JP2018147743A - Electrode and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that although safety is desired strongly for nonaqueous electrolyte secondary battery, internal electrode may be cracked when an impact is applied to the nonaqueous electrolyte secondary battery or an electrode, i.e., its one component, and to provide an electrode having tolerance to impact, and a nonaqueous electrolyte secondary battery.SOLUTION: An electrode includes a positive electrode, a negative electrode, and multiple separators, the positive electrode and the negative electrode are wound via the multiple separators, and the separator located on the outermost side in the winding lamination direction is in contact with the above-mentioned separator in the inside direction of the winding lamination direction.SELECTED DRAWING: Figure 5

Description

  Embodiments described herein relate generally to an electrode and a nonaqueous electrolyte secondary battery.

High-energy non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) have attracted attention as large-scale and large-capacity power sources used for electric vehicles (EV), hybrid vehicles (HEV), electric motorcycles, forklifts, etc. Development is being carried out to increase the size and capacity while taking into consideration the long life and safety. As a large-capacity power supply, an assembled battery containing a large number of batteries connected in series or in parallel has been developed to increase driving power.

JP 2013-16523 A

In general, safety is strongly desired for nonaqueous electrolyte secondary batteries. However, for example, when an impact is applied to a nonaqueous electrolyte secondary battery or an electrode that is one of its components, the internal electrode may be cracked. Therefore, the problem to be solved by the present invention is to provide an electrode and a non-aqueous electrolyte secondary battery that are resistant to impact.

In order to solve the above problem, an electrode of the present embodiment includes a positive electrode, a negative electrode, and a plurality of separators, and the positive electrode and the negative electrode are wound through the plurality of separators, The separator located on the outermost side in the stacking direction is in contact with the separator in the inner direction in the wound stacking direction.

The perspective view of the nonaqueous electrolyte secondary battery which concerns on embodiment. The disassembled perspective view of the nonaqueous electrolyte secondary battery which concerns on embodiment. The expansion | deployment perspective view of the winding electrode group used for the nonaqueous electrolyte secondary battery which concerns on embodiment. Schematic of the laminated structure of the electrode group used for the secondary battery which concerns on embodiment. Sectional drawing of the winding electrode group used for the nonaqueous electrolyte secondary battery which concerns on embodiment. Sectional drawing which looked at the cross section which follows the cross-sectional line of FIG. 2 from the arrow direction. Sectional drawing of the winding electrode group used for the nonaqueous electrolyte secondary battery which concerns on embodiment.

    Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a perspective view of a nonaqueous electrolyte secondary battery according to an embodiment.

As an example of the non-aqueous electrolyte secondary battery, FIGS. 1 and 2 show a non-aqueous electrolyte secondary battery 20. The nonaqueous electrolyte secondary battery 20 includes an outer can 1, a flat wound electrode group 2, a positive electrode lead 3, a negative electrode lead 4, an insulator 40, a positive electrode terminal 6, and a negative electrode terminal 7.

The outer can 1 is made of, for example, a metal such as aluminum, an aluminum alloy, iron, or stainless steel. The wound electrode group 2 is inserted from the first surface 61 of the outer can 1, and the outer can 1
It is housed so as to be directed in a direction perpendicular to the winding axis.

The wound electrode group 2 has a positive electrode current collecting tab 8a at one end and a negative electrode current collecting tab 9a at the other end.
FIG. 3 is a development view of the wound electrode group 2, and FIG. 4 shows a laminated structure of the wound electrode group 2. The positive electrode 8 includes a strip-shaped positive electrode current collector 8c made of, for example, a metal foil, and a positive electrode active material layer 8b formed on one or both surfaces thereof. The positive electrode active material layer 8b is formed such that a region having a constant width (non-coated portion) remains on one end side along the longitudinal direction of the strip-shaped positive electrode current collector 8c. This non-coated part is a positive electrode current collector 8c.
Is the exposed portion, and becomes the positive electrode current collecting tab 8a. Similarly, the negative electrode 9 includes a strip-shaped negative electrode current collector 9c made of, for example, a metal foil, and a negative electrode active material layer 9b formed on one surface or both surfaces thereof. The negative electrode active material layer 9b is formed in the strip-shaped negative electrode current collector 9c so that a region having a constant width (uncoated portion) remains on the other end side (the opposite side to one end of the positive electrode 8) along the longitudinal direction. . This uncoated portion is a portion where the negative electrode current collector 9c is exposed, and becomes a negative electrode current collecting tab 9a.

The positive electrode 8 and the negative electrode 9 are alternately stacked with the strip-shaped separators 10a and 10b. At this time,
The positive electrode current collecting tab 8a is formed on one end side in the winding axis direction, and the negative electrode current collecting tab 9a is formed on the other end side. The separator 10 a stacked under the positive electrode 8 has one end along the longitudinal direction thereof at the positive electrode 8.
It arrange | positions so that it may be located inside the edge part by the side of the positive electrode current collection tab. Thereby, the positive electrode current collection tab 8a protrudes from the positive electrode active material layer 8b, the negative electrode active material layer 9b, and the separator 10a which comprise the winding electrode group 2. FIG. In addition, the separator 10 a is arranged so that the other end along the longitudinal direction is located outside the other end of the positive electrode 8. The separator 10b sandwiched between the positive electrode 8 and the negative electrode 9 is disposed so that one end along the longitudinal direction is located inside the end portion of the negative electrode 9 on the negative electrode current collecting tab side. Thereby, the negative electrode current collection tab 9a protrudes from the positive electrode active material layer 8b, the negative electrode active material layer 9b, and the separator 10b which comprise the winding electrode group 2. FIG. In addition, separator 1
0b is arranged so that the other end along the longitudinal direction is located outside the other end of the negative electrode 9.

Winding the stacked separator 10a, positive electrode 8, separator 10b, negative electrode 9, and then
The flat wound electrode group 2 is formed by pressing.

The wound wound electrode group 2 is fastened with an insulating tape. The insulating tape covers an area other than the current collecting tab on the outermost periphery of the wound electrode group 2, and makes the area insulative. The number of turns of the insulating tape 30 may be one or more.

Next, the wound electrode group 2 which is a main characteristic part of this embodiment will be described in detail with reference to FIG. FIG. 5 is a cross-sectional view of the wound electrode group 2 used in the nonaqueous electrolyte secondary battery according to the embodiment.

As described above, the positive electrode 8, the separator 10a, the separator 10b, and the negative electrode 9 are wound,
The flat wound electrode group 2 is formed by pressing. Of the separator 10a and the separator 10b, the separator located on the outermost side in the wound stacking direction is the separator in the inner direction of the wound stacking direction. In contact with.

For example, in the wound electrode group 2 shown in FIG. 5, the separator 10b positioned on the outermost side in the wound stacking direction is in contact with the separator 10a in the inner side of the wound stacking direction and positioned on the outermost side in the wound stacking direction. The separator 10a is separated from the inner side of the wound lamination direction by the separator 10b.
In contact with.

Thus, by making the separator located at the outermost side in the winding stacking direction double, the separator plays a role like a cushion, and inside the double separator located at the outermost side in the winding stacking direction. The impact from the outside with respect to the positive electrode 8 or the negative electrode 9 provided can be relieved, and the crack of the positive electrode 8 or the negative electrode 9 can be prevented.

Further, when the electrode uses an aluminum foil, cracking is more likely to occur than when a copper foil is used. Therefore, when an aluminum foil is used for the electrode, it becomes a more effective impact mitigation method.

  Then, the secondary battery provided with the winding electrode group is demonstrated.

In the outer can 1, the first surface 61 on which the terminals are arranged is hermetically fixed to the third surface 63, the fourth surface 64, the fifth surface 65, and the sixth surface 66 by, for example, welding. Has been. The positive electrode terminal 6 and the negative electrode terminal 7 are caulked and fixed to the first surface 61 via insulating gaskets 14 and 15, respectively. The positive electrode terminal 6 and the negative electrode terminal 7 protrude from the back surface of the first surface 61 toward the inside of the outer can 1. The positive electrode terminal 6 and the negative electrode terminal 7 may be fixed by a hermetic seal using glass in addition to caulking and fixing (not shown) with the insulating gaskets 14 and 15. The first surface 61 includes an inlet 28 for injecting an electrolytic solution and a gas discharge valve 29 for discharging gas generated in the secondary battery.

  An insulator 41 is provided on the inner side of the outer can 1 with respect to the first surface 61.

The positive lead 3 includes a connection plate 3a electrically connected to the positive terminal 6, a through hole 3b opened in the connection plate 3a, and a bifurcated branch from the connection plate 3a. First and second clamping strips 3c, which are clamping parts extending in a direction perpendicular to
3d. The connection plate 3a is in contact with the back surface of the first surface 61 at the position of the positive electrode terminal 6 via the insulator 40, and the positive electrode terminal 6 protruding from the back surface of the first surface 61 caulks and fixes the through hole 3b. .

The first and second sandwiching strips 3c and 3d of the positive electrode lead 3 sandwich the positive current collecting tab 8a from the direction perpendicular to the winding axis, and the first and second sandwiching strips 3c and 3d and the positive current collecting tab 8a
Are joined by welding, for example.

Similarly, the negative electrode lead 4 has a connection plate 4a which is a connection part connected to the negative electrode terminal 7,
A through-hole 4b opened in the connection plate 4a, and a first and a second that are bifurcated from the connection plate 4a and that extend to the wound electrode group 2 in a direction perpendicular to the winding axis. Sandwiching strips 4c and 4d. The connection plate 4a is in contact with the back surface of the first surface 61 at the location of the negative electrode terminal 7 via the insulator 40, and through the through hole 4 to the negative electrode terminal 7 protruding from the back surface.
Secure b.

The first and second sandwiching strips 4c and 4d of the negative electrode lead 4 sandwich the negative current collecting tab 9a from the direction perpendicular to the winding axis, and the first and second sandwiching strips 4c and 4d and the negative current collecting tab 9a
Are joined by welding, for example.

  In addition, said welding may be implemented by methods, such as resistance welding and ultrasonic welding.

In the positive and negative electrode leads having the above structure, the first and second sandwiching strips can be evenly arranged with respect to the current collecting tab. In addition, since there are two (first and second) sandwich strips, the current collection distance is shortened. Thereby, current collection balance can be made favorable and current collection efficiency can be improved. Furthermore, since the lead having the first and second sandwiching strips does not concentrate heat at the junction between the current collecting tab and the first and second sandwiching strips and itself, a large current is passed. Even in this case, it is possible to maintain good electrical characteristics.

The positive and negative current collecting tabs and the positive and negative electrode leads may be joined in a state where the current collecting tabs are partially fixed by a fixing member as shown in FIG. That is, the positive electrode current collecting tab 8 a is fixed by the fixing member 11, and the negative electrode current collecting tab 9 a is also fixed by the fixing member 12.

The positive and negative electrode fixing members are arranged symmetrically when fixing the positive and negative current collecting tabs, but have the same shape. Therefore, the fixing member 12 for fixing the negative electrode current collecting tab 9a is taken as an example in FIG.
Will be described in detail. Since the negative electrode current collecting tab 9a is wound, the negative electrode current collecting tab 9a is formed of a hollow oblong bundle in which a plurality of current collecting tabs are overlapped. The fixing member 12 has U-shaped first and second holding portions 12a and 12b which are respectively fitted and bundled at two locations facing the short axis direction of the hollow ellipse near the center of the negative electrode current collecting tab 9a. And a flat connecting portion 12c that connects the first and second holding portions 12a and 2b inside the ellipse formed by the negative electrode current collecting tab 9a. Negative electrode current collecting tab 9a
Are joined to the first and second holding portions 12a and 12b by welding, for example.

The negative current collecting tab 9a to which the fixing member 12 is attached is sandwiched between the first and second holding strips 4c and 4d of the negative electrode lead 4. As a result, as shown in FIG. 6, the first clamping strip 4c
And the outer surface of the first holding portion 12a come into contact with each other, and the second holding strip 4d and the second holding portion 12
The outer surface of b contacts. At these contact points, the first and second clamping strips 4c,
4d and the 1st, 2nd holding | maintenance part 12a, 12b are joined by welding, for example.

  In addition, said welding may be implemented by methods, such as resistance welding and ultrasonic welding.

The fixing member 12 is formed from a conductive material such as metal. For this reason, the negative electrode 9 of the wound electrode group 2 is electrically connected to the negative electrode lead 4 through the fixing member 12 and further electrically connected to the negative electrode terminal 7 of the first surface 61 through the negative electrode lead 4.

By using such a fixing member, the thickness of the current collecting tab portion of the wound electrode group 2 can be reduced, and a space for arranging the leads in the outer can can be secured. Since it is not necessary to newly provide a space for leads, the energy density of the battery 20 can be improved.

Note that the fixing member may have a shape having only an independent U-shaped first holding part and / or second holding part and no connecting part. The first holding part and the second holding part may be independently fixed to the negative electrode current collecting tab 9a.

The structure of the fixing member 11 and the fixing form of the positive electrode current collecting tab 8a by the fixing member 11 are the same as those of the fixing member 12 and the negative electrode current collecting tab 9a described above. The fixing member 11 has U-shaped holding portions 11a and 11b and a flat connecting portion 11c.

According to the embodiment as described above, the wound electrode group 2 constituting the nonaqueous electrolyte secondary battery 20 is:
By making the separator located on the outermost side in the winding lamination direction double, the separator serves as a cushion, and is provided inside the double separator located on the outermost side in the winding lamination direction. Alternatively, the impact from the outside on the negative electrode 9 can be reduced, and cracking of the positive electrode 8 or the negative electrode 9 can be prevented.

(Modification)
A modification will be described. FIG. 7 is a cross-sectional view of a wound electrode group 200 used in a nonaqueous electrolyte secondary battery according to a modification.

As shown in FIG. 7, of the separator 10a and separator 10b of the wound electrode group 200 in the modified example, half of the area of the separator located on the outermost side in the wound stacking direction is in the inner direction of the wound stacking direction. It is in contact with the separator.

For example, in the wound electrode group 2 shown in FIG. 5, the separator 10b positioned on the outermost side in the wound stacking direction is in contact with the separator 10a in the inner side of the wound stacking direction and positioned on the outermost side in the wound stacking direction. The separator 10a is separated from the inner side of the wound lamination direction by the separator 10b.
In contact with.

In this way, by doubling the separator that is located on the outermost side in the winding stacking direction and subject to impact, the separator functions as a cushion and is positioned on the outermost side in the winding stacking direction. The impact from the outside with respect to the positive electrode 8 or the negative electrode 9 provided inside the double separator can be reduced, and cracking of the positive electrode 8 or the negative electrode 9 can be prevented.

The location where the separator is doubled is not limited to the position shown in FIG. 7. For example, the separator may be doubled on two longitudinal surfaces in the cross-sectional view of the wound electrode group 200 of FIG. 7. .

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions can be made without departing from the spirit of the invention.
Can be replaced or changed. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

2 ... wound electrode group, 8 ... positive electrode, 9 ... negative electrode, 10a, 10b ... separator

Claims (4)

A positive electrode;
A negative electrode,
A first separator;
A second separator;
With
The positive electrode and the negative electrode are wound and stacked via the first separator and the second separator,
The first separator located on the outermost side in the winding lamination direction is in contact with the second separator in the inner direction in the winding lamination direction.
electrode. A positive electrode;
A negative electrode,
A first separator;
A second separator;
With
The positive electrode and the negative electrode are wound and stacked via the first separator and the second separator,
At least half of the area of the first separator located on the outermost side in the winding lamination direction is in contact with the second separator in the inner direction of the winding lamination direction,
electrode. In a non-aqueous secondary battery comprising a positive electrode, a negative electrode, a first separator, and a second separator,
The positive electrode and the negative electrode are wound through a first separator and a second separator, and the first separator located on the outermost side in the wound stacking direction is arranged on the inner side in the wound stacking direction. In contact with the second separator in a direction,
Non-aqueous electrolyte secondary battery. In a non-aqueous secondary battery comprising a positive electrode, a negative electrode, a first separator, and a second separator,
The positive electrode and the negative electrode are wound and stacked via the first separator and the second separator,
At least half of the area of the first separator located on the outermost side in the winding lamination direction is in contact with the second separator in the inner direction of the winding lamination direction,
Non-aqueous electrolyte secondary battery.

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