Slurry

Abstract

To provide a slurry that can increase dispersibility.SOLUTION: The slurry includes a solvent, amorphous silicon particles, a solid electrolyte, and a dispersion agent. The solvent includes a low-polarity solvent for which the polarity item δp of the Hansen solubility parameter is not larger than 4, and the dispersion agent includes an amphiphilic polymer. The relative relaxation speed ratio, Rsp' / Rsp is smaller than 1.0 when the relative relaxation speed measured by the pulse NMR of a dispersion medium in which the solvent and the amorphous silicon particles are mixed is denoted by Rsp and the relative relaxation speed measured by the pulse NMR of a dispersion medium in which the solvent, the amorphous silicon particles, and the dispersion agent are mixed is denoted by Rsp'.SELECTED DRAWING: None

Description

Technical Field

[0001] This application relates to a slurry.

Background Art

[0002] When forming an active material layer of a battery, a slurry containing a material constituting the active material layer may be used. When using a slurry, an active material layer can be obtained by applying the slurry to a predetermined substrate and drying it.

[0003] Patent Document 1 discloses a slurry containing a sulfide solid electrolyte and two solvents. Further, it is described in the same document that the slurry may contain an active material. Patent Document 2 discloses a method for manufacturing a slurry containing an oxide active material, a solid electrolyte, a dispersion medium, and at least one of a conductive auxiliary material and a binder. Patent Document 3 discloses a suspension containing silicon nanoparticles, an organic solvent, and a dispersant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] When preparing a slurry containing a solvent, silicon particles, a sulfide solid electrolyte, and a dispersant, there is a problem that the dispersant preferentially adsorbs to the sulfide solid electrolyte, causing the silicon particles to aggregate. This is generally because the number of acid sites (e.g., Li) and basic sites (e.g., S) present on the surface of the sulfide solid electrolyte is larger than the number of acid sites and basic sites present on the surface of the silicon particles (the dispersant adsorbs to the acid sites and basic sites). Also, when the silicon particles aggregate, there is a problem that the dispersed solid electrolyte and silicon particles aggregate around the aggregate, forming aggregates. In particular, if aggregates of 100 μm or more are present, there is a risk of coating defects.

[0006] Therefore, in view of the above circumstances, a main object of the present disclosure is to provide a slurry capable of improving dispersibility.

Means for Solving the Problems

[0007] As one aspect for solving the above problems, the present disclosure provides a slurry containing a solvent, amorphous silicon particles, a solid electrolyte, and a dispersant, wherein the solvent includes a low-polarity solvent having a Hansen solubility parameter polar term δP of 4 or less, the dispersant contains an amphiphilic polymer, and when the relative relaxation rate measured by pulsed NMR of a dispersion medium obtained by mixing the solvent and the amorphous silicon particles is defined as Rsp, and the relative relaxation rate measured by pulsed NMR of a dispersion medium obtained by mixing the solvent, the amorphous silicon particles, and the dispersant is defined as Rsp´, a slurry in which the relative relaxation rate ratio Rsp´ / Rsp is less than 1.0 is provided.

Effects of the Invention

[0008] According to the slurry of the present disclosure, the dispersibility can be improved.

Brief Description of the Drawings

[0009]

Figure 1

Modes for Carrying Out the Invention

[0010] [Slurry] The slurry of the present disclosure contains a solvent, amorphous silicon particles, a solid electrolyte, and a dispersant. The solvent includes a low-polarity solvent having a polar term δP of the Hansen solubility parameter of 4 or less. The dispersant contains an amphiphilic polymer. When the relative relaxation rate measured by pulsed NMR of the dispersion medium in which the solvent and the amorphous silicon particles are mixed is defined as Rsp, and the relative relaxation rate measured by pulsed NMR of the dispersion medium in which the solvent, the amorphous silicon particles, and the dispersant are mixed is defined as Rsp', the relative relaxation rate ratio Rsp / Rsp' is less than 1.0.

[0011] By using amorphous silicon particles, surface defects and crystal grain boundaries can be reduced compared to crystalline silicon particles, and the surface energy can be lowered, so that aggregation can be suppressed. Further, since the solvent includes a low-polarity solvent having a polar term δP of the Hansen solubility parameter of 4 or less, the reaction between the solvent and the solid content in the slurry, particularly the solid electrolyte, can be suppressed. Furthermore, since the dispersant contains an amphiphilic polymer and the relative relaxation rate ratio Rsp / Rsp' is less than 1.0, the proportion of the amorphous silicon particles solvated through the dispersion medium can be increased, and the materials contained in the slurry can be appropriately dispersed. Therefore, according to the slurry of the present disclosure, the dispersibility can be improved.

[0012] In addition, the active material layer obtained from the slurry with low dispersibility had a problem of low peeling strength, but this problem can also be solved by the slurry of the present disclosure. That is, since the slurry of the present disclosure has high dispersibility, the active material layer obtained from the slurry has a peeling strength applicable to battery manufacturing.

[0013] Hereinafter, the slurry of the present disclosure will be further described.

[0014] [Solvent] The solvent in the present disclosure includes low-polarity solvents with a polar term δP of the Hansen solubility parameter of 4 or less. The solvent may include solvents other than the low-polarity solvents. The solvents other than the low-polarity solvents are not particularly limited and may be known solvents usually used in slurries.

[0015] (Low-polarity solvent) The low-polarity solvent has a polar term δP of the Hansen solubility parameter of 4 or less. The polar term δP of the Hansen solubility parameter can be obtained from Hansen Solubility Parameters: A user's handbook, Second Edition. Boca Raton, Fla: CRC Press. (Hansen, Charles (2007)). The unit of solubility is MPa 0.5 is.

[0016] Examples of the low-polarity solvent include tetralin (δP = 2), butyl butyrate (δP = 2.9), diisobutyl ketone (δP = 3.7), mesitylene (δP = 0.6), heptane (δP = 0), dibutyl ether (δP = 3.4), decane (δP = 0), toluene (δP = 1.4), etc. These may be used alone or in combination of multiple ones.

[0017] The content of the low-polarity solvent in the solvent is not particularly limited, but may be, for example, 50% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 100% by weight.

[0018] By containing the low-polarity solvent in the solvent, the reaction between the solvent and the solid content in the slurry, particularly the solid electrolyte, can be suppressed.

[0019] <Amorphous silicon particles> The slurry of the present disclosure contains amorphous silicon particles. As described above, the amorphous silicon particles can reduce surface defects and crystal grain boundaries and lower the surface energy compared to the crystalline silicon particles, so that aggregation can be suppressed.

[0020] The shape of the amorphous silicon particles is not particularly limited, and examples thereof include spherical, ellipsoidal, columnar, and flaky shapes. Further, the amorphous silicon particles may be porous.

[0021] The particle size of the amorphous silicon particles is not particularly limited, but it may be 0.1 μm or more, 1 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less.

[0022] As used herein, the "particle size" can be determined by observing the particles with a scanning electron microscope (SEM), aggregating the long sides of the rectangles circumscribing each particle as the diameter, and averaging by dividing by the number of particles. The number of particles to be measured is at least 10 or more. Preferably, it is 100 or more.

[0023] The content of the amorphous silicon particles with respect to the total solid content contained in the slurry is not particularly limited, but it may be, for example, 30% by weight or more, 50% by weight or more, 80% by weight or less, or 60% by weight or less.

[0024] <Solid electrolyte> The solid electrolyte of the present disclosure has Li ion conductivity and is not particularly limited as long as it is a solid electrolyte applicable to all-solid-state lithium ion batteries. The solid electrolyte may be glassy (amorphous), crystallized glassy, or crystalline. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Preferably, it is a sulfide solid electrolyte.

[0025] The sulfide solid electrolyte preferably contains an Li element, an M element (M is preferably at least one of P, Ge, Si, Sn, B, and Al), and an S element. The sulfide solid electrolyte may further contain a halogen element. Examples of the halogen element include F element, Cl element, Br element, and I element. Further, the amorphous sulfide solid electrolyte may further contain an O element.

[0026] As sulfide solid electrolytes, for example, Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -GeS 2 、Li 2 S-P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-P 2 S 5 -LiI-LiBr, Li 2 S-SiS 2 、Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3 、Li 2 S-P 2 S 5 -Z m S n (However, m and n are positive numbers. Z is any one of Ge, Zn, and Ga.), Li 2 S-GeS 2 、Li 2 S-SiS 2 -Li 3 PO 4 、Li 2 S-SiS 2 -Li x MO y(However, x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.) can be mentioned.

[0027] Examples of the oxide solid electrolyte include lithium lanthanum zirconium-containing composite oxide (LLZO), Al-doped LLZO, lithium lanthanum titanium-containing composite oxide (LLTO), Al-doped LLTO, lithium phosphorus oxynitride (LIPON), etc. Examples of the nitride solid electrolyte include, for example, Li 3 N, Li 3 N-LiI-LiOH. Examples of the halide solid electrolyte include, for example, LiF, LiCl, LiBr, LiI, LiI-Al 2 O 3 etc. can be mentioned.

[0028] The shape of the solid electrolyte is not particularly limited, and examples include spherical, ellipsoidal, columnar, and flaky.

[0029] The particle size of the solid electrolyte is not particularly limited, but it may be 0.1 μm or more, 1 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less.

[0030] The ratio of the solid electrolyte to the total solid content contained in the slurry is not particularly limited, but it may be, for example, 20% by weight or more, 30% by weight or more, 40% by weight or more, 60% by weight or less, or 50% by weight or less.

[0031] <Dispersant> The dispersant in the present disclosure contains an amphiphilic polymer. The dispersant may contain a dispersant other than the amphiphilic polymer. The dispersant other than the amphiphilic polymer is not particularly limited and may be a known dispersant usually used in slurries. For example, known surfactants can be mentioned.

[0032] The content of the dispersant relative to the total solid content contained in the slurry is not particularly limited. For example, it may be 0.1% by weight or more, 0.5% by weight or more, 0.8% by weight or more, 5% by weight or less, 2% by weight or less, or 1% by weight or less.

[0033] (Amphiphilic polymer) An amphiphilic polymer is a polymer having a hydrophilic functional group and a hydrophobic functional group. Examples of the hydrophilic functional group include nitrogen-containing functional groups having no reactive hydrogen such as a tertiary amino group, a pyridyl group, and an imidazole group. Examples of the hydrophobic functional group include a hydrocarbon group such as an alkyl group. The amphiphilic polymer may have two or more repeating units. Also, the polymerization form may be random or block. The amphiphilic polymer is not particularly limited as long as it is soluble in the above solvent. For example, polyalkyleneamine or a copolymer of an alkyl acrylate and a tertiary vinylamine (which may be a random copolymer or a block copolymer) can be mentioned.

[0034] Since the slurry contains an amphiphilic polymer, it can adsorb to both the solid electrolyte and the amorphous silicon particles, so that aggregation can be suppressed and the dispersibility of the slurry can be improved.

[0035] The molecular weight of the amphiphilic polymer is not particularly limited. For example, it may be 5000 to 50000, or 5000 to 10000. The molecular weight of the amphiphilic polymer can be converted from the elution time of size exclusion chromatography using a polystyrene standard.

[0036] The degree of polymerization of the amphiphilic polymer is not particularly limited. For example, it is 50 to 500. The degree of polymerization of the amphiphilic polymer can be converted from the elution time of size exclusion chromatography using a polystyrene standard.

[0037] The content of the amphiphilic polymer in the dispersant is not particularly limited, and may be, for example, 50% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 100% by weight.

[0038] <Binder> The slurry of the present disclosure may contain a binder as an optional component. The binder is not particularly limited as long as it is applicable to a lithium-ion battery. For example, butadiene rubber (BR), isobutylene rubber (IIR), acrylate butadiene rubber (ABR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), etc. may be mentioned. These may be used alone or in a plurality of types. Preferably, it is PVdF-HFP. This is because PVdF is polarized, easily adsorbed to the active material and the solid electrolyte, and tends to have high adhesive strength.

[0039] The content of the binder with respect to the total solid content contained in the slurry is not particularly limited, and may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.6% by weight or more, 0.8% by weight or more, 5% by weight or less, 2% by weight or less, 1.1% by weight or less, or 1% by weight or less.

[0040] <Conductive aid> The slurry of the present disclosure may contain a conductive aid as an optional component. The conductive aid is not particularly limited as long as it is applicable to a lithium-ion battery. For example, carbon materials such as acetylene black, ketjen black, and vapor-grown carbon fiber (VGCF), and metal materials such as nickel, aluminum, and stainless steel may be mentioned.

[0041] The content of the conductive aid with respect to the total solid content contained in the slurry is not particularly limited, and may be, for example, 1% by weight or more, 2% by weight or more, 4% by weight or more, 10% by weight or less, 8% by weight or less, or 6% by weight or less.

[0042] <Other components> The slurry may contain other components, such as various additives, etc., as necessary.

[0043] <Slurry> For the slurry of the present disclosure, when the relative relaxation rate measured by pulsed NMR of the dispersion medium in which a solvent and amorphous silicon particles are mixed is Rsp, and the relative relaxation rate measured by pulsed NMR of the dispersion medium in which a solvent, amorphous silicon particles, and a dispersant are mixed is Rsp´, the relative relaxation rate ratio Rsp´ / Rsp is less than 1.0.

[0044] The relative relaxation rate ratio Rsp´ / Rsp is calculated as follows. First, a blank of only the solvent, a sample 1 in which the solvent and amorphous Si particles are mixed at a weight ratio of 80:20, and a sample 2 in which the solvent, amorphous silicon particles, and a dispersant are mixed at a weight ratio of 80:19.7:0.3 are prepared. Next, using the blank and samples 1 and 2, the T2 relaxation times by the CPMG method using pulsed NMR are measured respectively. Then, (blank relaxation time) / (sample relaxation time) - 1 is calculated to calculate the relative relaxation rates Rsp and Rsp´ respectively. And the relative relaxation rate ratio Rsp´ / Rsp is calculated.

[0045] Since the relative relaxation rate ratio Rsp´ / Rsp is less than 1.0, the dispersant is likely to adsorb on the amorphous silicon particles. Therefore, the amorphous silicon particles are likely to be solvated, and the dispersibility of the slurry is improved.

[0046] The relative relaxation rate ratio Rsp´ / Rsp is not particularly limited as long as it is less than 1.0. For example, it may be 0.95 or less, 0.92 or less, 0.8 or more, or 0.81 or more.

[0047] The particle size of the slurry of the present disclosure is not particularly limited, but may be less than 100 μm, may be 50 μm or less, may be 20 μm or less, may be less than 20 μm, may be 0.1 μm or more, and may be 1 μm or more. The particle size of the slurry can be measured according to JIS K 5600-2-5:1999.

[0048] The slurry of the present disclosure can be obtained by mixing each component and a solvent. The mixing method is not particularly limited and can be carried out by a known method. For example, the slurry of the present disclosure can be obtained by mixing while adding each component to the solvent. The mixing method is not particularly limited, and a blender or ultrasonic waves may be used.

[0049] The slurry of the present disclosure is used to form an active material layer for a lithium-ion battery, particularly for an all-solid-state lithium-ion battery. The active material layer may be a positive electrode active material layer or a negative electrode layer, but is preferably a negative electrode active material layer.

[0050] [Method for manufacturing negative electrode active material layer] The method for manufacturing the negative electrode active material layer of the present disclosure includes a step of coating the slurry of the present disclosure on a substrate (coating step) and a step of drying the coated slurry (drying step). Since the slurry of the present disclosure has high dispersibility, the negative electrode active material layer obtained from the slurry has a peel strength applicable to battery manufacturing. Therefore, according to the method for manufacturing the negative electrode active material layer of the present disclosure, a negative electrode active material layer with suppressed occurrence of coating defects of the slurry can be obtained.

[0051] The coating step can be carried out by a known method. For example, general methods such as the doctor blade method, die coating method, gravure coating method, spray coating method, electrostatic coating method, and bar coating method can be mentioned. Further, the substrate on which the slurry is coated is not particularly limited and may be a metal foil, a current collector, or a solid electrolyte layer.

[0052] The drying process can be carried out by known methods. For example, the slurry may be heated in the range of 50°C to 200°C or lower. Also, the atmosphere may be set to an inert atmosphere or a reduced-pressure atmosphere.

[0053] The shape of the obtained negative electrode active material layer is not particularly limited, but it is preferably sheet-shaped. The thickness of the negative electrode active material layer is not particularly limited and may be appropriately set according to the desired battery performance. For example, it is in the range of 0.1 μm or more and 1 mm or less.

[0054] [Method for manufacturing all-solid-state battery] The method for manufacturing an all-solid-state battery of the present disclosure includes a step of forming a negative electrode active material layer (negative electrode active material layer forming step) by the method for manufacturing a negative electrode active material layer of the present disclosure, a step of forming a positive electrode active material layer (positive electrode active material layer forming step), and a step of forming a solid electrolyte layer (solid electrolyte layer forming step), and a step of laminating the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer in this order (laminating step). According to the method for manufacturing an all-solid-state battery of the present disclosure, an all-solid-state battery including a negative electrode active material layer in which the occurrence of coating defects of the slurry is suppressed can be obtained.

[0055] <Negative electrode active material layer forming step> The negative electrode active material layer forming step is carried out by the method for manufacturing a negative electrode active material layer of the present disclosure. In the negative electrode active material forming step, a negative electrode current collector may be used as the substrate on which the slurry is applied. Thereby, a negative electrode can be manufactured.

[0056] The material of the negative electrode current collector can be appropriately selected from known materials according to the purpose. For example, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. can be mentioned. The thickness of the negative electrode current collector is not particularly limited and may be appropriately set according to the desired battery performance. For example, it is in the range of 0.1 μm or more and 1 mm or less.

[0057] <Positive electrode active material layer forming step> The process of fabricating the positive electrode active material layer can be carried out by known methods. For example, the materials constituting the positive electrode active material layer are mixed dry and pressed to obtain the positive electrode active material layer. Alternatively, the materials constituting the positive electrode active material layer are dispersed in a solvent to form a slurry, and the obtained slurry is applied to a substrate and dried to obtain the positive electrode active material layer. A positive electrode current collector may be used as the substrate. Thereby, a positive electrode can be fabricated. Hereinafter, the positive electrode current collector and the positive electrode active material layer will be described.

[0058] The material of the positive electrode current collector is not particularly limited and can be appropriately selected from known materials according to the purpose. For example, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. can be mentioned. The thickness of the positive electrode current collector is not particularly limited and may be appropriately set according to the desired battery performance. For example, it is in the range of 0.1 μm or more and 1 mm or less.

[0059] The positive electrode active material layer contains at least a positive electrode active material. The positive electrode active material can be appropriately selected from known positive electrode active materials used in all-solid-state lithium-ion batteries. For example, lithium cobaltate, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, etc. can be mentioned. The particle size of the positive electrode active material is not particularly limited, but for example, it is in the range of 1 μm to 100 μm. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but for example, it is in the range of 50% by weight to 99% by weight. Also, the surface of the positive electrode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or lithium phosphate.

[0060] The positive electrode active material layer may optionally include a solid electrolyte. The solid electrolyte can be appropriately selected from known solid electrolytes used in all-solid-state lithium-ion batteries. For example, the solid electrolytes that can be contained in the above-mentioned slurry can be mentioned. The content of the solid electrolyte in the positive electrode active material layer is not particularly limited, but for example, it is in the range of 1% by weight to 50% by weight.

[0061] The positive electrode active material layer may optionally include a conductive aid. The conductive aid can be appropriately selected from known conductive aids used in all-solid-state lithium-ion batteries. For example, the conductive aids that can be contained in the above-described slurry can be mentioned. The content of the conductive aid in the positive electrode active material layer is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

[0062] The positive electrode active material layer may optionally include a binder. The binder can be appropriately selected from known binders used in all-solid-state lithium-ion batteries. For example, the binders that can be contained in the above-described slurry can be mentioned. The content of the binder in the positive electrode active material layer is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

[0063] The shape of the positive electrode active material layer is not particularly limited, but is preferably sheet-shaped. The thickness of the positive electrode active material layer is not particularly limited and can be appropriately set according to the desired battery performance. For example, it is in the range of 0.1 μm or more and 1 mm or less.

[0064] <Solid electrolyte layer manufacturing process> The solid electrolyte layer manufacturing process can be carried out by known methods. For example, a solid electrolyte layer can be obtained by dry-mixing the materials constituting the solid electrolyte layer and pressing them. Alternatively, a solid electrolyte layer can be obtained by dispersing the materials constituting the solid electrolyte layer in a solvent to form a slurry, applying the obtained slurry to a substrate, and drying it. The solid electrolyte layer will be described below.

[0065] The solid electrolyte layer contains at least a solid electrolyte. The solid electrolyte can be appropriately selected from known solid electrolytes used in all-solid-state lithium-ion batteries. For example, the solid electrolytes that can be contained in the above-described slurry can be mentioned. The content of the solid electrolyte in the solid electrolyte layer is not particularly limited, but is, for example, in the range of 50% by weight to 99% by weight.

[0066] Further, the solid electrolyte layer may optionally include a binder. The binder can be appropriately selected from known binders used in all-solid-state lithium-ion batteries. For example, the binders that can be contained in the slurry described above can be mentioned. The content of the binder in the solid electrolyte layer is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

[0067] The shape of the solid electrolyte layer is not particularly limited, but it is preferably sheet-shaped. The thickness of the solid electrolyte layer is not particularly limited and may be appropriately set according to the desired battery performance. For example, it is in the range of 0.1 μm or more and 1 mm or less.

[0068] <Lamination process> The lamination process is a process of laminating the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer in this order. After laminating these layers, a laminate can be obtained by pressing. The pressing method is not particularly limited, and examples include roll pressing and flat pressing. The linear pressure applied during roll pressing may be, for example, 1 t / cm or more and 10 t / cm or less. The surface pressure applied during flat pressing may be, for example, 800 MPa or more and 3000 MPa or less.

[0069] After the lamination process, the negative electrode current collector may be disposed on the surface of the negative electrode active material layer, and the positive electrode current collector may be disposed on the surface of the positive electrode active material layer.

[0070] In the case where the negative electrode current collector and the positive electrode current collector are used for the base material in the negative electrode active material layer manufacturing process and the positive electrode active material layer manufacturing process, in the lamination process, the negative electrode, the solid electrolyte layer, and the positive electrode are laminated in this order.

[0071] The all-solid-state battery obtained by the manufacturing method of the all-solid-state battery of the present disclosure may be a single cell or a laminated battery. The laminated battery may be a monopolar type laminated battery (parallel-connected laminated battery) or a bipolar type laminated battery (series-connected laminated battery). Examples of the shape of the all-solid-state battery include coin type, laminate type, cylindrical type, and rectangular type.

Examples

[0072] The slurry of the present disclosure will be further described using examples.

[0073] <Preparation of Slurry> Using the materials and contents shown in Table 1, slurries of Examples 1 to 2 and Comparative Examples 1 to 12 were prepared. First, the materials were put into a 5 mL container at once so that the total volume became 3.5 mL to prepare a slurry. Next, while cooling the obtained mixture to 10°C, ultrasonic waves with an amplitude of 40 μm and a frequency of 20 kHz were irradiated for 40 minutes using a φ3.5 mm ultrasonic horn to disperse. Thus, slurries of Examples 1 to 2 and Comparative Examples 1 to 12 were prepared.

[0074] The materials in Table 1 will be described. As the silicon active material (Si active material), amorphous silicon active material and crystalline silicon active material were used. As the solid electrolyte, a sulfide solid electrolyte was used. As the binder, PVdF-HFP or SBR was used. As the dispersant, an amphiphilic polymer or a low-molecular surfactant was used. As the amphiphilic polymer, polyalkyleneamine (molecular weight: about 5000) was used. As the low-molecular surfactant, alkylimidazoline (molecular weight: about 500) was used. As the conductive aid, VGCF was used. As the solvent, diisobutyl ketone (DIBK), tetralin, or butyl butyrate was used. Note that (δP) described in the solvent column is the numerical value of the polar term of the Hansen solubility parameter.

[0075] Also, in Table 1, the contents of the binder and the dispersant with respect to the total solid content are shown.

[0076] <XRD Measurement> Regarding the amorphous silicon particles and crystalline silicon particles used in the slurry, the diffraction intensity in the range of 2θ = 10 to 80°C was measured. Rigaku SmartLab was used as the XRD apparatus. The results are shown in Figure 1.

[0077] As shown in Fig. 1, the peak of the crystalline silicon particles was sharp, confirming that they were crystalline. On the other hand, the peak of the amorphous silicon particles was broad, confirming that they were amorphous.

[0078] <Pulse NMR measurement> First, a blank containing only the solvent, Sample 1 in which the solvent and the Si active material were mixed at a weight ratio of 80:20, and Sample 2 in which the solvent, the Si active material, and the dispersant were mixed at a weight ratio of 80:19.7:0.3 were prepared.

[0079] Next, for each sample, the T2 relaxation time was measured by the CPMG method using pulse NMR. Bruker minispec mq20 was used as the measuring device. Then, the relative relaxation rate was measured from (blank relaxation time) / (sample relaxation time) - 1. Here, the relative relaxation rates obtained from the blank and Sample 1 were defined as Rsp, and the relative relaxation rates obtained from the blank and Sample 2 were defined as Rsp'. Also, the relative relaxation rate ratio Rsp' / Rsp was calculated. The results are shown in Table 2.

[0080] Note that the locations indicated by "-" in Table 2 mean that they were not measured.

[0081] <Particle size measurement> The particle sizes of each slurry were measured. The particle size measurement method was carried out in accordance with JIS K 5600-2-5:1999. The results are shown in Table 2.

[0082] Note that the locations indicated by "-" in Table 2 mean that the aggregates had settled and could not be measured.

[0083] <Dispersibility evaluation> The state of the slurry was visually evaluated. When no aggregates were present, it was evaluated as "〇", and when aggregates were present, it was evaluated as "×". Also, when aggregates were present, the state of the aggregates was evaluated. When aggregates were present and had not settled, it was evaluated as "aggregation", and when the aggregates had settled, it was evaluated as "sedimentation". The results are shown in Table 2.

[0084] <Peel Strength Evaluation> A slurry was applied to a substrate and dried to obtain a coating film. When the obtained coating film was punched out with a hand punch, it was visually confirmed whether peeling or cracking occurred. Also, roll pressing was performed on the coating film, and it was visually confirmed whether peeling or cracking occurred. In both the hand punch and roll pressing, when no peeling occurred, it was evaluated as "〇", and when peeling occurred in either one or both, it was evaluated as "×". The results are shown in Table 2.

[0085]

Table 1

[0086]

Table 2

[0087] <Results> From Table 1 and Table 2, Examples 1 and 2 had good results in dispersion evaluation and peel strength evaluation. On the other hand, in Comparative Examples 1 to 12, at least one of the dispersion evaluation and peel strength evaluation was "×".

[0088] In Comparative Example 1, the binder amount with respect to the total solid content was larger compared to the conditions of Example 1, the particle size became 100 μm or more, and aggregation occurred in the slurry. In Comparative Example 2, the binder amount with respect to the total solid content was smaller compared to the conditions of Example 1, and peeling occurred in the coating film. In Comparative Example 3, since SBR with low affinity to particles was adopted compared to the conditions of Comparative Example 2, the particle size further became 100 μm or more, and aggregation occurred in the slurry. In Comparative Examples 4 and 5, the type of solvent was changed from the conditions of Comparative Example 3, and a solvent with a lower δP was adopted, but the results were not improved. In Comparative Examples 6 and 7, the content of the dispersant was reduced from the conditions of Comparative Example 4, but the results were not improved. In Comparative Examples 8 and 9, the content of the dispersant was reduced from the conditions of Comparative Example 3, but the results were not improved. In Comparative Example 10, the type of Si active material was changed from the conditions of Comparative Example 3, and crystalline silicon particles were adopted, but the results were not improved. In Comparative Example 11, the type of Si active material was changed from the conditions of Comparative Example 4, and crystalline silicon particles were adopted, but the results were not improved. In Comparative Example 12, the type of dispersant was changed from the conditions of Comparative Example 4, and a surfactant was adopted, but the results were not improved.

Claims

1. A slurry containing a solvent, amorphous silicon particles, a solid electrolyte, a dispersant, and a binder, wherein the solvent includes a low-polarity solvent having a polar term δP of the Hansen solubility parameter of 4 or less, the dispersant contains an amphiphilic polymer, the content of the binder with respect to the total solid content contained in the slurry is 0.8% by weight or more and 1.0% by weight or less, the amphiphilic polymer is a polyalkyleneamine, when the relative relaxation rate measured by pulsed NMR of the dispersion medium obtained by mixing the solvent and the amorphous silicon particles is defined as Rsp, and the relative relaxation rate measured by pulsed NMR of the dispersion medium obtained by mixing the solvent, the amorphous silicon particles, and the dispersant is defined as Rsp', a slurry in which the relative relaxation rate ratio Rsp' / Rsp is less than 1.

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