Lithium extraction method before reduction of recovered ternary positive electrode material carbon powder

Abstract

The invention relates to the technical field of recycling of waste lithium batteries, in particular to a lithium extraction method before reduction of recycled ternary positive electrode material carbon powder. According to the method provided by the invention, a microcosmic foaming structure is formed in the treatment process of the positive electrode powder by adding the pore-increasing reducing agent, so that the powder of the waste ternary positive electrode material is not easy to cake in the subsequent treatment process, the secondary crushing process is not needed, and finally, the relatively high lithium recovery rate of the waste ternary positive electrode material is realized; and the method is simple and easy to operate, is suitable for large-scale batch treatment of the waste ternary positive electrode material, and has a relatively good application prospect.

Description

Technical Field

[0001] The present application relates to the technical field of resource recovery of waste lithium batteries, and in particular to a method for recovering ternary positive electrode material carbon powder by pre-reduction and lithium extraction. Background Art

[0002] The traditional reduction roasting technology for lithium extraction from waste lithium batteries is as follows: carbon reduction uses the method of adding carbon powder to prepare experimental raw materials with different carbon contents, which are then roasted after being mixed evenly. In a nitrogen atmosphere, the waste lithium battery materials are heated to the required target temperature. After reaching the preset reaction temperature, the roasting reaction is carried out according to the set reaction time. After roasting, it is cooled to room temperature. After the roasted compacted materials are crushed and sieved, a fixed proportion of pure water is added to leach and extract lithium. The leaching process requires stirring and heating. After the leaching reaction is completed, the leachate is allowed to stand and naturally cool to room temperature. The lithium-rich leachate and filter residue are obtained by filtration, and the filter residue is further used to extract useful elements such as cobalt and nickel.

[0003] For example, Chinese patent application CN116590538A (under examination) discloses a method for preferentially extracting lithium from waste lithium batteries. This method can greatly reduce energy consumption, simplify the impurity removal process, improve the efficient leaching of lithium, and reduce the leaching of cobalt, nickel and manganese by adding carbon powder and sulfuric acid to the waste battery powder, then roasting and adding water for lithium leaching. Another example is Chinese patent application CN117693606A (under examination) discloses a method for selectively extracting lithium from waste lithium-ion battery powder by aluminum-carbon synergistic reduction. This method adds carbon powder, aluminum powder and alcohol to the waste battery powder, mixes and roasts, then introduces carbon dioxide to leaching lithium, and obtains lithium-rich liquid after solid-liquid separation. For example, Chinese patent application CN117144149A (under examination) discloses a preparation method for preferentially extracting lithium from waste ternary lithium-ion batteries. In this method, after disassembling and crushing the waste ternary lithium batteries, carbon powder is added to calcine in a carbon dioxide atmosphere to produce carbon monoxide reducing gas for reduction, and then the lithium metal is preferentially extracted through carbonization water leaching treatment. The water leaching residue is then treated with a series of chemical methods such as alkali leaching and acid leaching to achieve the purpose of recovering metal salts such as nickel, cobalt and manganese.

[0004] The above methods all have certain lithium extraction effects, but there are disadvantages such as complex processing process and insufficient lithium leaching rate, which cannot effectively realize the recycling of lithium in waste ternary positive electrode materials. Therefore, the purpose of this application is to provide a new method for extracting lithium from ternary positive electrode materials. In addition, when recycling waste ternary positive electrode materials, the high-temperature calcination process will cause the waste ternary battery positive electrode materials to shrink to form dense agglomerated powders. The crushed particles affect the immersion effect of the solution due to their dense structure, thereby affecting the leaching effect of lithium; in order to ensure a better lithium extraction effect, it is often necessary to increase the liquid-solid ratio or add more acid to increase the dissolution rate of lithium. Although the leaching rate of lithium can be increased, it will cause the lithium concentration of the leachate to decrease and cause other elements of nickel, cobalt and manganese to be leached at the same time. It is necessary to add concentration and impurity removal processes, which increases the recovery cost. Summary of the invention

[0005] The purpose of the present invention is to provide a method for recovering ternary positive electrode material carbon powder reduction pre-lithium extraction, by adding a pore-increasing reducing agent so that the waste ternary positive electrode material forms a microscopic foaming structure on the surface during the treatment process, so that the waste ternary positive electrode material does not need to add too much acid during the reaction process in the subsequent treatment process to have a good leaching effect, and finally the lithium extraction rate is high. The specific technical scheme of the present invention is as follows:

[0006] The present invention provides a method for recovering ternary positive electrode material carbon powder by reduction and pre-extraction of lithium, comprising the following steps:

[0007] Step 1, preparing a pore-increasing reducing agent using water, lauric acid, methyl cellulose and carbon powder as raw materials;

[0008] Step 2, adding the pore-increasing reducing agent to the powder of the waste ternary cathode material, mixing well, calcining under an inert atmosphere, and then cooling to obtain a mixed material 1;

[0009] Step 3, grinding and sieving the mixed material 1, then adding water and stirring, adjusting the pH value of the system to 5-7, and then heating to perform lithium leaching to obtain a mixed material 2;

[0010] Step 4: standing and cooling the mixed material 2 to room temperature, then performing solid-liquid separation, washing the obtained filter residue, collecting the obtained filtrate and washing liquid to obtain a lithium-rich solution.

[0011] Specifically, the mass ratio of the pore-increasing reducing agent to the powder of the waste ternary cathode material in step 2 is 5 to 20:100;

[0012] Specifically, the preparation method of the pore-increasing reducing agent in step 1 is to mix lauric acid, methyl cellulose and carbon powder, transfer the materials to a material turning machine, add a small amount of water by spraying during the slow turning process, and control the process to be completed within 2 minutes. After the materials are mixed, they are immediately dried and sieved to obtain the pore-increasing reducing agent;

[0013] More specifically, the drying temperature is 105-120°C;

[0014] More specifically, the added weight percentages of water, lauric acid, methyl cellulose and carbon powder are 6-11%, 3-7%, 4-9% and 73-87%;

[0015] Specifically, the inert atmosphere in step 2 is a nitrogen atmosphere or an argon atmosphere;

[0016] Specifically, the calcination temperature in step 2 is 660-750° C., and the calcination time is 60-150 min;

[0017] Specifically, in step 3, the pH value of the system is adjusted using a concentrated sulfuric acid solution;

[0018] Specifically, after adding water in step 3, the solid-liquid mass ratio is 1:2 to 8;

[0019] Specifically, in step 3, the heating temperature is 50-80° C., the stirring time is 30-150 min, and the stirring speed is 250-400 r / min;

[0020] Specifically, the washing reagent in step 4 is water;

[0021] Specifically, the method for solid-liquid separation in step 4 includes but is not limited to vacuum filtration.

[0022] Waste ternary positive electrode materials are easy to sinter at high temperatures, and the hardness of the sintered materials is relatively large, which is not conducive to lithium ion leaching. The present invention uses a specific pore-increasing reducing agent when treating waste positive electrode materials, which can make the powder of waste ternary positive electrode materials uniformly and stably dispersed in the system, and form a microscopic foaming structure on the surface of the powder of waste ternary positive electrode materials after calcination, thereby reducing the density of waste ternary positive electrode materials and the hardness of the materials, and increasing the contact area between the powder of waste ternary positive electrode materials and the system. The present invention has the following beneficial effects:

[0023] 1. The method provided by the present invention adopts a ternary positive electrode material having a microscopic foamed pore structure after pore-increasing reduction treatment, and also increases the contact area between the waste ternary positive electrode material and the system, so that the ternary positive electrode material is not easy to agglomerate during the subsequent treatment process, which is more convenient for subsequent reactions and improves the leaching rate and leaching efficiency of metallic lithium;

[0024] 2. The method of the present invention is simple and easy to operate, suitable for large-scale processing of ternary waste positive electrode materials, and has good application prospects. DETAILED DESCRIPTION

[0025] The technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0026] Examples 1 to 4 and Comparative Examples 1 to 3

[0027] A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction:

[0028] Step 1, mixing water, lauric acid, methyl cellulose and carbon powder, drying (120° C.) and sieving to obtain a pore-increasing reducing agent;

[0029] Step 2, adding 15 g of a pore-increasing reducing agent to 100 g of waste positive electrode powder, mixing the mixture, and calcining the mixture at 730° C. for 2 h in a nitrogen atmosphere, and then cooling the mixture to room temperature to obtain a mixed material 1;

[0030] Step 3, grinding the mixed material 1, then adding water to a solid-liquid ratio of 1:5, stirring at 250 r / min for 120 min, adjusting the pH value of the system to 6 with concentrated sulfuric acid, and then heating to 80° C. to leaching lithium to obtain a mixed material 2;

[0031] Step 4, standing and cooling the mixture 2 to room temperature, and then performing vacuum filtration to obtain a filtrate and a filter residue, washing the obtained filter residue with deionized water, collecting the filtrate and the washing liquid to obtain a lithium-rich solution;

[0032] The amounts of water, dodecanoic acid, methyl cellulose and carbon powder added when preparing the pore-increasing reducing agent in step 1 of Examples 1 to 4 and Comparative Examples 1 to 3 (based on the mass proportion of all raw materials) are set as shown in Table 1;

[0033] Table 1

[0034] Component content Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 water 8％ 6％ 11％ 9％ 8％ 8％ 0％ Dodecanoic acid 5％ 3％ 7％ 6％ 5％ 0％ 0％ Methylcellulose 6％ 4％ 9％ 7％ 0％ 6％ 0％ Toner 81％ 87％ 73％ 78％ 87％ 86％ 100％

[0035] ICP was used to detect the lithium ion content in the original waste ternary positive electrode material and the lithium-rich solutions prepared in Examples 1 to 4 and Comparative Examples 1 to 3, and then the lithium ion leaching rate was calculated. The results are shown in Table 2.

[0036] Leaching rate = (lithium ion concentration * (filtrate volume + washing liquid volume)) / total amount of lithium element in the waste ternary positive electrode material.

[0037] Table 2

[0038]

[0039] It can be seen from the test results in Table 2 that the method of the present invention is used to treat waste ternary positive electrode materials, and the leaching rate of lithium in the waste ternary positive electrode materials is relatively high, which can reach more than 97%; Comparative Example 1 does not add methyl cellulose, Comparative Example 2 does not add dodecanoic acid, and Comparative Example 3 adopts the existing mainstream method and only adds carbon powder for treatment. All of them cannot form a good microscopic pore structure on the surface of the waste ternary positive electrode material during the calcination process, resulting in agglomeration of the waste ternary positive electrode material during the treatment process, which in turn leads to poor lithium leaching effect.

[0040] Examples 5 to 7 and Comparative Examples 4 to 5

[0041] A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction:

[0042] Step 1, take 8g of water, 5g of dodecanoic acid, 6g of methyl cellulose and 81g of carbon powder, mix them, dry them (110°C) and sieve them to obtain a pore-increasing reducing agent;

[0043] Step 2, adding 15 g of a pore-increasing reducing agent to 100 g of waste positive electrode powder, mixing the mixture, and calcining the mixture at 660° C. for 150 min under a nitrogen atmosphere, and then cooling the mixture to room temperature to obtain a mixed material 1;

[0044] Step 3, grinding the mixed material 1, then adding water to a solid-liquid ratio of 1:3, stirring at 400 r / min for 150 min, adjusting the pH value of the system to 6.5 with concentrated sulfuric acid, and then heating to 60° C. for lithium leaching to obtain a mixed material 2;

[0045] Step 4, standing and cooling the mixture 2 to room temperature, and then performing vacuum filtration to obtain a filtrate and a filter residue, washing the obtained filter residue with deionized water, collecting the filtrate and the washing liquid to obtain a lithium-rich solution;

[0046] The pH value settings in step 3 of Examples 5 to 7 and Comparative Examples 4 to 5 are shown in Table 3; then referring to the test method of Examples 1 to 4, the lithium leaching rates in Examples 5 to 7 and Comparative Examples 4 to 5 are tested, and the results are shown in Table 3.

[0047] Table 3

[0048] Example 5 Example 6 Example 7 Comparative Example 4 Comparative Example 5 pH 5 6.5 7.5 4.5 8 Lithium leaching rate (%) 96.5 94.1 88.2 97.1 68.9 Manganese leaching rate (%) 47.5 29.85 2.62 51.71 1.24 Nickel leaching rate (%) 4.89 3.25 2.22 8.12 0.57 Cobalt leaching rate (%) 5.92 4.59 2.5 8.22 0.3

[0049] As can be seen from Table 3, when the pH value of the system is greater than 7.5, the manganese, nickel, and cobalt impurities have a lower leaching rate, but the lithium leaching rate is also relatively low and has a significant decrease. In this regard, the inventors speculate that when the system is too alkaline, it is not conducive to lithium leaching, resulting in poor lithium extraction effect; when the system is too acidic and the pH is lower than 5, as the acidity increases, the lithium leaching rate is higher, but the nickel, cobalt, and manganese impurity elements will also be leached together with the lithium element, which is not conducive to the selective leaching of lithium and the recovery of nickel, cobalt, and manganese metal elements.

[0050] Example 8

[0051] A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction:

[0052] Step 1, 10 g of water, 5 g of dodecanoic acid, 5 g of methyl cellulose and 80 g of carbon powder are mixed, dried (105° C.) and sieved to obtain a pore-increasing reducing agent;

[0053] Step 2, adding 5 g of a pore-increasing reducing agent to 100 g of waste positive electrode powder, mixing the mixture, calcining the mixture at 750° C. for 60 min under a nitrogen atmosphere, and then cooling the mixture to room temperature to obtain a mixed material 1;

[0054] Step 3, grinding the mixed material 1, then adding water to a solid-liquid ratio of 1:8, stirring at 300 r / min for 130 min, adjusting the pH value of the system to 6 with concentrated sulfuric acid, and then heating to 80° C. for lithium leaching to obtain a mixed material 2;

[0055] Step 4: standing and cooling the mixed material 2 to room temperature, and then performing vacuum filtration to obtain a filtrate and a filter residue, washing the obtained filter residue with deionized water, collecting the filtrate and the washing liquid to obtain a lithium-rich solution.

[0056] Example 9

[0057] A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction:

[0058] Step 1, 10 g of water, 5 g of dodecanoic acid, 5 g of methyl cellulose and 80 g of carbon powder are mixed, dried (110° C.) and sieved to obtain a pore-increasing reducing agent;

[0059] Step 2, adding 10 g of a pore-increasing reducing agent to 100 g of waste positive electrode powder, mixing the mixture, and calcining the mixture at 730° C. for 90 min under a nitrogen atmosphere, and then cooling the mixture to room temperature to obtain a mixed material 1;

[0060] Step 3, grinding the mixed material 1, then adding water to a solid-liquid ratio of 1:3, stirring at 350 r / min for 150 min, adjusting the pH value of the system to 6.5 with concentrated sulfuric acid, and then heating to 80° C. for lithium leaching to obtain a mixed material 2;

[0061] Step 4: standing and cooling the mixed material 2 to room temperature, and then performing vacuum filtration to obtain a filtrate and a filter residue, washing the obtained filter residue with deionized water, collecting the filtrate and the washing liquid to obtain a lithium-rich solution.

[0062] Example 10

[0063] A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction:

[0064] Step 1, 10 g of water, 5 g of dodecanoic acid, 5 g of methyl cellulose and 80 g of carbon powder are mixed, dried (110° C.) and sieved to obtain a pore-increasing reducing agent;

[0065] Step 2, adding 20 g of a pore-increasing reducing agent to 100 g of waste positive electrode powder, mixing the mixture, and calcining the mixture at 740° C. for 130 min under a nitrogen atmosphere, and then cooling the mixture to room temperature to obtain a mixed material 1;

[0066] Step 3, grinding the mixed material 1, then adding water to a solid-liquid ratio of 1:6, stirring at 400 r / min for 120 min, adjusting the pH value of the system to 7 with concentrated sulfuric acid, and then heating to 80° C. for lithium leaching to obtain a mixed material 2;

[0067] Step 4: standing and cooling the mixed material 2 to room temperature, and then performing vacuum filtration to obtain a filtrate and a filter residue, washing the obtained filter residue with deionized water, collecting the filtrate and the washing liquid to obtain a lithium-rich solution.

[0068] The leaching rates of lithium in Examples 8 to 10 were tested using the methods of Examples 1 to 4. The results are shown in Table 4.

[0069] Table 4

[0070] Example 8 Example 9 Example 10 Lithium leaching rate (%) 93.2 94.1 97.6

[0071] It can be seen from Table 4 that the method of the present invention has a better lithium extraction effect.

[0072] In summary, the method of the present invention adds a pore-increasing reducing agent when processing the powder of the ternary positive electrode material, which can form a microscopic foaming structure on the surface of the waste ternary positive electrode material during the calcination process, so that the waste ternary positive electrode material is not easy to agglomerate during the reaction process, and adding more acid or increasing the addition of water can improve the lithium leaching effect, and has a good selective extraction effect for lithium elements, which can better realize the recovery of lithium elements in waste ternary positive electrode materials, and has good application prospects. Although increasing the amount of water and acid can increase the leaching rate, it is not suitable to add too much acid and water in actual application, because it will increase the cost of the subsequent lithium carbonate precipitation process.

[0073] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for recovering ternary cathode material carbon powder by pre-reduction lithium extraction, characterized in that: The following steps are involved: Step 1, preparing a pore-increasing reducing agent using water, lauric acid, methyl cellulose and carbon powder as raw materials; Step 2, adding the pore-increasing reducing agent to the powder of the waste ternary cathode material, mixing well, calcining under an inert atmosphere, and then cooling to obtain a mixed material 1; Step 3, grinding and sieving the mixed material 1, then adding water and stirring, adjusting the pH value of the system to 5-7, and then heating to perform lithium leaching to obtain a mixed material 2; Step 4: standing and cooling the mixed material 2 to room temperature, then performing solid-liquid separation, washing the obtained filter residue, collecting the obtained filtrate and washing liquid to obtain a lithium-rich solution.

2. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The preparation method of the pore-increasing reducing agent in step 1 is to mix water, dodecanoic acid, methyl cellulose and carbon powder, and then dry and sieve them to obtain the pore-increasing reducing agent.

3. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The added mass proportions of water, lauric acid, methyl cellulose and carbon powder in step 1 are 6-11%, 3-7%, 4-9% and 73-87%.

4. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The mass ratio of the pore-increasing reducing agent to the powder of the waste ternary positive electrode material in step 2 is 5 to 20:

100.

5. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The inert atmosphere in step 2 is a nitrogen atmosphere or an argon atmosphere.

6. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The calcination temperature in step 2 is 660-750°C.

7. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: In step 3, the pH value of the system is adjusted using concentrated sulfuric acid solution.

8. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: After adding water in step 3, the solid-liquid mass ratio is 1:2-8.

9. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 1, characterized in that: The heating temperature in step 3 is 50-80°C.

10. The method for recovering ternary cathode material carbon powder by reduction and pre-lithium extraction according to claim 2, characterized in that: The drying temperature is 105-120°C.

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