JP6131557B2 - Lithium ion secondary battery - Google Patents

Description

The present invention relates to a lithium ion secondary battery .

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery as a power storage device that stores power supplied to the traveling motor. The secondary battery includes, for example, an electrode assembly configured by laminating a positive electrode and a negative electrode provided with tabs protruding from the end portions with a separator interposed therebetween. Further, for example, Patent Document 1 describes a configuration in which two separators are arranged on both sides of a positive electrode as a first electrode, and the periphery of the positive electrode is thermally welded. It is described that the whole part is thermally welded linearly.

JP 2002-252023 A

  As described above, in the configuration in which the entire region on the positive electrode tab side is thermally welded in a linear shape, there is a concern about the occurrence of wrinkles of the separator. Further, in an electrode assembly that accommodates the positive electrode as described above with two separators, it is required to suppress the displacement of the positive electrode with respect to the separator.

The present invention has been made in view of the above-described circumstances, and provides a lithium ion secondary battery that can suppress the occurrence of wrinkles in the separator while suitably suppressing the displacement of the positive electrode with respect to the separator. With the goal.

In order to achieve the above object, the invention according to claim 1 includes a positive electrode having a tab projecting at an end portion and having a positive electrode active material layer on both surfaces, and a first separator that covers one surface of the positive electrode. And a lithium ion secondary battery comprising an electrode assembly formed by laminating a second separator that covers the other surface of the positive electrode , and a negative electrode , the tab, the first separator, and the a first weld portion and the second separators are welded along the edge, and the second weld portion and the first separator and the second separator is welded, wherein the first weld portion the first separator and the second is formed Oite continuously to the first area facing the tabs to the stacking direction of the separator Rutotomoni is formed over the entire width of the tab, the second The welded portion is the first In a second region other than the band are intermittently forming a plurality, in the region of the region projecting from the end portion of the proximal Contact Keru the positive electrode before Symbol tab are the positive active material layer is formed The end of the positive electrode active material layer formed on the tab overlaps the first welded portion.

According to the invention, the separators are connected by second weld portion, is connected to the tab and the respective separators by the first welded portion. Thereby, the positional deviation between the separators is suppressed, and the positional deviation of the positive electrode with respect to the separator is suppressed.

Here, it is assumed that each welded portion is formed by heat treatment. In this case, it is considered that each separator is thermally contracted by heat treatment, and wrinkles are generated in each separator. On the other hand, from the viewpoint of suppressing the displacement between the positive electrode and the separator, it is preferable that the welding strength between the tab and the separator is higher.

On the other hand, according to this invention, while the 1st welding part is continuously formed over the whole width | variety of a tab , the 2nd welding part is formed in multiple numbers intermittently. Thereby, generation | occurrence | production of the wrinkles resulting from providing each welding part can be suppressed, suppressing the position shift of the positive electrode with respect to a separator suitably by ensuring the welding intensity | strength with a tab and a separator .
Moreover, said the site of the proximal side of the protruding area from the end of our Keru the positive electrode tab the positive electrode active material layer is formed, the ends of the formed in the tab the positive active material layer Overlaps the first weld. According to this invention, as a result of forming the positive electrode active material layer on the entire positive electrode, in the configuration in which the positive electrode active material layer is formed at the base end side portion of the tab, the end portion of the positive electrode active material layer Overlaps the first weld. In the first welded portion, the movement of lithium ions related to electrical conduction is regulated by heat treatment related to welding. Accordingly, the formation of the positive electrode active material layer on the entire positive electrode makes it possible to expand the region contributing to charging / discharging, and the lithium ion precipitates related to the electric conduction caused by the positive electrode active material layer formed on the tab. Occurrence can be suppressed.

According to this invention, generation | occurrence | production of the wrinkle in a separator can be suppressed, suppressing the position shift of the positive electrode with respect to a separator suitably.

The perspective view of a secondary battery. The exploded perspective view of an electrode assembly. The front view at the time of laminating | stacking in order of a separator, a negative electrode, and a positive electrode. The elements on larger scale showing the circumference of the 1st welding part and the 2nd welding part. (A) is a sectional view taken along line 5a-5a, and (b) is a sectional view taken along line 5b-5b. The front view of the positive electrode as a comparative example. The elements on larger scale which show the 1st welding part of another example. (A) is a perspective view which shows the positive electrode container of another example, (b) is a disassembled perspective view of the positive electrode container of another example.

Hereinafter will be described with reference to FIGS about a charge reservoir. This power storage device is mounted on vehicles (automobiles and industrial vehicles) and is used to drive a traveling motor (electric motor) mounted on the vehicle.

  As shown in FIG. 1, a secondary battery 10 as a power storage device is a lithium ion secondary battery, and includes a metal case 11 that forms an outer shell of the lithium ion secondary battery. The case 11 includes a rectangular box-shaped container 12 and a rectangular flat lid 13 that closes the opening of the container 12. For this reason, the secondary battery 10 has a rectangular outer shape. The case 11 contains an electrode assembly 14 and an electrolytic solution (not shown) as an electrolyte.

  The secondary battery 10 includes a positive electrode terminal 15 and a negative electrode terminal 16 that are accessible from outside the case 11. The positive electrode terminal 15 penetrates the case 11 while being insulated by the insulating ring 17. A part of the positive electrode terminal 15 is exposed outside the case 11, while another part is inside the case 11. Similarly, on the negative electrode side, the negative electrode terminal 16 penetrates the case 11 while being insulated by the insulating ring 17.

  As shown in FIG. 2, the electrode assembly 14 is a porous film in which a positive electrode 21 as a first electrode and a negative electrode 22 as a second electrode can pass ions (lithium ions) related to electrical conduction. It is configured by being stacked via a pair of formed separators 23 and 24. Each of the electrodes 21 and 22 and each of the separators 23 and 24 has a rectangular sheet shape.

  The positive electrode 21 includes a positive electrode metal foil (for example, an aluminum foil) 21a formed in a rectangular shape, and a positive electrode active material layer 21b formed on both surfaces of the positive electrode metal foil 21a. The negative electrode 22 has a rectangular negative metal foil (for example, copper foil) 22a formed slightly larger than the positive metal foil 21a, and a negative electrode active material layer 22b formed on both surfaces of the negative metal foil 22a. Have

  As shown in FIG. 3, the negative electrode 22 is formed to be slightly larger than the positive electrode 21. Specifically, the lengths of two adjacent sides of the negative electrode 22 are 2 adjacent to the positive electrode 21. It is set longer than the corresponding length of the side. The negative electrode active material layer 22b is formed larger than the positive electrode active material layer 21b so as to be able to cover the entire positive electrode active material layer 21b.

  The separators 23 and 24 have the same shape and are slightly larger than the positive electrode 21 and the negative electrode 22. Specifically, the lengths of the two adjacent sides of the separators 23 and 24 are set longer than the corresponding lengths of the two adjacent sides of the negative electrode 22. That is, the separators 23 and 24 are formed to have a size capable of overlapping and covering the electrodes 21 and 22.

  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 positive electrode 21 and the negative electrode 22 are covered with the separators 23 and 24.

  As shown in FIGS. 2 and 3, a positive electrode tab 31 protrudes from the end 21 c of the positive electrode 21. The positive electrode tab 31 is formed by protruding a part of the positive electrode metal foil 21a from the end portion 21c. The positive electrode tab 31 has a width in a direction orthogonal to the protruding direction of the positive electrode tab 31. The direction orthogonal to the protruding direction can also be said to be a direction along the end 21c of the positive electrode 21.

  A positive electrode active material layer 21b is formed on a part of the positive electrode tab 31, more specifically, on a proximal end side in the protruding direction, while a positive electrode active material layer 21b is formed on the other part of the positive electrode tab 31. The metal part is exposed.

  A negative electrode tab 32 protrudes from the end 22 c of the negative electrode 22. The negative electrode tab 32 is formed by protruding a part of the negative electrode metal foil 22a from the end 22c. In the negative electrode tab 32, the negative electrode active material layer 22b is formed at a portion on the proximal end side in the protruding direction, while the negative electrode active material layer 22b is not formed in other portions, and the metal portion is exposed.

Each of the two adjacent sides of the positive electrode 21 is a length excluding the positive electrode tab 31, and each of the two adjacent sides of the negative electrode 22 is a length excluding the negative electrode tab 32. is there.
As shown in FIG. 2, the electrodes 21 and 22 are arranged so that the same polarities of the tabs 31 and 32 are arranged in a row in the stacking direction, while different polarities are not aligned in the stacking direction. As shown in FIG. 1, each positive electrode tab 31 is gathered near one end side in the stacking direction of the electrode assembly 14, and the other end side opposite to the one end side in the gathered state. Wrapped towards. Similarly, each of the negative electrode tabs 32 is folded toward the other end side in a state of being collected on one end side in the stacking direction of the electrode assembly 14. And the electrode assembly 14 is accommodated in the case 11 so that the site | part in which each tab 31 and 32 is formed, and the lid | cover 13 to which each terminal 15 and 16 is attached oppose.

  Each positive electrode tab 31 and the positive electrode terminal 15 are electrically connected by welding to the positive electrode conductive member 51 made of metal. Each negative electrode tab 32 and the negative electrode terminal 16 are electrically connected by being welded to a negative electrode conductive member 52 made of metal. Thus, by accessing the terminals 15 and 16, the power of the electrode assembly 14 can be taken out of the case 11, and the power can be supplied to the electrode assembly 14.

  As shown in FIG. 2, the positive electrode 21, the first separator 23, and the second separator 24 are unitized to form a positive electrode housing 60. The positive electrode container 60 will be described in detail below.

  The positive electrode housing 60 is formed by sandwiching the positive electrode 21 between the separators 23 and 24. In this case, one surface of the positive electrode 21 is covered with the first separator 23 and the other surface is covered with the second separator 24.

  Here, since each separator 23 and 24 is formed larger than the positive electrode 21, in the positive electrode container 60, a part of each separator 23 and 24 is each edge part of the positive electrode 21 seeing from the lamination direction. It protrudes outward from 21c-21f. That is, each separator 23 and 24 is provided with each protrusion part 61 and 62 which protruded from each edge part 21c-21f of the positive electrode 21 seeing from the lamination direction. The protruding portions 61 and 62 are formed along the peripheral edges of the separators 23 and 24.

  The positive electrode housing 60 includes a first welded portion 71 in which the positive electrode tab 31 and the first separator 23 and the second separator 24 are welded, and the first separator 23 and the second separator 24 are welded in the first. Two welded portions 72 are provided. Further, the positive electrode housing 60 includes a third welded portion 73 that connects the separators 23 and 24.

  As shown in FIG. 4, the first welded portion 71 is continuously formed in a direction along the end portion 21 c of the positive electrode 21 in the first region Z1 facing the positive electrode tab 31 among the protruding portions 61 and 62. ing. In detail, the 1st welding part 71 is formed by heat-processing in the state which provided the optimal surface pressure with respect to the 1st area | region Z1 whole. In this case, the 1st welding part 71 is formed over the whole width | variety of the positive electrode tab 31, and is formed in the 1st area | region Z1 whole. If attention is paid to the fact that the first region Z1 is a surface, it can be said that the separators 23 and 24 and the positive electrode tab 31 are surface-welded.

  Here, as shown in FIG. 4, the end 21bb of the positive electrode active material layer 21b is disposed in the first region Z1 and overlaps the first welded portion 71. Therefore, as shown in FIG. 5A, the first welded portion 71 connects the portion where the metal portion of the positive electrode tab 31 is exposed to the separators 23 and 24, and the positive electrode active material layer 21b and each separator. 23 and 24 are connected. For convenience of illustration, FIG. 5A shows a cross-sectional view with the first separator 23.

  As shown in FIG. 4, the second welded portion 72 is a front end side in the protruding direction of the positive electrode tab 31 from the end portion 21 c of the positive electrode 21 in each of the protruding portions 61 and 62, and the second welded portion 72 other than the first region Z1 Two regions Z2 are formed. A plurality of second welds 72 are intermittently formed at predetermined intervals in the direction along the end 21c of the positive electrode 21 in the second region Z2. As shown in FIG. 5B, the second welded portion 72 is formed by heat-treating each separator 23, 24 with an optimum surface pressure applied thereto. It is connected.

  If attention is paid to the end portions 23a and 24a of the separators 23 and 24 on the front end side in the protruding direction with respect to the end portion 21c of the positive electrode 21, the first welded portion 71 has the end portion 23a in the first region Z1. 24a, and a plurality of second welded portions 72 are intermittently formed along the end portions 23a and 24a in the second region Z2.

  The third welded portion 73 will be described. As shown in FIG. 2, the third welded portion 73 is a portion of each protruding portion 61, 62 opposite to the welded portions 71, 72, specifically the positive electrode. 21 is provided at a portion protruding from an end 21d opposite to the end 21c in a direction orthogonal to the end 21d. The third welded portion 73 is formed by heat treatment in a state where an optimum surface pressure is applied to the separators 23 and 24, and is predetermined in a direction along the end portion 21d facing the end portion 21c of the positive electrode 21. Are arranged intermittently at intervals of. The positive electrode 21 is sandwiched between the first welding portion 71, the second welding portion 72, and the third welding portion 73 from the direction along the protruding direction of the positive electrode tab 31.

Next, the operation of this embodiment will be described.
The second welding portion 72 and the third welding portion 73 restrict the positive electrode 21 from protruding from the separators 23 and 24, and the positive electrode 21 is accommodated in the positive electrode housing 60. In this case, since the plurality of the second welded portions 72 and the third welded portions 73 are intermittently formed, the thermal contraction of the separators 23 and 24 due to the heat treatment is reduced as compared with the configuration formed linearly. Therefore, wrinkles are less likely to occur in the separators 23 and 24.

  On the other hand, the first welding portion 71 regulates the positional deviation between the positive electrode 21 and the separators 23 and 24 in the positive electrode housing 60. In this case, since the 1st welding part 71 is continuously formed in the 1st area | region Z1 in detail, in detail, the welding strength by the 1st welding part 71 is fully ensured.

  Moreover, in the 1st welding part 71, the hole which a lithium ion can pass is block | closed by the heat processing which concerns on welding, and passage of lithium ion is controlled. Therefore, as shown in FIG. 4, even in the case where a region Zx in which the positive electrode active material layer 21 b and the negative electrode active material layer 22 b are not opposed is formed in the first welded portion 71, lithium deposition Is unlikely to occur.

According to the embodiment described in detail above, the following excellent effects are obtained.
(1) A positive electrode tab 31, a first welded portion 71 in which the first separator 23 and the second separator 24 are welded, and a second welded portion 72 in which the first separator 23 and the second separator 24 are welded are provided. It was. And while forming the 1st welding part 71 continuously, two or more 2nd welding parts 72 were formed intermittently. Thereby, coexistence with suppression of the position shift of the positive electrode 21 with respect to each separator 23 and 24 and suppression of generation | occurrence | production of the wrinkles of each separator 23 and 24 can be aimed at.

  More specifically, the wrinkles of the separators 23 and 24 are generated due to the heat shrinkage of the separators 23 and 24. For this reason, when paying attention to the viewpoint of suppressing the generation of wrinkles in each separator 23, 24, it is preferable that a plurality of welding locations are intermittently formed in order to reduce the area of the location where the heat treatment is performed. On the other hand, when attention is paid to suitably suppressing the displacement of the positive electrode 21 with respect to the separators 23 and 24, it is preferable that the first welding portion 71 has a large welding area. In particular, since the welding strength between the separators 23 and 24 and the positive electrode tab 31 is lower than the welding strength between the separators 23 and 24, it is preferable that the welding area of the first welding portion 71 is large.

  On the other hand, according to the present embodiment, a plurality of second welded portions 72 are intermittently formed, while the first welded portion 71 is continuously formed. In detail, the 1st welding part 71 is surface welding. Thereby, the coexistence shown above can be achieved. In addition, as already demonstrated, since the 2nd welding part 72 is welding of each separator 23 and 24, the welding intensity | strength is high. For this reason, even if it is a case where multiple 2nd welding parts 72 are formed intermittently, desired welding intensity | strength is securable.

  (2) In particular, in a configuration in which heat treatment is performed for welding, optimum surface pressure and heating are required. For this reason, when the welding area is large, a large load is required to secure the surface pressure necessary for welding. Then, the equipment for welding by itself becomes large, and the cost tends to increase. On the other hand, according to this embodiment, since the location where surface welding is performed is limited to the first region Z1, it is easy to ensure the surface pressure necessary for welding. Thereby, the cost concerning welding can be reduced, and the cost of the secondary battery 10 can be reduced through it.

  (3) The positive electrode active material layer 21 b is formed on a part of the positive electrode tab 31. Thereby, the positive electrode active material layer 21b can be formed on the whole both surfaces of the positive electrode metal foil 21a, and the area | region which each active material layer 21b and 22b opposes can be enlarged. In such a configuration, the end portion of the positive electrode active material layer 21b formed on the positive electrode tab 31 overlaps the first welded portion 71 in which the movement of lithium ions is restricted. Thereby, precipitation of lithium resulting from forming the positive electrode active material layer 21b in a part of the positive electrode tab 31 can be suppressed.

  More specifically, the negative electrode active material layer 22b usually covers the positive electrode active material layer 21b in order to suppress the formation of a non-opposing portion that does not face the negative electrode active material layer 22b in the positive electrode active material layer 21b in the stacking direction. The positive electrode active material layer 21b is formed larger than the positive electrode active material layer 21b. For example, as illustrated in FIG. 6, in the positive electrode 121, the end portion 121 bb of the positive electrode active material layer 121 b is formed as a positive electrode so that the positive electrode active material layer 121 b is not formed at the base end side portion of the positive electrode tab 31. The electrode 121 is located in a direction opposite to the protruding direction of the positive electrode tab 31 than the end 121 c of the electrode 121. Therefore, the positive electrode active material layer 121b is not formed along the end portion 121c of the positive electrode 121, and the positive electrode uncoated portion 121d where the positive metal foil 121a is exposed is formed. The portion where the positive electrode uncoated portion 121d is formed is a region that does not contribute to charging / discharging. In this case, it is conceivable to form the positive electrode active material layer 121b so that the positive electrode uncoated portion 121d is not formed and the positive electrode active material layer 121b is not formed on the positive electrode tab 31, but with such high accuracy. It is difficult in the manufacturing process to form the positive electrode active material layer 121b.

  On the other hand, according to the present embodiment, the movement of lithium ions is restricted in the first welded portion 71. As a result, the positive electrode active material layer 21b is formed on the entire positive electrode metal foil 21a. As a result, even if the positive electrode active material layer 21b is formed at the base end side portion of the positive electrode tab 31, the positive electrode active material layer 21b. Since the end portion 21bb of the first electrode overlaps the first welded portion 71, lithium does not precipitate. Therefore, it is possible to achieve both expansion of a region contributing to charging / discharging by forming the positive electrode active material layer 21b on the entire positive electrode metal foil 21a and suppression of lithium precipitation that can be caused accordingly.

In addition, you may change the said embodiment as follows.
In embodiment, although the 1st welding part 71 was formed continuously, it is not restricted to this. For example, as shown in FIG. 7, a plurality of first welds 101 that are intermittently formed along the end 21 c of the positive electrode 21 may be provided. In this case, the interval L1 between the first welded portions 101 may be shorter than the interval L2 between the second welded portions 72. In addition, it can be said that the 1st welding part 71 of embodiment is a thing with the space | interval L1 of "0".

  Moreover, in the said structure, the location which can move a lithium ion exists in the 1st area | region Z1. In this case, the end 21bb of the positive electrode active material layer 21b may be arranged in a direction opposite to the protruding direction from the end 21c of the positive electrode 21 so that lithium deposition does not occur.

  In the embodiment, a plurality of the third welded portions 73 are intermittently provided on the opposite sides of the first welded portion 71 and the second welded portion 72 in each of the protruding portions 61 and 62, but this is not the only case. Absent. For example, a continuously formed welded portion may be provided, or a configuration in which the welded portions are connected by tape, an adhesive, or stitching may be employed.

  In the embodiment, as the second region Z2, a region other than the first region Z1 is adopted in each of the protruding portions 61 and 62, which is on the tip side in the protruding direction of the positive electrode tab 31 with respect to the end portion 21c of the positive electrode 21. However, it is not limited to this. The second region may be a region other than the first region Z1 among the protruding portions 61 and 62. For example, a region protruding from the end 21e or the end 21f of the positive electrode 21 in each of the protruding portions 61 and 62 may be a second region, and a plurality of welded portions may be intermittently formed in the second region. In other words, a plurality of second welding portions for welding the separators 23 and 24 may be formed intermittently in at least a part of the regions other than the first region Z1 in the protruding portions 61 and 62. It can be said that the second region is a region different from the first region Z1.

  In the embodiment, the positive electrode 21 is covered with the two separators 23 and 24. However, the present invention is not limited to this. For example, the positive electrode housing body 110 shown in FIGS. 8A and 8B is configured by bending an integrated separator 111 and sandwiching the positive electrode 21 by the separator 111. In this case, the bent portion 112 formed by bending the separator 111 functions as a unit that connects a portion covering one surface of the positive electrode 21 and a portion covering the other surface of the positive electrode 21. That is, as long as both surfaces of the positive electrode 21 can be covered, the “first separator” and the “second separator” may be separate members or a single member.

In the embodiment, the target covering the separators 23 and 24 is the positive electrode 21, but is not limited thereto, and may be the negative electrode 22.
In the embodiment, the plurality of second welds 72 are intermittently formed over the entire second region Z2, but the present invention is not limited thereto, and a plurality of second welds 72 are intermittently formed over a part of the second region Z2. It is good also as the structure currently made.

  In embodiment, although the positive electrode active material layer 21b was formed on both surfaces of the positive electrode 21, it is not restricted to this, What is necessary is just to be formed in at least one surface. Similarly, the negative electrode active material layer 22 b only needs to be formed on at least one surface of the negative electrode 22.

In the embodiment, the positive electrode tab 31 is welded to the separators 23 and 24 on both sides thereof, but is not limited thereto, and may be bonded to at least one separator.
In the embodiment, the secondary battery 10 is mounted on the vehicle, but is not limited thereto, and may be mounted on another device.

The present invention may be applied to other power storage devices such as electric double layer capacitors.
In embodiment, although the secondary battery 10 was a lithium ion secondary battery, it is not restricted to this, Other secondary batteries, such as nickel hydride, may be sufficient. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) a first electrode having an active material layer and having a tab projecting from an end; a first separator covering one surface of the first electrode; and a first electrode covering the other surface of the first electrode. In a power storage device including an electrode assembly in which two separators and a second electrode having a polarity different from that of the first electrode are stacked, the tabs in the first separator and the second separator and the stacking direction The first region opposite to the first region is restricted from passing ions related to electrical conduction, and an end portion of the active material layer is disposed in the first region.

  (B) a first electrode provided with a protruding tab at an end, a first separator covering one surface of the first electrode, a second separator covering the other surface of the first electrode, and the first In the power storage device including an electrode assembly configured by stacking a second electrode having a polarity different from that of one electrode, the tab and at least one of the first separator and the second separator are the end portions. A first welded portion welded along the second separator, and a second welded portion welded to the first separator and the second separator, wherein the first welded portion includes the first separator and the second welded portion. One or more are formed in the first region facing the tab in the separator in the stacking direction, and a plurality of the second welds are intermittently formed in the second region other than the first region. 1 The distance between welded parts Power storage device and wherein the narrower than an interval of 2 welded portion.

  The “interval of the first welded portion” includes “0”. That is, when the interval between the first welded portions is “0”, it means that there is one first welded portion continuously formed along the end portion of the first electrode. When the interval between the portions is not “0”, it means that there are a plurality of the first welded portions intermittently.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery (electric storage apparatus), 14 ... Electrode assembly, 21 ... Positive electrode, 21b ... Positive electrode active material layer, 21bb ... End of positive electrode active material layer, 23 ... 1st separator, 24 ... 2nd separator, DESCRIPTION OF SYMBOLS 31 ... Positive electrode tab, 60 ... Positive electrode container, 71 ... 1st welding part, 72 ... 2nd welding part, 73 ... 3rd welding part, 101 ... 1st welding part of another example, 121 ... Positive electrode as a comparative example , Z1... First region, Z2... Second region.

Claims (1)

End tabs are provided to protrude, and a second separator which covers the positive electrode having a positive electrode active material layer on both sides, a first separator which covers the one surface of the positive electrode, the other surface of the positive electrode, In a lithium ion secondary battery comprising an electrode assembly configured by laminating a negative electrode ,
And said tab, a first weld portion and the first separator and the second separators are welded along the edges,
A second welded portion in which the first separator and the second separator are welded;
With
Said first weld portion, said first separator and said second first area Oite formed continuously in Rutotomoni facing the tabs to the stacking direction of the separator, are formed over the entire width of said tab And
A plurality of the second welds are intermittently formed in a second region other than the first region;
The site of the previous SL Contact Keru proximal side region projecting from the end portion of the positive electrode tab is formed with the positive electrode active material layer,
End of the positive electrode active material layer formed on said tab, a lithium ion secondary battery, characterized by overlapping the first welded portion.