Secondary battery

Abstract

Provided is a secondary battery including a laminate having a separator, a negative electrode composite layer and a negative electrode current collector foil laminated on one face of the separator, a positive electrode composite layer, a positive electrode current collector foil and a resin layer laminated on the other face of the separator, an end face of the positive electrode composite layer formed more inward than an end face of the separator, an end face of the negative electrode composite layer and an end face of the resin layer, and an end face of the positive electrode current collector foil formed more inward than the end face of the positive electrode composite layer.

Description

Technical Field

[0001] This invention relates to a secondary battery. Background Technology

[0002] Japanese Patent Application Publication No. 2021-170486 discloses a battery in which the positive current collector 22A and the negative current collector 22B are of the same size (e.g., Figure 5, etc.). Summary of the Invention

[0003] In the past, foreign matter sometimes entered into batteries and penetrated the separator, causing a short circuit between the negative electrode composite material layer and the positive electrode current collector foil. This short circuit could become a large-scale short circuit, resulting in very serious problems.

[0004] In view of the above problems, the object of the present invention is to provide a secondary battery capable of suppressing large-scale short circuits.

[0005] This application discloses a secondary battery comprising a laminated body having a separator, wherein a negative electrode composite material layer and a negative electrode current collector foil are laminated on one side of the separator, and a positive electrode composite material layer, a positive electrode current collector foil, and a resin layer are laminated on the other side of the separator.

[0006] The end face of the positive electrode composite layer is formed to be further inward than the end face of the separator, the end face of the negative electrode composite layer, and the end face of the resin layer.

[0007] The end face of the positive electrode current collector foil is formed to be further inward than the end face of the positive electrode composite material layer.

[0008] The laminate can be bipolar.

[0009] The portion of the resin layer at the end that does not have a positive electrode composite layer can be configured to not contain conductive filler.

[0010] The distance between the end face of the positive electrode composite material layer and the end face of the positive electrode current collector foil can be within 2mm.

[0011] According to the secondary battery of the present invention, even if one end of the foreign object penetrates the separator and reaches the negative electrode composite material layer, the other end of the foreign object can be prevented from contacting the resin layer and touching the positive electrode current collector foil, thereby suppressing the occurrence of large-scale short circuits. Attached Figure Description

[0012] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0013] Figure 1 This is a diagram illustrating the stacked structure of the secondary battery 10.

[0014] Figure 2 This is a diagram illustrating the function of the secondary battery 10.

[0015] Figure 3A This is a diagram illustrating the experimental example.

[0016] Figure 3B This is a diagram illustrating the experimental example.

[0017] Figure 3C This is a diagram illustrating the experimental example. Detailed Implementation

[0018] Figure 1 The image shows a simplified example of a secondary battery 10. Figure 1 This is a diagram illustrating the stacked structure of the secondary battery 10. Figure 1 For ease of explanation, the structures required for the description are shown, and the battery casing and the like are omitted. Here, a secondary battery refers to any one of the following: an all-solid-state battery in which the electrolyte is composed of a solid electrolyte, a semi-solid-state battery in which at least a portion of the electrolyte is a solid electrolyte and also contains a liquid electrolyte, and a battery in which the electrolyte is only a liquid electrolyte. Hereinafter, an all-solid-state battery will be used as an example. The structures of the various parts in cases other than all-solid-state batteries are as known.

[0019] from Figure 1 As can be seen, the secondary battery 10 comprises a unit cell 11 and a resin layer 20 as one unit cell, and multiple units of the unit cell 11 and resin layer 20 are stacked in a repeating manner. The unit cell 11 has a separator 12, a negative electrode composite material layer 13 is stacked on one side of the separator 12, a negative electrode current collector foil 14 is stacked on the negative electrode composite material layer 13, a positive electrode composite material layer 15 is stacked on the other side of the separator 12, and a positive electrode current collector foil 16 is stacked on the positive electrode composite material layer 15. Furthermore, a resin layer 20 is stacked on the positive electrode current collector foil 16. The resin layer 20 is disposed between adjacent unit cells 11.

[0020] The resin layer 20 is sequentially stacked in this manner, with the unit stack 11 holding the resin layer 20, to form a secondary battery, which in this method is called a bipolar battery.

[0021] 1.1. Diaphragm

[0022] The separator 12 is a layer made of polyethylene or the like, and contains at least an electrolyte. When the secondary battery 10 is configured as an all-solid-state battery, the separator 12 can contain a solid electrolyte and any adhesive. The solid electrolyte can be an inorganic solid electrolyte as described later. The adhesive can be appropriately selected and used as the same adhesive used in the negative electrode composite material layer 13 described later. The materials in the separator 12 and the shape of the separator 12 can remain the same as in the past. In particular, from the viewpoint of being able to easily construct the secondary battery 10, a sheet-like separator 12 is preferred. In this case, the thickness of the separator 12 is preferably, for example, 0.1 μm to 1 mm, more preferably 1 μm to 100 μm. It is even more preferably 1 μm to 15 μm.

[0023] 1.2. Negative Electrode Composite Material Layer

[0024] The negative electrode composite material layer 13 is a layer that at least contains a negative electrode active material. When the secondary battery 10 is configured as an all-solid-state battery, in addition to the negative electrode active material, it can arbitrarily contain a solid electrolyte, a binder, and conductive additives. Known active materials can be used. Among known active materials, two materials with different potentials (charge / discharge potentials) for absorbing, storing, and releasing specified ions can be selected. The material exhibiting the higher potential is used as the positive electrode active material (described later), and the material exhibiting the lower potential is used as the negative electrode active material. For example, in the case of a lithium-ion battery, carbon materials such as graphite or hard carbon, various oxides such as lithium titanate, Si or Si alloys, or metallic lithium or lithium alloys can be used as the negative electrode active material.

[0025] The solid electrolyte is preferably an inorganic solid electrolyte. This is because it has a higher ionic conductivity and better heat resistance than organic polymer electrolytes. Examples of inorganic solid electrolytes include oxide solid electrolytes such as lithium lanthanum zirconate or sulfide solid electrolytes such as Li₂S-P₂S₅. In particular, sulfide solid electrolytes containing Li₂S-P₂S₅ are preferred, and sulfide solid electrolytes containing 50 mol% or more of Li₂S-P₂S₅ are even more preferred.

[0026] The adhesive can use a variety of adhesives such as butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylate butadiene rubber (ABR), and polyvinylidene fluoride (PVdF).

[0027] As a conductive additive, it can be made of carbon materials such as acetylene black or Ketjen black, or metal materials such as nickel, aluminum, and stainless steel.

[0028] The content of each component in the negative electrode composite layer 13 and the shape of the negative electrode composite layer 13 can remain the same as in the past. In particular, from the viewpoint of easily constructing the secondary battery 10, a sheet-like negative electrode composite layer is preferred. In this case, the thickness of the negative electrode composite layer 13 is preferably 0.1 μm to 1 mm, and more preferably 1 μm to 100 μm. It is preferable to determine the thickness of the negative electrode composite layer 13 in such a way that the capacity of the negative electrode is greater than that of the positive electrode.

[0029] 1.3. Negative electrode current collector foil

[0030] The negative electrode current collector foil 14 is a foil that performs current collection, made of metal foil or metal mesh, etc. Metal foil is particularly preferred. Examples of metals constituting the negative electrode current collector foil 14 include Cu, Ni, Fe, Ti, Co, Zn, and stainless steel. The negative electrode current collector foil 14 may have a coating on its surface for adjusting contact resistance, such as a carbon coating. The thickness of the negative electrode current collector foil 14 is not particularly limited. For example, it is preferably 0.1 μm to 1 mm, more preferably 1 μm to 100 μm.

[0031] 1.4. Positive Electrode Composite Material Layer

[0032] The positive electrode composite material layer 15 is a layer that contains at least the positive electrode active material. When the secondary battery 10 is an all-solid-state battery, in addition to the positive electrode active material, it can also arbitrarily contain solid electrolyte, binder, and conductive additives, etc.

[0033] The positive electrode active material can be any known active material. Among known active materials, two materials with different potentials (charge / discharge potentials) for absorbing, storing, and releasing specified ions can be selected. The material exhibiting the higher potential is used as the positive electrode active material, and the material exhibiting the lower potential is used as the aforementioned negative electrode active material. For example, in the case of a lithium-ion battery, lithium cobalt oxide, lithium nickel oxide, and LiNi oxide can be cited as positive electrode active materials. 1 / 3 Co 1 / 3 Mn 1 / 3 Various lithium-containing composite oxides, such as O2, lithium manganese oxide, and spinel-based lithium compounds.

[0034] The surface of the positive electrode active material can be coated with oxide layers such as lithium niobate, lithium titanate, or lithium phosphate.

[0035] The solid electrolyte, binder, and conductive additives can be appropriately selected and used to be the same as those used in the negative electrode composite material layer 13.

[0036] The content of each component in the positive electrode composite layer 15 can be the same as in the conventional method. Furthermore, from the viewpoint of being able to easily construct the secondary battery 10, a sheet-like positive electrode composite layer is preferred. In this case, the thickness of the positive electrode composite layer 15 is preferably 0.1 μm to 1 mm, and more preferably 1 μm to 150 μm.

[0037] Furthermore, from Figure 1 It can also be seen that the positive electrode composite material layer 15 is configured such that its end face is further inward than the end face of the separator 12, the end face of the negative electrode composite material layer 13, and the end face of the resin layer 20.

[0038] 1.5. Positive electrode current collector foil

[0039] The positive electrode current collector foil 16 is a conductive layer. Therefore, the positive electrode current collector foil 16 is composed of a metal foil or a metal mesh, etc. Among these, a metal foil is particularly preferred. Examples of metals constituting the positive electrode current collector foil 16 include Ni, Cr, Au, Pt, Al, Fe, Ti, Zn, alloys of these metals, and stainless steel. The positive electrode current collector foil 16 may have a coating layer on its surface for adjusting resistance, such as a carbon coating.

[0040] The thickness of the positive electrode current collector foil 16 is not particularly limited, but is preferably 0.1 μm to 1 mm, and more preferably 1 μm to 100 μm.

[0041] Here, from Figure 1 It is known that the positive electrode current collector foil 16 is configured such that its end face is further inward than the end face of the positive electrode composite material layer 15. As a result, the exposure of the positive electrode current collector foil 16 is eliminated, and as will be explained later, large-scale short circuits can be suppressed. Figure 1 The distance between the end face of the positive electrode current collector foil 16 (represented by T) and the end face of the positive electrode composite material layer 15 is not particularly limited, but is preferably 2 mm or less. If the distance is too large, end notches or the like may easily occur.

[0042] Furthermore, the end face of the positive current collector foil 16 can be as follows: Figure 1 It can be covered by the positive electrode composite material layer 15 as shown, or it can be left uncovered.

[0043] 1.6. Resin Layer

[0044] The resin layer 20 is a layer formed of resin. There are no particular limitations on the resin that forms the resin layer, but polyethylene or polypropylene are examples.

[0045] from Figure 1 It can be seen that the end of the resin layer 20 protrudes more than the positive electrode composite material layer 15, while the side surface of the diaphragm 12 is exposed.

[0046] Furthermore, to make the resin layer conductive, metallic fillers such as Ni can be dispersed in the resin. However, the conductivity can also be reduced only in the portion of the resin layer 20 where the positive electrode composite material layer 15 is not stacked.

[0047] 2. Effects, etc.

[0048] According to this method, the secondary battery, such as Figure 2 As shown, even if foreign matter A is mixed in, and one end of foreign matter A penetrates the separator 12 and reaches the negative electrode composite material layer 13, the other end of foreign matter A will not contact the positive electrode current collector foil 16 but will directly contact the resin layer 20. Therefore, short circuit between the negative electrode composite material layer 13 and the positive electrode current collector foil 16 can be prevented, thereby suppressing the occurrence of large-scale short circuits.

[0049] Furthermore, while bipolar secondary batteries have been described here, they are not limited to this and can also be applied to unipolar secondary batteries. In unipolar secondary batteries, at least a portion of the tabs is required for connection to an external current collector. In these tabs, the end face of the positive current collector foil cannot be positioned internally, thus preventing the formation of an exposed surface of the positive current collector foil opposite the separator. From this perspective, bipolar secondary batteries offer a more significant advantage compared to unipolar secondary batteries.

[0050] As an example, the temperature rise during forced internal short circuits was measured when a Ni-based foreign substance was mixed into the laminate of each test example. One end of the foreign substance penetrated the separator and reached the negative electrode composite layer, while the other end came into contact with the opposite surface of the separator. Here, Ni-Co-Mn oxide was used as the positive electrode active material for the positive electrode composite layer, aluminum foil was used as the positive electrode current collector foil, carbon was used as the negative electrode active material for the negative electrode composite layer, Cu was used as the negative electrode current collector foil, and polyethylene was used as the separator. The test examples are as follows.

[0051] Experimental Example 1: Figure 2 The method shown

[0052] Experimental Example 2: The method in which the end face of the positive electrode current collector foil extends to the end face of the resin layer ( Figure 3A )

[0053] Experimental Example 3: In addition to Figure 2 In addition to the method shown, a method is also shown where Ni filler is not included in the portion B protruding from the positive electrode composite layer in the resin layer to reduce conductivity. Figure 3B )

[0054] Experimental Example 4: Focusing on the tab portion in a unipolar manner ( Figure 3C )

[0055] As a result, a temperature rise of 8°C was confirmed in Test Example 1, a temperature rise of 50°C was confirmed in Test Example 2, a temperature rise of 3°C was confirmed in Test Example 3, and a temperature rise of 50°C was confirmed in Test Example 4.

Claims

1. A secondary battery comprising a laminate, the laminate having a separator, wherein a negative electrode composite material layer and a negative electrode current collector foil are laminated on one side of the separator, and a positive electrode composite material layer, a positive electrode current collector foil, and a resin layer are laminated on the other side of the separator. The secondary battery is characterized in that... The end face of the positive electrode composite material layer is formed to be further inward than the end face of the separator, the end face of the negative electrode composite material layer, and the end face of the resin layer. The end face of the positive electrode current collector foil is formed to be further inward than the end face of the positive electrode composite material layer.

2. The secondary battery according to claim 1, characterized in that, The laminate is bipolar.

3. The secondary battery according to claim 1 or 2, characterized in that, The portion of the resin layer at the end where the positive electrode composite material layer is not stacked does not contain conductive filler.

4. The secondary battery according to claim 1 or 2, characterized in that, The distance between the end face of the positive electrode composite material layer and the end face of the positive electrode current collector foil is within 2 mm.

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