All-solid-state power storage element and method for manufacturing the same

Abstract

To provide an all-solid-state power storage element having a layer containing a hydride-based lithium ion conductor and having high productivity, and a method for manufacturing the all-solid-state power storage element.SOLUTION: An all-solid-state energy storage element includes a layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state energy storage element and a method for manufacturing an all-solid-state energy storage element. [Background technology]

[0002] Due to their high energy density, non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. Non-aqueous electrolyte secondary batteries generally have a pair of electrically isolated electrodes and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring charge-transporting ions between the electrodes. Capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as energy storage elements other than non-aqueous electrolyte secondary batteries.

[0003] In recent years, all-solid-state energy storage elements have been proposed that use a solid electrolyte as the non-aqueous electrolyte instead of a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a liquid such as an organic solvent. Patent Document 1 describes an invention of an all-solid-state battery that uses a hydride solid electrolyte. Hereinafter, a hydride solid electrolyte having lithium ion conductivity will be referred to as a hydride-based lithium ion conductor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-209106 Summary of the Invention [Problem to be solved by the invention]

[0005] An all-solid-state energy storage element typically includes a positive electrode active material layer, a negative electrode active material layer, and an isolation layer disposed between these layers, with a solid electrolyte contained in at least one of these layers. In manufacturing an all-solid-state energy storage element, it is desirable to form the layer containing the solid electrolyte by coating a slurry, considering productivity and other factors. Furthermore, hydride-based lithium ion conductors have lower density than sulfide solid electrolytes and other materials, offering advantages such as reduced weight for all-solid-state energy storage elements. Therefore, the inventors attempted to prepare a slurry containing a hydride-based lithium ion conductor as the solid electrolyte, but found it difficult to prepare a slurry with good fluidity. Thus, it is not easy to increase the productivity of all-solid-state energy storage elements using hydride-based lithium ion conductors.

[0006] An object of the present invention is to provide an all-solid-state electricity storage element having a layer containing a hydride-based lithium ion conductor, which can be produced with high productivity, and a method for producing such an all-solid-state electricity storage element. [Means for solving the problem]

[0007] An all-solid-state energy storage element according to one aspect of the present invention includes a layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20° C. and 1 atmosphere.

[0008] A method for producing an all-solid-state energy storage element according to another aspect of the present invention includes forming a layer using a slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. [Effects of the Invention]

[0009] According to any one aspect of the present invention, it is possible to provide an all-solid-state energy storage element having a layer containing a hydride-based lithium ion conductor, which has high productivity, and a method for manufacturing such an all-solid-state energy storage element. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery, which is one embodiment of the all-solid-state energy storage element of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an electricity storage device including all-solid-state electricity storage elements according to a plurality of embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] First, an outline of the all-solid-state energy storage element and the method for manufacturing the all-solid-state energy storage element disclosed in this specification will be described.

[0012] [1] An all-solid-state energy storage element according to one aspect of the present invention includes a layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20° C. and 1 atmosphere.

[0013] The all-solid-state energy storage element described in [1] above is an all-solid-state energy storage element having a layer containing a hydride-based lithium ion conductor and is highly productive. While the reason for this is unclear, the following is presumed. Hydride-based lithium ion conductors have solubility and reactivity in various solvents, which is one of the reasons why it is difficult to prepare a good slurry containing a hydride-based lithium ion conductor and having flowability. The inventors conducted experiments using various solvents and found that hydride-based lithium ion conductors have low solubility and reactivity in aliphatic hydrocarbons that are liquid at 20°C and 1 atmosphere, and that using such aliphatic hydrocarbons as a solvent allows the preparation of a good slurry containing a hydride-based lithium ion conductor and having flowability. Furthermore, even in the layer obtained by coating and drying the slurry, components used as the solvent for the slurry are usually not completely removed and remain within the layer. That is, the layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere can be provided by coating a slurry that contains a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere and has good fluidity. Also, the layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere can be a layer provided by coating a slurry that contains a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. Therefore, the all-solid-state energy storage element described in [1] above has high productivity.

[0014] An "all-solid-state energy storage element" refers to an energy storage element consisting essentially of solid constituent members. In an all-solid-state energy storage element, a component used as a solvent for the slurry (such as an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere) may remain in the layer formed by coating and drying the slurry. The all-solid-state energy storage element may be a non-aqueous electrolyte energy storage element that uses only a solid electrolyte as the non-aqueous electrolyte, or may be a non-aqueous electrolyte energy storage element that does not use a non-aqueous electrolyte solution.

[0015] The types of aliphatic hydrocarbons in the layer that are liquid at 20°C and 1 atmosphere are identified by gas chromatography-mass spectrometry (GC-MS). Specifically, the method is as follows. (1) Extraction of aliphatic hydrocarbons that are liquid at 20°C and 1 atmosphere First, the all-solid-state energy storage element is disassembled, and each layer is removed and immersed in a suitable extraction solvent (e.g., toluene, hexane, etc.). The extraction solvent that has impregnated each layer is stirred using ultrasonic treatment or the like to extract the aliphatic hydrocarbons contained in each layer that are liquid at 20°C and 1 atmosphere into the extraction solvent. Next, filtration is performed to remove solid components (active material, binder, etc.), and the aliphatic hydrocarbons that are liquid at 20°C and 1 atmosphere are collected and diluted in the extraction solvent to obtain a measurement solution. (2) GC-MS The GC-MS analysis equipment used was the Shimadzu GCMS-TQ8040, and helium was used as the carrier gas. A measurement sample (aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere) is subjected to GC-MS analysis. The components contained in the sample are predicted from the MS spectrum of each peak in the obtained gas chromatogram. A known sample of the predicted components is subjected to GC-MS analysis. The retention time and MS spectrum of the peak corresponding to each predicted component in the measurement sample are compared with the retention time and MS spectrum of the peak of a known sample of each predicted component, and if they match, the above prediction is presumed to be correct. Note that the extraction solvent is excluded from this analysis.

[0016] [2] In the all-solid-state energy storage element according to [1] above, the layer may further contain a sulfide solid electrolyte.

[0017] Sulfide solid electrolytes have the property of easily reacting with polar solvents and deteriorating. In contrast, the all-solid-state energy storage element described in [2] above can be formed by coating a layer containing a hydride-based lithium ion conductor, a sulfide solid electrolyte, and the like, using a slurry containing an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere as a solvent. Therefore, the all-solid-state energy storage element described in [2] above is highly productive and can exhibit good charge / discharge performance with reduced deterioration of the sulfide solid electrolyte, etc.

[0018] [3] In the all-solid-state electricity storage element according to the above [1] or [2], the aliphatic hydrocarbon may be a chain saturated hydrocarbon.

[0019] By using a chain saturated hydrocarbon as the slurry solvent, it is possible to prepare a slurry containing a hydride-based lithium ion conductor and having good fluidity. Therefore, the all-solid-state energy storage element described in [3] above has higher productivity.

[0020] [4] In the all-solid-state electricity storage element according to any one of [1] to [3] above, the aliphatic hydrocarbon may have a boiling point of 160° C. or higher under 1 atmosphere.

[0021] Aliphatic hydrocarbons with a boiling point of 160°C or higher at 1 atmosphere are relatively unlikely to volatilize at room temperature. Therefore, when the solvent of the slurry used to form the layer containing the hydride-based lithium ion conductor or the like is an aliphatic hydrocarbon with a boiling point of 160°C or higher at 1 atmosphere, the solvent is unlikely to volatilize during the preparation and coating of the slurry, and as a result, the fluidity is unlikely to decrease. Therefore, the all-solid-state energy storage element described in [4] above has higher productivity.

[0022] [5] In the all-solid-state energy storage element according to any one of [1] to [4] above, the hydride-based lithium ion conductor may contain lithium borohydride.

[0023] Lithium borohydride is a substance that is more reactive to solvents and the like than other hydride-based lithium ion conductors (e.g., closo-based hydrides, etc.). Therefore, it is very difficult to form a layer by coating a slurry containing lithium borohydride, and improving the productivity of all-solid-state energy storage elements including a layer containing lithium borohydride is a particularly important issue. Therefore, in the all-solid-state energy storage element described in [5] above that includes a layer containing lithium borohydride, the layer can be formed by coating, and it is highly significant that the issue of providing an all-solid-state energy storage element that is highly productive can be resolved.

[0024] [6] A method for producing an all-solid-state energy storage element according to another aspect of the present invention includes forming a layer using a slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere.

[0025] A slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere has good fluidity. Therefore, according to the method for producing an all-solid-state energy storage element described in [6] above, a layer containing a hydride-based lithium ion conductor can be formed by coating the slurry, and an all-solid-state energy storage element can be produced with high productivity.

[0026] An all-solid-state energy storage element according to one embodiment of the present invention, a manufacturing method for an all-solid-state energy storage element, an energy storage device, and other embodiments will be described in detail. Note that the names of the components (elementary components) used in each embodiment may differ from the names of the components (elementary components) used in the background art.

[0027] <All-solid-state energy storage element> An all-solid-state energy storage element according to one embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and a container that houses them. The separator is a layer that is interposed between the positive electrode and the negative electrode and electrically insulates the positive electrode from the negative electrode, and contains a solid electrolyte that is a non-aqueous electrolyte. The solid electrolyte may also be contained in the positive electrode and the negative electrode. The all-solid-state energy storage element according to one embodiment of the present invention may be an all-solid-state battery.

[0028] An all-solid-state energy storage element 1 shown in FIG. 1 , which is one embodiment of the present invention, is an all-solid-state battery, i.e., a secondary battery in which a positive electrode 2 and a negative electrode 3 are arranged with a separator 4 interposed therebetween. The positive electrode 2 has a positive electrode substrate 5 and a positive electrode active material layer 6, with the positive electrode substrate 5 being the outermost layer of the positive electrode 2. The negative electrode 3 has a negative electrode substrate 7 and a negative electrode active material layer 8, with the negative electrode substrate 7 being the outermost layer of the negative electrode 2. In the all-solid-state energy storage element 1 shown in FIG. 1 , the negative electrode active material layer 8, the separator 4, the positive electrode active material layer 6, and the positive electrode substrate 5 are stacked in this order on the negative electrode substrate 7. An intermediate layer may be provided between the positive electrode substrate 5 and the positive electrode active material layer 6. Similarly, an intermediate layer may be provided between the negative electrode substrate 7 and the negative electrode active material layer 8. The all-solid-state energy storage element according to one embodiment of the present invention may further include other components such as a container. Other components such as a container are omitted from the all-solid-state energy storage element 1 shown in FIG. 1 .

[0029] The all-solid-state energy storage element according to one embodiment of the present invention may further include, for example, a positive electrode lead, a positive electrode external terminal, a negative electrode lead, and a negative electrode external terminal. The positive electrode lead and the negative electrode lead are housed in a container. The positive electrode external terminal and the negative electrode external terminal are provided outside the container. The positive electrode is electrically connected to the positive electrode external terminal via the positive electrode lead. The negative electrode is electrically connected to the negative electrode external terminal via the negative electrode lead.

[0030] Hereinafter, main components constituting an all-solid-state energy storage element according to one embodiment of the present invention will be described in detail, mainly in the case where the all-solid-state energy storage element is an all-solid-state battery, but this is not intended to limit the application of the present invention.

[0031] The lower and upper limits of each numerical range described in the embodiments of the present invention can be combined in any manner.

[0032] (layer(X)) An all-solid-state energy storage element according to one embodiment of the present invention includes a layer (hereinafter also referred to as "layer (X)") containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. In the all-solid-state energy storage element 1 shown in FIG. 1 , the layer (X) may be the positive electrode active material layer 6, the negative electrode active material layer 8, or the separator 4. That is, at least one layer of the positive electrode active material layer 6, the negative electrode active material layer 8, and the separator 4 contains a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. One or more layers of the positive electrode active material layer 6, the negative electrode active material layer 8, and the separator 4 may be the layer (X).

[0033] The hydride-based lithium ion conductor may be a complex hydride composed of lithium cations and complex ions. Examples of hydride-based lithium ion conductors include LiBH4 (lithium borohydride), LiAlH4, Li3AlH6, LiBH(CH3)3, LiBH(C2H5)3, LiNH2, Li2NH, Li[OC(CH3)3]3AlH, Li(OCH3)3AlH, Li(OC2H5)3H, and closo-based hydrides. Closo-based hydrides are complex hydrides having a cage-shaped cluster-type complex ion with a closo structure, and Li2B 12 H 12 , Li2B 10 H 10 , LiCB 11 H 12 , LiCB9H 10 Examples of the hydride-based lithium ion conductor include LiBH4-based lithium ion conductors, and LiBH4 is more preferred. The LiBH4-based lithium ion conductor refers to LiBH4 and compounds in which at least one hydrogen atom of LiBH4 is substituted with another atom or a substituent (e.g., an alkyl group). One or more types of hydride-based lithium ion conductors can be used.

[0034] The content of the hydride-based lithium ion conductor in layer (X) varies depending on, for example, whether layer (X) is a positive electrode active material layer, a negative electrode active material layer, or a separator layer. The lower limit of the content of the hydride-based lithium ion conductor in layer (X) may be 1 mass%, or may be 3 mass%, 5 mass%, 10 mass%, 15 mass%, 20 mass%, 30 mass%, 40 mass%, 50 mass%, or 60 mass%. The upper limit of the content may be 90 mass%, 80 mass%, 70 mass%, 60 mass%, 50 mass%, 40 mass%, 30 mass%, or 20 mass%.

[0035] The binder contained in layer (X) is not particularly limited, but is preferably a binder that dissolves or disperses in an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. Examples of such binders include hydrocarbon polymers such as styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), polyethylene, polypropylene, and polystyrene. Hydrocarbon rubbers such as SBR and EPDM are preferred, and SBR is more preferred. Other binders that can be used include those exemplified as binders used in the positive electrode active material layer described below. One or more binders can be used.

[0036] The content of the binder in the layer (X) is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 9% by mass, more preferably 1% by mass to 8% by mass, and even more preferably 3% by mass to 6% by mass. By setting the content of the binder within the above range, it is possible to stably maintain the hydride-based lithium ion conductor, etc.

[0037] The aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere may be an aliphatic hydrocarbon that has a melting point of less than 20°C and a boiling point of more than 20°C under 1 atmosphere.

[0038] The lower limit of the boiling point of the aliphatic hydrocarbon at 1 atmosphere is preferably 80°C, more preferably 100°C, even more preferably 120°C, even more preferably 140°C, even more preferably 160°C, and particularly preferably 170°C. When the boiling point of the aliphatic hydrocarbon at 1 atmosphere is equal to or higher than the lower limit, the stability of the fluidity of a slurry using this aliphatic hydrocarbon can be increased. On the other hand, the upper limit of the boiling point is preferably 250°C, more preferably 220°C, even more preferably 200°C, even more preferably 190°C, and particularly preferably 180°C. When the boiling point of the aliphatic hydrocarbon at 1 atmosphere is equal to or lower than the upper limit, the drying efficiency after coating of a slurry using this aliphatic hydrocarbon can be increased.

[0039] The lower limit of the number of carbon atoms of the aliphatic hydrocarbon may be, for example, 5, but is preferably 6, and more preferably 7, 8, 9, or 10. The upper limit of the number of carbon atoms may be, for example, 15, but is preferably 14, and more preferably 13, 12, 11, or 10.

[0040] The aliphatic hydrocarbon may be a chain aliphatic hydrocarbon such as an alkane, alkene, or alkyne, or may be a cyclic aliphatic hydrocarbon such as a cycloalkane or cycloalkene.

[0041] Examples of alkanes include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and pentadecane. Examples of alkenes include pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, and pentadecene. Examples of alkynes include pentyne, hexyne, hepsyne, ocyne, nonyne, decyne, undecyne, dodecyne, and pentadecyne. Examples of cycloalkanes include cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, and cyclodecane. Examples of cycloalkenes include cyclopentene, cyclohexene, methylcyclohexene, cycloheptene, cyclooctene, cyclononene, and cyclohexadiene. Among the above examples, structural isomers that are not liquid at 20°C and 1 atmosphere are excluded from the above aliphatic hydrocarbons.

[0042] The aliphatic hydrocarbon is preferably a chain aliphatic hydrocarbon, and is also preferably a saturated hydrocarbon (alkane or cycloalkane). The chain aliphatic hydrocarbon may be a linear aliphatic hydrocarbon or a branched aliphatic hydrocarbon. The aliphatic hydrocarbon is more preferably a chain saturated hydrocarbon (alkane). Particularly preferred alkanes include alkanes having 8 to 14 carbon atoms, such as octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane. Among these, from the viewpoint of drying efficiency after coating a slurry using such aliphatic hydrocarbons, alkanes having 8 to 12 carbon atoms are more preferred, and from the viewpoint of stability of the fluidity of the slurry, alkanes having 9 to 14 carbon atoms are also more preferred.

[0043] The content of the aliphatic hydrocarbon in layer (X) may be, for example, 0.0001% by mass or more and 1% by mass or less. The upper limit of the content may be 0.1%, 0.01%, or 0.001% by mass. The lower limit of the content may be 0.001% by mass.

[0044] Layer (X) preferably does not substantially contain components (other liquid components) that are liquid at 20°C and 1 atmosphere other than the aliphatic hydrocarbons. The content of the other liquid components in layer (X) is preferably 1 / 5 or less, more preferably 1 / 10 or less, and even more preferably 1 / 100 or less of the content of the aliphatic hydrocarbons, on a mass basis.

[0045] Layer (X) may contain a solid electrolyte other than a hydride-based lithium ion conductor. A solid electrolyte refers to an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. Examples of solid electrolytes other than hydride-based lithium ion conductors include sulfide solid electrolytes, oxide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes, with sulfide solid electrolytes being preferred. The solid electrolyte may be a crystalline solid electrolyte or an amorphous (glassy) solid electrolyte. A crystalline solid electrolyte refers to a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern. An amorphous solid electrolyte refers to a solid electrolyte in which substantially no peaks other than those derived from the raw materials are observed in the X-ray diffraction pattern, and a halo pattern is observed. One or more solid electrolytes other than hydride-based lithium ion conductors may be used.

[0046] The sulfide solid electrolyte preferably contains at least sulfur element and further contains lithium element. The sulfide solid electrolyte preferably has lithium ion conductivity. The sulfide solid electrolyte preferably also contains phosphorus element and preferably further contains a halogen element. The sulfide solid electrolyte preferably contains at least one of bromine element and iodine element as the halogen element.

[0047] When the sulfide solid electrolyte is a crystalline solid electrolyte, its crystal structure may be an argyrodite crystal structure, a Li3PS4 crystal structure, a Li4P2S6 crystal structure, or a Li7P3S 11 Crystal structure, Li 10 GeP2S 12Examples of sulfide solid electrolytes include sulfide solid electrolytes having crystalline structures such as a crystalline structure, a Thio-LISICON type crystalline structure, an inverse fluorite type crystalline structure, a crystalline structure (High Ion Conduction Phase: HICP) having diffraction peaks in the ranges of diffraction angle 2θ of 19.9° ± 0.5° and 29.3° ± 0.5° in an X-ray diffraction pattern using CuKα rays, a crystalline structure (Low Ion Conduction Phase: LICP) having diffraction peaks in the ranges of diffraction angle 2θ of 21.0 ± 0.5° and 28.0 ± 0.5° in an X-ray diffraction pattern using CuKα rays, and a crystalline structure having different diffraction peaks in the ranges of diffraction angle 2θ of 17.9° ± 0.5° or 19.1° ± 0.5°, a diffraction angle 2θ of 29.1° ± 0.5°, and a diffraction angle 2θ of 29.8° ± 0.5°, wherein any of these diffraction peaks is the largest diffraction peak.

[0048] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S 2n (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.) Li 10 GeP2S 12 etc.

[0049] The content of the sulfide solid electrolyte in layer (X) varies depending on, for example, whether layer (X) is a positive electrode active material layer, a negative electrode active material layer, or a separator layer. The lower limit of the content of the sulfide solid electrolyte in layer (X) may be 1 mass%, or may be 3 mass%, 5 mass%, 10 mass%, 20 mass%, 30 mass%, 40 mass%, 50 mass%, 60 mass%, or 70 mass%. The upper limit of the content may be 90 mass%, 80 mass%, 70 mass%, 60 mass%, 50 mass%, 40 mass%, 30 mass%, or 20 mass%.

[0050] The mass ratio of the hydride-based lithium ion conductor to the sulfide solid electrolyte in layer (X) (hydride-based lithium ion conductor:sulfide solid electrolyte) may be within a range of 1:99 to 90:10, 3:97 to 70:30, 5:95 to 60:40, 10:90 to 50:50, or 15:85 to 40:60.

[0051] The content of all solid electrolytes (hydride-based lithium ion conductors and other solid electrolytes) in layer (X) also varies depending on, for example, whether layer (X) is a positive electrode active material layer, a negative electrode active material layer, or a separator layer. The lower limit of the content of all solid electrolytes in layer (X) may be 1 mass%, or may be 5 mass%, 10 mass%, 15 mass%, 20 mass%, 30 mass%, 40 mass%, 50 mass%, 60 mass%, 70 mass%, 80 mass%, 90 mass%, or 95 mass%. The upper limit of the content may be 99 mass%, 95 mass%, 90 mass%, 80 mass%, 70 mass%, 60 mass%, 50 mass%, 40 mass%, 30 mass%, or 20 mass%.

[0052] The hydride-based lithium ion conductor and the sulfide solid electrolyte may form a composite. When the hydride-based lithium ion conductor and the sulfide solid electrolyte exist as a composite, there are advantages such as good ionic conductivity despite a relatively low density. The composite of the hydride-based lithium ion conductor and the sulfide solid electrolyte may have an argyrodite-type crystal structure.

[0053] The composite of the hydride-based lithium ion conductor and the sulfide solid electrolyte can be obtained by a known method, for example, by subjecting a mixture of the hydride-based lithium ion conductor and the sulfide solid electrolyte to mechanochemical treatment using a ball mill or the like.

[0054] The layer (X) may further contain other components in addition to the solid electrolyte (hydride-based lithium ion conductor and other solid electrolytes), binder, and aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. Examples of other components include those described below for the positive electrode active material layer, negative electrode active material layer, and separator layer.

[0055] When the layer (X) is, for example, a positive electrode active material layer or a negative electrode active material layer, it may contain a positive electrode active material or a negative electrode active material (hereinafter, the positive electrode active material and the negative electrode active material are also collectively referred to as "active material"). When the layer (X) is, for example, an isolation layer, it may not contain an active material. When the layer (X) contains an active material, the lower limit of the content of the active material in the layer (X) is preferably 50 mass%, and may be 60 mass%, 70 mass%, 80 mass%, or 90 mass%. The upper limit of the content of the active material in the layer (X) may be 99 mass%, 98 mass%, or 95 mass%. The lower limit of the total content of all solid electrolytes (hydride-based lithium ion conductors and other solid electrolytes), binder, and active material in the layer (X) is preferably 60 mass%, and may be 70 mass%, 80 mass%, 90 mass%, or 95 mass%. The upper limit of the total content of all solid electrolytes, binders and active materials in layer (X) may be 99.99 mass %, 99.9 mass %, 99 mass % or 95 mass %.

[0056] The layer (X) may contain, for example, a conductive agent. The layer (X) may not contain a conductive agent. When the layer (X) contains a conductive agent, the content of the conductive agent in the layer (X) may be 0.1% by mass or more and 10% by mass or less, 1% by mass or more and 9% by mass or less, or 3% by mass or more and 8% by mass or less. The content of the conductive agent in the layer (X) may be 5% by mass or less, or 2% by mass or less.

[0057] The layer (X) can be formed by applying and drying a slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. Details of the method for forming the layer (X) will be described later as one of the steps in the method for producing an all-solid-state energy storage element.

[0058] (positive electrode) As described above, the positive electrode has a positive electrode substrate and a positive electrode active material layer laminated on the positive electrode substrate directly or via an intermediate layer. Usually, the positive electrode has a portion where the positive electrode substrate is exposed. This exposed portion of the positive electrode substrate is usually connected to the above-mentioned positive electrode lead. The positive electrode may have a shape such as a sheet, plate, or strip.

[0059] The thickness of the positive electrode is appropriately set depending on the application of the all-solid-state energy storage element. The average thickness of the positive electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the positive electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the positive electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the positive electrode is the average thickness of the portion where the positive electrode active material layer is laminated on the positive electrode substrate directly or via an intermediate layer. In the case where the positive electrode substrate has both a portion where the positive electrode active material layer is laminated on both sides and a portion where the positive electrode active material layer is laminated on only one side, the average thickness of the portion where the positive electrode active material layer is laminated on both sides of the positive electrode substrate is referred to. In addition, in this specification, "average thickness" means the average value of thicknesses measured at any five positions.

[0060] The positive electrode substrate has electrical conductivity. In this specification, "having electrical conductivity" means that the volume resistivity is 10 -2 The volume resistivity is a value measured in accordance with JIS-H-0505 (1975). On the other hand, in this specification, "not having electrical conductivity" or "having (electrical) insulation" means that the volume resistivity is 10 7 This means that the resistance is Ω·cm or more.

[0061] Examples of materials for the positive electrode substrate include metals such as aluminum, titanium, iron, and alloys thereof (stainless steel, etc.). Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high electronic conductivity, and cost.

[0062] The positive electrode substrate has a shape such as a sheet, plate, or strip. Examples of the positive electrode substrate include foil, vapor-deposited film, mesh, and porous material, and foil is preferred. The positive electrode substrate may be, for example, aluminum foil or aluminum alloy foil.

[0063] The average thickness of the positive electrode substrate may be, for example, 3 μm or more and 50 μm or less. The lower limit of the average thickness of the positive electrode substrate may be 5 μm, 8 μm, 10 μm, or 15 μm. The upper limit of the average thickness of the positive electrode substrate may be 40 μm, 30 μm, 20 μm, or 15 μm.

[0064] The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer contains, for example, a conductive agent and a binder. When the intermediate layer contains a conductive agent, the contact resistance between the positive electrode substrate and the positive electrode active material layer can be reduced. Examples of the conductive agent and binder used in the intermediate layer include the same conductive agent and binder used in the positive electrode active material layer described below.

[0065] The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer contains optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler as needed. The positive electrode active material layer may be formed from a positive electrode mixture containing a positive electrode active material and other optional components. As in the all-solid-state energy storage element 1 of FIG. 1, the positive electrode active material layer may be provided on only one side of a positive electrode substrate having a shape such as a sheet. In another embodiment, the positive electrode active material layer may be provided on each side of the positive electrode substrate.

[0066] Known positive electrode active materials can be used for the positive electrode active material. Materials capable of absorbing and releasing lithium ions are typically used for the positive electrode active material of lithium ion secondary batteries. Examples of positive electrode active materials include lithium transition metal composite oxides, polyanion compounds, chalcogen compounds, sulfur-based materials, and lithium oxide. One or more positive electrode active materials can be used.

[0067] Examples of the transition metal elements contained in the lithium transition metal composite oxide include nickel element, cobalt element, manganese element and the like. The lithium transition metal composite oxide may contain a typical metal element such as aluminum element. Examples of the lithium transition metal composite oxide include a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure, a lithium transition metal composite oxide having a spinel type crystal structure and the like.

[0068] Examples of the lithium transition metal composite oxide having an α-NaFeO2 type crystal structure include those represented by Li 1+α Ma 1-α O2 (Ma is a metal element other than lithium element, including one or more kinds of transition metal elements. 0 ≦ α < 1.). Ma preferably contains one or more of Ni, Co and Mn. The total content of Ni, Co and Mn with respect to Ma ((Ni + Co + Mn) / Ma) is preferably 90 mol% or more, more preferably 98 mol% or more.

[0069] Examples of the lithium transition metal composite oxide having a spinel type crystal structure include those represented by Li β Mb2O4 (Mb is a metal element other than lithium element, including one or more kinds of transition metal elements. 0 < β ≦ 1.2.). Mb preferably contains Mn. The content of Mn with respect to Mb (Mn / Mb) is preferably 50 mol% or more, more preferably 80 mol% or more.

[0070] The polyanion compound is a compound composed of a polyanion (that is, a polyvalent oxoacid anion) and a cation. The polyanion compound preferably contains a lithium cation and a transition metal cation as the cation. Examples of the polyanion compound include LiFePO4, LiMnPO4, LiMn x Fe 1-x PO4 (0 < x < 1), LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F and the like. The surface of the particles of the polyanion compound may be coated with another material (such as a carbon material etc.).

[0071] Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and molybdenum dioxide.

[0072] Examples of sulfur-based materials include elemental sulfur, metal sulfides such as lithium sulfide, organic disulfide compounds, and organic sulfur compounds such as carbon sulfide compounds.

[0073] The atoms or polyanions in these materials serving as the positive electrode active material may be partially substituted with atoms or anion species of other elements, and the surfaces of these materials may be coated with other materials.

[0074] The positive electrode active material is usually particulate. The average particle size of the positive electrode active material is preferably, for example, 0.1 μm to 20 μm. Setting the average particle size of the positive electrode active material above the lower limit facilitates the production and handling of the positive electrode active material. Setting the average particle size of the positive electrode active material below the upper limit improves the electronic conductivity of the positive electrode active material layer. When a composite of the positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The term "average particle size" refers to the value at which the volume-based cumulative distribution (D50) reaches 50% as calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by laser diffraction / scattering in a diluted solution of particles diluted with a solvent in accordance with JIS-Z-8825 (2013). Methods for obtaining particles of the positive electrode active material and the negative electrode active material described below with a predetermined particle size can be known, for example, using a pulverizer or classifier.

[0075] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass to 99% by mass, more preferably 70% by mass to 98% by mass, and may be 80% by mass to 95% by mass. By setting the content of the positive electrode active material within this range, both high energy density and manufacturability of the positive electrode active material layer can be achieved.

[0076] The solid electrolyte used in the positive electrode active material layer may be the solid electrolyte exemplified in the description of the layer (X). The solid electrolyte used in the positive electrode active material layer may be a hydride-based lithium ion conductor. The solid electrolyte used in the positive electrode active material layer is preferably a sulfide solid electrolyte.

[0077] In the positive electrode active material layer, the solid electrolyte may form a complex with the positive electrode active material, and such a complex may further contain other components (e.g., a conductive agent) in addition to the solid electrolyte and the positive electrode active material.

[0078] When the positive electrode active material layer contains a solid electrolyte, the content of the solid electrolyte in the positive electrode active material layer is preferably 5% by mass or more and 50% by mass or less, and may be 10% by mass or more and 40% by mass or less, or may be 15% by mass or more and 30% by mass or less.

[0079] Conductive agents are usually components made of materials that have electrical conductivity. Even if the volume resistivity of a conductive agent cannot be measured directly, it is possible to measure the volume resistivity by measuring the volume resistivity of the conductive agent when the volume resistivity is 10 -2Conductive agents are materials known to have a resistivity of Ω·cm or less. Examples of conductive agents include carbon materials, metals, and conductive ceramics. Carbon materials are materials whose primary constituent element is carbon. The primary constituent element refers to the element with the highest content by mass. For example, the carbon content in a carbon material may be 80% by mass or more, 90% by mass or more, 95% by mass, 99% by mass, or 99.9% by mass or more. The carbon material is preferably a carbon material other than an uncarbonized polymer compound. Examples of carbon materials include graphite, non-graphitic carbon, and graphene-based carbon. Examples of non-graphitic carbon include carbon nanofiber, pitch-based carbon fiber, and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), and fullerene. Conductive agents may be in the form of powder, fiber, or the like. The conductive agent may be one or more kinds. The conductive agent may be a composite of these materials. For example, a composite material of carbon black and CNT may be used.

[0080] The content of the conductive agent in the positive electrode active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 9% by mass, and even more preferably 3% by mass to 8% by mass. The upper limit of the content of the conductive agent may be 5%, 4%, or 3% by mass. By setting the content of the conductive agent within the above range, it is possible to increase the energy density of the all-solid-state energy storage element.

[0081] Examples of the binder include a water-based binder and an organic solvent-based binder.

[0082] The aqueous binder is a binder that dissolves or disperses in water. The aqueous binder may be a binder that dissolves or disperses at 1 part by mass or more in 100 parts by mass of water at 20°C. When a positive electrode active material layer is formed using a positive electrode mixture paste whose dispersion medium is water or a mixed solvent mainly composed of water, an aqueous binder (a water-soluble or water-dispersible polymer material) can be used. Examples of aqueous binders include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polytetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene, nitrile-butadiene rubber, and cellulose.

[0083] The organic solvent-based binder is a binder that dissolves or disperses in an organic solvent (e.g., N-methylpyrrolidone). The organic solvent-based binder may be a binder that dissolves or disperses at 1 part by mass or more in 100 parts by mass of N-methylpyrrolidone at 20°C. When a positive electrode active material layer is formed using a positive electrode mixture paste whose dispersion medium is an organic solvent or a mixed solvent mainly containing an organic solvent, an organic solvent-based binder (a polymer material that is soluble or dispersible in an organic solvent) can be used. Examples of organic solvent-based binders include polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, polysiloxane, polyvinyl acetate, polymethyl methacrylate, polystyrene, polycarbonate, polyamide, polyimide, polyamideimide, crosslinked polymers of cellulose and chitosan pyrrolidone carboxylate, chitosan derivatives, and the like.

[0084] The binder may be a fluororesin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), a polyolefin (polyethylene, polypropylene, etc.), an elastomer (ethylene propylene diene rubber, styrene butadiene rubber, fluororubber, etc.), a polysaccharide polymer (cellulose, chitosan derivatives, etc.), etc. One or more types of binders may be used.

[0085] The content of the binder in the positive electrode active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 9% by mass, and more preferably 3% by mass to 8% by mass. The upper limit of the binder content may be 5%, 4%, or 3% by mass. By setting the binder content within the above range, it is possible to stably hold the positive electrode active material. The technology disclosed herein can also be implemented in an embodiment in which the positive electrode active material layer does not contain a binder.

[0086] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be deactivated in advance by methylation or the like. The thickener may also function as a binder. One or more types of thickeners may be used. When the positive electrode active material layer contains a thickener, the content of the thickener in the positive electrode active material layer is preferably 0.1% by mass or more and 8% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the positive electrode active material layer does not contain a thickener.

[0087] The filler is not particularly limited. The filler in the positive electrode active material layer may be a component other than the positive electrode active material, solid electrolyte, conductive agent, binder, and thickener, and may be a solid component intentionally added. The filler may be added as a component to fill gaps in the positive electrode active material layer, or may be added for other purposes. The filler may be an organic substance such as polyolefin, or an inorganic substance such as an inorganic oxide, hydroxide, or carbonate. One or more fillers may be used. When the positive electrode active material layer contains a filler, the content of the filler in the positive electrode active material layer may be 0.1% by mass or more and 8% by mass or less, usually preferably 5% by mass or less, and more preferably 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the positive electrode active material layer does not contain a filler.

[0088] The positive electrode active material layer may further contain other components in addition to the positive electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler. The other components include those unintentionally present in the positive electrode active material layer. The positive electrode active material layer may also contain unintentionally contained impurities as the other components, as long as the effects of the present invention are achieved. The upper limit of the content of the other components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally contained components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally contained impurities in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0089] The positive electrode active material layer may be layer (X) as described above. When the positive electrode active material layer is layer (X), the specific and preferred forms of the hydride-based lithium ion conductor, binder, aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere, and the like contained therein are the same as those described for each component contained in layer (X).

[0090] The thickness of the positive electrode active material layer is appropriately set depending on the type of positive electrode active material, the application of the all-solid-state energy storage device, and the like. The average thickness of one positive electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one positive electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one positive electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one positive electrode active material layer is, for example, 4 mg / cm. 2 More than 100mg / cm 2 The lower limit of the mass per unit area of ​​one positive electrode active material layer may be 6 mg / cm or less. 2 , 8 mg / cm 2 or 10 mg / cm 2The upper limit of the mass per unit area of ​​one positive electrode active material layer is 50 mg / cm. 2 , 20 mg / cm 2 , 15 mg / cm 2 , 12 mg / cm 2 or 10 mg / cm 2 may be.

[0091] (Negative electrode) As described above, the negative electrode has a negative electrode substrate and a negative electrode active material layer laminated on the negative electrode substrate directly or via an intermediate layer. Usually, the negative electrode has a portion where the negative electrode substrate is exposed. This exposed portion of the negative electrode substrate is usually connected to the above-mentioned negative electrode lead. The negative electrode may have a shape such as a sheet, plate, or strip.

[0092] The thickness of the negative electrode is appropriately set depending on the application of the all-solid-state energy storage element, etc. The average thickness of the negative electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the negative electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the negative electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the negative electrode is the average thickness of a portion where the negative electrode active material layer is laminated on the negative electrode substrate directly or via an intermediate layer. When the negative electrode substrate has both a portion where the negative electrode active material layer is laminated on both sides and a portion where the negative electrode active material layer is laminated on only one side, the average thickness of the portion where the negative electrode active material layer is laminated on both sides of the negative electrode substrate is used.

[0093] The negative electrode substrate is conductive. Examples of materials for the negative electrode substrate include metals such as copper, nickel, iron, and alloys thereof (such as stainless steel), and carbon materials. Among these, copper or copper alloys are preferred.

[0094] The negative electrode substrate has a shape such as a sheet, plate, or strip. Examples of the form of the negative electrode substrate include foil, vapor-deposited film, mesh, and porous material, and foil is preferred. The negative electrode substrate may be, for example, copper foil or copper alloy foil.

[0095] The average thickness of the negative electrode substrate may be, for example, 2 μm or more and 35 μm or less. The lower limit of the average thickness of the negative electrode substrate may be 3 μm, 4 μm, 5 μm, or 10 μm. The upper limit of the average thickness of the negative electrode substrate may be 30 μm, 20 μm, 15 μm, or 10 μm.

[0096] The structure of the intermediate layer of the negative electrode is not particularly limited, and can be selected from the structures exemplified for the intermediate layer of the positive electrode, for example.

[0097] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may contain optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler, as necessary. The optional components such as the solid electrolyte, the conductive agent, the binder, the thickener, and the filler may be selected from the materials exemplified for the positive electrode above. The negative electrode active material layer may be formed from a negative electrode mixture containing a negative electrode active material and other optional components. As in the all-solid-state energy storage element 1 of FIG. 1, the negative electrode active material layer may be provided on only one side of a negative electrode substrate having a shape such as a sheet. In another embodiment, the negative electrode active material layer may be provided on both sides of the negative electrode substrate.

[0098] The negative electrode active material can be a known negative electrode active material. A material capable of absorbing and releasing lithium ions is typically used as the negative electrode active material for lithium ion secondary batteries. Examples of the negative electrode active material include metallic lithium; metals or semimetals such as silicon and tin; metal oxides or semimetal oxides such as silicon oxide, titanium oxide, and tin oxide; and Li4Ti5O. 12 , LiTiO 2、 Examples of the negative electrode active material include titanium-containing oxides such as TiNbO; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon. The surface of the graphite may be coated with other materials such as non-graphitic carbon. One or more negative electrode active materials may be used.

[0099] "Graphite" refers to a graphite material that has an average lattice spacing (d 002) is a carbon material with a particle size of 0.33 nm or more and less than 0.34 nm. Graphite includes natural graphite and artificial graphite.

[0100] "Non-graphitic carbon" refers to carbon that has an average lattice spacing (d 002 ) refers to a carbon material in which the particle size is 0.34 nm or more and 0.42 nm or less. Non-graphitizable carbon includes non-graphitizable carbon and graphitizable carbon. "Non-graphitizable carbon" refers to a carbon material in which the particle size is 0.34 nm or more and 0.42 nm or less. 002 The term "easily graphitizable carbon" refers to a carbon material having a particle size of 0.36 nm or more and 0.42 nm or less. 002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0101] Here, the "discharged state" of a carbon material refers to a state in which the carbon material, which is a negative electrode active material, is discharged so that lithium ions that can be absorbed and released during charging and discharging are sufficiently released from the carbon material. For example, this refers to a state in which the open circuit voltage of a half cell using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and metallic lithium as a counter electrode is 0.7 V or higher.

[0102] The negative electrode active material may be in a particulate form. The average particle size of the negative electrode active material may be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, a polyphosphate compound, or the like, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the production or handling of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electronic conductivity of the negative electrode active material layer is improved.

[0103] The content of the negative electrode active material in the negative electrode active material layer is, for example, preferably 60% by mass to 99% by mass, more preferably 90% by mass to 98% by mass. By setting the content of the negative electrode active material within this range, both high energy density and manufacturability of the negative electrode active material layer can be achieved.

[0104] When the negative electrode active material is a metal such as metallic lithium, the negative electrode active material layer may be in the form of a foil. The metallic lithium may exist as pure metallic lithium consisting essentially of elemental lithium, or may exist as a lithium alloy containing other metal elements. When the negative electrode active material is a metal such as metallic lithium, the content of elemental lithium in the negative electrode active material layer may be 90% by mass or more, 99% by mass or more, or even 100% by mass.

[0105] When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. The content of the conductive agent in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a conductive agent.

[0106] Examples of the solid electrolyte used in the negative electrode active material layer include the solid electrolytes exemplified in the description of layer (X). The solid electrolyte used in the negative electrode active material layer may be a hydride-based lithium ion conductor.

[0107] When the negative electrode active material layer contains a solid electrolyte, the content of the solid electrolyte is preferably 5% by mass or more and 90% by mass or less, and may be 10% by mass or more and 70% by mass or less, or may be 20% by mass or more and 50% by mass or less.

[0108] When the negative electrode active material layer contains a binder, the content of the binder in the negative electrode active material layer is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 8% by mass. The content of the binder in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a binder.

[0109] When the negative electrode active material layer contains a thickener, the content of the thickener in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The content of the thickener in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a thickener.

[0110] The filler in the negative electrode active material layer may be a component other than the negative electrode active material, solid electrolyte, conductive agent, binder, and thickener, and may be a solid component intentionally added. The filler may be added as a component to fill gaps in the negative electrode active material layer, or may be added for other purposes. When the negative electrode active material layer contains a filler, the content of the filler in the negative electrode active material layer can be 0.1% by mass or more and 8% by mass or less, and typically 5% by mass or less is preferred, and 2% by mass or less is more preferred. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a filler.

[0111] The negative electrode active material layer may further contain components other than the negative electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler. These other components include those unintentionally present in the negative electrode active material layer. The negative electrode active material layer may also contain unintentionally present impurities as the other components, as long as the effects of the present invention are achieved. The upper limit of the content of the other components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally present components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally present impurities in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0112] The negative electrode active material layer may be layer (X) as described above. When the negative electrode active material layer is layer (X), the specific and preferred forms of the hydride-based lithium ion conductor, binder, aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere, and the like contained therein are the same as those described for each component contained in layer (X).

[0113] The thickness of the negative electrode active material layer is appropriately set depending on the type of negative electrode active material, the application of the all-solid-state energy storage element, and the like. The average thickness of one negative electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one negative electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one negative electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one negative electrode active material layer is, for example, 2 mg / cm. 2 More than 50mg / cm 2 The lower limit of the mass per unit area of ​​one negative electrode active material layer may be 3 mg / cm or less. 2 , 4 mg / cm 2 , 5 mg / cm 2 or 6 mg / cm 2 The upper limit of the mass per unit area of ​​one negative electrode active material layer is 30 mg / cm. 2 , 20 mg / cm 2 , 15 mg / cm 2 , 12 mg / cm 2 or 10 mg / cm 2 may be.

[0114] (isolation layer) The separator layer usually contains a solid electrolyte. The content of the solid electrolyte in the separator layer is preferably 70% by mass or more and 100% by mass or less. The content of the solid electrolyte in the separator layer may be 90% by mass or more, 99% by mass or more, or 100% by mass.

[0115] The separator layer may contain optional components such as additives (e.g., phosphate compounds such as LiPO, oxides, and halogen compounds), binders, thickeners, fillers, etc. The optional components such as binders, thickeners, and fillers can be selected from the materials exemplified for the positive electrode active material layer.

[0116] The separator layer may be the layer (X) as described above. When the separator layer is the layer (X), the specific and preferred forms of the hydride-based lithium ion conductor, binder, aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere, and the like contained therein are the same as those described for each component contained in the layer (X).

[0117] The average thickness of the separator layer is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 50 μm or less, and even more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the separator layer to the above lower limit or more, it is possible to insulate the positive electrode and the negative electrode with high reliability. By setting the average thickness of the separator layer to the above upper limit or less, it is possible to increase the energy density of the all-solid-state energy storage element.

[0118] (container) The container accommodates the positive electrode, the negative electrode, etc. in its internal space. Metallic materials such as aluminum and stainless steel, resinous materials, etc. are used as the container material, and metallic materials are preferred from the viewpoint of strength, etc. Composite materials of metallic materials and resinous materials, etc. may also be used.

[0119] The shape of the container is not particularly limited, and may be cylindrical, rectangular (square), disk-like, etc. The container may also be in the shape of a sheet formed from a metal resin composite film.

[0120] (shape, use, etc. of all-solid-state energy storage element) The shape of the all-solid-state energy storage element according to one embodiment of the present invention is not particularly limited, and may be, for example, a cylindrical battery, a prismatic battery, a flat battery, a coin battery, a button battery, or the like.

[0121] The use of the all-solid-state energy storage element according to one embodiment of the present invention is not particularly limited, and the all-solid-state energy storage element can be used, for example, as a power source for automobiles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, a power source for electronic devices such as personal computers and communication terminals, a power source for power storage, etc.

[0122] The all-solid-state energy storage element of the present invention may be used singly or in plural. When the required output and the required voltage are small, the all-solid-state energy storage element may be used singly. On the other hand, when at least one of the required output and the required voltage is large, the all-solid-state energy storage element may be used as an energy storage device in combination with other all-solid-state energy storage elements. In an energy storage device in which a plurality of all-solid-state energy storage elements are combined, at least one of the all-solid-state energy storage elements included in the energy storage device may be an all-solid-state energy storage element according to one embodiment of the present invention. The energy storage device will be described in detail later.

[0123] In an all-solid-state energy storage element according to one embodiment of the present invention, for example, the container may be constrained so as to maintain a constant thickness, or may not be constrained in this way. Furthermore, the container may be constrained so as to apply a constant load to it. When the container is constrained, expansion of the container due to charge / discharge cycles or the like is suppressed, and deterioration of charge / discharge performance may be suppressed. When the container is constrained, a load may or may not be applied to the positive electrode and negative electrode in the container. For example, a constraining member that performs such constraining may be provided in the all-solid-state energy storage element or the energy storage device.

[0124] <Method of manufacturing all-solid-state energy storage element> A method for producing an all-solid-state energy storage element according to one embodiment of the present invention comprises forming a layer using a slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere. Specifically, the layer (X) is formed by applying and drying the slurry. One embodiment of the present invention may be a slurry (slurry for producing an all-solid-state energy storage element) that contains a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere.

[0125] The slurry contains other components constituting layer (X) as necessary. Preferably, the slurry does not substantially contain components (other liquid components) that are liquid at 20°C and 1 atmosphere other than the aliphatic hydrocarbons. The content of the other liquid components in the slurry is preferably 1 / 5 or less, more preferably 1 / 10 or less, and even more preferably 1 / 100 or less of the content of the aliphatic hydrocarbons, on a mass basis.

[0126] The lower limit of the solid content ratio of the slurry is preferably 30% by mass, more preferably 40% by mass, and even more preferably 50% by mass. By setting the solid content ratio at or above the lower limit, it is possible to improve the drying efficiency of the slurry after coating. On the other hand, the upper limit of the solid content ratio is preferably 80% by mass, more preferably 70% by mass, and even more preferably 60% by mass. By setting the solid content ratio at or below the upper limit, it is possible to improve the fluidity of the slurry.

[0127] The drying conditions after coating the slurry are not particularly limited. The drying temperature is adjusted appropriately depending on the boiling point of the solvent (aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere), and may be, for example, 80°C to 250°C, or 100°C to 200°C. The drying time may be, for example, 5 minutes to 120 minutes, or 10 minutes to 60 minutes.

[0128] When the positive electrode active material layer, the negative electrode active material layer, or the separator layer is layer (X), the positive electrode active material layer, the negative electrode active material layer, or the separator layer can be provided by the above-mentioned method. For example, the positive electrode active material layer can be formed as layer (X) by applying the above-mentioned slurry to a positive electrode substrate and drying it. The negative electrode active material layer can be formed as layer (X) by applying the above-mentioned slurry to a negative electrode substrate and drying it. Furthermore, the separator layer can be formed as layer (X) by applying the above-mentioned slurry to a positive electrode active material layer or a negative electrode active material layer and drying it.

[0129] When the positive electrode active material layer, the negative electrode active material layer, or the separator layer is not layer (X), these layers can be formed by a conventional method. These layers can be formed, for example, by pressure molding a solid material containing the components contained in each layer, or by coating and drying a slurry containing the components contained in each layer. When a metal such as metallic lithium is used as the negative electrode active material, a metal foil can be used as the negative electrode active material layer.

[0130] <Electricity storage device> 2 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of electrically connected all-solid-state power storage elements 1. The power storage device 30 may include a bus bar (not shown) that electrically connects the plurality of all-solid-state power storage elements 1, a bus bar (not shown) that electrically connects the plurality of power storage units 20, etc. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more all-solid-state power storage elements 1.

[0131] <Other embodiments> The all-solid-state energy storage element and its manufacturing method of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0132] In the above embodiment, the all-solid-state energy storage element is used as a chargeable and dischargeable all-solid-state secondary battery, but the all-solid-state energy storage element may be of any type, shape, size, capacity, etc. The present invention can also be applied to various secondary batteries, electric double layer capacitors, lithium ion capacitors, and other capacitors.

[0133] For example, the all-solid-state energy storage element according to the present invention may include layers other than the positive electrode, the separator, and the negative electrode. The present invention can also be applied to an all-solid-state energy storage element including a bipolar electrode.

[0134] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0135] [Example 1] (Preparation of the complex) The hydride-based lithium ion conductor LiBH4 and the glassy sulfide solid electrolyte 0.75Li2S-0.25P2S5 (composition formula Li3PS4:LPS) were mixed in a molar ratio of 75:25 (approximately 27:73 by mass). 0.5 g of this mixture was placed in a sealed 80 mL zirconia pot containing 125 g of 4 mm diameter zirconia balls. This process was carried out in an argon atmosphere with a dew point below -50°C. The mixture was then rotated intermittently multiple times in a planetary ball mill (FRITSCH, Model No. Premium Line PL-7). This mechanochemical process yielded a composite of LiBH4 and LPS (LiBH4-LPS).

[0136] (Preparation of paste) Styrene butadiene rubber (SBR) as a binder was dissolved in decane as a solvent to prepare a binder solution with a concentration of 10 mass %. The prepared binder solution was added to the produced composite (LiBH4-LPS) and kneaded in a planetary centrifugal mixer. The binder solution was added so that the mass ratio of the solid content of the composite (LiBH4-LPS) to the binder was 95.0:5.0. Decane, a solvent, was further added to the obtained kneaded product, and the mixture was further kneaded in a planetary centrifugal mixer. The addition of the solvent and kneading were repeated to obtain a slurry with a solid content ratio of 58 mass%. The obtained slurry of Example 1 had sufficient fluidity.

[0137] [Example 2] A slurry with a solid content of 58 mass % was obtained in the same manner as in Example 1, except that tetradecane was used as the solvent instead of decane. The obtained slurry of Example 2 had sufficient fluidity.

[0138] [Example 3] A slurry with a solid content of 51% by mass was obtained in the same manner as in Example 1, except that cyclooctane was used as the solvent instead of decane. The obtained slurry of Example 3 had sufficient fluidity. However, the slurries of Examples 1 and 2 had better fluidity.

[0139] [Example 4] A slurry with a solid content of 58% by mass was obtained in the same manner as in Example 1, except that heptane was used instead of decane as the solvent. The obtained slurry of Example 4 had sufficient fluidity. However, since the boiling point of heptane is lower than that of decane and tetradecane and the solvent volatilizes quickly when left standing, it was suggested that the slurries of Examples 1 and 2 were superior in terms of subsequent workability.

[0140] [Comparative Example 1] An attempt was made to prepare a slurry for Comparative Example 1 in the same manner as in Example 1, except that butyl butyrate was used as the solvent instead of decane. Adding the binder solution to the composite (LiBH4-LPS) caused smoke to be emitted, and even when the solid content was reduced to 41 mass% by adding a solvent, a fluid slurry could not be obtained.

[0141] Comparative Example 2 An attempt was made to prepare a slurry for Comparative Example 2 in the same manner as in Example 1, except that anisole was used as the solvent instead of decane, but a fluid slurry could not be obtained.

[0142] Comparative Example 3 An attempt was made to prepare a slurry for Comparative Example 3 in the same manner as in Example 1, except that xylene was used as the solvent instead of decane, but a fluid slurry could not be obtained.

[0143] The above results are summarized in Table 1 below.

[0144] [Table 1]

[0145] In Comparative Example 1, it is believed that LiBH4 reacted with the ester group of butyl butyrate, which prevented the formation of a good slurry with good fluidity. In Comparative Examples 2 and 3, it is believed that LiBH4 dissolved in anisole or xylene, which prevented the formation of a good slurry with good fluidity. In Examples 1 to 4, it is believed that good slurries with good fluidity were obtained because the reactivity of LiBH4 with decane, tetradecane, cyclooctane, or heptane was low and the solubility of LiBH4 in decane, tetradecane, cyclooctane, or heptane was low. However, the slurries of Examples 1 and 2 had better fluidity than the slurry of Example 3, suggesting that they were superior in subsequent workability to the slurry of Example 4. [Industrial Applicability]

[0146] The present invention is applicable to all-solid-state energy storage elements used as power sources for electronic devices such as personal computers and communication terminals, automobiles, etc., and methods for manufacturing the same. [Explanation of symbols]

[0147] 1. All-solid-state energy storage element 2 Positive electrode 3 negative electrode 4 isolation layer 5. Positive electrode substrate 6 Cathode active material layer 7. Negative electrode substrate 8 Negative electrode active material layer 20 Energy storage unit 30 Energy storage device

Claims

1. An all-solid-state energy storage element comprising a layer containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere.

2. The all-solid-state energy storage element according to claim 1 , wherein the layer further comprises a sulfide solid electrolyte.

3. 3. The all-solid-state energy storage element according to claim 1, wherein the aliphatic hydrocarbon is a chain saturated hydrocarbon.

4. 3. The all-solid-state electricity storage element according to claim 1, wherein the aliphatic hydrocarbon has a boiling point of 160°C or higher at 1 atmospheric pressure.

5. 3. The all-solid-state energy storage element according to claim 1, wherein the hydride-based lithium ion conductor comprises lithium borohydride.

6. A method for manufacturing an all-solid-state energy storage element, comprising forming a layer using a slurry containing a hydride-based lithium ion conductor, a binder, and an aliphatic hydrocarbon that is liquid at 20°C and 1 atmosphere.

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