JP2018181544A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery arranged so as to be able to suppress the infiltration of moisture from outside a battery case to the inside and the leak of a nonaqueous electrolyte solution from inside the battery case to the outside, and to prevent the malfunction of a current interrupt mechanism and a gas-exhaust valve owing to the rise of an internal pressure of the battery case.SOLUTION: A nonaqueous electrolyte secondary battery herein disclosed comprises a gasket 500. The gasket includes: a first gasket 510 disposed so as to be in close contact with an inner face of a lid 22 and formed by a synthetic resin; and a second gasket 520 disposed between the first gasket 510 and a second lead part 424, and formed by an elastic resin higher, in gas permeability constant, than that of the first gasket 510. In addition, the second gasket has an insertion hole 522 of which the diameter is larger than that of an insertion hole 512 of the first gasket. Between the first gasket 510 and the second lead part 424, a gap A is formed adjacently to a side wall 524 of the insertion hole of the second gasket.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Lithium ion secondary batteries, sodium ion secondary batteries and other non-aqueous electrolyte secondary batteries are becoming increasingly important as power sources for vehicle mounting or as power sources for personal computers, portable terminals and the like. In particular, a lithium ion secondary battery which is light in weight and capable of obtaining a high energy density is preferably used as a high output power supply for vehicle mounting.

Such a non-aqueous electrolyte secondary battery includes, for example, a battery case to which a battery case main body and a lid are welded, an electrode body accommodated in the battery case, and a current collector electrically connected to the electrode body. Terminals (positive electrode current collector terminal and negative electrode current collector terminal) and terminals for external connection (positive electrode terminal and negative electrode terminal) provided on the outer surface of the lid (meaning the outer surface of the battery case, the same applies hereinafter) Is equipped. In this non-aqueous electrolyte secondary battery, the positive and negative electrode current collector terminals and the positive and negative electrode terminals are electrically connected through the insertion holes formed through the lid.
Further, the peripheral edge of the insertion hole is sealed (sealed) by sandwiching an insulating gasket between the lid and the current collection terminal inside the battery case and sealing (sealing), as well as the battery case and the current collection. Insulation with the terminals is performed.

  As said gasket, the thing of patent document 1 is known, for example. The gasket described in Patent Document 1 (FIG. 2 of Patent Document 1) has an insulating interposition portion sandwiched between the positive electrode terminal member (FIG. 1 of Patent Document 1) and the inner surface side of the battery case lid. The insulating intervening portion is made of a synthetic resin, and the degree of crystallinity is higher than the degree of crystallinity of the portions other than the insulating intervening portion (the insertion portion and the insulating side wall portion). In such a gasket, since the density of the insulating interposition part is high, it is difficult for molecules constituting the electrolytic solution to permeate through the insulating interposition part, so there is no possibility that the electrolytic solution leaks to the outside of the battery through the inside of the gasket.

JP, 2014-029839, A

By the way, in a non-aqueous electrolyte secondary battery in which the electrolyte solution is composed of a non-aqueous solvent, a gas such as carbon dioxide (CO ₂ ) is generated inside the battery case due to charge and discharge, overcharge or storage under high temperature. May. In addition, moisture may intrude into the inside of the battery to deteriorate the battery characteristics and generate the above-mentioned gas.
Therefore, in the non-aqueous electrolyte secondary battery, the cover is provided with a gas discharge valve for discharging the gas generated inside the battery case to the outside of the battery case. In addition, a non-aqueous electrolyte secondary battery is provided with a pressure-operated current interrupt device (CID: Current Interrupt Device) that shuts off the current path of the battery when the battery is overcharged. There is also a lithium ion secondary battery including a gas generating agent capable of generating a gas (for example, CO ₂ gas) by decomposing the non-aqueous electrolyte when a predetermined battery voltage is exceeded. The gas generating agent is decomposed when the battery is overcharged to generate a predetermined type of gas. And the internal pressure in a battery case rises by the gas pressure, and it is comprised so that the electric current interruption mechanism which detected the pressure rise may operate | move.

However, if the density of the gasket interposed between the lid and the current collection terminal is excessively high, permeation of gases such as carbon monoxide (CO) and carbon dioxide (CO ₂ ) to the outside of the battery is suppressed. Since the battery internal pressure tends to rise, an erroneous operation may occur such as the current shutoff mechanism and / or the gas discharge valve operating unexpectedly early. Also, conversely, if the density of the gasket is too low, an increase in the amount of water entering the inside of the battery case from the outside of the battery case may occur, which is not preferable.

  Therefore, the present invention has been created to solve the above-mentioned problems, and it is intended to suppress the infiltration of water from the outside of the battery case into the inside of the case, a current interrupting mechanism by the internal pressure increase of the battery case, and a gas discharge valve. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery capable of achieving both the malfunction prevention and the non-aqueous electrolyte secondary battery.

In order to achieve the above object, the present invention is
A battery case having a battery case body having an opening, a lid closing the opening, and a connection terminal for external connection provided on the outer surface side of the lid;
An electrode body housed inside the battery case,
A current collection terminal electrically connected to the electrode body at one end inside the battery case and electrically connected to the connection terminal via the insertion hole provided at the other end of the lid;
An insertion hole through which the current collection terminal is inserted is provided, and the battery case is provided with a gasket which is held between the lid and the current collection terminal inside the battery case and seals the space between the lid and the current collection terminal Provided is a non-aqueous electrolyte secondary battery.
And, the gasket of the non-aqueous electrolyte secondary battery disclosed herein is
A first gasket disposed in close contact with the inner surface of the lid and formed of a synthetic resin;
And a second gasket disposed between the first gasket and the current collector terminal and formed of an elastic resin having a gas permeability coefficient higher than that of the first gasket,
The diameter of the insertion hole of the second gasket is larger than the diameter of the insertion hole of the first gasket, and a gap adjacent to the side wall of the insertion hole of the second gasket is formed between the first gasket and the current collector terminal. It is characterized by

In the non-aqueous electrolyte secondary battery disclosed herein, the gasket is divided into two, a first gasket and a second gasket, and the second gasket is relatively gas permeable as compared to the first gasket. It is formed of an elastic resin having a high coefficient. The second gasket has an insertion hole larger than the first gasket, and is disposed between the first gasket and the current collecting terminal. Thus, an air gap adjacent to the side wall of the insertion hole of the second gasket is formed between the first gasket and the current collecting terminal.
In the non-aqueous electrolyte secondary battery having such a structure, the gas generated in the battery case first passes through the second gasket having a high gas permeability coefficient, and then passes through the gap adjacent to the second gasket, After that, it is discharged out of the battery case. That is, in the non-aqueous electrolyte secondary battery disclosed herein, a gas discharge path is formed which passes through the second gasket formed of an elastic resin having a high gas permeability coefficient and the air gap. Therefore, the gas generated in the battery case can be suitably discharged to the outside, and the erroneous operation of the current shutoff mechanism and the gas discharge valve due to the increase in the internal pressure of the battery case can be prevented.

On the other hand, when the gas discharge path excellent in gas permeability as described above is formed in order to suitably discharge the gas in the battery case, moisture easily infiltrates the inside of the battery case from the outside through the gas discharge path. Become. However, in the non-aqueous electrolyte secondary battery disclosed herein, when the battery is exposed to a high-temperature, high-humidity environment in which water easily infiltrates, the gas discharge path is blocked and water infiltrates into the case. Can be prevented.
Specifically, in the non-aqueous electrolyte secondary battery disclosed herein, the first gasket made of a synthetic resin expands when exposed to a high-temperature, high-humidity environment in which water easily intrudes from the outside. At this time, the second gasket made of the elastic resin is compressed, and the first gasket and the current collecting terminal come close to each other, so that the gap that constitutes the gas discharge path becomes smaller. As a result, the gas discharge path formed by the second gasket and the air gap is blocked by the first gasket, and it is possible to suppress the entry of moisture from the outside into the battery case.

BRIEF DESCRIPTION OF THE DRAWINGS It is a fragmentary sectional view which shows typically the external shape of the lithium ion secondary battery which is one Embodiment of the non-aqueous-electrolyte secondary battery disclosed here. It is a disassembled perspective view which shows the cover body and current collection terminal with which the lithium ion secondary battery shown in FIG. 1 was equipped. It is sectional drawing which shows typically the insulation structure at the side of the positive electrode of the lithium ion secondary battery shown in FIG. It is sectional drawing which shows typically the insulation structure by the side of the positive electrode shown in FIG. 3 when a lithium ion secondary battery is expose | bleached to high temperature and high humidity environment. It is a graph which shows the measurement result of the water permeation amount of Experiment 1-Experiment 3. FIG. It is a graph which shows the measurement result of the gas discharge amount of Experiment 1-Experiment 3. FIG. FIG. 6 is a cross-sectional view schematically showing an insulation structure on the positive electrode side of the lithium ion secondary batteries of Test Example 2 and Test Example 3.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, matters other than the matters specifically mentioned in the present specification and necessary for the practice of the present invention (for example, the general configuration and manufacturing process of the battery not characterizing the present invention) It can be understood as a design matter of a person skilled in the art based on the prior art. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field. Moreover, in each drawing, the same code | symbol is attached | subjected to the member and site | part which show the same effect | action. In addition, dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

In the present specification, the term "secondary battery" refers to a storage device in general that can be repeatedly charged and discharged, and is a term including so-called storage batteries such as lithium ion secondary batteries and storage elements such as electric double layer capacitors. Moreover, "a non-aqueous-electrolyte secondary battery" means the secondary battery provided with non-aqueous electrolyte (namely, electrolyte solution which contains a support electrolyte in non-aqueous solvent). The term "lithium ion secondary battery" refers to a secondary battery in which lithium ions are used as charge carriers and charge and discharge are performed by the movement of lithium ions between the positive and negative electrodes.
Hereinafter, the present invention will be described in detail by taking a flat angle lithium ion secondary battery as an example. The embodiments described below are not intended to limit the present invention to those described in such embodiments.

  FIG. 1 is a partial cross-sectional view schematically showing the outer shape of the lithium ion secondary battery according to the present embodiment, and FIG. 2 is a lid and a current collector terminal provided in the lithium ion secondary battery shown in FIG. It is an exploded perspective view showing. FIG. 3 is a cross-sectional view schematically showing an insulation structure on the positive electrode side of the lithium ion secondary battery shown in FIG. In the following description, the lithium ion secondary battery may be simply referred to as a battery.

  The lithium ion secondary battery 10 according to the present embodiment has a configuration in which a wound electrode body 30 provided with a predetermined battery constituent material is accommodated in a battery case 20 together with a suitable non-aqueous electrolyte. In the present embodiment, the lithium ion secondary battery 10 is a square battery, but the shape of the battery is not limited to a square, and may be a cylindrical shape or the like.

  The battery case 20 closes a so-called rectangular battery case main body 21 formed in a flat and bottomed rectangular parallelepiped shape, an opening 21A formed in the upper part of the battery case main body 21, and the opening 21A. And a lid 22. Specifically, the lid 22 is fitted by fitting the lid 22 into the opening 21A of the battery case body 21 and laser welding the seam 25 of the outer edge of the lid 22 and the battery case body 21 around the opening 21A. It is fixed to the battery case body 21 and seals the inside of the battery case 20.

  The material of the battery case 20 may be the same as that used in the conventional non-aqueous electrolyte secondary battery, and is not particularly limited. A battery case 20 mainly composed of a lightweight and thermally conductive metal material is preferable, and examples of such metal materials include aluminum, stainless steel, nickel plated steel, and the like. The battery case 20 (specifically, the battery case body 21 and the lid 22) used in the present embodiment is made of aluminum or an alloy mainly composed of aluminum.

  The outer shape of the lid 22 is a substantially rectangular shape that conforms to the shape of the opening 21A (the opening shape of the battery case body 21). At a central portion of the lid 22, a gas discharge valve 27 is provided to open the internal pressure by connecting the inside and the outside of the case when the internal pressure of the battery case 20 increases. Next to the gas discharge valve 27, an inlet 28 for injecting an electrolyte at the time of manufacturing the battery is provided. A pouring plug 29 is placed on the inlet 28 and fixed by welding. As a result, the inlet 28 is sealed (sealed).

  The wound electrode body 30 is housed in the battery case main body 21 so that the winding axis thereof is substantially parallel to the lid 22. Similar to the wound electrode body of a normal lithium ion secondary battery, the wound electrode body 30 has a sheet-like separator (separator sheet) 36 between the sheet-like positive electrode (positive electrode sheet) 32 and the negative electrode (negative electrode sheet) 34. It can be produced by laminating while being interposed, winding in the longitudinal direction, and kneading.

  The material and member itself which comprise the winding electrode body 30 may be the same as the electrode body with which the conventional lithium ion secondary battery is equipped, and are not particularly limited. The wound electrode body 30 of the present embodiment includes a positive electrode sheet 32 having a positive electrode active material layer on a long positive electrode current collector (for example, aluminum foil), and a long negative electrode current collector (for example, copper foil) A negative electrode sheet 34 having a negative electrode active material layer thereon and a separator sheet 36 are included.

As a positive electrode active material, the oxide type active material of the layer structure used for the positive electrode of a general lithium ion secondary battery, the oxide type active material of a spinel structure, etc. can be used preferably. Representative examples of such active materials include lithium transition metal oxides such as lithium cobalt-based oxides, lithium nickel-based oxides, and lithium manganese-based oxides. Examples of the negative electrode active material include carbon materials such as graphite (graphite), non-graphitizable carbon (hard carbon), and graphitizable carbon (soft carbon).
As the separator sheet 36, for example, a porous sheet made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide, a non-woven fabric, or the like can be used.

The non-aqueous electrolyte is filled in the battery case 20 and is interposed between the positive electrode sheet 32 and the negative electrode sheet 34. The non-aqueous electrolyte contains a support salt in a suitable non-aqueous solvent, and a non-aqueous electrolyte conventionally known as a lithium ion secondary battery can be used without particular limitation. For example, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) or the like can be used as the non-aqueous solvent. As the supporting salt, for example, it can be suitably used a lithium salt such as LiPF _6.

The positive electrode current collector terminal 40 is welded to the positive electrode sheet 32, and the negative electrode current collector terminal 80 is welded to the negative electrode sheet 34 so as to be electrically connected. These current collection terminals 40 and 80 are provided with positive and negative terminal lead holes (insertion holes) 242 and 244 respectively provided in the vicinity of one end and the other end in the longitudinal direction of the lid 22. It penetrates, respectively, and is pulled out from the inside of battery case 20 outside. As shown in FIG. 1 and FIG. 2, the positive electrode current collector terminal 40 electrically connects the positive electrode internal terminal 420 located mainly inside the battery case 20 and the positive electrode external terminal 460 located mainly outside the battery case 20. It has a connected configuration. The negative electrode current collector terminal 80 also has a configuration in which a negative electrode internal terminal 820 and a negative electrode external terminal 860, which are formed in substantially the same shape as the positive electrode side, are electrically connected.
Hereinafter, the terminal structure according to the present embodiment will be described in detail mainly on the positive electrode side, and the description will be simplified or omitted for the negative electrode side having a terminal structure of substantially the same shape.

As shown in FIG. 1, the lower end 422A of the positive electrode internal terminal 420 is joined and electrically connected to the positive electrode sheet 32, for example, by ultrasonic welding. As shown in FIG. 2, the positive electrode internal terminal 420 is formed following the upper end of the plate-like (strip-like) first lead portion 422 extending from the lower end 422A toward the lid 22 and the upper end of the first lead portion 422. Flat from the inside of the lid 22 (refers to the inner surface of the battery case; the same applies hereinafter). And a protrusion 426 extending substantially perpendicularly from the central portion of the plate surface of the second lead portion 424 to the outward direction of the battery.
The projecting portion 426 is configured as a rivet portion, and the rivet portion is penetrated through the terminal lead hole 242 and the insertion hole (rivet hole) 462A of the positive electrode external terminal 460, and caulking as shown in FIG. 420 and the positive electrode external terminal 460 are connected (fastened). As a constituent material of the positive electrode internal terminal 420 and the positive electrode external terminal 460, a metal material having high conductivity is preferable, and typically, aluminum is used.
The upper surface of the second lead portion 424 is in close contact with the gasket 500, and the projection 426 is inserted into the insertion holes 512 and 522 of the gasket 500, which will be described later.

  As shown in FIG. 2, the positive electrode external terminal 460 has a first connection portion 462 having an insertion hole 462A through which the protruding portion 426 of the positive electrode internal terminal 420 can be inserted, and the longitudinal direction of the lid 22 from the first connection portion 462 The second connection portion (outer end) 464 is formed to be stepped up in a step-like manner to the outside of the battery case 20 following the center side. As shown in FIG. 2, the second connection portion 464 is formed with a bolt insertion hole 464A through which the shaft portion 674 of the connection terminal (terminal bolt 670) for external connection can be inserted. The terminal bolt 670 is connected (fixed) to the positive electrode external terminal 460 by inserting the shaft portion 674 of the terminal bolt 670 upward from below into the bolt insertion hole 464A and tightening the fixing nut (not shown) to the shaft portion 674. be able to.

Further, in the present embodiment, the insulator 60 is disposed on the outer surface side of the lid 22 in order to prevent the positive electrode internal terminal 420, the positive electrode external terminal 460, and the terminal bolt 670 from energizing the lid 22. ing.
The insulator 60 has a second connection of the positive electrode external terminal 460 and the attachment portion 620 sandwiched between the vicinity of the terminal extraction hole 242 on the upper surface (surface) of the lid 22 and the first connection portion 462 of the positive electrode external terminal 460. And an extending portion 640 interposed between the portion 464 and the lid 22. The mounting portion 620 has a saucer that extends along the outer surface of the lid 22. The first connection portion 462 of the positive electrode external terminal 460 is disposed in accordance with the recess of the plate portion.
The extension portion 640 is formed with a bolt receiving hole 642 capable of receiving the head portion 672 of the terminal bolt 670. The head portion 672 of the terminal bolt 670 is formed to have a rectangular shape which is smaller than the bolt receiving hole 642 of the insulator 60 in the cross section perpendicular to the shaft portion 674. Terminal bolt 670 is restricted in rotation (the rotation is blocked) by inserting head portion 672 into bolt receiving hole 642, and shaft portion 674 protrudes through bolt insertion hole 464 A of positive electrode external terminal 460. It is arranged (mounted).

  In addition, the mounting portion 620 of the insulator 60 is provided with a through hole 622 through which the projection 426 of the positive electrode internal terminal 420 is inserted. Then, as shown in FIG. 3, a cylindrical convex portion 624 is provided around the through hole 622 on the lower surface of the insulator 60. The convex portion 624 is inserted into the terminal lead-out hole 242 of the lid 22, and prevents the lid 22 and the positive electrode internal terminal 420 from being energized within the terminal lead-out hole 242.

  The gasket 500 is a member held between the cover 22 and the positive electrode current collector terminal 40 (the second lead portion 424 of the positive electrode internal terminal 420) inside the battery case 20, and the cover 22 and the positive electrode current collector terminal It seals between 40 and. As shown in FIGS. 2 and 3, the gasket 500 according to the present embodiment includes two gaskets of a first gasket 510 and a second gasket 520.

The first gasket 510 is made of synthetic resin that is expanded and contracted by heat, and an insertion hole 512 for inserting the protrusion 426 of the positive electrode current collector terminal 40 is provided at the center. The insertion hole 512 has a diameter substantially equal to the outer diameter of the cylindrical convex portion 624 provided in the insulator 60, and the outer peripheral surface of the convex portion 624 is in close contact with the side wall of the insertion hole 512. There is.
Further, as shown in FIG. 3, one wide surface (upper surface) of the first gasket 510 is formed flat so as to be in close contact with the inner surface of the lid 22. On the other hand, on the other wide surface (lower surface) of the first gasket 510, an inclined surface is formed so that the thickness L4 of the first gasket 510 decreases as going radially outward of the insertion hole 512 There is.
As a constituent material of the first gasket 510, a resin material having relatively low permeability to moisture and gas (such as CO ₂ gas) as compared to the constituent material of a second gasket 520 described later is used. Specific examples include hydrophobic polyolefin resins (eg, polypropylene (PP), polyethylene (PE)), fluorine resins (eg, perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), etc.) It can be mentioned.

On the other hand, the second gasket 520 is made of an elastic resin having elasticity higher than that of the synthetic resin constituting the first gasket 510 described above. An insertion hole 522 for inserting the protrusion 426 of the positive electrode current collector terminal 40 is provided at the center of the second gasket 520. In the present embodiment, the insertion hole 522 of the second gasket 520 has a diameter larger than that of the insertion hole 512 of the first gasket 510.
The second gasket 520 is disposed between the first gasket 510 and the positive electrode current collector terminal 40 (the second lead portion 424 of the positive electrode internal terminal 420). Specifically, an inclined surface corresponding to the inclination of the lower surface of the first gasket 510 is formed on one wide surface (upper surface) of the second gasket 520, and the second gasket 520 is in close contact with the lower surface of the first gasket 510. There is. In addition, an inclined surface corresponding to the inclination of the upper surface of the second lead portion 424 of the positive electrode internal terminal 420 is formed on the other wide surface (lower surface) of the second gasket 520, and is closely attached to the second lead portion 424. doing.

As a constituent material of the second gasket 520, an elastic resin having higher permeability to moisture and gas (such as CO ₂ gas) as compared to the first gasket 510 is used. Specific examples of such an elastic resin include ethylene-propylene rubber, butyl rubber and the like. The gas permeability coefficient of the elastic resin used for the second gasket 520 is, for example, 100 to 1,500 (unit: 1 × 10 ⁻¹⁰ cm ³ (STP) · cm / (cm ² · s · cmHG)). Is preferred. Thus, the gas generated inside the battery case 20 can be discharged to the outside more suitably.

And in this embodiment, after arranging the 1st gasket 510 and the 2nd gasket 520 near the terminal lead-out hole 242 of the inner surface of lid 22, insulator 60 is carried out near the terminal lead-out hole 242 of the outer surface of lid 22. It arrange | positions and the positive electrode external terminal 460 is arrange | positioned further above. Then, the protruding portion 426 of the positive electrode internal terminal 420 is inserted into the terminal extraction hole 242 of the lid 22, and the first gasket 510 and the second gasket described above are formed between the inner surface of the lid 22 and the second lead portion 424. Hold 520 in place. Then, by pressing so as to sandwich the upper end of the protruding portion 426 of the positive electrode internal terminal 420 and the lower surface of the second lead portion 424, caulking is performed.
By this caulking process, the upper end of the projecting portion 426 is deformed into a disk shape to fix the positive electrode current collector terminal 40 to the lid 22, and between the lid 22 and the second lead portion 424 of the positive electrode current collector terminal 40. As a result of the gasket 500 being compressed, the periphery of the terminal extraction hole 242 is sealed (sealed).

At this time, in the present embodiment, since the diameter of the insertion hole 522 of the second gasket 520 is larger than the diameter of the insertion hole 512 of the first gasket 510, the lower surface of the first gasket 510 and the positive electrode current collector terminal 40 An air gap A adjacent to the side wall 524 of the insertion hole 522 of the second gasket 520 is formed between the second lead portion 424 and the upper surface).
In the non-aqueous electrolyte secondary battery 10 according to the present embodiment having such a structure, the gas discharge path B configured by the second gasket 520, the above-described air gap A, and the insulator 60 is formed. Since the second gasket 520 formed of an elastic resin having high gas permeability and the air gap A are disposed in the gas discharge path B, the gas generated inside the battery case 20 is suitably discharged to the outside. Can. For this reason, according to the present embodiment, it is possible to prevent the erroneous operation of the current shutoff mechanism and the gas discharge valve due to the increase in the internal pressure of the battery case 20.

On the other hand, since the gas discharge path B described above has high gas permeability, when the battery is exposed to a high-temperature and high-humidity environment, moisture easily infiltrates the inside from the outside of the battery case 20 through the gas discharge path B. There is a risk. However, in the non-aqueous electrolyte secondary battery 10 according to the present embodiment, when the battery is exposed to a high temperature and high humidity environment, as shown in FIG. The second gasket 520 is compressed to reduce the gap A. As described above, since the gas discharge path B is blocked by the first gasket 510, it is possible to prevent water from entering the inside of the battery case 20 even when the battery is exposed to a high temperature and high humidity environment.
In addition, the dimension L5 of the vertical direction of the space | gap A in a high temperature and high humidity environment is prescribed | regulated based on a following formula (1). In the following (1), L4 is the thickness of the first gasket, K is the thermal expansion coefficient of the first gasket, T1 is the battery temperature in a high temperature environment, and T2 is the battery temperature in a normal temperature environment. At this time, based on the following equation (1), the dimensions and the first dimensions of the members are set so that the sufficiently large air gap A is formed in the normal temperature environment and the air gap A is appropriately reduced in the high temperature and high humidity environment Preferably, the material of the gasket 510 is set.
L5 ≧ L4 × K × (T1-T2) (1)

  In the case where an inclined surface is provided on the lower surface of the first gasket 510 and the upper surface of the second gasket 520 is inclined to correspond to the inclined surface as in the present embodiment, the first gasket 510 thermally expands. When the second gasket 520 is compressed, the lower surface of the first gasket 510 and the upper surface of the second lead portion 424 can be in contact with each other to completely close the gap A. In this way, it is possible to more reliably prevent the entry of water in a high temperature and high humidity environment.

  In general, when the battery is exposed to a high temperature environment, components of the non-aqueous electrolyte (typically, non-aqueous solvent) may be vaporized and leak out of the battery case 20. In the present embodiment, as described above, when the battery is exposed to a high temperature environment, the gas discharge path B can be shut off by the expanded first gasket 510. Leakage can also be suitably prevented.

The dimensions of each member in the non-aqueous electrolyte secondary battery according to the present embodiment are preferably set appropriately in consideration of various conditions. For example, the relationship between the dimension L1 of the caulking portion of the protrusion 426, the dimension L2 of the air gap A in the radial direction of the insertion hole 522, and the dimension L3 of the second gasket 520 in the radial direction satisfies the following equation (2) Is preferable. As a result, the caulking pressure is appropriately applied to each of the first gasket 510 and the second gasket 520, so that the air gap A with a suitable longitudinal dimension L5 can be formed, and more preferably, inside the battery case 20. It will be possible to discharge the gas.
L1 ≧ L2 + L3 (2)

[Test example]
Hereinafter, although the test example regarding this invention is demonstrated, it is not intending limiting this invention to what is shown to this specific example.

  In this test example, three types of non-aqueous electrolyte secondary batteries having different gasket structures are manufactured, and for each battery, the amount of water intruding into the battery case and the discharge of carbon dioxide gas to the outside of the battery case The amount was measured.

1. Test Examples (1) Test Example 1
In Test Example 1, a lithium ion secondary battery 10 as shown in FIG. 1 was produced. Then, as shown in FIG. 3, the first gasket 510 and the second gasket 520 are disposed between the lid 22 and the second lead portion 424 and then caulking is performed to thereby form the first gasket 510 and the second gasket. The positive electrode current collector terminal 40 in which the air gap A adjacent to the second gasket 520 was formed between the lead 424 and the lead portion 424 was constructed. In addition, polyethylene (PE) whose thermal expansion coefficient is 0.00015 [K ^-1 ] is used as the material of the first gasket 510, and ethylene propylene diene rubber (EPDM) is used as the material of the second gasket 520. did. Further, the pressure of the above-described caulking process was set such that the compression rate of the first gasket 510 was 5% and the compression rate of the second gasket 520 was 15% in a normal temperature environment (20 ° C.).

  In the battery of Test Example 1, the dimension L1 of the caulking portion of the protrusion is 6 mm, the dimension L2 of the air gap in the radial direction is 2 mm, the dimension L3 of the second gasket in the radial direction is 4 mm, and the thickness L4 of the first gasket is 1 mm. The longitudinal dimension L5 of the air gap at 20 ° C. was set to 0.003 mm.

(2) Test example 2
In Test Example 2, as shown in FIG. 7, using a single gasket 700 made of polyethylene (PE), the pressure for caulking was set so that the compression ratio of the gasket 700 in a normal temperature environment would be 15%. A lithium ion secondary battery was produced under the same conditions as in Test Example 1 except for the following.

(3) Test Example 3
In Test Example 3, a lithium ion secondary battery was produced under the same conditions as in Test Example 2 except that the material of the gasket 700 was changed to ethylene propylene diene rubber (EPDM).

2. Evaluation test In this test, three lithium ion secondary batteries were manufactured in each test example, and the manufactured batteries were sealed containers set at 20 ° C., 45 ° C. and 60 ° C. (relative humidity (RH) 98% Stored for one month. Then, the amount of water entering the battery case was measured by a Karl Fischer moisture measuring device, and the amount of gas discharged out of the battery case was measured by gas chromatography (detector: TCD, BID). The measurement result of water infiltration is shown in FIG. 5, and the measurement result of gas discharge is shown in FIG.

As shown in FIG. 5, among the test examples 1 to 3, in the test example 3 using a gasket made of EPDM, the amount of water permeation in the normal temperature environment (20 ° C.) was similar to that of the other test examples. However, as the battery temperature increased, the amount of water intrusion increased significantly. From this, when a resin material with high gas permeability such as EPDM is used for the gasket, water is likely to infiltrate into the battery case, and the amount of water infiltration significantly increases particularly under a high temperature and high humidity environment exceeding 45 ° C. It turned out to do.
On the other hand, in Test Example 1, although the second gasket is configured by EPDM, the amount of water infiltration into the battery case is hard to increase even if the battery temperature rises, and a gasket made of PE is used The amount of water infiltration was suppressed to the same extent as in the test example 2 which is present. This is because, when the battery of Test Example 1 is exposed to a high temperature environment, as shown in FIG. 4, the first gasket expands to close the gap, and the first gasket made of PE is disposed on the gas discharge path. It is understood that.

Further, as shown in FIG. 6, the battery of Test Example 1 had the highest gas discharge amount in a normal temperature environment (20 ° C.). From this, as in the battery of Test Example 1, by forming the gas discharge path having the second gasket having high gas permeability and the air gap, the gas in the battery case is externally output via the gas discharge path. It turned out that it can discharge suitably and can prevent the malfunction of the electric current interruption mechanism by the internal pressure rise of a battery case, and a gas discharge valve.
In the battery of Test Example 1, when exposed to a high temperature environment, the gas emission tended to decrease. This is considered to be because the first gasket shuts off the gas discharge path due to expansion. However, even in this case, the gas discharge function is higher than that of the battery of Test Example 2 using a gasket made of PE, so it is considered that the increase in internal pressure of the battery case can be sufficiently suppressed.

  Although the specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

10 Lithium ion secondary battery (non-aqueous electrolyte secondary battery)
DESCRIPTION OF SYMBOLS 20 battery case 21 battery case main body 21A opening part 22 lid 25 joint 27 gas discharge valve 28 inlet 29 pouring liquid plug 30 wound electrode body 32 positive electrode sheet 34 negative electrode sheet 36 separator sheet 40 positive electrode current collection terminal (current collection terminal )
60 insulator 80 negative current collecting terminal 242 terminal extraction hole 420 positive internal terminal 422 first lead 422A lower end of first lead 424 second lead 426 protrusion 460 positive external terminal 462 first connection 462A positive external terminal Hole 464 Second connection portion 464A Bolt insertion hole 500, 700 Gasket 510 First gasket 512 First gasket insertion hole 520 Second gasket 522 Insertion hole of second gasket 524 Side wall of insertion hole of second gasket 620 Mounting portion 622 Penetration Hole 624 Convex part 640 Extension part 642 Bolt receiving hole 670 Terminal bolt (connection terminal)
672 terminal bolt head portion 674 shaft portion 820 negative electrode internal terminal 860 negative electrode external terminal A air gap B gas discharge path L1 dimension L2 of caulking part of projecting portion dimension of air gap in radial direction L3 dimension of second gasket in radial direction L4 first Gasket thickness L5 Longitudinal dimension of air gap

Claims (1)

A battery case having a battery case body having an opening, a lid closing the opening, and a connection terminal for external connection provided on the outer surface side of the lid;
An electrode body housed inside the battery case;
A collector terminal electrically connected to the electrode body at one end inside the battery case and electrically connected to the connection terminal at the other end through the insertion hole provided in the lid;
An insertion hole through which the current collection terminal is inserted is provided, and is held between the lid and the current collection terminal inside the battery case to seal the space between the lid and the current collection terminal With a gasket,
A non-aqueous electrolyte secondary battery comprising
The gasket is
A first gasket disposed in close contact with the inner surface of the lid and formed of a synthetic resin;
And a second gasket disposed between the first gasket and the current collector terminal and formed of an elastic resin having a gas permeability coefficient higher than that of the first gasket,
The diameter of the insertion hole of the second gasket is larger than the diameter of the insertion hole of the first gasket, and a gap adjacent to the side wall of the insertion hole of the second gasket is between the first gasket and the current collecting terminal Nonaqueous electrolyte secondary battery characterized by being formed.

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