JP2013182784A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery having formed on a side face of the battery case a cleavage groove consisting of a first curvature protrusively curved in one direction and a second curvature protrusively curved in a direction at an angle of 90 degrees or more against the protruding direction of the first curvature, in which the cleavage groove is composed to be surely cleavable depending on the internal pressure of the battery case, even when the battery case differs in size or in plate thickness.SOLUTION: The sealed battery comes with a battery case formed in shape of a hollow column having an electrode body and an electrolyte solution sealed therein. On a side face of the battery case is formed a cleavage groove constituting a cleavage line intersecting a ridge line. The cleavage groove has a such groove depth that a ratio in percentage of the plate thickness of the battery case to the thickness of the remaining wall portion divided by a width of the battery case when the side face of the battery case is viewed from the normal direction is 1.6%/mm or less.

Description

  The present invention relates to a sealed battery in which a cleavage groove is formed on a side surface of a battery case in which an electrode body and an electrolytic solution are sealed, and is cleaved when a pressure in the battery case becomes larger than a threshold value.

  2. Description of the Related Art Conventionally, a sealed battery is known in which a cleavage groove that is cleaved when a pressure in the battery case becomes larger than a threshold value is formed on a side surface of the battery case. In such a sealed battery, for example, as disclosed in Patent Document 1, a convex ridge line (ridge line) formed on the side surface of the battery case and when the battery case swells due to an increase in internal pressure, A cleavage groove is formed at the intersecting position. Thereby, when the pressure in the battery case becomes larger than the threshold value, the cleavage groove is broken by the deformation of the battery case, so that the gas in the battery case can be released to the outside.

Japanese Patent No. 4166028

  By the way, in the case of a configuration in which a cleavage groove is provided on the side surface of the battery case as in the configuration disclosed in Patent Document 1, there is a possibility that the cleavage groove may be cleaved by an impact received by the battery case when the battery is dropped or the like. is there. If it does so, the electrolyte solution in a battery case may leak.

  On the other hand, it is conceivable to make the shape of the cleavage line constituted by the cleavage groove difficult to be cleaved when the battery is dropped or the like. However, if the cleavage line has such a shape, the cleavage groove may not be easily cleaved even when the pressure in the battery case exceeds a threshold value.

  Further, in order to efficiently discharge the gas from the battery case, it is preferable that the cleavage line has such a shape that the opening portion becomes as large as possible when the cleavage groove is cleaved. However, if the area of the part to be cleaved is increased in order to enlarge the opening, the cleaved part may contact the electrode body in the battery case to cause a short circuit or damage the exterior film covering the battery case. There is sex.

  On the other hand, the cleavage line formed by the cleavage groove is projected in a direction that forms an angle of 90 degrees or more with respect to the projecting direction of the first curved section and the first curved section that projects in a projecting manner in one direction. The structure formed by the curve by which the 2nd bending part which curves in a line was alternately connected can be considered. By making the shape of such a cleavage line, the cleavage groove can be cleaved safely and easily according to the pressure in the battery case, and the opening of the cleaved portion can be enlarged. Moreover, the cleavage groove that forms the cleavage line having the above-described shape is less likely to be cleaved by an impact such as a drop of the battery, compared to the cleavage groove that forms a linear cleavage line.

  However, since the size and plate thickness of the battery case are different when the type of battery is different, the cleavage groove may not be cleaved according to the pressure in the battery case even in the shape of the cleavage line as described above.

  As described above, an object of the present invention is to form a first bending portion that protrudes in one direction on the side surface of the battery case, and a direction that forms an angle of 90 degrees or more with respect to the protruding direction of the first bending portion. In a sealed battery in which a cleaving groove formed by a curve in which the second curved portions that are curved in a projecting manner are alternately connected is formed, even when the size and thickness of the battery case are different, the internal pressure of the battery case It is to obtain a structure of a cleavage groove that can be more reliably cleaved.

  A sealed battery according to an embodiment of the present invention includes a hollow columnar battery case in which an electrode body and an electrolytic solution are enclosed, and the battery case swells on the side surface of the battery case due to an increase in internal pressure. In this case, a cleavage groove that forms a cleavage line that intersects a ridge line formed on the side surface of the battery case is formed, and the cleavage line is configured only by a curve, and the side surface of the battery case is A first bending portion that curves in a protruding manner in one direction as viewed from the normal direction, and a second bending portion that curves in a protruding manner in a direction that forms an angle of 90 degrees or more with respect to the protruding direction of the first bending portion; Are alternately connected, the first bending portion and the second bending portion are connected to each other at one end, and at least one of the first bending portion and the second bending portion is Intersects the ridgeline and the front The cleavage groove has a value obtained by dividing the percentage of the ratio of the thickness of the remaining portion to the plate thickness of the battery case by the width of the battery case when the side surface of the battery case is viewed from the normal direction. The groove depth is 1% / mm or less (first configuration).

  In the above configuration, the cleaving groove formed on the side surface of the battery case has a first bending portion that protrudes in one direction when the side surface of the battery case is viewed from the normal direction, and the first bending portion A cleavage line is formed of a curve in which second curved portions that project in a projecting manner in a direction that forms an angle of 90 degrees or more with respect to the projecting direction are alternately connected. The cleavage groove constituting the cleavage line having such a shape can be cleaved safely and easily according to the pressure in the battery case, and the opening of the cleaved portion can be enlarged. Moreover, the cleavage line is difficult to be cleaved by an impact such as dropping of the battery.

  The cleavage groove is a value obtained by dividing the ratio of the thickness of the remaining portion to the thickness of the battery case by the width of the battery case when the side surface of the battery case is viewed from the normal direction (hereinafter, ( (R / T) / W value) is 1.6% / mm or less. Therefore, even when the plate thickness and width of the battery case are different, the cleavage groove can be cleaved according to the pressure in the battery case.

  That is, as shown in FIG. 8, in the range where (R / T) / W value is 1.6% / mm or less, compared with the range where (R / T) / W value is larger than 1.6% / mm. Thus, the change amount of the operating pressure of the cleavage groove (the threshold value of the pressure at which the cleavage groove is cleaved) with respect to the change in (R / T) / W value is small. Therefore, in the range of (R / T) / W value of 1.6% / mm or less, the cleavage groove is not affected even if the groove depth or the battery case width changes somewhat due to errors during processing. Cleavage near the design value of working pressure. In addition, as described above, by defining the groove depth of the cleavage groove by (R / T) / W value, even in battery cases having different case widths or plate thicknesses, (R / T) / W value is 1 If a cleavage groove having a groove depth of 6% / mm or less is provided, the cleavage groove can be more reliably cleaved according to the pressure in the battery case.

  In the first configuration, the cleavage groove has a percentage of a ratio of a thickness of a remaining portion to a plate thickness of the battery case with respect to a thickness of the battery case when a side surface of the battery case is viewed from a normal direction. It is preferable to have a groove depth such that the value divided by the width ratio is 7.5% or less (second configuration).

  Thus, since the thickness of the battery case can be taken into consideration when determining the groove depth of the cleavage groove, a cleavage groove that can be more reliably cleaved can be obtained even when the thickness of the battery case is different.

  That is, as shown in FIG. 9, the ratio of the thickness of the remaining portion to the thickness of the battery case divided by the ratio of the width to the thickness of the battery case when the side surface of the battery case is viewed from the normal direction. In the range where 7.5% or less (hereinafter referred to as (R / T) / (W / D) value), compared with the range where (R / T) / (W / D) value is greater than 7.5%. Thus, the change amount of the working pressure of the cleavage groove with respect to the change of the (R / T) / (W / D) value is small. Therefore, in the range where the (R / T) / (W / D) value is 7.5% or less, even if the groove depth of the cleavage groove or the width, thickness, etc. of the battery case changes somewhat due to errors during processing, etc. The cleavage groove is cleaved near the design value of the operating pressure. Further, as described above, by defining the groove depth of the cleavage groove by the (R / T) / (W / D) value, even in battery cases having different case widths, thicknesses, and plate thicknesses, (R / T ) / (W / D) If a cleavage groove having a groove depth of 7.5% or less is provided, the cleavage groove can be more reliably cleaved according to the pressure in the battery case.

  In the first or second configuration, the cleavage line is preferably formed by combining the first bending portion and the second bending portion one by one (third configuration). By doing so, the cleavage groove constituting a simple shape (for example, S-shaped) cleavage line can more easily cleave the cleavage groove when the battery case is deformed, and the cleavage of the cleavage groove A large opening can be easily formed.

  In any one of the first to third configurations, the first bending portion is curved in a projecting manner toward an end portion of the battery case located on a base end side of the ridge line. The cleavage groove is preferably formed on a side surface of the battery case so that the first curved portion is positioned on the ridgeline (fourth configuration).

  As a result, the protrusion of the first bending portion is located at a position closer to the end of the battery case on the ridgeline, and therefore, the first bending portion located on the ridgeline is likely to be cleaved by deformation of the battery case. That is, as the battery case is deformed, the ridge line is generated from the periphery of the end portion of the battery case. Therefore, by forming the first bending portion into a shape that protrudes toward the end portion, the first bending portion is formed. The part can be cleaved at the initial stage of deformation of the battery case. Therefore, the cleavage groove can be more reliably cleaved by the deformation of the battery case.

  In any one of the first to fourth configurations, the cleavage groove is an end portion of the battery case that is located on a base end side of the ridge line when the side surface of the battery case is viewed from the normal direction. Therefore, it is preferable that the battery case is formed on the side surface of the battery case so as to be located within a half of the longitudinal length and the lateral length (fifth configuration).

  By carrying out like this, a cleavage groove can be provided in the base end side of the ridgeline formed on the side surface of a battery case. Thereby, the cleavage groove can be more reliably cleaved by the deformation of the side surface of the battery case accompanying the pressure change in the battery case.

  In any one of the first to fourth configurations, the cleavage groove is an end portion of the battery case that is located on a base end side of the ridge line when the side surface of the battery case is viewed from the normal direction. Therefore, it is preferable that the battery case is formed on the side surface of the battery case so as to be within a range of 1/3 of the longitudinal length and the lateral length (sixth configuration).

  Thereby, the cleavage groove can be provided at a position closer to the proximal end side of the ridgeline formed on the side surface of the battery case. Therefore, the cleavage groove can be further reliably cleaved by the deformation of the side surface of the battery case accompanying the pressure change in the battery case.

  According to the sealed battery of one embodiment of the present invention, the first bending portion that protrudes in one direction and protrudes in a direction that forms an angle of 90 degrees or more with respect to the protruding direction of the first bending portion. In the configuration in which the cleavage groove formed of a curve alternately connected to the second bending portion curved in a shape is formed on the side surface of the battery case, the groove depth of the cleavage groove is expressed by (R / T) / W value. The groove depth is set to 1.6% / mm or less. As a result, even in battery cases having different case thicknesses and widths, the cleavage groove can be more reliably cleaved according to the pressure in the battery case.

FIG. 1 is a perspective view showing a schematic configuration of a sealed battery according to an embodiment of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a side view illustrating a schematic configuration of the sealed battery according to the embodiment. FIG. 4 is a perspective view showing a vent operation state of the sealed battery. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a diagram illustrating a part of a calculation model of an S-shaped cleavage groove. FIG. 7 is a diagram showing only the cross section of the plane portion in the cross section taken along the line VII-VII in FIG. 6. FIG. 8 is a graph showing the results obtained by calculating and experimenting the relationship between the (R / T) / W value and the operating pressure. FIG. 9 is a graph showing the results obtained by calculating and experimenting the relationship between the (R / T) / (W / D) value and the operating pressure. FIG. 10 is a diagram showing the position of the cleavage groove provided in the flat portion of the battery case.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

(overall structure)
FIG. 1 is a perspective view showing a schematic configuration of a sealed battery 1 according to an embodiment of the present invention. The sealed battery 1 includes a bottomed cylindrical outer can 10, a cover plate 20 that covers the opening of the outer can 10, and an electrode body 30 that is accommodated in the outer can 10. By attaching the cover plate 20 to the outer can 10, a hollow columnar battery case 2 having a space inside is formed. In addition to the electrode body 30, a non-aqueous electrolyte (hereinafter simply referred to as an electrolyte) is also enclosed in the battery case 2.

  As shown in FIG. 2, the electrode body 30 has a positive electrode 31 and a negative electrode 32 formed in a sheet shape, for example, in a state where the separators 33 are positioned between them and below the negative electrode 32, respectively. It is the winding electrode body formed by winding in a spiral shape. The electrode body 30 is formed in a flat shape after being wound in a state where the positive electrode 31, the negative electrode 32, and the separator 33 are overlapped with each other.

  Here, in FIG. 2, only a few layers on the outer peripheral side of the electrode body 30 are illustrated. However, in FIG. 2, the illustration of the inner peripheral side portion of the electrode body 30 is omitted, and naturally, the positive electrode 31, the negative electrode 32, and the separator 33 are also present on the inner peripheral side of the electrode body 30. . Further, in FIG. 2, description of an insulator and the like disposed inside the battery of the cover plate 20 is also omitted.

The positive electrode 31 is obtained by providing positive electrode active material layers containing a positive electrode active material on both surfaces of a positive electrode current collector made of a metal foil such as aluminum. Specifically, the positive electrode 31 is coated with a positive electrode mixture containing a positive electrode active material that is a lithium-containing oxide capable of occluding and releasing lithium ions, a conductive additive, and a binder on a positive electrode current collector made of aluminum foil or the like. And then dried. As the lithium-containing oxide as the positive electrode active material, for example, a lithium composite oxide such as lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O ₄ , lithium nickel oxide such as LiNiO ₂ is used. Is preferred. Note that only one type of material may be used as the positive electrode active material, or two or more types of materials may be used. Further, the positive electrode active material is not limited to the above-described materials.

  In the negative electrode 32, negative electrode active material layers containing a negative electrode active material are provided on both sides of a negative electrode current collector made of a metal foil such as copper. Specifically, the negative electrode 32 is obtained by applying and drying a negative electrode mixture containing a negative electrode active material capable of inserting and extracting lithium ions, a conductive additive, a binder, and the like on a negative electrode current collector made of copper foil or the like. It is formed. As the negative electrode active material, for example, it is preferable to use a carbon material (such as graphite, pyrolytic carbon, coke, or glassy carbon) that can occlude and release lithium ions. The negative electrode active material is not limited to the above-described materials.

  A positive electrode lead 34 is connected to the positive electrode 31 of the electrode body 30, while a negative electrode lead 35 is connected to the negative electrode 32. As a result, the positive electrode lead 34 and the negative electrode lead 35 are drawn out of the electrode body 30. The tip end side of the positive electrode lead 34 is connected to the lid plate 20. On the other hand, the distal end side of the negative electrode lead 35 is connected to the negative electrode terminal 22 via a lead plate 27 as described later.

  The outer can 10 is a bottomed cylindrical member made of an aluminum alloy, and constitutes the battery case 2 together with the cover plate 20. As shown in FIG. 1, the outer can 10 is a bottomed cylindrical member having a bottom surface 11 in which a rectangular short side is formed in an arc shape. Specifically, the outer can 10 includes a bottom surface 11 and a flat cylindrical side wall 12 having a smooth curved surface. The side wall 12 includes a pair of opposed flat portions 13 (side surfaces) and a pair of semi-cylindrical portions 14 that connect the flat portions 13 to each other. The outer can 10 has a dimension in the thickness direction corresponding to the short side direction of the bottom surface 11 smaller than the width direction corresponding to the long side direction of the bottom surface 11 (for example, the thickness becomes about 1/10 of the width). Furthermore, it is formed in a flat shape. Further, since the outer can 10 is joined to the lid plate 20 connected to the positive electrode lead 34 as will be described later, it also serves as the positive electrode terminal of the sealed battery 1.

  As shown in FIG. 2, a polyethylene sheet for preventing a short circuit from occurring between the positive electrode 31 and the negative electrode 32 of the electrode body 30 through the outer can 10 is formed on the bottom inside the outer can 10. An insulator 15 is disposed. The above-described electrode body 30 is arranged so that one end portion is positioned on the insulator 15.

  The cover plate 20 is joined to the opening of the outer can 10 by welding so as to cover the opening of the outer can 10. The cover plate 20 is made of an aluminum alloy member, like the outer can 10, and has a rectangular short side formed in an arc shape so as to fit inside the opening of the outer can 10. Moreover, the through-hole is formed in the center part of the longitudinal direction in the cover board 20. As shown in FIG. An insulating packing 21 made of polypropylene and a negative electrode terminal 22 made of stainless steel are inserted into the through hole. Specifically, a substantially cylindrical insulating packing 21 into which a substantially columnar negative electrode terminal 22 is inserted is fitted to the peripheral portion of the through hole. The negative electrode terminal 22 has a configuration in which flat portions are integrally formed at both ends of a cylindrical shaft portion. The negative electrode terminal 22 is disposed with respect to the insulating packing 21 so that the flat surface portion is exposed to the outside and the shaft portion is positioned in the insulating packing 21. A stainless steel lead plate 27 is connected to the negative terminal 22. Thereby, the negative electrode terminal 22 is electrically connected to the negative electrode 32 of the electrode body 30 via the lead plate 27 and the negative electrode lead 35. An insulator 26 is disposed between the lead plate 27 and the lid plate 20.

  The lid plate 20 is formed with an electrolyte solution inlet 24 along with the negative electrode terminal 22. The injection port 24 is formed in a substantially circular shape in plan view. The injection port 24 has a small diameter portion and a large diameter portion so that the diameter changes in two steps in the thickness direction of the lid plate 20. The injection port 24 is sealed by a sealing plug 25 formed in a step shape corresponding to a change in the diameter of the injection port 24. The outer peripheral portion on the large diameter side of the sealing plug 25 and the peripheral portion of the injection port 24 are joined by laser welding so that no gap is generated between the sealing plug 25 and the peripheral portion of the injection port 24. Has been.

(Bento)
As shown in FIGS. 1 and 3, a cleavage groove 41 constituting the vent 23 is formed on the side surface of the outer can 10. Specifically, a cleavage groove 41 that forms a substantially S-shaped cleavage line is formed in the flat surface portion 13 extending in the width direction of the sealed battery 1 in the side wall 12 of the outer can 10. The cleavage groove 41 is configured to be cleaved when the pressure in the battery case 2 becomes larger than a threshold value.

  The cleavage groove 41 has a first curved portion 42 that protrudes in a protruding manner toward the outer side of the side surface (in one direction) and a side inward direction that is opposite to the outer side surface of the outer can 10. And a second bending portion 43 that curves in a projecting manner. In this embodiment, the protruding direction of the first bending portion 42 (the protruding direction of the convex portion, the same applies hereinafter) and the protruding direction of the second bending portion 43 are different by 180 degrees. The cleavage groove 41 constitutes a substantially S-shaped cleavage line as described above by connecting one end side of the second bending portion 43 to one end side of the first bending portion 42. That is, the cleavage line formed by the cleavage groove 41 is constituted only by a curve and has an inflection point in the middle.

  As described above, the cleavage groove 41 is formed in a substantially S shape having the first curved portion 42 and the second curved portion 43, so that the cleavage line is formed in a straight line or an arc shape as will be described in detail later. Compared to the case, it becomes easier to cleave according to the internal pressure of the battery case 2.

  Further, by forming the cleavage groove 41 in a substantially S shape, the cleavage groove 41 can be formed in a narrow range as compared with the case where the cleavage groove having the same length is formed in a straight line or an arc shape. In particular, when the cleavage groove is a straight line, if an impact is applied from the direction of the extended line of the straight line, there is a possibility that the cleavage groove is cracked at once. However, in the case of the above configuration, the cleavage is caused by the impact from a specific direction. It can be suppressed from occurring. Therefore, the cleavage groove 41 is not easily cleaved even when an impact due to dropping or the like is applied to the battery case 2.

  In the present embodiment, the cleavage groove 41 is formed thinner than the other portions of the plane portion 13. For example, the cleavage groove 41 is formed by pressing together with the outer can 10 when the outer can 10 is press-molded. Thereby, since work hardening occurs in the peripheral part of the cleavage groove 41 by press work, the strength of the peripheral part of the cleavage groove 41 can be improved. Therefore, even when an impact due to dropping or the like is applied to the sealed battery 1, it is possible to suppress the cleavage groove 41 from being cleaved by the impact.

  The cleavage groove 41 has a cross section formed in, for example, an inverted trapezoid (see FIG. 7). That is, the cross section of the cleavage groove 41 has an inverted trapezoidal shape in which the groove width decreases toward the groove bottom surface. In addition, the cross section of the cleavage groove 41 may be other cross-sectional shapes such as a quadrangular shape other than the trapezoidal shape, a triangular shape, or an elliptical shape.

  As will be described later, the cleavage groove 41 is a value obtained by dividing the ratio of the thickness of the remaining portion of the groove portion to the plate thickness of the flat portion 13 (hereinafter referred to as the remaining thickness ratio) by the case width of the battery case 2 (hereinafter referred to as the thickness of the battery case 2). , (Referred to as (R / T) / W value) is preferably 1.6% / mm or less, and more preferably, the groove depth of the cleavage groove 41 is (R / T) / W value is preferably 1.55% / mm or less, and more preferably, the groove depth of the cleavage groove 41 is (R / T) / W value of 1. The groove depth is preferably 36% / mm or less, and the groove depth of the cleavage groove 41 is set to the groove depth having the above (R / T) / W value, Even when the thickness and width of the battery case 2 are different, the cleavage groove 41 can be more reliably cleaved according to the pressure in the battery case 2.

  As shown in FIG. 3, the cleavage groove 41 has a ridge line L (a broken line in FIG. 3) formed in the outer can 10 when the battery case 2 swells as the internal pressure increases due to an internal short circuit of the sealed battery 1. ) Is provided above. Specifically, in the case of the present embodiment, the cleavage groove 41 is provided in the flat surface portion 13 of the outer can 10 so that the first curved portion 42 intersects the ridge line L. Moreover, the cleavage groove 41 is provided in the flat surface portion 13 so that the first curved portion 42 is curved in a projecting manner toward the corner portion (end portion) of the battery case 2 located on the base end side of the ridge line L. ing.

  Here, when the battery case 2 swells, the ridge line L is pulled to the outer peripheral portion of the battery case 2 (four corner portions in the case of the battery case 2 having the shape as in the present embodiment), and the outer can It is formed by raising a part of the ten flat portions 13. Therefore, as shown in FIG. 3, the ridge line L is formed so as to extend inward from the four corners of the battery case 2 in a side view of the battery case 2. In FIG. 3, the ridge line L is formed in a straight line extending inward from the four corners of the battery case 2. However, as described above, the battery case 2 swells and is formed in the flat portion 13 of the outer can 10. Since the raised portion to be formed becomes a ridgeline, the shape of the ridgeline L may be a curve, or the ridgelines L may be connected to each other.

  Since the ridge line L is a portion where the stress acting on the outer can 10 increases when the battery case 2 swells in the outer can 10, the cleavage groove 41 is provided so as to intersect the ridge line L as described above. Thus, the cleavage groove 41 is easily cleaved with the deformation of the outer can 10. Specifically, when the battery case 2 swells, the flat portion 13 of the outer can 10 is pulled along the ridge line L, and thus the flat portion 13 is cleaved by the cleavage groove 41 having low strength.

  In particular, as described above, the cleavage groove 41 is provided in the flat surface portion 13 so that the first curved portion 42 is curved in a projecting manner toward the corner portion of the battery case 2 located on the base end side of the ridge line L. Thus, the protrusion of the first curved portion 42 can be positioned closer to the corner of the battery case 2. Since the ridge line L is generated from the periphery of the corner of the battery case 2 as the battery case 2 is deformed, the first curved portion 42 positioned on the ridge line L can be cleaved at the initial stage of deformation of the battery case 2. .

  In this way, when cleavage occurs at a portion that intersects the ridge line L of the cleavage groove 41, the cleavage proceeds along the cleavage groove 41. Thereby, the entire cleavage groove 41 is cleaved. By the cleavage of the cleavage groove 41, substantially semicircular tongue portions 44 and 45 are formed as shown in FIG.

  Specifically, when the pressure in the battery case 2 becomes larger than the threshold value and the cleavage groove 41 is cleaved due to the deformation of the battery case 2, as shown in FIG. The tongue portions 44 and 45 are formed by the curved portion 43, respectively. That is, these tongue portions 44 and 45 are formed in a shape corresponding to the first curved portion 42 and the second curved portion 43 of the cleavage groove 41 (substantially semicircular in the case of this embodiment).

  At this time, as shown in FIG. 5, the flat portion 13 of the outer can 10 is in a state where the tongue portions 44 and 45 are floated with respect to other portions by the cleavage of the cleavage groove 41, and a gap 46 is formed. That is, when a cut is made in the flat portion 13 of the outer can 10 due to the cleavage of the tear groove 41, a portion on the ridge line L that is pulled to the corner of the outer can 10 is pulled outward and the tongue is pulled outward. The portions 44 and 45 are lifted with respect to other portions of the side wall 12 (open arrows in the figure). Gases and the like accumulated in the battery case 2 are discharged to the outside through a gap 46 formed between the tongue portions 44 and 45 and other portions of the flat surface portion 13. That is, a part of the plane portion 13 including the cleavage groove 41 functions as the vent 23.

  With the above-described configuration, the opening area of the cleavage portion can be increased by the amount that the tongue portions 44 and 45 are lifted, compared to the case where the cleavage line is linear, and the gas in the battery case 2 can be efficiently discharged to the outside. Can be discharged.

  Moreover, since the tongue portions 44 and 45 formed by the cleavage of the cleavage groove 41 protrude outward in the thickness direction of the battery case 2, the tongue portions 44 and 45 are in contact with the electrode body 30 in the battery case 2. Thus, a short circuit can be prevented from occurring.

  Further, in the case of the above-described configuration, the size of the tongue portion formed by the cleavage is smaller than when the cleavage groove having the same length as the cleavage groove 41 is provided so as to draw a semicircular cleavage line. Therefore, the tongue portions 44 and 45 can be prevented from interfering with an exterior film (not shown) that covers the side wall 12 of the battery case 2. Thereby, it can prevent that the tongue parts 44 and 45 interfere with an exterior film and prevent the cleavage of the cleavage groove 41. FIG.

  As shown in FIG. 3, the cleavage groove 41 is formed from the corner (end) of the battery case 2 located on the base end side of the ridge line L when viewed from the normal direction of the plane portion 13. It is provided within a range of ½ each of the directional length and the lateral length. Thereby, since the cleavage groove 41 can be provided on the base end side of the ridge line L in the flat portion 13, the cleavage groove 41 can be more reliably cleaved by the deformation of the flat portion 13.

  It should be noted that the cleavage groove 41 extends from the corner (end) of the battery case 2 located on the base end side of the ridge line L when viewed from the normal direction of the plane portion 13 to the length and width of the plane portion 13. More preferably, it is provided within a range of 1/3 of each of the directional lengths. By doing so, the cleavage groove 41 can be further brought closer to the proximal end side of the ridge line L in the flat surface portion 13, so that the cleavage groove 41 can be further reliably broken by the deformation of the flat surface portion 13.

(Relationship between the case width and thickness of the battery case and the remaining thickness ratio of the cleavage groove)
In the following description, in order to consider the influence of the size of the battery case 2, the remaining thickness R of the cleavage groove 41 with respect to the plate thickness T (see FIG. 7) of the flat portion 13 (the thickness of the remaining portion in the groove portion, FIG. 7) R / T (hereinafter referred to as the remaining thickness ratio) divided by the case width W of the battery case 2 (hereinafter referred to as (R / T) / W value). Hereinafter, the relationship between the (R / T) / W value and the operating pressure (the threshold value of the pressure at which the cleavage groove is cleaved) will be described using actual measurement results and calculation results. Here, the case width W (battery case width) of the battery case 2 is a width dimension of the battery case 2 when the flat portion 13 is viewed from the normal direction. In the case of this embodiment, the case width W means the distance from the outermost periphery of one semi-cylindrical portion 14 to the outermost periphery of the other semi-cylindrical portion 14.

  FIG. 6 schematically shows a part of the calculation model used in the following calculation. FIG. 6 shows a part of a calculation model of the battery case 2 in which the cleavage groove 41 is formed so as to draw a substantially S-shaped cleavage line. As shown in FIG. 6, in the following calculation, the cleavage groove 41 is positioned at a certain distance (X, Y in the drawing) from the semi-cylindrical portion 14 side and the bottom surface 11 side in the flat portion 13 of the battery case 2. Is provided. In the following calculation, X = 5 mm and Y = 6 mm, and the curvatures of the first curved portion 42 and the second curved portion 43 of the cleavage groove 41 are R = 5 mm and 6 mm, respectively. The cross section of the cleavage groove 41 is an inverted trapezoid whose groove width at the groove bottom surface is 0.03 mm and the angle between the groove side surfaces is 20 degrees (see FIG. 7).

  In the following calculation, LS-DYNA (registered trademark), which is structural analysis software, was used. Further, in the calculation, whether or not the cleavage groove was broken (whether or not the vent was activated) was determined using the following formula used for the determination of ductile fracture.

  Here, a and b are material parameters obtained from the material test result, σm represents an average stress, σ represents an equivalent stress, ε represents an equivalent strain, and dε represents an increment of the equivalent strain.

  In the above formula, when the value of I exceeded 1, it was assumed that the fracture started in the cleavage groove, and the internal pressure of the battery case at that time was taken as the operating pressure. In this calculation, a is set to 0.3 and b is set to 0.14.

  In FIG. 8, the result of calculating | requiring the relationship between (R / T) / W value and a working pressure is shown by a black rhombus. As can be seen from FIG. 8, when the (R / T) / W value becomes larger than 1.6% / mm, the operating pressure increases rapidly. That is, the range of (R / T) / W value less than or equal to 1.6% / mm is the amount of change in operating pressure compared to the range where (R / T) / W value is greater than 1.6% / mm. Is small. Therefore, if the (R / T) / W value is in the range of 1.6% / mm or less, the design value of the operating pressure is obtained even when the groove depth of the cleavage groove or the case width W of the battery case changes due to an error or the like. In the vicinity, the cleavage groove can be more reliably cleaved. Therefore, (R / T) / W value is preferably 1.6% / mm or less.

  A plurality of types of battery cases having different sizes and thicknesses (battery cases A, B, C, D, and E) are provided with a cleavage groove having the same shape at the same position as the above-described calculation model. The working pressure was confirmed. The result is shown in FIG. In addition, air was inject | poured in the battery case until the cleavage groove was ruptured, and the internal pressure of the battery case at the time of rupture was used as the operating pressure.

  The battery case A is a battery case having a case thickness D of 5.3 mm, a case width W of 50 mm, a case height H of 59 mm, and a plate thickness T of 0.27 mm.

  The battery case B is a battery case having a case thickness D of 4.6 mm, a case width W of 44 mm, a case height H of 61 mm, and a plate thickness T of 0.25 mm.

  The battery case C is a battery case having a case thickness D of 4.8 mm, a case width W of 43 mm, a case height H of 50 mm, and a plate thickness T of 0.25 mm.

  The battery case D is a battery case having a case thickness D of 4.8 mm, a case width W of 44 mm, a case height H of 61 mm, and a plate thickness T of 0.28 mm.

  The battery case E is a battery case having a case thickness D of 4.6 mm, a case width W of 51 mm, a case height H of 56 mm, and a plate thickness T of 0.25 mm.

  As shown in FIG. 8, the operating pressure is almost the same between the actual measurement result and the calculation result, and when the (R / T) / W value exceeds 1.6% / mm in the actual measurement result, The tendency to rise rapidly can also be simulated by calculation. Therefore, the actual state can be simulated by the present calculation method. As described above, the (R / T) / W value is preferably 1.6% / mm or less from the calculation result.

(Relationship between case width, case thickness and plate thickness of battery case and remaining thickness ratio of cleavage groove)
In the following description, in order to consider the influence of the case thickness in addition to the case width of the battery case described above, R / T is divided by the ratio W / D of the case width W and the case thickness D of the battery case. A value (hereinafter referred to as (R / T) / (W / D) value) is used. Hereinafter, the relationship between the (R / T) / (W / D) value and the operating pressure will be described using actual measurement results and calculation results. Here, the case thickness D of the battery case means the thickness of the edge portion on the cover plate 20 side of the battery case or the thickness of the edge portion on the bottom surface 11 side.

  The calculation method of the operating pressure and the experiment method of the cleavage groove cleavage are the same as in the case of the above (R / T) / W value.

  In FIG. 9, the result of calculating | requiring the relationship between a (R / T) / (W / D) value and an operating pressure is shown by a black rhombus. As can be seen from FIG. 9, when the (R / T) / (W / D) value becomes larger than 7.5%, the operating pressure increases rapidly. That is, the range in which the (R / T) / (W / D) value is 7.5% or less operates compared to the range in which the (R / T) / (W / D) value is greater than 7.5%. The amount of change in pressure is small. Therefore, if the (R / T) / (W / D) value is in the range of 7.5% or less, even when the groove depth of the cleavage groove, the case width W of the battery case, or the case thickness D changes due to an error or the like. The cleavage groove can be more reliably cleaved in the vicinity of the design value of the operating pressure. Therefore, the (R / T) / (W / D) value is preferably 7.5% or less. The range of the (R / T) / (W / D) value is within the range where the (R / T) / W value is 1.6% / mm or less.

  A plurality of types of battery cases having different sizes and thicknesses (battery cases A, B, C, D, and E) are provided with a cleavage groove having the same shape at the same position as the above-described calculation model. The working pressure was confirmed. The results are shown in FIG. 9 with white squares. In addition, air was inject | poured in the battery case until the cleavage groove was ruptured, and the internal pressure of the battery case at the time of rupture was used as the operating pressure.

  As shown in FIG. 9, the operating pressure is almost the same between the actual measurement result and the calculation result, and the operation is performed when the (R / T) / (W / D) value exceeds 7.5% in the actual measurement result. The tendency of the pressure to rise rapidly can also be simulated by calculation. Therefore, the actual state can be simulated by the present calculation method, and as described above, the (R / T) / (W / D) value is preferably 7.5% or less from the calculation result.

  As shown in FIG. 10, when the flat surface portion 13 is viewed from the normal direction, the cleavage groove 41 extends from the corner portion (end portion) of the battery case 2 where the base end side of the ridge line L is positioned to the longitudinal length of the flat surface portion 13. The range of the value of (R / T) / W as described above and (R The range of the value of / T) / (W / D) is more preferable. This is because if the cleavage groove 41 is provided in such a region, the cleavage groove 41 can be more reliably cleaved by deformation of the flat surface portion 13.

  In addition, when the planar portion 13 is viewed from the normal direction, the cleavage groove 41 extends from the corner portion (end portion) of the battery case 2 where the base end side of the ridge line L is located, to the longitudinal length H and the lateral direction of the planar portion 13. When the length W is within the range of 1/3 (in the area of the thick broken line in FIG. 10), the range of the value of (R / T) / W and (R / T) / ( The range of the value of (W / D) is more preferable. This is because if the cleavage groove 41 is provided in such a region, the cleavage groove 41 can be more reliably cleaved by the deformation of the flat surface portion 13.

(Effect of embodiment)
As described above, in the present embodiment, the flat portion 13 of the battery case 2 in the sealed battery 1 projects in the opposite direction to the first curved portion 42 that curves in a projecting manner in one direction in a side view. A cleavage groove 41 having a second curved portion 43 that is curved in a shape is provided. The value ((R / T) / W value) obtained by dividing the ratio of the remaining thickness R to the plate thickness T of the flat portion 13 by the case width W of the battery case 2 is 1.6% / mm. The groove depth is as follows. Thereby, even when the sizes of the battery case 2 are different, it is possible to form the cleaving groove 41 that is easily cleaved according to the width of the battery case 2. That is, in the battery cases 2 of various sizes, even when the groove depth of the cleavage groove 41 is slightly deviated from the design value, the cleavage groove 41 can be cleaved in the vicinity of the design value of the operating pressure.

  In addition to the above-described configuration, the cleavage groove 41 is a value obtained by dividing the ratio of the remaining thickness R to the plate thickness T of the flat portion 13 by the ratio of the case width W of the battery case 2 to the case thickness D ((R / The groove depth is such that (T) / (W / D)) is 7.5% or less. Thereby, the cleaving groove 41 that cleaves more reliably can be formed in consideration of the case width W and the case thickness D of the battery case 2. That is, in the battery cases 2 of various sizes, even when the groove depth of the cleavage groove 41 is slightly deviated from the design value, the cleavage groove 41 can be cleaved in the vicinity of the design value of the operating pressure.

(Other embodiments)
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented without departing from the spirit of the invention.

  In the embodiment, the cleavage groove 41 is provided so that the first curved portion 42 is positioned on the ridge line L. However, the cleavage groove 41 may be provided so that the second curved portion 43 is positioned on the ridge line L.

  Further, the present invention is not limited to the configuration of the above-described embodiment. If a part of the cleavage groove 41 is located on the ridge line L, the cleavage groove 41 may be provided at any position on the flat surface portion 13 of the outer can 10, The direction of the cleavage line formed by the cleavage groove 41 is not limited to the direction of the above-described embodiment.

  In the embodiment, the cleavage groove 41 has two curved portions 42 and 43. However, the cleavage groove may have three or more curved portions. Even in such a case, the cleavage groove is provided so as to form a cleavage line in which curved portions that project in a protruding manner in the opposite direction are alternately connected.

  In the embodiment, the cleavage groove 41 is formed by pressing. However, the cleavage groove 41 may be formed by laser processing, cutting processing, or the like.

  In the said embodiment, the cleavage groove | channel 41 is comprised by the continuous groove | channel. However, the cleavage groove 41 may be constituted by a plurality of independent groove portions by dividing the cleavage groove into a plurality of pieces.

  In the above-described embodiment, the cleavage groove 41 is formed in the first curved portion 42 that protrudes outwardly from the side surface in a side view of the outer can 10, and on the inner side surface that is opposite to the outer side surface. And a second bending portion 43 that curves in a projecting manner. However, the cleavage groove provided in the flat portion 13 of the battery case 2 may have a shape in which the protruding direction of the first bending portion and the protruding direction of the second bending portion have an angle of approximately 90 degrees or more. That is, the cleavage groove may have any shape as long as the protruding direction of the first bending portion and the protruding direction of the second bending portion have an angle of 90 degrees or more.

  In the said embodiment, the battery case 2 of the sealed battery 1 is made into the column shape which has the bottom face in which the rectangular short side was formed in circular arc shape. However, the shape of the battery case may be other shapes such as a hexahedron.

  In the embodiment, the sealed battery 1 is configured as a lithium ion battery. However, the sealed battery 1 may be a battery other than a lithium ion battery.

  The present invention can be used for a sealed battery in which a cleavage groove is formed on a side surface of a battery case.

1: Sealed battery, 2: Battery case, 10: Exterior can, 13: Plane portion (side surface), 30: Electrode body, 41: Cleavage groove, 42: First curved portion, 43: Second curved portion, L: Ridgeline

Claims (6)

A hollow column-shaped battery case in which an electrode body and an electrolyte solution are enclosed,
On the side surface of the battery case, a cleavage groove is formed that forms a cleavage line that intersects a ridge line formed on the side surface of the battery case when the battery case is swollen by an increase in internal pressure.
The cleavage line is configured only by a curve, and a first bending portion that curves in a protruding manner in one direction when the side surface of the battery case is viewed from the normal direction, and the protruding direction of the first bending portion And second curved portions that project in a projecting manner in a direction that forms an angle of 90 degrees or more, and are alternately connected,
The first bending portion and the second bending portion are connected to each other at one end,
At least one of the first curved portion and the second curved portion intersects the ridgeline,
The cleavage groove has a value obtained by dividing the percentage of the ratio of the thickness of the remaining portion to the plate thickness of the battery case by the width of the battery case when the side surface of the battery case is viewed from the normal direction. A sealed battery having a groove depth of 6% / mm or less. The sealed battery according to claim 1,
The cleavage groove is a value obtained by dividing the percentage of the ratio of the thickness of the remaining portion relative to the thickness of the battery case by the ratio of the width to the thickness of the battery case when the side surface of the battery case is viewed from the normal direction. A sealed battery having a groove depth such that is 7.5% or less. The sealed battery according to claim 1 or 2,
The cleavage line is a sealed battery in which the first bending portion and the second bending portion are combined one by one. The sealed battery according to any one of claims 1 to 3,
The first curved portion is curved in a projecting manner toward the end portion of the battery case located on the base end side of the ridgeline,
The cleaving groove is a sealed battery formed on a side surface of the battery case so that the first curved portion is positioned on the ridgeline. The sealed battery according to any one of claims 1 to 4,
When the side surface of the battery case is viewed from the normal direction, the cleavage groove has a longitudinal length and a lateral length in the battery case from the end of the battery case located on the base end side of the ridge line. A sealed battery formed on a side surface of the battery case so as to be positioned within a range of 1/2. The sealed battery according to any one of claims 1 to 4,
When the side surface of the battery case is viewed from the normal direction, the cleavage groove has a longitudinal length and a lateral length in the battery case from the end of the battery case located on the base end side of the ridge line. A sealed battery formed on a side surface of the battery case so as to be positioned within a range of 1/3.