JP2019160429A - Lithium recovery method - Google Patents

Abstract

To provide a lithium recovery method capable of effectively recovering lithium from battery slag that is obtained by roasting lithium ion battery waste.SOLUTION: A lithium recovery method of the present invention is a method for recovering lithium from battery slag that is obtained by roasting lithium ion battery waste. The method includes: a leaching step of leaching the battery slag containing lithium aluminate into an acidic solution; and a neutralization step of increasing the pH of a liquid after leaching, the liquid being obtained in the leaching step, to neutralize the liquid and performing solid-liquid separation to obtain a lithium solution.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for recovering lithium from a battery case obtained by roasting lithium ion battery waste.

  In recent years, it has been widely studied from the viewpoint of effective utilization of resources to recover valuable metals such as nickel and cobalt from lithium ion battery waste that is discarded due to product life and other reasons by wet processing. ing.

As an example of a method for recovering valuable metals from lithium ion battery waste, first, lithium ion battery waste is roasted, crushed and sieved to remove impurities such as aluminum to some extent (Patent Document 1). Etc.).
Next, a battery-like battery case obtained under sieving after sieving is added to the leaching solution and leached, and lithium, nickel, cobalt, manganese, aluminum, and the like that can be contained therein are dissolved in the leaching solution. Thereafter, each metal element dissolved in the post-leaching solution obtained by leaching as described above is separated. Here, in order to separate each metal leached in the liquid after leaching, for example, the liquid after leaching is subjected to multiple stages of solvent extraction, back extraction, etc. according to the metal to be separated. Thereby, a lithium-containing solution containing lithium ions is finally obtained (see Patent Documents 2 to 4).

Here, regarding the method as described above, in Patent Document 5, under the problem that “operation can be performed at low cost without using expensive chemicals and lithium and cobalt are separated and recovered safely”, “By reducing and roasting lithium cobaltate in a hydrogen stream at a temperature of 400 ° C. or higher, the lithium cobaltate compound form is changed to LiOH or Li ₂ O, and the roasted material is leached with water. Thus, it has been proposed that the lithium content in the baked product is eluted and the cobalt is distributed into the residue and recovered. And, by this, “without using an acid, it is possible to leach lithium with only water, and by using hydrogen or carbon as a reducing agent, it is not necessary to use an expensive acid, Also, no neutralizer is required. "

  Further, as a technology related to this, Patent Document 6 states that “lithium ion secondary battery can be efficiently recovered from lithium cobaltate, which is a positive electrode material of the lithium ion secondary battery, and reuse of the lithium ion secondary battery is disclosed. “Providing a method for recovering lithium that can be performed”, “a mixture obtained by mixing 1 part by mass or more of carbon with respect to 100 parts by mass of lithium cobaltate in an atmosphere, an oxidizing atmosphere, and a reducing property. It has been proposed that a roasted product containing lithium oxide that is roasted in any atmosphere is leached with water.

Japanese Patent Laying-Open No. 2015-195129 JP 2005-149889 A JP 2009-193778 A Japanese Patent No. 4581553 JP 2004-11010 A Japanese Patent No. 5535717

  However, it has been found that even if battery batteries obtained by roasting lithium ion battery waste are leached only with water, lithium is not sufficiently dissolved and the lithium leaching rate cannot be sufficiently increased. It was. Accordingly, in the methods of Patent Documents 5 and 6 described above, a large amount of lithium cannot be recovered at the initial stage of the treatment for the lithium ion battery waste.

  An object of the present invention is to cope with such problems, and the object of the present invention is to effectively recover lithium from a battery case obtained by roasting lithium ion battery waste. It is to provide a lithium recovery method that can be used.

  As a result of intensive studies, the inventor has newly found that lithium in a battery case obtained by roasting lithium ion battery waste can be included in the form of lithium aluminate. And when lithium aluminate is contained in the battery case, lithium aluminate is hardly soluble, so it cannot be effectively dissolved in water. Therefore, in the case of leaching with water as described above, the leaching rate of lithium is reduced. The knowledge that it cannot be improved greatly was obtained.

  Based on such knowledge, the lithium recovery method of the present invention is a method of recovering lithium from a battery cage obtained by roasting lithium ion battery waste, wherein the battery cage containing lithium aluminate is used. Are leached into an acidic solution, and neutralized by increasing the pH of the post-leaching solution obtained in the leaching step and neutralizing it, and solid-liquid separation to obtain a lithium solution.

  According to the lithium recovery method of the present invention, a leaching step of leaching a battery tank containing lithium aluminate into an acidic solution, and a neutralization to obtain a lithium solution by neutralizing the leached solution obtained in the leaching step By including a process, lithium can be effectively recovered from a battery container obtained by roasting lithium ion battery waste.

It is a flowchart which shows an example of the process which can apply the lithium collection | recovery method of one Embodiment of this invention. It is a graph which shows the result of the X-ray diffraction method performed with respect to the predetermined | prescribed battery case. It is a graph which shows the relationship at the time of leaching a lithium aluminate powder reagent in Test Example 1 of an Example, and Li and Al leaching rate. It is a graph which shows the relationship between pH at the time of neutralizing after the leaching of a lithium aluminate powder reagent in Test Example 1 of an Example, and a Li and Al neutralization rate. It is a graph which shows the relationship between the pH at the time of leaching a battery cage | basket in Test Example 2 of an Example, and Li, Al, and Co leaching rate. It is a graph which shows the relationship between the pH at the time of neutralizing after leaching of a battery cage | basket in Test Example 2 of an Example, and Li, Al, and Co neutralization rate.

The lithium recovery method according to one embodiment of the present invention will be described in detail below.
According to one embodiment of the present invention, there is provided a lithium recovery method comprising the above-described battery for recovering lithium from a lithium ion battery waste obtained by roasting lithium ion battery waste. It includes a leaching step of leaching the soot in an acidic solution, and a neutralization step of increasing the pH of the post-leaching solution obtained in the leaching step to neutralize and solid-liquid separate to obtain a lithium solution. This embodiment can be incorporated into the process illustrated in FIG. 1, for example.

(Lithium ion battery waste)
The lithium ion battery waste targeted in this embodiment is a lithium ion battery waste that can be used in various machines or devices such as mobile phones and other various electronic devices and automobiles. More specifically, for example, battery products that have been discarded or recovered due to product life, manufacturing defects, or other reasons, and effective use of resources can be achieved by targeting such lithium ion battery waste. Can be planned.

  Lithium ion battery waste includes positive electrode active materials that are lithium metal salts containing manganese, nickel and cobalt, as well as negative electrode materials containing carbon, iron and copper, and positive electrode active materials such as polyvinylidene fluoride (PVDF). An aluminum foil (positive electrode base material) applied and fixed by another organic binder or the like, and a casing containing aluminum as an exterior that wraps around the lithium ion battery waste may be included. Specifically, the lithium ion battery includes a single metal oxide composed of one element of lithium, nickel, cobalt, and manganese constituting the positive electrode active material and / or a composite metal oxide composed of two or more elements. As well as aluminum, copper, iron, carbon and the like.

(Roasting process)
In the roasting step, the lithium ion battery waste is heated. This roasting process generally raises the temperature of the lithium ion battery waste, detoxifies the internal electrolyte solution, decomposes the binder that binds the aluminum foil and the positive electrode active material, Promote the separation of the aluminum foil and the positive electrode active material during sieving to increase the recovery rate of the positive electrode active material recovered under the sieving. In some cases, metals such as cobalt contained in lithium ion battery waste , For the purpose of changing to a form that is easily dissolved by leaching with acid.

In the roasting step, it is generally considered suitable to heat lithium ion battery waste at a temperature range of 500 ° C. to 700 ° C. for 1 hour or longer. This is because the positive electrode active material is sufficiently decomposed to easily generate lithium carbonate that is easily dissolved in water, and even when water is used during leaching, the leaching rate with water can be increased. On the other hand, it is presumed that the fluidity of lithium carbonate is improved from around 723 ° C., which is the melting point of lithium carbonate, and the lithium aluminate that is hardly soluble in water is produced, thereby reducing the leaching rate due to water. . In general, there is temperature unevenness in the furnace and it is difficult to control the temperature of the roasting furnace, so lithium aluminate is generated.
However, in this embodiment, even when heated at a temperature exceeding the above temperature, for example, 700 ° C. to 1000 ° C. for 1 hour or longer, the battery tub can be effectively leached in the leaching step described later. It is. Therefore, in the roasting step, heating at a temperature of 500 ° C to 700 ° C is usually preferable, but heating at a temperature of 700 ° C to 1000 ° C may be used.

  Through such a roasting process, lithium in the lithium ion battery waste may be in a form such as lithium oxide or lithium carbonate that is easily dissolved even if part of it is water, At least a part of it becomes lithium aluminate that does not dissolve in water. Therefore, in order to dissolve such hardly soluble lithium aluminate, an acidic solution is used in the leaching step described later.

  As long as the temperature of the lithium ion battery waste can be controlled in the roasting process, various heating facilities such as a rotary kiln furnace and other various furnaces and a furnace that performs heating in an air atmosphere are provided. Can be used.

(Crushing and sieving process)
After the roasting step described above, a crushing step and a subsequent sieving step can be performed as necessary.
The crushing step is performed to selectively separate the positive electrode active material from the aluminum foil coated with the positive electrode active material while destroying the casing of the lithium ion battery waste. Here, various known apparatuses or devices can be used. Specific examples thereof include an impact-type pulverizer capable of crushing a lithium-ion battery waste while being cut, for example, a sample. A mill, a hammer mill, a pin mill, a wing mill, a tornado mill, a hammark crusher, etc. can be mentioned. Note that a screen can be installed at the exit of the pulverizer, whereby the lithium ion battery waste is discharged from the pulverizer through the screen when pulverized to a size that can pass through the screen.

  After the crushing step, for example, for the purpose of removing aluminum powder, the lithium ion battery waste is sieved using a sieve having an appropriate opening. Thereby, for example, aluminum or copper remains on the sieve, and lithium, cobalt or the like from which aluminum or copper has been removed to some extent can be obtained below the sieve.

(Leaching process)
In the leaching step, the battery cell obtained through the above-described steps is leached into the acidic solution. By this leaching step and a neutralization step described later, only lithium in the battery case can be selectively taken out and lithium can be recovered at an early stage in the treatment of lithium ion battery waste. As a result, it is possible to prevent substances contained in various reagents that can be used when recovering valuable metals from lithium ion battery waste from being mixed into lithium carbonate that is finally obtained. Lithium carbonate or the like is produced. In addition, since lithium can be separated at an early stage, it is possible to reduce the cost of reagents such as reagents, simplify the processing required to recover various metals, and reduce costs.

  Here, “battery cage” simply means a product obtained by subjecting lithium ion battery waste to a roasting process of at least some conditions, and whether or not a crushing and sieving process has been performed. Does not matter. The battery case is generally powdery or granular.

Here, the leaching process is performed for a battery case containing lithium aluminate. Lithium aluminate is a complex metal oxide of lithium and aluminum, and is generally expressed as LiAlO ₂ , and is produced by the reaction of lithium and aluminum by relatively high temperature roasting in lithium ion battery waste Is done. Lithium aluminate is sparingly soluble and does not dissolve in water. For this reason, in this leaching step, an acid solution is used to leach battery cells containing lithium aluminate.
The battery case containing lithium aluminate contains at least lithium and aluminum, and may further contain at least one selected from nickel, cobalt, manganese, copper, iron and carbon.

  The presence or absence of lithium aluminate in the battery case can be confirmed by performing X-ray diffraction (XRD) on the battery case and observing the peak intensity. For reference, FIG. 2 shows the XRD results for a given battery case.

  A battery case containing a relatively large amount of lithium aluminate is difficult to sufficiently increase the lithium leaching rate by water, but can be effectively leached by using an acidic solution as in this embodiment. It is.

  The acidic solution used in the leaching step can be an acidic solution of sulfuric acid, nitric acid, hydrochloric acid or other various acids. Among them, a sulfuric acid acidic solution is preferable in consideration of chemical cost and corrosivity.

  In the leaching step, it is preferable that the pH of the acidic solution is 1 to 6. If the pH is too high, there is a concern that the lithium aluminate in the battery case will not dissolve effectively. On the other hand, if the pH is too low, the leaching rate of cobalt may increase. From this viewpoint, the pH of the acidic solution is more preferably pH 2 to pH 4.

The pH of the acidic solution here means a pH at least at the end of the leaching process. During the leaching, the pH may fluctuate or rise in an acidic solution due to dissolution of lithium aluminate contained in the battery case or lithium carbonate that may be contained in others.
In order to lower the pH to a predetermined value, an acid such as sulfuric acid may be added continuously or intermittently over a predetermined number of times during leaching. Thus, when adding an acid on the way, even if it is not acidic at the time of addition of a battery case or the initial stage of leaching, it should just become an acidic solution in the middle.

  In the leaching step, the liquid temperature when the battery tub and the acidic solution are brought into contact with each other can be 25 ° C to 80 ° C. The pulp concentration can be 50 g / L to 500 g / L. This pulp concentration means the ratio of the dry weight (g) of the battery tub to the amount of acidic solution (L) that is contacted with the battery tub.

  The lithium concentration in the solution after leaching obtained by leaching the battery cell in the leaching step is preferably 2 g / L to 20 g / L, and more preferably a higher lithium concentration. The aluminum concentration is preferably 10 g / L or less. A lower aluminum concentration is better.

  In this leaching step, by lowering the pH of the acidic solution, not only lithium and aluminum but also valuable metals such as cobalt are dissolved, and these metal ions may be contained in the liquid after leaching. Cobalt and the like can be separated from lithium in a neutralization step described later. The cobalt concentration in the liquid after leaching is, for example, 5 g / L to 20 g / L, typically 10 g / L to 15 g / L.

(Neutralization process)
In the neutralization step, the pH of the post-leaching solution obtained in the leaching step is raised to neutralize the post-leaching solution. As a result, most of cobalt, aluminum and the like dissolved in the solution after leaching are precipitated and precipitated, while lithium is not so precipitated. Thereafter, the post-neutralized liquid obtained by neutralization in this way is subjected to solid-liquid separation using a known apparatus and method such as a filter press or thickener, so that lithium is mainly dissolved and contained. The solution can be obtained separately from the residue containing cobalt, aluminum or the like as a solid.

  In the neutralization step, the pH of the liquid after leaching is increased, so that alkali can be added to the liquid after leaching. Examples of the alkali include sodium hydroxide and calcium hydroxide. Among them, sodium hydroxide is preferable in terms of easy pH adjustment.

  By adding such an alkali, it is preferable to adjust the pH to 7 to 9 at least at the end of neutralization. The pH at this time is most preferably 8 in particular. When pH here is too low, we are anxious about cobalt and aluminum not precipitating enough.

  In the neutralization step, the temperature of the liquid after leaching can be preferably 50 ° C to 80 ° C, more preferably 60 ° C to 70 ° C. That is, when the temperature of the liquid after leaching is set to a relatively low temperature, there is a concern that the neutralized product may be poorly filtered.

Here, when aluminum ions and lithium ions are contained in the leached solution obtained in the leaching step, the molar ratio of lithium ions to the aluminum ions in the leached solution (Li / Al ratio) is 1.1 or more. It is preferable to relatively increase the lithium ions in the post-solution. Thereby, the aluminum contained in the precipitate when neutralizing the post-leaching solution in the neutralization step is not only gel-like Al (OH) ₃ but also crystalline LiAlO ₂ , LiAl ₂ (OH) _7, etc. The composite oxide and composite hydroxide are produced, and the powder is in a form close to powder. In this case, the time required for solid-liquid separation such as filtration can be shortened. In order to adjust the Li / Al ratio of the liquid after leaching, it can be adjusted by adding a lithium-containing material or the like to the liquid after leaching. As the lithium-containing material, a reagent can be used, but lithium carbonate, lithium hydroxide and other lithium compounds obtained in the treatment process of lithium ion battery waste, or at least one of them is dissolved in water. The resulting lithium aqueous solution can be obtained.

  The lithium solution obtained by solid-liquid separation after neutralization has a lithium concentration of, for example, 2 g / L or more, preferably 3 g / L or more, more preferably 5 g / L or more. On the other hand, the entire amount of aluminum in the lithium solution can be removed. The cobalt concentration in the lithium solution is preferably 0.1 g / L or less, more preferably 0.01 g / L or less. If the lithium concentration is low, there is a concern that a significant improvement in the recovery rate of lithium cannot be expected. If the cobalt concentration is high, there is a possibility that these recovery rates may decrease, and high-purity lithium may not be obtained. .

(Metal recovery process)
A recovery step can be performed on the residue obtained by solid-liquid separation in the neutralization step. In this recovery step, the residue is subjected to a predetermined process for separating and recovering valuable metals such as cobalt and other metals.
Here, various treatments for recovering the metal can be employed. As an example, for example, the residue is leached with an acid, and the solution is subjected to multiple stages of solvent extraction or neutralization. The solution obtained in each stage can be subjected to back extraction, electrolysis and the like.

(Lithium recovery process)
In order to recover lithium from the lithium solution obtained in the neutralization step, a lithium recovery step can be performed.
Here, neutralization and solid-liquid separation are performed to separate nickel ions, etc., after performing lithium concentration by extraction of a predetermined extraction solvent and back extraction in order to concentrate lithium ions in the lithium solution as necessary. In addition, carbonation to obtain lithium carbonate can be sequentially performed. Furthermore, you may refine | purify lithium carbonate after that.

  Next, the lithium recovery method of the present invention was experimentally carried out and the effects thereof were confirmed, and will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

(Test Example 1)
As a reference, a test using a lithium aluminate powder reagent was performed. When a predetermined lithium aluminate powder reagent was suspended in water, the pH was 11, and the lithium aluminate did not dissolve. When sulfuric acid was added and the pH was lowered, as shown in FIG. 3, lithium and aluminum were dissolved from the time when the pH was below 2, and the lithium leaching rate was about 60% at pH 0. .

Next, when sodium hydroxide was added to this solution to raise the pH, as shown in FIG. 4, when the pH reached 4, most of the aluminum was neutralized and precipitated. A part of this aluminum was precipitated and separated as aluminum hydroxide, and a solution in which lithium was dissolved could be obtained.
The leaching conditions were a pulp concentration of 100 g / L, a liquid temperature of 25 ° C., and the neutralization conditions were a liquid temperature of 70 ° C. In FIG. 4, the neutralization rate is calculated by (metal concentration before neutralization−metal concentration after neutralization) / metal concentration before neutralization × 100%.

  However, this test is only for the reagent and is considered to have different properties from the lithium aluminate in the battery case. This is because the reagent lithium aluminate produced under the predetermined conditions is different from the lithium aluminate in the battery case produced by roasting. The reagent lithium aluminate is considered to have a larger particle size than the lithium aluminate in the battery case. Therefore, it cannot be understood that the results of leaching pH and the like of this test performed on the reagent can be directly applied to the battery case. From this viewpoint, the following Test Example 2 was performed.

(Test Example 2)
About the battery tank obtained by baking the lithium ion battery waste, the sulfuric acid was added to water, each metal was leached as an acidic solution, and pH was raised after that and neutralized. The results are shown in FIGS. The leaching conditions were a pulp concentration of 100 g / L, a liquid temperature of 25 ° C., and the neutralization conditions were a liquid temperature of 70 ° C.

  As shown in FIG. 5, when no sulfuric acid was added, the lithium leaching rate was 50% or less, but as the pH was lowered by adding sulfuric acid, the lithium leaching rate increased to almost 100%. Thereafter, the filtrate after leaching was neutralized with sodium hydroxide. As shown in FIG. 6, aluminum had a pH of 4.5 to 5 and cobalt had a pH of 8, and almost all could be neutralized. Although lithium was lost by about 10% during neutralization, a lithium solution containing no impurities could be obtained. The amount of lithium that could be sent to the lithium recovery step was about 50% of the amount of lithium in the battery case, but it could be increased to 90% by lowering the pH and improving the lithium leaching rate.

Claims (9)

  A method for recovering lithium from a battery soot obtained by roasting lithium ion battery waste, wherein the battery soot containing lithium aluminate is leached into an acidic solution, and a leaching process. A lithium recovery method including a neutralization step of obtaining a lithium-dissolved solution by increasing the pH of the obtained leached solution to neutralize it and performing solid-liquid separation.   The lithium recovery method according to claim 1, wherein the pH of the acidic solution is set to 1 to 6 in the leaching step.   The lithium recovery method according to claim 1 or 2, wherein in the leaching step, an acid is added to the acidic solution to adjust a pH of the acidic solution.   The lithium recovery method according to claim 3, wherein the acid added to the acidic solution in the leaching step is sulfuric acid.   The lithium recovery method according to any one of claims 1 to 4, wherein in the neutralization step, the pH of the solution after leaching is adjusted to 7 to 9 by adding an alkali.   The lithium recovery method according to any one of claims 1 to 5, wherein the battery case is obtained by roasting lithium ion battery waste at a temperature of 700 ° C to 1000 ° C for 1 hour or more.   The lithium recovery method according to any one of claims 1 to 6, wherein a lithium concentration in the lithium solution is 2 g / L or more. The battery case further contains cobalt;
The method for recovering lithium according to any one of claims 1 to 7, wherein a cobalt concentration in the lithium solution is 0.1 g / L or less.   The liquid after leaching obtained in the leaching step contains aluminum ions and lithium ions, and the molar ratio of lithium ions to aluminum ions in the liquid after leaching is 1.1 or more. Lithium recovery method.