JP7690888B2 - slurry - Google Patents

Description

This application relates to slurries.

In order to form the active material layer of a battery, a slurry containing the materials that make up the active material layer may be used. When using a slurry, the active material layer is obtained by applying the slurry to a specified substrate and drying it.

Patent Document 1 discloses a slurry containing a sulfide solid electrolyte and two types of solvents. The document also describes that the slurry may contain an active material. Patent Document 2 discloses a method for producing a slurry containing an oxide active material, a solid electrolyte, a dispersion medium, and at least one of a conductive assistant and a binder. Patent Document 3 discloses a suspension containing silicon nanoparticles, an organic solvent, and a dispersant.

JP 2021-68673 A JP 2020-177755 A JP 2021-114483 A

When preparing a slurry containing a solvent, silicon particles, a sulfide solid electrolyte, and a dispersant, the dispersant preferentially adsorbs to the sulfide solid electrolyte, causing the silicon particles to aggregate. This is because the number of acid sites (e.g., Li) and base sites (e.g., S) present on the surface of the sulfide solid electrolyte is generally greater than the number of acid sites and base sites present on the surface of the silicon particles (the dispersant is adsorbed to the acid sites and base sites). In addition, when the silicon particles aggregate, the dispersed solid electrolyte and silicon particles aggregate around the aggregates, resulting in the problem of agglomerates. In particular, if aggregates of 100 μm or more are present, there is a risk of poor coating.

Therefore, the main objective of this disclosure is to provide a slurry that can improve dispersibility in light of the above circumstances.

As one aspect for solving the above problem, the present disclosure provides a slurry containing a solvent, amorphous silicon particles, a solid electrolyte, and a dispersant, the solvent including a low polarity solvent having a polarity term δP of the Hansen solubility parameter of 4 or less, the dispersant including an amphiphilic polymer, and a relative relaxation rate ratio Rsp'/Rsp of less than 1.0, where Rsp is the relative relaxation rate measured by pulse NMR of the dispersion medium in which the solvent and the amorphous silicon particles are mixed, and Rsp' is the relative relaxation rate measured by pulse NMR of the dispersion medium in which the solvent, the amorphous silicon particles, and the dispersant are mixed.

The slurry disclosed herein can improve dispersibility.

1 shows XRD spectra of amorphous silicon particles and crystalline silicon particles in an example.

[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 polarity term δP of the Hansen solubility parameter of 4 or less, the dispersant contains an amphiphilic polymer, and when the relative relaxation rate of the dispersion medium obtained by mixing the solvent and the amorphous silicon particles is Rsp and the relative relaxation rate of the dispersion medium obtained by mixing the solvent, the amorphous silicon particles, and the dispersant is Rsp', the relative relaxation rate ratio Rsp/Rsp' is less than 1.0.

By using amorphous silicon particles, surface defects and grain boundaries are reduced compared to crystalline silicon particles, and surface energy can be reduced, thereby suppressing aggregation. In addition, by including a low-polarity solvent with a polarity 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, by including an amphipathic polymer in the dispersant and having a relative relaxation rate ratio Rsp/Rsp' of less than 1.0, the proportion of amorphous silicon particles solvated via the dispersion medium can be increased, and the materials contained in the slurry can be appropriately dispersed. Therefore, the slurry of the present disclosure can improve dispersibility.

In addition, active material layers obtained from slurries with low dispersibility have a problem of low peel strength, but the slurry disclosed herein can solve this problem. In other words, because the slurry disclosed herein has high dispersibility, the active material layers obtained from the slurry have a peel strength that is applicable to battery manufacturing.

The slurry of this disclosure is further described below.

<Solvent>
The solvent in the present disclosure includes a low polarity solvent having a polarity term δP of the Hansen solubility parameter of 4 or less. The solvent may include a solvent other than the low polarity solvent. The solvent other than the low polarity solvent is not particularly limited, and may be a known solvent that is usually used for slurries.

(Low polarity solvent)
A low polarity solvent has a polarity term δP of the Hansen solubility parameter of 4 or less. The polarity 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 .

Low polarity solvents 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.

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.

By containing a low polarity solvent, the reaction between the solvent and the solids in the slurry, particularly the solid electrolyte, can be suppressed.

<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 grain boundaries and reduce surface energy compared to crystalline silicon particles, thereby suppressing aggregation.

The shape of the amorphous silicon particles is not particularly limited, and may be, for example, spherical, elliptical, cylindrical, or scaly. The amorphous silicon particles may also be porous.

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

In this specification, "particle size" can be determined by observing particles with a scanning electron microscope (SEM), counting the diameter of the long side of the rectangle circumscribing each particle, and dividing the average by the number of particles. The number of particles to be measured should be at least 10 or more. Preferably, it is 100 or more.

The content of amorphous silicon particles relative to the total solid content in the slurry is not particularly limited, but 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.

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

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

Examples of the sulfide solid electrolyte include 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 (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , and Li ₂ S-SiS ₂ -Li _x MO _y (where x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In).

Examples of oxide solid electrolytes include lithium lanthanum zirconium-containing composite oxide (LLZO), Al-doped LLZO, lithium lanthanum titanium-containing composite oxide (LLTO), Al-doped LLTO, and lithium oxynitride phosphate (LIPON). Examples of nitride solid electrolytes include Li ₃ N and Li ₃ N-LiI-LiOH. Examples of halide solid electrolytes include LiF, LiCl, LiBr, LiI, and LiI-Al ₂ O ₃ .

The shape of the solid electrolyte is not particularly limited, and examples include spheres, ellipsoids, columns, and scales.

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

The ratio of the solid electrolyte to the total solid content contained in the slurry is not particularly limited, but 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.

<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 that is usually used in slurries. For example, a known surfactant may be used.

The content of the dispersant relative to the total solid content in the slurry is not particularly limited, but may be, for example, 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.

(Amphiphilic polymer)
The amphiphilic polymer is a polymer having a hydrophilic functional group and a hydrophobic functional group. Examples of the hydrophilic functional group include reactive nitrogen-containing functional groups having no 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 kinds of repeating units. The polymerization form may be random or block. The amphiphilic polymer is not particularly limited as long as it is soluble in the above-mentioned solvent, and examples thereof include polyalkyleneamines and copolymers of alkyl acrylate and tertiary vinylamine (which may be random copolymers or block copolymers).

The slurry contains an amphiphilic polymer, which can adsorb to both the solid electrolyte and the amorphous silicon particles, suppressing aggregation and improving the dispersibility of the slurry.

The molecular weight of the amphiphilic polymer is not particularly limited, but may be, for example, 5,000 to 50,000, or 5,000 to 10,000. The molecular weight of the amphiphilic polymer can be calculated from the elution time of size exclusion chromatography using a polystyrene standard.

The degree of polymerization of the amphiphilic polymer is not particularly limited, but is, for example, 50 to 500. The degree of polymerization of the amphiphilic polymer can be calculated from the elution time of size exclusion chromatography using a polystyrene standard.

The content of the amphiphilic polymer in the dispersant 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.

<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 lithium ion batteries. For example, butadiene rubber (BR), butylene 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 combination. PVdF-HFP is preferable. This is because PVdF is polarized and easily adsorbed to active materials and solid electrolytes, and the binding force is easily increased.

The binder content relative to the total solid content in the slurry is not particularly limited, but 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.

<Conductive assistant>
The slurry of the present disclosure may contain a conductive assistant as an optional component. The conductive assistant is not particularly limited as long as it is a binder that can be applied to lithium ion batteries. 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 can be mentioned.

The content of the conductive additive relative to the total solid content in the slurry is not particularly limited, but 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.

<Other ingredients>
The slurry may contain other components, such as various additives, as necessary.

<Slurry>
In the slurry of the present disclosure, when the relative relaxation rate of a dispersion medium obtained by mixing a solvent and amorphous silicon particles is measured by pulse NMR as Rsp, and the relative relaxation rate of a dispersion medium obtained by mixing a solvent, amorphous silicon particles, and a dispersant is measured by pulse NMR as Rsp', the relative relaxation rate ratio Rsp'/Rsp is less than 1.0.

The relative relaxation rate ratio Rsp'/Rsp is calculated as follows. First, a blank containing only solvent, sample 1 in which solvent and amorphous Si particles are mixed in a weight ratio of 80:20, and sample 2 in which solvent, amorphous silicon particles, and dispersant are mixed in a weight ratio of 80:19.7:0.3 are prepared. Next, the blank and samples 1 and 2 are used to measure the T2 relaxation time using the CPMG method with pulsed NMR. Then, (blank relaxation time)/(sample relaxation time)-1 is calculated to calculate the relative relaxation rates Rsp and Rsp'. Then, the relative relaxation rate ratio Rsp'/Rsp is calculated.

When the relative relaxation rate ratio Rsp'/Rsp is less than 1.0, the dispersant is more easily adsorbed onto the amorphous silicon particles. Therefore, the amorphous silicon particles are more easily solvated, improving the dispersibility of the slurry.

The relative relaxation rate ratio Rsp'/Rsp is not particularly limited as long as it is less than 1.0, but may be, for example, 0.95 or less, 0.92 or less, 0.8 or more, or 0.81 or more.

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

The slurry of the present disclosure can be obtained by mixing each component with a solvent. The mixing method is not particularly limited, and can be performed by a known method. For example, the slurry of the present disclosure can be obtained by adding each component to a solvent while mixing. The mixing method is not particularly limited, and a blender or ultrasound may be used.

The slurry of the present disclosure is used to form an active material layer for a lithium ion battery, particularly 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.

[Method of manufacturing negative electrode active material layer]
The method for producing an anode active material layer according to the present disclosure includes a step of applying the slurry of the present disclosure to a substrate (application step) and a step of drying the applied slurry (drying step). The slurry of the present disclosure has high dispersibility, so that the anode active material layer obtained from the slurry has a peel strength applicable to battery production. Therefore, according to the method for producing an anode active material layer according to the present disclosure, an anode active material layer in which the occurrence of slurry application defects is suppressed can be obtained.

The coating process can be carried out by a known method. For example, common methods such as doctor blade method, die coating method, gravure coating method, spray coating method, electrostatic coating method, and bar coating method can be mentioned. In addition, the substrate to which the slurry is applied is not particularly limited, and may be a metal foil, a current collector, or a solid electrolyte layer.

The drying process can be carried out by a known method. For example, the slurry may be heated to a temperature range of 50°C to 200°C. The atmosphere may also be set to an inert atmosphere or a reduced pressure atmosphere.

The shape of the obtained negative electrode active material layer is not particularly limited, but it is preferably in the form of a sheet. The thickness of the negative electrode active material layer is not particularly limited and may be set appropriately according to the desired battery performance. For example, it is in the range of 0.1 μm to 1 mm.

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

<Negative electrode active material layer preparation process>
The negative electrode active material layer preparation step is carried out by the method for producing a negative electrode active material layer of the present disclosure. In the negative electrode active material preparation step, a negative electrode current collector may be used as a substrate to which the slurry is applied. This allows the negative electrode to be prepared.

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

<Positive electrode active material layer preparation process>
The positive electrode active material layer preparation step can be carried out by a known method. For example, the materials constituting the positive electrode active material layer are mixed in a dry state 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. This allows the positive electrode to be prepared. The positive electrode current collector and the positive electrode active material layer will be described below.

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

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. Examples include lithium cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), and lithium manganese oxide. The particle size of the positive electrode active material is not particularly limited, but is, for example, 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 is, for example, in the range of 50% by weight to 99% by weight. In addition, the surface of the positive electrode active material may be covered with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer.

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

The positive electrode active material layer may optionally contain a conductive assistant. The conductive assistant can be appropriately selected from known conductive assistants used in all-solid-state lithium-ion batteries. For example, the conductive assistants that can be contained in the slurry described above can be used. The content of the conductive assistant 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.

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

The shape of the positive electrode active material layer is not particularly limited, but a sheet shape is preferable. The thickness of the positive electrode active material layer is not particularly limited and may be set appropriately according to the desired battery performance. For example, it is in the range of 0.1 μm to 1 mm.

<Solid electrolyte layer production process>
The solid electrolyte layer preparation step can be carried out by a known method. For example, the materials constituting the solid electrolyte layer are mixed in a dry state and pressed to obtain the solid electrolyte layer. Alternatively, the materials constituting the solid electrolyte layer are dispersed in a solvent to form a slurry, and the obtained slurry is applied to a substrate and dried to obtain the solid electrolyte layer. The solid electrolyte layer will be described below.

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

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

The shape of the solid electrolyte layer is not particularly limited, but it is preferably in the form of a sheet. The thickness of the solid electrolyte layer is not particularly limited and may be set appropriately according to the desired battery performance. For example, it is in the range of 0.1 μm to 1 mm.

<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 thereof include roll pressing and flat plate 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 plate pressing may be, for example, 800 MPa or more and 3000 MPa or less.

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

When a negative electrode current collector and a positive electrode current collector are used as the substrate in the negative electrode active material layer preparation process and the positive electrode active material layer preparation process, the negative electrode, solid electrolyte layer, and positive electrode are laminated in this order in the lamination process.

The all-solid-state battery obtained by the manufacturing method of the all-solid-state battery disclosed herein may be a single cell or a stacked battery. The stacked battery may be a monopolar stacked battery (a stacked battery connected in parallel) or a bipolar stacked battery (a stacked battery connected in series). The shape of the all-solid-state battery may be, for example, a coin type, a laminate type, a cylindrical type, or a square type.

The slurry of this disclosure will be further explained using examples.

<Preparation of slurry>
The slurries of Examples 1-2 and Comparative Examples 1-12 were prepared using the materials and contents listed in Table 1. First, the materials were charged into a 5 mL container at once so that the total volume was 3.5 mL to prepare a slurry. Next, while cooling the resulting mixture to 10°C, an ultrasonic horn with a diameter of 3.5 mm was used to irradiate ultrasonic waves with an amplitude of 40 μm and 20 kHz for 40 minutes to disperse the mixture. In this way, the slurries of Examples 1-2 and Comparative Examples 1-12 were prepared.

The materials in Table 1 are explained below. Amorphous silicon active material and crystalline silicon active material were used as the silicon active material (Si active material). A sulfide solid electrolyte was used as the solid electrolyte. PVdF-HFP or SBR was used as the binder. An amphipathic polymer or a low molecular weight surfactant was used as the dispersant. Polyalkyleneamine (molecular weight: about 5000) was used as the amphipathic polymer. Alkyl imidazoline (molecular weight: about 500) was used as the low molecular weight surfactant. VGCF was used as the conductive additive. Diisobutyl ketone (DIBK), tetralin, or butyl butyrate was used as the solvent. The (δP) listed in the solvent column is the value of the polar term of the Hansen solubility parameter.

Table 1 also shows the binder and dispersant content relative to the total solids.

<XRD measurement>
The diffraction intensity of the amorphous silicon particles and crystalline silicon particles used in the slurry was measured in the range of 2θ=10 to 80° C. The Rigaku SmartLab was used as the XRD device. The results are shown in FIG.

As shown in Figure 1, the peak of the crystalline silicon particles is sharp, confirming that they are crystalline. On the other hand, the peak of the amorphous silicon particles is broad, confirming that they are amorphous.

<Pulsed NMR Measurement>
First, a blank containing only the solvent, sample 1 in which the solvent and the Si active material were mixed in a weight ratio of 80:20, and sample 2 in which the solvent, the Si active material, and the dispersant were mixed in a weight ratio of 80:19.7:0.3 were prepared.

Next, the T2 relaxation time of each sample was measured by the CPMG method using pulsed NMR. A Bruker minispec mq20 was used as the measuring device. The relative relaxation rate was then measured from (blank relaxation time)/(sample relaxation time)-1. Here, the relative relaxation rate calculated from the blank and sample 1 was designated Rsp, and the relative relaxation rate calculated from the blank and sample 2 was designated Rsp'. The relative relaxation rate ratio Rsp'/Rsp was also calculated. The results are shown in Table 2.

In addition, the points marked with "-" in Table 2 indicate that no measurement was performed.

<Particle size measurement>
The particle size of each slurry was measured in accordance with JIS K 5600-2-5:1999. The results are shown in Table 2.

In addition, the points marked with "-" in Table 2 indicate that the aggregates had settled and could not be measured.

<Dispersibility evaluation>
The state of the slurry was evaluated visually, and the absence of agglomerates was evaluated as "good", and the presence of agglomerates was evaluated as "poor". In addition, when agglomerates were present, the state of the agglomerates was evaluated. When agglomerates were present and did not settle, the state was evaluated as "agglomeration", and when the agglomerates settled, the state was evaluated as "settling". The results are shown in Table 2.

<Evaluation of peel strength>
The 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 crumbling occurred. In addition, the coating film was roll pressed and visually confirmed whether peeling or crumbling occurred. In both the hand punch and the roll press, the case where no peeling occurred was evaluated as "◯", and in either one or both, the case where peeling occurred was evaluated as "×". The results are shown in Table 2.

<Results>
As seen from Tables 1 and 2, Examples 1 and 2 had good results in the dispersion evaluation and peel evaluation. On the other hand, Comparative Examples 1 to 12 were rated "x" in at least one of the dispersion evaluation and the peel strength evaluation.

In Comparative Example 1, the binder amount relative to the total solid content was greater than that in Example 1, the particle size was 100 μm or more, and aggregation occurred in the slurry. In Comparative Example 2, the binder amount relative to the total solid content was less than that in Example 1, and peeling occurred in the coating film. In Comparative Example 3, SBR with a lower affinity with particles was used compared to the conditions of Comparative Example 2, so the particle size 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 used, but the results did not improve. In Comparative Examples 6 and 7, the content of the dispersant was reduced from the conditions of Comparative Example 4, but the results did not improve. In Comparative Examples 8 and 9, the content of the dispersant was reduced from the conditions of Comparative Example 3, but the results did not improve. In Comparative Example 10, the type of Si active material was changed from the conditions of Comparative Example 3 and crystalline silicon particles were used, but the results did not improve. In Comparative Example 11, the type of Si active material was changed from the conditions of Comparative Example 4 and crystalline silicon particles were used, but the results did not improve. In Comparative Example 12, the type of dispersant was changed from the conditions in Comparative Example 4, and a surfactant was used, but the results did not improve.

Claims (1)

A slurry containing a solvent, amorphous silicon particles, a solid electrolyte, a dispersant, and a binder,
The solvent includes a low polarity solvent having a polarity term δP of the Hansen solubility parameter of 4 or less;
The dispersant comprises an amphiphilic polymer;
The content of the binder relative to the total solid content of the slurry is 0.8 % by weight or more and 1.0% by weight or less,
the amphiphilic polymer is a polyalkyleneamine;
Rsp is the relative relaxation rate of the dispersion medium obtained by mixing the solvent and the amorphous silicon particles, as measured by pulse NMR;
Rsp' is the relative relaxation rate measured by pulse NMR of a dispersion medium obtained by mixing the solvent, the amorphous silicon particles, and the dispersant,
The relative relaxation rate ratio Rsp'/Rsp is less than 1.0;
slurry.