All-solid battery and method for manufacturing the same

Abstract

The present disclosure provides an all-solid battery having a novel structure. The all-solid battery of the present disclosure has at least one constituent unit cell, which is a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer stacked in this order, and a connection conductor layer is stacked on a surface on the positive electrode current collector layer side and / or a surface on the negative electrode current collector layer side of the constituent unit cell. The resistivity of the connection conductor layer is preferably less than the resistivity of the positive electrode current collector layer or the negative electrode current collector layer in which the connection conductor layer is stacked. The resistivity of the connection conductor layer is preferably 1 x 10 ‑6 Ωm or less.

Description

Technical Field

[0001] This invention relates to all-solid-state batteries and their manufacturing methods. Background Technology

[0002] All-solid-state batteries have a structure that replaces the separator and electrolyte used in conventional electrolyte-based lithium-ion batteries with a solid electrolyte. Solid electrolytes have high flame retardancy, and the energy density of the component is increased without the need for a cooling unit. They can also be charged at high speeds. Due to these characteristics, they are particularly expected to be practical for automotive applications.

[0003] Regarding the structure of all-solid-state batteries, Patent Document 1 discloses the following structure: a unit cell is obtained by forming a positive electrode layer on one side of a solid electrolyte and a negative electrode layer on the other side; the unit cell is then overlapped with a positive current collector and a negative current collector, the positive current collector is connected to the positive terminal, and the negative current collector is connected to the negative terminal; the terminals are then removed to the outside of the battery. However, in this structure, there is a problem that the internal resistance of the battery increases due to the resistance of the connection between the current collector and the terminal.

[0004] In response, Patent Document 2 discloses a stacked all-solid-state battery structure, in which the positive current collector is folded in such a way that the positive electrode layers of each electrode stack are electrically connected to each other, and the negative current collector is folded in such a way that the negative electrode layers of each electrode stack are electrically connected to each other. This reduces the resistance at the connection points between the positive and negative current collectors and the terminals in existing structures. However, this structure presents the challenge of increased manufacturing complexity.

[0005] On the other hand, when the solid electrolyte contains sulfur and copper is used as the current collector, there is a problem of increased resistance due to the formation of copper sulfide. Therefore, Patent Document 3 discloses an all-solid-state battery that suppresses copper sulfide formation and has excellent conductivity. This all-solid-state battery has a negative electrode current collector for all-solid-state batteries and a sulfur-containing solid electrolyte. The negative electrode current collector for all-solid-state batteries has a nickel film formed on both sides of electrolytic copper foil, rolled copper foil, or copper alloy foil. However, in this structure, since all the layers are bonded together, it is not possible to replace only the corresponding part when a defect occurs in a part of the layer, resulting in a low yield during production.

[0006] Existing technical documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-116156

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-113434

[0009] Patent Document 3: Japanese Patent Application Publication No. 2016-9526 Summary of the Invention

[0010] Therefore, the subject of this disclosure is to provide an all-solid-state battery with a novel structure.

[0011] The solution to the above problem is as follows:

[0012] Option 1

[0013] An all-solid-state battery is an all-solid-state battery having at least one constituent unit cell, wherein the constituent unit cell is formed by sequentially stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer.

[0014] A connecting conductor layer is stacked on the surface of the positive electrode current collector layer and / or the surface of the negative electrode current collector layer constituting the unit battery.

[0015] Option 2

[0016] According to the all-solid-state battery of Scheme 1, the resistivity of the connecting conductor layer is less than the resistivity of the positive electrode current collector layer or the negative electrode current collector layer on which the connecting conductor layer is stacked.

[0017] Option 3

[0018] According to the all-solid-state battery described in Scheme 1 or 2, the resistivity of the connecting conductor layer is 1×10⁻⁶. -6 Below Ωm.

[0019] Option 4

[0020] In any one of the embodiments 1 to 3, the all-solid-state battery, the connecting conductor layer is made of copper and / or aluminum.

[0021] Option 5

[0022] According to any one of Schemes 1 to 4, in the all-solid-state battery, the negative electrode active material layer contains a sulfide-based solid electrolyte, and the negative electrode current collector layer is made of stainless steel or nickel.

[0023] Option 6

[0024] A method for manufacturing an all-solid-state battery according to any one of embodiments 1 to 5, comprising the following steps in sequence:

[0025] A laminate is formed by stacking small units obtained by alternately stacking the constituent unit battery and the connecting conductor layer or by overlapping the constituent unit battery and the connecting conductor layer;

[0026] Connect the positive and negative terminals to the connecting conductor layer of the resulting laminate; and

[0027] The stack is sealed with an outer casing.

[0028] According to this disclosure, an all-solid-state battery with a novel structure can be provided. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the constituent unit cell 10A of the all-solid-state battery 1A according to the first embodiment of this disclosure.

[0030] Figure 2 This is a schematic diagram of the all-solid-state battery 1A according to the first embodiment of this disclosure.

[0031] Figure 3 This is a plan view of the all-solid-state battery 1A according to the first embodiment of this disclosure, viewed from the stacking direction.

[0032] Figure 4 This is a schematic diagram of the all-solid-state battery 1B according to the second embodiment of this disclosure.

[0033] Figure 5 This is a schematic diagram of an all-solid-state battery 1C according to the third embodiment of this disclosure.

[0034] Figure 6 This is a schematic diagram of an all-solid-state battery 1D according to the fourth embodiment of this disclosure.

[0035] Figure 7 This is a schematic diagram of an all-solid-state battery 1E according to the fifth embodiment of this disclosure.

[0036] Explanation of reference numerals in the attached figures

[0037] 1A, 1B, 1C, 1D and 1E all-solid-state batteries

[0038] 10A and 10B constitute a unit cell

[0039] 11 Positive current collector layer

[0040] 12 positive electrode active material layers

[0041] 13 Solid Electrolyte Layer

[0042] 14 negative electrode active material layer

[0043] 15 negative electrode current collector layers

[0044] 16 Insulators

[0045] 17 collector layers

[0046] 20 Connecting conductor layers

[0047] 20a Positive electrode connection conductor layer

[0048] 20b Negative electrode connection conductor layer

[0049] 30 positive extremes

[0050] 40 negative extremes

[0051] 50 outer body Detailed Implementation

[0052] All-Solid-State Batteries

[0053] The all-solid-state battery disclosed herein is an all-solid-state battery having at least one constituting unit cell. The constituting unit cell is formed by sequentially stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer. A connecting conductor layer is stacked on the surface of the positive electrode current collector layer and / or the surface of the negative electrode current collector layer constituting the unit cell.

[0054] The all-solid-state battery disclosed herein can have a single-layer structure comprising a single unit cell, or it can have a stacked structure obtained by alternately stacking multiple unit cells and connecting conductor layers.

[0055] By stacking multiple constituent unit cells, the charge / discharge capacity per unit volume can be further increased, and the internal resistance of the battery can be further reduced. Furthermore, in the all-solid-state battery of this disclosure, if a connecting conductor layer is disposed between each constituent unit cell, the constituent unit cells are not bonded to each other. Therefore, unlike the fully bonded structure of the stack disclosed in Patent Document 3, if some constituent unit cells are defective, only the corresponding constituent unit cells can be replaced, thus improving the yield rate during manufacturing.

[0056] Here, a series structure refers to a configuration where the positive current collector side of a unit cell contacts the connecting conductor, and the negative current collector side of a unit cell contacts the other side, with multiple unit cells stacked in the same polarity direction (bipolar structure). A parallel structure refers to a configuration where the positive current collector side of a unit cell contacts both sides of the positive connecting conductor, and the negative current collector side of a unit cell contacts both sides of the negative connecting conductor, with multiple unit cells stacked in alternating opposite polarities (unipolar structure). Using a series structure increases the battery voltage. Furthermore, using a parallel structure further increases the charge / discharge capacity and reduces the battery's internal resistance.

[0057] Figure 1 This is a schematic diagram illustrating the constituent unit cell of the all-solid-state battery according to the first embodiment of this disclosure. Furthermore, Figure 1 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0058] like Figure 1As shown, the all-solid-state battery 1A of the first embodiment of this disclosure has a constituent unit battery 10A having a structure in which a positive electrode current collector layer 11, a positive electrode active material layer 12, a solid electrolyte layer 13, a negative electrode active material layer 14, and a negative electrode current collector layer 15 are stacked sequentially. When the constituent unit battery 10A is viewed from the stacking direction, the positive electrode current collector layer 11 and the positive electrode active material layer 12 are disposed on the inner periphery of the solid electrolyte layer 13, the negative electrode active material layer 14, and the negative electrode current collector layer 15. In addition, an insulator 16 is disposed to surround the outer periphery of the positive electrode current collector layer 11 and the positive electrode active material layer 12. The insulator 16 has a mirror-frame shape surrounding the outer periphery of the positive electrode current collector layer 11 and the positive electrode active material layer 12.

[0059] By constructing a unit cell 10A having an insulator 16 as described above, short circuits caused by contact between the positive electrode current collector layer 11 and / or the positive electrode active material layer 12 and the negative electrode active material layer 14 and / or the negative electrode current collector layer 15 can be suppressed.

[0060] exist Figure 1 In the stacked configuration of the unit cell 10A, when viewed from the stacking direction, the insulator 16 is disposed at the ends of the positive current collector layer 11 and the positive active material layer 12, surrounding the entire outer periphery of the positive current collector layer 11 and the positive active material layer 12. Therefore, it can fill the gaps formed between the positive current collector layer 11 and / or the positive active material layer 12 and the solid electrolyte layer 13 and / or the negative active material layer 14. When viewed from the stacking direction, the insulator 16 can also be configured to surround the entire outer periphery of the negative active material layer 14 and the negative current collector layer 15.

[0061] Figure 2 This is a schematic diagram of the all-solid-state battery 1A according to the first embodiment of this disclosure. Furthermore, Figure 3 This is a plan view of the all-solid-state battery 1A according to the first embodiment of this disclosure, viewed from the stacking direction. Furthermore, Figure 2 and Figure 3 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0062] exist Figure 2 and Figure 3 In the all-solid-state battery 1A shown, a positive electrode connecting conductor layer 20a and a negative electrode connecting conductor layer 20b are stacked on the surface of the positive electrode current collector layer 11 and the surface of the negative electrode current collector layer 15 constituting the unit battery 10A, respectively. The unit battery 10A and each connecting conductor layer 20a and 20b are disposed within the outer casing 50. The positive electrode connecting conductor layer 20a is connected to the positive terminal 30, and the negative electrode connecting conductor layer 20b is connected to the negative terminal 40. The positive terminal 30 and the negative terminal 40 are structures that extend outward from the outer casing 50, allowing current to be extracted from them.

[0063] Figure 4 This is a schematic diagram of the all-solid-state battery 1B according to the second embodiment of this disclosure. Furthermore, Figure 4 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0064] Figure 4 The all-solid-state battery 1B of the second embodiment of this disclosure shown has a stacked structure (unipolar structure) in which three constituent unit cells 10A are connected in parallel. The all-solid-state battery 1B has a stacked structure in which the negative electrode current collector layer 15 constituting the unit cell 10A is in contact with the negative electrode connecting conductor layer 20b, and the positive electrode current collector layer 11 is in contact with the positive electrode connecting conductor layer 20a. Here, each constituent unit cell 10A is stacked alternately with its polarity reversed.

[0065] like Figure 4 As shown, in the case of stacking multiple units constituting a single cell 10A, multiple positive electrode connecting conductor layers 20a and negative electrode connecting conductor layers 20b are connected to the positive terminal 30 and the negative terminal 40, respectively. The connection method is the same as in the case of a single layer. They are sealed by the outer casing 50, with only a portion of the positive terminal 30 and the negative terminal 40 extending outward from the outer casing 50.

[0066] Figure 5 This is a schematic diagram of the all-solid-state battery 1C according to the third embodiment of this disclosure. Furthermore, Figure 5 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0067] Figure 5 The all-solid-state battery 1C of the third embodiment of this disclosure shown has a stacked structure (bipolar structure) with three constituent unit batteries 10A connected in series. The stacked structure has a negative electrode current collector layer 15 constituting a unit battery 10A and a positive electrode current collector layer 11 constituting another unit battery 10A, each in contact with both sides of a connecting conductor layer 20. At both ends of the stacked constituent unit batteries 10A in the stacking direction, similar to the single-layer case, a positive electrode connecting conductor layer 20a is stacked on the surface on the side of the positive electrode current collector layer 11, and then connected to the positive terminal 30. On the other hand, a negative electrode connecting conductor layer 20b is stacked on the surface on the side of the negative electrode current collector layer 15, and connected to the negative terminal 40. They are sealed by an outer casing 50, with only a portion of the positive terminal 30 and the negative terminal 40 extending outwards from the outer casing 50.

[0068] exist Figure 5 In the all-solid-state battery 1C shown, materials with low resistivity are preferred as the constituent materials of the connecting conductor layer 20, the positive electrode connecting conductor layer 20a, and the negative electrode connecting conductor layer 20b. Examples of such materials include aluminum, copper, nickel, and stainless steel (SUS). Two or more of these materials may also be used. Among them, aluminum or copper are preferred.

[0069] Figure 6This is a schematic diagram of an all-solid-state battery 1D according to the fourth embodiment of this disclosure. Furthermore, Figure 6 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0070] Figure 6 The all-solid-state battery 1D of the fourth embodiment of this disclosure shown has a stacked structure in which multiple constituent unit cells 10A are connected in series. The all-solid-state battery 1D of the fourth embodiment and... Figure 5 Compared to the all-solid-state battery 1C, it has a bipolar structure without a connecting conductor layer 20 sandwiched between the constituent cells 10A. By omitting the connecting conductor layer 20, the battery volume can be reduced and the energy density of the battery can be increased.

[0071] Figure 7 This is a schematic diagram of the all-solid-state battery 1E according to the fifth embodiment of this disclosure. Furthermore, Figure 7 This is not intended to limit the scope of the disclosed all-solid-state battery.

[0072] Figure 7 The all-solid-state battery 1E of the fifth embodiment of this disclosure shown has a stacked structure of two constituent unit cells connected in series. The constituent unit cell 10B (double-sided coated type) has the following structure: a negative electrode active material layer 14 and a solid electrolyte layer 13 are sequentially disposed on one side of the current collector layer 17, a positive electrode active material layer 12 is disposed on the other side, and an insulator 16 is disposed around its outer periphery. The all-solid-state battery 1E has a bipolar structure in which the two constituent unit cells 10B are stacked in such a way that the solid electrolyte layer 13 and the positive electrode active material layer 12 are in contact.

[0073] Figure 7 In the unit cell 10B, a laminate consisting of a positive active material layer 12 coated on one side of the positive current collector layer 11 and an insulator 16 disposed around its outer periphery is formed on the end face of the solid electrolyte layer 13 side, with the positive active material layer 12 in contact with the end face of the solid electrolyte layer 13 side. Additionally, a positive electrode connecting conductor layer 20a connected to the positive terminal 30 is in contact with the positive current collector layer 11. Furthermore, in the unit cell 10B, a laminate consisting of a negative active material layer 14 and a solid electrolyte layer 13 sequentially coated on one side of the negative current collector layer 15 is formed on the end face of the positive active material layer 12 side, with the solid electrolyte layer 13 in contact with the end face of the positive active material layer 12 side. Additionally, a negative electrode connecting conductor layer 20b connected to the negative terminal 40 is in contact with the negative current collector layer 15. They are sealed by the outer casing 50, with only a portion of the positive terminal 30 and the negative terminal 40 being exposed to the outside from the outer casing.

[0074] <Composition of a unit cell>

[0075] The all-solid-state battery disclosed herein has a constituent unit cell having a structure in which a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer are stacked in sequence.

[0076] When viewing the configuration of a unit cell from the stacking direction, the positive electrode current collector layer and the positive electrode active material layer can be disposed on the inner periphery of the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector layer. Alternatively, when viewing the configuration of a unit cell from the stacking direction, the outer periphery of the positive electrode current collector layer and the positive electrode active material layer can be aligned with the solid electrolyte layer. In this case, the positive electrode current collector layer, the positive electrode active material layer, and the solid electrolyte layer can be disposed on the inner periphery of the negative electrode active material layer and the negative electrode current collector layer.

[0077] This is because by ensuring that the positive electrode active material layer, especially its ends, is properly aligned with the solid electrolyte layer and the negative electrode active material layer, lithium ions moving from the positive electrode active material can easily insert into the negative electrode active material during charging. This suppresses the deposition of lithium metal on the surface of the positive electrode active material layer or at the interface between the positive electrode active material layer and the solid electrolyte layer, thereby suppressing internal short circuits within the unit battery.

[0078] Furthermore, in a structure where the positive current collector layer and the positive active material layer are disposed on the inner periphery of the solid electrolyte layer, the negative active material layer, and the negative current collector layer, an insulator can be disposed to surround the outer periphery of the positive current collector layer and the positive active material layer. The insulator can have a mirror-like shape surrounding the outer periphery of the positive current collector layer and the positive active material layer.

[0079] (Positive current collector layer)

[0080] The material constituting the positive electrode current collector layer is preferably one that will not react with the solid electrolyte or during charging and discharging at the positive electrode operating potential, and has low resistivity. Examples include aluminum, stainless steel (SUS, austenitic, martensitic, ferritic, austenitic-ferritic (2-phase)), and nickel. Two or more of these materials may also be used. Aluminum is particularly preferred.

[0081] Furthermore, in the all-solid-state battery disclosed herein, the positive electrode current collector layer can be made of aluminum, stainless steel, or nickel. This is because these metals have low reactivity with sulfide-based solid electrolytes.

[0082] (Positive electrode active material layer)

[0083] The positive electrode active material layer is preferably composed mainly of positive electrode active material and solid electrolyte.

[0084] Examples of positive electrode active materials include LiCoO2, LiMnO2, LiNiO2, NiCoMn ternary lithium oxides, NiCoAl ternary lithium oxides, and LiFePO4. Two or more of these can also be used.

[0085] Examples of solid electrolytes include Li₂S-P₂S₅ (Li₇P₃S₅). 11 ), Li 10 GeP2S 12 Sulfide-based solid electrolytes such as Li6PS5Cl and Li6PS5I, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li7La3Zr2O 12 Li 1.5 Al 0.5 Ge 1.5 Oxide-based solid electrolytes such as (PO4)3 are preferred. Two or more types may also be used. Sulfide-based solid electrolytes are preferred. When using sulfide-based solid electrolytes, it is preferable to coat the surface of the positive electrode active material with LiNbO3 to suppress the reaction of the positive electrode active material.

[0086] (Solid electrolyte layer)

[0087] The solid electrolyte layer is mainly composed of solid electrolytes. Examples of solid electrolytes include substances that constitute the positive electrode active material layer.

[0088] (Negative electrode active material layer)

[0089] The negative electrode active material layer is preferably composed mainly of negative electrode active material and solid electrolyte.

[0090] Examples of anode active materials include graphite, hard carbon, lithium titanate, titanium dioxide, silicon, and silicon oxide. Two or more of these materials can also be used.

[0091] Examples of solid electrolytes include substances that constitute the positive electrode active material layer.

[0092] (Negative electrode current collector layer)

[0093] The material constituting the negative electrode current collector layer is preferably one that will not react with the solid electrolyte or during charging and discharging within the negative electrode operating potential, and has low resistivity. Examples include stainless steel (SUS), carbon, nickel, and copper. Two or more of these materials may also be used.

[0094] Materials that constitute an insulator include, for example, resins such as polyethylene terephthalate (PET), polyimide (PI), and polyphenylene sulfide (PPS), as well as ceramics such as alumina. Two or more of these materials may also be used.

[0095] Furthermore, in the case where the negative electrode active material layer of the all-solid-state battery disclosed herein contains a sulfide-based solid electrolyte, the negative electrode current collector layer is preferably made of stainless steel or nickel. This is because these metals have low reactivity with the sulfide-based solid electrolyte.

[0096] <Connecting Conductor Layer>

[0097] The all-solid-state battery disclosed herein has a connecting conductor layer stacked on the surface of the positive electrode current collector layer and / or the surface of the negative electrode current collector layer constituting a unit cell.

[0098] In the all-solid-state battery disclosed herein, by bonding the positive and negative terminals to the connecting conductor layer, a structure can be formed that does not directly bond the positive and negative terminals to the positive and negative current collector layers constituting the unit cell. Furthermore, a structure can be formed that is simply stacked without bonding the positive and negative current collector layers constituting the unit cell to the connecting conductor layer.

[0099] Therefore, unlike conventional all-solid-state batteries where the positive and negative current collector layers are bonded to the positive and negative terminals, the all-solid-state battery disclosed herein allows for easy separation of the constituent unit cells even when configured as an all-solid-state battery. Thus, for example, during the manufacturing process of an all-solid-state battery, if a portion of the constituent unit cell malfunctions, it can be easily replaced with a non-malfunctioning constituent unit cell.

[0100] Therefore, by making full and efficient use of other constituent cells and components that make up an all-solid-state battery, the manufacturing yield of all-solid-state batteries can be improved.

[0101] Furthermore, an all-solid-state battery can be formed by alternately stacking constituent unit cells and connecting conductor layers (positive electrode connecting conductor layer and negative electrode connecting conductor layer). Therefore, all-solid-state batteries can be manufactured easily.

[0102] The positive and negative connection conductor layers preferably cover most or all of the positive and negative current collector layers, respectively. From the viewpoint of further reducing resistance per unit volume, a planar shape is preferred, but a grid or mesh shape is also acceptable. The positive and negative terminals can be connected to the positive and negative connection conductor layers at locations that do not overlap with the positive and negative current collector layers, respectively. From the viewpoint of further reducing resistance at the connection points, ultrasonic welding or spot welding is preferred as the connection method.

[0103] The resistivity of the positive and negative electrode connecting conductor layers is inversely proportional to their thickness. On the other hand, since the smaller the thickness of the connecting conductor layers, the greater the energy density per unit volume of the battery, it is preferable that the thickness of the positive and negative electrode connecting conductor layers be small. Specifically, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less.

[0104] The materials constituting the positive and negative electrode connecting conductor layers preferably have low resistivity. Examples include aluminum, copper, nickel, and stainless steel (SUS). Two or more of these materials may also be used. The resistivity of the connecting conductor layer is preferably lower than that of the positive or negative electrode current collector layer it contacts.

[0105] That is, preferably the resistivity of the positive electrode connecting conductor layer is less than the resistivity of the positive electrode current collector layer, and the resistivity of the negative electrode connecting conductor layer is less than the resistivity of the negative electrode current collector layer.

[0106] More specifically, the resistivity of the connecting conductor layer is preferably 1×10⁻⁶. -6 Below Ωm. Resistivity is determined according to JIS C 2525:1999.

[0107] The resistivity of the connecting conductor layer can be 1×10 -6 Below Ωm, 5×10 -7 Below Ωm, 1×10 -7 Below Ωm or 5×10 -8 Below Ωm.

[0108] Methods to reduce the resistance of the connecting conductor layer include, for example, using a metallic material with a lower resistivity than the material constituting the positive or negative current collector layer, and increasing the cross-sectional area by increasing the thickness of the connecting conductor.

[0109] Specifically, the connecting conductor layer can be made of copper and / or aluminum.

[0110] When a sulfide-based solid electrolyte is used as the solid electrolyte in the all-solid-state battery disclosed herein, the internal resistance of the all-solid-state battery may increase due to the reaction between the negative electrode current collector layer and the sulfide-based solid electrolyte, depending on the material used. In such cases, for example, materials with low reactivity with the sulfide-based solid electrolyte, such as stainless steel or nickel, can be considered as the material for the negative electrode current collector layer.

[0111] Furthermore, metals such as stainless steel or nickel generally have high resistivity. For example, the resistivity of stainless steel is more than 10 times that of copper. Therefore, if these metals are used as current collectors, the overall internal resistance of the all-solid-state battery will increase.

[0112] Regarding this point, when using a sulfide-based solid electrolyte as the solid electrolyte, it is preferable to use a material with low reactivity to the sulfide-based solid electrolyte, such as stainless steel or nickel, as the current collector layer, and a material with low resistivity, such as aluminum or copper, as the connecting conductor layer disposed on the current collector layer. With this structure, using a material with low reactivity to the sulfide-based solid electrolyte in the current collector layer can suppress the reaction between the current collector layer and the sulfide-based solid electrolyte, thus suppressing the increase in internal resistance. Simultaneously, the high resistivity of the current collector layer can be offset by the low resistivity of the connecting conductor layer, thereby reducing the overall internal resistance of the all-solid-state battery.

[0113] "Terminal"

[0114] Materials used to form the positive and negative terminals include, for example, aluminum, copper, and nickel. Two or more of these can also be used. A sealing film made of thermoplastic resin such as polypropylene can also be applied to the parts in contact with the outer casing, thereby reinforcing the heat-pressed seal.

[0115] "Exterior Body"

[0116] The outer casing is formed, for example, by a laminated film. To prevent the solid electrolyte constituting the unit cell from reacting with moisture in the atmospheric atmosphere and deteriorating, the outer casing preferably has gas barrier properties. The outer casing is preferably vacuum-sealed, thereby reducing the interfacial resistance of each layer.

[0117] Manufacturing Methods of All-Solid-State Batteries

[0118] The method for manufacturing an all-solid-state battery disclosed herein includes, for example, the following steps in sequence: alternately stacking multiple units constituting a unit cell and a connecting conductor layer, or alternately stacking units constituting a unit cell and a connecting conductor layer to form a laminate; connecting the positive terminal and the negative terminal to the connecting conductor layer of the obtained laminate; and sealing the laminate with an outer casing.

[0119] As Figure 2 and Figure 3The manufacturing method of the all-solid-state battery 1A shown can be exemplified by the following steps: integrating a stack of positive electrode current collector layer 11 and positive electrode active material layer 12, a solid electrolyte layer 13, and a stack of negative electrode active material layer 14 and negative electrode current collector layer 15, and configuring an insulator 16 to form a unit cell 10A; connecting a positive electrode connecting conductor layer 20a to a positive terminal 30; connecting a negative electrode connecting conductor layer 20b to a negative terminal 40; stacking the unit cell 10A on the negative electrode connecting conductor layer 20b in such a way that it contacts the negative electrode current collector layer 15 side; stacking the positive electrode connecting conductor layer 20a on the positive electrode current collector layer 11 side of the unit cell 10A; thereby forming a stack, then exposing a portion of the positive terminal 30 and the negative terminal 40, and sealing the stack with an outer casing 50.

[0120] Alternatively, a method may be described that sequentially includes the following steps: fixing a positive electrode connecting conductor layer 20a pre-connected with a positive terminal 30 and a negative electrode connecting conductor layer 20b connected with a negative terminal 40 to an outer casing 50; inserting a unit battery 10A between the positive electrode connecting conductor layer 20a and the negative electrode connecting conductor layer 20b, and then sealing the outer casing 50.

[0121] If the layers are stacked sequentially in the same direction, it is easier to manufacture, so the former method is preferred.

[0122] As Figure 4The manufacturing method of the all-solid-state battery 1B shown can be exemplified by a method comprising the following steps in sequence: integrating a stack of a positive electrode current collector layer 11 and a positive electrode active material layer 12, a solid electrolyte layer 13, and a stack of a negative electrode active material layer 14 and a negative electrode current collector layer 15, and providing an insulator 16 to form a unit cell 10A; stacking the unit cell 10A such that the negative electrode current collector layer 15 is in contact with the negative electrode connecting conductor layer 20b, and forming the unit cell 10A with the positive electrode current collector layer 15 in contact with the negative electrode connecting conductor layer 20b; and forming the unit cell 10A with the positive electrode current collector layer 14 in contact with the negative electrode connecting conductor layer 20b. A positive electrode connecting conductor layer 20a is stacked on the side of layer 11; the unit cell 10A is alternately stacked with the positive electrode connecting conductor layer 20a and the negative electrode connecting conductor layer 20b; outside the stacked range of the unit cell 10A, multiple positive electrode connecting conductor layers 20a are connected to the positive terminal 30; outside the stacked range of the unit cell 10A, multiple negative electrode connecting conductor layers 20b are connected to the negative terminal 40; a portion of the positive terminal 30 and the negative terminal 40 are exposed, and the stacked structure is sealed by the outer casing 50. As a process of alternately stacking the constituent unit battery 10A with the positive electrode connection conductor layer 20a and the negative electrode connection conductor layer 20b, a method can be described as follows: on the opposite side of the positive electrode connection conductor layer 20a, another constituent unit battery 10A is stacked in such a way that it contacts the positive electrode current collector layer 11 side, and the negative electrode connection conductor layer 20b is stacked on the negative electrode current collector layer 15 side of the constituent unit battery 10A; the constituent unit battery 10A and the positive electrode connection conductor layer 20a and the negative electrode connection conductor layer 20b are stacked in the same manner.

[0123] As Figure 5 The manufacturing method of the all-solid-state battery 1C shown can be exemplified by, for example, the method of manufacturing the all-solid-state battery 1C. Figure 4 The manufacturing method of the all-solid-state battery 1B shown also includes the following steps in sequence: fabricating a constituent unit battery 10A; connecting the positive electrode connecting conductor layer 20a to the positive terminal 30; connecting the negative electrode connecting conductor layer 20b to the negative terminal 40; alternately stacking the constituent unit battery 10A and the connecting conductor layer 20 to obtain a stacked structure; inserting the stacked structure between the positive electrode connecting conductor layer 20a and the negative electrode connecting conductor layer 20b, exposing a portion of the positive terminal 30 and the negative terminal 40, and sealing it through the outer casing 50.

[0124] Here, in Figure 5In the all-solid-state battery 1C shown, as a process of alternately stacking the constituent unit cell 10A and the connecting conductor layer 20, a method can be described that sequentially includes the following steps: a constituent unit cell 10A is stacked on the negative electrode connecting conductor layer 20b in such a way that it contacts the negative electrode current collector layer 15 side, and the connecting conductor layer 20 is stacked on the positive electrode current collector layer 11 side of the constituent unit cell 10A; another constituent unit cell 10A is stacked on the opposite side of the connecting conductor layer 20 in such a way that it contacts the negative electrode current collector layer 15 side, and the connecting conductor layer 20 is stacked on the positive electrode current collector layer 11 side of the other constituent unit cell 10A; the constituent unit cell 10A and the connecting conductor layer 20 are stacked in the same manner; after stacking the last constituent unit cell 10A, the positive electrode connecting conductor layer 20a is stacked on the positive electrode current collector layer 11 of the last constituent unit cell 10A.

[0125] As Figure 6 The manufacturing method of the all-solid-state battery 1D shown can be exemplified by the absence of a connecting conductor layer 20 between adjacent constituent unit cells 10A. Figure 5 The manufacturing method is the same as that used for the all-solid-state battery 1C shown.

[0126] As Figure 7 The manufacturing method of the all-solid-state battery 1E shown can be exemplified by a method comprising the following steps: a negative electrode active material layer 14 and a solid electrolyte layer 13 are sequentially stacked on one side of the current collector layer 17; a positive electrode active material layer 12 is disposed on the opposite side of the current collector layer 17 and an insulator 16 is disposed around it, thereby fabricating a unit cell 10B; a positive electrode connecting conductor layer 20a is connected to a positive terminal 30; a negative electrode connecting conductor layer 20b is connected to a negative terminal 40; and a negative electrode connecting conductor... A negative electrode current collector layer 15, a negative electrode active material layer 14, and a solid electrolyte layer 13 are stacked sequentially on layer 20b. A positive electrode active material layer 12 is stacked on the side of the solid electrolyte layer 13 to form the unit cell 10B. The unit cell 10B is formed by stacking in the same manner. On the side of the solid electrolyte layer 13, which forms the final unit cell 10B, a positive electrode active material layer 12 is stacked on the positive electrode current collector layer 11, and an insulator 16 is placed thereon, bringing it into contact with the positive electrode active material layer 12. Alternatively, in forming the unit cell 10A, layers without a positive electrode current collector layer 11 or a negative electrode current collector layer 15 are stacked together and finally inserted between the positive electrode connecting conductor layer 20a and the negative electrode connecting conductor layer 20b.

[0127] In the case of a unit cell constructed by stacking, in order to suppress misalignment of the stacked layers, an adhesive or the like can be applied to a part of the unit cell, insulator, positive electrode connecting conductor layer, negative electrode connecting conductor layer, or connecting conductor layer to fix it.

[0128] exist Figures 4-7In the aforementioned manufacturing method of the all-solid-state batteries 1B to 1E shown, the stacked structure can be disassembled after the lamination process, and the constituent unit batteries 10A, 10B, etc., can be easily removed. Therefore, if, for example, it is found after the lamination process that a part of the constituent unit batteries 10A or 10B is defective, it can be easily replaced with a qualified part, thereby improving the yield of battery production.

[0129] In addition, the following issues exist in conventional stacked solid-state batteries: In order to firmly bond the layers of the stacked structure that constitute a unit cell and reduce the interfacial resistance, the stacked body needs to be pressed together. However, the dimensions, materials, thicknesses and elastic moduli of each layer are different, so part of the structure is prone to damage and short circuit due to pressure concentration. Figures 4-7 The aforementioned manufacturing method of the all-solid-state battery shown can stack the constituent unit cells after pressing them together, so that the contact between the constituent unit cells becomes the contact between metal layers, the interface resistance becomes low, and therefore the battery can be manufactured without pressing them together.

[0130] exist Figures 4-7 In the manufacturing method of the all-solid-state batteries 1B to 1E of this type, the positive electrode connecting conductor layer 20a, the negative electrode connecting conductor layer 20b, the connecting conductor layer 20, the unit cells 10A and 10B, and the insulator 16 are stacked in various sequences as long as the final stacked configuration is as shown in the figure. For example... Figure 4 Alternatively, two negative current collector layers 15 constituting a unit battery 10A can be integrated on both sides of the negative electrode connecting conductor layer 20b, and then alternately overlapped with the positive electrode connecting conductor layer 20a to create a laminate.

[0131] [Example]

[0132] Examples 1 and 2 and Comparative Example 1

[0133] The following examples illustrate the invention. The invention is not limited thereto. First, the evaluation methods in each example and comparative example will be described.

[0134] <Resistivity Measurement>

[0135] The resistivity of the current collector layer and the connecting conductor layer used in each embodiment and comparative example was measured in accordance with JIS C2525:1999.

[0136] <Battery Internal Resistance Evaluation>

[0137] For the all-solid-state batteries produced by the various embodiments and comparative examples, charge-discharge tests were conducted at 25°C and a rate of 0.1C while the batteries were sandwiched between two flat plates under pressure. The charging capacity and discharging capacity were measured, and the internal resistance of the batteries was evaluated. Furthermore, regarding the C rate, 1C is the current used to charge the battery to its total capacity in 1 hour, and 0.1C is the current used to charge the battery to its total capacity in 10 hours.

[0138] Then, the battery was charged at 60°C and 2C rate, and the charging capacity was measured. After discharging at 0.1C rate, the charging capacity at 6C rate was measured, and the internal resistance of the battery was evaluated.

[0139] <Example 1>

[0140] (Positive electrode active material layer and positive electrode current collector layer)

[0141] Aluminum foil (resistivity 2.7 × 10⁻⁶) was used. -8 A slurry containing NiCoMn ternary lithium oxide (positive electrode active material) covered by LiNbO3 (20 μm thickness) is coated on the positive electrode current collector layer. The slurry contains a mixture of NiCoMn ternary lithium oxide (positive electrode active material) covered by LiNbO3, a sulfide solid electrolyte of silver sulfide type, carbon nanofiber "VGCF" (registered trademark)-H (conductive additive) and organic binder. The positive electrode active material layer is formed on the positive electrode current collector layer.

[0142] (Negative electrode active material layer and negative electrode current collector layer)

[0143] Stainless steel foil (resistivity 5.4 × 10⁻⁶) was used. -7 A negative electrode active material layer is formed on the negative electrode current collector layer by coating a slurry containing graphite (negative electrode active material), a sulfide-based solid electrolyte of silver-germanium ore type, and an organic binder.

[0144] (Solid electrolyte layer)

[0145] A mixture of a sulfide-based solid electrolyte and an organic binder is coated onto a stainless steel foil to form a solid electrolyte layer.

[0146] (Constitutes a unit battery)

[0147] The aforementioned positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer are integrated to form a unit cell. Furthermore, the stainless steel foil of the solid electrolyte layer is peeled off during the integration process.

[0148] A solid-state battery consisting of a single constituent cell is fabricated as described below. Stainless steel foil (resistivity 5.4 × 10⁻⁶) is used. -7An aluminum positive electrode conductor layer (resistivity 2.7 × 10 Ω·m, thickness 10 μm) was used as the positive electrode conductor layer, and the positive terminal was ultrasonically welded to it. Similarly, a stainless steel foil negative electrode conductor layer was used as the negative electrode conductor layer, and the negative terminal with a nickel coating applied to copper was ultrasonically welded to it. The negative electrode current collector layer constituting the unit cell was overlapped on the negative electrode conductor layer. On the end face of the positive electrode active material layer constituting the unit cell, the inner side of the insulating film was cut to the same size as the positive electrode active material layer. An aluminum foil (resistivity 2.7 × 10 Ω·m, thickness 10 μm) pre-connected with leads was placed on the positive electrode current collector layer side of the unit cell. -8 A connecting conductor layer (Ω·m, thickness 20μm) is used. The above-mentioned laminated structure is vacuum sealed using a laminated film of the outer casing.

[0149] <Example 2>

[0150] Aluminum foil is used as the positive electrode connecting conductor layer, and copper foil (resistivity 1.7 × 10⁻⁶) is used. -8 A solid-state battery was fabricated in the same manner as in Example 1, except that the negative electrode connecting conductor layer was Ω·m and 17μm thick.

[0151] <Comparative Example 1>

[0152] Instead of using a positive electrode connecting conductor layer and a negative electrode connecting conductor layer, a positive electrode current collector layer with one side longer than the positive electrode active material layer and a negative electrode current collector layer with one side longer than the negative electrode active material layer are used to make a unit cell. The positive terminal and the negative terminal are connected by ultrasonic welding outside the stacked range of the positive electrode current collector layer and the negative electrode current collector layer, and the all-solid-state cell is made in the same way as in Example 1.

[0153] The evaluation results of Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

[0154] Table 1

[0155]

[0156] Examples 1 and 2, which use stainless steel foil as the negative electrode current collector layer and a connecting conductor layer, show improved discharge and charge capacities compared to Comparative Example 1. Furthermore, Example 2, which uses aluminum foil as the positive electrode connecting conductor and copper foil as the negative electrode connecting conductor, further improves the charge capacity at a 6C rate.

[0157] Examples 3 and 4 and Comparative Example 2

[0158] <Example 3>

[0159] The all-solid-state battery of Example 3 was fabricated in the same manner as in Example 1. However, the amount of additive coating on the positive and negative active material layers differed slightly between the all-solid-state batteries of Example 1 and Example 3.

[0160] <Example 4>

[0161] Ten constituent unit cells produced in Example 3 were stacked in parallel with each other and vacuum-sealed with a laminated membrane of an outer casing, thereby producing the stacked all-solid-state battery of Example 4.

[0162] <Comparative Example 2>

[0163] Aluminum foil was used for the positive electrode current collector layer and stainless steel foil was used for the negative electrode current collector layer. Otherwise, 10 constituent unit cells, which were made in the same manner as Comparative Example 1, were stacked side by side and vacuum sealed with the laminate of the outer casing. Thus, the stacked all-solid-state battery of Comparative Example 2 was produced.

[0164] <Battery Review>

[0165] The all-solid-state battery of Example 3, as well as the stacked all-solid-state batteries of Example 4 and Comparative Example 2, were charged and discharged to measure their charging and discharging capacities. The results are shown in Table 2.

[0166] Table 2

[0167]

[0168] As shown in Table 2, the stacked all-solid-state battery of Example 4 has approximately 10 times the charging capacity and discharging capacity of the all-solid-state battery of Example 3.

[0169] On the other hand, the stacked all-solid-state battery in Comparative Example 2 was damaged and short-circuited during stacking.

Claims

1. An all-solid-state battery, comprising at least one constituent unit cell, wherein the constituent unit cell is formed by sequentially stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer. A connecting conductor layer is detachably stacked on the surface of the positive electrode current collector layer and / or the surface of the negative electrode current collector layer constituting the unit battery. A positive terminal is connected to the connecting conductor layer stacked on the surface of the positive current collector layer. A negative terminal is connected to the connecting conductor layer stacked on the surface of the negative current collector layer.

2. The all-solid-state battery according to claim 1, wherein the resistivity of the connecting conductor layer is less than the resistivity of the positive current collector layer or the negative current collector layer on which the connecting conductor layer is stacked.

3. The all-solid-state battery according to claim 1 or 2, wherein the resistivity of the connecting conductor layer is 1×10⁻⁶. -6 Below Ωm.

4. The all-solid-state battery according to any one of claims 1 to 3, wherein the connecting conductor layer is made of copper and / or aluminum.

5. The all-solid-state battery according to any one of claims 1 to 4, wherein the negative electrode active material layer contains a sulfide-based solid electrolyte, and the negative electrode current collector layer is made of stainless steel or nickel.

6. A method for manufacturing an all-solid-state battery according to any one of claims 1 to 5, comprising the following steps in sequence: A laminate is formed by stacking small units obtained by alternately stacking the constituent unit battery and the connecting conductor layer or by overlapping the constituent unit battery and the connecting conductor layer; Connect the positive and negative terminals to the connecting conductor layer of the resulting laminate; and The stack is sealed with an outer casing.

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