A method for recycling lithium element in ternary black powder

Abstract

The application provides a method for recycling lithium elements in ternary black powder, which comprises the following steps: step S1: using acid liquid to perform acid pickling on the ternary black powder to remove lithium carbonate in the ternary black powder, and filtering to obtain filtrate a and acid-pickling black powder; step S2: performing roasting on the acid-pickling black powder and a reducing agent under a first protective atmosphere, so that high-valence non-lithium active metal elements in the acid-pickling black powder are reduced into low-valence non-lithium active metal elements, and roasting black powder is obtained, wherein the roasting black powder further contains lithium oxide; wherein the reducing agent is carbon and / or carbon monoxide; the non-lithium active metal elements include nickel elements, cobalt elements and manganese elements; and step S3: performing water washing on the roasting black powder under a second protective atmosphere, so that lithium oxide in the roasting black powder is converted into lithium hydroxide and dissolved in water, and filtering to obtain filtrate b and water-washing precipitate. Through the method, the recycling cost can be reduced and the recycling rate of lithium elements can be improved.

Description

Technical Field

[0001] The present application belongs to the field of lithium battery recycling technology, and specifically relates to a method for recovering lithium elements in ternary black powder. Background Art

[0002] Traditional industrial ternary metal recovery typically utilizes hydrometallurgical methods. This process involves discharging batteries, mechanically crushing, sorting, and heat-treating them to produce ternary black powder. The ternary black powder is then acid-leached with concentrated acid (sulfuric acid) and a reducing agent (hydrogen peroxide) to produce a valuable metal solution. Manganese is then extracted using a P204 organic extractant, while nickel and cobalt are extracted using a P507 organic extractant. Lithium is then precipitated as lithium carbonate using a precipitant, and the element is recovered through filtration. This process involves post-process lithium extraction, meaning lithium is recovered at the end of the process. This results in significant lithium loss in the front-end steps, reducing recovery rates and lowering the purity of the nickel / cobalt / manganese sulfate products. To address this issue, the industry currently utilizes a combination of hydrometallurgical methods and pre-process lithium extraction techniques to recover ternary materials. The wet-fired process decomposes the ternary black powder by adding a reducing agent (C / CO / H2 / NG) during the pyrometallurgical roasting process. The lithium carbonate is then washed out with water to produce a lithium carbonate wash solution and other valuable metal solids. The lithium carbonate wash solution undergoes impurity removal and evaporation crystallization to obtain high-purity lithium carbonate, achieving pre-lithium extraction. The remaining valuable metal elements after eluting the lithium carbonate are then further recovered by wet metal extraction. However, the solubility of lithium carbonate obtained by the wet-fired process in aqueous solution is only approximately 13.3 g / L. This means that washing one ton of lithium carbonate requires at least 75.2 tons of water. Using a high-efficiency MVR evaporator to evaporate 75.2 tons of water, at an electricity cost of 50 yuan per ton of water, the electricity cost is approximately 3,760 yuan. The wet-fired process consumes a large amount of energy and increases the cost of lithium recovery.

[0003] Therefore, how to solve the problems of high water consumption and high cost in the current pre-lithium extraction technology for ternary lithium battery recycling is a key issue that needs to be solved urgently to achieve efficient, energy-saving and low-cost recycling of ternary batteries and protect the health and stability of the battery industry chain. Summary of the Invention

[0004] In view of this, the present application provides a method for recovering lithium elements in ternary black powder. By optimizing the fixed form of lithium elements recovered in ternary black powder, the recycling cost can be reduced and the recycling rate of lithium elements can be improved.

[0005] The present application provides a method for recovering lithium from ternary black powder, comprising the following steps:

[0006] Step S1: pickling the ternary black powder with an acid solution to remove lithium carbonate in the ternary black powder, and filtering to obtain a filtrate a and pickled black powder;

[0007] Step S2: roasting the pickled black powder and a reducing agent under a first protective atmosphere to reduce the high-valent non-lithium active metal elements in the pickled black powder to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also contains lithium oxide; wherein the reducing agent is carbon and / or carbon monoxide; and the non-lithium active metal elements include nickel, cobalt, and manganese;

[0008] Step S3: washing the roasted black powder with water under a second protective atmosphere to convert lithium oxide in the roasted black powder into lithium hydroxide which is dissolved in water, and filtering to obtain a filtrate b and a washed precipitate.

[0009] According to the present application, the lithium element in the ternary black powder can be fixed in the form of soluble lithium salt and lithium hydroxide through acid washing, roasting and water washing, which can effectively reduce the cost of recycling and utilizing the lithium element. At the same time, this method fixes the lithium element in the filtrate a and the filtrate b with less impurity metal elements, thereby improving the recovery rate of the lithium element.

[0010] In some embodiments, in step S1, the acid solution is hydrochloric acid and / or sulfuric acid, and the pH of the solution is controlled at 4 to 6.5 during the pickling process.

[0011] In some embodiments, the pickling conditions include: pickling time of 0.2-2 hours, a mass ratio of the ternary black powder to the acid solution of 1:0.1-5, and a stirring speed of 50-2000 r / min.

[0012] In some embodiments, step S1 comprises mixing ternary black powder with acid solution, acid washing with stirring for 0.2 to 2 hours, controlling the pH of the solution to 4 to 6.5 by dropwise addition of acid solution during the acid washing process, and filtering to obtain filtrate a and acid washed black powder. The stepwise addition of acid solution can stably control the pH of the system during the acid washing process, achieving efficient removal of lithium carbonate and reducing the removal of other impurities.

[0013] In some embodiments, the process further includes step S11: performing a first ion exchange resin on the filtrate a to remove impurity ions to obtain a lithium-containing washing solution a; and then performing a first evaporation crystallization treatment to obtain a lithium salt.

[0014] In some embodiments, the step S2 further includes: before the roasting, washing the pickled black powder with water and drying it in sequence, so that the moisture content of the pickled black powder is less than or equal to 20 ppm.

[0015] In some embodiments, in step S2, the first protective atmosphere is at least one of nitrogen, argon, and carbon dioxide, and the moisture content in the first protective atmosphere is less than or equal to 10 ppm.

[0016] In some embodiments, in step S2, the calcination conditions include: calcination at 400-900° C. for 0.5-6 h, and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

[0017] In some embodiments, in step S3, the second protective atmosphere is nitrogen and / or argon.

[0018] In some embodiments, the process further includes step S31: performing a decontamination treatment on the filtrate b using a second ion exchange resin to remove impurity ions to obtain a lithium-containing washing solution b; and then performing a second evaporation crystallization treatment to obtain lithium hydroxide.

[0019] In some embodiments, the water-washed precipitate obtained in step S3 includes a single substance and / or oxide corresponding to a non-lithium active metal element. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process flow chart for recovering lithium from ternary black powder according to Example 1 of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0022] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0024] As mentioned in the background technology section above, discarded ternary lithium batteries contain abundant valuable metal resources, and recycling them can effectively conserve resources and protect the environment. Hydrometallurgical processes reduce lithium recovery rates and the purity of the front-end nickel sulfate, cobalt, and manganese sulfate products. Hydrometallurgical processes combined with pyrometallurgical processes consume significant energy and increase lithium recovery costs.

[0025] Based on this, the inventors considered that the main reason why the cost of recovering lithium elements in related technologies is too high is that the form of fixed lithium elements in the recovery process is mainly lithium carbonate, and the solubility of lithium carbonate is low, and a large amount of water is required for washing, resulting in excessively high costs for subsequent evaporation, crystallization and collection. Table 1 shows the lithium equivalent solubility of lithium compounds in 100g of water. Under the temperature condition of 20°C, the lithium equivalent solubility of lithium hydroxide in 100g of water is 14.84 times that of lithium carbonate; the lithium equivalent solubility of lithium chloride in 100g of water is 54.84 times that of lithium carbonate. Converting the pre-lithium extraction product from low water-soluble lithium carbonate to highly water-soluble lithium chloride and lithium chloride can greatly reduce the water consumption for washing lithium.

[0026] Table 1

[0027]

[0028] Table 2 shows the theoretical water consumption for lithium washing using an MVR evaporator (assuming a water and electricity fee of 50 yuan per ton of evaporation) to generate different lithium compound products from one ton of lithium element. At 20°C, the electricity cost for evaporation and crystallization when the product is lithium hydroxide is 1 / 14.84 of that for lithium carbonate, and when the product is lithium chloride, the electricity cost is 1 / 54.84 of that for lithium carbonate. Converting the pre-lithium extraction product from low-water-soluble lithium carbonate to highly water-soluble lithium chloride and lithium hydroxide can significantly reduce energy consumption and lower production costs.

[0029] Table 2

[0030]

[0031] Therefore, the inventors have provided a method for recovering lithium from ternary black powder. This method fixes the lithium in the ternary black powder in the form of more soluble lithium chloride, lithium sulfate, and lithium hydroxide, thereby reducing the amount of washing water and, in turn, the cost of recovering the lithium. The following describes the embodiments provided in this application in detail.

[0032] The present application provides a method for recovering lithium from ternary black powder, comprising the following steps:

[0033] Step S1: pickling the ternary black powder with an acid solution to remove lithium carbonate in the ternary black powder, and filtering to obtain a filtrate a and pickled black powder;

[0034] Step S2: roasting the pickled black powder and the reducing agent under a first protective atmosphere to reduce the high-valent non-lithium active metal elements in the pickled black powder to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also contains lithium oxide; wherein the reducing agent is carbon and / or carbon monoxide; and the non-lithium active metal elements include nickel, cobalt, and manganese;

[0035] Step S3: washing the roasted black powder with water under a second protective atmosphere to convert lithium oxide in the roasted black powder into lithium hydroxide which is dissolved in water, and filtering to obtain a filtrate b and a washed precipitate.

[0036] According to the present application, generally speaking, the lithium element in the ternary black powder mainly exists in the positive electrode active material and the negative electrode active material. The residual lithium element in the negative electrode active material can easily generate lithium carbonate with oxygen, water and carbon dioxide in the air during the pretreatment of the ternary black powder. For the lithium carbonate in the ternary black powder, it can be washed with acid solution, so that the lithium carbonate can be dissolved and fixed in the filtrate a in the form of LiCl or Li2SO4. Since its solubility is higher than that of lithium carbonate, the cost of recycling the lithium element in the filtrate a is lower.

[0037] The lithium element in the acid-washed black powder obtained after the ternary black powder is acid-washed generally comes from the ternary material used as the positive electrode active material. By using carbon and / or carbon monoxide as a reducing agent to roast and reduce the metal oxide under a protective atmosphere, the high-valent non-lithium active metal element is reduced to a low-valent non-lithium active metal element, and the lithium element in the roasted black powder exists in the form of lithium oxide. As an example, using carbon monoxide as a reducing agent, the main equation of the roasting process is shown in formula (1):

[0038] 2LiNi x Co y Mn 1-x-y O2+(1+2x+2y)CO=Li2O+2xNi+2yCo+2(1-xy)MnO+

[0039] (1+2x+2y)CO2 formula (1)

[0040] Here, x, y, and 1-xy represent the molar ratios of various elements.

[0041] It should be noted that if moisture is present during the roasting process, Li2O will undergo reactions such as those described in equations (2) and (3). The Li2O generated from the ternary black powder reacts with H2O to generate LiOH, which then reacts with CO2 to generate lithium carbonate. H2O acts as a catalyst throughout the entire process, and a trace amount of moisture can produce a large amount of lithium carbonate. In other words, in the related art, the calcined product generally contains lithium in the form of lithium carbonate. In this application, the reducing agent must be carbon and / or carbon monoxide, so the oxidation product of the reducing agent will not contain water. The reducing agent is used to roast and reduce the pickled black powder under a protective atmosphere. The protective atmosphere can control its water content, allowing the lithium element to exist primarily in the form of lithium oxide.

[0042] Li2O+H2O=2LiOH (2)

[0043] 2LiOH+CO2=Li2CO3+H2O (3)

[0044] The calcined product is subsequently washed with water in a protective atmosphere, wherein lithium oxide reacts with water to be converted into lithium hydroxide and fixed in the filtrate b. Based on this, since the solubility of lithium hydroxide in water is much higher than that of lithium carbonate, the cost of recycling the lithium element in the filtrate b is lower.

[0045] Therefore, the present application can fix the lithium elements (lithium elements in the negative electrode and the positive electrode) in the ternary black powder in the form of soluble lithium salts and lithium hydroxide through acid washing, roasting and water washing, which can effectively reduce the cost of recycling and utilizing lithium elements. At the same time, this method fixes the lithium elements in the filtrate a and the filtrate b with less impurity metal elements, thereby improving the recovery rate of lithium elements.

[0046] It should be noted that ternary black powder has a well-known meaning in the art, and refers to black powder recycled from waste ternary lithium batteries. The main components are the positive electrode active materials and negative electrode active materials in the waste ternary lithium batteries.

[0047] In some embodiments, in step S1, the acid solution is hydrochloric acid and / or sulfuric acid, and the pH of the solution is controlled at 4-6.5 during the pickling process.

[0048] In some of the above embodiments, the acid solution uses hydrochloric acid and / or sulfuric acid, which can convert lithium carbonate into lithium chloride and lithium sulfate with better solubility, thereby reducing the cost of recycling lithium elements. Simultaneously, the pH of the solution during the pickling process is controlled to be between 4 and 6.5, which can reduce the dissolution of ternary materials from the ternary black powder, thereby further reducing the content of impurity elements in the filtrate a and improving the purity of the target product. For example, the pH of the solution during the pickling process can be 4, 4.5, 5, 5.5, 6, 6.5, or within the range of any of the above values.

[0049] In some embodiments, the pickling conditions include: pickling time of 0.2-2 hours, a mass ratio of ternary black powder to acid solution of 1:0.1-5, and a stirring speed of 50-2000 r / min.

[0050] In some of the above embodiments, lithium carbonate can fully react with the acid solution to be converted into a soluble lithium salt and fixed in the filtrate a. At this time, the recovery rate of lithium element in the ternary black powder can be further improved, and the purity of other metal elements in the ternary black powder can be improved.

[0051] In some embodiments, the ternary black powder is mixed with acid solution and pickled under stirring for 0.2 to 2 hours. During the pickling process, the pH of the solution is controlled to be 4 to 6.5 by adding acid solution dropwise, and the filtrate a and pickled black powder are obtained by filtration.

[0052] In some of the above embodiments, by adding acid during the pickling process to control the pH of the solution to 4-6.5, incomplete dissolution of lithium carbonate caused by the increase in pH during the pickling process can be suppressed, thereby further improving the recovery rate of lithium elements in the ternary black powder.

[0053] In some embodiments, the process further includes step S11: performing a first ion exchange resin on the filtrate a to remove impurity ions to obtain a lithium-containing washing solution a; and then performing a first evaporation crystallization treatment to obtain a lithium salt.

[0054] In some of the above embodiments, since some impurity ions, such as magnesium ions and calcium ions, may exist in the filtrate a, the impurity ions can be further removed by ion exchange resin, thereby further improving the purity of the target product and facilitating further processing and utilization.

[0055] In some embodiments, step S2 further includes: before roasting, washing and drying the pickled black powder in sequence, so that the moisture content in the pickled black powder is less than or equal to 20 ppm.

[0056] In some of the above embodiments, washing the pickling black powder with water can remove the acid on the surface of the pickling black powder, and then drying it to a moisture content of less than or equal to 20 ppm and then roasting it can further reduce the impact of moisture in the pickling black powder on the reduction process, reduce the generation of lithium carbonate, and thus further reduce the cost of recovering lithium elements.

[0057] In some embodiments, the pickling black powder is washed with water in a countercurrent manner, which can save washing water. The water after washing the pickling black powder can be recycled to re-configure the acid solution, which can further save costs.

[0058] In some embodiments, in step S2, the first protective atmosphere is at least one of nitrogen, argon, and carbon dioxide, and the moisture content in the first protective atmosphere is less than or equal to 10 ppm.

[0059] In some of the above embodiments, the protective gas in the first protective atmosphere can be nitrogen, argon and carbon dioxide. The protective gas can ensure the smooth progress of the redox reaction, and the high-valent non-lithium active metal elements in the pickling black powder are fully reduced to low-valent non-lithium active metal elements. At the same time, the moisture in the first protective atmosphere is controlled to be less than or equal to 10 ppm. Under this condition, the reaction of lithium oxide and carbon dioxide to form lithium carbonate can be further reduced, the purity of the target product can be further improved, and the cost of recovering lithium elements can be reduced.

[0060] In this process, in order to make the lithium element in the pickling black powder be roasted into Li2O as much as possible, a non-hydrogen reducing agent (i.e. carbon and / or carbon monoxide) is used, the moisture content in the pickling black powder is controlled to be less than or equal to 20ppm, and the roasting is required to be under a protective atmosphere with a water content of less than or equal to 10ppm. + It reacts catalytically with CO2 in an aqueous environment to generate Li2CO3.

[0061] In some embodiments, in step S2, the calcination conditions include: calcination at 400-900°C for 0.5-6h, and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

[0062] In some of the above embodiments, under this condition, the redox reaction can be fully carried out, and the high-valent non-lithium active metal elements in the pickling black powder can be fully reduced to low-valent non-lithium active metal elements, so that the lithium element and the non-lithium active metal elements can be fully separated by water washing, further improving the recovery rate and the purity of the recovered product.

[0063] In some embodiments, in step S3, the second protective atmosphere is nitrogen and / or argon.

[0064] In some of the above embodiments, the second protective atmosphere not only inhibits the re-oxidation of low-priced non-lithium active metal elements in the roasted black powder, but also inhibits the conversion of lithium oxide into lithium carbonate. When the second protective atmosphere is nitrogen and / or argon, the formation of lithium carbonate can be effectively reduced, thereby reducing the cost of recovering lithium elements.

[0065] In some embodiments, the process further includes step S31: performing a decontamination treatment on the filtrate b using a second ion exchange resin to remove impurity ions to obtain a lithium-containing washing solution b; and then performing a second evaporation crystallization treatment to obtain lithium hydroxide.

[0066] In some of the above embodiments, since some impurity ions, such as magnesium ions and calcium ions, may exist in the filtrate b, the impurity ions can be further removed by ion exchange resin, thereby further improving the purity of the target product and facilitating further processing and utilization.

[0067] In some embodiments, in step S11 and step S31, the first ion exchange resin and the second ion exchange resin are independently selected from at least one of Tulsimer® CH-93 resin and 732 cation exchange resin, the temperature of the first evaporation crystallization is 105-350° C., and the temperature of the second evaporation crystallization is 105-350° C.

[0068] In some embodiments, the water-washed precipitate obtained in step S3 includes a single substance and / or oxide corresponding to the non-lithium active metal element.

[0069] In some of the above embodiments, the single substance and / or oxide corresponding to the non-lithium active metal element in the water-washed precipitate can be recycled through further processing. Since the lithium content therein is reduced, the product obtained by further recycling has a higher purity.

[0070] The scheme of the present application is described below with reference to the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0071] Ternary black powder is obtained from waste electrolysis through disassembly, crushing, roasting and screening, with a roasting temperature of 300~400℃.

[0072] Example 1

[0073] Process flow chart as follows Figure 1 As shown, 200 g of ternary black powder was taken and tested by inductively coupled plasma spectroscopy (ICP), and the lithium content was 6.21%, that is, the lithium content was 12.6 g.

[0074] 200g of ternary black powder was added to 350g of hydrochloric acid solution with a pH of 5.3. After addition, 24.5g of 30% hydrochloric acid was added dropwise at a rotational speed of 100 r / min. The pH of the solution was controlled to be between 4 and 6.5. Stirring was continued for 30 minutes after the addition was completed. After the acid wash, the acid-washed black powder and filtrate a were filtered. Filtrate a was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, obtaining lithium-containing wash solution a. The lithium-containing wash solution a was evaporated and crystallized at 280°C to obtain 8.18g of lithium chloride with a purity of 99.42%.

[0075] The acid-washed black powder was countercurrently washed five times with deionized water and then dried at 320°C for 5 hours to remove moisture. After drying, the water content was determined to be 13 ppm. The dried black powder was then calcined at 700°C for 3 hours under a nitrogen atmosphere using CO as a reducing agent. The CO introduced during the calcination process was 25% of the mass of the ternary black powder, and the moisture content in the calcination atmosphere was controlled between 7 and 10 ppm. After calcination, the powder was washed with 400 g of deionized water under a nitrogen atmosphere and filtered to obtain low-valent metals or metal compounds, such as nickel, cobalt, and manganese, and filtrate b. The low-valent metals or metal compounds, such as nickel, cobalt, and manganese, were then subjected to a subsequent wet recovery process. Filtrate b was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, yielding a lithium-containing wash solution b. This wash solution b was then evaporated and crystallized at 280°C to yield 36.35 g of lithium hydroxide with a purity of 99.67%.

[0076] The comprehensive lithium recovery rate of the entire pre-lithium extraction process is 95.30%. The amount of water used for acid washing of lithium chloride and deionized water washing of lithium hydroxide is 773.6g, of which the amount of water used for deionized water washing of lithium hydroxide is 400g. The purity of lithium chloride obtained is 99.42%, and the purity of lithium hydroxide obtained is 99.67%.

[0077] Example 2

[0078] Take 300g of ternary black powder and use inductively coupled plasma spectroscopy (ICP) to test the lithium content, which is 4.90%, that is, the lithium content is 14.7g.

[0079] 300g of ternary black powder was added to 450g of hydrochloric acid solution with a pH of 4.7. After addition, 25g of 30% hydrochloric acid was added dropwise at a rotational speed of 100 r / min. The pH of the solution was controlled to be between 4 and 6.5. Stirring was continued for 30 minutes after the addition was completed. After the acid wash, the acid-washed black powder and filtrate a were filtered. The filtrate a was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, obtaining lithium-containing wash solution a. The lithium-containing wash solution a was evaporated and crystallized at 280°C to obtain 8.37g of lithium chloride with a purity of 99.59%.

[0080] The acid-washed black powder was countercurrently washed five times with deionized water and then dried at 320°C for 5 hours to remove moisture. After drying, the water content was determined to be 16 ppm. The dried black powder was then calcined at 700°C for 3 hours under a nitrogen atmosphere using CO as a reducing agent. The CO introduced during the calcination process was 30% of the mass of the ternary black powder, and the moisture content in the calcination atmosphere was controlled between 7 and 10 ppm. After calcination, the powder was washed with 600 g of deionized water under a nitrogen atmosphere to obtain low-valent metals or metal compounds, such as nickel, cobalt, and manganese, and a filtrate b. The low-valent metals or metal compounds, such as nickel, cobalt, and manganese, were then subjected to a subsequent wet recovery process. The filtrate b was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, yielding a lithium-containing wash solution b. This wash solution b was then evaporated and crystallized at 280°C to yield 44.24 g of lithium hydroxide with a purity of 99.62%.

[0081] The comprehensive lithium recovery rate of the entire pre-lithium extraction process is 96.20%. The amount of water used for acid-washing lithium chloride and deionized water-washing lithium hydroxide is 1075g. The purity of lithium chloride obtained is 99.59%, and the purity of lithium hydroxide obtained is 99.62%.

[0082] Example 3

[0083] 200 g of the homologous ternary black powder of Example 1 was taken and tested using inductively coupled plasma spectroscopy (ICP). The lithium content was 6.21%, that is, the lithium content was 12.6 g.

[0084] 200g of ternary black powder was added to 350g of hydrochloric acid solution with a pH of 5.3. After addition, 24.5g of 30% hydrochloric acid was added dropwise at a rotational speed of 100 r / min. The pH of the solution was controlled to be between 4 and 6.5. Stirring was continued for 30 minutes after the addition was completed. After the acid wash, the acid-washed black powder and filtrate a were filtered. Filtrate a was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, obtaining lithium-containing wash solution a. The lithium-containing wash solution a was evaporated and crystallized at 280°C to obtain 8.17g of lithium chloride with a purity of 99.39%.

[0085] The acid-washed black powder was countercurrently washed five times with deionized water and then dried at 320°C for 5 hours to remove moisture. After drying, the water content was determined to be 12 ppm. The dried black powder was then calcined at 700°C for 3 hours under a nitrogen atmosphere using CO as a reducing agent. The CO introduced during the calcination process was 25% of the mass of the ternary black powder, and the moisture content in the calcination atmosphere was controlled between 11 and 13 ppm. After calcination, the powder was washed with 1500 g of deionized water under a nitrogen atmosphere to obtain nickel, cobalt, and manganese (Ni, Co, and Manganese) low-valent metal compounds and filtrate b. The Ni, Co, and Manganese low-valent metal compounds were then subjected to a subsequent wet recovery process. Filtrate b was then treated with Tulsimer® CH-93 resin to remove high-valent metal ion impurities, yielding a lithium-containing wash solution b. This wash solution b was then evaporated and crystallized at 280°C to yield 36.99 g of lithium hydroxide with a purity of 95.13%. The resulting lithium hydroxide contained 1.6 g of lithium carbonate.

[0086] The comprehensive recovery rate of lithium in the entire pre-lithium extraction process is 95.17%. The amount of water used for pickling lithium chloride and washing lithium hydroxide with deionized water is 1874.4g, and the purity of lithium chloride obtained is 99.39%, and the purity of lithium hydroxide obtained is 95.13%. The amount of water used in washing lithium hydroxide is 1500g, which is 3.75 times the amount of water used in washing lithium hydroxide in Example 1, that is, the evaporation power consumption and evaporation electricity cost are also about 3.75 times that of Example 1. In addition, the purity of the obtained lithium hydroxide is reduced from 99.62% in Example 1 to 95.13%. The product is doped with lithium carbonate, and the product purity is low.

[0087] This shows that when other conditions are the same, controlling the moisture content in the atmosphere to below 10 ppm during the roasting process can further improve the purity of lithium hydroxide and reduce the amount of water used for lithium washing, thereby reducing the recovery cost.

[0088] Comparative Example 1

[0089] Take 200g of ternary black powder and use inductively coupled plasma spectroscopy (ICP) to test the lithium content, which is 6.21%, that is, the lithium content is 12.6g.

[0090] 200g of ternary black powder was calcined at 700°C for 3 hours under a nitrogen atmosphere using a CO / H2 mixture (water gas) as a reducing agent. The mass of the CO / H2 mixture introduced during the calcination process was 25% of the mass of the ternary black powder. After calcination, the powder was washed with 8600g of deionized water to obtain high-valent metal compounds such as nickel, cobalt, and manganese, as well as a washing liquid. The high-valent metal compounds, such as nickel, cobalt, and manganese, were then processed for wet recovery. After impurities were removed, the washing filtrate was evaporated and crystallized at 280°C to obtain 59.7g of lithium carbonate with a purity of 98.53%.

[0091] The comprehensive lithium recovery rate of the entire pre-lithium extraction process is 92.1%, and the water consumption for washing lithium carbonate is 8600 g, which is 11.17 times the water consumption for washing lithium in Example 1, that is, the evaporation power consumption and the evaporation electricity fee are also about 11.17 times that of Example 1.

[0092] The invention illustrates that the method for recovering lithium from ternary black powder provided in the present application can effectively improve the recovery rate of lithium and effectively reduce the cost.

[0093] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for recovering lithium from ternary black powder, characterized in that: The following steps are involved: Step S1: pickling the ternary black powder with an acid solution to remove lithium carbonate in the ternary black powder, and filtering to obtain a filtrate a and pickled black powder; Step S2: roasting the pickled black powder and a reducing agent under a first protective atmosphere to reduce the high-valent non-lithium active metal elements in the pickled black powder to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also contains lithium oxide; Wherein, the reducing agent is carbon and / or carbon monoxide; The non-lithium active metal elements include nickel, cobalt and manganese; The step S2 further includes: before the roasting, washing the pickled black powder with water and drying it in sequence, so that the moisture content of the pickled black powder is less than or equal to 20 ppm; The first protective atmosphere is at least one of nitrogen, argon and carbon dioxide, and the moisture content of the first protective atmosphere is less than or equal to 10 ppm; Step S3: washing the roasted black powder with water under a second protective atmosphere to convert lithium oxide in the roasted black powder into lithium hydroxide which is dissolved in water, and filtering to obtain a filtrate b and a washed precipitate.

2. The method according to claim 1, characterized in that In step S1, the acid solution is hydrochloric acid and / or sulfuric acid, and the pH of the solution is controlled at 4-6.5 during the pickling process.

3. The method according to claim 1 or 2, characterized in that The pickling conditions include: pickling time of 0.2-2 hours, a mass ratio of the ternary black powder to the acid solution of 1:0.1-5, and a stirring speed of 50-2000 r / min.

4. The method according to claim 1, wherein The step S1 comprises: The ternary black powder is mixed with acid solution and pickled for 0.2 to 2 hours under stirring conditions. During the pickling process, the pH of the solution is controlled to be 4 to 6.5 by adding acid solution dropwise. The filtrate a and pickled black powder are obtained by filtration.

5. The method according to claim 1, wherein The method further includes step S11: performing impurity removal treatment on the filtrate a using a first ion exchange resin to remove impurity ions to obtain a lithium-containing washing solution a; and then performing a first evaporation crystallization treatment to obtain a lithium salt.

6. The method according to claim 1, characterized in that In step S2, the calcination conditions include: calcination at 400-900° C. for 0.5-6 hours, and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

7. The method according to claim 1, characterized in that In step S3, the second protective atmosphere is nitrogen and / or argon.

8. The method according to claim 5, characterized in that The method further includes step S31: performing a decontamination treatment on the filtrate b using a second ion exchange resin to remove impurity ions to obtain a lithium-containing washing solution b; and then performing a second evaporation crystallization treatment to obtain lithium hydroxide.

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