All-solid-state battery and method for manufacturing the same

Abstract

To provide an all-solid battery and the like capable of suppressing the occurrence of delamination and cracking and propagation of delamination and cracking occurred.SOLUTION: An all-solid battery 100 has a structure including a positive current collector 6; a positive electrode layer 20 including a positive electrode active material 3 and a solid electrolyte 1; a solid electrolyte layer 10 containing a solid electrolyte 2; a negative electrode layer 30 including a negative electrode active material 4 and a solid electrolyte 5; and a negative electrode current collector 7, which are stacked in this order. The solid electrolyte layer 10 has a repeating structure in which a low porosity portion 11 and a high porosity portion 12 having a higher porosity than the low porosity portion 11 are repeated in the in-plane direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an all-solid-state battery and a manufacturing method thereof, and more particularly to an all-solid-state battery using a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and a manufacturing method thereof. [Background technology]

[0002] In recent years, the trend toward lighter and more cordless electronic devices such as personal computers and mobile phones has led to a demand for the development of reusable secondary batteries. Secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lead-acid batteries, and lithium-ion batteries. Among these, lithium-ion batteries are attracting attention due to their lightweight, high voltage, and high energy density.

[0003] In the field of automobiles, such as electric vehicles and hybrid vehicles, the development of high-capacity secondary batteries is becoming increasingly important, and the demand for lithium-ion batteries is on the rise.

[0004] A lithium-ion battery is composed of a positive electrode layer, a negative electrode layer, and an electrolyte disposed between them. The electrolyte can be a liquid electrolyte, such as lithium hexafluorophosphate, dissolved in an organic solvent, or a solid electrolyte. Currently, widely used lithium-ion batteries are flammable because they use an organic solvent-containing electrolyte. Therefore, materials, structures, and systems are required to ensure the safety of lithium-ion batteries. In contrast, using a non-flammable solid electrolyte as the electrolyte is expected to simplify the materials, structures, and systems described above, thereby increasing energy density, reducing manufacturing costs, and improving productivity. Hereinafter, batteries such as lithium-ion batteries that use a solid electrolyte will be referred to as "all-solid-state batteries."

[0005] Solid electrolytes can be broadly divided into organic solid electrolytes and inorganic solid electrolytes. Organic solid electrolytes have an ionic conductivity of 10 -6S / cm, and the ionic conductivity of the electrolyte is about 10 -3 The ionic conductivity of organic solid electrolytes is extremely low compared to the ionic conductivity of about 10 S / cm. Therefore, it is difficult to operate all-solid-state batteries using organic solid electrolytes in an environment of 25°C. Oxide-based solid electrolytes, sulfide-based solid electrolytes, and halide-based solid electrolytes are common inorganic solid electrolytes. The ionic conductivity of these is 10 -4 ~10 -3 The ionic conductivity is relatively high, at about 500 S / cm. Therefore, research and development of all-solid-state batteries using these materials has been actively conducted in recent years in order to increase the size and capacity of these batteries.

[0006] For example, Patent Document 1 discloses the configuration of a solid electrolyte layer in an all-solid-state battery in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated in this order. Patent Document 1 shows a configuration in which through-holes are formed in the solid electrolyte layer to prevent the propagation of peeling and cracking that occurs due to expansion and contraction of the positive electrode layer and the negative electrode layer during the battery charge and discharge process, thereby preventing a decrease in battery capacity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-86174 Summary of the Invention [Problem to be solved by the invention]

[0008] Generally, during the charge-discharge process of an all-solid-state battery, repeated charge-discharge cycles cause the positive electrode active material in the positive electrode layer and / or the negative electrode active material in the negative electrode layer to expand and contract, which can easily cause peeling and cracking at the interface between the positive electrode layer and the solid electrolyte layer and / or the interface between the negative electrode layer and the solid electrolyte layer.Furthermore, repeated charge-discharge cycles cause the peeling and cracking to propagate and expand, resulting in a decrease in battery capacity.

[0009] One example of a measure to prevent the propagation of such peeling and cracking is the configuration shown in Patent Document 1. In the all-solid-state battery disclosed in Patent Document 1, the solid electrolyte layer formed between the positive electrode layer and the negative electrode layer has a structure with through-holes, which make it difficult for peeling and cracking to propagate. However, local current concentration near the through-holes can cause rapid expansion and contraction and heat generation in the positive electrode active material and / or the negative electrode active material, potentially increasing the number of locations where peeling and cracking occur. In particular, the higher the charge / discharge capacity and charge / discharge rate, the more likely this problem is to occur.

[0010] Therefore, the present disclosure provides an all-solid-state battery and the like that can suppress the occurrence of peeling and cracking, as well as the propagation of peeling and cracking that has occurred. [Means for solving the problem]

[0011] An all-solid-state battery according to one embodiment of the present disclosure has a structure in which a positive electrode current collector, a positive electrode layer including a positive electrode active material and a first solid electrolyte, a solid electrolyte layer including a third solid electrolyte, a negative electrode layer including a negative electrode active material and a second solid electrolyte, and a negative electrode current collector are stacked in this order, and the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a higher porosity than the low-porosity portions are repeated in an in-plane direction.

[0012] A method for manufacturing an all-solid-state battery according to one embodiment of the present disclosure is a method for manufacturing the all-solid-state battery, and includes a solid electrolyte powder film formation step of spreading a third solid electrolyte composed of a plurality of particles in a film shape to form a powder film, a solid electrolyte pre-pressurization step of pressurizing the powder film to form a pre-pressurized powder film, and a solid electrolyte laser light irradiation step of irradiating the pre-pressurized powder film with laser light to form a laser photosintered film in which particles of the third solid electrolyte are partially sintered together. [Effects of the Invention]

[0013] According to the all-solid-state battery etc. according to the present disclosure, it is possible to suppress the occurrence of peeling and cracking, as well as the propagation of peeling and cracking that has occurred. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of an all-solid-state battery according to an embodiment. [Figure 2A] FIG. 2A is a schematic cross-sectional view illustrating a step of forming a positive electrode layer in the embodiment. [Figure 2B] FIG. 2B is a cross-sectional view illustrating a step of forming a negative electrode layer according to the embodiment. [Figure 2C] FIG. 2C is a cross-sectional view illustrating the solid electrolyte layer forming step according to the embodiment. [Figure 2D] FIG. 2D is a cross-sectional view illustrating the laminating step and the pressing step according to the embodiment. [Figure 3] FIG. 3 shows SEM observation images of the surfaces of a pre-pressed powder film and a laser photosintered film according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the necking state of particles of a solid electrolyte. [Figure 5] FIG. 5 is a schematic diagram showing the state of particles of the solid electrolyte in the formation of the solid electrolyte layer in the embodiment. [Figure 6] FIG. 6 is a schematic diagram showing an example of the arrangement of low porosity portions and high porosity portions in a top view of a solid electrolyte layer according to an embodiment. [Figure 7] FIG. 7 is a schematic diagram showing an example of the arrangement of low porosity portions and high porosity portions in a cross-sectional view of a solid electrolyte layer according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Summary of the Disclosure) An outline of one aspect of the present disclosure is as follows.

[0016] An all-solid-state battery according to one embodiment of the present disclosure has a structure in which a positive electrode current collector, a positive electrode layer including a positive electrode active material and a first solid electrolyte, a solid electrolyte layer including a third solid electrolyte, a negative electrode layer including a negative electrode active material and a second solid electrolyte, and a negative electrode current collector are stacked in this order, and the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a higher porosity than the low-porosity portions are repeated in an in-plane direction.

[0017] As a result, the repeated low-porosity regions in the in-plane direction within the solid electrolyte layer ensure ion mobility during charge and discharge even in the high-porosity regions, suppressing local current concentration and thereby suppressing the occurrence of peeling and cracking of each layer. Furthermore, at the interface on the positive electrode layer side and / or the negative electrode layer side of the solid electrolyte layer, the high-porosity regions within the solid electrolyte layer relieve stress due to expansion and contraction of the positive electrode active material in the positive electrode layer and / or the negative electrode active material in the negative electrode layer, so that even if peeling and cracking occur, the propagation of the peeling and cracking can be suppressed.

[0018] Furthermore, for example, the difference in porosity between the high porosity portion and the low porosity portion may be 5% or more and 40% or less.

[0019] This makes it difficult for the battery performance of the all-solid-state battery to be impaired, and also makes it possible to effectively suppress the occurrence of the above-mentioned peeling and cracking, as well as the propagation of the peeling and cracking that has occurred.

[0020] Furthermore, for example, the low porosity portions may be arranged in a line shape or a dot shape when viewed from above.

[0021] This simplifies the device for forming the low porosity portion.

[0022] Furthermore, for example, the repeating structure may have a different ratio of the low porosity portion to the high porosity portion between the outer periphery and the center of the solid electrolyte layer when viewed from above.

[0023] This makes it possible to adjust the balance between stress relaxation due to expansion and contraction of the active material and the ionic conductivity of the solid electrolyte layer in accordance with the characteristics, shape, etc. of the all-solid-state battery.

[0024] Furthermore, for example, at least one of the surface of the solid electrolyte layer facing the positive electrode layer and the surface of the solid electrolyte layer facing the negative electrode layer may have an uneven shape.

[0025] This increases the contact area between the solid electrolyte layer and the layer in contact with the surface of the solid electrolyte layer, improving the battery performance and further suppressing the occurrence of peeling.

[0026] Furthermore, for example, in the uneven shape, the convex portions may be formed by the low porosity portions.

[0027] As a result, the porosity of the convex portions is low, and therefore the concave-convex shape is easily maintained even when subjected to stress during the manufacturing process and use of the all-solid-state battery.

[0028] Furthermore, for example, the solid electrolyte layer may have a portion that is aligned with the low-porosity portion along the thickness direction and that is in contact with the positive electrode layer or the negative electrode layer and has a porosity higher than that of the low-porosity portion.

[0029] This allows the solid electrolyte layer to effectively relieve stress caused by expansion and contraction of the active material at the interface on the positive electrode layer side or the negative electrode layer side of the solid electrolyte layer.

[0030] Furthermore, for example, the solid electrolyte layer may have a portion that is aligned with the high-porosity portion along the thickness direction and that is in contact with the positive electrode layer or the negative electrode layer, and has a porosity lower than that of the high-porosity portion.

[0031] This increases the ionic conductivity of the solid electrolyte layer in the vicinity of the positive electrode layer and the negative electrode layer, making it more difficult for local current concentration to occur.

[0032] Furthermore, a manufacturing method of an all-solid-state battery according to one aspect of the present disclosure is the manufacturing method of the all-solid-state battery described above, and includes a solid electrolyte powder film forming step of forming a powder film by spreading a third solid electrolyte composed of a plurality of particles in a film shape, a solid electrolyte pre-pressurizing step of pressurizing the powder film to form a pre-pressurized powder film, and a solid electrolyte laser light irradiation step of irradiating the pre-pressurized powder film with laser light to form a laser photosintered film by partially sintering particles of the third solid electrolyte together.

[0033] As a result, the laser light irradiation partially promotes sintering between particles of the third solid electrolyte, reducing the spaces between the particles of the third solid electrolyte, making it possible to easily produce a solid electrolyte layer with a repeating structure in which low-porosity and high-porosity regions are repeated in the in-plane direction. Furthermore, there is no need to partially replace materials to form the repeating structure, and all-solid-state batteries can be manufactured by easily changing the arrangement of the low-porosity and high-porosity regions to suit battery specifications such as the all-solid-state battery size and charge / discharge conditions.

[0034] Furthermore, for example, the manufacturing method may further include a solid electrolyte pressing step of pressing the laser photosintered film.

[0035] This can improve the ionic conductivity of the solid electrolyte layer.

[0036] All-solid-state batteries according to embodiments will be described in detail below. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection of the components, and processes shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0037] Furthermore, in this specification, terms indicating the relationship between elements, such as parallelism, terms indicating the shape of elements, such as rectangle, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0038] In addition, each drawing is a schematic diagram in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present disclosure, and is not necessarily an exact illustration, and may differ from the actual shape, positional relationship, and proportion. In each drawing, the same reference numerals are used to denote substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0039] Furthermore, in this specification, the terms "upper" and "lower" in the configuration of an all-solid-state battery do not refer to the upper direction (vertically upper) and lower direction (vertically lower) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in the stacking configuration. Furthermore, the terms "upper" and "lower" are applied not only to the case where two components are arranged in close contact with each other, but also to the case where two components are arranged with a gap between them, with another component present between them.

[0040] In this specification, a cross-sectional view is a view showing a cross section of the center of an all-solid-state battery cut in the stacking direction, that is, in the thickness direction of each layer.

[0041] (Embodiment) <Configuration> [A. All-solid-state battery] An overview of the all-solid-state battery according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing a cross section of an all-solid-state battery 100 according to the present embodiment. The all-solid-state battery 100 according to the present embodiment includes a positive electrode current collector 6, a negative electrode current collector 7, a positive electrode layer 20 formed on the surface of the positive electrode current collector 6 closest to the negative electrode current collector 7 and containing a positive electrode active material 3 and a solid electrolyte 1, a negative electrode layer 30 formed on the surface of the negative electrode current collector 7 closest to the positive electrode current collector 6 and containing a negative electrode active material 4 and a solid electrolyte 5, and a solid electrolyte layer 10 disposed between the positive electrode layer 20 and the negative electrode layer 30 and containing a solid electrolyte 2 having at least ion conductivity. In other words, the all-solid-state battery 100 has a structure in which the positive electrode current collector 6, the positive electrode layer 20, the solid electrolyte layer 10, the negative electrode layer 30, and the negative electrode current collector 7 are stacked in this order. The solid electrolyte layer 10 is in contact with, for example, the positive electrode layer 20 and the negative electrode layer 30. Furthermore, the solid electrolyte layer 10 has a repeating structure in which low-porosity portions 11 and high-porosity portions 12 having a higher porosity than the low-porosity portions 11 are repeated in an in-plane direction. In other words, the in-plane direction is a direction perpendicular to the thickness direction of the solid electrolyte layer 10. In the repeating structure, the low-porosity portions 11 and the high-porosity portions 12 are repeatedly arranged in at least one predetermined direction among the directions perpendicular to the thickness direction of the solid electrolyte layer 10.

[0042] In this embodiment, solid electrolyte 1 is an example of a first solid electrolyte, solid electrolyte 5 is an example of a second solid electrolyte, and solid electrolyte 2 is an example of a third solid electrolyte.

[0043] The all-solid-state battery 100 is formed, for example, by the following method. First, a positive electrode layer 20 containing a positive electrode active material 3 is formed on a positive electrode current collector 6 made of metal foil. A negative electrode layer 30 containing a negative electrode active material 4 is formed on a negative electrode current collector 7 made of metal foil. A solid electrolyte layer 10 containing an ion-conductive solid electrolyte 2 is disposed between the positive electrode layer 20 and the negative electrode layer 30. The positive electrode current collector 6 and the negative electrode current collector 7 are then pressed from the outside at a pressure of, for example, 100 MPa to 1000 MPa, and the packing ratio of at least one layer of each is set to 55% or more and less than 100%, thereby obtaining the all-solid-state battery 100. A packing ratio of 55% or more reduces voids in the solid electrolyte layer 10, the positive electrode layer 20, or the negative electrode layer 30, thereby enhancing ionic conduction of lithium (Li) ions and electronic conduction, resulting in excellent charge / discharge characteristics. The packing ratio refers to the percentage of the total volume of each layer that is occupied by the material, excluding voids between the materials. The detailed manufacturing method of the all-solid-state battery 100 will be described later.

[0044] For example, terminals are attached to the pressed all-solid-state battery 100, and the battery is housed in a case. The case for the all-solid-state battery 100 may be, for example, an aluminum laminate bag, a case made of metal such as stainless steel (SUS), iron, or aluminum, or a case made of resin.

[0045] The solid electrolyte layer 10, the positive electrode layer 20, and the negative electrode layer 30 of the all-solid-state battery 100 according to this embodiment will be described below.

[0046] [B. Solid electrolyte layer] First, a description will be given of the solid electrolyte layer 10. The solid electrolyte layer 10 in the present embodiment includes a solid electrolyte 2, and may further include a binder.

[0047] [B-1. Solid electrolyte] The solid electrolyte 2 of this embodiment will be described. Examples of solid electrolyte materials used for the solid electrolyte 2 include sulfide-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes, which are commonly known materials. Any of sulfide-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes may be used as the solid electrolyte material. The type of sulfide-based solid electrolyte in this embodiment is not particularly limited. Examples of sulfide-based solid electrolytes include Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5. In particular, from the viewpoint of excellent lithium ion conductivity, the sulfide-based solid electrolyte may contain Li, P, and S. Furthermore, the sulfide-based solid electrolyte may contain P2S5 because of its high reactivity with and strong binding strength to the binder. The above description "Li2S-P2S5" means a sulfide-based solid electrolyte made using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0048] In this embodiment, the sulfide-based solid electrolyte is, for example, a sulfide-based glass ceramic containing Li2S and P2S5, and the molar ratio of Li2S to P2S5 may be within a range of 70:30 to 80:20, or may be within a range of 75:25 to 80:20. By maintaining the Li2S to P2S5 ratio within this range, a crystal structure with high ionic conductivity can be obtained while maintaining the Li concentration that affects battery characteristics. Furthermore, by maintaining the Li2S to P2S5 ratio within this range, the amount of P2S5 required for reaction and bonding with the binder can be easily secured.

[0049] The type of oxide-based solid electrolyte in this embodiment is not particularly limited. 0.57 La 0.29 TiO3, Li7La3Zr2O 12 , Li7La3Zr 2-x Nb x O 12 , Li7La3Zr2-x Ta x O 12 , Li5La3Ta2O 12 , Li3PO4, Li 1.5 Al 0.5 Ge 1.5 P3O 12 etc.

[0050] The solid electrolyte 2 is made up of, for example, a plurality of particles.

[0051] [B-2. Binder] The binder in this embodiment will be described. The binder is an adhesive material that does not have ionic or electronic conductivity and serves to bond materials within the solid electrolyte layer 10 together and between the solid electrolyte layer 10 and other layers. Known binders for batteries are used as the binder. The binder in this embodiment may also include a thermoplastic elastomer into which a functional group that improves adhesion strength has been introduced. The functional group may also be a carbonyl group. From the perspective of improving adhesion strength, the carbonyl group may also be maleic anhydride. The oxygen atoms of the maleic anhydride in the binder react with the solid electrolyte 2 to bond the solid electrolytes 2 together via the binder, creating a structure in which the binder is disposed between the solid electrolytes 2, thereby improving adhesion strength.

[0052] Examples of thermoplastic elastomers that can be used include styrene-butadiene-styrene (SBS) and styrene-ethylene-butadiene-styrene (SEBS). These have high adhesive strength and are highly durable in terms of the cycle characteristics of the battery. Hydrogenated thermoplastic elastomers may also be used as the thermoplastic elastomer. Use of hydrogenated thermoplastic elastomers improves reactivity and binding properties, as well as solubility in the solvent used to form the solid electrolyte layer 10.

[0053] The amount of binder added is, for example, 0.01% by mass or more and 5% by mass or less, or 0.1% by mass or more and 3% by mass or less, or 0.1% by mass or more and 1% by mass or less. By adding a binder in an amount of 0.01% by mass or more, bonding via the binder is more likely to occur, making it easier to obtain sufficient adhesion strength. Furthermore, by adding a binder in an amount of 5% by mass or less, deterioration of battery characteristics such as charge / discharge characteristics is less likely to occur. Furthermore, even if physical properties such as binder hardness, tensile strength, and tensile elongation change, for example, in the low temperature range, charge / discharge characteristics are less likely to deteriorate.

[0054] [C. Positive electrode layer] Next, the positive electrode layer 20 of this embodiment will be described. The positive electrode layer 20 of this embodiment includes a solid electrolyte 1 and a positive electrode active material 3. If necessary, the positive electrode layer 20 may further contain a conductive additive such as acetylene black or Ketjen Black (registered trademark) and a binder to ensure electronic conductivity. However, adding a large amount of additive can adversely affect battery performance, so the amount is preferably small enough to avoid adversely affecting battery performance. The weight ratio of the solid electrolyte 1 to the positive electrode active material 3 is, for example, in the range of 50:50 to 5:95 (solid electrolyte 1:cathode active material 3), and may also be in the range of 30:70 to 10:90. The volume ratio of the positive electrode active material 3 to the total volume of the positive electrode active material 3 and the solid electrolyte 1 is, for example, 60% to 80%. This volume ratio facilitates the establishment of both lithium ion conduction paths and electron conduction paths within the positive electrode layer 20.

[0055] The positive electrode current collector 6 is made of, for example, a metal foil, such as stainless steel (SUS), aluminum, nickel, titanium, or copper.

[0056] [C-1. Solid electrolyte] The solid electrolyte 1 is at least one selected from the solid electrolyte materials listed above in [B-1. Solid Electrolyte], and is not particularly limited. For example, the same solid electrolyte material as the solid electrolyte 2 is used for the solid electrolyte 1. Different solid electrolyte materials may be used for the solid electrolyte 1 and the solid electrolyte 2. Furthermore, the solid electrolyte 1 is composed of a plurality of particles.

[0057] [C-2. Binder] Since it is the same as the binder described above, the explanation will be omitted.

[0058] [C-3. Positive electrode active material] The positive electrode active material 3 in this embodiment will be described. As the material for the positive electrode active material 3 in this embodiment, for example, a lithium-containing transition metal oxide is used. Examples of lithium-containing transition metal oxides include LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiNiPO4, LiFePO4, and LiMnPO4, as well as compounds obtained by substituting one or two different elements for the transition metals in these compounds. Examples of compounds obtained by substituting one or two different elements for the transition metals in the above compounds include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.5 Mn 1.5 Known materials such as O2 can be used. The materials for the positive electrode active material 3 may be used alone or in combination of two or more.

[0059] The positive electrode active material 3 is composed of, for example, a plurality of particles. The particle diameter of the positive electrode active material 3 is not particularly limited, but is, for example, 1 μm or more and 10 μm or less.

[0060] [D. Negative electrode layer] Next, the anode layer 30 of this embodiment will be described. The anode layer 30 of this embodiment includes a solid electrolyte 5 and an anode active material 4. If necessary, a conductive additive such as acetylene black or ketjen black and a binder may be added to the anode layer 30 to ensure electronic conductivity. However, adding a large amount of additive can adversely affect battery performance, so the amount is preferably small enough to avoid adversely affecting battery performance. The ratio of the solid electrolyte 5 to the anode active material 4, in terms of weight, is, for example, in the range of 5:95 to 60:40, or may be in the range of 30:70 to 50:50. The volume ratio of the anode active material 4 to the total volume of the anode active material 4 and the solid electrolyte 1 is, for example, 60% to 80%. This volume ratio facilitates the establishment of both lithium ion conduction paths and electron conduction paths within the anode layer 30.

[0061] The negative electrode current collector 7 is made of, for example, a metal foil, such as SUS, copper, or nickel.

[0062] [D-1. Solid electrolyte] The solid electrolyte 5 is at least one selected from the solid electrolyte materials listed above in [B-1. Solid Electrolyte], and is not particularly limited. For example, the same solid electrolyte material as the solid electrolyte 1 and the solid electrolyte 2 is used for the solid electrolyte 5. Different solid electrolyte materials may be used for the solid electrolyte 5, the solid electrolyte 1, and the solid electrolyte 2. Furthermore, the solid electrolyte 5 is composed of, for example, a plurality of particles.

[0063] [D-2. Binder] Since it is the same as the binder described above, the explanation will be omitted.

[0064] [D-3. Negative electrode active material] The negative electrode active material 4 in this embodiment will be described. Examples of materials for the negative electrode active material 4 in this embodiment include metals that are easily alloyed with lithium, such as indium, tin, and silicon; carbon materials, such as hard carbon and graphite; lithium; and Li4Ti5O 12 , SiO x Known materials such as the above are used.

[0065] The negative electrode active material 4 is made up of, for example, a plurality of particles. The particle diameter of the negative electrode active material 4 is not particularly limited, but is, for example, 1 μm or more and 15 μm or less.

[0066] <Manufacturing method> Next, a method for manufacturing the all-solid-state battery 100 in this embodiment will be described. Specifically, a method for manufacturing the all-solid-state battery 100 including the solid electrolyte layer 10, the positive electrode layer 20, and the negative electrode layer 30 will be described. FIG. 2A is a cross-sectional view illustrating a step of forming the positive electrode layer 20 in the method for manufacturing the all-solid-state battery 100. FIG. 2B is a cross-sectional view illustrating a step of forming the negative electrode layer 30 in the method for manufacturing the all-solid-state battery 100. FIG. 2C is a cross-sectional view illustrating a solid electrolyte layer forming step in the method for manufacturing the all-solid-state battery 100. FIG. 2D is a cross-sectional view illustrating a lamination step and a pressing step in the method for manufacturing the all-solid-state battery 100.

[0067] The manufacturing method of the all-solid-state battery 100 includes, for example, a positive electrode layer forming step, a positive electrode layer pre-pressurizing step, a negative electrode layer forming step, a negative electrode layer pre-pressurizing step, a solid electrolyte layer forming step, a stacking step, and a pressing step.

[0068] In the positive electrode layer forming step ((a) in FIG. 2A), the positive electrode layer 20 is formed on the positive electrode current collector 6. In the positive electrode layer preliminary pressurizing step ((b) in FIG. 2A), the positive electrode layer 20 is compressed under pressure to an extent that it can be handled in a subsequent step.

[0069] In the negative electrode layer forming step ((c) in FIG. 2B), the negative electrode layer 30 is formed on the negative electrode current collector 7. In the negative electrode layer preliminary pressurizing step ((d) in FIG. 2B), the negative electrode layer 30 is compressed under pressure to an extent that it can be handled in a subsequent step.

[0070] Furthermore, in the solid electrolyte layer formation process ((e) to (h) in FIG. 2C ), a solid electrolyte layer 10 is formed. The solid electrolyte layer formation process includes, for example, a solid electrolyte powder film formation process, a solid electrolyte pre-pressurization process, a solid electrolyte laser light irradiation process, and a solid electrolyte pressing process. In the solid electrolyte powder film formation process ((e) in FIG. 2C ), a solid electrolyte 2 composed of multiple particles is spread in a film-like shape to form a powder film 14. In the solid electrolyte pre-pressurization process ((f) in FIG. 2C ), the powder film 14 is pressed at a predetermined pressure to form a pre-pressurized powder film 15. In the solid electrolyte laser light irradiation process ((g) in FIG. 2C ), laser light is irradiated at multiple locations on the pre-pressurized powder film 15 to form a laser photosintered film 16 in which particles of the solid electrolyte 2 are partially sintered together. In the solid electrolyte pressing process ((h) in FIG. 2C ), the laser photosintered film 16 is pressed at a predetermined pressure. Through these processes, the solid electrolyte layer 10 is formed. In the solid electrolyte pressing step, heating may be performed during pressing, if necessary.

[0071] In the solid electrolyte layer forming step, for example, the pressurizing conditions in the solid electrolyte pre-pressurizing step and the laser light irradiation conditions in the solid electrolyte laser light irradiation step are adjusted so that the solid electrolyte layer 10 has a repeating structure in which low-porosity portions 11 and high-porosity portions 12 are repeated in the in-plane direction.

[0072] Next, in the lamination step and pressing step ((i) and (j) in FIG. 2D ), the positive electrode layer 20 formed on the positive electrode current collector 6, the negative electrode layer 30 formed on the negative electrode current collector 7, and the formed solid electrolyte layer 10 are laminated together so that the solid electrolyte layer 10 is disposed between the positive electrode layer 20 and the negative electrode layer 30, and then pressed from the outside of the positive electrode current collector 6 and the negative electrode current collector 7.

[0073] The method of applying pressure in each of the above steps is not particularly limited, and may be, for example, a flat plate press or a roll press.

[0074] Next, each step will be described in detail.

[0075] [E1. Positive electrode layer deposition process] First, as shown in (a) of Fig. 2A, a positive electrode layer forming step is performed. The positive electrode layer 20 forming step (positive electrode layer forming step) in this embodiment can be performed by the following method.

[0076] The positive electrode layer formation process includes, for example, a mixture preparation process and a powder lamination process. In the mixture preparation process, the solid electrolyte 1 and the positive electrode active material 3 are prepared in a powder state without being slurried. If necessary, a binder and a conductive additive (not shown) are also prepared. The prepared materials are mixed under appropriate shear and pressure to produce a positive electrode mixture in which the positive electrode active material 3 and the solid electrolyte 1 are uniformly dispersed. In the powder lamination process, the prepared positive electrode mixture is uniformly laminated on the positive electrode current collector 6 to obtain a laminate. Laminating the powder positive electrode mixture into a film has the advantage of eliminating the drying process and reducing production costs compared to the conventional wet coating method in which a slurry dispersed in a solvent is applied. Furthermore, there is an advantage that the solvent, which contributes to a decrease in the battery performance of the all-solid-state battery 100, does not remain in the formed positive electrode layer 20. The positive electrode layer 20 may also be formed by forming a film from a slurried positive electrode mixture.

[0077] [E2. Positive electrode layer pre-pressurization process] 2A(b), a positive electrode layer pre-pressurizing step is performed. In the positive electrode layer pre-pressurizing step, the laminate including the positive electrode current collector 6, the solid electrolyte 1, and the positive electrode active material 3 obtained in the positive electrode layer film-forming step is pressed to densify the positive electrode mixture powder to a level that makes it easy to handle in subsequent steps, and a positive electrode layer 20 is formed as a powder compressed film.

[0078] [F1. Negative electrode layer deposition process] 2B(c), the negative electrode layer forming step is performed. In the negative electrode layer forming step (negative electrode layer forming step) of the present embodiment, the basic film forming method is the same as that of the above [E1. Positive electrode layer forming step], except that the material used is changed to the material for the negative electrode layer 30.

[0079] That is, in the anode layer film-forming step, for example, an anode mixture obtained by mixing a non-slurried powder state solid electrolyte 5, an anode active material 4, and, if necessary, a binder and a conductive additive (not shown) is layered on an anode current collector 7. Note that the anode layer 30 may also be formed by forming a film from a slurried anode mixture.

[0080] [F2. Negative electrode layer pre-pressurization process] Next, as shown in (d) of Fig. 2B, a negative electrode layer pre-pressurizing step is performed. In the negative electrode layer pre-pressurizing step, for example, a laminate including the negative electrode current collector 7, the solid electrolyte 5, and the negative electrode active material 4 obtained in the negative electrode layer film-forming step is pressed to densify the powder to a level that makes it easy to handle in subsequent steps, thereby forming the negative electrode layer 30 as a powder compressed film. In other words, the negative electrode layer pre-pressurizing step may be performed by the same method as in [E2. Positive electrode layer pre-pressurizing step].

[0081] [G. Solid electrolyte layer formation process] In the film-forming step of the solid electrolyte layer 10 (solid electrolyte layer film-forming step), a solid electrolyte 2 selected from the materials listed in [B-1. Solid Electrolyte] is used. Then, a mixture obtained by mixing the solid electrolyte 2 with a binder as needed is laminated in the form of a film on at least one of the positive electrode layer 20 obtained in the positive electrode layer pre-pressurizing step and the negative electrode layer 30 obtained in the negative electrode layer pre-pressurizing step.

[0082] 2C, the solid electrolyte 2 is laminated in film form on the anode layer 30, but this is not limiting. In the solid electrolyte layer forming step, the solid electrolyte 2 may be formed in film form directly on at least one of the positive electrode layer 20 and the negative electrode layer 30. In addition, in the solid electrolyte layer forming step, the solid electrolyte layer 10 formed on a substrate such as a polyethylene terephthalate (PET) film using the following method may be indirectly laminated on at least one of the positive electrode layer 20 and the negative electrode layer 30.

[0083] Here, the solid electrolyte layer forming step will be described in detail.

[0084] [G1. Solid electrolyte powder film formation process] First, as shown in FIG. 2C(e), in the solid electrolyte powder film formation step, a solid electrolyte 2 made up of a plurality of particles is spread in the form of a film to form a powder film 14. In the example shown in FIG. 2C(e), the powder film 14 is formed on the negative electrode layer 30. Here, the method for spreading the solid electrolyte 2 in the form of a film is not particularly limited. Examples of methods for spreading the solid electrolyte 2 in the form of a film include a method of supplying powder of the solid electrolyte 2 and flattening it with a squeegee or the like.

[0085] [G2. Solid electrolyte pre-pressurization process] Next, as shown in FIG. 2C (f), in the solid electrolyte pre-pressing step, the powder film 14 formed in the solid electrolyte powder film formation step is pressed at a predetermined pressure to form a pre-pressed powder film 15. The means for applying pressure in the solid electrolyte pre-pressing step are not particularly limited. Examples of the means for applying pressure in the solid electrolyte pre-pressing step include a flat press and a roll press. The purpose of the solid electrolyte pre-pressing step is to release air from the powder film 14 and bring the particles of the solid electrolyte 2 that make up the powder film 14 into close contact with each other. This varies depending on the state of close contact between the particles of the solid electrolyte 2. This changes the ease of sintering the solid electrolyte 2 in the next step, the solid electrolyte laser light irradiation step. The pressurizing conditions in the solid electrolyte pre-pressing step and the laser light irradiation conditions in the solid electrolyte laser light irradiation step are adjusted, for example, according to the material and particle diameter of the solid electrolyte 2.

[0086] [G3. Solid electrolyte laser light irradiation process] Next, as shown in (g) of FIG. 2C , in the solid electrolyte laser light irradiation step, laser light is irradiated onto the pre-pressurized powder film 15 formed in the solid electrolyte pre-pressurization step, thereby forming a laser photosintered film 16 in which particles of the solid electrolyte 2 constituting the pre-pressurized powder film 15 are partially sintered together. Here, by providing multiple locations in the laser photosintered film 16 that are irradiated with laser light, a structure is formed in which areas where sintering between particles is promoted and areas where sintering between particles is insufficient are alternately formed in the in-plane direction. Furthermore, by providing locations with high and low laser light energy, a structure in which areas where sintering between particles is promoted and areas where sintering between particles is insufficient may be alternately formed in the in-plane direction.

[0087] In the solid electrolyte laser light irradiation process, for example, sintering of particles is promoted in areas where the energy of the irradiated laser light is high, while sintering of particles is insufficient in areas where the laser light is not irradiated or where the energy of the irradiated laser light is low. As will be described in detail later, the porosity is low in areas where sintering of particles is promoted, and high in areas where sintering of particles is insufficient. This porosity relationship is a relative relationship comparing areas where sintering of particles is promoted with areas where sintering of particles is insufficient. This porosity relationship is maintained in the final all-solid-state battery 100, so the areas where sintering of particles is promoted become the low-porosity areas 11 described above, and the areas where sintering of particles is insufficient become the high-porosity areas 12 described above.

[0088] [G4. Solid electrolyte pressing process] Next, as shown in (h) of FIG. 2C, in the solid electrolyte pressing step, the laser photosintered film 16 formed in the solid electrolyte laser light irradiation step is pressed with a predetermined pressure to form the solid electrolyte layer 10. The pressing force in the solid electrolyte pressing step is, for example, greater than the pressing force in the solid electrolyte preliminary pressurization step. Furthermore, the laser photosintered film 16 may be pressed while being heated as needed.

[0089] The solid electrolyte pressing step can be combined with the pressing step described next, and may be omitted.

[0090] [H. Lamination and Pressing Processes] Next, as shown in (i) and (j) of FIG. 2D , a lamination step and a pressing step are performed. In the lamination step, the positive electrode layer 20, the solid electrolyte layer 10, and the negative electrode layer 30 are laminated in this order. In the pressing step, the laminated body formed in the lamination step is pressed. Specifically, in the lamination step and the pressing step, the positive electrode layer 20 formed on the positive electrode current collector 6, the negative electrode layer 30 formed on the negative electrode current collector 7, and the solid electrolyte layer 10 obtained through the respective film-forming steps and the respective preliminary pressing steps are laminated so that the solid electrolyte layer 10 is disposed between the positive electrode layer 20 and the negative electrode layer 30 (lamination step). Then, the positive electrode current collector 6 and the negative electrode current collector 7 are pressed from the outside (pressing step) to obtain an all-solid-state battery 100. Note that if the solid electrolyte pressing step is omitted, the pressing step also serves as the solid electrolyte pressing step for pressing the laser photosintered film 16.

[0091] The purpose of pressing is to increase the density of the positive electrode layer 20, the negative electrode layer 30, and the solid electrolyte layer 10. Increasing the density can improve the lithium ion conductivity and electronic conductivity in the positive electrode layer 20, the negative electrode layer 30, and the solid electrolyte layer 10, resulting in an all-solid-state battery 100 with good battery characteristics.

[0092] <Results of the study> In examining the process for realizing the structure of the all-solid-state battery 100 according to this embodiment, the following laser light sintered film 16 was formed. The solid electrolyte 2 constituting the following laser light sintered film 16 was Li, an oxide-based solid electrolyte. 0.57 La 0.29 TiO3 (lithium lanthanum titanium oxide: manufactured by Toho Titanium) particles were used.

[0093] First, particles of an oxide-based solid electrolyte (average particle diameter 0.9 μm) were spread on a substrate and the film thickness was adjusted with a squeegee to form a powder film 14 made of particles of the solid electrolyte 2. Further, a pre-pressure of 1 kPa to 1000 kPa, for example 100 kPa, was applied from the upper surface of the powder film 14 to form a pre-pressurized powder film 15.

[0094] Next, a CO2 laser beam was scanned and irradiated in stripes onto the upper surface of the pre-pressed powder film 15 to form a laser photosintered film 16. Surface observations of the pre-pressed powder film 15 before and after the laser beam irradiation were also performed using a scanning electron microscope (SEM). Figure 3 shows SEM images of the surfaces of the pre-pressed powder film 15 and the laser photosintered film 16. Figure 3(a) is an SEM image showing the upper surface of the pre-pressed powder film 15 before laser beam irradiation, and Figure 3(b) is an SEM image showing the upper surface of the laser photosintered film 16 formed by irradiating the pre-pressed powder film 15 with laser beam.

[0095] As a result of surface SEM observation, as shown in Figure 3(a), the pre-pressed powder film 15 before laser light irradiation was in a state in which particles of the oxide-based solid electrolyte were uniformly distributed. Meanwhile, as shown in Figure 3(b), it was confirmed that in the laser photosintered film 16, laser light irradiation caused necking between particles of the solid electrolyte 2 to progress, resulting in the formation of alternating in-plane regions A where sintering had progressed and regions B where necking between particles of the solid electrolyte 2 had not progressed sufficiently. It was also confirmed that the surface of the laser photosintered film 16 had an uneven structure consisting of regions A and B. On the surface of the laser photosintered film 16, regions A were convex and regions B were concave.

[0096] Here, the necking state of the particles of the solid electrolyte 2 in the portions A and B shown in FIG. 3(b) will be described with reference to FIG. 4. FIG. 4 is a schematic diagram showing the necking state of the particles of the solid electrolyte 2. As shown in FIG. 4, the necking of the particles of the solid electrolyte 2 means that the particles are bonded together, forming a constricted shape between the bonded particles. Furthermore, the progression of necking means that the bonding between the particles progresses, which increases the necking width, which is the width of the constricted portion between the particles. Therefore, when comparing the necking width C shown in FIG. 4 between the portions A and B shown in FIG. 3(b), it was confirmed that the necking width C of the solid electrolyte 2 in the portion A is 1.5 times or more larger than the necking width C of the solid electrolyte 2 in the portion B.

[0097] Next, the mechanism of behavior of particles of the solid electrolyte 2 when irradiated with laser light will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing the state of particles of the solid electrolyte 2 during the formation of the solid electrolyte layer 10. In Fig. 5, the substrate is not shown.

[0098] FIG. 5A is a schematic diagram showing a pre-pressed powder film 15 in which particles of the solid electrolyte 2 are formed into a film. As shown in FIG. 5A, in the pre-pressed powder film 15, spaces 17 exist between the particles of the solid electrolyte 2. By partially irradiating this pre-pressed powder film 15 with laser light 18, a laser photosintered film 16 shown in FIG. 5B is formed. Here, in areas 19 where sintering of the solid electrolyte 2 is promoted by irradiation with laser light 18, in other words, in areas 19 where the laser light irradiation energy is strong, necking of the particles of the solid electrolyte 2 progresses. As the necked particles of the solid electrolyte 2 are attracted to each other, the aforementioned spaces 17 decrease. In other words, in areas other than the areas 19 where the laser light irradiation energy is strong, that is, in areas where the laser light irradiation energy is weaker than that of the laser light irradiated at area 19 or where the laser light is not irradiated, the number of particles of the solid electrolyte 2 decreases, and necking does not progress sufficiently, so the amount of reduction in the spaces 17 is small. Therefore, the porosity is low at point 19, and the porosity is higher at points other than point 19. In other words, it is possible to intentionally create high and low porosity areas in the laser light-sintered film 16. Furthermore, due to this difference in the particle amount of the solid electrolyte 2, an uneven shape is formed on the surface of the laser light-sintered film 16, with point 19 being a convex portion. Note that it is also possible to form areas with different porosities by pressing with a press plate or the like having an uneven shape. In this case, unlike the method using laser light irradiation, the areas with high porosity become concave portions.

[0099] Furthermore, as shown in FIG. 5C , when the laser photosintered film 16 is pressed at a pressure of 1 MPa to 1000 MPa, the solid electrolyte layer 10 formed retains the porosity and the unevenness, although the absolute values of the porosity and the height of the unevenness change from those of the laser photosintered film 16. In particular, because the portion 19 is a convex portion, the portion 19 is easily pressed, and the porosity of the portion 19 is likely to decrease due to pressing. Due to this process and the behavior of the particles of the solid electrolyte 2, the low-porosity portion 11 and the high-porosity portion 12 described above are formed in the solid electrolyte layer 10. That is, the portion 19a in FIG. 5C corresponds to the low-porosity portion 11. Furthermore, due to the low-porosity portion 11 and the high-porosity portion 12, at least one of the surface of the solid electrolyte layer 10 facing the positive electrode layer 20 and the surface of the solid electrolyte layer 10 facing the negative electrode layer 30 has an uneven shape. In addition, in this uneven shape, the convex portions are formed by low-porosity portions 11, and the concave portions are formed by high-porosity portions 12. As a result, since the porosity of the convex portions is low, the uneven shape is likely to be maintained even when the all-solid-state battery 100 is subjected to stress during the manufacturing process and during use.

[0100] Here, the difference in porosity between the low-porosity portion 11 and the high-porosity portion 12, and the size of the uneven shape, can be adjusted by adjusting the pressure applied in the pre-pressing to form the pre-pressurized powder film 15, and the energy and irradiation interval of the laser light irradiation to form the laser light sintered film 16.

[0101] Thus, the solid electrolyte layer 10 formed by the above mechanism has a structure partially including low-porosity portions 11 and high-porosity portions 12, and is expected to have the effect of reducing stress caused by expansion and contraction of the active material during charge and discharge in the all-solid-state battery 100 in the high-porosity portions 12, thereby suppressing the occurrence and propagation of peeling and cracking. Furthermore, the uneven shape of the surface of the solid electrolyte layer 10 is expected to increase the contact area between the solid electrolyte layer and the positive electrode layer and / or the negative electrode layer, thereby improving battery performance and reducing peeling.

[0102] The porosity of the low-porosity portion 11 is, for example, 5% or more and 20% or less. The porosity of the high-porosity portion 12 is, for example, 25% or more and 45% or less. The difference between the porosity of the high-porosity portion 12 and the porosity of the low-porosity portion 11, i.e., the porosity difference expressed by the formula "porosity of high-porosity portion 12" minus "porosity of low-porosity portion 11," is, for example, 5% or more and 40% or less. When this porosity difference is 40% or less, the ionic conductivity of the solid electrolyte layer 10 is less likely to decrease, and the battery performance of the all-solid-state battery 100 is less likely to be impaired. When this porosity difference is 5% or more, the effect of suppressing the occurrence and propagation of peeling and cracking is enhanced. The porosity is measured, for example, by observing a cross section of the solid electrolyte layer 10. For example, in the observed cross section of the solid electrolyte layer 10, the percentage of the area of voids not occupied by the solid electrolyte 2 per certain area is defined as the porosity.

[0103] Furthermore, the necking width of the particles of solid electrolyte 2 in low-porosity portion 11 is, for example, 1.5 to 10 times the necking width of the particles of solid electrolyte 2 in high-porosity portion 12. When this ratio is 1.5 times or more, the effect of suppressing the occurrence and propagation of peeling and cracking is enhanced. Furthermore, when this ratio is 10 times or less, the ionic conductivity of high-porosity portion 12 is less likely to decrease, and the battery performance of all-solid-state battery 100 is less likely to be impaired.

[0104] Next, we will explain the arrangement of the low-porosity portions 11 and the high-porosity portions 12 in the solid electrolyte layer 10. In the repeating structure of the solid electrolyte layer 10, the positions and shapes of the low-porosity portions 11 and the high-porosity portions 12 can be freely adjusted, for example, by adjusting the position where the laser light is irradiated.

[0105] For example, the low-porosity portions 11 are arranged in a line shape or a dot shape. By arranging the low-porosity portions 11 in such a shape, it is possible to simplify the device for irradiating the laser light used to form the low-porosity portions 11.

[0106] Furthermore, the repeated structure has a different ratio of low-porosity portions 11 to high-porosity portions 12 between the outer periphery and the center of the solid electrolyte layer 10 when viewed from above. This makes it possible to adjust the balance between stress relaxation due to expansion and contraction of the active material and the ionic conductivity of the solid electrolyte layer 10 according to the characteristics and shape of the all-solid-state battery 100. The ratio is, for example, an area ratio. Furthermore, the center is, for example, a region inside the position where the distance between the center and the outer periphery of the solid electrolyte layer 10 is equal when viewed from above, and the outer periphery is a region outside the center.

[0107] Here, an example of the arrangement of the low porosity portion 11 and the high porosity portion 12 in a top view of the solid electrolyte layer 10 will be described with reference to FIG.

[0108] 6 is a schematic diagram showing an example of the arrangement of the low porosity portion 11 and the high porosity portion 12 in a top view of the solid electrolyte layer 10. Fig. 6 is a diagram showing the solid electrolyte layer 10 of the all-solid-state battery 100 as seen from above, that is, along the stacking direction.

[0109] For example, as shown in Figure 6(a), in the solid electrolyte layer laser light irradiation step, low-porosity portions 11 and high-porosity portions 12 are arranged in a stripe pattern by irradiating the solid electrolyte layer with laser light while scanning the laser light in a stripe pattern. The repeated structure shown in Figure 6(a) is a structure in which linear low-porosity portions 11 and high-porosity portions 12 are repeated along the in-plane direction of the solid electrolyte layer 10. This arrangement simplifies the device for irradiating the laser light used to form the low-porosity portions 11, and makes it easier to form the low-porosity portions 11 and high-porosity portions 12.

[0110] 6(b), for example, in the solid electrolyte layer laser light irradiation step, the laser light is scanned and irradiated in a circular pattern, so that the low-porosity portion 11 and the high-porosity portion 12 are arranged in a circular shape in top view, except for the high-porosity portion 12 located in the center. In the example shown in FIG. 6(b), the circular shape is a rectangular ring, but is not particularly limited thereto and may be a shape similar to the outer periphery of the solid electrolyte layer 10 or a circular ring. With this arrangement, in the solid electrolyte pressing step after the laser light irradiation, the material constituting the solid electrolyte layer 10 is less likely to flow from the center to the outer periphery in top view, and uniformity of the pressing pressure and film thickness between the center and the outer periphery is less likely to be impaired.

[0111] Furthermore, as shown in FIG. 6( c), for example, in the solid electrolyte layer laser light irradiation step, the laser light is irradiated by scanning radially from the center toward the periphery, so that low-porosity portions 11 are radially arranged in a top view, and high-porosity portions 12 are arranged so as to fill the spaces between the radial low-porosity portions 11. This arrangement increases the area per unit area to which the laser light is not irradiated from the center toward the periphery in a top view. In other words, the ratio of high-porosity portions 12 to low-porosity portions 11 increases. Since stress due to expansion and contraction of the active material in the all-solid-state battery 100 is greater closer to the periphery, increasing the proportion of high-porosity portions 12 toward the periphery facilitates alleviation of the stress due to expansion and contraction. In other words, this is effective for increasing the size of the all-solid-state battery 100.

[0112] Furthermore, as in the case of forming the arrangements shown in (a) to (c) of Figure 6, the laser light is not limited to being scanned and irradiated in a continuous straight line, but by scanning and irradiating the laser light in a broken line or in a dotted line, it is expected that the effect of alleviating distortion caused by local stress differences between the low porosity portion 11 and the high porosity portion 12 can be achieved.

[0113] Next, the arrangement of the low-porosity portion 11 and the high-porosity portion 12 in the thickness direction of the solid electrolyte layer 10 will be described. A multi-layer solid electrolyte layer 10 can be formed by repeating the steps described in [G. Solid Electrolyte Layer Formation Step] above, or by forming the solid electrolyte layer 10 on each of the positive electrode layer 20 and the negative electrode layer 30 using the method described in [G. Solid Electrolyte Layer Formation Step]. This allows the porosity to be varied along the thickness direction of the solid electrolyte layer 10. For example, the solid electrolyte layer 10 may include a layer having a repeating structure and a layer not having a repeating structure. In the solid electrolyte layer 10, the layer not having a repeating structure is disposed so as to contact at least one of the positive electrode layer 20 and the negative electrode layer 30, for example. An example of the arrangement of the low-porosity portion 11 and the high-porosity portion 12 in a cross-sectional view of the solid electrolyte layer 10 will be described with reference to FIG. 7 .

[0114] 7 is a schematic diagram showing an example of the arrangement of low-porosity portions 11 and high-porosity portions 12 in a cross-sectional view of a solid electrolyte layer 10. FIG. 7 is a diagram showing a cross section of the solid electrolyte layer 10 located between a positive electrode layer 20 and a negative electrode layer 30, cut in the thickness direction.

[0115] For example, as shown in (a) of Figure 7, layers composed of low-porosity portions 11 may be disposed in the solid electrolyte layer 10 at positions that correspond to the interface between the solid electrolyte layer 10 and the positive electrode layer 20 and the interface between the solid electrolyte layer 10 and the negative electrode layer 30. The solid electrolyte layer 10 shown in (a) of Figure 7 has low-porosity portions 11 that are aligned with high-porosity portions 12 in the thickness direction and that contact the positive electrode layer 20 and the negative electrode layer 30. Note that the low-porosity portions 11 aligned with the high-porosity portions 12 in the thickness direction may have a lower porosity than the high-porosity portions 12, and may have a different porosity from the low-porosity portions 11 in the repeating structure, i.e., the low-porosity portions 11 aligned with the high-porosity portions 12 in the in-plane direction. Furthermore, the solid electrolyte layer 10 may be configured not to include either the layer formed of the low porosity portion 11 in contact with the positive electrode layer 20 or the layer formed of the low porosity portion 11 in contact with the negative electrode layer 30.

[0116] This arrangement increases the ionic conductivity of the solid electrolyte layer 10 in the vicinity of the positive electrode layer 20 and the negative electrode layer 30, and makes it difficult for local current concentration to occur at the interface between the solid electrolyte layer 10 and the positive electrode layer 20 and at the interface between the solid electrolyte layer 10 and the negative electrode layer 30, even when a solid electrolyte 2 with low ionic conductivity is used.

[0117] 7(b), for example, layers composed of high-porosity portions 12 may be disposed in the solid electrolyte layer 10 at positions that correspond to the interface between the solid electrolyte layer 10 and the positive electrode layer 20 and the interface between the solid electrolyte layer 10 and the negative electrode layer 30. The solid electrolyte layer 10 shown in FIG. 7(b) has high-porosity portions 12 that are aligned with low-porosity portions 11 along the thickness direction and that contact the positive electrode layer 20 and the negative electrode layer 30. Note that the high-porosity portions 12 aligned with the low-porosity portions 11 along the thickness direction may have a higher porosity than the low-porosity portions 11, and may have a different porosity from the high-porosity portions 12 in the repeating structure, i.e., the high-porosity portions 12 aligned with the low-porosity portions 11 along the in-plane direction. Furthermore, the solid electrolyte layer 10 may be configured not to include either the layer formed of the high porosity portion 12 in contact with the positive electrode layer 20 or the layer formed of the high porosity portion 12 in contact with the negative electrode layer 30.

[0118] This arrangement makes it easier to alleviate stress caused by expansion and contraction of the active material near the interface between the solid electrolyte layer 10 and the positive electrode layer 20 and the interface between the solid electrolyte layer 10 and the negative electrode layer 30. Furthermore, in this arrangement, by using a material with high ionic conductivity as the solid electrolyte 2 that constitutes the solid electrolyte layer 10, deterioration of battery performance can be suppressed.

[0119] 7(c), the solid electrolyte layer 10 may be composed of multiple layers each having a repeating structure, and the low-porosity portions 11 and the high-porosity portions 12 may be arranged so that they are offset from each other between adjacent layers. This arrangement reduces variations in ionic conductivity due to differences in the density of the solid electrolyte 2 in the in-plane direction of the solid electrolyte layer 10, ensuring uniformity across the plane. The arrangements shown in FIGS. 7(a) to 7(c) may also be combined as appropriate.

[0120] Furthermore, by utilizing these arrangement concepts, the ionic conductivity in the end regions of the all-solid-state battery 100 (for example, within a 5 mm range from the end face when viewed along the stacking direction) can be set lower than in other regions, thereby making it possible to suppress unexpected battery reactions via the ends of the positive electrode layer 20 and the negative electrode layer 30, and the effect of suppressing short circuits can also be expected.

[0121] (Other embodiments) While the all-solid-state battery according to the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications conceivable by a person skilled in the art to the embodiments and other forms constructed by combining some of the components of the embodiments are also included in the scope of the present disclosure.

[0122] For example, in the above embodiment, the ions conducted in the all-solid-state battery 100 are lithium ions, but this is not limiting. The ions conducted in the all-solid-state battery 100 may be ions other than lithium ions, such as sodium ions, magnesium ions, potassium ions, calcium ions, or copper ions.

[0123] In the above embodiment, the repeating structure is formed by irradiating a laser beam, but this is not limiting. The repeating structure may be formed by using multiple types of materials for the solid electrolyte 2, adjusting the conditions for pressing the powder film 14, or the like. [Industrial Applicability]

[0124] The all-solid-state battery according to the present disclosure is expected to be applied to a variety of batteries, such as power sources for portable electronic devices and automotive batteries. [Explanation of symbols]

[0125] 1, 2, 5 Solid electrolyte 3 Cathode active material 4 Negative electrode active material 6 Positive electrode current collector 7 Negative electrode current collector 10 Solid electrolyte layer 11 Low porosity area 12 High porosity area 14 Powder film 15 Pre-pressed powder film 16 Laser photosintering film 17 Space 18 Laser Light 19, 19a locations 20 Positive electrode layer 30 negative electrode layer 100 solid state battery A, B part C necking width

Claims

1. a positive electrode current collector; a positive electrode layer including a positive electrode active material and a first solid electrolyte; a solid electrolyte layer including a third solid electrolyte; an anode layer including an anode active material and a second solid electrolyte; a negative electrode current collector and a negative electrode current collector stacked in this order, the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a porosity higher than that of the low-porosity portions are repeated in an in-plane direction; The difference between the porosity of the high porosity portion and the porosity of the low porosity portion is 5% or more and 40% or less. All-solid-state battery.

2. A positive electrode current collector; a positive electrode layer including a positive electrode active material and a first solid electrolyte; a solid electrolyte layer including a third solid electrolyte; an anode layer including an anode active material and a second solid electrolyte; a negative electrode current collector and a negative electrode current collector stacked in this order, the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a porosity higher than that of the low-porosity portions are repeated in an in-plane direction; The repeating structure has a different ratio of the low porosity portion to the high porosity portion between the outer periphery and the center of the solid electrolyte layer when viewed from above. All-solid-state battery.

3. A positive electrode current collector; a positive electrode layer including a positive electrode active material and a first solid electrolyte; a solid electrolyte layer including a third solid electrolyte; an anode layer including an anode active material and a second solid electrolyte; a negative electrode current collector and a negative electrode current collector stacked in this order, the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a porosity higher than that of the low-porosity portions are repeated in an in-plane direction; At least one of the surface of the solid electrolyte layer facing the positive electrode layer and the surface of the solid electrolyte layer facing the negative electrode layer has an uneven shape. All-solid-state battery.

4. In the uneven shape, the convex portions are formed by the low porosity portions. The all-solid-state battery according to claim 3 .

5. The low porosity portions are arranged in a line shape or a dot shape when viewed from above. The all-solid-state battery according to claim 1 .

6. The solid electrolyte layer has a portion with a higher porosity than the low-porosity portion, which is aligned with the low-porosity portion along the thickness direction and is in contact with the positive electrode layer or the negative electrode layer. The all-solid-state battery according to any one of claims 1 to 5.

7. The solid electrolyte layer has a portion that is aligned with the high-porosity portion along the thickness direction and is in contact with the positive electrode layer or the negative electrode layer, and has a lower porosity than the high-porosity portion. The all-solid-state battery according to any one of claims 1 to 5.

8. A method for producing the all-solid-state battery according to any one of claims 1 to 7, a solid electrolyte powder film forming step of forming a powder film by spreading a third solid electrolyte composed of a plurality of particles in a film shape; a solid electrolyte pre-pressing step of pressing the powder film to form a pre-pressed powder film; and a solid electrolyte laser light irradiation step of irradiating the pre-pressed powder film with laser light to form a laser photosintered film in which particles of the third solid electrolyte are partially sintered together. How solid-state batteries are manufactured.

9. A method for manufacturing an all-solid-state battery, comprising: The all-solid-state battery comprises: a positive electrode current collector; a positive electrode layer including a positive electrode active material and a first solid electrolyte; a solid electrolyte layer including a third solid electrolyte; an anode layer including an anode active material and a second solid electrolyte; a negative electrode current collector and a negative electrode current collector stacked in this order, the solid electrolyte layer has a repeating structure in which low-porosity portions and high-porosity portions having a porosity higher than that of the low-porosity portions are repeated in an in-plane direction; The method for producing the all-solid-state battery includes: a solid electrolyte powder film forming step of forming a powder film by spreading a third solid electrolyte composed of a plurality of particles in a film shape; a solid electrolyte pre-pressing step of pressing the powder film to form a pre-pressed powder film; and a solid electrolyte laser light irradiation step of irradiating the pre-pressed powder film with laser light to form a laser photosintered film in which particles of the third solid electrolyte are partially sintered together. How solid-state batteries are manufactured.

10. The method further includes a solid electrolyte pressing step of pressing the laser photosintered film. The method for producing the all-solid-state battery according to claim 8 or 9.

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