JP2014067532A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device that reduces resistance between a tab and a conductive member while favorably welding the tab and the conductive member together.SOLUTION: A secondary battery includes an electrode assembly 14 in which positive electrodes and negative electrodes 22 are laminated with respective separators 23 sandwiched therebetween. A negative electrode tab 32 is provided on ends 22c of the negative electrodes 22, and is welded to a negative electrode conductive member 42. A recess 51 provided in the negative electrode conductive member 42 forms a thick portion 61 and a thin portion 62. In the thin portion 62, the negative electrode tab 32 and the negative electrode conductive member 42 are welded together.

Description

  The present invention relates to a power storage device.

  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 provided with a tab protruding at an end. The secondary battery includes a conductive member that is welded to the tab and is electrically connected to a terminal provided in the case. By the way, as a technique related to welding, for example, Patent Document 1 describes that a compression plate portion having irregularities formed on an electrode substrate is provided, and a lead piece is welded to the irregularities.

JP-A-9-82332

  Here, when welding a tab and an electrically-conductive member, it is necessary to provide heat with respect to a welding object location. In this case, since the heat diffusion becomes easier as the thickness of the conductive member increases, the heat necessary for welding is less likely to be applied to the location to be welded.

  On the other hand, it is also conceivable to apply the technique for welding the compression plate portion and the lead piece described in Patent Document 1 to welding the tab and the conductive member. However, in the technique described in Patent Document 1, the size of the lead piece is determined by the compression recess space because the lead piece is accommodated in the compression recess space whose bottom is the compression plate portion, and the contact area is limited. The For this reason, when the technique described in Patent Document 1 is directly applied to the welding between the tab and the conductive member, it is assumed that the resistance between the tab and the conductive member is increased, and as a result, there is a concern about an increase in power loss. Is done.

  This invention is made in view of the situation mentioned above, and provides the electrical storage apparatus which can reduce resistance between a tab and a conductive member, performing welding of a tab and a conductive member suitably. Objective.

  To achieve the above object, the present invention has an electrode provided with a tab at an end, a conductive member welded to the tab, and a terminal provided in a case in which the electrode is accommodated. In the power storage device in which the conductive member and the terminal are electrically connected, the conductive member has a plate-like shape and has a thick part, a thin part, and a thick part having different thicknesses. A step portion serving as a boundary of the thin portion, and the tab is welded to a surface of the thin portion opposite to the surface on the step portion side.

  According to this invention, the tab and the conductive member are welded at the thin portion. Thereby, compared with the structure welded in a thick part, since thermal diffusion is reduced, the tab and the conductive member can be suitably welded. Moreover, since the tab is welded on the surface opposite to the surface on the stepped portion side in the thin-walled portion, the size of the tab is not limited to the stepped portion. Thereby, in order to aim at the improvement of a contact area with an electrically-conductive member, a tab can be enlarged. Therefore, the resistance between the tab and the conductive member can be reduced while suitably welding the tab and the conductive member.

  In a preferred example, the conductive member is provided with a recess that is recessed in the thickness direction, and the recess includes the stepped portion. According to this configuration, the thick part and the thin part and the step part as the boundary between the thick part and the thin part are formed by the concave portion provided in the conductive member. And the tab is welded to the surface on the opposite side to the surface at the level | step-difference part side in a thin part. Thereby, there exists an effect mentioned above.

  In a preferred example, the tab is in contact with a surface of the thick portion opposite to the surface on the stepped portion side. According to such a configuration, since the tab is in contact with the surface on the side opposite to the stepped portion in the thick portion, the tab is in contact with only the surface on the side opposite to the stepped portion in the thin portion. Compared with the configuration, the contact area can be improved.

  In a preferred example, the width of the tab is longer than the width of the surface on the stepped portion side in the thin portion. According to such a configuration, since the width of the tab is longer than the width of the surface on the stepped portion side in the thin portion, the tab and the surface on the side opposite to the surface on the stepped portion side are overlapped for welding. In this case, a part of the tab naturally comes into contact with the surface on the side opposite to the surface on the stepped portion side in the thick portion. Thereby, the improvement of a contact area can be aimed at more suitably.

  In a preferred example, the recess has an opening that opens in the thickness direction of the conductive member, and the thick portion is provided around the opening. According to such a configuration, if the welding electrode rod is inserted into the recess through the opening to perform welding, movement in the direction perpendicular to the thickness direction of the welding electrode rod is restricted. The Thereby, the welding defect of the tab and conductive member resulting from the position shift of the electrode rod for welding can be avoided.

  In a preferred example, the electrode is a negative electrode. Generally, aluminum is used for the tab provided on the positive electrode, and copper is used for the tab provided on the negative electrode. In this case, since copper has a lower resistance than aluminum, when electric power or the like related to welding is applied, the electric power or the like is not easily converted to Joule heat. For this reason, the negative electrode tab and the conductive member are more likely to cause poor welding than the positive electrode tab and the conductive member.

  In contrast, by adopting a configuration in which a thin portion is provided and welding is performed at the thin portion as described above, welding of the tab on the negative electrode side and the conductive member, which is more problematic than the positive electrode side, is suitably performed. be able to.

  In a preferred example, the power storage device is a secondary battery.

  According to this invention, it is possible to reduce the resistance between the tab and the conductive member while suitably welding the tab and the conductive member.

The exploded perspective view of a secondary battery. The perspective view of a secondary battery. The exploded perspective view of an electrode assembly. The perspective view which shows the periphery of a negative electrode tab and a negative electrode electrically-conductive member. The top view which shows the periphery of a negative electrode tab and a negative electrode electrically-conductive member. FIG. 6 is a sectional view taken along line 6-6 of FIG. FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. Sectional drawing for demonstrating a welding process. Sectional drawing which shows the recessed part of another example. Sectional drawing which shows the recessed part of another example. Sectional drawing which shows the recessed part of another example.

Hereinafter, an embodiment of a power storage device according to the present invention will be described with reference to FIGS.
As shown in FIG.1 and FIG.2, the secondary battery 10 as an electrical storage apparatus is provided with the case 11 which comprises the external shape. The case 11 includes a rectangular box-shaped container 12 and a rectangular flat lid 13 that closes an opening provided in the container 12. For this reason, the secondary battery 10 is a square battery whose outer shape is a square. The container 12 and the lid 13 are made of metal. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

  The secondary battery 10 includes an electrode assembly 14 housed in a case 11, and a positive electrode terminal 15 and a negative electrode terminal 16 that are used to exchange power with the electrode assembly 14. The terminals 15 and 16 are attached to the case 11, specifically the lid 13. The positive electrode terminal 15 penetrates the lid 13 while being insulated by the insulating ring 17, a part of the positive electrode terminal 15 is exposed outside the case 11, and another part is inside the case 11. Similarly, the negative electrode terminal 16 penetrates the case 11 while being insulated by the insulating ring 17. Thus, the terminals 15 and 16 can be accessed from outside the case 11.

  As shown in FIG. 3, the electrode assembly 14 includes a positive electrode 21 and a negative electrode 22 serving as electrodes via a separator 23 formed of a porous film through which ions (lithium ions) related to electric conduction can pass. It is configured by alternately stacking. Each of the electrodes 21 and 22 and the separator 23 has a rectangular sheet shape.

  The positive electrode 21 includes a rectangular positive metal foil (for example, aluminum foil) 21 a and a positive electrode active material layer 21 b provided on both surfaces of the positive metal foil 21 a. The negative electrode 22 has a rectangular negative metal foil (for example, copper foil) 22a and a negative electrode active material layer 22b provided 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. 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.

  Similarly, 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. The negative electrode tab 32 has a width in a direction orthogonal to the protruding direction of the negative electrode tab 32. It can be said that the direction orthogonal to the protruding direction is a direction along the end 22 c of the negative electrode 22.

  The electrodes 21 and 22 are overlapped 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 negative electrode tab 32 is gathered toward one end side in the stacking direction of the electrode assembly 14, and in the gathered state, toward the other end side opposite to the one end side. Is folded. Similarly, each positive electrode tab 31 is folded toward the other end side opposite to the one end side in a state where the positive electrode tabs 31 are gathered on one end side in the stacking direction of the electrode assembly 14. The electrode assembly 14 is accommodated in the case 11 in a state where the portion where the tabs 31 and 32 are located and the lid 13 provided with the terminals 15 and 16 face each other.

  As shown in FIG. 1, 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 15 and 16. The positive electrode conductive member 41 is made of metal (for example, aluminum), is welded to the positive electrode tab 31, and is electrically connected to the positive electrode terminal 15. The negative electrode conductive member 42 is made of metal (for example, copper), is welded to the negative electrode tab 32, and is electrically connected to the negative electrode terminal 16. Thereby, by accessing each of the terminals 15 and 16, the electric power of the electrode assembly 14 can be taken out of the case 11, and the electric power can be applied to the electrode assembly 14.

  Next, the welding mode between the negative electrode tab 32 and the negative electrode conductive member 42 will be described together with the detailed configuration of the negative electrode conductive member 42. In addition, since the welding aspect of the positive electrode tab 31 and the positive electrode conductive member 41 is the same as the welding aspect of the negative electrode tab 32 and the negative electrode conductive member 42, the detailed description is abbreviate | omitted.

  As shown in FIG. 4, the negative electrode conductive member 42 has a plate shape. The negative electrode conductive member 42 is attached in a state where a flat tab side plate surface 42 a on the negative electrode tab 32 side of both plate surfaces 42 a and 42 b orthogonal to the thickness direction is in contact with the negative electrode tab 32. In this case, the thickness direction of the negative electrode conductive member 42 coincides with the direction along the protruding direction of the negative electrode tab 32. The negative electrode tab 32 in contact with the tab side plate surface 42a constitutes the outermost layer of the negative electrode tab group G formed by overlapping the negative electrode tabs 32.

  As shown in FIGS. 4 and 5, the terminal-side plate surface 42 b opposite to the tab-side plate surface 42 a of the negative electrode conductive member 42 is provided with a recess 51 that is recessed in the thickness direction. The recess 51 is circular when viewed from the thickness direction of the negative electrode conductive member 42. As shown in FIG. 6, the recess 51 includes a bottom surface 52 located at a position recessed in the thickness direction from the terminal side plate surface 42b, and a stepped portion 53 formed between the bottom surface 52 and the terminal side plate surface 42b. . The step portion 53 extends along the thickness direction. The bottom surface 52 and the stepped portion 53 are continuous, and the terminal side plate surface 42b and the stepped portion 53 are continuous.

  Here, the thickness of the negative electrode conductive member 42 is thinner in the places where the recesses 51 are provided than in other places. That is, the negative electrode conductive member 42 has a thick portion 61 and a thin portion 62 having different thicknesses, and a step portion 53 as a boundary between the thick portion 61 and the thin portion 62. In addition, the recessed part 51 is formed by the press work which presses the plate-shaped negative electrode electrically-conductive member 42 locally, for example. For this reason, the thin portion 62 is harder than the thick portion 61.

  The recess 51 has an opening 54 that opens in the thickness direction of the negative electrode conductive member 42. There is a thick portion 61 around the opening 54. For this reason, the recess 51 is open in the thickness direction of the negative electrode conductive member 42, but is closed in a direction orthogonal to the thickness direction. In other words, the thick part 61 is disposed so as to surround the entire circumference of the thin part 62.

  The recess 51 is located at a portion where the negative electrode tab 32 is projected on the terminal-side plate surface 42 b when viewed from the thickness direction of the negative electrode conductive member 42. Specifically, as shown in FIG. 6, the recess 51 is located at a portion where an overlapping portion of all the negative electrode tabs 32 on the terminal-side plate surface 42 b is projected as viewed from the thickness direction of the negative electrode conductive member 42.

  As shown in FIG. 7, the width L <b> 1 of the negative electrode tab 32 is longer than the width L <b> 2 of the bottom surface 52 that is the surface on the stepped portion 53 side in the thin portion 62. The width L2 of the bottom surface 52 is the length of the bottom surface 52 in the width direction of the negative electrode tab 32. Further, the width L2 of the bottom surface 52 can be said to be the width of the opening 54.

  The negative electrode tab 32 is welded to a tab side plate surface 42 a opposite to the bottom surface 52, which is a surface on the stepped portion 53 side in the thin portion 62. That is, the welded portion P between the negative electrode tab 32 and the negative electrode conductive member 42 is in the thin portion 62. In the welded state, a part of the negative electrode tab 32 is in contact with the tab side plate surface 42 a opposite to the terminal side plate surface 42 b which is the surface on the stepped portion 53 side in the thick portion 61.

  Incidentally, the thickness of the negative electrode tab group G in which the negative electrode tabs 32 overlap is determined by the number of laminated negative electrodes 22. And, as the thickness of the negative electrode tab group G increases, poor welding between the negative electrode tab 32 and the negative electrode conductive member 42 tends to occur. For this reason, it is preferable to make the thickness of the thin portion 62 thinner as the thickness of the negative electrode tab group G increases. However, as the thickness of the thin portion 62 becomes thinner, the thin portion 62 becomes brittle. In view of this point, the thickness of the thin portion 62 is set thin within a range in which the strength of the thin portion 62 can be secured to some extent.

  In FIG. 6 and FIG. 7 and the like, the number of the negative electrodes 22 constituting the electrode assembly 14 is five, but actually, for example, about 60 to 80. Moreover, the thickness of the negative electrode tab 32 is 10 micrometers, for example. In this case, the thickness in the overlapping direction of the negative electrode tab group G in which the negative electrode tabs 32 overlap is about 0.6 to 0.8 mm. On the other hand, the thickness of the thin portion 62 is 0.3 to 1.0 mm.

Next, the welding process between the negative electrode tab 32 and the negative electrode conductive member 42 will be described.
As shown in FIG. 8, the negative electrode conductive member 42 is arranged so that the tab side plate surface 42 a contacts the negative electrode tab 32 in a state where the negative electrode tab 32 is gathered on one end side in the stacking direction of the electrode assembly 14. And each negative electrode tab 32 and the negative electrode electrically-conductive member 42 are inserted | pinched using a pair of electrode rods W1 and W2 for welding. In this case, the welding electrode rod W 1 on the negative electrode conductive member 42 side is inserted into the recess 51 through the opening 54 of the recess 51 and is in contact with the bottom surface 52 of the recess 51. Further, the welding electrode rod W2 on the negative electrode tab 32 side presses each negative electrode tab 32 via the contact plate W3. In this state, electric power for welding is applied between the pair of welding electrode rods W1, W2. Accordingly, the negative electrode tabs 32 are welded to each other, and the negative electrode tab 32 and the negative electrode conductive member 42 are welded at the thin portion 62.

  The diameters of the pair of welding electrode rods W1 and W2 are set so that the welding location P can have a desired welding strength. And the magnitude | size of the recessed part 51 is a magnitude | size which can insert the electrode rod W1 for welding by the side of the negative electrode electrically-conductive member 42. FIG.

Next, the operation of this embodiment will be described.
As already described, the negative electrode tab 32 and the negative electrode conductive member 42 are welded at the thin portion 62. Thereby, compared with the structure welded by the thick part 61, the heat which concerns on a diffusion is hard to spread | diffuse. Moreover, since the negative electrode tab 32 is welded by the tab side plate surface 42a opposite to the terminal side plate surface 42b having the concave portion 51 for forming the thin portion 62, the negative electrode tab 32 and the concave portion 51 are formed. The step portion 53 does not interfere.

According to the embodiment described in detail above, the following excellent effects are obtained.
(1) In the configuration in which the negative electrode conductive member 42 includes the thick portion 61 and the thin portion 62 having different thicknesses and the step portion 53 as a boundary between the thick portion 61 and the thin portion 62, The negative electrode tab 32 and the negative electrode conductive member 42 were welded. Thereby, compared with the structure welded by the thick part 61, since thermal diffusion is reduced, the negative electrode tab 32 and the negative electrode conductive member 42 can be welded suitably. Further, the negative electrode tab 32 is welded to a tab side plate surface 42 a opposite to the bottom surface 52 on the stepped portion 53 side in the thin portion 62. Thereby, the negative electrode tab 32 and the level | step-difference part 53 do not interfere. Therefore, the negative electrode tab 32 can be enlarged in order to improve the contact area between the negative electrode tab 32 and the negative electrode conductive member 42. Therefore, the resistance between the negative electrode tab 32 and the negative electrode conductive member 42 can be reduced while the negative electrode tab 32 and the negative electrode conductive member 42 are suitably welded.

  (2) In particular, since the copper constituting the negative electrode tab 32 has a lower resistance than the aluminum constituting the positive electrode tab 31, when electric power for welding is applied, the electric power is not easily converted to Joule heat. For this reason, the negative electrode tab 32 and the negative electrode conductive member 42 are more likely to cause poor welding than the positive electrode tab 31 and the positive electrode conductive member 41.

  In contrast, by adopting a configuration in which the thin portion 62 is provided and welding is performed at the thin portion 62 as described above, the negative electrode tab 32 and the negative electrode conductive member 42 are welded more easily than the positive electrode side. It can be suitably performed.

  (3) A recess 51 that is recessed in the thickness direction is provided on the terminal-side plate surface 42 b of the negative electrode conductive member 42. Thereby, the thick part 61 and the thin part 62, and the level | step-difference part 53 which is these boundary are formed. The negative electrode tab 32 is welded to the tab side plate surface 42a opposite to the bottom surface 52 of the recess 51. Therefore, the above-described effects can be obtained with a relatively simple configuration in which the recess 51 is provided.

  (4) The negative electrode tab 32 is in contact with the tab side plate surface 42a opposite to the terminal side plate surface 42b on the stepped portion 53 side in the thick portion 61. Thereby, since the welding area is improved, the resistance between the negative electrode tab 32 and the negative electrode conductive member 42 can be reduced.

  In particular, the width L1 of the negative electrode tab 32 was set longer than the width L2 of the bottom surface 52 of the recess 51. Thereby, by arranging the thin portion 62 and the negative electrode tab 32 so as to overlap each other, a part of the negative electrode tab 32 and the tab side plate surface 42 a of the thick portion 61 come into contact with each other. Therefore, the contact area can be improved more suitably.

  (5) The thick portion 61 is provided around the opening 54 of the recess 51. Accordingly, the recess 51 is opened in the thickness direction of the negative electrode conductive member 42, and is closed in a direction orthogonal to the thickness direction. Therefore, when the welding electrode bar W1 on the negative electrode conductive member 42 side is inserted into the recess 51 through the opening 54, the welding electrode bar W1 is not easily displaced in the direction perpendicular to the thickness direction. Therefore, it is possible to suppress poor welding due to the positional deviation.

In addition, you may change the said embodiment as follows.
In embodiment, although the recessed part 51 was opened in the thickness direction of the negative electrode electrically-conductive member 42, and was obstruct | occluded in the direction orthogonal to the said thickness direction, it is not restricted to this. For example, as shown in FIG. 9, the structure which provides the recessed part 91 opened in the thickness direction and the direction orthogonal to the thickness direction may be sufficient. The recess 91 may be configured to extend along the end 92 c of the negative electrode conductive member 92. In other words, the thin-walled portion 62 may be provided with the negative electrode conductive member 92 that constitutes the end portion 92c.

  In embodiment, although the level | step-difference part 53 followed the thickness direction of the negative electrode electrically-conductive member 42, it is not restricted to this. For example, as shown in FIG. 10, a stepped portion 101 that is inclined with respect to the thickness direction may be used. Moreover, as shown in FIG. 11, the curved level | step-difference part 102 may be sufficient. In short, if there is a thin portion 62 and a thick portion 61 having different thicknesses with the step portion as a boundary, the specific shape of the step portion is arbitrary.

  In the configuration as described above, the boundary between the stepped portions 101 and 102 and the bottom surface 52 forms the end of the thin portion 62, and the boundary between the stepped portions 101 and 102 and the terminal side plate surface 42b is thick. The end part of the part 61 is configured. For this reason, even if it is the above structures, it can be said that each level | step-difference part 101,102 comprises the boundary of the thick part 61 and the thin part 62. FIG. That is, when viewed from the thickness direction of the negative electrode conductive member 42, the stepped portion constituting the boundary between the thick portion 61 and the thin portion 62 may have a predetermined width.

  In the embodiment, the tab side plate surface 42a to which the negative electrode tab 32 is welded is a flat surface. However, the present invention is not limited to this. For example, a step portion may be formed on the tab side plate surface 42a. In this case, the step size of the step portion formed on the tab side plate surface 42a may be set shorter than the step size of the step portion 53 formed on the terminal side plate surface 42b.

  O The thickness of the thin portion 62 may be set thinner than the thickness of the negative electrode tab group G. Thereby, welding with the thin part 62 and the negative electrode tab group G can be performed suitably. Conversely, the thickness of the thin portion 62 may be made thicker than that of the negative electrode tab group G.

  In the embodiment, the welding mode between the positive electrode tab 31 and the positive electrode conductive member 41 is the same as the welding mode between the negative electrode tab 32 and the negative electrode conductive member 42, but is not limited thereto, and may be different. For example, the welding by the thin portion 62 may be applied only to the welding of the positive electrode tab 31 and the positive electrode conductive member 41. Conversely, the welding by the thin portion 62 is welded by the negative electrode tab 32 and the negative electrode conductive member 42. You may apply only to.

In the embodiment, only one recess 51 is provided. However, the present invention is not limited to this, and a plurality of recesses 51 may be provided.
In the embodiment, the electrode assembly 14 is a so-called laminated type in which a plurality of positive electrodes 21 and a plurality of negative electrodes 22 are provided, and these electrodes 21 and 22 are laminated via a separator 23. Not limited to. For example, a wound-type electrode assembly in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers may be used.

  In embodiment, although the recessed part 51 was circular seeing from the thickness direction of the negative electrode electrically-conductive member 42, it is not restricted to this, It is arbitrary. The welding electrode rod W1 is arbitrary as long as it can be inserted into the recess 51.

  In the embodiment, the size of each of the electrodes 21 and 22 is the same, but is not limited thereto, and the negative electrode 22 may be slightly larger than the positive electrode 21. In this case, the negative electrode active material layer 22b may be slightly larger than the positive electrode active material layer 21b.

  In the embodiment, the positive electrode active material layer 21b is configured to be on both surfaces of the positive electrode 21, but is not limited thereto, and may be configured to be only on one surface of the positive electrode 21. Similarly, the negative electrode active material layer 22b may be provided only on one side of the negative electrode 22.

In the embodiment, the same polarities of the conductive members 41 and 42 and the tabs 31 and 32 are made of the same metal, but are not limited thereto, and may be made of different metals.
(Circle) the object in which the secondary battery 10 of embodiment is mounted is arbitrary. For example, it may be mounted on a vehicle such as an automobile or an industrial vehicle, or may be mounted on a stationary power storage unit.

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.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 14 ... Electrode assembly, 15, 16 ... Terminal, 21, 22 ... Electrode, 31, 32 ... Tab, 41, 42 ... Conductive member, 51 ... Recess, 53 ... Step part 61 ... Thick part, 62 ... Thin part, 101,102 ... Step part of another example.

In order to achieve the above object, the present invention provides an electrode provided with a tab protruding from an end of a rectangular metal foil, a conductive member welded to the tab, and a case in which the electrode is accommodated. In the power storage device in which the conductive member and the terminal are electrically connected to each other, the conductive member is plate-shaped and has a thick portion with a different thickness, and a thin wall and parts, the thick portion, and has a stepped portion as a boundary of the thin portion, the width of the tab is longer than the width of the surface of the stepped portion side of the thin portion, said tab the The thick portion is welded on a flat surface opposite to the surface on the stepped portion side of the thin portion so that the end portion on one side in the width direction of the tab does not protrude from the end portion of the conductive member. this in contact with the flat surface opposite to the stepped portion of the surface of the parts The features.

According to this invention, the tab and the conductive member are welded at the thin portion. Thereby, compared with the structure welded in a thick part, since thermal diffusion is reduced, the tab and the conductive member can be suitably welded. Further, since the tab is welded on a flat surface opposite to the surface on the stepped portion side in the thin wall portion, the size of the tab is not limited to the stepped portion. Thereby, in order to aim at the improvement of a contact area with an electrically-conductive member, a tab can be enlarged. Therefore, the resistance between the tab and the conductive member can be reduced while suitably welding the tab and the conductive member.
Moreover, since the width of the tab is longer than the width of the surface on the stepped portion side in the thin portion, when the tab is overlapped with the surface on the side opposite to the stepped portion side in the thin portion, naturally, A part of the tab contacts a flat surface opposite to the surface on the stepped portion side in the thick portion. Thereby, the improvement of a contact area can be aimed at more suitably.

In a preferred example, the recess has an opening that opens in the thickness direction of the conductive member, and the thick portion is provided around the opening. According to such a configuration, if the welding electrode rod is inserted into the recess through the opening to perform welding, movement in the direction perpendicular to the thickness direction of the welding electrode rod is restricted. The Thereby, the welding defect of the tab and conductive member resulting from the position shift of the electrode rod for welding can be avoided.
In a preferred example, the thin portion is formed so as to extend along an end portion of the conductive member.

Claims (7)

Electrodes with tabs at the ends;
A conductive member welded to the tab;
A terminal provided in a case in which the electrode is accommodated,
In the power storage device in which the conductive member and the terminal are electrically connected,
The conductive member is plate-shaped and has a thick part and a thin part having different thicknesses, and
The thick part, and a step part as a boundary of the thin part,
The power storage device, wherein the tab is welded to a surface of the thin portion opposite to the surface on the side of the stepped portion. The conductive member is provided with a recess recessed in the thickness direction,
The power storage device according to claim 1, wherein the recess includes the stepped portion.   The power storage device according to claim 1, wherein the tab is in contact with a surface of the thick-walled portion that is opposite to the surface on the side of the stepped portion.   The power storage device according to claim 3, wherein a width of the tab is longer than a width of a surface of the thin portion on the side of the stepped portion. The recess has an opening that opens in the thickness direction of the conductive member,
The power storage device according to claim 2, wherein the thick portion exists around the opening.   The power storage device according to claim 1, wherein the electrode is a negative electrode.   It is a secondary battery, The electrical storage apparatus as described in any one of Claims 1-6.