Negative electrode, solid-state battery, and method for manufacturing solid-state battery

Abstract

The present application provides a negative electrode, a solid-state battery, and a method for manufacturing a solid-state battery. The negative electrode is a negative electrode in which a negative electrode current collector, a metal foil, and a negative electrode active material layer are sequentially stacked.

Description

Technical Field

[0001] This invention relates to a negative electrode, a solid-state battery, and a method for manufacturing a solid-state battery. Background Technology

[0002] In recent years, the importance of secondary batteries has been increasing. In addition to secondary batteries with electrolytes, the development of solid-state batteries using solid electrolytes is also underway. As an example of solid-state batteries, all-solid-state batteries have a solid electrolyte layer that replaces the electrolyte. Since they do not use flammable organic solvents, safety devices can be simplified, and they are superior in terms of manufacturing cost and productivity.

[0003] Japanese Patent Application Publication No. 2020-119696 discloses a secondary battery comprising an electrode body with an alternating structure of a positive electrode and a negative electrode sandwiching a solid electrolyte layer, at least a portion of which contains a sulfur-containing substance. In Japanese Patent Application Publication No. 2020-119696, the negative electrode comprises a negative electrode current collector made of Al, and a negative electrode active material layer formed on at least one surface of the negative electrode current collector. A plating layer made of Ni and / or Cr is formed on the surface of the negative electrode current collector where the negative electrode active material layer is formed. Furthermore, an uncoated portion of the negative electrode current collector, lacking either the plating layer or the negative electrode active material layer, is formed at the end of the negative electrode current collector, and an external connection terminal made of Al is bonded to this uncoated portion.

[0004] According to the secondary battery disclosed in Japanese Patent Application Publication No. 2020-119696, by placing a coating made of a metal element that does not readily react with the sulfur component contained in the electrolyte in the region where the negative electrode current collector is formed, Al can be used instead of Cu as the negative electrode current collector. Summary of the Invention

[0005] The problem that the invention aims to solve

[0006] However, the following problem exists: the plating layer disposed between the negative electrode current collector and the negative electrode active material layer sometimes forms micro-pinholes. Through these pinholes, lithium ions contained in the negative electrode active material layer come into contact with metals such as aluminum contained in the negative electrode current collector. This metal alloys with lithium, leading to a deterioration of battery characteristics. Therefore, an embodiment of the present invention aims to provide a negative electrode, a solid-state battery, and a method for manufacturing a solid-state battery that can prevent the metal constituting the negative electrode current collector from alloying with lithium.

[0007] Methods for solving problems

[0008] The present invention, which achieves the above objectives, includes the following methods.

[0009] <1> A negative electrode, which is a negative electrode having a negative current collector, a metal foil and a layer of negative active material stacked in sequence.

[0010] <2> According to the negative electrode described in <1>, the metal foil is a metal foil of a metal having a higher redox potential than the potential of the negative electrode side.

[0011] <3> The negative electrode according to <1> or <2>, wherein the metal foil is a nickel foil.

[0012] <4> The negative electrode according to any one of <1> to <3>, wherein the negative electrode current collector has a negative electrode ear-side end connected to the negative electrode ear, and the end of the negative electrode current collector opposite to the negative electrode ear-side end is disposed further inside the end of the metal foil.

[0013] <5> The negative electrode according to any one of <1> to <4>, wherein there is no adhesive layer between the metal foil and the negative electrode active material layer.

[0014] <6> A solid-state battery, comprising:

[0015] The negative electrode as described in any one of <1> to <5>;

[0016] A solid electrolyte layer disposed in contact with the negative electrode active material layer of the negative electrode; and

[0017] A positive electrode is disposed opposite to the negative electrode, sandwiching the solid electrolyte layer, and includes a positive current collector and a positive active material layer disposed on at least one main surface of the positive current collector.

[0018] <7> According to <6>, the solid-state battery has positive electrode active material layers disposed on two main surfaces of the positive electrode current collector, and the solid-state battery has the solid electrolyte layer and the negative electrode respectively stacked on these positive electrode active material layers, and the negative electrode current collector of the negative electrode is the outermost stack.

[0019] <8> The solid-state battery according to <7> has two or more of the aforementioned stacked bodies, with an adjacent stacked body sandwiching a negative electrode current collector. One of the adjacent stacked bodies has a negative electrode on one main surface of the negative electrode current collector, wherein the metal foil and the negative electrode active material layer are stacked thereon, and the other of the adjacent stacked bodies has a negative electrode on the other main surface of the negative electrode current collector, wherein the metal foil and the negative electrode active material layer are stacked thereon.

[0020] <9> A method for manufacturing a solid-state battery, comprising a negative electrode having a negative electrode active material layer, a positive electrode having a positive electrode active material layer, and a solid electrolyte layer disposed between the negative electrode and the positive electrode, comprising a step of fabricating the negative electrode as described in any one of <1> to <4> by laminating a negative electrode current collector with a metal foil.

[0021] <10> In the method for manufacturing a solid-state battery according to <9>, when the negative current collector is stacked with the metal foil, the end of the negative current collector opposite to the negative current collector tab end connected to the negative current collector tab is positioned further inside the end of the metal foil.

[0022] <11> According to the solid-state battery manufacturing method described in <9>, after the negative current collector is stacked with the metal foil, the end of the negative current collector opposite to the negative current collector tab side end connected to the negative current collector tab is cut together with the end of the metal foil along the stacking direction.

[0023] <12> A method for manufacturing a solid-state battery according to any one of <9> to <11>, wherein a negative electrode slurry containing a negative electrode active material is coated on the surface of the metal foil opposite to the surface of the negative electrode current collector.

[0024] <13> A method for manufacturing a solid-state battery according to any one of <9> to <12>, wherein, in the process, a negative electrode is formed by stacking metal foils on the two main surfaces of the negative electrode current collector, wherein the metal foils and the negative electrode active material layer are sequentially stacked on the two main surfaces of the negative electrode current collector.

[0025] Invention Effects

[0026] According to one embodiment of the present invention, a negative electrode, a solid-state battery, and a method for manufacturing a solid-state battery can be provided, which prevent the alloying of lithium contained in the negative electrode active material layer with the metal contained in the negative electrode current collector by providing a metal foil between the negative electrode current collector and the negative electrode active material layer. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the main part of the negative electrode shown as one embodiment of the present invention.

[0028] Figure 2 This is a cross-sectional view of the main part of a solid-state battery as an embodiment of the present invention.

[0029] Figure 3 This is a cross-sectional view of the main part of the negative electrode as shown in another embodiment of the present invention.

[0030] Figure 4This is a cross-sectional view of the main part of a solid-state battery as another embodiment of the present invention. Detailed Implementation

[0031] In this invention, the numerical range represented by “~” refers to the range in which the values ​​recorded before and after “~” are respectively the minimum and maximum values.

[0032] In this invention, within the segmented numerical ranges, the upper or lower limit value recorded within a certain numerical range can be replaced with the upper or lower limit value of other segmented numerical ranges. Similarly, within the numerical ranges described in this invention, the upper or lower limit value recorded within a certain numerical range can be replaced with the values ​​shown in the embodiments.

[0033] In this invention, the term "process" not only includes independent processes, but also includes processes that achieve their intended purpose, even if they cannot be clearly distinguished from other processes.

[0034] In this invention, a combination of two or more preferred methods is a more preferred method.

[0035] In this invention, the amount of each component refers to the total amount of the two or more substances that are equivalent to the component, unless otherwise stated.

[0036] When describing embodiments in this invention with reference to the accompanying drawings, the configuration of these embodiments is not limited to the configuration shown in the drawings. Furthermore, the dimensions of the components in each drawing are conceptual, and the relative relationships between the dimensions of the components are not limited thereto.

[0037] <Anode, Solid-State Battery>

[0038] The negative electrode of the present invention is a negative electrode in which a negative current collector, a metal foil, and a negative active material layer are sequentially stacked. In the negative electrode of the present invention, since a metal foil is disposed between the negative active material layer and the negative current collector, the metal foil can be used to prevent alloying between the metal contained in the negative current collector and the lithium contained in the negative active material layer. In particular, in the negative electrode of the present invention, by providing a metal foil between the negative current collector and the negative active material layer instead of a metal plating layer, the aforementioned alloying can be prevented more reliably. This is because metal plating layers such as nickel plating sometimes form fine pores called pinholes, and therefore, when using metal plating layers, alloying with lithium can sometimes occur through these pinholes. Therefore, by using the negative electrode of the present invention in a solid-state battery, the degradation of battery performance caused by the aforementioned alloying can be prevented, and excellent battery performance can be maintained for a long time.

[0039] Here, the metal foil is formed of a metal that does not form an alloy with the lithium contained in the negative electrode active material layer. For example, it is preferable that the metal foil is a metal foil of a metal having a higher redox potential than the potential on the negative electrode side. In a solid-state battery using the negative electrode of the present invention, by making the metal foil a metal foil of a metal having a higher redox potential than the potential on the negative electrode side, it is possible to prevent the formation of an alloy with the lithium contained in the negative electrode active material layer. As such a metal foil, metal foils formed of metals such as nickel, chromium, iron, gold, platinum, silver, and stainless steel can be used. In particular, nickel foil is preferred as the metal foil.

[0040] As one embodiment of the present invention, the negative electrode is shown as follows: Figure 1 The device shown includes a negative current collector 1, a metal foil 2, and a negative active material layer 3. Additionally, it includes... Figure 1 The solid-state battery with the negative electrode shown is as follows: Figure 2 The embodiment shown includes: a solid electrolyte layer 4 disposed in contact with the negative electrode active material layer 3, which is the negative electrode shown in this embodiment; and a positive electrode sandwiching the solid electrolyte layer 4 and disposed opposite to the negative electrode, and including a positive electrode current collector 6 and a positive electrode active material layer 5 disposed on at least one main surface of the positive electrode current collector 6. Furthermore, in Figure 2 In the solid-state battery shown, the negative electrode active material layer 3 has a first negative electrode active material layer 3A and a second negative electrode active material layer 3B, but it can also be a single layer or have two or more layers.

[0041] also, Figure 2 The solid-state battery shown has a positive electrode active material layer 5 disposed on the two main surfaces of the positive electrode current collector 6. Figure 2 In the solid-state battery shown, a solid electrolyte layer 4 and a negative electrode (negative electrode current collector 1, metal foil 2 and negative electrode active material layer 3) are stacked on these positive electrode active material layers 5, respectively. Figure 2 The solid-state battery shown has a negative electrode current collector 1, which forms the outermost layer of the stack. That is, in Figure 2 In the solid-state battery shown, the positive current collector 6 is positioned as the stacking direction ( Figure 2 At the center (in the direction of the middle arrow X), on the two main surfaces of the positive current collector 6, a positive active material layer 5, a solid electrolyte layer 4, a negative active material layer 3, a metal foil 2, and a negative current collector 1 are sequentially stacked. Furthermore, in... Figure 2 In the solid-state battery shown, an insulating layer 7 is provided at the position where it is connected to the end of the positive electrode active material layer 5 on the positive electrode current collector 6.

[0042] In addition, Figure 2In the solid-state battery shown, the negative current collector 1 has a negative current collector tab-side end 1A connected to a negative current collector tab (not shown). The end 1B of the negative current collector 1, opposite to the negative current collector tab-side end 1A, can be disposed further inside the end of the metal foil 2. Specifically, the end 1B can be located 1 μm to 10 μm inside the end of the metal foil 2, preferably 3 μm to 8 μm inside, and more preferably 4 μm to 6 μm inside. By disposing the end 1B of the negative current collector 1 further inside the end of the metal foil 2 in this way, short circuits between the negative current collector 1 and the positive active material layer 5 or the positive current collector 6 can be reliably prevented. Assuming that in a solid-state battery, a metal plating layer is disposed between the negative electrode current collector 1 and the negative electrode active material layer 3 instead of the metal foil 2, since the metal plating layer is formed on the main surface of the negative electrode current collector 1 by a plating method, it is impossible to place the end 1B of the negative electrode current collector 1 further inside the end of the metal plating layer. That is, in a solid-state battery, by using the metal foil 2 to replace the metal plating layer, the positional relationship between the negative electrode current collector 1 and the metal foil 2 can be freely adjusted.

[0043] However, the negative electrode and solid-state battery of the present invention are not limited to the configuration in which the end 1B of the negative electrode current collector 1, opposite to the auricle-side end 1A of the negative electrode current collector, is located further inside the end of the metal foil 2. For example, it can also be configured as follows: Figure 3 As shown, the end 1B of the negative current collector 1 overlaps with the end of the metal foil 2 in the lamination direction. For example, by forming a negative active material layer 3 on one main surface of the metal foil 2 and attaching the negative current collector 1 to the other main surface of the metal foil 2, and then cutting off the end 1B side of the negative current collector 1 along the lamination direction, it is possible to manufacture a device as shown. Figure 3 The diagram shows a negative electrode in which end 1B of the negative current collector 1 overlaps with end of the metal foil 2 in the stacking direction. Assuming a solid-state battery in which a metal plating layer replaces the metal foil 2 between the negative current collector 1 and the negative active material layer 3, due to the thinness of the metal plating layer, burrs generated at the cut surface of the negative current collector 1 would approach the negative active material layer 3, raising concerns about alloying with the lithium contained in the negative active material layer 3. In the solid-state battery of the present invention, since a metal foil 2 with a film thickness thicker than the metal plating layer is used, even if burrs are generated at the cut surface of the negative current collector 1, alloying with the lithium contained in the negative active material layer 3 can be prevented.

[0044] Furthermore, the negative electrode and solid-state battery of the present invention, such as Figure 1 and 2As shown, there is no adhesive layer between the metal foil 2 and the negative electrode active material layer 3. In other words, in the negative electrode and solid-state battery of the present invention, the metal foil 2 and the negative electrode active material layer 3 can be stacked without the aid of an adhesive layer. This is because the anchoring effect caused by the unevenness formed on the surface of the metal foil 2 can bond the metal foil 2 and the negative electrode active material layer 3. Assuming that a metal plating layer is used instead of the metal foil 2 in a solid-state battery, the anchoring effect on the surface of the metal plating layer for the negative electrode active material layer 3 cannot be expected, and an adhesive layer is needed to bond the negative electrode active material layer 3 to the metal plating layer. In addition, as mentioned above, alloying sometimes occurs due to pinholes formed on the metal plating layer, and an adhesive layer is needed to avoid this problem. In the negative electrode and solid-state battery of the present invention, since the metal foil 2 is provided, the adhesive layer required when using a metal plating layer is not required. In particular, in the solid-state battery of the present invention, when there is no adhesive layer between the metal foil 2 and the negative electrode active material layer 3, the negative electrode active material layer 3, the solid electrolyte layer 4, and the positive electrode active material layer 5 can be designed to be thicker by an amount equivalent to the thickness of the adhesive layer. As a result, the solid-state battery of the present invention can increase the battery capacity compared to the case with an adhesive layer.

[0045] However, the negative electrode and solid-state battery of the present invention are not limited to a configuration without an adhesive layer; they can also be configured with an adhesive layer. In this case, as the adhesive layer, a conductive carbon coating is preferably provided to electrically bond the metal foil 2 to the negative electrode active material layer 3. By providing a carbon coating, the negative electrode and solid-state battery of the present invention can more firmly bond the metal foil 2 to the negative electrode active material layer 3.

[0046] exist Figure 2 In the solid-state battery shown, the positive current collector 6 has a positive current collector tab-side end 6A connected to a positive current collector tab (not shown). Furthermore, the insulating layer 7 and the positive active material layer 5 are sequentially arranged starting from the positive current collector tab-side end 6A. Figure 2 The solid-state battery shown has an end insulating portion 8 at the end of the positive current collector 6 opposite to the positive current collector tab end 6A. It should be noted that, in this invention, the stacking direction refers to... Figure 2 As shown by arrow X, the positive electrode active material layer 5, solid electrolyte layer 4, etc. are stacked starting from the positive electrode current collector 6.

[0047] Furthermore, the solid-state battery of the present invention may also have two or more components. Figure 2 The solid-state battery stack shown. For example, as... Figure 4 As shown, more than two can be listed. Figure 2The solid-state battery shown comprises a stack of adjacent stacks sandwiching a negative electrode current collector 1, one of the adjacent stacks having a metal foil 2 and a negative electrode active material layer 3 stacked on one main surface of the negative electrode current collector 1, and the other of the adjacent stacks having a metal foil 2 and a negative electrode active material layer 3 stacked on the other main surface of the negative electrode current collector 1. That is, in the solid-state battery of the present invention, adjacent stacks can be configured with a single negative electrode current collector 1. Assuming that a metal plating layer is used instead of the metal foil 2 in the solid-state battery, it is difficult to form a metal plating layer on both main surfaces of the negative electrode current collector 1, thus making it impossible to configure adjacent stacks with a single negative electrode current collector 1. Therefore, compared to the case where a metal plating layer is used instead of the metal foil 2, the solid-state battery of the present invention can, for example, reduce the thickness by an amount equivalent to n-1 negative electrode current collectors 1 when having n stacks, allowing the negative electrode active material layer 3, the solid electrolyte layer 4, and the positive electrode active material layer 5 to be designed to be thicker. As a result, the solid-state battery of the present invention can increase the battery capacity compared with the case where a metal coating is used instead of the metal foil 2.

[0048] <Key Elements of Solid State Batteries>

[0049] (Positive current collector)

[0050] The positive current collector can be any material commonly used as a positive current collector in batteries. Furthermore, the positive current collector can be in the form of foil, plate, mesh, perforated metal, or foam. The positive current collector can be composed of metal foil or metal mesh. In particular, metal foil has excellent workability. The positive current collector can be composed of two or more foils. Examples of metals constituting the positive current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, from the viewpoint of ensuring oxidation resistance, the positive current collector can contain Al. Regarding the positive current collector, a coating can be applied to its surface for purposes such as adjusting resistance. Additionally, the positive current collector can also be deposited or vapor-deposited onto metal foil or a substrate. It should be noted that, in cases such as… Figure 1 When a layer of positive active material is stacked on a positive current collector as shown, an Al foil, for example, with a thickness of 10 μm, can be used as the positive current collector.

[0051] (Positive electrode active material layer)

[0052] The positive electrode active material layer contains at least a positive electrode active material, and may optionally contain an electrolyte, conductive additives, and binders. The positive electrode active material layer may also contain various other additives. As the positive electrode active material, substances known as positive electrode active materials for secondary batteries can be used. For example, the positive electrode active material may be selected from at least one of various lithium-containing compounds, elemental sulfur, and sulfur compounds. Regarding the lithium-containing compound used as the positive electrode active material, it may be lithium cobalt oxide, lithium nickel oxide, or Li... 1±α Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2±δ Lithium manganese oxide, spinel-based lithium compounds (from Li 1+x Mn 2-x-y M y Various lithium-containing oxides, such as lithium titanate and lithium metal phosphate (LiMPO4, etc., where M is selected from one or more of Al, Mg, Co, Fe, Ni, and Zn, representing heteroelemental substitutions of Li-Mn spinel), are used. In particular, when the positive electrode active material contains a lithium-containing oxide with at least one of Ni, Co, and Mn, and Li and O as constituent elements, even better performance can be expected. One type of positive electrode active material can be used alone, or two or more can be used in combination.

[0053] The shape of the positive electrode active material can be any shape commonly used in batteries. For example, the positive electrode active material can be granular. It can be solid or hollow, porous or interstitial. It can be a primary particle or a secondary particle composed of aggregates of multiple primary particles. Furthermore, a protective layer containing an ion-conducting oxide can be formed on the surface of the positive electrode active material. This facilitates the suppression of reactions between the positive electrode active material and sulfides (e.g., sulfide solid electrolytes). Examples of ion-conducting oxides include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, and Li4Ti5O. 12 , Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, etc.

[0054] (Solid electrolyte)

[0055] The solid electrolyte contained in the solid electrolyte layer preferably includes at least one type of solid electrolyte selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes and halide solid electrolytes.

[0056] As a sulfide solid electrolyte, it is preferable to contain sulfur (S) as the main anionic element, and in addition to S, it is preferable to also contain elements such as Li, A, and S. The A element is at least one selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may also contain at least one of O and a halogen element. Examples of halogen elements (X) include F, Cl, Br, and I. The composition of the sulfide solid electrolyte is not particularly limited, and examples include xLi₂S·(100-x)P₂S₅ (70≤x≤80) and yLiI·zLiBr·(100-yz)(xLi₂S·(1-x)P₂S₅) (0.7≤x≤0.8, 0≤y≤30, 0≤z≤30).

[0057] Sulfide solid electrolytes can have a composition represented by the following general formula (1).

[0058] Li 4-x Ge 1-x P x S4 (0<x<1)…Formula (1)

[0059] In equation (1), at least a portion of Ge can be substituted with at least one of the following groups: Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. Additionally, at least a portion of P can be substituted with at least one of the following groups: Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. A portion of Li can be substituted with at least one of the following groups: Na, K, Mg, Ca, and Zn. A portion of S can be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0060] As an oxide solid electrolyte, it is preferable to contain oxygen (O) as the main anionic element. For example, it may contain Li, Q (Q represents at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O. Examples of oxide solid electrolytes include garnet-type solid electrolytes, perovskite-type solid electrolytes, sodium superionic conductor (NASICON)-type solid electrolytes, Li-PO4-based solid electrolytes, and Li-BO4-based solid electrolytes. Examples of garnet-type solid electrolytes include, for instance, Li7La3Zr2O. 12 Li 7-x La3(Zr 2-x Nb x )O 12 (0≤x≤2), Li5La3Nb2O 12Examples of perovskite-type solid electrolytes include (Li,La)TiO3, (Li,La)NbO3, and (Li,Sr)(Ta,Zr)O3. Examples of sodium superionic conductor (NASICON)-type solid electrolytes include Li(Al,Ti)(PO4)3 and Li(Al,Ga)(PO4)3. Examples of Li-PO solid electrolytes include Li3PO4 and LIPON (a compound obtained by replacing some of the O in Li3PO4 with N). Examples of Li-BO solid electrolytes include Li3BO3 and compounds obtained by replacing some of the O in Li3BO3 with C.

[0061] As a halide solid electrolyte, a solid electrolyte comprising Li, M, and X is preferred (M represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br). Specifically, Li is preferred. 6-3z Y z X6 (X represents Cl or Br, z satisfies 0 < z < 2), Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5). In Li 6-3z Y z Among X6, considering its excellent lithium-ion conductivity, Li3YX6 (where X represents Cl or Br) is more preferred, and Li3YCl6 is even more preferred. Furthermore, from the viewpoint of suppressing the oxidative decomposition of sulfide solid electrolytes, Li... 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferably included together with solid electrolytes such as sulfide solid electrolytes.

[0062] (Solid electrolyte layer)

[0063] Examples of solid electrolyte layers used in semi-solid-state and all-solid-state batteries include those used as solid electrolyte layers. The thickness of the solid electrolyte layer is not particularly limited; for example, it can be selected within the range of 1 μm to 30 μm. The type of solid electrolyte contained in the solid electrolyte layer is not particularly limited. For example, solid electrolytes that can also be included in the aforementioned positive electrode active material layers can be selected. The solid electrolyte layer can be a single layer or a multilayer structure with two or more layers.

[0064] In the case where the solid-state battery of the present invention includes a solid electrolyte, an electrolyte solution of less than 10% by mass relative to the total electrolyte amount may be included together with the solid electrolyte. In the case where the battery of the present invention includes a solid electrolyte, the solid electrolyte may be a composite solid electrolyte comprising an inorganic solid electrolyte and a polymer electrolyte. In the case where the solid-state battery of the present invention includes an electrolyte solution as the electrolyte, there are no particular limitations on the type of electrolyte solution, and known electrolyte solutions may be used. Specifically, liquids obtained by dissolving lithium salts such as LiPF6 and LiFSI in an organic solvent can be cited as examples of electrolyte solutions.

[0065] (Negative electrode active material layer)

[0066] The negative electrode active material layer contains at least a negative electrode active material and may optionally further contain electrolytes, conductive additives, and binders. The negative electrode active material layer may contain various other additives. Examples of negative electrode active materials include carbon materials, active materials containing Si, lithium metal, lithium-containing alloys, metals or alloys capable of alloying with lithium, oxides, and transition metal nitrides. Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and artificial graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesophase carbon microspheres (MCMB), and mesophase pitch-based carbon fibers (MCF). Graphite materials may be coated with metals or amorphous carbon. Examples of active materials containing Si include elemental silicon, silicon alloys (e.g., alloys of Si with one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co, and Al), porous silicon, silicon inclusion compounds, and silicon oxides.

[0067] (Negative current collector)

[0068] As the negative electrode current collector, any material commonly used as a negative electrode current collector in batteries can be used. Furthermore, the negative electrode current collector can be in the form of foil, plate, mesh, perforated metal, or foam, etc. The negative electrode current collector can be a metal foil or metal mesh, or it can be a carbon sheet. The negative electrode current collector can be composed of two or more foils or sheets. Examples of metals constituting the negative electrode current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, from the viewpoint of ensuring resistance to reduction and minimizing alloying with lithium, the negative electrode current collector can contain at least one metal selected from Cu, Ni, and stainless steel.

[0069] (metal foil)

[0070] As described above, the metal foil is preferably a metal foil of a metal having a higher redox potential than that of the negative electrode side of the solid-state battery. Examples of metal foils that can be used include nickel foil, chromium foil, iron foil, gold foil, platinum foil, silver foil, and stainless steel foil. Furthermore, the metal foil may have a coating on its surface for purposes such as adjusting resistance. Alternatively, the metal foil may be formed by metal plating or vapor deposition. The metal foil can be a single sheet or two or more sheets. A layer may be present between the two or more metal foils. The thickness of the metal foil is not particularly limited; for example, it can be set to 0.1 μm to 10 μm, preferably 0.3 μm to 5 μm, and more preferably 0.5 μm to 2 μm. By setting the thickness of the metal foil within this range, alloying of lithium contained in the negative electrode active material layer between the negative electrode current collector and the negative electrode active material layer can be reliably prevented, and the reduction in battery capacity due to the thickness of the metal foil can be prevented.

[0071] (Carbon coating)

[0072] As described above, the carbon coating is an optional layer that can be omitted from the space between the metal foil and the negative electrode active material layer. When disposed between the metal foil and the negative electrode active material layer, the carbon coating functions as both an adhesive layer for bonding the negative electrode current collector to the negative electrode active material layer and a conductive layer for ensuring conductivity between the negative electrode current collector and the negative electrode active material layer. Examples of carbon materials contained in the carbon coating include graphite, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and artificial graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesophase carbon microspheres (MCMB), and mesophase pitch-based carbon fibers (MCF).

[0073] (outer body)

[0074] The solid-state battery of the present invention may further include an outer casing. The outer casing at least houses the electrode laminate described above. Examples of outer casings include laminated outer casings and shell-type outer casings. The laminated outer casing may be formed from a laminate (laminated film) having a metal layer containing a metal such as aluminum and a heat-sealing layer containing a resin that is melted by heating.

[0075] (Constrained Members)

[0076] The solid-state battery of the present invention may further include a constraint member. The constraint member applies a constraint pressure to the electrode stack along its thickness direction. The constraint pressure applied along the thickness direction of the electrode stack may, for example, be 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. The constraint pressure applied along the thickness direction of the electrode stack may, for example, be 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0077] <Solid-State Battery Manufacturing Method>

[0078] The solid-state battery manufacturing method of the present invention comprises a negative electrode having a negative electrode active material layer, a positive electrode having a positive electrode active material layer, and a solid electrolyte layer disposed between the negative electrode and the positive electrode. The method includes a step of fabricating the negative electrode of the present invention by laminating a negative electrode current collector with a metal foil. In the solid-state battery manufacturing method of the present invention, the negative electrode active material layer may be pre-formed on the side of the metal foil opposite to the side overlapping the negative electrode current collector, or it may be formed on the side of the metal foil opposite to the side overlapping the negative electrode current collector after the metal foil and the negative electrode current collector are laminated together. In the solid-state battery of the present invention, as described above, the negative electrode can be fabricated by laminating the negative electrode current collector with the metal foil without forming an adhesive layer.

[0079] Furthermore, when the solid-state battery manufacturing method of the present invention is applied to... Figures 1-2 In the manufacturing method of the solid-state battery shown, when the negative electrode current collector 1 and the metal foil 2 are laminated, the end 1B of the negative electrode current collector 1, which is opposite to the negative electrode current collector tab side end 1A connected to the negative electrode current collector tab, is positioned further inside the end of the metal foil 2. This allows for the manufacture of a solid-state battery as shown. Figure 1 and Figure 2 The solid-state battery shown reliably prevents short circuits between the negative electrode current collector 1 and the positive electrode active material layer 5 or the positive electrode current collector 6. However, in the manufacturing method of the solid-state battery of the present invention, it is also possible to manufacture a solid-state battery such as the one shown, by laminating the negative electrode current collector 1 and the metal foil 2, and then cutting off the end 1B of the negative electrode current collector 1 opposite to the negative electrode current collector tab side end 1A connected to the negative electrode current collector tab together with the end of the metal foil 2 along the lamination direction. Figure 3 The negative electrode is shown.

[0080] In the solid-state battery manufacturing method of the present invention, the negative electrode active material layer 3 can be formed by coating a negative electrode slurry containing the negative electrode active material onto the surface of the metal foil 2 opposite to the surface of the negative electrode current collector 1.

[0081] <Types and Uses of Batteries>

[0082] There is no particular limitation on the type of solid-state battery; lithium-ion batteries are typical. Furthermore, the solid-state battery of the present invention can be a primary battery or a secondary battery, with a secondary battery being preferred. This is because it can be repeatedly charged and discharged, making it useful, for example, as a battery for automotive applications. The solid-state battery can be a semi-solid-state battery, having a gel layer containing an electrolyte and a polymer between the electrodes and the solid electrolyte, or it can be an all-solid-state battery using a solid electrolyte as the electrolyte. The solid electrolyte can contain less than 10% by mass of electrolyte relative to the total electrolyte volume. An all-solid-state battery is preferred.

[0083] The application of the battery of the present invention is not particularly limited. Representative applications include power sources for vehicles, electronic devices, and power storage systems. It can also be used as a power source for mobile bodies other than vehicles (e.g., trains, ships, aircraft), and for electrical products such as information processing devices. Preferably, the battery of the present invention is used as a power source for vehicles, and more particularly as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles.

[0084] As vehicles, examples include electric four-wheelers, electric two-wheelers, gasoline vehicles, and diesel vehicles. Electric four-wheelers include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Electric two-wheelers include electric motorcycles and electric-assisted bicycles.

Claims

1. A negative electrode, which is a negative electrode having a negative current collector, a metal foil and a layer of negative active material stacked sequentially.

2. The negative electrode according to claim 1, wherein, The metal foil is a metal foil of a metal having a higher redox potential than that of the negative electrode side.

3. The negative electrode according to claim 1, wherein, The metal foil is a nickel foil.

4. The negative electrode according to claim 1, wherein, The negative current collector has a negative current collector ear-side end connected to the negative current collector ear, and the end of the negative current collector opposite to the negative current collector ear-side end is disposed further inside the end of the metal foil.

5. The negative electrode according to claim 1, wherein, There is no adhesive layer between the metal foil and the negative electrode active material layer.

6. A solid-state battery, comprising: The negative electrode according to any one of claims 1 to 5; A solid electrolyte layer disposed in contact with the negative electrode active material layer of the negative electrode; and A positive electrode is disposed opposite to the negative electrode, sandwiching the solid electrolyte layer, and includes a positive current collector and a positive active material layer disposed on at least one main surface of the positive current collector.

7. The solid-state battery according to claim 6, wherein, The positive electrode has positive electrode active material layers disposed on the two main surfaces of the positive electrode current collector. The solid-state battery has a solid electrolyte layer and a negative electrode stacked on these positive electrode active material layers, and the negative electrode current collector of the negative electrode is the outermost layer of the stack.

8. The solid-state battery according to claim 7, comprising two or more of the stacked bodies, wherein adjacent stacked bodies are stacked with a negative electrode current collector sandwiched between them, one of the adjacent stacked bodies having a negative electrode on one main surface of the negative electrode current collector having the metal foil and the negative electrode active material layer stacked thereon, and the other of the adjacent stacked bodies having a negative electrode on the other main surface of the negative electrode current collector having the metal foil and the negative electrode active material layer stacked thereon.

9. A method for manufacturing a solid-state battery, comprising a negative electrode having a negative electrode active material layer, a positive electrode having a positive electrode active material layer, and a solid electrolyte layer disposed between the negative electrode and the positive electrode, the method comprising a step of fabricating the negative electrode according to any one of claims 1 to 5 by laminating a negative electrode current collector with a metal foil.

10. The method for manufacturing a solid-state battery according to claim 9, wherein, When the negative current collector is stacked with the metal foil, the end of the negative current collector opposite to the negative current collector tab end connected to the negative current collector tab is positioned further inside the end of the metal foil.

11. The method for manufacturing a solid-state battery according to claim 9, wherein, After the negative current collector is stacked with the metal foil, the end of the negative current collector opposite to the end connected to the negative current collector tab is cut off together with the end of the metal foil along the stacking direction.

12. The method for manufacturing a solid-state battery according to claim 9, wherein, A negative electrode slurry containing a negative electrode active material is coated on the surface of the metal foil opposite to the surface that overlaps with the negative electrode current collector.

13. The method for manufacturing a solid-state battery according to claim 9, wherein, In the process described above, a negative electrode is formed by stacking metal foils on the two main surfaces of the negative current collector, thereby creating a negative electrode on which the metal foils and the negative active material layer are sequentially stacked on the two main surfaces of the negative current collector.

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