Method for recycling lithium element in retired ternary lithium battery positive electrode material

Abstract

The invention discloses a method for recovering a lithium element in a retired ternary lithium battery positive electrode material, and relates to the technical field of battery recovery, and the method comprises the following steps: S1, uniformly mixed carbon powder and ternary positive electrode recovery powder are placed in a reduction furnace, and a carbon thermal reduction reaction is carried out under the protection of a nitrogen atmosphere to obtain a reduced material; s2, the reduction material, pure water and grinding balls are put into a pressurized ball milling tank, carbon dioxide is introduced, ball milling is conducted in the high-pressure environment of 2-5 MPa, and ball milling slurry is obtained; s3, carrying out solid-liquid separation on the ball-milled slurry to obtain a lithium extraction leachate; s4, the lithium extraction leachate is subjected to impurity removal, concentration and thermal decomposition, and lithium carbonate crystals are obtained; and S5, washing, drying and crushing the lithium carbonate crystals to obtain the battery-grade lithium carbonate. According to the method disclosed by the invention, lithium is extracted by matching carbon dioxide with ball-milling water in a high-pressure environment, so that the leaching efficiency and the leaching rate of the lithium element in the reduced ternary positive electrode recycled powder can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling, and in particular to a method for recycling lithium elements in anode materials of retired ternary lithium batteries. Background Art

[0002] Ternary lithium battery, the full name of which is ternary polymer lithium battery, mainly refers to a lithium battery whose positive electrode material uses ternary positive electrode materials such as nickel cobalt manganese oxide.

[0003] The existing technical method for recovering lithium elements from retired ternary lithium battery positive electrode materials usually involves carbon thermal reduction roasting of the ternary positive electrode recovery powder to convert the lithium elements in the ternary positive electrode recovery powder into lithium oxide and lithium carbonate; then, the lithium oxide and lithium carbonate are converted into lithium bicarbonate that is easily soluble in water by carbonation water leaching, thereby achieving the leaching of lithium elements and facilitating the subsequent lithium extraction.

[0004] However, the current carbonation water leaching method is to introduce carbon dioxide for water leaching under normal pressure. The leaching efficiency of lithium is relatively low, and the leaching rate of lithium does not exceed 90wt%. In addition, the roasted product is compacted, which also reduces the leaching efficiency and leaching rate of lithium. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a method for recovering lithium elements in retired ternary lithium battery positive electrode materials. By using carbon dioxide and ball-milled water to leach lithium under a high-pressure environment, the leaching efficiency and leaching rate of lithium elements in the reduced ternary positive electrode recovery powder can be effectively improved.

[0006] The present invention provides a method for recovering lithium elements in retired ternary lithium battery positive electrode materials, comprising the following steps:

[0007] S1. placing the uniformly mixed carbon powder and ternary cathode recovery powder in a reduction furnace, and performing a carbon thermal reduction reaction under the protection of a nitrogen atmosphere to obtain a reduced material;

[0008] S2, putting the reducing material, pure water and grinding balls into a pressurized ball mill, introducing carbon dioxide, and ball milling under a high pressure environment of 2 to 5 MPa to obtain a ball mill slurry;

[0009] S3, performing solid-liquid separation on the ball-milled slurry to obtain a lithium extraction leaching solution;

[0010] S4, removing impurities, concentrating and thermally decomposing the lithium extraction leachate to obtain lithium carbonate crystals;

[0011] S5. Wash, dry and crush the lithium carbonate crystals to obtain battery-grade lithium carbonate.

[0012] Specifically, the carbon powder and the ternary positive electrode recycled powder are mixed in a mass ratio of 4 to 6:100.

[0013] Specifically, the carbon powder and the ternary positive electrode recovery powder are stirred and mixed for 2 to 4 hours.

[0014] Specifically, the carbothermal reduction reaction lasts for 2 to 4 hours.

[0015] Specifically, before step S2, the reduced material is crushed and passed through a 20-60 mesh sieve.

[0016] Specifically, the reducing material, the pure water and the grinding balls are put into the pressurized ball mill according to a mass ratio of 1:2 to 10:2.

[0017] Specifically, the speed range of the pressurized ball mill is 20 to 70 r / min, and the ball milling lasts for 4 to 8 hours.

[0018] Specifically, in step S4, the lithium extraction leaching solution is decontaminated by resin adsorption to obtain a first lithium bicarbonate solution.

[0019] Specifically, in step S4, the first lithium bicarbonate solution is concentrated by evaporation to obtain a second lithium bicarbonate solution; in the second lithium bicarbonate solution, the concentration of lithium ions ranges from 8 to 9 g / L.

[0020] Specifically, in step S4, the temperature range of the thermal decomposition is 70-80°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method of the present invention comprises the following steps: placing reducing materials, pure water and grinding balls into a pressurized ball milling tank, introducing carbon dioxide, and performing ball milling under a high-pressure environment of 2 to 5 MPa; wherein the high-pressure environment can significantly increase the solubility of carbon dioxide, and can form carbonic acid of sufficient concentration in the feed liquid; ball milling can fully break and disperse the reducing materials, so that lithium oxide and lithium carbonate in the reducing materials are fully exposed, and the exposed lithium oxide reacts with water to generate lithium hydroxide, and the lithium hydroxide reacts with carbonic acid to generate lithium carbonate, and all lithium carbonate reacts with sufficient carbonic acid to generate lithium bicarbonate; therefore, leaching lithium with carbon dioxide in combination with ball milling water under a high-pressure environment can not only effectively increase the reaction efficiency of carbonic acid and lithium carbonate, but also promote the full conversion of lithium carbonate into lithium bicarbonate, thereby effectively increasing the leaching efficiency and leaching rate of lithium element in the ternary positive electrode recovery powder after reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic flow chart of a method for recovering lithium elements from retired ternary lithium battery positive electrode materials in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for recovering lithium from retired ternary lithium battery positive electrode materials. Figure 1 The schematic diagram of the process of recovering lithium from the positive electrode material of retired ternary lithium batteries in an embodiment of the present invention is shown, comprising the following steps:

[0027] S1. placing the uniformly mixed carbon powder and ternary cathode recovery powder in a reduction furnace, and performing a carbon thermal reduction reaction under the protection of a nitrogen atmosphere to obtain a reduced material;

[0028] During the carbon thermal reduction reaction, the high-valent nickel, cobalt and manganese elements in the ternary positive electrode recovery powder are reduced to low-valent nickel, cobalt and manganese elements, which destroys the stable layered crystal structure of the ternary positive electrode material, releases the lithium element from the crystal lattice and converts it into easily leached lithium oxide and lithium carbonate, facilitating subsequent leaching.

[0029] In some specific embodiments, the carbon powder and the ternary positive electrode recovery powder are mixed in a mass ratio of 4 to 6:100, and the amount of carbon powder is appropriate, which is conducive to fully reducing the high-valent nickel, cobalt and manganese elements, and completely destroying the stable layered crystal structure of the ternary positive electrode material, thereby fully releasing the lithium element from the lattice and fully converting it into lithium oxide and lithium carbonate, which is conducive to ensuring the subsequent leaching rate of lithium elements; at the same time, the appropriate proportion of carbon powder can avoid the over-reduction of metal elements such as nickel, cobalt and manganese into metal elements, which is conducive to reducing the subsequent synergistic leaching of metal elements such as nickel, cobalt and manganese, thereby helping to improve the purity of subsequent lithium extraction. Among them, the carbon content of the carbon powder is 70 to 80wt%, which has good reducibility and is conducive to the efficient performance of the carbon thermal reduction reaction.

[0030] Moreover, the carbon powder and the ternary positive electrode recovery powder are stirred and mixed for 2 to 4 hours, so that the carbon powder and the ternary positive electrode recovery powder can be fully mixed and evenly mixed, so that the effective components of the ternary positive electrode recovery powder and the carbon powder are fully in contact, which is beneficial to improving the efficiency of the carbon thermal reduction reaction.

[0031] Specifically, the temperature range of the carbon thermal reduction reaction is 660-700°C, which can avoid the sintering of the ternary positive electrode recovery powder to form a hard block encapsulating the lithium element due to excessive temperature, and can also avoid the over-reduction of metal elements such as nickel, cobalt, and manganese to metal elements encapsulating the lithium element due to excessive temperature; on the one hand, it is beneficial to the subsequent leaching of lithium elements, and on the other hand, it is beneficial to reduce the subsequent synergistic leaching of metal elements such as nickel, cobalt, and manganese.

[0032] Furthermore, the carbon thermal reduction reaction lasts for 2 to 4 hours. The appropriate reaction time and the appropriate reaction temperature cooperate with each other, which can fully reduce the high-valent nickel, cobalt and manganese elements to low-valent nickel, cobalt and manganese elements, and completely destroy the stable layered crystal structure of the ternary positive electrode material, thereby fully releasing the lithium element from the lattice and fully converting it into lithium oxide and lithium carbonate that are easy to leach, which is beneficial to ensure the subsequent lithium element leaching rate; the appropriate reaction time and the appropriate reaction temperature cooperate with each other, and can further avoid sintering of the ternary positive electrode recovery powder and avoid excessive reduction of the ternary positive electrode recovery powder.

[0033] It should be noted that, after the carbon powder and the ternary positive electrode recovery powder mixed in a mass ratio of 4 to 6:100 are subjected to carbon thermal reduction reaction at 660 to 700°C and in a nitrogen atmosphere for 2 to 4 hours, the valence state of the nickel, cobalt and manganese elements in the reduced material obtained is +2; on the one hand, the +2-valent nickel, cobalt and manganese elements are not easily dissolved and leached by the carbonate solution, which can reduce the co-leaching amount of the nickel, cobalt and manganese elements during the lithium extraction process; on the other hand, the +2-valent nickel, cobalt and manganese elements are easily dissolved by acid solutions such as sulfuric acid (nickel, cobalt and manganese elements in too high or too low valence states are difficult to acidify), which facilitates the subsequent recovery of the nickel, cobalt and manganese elements.

[0034] In some specific embodiments, the reduction furnace is a steel belt reduction furnace, which has good material distribution uniformity, can continuously perform carbon thermal reduction reaction, and has high production efficiency.

[0035] S2, putting the reducing material, pure water and grinding balls into a pressurized ball mill, introducing carbon dioxide, and ball milling under a high pressure environment of 2 to 5 MPa to obtain a ball mill slurry;

[0036] Among them, the high-pressure environment of 2 to 5 MPa can significantly increase the solubility of carbon dioxide, thereby forming a sufficient concentration of carbonic acid in the slurry; ball milling can fully crush and disperse the reducing materials, so that the lithium oxide and lithium carbonate in the reducing materials are fully exposed, and the exposed lithium oxide reacts with water to form lithium hydroxide, and the lithium hydroxide reacts with carbonic acid to form lithium carbonate, and all lithium carbonate will react with sufficient carbonic acid to form lithium bicarbonate; therefore, using carbon dioxide in combination with ball milling water to leaching lithium under high-pressure environment can not only effectively improve the reaction efficiency of carbonic acid and lithium carbonate, but also promote the full conversion of lithium carbonate into lithium bicarbonate, thereby effectively improving the leaching efficiency and leaching rate of lithium element in the reduced ternary positive electrode recovery powder.

[0037] In some specific embodiments, before step S2, the reduced material is crushed and passed through a 20-60 mesh screen. The reduced material after crushing and screening has a more similar particle shape and size, which is conducive to the mutual collision and grinding between particles during the ball milling process, thereby fully exposing the lithium carbonate in the reduced material.

[0038] In some specific embodiments, the reducing material, the pure water and the grinding balls are put into the pressurized ball mill in a mass ratio of 1:2 to 10:2. On the one hand, it can ensure that the grinding balls have enough space to move and effectively grind the reducing material without causing excessive collision between the ascending and descending grinding balls, thereby causing energy waste and reduced efficiency; on the other hand, it can ensure that the solid-liquid ratio between the reducing material and the pure water is appropriate, which is conducive to the dissolution of carbon dioxide and the dissolution of lithium bicarbonate, thereby facilitating the leaching efficiency and leaching rate of lithium element in the reducing material.

[0039] Specifically, the speed range of the pressurized ball mill is 20 to 70 r / min, and the ball milling lasts for 4 to 8 hours. Under the premise of ensuring the leaching efficiency and leaching rate of lithium element in the reduced material, the leaching of metal elements such as nickel, cobalt and manganese caused by the small particle size of the powder ball milling can be avoided.

[0040] In some specific embodiments, after the reducing material, pure water and grinding balls are put into the pressurized ball mill, carbon dioxide is introduced until the tank pressure of the pressurized ball mill reaches 2-5 MPa, and then ball milling is started. Specifically, the air in the pressurized ball mill can be exhausted with carbon dioxide to form an oxygen-free environment, which is beneficial to prevent the nickel, cobalt and manganese elements in the reducing material from being oxidized to a high-valent state during the ball milling process.

[0041] Optionally, during the ball milling process, carbon dioxide can be continuously introduced to maintain the tank pressure of the pressurized ball mill at 2-5 MPa. On the one hand, a stable high-pressure environment can be maintained, and on the other hand, it can react with water to form carbonic acid of sufficient concentration; specifically, the flow range of carbon dioxide is 300-900 mL / s.

[0042] Optionally, during the ball milling process, a warning pressure value can be set for the pressurized ball mill. When the tank pressure of the pressurized ball mill is lower than the warning pressure value, carbon dioxide is added to the pressurized ball mill to the preset pressure value. This can reduce the process requirements for the equipment; specifically, 5MPa≥preset pressure value>warning pressure value≥2MPa.

[0043] Optionally, during the ball milling process, carbon dioxide can be introduced intermittently to maintain the tank pressure of the pressurized ball mill at 2-5 MPa, which can further reduce the process requirements on equipment; specifically, carbon dioxide is added to the pressurized ball mill every 10-30 minutes.

[0044] In some specific embodiments, the temperature range of the ball milling is 20 to 40°C. This temperature range, combined with the high-pressure environment, can not only allow carbon dioxide to fully react with water to generate carbonic acid, but also improve the reaction efficiency of carbonic acid and lithium carbonate, thereby facilitating the improvement of the leaching efficiency and leaching rate of lithium in the reducing material; moreover, the combination of the ball milling temperature range and the high-pressure environment makes the generation rate of carbonic acid controllable, avoids the pH value of the slurry from dropping too fast, and prevents the simultaneous leaching of nickel, cobalt and manganese elements.

[0045] In some specific embodiments, the grinding balls are stainless acid-resistant steel grinding balls that can resist corrosion from carbonic acid.

[0046] S3, performing solid-liquid separation on the ball-milled slurry to obtain a lithium extraction leaching solution;

[0047] Specifically, the grinding balls in the ball mill slurry are separated by a screen, and then filtered by a filter press to obtain lithium extraction leaching solution and lithium extraction leaching residue. Among them, the lithium extraction leaching residue contains rich valuable metals such as nickel, cobalt, manganese, etc., all of which have a valence of +2, and can be gradually recovered through sulfuric acid digestion leaching, impurity removal, extraction and other operations.

[0048] S4, removing impurities, concentrating and thermally decomposing the lithium extraction leachate to obtain lithium carbonate crystals;

[0049] The main component of the lithium extraction leaching solution is lithium bicarbonate. After impurity removal, concentration and thermal decomposition, high-purity lithium carbonate crystals can be obtained.

[0050] In some specific embodiments, in step S4, the lithium extraction leachate is decontaminated by resin adsorption to obtain a first lithium bicarbonate solution; impurities in the lithium extraction leachate can be effectively removed by resin adsorption to prevent the impurities from being subsequently mixed into lithium carbonate crystals.

[0051] Next, in step S4, the first lithium bicarbonate solution is concentrated by evaporation to obtain a second lithium bicarbonate solution; in the second lithium bicarbonate solution, the concentration range of lithium ions is 8 to 9 g / L, so that impurity ions such as calcium ions and magnesium ions are not easy to crystallize together with lithium ions, which is beneficial to improving the subsequent crystallization efficiency and crystallization quality of lithium carbonate.

[0052] Specifically, in step S4, the temperature range of the thermal decomposition is 70-80°C, which is beneficial to promote the decomposition of lithium bicarbonate to produce lithium carbonate on the one hand, and is beneficial to the precipitation of lithium carbonate on the other hand; moreover, within this temperature range, it is also beneficial to inhibit the entry of miscellaneous ions such as calcium ions and magnesium ions into lithium carbonate crystals.

[0053] In some specific embodiments, in step S4, during the thermal decomposition, adding seed crystals to the second lithium bicarbonate solution is beneficial to improving the crystallization efficiency and quality of lithium carbonate, and can effectively reduce the wall sticking phenomenon of lithium carbonate, thereby helping to improve the yield of lithium carbonate.

[0054] S5. Wash, dry and crush the lithium carbonate crystals to obtain battery-grade lithium carbonate.

[0055] When washing lithium carbonate crystals, since the solubility of lithium carbonate in hot water is low, the lithium carbonate crystals can be rinsed with hot water first and then cleaned with ethanol. This can not only reduce the loss of lithium carbonate, but also facilitate the rapid drying of the lithium carbonate crystals.

[0056] When drying lithium carbonate crystals, a disc dryer or a flash dryer is used to dry the lithium carbonate crystals, and the water content of lithium carbonate can be reduced to less than 1wt%. Preferably, a flash dryer is used to dry the lithium carbonate crystals, and the flash dryer has a crushing function, and can directly output dry and fine lithium carbonate powder.

[0057] The method for recycling lithium elements in retired ternary lithium battery positive electrode materials of the present invention realizes a three-phase reaction by leaching lithium with carbon dioxide in combination with ball-milled water under a high-pressure environment, which can effectively improve the leaching efficiency and leaching rate of lithium elements in the ternary positive electrode recovery powder after reduction, and can achieve a lithium element leaching rate of ≥93wt%; at the same time, the method of the present invention can also reduce the synergistic leaching amount of metal elements such as nickel, cobalt, and manganese, and improve the purity of lithium bicarbonate in the lithium extraction leachate, which is conducive to improving the purity of the lithium carbonate finally obtained; and, through the process control of impurity removal, concentration and thermal decomposition, the influence of impurity ions can be effectively reduced, which is conducive to improving the crystallization efficiency and crystallization quality of lithium carbonate, and a battery-grade lithium carbonate with high purity can be obtained. In addition, the carbon dioxide used in the method of the present invention is low in cost, and there is no need to leach lithium elements with sulfuric acid, and there is no need to use alkali to precipitate lithium elements, which reduces the consumption of acid and alkali auxiliary materials in the process of lithium element leaching and crystallization, and significantly reduces the recovery cost of lithium carbonate.

[0058] Example 1

[0059] (1) mixing carbon powder and ternary positive electrode recovery powder in a mass ratio of 4:100 and stirring for 2 hours; the carbon content of the carbon powder is 70wt%;

[0060] (2) placing the uniformly mixed carbon powder and ternary positive electrode recovery powder in a steel belt reduction furnace, and calcining them at 660° C. for 4 h under the protection of a nitrogen atmosphere to obtain a reduced material; after testing, it was found that the content of lithium element in the reduced material was 10.2wt%, the content of nickel element was 43.6wt%, the content of cobalt element was 18.5wt%, and the content of manganese element was 24.6wt%;

[0061] (3) The reducing material, pure water and grinding balls are placed in a pressurized ball mill according to a mass ratio of 1:5:2, and carbon dioxide is introduced until the tank pressure reaches 3 MPa. The ball mill is milled for 4 hours under high pressure, and carbon dioxide is added every 20 minutes to obtain a ball mill slurry. The speed of the pressurized ball mill is 30 r / min, and the temperature of the ball mill is 30°C.

[0062] (4) separating the grinding balls from the ball mill slurry through a sieve, and then filtering through a filter press to obtain a lithium extraction leaching solution and a lithium extraction leaching residue; after testing and calculation, it was found that the leaching rate of lithium element reached 93.2wt%, and the leaching rates of nickel, cobalt and manganese were 0.036wt%, 0.014wt% and 0.019wt%, respectively;

[0063] (5) removing impurities, concentrating and thermally decomposing the lithium extraction leaching solution to obtain lithium carbonate crystals;

[0064] (6) Washing, drying and crushing the lithium carbonate crystals to obtain battery-grade lithium carbonate; after testing, the battery-grade lithium carbonate has a lithium carbonate content of 99.61 wt %, an impurity content that meets standard requirements, a magnetic substance content of ≤0.0003 wt %, a moisture content of ≤0.25 wt %, and is in the form of white powder.

[0065] Example 2

[0066] (1) mixing carbon powder and ternary positive electrode recovery powder in a mass ratio of 5:100 and stirring for 3 hours; the carbon content of the carbon powder is 75wt%;

[0067] (2) placing the uniformly mixed carbon powder and ternary positive electrode recovery powder in a steel belt reduction furnace, and calcining them at 680° C. for 3 h under the protection of a nitrogen atmosphere to obtain a reduced material; after testing, it was found that the content of lithium in the reduced material was 10.2wt%, the content of nickel was 43.6wt%, the content of cobalt was 18.5wt%, and the content of manganese was 24.6wt%;

[0068] (3) The reducing material, pure water and grinding balls are put into a pressurized ball mill according to a mass ratio of 1:6:2, and carbon dioxide is introduced until the tank pressure reaches 4 MPa. The ball mill is milled for 6 hours under high pressure, and carbon dioxide is added every 20 minutes to obtain a ball mill slurry. The speed of the pressurized ball mill is 60 r / min, and the temperature of the ball mill is 40°C.

[0069] (4) separating the grinding balls from the ball mill slurry through a sieve, and then filtering through a filter press to obtain a lithium extraction leaching solution and a lithium extraction leaching residue; after testing and calculation, it was found that the leaching rate of lithium element reached 95.4wt%, and the leaching rates of nickel, cobalt and manganese were 0.063wt%, 0.021wt% and 0.039wt%, respectively;

[0070] (5) removing impurities, concentrating and thermally decomposing the lithium extraction leaching solution to obtain lithium carbonate crystals;

[0071] (6) Washing, drying and crushing the lithium carbonate crystals to obtain battery-grade lithium carbonate; after testing, the battery-grade lithium carbonate has a lithium carbonate content of 99.72 wt %, an impurity content that meets standard requirements, a magnetic substance content of ≤0.0003 wt %, a moisture content of ≤0.25 wt %, and is in the form of white powder.

[0072] Example 3

[0073] (1) mixing carbon powder and ternary positive electrode recovery powder in a mass ratio of 6:100 and stirring for 4 hours; the carbon content of the carbon powder is 80wt%;

[0074] (2) placing the uniformly mixed carbon powder and ternary positive electrode recovery powder in a steel belt reduction furnace, and calcining them at 700° C. for 2 h under the protection of a nitrogen atmosphere to obtain a reduced material; after testing, it was found that the content of lithium in the reduced material was 10.2wt%, the content of nickel was 43.6wt%, the content of cobalt was 18.5wt%, and the content of manganese was 24.6wt%;

[0075] (3) The reducing material, pure water and grinding balls are placed in a pressurized ball mill according to a mass ratio of 1:10:2, and carbon dioxide is introduced until the tank pressure reaches 5 MPa. The ball mill is milled for 8 hours under high pressure, and carbon dioxide is added every 20 minutes to obtain a ball mill slurry. The speed of the pressurized ball mill is 70 r / min, and the temperature of the ball mill is 20°C.

[0076] (4) separating the grinding balls from the ball mill slurry through a sieve, and then filtering through a filter press to obtain a lithium extraction leaching solution and a lithium extraction leaching residue; after testing and calculation, it was found that the leaching rate of lithium element reached 98.5wt%, and the leaching rates of nickel, cobalt and manganese were 0.096wt%, 0.045wt% and 0.082wt%, respectively;

[0077] (5) removing impurities, concentrating and thermally decomposing the lithium extraction leaching solution to obtain lithium carbonate crystals;

[0078] (6) Washing, drying and crushing the lithium carbonate crystals to obtain battery-grade lithium carbonate; after testing, the battery-grade lithium carbonate has a lithium carbonate content of 99.86 wt %, an impurity content that meets standard requirements, a magnetic substance content of ≤0.0003 wt %, a moisture content of ≤0.25 wt %, and is in the form of white powder.

[0079] It can be seen from Examples 1 to 3 that the method of the present invention can achieve a lithium element leaching rate of ≥93wt%, and the lithium element leaching rate can be as high as 98.5wt%; the leaching rates of nickel element, cobalt element and manganese element are all lower than 0.1wt%, and the leaching rates of nickel element, cobalt element and manganese element can all be lower than 0.05wt%; in the obtained battery-grade lithium carbonate, the lithium carbonate content is greater than 95wt%, and the lithium carbonate content can be as high as 99.86wt%.

[0080] The above is a detailed introduction to a method for recovering lithium elements in retired ternary lithium battery positive electrode materials provided by an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for recovering lithium from retired ternary lithium battery positive electrode materials, characterized in that: The following steps are involved: S1. placing the uniformly mixed carbon powder and ternary cathode recovery powder in a reduction furnace, and performing a carbon thermal reduction reaction under the protection of a nitrogen atmosphere to obtain a reduced material; S2, putting the reducing material, pure water and grinding balls into a pressurized ball mill, introducing carbon dioxide, and ball milling under a high pressure environment of 2 to 5 MPa to obtain a ball mill slurry; S3, performing solid-liquid separation on the ball-milled slurry to obtain a lithium extraction leaching solution; S4, removing impurities, concentrating and thermally decomposing the lithium extraction leachate to obtain lithium carbonate crystals; S5. Wash, dry and crush the lithium carbonate crystals to obtain battery-grade lithium carbonate.

2. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: The carbon powder and the ternary positive electrode recovery powder are mixed in a mass ratio of 4 to 6:

100.

3. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 2, characterized in that: The carbon powder and the ternary positive electrode recovery powder are stirred and mixed for 2 to 4 hours.

4. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: The carbon thermal reduction reaction lasts for 2 to 4 hours.

5. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: Before step S2, the reduced material is crushed and passed through a 20-60 mesh sieve.

6. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: The reducing material, the pure water and the grinding balls are put into the pressurized ball mill according to a mass ratio of 1:2 to 10:

2.

7. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: The speed range of the pressurized ball mill is 20-70 r / min, and the ball milling lasts for 4-8 hours.

8. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: In step S4, the lithium extraction leaching solution is decontaminated by resin adsorption to obtain a first lithium bicarbonate solution.

9. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 8, characterized in that: In step S4, the first lithium bicarbonate solution is concentrated by evaporation to obtain a second lithium bicarbonate solution; in the second lithium bicarbonate solution, the concentration of lithium ions ranges from 8 to 9 g / L.

10. The method for recovering lithium from retired ternary lithium battery positive electrode materials according to claim 1, characterized in that: In step S4, the temperature range of the thermal decomposition is 70-80°C.

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