Patent Application
20240194953
The present disclosure relates to a power storage device.
Patent Literature 1 proposes, as an example of a power storage device, a secondary battery including an electrode group in which a positive electrode and a negative electrode are located with a separator interposed therebetween, a case in which the electrode group is incorporated, a cap assembly coupled to the case to seal the case and electrically connected to the electrode group, a current collecting plate electrically connected to at least one of the positive electrode and the negative electrode, and an auxiliary current collecting plate installed between at least one electrode of the positive electrode and the negative electrode and a current collecting plate corresponding to the electrode.
As a current collecting structure for obtaining a high output, a so-called end surface current collecting structure has been studied. The end surface current collecting structure generally refers to a structure in which an exposed part of a current collector protrudes from an end surface of a wound body of an electrode and is welded to a current collecting plate. The end surface current collecting structure needs to suppress damage to the separator or the electrode due to spatter during welding.
In a case where an auxiliary current collecting plate is disposed between an electrode and a current collector plate as in Patent Literature 1, alignment of the auxiliary current collecting plate is important. Misalignment of the auxiliary current collecting plate causes a decrease in reliability in joining the current collecting plate and electrode by welding via the auxiliary current collecting plate.
An aspect of the present disclosure relates to a power storage device, including: a first electrode including a first current collector having an elongated sheet shape and a first active material layer supported on the first current collector; a second electrode including a second current collector having an elongated sheet shape and a second active material layer supported on the second current collector; a separator interposed between the first electrode and the second electrode; a non-aqueous electrolyte; and a first current collecting plate electrically connected to the first current collector, wherein the first electrode, the second electrode, and the separator constitute a columnar wound body, a first end of the first current collector in a longitudinal direction is a first exposed part not having the first active material layer and protruding from a first end surface of the wound body, a first tab extends from the first exposed part, the first tab covers at least a part of the first exposed part on an inner peripheral side inside the first tab, and the first current collector plate is welded to the first exposed part on an inner peripheral side inside the first tab via the first tab.
Another aspect of the present disclosure relates to a power storage device, including: a first electrode including a first current collector having an elongated sheet shape and a first active material layer supported on the first current collector; a second electrode including a second current collector having an elongated sheet shape and a second active material layer supported on the second current collector; a separator interposed between the first electrode and the second electrode; a non-aqueous electrolyte; and a first current collecting plate electrically connected to the first current collector, wherein the first electrode, the second electrode, and the separator constitute a columnar wound body, a first end of the first current collector in a longitudinal direction is a first exposed part not having the first active material layer and protruding from a first end surface of the wound body, a first tab extends from the first exposed part, the first tab covers at least a part of the first exposed part on an outer peripheral side inside the first tab, and the first current collector plate is welded to the first exposed part on an outer peripheral side inside the first tab via the first tab.
With the power storage device of the present disclosure, reliability in joining of a current collecting plate and an electrode is improved.
Part (a) of
Part (a) of
Hereinafter, exemplary embodiments of the present disclosure will be described. Note that, in the following description, exemplary embodiments of the present disclosure will be described by way of examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, and the like may be exemplified, but other numerical values, materials, and the like may be applied as long as the effect of the present disclosure can be obtained.
A power storage device according to the present disclosure includes a first electrode having an elongated sheet shape, a second electrode having an elongated sheet shape, a separator interposed between the first electrode and the second electrode, and a non-aqueous electrolyte. The first electrode, the second electrode, and the separator constitute a columnar wound body. That is, the first electrode and the second electrode are wound with the separator interposed therebetween.
The first electrode includes a first current collector having an elongated sheet shape and a first active material layer supported on the first current collector. The second electrode includes a second current collector having an elongated sheet shape and a second active material layer supported on the second current collector.
The power storage device according to the present disclosure has a so-called end surface current collecting structure. That is, the power storage device according to the present disclosure may include a first current collecting plate electrically connected to the first electrode, and may further include a second current collecting plate electrically connected to the second electrode. The first current collecting plate is electrically connected to the first current collector. The second current collecting plate is electrically connected to the second current collector.
A first end (first end in a width direction) of the first current collector in a longitudinal direction is a first exposed part having no first active material layer, and the first exposed part protrudes from a first end surface of the wound body. Further, a first end (first end in a width direction) of the second current collector in a longitudinal direction is a second exposed part having no second active material layer, and the second exposed par may protrude from a second end surface of the wound body. Note that a second end of the first current collector in the longitudinal direction may be a third exposed part having no first active material layer, or a second end of the second current collector in the longitudinal direction may be a fourth exposed part having no second active material layer. In this case, the third exposed part and the fourth exposed part usually do not protrude from the end surface of the wound body, and are usually covered and protected by an insulating member.
A first tab extends from the first exposed part, and the first tab covers at least a part of the first exposed part on the inner peripheral side inside the first tab. The first tab is a part protruding from a part of the first end of the first current collector in the longitudinal direction (that is, a part of the first exposed part). The first current collecting plate is welded to a position of the first exposed part on the inner peripheral side inside the first tab via the first tab. A joint is formed between the first current collecting plate and the first exposed part, the joint corresponding to at least a part (usually a part) of the first current collecting plate. The joint may have, for example, a linear shape, a spot shape, or the like.
Note that the first tab may cover at least a part of the outer peripheral side inside the first tab and be welded to a position on the outer peripheral side outside the first tab via the first tab. Here, in a case where the first tab covers at least a part of the inner peripheral side of the first exposed part and is welded, the dead space in the center of the wound body can be easily reduced as compared with a case where the first tab covers at least a part of the outer peripheral side of the first exposed part and is welded. In the first electrode, the first tab may extend toward the inner peripheral side, and in the second electrode, the second tab may extend toward the outer peripheral side. This configuration makes it possible to suppress the deviation of the current collection path of the current flowing in the wound body.
The second tab may extend from the second exposed part, and the second tab may cover at least a part of the second exposed part on the inner peripheral side inside the second tab. The second tab is a part protruding from a part of the first end of the second current collector in the longitudinal direction (that is, a part of the second exposed part). In this case, the second current collecting plate is welded to the second exposed part on the inner peripheral side inside the second tab via the second tab. A joint is formed between the second current collecting plate and the second exposed part, the joint corresponding to at least a part (usually a part) of the second current collecting plate. Here, the joint may as well have, for example, a linear shape, a spot shape, or the like. Similar to the first tab, the second tab may also cover at least a part of the outer peripheral side outside the second tab and be welded to a position on the outer peripheral side outside the second tab via the second tab. Note that in the power storage device of the present disclosure, the tab may be formed on at least one of the first and the second electrodes. Therefore, the other of the first and the second electrodes may not have an exposed part or a tab and may be collected via a ribbon-shaped or linear lead member.
Hereinafter, the first electrode and the second electrode may be simply referred to as an electrode without distinction. In addition, the first current collector and the second current collector may be simply referred to as a current collector without distinction, and the first active material layer and the second active material layer may be simply referred to as an active material layer without distinction. In addition, the first current collecting plate and the second current collecting plate may be simply referred to as a current collecting plate without distinction. In addition, the first to the fourth exposed parts may be simply referred to as an exposed part without distinction. The first tab and the second tab may be simply referred to as a tab without distinction.
The power storage device according to the present disclosure has the following advantages.
First, the presence of the tab can prevent spatter generated on the current collecting plate during welding from entering the wound body. It is easy to suppress damage and micro-short circuit of the insulating member such as the separator caused by spatter or the like during welding on the end surface of the wound body.
Second, the presence of the tab facilitates positioning of each member on the end surface of the wound body in a manufacturing process of the power storage device, as compared with a power storage device in which a current collecting member interposed between a current collecting plate such as an auxiliary current collecting plate and the wound body is housed in a case separately from the current collecting plate and the wound body. Since the tab extends from the exposed part of the current collector, a positional relationship between the tab and the exposed part protruding from the end surface of the wound body is limited. Thus, misalignment of a positional relationship between the current collecting plate and the tab is also easily improved.
Third, the presence of the tab makes it possible to efficiently collect current to the current collecting plate from a more outer peripheral side (for example, even from the outermost periphery) or from a more inner peripheral side of the exposed part on the end surface of the wound body. For example, in a case where the tab extends from the exposed part on the outer peripheral side outside the midpoint of the line segment connecting the center of the end surface of the wound body and the point on the outermost periphery of the exposed part, the region of the exposed part on the inner peripheral side inside the tab is sufficiently larger. In particular, in a case where the tab extends from the outermost periphery of the exposed part, the tab can widely cover a region on the inner peripheral side of the exposed part inside the outermost periphery. That is, the current collecting plate can be welded to a part close to the outermost periphery of the exposed part via the tab. In other words, on the end surface of the wound body, current can be efficiently collected to the current collecting plate from a wide region including the outermost periphery of the electrode.
In addition, when the tab covers the inner peripheral side of the exposed part, the exposed part is urged to bend to fall toward the inner peripheral side. As a result, an area where the exposed part is covered with the tab is increased, and a welding area between the current collecting plate and the exposed part can also be increased. Therefore, the current collection efficiency is improved, and the mechanical strength of the welded part can be improved. Furthermore, in a case where spatter during welding of the current collecting plate and the exposed part is scattered, the exposed part bent to fall toward the inner peripheral side, further suppressing contact of the spatter with the separator or the like in the wound body.
The tab may be a member separate from or continuous with the exposed part of the current collector. The tab and the exposed part may be cut out from one material (for example, metal foil) integrally with the current collector. In other words, the tab may be formed of a part of the current collector.
The current collecting plate desirably has a considerable thickness from the viewpoint of securing the ability to collect a relatively large current. On the other hand, the most important role of the tab is to suppress spatter during welding, and the tab may be thinner than the current collecting plates as long as the tab can assist current collection. Thickness T1 of the current collecting plate is, for example, 100 μm or more and 1000 μm or less. On the other hand, thickness T2 of the tab is, for example, 5 μm or more and 100 μm or less. The ratio of thickness T1 of the current collecting plate to thickness T2 of the tab, T1/T2, is, for example, 20 or more and 60 or less.
A plurality of tabs may extend from the exposed part. In this case, the plurality of tabs may cover the inner peripheral side of the exposed part, for example, in a radially or an angularly equivalent arrangement. Providing the plurality of tabs improves the balance of current collection from the entire wound body, and improves the shape balance of the wound body as well. Note that the angularly equivalent arrangement is not strictly defined, but means that the arrangement is generally targeted with respect to the center. Specifically, the tabs adjacent to each other may be disposed to form a central angle (for example, 2≤n≤6) of 360/n±5°.
The number of tabs extending from the exposed part of the current collector may be one or more, but may be two or more and eight or less, two or more and six or less, three or more and six or less, or four. The number of tabs may be determined according to the number of welded parts (joints) welded to the exposed part on the inner peripheral side via the tabs. From the viewpoint of simplifying the welding process, it is desirable that the number of tabs extending from the exposed part be one or more and four or less.
For example, in a case where four tabs radially extend from the exposed part, the current collecting plate may have a cross shape as viewed from an axial direction of the wound body.
A linear first insulating layer may be formed at a boundary between the first exposed part and the first active material layer. Similarly, a linear second insulating layer may be formed at a boundary between the second exposed part and the second active material layer. That is, at least one of the boundary between the first exposed part and the first active material layer and the boundary between the second exposed part and the second active material layer may be protected by the linear first and/or the linear second insulating layers. In this case, it is possible to more reliably suppress a micro-short circuit due to spatter during welding. Similarly, from the viewpoint of more reliably suppressing the micro-short circuit, a third insulating layer may be formed on the second end of the first electrode in the longitudinal direction, and a fourth insulating layer may be formed on the second end of the second electrode in the longitudinal direction. Hereinafter, the first to the fourth insulating layers may be simply referred to as an insulating layer without distinction.
The tab may be formed by cutting out a part of the outermost periphery of the current collector, leaving a continuous part, and folding back the continuous part to the end surface side of the wound body. In this case, since two tabs are formed by the cutout portion of the current collector, waste of material is reduced.
The power storage device according to the present disclosure is suitable for being configured as, for example, a non-aqueous electrolyte secondary battery, an alkaline secondary battery, or a capacitor, and contributes to high output of the non-aqueous electrolyte battery. The non-aqueous electrolyte battery includes a lithium ion secondary battery, an all-solid-state battery, and the like. In this case, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode. One of the first current collector and the second current collector is, for example, a positive electrode current collector formed of aluminum or an aluminum alloy, and the other is, for example, a negative electrode current collector formed of copper or a copper alloy.
The exposed part of the current collector and the current collecting plate is joined by, for example, laser welding. For example, the laser may be radiated to a plurality of places radially from the opposite side of the surface of the current collecting plate facing the end surface of the wound body. At this time, it is necessary to align the current collecting plate and the tab, and such alignment can be easily performed.
Hereinafter, a lithium ion secondary battery which is an example of the power storage device according to the present exemplary embodiment will be described more specifically with reference to the drawings.
Hereinafter, one of the positive electrode and the negative electrode may be referred to as a first electrode and the other may be referred to as a second electrode, one of the positive electrode current collector and the negative electrode current collector may be referred to as a first current collector and the other may be referred to as a second current collector, one of the positive electrode active material layer and the negative electrode active material layer may be referred to as a first active material layer and the other may be referred to as a second active material layer, one of the positive electrode current collector exposed part and the negative electrode current collector exposed part may be referred to as a first exposed part and the other referred to as a second exposed part, one of the positive electrode current collecting plate and the negative electrode current collecting plate may be referred to as a first current collecting plate and the other referred to as a second current collecting plate, and one of the positive electrode current collecting tab and the negative electrode current collecting tab may be referred to as a first tab and the other may be referred to as a second tab.
Positive electrode 10 has an elongated sheet shape, and as shown in
A sheet-shaped metallic material is used for positive electrode current collector 11. The sheet-shaped metallic material may be a metal foil, a metal porous body, an etching metal, or the like. As the metallic material, aluminum, an aluminum alloy, nickel, titanium, or the like may be used. A thickness of positive electrode current collector 11 is, for example, 10 μm to 100 μm.
Positive electrode active material layer 12 contains, for example, a positive active material, a conductive material, and a binding material. Positive electrode active material layer 12 is obtained, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive material, and a binding material to both surfaces of positive electrode current collector 11, drying the applied film, and then rolling the applied film. The positive electrode active material is a material that occludes and releases lithium ions. Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides.
Part (a) of
Negative electrode 20 has an elongated sheet shape, and as shown in
A sheet-shaped metallic material is used for negative electrode current collector 21. The sheet-shaped metallic material may be a metal foil, a metal porous body, an etching metal, or the like. As the metallic material, copper, a copper alloy, nickel, stainless steel, or the like may be used. The thickness of negative electrode current collector 21 is, for example, in a range from 10 μm to 100 μm inclusive.
Negative electrode active material layer 22 contains, for example, a negative electrode active material, a conductive material, and a binding agent. Negative electrode active material layer 22 is obtained, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a conductive material, and a binding material to both surfaces of negative electrode current collector 21, drying the applied film, and then rolling the applied film. The negative electrode active material is a material that occludes and releases lithium ions. Examples of the negative electrode active material include a carbon material, a metal compound, an alloy, and a ceramic material.
Part (a) of
Wound body 100 in
As the separator, for example, a microporous membrane made of a resin such as polyolefin, a woven fabric, a nonwoven fabric, or the like may be used. The thickness of the separator is, for example, in a range from 10 μm to 300 μm inclusive, preferably from 10 μm to 40 μm inclusive.
When positive electrode current collecting tab 11tb or negative electrode current collecting tab 21tb is bent toward the inner peripheral side, positive electrode current collector exposed part 11x or negative electrode current collector exposed part 21x covered with positive electrode current collecting tab 11tb or negative electrode current collecting tab 21tb is bent to fall toward the inner peripheral side.
The protrusion length of each tab may be, for example, equal to or less than radius R of the end surface of the wound body, may be equal to or more than half of radius R, or may be equal to or more than ⅔ of radius R. In the shown example, the protrusion length of each tab is about ¾ of radius R.
A material of positive electrode current collecting plate 14 is, for example, aluminum, an aluminum alloy, titanium, stainless steel, or the like. The material of the positive electrode current collecting plate may be the same as the material of positive electrode current collector 11. The material of negative electrode current collecting plate 24 is, for example, copper, a copper alloy, nickel, stainless steel, or the like. The material of negative electrode current collecting plate 24 may be the same as the material of negative electrode current collector 21.
The non-aqueous electrolyte has lithium ion conductivity and contains a lithium salt and a non-aqueous solvent that dissolves the lithium salt.
Positive electrode current collector exposed part 11x is in contact with a surface of positive electrode current collecting plate 14 facing the end surface of wound body 100. Positive electrode current collecting plate 14 and the inner peripheral side of positive electrode current collector exposed part 11x are welded via positive electrode current collecting tab 11tb extending from the outermost periphery of positive electrode current collector exposed part 11x. The other end of tab lead 15 having one end connected to positive electrode current collecting plate 14 is connected to the inner surface of sealing plate 220. Therefore, sealing plate 220 functions as an external positive electrode terminal.
On the other hand, negative electrode current collector exposed part 21x is in contact with a surface of negative electrode current collecting plate 24 facing the end surface of wound body 100. Negative electrode current collecting plate 24 and the inner peripheral side of negative electrode current collector exposed part 21x are welded via negative electrode current collecting tab 21tb extending from the outermost periphery of negative electrode current collector exposed part 21x. Negative electrode current collecting plate 24 is welded to welding member 25 provided on an inner bottom surface of case 210. Therefore, case 210 functions as an external negative-electrode terminal.
Since the power storage device according to the present disclosure has high output, the power storage device according to the present disclosure is suitable for in-vehicle use, for example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-058190 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/013358 | 3/23/2022 | WO |
