WO2008018241A1

WO2008018241A1 - Enclosed battery

Info

Publication number: WO2008018241A1
Application number: PCT/JP2007/062406
Authority: WO
Inventors: Hideaki Fujita
Original assignee: Panasonic Corporation
Priority date: 2006-08-10
Filing date: 2007-06-20
Publication date: 2008-02-14
Also published as: CN101501890A; CN101501890B; KR20090031444A

Abstract

A tubular electrode group obtained by winding a positive electrode plate and a negative electrode plate through a separator is inserted into a rectangular battery case along with electrolyte. A pressure release mechanism is provided on the lower surface of the battery case which is parallel with the winding axis of the electrode group. The pressure release mechanism is disposed at a position spaced apart from a projection line formed when the winding axis of the electrode group is projected at a right angle to the lower surface of the battery case.

Description

Specification

Sealed battery

Technical field

The present invention relates to a sealed battery that can ensure high safety even when the internal pressure of the battery increases.

Background art

[0002] Sealed batteries, in particular, chargeable / dischargeable sealed secondary batteries, are used in the fields where batteries with high energy density corresponding to downsizing and light weight are required as power sources for devices such as mobile phones and personal computers. In addition, the range of fields has expanded to fields where high power batteries are required as power sources for electric tools and hybrid vehicles. In particular, in the high-power field, the internal resistance of the sealed battery is designed to be as low as possible.Therefore, the positive and negative electrodes are affected by internal factors such as foreign matter mixed inside the battery and external factors such as external pressure. When the battery is short-circuited, a large current flows intensively in the short-circuited part, and the heat generated by this increases the pressure in the battery, which may damage the battery case itself or the joint part such as the sealing plate.

[0003] Conventionally, with respect to such a problem, by providing an explosion-proof valve at the lid of the battery case, when the pressure in the battery rises abnormally, the explosion-proof valve is operated to Measures have been taken to prevent damage to the battery case or the like by discharging the battery pack to the outside (see, for example, Patent Document 1).

[0004] However, since the electrode terminal is also disposed on the lid of the battery case where the explosion-proof valve is provided, there is a space limitation, and the size of the explosion-proof valve is limited. For example, when an explosion-proof valve is formed by making a part of the lid a thin part, it is necessary to make the thin part thin in order to ensure a predetermined operating pressure with a limited size. There is a limit to securing a thickness that does not break the thin part against impact.

[0005] Patent Document 2 describes a configuration in which an explosion-proof valve is provided in a battery case without being subjected to such restrictions. That is, by providing an explosion-proof valve composed of a groove-like thin part on the surface of the battery can, the force S can be operated at a predetermined operating pressure without being restricted by space. This explosion-proof valve is used to increase the pressure inside the outer can and cause the outer can to deform. Therefore, the thickness of the groove-like thin portion and the length of the groove are defined so that the explosion-proof valve is broken. In addition, this explosion-proof valve is formed on a part of the outer can that is not easily subject to drop impact, so it has high drop resistance.

Patent Document 1: Japanese Patent Laid-Open No. 10-106524

Patent Document 2: Japanese Patent Laid-Open No. 11-185714

Disclosure of the invention

Problems to be solved by the invention

[0006] Since the explosion-proof valve described in Patent Document 2 can be provided without being restricted in space, it is useful in terms of increasing the degree of freedom in design. Since the groove-like thin part is a mechanism that breaks, it is necessary to change the thickness of the groove-like thin part and the length of the groove depending on the position at which the explosion-proof valve is provided, and there is a problem that the design becomes complicated

[0007] In addition, when the pressure in the battery rises abnormally, the explosion-proof valve is activated to release the gas in the battery to the outside, preventing the battery case from being damaged, and impregnating the electrode group. If excessive electrolyte solution that remains is left in the battery case, the temperature inside the battery case is still maintained at a high temperature (the response speed of the temperature drop is higher than the response speed of the gas release). Slowly), the flammable electrolyte is heated and the temperature inside the battery case may increase further.

[0008] The present invention has been made in view of an energetic problem, and its main purpose is a pressure capable of quickly releasing the gas in the battery to the outside even if the pressure in the battery rises when an abnormality occurs. An object of the present invention is to provide a highly safe sealed battery having an opening mechanism.

[0009] In addition, when an abnormality occurs, the gas in the battery is released to the outside, and the highly safe sealed type is equipped with a pressure release mechanism that can quickly discharge the electrolyte remaining in the battery to the outside. To provide a battery.

Means for solving the problem

[0010] In order to solve the above problems, a sealed battery according to the present invention inserts a cylindrical electrode group, in which a positive electrode plate and a negative electrode plate are wound via a separator, together with an electrolyte into a rectangular battery case. In the sealed battery formed on the side of the battery case parallel to the winding axis of the electrode group In addition to providing a pressure release mechanism, a configuration is adopted in which the pressure release mechanism is disposed at a position separated from the projection line when the winding axis of the electrode group is projected at right angles to the side surface of the battery case.

[0011] In the sealed battery of the present invention, the region in the battery case defined by the cylindrical electrode group and the inner wall of the side surface of the battery case parallel to the winding axis of the electrode group is There is enough space to ensure the working pressure. Therefore, when the side surface of the battery case corresponding to the space, that is, the side surface of the battery case parallel to the winding axis of the electrode group, is projected perpendicularly to the side surface of the battery case. By disposing the pressure release mechanism at a position away from the projection line, the gas in the battery generated at the time of abnormality can be reliably and promptly released to the outside.

In a preferred embodiment, the electrode terminals of the positive electrode plate and the negative electrode plate are provided on the first side surface of the side surfaces of the battery case parallel to the winding axis of the electrode group, respectively. The mechanism is provided on the second side surface facing the first side surface.

[0013] In a preferred embodiment, the positive electrode plate and the electrode terminal of the negative electrode plate are provided on the first side surface of the battery case parallel to the winding axis of the electrode group, respectively. The opening mechanism is a third side surface adjacent to the first side surface, and is disposed at a position spaced apart from the projection line on the third side surface on the opposite side to the first side surface.

[0014] When a battery is loaded in a device, an electric vehicle, or the like, the first side surface of the battery case provided with the electrode terminals is often the upper surface (the surface opposite to the ground surface). For this reason, by providing a pressure release mechanism on the second side opposite to the first side, that is, the bottom surface (surface facing the ground), the gas in the battery generated in the event of an abnormality can be quickly released to the outside. The electrolyte remaining in the battery can be quickly discharged to the outside.

[0015] In addition, the pressure release mechanism is a third side surface adjacent to the first side surface, and is positioned away from the projection line on the third side surface opposite to the first side surface, that is, on the lower surface side. By disposing in this manner, the gas in the battery generated at the time of abnormality can be quickly released to the outside, and the electrolyte remaining in the lower vicinity in the battery can be quickly discharged to the outside.

The invention's effect [0016] According to the present invention, a highly safe sealed battery equipped with a pressure release mechanism capable of quickly releasing the gas in the battery to the outside even if the pressure in the battery rises when an abnormality occurs. The ability to provide S.

[0017] When an abnormality occurs, the gas in the battery is released to the outside, and the electrolyte solution remaining in the battery is quickly discharged to the outside. A type battery can be provided.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of a sealed battery in an embodiment of the present invention, where (a) is a top view, (b) is a front perspective view, (c) is a side perspective view, and (d) Is a bottom view.

[FIG. 2] (a) to (c) are views showing the arrangement of the pressure release mechanism in the present invention.

FIG. 3 is a diagram showing a configuration of a conventional cylindrical lithium ion secondary battery.

Explanation of symbols

1 electrode

2 Positive current collector

3 Negative current collector

4 Positive terminal

5 Negative terminal

6 Cover plate

7 Insulating material

8 Battery case

9 Injection hole

10 Explosion-proof valve (pressure release mechanism)

11 Space

12 Top view

13 Bottom

14 side

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following drawings In FIG. 2, components having substantially the same function are denoted by the same reference numerals for the sake of simplicity. In addition, this invention is not limited to the following embodiment.

FIG. 1 is a diagram schematically showing a configuration of a sealed battery in an embodiment of the present invention, where (a) is a top view, (b) is a front perspective view, (c) is a side perspective view, (D) is a bottom view.

[0022] As shown in Fig. 1 (b), a cylindrical electrode group 1 in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween is inserted into a rectangular battery case 8 together with an electrolytic solution. A pressure release mechanism 10 is provided on the lower surface 13 of the battery case 8 parallel to the winding axis AA of the electrode group 1. As shown in FIG. 1 (d), the pressure release mechanism 10 is located at a position separated from the projection line T-T force when the winding axis A_A of the electrode group 1 is projected onto the lower surface 13 of the battery case 8 at a right angle. Arranged

1 1

The

[0023] As shown in FIG. 1 (b), the cylindrical electrode group 1 and the inner walls of the side surfaces 12, 13, and 14 of the battery case 8 parallel to the winding axis A—A of the electrode group were partitioned. Area 11 in the battery case is a space. Normally, the electrode group 1 is elongated in the direction of the winding axis A—A, so that the area 11 is a space area wide enough to secure the operating pressure of the pressure release mechanism 10 when an abnormality occurs. I am doing. Therefore, the side surface of the battery case 8 corresponding to the region 11, that is, the side surface of the battery case 8 parallel to the winding axis AA of the electrode group 1 (the lower surface 13 in the present embodiment) Winding axis A— A projection line when A is projected perpendicularly to the side of the battery case 8 T— T force By disposing the pressure release mechanism 10 at a position apart, the gas in the battery generated in the event of an abnormality Can be reliably and promptly released to the outside.

In the present embodiment, the upper surface (first side surface) 12 of the side surfaces of the battery case 8 parallel to the winding axis A—A of the electrode group 1 is shown in FIG. Electrode terminals 4 and 5 connected to the positive current collector 2 and the negative current collector 3 are respectively provided. Normally, when a battery is loaded in a device or an electric vehicle, the side surface of the battery case 8 provided with the electrode terminals 4 and 5 becomes the upper surface 12. Therefore, the pressure release mechanism 10 is placed on the lower surface (the surface facing the upper surface 12). ) By providing at 13, the gas in the battery generated at the time of abnormality can be quickly released to the outside, and the electrolyte remaining in the battery can be quickly discharged to the outside.

[0025] Note that the pressure release mechanism 10 is not limited to the position shown in FIG. 1 (d), and any number of pressure release mechanisms 10 may be provided at any position as long as the projection line T-T force is also separated. it can. For example, the figure As shown in 2 (a), the two pressure release mechanisms 10 may be provided at positions facing the projection line on the lower surface 13. Alternatively, as shown in FIG. 2 (b), the pressure release mechanism 10 extends in a direction perpendicular to the projection line T-T, intersecting the projection line T-T on the lower surface 13.

1 1 1 1

You can set it up.

[0026] When the pressure release mechanism 10 is provided on the side surface 14 adjacent to the upper surface 12, as shown in FIG. 2 (c), the pressure release mechanism 10 is connected to the winding axis A-A of the electrode group 1. Is projected onto the side surface 14 of the battery case 8 at a right angle.

twenty two

It is preferable to arrange them at positions separated from each other. By disposing at such a position, when the gas in the battery generated at the time of abnormality is discharged to the outside, the electrolyte remaining in the vicinity of the lower part in the battery can be discharged to the outside.

The cylindrical electrode group 1 in the present invention is not limited to the shape shown in FIG. 1 (b), but also includes a flat cylindrical shape. In this case, the pressure release mechanism 10 is separated from the projection line T-T.

1 1

The distance is preferably longer than that in the case of the electrode group 1 that is not flattened. In this way, the pressure release mechanism 10 is arranged in the vicinity of the region 11 that forms a wider space, and the gas in the battery generated at the time of abnormality can be quickly released to the outside. .

[0028] Further, as shown in Fig. 1 (b), the rectangular battery case 8 in the present invention is not limited to a quadrangle but includes a polygonal one. Also in this case, the pressure release mechanism 10 was generated in the event of an abnormality by arranging the winding axis A—A of the electrode group 1 at a position separated from the projection line when projected perpendicularly to the side surface of the battery case 8. It is possible to release the gas in the battery to the outside reliably and quickly.

[0029] A specific configuration of the sealed battery in the present embodiment will be described in more detail with reference to FIGS. 1 (a) to 1 (d).

[0030] The electrode group 1 in which the positive electrode plate and the negative electrode plate are wound through a separator is connected to the positive electrode current collector plate 2 on the left side and the negative electrode current collector plate 3 on the right side. The positive electrode current collector plate 2 and the negative electrode current collector plate 3 are insulated by an insulating member 7 so as not to be short-circuited inside the battery case 8 constituted by the cover plate 6 and the casing. Further, a positive electrode terminal 4 is attached to the positive electrode current collector plate 2, and a negative electrode terminal 5 is attached to the negative electrode current collector plate 3, and these electrode terminals 4 and 5 protrude above the cover plate 6 arranged on the upper surface. Are arranged as follows. Here, the cover plate 6 and the casing are welded. Since the positive electrode terminal 4 and the negative electrode terminal 5 are sealed by the cover plate 6 and the liquid injection hole 9 is closed after the electrolytic solution is injected, the inside of the battery is kept sealed.

[0031] On the lower surface of the battery case 8, an explosion-proof valve (pressure release mechanism) 10 that is damaged when the pressure in the battery reaches a predetermined pressure is provided. The explosion-proof valve 10 is provided so that at least a part of the explosion-proof valve 10 is applied to the space 11 defined by the electrode group 1 and the inner wall of the battery case 8.

[0032] In nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries, electrolytes having high volatility and flammability such as cyclic carbonates and chain carbonates are used. Also, in order to obtain sufficient life characteristics, it is often necessary to add a little more electrolyte than electrode group 1 can sufficiently impregnate. In such a sealed battery, if an abnormality such as an internal short circuit occurs, the pressure inside the battery will increase at an accelerated rate due to the evaporation of the electrolyte due to heat generation, but the explosion-proof valve 10 may be partially applied to the space 11. Therefore, when an abnormality occurs, the gas in the battery can be quickly released to the outside, and the electrolyte remaining in the battery can be efficiently discharged to the outside.

Here, the explosion-proof valve 10 is designed to be destroyed when a predetermined pressure is reached, for example, by thin-wall processing or engraving. In addition to the explosion-proof valve 10, a pressure adjustment valve or a check valve may be used.

[0034] The positive electrode plate is composed of a positive electrode mixture containing a positive electrode active material and a positive electrode current collector made of foil.

Examples of the positive electrode active material include lithium cobaltate and modified products thereof (such as those obtained by eutectic aluminum and magnesium), lithium nickelate and modified products thereof (some of which nickel is replaced with cobalt, aluminum, etc.) In addition, composite oxides such as lithium manganate and modified products thereof can be used.

[0035] As the positive electrode active material, a conductive agent (eg, acetylene black, ketjen black, various dalafites), a binder (eg, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), etc.) ) If necessary, a thickener is mixed and kneaded with water or an organic solvent to prepare a positive electrode mixture slurry. Thereafter, a positive electrode mixture slurry is applied and dried on a positive electrode current collector such as an aluminum foil to form a positive electrode mixture layer. Here, at least one end in the longitudinal direction of the positive electrode plate is formed with an uncoated portion where no positive electrode mixture layer is formed. To do. Then, if necessary, the thickness of the positive electrode mixture layer is adjusted by a press and slit to a desired dimension to produce a positive electrode plate.

The negative electrode plate is composed of a negative electrode mixture containing a negative electrode active material and a negative electrode current collector made of foil.

As the negative electrode active material, for example, various natural graphites, artificial graphite or alloy composition materials can be used.

[0037] The negative electrode active material is mixed with a binder (for example, styrene butadiene rubber (SBR), PVdF, etc.) and, if necessary, a thickener, kneaded with water or an organic solvent, and the negative electrode mixture slurry is mixed. Make it. Thereafter, a negative electrode mixture slurry is applied and dried on a negative electrode current collector such as a copper foil to form a negative electrode mixture layer. Here, an uncoated portion in which the negative electrode mixture layer is not formed is formed on at least one end portion in the longitudinal direction of the negative electrode plate. Then, if necessary, the thickness of the negative electrode mixture layer is adjusted by a press and slit to a desired dimension to produce a negative electrode plate.

[0038] The separator is made of a material that is stable at any potential of the positive electrode plate and the negative electrode plate, for example, having high electrolyte holding power (eg, polypropylene, polyethylene, polyimide, polyamide, etc.). Sex film is used.

[0039] In order to connect the positive electrode plate to the positive electrode current collector plate (for example, aluminum) 2 and connect the negative electrode plate to the negative electrode current collector plate (for example, copper or nickel) 3, the positive electrode plate and the negative electrode plate are not connected. Electrode group 1 is fabricated so that the coated portions are on both end faces. Further, the positive electrode plate and the negative electrode plate are connected to the positive electrode current collector plate 2 and the negative electrode current collector plate 3 by, for example, laser welding or ultrasonic welding.

Example

Hereinafter, the present invention will be described in detail using examples.

[0041] (Battery A)

In a NiSO aqueous solution, the molar ratio of Ni: Co: Al = 7: 2: l

Four

A ternary system represented by Ni Co Al (〇H) is prepared by adding an acid salt to prepare a saturated aqueous solution and neutralizing the saturated aqueous solution while gradually dropping a sodium hydroxide solution while stirring.

0.7 0.2 0.1 2

The precipitate was produced by the coprecipitation method. This precipitate was filtered, washed with water, and dried at 80 ° C. to obtain a composite hydroxide. The average particle diameter of the obtained composite hydroxide was 10 _β m.

[0042] This composite hydroxide was heat-treated in the atmosphere at 900 ° C for 10 hours to obtain Ni Co Al ○ A ternary complex oxide represented by the formula (1) was obtained. Here, hold lithium hydroxide monohydrate so that the sum of the number of atoms of Ni, Co, and A1 is equal to the number of atoms of Li, and heat-treat at 800 ° C for 10 hours in air. By performing LiNi Co Al O

0.7 0.2 0.1 2

Got. By pulverizing and classifying the lithium nickel composite oxide, a positive electrode active material having an average particle size of 9.5 zm and a specific surface area of 0.4 m ² / g was obtained.

[0043] 3 kg of this positive electrode active material, 90 g of acetylene black, and PVdF solution lOOOOg were kneaded together with an appropriate amount of N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode slurry. This positive electrode slurry was applied and dried on an aluminum foil having a thickness of 15 × m and a width of 150 mm so that an uncoated part of 10 mm was left in the longitudinal direction of one end of the foil. This was pressed so that the total thickness was 100 zm, and then slit so that the uncoated width was 10 mm and the mixture coating width was 110 mm, to produce a positive electrode plate.

[0044] 3 kg of artificial graphite as a negative electrode active material, 75 g of a binder (solid weight 40 wt%) as rubber particles of styrene-butadiene copolymer, and 30 g of carboxymethyl cellulose (CMC) as a thickener And an appropriate amount of water were kneaded to prepare a negative electrode slurry. This negative electrode slurry was applied and dried on a copper foil having a thickness of 10 / im and a width of 150 mm so as to leave a 10 mm uncoated part in the longitudinal direction of one end of the foil. After this was pressed to a total thickness of 110 / m, it was slit so that the uncoated width was 10 mm and the mixture coating width was 114 mm, thereby producing a negative electrode plate.

[0045] The positive electrode plate and the negative electrode plate manufactured as described above were wound into a cylindrical shape with a positive electrode and a negative electrode current collector exposed at both ends via a polyethylene separator, and an electrode group (diameter 30 mm, length 80 mm) ) Was produced.

[0046] A positive electrode current collector plate made of aluminum was laser welded to the end surface on the positive electrode side of this electrode group, and a negative electrode current collector plate made of copper was laser welded to the end surface on the negative electrode side. Further, the positive electrode terminal was welded to the positive electrode current collector plate, the negative electrode current collector plate was welded to the negative electrode terminal, and fixed to the lid plate. After that, both ends of the electrode group are fixed with insulating members, and inserted into an aluminum rectangular housing with an explosion-proof valve with an area of 75 mm ² (5 X 15 mm) that opens at 10 atm. The lid plate was laser welded to form a battery case (width 35 mm x height 35 mm x length 90 mm). Here, all of the space provided inside the battery case (where the inner wall of the battery case and the electrode group do not contact) An explosion-proof valve was placed so that the explosion-proof valve could be engaged (corresponding to the position shown in Fig. 1 (d)).

[0047] On the other hand, lithium hexafluorophosphate (LiPF) as a solute was added to a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1: 3.

6

An electrolyte was prepared by dissolving at a concentration of dm ³ . 30 g of this electrolytic solution was injected into the battery case from the injection hole provided in the lid plate, impregnated in the electrode group, and finally sealed to produce a lithium ion secondary battery with a nominal capacity of 5 Ah. . The amount of excess electrolyte after impregnation with the liquid injection was about 10 g as a result of opening the battery case and removing it to measure the weight. From this, it can be considered that the electrode group in the initial state is impregnated with about 20 g of electrolyte.

[0048] The lithium ion secondary battery described above was arranged so that the surface of the battery case provided with the explosion-proof valve was the lower surface. This is designated as battery A which is an embodiment of the present invention.

[0049] (Battery

In battery A, a lithium ion secondary battery was fabricated in the same way as battery A, except that the explosion-proof valve was placed so that a part of the explosion-proof valve was opposed to the electrode group (corresponding to the position shown in Fig. 2 (b)). However, the battery case provided with the explosion-proof valve was arranged so that the surface thereof was the lower surface. This is designated as battery B which is an embodiment of the present invention.

[0050] (Battery C)

A lithium ion secondary battery similar to battery A was produced and placed so that the side of the battery case with the explosion-proof valve was the side. This is referred to as a battery C which is an embodiment of the present invention.

[0051] (Battery D)

A conventional cylindrical lithium ion secondary battery (35 mm in diameter and 90 mm in length) shown in Fig. 3 was produced. Specifically, an electrode group consisting of a positive electrode plate 101, a separator 103, and a negative electrode plate 102 similar to battery A (same dimensions as battery A) is inserted into a cylindrical battery case 104 and then the same composition as battery A. A cylindrical lithium-ion battery with a nominal capacity of 5 Ah is sealed by sealing the upper opening of the battery case 104 with a sealing plate 105 having an explosion-proof valve of the same area as the battery A. Produced. This lithium ion secondary battery was arranged so that the sealing plate 105 was on the upper surface. This is referred to as Battery D, which is a comparative example.

[0052] Five of each of the batteries described above were produced, and the following nail penetration test was performed in an environment of 25 ° C. First: 1. Charge / discharge with a current value of OA, a charge end voltage of 4.2V and a discharge end voltage of 3.0V. gave. As a result, it was confirmed that a discharge capacity close to the nominal capacity (5 Ah) was obtained. After that, 1. The battery was overcharged with a current value of OA to the end-of-charge voltage of 4.4V, each battery was fixed on the fixed base, and a nail with a radius of 1.5mm was passed through the central part of the battery case side.

[0053] A nail penetration test was performed under the conditions described above, and the amount of electrolyte remaining in the battery case, whether the battery case was damaged, the amount of battery case swelling, and the maximum battery temperature were evaluated. The results are shown in Table 1.

[0054] [Table 1]

[0055] Regarding battery A, it was observed that the explosion-proof valve was activated and opened several seconds after nail penetration, and the excess electrolyte in the battery case was discharged as mist. In addition, no damage was observed in any of the five batteries A after the test except for the explosion-proof valve, the battery case was not swollen as much as 0.2 mm, and no electrolyte remained in the battery case.

For battery B, as with battery A, it was observed that excess electrolyte in the battery case was discharged as mist. In addition, no damage to the batteries other than the explosion-proof valve was confirmed in any of the five batteries after the test, and the battery case swelled 0.5 mm compared to the battery A, in which no electrolyte remained in the battery case. And it was a little big. This is because the explosion-proof valve was placed at a position where the electrode group and the battery case were in contact with each other, and even when the explosion-proof valve was activated, the gas was not discharged smoothly compared to battery A. It is surmised that the battery case was deformed due to the increase in the pressure in the battery.

[0057] With respect to battery C, the amount of electrolyte remaining in the battery case was as high as 6g, although the battery case did not swell. This is because the explosion-proof valve was placed on the side of the battery case in spite of the space, so the electrolyte near the bottom of the battery case was completely removed. It is thought that it was not able to be discharged. However, no damage was observed in any of the five batteries C after the test, except for the explosion-proof valve, and the battery case swelled very little, indicating that gas was released quickly.

[0058] Regarding battery D, although the explosion-proof valve was activated, a part of the bottom of the three battery cases was damaged. This is different from batteries A to C, because the electrode group 'battery case is both cylindrical, so there is not enough space, and the explosion-proof valve is placed at the top, so gas is released quickly. It is presumed that the battery case was damaged because the increase in pressure was accelerated by the remaining electrolyte.

[0059] From the above results, by providing an explosion-proof valve on the side surface of the battery case corresponding to the space in the battery case partitioned by the cylindrical electrode group and the side surface of the battery case, This gas can be reliably and promptly released to the outside. Further, by providing an explosion-proof valve on the lower surface of the battery case, the gas in the battery generated in the event of an abnormality can be quickly released to the outside, and the electrolyte remaining in the battery can be quickly discharged to the outside.

As described above, the present invention has been described with reference to the preferred embodiments. However, the description is not a limitation, and various modifications can be made.

Industrial applicability

[0061] The present invention is useful for lithium ion secondary batteries that require safety at a high level, and can be applied not only to electronic devices but also to driving power sources for electric tools, electric vehicles, and the like.

Claims

The scope of the claims

[1] A sealed battery in which a cylindrical electrode group in which a positive electrode plate and a negative electrode plate are wound through a separator is inserted into a rectangular battery case together with an electrolyte,

A pressure release mechanism is provided on a side surface of the battery case parallel to the winding axis of the electrode group;

The sealed battery, wherein the pressure release mechanism is disposed at a position separated from a projection line when a winding axis of the electrode group is projected on the side surface at a right angle.

[2] Of the side surfaces, electrode terminals of the positive electrode plate and the negative electrode plate are respectively provided on the first side surface,

The sealed battery according to claim 1, wherein the pressure release mechanism is provided on a second side surface facing the first side surface.

[3] The hermetic battery according to claim 2, wherein at least two of the pressure release mechanisms are provided at a position facing each other with respect to the projection line on the second side surface and spaced apart from each other. .

4. The sealed battery according to claim 2, wherein the pressure release mechanism is provided so as to intersect the projection line on the second side surface and extend in a direction perpendicular to the projection line.

[5] Of the side surfaces, electrode terminals of the positive electrode plate and the negative electrode plate are respectively provided on the first side surface,

The pressure release mechanism is a third side surface adjacent to the first side surface, and is disposed at a position spaced apart from the projection line on the third side surface to the side opposite to the first side surface, The sealed battery according to claim 1.

6. The sealed battery according to claim 1, wherein the electrode group has a flat cylindrical shape.

7. The sealed battery according to claim 1, wherein a region in the battery case defined by the electrode group and the inner wall of the side surface forms a space.

[8] The sealed battery according to [1], wherein the pressure release mechanism includes an explosion-proof valve.