JP2006079959A - Flat nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat nonaqueous electrolyte secondary battery having a square external shape with improved sealing strength by calking. <P>SOLUTION: The flat nonaqueous electrolyte secondary battery is composed of: a bottomed cylinder-shaped outer can 1 having an open end folded inside by calking; a bottomed cylinder-shaped sealing can 3 having a flange part 4 projecting outward at the open end which is arranged at the open part of the outer can 1 so as to be surrounded by the folded part 2 of the outer can 1; and an insulation gasket 5 arranged between the folded part 2 of the outer can 1 and the flange part 4 of the sealing can 3. Respective edges 4a to 4d of the flange 4 of the sealing can 3 are bent outward, and a radius of curvature thereof satisfies a relation, 7W≤R≤15W (1), wherein W is a length of a part of the battery corresponding to respective edges 4a to 4d of the flange part 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flat non-aqueous electrolyte secondary battery having a non-circular outer shape.

  Downsizing of devices used has been accelerating mainly on small information terminals such as mobile phones and PDAs, and the secondary battery as the main power source is also required to be downsized. Cylindrical and square types, such as those found in lithium-ion batteries, are currently available for miniaturization, but when pursuing a thinner design, a metal case that also serves as the positive electrode terminal and a metal case that serves as the negative electrode terminal. A coin type constituted by caulking and fixing with a gasket is a simple and highly productive method. A flat battery, usually called a coin-type battery, maintains its sealing performance by pressurizing either the negative electrode case or the positive electrode case with caulking. However, since the circular parts are isotropically deformed and caulked, it is uniform. It gives stress and is highly reliable.

  On the other hand, due to an increase in electric power used by electronic devices, it is difficult to sufficiently extract the electric power required by the device using a conventional battery using a pellet shape as an electrode. In order to realize a high output, Patent Documents 1 and 2 achieve a high output by increasing the reaction area with an electrode having a wound structure.

Patent Document 3 relates to a coin-type battery that averages the strain rate applied to the electrode plate group when the coin-type battery is configured using the electrode group having a wound structure.
JP 2003-77457 A JP 2003-77543 A JP 2002-117900 A

  An object of the present invention is to improve the caulking sealing strength of a flat non-aqueous electrolyte secondary battery having a rectangular outer shape such as a rectangle or a square (a main surface has a square shape).

A flat nonaqueous electrolyte secondary battery according to the present invention is a bottomed rectangular tube, and an outer can whose opening end is bent inward by caulking,
A bottomed rectangular tube having a flange portion projecting outward at an opening end thereof, and a sealing can disposed at the opening portion of the outer can so that the flange portion is surrounded by a bent portion of the outer can,
An insulating gasket disposed between the bent portion of the outer can and the flange portion of the sealed can;
An electrode group disposed between the bottom inner surface of the outer can and the bottom inner surface of the sealing can,
Each side of the flange portion of the sealing can is curved outward, and the radius of curvature R satisfies the following expression (1).

7W ≦ R ≦ 15W (1)
However, W is a battery external dimension of the part corresponding to each side of the flange part.

  According to the present invention, it is possible to improve the caulking sealing strength of a flat nonaqueous electrolyte secondary battery having a rectangular outer shape such as a rectangle or a square.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 2, the outer can 1 having a bottomed rectangular cylindrical shape also serves as a single electrode (for example, positive electrode) terminal. Here, examples of the square (square) include a rectangle and a square. The outer can 1 has a U-shaped or curled bent portion 2 formed by bending the opening end inward by caulking. The sealing can 3 having a bottomed rectangular tube shape also serves as the other electrode (for example, negative electrode) terminal. The sealing can 3 has a flange portion 4 projecting outward from the opening. The sealing can 3 is disposed at the opening of the outer can 1, and the flange portion 4 is sandwiched by the bent portion 2 of the outer can 1 via the insulating gasket 5. That is, the sealing can 3 is caulked and fixed to the opening of the outer can 1 via the insulating gasket 5.

  Since the flange part 4 of the sealing can 3 is not provided with the reverse structure, the height of the sealing part can be reduced and the battery can be made thinner. Moreover, compared with the case where the reverse structure is provided, the bending width of the flange part 2 of the outer can 1 can be enlarged.

  The electrode group 6 has a structure in which a positive electrode 7 and a negative electrode 8 are wound in a flat shape with a separator 9 therebetween. The outer shape of the electrode group 6 is substantially square. It is desirable that the outer shape of the battery case formed from the sealing can 3 and the outer can 1 is substantially similar to the outer shape of the electrode group. Thereby, since the occupation rate of the electrode group with respect to a battery case can be made high, an energy density can be improved. The positive electrode 7 includes a positive electrode current collector (not shown) and a positive electrode active material-containing layer (not shown) supported on one or both surfaces of the positive electrode current collector. On the other hand, the negative electrode 8 includes a negative electrode current collector (not shown) and a negative electrode active material-containing layer (not shown) supported on one or both surfaces of the negative electrode current collector. One outermost layer of the electrode group 6 is a positive electrode current collector, and a positive electrode active material-containing layer is formed on the inner surface of the positive electrode current collector, but is formed as shown in FIG. It is also possible to have no configuration. The other outermost layer of the electrode group 6 is a negative electrode current collector, and a negative electrode active material-containing layer is formed on the inner surface of the negative electrode current collector, which is formed as shown in FIG. It is also possible to have an unconfigured configuration. In addition, the winding end end portion of the electrode group 6 is fixed by a winding tape 10.

  Such an electrode group 6 is accommodated in a liquid-tight space formed by the outer can 1 and the sealing can 3. Further, in the electrode group 6, the surface on which the positive electrode current collector is the outermost layer faces the bottom inner surface of the outer can 1, and the surface on which the negative electrode current collector is the outermost layer faces the bottom inner surface of the sealing can 3. Yes.

  For example, the positive electrode conductive layer 11 made of a metal porous plate is disposed between the outermost positive electrode current collector and the inner surface of the bottom of the outer can 1, and plays a role in improving the conduction between them. On the other hand, the negative electrode conductive layer 12 made of, for example, a metal porous plate is disposed between the outermost negative electrode current collector and the bottom inner surface of the sealing can 3, and plays a role in improving the conduction between them.

  In the flat nonaqueous electrolyte secondary battery having such a configuration, as shown in FIGS. 1 and 3, the sides 4 a to 4 d of the flange portion 4 of the sealing can 3 are curved in an arc shape toward the outside. ing. In each of the sides 4a to 4d, it is desirable that the radius of curvature R at the outermost protruding portion, that is, the portion having the maximum width X satisfies the following expression (1).

7W ≦ R ≦ 15W (1)
However, W is a battery external dimension of the part corresponding to each side 4a-4d of the flange part 4. FIG. When the outer shape of the battery is square, the lengths of the sides 4a to 4d are equal, and the battery outer dimension of the portion corresponding to each of the sides 4a to 4d is determined to be one numerical value, but when the outer shape of the battery is rectangular Since the short side and the long side exist, the value of W is determined for each side of the flange portion.

  Hereafter, the reason prescribed | regulated to said (1) Formula is demonstrated.

  In a battery having a circular outer shape represented by a coin shape or a button shape, it is important that the arrangement of the sealing plate and the outer can satisfy a concentric relationship. Assembling by caulking is processed with a circular mold having a radius smaller than the outermost periphery of the workpiece, but by matching the center of the circle, uniform stress is applied and high sealing performance can be obtained. Is possible. On the other hand, in the non-circular battery as in the present invention, unlike the circular shape, if the outermost peripheral shape of each component is similar, it is difficult to perform crimping uniformly. When non-circular parts are used for caulking, the non-machined parts subjected to caulking are processed by a generally similar die that is smaller than the outermost periphery of the non-machined parts. ) Goes through the bent form, and the corner goes through compression to reduce the opening width. The stress required for processing is large in the corner portion and small in the straight portion (side portion). The straight portion starts to be processed by a small stress, but the strength of the component tends to be low. Depending on the corner portion setting and the size of the battery, the deformation may affect the sealing can and the sealing performance may be lowered.

  In the present invention, the corners at the opening end of the outer can 1 are formed into a large arc shape by curving the sides 4a to 4d of the flange portion of the sealing can 3 outward so as to satisfy the above-described equation (1). Can be folded. As a result, the stress generated during the bending is easily dispersed, so that the corner portion can be bent into an arc shape with a sufficient width.

  By the way, even if the side portion of the flange portion 4 is a straight line and only the radius of curvature of the corner portion is increased, the corner portion at the open end of the outer can 1 can be bent into a large arc shape. Since the shape change from the corner part to the side part becomes steep, the sealing strength at this part may be reduced, leading to leakage. By making the shape change from the corner portion to the side portion in the flange portion continuous as in the present invention, the difference in sealing strength between the corner portion and the side portion can be reduced.

  As described above, the corner portion at the opening end of the outer can 1 can be bent with a larger radius of curvature, and the bending width can be sufficiently secured. At the same time, the sealing strength is continuous from the corner portion to the side portion. Therefore, the sealing strength can be improved. As a result, intrusion of moisture from the outside can be prevented, and even when the insulating gasket repeats expansion and contraction due to temperature changes, high liquid tightness can be maintained, and a non-aqueous electrolyte with high sealing reliability A secondary battery can be realized. A more preferable range is 9W ≦ R ≦ 13W.

  When the curvature radius R is smaller than 7 W, the shape of the sealing can is close to a circle. Since the shape of the electrode group is generally rectangular, the width of the flange portion 4 of the sealing can 3 is wide at the side and narrowed at the corner, and the narrowed corner is hardly sandwiched by the insulating gasket, and the caulking strength is reduced. . On the other hand, when the curvature radius R is set to be larger than 15 W, the effect is low because the outline of the flange portion 4 has a shape substantially similar to a straight line.

  The flat non-aqueous electrolyte secondary battery referred to in the present invention has a height in a direction perpendicular to the opening of the outer can 1 smaller than the width of a surface horizontal to the opening of the outer can 1. .

  As shown in FIG. 3, the corner portion 13 at the outer edge portion of the bent portion 2 of the outer can 1 and the corner portion 14 at the outer edge portion of the flange portion 4 of the sealing can 3 are respectively curved in a curved shape or an arc shape. Preferably it is. If the corners 13 and 14 are acute, large distortion may occur at the caulking stage, which may make it difficult to form a uniform sealing portion. On the other hand, when the curvature radii R1 and R2 of the corner portions 13 and 14 are increased, the outer shape of the battery approximates to a circle, and thus there is a possibility that a high energy density cannot be obtained. When the radius of curvature R1 and R2 of the corner portions 13 and 14 is reduced, the energy density is increased, but distortion generated in the corner portion when the caulking is fixed increases, and wrinkles and distortion are likely to occur, and uniform caulking may be difficult. There is. Preferably, when the length of one side of the battery is A and the length of the side perpendicular to this side is B, the curvature radii R1, R2 of the corner portions 13, 14 are (A + B) / 14 or more, (A + B) / A range of 8 or less is preferred.

  The radius of curvature R1 of the corner 13 at the outer edge of the bent portion 2 of the outer can 1 and the radius of curvature R2 of the corner 14 at the outer edge of the flange 4 of the sealing can 3 satisfy the following equation (2). desirable.

1.00 ≦ R2 / (R1−tR1−d) ≦ 1.08 (2)
Here, d is the distance between the end face 15 of the corner portion 14 that gives R2 and the inner wall surface of the outer can 1 facing this through the insulating gasket 5, and tR1 is the thickness of the outer can 1.

  By satisfying the above formula, it is possible to further relax the stress generated in the corner portion during bending. A more preferable range is 1.02 or more and 1.08 or less.

  The insulating gasket 5 is preferably made of a material that has little moisture ingress and low hygroscopicity. In addition, it is important to select a material that is less swellable with respect to the electrolytic solution and that takes into consideration the operating temperature. From such a viewpoint, preferred gasket materials include polyolefins such as polyethylene and polypropylene, and polyphenylene sulfide.

  As illustrated in FIG. 2 described above, when the opening area of the outer can 1 and the sealing can 3 is (outer can)> (sealing can), the outer can 1 includes the sealing can 3 via the insulating gasket 5. The shape can be made. The outer can 1 can contribute to sealing performance with the sealing can by compressing the insulating gasket 5 by caulking. It is the packing cross section and the path that contribute to the sealing performance. If the pressurized state is maintained through the insulating gasket 5 having a thin resin thickness, the reliability of the sealing is increased. In particular, the reliability of the sealing can be improved by partially forming the compression portion.

  The parts of the outer can 1, the insulating gasket 5, and the sealing can 3 are fitted together in the previous stage of caulking. In order to increase the reliability of the sealing, it is important to narrow the interval between the components. However, if there is no interval (clearance) between the components to some extent, a fitting failure may occur. It is not particularly necessary if there are many sealing parts in the battery, but in the design where the clearance between the parts is important, in the process of caulking, the open end of the outer can 1 is compressed to the extent that there is no deformation. You may give it.

  Moreover, it is important to suppress the explosion due to the looseness of the processed part such as caulking and the scattering of the contents against the increase in the internal pressure when used extraordinarily. For this, it is desirable to make the inner peripheral dimension of the bent portion 2 of the outer can 1 after crimping smaller than the outer peripheral dimension of the flange portion 4 of the sealing can 3. In such a configuration, since the flange portion 4 of the sealing can 3 is wrapped by the bent portion 2 of the outer can 1, it is possible to avoid the sealing can 3 from being detached from the outer can 1 due to an increase in internal pressure.

  In the caulking process, the caulking part is preferably formed by caulking once or twice or more depending on the shape of the workpiece. When the amount of deformation by caulking is small, a desired sealing can be realized by one caulking. In addition, when deformation due to processing is large, a desired crimped shape can be obtained by dividing the degree of deformation into multiple stages. The multi-stage process includes local caulking.

  The sealing can 3 and the outer can 1 can each be formed from a clad material of a metal such as stainless steel (SUS), aluminum or an aluminum alloy, and stainless steel, for example.

  The plate thickness of the sealing can 3 is desirably in the range of 0.2 mm to 0.4 mm. The plate thickness of the outer can 1 is desirably in the range of 0.2 mm to 0.4 mm.

Examples of the positive electrode active material include lithium cobalt-containing composite oxide (for example, LiCoO ₂ ), lithium nickel-containing composite oxide (for example, LiNiO ₂ ), and lithium nickel cobalt-containing composite oxide (for example, LiNi _0.8 Co _0.2 O ₂ ). And lithium manganese-containing composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ).

  Examples of the negative electrode active material include carbonaceous materials that occlude and release lithium, lithium titanate, silicon compounds, and composites thereof.

  Moreover, as a nonaqueous electrolyte, a liquid, a gel form, and a solid form can be used.

  In FIG. 1 described above, the positive and negative electrode conductive layers 11 and 12 are used in order to improve the electrical connection between the outermost positive and negative electrode current collectors of the electrode group 6 and the battery case. A resin electrode group guide as shown in FIG. 6 may be used.

  The electrode group guide 31 has a U shape as shown in FIG. 4 and is made of, for example, polyolefin such as polypropylene or polypropylene. The upper surface 31 a of the electrode group guide 31 is disposed between the negative electrode current collector 32, which is the outermost layer of the electrode group 6, and the separator 33. On the other hand, the lower surface 31 b of the electrode group guide 31 is disposed between the positive electrode current collector 34 of the outermost layer of the electrode group 6 and the separator 35. In this case, the active material-containing layer is not formed on both surfaces of the outermost positive / negative electrode current collector. Further, the rising wall 31c that connects the upper surface 31a and the lower surface 31b of the electrode group guide 31 is disposed on the spiral surface located on the back side of the spiral surface shown in FIG. According to such an electrode group guide 31, not only the positive and negative electrode current collectors of the outermost layer of the electrode group 6 and the battery case are electrically connected, but also the distortion of the electrode group 6 accompanying the progress of the charge / discharge cycle is reduced. It becomes possible to do.

  Further, instead of the electrode group guide having the structure described above, silicon is provided between the outermost negative electrode current collector of the electrode group and the separator and between the outermost positive electrode current collector and the separator of the electrode group. A rubber sheet may be arranged. This silicone rubber sheet has excellent resistance to non-aqueous electrolytes, and has a small amount of displacement with respect to expansion and contraction of the electrode group due to charge and discharge. Can be maintained for a long time.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.
Example 1
<Preparation of positive electrode>
Add 5 parts by mass of acetylene black and 5 parts by mass of graphite powder as a conductive agent to 100 parts by mass of LiCoO ₂ , add 5 parts by mass of polyvinylidene fluoride as a binder, dilute and mix with N-methylpyrrolidone, A positive electrode mixture was obtained. Next, a positive electrode active material-containing layer was formed by applying and drying a positive electrode mixture by a doctor blade method on both surfaces of an aluminum foil having a thickness of 0.02 mm as a positive electrode current collector, and then pressing and 20 mm width A slit was made to produce a positive electrode.

  Next, the positive electrode active material-containing layer of 10 mm from the edge of one side of the positive electrode was removed to expose the aluminum layer to form a current collector, which was cut to a length of 20 mm and a length of 200 mm. A positive electrode 7 was produced.

<Production of negative electrode>
2.5 parts by mass of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders are added to 100 parts by mass of graphitized mesophase pitch carbon fiber powder, diluted and mixed with ion-exchanged water, and a slurry-like negative electrode A mixture was obtained. The obtained negative electrode mixture was coated and dried in the same manner as in the case of the positive electrode on a 0.02 mm thick copper foil as a negative electrode current collector so that the thickness of the negative electrode active material-containing layer was 0.15 mm. A negative electrode was prepared by pressing and slitting to a width of 21 mm.

  Next, the negative electrode active material-containing layer of 23 mm from the end of one side of the negative electrode was removed to expose the copper layer to form a current collector, with a width of 21 mm and a length of 220 mm and a thickness of 0.15 mm. A negative electrode 8 was obtained.

<Battery assembly>
A separator 9 made of a polyethylene microporous film having a thickness of 25 μm and a width of 23 mm is interposed between the positive electrode 7 and the negative electrode 8. One outermost layer is a positive electrode current collector (aluminum foil) and the other outermost layer is a negative electrode collector. It wound so that it might become an electrical part (copper foil). The outermost flat surface was finished with the positive electrode current collector and the negative electrode current collector facing each other, and the end of the winding was fixed with a polyester adhesive tape 10. Then, flat plate press was performed until the electrode group became 2.3 mm. The produced electrode group was used after being dried at 85 ° C. for 12 hours.

  A polypropylene insulating gasket 5 was immersed in bron asphalt diluted with toluene as a sealant and dried at room temperature.

  Sealing can 3 was made of 0.25 mm SUS material. At this time, each side 4a to 4d of the flange portion 4 was processed to be bent outward so that the radius of curvature R was 330 mm. A nickel net having a thickness of 0.1 mm was welded as the negative electrode conductive layer 12 to the inner surface of the bottom of the obtained sealing can 3.

  The outer can 1 was manufactured by processing an aluminum layer of a clad material composed of 0.05 mm of aluminum and 0.2 mm of SUS as an inner surface. An aluminum net having a thickness of 0.2 mm was welded to the bottom inner surface of the obtained outer can 1 as the positive electrode conductive layer 11.

The insulating gasket 5 and the sealing can 3 were integrated in advance, and then dried under reduced pressure for 12 hours. LiBF ₄ is used as a supporting salt in a non-aqueous solvent in which the negative electrode current collector of the electrode group 6 is opposed to the nickel metal net 12 of the sealing can 3 and ethylene carbonate and γ-butyllactone are mixed at a volume ratio of 1: 3. A liquid non-aqueous electrolyte dissolved at a rate of 1.5 mol / L is injected, and the positive electrode current collector of the electrode group 6 is brought into contact with the aluminum metal net 11 of the outer can 1. 1 has the structure shown in FIG. 1 to FIG. 3 by bending the opening end inward using a mold, and the outer shape of thickness 3.2 mm, length 30 mm, width 30 mm is square. A flat nonaqueous electrolyte secondary battery was produced.

  In the obtained secondary battery, since the battery dimensions W corresponding to the sides 4a to 4d of the flange portion 4 of the sealing can 3 are all 30 mm, the radius of curvature R is 11 W when expressed by the battery dimension W.

  Further, the radius of curvature R1 of the corner portion 13 in the outer portion of the bent portion 2 of the outer can 1 was 6 mm. The radius of curvature R2 of the corner portion 14 at the outer edge portion of the flange portion 4 of the sealing can 3 was 5.7 mm. The distance d between the end surface 15 of the corner portion 14 and the inner wall surface of the outer can 1 facing this through the insulating gasket 5 was 0.3 mm. The plate thickness tR1 of the outer can is 0.25 mm. Therefore, R2 / (R1-tR1-d) was 1.05.

  Since the battery lengths A and B are both 30 mm, (A + B) / 14 is 4.3 mm, (A + B) / 8 is 7.5 mm, and the curvature radii R1 and R2 are (A + B) / 8 mm or more. The relationship of (A + B) / 14 or less was satisfied.

(Examples 2-5 and Comparative Examples 1-2)
Except that the curvature radius R, the curvature radius R1, and the curvature radius R2 of each side 4a to 4d of the flange portion 4 of the sealing can 3 are set as shown in Table 1 below, the same as described in the first embodiment. Thus, a flat nonaqueous electrolyte secondary battery was produced.

200 pieces of each of the obtained secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2 were prepared and subjected to initial charging for 24 hours at a constant current and a constant voltage of 4.2 V and 15 mA. In order to measure the discharge capacity of the battery, the battery was once discharged to 3.0 V at 15 mA. After charging again, 100 of them were left in a constant temperature and humidity chamber at 60 ° C. and 93% RH to conduct an environmental test. The 60 ° C. 93% RH constant temperature and humidity chamber was evaluated after 60 days, and the presence or absence of liquid leakage was confirmed visually. The number of leaks is shown in Table 1. The remaining 100 pieces were subjected to a thermal shock test of 1 cycle at −20 ° C. for 2 hours / 60 ° C. for 2 hours. After the test, the presence or absence of liquid leakage was visually confirmed. The number of leaks is shown in Table 1.

  As is apparent from Table 1, the secondary batteries of Examples 1 to 5 having a radius of curvature R of the flange portion 4 of the sealing can 3 of 7 W or more and 15 W or less are the number of leaks at high temperature and high humidity and the leak due to the thermal shock. Both of the numbers could be reduced. This indicates that the secondary batteries of Examples 1 to 5 are less likely to allow moisture to enter even in a humid atmosphere and that the caulking is not loosened even if the volume of the insulating gasket changes due to a temperature change. In particular, according to Examples 1, 4, and 5 having a curvature radius R of 9 W or more and 13 W or less, there was no number of liquid leaks at high temperature and high humidity and the number of liquid leaks due to thermal shock.

  On the other hand, the secondary battery of Comparative Example 1 having a radius of curvature R smaller than 7 W and the secondary battery of Comparative Example 2 having a radius of curvature R larger than 15 W are leaked at high temperature and high humidity and leaked due to thermal shock. Both increased in comparison with Examples 1-5.

  As described above, in the caulking of a substantially square battery, unlike a round shape (coin shape), uniform processing becomes difficult.However, according to the present invention, the sealing is highly reliable and is now widely used. It is possible to obtain the same or better reliability than the coin-type battery.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  The present invention is particularly advantageous for housing a substantially square power generation element capable of high-load discharge, and its industrial value is high because it can contribute to downsizing and high performance of equipment.

The typical top view showing the sealing can used for the flat type nonaqueous electrolyte secondary battery concerning one embodiment of the present invention. The principal part sectional drawing obtained when the flat nonaqueous electrolyte secondary battery in which the sealing can of FIG. 1 was incorporated was cut | disconnected along the thickness direction. FIG. 3 is a schematic top view of the flat nonaqueous electrolyte secondary battery in FIG. 2. The typical sectional view of the electrode group guide used with the flat type nonaqueous electrolyte secondary battery concerning the present invention. The side view which showed typically the state which integrated the electrode group guide of FIG. 4 in the electrode group. The typical top view of the electrode group with an electrode group guide shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Outer can, 2 ... Bending flange part, 3 ... Sealing can, 4 ... Flange part, 4a-4d ... Side of flange part, 5 ... Insulating gasket, 6 ... Electrode group, 7 ... Positive electrode, 8 ... Negative electrode, DESCRIPTION OF SYMBOLS 9 ... Separator, 10 ... Anti-winding tape, 11 ... Positive electrode conductive layer, 12 ... Negative electrode conductive layer, 31 ... Electrode group guide.

Claims (2)

An outer can with a bottomed rectangular tube shape, the opening end of which is bent inward by caulking,
A bottomed rectangular tube having a flange portion projecting outward at an opening end thereof, and a sealing can disposed at the opening portion of the outer can so that the flange portion is surrounded by a bent portion of the outer can,
An insulating gasket disposed between the bent portion of the outer can and the flange portion of the sealed can;
An electrode group disposed between the bottom inner surface of the outer can and the bottom inner surface of the sealing can,
A flat non-aqueous electrolyte secondary battery characterized in that each side of the flange portion of the sealing can is curved outward and the radius of curvature R satisfies the following formula (1).
7W ≦ R ≦ 15W (1)
However, W is a battery external dimension of the part corresponding to each side of the flange part. The radius of curvature R1 of the corner portion at the outer edge portion of the bent portion of the outer can and the radius of curvature R2 of the corner portion at the outer edge portion of the flange portion of the sealed can satisfy the following formula (2). The flat nonaqueous electrolyte secondary battery according to claim 1.
1.00 ≦ R2 / (R1−tR1−d) ≦ 1.08 (2)
Here, d is the distance between the corner portion that gives R2 and the inner wall surface of the outer can that faces this via the insulating gasket, and tR1 is the thickness of the outer can.

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