Electrode layer

Abstract

To provide an electrode layer with a low internal resistance mainly.SOLUTION: The above problem is solved by providing an electrode layer herein disclosed, which is one to be used for an all-solid battery. The electrode layer contains an electrode active substance, a sulfide solid electrolyte having an average particle size (D50) smaller than 1 μm, and an imidazoline-based dispersion material.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electrode layer. [Background technology]

[0002] All-solid-state batteries have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage of being easier to simplify safety devices compared to liquid-based batteries that use an electrolyte solution containing a flammable organic solvent. For example, Patent Document 1 discloses an all-solid-state lithium secondary battery in which the surface roughness Ra at the interface between the positive electrode mixture layer and the solid electrolyte layer is 1.0 μm or less. Patent Document 1 also discloses the use of an imidazoline-based dispersion material in the positive electrode mixture layer or the negative electrode mixture layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-161364 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the performance of all-solid-state batteries, an electrode layer with low internal resistance is required. The present disclosure has been made in view of the above-described circumstances, and a main object of the present disclosure is to provide an electrode layer with low internal resistance. [Means for solving the problem]

[0005] The present disclosure provides an electrode layer for use in an all-solid-state battery, the electrode layer containing an electrode active material and a sulfide solid electrolyte, the sulfide solid electrolyte having an average particle size (D 50 ) is less than 1 μm, and the electrode layer contains an imidazoline-based dispersion material.

[0006] According to the present disclosure, the average particle size (D 50By using a sulfide solid electrolyte having a specific range of .DELTA.) and an imidazoline-based dispersion material, an electrode layer with low internal resistance is obtained.

[0007] In the above disclosure, the electrode layer may further contain a rubber-based binder.

[0008] In the above disclosure, the electrode active material may include at least one of a transition metal oxide-based active material, a Si-based active material, and a carbon-based active material.

[0009] In the above disclosure, the electrode layer may be a positive electrode layer.

[0010] In the above disclosure, the electrode layer may be a negative electrode layer.

[0011] In the above disclosure, when the content of the electrode active material in the electrode layer is 100 parts by weight, the content of the imidazoline-based dispersant may be 0.005 parts by weight or more and 0.5 parts by weight or less.

[0012] In the above disclosure, the electrode layer may be a positive electrode layer, and the content of the imidazoline-based dispersion material may be 0.01 parts by weight or more and 0.135 parts by weight or less.

[0013] The present disclosure also provides an all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer and the negative electrode layer is the above-described electrode layer.

[0014] According to the present disclosure, by using the above-described electrode layer, an all-solid-state battery with low internal resistance is obtained. [Effects of the Invention]

[0015] The present disclosure has an effect of providing an electrode layer with low internal resistance. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of an all-solid-state battery according to the present disclosure. [Figure 2] 1 is a graph showing the results of Examples 3 to 7 and Comparative Examples 3 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0017] The electrode layer and the all-solid-state battery according to the present disclosure will be described in detail below.

[0018] A. Electrode layer The electrode layer in the present disclosure is an electrode layer used in an all-solid-state battery, and the electrode layer contains an electrode active material and a sulfide solid electrolyte, and the sulfide solid electrolyte has an average particle size (D 50 ) is less than 1 μm, and the electrode layer contains an imidazoline-based dispersion material.

[0019] According to the present disclosure, the average particle size (D 50 By using a sulfide solid electrolyte having an average particle diameter (D ) within a predetermined range and an imidazoline-based dispersion material, an electrode layer with low internal resistance can be obtained. 50 The internal resistance was significantly reduced by using an imidazoline-based dispersion material in combination with a sulfide solid electrolyte with an average particle size (D 50 ) to less than 1 μm and used in combination with an imidazoline-based dispersant, a good bonding interface was formed at the interface between the electrode active material and the sulfide solid electrolyte, resulting in a significant reduction in the interfacial resistance.

[0020] 1. Imidazoline-based dispersion material The electrode layer in the present disclosure contains an imidazoline-based dispersant. The imidazoline-based dispersant is a dispersant having an imidazoline skeleton (a nitrogen-containing heterocyclic structure derived from imidazole). The electrode layer may contain only one type of imidazoline-based dispersant, or may contain two or more types. Examples of imidazoline-based dispersants include compounds represented by the following general formula:

[0021] [ka]

[0022] In the above general formula, R 1 is an alkyl group or a hydroxyalkyl group. 1 The number of carbon atoms in R is, for example, 1 or more and 22 or less. In the hydroxyalkyl group, the hydroxyl group may be bonded to the terminal carbon opposite to the carbon bonded to N. 2 is an alkyl or alkenyl group. 2 The number of carbon atoms is, for example, 10 or more and 22 or less. The position and number of double bonds in the alkenyl group are not particularly limited. Specific examples of compounds represented by the above general formula include 1-hydroxyethyl-2-alkenylimidazoline (e.g., DISPER BYK-109 manufactured by BYK-Chemie).

[0023] In the electrode layer, when the content of the electrode active material is 100 parts by weight, the content of the imidazoline-based dispersant is preferably, for example, 0.005 parts by weight or more and 0.5 parts by weight or less. When the electrode layer is a negative electrode layer, the content of the imidazoline-based dispersant may be, for example, 0.01 parts by weight or more and 0.5 parts by weight or less, or 0.01 parts by weight or more and 0.46 parts by weight or less. When the electrode layer is a positive electrode layer, the content of the imidazoline-based dispersant may be, for example, 0.01 parts by weight or more and 0.25 parts by weight or less, or 0.01 parts by weight or more and 0.135 parts by weight or less.

[0024] In the electrode layer, when the content of the sulfide solid electrolyte is 100 parts by weight, the content of the imidazoline-based dispersion material is, for example, 0.1 to 5 parts by weight, or 0.5 to 3 parts by weight, or 1 to 2 parts by weight. The proportion of the imidazoline-based dispersion material in the electrode layer is, for example, 0.005 to 0.5% by volume.

[0025] 2.Sulfide solid electrolyte The electrode layer in the present disclosure contains a sulfide solid electrolyte. The sulfide solid electrolyte constitutes an ion conduction path in the electrode layer. The sulfide solid electrolyte may be in the form of, for example, particles. In the present disclosure, the average particle size (D 50 ) is usually less than 1 μm. 50 ) may be 0.95 μm or less, or may be 0.9 μm or less. On the other hand, the average particle diameter (D 50 ) is, for example, 0.01 μm or more, and may be 0.1 μm or more. 50 ) refers to the particle size (median diameter) at the cumulative 50% of the cumulative particle size distribution, and is calculated, for example, from measurements using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM).

[0026] A sulfide solid electrolyte typically contains sulfur (S) as a main anion element. For example, the sulfide solid electrolyte contains Li, A (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. A preferably contains at least P. The sulfide solid electrolyte may also contain at least one halogen selected from Cl, Br, and I. The sulfide solid electrolyte may also contain O.

[0027] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. When the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include a Thio-LISICON-type crystalline phase, an LGPS-type crystalline phase, and an Argyrodite-type crystalline phase.

[0028] The composition of the sulfide solid electrolyte is not particularly limited, but examples include xLiS·(100-x)P2S5 (70≦x≦80), yLiI·zLiBr·(100-yz)(xLiS·(1-x)P2S5) (0.7≦x≦0.8, 0≦y≦30, 0≦z≦30).

[0029] The sulfide solid electrolyte may have a composition represented by the general formula: Li 4-x Ge 1-x P x S4 (0 < x < 1). In the above general formula, at least a part of Ge may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, at least a part of P may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, a part of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a part of S may be substituted with a halogen (at least one of F, Cl, Br, and I).

[0030] As other compositions of the sulfide solid electrolyte, for example, Li 7-x-2y PS 6-x-y X y , Li 8-x-2y SiS 6-x-y X y , Li 8-x-2y GeS 6-x-y X y may be mentioned. In these compositions, X is at least one of F, Cl, Br, and I, and x and y satisfy 0 ≤ x, 0 ≤ y.

[0031] The sulfide solid electrolyte preferably has a high Li ion conductivity. The Li ion conductivity of the sulfide solid electrolyte at 25°C is, for example, 1×10 -4 S / cm or more, and preferably 1×10 -3 S / cm or more. The sulfide solid electrolyte preferably has a high insulation property. The electronic conductivity of the sulfide solid electrolyte at 25°C is, for example, 10 -6 S / cm or less, may be 10 -8 S / cm or less, and may be 10 -10 S / cm or less.

[0032] The proportion of the sulfide solid electrolyte in the electrode layer is, for example, 15% by volume or more and 75% by volume or less, or may be 15% by volume or more and 60% by volume or less. If the proportion of the sulfide solid electrolyte is low, there is a possibility that ion conduction paths are not sufficiently formed. On the other hand, if the proportion of the sulfide solid electrolyte is high, there is a possibility that the volumetric energy density will be low.

[0033] The ratio of the electrode active material to the total of the electrode active material and the sulfide solid electrolyte is, for example, 40% by volume or more and 80% by volume or less, or may be 50% by volume or more and 80% by volume or less, or may be 60% by volume or more and 70% by volume or less. If the ratio of the electrode active material is low, the volumetric energy density may be low. On the other hand, if the ratio of the electrode active material is high, the ion conduction path may not be sufficiently formed.

[0034] The total proportion of the electrode active material and the sulfide solid electrolyte in the electrode layer is, for example, 75% by volume or more and less than 100% by volume, or may be 80% by volume or more and less than 100% by volume, or 90% by volume or more and less than 100% by volume.

[0035] 3. Binder The electrode layer in the present disclosure may contain a binder, such as rubber-based binders including butadiene rubber, hydrogenated butadiene rubber, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, and ethylene propylene rubber, and fluorine-based binders including polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0036] Here, when the distance Ra calculated from the Hansen solubility parameter (HSP) is taken into consideration, the distance Ra1 between the sulfide solid electrolyte and the imidazoline-based dispersion material is preferably smaller than the distance Ra2 between the sulfide solid electrolyte and the binder. This is because the dispersing effect of the imidazoline-based dispersion material on the sulfide solid electrolyte can be easily obtained. The difference between Ra2 and Ra1 is, for example, 0.5 MPa. 1 / 2 or more, and 1.0 MPa 1 / 2Furthermore, for example, when comparing a rubber-based binder with a fluorine-based binder, the rubber-based binder has a lower affinity for the sulfide solid electrolyte than the fluorine-based binder, and therefore the dispersing effect of the imidazoline-based dispersant for the sulfide solid electrolyte can be more easily obtained.

[0037] The proportion of the binder in the electrode layer is, for example, 1% by volume or more and 20% by volume or less, and may be 5% by volume or more and 20% by volume or less.

[0038] 4. Electrode active material The electrode layer in the present disclosure contains an electrode active material. The electrode active material may be a positive electrode active material or a negative electrode active material.

[0039] Here, when the distance Ra calculated from the Hansen solubility parameter (HSP) is taken into consideration, the distance Ra3 between the electrode active material and the imidazoline-based dispersant is preferably smaller than the distance Ra4 between the electrode active material and the binder. This is because the dispersing effect of the imidazoline-based dispersant for the electrode active material can be easily obtained. The difference between Ra4 and Ra3 is, for example, 0.5 MPa. 1 / 2 or more, and 1.0 MPa 1 / 2 Furthermore, for example, when a rubber-based binder and a fluorine-based binder are compared, the rubber-based binder has a lower affinity for the electrode active material than the fluorine-based binder, and therefore the dispersing effect of the imidazoline-based dispersant for the electrode active material can be more easily obtained.

[0040] Examples of electrode active materials include transition metal oxide-based active materials, Si-based active materials, and carbon-based active materials. Transition metal oxide-based active materials are typically active materials containing Li, M (where M is one or more transition metal elements), and O. The transition metal element is a metal element belonging to any of Groups 3 to 11 of the periodic table, such as Ni, Co, Mn, Fe, Ti, and V. A portion of M may be substituted with a metal element (e.g., Al) belonging to any of Groups 12 to 14 of the periodic table. The transition metal oxide-based active material preferably has a crystalline phase. Examples of the crystalline phase include a rock salt layered crystalline phase and a spinel crystalline phase.

[0041] An example of a transition metal oxide active material is LiMe 1-x Al x Examples of such active materials include active materials represented by LiNiO2, LiCoO2, LiMnO2, Li(Ni,Co,Mn)O2, and Li(Ni,Co,Al)O2. Examples of such active materials include active materials represented by LiMe2O4 (Me is at least one of Ni, Co, and Mn). Examples of such active materials include LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4 is one example.

[0042] Another example of a transition metal oxide active material is lithium titanate. Lithium titanate (LTO) is a compound containing Li, Ti, and O. The composition of lithium titanate is, for example, Li x Ti y O z (3.5≦x≦4.5, 4.5≦y≦5.5, 11≦z≦13). x may be 3.7 or more and 4.3 or less, or 3.9 or more and 4.1 or less. y may be 4.7 or more and 5.3 or less, or 4.9 or more and 5.1 or less. z may be 11.5 or more and 12.5 or less, or 11.7 or more and 12.3 or less. Lithium titanate is Li4Ti5O12 It is preferable that the composition be represented by the following formula:

[0043] The Si-based active material is an active material containing at least Si, and examples thereof include simple Si, Si alloys, and silicon oxide (SiO). The Si alloy preferably contains Si as the main component. The carbon-based active material is an active material containing carbon (C) as the main component, and examples thereof include graphite and hard carbon.

[0044] When the electrode active material is a positive electrode active material, the surface of the positive electrode active material is preferably coated with an ion-conductive oxide. This is because it is possible to prevent the positive electrode active material from reacting with the sulfide solid electrolyte and generating a high-resistance layer. An example of the ion-conductive oxide is LiNbO3. The thickness of the ion-conductive oxide is, for example, 1 nm or more and 30 nm or less.

[0045] The electrode active material may be in the form of particles, for example. 50 ) is, for example, 10 nm or more and 50 nm or less, and may be 100 nm or more and 20 μm or less.

[0046] The proportion of the electrode active material in the electrode layer is, for example, 20% by volume or more and 80% by volume or less, or may be 30% by volume or more and 70% by volume or less, or 40% by volume or more and 65% by volume or less. If the proportion of the electrode active material is low, the volumetric energy density may be low. On the other hand, if the proportion of the electrode active material is high, the ion conduction path may not be sufficiently formed.

[0047] 5. Electrode layer The electrode layer in the present disclosure contains the above-mentioned electrode active material, sulfide solid electrolyte, and imidazoline-based dispersion material. The electrode layer may be a positive electrode layer or a negative electrode layer.

[0048] The electrode layer in the present disclosure may contain a conductive material. Examples of the conductive material include carbon materials, metal particles, and conductive polymers. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). The proportion of the conductive material in the electrode layer is, for example, 0.1% by volume or more and 10% by volume or less, and may be 0.3% by volume or more and 10% by volume or less. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0049] The method for producing an electrode layer in the present disclosure is not particularly limited. In the present disclosure, a method for producing an electrode layer used in an all-solid-state battery includes: 50 A method for producing an electrode layer can also be provided, which includes the steps of: preparing a paste containing a sulfide solid electrolyte having a particle size of less than 1 μm, an imidazoline-based dispersant, and a dispersion medium; applying the paste to form a coating layer; and drying the coating layer to remove the dispersion medium. The paste may further contain a conductive material. The method for applying the paste is not particularly limited, but examples include a blade method. The drying temperature for the coating layer is, for example, 80°C or higher and 120°C or lower. The drying time for the coating layer is, for example, 10 minutes to 5 hours.

[0050] B. All-solid-state battery Fig. 1 is a schematic cross-sectional view illustrating an example of an all-solid-state battery according to the present disclosure. The all-solid-state battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, a solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. 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 "A. Electrode layer."

[0051] According to the present disclosure, by using the above-described electrode layer, an all-solid-state battery with low internal resistance is obtained.

[0052] 1. Positive and negative electrode layers The positive electrode layer and the negative electrode layer in the present disclosure are the same as those described above in "A. Electrode Layer," and therefore will not be described here. In the present disclosure, (i) the positive electrode layer may correspond to the above-described electrode layer, and the negative electrode layer may not correspond to the above-described electrode layer, (ii) the positive electrode layer may not correspond to the above-described electrode layer, and the negative electrode layer may correspond to the above-described electrode layer, or (iii) both the positive electrode layer and the negative electrode layer may correspond to the above-described electrode layer.

[0053] 2.Solid electrolyte layer The solid electrolyte layer in the present disclosure is disposed between the positive electrode layer and the negative electrode layer. The solid electrolyte layer contains at least a solid electrolyte and may further contain a binder. The solid electrolyte and binder are the same as those described above in "A. Electrode Layer," 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.

[0054] 3.All-solid-state battery In the present disclosure, the term "all-solid-state battery" refers to a battery including a solid electrolyte layer (a layer containing at least a solid electrolyte). The all-solid-state battery in the present disclosure includes a power generating element having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The power generating element typically includes a positive electrode current collector and a negative electrode current collector. The positive electrode current collector is disposed, for example, on the surface of the positive electrode layer opposite the solid electrolyte layer. Examples of materials for the positive electrode current collector include metals such as aluminum, SUS, and nickel. Examples of shapes for the positive electrode current collector include foil and mesh. On the other hand, the negative electrode current collector is disposed, for example, on the surface of the negative electrode layer opposite the solid electrolyte layer. Examples of materials for the negative electrode current collector include metals such as copper, SUS, and nickel. Examples of shapes for the negative electrode current collector include foil and mesh.

[0055] The all-solid-state battery according to the present disclosure may include an exterior body that houses the power generating element. Examples of the exterior body include a laminate-type exterior body and a case-type exterior body. The all-solid-state battery according to the present disclosure may also include a restraining jig that applies a restraining pressure in the thickness direction to the power generating element. A known jig can be used as the restraining jig. The restraining pressure may be, for example, 0.1 MPa or more and 50 MPa or less, or 1 MPa or more and 20 MPa or less. If the restraining pressure is low, good ion conduction paths and good electron conduction paths may not be formed. On the other hand, if the restraining pressure is high, the restraining jig may become large, which may reduce the volumetric energy density.

[0056] The type of all-solid-state battery in the present disclosure is not particularly limited, but is typically a lithium-ion secondary battery. The uses of the all-solid-state battery are not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. It is particularly preferred that the all-solid-state battery be used as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles. The all-solid-state battery in the present disclosure may also be used as a power source for mobile objects other than vehicles (e.g., railways, ships, and aircraft), or as a power source for electrical appliances such as information processing devices.

[0057] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0058] [Example 1] (Preparation of negative electrode paste) Li4Ti5O as the negative electrode active material 12The negative electrode active material (LTO, density: 3.5 g / cc) was used. The negative electrode active material (LTO) was used as 100 parts by weight, and the conductive material (VGCF, density: 2 g / cc) was used as 1.1 parts by weight, the sulfide solid electrolyte (10LiI 15LiBr 75(0.75LiS 0.25P2S5), the average particle size D 50 33.6 parts by weight of a binder (SBR binder), 1.42 parts by weight of a binder, and 0.46 parts by weight of a dispersant (imidazoline dispersant, 1-hydroxyethyl-2-alkenylimidazoline) were weighed out. A dispersant (tetralin) was added to the mixture, and the solid content was adjusted to 53% by weight. The mixture was then mixed using an ultrasonic homogenizer (UH-50 manufactured by SMT Corporation). This produced a negative electrode paste.

[0059] (Preparation of positive electrode paste) The positive electrode active material is LiNi with a surface treatment of LiNbO3. 0.8 Co 0.15 Al 0.05 The positive electrode active material (NCA, density: 4.65 g / cc) was used. The positive electrode active material (NCA) was used as 100 parts by weight, and the conductive material (VGCF, density: 2 g / cc) was used as 2.4 parts by weight, the conductive material (acetylene black) was used as 0.3 parts by weight, the sulfide solid electrolyte (10LiI 15LiBr 75(0.75LiS 0.25P2S5), the average particle size D 50 25.6 parts by weight of cellulose acylate (0.9 μm, density: 2 g / cc) and 0.42 parts by weight of binder (SBR binder) were weighed out. A dispersion medium (tetralin) was added to the mixture, and the solid content was adjusted to 65% by weight, followed by mixing using an ultrasonic homogenizer (UH-50 manufactured by SMT Corporation). This produced a positive electrode paste.

[0060] (Preparation of SE layer paste) A polypropylene container was filled with a dispersion medium (heptane), a binder (heptane solution containing 5% by mass of butadiene rubber binder), and a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5-based glass ceramic, average particle size D 50The mixture was mixed for 30 seconds using an ultrasonic homogenizer (UH-50 manufactured by SMT Corporation). The container was then shaken for 3 minutes using a shaker. This resulted in a paste for the solid electrolyte layer (a paste for the SE layer).

[0061] (Fabrication of all-solid-state batteries) First, the positive electrode paste was applied to a positive electrode current collector (aluminum foil, 15 μm thick) using a blade method with an applicator. After application, the paste was dried on a hot plate at 100°C for 30 minutes. This resulted in a positive electrode having a positive electrode current collector and a positive electrode layer. Next, the negative electrode paste was applied to a negative electrode current collector (nickel foil, 22 μm thick). After application, the paste was dried on a hot plate at 100°C for 30 minutes. This resulted in a negative electrode having a negative electrode current collector and a negative electrode layer. Here, the basis weight of the negative electrode layer was adjusted so that the specific charge capacity of the negative electrode was 1.1 times the specific charge capacity of the positive electrode, assuming a specific charge capacity of 200 mAh / g.

[0062] Next, the positive electrode was pressed. The surface of the pressed positive electrode layer was coated with a paste for the SE layer using a die coater and dried on a hot plate at 100°C for 30 minutes. Then, roll pressing was performed at a linear pressure of 2 ton / cm. This resulted in a positive electrode-side laminate including a positive electrode current collector, a positive electrode layer, and a solid electrolyte layer. Next, the negative electrode was pressed. The surface of the pressed negative electrode layer was coated with a paste for the SE layer using a die coater and dried on a hot plate at 100°C for 30 minutes. Then, roll pressing was performed at a linear pressure of 2 ton / cm. This resulted in a negative electrode-side laminate including a negative electrode current collector, a negative electrode layer, and a solid electrolyte layer.

[0063] The positive electrode laminate and the negative electrode laminate were each punched and arranged so that the solid electrolyte layers faced each other, with an unpressed solid electrolyte layer placed between them. They were then roll-pressed at 160°C with a linear pressure of 2 ton / cm to obtain a power generating element having a positive electrode, a solid electrolyte layer, and a negative electrode in this order. The obtained power generating element was laminated and sealed, and restrained at 5 MPa to obtain an all-solid-state battery.

[0064] [Example 2, Comparative Examples 1 and 2] The average particle size (D 50 ) was changed as shown in Table 1, and the same procedure as in Example 1 was repeated to prepare an all-solid-state battery.

[0065] [evaluation] (Ionic conductivity measurement) Evaluation cells were fabricated using the negative electrode pastes prepared in Examples 1 and 2 and Comparative Examples 1 and 2. Specifically, the negative electrode paste was applied to aluminum foil and then dried on a hot plate at 100°C for 30 minutes to prepare an electrode. Next, lithium foil was placed on both sides of the electrode to prepare an electrode structure. Next, the two electrode structures were stacked facing each other and roll-pressed at a linear pressure of 5 ton / cm. Next, the resulting laminate was punched out, the thickness of the negative electrode layer was measured, and the laminate was sealed and restrained at 5 MPa to obtain an evaluation cell (symmetric cell). A constant voltage of -0.1 V to +0.1 V was applied to the obtained evaluation cell, and the current value was measured, and the resistance was calculated according to Ohm's law. The ionic conductivity of the negative electrode layer was calculated from the obtained resistance and the thickness of the negative electrode layer. The results are shown in Table 1.

[0066] (resistance measurement) The charging resistance of the all-solid-state batteries fabricated in Examples 1 and 2 and Comparative Examples 1 and 2 was measured. Specifically, the all-solid-state batteries were charged at a constant current equivalent to 1 C until the cell voltage reached 2.7 V, after which constant voltage charging was performed, and the charging was terminated when the charging current reached 0.01 C. Subsequently, the all-solid-state batteries were discharged at a constant current equivalent to 1 C until the cell voltage reached 1.5 V. This discharge capacity was repeated twice, and the discharge capacity of the second cycle was measured. Next, the all-solid-state batteries were charged at a constant current equivalent to 1 C to half the discharge capacity of the second cycle, and the SOC of the all-solid-state batteries was adjusted to 50%. Next, the all-solid-state batteries with an SOC of 50% were charged at a constant current equivalent to 41 C, and the voltage before charging and the voltage 5 seconds after the start of charging were measured. The difference between these voltages was divided by the current equivalent to 41 C to determine the charging resistance (DC resistance). The results are shown in Table 1. Note that the charging resistance in Table 1 is a relative value when Comparative Example 1 is set to 1.

[0067] [Table 1]

[0068] As shown in Table 1, in Examples 1 and 2 and Comparative Examples 1 and 2, the average particle size (D 50 The ionic conductivity of the negative electrode layer was similar regardless of the charge / discharge ratio. This suggests that the dispersibility of the sulfide solid electrolyte was similar. Note that uncharged LTO generally does not have ionic conductivity, so the ionic conductivity of the negative electrode layer depends on the ionic conductivity and dispersibility of the sulfide solid electrolyte. On the other hand, it was confirmed that the charging resistance was significantly lower in Examples 1 and 2 than in Comparative Examples 1 and 2. This is presumably because a good bonding interface was formed at the interface between the negative electrode active material and the sulfide solid electrolyte, significantly reducing the interfacial resistance.

[0069] [Example 3] A negative electrode paste was obtained in the same manner as in Example 1, except that no dispersant was used. A positive electrode paste was also obtained in the same manner as in Example 1, except that a dispersant (imidazoline-based dispersant, 1-hydroxyethyl-2-alkenylimidazoline) was further added so that the amount was 0.01 part by weight per 100 parts by weight of the positive electrode active material (NCA). The proportion of the dispersant in the solid content of the positive electrode paste was 0.0077% by volume. A solid-state battery was fabricated in the same manner as in Example 1, except that these negative electrode paste and positive electrode paste were used.

[0070] [Examples 4 to 6] All-solid-state batteries were fabricated in the same manner as in Example 3, except that the addition ratio of the dispersant in the negative electrode paste was changed as shown in Table 2.

[0071] Comparative Example 3 An all-solid-state battery was produced in the same manner as in Example 3, except that no dispersant was used in the positive electrode paste.

[0072] [Example 7] An all-solid-state battery was produced in the same manner as in Example 5, except that the binder in the positive electrode paste was changed from an SBR-based binder to a PVDF-based binder.

[0073] Comparative Example 4 An all-solid-state battery was produced in the same manner as in Example 7, except that no dispersant was used in the positive electrode paste.

[0074] [evaluation] The discharge resistance of the all-solid-state batteries fabricated in Examples 3 to 7 and Comparative Examples 3 and 4 was measured. Specifically, the SOC of the all-solid-state batteries was adjusted to 50% in the same manner as above. Next, the all-solid-state batteries with an SOC of 50% were subjected to constant current discharge at a current equivalent to 60 C, and the voltage before discharge and the voltage 2 seconds after the start of discharge were measured. The difference between these voltages was divided by the current equivalent to 60 C to determine the discharge resistance (DC resistance). The results are shown in Table 2 and FIG. 2. Note that the discharge resistance in Table 2 and FIG. 2 is a relative value when Comparative Example 3 is set to 1.

[0075] [Table 2]

[0076] As shown in Table 2 and FIG. 2, it was confirmed that Examples 3 to 6 had lower discharge resistance than Comparative Example 3. Similarly, it was confirmed that Example 7 had lower discharge resistance than Comparative Example 4. This is presumably because a good bonding interface was formed at the interface between the positive electrode active material and the sulfide solid electrolyte, significantly reducing the interfacial resistance. In particular, when Example 5 and Example 7 were compared, it was confirmed that the use of a rubber-based binder significantly reduced the discharge resistance.

[0077] [Example 8] In the same manner as in Example 1, a negative electrode paste was prepared.

[0078] [Example 9] A negative electrode paste was prepared in the same manner as in Example 8, except that a PVDF-based binder was used instead of the SBR-based binder.

[0079] [evaluation] The permeability of mesh filters was evaluated using the pastes prepared in Examples 8 and 9. Specifically, SUS mesh filters with a mesh size of 40 μm were used. As a result, Example 8 had higher filter permeability than Example 9. The reason for this was considered from the perspective of the distance Ra calculated from the Hansen solubility parameter (HSP). For example, the distance Ra of the imidazoline-based dispersion material and sulfide solid electrolyte (SE) was 10.7 MPa. 1 / 2 Similarly, the distance Ra between each material was calculated as shown in Table 3.

[0080] [Table 3]

[0081] As shown in Table 3, the distance Ra between the imidazoline-based dispersion and the sulfide solid electrolyte (SE) was smaller than that between the SBR-based binder and the sulfide solid electrolyte (SE), but larger than that between the PVDF-based binder and the sulfide solid electrolyte (SE). The smaller the distance Ra, the higher the affinity between each material. This suggests that the PVDF-based binder has a higher affinity with the sulfide solid electrolyte (SE) than the imidazoline-based dispersion, making it more susceptible to aggregation. On the other hand, the SBR-based binder has a lower affinity with the sulfide solid electrolyte (SE) than the imidazoline-based dispersion. Therefore, it is speculated that the imidazoline-based dispersion significantly enhanced the dispersion effect of the sulfide solid electrolyte (SE). A similar relationship was also observed for the anode active material (LTO). The distance Ra between the imidazoline-based dispersion and the active material was also calculated. The results are shown in Table 4.

[0082] [Table 4]

[0083] As shown in Table 4, Si has a higher affinity with the imidazoline-based dispersion material than LTO. Therefore, it was suggested that the same effect as in Example 1 could be obtained. A similar tendency was observed in NCM (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2). On the other hand, C (graphene) had a lower affinity with imidazoline-based dispersion materials than LTO. However, imidazoline-based dispersion materials usually have hydrophilic and hydrophobic parts, and when Ra was calculated for each, the distance between the hydrophilic part of the imidazoline-based dispersion material and C (graphene) was 12.5 MPa. 1 / 2 This suggests that the same effect as in Example 1 can be obtained in the case of C (graphene). [Explanation of symbols]

[0084] 1...Positive electrode layer 2...Anode layer 3...Solid electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...All-solid-state battery

Claims

1. A negative electrode layer for use in an all-solid-state battery, the negative electrode layer contains a negative electrode active material and a sulfide solid electrolyte, The sulfide solid electrolyte has an average particle size (D ５０ ) is less than 1 μm, The negative electrode layer contains an imidazoline-based dispersant.

2. The negative electrode layer according to claim 1 , further comprising a rubber-based binder.

3. 3. The negative electrode layer according to claim 1, wherein the negative electrode active material comprises at least one of a transition metal oxide-based active material, a Si-based active material, and a carbon-based active material.

4. 4. The negative electrode layer according to claim 1, wherein a content of the imidazoline-based dispersion material in the negative electrode layer is 0.005 parts by weight or more and 0.5 parts by weight or less, relative to 100 parts by weight of the negative electrode active material.

5. 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 the negative electrode layer is the negative electrode layer according to any one of claims 1 to 4.

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