JP7647501B2 - All-solid-state battery - Google Patents

Description

This application relates to solid-state batteries.

In solid-state batteries that have a negative electrode with a larger area than the positive electrode, a technique is known in which an insulating material is placed between the positive electrode current collector and the negative electrode to prevent short circuits caused by contact between the two.

For example, Patent Document 1 discloses an all-solid-state battery in which only the sides of the laminated battery are covered with resin. Patent Document 2 discloses a technology for providing an insulating layer on the end of the positive electrode.

Patent No. 6445601 JP 2021-57321 A

If the electrode surface on which the insulating layer is to be placed is rough, there is a problem that the insulating layer cannot be placed appropriately. For example, a part of the positive electrode may be removed by laser trimming, and the extension portion extending beyond the positive electrode may be covered with insulating resin tape. However, the surface of the extension portion exposed by laser trimming (e.g., the surface of the solid electrolyte layer) is rough, and there is a problem that the resin tape placed on one side of the extension portion may peel off due to the reaction force. When the resin tape peels off, the electrode protected by the resin tape is eventually exposed, and the burrs from the exposed electrode come into contact with the counter electrode, causing a short circuit.

In view of the above, the objective of this application is to provide an all-solid-state battery that can more effectively protect the extension portion.

As one aspect of the present disclosure for solving the above-mentioned problems, in an all-solid-state battery including at least one unit battery, the unit battery includes a first current collector layer, a first active material layer laminated on one side surface of the first current collector layer, a second active material layer laminated on the other side surface of the first current collector layer, a first solid electrolyte layer laminated on one side surface of the first active material layer, a second solid electrolyte layer laminated on the other side surface of the second active material layer, a third active material layer laminated on one side surface of the first solid electrolyte layer, a fourth active material layer laminated on the other side surface of the second solid electrolyte layer, a second current collector layer laminated on one side surface of the third active material layer, and a third current collector layer laminated on the other side surface of the fourth active material layer, wherein the first active material layer and the second active material layer are either a negative electrode active material layer or a positive electrode active material layer, and the first active material When the first active material layer and the second active material layer are negative active material layers, the third active material layer and the fourth active material layer are positive active material layers, and when the first active material layer and the second active material layer are positive active material layers, the third active material layer and the fourth active material layer are negative active material layers. In the unit battery, at least the first current collector layer extends outward from the third active material layer and the fourth active material layer to form an extension portion. The unit battery further includes a protective member for protecting the extension portion. The protective member is made of a material having a base layer and a first adhesive layer provided on a surface of the base layer that contacts the extension portion. The protective member is provided continuously over one side surface of the extension portion, a side surface of the extension portion, and the other side surface of the extension portion, and has a protective portion adhered to the extension portion by the first adhesive layer, and a protrusion protruding outward from the side surface of the protective member.

The protective member disposed in the all-solid-state battery of the present disclosure has a predetermined protrusion. This makes it possible to suppress peeling of the protective member due to the reaction force of the base layer. Therefore, according to the all-solid-state battery of the present disclosure, the extension can be protected more effectively.

FIG. 1 is a plan view of an all-solid-state battery 1000. 2 is a cross-sectional view of the all-solid-state battery 1000 taken along line AA in FIG. 1. FIG. 3 is a cross-sectional view focusing on one unit battery 100 in FIG. 2. 1A is a cross-sectional view illustrating an extension portion 40. FIG. 1B is a cross-sectional view illustrating a protection member 50. 11 is a cross-sectional view of a unit battery in which a protective member having only a protective portion is disposed on an extension portion. FIG. 2 is a cross-sectional view of a unit battery 200 including a protective member 150. FIG. 1A is a cross-sectional view of a unit battery 300 including a protective member 250. FIG. 1B is a cross-sectional view of only the protective member 250. 1 shows the peel strength evaluation results for Examples 1 and 2 and Comparative Example 1, in which protective members having a substrate layer thickness of 12.5 μm were used. 1 shows the peel strength evaluation results for Examples 3 and 4 using protective members with a substrate layer thickness of 7.5 μm.

[All-solid-state battery 1000]
The all-solid-state battery of the present disclosure will be described below with reference to an all-solid-state battery 1000 as one embodiment. FIG. 1 shows a plan view of the all-solid-state battery 1000 observed from the top in the stacking direction. FIG. 2 shows a cross-sectional view of the all-solid-state battery 1000 cut along A-A in FIG. 1. FIG. 3 shows a cross-sectional view focusing on one unit battery 100 in FIG. 2. FIG. 4 shows a cross-sectional view of the unit battery 100 when disassembled. The up-down direction of the paper in FIG. 2 and FIG. 3 may be referred to as the stacking direction, the left-right direction of the paper as the width direction, and the back-to-front direction of the paper as the depth direction.

As shown in FIG. 2, the all-solid-state battery 1000 is formed by stacking multiple unit batteries 100. However, the all-solid-state battery of the present disclosure may include at least one unit battery.

<Unit battery 100>
As shown in FIG. 3 , the unit battery 100 includes a first current collector layer 11, a first active material layer 21 laminated on one surface of the first current collector layer 11, a second active material layer 22 laminated on the other surface of the first current collector layer 11, a first solid electrolyte layer 31 laminated on one surface of the first active material layer 21, a second solid electrolyte layer 32 laminated on the other surface of the second active material layer 22, a third active material layer 23 laminated on one surface of the first solid electrolyte layer 31, a fourth active material layer 24 laminated on the other surface of the second solid electrolyte layer 32, a second current collector layer 12 laminated on one surface of the third active material layer 23, and a third current collector layer 13 laminated on the other surface of the fourth active material layer 24.

Here, the first active material layer 21 and the second active material layer 22 are either a negative electrode active material layer or a positive electrode active material layer, and when the first active material layer 21 and the second active material layer 22 are negative electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are positive electrode active material layers, and when the first active material layer 21 and the second active material layer 22 are positive electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are negative electrode active material layers.

In addition, in the unit battery 100, at least the first current collector layer 11 extends outward beyond the third active material layer 23 and the fourth active material layer 24 to form an extension portion 40. The unit battery 100 further includes a protective member 50 that protects the extension portion 40.

(First current collector layer 11)
The first collector layer 11 may be made of a metal foil or a metal mesh. Metal foil is particularly preferred. Examples of metals constituting the first collector layer 11 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. Cu is particularly preferred. The first collector layer 11 may have some kind of coating layer (e.g., a carbon coating layer) on its surface to adjust the resistance. The first collector layer 11 may be made of multiple layers. For example, the first collector layer 11 may be made of multiple metal foils stacked together. The thickness of the first collector layer 11 (the total thickness when it is made of multiple layers. The same applies to other layers) is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. When the first active material layer 21 and the second active material layer 22 described below are negative electrode active material layers, the first current collector layer 11 functions as a negative electrode current collector layer. On the other hand, when the first active material layer 21 and the second active material layer 22 are positive electrode active material layers, the first current collector layer 11 functions as a positive electrode current collector layer.

(First active material layer 21 and second active material layer 22)
In the unit battery 100, a first active material layer 21 is laminated on one side surface of the first current collector layer 11, and a second active material layer 22 is laminated on the other side surface of the first current collector layer 11. The first active material layer 21 may be composed of a plurality of layers. For example, an active material layer may be further laminated on the surface of one active material layer, and the first active material layer 21 may be composed of the plurality of layers as a whole. The second active material layer 22 may also be composed of a plurality of layers. The first active material layer 21 and the second active material layer 22 are either a negative electrode active material layer or a positive electrode active material layer. In particular, it is preferable that they are negative electrode active material layers. The first active material layer 21 and the second active material layer 22 may be layers containing the same type of material or layers containing different materials. It is preferable that they are layers containing the same type of material. Hereinafter, the negative electrode active material layer will be described.

The negative electrode active material layer contains at least a negative electrode active material. As the negative electrode active material, a known negative electrode active material may be used. For example, when forming a lithium ion battery, the negative electrode active material may be a silicon-based active material such as Si, a Si alloy, or silicon oxide; a carbon-based active material such as graphite or hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, a lithium alloy, or the like.

The negative electrode active material layer may optionally contain a solid electrolyte, a binder, a conductive assistant, etc. As the solid electrolyte, an inorganic solid electrolyte is preferable because it has a higher ionic conductivity than an organic polymer electrolyte and is more heat resistant than an organic polymer electrolyte. Preferred inorganic solid electrolytes include, for example, oxide solid electrolytes such as lithium lanthanum zirconate, LiPON, Li _1+X AlXGe _2-X (PO ₄ ) ₃ , Li-SiO-based glass, and Li-Al-S-O-based glass; Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Si ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -LiI-LiBr, LiI-Li ₂ S-P ₂ S ₅ , LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , and Li ₂ S-P ₂ S ₅ -GeS. Examples of the _sulfide solid electrolyte include sulfide solid electrolytes such as Li ₂ S-P _{2 S 5 and Li 2 S-P 2} S _{5 -LiI} -LiBr. In particular, sulfide solid electrolytes are preferred, sulfide solid electrolytes containing Li ₂ S-P ₂ S ₅ -LiI-LiBr are more preferred, and sulfide solid electrolytes containing Li 2 S-P 2 S 5 -LiI-LiBr are even more preferred. Examples of the binder include butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVdF), and the like. Examples of the conductive assistant include carbon materials such as acetylene black and ketjen black, and metal materials such as nickel, aluminum, and stainless steel.

The content of each component in the negative electrode active material layer may be the same as in the past. The shape of the negative electrode active material layer may also be the same as in the past. In particular, from the viewpoint of easily constructing the unit battery 100, a sheet-shaped negative electrode active material layer is preferable. In this case, the thickness of the negative electrode active material is preferably, for example, 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 150 μm or less. However, it is preferable to determine the size (area and thickness) of the negative electrode active material layer so that the capacity of the negative electrode is larger than the capacity of the positive electrode.

(First solid electrolyte layer 31 and second solid electrolyte layer 32)
In the unit battery 100, a first solid electrolyte layer 31 is laminated on one side surface of the first active material layer 21, and a second solid electrolyte layer 32 is laminated on the other side surface of the second active material layer 22. The first solid electrolyte layer 31 may be composed of a plurality of layers. For example, a solid electrolyte layer may be laminated on the surface of one solid electrolyte layer, and the first solid electrolyte layer 31 may be composed of the plurality of layers as a whole. The second solid electrolyte layer 32 may also be composed of a plurality of layers. The first solid electrolyte layer 31 and the second solid electrolyte layer 32 may be layers containing the same type of material or layers containing different materials. They are preferably layers containing the same type of material.

The solid electrolyte layer is a layer containing at least a solid electrolyte. As the solid electrolyte, the above-mentioned inorganic solid electrolyte is preferable, and a sulfide solid electrolyte is more preferable. In this case, the sulfide solid electrolyte contained in the solid electrolyte layer is preferably a sulfide solid electrolyte containing Li ₂ S-P ₂ S ₅ , and more preferably a sulfide solid electrolyte containing Li ₂ S-P ₂ S ₅ -LiI-LiBr.

The solid electrolyte layer may optionally contain a binder. The binder may be selected appropriately from the binders described above.

The content of each component in the solid electrolyte layer may be the same as in the past. The shape of the solid electrolyte layer may also be the same as in the past. In particular, from the viewpoint of easily constructing the unit battery 100, a sheet-shaped solid electrolyte layer is preferable. In this case, the thickness of the solid electrolyte layer is preferably, for example, 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

(Third Active Material Layer 23 and Fourth Active Material Layer 24)
In the unit battery 100, a third active material layer 23 is laminated on one side surface of the first solid electrolyte layer 31, and a fourth active material layer 24 is laminated on the other side surface of the second solid electrolyte layer 32. The third active material layer 23 may be composed of a plurality of layers. For example, an active material layer may be laminated on the surface of one active material layer to configure the third active material layer 23 as a whole of the plurality of layers. The fourth active material layer 24 may also be composed of a plurality of layers. When the above-mentioned first active material layer 21 and second active material layer 22 are negative electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are positive electrode active material layers. On the other hand, when the first active material layer 21 and the second active material layer 22 are positive electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are negative electrode active material layers. In particular, it is preferable that the third active material layer 23 and the fourth active material layer 24 are positive electrode active material layers. The third active material layer 23 and the fourth active material layer 24 may be layers containing the same type of material or layers containing different materials. They are preferably layers containing the same type of material. The positive electrode active material layer will be described below.

The positive electrode active material layer contains at least a positive electrode active material. The positive electrode active material may be a known positive electrode active material. For example, when forming a lithium ion battery, various lithium-containing composite oxides such as lithium cobalt oxide, lithium nickel oxide, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , lithium manganate, and spinel-based lithium compounds may be used as the positive electrode active material. The surface of the positive electrode active material may be covered with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer.

The positive electrode active material layer may optionally contain a solid electrolyte, a binder, a conductive assistant, and the like. As the solid electrolyte, the above-mentioned inorganic solid electrolyte is preferable. In particular, a sulfide solid electrolyte is preferable, a sulfide solid electrolyte containing Li ₂ S-P ₂ S ₅ is more preferable, and a sulfide solid electrolyte containing Li ₂ S-P ₂ S ₅ -LiI-LiBr is even more preferable. As the binder, for example, butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVdF), and the like can be mentioned. As the conductive assistant, a carbon material such as acetylene black or ketjen black, or a metal material such as nickel, aluminum, or stainless steel can be mentioned.

The content of each component in the positive electrode active material layer may be the same as in the past. The shape of the positive electrode active material layer may also be the same as in the past. In particular, from the viewpoint of easily constructing the unit battery 100, a sheet-shaped positive electrode active material layer is preferable. In this case, the thickness of the positive electrode active material layer is preferably, for example, 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 150 μm or less.

(Second current collector layer 12 and third current collector layer 13)
In the unit battery 100, the second current collector layer 12 is laminated on one side surface of the third active material layer 23, and the third current collector layer 13 is laminated on the other side surface of the fourth active material layer 24. The second current collector layer 12 may be made of a plurality of layers. For example, the second current collector layer 12 may be formed by overlapping a plurality of metal foils. The third current collector layer 13 may also be made of a plurality of layers. The second current collector layer 12 and the third current collector layer 13 may be layers containing the same type of material or layers containing different materials. Preferably, they are layers containing the same type of material. Furthermore, the first current collector layer 11 and the second current collector layer 12 may be layers containing the same type of material or layers containing different materials. Preferably, they are layers containing different materials. Furthermore, the first current collector layer 11 and the third current collector layer 13 may be layers containing the same type of material or layers containing different materials. Preferably, they are layers containing different materials.

The second collector layer 12 and the third collector layer 13 may be made of metal foil, metal mesh, or the like. Metal foil is particularly preferred. Metals constituting the second collector layer 12 and the third collector layer 13 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. Al is particularly preferred. The second collector layer 12 and the third collector layer 13 may have some kind of coating layer (e.g., a carbon coating layer) on their surfaces to adjust the resistance. Figures 2 and 3 show the second collector layer 12 and the third collector layer 13 in which a carbon coating layer is disposed at a position in contact with the second active material layer 22 and the third active material layer 23, respectively. That is, in FIG. 2, the second current collector layer 12 has a second current collector foil 12a and a carbon coating layer 12b, and the third current collector layer 13 has a third current collector foil 13a and a carbon layer 13b.

The thickness of each of the second collector layer 12 and the third collector layer 13 is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. In the unit battery 100, when the first active material layer 21 and the second active material layer 22 are negative electrode active material layers, the second collector layer 12 and the third collector layer 13 function as positive electrode collector layers. On the other hand, when the first active material layer 21 and the second active material layer 22 are positive electrode active material layers, the second collector layer 12 and the third collector layer 13 function as negative electrode collector layers.

(Extending portion 40)
In the unit battery 100, at least the first current collector layer 11 extends outward beyond the third active material layer 23 and the fourth active material layer 24 to form the extension portion 40. In other words, when viewed in the stacking direction of the layers, the area of the first current collector layer 11 is larger than each of the areas of the third active material layer 23 and the fourth active material layer 24. It is sufficient that the extension portion 40 includes at least the first current collector layer 11. Preferably, at least the first current collector layer 11, the first active material layer 21, and the second active material layer 22 extend outward beyond the third active material layer 23 and the fourth active material layer 24 to form the extension portion 40. More preferably, as shown in Figures 3 and 4, the first current collector layer 11, the first active material layer 21, the second active material layer 22, the first solid electrolyte layer 31, and the second solid electrolyte layer 32 extend outward beyond the third active material layer 23 and the fourth active material layer 24 to form an extension portion 40. The extension lengths of the first current collector layer 11, the first active material layer 21, the second active material layer 22, the first solid electrolyte layer 31, and the second solid electrolyte layer 32 may be the same or different. Preferably, the respective extension lengths are approximately the same, as shown in Figures 3 and 4.

(Protective Member 50)
The protective member 50 is a member that protects the extension portion 40, and is disposed in the depth direction as shown in FIG. 1. Also, as shown in FIG. 3 and FIG. 4, the protective member 50 is composed of a material having a base layer 51 and a first adhesive layer 52 provided on the surface of the base layer 51 that contacts the extension portion 40. In FIG. 4, the protective member 50 is formed by combining two resin tapes 53 having the base layer 51 and the first adhesive layer 52 provided on the other side surface of the base layer 51. Specifically, the protective member 50 is formed by overlapping the surfaces of the first adhesive layer 52 of the two resin tapes 53 so as to cover the extension portion 40. Here, there may be a portion where the first adhesive layers 52 are bonded to each other on the side surface of the extension portion 40. This is because the extension portion 40 is very thin, and such a portion may occur when the protective member 50 is disposed on the extension portion 40.

The protective member 50 thus formed has two parts. That is, the protective member 50 has a protective part 54 that is continuously provided over one surface of the extension portion 40, the side surface of the extension portion 40, and the other surface of the extension portion 40 and is adhered to the extension portion 40 by a first adhesive layer 52, and a protruding part 55 that protrudes outward from the side surface of the protective part 54.

The protective portion 54 is a member for preventing a short circuit caused by contact between the second collector layer 12 or the third collector layer 13 and the extension portion 40. It is also a member for preventing the extension portion 40 from slipping off. On the other hand, the protruding portion 55 is a member for suppressing the reaction force of the base material layer 51 constituting the protective portion 54 and improving the adhesive strength of the protective member 50 (protective portion 54).

If the surface of the extension 40 is rough, the protective part 54 may not adhere well and may peel off. In particular, when the extension 40 is formed by removing the widthwise ends of the third active material layer 23 and the fourth active material layer 24 by laser trimming, the exposed surfaces of the first solid electrolyte layer 31 and the second solid electrolyte layer 32 tend to become rough, so that the protective part 54 cannot be properly adhered to the extension 40. As an example, FIG. 5 shows a cross-sectional view of a protective member having only a protective part arranged on the extension. As shown in FIG. 5, when a protective part is arranged on the extension 40 having a rough surface, after a certain time has passed, one end of the protective part is likely to peel off due to the reaction force of the base layer. In addition, after a certain time has passed, the protective part may peel off until the side of the first collector layer is exposed, as shown by the arrow in FIG. 5. In such a case, there is a risk that burrs originating from the electrodes of the first collector layer, such as the first collector layer, may come into contact with the second collector layer and cause a short circuit. Burrs are generated when the electrodes are cut. In contrast, the protective member 50 has a protruding portion 55 in addition to the protective portion 54. By having the protruding portion 55, it is possible to prevent the end of the protective portion 54 from peeling off due to the reaction force of the base layer 51. Therefore, the protective member 50 has the effect of preventing the above-mentioned short circuit.

The base layer 51 is made of insulating resin. The type of resin is not particularly limited, but examples include thermoplastic resin and thermosetting resin. Thermosetting resin is preferable, and polyimide resin is more preferable. The thickness of the base layer 51 may be 7.5 μm or more, or 12.5 μm or less. This provides the protective member with sufficient strength.

The material of the first adhesive layer 52 is not particularly limited, and any known adhesive resin can be used as appropriate. Examples include acrylic resin, rubber resin, silicon resin, and urethane resin. The thickness of the first adhesive layer may be 4 μm or more, or 7 μm or less. This can improve the peel strength of the protective member 50.

The thickness of the protective member 50 is equal to or less than the length between the extension 40 and the second collector layer 12 or the third collector layer 13. Preferably, the thickness of the protective member 50 is equal to or less than 90% of the length between the extension 40 and the second collector layer 12 or the third collector layer 13. This is because if the protective member 50 comes into contact with the second collector layer 12 or the third collector layer 13, the adhesion between the second collector layer 12 or the third collector layer 13 and the third active material layer 23 or the fourth active material layer 24 may decrease, resulting in a decrease in battery performance. The thickness of the protective member 50 is the thickness of the protective member 50 (protective portion 54) disposed on one side surface or the other side surface of the extension 40. In the case of the protective member 50 having the configuration as shown in FIG. 3 and FIG. 4, the thickness of the protective member 50 is the sum of the thicknesses of the base layer 51 and the first adhesive layer 52.

In the case of the unit battery 100 shown in FIG. 3, the thickness of the protective member 50 (protective portion 54) on one side surface of the extension portion 40 is preferably thinner than the thickness of the third active material layer 23, and the thickness of the protective member 50 (protective portion 54) on the other side surface of the extension portion 40 is preferably thinner than the thickness of the fourth active material layer 24. The thickness of the protective member 50 (protective portion 54) on the side surface of the extension portion 40 is not particularly limited, and may be thick.

The protective member 50 (protective portion 54) may be in contact with the side surface of the third active material layer 23 or the side surface of the fourth active material layer 24, or a gap may exist between the protective member 50 and the side surface of the third active material layer 23 or the side surface of the fourth active material layer 24.

The widthwise length of the protrusion 55 is not particularly limited, but may be 1 mm or more and 5 mm or less, or 3 mm or more and 5 mm or less, from the viewpoint of further suppressing peeling of the end of the protective part 54. The thickness of the protrusion 55 is not particularly limited, and may be set appropriately. The position of the protrusion 55 on the side surface of the protective part 54 is not particularly limited, but it is sufficient that the protrusion 55 is located in the center part of the side surface of the protective part 54 in the stacking direction.

Next, we will explain protective member 150, which is another form of protective member 50. Figure 6 shows a cross-sectional view of a unit battery 200 including protective member 150. As shown in Figure 6, unit battery 200 differs from unit battery 100 in that it has protective member 150 instead of protective member 50, but the other components are the same.

The protective member 150 is formed by adding a second adhesive layer 156 to the protective member 50. The second adhesive layer 156 may be provided on at least one of the one side surface and the other side surface of the protective portion 54. Preferably, as shown in FIG. 6, the second adhesive layer 156 is provided on both the one side surface and the other side surface of the protective portion 54.

The second adhesive layer 156 fills the gap between the protective portion 54 and the second collector layer 12 or the third collector layer 13, and serves to prevent the intrusion of foreign matter therebetween. It also serves to suppress short circuits caused by burrs present on the collector layer. Furthermore, it serves to bond the protective member 150 to the second collector layer 12 or the third collector layer 13, and to improve the peel strength of the protective member 50 (protective portion 54). Therefore, the second adhesive layer 156 is disposed on one side surface or the other side surface, or both surfaces, of the protective portion 54. In FIG. 5, the second adhesive layer 156 is disposed on one side surface and the other side surface of the protective portion 54.

The material of the second adhesive layer 156 is not particularly limited, but the same type of material as the first adhesive layer 52 can be used. The thickness of the second adhesive layer 156 is not particularly limited, but is, for example, 1 μm or more. However, as described above, the thickness of the protective member 150 is not more than the length between the extension portion 40 and the second or third current collector layer 12, 13. Here, the thickness of the protective member 150 is the sum of the thicknesses of the base layer 51, the first adhesive layer 52, and the second adhesive layer 156.

Next, we will explain protective member 250, which is another form of protective member 50. Figure 7 shows a cross-sectional view of unit battery 300 including protective member 250. As shown in Figure 7, unit battery 300 differs from unit battery 100 in that it has protective member 250 instead of protective member 50, but the other components are the same.

As shown in FIG. 7, unlike the protective members 50 and 150, the protective member 250 is made of one material. Specifically, the protective member 250 has a form in which the protruding portions of the protective members 50 and 150 are integrated. More specifically, the protective member 250 has a Y-shaped base layer 251 and a first adhesive layer 252 arranged on the inner surface of the Y-shape (the surface that contacts the extension portion 40 of the base layer 251). In addition, the outer surfaces of the Y-shape (one side surface and the other side surface of the protective portion 254) may each have a second adhesive layer 256. Furthermore, there may be a portion where the first adhesive layers 252 arranged on the inner surface of the Y-shape are bonded to each other. In addition, in the Y-shaped protective member 250, the U-shaped portion is the protective portion 254, and the I-shaped portion is the protruding portion 255.

As such, the protective member of the present disclosure may be composed of one member, or may be composed of two or more members. In either case, the same effect is achieved.

<Other configurations>
A current collecting tab connected to each current collector layer may be provided in the all-solid-state battery 1000. The all-solid-state battery 1000 may be housed in a metal laminate exterior body such as an Al laminate exterior body.

[Method of manufacturing the all-solid-state battery 1000]
The method for producing the all-solid-state battery 1000 is not particularly limited, but for example, it can be produced as follows.

First, a first active material layer 21 is laminated on one surface of the first current collector layer 11, a second active material layer 22 is laminated on the other surface of the first current collector layer 11, a first solid electrolyte layer 31 is laminated on one surface of the first active material layer 21, a second solid electrolyte layer 32 is laminated on the other surface of the second active material layer 22, a third active material layer 23 is laminated on one surface of the first solid electrolyte layer 31, and a fourth active material layer 24 is laminated on the other surface of the second solid electrolyte layer 32.

Here, the first active material layer 21 and the second active material layer 22 are either a negative electrode active material layer or a positive electrode active material layer, and when the first active material layer 21 and the second active material layer 22 are negative electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are positive electrode active material layers, and when the first active material layer 21 and the second active material layer 22 are positive electrode active material layers, the third active material layer 23 and the fourth active material layer 24 are negative electrode active material layers. In addition, at least the first current collector layer 11 is extended outward in the width direction beyond the third active material layer 23 and the fourth active material layer 24 to form an extension portion 40.

The positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer can be prepared by a known method. For example, when preparing the positive electrode active material layer, the material constituting the positive electrode active material layer is dispersed in a predetermined organic solvent to form a slurry, and the slurry is applied to the surface of the current collector layer or the substrate, and then dried. The solid electrolyte layer and the negative electrode active material layer can also be prepared by a similar method. Then, the layers can be laminated as described above and pressed at a predetermined pressure to adhere to each other. In addition, the ends of the laminate may be removed by laser trimming in order to make the extension portion 40 extend beyond the third active material layer 23 and the fourth active material layer 24.

Next, a protective member is continuously arranged over one surface, the side surface, and the other surface of the extension portion 40. Then, the second current collector layer 12 is laminated on one surface of the third active material layer 23, and the third current collector layer 13 is laminated on the other surface of the fourth active material layer 24, thereby obtaining a unit battery 100. In addition, a plurality of the obtained unit batteries 100 may be laminated. Furthermore, the obtained all-solid-state battery 1000 may be appropriately housed in a battery case such as a metal laminate exterior body.

[Fabrication of all-solid-state battery]
Following the above-mentioned all-solid-state battery 1000, a test all-solid-state battery was produced. As the protective member, two resin tapes using polyimide resin for the base material layer were used. Then, as shown in FIG. 3, the resin tape was attached to the extended portion, and the protective member was arranged. The thicknesses of the base material layer, the first adhesive layer, and the protective member are shown in Table 1.

[evaluation]
The adhesive strength of the protective member was evaluated. The method was as follows. A resin tape with a width of 10 mm was attached to the surface of the trimmed solid electrolyte layer at a predetermined length, and a 90° peel test was performed at an angle of 90° and a speed of 50 mm/min. The test atmosphere was a dry environment with a temperature of 25°C. When the peel strength was 0.05 N or more, it was evaluated as "○", and otherwise it was evaluated as "×". The results are shown in Table 1, Figures 8 and 9.

The batteries themselves were also evaluated. Those suitable for use as batteries were rated "○", and those not suitable were rated "×". The results are shown in Table 1.

Furthermore, an overall evaluation was performed based on these results. If both of the above two evaluations were rated as ○, the evaluation was made as "○", and if at least one of them was rated as ×, the evaluation was made as "×". The results are shown in Table 1.

As shown in Table 1, Figure 8, and Figure 9, Examples 1 to 4 and Comparative Example 2 had sufficient peel strength. On the other hand, Comparative Example 1 had insufficient peel strength. It is believed that Comparative Example 1 had insufficient peel strength because the thickness of the first adhesive layer was thin. In addition, Comparative Example 1 had insufficient peel strength, so end peeling occurred after a certain period of time. For this reason, the battery evaluation was "x". Comparative Example 2 had sufficient peel strength, but the thickness of the protective member was thicker than the thickness of the positive electrode active material layer, so the adhesion between the positive electrode current collector layer and the positive electrode active material layer was likely to decrease, which in turn led to a decrease in battery performance. For this reason, the battery evaluation was "x". On the other hand, Examples 1 to 4 did not experience end peeling, and there was no concern about a decrease in battery performance. For this reason, the battery evaluation was "○". Based on the above results, the overall evaluations of Comparative Examples 1 and 2 were "×", and the overall evaluations of Examples 1 to 4 were "○".

REFERENCE SIGNS LIST 11 First current collector layer 12 Second current collector layer 13 Third current collector layer 21 First active material layer 22 Second active material layer 23 Third active material layer 24 Fourth active material layer 31 First solid electrolyte layer 32 Second solid electrolyte layer 40 Extension portion 50, 150, 250 Protective member 51, 251 Base material layer 52, 252 First adhesive layer 53 Resin tape 54, 254 Protective portion 55, 255 Protruding portion 156, 256 Second adhesive layer 100, 200, 300 Unit battery 1000 All-solid-state battery

Claims (1)

In an all-solid-state battery including at least one unit battery,
the unit battery comprises a first current collector layer, a first active material layer laminated on one surface of the first current collector layer, a second active material layer laminated on the other surface of the first current collector layer, a first solid electrolyte layer laminated on one surface of the first active material layer, a second solid electrolyte layer laminated on the other surface of the second active material layer, a third active material layer laminated on one surface of the first solid electrolyte layer, a fourth active material layer laminated on the other surface of the second solid electrolyte layer, a second current collector layer laminated on one surface of the third active material layer, and a third current collector layer laminated on the other surface of the fourth active material layer,
the first active material layer and the second active material layer are either a negative electrode active material layer or a positive electrode active material layer, when the first active material layer and the second active material layer are negative electrode active material layers, the third active material layer and the fourth active material layer are positive electrode active material layers, and when the first active material layer and the second active material layer are positive electrode active material layers, the third active material layer and the fourth active material layer are negative electrode active material layers,
in the unit battery, the first current collector layer , the first active material layer, the second active material layer, the first solid electrolyte layer, and the second solid electrolyte layer extend outward beyond the third active material layer and the fourth active material layer to form an extension portion,
The unit battery further includes a protective member for protecting the extension portion,
the protective member is made of a material having a base layer and a first adhesive layer provided on a surface of the base layer that comes into contact with the extended portion,
the protective member includes a protective portion that is continuously provided across one side surface of the extension portion, a side surface of the extension portion, and the other side surface of the extension portion, and is adhered to the extension portion by the first adhesive layer, and a protruding portion that protrudes outward from the side surface of the protective portion ;
The thickness of the first adhesive layer is 4 μm or more and 7 μm or less,
a thickness of the protective member disposed on one side surface or the other side surface of the extension portion is equal to or less than a length between the extension portion and the second current collector layer or the third current collector layer;
All-solid-state battery.