WO2025135672A1 - Lithium-containing aqueous sulfuric acid solution and method for preparing same - Google Patents

Abstract

The present invention relates to a lithium-containing aqueous sulfuric acid solution and a method for preparing same. This method for preparing the aqueous sulfuric acid solution comprises the steps of: obtaining a valuable metal recovery composition from waste batteries, the valuable metal recovery composition containing valuable metal alloys, lithium compounds, copper (Cu), and graphite; separating graphite from the valuable metal recovery composition; performing sulfuric acid leaching of valuable metals, lithium compounds, and copper (Cu) in the valuable metal recovery composition; recovering the valuable metals and the copper (Cu) through solid-liquid separation in a leached lithium-containing aqueous sulfuric acid solution; and removing residual impurities from the leached lithium-containing aqueous sulfuric acid solution after the recovery step.

Description

Aqueous sulfuric acid solution containing lithium and method for producing the same

The present invention relates to a raw material for battery manufacturing, and to a sulfuric acid aqueous solution containing lithium obtained from a spent battery and a method for manufacturing the same.

As the demand for electric vehicles increases worldwide, the problem of disposal of waste batteries generated from said electric vehicles is emerging as a social issue. In the case of lithium secondary batteries, which are the main raw materials of said waste batteries, organic solvents, explosive substances, and heavy metals such as Ni, Co, Mn, and Fe are contained, but in the case of Ni, Co, Mn, and Li, they have high scarcity value as valuable metals, and the recovery and recycling process after the lithium secondary batteries are discarded is emerging as an important research field.

Specifically, a lithium secondary battery mainly consists of copper and aluminum used as a current collector, Li, Ni, Co, Mn-containing oxides constituting a cathode material, and graphite utilized as an anode material, and includes a separator separating the cathode material and the anode material, and an electrolyte injected into the separator. The solvent used as the solvent and salt constituting the electrolyte is mainly a mixture of carbonate organic substances such as ethylene carbonate and propylene carbonate, and for example, LiPF ₆ is used.

In order to utilize the above-mentioned waste batteries, development is actively underway on a waste battery recycling process that crushes the waste batteries to produce intermediate materials such as waste battery shreds or black powder, and then recovers valuable metals through a post-process.

The recovered valuable metals are subjected to a process of recovering valuable metals such as Li, Ni, Co, and Mn within the battery through acid leaching. The acid leaching process uses an acid such as sulfuric acid to change the valuable metals within the battery into an ionized state and remove impurities. Valuable metals such as Ni, Co, or Mn within the sulfuric acid from which the impurities have been removed are extracted in the form of sulfides through a solvent extraction and crystallization process.

After sulfuric acid leaching, the Li content in the sulfuric acid is about 6 to 10 g/L, but after solvent extraction and crystallization of Ni, Co, Mn, etc., the Li remaining in the sulfuric acid is diluted to about 1 to 2 g/L. In order to manufacture raw materials for battery manufacturing, specifically lithium, by utilizing a low-concentration Li-containing aqueous sulfuric acid solution, a multi-stage impurity removal step and a Li concentration step are performed. The purity of Li ₂ CO ₃ or LiOH for battery manufacturing must be 99.5% or higher. Therefore, high extraction costs are required to obtain a material with the corresponding purity, and there is a problem of lowering the Li recovery rate. Therefore, research is needed on a method to solve the above problem.

In addition, as a method for obtaining lithium, a method can be performed in which lithium is extracted from lithium-containing ores such as spodumene containing lithium, by heat treatment at about 900° C. or higher, and then leaching with sulfuric acid to remove impurities. However, this method has the problem that a large amount of precipitate is generated when removing impurities, and excessive environmental treatment costs are required to bury the precipitate.

In addition, among the lithium-containing materials, there is a problem that the lithium oxide ( _Li2O ) or fluoride (LiF) form present in the cathode material causes lithium loss by vaporization of Li(g) or LiF(g) when exposed to high temperatures, thereby reducing the lithium recovery rate.

The problem to be solved by the present invention is to provide a lithium-containing sulfuric acid aqueous solution that can be used as a raw material for manufacturing a lithium secondary battery and contains a high concentration of lithium.

Another technical problem to be solved by the present invention is to provide a method for producing a lithium-containing sulfuric acid aqueous solution that can be used as a raw material for manufacturing a lithium secondary battery and contains a high concentration of lithium.

According to one embodiment of the present invention, a lithium-containing sulfuric acid aqueous solution is recovered from a spent battery, and includes lithium (Li), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), and residual impurities, and can satisfy the following equation 1.

<Formula 1>

1.0 ≤ [Al] = 0.0297 × [Li] ² + 1.3205 × [Li] ±5 ≤ 16.0

(In the above equation 1, [Li] and [Al] represent the concentrations (g/L) of Li and Al in the sulfuric acid solution containing lithium, respectively.)

In one embodiment, the aqueous sulfuric acid solution can satisfy the following equation 2.

<Formula 2>

0.05 ≤ [Ni] = 0.1907 × [Li] ² - 0.2689 × [Li] ±3 ≤ 16.0

(In the above equation 2, [Li] and [Ni] represent the concentrations (g/L) of Li and Ni in the sulfuric acid solution containing lithium, respectively.)

In one embodiment, the aqueous sulfuric acid solution can satisfy the following equation 3.

<Formula 3>

0.05 ≤ [Co] = 0.0624 × [Li] ² - 0.1078 × [Li] ±2 ≤ 14.0

(In the above equation 3, [Li] and [Co] represent the concentrations (g/L) of Li and Co in the sulfuric acid solution containing lithium, respectively.)

In one embodiment, the aqueous sulfuric acid solution can satisfy the following equation 4.

<Formula 4>

0.1 ≤ [Mn] = 0.0402 × [Li] ² + 0.117 × [Li] ±1 ≤ 12.0

(In the above equation 4, [Li] and [Mn] represent the concentrations (g/L) of Li and Mn in the sulfuric acid solution containing lithium, respectively.)

According to another embodiment of the present invention, a method for producing a sulfuric acid aqueous solution containing lithium includes the steps of obtaining a composition for recovering valuable metals, which comprises a valuable metal alloy, a lithium compound, copper (Cu), and graphite from a spent battery, separating graphite from the composition for recovering valuable metals, leaching the valuable metals, lithium compounds, and copper (Cu) in the composition for recovering valuable metals by sulfuric acid, performing solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium to recover the valuable metals and the copper (Cu), and removing residual impurities from the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step.

In one embodiment, at least a portion of the lithium compound may contain lithium disposed on a precious metal alloy. In one embodiment, the step of obtaining a composition for recovering precious metal may include the steps of preparing a battery containing lithium (Li), crushing the battery, and heat-treating the crushed battery waste at a range of 600 to 1,500° C.

In one embodiment, the step of heat-treating the crushed battery scrap at a range of 600 to 1,500° C. may contain lithium having an oxygen concentration of 0.1 to 2.0 vol%. In one embodiment, the step of separating graphite from the composition for recovering valuable metals may be performed by at least one of particle size separation, gravity separation, and flotation.

In one embodiment, the step of leaching the valuable metal, the lithium compound, and the copper (Cu) in the composition for recovering the valuable metal with sulfuric acid may be controlled so that the pH of the sulfuric acid aqueous solution containing lithium is in a range of 0.2 to 4.0. In one embodiment, the step of leaching the valuable metal, the lithium compound, and the copper (Cu) in the composition for recovering the valuable metal with sulfuric acid may be such that the equivalent ratio of the sulfuric acid is 0.5 to 4.0.

In one embodiment, the step of leaching the valuable metal, the lithium compound, and the copper (Cu) in the composition for recovering the valuable metal with sulfuric acid can be performed at a temperature range of 10 to 150° C. In one embodiment, the step of leaching the valuable metal, the lithium compound, and the copper (Cu) in the composition for recovering the valuable metal with sulfuric acid can supply an inert gas at a supply rate of 0.1 to 20.0 Nm ³ /hr.

In one embodiment, the method may include a step of removing impurities in the sulfuric acid aqueous solution containing lithium by adding sodium hydroxide (NaOH) between the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid and the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium.

In one embodiment, the step of removing impurities in the sulfuric acid aqueous solution may control the pH of the sulfuric acid aqueous solution to 3.0 to 8.0. In one embodiment, the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium and the step of removing residual impurities in the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step may include a step of removing impurities by an ion exchange method.

In one embodiment, the step of removing residual impurities of the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step may adjust the pH of the sulfuric acid aqueous solution containing lithium to a range of 8.5 to 12.0. In one embodiment, the step of preparing the battery containing lithium (Li) may include the step of freezing the battery.

According to one embodiment of the present invention, a sulfuric acid aqueous solution containing lithium contains a predetermined proportion of valuable metals, and thus can be utilized as a raw material for manufacturing a lithium secondary battery, and provides a sulfuric acid aqueous solution containing a high concentration of lithium.

According to another embodiment of the present invention, a method for producing a sulfuric acid aqueous solution containing lithium is provided, which comprises leaching a lithium-containing compound recovered from a lithium-containing battery with sulfuric acid according to temperature and pH conditions and removing impurities to produce a sulfuric acid aqueous solution as a high-purity lithium-containing raw material for producing a lithium-containing battery.

FIG. 1 is a graph showing changes in battery voltage according to cooling temperature according to one embodiment of the present invention.

FIG. 2 is a graph showing the relationship between battery weight, external cooling temperature, and cooling time according to one embodiment of the present invention.

FIGS. 3a and 3b are photographs showing a fire that occurred when crushing was performed after freezing for a shorter time than the minimum cooling time according to a comparative example of the present invention, and FIGS. 3c and 3d are photographs showing an example in which a fire did not occur when crushing was performed after freezing for a longer time than the minimum cooling time according to an embodiment of the present invention.

Figure 4 is a schematic diagram of the preparation of a high-purity lithium-containing sulfuric acid aqueous solution according to one embodiment of the present invention.

The terms first, second, and third, etc. are used to describe, but are not limited to, various parts, components, regions, layers, and/or sections. These terms are only used to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms include the plural forms as well, unless the context clearly dictates otherwise. The word "comprising," as used herein, specifies particular features, regions, integers, steps, operations, elements, and/or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components.

When a part is referred to as being "on" or "on" another part, it may be directly on or above the other part, or there may be other parts intervening. In contrast, when a part is referred to as being "directly on" another part, there are no other parts intervening.

Additionally, % in this specification means weight % unless otherwise specified.

Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined.

According to one embodiment of the present invention, a lithium-containing sulfuric acid aqueous solution has a high concentration of lithium and can be used as a raw material for producing lithium hydroxide used in the production of a cathode active material. Specifically, the lithium-containing sulfuric acid aqueous solution may be recovered from a spent battery.

In one embodiment, the lithium-containing sulfuric acid aqueous solution can include lithium (Li), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), and residual impurities. The residual impurities can include, for example, at least one of Ni, Co, Mn, Cu, Ti, Zn, Pb, P, Ca, Mg, B, K, Na, Si, Zr, and Fe.

In one embodiment, the sulfuric acid aqueous solution containing lithium can satisfy the following equation 1.

<Formula 1>

1.0 ≤ [Al] = 0.0297 × [Li] ² + 1.3205 × [Li] ±5 ≤ 16.0

(In the above equation 1, [Li] and [Al] represent the concentrations (g/L) of Li and Al in the sulfuric acid solution containing lithium, respectively.)

The above formula 1 may be a relationship for the concentration of Li and Al in a sulfuric acid aqueous solution containing lithium. The above formula 1 may specifically satisfy 1.0 to 16.0, more specifically, 2.5 to 12.0. When the above formula 1 is satisfied, it can be usefully applied to the production of LiOH used in the production of a high-nickel positive electrode active material, and there is an advantage of reducing the cost of the material due to the high lithium concentration.

If the above equation 1 exceeds the upper limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced. If the above equation 1 exceeds the lower limit of the above-mentioned range, there is a problem that Li is coprecipitated and lost during hydroxide precipitation for Al removal after leaching.

In one embodiment, the sulfuric acid aqueous solution containing lithium can satisfy the following equation 2.

<Formula 2>

0.05 ≤ [Ni] = 0.1907 × [Li] ² - 0.2689 × [Li] ±3 ≤ 16.0

(In the above equation 2, [Li] and [Ni] represent the concentrations (g/L) of Li and Ni in the sulfuric acid solution containing lithium, respectively.)

The above equation 2 may be a relationship for the concentration (g/L) of Li and Ni in the sulfuric acid aqueous solution. Specifically, the equation 2 may satisfy 0.05 to 16.0, and more specifically 0.3 to 7.5. When the equation 2 is satisfied, it can be usefully applied to the production of LiOH used in the production of a high-nickel positive electrode active material, and there is an advantage of reducing the cost of the material due to the high lithium concentration.

If the above equation 2 exceeds the upper limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced. If the above equation 2 exceeds the lower limit of the above-mentioned range, there is a problem that Li is coprecipitated and lost when generating hydroxide to remove Ni.

In one embodiment, the sulfuric acid aqueous solution containing lithium can satisfy the following equation 3.

<Formula 3>

0.05 ≤ [Co] = 0.0624 × [Li] ² - 0.1078 × [Li] ±2 ≤ 14.0

(In the above equation 3, [Li] and [Co] represent the concentrations (g/L) of Li and Co in the sulfuric acid solution containing lithium, respectively.)

The above equation 3 may be a relationship for the concentration (g/L) of Li and Co in a sulfuric acid aqueous solution containing lithium. Specifically, the above equation 2 may satisfy 0.05 to 14.0, and more specifically 0.15 to 6.0. When the above equation 3 is satisfied, it can be usefully applied to the production of LiOH used in the production of a high-nickel positive electrode active material, and there is an advantage of reducing the cost of the material due to the high lithium concentration.

If the above equation 3 exceeds the upper limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced. If the above equation 3 exceeds the lower limit of the above-mentioned range, there is a problem that Li is coprecipitated and lost when generating hydroxide to remove Co.

In one embodiment, the sulfuric acid aqueous solution containing lithium can satisfy the following equation 4.

<Formula 4>

0.1 ≤ [Mn] = 0.0402 × [Li] ² + 0.117 × [Li] ±1 ≤ 12.0

(In the above equation 4, [Li] and [Mn] represent the concentrations (g/L) of Li and Mn in the sulfuric acid solution containing lithium, respectively.)

The above equation 4 may be a relationship for the concentration (g/L) of Li and Mn in the sulfuric acid aqueous solution. Specifically, the equation 4 may satisfy 0.1 to 12.0, and more specifically 0.5 to 6.0. When the equation 4 is satisfied, it can be usefully applied to the production of LiOH used in the production of a high-nickel positive electrode active material, and there is an advantage of reducing the cost of the material due to the high lithium concentration.

If the above equation 4 exceeds the upper limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced. If the above equation 4 exceeds the lower limit of the above-mentioned range, there is a problem that Li is coprecipitated and lost when generating hydroxide to remove Mn.

In this way, since the lithium content in the sulfuric acid aqueous solution containing lithium satisfies the above-mentioned range, it is easy to achieve high capacity of the battery, and it can be usefully applied to the production of a positive electrode active material precursor for a lithium secondary battery with excellent structural stability.

According to another embodiment of the present invention, a method for producing a sulfuric acid aqueous solution containing lithium may include the steps of obtaining a composition for recovering valuable metals, which comprises a valuable metal alloy, a lithium compound, copper (Cu), and graphite from a spent battery, separating graphite from the composition for recovering valuable metals, leaching the valuable metals, lithium compounds, and copper (Cu) in the composition for recovering valuable metals using sulfuric acid, performing solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium to recover the valuable metals and the copper (Cu), and removing residual impurities from the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step.

The step of obtaining a composition for recovering valuable metals including a valuable metal alloy, a lithium compound, copper (Cu), and graphite from a spent battery may include the steps of preparing a battery containing lithium (Li), crushing the battery, and heat-treating the crushed battery waste at a temperature ranging from 600 to 1,500° C.

The step of preparing a battery containing lithium (Li) may include waste materials such as batteries that have reached the end of their useful life, positive electrode materials such as scrap, jelly rolls, and slurry constituting the waste battery, defective products generated during the manufacturing process, residues within the manufacturing process, and debris generated during the manufacturing process, for example, waste materials within the manufacturing process of a lithium ion battery.

In one embodiment, the step of preparing a battery containing lithium (Li) may include the step of freezing the battery. Specifically, when a certain pressure is applied to the battery, the separator is physically broken, which causes a high current to be formed due to a short circuit, which generates a spark, and the spark may ignite the electrolyte, which may cause a fire.

The step of freezing the battery above is to freeze the battery to suppress ignition of the liquid electrolyte contained within the battery, and then perform the crushing process, so that problems due to ignition of the electrolyte do not occur.

In one embodiment, the step of freezing the battery may be performed by cooling to a temperature in the range of -150° C. to -60° C. If the temperature exceeds the upper limit of the temperature range, the voltage remaining inside the battery may not be reduced to 0 V, which may cause a battery reaction due to a short circuit, and the electrolyte may not be completely frozen, which is not appropriate.

When the lower limit of the above temperature range is exceeded, the electrolyte is sufficiently frozen, the internal voltage of the battery is also lowered to 0 V, and even if a short circuit occurs in which the positive and negative electrodes are in direct contact, a battery reaction does not occur, so the battery temperature does not increase, and gas generation and combustion of the electrolyte do not occur. In addition, since the electrolyte is in a frozen state, the mobility of lithium ions is very low, so that the conduction characteristics according to the movement of lithium ions can be significantly reduced, and since vaporization of the electrolyte does not occur, flammable gases such as ethylene, propylene, and hydrogen may not be generated.

In the step of freezing the above battery, if the temperature exceeds the upper limit of the above temperature range, the voltage remaining inside the battery will not decrease to 0 V, which may cause a battery reaction due to a short circuit, and the electrolyte will not be completely frozen, which is not appropriate. If the temperature exceeds the lower limit of the above temperature range, there is an uneconomical problem because a lot of energy must be invested for freezing.

In one embodiment, the step of freezing the battery can be performed by cooling to a temperature range of -60 to -20° C. under a vacuum atmosphere condition of 100 torr or less. The step of freezing the battery can be performed at the temperature range that is capable of suppressing vaporization of the electrolyte. The vacuum atmosphere can be, for example, an inert gas, carbon dioxide, nitrogen, water, or a combination thereof.

Since the process is performed by controlling the pressure to a vacuum atmosphere of 100 torr or less, the supply of oxygen is suppressed, thereby preventing the electrolyte from reacting with oxygen, preventing an explosion caused by this, and suppressing the vaporization of the electrolyte, thereby preventing the generation of flammable gases such as ethylene, propylene, and hydrogen.

In the step of freezing the above battery, if carried out in an air atmosphere or at a pressure exceeding 100 torr, there is a problem that voltage may remain within the battery, and since the electrolyte is not in a frozen state in the temperature range of -60 to -20°C, the electrolyte may vaporize and explode due to a spark generated when a short circuit occurs due to the remaining voltage.

In one embodiment, the step of freezing the battery is a battery processing method satisfying the following equation 7.

[Formula 6]

Minimum cooling time (Hr) = A × (W ^0.33 )

(A = 4 × e(-0.02×dT), W = battery weight (Kg), dT = │external cooling temperature - target temperature│, ││ indicates absolute value)

In one embodiment, the step of freezing the battery may include the step of cooling the battery to -150° C. to -20° C. In one embodiment, the step of preparing the battery may include the step of performing a forced discharge.

The step of crushing the battery may obtain crushed material by using a crusher. The crushing may include, as a non-limiting example, crushing the waste battery by applying physical or mechanical force and crushing it into fine powder. The crushing step may separate some large impurities, such as aluminum (Al), copper (Cu), iron (Fe), and plastic, from among the impurities included in the waste battery. The state in which the large impurities are separated is called black powder, and the crushing step may produce a battery crushed material such as black powder.

In one embodiment, the battery scrap may include aluminum (Al), manganese (Mn), lithium (Li), copper (Cu), cobalt (Co), nickel (Ni), carbon (C) and residual impurities. In one embodiment, the black powder includes 5 to 40 wt% of nickel (Ni), 1 to 20 wt% of cobalt (Co), 1 to 15 wt% of manganese (Mn), 0.5 to 5 wt% of lithium (Li), 10 to 70 wt% of carbon (C), 0.0001 to 20 wt% of aluminum (Al), and 0.0001 to 20 wt% of copper (Cu), and the sum of impurities such as iron (Fe) and phosphorus (P) may be less than 10 wt%. The components of the above black powder may vary depending on the ratio of nickel, cobalt, and manganese, and the nickel, cobalt, and manganese may be controlled by the positive electrode oxide in the lithium secondary battery when the lithium secondary battery is crushed.

In one embodiment, the step of crushing the battery may be a crushing method using at least one of shear, compression, and tensile force. Specifically, the step of crushing may be crushed by, for example, at least one of a hammer mill, a ball mill, and a stirred ball mill. The hammer mill may perform at least one of the steps of disintegration, punching, and milling, and it is clear that the crushing may be performed using various types of crushing or crushing devices, for example, an industrial crusher, as a non-limiting example. In one embodiment, the particle size of the battery crushed material may be within 50 mm, specifically, within 30 mm. If it is larger than the above range, there is an uneconomical problem because more energy is required in the heat treatment step described below.

The step of heat-treating the shredded battery waste in the range of 600 to 1,500° C. may be a step of dry heat-treating the battery waste. Specifically, the step of heat-treating may include putting the shredded battery into a heating furnace capable of raising the temperature to a temperature higher than the melting point. The step of dry heat-treating the shredded battery (S200) may involve heat treatment conditions that perform a high-temperature reduction reaction without going through a melting step.

In one embodiment, the heat treatment conditions may involve heat treatment conditions in a range of 900 to 1,800° C. Specifically, the range may be performed in a range of 1,200 to 1,800° C., and more specifically, 1,300 to 1,700° C. If the upper limit of the range is exceeded, there is a problem of loss due to lithium vaporization, and if the lower limit of the range is exceeded, there is a problem of sintering and reduction of alloy elements not progressing. In the above temperature range, the carbon in the crushed material can be minimally burned, and the reduction reaction can be performed in a state where there is almost no generation of carbon dioxide.

In one embodiment, the step (S200) of dry heat treating the crushed material may be performed in a gas atmosphere of at least one of an inert gas, carbon dioxide, carbon monoxide, and hydrocarbon gas. In the case of the inert gas, it may include, for example, at least one of argon and nitrogen. By performing a reduction reaction of the crushed material in the gas atmosphere, a valuable metal recovery alloy including the valuable metal contained in the crushed material as a component can be effectively recovered.

In one embodiment, a portion of the gas atmosphere may contain impurities including residual oxygen. If the content of oxygen among the impurities is high, it may form carbon dioxide by combining with the components of the shredded material during the reduction reaction process, and thus, there is a problem that it is difficult to recover by being gasified together with lithium.

In one embodiment, the average oxygen partial pressure in the dry heat treatment step may be in the range of 0.01 to 1 atm. Specifically, when the oxygen partial pressure is higher than the above value, there is a problem of lithium loss and a large amount of carbon dioxide being generated in a local high-temperature state. When the oxygen partial pressure is lower than the lower limit of the above range, there is a problem of a decrease in the Li recovery rate due to the low temperature of LiAlO ₂ formation.

Specifically, in the dry heat treatment step, a composition for recovering valuable metals is provided by alloying components such as nickel, cobalt, manganese and lithium-containing oxides in the crushed material, which may include valuable metals and residual impurities. The composition for recovering valuable metals may include, for example, aluminum (Al), manganese (Mn), lithium (Li), copper (Cu), cobalt (Co), nickel (Ni), carbon (C) and residual impurities. Specifically, the composition for recovering valuable metals may include a valuable metal recovery alloy and a lithium compound. Specifically, the composition for recovering valuable metals may include a valuable metal alloy, a lithium compound, copper (Cu), and graphite.

The above valuable metal recovery alloy may include 45 wt% or more of the valuable metal and the remainder being impurities, based on 100 wt% of the total composition of the alloy. The valuable metal recovery alloy may include at least one of the valuable metals such as nickel (Ni), cobalt (Co), manganese (Mn), lithium (Li), carbon (C), aluminum (Al), and copper (Cu) and the remainder being impurities. In the present specification, the valuable metal may mean an expensive metal component included in a battery, and may mean nickel, cobalt, manganese, aluminum, copper, and lithium. In one embodiment, the valuable metal may be 70 wt% or more.

In one embodiment, lithium (Li) among the above metals may be included in a range of 0.01 to 5 wt%. Since the lithium satisfies the above range, there is an advantage in that the Li recovery rate can be maximized during the Li refining process. If it exceeds the upper limit of the above range, there is a problem of reduced Ni and Co recovery rates, and if it exceeds the lower limit of the above range, there is a problem of increased process costs due to reduced Li recovery rates during the Li refining process.

In one embodiment, the valuable metal recovery alloy may contain copper (Cu) in an amount of 0.02 wt% or more. Specifically, the valuable metal recovery alloy may contain copper (Cu) in a range of 0.1 to 15 wt%. When the content of the copper is outside the upper limit of the range, there is a problem of process cost due to an increase in the amount of CuSO ₄ precipitation in leaching and solvent extraction, and when the content of the copper is outside the lower limit of the range, it is difficult to produce low-melting-point Ni-Co-Mn, resulting in a problem of an increase in the amount of unreacted materials.

In one embodiment, the copper may be combined with nickel (Ni) among the valuable metals to form an alloy. In one embodiment, the nickel may be included in a range of 5 to 40 wt%. When the nickel is outside the upper limit of the range, there is a problem of a decrease in the leaching rate due to the formation of nickel carbide (Ni ₃ C), and when the nickel is outside the lower limit of the range, there is a problem of a decrease in the Ni recovery rate in leaching and solvent extraction.

In one embodiment, the valuable metal recovery alloy may contain graphite in an amount of 7 wt% or less. Specifically, the content of the graphite may be in the range of 1 to 6 wt%, and more specifically, 2 to 5 wt%. Since the content of the graphite in the valuable metal recovery alloy satisfies the above-described range, the content of graphite may be reduced during acid leaching, thereby improving leaching efficiency, and the recovery of the graphite may reduce _CO2 generation.

If the upper limit of the above range is exceeded, there is a problem that the anode material remains unreacted, alloying is not properly performed, and the metal oxide remains in the cathode material. If the lower limit of the above range is exceeded, there is a problem that lithium loss due to high temperature may occur.

In one embodiment, the valuable metal recovery alloy may contain aluminum (Al) in a range of 0.25 to 30 wt %. If the content of the aluminum is outside the upper limit of the range, there is a problem of reduced Ni and Co recovery rates during the leaching and solvent extraction processes, and if the content of the aluminum is outside the lower limit of the range, it is difficult to produce LiAlO ₂ , resulting in a problem of reduced Li recovery rates.

The content of the valuable metal in the above-mentioned valuable metal recovery composition may include 45 wt%. Specifically, the valuable metal recovery composition may include nickel as a basic component, but may also include materials such as cobalt, manganese, copper, aluminum, and lithium.

In one embodiment, the lithium content in the composition may be comprised in a range of 0.1 to 10 wt %. Specifically, the lithium content in the composition may be comprised in a range of 8 to 10 wt %.

The content of lithium in the above composition may include not only the content of the valuable metal recovery alloy but also the content of lithium included in the lithium compound. If it exceeds the upper limit of the above range, there is a problem that lithium is lost by a process in which oxygen burns carbon rather than an oxygen-free reaction, and thus lithium recovery among expensive valuable metals in the battery becomes impossible. If it exceeds the lower limit of the above range, there is a problem that the recovery rate of valuable metals is reduced.

The lithium compound may be a precious metal reactant including a lithium compound including _{at least one of LiAlO 2 , Li 5 AlO 4 , LiAl 5 O 8 , Li 2 CO 3 , LiF, Li 3 PO 4 , Li 4 P 2 O 7 , LiPO 3 , Li 2 SiO 3 , Li 4 SiO 4 , Li 2} Si 2 O 5 , LiFeO 2 , LiFe ₅ O _{8 , Li 3 Fe 5 O 8} , and Li ₅ FeO ₄ , wherein the compound may include lithium in an amount of 4 to 35 wt% based on 100 wt% of the total. In one embodiment, at least a portion of the lithium compound may be disposed on the precious metal alloy. Specifically, at least a portion of the lithium compound may be combined into a compound by physically or chemically bonding lithium and aluminum included in the composition to each other.

For example, when recovering valuable metals from a spent battery, the valuable metals in the spent battery exist in the form of oxides, and reduction occurs by graphite in the negative electrode material at the process temperature and oxygen atmosphere of the present invention described below. At this time, the copper in the current collector may melt and exist in a liquid state, and may play a role in agglomerating the reduced valuable metals. The aluminum of the current collector and other current collectors may participate in a partial reduction reaction with the positive electrode oxide, and the remainder may react with lithium and remain as lithium-aluminum oxide. Specifically, the composition for recovering valuable metals may include a lithium compound, and the lithium compound may be manufactured by the reduction reaction. For example, the lithium compound may be lithium-aluminate (2LiAlO ₂ ).

The above graphite may be composed of a graphite material having a graphitization degree of 50% or more and a weight ratio of 70% or more of the total weight.

The step of separating graphite from the composition for recovering the valuable metal may cause powder containing a valuable metal alloy containing sulfuric acid and nickel to float and disappear between graphite particles, which does not dissolve during sulfuric acid leaching and has hydrophobic characteristics. To prevent this, a step of removing graphite from the composition for recovering the valuable metal may be performed in advance.

In one embodiment, the step of separating graphite from the composition for recovering precious metals can be performed through at least one of particle size separation, gravity separation, and flotation.

The step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid can be performed at a pH of the sulfuric acid aqueous solution containing lithium of 0.2 to 4.0, specifically 0.5 to 3.0, and more specifically 0.8 to 2.0. When the pH satisfies the above range, there is an advantage of excellent selective leaching of Li.

If the pH exceeds the upper limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced. If the pH exceeds the lower limit of the above-mentioned range, there is a problem that valuable metals and copper are excessively leached.

The step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid may be such that the equivalent ratio of the sulfuric acid is 0.5 to 4.0, specifically 0.8 to 3.5, and more specifically 1.0 to 3.0. When the equivalent ratio of the sulfuric acid satisfies the above range, the leaching rate of the valuable metal recovery alloy can be increased while minimizing the content of sulfuric acid.

If the equivalent ratio of the sulfuric acid is outside the upper limit of the above-mentioned range, there is a problem that valuable metals and copper are excessively leached. If the equivalent ratio of the sulfuric acid is outside the lower limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced.

In the step of leaching the above-mentioned valuable metal recovery alloy with sulfuric acid, the temperature at which the process is performed is 10 to 150°C, specifically 20 to 120°C, and more specifically 40 to 90°C. When the temperature at which the process is performed satisfies the above range, the phenomenon of boiling over of the sulfuric acid is suppressed, while the leaching efficiency is excellent.

If the above-mentioned operating temperature is outside the upper limit of the above-mentioned range, there is a problem that valuable metals and copper are excessively leached. If the above-mentioned operating temperature is outside the lower limit of the above-mentioned range, there is a problem that lithium leaching is delayed and the lithium recovery rate is reduced.

The step of leaching the above valuable metal recovery alloy, lithium compound, and Cu with sulfuric acid can be performed while supplying an inert gas at a supply rate of 0.1 to 20.0 Nm ³ /hr, specifically 1 to 15 Nm ³ /hr, and more specifically 3 to 8 Nm ³ /hr. The inert gas can be nitrogen, argon, helium, or the like. When the oxygen is supplied within the above supply rate range, the selective leaching rate of Li can be accelerated in the process of leaching the valuable metal recovery alloy.

If the supply speed of the above gas exceeds the upper limit of the above-mentioned range, there is a problem of excessive leaching of valuable metals and copper. If the supply speed of the above gas exceeds the lower limit of the above-mentioned range, there is a problem of delayed leaching of lithium, resulting in a decrease in the lithium recovery rate.

The step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium is such that the sulfuric acid aqueous solution containing the leached lithium is separated in a liquid phase, and the valuable metal and the copper (Cu) can be separated in a solid phase.

In one embodiment, the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in a sulfuric acid aqueous solution containing the leached lithium may include a step of magnetic separation to separate the valuable metal and Cu after the solid-liquid separation. By further including a magnetic separation step after the solid-liquid separation step, copper can be recovered more easily.

In one embodiment, the method may include a step of removing impurities in the sulfuric acid aqueous solution containing lithium by adding sodium hydroxide (NaOH) between the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid and the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium.

In one embodiment, the step of removing impurities in the sulfuric acid aqueous solution may control the pH of the sulfuric acid aqueous solution to 3.0 to 8.0. Specifically, the pH may be 4.0 to 7.0. The step of removing impurities in the sulfuric acid aqueous solution may be a step for removing impurities in the sulfuric acid aqueous solution before performing a solid-liquid separation process to produce a sulfuric acid aqueous solution containing a high concentration of lithium. Specifically, the impurities may include at least one element among, for example, Ni, Co, Mn, Cu, Ti, Zn, Pb, P, Ca, Mg, B, K, Na, Si, and Fe.

The step of removing residual impurities in the sulfuric acid aqueous solution containing the lithium leached above after the recovery step can remove residual impurities, for example, elements such as Mg or Ca, in the sulfuric acid aqueous solution containing the lithium recovered by solid-liquid separation.

In one embodiment, the step of removing residual impurities of the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step may adjust the pH of the sulfuric acid aqueous solution containing lithium to a range of 8.5 to 12.0. Specifically, the pH may be 9.0 to 11.0. By satisfying the above-described range, residual impurities such as Ca and Mg in the lithium sulfate can be easily removed, thereby providing a sulfuric acid aqueous solution containing lithium having a high lithium concentration.

In one embodiment, the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium and the step of removing residual impurities in the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step may include a step of removing impurities by an ion exchange method.

The step of removing impurities by the above ion exchange method may be a step of removing elements such as Zr, T, B, or F remaining in small amounts in the sulfuric acid aqueous solution containing lithium recovered by solid-liquid separation.

Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims described below.

<Experimental example>

Preparation of a composition for the recovery of valuable metals

<Battery internal temperature according to minimum freezing time>

The battery pack used in the example was crushed without refrigeration using the same crusher as in the example. During the crushing process, a flame occurred due to a short circuit, as shown in Figs. 3a and 3b. At this time, the battery used was a 622NCM battery.

In this way, through examples and comparative examples, it can be confirmed that the battery crushing step has excellent stability because a step of freezing a battery pack including the battery before crushing the battery is included, and thus no short circuit occurs and no flame is generated.

Figure 1 shows the change in voltage of a battery according to cooling temperature according to one embodiment of the present invention.

Referring to Fig. 1, when the battery is frozen to -80°C and the battery voltage is measured, the battery pack shows almost the same voltage at a high temperature of about 40°C, room temperature, and -60°C, so it can be confirmed that the battery characteristics are not lost. Next, it was confirmed that when the temperature decreases from -60°C to -70°C, the voltage decreases rapidly, and the voltage becomes 0 below -70°C. In this way, it was confirmed that a short circuit does not occur when the battery is frozen to -60 to -150°C.

FIG. 2 is a graph showing the relationship between battery weight, external cooling temperature, and cooling time according to one embodiment of the present invention.

Referring to FIG. 2, it can be confirmed that the battery processing method according to one embodiment of the present invention can derive a minimum cooling time for cooling the battery in the step of freezing the battery. Specifically, it can be confirmed that the minimum cooling time is related to the battery weight, the external cooling temperature, and the target temperature.

More specifically, when the target temperature is set to -70℃ and the battery weights are 2.5 kg (A), 10 kg (B), 20 kg (C), and 50 kg (D), the external cooling temperature and the minimum cooling time are shown. When cooling the battery, it can be confirmed that the electrolyte of the battery starts cooling after a certain period of time and the voltage becomes 0. Through this, it can be confirmed that a minimum maintenance time is required to sufficiently cool the inside, specifically the electrolyte, when cooling the battery.

Specifically, in a heat transfer situation for cooling where heat is taken out to the outside, when considering the specific heat of the battery itself, it can be confirmed that the battery weight and time for cooling are required. In this way, in the present invention, the minimum time required for cooling can be confirmed by using the external cooling temperature for refrigeration, the target temperature, and the battery weight to cool the battery.

Table 1 below lists the minimum cooling time based on battery weight and external cooling temperature.

Battery weight
[Kg] external
cooling
temperature
[℃] target
temperature
[℃] Equation 2 Minimum
cooling
hour
[h] A_1 2.5 -120 -70 1.9 1.9 A_2 2.5 -100 -70 2.9 2.9 A_3 2.5 -80 -70 4.4 4.4 B_1 10 -120 -70 3.1 3.1 B_2 10 -100 -70 4.6 4.6 B_3 10 -80 -70 7.0 7.0 C_1 20 -120 -70 3.9 3.9 C_2 20 -100 -70 5.8 5.8 C_3 20 -80 -70 8.8 8.8 D_1 50 -120 -70 5.3 5.3 D_2 50 -100 -70 7.9 7.9 D_3 50 -80 -70 11.9 11.9

Looking at Table 1 above, it can be seen that the smaller the battery weight, the shorter the minimum cooling time required for the battery to be cooled. In addition, it can be seen that when the value of Equation 2 derived from the relationship according to the battery weight, external cooling temperature, and target temperature is cooled with the minimum cooling time, the battery, specifically, the electrolyte of the battery, is cooled. In addition, when the battery is cooled for a time longer than the value of Equation 2, a fire does not occur in the post-process, that is, the process of crushing the battery.

FIGS. 3a and 3b are photographs showing a fire that occurred when crushing was performed after freezing for a shorter time than the minimum cooling time according to a comparative example of the present invention, and FIGS. 3c and 3d are photographs showing an example in which a fire did not occur when crushing was performed after freezing for a longer time than the minimum cooling time according to an embodiment of the present invention.

Referring to FIGS. 3a and 3b, the fire occurrence status of shredded material when frozen for a time shorter than the minimum cooling time required for cooling the battery was tested. In the test, when the battery weight was 25 kg, the external cooling temperature was -95°C, and the target freezing temperature was -70°C, the value of Equation 2 below was 7 hours, and the test was performed for 5 hours, which is lower than the value of Equation 2 above.

<Formula 2>

Minimum cooling time = A × (W ^0.33 )

(In the above equation 2, A = 4 × e ^{(-0.02 × dT)} , W = battery weight (Kg), dT = │external cooling temperature - target temperature│, ││ represents an absolute value)

Referring to Figures 3c and 3d, the fire occurrence status of the shredded material was tested when the battery was frozen for a minimum freezing time required for cooling. The above experiment was performed with the same battery weight as Figures 3a and 3b, the external cooling temperature, and the minimum freezing time of 7 hours or more.

Table 2 below compares the fire occurrence status of the examples and comparative examples according to the same battery weight, external cooling temperature, and minimum freezing time according to 3a to 3d. The determination of the fire occurrence status was made as follows: if fire occurrence was observed after battery crushing, “O”; otherwise, “X”.

Battery Weight [Kg] External cooling temperature [℃] Target temperature
[℃] Equation 2 Actual cooling time [h] Fire outbreak Comparative example 25 - 95 - 70 7.0 5 O Example 25 - 95 - 70 7.0 7 X

Looking at Table 2 above, it can be seen that if the battery is cooled to a value smaller than the value of Equation 2 corresponding to the minimum cooling time, the electrolyte is not cooled, resulting in a fire after the battery is crushed. In this way, it can be seen that if the battery is cooled with the value of Equation 2 as the minimum cooling time, the crushed material can be stably utilized without a fire occurring after the battery is crushed.

<Battery shredder calcination heat treatment>

The step of sintering and heat treating the above battery shreds was performed by dry heat treatment under conditions of oxygen 5 vol% or less in a temperature range of 700 to 1,350°C. Specifically, the sintering and heat treatment of this experiment was performed by dry heat treatment in a temperature range of 900 to 1,200°C, specifically about 1,100°C, and under conditions of oxygen 3 vol% or less, to obtain a composition for recovering valuable metals.

At this time, the size of the battery shreds is 10 to 20 mm in the long axis among width, length, and height, the graphite content is 5% or more, and the impurity content of plastic or iron pieces such as Al covers and PCB substrates of the shreds is less than 5%.

The composition for recovering precious metals manufactured through the above-mentioned step of sintering and heat treating comprises a core part including precious metals and a shell part including a lithium-containing compound disposed on the core part, a precious metal alloy, a lithium compound, copper, and graphite.

<Separation from a composition for recovery of valuable metals>

The composition for recovering the precious metal obtained through a high-temperature reduction process was separated into magnetic and non-magnetic substances through a magnetic separator having a magnetic strength of 3000 Gauss.

Thereafter, the non-magnetic material separated through the magnetic separation was subjected to flotation separation using Denver Sub_A flotation equipment at the following conditions: 30% ore concentration, 500 rpm impeller rotation speed, 0.1 ml/100g kerosene, and 0.1 ml/100g MIBC. Through the flotation separation, light graphite powder floated to the top of the shaft, and this was separated to recover the graphite.

Through the above flotation process, graphite was separated as a flotation material, and lithium-containing material was separated as a precipitate and recovered.

After that, the magnetic material that has undergone magnetic separation is ground using an Attrition Mill, which is a vertical stirring mill, under the conditions of 500 rpm, impeller tip speed 2.8 m/sec, grinding time 60 minutes, and solid content weight 30%. It was confirmed that the magnetic material, which is composed of a core part including a valuable metal and a shell part including a compound including lithium disposed on the core part, was separated into the core part and the shell part through the grinding process. In order to further separate the alloy core part containing the valuable metal and the lithium compound from the resultant product that has gone through the grinding process, the magnetic material and the non-magnetic material were separated using a magnetic separator of 3000 Gauss.

Afterwards, particle size separation was performed using a mesh having a mesh size of 75 ㎛ to recover coarse particles of NCM alloy and fine particles of Li oxide.

The valuable metal-containing alloy, lithium compound, and Cu were obtained through the magnetic separation, flotation separation, and particle size separation described above.

<Selective leaching step of lithium>

A valuable metal-containing alloy, a lithium compound, and Cu were obtained through a high-temperature heat treatment process, and lithium (Li) was selectively leached from the valuable metal-containing alloy, the lithium compound, and Cu through sulfuric acid leaching. The leaching of lithium can be explained by the following reaction formulas.

[Reaction Scheme 1] Ni(s)+H ₂ SO _4(aq) = NiSO _4(aq) +H _2(g) , △G ^o m = -46.3 (kJ/mol)

[Scheme 2] Co(s)+H ₂ SO _4(aq) = CoSO _4(aq) +H _2(g) , △G ^o m = -54.7 (kJ/mol)

[Reaction Scheme 3] Li ₂ O(s)+H ₂ SO _4(aq) = Li ₂ SO _4(aq) +H2O _(aq) , △G ^o m = -260.5 (kJ/mol)

[Reaction Scheme 4] Cu(s)+H ₂ SO _4(aq) = CuSO _4(aq) +H _2(g) , △G ^o m = 69.5 (kJ/mol)

According to the above reaction formulas 1 and 2, when Ni and Co are leached in sulfuric acid, the Gibbs free energy is -46 to -53 kJ/mol, which is about 20% lower than the Gibbs free energy of -260.5 kJ/mol when lithium oxide is leached in sulfuric acid, confirming that the leaching reaction is not accelerated. In the case of Cu, the Gibbs free energy is high at 69.5 kJ/mol compared to Ni, Co, and Li, confirming that leaching in sulfuric acid is not easy.

Lithium-containing alloys and lithium compounds obtained through high-temperature heat treatment were selectively subjected to lithium leaching for 120 minutes at a pH range of 0.4 to 2.0, a temperature of 50°C, and a sulfuric acid equivalent ratio of 0.8 to 2.0 M. At this time, the experiment was conducted so that the leaching rate of lithium in the sulfuric acid aqueous solution was 6 g/L assuming 100%.

Tables 3 to 5 below show the results of lithium leaching over time when the sulfuric acid equivalent ratios were 1.0 M, 1.2 M, and 1.6 M, respectively. Specifically, Table 3 below shows the results of selective Li leaching over time (g/L) (sulfuric acid equivalent ratio = 1.0 M, temperature = 50 °C), Table 4 below shows the results of selective Li leaching over time (g/L) (sulfuric acid equivalent ratio = 1.2 M, temperature = 50 °C), and Table 5 below shows the results of selective Li leaching over time (g/L) (sulfuric acid equivalent ratio = 1.6 M, temperature = 50 °C).

Time (minutes) Li Al Ni Co Mn Cu 0 0 0 0 0 0 0 30 4.15 5.99 2.19 0.64 1.17 0.11 60 4.89 7.72 3.29 0.96 1.49 0.18 90 5.45 8.64 3.98 1.17 1.68 0.24 120 5.81 9.20 4.46 1.31 1.79 0.28

Time (minutes) Li Al Ni Co Mn Cu 0 0 0 0 0 0 0 30 4.18 5.45 2.09 0.61 1.13 0.24 60 5.04 7.85 3.51 1.03 1.578 0.31 90 5.42 8.89 4.26 1.25 1.80 0.48 120 5.88 9.74 4.67 1.44 1.97 0.65

Time (minutes) Li Al Ni Co Mn Cu 0 0 0 0 0 0 0 30 4.28 4.72 0.76 0.33 1.60 0.31 60 5.17 7.57 1.52 0.59 1.76 0.38 90 5.68 9.06 2.43 0.90 1.93 0.59 120 5.99 9.82 3.55 1.27 2.22 0.81

Looking at Tables 3 to 5 above, it can be confirmed that when lithium is leached at a temperature of 50℃ for less than 120 minutes, a lithium leaching rate of 94 to 99% or more can be secured depending on the sulfuric acid equivalent ratio. In addition, at the same time, it was confirmed that the leaching concentrations of Ni, Co, and Mn can be controlled to 5 g/L or less, and the leaching concentration of Cu can be controlled to 1 g/L or less.

<Removal of impurities in lithium-containing sulfuric acid solution>

The sulfuric acid aqueous solution containing lithium that has undergone the lithium leaching process described above contains impurities of Ni, Co, Mn, Cu, Ti, Zn, Pb, P, Ca, Mg, B, K, Na, Si, and Fe. In order to remove the impurities in the sulfuric acid aqueous solution from the above impurities, an impurity removal process was performed.

In order to remove impurities in the sulfuric acid aqueous solution, the lithium-containing sulfuric acid aqueous solution obtained through the sulfuric acid leaching process of the sulfuric acid aqueous solution containing lithium was adjusted to pH 3.0 to 8.0 by adding sodium hydroxide (NaOH) into the sulfuric acid aqueous solution according to the following reaction formulas 5 and 6. By adjusting the sulfuric acid aqueous solution to the above-mentioned pH range, the impurities of Ni, Co, Mn, Cu, Ti, Zn, Pb, P, Ca, Mg, B, K, Na, Si, and Fe remaining in the sulfuric acid aqueous solution were removed.

[Scheme 5] Me ₂ (SO ₄ ) _3(aq) + 6NaOH = 2Me(OH) ₃ (s)+3Na ₂ SO _4(aq) +H ₂ SO _4(aq)

(Me = Fe, Al, Ti)

[Scheme 6] MeSO _{4 (aq)} + 2NaOH = Me(OH) ₂ (s)+Na ₂ SO _4(aq) +H ₂ SO _4(aq)

(Me = Ni, Co, Mn, Cu, Zn, Pb)

<High-value separation>

A solid-liquid separation was performed to separate the precipitated material in the sulfuric acid aqueous solution from which the aforementioned impurities were removed. Through the solid-liquid separation, the precipitated material in the sulfuric acid aqueous solution was separated, and a high-purity lithium-containing sulfuric acid aqueous solution was separated separately.

<Removal of additional impurities>

Thereafter, a process was performed to remove impurities such as Zr, T, B, and F remaining in small amounts in the highly separated sulfuric acid aqueous solution by an ion exchange method. Thereafter, in order to further remove impurities such as Ca and Mg remaining in the sulfuric acid aqueous solution, the pH of the sulfuric acid aqueous solution was adjusted to 8.5 to 12.0 to produce a high-purity Ni-containing sulfuric acid aqueous solution.

Table 6 below shows the concentration of lithium-containing sulfuric acid aqueous solution that has undergone the lithium leaching step and the impurity removal step.

division
(g/L) Li Al Ni Co Mn Cu Fe Ti Ca Mg Zn Pb After leaching 5.99 9.82 3.55 1.27 2.22 0.81 0.05 0.02 0.26 0.11 0.005 0.004 After removing impurities 5.90 0.003 0.001 0.001 0.002 0.002 0.001 0.001 0.004 0.003 0.001 0.001

Looking at Table 6 above, it was confirmed that the sulfuric acid aqueous solution containing lithium of the present invention has a high lithium concentration and a low impurity concentration, and thus a high-purity sulfuric acid aqueous solution that can be used to manufacture raw materials for lithium secondary batteries, specifically, cathode materials, was manufactured.

Table 7 below compares the concentrations of a lithium-containing sulfuric acid aqueous solution of the present invention, a sulfuric acid aqueous solution extracted from spodumene, and a lithium-containing sulfuric acid aqueous solution of a prototype generally used in the manufacture of cathode materials.

Distinction (g/L) Li Al Ni Co Mn Equation 1 Equation 2 Equation 3 Equation 4 note Example 5.99 9.82 3.55 1.27 2.22 O O O O Extract from waste batteries Comparative example 7.5 54.8 0.004 0.006 0.2 X X X X Spodumene extract Comparative example 4.8 0.5 21.4 10.2 9.7 X X X X Black Mass (Prototype)

Referring to Table 7 above, it can be confirmed that the lithium-containing sulfuric acid aqueous solution recovered from a spent battery, as in the present invention, satisfies Equations 1 to 4, which are the characteristics of the present invention. In contrast, it was confirmed that the sulfuric acid aqueous solution extracted through a leaching process from spodumene and the generally recovered black mass sample did not satisfy Equations 1 to 4, which are the characteristics of the present invention. In addition, the lithium-containing sulfuric acid aqueous solution recovered from a spent battery of the present invention has a higher lithium content than the aluminum content compared to the spodumene extract of the comparative example, so that the amount of aluminum hydroxide generated during solid-liquid separation is less, which is advantageous for solid-liquid separation. It can be confirmed that the lithium content of the lithium-containing sulfuric acid aqueous solution recovered from a spent battery of the present invention is higher than that of the black mass of the comparative example. In addition, since the lithium content is high compared to the Ni, Co, and Mn content in the sulfuric acid solution, there is an advantage in that the loss of Ni, Co, and Mn can be reduced compared to black mass with high Ni, Co, and Mn content when removing impurities by adding NaOH.

Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

Claims (18)

A step of obtaining a composition for recovering valuable metals including a valuable metal alloy, a lithium compound, copper (Cu), and graphite from a spent battery; A step of separating graphite from the composition for recovering valuable metals; A step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid; A step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in a sulfuric acid aqueous solution containing the leached lithium; and A method for producing a sulfuric acid aqueous solution containing lithium, comprising a step of removing residual impurities from a sulfuric acid aqueous solution containing the leached lithium that has undergone a recovery step. In the first paragraph, A method for producing an aqueous sulfuric acid solution containing lithium, wherein at least a portion of the lithium compound is disposed on a metal alloy. In the first paragraph, The step of obtaining a composition for recovering valuable metals comprises: A step for preparing a battery containing lithium (Li); The step of crushing the above battery; A method for producing a lithium-containing sulfuric acid aqueous solution, comprising the step of heat-treating shredded battery waste at a temperature ranging from 600 to 1,500° C. In the third paragraph, A method for producing a lithium-containing sulfuric acid aqueous solution, wherein the step of heat-treating the above-mentioned crushed battery waste at a range of 600 to 1,500° C. is performed at an oxygen concentration range of 0.1 to 2.0 vol%. In the third paragraph, A method for producing a lithium-containing sulfuric acid aqueous solution, wherein the step of separating graphite from the composition for recovering precious metals is performed by at least one of particle size separation, specific gravity separation, and flotation. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, wherein the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid controls the pH of the sulfuric acid aqueous solution containing lithium in a range of 0.2 to 4.0. In the first paragraph, The step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid is a method for producing a sulfuric acid aqueous solution containing lithium having an equivalent ratio of sulfuric acid of 0.5 to 4.0. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, wherein the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal using sulfuric acid is performed at a temperature range of 10 to 150° C. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, wherein the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal using sulfuric acid is performed by supplying an inert gas at a supply rate of 0.1 to 20.0 Nm ³ /hr. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, comprising a step of removing impurities in the sulfuric acid aqueous solution containing lithium by adding sodium hydroxide (NaOH) between the step of leaching the valuable metal, lithium compound, and copper (Cu) in the composition for recovering the valuable metal with sulfuric acid and the step of recovering the valuable metal and the copper (Cu) by solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium. In Article 10, A method for producing a sulfuric acid aqueous solution containing lithium, wherein the step of removing impurities in the sulfuric acid aqueous solution controls the pH of the sulfuric acid aqueous solution to 3.0 to 8.0. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, comprising a step of removing impurities by an ion exchange method between the step of recovering the valuable metal and the copper (Cu) by performing solid-liquid separation in the sulfuric acid aqueous solution containing the leached lithium and the step of removing residual impurities in the sulfuric acid aqueous solution containing the leached lithium that has undergone the recovery step. In the first paragraph, A method for producing a sulfuric acid aqueous solution containing lithium, wherein the step of removing residual impurities of the sulfuric acid aqueous solution containing the lithium that has undergone the above recovery step adjusts the pH of the sulfuric acid aqueous solution containing lithium to a range of 8.5 to 12.0. In the third paragraph, A method for producing a lithium-containing sulfuric acid aqueous solution, wherein the step of preparing a battery containing the lithium (Li) includes the step of freezing the battery. As recovered from waste batteries, Containing lithium (Li), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), and residual impurities, A sulfuric acid aqueous solution containing lithium satisfying the following equation 1. <Formula 1> 1.0 ≤ [Al] = 0.0297 × [Li] ² + 1.3205 × [Li] ±5 ≤ 16.0 (In the above equation 1, [Li] and [Al] represent the concentrations (g/L) of Li and Al in the sulfuric acid solution containing lithium, respectively.) In Article 15, A sulfuric acid aqueous solution containing lithium satisfying the following equation 2. <Formula 2> 0.05 ≤ [Ni] = 0.1907 × [Li] ² - 0.2689 × [Li] ±3 ≤ 16.0 (In the above equation 2, [Li] and [Ni] represent the concentrations (g/L) of Li and Ni in the sulfuric acid solution containing lithium, respectively.) In Article 15, A sulfuric acid aqueous solution containing lithium satisfying the following equation 3. <Formula 3> 0.05 ≤ [Co] = 0.0624 × [Li] ² - 0.1078 × [Li] ±2 ≤ 14.0 (In the above equation 3, [Li] and [Co] represent the concentrations (g/L) of Li and Co in the sulfuric acid solution containing lithium, respectively.) In Article 15, A sulfuric acid aqueous solution containing lithium satisfying the following equation 4. <Formula 4> 0.1 ≤ [Mn] = 0.0402 × [Li] ² + 0.117 × [Li] ±1 ≤ 12.0 (In the above equation 4, [Li] and [Mn] represent the concentrations (g/L) of Li and Mn in the sulfuric acid solution containing lithium, respectively.)

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