JP6731157B2 - Square rechargeable battery - Google Patents

Description

The present invention relates to a prismatic secondary battery. Specifically, the present invention relates to a prismatic secondary battery including an electrode body having a structure in which a plurality of positive and negative electrodes are alternately stacked and a current collecting structure.

Secondary batteries such as lithium-ion secondary batteries and nickel-hydrogen batteries have been favorably used not only for so-called portable power sources such as personal computers and mobile terminals but also as vehicle driving power sources in recent years. In particular, a lithium ion secondary battery that is lightweight and obtains high energy density is preferable as a high output power source for driving vehicles such as electric vehicles (EV), plug-in hybrid vehicles (PHV), and hybrid vehicles (HV), and will continue to be used in the future. It is expected that demand will increase.
As a typical form of this type of secondary battery, a rectangular secondary battery including a so-called laminated electrode body having a structure in which a large number of rectangular sheet-shaped positive and negative electrodes are alternately laminated with a separator interposed therebetween ( That is, a prismatic secondary battery including a secondary battery including a battery case having a rectangular parallelepiped structure in which each surface is rectangular (the same applies hereinafter).
Since the laminated electrode body has a relatively large battery capacity per unit volume, it is suitable as a vehicle driving power source for which high capacity and high output are desired. Can be easily adjusted. For example, in Patent Document 1, a laminated electrode body in which a rectangular sheet-shaped separator is interposed and a rectangular sheet-shaped positive electrode sheet and a negative electrode sheet are alternately laminated to form a wide surface having a rectangular shape and having a predetermined thickness There is disclosed an example of a laminated film-sealed secondary battery provided with.

Further, as another mode different from the above laminated film sealing type in a secondary battery employing a laminated electrode body, a laminated electrode is typically provided in a rectangular (box) battery case made of metal. An example is a prismatic secondary battery having a structure in which a body is housed and the opening of the case is sealed by welding or the like. In the secondary battery having such a configuration, since the electrode body is housed in the rectangular battery case, the battery itself has physical strength that is stronger against external impact than the laminated film sealing type. Therefore, it can be said that the battery has a preferable form from the viewpoint of safety.
Further, by changing the size and capacity of the rectangular (box-shaped) battery case to be used, the size and capacity of the electrode body to be housed can be easily changed. Therefore, a high-capacity secondary battery can be easily provided. For example, Patent Document 2 describes a secondary battery having a sealed structure in which a rectangular (box-shaped) battery case of this type accommodates a stacked electrode body having a rectangular wide surface.

JP, 2015-115268, A JP, 2015-210922, A

In the rectangular secondary battery having a structure in which the laminated electrode body is housed in a rectangular battery case, the structural stability of the laminated electrode body itself in the case is further improved as compared with the above-mentioned laminated film sealed type battery. It is necessary to devise to make it. That is, since the laminated electrode body has a structure in which positive electrode sheets and negative electrode sheets are alternately laminated with a separator interposed therebetween, structural stability in a battery case made of metal or other hard material and shape is relatively high. Low. Therefore, in order to maintain high-rate charging/discharging, which is suitable as a power source for driving a vehicle, for a long period of time, it is important that the structure of the laminated electrode body is stably held in the battery case.
In particular, it is necessary to realize a high holding force between the positive and negative electrode sheets and the separator in the stacking direction of the stacked electrode body in order to prevent the positional deviation between the stacked positive and negative electrode sheets. For example, in the electrode body disclosed in Patent Document 2 described above, since the positional displacement does not occur between the stacked positive and negative electrode sheets, the stacking surface of the stacked electrode body (the side surface of the stacked electrode body in the stacking direction of the positive and negative electrode sheets). The same shall apply hereinafter) from one wide surface (which means either one of the outer surfaces of both ends of the laminated electrode body in the laminating direction corresponding to the shape of the positive and negative electrode sheets. The same applies hereinafter) to the other. The holding tape is attached to the wide surface of the.
Furthermore, the current collecting structure of the laminated electrode body of the aspect described in Patent Document 1 or Patent Document 2 (specifically, the current collecting tap structure overhanging from a part of the periphery of the electrode body) is However, it cannot be said to be sufficient as a vehicle drive power source that requires rapid high-rate charging and discharging with a relatively large current when traveling with vibration, and there is room for improvement in such a current collecting structure.
The present invention was created to solve the above-mentioned problems relating to a secondary battery including a laminated electrode body, and can realize a high capacity particularly suitable as a power source for driving a vehicle (secondary battery for mounting on a vehicle). Provided is a rectangular secondary battery having a laminated electrode body, which has good structural stability even when mounted on a vehicle and has a current collecting structure excellent in high-rate charge/discharge characteristics. The purpose is to do.

In order to achieve the above object, the present invention provides
It is composed of a bottomed rectangular parallelepiped case body having a pair of wide surfaces and an opening formed in one of the side surfaces adjacent to the wide surfaces, and a rectangular plate-shaped lid closing the opening. Square battery case,
A positive electrode having a rectangular sheet-shaped positive electrode current collector and a positive electrode active material layer formed on the current collector, a rectangular sheet-shaped negative electrode current collector, and a negative electrode active material layer formed on the current collector And a laminated type electrode body having a structure in which a negative electrode having the above is alternately laminated with a rectangular sheet separator interposed therebetween.
The prismatic secondary battery disclosed here is
Inside the case, a positive electrode current collector terminal and a negative electrode current collector terminal that are electrically connected to an external connection terminal are provided,
A positive electrode current collector exposed portion having no positive electrode active material layer is formed at one end of each of the laminated positive electrodes in a direction parallel to the lid, along a direction orthogonal to the lid. And
A negative electrode current collector exposed portion having no negative electrode active material layer is formed at one end of each of the laminated negative electrodes in a direction parallel to the lid, along a direction orthogonal to the lid. And
The positive electrode current collector exposed portion is laminated at one end portion in the direction parallel to the lid body, and the negative electrode current collector exposed portion is laminated at the other end portion in the direction,
The positive electrode current collector exposed portion and the negative electrode current collector exposed portion that are stacked together constitute a plurality of current collecting bundles that are divided into two or more in the stacking direction and are bundled. Each of the current collecting bundles is separately and individually joined to the current collecting terminal on the same pole side.
In the prismatic secondary battery disclosed herein, the number of the current collecting fluxes on each of the positive and negative electrode sides is determined by the following formula ( Maximum allowable thickness M (mm) of partitioned electrode body obtained in 1):
M=18.7×H/W+1.4 (1)
(H in the formula is a side length (mm) of the positive electrode current collector in a direction orthogonal to the lid body,
W is a side length (mm) in a direction parallel to the lid of the separator. )
It is characterized in that it is set not to exceed.
It should be noted that in the present specification, the above-mentioned “partitioned electrode body laminated portion belonging to the current collection flux” means, in any one of the positive and negative electrode side current collection fluxes, a positive electrode (negative electrode) current collection which constitutes the current collection flux. It refers to an electrode body laminated portion arranged between two outermost (both ends in the lamination direction) positive electrode (negative electrode) current collectors of the body in the electrode body lamination direction.

The present inventor examined a good number of current collecting fluxes in the case of forming a plurality of current collecting fluxes by dividing the current collector exposed portion of the positive electrode (negative electrode) to be laminated in the laminated electrode body. When the number of divisions is too small (that is, when the divided electrode body laminated portions belonging to the individual current collecting fluxes are relatively thick), the self-weight and size of the divided electrode body laminated portions belonging to each current collecting flux may be reduced. Due to the influence, relative positional deviation (sheet deviation) may occur between the divided electrode body laminated portions belonging to the adjacent current collecting bundles. Such a positional shift is not preferable because it may lower the mechanical strength of the electrode body itself and may lower the electrical performance such as the current collecting function.
Further, according to the study by the inventor, the thickness of the partitioned electrode body laminated portion belonging to the current collecting flux in which the positional deviation easily occurs is determined by the rectangular sheet-shaped positive and negative electrode current collectors and separators constituting the laminated electrode body. Shape, specifically, when the wide surface of the laminated electrode body has a vertically long rectangular shape and a horizontally long rectangular shape when the direction parallel to the lid is horizontal and the direction perpendicular to the lid is vertical). It was newly found that

As a result of various studies from this viewpoint, in the rectangular laminated electrode body, the maximum allowable thickness M() of the partitioned electrode body derived from the above formula (1) is derived from the thickness of the partitioned electrode body laminated portion belonging to each current collecting flux. The present invention has found that by determining the number of current collection fluxes so as not to exceed 10 mm), it is possible to effectively suppress an undesired positional deviation between the partitioned electrode body laminated portions belonging to the adjacent current collection fluxes. Came to create.
That is, according to the prismatic secondary battery disclosed herein, between the divided electrode body laminated portions belonging to the adjacent current collecting bundles that may adversely affect the mechanical characteristics and/or the electric characteristics of the laminated electrode body. Of the rectangular sheet-like positive and negative electrodes and/or separators in which the relative displacement is suppressed, and a current collecting structure (current collecting member disclosed herein) capable of favorably realizing high capacity and high rate charging/discharging is formed. A type secondary battery can be provided.
Preferably, the side length W (mm) in the direction parallel to the lid of the separator is substantially equal to the longer one of the positive electrode active material layer and the negative electrode active material layer in the same direction.

A preferred embodiment of the prismatic secondary battery disclosed herein is
The positive electrode current collector terminal and the negative electrode current collector terminal are provided with current collectors for individually joining the plurality of current collection fluxes on the same pole side, respectively, the same number as the plurality of current collection fluxes, and mutually spaced apart. It is characterized by being provided with a space.
In this way, by using the positive electrode current collector terminal and the negative electrode current collector terminal in which the same number of current collecting units as the plurality of current collecting fluxes are provided at intervals, the adjacent current collecting fluxes are mutually The current can be effectively collected without any obstacle. Therefore, an efficient current collecting (conducting) path is easily formed, and charging/discharging with a relatively large current (high-rate charging/discharging) can be suitably performed.

It is a perspective view which shows typically the external shape of the square type secondary battery (lithium ion secondary battery) of the airtight structure which concerns on one Embodiment. It is a perspective view which shows typically the structure of the laminated electrode body with which the square secondary battery shown in FIG. 1 is equipped. It is a figure which illustrates typically the current collection structure which concerns on one Embodiment. FIG. 3 is a cross-sectional view schematically illustrating a plurality of current collecting fluxes on each of the positive and negative electrode sides of the laminated electrode body according to the embodiment. It is a figure which illustrates typically several positive and negative electrode side current collection fluxes of the laminated electrode body which concerns on other one Embodiment. (A), (b) and (c) is a perspective view showing an example of a current collection terminal from which the number of current collection parts (current collection plates) differs mutually. 6 is a graph showing the relationship between the electrode body thickness and H/W ratio when a vibration input of a predetermined acceleration is applied, and the number of divisions (the number of current collection fluxes) of the current collector exposed portion that does not cause positional displacement. It is a graph which shows the relationship between the maximum allowable thickness M (mm) of a partition electrode body, and the H/W ratio in a laminated electrode body. (A) And (b) is a figure which illustrates typically the current collection structure (a plurality of current collection flux) of each positive and negative electrode side of the lamination type electrode object concerning one embodiment. (A), (b) and (c) is a perspective view which shows the example of the current collection terminal from which the number of slits mutually differs. It is explanatory drawing which shows typically the current collection structure constructed using the current collection terminal shown to FIG. 10 (a), (a) is a front view, (b) is a side view by the side of a positive electrode.

Hereinafter, a preferred embodiment of a lithium ion secondary battery as an example of the prismatic secondary battery disclosed herein will be described in detail with reference to the drawings. The dimensional relationship (length, width, thickness, etc.) in each drawing is not intended to accurately reflect the actual dimensional relationship because importance is placed on ease of understanding of the description. In addition, the same reference numerals are given to members and parts that have the same action, and duplicate explanations are omitted or simplified. Matters other than the matters particularly referred to in the present specification and necessary for implementation can be grasped as design matters of a person skilled in the art based on conventional technology in the field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field.
The present invention is not limited to the lithium-ion secondary battery shown in the following embodiments, but can be applied to other rectangular secondary batteries that can be equipped with a laminated electrode body, such as an electric double layer capacitor, a lithium-ion capacitor, and a sodium-ion secondary battery. The invention can be preferably implemented.
In the present specification, the “active material” refers to a material that is involved in storage and release of charge carriers (eg, lithium ions in a lithium ion secondary battery) on the positive electrode side or the negative electrode side. The numerical ranges A to B (A and B are arbitrary numbers) in the present specification indicate A or more and B or less.

As shown in FIG. 1, in the lithium ion secondary battery 10 according to the present embodiment, a flat laminated electrode body 50 (FIG. 2) is used together with an electrolyte (a non-aqueous electrolyte solution) not shown in the drawings. The prismatic secondary battery has a sealed structure and is housed in a flat prismatic battery case 12 corresponding to the shape of the electrode body 50 (that is, an outer container of the lithium ion secondary battery 10).
The battery case 12 has a box shape (that is, a rectangular parallelepiped shape with a bottom) in which an opening is formed on one side surface (corresponding to the upper surface in a normal use state of the lithium ion secondary battery 10) adjacent to the wide surface. It is composed of a main body 14 and a rectangular plate-shaped lid 16 attached to the opening and closing the opening. By welding the lid 16 to the peripheral edge of the opening of the case body 14, a pair of case wide surfaces facing the rectangular wide surface of the flat laminated electrode body 50 and adjacent to the case wide surface. A battery case 12 having a hexahedron (rectangular parallelepiped) closed structure with four narrow rectangular side surfaces (that is, one of them is composed of the lid 16) is formed.
Although not particularly limited, as a preferred size of the battery case of this type of battery, the length of the long side of the case body 14 and the lid body 16: 80 mm to 200 mm, the short side of the case body 14 and the lid body 16 The side length (that is, the thickness of the battery case 12): 5 mm to 50 mm (for example, 8 mm to 40 mm), and the height of the battery case 12: 70 mm to 150 mm can be exemplified. The size of the laminated electrode body 50 is not particularly limited as long as it can be accommodated in the battery case used.
The material of the battery case 12 (case body 14 and lid 16) may be the same as that used in the conventional secondary battery of this type, and is not particularly limited. Examples include aluminum, stainless steel, nickel-plated copper and the like.

As shown in FIG. 1, a negative electrode terminal 18 and a positive electrode terminal 20 which are external connection terminals are integrally formed on the outer surface side of the lid body 16. The lid 16 has a thin safety valve 40 configured to release the internal pressure of the battery case 12 when the internal pressure rises above a predetermined level, and a liquid injection port 42 for supplying a non-aqueous electrolyte. Are formed. FIG. 1 shows a state after completion of the liquid injection, and the liquid injection port 42 is sealed by a sealing material 43. The mechanism of the safety valve 40 and the sealing form of the liquid injection port 42 may be the same as those of the conventional battery of this type, and no special configuration is required.

As shown in FIG. 2, the laminated electrode body 50 according to the present embodiment includes a rectangular sheet-shaped positive electrode (hereinafter referred to as “positive electrode sheet 51”) and a rectangular sheet-shaped negative electrode similar to the positive electrode sheet 51 (hereinafter, referred to as “positive electrode sheet 51”). “Negative electrode sheet 55”) is alternately laminated with a similar rectangular sheet-shaped separator 58 (FIG. 3) interposed therebetween.
The positive electrode sheet 51 has a positive electrode active material layer (not shown) formed on both sides of a rectangular sheet-shaped positive electrode current collector 52, while the negative electrode sheet 55 has both sides of a rectangular sheet-shaped negative electrode current collector 56. A negative electrode active material layer (not shown) is formed on.
One end of the rectangular positive electrode current collector 52 in a direction parallel to the lid 16 (hereinafter also referred to as “long side direction”) has a direction orthogonal to the lid 16 (hereinafter “short side direction”). (Also referred to as "), a positive electrode current collector exposed portion 52A having no positive electrode active material layer is formed in a strip shape. Similarly, at the other end portion of the rectangular negative electrode current collector 56 in the long side direction, a negative electrode current collector exposed portion 56A having no negative electrode active material layer is formed in a strip shape along the short side direction. ..

As shown in FIG. 2, the positive electrode sheet 51 and the negative electrode sheet 55 are slightly displaced in the long side direction, and the positive electrode current collector exposed portion 52A protrudes from one end portion of the separator 58 in the long side direction, and The negative electrode collector exposed portion 56A is stacked so as to protrude from the other end. As a result, a portion where the positive electrode current collector exposed portion 52A and a negative electrode current collector exposed portion 56A are laminated at one end and the other end in the long side direction of the laminated electrode body 50, respectively. A part is formed. The plurality of current collecting fluxes described above are formed in each of the positive electrode current collector exposed portion 52A and the negative electrode current collector exposed portion 56A, which will be described later.

The materials (positive electrode active material, negative electrode active material, conductive material, binder, etc.) and constituent members (positive electrode current collector, negative electrode current collector) that form the positive and negative electrodes of the laminated electrode body 50 that forms the lithium ion secondary battery. , Etc.) and the electrolyte (solvent forming the non-aqueous electrolyte, lithium salt, etc.) may be the same as those used for forming a conventional general lithium ion secondary battery. Since it does not characterize any of the above, detailed description thereof will be omitted.

Next, the current collecting structure in the lithium ion secondary battery 10 according to the present embodiment will be described.
As shown in FIG. 3, the positive electrode current collector exposed portion 52A and the negative electrode current collector exposed portion 56A of the stacked electrode body 50 housed in the battery case 12 are respectively connected to the positive electrode current collector terminal 32 and the negative electrode current collector. The current collecting portions (current collecting plates) 33 and 37 of the terminal 36 are joined by welding (reference numeral S indicates a welded portion). The positive electrode current collecting terminal 32 and the negative electrode current collecting terminal 36 are electrically connected to the positive electrode terminal 20 and the negative electrode terminal 18 provided on the lid body 16, respectively. The current collecting structure including the positive electrode current collecting terminal 32 and the negative electrode current collecting terminal 36 constitutes an electrical path connecting the laminated electrode body 50 with the positive electrode terminal 20 and the negative electrode terminal 18.

As shown in FIG. 4, the laminated electrode body 50 is constructed by laminating the positive electrode sheet 51, the negative electrode sheet 55, and the separator 58 in a desired number of sets. In the present embodiment, considering the characteristics of the lithium ion secondary battery, one more negative electrode sheet 55 is stacked than the positive electrode sheet 51 so that both ends in the stacking direction are the negative electrode sheets 55A and 55Z. .. Further, in order to further improve the insulating property in the battery case 12, a separator 58 is further arranged on the outer surface side of the negative electrode sheet 55A at one end in the stacking direction, and similarly, the negative electrode sheet 55Z at the other end is arranged. A separator 58 is also arranged on the outer surface side. Alternatively, instead of the separator 58 on the outermost surface, a film (not shown) made of an insulating synthetic resin (for example, polyolefin) may be disposed between the laminated electrode body 50 and the inner wall of the case 12. Good.
In addition, the material of the separator 58 is not particularly limited, and a material that has been frequently used in this type of rectangular secondary battery (lithium ion secondary battery) can be used. For example, a separator made of a polyolefin porous sheet such as polyethylene or polypropylene may be used.

As shown in FIG. 4, in the current collecting structure of the laminated electrode body 50 according to the present embodiment, the positive electrode current collector exposed portion 52A and the negative electrode current collector exposed portion 56A are each divided into two or more in the stacking direction. A plurality of current collecting bundles 80 and 90 that are bundled together are configured. In addition, in FIG. 4, two current collecting fluxes 80 and 90 are provided on each of the positive and negative electrode sides in order to simplify the explanation of the current collecting structure and to make it easy to understand. .. For example, in the laminated electrode body 50 shown in FIG. 5, the positive electrode side is divided into three current collecting fluxes 80 and the negative electrode side is divided into four current collecting fluxes 90. In this way, the numbers of divisions on the positive and negative electrode sides are the same. It is not necessary and may be different from each other.
As shown in FIG. 4, in the laminated electrode body 50 according to the present embodiment, it exists between the negative electrode sheet 55A at one end in the stacking direction and the negative electrode sheet 55Z at the other end in the stacking direction. Any of the separators 58 between the positive electrode and the negative electrode is arranged in a state of being included in any of the positive electrode current collecting bundles 80 and/or any of the negative electrode current collecting bundles 90. Therefore, as shown by the vertical arrows in FIG. 4, the current collector exposed portions 52A and 56A at both ends in the stacking direction, that is, the two current collector exposed portions that form the outer surfaces of the current collecting bundles 80 and 90. The positive and negative electrode sheets 51 and 55 and the separator 58 sandwiched by the 52A and 56A have positive stress as a stress generated by bundling a plurality of current collectors (exposed portions) to form the current collector bundles 80 and 90. A pressure is generated in the negative electrode stacking direction. Such a pressure enhances the holding power of the positive and negative electrode sheets 51 and 55 and the separator 58 that are stacked inside the current collecting bundle, and positions the positive and negative electrodes and the separator that are stacked inside the current collecting bundle in the lateral direction with respect to the stacking direction. The deviation can be suppressed.

In the positive electrode current collecting terminal 32 and the negative electrode current collecting terminal 36 according to the present embodiment, current collecting portions (current collecting plates) 33, 37 for individually joining the plurality of current collecting bundles 80, 90 respectively collect current. The same number as the bundle is provided at intervals. One suitable form is shown in FIG. Note that FIG. 6 shows a preferred example of the positive and negative electrode current collector terminals 32A, 32B, 32C. It can be used for both the positive electrode current collecting terminal and the negative electrode current collecting terminal.
The current collector terminals 32A, 32B, 32C shown in (a) to (c) of FIG. 6 are part of the positive and negative electrode current collector exposed portions 52A, 56A constituting the outer surfaces of the corresponding current collector bundles 80, 90. And welded together. Specifically, the current collecting terminals 32A, 32B, and 32C according to the present embodiment are roughly arranged on the connection part 34 arranged on the inner surface side of the case of the lid body 16 and on the outer surface side of the case body of the lid body 16. The connection projections 35 that are connected (fitted) to the positive electrode terminal 20 that is an external connection terminal and the converged tip portions of the corresponding current collecting bundles 80 and 90 (hereinafter referred to as “converging portions 81 and 91”). And a plate-shaped current collecting portion (current collecting plate) 33 joined to a part of the outer surfaces of the converging portions 81 and 91 of the current collecting bundles 80 and 90 by welding. Further, the current collectors 33 are preferably provided at equal intervals and at a required number, that is, the same number as the corresponding current collection flux. As illustrated, all of the plurality of current collectors 33 provided are connected to the connection part 34.
With such a configuration, the current collecting structure on the positive electrode (negative electrode) side can be formed by one positive electrode (negative electrode) current collecting terminal regardless of the number of current collecting bundles 80 and 90. Further, it is possible to effectively collect current without the adjacent current collecting bundles interfering with each other.

Next, a description will be given of a suitable method for determining the number of current collection fluxes when the positive (negative) pole current collector exposed portion of the laminated electrode body is divided into a plurality of current collection fluxes.
The symbols H and W in FIG. 2 described above are respectively parallel to the side length: H (mm) in the direction orthogonal to the lid of the positive electrode current collector (that is, the vertical direction in the figure) and the lid of the separator. The side length in the direction (that is, the lateral direction in the drawing): W (mm) is shown.
The present inventor has variously changed the shape (specifically, H/W ratio) of the wide surface of the laminated electrode body 50 and the thickness (D: mm in FIG. 2) of the electrode body 50 as a test sample. The relationship between the resistance to positional deviation and the number of divisions of the exposed portion of the positive and negative electrode current collectors in the stacking direction (that is, the number of current collecting fluxes) was examined. Specifically, it was investigated in detail whether or not a positional deviation occurred between the current collecting fluxes by applying a vibration input of a predetermined acceleration to the test electrode body. FIG. 7 is a graph showing the result.

As is clear from the results shown in FIG. 7, regarding the laminated electrode body having a wide rectangular surface, even if the electrode body has the same thickness (D: mm), the vibration of a predetermined acceleration is caused by the difference in H/W ratio. The number of divisions (the number of current collection bundles) of the exposed portion of the current collector that does not cause a positional shift when an input is applied is different. For example, in the case of an electrode body having an H/W ratio of 0.25, when the electrode body thickness is 40 mm (50 mm), misalignment is required unless the number of divisions (the number of current collection fluxes) is 6 (8) or more. It can be seen that
On the other hand, in the case of an electrode body having an H/W ratio of 1, it can be seen that when the electrode body thickness is 40 mm (50 mm), the number of divisions (the number of collecting fluxes) should be three (5) or more.

Next, based on the above results, a graph is created that plots the relationship between the H/W ratio and the thickness (mm) of the section of the electrode body stacked that belongs to one current collecting flux that is resistant to displacement. did. The results are shown in Fig. 8.
As is clear from the results shown in FIG. 8, the maximum value of the thickness of the divided electrode body laminated portion belonging to one current collecting flux that is resistant to the positional deviation, that is, the maximum allowable thickness M (mm) of the divided electrode body ) Has a correlation with the H/W ratio in the laminated electrode body. That is, the following expression (1) is derived from the result shown in FIG.
M=18.7×H/W+1.4 (1)
Here, M in the formula is the maximum allowable thickness (mm) of the partition electrode body, H is the side length (mm) in the direction orthogonal to the lid of the positive electrode current collector, and W is the lid of the separator. It is the side length (mm) in the direction parallel to the body.
Preferably, the side length W (mm) in the direction parallel to the lid of the separator is substantially equal to the longer length of the positive electrode active material layer and the negative electrode active material layer in the same direction. Thereby, W in the above formula (1) can be replaced with the longer side length (W': mm) of the positive electrode active material layer and the negative electrode active material layer in the direction parallel to the lid. ..

Based on the formula (1), by keeping the thickness of the divided electrode body laminated portion belonging to each current collecting flux from exceeding the above M, the distance between the divided electrode body laminated portions belonging to the adjacent current collecting flux is increased. It is possible to suppress the occurrence of relative positional deviation (sheet deviation). Therefore, the relative displacement between the positive and negative electrodes and the separator in the form of a rectangular sheet, which adversely affects the mechanical characteristics and/or the electrical characteristics of the laminated electrode assembly, is suppressed, and high capacity and high rate charge/discharge are favorably performed. It is possible to provide a prismatic secondary battery including a current collection structure that can be realized (that is, a current collection structure including the current collection member disclosed herein).
It should be noted that the thickness of the partitioned electrode body laminated portion belonging to each current collection flux does not need to be uniform unless it exceeds the above M value. In this case, preferably, when there are positive and negative electrode current collecting bundles 80 and 90 having a relatively thin sectioned electrode body laminated portion, such as the electrode body shown in FIGS. It is preferable to dispose it on the outer side in the stacking direction because higher positional displacement resistance can be exhibited.

Although the preferred embodiment of the present invention has been described above, the technical idea of the present invention is not limited to the described embodiment. For example, by using the above formula (1), the number of current collection fluxes may be determined by dividing so as to have a suitable thickness of the sectioned electrode body laminated portion. You may use the separator with an adhesive which added the adhesive to. By having such an adhesive, the adhesive force with at least one (or both) of the positive electrode sheet and the negative electrode sheet to be laminated can be further increased.

Further, the positive and negative electrode current collector terminals used are not limited to those provided with the plate-shaped current collectors described above. Hereinafter, as a further preferred embodiment of the positive and negative electrode current collector terminal, a positive and negative electrode current collector terminal including a plurality of slits as current collectors for inserting and welding a convergent portion of a current collecting flux will be described with reference to the drawings. ..

The current collector terminals 61A, 61B, and 61C for positive and negative electrodes according to the present embodiment shown in FIG. 10 roughly include a connecting portion 63 arranged on the case inner surface side of the lid body 16 and a case outer surface of the lid body 16. The connection projections 65 connected (fitted) to the positive and negative electrode terminals 20 and 18, which are external connection terminals arranged on the side, and the corresponding converging portions 81 and 91 of the current collecting bundles 80 and 90 are joined by welding. And a joint plate 62 having a slit 64 formed therein.
The slit 64 corresponds to the current collector according to this embodiment. That is, as shown in (a) to (c) of FIG. 10, the number of slits 64 (six, four, and three in this case) corresponding to the number of corresponding current collecting bundles 80 and 90 is positive and negative electrode laminated. It is formed orthogonal to the direction and in the short side direction of the electrode body 50. Specifically, the joint plate 62 in which the plurality of slits 64 are formed is formed in a comb shape. The slits 64 are formed at intervals corresponding to the arrangement intervals of the converging portions 81. The opening width of each slit 64 is formed to be equal to or larger than the thickness of the converging portions 81 and 91 for inserting the converging portions 81 and 91.
Then, the respective converging portions 81, 91 of the current collecting bundles 80, 90 corresponding to the respective slits 64 are inserted. At this time, it is preferable that the tips of the converging portions 81 and 91 are slightly projected from the slits 64. Then, the tip portions of the respective converging portions 81 and 91 and the joint plate 62 (specifically, the peripheral portion of the slit 64) are welded by ultrasonic welding or the like, and the respective converging portions 81 and 91 and the current collecting terminal 61A. To join. That is, the positive and negative electrodes are electrically connected to the converging portions 81 and 91 and the collector terminal 61A.

In the embodiment described above, since a plurality of slits (for example, six, four, or three as shown in FIG. 10) are formed in one joint plate 62, the number of current collecting bundles 80, 90 is increased. However, the current collecting structure on the positive electrode (negative electrode) side can be formed by one positive electrode (negative electrode) current collecting terminal. Further, it is possible to effectively collect current without the adjacent current collecting bundles interfering with each other.
Furthermore, even when the number of current collection fluxes and the intervals of the converging portions are different between the positive and negative electrodes as shown in FIG. 9 described above, by using the current collection terminals having the corresponding number of slits at predetermined intervals, The current collecting structure can be easily constructed without increasing the volume occupied by the current collecting terminal itself. The positive electrode current collector terminal and the negative electrode current collector terminal forming the current collector structure of the lithium ion secondary battery 10 according to the present embodiment change the shape and size of the entire current collector terminal by adjusting the number of slits (for example, It is possible to easily deal with the number of divisions of the exposed portion of the positive and negative electrode current collectors of the laminated electrode body in the laminating direction without increasing the size. Therefore, even if the number of divided positive and negative electrode current collector exposed portions in the stacking direction increases, the weight of the positive and negative electrode current collector terminals does not increase. On the contrary, if the number of divisions is increased, the number of slits is increased, and it can be said that the weight of the positive and negative electrode current collector terminals is correspondingly reduced. Therefore, it is possible to prevent the prismatic secondary battery (for example, a lithium ion secondary battery) from increasing in size and weight.

Further, as shown in FIGS. 11A and 11B, the range in which the bonding plate 62 of the positive and negative electrode current collector terminal 61A overlaps the positive and negative electrode current collector exposed portions 52A and 56A is substantially the same as the thickness of the bonding plate 62. Can be said.
Therefore, the current collecting structure can be configured without enlarging the exposed portion of the positive and negative electrode current collectors. That is, as shown in FIG. 11A, the area required for joining the positive and negative electrode current collector terminals 61A and the positive and negative electrode current collector exposed portions 52A and 56A is equal to the thickness of the joining plate 62. Only need be. For this reason, since it suffices to form the positive and negative electrode collector exposed portions 52A and 56A (and thus the current collecting flux) of a relatively compact size, the area of the positive and negative electrode active material layer can be expanded in the long side direction. Thereby, the battery capacity can be increased.

As described above, the prismatic secondary battery such as the lithium ion secondary battery disclosed herein has a current collecting structure that can favorably realize high capacity and high rate charge/discharge of the battery. Therefore, it can be suitably used as a vehicle driving power source (vehicle mounted secondary battery).

10 lithium-ion secondary battery 12 battery case 14 case body 16 lid 18 negative electrode terminal 20 positive electrode terminal 32, 32A, 32B, 32C positive electrode current collecting terminal 33 current collecting portion 34 connecting portion 35 connecting protrusion 36 negative electrode current collecting terminal 37 collecting Electrode part 50 Laminated electrode body 51 Positive electrode sheet 52 Positive electrode current collector 52A Positive electrode current collector exposed part 55 Negative electrode sheet 56 Negative electrode current collector 56A Negative electrode current collector exposed part 58 Separator 61A, 61B, 61C Current collecting terminal 62 Bonding plate 63 Connection part 64 Slit (current collecting part)
65 Connection projection 80 Positive electrode current collection flux 81 Convergence part 90 Negative electrode current collection flux 91 Convergence part S Welding part

Claims (3)

It is composed of a bottomed rectangular parallelepiped case body having a pair of wide surfaces and an opening formed in one of the side surfaces adjacent to the wide surfaces, and a rectangular plate-shaped lid closing the opening. Square battery case,
A positive electrode having a rectangular sheet-shaped positive electrode current collector and a positive electrode active material layer formed on the current collector, a rectangular sheet-shaped negative electrode current collector, and a negative electrode active material layer formed on the current collector A negative electrode having and a laminated electrode body having a structure in which rectangular sheet-shaped separators are alternately laminated while interposing a rectangular sheet-shaped separator therebetween,
A prismatic lithium-ion secondary battery comprising:
Inside the case, a positive electrode current collector terminal and a negative electrode current collector terminal that are electrically connected to an external connection terminal are provided,
A positive electrode current collector exposed portion having no positive electrode active material layer is formed at one end of each of the laminated positive electrodes in a direction parallel to the lid, along a direction orthogonal to the lid. And
A negative electrode current collector exposed portion having no negative electrode active material layer is formed at one end of each of the laminated negative electrodes in a direction parallel to the lid, along a direction orthogonal to the lid. And
The positive electrode current collector exposed portion is laminated at one end portion in the direction parallel to the lid body, and the negative electrode current collector exposed portion is laminated at the other end portion in the direction,
The positive electrode current collector exposed portion and the negative electrode current collector exposed portion that are stacked together constitute a plurality of current collecting bundles that are divided into two or more in the stacking direction and are bundled. Each of the current collecting flux of, is individually and separately joined to the current collecting terminal of the same pole side,
Here, the thickness of the laminated electrode body is 10 mm or more and 50 mm or less,
The number of the current collecting fluxes on each of the positive and negative electrode sides is the maximum allowable thickness M (mm) of the partitioned electrode body obtained by the following formula (1) when the thickness of the partitioned electrode body laminated portion belonging to each current collecting flux is ):
M=18.7×H/W+1.4 (1)
(H in the formula is a side length (mm) of the positive electrode current collector in a direction orthogonal to the lid body,
W is a side length (mm) in a direction parallel to the lid of the separator. )
A prismatic lithium-ion secondary battery characterized by being set so as not to exceed. The positive electrode current collector terminal and the negative electrode current collector terminal are provided with current collectors for individually joining the plurality of current collection fluxes on the same pole side, respectively, the same number as the plurality of current collection fluxes, and mutually spaced apart. The prismatic lithium-ion secondary battery according to claim 1, wherein the prismatic lithium-ion secondary battery is provided. The prismatic lithium-ion secondary battery according to claim 1, wherein the separator is a polyolefin porous sheet.

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