JP6973999B2 - Sulfide solid state battery - Google Patents

Description

The present invention relates to a sulfide solid state battery.

Regarding a sulfide solid-state battery, a technique of adopting an electrode active material having a coating layer formed on the surface is known for the purpose of improving the performance of the battery. For example, Patent Document 1 describes a sulfide solid having a positive electrode mixture containing a positive _{electrode active material (LiNi 0.5} Mn _1.5 O _{4) having a coating material on the surface, a conductive material, and a sulfide solid electrolyte.} Batteries are disclosed.

Japanese Unexamined Patent Publication No. 2016-081822

However, in such a sulfide solid-state battery, there is a problem that the sulfide solid electrolyte is decomposed on the surface of the conductive material having a high potential, and the capacity retention rate is lowered. FIG. 5 is a schematic partial cross-sectional view (FIG. 5 (a)) and an enlarged view (FIG. 5 (b)) of a conventional positive electrode mixture for explaining the estimation mechanism of decomposition of the sulfide solid electrolyte.
As shown in FIG. 5A, the conventional positive electrode mixture 200 for a sulfide solid-state battery contains a positive electrode active material 11 as a base material thereof. Examples of the positive electrode active material 11 include a high-potential positive electrode active material such as _{LiNi 0.5} Mn _1.5 O _4. The surface of the positive electrode active material 11 is covered with an oxide layer 12. The oxide layer 12 mainly serves as a protective layer for the positive electrode active material 11, and examples of the material thereof include Li ₃ PO ₄ . A material having a low redox potential is usually used for the oxide layer 12.
In addition, the carbon conductive material 13 and the sulfide solid electrolyte 14 are present on the surface of the positive electrode mixture 200. These materials are usually present on the surface of the oxide layer 12, but are also present on the surface where the coating of the oxide layer 12 is interrupted and the positive electrode active material 11 is exposed.
As shown by the dashed line arrow in FIG. 5A, in the discharge reaction, the positive electrode mixture 200 mainly ^{takes in electrons (e −} ) from the surface of the carbon conductive material 13 and mainly the surface of the sulfide solid electrolyte 14. Lithium ion (Li ⁺ ) is taken in from.

FIG. 5B is an enlarged cross-sectional schematic view of the frame 15 of the alternate long and short dash line in FIG. 5A, showing the vicinity of the interface between the positive electrode active material 11 and the carbon conductive material 13.
For example, when LiNi _0.5 Mn _1.5 O ₄ (oxidation-reduction potential: 4.8 V (vs. Li ^/ Li +)) is used as the positive electrode active material 11, it becomes unstable at a high potential and the oxygen component. Is easy to release. The oxygen component here means an oxygen atom, an oxygen molecule, ozone, an oxygen radical, or the like.
On the other hand, the sulfide solid electrolyte 14 is decomposed by contact with a high-potential substance such as the carbon conductive material 13, and releases a sulfur component (S in FIG. 5B). The sulfur component here means a sulfur atom, a sulfur molecule (including each allotrope), a sulfur radical, and the like. As shown by the arrow of the alternate long and short dash line in FIG. 5B, it is considered that this sulfur component passes through the oxide layer 12 and the carbon conductive material 13 and finally diffuses into the positive electrode active material 11.
The sulfur component diffused in the positive electrode active material 11 becomes a stable sulfuric acid component (SO ₄ etc.) by combining with the oxygen component, or reacts with the positive electrode active material 11 itself to form a highly resistant substance such as MnS. Or generate. It is considered that the generation of these sulfuric acid components and high resistance substances in the positive electrode active material 11 changes the composition of the positive electrode active material 11 and results in a decrease in the capacity retention rate of the entire battery.

The present invention has been accomplished in view of the above circumstances regarding the positive electrode mixture of a sulfide solid-state battery, and an object of the present invention is to provide a sulfide solid-state battery having a higher capacity retention rate than the conventional one.

The sulfide solid battery of the present invention is a sulfide solid battery including a positive electrode layer containing a positive electrode mixture, a negative electrode layer, and a sulfide solid electrolyte layer existing between the positive electrode layer and the negative electrode layer. The positive electrode mixture contains a high-potential positive electrode active material whose surface is coated with an oxide, a carbon conductive material, and a sulfide solid electrolyte, and the carbon conductive material has Nb ₂ O ₅ or Al on its surface. It is characterized by comprising a coat layer containing ₂ O _3.

According to the present invention, _{by providing a coat layer containing Nb 2} O ₅ or Al ₂ O ₃ on the carbon conductive material, the coat layer does not become in a high potential state, so that the carbon conductive material and the sulfide solid electrolyte are used. The decomposition of the sulfide solid electrolyte and the release of the sulfur component due to the contact with the sulfide are suppressed. As a result, the production of a highly resistant substance due to the reaction between the released sulfur component and the high-potential positive electrode active material is suppressed, so that the capacity retention rate can be improved as compared with the conventional case.

It is a figure which shows an example of the layer structure of the sulfide solid state battery of this invention, and is the figure which schematically shows the cross section cut in the stacking direction. It is a TEM image of the magnification (200,000 times or 1.2 million times) which took the measurement result by HADDF of the carbon conductive material of Production Example Nb-1. It is the EDX spectrum line analysis result of the carbon conductive material of Production Example Nb-1. It is an SEM image of the carbon conductive material of Production Example Al-1. It is a partial cross-sectional schematic diagram of the conventional positive electrode mixture and its enlarged view for demonstrating the estimation mechanism of decomposition of a sulfide solid electrolyte.

The sulfide solid battery of the present invention is a sulfide solid battery including a positive electrode layer containing a positive electrode mixture, a negative electrode layer, and a sulfide solid electrolyte layer existing between the positive electrode layer and the negative electrode layer. The positive electrode mixture contains a high-potential positive electrode active material whose surface is coated with an oxide, a carbon conductive material, and a sulfide solid electrolyte, and the carbon conductive material has Nb ₂ O ₅ or Al on its surface. It is characterized by comprising a coat layer containing ₂ O _3.

FIG. 1 is a diagram showing an example of the layer structure of the sulfide solid-state battery of the present invention, and is a diagram schematically showing a cross section cut in the stacking direction. The sulfide solid-state battery 100 includes a positive electrode layer 1, a negative electrode layer 2, and a sulfide solid electrolyte layer 3 existing between the positive electrode layer 1 and the negative electrode layer 2.
The sulfide solid-state battery of the present invention is not necessarily limited to this example. For example, a positive electrode current collector may be provided on the outside of the sulfide solid-state battery 100 and in contact with the positive electrode layer 1. Further, a negative electrode current collector may be provided on a portion outside the sulfide solid-state battery 100 and in contact with the negative electrode layer 2.

The positive electrode layer 1 is a layer containing at least a positive electrode mixture. In addition to the positive electrode mixture, the positive electrode layer 1 may appropriately contain a binder or the like, if necessary.
The positive electrode mixture contains a high-potential positive electrode active material, a carbon conductive material, and a sulfide solid electrolyte.

In the present invention, the "high potential positive electrode active material" means a positive electrode active material having ^{an oxidation-reduction potential of 4.5 V (vs. Li / Li +) or more.} Examples of the high-potential positive electrode active material include LiNi _0.5 Mn _1.5 O _{4 and the} like.
The surface of the high-potential positive electrode active material used in the present invention is coated with an oxide. Examples of the oxide include Li ₃ PO _{4 and the} like.
The shape of the high-potential positive electrode active material is not particularly limited, and examples thereof include a granular shape and a thin film shape.

Examples of the carbon conductive material used in the present invention include carbon materials such as vapor-grown carbon fiber, acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), and carbon nanofiber (CNF). Can be mentioned. The shape of the carbon conductive material is not particularly limited, and examples thereof include granular and fibrous materials.

The carbon conductive material used in the present invention is provided with a coat layer containing _{Nb 2} O ₅ or Al ₂ O _{3 on its surface.} By providing the coat layer on the carbon conductive material, the decomposition of the sulfide solid electrolyte (and the generation of the sulfur component) due to the contact between the carbon conductive material and the sulfide solid electrolyte is suppressed. This is because _{the oxidation-reduction potential of the coat layer containing Nb 2} O ₅ or Al ₂ O ₃ is not included in the potential range of the positive electrode layer (3.0 to 4.8 V vs. Li / Li ^{+) during charging and discharging of the battery.} Moreover, since the electron conductivity of the coat layer is low (that is, the insulating property is high), the coat layer blocks the contact between the carbon conductive material and the sulfide solid electrolyte, whereby the sulfide solid electrolyte and the high potential substance are present. This is because contact with (carbon conductive material, etc.) can be avoided. As a result, the production of a high resistance substance due to the reaction between the sulfur component derived from the sulfide solid electrolyte and the positive electrode active material is suppressed, so that the capacity retention rate of the sulfide solid battery is improved.

The coat layer may cover only a part of the surface of the carbon conductive material, or may cover the entire surface of the carbon conductive material. As shown in Examples described later, the capacity retention rate is improved for both the film-like coat covering the entire surface of the carbon conductive material (Example 1) and the granular coat covering a part of the surface of the carbon conductive material (Example 2). The effect of is seen. However, since it is easy to suppress the decomposition of the sulfide solid electrolyte, the higher the ratio of the portion covered with the coat layer to the entire surface of the carbon conductive material, the more preferable, and the entire surface of the carbon conductive material has a uniform thickness. It is more preferable that it is covered with a coating layer.
In the present invention, the thickness of the coat layer is not particularly limited. The thickness of the coat layer is preferably 0.4 nm or more and 50 nm or less, more preferably 1.0 nm or more and 20 nm or less, and further preferably 2.0 nm or more and 10 nm or less. If the thickness of the coat layer is less than 0.4 nm, the effect of suppressing the decomposition of the sulfide solid electrolyte may be reduced. On the other hand, when the thickness of the coat layer exceeds 50 nm, the electronic resistance at the interface between the materials in the positive electrode mixture may increase.

The method for forming the coat layer on the surface of the carbon conductive material is not particularly limited. For example, in addition to the pulsed laser deposition (PLD) method, a vapor phase method typified by an atomic layer deposition (ALD) method can be used to form a coat layer on the surface of the carbon conductive material. Among these methods, it is preferable to form a coat layer by a vapor phase method represented by an atomic layer deposition (ALD) method or the like. This is because it is easy to form a coat layer having a uniform thickness.
_{When a coat layer containing Nb 2} O ₅ is formed by the atomic layer deposition (ALD) method, for example, niobium ethoxide can be used as the Nb raw material and water can be used as the oxygen source.
_{When forming a coat layer containing Al 2} O ₃ by the atomic layer deposition (ALD) method, for example, trimethylaluminum can be used as an Al raw material and water can be used as an oxygen source.
_{When forming a coat layer containing LiNbO 3} by the atomic layer deposition (ALD) method, for example, lithium t-butoxide as a Li raw material, niobium ethoxydo as an Nb raw material, and water as an oxygen source can be used.
The film formation rate is preferably 0.3 Å or more and 3 Å or less per cycle. The suitable number of cycles is a value obtained by dividing the thickness of the suitable coat layer by the film formation rate.

Whether or not the surface of the carbon conductive material is covered with a coat layer can be determined, for example, by observation with a scanning electron microscope (SEM) or energy dispersive X-ray spectroscopy (Transmission Electron) of a transmission electron microscope. It can be confirmed by observation by a high-angle scattering dark-field method (High-Angle Anal Dark-Field: HAADF) using a Microscope-Energy Dispersive X-ray Spectroscopic; TEM-EDX. In particular, in the case of observation by HAADF using TEM-EDX, the composition ratio of the elements in the cross section of the carbon conductive material can be examined by EDX spectral line analysis, and the detailed coating form of the coat layer can be confirmed.

The sulfide solid electrolyte used for the positive electrode layer is not particularly limited, and examples thereof include Li ₂ S / P ₂ S ₅ .

The sulfide solid electrolyte layer is a layer existing between the positive electrode layer and the negative electrode layer. Ion conduction between the positive electrode active material and the negative electrode active material is performed through the sulfide solid electrolyte layer.
Examples of the sulfide solid electrolyte layer include a layer containing _{Li 2} S / P ₂ S _5.
The thickness of the sulfide solid electrolyte layer is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, and more preferably 0.1 μm or more and 300 μm or less.

The negative electrode layer contains at least a negative electrode active material, and may contain a sulfide solid electrolyte or the like, if necessary.
As the negative electrode active material that can be contained in the negative electrode layer, a negative electrode active material that can occlude and release lithium ions can be appropriately used. Examples of such a negative electrode active material include a carbon active material, an oxide active material, a metal active material, and the like. Among these, the carbon active material is not particularly limited as long as it contains carbon, and examples thereof include graphite.
As the sulfide solid electrolyte that can be contained in the negative electrode layer, for example, Li ₂ S / P ₂ S ₅ can be exemplified.

The sulfide solid-state battery is manufactured by forming a positive electrode layer on one surface of the sulfide solid electrolyte layer and forming a negative electrode layer on the other surface of the sulfide solid electrolyte layer. The sulfide solid-state battery may be used in a state of being housed in an exterior body.

1. 1. Coating of carbon conductive material by atomic layer deposition (ALD) method [Production Example Nb-1]
A coat layer was formed on the surface of acetylene black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.), which is a carbon conductive material, by the ALD method. At the time of ALD film formation, niobium ethoxydo (manufactured by Japan Advanced Chemicals Co., Ltd.) was used as an Nb raw material, and water was used as an oxygen source. The temperature of niobium ethoxyd was 200 ° C., the temperature of water was 20 ° C., and the temperature of the reaction layer was 200 ° C. Further, by setting the film formation rate to 0.4 Å per cycle, using nitrogen gas as the carrier gas, and repeating the film formation over 50 cycles, a coat layer mainly composed of _{Nb 2} O _{5 is formed on the surface of acetylene black.} Was formed. From the film forming conditions of ALD film forming, it is considered that the thickness of the coat layer is about 2 nm.

[Manufacturing Examples Nb-2 to Nb-6]
In the above-mentioned production example Nb-1, the number of times of repeating the film formation is 10 cycles (production example Nb-2), 25 cycles (production example Nb-3), 75 cycles (production example Nb-4), 125 cycles (production example Nb). A coat layer mainly composed of _{Nb 2} O ₅ was formed on the surface of acetylene black by the same process as that of Production Example Nb-1, except that the cycle was -5) or 175 cycles (Production Example Nb-6).
From the film forming conditions of ALD film forming, the thickness of each coat layer is about 0.4 nm (Production Example Nb-2), about 1 nm (Production Example Nb-3), about 3 nm (Production Example Nb-4), respectively. It is considered to be about 5 nm (Production Example Nb-5) or about 7 nm (Production Example Nb-6).

[Manufacturing Example LiNb-1]
A coat layer was formed on the surface of acetylene black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.), which is a carbon conductive material, by the ALD method. At the time of ALD film formation, lithium t-butoxide (manufactured by Japan Advanced Chemicals Co., Ltd.) was used as a Li raw material, niobium ethoxydo (manufactured by Japan Advanced Chemicals Co., Ltd.) was used as an Nb raw material, and water was used as an oxygen source. The temperature of lithium t-butoxide was 140 ° C, the temperature of niobium ethoxyd was 200 ° C, the temperature of water was 20 ° C, and the temperature of the reaction layer was 235 ° C. Further, by setting the film formation rate to 2 Å per cycle, using nitrogen gas as the carrier gas, and repeating the film formation over 10 cycles, the surface of acetylene black is coated with a composite oxide of Li and Nb as a main component. Formed a layer. From the film forming conditions of ALD film forming, it is considered that the thickness of the coat layer is about 2 nm.

[Manufacturing Example Al-1]
A coat layer was formed on the surface of acetylene black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.), which is a carbon conductive material, by the ALD method. At the time of ALD film formation, trimethylaluminum (manufactured by Japan Advanced Chemicals Co., Ltd.) was used as an Al raw material, and water was used as an oxygen source. The temperature of trimethylaluminum was 20 ° C., the temperature of water was 20 ° C., and the temperature of the reaction layer was 200 ° C. Further, by setting the film formation rate to 1 Å per cycle, using nitrogen gas as the carrier gas, and repeating the film formation over 30 cycles, a coat layer mainly composed of _{Al 2} O _{3 is formed on the surface of acetylene black.} bottom. From the film forming conditions of ALD film forming, it is considered that the thickness of the coat layer is about 3 nm.

[Manufacturing Example Al-2]
_{In the above Production Example Al-1, Al 2} O ₃ was applied to the surface of acetylene black by the same process as Production Example Al-1 except that the number of times of film formation was set to 10 cycles (Production Example Al-2). A coat layer mainly composed of aluminum was formed.
From the film forming conditions of ALD film forming, it is considered that the thickness of the coat layer is about 1 nm.

2. 2. Fabrication of Solid Sulfide Battery [Example 1]
As the positive electrode active material, using _LiNi 0.5 _Mn 1.5 _{O 4} having a surface coated with _Li 3 PO _{4. In addition, Li 2} S / P ₂ S ₅ (in-house synthesized product) was used as the sulfide solid electrolyte. These positive electrode active materials and sulfide solid electrolytes were mixed at a positive electrode active material: sulfide solid electrolyte = 50:50 (volume ratio). To further the mixture, Production Example Nb-1 carbon conductive material (coating layer: mainly _Nb 2 _{O 5,} the thickness of the coating layer: about 2 nm) and at a rate of 10 vol% with respect to the positive electrode active material Addition was made to prepare a positive electrode mixture.
Further, natural graphite as a negative electrode active material and the above Li ₂ S / P ₂ S ₅ were mixed at a ratio of natural graphite: sulfide solid electrolyte = 50:50 (volume ratio) to prepare a negative electrode mixture.
The above Li ₂ S / P ₂ S ₅ 50 mg was processed into a solid electrolyte layer. A positive electrode layer was prepared using 20 mg of the positive electrode mixture on one surface of the solid electrolyte layer. Further, a negative electrode layer was prepared using 20 mg of the negative electrode mixture on the other surface of the solid electrolyte layer, and the sulfide solid state battery of Example 1 was prepared.

[Example 2]
In the first embodiment, the carbon conductive material of the Production Example Nb-1, Production Example Al-1 carbon conductive material (coating layer: mainly _Al 2 _{O 3,} the thickness of the coating layer: about 3 nm) instead of Except for the above, the same steps as in Example 1 were carried out to prepare a sulfide solid-state battery of Example 2.

[Comparative Example 1]
In Example 1, the same steps as in Example 1 were carried out except that the carbon conductive material of Production Example Nb-1 was replaced with acetylene black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.), and Comparative Example. 1 sulfide solid-state battery was produced.

3. 3. TEM observation The carbon conductive material of Production Example Nb-1 was measured by the high-angle scattering dark-field method (HAADF) using the energy dispersive X-ray spectroscopy (TEM-EDX) of a transmission electron microscope, and the carbon conductivity was measured. The structure and composition of the material surface were analyzed.

2 (a) and 2 (b) are TEM images of the measurement results of the carbon conductive material of Production Example Nb-1 by HADDF.
The measurement conditions of HAADF are as follows. That is, using an electric field radiation transmission electron microscope (manufactured by JEOL Ltd., JEM-2100F, attached with Cs correction), a magnification of 200,000 times (Fig. 2 (a)) and a magnification of 1.2 million times (Fig. 2) at an acceleration voltage of 200 kV. In 2 (b)), dark-field STEM observation (Scanning Transmission Electron Microscope) was performed, respectively. In FIGS. 2 (a) and 2 (b), heavy elements are shown in white. Further, FIG. 2 (b) is a photograph in which the inside of the frame of FIG. 2 (a) is further enlarged.
In particular, as can be seen from FIG. 2 (b), in the carbon conductive material, the relatively dark inner layer is almost uniformly covered with the relatively light-colored layer having a thickness of several nanometers. From this, it was confirmed that in Production Example Nb-1, the uniform coating of carbon by _{Nb 2} O _{5 was successful.}

For the line portion (120 nm) indicated by the arrow in FIG. 2 (b), 120-point EDX spectra were measured at 1 nm intervals. FIG. 3 shows the results of the EDX spectrum line analysis, and more specifically, the intensity profiles of C-Kα, OKα, and Nb-Kβ obtained from each EDX spectrum are superimposed.
From FIG. 3, it can be seen that the peaks of the elements C, O, and Nb appear from 25 nm to 110 nm in the line portion. Maximum peaks of elements O and Nb appear at the end of the line from 25 nm to 38 nm and from 98 nm to 110 nm, respectively, and the central part (the part from 38 nm to 98 nm of the line) is the element. The maximum peak of C appears. This result indicates that the carbon conductive material is uniformly covered with the _{Nb 2} O _{5 coat layer.}

4. SEM Observation With respect to the carbon conductive material of Production Example Al-1, the structure of the surface of the carbon conductive material was observed using a transmission electron microscope (SEM).
The SEM observation conditions are as follows. That is, using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number: SU8000), SEM observation was performed at an acceleration voltage of 1.0 kV and a magnification of 200,000 times.

FIG. 4 is an SEM image of the carbon conductive material of Production Example Al-1. In FIG. 4, the aluminum element is shown in white.
From FIG. 4, white spots are intermittently observed on the surface of the carbon conductive material. _{This indicates that the Al 2} O ₃ coat layer is selectively formed on the edge portion (tip portion) of the surface of the carbon conductive material. That is, the light black portion in FIG. 4 shows the terrace portion (flat portion) on the surface of the carbon conductive material, and the white portion in the figure shows the Al ₂ O ₃ coat layer on the edge portion of the surface of the carbon conductive material. From this, it was confirmed that in Production Example Al-1, selective coating of the surface of the carbon conductive material was successful with _{Al 2} O _3.

5. Charging / discharging test When the test electrode is a positive electrode and metallic Li is a negative electrode, the process of desorbing lithium ions from the test electrode is referred to as "charging", and the process of inserting lithium ions into the test electrode is referred to as "discharge". The charge / discharge test was performed on the battery of Example 2, the battery of Example 2, and the battery of Comparative Example 1. As the measuring device, a charge / discharge test device (HJ-1001 SM8A manufactured by Hokuto Denko) was used. The measurement conditions were a current value of 0.2 mA / cm ² in the first cycle, a voltage at the end of discharge of 3.5 V (counter electrode graphite), a voltage at the end of charging of 4.9 V (counter electrode graphite), and a temperature of 25 ° C. The 0.1C rate was calculated from the measured cell capacity. As conditioning, charging and discharging were performed three times at a rate of 0.1 C. The discharge capacity in this third conditioning was defined as the "initial discharge capacity". Then, it was charged until the charged state (SOC) became 60%, allowed to stand for 30 minutes, and then AC impedance was measured at 25 ° C. to estimate the resistance of the arc component.
Then, charging and discharging were performed for 100 cycles under the conditions of 60 ° C., 0.1 C rate, a voltage at the end of discharge of 3.5 V (counter electrode graphite), and a voltage at the end of charging of 4.9 V (counter electrode graphite). Then, after the 100th cycle of charging / discharging is completed, charging / discharging is performed under the conditions of 25 ° C., 0.1 C rate, discharge end voltage 3.5 V (counter electrode graphite), and charge end voltage 4.9 V (counter electrode graphite). The discharge capacity at this time was defined as "discharge capacity after cycle test".

6. Results and Discussion Table 1 below is a table comparing the properties of the coat layer and the evaluation results for Examples 1 to 2 and Comparative Example 1. The “capacity” in Table 1 below means the discharge capacity after the cycle test. Further, the "capacity retention rate" in Table 1 below is calculated by the following formula.
Capacity retention rate (%) = ([Discharge capacity after cycle test] / [Initial discharge capacity]) x 100

From Table 1 above, the battery using the carbon conductive material without the coat layer (Comparative Example 1) had a capacity retention rate of only 53%. On the other hand, _{the battery using the carbon conductive material having the Nb 2} O ₅ coat layer (Example 1) and the battery using the carbon conductive material having the Al ₂ O ₃ coat layer (Example 2) are both. The capacity retention rate exceeded 60%, and it was confirmed that the capacity retention rate was significantly improved as compared with Comparative Example 1. From this result, it was demonstrated that the sulfide solid-state battery using the carbon conductive material whose surface is coated with _{Nb 2} O ₅ or Al ₂ O _{3 has a higher capacity retention rate than the conventional sulfide solid-state battery.}
Further, from Table 1 above, the capacity retention rate is improved in both the film-like coat covering the entire surface of the carbon conductive material (Example 1) and the granular coat covering a part of the surface of the carbon conductive material (Example 2). The effect of is seen. However, since the capacity retention rate of Example 1 is higher than that of Example 2, it can be said that the film-like coat is more effective in improving the capacity retention rate than the granular coat.

1 Positive electrode layer 2 Negative electrode layer 3 Sulfurized solid electrolyte layer 11 Positive electrode active material 12 Oxide layer 13 Carbon conductive material 14 Sulfurized solid electrolyte 15 One-point chain wire frame showing enlarged part 100 Sulfurized solid-state battery 200 Conventional sulfide solid-state battery Positive electrode mixture for

Claims (1)

In a sulfide solid-state battery including a positive electrode layer containing a positive electrode mixture, a negative electrode layer, and a sulfide solid electrolyte layer existing between the positive electrode layer and the negative electrode layer.
The positive electrode mixture contains a high-potential positive electrode active material whose surface is coated with an oxide, a carbon conductive material, and a sulfide solid electrolyte.
The carbon conductive material has a coat layer containing _{Nb 2} O ₅ or Al ₂ O ₃ on its surface.
The high potential positive electrode active material, oxidation-reduction potential and said positive electrode active material der Rukoto above 4.5V (vs.Li/Li ^+), sulfide solid battery.

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