JP5779859B2 - battery - Google Patents

Description

  The present invention relates to a battery including a power generation element in which a foil-like positive electrode plate and a foil-like negative electrode plate are arranged with a separator interposed therebetween.

Such a battery is a battery in which an active material layer is formed on each of a foil-like positive electrode plate and a foil-like negative electrode plate and arranged opposite to each other with a separator interposed therebetween. As a form, for example, as described in Patent Document 1 and Patent Document 2 below, a foil-shaped positive electrode plate and a foil-shaped negative electrode plate each formed in a long strip shape are wound with a separator interposed therebetween. The form etc. which comprise an electric power generation element are known well.
In the power generation element configured as described above, a high energy density is realized by housing a large-area foil-like positive electrode plate or the like in a housing having a small volume.
In a battery including a power generation element as described above, heat (Joule heat) generated by an electrical short circuit (internal short circuit) between the positive electrode side and the negative electrode side in the power generation element may increase.
As measures for improving safety when such an internal short circuit occurs, for example, measures such as appropriately applying an insulating coating to the foil-like positive electrode plate are considered.

Japanese Patent Laid-Open No. 11-339839 JP 2009-245683 A

However, it has been found that the above countermeasures alone are not always sufficient as countermeasures against internal short circuits.
The present invention has been made in view of such circumstances, and an object thereof is to make it possible to more effectively cope with an internal short circuit of a power generation element.

According to a first aspect of the present application, there is provided a battery including a power generation element in which a foil-like positive electrode plate and a foil-like negative electrode plate are disposed with a separator interposed therebetween. The power generation element includes the foil-like positive electrode plate and the foil-like negative electrode. The foil-shaped positive electrode plate or the foil-shaped negative electrode plate is formed by winding the plate with the separator interposed therebetween, and the contour of the corner portion on the outermost periphery of the winding forms two corners. The straight line is configured to be positioned on the inner side of a virtual outline that intersects and extends, and the outline is formed as a straight line that intersects two straight lines forming the corner at an obtuse angle .

That is, the foil-like negative electrode plate or the like is often formed into a shape having a corner portion, for example, as a rectangular shape such as a long band shape.
Causes of internal short-circuiting include cases where foreign matter enters the battery case and the foreign matter adheres to the power generation element and presses it. In extreme cases, nails are driven from the outside of the case. .
In this way, when a foil-like negative electrode plate or the like is pressed against a foreign substance, the contact point with the foreign substance or the like on the foil-like negative electrode plate is acted upon by a force that is pulled up from the surrounding portion in a form that resists the pressing force from the foreign substance. To do. When this pulling-up force acts symmetrically from the surroundings, even if the foil-like negative electrode plate or the like is broken by the pressing force from the foreign matter, there is a strong tendency that the foil-like negative electrode plate or the like is simply torn.
On the other hand, at the end of a foil-like negative electrode plate or the like, the above-described force pulled up from the periphery is not symmetrical, which is problematic.

For example, in FIG. 10 (a), if the object is pressed by a foreign object or the like at the position indicated by the black circle A, the force that is pulled up from the periphery acts in the form schematically indicated by the arrow in the figure. . Although there is no symmetry as a whole at the position shown in FIG. 10 (a), in the direction along the edge 101, a force acts from both sides of the position of the black circle A. Even when the negative electrode plate or the like is broken, the tendency of the foil-like negative electrode plate or the like to be simply torn is increased.
However, as shown in FIG. 10 (b), when a pressing force such as the above-mentioned foreign matter acts on the tip of the corner (indicated by a black circle B in FIG. 10 (b)), it acts as indicated by an arrow. Since the symmetry of the force is greatly broken, the tip of the corner is pushed together with the foreign matter or the like by the pressing force of the foreign matter or the like, or is pulled into the foreign matter or the like, and the degree of the internal short circuit is increased. This means that the degree of the internal short circuit is remarkably increased as compared with a state where the foil-like negative electrode plate or the like is simply torn.
Therefore, for example, as illustrated in FIG. 10C, the contour at the corner is a virtual contour (two points in FIG. 10C) obtained by extending and intersecting two straight lines forming the corner. The shape is such that the tip does not exist at the corners so as to be located on the inner side (indicated by the chain line 102).
By doing so, when a pressing force such as a foreign substance is applied at the position indicated by the black circle C arrow in FIG. 10C, the force indicated by the arrow in FIG.
The action state of the force from the surroundings is similar to that in FIG. 10 (a), and even if the foil-like negative electrode plate or the like breaks due to the pressing force from the foreign matter than that shown in FIG. 10 (b). There is a strong tendency for the foil-like negative electrode plate or the like to be torn.
As is apparent from the description in FIG. 10, the shape of the cutout corners as shown in FIG. 10C is the size of the assumed foreign matter or the like. It will be set accordingly.
Furthermore, as a special circumstance in the wound battery, i) there is an end portion that is easily deformed by a stress from a foreign substance on the outermost periphery, and ii) an inner electrode that is in contact with the end portion via a separator, and an inner side thereof. There is no similar shape, and there is a strong tendency that the foil-like negative electrode plate or the like is simply torn by the pressing force from the foreign matter. Retraction is easily promoted even when a pressing force is applied in a state where the end shape of i) is adjacent to the shape of ii). Therefore, it is very effective to set the contour shape of the corner as described above to suppress digging.
Furthermore, by forming the contour shape of the corner as a straight line that intersects the straight line of the two sides forming the corner at an obtuse angle, a force to be pulled up from the surroundings when a pressing force due to a foreign object or the like is applied is secured. The degree of internal short circuit can be reduced.

Further, the second invention of the present application, in addition to the configuration of the first invention, the foil-like positive electrode plate and the foil-like negative electrode plate, respectively, an active material layer forming portion in which an active material layer is formed; An uncoated portion that does not form an active material layer, and the uncoated portion of the foil-shaped positive electrode plate and the uncoated portion of the foil-shaped negative electrode plate are at end portions on different sides. The foil-like positive electrode plate and the foil-like negative electrode plate are positioned so as to protrude in different directions, and the active material layer formation position in the thickness direction view is displaced, A corner portion of the active material layer forming portion that is disposed in a state where the corner portion of the active material layer forming portion and the other uncoated portion overlap in the thickness direction view and overlaps the uncoated portion in the thickness direction view. Is configured so as to be located on the inner side of a virtual contour obtained by extending and intersecting two straight lines forming the corners.
That is, a configuration in which an uncoated portion in which an active material layer is not formed is formed on a foil-like positive electrode plate and a foil-like negative electrode plate, and wiring is drawn out from the uncoated portion, for electric wiring for extracting electric power from the power generation element In many cases.
In such a case, as an occurrence mode of the internal short circuit due to the above-described foreign matter or the like, the active material layer of one of the positive and negative electrode plates may be in contact with the uncoated portion of the other electrode plate. Although it is possible, it is known that the Joule heat generated by such an internal short circuit increases.
Therefore, it is more effective to set the contour shape of the corner as described above to suppress the degree of internal short circuit.

According to the first invention, the degree of internal short circuit can be suppressed by appropriately setting the contour shape of the corner of the foil-shaped positive electrode plate or foil-shaped negative electrode plate, and is more effective for the internal short circuit of the power generation element. It became possible to cope with.
Furthermore, it is possible to reduce the degree of internal short-circuiting very effectively by suppressing the retraction caused by the pressing force from the foreign matter.
Furthermore, by forming the contour shape of the corner as a straight line that intersects the straight line of the two sides forming the corner at an obtuse angle, the degree of the internal short circuit can be reduced, and it is more effective for the internal short circuit of the power generation element. It became possible to cope with.
Moreover, according to the said 2nd invention, the degree of the internal short circuit by the contact with an active material layer and an uncoated part can be made small, and it can cope with an internal short circuit effectively .

1 is an external perspective view of a battery according to an embodiment of the present invention. The perspective view which shows the inside of the battery concerning embodiment of this invention. The front view which shows the inside of the battery concerning embodiment of this invention The figure which shows the foil-like negative electrode plate etc. concerning embodiment of this invention The perspective view which shows the winding process of the electric power generation element concerning embodiment of this invention The schematic diagram of the electric power generation element concerning embodiment of this invention The front view of the electric power generation element concerning embodiment of this invention The figure which shows the foil-shaped negative electrode plate concerning another embodiment of this invention, etc. The front view of the electric power generation element concerning another embodiment of this invention Schematic diagram for explaining the present invention

Hereinafter, embodiments of the secondary battery of the present invention will be described with reference to the drawings.
In the present embodiment, a nonaqueous electrolyte secondary battery (more specifically, a lithium ion battery) will be described as an example.

[Configuration of Nonaqueous Electrolyte Secondary Battery RB]
As shown in the perspective views of FIGS. 1 and 2 and the front view of FIG. 3, the nonaqueous electrolyte secondary battery RB of the present embodiment has a bottomed cylindrical shape (more specifically, a bottomed rectangular cylindrical shape). The can body 1 has a casing BC formed by covering the open surface of the can body 1 with a substantially flat lid portion 2 and welding it. The lid portion 2 is formed in a strip-like rectangle, and the casing BC has a flat rectangular parallelepiped shape as a whole. FIG. 2 illustrates the internal configuration of the casing BC by removing the can body 1 from the completed secondary battery RB (shown in FIG. 1). FIG. 3 shows the can body 1 and a power generation element 3 to be described later by a two-dot chain line in a form of seeing through the inside of the casing BC.

The power generation element 3 and the current collectors 4 and 6 shown in FIGS. 2 and 3 are housed and disposed in the housing BC in a state of being immersed in the electrolytic solution. Therefore, the casing BC is a container for storing the power generation element 3.
The power generation element 3 has a foil-like positive electrode plate and a foil-like negative electrode plate arranged with a separator in between, and will be described in detail later, but each of a pair of electrode plates composed of a foil-like positive electrode plate and a foil-like negative electrode plate. The active material is applied and wound around a separator.
In the power generation element 3, the active material uncoated portion of the foil-shaped positive electrode plate is laterally extended and welded to the current collector 4, and the active material uncoated portion of the foil-shaped negative electrode plate is disposed on the opposite side. It is extended and welded to the current collector 6.

The metal lid 2 includes a positive current collector 4 and a terminal bolt 5 which is a positive electrode terminal connected to the current collector 4, a negative current collector 6 and its current collector. A terminal bolt 7 which is a negative electrode terminal connected to 6 is attached, and the current collectors 4 and 6 electrically connect the power generation element 3 with the electrode terminals arranged on the outer side of the casing BC. Connected to.
The terminal bolt 5 is fixedly attached to the lid portion 2 by sandwiching a pair of packings 9 and 10 arranged with the lid portion 2 sandwiched between the head of the terminal bolt 5 and the current collector 4. This is done by caulking the rivet 5a formed on the head.
The negative electrode side has the same structure, and a pair of packings 11, 12 arranged with the lid 2 sandwiched between them are sandwiched between the head of the terminal bolt 7 and the current collector 6, and placed on the head of the terminal bolt 7. The terminal bolt 7 is fixed to the lid by caulking the formed rivet 7a (see FIG. 3).
The electrode structure on the negative electrode side including the terminal bolts 5 and 7 and the current collectors 4 and 6 and the electrode structure on the positive electrode side are in a symmetrical arrangement, and only the material of the metal member is different.
The metal member on the positive electrode side is made of aluminum, and the metal member on the negative electrode side is made of copper.

[Manufacturing process of secondary battery RB]
Next, the manufacturing process of the secondary battery RB will be schematically described.
First, assembly of the power generation element 3 will be described.
As schematically shown in FIG. 4, the power generation element 3 includes a foil-like positive electrode plate 22 in which an active material layer is formed by applying a positive electrode active material to both front and back surfaces of a long strip-like aluminum foil, and a copper foil The foil-like negative electrode plate 23 in which the active material layer for the negative electrode is applied to both the front and back surfaces and the active material layer is formed is manufactured by winding the separator around the winding core. The winding direction is such that the long side of the foil-like positive electrode plate or the like is wound around the core.
In FIG. 4, the width direction of the foil-like positive electrode plate 22 or the like is indicated by an arrow D, and the direction perpendicular to the arrow D (the vertical direction on the paper surface) is the longitudinal direction. The positional relationship between the foil-like positive electrode plate 22 and the foil-like negative electrode plate 23 in the width direction (arrow D direction) in FIG. 4 is displayed in accordance with the positional relationship when these are wound around the core. Further, the upper end portion in FIG. 4 indicates the start end side where winding starts on the winding core, and the lower end portion indicates the end of winding.
Each of the foil-like positive electrode plate 22 and the foil-like negative electrode plate 23 has uncoated portions 22a and 23a in which no active material layer is formed at the end in the width direction. The portions other than the uncoated portions 22a and 23a indicated by hatching in the negative electrode plate 23 are active material layer forming portions 22b and 23b in which an active material layer is formed.

As shown in FIG. 4, the uncoated part 22a of the foil-like positive electrode plate 22 and the uncoated part 23a of the foil-like negative electrode plate 23 are located at end portions on the different sides in the width direction. It protrudes from the other parts and members at the end, and has an arrangement posture that protrudes in different directions.
Further, as shown as “ΔW” in FIG. 4, the active material layer forming portion 23 b of the foil-like negative electrode plate 23 is longer in the width direction than the active material layer forming portion 22 b of the foil-like positive electrode plate 22. In a state where the two are wound and overlapped, the active material layer forming position in the thickness direction is displaced, and the active material layer forming part 23b on the negative electrode side protrudes from the active material layer forming part 22b on the positive electrode side It becomes.
Thus, the foil-like negative electrode plate 23 is set so that the active material layer formation area in the thickness direction is larger than that of the foil-like positive electrode plate 22, and the positive electrode-side active material layer forming portion 22b Since the edge is covered with the active material layer forming part 23b on the negative electrode side, Li deposition due to lack of acceptability of Li ions on the negative electrode side is prevented, and the positive electrode active material is effectively utilized. Yes.
Further, with respect to the foil-like negative electrode plate 23, the corner 23d of the active material layer forming portion 23b of the foil-like negative electrode plate 23 is convex outward at the lower end in FIG. It is cut out to form an arc shape, and the outline of the corner portion 23d extends by extending a straight line of two sides (the left side and the lower side of the active material layer forming portion 23b in FIG. 4) forming the corner portion. It is configured to be located inside the virtual contour (contour indicated by a two-dot chain line F forming a right angle).

[Pole winding process]
The winding process of the foil-like positive electrode plate 22, the foil-like negative electrode plate 23, and the separator 24 is performed as schematically shown in FIG.
In FIG. 5, the winding roller 26 is passed through the hollow portion of the winding core 21, and the foil-shaped positive electrode is interposed between the winding roller 26 and the pressure roller 27 that is pressure-bonded to the outer peripheral surface of the winding roller 26. A state in which the plate 22, the foil-like negative electrode plate 23 and the separator 24 are fed and wound is schematically shown. The winding around the core 21 is performed by superposing the foil-like negative electrode plate 23, the separator 24, the foil-like positive electrode plate 22 and the separator 24 in this order from the inner peripheral side. Of these, the two separators 24 have their longitudinal end portions (end portions on the winding start side) fixed to the outer periphery of the core 21 by tape fastening or heat welding.
At the winding start position shown in FIG. 5, the foil-like negative electrode plate 23 is wound so as to be sandwiched between the core 21 and the separator 24, and the foil-like positive electrode plate 22 is sandwiched between the two separators 24. start.
The positional relationship in the axial direction when winding the foil-like positive electrode plate 22 or the like around the winding core 21 is as shown in FIG. 4, and the width direction of the foil-like positive electrode plate 22 or the like is the winding axis direction.

[Pressing process]
After winding the foil-shaped positive electrode plate 22 and the like having a predetermined length as described above, the foil-shaped positive electrode plate 22 is removed from the winding roller 26 and further in the normal direction of the outer peripheral surface (direction perpendicular to the winding axis direction). The flat power generation element 3 is formed by pressing to form a flat shape.
FIG. 6 schematically shows a state in which the foil-like positive electrode plate 22 and the like are wound around the winding core 21 in a flat shape, as viewed from the winding axis direction.
As shown in FIG. 6, the length of the foil-like positive electrode plate 22 is such that, in the foil-like positive electrode plate 22 and the foil-like negative electrode plate 23, the foil-like negative electrode plate 23 is positioned on the outer peripheral side of the foil-like positive electrode plate 22. The separator 24 is set to a length that is located further to the outer peripheral side than the foil-like negative electrode plate 23.

FIG. 7 shows the power generation element 3 pressed as described above in a front view with the separator 24 removed.
In FIG. 7, the outermost foil-like negative electrode plate 23 appears, and the end position in the width direction of the active material layer forming portion 22b of the foil-like positive electrode plate 22 is indicated by a pair of left and right broken lines E. Yes.
As shown in FIG. 7, at the terminal portion 23 c of the foil-like negative electrode plate 23, the corner 23 d of the active material layer forming portion 23 b of the foil-like negative electrode plate 23 and the uncoated portion 22 a of the foil-like positive electrode plate 22 are thick. The positional relationship overlaps when viewed from the direction.
As described above, the contour of the corner 23d is a virtual contour obtained by extending and intersecting two straight lines (the left side and the lower side of the active material layer forming portion 23b in FIG. 4) forming the corner 23d. It is configured so as to be located on the inner side of the (contour that forms a right angle). By adopting such a contour shape, even if a pressing force such as a foreign substance acts on this portion, the foil-like negative electrode plate 23 is involved. Is suppressed as much as possible. Note that the effect of the present invention increases as the corner rounding dimension increases when the contour of the corner 23d is formed in an outwardly convex arc shape. It is done.

[Case assembly process]
Next, the assembly of the lid part 2 will be described.
The lid 2 sandwiches the current collectors 4, 6 and the terminal bolts 5, 7 between the packings 9, 10, 11, 12 on a metal plate material in which electrode mounting holes for attaching the terminal bolts 5, 7 are formed. In this state, the rivets 5a and 7a are caulked and fixed.
Next, the uncoated portions 22a and 23a of the power generation element 3 are welded and connected to the current collectors 4 and 6 fixed to the lid portion 2 as described above, so that the lid portion 2 and the power generation element 3 Is integrated.
As shown in FIG. 3, the current collectors 4 and 6 are formed in a substantially L shape as a whole, and the connection portions 4 a and 6 a with the power generation element 3 are in the state in which the parts BC and The power generation element 3 is bent so as to be substantially parallel to the flat surface of the power generation element 3.
After assembling the member on the lid 2 side and the power generation element 3 as described above, the power generation element 3 is further housed in the can 1 and the lid 2 and the can 1 are welded together.
Thereby, the assembly of the casing BC of the secondary battery RB is completed.
When the assembly of the case BC is completed, an electrolyte is then injected into the case BC from an injection port (not shown). When the injection of the electrolyte is completed, the initial charge of the secondary battery RB is performed under predetermined charging conditions. The secondary battery RB is completed by performing (preliminary charging) and further performing aging and the like.

[Another embodiment]
Hereinafter, other embodiments of the present invention will be listed.
(1) In the embodiment described above, the contour shape of the corner portion 23d of the active material layer forming portion 23b in the foil-like negative electrode plate 23 is an imaginary crossing by extending the straight lines on the two sides forming the corner portion. As a specific example for forming a shape located inside the contour, a case of forming a circular arc convex outward is illustrated, but the specific shape can be appropriately changed.
For example, as shown in FIG. 8, the outline of the corner portion 23d of the active material layer forming portion 23b in the foil-like negative electrode plate 23 is two sides (left side and lower side of the active material layer forming portion 23b) forming the corner portion 23d. It may be formed as a straight line G that intersects the straight line at an obtuse angle. FIG. 8 corresponds to FIG. 4 of the above-described embodiment, and corresponding portions are denoted by the same reference numerals.
In the example illustrated in FIG. 8, the case where the straight line G forms 135 degrees with the two sides is illustrated.
FIG. 9 shows the power generation element 3 created in the same process as the above embodiment using the foil-like positive electrode plate 22 shown in FIG. FIG. 9 corresponds to FIG. 7 in the above-described embodiment, and here, corresponding portions and the like are denoted by the same reference numerals.
In the case shown in FIG. 9 as well, in the end embodiment 23c of the foil-like negative electrode plate 23, the corner 23d of the active material layer forming portion 23b of the foil-like negative electrode plate 23 is the same as described in FIG. And the uncoated portion 22a of the foil-like positive electrode plate 22 are overlapped with each other when viewed in the thickness direction.
The contour of the corner 23d is cut out by the straight line G, and two straight lines (the left side and the lower side of the active material layer forming portion 23b in FIG. 4) forming the corner 23d are extended and intersected. It is configured to be located inside the virtual contour (contour that forms a right angle). By adopting such a contour shape, even if a pressing force such as foreign matter acts on this portion, the foil-shaped negative electrode The entrainment of the plate 23 is suppressed as much as possible. In addition, the effect of this invention becomes large as the corner drop dimension in this case becomes large, but the effect will be acquired reliably by setting it as 2 mm or more.

(2) In the above embodiment, the outline of the corner of the foil-like negative electrode plate 23 is formed in an outwardly convex arc shape, and the straight lines on the two sides forming the corner 23d are extended to intersect. Although the case where it comprises so that it may be located inside the made virtual outline is illustrated, you may form the outline of the corner | angular part of the foil-like positive electrode plate 22 in such a shape.
(3) In the above embodiment, the case where the power generating element 3 is configured by winding the foil-like positive electrode plate 22 and the foil-like negative electrode plate 23 with the separator interposed therebetween is exemplified. The present invention can also be applied to a case where the power generating element is configured in such a manner that a single foil-like positive electrode plate and a foil-like negative electrode plate are laminated with a separator interposed therebetween.

DESCRIPTION OF SYMBOLS 3 Electric power generation element 22 Foil-like positive electrode plate 23 Foil-like negative electrode plate 22a, 23a Uncoated part 22b, 23b Active material layer formation part 24 Separator

Claims (2)

A battery provided with a power generation element in which a foil-like positive electrode plate and a foil-like negative electrode plate are arranged with a separator interposed therebetween,
The power generating element is configured by winding the foil-like positive electrode plate and the foil-like negative electrode plate with the separator interposed therebetween,
The foil-shaped positive electrode plate or the foil-shaped negative electrode plate has a contour of a corner at the outermost periphery of the winding inside an imaginary contour obtained by extending and intersecting two straight lines forming the corner. configured to be positioned,
The battery in which the outline is formed as a straight line that intersects with a straight line of two sides forming the corner portion at an obtuse angle . The foil-like positive electrode plate and the foil-like negative electrode plate are each provided with an active material layer forming part in which an active material layer is formed, and an uncoated part in which an active material layer is not formed,
The uncoated portion of the foil-shaped positive electrode plate and the uncoated portion of the foil-shaped negative electrode plate are located at end portions on different sides and arranged in a state protruding in different directions,
In the foil-like positive electrode plate and the foil-like negative electrode plate, the formation position of the active material layer in the thickness direction is shifted, and the corner of one active material layer forming portion and the other uncoated portion Are arranged in a state of overlapping in the thickness direction view,
The outline of the corner portion of the active material layer forming portion overlapping the uncoated portion in the thickness direction is on the inner side of a virtual contour obtained by extending and intersecting two straight lines forming the corner portion. The battery according to claim 1, wherein the battery is configured to be positioned.

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