JP2015159086A - power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of appropriately holding electrodes and a separator even when an electrode assembly expands in the lamination direction of the electrodes.SOLUTION: A secondary battery 10 comprises: an electrode assembly 14 in which electrodes are laminated via a separator; and tape 50 which holds the electrodes and the separator. The tape 50 is folded along the outer shape of the electrode assembly 14 and attached over a pair of edge faces 14a and 14b via one of lateral faces 14c to 14f. Here, at least part of a lateral-face attached portion 51 attached to one of the lateral faces 14c to 14f of the tape 50 has higher flexibility compared with that of an edge-face attached portion 52 attached to the pair of edge faces 14a and 14b.

Description

  The present invention relates to a power storage device.

  As an example of a power storage device, one having an electrode assembly in which electrodes are stacked via a separator and a tape attached to the electrode assembly and holding the electrode and the separator is known (for example, Patent Document 1). reference). For example, Patent Document 2 describes a battery elastic band or sheet that is used for fixing an electrode assembly and has rubber elasticity.

JP 2013-25999 A JP H11-297348

  Here, when the tape is affixed to the electrode assembly as in Patent Document 1, when the electrode assembly expands in the electrode stacking direction along with charge and discharge, the tape is applied to the electrode assembly. The local load increases, resulting in inconveniences such as dendrite precipitation. Further, if the tape is peeled off as the electrode assembly expands in the electrode stacking direction, a stacking deviation of the electrode and the separator may occur.

  An object of the present invention is made in view of the above-described circumstances, and provides a power storage device that can suitably hold an electrode and a separator even when the electrode assembly expands in the electrode stacking direction. is there.

  The power storage device that achieves the above object includes an electrode assembly in which electrodes are stacked via a separator, and a tape that holds the electrode and the separator, and the electrode assembly has a rectangular parallelepiped shape, A pair of end faces orthogonal to the electrode stacking direction; and a side surface orthogonal to the pair of end faces; the tape is bent along the outer shape of the electrode assembly; At least a part of the side facing portion that is present across the pair of three end surfaces and connects the end surface pasting portions that are pasted to the pair of end surfaces of the tape and that faces the side surfaces is the end surface pasting It has a higher stretchability than the portion.

  According to such a configuration, since at least a part of the side facing portion has higher elasticity than the end surface pasting portion, the side facing portion becomes in the electrode stacking direction as the electrode assembly expands in the electrode stacking direction. extend. Thereby, an increase in the load from the tape to the electrode assembly accompanying the expansion of the electrode assembly in the electrode stacking direction can be reduced. On the other hand, since the end surface pasting portion is relatively low stretchable, the end surface pasting portion is hardly peeled off even when the side facing portion extends in the electrode stacking direction. Therefore, various inconveniences associated with expansion of the electrode assembly in the electrode stacking direction, an increase in load on the electrode assembly, and tape peeling can be suppressed.

  About the said electrical storage apparatus, it is good for the whole said side surface opposing part to have a stretching property higher than the said end surface sticking part. According to this configuration, since the entire side facing portion has higher stretchability than the end surface pasting portion, the side facing portion more preferably follows the expansion of the electrode assembly in the electrode stacking direction. Can do. Thereby, the increase in the load to the electrode assembly accompanying the expansion | swelling of the electrode assembly in the lamination direction of an electrode can be reduced more suitably.

  In the power storage device, it is preferable that the end surface pasting portion is subjected to a curing process, while at least a part of the side surface facing portion is not subjected to the curing process. According to such a configuration, the level of stretchability is generated depending on the presence or absence of the curing treatment, so there is no need to make the materials different between the end face pasting portion and the side facing portion. Thereby, at least one part of a side surface opposing part can be made highly elastic rather than an end surface sticking part comparatively easily. In addition, with a hardening process, heat processing, UV irradiation processing, etc. can be considered, for example.

  In the power storage device, it is preferable that the side facing portion is less likely to extend in a direction along the side surface and orthogonal to the electrode stacking direction, as compared with the electrode stacking direction. According to such a configuration, inconvenience caused by the tape extending along the side surface of the electrode assembly and in the direction orthogonal to the stacking direction of the electrodes, for example, the end portions of the electrode and separator constituting the side surface of the electrode assembly are It is possible to suppress the occurrence of misalignment due to stretching.

  The power storage device may be a secondary battery.

  According to this invention, even when the electrode assembly expands in the electrode stacking direction, the electrode and the separator can be suitably held.

The perspective view which shows the external shape of a secondary battery. The exploded perspective view of an electrode assembly. The exploded perspective view of a secondary battery. FIG. 4 is a sectional view taken along line 4-4 of FIG. The graph which shows the relationship between the thickness of an electrode assembly, and the load provided to an electrode assembly. The perspective view which shows the electrode assembly with which the tape of another example was affixed. The perspective view which shows the electrode assembly with which the tape of another example was affixed.

  Hereinafter, an embodiment of a power storage device will be described with reference to FIGS. For the convenience of illustration, the cured region A1 is indicated by a dot hatch. In FIG. 4, the electrode assembly 14 is shown in a simplified manner.

  As shown in FIG. 1, a secondary battery 10 as a power storage device includes a rectangular parallelepiped case 11. The case 11 includes a bottomed box-shaped case main body 12 that opens upward, and a rectangular flat plate-shaped lid 13 that closes the opening of the case main body 12.

  The secondary battery 10 includes an electrode assembly 14 and an electrolytic solution 15 housed in a case 11, and a positive terminal 16 and a negative terminal 17 that exchange power with the electrode assembly 14. Each terminal 16, 17 is on the lid 13 of the case 11 and is arranged in a state of penetrating the lid 13. In addition, the secondary battery 10 of this embodiment is a lithium ion battery, for example.

  As shown in FIG. 2, the electrode assembly 14 has a structure in which positive electrodes 21 and negative electrodes 22 are alternately stacked via separators 23, which are porous films through which ions related to electrical conduction can pass. Each of the electrodes 21 and 22 and the separator 23 is a rectangular sheet.

  The positive electrode 21 includes a rectangular positive metal foil (for example, an aluminum foil) 21a and positive electrode active material layers 21b on both surfaces of the positive metal foil 21a. The negative electrode 22 includes a rectangular negative metal foil (for example, copper foil) 22a and negative electrode active material layers 22b on both surfaces of the negative metal foil 22a. In the state constituting the electrode assembly 14, the positive electrode active material layer 21 b is covered with the negative electrode active material layer 22 b, and the electrodes 21 and 22 are covered with the separator 23.

  As shown in FIG. 2, the positive electrode 21 has a positive electrode tab 31 having a shape protruding from the end 21c. Similarly, the negative electrode 22 has a negative electrode tab 32 having a shape protruding from the end 22c. The electrodes 21 and 22 are stacked so that the same polarities of the tabs 31 and 32 are arranged in a row. As shown in FIG. 3, the negative electrode tabs 32 are gathered together in one of the stacking directions Y of the electrodes 21, 22 and folded back to the other in the gathered state. Similarly, each positive electrode tab 31 is folded back to the other side in a state where the positive electrode tabs 31 are gathered toward one side in the stacking direction Y of the electrodes 21 and 22.

  As shown in FIG. 3, the electrode assembly 14 has a rectangular parallelepiped shape. Here, on the outer periphery of the electrode assembly 14, a pair of surfaces orthogonal to the stacking direction Y of the electrodes 21 and 22 are simply referred to as a pair of end surfaces 14a and 14b. Of the four side surfaces 14c to 14f orthogonal to the pair of end surfaces 14a and 14b on the outer periphery of the electrode assembly 14, the surface with the tabs 31 and 32 is referred to as the upper side surface 14c, and the side opposite to the upper side surface 14c. One surface is referred to as a lower surface 14d. Of the four side surfaces 14c to 14f, surfaces parallel to both the facing direction Z between the upper side surface 14c and the lower side surface 14d and the stacking direction Y of the electrodes 21 and 22 are referred to as a left side surface 14e and a right side surface 14f. Each of the side surfaces 14 c to 14 f is configured by the respective ends of the electrodes 21 and 22 and the separator 23. For example, the upper side surface 14c of the electrode assembly 14 includes an end 21c of the positive electrode 21, an end 22c of the negative electrode 22, and an end 23c of the separator 23 (see FIG. 2).

  A direction orthogonal to both the facing direction Z and the stacking direction Y of the electrodes 21 and 22 is referred to as a width direction X of the electrode assembly 14. The width direction X of the electrode assembly 14 is a direction along the upper side surface 14 c or the lower side surface 14 d and is a direction orthogonal to the stacking direction Y of the electrodes 21 and 22. The facing direction Z is a direction along the left side surface 14 e or the right side surface 14 f and is a direction orthogonal to the stacking direction Y of the electrodes 21 and 22.

  As shown in FIG. 3, the secondary battery 10 includes a positive electrode conductive member 41 and a negative electrode conductive member 42 that electrically connect the same polarities of the tabs 31 and 32 and the terminals 16 and 17. Each of the conductive members 41 and 42 has a plate shape and is disposed between the lid 13 of the case 11 and the electrode assembly 14. The positive electrode conductive member 41 is bonded to both the positive electrode tab 31 and the positive electrode terminal 16. Similarly, the negative electrode conductive member 42 is bonded to both the negative electrode tab 32 and the negative electrode terminal 17. As a joining mode, for example, welding is conceivable.

  As shown in FIGS. 3 and 4, the secondary battery 10 includes an insulating sheet 43 that insulates the electrode assembly 14 from the case 11. The insulating sheet 43 has, for example, a box shape opened upward by bending a single rectangular resin sheet. The electrode assembly 14 is accommodated in a box-shaped insulating sheet 43.

  The secondary battery 10 includes a plurality of tapes 50 that hold the positive electrode 21, the negative electrode 22, and the separator 23. Each of the plurality of tapes 50 is bent along the outer shape of the electrode assembly 14 and exists across the pair of end surfaces 14a and 14b of the electrode assembly 14 via any one of the side surfaces 14c to 14f. .

  Details of the tape 50 will be described in detail with reference to FIGS. The plurality of tapes 50 have basically the same configuration except that the points where the tapes are affixed are different, so that only the ones that are affixed to the left side surface 14e among the plurality of tapes 50. This will be described in detail. Further, in FIG. 3, the tape 50 attached to the region indicated by the two-dot chain line of the electrode assembly 14 is shown in an exploded manner.

  As shown in FIGS. 3 and 4, the entire side surface sticking portion 51 attached to the left side surface 14 e of the tape 50 is more than the end surface attaching portion 52 attached to the pair of end surfaces 14 a and 14 b of the tape 50. Also has high elasticity. The side sticking part 51 has an elongation rate of 5% or more, for example. In addition, with respect to the elongation, for example, a numerical value obtained by a measurement based on JIS K6251 or JIS K7127 can be considered.

  The side sticking part 51 has connected the end surface sticking parts 52 currently affixed on a pair of end surface 14a, 14b. And the side sticking part 51 has opposed the left side surface 14e. The side sticking part 51 corresponds to a side facing part.

  The end surface pasting portion 52 of the tape 50 is a cured region A1 that has been subjected to a curing process, and the side surface pasting portion 51 is an uncured region A2 that has not been subjected to a curing process. Specifically, the tape 50 includes a base material and an adhesive layer on the surface of the base material, and the base material is a thermosetting resin, a UV curable resin, or the like that is cured by a curing process such as a heat treatment or a UV irradiation process. It consists of The base material of the end surface pasting portion 52 is subjected to a curing process, while the base material of the side surface pasting portion 51 is not subjected to a curing process.

  Incidentally, although the specific manufacturing process of the secondary battery 10 of the present embodiment is arbitrary, for example, the electrodes 21 and 22 are alternately stacked via the separator 23 to form the electrode assembly 14, and the electrodes A tape 50 that is not subjected to the curing process is attached to the assembly 14. And it is good to perform hardening processing, such as a heat processing and UV irradiation processing, only with respect to the end surface sticking part 52 among the tapes 50 stuck.

  In addition, instead of the configuration in which the local curing process is performed, the entire tape 50 is subjected to a heating process or a UV irradiation process in a state where a masking process such as a masking tape is applied to the side-applied portion 51, for example. May be.

  Next, the effect | action of this embodiment is demonstrated using FIG. 5 shows the thickness D of the electrode assembly 14 (see FIG. 4), which is the length of the electrode assembly 14 in the stacking direction Y of the electrodes 21 and 22, and the electrode assembly 14 from the stacking direction Y of the electrodes 21 and 22. It is a graph which shows the relationship with the load provided to. The straight line in FIG. 5 shows a change in the load of the electrode assembly 14 when the tape 50 of the present embodiment is affixed. The two-dot chain line in FIG. The change of the load of the electrode assembly 14 when an adhesive tape is affixed is shown.

  As shown in FIG. 5, the change in the load applied to the electrode assembly 14 with respect to the increase in the thickness D of the electrode assembly 14 varies depending on the stretchability of the side-applied portion 51. Specifically, under the condition that the thickness D of the electrode assembly 14 is increased by δD from the initial value D0, the increase amount F1 of the load applied to the electrode assembly 14 when the tape 50 of this embodiment is used is The increase amount F0 of the load applied to the electrode assembly 14 when the tape of the comparative example is used is smaller.

According to the embodiment described above in detail, the following effects are obtained.
(1) The secondary battery 10 includes a tape 50 that is bent along the outer shape of the electrode assembly 14 and is bonded across the pair of end surfaces 14a and 14b via any one of the side surfaces 14c to 14f. ing. The side surface sticking portion 51 attached to any one of the side surfaces 14c to 14f of the tape 50 has higher stretchability than the end surface attaching portions 52 attached to the pair of end surfaces 14a and 14b. As a result, as the electrode assembly 14 expands in the stacking direction Y of the electrodes 21, 22, the side-applied portion 51 extends, so that the electrode assembly 14 is given against the increase in the thickness D of the electrode assembly 14. The increase in load can be reduced.

  Here, for example, in the case where the end surface pasting portion 52 is highly stretchable, when the side surface pasting portion 51 extends in the stacking direction Y of the electrodes 21 and 22, the end surface pasting portion 52 is pulled and tends to stretch. Then, a force works at the boundary between the end face pasting portion 52 and the end faces 14a and 14b, and the end face pasting portion 52 may be peeled off.

  On the other hand, since the end surface pasting portion 52 of the tape 50 of the present embodiment is low stretchable, the side pasting portion 51 is pulled due to extending in the stacking direction Y of the electrodes 21 and 22. Even if there is, it is hard to come off. Thereby, it can suppress that the tape 50 peels, reducing the increase in the load provided to the electrode assembly 14 with respect to the increase in the thickness D of the electrode assembly 14. FIG. Therefore, the electrodes 21 and 22 and the separator 23 can be suitably held.

  (2) In particular, since the entire side-applied portion 51 has high stretchability, the tape 50 can follow the increase in the thickness D of the electrode assembly 14 more suitably. Thereby, the increase in the load to the electrode assembly 14 accompanying the increase in the thickness D of the electrode assembly 14 can be reduced more suitably.

  (3) While the end surface pasting portion 52 is subjected to a curing process, the side surface pasting portion 51 is not subjected to a curing process. Thereby, the elasticity of both can be made different, without making the material of the tape 50 differ by the end surface sticking part 52 and the side surface sticking part 51. FIG. In particular, when a tape obtained by joining materials having different stretchability is stretched, there is a problem that a shearing force is applied to the joining surface and the tape is torn. On the other hand, according to the present embodiment, the above-described inconvenience can be avoided because the above-described joining surface does not occur.

In addition, you may change the said embodiment as follows.
○ In the embodiment, the entire side-applied portion 51 has high stretchability, but is not limited to this, and a configuration in which a part of the side-applied portion 51 has higher stretchability than the end-face attached portion 52 is provided. It may be. In short, it is only necessary that at least a part of the side-applied portion 51 has high elasticity.

  ○ A tape that is softened by a softening process may be used. In this case, it is preferable that at least a part of the side surface pasting portion 51 is softened, while the end surface pasting portion 52 is not softened. Even in this case, the effects of the above-described embodiment are achieved. The softening treatment is, for example, heat treatment or UV irradiation treatment.

  As shown in FIG. 6, the side sticking portion 51 includes a plurality of hardened regions A1 that are hardened and extend in the opposite direction Z in the stacking direction Y of the electrodes 21 and 22. Also good. In this case, the uncured region A2 is a region other than the cured region A1 in the side surface pasting portion 51. Thereby, the side sticking part 51 is hard to extend in the facing direction Z as compared with the stacking direction Y of the electrodes 21 and 22. Therefore, inconvenience caused by the side sticking portion 51 extending in the facing direction Z, for example, the ends of the electrodes 21 and 22 and the separator 23 constituting the left side surface 14e of the electrode assembly 14 are in the facing direction Z of the side sticking portion 51. It can be suppressed that the electrodes 21 and 22 and the separator 23 are misaligned due to being stretched by the extension. The same applies to the tape 50 attached to the other side surfaces 14c, 14d, 14f.

  In addition, in the said other example, although it was the structure which anisotropy produced in the elasticity of the tape 50 by the hardening area | region A1 extended in the opposing direction Z, it is not restricted to this, Anisotropy in elasticity You may use the tape comprised with the material which has this. When a tape that is softened by the softening process is used, it is preferable that a plurality of softened areas that extend in the stacking direction Y of the electrodes 21 and 22 exist side by side in the facing direction Z.

  A specific configuration for making the stretchability different between the side surface pasting portion 51 and the end surface pasting portion 52 is arbitrary. For example, a tape made of a material that softens or hardens when impregnated in the electrolytic solution 15 and a masking tape that masks a part of the tape may be used. In this case, when a tape made of a softening material is used, a masking tape may be attached to the end face attaching portion 52. On the other hand, when using a tape made of a material that hardens, a masking tape is preferably affixed to the side surface affixing portion 51.

  As shown in FIG. 7, a plurality of slits 60 may exist over the entire side surface pasting portion 51. In this case, even if the entire tape 50 is in the uncured region A2, the side-applied portion 51 has higher stretchability than the end-surface applied portion 52. The number of slits 60 is arbitrary and may be one. Moreover, the slit 60 may exist in the one part area | region of the side sticking part 51. FIG. In short, it is preferable that one or a plurality of slits 60 exist in at least a part of the side-applied portion 51.

(Circle) the end surface sticking part 52 may be comprised with the low elastic material, and the side sticking part 51 may be comprised with the high elastic material.
A tape may be separately attached to the end surface attaching portion 52. Even in this case, the end face pasting portion 52 is less stretchable than the side face pasting portion 51. In addition, the tape affixed separately to the end surface sticking part 52 is good in a comparatively low-stretch thing.

  The electrode assembly may be a wound type in which electrodes are stacked by winding a long positive electrode and a negative electrode through a long separator. In this case, the electrode assembly includes a pair of flat surfaces orthogonal to the electrode stacking direction, and an upper side surface and a lower side surface orthogonal to the winding axis direction. In this case, the tape 50 is good to be affixed across a pair of flat surfaces via the upper side surface or the lower side surface. And it is good for at least one part of the side surface sticking part affixed on the upper surface or the lower surface in a tape to have a higher elasticity than the part affixed on the flat surface.

  In embodiment, although the side surface sticking part 51 was affixed on either of each side surface 14c-14f of the electrode assembly 14, it is not restricted to this, It does not need to be affixed. For example, the portion of the tape 50 facing the pair of end surfaces 14a and 14b may have an adhesive layer, while the portion facing each of the side surfaces 14c to 14f may have no adhesive layer. The point is that the tape is connected to the pair of end surfaces 14a and 14b of the electrode assembly 14 and the side surface portions 52c are connected to each other and face each of the side surfaces 14c to 14f. What is necessary is just to have an opposing part.

The number of tapes 50 attached to the electrode assembly 14 is arbitrary, and may be one. The position of the tape 50 attached to the electrode assembly 14 is arbitrary.
The secondary battery 10 may be mounted on a vehicle and used for traveling, or may be used as a stationary power source.

  The secondary battery 10 is a lithium ion battery, but is not limited thereto, and may be another secondary battery. In short, any ion may be used as long as ions move between the positive electrode active material layer 21b and the negative electrode active material layer 22b and transfer charges. Further, an electric double layer capacitor may be used as the power storage device.

Next, a preferable example that can be grasped from the embodiment and another example will be described below.
(A) While at least a part of the side facing portion is softened, the end surface affixed portion may not be softened.

(B) A tape may be separately attached to the end face facing portion.
(C) One or a plurality of slits may exist in at least a part of the side facing portion.

  (D) In the side facing portion, a plurality of hardened regions extending in the direction perpendicular to the electrode stacking direction along the side surfaces of the electrode assembly, which are subjected to the hardening process, are arranged in the electrode stacking direction. May be present.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 14 ... Electrode assembly, 14a, 14b ... A pair of end surface of electrode assembly, 14c-14f ... Side surface, 21, 22 ... Electrode, 23 ... Separator, 50 ... Tape, 51 ... Side sticking part (side facing part), 52...

Claims (5)

An electrode assembly in which electrodes are stacked via a separator;
A tape holding the electrode and the separator;
With
The electrode assembly has a rectangular parallelepiped shape, and has a pair of end surfaces orthogonal to the electrode stacking direction, and a side surface orthogonal to the pair of end surfaces,
The tape is bent along the outer shape of the electrode assembly and exists across the pair of end surfaces of the electrode assembly via the side surface,
At least a part of the side surface facing portion that connects the end surface pasting portions pasted to the pair of end surfaces of the tape and faces the side surface has higher elasticity than the end surface pasting portion. Power storage device.   The power storage device according to claim 1, wherein the entire side facing portion has higher elasticity than the end surface pasting portion.   The power storage device according to claim 1, wherein the end surface pasted portion is subjected to a curing process, and at least a part of the side surface facing portion is not subjected to the curing process.   The power storage device according to any one of claims 1 to 3, wherein the side-facing portion is less likely to extend along the side surface and in a direction perpendicular to the stacking direction of the electrodes as compared to the stacking direction of the electrodes.   The power storage device according to claim 1, wherein the power storage device is a secondary battery.