All-solid-state battery and method for manufacturing the same

Abstract

A primary object of the present disclosure is to provide an all-solid-state battery having a dispersant-containing layer in which the solid electrolyte has good dispersibility. [Solution] The present disclosure solves the above problem by providing an all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is a dispersant-containing layer containing at least a solid electrolyte and a dispersant, the amine value of the dispersant is 20 mgKOH / g or more and 200 mgKOH / g or less, the weight-average molecular weight of the dispersant is less than 1,500,000 g / mol, and the proportion of the dispersant in the dispersant-containing layer is 0.1 wt % or more and 20 wt % or less.

Description

[Technical Field]

[0001] The present disclosure relates to an all-solid-state battery and a method for manufacturing the same. [Background technology]

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage of being easier to simplify safety devices compared to liquid-based batteries that use electrolytes containing flammable organic solvents. Carbon materials may be used as conductive materials in the positive electrode and negative electrode layers of all-solid-state batteries, and dispersants that improve the dispersibility of these carbon materials are known. For example, Patent Document 1 discloses a dispersant for carbon materials that contains a copolymer containing nitrogen atoms.

[0003] Furthermore, although not related to all-solid-state batteries, Patent Document 2 discloses a dispersant containing a carboxylic acid and an amine. Patent Document 2 also discloses the use of this dispersant to remove deposits formed inside an engine. Furthermore, like Patent Document 2, Patent Document 3, although not related to all-solid-state batteries, discloses a binder composition for lithium-ion secondary battery electrodes that contains a water-soluble polymer X (with an electrolyte swelling rate of 120% by mass or less), an amphoteric dispersant Y, and a solvent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-046796 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-065848 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-149313 Summary of the Invention [Problem to be solved by the invention]

[0005] In liquid-based batteries, ions are conducted via a fluid electrolyte. In contrast, in all-solid-state batteries, ions are conducted via a solid electrolyte that does not have fluidity. To form a good ion conduction path, it is preferable to improve the dispersibility (uniformity and stability of dispersion) of the solid electrolyte.

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide an all-solid-state battery having a dispersant-containing layer in which the dispersibility of a solid electrolyte is good. [Means for solving the problem]

[0007] In order to solve the above problems, the present disclosure provides an all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is a dispersant-containing layer containing at least a solid electrolyte and a dispersant, the amine value of the dispersant is 20 mgKOH / g or more and 200 mgKOH / g or less, the weight-average molecular weight of the dispersant is less than 1,500,000 g / mol, and the proportion of the dispersant in the dispersant-containing layer is 0.1 wt % or more and 20 wt % or less.

[0008] According to the present disclosure, by using a specific dispersant in a predetermined ratio, it is possible to obtain an all-solid-state battery having a dispersant-containing layer in which the dispersibility of the solid electrolyte is good.

[0009] In the above disclosure, the weight average molecular weight of the dispersant may be 300 g / mol or more and 150,000 g / mol or less.

[0010] In the above disclosure, the acid value of the dispersant may be 0 mgKOH / g or more and 50 mgKOH / g or less.

[0011] In the above disclosure, the dispersant-containing layer may contain an aminoamide as the dispersant.

[0012] In the above disclosure, the aminoamide may contain at least one of an unsaturated polyaminoamide and an alkylol aminoamide.

[0013] In the above disclosure, the dispersant-containing layer may contain a polyester-polyamine copolymer as the dispersant.

[0014] In the above disclosure, the positive electrode layer may be the dispersant-containing layer, and the proportion of the solid electrolyte in the positive electrode layer may be 10% by weight or more and 30% by weight or less.

[0015] In the above disclosure, the negative electrode layer may be the dispersant-containing layer, and the proportion of the solid electrolyte in the negative electrode layer may be 10% by weight or more and 30% by weight or less.

[0016] In the above disclosure, the solid electrolyte layer may be the dispersant-containing layer, and the proportion of the solid electrolyte in the solid electrolyte layer may be 60% by weight or more.

[0017] The present disclosure also provides a method for manufacturing the above-mentioned all-solid-state battery, in which the dispersant-containing layer is formed using a slurry containing at least the solid electrolyte and the dispersant.

[0018] According to the present disclosure, by using a slurry containing a specific dispersant, it is possible to obtain an all-solid-state battery having a dispersant-containing layer in which the solid electrolyte has good dispersibility. [Effects of the Invention]

[0019] The all-solid-state battery according to the present disclosure has the effect of having a dispersant-containing layer in which the dispersibility of the solid electrolyte is good. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of an all-solid-state battery according to the present disclosure. [Figure 2]1 is a flowchart illustrating a method for manufacturing an all-solid-state battery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] The all-solid-state battery and the method for manufacturing the all-solid-state battery according to the present disclosure will be described in detail below.

[0022] A. All-solid-state battery Fig. 1 is a schematic cross-sectional view illustrating an example of an all-solid-state battery according to the present disclosure. As shown in Fig. 1, an all-solid-state battery 10 includes a positive electrode layer 1, a negative electrode layer 2, a solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. At least one of the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layer 3 is a dispersant-containing layer that contains at least a solid electrolyte and a dispersant.

[0023] According to the present disclosure, by using a specific dispersant in a predetermined ratio, an all-solid-state battery having a dispersant-containing layer with good dispersibility of the solid electrolyte can be obtained. For example, in a layer where the solid electrolyte is locally aggregated, the ion conduction paths tend to be insufficient. In particular, in an electrode layer containing an active material, if the ion conduction paths are insufficient, a portion of the active material may become isolated, resulting in insufficient capacity. Therefore, it is preferable to improve the dispersibility (uniformity and stability of dispersion) of the solid electrolyte.

[0024] In the present disclosure, a specific dispersant is used in a predetermined ratio. As a result, the dispersibility of the solid electrolyte is improved, and the ionic conductivity in the dispersant-containing layer is improved. Furthermore, the improved dispersibility of the solid electrolyte in the dispersant-containing layer improves the cycle characteristics.

[0025] 1. Dispersant-containing layer The dispersant-containing layer contains at least a solid electrolyte and a dispersant.

[0026] (1) Dispersant The dispersant has an amine value. Solid electrolytes typically have affinity for amines. Therefore, a dispersant with an amine value adsorbs to the solid electrolyte, thereby improving the dispersibility of the solid electrolyte. The amine value of the dispersant is typically 20 mg KOH / g or more, and may be 30 mg KOH / g or more. If the amine value of the dispersant is too low, the effect of improving the dispersibility of the solid electrolyte may not be achieved. On the other hand, the amine value of the dispersant is typically 200 mg KOH / g or less, and may be 150 mg KOH / g or less. If the amine value of the dispersant is too high, the solubility in organic solvents (dispersion media) may decrease, and the effect of improving the dispersibility of the solid electrolyte may not be achieved. Furthermore, if the amine value of the dispersant is too high, the production of the dispersant itself may become difficult. The amine value of the dispersant is determined by measurement based on DIN (Deutsche Institut fur Normung) 16945. Specifically, 0.9 g to 1.3 g of sample is added to a 200 ml beaker and 50 ml of glacial acetic acid is added. Then, titration is performed using a 0.1 N HClO4 / acetic acid solution and an automatic potentiometer (Tirator-DL 40, Mettler, Ag / AgCl electrode). The amine value is then determined using the following formula: Amine number (mgKOH / g) = (ab) × 5.61 / E a is the amount (ml) of 0.1N HClO4 required for titration, b is the amount (ml) of 0.1N HClO4 required for titration of the blank, and E is the weight (g) of the sample.

[0027] The dispersant may or may not have an acid value, with the former being preferred. That is, the acid value of the dispersant may be greater than 0 or may be 0, with the former being preferred. Solid electrolytes typically have affinity for acids. Therefore, a dispersant with an acid value adsorbs to the solid electrolyte, improving the dispersibility of the solid electrolyte. It is presumed that the amine value is more advantageous than the acid value in improving dispersibility. The acid value of the dispersant is, for example, 10 mg KOH / g or more, or 20 mg KOH / g or more. On the other hand, the acid value of the dispersant is, for example, 150 mg KOH / g or less, or may be 100 mg KOH / g or less, or may be 50 mg KOH / g or less. The acid value of the dispersant is determined by measurement based on DIN EN ISO 2114. Specifically, 0.9 g to 1.3 g of a sample is placed in an 80 ml beaker, and 50 ml of acetone is added. Then, titration is carried out using a 0.1N NaOH aqueous solution and an automatic potentiometer (Tirator-DL 40, Mettler, Ag / AgCl electrode). The acid value is then determined by the following formula: Acid value (mgKOH / g)=(ab)×5.61 / E a is the amount (ml) of 0.1N NaOH required for titration, b is the amount (ml) of 0.1N NaOH required for titration of the blank, and E is the weight (g) of the sample.

[0028] The weight-average molecular weight of the dispersant is, for example, 200 g / mol or more, and may be 300 g / mol or more, 1,000 g / mol or more, or 1,500 g / mol or more. If the weight-average molecular weight of the dispersant is too small, the effect of improving the dispersibility of the solid electrolyte may not be obtained. On the other hand, the weight-average molecular weight of the dispersant is usually less than 1,500,000 g / mol, and may be 150,000 g / mol or less, or 100,000 g / mol or less. If the weight-average molecular weight of the dispersant is too large, the number of molecules of the dispersant decreases relatively, and the effect of improving the dispersibility of the solid electrolyte may not be obtained. The weight-average molecular weight (M W ) is determined as a polystyrene equivalent value by the GPC method.

[0029] The dispersant has an amino group in its molecule. The amino group may be -NH2, -NHR (R is an element or group other than hydrogen), or -NRR' (R and R' are each independently an element or group other than hydrogen). The dispersant may or may not have an amide bond (-NH-CO-) in its molecule. The dispersant may or may not have a hydroxyl group (-OH group) in its molecule. The dispersant may or may not have a branched structure in its molecule.

[0030] The dispersant may be an aminoamide (amine amide). An aminoamide is a compound having an amino group and an amide bond in the molecule. The N element in the amino group and the C element in the amide bond are preferably bonded via one or more C elements. Examples of aminoamides include unsaturated polyaminoamides and alkylol aminoamides. The unsaturated polyaminoamide may be, for example, a salt of unsaturated polyamine amides and lower molecular weight acidic polyesters. The unsaturated polyaminoamide may also be, for example, a reaction product of tall-oil fatty acids with polyethylene glycol, maleic anhydride, and unsaturated polyamine amide salt (e.g., a reaction product of tall-oil fatty acids and diethylene triamine). The alkylolaminoamide may be, for example, a condensation product of tall-oil fatty acids with 2-[(2-aminoethyl)amino]ethanol. Alternatively, the dispersant may be a polyamine copolymer. Examples of polyamine copolymers include polyester-polyamine copolymers.

[0031] The proportion of the dispersant in the dispersant-containing layer is typically 0.1 wt % or more, and may be 0.5 wt % or more. If the proportion of the dispersant is too low, the effect of improving the dispersibility of the solid electrolyte may not be obtained. On the other hand, the proportion of the dispersant in the dispersant-containing layer is typically 20 wt % or less, and may be 15 wt % or less, 10 wt % or less, or 5 wt % or less. If the proportion of the dispersant is too high, the proportion of the solid electrolyte may be relatively low, and the ionic conductivity in the dispersant-containing layer may be reduced. The dispersant-containing layer may contain only one type of dispersant, or may contain two or more types of dispersants.

[0032] (2) Solid electrolyte The solid electrolyte improves the ionic conductivity of the dispersant-containing layer. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Among these, sulfide solid electrolytes are preferred because they have high ionic conductivity and high affinity with the dispersant.

[0033] Examples of sulfide solid electrolytes include solid electrolytes containing Li, X (wherein X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of halogen elements include F, Cl, Br, and I.

[0034] The sulfide solid electrolyte has an anion structure with an ortho-composition (PS4 3- Structure, SiS4 4- Structure, GeS4 4- Structure, AlS3 3- Structure, BS3 3-It is preferable that the sulfide solid electrolyte has an anion structure having an ortho-composition (xLi2S-(1-x)P2S5) as the main anion component, because this has high chemical stability. The proportion of the anion structure having an ortho-composition is, for example, 70 mol % or more, and may be 90 mol % or more, based on the total anion structures in the sulfide solid electrolyte. The proportion of the anion structure having an ortho-composition can be determined by, for example, Raman spectroscopy, NMR, or XPS. Specific examples of sulfide solid electrolytes include xLi2S-(1-x)P2S5 (x is 0.7 or more and 0.8 or less), and yLiI-zLiBr-(100-yz)Li3PS4 (y is 0 or more and 30 or less, and z is 0 or more and 30 or less).

[0035] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte or a glass-ceramic-based sulfide solid electrolyte. The glass-based sulfide solid electrolyte can be obtained by vitrifying raw materials. The glass-ceramic-based sulfide solid electrolyte can be obtained, for example, by heat-treating the above-mentioned glass-based sulfide solid electrolyte. In addition, it is preferable that the sulfide solid electrolyte has a predetermined crystal structure. Examples of the crystal structure include a Thio-LISICON-type crystal structure, an LGPS-type crystal structure, and an Argyrodite-type crystal structure.

[0036] Examples of oxide solid electrolytes include Li7La3Zr2O 12 Examples of the solid electrolytes include garnet-type solid electrolytes such as (Li,La)TiO3, perovskite-type solid electrolytes such as (Li,La)TiO3, and Nasicon-type solid electrolytes such as Li(Al,Ti)(PO4)3. Examples of the solid electrolytes include nitrides such as Li3N, and examples of the solid electrolytes include halide materials such as LiCl, LiI, and LiBr.

[0037] The solid electrolyte may be in the form of particles, for example. The average particle size (D 50 ) is, for example, 0.05 μm or more, and may be 0.1 μm or more. On the other hand, the average particle diameter (D 50) is, for example, 50 μm or less, and may be 20 μm or less. The average particle size of the solid electrolyte can be calculated from measurements using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM).

[0038] (3) Dispersant-containing layer In the present disclosure, at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is a dispersant-containing layer. Furthermore, two of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may be dispersant-containing layers, or all of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may be dispersant-containing layers.

[0039] 2. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material and may further contain at least one of a solid electrolyte, a conductive material, a binder, and a dispersant. Alternatively, the positive electrode layer may be the dispersant-containing layer described above. In this case, the positive electrode layer contains at least a positive electrode active material, a solid electrolyte, and a dispersant.

[0040] Examples of the positive electrode active material include oxide active materials, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0041] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. By providing the coating layer, it is possible to suppress the reaction between the oxide active material and the solid electrolyte (particularly, a sulfide solid electrolyte). An example of the Li-ion conductive oxide is LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less.

[0042] The positive electrode active material may be in the form of particles, for example. 50 ) is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less. 50 ) can be calculated, for example, from observation using a scanning electron microscope (SEM).

[0043] The solid electrolyte and dispersant are the same as those described above in "1. Dispersant-Containing Layer," and therefore will not be described here. The proportion of the solid electrolyte in the positive electrode layer is, for example, 5% by weight or more, and may be 10% by weight or more, or 15% by weight or more. If the proportion of the solid electrolyte is too low, a good ion conduction path may not be formed in the positive electrode layer. On the other hand, the proportion of the solid electrolyte in the positive electrode layer is, for example, 40% by weight or less, and may be 30% by weight or less, or may be 25% by weight or less. If the proportion of the solid electrolyte is too high, the proportion of the positive electrode active material will be relatively low, and the energy density of the all-solid-state battery may be reduced.

[0044] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of binders include fluoride-based binders and rubber-based binders. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0045] 3. Negative electrode layer The negative electrode layer is a layer containing at least a negative electrode active material and may further contain at least one of a solid electrolyte, a conductive material, a binder, and a dispersant. Alternatively, the negative electrode layer may be the dispersant-containing layer described above. In this case, the negative electrode layer contains at least a negative electrode active material, a solid electrolyte, and a dispersant.

[0046] Examples of negative electrode active materials include metal active materials, carbon active materials, and oxide active materials. Examples of metal active materials include simple metals and metal alloys. Examples of metal elements contained in metal active materials include Si, Sn, In, and Al. Metal alloys are preferably alloys containing the above metal elements as the main component. Examples of carbon active materials include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of oxide active materials include Li4Ti5O 12 Lithium titanates such as those mentioned above are also included.

[0047] The solid electrolyte and dispersant are the same as those described above in "1. Dispersant-Containing Layer," and therefore will not be described here. The proportion of the solid electrolyte in the negative electrode layer is, for example, 5 wt % or more, and may be 10 wt % or more, or 15 wt % or more. If the proportion of the solid electrolyte is too low, a good ion conduction path may not be formed in the negative electrode layer. On the other hand, the proportion of the solid electrolyte in the negative electrode layer is, for example, 40 wt % or less, and may be 30 wt % or less, or may be 25 wt % or less. If the proportion of the solid electrolyte is too high, the proportion of the negative electrode active material will be relatively low, and the energy density of the all-solid-state battery may be reduced.

[0048] The conductive material and binder are the same as those described above in "2. Positive electrode layer," and therefore, a description thereof will be omitted here. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0049] 4.Solid electrolyte layer The solid electrolyte layer is a layer disposed between the positive electrode layer and the negative electrode layer and containing at least a solid electrolyte. The solid electrolyte layer may further contain at least one of a binder and a dispersant. The solid electrolyte layer may also be the dispersant-containing layer described above.

[0050] The solid electrolyte, dispersant, and binder used in the solid electrolyte layer are the same as those described above in "1. Dispersant-Containing Layer" and "2. Positive Electrode Layer," and therefore will not be described here. The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but may be, for example, 60% by weight or more, 80% by weight or more, or 95% by weight or more. On the other hand, the proportion of the solid electrolyte in the solid electrolyte layer may be 100% by weight or less. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0051] 5.All-solid-state battery The all-solid-state battery according to the present disclosure preferably includes a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0052] The all-solid-state battery according to the present disclosure may further include a constraining jig that applies a constraining pressure to the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in the thickness direction. The constraining pressure is, for example, 0.1 MPa or more, or may be 1 MPa or more, or may be 5 MPa or more. By applying the constraining pressure, the ionic conductivity and electronic conductivity of the all-solid-state battery are improved. On the other hand, the constraining pressure is, for example, 100 MPa or less, or may be 50 MPa or less, or may be 20 MPa or less. If the constraining pressure is too high, the constraining jig may become large.

[0053] The type of all-solid-state battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. The all-solid-state battery in the present disclosure may be a primary battery or a secondary battery, with secondary batteries being preferred. This is because the battery can be repeatedly charged and discharged, making it useful, for example, as an in-vehicle battery. The all-solid-state battery in the present disclosure may be a single cell or a stacked battery. The stacked battery may be a monopolar stacked battery (a parallel-connected stacked battery) or a bipolar stacked battery (a series-connected stacked battery). Examples of the shape of the all-solid-state battery include a coin type, a laminated type, a cylindrical type, and a prismatic type.

[0054] B. Manufacturing method of all-solid-state batteries Fig. 2 is a flowchart illustrating a method for manufacturing an all-solid-state battery according to the present disclosure. As shown in Fig. 2, the method for manufacturing an all-solid-state battery preferably includes a cathode layer forming step of forming a cathode layer, an anode layer forming step of forming an anode layer, a solid electrolyte layer forming step of forming a solid electrolyte layer, and a pressing step of arranging the cathode layer, solid electrolyte layer, and anode layer in this order and pressing them. In particular, according to the present disclosure, at least one of the cathode layer, anode layer, and solid electrolyte layer is a dispersant-containing layer, and the dispersant-containing layer is formed using a slurry containing at least a solid electrolyte and a dispersant.

[0055] According to the present disclosure, by using a slurry containing a specific dispersant, it is possible to obtain an all-solid-state battery having a dispersant-containing layer in which the solid electrolyte has good dispersibility.

[0056] Examples of methods for forming the dispersant-containing layer include a method including a coating process in which a slurry containing at least a solid electrolyte and a dispersant is applied to a substrate to form a coating layer, and a drying process in which the coating layer is dried to form a dispersant-containing layer.

[0057] The slurry used in the coating process contains at least a solid electrolyte and a dispersant. When the dispersant-containing layer is a positive electrode layer, the slurry further contains a positive electrode active material. Similarly, when the dispersant-containing layer is a negative electrode layer, the slurry further contains a negative electrode active material. Furthermore, the slurry may further contain at least one of a conductive material and a binder, as necessary.

[0058] The dispersion medium used in the slurry is not particularly limited, but examples thereof include ketone compounds such as methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, dibutyl ketone, and diisobutyl ketone; ether compounds such as diethylene glycol diethyl ether, cyclopentyl methyl ether, dibutyl ether, dipentyl ether, and anisole; and ester compounds such as ethyl butyrate, butyl butyrate, and 2-methylbutyl butyrate. The ketone compounds, ether compounds, and ester compounds may or may not have a cyclic structure, but the latter are preferred. This is because they have low reactivity with solid electrolytes (especially sulfide solid electrolytes).

[0059] The method for preparing the slurry is not particularly limited. For example, it is preferable to prepare a first solution by dissolving a dispersant in a dispersion medium, and then add and disperse the solid electrolyte in the first solution. This is because the dispersibility of the solid electrolyte is increased. Furthermore, when preparing a slurry containing other materials such as an active material, a conductive material, and a binder in addition to the solid electrolyte and dispersant, it is preferable to add the solid electrolyte to the first solution to prepare the first dispersion, and then add the other materials. In other words, it is preferable to add only the solid electrolyte to the first solution. This is because the dispersibility of the solid electrolyte is increased.

[0060] Examples of dispersion methods include methods using common devices such as a dissolver, homomixer, kneader, roll mill, sand mill, attritor, ball mill, vibrator mill, high-speed impeller mill, ultrasonic homogenizer, and shaker.

[0061] Examples of substrates used in the coating process include current collectors and transfer sheets. Examples of transfer sheets include resin sheets such as fluorine-based resin sheets and metal sheets. Examples of methods for applying the slurry include common methods such as doctor blade coating, die coating, gravure coating, spray coating, electrostatic coating, and bar coating.

[0062] The drying temperature in the drying treatment is, for example, 60°C or higher, or may be 80°C or higher, or 100°C or higher. On the other hand, the drying temperature is, for example, 220°C or lower, or may be 200°C or lower, or may be 170°C or lower, or may be 160°C or lower. Methods for drying the coating layer include common methods such as hot air drying, infrared drying, reduced pressure drying, and dielectric heating drying. Examples of drying atmospheres include inert gas atmospheres such as Ar gas atmospheres and nitrogen gas atmospheres. Furthermore, drying may be performed under atmospheric pressure or under reduced pressure.

[0063] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0064] [Example 1]

[0065] (Fabrication of positive electrode structure) Positive electrode active material (LiNi coated with LiNbO3) 1 / 3 Mn 1 / 3 Co 1 / 3 The following materials were weighed: 64.4 parts by weight of LiI-LiO, 27.6 parts by weight of a sulfide solid electrolyte (LiI-LiO-LiS-P2S5), 3 parts by weight of a conductive material (vapor-grown carbon fiber), 4 parts by weight of a PVDF binder solution in solid content, and 1 part by weight of a dispersant (unsaturated polyaminoamide, A1). The weight ratio of the positive electrode active material to the sulfide solid electrolyte was 70:30.

[0066] Next, methyl isobutyl ketone was prepared, and the weighed dispersant was added and dissolved. After confirming the dissolution of the dispersant, the weighed sulfide solid electrolyte was added and dispersed for 1 minute using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). Then, the weighed other materials (positive electrode active material, binder, conductive material) were added, and methyl isobutyl ketone was added so that the solid content was 60 wt%. The resulting mixture was dispersed for 1 minute using an ultrasonic homogenizer to obtain a slurry.

[0067] The slurry was then applied to the surface of a positive electrode current collector (aluminum foil) using an applicator, allowed to dry naturally for 5 minutes, and then dried with hot air at 100° C. for 60 minutes, thereby obtaining a positive electrode structure having a positive electrode current collector and a positive electrode layer.

[0068] (Fabrication of negative electrode structure) Negative electrode active material (natural graphite, D 50 67.2 parts by weight of anode active material (LiI-Li2O-Li2S-P2S5) with a particle size of 15 μm, 28.8 parts by weight of sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5), and 4 parts by weight of PVDF binder solution in terms of solid content were weighed out. The weight ratio of the negative electrode active material to the sulfide solid electrolyte was negative electrode active material:sulfide solid electrolyte = 70:30.

[0069] Next, methyl isobutyl ketone was prepared, and the weighed sulfide solid electrolyte was added and dispersed for 1 minute using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). After that, the weighed other materials (negative electrode active material, binder) were added, and then methyl isobutyl ketone was added so that the solid content was 55 wt%. The resulting mixture was dispersed for 1 minute using an ultrasonic homogenizer to obtain a slurry.

[0070] The slurry was then applied to the surface of a negative electrode current collector (SUS foil) using an applicator, allowed to dry naturally for 5 minutes, and then dried with hot air at 100° C. for 60 minutes, thereby obtaining a negative electrode structure having a negative electrode current collector and a negative electrode layer.

[0071] (Preparation of solid electrolyte layer) 96 parts by weight of sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5) and 4 parts by weight of PVDF binder solution were weighed. These were mixed, and methyl isobutyl ketone was added to make the solid content 45% by weight. The resulting mixture was dispersed with an ultrasonic homogenizer for 1 minute to obtain a slurry.

[0072] Thereafter, the slurry was applied to the surface of a substrate (aluminum foil) using an applicator, allowed to dry naturally for 5 minutes, and then dried with hot air for 30 minutes at 100° C. This resulted in a solid electrolyte layer being obtained on the substrate.

[0073] (Fabrication of all-solid-state batteries) In an inert gas atmosphere, the substrate was peeled off from the solid electrolyte layer, and a positive electrode structure was placed on one side of the solid electrolyte layer, and a negative electrode structure was placed on the other side of the solid electrolyte layer. The resulting laminate was pressed at 4.3 tons to obtain an all-solid-state battery. [Examples 2 to 11]

[0074] All-solid-state batteries were obtained in the same manner as in Example 1, except that the type and ratio of the dispersant in the positive electrode layer were changed as shown in Tables 1 and 2. In Tables 1 to 4, CA represents the positive electrode layer, SE represents the solid electrolyte layer, and AN represents the negative electrode layer. Regarding the type of dispersant, Group A represents unsaturated polyaminoamide, Group B represents alkylol aminoamide, and Group C represents a polyester-polyamine copolymer. [Example 12]

[0075] (Fabrication of positive electrode structure) Without using a dispersant, the positive electrode active material (LiNi coated with LiNbO3) 1 / 3 Mn 1 / 3 Co 1 / 3 A positive electrode structure was obtained in the same manner as in Example 1, except that 65.1 parts by weight of LiI-LiO, 27.9 parts by weight of a sulfide solid electrolyte (LiI-LiO-LiS-P2S5), 3 parts by weight of a conductive material (vapor-grown carbon fiber), and 4 parts by weight of a PVDF binder solution in terms of solid content were used.

[0076] (Fabrication of negative electrode structure) Negative electrode active material (natural graphite, D 50 The following were weighed: 66.5 parts by weight of anode active material (LiI-Li2O-Li2S-P2S5), 28.5 parts by weight of sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5), 4 parts by weight of PVDF binder solution in terms of solid content, and 1 part by weight of dispersant (unsaturated polyaminoamide, A1). The weight ratio of the negative electrode active material to the sulfide solid electrolyte was 70:30.

[0077] Next, methyl isobutyl ketone was prepared, and the weighed dispersant was added and dissolved. After confirming the dissolution of the dispersant, the weighed sulfide solid electrolyte was added and dispersed for 1 minute using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). Thereafter, the weighed other materials (negative electrode active material, binder) were added, and further, methyl isobutyl ketone was added so that the solid content was 55 wt %. The obtained mixture was dispersed for 1 minute using an ultrasonic homogenizer to obtain a slurry. A negative electrode structure was obtained in the same manner as in Example 1, except that the obtained slurry was used.

[0078] (Preparation of solid electrolyte layer) A solid electrolyte layer was obtained in the same manner as in Example 1.

[0079] (Fabrication of all-solid-state batteries) An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained positive electrode structure, negative electrode structure, and solid electrolyte layer were used. [Example 13]

[0080] First, a positive electrode structure (a positive electrode structure not containing a dispersant) was obtained in the same manner as in Example 12. Next, a negative electrode structure (a negative electrode structure not containing a dispersant) was obtained in the same manner as in Example 1. Next, 93 parts by weight of a sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5), 4 parts by weight of a PVDF binder solution in terms of solid content, and 3 parts by weight of a dispersant (unsaturated polyaminoamide, A1) were weighed. These were mixed, and methyl isobutyl ketone was added so that the solid content was 45% by weight. The resulting mixture was dispersed using an ultrasonic homogenizer for 1 minute to obtain a slurry. A solid electrolyte layer was obtained in the same manner as in Example 1, except that the obtained slurry was used. An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained positive electrode structure, negative electrode structure, and solid electrolyte layer were used. [Example 14]

[0081] First, a positive electrode structure (positive electrode structure containing a dispersant) was obtained in the same manner as in Example 1. Next, a negative electrode structure (negative electrode structure containing a dispersant) was obtained in the same manner as in Example 12. Next, a solid electrolyte layer (solid electrolyte layer containing a dispersant) was obtained in the same manner as in Example 13. An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained positive electrode structure, negative electrode structure, and solid electrolyte layer were used. [Comparative Example 1]

[0082] An all-solid-state battery was obtained in the same manner as in Example 1, except that no dispersant was used in the positive electrode layer and the composition of the slurry used in the positive electrode layer was changed as shown in Table 4. [Comparative Examples 2 to 6]

[0083] An all-solid-state battery was obtained in the same manner as in Example 1, except that the type and ratio of the dispersant in the positive electrode layer were changed as shown in Table 4.

[0084] [evaluation] (dispersibility) The dispersibility of the solid electrolyte was evaluated using the slurries containing the dispersant prepared in Examples 1 to 14 and Comparative Examples 1 to 6. The dispersibility evaluation was performed using a grind gauge (0 to 100 μm scale) based on JIS 5600-2-5:1999 (ISO1524:1983). A: Less than 10 μm... better B: 10 μm or more and less than 30 μm... Good C: 30 μm or more and less than 70 μm... bad D: 70 μm or more...worse

[0085] (resistivity) The Li-ion resistivity of the all-solid-state batteries obtained in Examples 1 to 14 and Comparative Examples 1 to 6 was determined by AC impedance analysis. A Solartron 1260 was used for the measurements, and the measurement conditions were an applied voltage of 10 mV, a measurement frequency range of 0.01 MHz to 1 MHz, and room temperature. The all-solid-state batteries were also adjusted for the measurements as follows: First, the all-solid-state batteries before charging were charged at a constant current of 0.1 C in an environment of 25°C ± 1°C until the terminal voltage reached the set voltage, and then charged for 1 hour by constant-current, constant-voltage charging, which involved constant-voltage charging to maintain the set voltage. Next, constant-current, constant-voltage discharge was performed at a current of 0.2 C for 10 hours down to 4.2 V. Subsequently, constant-current, constant-voltage charging was performed at a current of 0.2 C in an environment of 25°C ± 1°C up to 4.0 V. A: Less than 0.9Ω·m... better B: 0.9Ω·m or more and less than 2.4Ω·m... Good C: 2.4Ω·m or more but less than 5.5Ω·m... Poor D: 5.5Ω·m or more...worse

[0086] (Cycle characteristics) The all-solid-state batteries obtained in Examples 1 to 14 and Comparative Examples 1 to 6 were repeatedly subjected to constant current charge and discharge (CC charge and discharge) in the range of 4.2 V to 2.5 V. Charge and discharge were performed at a current value of 1.0 C in an environment of 25°C ± 1°C. The capacity retention rate was calculated by dividing the discharge capacity at the 200th cycle by the discharge capacity at the 1st cycle. The evaluation criteria for the capacity retention rate (cycle characteristics) are as follows: A: 90% or more... better B: 85% or more but less than 90% ... Good C: 80% or more but less than 85% ... Poor D: Less than 80% ... worse Tables 1 to 4 show the results of the cycle characteristics.

[0087] [Table 1]

[0088] [Table 2]

[0089] [Table 3]

[0090] [Table 4]

[0091] As shown in Tables 1 to 3, it was confirmed that good dispersibility was obtained in all of Examples 1 to 14. Note that, although good dispersibility was obtained in Example 2, the resistivity and cycle characteristics were not good. On the other hand, in Example 3, all of the dispersibility, resistivity, and cycle characteristics were good. This suggests that the proportion of dispersant is preferably 15 wt % or less.

[0092] On the other hand, as shown in Table 4, it was confirmed that good dispersibility was not obtained in any of Comparative Examples 1 to 6. The reason for this is presumably because no dispersant was used in Comparative Example 1. The reason for this is presumably because the proportion of dispersant in Comparative Example 2 was too low. The reason for this is presumably because the amine value of the dispersant in Comparative Example 3 was too high. The reason for this is presumably because the amine value of the dispersant in Comparative Examples 4 and 5 was too low. The reason for this is presumably because the weight-average molecular weight of the dispersant in Comparative Example 6 was too high. Furthermore, the resistivity and cycle characteristics were not good in Comparative Examples 1 to 6.

[0093] In this way, it was confirmed that by using a specific dispersant in a predetermined ratio, a dispersant-containing layer in which the solid electrolyte is well dispersed can be obtained. [Explanation of symbols]

[0094] 1...Positive electrode layer 2...Anode layer 3...Solid electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...All-solid-state battery

Claims

1. An all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer is a dispersant-containing layer containing at least a solid electrolyte and a dispersant; the dispersant-containing layer contains, as the dispersant, at least one of an aminoamide and a polyester-polyamine copolymer; the aminoamide contains at least one of an unsaturated polyaminoamide and an alkylol aminoamide; the unsaturated polyamine amide is at least one of (i) a salt of an unsaturated polyamine amide and a low-molecular-weight polyester acid, and (ii) a reaction product of tall oil fatty acid, polyethylene glycol, maleic anhydride, and an unsaturated polyamine amide salt; The amine value of the dispersant is 20 mgKOH / g or more and 200 mgKOH / g or less, The weight average molecular weight of the dispersant is 150,000 g / mol or less, a proportion of the dispersant in the dispersant-containing layer of 0.1% by weight or more and 20% by weight or less;

2. 2. The all-solid-state battery according to claim 1, wherein the weight average molecular weight of the dispersant is 300 g / mol or more and 150,000 g / mol or less.

3. 3. The all-solid-state battery according to claim 1, wherein the dispersant has an acid value of 0 mgKOH / g or more and 50 mgKOH / g or less.

4. The all-solid-state battery according to claim 1 , wherein the dispersant-containing layer contains the alkylol aminoamide as the dispersant.

5. 5. The all-solid-state battery according to claim 4, wherein the alkylol aminoamide is a condensate of tall oil fatty acid and 2-[(2-aminoethyl)amino]ethanol.

6. 4. The all-solid-state battery according to claim 1, wherein the dispersant-containing layer contains the polyester-polyamine copolymer as the dispersant.

7. the positive electrode layer is the dispersant-containing layer, 7. The all-solid-state battery according to claim 1, wherein the proportion of the solid electrolyte in the positive electrode layer is 10% by weight or more and 30% by weight or less.

8. the negative electrode layer is the dispersant-containing layer, 8. The all-solid-state battery according to claim 1, wherein the proportion of the solid electrolyte in the negative electrode layer is 10% by weight or more and 30% by weight or less.

9. the solid electrolyte layer is the dispersant-containing layer, 9. The all-solid-state battery according to claim 1, wherein the proportion of the solid electrolyte in the solid electrolyte layer is 60% by weight or more.

10. A method for producing an all-solid-state battery according to any one of claims 1 to 9, the dispersant-containing layer is formed using a slurry containing at least the solid electrolyte and the dispersant.

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