JP2013178997A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which is capable of effectively reducing stress applied to positive and negative electrode leads and allows a collector part to be easily formed.SOLUTION: The secondary battery includes an electrode body (10) in which a positive electrode (1) having a positive electrode lead (11) and a negative electrode (2) having a negative electrode lead (12) are arranged facing each other via a separator (3a). At least one of the positive electrode lead (11) and the negative electrode lead (12) has a bent portion (11B, 12B) formed in a region facing the separator (3a).

Description

  The present invention relates to a secondary battery.

  In recent years, batteries have been used not only for power sources of mobile information terminals such as mobile phones, notebook personal computers, and PDAs, but also for robots, electric vehicles, backup power sources, etc., and further increase in capacity is required. It has become like this. In response to such demands, lithium ion batteries have a high energy density and high capacity, and are therefore widely used as drive power sources as described above.

  Battery types of such lithium ion batteries can be broadly divided into a spiral type in which a spiral electrode body is enclosed in an exterior body, and a laminated electrode body in which a plurality of rectangular electrodes are laminated, and an exterior can or laminate film is welded. And a laminated type (laminated type prismatic lithium ion battery) encapsulated in a laminated outer package produced by doing so.

  Among these lithium ion batteries, the specific structure of the laminated electrode body of the laminated battery is a sheet-like positive electrode plate with a positive electrode lead extended and a sheet-like negative electrode plate with a negative electrode lead extended, The configuration is such that a required number of layers are stacked via a separator.

  In the lithium ion battery, the positive and negative electrode leads are usually made of a thin metal foil with a thickness of several tens of μm, while the positive and negative electrode plates are fixed in a relatively stable manner. It is composed. For this reason, the electrode expands or increases in thickness with charge / discharge, or an external force is applied to the completed battery due to dropping, etc., causing stress to be concentrated on the positive and negative electrode leads, causing cracks, tearing, etc. There is a problem in that the damage of the positive and negative electrode leads may be peeled off, or the damaged or peeled part of the positive and negative electrode leads may break through the separator to cause a short circuit.

  To solve such a problem, for example, as disclosed in Patent Document 1 and Patent Document 2, bending or sagging is applied to the middle part of the positive and negative electrode leads to reduce stress caused by expansion or increase in thickness of the electrode. A configuration has been proposed.

JP 2011-81925 A JP-A-9-147829

  However, in an electrode body of a lithium ion battery, not only the above-described stacked battery but also a spiral battery, a positive electrode and a negative electrode are arranged to face each other via a separator, and a positive electrode lead and a negative electrode lead extend from the positive electrode and the negative electrode, respectively. It is customary to have a configuration that can be used. In this configuration, stress is particularly easily applied to the base end portion (root portion) where the positive and negative electrode leads extend, that is, the position between the separators. In particular, in a stacked battery, a large number of stacked positive and negative electrode leads are shaped so as to be focused and folded on one side in the stacking direction, thereby reducing the space occupied by the current collector as much as possible. In this case, however, the positive and negative electrode leads located farther from the converging part are bent more greatly at the base end part (root part), so that a greater stress is applied. (In this specification, the term “current collector” is basically a broad concept including current collecting members such as positive and negative electrode leads, positive and negative current collector terminals, and spaces around the current collecting member. In this case, it implies a part where the positive and negative electrode leads are bent, a joint part between the positive and negative electrode leads and the positive and negative current collecting terminals, etc.)

  On the other hand, in Patent Document 1 and Patent Document 2 described above, stress is absorbed by bending or sagging in the middle part of the positive and negative electrode leads, thereby reducing the stress applied to the base end part (root part). Yes. However, depending on this configuration, it is not possible to sufficiently reduce the stress caused by bending particularly at the base end portion (root portion) as described above.

  In addition, since the positive and negative electrode leads are made of a thin metal foil as described above, the position of the positive and negative electrode leads is difficult to stabilize when the current collector is formed by bending, bundling, or joining them. There is also a problem that it is difficult to perform the forming operation. In particular, as disclosed in Patent Document 1 and Patent Document 2, when a bend or a slack is formed in the middle part of the positive and negative electrode leads, the positive and negative electrode leads are more easily deformed in the bending direction and are restored to the original state. The property tends to cause deformation in the extending direction, and the position tends to become more unstable. In addition, the deflection and sagging can be formed by giving a margin to the length of the positive and negative electrode leads without being formed in advance, but according to this, when forming the current collector Therefore, it is necessary to join the positive and negative electrode leads to a predetermined position while maintaining a posture in which bending and sagging are formed, and this work is troublesome. For these reasons, in the configurations disclosed in Patent Document 1 and Patent Document 2, it is more difficult to perform the work of bundling and joining the positive and negative electrode leads.

  In view of the above points, an object of the present invention is to provide a secondary battery that can effectively reduce stress applied to positive and negative electrode leads and can easily form a current collector. .

In order to achieve the above object, the secondary battery according to the present invention is:
A secondary battery comprising an electrode body configured such that a positive electrode having a positive electrode lead and a negative electrode having a negative electrode lead are arranged to face each other via a separator,
At least one of the positive electrode lead and the negative electrode lead has a bent portion in a region facing the separator.

  In the present invention, the “bent portion” in the positive electrode lead or the negative electrode lead is a portion formed so as not to extend substantially along a straight line (in the case where the positive electrode lead or the negative electrode lead is a sheet, This means a portion formed so as not to have a shape extending along one plane, and implies a portion having an arbitrary bent shape such as not only a bent shape but also a curved shape.

  According to the configuration of the present invention, since the bent portion is formed in the region facing the separator in the positive and negative electrode leads, the stress applied to the positive and negative electrode leads is absorbed by the bent portion, whereby the base end portion of the positive and negative electrode leads The stress is effectively reduced at the (root part). In particular, the stress applied when the positive and negative electrode leads are bent at the base end portion (base portion) is absorbed by the bent portion formed at the base end portion (base portion), so that the effect of reducing the stress is great. On the other hand, even when stress is applied to the positive and negative electrode leads when the electrode expands or thickens due to charge / discharge, or the battery drops, etc., the stress is absorbed by the bent portion and reduced.

  In general, since the thickness of the positive and negative electrode leads is significantly smaller than the thickness of the positive and negative electrodes on which the positive and negative electrode active material layers are formed, the positive and negative electrode leads do not have a bent portion and are substantially linear. In the region facing the separator, the posture is a certain posture with a certain distance between the separator and the floating posture. On the other hand, according to the configuration of the present invention, since the bent portion is formed in the region facing the separator in the positive and negative electrode leads, the bent portion is supported in contact with the separator. That is, the positive and negative electrode leads are held in such a posture that the space between the positive and negative electrodes is filled with the bent portion. As a result, the positive and negative electrode leads are stably held by the posture supported by the separator without being in a floating posture in the region facing the separator. In other words, the positive and negative electrode leads become more unstable when the middle part of the positive and negative electrode leads is bent as described above, whereas the area facing the separator in the positive and negative electrode leads as in the configuration of the present invention. By forming the bent portion in the positive and negative electrode leads, the positive and negative electrode leads become more stable. From the above, according to the configuration of the present invention, the positions of the positive and negative electrode leads are more stable, and the current collector is easily formed.

  A plurality of positive electrode leads and a plurality of negative electrode leads may protrude from the electrode body.

  In the case of not only a laminated battery having a laminated electrode body but also a spiral (winding) battery having a spiral electrode body, a plurality of positive leads and a plurality of negative leads protrude from the electrode body. It is possible to have a configuration. In this case, the plurality of positive and negative electrode leads are bundled and joined to the positive and negative current collecting terminals. For this reason, as will be described later, a great stress is applied along with this joining. Therefore, the effect of the present invention in which the stress is reduced by the bent portion formed in the region facing the separator in the positive and negative electrode leads is further exhibited. In addition, as the number of positive and negative electrode leads increases, the work of bending and bundling the positive and negative electrode leads becomes more complicated. Therefore, the positive and negative electrode leads are stably held by forming a bent portion in a region facing the separator. The effect of the present invention as described above will be further exhibited.

  It is desirable that the electrode body is a laminated electrode body formed by alternately laminating a plurality of positive electrode plates having positive electrode leads and negative electrode plates having negative electrode leads with separators interposed therebetween.

  In the case of a laminated battery including a laminated electrode body, a plurality of positive and negative electrode leads are laminated together with a positive and negative electrode plate, and the plurality of positive and negative electrode leads are bundled and joined to a positive and negative electrode current collecting terminal. For this reason, in particular, when the number of stacked layers increases, the more the positive and negative electrode leads are located closer to the end in the stacking direction, the more the base end portion (root portion) is bent and the greater the stress is applied. For example, when a plurality of positive and negative electrode leads are joined to the positive and negative electrode current collector terminals by welding, a large tensile stress is applied by pressing with a welding rod or a horn. Furthermore, for example, when ultrasonic welding is used, there is also a problem that the positive and negative electrode active materials of the positive and negative electrode plates drop off due to ultrasonic vibration. Therefore, in the case of the stacked battery, the effect of the present invention in which the stress is reduced by the bent portion formed in the region facing the separator in the positive and negative electrode leads is further exhibited, and the ultrasonic vibration is also caused by the bent portion. The structure of the present invention is advantageous because the positive and negative electrode active materials are prevented from falling off by being attenuated. In addition, as the number of stacked layers increases, the work of bending and bundling the positive and negative electrode leads becomes more cumbersome. Therefore, the positive and negative electrode leads are stably held by forming a bent portion in a region facing the separator. The effect of the present invention will be further exhibited.

  It is desirable that the positive electrode lead is focused on one outermost surface side in the stacking direction of the stacked electrode body, and the negative electrode lead is focused on one outermost surface side in the stacking direction of the stacked electrode body.

  In the case of a stacked battery, a structure in which a plurality of stacked positive and negative electrode leads are focused on one of the outermost surfaces in the stacking direction (hereinafter referred to as “one focusing structure”) rather than focusing at the center in the stacking direction. More preferably, the structure is such that the tip portion of the one outermost surface side converging portion is bent to the other outermost surface side in the stacking direction and connected to the current collecting terminal (hereinafter also referred to as “bending structure”). It is more preferable to reduce the volume loss and to save more space in the current collector. However, in the case where the positive and negative electrode leads have one focusing structure as described above, the positive and negative electrode leads that are located farther from the converging portion before focusing, that is, the positive and negative electrode leads that are positioned closer to the other outermost surface in the stacking direction. As a result, a large tensile stress is applied due to focusing, and it is easily damaged. On the other hand, when the positive and negative electrode leads are bent, on the other hand, the positive and negative electrode leads that were closer to the converging part before focusing, that is, the positive and negative leads that are closer to the outermost surface side where the converging part is located. As the negative electrode lead is bent, a greater tensile stress is applied by bending, and the negative electrode lead is more susceptible to damage. Further, even in the case of the one-side focusing structure or the bending structure, when a plurality of positive and negative electrode leads are joined to the positive and negative current collecting terminals, a tensile stress is applied, for example, by pressing with a welding rod or a horn. . Furthermore, in the case of a converging structure or a bent structure, the positive and negative electrode leads are deformed by converging or bending, so that there is a problem that the position tends to become more unstable.

  From the above, when the positive and negative electrode leads have a one-side focusing structure or a bent structure, the effect of the present invention, that is, the stress is reduced by the bent portion formed in the region facing the separator in the positive and negative electrode leads, The effect that the positive and negative electrode leads are stably held will be further exhibited.

  It is desirable that the bent portion has a substantially wave shape in a side view.

  As the bent portion, any shape is possible as long as it is not a shape that extends substantially in a straight line when viewed from the side. For example, when the positive and negative electrode leads are in a sheet shape, the shape is locally a hump, a cone, and a rectangular parallelepiped. A shape or the like that rises in a shape such as a shape is also possible. However, in such a shape, it is difficult to obtain sufficient stress absorbability, and it may be difficult to form the stress. On the other hand, one or two or more bent portions that are bent so as to be bent in a substantially “<” shape on one side when viewed from the side or in a round shape while the positive and negative electrode leads are extended By forming a bent portion having a substantially wave shape when viewed from the side, the positive and negative electrode leads become spring-like, and the stress absorption is good, and can be easily formed by bending. That is, with a simple configuration, it is possible to provide a bent portion that can effectively absorb stress and can stably hold the positive and negative electrode leads.

  According to the present invention, in the secondary battery, it is possible to effectively reduce the stress applied to the positive and negative electrode leads to prevent breakage and peeling, and to easily hold the positive and negative electrode leads and facilitate the current collecting part. Can be formed.

It is a figure which shows a part of secondary battery of this invention, Comprising: The figure (a) is a top view of a positive electrode, The figure (b) is a perspective view of a separator, The figure (c) is arrange | positioning a positive electrode inside. It is a top view which shows the bag-shaped separator. It is a top view of the negative electrode plate used for the secondary battery of this invention. It is a disassembled perspective view of the laminated electrode body used for the secondary battery of this invention. It is a top view of the laminated electrode body used for the secondary battery of this invention. It is a schematic cross section which shows the situation of the extension part of the positive electrode lead of the positive electrode plate in the laminated electrode body of the secondary battery of this invention, and the negative electrode lead of a negative electrode plate. It is a side view which shows the condition which performs the 1st step (focusing and cutting | disconnection of a positive / negative electrode lead) in the manufacturing process of the secondary battery of this invention. It is a side view which shows the condition which performs the 2nd step (connection of positive / negative current collection terminal) in the manufacturing process of the secondary battery of this invention. It is a side view which shows the condition which performs the 3rd step (formation of an insulating layer) in the manufacturing process of the secondary battery of this invention. It is a side view which shows the condition which performs the 4th step (bending of a positive / negative current collector terminal) in the manufacturing process of the secondary battery of this invention. It is a side view which shows the condition which performs the 5th step (bending and positioning of a positive / negative electrode current collection junction part) in the manufacturing process of the secondary battery of this invention. It is a top view which shows the laminated electrode body which joined the positive / negative electrode current collection terminal to the positive / negative electrode lead. It is a perspective view of the state which inserted the laminated electrode body into the exterior body used for the secondary battery of this invention. It is a model longitudinal cross-sectional view of the positive electrode current collection part in the secondary battery of this invention. It is a schematic cross section which shows the situation of the extension part vicinity of the positive electrode lead of a positive electrode plate, and the negative electrode lead of a negative electrode plate in the laminated electrode body of the secondary battery which concerns on another embodiment of this invention. It is a schematic cross section which shows the situation of the extension part vicinity of the positive electrode lead of a positive electrode plate, and the negative electrode lead of a negative electrode plate in the laminated electrode body of the secondary battery which concerns on another embodiment of this invention. It is a schematic diagram explaining the mountain height of a bending part.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the following best modes, and can be implemented with appropriate modifications without departing from the spirit of the present invention. It is a thing.

[First Embodiment]
[Production of positive electrode]
90% by mass of LiCoO ₂ as a positive electrode active material, 5% by mass of carbon black as a conductive agent, 5% by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone as a solvent ( NMP) solution was mixed to prepare a positive electrode slurry. This positive electrode slurry was applied to both surfaces of an aluminum foil (thickness: 15 μm) as a positive electrode current collector. Then, after removing the solvent by heating and compressing to a thickness of 0.3 mm with a roller, as shown in FIG. 1 (a), cut to have a width L1 = 86mm and a height L2 = 86mm. A positive electrode plate 1 having a positive electrode active material layer 1a on both sides was produced. At this time, an active material uncoated portion having a width L3 = 30 mm and a height L4 = 20 mm is extended from one end portion (the left end portion in FIG. 1A) of one side extending in the width L1 direction of the positive electrode plate 1. Lead 11 was obtained.

(Production of negative electrode)
A slurry for negative electrode by mixing 96% by mass of graphite powder as a negative electrode active material, 2% by mass of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as binders, and pure water as a solvent. Was prepared. This negative electrode slurry was applied to both surfaces of a copper foil (thickness: 10 μm) as a negative electrode current collector. Thereafter, the solvent is removed by heating, and after compressing to a thickness of 0.3 mm with a roller, as shown in FIG. 2, the sheet is cut to have a width L7 = 90 mm and a height L8 = 90 mm. A negative electrode plate 2 having a negative electrode active material layer 2a was produced. At this time, the width L9 = 30 mm and the height L10 = 20 mm from the end (right end in FIG. 2) opposite to the positive electrode lead 11 formation side end of the positive electrode plate 1 on one side extending in the width direction of the negative electrode plate 2. The active material uncoated portion was extended to form a negative electrode lead 12.

(Formation of bent part)
As shown in FIG. 1 (a), the positive electrode lead 11 of the positive electrode plate 1 is bent in the vicinity of the base end portion (root portion) so as to have a substantially "<" shape in side view, and details will be described later. The bent part 11B is formed. On the other hand, as shown in FIG. 2, the bent portion 12 </ b> B is formed by similarly bending the vicinity of the base end portion (root portion) of the negative electrode lead 12 of the negative electrode plate 2.

[Production of bag-shaped separator with positive electrode plate arranged inside]
After placing the positive electrode plate 1 between two rectangular polypropylene (PP) separators 3a (thickness 30 μm) having a width L5 = 90 mm and a height L6 = 94 mm as shown in FIG. As shown in FIG. 1C, a bag-like separator in which the positive electrode plate 1 is housed and arranged inside by fusing three sides of the separator 3a other than the side from which the positive electrode lead 11 protrudes at the fusion part 4. 3 was produced.
As described above, the separator 3a is formed with a height L6 of 94 mm and 4 mm larger than the height L8 of the negative electrode plate 2 = 90 mm. Therefore, the separator 3a is formed in the direction in which the positive electrode lead 11 protrudes from the bag-shaped separator 3. It extends longer than the negative electrode plate 2. Thereby, the short circuit by the position shift of the negative electrode plate 2 does not arise more easily.

  At this time, an insulating resin is applied to both surfaces of the base end portion (base side portion) of the bent portion 11B of the positive electrode lead 11 of the positive electrode plate 1 so that the negative electrode plate 2 protrudes outside the separator 3a. In such a case, an insulating layer (protective layer) 11S that prevents a short circuit due to contact with the base end portion (root portion) of the positive electrode lead 11 is formed.

(Production of laminated electrode body)
Thirty-five bag-shaped separators 3 and 36 negative-electrode plates 2 with the positive electrode plate 1 disposed therein were prepared, and the bag-shaped separators 3 and the negative electrode plates 2 were alternately laminated as shown in FIG. At that time, the negative electrode plate 2 was positioned at both ends in the stacking direction, and the insulating sheets 5 made of polypropylene (PP) having the same dimensions and the same shape as the separator 3a were arranged on both outer sides thereof. Next, as shown in FIG. 4, both end surfaces of this laminate were connected with an insulating tape 26 for maintaining the shape to obtain a laminate electrode assembly 10.

  The situation in the vicinity of the extending portion of the positive electrode lead 11 of the positive electrode plate 1 and the negative electrode lead 12 of the negative electrode plate 2 in the laminated electrode body 10 is as schematically shown in FIG. As shown in the figure, the positive electrode lead 11 extends from the center in the thickness direction of the positive electrode plate 1, that is, from between the positive electrode active material layers 1 a on both sides, and its base end (base portion), that is, the positive electrode of the positive electrode plate 1. The protective layer 11S is formed in a region adjacent to the active material layer 1a. Further, the bent portion 11B is formed in the vicinity of the base end portion (root portion) of the positive electrode lead 11, that is, in a region adjacent to the protective layer 11S. The bent portion 11B has a substantially "<" shape when viewed from the side by bending it at an obtuse angle at three equally spaced points so as to be recessed in one side (downward in FIG. 5) in an isosceles triangle shape when viewed from the side. It is formed to become. A distance n11 from one end of the bent portion 11B to the center is 0.75 mm. The peak height d1 of the bent portion 11B is 0.13 to 0.16 mm, which is about a half of the thickness t1 of the positive electrode plate 1 = 0.3 mm. In other words, the positive electrode active material on one side of the positive electrode plate 1 It is approximately equal to the thickness of the layer 1a. That is, d1≈0.5t1. A distance n12 from the end of the positive electrode active material layer 1a of the positive electrode plate 1 to the center of the bent portion 11B is 6 mm. A distance n13 from the center of the bent portion 11B to the edge of the separator 3a (bag-like separator 3) is 1 mm. A distance n14 from the end edge of the separator 3a to the end position after the positive electrode lead 11 is focused as described later is 0.45 mm. Further, as the positive electrode lead 11 is converged, it is bent to one side (downward in FIG. 5) to form a curved portion 11R. The diameter of the curved portion 11R is 0.6 mm.

  A bent portion 12B is formed on the negative electrode lead 12 of the negative electrode plate 2 at a position aligned with the bent portion 11B of the positive electrode lead 11. In the vicinity of the extended portion of the negative electrode lead 12 of the negative electrode plate 2, a protective layer is formed in that a distance n22 from the end of the negative electrode active material layer 2a of the negative electrode plate 2 to the center of the bent portion 12B is 4 mm. The dimensions of each part (distance n21 from one end of the bent part 12B to the center, the peak height d2 of the bent part 12B, the thickness t2 of the negative electrode plate 2, the edge of the separator 3a from the center of the bent part 12B, The distance n23 from the edge of the separator 3a to the end position after focusing and the diameter of the curved portion 12R) and the shape are the same as those of the positive electrode lead 11.

[Shaping and connection of current collector]
According to the following procedures a) to e), the positive and negative electrode leads 11 and 12 in the laminated electrode body 10 were shaped (focused, cut, bent, etc.) and connected to the positive and negative electrode collector terminals 15 and 16. 6 to 10 schematically showing the following description and processes, basically, the case of the positive electrode side (the positive electrode lead 11 and the positive electrode current collecting terminal 15) is shown. The same applies to the structure and function (effects) obtained.

a) First step (focusing and cutting of positive and negative electrode leads)
As shown in FIG. 6, the stacked positive electrode lead 11 is focused from above as indicated by an arrow A12 while the laminated electrode body 10 is held by a work presser 41 so as to be sandwiched from above and below as indicated by an arrow A11. The heads 42 are collectively pushed down and focused so as to be brought closer to one side (lower side in FIG. 6) in the stacking direction of the stacked electrode body 10. Next, the surplus portion of the positive electrode lead 11 extending from the converging portion B11 to the tip side was cut at the cutting position C11 to align the tip.

  According to the first step, the positive electrode lead 11 has a one-focus structure. First, the current collector is effectively saved in space. At this time, the positive electrode lead 11 located farther from the converging part B11 (upward in FIG. 6) before converging, that is, closer to the outermost surface side opposite to the converging part B11 (upper side in FIG. 6) in the stacking direction. As the positive electrode lead 11 is pushed down by the focusing head 42, a larger tensile stress is applied, but this tensile stress is absorbed by the bent portion 11B and is effectively reduced. In particular, at this time, the positive electrode lead 11 is subjected to tensile stress so as to be pulled down, but since the bent portion 11B is bent downward and protrudes, the central portion of the bent portion 11B (the lower end in FIG. 6) Is supported by a posture that abuts against the separator 3a from above, that is, a posture placed on the separator 3a. Therefore, the tensile stress is efficiently transmitted to the bent portion 11B and absorbed. It is easy to be done.

  In the first step, when the laminated electrode body 10 is held in such a posture that the lamination direction coincides with the vertical direction for the focusing operation, the positive electrode lead 11 tends to hang down due to gravity. . However, at this time, as described above, since the bent portion 11B is supported by the posture placed on the separator 3a, the posture in which the positive electrode lead 11 floats in the region facing the separator 3a. Instead, it is stably held by the posture supported by the separator 3a. Thereby, the position of the positive electrode lead 11 is stable and the shaping work is facilitated.

b) Second step (connection of positive and negative current collecting terminals)
As shown in FIG. 7, the positive and negative plates 1 and 2 of the positive electrode current collector terminal 15 are arranged so as to overlap the portion extending from the converging part B11 of the positive electrode lead 11 to the front end side from below, and the upper and lower parts are placed in this state. The ultrasonic horn 43T and the anvil 43B are set and ultrasonic welding is performed. As shown in FIG. 11, the positive electrode made of an aluminum plate having a width of 30 mm and a thickness of 0.4 mm is provided at the tip of the positive electrode lead 11 and the negative electrode lead 12. The current collecting terminal 15 and the negative electrode current collecting terminal 16 made of a copper plate having a width of 30 mm and a thickness of 0.4 mm were joined.

  7, 11 and other drawings, reference numeral 31 denotes a positive and negative current collecting terminal 15, 16 in the width direction in order to ensure sealing when an exterior body 18 to be described later is heat sealed. A resin sealing material (glue material) molded so as to adhere to the belt along the belt is indicated.

  In the second step, although the positive electrode lead 11 and the positive electrode current collecting terminal 15 are joined by ultrasonic welding, the positive electrode lead 11 is somewhat stressed. At this time, the positive electrode lead 11 is already in the first step. However, it is considered that the positive electrode lead 11 is not so stressed because it has a focusing structure. However, even if stress is applied, it is absorbed by the bent portion 11B and effectively reduced. Further, when the ultrasonic vibration due to ultrasonic welding is transmitted from the positive electrode lead 11 to the positive electrode active material layer 1a of the positive electrode plate 1, the positive electrode active material may fall off, but this ultrasonic vibration is also attenuated by the bent portion 11B. This effectively prevents the positive electrode active material from falling off.

c) Third step (formation of insulating layer)
As shown in FIG. 8, the side surface of the positive electrode lead 11 that is one side surface of the joint portion (hereinafter also referred to as “positive electrode current collector joint portion”) F11 between the positive electrode lead 11 and the positive electrode current collecting terminal 15 (upper side surface in FIG. 8). An insulating layer (hereinafter also referred to as “inner insulating layer 44N”) is formed by attaching polyimide insulating tape 44N having a size of 30 mm × 5 mm × thickness 35 μm to the side surface of positive electrode current collector terminal 15 which is the other side surface (in FIG. 7). A polyimide insulating tape 44E having a size of 30 mm × 12 mm × thickness 70 μm was attached to the lower surface to form an insulating layer (hereinafter also referred to as “outer insulating layer 44E”).

  At this time, the insulating tape 44N that becomes the inner insulating layer 44N is attached so as to cover the vicinity of the converging portion B11 of the positive electrode lead 11 to slightly outside the tip, and the positive and negative plates in the insulating tape 44E that becomes the outer insulating layer 44E. The first and second sides (the base end side of the positive electrode lead 11) are pasted so as to slightly overlap the leading edge of one side surface (that is, the lower surface of the lower insulating sheet 5 in FIG. 8) in the stacking direction of the stacked electrode body 10. Then, the current collector drawing-out side (the tip side of the positive electrode lead 11) was attached so as to overlap the positive electrode current collecting terminal 15 and the ends of the resin sealing material (glue material) 31. Thus, the metal portion of the side surface of the positive electrode lead 11 (upper side surface in FIG. 8) which is one side surface in the positive electrode current collecting joint portion F11 is almost entirely covered with the insulating tape 44N which becomes the inner insulating layer 44N. Further, the side surface of the positive electrode current collector terminal 15 (the lower surface in FIG. 8), which is the other side surface, is entirely between the insulating sheet 5 of the laminated electrode body 10 and the resin sealing material (glue material) 31 of the positive electrode current collector terminal 15. So that the metal part was not exposed.

d) Fourth step (bending of positive and negative current collecting terminals)
As shown in FIG. 9, the positive electrode current collector joint portion F11 protrudes to the front end side from the positive electrode current collector joint portion F11 at the positive electrode current collector terminal 15 while being held and fixed so as to be pressed by the pressers 45T and 45B from above and below. A portion, that is, a portion extending from the positive and negative electrode plates 1 and 2 side end (laminated electrode body 10 side end) of the positive electrode current collecting terminal 15 to the current collector drawing side (front end side) from the position of 8 mm is shown by an arrow A13. Was bent outward (downward in FIG. 9) so as to have a side view shape (L shape).

e) Fifth step (bending and positioning of the positive and negative current collecting joints)
As shown in FIG. 10, the positive and negative electrode plates 1, 2 are more positive than the positive electrode current collector joint F 11 so that the positive electrode current collector joint F 11 is substantially parallel to the stacking direction (vertical direction in FIG. 10) of the stacked electrode body 10. At the side portion (the base end portion of the positive electrode lead 11), it was bent inward (upward in FIG. 10) as indicated by an arrow A14. Then, a polyimide insulating tape (hereinafter also referred to as “tethered tape”) 46 having a size of 30 mm × 10 mm × thickness 35 μm is installed between the positive electrode current collector terminal 15 and the laminated electrode body 10 as a positive electrode current collector junction F11. In this way, the positive electrode lead 11 was held in a predetermined bent state and positioned.

  At this time, the positive electrode current collector joint portion F11 where the positive electrode current collector terminal 15 made of a metal plate having a certain thickness exists and the front end side thereof are arranged between the positive electrode current collector joint portion F11 and the positive and negative electrode plates 1 and 2. Since only the positive electrode lead 11 made of the laminated metal foil exists at the converging portion B11 or its vicinity, the positive electrode current collecting joint portion F11 and the front end side thereof are easily bent together with the positive electrode current collecting terminal 15. be able to.

  At this time, the positive and negative electrode plates 1 and 2 side (base end side of the positive electrode lead 11) of the mooring tape 46 is the other side surface in the stacking direction of the stacked electrode body 10 (that is, the upper surface of the upper insulating sheet 5 in FIG. 10). The current collector lead-out side (the front end side of the positive electrode lead 11) is overlapped with the ends of the positive electrode current collector terminal 15 and the resin sealing material (glue material) 31. Sticked. As a result, the entire area between the insulating sheet 5 of the laminated electrode body 10 and the resin sealing material (glue material) 31 of the positive electrode current collector terminal 15 at the front end side portion (upper part in FIG. 10) of the positive electrode current collector joint F11. It was covered so that the metal part was not exposed.

  According to the fifth step, the positive electrode lead 11 has a bent structure, and thereby, together with the one focusing structure in the first step described above, the current collector is effectively saved in space. In this bent structure, contrary to the case of the one-side focusing structure, the positive electrode lead 11 that is closer to the focusing portion B11 (the lower position in FIG. 10) before focusing, that is, the one having the focusing portion B11. The positive lead 11 located closer to the outermost surface side (downward in FIG. 10) is subjected to a greater tensile stress due to the bending, but this tensile stress is also absorbed by the bent portion 11B and effectively reduced. It has become.

  On the other hand, when the positive electrode lead has a bent structure as described above, the positive electrode lead is originally expanded at the bent portion and tends to return to its original shape. It is easy to deform so as to extend in the extending direction in the state. When such a deformation occurs, there is a problem that the resin sealing material (glue material) disposed on the positive electrode current collector terminal is detached from the heat-welded portion of the laminate outer package and a short circuit occurs. Further, in the case of a folded structure, when the laminated outer package is sealed under reduced pressure, the laminated film of the outer package enters between the folded positive electrode leads while the folded positive electrode lead is spread, and a wrinkle is formed on the outer package. As a result, the laminate film is damaged, causing a short circuit. On the other hand, since the mooring tape 46 is provided as the mooring means as described above, the positive electrode lead 11 is held in the bent state and positioned, and the deformation extending in the extending direction is effectively suppressed. Therefore, a short circuit due to a displacement of the positive electrode current collecting terminal 15 is also effectively suppressed. In addition, a situation in which a laminate film 17 of the outer package 18 described later enters between the bent positive electrode leads 11 to form wrinkles on the outer package 18 is also effectively suppressed.

[Encapsulation in exterior body]
As shown in FIG. 12, the laminated electrode body 10 is inserted into an exterior body 18 composed of a laminate film 17 formed so that the electrode body can be installed in advance, and only the positive electrode current collector terminal 15 and the negative electrode current collector terminal 16 are present. One side except for the side where the positive electrode current collector terminal 15 and the negative electrode current collector terminal 16 are located was left so as to protrude from the outer package 18 to the outside, and heat fusion was performed.

[Encapsulation and sealing of electrolyte]
LiPF ₆ is 1M (moles) in a mixed solvent in which ethylene carbonate (EC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 30:70 from one side where the outer package 18 is not thermally welded. The electrolytic solution dissolved at a rate of 1 / liter) was injected. Finally, one side of the outer package 18 that was not thermally welded was thermally welded to produce a battery A1 having a positive electrode current collector shown in FIG.

  According to the configuration of the battery A1, as described above, the stress applied to the positive and negative electrode leads 11 and 12 in the laminated electrode body 10 is absorbed by the bent portions 11B and 12B in the shaping / connecting step of the current collector in the manufacture of the battery. In addition, the positive and negative electrode leads 11 and 12 are stably held by the bent portions 11B and 12B, so that the current collector can be easily shaped. In addition, even when the battery after completion is used, the positive and negative leads 11 and 12 are applied to the positive and negative electrode leads 11 and 12 when the electrode expands or increases in thickness due to charging / discharging, or when an external force is applied to the battery due to dropping or the like. Such stress is also absorbed by the bent portions 11B and 12B and effectively reduced.

[Second Embodiment]
14 to 16 are schematic partial cross-sectional views of various secondary batteries according to other embodiments of the present invention. 14 to 16 are schematic partial cross-sectional views showing portions corresponding to FIG. As is apparent from FIGS. 14 to 16, many of the parts and members of various secondary batteries according to these other embodiments are basically the same as the parts and members in the first embodiment. Yes. For this reason, in the following description and FIGS. 14 to 16, the same reference numerals are given to the same parts or members as those in the first embodiment, and the description thereof is basically omitted unless necessary. .

<Basic configuration and effect of battery A2>
In battery A2 shown in FIG. 14, bent portions 51B and 52B are formed in the vicinity of the base end portions (root portions) of positive electrode lead 51 and negative electrode lead 52, respectively, and these bent portions 51B and 52B are schematically in side view. It has a wave shape. The bent portions 51B and 52B are respectively depressed in the positive electrode lead 51 and the negative electrode lead 52 while curving so as to form a substantially bow shape in a side view (downward in FIG. 14) to form a concave portion (bent shape portion). Further, by forming three concave portions in succession, as a whole, it extends along the extending direction of the positive electrode lead 51 and the negative electrode lead 52 while meandering in the thickness direction (vertical direction in FIG. 14) in a side view. It is formed so as to form a wave shape.

  The bent portions 51B and 52B are formed by, for example, a method of pressing a lead from above and below with a mold.

  According to the configuration of the battery A2, since the bent portions 51B and 52B of the positive electrode lead 51 and the negative electrode lead 52 have a substantially wave shape in a side view, spring-like elasticity, particularly extensibility, is further improved. . Further, since the positive electrode lead 51 and the negative electrode lead 52 are supported by the posture placed on the separator 3a at a plurality of locations (three valley bottom portions in the present embodiment) in the bent portions 51B and 52B, stability is improved. Further improve. That is, with a simple configuration, stress applied to the positive electrode lead 51 and the negative electrode lead 52 can be absorbed more effectively, and the positive electrode lead 51 and the negative electrode lead 52 can be held more stably. Yes.

<Battery A3>
In the battery A3 shown in FIG. 15, bent portions 61B and 62B having a rough wave shape when viewed from the side are formed in the vicinity of the base end portions (root portions) of the positive electrode lead 61 and the negative electrode lead 62 as in the case of the battery A2 described above. The bent portions 61B and 62B are recessed while being curved so as to form a substantially bow shape in a side view on one side (downward in FIG. 15) in the positive electrode lead 61 and the negative electrode lead 62, respectively. Later, in order to form a symmetric shape, the other side (upward in FIG. 15) is bent while being curved so as to form a substantially bow shape in a side view, and a bent portion that is bent into a generally S-shape is formed. Further, by continuously forming three bent portions, the meandering between the adjacent separators 3a as a whole in the thickness direction (vertical direction in FIG. 15) can be avoided. It is formed so as to form the outline wave shape extending along the extending direction of the positive electrode lead 61 and the anode lead 62.

  According to the configuration of the battery A3, the positive electrode lead 61 and the negative electrode lead 62 are provided at one of the bent portions 61B and 62B (lower side in FIG. 15) at a plurality of locations (three valley bottom portions in this embodiment). In addition to being in contact with the separator 3a on the side (lower side in FIG. 15), the other side (upper side in FIG. 15) on the other side (upper side in FIG. 15) on the other side (upper side in FIG. 15) It is held in a posture that also contacts the separator 3a. That is, the positive electrode lead 61 and the negative electrode lead 62 are held in such a posture that the interval between the adjacent separators 3a is filled with the bent portions 61B and 62B. As a result, the positive electrode lead 61 and the negative electrode lead 62 are held more stably. Further, for example, when the laminated electrode body is held in such a posture that the lamination direction coincides with the vertical direction, that is, in a lying position, for the purpose of focusing the positive electrode lead 61 and the negative electrode lead 62, the laminated electrode body is laminated. Even if any one of the two surfaces orthogonal to the direction is the upper side, the bent portions 61B and 62B can function in the same manner.

[Other matters]
(1) In the first embodiment, a plurality of the positive electrode plate 1 having the positive electrode lead 11 and the negative electrode plate 2 having the negative electrode lead 12 are provided via the separator 3a (35 positive electrode plates 1 and negative electrode plates). The laminated battery A1 having the laminated electrode body 10 configured by alternately laminating 2) is produced. Instead, for example, a sheet-like positive electrode having a positive electrode lead and a negative electrode lead are provided. It is good also as a spiral battery which comprised the sheet-like negative electrode which it has opposingly arrange | positions through a separator, and enclosed the electrode body formed by winding this in a spiral shape in an exterior body.

(2) In the above embodiment, the positive electrode lead 11 and the negative electrode lead 12 have one converging structure and a bent structure. However, as a shaping structure of the positive and negative electrode leads, a bonding structure with the positive and negative current collecting terminals, etc. Is not particularly limited. For example, in the case of a laminated electrode body, an arbitrary structure such as a structure in which the positive and negative electrode leads are focused at the center in the laminating direction can be used.

(3) In the first embodiment, the bent portions 11B and 12B are formed on both the positive electrode lead 11 and the negative electrode lead 12, but the bent portion is only one of the positive electrode lead and the negative electrode lead. You may make it provide in. In particular, there are leads that are more likely to break or become unstable when stressed depending on the material and thickness, such as leads made of aluminum foil or copper foil having a thickness of about 10 to 30 μm. is there. Therefore, it is desirable to provide a bent portion on at least such a lead.

(4) In the first embodiment, in the positive and negative electrode leads 11 and 12, the bent portions 11B and 12B are formed in the region facing the separator 3a in the vicinity of the base end portion (base portion). However, in addition to this, a bent portion may be formed in another portion of the positive and negative electrode leads 11 and 12, for example, an intermediate portion.

(5) In the first embodiment, a laminate exterior body made of a laminate material is used as the exterior body 18, and thus the battery A <b> 1 is configured as a laminate exterior body battery. You may make it use arbitrary film exterior bodies other than a body, and also a battery can. However, in the case of a soft outer package such as a film outer package such as a laminate outer package, an external force is easily transmitted to the inside, so that the positive and negative electrode leads are easily damaged. The effect of the configuration of the present invention as described above is further exhibited. In particular, in the case of a laminate outer package, for example, the positive and negative electrode leads may break and break through the insulating layer of the laminate outer package. The effect by the structure of this invention is exhibited more. Furthermore, in particular, the configuration in which the insulating members such as the inner insulating layer (insulating tape) 44N and the outer insulating layer (insulating tape) 44E as in the first embodiment are arranged is a laminate outer package that may be short-circuited. This is particularly effective when using. Further, an insulating cover can be used in place of the outer insulating layer (insulating tape) 44E. As this insulating cover, it is preferable to use a sheet-like or plate-like resin member that is bent.

As a laminate material, for example,
Aluminum, aluminum alloy, stainless steel, etc. as the metal layer
Polyethylene, polypropylene, etc. as the inner layer (inside the battery)
Nylon, polyethylene terephthalate (PET), PET / nylon laminated film, etc. as the outer layer (battery outer side)
What is comprised using each is mentioned.

(6) Bending height of the bent portion, that is, a distance between these two planes when the bent portion is sandwiched between two parallel planes from both sides in the bending direction (also referred to as “mountain height” in this specification) ) Is preferably regulated within a predetermined range with respect to the thickness of the positive electrode or the negative electrode. Here, a preferable range as the peak height of the bent portion is, for example, as shown schematically in FIG. 16A, the bent direction A10 of the bent portion M10, that is, the positive electrode lead extending from the positive electrode or the negative electrode (positive negative electrode) E10. The direction A10 in which the bent portion M10 is bent along the direction orthogonal to the extending direction of the negative electrode lead (positive / negative electrode lead) P10 is both sides (upper and lower sides in FIG. 16A). In the case of such a bi-directional bending portion M10 and as schematically shown in FIG. 16B, the bending direction A20 of the bending portion M20 is exclusively on one side (lower side in FIG. 16B). This is different from the case of such a unidirectional bent portion M20.

In the case of the bi-directional bent portion M10, when the height of the bent portion M10 is d and the thickness of the positive and negative electrodes E10 is t, the d and t are the following formula (1), preferably the following formula (2 More preferably, it is desirable to satisfy the following formula (3).
0.25t ≦ d ≦ 2.0t (1)
0.25t ≦ d ≦ 1.5t (2)
0.40t ≦ d ≦ 1.2t (3)

  When 0.25t ≦ d as in the above formula (1), the peak height d of the bent portion M10 is sufficient, so that the stress can be absorbed effectively and the positive and negative electrode leads P10 can be stably held. It can be a bent part. On the other hand, d ≦ 2.0t as in the above formula (1) is desirable because it is possible to avoid an excessive increase in the thickness of the region where the bent portion M10 overlaps. In the above range, when the peak height d of the bent portion M10 is larger than the thickness t of the positive and negative electrodes E10, that is, when t <d ≦ 2.0t, the bent portion is disposed when placed in the separator. If M10 is elastically deformed so as to shrink in the bending direction A10 and is pushed into the separator, the stability is further improved.

On the other hand, in the case of the unidirectional bent portion M20, when the peak height of the bent portion is d and the thickness of the positive and negative electrodes E20 is t, the d and t are the following formula (4), and more preferably: It is desirable to satisfy Expression (5).
0.25t ≦ d ≦ 0.75t (4)
0.25t <d <0.75t (5)

  When 0.25t ≦ d as in the above equation (4), the peak height d of the bent portion M20 is sufficient, and the stress can be absorbed effectively and the positive and negative electrode leads P20 can be stably held. It can be set as the bending part M20. On the other hand, d ≦ 0.75t as in the above formula (4) is desirable because it is possible to avoid an excessive increase in the thickness of the region where the bent portion M20 overlaps.

  In each of FIGS. 16 (a) and 16 (b), phantom lines S10 and S20 indicated by chain lines indicate the above-described bidirectional-type bent portion M10 or unidirectional-type bent portion M20 on both sides in the bent directions A10 and A20, respectively. 2 represents the position of each of the two planes when it is assumed to be sandwiched between two parallel planes.

(7) The positive electrode active material is not limited to the above-described lithium cobalt oxide, and lithium composite oxide containing cobalt such as cobalt-nickel-manganese, aluminum-nickel-manganese, aluminum-nickel-cobalt, nickel, or manganese. Or a spinel type lithium manganate may be used.

(8) As the negative electrode active material, in addition to graphite such as natural graphite and artificial graphite, graphite, coke, tin oxide, lithium metal, silicon, and a mixture thereof can be used to insert and desorb lithium ions. It doesn't matter. In particular, since negative electrodes using elements such as Al, Sn, Si, and alloys thereof as a negative electrode active material expand and contract greatly with charge and discharge, the stress applied to the positive and negative electrode leads is absorbed and reduced at the bent portion. The effect of the present invention as described above is further exhibited.

(9) The electrolyte solution is not particularly limited to that shown in the present embodiment. Examples of the lithium salt include LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F). ₅ ) ₂ , LiPF _6-x (C _n F _{2n + 1} ) _x [where 1 <x <6, n = 1 or 2] and the like can be used, and one or more of these can be used in combination. The concentration of the supporting salt is not particularly limited, but is preferably 0.8 to 1.8 mol per liter of the electrolyte. In addition to the above EC and MEC, the solvent species include carbonate solvents such as propylene carbonate (PC), γ-butyrolactone (GBL), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). More preferably, a combination of a cyclic carbonate and a chain carbonate is desirable.

  The present invention can be suitably applied to a power source for high output applications such as power mounted on a robot, an electric vehicle, or the like, or a backup power source.

1: positive electrode 11: positive electrode lead 2: negative electrode 12: negative electrode lead 3a: separator 10: (laminated) electrode bodies 11B, 12B: bent portion

Claims (8)

A secondary battery comprising an electrode body configured such that a positive electrode having a positive electrode lead and a negative electrode having a negative electrode lead are arranged to face each other via a separator,
At least one of the positive electrode lead and the negative electrode lead has a bent portion in a region facing the separator.   The secondary battery according to claim 1, wherein a plurality of positive leads and a plurality of negative leads protrude from the electrode body.   The said electrode body is a lamination | stacking electrode body comprised by laminating | stacking multiple sheets of the positive electrode plate which has a positive electrode lead, and the negative electrode plate which has a negative electrode lead through a separator, respectively. Secondary battery described in 1.   The positive electrode lead is focused on one outermost surface side in the stacking direction of the stacked electrode body, and the negative electrode lead is focused on one outermost surface side in the stacking direction of the stacked electrode body. The secondary battery as described.   5. The secondary battery according to claim 4, wherein a tip portion of one of the positive electrode lead and the negative electrode lead is bent toward the other outermost surface side in the stacking direction than the converging portion on one outermost surface side.   The secondary battery according to claim 1, wherein the bent portion has a substantially wave shape in a side view. The bent portion is formed so as to bend on both sides with respect to the extending direction of the positive electrode lead or the negative electrode lead, and when the peak height of the bent portion is d and the thickness of the positive electrode or the negative electrode is t, The secondary battery in any one of Claims 1-6 with which d and t satisfy | fill following formula (6).
25t ≦ d ≦ 2.0t (6) When the bent portion is formed to be bent only on one side with respect to the extending direction of the positive electrode lead or the negative electrode lead, the peak height of the bent portion is d, and the thickness of the positive electrode or the negative electrode is t. The secondary battery according to any one of claims 1 to 6, wherein the d and t satisfy the following formula (7).
0.25t ≦ d ≦ 0.75t (7)

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