JP2011154971A - Cylindrical secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a foreign matter from entering a cylindrical secondary battery from between a positive electrode and a separator to prevent short-circuiting in the cylindrical secondary battery. <P>SOLUTION: A positive lead 16 of a positive electrode 11 is welded to a positive collector 31. An insulating layer 18 is formed on a first separator 13 disposed inwardly of and adjacent to the positive lead 16 on a positive-lead 16 facing side of the first separator 13 at a location facing the positive lead 16. Since the positive lead 16 abuts on the insulating layer 18, a clearance between the positive electrode 11 and an outer second separator 14 is made smaller. This prevents a foreign matter from entering from between the positive electrode 11 and the separator 14. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cylindrical secondary battery.

  In a cylindrical secondary battery represented by a lithium secondary battery or the like, a positive electrode formed with a positive electrode mixture and a negative electrode formed with a negative electrode mixture are wound around a shaft core via a separator. An electrode group is configured. The positive electrode mixture is formed on both surfaces of the positive electrode sheet, and one side edge portion in the longitudinal direction of the positive electrode sheet is a positive electrode mixture untreated portion where no positive electrode mixture is formed. Since the positive electrode is welded to the positive electrode current collecting member in the untreated portion of the positive electrode mixture, a positive lead called a tab is usually formed integrally with the positive electrode sheet by pressing or the like. The same applies to the negative electrode side, in which the negative electrode mixture is formed on both sides of the negative electrode sheet, and is welded to the negative electrode current collector member on the negative electrode mixture untreated portion provided at one side edge in the longitudinal direction of the negative electrode sheet. The negative electrode lead is formed integrally with the negative electrode sheet by pressing or the like.

The positive electrode and the negative electrode in the electrode group may be short-circuited when, for example, burrs or the like generated when the positive lead or the negative lead is formed by pressing pierce the separator. As described above, when the positive electrode and the negative electrode are short-circuited in a spot manner, battery performance is deteriorated such that a necessary voltage cannot be obtained.
For this reason, there is known a structure in which the side opposite to the one side in the longitudinal direction where the positive electrode lead is provided in the positive electrode sheet where burrs are likely to occur is covered by folding the adjacent separator. Yes. In this way, there is no risk of burrs or the like breaking through the two separators, and an internal short circuit can be prevented (for example, see Patent Document 1).

JP 2008-4476 A

However, even after the electrode group is housed in the battery container and the nonaqueous electrolyte is injected into the battery container, an internal short circuit occurs. Although the details of this phenomenon will be described later, the main point is that ions are generated from the positive electrode side due to the foreign matter mixed in the non-aqueous electrolyte, penetrate the separator and grow on the negative electrode, that is, on the negative electrode. This is due to the phenomenon of deposition and deposition. As a result, the deposit produced on the negative electrode causes an internal short circuit between the positive electrode and the negative electrode.
The invention described in the above-mentioned prior art does not solve the internal short circuit caused by this phenomenon.

  A cylindrical secondary battery of the present invention includes an electrode group in which a first separator, a positive electrode, a second separator, and a negative electrode are stacked and wound around an axis, and a positive current collecting member. A cylindrical secondary battery in which a positive electrode lead connected to a positive electrode current collecting member is formed on the positive electrode, wherein at least the side facing the positive electrode in the first separator or the second separator adjacent to the positive electrode An insulating layer is provided at a location corresponding to the positive electrode lead.

  According to the cylindrical secondary battery of the present invention, the positive electrode lead connected to the positive electrode current collector is in contact with the insulating layer formed on the separator adjacent to the positive electrode current collector and is prevented from being deformed. It will not be greatly inclined toward the electric member side. This prevents an increase in the gap between the positive electrode sheet and the separator adjacent to the outside of the positive electrode sheet. Alternatively, even if the positive electrode lead is inclined and connected to the positive electrode current collector member side, an insulating layer is formed on the separator adjacent to the side opposite to the positive electrode current collector member side, so the gap between this insulating layer and the positive electrode sheet Can be reduced by the thickness of the insulating layer. For this reason, it is possible to prevent foreign matter from entering the electrode group that causes an internal short circuit.

Sectional drawing which shows Embodiment 1 of the cylindrical secondary battery of this invention. FIG. 2 is an exploded perspective view of the cylindrical secondary battery shown in FIG. 1. The perspective view of the state which cut | disconnected a part for showing the detail of the electrode group of FIG. The expanded sectional view which concerns on the principal part of this invention which shows the joining state of the electrode group illustrated by FIG. 1, and a positive electrode current collection member. FIG. 5 is an enlarged plan view of a positive electrode sheet and a separator of the electrode group illustrated in FIG. 4. The perspective view for demonstrating the method of forming an insulating layer in a separator. The perspective view for demonstrating the preparation methods of an electrode group. The expanded sectional view which shows Embodiment 2 of this invention.

(Embodiment 1)
-Structure of cylindrical secondary battery-
Hereinafter, a cylindrical secondary battery of the present invention will be described with reference to the drawings, taking a lithium ion cylindrical secondary battery as an embodiment.
FIG. 1 is a cross-sectional view showing an embodiment of the cylindrical secondary battery of the present invention, and FIG. 2 is an exploded perspective view of the cylindrical secondary battery shown in FIG.
The cylindrical secondary battery 1 has dimensions of, for example, an outer diameter of 40 mmφ and a height of 100 mm.
In the cylindrical secondary battery 1, components for power generation described below are accommodated in a bottomed cylindrical battery container 2 and a hat-type upper lid 3. The bottomed cylindrical battery case 2 is formed with a groove 2a protruding on the inner side of the battery case 2 on the upper end side which is the open side.

Reference numeral 10 denotes an electrode group having a shaft core 15 at the center, and a positive electrode and a negative electrode wound around the shaft core 15. FIG. 3 is a perspective view showing the details of the structure of the electrode group 10, with a part thereof cut. As shown in FIG. 3, the electrode group 10 has a configuration in which a positive electrode 11, a negative electrode 12, and first and second separators 13 and 14 are wound around an axis 15.
The shaft core 15 has a hollow cylindrical shape, and the negative electrode 12, the first separator 13, the positive electrode 11, and the second separator 14 are laminated and wound on the shaft core 15 in this order. Inside the innermost negative electrode 12, the first separator 13 and the second separator 14 are wound several times (one turn in FIG. 3). The outermost periphery is the negative electrode 12 and the first separator 13 wound around the outer periphery. The first separator 13 at the outermost periphery is stopped by the adhesive tape 19 (see FIG. 2).

  The positive electrode 11 is formed of an aluminum foil and has a long shape. The positive electrode 11 includes a positive electrode sheet 11a and a positive electrode processing portion in which a positive electrode mixture 11b is applied to both surfaces of the positive electrode sheet 11a. The upper side edge along the longitudinal direction of the positive electrode sheet 11a is a positive electrode mixture untreated portion 11c where the positive electrode mixture 11b is not applied and an aluminum foil is exposed. In the positive electrode mixture untreated portion 11 c, a large number of positive electrode leads 16 protruding upward in parallel with the shaft core 15 are integrally formed at equal intervals.

  The positive electrode mixture 11b includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. The positive electrode active material is preferably lithium oxide. Examples include lithium cobaltate, lithium manganate, lithium nickelate, lithium composite oxide (lithium oxide containing two or more selected from cobalt, nickel, and manganese). The positive electrode conductive material is not limited as long as it can assist transmission of electrons generated by the occlusion / release reaction of lithium in the positive electrode mixture to the positive electrode. Examples of the positive electrode conductive material include graphite and acetylene black.

  The positive electrode binder can bind the positive electrode active material and the positive electrode conductive material, and can bind the positive electrode mixture and the positive electrode current collector, and should not deteriorate significantly due to contact with the non-aqueous electrolyte. There is no particular limitation. Examples of the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber. The method for forming the positive electrode mixture layer is not limited as long as the positive electrode mixture is formed on the positive electrode. As an example of a method of forming the positive electrode mixture 11b, a method of applying a dispersion solution of constituent materials of the positive electrode mixture 11b on the positive electrode sheet 11a can be given.

  Examples of a method for applying the positive electrode mixture 11b to the positive electrode sheet 11a include a roll coating method and a slit die coating method. As an example of a solvent for the dispersion solution in the positive electrode mixture 11b, N-methylpyrrolidone (NMP), water, or the like is added, and the kneaded slurry is uniformly applied to both sides of an aluminum foil having a thickness of 20 μm and dried. Cut. An example of the coating thickness of the positive electrode mixture 11b is about 40 μm on one side. When cutting the positive electrode sheet 11a, the positive electrode lead 16 is integrally formed. All the positive leads 16 have substantially the same length.

  The negative electrode 12 is formed of a copper foil and has a long shape. The negative electrode 12 includes a negative electrode sheet 12a and a negative electrode processing portion in which a negative electrode mixture 12b is applied to both surfaces of the negative electrode sheet 12a. The lower side edge along the longitudinal direction of the negative electrode sheet 12a is a negative electrode mixture untreated portion 12c where the negative electrode mixture 12b is not applied and the copper foil is exposed. In the negative electrode mixture untreated portion 12c, a large number of negative electrode leads 17 extending in the direction opposite to the positive electrode lead 16 are integrally formed at equal intervals.

  The negative electrode mixture 12b includes a negative electrode active material, a negative electrode binder, and a thickener. The negative electrode mixture 12b may have a negative electrode conductive material such as acetylene black. Graphite carbon is preferably used as the negative electrode active material. By using graphite carbon, a lithium ion secondary battery for a plug-in hybrid vehicle or an electric vehicle requiring a large capacity can be manufactured. The formation method of the negative electrode mixture 12b is not limited as long as the negative electrode mixture 12b is formed on the negative electrode sheet 12a. As an example of a method of applying the negative electrode mixture 12b to the negative electrode sheet 12a, a method of applying a dispersion solution of constituent materials of the negative electrode mixture 12b onto the negative electrode sheet 12a can be mentioned. Examples of the coating method include a roll coating method and a slit die coating method.

  As an example of a method of applying the negative electrode mixture 12b to the negative electrode sheet 12a, N-methyl-2-pyrrolidone or water as a dispersion solvent is added to the negative electrode mixture 12b, and the kneaded slurry is made of a rolled copper foil having a thickness of 10 μm. Apply uniformly on both sides, dry, and then cut. An example of the coating thickness of the negative electrode mixture 12b is about 40 μm on one side. When the negative electrode sheet 12a is cut, the negative electrode lead 17 is integrally formed. All the negative leads 17 have substantially the same length.

The width of the first separator 13 and the second separator 14 is W _S , the width of the negative electrode mixture 12b formed on the negative electrode sheet 12a is W _C , and the width of the positive electrode mixture 11b formed on the positive electrode sheet 11a is W _A. In this case, it is formed so as to satisfy the following formula.
W _S > W _C > W _A (see FIG. 3)
That is, the width W _{C of the} negative electrode mixture 12b is always larger than the width W _{A of the} positive electrode mixture 11b. This is because in the case of a lithium ion secondary battery, lithium as the positive electrode active material is ionized and penetrates the separator, but the negative electrode sheet is not formed on the negative electrode side and the negative electrode sheet 12a is exposed. This is because lithium is deposited on 12a and causes an internal short circuit.

The separator 13 is, for example, a polyethylene porous film having a thickness of 40 μm.
1 and 3, a hollow cylindrical shaft core 15 is formed with a large-diameter groove 15a on the inner surface of the upper end portion in the axial direction (vertical direction in the drawing), and a positive current collecting member 31 is press-fitted into the groove 15a. Has been. The positive electrode current collecting member 31 is formed of, for example, aluminum, and has a disk-like base portion 31a, a lower cylindrical portion 31b that protrudes toward the shaft core 15 side at the inner peripheral portion of the base portion 31a and is press-fitted into the inner surface of the shaft core 15. And an upper cylindrical portion 31c protruding toward the upper lid 3 at the outer peripheral edge. An opening 31d (see FIG. 2) for discharging a gas generated inside the battery is formed in the base 31a of the positive electrode current collecting member 31.

  All of the positive leads 16 of the positive electrode sheet 11 a are welded to the upper cylindrical portion 31 c of the positive current collector 31. In this case, as shown in FIG. 2, the positive electrode lead 16 is overlapped and bonded onto the upper cylindrical portion 31 c of the positive electrode current collecting member 31. Since each positive electrode lead 16 is very thin, a large current cannot be taken out by one. Therefore, a large number of positive leads 16 are formed at predetermined intervals over the entire length from the start to the end of winding around the shaft core 15.

Since the positive electrode current collecting member 31 is oxidized by the electrolytic solution, the reliability can be improved by forming it with aluminum. As soon as the surface of aluminum is exposed by some processing, an aluminum oxide film is formed on the surface, and this aluminum oxide film can prevent oxidation by the electrolytic solution.
Moreover, by forming the positive electrode current collecting member 31 from aluminum, the positive electrode lead 16 of the positive electrode sheet 11a can be welded by ultrasonic welding, spot welding, or the like.

On the outer periphery of the lower end portion of the shaft core 15, a step portion 15b having a small outer diameter is formed, and the negative electrode current collector 21 is press-fitted and fixed to the step portion 15b. The negative electrode current collecting member 21 is formed of, for example, copper, and an opening 21b that is press-fitted into the step portion 15b of the shaft core 15 is formed in a disk-shaped base portion 21a. An outer peripheral cylindrical portion 21c that protrudes out is formed.
All of the negative electrode leads 17 of the negative electrode sheet 12a are welded to the outer peripheral cylindrical portion 21c of the negative electrode current collecting member 21 by ultrasonic welding or the like. Since each negative electrode lead 17 is very thin, a large number of negative leads 17 are formed at predetermined intervals over the entire length from the start of winding to the shaft core 15 to take out a large current.

The negative electrode lead 17 of the negative electrode sheet 12a and the ring-shaped pressing member 22 are welded to the outer periphery of the outer peripheral cylindrical portion 21c of the negative electrode current collecting member 21. A number of the negative electrode leads 17 are brought into close contact with the outer periphery of the outer peripheral cylindrical portion 21c of the negative electrode current collecting member 21, and the holding member 22 is wound around the outer periphery of the negative electrode lead 17 to be temporarily fixed, and are welded in this state.
A negative electrode conducting lead 23 made of copper is welded to the lower surface of the negative electrode current collecting member 21.
The negative electrode conducting lead 23 is welded to the battery container 2 at the bottom of the battery container 2. The battery container 2 is formed of, for example, carbon steel having a thickness of 0.5 mm, and the surface thereof is plated with nickel. By using such a material, the negative electrode energizing lead 23 can be welded to the battery container 2 by resistance welding or the like.

The positive electrode lead 16 of the positive electrode sheet 11 a and the ring-shaped pressing member 32 are welded to the outer periphery of the upper cylindrical portion 31 c of the positive electrode current collecting member 31. A number of the positive leads 16 are brought into close contact with the outer periphery of the upper cylindrical portion 31 c of the positive current collecting member 31, and the pressing member 32 is wound around the outer periphery of the positive lead 16 and temporarily fixed, and is welded in this state.
A large number of positive electrode leads 16 are welded to the positive electrode current collecting member 31, and a large number of negative electrode leads 17 are welded to the negative electrode current collecting member 21, whereby the positive electrode current collecting member 31, the negative electrode current collecting member 21 and the electrode group 10 are integrated. A unitized power generation unit 20 is configured (see FIG. 2). However, in FIG. 2, for the convenience of illustration, the negative electrode current collecting member 21, the pressing member 22, and the negative electrode energizing lead 23 are illustrated separately from the power generation unit 20.

  In addition, a flexible first connecting member 33 formed by laminating a plurality of aluminum foils is welded and joined to the upper surface of the base portion 31a of the positive electrode current collecting member 31. The first connecting member 33 can flow a large current by laminating and integrating a plurality of aluminum foils, and is provided with flexibility. In other words, it is necessary to increase the thickness of the connecting member in order to pass a large current, but if it is formed of a single metal plate, the rigidity increases and the flexibility is impaired. Therefore, a large number of aluminum foils having a small thickness are laminated to give flexibility. The connecting member 33 has a thickness of, for example, about 0.5 mm, and is formed by stacking five aluminum foils having a thickness of 0.1 mm.

On the upper cylinder part 31c of the positive electrode current collecting member 31, a ring-shaped insulating plate 41 made of an insulating resin material having a circular opening 41a is placed.
The insulating plate 41 has an opening 41a (see FIG. 2) and a side portion 41b protruding downward. A connection plate 35 is fitted in the opening 41 a of the insulating material 41. A flexible second connection member 34 is fixed to the lower surface of the connection plate 35 by being welded to the connection plate 35. The second connecting member 34 can flow a large current by laminating and integrating a large number of aluminum foils, and is provided with flexibility.

  The first connecting member 33 and the second connecting member 34 are fixed at one end side by welding as shown in FIG. 2 before injecting the nonaqueous electrolyte into the battery container 2. On the other hand, the other end side is an open end. After injecting the non-aqueous electrolyte, the open ends of the first connecting member 33 and the second connecting member 34 are welded as shown in FIG.

  The connection plate 35 is formed of an aluminum alloy, and has a substantially dish shape that is substantially uniform except for the central portion and is bent at a slightly lower position on the central side. The thickness of the connection plate 35 is, for example, about 1 mm. At the center of the connecting plate 35, a thin dome-shaped projection 35a is formed, and a plurality of openings 35b (see FIG. 2) are formed around the projection 35a. The opening 35b also has a function of releasing gas generated inside the battery. The connection plate 35 has an opening 36 for welding the first connection member 33 and the second connection member 34.

  The protrusion 35 a of the connection plate 35 is joined to the bottom surface of the center portion of the diaphragm 37 by resistance welding or friction diffusion bonding. The diaphragm 37 is formed of an aluminum alloy, and has a circular cut 37 a centering on the center of the diaphragm 37. The cut 37a is formed by crushing the upper surface side into a V shape by pressing and thinning the remainder. The diaphragm 37 is provided for ensuring the safety of the battery. When the internal pressure of the battery rises, as a first stage, the diaphragm 37 warps upward, peels off the joint with the protruding portion 35a of the connection plate 35, and connects the connection plate 35. The connection with the connection plate 35 is cut off. As a second stage, when the internal pressure still rises, it has a function of cleaving at the cut 37a and releasing the internal gas.

The diaphragm 37 fixes the peripheral portion of the upper lid 3 at the peripheral portion. As shown in FIG. 2, the diaphragm 37 initially has a side portion 37 b erected vertically toward the upper lid 3 side at the peripheral portion. The upper lid 3 is accommodated in the side portion 37b, and the side portion 37b is bent and fixed to the upper surface side of the upper lid 3 by caulking.
The upper lid 3 is made of iron such as carbon steel and is nickel-plated. The upper lid 3 is a disc-shaped peripheral edge 3a that contacts the diaphragm 37, and a headless bottomless cylinder 3b that protrudes upward from the peripheral edge 3a. Having a hat shape. A plurality of openings 3c are formed in the cylindrical portion 3b. The opening 3c is for releasing gas to the outside of the battery when the diaphragm 37 is cleaved by the gas pressure generated inside the battery.
When the upper lid 3 is made of iron, it can be joined to another cylindrical secondary battery made of iron by spot welding when joining in series with another cylindrical secondary battery. It is.

A gasket 43 is provided so as to cover the side portion 37 b and the peripheral edge portion of the diaphragm 37. As shown in FIG. 2, the gasket 43 is initially formed with an outer peripheral wall portion 43 b erected substantially vertically toward the upper direction on the peripheral edge of the ring-shaped base portion 43 a, and on the inner peripheral side. , And a cylindrical portion 43c formed to hang substantially vertically downward from the base portion 43a.
As will be described in detail later, the outer peripheral wall 43b of the gasket 43 is bent together with the battery container 2 by a press or the like, and the diaphragm 37 and the upper lid 3 are pressed in the axial direction by the base 43a and the outer peripheral wall 43b. It is caulked. Thereby, the upper lid 3 and the diaphragm 37 are fixed to the battery container 2 via the gasket 43.

  A predetermined amount of non-aqueous electrolyte is injected into the battery container 2. As an example of the non-aqueous electrolyte, it is preferable to use a solution in which a lithium salt is dissolved in a carbonate solvent. Examples of the lithium salt include lithium fluorophosphate (LiPF6), lithium fluoroborate (LiBF4), and the like. Examples of carbonate solvents include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), or a mixture of solvents selected from one or more of the above solvents, Is mentioned.

FIG. 4 is an enlarged cross-sectional view according to a main part of the present invention, showing a joined state of the electrode group and the positive electrode current collector shown in FIG. FIG. 5 is an enlarged plan view of the positive electrode sheet and the separator of the electrode group shown in FIG.
As described above, the positive electrode lead 16 formed on the positive electrode 11 is welded to the outer periphery of the upper cylindrical portion 31 c of the positive electrode current collecting member 31 by ultrasonic welding or the like. In this case, in the conventional structure, the positive electrode lead 16 ′ is pulled toward the positive electrode current collecting member 31, and the portion side of the positive electrode lead 16 ′ is inclined toward the positive electrode current collecting member 31 side as shown by the two-dot chain line. To the positive electrode current collecting member 31. For this reason, a large gap G is generated between the positive electrode lead 16 ′ and the outer second separator 14 adjacent to the positive electrode lead 16 ′. Here, since the center side of the positive electrode current collecting member 31 is the shaft core 15 side, the positive electrode current collecting member 31 side is referred to as an inner side, and the opposite side to the positive electrode current collecting member 31 side is referred to as an outer side.

  By the way, in the non-aqueous electrolyte injected into the battery container 2, a large number of minute conductive foreign matters are mixed. Such foreign matter is generated in the manufacturing process of the positive electrode sheet 11 and the negative electrode sheet 12, the processing process of the battery container 2, the welding process of the positive electrode lead 16 to the positive electrode current collecting member 31, and is mixed in the non-aqueous electrolyte. . When a large gap G is generated between the positive electrode lead 16 ′ and the adjacent second separator 14 on the outside as in the conventional structure, the gap G is generated in each step and is generated in the non-aqueous electrolyte. The mixed foreign matter enters between the positive electrode 11 and the second separator 14. Since a predetermined potential, for example, 4.1 V, is applied between the positive electrode 11 and the negative electrode 12, foreign matter that has entered between the positive electrode 11 and the second separator 14 is ionized and penetrates the separator. It flows to the negative electrode 12 side. Then, it grows and deposits on the negative electrode 12 and is deposited. This deposit causes a phenomenon in which the positive electrode and the negative electrode are short-circuited.

  Therefore, in the cylindrical secondary battery of the present invention, along the longitudinal direction of the side edge corresponding to the positive electrode lead 16 on the side facing the positive electrode 11 in the inner first separator 13 adjacent to the positive electrode lead 16. An insulating layer 18 is formed to prevent foreign matter from entering between the positive electrode lead 16 and the second separator 14. As shown in FIG. 5, the insulating layer 18 is formed slightly wider than the positive electrode lead 16 at a location corresponding to the positive electrode lead 16.

  As described above, in the cylindrical secondary battery of the present invention, the first separator 13 disposed adjacent to the inside of the positive electrode lead 16 has a position facing the positive electrode lead 16 on the side facing the positive electrode lead 16. An insulating layer 18 is formed. Therefore, as shown in FIG. 4, the positive electrode lead 16 does not contact the insulating layer 18, and the root portion of the positive electrode lead 16 does not incline inward. Since the base portion of the positive electrode lead 16 is not inclined inward, a large gap does not occur between the positive electrode sheet 11 a and the second separator 14 in the portion where the positive electrode lead 16 is formed. Therefore, it is possible to prevent foreign matter from entering between the positive electrode sheet 11a and the second separator 14.

  In this case, each insulating layer 18 is formed in a discontinuous state separated in a portion corresponding to between the positive electrode leads 16. Thus, by forming the insulating layers 18 separately at the portions corresponding to between the positive electrode leads 16, when the electrode group 10 is manufactured by winding the positive electrode 11 or the like around the shaft core 15, the insulating layer Since the thickness 18 does not hinder winding, the electrode group 10 can be easily formed.

The insulating layer 18 can be formed of a resin material such as polyethylene. Not only organic resin materials but also inorganic materials may be used. It may be a non-woven fabric or a woven fabric. Moreover, a porous film may be sufficient.
The thickness of the insulating layer 18 is desirably equal to or less than the thickness of the positive electrode mixture 11b. If the thickness of the insulating layer 18 is greater than the thickness of the positive electrode mixture 11b, the positive electrode lead 16 is deformed, for example, tilted in the opposite direction while the positive electrode lead 16 is welded to the positive electrode current collector 31. The internal stress increases, which is not preferable for securing the strength of the positive electrode lead 16.

  FIG. 6 is a perspective view showing an example of a method for forming the insulating layer 18. The insulating layer 18 is formed on the ribbon 51 at a predetermined interval. The pitch of the insulating layer 18 is the same as the pitch of the positive electrode lead 16. The ribbon 51 is fed from the feeding roller 61 and wound around the winding roller 62 via the heating roller 52. The first separator 13 is guided by the guide rollers 64 and 65 and transferred in the direction A in FIG.

  The ribbon 51 on which the first separator 13 and the insulating layer 18 are formed by the heating roller 52 and the guide roller 65 is transferred in the A direction while being heated under pressure. As a result, the insulating layer 18 formed on the ribbon 51 is transferred to the first separator 13. The first separator 13 to which the insulating layer 18 has been transferred is wound around a winding roller (not shown). After the insulating layer 18 is transferred to the first separator 13, the ribbon 51 is taken up by the take-up roller 62.

  In the above, the insulating layer 18 is formed on the entire surface of the ribbon 51, the heating roller 52 has a shape in which the thermocompression bonding part protrudes, and the dimension between the thermocompression bonding parts is the dimension between the positive electrode leads 16. It may be of a different structure. If such a heating roller is used, only the portion of the insulating layer 18 formed on the entire surface of the ribbon 51 corresponding to the positive electrode lead 16 is transferred to the first separator 13 at the same pitch as that of the positive electrode lead 16. .

FIG. 7 is a perspective view showing an example of a method for forming the electrode group 10 using the first separator 13 having the insulating layer 18 formed as described above.
In FIG. 7, the positive electrode 11, the first separator 13, the negative electrode 12, and the second separator 14 are laminated in this order from the outer side to the inner side of the shaft core 15, and guided to the shaft core 15 by the guide roller 66. Be beaten.

  Although not shown in FIG. 7, as described above, the positive electrode 11 includes the positive electrode sheet 11a and the positive electrode mixture 11b formed on both surfaces of the positive electrode sheet 11a. A positive electrode lead 16 is integrally formed on the positive electrode sheet 11a. The negative electrode lead 12 is formed with a negative electrode sheet 12a and a negative electrode mixture 12b formed on both surfaces of the negative electrode sheet 12a. A negative electrode lead 17 is integrally formed on the negative electrode sheet 12a.

The shaft core 15 is rotated counterclockwise in FIG. 7 by a rotating shaft 67 fitted in a hollow portion formed in the axial direction. As the shaft core 15 rotates, the first separator 13, the positive electrode 11, the second separator 14, and the negative electrode 12 are wound around the shaft core 15 by being guided by the guide roller 66.
In this case, the first separator 13 is wound around the shaft core 15 with the surface on which the insulating layer 18 is formed facing the positive electrode sheet 11 a and the insulating layer 18 being positioned at a position corresponding to the positive electrode lead 16. The

In FIG. 7, the second separator 14 is illustrated closest to the shaft core 15 side, but this is to clearly illustrate the positional relationship between the positive electrode sheet 11 and the first separator 13. It is convenient. Actually, as shown in FIGS. 3 and 4, the positive electrode 11 is laminated on the inner side of the second separator 14, and the first separator 13 is further laminated on the inner side, and the first separator 13 is arranged on the innermost side. Has been.
Next, an example of a method for manufacturing the cylindrical secondary battery having the above configuration will be described.

-Manufacturing method of cylindrical secondary battery-
A positive electrode 11 is produced in which a positive electrode mixture 11b and a positive electrode mixture untreated portion 11c are formed on both surfaces of the positive electrode sheet 11a, and a large number of positive electrode leads 16 are integrally formed on the positive electrode sheet 11a. Moreover, the negative electrode mixture 12b and the negative electrode process part 12c are formed in both surfaces of the negative electrode sheet 12a, and the negative electrode 12 by which many negative electrode leads 17 were integrally formed in the negative electrode sheet 12a is produced.

Moreover, the 1st separator 13 and the 2nd separator 14 are prepared. At this time, as shown in FIG. 6, an insulating layer 18 is formed on the first separator 13 with the same pitch as that of the positive electrode lead 16 and slightly wider than the width of the positive electrode lead 16.
Then, the innermost side edge portions of the first separator 13 and the second separator 14 are welded to the shaft core 15. Next, the first separator 13 and the second separator 14 are wound around the shaft 15 one to several times, and then, as shown in FIG. 7, the second separator 14 and the first separator 13 The negative electrode 12 is sandwiched therebetween, and the shaft core 15 is wound at a predetermined angle. Next, the positive electrode 11 is sandwiched between the first separator 13 and the second separator 14. In this state, the electrode group 10 is manufactured by winding a predetermined number of turns.

  A negative electrode current collecting member 21 is attached to the lower portion of the shaft core 15 of the electrode group 10. The negative current collector 21 is attached by fitting the opening 21 b of the negative current collector 21 into a step portion 15 b provided at the lower end of the shaft 15. Next, the negative electrode lead 17 is distributed almost uniformly around the entire outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting member 21, and the pressing member 22 is wound around the outer periphery of the negative electrode lead 17. Then, the negative electrode lead 17 and the pressing member 22 are welded to the negative electrode current collecting member 21 by ultrasonic welding or the like. Next, the negative electrode energizing lead 23 straddling the lower end surface of the shaft core 15 and the negative electrode current collecting member 21 is welded to the negative electrode current collecting member 21.

  Next, one end of the first connecting member 33 is welded to the base 31a of the positive electrode current collecting member 31 by, for example, ultrasonic welding. Next, the lower cylindrical portion 31 b of the positive electrode current collecting member 31 to which the first connecting member 33 is welded is fitted into a groove 15 a provided on the upper end side of the shaft core 15. In this state, the positive electrode lead 16 is distributed almost uniformly around the entire periphery of the upper cylindrical portion 31 c of the positive electrode current collecting member 31, and the pressing member 32 is wound around the outer periphery of the positive electrode 16. Then, the positive electrode lead 16 and the pressing member 32 are welded to the positive electrode current collecting member 31 by ultrasonic welding or the like. In this way, the power generation unit 20 illustrated in FIG. 2 is produced.

Next, the power generation unit 20 produced through the above-described steps is accommodated in a metal bottomed cylindrical member having a size that can accommodate the power generation unit 20. The bottomed cylindrical member is the battery container 2. Hereinafter, in order to simplify and clarify the description, this bottomed cylindrical member will be described as the battery container 2.
The negative electrode conducting lead 22 of the power generation unit 20 housed in the battery container 2 is welded to the battery container 2 by resistance welding or the like. In this case, although not shown, the electrode rod is inserted into the hollow shaft of the shaft core 15 from the outside of the battery case 2, and the negative electrode conducting lead 23 is pressed against the bottom of the battery case 2 by the electrode rod and welded. Next, a part of the upper end portion side of the battery container 2 is drawn and protrudes inward to form a substantially V-shaped groove 2a on the outer surface.
The groove 2 a of the battery container 2 is formed so as to be positioned in the upper end portion of the power generation unit 20, in other words, in the vicinity of the upper end portion of the positive electrode current collecting member 31.

  Next, a predetermined amount of non-aqueous electrolyte is injected into the battery container 2 in which the power generation unit 20 is accommodated. When injecting the non-aqueous electrolyte, the first connecting member 33 is bent to a position that does not obstruct the injection. Further, after the injection of the non-aqueous electrolyte is completed, the non-aqueous electrolyte is deformed and the open end portion is disposed at a position corresponding to the opening 36 of the connection plate 35.

  On the other hand, the upper lid 3 is fixed to the diaphragm 37. The diaphragm 37 and the upper lid 3 are fixed by caulking or the like. As shown in FIG. 2, since the side wall 37 b of the diaphragm 37 is initially formed perpendicular to the base portion 37 a, the peripheral edge portion 3 a of the upper lid 3 is disposed in the side wall 37 b of the diaphragm 37. Then, the side wall 37b of the diaphragm 37 is deformed by a press or the like so as to cover the upper and lower surfaces and the outer peripheral side surface of the peripheral portion of the upper lid 3 and press-contact.

  Further, the connection plate 35 is fitted and attached to the opening 41 a of the insulating plate 41. And the projection part 35a of the connection board 35 is welded to the bottom face of the diaphragm 37 with which the upper cover 3 was fixed. As the welding method in this case, resistance welding or friction diffusion bonding can be used. By welding the connection plate 35 and the diaphragm 37, the insulating plate 41 fitted with the connection plate 35 and the upper lid 3 fixed to the connection plate 35 are integrated with the connection plate 35 and the diaphragm 37. Next, one end of the second connection member 34 is welded to the connection plate 35 by ultrasonic welding or the like. The open end of the second connection member 34 is disposed at a position corresponding to the opening 36 of the connection plate 35.

  Next, the gasket 43 is accommodated on the groove 2 a of the battery container 2. As shown in FIG. 2, the gasket 43 in this state has a structure having an outer peripheral wall 43b perpendicular to the base 43a above the ring-shaped base 43a. With this structure, the gasket 43 remains inside the upper portion of the groove 2 a of the battery container 2. The gasket 43 is formed of rubber and is not intended to be limited, but an example of one preferred material is ethylene propylene copolymer (EPDM). For example, when the battery container 2 is made of carbon steel having a thickness of 0.5 mm and the outer diameter is 40 mmΦ, the thickness of the gasket 43 is about 10 mm.

  Next, the diaphragm 37 in which the upper lid 3, the connection plate 35, and the insulating plate 41 are integrated is placed on the cylinder portion 43 c of the gasket 43 with its peripheral edge corresponding to the cylinder portion 43 c of the gasket 43. In this case, the upper cylindrical portion 31 c of the positive electrode current collecting member 31 is fitted to the outer periphery of the side portion 41 b of the insulating plate 41. In this state, the open end of the second connection member 34 is overlapped with the open end of the first connection member 33, and the open ends of the first connection member 33 and the second connection member 34 are spotted together. Weld by welding. When welding the first connecting member 33 and the second connecting member 34, as described above, the first connecting member 33 and the second connecting member 34 are deformed in order to displace the positions of the respective open ends. However, since each is formed by laminating a plurality of thin metal foils such as aluminum foils, it has sufficient flexibility for deformation.

In this state, the diaphragm 37 is fixed to the battery container 2 together with the gasket 43 by a so-called caulking process in which a portion between the groove 2a and the upper end surface of the battery container 2 is compressed by pressing.
Thereby, the diaphragm 37, the upper lid 3, the connection plate 35, and the insulating plate 41 are fixed to the battery container 2 via the gasket 43, and the positive electrode current collector 31 and the upper lid 3 are connected to the first connection member 33, the second The cylindrical secondary battery shown in FIG. 1 is manufactured by conductive connection through the connection member 34, the connection plate 35, and the diaphragm 37.

  As described above, in the cylindrical secondary battery according to the first embodiment of the present invention, the first separator 13 adjacent to the inside of the positive electrode lead 16, that is, the positive electrode current collecting member 31 side, is provided at a position corresponding to the positive electrode lead 16. A positioned insulating layer 18 was formed. The positive electrode lead 16 connected to the positive electrode current collecting member 31 is in contact with the insulating layer 18 formed on the first separator 13. For this reason, it is possible to prevent the positive electrode lead 16 from being deformed by being pulled toward the positive electrode current collecting member 31 side. Thus, since the deformation of the positive electrode lead 16 is prevented, it is possible to prevent an increase in the gap between the positive electrode lead 16 and the second separator 14 adjacent to the outside thereof. As a result, foreign matter can be prevented from entering through the gap between the positive electrode lead 16 and the second separator 14 adjacent to the outside, and as a result, internal short circuit caused by ionization of the foreign matter by the positive electrode can be prevented. The effect of doing.

  In addition, since the insulating layer 18 formed on the first separator 13 is discontinuously provided so as to be separated between the insulating layers 18, the insulating layer 18 is formed when the electrode group 10 is formed by winding around the shaft core 15. Therefore, the electrode group 10 can be easily manufactured. Further, since the thickness of the insulating layer 18 is equal to or less than the thickness of the positive electrode mixture 11b, the positive electrode lead 13 is inclined in the reverse direction with the positive electrode lead 16 welded to the positive electrode current collecting member 31. Therefore, it is possible to ensure connection strength because it prevents the excessive stress from acting.

(Embodiment 2)
FIG. 8 is an enlarged cross-sectional view showing Embodiment 2 of the cylindrical secondary battery of the present invention.
In the second embodiment, the insulating layer 18 is formed along the longitudinal direction of the side edge corresponding to the positive electrode lead 16 on the side facing the positive electrode 11 in the second separator 14 adjacent to the outside of the positive electrode sheet 11a. ing.
In the second embodiment, the positive electrode lead 16 welded to the positive electrode current collector 31 is pulled toward the positive electrode current collector 31 and tilted. For this reason, a gap is generated between the positive electrode lead 16 and the second separator 14 adjacent to the outside of the positive electrode lead 16. However, since the insulating layer 18 is formed on the side facing the positive electrode lead 16 of the second separator 14, the gap between the second separator 14 and the positive electrode lead 16 is equal to the thickness of the insulating layer 18. Becomes smaller.

In the second embodiment, reducing the gap between the second separator 14 and the positive electrode sheet 11a by providing the insulating layer 18 prevents a relatively large foreign substance that causes an internal short circuit from entering.
For this reason, even with the structure illustrated in FIG. 8, it is possible to prevent foreign matters from entering between the positive electrode sheet 11 a and the second separator 14, and to obtain an effect of preventing an internal short circuit.
In the second embodiment, the other configurations are the same as those in the first embodiment, and the same configurations are denoted by the same reference numerals and description thereof is omitted.

  The same applies to the second embodiment, and the insulating layer 18 is formed on the side edge corresponding to the positive electrode lead 16 on the side facing the positive electrode 11 in the second separator 14 adjacent to the outer side of the positive electrode sheet 11a. You may make it form continuously along a longitudinal direction.

  In each of the above embodiments, the lithium secondary battery has been described as an example of the cylindrical secondary battery. However, the present invention is not limited to the lithium battery, and other cylindrical types such as a nickel hydride battery and a nickel cadmium battery. The present invention can also be applied to secondary batteries.

  In addition, the cylindrical secondary battery of the present invention can be variously modified and configured within the scope of the gist of the invention. In short, the first separator, the positive electrode, the second separator, and the negative electrode A cylindrical secondary battery comprising an electrode group in which electrodes are stacked and wound around an axis, and a positive electrode current collector, wherein a positive electrode lead connected to the positive electrode current collector is formed on the positive electrode In the first separator or the second separator adjacent to the positive electrode, an insulating layer may be provided at least at a position corresponding to the positive electrode lead on the side facing the positive electrode.

DESCRIPTION OF SYMBOLS 1 Cylindrical secondary battery 2 Battery container 3 Upper cover 10 Electrode group 11 Positive electrode 11a Positive electrode sheet 11b Positive electrode mixture 12 Negative electrode 12a Negative electrode sheet 12b Negative electrode mixture 13 1st separator 14 2nd separator 15 Axis core 16 Positive electrode lead 17 Negative electrode lead 18 Insulating layer 20 Power generation unit 21 Negative electrode current collecting member 31 Positive electrode current collecting member 33 First connecting member 34 Second connecting member 35 Connecting plate 37 Cleavage plate 41 Insulating plate 43 Gasket

Claims (5)

  A first separator, a positive electrode, a second separator, and a negative electrode, and an electrode group wound around an axis, and a positive current collector; A positive electrode lead connected to the positive electrode, wherein the positive electrode lead on the side facing at least the positive electrode in the first separator or the second separator adjacent to the positive electrode A cylindrical secondary battery, characterized in that an insulating layer is provided at a location corresponding to.   2. The cylindrical secondary battery according to claim 1, wherein the thickness of the insulating layer is equal to or less than the thickness of the positive electrode mixture formed on the positive electrode sheet surface of the positive electrode facing the insulating layer. A cylindrical secondary battery characterized by the above.   3. The cylindrical secondary battery according to claim 1, wherein the insulating layer is provided on the first separator on the inner side adjacent to the positive electrode. 4. Secondary battery.   3. The cylindrical secondary battery according to claim 1, wherein the insulating layer is provided on the second separator on the outer side adjacent to the positive electrode. 4. Secondary battery. 5. The cylindrical secondary battery according to claim 1, wherein the insulating layer is formed separately between the positive electrode leads. 6.

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