Manufacturing device and manufacturing method of positive electrode active material for lithium ion secondary battery

Abstract

This disclosure relates to an apparatus and method for manufacturing positive electrode active materials for lithium-ion secondary batteries. An apparatus for manufacturing positive electrode active materials for lithium-ion secondary batteries, capable of improving productivity, is provided. The apparatus includes a conveying unit and a heating unit. The conveying unit conveys a positive electrode active material material comprising a metal compound and a lithium compound. The heating unit heats the positive electrode active material material. The heating unit has at least one heating roller that heats the positive electrode active material material through heat conduction. The wrap angle of the at least one heating roller is greater than 180° and less than 360°.

Description

Technical Field

[0001] This application relates to an apparatus and a method for manufacturing positive electrode active materials for lithium-ion secondary batteries. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in power supplies for laptops, portable devices, and vehicles. Therefore, there is a need to improve the productivity of lithium-ion rechargeable batteries, as well as the productivity of the positive electrode active materials used in them.

[0003] A typical method for manufacturing positive electrode active materials for lithium-ion secondary batteries is as follows. First, a metal hydroxide containing nickel, etc., which will serve as a precursor, is mixed with a lithium compound (e.g., lithium hydroxide, lithium carbonate, etc.) to obtain a positive electrode active material. Next, the positive electrode active material is pre-fired (simulated firing) to oxidize it. Specifically, the metal hydroxide is oxidized to a metal oxide, and the lithium compound is oxidized to lithium oxide. Then, the pre-fired positive electrode active material is filled into a prescribed crucible and fired. During firing, the metal oxide and lithium oxide in the positive electrode active material react to obtain lithium metal oxide, which serves as the positive electrode active material. Furthermore, the obtained positive electrode active material is recycled and utilized in lithium-ion secondary batteries. For example, such a method for manufacturing positive electrode active materials is disclosed in Patent Documents 1-3.

[0004] In the pre-firing process of the positive electrode active material, a firing apparatus such as a rotary kiln is used. A rotary kiln is a device that can simultaneously stir and heat the positive electrode active material in an oxidizing atmosphere, thereby promoting the oxidation of the positive electrode active material. The reason for pre-firing the positive electrode active material is that the oxidation reaction of metal hydroxides and lithium compounds is an endothermic reaction; therefore, it is to prevent uneven temperature distribution of the positive electrode active material due to the endothermic reaction during the firing process.

[0005] In the firing process of the positive electrode active material, a firing apparatus such as a roller hearth kiln is used. The roller hearth kiln can heat the positive electrode active material at a higher temperature than in the pre-firing process, and can manufacture the positive electrode active material by reacting the metal oxide and lithium oxide in the material. Furthermore, pressure can be applied to increase the density of the positive electrode active material when filling it into the sagger. By increasing the density of the positive electrode active material, the contact area between the metal oxide and lithium oxide in the material increases, thus promoting firing.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-113429

[0009] Patent Document 2: Japanese Patent Application Publication No. 2019-175694

[0010] Patent Document 3: Japanese Patent Application Publication No. 2020-198195 Summary of the Invention

[0011] Since rotary kilns are used to oxidize metal hydroxides and / or lithium compounds, it is necessary to actively feed air or oxygen into the kiln to create an oxidizing atmosphere. However, this active feeding of air or oxygen increases production costs.

[0012] A roller hearth furnace is a device used to sinter pre-fired positive electrode active material. To ensure uniform heating, the positive electrode active material needs to be filled into a sagger. However, due to the flow pattern of hot air within the furnace, the positive electrode active material is prone to temperature inhomogeneity. When heating the positive electrode active material for a short time while it is under these uneven temperatures, the crystallinity of the manufactured positive electrode active material deviates. Therefore, when using a roller hearth furnace to manufacture positive electrode active materials, prolonged heating of the material is necessary to suppress temperature inhomogeneity, which increases production costs. Furthermore, the need for prolonged heating necessitates the large-scale construction of the equipment.

[0013] Therefore, the purpose of this application is to provide an apparatus and method for manufacturing positive electrode active materials for lithium-ion secondary batteries that can improve productivity.

[0014] As a means of solving the above-mentioned problems, this disclosure provides an apparatus for manufacturing positive electrode active material for lithium-ion secondary batteries, which includes a transport unit and a heating unit. The transport unit transports positive electrode active material material, which includes a lithium compound and a metal compound, wherein the metal compound includes at least one metal element selected from nickel, cobalt and manganese. The heating unit heats the positive electrode active material material and has at least one heating roller. The heating roller heats the positive electrode active material material by heat conduction. The wrap angle of the at least one heating roller is greater than 180° and less than 360°.

[0015] The manufacturing apparatus described above can also be configured as follows: that is, the manufacturing apparatus may have a plurality of heating rollers, wherein heating rollers that heat one side of the positive electrode active material and heating rollers that heat the other side of the positive electrode active material are alternately arranged from the upstream side to the downstream side in the transport direction, and adjacent heating rollers are arranged facing each other in such a way that the positive electrode active material is clamped in.

[0016] In the aforementioned manufacturing apparatus, the heating section can heat the positive electrode active material to 700°C or higher and 1000°C or lower. Furthermore, in the aforementioned manufacturing apparatus, the heating section can heat the positive electrode active material under an oxidizing atmosphere.

[0017] In the aforementioned manufacturing apparatus, the conveying unit may have a conveying member made of a porous heat-resistant component, and the heating roller may heat the positive electrode active material through the porous heat-resistant component.

[0018] The aforementioned manufacturing apparatus may also include a forming unit upstream of the heating section in the transport direction for forming the positive electrode active material into a sheet shape. Additionally, the aforementioned manufacturing apparatus may include a recovery section for recovering the positive electrode active material obtained through the heating section.

[0019] As a means of solving the above-mentioned problems, this disclosure provides a method for manufacturing a positive electrode active material for lithium-ion secondary batteries, which includes a positive electrode active material material preparation step and a heating step for heating the positive electrode active material material. In the positive electrode active material material preparation step, a lithium compound and a metal compound are mixed to obtain a positive electrode active material material, wherein the metal compound contains at least one metal element selected from nickel, cobalt, and manganese. In the heating step, at least one heating roller is used to transport the positive electrode active material material while heating it by heat conduction, wherein the wrap angle of the at least one heating roller is more than 180° and less than 360°.

[0020] In the heating process of the above manufacturing method, heating rollers can be used to alternately heat both sides of the positive electrode active material and heat one side of the positive electrode active material.

[0021] In the above manufacturing method, during the heating step, the positive electrode active material can be heated to 700°C or higher and 1000°C or lower. Furthermore, in the above manufacturing method, during the heating step, the positive electrode active material can be heated under an oxidizing atmosphere. Moreover, in the above manufacturing method, during the heating step, the positive electrode active material can be heated through a porous heat-resistant component.

[0022] The manufacturing method described above may also include a forming step that shapes the positive electrode active material into a sheet shape before the heating step. Additionally, the manufacturing method may include a recovery step that recycles the positive electrode active material obtained through the heating step.

[0023] According to this disclosure, the manufacturing productivity of positive electrode active materials can be improved. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an apparatus 100 for manufacturing positive electrode active materials for lithium-ion secondary batteries.

[0025] Figure 2 This is a diagram used to illustrate the wrap angle x.

[0026] Figure 3 This is an enlarged view of the heating roller 31 and the contact roller 32.

[0027] Figure 4 This is a flowchart of a method 1000 for manufacturing positive electrode active material for lithium-ion secondary batteries.

[0028] Figure 5 This is a flowchart of the manufacturing method of positive electrode active material for lithium-ion secondary batteries 2000.

[0029] Figure 6 This is a flowchart of method 3000 for manufacturing positive electrode active material for lithium-ion secondary batteries.

[0030] Explanation of reference numerals in the attached figures

[0031] 1: Positive electrode active material

[0032] 2: Positive electrode active material

[0033] 10: Delivery Unit

[0034] 11: Transporting components

[0035] 20: Forming Unit

[0036] 30: Heating section

[0037] 31: Heating roller

[0038] 32: Contact Roller

[0039] 40: Recycling Department

[0040] 41: Roller

[0041] 100: Apparatus for manufacturing positive electrode active materials for lithium-ion secondary batteries Detailed Implementation

[0042] [Apparatus for manufacturing positive electrode active materials for lithium-ion secondary batteries]

[0043] The apparatus for manufacturing positive electrode active material for lithium-ion secondary batteries disclosed herein will be described with reference to an embodiment of an apparatus 100 for manufacturing positive electrode active material for lithium-ion secondary batteries (which is sometimes referred to as "manufacturing apparatus 100" in this specification). Figure 1 A schematic diagram of the manufacturing apparatus 100 is shown. Here, Figure 1 The left and right directions are used as the transport direction, the up and down direction is used as the height direction, and the front and back direction (inside and outside direction) is used as the width direction.

[0044] like Figure 1 As described, the manufacturing apparatus 100 includes a transport unit 10, a forming unit 20, a heating unit 30, and a recovery unit 40. Furthermore, in Figure 1 The document describes positive electrode active material 1 as a raw material and positive electrode active material 2 as a product.

[0045] <Positive Electrode Active Material 1>

[0046] The positive electrode active material 1 is a material containing metal compounds and lithium compounds. Alternatively, it may contain degraded and fragmented positive electrode active material 2, such as recycled materials. Even with degraded positive electrode active material 2, it can be sintered in the heating section 30 with high heat homogeneity.

[0047] The positive electrode active material 1 can be obtained by mixing these materials. The mixing method is not particularly limited and can be any known method. For example, a mortar and pestle can be used for mixing, or a blender can be used for mixing.

[0048] (Metallic compounds)

[0049] A metal compound is a compound containing at least one metallic element selected from nickel, cobalt, and manganese. Additionally, a metal compound may contain nickel, nickel and cobalt, or nickel, cobalt, and manganese. Furthermore, it may contain other metallic elements. For example, a metal compound may also contain aluminum. Alternatively, a metal compound may contain aluminum instead of manganese.

[0050] For example, in a metallic compound, the molar ratio of each metallic element can be Ni:Co:Mn = x:y:z (x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1), or Ni:Co:Al = x:y:z (x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1).

[0051] The metal compound can be a metal hydroxide, metal oxide, metal carbonate, or metal perhydroxide. These metal compounds can be used alone or in combination. Preferably, the metal compound is a metal hydroxide or metal oxide.

[0052] As a metal hydroxide, known metal hydroxides containing at least one metallic element selected from nickel, cobalt, and manganese can be used. Examples include Ni. x Co y Mn z (OH) 2+α (x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ α < 1), and Ni x Co yAl z (OH) 2+α (x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ α < 1). As a metal oxide, known metal oxides containing at least one metallic element selected from nickel, cobalt, and manganese can be used. Examples include Ni. x Co y Mnz(O) 2+α (x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1, -1 ≤ α < 0), and Ni x Co y Al z (O) 2+α (x=1-y-z, 0≤y<1, 0≤z<1, -1≤α<0).

[0053] Metal compounds can be prepared using known methods. Examples of methods for preparing metal hydroxides and metal oxides are shown below. However, the methods for preparing metal compounds are not limited to these.

[0054] For example, crystallization can be used as a method for preparing metal hydroxides. The following describes an example of a method for preparing metal hydroxides using crystallization.

[0055] First, a metal source solution is prepared by dissolving the Ni, Co, and Mn (or Al) sources in an aqueous solvent (e.g., deionized water). Various metal salts (i.e., Ni, Co, and Mn (or Al) salts) can be used as metal sources. The type of metal salt is not particularly limited; known metal salts such as hydrochlorides, sulfates, nitrates, carbonates, and hydroxides can be used. The order in which these metal sources are added to the aqueous solvent is not particularly limited. Alternatively, aqueous solutions of each metal source can be prepared separately and then mixed. The proportions of the metal sources are appropriately adjusted to obtain the desired metal hydroxide.

[0056] Next, under an inert gas atmosphere, a metal source solution and an aqueous NH3 solution are added dropwise to the alkaline aqueous solution while stirring. The alkaline aqueous solution can be an aqueous sodium hydroxide solution, etc. The pH of the alkaline aqueous solution is set to, for example, 11 to 13. The aqueous NH3 solution is added dropwise while maintaining a concentration of, for example, 5 g / L to 15 g / L. Since the pH of the reaction solution gradually decreases by adding the metal source solution and the aqueous NH3 solution to the alkaline aqueous solution, the pH can also be maintained within a specified range by appropriately adding the alkaline aqueous solution.

[0057] Then, after a certain period, suction filtration is performed to recover the precipitate. The obtained precipitate is then washed with water and dried to obtain the metal hydroxide. The water washing of the precipitate can be performed multiple times. The precipitate can be dried by air drying or by heating. Heating can be carried out at temperatures, for example, 120–300°C. The drying time is, for example, 6–18 hours.

[0058] Oxidative roasting involves heating a metal hydroxide under an oxidizing atmosphere. The heating temperature is not particularly limited as long as it is sufficient to convert the metal hydroxide into a metal oxide; for example, 700°C to 800°C. The heating time is also not particularly limited, as long as it is sufficient to convert the metal hydroxide into a metal oxide; for example, 0.5 hours to 3 hours. This heating can be carried out using a roasting apparatus such as a rotary kiln.

[0059] The average particle size of the metal compound is not particularly limited, for example, it is in the range of 1 μm to 1 mm. In this specification, the term "average particle size" refers to the particle size at which the cumulative value of the particle size distribution on a volume basis obtained by laser diffraction-scattering method is 50%, i.e., the median particle size.

[0060] The proportion of metal compounds in the positive electrode active material is appropriately set to obtain the desired positive electrode active material.

[0061] (Lithium compounds)

[0062] Lithium compounds are not particularly limited to any compound containing lithium; well-known lithium compounds can be used. Examples include lithium oxide, lithium hydroxide, lithium nitrate, and lithium carbonate. Lithium hydroxide, lithium nitrate, and lithium carbonate can be oxidized to lithium oxide.

[0063] The type of lithium compound is appropriately selected based on the type of metal compound. This is because the heating temperature (firing temperature) varies depending on the type of metal compound. For example, when using metal hydroxides or metal oxides containing nickel, cobalt, and manganese as the metal compound, a firing temperature of around 800°C is required, so lithium carbonate is preferred. Conversely, when using metal hydroxides or metal oxides containing nickel, cobalt, and aluminum as the metal compound, a firing temperature of around 500°C is required, so lithium hydroxide is preferred.

[0064] The proportion of lithium compounds in the positive electrode active material is appropriately set to obtain the desired positive electrode active material.

[0065] (Shape of positive electrode active material 1)

[0066] The shape of the positive electrode active material 1 is not particularly limited and can be sheet-like. By making the positive electrode active material 1 sheet-like, it becomes easier to heat it evenly to the interior. As a result, heating unevenness is reduced, and deviations in the crystallinity of the manufactured positive electrode active material 2 are suppressed. In addition, by making the positive electrode active material 1 sheet-like, it can be easily broken down in the recovery section 40.

[0067] The thickness of the sheet-like positive electrode active material 1 is not particularly limited. For example, it can be 0.1 mm or more, 0.5 mm or more, 1 mm or more, 2 mm or more, less than 50 mm, less than 30 mm, less than 30 mm, less than 20 mm, less than 10 mm, or less than 5 mm. If the sheet-like positive electrode active material 1 is too thick, it will be difficult to heat it uniformly; if it is too thin, the productivity will decrease.

[0068] The positive electrode active material 1 can be formed into a sheet using the forming unit 20 and / or the heating roller 31, but it can also be formed into a sheet in advance by pressing or the like. However, the positive electrode active material 1 can also be formed into a sheet in advance, and then the positive electrode active material 1 can be formed into a specified thickness using the forming unit 20 and / or the heating roller 31.

[0069] <Transportation Unit 10>

[0070] The transport unit 10 is a component used to transport the positive electrode active material 1. For example... Figure 1 As shown, the transport unit 10 includes a transport member 11 for transporting the positive electrode active material 1. Additionally, the transport unit 10 includes a drive unit (not shown) for driving the transport member 11.

[0071] (Transporting component 11)

[0072] The transport member 11 is a component (transfer type) for transporting the positive electrode active material 1. The transport member 11 is a sheet-like component, driven from the upstream side to the downstream side in the transport direction by a drive unit. The transport member 11 transports the positive electrode active material 1 in a state where it is loaded, therefore it needs to be positioned below the positive electrode active material 1. Alternatively, it can be arranged as follows... Figure 1 As described, it is also disposed on top of the positive electrode active material 1. That is, the positive electrode active material 1 can also be transported in a state where it is held by the transport member 11.

[0073] As will be described later, the manufacturing apparatus 100 heats the positive electrode active material 1 by contact heating. Therefore, the positive electrode active material 1 could be heated by direct contact with the heating roller 31, but this would cause the positive electrode active material 1 to adhere to the heating roller 31, resulting in a decrease in productivity. Therefore, in the manufacturing apparatus 100, by having the heating roller 31 contact the positive electrode active material 1 through the transport member 11, the adhesion of the positive electrode active material 1 to the heating roller 31 is suppressed. For this reason, when heating the positive electrode active material 1 above and below, the positive electrode active material 1 can be held and transported by the transport member 11.

[0074] Since the conveying member 11 is in contact with the heating roller 31, it needs to be made of a component (heat-resistant component) that is resistant to the heating temperature of the heating section 30. For example, the heat-resistant component needs to have a heat resistance of 900°C or higher. Examples of such heat-resistant components include quartz glass cloth and silica fiber cloth.

[0075] In the case where the positive electrode active material 1 contains materials such as metal hydroxides and lithium hydroxides that are oxidized into oxides, oxygen needs to be introduced from the outside in order to carry out the firing of the positive electrode active material 1. Furthermore, the positive electrode active material 1 sometimes generates gases such as water (water vapor) and carbon dioxide during firing. Therefore, the firing of the positive electrode active material 1 is preferably carried out in an environment where gas exchange is possible. Therefore, the transport member 11 can also be made of a porous heat-resistant member capable of efficient gas exchange with the outside. The pore size of the porous heat-resistant member is not particularly limited as long as it allows for efficient gas exchange and prevents leakage of the positive electrode active material 1 to the outside. For example, the pore size of the porous heat-resistant member can be less than 20 μm, less than 10 μm, less than 5 μm, more than 3 μm, more than 1 μm, or more than 0.5 μm. If the pore size of the porous heat-resistant member is too large, the positive electrode active material 1 is prone to leakage to the outside; if it is too small, the efficiency of gas exchange with the outside is reduced. Examples of such porous heat-resistant components include fibrous heat-resistant components. Examples include quartz glass cloth and silica fiber cloth.

[0076] Here, the pore size of the porous heat-resistant component is the length of the diagonal of the mesh, calculated based on the fiber diameter and product density (unit: fibers / mm).

[0077] <Forming Unit 20>

[0078] The forming unit 20 is a component that shapes the positive electrode active material 1 into a sheet shape. For example... Figure 1As described, the forming unit 20 is positioned upstream of the heating section 30 in the transport direction. Furthermore, in the manufacturing apparatus 100, the forming unit 20 is an arbitrary component. This is because, as described above, the positive electrode active material 1 can also be pre-formed into a sheet shape.

[0079] As forming unit 20, a powder quantity control component can be used to form a sheet-like structure by controlling the powder quantity of the transported positive electrode active material 1. For example, Figure 1 The powder quantity control tool described herein. Additionally, a component formed by pressing the positive electrode active material 1 into a sheet shape can be cited as an example.

[0080] The thickness of the sheet-like positive electrode active material 1 formed by the forming unit 20 is not particularly limited. For example, it can be 0.1 mm or more, 0.5 mm or more, 1 mm or more, 2 mm or more, less than 50 mm, less than 30 mm, less than 30 mm, less than 20 mm, less than 10 mm, or less than 5 mm.

[0081] <Heating section 30>

[0082] The heating section 30 is used to heat (fire) the positive electrode active material 1. For example... Figure 1 As described, the heating unit 30 has a rectangular housing and six heating rollers 31 are provided inside the housing. In addition, the heating unit 30 has contact rollers 32 at positions adjacent to the heating rollers 31 on the upstream and downstream sides in the transport direction.

[0083] The heating unit 30 can heat the positive electrode active material 1 to 700°C or higher, 800°C or higher, 900°C or higher, 1100°C or lower, or 1000°C or lower. Anyone skilled in the art can set the temperature to appropriately sinter the positive electrode active material 1. The positive electrode active material 1 is heated by contact with the heating roller 31, as described later. Therefore, the heating roller 31 is actually heated to a predetermined temperature. Furthermore, the temperatures of the heating rollers 31 can be the same or different. For example, the heating roller 31 disposed on the upstream side of the transport direction can be set to a low temperature for oxidation purposes, while the heating roller 31 disposed on the downstream side of the transport direction can be set to a high temperature for sintering purposes.

[0084] The heating section 30 can also heat the positive electrode active material 1 in an oxidizing atmosphere. This is to promote the oxidation reaction of the positive electrode active material 1. To create an oxidizing atmosphere inside, the heating section 30 is equipped with an air supply section (not shown). By supplying air or oxygen into the interior of the heating section from the air supply section, the heating section 30 can be maintained in an oxidizing atmosphere. Alternatively, air or oxygen can be continuously supplied in a manner that maintains the heating section 30 at a negative pressure. A known blower or the like can be used as the air supply section. Furthermore, if the positive electrode active material does not contain materials that undergo an oxidation reaction, since it is not necessary to oxidize the positive electrode active material 1 in the heating section 30, it is not necessary to create an oxidizing atmosphere in the heating section 30.

[0085] In this specification, "oxidizing atmosphere" refers to an atmosphere capable of oxidizing the target material. For example, it could be an atmosphere in a space supplied with and filled with a gas containing 1% or more oxygen (e.g., air or oxygen). The oxygen concentration in the space can be appropriately set according to the rate of oxidation of the target material.

[0086] (Heating roller 31)

[0087] The heating roller 31 is a component that heats the positive electrode active material 1 through heat conduction. "Heating the positive electrode active material 1 through heat conduction" refers to contact heating, meaning that the heating roller is in direct or indirect contact with the positive electrode active material 1. "Indirectly" means that the heating roller 31 is in contact with the positive electrode active material 1 through other components. Figure 1 In this process, the heating roller 31 is brought into contact with the positive electrode active material 1 through the transport member 11 to heat the material. Alternatively, the heating roller 31 may be brought into contact with the positive electrode active material 1 through a member other than the transport member 11, or through the transport member 11 and other members, to heat the material. In this specification, unless otherwise specified, "direct or indirect contact" is sometimes simply expressed as "contact".

[0088] The heating roller 31 heats the positive electrode active material 1 through contact heating, characterized by efficient heating of the contact area and high heat uniformity. Therefore, the firing time of the positive electrode active material 1 can be reduced, and crystallinity deviations can be suppressed. Furthermore, due to the high heat uniformity of contact heating, although conventional manufacturing of positive electrode active materials requires two heating processes—pre-firing and firing—the manufacturing apparatus 100 can obtain the positive electrode active material by firing the material in a single process. Therefore, the manufacturing apparatus 100 improves the productivity of positive electrode active material manufacturing. Additionally, by shortening the heating time, the equipment can be miniaturized.

[0089] In addition, by using the heating roller 31, the positive electrode active material 1 can be heated while being transported, thus enabling continuous production of the positive electrode active material 2.

[0090] like Figure 1 As described, the heating unit 30 has six heating rollers 31. The arrangement and number of the heating rollers 31 are not particularly limited. Figure 1 As described, heating rollers for heating one side (e.g., the top) and the other side (e.g., the bottom) of the positive electrode active material 1 can be alternately arranged from upstream to downstream in the transport direction. This allows for uniform heating of both sides of the positive electrode active material 1, thereby reducing temperature unevenness.

[0091] Furthermore, adjacent heating rollers 31 can be arranged facing each other to clamp the positive electrode active material 1. This allows for simultaneous heating of both sides of the positive electrode active material 1, thereby improving heating efficiency and reducing temperature unevenness. Additionally, by arranging adjacent heating rollers 31 facing each other, pressure can be applied and the positive electrode active material 1 heated. That is, the positive electrode active material 1 can be heated and formed into a sheet. The thickness of the sheet-like positive electrode active material 1 can be adjusted by adjusting the gap between the facing heating rollers 31. For example, the gap between the facing heating rollers 31 can be gradually narrowed from the upstream side to the downstream side in the transport direction. This allows the heating rollers 31 to be arranged to reliably clamp the positive electrode active material 1, thus reducing temperature unevenness. Moreover, since the heating rollers 31 are not intended for forming the positive electrode active material 1, the gap between the heating rollers 31 can be adjusted less strictly.

[0092] The heating rollers 31 are arranged facing each other and are set with a specified wrap angle. Figure 2 A diagram illustrating the wrap angle is shown. Additionally, Figure 3 Show Figure 1 Enlarged view of heating roller 31 and contact roller 32.

[0093] The term "corner wrapping" refers to... Figure 2 , Figure 3 The center angle of the heating roller 31, indicated by "x", is determined based on the range from the point of contact between the positive electrode active material 1 (conveyor member 11) and the heating roller 31 until its separation. This is achieved through... Figure 2By setting the wrap angle x of the heating roller 31 as shown, the contact area between the heating roller 31 and the positive electrode active material 1 can be increased, thereby improving the heating efficiency. Furthermore, since the positive electrode active material 1 can be moved by smoothing it, heating unevenness can be reduced, and gas exchange can be promoted. Adhesion of the positive electrode active material 1 to the heating roller 31 can also be suppressed. Moreover, the positive electrode active material 1 sandwiched between the opposing heating rollers 31 is fired by being heated from both sides; on the other hand, the positive electrode active material 1, although not sandwiched between heating rollers 31 but in contact with one heating roller 31, can be heated on the contact surface while gas exchange occurs on the open surface that has not been in contact with the heating roller 31, thus promoting the firing of the positive electrode active material 1. Therefore, by using the method shown... Figure 1 , Figure 3 The heating roller 31 is configured as shown, which can alternately heat both sides of the positive electrode active material 1 (heat forming) and heat one side of the positive electrode active material 1, thereby alternating heating and efficient gas exchange to promote firing.

[0094] The wrap angle x of the heating roller 31 is greater than 180° and less than 360°. By setting the wrap angle x to greater than 180°, the positive electrode active material 1 is transported in the height direction, thus promoting the rolling of the positive electrode active material 1 during transport, improving heat uniformity, and promoting gas exchange. This suppresses uneven oxidation of the positive electrode active material 2 as a product, improving its quality. Furthermore, since the contact time between the heating roller 31 and the positive electrode active material 1 can be extended, the equipment can be miniaturized. Therefore, compared to the case where the wrap angle x is less than 180°, the manufacturing productivity of the positive electrode active material 2 can be improved. The wrap angle x can be set to 210° or more, 240° or more, 270° or more, 300° or more, less than 360°, less than 350°, or less than 330°.

[0095] The wrap angle x can be set according to the configuration of the heating roller 31 and the contact roller 32. Figure 1 , Figure 3 In this configuration, heating rollers 31 are arranged such that their wrap angles x are predetermined. This arrangement allows the wrap angles x of the heating rollers 31, except for the upstream and downstream heating rollers 31, to be set to desired values. Furthermore, in the transport direction, contact rollers 32 are arranged adjacent to the upstream and downstream heating rollers 31. This allows the wrap angles of the upstream and downstream heating rollers 31 to be set to desired values.

[0096] like Figure 3As shown, the heating rollers 131 are respectively configured such that the straight line connecting the centers of adjacent heating rollers 131 coincides with one of the straight lines forming the wrap angle. This ensures that the positive electrode active material 1 is always in contact with the heating rollers 131, thereby improving heating efficiency and shortening heating time.

[0097] The material of the heating roller 31 is not particularly limited. For example, the heating roller 31 can be made of a material with heat resistance of 1000°C or higher. Examples of such materials include inorganic materials such as ceramics and metallic materials such as iron.

[0098] The heating roller can rotate in either forward (in the same direction as the conveying direction) or reverse (in the opposite direction to the conveying direction). The rotational speed of the heating roller is not particularly limited. Those skilled in the art can appropriately select the most suitable rotational direction and speed that balances heat evenness and economy.

[0099] The surface of the heating roller 31 can also be uneven. By having an uneven surface, the positive electrode active material 1 in contact with the heating roller 31 can be moved, thereby reducing uneven heating and promoting gas exchange. In addition, it can also suppress the adhesion of the positive electrode active material 1 to the heating roller.

[0100] The length of the heating roller 31 in the width direction is not particularly limited, but can be set to, for example, the same length as the length of the conveying member 11 in the width direction. The diameter of the heating roller 31 is appropriately set from the viewpoint of the size of the heating section 30 and the proper heating of the positive electrode active material 1.

[0101] (Contact roller 32)

[0102] Contact rollers 32 are respectively positioned adjacent to the heating rollers 31 on the upstream and downstream sides of the conveying direction. As described above, the contact rollers 32 are used to set the wrap angle of the adjacent heating rollers 31. The contact rollers 32 can be positioned facing the adjacent heating rollers 31.

[0103] However, in the manufacturing apparatus 100, the contact roller 32 is an arbitrary component. Furthermore, the number of contact rollers 32 can be at least one. Moreover, the position of the contact roller 32 is not particularly limited, as long as it is positioned adjacent to the heating roller 31 with the set wrap angle.

[0104] The material of the contact roller 32 is not particularly limited. For example, it can be appropriately selected from the material of the heating roller 31. The length of the contact roller 32 in the width direction is not particularly limited, but can be set to, for example, the same length as the length in the width direction of the conveying member 11. The diameter of the contact roller 32 can be appropriately set based on the size of the heating section 30 and the wrap angle of the heating roller 31.

[0105] <Recycling Department 40>

[0106] The recovery unit 40 is a component that recovers the positive electrode active material 2 obtained through the heating unit 30. For example... Figure 1 As shown, when the positive electrode active material 2 is transported by clamping it with the transport member 11, the positive electrode active material 2 inside can be recovered by separating the transport member 11 in the recovery section 40. For this separation of the transport member 11, a predetermined roller 41 can be appropriately configured. Furthermore, the recovered positive electrode active material 2 can also be crushed. The crushing method for the positive electrode active material 2 is not particularly limited; the positive electrode active material 2 can be crushed using a hammer or the like after recovery. Additionally, when the positive electrode active material 1 is in sheet form, since the obtained positive electrode active material 2 is also in sheet form, it can be easily crushed. For example, as... Figure 1 As shown, the process involves simply recycling the positive electrode active material 2 to break it down.

[0107] When a porous heat-resistant component is used for the transport component 11, sometimes a positive electrode active material 2 is embedded in the internal pores. In such cases, by applying vibration while the transport component 11 is flipped over, air is sprayed onto the surface that has never been in contact with the positive electrode active material 2. Figure 1 (The arrows, etc.) can recover the positive electrode active material 2 buried inside, thereby improving productivity. Devices that apply vibration can be, for example, a vibration knocker. Devices that blow air can be, for example, a blower.

[0108] <Positive Electrode Active Material 2>

[0109] The positive electrode active material 2 obtained using the manufacturing apparatus 100 has a composition in which lithium is intercalated into a metal oxide. For example, the molar ratio of each metal element in the positive electrode active material 2 can be Li:Ni:Co:Mn = s:x:y:z (0.8 ≤ s ≤ 1.2, x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1), or it can be Li:Ni:Co:Al = s:x:y:z (0.8 ≤ s ≤ 1.2, x = 1 - y - z, 0 ≤ y < 1, 0 ≤ z < 1). Alternatively, the composition of the positive electrode active material 2 can be Li... s Ni x Co y Mn z (O) 2+α (0.8≤s≤1.2, x=1-y-z, 0≤y<1, 0≤z<1,-0.5≤α<0.5), could be Li s Ni x Co y Al z (O) 2+α(0.8≤s≤1.2, x=1-y-z, 0≤y<1, 0≤z<1, -0.5≤α<0.5).

[0110] Furthermore, since the positive electrode active material 1 is sintered through contact heating, deviations in the crystallinity of the resulting positive electrode active material 2 are suppressed. The crystallinity deviation is determined by XRD-based crystallite size measurement, and an optimal crystallite size (in nm) range is set to match the battery evaluation results of the positive electrode active material 2. For example, the crystallite size deviation range can be approximately ±200 nm, ±100 nm, or ±50 nm.

[0111] <Supplement>

[0112] In the manufacturing apparatus 100, multiple heating rollers 31 are used, but the manufacturing apparatus of this disclosure is not limited to this; at least one heating roller is sufficient. This is because only the number required for sintering the positive electrode active material 1 is needed. Furthermore, in the manufacturing apparatus of this disclosure, it is sufficient for at least one heating roller to have a wrap angle exceeding 180° and below 360°. This improves productivity. However, the more heating rollers with wrap angles exceeding 180° and below 360° are used, the greater the productivity improvement effect. Therefore, the wrap angle of all heating rollers can be set to exceed 180° and below 360°.

[0113] [Manufacturing method of positive electrode active material for lithium-ion secondary batteries]

[0114] The method for manufacturing the positive electrode active material for lithium-ion secondary batteries disclosed herein will be described with reference to a method 1000 for manufacturing the positive electrode active material for lithium-ion secondary batteries according to an embodiment (sometimes referred to as "manufacturing method 1000" in this specification).

[0115] Figure 4 A flowchart illustrating manufacturing method 1000 is shown. (Example) Figure 4 As shown, the manufacturing method 1000 includes a positive electrode active material preparation step S1, a forming step S2, a heating step S3, and a recycling step S4. Furthermore, the forming step S2, the heating step S3, and the recycling step S4 can be performed using the manufacturing apparatus disclosed herein.

[0116] <Cathode Active Material Fabrication Process S1>

[0117] Step S1, the process for producing the positive electrode active material, involves mixing a metal compound and a lithium compound to obtain the positive electrode active material. The metal compound, lithium compound, and positive electrode active material have been described previously and are therefore omitted here. Furthermore, the mixing method has also been described previously and is therefore omitted here.

[0118] <Forming process S2>

[0119] The forming process S2 is arbitrary and is performed before the heating process S3. The forming process S2 is the process of forming the positive electrode active material into a sheet shape. The method for forming the positive electrode active material into a sheet shape is not particularly limited. For example, the forming method described above can be used.

[0120] <Heating process S3>

[0121] Heating step S3 is a process of heating (firing) the positive electrode active material. Specifically, heating step S3 is a process of heating the positive electrode active material through heat conduction. The method of heating the positive electrode active material has been described above, so it will not be explained here.

[0122] <Recycling Process S4>

[0123] Recovery step S4 is a step to recover the positive electrode active material obtained through heating step S3. The method for recovering the positive electrode active material is not particularly limited. For example, the recovery method described above can be used.

[0124] <Other methods>

[0125] Figure 5 A method 2000 for manufacturing a positive electrode active material for lithium-ion secondary batteries (sometimes referred to as "manufacturing method 2000" in this specification) is shown. Manufacturing method 2000 is a manufacturing method obtained by adding an oxidation calcination step S5 to manufacturing method 1000. The oxidation calcination step S5 is a step performed before the positive electrode active material preparation step S1, in which a metal hydroxide is heated under an oxidizing atmosphere. The oxidation calcination method for the metal hydroxide has been described previously and is therefore omitted here. By providing the oxidation calcination step S5, a metal oxide can be obtained. Since the oxidation of metal hydroxide is an endothermic reaction, there is a concern that temperature inhomogeneity may occur if a positive electrode active material containing metal hydroxide is used in the heating step S3. Therefore, in manufacturing method 2000, an oxidation calcination step S5 is provided to pre-oxidize the metal hydroxide. However, since contact heating is used in the heating step S3, temperature inhomogeneity can be reduced even when using a positive electrode active material containing metal hydroxide.

[0126] Figure 6A method 3000 for manufacturing a positive electrode active material for lithium-ion secondary batteries (sometimes referred to as "manufacturing method 3000" in this specification) is shown. Manufacturing method 3000 is a method in which a pre-firing step S6 is performed before the forming step S2. The pre-firing step S6 is a step in which the positive electrode active material material is heated in an oxidizing atmosphere. Through the pre-firing step S6, metal hydroxides can be oxidized to metal oxides, and lithium compounds such as lithium hydroxides can be oxidized to lithium oxide. Since such an oxidation reaction is endothermic, by utilizing the pre-firing step S6 to complete the oxidation of the positive electrode active material material, temperature unevenness of the positive electrode active material material can be reduced in the heating step S3, and firing can be performed in a short time. However, since contact heating is used in the heating step S3, even without the pre-firing step S6, the positive electrode active material material containing metal hydroxides, etc., can be appropriately fired to obtain the positive electrode active material.

[0127] The heating temperature for the pre-firing process S6 is, for example, 700°C to 800°C. The heating time is, for example, 0.5 hours to 3 hours. Such heating can be carried out using a firing apparatus such as a rotary kiln.

[0128] Furthermore, in the manufacturing method disclosed herein, the oxidation roasting step S5 and the pre-firing step S6 can also be combined.

[0129] The apparatus and method for manufacturing the positive electrode active material for lithium-ion secondary batteries disclosed herein have been described above using various embodiments. This disclosure employs contact heating, which heats the positive electrode active material material via thermal conduction. Contact heating is characterized by efficient heating of the contact area and low temperature uniformity (high heat homogeneity) at the contact area. Therefore, this disclosure, employing contact heating, can reduce the firing time of the positive electrode active material material and suppress crystallinity deviations. Furthermore, unlike conventional methods, this disclosure allows for firing the positive electrode active material material using a single heating section (heating process) to obtain the positive electrode active material. Moreover, by shortening the heating time, the equipment can be miniaturized.

[0130] Furthermore, in this disclosure, the wrap angle x of at least one heating roller is set to be greater than 180° and less than 360°. This allows for the transport of the positive electrode active material in the height direction, thus promoting the rolling of the positive electrode active material during transport, improving heat uniformity, and facilitating gas exchange. Consequently, uneven oxidation of the positive electrode active material as a product is suppressed, improving its quality. Additionally, the contact time between the heating roller and the positive electrode active material can be extended, thus enabling further miniaturization of the equipment.

[0131] In summary, according to this disclosure, the manufacturing productivity of positive electrode active materials can be improved.

[0132] Industrial availability

[0133] The positive electrode active material manufactured according to this disclosure can be used in the positive electrode of any battery, including non-aqueous lithium-ion secondary batteries, aqueous lithium-ion secondary batteries, and all-solid-state lithium-ion secondary batteries.

Claims

1. A method for manufacturing a positive electrode active material for lithium-ion secondary batteries, comprising: The process for manufacturing positive electrode active material involves mixing a lithium compound with a metal compound to obtain the positive electrode active material, wherein the metal compound contains at least one metal element selected from nickel, cobalt, and manganese; and The heating process involves heating the positive electrode active material. In the heating process, multiple heating rollers are used to transport the positive electrode active material while simultaneously heating it through heat conduction. At least one of the heating rollers has a wrap angle exceeding 180° and less than 360°, wherein the wrap angle is the center angle of the heating roller, calculated from the point of contact between the positive electrode active material and the heating roller until its separation. In the heating process, the heating roller is used to alternately heat both sides of the positive electrode active material and one side of the positive electrode active material.

2. The manufacturing method according to claim 1, In the heating process, the positive electrode active material is heated to above 700°C and below 1000°C.

3. The manufacturing method according to claim 1 or 2, In the heating process, the positive electrode active material is heated in an oxidizing atmosphere.

4. The manufacturing method according to claim 1 or 2, The heating roller heats the positive electrode active material through a porous heat-resistant component.

5. The manufacturing method according to claim 1 or 2, Prior to the heating process, there is a forming process in which the positive electrode active material is shaped into a sheet.

6. The manufacturing method according to claim 1 or 2, It has a recovery process for recovering the positive electrode active material obtained through the heating process.

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