Method for directly preparing battery-grade lithium carbonate

Abstract

The invention provides a method for directly preparing battery-grade lithium carbonate, which comprises the following steps: 1) adding a sodium hydroxide solution into a lithium-containing solution tomake the pH value of the whole solution reach 12 or above, thus removing impurity metal ions in the solution, and filtering the solution to obtain a first refined lithium solution; 2) adding dilute acid into the first refined lithium solution, and adjusting the pH value to be less than or equal to 3 to obtain a second refined lithium solution; 3) adding a chelating agent into the second refined lithium solution, and then adding a sodium hydroxide solution to adjust the pH value of the solution to 6-8 to obtain a third refined lithium solution; and 4) adding a sodium carbonate solution into the third refined lithium solution, heating the third refined lithium solution to form a precipitate, and filtering the solution, and washing and drying the obtained precipitate to obtain the battery-grade lithium carbonate. According to the method, dilute acid is used for reversely adjusting the pH value, then EDDHA-Na is used for complexing metal impurity elements, then NaOH is used for reverselyadjusting the pH value, residual metal impurity elements are well removed, and the purity of lithium carbonate is improved.

Description

technical field [0001] The invention belongs to the field of inorganic chemistry and relates to a separation and extraction process of inorganic substances, in particular to a preparation method of battery-grade lithium carbonate. Background technique [0002] There are currently three main production methods for battery-grade lithium carbonate. The first is the causticization method, which is to remove calcium, magnesium and other impurities through the causticization method of lime milk and industrial grade lithium carbonate, and the filtrate is LiOH solution, and LiOH·H 2 O crystals, at this time, CO is introduced into the solution 2 , and finally high-purity lithium carbonate precipitates are obtained. This method has relatively strict requirements on condition control such as temperature, reaction ratio, and time, and is not suitable for large-scale production. The second is the hydrogenation method, which is also a commonly used method at present. It is to mix the c...

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Problems solved by technology

This method has strict requirements on condition control such as temperature, reaction ratio, time, etc., and is not suitable for large-scale production

The second is the hydrogenation method, which is also a commonly used method at present. It is to mix the crude lithium carbonate and water in a certain ratio, control a certain temperature, and feed high-purity carbon dioxide into the slurry for a certain period of time until the lithium carbonate slurry is completely converted into Lithium bicarbonate solution, through filtration, impurity removal and other processes to obtain a clear lithium bicarbonate solution, and then through alkali precipitation or thermal decomposition to obtain high-purity lithium carbonate, this method has low reaction requirements and is suitable for industrial production, but due to CO 2 Insufficient utilization leads to low efficiency

The third is the complexation impurity removal method, which is to add a complexing agent to complex the impurity ions before and during the hydrogenation treatment. Because the complexes are easily soluble in water, the cations in the insoluble calcium and magnesium salts are converted into Complexes are used to achieve the purpose of removing impurities. This method requires more than 6 times the amount of complexed ions, and the cost is relatively high.