JP2006302509A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent winding displacement in formation of an electrode group for improving yield of a battery and providing a battery with improved reliability even when an insulation tape is stuck to a welding position in a positive/negative electrode current collection tab. <P>SOLUTION: In a spiral electrode group mounted inside an armor casing, a positive electrode plate 10, in which an active material 12 is applied to both faces of long metal foil 11, and a negative electrode plate 20, in which an active material 22 is applied to both faces of long metal foil 21, are wounded up face to face via a separator 40. An uncoated part 13, on which the active material 12 is not applied, is formed in the longitudinal intermediate part in the positive electrode plate 10, and the current collection tab 14 is connected to the uncoated part 13, while an insulting tape 15 is stuck to cover the uncoated part 13 and the current collection tab 14. A ratio of the surface roughness Ra1 of the insulation tape 15 to the surface roughness Ra2 of the positive electrode plate 10 ranges from 0.5 to 1.5 (0.5Ra2≤Ra1≤1.5Ra2). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is provided with a spiral electrode plate group, in which a positive electrode plate and a negative electrode plate coated with an active material on both sides of a long metal foil are wound so as to face each other via a separator, in an outer can. Battery.

In general, a non-aqueous electrolyte secondary battery such as a lithium ion battery is manufactured as follows. That is, a positive electrode active material made of LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O _4, etc. is mixed with a carbon-based conductive agent and an organic solvent to produce a slurry or paste, which is made of a long foil made of aluminum foil or the like. A strip-like positive electrode plate is prepared by applying to a metal foil. On the other hand, a negative electrode active material made of natural graphite and a binder are dissolved in an organic solvent to prepare a slurry or paste, which is applied to a long metal foil made of copper foil or the like to produce a strip-shaped negative electrode plate. To do.

  These belt-like positive electrode plate and belt-like negative electrode plate are overlapped with a separator made of a polyethylene microporous film in between, wound by a winder, and then taped to the outermost periphery to form a spiral electrode plate group. . Then, after inserting this into the outer can, the negative electrode lead (negative electrode current collecting tab) connected to the strip-shaped negative electrode plate and the bottom of the outer can can be connected, and the positive electrode lead (positive electrode collector) connected to the strip-shaped positive electrode plate. Electrical tab) and the positive terminal. Next, after injecting a non-aqueous electrolyte in which an electrolyte salt is added to an organic solvent (for example, a mixed solvent composed of EC and DEC) into the outer can, the lithium ion battery is manufactured by sealing the opening of the outer can in an airtight manner. Is done.

By the way, in the spiral electrode group described above, for example, as shown in Patent Document 1, a boundary portion between a positive electrode active material or a negative electrode active material applied region and an uncoated region, a positive electrode lead (positive electrode current collecting tab) or The occurrence rate of short circuit increases at the part where the applied pressure increases locally when wound in a spiral shape, such as the welding position of the negative electrode lead (negative electrode current collecting tab). An insulating tape is attached to prevent a short circuit due to contact with the counter electrode at the site.
JP 2002-42881 A

  However, as shown in Patent Document 1 described above, when an electrode plate having an insulating tape attached to a welding position of a positive electrode lead (positive electrode current collecting tab) or a negative electrode lead (negative electrode current collecting tab) is used, the electrode plate has a spiral shape. When winding, there arises a problem that winding deviation occurs at the boundary of the insulating tape. This is because unevenness is formed in the positive electrode lead (positive electrode current collecting tab) part or negative electrode lead (negative electrode current collecting tab) part, and twisting occurs in this part during winding. It is thought that. In addition, it is considered that slippage occurred in the separator on the insulating tape portion due to the friction coefficient being different between the surface of the insulating tape portion and the surface of the electrode plate, and the winding deviation occurred. Here, when a winding deviation occurs in the electrode plate group, the positive and negative electrode plates come into contact with each other, causing an internal short circuit problem. In addition, when the winding deviation occurs in the electrode plate group, there arises a problem that the electrode plate group cannot be inserted into a predetermined position in the outer can.

  Therefore, the present invention has been made in view of the above problems, and even if an insulating tape is attached to the welding position of the positive electrode lead (positive electrode current collecting tab) or the negative electrode lead (negative electrode current collecting tab), An object of the present invention is to provide a battery in which winding deviation is less likely to occur during formation of the electrode plate group, the yield of the battery is improved, and the reliability is improved.

  In order to achieve the above object, the battery of the present invention has a spiral shape in which a positive electrode plate coated with an active material on both sides of a long metal foil and a negative electrode plate are wound so as to face each other through a separator. The electrode plate group is provided in the outer can. One electrode plate of the positive electrode plate and the negative electrode plate has an uncoated portion to which an active material is not applied formed in an intermediate portion in the longitudinal direction, and a current collecting tab is connected to the uncoated portion. Insulating tape is stuck so as to cover the coating portion and the current collecting tab, and the surface roughness Ra1 of the insulating tape is 0. 0 relative to the surface roughness Ra2 of the electrode plate to which the insulating tape is stuck. 5 or more and 1.5 or less (0.5Ra2 ≦ Ra1 ≦ 1.5Ra2).

  As described above, when the surface roughness Ra1 of the insulating tape is 0.5 to 1.5 with respect to the surface roughness Ra2 of the electrode plate to which the insulating tape is attached, the insulating tape By approximating the coefficient of friction between the surface of the part and the surface of the electrode plate, slippage of the separator on the insulating tape part is suppressed, and occurrence of winding deviation can be prevented.

  In this case, the electrode plate in which the uncoated portion where the active material is not applied is formed in the middle portion in the longitudinal direction is the positive electrode plate, and the negative electrode plate is one end portion in the longitudinal direction which becomes the winding end portion when wound. It is desirable that an uncoated portion where the active material is not coated is formed and a current collecting tab is connected to the uncoated portion, because the current collecting tabs can be prevented from overlapping each other. The insulating tape is preferably made of polypropylene, polyphenylene sulfide, or polyimide, and has been surface processed by, for example, a gravure roll so that the surface roughness is Ra1.

  Hereinafter, a preferred embodiment when the present invention is applied to a lithium ion battery will be described with reference to FIGS. 1 to 2, but the present invention is not limited to this embodiment at all. It is possible to carry out by appropriately changing without changing the purpose. FIG. 1 is a diagram schematically showing a laminate in which a positive electrode plate and a negative electrode plate used in a lithium ion battery are overlapped, FIG. 1 (a) is a top view thereof, and FIG. FIG. 2 is an enlarged cross-sectional view schematically showing an enlarged AA cross section of the positive electrode plate in FIG. 1A and a state in which a separator and a negative electrode plate are arranged on the upper and lower sides. FIG. 2 is a cross-sectional view schematically showing a state in which a spiral electrode plate group produced by winding the laminate shown in FIG. 1 in a spiral shape is housed in an outer can and configured in a battery. .

1. Positive Electrode Plate A positive electrode mixture was prepared by mixing LiCoO ₂ powder having an average particle diameter of 5 μm as a positive electrode active material and artificial graphite powder as a positive electrode conductive material at a mass ratio of 9: 1. The obtained positive electrode mixture and a binder solution obtained by dissolving 5% by mass of a binder composed of polyvinylidene fluoride (PVdF) in an organic solvent composed of N-methyl-2-pyrrolidone (NMP) A positive electrode mixture slurry was prepared by mixing and kneading so that the ratio was 95: 5. Next, an aluminum foil (foil thickness: 15 μm) as a positive electrode current collector 11 was prepared, and a positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 11 made of this aluminum foil using a doctor blade or the like.

Next, after passing through the dryer to dry the positive electrode mixture slurry, the positive electrode active material layer 12 was formed on both surfaces of the positive electrode current collector 11 by rolling with a roll press. In this case, the positive electrode mixture slurry is applied so that the mass after drying of the positive electrode active material layer 12 is 480 g / m ^2, and the packing density of the positive electrode active material layer 12 after drying becomes 3.7 g / cm ³ . In addition, the uncoated portion 13 having a width of 15 mm in the width direction was formed in the intermediate portion of the positive electrode plate 10. Then, after cutting so that it might become a predetermined dimension (width: 55 mm, length: 600 mm), it was made to vacuum-dry at 150 degrees for 2 hours, and the positive electrode plate 10 was produced.

  Next, a positive electrode current collecting tab 14 made of a metal plate having a thickness of 0.1 mm (for example, made of aluminum and having a width of 5 mm and a length of 50 mm) is formed on the uncoated portion 13 formed in the intermediate portion of the positive electrode plate 10. Welded. Then, an insulating tape (for example, made of polypropylene, made of polyphenylene sulfide, made of polyimide, width: 20 mm, length: 57 mm, thickness 30 μm) 15 is bonded on the uncoated portion 13 and the positive electrode current collecting tab 14 with an adhesive ( For example, it was attached with a rubber-based adhesive, an acrylic-based adhesive, or the like. In this case, the insulating tape 15 used was a tape having a thickness of 30 μm made of polypropylene as a base material, and was prepared to have a predetermined surface roughness (Ra1) using a gravure roll at the time of base material preparation. .

  Here, the positive electrode plate 10 to which the insulating tape 15 prepared so that the surface roughness (Ra1) was 3 μm was attached was used as the positive electrode plate a. Similarly, an insulating tape 15 having a surface roughness (Ra1) of 5 μm attached thereto is used as a positive electrode plate b, and an insulating tape 15 having a surface roughness (Ra1) of 10 μm is prepared. Is the positive electrode plate c, and the one with the insulating tape 15 prepared so that the surface roughness (Ra1) is 15 μm is the positive electrode plate d, and the surface roughness (Ra1) is 18 μm. Thus, the thing which stuck the insulating tape 15 prepared in this way was made into the positive electrode plate e.

2. Negative electrode plate On the other hand, a dispersion (solid) of a negative electrode active material composed of flaky natural graphite (d ₀₀₂ : 3.356 mm, Lc: 1000 mm, average particle size: 20 μm) and a styrene-butadiene rubber (SBR) Min: 48% by mass) was dispersed in water. Next, a thickening agent, carboxymethyl cellulose (CMC), was added thereto to prepare a negative electrode mixture slurry. In this case, the solid mass composition ratio after drying was adjusted to be graphite: SBR: CMC = 100: 3: 2. Next, a copper foil (foil thickness: 10 μm) was prepared as the negative electrode current collector 21, and the negative electrode mixture slurry was uniformly applied to both surfaces of the negative electrode current collector 21 made of this copper foil using a doctor blade or the like.

Next, the negative electrode mixture slurry was dried by passing through a dryer, and then rolled with a roll press to form negative electrode active material layers 22 on both surfaces of the negative electrode current collector 21. In this case, the negative electrode mixture slurry is applied so that the mass of the negative electrode active material layer 22 after drying is 200 g / m ^2, and the filling density of the negative electrode active material layer 22 after drying is 1.7 g / cm ³ . In addition, the uncoated portion 23 having a width of 15 mm was formed at the end. Then, after cutting so that it might become a predetermined dimension (width: 57mm, length: 650mm), it was made to vacuum-dry at 110 degrees for 2 hours, and the negative electrode plate 20 was produced. A metal plate (for example, made of nickel, having a width of 5 mm and a length of 0.1 mm) is applied to the unapplied portion 23 at the end (the portion that will be the end of the winding when it is wound later in a spiral). : 50 mm) negative electrode current collecting tab 24 was welded.

3. Lithium ion battery Next, a separator made of a microporous film made of polypropylene between the positive electrode plate 10 (a, b, c, d, e) and the negative electrode plate 20 produced as described above. Laminated 30 as shown in FIGS. 1 (a) and 1 (b). Thereafter, this was wound in a spiral shape by a winder to produce a spiral electrode plate group. Next, after the insulating plates 15 and 25 are respectively disposed above and below the spiral electrode plate group, these spiral electrode plate groups are respectively inserted into a bottomed cylindrical cylindrical outer can 40 also serving as a negative electrode terminal made of stainless steel. did. Next, a negative electrode current collecting tab 24 extending from the negative electrode plate 20 of the spiral electrode plate group was welded to the inner bottom surface of the outer can 40. On the other hand, the positive electrode current collecting tab 14 extending from the positive electrode plate 10 of the spiral electrode plate group was welded to the lower surface of the lid body 42 b of the sealing body 42.

Thereafter, the annular groove 41 was formed by grooving the upper outer peripheral surface of the outer can 40. Thereafter, an electrolytic solution obtained by adding 1 M LiPF ₆ as an electrolyte salt to an equal volume mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was injected into the metal outer can 40. Next, the sealing gasket 43 attached to the outer periphery of the sealing body 42 is placed on the annular groove 41 of the outer can 40, and the distal end portion of the outer can 40 is crimped to the sealing body 42 side to seal it. Lithium ion batteries A, B, C, D, and E having a size and a capacity of 1800 mAh were produced. Here, a battery using the positive electrode plate a is referred to as a battery A, a battery using the positive electrode plate b is referred to as a battery B, a battery using the positive electrode plate c is referred to as a battery C, and a battery using the positive electrode plate d is referred to as a battery D. A battery E was prepared using the positive electrode plate e.

  Note that the sealing body 42 includes a positive electrode cap 42 a serving as a positive electrode terminal and a lid body 42 b that seals the opening of the outer can 40. In the sealing body 42 composed of the positive electrode cap 42a and the lid body 42b, a conductive elastic deformation plate 42c that deforms when the gas pressure inside the battery rises and reaches a predetermined set pressure, and resistance when the temperature rises. A PTC (Positive Temperature Coefficient) element 42d whose value increases is provided. Thereby, when an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC element 42d increases its resistance value and decreases the overcurrent. Then, when the gas pressure inside the battery rises and exceeds a predetermined set pressure, the conductive elastic deformation plate 42c is deformed, and the contact between the conductive elastic deformation plate 42c and the lid 42b is cut off, and an overcurrent or short circuit occurs. The current is interrupted.

4). Measurement (1) Measurement of surface roughness (μm) Next, when manufacturing lithium ion batteries A, B, C, D, E as described above, surface roughness Ra2 (μm) of positive electrode plates a to e used. ) Measured using a semiconductor laser microscope, it was 10 μm (Ra2 = 10 μm: arithmetic average value). In addition, it was 3 micrometers when the surface roughness (Ra1) of the insulating tape 15 stuck on the positive electrode plate a was measured similarly. Further, the surface roughness (Ra1) of the insulating tape 15 attached to the positive electrode plate b is 5 μm, and the surface roughness (Ra1) of the insulating tape 15 attached to the positive electrode plate c is 10 μm. The surface roughness (Ra1) of the adhered insulating tape 15 was 15 μm, and the surface roughness (Ra1) of the insulating tape 15 adhered to the positive electrode plate e was 18 μm.

(2) Measurement of winding deviation Further, when the lithium ion batteries A, B, C, D, and E are produced as described above, a spiral electrode plate group is formed by winding in a spiral shape, and then transmitted X-rays Was used to measure the relative positions of the positive electrode plate 10 and the negative electrode plate 20. Then, when it was determined that the spiral electrode plate group in which the positive electrode plate 10 protruded upward or downward from the width of the negative electrode plate 20 was unwinding, the results shown in Table 1 below were obtained.

  As is clear from the results in Table 1 above, in the battery A using the positive electrode plate a to which the insulating tape 15 having the surface roughness Ra1 of 3 μm (Ra1 = 0.3Ra2) is attached, the occurrence rate of winding deviation is high. It turns out that it is as large as 13%. In addition, it can be seen that also in the battery E using the positive electrode plate e to which the insulating tape 15 having a surface roughness Ra1 of 18 μm (Ra1 = 1.8Ra2) is attached, the occurrence rate of winding deviation is as large as 10%.

  On the other hand, the battery B using the positive electrode plate b on which the insulating tape 15 having a surface roughness Ra1 of 5 μm (Ra1 = 0.5Ra2) was attached, and the surface roughness Ra1 of 15 μm (Ra1 = 1.5Ra2) It can be seen that in the battery D using the positive electrode plate d to which the insulating tape 15 is attached, the rate of occurrence of winding deviation is 5%, which is less than half of the batteries A and E. Furthermore, it was found that no winding deviation occurred in the battery C using the positive electrode plate c to which the insulating tape 15 having a surface roughness Ra1 of 10 μm (Ra1 = Ra2) was attached.

  In the batteries B to D, the insulating tape 15 used for the positive plates b to d has a surface roughness Ra1 of 5 μm to 15 μm, and ± 50% with respect to 10 μm of the surface roughness Ra2 of the positive plate 10. (0.5Ra2 ≦ Ra1 ≦ 1.5Ra2). For this reason, when the coefficient of friction between the surface of the insulating tape 15 part and the surface of the electrode plate 10 approximates, the slip of the separator 30 on the insulating tape part 15 is suppressed, and the occurrence of winding deviation is suppressed. It is thought that it was done.

  On the other hand, in the battery A, the insulating tape 15 used for the positive electrode plate a has a surface roughness Ra1 of 3 μm and is −70% (0.3Ra2 = Ra1) with respect to 10 μm of the surface roughness Ra2 of the positive electrode plate 10. It has become. For this reason, it is considered that the difference in the friction coefficient between the surface of the insulating tape 15 part and the surface of the electrode plate 10 increases, causing the separator 30 on the insulating tape part 15 to slip and causing the winding deviation.

  In the battery E, the insulating tape 15 used for the positive electrode plate e has a surface roughness Ra1 of 18 μm, which is + 80% (1.8Ra2 = Ra1) with respect to 10 μm of the surface roughness Ra2 of the positive electrode plate 10. It has become. For this reason, it is considered that the difference in the friction coefficient between the surface of the insulating tape 15 part and the surface of the electrode plate 10 increases, causing the separator 30 on the insulating tape part 15 to slip and causing the winding deviation.

  From the above, the surface roughness Ra1 of the insulating tape 15 is 0.5 or more and 1.5 or less (0.5Ra2 ≦ Ra1 ≦) with respect to the surface roughness Ra2 of the positive electrode plate 10 to which the insulating tape 15 is adhered. It can be said that 1.5Ra2) is preferable. As described above, when the surface roughness Ra1 of the insulating tape 15 is regulated, the friction coefficient between the surface of the insulating tape 15 part and the surface of the positive electrode plate 10 is approximated, thereby suppressing the slip of the separator 30 on the insulating tape 15 part. As a result, the occurrence of winding deviation can be prevented.

  In the above-described embodiment, an example in which natural graphite is used as a negative electrode active material of a nonaqueous electrolyte battery has been described. However, in addition to natural graphite, carbon-based materials that can occlude / desorb lithium ions, such as graphite and carbon, are used. Black, coke, glassy carbon, carbon fiber, or a fired body thereof is preferable. Further, an oxide or silicon that can occlude and desorb lithium ions such as tin oxide and titanium oxide, or a compound thereof may be used.

Further, in the above-described embodiment, an example in which LiCoO ₂ is used as the positive electrode active material of the nonaqueous electrolyte battery has been described. However, in addition to LiCoO ₂ , a lithium-containing transition metal compound that can accept lithium ions as a guest, for example, LiNiO ₂ LiCo _X Ni _(1-X) O ₂ , LiNi _X Mn _(1-X) O ₂ , LiCrO ₂ , LiVO ₂ , αLiFeO ₂ , LiTiO ₂ , LiScO ₂ , LiYO ₂ , LiMn ₂ O _{4 and the} like are preferable, In particular, it is preferable to use LiNiO ₂ , LiCo _X Ni _(1-X) O ₂ , LiNi _X Mn _(1-X) O ₂ alone, or a mixture of two or more of these. Further, a conductive polymer such as polyacetylene or polyaniline may be used.

The electrolyte is an ionic conductor in which a lithium salt is dissolved as a solute in an organic solvent, has high ionic conductivity, and is chemically and electrochemically stable for both positive and negative electrodes. If the possible temperature range is wide, the safety is high, and the cost is low, it can be used. For example, as the organic solvent, in addition to the mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC), propylene carbonate (PC), sulfolane (SL), tetrahydrofuran (THF), γ-butyrolactone (GBL), dimethyl Carbonate (DMC), ethyl methyl carbonate (EMC), 1,2 dimethoxyethane (DME) and the like, or a mixed solvent thereof is preferable. Further, a lithium salt having a strong electron-withdrawing property is used as a solute. In addition to LiPF ₆ , for example, LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO _{3 and the} like are preferable.

  Furthermore, in the above-described embodiment, an example in which the present invention is applied to a cylindrical battery has been described. However, the present invention is not limited to a cylindrical shape, and a spiral electrode plate group and a flat electrode plate group that is crushed and flattened are used. If it is a battery, it is possible to apply to the battery of other shapes, such as a square. Further, in the above-described embodiment, an example in which the present invention is applied to a lithium ion battery has been described. However, in addition to a lithium ion battery, the present invention is also applied to various batteries such as a nickel-cadmium storage battery and a nickel-hydrogen storage battery. Is possible.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the laminated body which piled up the positive electrode plate and negative electrode plate which are used for the lithium ion battery of this invention, Fig.1 (a) is the top view, FIG.1 (b) is FIG. It is an expanded sectional view which expands and shows typically the state which has arrange | positioned the separator and the negative electrode plate to the upper and lower sides while expanding and showing typically the AA cross section of the positive electrode plate of (a). FIG. 2 is a cross-sectional view schematically showing a state in which a spiral electrode plate group produced by winding the laminate shown in FIG. 1 in a spiral shape is housed in an outer can and configured in a battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Positive electrode plate, 11 ... Positive electrode collector, 12 ... Positive electrode active material layer, 13 ... Uncoated part, 14 ... Positive electrode current collection tab, 15 ... Insulation tape, 20 ... Negative electrode plate, 21 ... Negative electrode current collector, 22 DESCRIPTION OF SYMBOLS ... Negative electrode active material layer, 23 ... Uncoated part, 24 ... Negative electrode current collection tab, 30 ... Separator, 40 ... Exterior can, 41 ... Annular groove part, 42 ... Sealing body, 42a ... Positive electrode cap, 42b ... Lid body, 42c ... Conductive elastic deformation plate, 42d ... PTC element, 43 ... sealing gasket

Claims (3)

A battery having a spiral electrode plate group in which a positive electrode plate and a negative electrode plate coated with an active material on both sides of a long metal foil are wound so that they face each other through a separator. And
One electrode plate of the positive electrode plate and the negative electrode plate has an uncoated portion with no active material applied at an intermediate portion in the longitudinal direction, a current collecting tab is connected to the uncoated portion, and the uncoated portion Insulating tape is attached so as to cover the application part and the current collecting tab,
The surface roughness Ra1 of the insulating tape is 0.5 or more and 1.5 or less (0.5Ra2 ≦ Ra1 ≦ 1.5Ra2) with respect to the surface roughness Ra2 of the electrode plate to which the insulating tape is attached. A battery characterized by.   An electrode plate in which an uncoated portion with no active material is formed in an intermediate portion in the longitudinal direction is a positive electrode plate, and the negative electrode plate is at one end portion in the longitudinal direction which becomes a winding end portion when wound. The battery according to claim 1, wherein an uncoated portion with no active material is formed, and a current collecting tab is connected to the uncoated portion. 3. The battery according to claim 1, wherein the insulating tape is made of propylene, polyphenylene sulfide, or polyimide, and is surface-treated so that the surface roughness is Ra1. .

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