How is lithium extracted chemically?

Acid leaching method

Put the used lithium battery electrode materials after pretreatment (e.g. crushing, sorting) into an acid solution. Commonly used acids include sulfuric acid and hydrochloric acid. For example, taking sulfuric acid as an example, under appropriate temperature and stirring conditions, lithium compounds (such as lithium cobalt oxides, etc.) in the electrode materials will react with sulfuric acid to generate soluble salts such as lithium sulfate into the solution. The reaction equation (in the case of lithium cobalt oxide).

The insoluble impurities are then removed by filtration to obtain a filtrate containing lithium.

Finally, the lithium in the filtrate can be further separated and purified by precipitation method and solvent extraction method. Precipitation method is to add precipitant to make lithium form precipitation, such as adding sodium carbonate to make lithium form lithium carbonate precipitation; solvent extraction method is the use of organic solvents for selective extraction of lithium, lithium from the aqueous phase to the organic phase, to achieve the purpose of separation and purification.

Scope of application and advantages and disadvantages:

Applicable to many types of lithium battery electrode materials, especially metal oxide electrode materials containing lithium.

The advantage is that lithium can be effectively leached from the electrode material, and the extraction efficiency is high. The disadvantage is that the use of acid solution may produce corrosive waste gas, waste water and other environmental problems, and the subsequent separation and purification steps are more complex.

Alkaline leaching method

Put the waste lithium battery electrode materials into the alkali solution, commonly used alkali such as sodium hydroxide. Under certain reaction conditions, some lithium compounds will react with alkali. For example, some lithium-containing aluminate materials will react in the alkali solution so that lithium enters the solution.

The alkali solution containing lithium is obtained after filtration, and the lithium element can be subsequently precipitated out in the same way by precipitation method, such as joining suitable precipitating agents to generate precipitates such as lithium carbonate for recovery.

Scope of application and advantages and disadvantages:

For some specific lithium-containing compound structures, the alkaline leaching method may be more effective.

The advantage is that alkaline leaching may be less corrosive to equipment than acid leaching. However, the reaction selectivity of alkaline leaching may not be as good as that of acid leaching, and wastes such as slag generated by alkaline leaching need to be disposed of properly.