Secondary battery
The secondary battery design addresses the issue of tab lead breakage due to expansion and contraction by incorporating a laminate structure with slidable contact points between current collector tabs and leads, enhancing durability and minimizing size constraints.
Patent Information
- Application Number
- JP2023196794
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-20
- Publication Date
- 2025-05-30
AI Technical Summary
Existing secondary batteries face challenges in minimizing battery size while preventing tab lead breakage due to expansion and contraction during charging and discharging, which also affects durability.
The secondary battery design includes a laminate structure with expandable and contractible electrode layers, and current collector tabs with slidable contact points to reduce tensile stress and prevent breakage.
This configuration effectively suppresses breakage of tab leads and enhances durability by allowing the current collector tabs and leads to slide relative to each other during expansion and contraction.
Smart Images
Figure 2025083106000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a secondary battery that expands and contracts during charging and discharging.
Background Art
[0002] A secondary battery is known in which a plurality of flat plate-shaped positive electrodes, a solid electrolyte membrane, and negative electrodes are laminated and housed in a container. In such a secondary battery, current collectors are provided on the positive electrode and the negative electrode, respectively, and a plurality of positive electrode tab leads and negative electrode tab leads are bundled together and connected to a positive electrode terminal and a negative electrode terminal. In such a secondary battery using a solid electrolyte, the thickness of the battery changes due to the expansion and contraction of the electrode layer during charging and discharging. For this reason, for example, when the thickness of the battery increases due to charging and a tension exceeding the allowable stress is applied to the current collector, the current collector may break.
[0003] Patent Document 1 discloses a configuration for suppressing breakage of the current collector due to a change in the thickness of the battery during use. Specifically, by providing a bend in the tab lead to have an extra length, when the distance from the connection portion between the electrode of the battery and the tab lead to the connection portion between the tab lead and the terminal of each electrode increases due to an increase in thickness, the extra length compensates for the elongation between the connection portions, and reduces the tension applied to the tab lead.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, in the configuration of the above-mentioned document, the greater the number of stacked layers, the longer the extra length needs to be, and it is difficult to miniaturize the battery in order to secure space for the bent tab lead. In addition, since bending stress is repeatedly generated at each connection part by repeatedly charging and discharging, there is room for improvement in terms of durability.
[0006] Therefore, an object of the present invention is to provide a secondary battery that can suppress breakage of a tab lead caused by expansion and contraction in a secondary battery in which an electrode expands and contracts during charge and discharge.
Means for Solving the Problems
[0007] According to an aspect of the present invention, there is provided a secondary battery including a laminate in which a positive electrode layer and a negative electrode layer are laminated with an electrolyte layer interposed therebetween, and an exterior body that houses the laminate, and at least the negative electrode layer among the positive electrode layer and the negative electrode layer expands and contracts as lithium ions as carrier ions move. This secondary battery includes a current collector foil having a lead portion extending in a direction orthogonal to the stacking direction of the laminate from the positive electrode layer and the negative electrode layer, and a current collector tab having a first flat portion facing the side surface from which the lead portion of the laminate is taken out and a second flat portion extending in a direction away from the side surface, and the first flat portion of the current collector tab and the lead portion are in slidable contact with each other.
Effects of the Invention
[0008] According to the above aspect, in a secondary battery in which an electrode expands and contracts during charge and discharge, it is possible to provide a secondary battery that can suppress breakage of a tab lead caused by expansion and contraction.
Brief Description of the Drawings
[0009]
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[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011] First, the configuration and problems of a conventionally known laminated secondary battery 1 will be described.
[0012] FIG. 1 is a cross-sectional view along the stacking direction of a conventional secondary battery 1. Here, an all-solid-state battery in which the negative electrode active material is lithium metal, the electrolyte layer is a solid electrolyte, and the electrolyte contained in the electrolyte layer and the positive electrode layer is a sulfide solid electrolyte will be described as an example.
[0013] The secondary battery 1 has a structure in which a laminate 2 in which a charge-discharge reaction progresses is sealed inside a laminate film 3 as an exterior body. The laminate 2 is formed by laminating a flat substantially rectangular positive electrode layer 14, an electrolyte layer 4, and a negative electrode layer 15 in their respective thickness directions. The positive electrode layer 14 has a configuration in which positive electrode active material layers 8 containing a positive electrode active material are disposed on both surfaces of a positive electrode current collector foil 7. The negative electrode layer 15 has a structure in which negative electrode active material layers 6 containing a negative electrode active material are disposed on both surfaces of a negative electrode current collector foil 5. Specifically, one positive electrode active material layer 8 and the adjacent negative electrode active material layer 6 face each other with the solid electrolyte layer 4 interposed therebetween, and the positive electrode layer 14, the solid electrolyte layer 4, and the negative electrode layer 15 are laminated in this order. Thereby, the adjacent positive electrode layer 14, solid electrolyte layer 4, and negative electrode layer 15 constitute one single cell 9. Therefore, it can be said that the secondary battery 1 has a configuration in which a plurality of single cells 9 are laminated and electrically connected in parallel.
[0014] The positive electrode current collector foil 7 and the negative electrode current collector foil 5 are electrically connected to a positive electrode current collector tab 10 and a negative electrode current collector tab 11 via a positive electrode lead 12 and a negative electrode lead 13, respectively. The positive electrode current collector tab 10 and the negative electrode current collector tab 11 are configured such that a part thereof is led out to the outside of the laminate film 3 so as to be sandwiched between the ends of the laminate film 3.
[0015] In the secondary battery 1 having the above-described configuration, the negative electrode layer 15 expands and contracts with charge and discharge. When the electrolyte contained in the electrolyte layer 4 and the positive electrode layer 14 is a sulfide solid electrolyte, the positive electrode layer 14 also expands and contracts in the same manner. Then, bending stress is generated at the joint between the positive electrode lead 12 and the positive electrode current collector tab 10 and at the joint between the negative electrode lead 13 and the negative electrode current collector tab 11 during the expansion and contraction process, and tensile stress is generated in the positive electrode lead 12 and the negative electrode lead 13 during the expansion process. For this reason, there is a risk that the positive electrode lead 12 and the negative electrode lead 13 may break during repeated charge and discharge. And, for example, there is also a risk that the broken positive electrode lead 12 may contact the negative electrode layer 15 and cause a short circuit.
[0016] Therefore, in the present embodiment, by configuring the secondary battery 1 as described below, the above-described breakage and short circuit are prevented.
[0017] [First Embodiment] FIG. 2 is a cross-sectional view of the secondary battery 1 according to this embodiment. The same members as those in FIG. 1 are denoted by the same reference numerals. Hereinafter, the description will focus on the differences from the conventional secondary battery 1 in FIG. 1.
[0018] When the positive electrode leads 12 of each positive electrode layer 14 are the first positive electrode lead 12A, the second positive electrode lead 12B, and the third positive electrode lead 12C in order from above in the stacking direction, they are connected on the side opposite to the laminate 2, and a part thereof forms a flat portion 12D along the side surface extending in the stacking direction of the laminate 2.
[0019] FIGS. 3(a) and (b) show examples of the connection forms of the first positive electrode lead 12A to the third positive electrode lead 12C. In FIG. 3(a), the tip portions of the first positive electrode lead 12A to the third positive electrode lead 12C extending from the laminate 2 are connected by welding or the like, and a part of the tip side of the uppermost first positive electrode lead 12A and the lowermost third positive electrode lead 12C forms the flat portion 12D. In FIG. 3(b), a predetermined range forms the flat portion 12D from the end of the first positive electrode lead 12A extending from the uppermost positive electrode layer 14 of the laminate 2, and the second positive electrode lead 12B and the third positive electrode lead 12C are connected to the first positive electrode lead 12A. Note that the connection form is not limited to these, and any configuration having the flat portion 12D in contact with the positive electrode current collector tab 10 described later may be used.
[0020] The same applies to the negative electrode lead 13. When the negative electrode leads 13 of each negative electrode layer 15 are the first negative electrode lead 13A, the second negative electrode lead 13B, and the third negative electrode lead 13C in order from above in the stacking direction, they are connected on the side opposite to the laminate 2, and a part thereof forms a flat portion 13D along the side surface extending in the stacking direction of the laminate 2. The connection form is the same as that of the positive electrode lead 12.
[0021] The positive electrode current collecting tab 20 includes a first flat portion 20A facing the flat portion 12D of the positive electrode lead 12, and a second flat portion 20B extending in a direction away from the laminate 2. In FIG. 2, an L-shaped positive electrode current collecting tab 20 in which the second flat portion 20B extends from the lower end of the first flat portion 20A is shown, but the present invention is not limited to this, and any configuration including the first flat portion 20A and the second flat portion 20B may be used. Variations in the configuration will be described later.
[0022] The flat portion 12D of the positive electrode lead 12 and the first flat portion 20A of the positive electrode current collecting tab 20 are in slidable contact. When the first flat portion 20A of the positive electrode current collecting tab 20 is pressed against the flat portion 12D of the positive electrode lead 12 by the contraction force of the laminate film 3, the contact state is maintained even during sliding. Note that a pressing force applying mechanism for pressing the first flat portion 20A of the positive electrode current collecting tab 20 against the flat portion 12D of the positive electrode lead 12 may be further provided.
[0023] When the laminate 2 expands and contracts, the flat portion 12D of the positive electrode lead 12 moves in the stacking direction. At this time, if the flat portion 12D and the first flat portion 20A are connected by welding or the like, the positive electrode lead 12 swings with the connection portion as the base end, and bending stress is generated. Further, the closer the connection destination of the positive electrode lead 12, the positive electrode layer 14, is to the end in the stacking direction, the greater the displacement accompanying the expansion and contraction of the connection portion between the positive electrode lead 12 and the positive electrode layer 14, and the greater the tensile stress generated.
[0024] However, in the present embodiment, since the two are in slidable contact, the above-described swinging does not occur. Further, it is possible to suppress the tensile stress when the connection portion between the positive electrode lead 12 and the positive electrode layer 14 is displaced due to expansion and contraction. As a result, breakage of the positive electrode lead 12 due to expansion and contraction of the secondary battery 1 can be suppressed, and a short circuit accompanying the breakage can also be suppressed.
[0025] In order to suppress a change in the contact area between the positive electrode lead 12 and the positive electrode current collecting tab 20 due to the sliding of the positive electrode lead 12 with respect to the positive electrode current collecting tab 20, the stacking direction dimension A of the first flat portion 20A is set to 50% or more of the stacking direction dimension B in the fully discharged state of the laminate 2 (FIG. 4).
[0026] The relationship between the negative electrode current collector tab 21 and the negative electrode lead 13 is the same as the relationship between the positive electrode current collector tab 20 and the positive electrode lead 12.
[0027] FIG. 5 illustrates the configuration of variations of the positive electrode current collector tab 20. (a) is a side view seen from the side of the secondary battery 1 as in FIG. 2, and (b) to (f) are top views seen from above the secondary battery 1.
[0028] (b) is a bent rectangular flat plate. (c) is a structure in which the width of the second flat portion 20B (the vertical dimension in FIG. 5) is made narrower than the width of the first flat portion 20A. Note that the position of the second flat portion 20B may be shifted in the width direction. (d) is a structure in which the shape of the second flat portion 20B is trapezoidal. (e) is a structure in which the length of the long side of the trapezoidal second flat portion 20B is made shorter than the width of the first flat portion 20A. (f) is a structure in which the width of the first flat portion 20A is made smaller than the width of the second flat portion. Note that there are various variations such as chamfering the corners of the second flat portion 20B in (b) to (f), or making each side of the second flat portion 20B into a curve. The same applies to the negative electrode current collector tab 21.
[0029] FIG. 6 illustrates variations in the arrangement of the positive electrode current collector tab 20 and the negative electrode current collector tab 21. (a) is the arrangement shown in FIG. 2.
[0030] (b) is a structure in which the top and bottom of the positive electrode current collector tab 20 in (a) are reversed. (c) is a structure in which the positive electrode current collector tab 20 and the negative electrode current collector tab 21 face one side surface of the secondary battery 1, and the second flat portions 20B, 21B of both current collector tabs 20, 21 are arranged so as to be on the lower end side of the secondary battery 1. (d) is a structure in which the top and bottom of the negative electrode current collector tab 21 in (c) are reversed. (e) is a structure in which the negative electrode current collector tab 21 in (a) is arranged on the side surface orthogonal to the side surface facing the positive electrode current collector tab 20. (f) is a structure in which the top and bottom of the positive electrode current collector tab 20 in (e) are reversed.
[0031] So far, the case where the sides of the positive electrode current collector tab 20 and the negative electrode current collector tab 21 are L-shaped has been described, but it is not limited to this. Variations in the side shape of the positive electrode current collector tab 20 will be illustrated and described with reference to FIG. 7.
[0032] (a) shows the case where the angle θ formed by the first flat portion 20A and the second flat portion 20B is an acute angle. (b) shows the case where a third flat portion 20C covering the upper surface of the laminate 2 is provided. (c) shows the case where a crank portion 20D is provided between the first flat portion 20A and the second flat portion 20B. There are also various other variations.
[0033] As described above, in the present embodiment, a secondary battery 1 is provided, which includes a laminate 2 in which a positive electrode layer 14 and a negative electrode layer 15 are laminated with an electrolyte layer 4 interposed therebetween, and a laminate film 3 as an exterior body for housing the laminate 2. As lithium ions as carrier ions move, at least the negative electrode layer 15 among the positive electrode layer 14 or the negative electrode layer 15 expands and contracts. This secondary battery 1 includes current collector foils 5 and 7 having lead portions 12 and 13 extending in a direction orthogonal to the lamination direction of the laminate 2 from the positive electrode layer 14 and the negative electrode layer 15, and current collector tabs 20 and 21 having a first flat portion 20A, 21A facing the side from which the lead portions 12 and 13 of the laminate 2 are taken out and a second flat portion 20B, 21B extending in a direction away from the side surface. The first flat portions 20A, 21A of the current collector tabs 20, 21 and the lead portions 12, 13 are slidably and electrically connected to each other. Note that the electrolyte used in the electrolyte layer 4 is a solid electrolyte. Thereby, even when the laminate 2 expands and contracts with charging and discharging of the secondary battery 1, deformation and breakage in the vicinity of the contact portion between the current collector tabs 20, 21 and the lead portions 12, 13 can be suppressed.
[0034] In the present embodiment, the negative electrode active material is lithium metal, and the electrolyte contained in the electrolyte layer 4 and the positive electrode layer 14 is a sulfide solid electrolyte. In such a secondary battery 1, since the positive electrode layer 14 and the negative electrode layer 15 expand and contract, the displacement amount of the lamination direction dimension of the laminate 2 becomes large. However, with the above configuration, deformation and breakage in the vicinity of the contact portion between the current collector tabs 20, 21 and the lead portions 12, 13 can be suppressed.
[0035] [Modification Example] Next, a modification example of the positive current collector tab 20 and the negative current collector tab 21 will be described. This modification example also belongs to the scope of the present invention as in the first embodiment.
[0036] The difference from the first embodiment lies in the structures of the positive current collector tab 20 and the negative current collector tab 21. The positive current collector tab 20 and the negative current collector tab 21 in the first embodiment are formed by bending a single flat plate, while the positive current collector tab 20 and the negative current collector tab 21 in this modification example are formed by combining a plurality of members. Since the positive current collector tab 20 and the negative current collector tab 21 have the same structure, only the positive current collector tab 20 will be described here.
[0037] FIG. 8 is a cross-sectional view along the stacking direction of the secondary battery 1 according to the modification example. The point that the positive current collector tab 20 includes the first flat portion 20A and the second flat portion 20B is the same as in the above embodiment. However, in the positive current collector tab 20 according to the modification example, the member forming the first flat portion 20A and the member forming the second flat portion 20B are joined by welding or the like so as to form a T shape. Even with such a structure, the same operational effects as in the first embodiment are achieved.
[0038] Also in the case of the modification example, the stacking direction dimension A of the first flat portion 20A is set to be 50% or more of the stacking direction dimension B in the fully discharged state of the laminate 2 (FIG. 9).
[0039] FIG. 10 is a diagram showing variations of the positive current collector tab 20 according to the modification example. (a) shows a case where the angle θ formed by the first flat portion 20A and the second flat portion 20B is an acute angle. (b) shows a case where an inclined portion 20E is provided between the first flat portion 20A and the second flat portion 20B.
[0040] [Second Embodiment] Next, a second embodiment of the present invention will be described.
[0041] FIG. 11 is a cross-sectional view of the secondary battery 1 according to the present embodiment. The difference from the first embodiment is that a positive electrode conductor 30A is interposed between the positive electrode current collector tab 20 and the positive electrode lead 12, and a negative electrode conductor 30B is interposed between the negative electrode current collector tab 21 and the negative electrode lead 13, respectively. Since the positive electrode conductor 30A and the negative electrode conductor 30B have the same structure except for the dimension in the stacking direction, only the positive electrode conductor 30A will be described here.
[0042] The positive electrode conductor 30A has one surface that contacts the first flat portion 20A of the positive electrode current collector tab 20 and the other surface that contacts the positive electrode lead 12, and is configured to be in slidable contact with at least the positive electrode lead 12.
[0043] When the positive electrode current collector tab 20 is formed of a nickel-plated copper plate and the positive electrode lead 12 is formed of a copper foil, the material of the positive electrode conductor 30A may be the same as either the positive electrode current collector tab 20 or the positive electrode lead 12, or may be different from both. Examples of materials different from both include graphite sheets.
[0044] In addition, in order to suppress changes in the contact area, the dimension of the positive electrode conductor 30A in the stacking direction is the same as that of the first flat portion 20A of the positive electrode current collector tab 20 and is 50% or more of the dimension of the laminate 2 in the stacking direction in the fully discharged state.
[0045] As described above, in the present embodiment, the conductor 30 is interposed between the first flat portions 20A and 21A and the lead portions 12 and 13, and the conductor 30 and the lead portions 12 and 13 are in slidable contact. Even with such a configuration, the same operational effects as those of the first embodiment are achieved.
[0046] In this embodiment, the conductor 30 may be made of the same material as either of the current collecting tabs 20, 21 or the lead portions 12, 13, or may be made of a material different from any of the current collecting tabs 20, 21 and the lead portions 12, 13. Whichever material is used, the same operational effects as those of the first embodiment are achieved. When determining the material of the conductor 30, heat extraction property (heat dissipation property) may be included as one of the selection criteria. The higher the heat dissipation property of the conductor 30, the greater the proportion of the heat generated in the secondary battery 1 that is released to the outside through the conductor 30, so that the cooling performance of the secondary battery 1 can be improved.
[0047] As described above, the embodiments and modification examples of the present invention have been explained. However, the above embodiments and modification examples merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. For example, the first embodiment, the modification example, and the second embodiment may be combined as appropriate.
Explanation of Reference Numerals
[0048] 1 Secondary battery, 2 Laminate, 3 Laminate film, 4 Electrolyte layer, 5 Negative electrode current collecting foil, 6 Negative electrode active material layer, 7 Positive electrode current collecting foil, 8 Positive electrode active material layer, 9 Short battery layer, 10 Positive electrode current collecting tab, 11 Negative electrode current collecting tab, 12 Positive electrode lead, 13 Negative electrode lead, 14 Positive electrode layer, 15 Negative electrode layer, 20 Positive electrode current collecting tab, 21 Negative electrode current collecting tab, 30 Conductor
Claims
1. A laminate in which a positive electrode layer and a negative electrode layer are laminated via an electrolyte layer, An exterior body that houses the laminate, Comprising, In a secondary battery in which at least the negative electrode layer among the positive electrode layer and the negative electrode layer expands and contracts as lithium ions as carrier ions move, A current collector foil having a lead portion extending in a direction orthogonal to the lamination direction of the laminate from the positive electrode layer and the negative electrode layer, A current collector tab having a first flat portion facing a side surface from which the lead portion of the laminate is taken out and a second flat portion extending in a direction away from the side surface, Comprising, A secondary battery characterized in that the first flat portion of the current collector tab and the lead portion are slidably and electrically connected.
2. In the secondary battery according to Claim 1, A secondary battery in which the electrolyte used in the electrolyte layer is a solid electrolyte.
3. In the secondary battery according to Claim 1, A conductor is interposed between the first flat portion and the lead portion, and the conductor and the lead portion are in slidable contact with each other. A secondary battery.
4. In the secondary battery according to Claim 3, The conductor is formed of the same material as either the current collector tab or the lead portion. A secondary battery.
5. In the secondary battery according to Claim 3, The conductor is formed of a material different from both the current collector tab and the lead portion. A secondary battery.
6. In the secondary battery according to Claim 1, A secondary battery in which the negative electrode active material is lithium metal.
7. In the secondary battery according to Claim 1, A secondary battery in which the electrolytes contained in the electrolyte layer and the positive electrode layer are sulfide solid electrolytes.
Citation Information
Patent Citations
Nonaqueous solid electrolyte battery
JP2011081925A