JP5334894B2 - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a high capacity and a high output while securing safety by reducing the deviation of temperature distribution inside an electrode. <P>SOLUTION: A shaft core 10 of a wound electrode group is formed by bonding an aluminum positive electrode shaft core part 12 and a copper negative electrode shaft core part 11 together while insulating them from each other with an insulating material 13. The positive electrode shaft core part 12 has a positive electrode current collecting plate 12b formed at one end, and a joint portion 12J formed at the other end to form a "shiplap" joint in the thickness direction. The negative electrode shaft core part 11 has a negative electrode current collecting plate 11b formed at one end, and a joint portion 11J formed at the other end. The positive electrode shaft core part 12 and the negative electrode shaft core part 11 are bonded at their joint portions together with the insulating material 13 over both sides of which an adhesive material is applied. To current collecting portions 12a, 11a of the positive electrode shaft core part 12 and the negative electrode shaft core part 11, aluminum and copper electrode connection plates are connected, respectively, with ultrasonic welding. Thus, the shaft core is connected to an external thermal load in an electrical and heat conductive manner. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a lithium ion secondary battery in which a wound electrode group in which a positive electrode plate and a negative electrode plate are wound around an axis via a separator is accommodated in a battery container.

  In a large-sized lithium ion battery used for a power source for an electric vehicle, a porous polyethylene film is used as a separator separating positive and negative electrodes. When the large lithium ion secondary battery is overcharged, the heat generated by the chemical reaction between the non-aqueous electrolyte and the active material causes the polyethylene to soften and melt and shut down (block the pores and block the passage of lithium ions). Therefore, since charging / discharging is interrupted, it is possible to prevent a sudden rise in battery temperature.

  However, at the time of overcharging, there is a possibility that the temperature distribution inside the wound electrode group is biased and the progress of the shutdown of the porous separator may vary.

  In order to suppress an increase in battery temperature, for example, a cylindrical battery that dissipates heat inside the battery to the outside of the battery by arranging a metal shaft core at the center of the wound electrode group is known ( Patent Document 1).

Japanese Patent Laid-Open No. 10-92469

  The secondary battery of Patent Document 1 dissipates heat inside the battery from the battery container with a metal shaft core, but the temperature rise cannot be sufficiently suppressed because the shaft core and the positive and negative electrode plates are not connected.

(1) The lithium ion secondary battery according to the invention of claim 1 includes a positive electrode plate and a negative electrode plate in which an electrode layer is formed and a current collecting part on which the electrode layer is not formed is disposed on one side in the width direction. A wound electrode group wound around the separator so that the current collectors are opposite to each other, and a flat rectangular battery outer container containing the wound electrode group and having a negative electrode external terminal and a positive electrode external terminal; , extends in the center of the wound electrode group, wherein the current collector negative electrode axis portion connected to the (negative electrode current collecting portion) of the negative electrode plate, wherein the current collector of the positive electrode plate (positive electrode current collecting portion And a shaft core having an insulator that electrically insulates the negative electrode shaft portion and the positive electrode shaft core portion, and the negative electrode current collector portion is the negative electrode shaft core portion. Connected to the negative electrode external terminal via the positive electrode current collector via the positive electrode shaft core Characterized in that it is connected to the positive electrode external terminal Te. ( 2 ) The invention according to claim 2 is the lithium ion secondary battery according to claim 1 , wherein the wound electrode group includes a battery outer container such that the shaft core extends in a width direction of the battery outer container. The negative electrode shaft core portion is connected to a negative electrode connection member connected to the external negative electrode terminal, and the positive electrode shaft core portion is connected to a positive electrode connection member connected to the positive electrode external terminal. It is characterized by.
( 3 ) The invention of claim 3 is the lithium ion secondary battery according to claim 2 , wherein the negative electrode shaft core portion is electrically and thermally conductively connected to the negative electrode current collector and the negative electrode connecting member. The positive electrode shaft core portion is electrically and thermally conductively connected to the positive electrode current collector and the positive electrode connecting member.
( 4 ) The invention according to claim 4 is the lithium ion secondary battery according to claim 3 , wherein the wound electrode group is wound around the negative electrode core part and the positive electrode core part constituting the shaft core. The negative electrode shaft core part is provided with a core part (negative electrode core part) to which the negative electrode current collector part of the wound electrode group is connected, and the negative electrode connecting member provided at an end of the core part. A positive electrode shaft core portion connected to the positive electrode current collector portion of the wound electrode group (positive electrode core portion). And a current collector plate (axial positive electrode current collector plate) provided at an end portion of the winding core portion and connected to the positive electrode connecting member.
( 5 ) The invention of claim 5 is the lithium ion secondary battery according to claim 4 , wherein the negative electrode core part and the positive electrode core part are arranged in parallel to the wide side surface of the flat battery outer case. The axial negative electrode current collector plate and the axial positive electrode current collector plate are arranged in a direction orthogonal to the winding core part and are arranged in parallel to the narrow side surface of the flat battery outer container. It is characterized by that.
( 6 ) The invention according to claim 6 is the lithium ion secondary battery according to claim 5 , wherein the negative electrode core portion is connected to a negative electrode current collector portion of the negative electrode plate, and the axial negative electrode current collector plate is connected to the negative electrode. Each of the members is ultrasonically welded, the positive electrode core portion is ultrasonically welded to the positive electrode current collector of the positive electrode plate, and the axial core positive electrode current collector plate is ultrasonically welded to the positive electrode connecting member.
( 7 ) The invention according to claim 7 is the lithium ion secondary battery according to any one of claims 1 to 6 , wherein the insulator includes the negative electrode core part and the positive electrode core part. The negative electrode shaft core portion and the positive electrode shaft core portion have a width that is equal to or greater than a width of each of the positive and negative electrode current collector portions of the positive and negative electrode plates .
(8) According to an eighth aspect of the present invention, in the lithium ion secondary battery according to any one of the first to seventh aspects, a separator having at least one turn is wound on the outer surface of the shaft core. The electrode layer of the negative electrode plate and the electrode layer of the positive electrode plate are insulated from the shaft core.
( 9 ) In the lithium ion secondary battery according to the invention of claim 9 , the current collector is formed by interposing a positive electrode plate and a negative electrode plate each having a current collector portion on which one electrode layer is not formed on one side in the width direction through a separator. A wound electrode group wound so as to be opposite to each other, a battery exterior container containing the wound electrode group and having a negative electrode external terminal and a positive electrode external terminal, and a negative electrode extending in the center of the wound electrode group the electrode layer of the plate and the positive electrode plate possess the axis of metal that is connected to the battery outer case while being insulated, battery outer container is a flat rectangular, both ends of the shaft core, facing the battery outer container It is provided so that it may stretch between narrow side surfaces .

(11) A lithium ion secondary battery according to an eleventh aspect of the present invention includes a positive electrode plate and a negative electrode plate in which an electrode layer is formed and a current collecting portion on which the electrode layer is not formed is disposed on one side in the width direction. A wound electrode group wound through a separator so that the current collecting parts are opposite to each other, a battery outer container containing the wound electrode group and having a negative external terminal and a positive external terminal, It has a metal shaft core that extends to the center of the rotating electrode group and is connected to the battery outer casing while being insulated from the electrode layer of the negative electrode plate and the positive electrode plate.
(12) The lithium ion secondary battery according to claim 12 is the lithium ion secondary battery according to claim 12, wherein the battery outer casing is a flat rectangular shape, and both ends of the shaft core are between the opposing narrow side surfaces of the battery outer casing. It is provided so that it may stretch on.

  According to the present invention, heat generated inside the electrode group can be effectively radiated to the outside of the battery outer casing.

BRIEF DESCRIPTION OF THE DRAWINGS The external view which shows 1st Embodiment of the lithium ion secondary battery by this invention. The perspective view which shows the connection condition of the winding electrode group and lid | cover of the lithium ion secondary battery of FIG. The disassembled perspective view of the lithium ion secondary battery of FIG. The perspective view which shows the winding electrode group in 1st Embodiment of the lithium ion secondary battery by this invention. The front view which shows the electrode plate in the wound electrode group of FIG. The perspective view which shows the axial center in the wound electrode group of FIG. The perspective view which shows the axial center in 2nd Embodiment of the lithium ion secondary battery by this invention. The perspective view which shows the axial center in 3rd Embodiment of the lithium ion secondary battery by this invention. The perspective view which shows the axial center in 4th Embodiment of the lithium ion secondary battery by this invention. The disassembled perspective view which shows 5th Embodiment of the lithium ion secondary battery by this invention. FIG. 11 is a cross-sectional view of the lithium ion secondary battery in FIG. 10. The perspective view which shows the axial center of the lithium ion secondary battery of FIG. The perspective view which shows the axial center of the reference embodiment 1 of the lithium ion secondary battery by this invention. The perspective view which shows the axial center of the reference embodiment 2 of the lithium ion secondary battery by this invention.

[First embodiment]
With reference to FIGS. 1-6, embodiment of the square battery by this invention is described.
[Overall configuration of prismatic battery]
1 to 3, a rectangular battery 70 is configured by housing a flat wound electrode group 20 in a battery container 78 via an insulating sheet 79. The rectangular opening of the battery container 78 is sealed by laser welding a rectangular battery lid 75 to the battery container 78. The battery lid 75 is provided with a positive external terminal 73 and a negative external terminal 71. Electric power is supplied to the external load via the external terminals 73 and 71, or external generated power is charged to the wound electrode group 20 via the external terminals 73 and 71.

  The battery container 78 sealed with the battery lid 75 is referred to as a battery outer container. In this battery exterior container, a pair of wide side surfaces PW, a pair of narrow side surfaces PN, a bottom surface PB, and a battery lid 75 constitute a rectangular parallelepiped flat rectangular container.

  2 and 3, a positive electrode connecting member 74 is connected to the positive electrode shaft core portion 12 by ultrasonic welding, and the positive electrode connecting member 74 is connected to a positive electrode external terminal 73 of a flat lithium ion secondary battery. Has been. On the other hand, a negative electrode connecting member 72 is connected to the negative electrode shaft portion 11 by ultrasonic welding, and the negative electrode connecting member 72 is connected to a negative electrode external terminal 71 of the flat lithium ion secondary battery.

  The connection members 74 and 72 and the external terminals 73 and 71 are electrically insulated from the battery lid 75 by an insulating material (not shown). Further, a sealing material (not shown) is provided in the through hole of the battery lid 75 to prevent liquid leakage from the battery container.

  The battery lid 75 is provided with a liquid injection port 76 for injecting an electrolytic solution into the battery container 78, and the liquid injection port 76 is sealed by a liquid injection plug 80 after the electrolytic solution is injected. The battery cover 75 is also provided with a gas discharge valve 77. When the pressure in the battery container rises, the gas discharge valve 77 is opened to discharge gas from the inside, and the pressure in the battery container is reduced.

  The battery container 78 and the battery lid 75 are both made of an aluminum alloy. The positive side connecting member 74 and the external terminal 73 are made of an aluminum alloy, and the negative side connecting member 72 and the external terminal 71 are made of a copper alloy.

[Whole electrode group configuration]
As shown in FIG. 4, the wound electrode group 20 is formed by flattening the positive and negative electrode plates 40 and 30 with a separator 60 interposed around the shaft core 10 composed of the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11. It is composed by winding up to. As will be described later, the shaft core 10 is formed by integrating a positive electrode shaft core portion 12 constituting a positive electrode shaft core portion and a negative electrode shaft core portion 11 constituting a negative electrode shaft core portion via an insulating material 13 (see FIG. 6). It is a thing. The positive and negative electrode plates 40 and 30 are electrically and thermally conductively connected to the shaft core 10, respectively.

  The positive and negative electrode plates 40 and 30 have electrode layers 41 and 31 in which an active material mixture is applied on the positive and negative electrode current collector foils, at one end portion in the width direction (direction orthogonal to the winding direction) of each electrode foil. Are provided with positive and negative electrode current collectors 50a and 50b, respectively, to which no active material mixture is applied. Therefore, the positive and negative electrode current collectors 50a and 50b are formed at positions opposite to the width direction (axial core extending direction) of the wound electrode group 20, respectively. The positive electrode current collector 50a of the positive electrode plate 40 is connected to the positive electrode shaft core portion 12, and the negative electrode current collector portion 50b of the negative electrode plate 30 is connected to the negative electrode shaft core portion 11, respectively. Electrically and thermally conductively connected to the core parts 12 and 11.

[Electrode plate]
FIG. 5 shows a front view of the positive and negative electrode plates.
The positive and negative electrode plates 40 and 30 are configured by applying the active material mixture 41 and 31 on the positive and negative electrode current collector foil 50, and at one end portion in the width direction (direction orthogonal to the winding direction), Positive and negative electrode current collectors 50a and 50b to which the agents 41 and 31 are not applied are provided. The positive and negative electrode current collectors 50a and 50b are formed at opposite positions in the width direction of the wound electrode group 20, respectively.

  In the negative electrode plate 30, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a binder to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and N as a dispersion solvent. -Negative electrode mixture 31 was prepared by adding and kneading methyl pyrrolidone (hereinafter referred to as NMP). This negative electrode mixture 31 was applied to both sides of a 10 μm thick copper foil leaving a solid current collecting part 50b. Then, the negative electrode active material application part thickness 70micrometer negative electrode plate 30 which does not contain copper foil was obtained by drying, pressing, and cutting.

  In this embodiment, amorphous carbon is exemplified as the negative electrode active material. However, the present invention is not limited thereto, and natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, coke, etc. The carbonaceous material or the like may be used, and the particle shape is not particularly limited to a scaly shape, a spherical shape, a fibrous shape, a massive shape, or the like.

  Moreover, in this embodiment, although the example which used PVDF for the binder was shown, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose Polymers such as cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

Regarding the positive electrode plate 40, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. A positive electrode mixture 41 was prepared by adding NMP as a dispersion solvent thereto and kneading. This positive electrode mixture 41 was applied to both surfaces of an aluminum foil having a thickness of 20 μm, leaving a plain current collecting part 50a. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode plate 40 having a positive electrode active material application portion thickness of 90 μm that does not include an aluminum foil.

[Electrolyte]
In the lithium ion secondary battery according to the first embodiment using the positive and negative electrode plates 40 and 30 described above, an electrolytic solution exemplified below can be used. For example, a solution obtained by dissolving lithium hexafluorophosphate in a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) at a volume ratio of 1: 1: 1 to 1 mol / L. Use.

[Axis core]
As shown in FIG. 6, the shaft core 10 of the wound electrode group 20 is made of a positive electrode shaft core portion 12 made of aluminum or aluminum alloy as in the case of the positive electrode plate 40 and copper or copper alloy as in the case of the negative electrode plate 30. The negative electrode shaft core portion 11 is joined via an insulating material 13. The positive electrode shaft core portion 12 has a positive electrode core portion 12a and a positive electrode current collector plate 12b, and the negative electrode shaft core portion 11 has a negative electrode core portion 11a and a negative electrode current collector plate 11b.

A positive electrode current collector plate 12b is connected in a T-shape to one end of the positive electrode core 12a, and a joint portion 12J is formed on the other end to form a joint in the thickness direction. A negative electrode current collector plate 11b is connected in a T shape at one end of the negative electrode core portion 11a, and a joint portion 11J is formed at the other end portion to form a joint in the thickness direction. The positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are bonded to each other at the joint portions 12J and 11J by an insulating material (insulator) 13 in which an adhesive material is applied to both surfaces. As the insulating material 13, for example, a PPS resin having high heat resistance is used, and an acrylic resin is used as an adhesive material.
As described above, the shaft core 10 is formed in a three-layer flat plate shape in which insulation between the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 is ensured.

  That is, the negative electrode core part 11a and the positive electrode core part 12a are flat plates arranged in parallel to the wide side surface PW of the flat battery outer casing. Moreover, the negative electrode current collector plate 11b and the positive electrode current collector plate 12b are flat plates that are arranged orthogonal to the winding core portions 11a and 12a and are arranged in parallel to the narrow side surface PN of the flat battery outer casing.

  The positive electrode current collector 50 a extending along one long side of the wound electrode group 20 is connected to the positive electrode core part 12 a of the positive electrode shaft core part 12 by ultrasonic welding. The negative electrode current collector 50b extending along the side long side is connected to the negative electrode core part 11a of the negative electrode shaft core part 11 by ultrasonic welding. Thus, the positive electrode shaft core portion 12 and the positive electrode current collector portion 50a, and the negative electrode shaft core portion 11 and the negative electrode current collector portion 50b are electrically and thermally conductively connected, respectively.

  By forming the positive and negative current collector plates 12b and 11b, the positive electrode connecting member 74 and the positive electrode current collector plate 12b, and the negative electrode connecting member 72 and the negative electrode current collector plate 11b can be welded with a sufficient contact area, and good welding quality can be obtained. Can be secured.

  The width W of the shaft core 10 is equal to or greater than the width of the wound electrode group 20 because it is necessary to connect to the positive and negative electrode plates 40 and 30 at the current collectors 50 a and 50 b at both ends of the wound electrode group 20. Further, the minimum widths W12min and W11min of the positive and negative electrode winding core parts 12a and 11a are larger than the widths of the current collecting parts 50a and 50b.

  Since the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are insulated by the insulating material 13, the positive electrode external terminal 73 and the negative electrode external terminal 71 are insulated from each other by the insulating material 13 of the shaft core 10.

[Function and effect]
The effects of the lithium ion secondary battery 20 of the first embodiment described above will be described.
(1) At the winding center of the wound electrode group 20, the metal shaft core 12 made of the same material as the positive electrode connection member 74 and the metal shaft core 11 made of the same material as the negative electrode connection member 72 are connected by the insulating material 13. However, a single shaft core 10 is disposed, and the positive and negative shaft core portions 12 and 11 are joined to the positive and negative connection members 74 and 72. With such a structure, the heat inside the wound electrode group 20 is generated from the positive electrode shaft core portion 12 connected to the positive electrode current collector portion 50a and the negative electrode shaft core portion 11 connected to the negative electrode current collector portion 50b. The heat is radiated from the external terminals 73 and 71 of the respective poles that pass through the connection members 74 and 72 and protrude above the both ends of the battery lid 75.

  Therefore, the thermal resistance of the path from the shaft core 10 to the external terminals 73 and 71 can be reduced. As a result, for example, heat generated due to heat generated by a chemical reaction between the non-aqueous electrolyte and the active material at the time of battery abnormality such as overcharge is easily conducted from the shaft core 10 through the connecting members 74 and 72 to be radiated. Thus, an increase in the battery internal temperature can be suppressed.

  In addition, since the bias of the temperature distribution of the entire wound electrode group is reduced, the shutdown of the porous separator proceeds almost uniformly, and the safety when the battery is abnormal can be ensured.

(2) Since the positive electrode shaft core portion 12 and the positive electrode current collector portion 50a, and the negative electrode shaft core portion 11 and the negative electrode current collector portion 50b are independently and electrically connected to each other, the positive and negative electrode plates 30 , 40 is quickly transferred from the shaft core 10 to the external terminals 73 and 71 to be dissipated, so that uniform temperature distribution is promoted.

[Comparison evaluation]
In order to confirm the above-mentioned effect, after attaching a thermocouple to the side surface portion of the battery case 78 of the battery, keeping the outside air temperature at 25 ° C., and repeating charging / discharging 5 times at a current value (10 CA) at a 10 hour rate The time until the side surface temperature became 25 ° C., the same as the outside air temperature, was measured.

For comparison, the shaft core (Comparative Example 1) having the same shape and size as the shaft core 10 of the first embodiment is integrally formed only by the same material as the insulating agent 13. The shaft core of Comparative Example 1 was not joined to the electrode current collectors 50a and 50b, and the electrode current collectors 50a and 50b were directly joined to the connecting members 74 and 72.
A test similar to that of the first embodiment was performed on a comparative flat lithium ion secondary battery including the axial core of Comparative Example 1 as described above.

  As a result, the side surface temperature of the battery of the first embodiment reached 25 ° C. in 39% earlier than the side surface temperature of the flat lithium ion secondary battery of Comparative Example 1. From this result, it was proved that the heat dissipation of the lithium ion secondary battery of the first embodiment was improved.

[Second Embodiment]
Next, a second embodiment in which the present invention is applied to a flat lithium ion secondary battery will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment in a figure, or an equivalent, and description is abbreviate | omitted.

  The shaft core 10 is the same as that of the first embodiment in terms of the total width and length. As shown in FIG. 7, both the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are formed in a T shape, and the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are interposed between the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11. An insulating plate 14 integrated with the shaft core portion 11 by molding is formed.

  Since the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are insulated from each other by the insulating plate 14 and both are separated by the length of the insulating plate 14, extremely high insulation is ensured. The second embodiment is configured in the same manner as the flat lithium ion secondary battery of the first embodiment except that the shaft core 10 is changed in this way.

In order to confirm the effect of this embodiment, the same test as that of the first embodiment was performed.
For comparison, the shaft core of Comparative Example 2 having the same shape and dimensions as those of the shaft core 10 of the second embodiment is integrally formed only from the same material as the insulating plate 14. The shaft core of Comparative Example 2 was not joined to the electrode current collectors 50a and 50b, and the electrode current collectors 50a and 50b were joined to the connection members 74 and 72 directly.

  A test similar to that of the second embodiment was performed on the flat lithium ion secondary battery including the shaft core of Comparative Example 2 as described above. As a result, the side temperature of the battery of the second embodiment reached 25 ° C. in 2% earlier than the side temperature of the flat lithium ion secondary battery of Comparative Example 2. From this result, it can be said that the heat dissipation of the second embodiment was almost the same as that of the battery using the shaft core of Comparative Example 2. This is probably because the metal part of the shaft core is short, so that a large difference in heat dissipation effect was not produced compared to the battery to be compared.

[Third Embodiment]
Next, a third embodiment in which the present invention is applied to a flat lithium ion secondary battery will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment in a figure, or an equivalent, and description is abbreviate | omitted.

  In the third embodiment, as in the second embodiment, the positive electrode core portion 12 and the negative electrode core portion 11 are connected by interposing an insulating plate 14 by molding. The width W14 of the insulating plate 14 is shorter than that of the insulating material 14 of the second embodiment, and is approximately the same length as the widths W12 and W11 of the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11. That is, the widths W12 and W11 of the positive electrode shaft core portion 12 and the negative electrode shaft core portion 11 are longer than the widths W12 and W11 of the second embodiment. Other configurations are the same as those of the second embodiment.

In order to confirm the effect of this embodiment, the same test as that of the first embodiment was performed.
For comparison, the shaft core of Comparative Example 3 having the same shape and size as the shaft core 10 of the third embodiment is integrally formed only by the same material as the insulating plate 14. The shaft core of Comparative Example 3 was not joined to the electrode current collectors 50a and 50b, and the electrode current collectors 50a and 50b were joined to the connection members 74 and 72 directly.

  A test similar to that of the third embodiment was performed on the flat lithium ion secondary battery including the shaft core of Comparative Example 3 as described above. As a result, the side surface temperature of the battery of the third embodiment reached 25 ° C. in a time 17% faster than the side surface temperature of the flat lithium ion secondary battery of Comparative Example 3.

  From this result, it can be said that the heat dissipation of the third embodiment is improved. However, compared to the first embodiment in which the metal portion of the shaft core 10 exists up to the center of the wound electrode group 20, the insulating plate 14 is present in a certain range, so that the heat dissipation effect is inferior to the first embodiment. .

[Fourth Embodiment]
Next, a fourth embodiment in which the present invention is applied to a flat lithium ion secondary battery will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment in a figure, or an equivalent, and description is abbreviate | omitted.

The fourth embodiment employs joint portions 11J and 12J of “aijakuri joint” in the width direction instead of the joint portions 11J and 12J of “aijakuri joint” in the thickness direction of the first embodiment. .
Other configurations are the same as those of the first embodiment.

In order to confirm the effect of this embodiment, the same test as that of the first embodiment was performed.
For comparison, the shaft core of Comparative Example 4 having the same shape and dimensions as the shaft core 10 of the fourth embodiment is integrally formed only by the same material as the insulating material 13. The shaft core of Comparative Example 4 was not joined to the electrode current collectors 50a and 50b, and the electrode current collectors 50a and 50b were joined to the connection members 74 and 72 directly.

A test similar to that of the fourth embodiment was performed on the flat lithium ion secondary battery including the shaft core of Comparative Example 4 as described above. As a result, the side surface temperature of the battery of the fourth embodiment reached 25 ° C. in 36% earlier than the side surface temperature of the comparative flat lithium ion secondary battery.
From this result, it can be said that the heat dissipation of the fourth embodiment is improved.

[Fifth Embodiment]
Next, a fifth embodiment in which the present invention is applied to a flat lithium ion secondary battery will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment in a figure, or an equivalent, and description is abbreviate | omitted.

  As shown in FIGS. 10 to 12, the fifth embodiment includes an integral flat plate-shaped shaft core 10 </ b> A. The shaft core 10 </ b> A is formed by integrally molding the shaft core body 10 a and contact plates 10 b and 10 c that are provided at both ends of the shaft core body 10 a and are in contact with the inner surface of the battery container 78. The shaft core 10A is made of a metal such as aluminum, and is insulated from the current collectors 50a and 50b of the positive and negative electrode plates 40 and 30 by a separator. The shaft core 10A is not connected to the positive and negative electrode plates 40 and 30 and functions only as a heat conductor.

  10 and 11, each of the positive and negative electrode connecting members 74A and 72A has a different shape from each of the positive and negative electrode connecting members 74 and 72 of the first embodiment. That is, each of the positive and negative electrode connecting members 74A and 72A includes upper flat plate portions 74a and 72a and lower bifurcated portions 74b and 72b extending downwardly from the upper flat plate portions 74a and 72a. The lower bifurcated portions 74b and 72b are joined to the positive and negative current collecting portions 50a and 50b of the wound electrode group 20 by ultrasonic welding, respectively.

  The contact plates 10a and 10b of the shaft core 10A are in direct contact with each other so as to stretch on the inner surface of the battery case 78. Thereby, the heat generated inside the wound electrode group 20 is immediately transmitted to the battery container 78 via the shaft core 10A. Thereby, high heat dissipation performance is obtained. Moreover, the vibration suppression effect inside the container of the wound electrode group 20 can also be expected.

[ Reference Embodiment 1 ]
FIG. 13 is a diagram showing an axis 110 when the present invention is applied to a cylindrical lithium ion secondary battery.

In a cylindrical lithium ion secondary battery, a wound electrode group is housed in a bottomed cylindrical container having an opening at one end, an electrolyte is injected into the container, and then the opening is closed by a sealing body. Consists of. The wound electrode group is configured by winding a positive electrode plate and a negative electrode plate around a shaft core 110 shown in FIG.
The internal structure of the cylindrical lithium ion secondary battery is well known, and detailed description and illustration are omitted.

  A shaft core 110 shown in FIG. 13 has an aluminum positive electrode pipe 12 and a copper negative electrode pipe 111. The positive electrode pipe 112 and the negative electrode pipe 111 have “joint joints” 112J and 111J, and the joint parts 112J and 111J are bonded together by an insulating material (insulator) 113 as in the first embodiment. It is joined by "joint".

  The positive electrode 112 is welded with a positive electrode current collector not coated with the positive electrode mixture of the positive electrode plate, and the negative electrode 111 is welded with a negative electrode current collector uncoated with the negative electrode mixture of the negative electrode plate. . The positive electrode pipe 112 is electrically and thermally conductively connected to the positive electrode current collector, and the negative electrode pipe 111 is electrically and thermally conductively connected to the negative electrode current collector.

  The axial core 110 extends in the axial direction of the cylindrical battery case, the positive pipe 112 is electrically and thermally conductively connected to the positive external terminal, and the negative pipe 111 is electrically and thermally conductively connected to the negative external terminal. The heat of the wound electrode group is radiated to the outside. A positive electrode current collector component is fitted to the upper end of the positive electrode pipe 112, and the positive electrode current collector component is connected to an upper lid serving as a positive electrode external terminal by a positive electrode lead. A negative electrode current collector component is fitted to the lower end of the copper pipe 111, and the negative electrode current collector component is connected to the bottom of the container serving as a negative electrode external terminal by a negative electrode lead.

The cylindrical lithium ion secondary battery of Reference Embodiment 1 also has the same effect as that of the first embodiment. Further, the shaft core 110 of the present embodiment can be easily manufactured, the cost is low, and desired characteristics are obtained. It may be on the rod .

[Reference Embodiment 2]
FIG. 14 is a diagram showing a shaft core 210 when the present invention is applied to a cylindrical lithium ion secondary battery.

In the reference embodiment 2 , in place of the “joint joint” in the reference embodiment 1 , the positive electrode rod 212 and the negative electrode rod 211 are connected by the insulating rod 214 by molding as in the third embodiment. The insulating rod 214 is integrated between the positive electrode rod 212 and the negative electrode rod 211 by molding. The lengths of the positive electrode rod 212 and the negative electrode rod 211 are substantially equal, and the insulating rod 214 is about half the length of the positive electrode rod 212 and the negative electrode rod 211.

  The positive electrode rod 212 and the negative electrode rod 211 are insulated from each other by an insulating rod (insulator) 214, and are separated from each other by the length of the insulating rod 214, so that high insulation is ensured. The present embodiment is configured in the same manner as the cylindrical lithium ion secondary battery of the sixth embodiment, except that the shaft core 210 is changed in this way.

The cylindrical lithium ion secondary battery of Reference Embodiment 2 also has the same effect as that of the first embodiment. Further, the shaft core 110 of the present embodiment can be easily manufactured, the cost is low, and desired characteristics are obtained.

(1) In the first to fifth embodiments and the reference embodiments 1 and 2 described above, PVDF is used as a binder for the mixture layers 31 and 41 in the positive electrode plate 40 and the negative electrode plate 30. Fluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, fluorine Polymers such as chloroprene and acrylic resins, and mixtures thereof can be used.

(2) In the first to fifth embodiments and the reference embodiments 1 and 2 described above, lithium manganate having a stoichiometric composition (LiMn ₂ O ₄ ) is exemplified as the positive electrode active material, but has a spinel crystal structure. other lithium manganate (e.g., Li1 ₊ xMn 2 -xO ₄₎ or lithium manganese composite oxide part of the lithium manganate was replaced or doped with a metal element _{(e.g., Li1 + xMyMn 2 -x-yO} 4, M is Co, Ni , Fe, Cu, Al, Cr, Mg, Zn, V, Ga, B, F) or lithium cobaltate or lithium titanate having a layered crystal structure, or a part thereof is replaced with a metal element or A doped lithium-metal composite oxide may be used.

(3) In the first to fifth embodiments and the reference embodiments 1 and 2 described above, the insulating materials 13 and 113 and the insulating plates 14 and 214 of the shaft core use, for example, PPS resin having high heat resistance. An acrylic resin is used as the adhesive material, but the material is not limited to this as long as the insulating property is maintained and the adhesive strength is high.

(4) In the first to fifth embodiments and the reference embodiments 1 and 2 described above, an example in which aluminum and copper are used for the shaft core has been shown. However, the present invention is not limited to this. For example, an aluminum alloy There is no particular limitation as long as it has conductivity without being corroded by the battery potential of each electrode, such as copper alloy or nickel.

(5) In the first to fifth embodiments and the first and second embodiments described above, by winding only the separator 60 around the shaft core 10 one or more times in advance, Insulation between the negative electrode current collector 50b and the negative electrode shaft core 11 and the positive electrode current collector 50a is secured, but an insulating separator different from the separator 60 may be wound around the shaft 10.

(6) In the first to fifth embodiments and the first and second embodiments described above, the current collecting portions 50a and 50b of the positive and negative electrode plates 40 and 30, the positive electrode core portion 12 of the shaft core 10, and the negative electrode shaft The core 11 is joined by ultrasonic welding, but there is no particular limitation as long as it can be joined electrically and thermally conductively by resistance welding or other joining methods. The positive and negative connection members 74 and 72 and the axial collector plates 112b and 11b may be mechanically fastened with screws or the like.

In the first to fifth embodiments (7) above description, an example using LiPF ₆ as an electrolyte, it is not limited thereto, for _{example, LiClO 4, LiAsF 6, LiBF} 4, LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SOLi, or a mixture thereof can be used. Moreover, in this embodiment, although the example which used the mixed solvent of EC and DMC was shown as the solvent of nonaqueous electrolyte solution, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, 1, 2- dimethoxyethane, , 2-diethoxyethane, γ-butyllactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, propionitrile, etc. A mixed solvent of seeds or more may be used, and the mixing ratio is not limited.

(8) Although the shaft core 10 is integrally formed of metal in the fifth embodiment, it may be constituted by two metal members that are insulated and separated in the center as in the first to fourth embodiments. In this case, only the shaft core portion having the same potential as the potential of the battery container needs to be electrically and thermally conductively connected to the container, and the shaft core portions of other potentials need to be electrically and thermally conductively insulated.

(9) In Reference Embodiments 1 and 2 , the shapes shown in FIGS. 13 and 14 are adopted for the shaft core, which is a feature of the present invention, but the metal that can withstand the potential of the positive electrode is insulated from the metal that can withstand the potential of the negative electrode. It is not limited to this as long as it has a structure insulated with a material.

(10) In the first to fifth embodiments, the positive electrode shaft core portion 12 of the shaft core 10 and the external positive electrode 73 are electrically and thermally conductively connected by the positive electrode connecting member 74, and the negative electrode shaft core of the shaft core 10 is connected. Although the part 11 and the external negative electrode 71 are electrically and thermally conductively connected by the negative electrode connecting member 72, this connection structure is not limited to the shape and structure of the embodiment.

10, 10A, 110, 210: shaft cores 11, 110, 210: negative electrode shaft core portion 11a: negative electrode core portion 11b: negative electrode current collector plate 12, 112, 212: positive electrode shaft core portion 12a: negative electrode core portion 12b: Negative electrode collector plate 13: Insulating material 14: Insulating plate 20: Winding electrode group 30: Negative electrode plate 31: Negative electrode mixture layer 40: Positive electrode plate 41; Positive electrode mixture layer 50: Electrode foils 50a, 50b: Current collector 60 : Separator 70: Battery 71: External negative electrode terminal 72: Negative electrode connection plate 73: External positive electrode terminal 74: Positive electrode connection plate 75: Lid 78: Battery container

Claims (9)

An electrode layer is formed, and a current collecting part in which the electrode layer is not formed is arranged so that the current collecting part is opposite to each other through a separator with a positive electrode plate and a negative electrode plate arranged on one side in the width direction. A wound electrode group wound;
A flat rectangular battery outer case that houses the wound electrode group and has a negative external terminal and a positive external terminal;
It extends in the center of the wound electrode group, the current collector negative electrode axis portion connected to the (negative electrode current collecting portion) of the negative electrode plate, the current collector of the positive electrode plate (positive electrode current collecting portion) And a positive electrode shaft core portion connected to the shaft, and a shaft core having an insulator that electrically insulates the negative electrode shaft core portion and the positive electrode shaft core portion,
The negative current collector is connected to the negative external terminal via the negative axial core, and the positive current collector is connected to the positive external terminal via the positive axial core. Lithium ion secondary battery. The lithium ion secondary battery according to claim 1 ,
The wound electrode group is accommodated in the battery outer container so that the axial core extends in the width direction of the battery outer container,
The negative electrode shaft core part is connected to a negative electrode connection member connected to the external negative electrode terminal, and the positive electrode shaft core part is connected to a positive electrode connection member connected to the positive electrode external terminal. Lithium ion secondary battery. The lithium ion secondary battery according to claim 2 ,
The negative electrode shaft core portion is electrically and thermally conductively connected to the negative electrode current collector and the negative electrode connection member,
The lithium ion secondary battery, wherein the positive electrode shaft core portion is electrically and thermally conductively connected to the positive electrode current collector and the positive electrode connecting member. The lithium ion secondary battery according to claim 3 ,
The wound electrode group is wound around the negative electrode core part and the positive electrode core part constituting the shaft core,
The negative electrode shaft core part is connected to the winding core part (negative electrode winding core part) to which the negative electrode current collector part of the wound electrode group is connected and to the negative electrode connecting member provided at an end of the winding core part. Current collector plate (shaft core negative electrode current collector plate),
The positive electrode shaft core portion is connected to the winding core portion (positive electrode core portion) to which the positive electrode current collector portion of the wound electrode group is connected and to the positive electrode connecting member provided at an end of the winding core portion. A lithium ion secondary battery comprising a current collector plate (axial positive electrode current collector plate). The lithium ion secondary battery according to claim 4 ,
The negative electrode core part and the positive electrode core part are flat plates arranged in parallel to the wide side surface of the flat battery outer casing, and the axial negative electrode current collector plate and the axial positive electrode current collector plate A lithium ion secondary battery, characterized in that the lithium ion secondary battery is a flat plate arranged orthogonal to the core and parallel to the narrow side surface of the flat battery case. The lithium ion secondary battery according to claim 5 ,
The negative electrode core portion is ultrasonically welded to the negative electrode current collector portion of the negative electrode plate, and the axial core negative electrode current collector plate is ultrasonically welded to the negative electrode connection member, respectively.
The lithium ion secondary battery, wherein the positive electrode core is ultrasonically welded to the positive electrode current collector of the positive electrode plate, and the axial core positive electrode current collector is ultrasonically welded to the positive electrode connecting member. The lithium ion secondary battery according to any one of claims 1 to 6 ,
The insulator is provided over a predetermined length between the negative electrode core part and the positive electrode core part,
A width of the negative electrode shaft core portion and the positive electrode shaft core portion is equal to or greater than a width of each of the positive and negative electrode current collecting portions of the positive and negative electrode plates. The lithium ion secondary battery according to any one of claims 1 to 7 ,
A lithium ion secondary battery, wherein a separator having at least one turn is wound on an outer surface of the shaft core, and the electrode layer of the negative electrode plate and the electrode layer of the positive electrode plate are insulated from the shaft core. An electrode layer is formed, and a current collecting part in which the electrode layer is not formed is arranged so that the current collecting part is opposite to each other through a separator with a positive electrode plate and a negative electrode plate arranged on one side in the width direction. A wound electrode group wound;
A battery outer case containing the wound electrode group and having a negative electrode external terminal and a positive electrode external terminal;
It extends in the center of the wound electrode group, wherein the negative electrode plate and a positive plate electrode layer possess a axial core made of metal that is connected to the battery outer case while being insulated,
The battery outer container is a flat rectangular shape, and both ends of the shaft core are provided so as to be stretched between the opposing narrow side surfaces of the battery outer container .

Images