Electrode slurry, electrode layer, all-solid-state battery, and method for manufacturing electrode slurry

Abstract

To provide an electrode slurry having a good dispersibility of a fibrous conductive material.SOLUTION: In the present disclosure, an electrode slurry for use in an all-solid-state battery includes an electrode active material having a hydroxyl group, a fibrous conductive material having an acidic functional group, a solid electrolyte, and a dispersion medium.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrode slurry, an electrode layer, an all-solid-state battery, and a method for producing an electrode slurry. [Background technology]

[0002] An all-solid-state battery is a battery having a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and has the advantage that it is easier to simplify safety devices compared to liquid-based batteries having an electrolyte solution containing a flammable organic solvent. As a method for forming an electrode layer (positive electrode layer or negative electrode layer) in an all-solid-state battery, a method using an electrode slurry in which an electrode active material, a conductive material, and a solid electrolyte are dispersed in a dispersion medium is known. Specifically, the electrode layer is obtained by applying the electrode slurry and drying it. In addition, although it is not a technology related to all-solid-state batteries, Patent Document 1 discloses a carbon nanotube dispersion paste containing carbon nanotubes and an organic solvent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-080910 Summary of the Invention [Problem to be solved by the invention]

[0004] The electrode slurry used in the all-solid-state battery may contain a dispersion medium with low polarity in order to suppress the decomposition of the solid electrolyte. In addition, fibrous conductive materials such as carbon nanotubes tend to form a bundle structure. Therefore, even if the fibrous conductive material is dispersed in a dispersion medium with low polarity, it is difficult to sufficiently disperse the fibrous conductive material.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide an electrode slurry having good dispersibility of a fibrous conductive material. [Means for solving the problem]

[0006] [1] An electrode slurry for use in an all-solid-state battery, An electrode slurry comprising an electrode active material having a hydroxyl group, a fibrous conductive material having an acidic functional group, a solid electrolyte, and a dispersion medium.

[0007] [2] The electrode slurry according to [1], wherein the proportion of the hydroxyl groups in the electrode active material is 30 μmol / g or more as measured by a CO2-TPD method.

[0008] [3] The electrode slurry according to [1] or [2], wherein the proportion of the acidic functional groups in the fibrous conductive material is 10 μmol / g or more as measured by potentiometric back titration.

[0009] [4] The electrode slurry according to any one of [1] to [3], wherein the electrode active material is a Si-based active material, the fibrous conductive material is a carbon nanotube, and the solid electrolyte is a sulfide solid electrolyte.

[0010] [5] The electrode slurry according to any one of [1] to [4], wherein the slurry particle size is 90 μm or less.

[0011] [6] The electrode slurry according to any one of [1] to [5], wherein when the electrode slurry is applied and dried to form a coating layer, the coating layer has a surface roughness of 5 μm or less based on ISO 25178.

[0012] [7] An electrode layer for use in an all-solid-state battery, An electrode layer comprising: an electrode active material having a hydroxyl group; a fibrous conductive material having an acidic functional group; and a solid electrolyte.

[0013] [8] The electrode layer according to [7], wherein, in a cross section of the electrode layer, the number of agglomerates of the fibrous conductive material having an aspect ratio of 5 or more and 1000 or less and a long side of 2 μm or more is 10 or less when confirmed in an area of ​​50 μm x 200 μm.

[0014] [9] The electrode layer according to [7] or [8], wherein the proportion of the hydroxyl groups in the electrode active material, as measured by a CO2-TPD method, is 30 μmol / g or more.

[0015]

[10] The electrode layer according to any one of [7] to [9], wherein the proportion of the acidic functional groups in the fibrous conductive material, as measured by potentiometric back titration, is 10 μmol / g or more.

[0016]

[11] The electrode layer according to any one of [7] to

[10] , wherein the electrode active material is a Si-based active material, the fibrous conductive material is a carbon nanotube, and the solid electrolyte is a sulfide solid electrolyte.

[0017]

[12] 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 and the negative electrode layer is the electrode layer according to any one of [7] to

[11] .

[0018]

[13] The all-solid-state battery according to

[12] , wherein the negative electrode layer is the electrode layer.

[0019]

[14] The all-solid-state battery according to

[13] , wherein the positive electrode layer contains a rock-salt layered active material, and the solid electrolyte layer contains a sulfide solid electrolyte.

[0020]

[15] A method for producing an electrode slurry for use in an all-solid-state battery, comprising: a first dispersion treatment step of adding an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group to a dispersion medium and performing a first dispersion treatment to obtain a precursor slurry; a second dispersion treatment step of adding a solid electrolyte to the precursor slurry and performing a second dispersion treatment to obtain the electrode slurry; The method for producing an electrode slurry comprising the steps of: Effect of the Invention

[0021] The present disclosure has an effect of providing an electrode slurry having good dispersibility of the fibrous conductive material. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an all-solid-state battery according to the present disclosure. [Diagram 2] FIG. 1 is a schematic diagram illustrating the effects of the present disclosure. [Diagram 3] FIG. 2 is a flow diagram illustrating a method for producing an electrode slurry in the present disclosure. [Figure 4] FIG. 4 is a flow diagram illustrating a method for producing an electrode slurry in a reference example. [Diagram 5] 3 shows cross-sectional SEM images of electrode layers obtained in the examples and the reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the electrode slurry, the electrode layer, the all-solid-state battery, and the method for producing the electrode slurry according to the present disclosure will be described in detail.

[0024] A. Electrode slurry The electrode slurry in the present disclosure is used to manufacture electrode layers (positive electrode layer, negative electrode layer) of an all-solid-state battery. As shown in FIG. 1, an all-solid-state battery 10 has a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2. The electrode slurry in the present disclosure is usually used to manufacture the positive electrode layer 1 or the negative electrode layer 2. The electrode slurry in the present disclosure also contains an electrode active material having a hydroxyl group, a fibrous conductive material having an acidic functional group, a solid electrolyte, and a dispersion medium.

[0025] According to the present disclosure, an electrode slurry having good dispersibility of the fibrous conductive material is obtained by combining an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group. As described above, the electrode slurry used in the all-solid-state battery often contains a dispersion medium having low polarity in order to suppress decomposition of the solid electrolyte. In particular, when a highly reactive solid electrolyte such as a sulfide solid electrolyte is used, a dispersion medium having low polarity is used. On the other hand, a fibrous conductive material such as carbon nanotubes is likely to form a bundle structure. Therefore, even if the fibrous conductive material is dispersed in a dispersion medium having low polarity, it is difficult to sufficiently disperse the fibrous conductive material.

[0026] In contrast, according to the present disclosure, an electrode active material having a hydroxyl group is used in combination with a fibrous conductive material having an acidic functional group. As shown in FIG. 2, the hydroxyl group present on the surface of the electrode active material 11 interacts with the acidic functional group present on the surface of the fibrous conductive material 12, thereby suppressing aggregation of the fibrous conductive material 12. In the present disclosure, the aggregation of the fibrous conductive material 12 is suppressed by using an electrode active material having a hydroxyl group, but the aggregation of the fibrous conductive material 12 is further effectively suppressed by employing the method described in "D. Method for producing electrode slurry" described later.

[0027] 1. Electrode active material The electrode slurry contains an electrode active material having a hydroxyl group. The presence of a hydroxyl group in the electrode active material can be confirmed by infrared spectroscopy (IR method). Specifically, a peak derived from an OH bond is usually observed at 3000 cm-1 More than 3600cm -1 In addition, for example, when the electrode active material is a Si-based active material described later, the peak due to the Si-O bond usually appears in the range of 900 cm -1 appears nearby.

[0028] The ratio of hydroxyl groups in the electrode active material can be determined by a temperature programmed desorption method (CO2-TPD method) using CO2. The ratio of hydroxyl groups in the electrode active material is, for example, 30 μmol / g or more, may be 40 μmol / g or more, or may be 50 μmol / g or more. On the other hand, the ratio of hydroxyl groups in the electrode active material is, for example, 150 μmol / g or less.

[0029] A typical example of an electrode active material having a hydroxyl group is a Si-based active material. The Si-based active material is an active material mainly composed of Si. The Si-based active material may be a simple substance of Si, a Si alloy, or a Si oxide. The Si-based active material may have a diamond crystal phase, a clathrate I crystal phase, or a clathrate II crystal phase. In the clathrate I or II crystal phase, a polyhedron (cage) including a pentagon or hexagon is formed by a plurality of Si elements. This polyhedron has a space inside that can encapsulate metal ions such as Li ions, and therefore can suppress volume change due to charging and discharging.

[0030] The Si-based active material preferably has a clathrate II type crystal phase as a main phase. The composition of the Si-based active material is not particularly limited, but may be Na x S 136 It is preferable that the composition is represented by (0≦x≦24). x may be 0 or may be greater than 0. On the other hand, x may be 20 or less, 10 or less, or 5 or less. The composition of the Si-based active material can be determined by, for example, EDX, XRD, XRF, ICP, or atomic absorption spectrometry.

[0031] Another example of the electrode active material having a hydroxyl group is a carbon-based active material. The carbon-based active material is an active material containing inorganic C (carbon) as a main component, such as graphite. Another example of the electrode active material having a hydroxyl group is an active material containing at least one of Cd, In, Pb, Ga, Ge, Sn, Al, Bi, and Sb.

[0032] The electrode active material having a hydroxyl group preferably has voids inside the primary particles. The presence of voids inside the primary particles can suppress volume changes due to charging and discharging. The ratio of voids in the primary particles (porosity) is, for example, 4% or more, and may be 10% or more. Meanwhile, the porosity is, for example, 40% or less, and may be 20% or less. The porosity can be obtained, for example, by the following procedure. First, a cross section of the electrode active material is observed with a SEM (scanning electron microscope) to obtain a photograph of the particles. From the obtained photograph, solid parts and void parts are clearly distinguished using image analysis software and binarized. The areas of the solid parts and void parts are obtained, and the porosity (%) is calculated from the following formula. Porosity (%) = 100 × (area of ​​void part) / ((area of ​​solid part) + (area of ​​void part))

[0033] The electrode active material having a hydroxyl group is preferably a Si-based active material (porous Si) having voids inside the primary particles.

[0034] The electrode active material may be a positive electrode active material or a negative electrode active material. The shape of the electrode active material is, for example, particulate. The average particle size of the electrode active material is, for example, 0.5 μm or more and 30 μm or less, and may be, for example, 0.5 μm or more and 15 μm or less. In the present disclosure, the average particle size is defined as the volume cumulative particle size D measured by a laser diffraction scattering type particle size distribution measuring device. 50 The ratio of the electrode active material in the solid content of the electrode slurry is not particularly limited, but may be, for example, 10% by weight or more and 90% by weight or less, or may be 30% by weight or more and 80% by weight or less, or may be 50% by weight or more and 70% by weight or less.

[0035] 2. Fibrous conductive material The electrode slurry contains a fibrous conductive material having an acidic functional group. Examples of the acidic functional group include a carboxy group (-COOH) and a nitro group (-NO2). The presence of an acidic functional group in the fibrous conductive material can be confirmed by infrared spectroscopy (IR method). For example, the presence of a carboxy group (-COOH) in the fibrous conductive material can be confirmed by detecting a peak (3000 cm) derived from an OH bond. -1 More than 3600cm -1 Peaks appearing in the range below 1500 cm -1 More than 1800cm -1 This can be confirmed by the presence of a peak in the range below.

[0036] The ratio of acidic functional groups in the fibrous conductive material can be determined by potentiometric back titration. The ratio of acidic functional groups in the fibrous conductive material is, for example, 10 μmol / g or more, may be 30 μmol / g or more, or may be 50 μmol / g or more. Note that acetylene black (AB), which is a particulate conductive material, may have acidic functional groups (carboxy groups), but the ratio is about 5 μmol / g.

[0037] Examples of the material of the fibrous conductive material having an acidic functional group include carbon materials, metal materials, and conductive resin materials, among which carbon materials are preferred. This is because they have excellent electronic conductivity, light weight, and durability. Examples of the fibrous conductive material having an acidic functional group include carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The carbon nanotubes (CNTs) may be single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs).

[0038] The aspect ratio (long side / short side) of the fibrous conductive material having an acidic functional group is not particularly limited, but may be, for example, 2 to 1000, 10 to 750, or 50 to 500. The length of the long side of the fibrous conductive material is not particularly limited, but may be, for example, 0.1 μm to 80 μm, or 0.5 μm to 60 μm. On the other hand, the length of the short side of the fibrous conductive material is not particularly limited, but may be, for example, 0.5 nm to 100 nm, or 1 nm to 30 nm.

[0039] The electrode slurry may contain a fibrous conductive material having no acidic functional group, or may contain a particulate conductive material, in addition to the fibrous conductive material having an acidic functional group. Examples of particulate conductive materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB). The ratio of the fibrous conductive material having an acidic functional group to all conductive materials contained in the electrode slurry is, for example, 50% by weight or more, may be 70% by weight or more, or may be 90% by weight or more.

[0040] The proportion of the fibrous conductive material having an acidic functional group in the solid content of the electrode slurry is not particularly limited, but may be, for example, 0.05% by weight to 5% by weight, and may be 0.1% by weight to 3% by weight.

[0041] 3.Solid electrolyte The electrode slurry contains a solid electrolyte. The solid electrolyte is usually an inorganic solid electrolyte. Examples of inorganic solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes, and among these, sulfide solid electrolytes are preferred. This is because the sulfide solid electrolyte has high ionic conductivity. In addition, since the sulfide solid electrolyte is highly reactive, it is necessary to use a dispersion medium with low polarity. Even when a dispersion medium with low polarity is used, an electrode slurry with good dispersibility of the fibrous conductive material can be obtained by combining an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group.

[0042] Sulfide solid electrolytes usually contain at least Li element and S element. The sulfide solid electrolyte preferably further contains an M element (M is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In). Also, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, I.

[0043] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include Thio-LISICON type crystalline phase, argyrodite type crystalline phase, and LGPS type crystalline phase.

[0044] The composition of the sulfide solid electrolyte is not particularly limited, and examples include xLi2S·(1-x)P2S5 (0.5≦x<1), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In these compositions, x preferably satisfies 0.7≦x≦0.8.

[0045] Another example of the composition of the sulfide solid electrolyte is Li 4-x M 1-x P x S4 (0<x<1). M is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi. Also, part of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. Another example of the composition of the sulfide solid electrolyte is Li 7-x-2y PS 6-x-y X y where X is at least one of F, Cl, Br, I, and x and y satisfy 0≦x, 0≦y. Also, part of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. Further, part of S may be substituted with oxygen (O).

[0046] The shape of the solid electrolyte is, for example, particulate. The average particle size of the solid electrolyte is, for example, 0.1 μm to 30 μm, and may be 0.5 μm to 15 μm. The ratio of the solid electrolyte in the solid content of the electrode slurry is not particularly limited, and may be, for example, 10 wt % to 70 wt %, 20 wt % to 60 wt %, or 30 wt % to 50 wt %.

[0047] 4.Dispersion medium The electrode slurry contains a dispersion medium. The dispersion medium preferably has low polarity, because this can suppress deterioration of the solid electrolyte (particularly the sulfide solid electrolyte). The polarity of the dispersion medium can be determined, for example, by the Hansen solubility parameter. Specifically, the dispersion medium preferably 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)).

[0048] Examples of the dispersion medium include butyl butyrate (δP=2.9), heptane (δP=0), diisobutyl ketone (δP=3.7), tetralin (δP=2), mesitylene (δP=0.6), dibutyl ether (δP=3.4), decane (δP=0), and toluene (δP=1.4). The electrode slurry may contain only one type of dispersion medium, or may contain two or more types. The solid content concentration of the electrode slurry is not particularly limited, and may be, for example, 30% by weight or more and 70% by weight or less, or 40% by weight or more and 60% by weight or less.

[0049] 5. Electrode Slurry The electrode slurry may further contain a binder. Examples of the binder include fluoride-based binders such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber; and rubber-based binders such as butadiene rubber, hydrogenated butadiene rubber, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, and ethylene propylene rubber.

[0050] From the viewpoint of dispersibility, the slurry particle size of the electrode slurry is preferably small. The slurry particle size of the electrode slurry is, for example, 90 μm or less, may be 80 μm or less, may be 60 μm or less, or may be 40 μm or less. On the other hand, the slurry particle size of the electrode slurry is, for example, 5 μm or more. The slurry particle size of the electrode slurry can be determined based on JIS K5600-2-5.

[0051] In addition, when the electrode slurry is applied and dried to form a coating layer, the surface roughness of the coating layer (surface roughness based on ISO25178) is preferably small from the viewpoint of dispersibility. The surface roughness of the coating layer is, for example, 5 μm or less, may be 3 μm or less, or may be 1 μm or less. The coating layer to be measured is preferably formed by applying the electrode slurry with a blade at a gap of 100 μm and drying it.

[0052] The method for producing the electrode slurry is not particularly limited, but may be, for example, the method described in "D. Method for producing electrode slurry" below.

[0053] B. Electrode layer The electrode layer in the present disclosure is used in an all-solid-state battery and contains an electrode active material having a hydroxyl group, a fibrous conductive material having an acidic functional group, and a solid electrolyte.

[0054] According to the present disclosure, by using a combination of an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group, the dispersibility of the fibrous conductive material becomes an electrode layer. The electrode active material, the fibrous conductive material, and the solid electrolyte are the same as those described in "A. Electrode Slurry" above.

[0055] The electrode layer may be a positive electrode layer containing a positive electrode active material, or may be a negative electrode layer containing a negative electrode active material. In addition, when observing the cross section of the electrode layer, it is preferable that the number of aggregates of the fibrous conductive material is small. Specifically, when the number of aggregates of the fibrous conductive material having an aspect ratio of 5 to 1000 and a long side of 2 μm or more is confirmed in an area of ​​50 μm×200 μm, the number of aggregates is, for example, 10 or less, 8 or less, 5 or less, or 3 or less.

[0056] The thickness of the electrode layer is not particularly limited, but may be, for example, 0.1 μm or more and 1000 μm or less, 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less. In addition, as a method for forming the electrode layer, for example, a method of applying an electrode slurry and drying it can be mentioned. The electrode layer is usually used in an all-solid-state battery. In addition, in the present disclosure, a battery member used in an all-solid-state battery and having at least an electrode layer can also be provided.

[0057] C. All-solid-state battery Fig. 1 is a schematic cross-sectional view illustrating an example of an all-solid-state battery in the present disclosure. The all-solid-state battery 10 shown in Fig. 1 has 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. In the present disclosure, at least one of the positive electrode layer 1 and the negative electrode layer 2 is the electrode layer described above in "B. Electrode layer".

[0058] According to the present disclosure, by using the above-mentioned electrode layer, an all-solid-state battery with low resistance is obtained.

[0059] 1. Positive and negative electrode layers In the present disclosure, the positive electrode layer may be the electrode layer described above, the negative electrode layer may be the electrode layer described above, or both the positive electrode layer and the negative electrode layer may be the electrode layer described above. The positive electrode layer contains at least a positive electrode active material.

[0060] For example, when the negative electrode layer is the above-mentioned electrode layer, the type of the positive electrode active material contained in the positive electrode layer is not particularly limited. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4 and the like; and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0061] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and a solid electrolyte (especially 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.

[0062] For example, when the positive electrode layer is the above-mentioned electrode layer, the type of the negative electrode active material contained in the negative electrode layer is not particularly limited. Examples of the negative electrode active material include metal active materials such as Li and Sn, carbon active materials such as graphite, and oxide active materials such as lithium titanate.

[0063] The positive electrode layer may further contain at least one of a solid electrolyte, a conductive material, and a binder in addition to the positive electrode active material. Similarly, the negative electrode layer may further contain at least one of a solid electrolyte, a conductive material, and a binder in addition to the negative electrode active material. The solid electrolyte, the conductive material, and the binder are the same as those described above in "A. Electrode Slurry".

[0064] 2.Solid electrolyte layer The solid electrolyte layer is a layer disposed between the positive electrode layer and the negative electrode layer, and contains at least a solid electrolyte. The solid electrolyte layer may further contain a binder. The solid electrolyte and the binder are the same as those described in "A. Electrode Slurry" above, and therefore will not be described here. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, and may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less.

[0065] 3.Other configurations The all-solid-state battery of the present disclosure preferably has a positive electrode current collector that collects the positive electrode layer and a negative electrode current collector that collects the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0066] The all-solid-state battery of the present disclosure may further include a restraining tool that applies a restraining pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer along the thickness direction. By using the restraining tool, a good ion conduction path and a good electron conduction path are formed. The restraining pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, or may be 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, may be 50 MPa or less, or may be 20 MPa or less.

[0067] 4.All-solid-state battery The type of all-solid-state battery in the present disclosure is not particularly limited, but is typically a lithium-ion secondary battery. In addition, the use of the all-solid-state battery includes, for example, a power source for vehicles such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), a gasoline vehicle, and a diesel vehicle. In particular, it is preferable to use the all-solid-state battery as a driving power source for a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or an electric vehicle (BEV). In addition, the all-solid-state battery may be used as a power source for a moving body other than a vehicle (for example, a railway, a ship, or an aircraft), or may be used as a power source for an electric product such as an information processing device. In addition, the manufacturing method of the all-solid-state battery is not particularly limited, and a known method can be adopted.

[0068] D. Electrode Slurry Manufacturing Method Fig. 3 is a flow diagram illustrating a method for producing an electrode slurry in the present disclosure. As shown in Fig. 3, an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group are added to a dispersion medium, and a first dispersion treatment is performed to obtain a precursor slurry (first dispersion treatment step). Next, a solid electrolyte is added to the obtained precursor slurry, and a second dispersion treatment is performed to obtain an electrode slurry (second dispersion treatment step).

[0069] According to the present disclosure, in the first dispersion treatment step, an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group are simultaneously dispersed, and then a solid electrolyte is added and a second dispersion treatment is performed, thereby obtaining an electrode slurry with good dispersibility of the fibrous conductive material.

[0070] 1. First dispersion process The first dispersion process is a process of adding an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group to a dispersion medium, and performing a first dispersion process to obtain a precursor slurry. The dispersion medium, the electrode active material having a hydroxyl group, and the fibrous conductive material having an acidic functional group are the same as those described in "A. Electrode Slurry" above.

[0071] In the first dispersion treatment step, the first dispersion treatment is performed on a dispersion liquid in which an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group are added to a dispersion medium. A binder may be further added to the dispersion medium. That is, the first dispersion treatment may be performed on a dispersion liquid containing an electrode active material, a fibrous conductive material, and a binder. On the other hand, the first dispersion treatment may be performed on a dispersion liquid containing an electrode active material and a fibrous conductive material, and then a binder may be added to the dispersion liquid and an additional dispersion treatment may be performed. The additional dispersion treatment is preferably performed before the second dispersion treatment step described below.

[0072] Examples of the first dispersion treatment include ultrasonic dispersion treatment and stirring treatment. The treatment time of the first dispersion treatment is not particularly limited, but may be, for example, 1 minute to 60 minutes, and may be, for example, 3 minutes to 30 minutes. The temperature during the first dispersion treatment is not particularly limited, but may be, for example, room temperature.

[0073] 2. Second dispersion processing step The second dispersion treatment step is a step of adding a solid electrolyte to the precursor slurry and performing a second dispersion treatment to obtain an electrode slurry. The solid electrolyte is the same as that described above in "A. Electrode slurry."

[0074] In the second dispersion treatment step, a solid electrolyte is added to the precursor slurry, and the second dispersion treatment is performed. A binder may be further added to the precursor slurry to which the solid electrolyte has been added, and the second dispersion treatment may be performed.

[0075] Examples of the second dispersion treatment include ultrasonic dispersion treatment and stirring treatment. The treatment time of the second dispersion treatment is not particularly limited, but may be, for example, 1 minute to 60 minutes, and may be, for example, 3 minutes to 30 minutes. The temperature during the second dispersion treatment is not particularly limited, but may be, for example, room temperature.

[0076] 3. Electrode slurry The electrode slurry obtained through the above-mentioned steps is the same as that described above in "A. Electrode slurry."

[0077] The present disclosure is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present disclosure and that exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0078] [Example 1] (Preparation of negative electrode slurry) A negative electrode slurry was prepared according to the flow shown in Figure 3. Specifically, 0.002 g of single-walled carbon nanotubes (SWCNTs, length: 5 μm, fiber diameter: 3 nm, ratio of carboxyl groups: 55 μmol / g) and 0.002 g of porous Si (D 50 :500nm, specific surface area:50m 2 1g of anode powder (1.2g / g, hydroxyl group ratio: 56μmol / g) and 0.8g of binder solution (diisobutyl ketone solution containing PVDF-HFP at a concentration of 5% by weight) were added, and ultrasonic treatment (first dispersion treatment) was performed under conditions of amplitude 40μm, frequency 20kHz, and 3 minutes to obtain a precursor slurry. Next, 1.2g of sulfide solid electrolyte (Li3PS4-based glass ceramics containing LiI and LiBr) was added to the obtained precursor slurry, and ultrasonic treatment (second dispersion treatment) was performed under conditions of amplitude 40μm, frequency 20kHz, and 3 minutes to obtain a negative electrode slurry.

[0079] (Preparation of negative electrode) The obtained negative electrode slurry was applied to a roughened Ni foil (negative electrode current collector) with a blade at a gap of 340 μm and dried, thereby obtaining a negative electrode having a negative electrode current collector and a negative electrode layer.

[0080] (Preparation of solid electrolyte layer) 0.4g of sulfide solid electrolyte (Li3PS4-based glass ceramics containing LiI and LiBr) and 0.05g of binder solution (heptane solution containing acrylonitrile-butadiene rubber at a concentration of 5% by weight) were added to 0.8g of heptane, and ultrasonic treatment was performed under conditions of amplitude 40μm, frequency 20kHz, and 10 minutes to obtain a slurry. The obtained slurry was blade coated on a stainless steel foil (substrate) with a gap of 50μm and dried. As a result, a transfer member having a substrate and a solid electrolyte layer was obtained.

[0081] (Preparation of positive electrode) 1g of butyl butyrate was mixed with the positive electrode active material (LiNi 0.8 Co 0.15 Al 0.05 2g of ethanol (O2, NCA), 0.03g of multi-walled carbon nanotubes (MWCNT), 0.3g of sulfide solid electrolyte (Li3PS4-based glass ceramics containing LiI and LiBr), and 0.3g of binder solution (butyl butyrate solution containing PVDF-HFP at a concentration of 5% by weight) were added, and ultrasonic treatment was performed under conditions of amplitude 40 μm, frequency 20 kHz, and 10 minutes to obtain a positive electrode slurry. The obtained positive electrode slurry was blade coated on Al foil (positive electrode current collector) with a gap of 300 μm and dried. As a result, a positive electrode having a positive electrode current collector and a positive electrode layer was obtained.

[0082] (Battery Construction) The negative electrode and the transfer member were overlapped so that the negative electrode layer of the negative electrode and the solid electrolyte layer of the transfer member faced each other, and roll-pressed under conditions of a linear pressure of 3 t / cm and room temperature to obtain a negative electrode laminate. Similarly, the positive electrode and the transfer member were overlapped so that the positive electrode layer of the positive electrode and the solid electrolyte layer of the transfer member faced each other, and roll-pressed under conditions of a linear pressure of 4 t / cm and room temperature to obtain a positive electrode laminate. Thereafter, the positive electrode laminate and the negative electrode laminate were overlapped so that the solid electrolyte layers faced each other, and the solid electrolyte layers were bonded together. This resulted in a battery.

[0083] [Examples 2 to 5] A negative electrode slurry was obtained in the same manner as in Example 1, except that the particle size and specific surface area of ​​the porous Si were changed to the values ​​shown in Table 1. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0084] [Example 6] A negative electrode slurry was obtained in the same manner as in Example 1, except that multi-walled carbon nanotubes (MWCNTs, length: 5 μm, fiber diameter: 150 nm, proportion of carboxyl groups: 60 μmol / g) having a carboxyl group were used instead of SWCNTs. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0085] [Examples 7 to 10] A negative electrode slurry was obtained in the same manner as in Example 6, except that the particle size and specific surface area of ​​the porous Si were changed to the values ​​shown in Table 1. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0086] [Example 11] Except for using solid Si nanoparticles instead of porous Si, a negative electrode slurry was obtained in the same manner as in Example 1. Except for using the obtained negative electrode slurry, a battery was obtained in the same manner as in Example 1.

[0087] [Examples 12 and 13] A negative electrode slurry was obtained in the same manner as in Example 1, except that the particle size and specific surface area of ​​the Si nanoparticles were changed to the values ​​shown in Table 1. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used. [Example 14] A negative electrode slurry was obtained in the same manner as in Example 6, except that solid Si nanoparticles were used instead of porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0088] [Reference example 1] A negative electrode slurry was prepared according to the flow shown in FIG. 4. Specifically, 0.002 g of SWCNT and 0.8 g of binder solution were added to 2.7 g of diisobutyl ketone as a dispersion medium, and ultrasonic treatment (dispersion treatment X) was performed under conditions of amplitude 40 μm, frequency 20 kHz, and 3 minutes to obtain a first precursor slurry. Next, 1 g of porous Si was added to the obtained first precursor slurry, and ultrasonic treatment (dispersion treatment Y) was performed under conditions of amplitude 40 μm, frequency 20 kHz, and 3 minutes to obtain a second precursor slurry. Next, 1.2 g of sulfide solid electrolyte was added to the obtained second precursor slurry, and ultrasonic treatment (dispersion treatment Z) was performed under conditions of amplitude 40 μm, frequency 20 kHz, and 3 minutes to obtain a negative electrode slurry. Note that each material used in the negative electrode slurry is the same as each material in Example 2. In addition, a battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0089] [Reference example 2] A negative electrode slurry was obtained in the same manner as in Reference Example 1, except that the MWCNT used in Example 6 was used instead of the SWCNT. In addition, a battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0090] [Reference example 3] Except for using solid Si nanoparticles instead of porous Si, a negative electrode slurry was obtained in the same manner as in Reference Example 1. Except for using the obtained negative electrode slurry, a battery was obtained in the same manner as in Example 1.

[0091] [Reference example 4] A negative electrode slurry was obtained in the same manner as in Reference Example 2, except that solid Si nanoparticles were used instead of porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained negative electrode slurry was used.

[0092] [Table 1]

[0093] [evaluation] (Slurry particle size) The slurry particle size was measured using the negative electrode slurries prepared in Examples 1 to 14 and Reference Examples 1 to 4. Specifically, the slurry particle size was measured based on JIS K5600-2-5. The results are shown in Table 2.

[0094] (Surface roughness based on ISO25178) The negative electrode slurries prepared in Examples 1 to 14 and Reference Examples 1 to 4 were blade coated on roughened Ni foil with a gap of 100 μm, and then dried. Thus, evaluation samples were obtained. The surfaces of the obtained evaluation samples were measured at a magnification of 500 times using a digital microscope (Keyence VHX-8000) to determine the surface roughness based on ISO25178. The results are shown in Table 2.

[0095] (cell resistance) The resistance of the batteries obtained in Examples 1 to 14 and Reference Examples 1 to 4 was measured. Specifically, the batteries were CCCV charged at C / 10 to 4.35V. Then, CCCV discharged at C / 3 to 3.35V. Then, further discharge was performed at 7C, and the cell resistance was calculated from the voltage change and current value for 10 seconds. The results are shown in Table 2.

[0096] (Electronic Conductivity) The electronic conductivity was measured using the negative electrodes prepared in Examples 1 to 14 and Reference Examples 1 to 4. Specifically, the negative electrodes were 2 The two punched negative electrodes were then stacked so that the negative electrode layers faced each other. The stacked laminate was restrained in the thickness direction, and the resistance was measured to determine the electronic conductivity. The results are shown in Table 2.

[0097] (Number of aggregates) The number of conductive material aggregates was measured using the negative electrode layers prepared in Examples 1 to 14 and Reference Examples 1 to 4. Specifically, the cross section of the negative electrode layer was observed at a magnification of 400 times using a scanning electron microscope (SEM, Hitachi FE-SEM SU-8200). Then, the number of conductive material aggregates having an aspect ratio of 5 to 1000 and a long side of 2 μm or more was confirmed in an area of ​​50 μm × 200 μm. This operation was performed 10 times, and the average value was taken as the number of conductive material aggregates. The results are shown in Table 2. Furthermore, as shown in FIG. 5(a), almost no conductive material aggregates were confirmed in the negative electrode layer prepared in Example 1. On the other hand, as shown in FIG. 5(b), a plurality of aggregates (areas surrounded by black circles) were confirmed in the negative electrode layer prepared in Reference Example 1.

[0098] [Table 2]

[0099] As shown in Table 1, it was confirmed that the dispersibility of the fibrous conductive material in the electrode slurry was good in Examples 1 to 14 and Reference Examples 1 to 4. In this way, by using a combination of an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group, an electrode slurry with good dispersibility of the fibrous conductive material was obtained.

[0100] Among them, it was confirmed that Examples 1 to 5 have smaller slurry particle size, smaller surface roughness, smaller cell resistance, higher electronic conductivity, and fewer aggregates than Reference Example 1. Similarly, it was confirmed that Examples 6 to 10 have smaller slurry particle size, smaller surface roughness, smaller cell resistance, higher electronic conductivity, and fewer aggregates than Reference Example 2. Thus, it was confirmed that in the present disclosure, simultaneous dispersion is more preferable than sequential dispersion. Furthermore, based on the above results, in the present disclosure, the average particle size D of the porous Si 50 The average particle diameter D of the porous Si is preferably 300 nm or more and 1200 nm or less. 50 In the present disclosure, the specific surface area of ​​the porous Si may be 500 nm or more and 1000 nm or less. 2 / g or more 800m 2 The specific surface area of ​​the porous Si is preferably 50 m 2 / g or more 600m 2 / g or less.

[0101] In addition, it was confirmed that Example 11 had a smaller slurry particle size, smaller surface roughness, smaller cell resistance, higher electronic conductivity, and fewer aggregates than Reference Example 3. In addition, it was confirmed that Example 14 had a smaller slurry particle size, smaller surface roughness, smaller cell resistance, higher electronic conductivity, and fewer aggregates than Reference Example 4. In addition, based on the results of Examples 11 and 12, in the present disclosure, the particle size D of the Si nanoparticles 50 The average particle size D of the Si nanoparticles is preferably less than 100 nm. 50 On the other hand, the average particle size D of the Si nanoparticles may be 80 nm or less, or 60 nm or less. 50 In the present disclosure, the specific surface area of ​​the Si nanoparticles may be 20 nm or more. 2 The specific surface area of ​​the Si nanoparticles is preferably greater than 30 m 2 / g or more, 2 On the other hand, the specific surface area of ​​Si nanoparticles is 70 m 2 / g or less. [Explanation of symbols]

[0102] 1 ... Positive electrode layer 2 ... Negative electrode layer 3...Solid electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...All-solid-state battery

Claims

1. An electrode slurry for use in an all-solid-state battery, An electrode slurry comprising an electrode active material having a hydroxyl group, a fibrous conductive material having an acidic functional group, a solid electrolyte, and a dispersion medium.

2. CO ２ The electrode slurry according to claim 1, wherein the proportion of the hydroxyl groups in the electrode active material measured by a TPD method is 30 μmol / g or more.

3. 2. The electrode slurry according to claim 1, wherein the proportion of the acidic functional groups in the fibrous conductive material is 10 μmol / g or more as measured by potentiometric back titration.

4. 2. The electrode slurry according to claim 1, wherein the electrode active material is a Si-based active material, the fibrous conductive material is a carbon nanotube, and the solid electrolyte is a sulfide solid electrolyte.

5. 2. The electrode slurry of claim 1, wherein the slurry particle size is 90 μm or less.

6. The electrode slurry according to claim 1, wherein when the electrode slurry is applied and dried to form a coating layer, the coating layer has a surface roughness based on ISO25178 of 5 μm or less.

7. An electrode layer for use in an all-solid-state battery, An electrode layer comprising: an electrode active material having a hydroxyl group; a fibrous conductive material having an acidic functional group; and a solid electrolyte.

8. The electrode layer according to claim 7, wherein, in a cross section of the electrode layer, the number of agglomerates of the fibrous conductive material having an aspect ratio of 5 or more and 1000 or less and a long side of 2 μm or more is confirmed in an area of ​​50 μm x 200 μm, and the number of the agglomerates is 10 or less.

9. CO ２ The electrode layer according to claim 7, wherein the proportion of the hydroxyl groups in the electrode active material measured by a TPD method is 30 μmol / g or more.

10. 8. The electrode layer according to claim 7, wherein the proportion of the acidic functional groups in the fibrous conductive material is 10 μmol / g or more as measured by potentiometric back titration.

11. 8. The electrode layer according to claim 7, wherein the electrode active material is a Si-based active material, the fibrous conductive material is a carbon nanotube, and the solid electrolyte is a sulfide solid electrolyte.

12. 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, An all-solid-state battery, wherein at least one of the positive electrode layer and the negative electrode layer is the electrode layer according to any one of claims 7 to 11.

13. The all-solid-state battery of claim 12 , wherein the negative electrode layer is the electrode layer.

14. 14. The all-solid-state battery according to claim 13, wherein the positive electrode layer contains a rock-salt layered active material, and the solid electrolyte layer contains a sulfide solid electrolyte.

15. A method for producing an electrode slurry for use in an all-solid-state battery, comprising: a first dispersion treatment step of adding an electrode active material having a hydroxyl group and a fibrous conductive material having an acidic functional group to a dispersion medium and performing a first dispersion treatment to obtain a precursor slurry; a second dispersion treatment step of adding a solid electrolyte to the precursor slurry and performing a second dispersion treatment to obtain the electrode slurry; The method for producing an electrode slurry comprising the steps of:

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