TW202406196A - Solid electrolyte sheet, method for manufacturing same, and solid-state battery equipped with same - Google Patents

Abstract

A solid electrolyte sheet (10) has a first solid electrolyte layer (11), and a second solid electrolyte layer (12) disposed adjacent to the first solid electrolyte layer (11). The first solid electrolyte layer (11) includes a solid electrolyte containing a crystal phase having an argyrodite crystal structure. The second solid electrolyte layer (12) includes a solid electrolyte containing a lithium (Li) element, an A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn), and antimony (Sb)), a phosphor (P) element, a sulfur (S) element, and a halogen (X) element.

Description

Solid electrolyte sheet, manufacturing method thereof and solid battery having the same

The invention relates to a solid electrolyte sheet and a manufacturing method thereof. Furthermore, the present invention relates to a solid battery including a solid electrolyte sheet.

Since solid-state batteries do not use flammable organic solvents, they can simplify safety devices and have excellent manufacturing costs and productivity. They are also characterized by being stacked in series within cells to achieve higher voltages. In solid electrolytes used in solid batteries, since lithium ions do not move except for them, it is expected that safety and durability will be improved, for example, side reactions caused by the movement of anions will not occur.

There are cases where solid electrolyte sheets are used in the manufacture of solid batteries. For example, Patent Document 1 describes a method of manufacturing a solid electrolyte sheet provided with a porous base material and assembling the solid electrolyte sheet into a solid battery. Prior technical literature patent documents

Patent Document 1: Japanese Patent Application Publication No. 2018-129307

The solid electrolyte sheet described in Patent Document 1 is produced by forming an adhesive layer on one side of a porous base material such as nonwoven fabric, and attaching powder of the solid electrolyte thereon to form a molded body, and then subjecting the molded body to Pressure is applied to produce the above-mentioned solid electrolyte sheet. Therefore, in this method, only a solid electrolyte sheet including a single type of solid electrolyte is obtained, or only a solid electrolyte sheet including a mixture of two or more solid electrolytes is obtained. However, recently, requirements for the performance of solid-state batteries have become increasingly stringent, and solid electrolyte sheets are required to further improve their performance. However, there is a limit to improving the performance of the solid electrolyte sheet described in Patent Document 1.

Therefore, an object of the present invention is to provide a solid electrolyte sheet with improved performance compared with the previous one.

The present invention provides a solid electrolyte sheet having a first solid electrolyte layer and a second solid electrolyte layer arranged adjacent to the first solid electrolyte layer, The first solid electrolyte layer includes a solid electrolyte including a crystal phase having a pyrogermanite crystal structure, The second solid electrolyte layer includes lithium (Li) element, A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P) Solid electrolyte of element, sulfur (S) element and halogen (X) element.

Furthermore, the present invention provides a solid battery including the above-described solid electrolyte sheet, a negative electrode layer disposed on the first solid electrolyte layer side of the solid electrolyte sheet, and a negative electrode layer disposed on the second solid electrolyte layer side of the solid electrolyte sheet. positive electrode layer, The above-mentioned negative electrode layer contains metallic lithium, or metallic lithium can be precipitated through charging and discharging of the above-mentioned solid battery.

Furthermore, the present invention provides a method for manufacturing a solid electrolyte sheet, which includes the following steps: A first member having a first carrier sheet and a first coating film containing a first solid electrolyte formed on the carrier sheet, and a second carrier sheet and a first coating film containing a second solid electrolyte formed on the carrier sheet are prepared. 2. The second component of the coating film; The first member and the second member are overlapped so that the first coating film and the second coating film face each other and a porous base material sheet is interposed between the two coating films to produce a laminate; Press the above-mentioned laminated body in its thickness direction; and Peel and remove the first carrier sheet and the second carrier sheet from the above-mentioned laminate; and The first solid electrolyte layer includes a sulfide solid electrolyte including a crystal phase having a sulfide-germanite crystal structure, The second solid electrolyte layer includes lithium (Li) element, A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P) Solid electrolyte of element, sulfur (S) element and halogen (X) element.

Hereinafter, the present invention will be described based on preferred embodiments of the present invention. The invention relates to a solid electrolyte sheet. As shown in FIG. 1 , the solid electrolyte sheet 10 includes at least a first solid electrolyte layer 11 and a second solid electrolyte layer 12 . The first solid electrolyte layer and the second solid electrolyte layer are distinguished by the type of solid electrolyte contained therein. The solid electrolyte sheet 10 may or may not have other components between the first solid electrolyte layer 11 and the second solid electrolyte layer 12 . That is, as shown in FIG. 1 , the first solid electrolyte layer 11 and the second solid electrolyte layer 12 may be directly connected and laminated, or the first solid electrolyte layer 11 and the second solid electrolyte layer 12 may be laminated via other members. Preferably, the solid electrolyte sheet 10 has self-supporting properties even if the solid electrolyte sheet 10 is in any form. The fact that the solid electrolyte sheet 10 is self-supporting means that it can maintain its form as a solid electrolyte layer. From this point of view, in the manufacturing process of a battery using the solid electrolyte sheet 10 , it is preferable that the solid electrolyte sheet 10 has such strength that wrinkles or wrinkles are not generated. Furthermore, in FIG. 1 , symbol 20 represents the negative electrode layer, and symbol 21 represents the positive electrode layer. In addition, each member in Figure 1 is shown schematically, and its thickness does not represent the actual thickness. The same applies to FIGS. 2 to 4 shown below.

[1] First solid electrolyte layer The first solid electrolyte layer is used to conduct lithium ions between the positive electrode layer and the negative electrode layer. For this purpose, the first solid electrolyte layer contains a solid electrolyte including a crystal phase having a pyrogermanite crystal structure (hereinafter, this solid electrolyte is also referred to as the “first solid electrolyte”). The so-called argyrogermanite crystal structure refers to the crystal structure of the compound group derived from the mineral represented by the chemical formula: Ag ₈ GeS ₆ . Whether or not the first solid electrolyte has a crystal phase having a pyrogermanite crystal structure can be confirmed by measurement using X-ray diffraction (hereinafter also referred to as “XRD”). For example, in the diffraction pattern measured by XRD using the CuKα1 line, the crystal phases of the argyrogermanite type crystal structure are at the positions of 2θ=25.5°±1.0°, 30.0°±1.0°, and 30.9°±1.0°. Represents the characteristic diffraction peak. Furthermore, depending on the element species constituting the first solid electrolyte, in addition to the above-mentioned diffraction peaks, there may be cases where 2θ=15.3°±1.0°, 18.0°±1.0°, 44.3°±1.0°, and 47.2°±1.0 °, 51.7°±1.0°, 58.3°±1.0°, 60.7°±1.0°, 61.5°±1.0°, 70.4°±1.0° and 72.6°±1.0° show characteristic diffraction peaks. The identification of the diffraction peak from the argyrogermanite type crystal structure uses, for example, the information in PDF No. 00-034-0688.

From the viewpoint of further improving the performance of the battery including the solid electrolyte sheet of the present invention, the first solid electrolyte preferably contains at least lithium (Li) element, phosphorus (P) element and sulfur (S) element, and more preferably It contains at least lithium (Li) element, phosphorus (P) element, sulfur (S) element and halogen (X) element. In this case, from the viewpoint of improving the lithium ion conductivity, it is preferable that the first solid electrolyte is composed of the composition formula (I): Li _a PS _b X _c (X is a fluorine (F) element, a chlorine (Cl) element , bromine (Br) element, iodine (I) element at least one) represents.

In the composition formula (I), a representing the molar ratio of the Li element is preferably, for example, 3.0 or more, particularly preferably 4.0 or more, and particularly preferably 5.0 or more. On the other hand, the above-mentioned a is, for example, preferably 6.5 or less, particularly preferably 5.9 or less, and particularly preferably 5.6 or less. With a in this range, the cubic system sulfide germanium crystal structure near room temperature (25°C) is more stable, thereby allowing lithium ion pores to be fully introduced into the structure, and as a result, lithium can be effectively increased. Ionic conductivity.

In the composition formula (I), b is, for example, preferably 3.5 or more, particularly preferably 4.0 or more, and particularly preferably 4.2 or more. On the other hand, the above-mentioned b is, for example, preferably 5.5 or less, particularly preferably 4.9 or less, and particularly preferably 4.7 or less. When b is within the above range, the argyrogermanite crystal structure near room temperature (25° C.) is further stabilized, and the lithium ion conductivity is effectively increased.

In the composition formula (I), c is, for example, preferably 0.1 or more, particularly preferably 1.1 or more, and particularly preferably 1.4 or more. On the other hand, the above c is preferably, for example, 2.5 or less, particularly preferably 2.0 or less, and particularly preferably 1.8 or less.

Furthermore, the first solid electrolyte may be represented by the composition formula (II): Li _7-d PS _6-d X _d . The composition represented by the composition formula (II) is the stoichiometric composition of the argyrogermanite crystal phase. In the composition formula (II), X is synonymous with the composition formula (I).

In the composition formula (II), d is, for example, preferably 0.4 or more, particularly preferably 0.8 or more, and particularly preferably 1.2 or more. On the other hand, the above d is preferably, for example, 2.2 or less, particularly preferably 2.0 or less, and particularly preferably 1.8 or less.

Furthermore, the first solid electrolyte may be represented by the composition formula (III): Li _7-d-2e PS _6-de X _d . The pyrogermanite-type crystal phase having the composition represented by the composition formula (III) is produced, for example, by the reaction of the pyrogermanite-type crystal phase having the composition represented by the composition formula (II) and P ₂ S ₅ (phosphorus pentasulfide). generate.

In the composition formula (III), e is a value representing the deviation of the Li ₂ S component from the stoichiometric composition represented by the composition formula (II). For example, e is preferably -0.9 or more, particularly preferably -0.6 or more, and particularly preferably -0.3 or more. On the other hand, the above e is preferably, for example, (-d+2) or less, particularly preferably (-d+1.6) or less, particularly preferably (-d+1.0) or less.

In the first solid electrolyte, the atomic number ratio X/P of the On the other hand, the atomic number ratio X/P is, for example, preferably 2.5 or less, more preferably 2.3 or less, still more preferably 2.2 or less. When the atomic number ratio X/P is within the above range, the lithium ion conductivity is further improved. The atomic number ratio X/P can be measured, for example, by high-frequency inductively coupled plasma emission spectrometry (ICP emission spectrometry) or SEM-EDS analysis.

In particular, when the X element contains at least a Cl element and a Br element, the atomic number ratio of the total of the Cl element and the Br element to the P element (Cl+Br)/P is preferably greater than 1.0, and more preferably 1.1 or more, and further It is preferably 1.2 or more, and further preferably 1.4 or more. On the other hand, the atomic number ratio (Cl+Br)/P is, for example, preferably 2.5 or less, more preferably 2.3 or less, still more preferably 2.0 or less. It is preferable that the atomic number ratio (Cl+Br)/P is within the above range because the lithium ion conductivity can be further improved. The atomic number ratio (Cl+Br)/P can be measured, for example, by elemental analysis using high-frequency inductively coupled plasma emission spectrometry (ICP emission spectrometry) or a scanning electron microscope equipped with EDS (SEM-EDS).

The first solid electrolyte is preferably one of the above composition formulas (I) to (III), especially one represented by the composition formula (IV) Li _7-d PS _6-d Cl _d1 Br _d2 . In the above composition formula (IV), the total molar ratio d (=d1+d2) of Cl and Br is preferably greater than 1.0, for example, more preferably 1.2 or more, and particularly preferably 1.4 or more. On the other hand, the total molar ratio d is, for example, preferably less than 2.5, particularly preferably less than 2.0, particularly preferably 1.8 or less, and still more preferably 1.7 or less. When the total molar ratio d is within the above range, the generation of heterogeneous phases can be sufficiently controlled, and the decrease in ion conductivity can be effectively suppressed.

In the above composition formula, the ratio of the molar ratio of Br to the molar ratio of Cl (d2/d1) is preferably, for example, 0.1, particularly preferably 0.3 or more, and particularly preferably 0.5 or more. On the other hand, the molar ratio is preferably, for example, 10 or less, particularly preferably 5 or less, and particularly preferably 3 or less. When the molar ratio is within the above range, the lithium ion conductivity can be further improved.

In the above composition formula, d1 representing the molar ratio of Cl is, for example, preferably 0.3 or more, particularly preferably 0.4 or more, and particularly preferably 0.6 or more. On the other hand, the above-mentioned d1 is, for example, preferably 1.5 or less, particularly preferably 1.2 or less, and particularly preferably 1.0 or less. When d1 is equal to or higher than the above lower limit value, the lithium ion conductivity can be further improved. On the other hand, when d1 is equal to or less than the above upper limit, the first solid electrolyte can be easily obtained.

In the above composition formula, d2 representing the molar ratio of Br is, for example, preferably 0.3 or more, particularly preferably 0.4 or more, and particularly preferably 0.6 or more. On the other hand, the above-mentioned d2 is, for example, preferably 1.5 or less, particularly preferably 1.2 or less, and particularly preferably 1.0 or less. When d2 is equal to or higher than the above-mentioned lower limit, the first solid electrolyte can be easily obtained. On the other hand, when d2 is equal to or less than the above upper limit, the lithium ion conductivity can be further improved.

When the first solid electrolyte is any one of the above composition formulas (I), (II), (III) and (IV), if the X element contains the Br element, the lithium ion conductivity is further improved, Therefore it is better.

From the viewpoint of maintaining the lithium ion conductivity of the first solid electrolyte, it is preferable that the first solid electrolyte does not contain the following A element as much as possible. From this point of view, in the first solid electrolyte, the atomic number ratio of the A element to the P element is preferably 0.5 or less, more preferably 0.2 or less, and still more preferably 0.1 or less. Most preferably, the atomic ratio of the A element to the P element is 0, that is, the first solid electrolyte does not contain the A element. The meaning of “not containing element A” does not include the intentional inclusion of element A in the first solid electrolyte. Therefore, when the first solid electrolyte inevitably contains a trace amount of element A, it is considered to be “not containing element A”.

[2] Second solid electrolyte layer The second solid electrolyte layer contains a solid electrolyte containing Li element, A element, P element, S element, and X element (hereinafter, this solid electrolyte is also referred to as “second solid electrolyte”). A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb). The A elements may be used individually, or two or more types may be used in combination.

The second solid electrolyte layer is used to suppress the growth of dendritic crystals of metallic lithium during charging of the secondary battery provided with the solid electrolyte sheet of the present invention. From this point of view, it is preferable that the second solid electrolyte contained in the second solid electrolyte layer has reactivity with lithium in addition to lithium ion conductivity. Since the second solid electrolyte has such properties, as shown in FIG. 2 , the lithium dendrites 30 and the second solid grow from the self-electrode layer 20 through the first solid electrolyte layer 11 to the second solid electrolyte layer 12 The second solid electrolyte contained in the electrolyte layer 12 reacts to generate a high-resistance material 31, thereby preventing excessive growth of the dendrite 30. As a result, the battery provided with the solid electrolyte sheet of the present invention has excellent cycle characteristics.

In contrast, as shown in FIG. 3 , when only the second solid electrolyte layer 12 is used without providing the first solid electrolyte layer, a high-resistance substance 31 is generated between the negative electrode layer 20 and the second solid electrolyte layer 12 . , which becomes an obstacle to the conduction of lithium ions, so the battery does not work.

From the viewpoint of suppressing the growth of dendritic crystals of metallic lithium, the atomic number ratio of the A element to the P element in the second solid electrolyte system is preferably 0.3 or more, particularly preferably 0.6 or more, and particularly preferably 0.9 or more. On the other hand, the above-mentioned atomic number ratio is preferably 1.9 or less, particularly preferably 1.7 or less, and particularly preferably 1.5 or less.

Since the second solid electrolyte contains sulfur element, it is a sulfide. That is, the second solid electrolyte is a sulfide solid electrolyte (the first solid electrolyte is also a sulfide solid electrolyte). Examples of the sulfide solid electrolyte include the following. ・Contains sulfides of Li, Si, P, S and halogen. ・Contains sulfides of Li, Sn, P, S and halogens. ・Contains sulfides of Li, Sb, P, S and halogens. ・Contains sulfides of Li, Ge, P, S and halogens.

Examples of sulfides containing Li, Si, P, S and halogen include those represented by the composition formula Li _10+a A _1+b P _2+c S _12+d X _e (where -0.5<a<0.5,-1.0<b<1.0,-1.0<c<1.0,-1.5<d≦0,0≦e<0.5, a+4×b+5×c-2×d-e=0). Specific examples thereof include Li _9.54 Si _1.335 P _1.44 S _10.89 Cl _0.30 and the like.

Furthermore, whether the second solid electrolyte has a crystal phase of a pyrogermanite crystal structure is not critical in the present invention. The second solid electrolyte may have a crystal phase of a pyrogermanite crystal structure, or may not have a sulfide germanium crystal structure. The crystal phase of germanium mineral crystal structure. In addition, it is not critical in the present invention whether the second solid electrolyte is crystalline or amorphous.

[3] Third solid electrolyte layer As shown in FIG. 4 , the solid electrolyte sheet 10 may include a third solid electrolyte layer 13 in addition to the first solid electrolyte layer 11 and the second solid electrolyte layer 12 described above. Specifically, the third solid electrolyte layer 13 may be disposed on the surface of the second solid electrolyte layer 12 opposite to the surface facing the first solid electrolyte layer 11 . The third solid electrolyte layer 13 is disposed to improve the performance of the solid electrolyte sheet 10 , especially to improve the contact strength with the positive electrode layer 21 . From this point of view, it is preferable that the third solid electrolyte layer 13 contains the first solid electrolyte similarly to the first solid electrolyte layer 11 .

〔4〕Solid electrolyte sheet

The thickness of the first solid electrolyte layer constituting the solid electrolyte sheet of the present invention is, for example, preferably 0.1 μm or more, particularly preferably 1 μm or more, and particularly preferably 3 μm or more. On the other hand, the thickness of the first solid electrolyte layer is, for example, preferably 500 μm or less, particularly preferably 300 μm or less, and particularly preferably 100 μm or less.

The thickness of the second solid electrolyte layer constituting the solid electrolyte sheet of the present invention can be made the same as the thickness of the above-mentioned first solid electrolyte layer, so the description here is omitted.

When the solid electrolyte sheet of the present invention has the third solid electrolyte layer 13 as shown in FIG. 4 , its thickness can be made the same as the thickness of the above-mentioned first solid electrolyte layer, so the description here is omitted.

The thickness of each solid electrolyte layer constituting the solid electrolyte sheet is measured by observing the cross section of the solid electrolyte sheet under a microscope.

From the viewpoint of further improving the self-supporting property of the solid electrolyte sheet, it is preferable that the solid electrolyte sheet has a porous base material sheet in addition to each of the solid electrolyte layers described so far. In the present invention, for example, a first solid electrolyte layer, a porous base material sheet, and a second solid electrolyte layer can be stacked in this order to obtain a solid electrolyte sheet. When the solid electrolyte sheet also has a third solid electrolyte layer, in addition to disposing the porous base material sheet between the first solid electrolyte layer and the second solid electrolyte layer, the second solid electrolyte layer and the third solid electrolyte layer may also be disposed between the porous base material sheet and the third solid electrolyte layer. A porous base material sheet is arranged between the electrolyte layers. In this case, the two porous base material sheets may be of the same type, or may be of different types.

The so-called "porous" in the porous base material sheet refers to the state of having a large number of pores. The porous base material sheet only needs to have pores filled and contacted by the first solid electrolyte layer and the second solid electrolyte layer when forming the solid electrolyte sheet, and may also be composed of a plurality of fibrous materials. Preferably, the porous base material sheet has pores extending from one surface to the other surface of the porous base material sheet. The size of the pores may be such that at least part of the particles of the first solid electrolyte or the particles of the second solid electrolyte can be filled when the solid electrolyte sheet is formed. The pores in the porous base material sheet may be any of micropores, mesopores, and macropores, for example. The pores can also be interconnected.

In particular, since sufficient self-supporting properties and moderate flexibility can be imparted to the solid electrolyte sheet, the porous base material sheet is preferably a fiber sheet. Examples of the fiber sheet include nonwoven fabrics, woven fabrics, and knitted fabrics, and nonwoven fabrics are particularly preferred. When the porous base material sheet is a fiber sheet, "porous" refers to a state having voids formed in the gaps between fibers.

There are various types of nonwoven fabrics depending on the type of fiber used to make the nonwoven fabric (fiber length, fiber diameter, fiber material, etc.), the type of manufacturing method (for example, the method of forming the fabric, the method of combining the fibers of the fabric, etc.). The nonwoven fabric used as the porous base sheet is not particularly limited as long as a desired solid electrolyte sheet can be obtained. Examples of nonwoven fabrics include orthogonal fiber nonwoven fabrics, long fiber nonwoven fabrics, short fiber nonwoven fabrics, wet nonwoven fabrics, dry nonwoven fabrics, air-laid nonwoven fabrics, carded nonwoven fabrics, parallel nonwoven fabrics, cross nonwoven fabrics, random nonwoven fabrics, and spunbonded fabrics. Nonwoven fabrics, melt blown nonwoven fabrics, flash spun nonwoven fabrics, chemically bonded nonwoven fabrics, spunlace nonwoven fabrics, needle punched nonwoven fabrics, stitch bonded nonwoven fabrics, thermal bonded nonwoven fabrics, exploded fiber nonwoven fabrics, tow tow nonwoven fabrics, separated fiber nonwoven fabrics, composite nonwoven fabrics, Laminated non-woven fabrics, coated non-woven fabrics, laminated non-woven fabrics, etc. Among them, cross-type nonwoven fabric is preferred. Cross-type nonwoven fabrics are better in that the strength ratio in the length direction X and width direction Y, weight per unit area, etc. can be easily adjusted. Preferably, the strength ratio in the length direction X and width direction Y of the cross-type nonwoven fabric is uniformly adjusted. The weight per unit area of cross-type nonwoven fabrics can be low or high. Examples of cross-type nonwoven fabrics include polyolefin mesh fabrics (see Japanese Patent Application Laid-Open No. 2007-259734). In addition, the specific basis weight of the nonwoven fabric can be the same as that described in Japanese Patent Application Laid-Open No. 2018-129307, for example, so the description here is omitted.

The material, porosity, air permeability, thickness, etc. constituting the porous base sheet can be the same as those used for a general solid electrolyte sheet. For example, it can be the same as the porous base material sheet described in Japanese Patent Application Laid-Open No. 2018-129307, so the description here is omitted.

Regardless of whether the third solid electrolyte layer or the porous base material sheet is used additionally, the solid electrolyte sheet having the first solid electrolyte layer and the second solid electrolyte layer preferably has a predetermined thickness. Specifically, the thickness of the solid electrolyte sheet of the present invention is, for example, preferably 0.2 μm or more, particularly preferably 5 μm or more, and particularly preferably 10 μm or more. On the other hand, the thickness of the solid electrolyte sheet is preferably, for example, 1000 μm or less, particularly preferably 500 μm or less, and particularly preferably 110 μm or less. By having the thickness of the solid electrolyte sheet having the above lower limit, the function of insulating electron conduction between the positive electrode and the negative electrode can be fully exerted. On the other hand, by having the thickness of the solid electrolyte sheet having the above upper limit, the resistance of ion conduction of the solid electrolyte sheet can be sufficiently reduced. Furthermore, the thickness of the solid electrolyte sheet is measured using cross-sectional observation or a thickness gauge.

[5] Manufacturing method of solid electrolyte sheet Next, a preferred manufacturing method of the solid electrolyte sheet will be described, taking the solid electrolyte sheet 10 shown in FIG. 1 as an example. This manufacturing method is roughly divided into the following steps. (1) Steps to prepare the first component and the second component. (2) A step of manufacturing a laminated body using the first member and the second member. (3) The step of pressurizing the laminated body. (4) The step of peeling and removing the carrier sheet from the laminate. Each step is explained below.

(1) Steps to prepare the first component and the second component In this step, a first member having a first carrier sheet and a first coating film containing a first solid electrolyte formed on the carrier sheet is prepared. Furthermore, in this step, a second member having a second carrier sheet and a second coating film containing a second solid electrolyte formed on the carrier sheet is prepared. It is preferable that the first carrier sheet and the second carrier sheet have strength to support the first coating film and the second coating film and have flexibility.

The thickness of the first carrier sheet and the second carrier sheet can be appropriately selected according to the materials constituting the carrier sheets. It is preferable that the thickness of the carrier sheets is self-supporting. Furthermore, by adjusting the thickness of the carrier sheet, it can also be made into a flexible carrier sheet. The thickness of each carrier sheet is not particularly limited. For example, it may be independently 5 μm or more, 10 μm or more, or 15 μm or more. On the other hand, the thickness of each carrier sheet may be, for example, 1000 μm or less, 200 μm or less, especially 100 μm or less.

Preferably, the material constituting each carrier sheet is independently, for example, at least one of resin, glass and metal. That is, each carrier sheet is preferably at least one of carrier resin, carrier glass, and carrier metal foil. Each carrier sheet may have a multilayer structure in which two or more types of carrier resin, carrier glass, and carrier metal foil are laminated, for example.

Examples of materials contained in the carrier resin include acrylic resin, polyester resin, cellulose derivative resin, polyvinyl acetal resin, polyvinyl butyral resin, vinyl chloride-vinyl acetate copolymer, chlorine Resins such as polyolefins and copolymers of these resin groups. As the carrier glass, for example, glass cloth, which is a fabric of glass fiber, can be used. Examples of materials constituting the carrier metal foil include alloys of copper, stainless steel, aluminum, nickel, silver, gold, chromium, cobalt, tin, zinc, brass, and the like.

The first carrier sheet and the first coating film are directly connected, and there may be no other layer between the two, or there may be one or more other layers between the two. In either case, it is preferable that the first carrier sheet and the first coating film are releasably laminated. The same applies to the second carrier sheet and the second coating film. The term "the carrier sheet and the coating film are laminated so as to be peelable" means that they can be peeled off without destroying their respective structures. The peel strength between the carrier sheet and the coating film is, for example, preferably 10 N/10 mm or less, particularly preferably 7 N/10 mm or less, and particularly preferably 4 N/10 mm or less. This is because when the peeling strength is within the above range, the carrier sheet and the coating film can be peeled off satisfactorily. As a method of measuring the peel strength, for example, the following method can be mentioned: A laminate in which the target layer is laminated is cut into a short strip shape of 10 mm wide, and an interlayer peel test (180-degree peeling test) is performed using a tensile and compression testing machine. , test speed 50 mm/min).

When the carrier sheet and the coating film are laminated so as to be releasable, peeling processing may be performed on the side facing the coating film among the two main surfaces of the carrier sheet. Examples of the peeling treatment include surface smoothing, application of a resin release agent, and the like.

The coating film formed on the carrier sheet contains the first solid electrolyte or the second solid electrolyte and a solvent. Examples of the solvents include, for example, non-polar solvents such as heptane, methylcyclohexane and toluene, aprotic polar solvents such as methyl isobutyl ketone and cyclohexanone, or mixtures thereof.

Both the first solid electrolyte and the second solid electrolyte contained in the coating film have the form of particles. The size of the particles is represented by the volume cumulative particle diameter D ₅₀ in the cumulative volume 50% by laser diffraction scattering particle size distribution measurement method. For example, it is preferably 1 μm or more, more preferably 2 μm or more, and still more preferably 3 μm or more. On the other hand, the above-mentioned D ₅₀ is, for example, preferably 100 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less.

Examples of a method for mixing the first solid electrolyte or the second solid electrolyte and the solvent include an ultrasonic homogenizer, an oscillator, a thin film rotary mixer, a dispersing mixer, a homogenizing mixer, a kneader, a roller mill, and a sand mill. Machine, grinder, ball mill, pulverizer, high-speed impeller grinder, etc.

After mixing the first solid electrolyte or the second solid electrolyte and the solvent in this way, the slurry obtained by mixing is applied to one surface of the first carrier sheet or the second carrier sheet. Examples of the coating method include a doctor blade method, a die coating method, a gravure coating method, a spray coating method, an electrostatic coating method, a rod coating method, and the like. The first coating film and the second coating film are formed by applying the slurry on one side of the carrier sheet.

From the viewpoint of the coating properties of the slurry, the solid content concentration of each coating film thus obtained is preferably, for example, 40 mass % or more, more preferably 50 mass % or more, and still more preferably 60 mass %. %above. On the other hand, the solid content concentration is preferably, for example, 90 mass% or less, and further preferably 80 mass% or less.

After each coating film is formed, the liquid component may be appropriately removed. Examples of methods for removing liquid components include warm air drying, hot air drying, infrared drying, reduced pressure drying, and induction heating drying. In this way, the first member having the first carrier sheet and the first coating film including the first solid electrolyte formed on the carrier sheet is prepared, and the first member having the second carrier sheet and the second coating film including the second solid electrolyte formed on the carrier sheet is prepared. The second member of the second coating film of the solid electrolyte.

(2) Steps for manufacturing a laminated body using the first member and the second member The first member and the second member prepared in step (1) are overlapped so that the first coating film and the second coating film face each other and a porous base material sheet is interposed between the two coating films. Thereby, a laminated body in which the first carrier sheet, the first coating film, the porous base material sheet, the second coating film, and the second carrier sheet are laminated in this order is obtained. By including an appropriate amount of solvent in the first coating film and the second coating film, part of the first coating film and the second coating film are filled into the pores of the porous base material sheet. This filling is confirmed in the pressurization step which is the next step. (3) Steps to pressurize the laminated body The step of pressurizing the laminated body is performed as described above in order to reliably fill the first coating film and the second coating film into the pores of the porous base material sheet. For this purpose, the laminate can be pressed at least in the thickness direction. For example, a uniaxial press can be used to pressurize the laminated body in the thickness direction. Alternatively, CIP (cold isostatic pressing) can be used to isotropically pressurize the entire laminated body.

The pressure applied in this step is preferably to the extent that the first solid electrolyte and the second solid electrolyte are filled into the pores of the porous base material sheet. Moreover, it is preferable that the pressure applied in this step is sufficient to peel the first carrier sheet and the second carrier sheet from the laminated body.

(4) Steps of peeling and removing the carrier sheet from the laminate In this step, the first carrier sheet and the second carrier sheet are peeled and removed from the pressurized laminate. Peeling went off smoothly. The reason for this is presumed to be as follows. In this step, the particles of the first solid electrolyte and the particles of the second solid electrolyte are compressed by applying pressure, and the contact surfaces with the first carrier sheet and the second carrier sheet are changed. In contrast, the first carrier sheet And the contact surface between the second carrier sheet and the first solid electrolyte layer and the second solid electrolyte layer does not change due to pressurization. It is considered that due to this situation, a difference in the volume change rate occurs at the interface between the first solid electrolyte layer and the first carrier sheet and the second solid electrolyte layer and the second carrier sheet. As a result, the first carrier sheet and the second carrier sheet Able to peel off.

By peeling each carrier sheet from the laminate in this way, the target solid electrolyte sheet is obtained, that is, a solid electrolyte including a first solid electrolyte layer, a second solid electrolyte layer, and a porous base material sheet located between the two electrolyte layers. piece.

According to the above manufacturing method, a solid electrolyte sheet with a multilayer structure can be easily obtained. In contrast, conventionally, a solid electrolyte sheet was produced by immersing a porous base material sheet serving as a support in a slurry containing a solid electrolyte, thereby impregnating the porous base material sheet with the solid electrolyte, or by A slurry containing a solid electrolyte is coated on one side of the sheet to produce a solid electrolyte sheet. Therefore, in the previous technology, it is impossible to manufacture a solid electrolyte sheet with a multi-layer structure.

[6] Batteries with solid electrolyte sheets An example of a battery including a solid electrolyte sheet produced by the above method is shown in FIGS. 1 and 4 . The battery 40 shown in the figures may include a negative electrode layer 20 disposed on the first solid electrolyte layer 11 side of the solid electrolyte sheet 10 and a positive electrode disposed on the second solid electrolyte layer 12 side of the solid electrolyte sheet 10 Layer 21 solid battery.

The negative electrode layer 20 in the battery 40 may include metallic lithium, for example. Alternatively, the negative electrode layer 20 may be made of a material capable of precipitating metallic lithium through charging and discharging of the battery 40 . Alternatively, the negative electrode layer 20 may also be composed of a material that can absorb lithium, such as graphite.

On the other hand, the positive electrode layer 21 in the battery 40 may include sulfur element, for example. Alternatively, the positive electrode layer 21 may be composed of a previously well-known positive electrode active material of a lithium ion battery. Examples of such positive electrode active materials include oxide active materials containing lithium transition metals. Specific examples include rock salt layered active materials such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , and lithium manganate (LiMn ₂ O ₄ ), Li(Ni _0.5 Mn _1.5 )O ₄ , Li _1+x Mn _2-xy M _y O ₄ (M is one selected from the group consisting of Al, Mg, Co, Fe, Ni, Zn Spinel-type active materials such as above), olivine _- type active materials such as lithium titanate ( _LixTiOy ), _LiFePO4 , _LiMnPO4 , _LiCoPO4 , _LiNiPO4, etc.

In this battery 40, even when the negative electrode layer 20 is composed of, for example, metallic lithium, the growth of dendrites of metallic lithium due to charging can be effectively suppressed, thereby having the advantage of improving cycle characteristics.

Regarding the above embodiments, the present invention further discloses the following solid electrolyte sheets, manufacturing methods thereof, and solid batteries using the solid electrolyte sheets. [1] A solid electrolyte sheet having a first solid electrolyte layer and a second solid electrolyte layer, The above-mentioned first solid electrolyte layer includes a solid electrolyte including a crystal phase having a pyrogermanite crystal structure, The above-mentioned second solid electrolyte layer includes a lithium (Li) element, an A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P ) element, sulfur (S) element and halogen (X) element solid electrolyte. [2] The solid electrolyte sheet according to [1], wherein the first solid electrolyte layer, the porous base material sheet, and the second solid electrolyte layer are laminated in this order. [3] The solid electrolyte sheet according to [1] or [2], wherein the solid electrolyte contained in the first solid electrolyte layer contains lithium (Li) element, phosphorus (P) element and sulfur (S) element, The atomic ratio of element A to element phosphorus (P) is 0.5 or less. [4] The solid electrolyte sheet according to any one of [1] to [3], wherein the atomic ratio of the solid electrolyte A element to the phosphorus (P) element contained in the second solid electrolyte layer is: Above 0.3 and below 1.9. [5] A solid battery including the solid electrolyte sheet according to any one of [1] to [4], a negative electrode layer disposed on the side of the first solid electrolyte layer in the solid electrolyte sheet, and a negative electrode layer disposed on the solid electrolyte sheet. The positive electrode layer on the side of the above-mentioned second solid electrolyte layer in the solid electrolyte sheet, The above-mentioned negative electrode layer contains metallic lithium, or metallic lithium can be precipitated through charging and discharging of the above-mentioned solid battery. [6] A method of manufacturing a solid electrolyte sheet, which includes the following steps: A first member having a first carrier sheet and a first coating film containing a first solid electrolyte formed on the carrier sheet, and a second carrier sheet and a first coating film containing a second solid electrolyte formed on the carrier sheet are prepared. 2. The second component of the coating film; The above-mentioned first member and the above-mentioned second member are overlapped so that the above-mentioned first coating film and the above-mentioned second coating film face each other and a porous base material sheet is interposed between the two coating films to produce a laminate; Press the above-mentioned laminated body in its thickness direction; and Peel and remove the above-mentioned first carrier sheet and the above-mentioned second carrier sheet from the above-mentioned laminated body; and The above-mentioned first solid electrolyte layer includes a sulfide solid electrolyte including a crystal phase having a pyrogermanite type crystal structure, The above-mentioned second solid electrolyte layer includes a lithium (Li) element, an A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P ) element, sulfur (S) element and halogen (X) element solid electrolyte. Example

[Reference Example 1] In this reference example, a model solid battery having the structure shown in Fig. 1 was manufactured according to the following steps. (1) Preparation of the first solid electrolyte As the first solid electrolyte, a lithium ion conductive sulfide powder represented by the composition formula Li _5.8 PS _4.8 Cl _1.2 is prepared.

(2) Preparation of the second solid electrolyte As the second solid electrolyte, a lithium ion conductive sulfide powder represented by the composition formula Li _9.54 Si _1.335 P _1.44 S _10.89 Cl _0.30 was prepared.

(3) Preparation of positive electrode active material and positive electrode mixture The positive electrode active material is prepared as follows. A powder of lithium ion conductive sulfide represented by the composition formula Li _5.8 PS _4.8 Cl _1.2 is prepared. As the conductive material, Ketjen Black (registered trademark) EC300, a conductive carbon black manufactured by Lion Specialty Chemical, was used. The conductive material has a particle diameter _D50 of 0.04 μm. The conductive material and the above-mentioned lithium ion conductive sulfide powder were mixed at a mass ratio of 5:1 to form a composite. The mixing system was performed using a planetary ball mill (P-7 manufactured by Fritsch) at 500 rpm (centrifugal acceleration 19.1 G) for 10 hours. Then, the composite material was pulverized in a mortar, and the particles were sized using a sieve with a mesh size of 53 μm to obtain a positive electrode active material powder with a particle size D ₅₀ of 3.2 μm. The positive electrode mixture was prepared by mixing the obtained positive electrode active material powder with a separately prepared lithium ion conductive sulfide represented by the composition formula Li _5.4 PS _4.4 Cl _0.8 Br _0.8 in a mortar at a mass ratio of 60:40. . All the above operations are performed in a glove box that has been replaced with fully dry Ar gas (dew point -60°C or below).

(4) Manufacturing of solid batteries The lower opening of a polypropylene cylindrical container (opening diameter 10.5 mm, height 18 mm) with upper and lower openings was blocked with a negative electrode (made of SUS), the first solid electrolyte powder was placed on it, and a positive electrode (SUS) was placed on it. (prepared)) and then uniaxially pressed at 100 MPa to form the first solid electrolyte layer. The positive electrode was temporarily removed, and the second solid electrolyte powder was placed on the first solid electrolyte layer and plugged again with the positive electrode, and uniaxially pressed at 100 MPa to form the second solid electrolyte layer. The positive electrode is removed again, and the positive electrode mixture powder is placed on the second solid electrolyte layer and plugged with the positive electrode. After uniaxially pressing the positive electrode and the negative electrode at 300 MPa, the cylindrical container was turned upside down and the negative electrode was removed. A metal lithium foil with a thickness of 200 μm was placed on the first solid electrolyte layer and the negative electrode was used. The electrode is clogged. A solid battery in which metallic lithium, a first solid electrolyte layer, a second solid electrolyte layer, and a positive electrode mixture layer are laminated in this order is produced. The production of solid-state batteries is carried out in a glove box that has been replaced with fully dry argon (dew point -60°C or below).

[Comparative example 1] In this comparative example, as the solid electrolyte layer in Reference Example 1, the second solid electrolyte layer was not formed, but only the first solid electrolyte layer was formed. Except for this, a solid battery was obtained in the same manner as Reference Example 1.

〔evaluate〕 Regarding the solid batteries obtained in Reference Example 1 and Comparative Example 1, cycle characteristics and efficiency were measured. The results are shown in Figures 5 to 7. Figures 5 to 7 are graphs showing cycle characteristics of charging capacity, discharge capacity, and efficiency, respectively. The measurement sequence of cycle characteristics and efficiency is as follows. The cycle characteristics are evaluated by setting the current 1C rate during charging and discharging to 2.0 mA, and repeating 0.1C CC-CV charging and 0.1C CC discharging. The cut-off voltages during charging and discharging are set to 3.0 V and 1.0 V respectively. The efficiency of the nth cycle is defined as (discharge capacity of the nth cycle)/(charge capacity of the nth cycle).

According to the results shown in Figures 5 to 7, it can be seen that the solid battery obtained in Reference Example 1 exhibits stable capacity and maintains a high capacity even if the charge and discharge cycles are repeated, compared with the solid battery of Comparative Example 1. of efficiency. In the cycle characteristics of the charging capacity shown in Figure 5, the capacity of the comparative example changes significantly as the number of cycles increases. This phenomenon represents the formation or growth of dendrites. On the other hand, it can be seen that the reference example exhibits stable charging capacity and suppresses the formation of dendrites. In the cycle characteristics of the discharge capacity shown in FIG. 6 , in the comparative example, the capacity disappeared as the number of cycles increased, whereas in the reference example, the capacity was maintained. In the cycle characteristics of efficiency shown in Figure 7, the efficiency of the reference example is maintained relatively high. Based on these results, it is expected that a solid battery using a solid electrolyte sheet instead of a powdered solid electrolyte layer can maintain high efficiency without losing capacity even if cycles of charge and discharge are repeated, as in the reference example. [Industrial availability]

According to the present invention, a solid electrolyte sheet with improved performance compared with the previous one can be provided.

10:Solid electrolyte tablet 11: 1st solid electrolyte layer 12: 2nd solid electrolyte layer 20: Negative layer 21: Positive electrode layer 30:Dendrite 31: High resistance material 40:Battery

FIG. 1 is a schematic diagram showing the structure of a battery equipped with the solid electrolyte sheet of the present invention. FIG. 2 is a schematic diagram showing a state when the battery shown in FIG. 1 is operated. FIG. 3 is a schematic diagram showing the state when the previous battery is operated. FIG. 4 is a schematic diagram showing the structure of another battery equipped with the solid electrolyte sheet of the present invention. FIG. 5 is a graph showing the cycle characteristics of the charging capacity of the batteries obtained in the reference example and the comparative example. FIG. 6 is a graph showing the cycle characteristics of the discharge capacity of the batteries obtained in the reference example and the comparative example. FIG. 7 is a graph showing the cycle characteristics of the battery efficiency obtained in the reference example and the comparative example.

10:Solid electrolyte tablet

11: 1st solid electrolyte layer

12: 2nd solid electrolyte layer

20: Negative layer

21: Positive electrode layer

40:Battery

Claims (6)

A solid electrolyte sheet having a first solid electrolyte layer and a second solid electrolyte layer, The above-mentioned first solid electrolyte layer includes a solid electrolyte including a crystal phase having a pyrogermanite crystal structure, The above-mentioned second solid electrolyte layer includes a lithium (Li) element, an A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P ) element, sulfur (S) element and halogen (X) element solid electrolyte. The solid electrolyte sheet of claim 1, wherein the first solid electrolyte layer, the porous base material sheet, and the second solid electrolyte layer are laminated in this order. The solid electrolyte sheet of claim 1, wherein the solid electrolyte contained in the first solid electrolyte layer contains lithium (Li) element, phosphorus (P) element and sulfur (S) element, The atomic ratio of element A to element phosphorus (P) is 0.5 or less. The solid electrolyte sheet of claim 1, wherein the atomic ratio of the solid electrolyte A element contained in the second solid electrolyte layer to the phosphorus (P) element is 0.3 or more and 1.9 or less. A solid battery comprising the solid electrolyte sheet according to any one of claims 1 to 4, a negative electrode layer disposed on the side of the first solid electrolyte layer in the solid electrolyte sheet, and the above-mentioned first solid electrolyte layer disposed in the solid electrolyte sheet. The positive electrode layer on the second solid electrolyte layer side, The above-mentioned negative electrode layer contains metallic lithium, or metallic lithium can be precipitated through charging and discharging of the above-mentioned solid battery. A method for manufacturing solid electrolyte sheets, which includes the following steps: A first member having a first carrier sheet and a first coating film containing a first solid electrolyte formed on the carrier sheet, and a second carrier sheet and a first coating film containing a second solid electrolyte formed on the carrier sheet are prepared. 2. The second component of the coating film; The above-mentioned first member and the above-mentioned second member are overlapped so that the above-mentioned first coating film and the above-mentioned second coating film face each other and a porous base material sheet is interposed between the two coating films to produce a laminate; Pressurize the above-mentioned laminated body in its thickness direction; and Peel and remove the above-mentioned first carrier sheet and the above-mentioned second carrier sheet from the above-mentioned laminated body; and The above-mentioned first solid electrolyte layer includes a sulfide solid electrolyte including a crystal phase having a pyrogermanite type crystal structure, The above-mentioned second solid electrolyte layer includes a lithium (Li) element, an A element (A represents at least one element selected from silicon (Si), germanium (Ge), tin (Sn) and antimony (Sb)), phosphorus (P ) element, sulfur (S) element and halogen (X) element solid electrolyte.