JP2024055335A - Method for producing positive electrode active material - Google Patents

Abstract

[Problem] A method for removing impurities from a positive electrode mixture and regenerating a positive electrode active material is disclosed. [Solution] The disclosed method is a method for producing a positive electrode active material, and includes the steps of contacting a positive electrode mixture with a molten compound containing Li and Na to obtain an intermediate material containing the positive electrode active material, washing the intermediate material with water to obtain a washed material containing the positive electrode active material, and drying the washed material to obtain the positive electrode active material. [Selected Figure] Figure 1

Description

This application discloses a method for producing a positive electrode active material.

Patent Document 1 discloses a method for recovering positive electrode active material particles from the electrode plate of a non-aqueous electrolyte secondary battery. The method disclosed in Patent Document 1 can also be said to be a method for producing a positive electrode active material from a positive electrode mixture.

JP 2014-203567 A

The positive electrode active material in the positive electrode mixture has impurities (e.g., those derived from the electrolyte, additives, etc.) adhering to its surface. In addition to the positive electrode active material, the positive electrode mixture may also contain components derived from conductive additives, binders, dispersants, etc. When producing a positive electrode active material from the positive electrode mixture, a new technology is needed to remove components other than the positive electrode active material from the positive electrode mixture.

The present application discloses the following aspects as means for solving the above problems.
<Aspect 1>
A method for producing a positive electrode active material, comprising:
contacting a positive electrode mixture with a molten compound containing Li and Na to obtain an intermediate material containing the positive electrode active material;
washing the intermediate material with water to obtain a washed product containing the positive electrode active material; and drying the washed product to obtain the positive electrode active material.
A manufacturing method comprising:
<Aspect 2>
The molten compound comprises LiOH and NaOH;
The method for producing embodiment 1.
<Aspect 3>
The temperature of the molten compound is 470° C. or more and 800° C. or less.
The method for producing aspect 1 or 2.
<Aspect 4>
The positive electrode mixture includes the positive electrode active material, a Li compound attached to the positive electrode active material, and a carbon-containing component.
The method for producing any one of Aspects 1 to 3.
<Aspect 5>
By bringing the positive electrode mixture into contact with the molten compound, at least a portion of the Li in the Li compound is replaced with Na, and at least a portion of the carbon-containing component is oxidized and removed.
The method for producing aspect 4.

According to the method disclosed herein, when producing a positive electrode active material from a positive electrode mixture, components other than the positive electrode active material contained in the positive electrode mixture are easily removed. For example, it is possible to remove impurities from a positive electrode mixture recovered from a battery and regenerate the positive electrode active material to the same quality as a new one.

1 shows a schematic flow of the manufacturing method of the present disclosure. 10A and 10B are schematic diagrams illustrating other examples of contact forms between the molten compound and the positive electrode mixture. 1 shows an example of a flow from dismantling a battery to obtaining a positive electrode active material in the case of recycling the battery.

1. Manufacturing method of the positive electrode active material Figure 1 shows a schematic flow of a manufacturing method of the positive electrode active material according to one embodiment. As shown in Figure 1, the manufacturing method of the positive electrode active material of the present disclosure includes contacting a positive electrode mixture 20 with a molten compound 10 containing Li and Na to obtain an intermediate material 30 containing the positive electrode active material 1 (step S1), washing the intermediate material 30 with water to obtain a washed material 40 containing the positive electrode active material 1 (step S2), and drying the washed material 40 to obtain the positive electrode active material 1 (step S3).

1.1 Step S1
In step S1, the positive electrode mixture 20 is brought into contact with a molten compound 10 containing Li and Na to obtain an intermediate material 30 containing a positive electrode active material 1. By step S1, for example, some components other than the positive electrode active material 1 contained in the positive electrode mixture 20 (e.g., Li compounds derived from an electrolyte solution, additives, etc.) can be converted into compounds that are easily dissolved in water (e.g., Na compounds, etc.). In addition, some components other than the positive electrode active material 1 contained in the positive electrode mixture 20 (e.g., carbon-containing components derived from a conductive assistant or binder, etc.) can be oxidized and removed by heating.

1.1.1 Molten Compound The molten compound 10 contains Li and Na. The term "molten compound" as used herein refers to a compound that is in a molten state due to heating. In the molten compound 10, Li and Na may be present, for example, in the form of ions or in the form of a compound. The molar ratio of Li and Na contained in the molten compound 10 is not particularly limited.

The molten compound 10 may be, for example, a mixture of a Li compound and a Na compound that is heated and melted. Examples of the Li compound and the Na compound include various salts and hydroxides. The molten compound 10 may be a mixture of LiOH and NaOH that is heated and melted. When the molten compound 10 contains LiOH and NaOH, impurities contained in the positive electrode mixture 20 can be easily converted into water-soluble Na compounds by contacting the molten compound 10 with the positive electrode mixture 20, and Li can also be easily supplied to the positive electrode active material 1 contained in the positive electrode mixture 20. The temperature of the molten compound 10 may be sufficiently lower than the temperature at which the positive electrode active material 1 is sintered. For example, the temperature of the molten compound 10 may be 470°C or higher and 800°C or lower. At such a temperature, the generation of water-soluble Na compounds can be more efficiently generated, and the carbon-containing components contained in the positive electrode mixture 20 can be easily oxidized and removed.

1.1.2 Positive Electrode Composite The positive electrode composite 20 may be, for example, recovered from a battery. The battery may be a battery for recycling, such as a used battery. In other words, the manufacturing method of the present disclosure may include recovering the positive electrode composite from the battery before step S1. A specific example of recovering the positive electrode composite from the battery will be described later.

The positive electrode mixture 20 may contain common materials that constitute the positive electrode active material layer of a battery. In addition to the positive electrode active material 1, the positive electrode mixture 20 contains other components. Examples of the other components include Li compounds derived from the electrolyte or additives, and carbon-containing components derived from conductive additives or binders. The other components may be attached to the surface of the positive electrode active material 1, or may exist independently of the positive electrode active material 1.

The positive electrode active material 1 contained in the positive electrode mixture 20 may be, for example, a lithium-containing compound. The lithium-containing compound as the positive electrode active material 1 may be various lithium-containing oxides such as lithium cobalt oxide, lithium nickel oxide, Li _1±α Ni _1/3 Co _1/3 Mn _1/3 O _2±δ , lithium manganate, spinel-based lithium compounds (Li _1+x Mn _2-x-y M _y O ₄ (M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn) substituted Li-Mn spinel having a composition represented by such), lithium titanate, and lithium metal phosphate (LiMPO ₄ , M is one or more selected from Fe, Mn, Co, and Ni). The positive electrode active material 1 may be composed of one type of compound, or may be a combination of two or more types of compounds.

The positive electrode active material 1 in the positive electrode mixture 20 has impurities attached to its surface, for example, derived from an electrolyte or additives. More specifically, in the positive electrode mixture 20 recovered from a secondary battery that has undergone charging and discharging, a coating of impurities (for example, a coating containing a phosphorus-based compound, a fluorine-based compound, or a sulfur-based compound derived from an electrolyte or additive, more specifically, a hydrocarbon-based coating containing at least one selected from LiF, Li ₃ PO ₄ , and Li ₂ SO ₄ in a portion thereof) is formed on the surface of the positive electrode active material 1, and the coating remains without volatilizing even in an oxidizing atmosphere of 900 ° C. or higher. In addition, the coating has low solubility in water and is difficult to remove by washing with water. Furthermore, if the coating is to be dissolved and removed by an organic solvent, a large amount of organic solvent is required, which is industrially unsuitable (high cost).

In contrast, according to the manufacturing method of the present disclosure, by bringing the positive electrode mixture 20 into contact with the molten compound 10, the Li in the impurities can be replaced with Na, and the impurities can be converted into water-soluble Na compounds. On the other hand, the positive electrode active material 1 in the positive electrode mixture 20 can occlude Li contained in the molten compound 10 and Li separated from the impurities by the above-mentioned Na replacement, but does not substantially occlude Na. That is, when the positive electrode active material 1 contained in the positive electrode mixture 20 is, for example, Li-deficient in terms of its crystal structure, by bringing the positive electrode mixture 20 into contact with the molten compound 10, Li can be supplied to the positive electrode active material 1, and the positive electrode active material 1 can be converted into one more suitable as an active material (for example, one having the same crystallinity as a new product immediately after synthesis).

The positive electrode mixture 20 may also contain carbon-containing components derived from the conductive additive, binder, etc. In this case, the positive electrode mixture 20 may be brought into contact with the molten compound 10, thereby oxidizing and removing the carbon-containing components. In this regard, as described below, the positive electrode mixture 20 may be brought into contact with the molten compound 10 in an oxygen-containing atmosphere in order to more efficiently oxidize and remove the carbon-containing components.

In this manner, the positive electrode mixture 20 may include the positive electrode active material 1, a Li compound (e.g., a phosphorus-based compound, a fluorine-based compound, or a sulfur-based compound derived from an electrolyte or an additive, more specifically, at least one selected from LiF, _Li3PO4 , _{Li2SO4 , etc.} ) attached to the positive electrode active material 1, and a carbon-containing component (e.g., derived from a conductive assistant, a binder, etc.). In this case, in step S1, the positive electrode mixture 20 may be brought into contact with the molten compound 10 to replace at least a portion of the Li in the Li compound with Na, and at least a portion of the carbon-containing component may be oxidized and removed.

In addition to the above components, the positive electrode composite 20 may contain other components derived from the negative electrode composite or the electrolyte. For example, the negative electrode composite or the electrolyte may contain a carbon-containing component.

1.1.3 Contact Form The form of contact between the molten compound 10 and the positive electrode mixture 20 is not particularly limited. In step S1, for example, the positive electrode mixture 20 may be immersed in the molten compound 10. Specifically, for example, as shown in FIG. 1, the molten compound 10 may be heated and held inside a heating furnace 102 (for example, a screw-type heating furnace), and the positive electrode mixture 20 may be supplied from a container 101 to the molten compound 10 inside the heating furnace 102, thereby immersing the positive electrode mixture 20 in the molten compound 10. By immersing the positive electrode mixture 20 in the molten compound 10, the molten compound 10 can be uniformly supplied to the surface of the positive electrode active material 1 in the positive electrode mixture 20, and impurities attached to the surface of the positive electrode active material 1 can be efficiently converted into water-soluble Na compounds. In step S1, after the molten compound 10 and the positive electrode mixture 20 are brought into contact with each other, the excess molten compound may be drained off to obtain an intermediate material 30.

Alternatively, as shown in FIG. 2, in step S1, the components constituting the molten compound 10 (e.g., Li compound and Na compound) in an unmelted state are mixed with the positive electrode composite material 20 to obtain a mixture 50, and the mixture 50 is fed from the container 101 to a heating furnace 106 (e.g., a kiln furnace) optionally via a screw feeder 105 or the like, and the mixture 50 is heated in the heating furnace 106 to melt a part of the mixture 50 (the components constituting the molten compound 10) to form the molten compound 10, and the molten compound 10 may come into contact with the positive electrode composite material 20.

1.1.4 Contact Temperature The contact temperature between the molten compound 10 and the positive electrode composite material 20 may be a temperature at which the molten compound 10 can be melted as described above, and is sufficiently lower than the temperature at which the positive electrode active material 1 is sintered. For example, as described above, the contact temperature may be 470° C. or higher and 800° C. or lower. At such a temperature, it is also possible to oxidize and remove at least a portion of the carbon-containing component contained in the positive electrode composite material 20.

1.1.5 Contact Atmosphere The contact atmosphere between the molten compound 10 and the positive electrode composite material 20 may be an atmosphere capable of promoting the oxidative removal of the carbon-containing component as described above, or may be another atmosphere. For example, it may be an oxygen-containing atmosphere such as an air atmosphere, an air atmosphere, or an oxygen atmosphere. When the positive electrode active material 1 is a Li-containing oxide, the crystal structure of the Li-containing oxide is easily maintained by contacting the molten compound 10 with the positive electrode composite material 20 in an oxygen-containing atmosphere. The pressure during contact is not particularly limited.

1.1.6 Intermediate material The intermediate material 30 containing the positive electrode active material 1 is obtained by the above-mentioned step S1. The intermediate material 30 may contain, in addition to the positive electrode active material 1, a Na compound (for example, at least one of sodium carbonate, sodium fluoride, sodium phosphate, sodium sulfate, and sodium hydroxide), a lithium compound (for example, lithium hydroxide), and the like. The Na compound may include, in addition to the Na compound constituting the above-mentioned molten compound 10, a Na substitute of an impurity attached to the surface of the positive electrode active material 1 (a Na compound in which Li contained in the impurity is substituted with Na). In addition, the intermediate material 30 may contain a carbon-containing component remaining. Even if the carbon-containing component cannot be oxidized and removed in step S1, the carbon-containing component can be oxidized and removed in a subsequent step. For example, the carbon-containing component may be oxidized and removed after step S3 (drying).

1.2 Step S2
In step S2, the intermediate material 30 obtained in step S1 is washed with water to obtain a washed object 40 including the positive electrode active material 1. In step S2, for example, water-soluble components (e.g., the above-mentioned Na compound) included in the intermediate material 30 can be dissolved and removed.

1.2.1 Form of Water Washing The intermediate material 30 may be washed with water by a known means. The temperature and time during water washing are not particularly limited, and may be any temperature and time that can sufficiently dissolve and remove the water-soluble components contained in the intermediate material 30. As shown in FIG. 1, during water washing, the intermediate material 30 may be washed while being stirred using a stirring vessel 103. Furthermore, during water washing, solid-liquid separation may be performed using a filtration device 104 or the like, as shown in FIG. Furthermore, during water washing, the amount of surplus Li may be controlled by adjusting the amount of washing water.

1.2.2 Washed object By the above-mentioned step S2, a washed object 40 including the positive electrode active material 1 is obtained. The washed object 40 may contain water in addition to the positive electrode active material 1 as a solid content. The water may be contained in the form of a hydrate or the like.

1.3 Step S3
In step S3, the washed object 40 obtained in step S2 is dried to obtain the positive electrode active material 1. As described above, the washed object 40 contains water, and by drying and removing the water, a positive electrode active material 1 with higher performance is obtained. The washed object 40 may be dried by a known means. The temperature and time during drying are not particularly limited, and may be any temperature and time that can sufficiently remove the water contained in the washed object 40. For example, by drying at a temperature of 130° C. or higher, a positive electrode active material 1 with a small amount of hydrates is obtained. The upper limit of the temperature may be any temperature at which the positive electrode active material 1 does not sinter.

1.4 Other Steps The manufacturing method of the present disclosure may include at least the above steps S1 to S3, and may further include other steps. For example, the manufacturing method may include various steps for recycling battery materials (such as crushing batteries and recovering liquid). In addition to steps S1 to S3, the manufacturing method may include a step of oxidizing and removing carbon-containing components, etc.

2. Recycling method for battery materials The technology of the present disclosure also has an aspect of a recycling method for battery materials. For example, as shown in Fig. 3, the recycling method for battery materials of the present disclosure may include crushing and dismantling the battery (crushing step), further crushing the crushed battery to peel off the composite material from the electrode (secondary crushing step), evaporating the electrolyte component contained in the crushed material (liquid recovery step), separating at least a part of the materials other than the composite material from the materials contained in the crushed material (separation step), and the above steps S1 to S3.

2.1 Crushing Process In the crushing process, the batteries may be crushed by a known crusher. Examples of the crusher include a shredder. The batteries to be crushed in the crushing process may include both a positive electrode and a negative electrode, or may include only a positive electrode (if the batteries are scraps, it is easy to crush only the positive electrode).

2.2 Secondary Crushing Process In the secondary crushing process, the composite material may be peeled off from the electrodes by a known crusher. Examples of the crusher in this case include a chain mill. In the secondary crushing process, for example, the electrodes can be separated into the composite material (black mass) and the current collector foil. The above-mentioned crushing process and the secondary crushing process may be performed simultaneously.

2.3 Liquid recovery step In the liquid recovery step, the electrolyte component contained in the crushed material may be evaporated using a known dryer. In the liquid recovery step, the crushed material may be dried under reduced pressure.

2.4 Separation Step In the separation step, for example, materials that are relatively heavier than the composite material (exterior case, current collector terminal, etc.), lighter materials (separator, insulating film), metal foils (aluminum foil, copper foil), etc. are separated and removed to obtain a composite material (black mass). If only the positive electrode is crushed in the above crushing step, substantially only the positive electrode composite material is obtained by the separation step. In the separation step, materials with a large specific gravity and materials with a small specific gravity may be separated by dry separation such as air flow separation.

2.5 Steps S1 to S3
Steps S1 to S3 are as described above.

3. Effects As described above, according to the technology of the present disclosure, for example, when recycling a battery, the positive electrode active material can be regenerated without returning it to the raw material. Specifically, from the positive electrode mixture (black mass) obtained after separating the current collector foil from the electrode, impurities can be easily washed away with water, and only the positive electrode active material can be separated in a mass production manner, and the positive electrode active material can be regenerated to the same quality as a new product. The technology of the present disclosure uses an inexpensive molten compound (e.g., NaOH, etc.), does not require an organic solvent, and can be said to be a low-cost technology with low carbon dioxide emissions.

Reference Signs List 1 Positive electrode active material 10 Molten compound 20 Positive electrode mixture 30 Intermediate material 40 Washed material 50 Mixture 101 Container 102 Heating furnace (screw type heating furnace)
103 Stirring vessel 104 Filtration device 105 Screw feeder 106 Heating furnace (kiln furnace)

Claims (5)

A method for producing a positive electrode active material, comprising:
contacting a positive electrode mixture with a molten compound containing Li and Na to obtain an intermediate material containing the positive electrode active material;
washing the intermediate material with water to obtain a washed product containing the positive electrode active material; and drying the washed product to obtain the positive electrode active material.
A manufacturing method comprising: The molten compound comprises LiOH and NaOH;
The method of claim 1 . The temperature of the molten compound is 470° C. or more and 800° C. or less.
The method according to claim 2 . The positive electrode mixture includes the positive electrode active material, a Li compound attached to the positive electrode active material, and a carbon-containing component.
The method according to any one of claims 1 to 3. By bringing the positive electrode mixture into contact with the molten compound, at least a portion of the Li in the Li compound is replaced with Na, and at least a portion of the carbon-containing component is oxidized and removed.
The method according to claim 4.

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