture in which the thickness of the positive electrode mixture is decreased and the thickness b of the positive electrode plate in that portion is coated with another positive electrode mixture. The thickness of the worn part is not more than a.
[Selection] Figure 2

Description

  The present invention relates to insulation of a battery, particularly a positive electrode plate mixture terminal portion of the battery.

  In recent years, with the widespread use of portable and cordless devices such as mobile phones and notebook computers, the demand for batteries as power sources is increasing. In particular, there is a demand for the development of a secondary battery that is small, lightweight, has high energy density, and can be repeatedly charged and discharged. As such batteries, non-aqueous electrolyte secondary batteries, particularly lithium ion secondary batteries using lithium-containing composite oxides such as lithium cobaltate for the positive electrode and carbon materials etc. for the negative electrode, are actively researched and developed. ing.

  A battery using this type of non-aqueous electrolyte has a lower ionic conductivity than an aqueous battery. For this reason, in order to improve current characteristics, it is common to increase the electrode surface area of the positive electrode plate and the negative electrode plate to constitute the electrode plate group. There is a proposal to provide a portion where the current collector is exposed at an uncoated portion, and to ensure safety due to external pressure (see, for example, Patent Document 1). Furthermore, there is a proposal to form an insulating layer in a portion facing the negative electrode mixture coated portion in the positive electrode mixture uncoated portion (see, for example, Patent Document 2).

However, when the insulating layer according to Patent Document 2 is formed after the mixture is applied, the edge of the mixture terminal portion can be covered, but the thickness of this portion is increased, and a convex portion is formed on the outer diameter of the electrode plate group. When it is inserted into the battery case, there is a problem that the separator is rubbed in the battery case to be damaged and torn, or the mixture falls off and causes internal leakage.
Japanese Patent Laid-Open No. 9-180761 JP 2004-259625 A

  Therefore, the present invention solves the above-mentioned conventional problems, can smoothly insert the electrode plate group into a limited battery case, eliminates damage to the separator, does not cause internal leakage, and has a sufficient capacity. It is an object to provide a battery having

  In order to achieve this object, the battery of the present invention has a positive electrode plate coated with a positive electrode mixture containing a positive electrode active material on a positive electrode current collector and a negative electrode mixture containing a negative electrode active material applied onto a negative electrode current collector. In a battery in which a group of electrode plates formed by winding a negative electrode plate through a separator is housed in a case, insulation is provided at the coating end of the positive electrode mixture in which the thickness of the positive electrode mixture decreases in an inclined manner The tape is stuck, The thickness of the positive electrode plate of the part is below the thickness of the part by which the other positive electrode plate mixture is applied, It is characterized by the above-mentioned.

  Insulating the insulating tape by attaching the insulating tape from the portion where there is no edge at the coating end of the positive electrode mixture and the thickness is inclined to decrease to the portion where the current collector is exposed without the mixture Even if a tape is applied, the thickness of the part where the other positive electrode mixture is applied is less than the thickness, so even if it is inserted into the battery case, the separator will be rubbed in the battery case and damaged or broken. A battery without internal leakage can be obtained without the agent falling off.

  As is clear from the above description, according to the present invention, the insulating tape has a current collector without a mixture from the portion where the coating end portion of the positive electrode mixture has no edge portion and the thickness is inclined and decreased. Even if it is inserted into the battery case because of the thickness of the part where the other positive electrode mixture is applied, even if the insulating tape is applied, the separator will remain in the battery. A battery without internal leakage can be obtained without being damaged by being rubbed in the case and being torn or the mixture being dropped.

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

  FIG. 1 is a cross-sectional view of a cylindrical lithium secondary battery of the present invention. As shown in FIG. 1, an electrode plate group in which a positive electrode plate 11 and a negative electrode plate 13 are spirally wound via a separator 15 is accommodated in a bottomed cylindrical battery case 18. The negative electrode lead 14 connected to the case 18 is electrically connected to the case 18 via the lower insulating ring 17, and the positive electrode lead 12 connected to the positive electrode plate 11 is connected to the internal terminal of the sealing plate 20 via the upper insulating ring 16. Electrically connected, a non-aqueous electrolyte (not shown) is injected, and the sealing plate 20 and the battery case 18 are caulked and sealed via an insulating gasket 19.

  This positive electrode plate 11 is made by kneading and dispersing a positive electrode active material and a binder, and if necessary, a conductive agent in a dispersion medium on one or both sides of a current collector made of an aluminum foil, a lathed or etched foil. The paste is intermittently applied, dried, and then rolled to produce the positive electrode plate 11.

  Examples of the binder include a fluororesin material that maintains adhesion between active materials, a polymer material having a polyalkylene oxide skeleton, and a styrene-butadiene copolymer. As the fluorine resin material, polyvinylidene fluoride (PVDF), copolymer P (VDF-HFP) of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) is preferable.

  As the conductive agent added as necessary, carbon-based conductive materials such as acetylene black, graphite, and carbon fiber are preferable.

  As the dispersion medium, a dispersion medium in which the binder can be dissolved is suitable. In the case of the organic binder, an organic solvent such as acetone, cyclohexanone, N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), or the like is used. Single or a mixed dispersion medium in which these are mixed is preferable. In the case of an aqueous binder, water is preferable.

  The apparatus for kneading and dispersing is not particularly limited. For example, a double-arm kneader, a planetary mixer, a homomixer, a pin mixer, a kneader, a homogenizer, and the like can be used. You may use it in combination of 2 or more types.

  In addition, the coating is not particularly limited, and the paste kneaded and dispersed as described above, for example, slit die coater, reverse roll coater, lip coater, blade coater, knife coater, gravure coater, Can be applied easily using a dip coater, etc. By adjusting the speed at which the application nozzle is closed, there is no edge at the application end of the positive electrode mixture, and the thickness decreases with an inclination. The dimension of this part is preferably in the range of 3 mm to 15 mm from the viewpoint of securing the battery capacity without causing an edge at the coating terminal part.

  And by attaching the insulating tape from this part to the part where there is no mixture and the current collector is exposed, even if the insulating tape is applied, the other positive electrode mixture is applied. It can be made below the thickness.

  The negative electrode plate 6 is prepared by applying, drying, and rolling a paste obtained by kneading and dispersing a negative electrode active material and a binder, and if necessary, a conductive agent in a dispersion medium on one side or both sides of a current collector. Can do.

  The copper or copper alloy used as the negative electrode current collector is not particularly limited, and examples thereof include rolled foil, electrolytic foil, and the shape may be foil, perforated foil, expanded material, lath material, and the like. I do not care.

As the negative electrode active material, for example, a material containing graphite having a graphite-type crystal structure capable of inserting and extracting lithium ions, such as natural graphite and artificial graphite, is used. In particular, it is preferable to use a carbon material having a graphite-type crystal structure in which the lattice spacing ( ₀₀₂ ) has an interval (d ₀₀₂ ) of 0.3350 to 0.3400 nm.

  As the binder, the dispersion medium, and the conductive agent and plasticizer that can be added as necessary, the same materials as those for the positive electrode can be used.

  The separator is preferably a microporous polyolefin resin such as polyethylene resin or polypropylene resin.

  The non-aqueous electrolyte is composed of a non-aqueous solvent and an electrolyte. As the non-aqueous solvent, γ-butyrolactone (GBL), which is a cyclic carbonate, may be used alone, and as other components, cyclic carbonate and Two or more chain carbonates may be used in combination with γ-butyrolactone (GBL). The cyclic carbonate is preferably at least one selected from ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and the like, and the content of γ-butyrolactone (GBL) is The volume ratio is preferably 50% or more.

Examples of the electrolyte include lithium salts having a strong electron-withdrawing property, such as 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 or the like can be used alone or in combination of two or more. These electrolytes are preferably dissolved at a concentration of 0.5 M / L to 2.0 M / L in the non-aqueous solvent.

  The present invention will be described in detail using examples and comparative examples, but these do not limit the present invention in any way.

Example 1
The positive electrode plate 11 was produced as follows. First, 100 parts by mass of LiCoO ₂ powder as a positive electrode active material, 5 parts by mass of acetylene black as a conductive agent, and 7 parts by mass of an aqueous dispersion (solid content 50% by mass) of polytetrafluoroethylene (PTFE) as a binder. Then, 83 parts by mass of an aqueous solution of carboxymethyl cellulose (solid content: 1% by mass) as a thickener was blended, and a positive paste was prepared by kneading and dispersing for 120 minutes with a planetary mixer.

  Next, this positive electrode paste was applied to both surfaces using a slit die coater on a current collector 23 made of a strip-shaped aluminum foil having a thickness of 20 μm, and dried at 120 ° C. for 10 minutes. The mixture layer 22 was rolled twice at a linear pressure of 1000 kg / cm so as to have a thickness of 200 μm.

  As shown in FIG. 2, by adjusting the closing speed of the slit die coater coating nozzle, there is no edge portion at the coating end portion of the positive electrode mixture, and a portion where the thickness is inclined and decreased is produced. The insulating tape 21 was stuck from the central part of this part to the part where there was no mixture and the current collector was exposed. The thickness a of the positive electrode mixture 11 of the positive electrode plate 11 is 200 μm, the thickness b of the insulating tape 21 is 50 μm, the maximum thickness c of the portion to which the insulating tape 21 is attached is 200 μm, and the thickness of the positive electrode mixture is decreased. The dimension d of the part was 5.0 mm.

  One end side of the positive electrode lead 12 made of aluminum was spot-welded to the exposed portion of the current collector, and a positive electrode insulating tape was attached to the positive electrode lead 12.

  Moreover, the negative electrode plate 13 was produced as follows. First, 100 parts by mass of scaly graphite capable of occluding and releasing lithium as a negative electrode active material, 8 parts by mass of an aqueous dispersion (solid content 48%) of styrene butadiene rubber (SBR) as a binder, a thickener As an anode paste, 80 parts by mass of an aqueous solution of carboxymethyl cellulose (solid content 1% by mass) was added, water was added as a dispersion medium, and the mixture was kneaded and dispersed for 90 minutes with a planetary mixer.

  Next, this negative electrode paste was intermittently applied to one side using a slit die coater on a 14 μm thick strip-shaped copper foil, dried at 120 ° C. for 10 minutes, and then the back side was similarly applied and dried. After that, it was rolled three times at a linear pressure of 110 kg / cm so that the thickness became 180 μm.

  One end of a nickel negative electrode lead 14 was spot-welded to the exposed portion of the rolled negative electrode plate, and a negative electrode insulating tape was attached to the negative electrode lead 14.

  The positive electrode plate 11 and the negative electrode plate 13 thus manufactured are insulated through a separator 15 made of a microporous polyethylene resin having a thickness of 25 μm, and are adhered to the application terminal portion of the positive electrode mixture of the positive electrode plate 11. After fixing the winding terminal portion of the electrode plate group wound in a spiral shape so that the position of the insulating tape 21 is disposed in the negative electrode mixture layer region of the negative electrode plate 13 facing, FIG. The negative electrode connected to the negative plate 13 is connected to the sealing plate 20 at the other end of the positive electrode lead 12 connected to the positive electrode plate 11. The other end of the lead 14 was connected to the bottom of the battery case 18, and an upper insulating plate 16 and a lower insulating plate 17 were arranged above and below the electrode plate group.

Furthermore, after pouring a predetermined amount of an electrolytic solution in which 1.3 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte in a mixed solvent of ethylene carbonate and ethyl methyl carbonate, the polypropylene resin gasket 19 was passed through. The battery case 18 was sealed with the sealing plate 20 to produce a battery having a size of 18650 and a battery capacity of 2000 mAh.

(Example 2)
As shown in FIG. 2, the positive electrode mixture portion thickness a of the positive electrode plate 200 is 200 μm, the thickness b of the insulating tape 21 is 30 μm, the maximum thickness c of the portion where the insulating tape 21 is adhered is 180 μm, and the thickness of the positive electrode mixture is A battery of Example 2 was made in the same manner as Example 1 except that the dimension d of the portion that was inclined and decreased was 5.0 mm.

(Comparative Example 1)
As shown in FIG. 3, by adjusting the closing speed of the slit die coater coating nozzle, there is an edge at the coating end of the positive electrode mixture, there is almost no inclination of the thickness, and there is no mixture. The positive electrode plate 11 which becomes a part where the body is exposed was produced. The positive electrode mixture portion thickness a of the positive electrode plate 11 is 200 μm, there is no insulating tape 21, and the dimension d of the portion where there is almost no inclination of the thickness of the positive electrode mixture is 1.5 mm. Thus, a battery of Comparative Example 1 was produced.

(Comparative Example 2)
As shown in FIG. 4, the positive electrode mixture portion thickness a of the positive electrode plate 200 is 200 μm, the thickness b of the insulating tape 21 is 50 μm, the maximum thickness c of the portion to which the insulating tape 21 is attached is 230 μm, and the thickness of the positive electrode mixture is A battery of Comparative Example 2 was fabricated in the same manner as in Example 1 except that the dimension d of the portion that was inclined and decreased was 5.0 mm.

  Table 1 shows the results of inspection for the presence or absence of leakage failure using 1000 batteries of Examples 1 to 2 and Comparative Examples 1 to 2 produced as described above. Note that a voltage of 450 V was applied to the positive and negative leads, the resistance value was measured, a resistance value of 10 MΩ or less was determined to be a leak failure, and the failure rate was calculated.

  As is apparent from Table 1, no internal leakage occurred in the batteries of Examples 1 and 2, but in the batteries of Comparative Examples 1 and 2, the leakage failure rate due to internal leakage was 1.8% and 0%, respectively. .8% produced. In the case of the battery of Comparative Example 1, since the insulating tape is not attached to the positive electrode mixture application terminal portion, it is considered that leakage occurred due to the edge of the application terminal portion. Moreover, when the battery of Comparative Example 2 was disassembled, it was confirmed that the separator in the portion where the outer diameter of the electrode plate group swelled in a convex shape was torn or the mixture was dropped. This is because the electrode plate group of the battery of Comparative Example 2 is partially convex in outer diameter due to the influence of the mixture end tape portion, and is rubbed against the case when the electrode plate group is inserted into the battery case. It is presumed that the separator was torn or the mixture was dropped.

  According to the battery of the present invention, even if the separator is inserted into the battery case, the separator is not rubbed and damaged due to damage in the battery case, and the mixture does not fall off, thereby obtaining a battery having no internal leak. It is useful as a power source for portable devices such as mobile phones and notebook computers, and cordless devices.

The longitudinal cross-sectional view of the cylindrical battery in one Embodiment of this invention Sectional drawing of the positive electrode mixture terminal part of the embodiment Sectional view of the terminal portion of the positive electrode mixture of the conventional example Sectional drawing of the other positive electrode mixture terminal part of a prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Positive electrode plate 12 Positive electrode lead 13 Negative electrode plate 14 Negative electrode lead 15 Separator 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Insulating gasket 20 Sealing plate 21 Insulating tape 22 Positive electrode mixture layer 23 Current collector a Positive electrode mixture coating part The thickness of the positive electrode plate b The thickness of the insulating tape c The thickness of the positive electrode plate where the insulating tape is applied d The dimension of the portion where the thickness of the positive electrode mixture is decreasing

Claims (1)

A positive electrode plate coated with a positive electrode mixture containing a positive electrode active material on a positive electrode current collector and a negative electrode plate coated with a negative electrode mixture containing a negative electrode active material on a negative electrode current collector were wound through a separator. In a battery in which an electrode plate group is housed in a case, an insulating tape is attached to a terminal end of the positive electrode mixture in which the thickness of the positive electrode mixture decreases in an inclined manner. The thickness of the battery is equal to or less than the thickness of the portion where the other positive electrode plate mixture is applied.

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