JP2007165117A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery which prevents the damage of current collector leads involved in rewinding of an electrode group. <P>SOLUTION: The lithium ion secondary battery has a winding group 6 into which a cathode plate and an anode plate are wound on an axial core 11, and flanges 7 arranged on both sides of the winding group 6 and having a smaller diameter D<SB>2</SB>than the diameter D<SB>1</SB>of the winding group 6. To the circumferential surface of the flange 7, the current collector leads 9 led out from the cathode and anode plates are connected. When the gap is made h between the end surface of the winding group 6 and the end surface of the winding group 6 side of the flange part 7, the length from a lead-out position of the current collector lead 9 at the outermost circumference to the connection position is set at ≥(D<SB>1</SB>-D<SB>2</SB>)/2+h. The diameter D<SB>2</SB>of the flange 7, considering a deviation amount c is set at D<SB>2</SB>≤D<SB>1</SB>-c<SP>2</SP>/h between the lead-out position of the current collector lead 9 at the outermost circumference involved in rewinding of the winding group 6 in the horizontal direction when the axial core 11 is made vertical and the connection position, thereby securing the length of the current collector leads 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a secondary battery, and in particular, includes an electrode group in which strip-shaped positive and negative electrode plates are wound, and disk-shaped current collecting members respectively disposed on both sides of the electrode group, and each is derived from the positive and negative electrode plates. The present invention relates to a secondary battery in which tips of a large number of current collecting leads are joined to the outer periphery of a current collecting member.

  Non-aqueous electrolyte secondary batteries have high energy density and are used in various applications. In recent years, large nonaqueous electrolyte secondary batteries have also been developed, and are used, for example, as power sources for hybrid electric vehicles that use a motor and an internal combustion engine in combination as a power source. In such applications, high input / output characteristics are required for batteries, and lithium ion secondary batteries are attracting attention as batteries that meet these requirements.

  Usually, a lithium ion secondary battery has the following winding internal structure. That is, an electrode group (winding group) in which positive and negative electrode plates each coated with an active material on a metal foil are formed in a band shape, and the positive and negative electrode plates are wound in a cross-sectional spiral shape so as not to directly contact through a separator. Is formed. When the positive and negative electrode plates are wound, they are wound while applying tension to prevent twisting. And an electrode group is accommodated in a cylindrical battery container, and after pouring electrolyte solution, a battery container is sealed with a battery cover.

  In a lithium ion secondary battery that requires high input / output characteristics such as a power source for an electric vehicle, a large number of current collecting leads are led out from the positive and negative electrode plates in order to reduce internal resistance. In order to increase the output of the battery, for example, the current collecting lead can be directly collected by processing it into a strip shape by leaving an active material uncoated on a part of the metal foil that is a positive and negative electrode current collector. Electrical leads are formed. The leading ends of the current collecting leads led out from the positive and negative electrode plates are joined to the outer periphery of a disk-shaped current collecting member disposed on each side of the electrode group. Also, in order to securely join the current collecting lead and the current collecting member, for example, the strip-shaped current collecting lead is welded between the outer peripheral portion of the end surface of the disk-shaped current collecting member and the one surface side of the metal ring. The technique to do is also disclosed (refer patent document 1).

JP 2001-118561 A

  However, in a wound secondary battery, vibration and temperature change are applied during use of the battery, and the active material expands and contracts due to repeated charge and discharge. Due to the tension, an unstable rewound occurs on the outer periphery of the electrode group. When the electrode group is rolled back, the current collecting lead joined to the current collecting member is damaged (cut), causing an increase in internal resistance and a decrease in output. Further, the cut surface of the current collecting lead may press the separator, contact the opposing electrode and cause a short circuit between the positive and negative electrodes.

  In view of the above-described case, an object of the present invention is to provide a secondary battery that can prevent a current collecting lead from being damaged when the electrode group is rolled back.

In order to solve the above-mentioned problems, the present invention comprises an electrode group in which strip-like positive and negative electrode plates are wound, and disk-shaped current collecting members respectively disposed on both sides of the electrode group, and the positive and negative electrode plates In the secondary battery in which the tip portions of a large number of current collecting leads respectively led out from are joined to the outer periphery of the current collecting member, the current collecting member has a smaller diameter than the electrode group, When the diameter is D ₁ , the diameter of the current collecting member is D ₂ , and the distance between the end face of the electrode group and the end face of the current collecting member on the electrode group side is h, it is located on the outermost periphery of the electrode group The current collecting lead has a length from the lead-out position at the end face of the electrode group to the joining position at the end face of the current collecting member is not less than (D ₁ -D ₂ ) / 2 + h, and the axis of the electrode group When the direction is vertical, the return direction when viewed from the side of the electrode group is the direction of the axis. The shift amount in the horizontal direction between the derived position and the bonding position due to the return Maki of the electrode group in the case of the horizontal direction is taken as c for, the collector diameter D ₂ of the member D ₂ ≦ D It is characterized by satisfying the relationship of ₁ −c ² / h.

The distance between the lead-out position on the end face of the electrode group of the current collecting lead and the joining position on the end face of the current collecting member when the electrode group is rolled back is D ₁ , D ₂ (D ₁ > D ₂ ), h, and c are defined as described above, [c ² + h ² + {(D ₁ −D ₂ ) / 2} ² ] ^0.5 . In the present invention, in order to prevent the collector lead from being damaged due to the electrode group being rolled back, the lead-out position when the length from the lead-out position of the current-collecting lead located on the outermost circumference to the joining position is shifted, and What is necessary is just to be more than the distance between joining positions. That is, since it is the length from the outlet position of the current collecting lead positioned in the outermost periphery to the joining position _{(D 1 -D 2) / 2} + h or _{more, (D 1 -D 2) /} 2 + h ≧ [c 2 + h ² + {(D ₁ −D ₂ ) / 2} ² ] ^0.5 only needs to be satisfied, and if the relationship D ₂ ≦ D ₁ −c ² / h, which is developed and arranged, is satisfied. Good. According to the present invention, since the diameter D _{2 of the} current collecting member satisfies the relationship of D ₂ ≦ D ₁ −c ² / h, the diameter D of the current collecting member is taken into account by the amount of displacement c associated with the electrode group rolling back. _Since the length from the lead-out position of the current collecting lead located on the outermost periphery of the electrode group to the joining position is ensured by the amount ₂ is made smaller than the diameter D _{1 of} the electrode group, Breakage of the current collecting lead can be prevented.

In this case, the current collecting lead located on the outer periphery of the electrode group among the current collecting leads is along the horizontal direction on the end surface of the electrode group and rises along the vertical direction and is joined to the outer periphery of the current collecting member. For example, the length from the lead-out position of the outermost current collecting lead to the joining position can be set to (D ₁ −D ₂ ) / 2 + h or more. In addition, the current collecting lead may have a positive electrode made of aluminum and a negative electrode made of copper.

According to the present invention, to satisfy the relation of the diameter D ₂ is _{D 2 ≦ D 1 -c 2 /} h of the current collecting member, even if the return Maki electrode group, is possible to prevent damage to the collector lead The effect that it is possible can be acquired.

  Embodiments in which the present invention is applied to a cylindrical lithium ion secondary battery will be described below with reference to the drawings.

(Constitution)
As shown in FIG. 1, the cylindrical lithium ion secondary battery 20 of the present embodiment includes a cylindrical battery container 5 and a hollow cylindrical shaft core 11 with a strip-like positive and negative electrode plate having a spiral cross section through a separator. A wound group (electrode group) 6 is provided.

  On both sides of the wound group 6, on the substantially extension line of the shaft core 11, a positive pole column whose tip portion constitutes the positive electrode external terminal 1 and a negative pole column whose tip portion constitutes the negative electrode external terminal 1 ′ are shafts. The hollow portion of the core 11 is fitted. The positive and negative external terminals 1, 1 ′ are formed with a flange portion 7 as a disk-shaped current collecting member protruding integrally from the periphery. On the peripheral surface (outer periphery) of the flange portion 7, the tip end portions of the current collecting leads 9 respectively led out from the positive electrode plate and the negative electrode plate are joined by ultrasonic welding.

As shown in FIG. 2, the wound group 6 has a diameter D ₁ , and the flange portion 7 of the positive and negative external terminals 1, 1 ′ has a diameter D ₂ that is smaller than the diameter D ₁ of the wound group 6. ing. A gap h is formed between the end surface of the winding unit 7 on the winding group 6 side and the end surface of the winding group 6. The current collecting lead 9 led out from the positive and negative electrode plates positioned outside the peripheral surface of the winding part 7 and on the outer peripheral side of the winding group 6 is once along the end surface of the winding group 6, and the tip part is the hook part 7. It rises in the direction of the collar part 7 so as to be parallel to the peripheral surface of. For this reason, the current collecting leads 9 led out from the positive and negative electrode plates located on the outermost periphery of the winding group 6 are arranged on the end surface of the winding part 7 on the winding group 6 side from the leading position on the end surface of the winding group 6. The length to the joining position is (D ₁ −D ₂ ) / 2 + h or more.

The diameter D ₂ of the flange portion 7 is set as follows. As shown in FIG. 3A, when viewed from the side of the wound group 6, the current collecting lead 9 located on the outermost periphery extends straight from the wound group 6 to the peripheral surface of the flange portion 7. When the winding group 6 rolls back, as shown in FIG. 3B, the lead-out position and the joining position of the current collecting lead 9 are displaced in the horizontal direction when the shaft core 11 is vertical. Since this deviation becomes maximum at the outermost periphery of the winding group 6, when the horizontal deviation amount c between the lead-out position of the current collecting lead 9 located at the outermost periphery of the winding group 6 and the joining position is set. The diameter D ₂ is set so as to satisfy the relationship of D ₂ ≦ D ₁ -c ² / h (hereinafter referred to as Expression (1)). Therefore, the diameter _{D 2} of the flange portion 7, the partial smaller than the diameter _{D 1} of the winding group 6 ^c 2 / h.

  As shown in FIG. 1, on the outer side of the flange portion 7 of the positive and negative external terminals 1, 1 ′, a second ceramic washer 3 ′ (alumina, thickness of the portion in contact with the back surface of the battery cover 4 is 2 mm, inner diameter is 16 mm, Each having an outer diameter of 25 mm). Around the second ceramic washer 3 ′, an O-ring 16 made of rubber (EPDM) is disposed, and a disk-shaped battery lid 4 is placed. The peripheral end surface of the battery lid 4 is fitted into the opening of the battery container 5, and both contact parts are joined together by laser welding.

The positive and negative external terminals 1, 1 ′ pass through a hole in the center of the battery cover 4 and protrude outward in the opposite direction from the battery cover 4. On the outside of the battery lid 4, the positive and negative external terminals 1, 1 ′ are provided with a flat first ceramic washer 3 (thickness 2 mm, made of alumina, inner diameter 16 mm, outer diameter 28 mm), metal washer 14 (from the bottom of the nut 2). Smooth) are fitted in this order. Metal nuts 2 are respectively screwed to the tips of the positive and negative external terminals 1 and 1 ′. For this reason, the battery lid 4 is fastened and fixed between the flange 7 and the nut 2 via the second ceramic washer 3 ′, the first ceramic washer 3, and the metal washer 14. The tightening torque value is set to 6.9 N · m (70 kgf · cm). The metal washer did not rotate until the tightening operation was completed. In this state, the power generation element inside the battery container 5 is blocked from the outside air by the compression of the O-ring 16. The battery cover 4 is provided with a gas discharge valve 10 that cleaves in response to an increase in the internal pressure of the battery. The cleavage pressure of the gas discharge valve is set to 1.3 to 1.8 MPa (13 to 18 kg / cm ² ).

A nonaqueous electrolytic solution is injected into the battery container 5 through a liquid injection port 15 formed in the battery lid 4. In this example, 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a non-aqueous electrolyte in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1. Things are used. The lithium ion secondary battery 20 is completed by sealing the liquid injection port 15. In this example, the battery container 5 is set to have an outer diameter of 67 mm and an inner diameter of 66 mm, and the injection amount of the non-aqueous electrolyte is set to 480 g.

In the wound group 6 inserted into the battery case 5, the positive electrode plate and the negative electrode plate are wound through a polyethylene separator having a thickness of 40 μm so that the two electrode plates do not directly contact each other. The current collecting leads 9 respectively led out from the positive electrode plate and the negative electrode plate are wound so as to be positioned on both end surfaces on the opposite sides of the wound group 6. At the time of winding, in order to prevent the positive and negative electrode plates from slipping, the winding is performed while applying tension. An insulating coating 8 is applied to the entire outer periphery of the wound group 6. For the insulating coating 8, a pressure-sensitive adhesive tape in which a pressure-sensitive adhesive containing hexamethacrylate is applied to one surface of a polyimide base material is used. This adhesive tape is wound around the outer peripheral surface of the wound group 6 several times. The positive electrode plate, negative electrode plate, by adjusting the length of the separator, diameter D ₁ of the winding group 6 is set to 64 ± 0.5 mm.

The positive electrode plate constituting the wound group 6 has an aluminum foil having a thickness of 20 μm as a positive electrode current collector. A positive electrode mixture containing a positive electrode active material is applied to both surfaces of the aluminum foil. As the positive electrode active material, lithium manganate (LiMn ₂ O ₄ ), which is a lithium transition metal double oxide capable of releasing and accommodating lithium by charging and discharging, is used. In the positive electrode mixture, lithium manganate powder, scaly graphite (average particle diameter: 5 μm) as a conductive agent, and polyvinylidene fluoride (hereinafter abbreviated as PVDF) as a binder (binder) are blended. The blending ratio is set to, for example, a mass ratio of 85: 10: 5. When the positive electrode mixture is applied to the aluminum foil, a dispersion solvent N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is added, and the applied amount of the positive electrode mixture after drying is 280 g / m ^2. It is applied to become. An uncoated portion having a width of 50 mm is left on the side edge on one side in the longitudinal direction of the positive electrode plate. The positive electrode plate is dried, pressed, and cut to a length of 6000 mm. The positive electrode active material mixture layer has a width of 300 mm and a thickness (including aluminum foil) of 230 μm.

  A notch is formed in the uncoated part on the side edge on one side in the longitudinal direction, and the current collecting lead 9 is constituted by the remaining part of the notch. For this reason, the positive electrode current collecting lead 9 is made of aluminum. Adjacent current collecting leads 9 are set at an interval of 20 mm, the width of the current collecting leads 9 is 10 mm, and the width of the uncoated portion of the notch is 2 mm.

On the other hand, the negative electrode plate has a rolled copper foil having a thickness of 10 μm as a negative electrode current collector. A negative electrode mixture containing a negative electrode active material is coated on both surfaces of the rolled copper foil. Amorphous carbon is used for the negative electrode active material. In the negative electrode mixture, amorphous carbon and binder PVDF are blended, and the blending ratio is set to 90:10, for example. When the negative electrode mixture is applied to the rolled copper foil, NMP as a dispersion solvent is added, and the negative electrode mixture after drying is applied in an amount of 66 g / m ² . An uncoated portion with a width of 50 mm is left on the side edge on one side in the longitudinal direction of the negative electrode plate. The negative electrode plate is dried, pressed, and cut to a length of 6200 mm. A current collecting lead 9 is formed on the uncoated portion of the negative electrode mixture in the same manner as the positive electrode plate. For this reason, the negative electrode current collecting lead 9 is made of copper. The negative electrode active material mixture layer has a width of 306 mm and a thickness (including copper foil) of 140 μm.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 20 of the present embodiment will be described.

  In the conventional lithium ion secondary battery, the current collecting leads led out from both end faces of the wound group are joined so as to have a shortest length to the current collecting members arranged on both sides of the wound group. However, during use of the battery, vibrations, temperature changes, expansion and contraction of the active material accompanying repeated charge / discharge, etc. occur, so that the winding group is rolled back by the tension applied during the preparation of the winding group. Since this rollback occurs along the winding direction of the wound group, the amount of rollback increases toward the outer periphery of the wound group. For this reason, the current collecting lead located on the outermost periphery of the wound group is cut as the wound group is rolled back, causing a decrease in battery output. Further, the cut surface of the cut current collecting lead breaks the separator and causes a short circuit between the positive and negative electrodes. This is presumably because the length of the current collecting lead is insufficient. If the length of the current collecting lead is increased in order to avoid this, the current collecting lead is slackened and jumps out of the peripheral surface of the wound group, so that there is a risk of cutting during handling during battery production. The lithium ion secondary battery 20 of the present embodiment solves these problems.

In the lithium ion secondary battery 20 of the present embodiment, the diameter D ₂ of the flange portion 7 of the positive and negative external terminals 1, 1 ′ is set smaller than the diameter D ₁ of the wound group 6. Further, the current collecting lead 9 located on the outermost periphery of the winding group 6 is along the end surface of the winding group 6, and the tip portion is in the direction of the flange portion 7 so as to be parallel to the peripheral surface of the flange portion 7. Standing up. For this reason, the length of the current collecting lead 9 located on the outermost periphery from the lead-out position on the end face of the wound group 6 to the joining position on the end face on the wound group 6 side of the saddle portion 7 is (D ₁ − D ₂ ) / 2 + h or more. Thus, it is possible to secure the length of the current collector leads 9 positioned in the outermost periphery in minutes of reduced diameter D ₂ of the flange portion 7.

Moreover, since the production of the lithium ion secondary battery 20 is usually performed in a room temperature (25 ° C.) environment, when the lithium ion secondary battery 20 is used in a low temperature environment, a metal foil collection is used. It is conceivable that the electric lead 9 contracts and breaks. Therefore, the current collecting lead 9 needs to have a length margin. In the present embodiment, since the length of the outermost current collecting lead 9 is (D ₁ −D ₂ ) / 2 + h or more, damage can be prevented even if the current collecting lead 9 contracts in a low temperature environment.

Further, when the shaft core 11 is vertical and the winding return direction when viewed from the side surface side of the winding group 6 is the horizontal direction with respect to the shaft core 11, the cluster positioned on the outermost periphery accompanying the winding back of the winding group 6. Assuming that the horizontal displacement amount c between the lead-out position of the electric lead 9 and the joint position is, the distance b between the lead-out position and the joint position is b = [c ² + h ² + {(D ₁ −D ₂ ) / 2. } ² ] ^0.5 (see also FIG. 3B). At this time, in order to prevent the current collecting lead 9 from being damaged, the length of the current collecting lead 9 located on the outermost periphery may be set larger than the distance b, and (D ₁ −D ₂ ) / 2 + h ≧ [c ² + H ² + {(D ₁ −D ₂ ) / 2} ² ] ^0.5 only needs to be satisfied. Expanding organize this relationship, the diameter _{D 2} of the flange portion 7 the relationship of formula (1), namely, it satisfies the relationship of ^{_{D 2 ≦ D 1 -c 2 /}} h. In a lithium-ion secondary battery 20 of the present embodiment, since the diameter D ₂ of the flange portion 7 meets the relation of the formula (1), to the joining position from the outlet position of the current collecting lead 9 positioned in the outermost periphery length Is larger than the distance b, it is possible to prevent the current collecting lead 9 from being damaged even if the wound group 6 is rolled back. Accordingly, it is possible to prevent a decrease in battery output, and it is possible to prevent a short circuit between the positive and negative electrodes without damaging the separator.

  In the lithium ion secondary battery 20 of the present embodiment, the example in which the current collecting lead 9 is formed by notching the side edges of the positive and negative current collectors is shown, but the present invention is not limited to this. Alternatively, a separately produced current collector lead may be joined to the current collector by welding or the like. At this time, if the current collector lead 9 of the positive electrode is made of aluminum and the current collector lead 9 of the negative electrode is made of copper, the resistance generated at the junction with the current collector can be reduced. Needless to say, the number and interval of the current collecting leads 9 are not limited. Further, the current collecting lead 9 is provided along the end surface of the winding group 6, and it is sufficient that the tip end portion rises in the direction of the flange portion 7 so as to be parallel to the peripheral surface of the flange portion 7, and is bent at a right angle. It does not have to be.

  Moreover, in the lithium ion secondary battery 20 of this embodiment, although the large lithium ion secondary battery used for the power source for electric vehicles etc. was illustrated, this invention is limited to the magnitude | size of a battery and a battery capacity. is not. In addition to the present embodiment, the battery structure may be, for example, a cylindrical battery having a structure in which a battery top cover is sealed by caulking on a bottomed cylindrical container (can). In particular, a battery as a power source for an electric vehicle is required to have relatively high capacity and high output characteristics, so that the application of the present invention is preferable. Further, the present invention can be applied to a wound secondary battery other than a lithium ion secondary battery, and the shape of the battery container is not limited to a cylindrical shape. The present invention can also be applied to a battery housed in a battery container.

  Furthermore, in the lithium ion secondary battery 20 of the present embodiment, lithium transition metal double oxide lithium manganate was shown as the positive electrode active material, but the present invention is not particularly limited. For example, the effect of the present invention is not hindered by lithium cobaltate, lithium nickelate, a composite oxide of lithium and manganese, cobalt, nickel, or other element doped materials doped with elements other than manganese, cobalt, and nickel. The crystal structure is not limited, and may be a spinel crystal structure or a layered crystal structure.

  Furthermore, in the lithium ion secondary battery 20 of the present embodiment, amorphous carbon is shown as the negative electrode active material, but the present invention is not particularly limited. For example, natural graphite and various artificial graphite materials Carbonaceous materials such as coke may be used. Also, the shape is not particularly limited, such as a scale shape, a spherical shape, a fiber shape, or a lump shape.

  Furthermore, as binders that can be used in other embodiments, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyano There are polymers such as ethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, vinyl alcohol, and mixtures thereof.

Moreover, in the lithium ion secondary battery 20 of this embodiment, 1 mol / liter of lithium hexafluorophosphate is added to a non-aqueous electrolyte in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1. Although the liter dissolved is shown, the present invention is not limited to this. As the non-aqueous electrolyte, a commonly used non-aqueous electrolyte in which a general lithium salt is used as an electrolyte and dissolved in an organic solvent can be used. The lithium salt and organic solvent used are not particularly limited. For example, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, or a mixture thereof can be used. Examples of organic solvents other than the present embodiment include propylene carbonate, ethylene carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl. -1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, or a mixed solvent of two or more of these can be used. The mixing ratio is not limited.

  Furthermore, in this embodiment, although the base material is a polyimide and the adhesive tape which apply | coated the adhesive which consists of hexamethacrylates to the one side was used for the insulation coating 8, it does not restrict | limit in particular. For example, the base material is a polyolefin such as polypropylene or polyethylene, and an adhesive tape in which an acrylic adhesive such as hexamethacrylate or butyl acrylate is applied on one or both sides, or a tape made of polyolefin or polyimide that does not apply an adhesive. It can be preferably used.

Then, in accordance with the present embodiment, for example of the lithium ion secondary battery 20 manufactured by changing the diameter D ₂ of the flange portion 7 will be described. In addition, it describes together about the battery of the comparative example produced for the comparison.

(Example 1-1)
As shown in Table 1 below, in Examples 1-1, the diameter _{D 2} is set to 35.2 mm, the distance h between the end surface of the end face of the winding group 6 and the collar portion 7 is set to 5.0 mm. Since the diameter _{D 1} of the winding group 6 is 64 mm, the diameter _{D 2} corresponds 55.0% of the diameter _{D 1.} Further, when 100 cycles of charging / discharging were performed with this battery, a deviation of about 10 mm occurred between the lead-out position of the outermost current collecting lead 9 and the joining position as the winding group 6 was rolled back. Since this deviation did not increase even after repeated charge / discharge cycles, the deviation c was set to 10 mm. Therefore, in the battery of Example 1-1, the right side of Expression (1) is D ₁ −c ² / h = 64−10 ² /5=44.0.

(Example 1-2 to Example 1-3)
As shown in Table 1, in Examples 1-2 to Example 1-3, except for changing the diameter _{D 2} were the same as in Example 1. And in Example 1-2 38.4 mm (equivalent 60.0% of the diameter _{D 1),} was in Example 1-3 44.0 mm (equivalent 68.8% of the diameter _{D 1).}
(Comparative Example 1-1 to Comparative Example 1-3)

As shown in Table 1, in Comparative Examples 1-1 to 1-3, except for changing the diameter _{D 2} were the same as in Example 1. And in Comparative Example 1-1 44.8 mm (equivalent to 70.0 with a diameter _{D 1),} and in Comparative Example 1-2 51.2 mm (equivalent to 80.0% of the diameter _{D 1),} Comparative Example 1 and the at 3 64.0 mm (corresponding to 100% of the diameter _{D 1).} Accordingly, the batteries of Comparative Examples 1-1 to 1-3 are conventional batteries that do not satisfy the relationship of the formula (1).

(Evaluation)
About each battery of an Example and a comparative example, after charging / discharging 100 cycles, the battery was disassembled and the damage condition of the current collection lead was determined. Judgment was made into three stages: ○: no current collector lead breakage (cut), Δ: less than 5 current collector lead breaks, and x: 5 current collector lead breaks or more. The determination results are also shown in Table 1.

As shown in Table 1, Comparative Example 1-1 the flange portion 7 has a diameter D ₂ that does not satisfy the equation (1), the lithium ion secondary battery of Comparative Example 1-2 and Comparative Example 1-3, wound The current collector lead was cut off as the group returned. In contrast, Examples 1-1 the flange portion 7 and the diameter _{D 2} which satisfy the formula (1), the lithium ion secondary battery 20 of Example 1-2 and Example 1-3, the winding group 6 There was no breakage of the current collecting lead 9 due to the return. This is presumably because the current collecting lead 9 fixed to the peripheral surface of the collar portion 7 has a sufficient length that allows the winding group 6 to be pulled due to rolling back. Therefore, in order to prevent damage to the collector lead 9 with the return Maki winding group 6, it is important that the flange portion 7 and the diameter D ₂ which satisfy the formula (1), clear that became.

  The present invention contributes to the manufacture and sale of secondary batteries in order to provide a secondary battery that can prevent the current collecting lead from being damaged due to the electrode group being rolled back, and thus has industrial applicability.

It is sectional drawing which shows the outline of the cylindrical lithium ion secondary battery of embodiment to which this invention is applied. It is sectional drawing which shows arrangement | positioning from the derived | leading-out position of the current collection lead located in the outermost periphery of the winding group of the cylindrical lithium ion secondary battery of embodiment to the joining position to a collar part. It is a side view which shows the positional relationship of the winding group when the cylindrical lithium ion secondary battery of embodiment is seen from the side surface, a current collection lead, and a collar part, (A) is immediately after winding group production, (B ) Indicates after the return of the winding group.

Explanation of symbols

1 Positive external terminal 1 'Negative external terminal 6 Winding group (electrode group)
7 buttock (current collecting member)
9 Current collecting lead 11 Shaft core 20 Cylindrical lithium ion secondary battery (secondary battery)

Claims (3)

A plurality of current collector leads each of which is led out from the positive and negative electrode plates, each of which includes a group of electrodes wound with a belt-like positive and negative electrode plate and a disk-shaped current collecting member disposed on each side of the electrode group; In the secondary battery in which the part is joined to the outer periphery of the current collecting member, the current collecting member has a smaller diameter than the electrode group, and the diameter of the electrode group is D ₁ and the diameter of the current collecting member is D ₂ , when the distance between the end face of the electrode group and the end face on the electrode group side of the current collecting member is h, the current collecting lead located on the outermost periphery of the electrode group is at the end face of the electrode group The length from the lead-out position to the joining position at the end face of the current collecting member is not less than (D ₁ −D ₂ ) / 2 + h, and the axial direction of the electrode group is vertical, as viewed from the side of the electrode group. The electric power when the whirling return direction is horizontal with respect to the axial direction. The shift amount in the horizontal direction between the derived position due to the return Maki group and the bonding position when is c, the diameter D ₂ of the current collector member is the relation _{D 2 ≦ D 1 -c 2 /} h A secondary battery characterized by satisfying.   Among the current collecting leads, a current collecting lead located on the outer periphery of the electrode group extends along the horizontal direction on the end surface of the electrode group, rises along the vertical direction, and is joined to the outer periphery of the current collecting member. The secondary battery according to claim 1, wherein:   The secondary battery according to claim 1, wherein the current collecting lead has a positive electrode made of aluminum and a negative electrode made of copper.

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