Method for selectively extracting lithium through pyrolysis of waste ternary lithium battery black powder and diaphragm

Abstract

The invention discloses a method for selectively extracting lithium by pyrolyzing black powder and a diaphragm of a waste ternary lithium battery, and relates to a method for selectively extracting lithium from a ternary lithium battery. The method aims at solving the technical problems that an existing method for extracting lithium from the waste ternary lithium battery wastes carbon resources, is too high in acid consumption and complex in process, and a water immersion method is poor in lithium selectivity and prone to co-dissolution of transition metal, so that the subsequent separation difficulty is large. The high-valence nickel, cobalt and manganese are reduced into water-insoluble metal or low-valence oxide through the synergistic effect of the pyrolyzed diaphragm and endogenous carbon, meanwhile, the lattice structure of lithium is directionally destroyed, lithium is selectively released, water-soluble lithium salt Li2CO3 is generated, and efficient and selective leaching of lithium is achieved. The method not only improves the recovery rate of lithium, but also reduces the waste of valuable metals such as nickel, cobalt and manganese, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to a method for selectively extracting lithium from ternary lithium batteries. Background Technology

[0002] With the booming development of the new energy vehicle industry, the recycling of spent ternary lithium batteries has become a crucial issue that urgently needs to be addressed. Ternary lithium batteries contain abundant valuable metals such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). These metals not only have high economic value but also play a vital role in resource recycling and environmental protection. However, existing ternary lithium battery recycling technologies have many shortcomings, limiting their efficiency and economic viability in practical applications. Traditional acid leaching processes require high-concentration acid solutions to dissolve high-valence metal ions in the ternary lithium battery powder. Conventional water leaching methods have poor selectivity for lithium, and transition metals are easily co-soluble, leading to significant difficulties in subsequent separation. In traditional acid leaching, lithium competes with nickel, cobalt, and manganese ions for dissolution in a strongly acidic environment, necessitating secondary separation in the lithium recovery process, thus increasing the cost of lithium recovery. This high acid consumption not only increases production costs but also puts considerable pressure on the environment.

[0003] Patent CN118326175A discloses a method for pre-extracting lithium from ternary lithium battery black powder. Specifically, it involves dry mixing ternary black powder with sodium sulfate and an organic carbon source. The mixture undergoes a pyrolysis reduction reaction under a nitrogen atmosphere. The pyrolysis product is then slurried, stirred, and subjected to solid-liquid separation with water to achieve selective lithium leaching. However, this method has the following drawbacks: the organic carbon sources mentioned in the patent include oxalic acid, citric acid, starch, pine needle powder, and cellulose-rich dried leaf powder. While these materials are widely available, cost and supply stability need to be considered in actual industrial production. Patent CN114032384A discloses a method for water leaching lithium from waste lithium batteries. Specifically, it involves mixing and ball-milling natural graphite powder and waste nickel-cobalt-manganese lithium oxide cathode material. The milled material is then calcined and water-leached. The filtration yields a ternary leachate containing lithium and a ternary leachate residue containing nickel, cobalt, and manganese. However, it has the following drawbacks: the ternary black powder itself contains residual carbon, but the patent treats it as an invalid component and forces the addition of exogenous graphite, which leads to a surge in raw material costs and increases the pretreatment process. Summary of the Invention

[0004] The present invention aims to address the technical problems of existing methods for lithium extraction from waste ternary lithium batteries, such as waste of carbon resources, excessive acid consumption, complex processes, poor selectivity of lithium in water immersion methods, and easy co-solubility of transition metals, which leads to difficulties in subsequent separation. The invention provides a method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator.

[0005] The method for selective lithium extraction from waste ternary lithium battery black powder and separator of the present invention is carried out according to the following steps:

[0006] 1. The membrane containing reducing carbon obtained from the processing of waste ternary lithium batteries is crushed to obtain processed membrane powder.

[0007] 2. The membrane powder obtained in step 1 and the waste ternary lithium battery black powder are mixed and placed in the same ceramic boat, and then calcined in a tube furnace under a protective atmosphere.

[0008] Third, add the product obtained from the roasting in step two to deionized water, and then leach it under the conditions of room temperature and stirring to obtain lithium ions in the leachate.

[0009] This invention proposes a method for selective lithium extraction through pyrolysis of waste ternary lithium battery black powder and separator. The ternary lithium battery black powder contains a positive electrode and a negative electrode, with the negative electrode being graphite. The ternary lithium battery black powder acts as a reducing endogenous carbon. The separator is composed of polyolefin polymer materials, which, after pyrolysis, break CH bonds, readily forming substances such as CO and CO2. The formation of CO2 is much less difficult than that of inorganic carbons such as graphite, and the reaction temperature is also lower. The separator, after high-temperature pyrolysis, more easily undergoes carbothermic reduction with the ternary lithium battery black powder to generate CO2. After the membrane is pyrolyzed, its synergistic effect with endogenous carbon reduces high-valence nickel, cobalt, and manganese to water-insoluble metals or low-valence oxides. Simultaneously, it directionally disrupts the lithium crystal structure, selectively releasing lithium to obtain lithium oxide. Li₂O reacts with CO₂ to form the water-soluble lithium salt Li₂CO₃. The generation of a large amount of CO₂ is crucial for Li water leaching; therefore, adding organic carbon (i.e., the membrane) during the roasting process promotes lithium leaching, achieving highly efficient and selective lithium leaching. This process relies solely on water leaching, eliminating the need for acid leaching, resulting in low cost and environmental friendliness. This invention not only improves lithium recovery rates but also reduces the waste of valuable metals such as nickel, cobalt, and manganese, demonstrating significant economic and environmental benefits.

[0010] The beneficial effects of this invention are:

[0011] Unlike existing technologies, the method of this invention can achieve a lithium selectivity of over 50% in water leaching, a transition metal dissolution rate of less than 1%, and an overall lithium leaching rate of over 98%, achieving selective lithium extraction without acid leaching, resulting in low cost and environmental friendliness. Compared with traditional lithium extraction methods, this invention can achieve selective and efficient separation of lithium and transition metals, overcoming the limitations of traditional processes. It solves the problems of traditional acid leaching methods requiring large amounts of strong acid, complex processes, poor lithium selectivity in water leaching, and easy co-solubility of transition metals, leading to difficulties in subsequent separation. Attached Figure Description

[0012] Figure 1The graph shows the lithium ion leaching rate at different pyrolysis times in Experiment 2 at a pyrolysis temperature of 450℃.

[0013] Figure 2 The graph shows the leaching rate of lithium ions at different calcination temperatures and for the uncalcined sample in Experiment 3.

[0014] Figure 3 XRD patterns of the product at different calcination temperatures and before calcination in Experiment 3, showing the temperature of the waste ternary lithium battery (NCM) black powder.

[0015] Figure 4 The graph shows the leaching rate data of lithium ions in Experiment 1, Comparative Experiment 1, and Comparative Experiment 2.

[0016] Figure 5 The images show the leaching of lithium ions, nickel ions, cobalt ions, and manganese ions in the ternary lithium batteries used in Experiment 1, Comparative Experiment 1, and Comparative Experiment 2. Detailed Implementation

[0017] Specific Implementation Method 1: This implementation method is a selective lithium extraction method using pyrolysis of waste ternary lithium battery black powder and separator, specifically carried out according to the following steps:

[0018] 1. The membrane containing reducing carbon obtained from the processing of waste ternary lithium batteries is crushed to obtain processed membrane powder.

[0019] 2. The membrane powder obtained in step 1 and the waste ternary lithium battery black powder are mixed and placed in the same ceramic boat, and then calcined in a tube furnace under a protective atmosphere.

[0020] Third, add the product obtained from the roasting in step two to deionized water, and then leach it under the conditions of room temperature and stirring to obtain lithium ions in the leachate.

[0021] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the treatment method for obtaining the separator with reducing carbon from the waste ternary lithium batteries in step one is as follows: the waste ternary lithium batteries are sequentially subjected to charged crushing and pyrolysis treatment. Everything else is the same as in Specific Implementation Method One.

[0022] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the pulverization in step one is carried out using a pulverizer, with a pulverization time of 1 to 3 hours and a pulverization speed of 1000 to 1500 r / min. Everything else is the same as in Specific Implementation Method 2.

[0023] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the mass ratio of the separator powder and the waste ternary lithium battery black powder mentioned in step two is 1:10. Everything else is the same as in Specific Implementation Methods One to Three.

[0024] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the roasting temperature in step two is 600℃ and the time is 3 hours. Everything else is the same as in Specific Implementation Method Four.

[0025] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the protective atmosphere described in step two is nitrogen, argon, or carbon dioxide. Everything else is the same as in Specific Implementation Method Five.

[0026] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the mass ratio of the product obtained from calcination in Step Two of Step Three to the volume ratio of deionized water is 1g:(20mL~150mL). Everything else is the same as in Specific Implementation Method Six.

[0027] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the leaching time in step three is 1 to 3 hours. Everything else is the same as in Specific Implementation Method Seven.

[0028] The invention was verified using the following experiments:

[0029] Experiment 1: This experiment demonstrates a selective lithium extraction method using pyrolysis of waste ternary lithium battery black powder and separator. The specific steps are as follows:

[0030] 1. The membrane containing reduced carbon obtained by sequentially crushing and pyrolysis of waste ternary lithium batteries (NCM) is pulverized to obtain the treated membrane powder; the pulverization is carried out by a pulverizer for 2 hours at a speed of 1500 r / min.

[0031] 2. Mix 0.2g of the separator powder obtained in step 1 with 2g of waste ternary lithium battery black powder and place them in the same ceramic boat. Then, calcine them in a tube furnace under a protective atmosphere at a temperature of 600℃ for 3 hours. The protective atmosphere is carbon dioxide, the gas flow rate is 160mL / min, and the heating rate is 10℃ / min.

[0032] The waste ternary lithium battery black powder is obtained by crushing, pyrolyzing and sieving waste ternary lithium batteries while they are charged, including positive and negative electrodes, with a sieve mesh size of 500 mesh (this step is a conventional technique).

[0033] 3. ① Add 2g of the product obtained from the roasting in step 2 to 140mL of deionized water, and then leach it for 1h under the conditions of room temperature and stirring. Then filter the solution to obtain the filter residue.

[0034] ② The operation of step ① was repeated 3 times on the filter residue. Finally, the total leaching rate of lithium ions in the 4 water leaching solutions was 98.28% after a total of 4 water leachings, as determined by atomic absorption spectrometry.

[0035] Comparative Experiment 1: The difference between this experiment and Experiment 1 is that no roasting or diaphragm was added, but an acid leaching process was used. The specific steps are as follows:

[0036] 1. Add 2g of waste ternary lithium battery (NCM) black powder to 140mL of deionized water, and then leach for 1h under room temperature and stirring conditions. Then filter the solution to obtain filter residue.

[0037] The waste ternary lithium battery black powder is obtained by crushing, pyrolyzing and sieving waste ternary lithium batteries while they are charged, including positive and negative electrodes, with a sieve mesh size of 500 mesh (this step is a conventional technique).

[0038] 2. The operation of step one was repeated 3 times on the filter residue. Finally, the total leaching rate of lithium ions in the 4 water leaching solutions was 34.14% after a total of 4 water leachings by atomic absorption spectrometry.

[0039] Third, the filter residue obtained in step two was dried, and then added to a round-bottom flask. 15 mL of 2.5 mol / L sulfuric acid solution was added to the flask, and the mixture was reacted in a constant-temperature oil bath at 80℃ and 400 rpm for 1 hour. The leached slurry was filtered to obtain filter residue and filtrate. The leaching rate of lithium ions in the filtrate was measured to be 58.29% using an atomic absorption spectrometer. This value is the leaching rate of lithium ions by acid leaching. After adding the leaching rate of water leaching in step two, the total lithium ion leaching rate in this comparative experiment was 92.43%, which is lower than 98.28% in experiment one. Moreover, the comparative experiment also used an acid leaching process.

[0040] Comparative Experiment 2: The difference between this experiment and Experiment 1 is that a diaphragm was not added, but an acid leaching process was used. The specific steps are as follows:

[0041] 1. Place 2g of waste ternary lithium battery (NCM) black powder in a ceramic boat and calcine it in a tube furnace under a protective atmosphere at a temperature of 600℃ for 3 hours. The protective atmosphere is carbon dioxide, the gas flow rate is 160mL / min, and the heating rate is 10℃ / min.

[0042] The waste ternary lithium battery black powder is obtained by crushing, pyrolyzing and sieving waste ternary lithium batteries while they are charged, including positive and negative electrodes, with a sieve mesh size of 500 mesh (this step is a conventional technique).

[0043] 2. ① Add 2g of the product obtained from the roasting in step one to 140mL of deionized water, and then leach it for 1h under the conditions of room temperature and stirring. Then filter the solution to obtain the filter residue.

[0044] ② The operation of step ① was repeated 3 times on the filter residue. Finally, the total leaching rate of lithium ions in the 4 water leaching solutions was measured by atomic absorption spectrometry after a total of 4 water leachings. The result was 63.47%.

[0045] Third, the filter residue obtained in step two was dried, and then added to a round-bottom flask. 12 mL of 1.5 mol / L sulfuric acid solution was added to the flask, and the mixture was reacted in a constant-temperature oil bath at 80℃ and 400 rpm for 1 hour. The leached slurry was filtered to obtain filter residue and filtrate. The lithium ion leaching rate in the filtrate was measured to be 32.15% using an atomic absorption spectrometer. This value is the lithium ion leaching rate by acid leaching. After adding the leaching rate by water leaching in step two, the total lithium ion leaching rate in this comparative experiment was 95.62%, which is lower than 98.28% in experiment one. Moreover, the comparative experiment also used an acid leaching process.

[0046] Experiment 2: The difference between this experiment and Comparative Experiment 2 is that the roasting temperature in Step 1 was 450℃, and the roasting times were 1h, 2h, 3h, 4h, and 5h for comparison. Everything else was the same as Comparative Experiment 2.

[0047] Figure 1 The graph shows the lithium ion leaching rate at different pyrolysis times in Experiment 2 at a pyrolysis temperature of 450℃. It can be seen that as the pyrolysis time increases, the lithium ion leaching rate first increases and then tends to stabilize. This indicates that extending the pyrolysis time can effectively convert lithium in the ternary black powder of lithium batteries into soluble lithium, and the lithium leaching rate gradually increases.

[0048] Experiment 3: The difference between this experiment and Comparative Experiment 2 is that the roasting temperatures in Step 1 were compared at 450℃, 600℃, 700℃, 800℃, and 900℃, and the roasting time was 3 hours. Everything else was the same as in Comparative Experiment 2.

[0049] Figure 2 The graph shows the lithium ion leaching rates at different calcination temperatures and for the uncalcined sample in Experiment 3. It can be seen that as the calcination temperature increases, the lithium ion leaching rate first increases and then decreases. This indicates that increasing the temperature can convert lithium into soluble Li salts. Further increases in temperature may lead to structural compaction of the soluble Li salts, resulting in a decrease in the lithium ion leaching rate. Specifically, for the uncalcined sample (… Figure 2The first column from the left corresponds to the water immersion rate of lithium ions in Comparative Experiment 1, which is 34.14%. When the calcination temperature is increased to 600℃, the water immersion rate of lithium ions obtained (corresponding to Comparative Experiment 2) is 63.47%, which is double the water immersion rate, demonstrating the reliability of the conclusion.

[0050] Figure 3 The XRD patterns of waste ternary lithium battery (NCM) black powder from Experiment 3 at different calcination temperatures and before calcination show that as the calcination temperature increases, the height of peak C (111) (I) increases. D The peak gradually decreases, and the height of the Li2CO3 peak on the crystal plane (002) (I) gradually decreases. G The temperature gradually increases. As the calcination temperature rises, I... D / I G A smaller ratio indicates that more carbon is gradually converted into soluble Li₂CO₃. Therefore, the water leaching rate of lithium ions is highest when calcined at 600℃.

[0051] Figure 4 The graph shows the lithium-ion leaching rate data for Experiment 1, Comparative Experiment 1, and Comparative Experiment 2. As an organic carbon structure, the separator is more easily carbonothermally reduced to CO2 by ternary black powder after high-temperature pyrolysis. In Experiment 1, the synergistic effect of separator pyrolysis and endogenous carbon significantly increased the conversion rate of Li2CO3 in the ternary black powder, resulting in the highest lithium-ion leaching rate in Experiment 1.

[0052] Figure 5 This image shows the leaching of lithium ions, nickel ions, cobalt ions, and manganese ions in ternary lithium batteries from Experiment 1, Comparative Experiment 1, and Comparative Experiment 2. In Experiment 1, during the water immersion stage, Li... + The leaching rate reached 98.28%, with no transition metals leaching out. During the roasting process, the reducing gas generated by the diaphragm pyrolysis synergistically interacts with the endogenous carbon in the black powder, converting lithium into soluble Li₂CO₃. High-valence Ni, Co, and Mn are reduced to water-insoluble metals and low-valence oxides, achieving selective lithium extraction during the water leaching process. Comparative experiments one and two used sulfuric acid to dissolve the low-valence oxides during the acid leaching stage, leading to the leaching of transition metals in both experiments. After comparison, experiment one showed the best selective lithium extraction effect, ultimately achieving acid-free selective lithium extraction through pyrolysis regulated by the endogenous carbon in ternary black powder.

Claims

1. A method for selective lithium extraction via pyrolysis of waste ternary lithium battery black powder and separator, characterized in that... The method is performed according to the following steps:

1. The membrane containing reducing carbon obtained from the processing of waste ternary lithium batteries is crushed to obtain processed membrane powder.

2. The membrane powder obtained in step 1 and the waste ternary lithium battery black powder are mixed and placed in the same ceramic boat, and then calcined in a tube furnace under a protective atmosphere. Third, add the product obtained from the roasting in step two to deionized water, and then leach it under the conditions of room temperature and stirring to obtain lithium ions in the leachate.

2. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator as described in claim 1, characterized in that... The treatment method for the separator with reducing carbon obtained from the waste ternary lithium battery in step one is as follows: the waste ternary lithium battery is subjected to charged crushing and pyrolysis treatment in sequence.

3. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator as described in claim 1, characterized in that... The pulverization in step one is carried out by a pulverizer, with a pulverization time of 1 to 3 hours and a pulverization speed of 1000 r / min to 1500 r / min.

4. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator as described in claim 1, characterized in that... The mass ratio of the separator powder to the waste ternary lithium battery black powder mentioned in step two is 1:

10.

5. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator according to claim 1, characterized in that... The roasting temperature in step two is 600℃ and the time is 3 hours.

6. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator according to claim 1, characterized in that... The protective atmosphere mentioned in step two is nitrogen, argon, or carbon dioxide.

7. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator according to claim 1, characterized in that... In step three, the mass ratio of the product obtained from calcination in step two to the volume ratio of deionized water is 1 g: (20 mL to 150 mL).

8. The method for selective lithium extraction by pyrolysis of waste ternary lithium battery black powder and separator according to claim 1, characterized in that... The leaching time in step three is 1 to 3 hours.

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