JP2016191143A - Lithium extraction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium extraction method which can efficiently extract lithium in a lithium ion battery with a simple operation.SOLUTION: A lithium extraction method comprises a calcining step of calcining a lithium ion battery to obtain a calcined product, a crushing step of crushing the calcined product to obtain a crushed product, a sieving step of sieving the crushed product to obtain granules of a predetermined diameter, and a hydrothermal treatment step of heating an alkali metal salt aqueous solution having a specified quantity of granules added thereto.SELECTED DRAWING: None

Description

  The present invention relates to a lithium extraction method.

  In recent years, demand for lithium ion batteries has been increasing in industrial fields such as mobile phones, household electrical appliances, and automobiles. In addition, lithium ion batteries using iron phosphate have been developed as positive electrode materials for lithium ion batteries.

  Lithium is an expensive valuable metal, and was obtained by pre-roasting a lithium ion battery at a temperature of 400 ° C. or lower in order to recover lithium from a defective product or a lithium ion battery containing iron phosphate after use. The powdered product was oxidized and roasted at a temperature of 400 ° C. or higher, and then reduced and roasted at a temperature of 400 to 750 ° C. to produce a reduced roasted product, in which the alkaline earth metal hydroxide was suspended. A method has been proposed in which a reduced roasted product is immersed in an aqueous solution, lithium in the reduced roasted product is eluted in water, and lithium is recovered (Patent Document 1).

In addition, a method for extracting lithium by hydrothermal treatment using only water for a positive electrode material in which lithium cobaltate (LiCoO ₂ ) is applied to an aluminum foil has been proposed (Non-patent Document 1).

JP 2012-229481 A

Waste Management and the Environment III, 92, 3-12 (2006)

  In the method of recovering lithium described in Patent Literature 1, valuable metals such as cobalt, nickel, manganese, and lithium contained in the lithium ion battery are separated and recovered, so that multiple roasting treatments and alkaline earth metals are performed. The reduced roasted product is soaked in an aqueous solution in which the hydroxide is suspended.

  However, in the method described in Patent Document 1, the concentration of lithium eluted from the reduced roasted product in the aqueous solution after immersion is low, and there is a need to increase the lithium concentration. Therefore, the collection method becomes complicated, and the time for collection becomes long, which may increase the collection cost.

  Further, in the lithium extraction method described in Non-Patent Document 1, since various positive electrode materials are mixed in the discarded lithium ion battery, the lithium extraction rate is increased by changing the properties in the aqueous solution in the hydrothermal treatment. May decrease. Therefore, it is necessary to establish a lithium extraction technique capable of extracting lithium from a lithium ion battery in which constituent materials such as various positive electrode materials, negative electrode materials, and electrolytes are mixed.

  Accordingly, an object of the present invention is to provide a lithium extraction method capable of efficiently extracting lithium in a lithium ion battery even in a lithium ion battery containing phosphorus.

The present invention provides the following lithium extraction methods [1] to [5].
[1] A roasting step of roasting a lithium ion battery to obtain a roasted product containing phosphorus, a crushing step of crushing the roasted product to obtain a crushed product, sieving the crushed product, A lithium extraction method comprising a sieving step for obtaining a granular material having a particle size and a hydrothermal treatment step for heating an aqueous alkali metal salt solution to which a predetermined amount of the granular material is added.
[2] The lithium extraction method according to [1], wherein the alkali metal salt in the alkali metal salt aqueous solution is a sodium salt or a potassium salt.
[3] A lithium extraction method according to [1] or [2], wherein the molar ratio of alkali metal to lithium in the alkali metal salt aqueous solution is 0.05 to 1.0.
[4] The lithium extraction method according to any one of [1] to [3], wherein the hydrothermal treatment step is performed at a temperature in a range of 150 [° C.] to 200 [° C.] with the alkali metal salt aqueous solution. Lithium extraction method using hydrothermal treatment.

  According to the lithium extraction method of the present invention, hydrothermal treatment is performed in an alkali metal salt aqueous solution in which particles obtained by roasting a lithium ion battery are dispersed. Lithium can be extracted efficiently.

  In order to solve the above-mentioned problems, the inventors have conducted various studies on methods for efficiently extracting lithium in a lithium ion battery containing phosphorus. As a result, phosphorus obtained from a roasted lithium ion battery has been obtained. It has been found that the extraction rate of lithium can be improved by hydrothermally treating a predetermined aqueous solution of alkali metal salt to which a granular material containing bismuth has been added, leading to the present invention.

  That is, the present invention includes a roasting step of roasting a lithium ion battery to obtain a roasted product, a crushing step of crushing the roasted product to obtain a crushed product, and sieving the crushed product to obtain predetermined particles. The present invention provides a lithium extraction method comprising a sieving step for obtaining a granular material having a diameter, and a hydrothermal treatment step for heat-treating an aqueous alkali metal salt solution to which a predetermined amount of the granular material is added. .

  Hereinafter, as an embodiment of the present invention, a lithium extraction method for extracting lithium from a defective lithium ion battery discharged from a manufacturing process, a used lithium ion battery or the like will be described.

[Roasting process]
In the lithium extraction method of this embodiment, first, a lithium ion battery is roasted to obtain a roasted product (roasting step). This is because organic substances that thermally decompose at a relatively low temperature, such as an electrolyte in a lithium ion battery, a positive electrode material such as polyvinylidene fluoride and a binder in a negative electrode material, are gasified and burned and removed from the system.

The roasted product obtained by roasting the lithium ion battery contains phosphorus contained in olivine type compounds such as LiFePO ₄ and LiMnPO ₄ as positive electrode materials of the lithium ion battery, LiFP ₆ added to the electrolyte, and the like. It is a roasted product.
In addition to the olivine type compound, the positive electrode material of the lithium ion battery includes layered rock salt type compounds such as LiCoO ₂ and LiNiO _{2 that} do not contain phosphorus, LiMn ₂ O ₄ , Li [Ni _0.5 Mn _0.5 ] O _4, etc. There are spinel compounds and the like, but it is sufficient that phosphorus is contained in the powder obtained by baking.

  The roasting temperature is preferably in the range of 400 [° C.] to 700 [° C.]. When the roasting temperature is less than 400 [° C.], the pyrolysis of the organic material contained in the electrolyte solution in the lithium ion battery and the removal outside the system become insufficient, and the roasted product is obtained by the roasting process. Ash is formed in a lump. Therefore, in the subsequent sieving step, it may be difficult to obtain a granular material having a desired particle size, which may reduce the lithium extraction rate.

  Further, when the roasting temperature exceeds 700 [° C.], the aluminum foil and the copper foil in the lithium ion battery are melted, so that the roasted ash that is a roasted product including the positive electrode material is formed in a lump. Therefore, in the sieving step, it may be difficult to obtain a granular material having a desired particle size, which may reduce the extraction rate of lithium.

Examples of the roasting furnace in which the lithium ion battery is roasted include furnaces such as an electric furnace, a tunnel furnace, and a rotary kiln. The furnace atmosphere used in the roasting process includes an air atmosphere, a reducing atmosphere containing a reducing gas species such as CO and H ₂ , an inert atmosphere composed of an inert gas such as N ₂ and Ar, and a vacuum. A non-oxidizing atmosphere including an atmosphere is mentioned. When the casing of the lithium ion battery is made of resin, a reducing atmosphere or an inert atmosphere is preferable in order to suppress an increase in heat due to resin ignition.

[Crushing process]
Next, the roasted product obtained by the roasting step is crushed to obtain a crushed product (crushing step). Crushing the positive electrode material, the metal container, the metal part or the resin part, and the lump such as aluminum foil and copper foil, etc. constituting the lithium ion battery, and the predetermined particle size in the subsequent sieving step It is for classifying the granular material. The meaning of “crushing” in the crushing process includes not only crushing the roasted product but also dismantling the roasted product. In addition, in order to bake after crushing a lithium ion battery, you may provide a crushing process as a pre-process of a roasting process.

  Although the crushing of the crushing process of this embodiment is performed using the crushing equipment containing a crusher, you may use the well-known method by a shear force, a collision, compression, etc.

[Sieving process]
Next, the crushed material obtained in the crushing step is sieved to obtain a granular material having a predetermined particle size (sieving step). Specifically, using a sieve such as a vibration sieve or a rotary sieve, metal parts, a lump containing copper, aluminum, iron, unburned resin, etc., lithium contained in the positive electrode material, carbon, etc. It separates from the granular material of the roasted ash containing.

  The particle size of the powder obtained by the sieving step is preferably 1.0 [mm] or less. This is because when the particle size of the powder particles exceeds 1.0 [mm], lithium is difficult to elute in the subsequent hydrothermal treatment step.

  In addition, the lump obtained by the sieving process other than the granular material can recover copper, aluminum, iron or the like by a known sorting operation such as specific gravity sorting or magnetic force sorting.

[Hydrothermal treatment process]
Next, an alkali metal salt aqueous solution to which a predetermined amount of powder is added is put into a pressure vessel and mixed, and then heated so that the alkali metal salt aqueous solution is in a subcritical state and subjected to hydrothermal treatment (hydrothermal treatment step). ). This is because lithium is eluted into the aqueous solution from the granular material (roasted ash) obtained by the sieving step. In addition, the hydrothermal treatment in this embodiment means heating the aqueous alkali metal salt solution to which a predetermined amount of powder is added in a sealed pressure vessel.

  The aqueous alkali metal salt solution is prepared by adding a predetermined amount of powder particles to a solution obtained by dissolving an alkali metal salt in water. In addition, as a method of mixing powder, water and alkali metal salt, a method of adding powder and alkali metal salt to water and mixing, and adding powder to an aqueous alkali metal salt solution prepared to a predetermined concentration And a method of mixing them.

  The alkali metal salt is an alkali metal hydroxide, alkali metal chloride, alkali metal nitrate, alkali metal sulfate, alkali metal acetate, or the like. Among the alkali metal salts, sodium salt or potassium salt is preferable.

  Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Examples of the alkali metal chloride include sodium chloride and potassium chloride. Examples of the alkali metal nitrate include sodium nitrate and potassium nitrate. Examples of the alkali metal sulfate include sodium sulfate and potassium sulfate. Examples of the alkali metal acetate include sodium acetate and potassium acetate.

  As an alkali metal salt, for example, by adding sodium salt or potassium salt, the eluted phosphoric acid reacts with sodium or potassium to produce highly soluble sodium phosphate or potassium phosphate, and the reaction between lithium and phosphoric acid. By suppressing the precipitation of lithium phosphate having a low solubility produced by the above, it is possible to maintain the state in which phosphorus is dissolved in the solution and to increase the extraction rate.

  The hydrothermal treatment step is preferably performed at a temperature in the range of 150 [° C.] to 200 [° C.]. When the temperature of the hydrothermal treatment step is lower than 150 [° C.], the amount of lithium dissolved in the aqueous solution is lowered, and the extraction rate of lithium is lowered. On the other hand, when the temperature of the hydrothermal treatment process exceeds 200 [° C.], for example, the vapor pressure of the heat medium for heating becomes high, and it becomes necessary to use an expensive pressure vessel, which causes an increase in the extraction cost of lithium. become.

  The treatment time of the hydrothermal treatment step is preferably 6 [hour] to 48 [hour]. When the treatment time is less than 6 [hours], lithium cannot be sufficiently eluted from the powder and the concentration of lithium in the aqueous alkali metal salt solution after the hydrothermal treatment step becomes low. As a result, the extraction rate of lithium decreases. On the other hand, the amount of lithium eluted into the aqueous solution can be increased by lengthening the treatment time. However, when the treatment time exceeds 48 hours, the concentration of lithium eluted in the aqueous solution reaches the saturation concentration. Therefore, it is not preferable from the viewpoint of lithium extraction cost.

  The alkali metal in the aqueous alkali metal salt solution can be adjusted by the amount of the alkali metal salt to be added and mixed, and the molar ratio (number of moles of alkali metal / number of moles of lithium with respect to lithium contained in the granular material). ) In the range of 0.05 to 1.0. When the molar ratio is less than 0.05, lithium iron phosphate is generated and the extraction rate of lithium is lowered. On the other hand, when the molar ratio exceeds 1.0, the increase in the extraction rate of lithium is small, which is not preferable in view of the cost of the additive.

  The amount of the alkali metal salt aqueous solution with respect to the mass of the powder in the alkali metal salt aqueous solution, that is, the solid-liquid ratio (powder [g] / alkali metal salt aqueous solution [l (liter)]) is 3.3 [g. / L] to 20 [g / l] are preferable.

  When the solid-liquid ratio is less than 3.3 [g / l], the amount of powder is small and the lithium content is small, so the lithium concentration in the aqueous alkali metal salt solution after the hydrothermal treatment step is low. As a result, when recovering lithium from the extract, it becomes difficult to recover lithium, and the recovery rate as a lithium compound from the extract is reduced. On the other hand, when the solid-liquid ratio exceeds 20 [g / l], the solid component composed of the granular material in the alkali metal salt aqueous solution increases, and the amount of lithium dissolved in the aqueous solution decreases. As a result, the extraction rate of lithium decreases.

[Recovery process]
After stopping the heat treatment in the hydrothermal treatment step, the alkali metal salt aqueous solution in the pressure vessel is cooled. Thereafter, the cooled aqueous solution is filtered to recover lithium in the filtrate (recovery step). When the aqueous solution after cooling is filtered, high purity lithium can be transferred to the filtrate side. Therefore, a known method such as a method of blowing carbon dioxide or a method of adding a carbonate such as ammonium carbonate or sodium carbonate is used. Through the carbonation reaction, lithium can be recovered in high yield as lithium carbonate.

  Moreover, according to this method, an expensive chemical | medical agent is not required and a complicated installation and operation are not required, Therefore The reduction of the extraction cost of lithium and the enlargement of an apparatus can be achieved easily.

  In addition, from solids (residues) obtained by filtration, metals such as iron contained in the solids are recovered using hydroxide precipitation, metal smelting, etc. by magnetic separation, acid treatment and alkali treatment. Can do.

  Below, the Example and comparative example which extracted lithium from the lithium ion battery which has the positive electrode material of lithium iron phosphate using the lithium extraction method of this embodiment are shown.

Example 1
After the discarded lithium-ion battery for automobiles is roasted at a temperature of 600 [° C.] in an N ₂ atmosphere, it is crushed using a shear crusher, and the crushed material obtained using a classifier is sieved. A granular material having a particle size of 1.0 [mm] or less was obtained. Table 1 shows the composition ratio of the granular material. The other columns in Table 1 are trace components including carbon of the negative electrode material, oxygen contained in the positive electrode material, and the like.

  Next, the granular material was added to the sodium hydroxide aqueous solution so that the amount of sodium was 0.10 in terms of molar ratio with respect to the amount of lithium in the granular material. Specifically, sodium hydroxide aqueous solution 60 [ml] which mixed sodium hydroxide aqueous solution 0.76 [g] prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] and distilled water was mixed. Was put into a 100 [ml] pressure vessel.

  Then, after adding 0.2 [g] of the granular material to the sodium hydroxide aqueous solution 60 [ml] in the pressure vessel and dispersing so that the solid-liquid ratio becomes 3.3 [g / l], the pressure is increased. The container was sealed. Water subjected to hydrothermal treatment in which the temperature inside the pressure vessel (treatment temperature) is 200 [° C.] and the pressure (treatment pressure) is 1.55 [MPa] for 24 [hours], and then water to which powder is added The aqueous sodium oxide solution was cooled to 30 [° C.] or less.

After cooling, the aqueous solution in the pressure vessel was filtered. The components in the filtrate were measured, and the extraction rate [%] of lithium from the granular material was determined according to the following calculation formula. The extraction rate of lithium was 82 [%].
Lithium extraction rate = lithium dissolved in filtrate [mg] / lithium in powder [mg] × 100

(Example 2)
Hydrothermal treatment was performed in the same manner as in Example 1 except that the hydrothermal treatment retention time was set to 48 [hours]. The lithium extraction rate was 89 [%].

Example 3
The hydrothermal treatment was performed in the same manner as in Example 1 except that the holding time of the hydrothermal treatment was set to 6 [hours]. The lithium extraction rate was 72 [%].

Example 4
1. Sodium hydroxide aqueous solution prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] so that the sodium amount is 0.29 in a molar ratio with respect to the lithium amount in the granular material. Hydrothermal treatment was performed in the same manner as in Example 1 except that the powder 0.2 [g] was added to and dispersed in an aqueous solution of sodium hydroxide 60 [ml] in which 3 [g] and distilled water were mixed. The lithium extraction rate was 90 [%].

(Example 5)
2. A sodium hydroxide aqueous solution prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] so that the sodium amount is 0.48 in molar ratio with respect to the lithium amount in the granular material. Hydrothermal treatment was performed in the same manner as in Example 1 except that the powder 0.2 [g] was added to and dispersed in an aqueous solution of sodium hydroxide 60 [ml] in which 8 [g] and distilled water were mixed. The lithium extraction rate was 90 [%].

(Example 6)
6. Sodium hydroxide aqueous solution prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] so that the amount of sodium is 0.97 in terms of molar ratio with respect to the amount of lithium in the granular material. Hydrothermal treatment was performed in the same manner as in Example 1 except that the powder 0.2 [g] was added to and dispersed in an aqueous solution of sodium hydroxide 60 [ml] in which 6 [g] and distilled water were mixed. The lithium extraction rate was 88 [%].

(Example 7)
4 [g] of sodium hydroxide was distilled so that the solid-liquid ratio was 16.7 [g / l] so that the sodium amount was 0.29 in terms of molar ratio with respect to the lithium amount in the granular material. Disperse by adding 1.0 [g] of granular material to sodium hydroxide aqueous solution 60 [ml] mixed with 11.5 [g] sodium hydroxide aqueous solution prepared by dissolving in water 996 [g] and distilled water. Except for this, hydrothermal treatment was performed in the same manner as in Example 1. The lithium extraction rate was 68 [%].

(Example 8)
Hydrothermal treatment was performed in the same manner as in Example 4 except that the treatment temperature was 150 [° C.] and the treatment pressure was 0.47 [MPa]. The lithium extraction rate was 67 [%].

Example 9
Sodium hydroxide aqueous solution prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] so that the sodium amount is 0.08 in terms of molar ratio with respect to the amount of lithium in the granular material. Hydrothermal treatment was performed in the same manner as in Example 1 except that powder [0.2 [g] was added and dispersed in sodium hydroxide aqueous solution 60 [ml] in which 64 [g] and distilled water were mixed. The lithium extraction rate was 77 [%].

(Example 10)
A sodium hydroxide aqueous solution prepared by dissolving sodium hydroxide 4 [g] in distilled water 996 [g] so that the sodium amount is 0.05 in terms of molar ratio with respect to the lithium amount in the granular material. Hydrothermal treatment was performed in the same manner as in Example 1 except that powder [0.2 [g] was added and dispersed in sodium hydroxide aqueous solution 60 [ml] in which 38 [g] and distilled water were mixed. The lithium extraction rate was 69 [%].

(Example 11)
Potassium hydroxide (5.61 [g]) was dissolved in distilled water (994.4 [g]) so that the molar amount of potassium was 1.0 with respect to lithium in the granular material used in Example 1. A potassium hydroxide aqueous solution 60 [ml] mixed with 7.88 [g] potassium hydroxide aqueous solution and distilled water was added.
And after adding and disperse | distributing the granular material 0.2 [g] to 60 [ml] potassium hydroxide aqueous solution in a pressure vessel so that a solid-liquid ratio may be 3.3 [g / l], pressure The container was sealed. Water subjected to hydrothermal treatment in which the temperature inside the pressure vessel (treatment temperature) is 200 [° C.] and the pressure (treatment pressure) is 1.55 [MPa] and held for 6 [hours], and then water to which powder is added The aqueous potassium oxide solution was cooled to 30 [° C.] or less.
After cooling, the aqueous solution in the pressure vessel was filtered. The components in the filtrate were measured, and the extraction rate [%] of lithium from the granular material was determined. The extraction rate of lithium was 68 [%].

(Example 12)
The granular material was added to the aqueous sodium chloride solution so that the amount of sodium in the molar ratio was 1.0 with respect to the amount of lithium in the granular material used in Example 1. Specifically, sodium chloride aqueous solution 60 [ml] which mixed sodium chloride aqueous solution 7.88 [g] prepared by dissolving sodium chloride 5.84 [g] in distilled water 994.2 [g] and distilled water was mixed. Was put into a 100 [ml] pressure vessel.
Then, after adding 0.2 [g] of the granular material to 60 [ml] of the sodium chloride aqueous solution in the pressure vessel and dispersing so that the solid-liquid ratio becomes 3.3 [g / l], the pressure vessel Sealed. Hydrochloric treatment with the internal temperature of the pressure vessel (treatment temperature) held at 200 [° C.] and the pressure (treatment pressure) held at 1.55 [MPa] for 6 [hours] followed by chlorination with the addition of powder particles The aqueous sodium solution was cooled to 30 [° C.] or less.
After cooling, the aqueous solution in the pressure vessel was filtered. The components in the filtrate were measured, and the extraction rate [%] of lithium from the granular material was determined according to the calculation formula described in Example 1. The extraction rate of lithium was 100 [%].

(Example 13)
Sodium chloride aqueous solution prepared by dissolving sodium chloride 5.84 [g] in distilled water 994.2 [g] so that the amount of sodium is 0.50 in molar ratio to the amount of lithium in the granular material. The hydrothermal treatment was performed in the same manner as in Example 12 except that 0.2 [g] of the granular material was added and dispersed in 60 [ml] of an aqueous sodium chloride solution obtained by mixing 3.94 [g] and distilled water. . The lithium extraction rate was 83 [%].

(Example 14)
Instead of sodium chloride used in Example 12, potassium chloride was used. Specifically, prepared by dissolving 7.45 [g] of potassium chloride in 994.2 [g] of distilled water so that the molar amount of potassium is 1.0 with respect to lithium in the granular material. The same water as in Example 12 except that the powder 0.2 [g] was added to and dispersed in the potassium chloride aqueous solution 60 [ml] obtained by mixing the potassium chloride aqueous solution 7.88 [g] and distilled water. Heat treatment was performed. The extraction rate of lithium was 77 [%].

(Example 15)
Instead of sodium chloride used in Example 12, sodium nitrate was used. Specifically, sodium nitrate aqueous solution 7 prepared by dissolving 8.50 g of sodium nitrate in 992 [g] of distilled water so that the sodium amount is 1.0 in terms of molar ratio with respect to lithium in the granular material. Hydrothermal treatment was performed in the same manner as in Example 12 except that 0.2 [g] of the granular material was added and dispersed in 60 [ml] of sodium nitrate aqueous solution in which .88 [g] and distilled water were mixed. The extraction rate of lithium was 71 [%].

(Example 16)
Instead of sodium chloride used in Example 12, potassium nitrate was used. Specifically, an aqueous potassium nitrate solution prepared by dissolving 10.1 [g] of potassium nitrate in 990 [g] of distilled water so that the amount of potassium is 1.0 in terms of molar ratio with respect to lithium in the granular material. Hydrothermal treatment was performed in the same manner as in Example 12 except that powder [0.2 [g] was added and dispersed in potassium nitrate aqueous solution 60 [ml] mixed with 7.88 [g] and distilled water. The extraction rate of lithium was 70 [%].

(Comparative Example 1)
Hydrothermal treatment was performed in the same manner as in Example 1 except that the sodium hydroxide aqueous solution was not added and distilled water was changed to 60 [ml] and the hydrothermal treatment retention time was changed to 6 [hours]. The lithium extraction rate was 36 [%].

  Table 2 shows the molar ratio [−] of the number of moles of sodium to the number of moles of lithium, the treatment time [hour] of hydrothermal treatment, the temperature inside the pressure vessel in hydrothermal treatment (treatment temperature) [° C.], and the powder A lithium extraction condition and a lithium extraction rate [%] consisting of a solid-liquid ratio [g / l] of an aqueous sodium hydroxide solution to which granules are added are shown.

  As shown in Examples 1 to 16 of Table 2, hydrothermal treatment of aqueous solutions of alkali metal salts such as aqueous sodium hydroxide and aqueous sodium chloride to which powders obtained by roasting lithium ion batteries were added It can be seen that the lithium in the lithium ion battery can be extracted efficiently by a simple operation. By adding alkali metal salts such as alkali metal hydroxide, alkali metal chloride, alkali metal nitrate, etc., the eluted phosphoric acid reacts with sodium and potassium, and sodium phosphate and potassium phosphate with high solubility By suppressing the precipitation of lithium phosphate with a low solubility generated by the reaction between lithium and phosphoric acid, it is possible to maintain the phosphorus dissolved in the solution and increase the extraction rate. Guessed.

  As shown in Comparative Example 1, it can be seen that when no sodium hydroxide aqueous solution was added, the decomposition reaction of the lithium compound was not promoted, and the amount of lithium eluted from the granular material decreased.

Claims (4)

A roasting step of roasting a lithium ion battery to obtain a roasted product containing phosphorus;
Crushing step of crushing the roasted material to obtain a crushed material;
Sieving the crushed material to obtain a granular material having a predetermined particle size; and
A lithium extraction method comprising: a hydrothermal treatment step of heating an alkali metal salt aqueous solution to which a predetermined amount of powder is added. The lithium extraction method according to claim 1,
The lithium extraction method, wherein the alkali metal salt in the alkali metal salt aqueous solution is a sodium salt or a potassium salt. The lithium extraction method according to claim 1 or 2,
The lithium extraction method prepared so that the molar ratio of the alkali metal to lithium in the alkali metal salt aqueous solution may be 0.05 to 1.0. It is a lithium extraction method as described in any one of Claims 1-3,
The hydrothermal treatment step is a lithium extraction method in which the alkali metal salt aqueous solution is hydrothermally treated at a temperature in the range of 150 [° C.] to 200 [° C.].