Solid electrolyte-electrode assembly, method for producing same, solid electrolyte, method for producing active material, and solid electrolyte battery

Abstract

The present invention addresses the problem of providing a method for producing a solid electrolyte-electrode assembly capable of reducing interface resistance by making it unlikely for a gap to exist at the interface between a solid electrolyte and an electrode.　This method for producing a solid electrolyte-electrode assembly according to the present invention involves incorporating a lithium-ion compound into an amorphous metal oxide-forming composition when forming a solid electrolyte, and comprises: a step for preparing an amorphous metal oxide-forming composition by reacting a metal compound containing a titanium atom and an acid compound selected from the group consisting of peroxo acids, and preparing a metal oxide precursor solution which has an acid as a ligand; and a solid electrolyte-electrode assembly-forming step for contacting mist or vapor comprising the amorphous metal oxide-forming composition to the surface of a substrate heated to 150-700°C, and forming a solid electrolyte-electrode assembly comprising the amorphous metal oxide on the surface of the substrate.

Description

Solid electrolyte-electrode assembly and method for producing the same, method for producing solid electrolyte and active material, and solid electrolyte battery

[0001] The present invention relates to a solid electrolyte-electrode assembly and a method for producing the same, a method for producing a solid electrolyte and an active material, and a solid electrolyte battery.

[0002] Conventionally, organic electrolytes have been widely used as ionic conductors in devices that require ion transport for their operation, such as lithium-ion batteries (LIBs), fuel cells, and electrochromic devices (ECDs). However, organic electrolytes are flammable, and solid electrolytes as solid ionic conductors are desired from the viewpoints of safety and durability.

[0003] Among these, all-solid-state batteries have the advantages of not requiring a separator compared to conventional batteries that contain liquid, making it possible to stack them in a single package, which was previously difficult to do, to avoid liquid junctions, and being stable at high temperatures because they do not contain a liquid electrolyte, making them highly stable and suitable for a wide range of applications. For example, all-solid-state batteries are currently expected to be used in a wide range of applications, including in-vehicle applications, power transmission systems, communication power sources, and transportation infrastructure.

[0004] As a solid electrolyte, a solid ion conductor containing an amorphous metal oxide such as silicon oxide or titanium oxide and an acid compound contained in the metal oxide has been proposed (see Patent Document 1).

[0005] Japanese Patent Publication No. 2023-111573

[0006] However, oxide all-solid-state batteries have issues with the movement of Li ions at the solid electrolyte and electrode interface, making them generally difficult to scale up. One factor behind this is the formation of gaps at the interface between the hard oxide electrolyte and the electrode, which expands and contracts during charging and discharging, hindering the movement of Li ions. Side reactions are particularly likely to occur at the high-energy negative electrode interface, and this hinders cycle degradation and short circuits.

[0007] The present invention was completed in view of the above-mentioned circumstances, and an object of the present invention is to provide a solid electrolyte-electrode assembly that can reduce interfacial resistance by making it difficult for gaps to occur at the interface between the solid electrolyte and the electrode, a method for producing the same, a method for producing a solid electrolyte and an active material, and a solid electrolyte battery.

[0008] In order to solve the above problems, the present inventors attempted to manufacture a solid electrolyte battery in which the solid electrolyte and the negative electrode are made of amorphous titanium oxide (a-TiOx), and the solid electrolyte / negative electrode laminate structure is formed simultaneously, and found that this battery can exhibit high performance. Based on these findings, the present inventors have completed the present invention.

[0009] (1) That is, a solid electrolyte-electrode assembly that solves the above-mentioned problems is a solid electrolyte-electrode assembly having a film-like solid electrolyte and a film-like electrode which is at least one of a positive electrode and a negative electrode and is formed by being laminated integrally with the solid electrolyte, wherein the refractive index at the boundary between the solid electrolyte and the electrode changes gradually, the solid electrolyte and the electrode each contain an amorphous metal oxide having a three-dimensional structure containing an oxide of one or more metals selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon, and an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, and each of the amorphous metal oxides has an independently determinable composition, and the solid electrolyte further contains free lithium ions in voids in the three-dimensional structure.

[0010] In particular, the free lithium ions are preferably ions derived from a compound selected from the following lithium salt compound group: (Compound group) LiPF ６ , LiPF ３ (CF ２ CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ , LiSCN, LiPF ３ (CF ３ ) ３ , LiN (CN) ２ , LiClO ４ , LiBF４ , LiAsF ６ , LiCF ３ SO ３ , Li(FSO ２ ) ２ N, Li(CF ３ SO ２ ) ３ C, LiSbF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , LiB(C ２ O ４ ) ２ , LiBF ４ , LiCF ３ SO ３ , LiNO ３ , C.H. ３ COOLi, LiCl, CH ３ CH ２ OLi, CH ３ OLi, LiOH, Li ２ CO ３

[0011] (2) A method for producing a solid electrolyte-electrode assembly of the present invention that solves the above-mentioned problems is a method for producing the solid electrolyte battery of the present invention described above, comprising: a metal oxide amorphous-forming composition preparation step of reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid to prepare a metal oxide precursor solution having an acid as a ligand, and preparing an amorphous metal oxide forming composition from the metal oxide precursor solution; and a solid electrolyte-electrode assembly formation step of contacting a mist or vapor of the amorphous metal oxide forming composition with a surface of a base material heated to 150°C to 700°C to form the solid electrolyte-electrode assembly made of the amorphous metal oxide on the surface of the base material, wherein a lithium ion compound is contained in the amorphous metal oxide forming composition when the solid electrolyte is formed in the solid electrolyte-electrode assembly formation step.

[0012] In particular, it is preferable to form the mist or vapor by irradiating the amorphous metal oxide forming composition with ultrasonic waves.

[0013] (3) A method for producing a solid electrolyte that solves the above-mentioned problems includes: a step of preparing a composition for forming an amorphous metal oxide, which comprises reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, to prepare a composition for forming an amorphous metal oxide, which contains a metal oxide precursor having an acid as a ligand and a lithium ion compound; and a step of bringing a mist or vapor of the composition for forming an amorphous metal oxide into contact with the surface of a substrate heated to 150°C to 700°C, to form the solid electrolyte made of the amorphous metal oxide on the surface of the substrate.

[0014] (4) A method for producing an active material that solves the above-mentioned problems includes: a step of preparing a composition for forming an amorphous metal oxide, which comprises reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, to prepare a composition for forming an amorphous metal oxide, which contains a metal oxide precursor having an acid as a ligand; and a step of forming a solid electrolyte, which comprises bringing a mist or vapor of the composition for forming an amorphous metal oxide into contact with the surface of a substrate heated to 150°C to 700°C, to form the solid electrolyte made of the amorphous metal oxide on the surface of the substrate.

[0015] (5) A solid electrolyte battery that solves the above problems has the above-mentioned solid electrolyte-electrode assembly of the present invention.

[0016] The solid electrolyte-electrode assembly of the present invention has the above-described structure, and therefore has little or no gap at the interface between the solid electrolyte and the electrode, thereby reducing the interfacial resistance between the solid electrolyte and the electrode.

[0017] FIG. 1 is a schematic diagram of an apparatus used in producing the electrodes and solid electrolyte-electrode assemblies of the present examples. FIG. 2 is a charge / discharge curve of a test sample of Example 1. FIG. 3 is a charge / discharge curve of a test sample of Comparative Example 1. FIG. 4 is a charge / discharge curve of a test sample of Comparative Example 2. FIG. 5 is a charge / discharge curve of a test battery of Example 2. FIG. 6 is a cyclic voltammetry of a test battery of Example 2 (5 sweeps). FIG. 7 is a cyclic voltammetry of a test battery of Example 2 (10 sweeps). FIG. 8 is an AC impedance measurement result of a test sample of Example 3. FIG. 9 is an AC impedance measurement result of a test sample of Example 4. FIG. 10 is an AC impedance measurement result of a test sample of Comparative Example 1. FIG. 11 is an AC impedance measurement result of a test sample of Test Example 2 (two-ply of Example 3). FIG. 11 is a cyclic voltammetry measurement result of a test sample of Example 5. FIG. 12 is an AC impedance measurement result of a test sample of Example 5.

[0018] The solid electrolyte-electrode assembly and its manufacturing method, the solid electrolyte and active material manufacturing method, and the solid electrolyte battery of the present invention will be described in detail below based on the following embodiments. The numerical ranges "x to y" described in this specification include a lower limit x and an upper limit y. A new numerical range can be formed by arbitrarily combining these upper and lower limits, as well as the numerical values ​​listed in the specification or examples. The new numerical range can also be a range that does not include one or both of the upper and lower limits. For example, a range greater than x or a range less than y can be adopted. Furthermore, numerical values ​​arbitrarily selected from any of the above numerical ranges can be used as the upper and lower limits of the new numerical range.

[0019] (Solid electrolyte-electrode assembly, solid electrolyte, active material, solid electrolyte battery) The solid electrolyte-electrode assembly of the present embodiment is a film-like member formed by integrally laminating a film-like solid electrolyte and a film-like electrode. The solid electrolyte battery of the present embodiment has the solid electrolyte-electrode assembly of the present embodiment and other members that are adopted as necessary.

[0020] The solid electrolyte-electrode assembly of the present embodiment can be used in various batteries such as solid electrolyte batteries, and in various sensors. Examples of the various batteries include lithium ion batteries, and examples of the various sensors include optical sensors (including solar cells) and ion sensors.

[0021] In the solid electrolyte-electrode assembly of this embodiment, the film-like solid electrolyte and film-like electrodes are laminated so as to be integral. Here, "integrated" means that the refractive index in a cross section perpendicular to the joining surface of the solid electrolyte-electrode assembly changes smoothly across the joining surface. Note that the case where the refractive index is constant is also included in the case where the refractive index changes smoothly. It is preferable that the solid electrolyte-electrode assembly of this embodiment is manufactured integrally from the beginning, rather than by integrating membranes manufactured separately. The method of manufacturing integrally from the beginning will be described later.

[0022] The thickness of the film-like solid electrolyte is not particularly limited, but can be exemplified as about 5000 nm to 1 nm, with the lower limit of the thickness being 1 nm, 50 nm, or 100 nm, and the upper limit being 100 nm, 1000 nm, or 5000 nm.

[0023] The thickness of the film-like electrode is not particularly limited, but can be exemplified as about 10,000 nm to 1 nm, with lower limits of 1 nm, 50 nm, and 100 nm and upper limits of 100 nm, 1,000 nm, and 10,000 nm.

[0024] The thickness of the solid electrolyte-electrode assembly is not particularly limited, but can be exemplified as about 15,000 nm to 2 nm, with lower limits of 2 nm, 100 nm, and 200 nm and upper limits of 100 nm, 1,000 nm, and 15,000 nm.

[0025] The solid electrolyte and electrode of this embodiment each contain an amorphous metal oxide whose composition can be determined independently. As used herein, "amorphous" means that, based on a spectrum measured by XRD, the proportion of a halo pattern area relative to the total peak area is 50% or more, preferably 75% or more, and more preferably 99% or more.

[0026] Specifically, the diffraction intensity is measured using a parallel beam optical system with an incident angle of 0.3°, with 2θ ranging from 10° to 80° in 0.05° steps, at a fixed time of 5° / min. If no clear peaks indicating a crystalline structure are found in the resulting curve, or if a peak is found, the area of ​​the halo pattern excluding the peak area falls within the above-mentioned range, the film is confirmed to be amorphous.

[0027] The amorphous metal oxide that forms the solid electrolyte-electrode assembly of this embodiment has a three-dimensional structure containing a metal oxide and an acid compound. Here, the three-dimensional structure refers to a structure in which the metal oxide and the acid compound are dispersed at a molecular level or a state close to the molecular level, and has voids through which at least lithium ions can move. These voids contain free lithium ions. The method for forming such a three-dimensional structure is not particularly limited, but will be described in detail below.

[0028] The metal oxide is an oxide of one or more metals selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon. There are no particular limitations on the oxide. The acid compound is selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid. The content of the acid compound is preferably such that the amount of carbon atoms contained in the amorphous metal oxide as detected by X-ray photoelectron spectroscopy is 1% by mass to 20% by mass, and more preferably 1% by mass to 5% by mass, relative to the total solid content of the amorphous metal oxide.

[0029] The measurement conditions for X-ray photoelectron spectroscopy in the present disclosure are as follows. The X-rays used are Mg-Kα rays with an output of 10 kV and 100 mA. The peaks of the obtained elements (Li 1s, C 1s, O 1s, Si 2p, Ge 2p, or Ti 2p derived from metal oxides) are subjected to background correction using the Tugard method, and the peaks are separated using a Gaussian function. The area of ​​each separated peak is corrected by the sensitivity factor of each element, and the peak area ratio is calculated to obtain the carbon atom (C) content.

[0030] The film-like solid electrolyte and active material further contain free lithium ions in the voids in the three-dimensional structure. The free lithium ions are preferably ions derived from a compound selected from the group of lithium salt compounds listed below. The free lithium ion concentration is not particularly limited, but the lower limit of the lithium content can be approximately 0 atomic weight %, 0.5 atomic weight %, or 1.5 atomic weight %, and the upper limit can be approximately 2 atomic weight %, 5 atomic weight %, or 10 atomic weight %.

[0031] (Compound group) LiPF ６ , LiPF ３ (CF ２ CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ , LiSCN, LiPF ３ (CF ３ ) ３ , LiN (CN) ２ , LiClO ４ , LiBF ４ , LiAsF ６ , LiCF ３ SO ３ , Li(FSO ２ ) ２ N, Li(CF ３ SO ２ ) ３ C, LiSbF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , LiB(C ２ O ４ ) ２ , LiBF ４ , LiCF ３ SO ３ , LiNO ３ , C.H. ３ COOLi, LiCl, CH ３ CH ２ OLi, CH ３ OLi, LiOH, Li ２ CO ３Among these, LiPF is an ion source for free lithium ions with better mobility. ６ , LiPF ３ (CF ２ CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ , LiSCN, LiPF ３ (CF ３ ) ３ , LiClO ４ etc.

[0032] Solid Electrolyte and Active Material The above-mentioned explanation of the solid electrolyte and active material (electrode) in the solid electrolyte-electrode assembly is applicable as is, so further explanation will be omitted.

[0033] Solid Electrolyte Battery A solid electrolyte battery includes a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive and negative electrodes. The solid electrolyte battery of this embodiment is configured as a solid electrolyte-electrode assembly in which the solid electrolyte and at least one of the positive and negative electrodes are integrated.

[0034] The electrode (positive electrode or negative electrode) not included in the solid electrolyte-electrode assembly is not particularly limited, and the positive electrode and negative electrode of a known all-solid-state battery can be applied.

[0035] The positive electrode is NiO, LiFePO ４ , LiCoO ２ , LiMnO ２ , LiMn ２ O ４ , LiNi ０．５ Mn １．５ O ４ , Li(Ni １／３ Co １／３ Mn １／３ ) O ２ , LiNiO ２ The negative electrode is WO ３ , TiO ２ , C, Si, Li ４ Ti ５ O １２ etc.

[0036] (Methods for producing solid electrolyte-electrode assembly, and methods for producing solid electrolyte and active material) - Method for producing solid electrolyte-electrode assembly The method for producing a solid electrolyte-electrode assembly of this embodiment includes a step of preparing a composition for forming an amorphous metal oxide, a step of forming a solid electrolyte-electrode assembly, and other steps that can be adopted as necessary. The method for producing a solid electrolyte-electrode assembly of this embodiment is a method for integrally producing a film-like solid electrolyte and a film-like electrode. The electrode can contain an active material.

[0037] The amorphous metal oxide-forming composition preparation step is a step of reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid to prepare an amorphous metal oxide-forming composition from a metal oxide precursor solution having an acid as a ligand. The amorphous metal oxide-forming composition is a composition that changes into an amorphous metal oxide by heating in the solid electrolyte-electrode assembly formation step described below.

[0038] The metal compound is not particularly limited as long as it contains the above metal atoms. Alternatively, a compound in which an acid compound is coordinated in the molecular structure from the beginning may be used. Examples include alkoxides containing each metal, compounds in which an acid compound such as titanium tetrachloride is not coordinated, and compounds in which an acid compound such as peroxotitanic acid or titanium diisopropoxide bis(acetylacetonate) is coordinated.

[0039] Examples of acid compounds include compounds selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid. These acid compounds are reacted with the metal compounds described above to form metal oxide precursors with the acid as a ligand. When an acid compound is originally coordinated, it can be used as the metal oxide precursor as is. The amount of acid compound added is not particularly limited, but based on the product of the coordination number and the number of atoms of the contained metal atoms, the number of ligands derived from the acid compound is preferably 1% to 60%, more preferably 3% to 40%, and even more preferably 5% to 20%.

[0040] The obtained metal oxide precursor is dissolved in an appropriate solvent to prepare a metal oxide precursor solution. The solvent should not react with and inactivate the metal oxide precursor or the lithium salt compound described below. It is preferable to use a solvent that can be easily removed by volatilization or the like in the solid electrolyte-electrode assembly formation step.

[0041] Specific examples of solvents that may be used include organic solvents such as monohydric alcohols such as methanol, ethanol, butanol, and isopropanol, ethers such as ethyl ether and dimethyl ether, and ketones such as acetone, as well as mixed solvents of the above-mentioned organic solvents with water.

[0042] The amount of solvent added is preferably set to a concentration such that the viscosity of the resulting metal oxide precursor solution is sufficiently easy to handle when it is converted into mist in the solid electrolyte-electrode assembly forming step described below, and the solvent is easily removed from the substrate. Furthermore, when the metal oxide precursor is in a liquid state from the beginning, it can be used as is, and in that case it is called a metal oxide precursor solution even if it does not contain a solvent.

[0043] The amorphous metal oxide forming composition preparation step can include a lithium ion-containing solution preparation step. The lithium ion-containing solution preparation step is a step of dissolving a lithium salt compound in an organic solvent to prepare a lithium ion-containing solution. The prepared lithium ion-containing solution is mixed with the amorphous metal oxide forming composition when forming the solid electrolyte. If not mixed, it corresponds to an electrode (which may contain an active material).

[0044] The organic solvent used in preparing the lithium ion-containing liquid can be any solvent that can dissolve a lithium salt compound and generate lithium ions. Examples of organic solvents include monohydric alcohols such as methanol, ethanol, butanol, and isopropanol, ethers such as ethyl ether and dimethyl ether, and ketones such as acetone, as well as mixed solvents of the above-mentioned organic solvents with water. The content of the lithium salt compound in the lithium ion-containing liquid is preferably an amount that results in a lithium ion concentration in the lithium ion-containing liquid of 1% by mass to 15% by mass, and more preferably an amount that results in a lithium ion concentration in the lithium ion-containing liquid of 2% by mass to 5% by mass.

[0045] As the lithium salt compound, the lithium salt compound described above in connection with the solid electrolyte-electrode assembly of this embodiment can be used. For example, LiPF ６ , LiPF ３ (CF ２ CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ , LiSCN, LiPF ３ (CF ３ ) ３ , LiN (CN) ２ , LiClO ４ , LiBF ４ , LiAsF ６ , LiCF ３ SO ３ , Li(FSO ２ ) ２ N, Li(CF ３ SO ２ ) ３ C, LiSbF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , LiB(C ２ O ４ ) ２ , LiBF ４ , LiCF ３ SO ３ , LiNO３ , C.H. ３ COOLi, LiCl, CH ３ CH ２ OLi, CH ３ OLi, LiOH, Li ２ CO ３ One of these can be used alone, or two or more can be used in combination.

[0046] The solid electrolyte-electrode assembly forming step is a step in which a mist or vapor of an amorphous metal oxide forming composition is brought into contact with the surface of a substrate heated to 150° C. to 700° C. to form a layer of amorphous metal oxide on the surface of the substrate. When forming a layer corresponding to the solid electrolyte, lithium ions are contained in the amorphous metal oxide forming composition, and when forming a layer corresponding to the electrode, the amorphous metal oxide forming composition is used as is.

[0047] In addition, when the amorphous metal oxide alone does not exhibit sufficient conductivity, a conductive additive can be added. Examples of the conductive additive include carbon materials such as carbon black. Particulate conductive additives can be used and dispersed in the amorphous metal oxide forming composition to form a mist, which can then be dispersed in the layered electrode.

[0048] The method for misting the amorphous metal oxide-forming composition is not particularly limited, but it is preferable to employ atomization by ultrasonic irradiation. The resulting mist is delivered to a substrate by a carrier gas and allowed to collide with the substrate, thereby forming a layer of solid electrolyte on the surface of the substrate. The surface of the substrate is heated to 150°C to 700°C, and volatile components such as the solvent contained in the amorphous metal oxide-forming composition are removed, thereby forming a layer of solid electrolyte. The heating temperature of the substrate can be set to a lower limit of 200°C, 250°C, or 300°C, and an upper limit of 600°C, 550°C, 500°C, 450°C, or 400°C. Setting the temperature to a value equal to or higher than the lower limit ensures reliable removal of the solvent, while setting the temperature below the upper limit suppresses the progression of side reactions, etc.

[0049] The supply rate of the mist to the substrate surface varies depending on the temperature of the substrate surface and the supply rate of the carrier gas, but a rate that can remove the solvent at a sufficient rate and does not leave any solvent in the formed solid electrolyte can be adopted.

[0050] The composition of the mist supplied to the substrate surface may be constant or may vary. By changing the composition of the mist, the composition of the resulting film can also be changed in the thickness direction. For example, the composition can be changed between the solid electrolyte portion and the electrode portion. Examples of methods for changing the composition of the mist include a method in which two or more types of amorphous metal oxide forming compositions are prepared and the mist is generated by sequentially switching between them, and a method in which mists are generated from two or more types of amorphous metal oxide forming compositions and the mixing ratio between them is changed.

[0051] The substrate is appropriately selected depending on the application of the solid electrolyte-electrode assembly of this embodiment. When the solid electrolyte-electrode assembly is applied to a lithium ion battery, it is preferable that the substrate also functions as a current collector, and in that case, stainless steel, copper, aluminum, etc. can be used depending on the type of electrode. Other examples of substrates on which the solid electrolyte-electrode assembly is provided include insulators such as glass and semiconductors such as silicon.

[0052] Other methods for producing a solid electrolyte-electrode junction: Part 1 This method employs a method in which a material generated by laser irradiation or sputtering is collided with the surface of a substrate, and the material is supplied in accordance with the composition of the solid electrolyte-electrode junction to form a film.

[0053] Films produced by laser irradiation or sputtering can be easily made amorphous, and can be integrally formed on the solid electrolyte and the electrode regardless of differences in composition. Specifically, the method for producing a solid electrolyte-electrode assembly of this embodiment includes a target material preparation step and a film formation step.

[0054] The target material preparation process is a process for preparing a target material having a composition corresponding to the composition of the solid electrolyte and electrodes. The target material may have any degree of crystallinity because its crystalline structure is destroyed by laser irradiation or sputtering.

[0055] The target material may be composed of one type of material that matches the composition of the solid electrolyte-electrode assembly, or may be a combination of two or more types of materials that form the solid electrolyte and electrode. For example, if the only difference between the composition of the solid electrolyte and the composition of the electrode is the addition of lithium ions, the target material is composed of a target material that corresponds to the composition of the electrode and a lithium source that is the difference, and control is performed so that only the target material that corresponds to the composition of the electrode is used when forming the electrode film, and the lithium source is also used as a target material when forming the solid electrolyte film.

[0056] Other Methods for Producing a Solid Electrolyte-Electrode Joint: Part 2 This method is a method for producing a solid electrolyte-electrode joint by forming an amorphous metal oxide contained in the solid electrolyte-electrode joint of this embodiment by a sol-gel method. Specifically, this method is a film formation method in which raw materials for the sol-gel method are supplied to the surface of a substrate in accordance with the composition of the solid electrolyte-electrode joint.

[0057] The method for manufacturing a solid electrolyte-electrode assembly according to this embodiment includes a sol-gel precursor preparation step and a film formation step. The sol-gel precursor preparation step is a step of preparing a sol-gel precursor, which is an alkoxide or halide of a metal element contained in the amorphous metal oxide of the solid electrolyte-electrode assembly. In the film formation step, the sol-gel precursor is formed into a film on the surface of a substrate. The film formation method is not particularly limited, but a flowable sol-gel precursor can be used, and general film formation procedures such as spin coating or film formation using a coater can be employed.

[0058] The sol-gel precursor may be composed of one material that matches the composition of the solid electrolyte-electrode joint, or may be a combination of two or more materials that form the solid electrolyte and electrode. For example, if the only difference between the composition of the solid electrolyte and the composition of the electrode is the addition of lithium ions, the sol-gel precursor is composed of a sol-gel precursor that corresponds to the composition of the electrode and a lithium source that is the difference between them, and when forming a film of the electrode, only the sol-gel precursor that corresponds to the composition of the electrode is used, and when forming a film of the solid electrolyte, a sol-gel precursor that also includes the lithium source is used.

[0059] Manufacturing Method of Solid Electrolyte and Active Material The method for manufacturing the solid electrolyte and the active material (electrode) from the above-described method for manufacturing a solid electrolyte-electrode assembly can be directly applied to the method for manufacturing the solid electrolyte of this embodiment by extracting the steps, and therefore further explanation will be omitted.

[0060] The solid electrolyte-electrode assembly, its manufacturing method, and solid electrolyte battery of the present invention will be described in detail below with reference to examples.

[0061] (Preparation of Test Sample) A solid electrolyte-electrode assembly was prepared on the surface of a substrate 50 using a mist CVD apparatus as shown in Fig. 1. The mist CVD apparatus is an apparatus that turns an amorphous metal oxide forming composition into mist and layers it on the surface of a substrate.

[0062] The prepared amorphous metal oxide forming composition 80 is held in a storage container 10. An ultrasonic irradiation device is provided at the bottom of the storage container 10, and the amorphous metal oxide forming composition 80 held inside is turned into mist.

[0063] The storage container 10 is connected to a mist gas inlet path 22, which introduces a carrier gas (mist gas) from the outside and carries the mist generated inside to the outside, and a mist gas outlet path 21, which discharges the mist gas to the outside of the storage container 10. The mist gas outlet path 21 is connected to a carrier gas inlet path 23, which introduces a carrier gas to mix with the mist gas and adjust the mist concentration in the mist gas and the flow rate of the mist gas. The amount of carrier gas flowing through the mist gas inlet path 22 and the carrier gas inlet path 23 is adjusted by a regulator 24.

[0064] The mist is carried to the nozzle 30 as mist gas and sprayed toward the surface of the substrate 50. The substrate 50 is heated to a predetermined temperature by a base 40 with a built-in heater, and the sprayed mist is layered on the surface of the heated substrate 50. The base 40 can move the substrate 50 in the horizontal direction, allowing the mist to adhere evenly to the surface of the substrate 50 and forming a uniform layer.

[0065] (Test 1: Evaluation of electrode: oxidation-reduction of Ti) - Electrode production A 50 mM titanium diisopropoxide bis(acetylacetonate) methanol solution was prepared as a composition for forming an amorphous metal oxide (preparation step of composition for forming an amorphous metal oxide). This composition for forming an amorphous metal oxide was irradiated with ultrasonic waves (2.4 MHz) to form a mist in a storage container 10, and nitrogen gas was introduced as a carrier gas at a flow rate of 4.0 L / min.

[0066] The mist gas discharged from the storage container 10 to the outside through the mist gas discharge path 21 at the same speed was mixed with a carrier gas at a flow rate of 8.0 L / min and supplied to the nozzle 30, and the solid electrolyte was layered on the stainless steel substrate 50 heated to 300° C. Here, the substrate 50 was swept horizontally at 5 mm / sec to form a uniform layer of solid electrolyte on the surface of the substrate 50 (sweeping), and this operation was repeated 10 times to form a layer of solid electrolyte of 0.1 mg / cm on the surface of the substrate 50. ２ A layer was formed so as to obtain a test sample of Example 1. A part of the test sample was annealed at 700° C. to improve the crystallinity, and the result was used as a test sample of Comparative Example 1.

[0067] As a comparative example, a composite material obtained by mixing 3 parts by mass of titanium oxide particulate material (volume average particle size 0.1 μm), 1 part by mass of polyvinylvinylidene fluoride as a binder, and 1 part by mass of Ketjen black as a conductive additive was applied to the base 40 at a density of 5 mg / cm ２ The electrode of Comparative Example 2 was produced by applying, drying, and pressing the coated layer so that the thickness of the coated layer was 1 / 4 mm.

[0068] - Battery Production A test battery was formed by attaching metallic lithium to the amorphous metal oxide side of the obtained test sample via a polypropylene separator.６ The amorphous metal oxide prepared here acts as an electrode.

[0069] ・Evaluation Ambient temperature 25℃, capacity 300mAhg －1 The battery was repeatedly charged and discharged at 0.2 C. The potential was measured. The charge and discharge were controlled so that the potential did not exceed the range of 1.0 V to 3.5 V. ２ The charge / discharge curves are shown in Figures 2 to 4.

[0070] From the results of the example shown in FIG. 2, the 300 mAh setting was used when charging and discharging. －1 It was found that the charge and discharge were generally stable as they were. In contrast, in Comparative Example 1, in which annealing was performed to improve the crystallinity, the potential quickly exceeded 3.5 V upon charging, and it was found that lithium ions were difficult to introduce into the electrode made of a solid electrolyte. In addition, in Comparative Example 2, which was made of a composite material, the capacity was 200 mAhg, which is lower than that of the Example. －1 It was found that the capacity was low because the voltage exceeded the range of 3.5 V at about this level. It was also found that the conductivity of Comparative Example 2 was lower than that of the Examples.

[0071] (Test 2: Evaluation of Electrode: Dissolution and Deposition of Li) An electrode of Example 2 was prepared in the same manner as in Example 1, except that the substrate was changed to copper, the number of sweeps was increased to 5 in addition to 10, and the substrate temperature was increased to 250°C. A battery for evaluation was prepared using the obtained electrode in the same manner as in Test 1. A charge-discharge test was conducted on this battery at an ambient temperature of 25°C and 0.3 mA / cm. ２ The charge and discharge were repeated at 1000 V. The charge and discharge were controlled so that the potential did not exceed the range of -0.1 V to 1.0 V. CV measurements were performed at 25°C with a scanning potential of 1 mV / s for 9 cycles. The potential and current density were measured. ２ The charge-discharge curves of Li-aTiO are shown in Figure 5. ２ The cyclic voltammetry curves of the above are shown in FIG. 6 (five sweeps) and FIG. 7 (ten sweeps).

[0072] As is clear from Figures 5 to 7, it was found that Li metal could be stably precipitated and dissolved. Furthermore, when the number of sweeps was increased from 5 to 10 and the film thickness was increased, the current density decreased. This was presumably due to the slow migration of Li ions.

[0073] (Test 3: Evaluation of solid electrolyte) The amorphous metal oxide composition was prepared by adding LiPF 6 at a concentration of 100 mM. ６ A layer of amorphous metal oxide (solid electrolyte) containing lithium ions was formed on the surface of a copper substrate in the same manner as in Example 2 in Test Example 2, except that the copper substrate contained lithium ions and the number of sweeps was 30. Test samples were also produced in the same manner as in Example 2, except that the number of sweeps was 30 (Example 4) and 20 (Test Example 1). Furthermore, a sample was also prepared in which two samples of Example 3 were bonded together on the solid electrolyte side (Test Example 2).

[0074] Evaluation AC impedance measurements were performed for Examples 3 and 4 and Test Examples 1 and 2. The results are shown in Fig. 8 (Example 3), Fig. 9 (Example 4), Fig. 10 (Test Example 1), and Fig. 11 (Test Example 2). When the number of sweeps was 30, the internal resistance was about 80,000 Ω for Example 4, which did not contain lithium ions, whereas the internal resistance was reduced to about 10,000 Ω for Example 3, which contained lithium ions at a concentration of 100 mM, demonstrating that the inclusion of lithium ions allows the material to be used as a solid electrolyte.

[0075] However, in Test Example 1, which had a smaller number of sweeps (20 times) than in Example 4, a short circuit was observed due to the thin layer. In other words, it was found that a thickness sufficient to prevent short circuits is necessary for the layer to function as a solid electrolyte. Furthermore, in consideration of the results of Test Example 2, it was found that even in Example 3, which had a low internal resistance when used alone, mechanical contact alone did not sufficiently promote the movement of lithium ions.

[0076] (Test 4: Study of solid electrolyte battery) - Electrode production A 50 mM titanium diisopropoxide bis(acetylacetonate) methanol solution was prepared as a composition for forming an amorphous metal oxide (preparation step of composition for forming an amorphous metal oxide). This composition for forming an amorphous metal oxide was irradiated with ultrasonic waves (2.4 MHz) to form a mist in a storage container 10, and nitrogen gas was introduced as a carrier gas at a flow rate of 4.0 L / min.

[0077] The mist gas discharged from the storage container 10 to the outside through the mist gas discharge path 21 at the same speed was mixed with a carrier gas at a flow rate of 8.0 L / min and supplied to the nozzle 30, and the solid electrolyte was layered on the stainless steel substrate 50 heated to 300° C. Here, the substrate 50 was swept horizontally at 5 mm / sec to form a uniform layer of solid electrolyte on the surface of the substrate 50 (sweeping), and this operation was repeated five times to form a layer of solid electrolyte of 0.1 mg / cm on the surface of the substrate 50. ２ The layered electrodes were formed so that

[0078] Subsequently, LiPF 6 is added to the amorphous metal oxide forming composition. ６ A composition containing the above at a concentration of 100 mM was prepared, and a layered solid electrolyte was formed on the layered electrode by sweeping 30 times to produce a solid electrolyte-electrode assembly, which was used as the test sample of Example 5.

[0079] A test battery was formed by attaching metallic lithium to the solid electrolyte side of the obtained test sample via a polypropylene separator. Cyclic voltammetry was measured on this test battery at a scanning rate of 1 mV / s over a potential range of -0.1 V to 0.4 V, and the results are shown in Figure 12. AC impedance was measured on this test battery at an applied voltage of 100 mV and a measurement frequency range of 7 MHz to 200 mHz, and the results are shown in Figure 13.

[0080] The results in Figure 12 show that Li metal can be repeatedly deposited and dissolved within the electrode, confirming that Li metal dissolves or deposits in the electrode. Furthermore, the results in Figure 13 show that the internal resistance is small, at approximately 1000 Ω. These results indicate that in this test battery, Li ions reach the electrode (negative electrode) via the solid electrolyte, allowing charge and discharge to proceed at the negative electrode. As described above, it was found that the layer made of amorphous metal oxide produced by the method of this example functions as a solid electrolyte when a lithium salt compound is added.

[0081] REFERENCE SIGNS LIST 10... storage container 21... mist gas discharge path 22... mist gas introduction path 23... carrier gas introduction path 24... regulator 40... base 50... substrate

Claims

1. A solid electrolyte-electrode assembly having a film-like solid electrolyte and at least one of a positive electrode and a negative electrode, which is a film-like electrode formed by integrally laminating the solid electrolyte, wherein the refractive index at the boundary between the solid electrolyte and the electrode changes gradually, the solid electrolyte and the electrode each contain an amorphous metal oxide having a three-dimensional structure containing an oxide of one or more metals selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon, and an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, and each having an independently determinable composition, and the solid electrolyte further contains free lithium ions in voids in the three-dimensional structure.

2. The solid electrolyte-electrode assembly according to claim 1, wherein the free lithium ions are ions derived from a compound selected from the following lithium salt compound group: (Compound group) LiPF ６ , LiPF ３ (CF ２ CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ , LiSCN, LiPF ３ (CF ３ ) ３ , LiN (CN) ２ , LiClO ４ , LiBF ４ , LiAsF ６ , LiCF ３ SO ３ , Li(FSO ２ ) ２ N, Li(CF ３ SO ２ ) ３ C, LiSbF ６ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , LiB(C ２ O ４ ) ２ , LiBF ４ , LiCF ３ SO ３ , LiNO ３ , C.H. ３ COOLi, LiCl, CH ３ CH ２ OLi, CH ３ OLi, LiOH, Li ２ CO ３ 3. A method for producing the solid electrolyte-electrode junction according to claim 1 or 2, comprising: a metal oxide amorphous-forming composition preparation step of reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid to prepare a metal oxide precursor solution having an acid as a ligand, and preparing an amorphous metal oxide forming composition from the metal oxide precursor solution; and a solid electrolyte-electrode junction formation step of contacting a mist or vapor of the amorphous metal oxide forming composition with the surface of a base material heated to 150°C to 700°C to form the solid electrolyte-electrode junction made of the amorphous metal oxide on the surface of the base material, wherein a lithium ion compound is contained in the amorphous metal oxide forming composition when the solid electrolyte is formed in the solid electrolyte-electrode junction formation step.

4. The method for producing a solid electrolyte-electrode joint according to claim 3, wherein the mist or vapor is formed by irradiating the amorphous metal oxide forming composition with ultrasonic waves.

5. A method for producing an active material, comprising: a step of preparing a composition for forming an amorphous metal oxide, which comprises reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, to prepare a composition for forming an amorphous metal oxide, which contains a metal oxide precursor having an acid as a ligand; and a step of contacting a mist or vapor of the composition for forming an amorphous metal oxide with the surface of a substrate heated to 150°C to 700°C, to form a solid electrolyte made of an amorphous metal oxide on the surface of the substrate.

6. A method for producing a solid electrolyte-electrode junction according to claim 1 or 2, comprising: a target material preparation step of preparing a target material made of the metal oxide; and a film formation step of causing the metal compound ejected from the target material by ablation through laser irradiation and / or sputtering through voltage application to collide with the surface of a substrate to form a film, wherein the film formation step is a step in which, when forming the solid electrolyte, a lithium source containing lithium is also used in addition to the target material to gradually change the composition to form a film.

7. A method for producing a solid electrolyte-electrode junction according to claim 1 or 2, comprising: a sol-gel precursor preparation step of preparing a sol-gel precursor consisting of a metal alkoxide or halide containing a metal element contained in the metal compound; a film formation step of applying a solution containing the sol-gel precursor onto a substrate to form a film; and an amorphous metal oxide formation step of, after the film formation step, carrying out a hydrolysis and / or polycondensation reaction and heating to form the amorphous metal oxide, wherein the film formation step is a step of introducing a lithium source when forming a film on a portion corresponding to the solid electrolyte, and eliminating or reducing the amount of the lithium source when forming a film on a portion corresponding to the electrode.

8. A method for producing a solid electrolyte, comprising: a step of preparing a composition for forming an amorphous metal oxide, which comprises reacting a metal compound containing a metal atom selected from the group consisting of titanium, germanium, aluminum, phosphorus, and silicon with an acid compound selected from the group consisting of formic acid, carbonic acid, phosphoric anhydride, oxalic acid, citric acid, and peroxoacid, to prepare a composition for forming an amorphous metal oxide, which contains a metal oxide precursor having an acid as a ligand and a lithium ion compound; and a step of contacting a mist or vapor of the composition for forming an amorphous metal oxide with the surface of a substrate heated to 150°C to 700°C, to form a solid electrolyte made of an amorphous metal oxide on the surface of the substrate.

9. A solid electrolyte battery comprising the solid electrolyte-electrode assembly according to claim 1 or 2.

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