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Example 1
1 kg of positive electrode material separated from waste lithium secondary batteries was heat-treated at 450° C. for 1 hour. The heat-treated positive electrode material was cut into small units and pulverized by milling to obtain a Li—Ni—Co—Mn oxide positive electrode active material sample (step S10 ).
0.1 kg of the positive electrode active material sample is added to 0.6 kg of 3M sulfuric acid solvent, and 0.4 times the amount of hydrogen peroxide corresponding to the reaction equivalent of the positive electrode active material is made into a 35% hydrogen peroxide solution and added to the 3M sulfuric acid solvent, and reacted for 6 hours at 80° C. and 1 standard atmospheric pressure (atm). The residual positive electrode active material and the solution remaining after the reaction are separated to form a first leachate and residual positive electrode active material (step S20).
The residual positive electrode active material is added to a 3M sulfuric acid solvent, and 1.0 times the amount of hydrogen peroxide corresponding to the reaction equivalent of the residual positive electrode active material is prepared into a 35% hydrogen peroxide solution and added to the 3M sulfuric acid solvent, and reacted for 6 hours. The solution formed after the reaction is separated to form a second leachate (step S30).
The first leaching solution formed is added to the process of extracting cobalt to recover cobalt, and is continuously added to the process of extracting nickel to recover nickel. In addition, the second leaching solution is added to the process of extracting manganese to recover manganese, and is continuously added to the process of extracting cobalt and the process of extracting nickel to recover cobalt and nickel (step S40).
In the process of extracting manganese, a 50% saponified 1M D2EHPA solution is used as an extractant. Specifically, D2EHPA is diluted with kerosene to prepare a 1M D2EHPA solution, and NaOH corresponding to 50% of the molar number of D2EHPA is added to the diluted 1M D2EHPA solution and a saponification process is performed to obtain the 50% saponified 1M D2EHPA solution. The obtained 50% saponified 1M D2EHPA (organic phase) and the second leachate (aqueous phase) are mixed so that the ratio of organic phase/aqueous phase is 4.5, and manganese is extracted.
In addition, 40% saponified 0.8M Cyanex 272 was used as an extractant in the process of extracting cobalt. The 40% saponified 0.8M Cyanex 272 (organic phase) and the second leachate (aqueous phase) were mixed so that the organic phase/aqueous phase ratio was 2.0, and cobalt was extracted.
In addition, 60% saponified 1M PC88A was used as an extractant in the process of extracting nickel. The 60% saponified 1M PC88A (organic phase) and the second leaching solution (aqueous phase) were mixed so that the organic phase/aqueous phase ratio was 3.5, and nickel was extracted.
Technical Effects
In the method for recovering transition metals of a lithium secondary battery according to the above exemplary embodiment, a first leachate as a solution rich in cobalt and nickel can be prepared by adding a relatively small amount of a reducing agent, and a second leachate as a solution rich in manganese can be prepared by adding a relatively large amount of a reducing agent to the residual positive active material remaining after preparing the first leachate. In this case, by directly adding the first leachate to the process of extracting cobalt and nickel, cobalt can be recovered with high purity, and by adding the second leachate to the process of extracting manganese, a high manganese extraction rate can be achieved. Therefore, the recovery efficiency of transition metals of lithium secondary batteries can be improved.
