A method for high-pressure treatment-assisted recycling of lithium battery materials

Abstract

The present invention discloses a method for assisting the recycling of lithium battery materials by high-pressure treatment, aiming to solve the problem that the leaching rate of metal ions of the positive black powder and the negative black powder needs to be improved during acid leaching in the existing lithium battery recycling technology. This method pre-polarizes the dried positive black powder or negative black powder by using a pulsed DC electric field or a constant DC electric field to enhance the reaction activity of metal atoms, and then performs acid leaching operation. Experiments show that the acid leaching and impurity removal effect of the negative electrode graphite after high-pressure treatment is significantly improved, and the leaching rate of metal ions in the positive black powder is greatly increased. Moreover, the experimental principle and operation of this method are simple, and the experiment has strong repeatability. As a pretreatment method for black powder recycling, it does not limit the subsequent treatment means for different product requirements, providing a new way for the process optimization of waste lithium battery recycling.

Description

Technical Field

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

[0002] Taking the recycling of ternary lithium batteries as an example, the existing recycling process usually includes steps such as electrolyte solution discharging, drum crushing, screening, drying, grinding into powder, high-temperature pyrolysis, and air classification to obtain positive and negative black powders. Generally speaking, the positive 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 graphite is also of great significance to the environment and resources. Moreover, with the increasing number of waste lithium batteries, there is great economic potential. Subsequently, the positive and negative black powders are mostly converted into corresponding salts under the action of concentrated acid. For the negative black powder, acid leaching is used to remove impurities such as lithium, iron, copper, and aluminum to improve the purity of negative graphite; for the positive black powder, acid leaching can leach out 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 recycling efficiency. Therefore, how to improve the leaching efficiency has become the key to the recycling work. Currently, the metal ion leaching rate is often increased by stirring and heating or directly pressurizing during acid leaching. The present invention proposes an innovative method of pre-polarizing the positive and negative black powders by pulsed DC electric field or constant DC electric field to improve the concentrated acid leaching rate. Summary of the Invention

[0003] The prior art has limitations in improving the acid leaching efficiency of positive and negative black powders of lithium batteries. Although there are methods such as stirring and heating or directly pressurizing during acid leaching, the improvement effect still does not meet the requirements. For example, during the acid leaching process, for the positive black powder without special pretreatment, the leaching rates of nickel and cobalt are close to 90%, and the manganese element is basically not leached. The impurity removal of the negative black powder is not thorough enough, affecting the recycling and utilization value of subsequent materials. In addition, pretreatment methods such as sulfuric acid curing are relatively complex in operation, have strict requirements for conditions, are difficult to be widely promoted and applied, cannot efficiently achieve the maximum recycling and reuse of lithium resources, and are also difficult to meet the increasing demand for the treatment of waste lithium batteries.

[0004] The present invention aims to overcome the deficiencies of the prior art and provides a method for assisting in recycling lithium battery materials by high-pressure treatment. By pre-polarizing the positive black powder or negative black powder with a pulsed DC electric field or a constant DC electric field, the separation of positive and negative charge centers of metal atoms is achieved, enhancing their chemical reaction activity, and then greatly improving the leaching rate of metal ions in the subsequent acid leaching process, improving the acid leaching and impurity removal effect of negative graphite, opening up a new path for the optimization of waste lithium battery recycling processes, and simultaneously meeting the urgent needs of environmental protection and resource recycling.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is:

[0006] A method for high-pressure treatment-assisted recycling of lithium battery materials, including high-pressure pretreatment of dried positive black powder or negative black powder, and the high-pressure pretreatment uses pulsed DC electric field or constant DC electric field.

[0007] Further, 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.

[0008] Further, before high-pressure pretreatment, the positive black powder or negative black powder is dried at 80 °C for more than 24 h to make the water content of the powder less than 2%.

[0009] Further, when performing high-pressure pretreatment on the negative black powder, take 5 g of the dried negative black powder and place it in a pulsed DC electric field or a constant DC electric field to be polarized at a voltage of 100 - 1000 V for 1 - 5 h. Then mix the polarized negative black powder with 2 mol / L sulfuric acid, stir at 80 °C for 3 - 5 h, filter, add deionized water to the leached solid matter to adjust it to neutral, and heat at 80 °C for more than 12 h to obtain acid-leached purified graphite.

[0010] Further, when performing high-pressure pretreatment on the positive black powder, take 5 g of the dried positive black powder and place it in a pulsed DC electric field or a constant DC electric field to be polarized at a voltage of 100 - 1000 V for 1 - 5 h. Then mix the polarized positive black powder with 1 mol / L sulfuric acid and stir at 80 °C for 1 - 5 h.

[0011] Further, during the high-pressure treatment process, the positive or negative black powder needs to be encapsulated to prevent the polarized powder from splashing due to electrostatic force.

[0012] Further, the acid-leached purified graphite has a low impurity content, with Al, Cu, and Fe all less than 50 ppm, and can be used as the negative electrode material for lithium secondary batteries after heat treatment at 1500 - 3000 °C.

[0013] Further, the positive black powder or negative black powder is derived from lithium batteries including lithium iron phosphate, lithium cobaltate, lithium titanate, ternary, etc.

[0014] Further, the acid-leaching selected solution includes one or more of concentrated sulfuric acid, hydrochloric acid, and nitric acid.

[0015] Further, the method is applicable to improving the leaching rate of metal ions in the positive and negative black powders during the acid-leaching process in the recycling of waste lithium batteries, as well as the acid-leaching impurity removal effect of negative electrode graphite.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 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.

[0018] 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.

[0019] 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

[0020] Figure 1 It is an implementation flow chart of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0022] Implementation process: Set up two implementation samples and two control samples. The specific implementation process is as follows: Figure 1 shown.

[0023] Implementation sample 1 (polarized negative electrode black powder):

[0024] 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.

[0025] 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).

[0026] 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).

[0027] 3. Mix the polarized negative black powder with 2 mol / L concentrated sulfuric acid and stir at 80 °C for 3 h (at this time, mainly remove elements such as copper, aluminum, iron, and lithium through sulfuric acid leaching).

[0028] 4. After filtration, add deionized water to the leached solid to adjust it to neutral, and heat at 80 °C for 12 h to obtain acid-leached purified graphite.

[0029] Example Two (Polarized Positive Black Powder):

[0030] 1. Dry the positive black powder at 80 °C for 24 h to remove moisture (the moisture content of the powder needs to be lower than 2% during DC electric field treatment).

[0031] 2. Take 5 g of the dried positive black powder and place it in a pulsed DC electric field or a constant DC electric field to polarize for 1 h at a voltage of 1000 V (here, if a pulsed DC electric field is selected, its voltage value needs to be higher than that of the constant DC electric field, and the frequency is 10 - 1000 Hz).

[0032] 3. Mix the polarized positive black powder with 1 mol / L concentrated sulfuric acid and stir at 80 °C for 3 h (at this time, displace rare metal ions such as lithium, nickel, cobalt, and manganese through sulfuric acid).

[0033] Control Sample One (Negative Black Powder):

[0034] 1. Dry the negative black powder at 80 °C for 24 h to remove moisture.

[0035] 2. Take 5 g of the dried negative black powder and mix it with 2 mol / L concentrated sulfuric acid and stir at 80 °C for 3 h.

[0036] 3. After filtration, add deionized water to the leached solid to adjust it to neutral, and heat at 80 °C for 12 h to obtain acid-leached purified graphite.

[0037] Control Sample Two: (Positive Black Powder)

[0038] 1. Dry the positive black powder at 80 °C for 24 h to remove moisture.

[0039] 2. Take 5 g of the dried positive black powder and mix it with 1 mol / L concentrated sulfuric acid and stir at 80 °C for 1 h.

[0040] Table 1 Main Chemical Compositions of Negative Purified Graphite

[0041]

[0042] From the main chemical components of the purified graphite of the negative electrode in Table 1, it can be seen that in Control Group 1 (acid-leached and purified graphite without high-pressure treatment), there are relatively more impurities of copper, aluminum, and iron elements, and even trace amounts of lithium elements have not been removed. This part may be lithium carbide embedded in the graphite crystal structure. In Experimental Group 1 (acid-leached and purified graphite with high-pressure treatment), the carbon element occupies a larger mass ratio, corresponding to a significant reduction in the contents of copper, aluminum, and iron element impurities, and the lithium element is basically removed. It shows that the pulsed DC electric field treatment is helpful for acid-leaching and impurity removal of the negative electrode graphite. The high-pressure treatment enhances the reaction activity of metal ions, thereby effectively promoting the formation of metal ion sulfates in concentrated sulfuric acid and enhancing the effect of acid-leaching and purifying graphite with sulfuric acid.

[0043] Table 2 Leaching rates of each element in the positive electrode leaching solution (calculated based on the change in the mass of the leaching residue)

[0044]

[0045] Regarding the leaching rates of the four metal ions in the positive electrode leaching solution in Table 2, in the acid-leaching solution of the positive electrode powder without high-pressure treatment, the leaching rates of nickel and cobalt are close to 90%, the lithium element is relatively high at 97.4%, considering it is the most active, and the manganese element is basically not leached. In the leaching solution of the positive electrode powder 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 element is detected microscopically. (Here, there are multivalent manganese ions, including +3 and +2, with more +3 valence and less +2 valence. Sulfuric acid acid-leaching can only displace +2 valence manganese ions. Therefore, in the case of not adding a reducing agent, the leaching rate of manganese is generally very low). This shows that the activity of metal ions in the positive electrode black powder is enhanced after pulsed DC electric field treatment, making the displacement reaction of sulfuric acid more complete, manifested as higher leaching rates of each metal element.

[0046] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention 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 protection scope determined by the claims.

Claims

1. A method for assisting in the recovery of lithium battery materials by high-pressure treatment, characterized in that, It includes high-voltage pretreatment of the dried positive black powder or negative black powder, and the high-voltage pretreatment uses a pulsed DC electric field or a constant DC electric field; When performing high-voltage pretreatment on the positive black powder, take 5 g of the dried positive black powder and place it in a pulsed DC electric field or a constant DC electric field to be polarized at a voltage of 100 - 1000 V for 1 - 5 h. Then mix the polarized positive black powder with 1 mol / L concentrated sulfuric acid and stir at 80 °C for 1 - 5 h; When performing high-voltage pretreatment on the negative black powder, take 5 g of the dried negative black powder and place it in a pulsed DC electric field or a constant DC electric field to be polarized at a voltage of 100 - 1000 V for 1 - 5 h. Then mix the polarized negative black powder with 2 mol / L concentrated sulfuric acid, stir at 80 °C for 3 - 5 h, filter, add deionized water to the leached solid matter to adjust it to neutral, and heat at 80 °C for more than 12 h to obtain acid-leached purified graphite; The acid-leached purified graphite has a low impurity content, with Al, Cu, and Fe all less than 50 ppm, and can be used as the negative electrode material of a lithium secondary battery after heat treatment at 1500 - 3000 °C.

2. The method for assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, wherein, 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 assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, characterized in that, Before performing high-voltage pretreatment, dry the positive black powder or negative black powder at 80 °C for more than 24 h to make the water content of the powder less than 2%.

4. The method for assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, wherein During the high-voltage treatment process, it is necessary to encapsulate the positive or negative black powder to prevent the polarized powder from splashing due to electrostatic force.

5. The method for assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, wherein, The positive black powder or negative black powder is derived from lithium batteries including lithium iron phosphate, lithium cobaltate, lithium titanate, ternary, etc.

6. The method for assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, wherein The selected solution for acid leaching includes one or more of concentrated sulfuric acid, hydrochloric acid, and nitric acid.

7. The method for assisting in recycling lithium battery materials by high-pressure treatment according to claim 1, wherein The method is applicable to improving the leaching rate of metal ions in the positive and negative black powders during the acid leaching process in the recycling process of waste lithium batteries, as well as the acid-leaching impurity removal effect of the negative electrode graphite.

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