Cathode mixture and battery

Abstract

To provide cathode mixture that can restrain an increase in resistance that accompanies an increase in the potential of a cathode active material layer.SOLUTION: A cathode mixture includes a cathode active material, a first solid electrolyte, a first conductive material that is a particulate carbon material, and a second conductive material that is a fibrous carbon material. The D / G ratio of the first conductive material is 1.0 or less, the D / G ratio of the second conductive material is 0.5 or less, and the proportion of the first conductive material relative to the total of the first and second conductive materials is 5 mass% or more and 30 mass% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a positive electrode composite material and a battery.

Background Art

[0002] A solid battery has an electrolyte layer containing a solid electrolyte between a positive electrode active material layer and a negative electrode active material layer. The positive electrode active material layer contains at least a positive electrode active material, and may further contain a solid electrolyte for improving ion conductivity and a conductive material for improving electron conductivity.

[0003] For example, Patent Document 1 discloses a positive electrode material including a mixture of a positive electrode active material, a solid electrolyte, and a conductive material, the conductive material including a first conductive material having an average major axis diameter of 1 μm or more and a second conductive material having an average particle diameter of more than 23 nm and 100 nm or less, and the ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte being 50% or more and 90% or less. Patent Document 2 discloses a positive electrode for an all-solid-state battery having a molded body of a positive electrode composite agent containing a positive electrode active material, a sulfide-based solid electrolyte, and a conductive auxiliary agent, the conductive auxiliary agent containing fibrous carbon and granular carbon, and the thickness of the molded body of the positive electrode composite agent being 250 μm or more.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since a solid electrolyte is less likely to be oxidatively decomposed than a general electrolyte solution, during charging, the positive electrode active material layer containing the solid electrolyte can be set to a high potential, and as a result, a battery with a high voltage can be obtained. On the other hand, when the positive electrode active material layer is set to a high potential, an increase in resistance is likely to occur.

[0006] The present disclosure has been made in view of the above circumstances, and a main object thereof is to provide a positive electrode composite material capable of suppressing an increase in resistance accompanying an increase in the potential of a positive electrode active material layer.

Means for Solving the Problems

[0007] [1] A positive electrode composite material including a positive electrode active material, a first solid electrolyte, a first conductive material that is a particulate carbon material, and a second conductive material that is a fibrous carbon material, wherein the D / G ratio of the first conductive material is 1.0 or less, the D / G ratio of the second conductive material is 0.5 or less, and the ratio of the first conductive material to the total of the first conductive material and the second conductive material is 5% by mass or more and 30% by mass or less.

[0008] [2] The positive electrode composite material according to [1], wherein the ratio of the first conductive material to the total of the first conductive material and the second conductive material is 8% by mass or more and 20% by mass or less.

[0009] [3] the first solid electrolyte is a sulfide solid electrolyte, and the positive electrode active material is coated with a second solid electrolyte that is an oxide solid electrolyte. The positive electrode composite material according to [1] or [2].

[0010] [4] A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer contains the positive electrode composite material according to any one of [1] to [3].

[0011] [5] The above battery includes a control device that controls the potential of the above positive electrode active material layer to 4.0 V (vs. Li / Li + ) or higher during charging, and is the battery according to [4].

Advantages of the Invention

[0012] The positive electrode composite material in the present disclosure has the effect of suppressing an increase in resistance accompanying the increase in the potential of the positive electrode active material layer.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0014] Hereinafter, the positive electrode composite material and the battery in the present disclosure will be described in detail with reference to the drawings. Each of the drawings shown below is schematically shown, and the size and shape of each part are appropriately exaggerated for easy understanding.

[0015] A. Positive Electrode Composite Material FIG. 1 is a schematic cross-sectional view showing an enlarged part of the positive electrode composite material in the present disclosure. As shown in FIG. 1, the positive electrode composite material 10 includes a positive electrode active material 1, a first solid electrolyte 2, a first conductive material 3a which is a particulate carbon material, and a second conductive material 3b which is a fibrous carbon material. The D / G ratios of the first conductive material 3a and the second conductive material 3b are within a predetermined range. Also, the mass ratio of the first conductive material 3a to the total of the first conductive material 3a and the second conductive material 3b is within a predetermined range.

[0016] According to the present disclosure, by combining and using a predetermined first conductive material and a second conductive material at a predetermined ratio, a positive electrode composite material capable of suppressing an increase in resistance associated with the high potential of the positive electrode active material layer can be obtained. As described above, since the solid electrolyte is less likely to be oxidatively decomposed than a general electrolytic solution, during charging, the positive electrode active material layer containing the solid electrolyte can be set to a high potential, and as a result, a battery with a large voltage can be obtained. On the other hand, when the positive electrode active material layer is set to a high potential, an increase in resistance is likely to occur. In contrast, in the present disclosure, by combining and using a first conductive material which is a particulate carbon material and has a low D / G ratio, and a second conductive material which is a fibrous carbon material and has a low D / G ratio at a predetermined ratio, an increase in resistance associated with the high potential of the positive electrode active material layer can be suppressed. Since a material with a low D / G ratio has few defects, side reactions are less likely to occur even when the positive electrode active material layer is set to a high potential.

[0017] 1. Conductive Material The positive electrode composite material in the present disclosure includes, as a conductive material, a first conductive material which is a particulate carbon material and a second conductive material which is a fibrous carbon material.

[0018] The first conductive material is a particulate carbon material. Examples of the particulate carbon material include acetylene black (AB) and ketjen black (KB). The particulate carbon material may be primary particles or secondary particles in which the primary particles are aggregated. The average particle size of the first conductive material is, for example, 10 nm or more and 5 μm or less, and may be 60 nm or more and 200 nm or less. The average particle size in the present disclosure refers to the volume cumulative particle size D measured by a laser diffraction / scattering particle size distribution measuring device. 50 means.

[0019] In Raman spectroscopic measurement, with respect to the intensity of the G band (peak near 1577 cm -1 ), the D band (1346 cm -1The ratio of the intensity of the peak (near the peak) is referred to as the D / G ratio. The G band is a peak derived from the in-plane vibration of the six-membered ring of carbon, and the D band is a peak derived from defects. Therefore, a small D / G ratio means few defects. The D / G ratio of the first conductive material is usually 1.0 or less, and may be 0.8 or less. As the conditions for Raman spectroscopy measurement, for example, a condition of using a Raman spectrophotometer (DXR3xi imaging microscope Raman, manufactured by Yamato Scientific Co., Ltd.), laser energy: 1.5 mW, exposure time: 50 Hz, and number of scan times: 50 times can be mentioned.

[0020] In the positive electrode composite material, the first conductive material may be uniformly arranged or non-uniformly arranged. Among them, it is preferable that the first conductive material is arranged so as to coat the positive electrode active material directly or via another layer (for example, the second solid electrolyte described later). Let the mass of the first conductive material in the positive electrode composite material be M T and the mass of the first conductive material covering the first conductive material be M1. The ratio of M1 to M T is, for example, 50% by mass or more, may be 70% by mass or more, and may be 90% by mass or more.

[0021] The second conductive material is a fibrous carbon material. Examples of the fibrous carbon material include carbon fiber (CF), carbon nanotube (CNT), and carbon nanofiber (CNF). The carbon nanotube (CNT) may be a single-walled carbon nanotube (SWNT) or a multi-walled carbon nanotube (MWNT). The average diameter of the second conductive material is, for example, 1 nm or more and 50 nm or less. The average length of the second conductive material is, for example, 500 nm or more and 50 μm or less.

[0022] The D / G ratio of the second conductive material is usually 0.5 or less, and may be 0.4 or less. It is preferable that the D / G ratio of the second conductive material is smaller than the D / G ratio of the first conductive material. Also, the second conductive material may be uniformly or non-uniformly arranged in the positive electrode composite material. Among them, the first conductive material is arranged to coat the positive electrode active material directly or via another layer (for example, the second solid electrolyte described later). Furthermore, it is preferable that the second conductive material is uniformly arranged in the positive electrode composite material.

[0023] When the electronic conductivity (25°C) of the first conductive material is C1 and the electronic conductivity (25°C) of the second conductive material is C2, the ratio of C1 to C2 is, for example, 1.0 or less, and may be 0.8 or less, or may be 0.6 or less. Also, when the powder resistance of the first conductive material is r1 and the powder resistance of the second conductive material is r2, the ratio of r1 to r2 is, for example, 1.0 or more, and may be 1.3 or more, or may be 1.6 or more.

[0024] The ratio of the first conductive material to the total of the first and second conductive materials is, for example, 5% by mass or more and 30% by mass or less, and may be 8% by mass or more and 20% by mass or less. Also, the ratio of the first conductive material in the positive electrode composite material (solid content) is, for example, 0.1% by mass or more and 5% by mass or less, and may be 0.5% by mass or more and 3% by mass or less. The ratio of the second conductive material in the positive electrode composite material (solid content) is, for example, 0.1% by mass or more and 5% by mass or less, and may be 0.5% by mass or more and 3% by mass or less.

[0025] The total ratio of the first and second conductive materials in the positive electrode composite material (solid content) is not particularly limited, but is, for example, 10% by mass or less, and may be 8% by mass or less, may be 6% by mass or less, or may be 4% by mass or less. On the other hand, the total ratio of the first and second conductive materials is, for example, 1% by mass or more.

[0026] 2. The first solid electrolyte Examples of the first solid electrolyte in the present disclosure include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, and complex hydrides. Among these, sulfide solid electrolytes are particularly preferred because of their high ionic conductivity. Sulfide solid electrolytes usually contain sulfur (S) as the main component of the anion element. Oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes usually contain oxygen (O), nitrogen (N), and halogen (X) as the main components of the anion element, respectively.

[0027] The sulfide solid electrolyte preferably contains, for example, Li element, X element (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S element. The sulfide solid electrolyte may further contain at least one of O element and halogen element. Note that the sulfide solid electrolyte preferably contains S element as the main component of the anion element.

[0028] Examples of the sulfide solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers. Z is any one of Ge, Zn, Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, In).

[0029] The first solid electrolyte may be glassy or may have a crystalline phase. Examples of the crystalline phase include a Thio-LISICON type crystalline phase, an argyrodite type crystalline phase, and an LGPS type crystalline phase. The shape of the first solid electrolyte is usually particulate. The average particle size of the first solid electrolyte is, for example, 0.0 more than 1 μm. On the other hand, the average particle size of the first solid electrolyte is, for example, 10 μm or less, and may be 5 μm or less. Further, the ionic conductivity of the first solid electrolyte at 25 ° C is, for example, 1 × 10 -4 S / cm or more, and may be 1 × 10 -3 S / cm or more.

[0030] The ratio of the first solid electrolyte in the positive electrode composite material (solid content) is not particularly limited, but is, for example, 30% by mass or more and 70% by mass or less, and may be 40% by mass or more and 60% by mass or less.

[0031] 3. Positive electrode active material Examples of the positive electrode active material in the present disclosure include oxide active materials. Examples of the oxide active material include rock salt layer type active materials such as LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, spinel type active materials such as LiMn2O4, LiNi 0.5 Mn 1.5 O4, Li4Ti5O 12 and olivine type active materials such as LiFePO4.

[0032] As shown in FIG. 2, it is preferable that the positive electrode active material 1 is coated with the second solid electrolyte 4. This is because it is possible to suppress the reaction between the positive electrode active material (particularly the oxide active material) and the first solid electrolyte (particularly the sulfide solid electrolyte) and the formation of a high resistance layer. Examples of the second solid electrolyte include oxide solid electrolytes. Examples of the oxide solid electrolyte include LiNbO3, LiBPO4, Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12, Li2Ti2O5, Li2ZrO3, Li2MoO4, Li2WO4, etc. are mentioned. The coating rate (area ratio) of the oxide solid electrolyte is, for example, 70% or more, and may be 80% or more, or may be 90% or more. The thickness of the oxide solid electrolyte is, for example, 0.1 nm or more and 100 nm or less, and may be 1 nm or more and 20 nm or less.

[0033] The ratio of the positive electrode active material in the positive electrode composite material (solid content) is not particularly limited, but is, for example, 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, or 80% by mass or more.

[0034] 4. Positive electrode composite material The positive electrode composite material in the present disclosure may contain a binder. Examples of the binder include rubber-based binders such as butylene rubber (BR) and styrene-butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVDF). The ratio of the binder in the positive electrode composite material (solid content) is not particularly limited, but is, for example, 5% by mass or less, and may be 3% by mass or less.

[0035] The positive electrode composite material in the present disclosure may be a powder containing each of the above-described materials, or may be a slurry in which each of the above-described materials is dispersed in a dispersion medium. The type of the dispersion medium is not particularly limited, and known materials can be used. Further, the positive electrode composite material in the present disclosure is preferably used in a battery.

[0036] B. Battery Figure 3 is a schematic cross-sectional view illustrating the battery in the present disclosure. The battery 20 shown in Figure 3 includes a positive electrode active material layer 11, a negative electrode active material layer 12, an electrolyte layer 13 disposed between the positive electrode active material layer 11 and the negative electrode active material layer 12, a positive electrode current collector 14 that collects current from the positive electrode active material layer 11, and a negative electrode current collector 15 that collects current from the negative electrode active material layer 12. Further, the positive electrode active material layer 11 contains the positive electrode composite material described in the above "A. Positive electrode composite material".

[0037] According to the present disclosure, since the positive electrode active material layer contains the positive electrode composite material described above, a battery is obtained that suppresses an increase in resistance associated with a high potential of the positive electrode active material layer.

[0038] 1. Positive Electrode The positive electrode in the present disclosure has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains the positive electrode composite material described above. The thickness of the positive electrode active material layer is, for example, 1 μm or more and 500 μm or less. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, and carbon. Examples of the shape of the positive electrode current collector include a foil shape. The thickness of the positive electrode current collector is, for example, 1 μm or more and 500 μm or less.

[0039] 2. Negative Electrode The negative electrode in the present disclosure has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains at least a negative electrode active material, and may further contain at least one of a conductive material, an electrolyte, and a binder. The negative electrode active material layer preferably contains a solid electrolyte as the electrolyte. Examples of the negative electrode active material include Li-based active materials such as Li and Li alloys, Si-based active materials such as Si and Si alloys, oxide active materials such as Li4Ti5O 12 and carbon-based active materials such as graphite. Also, the conductive material, solid electrolyte, and binder are the same as those described in the above "A. Positive Electrode Composite Material". The thickness of the negative electrode active material layer is, for example, 1 μm or more and 500 μm or less.

[0040] Examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon. Examples of the shape of the negative electrode current collector include a foil shape. The thickness of the negative electrode current collector is, for example, 1 μm or more and 500 μm or less.

[0041] 3. Electrolyte Layer The electrolyte layer in the present disclosure contains at least an electrolyte. The above electrolyte is preferably a solid electrolyte. A battery in which the electrolyte layer contains a solid electrolyte is called a solid battery. The solid battery may be an all-solid battery or a semi-solid battery. Regarding the solid electrolyte, it is the same as the content described in the above "A. Positive electrode composite material". Further, the electrolyte layer may be a layer containing an electrolytic solution. Further, the electrolyte layer may contain a binder. Regarding the binder, it is the same as the content described in the above "A. Positive electrode composite material". Further, the thickness of the electrolyte layer is, for example, 1 μm or more and 500 μm or less.

[0042] 4. Battery The battery in the present disclosure preferably includes a control device that controls the potential of the positive electrode active material layer to 4.0 V (vs. Li / Li + ) or more during charging. Even when the positive electrode active material layer is at a high potential, by using the positive electrode active material layer containing the above-described positive electrode composite material, an increase in resistance can be suppressed. During charging, the potential of the positive electrode active material layer may be controlled to 4.5 V (vs. Li / Li + ) or more. Although the potential of the positive electrode active material layer increases during charging, it is preferable that the control device is configured not to stop charging until the potential of the positive electrode active material layer reaches a predetermined value or more.

[0043] The use of the battery in the present disclosure is not particularly limited, and examples include power sources for vehicles such as hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs), electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, it is preferably used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or an electric vehicle (BEV). Further, the battery may be used as a power source for a moving body other than a vehicle (for example, a railway, a ship, an aircraft), or may be used as a power source for an electric product such as an information processing device.

[0044] In addition, in the present disclosure, there is provided a battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer includes a positive electrode active material, a first solid electrolyte, a first conductive material which is a particulate carbon material, and a second conductive material which is a fibrous carbon material, the ratio of the first conductive material to the total of the first conductive material and the second conductive material is 5% by mass or more and 30% by mass or less, and the battery includes a control device configured to control the potential of the positive electrode active material layer to 4.0 V (vs. Li / Li + ) or more during charging.

[0045] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are illustrative, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Examples

[0046] [Example 1] (Fabrication of positive electrode) A positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) and a second solid electrolyte (LiBPO4) were put into a kneader and kneaded under the conditions of 2000 rpm for 2 minutes to obtain a coated active material. Then, the first conductive material (particulate carbon material, D / G ratio: 0.9, average particle diameter D 50 : 75 nm) was put into the kneader so that the content thereof became 0.7% by mass, and kneaded under the conditions of 2000 rpm for 2 minutes to obtain a coated active material containing the first conductive material. Next, the coated active material containing the first conductive material and a sulfide solid electrolyte (Li2S-P2S5-based glass ceramics containing LiI, average particle diameter D 50: 0.8 μm), the positive electrode active material and the sulfide solid electrolyte were weighed so that the volume ratio was 7:3, and these were put into heptane together with 2.3% by mass of a second conductive material (fibrous carbon material, D / G ratio: 0.26, fiber diameter: 30 nm, fiber length: 600 nm) and 0.7% by mass of a binder (butadiene rubber). Next, the positive electrode composite material was produced by mixing the above materials. After the produced positive electrode composite material was sufficiently dispersed with an ultrasonic homogenizer (UH-50 manufactured by SMT), it was coated on a positive electrode current collector (aluminum foil) and dried at 100 °C for 30 minutes. Then, by punching out into a size of 1 cm 2 a positive electrode having a positive electrode current collector and a positive electrode active material layer was obtained.

[0047] (Fabrication of negative electrode) In a kneading container of a film mixing device (30-L type manufactured by Primix), a sulfide solid electrolyte (Li2S-P2S5-based glass ceramics containing LiI, average particle diameter D 50 : 0.8 μm), 1% by mass of a conductive material (vapor-grown carbon fiber), 2% by mass of a binder (butadiene rubber), and heptane were put in, and stirred under the conditions of 20,000 rpm for 30 minutes. Next, a negative electrode active material (Li4Ti5O 12 particles, average particle diameter D 50 = 1 μm) and the sulfide solid electrolyte were put into the kneading container so that the volume ratio was 6:4, and the negative electrode composite material was produced by stirring with a film mixing device under the conditions of 15,000 rpm for 60 minutes. The produced negative electrode composite material was coated on a negative electrode current collector (copper foil) and dried at 100 °C for 30 minutes. Then, by punching out into a size of 1 cm 2 a negative electrode having a negative electrode current collector and a negative electrode active material layer was obtained.

[0048] (Fabrication of solid electrolyte layer) 64.8 mg of a sulfide solid electrolyte (Li2S-P2S5-based glass ceramics containing LiI, average particle diameter D 2 : 2.5 μm) was put into a cylindrical ceramic having an inner diameter cross-sectional area of 1 cm 50 After smoothing, it was pressed at 1 ton / cm 2 to obtain a solid electrolyte layer.

[0049] (Fabrication of Battery) The positive electrode was placed on one surface of the solid electrolyte layer, and the negative electrode was placed on the other surface of the solid electrolyte layer, and pressed at 6 ton / cm 2 for 1 minute. Next, stainless steel rods were placed on the positive electrode side and the negative electrode side, respectively, and restrained at 1 ton to obtain a battery.

[0050] [Examples 2 to 6] A battery was obtained in the same manner as in Example 1, except that the contents and types of the first conductive material and the second conductive material were changed to those described in Table 1.

[0051] [Comparative Example 1] A battery was obtained in the same manner as in Example 1, except that the first conductive material was not used and the content of the second conductive material was changed to 3% by mass.

[0052] [Evaluation] For the batteries obtained in Examples 1 to 6 and Comparative Example 1, the capacity was confirmed by constant current-constant voltage charging and discharging at a rate of 1 / 3C, and then adjusted to 40% SOC at a rate of 1 / 3C. Thereafter, CC discharge was performed under the conditions of a current value of 0.3C and 0.1 seconds, and the voltage drop amount (ΔV) and the current (I) during discharge were measured. From the measurement results, the initial battery resistance R (=ΔV / I) was obtained according to Ohm's law. Next, as a durability test, the positive electrode potential was set to 4.5V, and trickle charging was performed at 60°C for 2 weeks. Thereafter, in the same manner as above, the battery resistance R' after durability was obtained, and the resistance increase rate was obtained. The results are shown in Table 1.

[0053] In addition, for the batteries obtained in Examples 1 to 6 and Comparative Example 1, capacity confirmation was performed by constant current-constant voltage charging and discharging at a rate of 1 / 3C, and then adjusted to 50% SOC at a rate of 1 / 3C. The AC impedance was measured at 10 mV, 0.1 Hz to 106 Hz, an arc was fitted to the Cole-Cole plot, and the distance between two points of the intersection of the fitted arc and the real axis was determined as the reaction resistance (initial resistance). The results are shown in Table 1. In Table 1, the initial resistances of Examples 1 to 6 are relative values when the initial resistance of Comparative Example 1 is set to 1.00.

[0054]

Table 1

[0055] As shown in Table 1, it was confirmed that in Examples 1 to 6, the resistance increase rate before and after durability was lower than that in Comparative Example 1. That is, by setting the ratio of the first conductive material to the total of the first conductive material and the second conductive material (a / (a + b)) within a specific range, a positive electrode composite material capable of suppressing the resistance increase accompanying the high potential of the positive electrode active material layer was obtained. Further, as in Examples 1 and 4, by setting (a / (a + b)) relatively high (for example, to 20% to 30%), it was confirmed that the resistance increase rate before and after durability could be significantly reduced. On the other hand, as in Examples 2, 3, 5, and 6, by setting the ratio of the first conductive material to the total of the first conductive material and the second conductive material (a / (a + b)) relatively low (for example, to 8% to 20%), it was confirmed that a reduction in the initial resistance could also be achieved.

Explanation of symbols

[0056] 1... Positive electrode active material 2... First solid electrolyte 3... Conductive material 4... Second solid electrolyte 11... Positive electrode active material layer 12... Negative electrode active material layer 13... Electrolyte layer 14... Positive electrode current collector 15... Negative electrode current collector 20... Battery

Claims

1. A positive electrode composite material comprising a positive electrode active material, a first solid electrolyte, a first conductive material which is a particulate carbon material, and a second conductive material which is a fibrous carbon material, wherein the D / G ratio of the first conductive material is 1.0 or less, the D / G ratio of the second conductive material is 0.5 or less, and the ratio of the first conductive material to the total of the first conductive material and the second conductive material is 5% by mass or more and 30% by mass or less. The positive electrode composite material.

2. The positive electrode composite material according to claim 1, wherein the ratio of the first conductive material to the total of the first conductive material and the second conductive material is 8% by mass or more and 20% by mass or less.

3. The first solid electrolyte is a sulfide solid electrolyte, and the positive electrode active material is coated with a second solid electrolyte which is an oxide solid electrolyte. The positive electrode composite material according to claim 1.

4. A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer contains the positive electrode composite material according to any one of claims 1 to 3. The battery.

5. The battery according to claim 4, comprising a control device that controls the potential of the positive electrode active material layer to be 4.0 V (vs. Li / Li ＋ ) or more during charging.

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