KR20150086143A - Method of manufacturing electrode active material and cathod active material manufactured by the method - Google Patents

Abstract

The present invention discloses an electrode active material preparation method. The method includes the steps of: adding the metal oxide included in a secondary battery into a sulfuric acid solution; adding hydrogen peroxide to the sulfuric acid solution including the metal oxide after a predetermined period of time elapses from the previous step; initiating the reaction between the solution including the hydrogen peroxide and an sulfuric acid solution and removing the precipitate produced in the reaction; removing the metal impurities from the solution without the precipitate by using a solvent extraction method; and preparing lithium metal oxide by using the solution without the metal impurities.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing an electrode active material and a cathode active material produced by the method. BACKGROUND ART < RTI ID = 0.0 >

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing an electrode active material and a cathode active material produced by the method, and more particularly, to a method of producing an electrode active material by recycling spent lithium battery and a cathode active material produced by the method will be.

Worldwide, the amount of waste metal resources is steadily increasing, but its recycling is low, resulting in environmental pollution and waste of resources. As a result, interest in utilization of waste metal resources has increased, and technology for recycling waste batteries has been developed.

Waste manganese batteries, waste alkaline manganese batteries, and waste oxidized batteries are currently in operation in recycling plants in the US, Japan and Europe. However, waste lithium secondary batteries are being recycled to an extremely limited extent due to the explosion problem.

Some small domestic companies have studied the feasibility of recovering metals such as copper and cobalt oxide and their feasibility, but they have not progressed due to lack of technology. At present, we are conducting research on the commercialization of recycling process of waste lithium ion battery in Korea. We have developed a physical process for selectively separating and separating cathode active material from waste lithium ion battery and a chemical treatment process for maximizing the recovery rate of cobalt rare metal Some companies have been trying to develop the catalyst, but the yield and purity are low.

The lithium secondary battery cathode material market is expected to lead the market for lithium-ion rechargeable batteries (EV) since 2018, of which NMC is expected to be the mainstay. In addition, it is very important for Korean companies to recycle Cobalt and Nickel from the anode materials of the rechargeable battery NMC, as the market share of the lithium rechargeable battery market is expected to increase sharply to 54% by 2020. In this regard, there is a growing need for recovery techniques and methods that can be recycled into secondary battery cathode active materials.

It is an object of the present invention to provide a method for producing an electrode active material by recycling spent lithium secondary battery and a cathode active material produced by the method.

According to another aspect of the present invention, there is provided a method of producing an electrode active material, the method including: inputting a metal oxide contained in a secondary battery into an aqueous solution of sulfuric acid; , Introducing hydrogen peroxide into the aqueous sulfuric acid solution into which the metal oxide has been introduced, reacting the hydrogen peroxide-introduced solution with a basic solution, removing the precipitate produced by the reaction, removing the precipitate by a solvent extraction method Removing metal impurities from the solution, and producing the lithium metal oxide using the solution from which the metal impurities have been removed.

In this case, the secondary battery may be a discarded lithium secondary battery or a rechargeable lithium secondary battery at least once.

Meanwhile, a method of producing an electrode active material according to an embodiment of the present invention includes separating a positive electrode material applied to a current collector of the secondary battery from the current collector, and pulverizing the separated positive electrode material to form a powder Wherein the step of introducing the metal oxide into the aqueous sulfuric acid solution may include the step of injecting the metal oxide-containing powder into the aqueous sulfuric acid solution.

Meanwhile, the step of removing metal impurities by the solvent extraction method includes a first solvent extraction step of removing metal impurities from a solution in which the precipitates are removed by using D2EHPA (Di (2-ethylhexyl) phosphoric acid); And a second solvent extraction step of removing metal impurities remaining in the solution from which the precipitate has been removed by using C272 (bis (2,4, 4-trimethylpentyl phosphinic acid) after the first solvent extraction step .

Meanwhile, the step of removing metal impurities by the solvent extraction method may include extracting at least one metal impurity of Zn, Al, Cu, Mn and Mg contained in the solution from which the precipitate has been removed with the solvent extracting agent .

Meanwhile, the solution in which the metal impurities are removed is a high concentration cobalt sulfate solution, and the step of producing the lithium metal oxide comprises mixing the high concentration cobalt sulfate solution with oxalic acid, Mixing lithium or lithium carbonate, and then heat-treating the mixture.

Meanwhile, the metal oxide may include LiCoO ₂ or LiNiO ₂ .

Meanwhile, the aqueous sulfuric acid solution into which the metal oxide has been introduced or the solution into which the hydrogen peroxide has been introduced may contain at least one of cobalt ion, lithium ion, manganese ion, zinc ion and copper ion.

Meanwhile, the solution from which the precipitate is removed may contain at least one metal impurity such as Zn, Al, Cu, and Mn.

According to the various embodiments as described above, the cathode active material can be obtained from the spent lithium secondary battery at a high recovery rate.

1 is a flow chart for explaining a method of manufacturing an electrode active material according to an embodiment of the present invention;
2 to 3 are graphs showing experimental results of solvent extraction according to an embodiment of the present invention,
FIG. 4 is a graph showing the results of X-ray diffraction analysis of the electrode active material according to an embodiment of the present invention.
FIG. 5 is a graph showing the results of X-ray diffraction analysis to determine whether lithium cobalt oxyanion (LiCoO ₂ ) was obtained by the electrode active material production method according to an embodiment of the present invention,
6 is a view showing the shape of lithium cobalt oxide (LiCoO ₂ ) obtained according to an electrode active material production method according to an embodiment of the present invention, and
7 to 8 are electrochemical characteristics evaluation results of the electrode active material obtained according to the method of producing an electrode active material according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 is a flowchart illustrating a method of producing an electrode active material according to an embodiment of the present invention.

According to the present method for producing an electrode active material, a waste lithium secondary battery that has been discarded after several charge and discharge operations can be used. The spent lithium battery is a battery that has a full life span but contains valuable metals such as cobalt, nickel, zinc, manganese, and lithium. According to various embodiments of the present invention, a valuable metal such as nickel or lithium can be recovered from the electrode material of a spent lithium secondary battery at a high recovery rate, thereby producing a new electrode active material, which has a great effect of recycling resources.

Referring to FIG. 1, the electrode material applied to the current collector of the secondary battery is separated from the current collector (S110). The electrode material can be separated from the current collector by various methods such as physical shock to the secondary battery or dissolution of the electrode material used for fixing the electrode material to the current collector. Here, the electrode material means a positive electrode active material or a negative electrode active material.

The separated electrode material may be used in the next step as it is in the subsequent step, but it may be used in the form of powder by being pulverized by a blender or a ball milling method.

Next, a process of leaching the metal oxide contained in the separated electrode material using an aqueous sulfuric acid solution is performed (S120). Specifically, the electrode material separated in the preceding step is introduced into the aqueous sulfuric acid solution. After a certain period of time after the addition, the metal oxide in the electrode material is dissolved and leached by the aqueous sulfuric acid solution.

The leaching amount of the metal oxide may vary depending on the amount of the acid, the leaching time or the temperature. In particular, in order to increase the leaching amount of the cobalt, hydrogen peroxide can be added together with sulfuric acid according to an embodiment of the present invention. When the hydrogen peroxide solution is further added, the amount of cobalt leached can be increased by controlling the order of addition of sulfuric acid and hydrogen peroxide, and the time of addition. According to an embodiment of the present invention, after the metal oxide is first leached into the aqueous sulfuric acid solution, the hydrogen peroxide may be further injected into the aqueous sulfuric acid solution after a predetermined period of time to increase the leaching amount of the cobalt.

In the next step, the metal oxide is neutralized with the leached acidic solution (S120). Specifically, various metal sulfides such as CoSO ₄ , Li ₂ So ₄ , NiSO ₄ , and MgSO ₄ are dissolved in the acid solution in which the metal oxide is leached. When the pH is controlled by adding a basic substance to the solution in which the metal sulfide is dissolved, most metal impurities except cobalt can be precipitated. At this time, caustic soda (sodium hydroxide) can be used as a basic substance.

The precipitated substance can be removed by filtration or the like. On the other hand, since the remaining solution from which precipitated substances are removed may contain not only a large amount of cobalt but also a small amount of metal impurities, it is required to separate only metal impurities in order to increase cobalt purity.

In order to remove metal impurities and obtain high purity cobalt, a solvent extraction step may be further performed (140). Specifically, in this step, the precipitated material is removed in the neutralization step, and the solvent extractant is added to the remaining solution to remove the remaining metal impurities by a solvent extraction method.

The solvent extraction method means to dissolve one kind (sometimes two or more kinds) of constituent substances in a solid or a liquid by using a solvent extracting agent to separate them. It is mainly used for recovering rare metals and for separating difficult materials. There are batch systems using mixer and separator, and countercurrent multi-stage system of continuous tower. Examples of the solvent extractant for extracting metals include D2EHPA (Di (2-ethylhexyl) phosphoric acid) or C272 (Bis, 2,4-trimethylpentyl phosphinic acid).

According to one embodiment of the present invention, the solvent extraction step may comprise a first solvent extraction step using D2EHPA and a second solvent extraction step using C272.

Specifically, in the first solvent extraction step, D2EHPA is added to the solution to remove impurities such as Zn, Al, Cu, and Mn from the solution in which the precipitated substance has been removed after the neutralization step, followed by stirring. After a certain period of time, metal impurities dissolve in the D2EHPA solution and can be extracted and removed with the D2EHPA solution.

In the second solvent extraction step, metal impurities that have not been removed in the first solvent extraction step can be removed secondarily. Specifically, C272 is added to the solution obtained from the first solvent extraction step, and the remaining impurities are removed by extraction in the same manner as in the first solvent extraction step. Particularly in the second solvent extraction step, Mg or Ni which has not been completely removed in the first solvent extraction step can be removed. Further, the above-described solvent extraction step can be repeated to further increase the cobalt purity in the solution.

In the next step, a cathode active material is produced using a solution from which metal impurities are removed (S150). Specifically, the solution from which metal impurities are removed through the solvent extraction step is a cobalt sulfate solution of high concentration, and LiCoO ₂ , which is a cathode active material, can be produced using cobalt sulfate. The production of LiCoO ₂ from cobalt sulfate can be accomplished through various conventional techniques. Among them, an example is as follows.

First, the cobalt sulfate solution and oxalic acid are mixed at a certain ratio, and after a certain period of time, precipitates are formed by the reaction of cobalt sulfate and oxalic acid. After washing the precipitate with distilled water and drying at high temperature, heat the dried sample in an oxygen atmosphere. Through this heat treatment, Co ₃ O ₄ can be obtained, and the obtained Co ₃ O ₄ can be mixed with lithium hydroxide or lithium carbonate and then heat-treated to produce lithium cobalt oxide (LiCo ₃ O ₂ ) having high purity.

Hereinafter, the present invention will be described in more detail with reference to specific experimental examples. However, it should be understood that the present invention is not limited thereto.

[Experimental Example]

The portion of the collector of the spent lithium secondary battery coated with the positive electrode material is physically removed. Then, the separated positive electrode material is pulverized and obtained in powder form.

In order to dissolve the metal contained in the positive electrode material in powder form, the powder is put into a sulfuric acid solution. At this time, the amount of sulfuric acid was determined by using a reaction formula when various metal substances expected to be contained in the cathode material reacted with sulfuric acid.

Table 1 is a table showing the amount of sulfuric acid necessary for leaching the metal oxide contained in 100 g of the pulverized raw material (anode material powder) through the chemical reaction formula.

Table 1

As summarized in Table 1, the sulfuric acid required for leaching the metal oxide contained in 100 g of the raw material was determined to be 151.3 g. In this Experimental Example, 150 g of sulfuric acid and 300 cc of water were added to 100 g of the raw material to leach the metal oxide.

In order to determine the optimal conditions for leaching metal oxides using sulfuric acid, the amount of sulfuric acid and the leaching time were experimentally measured.

As the leaching time increased, the main purpose of this experiment was to increase the leaching amount of cobalt, but there was no significant change after 4 hours and the leaching amount of cobalt was not changed even when the amount of sulfuric acid was increased to 150 g or more. Therefore, the amount of sulfuric acid and the leaching time required for leaching metal oxide from the raw material were 150 g of sulfuric acid and the leaching time was 4 hours or more. At this time, the leaching rate of cobalt was about 45%.

In the above experiment, hydrogen peroxide was added together with sulfuric acid because sulfuric acid alone had a limitation in raising the amount of cobalt leached. The order of addition of sulfuric acid and hydrogen peroxide, reaction temperature, and reaction time were used as variables at this time. The amount of hydrogen peroxide was determined by the reaction equation of hydrogen peroxide and cobalt oxide.

The optimal conditions for the determination of the optimum cobalt content were 100 g of sulfuric acid, 64 g of hydrogen peroxide, a reaction temperature of 95 ^° C, and a reaction time of 4 hours. The leaching rate of cobalt was 99.7%.

The next step is the neutralization process step.

The neutralization step is a step of coprecipitating impurities excluding the metal other than cobalt, that is, cobalt, out of the metal oxides dissolved in the leaching step by adjusting the pH using caustic soda.

The variables in the neutralization step are the amount of caustic soda, the stirring time, and the stirring temperature.

Optimum conditions were obtained with caustic soda 12.5% stirring time 45 min and stirring temperature 50oC. At this time, the co-deposition rates were Co 1.2%, Ni 0.8%, Fe 100%, Al 96.7%, Zn 99.4% and Cu 99.5%. Cobalt also coprecipitated at 1.2%, but most of the impurities were coprecipitated. However, since the co-deposition rate of Ni was only 0.8%, the solvent extraction was performed to remove Ni and remaining trace impurities through the next step.

The following is the solvent extraction step.

In the solvent extraction step, the coprecipitated material was removed from the neutralization step, and impurities were extracted by using D2EHPA and C272 successively in the remaining solution.

2 and 3 are experimental results of solvent extraction using D2EHPA and C272. In this experiment, stirring time and agitation temperature were 5 minutes and room temperature and pH was controlled. As shown in FIG. 2, it was confirmed that a large amount of impurities such as Zn, Al, Cu, and Mn were extracted as the pH was increased. Also, it was observed that some of the Co was extracted by the solvent, but this solution can increase the Co recovery rate through recycling several times.

3 shows the result of solvent extraction of impurities using C272. It was confirmed that Mg and Ni, which were not completely removed by the process using D2EHPA, were removed by solvent extraction of Co according to pH.

Table 2 shows the results of the component analysis after the solvent extraction step. Most of the impurities were not detected, only Mg and Na were slightly detected, but the detected low contents were such that they had no influence on the production of the cathode active material to be tested. As a result, very pure cobalt sulfide was obtained.

Table 2

As a next step, lithium cobalt oxide, which is a cathode active material of a secondary battery, was prepared using a high concentration of cobalt sulfate solution obtained through the solvent extraction step.

The process for preparing lithium cobalt oxide is as follows. First, the cobalt sulfate solution and oxalic acid are mixed at a ratio of 1: 1.3, and the precipitate formed by mixing is filtered. The precipitate is washed with distilled water and dried for 24 hours at 60 ^° C for 12 hours. Dry samples are heat treated at 350 ° C for 5 hours in an oxygen atmosphere. Through this heat treatment, Co ₃ O ₄ can be obtained.

Since pure cobalt oxide, which is the final cathode material, can be obtained only by preparing pure Co ₃ O ₄ , it is confirmed by X-ray diffraction analysis whether or not Co ₃ O _{4 is} prepared, and the result is shown in FIG. For comparison, the X-ray diffraction results of JCPDS, an international standard for Co ₃ O ₄ (denoted as "Co ₃ O ₄ -Ref" in FIG. 4) are also shown in FIG. As can be seen from FIG. 4, it can be seen that pure Co ₃ O ₄ was obtained.

Finally, the previously prepared Co ₃ O ₄ and Li ₂ CO ₃ were mixed and heat-treated at 900 ^° C for 10 hours in an oxygen atmosphere to obtain lithium cobalt oxide as a cathode active material for a lithium secondary battery. X-ray diffraction analysis was carried out to confirm that pure lithium cobalt oxide (LiCoO ₂ ) was obtained. For comparison, the results of X-ray diffraction of JCPDS (labeled "LiCoO ₂ -Ref" in FIG. 5) Respectively. As shown in FIG. 5, pure lithium cobalt oxide (LiCoO ₂ ) was obtained.

FIG. 6 is a view showing the shape of lithium cobalt oxide (LiCoO ₂ ) obtained through the process described above. Lithium cobalt oxide with a rod shape and various particle sizes was prepared.

Finally, the electrochemical characteristics were evaluated using lithium cobalt oxide obtained in this Experimental Example. The anode size was 10.0mm, the cut-off voltage was 3.0 ~ 4.3V, the C-rate was 1, and the cathode was lithium metal.

In order to compare lithium cobalt oxide prepared in this experiment with currently available lithium cobalt oxide, an electrode was prepared under the same conditions as the two cathode materials, and the electrochemical characteristics were evaluated.

7 to 8 show the specific capacities of the electrodes according to the number of cycles obtained through the electrochemical property evaluation. In FIG. 7, the term "commercialized electrode material" is the result obtained using commercially available products. In FIG. 8, the term "the present invention electrode material" is a result obtained using the cathode active material obtained in the present invention.

Specifically, referring to FIGS. 7 to 8, in the case of an electrode made of commercially available lithium cobalt oxide, the initial capacity was somewhat higher than that of the electrode obtained in the present invention, but showed a tendency to decrease constantly as the cycle number increased . On the other hand, the electrode obtained in the present experimental example shows little decrease in capacity even when the cycle is increased. It can be confirmed that the capacity after 30 cycles was higher than that obtained in this Experimental Example. That is, it was confirmed that the electrochemical characteristics of lithium cobalt oxide obtained in this Experimental Example were superior to those sold in the market.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It goes without saying that the example can be variously changed. Accordingly, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. * * * * * Recently Added Patents

Claims (9)

A method for producing an electrode active material,
Charging a metal oxide contained in the secondary battery into an aqueous sulfuric acid solution;
Introducing hydrogen peroxide into the aqueous sulfuric acid solution into which the metal oxide has been introduced after a predetermined time has elapsed after the step of injecting;
Reacting the hydrogen peroxide solution with a basic solution and removing the precipitate produced by the reaction;
Removing metal impurities from the solution from which the precipitate has been removed by a solvent extraction method; And
And producing a lithium metal oxide by using the solution from which the metal impurities are removed. The method according to claim 1,
The secondary battery includes:
Wherein the lithium secondary battery is a lithium secondary battery which is discarded, or lithium secondary battery which has been charged and discharged at least once. The method according to claim 1,
Separating the positive electrode material applied to the current collector of the secondary battery from the current collector; And
And grinding the separated positive electrode material to form a powder,
Wherein the step of introducing the metal oxide into the aqueous sulfuric acid solution comprises:
And introducing the powder containing the metal oxide into an aqueous sulfuric acid solution. The method according to claim 1,
The step of removing the metal impurities by the solvent extraction method comprises:
A first solvent extraction step of removing metal impurities in the solution from which the precipitate has been removed using D2EHPA (Di (2-ethylhexyl) phosphoric acid); And
And a second solvent extraction step of removing metal impurities remaining in the solution from which the precipitate has been removed by using C272 (bis (2,4, 4-trimethylpentyl phosphinic acid) after the first solvent extraction step By weight based on the total weight of the electrode active material. The method according to claim 1,
The step of removing the metal impurities by the solvent extraction method comprises:
Wherein at least one metal impurity selected from the group consisting of Zn, Al, Cu, Mn, and Mg contained in the solution from which the precipitate is removed is extracted with the solvent extractant. The method according to claim 1,
The solution from which the metal impurities are removed is a high concentration cobalt sulfate solution,
Wherein the step of producing the lithium metal oxide comprises:
Mixing the high concentration cobalt sulfate solution with oxalic acid; And
And mixing the precipitate generated by the mixing with lithium hydroxide or lithium carbonate, followed by heat treatment. The method according to claim 1,
Wherein the metal oxide comprises LiCoO ₂ or LiNiO ₂ . The method according to claim 1,
The aqueous sulfuric acid solution into which the metal oxide has been introduced or the solution into which the hydrogen peroxide has been introduced,
Wherein the electrode active material comprises at least one of cobalt ions, lithium ions, manganese ions, zinc ions, and copper ions. The method according to claim 1,
The solution from which the precipitate has been removed,
And at least one metal impurity selected from Zn, Al, Cu and Mn.

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