WO2023176111A1

WO2023176111A1 - Power storage element

Info

Publication number: WO2023176111A1
Application number: PCT/JP2023/000573
Authority: WO
Inventors: 好浩山本; 尚樹岡田
Original assignee: 株式会社Ｇｓユアサ
Priority date: 2022-03-15
Filing date: 2023-01-12
Publication date: 2023-09-21

Abstract

This power storage element comprises: an electrode body that has a laminated part in which an electrode plate is laminated; and a conductive member that is welded to the laminated part. The electrode plate has a collector foil and an active material layer formed on the collector foil. The laminated part is formed by lamination of a non-formation part in which the active material layer is not formed on the collector foil. The laminated part and the conductive member have differing concentrations of an additive.

Description

Energy storage element

The present invention relates to a power storage element including an electrode body and a current collector.

BACKGROUND ART Conventionally, a power storage element is widely known which includes an electrode body in which electrode plates are laminated and a current collector, and in which the electrode body and the current collector are welded. For example, Patent Document 1 discloses a secondary battery (power storage element) in which an electrode body in which positive and negative electrodes are stacked and a current collector terminal (current collector) are welded together.

Japanese Patent Application Publication No. 2019-207749

In the above-mentioned conventional power storage element, when welding the electrode body and the current collector, due to thermal contraction of the melted part, breakage may occur at the boundary between the melted part and the unmelted part, resulting in cracks. This may reduce the reliability of the fused portion, such as reducing the bonding strength between the laminated portion and the current collector or increasing the resistance.

An object of the present invention is to provide a power storage element that can improve reliability in a molten part.

A power storage element according to an embodiment of the present invention includes an electrode body having a laminated part in which electrode plates are laminated, and a conductive member welded to the laminated part, and the electrode plate has a current collector foil. and an active material layer formed on the current collector foil, the laminated portion is formed by laminating non-formed portions of the current collector foil where the active material layer is not formed, The concentration of the additive is different between the laminated portion and the conductive member.

According to the power storage element according to one embodiment of the present invention, it is possible to improve reliability in the melted part.

FIG. 1 is a perspective view showing the appearance of a power storage element according to an embodiment. FIG. 2 is an exploded perspective view and a side view showing each component of the power storage device according to the embodiment. FIG. 3 is a perspective view showing the structure of the electrode body according to the embodiment. FIG. 4 is a cross-sectional view and a plan view showing a configuration in which a positive electrode current collector, a laminated portion of an electrode assembly, and a positive electrode backing plate according to the embodiment are welded together. FIG. 5 is a cross-sectional view showing a process of welding the positive electrode current collector, the laminated portion, and the positive electrode backing plate according to the embodiment. FIG. 6 is a schematic diagram showing the concentration distribution of additives within the melting zone according to the embodiment.

(1) A power storage element according to an embodiment of the present invention includes an electrode body having a laminated portion in which electrode plates are laminated, and a conductive member welded to the laminated portion, and the electrode plate includes: The current collecting foil includes a current collecting foil and an active material layer formed on the current collecting foil, and the laminated portion is formed by laminating non-forming portions in which the active material layer is not formed in the current collecting foil. The concentration of the additive is different between the laminated portion and the conductive member.

According to the power storage element according to an embodiment of the present invention, the concentration of the additive is different between the laminated portion formed by laminating the non-formed portion and the conductive member. As a result, the fused part where the laminated part and the conductive member are melted by welding has a different concentration of the additive from the unfused part other than the fused part in the laminated part. Since the properties of the melted part and the non-melted part can be made different, reliability in the melted part can be improved by selecting the type of additive.

(2) In the energy storage element according to (1) above, the fused portion where the laminated portion and the conductive member are melted may have a linear expansion coefficient smaller than that of the non-fused portion of the laminated portion other than the fused portion. good.

According to the electricity storage element described in (2) above, the coefficient of linear expansion of the melted part is smaller than that of the non-melted part due to the additive. Therefore, the amount of thermal contraction of the molten portion during solidification can be reduced. If the amount of thermal contraction of the fused portion is large, cracks are likely to occur at the boundary between the fused portion and the non-fused portion, but in this embodiment, the amount of thermal contraction of the fused portion is small, so the occurrence of cracks can be suppressed. Therefore, it is possible to improve the reliability in the melted part.

(3) In the electricity storage element described in (2) above, an additive that reduces the coefficient of linear expansion may be added to the conductive member in a larger amount than the laminated portion.

According to the electricity storage element described in (3) above, since the conductive member contains a larger amount of additive that reduces the coefficient of linear expansion than the laminated part, the molten part can be removed by simply welding the conductive member to the laminated part. The coefficient of linear expansion can be made smaller than that of the non-molten part.

(4) In the power storage element according to any one of (1) to (3) above, each of the current collector foil and the conductive member may be made of Al as a main material, and the additive may be Si.

The inventors of the present invention have found that when the laminated portion is a stack of current collector foils made of aluminum or aluminum alloy, cracks are likely to occur at the boundary between the fused portion and the non-fused portion. Furthermore, the inventors of the present invention have discovered that when Si is added to the conductive member, the coefficient of linear expansion is reduced, and it is possible to suppress the occurrence of cracks at the boundary between the melted part and the non-melted part. According to the electricity storage element described in (4) above, even if each of the current collector foil and the conductive member is made of Al as a main material, it is possible to suppress the occurrence of cracks at the boundary between the melted part and the non-melted part.

(5) In the energy storage element according to any one of (1) to (4) above, the concentration of the additive in the outer peripheral part of the fused part where the laminated part and the conductive member are melted is lower than the concentration of the additive in the center of the fused part. % of the additive.

According to the electricity storage element described in (5) above, the concentration of the additive in the outer peripheral part of the melting part is higher than the concentration of the additive in the central part of the melting part. Therefore, when the additive is an additive that reduces the coefficient of linear expansion, the coefficient of linear expansion is smaller in the outer peripheral portion, making it difficult to shrink due to heat. Therefore, it is possible to more reliably suppress the occurrence of cracks at the boundary between the fused portion and the unfused portion, that is, the boundary between the outer peripheral portion and the unfused portion.

(6) In the electricity storage element according to (4) or (5) above, the concentration of the Si in the conductive member may be 1.0% by mass or more and 25.0% by mass or less.

According to the electricity storage element described in (6) above, the effect of suppressing the occurrence of cracks at the boundary between the melted part and the non-melted part is particularly high.

(7) A power storage element according to another embodiment of the present invention includes an electrode body having a laminated portion in which electrode plates are laminated, and a conductive member welded to the laminated portion, wherein the electrode plate is , comprising a current collector foil and an active material layer formed on the current collector foil, and the laminated portion is formed by laminating non-formed portions of the current collector foil where the active material layer is not formed. The Si concentration of the conductive member is higher than the Si concentration of the laminated portion.

According to a power storage element according to another embodiment of the present invention, the concentration of Si in the conductive member is higher than the concentration of Si in the laminated portion in which the non-formed portion is laminated. As a result, the Si concentration in the fused portion where the laminated portion and the conductive member are melted by welding becomes higher than the Si concentration in the non-fused portion of the laminated portion other than the fused portion. Therefore, the occurrence of cracks at the boundary between the melted part and the non-melted part can be suppressed.

(8) In the energy storage element according to (7) above, even if the concentration of Si in the outer peripheral part of the melted part where the laminated part and the conductive member are melted is higher than the concentration of Si in the central part of the melted part. good.

According to the electricity storage element described in (8) above, the concentration of Si in the outer peripheral part of the molten part is higher than the concentration of Si in the central part of the molten part, so the coefficient of linear expansion is smaller in the outer periphery, and heat It becomes difficult to contract. Therefore, it is possible to more reliably suppress the occurrence of cracks at the boundary between the fused portion and the unfused portion, that is, the boundary between the outer peripheral portion and the unfused portion.

(9) In the energy storage element according to (7) or (8) above, the concentration of Si in the outer peripheral part of the laminated part and the melted part where the conductive member is melted is 1.0% by mass or more and 10.0% by mass. It may be the following.

According to the electricity storage element described in (9) above, the effect of suppressing the occurrence of cracks at the boundary between the melted part and the non-melted part is particularly high.

(Embodiment)
Hereinafter, a power storage element according to an embodiment of the present invention (including variations thereof) will be described with reference to the drawings. The embodiments described below are all inclusive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, manufacturing steps, order of manufacturing steps, etc. shown in the following embodiments are merely examples, and do not limit the present invention. In each figure, dimensions etc. are not strictly illustrated. In each figure, the same or similar components are designated by the same reference numerals.

In the following description and drawings, the direction of arrangement of a pair of electrode terminals (positive electrode and negative electrode, the same applies hereinafter) of a power storage element, the arrangement direction of a pair of current collectors, the arrangement direction of a pair of backing plates, or the arrangement direction of a pair of containers, The direction in which the short sides of the two sides face each other is defined as the X-axis direction. The direction in which the pair of long sides of the container face each other or the thickness direction of the container or the electrode body is defined as the Y-axis direction. The direction in which the current collector and the electrode body are arranged, the direction in which the current collector and the backing plate are arranged, the direction in which the electrode terminal and the electrode body are arranged, the direction in which the container body and the lid of the energy storage element are arranged, or the vertical direction. , defined as the Z-axis direction. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect with each other (orthogonal in this embodiment). Depending on the usage mode, the Z-axis direction may not be the vertical direction, but for convenience of explanation, the Z-axis direction will be described as the vertical direction below.

In the following description, the X-axis plus direction indicates the arrow direction of the X-axis, and the X-axis minus direction indicates the opposite direction to the X-axis plus direction. When simply referred to as the X-axis direction, it refers to both or one of the X-axis plus direction and the X-axis minus direction. The same applies to the Y-axis direction and the Z-axis direction. Expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where the directions or orientations are not strictly speaking. For example, when two directions are parallel, it does not only mean that the two directions are completely parallel, but also that they are substantially parallel, that is, they may differ by a few percent, for example. means. Furthermore, in the following description, when expressed as "insulation", it means "electrical insulation".

[1 General explanation of energy storage element]
First, a general description of the power storage element 10 in this embodiment will be given. FIG. 1 is a perspective view showing the appearance of a power storage element 10 according to an embodiment. FIG. 2 is an exploded perspective view and a side view showing each component of the power storage element 10 according to the embodiment. Specifically, (a) of FIG. 2 is an exploded perspective view of the power storage element 10. FIG. 2B is a side view showing the structure of the laminated portion 620 of the electrode body 600 sandwiched and welded between the current collector 500 and the backing plate 700, as viewed from the positive direction of the X-axis.

The power storage element 10 is a secondary battery (single battery) that can charge and discharge electricity, and specifically, is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. The power storage element 10 is used for power storage, power supply, or the like. Specifically, the power storage element 10 is used for driving or starting an engine of a moving object such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway. Used as batteries, etc. Examples of the above-mentioned vehicles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel oil, liquefied natural gas, etc.) vehicles. Examples of the above-mentioned railway vehicles for electric railways include electric trains, monorails, linear motor cars, and hybrid electric trains equipped with both a diesel engine and an electric motor. The power storage element 10 can also be used as a stationary battery used for home or business use.

The power storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The power storage element 10 may be not a secondary battery but a primary battery that allows the user to use the stored electricity without charging it. Power storage element 10 may be a battery using a solid electrolyte. The power storage element 10 may be a pouch type power storage element. In this embodiment, a flat rectangular parallelepiped-shaped (prismatic) power storage element 10 is illustrated, but the shape of the power storage element 10 is not limited to the rectangular parallelepiped shape, and may be a cylinder shape, an elongated cylinder shape, or a shape other than a rectangular parallelepiped. It may also have a prismatic shape or the like.

As shown in FIG. 1, the power storage element 10 includes a container 100, a pair (positive electrode and negative electrode) of electrode terminals 200, and a pair (positive electrode and negative electrode) of upper gaskets 300. As shown in FIG. 2, inside the container 100, there are a pair (positive electrode and negative electrode) of lower gaskets 400, a pair (positive electrode and negative electrode) of current collectors 500, an electrode body 600, and a pair (positive electrode and negative electrode) of lower gaskets 400. ) is accommodated. Although an electrolytic solution (non-aqueous electrolyte) is sealed inside the container 100, illustration thereof is omitted. The type of electrolytic solution is not particularly limited as long as it does not impair the performance of the power storage element 10, and various types can be selected. In addition to the above-mentioned components, a spacer disposed on the side or below the electrode body 600, an insulating film that wraps around the electrode body 600, etc. may be disposed.

The container 100 is a rectangular parallelepiped-shaped (prismatic or box-shaped) case that includes a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member that constitutes the main body of the container 100 and has a bottom. The container body 110 has a pair of short sides on both sides in the X-axis direction, a pair of long sides on both sides in the Y-axis direction, and a bottom surface on the negative Z-axis side. The lid 120 is a rectangular plate-like member that constitutes the lid of the container 100, and is arranged to extend in the X-axis direction in the Z-axis plus direction of the container body 110. The lid 120 includes a gas discharge valve 121 that releases the pressure when the pressure inside the container 100 increases excessively, a liquid injection part 122 for injecting electrolyte into the inside of the container 100, and the like. is provided.

With this configuration, the container 100 has a structure in which the inside is sealed by housing the electrode body 600 and the like inside the container body 110 and then joining the container body 110 and the lid 120 by welding or the like. ing. The material of the container 100 (container main body 110 and lid body 120) is not particularly limited, and can be made of weldable metal such as stainless steel, aluminum, aluminum alloy, iron, plated steel plate, etc., but resin can also be used. can.

The electrode body 600 is a power storage element (power generation element) that includes a positive electrode plate, a negative electrode plate, and a separator and can store electricity. The electrode body 600 is formed by winding layers arranged in such a manner that a separator is sandwiched between a positive electrode plate and a negative electrode plate. As a result, the non-formed portion (active material uncoated portion) of the positive electrode plate where no active material layer is formed is laminated to form the laminated portion 620 of the positive electrode. Similarly, portions of the negative electrode plate where no active material layer is formed (active material uncoated portions) are laminated to form a laminated portion 630 of the negative electrode. That is, the electrode body 600 includes an electrode body main body part 610 and

laminated parts

620 and 630 that protrude from a part of the electrode body main body part 610 in the Z-axis positive direction and extend in the Y-axis positive direction. In this embodiment, the electrode body 600 is a wound type electrode body having an oval shape when viewed from the Z-axis direction, but it may have an elliptical shape, a circular shape, or any other shape when viewed from the Z-axis direction. But that's fine. A detailed description of the configuration of the electrode body 600 will be given later.

The electrode terminal 200 is a terminal member (positive electrode terminal and negative electrode terminal) that is electrically connected to the electrode body 600 via the current collector 500. The electrode terminal 200 is a metal terminal for guiding electricity stored in the electrode body 600 to the external space of the power storage element 10 and for introducing electricity into the internal space of the power storage element 10 to store electricity in the electrode body 600. It is a manufactured member. The electrode terminal 200 is made of a conductive member such as metal such as aluminum, aluminum alloy, copper, or copper alloy. The electrode terminal 200 is connected (joined) to the current collector 500 and attached to the lid 120 by caulking or the like.

Specifically, the electrode terminal 200 has a shaft portion 201 (rivet portion) extending downward (in the negative Z-axis direction). Then, the shaft portion 201 is inserted into the through hole 301 of the upper gasket 300, the through hole 123 of the lid 120, the through hole 401 of the lower gasket 400, and the through hole 501 of the current collector 500, and is caulked. . Thereby, the electrode terminal 200 is fixed to the lid 120 together with the upper gasket 300, the lower gasket 400, and the current collector 500. The method of connecting (joining) the electrode terminal 200 and the current collector 500 is not limited to caulking, but may include welding such as ultrasonic welding, laser welding, or resistance welding, or a mechanical method other than caulking such as screw fastening. Bonding or the like may also be used.

The current collector 500 is a flat and rectangular current collecting member (a positive electrode current collector 500a and a negative electrode current collector 500b) that electrically connects the electrode body 600 and the electrode terminal 200. Current collector 500 is an example of a conductive member according to the present invention. The positive electrode current collector 500a is connected (joined) to the positive electrode laminated portion 620 of the electrode body 600 by welding, and as described above, is joined to the positive electrode terminal 200 by caulking or the like. The negative electrode current collector 500b is connected (joined) to the negative electrode laminated portion 630 of the electrode body 600 by welding, and as described above, is joined to the negative electrode terminal 200 by caulking or the like. The positive electrode current collector 500a is made of a material in which additives are added to aluminum. Any additive may be used as long as it makes the coefficient of linear expansion smaller after addition than before addition. For example, by adding Si (silica) to aluminum, it is possible to make the linear expansion coefficient after addition smaller than the linear expansion coefficient before addition. In the present embodiment, the positive electrode current collector 500a is made of an aluminum alloy (Al-Si alloy) in the 4000 range under the international aluminum alloy name, and contains 4.5 to 13.5 mass% of Si. There is. The Si content of the positive electrode current collector 500a is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, and 4. It is particularly preferable that the amount is .0% by mass or more. The Si content of the positive electrode current collector 500a is preferably 25.0% by mass or less, more preferably 20.0% by mass or less, even more preferably 15.0% by mass or less, 13 It is particularly preferable that the amount is .5% by mass or less. That is, the Si content of the positive electrode current collector 500a is preferably 1.0% by mass or more and 25.0% by mass or less, more preferably 2.0% by mass or more and 20.0% by mass or less, It is more preferably 3.0% by mass or more and 15.0% by mass or less, and particularly preferably 4.0% by mass or more and 13.5% by mass or less. The negative electrode current collector 500b is made of metal such as copper or copper alloy, like the later-described negative electrode current collector foil of the electrode body 600.

The patch plate 700 is placed at a position sandwiching the

laminated portion

620 or 630 of the electrode body 600 between the current collector 500 and the

laminated portion

620 or 630 between the current collector 500 and the

laminated portion

620 or 630. This is an example of a member (positive electrode patch plate 700a, negative electrode patch plate 700b) that is joined (welded) to

section

620 or 630. Current collector 500 is an example of a conductive member according to the present invention. In the present embodiment, the backing plate 700 is a flat and rectangular member, and is arranged in the negative Z-axis direction of the

laminated portion

620 or 630, and is connected to the laminated portion 620 or the current collector 500 in the Z-axis direction. 630 (see FIG. 2(b)). Like the positive electrode current collector 500a, the positive electrode backing plate 700a is made of an aluminum alloy (Al-Si alloy) in the 4000 series under the international aluminum alloy name, and contains 4.5 to 13.5 mass% of Si. ing,. The Si content of the positive electrode backing plate 700a is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, and 4. It is particularly preferable that the content is 0% by mass or more. The Si content of the positive electrode backing plate 700a is preferably 25.0% by mass or less, more preferably 20.0% by mass or less, even more preferably 15.0% by mass or less, 13. It is particularly preferable that the content is 5% by mass or less. That is, the Si content of the positive electrode backing plate 700a is preferably 1.0% by mass or more and 25.0% by mass or less, more preferably 2.0% by mass or more and 20.0% by mass or less, and 3. It is more preferably .0 mass % or more and 15.0 mass % or less, and particularly preferably 4.0 mass % or more and 13.5 mass % or less. The negative electrode contact plate 700b is made of metal such as copper or copper alloy, like the negative electrode current collector foil of the electrode body 600.

With such a configuration, the current collector 500, the stacked

portion

620 or 630, and the patch plate 700 are welded with the stacked

portion

620 or 630 of the electrode body 600 sandwiched between the current collector 500 and the patch plate 700. , a melted part 800 (see FIG. 2(b)) is formed. In this embodiment, one melting section 800 is formed for one current collector 500, but the number of melting sections 800 is not particularly limited. A detailed explanation of the configuration in which the stacked

portion

620 or 630 of the current collector 500 and the electrode body 600 and the backing plate 700 are welded will be described later.

The upper gasket 300 is a flat insulating sealing member ( gasket). The lower gasket 400 is a flat insulating sealing member (gasket) that is disposed between the lid 120 and the current collector 500, and insulates and seals between the lid 120 and the current collector 500. ). The upper gasket 300 and the lower gasket 400 are made of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), Polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), ABS resin, or their It is made of an insulating resin such as a composite material.

[2 Description of the structure of the electrode body]
Next, the configuration of the electrode body 600 will be described in detail. FIG. 3 is a perspective view showing the configuration of an electrode body 600 according to the embodiment. Specifically, FIG. 3(a) shows the structure of the electrode body 600 shown in FIG. 2 in a partially unfolded state, and FIG. 3(b) shows the structure of the electrode body 600 after winding. The configuration of a body 600 is shown.

As shown in FIG. 3A, the electrode body 600 is formed by alternately stacking and winding a positive electrode plate 640, a negative electrode plate 650, and separators 661 and 662. That is, the electrode body 600 is formed by stacking a positive electrode plate 640, a separator 661, a negative electrode plate 650, and a separator 662 in this order and winding them.

The positive electrode plate 640 is an electrode plate (electrode plate) in which a positive electrode active material layer 642 is formed on the surface of a positive electrode current collector foil 641. The positive electrode current collector foil 641 is an example of a current collector foil (base material) according to the present invention, and the positive electrode active material layer 642 is an example of an active material layer (mixture material layer) according to the present invention. The positive electrode current collector foil 641 is a long strip-shaped metal foil made of aluminum, aluminum alloy, or the like. In other words, the main material of the positive electrode current collector foil 641 is aluminum (Al). In the positive electrode current collector foil 641, the concentration of the additive added in the positive electrode current collector 500a and the positive electrode patch plate 700a is 0.3% or less.

The negative electrode plate 650 is an electrode plate (electrode plate) in which a negative electrode active material layer 652 is formed on the surface of a negative electrode current collector foil 651, which is a long strip-shaped metal foil made of copper, copper alloy, or the like. As the negative electrode current collector foil, materials that are stable against oxidation-reduction reactions during charging and discharging can be used, such as nickel, iron, stainless steel, titanium, fired carbon, conductive polymers, conductive glass, and Al-Cd alloys. Known materials can also be used as appropriate. As the positive electrode active material used in the positive electrode active material layer 642 and the negative electrode active material used in the negative electrode active material layer 652, any known material can be used as long as it is a positive electrode active material and negative electrode active material that can intercalate and extract lithium ions. can be used.

For example, as the positive electrode active material, polyanionic compounds such as LiMPO ₄ , LiMSiO ₄ , LiMBO ₃ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), lithium titanate, Spinel-type lithium manganese oxides such as LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ , LiMO ₂ (M is one or more transition metals selected from Fe, Ni, Mn, Co, etc.) lithium transition metal oxides such as lithium transition metal oxides, etc. can be used. Examples of negative electrode active materials include lithium metal, lithium alloys (lithium metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and Wood alloys). , alloys that can absorb and release lithium, carbon materials (e.g. graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature firing carbon, amorphous carbon, etc.), silicon oxides, metal oxides, lithium metal oxides ( (Li ₄ Ti ₅ O ₁₂ , etc.), polyphosphoric acid compounds, or compounds of transition metals and Group 14 to Group 16 elements, such as Co ₃ O ₄ and Fe ₂ P, which are generally called conversion negative electrodes. .

The separators 661 and 662 are microporous sheets made of resin. As the material for the separators 661 and 662, any known material can be used as appropriate, as long as it does not impair the performance of the power storage element 10. For example, as the separators 661 and 662, a woven fabric or nonwoven fabric insoluble in organic solvents, a synthetic resin microporous membrane made of polyolefin resin such as polyethylene, or the like can be used.

The positive electrode plate 640 has a plurality of rectangular tabs 643 protruding in the Z-axis plus direction at the end in the Z-axis plus direction, and the plurality of tabs 643 are arranged in a stacked state in the Y-axis direction. be done. Similarly, the negative electrode plate 650 has a plurality of rectangular tabs 653 protruding in the Z-axis plus direction at the end in the Z-axis plus direction, and the plurality of tabs 653 are stacked in the Y-axis direction. placed in the state. The

tabs

643 and 653 are portions where the active material layer (mixture material layer) is not formed and the current collector foil is exposed. That is, the tab 643 of the positive electrode plate 640 is an example of a non-formed portion according to the present invention. The shapes of

tabs

643 and 653 are not particularly limited.

Then, as shown in FIG. 3(b), the plurality of stacked tabs 643 are bundled to form a stacked portion 620 that extends in the positive direction of the Z-axis. Similarly, a plurality of laminated tabs 653 are bundled to form a laminated portion 630 that extends in the positive direction of the Z-axis. These

laminated parts

620 and 630 are, for example, welded together with the current collector 500 and the patch plate 700 while being sandwiched between the current collector 500 and the patch plate 700 in the Y-axis direction, and then the current collector 500 and the patch plate 700 are welded together. It is bent along with 700 in the positive direction of the Y axis. As a result, as shown in FIG. 2B, the

laminated parts

620 and 630 are sandwiched between the current collector 500 and the backing plate 700 in the Z-axis direction. The

laminated parts

620 and 630 may not be bent in the positive Y-axis direction, but may be placed between the current collector 500 and the backing plate 700 in the Y-axis direction.

The electrode body main body part 610 is a part that constitutes the main body of the electrode body 600, and specifically, it is a part of the electrode body 600 other than the

laminated parts

620 and 630. The electrode main body portion 610 is an elongated columnar or elongated cylindrical portion formed by winding the portions of the positive electrode plate 640 and the negative electrode plate 650 on which the active material layers are formed, and the separators 661 and 662. The electrode body 600 is provided with a non-formed part (active material uncoated part) in which no active material layer is formed at the end of the electrode plate (positive electrode plate 640 or negative electrode plate 650), and a tab is formed from the active material layer non-formed part. In the case of a configuration in which the tab (tab 643 or 653) extends, the electrode main body portion 610 does not include the non-formed portion. That is, in the case of this configuration, the laminated portion 620 (or 630) is a portion where a plurality of tabs 643 (or a plurality of tabs 653) and the non-formed portion are laminated. As a result, the electrode main body section 610 has a pair of curved electrode body curved parts 611 on both sides in the X-axis direction, and a pair of flat shaped electrode body curved parts 611 connecting the pair of electrode body curved parts 611 on both sides in the Y-axis direction. The electrode body has a flat portion 612.

[3 Description of the welding configuration of the positive electrode current collector, laminated portion, and positive electrode backing plate]
Next, the configuration in which the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a are welded together will be described in detail. The configuration in which the negative electrode current collector 500b, the laminated portion 630, and the negative electrode backing plate 700b are welded is basically the same, so a description of this configuration will be omitted.

FIG. 4 is a cross-sectional view and a plan view showing a configuration in which a positive electrode current collector 500a, a laminated portion 620 of an electrode body 600, and a positive electrode backing plate 700a according to the embodiment are welded together. Specifically, (a) in FIG. 4 shows the welded state of the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a in a plane that includes the central axis of the welded portion 800 and is parallel to the YZ plane. FIG. 3 is a cross-sectional view showing the configuration when cut at In FIG. 4(a), for convenience of explanation, the top and bottom of FIG. 2 are reversed, and the negative Z-axis direction is shown facing upward. FIG. 4B is a plan view (top view, bottom view in FIG. 2) showing the configuration of FIG. 4A when viewed from the negative Z-axis direction (above, bottom in FIG. 2).

FIG. 5 is a cross-sectional view showing a process of welding the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a according to the embodiment. Specifically, FIG. 5(a) shows the state before welding the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a, and FIG. 5(b) shows the positive electrode current collector 500a, The state after welding the laminated part 620 and the positive electrode backing plate 700a is shown. (a) and (b) of FIG. 5 are diagrams corresponding to (a) of FIG. 4.

As shown in FIG. 4, the positive electrode current collector 500a and the backing plate 700 are arranged at positions sandwiching the laminated part 620 in which the tab 643 of the positive electrode plate 640 of the electrode body 600 is laminated, and together with the laminated part 620. Welded. As a result, a melted portion 800 is formed in the positive electrode current collector 500a, the laminated portion 620, and the positive electrode backing plate 700a, in which the positive electrode current collector 500a, the laminated portion 620, and the backing plate 700a are melted.

The melted part 800 is a part where the positive electrode current collector 500a, the laminated part 620, and the positive electrode backing plate 700a are melted and solidified by laser welding. Specifically, as shown in FIG. 5A, the flat plate-shaped portion (flat plate portion) of the positive electrode current collector 500a and the flat plate-shaped portion (flat plate portion) of the positive electrode backing plate 700a are connected to the laminated portion 620. They are arranged with a flat part (flat part) sandwiched between them. Then, these parts are irradiated with laser light L from the negative Z-axis direction. As a result, as shown in FIG. 5B, the flat plate portion of the positive electrode current collector 500a, the flat portion of the laminated portion 620, and the flat plate portion of the positive electrode backing plate 700a are melted to form a melted portion 800. Ru.

Here, as described above, the laminated portion 620 of the electrode body 600 is formed by laminating a plurality of tabs 643 on which the positive electrode active material layer 642 is not formed. Since each tab 643 is a part of the positive electrode current collector foil 641, similarly to the positive electrode current collector foil 641, the laminated portion 620 is also formed mainly of aluminum, and the concentration of additives is low. On the other hand, the positive electrode current collector 500a and the positive electrode backing plate 700a are mainly made of aluminum, and additives are added thereto. That is, the laminated part 620 in which the concentration of the additive is lower than that of the positive electrode current collector 500a and the positive electrode patch plate 700a, and the positive electrode current collector 500a and the positive electrode patch plate 700a containing the additive are mixed to form the melted part 800. is formed. Therefore, the melting zone 800 exhibits characteristics caused by the additive.

Specifically, in the melted zone 800, Si added to the positive electrode current collector 500a and the positive electrode backing plate 700a is mixed with aluminum, so the coefficient of linear expansion is low due to Si. On the other hand, the portion of the laminated portion 620 other than the melted portion 800 is a non-melted portion 810 that is not melted by laser welding. In the non-melted part 810, the concentration of Si is lower than that in the fused part 800, so that characteristics caused by Si are difficult to exhibit. As a result, the coefficient of linear expansion of the melted part 800 becomes smaller than that of the non-melted part 810, and the amount of thermal contraction of the melted part 800 during solidification becomes smaller. If the amount of thermal contraction of the fused portion 800 is large, cracks are likely to occur at the boundary between the fused portion 800 and the non-fused portion 810, but in this embodiment, the amount of thermal contraction of the fused portion 800 is small, so that the generation of cracks can be suppressed. I can do it.

The coefficient of linear expansion is measured by the following method. The power storage element 10 is disassembled, and the melted portion 800 and the unmelted portion 810 are taken out. The melted portion 800 and non-melted portion 810 taken out are immersed in epoxy resin and hardened. The cured fused portion 800 and non-fused portion 810 are cut in a direction parallel to the lamination direction of the electrode plates in the laminated portion 620. Polish the cut section to make it smooth. The smoothed cross section is placed in a high-temperature X-ray diffraction device together with a heater to measure changes in the lattice constant with respect to temperature, and the linear expansion coefficients of the melted part 800 and the non-melted part 810 are calculated, respectively.

FIG. 6 is a schematic diagram showing the concentration distribution of additives within the melting zone 800 according to the embodiment. The concentration of the additive is measured by the following method. The power storage element 10 is disassembled, and the laminated portion 620 and the conductive member (the positive electrode current collector 500a and the positive electrode backing plate 700a) are taken out. The laminated portion 620 and the conductive member taken out are immersed in epoxy resin and hardened. The cured laminated portion 620 and the conductive member are cut in a direction parallel to the stacking direction of the electrode plates in the laminated portion 620 in a region including the melted portion 800. Polish the cut section to make it smooth. The concentration of the additive in the smoothed cross section is measured using an electron probe microanalyzer (EPMA). In the melt zone 800 of FIG. 6, the color density indicates the additive concentration. In other words, the darker the color, the higher the concentration of the additive. As shown in FIG. 6, the concentration of the additive at the outer periphery of the melting section 800 is higher than the concentration of the additive at the center of the melting section 800. In other words, the outer peripheral portion of the fusion zone 800 has a smaller coefficient of linear expansion and is less susceptible to thermal contraction. Therefore, it is possible to more reliably suppress the occurrence of cracks at the boundary between the fused portion 800 and the non-fused portion 810, that is, the boundary between the outer peripheral portion of the fused portion 800 and the non-fused portion 810. The outer periphery of the fusion zone 800 is a region within a length of 20% of the maximum depth of the fusion zone 800 from the periphery in the cross section of the fusion zone 800 . The central portion of the melting section 800 is a region other than the outer circumference in the cross section of the melting section 800. The maximum depth of the fusion zone 800 is the maximum length of the fusion zone 800 in the stacking direction of the electrode plates. The concentration of the additive in the outer periphery of the melting section 800, the center section of the melting section 800, the laminated section 620, or the conductive member is as follows: It is the average value of the additive concentration in each member.

The Si content in the outer peripheral portion of the melting zone 800 is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, It is particularly preferable that the content is 4.0% by mass or more. The Si content in the outer peripheral portion of the melting zone 800 is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, and even more preferably 8.0% by mass or more. That is, the Si content in the outer peripheral portion of the melting zone 800 is preferably 1.0% by mass or more and 10.0% by mass or less, and more preferably 2.0% by mass or more and 9.0% by mass or less. , more preferably 3.0% by mass or more and 8.0% by mass or less, particularly preferably 4.0% by mass or more and 8.0% by mass or less.

[4 Explanation of effects]
As described above, according to the power storage element 10 according to the embodiment of the present invention, the laminated portion 620 in which the non-formed portions are laminated and the conductive member (the positive electrode current collector 500a and the positive electrode backing plate 700a), Since the concentrations of the additives are different, the concentrations of the additives will be different between the melting section 800 and the non-melting section 810. In this embodiment, the concentration of the additive in the laminated portion 620 in which the non-formed portion (tab 643) of the positive electrode current collector foil 641 is laminated is lower than the concentration of the additive in the conductive member. When a conductive member to which an additive is added is welded to such a laminated portion 620 to form a fused portion 800, the concentration of the additive in the fused portion 800 increases. In other words, although the laminated portion 620 alone could not exhibit the characteristics, the melting portion 800 can exhibit the characteristics caused by the additive. On the other hand, in the non-melting part 810, the concentration of the additive is low, so that the properties caused by the additive are not easily exhibited. In this way, even if the concentration of the additive in the current collector foil is low, it is possible to make the characteristics of the melted part 800 and the non-melted part 810 different, so if the type of additive is selected, the properties of the melted part 800 and the unmelted part 810 can be made different. It is possible to increase the reliability at 800.

In the electricity storage element 10 described above, the linear expansion coefficient of the fused portion 800 is smaller than that of the non-fused portion 810 due to the additive. Therefore, the amount of thermal contraction of the melted portion 800 during solidification can be reduced. If the amount of thermal contraction of the fused portion 800 is large, cracks are likely to occur at the boundary between the fused portion 800 and the non-fused portion 810, but in this embodiment, the amount of thermal contraction of the fused portion 800 is small, so that the generation of cracks can be suppressed. I can do it. Therefore, reliability in the melting section 800 can be improved.

Since the conductive member (the positive electrode current collector 500a and the positive electrode backing plate 700a) contains more additives that reduce the coefficient of linear expansion than the laminated part 620, simply welding the conductive member to the laminated part 620 melts the conductive member. The coefficient of linear expansion of the portion 800 can be made smaller than that of the unfused portion.

Here, if Si is added to Al, the linear expansion coefficient will decrease. Therefore, in this embodiment, each of the positive electrode current collector foil 641 and the conductive member is made of Al as a main material, and Si is used as an additive. In other words, an aluminum alloy (Al--Si alloy) in the 4000 range under the International Aluminum Alloy Name can be used as the conductive member, and the conductive member can be easily manufactured.

Since the concentration of the additive in the outer peripheral part of the melting section 800 is higher than the concentration of the additive in the central part of the melting part 800, the coefficient of linear expansion is smaller in the outer peripheral part, making it difficult to thermally shrink. Therefore, it is possible to more reliably suppress the occurrence of cracks at the boundary between the fused portion 800 and the unfused portion 810, that is, the boundary between the outer peripheral portion and the unfused portion 810.

[5 Description of modification]
Although the power storage element 10 according to the present embodiment has been described above, the present invention is not limited to the above embodiment. The embodiments disclosed this time are illustrative in all respects and are not restrictive, and the scope of the present invention includes all changes within the meaning and scope equivalent to the scope of the claims. .

In the embodiment described above, Si is exemplified as an additive contained in the conductive member (the positive electrode current collector 500a and the positive electrode backing plate 700a), and the case where the characteristics caused by this Si are exhibited in the fusion zone 800 is exemplified. . In the above embodiment, Si is exemplified as an additive that can adjust the coefficient of linear expansion, but additives other than Si may be used as long as they can adjust the coefficient of linear expansion.

In the above embodiment, the electrode body 600 is a wound type electrode body in which the winding axis is perpendicular to the lid body 120, but it is a stacked type electrode body in which flat plates are laminated, or a stack type in which plate-like plates are laminated. Alternatively, a bellows-shaped electrode body in which a separator is folded into a bellows shape may be used. The electrode body 600 may be a wound type electrode body in which the winding axis is parallel to the lid body 120. The

laminated parts

620 and 630 may be the ends of the electrode body 600 that protrude from the entire electrode body part 610 of the electrode body 600 instead of the tabs.

In the above embodiment, the fused portion 800 is formed by laser welding, but it may be formed by a joining method other than laser welding, such as resistance welding.

In the embodiment described above, the melting part 800 has a circular shape when viewed from the Z-axis direction, but it may have a shape other than a circular shape such as an elliptical shape, an elliptical shape, a polygonal shape, etc., or a circular shape, etc. It may be annular.

In the embodiment described above, the molten part 800 is formed so as to penetrate through the backing plate 700 in the thickness direction (Z-axis direction). It may be formed in a state. In this case, the melted portion 800 does not need to penetrate the backing plate 700 in the thickness direction (Z-axis direction). That is, the melted portion 800 of the current collector 500, the laminated portion 620, and the backing plate 700 may be formed by irradiating laser light from the current collector 500 side (Z-axis positive direction).

In the above embodiment, the case where the additive is added to each of the positive electrode current collector 500a and the positive electrode patch plate 700a is illustrated, but the additive is added only to one of the positive electrode current collector and the positive electrode patch plate. It's okay.

In the above embodiment, the current collector 500 and the backing plate 700 are welded to each of the

laminated parts

620 and 630, but only the current collector may be welded to the laminated part. In this case, for example, an additive may be added to the positive electrode current collector. The power storage element 10 does not need to include the backing plate 700.

In the above embodiment, the case where the concentration of the additive in the outer peripheral part of the melting part 800 is higher than the concentration of the additive in the central part of the melting part 800 is exemplified. However, the concentration distribution of the additive within the melt zone may be arbitrary. For example, the concentration of the additive at the outer periphery of the melting zone may be lower than the concentration of the additive at the center of the melting zone. Furthermore, the concentration distribution of the additive may be uniform within the melting zone, or the concentration distribution of the additive may be irregular within the melting zone.

Embodiments constructed by arbitrarily combining the components included in the above embodiments and their modifications are also included within the scope of the present invention.

The present invention can be applied to power storage elements such as lithium ion secondary batteries.

10 Energy storage element 100 Container 110 Container body 120 Lid 121 Gas discharge valve 122 Liquid injection part 123 Through hole 200 Electrode terminal 201 Shaft 300

Upper gasket

301, 401, 501 Through hole 400 Lower gasket 500 Current collector 500a Positive electrode current collector (Conductive member)
500b Negative electrode current collector 600 Electrode body 610 Electrode body main body part 611 Electrode body curved part 612 Electrode body

flat part

620, 630 Laminated part 640 Positive electrode plate (electrode plate)
641 Positive electrode current collector foil (current collector foil)
642 Positive electrode active material layer (mixture material layer)
643, 653 Tab (non-formed part)
650 Negative electrode plate 651 Negative electrode current collector foil 652 Negative electrode active material layers 661, 662 Separator 700 Backing plate 700a Positive electrode backing plate (conductive member)
700b Negative electrode patch plate 800 Melting section 810 Non-melting section

Claims

an electrode body having a laminated portion in which electrode plates are laminated;
a conductive member welded to the laminated portion,
The electrode plate has a current collector foil and an active material layer formed on the current collector foil,
The laminated portion is formed by laminating non-formed portions in which the active material layer is not formed in the current collector foil,
The laminated portion and the conductive member have different concentrations of additives.
The energy storage element according to claim 1 , wherein a melted portion where the laminated portion and the conductive member are melted has a linear expansion coefficient smaller than a non-melted portion of the laminated portion other than the melted portion.
The electricity storage element according to claim 2, wherein the conductive member contains a larger amount of an additive that reduces the coefficient of linear expansion than the laminated portion.
Each of the current collector foil and the conductive member is made of Al as a main material,
The electricity storage element according to claim 1 or 2, wherein the additive is Si.
The power storage element according to claim 1, wherein the concentration of the additive in the outer peripheral part of the melted part where the laminated part and the conductive member are melted is higher than the concentration of the additive in the central part of the melted part.
The electricity storage element according to claim 4, wherein the concentration of the Si in the conductive member is 1.0% by mass or more and 25.0% by mass or less.
an electrode body having a laminated portion in which electrode plates are laminated;
a conductive member welded to the laminated portion,
The electrode plate has a current collector foil and an active material layer formed on the current collector foil,
The laminated portion is formed by laminating non-formed portions in which the active material layer is not formed in the current collector foil,
The concentration of Si in the conductive member is higher than the concentration of Si in the laminated portion.
Energy storage element.
The electricity storage element according to claim 7, wherein the concentration of Si in the outer peripheral part of the melted part where the laminated part and the conductive member are melted is higher than the concentration of Si in the central part of the melted part.
The power storage element according to claim 7 or 8, wherein the concentration of Si in the outer peripheral portion of the laminated portion and the melted portion where the conductive member is melted is 1.0% by mass or more and 10.0% by mass or less.