Secondary batteries

Abstract

This invention provides a secondary battery that can maintain and repair the conductive path even if the current collector foil breaks. [Solution] The secondary battery 1 comprises a battery element 2 having a negative electrode layer, an electrolyte layer containing a solid electrolyte, and a positive electrode layer; a pair of current collector foils 3 and 4 arranged to sandwich the battery element 2; a tab 5 arranged on the surface of the leading edge of the current collector foil 3; and a conductive resin layer 6. The resin layer 6 is arranged on the current collector foil 3 and the tab 5 so as to cover the boundary portion 7 between the current collector foil 3 and the tab 5 on the surface side of the current collector foil 3. Alternatively, the resin layer 6 is arranged on the current collector foil 3 so as to straddle the boundary portion 7 between the current collector foil 3 and the tab 5 on the back side of the current collector foil 3.

Description

Technical Field

[0001] The present invention relates to a secondary battery.

Background Art

[0002] As a secondary battery, one having a structure in which a negative electrode current collector foil, a negative electrode layer, an electrolyte layer including a solid electrolyte, a positive electrode layer, and a positive electrode current collector foil are laminated in this order is known. In this specification, a laminated structure including a negative electrode layer, an electrolyte layer including a solid electrolyte, and a positive electrode layer may be referred to as a battery element.

[0003] In the manufacturing process of such a secondary battery, a process of pressing the battery element is included for the purpose of obtaining good charge and discharge characteristics.

[0004] In relation to the above, Patent Document 1 discloses a method for manufacturing an electrode body in which a positive electrode having a positive electrode layer and a solid electrolyte layer on both sides of a positive electrode current collector foil and a negative electrode having a negative electrode layer and a solid electrolyte layer on both sides of a negative electrode current collector foil and having a size larger than that of the positive electrode are laminated. In this manufacturing method, a film thickness displacement amount that does not cause breakage of the current collector foil is obtained in advance by measuring the film thickness of a press portion to which a press pressure is applied and a non-press portion that is not laminated on the positive electrode and to which no press pressure is applied, and pressing and laminating are performed with a press pressure based on the film thickness displacement amount. According to the invention of Patent Document 1, it is said that the occurrence of breakage of the current collector foil can be suppressed even when the current collector foil is pressed together with the battery element.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, in the manufacturing and pressurization process of secondary batteries, tabs that electrically connect the secondary battery to an external device are sometimes placed on the current collector foil, and then the entire secondary battery, including the tabs, is pressurized. In this case, current collector foil breakage is likely to occur, especially at the boundary between the tab and the current collector foil. If current collector foil breakage occurs, the conductive path is severed, which may lead to problems such as increased internal resistance or inability to charge or discharge.

[0007] On the other hand, if the press pressure is adjusted as described in Patent Document 1 in order to suppress the occurrence of the current collector foil breakage mentioned above, it may not be possible to apply a uniform and sufficient load to the entire battery element. This may hinder the original purpose of obtaining good charge and discharge characteristics.

[0008] In contrast, if the conductive path can be maintained and repaired even if the current collector foil breaks, the above-mentioned problems can be solved.

[0009] Therefore, the object of the present invention is to provide a secondary battery that can maintain and repair the conductive path even if the current collector foil breaks. [Means for solving the problem]

[0010] According to one aspect of the present invention, a secondary battery is provided comprising a battery element having a negative electrode layer, an electrolyte layer containing a solid electrolyte, and a positive electrode layer; a pair of current collector foils arranged to sandwich the battery element; a tab disposed on the surface of the leading edge of the current collector foil; and a conductive resin layer. The resin layer is disposed on the current collector foil and the tab so as to cover the boundary between the current collector foil and the tab on the surface side of the current collector foil. Alternatively, the resin layer is disposed on the current collector foil so as to straddle the boundary between the current collector foil and the tab on the back side of the current collector foil. [Effects of the Invention]

[0011] According to the present invention, a secondary battery is provided in which a conductive resin layer can maintain and repair the conductive path even if the current collector foil breaks. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a view of the secondary battery according to the first embodiment, seen from above. [Figure 2] Figure 2 is a cross-sectional view showing the XX' section of Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing the XX' section of Figure 1, illustrating the state in which the current collector foil has broken. [Figure 4] Figure 4 is a schematic diagram illustrating the process by which the resin layer repairs the severed conductive paths upon heating. [Figure 5] Figure 5 is a view of the secondary battery according to the first embodiment, seen from above, showing the resin layer arranged to cover the entire circumference of the boundary. [Figure 6] Figure 6 is a view of the secondary battery according to the second embodiment, seen from above. [Figure 7] Figure 7 is a cross-sectional view showing the YY' section of Figure 6. [Figure 8] Figure 8 is a cross-sectional view showing the YY' section of Figure 6, illustrating the state in which the current collector foil has broken. [Figure 9] Figure 9 is a view from above of the secondary battery according to the second embodiment, showing the resin layer arranged to span the entire circumference of the boundary. [Figure 10A] Figure 10A is a cross-sectional view of a modified secondary battery. [Figure 10B] Figure 10B is a cross-sectional view of a modified secondary battery. [Figure 11A] Figure 11A is a cross-sectional view illustrating a secondary battery having multiple negative electrode current collector foils and positive electrode current collector foils. [Figure 11B] Figure 11B is a cross-sectional view illustrating a secondary battery having multiple negative electrode current collector foils and positive electrode current collector foils. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings.

[0014] (First Embodiment) FIG. 1 is a view of the secondary battery 1 according to the first embodiment as seen from above. As shown in FIG. 1, the secondary battery 1 has a battery element 2, a negative electrode current collector foil 3, and a positive electrode current collector foil 4. The battery element 2, the negative electrode current collector foil 3, and the positive electrode current collector foil 4 are housed inside a sheet-like exterior body 8. Further, the secondary battery 1 has a configuration in which a tab 5 functioning as an input / output terminal protrudes from the inside of the exterior body 8 toward the outside, and is provided as a so-called laminated cell.

[0015] FIG. 2 is a cross-sectional view showing the XX' cross-section of FIG. 1. As shown in FIG. 2, the battery element 2 is disposed so as to be sandwiched between the negative electrode current collector foil 3 and the positive electrode current collector foil 4. The battery element 2 has a configuration in which a negative electrode layer (not shown), an electrolyte layer containing a solid electrolyte, and a positive electrode layer are laminated. The negative electrode layer is disposed on the side of the negative electrode current collector foil 3, and the positive electrode layer is disposed on the side of the positive electrode current collector foil 4. The electrolyte layer is disposed so as to be sandwiched between these negative electrode layer and positive electrode layer. The secondary battery 1 according to the present embodiment includes solid batteries such as semi-solid batteries and all-solid batteries.

[0016] Although not shown in FIGS. 1 and FIG. 2, in order to prevent the negative electrode current collector foil 3 and the positive electrode current collector foil 4 from contacting and short-circuiting during the process of pressing the battery element in the manufacture of the secondary battery described later, for example, an insulating layer is sandwiched between both current collector foils, or an insulating tape is attached to both current collector foils.

[0017] The negative electrode current collector foil 3 and the positive electrode current collector foil 4 are film-like metal foils. As the negative electrode current collector foil 3, for example, thin films such as copper, copper alloy, nickel, and nickel alloy can be used. As the positive electrode current collector foil 4, for example, aluminum foil can be used.

[0018] As shown in FIG. 2, the tab 5 is disposed on the surface of the tip portion of the negative electrode current collector foil 3. The tab 5 is a metal plate that electrically connects an external device and the secondary battery 1. As the tab 5, for example, a nickel plate, a copper alloy plate, or the like can be used.

[0019] In this embodiment, the secondary battery 1 is provided with a conductive resin layer 6 at the connection point between the tab 5 and the negative electrode current collector foil 3. As shown in Figures 1 and 2, the resin layer 6 is arranged on the negative electrode current collector foil 3 and the tab 5 so as to cover the boundary portion 7 between the negative electrode current collector foil 3 and the tab 5 on the surface side of the negative electrode current collector foil 3.

[0020] More specifically, the resin layer 6 is formed as a roughly rectangular sheet member, and this resin layer 6 is attached to the upper surfaces of the negative electrode current collector foil 3 and the tab 5 so as to straddle the boundary portion 7 between the negative electrode current collector foil 3 and the tab 5. This prevents the boundary portion 7, which is the connection boundary between the negative electrode current collector foil 3 and the tab 5, from being exposed.

[0021] Please note that the configuration described above can be applied not only to the negative electrode current collector foil 3 but also to the positive electrode current collector foil 4. This also applies to the configuration described below.

[0022] In the manufacturing process of secondary batteries equipped with an electrolyte layer containing a solid electrolyte, a step of pressurizing the battery elements is included in order to obtain good charge and discharge characteristics. In this process, after placing tabs on the current collector foil, the entire secondary battery, including the current collector foil and tabs, may be pressurized by isotropic pressing. In this case, the current collector foil is particularly prone to tearing or ripping at the boundary between the current collector foil and the tabs. If the current collector foil is torn or ripped, the conductive path is severed, which may lead to problems such as an increase in the internal resistance of the battery or the inability to charge or discharge.

[0023] In contrast, according to the secondary battery 1 of this embodiment, since the resin layer 6 is arranged to cover the boundary portion 7, even if a cut or tear occurs in the negative electrode current collector foil 3 at the boundary portion 7, the resin layer 6 will cover the cut or tear as shown in Figure 3. Since the resin layer 6 is conductive, the conductive path is maintained and repaired by the resin layer 6.

[0024] In Figure 1, the resin layer 6 does not cover a portion of the boundary 7 (near the left end of the negative electrode current collector foil 3 in Figure 1), but as shown in Figure 5, it may cover the entire boundary 7. That is, the resin layer 6 may be placed on the negative electrode current collector foil 3 and tab 5 so as to cover the entire circumference of the boundary 7. In this case, from the viewpoint of reducing the amount of resin used, as shown in Figure 5, the resin layer 6 may be placed only along the boundary 7.

[0025] Furthermore, as shown in Figure 2, it is preferable that the resin layer 6 is attached to the negative electrode current collector foil 3 and tab 5 so as to be in close contact with the boundary portion 7. In other words, it is preferable that there is no gap between the resin layer 6 and the boundary portion 7.

[0026] Furthermore, the thickness of the resin layer 6 is, for example, 0.001 to 1 mm, preferably 0.001 to 0.1 mm, in order to suppress cuts or tears in the current collector foil caused by the resin layer 6 during the manufacturing and pressurization of the secondary battery 1.

[0027] Next, we will describe the detailed configuration for imparting conductivity to the resin layer 6.

[0028] In a preferred example, the resin layer 6 contains a metal; that is, a metal is dispersed in the resin forming the resin layer 6. Examples of the metal include copper, nickel, and iron nitride. The form of the metal is not particularly limited. In a preferred embodiment, the metal is particulate. The shape of the metal particles is not particularly limited. The metal particles may be spherical, linear, or amorphous.

[0029] The metal content that may be included in the resin layer 6 is, for example, 60% to 95% by mass, preferably 70% to 90% by mass, and more preferably 75% to 85% by mass.

[0030] Furthermore, if the negative electrode layer in battery element 2 contains lithium, the metal in resin layer 6 should be copper and / or nickel, which do not react well with lithium.

[0031] In another preferred example, the resin layer 6 includes a conductive resin (conductive resin). In this case, the resin layer 6 may be formed solely of the conductive resin. Alternatively, the resin layer 6 may be formed from a resin composition containing both a non-conductive resin and a conductive resin.

[0032] Examples of conductive resins include polyacetylene, polyaniline, polypyrrole, and PEDOT.

[0033] Furthermore, the preferred embodiments of the resin layer 6 described above are not mutually exclusive, but can be combined within a non-contradictory range. That is, the resin layer 6 may contain both metal and conductive resin.

[0034] Furthermore, from the viewpoint of further improving the repair performance of cuts and tears in the current collector foil, the resin layer 6 may also contain a thermoplastic resin. In this case, the resin layer 6 is formed from a resin composition containing a thermoplastic resin together with a metal and / or a conductive resin.

[0035] Examples of thermoplastic resins include polyethylene, polypropylene, polystyrene, AS resin, ABS resin, polyvinyl chloride, acrylic resin, PET resin, PVA resin, polyvinylidene chloride, polyvinylidene fluoride, nylon 6, nylon 66, nylon 12, acetal resin, polycarbonate, PBT resin, polyphenylene sulfide, polyimide resin, polyetherimide, polysulfone, fluororesin, and polyamideimide.

[0036] The following describes the effects and benefits of the secondary battery 1 according to this embodiment.

[0037] In this embodiment, the secondary battery 1 has a conductive resin layer 6 placed on the negative electrode current collector foil 3 and the tab 5 such that it covers the boundary 7 between the negative electrode current collector foil 3 and the tab 5.

[0038] With this configuration, even if the negative electrode current collector foil 3 is cut or torn at the boundary 7 during the manufacturing or pressurization of the secondary battery 1, the conductive resin layer 6 will cover the cut or torn area. Therefore, the conductive path can be maintained and repaired by the resin layer 6.

[0039] Furthermore, in the secondary battery 1 according to this embodiment, the resin layer 6 contains metal.

[0040] With this configuration, high conductivity can be imparted to the resin layer 6.

[0041] Furthermore, in the secondary battery 1 according to this embodiment, if the negative electrode layer included in the battery element 2 contains lithium, the metal included in the resin layer 6 is copper and / or nickel, which are poorly reactive with lithium.

[0042] If lithium is present in the negative electrode layer, and the resin layer 6 contains a metal that readily reacts with lithium, there is a risk that the lithium in the negative electrode layer and the resin layer 6 may react unintentionally. However, with the above configuration, it is possible to suppress the unintentional reaction between the lithium in the negative electrode layer and the resin layer 6.

[0043] Furthermore, in the secondary battery 1 according to this embodiment, the resin layer 6 includes a conductive resin.

[0044] With this configuration, high conductivity can be imparted to the resin layer 6.

[0045] Furthermore, in the secondary battery 1 according to this embodiment, the resin layer 6 includes a thermoplastic resin.

[0046] With this configuration, as shown in Figure 4, when the resin layer 6 is heated after a cut or tear occurs in the negative electrode current collector foil 3 at the boundary 7, the resin layer 6 softens and deforms, and enters the cut or tear. In other words, the conductive resin layer 6 can fill the cut or tear. As a result, even if the current collector foil is cut, the conductive path can be more reliably maintained and repaired by heating the resin layer 6.

[0047] Furthermore, in the secondary battery 1 according to this embodiment, the resin layer 6 is arranged on the negative electrode current collector foil 3 and the tab 5 so as to cover the entire circumference of the boundary portion 7 on the surface side of the negative electrode current collector foil 3, as shown in Figure 5.

[0048] With this configuration, even if a current collector foil break occurs at any point along the boundary 7, the conductive path can be more reliably maintained and repaired.

[0049] Furthermore, in the secondary battery 1 according to this embodiment, the resin layer 6 is attached to the negative electrode current collector foil 3 and the tab 5 so as to be in close contact with the boundary portion 7.

[0050] With this configuration, even if a cut or tear occurs in the negative electrode current collector foil 3 at the boundary 7, the conductive path can be maintained and repaired more reliably.

[0051] (Second Embodiment) Next, a secondary battery 1 according to the second embodiment will be described. In the secondary battery 1 according to this embodiment, the position where the resin layer 6 is arranged differs from that of the first embodiment. The second embodiment, like the first embodiment, falls within the scope of the present invention. Furthermore, detailed explanations of aspects that can be adopted in the same configuration as the embodiments described above will be omitted.

[0052] Figure 6 is a view of the secondary battery 1 according to the second embodiment, seen from above. Figure 7 is a cross-sectional view showing the YY' section of Figure 6.

[0053] As shown in Figures 6 and 7, in this embodiment, the conductive resin layer 6 is arranged on the negative electrode current collector foil 3 so as to straddle the boundary portion 7 between the negative electrode current collector foil 3 and the tab 5 on the back side of the negative electrode current collector foil 3. More specifically, a substantially rectangular resin layer 6 is attached to the lower surface of the negative electrode current collector foil 3 so as to straddle the boundary portion 7 between the negative electrode current collector foil 3 and the tab 5.

[0054] With this configuration, as shown in Figure 8, even if the negative electrode current collector foil 3 is cut or torn at the boundary 7 during the manufacturing or pressurization of the secondary battery 1, the conductive resin layer 6 will cover the cut or torn area. Therefore, the conductive path can be maintained and repaired by the resin layer 6.

[0055] Furthermore, as shown in Figure 9, the resin layer 6 may span the entire boundary portion 7. That is, the resin layer 6 may be placed on the negative electrode current collector foil 3 on the back side of the negative electrode current collector foil 3 so as to span the entire circumference of the boundary portion 7. In this case, from the viewpoint of reducing the amount of resin used, as shown in Figure 9, the resin layer 6 may be placed only in the area along the boundary portion 7.

[0056] With this configuration, even if a current collector foil break occurs at any point along the boundary 7, the conductive path can be more reliably maintained and repaired.

[0057] Furthermore, the conductive and thermoplastic configurations of the resin layer 6 described in the first embodiment can also be adopted in this embodiment.

[0058] The secondary battery 1 according to the first and second embodiments has been described above. Next, modifications of the secondary battery 1 according to these embodiments will be described. The modifications described below are also within the scope of the present invention, just like the embodiments. Furthermore, detailed explanations of aspects that can be adopted in the same way as the embodiments described above will be omitted.

[0059] (modified version) Figures 10A and 10B are cross-sectional views of a modified secondary battery 1. As shown in Figures 10A and 10B, in this modified example, the thickness of the resin layer 6 decreases towards the edges of the resin layer 6.

[0060] As shown in Figures 2 and 7, when the edges of the resin layer 6 are thick, pressurizing the entire secondary battery 1, including the resin layer 6, during manufacturing can cause excessive load on the edges of the resin layer 6, potentially leading to current collector foil breakage. In contrast, thinning the edges of the resin layer 6 makes it less likely for excessive load to be applied to the edges. This suppresses breakage or tearing of the negative electrode current collector foil 3 at the edges of the resin layer 6 during pressurization.

[0061] Although embodiments and modifications thereof of the present invention have been described above, the configurations described above represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0062] In this embodiment, the secondary battery 1 has been described as having a pair of negative electrode current collector foils 3 and positive electrode current collector foils 4 arranged to sandwich the battery element 2. However, as shown in Figure 11A or Figure 11B, a plurality of negative electrode current collector foils 3 and a plurality of positive electrode current collector foils 4 may be arranged to alternately sandwich the battery element 2.

[0063] In this case, the multiple negative electrode current collector foils 3 are grouped together on the side of the battery element 2, and the multiple positive electrode current collector foils 4 are grouped together on the side opposite to the battery element 2. The tab 5 is also positioned on the outermost surface of the grouped multiple negative electrode current collector foils 3, as shown in Figure 11A or Figure 11B.

[0064] As shown in Figure 11A, when the resin layer 6 is placed on the surface side of the negative electrode current collector foil 3, the resin layer 6 is placed on the negative electrode current collector foil 3 and the tab 5 so as to cover the boundary portion 7 between the current collector foil and the tab 5 at the outermost surface of the negative electrode current collector foil 3.

[0065] On the other hand, as shown in Figure 11B, when the resin layer 6 is placed on the back side of the negative electrode current collector foil 3, the resin layer 6 is placed on the negative electrode current collector foil 3 on the back side of the negative electrode current collector foil 3, which is located on the outermost surface, so as to straddle the boundary portion 7 between the negative electrode current collector foil 3 and the tab 5. [Explanation of Symbols]

[0066] 1: Secondary battery, 2: Battery element, 3: Negative electrode current collector foil, 4: Positive electrode current collector foil, 5: Tab, 6: Resin layer, 7: Boundary, 8: Outer casing

Claims

1. A battery element having a negative electrode layer, an electrolyte layer containing a solid electrolyte, and a positive electrode layer, A pair of current-collecting foils are arranged so as to sandwich the aforementioned battery element, A tab is placed on the surface of the tip of the current collector foil, A conductive resin layer, Equipped with, The resin layer is disposed on the current collector foil and the tab so as to cover the boundary between the current collector foil and the tab on the surface side of the current collector foil, or disposed on the current collector foil so as to straddle the boundary between the current collector foil and the tab on the back side of the current collector foil. Secondary battery.

2. A secondary battery according to claim 1, The aforementioned resin layer contains metal, Secondary battery.

3. A secondary battery according to claim 2, The negative electrode layer contains lithium, The aforementioned metal includes copper and / or nickel. Secondary battery.

4. A secondary battery according to any one of claims 1 to 3, The aforementioned resin layer includes a conductive resin. Secondary battery.

5. A secondary battery according to any one of claims 1 to 3, The aforementioned resin layer includes a thermoplastic resin. Secondary battery.

6. A secondary battery according to any one of claims 1 to 3, The resin layer is disposed on the current collector foil and the tab so as to cover the entire circumference of the boundary on the surface side of the current collector foil, or disposed on the current collector foil so as to straddle the entire circumference of the boundary on the back side of the current collector foil. Secondary battery.

7. A secondary battery according to any one of claims 1 to 3, The thickness of the resin layer decreases towards the edges of the resin layer. Secondary battery.

8. A secondary battery according to any one of claims 1 to 3, When the resin layer is positioned on the surface side of the current collector foil, the resin layer is attached to the current collector foil and the tab so as to be in close contact with the boundary. Secondary battery.

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