Electrode slurry, electrode layer, solid-state battery and method for producing an electrode slurry

Abstract

A main objective of the present invention is to provide an electrode slurry in which the dispersibility of a fibrous conductive material is good. The present invention achieves this objective by providing an electrode slurry for use in a solid-state battery, wherein the electrode slurry comprises an active electrode material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, a solid electrolyte, and a dispersion medium.

Description

Technical area

[0001] The present invention relates to an electrode slurry, an electrode layer, a solid-state battery, and a method for producing an electrode slurry. State of the art

[0002] A solid-state battery is a battery comprising a solid electrolyte layer between a cathode layer and an anode layer. One of its advantages is that simplification of a safety device can be more easily achieved compared to a liquid-based battery containing a liquid electrolyte containing a flammable organic solvent. As a method for forming a layer of electrodes (cathode layer or anode layer) in a solid-state battery, a method using an electrode slurry in which an active electrode 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.Although it is not a technology related to a solid-state battery, Patent Literature 1 discloses a carbon nanotube dispersion paste containing a carbon nanotube and an organic solvent. List of citationsPatent literature

[0003] Patent Literature 1: Japanese Patent Application (JP-A) No. 2023-080910 Summary of the inventionTechnical task

[0004] The electrode slurry used for a solid-state battery may contain a low-polarity dispersion medium to inhibit the decomposition of the solid electrolyte.

[0005] In addition, a fibrous conductive material such as a carbon nanotube tends to form a bundle structure. Therefore, it is difficult to sufficiently disperse the fibrous conductive material, even when dispersed in a low-polarity dispersion medium.

[0006] The present invention has been made in view of the above circumstances, and a main object thereof is to provide an electrode slurry in which the dispersibility of a fibrous conductive material is good. Solution to the problem [1] An electrode slurry used for a solid-state battery, the electrode slurry comprising: an active electrode material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, a solid electrolyte, and a dispersion medium. [2] The electrode slurry according to [1], wherein a content of the hydroxyl group in the active electrode material, measured by a CO2-TPD method, is 30 µmol / g or more. [3] The electrode slurry according to [1] or [2], wherein a content of the acidic functional group in the fibrous conductive material, measured by a potentiometric back titration, is 10 µmol / g or more. [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. [5] Electrode slurry according to any one of items [1] to [4], wherein the particle size of the slurry is 90 µm or less. [6] The electrode slurry according to any one of items [1] to [5], wherein, when a coating layer is formed by applying and drying the electrode slurry, the surface roughness of the coating layer is 5 µm or less according to ISO 25178. [7] An electrode layer used for a solid-state battery, the electrode layer comprising: an active electrode material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, and a solid electrolyte. [8] The electrode layer according to [7], wherein when the number of an aggregate of the fibrous conductive material whose aspect ratio is 5 or more and 1000 or less and whose longer side is 2 μm or more in the cross section of the electrode layer is confirmed in a range of 50 μm * 200 μm, the number of aggregates is 10 pieces or less. [9] The electrode layer according to [7] or [8], wherein a content of the hydroxyl group in the active electrode material, measured by a CO2-TPD method, is 30 µmol / g or more.

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

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

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

[12] A solid-state battery comprising a cathode layer, an anode layer, and a solid electrolyte layer disposed between the cathode layer and the anode layer, wherein: at least one of the cathode layer and the anode layer is the electrode layer according to one of the items [7] to

[11] .

[13] Solid-state battery according to

[12] , where the anode layer is the electrode layer.

[14] Solid-state battery according to

[13] , wherein the cathode layer contains a rock-salt bed type active material and the solid electrolyte layer contains a sulfide solid electrolyte.

[15] A method for producing an electrode slurry used for a solid-state battery, the method comprising: a first dispersion treatment step in which a first dispersion treatment is carried out by adding an electrode active material comprising a hydroxyl group and a fibrous conductive material comprising an acidic functional group to a dispersion medium to obtain a precursor slurry; and a second dispersion treatment step of performing a second dispersion treatment by adding a solid electrolyte to the precursor slurry to obtain the electrode slurry. Advantageous effects of the invention

[0007] The present invention exhibits the effect of providing an electrode slurry having excellent dispersibility of a fibrous conductive material. Short description of the drawings Fig. 1 is a schematic cross-sectional view illustrating the solid-state battery of the present invention. Fig. 2 is a diagram explaining the effect of the present invention. Fig. 3 is a flowchart illustrating the process for preparing the electrode slurry in the present invention. Fig. Figure 4 is a flow chart illustrating the process for preparing the electrode slurry in Reference Examples. Fig. 5A and Fig. 5B are cross-sectional SEM images of the electrode layers obtained in Examples and Reference Examples. Description of the embodiments

[0008] The electrode slurry, the electrode layer, the solid-state battery, and the method for producing the electrode slurry of the present invention are explained in detail below. A. Electrode slurry

[0009] The electrode slurry of the present invention is used to prepare an electrode layer (cathode layer, anode layer) of a solid-state battery. As described in Fig.As shown in Figure 1, the all-solid-state battery 10 includes a cathode layer 1, an anode layer 2, and a solid electrolyte layer 3 disposed between the cathode layer 1 and the anode layer 2. The electrode slurry of the present invention is typically used to prepare the cathode layer 1 or the anode layer 2. Furthermore, the electrode slurry of the present invention includes an electrode active material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, a solid electrolyte, and a dispersion medium.

[0010] According to the present invention, the combination of the electrode active material comprising a hydroxyl group and the fibrous conductive material comprising an acidic functional group enables excellent dispersibility of the fibrous conductive material in the electrode slurry. As described above, the electrode slurry used for the solid-state battery often contains a low-polarity dispersion medium to inhibit the decomposition of the solid electrolyte. Particularly, when using a high-reactivity solid electrolyte such as a sulfide solid electrolyte, a low-polarity dispersion medium is used. A fibrous conductive material such as a carbon nanotube easily forms a bundle structure.For this reason, sufficient dispersion of the fibrous conductive material is difficult even if the fibrous conductive material is dispersed in a dispersion medium with low polarity.

[0011] In contrast, according to the present invention, the electrode active material comprising a hydroxyl group and the fibrous conductive material comprising an acidic functional group are used in combination. As in Fig.As shown in Figure 2, the hydroxyl group present on the surface of the electrode active material 11 and the acidic functional group present on the surface of the fibrous conductive material 12 interact to inhibit the aggregation of the fibrous conductive material 12. In the present invention, the aggregation of the fibrous conductive material 12 is inhibited by using the electrode active material comprising a hydroxyl group, but in particular, the aggregation of the fibrous conductive material 12 is further effectively inhibited when the method described later in "D. Method for Producing Electrode Slurry" is employed. 1. Active electrode material

[0012] The electrode slurry contains an active electrode material that includes a hydroxyl group. Whether the active electrode material includes the hydroxyl group or not can be confirmed by infrared spectroscopy (IR method). In particular, a peak derived from an OH bond usually appears in the range of 3000 cm -1 or more and 3600 cm -1 or less. For example, when the active electrode material is a Si-based active material described later, a peak derived from the Si-O bond usually appears near 900 cm -1 .

[0013] The hydroxyl group content in the active electrode material can be achieved using a temperature-programmed deposition method using CO2 (CO2-TPD method). For example, the hydroxyl group content in the active electrode material is 30 µmol / g or more, can be 40 µmol / g or more, and can be 50 µmol / g or more. The hydroxyl group content in the active electrode material is 150 µmol / g or less, for example.

[0014] Typical examples of the active electrode material containing a hydroxyl group may include a Si-based active material. The Si-based active material is an active material composed mainly 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 also include a diamond-type crystal phase, a silicon clathrate I-type crystal phase, or a clathrate II-type crystal phase. In the clathrate I-type or II-type crystal phase, a plurality of Si elements form a polyhedron (cage) comprising pentagons or hexagons. This polyhedron has an internal space that can accommodate metal ions such as Li ions, and thus, the volume change due to charge and discharge can be suppressed.

[0015] The Si-based active material preferably comprises the clathrate II-type crystal phase as the main phase. The composition of the Si-based active material is also not particularly limited, but is preferably Na x Si 136 (0 ≤ x ≤ 24). The "x" can be 0 and can be greater than 0. The "x" can be 20 or less, 10 or less, and 5 or less. The composition of the Si-based active material can be obtained, for example, by EDX, XRD, XRF, ICP, or an atomic absorption method.

[0016] Other examples of the electrode active material containing a hydroxyl group may include a carbon-based active material. The carbon-based active material is an active material containing inorganic C (carbon) as the main component, and examples include graphite. Other examples of the electrode active material containing a hydroxyl group may include an active material containing at least one of Cd, In, Pb, Ga, Ge, Sn, Al, Bi, and Sb.

[0017] The active electrode material comprising a hydroxyl group preferably includes a void within the primary particle. When a void exists within the primary particle, volume change due to charge and discharge can be inhibited. The proportion of the void (void fraction) in the primary particle is, for example, 4% or more, and may be 10% or more. The void fraction is, for example, 40% or less, and may be 20% or less. The void fraction can be obtained, for example, in the following way. First, the cross-section of the active electrode material is observed with an SEM (scanning electron microscope) to obtain an image of the particle. On the obtained image, the solid part and the void part are differentiated and binarized using image analysis software. The areas of the solid part and the void part are determined.empty part are obtained and the void ratio (%) is calculated using the following equation. Void fraction (%) = 100 * (area of ​​the cavity) / ((area of ​​the solid part) + (area of ​​the cavity))

[0018] The active electrode material comprising a hydroxyl group is preferably a Si-based active material comprising voids within the primary particle (porous Si).

[0019] The active electrode material may be a cathode active material and an anode active material. Examples of the shape of the active electrode material may include a granular shape. The average particle size of the active electrode material is, for example, 0.5 µm or more and 30 µm or less, and may be 0.5 µm or more and 15 µm or less. In the present invention, the average particle size refers to the volume accumulation particle size D 50, which is measured using a laser diffraction particle distribution measuring device. The proportion of the active electrode material in the solid content of the electrode slurry is also not particularly limited, but may be, for example, 10 wt% or more and 90 wt% or less, 30 wt% or more and 80 wt% or less, and 50 wt% or more and 70 wt% or less. 2. fibrous conductive material

[0020] The electrode slurry contains a fibrous conductive material comprising an acidic functional group. Examples of the acidic functional group may include a carboxyl group (-COOH) and a nitro group (-NO2). Whether the fibrous conductive material comprises the acidic functional group or not can be confirmed by infrared spectroscopy (IR method). Whether the fibrous conductive material comprises, for example, the carboxyl group (-COOH) or not can be determined by the presence of the peak derived from the OH bond (peak appears in the range of 3000 cm). -1 or more and 3600 cm -1 or less) and the peak derived from the C=O bond (peak appears in the region of 1500 cm -1 or more and 1800 cm -1 or less).

[0021] The proportion of the acidic functional group in the fibrous conductive material can be determined by potentiometric back titration. For example, the proportion of the acidic functional group in the fibrous conductive material is 10 µmol / g or more, may be 30 µmol / g or more, and may be 50 µmol / g or more. Incidentally, acetylene black (AB), a particulate conductive material, may contain an acidic functional group (carboxyl group), but the proportion is about 5 µmol / g.

[0022] Examples of the fibrous conductive material containing an acidic functional group may include a carbon material, a metal material, and a conductive resin material, among which the carbon material is preferable. This is because the carbon material has excellent electronic conductivity, light weight, and long service life. Examples of the fibrous conductive material containing an acidic functional group may include a carbon nanotube (CNT) and a carbon nanofiber (CNF). The carbon nanotube (CNT) may be a single-layer carbon nanotube (SWCNT) and a multilayer carbon nanotube (MWCNT).

[0023] The aspect ratio (long side / short side) of the fibrous conductive material containing an acidic functional group is not particularly limited, but may be, for example, 2 or more and 1000 or less, 10 or more and 750 or less, and 50 or more and 500 or less. The length of the long side of the fibrous conductive material is not particularly limited, and may be, for example, 0.1 μm or more and 80 μm or less, and 0.5 μm or more and 60 μm or less. The length of the short side of the fibrous conductive material is not particularly limited, and may be, for example, 0.5 nm or more and 100 nm or less, and may be 1 nm or more and 30 nm or less.

[0024] The electrode slurry may contain, in addition to the fibrous conductive material containing an acidic functional group, a fibrous conductive material not containing an acidic functional group and a particulate conductive material. Examples of the particulate conductive material may include a particulate carbon material such as acetylene black (AB) and Ketjen black (KB). The proportion of the fibrous conductive material containing an acidic functional group among all the conductive materials contained in the electrode slurry is, for example, 50 wt% or more, may be 70 wt% or more, and may be 90 wt% or more.

[0025] The proportion of the fibrous conductive material comprising an acidic functional group in the solid content of the electrode slurry is not particularly limited and is, for example, 0.05 wt% or more and 5 wt% or less, and may be 0.1 wt% or more and 3 wt% or less. 3. Solid electrolyte

[0026] The electrode slurry contains a solid electrolyte. The solid electrolyte is usually an inorganic solid electrolyte. Examples of the inorganic solid electrolyte include a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, and a halide solid electrolyte. Sulfide solid electrolyte is particularly preferable. This is because the ionic conductivity of the sulfide solid electrolyte is high. Furthermore, because the reactivity of the sulfide solid electrolyte is high, it is necessary to use a low-polarity dispersion medium. Even when using a low-polarity dispersion medium, the combination of the active electrode material containing a hydroxyl group and the fibrous conductive material containing an acidic functional group enables excellent dispersibility of the fibrous conductive material in the electrode slurry.

[0027] The sulfide solid electrolyte typically contains at least one Li element and one S element. It is preferable for the sulfide solid electrolyte to also contain an M element (M is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). The sulfide solid electrolyte may also contain a halogen element such as F, Cl, Br, and I.

[0028] The sulfide solid electrolyte can be a glass-based (amorphous-based) sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, and a crystal-based sulfide solid electrolyte. The sulfide solid electrolyte can include a crystal phase. Examples of the crystal phase can include a thio-LISICON-type crystal phase, an argyrodite-type crystal phase, and an LGPS-type crystal phase.

[0029] There are no specific restrictions on the composition of the sulfide solid electrolyte, and examples include xLi2S (1-x)P2S5 (0.5≤x<1) and yLiIz LiBr (100-yz)(xLi2S (1-x)P2S5) (0.5≤x<1, 0≤y≤30, 0≤z≤30). In these compositions, it is preferable that "x" satisfies 0.7≤x≤0.8.

[0030] Other examples of the composition of the sulfide solid electrolyte can be 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. Part of Li can also be replaced by at least one of Na, K, Mg, Ca, and Zn. Other examples of the composition of the sulfide solid electrolyte can be Li 7-x-2y PS 6-x-y X yX is at least one of F, Cl, Br, and I, and x and y satisfy 0 ≤ x, 0 ≤ y. Also, a portion of Li may be replaced by at least one of Na, K, Mg, Ca, and Zn. Furthermore, a portion of S may be replaced by oxygen (o).

[0031] The shape of the solid electrolyte is, for example, a granular form. The average particle size of the solid electrolyte is, for example, 0.1 μm or more and 30 μm or less, and may be 0.5 μm or more and 15 μm or less. The proportion of the solid electrolyte in the solid content of the electrode slurry is also not particularly limited and may be, for example, 10 wt% or more and 70 wt% or less, 20 wt% or more and 60 wt% or less, and 30 wt% or more and 50 wt% or less. 4. Dispersion medium

[0032] The electrode slurry contains a dispersion medium. The polarity of the dispersion medium is preferably low. This is to inhibit the deterioration of the solid electrolyte (especially sulfide solid electrolyte). The polarity of the dispersion medium can be specified, for example, by Hansen solubility parameters. Specifically, the dispersion medium preferably has a polarity section (δP) of 4 or less in the Hansen solubility parameters. The polarity section (δP) of the Hansen solubility parameters can be obtained from the manual "Hansen Solubility Parameters: A User's Handbook, Second Edition" (Hansen, Charles (2007)) published by CRC Press, Boca Raton, Florida, USA.

[0033] Examples of dispersion media may include: butyl butylate (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, but it may also contain two or more types. There are also no specific restrictions on the solid concentration of the electrode slurry, but it may be, for example, 30 wt% more and 70 wt% or less, or 40 wt% more and 60 wt% or less. 5. Electrode slurry

[0034] The electrode slurry may further contain a binder. Examples of the binder may include a fluoride-based binder such as polyvinylidene fluoride (PVDF), a polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and a fluororubber; and a rubber-based binder such as a butadiene rubber, a butadiene hydride rubber, a styrene-butadiene rubber (SBR), a styrene-butadiene hydride rubber, a nitrile-butadiene rubber, a nitrile-butadiene hydride rubber, and an ethylene-propylene rubber.

[0035] The particle size of the electrode slurry is preferably small from the perspective of dispersibility. The particle size of the electrode slurry is, for example, 90 µm or less, but may be 80 µm or less, 60 µm or less, or 40 µm or less. The particle size of the electrode slurry is, for example, 5 µm or more. The particle size of the electrode slurry can be obtained based on JISK5600-2-5.

[0036] When the electrode slurry is applied to form a coating and dried, the surface roughness (surface roughness based on ISO25178) of the coating layer is preferably low from the perspective of dispersibility. The surface roughness of the coating layer is, for example, 5 µm or less, may be 3 µm or less, and may be 1 µm or less. The coating layer to be measured is preferably formed by doctoring the electrode slurry with a gap of 100 µm and drying it.

[0037] There are no particular restrictions on the method for preparing the electrode slurry, but examples thereof may include the method described later in “D. Method for preparing the electrode slurry.” B. Electrode layer

[0038] The electrode layer of the present invention is used for a solid-state battery and contains an electrode active material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, and a solid electrolyte.

[0039] According to the present invention, the combination of the active electrode material containing a hydroxyl group and the fibrous conductive material containing an acidic functional group enables excellent dispersibility of the fibrous conductive material in the electrode layer. The active electrode material, the fibrous conductive material, and the solid electrolyte have the same components as those described above under "A. Electrode Slurry."

[0040] The electrode layer may be a cathode layer containing a cathode active material, and may be an anode layer containing an anode active material. When viewing the cross section of the electrode layer, the number of aggregates of the fibrous conductive material is preferably small. Specifically, when the number of aggregates of the fibrous conductive material whose aspect ratio is 5 or more and 1000 or less, and whose longer side is 2 μm or more, is confirmed within a range of 50 μm * 200 μm, the number of aggregates is 10 pieces or less, may be 8 pieces or less, may be 5 pieces or less, and may be 3 pieces or less.

[0041] The thickness of the electrode layer is not particularly limited and may be, for example, 0.1 μm or more and 1000 μm or less, 0.1 μm or more and 500 μm or less, and 0.1 μm or more and 100 μm or less. Examples of the method for forming the electrode layer may also include a method in which the electrode slurry is coated and dried. The electrode layer is normally used for an all-solid-state battery. The present invention can also provide a battery element used for an all-solid-state battery and comprising at least the electrode layer. C. Solid-state battery

[0042] Fig. 1 is a schematic cross-sectional view illustrating the solid-state battery of the present invention. Fig.1 comprises a cathode layer 1, an anode layer 2, a solid electrolyte layer 3 arranged between the cathode layer 1 and the anode layer 2, a cathode current collector 4 for collecting currents of the cathode layer 1, and an anode current collector 5 for collecting currents of the anode layer 2. In the present invention, at least one of the cathode layer 1 and the anode layer 2 is the electrode layer described above under “B Electrode Layer”.

[0043] According to the present invention, the use of the electrode layer described above enables the solid-state battery to have low resistance. 1. Cathode layer and anode layer

[0044] According to the present invention, the cathode layer may be the electrode layer described above, the anode layer may be the electrode layer described above, and both the cathode layer and the anode layer may be the electrode layer described above. The cathode layer contains at least one active cathode material.

[0045] For example, if the anode layer is the electrode layer described above, there are no particular restrictions on the type of cathode active material contained in the cathode layer. Examples of the cathode active material may include an oxide active material. Examples of the oxide active material may include a rock salt bed type active material such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and LiNi 0,8 Co 0,15 Al 0,05 O2, a spinel type active material such as LiMn2O4, Li4Ti5O 12 and Li(Ni0,5 Mn 1,5 )O4 and an olivine-type active material such as LiFePO4, LiMnPO4, LiNiPO4 and LiCoPO4.

[0046] A coating layer containing conductive Li-ion oxide can be formed on the surface of the active oxide material. This inhibits the reaction of the active oxide material with the solid electrolyte (especially a sulfide solid electrolyte). Examples of the conductive Li-ion oxide include LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less.

[0047] For example, if the cathode layer is the electrode layer described above, there are no particular restrictions on the type of anode active material contained in the anode layer. Examples of the anode active material may include a metal active material such as Li and Sn, a carbon active material such as graphite, and an oxide active material such as lithium titanate.

[0048] In addition to the active cathode material, the cathode layer may contain at least one type of solid electrolyte, a conductive material, and a binder. Similarly, the anode layer may contain at least one type of solid electrolyte, a conductive material, and a binder in addition to the active anode material. The solid electrolyte, the conductive material, and the binder have the same components as those described above under "A. Electrode Slurry." 2. Solid electrolyte layer

[0049] The solid electrolyte layer is a layer disposed between the cathode layer and the anode layer and containing at least one solid electrolyte. The solid electrolyte layer may further contain a binder. The solid electrolyte and the binder have the same components as those described above under "A. Electrode Slurry"; therefore, the descriptions are omitted here. The thickness of the solid electrolyte layer is, for example, 0.1 µm or more and 1000 µm or less, may be 0.1 µm or more and 500 µm or less, and may be 0.1 µm or more and 100 µm or less. 3. Other compositions

[0050] The solid-state battery of the present invention preferably comprises a cathode current collector for collecting currents from the cathode layer and an anode current collector for collecting currents from the anode layer. Examples of the material for the cathode current collector may include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material for the anode current collector may include SUS, copper, nickel, and carbon.

[0051] The all-solid-state battery of the present invention may further comprise a holding device that applies a holding pressure along the thickness direction of the cathode layer, the electrolyte layer, and the anode layer. By using the holding device, an excellent ion conduction path and an excellent electron conduction path can be formed. The holding pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, and may be 5 MPa or more. The holding pressure is, for example, 100 MPa or less, may be 50 MPa or less, and may be 20 MPa or less. 4. Solid-state battery

[0052] The type of the solid-state battery of the present invention is not particularly limited, but is typically a lithium-ion secondary battery. Further, examples of applications of the solid-state battery may include a power source for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline-powered automobiles, and diesel-powered automobiles. In particular, it is preferably used as a power source for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). The solid-state battery can also be used as a power source for moving bodies other than vehicles (e.g., railway vehicles, ships, and aircraft) and as a power source for electronic products such as information processing equipment.In addition, there are no particular restrictions on the method for manufacturing the solid-state battery, and known methods can be used. D. Process for preparing an electrode slurry

[0053] Fig. Figure 3 is a flow chart illustrating the process for preparing the electrode slurry of the present invention. As shown in Fig.As shown in Figure 3, a first dispersion treatment is performed by adding an electrode active material comprising a hydroxyl group and a fibrous conductive material comprising an acidic functional group to a dispersion medium to obtain a precursor slurry (a first dispersion treatment step). Next, a second dispersion treatment is performed by adding a solid electrolyte to the obtained precursor slurry to obtain the electrode slurry (a second dispersion treatment step).

[0054] According to the present invention, in the first dispersion treatment step, the electrode active material comprising a hydroxyl group and the fibrous conductive material comprising an acidic functional group are simultaneously dispersed, and then, after adding a solid electrolyte, the second dispersion treatment is performed; thus, the electrode slurry having excellent dispersibility of the fibrous conductive material can be obtained. 1. First dispersion treatment step

[0055] The first dispersion treatment step is a step of performing a first dispersion treatment by adding an electrode active material comprising a hydroxyl group and a fibrous conductive material comprising an acidic functional group to a dispersion medium to obtain a precursor slurry. The dispersion medium, the electrode active material comprising a hydroxyl group, and the fibrous conductive material comprising an acidic functional group have the same composition as that described above in "A. Electrode Slurry."

[0056] In the first dispersion treatment step, a first dispersion treatment is performed on a dispersion liquid in which the active electrode material containing a hydroxyl group and the fibrous conductive material containing an acidic functional group are added to a dispersion medium. A binder may be further added to the dispersion medium. In other words, the first dispersion treatment may be performed on a dispersion liquid containing the active electrode material, the fibrous conductive material, and a binder. Further, the first dispersion treatment may be performed on the dispersion liquid containing the active electrode material and the fibrous conductive material, and then an additional dispersion treatment may be performed after adding a binder to the dispersion liquid.The additional dispersion treatment is preferably carried out before the second dispersion treatment step described later.

[0057] Examples of the first dispersion treatment may include ultrasonic dispersion treatment and stirring treatment. There are no specific restrictions on the treatment time of the first dispersion treatment, but it may, for example, be 1 minute or more and 60 minutes or less, or 3 minutes or more and 30 minutes or less. The temperature at the time of the first dispersion treatment is not particularly limited, but, for example, it may be room temperature. 2. Second dispersion treatment step

[0058] The second dispersion treatment step is a step of performing a second dispersion treatment by adding a solid electrolyte to the precursor slurry to obtain the electrode slurry. The solid electrolyte has the same composition as that described above in "A. Electrode Slurry."

[0059] In the second dispersion treatment step, the second dispersion treatment is performed by adding the solid electrolyte to the precursor slurry. A binder may be further added to the precursor slurry into which the solid electrolyte is added, and then the second dispersion treatment may be performed.

[0060] Examples of the second dispersion treatment may include ultrasonic dispersion treatment and stirring treatment. There are no specific restrictions on the treatment time of the second dispersion treatment, but it may, for example, be 1 minute or more and 60 minutes or less, or 3 minutes or more and 30 minutes or less. The temperature at the time of the second dispersion treatment is not particularly limited, but it may, for example, be room temperature. 3. Electrode slurry

[0061] The electrode slurry obtained by the above steps has the same composition as that described above under “A. Electrode slurry”.

[0062] Furthermore, the present invention is not limited to the embodiments. The embodiments are for illustrative purposes, and all other variations are intended to be included within the technical scope of the present invention if they have substantially the same nature as the technical idea described in the claims of the present invention and have a similar operation and effect. Examples[Example 1]<Herstellung von Anodenschlamm>

[0063] An anode sludge was prepared according to Fig. 3. Specifically, 2.7 g of a dispersion medium diisobutyl ketone, 0.002 g of a single-layer carbon nanotube comprising a carboxyl group (SWCNT, length: 5 µm, fiber diameter: 3 nm, carboxyl group content: 55 µmol / g), 1 g of a porous Si comprising a hydroxyl group (D 50 : 500 nm, specific surface area: 50 m 2 / g, hydroxyl group content: 56 μmol / g) and 0.8 g of a binder solution (diisobutyl ketone solution containing PVDF-HFP at a concentration of 5 wt%) were added, and ultrasonic dispersion (first dispersion) was performed on the product under the conditions of amplitude: 40 μm, frequency: 20 kHz, and 3 minutes, thereby obtaining a precursor slurry. Next, 1.2 g of a sulfide solid electrolyte (Li3PS4-based glass-ceramic comprising LiI and LiBr) was added to the obtained precursor slurry, and ultrasonic dispersion (second dispersion) was performed on the product under the conditions of amplitude: 40 μm, frequency: 20 kHz, and 3 minutes, thereby obtaining an anode slurry. <Herstellung der Anode>

[0064] The resulting anode slurry was coated onto a roughened Ni foil (anode current collector) with a gap of 340 µm using a doctor blade and dried. This resulted in an anode comprising an anode current collector and an anode layer. <Herstellung der Festelektrolytschicht>

[0065] To 0.8 g of heptane, 0.4 g of a sulfide solid electrolyte (Li3PS4-based glass-ceramic comprising LiI and LiBr) and 0.05 g of a binder solution (heptane solution containing an acrylonitrile-butadiene rubber at a concentration of 5 wt%) were added, and ultrasonic dispersion of the product was performed under the following conditions: amplitude: 40 µm, frequency: 20 kHz, and for 10 minutes to obtain a slurry. The resulting slurry was coated onto a stainless steel foil (substrate) with a 50 µm gap using a doctor blade and dried. A transfer element comprising the substrate and a solid electrolytic layer was obtained. <Herstellung der Kathode>

[0066] To 1 g of butyl butyrate, 2 g of an active cathode material (LiNi 0,8 Co 0,15 Al 0,05O2, NCA), 0.03 g of a multilayer carbon nanotube (MWCNT), 0.3 g of a sulfide solid electrolyte (Li3PS4-based glass-ceramic comprising LiI and LiBr), and 0.3 g of a binder solution (butyl butyrate solution containing PVDF-HFP at a concentration of 5 wt%) were added, and the product was subjected to ultrasonic treatment under the following conditions: amplitude: 40 μm, frequency: 20 kHz, and 10 minutes to obtain a cathode slurry. The obtained cathode slurry was coated onto an Al foil (cathode current collector) with a gap of 300 μm using a doctor blade and dried. This resulted in a cathode comprising a cathode current collector and a cathode layer. <Herstellung der Batterie>

[0067] The anode and the transfer element were overlapped so that the anode layer in the anode and the solid electrolyte layer in the transfer element faced each other, and the product was roll-pressed under conditions of a linear load of 3 t / cm and room temperature to obtain a layered anode body. Similarly, the cathode and the transfer element were overlapped so that the cathode layer in the cathode and the solid electrolyte layer in the transfer element faced each other, and the product was roll-pressed under conditions of a linear load of 4 t / cm and room temperature to obtain a layered cathode body. After that, the layered cathode body and the layered anode body were overlapped so that the solid electrolyte layers faced each other, and the solid electrolyte layers were bonded. This resulted in a battery. [Examples 2 to 5]

[0068] An anode 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 each changed to the values ​​shown in Table 1. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used in each case. [Example 6]

[0069] An anode slurry was obtained in the same manner as in Example 1, except that a multilayer carbon nanotube containing a carboxyl group (MWCNT, length: 5 µm, fiber diameter: 150 nm, carboxyl group content: 60 µmol / g) was used instead of SWCNT. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Examples 7 to 10]

[0070] An anode 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 anode slurry was used in each case. [Example 11]

[0071] An anode slurry was obtained in the same manner as in Example 1, except that a solid Si nanoparticle was used instead of the porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Examples 12 to 13]

[0072] An anode slurry was obtained in the same manner as in Example 1, except that the particle size and specific surface area of ​​the Si nanoparticle 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 anode slurry was used in each case. [Example 14]

[0073] An anode slurry was obtained in the same manner as in Example 6, except that a solid Si nanoparticle was used instead of the porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Reference Example 1]

[0074] An anode slurry was prepared according to the Fig.4. Specifically, diisobutyl ketone, 0.002 g of SWCNT, and 0.8 g of a binder solution were added to 2.7 g of a dispersion medium, and ultrasonic treatment (dispersion treatment X) was performed under the 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 on the product under the conditions of amplitude: 40 µm, frequency: 20 kHz, and 3 minutes to obtain a second precursor slurry. Next, 1.2 g of a sulfide solid electrolyte was added to the obtained second precursor slurry, and ultrasonic treatment (dispersion treatment Z) was performed on the product under the conditions of amplitude: 40 µm, frequency: 20 kHz, and 3 minutes to obtain an anode slurry.Incidentally, all the materials used for the anode slurry were the same as in Example 2. In addition, a battery was obtained in the same manner as in Example 1 except that the obtained anode slurry was used. [Reference Example 2]

[0075] An anode slurry was obtained in the same manner as in Reference Example 1, except that the MWCNT used in Example 6 was used instead of SWCNT. Furthermore, a battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Reference Example 3]

[0076] An anode slurry was obtained in the same manner as in Reference Example 1, except that a solid Si nanoparticle was used instead of the porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Reference Example 4]

[0077] An anode slurry was obtained in the same manner as in Reference Example 2, except that a solid Si nanoparticle was used instead of the porous Si. A battery was obtained in the same manner as in Example 1, except that the obtained anode slurry was used. [Table 1] conductive material active material Particle size (nm) specific surface area (m 2 / G) Dispersion type Example 1 SWCNT Porous Si 500 50 simultaneously Example 2 SWCNT Porous Si 1000 50 simultaneously Example 3 SWCNT Porous Si 1000 100 simultaneously Example 4 SWCNT Porous Si 1000 300 simultaneously Example 5 SWCNT Porous Si 1000 600 simultaneously Example 6 MWCNT Porous Si 500 50 simultaneously Example 7 MWCNT Porous Si 1000 50 simultaneously Example 8 MWCNT Porous Si 1000 100 simultaneously Example 9 MWCNT Porous Si 1000 300 simultaneously Example 10 MWCNT Porous Si 1000 600 simultaneously Example 11 SWCNT Si nanoparticles 50 50 simultaneously Example 12 SWCNT Si nanoparticles 100 20 simultaneously Example 13 SWCNT Si nanoparticles 200 10 simultaneously Example 14 MWCNT Si nanoparticles 50 50 simultaneously Ref. Example 1 SWCNT Porous Si 1000 50 individually Ref. Example 2 MWCNT Porous Si 1000 50 individually Ref. Example 3 SWCNT Si nanoparticles 50 50 individually Ref. Example 4 MWCNT Si nanoparticles 50 50 individually [Evaluation]<Partikelgröße der Aufschlämmung>

[0078] The particle size of the slurry was measured using the anode slurries prepared in Examples 1 to 14 and Reference Examples 1 to 4, respectively. Specifically, the particle size of the slurry was measured based on JISK5600-2-5. The results are shown in Table 2. <Oberflächenrauheit basierend auf ISO25178>

[0079] The anode slurry prepared in Examples 1 to 14 and Reference Examples 1 to 4 was applied to a roughened Ni foil with a squeegee and dried with a spatula, respectively. Evaluation samples were obtained. The surfaces of the obtained evaluation samples were measured using a digital microscope (VHX-8000 from KEYENCE CORPORATION) with a 500x field of view, and the surface roughness was determined based on ISO25178. The results are shown in Table 2. <zellwiderstand>

[0080] The resistance of the batteries obtained in Examples 1 to 14 and Reference Examples 1 to 4 was measured, respectively. Specifically, the batteries were CCCV charged at C / 10 to 4.35 V and then CCCV discharged at C / 3 to 3.35 V. Afterward, another discharge was performed at 7 C, and the cell resistances were obtained from the voltage change in 10 seconds and the current value. The results are shown in Table 2. <Elektronenleitfähigkeit>

[0081] The electronic conductivity was measured using anodes prepared in Examples 1 to 14 and Reference Examples 1 to 4. Specifically, the anode was measured at 1 cm 2 punched out, and two of the punched out anodes were overlapped so that the anode layers faced each other. An overlapped layered body was clamped in a thickness direction, the resistance was measured, and the electronic conductivity was obtained. The results are shown in Table 2. <Die Anzahl der Aggregate>

[0082] The number of conductive material aggregates was counted using the anode layers prepared in Examples 1 to 14 and Reference Examples 1 to 4. Specifically, the cross sections of the anode layers were observed using a scanning electron microscope (SEM, FE-SEM SU-8200 from Hitachi) with a field of view of 400x magnification. Upon observation, the number of conductive material aggregates whose aspect ratio was 5 or more and 1000 or less, and whose longer side was 2 μm or more, was confirmed to be in a range of 50 μm * 200 μm. This process was repeated ten times, and the average value was determined in each case as the number of conductive material aggregates. The results are shown in Table 2. As in Fig. 5A, the aggregate of the conductive material in the anode layer prepared in Example 1 was rarely confirmed. As shown in Fig. As shown in Figure 5B, a plurality of aggregates (parts surrounded by black circles) were confirmed in the anode layer prepared in Reference Example 1. [Table 2] Slurry particle size (µ / m) Surface roughness (µm) Cell resistance (Ω cm 2 ) Electron conductivity (mS / m) Number of units Example 1 30 0,4 23,4 2,94 3 Example 2 30 0,5 23,3 2,72 1 Example 3 30 0,4 22,3 2,95 1 Example 4 40 0,6 21,1 2,88 2 Example 5 50 0,4 23,3 3,04 1 Example 6 30 0,5 23,2 2,32 6 Example 7 30 0,8 24,4 2,09 8 Example 8 30 0,6 24,1 2,22 7 Example 9 30 0,7 22,8 2,15 8 Example 10 40 0,4 24,3 - 5 Example 11 30 0,2 19,6 2,87 2 Example 12 90 9,5 21,5 1,88 8 Example 13 90 8,7 23,2 1,76 9 Example 14 30 0,6 20,3 2,11 5 Ref. Example 1 >100 10,3 25,0 1,72 17 Ref. Example 2 >100 9,0 27,2 1,31 14 Ref. Example 3 >100 10,5 24,8 1,82 13 Ref. Example 4 >100 10,2 26,8 1,35 14

[0083] As shown in Table 1, it was confirmed that the dispersibility of the fibrous conductive material in the electrode slurries in Examples 1 to 14 and Reference Examples 1 to 4 was excellent. Thus, an electrode slurry having excellent dispersibility of the fibrous conductive material was obtained when the electrode active material comprising a hydroxyl group and the fibrous conductive material comprising an acidic functional group were used in combination.

[0084] Above all, in Examples 1 to 5, as compared with Reference Example 1, it was confirmed that the particle size of the slurry was smaller, the surface roughness was smaller, the cell resistance was lower, the electronic conductivity was higher, and the number of aggregates was lower. Similarly, in Examples 6 to 10, as compared with Reference Example 2, it was confirmed that the particle size of the slurry was smaller, the surface roughness was smaller, the cell resistance was lower, the electronic conductivity was higher, and the number of aggregates was lower. Thus, in the present invention, it was confirmed that the dispersion was simultaneously preferable to a single dispersion. In addition, based on the results of the present invention, the average particle size D 50 of the porous Si is preferably 300 nm or more and 1200 nm or less. The average particle size D 50 of the porous Si may be 500 nm or more and 1000 nm or less. Furthermore, in the present invention, the specific surface area of ​​the porous Si is preferably 30 m 2 / g or more and 800 m 2 / g or less. The specific surface area of ​​porous Si can be 50 m 2 / g or more and 600 m 2 / g or less.

[0085] Furthermore, in Example 11, compared to Reference Example 3, it was confirmed that the particle size of the slurry was smaller, the surface roughness was smaller, the cell resistance was lower, the electronic conductivity was higher, and the number of aggregates was lower. Also, in Example 14, compared to Reference Example 4, it was confirmed that the particle size of the slurry was smaller, the surface roughness was smaller, the cell resistance was lower, the electronic conductivity was higher, and the number of aggregates was lower. Also based on the results of Example 11 and Example 12, in the present invention, the particle size D 50 of the Si nanoparticle is preferably less than 100 nm. The average particle size D 50 of the Si nanoparticle can be 80 nm or less and 60 nm or less. The average particle size D 50 of the Si nanoparticle may be 20 nm or more. Furthermore, in the present invention, the specific surface area of ​​the Si nanoparticle is preferably greater than 20 m 2 / g. The specific surface area of ​​the Si nanoparticles can be 30 2 m / g or more and 40 2 m / g or more. The specific surface area of ​​the Si nanoparticles can be 70 2 m / g or less. List of reference symbols 1 cathode layer 2 Anode layer 3 Solid electrolyte layer 4 Cathode current collector 5 Anode current collector 10 solid-state battery QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-080910

[0003] Cited non-patent literature

[0000] Hansen Solubility Parameters: A user's handbook, Second Edition" (Hansen, Charles (2007)) by CRC Press, Boca Raton, Florida, USA

[0032] < / zellwiderstand>

Claims

[1] Electrode slurry used for a solid-state battery, wherein the electrode slurry characterized by is that it includes: an active electrode material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, a solid electrolyte, and a dispersion medium. [2] Electrode slurry according to claim 1, characterized by that a content of the hydroxyl group in the active electrode material, measured by a CO2-TPD method, is 30 µmol / g or more. [3] Electrode slurry according to claim 1, characterized by that a proportion of the acidic functional group in the fibrous conductive material, measured by a potentiometric back titration, is 10 µmol / g or more. [4] Electrode slurry according to claim 1, characterized bythat the active electrode 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] Electrode slurry according to claim 1, characterized by that the particle size of the slurry is 90 µm or less. [6] Electrode slurry according to claim 1, characterized by that when a coating layer is formed by applying and drying the electrode slurry, the surface roughness of the coating layer is 5 µm or less based on ISO25178. [7] Electrode layer used for a solid-state battery, wherein the electrode layer characterized by is that it includes: an active electrode material comprising a hydroxyl group, a fibrous conductive material comprising an acidic functional group, and a solid electrolyte. [8] Electrode layer according to claim 7, characterized by that when the number of an aggregate of the fibrous conductive material whose aspect ratio is 5 or more and 1000 or less and whose longer side is 2 μm or more in the cross section of the electrode layer is confirmed in a range of 50 μm * 200 μm, the number of the aggregate is 10 pieces or less. [9] A solid-state battery comprising a cathode layer, an anode layer, a solid electrolyte layer disposed between the cathode layer and the anode layer, characterized by that at least one of the cathode layer and the anode layer is the electrode layer according to one of claims 7 or 8. [10] A method for producing an electrode slurry used for a solid-state battery, the method comprising characterized by is that it includes: a first dispersion treatment step of performing a first dispersion treatment by adding an electrode active material comprising a hydroxyl group and a fibrous conductive material comprising an acidic functional group to a dispersion medium to obtain a precursor slurry; and a second dispersion treatment step of performing a second dispersion treatment by adding a solid electrolyte to the precursor slurry to obtain the electrode slurry.

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