Battery and multilayer structure for batteries

Abstract

The present invention provides a battery (10) that has a self-supporting multilayer structure which comprises: a solid electrolyte sheet (11) that contains a solid electrolyte; a first active material layer (12) that is formed on one main surface of the solid electrolyte sheet (11), while containing a first active material; and a second active material layer (13) that is formed on the other main surface of the solid electrolyte sheet (11), while containing a second active material. It is preferable that the solid electrolyte sheet (11) has a first active material layer-side extension part (11C) which outwardly extends from the peripheral edge of the first active material layer (12), or a second active material layer-side extension part (11D) which outwardly extends from the peripheral edge of the second active material layer (13).

Description

Battery and laminated structure for battery

[0001] The present invention relates to a battery and a laminate structure for a battery.

[0002] In recent years, CO ２ Secondary batteries have been attracting attention as an effort to prevent global warming by reducing CO2 emissions. One type of secondary battery is a bipolar battery, which is a small, high-energy-density battery used as a power source for vehicles and the like. In this battery, a positive electrode active material layer including a current collector is formed on one main surface of a solid electrolyte layer, and a negative electrode active material layer including a current collector is formed on the other main surface of the solid electrolyte layer. In this battery, to prevent misalignment of the positive electrode active material layer and the negative electrode active material layer with respect to the main surface of the solid electrolyte, the areas of the positive electrode active material layer and the negative electrode active material layer, i.e., the current collectors, are made larger relative to the area of ​​the main surface of the solid electrolyte layer. However, to prevent electrical connection between the current collectors and short-circuiting, an insulating member is usually inserted between the current collectors.

[0003] However, in the bipolar battery described above, the insertion of insulating members increases the number of manufacturing steps and complicates the battery structure. Furthermore, the insertion of insulating members increases the battery weight. In consideration of these problems, Patent Document 1 discloses a technology that uses a current collector whose conductivity in the thickness direction is higher than that in the surface direction so that current flows only in the thickness direction.

[0004] Japanese Patent Application Laid-Open No. 2007-213930

[0005] However, the technology described in Patent Document 1 requires the current collector to be composed of a non-conductive polymer material and conductive particles, which limits the selection of materials and complicates the manufacturing process of the current collector. Therefore, an object of the present invention is to provide a battery that has a simple configuration and can suppress the occurrence of short circuits.

[0006] As a result of intensive research to solve the above-mentioned problems, the inventors have found that by using a solid electrolyte sheet as a solid electrolyte layer, an electrode layer can be formed at any position on the solid electrolyte layer and the occurrence of a short circuit can be suppressed. That is, the present invention provides a battery having a self-supporting laminated structure including: a solid electrolyte sheet containing a solid electrolyte, a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material, and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material.

[0007] The present invention also provides a self-supporting laminate structure for a battery, comprising: a solid electrolyte sheet containing a solid electrolyte; a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material; and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material.

[0008] Fig. 1(a) is a perspective view of a laminated structure for a battery according to an embodiment of the present invention, and Fig. 1(b) is a cross-sectional view taken along line II in Fig. 1(a). Fig. 2 is a perspective view of a laminated structure for a battery according to another embodiment of the present invention, and Fig. 2(b) is a cross-sectional view taken along line II-II in Fig. 2(a). Fig. 3(a) is a perspective view showing an assembly for producing the laminated structure for a battery shown in Fig. 2(a), and Fig. 3(b) is a cross-sectional view taken along line III-III in Fig. 3(a).

[0009] The present invention will be described below based on preferred embodiments. Figure 1 is a schematic diagram of a battery according to an embodiment of the present invention. Figure 1(a) is a perspective view of a laminated structure in the battery, and Figure 1(b) is a cross-sectional view taken along dashed line II in Figure 1(a).

[0010] The battery 10 shown in FIG. 1 includes a self-supporting solid electrolyte sheet 11 containing a solid electrolyte, a first active material layer 12 formed on a main surface 11A of the solid electrolyte sheet 11, and a second active material layer 13 formed on a back surface 11B of the solid electrolyte sheet 11. The battery 10 includes a battery laminate structure including these three components 11, 12, and 13. In this laminate structure, the three components 11, 12, and 13 are integrated, and the laminate structure is self-supporting and highly easy to handle, as described below. In this specification, "integrated" means that two adjacent components of the three components 11, 12, and 13 are arranged so that they cannot be separated during normal handling. In this specification, "self-supporting" refers to the rigidity of the laminate structure, and "having self-supporting properties" means that the laminate structure can maintain its shape without using a support member separate from the laminate structure. Furthermore, in this specification, a sheet refers to a member having a first main surface and a second main surface located opposite the first main surface, and having a thickness, which is the distance between the two main surfaces, that is extremely small compared to the longitudinal and lateral dimensions of the main surfaces (for example, the thickness is 1 / 100 or less of the longitudinal and lateral dimensions).

[0011] The battery 10 of this embodiment uses a self-supporting solid electrolyte sheet 11. This allows the battery 10 to have a self-supporting laminated structure, and as described below, the first active material layer 12 and the second active material layer 13 can be formed at any desired location on the solid electrolyte sheet 11. As a result, as shown in FIG. 1 , the first active material layer 12 and the second active material layer 13 can be disposed, for example, at approximately the center of the main surface 11A and the back surface 11B of the solid electrolyte sheet 11. As a result, the solid electrolyte sheet 11 has a first active material layer-side extension 11C (hereinafter sometimes referred to as a "first outer peripheral edge") extending outward from the periphery of the first active material layer 12, or a second active material layer-side extension 11D (hereinafter sometimes referred to as a "second outer peripheral edge") extending outward from the periphery of the second active material layer 13.

[0012] Therefore, when the battery 10 of this embodiment is assembled into a bipolar battery, it is possible to effectively prevent short circuits caused by contact between adjacent first active material layers 12 and second active material layers 13. In other words, by using a self-supporting solid electrolyte sheet 11 as the solid electrolyte layer, it is possible to provide a battery 10 having a self-supporting laminated structure, and it is possible to provide a battery 10 that can prevent short circuits between the electrodes that constitute the battery 10, i.e., the first active material layers 12 and the second active material layers 13, with a simple configuration.

[0013] Specifically, when the areas of the main surface 11A and the back surface 11B of the solid electrolyte sheet 11 are A, the area of ​​the main surface 12A or 13A of the first active material layer 12 or the second active material layer 13 is B, and the larger area of ​​the first outer peripheral edge portion 11C or the second outer peripheral edge portion 11D of the solid electrolyte sheet 11 is C, the ratio of the area C to the area A can be preferably 1 / 20 or less, more preferably 1 / 25 or less, and even more preferably 1 / 30 or less. In other words, since there is no need to increase the area of ​​the solid electrolyte sheet 11 more than necessary to suppress the occurrence of a short circuit, the structure of the battery 10 can be simplified and the battery 10 can be made smaller. The first outer peripheral edge portion 11C and the second outer peripheral edge portion 11D are regions of the solid electrolyte sheet 11 that are outside the regions where the first active material layer 12 and the second active material layer 13 are disposed. It is preferable that first outer peripheral edge portion 11C extends from the entire peripheral area of ​​first active material layer 12. Similarly, it is preferable that second outer peripheral edge portion 11D extends from the entire peripheral area of ​​second active material layer 13.

[0014] 2A and 2B are schematic diagrams of a laminate structure for a battery according to another embodiment of the present invention. Fig. 2A is a perspective view of the laminate structure, and Fig. 2B is a cross-sectional view taken along dashed line II-II in Fig. 2A. In Fig. 2, the same reference numerals are used for components that are the same as or similar to those in the laminate structure shown in Fig. 1.

[0015] The laminate structure provided in the battery 20 shown in Fig. 2 is an example in which the ratio of area C to area A in the embodiment shown in Fig. 1 described above is set to 0. That is, this is an example in which area A of the solid electrolyte sheet 11 is set to the same as area B of the first active material layer 12 and the second active material layer 13, and the first outer peripheral edge portion 11C and the second outer peripheral edge portion 11D of the solid electrolyte sheet 11 do not exist. Therefore, in a plan view of the laminate structure, the periphery of the solid electrolyte sheet 11, the periphery of the first active material layer 12, and the periphery of the second active material layer 13 are in the same position.

[0016] In this embodiment, the area A of the solid electrolyte sheet 11 is the same as the area B of the first active material layer 12 and the second active material layer 13, which not only simplifies the structure of the battery 20 but also enables further miniaturization of the battery 20. Therefore, even when a plurality of batteries 20 are connected to form a predetermined battery cell, the battery cell can be made smaller.

[0017] Although known literature illustrates a battery configuration having the form shown in FIG. 2 , this battery configuration is merely described for the sake of simplicity and convenience, and unlike the battery 20 of the present embodiment, the area A of the solid electrolyte sheet 11 is not substantially the same as the area B of the first active material layer 12 and the second active material layer 13.

[0018] In fact, the laminate structure used in the battery 20 shown in FIG. 2 is obtained by setting a punching portion 25 in an assembly 20X and punching the assembly 20X in the thickness direction at the punching portion 25, as shown in FIGS. 3( a) and 3(b). This manufacturing method is not known in the past, and the battery 20 including the laminate structure shown in FIG. 2 manufactured by such an undisclosed method is also not known in the past. FIG. 3( a) is a perspective view showing an assembly for manufacturing the battery shown in FIG. 2(a), and FIG. 3(b) is a cross-sectional view taken along line III-III in FIG. 3(a). The punching portion 25 refers to a region that penetrates through all of the solid electrolyte sheet 11, the first active material layer 12, and the second active material layer 13 in the thickness direction in a plan view of the laminate structure.

[0019] The thickness of the solid electrolyte sheet 11 is preferably, for example, 3 μm or more, more preferably 5 μm or more, and particularly preferably 10 μm or more. On the other hand, the thickness of the solid electrolyte sheet 11 is preferably, for example, 100 μm or less, more preferably 80 μm or less, and particularly preferably 15 μm or less. When the thickness of the solid electrolyte sheet 11 is within the above range, the relative density of the solid electrolyte sheet 11, and therefore the solid electrolyte, is improved, the ionic conductivity can be improved while maintaining low electronic conductivity, and the mechanical strength can also be improved. The thickness of the solid electrolyte sheet 11 can be measured, for example, by observing the cross section of the solid electrolyte sheet 11 with a microscope. It can also be measured using a thickness gauge. In either case, the thickness is measured at any 10 or more positions, and the arithmetic average value of the measured values ​​is defined as the thickness of the solid electrolyte sheet 11.

[0020] The solid electrolyte sheet 11 used in the present invention preferably includes a solid electrolyte and a support (not shown). This provides the solid electrolyte sheet 11 with higher self-supporting properties and improved handleability. Furthermore, the laminated structure constituting the above-described batteries 10 and 20 can be successfully obtained. The proportion of the solid electrolyte contained in the solid electrolyte sheet is preferably, for example, 50.0 mass % or more, more preferably 70.0 mass % or more, and particularly preferably 90.0 mass % or more. On the other hand, the proportion of the solid electrolyte contained in the solid electrolyte sheet is preferably, for example, 99.5 mass % or less. By having the proportion of the solid electrolyte in the solid electrolyte sheet 11 within the above range, the solid electrolyte sheet 11 can have superior relative density, ionic conductivity, and mechanical strength. The upper limit of the proportion of the solid electrolyte contained in the solid electrolyte sheet is 100 mass %.

[0021] The porosity of the solid electrolyte sheet 11 may be, for example, 1% or more, 1.5% or more, or 2% or more. On the other hand, the porosity of the solid electrolyte sheet 11 is, for example, preferably 50% or less, more preferably 45% or less, and even more preferably 30% or less. When the porosity of the solid electrolyte sheet 11 is within the above range, the solid electrolyte sheet 11 can have better relative density, ionic conductivity, and mechanical strength.

[0022] The support is preferably a porous substrate. The solid electrolyte is preferably supported in the pores of the porous substrate. The term "porous" in the porous substrate refers to a state in which a large number of pores are present. The porous substrate preferably has pores that extend from one surface to the other surface of the porous substrate. The size of the pores may be such that at least a portion of the particles of the solid electrolyte are filled in the pores when the solid electrolyte sheet 11 is formed. The pores may be interconnected.

[0023] The porous substrate is preferably a fiber sheet, in particular, because it can provide sufficient self-supporting property and appropriate flexibility to the solid electrolyte sheet 11. Examples of the fiber sheet include nonwoven fabric, woven fabric, and knitted fabric, and nonwoven fabric is particularly preferred. When the porous substrate sheet is a fiber sheet, the term "porous" refers to a state in which voids are generated between the fibers.

[0024] There are various types of nonwoven fabrics depending on the type of fibers (fiber length, fiber diameter, fiber material, etc.) used in the production of the nonwoven fabric, the type of production method (e.g., web formation method, web fiber bonding method, etc.), etc. The nonwoven fabric used as the porous substrate sheet is not particularly limited as long as it can produce a desired solid electrolyte sheet. Examples of nonwoven fabrics include orthogonal fiber nonwoven fabrics, long fiber nonwoven fabrics, short fiber nonwoven fabrics, wet-laid nonwoven fabrics, dry-laid nonwoven fabrics, air-laid nonwoven fabrics, carded nonwoven fabrics, parallel nonwoven fabrics, cross-laid nonwoven fabrics, random nonwoven fabrics, spunbonded nonwoven fabrics, meltblown nonwoven fabrics, flash-spun nonwoven fabrics, chemically bonded nonwoven fabrics, hydroentangled nonwoven fabrics, needle-punched nonwoven fabrics, stitch-bonded nonwoven fabrics, thermally bonded nonwoven fabrics, burst fiber nonwoven fabrics, tow-opened nonwoven fabrics, split fiber nonwoven fabrics, composite nonwoven fabrics, laminated nonwoven fabrics, coated nonwoven fabrics, and laminated nonwoven fabrics. Of these, cross-laid nonwoven fabrics are preferred. Cross-laid nonwoven fabrics are preferred because the strength ratio in the length direction X and the width direction Y, the basis weight, etc. can be easily adjusted. It is preferable to adjust the strength ratio in the length direction X and the width direction Y of a cross-laid nonwoven fabric uniformly. The basis weight of the cross-type nonwoven fabric may be low or high. An example of a cross-type nonwoven fabric is polyolefin mesh cloth (see JP 2007-259734 A). Note that the specific basis weight of the nonwoven fabric can be the same as that described in, for example, JP 2018-129307 A, and therefore will not be described here.

[0025] The material, porosity, air permeability, thickness, etc. constituting the porous substrate can be the same as those of the porous substrate sheet used in a general solid electrolyte sheet. For example, the porous substrate sheet can be the same as that described in JP 2018-129307 A, and therefore description thereof will be omitted here.

[0026] The solid electrolyte layer is a layer that conducts lithium ions between the positive electrode layer and the negative electrode layer in a solid-state battery. For this purpose, the solid electrolyte contained in the solid electrolyte layer preferably contains a crystalline phase having an argyrodite-type crystalline structure. The argyrodite-type crystalline structure has the chemical formula: Ag ８ GeS ６This is a crystalline structure possessed by a group of compounds derived from minerals represented by the formula: Whether or not a solid electrolyte has a crystalline phase of the argyrodite-type crystalline structure can be confirmed by measurement using X-ray diffraction (hereinafter also referred to as "XRD"). For example, in a diffraction pattern measured by XRD using CuKα1 radiation, a crystalline phase of the argyrodite-type crystalline structure exhibits characteristic diffraction peaks at 2θ = 25.5° ± 1.0°, 30.0° ± 1.0°, and 30.9° ± 1.0°. Depending on the elemental species constituting the solid electrolyte, in addition to the diffraction peaks described above, characteristic diffraction peaks may also be observed at 2θ = 15.3° ± 1.0°, 18.0° ± 1.0°, 44.3° ± 1.0°, 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°. To identify the diffraction peaks derived from the argyrodite-type crystal structure, for example, data from PDF No. 00-034-0688 is used.

[0027] The solid electrolyte preferably contains at least lithium (Li), phosphorus (P), and sulfur (S), and more preferably contains at least lithium (Li), phosphorus (P), sulfur (S), and halogen (X). In this case, the solid electrolyte is represented by the composition formula (I): Li ａ P.S. ｂ X ｃ (X is at least one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I)) is preferred from the viewpoint of improving lithium ion conductivity.

[0028] In composition formula (I), a, which indicates the molar ratio of Li element, is preferably, for example, 3.0 or more, more preferably 4.0 or more, and particularly preferably 5.0 or more. On the other hand, a is preferably, for example, 6.5 or less, more preferably 5.9 or less, and particularly preferably 5.6 or less. When a is in this range, the cubic argyrodite-type crystal structure at around room temperature (25°C) becomes more stable, allowing lithium ion vacancies to be sufficiently introduced into the structure, and as a result, lithium ion conductivity can be effectively increased.

[0029] In composition formula (I), b is preferably, for example, 3.5 or more, more preferably 4.0 or more, and particularly preferably 4.2 or more. On the other hand, b is preferably, for example, 5.5 or less, more preferably 4.9 or less, and particularly preferably 4.7 or less. When b is within the above range, the argyrodite-type crystal structure becomes more stable at around room temperature (25°C), and lithium ion conductivity is effectively increased.

[0030] In composition formula (I), c is preferably, for example, 0.1 or more, more preferably 1.1 or more, and particularly preferably 1.4 or more, while c is preferably, for example, 2.5 or less, more preferably 2.0 or less, and particularly preferably 1.8 or less.

[0031] The solid electrolyte has the composition formula (II): Li ７－ｄ P.S. ６－ｄ X ｄ The composition represented by composition formula (II) is a stoichiometric composition of an argyrodite-type crystal phase. In composition formula (II), X has the same meaning as in composition formula (I).

[0032] In composition formula (II), d is preferably, for example, 0.4 or more, more preferably 0.8 or more, and particularly preferably 1.2 or more, while d is preferably, for example, 2.2 or less, more preferably 2.0 or less, and particularly preferably 1.8 or less.

[0033] The solid electrolyte has the composition formula (III): Li ７－ｄ－２ｅ P.S. ６－ｄ－ｅ X ｄ The argyrodite-type crystalline phase having the composition represented by the composition formula (III) may be, for example, a mixture of an argyrodite-type crystalline phase having the composition represented by the composition formula (II) and P ２ S ５ It is produced by reaction with diphosphorus pentasulfide.

[0034] In the composition formula (III), e is the Li from the stoichiometric composition represented by the composition formula (II).２ e is a value indicating the deviation of the S component. For example, e is preferably −0.9 or more, more preferably −0.6 or more, and particularly preferably −0.3 or more. On the other hand, e is preferably (−d+2.0) or less, more preferably (−d+1.6) or less, and particularly preferably (−d+1.0) or less.

[0035] In the solid electrolyte, the atomic ratio X / P of the X element to the P element is, for example, preferably greater than 1.0, more preferably 1.1 or more, even more preferably 1.2 or more, and even more preferably 1.4 or more. On the other hand, the atomic ratio X / P is, for example, preferably 2.5 or less, more preferably 2.3 or less, and even more preferably 2.2 or less. When the atomic ratio X / P is within the above range, lithium ion conductivity is further improved. The atomic ratio X / P can be measured, for example, by inductively coupled plasma atomic emission spectroscopy (ICP atomic emission spectroscopy) or SEM-EDS analysis.

[0036] In particular, when the X element includes at least Cl and Br, the atomic ratio (Cl + Br) / P of the total of Cl and Br to P is preferably greater than 1.0, more preferably 1.1 or greater, even more preferably 1.2 or greater, and even more preferably 1.4 or greater. On the other hand, the atomic ratio (Cl + Br) / P is preferably 2.5 or less, more preferably 2.3 or less, and even more preferably 2.0 or less. Having the atomic ratio (Cl + Br) / P within the above range further improves lithium ion conductivity, which is preferable. The atomic ratio (Cl + Br) / P can be measured, for example, by elemental analysis using inductively coupled plasma atomic emission spectroscopy (ICP atomic emission spectroscopy) or a scanning electron microscope equipped with EDS (SEM-EDS).

[0037] The solid electrolyte is, among the above-mentioned composition formulas (I) to (III), particularly, composition formula (IV) Li ７－ｄ P.S. ６－ｄ Cl ｄ１ Br ｄ２In the composition formula (IV), the total molar ratio d (= d1 + d2) of Cl and Br is preferably greater than 1.0, more preferably 1.2 or more, and particularly preferably 1.4 or more. On the other hand, the total molar ratio d is preferably less than 2.5, more preferably less than 2.0, particularly preferably 1.8 or less, and even more preferably 1.7 or less. When the total molar ratio d is within the above range, the formation of heterophases can be sufficiently controlled, and a decrease in ionic conductivity can be effectively suppressed.

[0038] In the composition formula, the ratio of the molar ratio of Br to the molar ratio of Cl (d2 / d1) is preferably, for example, 0.1, more preferably 0.3 or more, and particularly preferably 0.5 or more. On the other hand, the molar ratio is, for example, preferably 10 or less, more preferably 5 or less, and particularly preferably 3 or less. When the molar ratio is within the above-mentioned range, lithium ion conductivity can be further improved.

[0039] In the composition formula, d1, which indicates the molar ratio of Cl, is preferably, for example, 0.3 or more, more preferably 0.4 or more, and particularly preferably 0.6 or more. On the other hand, d1 is preferably, for example, 1.5 or less, more preferably 1.2 or less, and particularly preferably 1.0 or less. When d1 is equal to or greater than the lower limit, lithium ion conductivity can be further increased. On the other hand, when d1 is equal to or less than the upper limit, the solid electrolyte can be more easily obtained.

[0040] In the composition formula, d2, which indicates the molar ratio of Br, is preferably, for example, 0.3 or more, more preferably 0.4 or more, and particularly preferably 0.6 or more. On the other hand, d2 is, for example, preferably 1.5 or less, more preferably 1.2 or less, and particularly preferably 1.0 or less. When d2 is equal to or greater than the lower limit, a solid electrolyte is easily obtained. On the other hand, when d2 is equal to or less than the upper limit, lithium ion conductivity can be further increased.

[0041] In any case where the solid electrolyte is represented by any of the composition formulas (I), (II), (III) and (IV), it is preferable that the X element contains Br, since this further improves the lithium ion conductivity.

[0042] The first active material layer 12 and the second active material layer 13 may each contain a positive electrode active material or a negative electrode active material. When the first active material contained in the first active material layer 12 is a positive electrode active material and the second active material contained in the second active material layer 13 is a negative electrode active material, the battery 10 may be used, for example, as a bipolar battery. Specifically, a bipolar battery can be provided by connecting the first active material layer 12 in one laminate structure and the second active material layer 13 in another laminate structure in series so that the two laminate structures face each other via a current collector. The first active material contained in the first active material layer 12 and the second active material contained in the second active material layer 13 may both be a positive electrode active material or a negative electrode active material.

[0043] The positive electrode active material may be, for example, an oxide active material containing lithium and a transition metal. Specifically, lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), LiNi １／３ Co １／３ Mn １／３ O ２ rock salt layered active materials such as lithium manganese oxide (LiMn ２ O ４ ), Li(Ni ０．５ Mn １．５ ) O ４ , Li １＋ｘ Mn ２－ｘ－ｙ M ｙ O ４ (M is one or more selected from the group consisting of Al, Mg, Co, Fe, Ni, and Zn), and lithium titanate (Li ｘ TiO ｙ ), LiFePO ４ , LiMnPO ４ , LiCoPO ４ , LiNiPO ４On the other hand, examples of the negative electrode active material include Si and Si alloys, carbon materials such as graphite and hard carbon, various oxides such as lithium titanate, metallic lithium, and lithium alloys.

[0044] The content of the active material contained in the first active material layer 12 and the second active material layer 13 is not particularly limited as long as it is sufficient to function as an electrode. When the first active material layer 12 or the second active material layer 13 contains a positive electrode active material, the content of the positive electrode active material is, for example, preferably 50% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 75% by mass or more, when the total mass of the active material layer is taken as 100% by mass. On the other hand, the content of the positive electrode active material can be, for example, 99% by mass or less.

[0045] When the first active material layer 12 or the second active material layer 13 contains a negative electrode active material, the content of the negative electrode active material is, for example, preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 70% by mass or more, when the total mass of the active material layer is taken as 100% by mass. On the other hand, the content of the negative electrode active material can be, for example, 99% by mass or less.

[0046] The first active material layer 12 and the second active material layer 13 may contain a solid electrolyte. The solid electrolyte is not particularly limited. The solid electrolyte is preferably the solid electrolyte described above. The content of the solid electrolyte contained in the first active material layer 12 and the second active material layer 13 is not particularly limited as long as the electrode including the first active material layer 12 and the second active material layer 13 exhibits the desired function. When the total mass of the active material layers is taken as 100 mass%, the content of the solid electrolyte may be, for example, 1 mass% or more and 80 mass% or less for the first active material layer 12 and the second active material layer 13, independently.

[0047] The first active material layer 12 and the second active material layer 13 may contain conductive materials, binders, and various additives as necessary. Examples of conductive materials include carbon materials such as vapor-grown carbon fiber (VGCF) and carbon nanofibers, as well as metal materials. Examples of binders include polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), butadiene rubber (BR), and styrene-butadiene rubber (SBR), or combinations thereof.

[0048] Next, a preferred method for manufacturing the battery of the present invention will be described using as an example a method for manufacturing the battery 10 in the embodiment shown in FIG. 1. First, a solid electrolyte sheet 11 is manufactured. This manufacturing process is broadly divided into the following steps: (1) a step of preparing a laminate member; (2) a step of manufacturing a laminate using the laminate member; (3) a step of pressurizing the laminate; and (4) a step of peeling and removing the carrier sheet from the laminate. Each step will be described below.

[0049] (1) Step of Preparing a Laminated Member In this step, a laminated member is prepared, which includes a carrier sheet and a coating film containing a solid electrolyte formed on the carrier sheet. The carrier sheet is preferably one that is strong enough to support the coating film and flexible enough to support the coating film.

[0050] The thickness of the carrier sheet can be appropriately selected depending on the material constituting the carrier sheet, and is preferably a thickness that allows the carrier sheet to have self-supporting properties. Furthermore, the thickness of the carrier sheet may be adjusted to provide flexibility. The thickness of the carrier sheet is not particularly limited, but may be, for example, 5 μm or more, 10 μm or more, or 15 μm or more. On the other hand, the thickness of the carrier sheet may be, for example, 1000 μm or less, 200 μm or less, and particularly 100 μm or less.

[0051] The material constituting the carrier sheet is preferably at least one of resin, glass, and metal, for example. That is, the carrier sheet is preferably at least one of carrier resin, carrier glass, and carrier metal foil. The carrier sheet may have a multilayer structure in which two or more of carrier resin, carrier glass, and carrier metal foil are laminated.

[0052] 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, chlorinated polyolefin, and copolymers of these resin groups.

[0053] As the carrier glass, for example, glass cloth, which is a woven fabric of glass fibers, can be used.

[0054] Examples of materials that can be used to form the carrier metal foil include copper, stainless steel, aluminum, nickel, silver, gold, chromium, cobalt, tin, zinc, and alloys of these.

[0055] There may be no other layer between the carrier sheet and the coating film, or one or more other layers may be present between them. In either case, it is preferable that the carrier sheet and the coating film are peelably laminated. "Peeling" the carrier sheet and the coating film means that they can be peeled off without destroying their respective structures. The peel strength between the carrier sheet and the coating film is preferably, for example, 10 N / 10 mm or less, more preferably 7 N / 10 mm or less, and particularly preferably 4 N / 10 mm or less. A peel strength within the above range ensures good peeling between the carrier sheet and the coating film. For example, a method for measuring the peel strength may involve cutting a laminate having the target layers into a 10 mm wide strip and conducting an interlayer peel test (180-degree peel, test speed 50 mm / min) using a tension / compression tester.

[0056] When the carrier sheet and the coating film are laminated in a peelable manner, the surface of the two main surfaces of the carrier sheet facing the coating film can be subjected to a release treatment, such as smoothing the surface or applying a resinous release agent.

[0057] The coating film formed on the carrier sheet contains a solid electrolyte and a solvent, which may be, independently of one another, a nonpolar solvent such as heptane, methylcyclohexane, or toluene, an aprotic polar solvent such as methyl isobutyl ketone or cyclohexanone, or a mixture thereof.

[0058] The solid electrolyte contained in the coating film has a particle form. The particle size is measured by a laser diffraction / scattering particle size distribution measurement method using a volume cumulative particle size D at a cumulative volume of 50% by volume. ５０ It is preferable that the thickness is 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. ５０ is, for example, preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less.

[0059] Examples of methods for mixing the solid electrolyte and the solvent include an ultrasonic homogenizer, a shaker, a thin film rotary mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, and a high-speed impeller mill.

[0060] After the solid electrolyte and the solvent are mixed in this manner, the resulting slurry is applied to one side of a carrier sheet. Examples of application methods include doctor blade coating, die coating, gravure coating, spray coating, electrostatic coating, and bar coating. By applying the slurry to one side of the carrier sheet, a coating film is formed.

[0061] From the viewpoint of the coating properties of the slurry, the solid content of the coating film thus obtained is preferably, for example, 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, while the solid content is, for example, preferably 90% by mass or less, and more preferably 80% by mass or less.

[0062] After the coating film is formed, the liquid component may be appropriately removed. Examples of methods for removing the liquid component include warm air drying, hot air drying, infrared drying, reduced pressure drying, and dielectric heating drying. In this manner, a laminate member having a carrier sheet and a coating film containing a solid electrolyte formed on the carrier sheet is prepared.

[0063] (2) Step of manufacturing a laminate using a lamination member The lamination member prepared in step (1) is, for example, disposed on a support made of the porous substrate so that the coating film containing the solid electrolyte of the lamination member faces the support, thereby obtaining a laminate in which the lamination member is stacked on the support. Since the coating film contains an appropriate amount of solvent, a portion of the coating film fills the pores of the porous substrate. This filling is ensured in the next step, the pressurization step.

[0064] (3) Step of Pressurizing the Stack When the solid electrolyte sheet has a support made of a porous substrate, the step of pressing the stack is carried out so that the pores of the porous substrate are filled with the coating, i.e., at least a portion of the solid electrolyte particles. For this purpose, the stack is pressed at least in the thickness direction. For example, the stack can be pressed in the thickness direction using a uniaxial press. Alternatively, the entire stack can be isostatically pressed by CIP (cold isostatic pressing).

[0065] The pressure can be adjusted appropriately depending on the type of porous substrate constituting the laminate, the amount of solid electrolyte contained in the coating film, etc. Specific pressure is, for example, preferably 100 MPa or more, more preferably 350 MPa or more, and even more preferably 700 MPa or more.

[0066] (4) Step of Peeling and Removing Carrier Sheet from Laminate In this step, the carrier sheet is peeled and removed from the laminate after pressing. By peeling the carrier sheet from the laminate in this manner, the desired solid electrolyte sheet 11, i.e., the solid electrolyte sheet 11 in which the support is embedded in the solid electrolyte, is obtained.

[0067] Next, the first active material layer 12 and the second active material layer 13 are formed on the main surface 11A and the back surface 11B of the solid electrolyte sheet 11 obtained as described above.

[0068] First, an electrode slurry containing an active material and a solvent is prepared. The active material is a positive electrode active material or a negative electrode active material as described above, and typically has a particle form. The particle size of the active material is measured by a volume cumulative particle size D at 50% of the cumulative volume measured by a laser diffraction / scattering particle size distribution measurement method. ５０ It is preferable that the thickness is 0.1 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. ５０ is, for example, preferably 100 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.

[0069] Examples of the solvent include non-polar solvents such as heptane, methylcyclohexane, and toluene, aprotic polar solvents such as methyl isobutyl ketone and cyclohexanone, and mixtures thereof.

[0070] The electrode slurry may contain other materials in addition to the active material and the solvent, such as a binder, a conductive material, a solid electrolyte, and various additives.

[0071] Examples of methods for mixing the electrode slurry include an ultrasonic homogenizer, a shaker, a thin film rotary mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, and a high-speed impeller mill. From the viewpoint of the coatability of the slurry, the solid content concentration of the electrode slurry is preferably, for example, 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. On the other hand, the solid content concentration is, for example, preferably 90% by mass or less, and more preferably 80% by mass or less.

[0072] Once the electrode slurry is prepared, it is applied to the main surface 11A and the back surface 11B of the solid electrolyte sheet 11. Examples of application methods include doctor blade, die coating, gravure coating, spray coating, electrostatic coating, and bar coating. Once the coating film is formed, it is dried to remove the liquid component. By appropriately setting the drying conditions, the amount of liquid component contained in the coating film can be adjusted to a desired range. Examples of drying methods include warm air drying, hot air drying, infrared drying, reduced pressure drying, and dielectric heating drying. This forms an active material layer 2 that is substantially dry. By appropriately adjusting the amount of electrode slurry applied, the first active material layer 12 and the second active material layer 13 can be formed with the desired thickness.

[0073] When manufacturing the battery 20 shown in FIG. 2, the punching step shown in FIG. 3 may be added after the above-described steps.

[0074] The battery obtained in this manner is useful as a solid-state battery. In this specification, the term "solid-state battery" includes not only solid-state batteries that do not contain any liquid or gel-like substance as an electrolyte, but also batteries that contain, for example, 50 mass % or less, 30 mass % or less, or 10 mass % or less of a liquid or gel-like substance as an electrolyte.

[0075] In view of the above embodiments, the present invention includes the following batteries and laminate structures for batteries. [1] A battery having a self-supporting laminate structure including: a solid electrolyte sheet containing a solid electrolyte; a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material; and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material. [2] The battery according to [1], wherein the solid electrolyte sheet has a first active material layer-side extending portion extending outward from the periphery of the first active material layer, or a second active material layer-side extending portion extending outward from the periphery of the second active material layer. [3] The battery according to [1] or [2], wherein the larger of the areas of the first active material layer-side extending portion and the second active material layer-side extending portion in a planar view is defined as C, and when the area of ​​the solid electrolyte sheet in a planar view is defined as A, the ratio of area C to area A is 1 / 20 or less. [4] The battery according to any one of [1] to [3], wherein the thickness of the solid electrolyte sheet is 3 μm or more and 100 μm or less. [5] The battery according to any one of [1] to [4], wherein the proportion of the solid electrolyte in the solid electrolyte sheet is 50.0 mass % or more and 99.5 mass % or less. [6] The battery according to any one of [1] to [5], wherein the solid electrolyte sheet has a support. [7] The battery according to [6], wherein the support is made of a porous substrate, and the solid electrolyte is supported in pores of the porous substrate. [8] The battery according to any one of [1] to [7], wherein the solid electrolyte contains a crystalline phase having an argyrodite-type crystal structure. [9] The battery according to any one of [1] to [8], wherein the first active material is a positive electrode active material and the second active material is a negative electrode active material.

[10] The battery according to [9], wherein the first active material layer of one of the laminate structures and the second active material layer of the other of the laminate structures are connected in series so as to face each other with a current collector interposed therebetween.

[11] The battery according to any one of [1] to [8], wherein the first active material and the second active material are both a positive electrode active material or a negative electrode active material.

[12] A self-supporting laminate structure for a battery, comprising: a solid electrolyte sheet containing a solid electrolyte, a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material, and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material.

[13] The laminate structure for a battery according to

[12] , wherein the laminate structure for a battery has, at its outer edge, a portion to be punched out that penetrates the solid electrolyte sheet, the first active material layer, and the second active material layer in a thickness direction.

[0076] According to the present invention, it is possible to provide a battery that has a simple configuration and is capable of suppressing the occurrence of short circuits.

Claims

1. A battery having a self-supporting laminated structure comprising: a solid electrolyte sheet containing a solid electrolyte; a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material; and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material.

2. The battery according to claim 1, wherein the solid electrolyte sheet has a first active material layer side extension portion extending outward from the periphery of the first active material layer, or a second active material layer side extension portion extending outward from the periphery of the second active material layer.

3. The battery according to claim 1, wherein the larger of the areas of the first active material layer side extension portion and the second active material layer side extension portion in a planar view is defined as C, and the area of ​​the solid electrolyte sheet in a planar view is defined as A, and the ratio of area C to area A is 1 / 20 or less.

4. The battery according to claim 1, wherein the thickness of the solid electrolyte sheet is 3 μm or more and 100 μm or less.

5. The battery according to claim 1, wherein the proportion of the solid electrolyte in the solid electrolyte sheet is 50.0% by mass or more and 99.5% by mass or less.

6. The battery of claim 1, wherein the solid electrolyte sheet has a support.

7. The battery according to claim 6, wherein the support is made of a porous substrate, and the solid electrolyte is supported within the pores of the porous substrate.

8. The battery of claim 1, wherein the solid electrolyte comprises a crystalline phase having an argyrodite-type crystal structure.

9. The battery of claim 1, wherein the first active material is a positive electrode active material and the second active material is a negative electrode active material.

10. The battery according to claim 9, wherein the two laminate structures are connected in series so that the first active material layer in one of the laminate structures and the second active material layer in the other of the laminate structures face each other via a current collector.

11. The battery according to claim 1, wherein the first active material and the second active material are both positive electrode active materials or negative electrode active materials.

12. A self-supporting laminate structure for a battery, comprising: a solid electrolyte sheet containing a solid electrolyte; a first active material layer formed on one main surface of the solid electrolyte sheet and containing a first active material; and a second active material layer formed on the other main surface of the solid electrolyte sheet and containing a second active material.

13. The laminate structure for a battery according to claim 12, wherein the laminate structure for a battery has a portion to be punched that penetrates the solid electrolyte sheet, the first active material layer, and the second active material layer in the thickness direction.