Method for producing lithium carbonate

1. A method for producing lithium carbonate from lithium ion battery waste, the lithium ion battery waste comprising battery positive material components containing Li and at least one metal selected from Co, Ni and Mn, wherein the method comprises:

a wet process, wherein the at least one metal of the battery positive material components is separated from the lithium ion battery waste to obtain crude lithium carbonate,

a dissolution step of dissolving the crude lithium carbonate in a liquid while feeding a carbon dioxide gas; and a decarbonization step of heating a lithium dissolved solution obtained in the dissolution step to release carbonic acid, and

wherein when dissolving the crude lithium carbonate in the liquid in the dissolution step, the liquid is stirred in a reaction vessel using a stirrer, and a ratio of a diameter (d) of a stirring blade of the stirrer to an inner diameter (D) of the reaction vessel (d/D) is from 0.2 to 0.5.

2. The method according to claim 1 , wherein, in the dissolution step, a ratio (P/V) of a stirring power (P) of the stirrer to a volume (V) of the liquid with the crude lithium carbonate introduced is from 0.3 kW/m 3 to 1.0 kW/m 3 .

3. The method according to claim 1 , wherein, in the dissolution step, a peripheral speed of the stirrer is from 1.3 m/s to 1.9 m/s.

4. The method according to claim 1 , wherein, in the dissolution step, a rate of the carbon dioxide gas fed to the liquid is 0.6 L/min/L or less.

5. The method according to claim 1 , further comprising a washing step of washing the crude lithium carbonate before the dissolution step.

6. The method according to claim 5 , wherein the washing step comprises a washing operation, wherein in the washing operation, the crude lithium carbonate is brought into contact with pure water, the water being present in an amount that is 0.5 to 2 times a wet weight of the crude lithium carbonate, then the water and crude lithium carbonate are stirred to form a slurry, and then a solid-liquid separation of the slurry is performed to recover the crude lithium carbonate.

7. The method according to claim 6 , wherein in the washing step, the washing operation is carried out a plurality of times.

8. The method according to claim 1 , wherein, after the wet process and prior to the dissolution step, the following steps are carried out:

a pH-increasing step of increasing a pH of an acidic solution obtained after separating the at least one metal of the battery positive electrode material components from the lithium ion battery waste; and a carbonization step of carbonizing Li in the solution obtained in the pH-increasing step.

9. The method according to claim 8 ,

wherein the acidic solution comprises Ni ions and Mg ions; and

wherein the pH-increasing step comprises increasing a pH of the acidic solution to 12.0 to 13.0.

10. The method according to claim 8 ,

wherein the acidic solution comprises Ni ions, but does not comprise Mg ions; and

wherein the pH-increasing step comprises increasing a pH of the acidic solution to 10.0 to 10.5.

11. The method according to claim 1 , wherein the dissolution step comprises bringing the crude lithium carbonate into contact with pure water, then stirring the water and crude lithium carbonate to form a slurry and then feeding carbonate ions to the slurry to dissolve the crude lithium carbonate.

12. The method according to claim 11 , wherein, in the dissolution step, the pure water is used in an amount that a Li concentration is from 7 g/L to 9 g/L, assuming that the total amount of the crude lithium carbonate is dissolved in the pure water at 25° C.