JP2023183355A - Recycled cathode material and manufacturing method thereof, method of using recycled cathode material, recycled cathode, and lithium ion secondary battery - Google Patents

Abstract

To provide a recycled cathode material that can be manufactured from an end-of-life lithium-ion secondary battery with less environmental impact and low recycling costs, and has excellent performance comparable to that of normal lithium-ion secondary battery cathode, a manufacturing method thereof, a method of using a recycled cathode material, a recycled cathode, and a lithium ion secondary battery.SOLUTION: A recycled positive electrode material containing lithium, nickel, cobalt, and manganese, 0.3 mass % or more and 3 mass% or less of aluminum, and less than 1 mass% of at least one of copper and iron.SELECTED DRAWING: None

Description

The present invention relates to a recycled cathode material, a method for manufacturing the recycled cathode material, a method for using the recycled cathode material, a recycled cathode, and a lithium ion secondary battery.

The applications of lithium ion secondary batteries are rapidly expanding from the electronics field to the automobile field. In particular, in the automotive field, demand for large batteries is expected to rapidly increase due to higher capacity units for use in hybrid vehicles and electric vehicles. As demand for such lithium ion secondary batteries increases, the amount of lithium ion secondary batteries that have reached the end of their product life also increases.

On the other hand, since lithium-ion secondary batteries use expensive metal materials as their positive electrode materials, recycling metal materials from lithium-ion secondary batteries that have reached the end of their product life is an important industrial issue. It is.

For example, impurities are removed from a waste battery, waste cathode material, or a mixture thereof containing impurities and a metal group consisting of at least two selected from Co, Ni, and Mn, and the metal group is converted into a mixture of the metal salts. A collection method has been proposed (for example, see Patent Document 1). In this proposal, a mixture of recovered metal salts is used to manufacture a cathode material.

Patent No. 5847742

However, in order to recycle metal materials from lithium ion secondary batteries that have reached the end of their product life, it is required that the environmental burden associated with recycling be small and that the cost of recycling be low. In addition, when manufacturing cathode materials using nickel, cobalt, and manganese recovered from lithium-ion secondary batteries that have reached the end of their product life, recycled lithium-ion secondary batteries manufactured using the cathode materials can be used as normal lithium-ion secondary batteries. Comparable to ion secondary batteries (lithium ion secondary batteries that do not use metal materials recycled from lithium ion secondary batteries for the positive electrode material are hereinafter referred to as "normal lithium ion secondary batteries"). It is required to have excellent performance. However, for example, the method described in Patent Document 1 uses a complicated separation process and a large amount of expensive extractants, and there were concerns that the environmental burden associated with recycling would be large and the cost would increase.

An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, the present invention can be manufactured from a lithium ion secondary battery that has reached the end of its product life with less environmental impact and low recycling costs, and has excellent performance comparable to that of the positive electrode material of ordinary lithium ion secondary batteries. The present invention aims to provide a recycled cathode material, a method for producing the recycled cathode material, a method for using the recycled cathode material, a recycled cathode, and a lithium ion secondary battery.

Means for solving the above problem are as follows. That is,
<1> Lithium, nickel, cobalt, and manganese,
0.3% by mass or more and 3% by mass or less of aluminum,
less than 1% by mass of at least one of copper and iron;
This is a recycled cathode material characterized by containing.
<2> The regenerated positive electrode according to <1>, which contains at least one of calcium and magnesium, and has a content of at least one of calcium and magnesium of 0.02% by mass or more and 0.1% by mass or less. It is a material.
<3> The recycled positive electrode material according to any one of <1> to <2>, wherein the aluminum content is 0.5% by mass or more and 2.5% by mass or less.
<4> The recycled positive electrode material according to any one of <1> to <2>, wherein the lithium content is 5% by mass or more and 9% by mass or less.
<5> The copper content is 0.01% by mass or less,
The recycled positive electrode material according to any one of <1> to <2>, wherein the iron content is 0.6% by mass or less.
<6> The copper content is 0.0005% by mass or more and 0.005% by mass or less,
The recycled positive electrode material according to <5> above, wherein the iron content is 0.002% by mass or more and 0.6% by mass or less.
<7> The aluminum (Al) content (mass%), the copper (Cu) content (mass%), and the iron (Fe) content (mass%) are expressed by the following formula, Al/ The recycled positive electrode material according to any one of <1> to <2> above, satisfying (Al+Cu+Fe)≧0.4.
<8> The recycled positive electrode material according to any one of <1> to <2>, containing the nickel, the cobalt, and the manganese in a total amount of 50% by mass or more.
<9> A method for manufacturing the recycled cathode material according to any one of <1> to <2>, comprising:
a heat treatment step of obtaining a heat-treated product by heat-treating a lithium ion secondary battery;
A crushing step of crushing the heat-treated product to obtain a crushed product;
a physical sorting step of physically sorting the crushed material to obtain a physically processed material;
an acid treatment step of adding an acidic solution to the physically treated product to obtain an acid treatment solution;
an iron removal step of adding an oxidizing agent to the acid treatment solution, then adding an alkaline solution, and filtering out the iron hydroxide precipitate;
an alkali treatment step of mixing the filtrate after the iron removal step with an alkaline solution;
A method for producing a recycled cathode material, comprising:
<10> The method for producing a recycled positive electrode material according to <9> above, including a lithium source addition step of adding a lithium source.
<11> An assembly step of assembling a lithium ion secondary battery having the recycled cathode material according to any one of <1> to <2>;
The lithium ion secondary battery assembled in the above assembly process is charged from a cell voltage of around 0V to 4.3V to 4.6V, and then charged from a cell voltage of 0V to 3.5V to a range of 4.3V to 4.6V. an activation step of discharging;
1 is a method of using recycled cathode material characterized by comprising:
<12> A recycled positive electrode comprising the recycled positive electrode material according to any one of <1> to <2>.
<13> A lithium ion secondary battery comprising the regenerated positive electrode according to <12>.

According to the present invention, various conventional problems can be solved, and lithium ion secondary batteries that have reached the end of their product life can be manufactured with less environmental impact and low recycling costs, and can be used as cathode materials for ordinary lithium ion secondary batteries. It is possible to provide a recycled cathode material, a method for manufacturing the recycled cathode material, a method for using the recycled cathode material, a recycled cathode, and a lithium ion secondary battery that have comparable excellent performance.

FIG. 1 is a flow diagram showing an example of the method for producing recycled cathode material of the present invention. FIG. 2 is a schematic diagram showing an example of a coin cell type lithium ion secondary battery used in Examples. FIG. 3 is a graph showing the relationship between the number of cycles and the specific capacity of the positive electrode material in the full cell cycle test of Example 1. FIG. 4 is a graph showing the relationship between the number of cycles and the specific capacity of the positive electrode material in the full cell cycle test of Comparative Example 1. FIG. 5 is a graph showing the relationship between the number of cycles and the specific capacity of the positive electrode material in the full cell cycle test of Comparative Example 2. FIG. 6 is a graph showing the relationship between the specific capacity of the positive electrode material and the cell voltage in the full cell cycle test of Example 1. FIG. 7 is a graph showing the relationship between the specific capacity of the positive electrode material and the cell voltage in the full cell cycle test of Comparative Example 1. FIG. 8 is a graph showing the relationship between the specific capacity of the positive electrode material and the cell voltage in the full cell cycle test of Comparative Example 2.

(Recycled cathode material)
The recycled positive electrode material of the present invention contains lithium, nickel, cobalt, and manganese, 0.3% by mass or more and 3% by mass or less of aluminum, and less than 1% by mass of at least one of copper and iron, Furthermore, other components may be contained as necessary.

The recycled cathode material of the present invention and the lithium ion secondary battery using the recycled cathode material can be charged and discharged at an upper limit cell voltage of 0.1V to 0.4V higher than the upper limit cell voltage of 4.2V in normal charging and discharging. By doing this, Li is easily desorbed from the recycled cathode, and once Li is desorbed, it can be repeatedly desorbed and inserted. The cathode material (hereinafter referred to as "ordinary cathode material") can exhibit the same level of specific capacity as a lithium-ion secondary battery using a lithium-ion secondary battery using a cathode material (hereinafter referred to as "ordinary cathode material"), and is superior to a lithium-ion secondary battery using a normal cathode material. Cycle characteristics can be achieved.

In the present invention, the lithium, the nickel, the cobalt, the manganese, the aluminum, the copper, and the iron include each of the following metal elements: lithium, nickel, cobalt, manganese, aluminum, copper, and iron; It also includes each metal element contained in the oxide or hydroxide of the metal element (ie, a compound combined with another element). In addition, "oxide" or "hydroxide" refers to each metal oxide or metal hydroxide, and at least one of a composite oxide containing each metal element or a composite hydroxide containing each metal element. including.

The content of aluminum is 0.3% by mass or more and 3% by mass or less, preferably 0.5% by mass or more and 2.5% by mass or less, and more preferably 0.7% by mass or more and 1.5% by mass or less. . If the aluminum content is 0.3% by mass or more and 3% by mass or less, the normal charge/discharge limit cell voltage range of 0.1V to 0.4V higher than 4.2V, which is the upper limit cell voltage in normal charging and discharging. It exhibits better cycle characteristics than lithium ion secondary batteries using positive electrode materials, and the difference from normal lithium ion secondary battery positive electrode materials becomes clear.

The lithium content is preferably 4% by mass or more and 10% by mass or less, more preferably 5% by mass or more and 9% by mass or less, and even more preferably 7% by mass or more and 8.5% by mass or less.

The total content of nickel, cobalt, and manganese is preferably 50% by mass or more, more preferably 55% by mass or more. The respective contents of nickel, cobalt, and manganese can be adjusted depending on the desired characteristics of the battery. For example, a positive electrode material for NCM811 may contain nickel in an amount of 15% by mass or more and 52% by mass or less, cobalt in an amount of 6% by mass or more and 25% by mass or less, and manganese in an amount of 6% by mass or more and 25% by mass or less. Further, a positive electrode material for NCM111 can contain nickel, cobalt, and manganese in an amount of 10% by mass or more and 30% by mass or less, respectively.

The recycled positive electrode material of the present invention contains less than 1% by mass of at least one of copper and iron.
The content of copper is less than 1% by mass, preferably 0.01% by mass or less, and more preferably 0.0005% by mass or more and 0.005% by mass or less.
The iron content is less than 1% by mass, preferably 0.6% by mass or less, and more preferably 0.002% by mass or more and 0.6% by mass or less.
If less than 1% by mass of at least one of copper and iron is contained, normal positive electrode materials cannot be used in the range of upper limit cell voltage 0.1V to 0.4V higher than 4.2V, which is the upper limit cell voltage in normal charging and discharging. It shows better cycle characteristics than conventional lithium-ion secondary batteries, and clearly differentiates it from the positive electrode materials of regular lithium-ion secondary batteries.

It is preferable that at least one of calcium and magnesium is included. The content of at least one of calcium and magnesium is preferably 0.02% by mass or more and 0.1% by mass or less, more preferably 0.04% by mass or more and 0.09% by mass or less.
When metals recycled from lithium ion secondary batteries are used, they often contain calcium and magnesium, but it was confirmed that this level of content would not have a major effect on the characteristics of batteries using recycled cathode materials.

The content of aluminum (Al) (mass%), the content of copper (Cu) (mass%), and the content of iron (Fe) (mass%) are determined by the following formula, Al/(Al+Cu+Fe)≧0 It is preferable to satisfy the following formula, Al/(Al+Cu+Fe)≧0.5, and it is even more preferable to satisfy the following formula, Al/(Al+Cu+Fe)≧0.6, It is particularly preferable to satisfy the formula, Al/(Al+Cu+Fe)≧0.7, and it is particularly preferable to satisfy the following formula, Al/(Al+Cu+Fe)≧0.8, and the following formula, Al/(Al+Cu+Fe)≧0 It is even more particularly preferable to satisfy .9.
By satisfying the following formula, Al/(Al+Cu+Fe)≧0.4, normal lithium Shows better cycle characteristics than ion secondary batteries.

The content of each metal element can be measured using, for example, ICP analysis or fluorescent X-ray analysis.

<Other ingredients>
Other components are not particularly limited and may be included as long as the effects of the present invention are achieved, such as Na, O, fluorine (F), and the like.

The recycled positive electrode material of the present invention, which contains lithium, nickel, cobalt, and manganese, 0.3% by mass or more and 3% by mass or less of aluminum, and less than 1% by mass of at least one of copper and iron, includes the following: It can be suitably manufactured by the method for manufacturing a recycled cathode material of the present invention as described.

(Method for manufacturing recycled cathode material)
The method for producing recycled cathode material of the present invention is a method for producing recycled cathode material of the present invention, which includes a heat treatment step, a crushing step, a physical sorting step, an acid treatment step, an iron removal step, and an alkali removal step. It preferably includes a lithium source addition step, and further includes other steps as necessary.
Here, FIG. 1 is a flow diagram showing an example of a method for manufacturing a recycled cathode material of the present invention. Hereinafter, with reference to FIG. 1, a method for manufacturing a recycled cathode material of the present invention will be described.

<Lithium ion secondary battery to be treated>
The lithium ion secondary battery to be treated is not particularly limited and can be selected as appropriate depending on the purpose. For example, a defective lithium ion secondary battery generated during the manufacturing process of lithium ion secondary batteries , lithium ion secondary batteries that are discarded due to defects in the equipment being used or the end of the lifespan of the equipment used, and used lithium ion secondary batteries that are discarded due to the end of their lifespan.

A lithium ion secondary battery is a secondary battery that charges and discharges by moving lithium ions between a positive electrode and a negative electrode. Examples include those that include a liquid or solid electrolyte) and an outer container that is a battery case.

The shape, structure, size, material, etc. of the lithium ion secondary battery to be treated are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the lithium ion secondary battery include a laminate type, a cylindrical shape, a button shape, a coin shape, a square shape, and a flat shape.

-Positive electrode-
The positive electrode is not particularly limited as long as it has a positive electrode material on the positive electrode current collector, and can be appropriately selected depending on the purpose. The shape of the positive electrode is not particularly limited and can be appropriately selected depending on the purpose, such as a flat plate or a sheet.

The shape, structure, size, material, etc. of the positive electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the positive electrode current collector include a foil shape. Examples of the material of the positive electrode current collector include stainless steel, nickel, aluminum, copper, titanium, and tantalum. Among these, aluminum is widely used.

The constituent members of the positive electrode material can be selected as appropriate depending on the purpose, such as a positive electrode material that includes at least a positive electrode active material containing rare valuables, and optionally a conductive agent and a binder resin. . There are no particular restrictions on rare valuables, and they can be selected as appropriate depending on the purpose, but cobalt, nickel, and manganese are often used.

Examples of positive electrode active materials include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and lithium cobalt nickel oxide (LiCo _1/2 Ni _1/2 O ₂ ), ternary materials (“NMC”, i.e., _LiNix Co _y Mn _z O ₂ , x+y+z=1, and x, y, and z are each greater than 0 and less than 1), nickel-based materials (“NCA”, i.e. _LiNix Co _y Al _z O ₂ , x+y+z=1 and x, y, z are each greater than 0 and less than 1), or a composite of any combination thereof x+y+z=1 and x, y, z are greater than 0 and less than 1, respectively.

The conductive agent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include carbon black, graphite, carbon fiber, metal carbide, and the like.

The binder resin is not particularly limited and can be selected as appropriate depending on the purpose. Examples include homopolymers or copolymers of vinylidene fluoride, tetrafluoroethylene, acrylonitrile, ethylene oxide, and styrene-butadiene rubber. Examples include.

-Negative electrode-
The negative electrode is not particularly limited as long as it has a negative electrode material on the negative electrode current collector, and can be appropriately selected depending on the purpose. The shape of the negative electrode is not particularly limited and can be appropriately selected depending on the purpose, such as a flat plate or a sheet.

The shape, structure, size, material, etc. of the negative electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the negative electrode current collector include a foil shape. Examples of the material of the negative electrode current collector include stainless steel, nickel, aluminum, copper, titanium, and tantalum. Among these, copper is preferred.

The negative electrode material is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include graphite, carbon materials such as hard carbon, titanate, silicon, and composites thereof.

Note that the positive electrode current collector and the negative electrode current collector have a laminate structure, and the laminate is not particularly limited and can be appropriately selected depending on the purpose.

<Heat treatment process>
The heat treatment step is a step of heat-treating a lithium ion secondary battery to obtain a heat-treated product.
As shown in FIG. 1, first, a heat treatment step is performed on a lithium ion secondary battery to be treated. The heat treatment temperature is not particularly limited as long as it is higher than the melting point of the current collector with a lower melting point and lower than the melting point of the current collector with a higher melting point among the positive electrode current collector and negative electrode current collector. Although the temperature can be selected as appropriate, the temperature is preferably 670°C or higher, more preferably 670°C or higher and 1,100°C or lower, even more preferably 700°C or higher and 1,000°C or lower, particularly preferably 700°C or higher and 900°C or lower. When the heat treatment temperature is 670°C or higher, the current collector with a low melting point is sufficiently embrittled, and when the heat treatment temperature is 1,100°C or lower, the current collector with a low melting point, the current collector with a high melting point, and the exterior are damaged. Embrittlement of both containers can be suppressed, and separation efficiency between the current collector and the outer container by crushing and classification can be maintained. In addition, when the outer container of the lithium ion secondary battery melts during the heat treatment, a tray for collecting the molten metal is disposed at the bottom of the lithium ion secondary battery, so that the metal from the outer container and the electrode parts can be easily separated.

By performing heat treatment at a predetermined heat treatment temperature, for example, in a laminate in which the positive electrode current collector is aluminum foil and the negative electrode current collector is copper, the positive electrode current collector made of aluminum foil becomes brittle, resulting in fracture as described below. It becomes easier to make the particles finer in the process. This embrittlement of the positive electrode current collector occurs due to melting or oxidation reaction. Further, the aluminum that has melted and flowed down is collected in a tray. On the other hand, since the negative electrode current collector made of copper is heat-treated at a temperature below the melting point of copper, it does not melt and can be highly sorted in the magnetic sorting process described below. In addition, when either the laminate or the lithium ion secondary battery is housed in an oxygen-shielded container and heat-treated, the positive electrode current collector made of aluminum foil melts and becomes brittle, making it more likely to become fine particles in the crushing process described later. Become. On the other hand, the negative electrode current collector made of copper is heat-treated at a low oxygen partial pressure due to the oxygen shielding effect of the oxygen shielding container and the reduction effect of the negative electrode active material such as carbon contained in the laminate or lithium ion secondary battery. Therefore, embrittlement due to oxidation does not occur. Therefore, by crushing in the crushing process, the positive electrode current collector is finely crushed, and the negative electrode current collector remains as coarse particles even after crushing, so that it can be sorted more effectively and highly in the classification and sorting process described later. Become.

The heat treatment time is not particularly limited and can be selected as appropriate depending on the purpose, but is preferably 1 minute or more and 5 hours or less, more preferably 1 minute or more and 2 hours or less, and particularly preferably 1 minute or more and 1 hour or less. . The heat treatment time may be a heat treatment time that allows the current collector having a low melting point to reach a desired temperature, and the holding time may be short. When the heat treatment time is within a particularly preferable range, it is advantageous in terms of the cost required for heat treatment.

The method of heat treatment is not particularly limited and can be appropriately selected depending on the purpose. For example, it may be carried out using a heat treatment furnace. Examples of the heat treatment furnace include rotary kilns, fluidized bed furnaces, tunnel furnaces, batch furnaces such as muffles, cupolas, and stoker furnaces.

The atmosphere used for the heat treatment is not particularly limited and can be appropriately selected depending on the purpose, but the heat treatment can be carried out in air. An atmosphere with a low oxygen concentration is preferable because the metal derived from the positive electrode current collector and the metal derived from the negative electrode current collector can be recovered with high quality and high recovery rate.

As a method for realizing the above-mentioned low-oxygen atmosphere, the lithium ion secondary battery or the laminate may be housed in an oxygen-shielding container and heat-treated. The material of the oxygen-shielding container is not particularly limited as long as it does not melt at the above-mentioned heat treatment temperature, and can be appropriately selected depending on the purpose. Examples include iron, stainless steel, and the like. In order to release the gas pressure caused by combustion of the electrolyte in the lithium ion secondary battery or the laminate, the oxygen shielding container is preferably provided with an opening. The opening area of the opening is preferably 12.5% or less of the surface area of the outer container in which the opening is provided. More preferably, the opening area of the opening is 6.3% or less of the surface area of the outer container in which the opening is provided. If the opening area of the opening exceeds 12.5% of the surface area of the outer container, most of the current collector will be easily oxidized by heat treatment. There are no particular restrictions on the shape, size, location, etc. of the opening, and these can be selected as appropriate depending on the purpose.

Here, it is also preferable to perform qualitative and quantitative analysis of the metal elements contained in the heat-treated product obtained in the heat treatment step using fluorescent X-ray analysis or the like, if desired. This is because the metal components contained in the heat-treated product may differ depending on the lithium ion secondary battery to be treated.

Based on the results of this qualitative and quantitative analysis, it is possible to group heat-treated products with similar metal component compositions and send the heat-treated products divided into groups to the crushing process described below to stabilize the metal component composition of the recycled cathode material. This is a preferable configuration from the viewpoint of

<Crushing process>
The crushing step is a step of crushing the heat-treated product to obtain a crushed product.
As for crushing, for example, methods of crushing by impact include a method of throwing it with a rotating impact plate and hitting it against a collision plate to apply an impact, a method of hitting the heat-treated product with a rotating batter (beater), For example, it can be carried out using a hammer crusher, a chain crusher, or the like. Another method is to hit the heat-treated product with balls or rods made of ceramics, iron, etc., and can be carried out using a ball mill, a rod mill, or the like. Alternatively, crushing can be carried out by crushing with a twin-shaft crusher having a short blade width or blade length that crushes by compression.

The impact promotes the crushing of the active material and the low melting point current collector by obtaining a crushed material, while the high melting point current collector whose morphology has not changed significantly exists in the form of a foil or the like. . Therefore, in the crushing process, the current collector with a high melting point is only cut, and the fineness of the current collector with a high melting point progresses more slowly than with the current collector with a low melting point. In the process, it is possible to obtain a crushed material in which a current collector with a low melting point and a current collector with a high melting point can be efficiently separated.

The crushing time is not particularly limited and can be selected as appropriate depending on the purpose, but the processing time per 1 kg of lithium ion secondary battery is preferably 1 second or more and 30 minutes or less, more preferably 2 seconds or more and 10 minutes or less. Preferably, 3 seconds or more and 5 minutes or less is particularly preferable. If the crushing time is less than 1 second, it may not be crushed, and if it exceeds 30 minutes, it may be crushed excessively. Further, it is preferable that the maximum particle size of the crushed material is 10 mm or less.

<Physical sorting process>
The physical sorting step is a step of physically sorting the crushed material to obtain a physically processed material.
-Classification and sorting process-
As the physical sorting step, a classification and sorting step can be performed in which the crushed material obtained in the crushing step is classified into coarse grain products and fine grain products. The classification method is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a vibrating sieve, a multistage vibrating sieve, a cyclone, a standard sieve according to JIS Z8801, a wet vibrating table, an air table, and the like.

The classification point used in the classification and selection step is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.45 mm or more, and more preferably 0.6 mm or more and 2.4 mm or less. If the classification point exceeds 2.4 mm, metals originating from the outer container and having a higher melting point may be mixed into the fine grain product, and the separation performance from cobalt and nickel originating from the active material may deteriorate. On the other hand, if the classification point is less than 0.45 mm, the metal and active material derived from the current collector with a low melting point will be mixed into the coarse grain product, and the amount of metal and active material derived from the current collector with a high melting point in the coarse grain product will increase. The metal quality is reduced and the recovery of cobalt and nickel from the active material to the fine grain product may be less than 60%. In addition, when a sieve is used as a classification method, by placing a disintegration accelerator, such as stainless steel balls or alumina balls, on the sieve, small crushed items adhering to large crushed items can be separated from large crushed items. By separating, large crushed materials and small crushed materials can be efficiently separated. Thereby, the quality of the metal to be recovered can be further improved. Note that the crushing step and the classification and sorting step can also be performed simultaneously. For example, the heat-treated product obtained in the heat treatment step may be crushed while the crushed product is classified into coarse grain products and fine grain products (crushing/classification).

Through the above-mentioned classification, metals derived from the outer container and the current collector with a high melting point can be recovered as coarse particles, and concentrates of cobalt, nickel, and lithium derived from active materials can be recovered as fine particles (black mass). can do. Note that the fine grain product may be classified again. By removing fine grains of, for example, 150 μm or less from the fine grain products in this re-classification, non-magnetic particles can be obtained by wet magnetic sorting (hereinafter sometimes referred to as "magnetic sorting", abbreviated as "magnetic sorting"). The amount of negative electrode active material contained in the negative electrode active material can be reduced.

-Magnetic selection process-
As the physical sorting step, a dry magnetic separation step can be performed on the crushed material obtained in the crushing step or the coarse grain product obtained in the classification and sorting step. Iron is recovered as a magnetized substance, and metal derived from the negative electrode current collector, such as copper, is recovered as a non-magnetized substance.
As the physical sorting step, a wet magnetic separation step (wet magnetic separation) can be more preferably performed on the crushed material obtained in the crushing step or the fine grain product (black mass) obtained in the classification and sorting step. . Cobalt and nickel concentrates are recovered as magnetic materials.
When performing magnetic separation on the fine grain products obtained in the classification and sorting process, when magnetic separation is carried out in a dry manner, particle aggregation occurs due to moisture adhering between the particles, and the metal particles derived from the negative electrode current collector and the fine grain products contain 10% by mass or more. It is not possible to sufficiently separate the negative electrode active material particles from the cobalt and nickel particles. In the present invention, in a wet magnetic separation process, a material derived from the negative electrode active material and a metal derived from the negative electrode current collector are separated into a non-magnetic material slurry, and cobalt and nickel are recovered into the magnetic material to obtain a physically treated product. Although manganese is not ferromagnetic at room temperature, when it forms a composite oxide together with cobalt and nickel in a lithium ion secondary battery, it accompanies cobalt and nickel when they are magnetically separated. Therefore, a considerable amount of manganese can also be recovered through magnetic separation. The magnetic force during magnetic separation is preferably 1,500G to 8,000G.

On the other hand, lithium is dissolved in the liquid during slurrying of raw materials and wet magnetic separation, and is separated into a non-magnetic material slurry. By subjecting this non-magnetic substance slurry to solid-liquid separation, the metal derived from the negative electrode current collector and the negative electrode active material can be separated into residues. Furthermore, carbon dioxide gas is blown into the liquid separated by solid-liquid separation to precipitate as lithium carbonate, and lithium is recovered. Note that, before blowing in the carbon dioxide gas, a pretreatment process such as a liquid concentration process for the purpose of removing impurities and increasing the lithium concentration may be performed. For example, fluorine is recovered in the remaining liquid. Therefore, the fluorine content in the physically treated product can be less than 1%. A leaching process is necessary to recover lithium and separate fluorine from cobalt and nickel, but in the present invention, in the wet magnetic separation process, lithium is leached with water and fluorine is leached away, and cobalt and nickel of the metal derived from the negative electrode current collector are removed. Since nickel separation can be performed at the same time, the number of steps can be reduced.

<Acid treatment process>
The acid treatment step is a step of adding an acidic solution to the physically treated material to obtain an acid treatment solution.
This is a process in which an acid such as HCl, HNO ₃ or H ₂ SO ₄ is added to the physically treated material to dissolve the metal element in the acidic solution.
For example, the physically treated product after acid addition is heated at 20° C. to 180° C. for 0.1 to 3 hours to thermally decompose the metal elements in the physically treated product and dissolve them in the acidic solution. After the thermal decomposition is completed, the acidic solution may be allowed to cool, the acidic solution may be filtered to remove undissolved residues in the acidic solution, and the filtrate may be recovered. In addition to using the acid alone, for example, HCl may be added to the physically treated material and heated, and then HNO ₃ may be added and heated.
Various filtration methods can be used, such as membrane filters and filter paper. It is also preferable to use cross-flow filtration.

<Iron removal process>
The iron removal step is a step of adding an oxidizing agent to the acid treatment solution, then adding an alkaline solution, and filtering out the iron hydroxide precipitate.
An oxidizing agent (hydrogen peroxide) is added to the acid treatment solution after the acid treatment step, and the redox potential is adjusted to a positive side of 500 mVEh/V. Thereafter, an alkaline solution is added to the acid treatment solution whose redox potential has been adjusted, and the pH is adjusted to 3 to 5.5 to form a precipitate of iron hydroxide. The filtrate and the iron hydroxide precipitate are separated by filtration.
Various filtration methods can be used, such as membrane filters and filter paper. It is also preferable to use cross-flow filtration.

<Alkali treatment process>
The alkali treatment step is a step of mixing the filtrate after the iron removal step with an alkaline solution.
This is a step in which the filtrate after the iron removal step is mixed with an alkaline solution to adjust the pH to 9 to 14, and the metal elements in the filtrate are produced as hydroxide precipitates.

For example, an aqueous NaOH solution of 0.5 mol/L to 10 mol/L is added as an alkaline solution to the collected filtrate, and the pH of the filtrate is adjusted to 9 to 14 to form a hydroxide precipitate. Once the alkali addition is complete, the filtrate is filtered to collect the hydroxide precipitate.
Various filtration methods can be used, such as membrane filters and filter paper. It is also preferable to use cross-flow filtration.

This is a step of washing the recovered hydroxide precipitate to obtain a recycled positive electrode material precursor.
For example, the recovered hydroxide precipitate is heated to 20° C. to 200° C. for 0.1 to 48 hours, and then ignited and dried to obtain a dry product. Crush the dry product to obtain a pulverized product. The same amount to 10 times the amount (weight) of water is added to the pulverized material to obtain a slurry. The resulting slurry is filtered to collect the hydroxide precipitate.
Various filtration methods can be used, such as membrane filters and filter paper. It is also preferable to use cross-flow filtration.

The recovered hydroxide precipitate is dried by heating at 20° C. to 200° C. for 0.1 hour to 48 hours, and a recycled positive electrode material precursor can be obtained.
The obtained recycled positive electrode material precursor is a solid substance. In the subsequent steps, the recycled positive electrode material precursor may be handled as a solid or may be made into a slurry. Even when it is made into a slurry, the recycled positive electrode material precursor contained in the slurry remains solid.
Note that the salt remaining in the hydroxide precipitate may be removed by washing after adding a lithium source to the recycled positive electrode material precursor in the latter stage.

<Lithium source addition process>
The lithium source addition step is a step of adding a recycled positive electrode material precursor and a predetermined amount of lithium source.
Examples of the lithium source include lithium carbonate, lithium hydroxide, lithium nitrate, and lithium chloride.
The amount of the lithium source to be added is not particularly limited and can be selected as appropriate depending on the purpose, but the amount of lithium source added is 0. The amount is preferably .8 equivalent or more and 2.0 equivalent or less.

<Crushing and mixing process>
The pulverization and mixing step is a step of pulverizing a mixture to which a predetermined amount of a lithium source has been added.
The mixture to which a predetermined amount of lithium source has been added is ground to obtain a ground mixture. The pulverization can be performed using, for example, a disc mill, mixer mill, bead mill, vibration mill, ball mill, planetary ball mill, attritor, or the like.

<Baking process>
The obtained pulverized mixture is fired in an alumina crucible under atmospheric conditions at 600°C for 1 hour and then held at 900°C for 4 hours to obtain a fired product. The holding temperature for firing is preferably 650°C to 900°C. The holding time for firing is preferably 0.1 to 20 hours, more preferably 0.5 to 8 hours. In the recycled positive electrode material after firing the recycled positive electrode material precursor, iron, copper, and aluminum are converted into oxides. Specifically, iron, copper, and aluminum, which were mostly hydroxides in the recycled positive electrode material precursor, have become oxides.

<Crushing process>
The recycled cathode material of the present invention can be obtained by pulverizing the obtained fired product using a disk mill or the like.
Note that, as described above, the pulverized material after firing can be subjected to cleaning treatment, and in this case, after the cleaning treatment, the firing step can be performed again to obtain a recycled positive electrode material.

The obtained recycled positive electrode material of the present invention contains lithium, nickel, cobalt, and manganese, 0.3% by mass to 3.0% by mass of aluminum, and less than 1% by mass of at least one of copper and iron. It is possible to achieve the same level of specific capacity as a lithium-ion secondary battery using a normal cathode material, and to achieve better cycle characteristics than a lithium-ion secondary battery using a normal cathode material. .

In the method for manufacturing a recycled positive electrode material of the present invention, the recycled positive electrode material of the present invention can be used as a raw material.
If there is a difference between the composition of the metal elements that function as the target cathode material in the recycled cathode material and the composition of the metal elements in the obtained recycled cathode material of the present invention, adjust the composition of the metal elements in the recycled cathode material. can be carried out. That is, a recycled positive electrode material can be manufactured using the recycled positive electrode material of the present invention as a raw material.
Possible methods for adjusting the composition of the metal elements include, for example, a method of appropriately preparing physically treated products having different metal element compositions, a method of adding a missing metal element, and the like. The specific amount to be added may be determined based on the results of qualitative and quantitative analysis of the metal elements contained in the physically processed material by ICP analysis or fluorescent X-ray analysis.

(How to use recycled cathode material)
A method for using the recycled cathode material of the present invention includes an assembly process for assembling a lithium ion secondary battery having the recycled cathode material of the present invention;
The lithium ion secondary battery assembled in the above assembly process is charged from a cell voltage of around 0V to 4.3V to 4.6V, and then charged from a cell voltage of 0V to 3.5V to a range of 4.3V to 4.6V. The method includes an activation step of performing discharge, and further includes other steps as necessary.
In the activation step, charging and discharging is preferably performed at an upper limit cell voltage that is 0.1 V to 0.4 V higher than 4.2 V, which is the upper limit cell voltage in normal charging and discharging, and is 0.2 V to 0.3 V higher. is even more preferable. Specifically, from 0V to 3.5V, which is the upper limit cell voltage higher than the normal cell voltage range of 2.5V to 4.2V, one to five charge/discharge cycles were performed at 4.3V to 4.6V. It can be carried out twice (preferably three times). The lower limit cell voltage is more preferably 1.5V to 3.5V, and even more preferably 2.0V to 3.0V, from the viewpoint of charge/discharge cycle time.
According to the method of using a recycled cathode material of the present invention, by performing the activation step, cycle characteristics superior to those of a cathode material of a normal lithium ion secondary battery can be achieved.

(Regenerated positive electrode)
The recycled positive electrode of the present invention includes the recycled positive electrode material of the present invention, and further contains other components as necessary.
It contains the recycled cathode material of the present invention as a cathode active material, and contains a conductive agent, a binder resin, etc. as other components.
The regenerated positive electrode of the present invention can be produced by performing charge/discharge cycles several times at an upper limit cell voltage range of 0.1V to 0.4V higher than the upper limit cell voltage of 4.2V in normal charge/discharge. It has better cycle characteristics than positive electrode materials for secondary batteries.

(Lithium ion secondary battery)
The lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode, and a separator, and the positive electrode includes the recycled positive electrode material of the present invention.
The lithium ion secondary battery according to the present invention can be manufactured using the recycled positive electrode material according to the present invention by a known lithium ion secondary battery method.
The lithium ion secondary battery of the present invention having the recycled positive electrode material of the present invention has an upper limit cell voltage of 0V to 4V, which is 0.1V to 0.4V higher than the upper limit cell voltage of 4.2V in normal charging and discharging. At .6V, it has better cycle characteristics than lithium ion secondary batteries using normal positive electrode materials.
In addition, the lithium ion secondary battery of the present invention having the recycled cathode material of the present invention has a cell voltage range of 0V to 3.5V to 4.3V to 4.3V, which is higher than the normal cell voltage range of 2.5V to 4.2V. By increasing the voltage to 4.6V, Li is easily desorbed from the regenerated positive electrode, and once desorbed Li can be repeatedly desorbed and inserted, which is equivalent to a lithium ion secondary battery using a normal cathode material. In addition to being able to express specific capacity, it is also possible to achieve cycle characteristics that are superior to lithium ion secondary batteries using ordinary positive electrode materials.

Examples of the present invention will be described below, but the present invention is not limited to these Examples in any way.

(Comparative example 1)
<Manufacture of recycled cathode material>
-Heat treatment process-
The battery pack (approximately 75 kg) of the lithium-ion secondary battery to be treated was heat-treated at a temperature of 800°C (after being heated for 1 hour, then for 2 hours) using a batch burner furnace manufactured by Ecosystem Akita Co., Ltd. as the heat treatment equipment. A heat-treated product was obtained by performing heat treatment.

-Crushing process-
Next, a hammer crusher (Makino type swing hammer crusher HC-20-3.7, manufactured by Makino Sangyo Co., Ltd.) was used as a crushing device, and the frequency was 50 Hz (hammer peripheral speed 38 m/sec), and the screen at the exit part was a rostr type opening hole. The heat-treated product (heat-treated lithium ion secondary battery) obtained in the heat treatment step was crushed under the conditions of 30 mm x 200 mm to obtain a crushed product of a lithium ion secondary battery.

-Classification process-
Next, the crushed lithium ion secondary battery was sieved using a sieve with a sieve opening of 1.2 mm (diameter 200 mm, manufactured by Tokyo Screen Co., Ltd.) to obtain a sieved product (coarse particle product). A crushed product was obtained as an undersieve product (medium grain product).

-Magnetic sorting process-
The obtained crushed material was subjected to wet magnetic separation using a drum-type magnetic separator at a magnetic force of 1500 G, a drum rotation speed of 45 rpm, a solid-liquid ratio of 10%, and a slurry supply rate of 100 mL/min, and the physically treated material was recovered.

-Acid treatment process-
5 g of the obtained physically treated product was placed in a 500 mL conical beaker, 100 mL of hydrochloric acid (12N) was added, and the mixture was thermally decomposed using a hot plate at 70° C. to 100° C. for 1 hour. When the reaction subsided, 100 mL of ion-exchanged water was added, and then 100 mL of HNO ₃ (14N) was added to make an acidic solution. Then, the mixture was thermally decomposed using a 160° C. hot plate for 1 hour until the reaction subsided. After cooling the acidic solution, No. Undissolved residue in the acidic solution was removed using 5C filter paper, and the filtrate was collected.

-Alkali treatment process-
A % NaOH aqueous solution having a concentration of about 7.5% by weight was added to the collected filtrate to adjust the pH value to 12 and precipitate the hydroxide. And No. The hydroxide was collected using 5C filter paper. The recovered hydroxide was dried in a constant temperature bath at 105° C., crushed in a mortar, and then poured into a sufficient amount of ion-exchanged water to wash away water-soluble salts. The water-washed hydroxide is No. It was collected using 5C filter paper and dried in a constant temperature bath at 105°C to obtain a recycled positive electrode material precursor.

-Lithium source addition process-
To the obtained recycled cathode material precursor, lithium carbonate equivalent to 1.0 equivalent to the total of cobalt, nickel, and manganese hydroxides contained was added, and pulverized and mixed using a disk mill to obtain a pulverized mixture. I got it. The pulverized mixture was placed in an alumina crucible and fired under atmospheric conditions at 600°C for 1 hour and then at 800°C for 4 hours to obtain a fired product.
The fired product was pulverized using a disk mill to obtain a recycled positive electrode material of Comparative Example 1.

(Example 1)
The following acid treatment step was performed in place of the acid treatment step in Comparative Example 1, and the following iron removal step was performed between the acid treatment step and the alkali treatment step, and the resulting recycled positive electrode material precursor contained A recycled positive electrode material of Example 1 was obtained in the same manner as Comparative Example 1, except that lithium carbonate was added in an amount equivalent to 1.25 equivalents to the total of cobalt, nickel, and manganese hydroxides. .

-Acid treatment process-
30 g of the resulting physically treated product was placed in a 1,000 mL upright beaker, and 1,000 mL of 20% by weight sulfuric acid was added to form an acidic solution. Then, it was thermally decomposed using a 150° C. hot plate for 4 hours. After cooling the acidic solution, No. Undissolved residue in the acidic solution was removed using 5C filter paper, and the filtrate was collected.

-Iron removal process-
An oxidizing agent (hydrogen peroxide) was added to the acid treatment solution after the acid treatment step, and the redox potential was adjusted to 650 mV (Ag/AgCl). Thereafter, an alkaline solution was added to the acid treatment solution in which the redox potential had been adjusted, and the pH was adjusted to 4.7 to produce a precipitate of iron hydroxide. The filtrate and iron hydroxide precipitate were separated by filtration.

(Comparative example 2)
A commercially available common cobalt-nickel-manganese positive electrode material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , PLB-H1, manufactured by Gelon LIB Group Ltd.) was prepared.

Next, each of the obtained recycled cathode materials was acid-decomposed with a mixed acid of HCl and HNO ₃ and then analyzed using ICP-AES (SPECTRO GREEN, manufactured by Hitachi High-Tech Science Co., Ltd.). The results are shown in Tables 1-1 and 1-2. Note that the unit of content of each element in Tables 1-1 and 1-2 is mass %.

<Battery manufacturing>
(1) Manufacture of positive electrode The recycled positive electrode materials according to Example 1 and Comparative Examples 1 and 2 were used as active materials, acetylene black (Denka Black, manufactured by Denka Co., Ltd.) was used as a conductive agent, and polyvinylidene fluoride (KF Polymer) was used as a binder. F #9130, manufactured by Kureha Co., Ltd.), and N-methylpyrrolidone was prepared as a solvent.
Then, recycled positive electrode material: acetylene black: polyvinylidene fluoride was mixed in a ratio of 80:10:10 (% by mass) to form a mixture. N-methylpyrrolidone was added to the mixture to obtain a slurry. The amount of N-methylpyrrolidone added to the mixture was such that the mass ratio of the mixture:N-methylpyrrolidone was 1:1.25.
The resulting slurry was stirred for 10 minutes using a stirrer, and then applied using a Baker applicator to form a coated product and dried in a dryer at 100°C. After pressing the dried coating material for 4 tons, a positive electrode was punched out to a diameter of 15 mm.

(2) Manufacture of negative electrode Graphite (CGB-10, manufactured by Nippon Graphite Industries Co., Ltd.) is used as an active material, acetylene black (Denka Black, manufactured by Denka Co., Ltd.) is used as a conductive agent, and carboxymethyl cellulose (Celogen 7A, manufactured by Denka Co., Ltd.) is used as a binder. (manufactured by Ichi Kogyo Seiyaku Co., Ltd.), styrene-butadiene rubber (TRD2001, manufactured by JSR Corporation), and pure water as a solvent were prepared.
Then, a mixture was prepared by mixing graphite: acetylene black: carboxymethyl cellulose: styrene-butadiene rubber in a ratio of 90:5:2.5:2.5 (% by mass). Distilled water was added to the mixture to obtain a slurry. The amount of distilled water added to the mixture was such that the mass ratio of the mixture: distilled water was 1:1.6.
The obtained slurry was subjected to stirring, coating, drying, pressing, and punching in the same manner as in the production of the positive electrode described above to produce a negative electrode.

(3) Assembling a lithium ion secondary battery Using a CR2032 type coin cell in a glove box filled with pure argon gas, as shown in FIG. The negative electrode 5, spacer 6, washer 7, and negative electrode current collector 8 were laminated in this order to assemble full cells according to Example 1 and Comparative Examples 1 and 2. The full cell used graphite as an active substance, and the assumed specific capacity of graphite was 340 mAh/g.
The separator used was porous polypropylene (#2500, manufactured by Celgard LLC) with a diameter of 19 mm, the electrolyte used LiPF ₆ at a concentration of 1 mol/L as the solute, and ethylene carbonate + diethyl carbonate (volume ratio 1:1) was used as the solvent. there was.
In the case of a full cell, the assumed specific capacity of normal cathode material and recycled cathode material was varied in the range of 100mAh/g to 150mAh/g depending on the cell voltage range during charging and discharging, but the ratio of negative electrode capacity to positive electrode capacity (NP ratio ) was set to 1.2. The assumed specific capacity of the cathode material used in the full cell shall be specified in each case.

3. Battery charge/discharge test A charge/discharge test using a cycle test was carried out on the manufactured full cells according to Example 1 and Comparative Examples 1 and 2 as follows, and the regeneration according to Example 1 and Comparative Examples 1 and 2 was carried out as follows. The charge/discharge specific capacity and Coulomb efficiency (charge/discharge efficiency, hereinafter simply referred to as efficiency) of the positive electrode material were measured. In the case of a full cell, the performance of the cell was evaluated using the positive electrode reference specific capacity, which is the capacity measured during charging and discharging of the cell divided by the mass of recycled positive electrode material in the cell.

(1) Full cell charge/discharge test (I) (full cell cycle test)
Charging and discharging were carried out at a constant current density under the following conditions.
Test temperature: 25℃
Cell voltage range: 2.5V to 4.2V (Initial charge: 0V to 4.2V)
Current density: 2C
Number of cycles: 500 cycles Assumed specific capacity of normal cathode material: 140mAh/g
However, 1C = 140mA/g - normal cathode material Assumed specific capacity of recycled cathode material: 100mAh/g
However, 1C=100mA/g - Regenerated positive electrode material The results of the relationship between the number of cycles and specific capacity characteristics in the cycle test are shown in FIGS. 3 to 5 and Table 2. Further, the results of the relationship between specific capacity and cell voltage in the cycle test are shown in FIGS. 6 to 8. However, in FIGS. 3 to 5, the horizontal axis is the number of cycles, the left vertical axis is the specific capacity, and the right vertical axis is the efficiency. When the charging specific capacity was plotted as □, the discharging specific capacity as ◇, and the efficiency as ○, the plots of charging specific capacity: □ and discharging specific capacity: ◇ overlapped.

(II) (Full cell cycle test, 2.5V to 4.4V (first charge: 0V to 4.4V))
The cell voltage range was raised to 2.5V to 4.4V, and a cycle test was conducted in the same manner as above. The assumed specific capacity of all positive electrode materials was 150 mAh/g. However, 1C=150mA/g. The results are shown in Table 3.

If charging and discharging is performed in advance in a range of upper limit cell voltage that is 0.2V higher than 4.2V, which is the upper limit cell voltage in normal charging and discharging, a greater effect of improving cycle characteristics is shown compared to Comparative Examples 1 and 2. I understand.
This shows that when the upper limit cell voltage is increased, that is, when the potential of the positive electrode is further increased, Li is more easily desorbed from the regenerated positive electrode of Example 1, and once desorbed Li can be repeatedly desorbed and inserted thereafter. Ta. Example 1 can exhibit better specific capacity than Comparative Examples 1 and 2 when used in the normal cell voltage range of 2.5V to 4.2V, but when used at a high upper limit cell voltage of 2.5V to 4.4V, It was found that within this range, the effect of improving battery characteristics compared to Comparative Examples 1 and 2 becomes more significant.

(III) (Full cell 2.5V to 4.4V, 0.1C, after 3 cycles, cycle test 2.5V to 4.2V)
For the full cell of Example 1, after 3 cycles of charging and discharging at 2.5V to 4.4V (initial charge: 0V to 4.4V) and 0.1C, the above conditions were applied in the cell voltage range of 2.5V to 4.2V. A cycle test was conducted in the same manner as above. The assumed specific capacity of all positive electrode materials was 140 mAh/g. However, 1C=140mA/g. The results are shown in Table 4.

(Example 2)
(IV) (Full cell 2.5V to 4.3V, 0.1C, after 3 cycles, cycle test 2.5V to 4.2V)
A full cell assembled in the same manner as in Example 1 was charged and discharged for 3 cycles at 2.5V to 4.3V (however, the initial charge was 0V to 4.3V) and 0.1C. Thereafter, a cycle test was conducted in the same manner as above in a cell voltage range of 2.5V to 4.2V. In this case as well, the assumed specific capacity of all positive electrode materials was 140 mAh/g. However, 1C=140mA/g. The results are shown in Table 4.

(Example 3)
(V) (Full cell 2.5V to 4.5V, 0.1C, after 3 cycles, cycle test 2.5V to 4.2V)
After performing 3 cycles of charging and discharging at 2.5V to 4.5V (however, the first charge was 0V to 4.5V) and 0.1C to a full cell assembled in the same manner as in Example 1, the cell A cycle test was conducted in the same manner as above in the voltage range of 2.5V to 4.2V. In this case as well, the assumed specific capacity of all positive electrode materials was 140 mAh/g. However, 1C=140mA/g. The results are shown in Table 4.

From the results in Table 4, even when the assumed specific capacity of the cathode material is 140mAh/g, the full cell of Example 1 can be obtained by performing three cycles of charging and discharging at 2.5V to 4.4V and 0.1C in advance. , 2.5 V to 4.4 V, and 0.1 C without performing 3 cycles of charging and discharging in advance, it was found that cycle characteristics were even better than those of the full cells of Comparative Examples 1 and 2.

The full cell of Example 1 had a higher specific capacity of the recycled cathode material than the full cells of Examples 2 and 3, and also maintained a high retention rate after the cycle test.
On the other hand, compared to Example 2, the recycled positive electrode material showed high cycle stability by going through the step of activating the cell at a higher voltage as in Examples 1 and 3. In addition, since a cell voltage higher than 4.6V is likely to greatly accelerate the decomposition of the electrolyte of the lithium ion secondary battery, the highest cell voltage in the activation step is preferably 4.3V to 4.5V. Among these, it was confirmed that 4.4V is more preferable.

1 Positive electrode current collector 2 Positive electrode 3 Separator 4 Gasket 5 Negative electrode 6 Spacer 7 Washer 8 Negative electrode current collector 10 Lithium ion secondary battery

Claims (13)

lithium, nickel, cobalt, and manganese;
0.3% by mass or more and 3% by mass or less of aluminum,
less than 1% by mass of at least one of copper and iron;
A recycled cathode material characterized by containing. The recycled positive electrode material according to claim 1, which contains at least one of calcium and magnesium, and has a content of at least one of calcium and magnesium of 0.02% by mass or more and 0.1% by mass or less. The recycled positive electrode material according to any one of claims 1 to 2, wherein the aluminum content is 0.5% by mass or more and 2.5% by mass or less. The recycled cathode material according to claim 1, wherein the lithium content is 5% by mass or more and 9% by mass or less. The copper content is 0.01% by mass or less,
The recycled cathode material according to any one of claims 1 to 2, wherein the iron content is 0.6% by mass or less. The copper content is 0.0005% by mass or more and 0.005% by mass or less,
The recycled positive electrode material according to claim 5, wherein the iron content is 0.002% by mass or more and 0.6% by mass or less. The aluminum (Al) content (mass %), the copper (Cu) content (mass %), and the iron (Fe) content (mass %) are expressed by the following formula, Al/(Al+Cu+Fe) The recycled cathode material according to any one of claims 1 to 2, which satisfies ≧0.4. The recycled cathode material according to any one of claims 1 to 2, containing the nickel, the cobalt, and the manganese in a total amount of 50% by mass or more. A method for manufacturing a recycled cathode material according to any one of claims 1 to 2, comprising:
a heat treatment step of obtaining a heat-treated product by heat-treating a lithium ion secondary battery;
A crushing step of crushing the heat-treated product to obtain a crushed product;
a physical sorting step of physically sorting the crushed material to obtain a physically processed material;
an acid treatment step of adding an acidic solution to the physically treated product to obtain an acid treatment solution;
an iron removal step of adding an oxidizing agent to the acid treatment solution, then adding an alkaline solution, and filtering out the iron hydroxide precipitate;
an alkali treatment step of mixing the filtrate after the iron removal step with an alkaline solution;
A method for producing a recycled cathode material, comprising: The method for producing a recycled cathode material according to claim 9, comprising a lithium source addition step of adding a lithium source. An assembly step of assembling a lithium ion secondary battery having the recycled cathode material according to any one of claims 1 to 2;
The lithium ion secondary battery assembled in the above assembly process is charged from a cell voltage of around 0V to 4.3V to 4.6V, and then charged from a cell voltage of 0V to 3.5V to a range of 4.3V to 4.6V. an activation step of discharging;
A method of using a recycled cathode material characterized by comprising: A recycled positive electrode comprising the recycled positive electrode material according to any one of claims 1 to 2. A lithium ion secondary battery comprising the regenerated positive electrode according to claim 12.

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