KR20130138523A - Recycling method of electrode active material of metal oxide, electrode active material of metal oxide for lithium secondary battery, electrode for lithium secondary battery, and lithium secondary battery fabricated thereby - Google Patents

Abstract

The present invention relates to a method for recycling a lithium secondary battery metal oxide electrode active material. The present invention provides a first step of preparing an electrode scrap containing a metal oxide electrode active material generated during the manufacturing process of a lithium secondary battery; Heat treating the electrode scrap in an air atmosphere or an air and nitrogen mixed gas atmosphere to carbonize a binder present in the electrode scrap; And recovering a metal oxide electrode active material from the electrode scrap. According to the present invention, it is possible to minimize environmental pollution by a simple physical heat treatment and separation method, and to recycle the metal scrap electrode active material contained in the electrode or the scrap generated during the electrode and battery manufacturing process at a simple process and low cost. .

Description

Recycling method of electrode active material of metal oxide, electrode active material of metal oxide for lithium secondary battery, electrode for lithium secondary battery, and lithium secondary battery fabricated

The present invention relates to a method for recycling a metal oxide electrode active material, a metal oxide electrode active material for a lithium secondary battery, a lithium secondary battery electrode and a lithium secondary battery manufactured according to the present invention.

Lithium secondary batteries are secondary batteries having excellent performances such as high capacity, high output, and long life, and are widely used in small electronic products such as electronic devices, portable computers, and mobile phones. In particular, as attention to green growth and renewable energy has recently been focused, demand for large-capacity lithium secondary batteries is expected to increase rapidly as electric vehicles are commercialized.

A lithium secondary battery active material, a metal oxide electrode material has been a number of kinds of materials have been developed, conventional LiCoO ₂ electrode active material, the three-component _{(LiNi 0 .5 Mn 0 .3 Co} 0 .2 O 2, LiCo 1/3 far In recent years, Li ₄ Ti ₅ O ₁₂ has been spotlighted as a negative electrode material of a large-capacity lithium secondary battery for electric vehicles, together with electrode active materials such as Ni _1/3 Mn _1/3 O ₂ and LiMn ₂ O ₄ electrode active materials.

As described above, the lithium secondary battery market and industry are expected to expand rapidly, but since lithium (Li) and related compounds, which are essential metals for the positive electrode active material, are not present in Korea, all of them are imported and used overseas. Therefore, it is necessary to collect and recycle the cathode active material scrap generated in the lithium secondary battery manufacturing process or the lithium secondary battery cathode active material that is discarded after use in a country without an existing resource such as Korea.

In the conventional method of extracting or recovering various metals and compounds such as lithium from a lithium secondary battery metal oxide electrode active material material, the electrode active material material separated from a waste lithium battery may be hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ) or nitric acid. Dissolve in (HNO ₃ ) and neutralize with alkali to precipitate and recover cobalt, nickel, etc. by hydroxide, or separate the metal such as cobalt, manganese, nickel from the electrode active material solution by solvent extraction Use

As such, the conventional metal oxide electrode active material treatment method is mainly for recovery of cobalt and nickel, and lithium has not been of much interest because it is cheaper than cobalt and nickel in terms of price. However, lithium resources are very limited, and large-capacity lithium secondary batteries for electric vehicles and electric power storage are enormous and if not recycled, there is a problem of resource shortage and environmental pollution. This is expected to be very important.

In addition, in the conventional method for processing a metal oxide electrode active material, since most metal oxide electrode active material is dissolved in a strongly acidic solution, and then expensive metals such as lithium, cobalt, and nickel in the solution are separated and recovered. In addition to excessive process costs for the highly separated metals, strong acid must be used to dissolve the metal oxide electrode active material, which causes severe environmental pollution due to evaporation into the atmosphere, and particularly corrosion of the equipment due to acid. Very serious.

In particular, since the composition of the metal oxide electrode active material contained in the electrode scrap or the battery during the electrode and battery manufacturing process is intact, the existing chemical recovery method does not generate pollutants and is not economical. I need a way.

Korean Laid-Open Patent Publication No. 10-2012-0031831 includes (a) dissolving a lithium battery cathode active material in an oxalic acid solution to obtain a solution in which lithium is dissolved, and (b) adding soda ash to the solution in which lithium is dissolved, thereby removing impurities. Disclosed is a method for recovering lithium from a lithium battery cathode active material comprising a step of separating and precipitating and separating (c) a lithium dissolved solution with lithium carbonate through a step (b) and a solution of lithium dissolved therein. have. Korean Laid-Open Patent Publication No. 10-2012-0031832 (a) dissolving a lithium oxide positive electrode active material containing LiFePO4 and iron powder in an aqueous solution of phosphoric acid to obtain a solution in which LiFePO4 is dissolved, (b) the LiFePO4 is dissolved Precipitating and separating the iron and impurities by adding caustic soda to the prepared solution; and (c) precipitating and separating lithium with lithium phosphate by mixing LiFePO 4 dissolved solution and ethanol through step (b). A method for recovering lithium from a water-based lithium battery cathode active material is disclosed.

The present invention minimizes environmental pollution by a simple physical heat treatment and separation method, and can recycle the metal scrap electrode active material contained in the battery or the electrode scrap generated during the electrode and battery manufacturing process with a simple process and low cost. To provide.

One embodiment of the present invention provides a first step of providing an electrode scrap containing a metal oxide electrode active material generated during the manufacturing process of the lithium secondary battery; Heat treating the electrode scrap in an air atmosphere or an air and nitrogen mixed gas atmosphere to carbonize a binder present in the electrode scrap; And a third step of recovering the metal oxide electrode active material from the electrode scrap.

After the third step, the method may further include forming a lithium secondary battery electrode by using the recovered metal oxide electrode active material.

The metal oxide may include one or more selected from the group consisting of LiMO ₂ , LiMn ₂ O _4, and Li ₄ Ti ₅ O ₁₂ , and M may include one or more selected from the group consisting of Ni, Co, and Mn.

The metal oxide may include _{LiNi 0 .5 Mn 0 .3 Co 0} .2 O 2, LiCoO 2, LiMn 2 O 4 and Li ₄ at least one selected from the group consisting of Ti ₅ O _12.

The heat treatment may be performed for 300 to 700 ℃, 30 minutes ~ 2 hours.

The second step may include a process of grinding and sieving.

Air in the mixed gas may be 0.5 to 50% by volume.

Another embodiment of the present invention may be a metal oxide electrode active material for a lithium secondary battery prepared according to the above method.

Another embodiment of the present invention may be a lithium secondary battery electrode comprising a metal oxide electrode active material prepared according to the above method.

Another embodiment of the present invention may be a lithium secondary battery comprising an electrode for a lithium secondary battery prepared according to the above method.

According to the present invention, it is possible to minimize environmental pollution by a simple physical heat treatment and separation method, and to recycle the metal scrap electrode active material contained in the battery or the electrode scrap generated during the electrode and battery manufacturing process with a simple process and low cost. have.

The present invention is not only improved performance compared to the conventional metal oxide electrode active material, but also can be manufactured in a low cost and environmentally friendly way to commercialize this lithium secondary battery having the characteristics of high power, high energy density, high energy efficiency, long life Can be provided.

The metal oxide electrode active material for a lithium secondary battery recycled by the present invention can recover a large amount of metal oxide electrode active material for an economical and excellent performance because the manufacturing method is made of a simple and environmentally friendly manufacturing process.

1 is a process flow diagram for a method for recycling a metal oxide electrode active material according to one embodiment of the present invention.
2 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 1 and Comparative Example 1. FIG.
3 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 2 and Comparative Example 2. FIG.
4 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 3 and Comparative Example 3. FIG.
5 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 4 and Comparative Example 4. FIG.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

Furthermore, embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Accordingly, the shapes and sizes of the elements in the drawings may be exaggerated for clarity of description, and the elements denoted by the same reference numerals in the drawings are the same elements.

1 is a process flow diagram for a method for recycling a metal oxide electrode active material according to one embodiment of the present invention.

1, one embodiment of the present invention provides a first step (S1) of preparing an electrode scrap containing a metal oxide electrode active material generated during the manufacturing process of a lithium secondary battery; A second step (S2) of carbonizing the binder present in the electrode scrap by heat-treating the electrode scrap in an air atmosphere or an air and nitrogen mixed gas atmosphere; And a third step (S3) of recovering the metal oxide electrode active material from the electrode scrap.

First, an electrode scrap containing a metal oxide electrode active material generated during a manufacturing process of a lithium secondary battery may be prepared in a first step (S1).

The lithium secondary battery electrode may be manufactured as follows. That is, the electrode may be prepared by mixing an electrode active material, a conductive material and a binder with an organic solvent to prepare a slurry, applying the slurry onto a thin conductive metal plate, and drying the slurry. The electrode sheet for a lithium secondary battery may be cut into a desired shape and used as an electrode of a lithium secondary battery, and the scrap generated during the cutting process may be collected to prepare an electrode scrap.

The binder may be an aqueous binder or an organic binder. Specifically, the present invention is not limited thereto, but a polymer solution containing sodium carboxymethyl cellulose (1 wt% in water) and styrene butadiene rubber (40 wt% in water) may be used as a binder, and PVDF (polyvynilidene) as an organic binder. fluoride) can be used. The conductive material is not particularly limited as long as it can impart conductivity to the electrode. Specifically, carbon black (trade name: Denka Black) or graphite (trade name: KS6) may be used. The conductive metal thin plate is not particularly limited as long as it has excellent electronic conductivity, and specifically, may include one or more selected from the group consisting of an aluminum thin plate, a copper thin plate, a gold thin plate, a silver thin plate and a platinum thin plate.

The present embodiment relates to a technique for recycling electrode scrap generated during the production of a lithium secondary battery. Moreover, the electrode which exists in the battery judged as defect in the manufacturing process is also made into the object. Since they are not yet used, lithium in the electrode active material can be recycled without recharging. The lithium secondary battery electrode may have a structure in which an electrode active material layer is formed on a conductive metal thin plate.

The present embodiment relates to a method for recycling a metal oxide used as an electrode active material of a lithium secondary battery. The metal oxide may include one or more selected from the group consisting of LiMO ₂ , LiMn ₂ O _4, and Li ₄ Ti ₅ O ₁₂ , and M may include one or more selected from the group consisting of Ni, Co, and Mn. More specifically, the metal oxide may include _{LiNi 0 .5 Mn 0 .3 Co 0} .2 O 2, LiCoO 2, LiMn 2 O 4 and at least one selected from the group consisting of Li ₄ Ti ₅ O _12. However, the metal oxide is not particularly limited as long as it is a metal oxide that can be used as an electrode active material of a lithium secondary battery, and is not limited to the materials listed above. In addition, the electrode active material of a lithium secondary battery may be a positive electrode active material or a negative electrode active material.

Next, the electrode scrap may be heat-treated in the second step to carbonize the binder present in the electrode scrap (S2);

The electrode scrap may include a conductive metal thin plate and an electrode active material layer, and the electrode active material layer may contain a binder. The binder may be thermally decomposed at high temperature as an organic polymer material and remain in the form of carbon after pyrolysis, which may function as a conductive material as in the case of carbon black. In order to carbonize the binder, the electrode scrap is heat-treated, and the carbonized binder partially covers the surface of the electrode active material, thereby improving the conductivity of the electrode and ultimately improving the performance of the lithium secondary battery.

The heat treatment may be performed for 30 minutes to 2 hours in an air atmosphere or a mixed gas atmosphere of air and nitrogen. The concentration of oxygen in the air is about 21% by volume.

The ratio of air in the mixed gas of air and nitrogen may be 0.5 to 50% by volume. In this case, only the binder can be carbonized without changing the composition and structure of the metal oxide electrode active material. If the amount of air is more than 50% by volume, carbon is less generated by carbonization, and if the amount of air is less than 0.5% by volume, carbon may be generated.

Since heat treatment in an inert or reducing atmosphere may change the composition and structure due to partial reduction of the metal oxide, the heat treatment time is shortened so that the organic matter is not oxidized and carbides remain in the temperature range where the organic matter is carbonized in the oxidizing atmosphere. It is also possible to use a mixture of air and nitrogen to reduce the oxygen (air) concentration in order to control and reduce the degree of oxidation to leave more carbides.

When the heat treatment temperature is lower than 300 ° C., the binder present in the electrode scrap may not be carbonized, and the current collector may not be separated from the electrode active material layer. If the heat treatment temperature is higher than 700 ℃ phase change of the electrode active material may occur, the crystallinity and particle size of the electrode active material may be increased, the performance of the battery may be lowered, a lot of energy is consumed and it may be uneconomical.

The heat treatment time may be 30 minutes to 2 hours. If the heat treatment time is shorter than 30 minutes, the binder may not be carbonized. If the heat treatment time is longer than 2 hours, the performance of the battery may be degraded due to the phase change of the electrode active material, the increase of crystallinity, and the increase in the particle size. It can be consumed and uneconomical.

Next, a metal oxide electrode active material may be recovered from the electrode scrap in a third step, and the third step may include a process of polishing and sieveing (S3).

When the heat treatment is performed, the conductive metal sheet used as the current collector can be easily separated from the electrode active material layer due to the thermal expansion difference between the electrode active material layer and the conductive metal sheet used as the current collector. The separated electrode active material layer may be polished and sieved to completely remove the remaining conductive metal and recover the electrode active material powder. 200 mesh sieves can be used for sifting

After the third step, using the recovered metal oxide electrode active material to form a lithium secondary battery electrode (S4) may be further included.

Specifically, 80 to 98% by weight of the recovered metal oxide electrode active material, 1 to 10% by weight of the binder, and 1 to 10% by weight of the conductive material may be mixed. At this time, the binder may be a polymer solution containing sodium carboxymethyl cellulose (1 wt% in water) and styrene butadiene rubber (40 wt% in water) or PVdF polymer solution dissolved in NMP (N-methyl-pyrrolidinone). . As the conductive material, carbon black and graphite may be mixed and used.

Further, in order to homogeneously mix the above slurry, a homogenizer may be used to stir at high speed for 40 minutes at 5,000 rpm. A lithium secondary battery electrode can be manufactured by applying a homogenized slurry to a 20 μm thick aluminum thin film or a copper thin film using a doctor blade method at a constant thickness, such as 80 to 250 μm.

Since the binder may remain in a carbonized state on the surface of the recovered electrode active material, and carbide may serve as a conductive material, an electrode manufactured using the recovered electrode active material may have better conductivity. In addition, since the recovered electrode active material is already coated with carbides, the amount of the conductive material added can be reduced, thereby reducing the cost.

Another embodiment of the present invention may be a metal oxide electrode active material for a lithium secondary battery prepared according to the above method. In this embodiment, the matter regarding an electrode scrap, binder carbonization, electrode active material collection | recovery, a electrically conductive material, etc. is the same as what was demonstrated in previous embodiment.

Another embodiment of the present invention may be a lithium secondary battery electrode comprising a metal oxide electrode active material prepared according to the above method. In this embodiment, the matter regarding an electrode scrap, binder carbonization, electrode active material collection | recovery, a electrically conductive material, etc. is the same as what was demonstrated in previous embodiment.

Another embodiment of the present invention may be a lithium secondary battery comprising an electrode for a lithium secondary battery prepared according to the above method. In this embodiment, the matter regarding an electrode scrap, binder carbonization, electrode active material collection | recovery, a electrically conductive material, etc. is the same as what was demonstrated in previous embodiment.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example 1

Prepared by _{LiNi 0 .5 Mn 0 .3 Co 0} .2 O anode scrap remaining after residue ₂ by cutting a lithium secondary battery positive electrode sheet in a lithium secondary battery positive electrode manufacturing process using a positive electrode active material used as an anode of a lithium secondary battery It was.

For reference, the lithium secondary battery positive electrode was prepared as follows. In other words, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ powder as an electrode active material, sodium carboxymethyl cellulose (1 wt% in water) and styrene butadiene rubber (40 wt% in water) as a binder, carbon black as a conductive material (Trade name: Denka Black) and graphite (trade name: KS6) were used in combination. After mixing the electrode active material, the binder and the conductive material into an organic solvent, and ball milling to prepare an electrode active material slurry, the slurry is applied on a 20 μm thick aluminum sheet to a thickness of 150 μm to form an electrode active material A layer was formed and dried in an oven to prepare a cathode sheet for a lithium secondary battery.

The recovered anode scrap was placed in a tubular furnace and heat treated at 450 ° C. for 30 minutes in an air atmosphere to carbonize the binder present in the anode scrap.

After physically separating the aluminum current collector from the heat-treated amount, the remaining aluminum current collector was separated first by grinding the remainder, and then sieving with a 200 mesh sieve to completely remove the aluminum current collector secondarily, thereby coating carbon coated LiNi. _0.5 Mn _0.3 Co _0.2 O ₂ cathode active material was recovered.

10 g of the recovered electrode active material, 0.1 g of carbon black as a conductive material, and 10 g of a polymer solution containing sodium carboxymethyl cellulose (1 wt% in water) and styrene butadiene rubber (40 wt% in water) as binders After adjusting to about 20,000 cp which is a viscosity which is easy to apply | coat to an aluminum thin film, it stirred for 40 minutes at the high speed of 5,000 rpm using the mixer. The stirred slurry was applied to a 20 μm thick aluminum thin film using a doctor blade method to a thickness of 100 μm to prepare a cathode for a lithium secondary battery.

The prepared lithium secondary battery electrode is used as an anode, graphite is used as a cathode, a polypropylene membrane is placed between the anode and the cathode as a separator, and ethyl carbonate / ethyl methyl carbonate / dimethyl carbonate is 1: 1 by volume as an electrolyte. A solution in which 1 M LiPF ₆ lithium salt was dissolved was mixed into an organic solvent mixed with each other, and a lithium secondary battery was assembled with the outer housing in the form of an aluminum pouch.

Example 2

The same as in Example 1 except that LiCoO ₂ is used as the positive electrode active material.

Example 3

The same as in Example 1 except for using LiMn ₂ O ₄ as the positive electrode active material.

Example 4

In the negative electrode manufacturing process for a lithium secondary battery using Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, the negative electrode sheet for a lithium secondary battery was cut and used as a negative electrode of a lithium secondary battery, and the remaining residues were prepared as negative electrode scrap.

The recovered negative scrap was placed in a tubular furnace and heat treated at 450 ° C. for 30 minutes in a mixed gas atmosphere of air and nitrogen having an air volume of 5% by volume to carbonize the binder present in the negative electrode scrap.

Grinding the heat-treated Li ₄ Ti ₅ O ₁₂ negative electrode firstly separates the copper current collector, sieving with a 200 mesh sieve to completely remove the copper current collector, and thermally decomposing the binder to obtain a carbon-covered Li ₄ Ti ₅ O ₁₂ negative electrode active material. Recovered.

10 g of recovered Li ₄ Ti ₅ O ₁₂ anode active material, carbon black 0.1g as conductive material, sodium carboxymethyl cellulose (1 wt% in water) and styrene butadiene rubber (40 wt% in water) as binder 10 g was mixed and adjusted to about 20,000 cp, which is a viscosity easily applied to the copper thin film, and then stirred for 40 minutes at a high speed of 5,000 rpm using a mixer. The stirred slurry was applied to a 20 μm thick copper thin film using a doctor blade method to form a negative electrode active material layer, and dried in an oven to prepare a negative electrode for a lithium secondary battery.

The prepared electrode is used as a cathode, the electrode manufactured using commercially available LiCoO ₂ is used as an anode, and a polypropylene (PP) membrane is placed between the anode and the cathode as a separator, and ethyl carbonate / ethyl methyl carbonate / dimethyl as an electrolyte. A solution in which 1 M LiPF ₆ lithium salt was dissolved was injected into an organic solvent in which carbonate was mixed at a volume ratio of 1: 1: 1, and an aluminum pouch-type battery was assembled.

Comparative Example 1

Original LiNi _{0 .5} not to reprocess the same as that of Mn _{0 .3} Co _{0 .2} O, except that the embodiment ₂ was used in Example 1.

Comparative Example 2

Same as in Example 2, except that the original LiCoO ₂ without retreatment was used.

Comparative Example 3

Same as in Example 3, except that the original LiMn ₂ O ₄ without reprocessing was used.

Comparative Example 4

The same as in Example 4, except that the original Li ₄ Ti ₅ O ₁₂ without reprocessing was used.

The capacity and cycle performance of the lithium secondary batteries according to the Examples and Comparative Examples were evaluated using the constant current method, and the results are shown in FIGS. 2 to 4.

2 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 1 and Comparative Example 1. FIG. 3 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 2 and Comparative Example 2. FIG. 4 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 3 and Comparative Example 3. FIG. 5 is a diagram illustrating cycle performance and discharge voltage characteristics of a lithium secondary battery according to Example 4 and Comparative Example 4. FIG.

2 to 5, it can be seen that the battery according to the embodiment is inferior to the cycle performance and the high rate discharge characteristic at 1C, and in some cases, is superior to those of the comparative example. This is because the metal oxide electrode active material recovered according to the present invention has improved electrical conductivity of the electrode because carbon is partially coated on the surface of the electrode active material by heat treatment.

The terms used in the present invention are intended to illustrate specific embodiments and are not intended to limit the invention. The singular presentation should be understood to include plural meanings, unless the context clearly indicates otherwise.

The word " comprises " or " having " means that there is a feature, a number, a step, an operation, an element, or a combination thereof described in the specification.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims.

It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

Claims (10)

A first step of preparing an electrode scrap containing a metal oxide electrode active material generated during a manufacturing process of a lithium secondary battery;
Heat treating the electrode scrap in an air atmosphere or an air and nitrogen mixed gas atmosphere to carbonize a binder present in the electrode scrap; And
Recovering a metal oxide electrode active material from the electrode scrap;
Recycling method of the metal oxide electrode active material comprising a.
The method of claim 1,
And after the third step, forming a lithium secondary battery electrode using the recovered metal oxide electrode active material.
The method of claim 1,
The metal oxide includes at least one selected from the group consisting of LiMO ₂ , LiMn ₂ O ₄ and Li ₄ Ti ₅ O ₁₂ , wherein M is at least one selected from the group consisting of Ni, Co and Mn Recycling method of active material.
The method of claim 1,
The metal oxide is _{LiNi 0 .5 Mn 0 .3 Co 0} .2 O 2, LiCoO 2, LiMn 2 O 4 and Li ₄ Ti ₅ O recycling of the metal oxide electrode active material comprising at least one selected from the group consisting of ₁₂ .
The method of claim 1,
The heat treatment is 300 ℃ ~ 700 ℃, recycling method of a metal oxide electrode active material is performed for 30 minutes to 2 hours.
The method of claim 1,
The second step is a method of recycling a metal oxide electrode active material comprising a process of grinding and sieve.
The method of claim 5,
Air in the mixed gas is 0.5 to 50% by volume of the metal oxide electrode active material recycling method.
Metal oxide electrode active material for a lithium secondary battery prepared according to the method of claim 1.
A lithium secondary battery electrode comprising the metal oxide electrode active material of claim 8.
A lithium secondary battery comprising the lithium secondary battery electrode of claim 9.

Images