Sulfur-containing oxide-based positive electrode active material and manufacturing method thereof

Abstract

To provide a method for manufacturing a sulfur-containing oxide-based positive electrode active material that is less likely to be contaminated with sulfur-containing substances, and a sulfur-containing oxide-based positive electrode active material that is less likely to be contaminated with sulfur-containing substances.SOLUTION: The manufacturing method of a sulfur-containing oxide-based positive electrode active material includes a reaction step of contacting an oxide-based positive electrode active material with a sulfur-containing gas to generate a sulfur-containing oxide-based positive electrode active material, and a sulfur-containing material removal step of removing sulfur-containing material mixed into the sulfur-containing oxide-based positive electrode active material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sulfur-containing oxide-based cathode active material and a method for producing the same.

Background Art

[0002] In recent years, research and development have been conducted on lithium-ion secondary batteries that contribute to energy efficiency in order to enable more people to access affordable, reliable, sustainable, and advanced energy. As cathode active materials for lithium-ion secondary batteries, oxide-based cathode active materials containing lithium and transition metals are known. In order to improve the electrochemical properties of oxide-based cathode active materials, sulfur-containing oxide-based cathode active materials in which a part of the oxygen in the oxide-based cathode active material is replaced with sulfur have been studied. As a method for producing sulfur-containing oxide-based cathode active materials, a method is known in which an oxide-based cathode active material is heated in the presence of a sulfur-containing gas to cause a solid-gas reaction between the oxide-based cathode active material and the sulfur-containing gas (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the method for producing a sulfur-containing oxide-based positive electrode active material using a solid-gas reaction, it is preferable not to release the sulfur-containing gas to the outside. In order to prevent the release of the sulfur-containing gas to the outside, it is effective to carry out the solid-gas reaction between the oxide-based positive electrode active material and the sulfur-containing gas in a sealed container. However, according to the study by the present inventors, unreacted sulfur-containing gas remains in the sealed container after the solid-gas reaction, and a solidified sulfur-containing substance is generated from the remaining sulfur-containing gas, which may be mixed into the sulfur-containing oxide-based positive electrode active material. It has been found that a sulfur-containing oxide-based positive electrode active material mixed with a sulfur-containing substance has an increased resistance, and a lithium-ion secondary battery using this may have deteriorated electrical characteristics.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a sulfur-containing oxide-based positive electrode active material in which sulfur-containing substances are less likely to be mixed, and a sulfur-containing oxide-based positive electrode active material in which the amount of sulfur-containing substances mixed is small.

Means for Solving the Problems

[0006] (1) A method for producing a sulfur-containing oxide-based positive electrode active material, comprising a reaction step of bringing an oxide-based positive electrode active material into contact with a sulfur-containing gas to produce a sulfur-containing oxide-based positive electrode active material, and a sulfur-containing substance removing step of removing sulfur-containing substances mixed in the sulfur-containing oxide-based positive electrode active material.

[0007] In the production method of (1), since the sulfur-containing substance removing step is performed after the reaction step, even if sulfur-containing substances are generated in the reaction step, the obtained sulfur-containing oxide-based positive electrode active material has a reduced amount of sulfur-containing substances mixed therein. Therefore, according to the production method of (1), a sulfur-containing oxide-based positive electrode active material with higher purity and excellent electrical characteristics can be produced.

[0008] (2) The method for producing a sulfur-containing oxide-based positive electrode active material according to (1), wherein the sulfur-containing gas is sulfur gas.

[0009] According to the production method of (2), since the sulfur-containing gas is sulfur gas and has high reactivity, a sulfur-containing oxide-based positive electrode active material can be efficiently produced.

[0010] (3) In the reaction step, sulfur gas is generated by heating a container containing the oxide-based positive electrode active material and sulfur in elemental form, and the oxide-based positive electrode active material is brought into contact with the sulfur gas. The method for producing a sulfur-containing oxide-based positive electrode active material according to (2).

[0011] According to the production method of (3), since the container containing the oxide-based positive electrode active material and sulfur in elemental form is heated, the sulfur gas generated by heating the sulfur in elemental form is less likely to flow out to the outside. Therefore, according to the production method of (3), a sulfur-containing oxide-based positive electrode active material can be industrially advantageously produced.

[0012] (4) After the container containing the oxide-based positive electrode active material and the sulfur in elemental form is depressurized until the pressure becomes less than 1×10 3 Pa, the container is sealed and heated. The method for producing a sulfur-containing oxide-based positive electrode active material according to (3).

[0013] According to the production method of (4), since the pressure in the sealed container is as low as less than 1×10 3 Pa, the condensation temperature of the sulfur-containing gas becomes low. For this reason, the heating temperature in the reaction step can be lowered. Therefore, according to the production method of (4), a sulfur-containing oxide-based positive electrode active material can be produced more industrially advantageously.

[0014] (5) After the reaction step and before the sulfur-containing substance removal step, a cooling step of cooling the sulfur-containing oxide-based positive electrode active material is included. The method for producing a sulfur-containing oxide-based positive electrode active material according to (3) or (4).

[0015] According to the production method of (5), since the sulfur-containing oxide-based positive electrode active material is cooled in the cooling step, unreacted sulfur-containing gas is likely to form sulfur-containing substances. After sulfur-containing substances are formed in the cooling step, by performing the sulfur-containing substance removal step, unreacted sulfur-containing gas remaining in the reaction step can be efficiently removed as sulfur-containing substances.

[0016] (6) In the sulfur-containing substance removal step, the method for removing the sulfur-containing substance is a method of heating the sulfur-containing oxide-based positive electrode active material to vaporize the sulfur-containing substance to generate a sulfur-containing vaporized product. The method for producing a sulfur-containing oxide-based positive electrode active material according to any one of (1) to (5).

[0017] According to the production method of (6), since the sulfur-containing substance mixed in the sulfur-containing oxide-based positive electrode active material is removed as a sulfur-containing vaporized product, the sulfur-containing substance can be removed regardless of the particle size of the sulfur-containing substance, and it is possible to obtain a sulfur-containing oxide-based positive electrode active material with an even lower amount of sulfur-containing substance mixed therein.

[0018] (7) In the sulfur-containing substance removal step, the sulfur-containing oxide-based positive electrode active material is heated in a sealed container. The method for producing a sulfur-containing oxide-based positive electrode active material according to (6).

[0019] According to the production method of (7), since the sulfur-containing oxide-based positive electrode active material is heated in a sealed container, the vaporized sulfur-containing vaporized product can be removed more efficiently without being released to the outside.

[0020] (8) In the sulfur-containing substance removal step, the sealed container is heated so as to have a temperature gradient, the sulfur-containing oxide-based positive electrode active material is heated at the position where the temperature of the sealed container is the highest, and the sulfur-containing vaporized product is solidified at the position where the temperature of the sealed container is the lowest. The method for producing a sulfur-containing oxide-based positive electrode active material according to (7).

[0021] According to the production method of (8), since the sulfur-containing vaporized product is solidified at the position where the temperature of the sealed container is the lowest, the sulfur-containing vaporized product can be efficiently recovered.

[0022] (9) In the sulfur-containing substance removal step, a part of the sealed container is heated. The method for producing a sulfur-containing oxide-based positive electrode active material according to (7) or (8).

[0023] According to the manufacturing method of (9), since a part of the sealed container is heated, it is possible to surely heat the sealed container so as to have a temperature gradient.

[0024] (10) In the sulfur-containing substance removing step, the method for removing the sulfur-containing substance is a method of classifying the sulfur-containing oxide-based positive electrode active material to separate the sulfur-containing oxide-based positive electrode active material and the sulfur-containing substance, and the manufacturing method of the sulfur-containing oxide-based positive electrode active material according to any one of (1) to (5).

[0025] According to the manufacturing method of (10), since heating and cooling are not required, the sulfur-containing substance mixed in the sulfur-containing oxide-based positive electrode active material can be removed quickly and simply.

[0026] (11) The manufacturing method of the sulfur-containing oxide-based positive electrode active material according to any one of (1) to (10), wherein the oxide-based positive electrode active material contains at least one transition metal element selected from the group consisting of nickel, cobalt, and manganese and lithium.

[0027] According to the manufacturing method of (11), sulfur can be contained in the oxide-based positive electrode active material that is widely used for lithium ion batteries.

[0028] (12) The manufacturing method of the sulfur-containing oxide-based positive electrode active material according to any one of (1) to (11), wherein the oxide-based positive electrode active material is for a lithium ion battery.

[0029] According to the manufacturing method of (12), a sulfur-containing oxide-based positive electrode active material useful for a lithium ion battery can be obtained.

[0030] (13) A reaction step of generating a sulfur-containing oxide-based positive electrode active material by bringing an oxide-based positive electrode active material into contact with a sulfur-containing gas in a sealed container, and a sulfur-containing substance removing step of heating the sulfur-containing oxide-based positive electrode active material in the sealed container to vaporize the sulfur-containing substance mixed in the sulfur-containing oxide-based positive electrode active material to generate a sulfur-containing vapor, the manufacturing method of the sulfur-containing oxide-based positive electrode active material including the above steps.

[0031] According to the manufacturing method of (13), since the reaction step and the sulfur-containing substance removal step are carried out using the same sealed container, a sulfur-containing oxide-based positive electrode active material with higher purity and excellent electrical characteristics can be manufactured without releasing sulfur-containing gas and sulfur-containing oxides to the outside.

[0032] (14) A sulfur-containing oxide-based positive electrode active material obtained by the manufacturing method of the sulfur-containing oxide-based positive electrode active material according to any one of (1) to (13).

[0033] (14) The sulfur-containing oxide-based positive electrode active material has a small amount of sulfur-containing substances mixed therein because it is obtained by the above-described manufacturing method of the sulfur-containing oxide-based positive electrode active material. Therefore, it has excellent electrical characteristics.

Advantages of the Invention

[0034] According to the present invention, it is possible to provide a manufacturing method of a sulfur-containing oxide-based positive electrode active material in which sulfur-containing substances are less likely to be mixed, and a sulfur-containing oxide-based positive electrode active material with a small amount of sulfur-containing substances mixed therein.

Brief Description of the Drawings

[0035]

Figure 1

Modes for Carrying Out the Invention

[0036] Hereinafter, embodiments of the present invention will be described.

[0037] The manufacturing method of a sulfur-containing oxide-based positive electrode active material according to an embodiment of the present invention includes a reaction step and a sulfur-containing substance removal step. A cooling step may be performed after the reaction step and before the sulfur-containing substance removal step.

[0038] The reaction step is a step of bringing an oxide-based positive electrode active material into contact with a sulfur-containing gas to produce a sulfur-containing oxide-based positive electrode active material.

[0039] As the oxide-based cathode active material, an oxide containing lithium and a transition metal can be used. As the oxide-based cathode active material, for example, a layered rock salt-type oxide, a spinel-type oxide, or an olivine-type oxide can be used. Examples of the layered rock salt-type oxide include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), LiNi p Mn q Co r O2 (p + q + r = 1), LiNi p Al q Co r O2 (p + q + r = 1) can be mentioned. Examples of the spinel-type oxide include lithium manganate (LiMn2O4), Li 1+x Mn 2-x-y MO4 (x + y = 2, M = at least one selected from Al, Mg, Co, Fe, Ni, and Zn), a hetero-element substituted Li-Mn spinel represented by this, lithium titanate (LiTi2O4, Li4Ti5O 12 ) can be mentioned. Examples of the olivine-type oxide include lithium metal phosphate (LiMPO4, M = at least one selected from Fe, Mn, Co, and Ni). The oxide-based cathode active material may be an oxide containing at least one transition metal element selected from the group consisting of nickel, cobalt, and manganese and lithium. The oxide-based cathode active material may be for a lithium-ion battery, particularly for a non-aqueous solvent lithium-ion battery.

[0040] The average particle size of the oxide-based cathode active material may be, for example, in the range of 0.1 μm or more and 100 μm or less, preferably in the range of 0.2 μm or more and 30 μm or less. The oxide-based cathode active material having an average particle size within this range has a large surface area, and a solid-gas reaction with the sulfur-containing gas is likely to occur.

[0041] As the sulfur-containing gas, a gas generated by heating a sulfur-containing substance can be used. The sulfur-containing gas may be, for example, sulfur gas generated by heating elemental sulfur. The elemental sulfur is not particularly limited, and for example, any of rhombic sulfur, monoclinic sulfur, and rubbery sulfur can be used. The elemental sulfur may be used alone or in combination of two or more. Since sulfur gas has high reactivity, the sulfur-containing oxide-based positive electrode active material can be efficiently produced by using sulfur gas.

[0042] As a method of bringing the oxide-based positive electrode active material into contact with the sulfur-containing gas, a method of accommodating the oxide-based positive electrode active material and the sulfur-containing substance in a sealed container and heating the sealed container can be used. The oxide-based positive electrode active material and the sulfur-containing substance may be accommodated in the sealed container in a mixed state, or may be accommodated in the sealed container in a separated state.

[0043] FIG. 1 is a cross-sectional view showing a reaction vessel that can be used in a method for producing a sulfur-containing oxide-based positive electrode active material according to an embodiment of the present invention.

[0044] As shown in FIG. 1, the reaction vessel 10 is an array-type reaction vessel in which a first sample chamber 11 and a second sample chamber 12 are connected by a hollow connecting portion 13. The first sample chamber 11 contains the oxide-based positive electrode active material 1, and the second sample chamber 12 contains the sulfur-containing substance 2. By heating the reaction vessel 10, the sulfur-containing gas generated by the sublimation of the sulfur-containing substance 2 diffuses into the first sample chamber 11 through the hollow connecting portion 13, and in the first sample chamber 11, a solid-gas reaction occurs with the oxide-based positive electrode active material 1 to generate a sulfur-containing oxide-based positive electrode active material.

[0045] The first sample chamber 11 and the second sample chamber 12 of the reaction vessel 10 each have a sample introduction hole (not shown). After introducing the oxide-based positive electrode active material 1 through the sample introduction hole of the first sample chamber 11 and introducing the sulfur-containing substance 2 through the sample introduction hole of the second sample chamber 12, the reaction vessel 10 can be sealed by sealing the sample introduction hole.

[0046] The pressure inside the reaction vessel 10 is 1×103 It may be less than Pa. By reducing the pressure inside the reaction vessel 10, the sublimation temperature of the sulfur-containing substance 2 decreases, and the condensation temperature of the generated sulfur-containing gas becomes lower. Therefore, the heating temperature in the reaction step can be lowered. Thereby, deterioration of the oxide-based positive electrode active material 1 due to heating can be suppressed.

[0047] For heating the reaction vessel 10, a heating device such as a tubular furnace or a muffle furnace can be used, for example. The heating temperature may be, for example, in the range of 150°C or higher and 500°C or lower, preferably in the range of 150°C or higher and 400°C or lower, and more preferably in the range of 150°C or higher and 300°C or lower. The heating time varies depending on conditions such as the size of the reaction vessel 10 and the heating temperature, but is in the range of 1 hour or longer and 20 hours or shorter.

[0048] The cooling step is a step of cooling the sulfur-containing oxide-based positive electrode active material obtained in the reaction step. The cooling step may be performed in the reaction vessel 10. For example, the cooling step may be performed by stopping the heating of the reaction vessel 10. By stopping the heating of the reaction vessel 10, the unreacted sulfur-containing gas remaining in the reaction vessel 10 solidifies, a sulfur-containing substance is generated, and it is mixed into the sulfur-containing oxide-based positive electrode active material, and the amount of the sulfur-containing gas in the reaction vessel 10 is reduced.

[0049] In the sulfur-containing substance removal step, the sulfur-containing substance mixed into the sulfur-containing oxide-based positive electrode active material is removed. As a method for removing the sulfur-containing substance, a heating method and a classification method can be used.

[0050] The heating method is a method of heating a sulfur-containing oxide-based positive electrode active material to vaporize sulfur-containing substances and separating the sulfur-containing oxide-based positive electrode active material from the vaporized sulfur-containing compounds. The heating of the sulfur-containing oxide-based positive electrode active material may be performed in a sealed container. When performing in a sealed container, the sealed container may be heated so as to have a temperature gradient. For example, by heating the sulfur-containing oxide-based positive electrode active material at the position where the temperature of the sealed container is the highest and solidifying the sulfur-containing compound at the position where the temperature of the sealed container is the lowest, the sulfur-containing oxide-based positive electrode active material and the sulfur-containing compound may be separated. When using the reaction vessel 10 as the sealed container, the first sample chamber 11 is heated and the second sample chamber 12 is not heated. By heating the first sample chamber 11, the sulfur-containing substances mixed in the sulfur-containing oxide-based positive electrode active material in the first sample chamber 11 are vaporized. The generated sulfur-containing compound diffuses through the hollow connecting portion 13 into the second sample chamber 12 and is cooled and solidified in the second sample chamber 12. As a result, the concentration of the sulfur-containing compound in the reaction vessel 10 decreases. Therefore, even if the heating is stopped and the first sample chamber 11 is cooled, sulfur-containing substances are less likely to mix into the sulfur-containing oxide-based positive electrode active material in the first sample chamber 11. By using the heating method, sulfur-containing substances can be removed regardless of the particle size of the sulfur-containing substances, and it is possible to obtain a sulfur-containing oxide-based positive electrode active material with a smaller amount of sulfur-containing substances mixed therein.

[0051] When removing sulfur-containing substances by the heating method, the reaction step, the cooling step, and the sulfur-containing substance removal step may be continuously performed using the same sealed container. By performing continuously, the manufacturing time of the sulfur-containing oxide-based positive electrode active material can be shortened.

[0052] The classification method is a method of classifying a sulfur-containing oxide-based positive electrode active material and separating and removing sulfur-containing substances mixed in the sulfur-containing oxide-based positive electrode active material. For example, a sieve can be used for classifying the sulfur-containing oxide-based positive electrode active material. By using the classification method, steps such as heating and cooling are not required, so sulfur-containing substances with a small amount of sulfur-containing substances mixed therein can be removed quickly and simply. After removing sulfur-containing substances by the classification method, sulfur-containing substances may be removed by the heating method.

[0053] The sulfur-containing oxide-based cathode active material of this embodiment is obtained by the above-described production method. The sulfur-containing oxide-based cathode active material can be used, for example, as a cathode active material of a lithium-ion secondary battery.

[0054] According to the production method of the sulfur-containing oxide-based cathode active material of this embodiment configured as described above, since the sulfur-containing substance removal step is performed after the reaction step, even if sulfur-containing substances are generated in the reaction step, the amount of sulfur-containing substances mixed in the obtained sulfur-containing oxide-based cathode active material is reduced and it is difficult to be mixed. Therefore, according to the production method of this embodiment, a sulfur-containing oxide-based cathode active material with higher purity and excellent electrical characteristics can be produced.

[0055] The sulfur-containing oxide-based cathode active material of this embodiment is obtained by the above-described production method of the sulfur-containing oxide-based cathode active material. Therefore, the sulfur-containing oxide-based cathode active material of this embodiment has a small amount of sulfur-containing substances mixed in and excellent electrical characteristics.

[0056] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments. In the production method of this embodiment, as a method of bringing the oxide-based cathode active material into contact with the sulfur-containing gas, a method of accommodating the oxide-based cathode active material and the sulfur-containing substance in a sealed container and heating the sealed container is used, but it is not limited thereto. For example, a sulfur-containing gas may be supplied from the outside into the sealed container. When supplying a sulfur-containing gas from the outside, it is not necessary to heat the sealed container.

Example

[0057] Hereinafter, the present invention will be described with reference to examples.

[0058] [Example 1] A quartz array-type reaction vessel in which a first sample chamber having a sample introduction hole and a second sample chamber having a sample introduction hole are connected by a hollow connecting portion was prepared. This quartz array-type reaction vessel was heated to 150 °C, placed in a glove box, and allowed to cool. Next, a powder funnel was inserted into the sample introduction hole of the second sample chamber of the quartz array-type reaction vessel, and 0.791 g of sulfur was introduced. Then, another powder funnel was inserted into the sample introduction hole of the first sample chamber, and 100.00 g of a positive electrode active material powder (composition: Li 1.000 Ni 0.8000 O2, average particle diameter: 20 μm) was introduced. Next, after sealing the sample introduction holes of the first sample chamber and the second sample chamber, the quartz array-type reaction vessel was taken out of the glove box. Next, after opening the sample introduction holes of the first sample chamber and the second sample chamber, a vacuum pump was connected to the sample introduction holes, and the inside of the quartz array-type reaction vessel was depressurized. When the pressure inside the quartz array-type reaction vessel reached 6 Pa, the sample introduction holes of the first sample chamber and the second sample chamber were sealed off using a gas burner, and the quartz array-type reaction vessel was sealed. Next, the quartz array-type reaction vessel was installed in a tubular furnace (KTF055N2, J-Techno Thermo System Co., Ltd.), and the temperature of the quartz array-type reaction vessel was raised to 290 °C at a rate of 1 °C / min, and then heat-treated at 290 °C for 8 hours. After the heat treatment, the quartz array-type reaction vessel was taken out of the tubular furnace and allowed to cool to room temperature (reaction process). As a result of visually observing the sulfur-containing positive electrode active material powder after the reaction process, it was confirmed that sulfur with a particle diameter of about 1 mm was mixed in. Next, as a sulfur-containing substance removal process, the quartz array-type reaction vessel was installed in a tubular furnace (ARF50K, Asahi Rika Seisakusho Co., Ltd.) so that the second sample chamber protruded from the tubular furnace, and heat-treated for 3 hours so that the temperature at the center of the first sample chamber became 290 °C. After the heat treatment, the quartz array-type reaction vessel was taken out of the tubular furnace, placed in a glove box, and allowed to cool. After cooling, the sulfur-containing positive electrode active material powder was recovered from the quartz array-type reaction vessel. As a result of visually observing the recovered sulfur-containing positive electrode active material powder, no sulfur was found to be mixed in. On the other hand, a large amount of sulfur-containing substances adhered to the inner surface of the second sample chamber after cooling. This is because the sulfur mixed in the sulfur-containing positive electrode active material powder obtained in the reaction process and the sulfur-containing gas generated by heating in the sulfur-containing substance removal process were cooled in the second sample chamber and adhered to the inner surface of the second sample chamber.

[0059] [Example 2] A sulfur-containing positive electrode active material powder was produced in the same manner as in Example 1, except that the heat treatment in the reaction step was carried out at 250 °C for 8 hours. Similar to Example 1, no sulfur contamination was observed in the sulfur-containing positive electrode active material powder after the sulfur-containing substance removal step, and a large amount of sulfur adhered to the inner surface of the second sample chamber as in Example 1.

[0060] [Example 3] A sulfur-containing positive electrode active material powder was produced in the same manner as in Example 1, except that the heat treatment in the reaction step was carried out at 270 °C for 8 hours. Similar to Example 1, no sulfur contamination was observed in the sulfur-containing positive electrode active material powder after the sulfur-containing substance removal step, and a large amount of sulfur adhered to the inner surface of the second sample chamber as in Example 1.

[0061] [Evaluation] 100 mg of the sulfur-containing positive electrode active material powder obtained in Examples 1 to 3 was put into concentrated nitric acid and dissolved by microwave heat treatment. The obtained solution was diluted, and the respective elements of Li, Ni, and S in the obtained diluted solution were quantitatively analyzed using an ICP emission spectrometer. The obtained contents of Li, Ni, and S were converted into molar ratios. The results are shown in Table 1 below. Also, the theoretical composition ratio of the positive electrode active material was determined from the obtained contents of Li and Ni. The value obtained by dividing the molar ratio of the obtained S by the molar ratio of oxygen in the theoretical composition ratio of the positive electrode active material and taking it as a percentage was calculated as the sulfur substitution rate. The results are shown in Table 1 below.

[0062]

Table 1

[0063] [Example 4] The amount of sulfur introduced into the second sample chamber of the quartz array type reaction vessel was set to 0.159 g, the amount of the positive electrode active material powder introduced into the first sample chamber was set to 10.325 g, and a muffle furnace was used instead of a tubular furnace. The reaction process was carried out in the same manner as in Example 1 except that the heat treatment was performed at 180 °C for 8 hours. As a result of visually observing the sulfur-containing positive electrode active material powder after the reaction process, the mixing of sulfur with a particle size of about 1 mm was confirmed. The mixture containing the positive electrode active material powder and sulfur was classified using a sieve with an opening of 180 μm. As a result of visually observing the sulfur-containing positive electrode active material powder that passed through the sieve, no mixing of sulfur was found.

[0064] [Example 5] The amount of sulfur introduced into the second sample chamber of the quartz array type reaction vessel was set to 0.154 g, the amount of the positive electrode active material powder introduced into the first sample chamber was set to 10.170 g, and the reaction process was carried out in the same manner as in Example 4 except that the heat treatment was performed at 200 °C for 8 hours. As a result of visually observing the sulfur-containing positive electrode active material powder after the reaction process, the mixing of sulfur with a particle size of about 1 mm was confirmed. The mixture containing the positive electrode active material powder and sulfur was classified using a sieve with an opening of 180 μm. As a result of visually observing the sulfur-containing positive electrode active material powder that passed through the sieve, no mixing of sulfur was found.

[0065] Regarding the sulfur-containing positive electrode active material powders obtained in Examples 1 to 3, in the same manner as above, the contents of Li, Ni, and S were measured, and the molar ratio and sulfur substitution rate were calculated. The results are shown in Table 2 below.

[0066]

Table 2

[0067] From the above results, it was confirmed that according to the present invention, by performing the sulfur-containing substance removal step, a sulfur-containing oxide-based positive electrode active material with a small amount of sulfur-containing substance mixing can be produced.

Explanation of Signs

[0068] 1 Oxide-based positive electrode active material 2 Sulfur-containing substance 10 Reaction vessel 11 First sample chamber 12 Second sample chamber 13 Hollow connecting part

Claims

1. A reaction step of bringing an oxide-based cathode active material into contact with a sulfur-containing gas to produce a sulfur-containing oxide-based cathode active material, and A method for producing a sulfur-containing oxide-based cathode active material, comprising a sulfur-containing substance removing step of removing sulfur-containing substances mixed in the sulfur-containing oxide-based cathode active material.

2. The method for producing a sulfur-containing oxide-based cathode active material according to claim 1, wherein the sulfur-containing gas is sulfur gas.

3. In the reaction step, sulfur gas is generated by heating a container containing the oxide-based cathode active material and sulfur, and the oxide-based cathode active material is brought into contact with the sulfur gas. The method for producing a sulfur-containing oxide-based cathode active material according to claim 2.

4. The method for producing a sulfur-containing oxide-based cathode active material according to claim 3, wherein the container containing the oxide-based cathode active material and the sulfur is depressurized until it becomes less than 1×10 ３ Pa, and then the container is sealed and heated.

5. The method for producing a sulfur-containing oxide-based cathode active material according to claim 3, including a cooling step of cooling the sulfur-containing oxide-based cathode active material after the reaction step and before the sulfur-containing substance removing step.

6. In the sulfur-containing substance removing step, the method for removing the sulfur-containing substance is a method of heating the sulfur-containing oxide-based cathode active material to vaporize the sulfur-containing substance to produce a sulfur-containing vaporized product. The method for producing a sulfur-containing oxide-based cathode active material according to claim 1 or 2.

7. In the sulfur-containing substance removing step, the sulfur-containing oxide-based cathode active material is heated in a sealed container. The method for producing a sulfur-containing oxide-based cathode active material according to claim 6.

8. In the sulfur-containing substance removing step, the sealed container is heated so as to have a temperature gradient, the sulfur-containing oxide-based cathode active material is heated at the position where the temperature of the sealed container is the highest, and the sulfur-containing vaporized product is solidified at the position where the temperature of the sealed container is the lowest. The method for producing a sulfur-containing oxide-based cathode active material according to claim 7.

9. In the sulfur-containing substance removing step, a part of the sealed container is heated. The method for producing a sulfur-containing oxide-based cathode active material according to claim 7.

10. In the sulfur-containing substance removing step, the method for removing the sulfur-containing substance is a method of classifying the sulfur-containing oxide-based cathode active material to separate the sulfur-containing oxide-based cathode active material and the sulfur-containing substance. The method for producing a sulfur-containing oxide-based cathode active material according to claim 1 or 2.

11. The method for producing a sulfur-containing oxide-based cathode active material according to claim 1 or 2, wherein the oxide-based cathode active material contains at least one transition metal element selected from the group consisting of nickel, cobalt, and manganese, and lithium.

12. The method for producing a sulfur-containing oxide-based positive electrode active material according to claim 1 or 2, wherein the oxide-based positive electrode active material is for a lithium-ion battery.

13. A reaction step of generating a sulfur-containing oxide-based positive electrode active material by bringing an oxide-based positive electrode active material into contact with a sulfur-containing gas in a sealed container, and a sulfur-containing substance removing step of heating the sulfur-containing oxide-based positive electrode active material in the sealed container to vaporize sulfur-containing substances mixed in the sulfur-containing oxide-based positive electrode active material to generate sulfur-containing vaporized products, the method for producing a sulfur-containing oxide-based positive electrode active material.

14. A sulfur-containing oxide-based positive electrode active material obtained by the method for producing a sulfur-containing oxide-based positive electrode active material according to claim 1 or 2.

Images