JP2019175838A - Anode, and sulfide solid-state battery - Google Patents

Abstract

To solve such a problem that, when an anode current collector layer made from copper, and an anode mixture layer containing a sulfide solid electrolyte are used to compose an anode, copper reacts with the sulfide solid electrolyte to generate copper sulfide, and the resistance of the interface between the anode current collector layer and the anode mixture layer increases.SOLUTION: An anode current collector layer is alloyed to lower the reactivity to a sulfide solid electrolyte. Specifically, an anode includes an anode mixture layer, and an anode current collector layer that is in contact with the anode mixture layer. The anode mixture layer contains an anode active material and a sulfide solid electrolyte, and at least a surface of the anode current collector layer is made from a material that contains an alloy of copper and metal of a higher ionization tendency than copper, the surface being in contact with the anode mixture layer.SELECTED DRAWING: Figure 1

Description

  The present application discloses a negative electrode and a sulfide solid state battery using a sulfide solid electrolyte.

  In a sulfide solid state battery including a negative electrode, a positive electrode, and a solid electrolyte layer, when the negative electrode is configured using a negative electrode current collector layer made of copper and a negative electrode mixture layer containing a sulfide solid electrolyte, copper and sulfide solid electrolyte Reacts with each other to produce copper sulfide and the like, resulting in an increase in resistance at the interface between the negative electrode current collector layer and the negative electrode mixture layer, and irreversible reaction between copper sulfide and lithium ions, resulting in a decrease in battery capacity. There is a problem. As one means for solving this problem, Patent Document 1 discloses providing a reaction suppression layer containing a predetermined element between a negative electrode mixture layer and a negative electrode current collector layer.

  In addition, as disclosed in Patent Document 2, a technique for suppressing a reaction between an active material and a sulfide solid electrolyte in a sulfide solid battery is known, but a negative electrode current collector layer, a sulfide solid electrolyte, and It is difficult to use it as a technique for suppressing the reaction.

JP 2012-049023 A JP 2011-060649 A

  In the technique disclosed in Patent Document 1, it is necessary to add a reaction suppression layer between the negative electrode mixture layer and the negative electrode current collector layer, and the problem that the battery manufacturing process becomes complicated and the volume energy of the battery There is a problem that the density is reduced. That is, the problem is how to suppress the reaction between the negative electrode current collector layer and the sulfide solid electrolyte in the negative electrode mixture layer without adding a reaction suppression layer separately.

  The present application includes, as one means for solving the above problems, a negative electrode mixture layer and a negative electrode current collector layer in contact with the negative electrode mixture layer, and the negative electrode mixture layer includes a negative electrode active material and a sulfide. A solid electrolyte, and at least a surface of the surface of the negative electrode current collector layer that is in contact with the negative electrode mixture layer is made of a material including copper and an alloy of metal having a higher ionization tendency than copper, A negative electrode is disclosed.

  In the negative electrode of the present disclosure, it is preferable that the alloy includes copper and at least one selected from zinc, beryllium, and tin.

  In the negative electrode of the present disclosure, the alloy preferably includes copper and zinc.

  In the negative electrode of the present disclosure, the negative electrode active material preferably contains a silicon-based active material.

  In the negative electrode of the present disclosure, the negative electrode current collector layer preferably has a tensile strength of 500 MPa or more.

  In the negative electrode of the present disclosure, the elongation at break of the negative electrode current collector layer is preferably 7.95% or more.

  As one of means for solving the above-described problems, the present application discloses a sulfide solid state battery including the negative electrode of the present disclosure, a positive electrode, and a solid electrolyte layer provided between the negative electrode and the positive electrode. .

  According to the inventor's new knowledge, when alloyed with a combination of copper and a metal that has a higher ionization tendency than copper, compared to the case of copper alone, the electrochemical reactivity to the sulfide solid electrolyte is lower. Lower. In addition, even when the alloy reacts electrochemically with the sulfide solid electrolyte, it is considered that a metal having a higher ionization tendency than copper and the sulfide solid electrolyte react preferentially, which is disadvantageous for the charge / discharge reaction. The production | generation of the copper sulfide which becomes can be suppressed. That is, like the negative electrode of the present disclosure, the surface of the negative electrode current collector layer is made of a material containing a predetermined alloy, so that the negative electrode current collector layer and the negative electrode composite material can be added without adding a new reaction suppression layer. Reaction with the sulfide solid electrolyte in the layer can be suppressed.

1 is a schematic diagram for explaining an example of a negative electrode 100. FIG. 3 is a schematic diagram for explaining an example of a negative electrode current collector 10. FIG. It is the schematic for demonstrating the structure of the sulfide solid battery 1000. FIG. It is the schematic for demonstrating the structure of the evaluation apparatus used in the Example. It is a figure which shows the CV evaluation result of the comparative example 1. It is a figure which shows the CV evaluation result of Example 1. It is a figure which shows the CV evaluation result of Example 2. It is a figure which shows the CV evaluation result of Example 3. It is a figure which shows the CV evaluation result of the comparative example 2. It is the figure which compared the tensile strength of various copper alloy foil (Example 1A-3A, Example 1B-3B) and copper foil (Comparative Example 1A, Comparative Example 1B). It is the figure which compared the breaking elongation of various copper alloy foil (Example 1B, Example 3B) and copper foil (Comparative Example 1A, Comparative Example 1B).

1. Negative electrode 100
As shown in FIG. 1, the negative electrode 100 includes a negative electrode mixture layer 20 and a negative electrode current collector layer 10 in contact with the negative electrode mixture layer 20. As shown in FIG. 1, the negative electrode mixture layer 20 includes a negative electrode active material 21 and a sulfide solid electrolyte 22. As shown in FIGS. 1 and 2, at least the surface of the negative electrode current collector layer 10 that is in contact with the negative electrode mixture layer 20 has a material 11 containing an alloy of copper and a metal having a higher ionization tendency than copper. Consists of.

1.1. Negative electrode current collector layer 10
The negative electrode current collector layer 10 is made of a material 11 containing at least a surface in contact with the negative electrode mixture layer 20 of the surface thereof and containing an alloy of copper and a metal having a higher ionization tendency than copper. Thereby, the reaction between the negative electrode current collector layer 10 and the sulfide solid electrolyte 22 in the negative electrode mixture layer 20 is suppressed. Whether or not the surface of the negative electrode current collector layer 10 is composed of the material 11 can be easily determined by elemental analysis or the like of the surface of the negative electrode current collector layer 10. Specific examples of metals having a higher ionization tendency than copper include bismuth (Bi), antimony (Sb), lead (Pb), tin (Sn), nickel (Ni), cobalt (Co), cadmium (Cd), iron (Fe), chromium (Cr), zinc (Zn), tantalum (Ta), manganese (Mn), zirconium (Zr), titanium (Ti), aluminum (Al), beryllium (Be), thorium (Th), magnesium (Mg), sodium (Na), calcium (Ca), strontium (Sr), barium (Ba), potassium (K), rubidium (Rb), cesium (Cs), lithium (Li) and the like. Among these, zinc (Zn), beryllium (Be), and tin (Sn) are preferable, and zinc (Zn) is particularly preferable. That is, the above alloy may contain copper and at least one selected from zinc, beryllium and tin, or may contain copper and zinc. The alloy may contain only one type of metal having a higher ionization tendency than copper, or may contain two or more types.

  The composition of the alloy of copper and a metal having a higher ionization tendency than copper is arbitrary, and may be appropriately determined in consideration of the conductivity of the negative electrode current collector layer 10 and the like. For example, in the alloy, the total of copper and a metal having a higher ionization tendency than copper is 100 atm%, copper is 5 atm% or more and 99 atm% or less, a metal having a higher ionization tendency than copper (the metal is composed of two or more kinds). In some cases, the total concentration is preferably 1 atm% or more and 95 atm% or less. More preferably, copper is contained at 20 atm% or more and 96 atm% or less, and a metal having a higher ionization tendency than copper is contained at 4 atm% or more and 80 atm% or less. More preferably, copper is contained at 50 atm% or more and 96 atm% or less, and a metal having a higher ionization tendency than copper is contained at 4 atm% or more and 50 atm% or less. Particularly preferably, copper is contained at 65 atm% or more and 96 atm% or less, and a metal having a higher ionization tendency than copper is contained at 4 atm% or more and 35 atm% or less. The alloy may contain inevitable impurities. The concentration of inevitable impurities is preferably 1 atm% or less, with the entire alloy being 100 atm%.

  The material 11 may contain other elements and components other than the above alloy as long as the above problems can be solved in consideration of contamination and the like. For example, an inevitable oxide film or the like may be formed on a part of the surface of the negative electrode current collector layer 10, that is, the material 11 may contain an inevitable oxide or the like. The material 11 may contain unavoidable moisture. The material 11 may partially contain a metal having a lower ionization tendency than copper as long as the above problem can be solved. However, from the viewpoint of exerting a more remarkable effect, the material 11 is preferably made of an alloy of copper and a metal having a higher ionization tendency than copper.

  The negative electrode current collector layer 10 only needs to have at least a surface in contact with the negative electrode composite material layer 20 made of the material 11, and the forms (shapes) thereof are various. Only the surface of the negative electrode current collector layer 10 may be composed of the material 11, or the entire surface and inside may be composed of the material 11. For example, as shown in FIG. 2 (A), it may be a foil-like or sheet-like negative electrode current collector layer 10a made of the above-described material 11, or as shown in FIG. 2 (B). 11 or a negative electrode current collector layer 10b having a mesh shape or a punching metal shape. The negative electrode current collector layers 10a and 10b can be easily manufactured, for example, by molding the material 11 described above. Alternatively, as illustrated in FIG. 2C, a negative electrode current collector layer 10 c formed by covering the surface of a base material 12 made of a material different from the above-described material 11 with the above-described material 11 may be used. That is, the surface and the inside of the negative electrode current collector layer 10 may be composed of different materials. The negative electrode current collector layer 10c can be easily manufactured by thinly coating the above-described material 11 on the surface of the substrate 12 by, for example, plating or sputtering. The base material 12 should just be what can ensure the mechanical strength and durability as the negative electrode collector 10c. For example, the base material 12 may be made of a metal different from the material 11 described above, or the base material 12 may be made of a material (resin or the like) other than metal.

  The thickness of the negative electrode current collector layer 10 is not particularly limited. The thickness can be the same as the thickness of the negative electrode current collector layer in the conventional negative electrode. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. According to the knowledge of the present inventor, at least the surface of the surface of the negative electrode current collector layer 10 that contacts the negative electrode mixture layer 20 is composed of the material 11 regardless of the thickness of the negative electrode current collector layer 10. By doing so, the reaction between the negative electrode current collector layer 10 and the sulfide solid electrolyte 22 in the negative electrode mixture layer 20 can be suppressed. Of the surface of the negative electrode current collector layer 10, at least a portion in contact with the sulfide solid electrolyte 22 may be formed of the material 11.

  When manufacturing the negative electrode 100, from the viewpoint of improving the filling rate of the negative electrode mixture layer 20, the negative electrode mixture layer 20 may be roll-pressed together with the negative electrode current collector layer 10 at a high pressure. Here, from the viewpoint of productivity and the like, it is preferable to suppress breakage of the negative electrode current collector layer 10 during the roll press. In order to suppress breakage of the negative electrode current collector layer during roll press, for example, it is effective to increase the thickness of the negative electrode current collector layer, but in the negative electrode 100, the thickness of the negative electrode current collector layer 10 is increased. In such a case, the volume energy density of the battery is lowered. Therefore, it is preferable to suppress breakage of the negative electrode current collector layer 10 during roll pressing without increasing the thickness of the negative electrode current collector layer 10 as much as possible.

According to the new knowledge of the present inventor, the negative electrode current collector layer 10 having a predetermined mechanical strength can suppress breakage of the negative electrode current collector layer 10 during the roll press of the negative electrode 100. Specifically, the negative electrode current collector layer 10 preferably has a tensile strength of 500 MPa or more. Alternatively, the negative electrode current collector layer 10 is more preferably configured to include a metal foil having a tensile strength of 500 MPa or more. The lower limit of the tensile strength is more preferably 600 MPa or more, and still more preferably 800 MPa or more. The upper limit is not particularly limited. The negative electrode current collector layer 10 having such tensile strength can be easily obtained, for example, by adjusting the alloy composition in the negative electrode current collector layer 10 or by subjecting the negative electrode current collector layer 10 to work hardening. Can be produced. When the negative electrode current collector layer subjected to work hardening treatment is further subjected to a heat treatment such as annealing, the tensile strength of the negative electrode current collector layer tends to decrease.
In addition, in this application, "the tensile strength of a negative electrode collector layer" means the tensile strength measured based on JISZ2241: 2011 by making a negative electrode collector layer (for example, metal foil) itself into a test piece.

Further, according to the new knowledge of the present inventor, when the elongation at break of the negative electrode current collector layer 10 is not less than a predetermined value, the breakage of the negative electrode current collector layer 10 during the roll press of the negative electrode 100 can be suppressed. . Specifically, the elongation at break of the negative electrode current collector layer 10 is preferably 7.95% or more. Alternatively, the negative electrode current collector layer 10 is more preferably configured to include a metal foil having a fracture extension of 7.95% or more. The lower limit of elongation at break is more preferably 14% or more. The negative electrode current collector layer 10 having such elongation at break can be easily produced, for example, by adjusting the alloy composition in the negative electrode current collector layer 10.
In the present application, “breaking elongation of the negative electrode current collector layer” refers to elongation at break measured according to JIS Z 2241: 2011 using the negative electrode current collector layer (for example, metal foil) itself as a test piece.

1.2. Negative electrode mixture layer 20
As shown in FIG. 1, the negative electrode mixture layer 20 includes a negative electrode active material 21 and a sulfide solid electrolyte 22. By including the sulfide solid electrolyte 22 in the negative electrode mixture layer 20, a part of the surface of the negative electrode current collector layer 10 that contacts the negative electrode mixture layer 20 is in contact with the sulfide solid electrolyte 22. Become. The negative electrode mixture layer 20 may optionally contain a conductive additive, a binder, and other additives (thickener, etc.).

  As the negative electrode active material 21 contained in the negative electrode mixture layer 20, any known negative electrode active material of a sulfide solid state battery can be adopted. Of the known active materials, a material having a lower charge / discharge potential than the positive electrode active material 41 described later may be used as the negative electrode active material. For example, silicon-based active materials such as Si, Si alloys and silicon oxides as the negative electrode active material 21; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium and lithium alloys Can be used. The negative electrode active material 21 may be used alone or in combination of two or more. The shape of the negative electrode active material 21 is not particularly limited. For example, it is preferable to form particles or thin films. The content of the negative electrode active material 21 in the negative electrode mixture layer 20 is not particularly limited, and may be equal to the amount of the negative electrode active material contained in the conventional negative electrode mixture layer.

  In a conventional negative electrode, when a negative electrode is formed by laminating a negative electrode mixture layer containing a silicon-based active material and a sulfide solid electrolyte on the surface of a negative electrode current collector layer made of copper, the copper is formed in the silicon-based active material OCV. And sulfide solid electrolyte may react. That is, immediately after the negative electrode mixture layer is formed on the surface of the negative electrode current collector layer, the negative electrode current collector layer may react with the sulfide solid electrolyte in the negative electrode mixture layer. On the other hand, in the negative electrode 100 of the present disclosure, the surface of the negative electrode current collector 10 that comes into contact with the negative electrode mixture layer 20 is composed of the material 11 described above. Even when the negative electrode mixture layer 20 including the electrolyte is laminated to form the negative electrode 100, the reaction between the negative electrode current collector layer 10 and the sulfide solid electrolyte 22 in the negative electrode mixture layer 20 is suppressed. That is, in the negative electrode 100 of the present disclosure, an excellent effect can be exhibited even when the negative electrode active material 21 includes a silicon-based active material.

As the sulfide solid electrolyte 22 contained in the negative electrode mixture layer 20, any known sulfide can be adopted as a solid electrolyte of a sulfide solid battery. For example, a solid electrolyte containing Li, P and S as constituent elements can be used. Specifically, Li ₂ S—P ₂ S ₅ , Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Si ₂ S—P ₂ S ₅ , LiI—LiBr—Li ₂ S—P _{2 S 5, LiI-Li 2} S-P 2 S 5, LiI-Li 2 O-Li 2 S-P 2 S 5, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 _{S 5, Li 2 S-P} 2 S 5 -GeS 2 , and the like. Among these, a sulfide solid electrolyte containing Li ₂ S—P ₂ S ₅ is more preferable. The sulfide solid electrolyte 22 may be used alone or in combination of two or more. The shape of the sulfide solid electrolyte 22 is not particularly limited. For example, it can be particulate. The content of the sulfide solid electrolyte 22 in the negative electrode mixture layer 20 is not particularly limited, and may be equal to the amount of the sulfide solid electrolyte contained in the conventional negative electrode mixture layer.

  The negative electrode mixture layer 20 may contain an inorganic solid electrolyte other than the sulfide solid electrolyte 22 in addition to the sulfide solid electrolyte 22 within a range in which a desired effect can be exhibited. For example, oxide solid electrolyte.

  As the conductive auxiliary agent contained as an optional component in the negative electrode mixture layer 20, any known conductive auxiliary agent used in a sulfide solid state battery can be adopted. For example, carbon materials such as acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF) and graphite; nickel, aluminum, stainless steel, etc. The metal material can be used. A carbon material is particularly preferable. Only 1 type may be used for a conductive support agent alone, and 2 or more types may be mixed and used for it. The shape of the conductive auxiliary agent is not particularly limited. For example, it is preferable to form particles or fibers. The content of the conductive additive in the negative electrode mixture layer 20 is not particularly limited, and may be equal to the amount of the conductive additive included in the conventional negative electrode mixture layer.

  As the binder contained in the negative electrode mixture layer 20 as an optional component, any known binder can be employed as a binder employed in the sulfide solid state battery. For example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), etc. are used. be able to. Only one type of binder may be used alone, or two or more types may be mixed and used. The content of the binder in the negative electrode mixture layer 20 is not particularly limited, and may be the same as the amount of the binder contained in the conventional negative electrode mixture layer.

  The negative electrode 100 having the above configuration includes a negative electrode active material 21, a sulfide solid electrolyte 22, a conductive auxiliary agent and a binder, which are optional components, and a kneaded mixture in a non-aqueous solvent. Then, the electrode composition can be easily manufactured by undergoing a process such as coating on the surface of the negative electrode current collector 10, drying and optionally pressing. However, the method is not limited to such a wet method, and the negative electrode 100 can be manufactured by press molding in a dry method. When the sheet-like negative electrode mixture layer 20 is thus formed on the surface of the negative electrode current collector 10, the thickness of the negative electrode mixture layer 20 is preferably, for example, 0.1 μm or more and 1 mm or less, and preferably 1 μm or more and 100 μm. The following is more preferable.

2. Sulfide solid state battery 1000
FIG. 3 schematically shows the configuration of the sulfide solid state battery 1000. The sulfide solid state battery 1000 includes the negative electrode 100 of the present disclosure, the positive electrode 200, and the solid electrolyte layer 300 provided between the negative electrode 100 and the positive electrode 200. The solid electrolyte layer 300 is in contact with the negative electrode mixture layer 20 of the negative electrode 100 and the positive electrode mixture layer 40 of the positive electrode 200. In FIG. 3, terminals, battery cases, and the like are omitted. The configurations of the positive electrode 200 and the solid electrolyte layer 300 in the sulfide solid state battery 1000 are obvious, but an example will be described below.

2.1. Positive electrode 200
As shown in FIG. 3, the positive electrode 200 includes a positive electrode mixture layer 40 and a positive electrode current collector layer 30 that contacts the positive electrode mixture layer 40.

2.1.1. Positive electrode current collector layer 30
The positive electrode current collector layer 30 may be made of a metal foil, a metal mesh, or the like. Metal foil is particularly preferable. Examples of the metal constituting the positive electrode current collector layer 30 include stainless steel, nickel, chromium, gold, platinum, aluminum, iron, titanium, and zinc. The positive electrode current collector layer 30 may be a metal foil or base material plated and vapor-deposited with these metals. The thickness of the positive electrode current collector layer 30 is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

2.1.2. Positive electrode mixture layer 40
As shown in FIG. 3, the positive electrode mixture layer 40 includes a positive electrode active material 41. Moreover, the positive electrode mixture layer 40 may optionally contain a solid electrolyte 42, a conductive additive, a binder, and other additives (thickeners and the like).

As the positive electrode active material 41 included in the positive electrode mixture layer 40, any known positive electrode active material of a sulfide solid state battery can be adopted. Of the known active materials, a material having a charge / discharge potential more noble than the above-described negative electrode active material 21 may be used as the positive electrode active material. For example, as the positive electrode active material 41, lithium cobaltate, lithium nickelate, Li (Ni, Mn, Co) O ₂ (Li _{1 + α} Ni _1/3 Mn _1/3 Co- _1/3 O ₂ ), lithium manganate, spinel Type lithium composite oxide, lithium titanate, lithium metal phosphate (LiMPO ₄ , M is at least one selected from Fe, Mn, Co, Ni) and the like can be used. The positive electrode active material 41 may be used alone or in combination of two or more. The positive electrode active material 41 may have a coating layer such as lithium niobate, lithium titanate, or lithium phosphate on the surface. The shape of the positive electrode active material 41 is not particularly limited. For example, it is preferable to form particles or thin films. The content of the positive electrode active material 41 in the positive electrode mixture layer 40 is not particularly limited and may be equal to the amount of the positive electrode active material contained in the conventional positive electrode mixture layer.

  As the solid electrolyte 42 contained as an optional component in the positive electrode mixture layer 40, any known solid electrolyte for a sulfide solid state battery can be used. For example, the above-described sulfide solid electrolyte is preferably used. However, an inorganic solid electrolyte other than the sulfide solid electrolyte may be included in addition to the sulfide solid electrolyte as long as a desired effect can be exhibited. The shape of the solid electrolyte 42 is not particularly limited. For example, it is preferable to use particles. The content of the solid electrolyte 42 in the positive electrode mixture layer 40 is not particularly limited, and may be equal to the amount of the solid electrolyte contained in the conventional positive electrode mixture layer.

  As the conductive auxiliary agent contained as an optional component in the positive electrode mixture layer 40, any known conductive auxiliary agent used in a sulfide solid state battery can be used. For example, carbon materials such as acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF) and graphite; nickel, aluminum, stainless steel, etc. The metal material can be used. A carbon material is particularly preferable. Only one type of conductive auxiliary may be used alone, or two or more types may be used in combination. The shape of the conductive auxiliary agent is not particularly limited. For example, it is preferable to use particles. The content of the conductive additive in the positive electrode mixture layer 40 is not particularly limited, and may be equal to the amount of the conductive additive included in the conventional positive electrode mixture layer.

  As the binder contained in the positive electrode mixture layer 40 as an optional component, any known binder can be employed as a binder employed in the sulfide solid state battery. For example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or the like can be used. Only one type of binder may be used alone, or two or more types may be mixed and used. The content of the binder in the positive electrode mixture layer 40 is not particularly limited, and may be equal to the amount of the binder contained in the conventional positive electrode mixture layer.

  The positive electrode 200 having the above configuration was obtained by mixing a positive electrode active material 41 and a solid electrolyte 42, a binder, a conductive auxiliary agent, and the like optionally contained in a non-aqueous solvent and kneading the slurry. Thereafter, the electrode composition can be easily manufactured by undergoing processes such as coating on the surface of the positive electrode current collector 30, drying, and optional pressing. However, the method is not limited to such a wet method, and the positive electrode 200 can be manufactured by press molding in a dry method. When the sheet-like positive electrode mixture layer 40 is formed on the surface of the positive electrode current collector 30 in this manner, the thickness of the positive electrode mixture layer 40 is preferably, for example, from 0.1 μm to 1 mm, and preferably from 1 μm to 100 μm. The following is more preferable.

2.2. Solid electrolyte layer 300
The solid electrolyte layer 300 has a function of insulating the negative electrode 100 and the positive electrode 200 and conducting lithium ions between the negative electrode 100 and the positive electrode 200. The solid electrolyte layer 300 includes at least the solid electrolyte 51. Moreover, it is preferable that the solid electrolyte layer 300 contains the binder.

2.2.1. Solid Electrolyte The solid electrolyte 51 included in the solid electrolyte layer 300 may be appropriately selected from those exemplified as the solid electrolyte that can be included in the negative electrode mixture layer 20 and the positive electrode mixture layer 40 described above. In particular, a sulfide solid electrolyte is preferable, and a sulfide solid electrolyte containing Li ₂ S—P ₂ S ₅ is more preferable. The solid electrolyte 51 may be used alone or in combination of two or more. The solid electrolyte 51 may have a general shape, that is, a particulate shape. The content of the solid electrolyte 51 in the solid electrolyte layer 300 is not particularly limited, and may be determined as appropriate according to the intended battery performance. For example, it is preferable that the solid electrolyte layer 300 as a whole is 100% by mass and the solid electrolyte content is 90% by mass or more. More preferably, it is 95 mass% or more.

2.2.2. Binder The solid electrolyte layer 300 preferably contains a binder. Binders that can be included in the solid electrolyte layer 300 are known. For example, what is necessary is just to select suitably from what was illustrated as a binder which can be contained in said negative electrode compound material layer 20 or positive electrode compound material layer 40. FIG.

  The solid electrolyte layer 300 having the above configuration is obtained by mixing the solid electrolyte 51 and a binder to be optionally contained in a non-aqueous solvent and kneading to obtain a slurry-like electrolyte composition. It can be easily manufactured through a process such as applying to the surface of the substrate (or the surface of the negative electrode mixture layer 20 or the surface of the positive electrode mixture layer 40), drying and optionally pressing. However, the method is not limited to such a wet method, and the solid electrolyte layer 300 can also be manufactured by press molding in a dry method. Thus, when forming the sheet-like solid electrolyte layer 300, it is preferable that the thickness of the solid electrolyte layer 300 is 0.1 micrometer or more and 1 mm or less, for example, and it is more preferable that they are 1 micrometer or more and 100 micrometers or less.

2.3. Other Configurations The sulfide solid battery 1000 does not necessarily need to be all solid. The sulfide solid state battery 1000 may partially contain a liquid such as an electrolytic solution as long as the battery performance is not impaired.

  The sulfide solid state battery 1000 having the above configuration can be manufactured, for example, as follows. That is, the manufacturing method of the sulfide solid state battery 1000 includes a step of manufacturing the negative electrode 100, the positive electrode 200, and the solid electrolyte layer 300 by the above method, and a step of stacking the negative electrode 100, the positive electrode 200, and the solid electrolyte layer 300. . In this way, the negative electrode 100, the solid electrolyte layer 300, and the positive electrode 200 are laminated to form a laminated body, an appropriate terminal and the like are attached, and the laminated body is sealed in a battery case. Can be manufactured.

1. Evaluation of Reactivity between Negative Electrode Current Collector Layer and Sulfide Solid Electrolyte As shown in FIG. 4, a sulfide solid electrolyte (Li ₂ SP) is interposed between a predetermined metal foil and an In-Li foil (thickness 80 μm). nipping a layer made of ₂ S ₅ from the main component) (thickness 450 [mu] m), to connect the metal foil and an in-Li foil to a power supply, cyclic voltammetry reactivity between the metal foil and the sulfide solid electrolyte (CV ). The types of metal foil used in Examples and Comparative Examples are as follows.

Comparative Example 1 Copper (Cu) foil, thickness 10 μm
Example 1 Copper-beryllium alloy (CuBe) foil, copper: beryllium = 88 atm%: 12 atm%, thickness 10 μm
Example 2 Copper-zinc alloy (CuZn) foil, copper: zinc = 65 atm%: 35 atm%, thickness 10 μm
Example 3 Copper-tin alloy (CuSn) foil (containing a slight amount of phosphorus (P) as an impurity), copper: tin = 96 atm%: 3 atm%, thickness 10 μm
Comparative Example 2 Copper-silver alloy (CuAg) foil, copper: silver = 81 atm%: 19 atm%, thickness 50 μm

  5-9 show the CV results for each of the examples and comparative examples. 5 corresponds to Example 1, FIG. 6 corresponds to Example 1, FIG. 7 corresponds to Example 2, FIG. 8 corresponds to Example 3, and FIG. In FIG. 5, the vertical axis is 100 times that of FIGS. 5-9, it can be said that the electrochemical reactivity with a sulfide solid electrolyte is so high that the fluctuation | variation of an electric current density (vertical axis) is large.

  As is apparent from the results shown in FIG. 5, in Comparative Example 1 using a copper foil as the metal foil, the current density variation at CV is large, and the electrochemical reactivity between the copper foil and the sulfide solid electrolyte is high. I understand that it is expensive.

  On the other hand, as is clear from the results shown in FIGS. 6 to 8, for Examples 1 to 3 using an alloy foil of copper and a metal (beryllium, zinc or tin) having a higher ionization tendency than copper, the current at CV It can be seen that the density fluctuation is small and the electrochemical reactivity between the alloy foil and the sulfide solid electrolyte is low (about 1/1000 compared with Comparative Example 1). In particular, in Example 2 using an alloy foil of copper and zinc, it can be seen that the electrochemical reactivity between the alloy foil and the sulfide solid electrolyte is further reduced.

  Moreover, as is clear from the results shown in FIGS. 6 to 8, in Examples 1 to 3, even when CV is repeated, the reaction between the alloy foil and the sulfide solid electrolyte hardly proceeds. That is, a reaction between the alloy and the sulfide solid electrolyte occurs on the surface of the alloy foil in contact with the sulfide solid electrolyte, but the reaction between the alloy and the sulfide solid electrolyte does not easily proceed to the deep part of the alloy foil. it is conceivable that. That is, regardless of the thickness of the foil, it is considered that a sufficient effect can be ensured by configuring at least the surface of the foil surface that contacts the sulfide solid electrolyte with a material containing a predetermined alloy.

  As is apparent from the results shown in FIG. 9, the comparative example 2 using an alloy foil of copper and a metal (silver) having a lower ionization tendency than copper is different from the examples 1 to 3 in the alloy foil. It can be seen that the reaction between the solid electrolyte and the sulfide solid electrolyte cannot be suppressed.

  In Examples 1 to 3, beryllium, zinc, and tin are shown as examples of metals having a higher ionization tendency than copper. However, the technology of the present disclosure is not limited to metals other than these as metals having a higher ionization tendency than copper. Even when a metal is used, the same effect is considered to be exhibited. Specific examples other than beryllium, zinc and tin include bismuth (Bi), antimony (Sb), lead (Pb), nickel (Ni), cobalt (Co), cadmium (Cd), iron (Fe), chromium (Cr ), Tantalum (Ta), manganese (Mn), zirconium (Zr), titanium (Ti), aluminum (Al), thorium (Th), magnesium (Mg), sodium (Na), calcium (Ca), strontium (Sr) ), Barium (Ba), potassium (K), rubidium (Rb), cesium (Cs), lithium (Li) and the like.

  In Examples 1 to 3 described above, the copper-based alloy having a predetermined composition is shown. However, in the technology of the present disclosure, the composition of the copper-based alloy is not particularly limited. In addition to the reactivity with the sulfide solid electrolyte, the alloy composition may be appropriately determined according to the intended battery performance, taking into account the conductivity as the negative electrode current collector layer.

2. 2. Study on mechanical strength of negative electrode current collector layer 2.1. Tensile strength In a PP container, butyl butyrate, a 5 wt% butyl butyrate solution of a PVdF binder (manufactured by Kureha), and silicon (manufactured by Kojun Chemical Co., Ltd., average particle diameter (D ₅₀ ): 5 μm) as a negative electrode active material Then, a sulfide solid electrolyte was added, and the mixture was stirred for 30 seconds with an ultrasonic dispersion device (UH-50 manufactured by SMT Corporation). Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Kagaku Co., Ltd.) for 30 minutes, and further stirred with an ultrasonic dispersion device for 30 seconds. Further, the mixture was shaken with a shaker for 3 minutes to obtain a negative electrode mixture slurry. The obtained negative electrode mixture slurry was coated on a metal foil having various tensile strengths by a blade method using an applicator. After natural drying, it was dried on a hot plate at 100 ° C. for 30 minutes to form a negative electrode mixture layer on the surface of the metal foil. Thereafter, after the solid electrolyte layer and the positive electrode mixture layer formed by coating are stacked on the negative electrode mixture layer by transfer, the electrode body (negative electrode mixture layer + solid electrolyte layer + positive electrode mixture layer) prepared by transfer is used. Roll press was performed at a maximum linear pressure (linear pressure 5 t / cm) and a feed rate of 0.5 m / min for the purpose of improving the filling rate and drawing out the characteristics of the battery.

  When the presence or absence of breakage of the metal foil after the roll press was confirmed, when using a metal foil having a tensile strength of 500 MPa or more measured in accordance with JIS Z 2241: 2011, the metal foil does not depend on the composition. It was found that the negative electrode can be produced without breaking the metal foil.

  The various copper alloy foils and copper foils shown below were subjected to a tensile test in accordance with JIS Z 2241: 2011, and the tensile strength was measured. The results are shown in FIG.

Comparative Example 1A Rolled copper (Cu) foil, thickness 10 μm
Comparative Example 1B: High-strength copper (Cu) foil (SEED manufactured by Nippon Electrolytic Co., Ltd.), thickness of about 10 μm, crystal grain refinement treatment with the purpose of improving the strength of metal Example 1A: copper-beryllium alloy (CuBe) foil , Copper: beryllium = 88 atm%: 12 atm%, thickness 10 μm, work hardening treatment present, annealing after work hardening treatment None 1B. Copper-beryllium alloy (CuBe) foil, copper: beryllium = 88 atm%: 12 atm%, thickness Example 2A: Copper-zinc alloy (CuZn) foil, copper: zinc = 65 atm%: 35 atm%, thickness 10 μm, work hardening treatment present, after work hardening treatment 10 μm, work hardening treatment present, annealing after work hardening treatment Unannealed Example 2B Copper-zinc alloy (CuZn) foil, copper: zinc = 65 atm%: 35 atm%, thickness 10 μm, work hardening treatment present, work hard Example 3A: Annealing after treatment Example: Copper-tin alloy (CuSn) foil (containing a slight amount of phosphorus (P) as an impurity), copper: tin = 96 atm%: 3 atm%, thickness 10 μm, work hardening treatment present, work hardening Annealing after treatment No Example 3B Copper-tin alloy (CuSn) foil (including a slight amount of phosphorus (P) as impurities), copper: tin = 96 atm%: 3 atm%, thickness 10 μm, work hardening treatment present, work hardening Annealed after treatment

  As shown in FIG. 10, even if it is a metal foil having the same composition and the same thickness, the tensile strength of the metal foil can be changed depending on the presence or absence of work hardening treatment or the presence or absence of heat treatment (annealing). As shown in FIG. 10, the copper alloy foils according to Examples 1 to 3 are materials whose tensile strength can greatly exceed 500 MPa, and can sufficiently withstand a roll press when manufacturing a negative electrode. I understood. That is, it can be said that the alloy constituting the negative electrode current collector layer preferably contains copper and at least one selected from zinc, beryllium and tin.

2.2. Elongation at break Form a negative electrode mixture layer on the surface of the metal foil in the same procedure as in the evaluation of tensile strength, and then improve the filling rate of the negative electrode mixture layer while maintaining the material properties of the negative electrode mixture layer Roll pressing was performed at a maximum linear pressure (5 t / cm) and a feed rate of 0.5 m / min.

  When the presence or absence of breakage of the metal foil after the roll press was confirmed, when a metal foil having a break elongation measured in accordance with JIS Z 2241: 2011 of 7.95% or more was used, the metal foil depends on the composition of the metal foil. In addition, even if the metal foil has a tensile strength of less than 500 MPa, a negative electrode is produced without breaking the metal foil even when a roll press with a linear pressure of 5 t / cm and a feed rate of 0.5 m / min is performed. I found it possible.

  Breaking elongation was measured based on JIS Z 2241: 2011 about the copper alloy foil similar to said Example 1B and Example 3B, and the copper foil similar to Comparative Example 1A and Comparative Example 1B. The results are shown in FIG. As shown in FIGS. 10 and 11, the copper alloy foils according to Example 1B and Example 3B have a tensile strength of less than 500 MPa, but the elongation at break greatly exceeds 7.95%. It was found that it can sufficiently withstand the roll press.

As described above, in order to suppress breakage of the negative electrode current collector layer during roll press during negative electrode production, the negative electrode current collector layer preferably satisfies at least one of the following requirements (1) and (2). I understood that.
(1) The negative electrode current collector layer has a tensile strength of 500 MPa or more. (2) The negative electrode current collector layer has a breaking elongation of 7.95% or more.

  The sulfide solid state battery including the negative electrode of the present disclosure can be used widely and suitably from a small power source for portable devices to a large power source for on-vehicle use.

DESCRIPTION OF SYMBOLS 100 Negative electrode 10 Negative electrode collector layer 20 Negative electrode composite material layer 200 Positive electrode 30 Positive electrode collector layer 40 Positive electrode composite material layer 300 Solid electrolyte layer 1000 Sulfide solid battery

Claims (7)

A negative electrode mixture layer and a negative electrode current collector layer in contact with the negative electrode mixture layer,
The negative electrode mixture layer includes a negative electrode active material and a sulfide solid electrolyte,
Of the surfaces of the negative electrode current collector layer, at least the surface in contact with the negative electrode mixture layer is made of a material containing an alloy of copper and a metal having a higher ionization tendency than copper,
Negative electrode. The alloy includes copper and at least one selected from zinc, beryllium and tin;
The negative electrode according to claim 1. The alloy includes copper and zinc;
The negative electrode according to claim 1 or 2. The negative electrode active material includes a silicon-based active material,
The negative electrode according to any one of claims 1 to 3. The negative electrode current collector layer has a tensile strength of 500 MPa or more.
The negative electrode of any one of Claims 1-4. The breaking elongation of the negative electrode current collector layer is 7.95% or more,
The negative electrode of any one of Claims 1-4. A sulfide solid state battery comprising: the negative electrode according to claim 1; a positive electrode; and a solid electrolyte layer provided between the negative electrode and the positive electrode.