Method for recycling lithium battery material under assistance of high-voltage treatment

Abstract

The invention discloses a method for high-voltage treatment assisted recovery of a lithium battery material, and aims to solve the problem that the metal ion leaching rate needs to be improved when positive electrode black powder and negative electrode black powder are subjected to acid leaching in an existing lithium battery recovery technology. According to the method, pre-polarization treatment is conducted on dried positive electrode black powder or negative electrode black powder through a pulse direct-current electric field or a constant direct-current electric field, the reaction activity of metal atoms is enhanced, and then acid leaching operation is conducted. Experiments show that the acid leaching impurity removal effect of the negative electrode graphite subjected to high-pressure treatment is remarkably improved, the leaching rate of metal ions in the positive electrode black powder is greatly improved, the method is simple in experimental principle and operation and high in experimental repeatability, and as a pretreatment mode for black powder recovery treatment, subsequent treatment means for different product requirements are not limited, and the method is suitable for industrial production. And a new way is provided for optimizing a waste lithium battery recycling process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and in particular to a method for high-pressure treatment-assisted recycling of lithium battery materials. Background Art

[0002] Taking the recycling of ternary lithium batteries as an example, the existing recycling process usually includes steps such as electrolyte solution discharge, drum crushing, screening, drying, grinding into powder, high-temperature pyrolysis, and airflow sorting to obtain positive and negative electrode black powder. Generally speaking, the positive electrode black powder of ternary batteries contains rare metals such as nickel, cobalt, and manganese, and has extremely high economic added value. The recycling of materials such as negative electrode graphite is also of great significance to the environment and resources, and with the increase in the number of waste lithium batteries, the economic potential is huge. Subsequently, the positive and negative electrode black powders are mostly generated under the action of concentrated acid to generate corresponding salts. For the negative electrode black powder, acid leaching is used to remove impurities such as lithium, iron, copper, and aluminum, and to improve the purity of the negative electrode graphite; for the positive electrode black powder, acid leaching can leach a large amount of lithium, nickel, and cobalt elements, and a small amount of manganese elements. The acid leaching effect is directly related to the recovery efficiency, so how to improve the leaching efficiency becomes the key to the recycling work. Currently, the leaching rate of metal ions is often improved by stirring and heating or directly pressurizing during acid leaching. The present invention proposes an innovative method of using a pulsed DC electric field or a constant DC electric field to pre-polarize the positive and negative electrode black powders to improve the concentrated acid leaching rate. Summary of the invention

[0003] Existing technologies have limitations in improving the efficiency of acid leaching of black powder in the positive and negative electrodes of lithium batteries. Although there are methods of stirring and heating or directly pressurizing during acid leaching, the improvement effect still does not meet the demand. For example, during the acid leaching process, the nickel and cobalt leaching rates of the positive electrode black powder that has not undergone special pretreatment are close to 90%, and the manganese element can hardly be leached. The removal of impurities in the negative electrode black powder is not thorough enough, which affects the subsequent recycling value of the materials. In addition, pretreatment methods such as sulfuric acid aging are relatively complex to operate and have strict requirements on conditions. They are difficult to promote and apply widely, and cannot efficiently realize the maximum recovery and reuse of lithium resources. It is also difficult to cope with the growing demand for the treatment of waste lithium batteries.

[0004] The present invention aims to overcome the deficiencies of the prior art and provide a method for high-pressure treatment-assisted recovery of lithium battery materials. The positive electrode black powder or the negative electrode black powder is prepolarized by a pulsed direct current electric field or a constant direct current electric field to separate the positive and negative charge centers of the metal atoms, enhance their chemical reaction activity, and thus greatly improve the leaching rate of metal ions in the subsequent acid leaching process, improve the acid leaching and impurity removal effect of the negative electrode graphite, open up a new path for the optimization of the waste lithium battery recycling process, and meet the urgent needs of environmental protection and resource recycling.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: A method for high-pressure treatment-assisted recovery of lithium battery materials comprises high-pressure pretreatment of dried positive electrode black powder or negative electrode black powder, wherein the high-pressure pretreatment adopts a pulsed direct current electric field or a constant direct current electric field.

[0006] Furthermore, the voltage value of the pulsed DC electric field is higher than that of the constant DC electric field, and the pulse frequency is 10-1000 Hz.

[0007] Furthermore, before the high-pressure pretreatment, the positive electrode black powder or the negative electrode black powder is dried at 80° C. for more than 24 hours to make the water content of the powder less than 2%.

[0008] Furthermore, when the negative electrode black powder is subjected to high-voltage pretreatment, 5 g of the dried negative electrode black powder is placed in a pulsed DC electric field or a constant DC electric field at a voltage of 100-1000 V for polarization for 1-5 hours, and then the polarized negative electrode black powder is mixed with 2 mol / L concentrated sulfuric acid, stirred at 80°C for 3-5 hours, and then filtered. Deionized water is added to the leached solid to adjust it to neutrality, and heated at 80°C for more than 12 hours to obtain acid-leached purified graphite.

[0009] Furthermore, when the positive electrode black powder is subjected to high-voltage pretreatment, 5 g of the dried positive electrode black powder is placed in a pulsed DC electric field or a constant DC electric field at a voltage of 100-1000 V for 1-5 hours, and then the polarized positive electrode black powder is mixed with 1 mol / L concentrated sulfuric acid and stirred at 80°C for 1-5 hours.

[0010] Furthermore, during the high-voltage treatment process, the positive or negative electrode black powder needs to be encapsulated to prevent the powder from splashing due to electrostatic force after polarization.

[0011] Furthermore, the impurity content of the purified graphite after acid leaching is low, with Al, Cu and Fe all below 50 ppm, and it can be used as a negative electrode material for lithium secondary batteries after heat treatment at 1500-3000°C.

[0012] Furthermore, the positive electrode black powder or the negative electrode black powder comes from lithium batteries including lithium iron phosphate, lithium cobalt oxide, lithium titanate, ternary and the like.

[0013] Furthermore, the solution selected for acid leaching includes one or more of concentrated sulfuric acid, hydrochloric acid, and nitric acid.

[0014] Furthermore, the method is suitable for improving the leaching rate of metal ions in positive and negative electrode black powder during acid leaching in the process of recycling waste lithium batteries, as well as the acid leaching impurity removal effect of negative electrode graphite.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The core point of the invention is to pre-polarize the positive electrode black powder or the negative electrode black powder by a pulsed DC electric field or a constant DC electric field to enhance the reactivity of the metal atoms therein, thereby greatly improving the effect of sulfuric acid leaching.

[0016] 2. The current mainstream methods for improving acid leaching efficiency, such as pressurization, heating or sulfuric acid aging during acid leaching, have limited improvement and complex operation. The present invention takes a different approach and designs a method for high-pressure treatment to assist in the recovery of lithium batteries. The positive electrode black powder (or negative electrode black powder) is treated by prepolarization with a pulsed DC electric field or a constant DC electric field to improve the concentrated acid leaching rate. Prepolarization separates the positive and negative charge centers of metal atoms, making it easier to react with the negative ion groups in the acid to form corresponding salts, greatly improving the concentrated acid treatment leaching rate.

[0017] 3. The method of the present invention has significant advantages. It not only significantly improves the leaching rate of positive electrode black powder, but also enhances the effect of removing impurities from negative electrode graphite by acid leaching. As a pretreatment method for black powder recovery, it does not restrict subsequent specific treatment methods based on different product requirements, such as electrolytic recovery of high-purity metal elements after positive electrode acid leaching, and high-temperature heat treatment after negative electrode acid leaching to meet the standards of lithium battery negative electrode materials. The present invention opens up a new path for optimizing the recycling process of waste lithium batteries, and has great promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an implementation flow chart of the present invention. DETAILED DESCRIPTION

[0019] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0020] Implementation process: Set up two implementation samples and two control samples. The specific implementation process is as follows: Figure 1 shown.

[0021] Implementation sample 1 (polarized negative electrode black powder): Here we start processing directly from the negative electrode black powder. The initial process is: recycle used batteries - let them stand in a 1mol / LNaCl solution for 24 hours to fully discharge - use a roller and grinder to crush and grind the batteries into powder - use an airflow separation process to separate the positive and negative electrode black powders.

[0022] 1. Dry the negative electrode black powder at 80°C for 24 hours to remove moisture (the moisture content of the powder must be less than 2% during DC electric field treatment).

[0023] 2. Take 5g of dried negative electrode black powder and place it in a pulsed DC electric field at a voltage of 1000V for 1h (if a pulsed DC electric field is used here, its voltage value must be higher than the constant DC electric field, and the pulse frequency must be 10-1000Hz).

[0024] 3. Mix the polarized negative electrode black powder with 2 mol / L concentrated sulfuric acid and stir at 80°C for 3 hours (at this time, sulfuric acid leaching is used to mainly remove elements such as copper, aluminum, iron, and lithium).

[0025] 4. After filtering, add deionized water to the leached solid to adjust it to neutrality, and heat it at 80°C for 12 hours to obtain acid-leached purified graphite.

[0026] Implementation sample 2 (polarized positive electrode black powder): 1. Dry the positive electrode black powder at 80°C for 24 hours to remove moisture (the moisture content of the powder must be less than 2% during DC electric field treatment).

[0027] 2. Take 5g of dried positive black powder and place it in a pulsed DC electric field or a constant DC electric field at a voltage of 1000V for 1h (if a pulsed DC electric field is used here, its voltage value must be higher than that of a constant DC electric field, and the frequency must be 10-1000Hz).

[0028] 3. Mix the polarized positive electrode black powder with 1 mol / L concentrated sulfuric acid and stir at 80°C for 3 hours (at this time, rare metal ions such as lithium, nickel, cobalt, and manganese are replaced by sulfuric acid).

[0029] Control sample 1 (negative black powder): 1. Dry the negative electrode black powder at 80℃ for 24h to remove moisture.

[0030] 2. Take 5g of the dried negative electrode black powder and mix it with 2mol / L concentrated sulfuric acid, and stir it at 80℃ for 3h.

[0031] 3. After filtering, add deionized water to the leached solid to adjust it to neutrality, and heat it at 80°C for 12 hours to obtain acid-leached purified graphite.

[0032] Control sample 2: (positive electrode black powder) 1. Dry the positive electrode black powder at 80°C for 24 hours to remove moisture.

[0033] 2. Take 5g of dried positive electrode black powder and mix it with 1mol / L concentrated sulfuric acid, and stir it at 80℃ for 1h.

[0034] Table 1 Main chemical components of purified graphite for negative electrode

[0035] From the main chemical composition of the negative electrode purified graphite in Table 1, it can be seen that the control group 1 (acid-leached purified graphite without high-pressure treatment) contains more copper, aluminum and iron impurities, and even a trace of lithium has not been removed. This part may be lithium carbide embedded in the graphite crystal structure. In the implementation group 1 (acid-leached purified graphite with high-pressure treatment), the carbon element occupies a larger mass ratio, corresponding to a significant reduction in the impurity content of copper, aluminum and iron elements, and the lithium element is basically removed. It shows that pulsed DC electric field treatment is helpful for acid leaching and impurity removal of negative electrode graphite, and high-pressure treatment enhances the reactivity of metal ions, thereby effectively promoting the formation of metal ion sulfates in concentrated sulfuric acid, thereby enhancing the effect of sulfuric acid acid leaching and purifying graphite.

[0036] Table 2 Leaching rate of each element in the positive electrode leaching solution (calculated based on the change in the mass of the leached residue)

[0037] From the leaching rates of the four metal ions in the positive electrode leaching solution in Table 2, it can be seen that in the acid leaching leaching solution of the positive electrode powder without high pressure treatment, the leaching rates of nickel and cobalt are close to 90%, and the lithium element is relatively high at 97.4%, considering that it is the most active, while the manganese element is basically absent. In the positive electrode powder leaching solution after high pressure treatment, the leaching rates of nickel and cobalt ions are significantly increased to 99%, and at the same time, 3% of manganese is detected in trace amounts. (Here, manganese ions exist in multiple valences, including +3 and +2, with more +3 valence and less +2 valence. Sulfuric acid leaching can only replace +2 valence manganese ions. Therefore, in the absence of a reducing agent, the leaching rate of manganese is generally very low.) This shows that the activity of the metal ions in the positive electrode black powder is enhanced after the pulsed DC electric field treatment, making the replacement reaction of sulfuric acid more thorough, which is manifested as a higher leaching rate of each metal element.

[0038] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for high pressure treatment assisted recovery of lithium battery materials, characterized in that: The method comprises performing high-voltage pretreatment on the dried positive electrode black powder or negative electrode black powder, wherein the high-voltage pretreatment adopts a pulsed direct current electric field or a constant direct current electric field.

2. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: The voltage value of the pulsed DC electric field is higher than that of the constant DC electric field, and the pulse frequency is 10-1000 Hz.

3. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: Before high-pressure pretreatment, the positive electrode black powder or the negative electrode black powder is dried at 80° C. for more than 24 hours to make the moisture content of the powder less than 2%.

4. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: When the negative electrode black powder is subjected to high-voltage pretreatment, 5 g of the dried negative electrode black powder is placed in a pulsed DC electric field or a constant DC electric field at a voltage of 100-1000 V for polarization for 1-5 hours, and then the polarized negative electrode black powder is mixed with 2 mol / L concentrated sulfuric acid, stirred at 80°C for 3-5 hours, and then filtered. Deionized water is added to the leached solid to adjust it to neutrality, and heated at 80°C for more than 12 hours to obtain acid-leached purified graphite.

5. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: When the positive electrode black powder is subjected to high-voltage pretreatment, 5 g of dried positive electrode black powder is placed in a pulsed DC electric field or a constant DC electric field at a voltage of 100-1000 V for polarization for 1-5 hours, and then the polarized positive electrode black powder is mixed with 1 mol / L concentrated sulfuric acid and stirred at 80°C for 1-5 hours.

6. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: During the high-voltage treatment process, the positive or negative black powder needs to be encapsulated to prevent the powder from splashing due to electrostatic force after polarization.

7. The method for recovering lithium battery materials by high pressure treatment according to claim 4, characterized in that: The impurity content of the purified graphite after acid leaching is low, with Al, Cu and Fe all below 50 ppm. After heat treatment at 1500-3000°C, it can be used as a negative electrode material for lithium secondary batteries.

8. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: The positive electrode black powder or negative electrode black powder comes from lithium batteries including lithium iron phosphate, lithium cobalt oxide, lithium titanate, ternary and the like.

9. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 7, characterized in that: The solution selected for acid leaching includes one or more of concentrated sulfuric acid, hydrochloric acid, and nitric acid.

10. The method for high pressure treatment assisted recovery of lithium battery materials according to claim 1, characterized in that: The method is suitable for improving the leaching rate of metal ions in positive and negative electrode black powder during the acid leaching process in the recycling process of waste lithium batteries, as well as the acid leaching impurity removal effect of negative electrode graphite.

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