Method for recycling residual lithium in reaction mother liquor in preparation of electrode materials by hydrothermal method

Abstract

The invention discloses a method for recycling residual lithium in reaction mother liquor in preparation of electrode materials by a hydrothermal method. Lithium hydroxide is added in the reaction mother liquor; the solid-liquid separation is performed after the heating reaction; the solid-liquid separation is performed again after the reaction between precipitates and phosphoric acid; obtained clarified solution is used as raw materials for preparing the electrode materials by the hydrothermal method; lithium sulfate is separated from the first-separated clarified solution through an ion exchange membrane; remained solvent is concentrated and recycled; lithium ions and sulfate ions in obtained lithium sulfate water solution are separated through a bipolar membrane, and are combined with hydroxide ions and hydrogen ions obtained through water electrolysis to obtain lithium hydroxide solution and sulfuric acid solution; and the lithium hydroxide solution is concentrated as the raw materials for preparing the electrode materials by the hydrothermal method. The method is wide in application range, greatly reduces the cost of the raw materials for production by the hydrothermal method,adds no new raw materials, achieves good recycling effect, simple procedures and high cost performance, and facilitates application and popularization in industrial production.

Description

technical field [0001] The invention belongs to the field of lithium battery electrode materials, and in particular relates to a method for recycling residual lithium in a reaction mother liquor of electrode materials prepared by a hydrothermal method. Background technique [0002] Lithium phosphate compounds with an olivine structure in lithium-ion batteries, such as lithium iron phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium manganese iron phosphate, lithium manganese phosphate, etc., can be used as cathode materials for lithium-ion secondary batteries. Lithium iron phosphate has been widely used in new energy buses, solar and wind power storage and other fields. [0003] The current industrial production technology of olivine structure electrode materials is based on the high-temperature solid-state method, but a large amount of polluting gases will be generated during the sintering process of the high-temperature solid-state method, and the batch ...

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Problems solved by technology

Residual lithium leads to high production (raw material) costs for the preparation of electrode materials by the hydrothermal process, which also makes it difficult for the hydrothermal process to be widely used in the industrial production of lithium battery electrode materials at this stage

[0006] Some studies have begun to explore the method of fully recycling lithium in the mother liquor of the hydrothermal method. Patent CN107915239A discloses a method for preparing high-purity lithium sulfate by reacting mother liquor with lithium iron phosphate. This method can obtain lithium sulfate with a purity of more than 99%. , but the method can only be used for the reaction mother liquor of lithium iron phosphate material, the scope of application is narrow, and sodium ions are introduced, and the recovered lithium sulfate cannot be directly recycled as raw materials for hydrothermal reaction, which reduces the use value

In addition, there are also some chemical methods, adding a precipitating agent such as barium hydroxide to the reaction mother liquor, and obtaining lithium hydroxide after separating the barium sulfate precipitation, but this method will introduce new impurities (such as barium ions) and lose part of the organic solvent. And additionally prolong the preparation process, increase the difficulty of preparation control and energy consumption, the recycling scheme is less cost-effective, and it is easy to cause adverse effects on the environment

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