JP2013073873A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce risk that an electrode group moves to a sealing plate side and blocks a gas discharge passage accompanying discharge of large amount of gas generated inside of a battery to outside in an abnormal case.SOLUTION: A structure in which an upper insulation plate disposed between the electrode group and the sealing plate and an internal core disposed on a center part of the electrode group are integrally molded is used. Therefore, strength of the center part of the upper insulation plate on which discharge pressure of gas concentrates in an abnormal case can be increased and movement of the electrode group due to breakage of the upper insulation plate can be suppressed. Thereby, blocking of the gas discharge passage can be prevented and safety of the battery can be improved.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a structure for improving safety in a cylindrical battery.

  In general, a cylindrical battery is configured such that a power generation element is housed together with an electrolyte in a bottomed cylindrical metal battery case, and the opening is sealed with a sealing plate (including an assembly sealing body). In a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, an electrode group serving as a power generation element is configured by, for example, winding a separator between a positive electrode and a negative electrode and winding it in a spiral shape. The separator has a function of insulating the positive electrode and the negative electrode and holding the electrolyte. Further, a positive electrode lead or a negative electrode lead derived from the positive electrode or the negative electrode is connected to the sealing plate and the battery case, respectively, and serves as an external terminal of the positive electrode or the negative electrode. An upper insulating plate is provided between the electrode group inserted in the battery case and the sealing plate, and a lower insulating plate is provided between the electrode group and the battery case, so that the electrode group can be a sealing plate or a battery case. And is electrically insulated. In the battery case, a groove portion protruding inward is formed on the upper portion of the upper insulating plate, and the movement of the upper insulating plate in the upper direction is suppressed by the groove portion, and the electrode group is fixed by the upper insulating plate. .

  In such a non-aqueous electrolyte secondary battery (hereinafter sometimes simply referred to as “battery”), a strong impact is applied from the outside due to dropping or the like, so that the electrode group can move and be damaged in the battery case. There was sex.

  In response to the above problem, for example, it has been proposed to suppress the movement of the electrode group by using an upper insulating plate provided with a protrusion so as to correspond to the peripheral part of the electrode group (see, for example, Patent Document 1). In addition, by forming a through hole in the center of the upper insulating plate processed into an elastic body shape, press the center core into the through hole, and fix the upper insulating plate by stretching with the inner wall and the center core of the battery case A structure for suppressing the movement of the electrode group has also been proposed (see, for example, Patent Document 2).

JP 2006-351471 A JP 2003-317805 A

  A general non-aqueous electrolyte secondary battery is a gas that operates when the internal pressure of the battery case reaches a predetermined value in preparation for the occurrence of gas in the battery case due to abnormalities such as overcharging or internal short circuit. A discharge mechanism is provided on the sealing plate.

  However, in recent years, with the increase in the number of functions of electronic devices, the capacity of batteries has been increasing, and it is expected that the amount of gas generated when an abnormality such as that described above will increase.

  In such a situation, when the gas discharge mechanism of the sealing plate is activated due to the abnormality of the battery, the upper insulating plate as in Patent Document 1 has a weak strength near the central portion where the gas discharge pressure is concentrated, There was a possibility that the insulating plate was broken at the center. Therefore, there is a risk that the electrode group moves to the upper part and blocks the gas discharge channel formed in the sealing plate.

On the other hand, as in Patent Document 2, when the core is pressed into the through hole of the upper insulating plate processed into an elastic body shape, the electrode group may be pressed and damaged by the upper insulating plate. In addition, the upper insulating plate is deformed and its height position and levelness varies, so the upper insulating plate is bitten and damaged in the process of forming a groove part that suppresses the movement of the upper insulating plate in the battery case. There are things to do.

  The present invention has been made in view of such problems, and is highly productive. Even when an abnormality occurs, the gas discharge flow path is not shut off, and the gas is quickly discharged outside the battery case, thereby being excellent in safety. An object is to provide a nonaqueous electrolyte secondary battery.

  In order to achieve the above object, the nonaqueous electrolyte secondary battery of the present invention accommodates an electrode group in which a positive electrode and a negative electrode are wound through a separator in a bottomed cylindrical battery case having an opening, A nonaqueous electrolyte secondary battery in which the opening is sealed with a sealing plate having a gas discharge mechanism, and an upper insulating plate is disposed between the electrode group and the sealing plate, and the battery case includes A groove portion that protrudes inward is formed at the upper portion of the upper insulating plate, and a central core is disposed at the center of the electrode group, and the upper insulating plate and the central core are integrally formed structures. It is characterized by being.

  According to the present invention, since the upper insulating plate and the core are integrally formed, it is not necessary to press-fit the core into the upper insulating plate. Accordingly, it is possible to prevent damage to the electrode group due to being pressed by the upper insulating plate and damage during the assembly process due to deformation of the upper insulating plate, and reduce manufacturing defects.

  In addition, the central portion of the upper insulating plate of the present invention is strong because it is integrally formed with the core. Therefore, even when a large amount of gas is generated due to battery abnormality and the gas discharge pressure near the center increases, damage to the upper insulating plate is prevented, and movement to the upper part of the electrode group is suppressed. The gas discharge channel of the sealing plate is secured. Therefore, the gas at the time of abnormality can be quickly discharged out of the battery case, and a nonaqueous electrolyte secondary battery excellent in safety can be realized.

  According to the present invention, the non-aqueous electrolyte secondary battery is excellent in safety because it is highly productive and does not block the gas discharge channel even in an abnormal state, and efficiently discharges the gas to the outside of the battery case. Can be provided.

Sectional drawing which shows schematic structure of the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. The perspective view of the structure which integrally molded the upper insulating board and center core which concern on one Embodiment of this invention. Sectional drawing which shows schematic structure of the nonaqueous electrolyte secondary battery which concerns on other embodiment of this invention. (A) Top view of a structure in which an upper insulating plate and a core according to another embodiment of the present invention are integrally formed, and (b) a sectional view

  The non-aqueous electrolyte secondary battery of the present invention stores an electrode group in which a positive electrode and a negative electrode are wound through a separator in a bottomed cylindrical battery case having an opening, and the opening has a gas discharge mechanism. A non-aqueous electrolyte secondary battery sealed with a sealing plate having an upper insulating plate disposed between the electrode group and the sealing plate; A protruding groove is formed, a central core is disposed at the center of the electrode group, and the upper insulating plate and the central core are integrally formed structures.

As described above, in the present invention, by using a structure in which the upper insulating plate and the core are integrally formed, there is no need to press-fit the core into the through hole of the upper insulating plate, and the upper insulating plate is pressed against the upper insulating plate. Therefore, it is possible to prevent damage to the electrode group due to the above, and damage during the assembly process due to deformation of the upper insulating plate, thereby preventing manufacturing defects.

  In addition, by inserting the center core, the installation of the upper insulating plate is completed at the same time, so the number of man-hours can be reduced, and since it is integrally molded with the center core, the height position and levelness of the upper insulating plate are accurate. It can be installed well. Therefore, for example, by setting the distance from the bottom surface of the upper insulating plate to the end of the core, and inserting the end of the core until it hits the bottom surface of the battery case, Positioning can be performed, and a space (a space surrounded by the battery case and the upper insulating plate) in which the electrode group is accommodated can be easily and accurately defined.

  As described above, in the battery having the electrode group formed by winding, since there is a gap in the center portion, when a sudden pressure rise occurs when the battery is abnormal, the pressure inside the battery case is not uniform, especially The pressure density at the center increases instantaneously. Therefore, the pressure applied to the central portion of the upper insulating plate located above the electrode group is also increased.

  On the other hand, in the present invention, since the upper insulating plate is integrated with the center core, the strength is high and the destruction can be prevented. Therefore, the upper insulating plate suppresses the movement of the electrode group, so that a gas discharge channel can be secured and gas can be quickly discharged outside the battery case. In addition, since the strength of the upper insulating plate is increased, it is possible to enlarge the through hole for gas discharge provided in the upper insulating plate, and thereby the gas can be discharged more efficiently. In the upper insulating plate of the present invention, the thickness near the center may be increased. Thereby, the strength of the upper insulating plate can be further improved.

  In the present invention, the structure in which the upper insulating plate and the core are integrally molded is, for example, a metal core inserted into a resin injection mold, and the upper insulating plate is resin-molded at the end of the core. It can be formed by molding. In this case, in order to ensure the strength at the connection portion between the core and the upper insulating plate, it is desirable to make the connection area as wide as possible. Specifically, irregularities may be provided in the portion of the central core that comes into contact with the resin, and the end portion of the central core may have a shape in which the diameter is expanded along the upper surface of the upper insulating plate. Furthermore, the upper insulating plate and the core can be formed of the same resin by resin injection molding or the like. Alternatively, the upper insulating plate may be integrally formed by casting or the like, and at least a surface that contacts the electrode group may be covered with an insulator. When the structure is formed of a metal having a high hardness as described above, the strength of the upper insulating plate can be further improved, and the movement of the electrode group can be more effectively suppressed.

  The resin used for the structure is preferably at least one selected from polyolefin resins and polyimide resins from the viewpoint of heat resistance. Moreover, from a viewpoint of heat resistance and strength, the glass cloth may be a base material and may be composed of a phenol resin containing an inorganic additive. The inorganic additive is preferably at least one selected from the group consisting of alumina, silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and calcium carbonate.

  Moreover, it is preferable to use iron, aluminum, an aluminum alloy, copper, stainless steel, etc. as a metal used for the said structure.

  In the nonaqueous electrolyte secondary battery according to the present invention, it is preferable that the upper insulating plate constituting the structure has a curved shape and is curved toward the electrode group.

According to such a configuration, even if the pressure applied to the central portion of the upper insulating plate is increased, the curved shape further increases the strength of the central portion, and the destruction of the upper insulating plate can be suppressed. As a result, it is possible to prevent the gas discharge channel from being blocked by the movement of the electrode group, and to efficiently discharge the gas to the outside of the battery. Furthermore, even if the upper insulating plate moves in the direction of the sealing plate and the outer edge portion of the upper insulating plate is in contact with the sealing plate, the structure is curved in the direction of the electrode group. It is possible to prevent the gas discharge flow path of the sealing plate from being blocked. In order to suppress the movement of the electrode group, the thicker the upper insulating plate, the higher the strength, which is desirable. It becomes.

  In the present invention, the curved upper insulating plate desirably has a curvature of 0.02 / mm or more and 0.07 / mm or less. A curvature smaller than 0.02 / mm is not desirable because the pressure resistance against deformation is low and the movement of the electrode group cannot be sufficiently suppressed. Moreover, when larger than 0.07 / mm, it is undesirable from a viewpoint of the utilization efficiency of battery internal space.

  In the present invention, the upper insulating plate preferably has a thickness of 0.3 mm to 1.0 mm. If it is thinner than 0.3 mm, it is not desirable because a sufficient pressure resistance against deformation cannot be obtained, and the effect of suppressing the movement of the electrode group becomes small. On the other hand, if it is thicker than 1.0 mm, it occupies more volume than necessary in the battery case and the capacity is lost, and it is not desirable from the viewpoint of cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a cylindrical lithium ion secondary battery according to an embodiment of the present invention, and FIG. 2 is a structure in which an upper insulating plate and a core used in the battery of FIG. 1 are integrally formed. It is a perspective view which shows a body. A battery 100 in FIG. 1 is a cylindrical lithium ion secondary battery, and includes an electrode group 4 formed by spirally winding a positive electrode 1, a negative electrode 2, and a separator 3 interposed therebetween. ing. The electrode group 4 is housed in a bottomed cylindrical metal battery case 5 together with a nonaqueous electrolyte (not shown). The opening of the battery case 5 is sealed by the sealing plate 19 through the outer gasket 7, whereby the electrode group 4 and the nonaqueous electrolyte are sealed inside the battery case 5.

  Here, a structure 20 in which the upper insulating plate 10 and the core 18 are integrally formed is installed inside the battery case 5, and the core 18 portion of the structure 20 is used as a central gap portion of the electrode group 4. By inserting, the upper insulating plate 10 portion of the structure 20 is disposed above the electrode group 4. The outer edge portion of the upper insulating plate 10 is supported by a groove portion 17 formed in the battery case, and the electrode group is fixed by the upper insulating plate 10. A lower insulating plate 16 is disposed below the electrode group 4.

  The sealing plate 19 includes a conductor-shaped terminal plate 11, an annular PTC (positive temperature coefficient) thermistor plate 12, a circular upper valve body 13 and a lower valve body 14, a filter 6, and an insulation It is comprised from the cyclic | annular inner gasket 15 which consists of a body. The inner gasket 15 is disposed between the peripheral portion of the upper valve body 13 and the peripheral portion of the lower valve body 14 so that the peripheral portion of the upper valve body 13 and the peripheral portion of the lower valve body 14 are in contact with each other. Is preventing. In addition, the inner gasket 15 is interposed between the filter 6 and the peripheral edge of the terminal plate 11 so as not to contact each other.

  The terminal plate 11, the PTC thermistor plate 12, and the upper valve body 13 are connected at their peripheral portions. Moreover, the upper side valve body 13 and the lower side valve body 14 are connected in those center parts. Further, the lower valve body 14 and the filter 6 are connected at their peripheral edge portions. As a result, the terminal plate 11 and the filter 6 are electrically connected to each other.

  The positive electrode 1 is connected to the filter 6 through a positive electrode lead 8, and the terminal plate 11 is an external terminal of the positive electrode. On the other hand, the negative electrode 2 is joined to the bottom surface of the battery case 5 via the negative electrode lead 9, and the battery case 5 serves as an external terminal of the negative electrode.

  The terminal plate 11 of the sealing plate 19 has a plurality of external exhaust holes 11a, and the filter 6 also has a plurality of internal exhaust holes 6a. In the upper valve body 13 and the lower valve body 14, an annular groove is formed at the center, and when the groove is broken, a valve hole is formed there. For example, in the battery 100, when a gas due to an abnormality such as an internal short circuit or overcharge occurs and the pressure inside the battery 100 increases, the groove of the lower valve body 14 is pushed through to form a valve hole, and the current path is Blocked. When the pressure in the battery 100 further increases, the groove of the upper valve body 13 is broken to form a valve hole. As a result, the gas generated in the battery 100 is discharged to the outside of the battery through the internal exhaust hole 6a of the filter 6, the valve holes of the lower valve body 14 and the upper valve body 13, and the external exhaust holes 11a of the terminal plate 11. Is done. Thus, the sealing plate 19 is provided with a gas discharge mechanism that operates when the internal pressure of the battery case 5 reaches a predetermined value.

  When the gas discharge mechanism as described above operates, the wound electrode group concentrates gas discharge because a space is formed at the center. Further, when the pressure inside the battery case 5 rises abnormally, gas passes through the through hole 10 a of the upper insulating plate 10 and is discharged toward the internal exhaust hole 6 a of the filter 6. Therefore, according to the conventional nonaqueous electrolyte secondary battery, the upper insulating plate 10 is deformed or destroyed by the pressure of the gas discharged in the event of an abnormality as described above, and the electrode group 4 is separated from the upper insulating plate 10 and the filter 6. , While moving into a space between them, the through hole 10a of the upper insulating plate 10 and the internal exhaust hole 6a of the filter 6 may be blocked. According to the present invention, the structure 20 in which the upper insulating plate 10 and the core 18 are integrally formed as shown in FIG. 2 is installed in the battery. Therefore, the central portion of the upper insulating plate 10 is integrally formed with the core 18 and is firmly fixed. Therefore, deformation and destruction of the upper insulating plate 10 can be prevented, and movement of the electrode group 4 can be suppressed. Furthermore, by using such a structure 20, the two steps of inserting the core and installing the upper insulating plate can be reduced to one step, so that the productivity can be improved.

(Embodiment 2)
FIG. 3 is a cross-sectional view showing a schematic configuration of a nonaqueous electrolyte secondary battery according to another embodiment of the present invention, and FIG. 4 is a view of a structure in which an upper insulating plate and a core used in the battery are integrally formed ( It is a top view and (b) sectional drawing.

  The battery 200 of the embodiment shown in FIG. 3 also has a gas discharge mechanism similar to that in FIG. The upper insulating plate 21 and the inner core 22 are a structure 23 that is integrally formed. Here, in the present embodiment, the upper insulating plate 21 has a structure curved toward the electrode group 4. Thus, by making the upper insulating plate 21 curved in the direction of the electrode group, the strength against the gas discharge pressure in the central portion can be further increased. It is possible to prevent the portion from being damaged and to prevent the gas discharge path from being blocked by the movement of the electrode group 4.

  The curvature of the upper insulating plate 21 can increase the strength of the upper insulating plate 21 by increasing the curvature, but the capacity that can be accommodated in the electrode group 4 is reduced and the battery capacity is reduced. / Mm or more and 0.07 / mm or less is desirable. Similarly, the thickness of the upper insulating plate 21 can increase the strength of the upper insulating plate 21 by increasing the thickness, but the capacity that can be accommodated in the electrode group 4 is reduced and the battery capacity is reduced. It is desirable to set it to 3 mm or more and 1.0 mm or less.

As mentioned above, although embodiment of this invention was described, the shape of the through-holes 10a and 21a of the upper insulating plates 10 and 21, and a position and the number are not limited to the form shown in FIG.2 and FIG.4. In the present invention, the mechanism for discharging the gas generated in the battery 100 is not limited to the structure shown in FIGS. 1 and 3, and may be another structure.

  When the nonaqueous electrolyte secondary battery of the present invention is a lithium ion secondary battery, the following materials can be used as constituent materials.

  The positive electrode 1 can be configured by forming a positive electrode active material layer on a positive electrode current collector. As the positive electrode current collector, aluminum, an aluminum alloy, stainless steel, titanium, a titanium alloy, or the like can be used. Among them, aluminum or an aluminum alloy is preferable because electrochemical elution or the like hardly occurs.

  As the positive electrode active material, a lithium-containing transition metal compound, for example, a composite metal oxide of lithium and at least one metal selected from cobalt, manganese, nickel, chromium, iron, and vanadium can be used. Among these, particularly when a lithium nickel composite oxide is used, the effect of the present invention is more exhibited. When lithium nickel-based composite oxide is used as the positive electrode active material, the amount of gas generated at the time of abnormality is about three times larger than that of lithium cobalt-based composite oxide. Even in this case, the effect can be obtained by the present invention.

  The positive electrode active material layer prepares a slurry-like mixture in which a positive electrode active material, a binder, and a conductive agent are kneaded and dispersed together with a dispersion medium, and the mixture is attached to the positive electrode current collector. Can be formed.

  The negative electrode 2 can be configured by forming a negative electrode active material layer on a negative electrode current collector. As the negative electrode current collector, copper, copper alloy, nickel, nickel alloy, stainless steel, aluminum, aluminum alloy, etc. can be used. Among them, copper, copper alloy, nickel or nickel alloy can be electrochemically eluted. And the like are less likely to occur. As the negative electrode active material, a material having a graphite type crystal structure capable of reversibly occluding and releasing lithium ions, such as natural graphite, spherical or fibrous artificial graphite, non-graphitizable carbon (hard carbon), easy graphite Carbon materials such as carbonizable carbon (soft carbon), metal oxide materials such as tin oxide and silicon oxide, silicon-containing compounds such as silicon and silicide, and the like can be used. The negative electrode active material layer can be formed by adhering a negative electrode active material, a binder, a dispersion medium, and, if necessary, a slurry-like mixture containing a conductive material to the negative electrode current collector.

  As the separator 3, a polyolefin-based material can be used, and a combination of a polyolefin-based material and a heat-resistant material is preferably used. Examples of the polyolefin porous film include polyethylene, polypropylene, and an ethylene-propylene copolymer porous film. These resins can be used alone or in combination of two or more. As the heat resistant material, a film made of a heat resistant resin such as aramid, polyimide, polyamideimide, or a mixture of a heat resistant resin and an inorganic filler can be used.

The electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent. Examples of the nonaqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and linear carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further, as the lithium salt, a lithium salt having a strong electron attractive property, for example, LiPF ₆ , LiBF ₄ , LiClO _4, or the like is used.

  Examples of the present invention will be described. The present invention is not limited to the following examples. A test body comprising a lithium ion secondary battery was produced as follows.

Example 1
(1) Preparation positive electrode active material for the positive electrode, the average particle diameter was used _LiNi 0.8 _Co 0.15 _{Al 0.05} O ₂ is 12 [mu] m. A positive electrode mixture paste was prepared by mixing 100 parts by weight of a positive electrode active material, 1.7 parts by weight of polyvinylidene fluoride as a binder, and 2.5 parts by weight of acetylene black as a conductive agent in a liquid component.

  The positive electrode mixture paste was applied to both sides of a positive electrode current collector made of aluminum foil except for the connecting portion of the positive electrode lead 8 and dried to produce a positive electrode precursor, and then rolled. A positive electrode 1 was obtained. At this time, the positive electrode precursor was rolled so as to have a thickness of 128 μm. The aluminum foil used as the positive electrode current collector had a length of 667 mm, a width of 57 mm, and a thickness of 15 μm.

(2) Production of negative electrode Graphite having an average particle diameter of 20 μm was used as the negative electrode active material. 100 parts by weight of the negative electrode active material, 0.6 parts by weight of polyvinylidene fluoride as a binder, 1 part by weight of carboxymethyl cellulose as a thickener, and an appropriate amount of water are stirred in a double-arm kneader. Thus, a negative electrode mixture paste was obtained.

  The negative electrode mixture paste was applied to both sides of the negative electrode current collector made of copper foil except for the connecting portion of the negative electrode lead 9 and dried to produce a negative electrode precursor, and then rolled. A negative electrode 2 was obtained. At this time, the negative electrode precursor was rolled so as to have a thickness of 155 μm. The copper foil used as the negative electrode current collector had a length of 745 mm, a width of 58.5 mm, and a thickness of 8 μm.

(3) Preparation of non-aqueous electrolyte The non-aqueous electrolyte is prepared by mixing 1.0 mol / L of lithium hexafluorophosphate (LiPF ₆ ) into a mixed solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 1. It was prepared by dissolving at a concentration of

(4) Preparation of sealing plate The sealing plate shown in FIG. 1 was prepared. The upper valve body 13 and the lower valve body 14 were made of aluminum. The terminal board 11 was made of iron. The filter 6 was made of aluminum. The inner gasket 15 was made of polypropylene.

(5) Battery assembly The positive electrode and the negative electrode produced as described above were laminated with the separator 3 interposed therebetween to obtain a laminate. For the separator 3, a polyethylene porous film having a thickness of 20 μm was used. The positive electrode lead 8 was connected to the winding start portion of the positive electrode of the laminate, and the negative electrode lead 9 was connected to the winding end portion of the negative electrode. In this state, the laminated body was wound in a spiral shape to obtain an electrode group 4.

The electrode group 4 obtained as described above was housed in an iron battery case 5. At this time, the positive electrode lead 8 was welded to the filter 6 of the sealing plate 19 with the outer gasket 7 made of polypropylene attached to the peripheral portion by laser welding, and the negative electrode lead 9 was welded to the bottom surface of the battery case 5 by resistance welding. A battery case 5 having a diameter (outer diameter) of 18 mm, a height of 65 mm, and a can wall thickness of 0.15 mm was used. The thickness of the battery case 5 is close to the thickness of the battery case of a cylindrical lithium ion secondary battery that is usually commercially available. A lower insulating plate 16 is disposed below the electrode group 4, and a polypropylene structure 20 in which the upper insulating plate 10 and the core 18 are integrally formed on the central gap portion and the upper side of the electrode group 4. (A = 18mm
B = 0 mm, curvature 0 / mm, thickness 1.5 mm, c = 59 mm, d = 2.5 mm). Here, the curvature was obtained by measuring the dimensions a and b shown in FIG. 4 and calculating the value of 2b / {(a / 2) ² + b ² }.

  After injecting the non-aqueous electrolyte into the battery case 5, a groove projecting inward so as to go around the battery case 5 in the circumferential direction at the top of the upper insulating plate 10 at a position 5 mm from the opening end of the battery case 5. 17 was formed, and the electrode group 4 was fixed via the upper insulating plate 10 by the groove 17.

  Next, after placing the sealing plate 19 with the outer gasket 7 on the opening of the battery case 5 so as to be placed on the groove 17 of the battery case, the opening of the battery case 5 may be bent inward. The battery case 5 was sealed. As described above, a test body having a diameter of 18 mm and a height of 65 mm was produced. The design capacity of this lithium ion secondary battery was 2600 mAh.

(Example 2)
Polypropylene structure 20 (a = 18 mm, b = 0.5 mm, curvature 0.01 / mm, thickness 1.5 mm, c = 58.5 mm, d) in which the curved upper insulating plate and the core are integrally formed. = 2.5 mm) was used in the same manner as in Example 1 except that a test specimen was produced.

(Example 3)
Polypropylene structure 20 (a = 18 mm, b = 1.0 mm, curvature 0.02 / mm, thickness 0.3 mm, c = 58 mm, d = 2) in which a curved upper insulating plate and a core are integrally formed. 0.5 mm) was used in the same manner as in Example 1 to prepare a test specimen.

Example 4
Polypropylene structure 20 (a = 18 mm, b = 1.0 mm, curvature 0.02 / mm, thickness 1.0 mm, c = 58 mm, d = 2) in which a curved upper insulating plate and a core are integrally formed. 0.5 mm) was used in the same manner as in Example 1 to prepare a test specimen.

(Example 5)
Polypropylene structure 20 (a = 18 mm, b = 1.0 mm, curvature 0.02 / mm, thickness 1.5 mm, c = 58 mm, d = 2) in which a curved upper insulating plate and a core are integrally formed. 0.5 mm) was used in the same manner as in Example 1 to prepare a test specimen.

(Comparative Example 1)
An upper insulating plate made of polypropylene (a = 18 mm, b = 0 mm, curvature 0 / mm, thickness 1.5 mm) and an iron core (c = 59 mm, d = 2.5 mm) having a through hole in the center. A test specimen was prepared by inserting a core into the central gap of the electrode group, placing an upper insulating plate on the upper side of the electrode group, and press-fitting the core into the through hole of the upper insulating plate. Otherwise, a test specimen was prepared in the same manner as in Example 1.

(Comparative Example 2)
An upper insulating plate made of polypropylene (a = 18 mm, b = 0 mm, curvature 0 / mm, thickness 1.5 mm) and an iron core (c = 59 mm, d = 2.5 mm) having a through hole in the center. A test body was prepared by placing an upper insulating plate on the upper side of the electrode group, and then inserting a core from the through hole of the upper insulating plate into the central gap of the electrode group. Otherwise, a test specimen was prepared in the same manner as in Example 1.

(Manufacturing defect rate)
In the battery case, a groove portion protruding inward so as to make a round in the circumferential direction of the battery case was formed on the upper side of the upper insulating plate, the manufactured battery was taken out, and the occurrence rate of defects in the assembly process was examined. Specifically, for each of the 500 batteries of the examples and comparative examples, the presence or absence of pressure marks on the upper part of the electrode group and the presence or absence of biting of the upper insulating plate at the time of forming the groove were visually observed, and either one occurred. The defect rate was calculated using the number of defects as the number of defects.

(Heating test)
A heating test was performed on the manufactured specimen under the following conditions. First, the battery was charged with a current of 1500 mA under a 25 ° C. environment until the battery voltage reached 4.25V. The charged specimen was placed on a hot plate and heated from 25 ° C. to 200 ° C. so that the temperature increased by 1 ° C. per second. And the battery after a test was decomposed | disassembled and the movement amount to the upper direction of an electrode group was measured. These results are shown in (Table 1).

  As shown in Table 1, in Examples 1 to 5, no manufacturing failure occurred in the process of integrating the insulating plate and the core. On the other hand, in the comparative example, in the process of forming the groove of the battery case, the upper insulating plate is pushed by the core due to the biting of the upper insulating plate and the position of the through hole between the core and the upper insulating plate being shifted. Manufacturing defect that damaged the electrode group.

  Moreover, in the heating test, in Example 1 using the structure in which the upper insulating plate and the core were integrally formed, the movement of the electrode group was suppressed as compared with the comparative example. This is considered to be due to the fact that the strength of the central portion of the upper insulating plate is increased by adopting an integral structure. Further, in Examples 2 to 5 in which the upper insulating plate was curved, the movement of the electrode group was not confirmed.

  As described above, in the battery of the embodiment, the gas discharge flow path of the sealing plate can be prevented from being blocked by the movement of the electrode group, and the safety of the battery can be improved.

According to the present invention, a nonaqueous electrolyte secondary battery with improved safety can be provided. Such a battery of the present invention can be used as a power source for portable electronic devices such as personal computers, mobile phones, mobile devices, personal digital assistants (PDAs), portable game devices, and video cameras. Further, it is also useful as a power source for assisting driving of an electric motor in a traffic device such as a hybrid car, an electric vehicle, and a fuel cell vehicle. It is also useful as a power source for driving electric tools, vacuum cleaners, robots, and the like, and is also useful as a power source for plug-in HEVs.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrode group 5 Battery case 6 Filter 6a Internal exhaust hole 7 Outer gasket 8 Positive electrode lead 9 Negative electrode lead 10, 21 Upper insulating board 10a, 21a Through-hole 11 Terminal board 11a External exhaust hole 12 PTC thermistor board 13 Upper valve body 14 Lower valve body 15 Inner gasket 16 Lower insulating plate 17 Groove parts 18 and 22 Core 19 Sealing plate 20 and 23 Structure 100 and 200 Battery

Claims (4)

A nonaqueous electrolyte secondary in which an electrode group in which a positive electrode and a negative electrode are wound via a separator is housed in a bottomed cylindrical battery case having an opening, and the opening is sealed with a sealing plate having a gas discharge mechanism A battery,
An upper insulating plate is disposed between the electrode group and the sealing plate, and the battery case has a groove portion protruding inward at the upper portion of the upper insulating plate,
A non-aqueous electrolyte secondary battery, wherein a central core is disposed in a central portion of the electrode group, and the upper insulating plate and the central core are a unitary structure.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the upper insulating plate has a curved shape and is curved toward the electrode group.   The nonaqueous electrolyte secondary battery according to claim 2, wherein a curvature of the upper insulating plate is 0.02 / mm or more and 0.07 / mm or less.   The non-aqueous electrolyte secondary battery according to claim 2 or 3, wherein the upper insulating plate has a thickness of 0.3 mm to 1.0 mm.