JP6900672B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage equipment comprising an electrode assembly having a layered structure in which insulated electrodes of different polarities, and an insulating sheet covering the electrode assembly.

Power storage devices such as secondary batteries and capacitors are widely used as power sources because they can be recharged and can be used repeatedly. As a secondary battery, there is a battery provided with a laminated electrode assembly in which a plurality of rectangular sheet-shaped positive electrodes and negative electrodes are laminated with a separator interposed therebetween. In addition, there is also one provided with a wound electrode assembly in which a band-shaped positive electrode and a band-shaped negative electrode are wound with a band-shaped separator in between.

The electrode assembly is generally covered with an insulating exterior and insulated from the outside and the case that houses the electrode assembly. For example, in the battery described in Patent Document 1, the electrode assembly (a part of the battery element) is covered with an exterior body composed of a pair of laminated sheets. One of the pair of laminated sheets is formed larger than the other laminated sheet. Then, the protruding portion of one laminated sheet from the region facing the other laminated sheet is folded back so as to hold the end portion of the other laminated sheet and the support member, and heat is applied to the folded portion. The folded laminated sheet and the support member are heat-welded.

Republished WO 2012/176711

In the laminated sheet heat-welded in this way, the portion directly heated by the heater or the like (heat-entry portion) is more likely to deteriorate than the other portions. When the laminated sheet is torn due to deterioration of the heat input portion, the torn portion may be exposed to the outside of the laminated sheet, that is, to the outside of the battery. Such a problem occurs not only in the electrode assembly housed in the laminated sheet but also in the electrode assembly covered with the insulating sheet.

The present invention has been made to solve the above problems, its object is to provide a power storage equipment which can prevent the torn heat input portion is exposed.

The power storage device for solving the above problems includes an electrode assembly having a layered structure in which electrodes having different polarities are insulated from each other, and an insulating sheet covering the electrode assembly, and the insulating sheet is the electrode assembly. The pair of surplus portions are a power storage device having a pair of surplus portions that protrude from the surface of the solid and face each other, and the pair of surplus portions are heat-welded welded portions, and one of the pair of surplus portions is heat. It has a heat input portion that has been heated at the time of welding, the heat input portion constitutes a part of the welded portion, and the other surplus portion has a cover portion that covers the heat input portion from the outside . It is a gist that the electrode assembly covered with the insulating sheet is housed in a metal case.

According to this, even if the heat input portion deteriorates and tears, the torn portion is covered by the cover portion of the surplus portion (the other surplus portion) existing outside the heat input portion. Therefore, it is possible to prevent the torn heat input portion from being exposed.

Further, since one of the pair of surplus portions has a heat input portion, the number of heaters used for heat welding can be reduced as compared with the case where both of the surplus portions have heat input portions. ..

According to this, the inner side surface of the case is located on the outer side of the cover portion. Therefore, the state in which the heat input portion is covered by the cover portion can be maintained by the contact between the cover portion and the inner surface of the case. Therefore, it is possible to further prevent the torn heat input portion from being exposed. As a result, even if the electrode assembly is exposed from the torn heat input portion, the cover portion suppresses the occurrence of a short circuit between the electrode assembly and the metal case.

Further, regarding the power storage device, it is preferable that the electrode assembly is a laminated electrode assembly, and the welded portion is located at the center of the electrode assembly in the stacking direction.
According to this, even if the cover portion covers the heat input portion, the cover portion is less likely to protrude outward from the end face in the stacking direction of the electrode assembly. Therefore, the increase in size of the power storage device is suppressed.

According to the present invention, it is possible to prevent the electrode assembly from being exposed.

An exploded perspective view of the secondary battery of the embodiment. The perspective view which shows the appearance of a secondary battery. An exploded perspective view showing the components of the electrode assembly. (A), (b) and (d) are schematic plan views for explaining a procedure for covering the electrode assembly with an insulating film, (c) is a partially enlarged view of (b), and (e) is one of (d). Enlarged view of the part. Schematic cross-sectional view of a secondary battery. The perspective view of the electrode assembly of another example.

Hereinafter, embodiments embodying the present invention will be described with reference to FIGS. 1 to 5.
As shown in FIGS. 1 and 2, the secondary battery 10 as a power storage device includes a case 11. The secondary battery 10 includes an electrode assembly 12 housed in a case 11. The case 11 has a rectangular parallelepiped main body member 13 and a rectangular flat plate-shaped lid member 14 that closes the opening 13a of the main body member 13. The main body member 13 and the lid member 14 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a square battery having a square appearance. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

The secondary battery 10 includes a positive electrode terminal 15 and a negative electrode terminal 16 for extracting electricity from the electrode assembly 12. The positive electrode terminal 15 and the negative electrode terminal 16 are exposed to the outside of the case 11 through a pair of holes 14a arranged side by side at a predetermined interval in the lid member 14. Further, a ring-shaped insulating ring 17a for insulating from the case 11 is attached to the positive electrode terminal 15 and the negative electrode terminal 16, respectively.

As shown in FIG. 3, the electrode assembly 12 includes a sheet-shaped positive electrode 20 and a sheet-shaped negative electrode 21 as electrodes having different polarities. The positive electrode electrode 20 has a positive electrode metal foil (aluminum foil in this embodiment) 22 and a positive electrode active material layer 23 formed by applying a positive electrode active material on both surfaces thereof. The negative electrode electrode 21 has a negative electrode metal foil (copper foil in this embodiment) 24 and a negative electrode active material layer 25 formed by applying a negative electrode active material on both surfaces thereof. The electrode assembly 12 is a laminated body having a layered structure in which a microporous film separator 26 is interposed between the positive electrode 20 and the negative electrode 21. As shown in FIG. 5, for example, the electrode assembly 12 is configured by alternately stacking a plurality of positive electrode electrodes 20 and a plurality of negative electrode electrodes 21. That is, the electrode assembly 12 has a plurality of sets composed of the positive electrode 20, the negative electrode 21, and the separator 26.

As shown in FIG. 3, the positive electrode electrode 20 includes a positive electrode current collecting tab 28 made of a positive electrode metal foil 22 at an edge (one end). The positive electrode current collecting tab 28 is formed at the same position and in the same shape on each positive electrode 20 constituting the electrode assembly 12. Further, the negative electrode electrode 21 is provided with a negative electrode current collecting tab 30 made of a negative electrode metal foil 24 at an edge (one end). The negative electrode current collecting tab 30 is formed at the same position and in the same shape on each negative electrode 21 constituting the electrode assembly 12.

The positive electrode electrodes 20 are laminated so that the positive electrode current collecting tabs 28 are arranged in a row along the stacking direction X of the electrode assembly 12. Similarly, the negative electrode electrodes 21 are laminated so that the negative electrode current collecting tabs 30 are arranged in a row along the stacking direction X of the electrode assembly 12 so that the negative electrode current collecting tabs 30 do not overlap with the positive electrode current collecting tabs 28. .. Then, as shown in FIG. 1, each positive electrode current collecting tab 28 is collected in a range from one end to the other end of the stacking direction X in the electrode assembly 12 to form a positive electrode current collecting group 31. The positive electrode terminal 15 is electrically joined to the positive electrode current collecting group 31. Similarly, as shown in FIG. 1, each negative electrode current collecting tab 30 is also collected in the range from one end to the other end of the stacking direction X in the electrode assembly 12 to form a negative electrode current collecting group 32. The negative electrode terminal 16 is electrically connected to the negative electrode current collecting group 32.

As shown in FIG. 1, the electrode assembly 12 of this embodiment is a rectangular parallelepiped having six faces. The six surfaces of the electrode assembly 12 are the surfaces 12a and 12b that are both sides of the electrode assembly 12 in the stacking direction X, and four side surfaces that are connected to the two surfaces and are orthogonal to the stacking direction X of the electrode assembly 12. It consists of 12c, 12d, 12e, and 12f. The side surface 12e is a current collecting side side surface on which the positive electrode current collecting tab 28 and the negative electrode current collecting tab 30 project. The positive electrode current collecting tab 28 and the negative electrode current collecting tab 30 project in the same direction from one side surface 12e. Further, the side surface 12f is a bottom side surface as an opposite surface facing the side surface 12e. Further, the side surfaces 12c and 12d are side surfaces orthogonal to the side surfaces 12e and 12f, respectively, and are surfaces facing each other in the width direction Y orthogonal to the stacking direction X of the electrode assembly 12.

As shown in FIGS. 1 and 5, the electrode assembly 12 is covered with an insulating film 33 as an insulating sheet. The insulating film 33 is an insulating sheet for insulating the electrode assembly 12 from the metal case 11, and is made of polypropylene (PP), for example. The insulating film 33 is formed in a bag shape by folding and welding one insulating film 33.

Here, the insulating film 33 before welding will be described.
As shown in FIG. 4A, the insulating film 33 includes a rectangular first region 33a larger than the surface 12a of the electrode assembly 12 and a rectangular second region 33b larger than the surface 12b of the electrode assembly 12. It has a rectangular third region 33c that is larger than the side surface 12f of the electrode assembly 12. The first region 33a is a portion that covers the entire surface 12a of the electrode assembly 12, the second region 33b is a portion that covers the entire surface 12b of the electrode assembly 12, and the third region 33c is the electrode assembly. It is a portion that covers the entire surface of the side surface 12f of the solid body 12.

The first region 33a includes a protruding portion 34 protruding from the surface 12a of the electrode assembly 12 on one side in the width direction Y, and a protruding portion 35 protruding from the surface 12a in the width direction Y on the other side. The second region 33b includes a protruding portion 36 protruding from the surface 12b of the electrode assembly 12 on one side in the width direction Y, and a protruding portion 37 protruding from the surface 12b in the width direction Y on the other side. The third region 33c includes a protruding portion 38 protruding from the side surface 12f of the electrode assembly 12 on one side in the width direction Y, and a protruding portion 39 protruding from the other side in the width direction Y. The protruding dimensions of the protruding portions 34 and 36 and the protruding dimensions of the protruding portions 35 and 37 from the surfaces 12a and 12b of the electrode assembly 12 are shorter than the dimensions of the electrode assembly 12 in the stacking direction X.

Next, the insulating film 33 that covers the electrode assembly 12 will be described.
As shown in FIGS. 1 and 5, the insulating film 33 has a covering portion 41 that covers the side surface 12c of the electrode assembly 12. The covering portion 41 is composed of a root portion 34a of the protruding portion 34 and a root portion 36a of the protruding portion 36. Further, the insulating film 33 has a polymerized portion 42 that protrudes from the covering portion 41. The polymerization portion 42 is composed of a surplus portion 34b which is a tip portion of the protruding portion 34 and a surplus portion 36b which is a tip portion of the protruding portion 36 facing the surplus portion 34b. The insulating film 33 has a welded portion 43 in which the surplus portion 34b of the protruding portion 34 and the surplus portion 36b of the protruding portion 36 are hot-welded. The welded portion 43 of the present embodiment is located at the center of the stacking direction X of the electrode assembly 12 and near the side surface 12c. The welded portion 43 is formed by applying heat to one of the surplus portions 36b. The insulating film 33 has a heat input portion 43a that has entered heat into the surplus portion 36b. The heat input portion 43a is composed of a part of the welding portion 43. Further, the insulating film 33 has a cover portion 34c that covers the heat input portion 43a from the outside. The cover portion 34c is composed of a pair of surplus portions 34b and 36b that are not welded portions 43 in the other surplus portion 34b.

The insulating film 33 has a covering portion 44 that covers the side surface 12d of the electrode assembly 12. The covering portion 44 is composed of a root portion 35a of the protruding portion 35 and a root portion 37a of the protruding portion 37. Further, the insulating film 33 has a polymerized portion 45 that protrudes from the covering portion 44. The polymerization portion 45 is composed of a surplus portion 35b which is a tip portion of the protruding portion 35 and a surplus portion 37b which is a tip portion of the protruding portion 37 facing the surplus portion 35b. The insulating film 33 has a welded portion 46 in which the surplus portion 35b of the protruding portion 35 and the surplus portion 37b of the protruding portion 37 are hot-welded. The welded portion 46 of the present embodiment is located at the center of the stacking direction X of the electrode assembly 12 and near the side surface 12d. The welded portion 46 is formed by applying heat to one of the surplus portions 37b. The insulating film 33 has a heat input portion 46a that has entered heat into the surplus portion 37b. The heat input portion 46a is composed of a part of the welding portion 46. Further, the insulating film 33 has a cover portion 35c that covers the heat input portion 46a from the outside. The cover portion 35c is composed of a pair of surplus portions 35b and 37b that are not welded portions 46 in the other surplus portion 35b.

In this way, the insulating film 33 covers five surfaces of the electrode assembly 12, excluding the side surface 12e. Then, the electrode assembly 12 covered with the insulating film 33 is inserted through the opening 13a of the main body member 13 and housed in the case 11.

Next, the procedure of covering the electrode assembly 12 with the insulating film 33 will be described in detail.
First, as shown in FIG. 4A, the electrode assembly 12 is arranged between the insulating films 33 bent in a U shape. At this time, the first region 33a of the insulating film 33 faces the surface 12a of the electrode assembly 12, the second region 33b of the insulating film 33 faces the surface 12b of the electrode assembly 12, and the third region of the insulating film 33 faces. 33c is opposed to the side surface 12f of the electrode assembly 12. Further, by arranging the electrode assembly 12 at the center of the insulating film 33 in the width direction Y, the protruding portions 34 to 39 of the first to third regions 33a to 33c are in a state of protruding from the electrode assembly 12.

Then, as shown in FIG. 4B, the protruding portions 34, 36, 38 protruding from the side surface 12c side of the electrode assembly 12 in the width direction Y are bent along the side surface 12c of the electrode assembly 12. At this time, the protruding portions 38 are bent first so that the protruding portions 38 are on the inside and the protruding portions 34 and 36 are on the outside, and then the protruding portions 34 and 36 are bent. As a result, the covering portion 41 is formed by the root portions 34a and 36a of the protruding portions 34 and 36 that cover the side surface 12c of the electrode assembly 12, and the surplus tip portions that do not cover the side surface 12c become the surplus portions 34b and 36b. .. Then, the surplus portions 34b and 36b are bent and stacked so as to be separated from the side surface 12c at the center of the stacking direction X, so that the surplus portion 34b and the surplus portion 36b become the overlapping portion 42.

Next, as shown in FIGS. 4 (b) and 4 (c), heat is input by pressing the heater 51 against the root portion of one of the surplus portions 36b of the pair of surplus portions 34b and 36b. The pair of surplus portions 34b and 36b are heat welded. As a result, the welding portion 43 is formed in the pair of surplus portions 34b and 36b, and the heat input portion 43a is formed in the portion where the heater 51 is pressed against the one surplus portion 36b.

Similarly, the protruding portions 35, 37, 39 protruding from the side surface 12d side of the electrode assembly 12 in the width direction Y are bent along the side surface 12d of the electrode assembly 12. At this time, the protruding portions 39 are bent first so that the protruding portions 39 are on the inside and the protruding portions 35 and 37 are on the outside, and then the protruding portions 35 and 37 are bent. As a result, the covering portion 44 is formed by the root portions 35a and 37a of the protruding portions 35 and 37 that cover the side surface 12d of the electrode assembly 12, and the surplus tip portions that do not cover the side surface 12d become the surplus portions 35b and 37b. .. Then, the surplus portions 35b and 37b are bent and stacked so as to be separated from the side surface 12d at the center of the stacking direction X, so that the surplus portion 35b and the surplus portion 37b become the overlapping portion 45.

Next, heat is input by pressing the heater 52 against the root portion of one of the surplus portions 37b of the pair of surplus portions 35b and 37b, and the pair of surplus portions 35b and 37b are heat-welded. As a result, the welding portion 46 is formed in the pair of surplus portions 35b and 37b, and the heat input portion 46a is formed in the portion where the heater 52 is pressed against the surplus portion 37b. By forming the welded portions 43 and 46 in this way, the insulating film 33 has a bottomed bag shape.

Then, as shown in FIGS. 4D and 4E, one of the surplus portions 36b is formed by bending the polymerization portion 42 (a pair of surplus portions 34b and 36b having a welding portion 43) in the direction of the arrow α. It faces the side surface 12c of the electrode assembly 12. Therefore, when the polymerization portion 42 is bent, a part of the other surplus portion 34b becomes a cover portion 34c that covers the heat input portion 43a from the outside. Similarly, by bending the polymerization portion 45 (a pair of surplus portions 35b, 37b having a welding portion 46) in the direction of arrow β, one surplus portion 37b is made to face the side surface 12d of the electrode assembly 12. Therefore, when the polymerization portion 45 is bent, a part of the other surplus portion 35b becomes a cover portion 35c that covers the heat input portion 46a from the outside.

Next, the operation of the secondary battery 10 of the present embodiment will be described.
Generally, in the heat-welded insulating film 33 as in the present embodiment, the heat input portions 43a and 46a to which the heaters 51, 52 and the like are directly applied and heat is input are different from other non-heat input portions. Although it is more likely to deteriorate in comparison, it is covered from the outside by the cover portions 34c and 35c of the surplus portions 34b and 35b.

Next, the effect of this embodiment will be described.
(1) Of the pair of surplus portions 34b and 36b, one surplus portion 36b has a heat input portion 43a, and the other surplus portion 34b has a cover portion 34c that covers the heat input portion 43a from the outside. .. Therefore, even if the heat input portion 43a deteriorates and tears, the torn portion is covered by the cover portion 34c existing on the outside of the heat input portion 43a. As a result, it is possible to prevent the torn heat input portion 43a from being exposed.

Similarly, of the pair of surplus portions 35b and 37b, one surplus portion 37b has a heat input portion 46a, and the other surplus portion 35b has a cover portion 35c that covers from the outside. Therefore, even if the heat input portion 46a deteriorates and tears, the torn portion is covered by the cover portion 35c existing on the outside of the heat input portion 46a. As a result, it is possible to prevent the torn heat input portion 46a from being exposed.

(2) Of the pair of surplus portions 34b and 36b, since only one surplus portion 36b has the heat input portion 43a, as compared with the case where both the surplus portion 34b and the surplus portion 36b have the heat input portion 43a, The number of heaters 51 used for heat welding can be reduced.

Similarly, of the pair of surplus portions 35b and 37b, since only one surplus portion 37b has the heat input portion 46a, as compared with the case where both the surplus portion 35b and the surplus portion 37b have the heat input portion 46a, The number of heaters 52 used for heat welding can be reduced.

(3) The electrode assembly 12 is housed in a metal case 11 in a state of being covered with an insulating film 33. That is, the inner side surface of the case 11 is located on the outer side of the cover portions 34c and 35c. Therefore, the contact between the cover portions 34c and 35c and the inner surface of the case 11 can maintain the state in which the cover portions 34c and 35c cover the heat input portions 43a and 46a. Therefore, it is possible to further prevent the torn heat input portions 43a and 46a from being exposed. As a result, even if the electrode assembly 12 is exposed from the torn heat input portions 43a and 46a, the cover portions 34c and 35c suppress the occurrence of a short circuit between the electrode assembly 12 and the metal case 11.

(4) Since the welding portions 43 and 46 are located at the center of the stacking direction X of the electrode assembly 12, even if the cover portions 34c and 35c cover the heat input portions 43a and 46a, the cover portions 34c and 35c are electrodes. It does not protrude outside the end face of the assembly 12 in the stacking direction X. Therefore, the increase in size of the secondary battery 10 is suppressed.

The above embodiment may be changed as follows.
◯ The electrode assembly 12 may be a winding type electrode assembly.
The positive electrode active material layer 23 of the positive electrode electrode 20 is formed on both sides of the positive electrode metal foil 22, but may be formed on only one side. The negative electrode active material layer 25 of the negative electrode electrode 21 is formed on both sides of the negative electrode metal foil 24, but may be formed on only one side.

○ The type of the insulating sheet is not limited to the insulating film 33, and may be a laminated sheet.
○ The dimensions of the protruding portions 34 to 37 of the first and second regions 33a and 33b may be changed within a range in which the welded portions 43 and 46 can be formed. However, from the viewpoint of suppressing the increase in size of the secondary battery 10, it is preferable that the dimensions do not protrude outside the end face of the electrode assembly 12 in the stacking direction X when the overlapping portions 42 and 45 are bent. ..

-In the above embodiment, the heat input portion 43a is used as the root portion of the surplus portion 36b, but it may be changed to the root portion of the surplus portion 34b. In this case, the polymerization portion 42 is bent so that the surplus portion 36b covers the surplus portion 34b from the outside.

Further, although the heat input portion 46a was used as the root portion of the surplus portion 37b, it may be changed to the root portion of the surplus portion 35b. In this case, the polymerization portion 45 is bent so that the surplus portion 37b covers the surplus portion 35b from the outside.

O The electrode assembly 12 may be covered with a plurality of insulating films 33.
○ Depending on the shape of the insulating film 33 and the like, the surfaces of the insulating film 33 on which the overlapping portions 42 and 45 are provided may be provided only on the side surfaces 12c or only the side surfaces 12d, or may be provided on the side surfaces 12e and 12f and the surfaces 12a and 12b. ..

○ The welded portions 43 and 46 may be located at positions deviated from the center of the stacking direction X of the electrode assembly 12.
○ In the above embodiment, the welded portion 43 is formed at the root portion of the pair of surplus portions 34b and 36b, and the welded portion 46 is formed at the root portion of the pair of surplus portions 35b and 37b. The range in which is formed may be changed as appropriate.

○ In the above embodiment, after the protruding portions 38 and 39 are bent along the side surfaces 12c and 12d of the electrode assembly 12, the protruding portions 34 to 37 are welded, but after the protruding portions 34 to 37 are welded. , The protruding portions 38, 39 may be bent. In this case, as shown in FIG. 6, when the overlapping portions 42 and 45 are bent, the welded protruding portions 38 and 39 are bent in the same direction as the bending direction of the overlapping portions 42 and 45. After that, in the protruding portions 38 and 39, the portions protruding from the side surfaces 12c and 12d of the electrode assembly 12 are bent along the side surfaces 12c and 12d.

○ The material of the insulating film 33 is not limited to polypropylene (PP), and other materials such as polyphenylene sulfide (PPS) may be used.
○ The method for forming the welded portions 43 and 46 may be ultrasonic welding instead of thermal welding by the heaters 51 and 52.

○ The power storage device can also be applied to a power storage device other than a secondary battery, such as a capacitor.
○ The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. In short, it suffices as long as the ions move between the active material for the positive electrode and the active material for the negative electrode and transfer charges.

Next, the technical idea that can be grasped from the above embodiment and another example will be added below.
(B) A power storage device characterized by being a secondary battery.

11 ... Case, 12 ... Electrode assembly, 12a, 12b ... Surface as surface, 12c, 12d, 12e, 12f ... Side surface as surface, 20 ... Positive electrode as electrode, 21 ... Negative electrode as electrode, 33 ... Insulating film as an insulating sheet, 34b, 35b, 36b, 37b ... surplus part, 34c, 35c ... cover part, 42,45 ... overlapping part, 43,46 ... welding part, 43a, 46a ... heat input part, X ... laminated direction.

Claims (2)

An electrode assembly having a layered structure in which electrodes of different polarities are insulated from each other,
An insulating sheet covering the electrode assembly is provided.
The insulating sheet has a pair of surplus portions that protrude from the surface of the electrode assembly and face each other, and the pair of surplus portions is a power storage device having a heat-welded welded portion.
One of the pair of surplus portions has a heat input portion that has been heated during heat welding, and the heat input portion constitutes a part of the welded portion.
The other surplus portion has a cover portion that covers the heat input portion from the outside .
A power storage device in which the electrode assembly covered with the insulating sheet is housed in a metal case. The electrode assembly is a laminated electrode assembly, and the electrode assembly is a laminated electrode assembly.
The power storage device according to claim 1, wherein the welded portion is located at the center of the electrode assembly in the stacking direction.

Images