KR20210054946A - Method for producing lithium hydroxide monohydrate - Google Patents

Abstract

The present invention relates to a method for producing lithium hydroxide monohydrate from positive electrode material washing water, and more specifically, to a method for producing lithium hydroxide monohydrate, which can be used for a lithium ion secondary battery by recovering lithium from the positive electrode material washing water. According to the present invention, there is an effect that lithium contained in the positive electrode material washing water can be recycled to produce the lithium hydroxide monohydrate. In particular, there is an effect that the lithium hydroxide monohydrate that can be used for a lithium ion secondary battery can be produced by recovering the lithium from the washing water generated in a process of washing a waste positive electrode material of the lithium ion secondary battery.

Description

Method for producing battery-grade lithium hydroxide monohydrate from cathode material washing water{METHOD FOR PRODUCING LITHIUM HYDROXIDE MONOHYDRATE}

The present invention relates to a method for producing a battery-grade lithium hydroxide monohydrate from the positive electrode material washing water. More specifically, it relates to a method for producing lithium hydroxide monohydrate that can be used for a lithium ion secondary battery by recovering lithium from the positive electrode material washing water.

The secondary battery is composed of major components such as a positive electrode material, a negative electrode material, a separator and an electrolyte, and the raw material cost of these major components accounts for about 75% of the manufacturing cost of the secondary battery. Of these, about 35-40% is the cost of the cathode material, and the cathode material accounts for about 25-30% of the manufacturing cost of the secondary battery.

Recently, the need for high-capacity batteries with increased mileage has emerged as the demand for electric vehicles has increased, and the demand for batteries with a charging capacity of more than 60 kWh has been greatly increased, and secondary batteries for electric vehicles are mainly characterized by high stability or high capacity and high output characteristics. There is a trend of using cathode materials such as NCA and High-Ni NCM 811 with a nickel content of 80 mol% or more.

Unlike conventional cathode materials, NCA and NCM 811 cathode materials are manufactured using lithium hydroxide instead of lithium carbonate as a lithium source, which is relatively excellent and low in reactivity when the nickel content is 80 mol% or more in the cathode material manufacturing process. This is because the electric storage capacity characteristics are realized only when lithium hydroxide, which can be fired at temperature, is used. Therefore, the market for lithium hydroxide, a raw material for high-Ni cathode materials, is expected to grow rapidly in proportion to this.

The cathode material includes a process of mixing and firing a lithium compound and a precursor (hydroxide such as nickel, cobalt, manganese, etc.), and then washing the water-soluble unreacted material with water to reduce the defect rate of the cathode material. Waste water (washing water) is generated. The amount of washing water generated at this time is 1 to 10 times the weight of the cathode material, and the concentration of lithium contained in the washing water is reported to reach 100 to 10,000 ppm.

As the electric vehicle market increases, the amount of washing in the cathode material production process is expected to increase in the future.Since lithium discharged from the process washing water generated in the current cathode material manufacturing process cannot be recovered due to the lack of extraction technology, the technology for this Development is in desperate need.

Publication No. 10-2019-0119329 (released on October 22, 2019)

An object of the present invention is to provide a method for producing lithium hydroxide monohydrate that can be used for a lithium ion secondary battery by recovering lithium from the washing water generated in the process of washing the waste cathode material of a lithium ion secondary battery.

The object of the present invention is not limited to the above-mentioned object, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the object of the present invention described above, the present invention comprises the steps of: (a) adding an aluminum source to the positive electrode material washing water containing lithium to precipitate it in the form of a lithium-aluminum compound, and (b) precipitated lithium-aluminum. The step of separating into lithium sulfate and aluminum oxide by adding and roasting a sulfur (S) source to the compound, and (c) leaching the lithium sulfate-aluminum oxide product separated in step (b) with water to form a lithium sulfate solution And (d) converting the solution into a mixed solution of lithium hydroxide and sulfate by adding hydroxide to the lithium sulfate solution obtained in step (c), and (e) from the mixed solution of lithium hydroxide and sulfate. It provides a method for producing lithium hydroxide monohydrate comprising the steps of separating sulfate and (f) preparing lithium hydroxide monohydrate through an evaporation crystallization process.

In a preferred embodiment, in the step (a), the aluminum source is aluminum (Al), sodium aluminate (NaAlO ₂ ), aluminum hydroxide (Al (OH) ₃ ), alumina hydrate (AlOH), aluminum oxide ( Al ₂ O ₃ ), sodium aluminate hydrate (NaAl(OH) ₄ ), potassium aluminate (KAlO ₂ ), potassium aluminate hydrate (KAl(OH) ₄ ), sodium aluminum sulfate (NaAl(SO ₄ ) ₂ ), Potassium aluminum sulfate (KAl(SO ₄ ) ₂ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), ammonium aluminum sulfate ((NH ₄ )Al(SO ₄ ) ₂ ), aluminum chloride (AlCl ₃ ), aluminum nitrate ( Al (NO ₃ ) ₃ ), aluminum perchlorate (Al (ClO ₄ ) ₃ ), aluminum chlorohydrate (Al ₂ (OH) ₅ Cl), and one selected from the group consisting of combinations thereof.

In a preferred embodiment, in step (a), aluminum is added so that the molar ratio of aluminum and lithium is 1:1 to 5:1.

In a preferred embodiment, in the step (b), the sulfur (S) source is sulfuric acid (H ₂ SO ₄ ) or aluminum sulfate (Al _{2 (} SO ₄ ) ₃ ).

In a preferred embodiment, in step (b), sulfur is added so that the molar ratio of sulfur and lithium is 0.2:1 to 2:1, the roasting temperature is 100 to 1,000°C, and the roasting time is 0.5 to 10 hours. It is characterized by that.

In a preferred embodiment, in the step (d), the hydroxide is sodium hydroxide (NaOH), and the sulfate is sodium sulfate.

In a preferred embodiment, in the step (d), the sodium hydroxide (NaOH) is added and reacted for 0.5 to 10 hours at a pH range of 8 to 14 to convert to a mixed solution of lithium hydroxide and sodium sulfate.

In a preferred embodiment, the step (e) is carried out through cooling separation using a difference in solubility depending on the temperature of sodium sulfate, and the mixed solution of lithium hydroxide and sodium sulfate is prepared in a temperature range of -10 to 10°C for 0.5 to 10 hours. During the reaction, it is separated into a lithium hydroxide solution and sodium sulfate.

The present invention has the following excellent effects.

According to the present invention, there is an effect of recycling lithium contained in the positive electrode material washing water to produce lithium hydroxide monohydrate. In particular, there is an effect of recovering lithium from the washing water generated in the process of washing the waste cathode material of a lithium ion secondary battery to produce lithium hydroxide monohydrate that can be used for a lithium ion secondary battery.

1 is a flowchart illustrating a method of manufacturing lithium hydroxide monohydrate from washing water of a cathode material according to an embodiment of the present invention.
FIG. 2 is an SEM photograph of a Li-Al compound obtained through step (b) of an example of the present invention, and FIG. 3 is an XRD analysis result of the Li-Al compound.
4 is an XRD analysis result of lithium hydroxide monohydrate prepared according to an embodiment of the present invention.

As for terms used in the present invention, general terms that are currently widely used are selected, but in certain cases, some terms are arbitrarily selected by the applicant. In this case, the meanings described or used in the detailed description of the invention are considered rather than the names of simple terms. Therefore, the meaning should be grasped.

The technical feature of the present invention resides in a method for producing lithium hydroxide monohydrate that can be used for a lithium ion secondary battery by recovering lithium from the washing water generated in the process of washing the waste cathode material of a lithium ion secondary battery.

Accordingly, the method for producing lithium hydroxide monohydrate according to the present invention includes the steps of: (a) adding an aluminum source to the positive electrode material washing water containing lithium to precipitate it in the form of a lithium-aluminum compound, and (b) precipitated lithium- The steps of separating into lithium sulfate and aluminum oxide by adding and roasting a sulfur (S) source to the aluminum compound, and (c) leaching the lithium sulfate-aluminum oxide product separated in step (b) with water to obtain a lithium sulfate solution. And (d) converting the solution into a mixed solution of lithium hydroxide and sulfate by adding hydroxide to the lithium sulfate solution obtained in step (c), and (e) from the mixed solution of lithium hydroxide and sulfate. Separating the sulfate and (f) preparing lithium hydroxide monohydrate through an evaporation crystallization process.

Hereinafter, the technical configuration of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. The same reference numerals used to describe the present invention throughout the specification denote the same elements.

1 is a flowchart illustrating a method of manufacturing lithium hydroxide monohydrate from washing water of a cathode material according to an embodiment of the present invention.

Referring to FIG. 1, first (a) an aluminum source is added to the positive electrode material washing water containing lithium to precipitate it in the form of a lithium-aluminum compound (S10). In the present invention, the washing water generated in the process of washing the waste cathode material of the lithium ion secondary battery was used, and the concentration of lithium contained in the washing water is about 100 to 10,000 ppm.

The aluminum source is aluminum (Al), sodium aluminate (NaAlO ₂ ), aluminum hydroxide (Al (OH) ₃ ), alumina hydrate (AlOH), aluminum oxide (Al ₂ O ₃ ), sodium aluminate hydrate (NaAl ( OH) ₄ ), potassium aluminate (KAlO ₂ ), potassium aluminate hydrate (KAl(OH) ₄ ), sodium aluminum sulfate (NaAl(SO ₄ ) ₂ ), potassium aluminum sulfate (KAl(SO ₄ ) ₂ ), sulfuric acid Aluminum (Al ₂ (SO ₄ ) ₃ ), aluminum ammonium sulfate ((NH ₄ )Al(SO ₄ ) ₂ ), aluminum chloride (AlCl ₃ ), aluminum nitrate (Al(NO ₃ ) ₃ ), aluminum perchlorate (Al( ClO ₄ ) ₃ ), aluminum chlorohydrate (Al ₂ (OH) ₅ Cl), and may include one selected from the group consisting of a combination thereof.

In the step (a) (S10), aluminum was added so that the molar ratio of aluminum and lithium was 1:1 to 5:1, and reacted for 0.1 to 24 hours to induce a precipitation reaction of the lithium-aluminum compound. The reaction mechanism occurring in the precipitation process is as shown in [Scheme 1].

[Scheme 1]

Li ⁺ + Al ²⁺ + xH ₂ O = LiAl ₂ (OH) ₇ xH ₂ O

Subsequently, (b) a sulfur (S) source is added to the precipitated lithium-aluminum compound and roasted to separate lithium sulfate and aluminum oxide (S20).

A sulfur (S) source is added to the lithium-aluminum compound obtained in step (a) for sulfation, so that lithium can be separated in a liquid form of lithium sulfate, and aluminum can be separated in a solid form of an oxide. The sulfur source is sulfuric acid (H ₂ SO ₄ ) or aluminum sulfate (Al _{2 (} SO ₄ ) ₃ ).

Here, the sulfur source is added so that the molar ratio of sulfur and lithium is 0.2:1 to 2:1, and the roasting temperature is reacted at 100°C to 1,000°C for 0.5 to 10 hours to induce a sufficient thermal decomposition reaction of lithium and aluminum. . The chemical reaction mechanism that occurs in the sulfation process is shown in [Scheme 2].

[Scheme 2]

_{LiAl 2 (OH) 7 · xH} 2 O + SO 4 2- = Li 2 SO 4 + Al 2 O 3 + xH 2 O

Subsequently, (c) the lithium sulfate-aluminum oxide obtained separated in step (b) is leached with water and recovered in the form of a lithium sulfate solution (S30). That is, water is added to the roasted product obtained in step (b) at a ratio of 0.1 to 100 times that of the roasted material to obtain a liquid lithium sulfate aqueous solution.

In the water leaching process according to the embodiment of the present invention, the amount of aluminum oxide dissolved in water is minimized, and the lithium concentration of the water leaching solution is increased as much as possible to have a lithium concentration of 10 g/L to 25 g/L or more, and 0.5 It is preferable to carry out to 10 hours or more so that sufficient lithium is leached.

Subsequently, (d) hydroxide is added to the lithium sulfate solution obtained in step (c) to convert the solution into a mixed solution of lithium hydroxide and sulfate (S40). Here, the hydroxide is sodium hydroxide (NaOH), and the sulfate to be converted is sodium sulfate.

That is, in step (d), sodium hydroxide is added to the lithium sulfate solution obtained in step (c) to induce a conversion reaction to lithium hydroxide to prepare a mixed solution of sodium sulfate and lithium hydroxide. At this time, in the lithium hydroxide conversion process of lithium sulfate, a molar ratio of sodium hydroxide and lithium as a source of hydroxyl groups is added in a molar ratio of 0.5 to 2 (maintaining a pH range of 8 to 14), and 20° C. to 80 for 0.5 to 10 hours. It is preferable to proceed at ℃ so that a sufficient reaction can be made. The mechanism of the conversion reaction of lithium sulfate to lithium hydroxide is as shown in [Scheme 3].

[Scheme 3]

Li ₂ SO ₄ + 2NaOH = 2LiOH + Na ₂ SO ₄

Subsequently, (e) the sulfate is separated from the mixed solution of the lithium hydroxide and sulfate (S50). In the embodiment of the present invention, sodium sulfate was separated by cooling the mixed solution of lithium hydroxide and sodium sulfate.

Here, in the step (e), it is carried out through cooling separation using a difference in solubility depending on the temperature of sodium sulfate, and the mixture solution of lithium hydroxide and sodium sulfate is reacted at a temperature range of -10 to 10°C for 0.5 to 10 hours to oxidize. Separated into lithium solution and sodium sulfate. That is, crystallization of sodium sulfate was induced through cooling separation, and the sodium sulfate crystal obtained in a solid phase was separated from the lithium hydroxide solution by performing solid-liquid separation.

Finally, (f) lithium hydroxide monohydrate is prepared through the evaporation crystallization process (S60). In an embodiment of the present invention, the lithium hydroxide solution obtained in the sodium sulfate separation process was subjected to a silver crystallization process, a re-dissolution process, and a recrystallization process to prepare a final lithium hydroxide monohydrate.

Example 1

(S10) Preparation of cathode material washing water

Prepare the washing water generated in the process of washing the waste cathode material of the lithium ion secondary battery. The chemical analysis values of the positive electrode material washing water generated by the actual positive electrode material manufacturer are shown in [Table 1] (ICP analysis values of the positive electrode material washing water).

(S20) Lithium recovery through precipitation

To 200 mL of the positive electrode material washing water _{, 7.87 g of NaAlO 2 and} 7.48 g of Al (OH) ₃ were added at an Al/Li molar ratio of 3, and the reaction was performed for 10 hours or more. When NaAlO ₂ was added, 14.4 mg/L of lithium remained in the solution after the reaction, and _{1.51 mg/L of lithium remained when Al(OH) 3} was added, resulting in a lithium recovery rate of 98.79% and 99.87%, respectively. As a result, it was confirmed that most of the lithium was precipitated and recovered in the form of a lithium aluminum compound. The analysis results of the recovered lithium-aluminum compound are shown in FIGS. 2 and 3.

FIG. 2 is an SEM photograph of a Li-Al compound obtained through step (b) of an example of the present invention, and FIG. 3 is an XRD analysis result of the Li-Al compound.

(S30) Lithium sulfate conversion process and water leaching of insoluble lithium compounds

The precipitated lithium-aluminum compound 20g and aluminum sulfate 10g evenly mixed with 2g of water 2g and lithium-aluminum compound 3g, 5M sulfuric acid 15ml, water 5ml mixed with different parameters to 650 ~ 750 ℃ roasting to proceed with water leaching Was carried out. As a result of the experiment, it was confirmed that the lithium concentration in the obtained lithium sulfate solution was 30.8 g/L, and the final lithium recovery rate was 89.9%.

(S40) Lithium sulfate-lithium hydroxide conversion process

The obtained lithium sulfate solution was stirred by adding 1 kg of a 50% sodium hydroxide solution to 4.5 L of 18.75 g/L. The pH was adjusted in the range of 11 to 12, and a mixed solution of lithium hydroxide and sodium sulfate was obtained.

(S50) sodium sulfate separation process

The obtained mixed solution was cooled to 0° C. or lower to react for 2 hours or more, and sodium sulfate was cooled and crystallized to perform solid-liquid separation, and then 3.6 L of lithium hydroxide solution and 2.1 kg of sodium sulfate decahydrate were obtained. At this time, it was confirmed that the lithium recovered as the lithium hydroxide solution was 95%.

(S60) Manufacture of lithium hydroxide through crystallization, washing, and re-dissolution

The lithium hydroxide solution thus obtained was first crystallized, washed, re-dissolved, and recrystallized to obtain 105.6 g of lithium hydroxide. Chemical analysis values of the obtained lithium hydroxide monohydrate are summarized in [Table 2] below.

4 is an XRD analysis result of lithium hydroxide monohydrate prepared according to an embodiment of the present invention, and it can be confirmed that a high purity lithium hydroxide monohydrate of 99.5% was finally prepared.

Although the present invention has been shown and described with a preferred embodiment as described above, it is not limited to the above-described embodiment, and within the scope not departing from the spirit of the present invention, to those of ordinary skill in the art. Various changes and modifications will be possible.

Claims (8)

(a) adding an aluminum source to the positive electrode material washing water containing lithium to precipitate it in the form of a lithium-aluminum compound;
(b) separating the precipitated lithium-aluminum compound into lithium sulfate and aluminum oxide by adding a sulfur (S) source and roasting;
(c) leaching the lithium sulfate-aluminum oxide product separated in step (b) with water and recovering it in the form of a lithium sulfate solution;
(d) adding a hydroxide to the lithium sulfate solution obtained in step (c) to convert it into a mixed solution of lithium hydroxide and sulfate;
(e) separating the sulfate from the mixed solution of lithium hydroxide and sulfate; And
(f) preparing lithium hydroxide monohydrate through an evaporation crystallization process. The method of claim 1,
In the step (a), the aluminum source is aluminum (Al), sodium aluminate (NaAlO ₂ ), aluminum hydroxide (Al (OH) ₃ ), alumina hydrate (AlOH), aluminum oxide (Al ₂ O ₃ ), Sodium aluminate hydrate (NaAl(OH) ₄ ), potassium aluminate (KAlO ₂ ), potassium aluminate hydrate (KAl(OH) ₄ ), sodium aluminum sulfate (NaAl(SO ₄ ) ₂ ), potassium aluminum sulfate (KAl( SO ₄ ) ₂ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), ammonium aluminum sulfate ((NH ₄ )Al(SO ₄ ) ₂ ), aluminum chloride (AlCl ₃ ), aluminum nitrate (Al(NO ₃ ) ₃ ), aluminum perchlorate (Al(ClO ₄ ) ₃ ), aluminum chlorohydrate (Al ₂ (OH) ₅ Cl), and a method for producing lithium hydroxide monohydrate, characterized in that it comprises one selected from the group consisting of a combination thereof . The method of claim 2,
In the step (a), aluminum is added so that the molar ratio of aluminum and lithium is 1:1 to 5:1. The method of claim 1,
In step (b), the sulfur (S) source is sulfuric acid (H ₂ SO ₄ ) or aluminum sulfate (Al _{2 (} SO ₄ ) ₃ ). The method of claim 4,
In the step (b), sulfur is added so that the molar ratio of sulfur and lithium is 0.2:1 to 2:1, the roasting temperature is 100 to 1,000°C, and the roasting time is 0.5 to 10 hours. Method for producing monohydrate. The method of claim 1,
In the step (d), the hydroxide is sodium hydroxide (NaOH), and the sulfate is sodium sulfate. The method of claim 6,
In the step (d), the sodium hydroxide (NaOH) is added and reacted for 0.5 to 10 hours in a pH range of 8 to 14 to convert to a mixed solution of lithium hydroxide and sodium sulfate. Way. The method of claim 7,
The step (e) is carried out through cooling separation using a difference in solubility depending on the temperature of sodium sulfate, and a lithium hydroxide solution by reacting the mixed solution of lithium hydroxide and sodium sulfate at a temperature range of -10 to 10°C for 0.5 to 10 hours. Method for producing lithium hydroxide monohydrate, characterized in that separating with sodium persulfate.

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