Secondary batteries

Abstract

To provide a secondary battery which can improve heat resistance and sealability of a heat seal region of an exterior member.SOLUTION: In a secondary battery 10, an electrode laminate 11 where a positive electrode and a negative electrode are stacked through an electrolyte is externally coated with an exterior member 12. The exterior member 12 has an exterior region 12a externally coating the electrode laminate 11, a heat seal region 12b, and an intermediate region 12c existing between the exterior region 12a and the heat seal region 12b. In the exterior region 12a, a layer containing a first rein, a layer containing a second resin, a layer containing metal and a layer containing a third resin are sequentially stacked, from the side of the electrode laminate 11. In the heat seal region 12b, the layer containing the metal and the layer containing the third resin are sequentially stacked on both surfaces of the layer containing the second resin. In the intermediate region 12c, resin reservoir R containing the first resin is formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that many people have access to affordable, reliable, sustainable and advanced energy.

[0003] Patent Document 1 describes an electricity storage device comprising a positive electrode, a separator, a negative electrode, an electrolyte, and a content having a tab consisting of a lead and a tab sealant, and an exterior material in which at least a metal foil layer, a corrosion prevention treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one side of a base layer. The exterior material has the sealant layers bonded together, and a heat-sealed portion formed at the peripheral edge thereof, and the content is housed and sealed so that a portion of the tab is positioned outside. Furthermore, the adhesive resin layer contains a dispersed olefin-based elastomer, and a resin pool of the sealant layer is formed inside the heat-sealed portion. Furthermore, a polypropylene resin film is used as the sealant layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2015-228387 Summary of the Invention [Problem to be solved by the invention]

[0005] However, polypropylene resin films have a low melting point, which may cause the temperature of the heat-sealed area to rise and soften, making it desirable to improve the heat resistance and sealability of the heat-sealed area of ​​the exterior member.

[0006] An object of the present invention is to provide a secondary battery capable of improving the heat resistance and sealability of the heat seal area of ​​the exterior member. [Means for solving the problem]

[0007] In one aspect of the present invention, in a secondary battery, an electrode stack in which a positive electrode and a negative electrode are stacked with an electrolyte interposed therebetween is packaged in an exterior member, and the exterior member has an exterior region that packages the electrode stack, a heat seal region, and an intermediate region that exists between the exterior region and the heat seal region, and the exterior region has, from the electrode stack side, a layer containing a first resin, a layer containing a second resin, a layer containing a metal, and a layer containing a third resin that are sequentially stacked, and the heat seal region has the layer containing the metal and the layer containing the third resin that are sequentially stacked on both sides of the layer containing the second resin, and the intermediate region has a resin reservoir that contains the first resin.

[0008] Another aspect of the present invention is a secondary battery in which an electrode stack, in which a positive electrode and a negative electrode are stacked with an electrolyte interposed therebetween, is packaged in an exterior member, and the exterior member has an exterior region that packages the electrode stack, a heat seal region, and an intermediate region that exists between the exterior region and the heat seal region, and the exterior region has, from the electrode stack side, a layer containing a first resin or a layer containing a second resin, a layer containing a metal, and a layer containing a third resin that are sequentially stacked, and the heat seal region has the layer containing the metal and the layer containing the third resin that are sequentially stacked on both sides of the layer containing the second resin, and the intermediate region has a resin reservoir that contains the first resin.

[0009] The secondary battery may be a solid-state battery.

[0010] The electrode stack may be formed by stacking the positive electrode and the negative electrode with a solid electrolyte layer interposed therebetween.

[0011] Another aspect of the present invention is a method for manufacturing a secondary battery, comprising the steps of covering both sides of an electrode laminate, in which a positive electrode and a negative electrode are stacked with an electrolyte interposed therebetween, with a laminate film in which a layer containing a first resin, a layer containing a second resin, a layer containing a metal, and a layer containing a third resin are stacked in that order from the electrode laminate side, and heat-sealing the laminate film covering both sides of the electrode laminate, wherein during the heat-sealing, the first resin is caused to flow toward the electrode laminate side to form a resin reservoir containing the first resin. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a secondary battery that can improve the heat resistance and sealability of the heat seal area of ​​the exterior member. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating an example of a secondary battery according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view showing the laminated structure in the exterior region and the heat seal region of FIG. 1. FIG. [Figure 3] 2A to 2C are cross-sectional views illustrating an example of a method for manufacturing the secondary battery of FIG. [Figure 4] 1. FIG. 4 is a cross-sectional view illustrating another example of the method for manufacturing the secondary battery of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows an example of the secondary battery of this embodiment.

[0016] In the secondary battery 10, an electrode laminate 11, which includes a positive electrode and a negative electrode stacked with an electrolyte interposed therebetween, is packaged in a packaging member 12. The packaging member 12 has a packaging region 12a that packages the electrode laminate 11, a heat-sealed region 12b, and an intermediate region 12c that is located between the packaging region 12a and the heat-sealed region 12b. In the packaging region 12a, a layer 21 containing a first resin, a layer 22 containing a second resin, a layer 23 containing a metal, and a layer 24 containing a third resin are sequentially stacked from the electrode laminate 11 side (see FIG. 2(a)). In the heat-sealed region 12b, a layer 23 containing a metal and a layer 24 containing a third resin are sequentially stacked on both sides of the layer 22A containing the second resin (see FIG. 2(b)). This improves the heat resistance of the heat-sealed region 12b. In the intermediate region 12c, a resin reservoir R containing the first resin is formed. This improves the sealability of the heat-sealed region 12b.

[0017] The first resin is not particularly limited as long as it is a thermoplastic resin that flows toward the electrode laminate 11 during heat sealing, which will be described later. Examples include polypropylene (melting point 160°C), low-density polyethylene (melting point 95 to 130°C), high-density polyethylene (melting point 120 to 140°C), polystyrene (melting point 100°C), AS resin (melting point 115°C), polyvinyl chloride (melting point 85 to 200°C), ABS resin (melting point 100 to 125°C), etc.

[0018] The melting point of the first resin is not particularly limited, but is, for example, 120°C or higher and 170°C or lower.

[0019] The thickness of the layer 21 containing the first resin is not particularly limited, but is, for example, not less than 35 μm and not more than 320 μm.

[0020] The second resin is not particularly limited as long as it is a thermoplastic resin that does not flow toward the electrode laminate 11 during heat sealing, which will be described later. Examples of the second resin include polyethylene terephthalate (PET; melting point 260°C), polyvinyl chloride (melting point 85 to 200°C), polyvinyl alcohol (melting point 200°C), polyvinylidene chloride (melting point 210°C), polyamide (melting point 170 to 265°C), polybutylene terephthalate (melting point 230 to 270°C), and polyphenylene sulfide (melting point 290°C).

[0021] The melting point of the second resin is not particularly limited, but is, for example, 170°C or higher and 290°C or lower.

[0022] The thickness of the second resin-containing layer 22 is not particularly limited, but is, for example, 12 μm or more and 80 μm or less. The thickness of the second resin-containing layer 22A is not particularly limited, but is, for example, 24 μm or more and 160 μm or less.

[0023] The exterior region 12a does not necessarily have to be formed with the layer 21 containing the first resin or the layer 22 containing the second resin, which improves the energy density of the secondary battery 10.

[0024] The metal is not particularly limited, but examples thereof include aluminum.

[0025] The thickness of the metal-containing layer 23 is not particularly limited, but is, for example, 40 μm or more and 80 μm or less.

[0026] The third resin is not particularly limited as long as the layer 24 containing the third resin does not melt and become damaged during the heat sealing described below, but examples thereof include polyethylene terephthalate, polyvinyl chloride, polyvinyl alcohol, polyvinylidene chloride, polyamide, polybutylene terephthalate, polyphenylene sulfide, etc.

[0027] The melting point of the third resin is preferably equal to or higher than the melting point of the second resin.

[0028] The thickness of the layer 24 containing the third resin is not particularly limited, but is, for example, 15 μm or more and 25 μm or less.

[0029] The electrode laminate is in a sheet form, and each electrode has an electrode composite layer formed on an electrode current collector. That is, the positive electrode has a positive electrode composite layer formed on a positive electrode current collector, and the negative electrode has a negative electrode composite layer formed on a negative electrode current collector. The electrolyte is not particularly limited, but is contained in, for example, an electrolytic solution impregnated in a general resin porous membrane (separator). When the secondary battery 10 is a solid-state battery, the electrolyte is contained in a gel electrolyte layer, a solid electrolyte layer, or the like.

[0030] The electrode laminate may have a plurality of positive electrodes and / or negative electrodes, as long as the positive electrodes and negative electrodes are stacked with the electrolyte interposed therebetween. Examples of the stack structure of an electrode laminate having a plurality of positive electrodes and / or negative electrodes include positive electrode / electrolyte / negative electrode / electrolyte / positive electrode. In this case, the electrode laminate can be produced by, for example, roll pressing.

[0031] The method for manufacturing the secondary battery 10 includes the steps of covering both sides of the electrode laminate 11 with a laminate film L in which, from the electrode laminate 11 side, a layer 21 containing a first resin, a layer 22 containing a second resin, a layer 23 containing a metal, and a layer 24 containing a third resin (see FIG. 2(a)) are laminated in that order, and heat-sealing the laminate film L covering both sides of the electrode laminate 11. When heat-sealing the laminate film L, a heat seal bar 31 is moved toward the electrode laminate 11, causing the first resin to flow toward the electrode laminate 11 and forming a resin pool R containing the first resin.

[0032] The heat sealing conditions such as the temperature and movement speed of the heat seal bar 31 can be set appropriately depending on the melting points of the first resin and the second resin.

[0033] Alternatively, instead of the heat seal bar 31, a heat seal roll 41 may be used, and the heat seal roll 41 may be moved toward the electrode laminate 11 while rotating in a direction D in which the first resin flows toward the electrode laminate 11 (see FIG. 4). This reduces friction of the laminate film L.

[0034] Hereinafter, a case where the secondary battery of this embodiment is an all-solid-state lithium secondary battery will be described.

[0035] The positive electrode current collector is not particularly limited, but may be, for example, aluminum foil.

[0036] The positive electrode mixture layer contains a positive electrode active material, and may further contain a solid electrolyte, a conductive additive, a binder, and the like.

[0037] The positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. For example, LiCoO2, Li(Ni 5 / 10 Co 2 / 10 Mn 3 / 10 )O 2、 Li(Ni) 6 / 10 Co 2 / 10 Mn 2 / 10 )O 2、 Li(Ni) 8 / 10 Co 1 / 10 Mn 1 / 10 )O 2、 Li(Ni) 0.8 Co 0.15 Al 0.05 )O 2、 Li(Ni) 1 / 6 Co 4 / 6 Mn 1 / 6 )O 2、 Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3 )O 2、 Examples include LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, and sulfur.

[0038] The solid electrolyte constituting the solid electrolyte layer is not particularly limited as long as it is a material capable of conducting lithium ions, and examples thereof include oxide-based electrolytes and sulfide-based electrolytes.

[0039] The negative electrode mixture layer contains a negative electrode active material, and may further contain a solid electrolyte, a conductive additive, a binder, and the like.

[0040] The negative electrode active material is not particularly limited as long as it is capable of absorbing and releasing lithium ions, and examples thereof include metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, carbon materials, etc. Examples of carbon materials include artificial graphite, natural graphite, hard carbon, soft carbon, etc.

[0041] The negative electrode current collector is not particularly limited, but examples thereof include copper foil.

[0042] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Explanation of symbols]

[0043] 10 Secondary battery 11 Electrode laminate 12 Exterior materials 12a Exterior area 12b Heat seal area 12c intermediate area 21 first resin-containing layer 22, 22A Layer containing second resin 23 Metal-containing layer 24 Third resin-containing layer 31 Heat seal bar 41 Heat seal roll L Laminate Film R Resin reservoir containing the first resin

Claims

1. an electrode stack in which a positive electrode and a negative electrode are stacked with an electrolyte interposed therebetween is packaged with an exterior member; the exterior member has an exterior region that exteriors the electrode stack, a heat-sealed region, and an intermediate region that is present between the exterior region and the heat-sealed region, the exterior region includes a layer containing a first resin, a layer containing a second resin, a layer containing a metal, and a layer containing a third resin, which are sequentially stacked from the electrode stack side; the heat seal region is formed by laminating the metal-containing layer and the third resin-containing layer in this order on both sides of the second resin-containing layer, the intermediate region has a resin reservoir containing the first resin formed therein; the first resin is a thermoplastic resin that flows when forming the heat seal region, The second resin is a thermoplastic resin that does not flow when the heat seal region is formed.

2. an electrode stack in which a positive electrode and a negative electrode are stacked with an electrolyte interposed therebetween is packaged with an exterior member; the exterior member has an exterior region that exteriors the electrode stack, a heat-sealed region, and an intermediate region that is present between the exterior region and the heat-sealed region, the exterior region includes a layer containing a first resin, a layer containing a metal, and a layer containing a third resin stacked in this order from the electrode stack side, the heat seal region is formed by laminating the metal-containing layer and the third resin-containing layer in this order on both sides of a second resin-containing layer, the intermediate region has a resin reservoir containing the first resin formed therein; the first resin is a thermoplastic resin that flows when forming the heat seal region, The second resin is a thermoplastic resin that does not flow when the heat seal region is formed.

3. The secondary battery according to claim 1 or 2, which is a solid-state battery.

4. The secondary battery according to claim 3 , wherein the electrode stack is formed by stacking the positive electrode and the negative electrode with a solid electrolyte layer interposed therebetween.

5. A method for manufacturing the secondary battery according to claim 1, comprising: covering both surfaces of the electrode laminate with a laminate film in which a layer containing the first resin, a layer containing the second resin, a layer containing the metal, and a layer containing the third resin are sequentially laminated from the electrode laminate side; and a step of heat-sealing a laminate film covering both sides of the electrode stack to form the heat-sealed area, The method for manufacturing a secondary battery includes causing the first resin to flow toward the electrode stack to form the resin pool when forming the heat seal region.

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