KR20190114782A - Anode, and sulfide solid-state battery - Google Patents

Abstract

When a negative electrode is formed using a negative electrode current collector layer made of copper and a negative electrode mixture layer containing a sulfide solid electrolyte, copper and a sulfide solid electrolyte react to generate copper sulfide, and resistance at the interface between the negative electrode current collector layer and the negative electrode mixture layer increases. The negative electrode current collector layer is alloyed to reduce the reactivity with the sulfide solid electrolyte. Specifically, the negative electrode includes 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 contains a negative electrode active material and a sulfide solid electrolyte. At least one surface of surfaces of the negative electrode current collector layer in contact with the negative electrode mixture layer contains an alloy of copper and a metal having a higher ionization tendency than copper.

Description

Negative and Sulfide Solid Cells {ANODE, AND SULFIDE SOLID-STATE BATTERY}

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

In a sulfide solid battery having a negative electrode, a positive electrode, and a solid electrolyte layer, when a negative electrode is formed by using a negative electrode current collector layer made of copper and a negative electrode mixture layer containing a sulfide solid electrolyte, copper and a sulfide solid electrolyte react to sulfide There arises a problem that the capacity of the battery decreases due to the formation of copper, an increase in resistance at the interface between the negative electrode current collector layer and the negative electrode mixture layer, or irreversible reaction of copper sulfide and lithium ions. As one means for solving this problem, Patent Document 1 discloses providing a reaction suppression layer containing a predetermined element between the negative electrode mixture layer and the negative electrode current collector layer.

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

Japanese Patent Laid-Open No. 2012-049023 Japanese Laid-Open Patent Publication No. 2011-060649

In the technique disclosed in Patent Literature 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 manufacturing process of the battery becomes complicated and the volume energy density of the battery become small. There is. 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 additionally adding a reaction suppression layer.

The present application provides a negative electrode mixture layer and a negative electrode current collector layer in contact with the negative electrode mixture layer as one of means for solving the above problems, wherein the negative electrode mixture layer includes a negative electrode active material and a sulfide solid electrolyte. Disclosed is a negative electrode in which at least one of the surfaces of the negative electrode current collector layer 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.

In the negative electrode of this indication, it is preferable that the said alloy contains at least 1 chosen from copper, zinc, beryllium, and tin.

In the negative electrode of this indication, it is preferable that the said alloy contains copper and zinc.

In the negative electrode of the present disclosure, it is preferable that the negative electrode active material contains a silicon-based active material.

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

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

This application discloses a sulfide solid battery provided with the negative electrode of this indication, a positive electrode, and the solid electrolyte layer provided between the said negative electrode and the said positive electrode as one of the means for solving the said subject.

According to the new findings of the present inventors, when alloying a combination of copper and a metal having a higher ionization tendency than copper, the electrochemical reactivity to a sulfide solid electrolyte is lower than that of copper alone. Moreover, even when the said alloy reacts electrochemically with a sulfide solid electrolyte, it can be considered that metal and sulfide solid electrolyte which have a higher ionization tendency than copper preferentially react, and suppress generation | occurrence | production of copper sulfide which becomes disadvantageous to a charge / discharge reaction. can do. That is, like the negative electrode of the present disclosure, by forming the surface of the negative electrode current collector layer by a material containing a predetermined alloy, the sulfide solid electrolyte in the negative electrode current collector layer and the negative electrode mixture layer is not added to the reaction suppression layer. Can suppress the reaction.

1 is a schematic view for explaining an example of the negative electrode 100.
2 is a schematic view for explaining an example of the negative electrode current collector 10.
3 is a schematic view for explaining the configuration of the sulfide solid battery 1000.
4 is a schematic view for explaining the configuration of the evaluation apparatus used in the embodiment.
5 is a diagram showing a result of CV evaluation in Comparative Example 1. FIG.
6 is a diagram showing a result of CV evaluation in Example 1. FIG.
7 is a diagram illustrating a result of CV evaluation in Example 2. FIG.
8 is a diagram illustrating a result of CV evaluation in Example 3. FIG.
9 is a diagram illustrating a result of CV evaluation in Comparative Example 2. FIG.
10 is a diagram comparing tensile strengths of various copper alloy foils (Examples 1A to 3A, Examples 1B to 3B) and copper foils (Comparative Example 1A and Comparative Example 1B).
11 is a diagram comparing break elongation of various copper alloy foils (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 current collector layer 10 in contact with the negative electrode mixture layer 20 and 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. 1 and 2, the surface of the surface of the negative electrode current collector layer 10 that contacts at least the negative electrode mixture layer 20 includes a material containing an alloy of copper and metal having a higher ionization tendency than copper. It is comprised by (11).

1.1. Negative current collector layer (10)

The negative electrode current collector layer 10 is made of a material 11 including at least a surface of the surface contacting the negative electrode mixture layer 20 including an alloy of copper and a metal having a higher ionization tendency than copper. As a result, 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 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), and 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. Especially, zinc (Zn), beryllium (Be), and tin (Sn) are preferable, and zinc (Zn) is especially preferable. That is, the said alloy may contain at least 1 selected from copper, zinc, beryllium, and tin, and may contain copper and zinc. The alloy may contain only 1 type or 2 or more types of metals which are higher in ionization tendency than copper.

The composition of the alloy of copper and metal with a higher ionization tendency than copper is arbitrary, and what is necessary is just to determine suitably, taking into consideration the electroconductivity of the negative electrode collector layer 10, etc. For example, the alloy is a total of a metal having a higher ionization tendency than copper and copper at 100 atm%, and a copper having a higher ionization tendency than 5 atm% or more and 99 atm% or less than copper (there are two or more types of metals). It is preferable to contain 1 atm% or more and 95 atm% or less) as the total concentration. More preferably, 20 at% or more and 96 atm% or less of copper, and 4 atm% or more and 80 atm% or less of a metal having a higher ionization tendency than copper are included. More preferably, at least 50 atm% and at most 96 atm% of copper, and at least 4 atm% and at most 50 atm% of metal having a higher ionization tendency than copper. Particularly preferably, at least 65 atm% and at most 96 atm% of copper, and at least 4 atm% and at most 35 atm% of metal having a higher ionization tendency than copper. In addition, the alloy may contain inevitable impurities. It is preferable that the density | concentration of an unavoidable impurity makes 1 atm% or less the whole alloy as 100 atm%.

The material 11 may contain other elements and components other than said alloy in the range which can solve the said subject in consideration of contamination etc. 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. In addition, the material 11 may contain inevitable moisture. The material 11 may contain some metals with a lower ionization tendency than copper in the range which can solve the said subject. 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.

In the negative electrode current collector layer 10, at least a surface of the negative electrode current collector layer 20 that is in contact with the negative electrode mixture layer 20 may be formed of a material 11, and its shape (shape) may vary. In the negative electrode current collector layer 10, only the surface may be composed of the material 11, and the entire surface and the inside may be composed of the material 11. For example, as shown in FIG. 2 (A), the foil-shaped or sheet-shaped negative electrode collector layer 10a which consists of said material 11 may be sufficient, and is shown to FIG. 2 (B). As described above, the negative electrode current collector layer 10b having a mesh shape or a punched metal shape made of the material 11 may be used. The negative electrode current collector layers 10a and 10b can be easily manufactured by, for example, molding the material 11 described above. Alternatively, as shown in FIG. 2C, the negative electrode current collector layer formed by coating the material 11 on the surface of the substrate 12 made of a material different from the material 11 described above. (10c) may be sufficient. That is, the surface and the inside of the negative electrode current collector layer 10 may be made of different materials. The negative electrode current collector layer 10c can be easily manufactured by, for example, coating the above-described material 11 on the surface of the substrate 12 by plating or sputtering thinly. The base material 12 should just be able to ensure the mechanical strength and durability as the negative electrode collector 10c. For example, the base material 12 may be comprised by the metal different from the above-mentioned material 11, and the base material 12 may be comprised by materials (resin etc.) other than metal.

The thickness of the negative electrode current collector layer 10 is not particularly limited. The thickness can be the same as that of the negative electrode current collector layer in the conventional negative electrode. For example, it is preferable that they are 0.1 micrometer or more and 1 mm or less, and it is more preferable that they are 1 micrometer or more and 100 micrometers or less. In addition, according to the knowledge of the present inventors, regardless of the thickness of the negative electrode current collector layer 10, the surface 11 in contact with the negative electrode mixture layer 20 among the surfaces of the negative electrode current collector layer 10 is the material 11 described above. 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. At least a portion of the surface of the negative electrode current collector layer 10 that contacts the sulfide solid electrolyte 22 may be formed of the material 11.

When manufacturing the negative electrode 100, the negative electrode mixture layer 20 may be rolled at high pressure together with the negative electrode current collector layer 10 from the viewpoint of improving the filling rate of the negative electrode mixture layer 20. Here, from the viewpoint of productivity or the like, it is preferable to suppress the breakage of the negative electrode current collector layer 10 at the time of the roll press. In order to suppress the breakage of the negative electrode current collector layer at the time of roll pressing, for example, it is effective to increase the thickness of the negative electrode current collector layer, but the thickness of the negative electrode current collector layer 10 in the negative electrode 100 is increased. When it increases, the volume energy density of a battery will fall. Therefore, it is preferable to suppress the 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 inventors, the breakdown of the negative electrode current collector layer 10 at the time of roll pressing of the negative electrode 100 can be suppressed by the negative electrode current collector layer 10 having a predetermined mechanical strength. Specifically, the tensile strength of the negative electrode current collector layer 10 is preferably 500 MPa or more. Or, it is more preferable that the negative electrode current collector layer 10 includes 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. For example, the negative electrode current collector layer 10 having such tensile strength can be easily adjusted by adjusting an alloy composition in the negative electrode current collector layer 10 or by performing a work hardening treatment on the negative electrode current collector layer 10. Can be made. When the heat treatment such as annealing is further performed on the negative electrode current collector layer subjected to the work hardening treatment, 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 electrical power collector layer" means the tensile strength measured based on JISZ22241: 2011, using a negative electrode electrical power collector layer (for example, metal foil) itself as a test piece.

Moreover, according to the new knowledge of the present inventors, when the elongation at break of the negative electrode current collector layer 10 is more than predetermined, the breakage of the negative electrode current collector layer 10 at the time of roll pressing 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. Or, it is more preferable that the negative electrode current collector layer 10 is formed of a metal foil having an elongation at break of 7.95% or more. The lower limit of breaking elongation is more preferably 14% or more. The negative electrode current collector layer 10 having such elongation at break can be easily produced by, for example, adjusting the alloy composition in the negative electrode current collector layer 10.

In addition, in this application, "break elongation of a negative electrode electrical power collector layer" means break elongation measured based on JISZ22241: 2011, using a 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. Since the sulfide solid electrolyte 22 is included in the negative electrode mixture layer 20, a part of the surface of the surface of the negative electrode current collector layer 10 that contacts the negative electrode mixture layer 20 comes into contact with the sulfide solid electrolyte 22. . The negative electrode mixture layer 20 may optionally contain a conductive assistant, a binder, and other additives (such as thickeners).

As the negative electrode active material 21 included in the negative electrode mixture layer 20, all known ones can be used as the negative electrode active material of the sulfide solid battery. What is necessary is just to make a negative electrode active material the substance which shows the electric potential whose charge / discharge potential was lower than the positive electrode active material 41 mentioned later among the well-known active materials. For example, as the negative electrode active material 21, silicon type active materials, such as Si, a Si alloy, and silicon oxide; Carbon-based active materials such as graphite and hard carbon; Various oxide-based active materials such as lithium titanate; Metal lithium, lithium alloy, etc. can be used. The negative electrode active material 21 may be used singly or in combination of two or more kinds thereof. The shape of the negative electrode active material 21 is not particularly limited. For example, it is preferable to set it as particle shape or thin film shape. Content of the negative electrode active material 21 in the negative electrode mixture layer 20 is not specifically limited, What is necessary is just to be equal to the quantity of the negative electrode active material contained in a conventional negative electrode mixture layer.

In a conventional negative electrode, when a negative electrode is formed by stacking 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, copper and a sulfide solid electrolyte may react at OCV of the silicon-based active material. There was. That is, there was a possibility that the sulfide solid electrolyte in the negative electrode current collector layer and the negative electrode mixture layer reacted immediately after the negative electrode mixture layer was formed on the surface of the negative electrode current collector layer. In contrast, in the negative electrode 100 of the present disclosure, the surface of the negative electrode current collector 10 that is in contact with the negative electrode mixture layer 20 is composed of the above-described material 11, and thus, a silicon-based active material and a sulfide solid. Even when the negative electrode 100 is formed by stacking the negative electrode mixture layers 20 including the electrolyte, 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, even when the negative electrode active material 21 contains a silicon-based active material, excellent effects can be exhibited.

As the sulfide solid electrolyte 22 included in the negative electrode mixture layer 20, any known sulfide may be employed as the sulfide solid electrolyte of the sulfide solid battery. For example, a solid electrolyte containing Li, P and S can be used as the constituent element. Specifically, Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Si ₂ SP ₂ S ₅ , LiI-LiBr-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ S ₅ , LiI-Li ₂ O-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ -GeS _2, etc. Can be mentioned. Among these, sulfide solid electrolytes containing Li ₂ SP ₂ S ₅ are particularly preferable. The sulfide solid electrolyte 22 may be used alone or in combination of two or more kinds thereof. The shape of the sulfide solid electrolyte 22 is not particularly limited. For example, it can be set as particle shape. 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, in addition to the sulfide solid electrolyte 22, inorganic solid electrolytes other than the sulfide solid electrolyte 22 in a range capable of exhibiting a desired effect. For example, it is an oxide solid electrolyte.

As the conductive aid contained in the negative electrode mixture layer 20 as an optional component, all known ones may be employed as the conductive aid employed in the sulfide solid battery. For example, carbon materials, such as acetylene black (AB), Ketjen black (KB), vapor-phase carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF), and graphite; Metal materials, such as nickel, aluminum, stainless steel, can be used. Especially carbon material is preferable. Only one type of conductive assistant may be used, or two or more types may be mixed and used. The shape of the conductive assistant is not particularly limited. For example, it is preferable to set it as particle shape or fiber shape. The content of the conductive assistant in the negative electrode mixture layer 20 is not particularly limited, and may be equal to the amount of the conductive assistant included in the conventional negative electrode mixture layer.

As the binder contained in the negative electrode mixture layer 20 as an optional component, all known ones can be used as the binder employed in the sulfide solid battery. For example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), Polyimide (PI) and the like can be used. Only 1 type may be used for a binder, and 2 or more types may be mixed and used for it. Content of the binder in the negative electrode mixture layer 20 is not specifically limited, What is necessary is just to be equal to the quantity of the binder contained in the conventional negative electrode mixture layer.

The negative electrode 100 having the above structure is obtained by mixing the negative electrode active material 21, the sulfide solid electrolyte 22, an optional conductive assistant, and the like with a binder in a nonaqueous solvent to obtain a slurry-like electrode composition. The electrode composition can be easily prepared by applying the electrode composition to the surface of the negative electrode current collector 10, drying it, and optionally pressing it. However, it is not limited to such a wet method, but it is also possible to manufacture the negative electrode 100 by press molding dryly. In this way, when the sheet-like negative electrode mixture layer 20 is formed on the surface of the negative electrode current collector 10, the thickness of the negative electrode mixture layer 20 is preferably 0.1 μm or more and 1 mm or less, for example. 1 It is more preferable that they are more than 100 micrometers.

2. Sulfide Solid Battery (1000)

The structure of the sulfide solid battery 1000 is shown schematically in FIG. The sulfide solid battery 1000 includes a negative electrode 100 of the present disclosure, a positive electrode 200, and a 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. 3, terminals, battery cases, etc. are abbreviate | omitted and shown. Although the structure of the positive electrode 200 and the solid electrolyte layer 300 in the sulfide solid battery 1000 is obvious, 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 in contact with the positive electrode mixture layer 40.

2.1.1. Positive electrode current collector layer (30)

What is necessary is just to comprise the positive electrode electrical power collector layer 30 with metal foil, a metal mesh, etc. Especially metal foil is preferable. Examples of the metal constituting the positive electrode current collector layer 30 include stainless steel, nickel, chromium, gold, platinum, aluminum, iron, titanium, zinc and the like. The positive electrode current collector layer 30 may be obtained by plating and depositing these metals on a metal foil or a base material. The thickness of the positive electrode current collector layer 30 is not particularly limited. For example, it is preferable that they are 0.1 micrometer or more and 1 mm or less, and it is more preferable that they are 1 micrometer or more and 100 micrometers or less.

2.1.2. Positive electrode mixture layer (40)

As shown in FIG. 3, the positive electrode mixture layer 40 includes the positive electrode active material 41. In addition, the positive electrode mixture layer 40 may optionally include the solid electrolyte 42, the conductive assistant, the binder, and other additives (such as thickeners).

As the positive electrode active material 41 included in the positive electrode mixture layer 40, all known ones can be used as the positive electrode active material of the sulfide solid battery. What is necessary is just to make the positive electrode active material the substance of the known active material which shows a potential with a charge / discharge potential more precious than the negative electrode active material 21 mentioned above. For example, lithium cobalt, lithium nickelate, Li (Ni, Mn, Co) O ₂ (Li _{1 + α} Ni _1/3 Mn _1/3 Co _1/3 O ₂ ), manganese as the positive electrode active material 41 lithium, spinel type lithium composite oxide, lithium titanate, a lithium metal phosphate can be used lithium-containing oxides (LiMPO _4, M is at least one selected from Fe, Mn, Co, Ni) and the like. The positive electrode active material 41 may be used individually by 1 type, or may mix and use 2 or more types. The positive electrode active material 41 may have a coating layer such as lithium niobate, lithium titanate or lithium phosphate on its surface. The shape of the positive electrode active material 41 is not particularly limited. For example, it is preferable to set it as particle shape or thin film shape. 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 included as an optional component in the positive electrode mixture layer 40, all known ones may be employed as the solid electrolyte of the sulfide solid battery. For example, the sulfide solid electrolyte described above is preferably employed. . However, in addition to the sulfide solid electrolyte, inorganic solid electrolytes other than the sulfide solid electrolyte may be included in a range capable of exhibiting a desired effect. The shape of the solid electrolyte 42 is not particularly limited. For example, it is preferable to set it as particle shape. 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 aid contained in the positive electrode mixture layer 40 as an optional component, all known ones may be adopted as the conductive aid employed in the sulfide solid battery. For example, carbon materials, such as acetylene black (AB), Ketjen black (KB), vapor-phase carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF), and graphite; Metal materials, such as nickel, aluminum, stainless steel, can be used. Especially carbon material is preferable. Only one type of conductive assistant may be used, or two or more types may be mixed and used. The shape of the conductive assistant is not particularly limited. For example, it is preferable to set it as particle shape. The content of the conductive assistant in the positive electrode mixture layer 40 is not particularly limited, and may be equal to the amount of the conductive assistant included in the conventional positive electrode mixture layer.

As the binder contained in the positive electrode mixture layer 40 as an optional component, all known ones can be used as the binder employed in the sulfide solid battery. For example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), etc. Can be used. Only 1 type may be used for a binder individually, and 2 or more types may be mixed and used for it. Content of the binder in the positive electrode mixture layer 40 is not specifically limited, What is necessary is just to be equal to the quantity of the binder contained in the conventional positive electrode mixture layer.

The positive electrode 200 having the above configuration is obtained by mixing and mixing a positive electrode active material 41 with a solid electrolyte 42, a binder, a conductive assistant, and the like optionally contained in a nonaqueous solvent to obtain a slurry-like electrode composition. The composition can be easily prepared by applying a composition to the surface of the positive electrode current collector 30, drying and pressing it optionally. However, it is not limited to such a wet method, and it is also possible to manufacture the positive electrode 200 by press molding dryly. Thus, when forming the sheet-like positive electrode mixture layer 40 on the surface of the positive electrode collector 30, it is preferable that the thickness of the positive electrode mixture layer 40 is 0.1 micrometer or more and 1 mm or less, for example, 1 It is more preferable that they are more than 100 micrometers.

2.2. Solid electrolyte layer 300

The solid electrolyte layer 300 insulates the negative electrode 100 and the positive electrode 200 and has a function of conducting lithium ions between the negative electrode 100 and the positive electrode 200. The solid electrolyte layer 300 includes at least a solid electrolyte 51. In addition, the solid electrolyte layer 300 preferably includes a binder.

2.2.1. Solid electrolyte

What is necessary is just to select the solid electrolyte 51 contained in the solid electrolyte layer 300 suitably from what was illustrated as solid electrolyte which can be contained in the said negative electrode mixture layer 20 and the positive electrode mixture layer 40. In particular, a sulfide solid electrolyte is preferable, and a sulfide solid electrolyte containing Li ₂ SP ₂ S ₅ is more preferable. Only 1 type may be used for the solid electrolyte 51, and 2 or more types may be mixed and used for it. The shape of the solid electrolyte 51 may be a general shape, that is, a particle shape. Content of the solid electrolyte 51 in the solid electrolyte layer 300 is not specifically limited, What is necessary is just to determine suitably according to the performance of the target battery. For example, it is preferable to make the whole solid electrolyte layer 300 whole 100 mass%, and to make content of a solid electrolyte 90 mass% or more. More preferably, it is 95 mass% or more.

2.2.2. bookbinder

The solid electrolyte layer 300 preferably contains a binder. Binders that may 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 included in the negative electrode mixture layer 20 and the positive electrode mixture layer 40 mentioned above.

The solid electrolyte layer 300 having the above structure is obtained by kneading a solid electrolyte 51 and a binder or the like optionally contained in a nonaqueous solvent to obtain a slurry-like electrolyte composition. And the surface of the negative electrode mixture layer 20 or the surface of the positive electrode mixture layer 40), and can be easily produced by going through a process of drying and pressing it optionally. However, it is not limited to such a wet method, It is also possible to manufacture the solid electrolyte layer 300 by press molding dryly. In this way, when the sheet-like solid electrolyte layer 300 is formed, the thickness of the solid electrolyte layer 300 is preferably, for example, 0.1 µm or more and 1 mm or less, and more preferably 1 µm or more and 100 µm or less. .

2.3. Other composition

In addition, in the sulfide solid battery 1000, not all of the constituent materials are necessarily solid. The sulfide solid battery 1000 may contain a liquid such as an electrolytic solution in a portion within a range that does not impair battery performance.

The sulfide solid battery 1000 having the above structure can be manufactured, for example, as follows. That is, the manufacturing method of the sulfide solid battery 1000 is the process of manufacturing the negative electrode 100, the positive electrode 200, and the solid electrolyte layer 300 by the said method, the negative electrode 100, the positive electrode 200, A step of stacking the solid electrolyte layer 300 is provided. In this manner, the negative electrode 100, the solid electrolyte layer 300, and the positive electrode 200 are laminated to form a laminate, and after the appropriate terminals and the like are attached, the sulfide solid battery 1000 is sealed by encapsulating the laminate in a battery case. ) Can be prepared.

EXAMPLE

1. Evaluation of Reactivity of Negative Electrode Current Collector Layer and Sulfide Solid Electrolyte

4, the sheathed layers (thickness 450㎛) comprising a sulfide solid electrolyte (which is mainly composed of Li ₂ SP ₂ S ₅₎ between the metal foil and the predetermined In-Li foil (thickness 80㎛), The metal foil and the In-Li foil were connected to a power source, and the reactivity of the metal foil and the sulfide solid electrolyte was evaluated by cyclic voltammetry (CV). The kind of metal foil used by the Example and the comparative example is as follows.

Comparative example 1. Copper (Cu) foil, 10 μm thick

Example 1. Copper- beryllium alloy (CuBe) foil, copper: beryllium = 88atm%: 12atm%, thickness 10㎛

Example 2 Copper-zinc alloy (CuZn) foil, copper: zinc = 65atm%: 35atm%, thickness 10㎛

Example 3. Copper-tin alloy (CuSn) foil (contains slightly phosphorus (P) as impurity), copper: tin = 96atm%: 3atm%, thickness 10㎛

Comparative example 2. Copper-silver alloy (CuAg) foil, copper: silver = 81atm%: 19atm%, thickness 50㎛

5-9 shows the CV result about each Example and a comparative example. 5 corresponds to Comparative Example 1, FIG. 6 shows Example 1, FIG. 7 shows Example 2, FIG. 8 shows Example 3 and FIG. In addition, in FIG. 5, the vertical axis | shaft is made 100 times compared with FIGS. 6-8. 5 to 9, it can be said that the greater the variation in current density (vertical axis), the higher the electrochemical reactivity with the sulfide solid electrolyte.

As is clear from the results shown in FIG. 5, for Comparative Example 1 using copper foil as the metal foil, it can be seen that the variation of the current density in CV is large and the electrochemical reactivity of the copper foil and the sulfide solid electrolyte is high. .

On the other hand, as is clear from the results shown in Figs. 6 to 8, for Examples 1 to 3 using alloy foil of copper and a metal (beryllium, zinc or tin) having a higher ionization tendency than copper, the current density in CV It can be seen that the variation of is small and the electrochemical reactivity of the alloy foil and the sulfide solid electrolyte is low (about a thousandth as compared with Comparative Example 1). In particular, in Example 2 using the alloy foil of copper and zinc, it turns out that the electrochemical reactivity of alloy foil and a sulfide solid electrolyte becomes smaller.

In addition, 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 is difficult to proceed. That is, the 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 may be considered to be difficult to proceed to the deep portion of the alloy foil. That is, regardless of the thickness of the foil, it may be considered that a sufficient effect can be secured by configuring the surface of the foil in contact with at least the sulfide solid electrolyte with a material containing a predetermined alloy.

In addition, as is clear from the results shown in FIG. 9, in Comparative Example 2 using alloy foil of copper and metal (silver) having a lower ionization tendency than copper, alloy foil and sulfide solids were different from Examples 1 to 3. It can be seen that the reaction of the electrolyte cannot be suppressed.

In Examples 1 to 3, beryllium, zinc, and tin were shown as examples of metals having a higher ionization tendency than copper, but the technique of the present disclosure uses metals other than these as metals having a higher ionization tendency than copper. In this case, it can be considered that the same effect is exerted. 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 the said Examples 1-3, the copper alloy which has a predetermined composition was shown, but in the technique of this indication, the composition of a copper alloy is not specifically limited. In addition to the reactivity with the sulfide solid electrolyte, the alloy composition may be appropriately determined in accordance with the intended battery performance while taking into consideration the conductivity as the negative electrode current collector layer.

2. Study on the mechanical strength of the negative electrode current collector layer

2.1. The tensile strength

To a container made of PP, butyl butyrate, a 5 wt% butyl butyrate solution of a PVdF-based binder (manufactured by Kureha), silicon (manufactured by High Purity Chemical Co., Ltd., average particle size (D ₅₀ ): 5 µm), and a sulfide solid electrolyte were added as a negative electrode active material. And it stirred for 30 second with the ultrasonic dispersion apparatus (UH-50 made from SMT). Next, the vessel was shaken for 30 minutes with a shaker (TTM-1, manufactured by Shibata Science Co., Ltd.), and further stirred for 30 seconds with an ultrasonic dispersion device. Furthermore, it stirred for 3 minutes on the shaker, and obtained the 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 dried for 30 minutes on a 100 degreeC hotplate, and the negative electrode mixture layer was formed on the surface of metal foil. Thereafter, the solid electrolyte layer and the positive electrode mixture layer formed by coating are stacked on the negative electrode mixture layer by transfer, and then the filling rate of the electrode body (negative electrode mixture layer + solid electrolyte layer + positive electrode mixture layer) produced by transfer is improved. The roll press was performed at the maximum linear pressure (linear pressure 5t / cm), and the feed rate of 0.5 m / min in order to derive the characteristic of a battery.

When the presence or absence of fracture of the metal foil after the roll press was confirmed, when a metal foil having a tensile strength of 500 MPa or more measured according to JIS Z 2241: 2011 was used, the negative electrode could be produced without breaking the metal foil regardless of the composition of the metal foil. Could know.

About the various copper alloy foil and copper foil shown below, the tensile test was done based on JISZ22241: 2011, and the tensile strength was measured. The results are shown in FIG.

Comparative example 1A. Rolled Copper (Cu) Foil, Thickness 10㎛

Comparative example 1B. High-strength copper (Cu) foil (SEED manufactured by Nippon Electric Industries, Ltd.), approximately 10 μm thick, grain refinement treatment oil for the purpose of improving the strength of metal

Example 1A. Copper- beryllium alloy (CuBe) foil, copper: beryllium = 88atm%: 12atm%, thickness 10㎛, work hardening treatment oil, annealing after work hardening treatment

Example 1B. Copper- beryllium alloy (CuBe) foil, copper: beryllium = 88atm%: 12atm%, thickness 10㎛, work hardening treatment oil, annealing oil after work hardening treatment

Example 2A. Copper-zinc alloy (CuZn) foil, copper: zinc = 65atm%: 35atm%, thickness 10㎛, work hardening treatment oil, annealing after work hardening treatment

Example 2B. Copper-zinc alloy (CuZn) foil, copper: zinc = 65atm%: 35atm%, thickness 10 micrometers, work hardening treatment oil, annealing oil after work hardening treatment

Example 3A. Copper-tin alloy (CuSn) foil (contains slightly phosphorus (P) as impurity), copper: tin = 96atm%: 3atm%, thickness 10 μm, work hardening treatment oil, no annealing after work hardening treatment

Example 3B. Copper-tin alloy (CuSn) foil (slightly contains phosphorus (P) as impurity), copper: tin = 96atm%: 3atm%, thickness 10 μm, work hardening treatment oil, annealing oil after work hardening treatment

As shown in FIG. 10, even if it was the metal foil which has the same thickness with the same composition, the tensile strength of metal foil can change with the presence or absence of the work hardening process, or the presence or absence of heat processing (annealing). As shown in FIG. 10, it turned out that the copper alloy foil which concerns on Examples 1-3 is a material with which tensile strength can greatly exceed 500 Mpa, and can fully endure the roll press at the time of manufacturing a negative electrode. In other words, it can be said that the alloy constituting the negative electrode current collector layer preferably contains at least one selected from copper, zinc, beryllium, and tin.

2.2. Breaking elongation

The maximum linear pressure at which the negative electrode mixture layer is formed on the surface of the metal foil in the same procedure as in the evaluation of the tensile strength, and thereafter, the filling rate of the negative electrode mixture layer can be improved while maintaining the properties of the material of the negative electrode mixture layer ( 5 t / cm) and roll press at a feed rate of 0.5 m / min.

When the presence or absence of fracture of the metal foil after roll press was confirmed, when the metal foil whose breaking elongation measured based on JIS Z 2241: 2011 was 7.95% or more was used, the tensile strength of the said metal foil was 500 MPa regardless of the composition of the said metal foil. Even if it was less, it turned out that the negative electrode can be manufactured, without breaking the said metal foil, even if it carries out a roll press of linear pressure 5t / cm and a feed rate of 0.5m / min.

Breaking elongation was measured based on JIS Z 2241: 2011 about the copper alloy foil similar to Example 1B and Example 3B mentioned above, and the copper foil similar to Comparative Example 1A and Comparative Example 1B. The results are shown in FIG. 10 and 11, although the copper alloy foil which concerns on Example 1B and Example 3B has a tensile strength of less than 500 Mpa, the elongation at break greatly exceeds 7.95%, and is used for the roll press at the time of manufacturing a negative electrode. It can be seen that it can withstand enough.

As described above, in order to suppress the breakage of the negative electrode current collector layer during roll press at the time of negative electrode production, it was found that the negative electrode current collector layer preferably satisfies at least one of the following requirements (1) and (2). .

(1) The tensile strength of the negative electrode current collector layer is 500 MPa or more

(2) The elongation at break of the negative electrode current collector layer is 7.95% or more

[Industry availability]

The sulfide solid-state battery provided with the negative electrode of the present disclosure can be suitably used from a small power supply such as a portable device to a large power supply such as a vehicle.

100: negative electrode
10: negative electrode current collector layer
20: negative electrode mixture layer
200: positive electrode
30: positive electrode current collector layer
40: positive electrode mixture layer
300: solid electrolyte layer
1000: Sulfide Solid Battery

Claims (7)

And a negative electrode current collector layer in contact with the negative electrode mixture layer and the negative electrode mixture layer,
The negative electrode mixture layer contains a negative electrode active material and a sulfide solid electrolyte,
The surface of the said negative electrode electrical power collector layer which contacts at least the said negative electrode mixture layer is comprised by the material containing the alloy of copper and metal with a higher ionization tendency than copper. The method of claim 1,
And the alloy includes copper and at least one selected from zinc, beryllium and tin. The method according to claim 1 or 2,
A negative electrode, wherein the alloy comprises copper and zinc. The method according to any one of claims 1 to 3,
A negative electrode, wherein the negative electrode active material contains a silicon-based active material. The method according to any one of claims 1 to 4,
The negative electrode whose tensile strength of the said negative electrode electrical power collector layer is 500 Mpa or more. The method according to any one of claims 1 to 4,
The negative electrode of which the elongation at break of the said negative electrode collector layer is 7.95% or more. The sulfide solid battery provided with the negative electrode as described in any one of Claims 1-6, a positive electrode, and the solid electrolyte layer provided between the said negative electrode and the said positive electrode.

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