Method for recycling lithium element in ternary black powder

Abstract

The invention provides a method for recovering lithium element in ternary black powder, which comprises the following steps: step S1: carrying out acid pickling on the ternary black powder by using acid liquor to remove lithium carbonate in the ternary black powder, and filtering to obtain filtrate a and acid-pickled black powder; s2, roasting the acid pickling black powder and a reducing agent in a first protective atmosphere to reduce high-valence non-lithium active metal elements in the acid pickling black powder into low-valence non-lithium active metal elements to obtain roasted black powder which further contains lithium oxide; wherein the reducing agent is carbon and / or carbon monoxide; the non-lithium active metal elements comprise a nickel element, a cobalt element and a manganese element; and S3, washing the roasted black powder in a second protective atmosphere to convert lithium oxide in the roasted black powder into lithium hydroxide, dissolving the lithium hydroxide in water, and filtering to obtain filtrate b and washing precipitate. The method can reduce the recycling cost and improve the recycling rate of the lithium element.

Description

Technical Field

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

[0002] Lithium-ion batteries were commercialized in 1991 and have since flourished around the world. Among them, ternary lithium batteries have been widely used in electric vehicles, 3C digital products, and new energy storage fields due to their wide operating temperature range, low self-discharge rate, no memory effect, and high energy density. According to statistics, my country's ternary battery production in 2020-2022 was 48.5GWh, 93.9GWh, and 212.5GWh, respectively, with an average annual growth rate of over 100%. It is expected that ternary lithium batteries will continue to develop rapidly with the new energy vehicle and energy storage industries. However, ternary lithium batteries usually need to be retired after about 1,200 cycles and reach the end of their service life. The rapid development of ternary lithium batteries has led to the production of a large number of retired batteries. As a country with scarce lithium resources, my country is heavily dependent on imports of lithium resources. In recent years, the price of imported lithium has been high, which has greatly increased the manufacturing cost of ternary lithium batteries. In addition, the rapid development of ternary lithium batteries will also consume a large amount of resources such as Ni, Mn, Co, and Cu, and domestic mineral resources are difficult to support such large-scale production consumption. Retired ternary lithium batteries are also known as urban mines. The content of elements such as Li (1.9%), Ni (12.1%), Co (2.3%), and Cu (13.3%) contained in them is much higher than that of metal ores. How to efficiently and environmentally friendly recycle and reuse the valuable metal components in ternary lithium batteries, reduce my country's dependence on foreign mineral resources, and promote the development of my country's new energy industry is a widely concerned issue.

[0003] Traditional industrial ternary recycling usually adopts the form of hydrometallurgy. The wet ternary recycling process discharges the battery, mechanically crushes, sorts, and heat treats it into ternary black powder, and then leaches the ternary black powder into a valuable metal solution through concentrated acid (sulfuric acid) and reducing agent (hydrogen peroxide), and then extracts manganese through P204 organic extractant, extracts nickel / cobalt through P507 organic extractant, and then adds a precipitant to precipitate lithium into lithium carbonate and recover lithium through filtration. This process is post-lithium extraction, that is, lithium is recovered at the end of the process, resulting in a large loss of lithium in the front-end process, reducing the recovery rate, and causing the purity of the front-end product nickel / cobalt / manganese sulfate to decrease. In order to solve this problem, the current industry usually uses a wet pyrolysis method combined with a pre-lithium extraction technology to recover ternary materials. The wet + pyrometallurgical process decomposes the ternary black powder by adding a reducing agent (C / CO / H2 / NG) during the pyrometallurgical roasting of the black powder, and then washes out the lithium carbonate therein to obtain a lithium carbonate washing solution and the remaining valuable metal solids. The lithium carbonate washing solution is subjected to impurity removal and evaporation crystallization to obtain high-purity lithium carbonate, thereby realizing pre-lithium extraction. The remaining valuable metal elements after eluting the lithium carbonate continue to be recovered by wet method. However, the solubility of lithium carbonate obtained by the wet + pyrometallurgical process in aqueous solution is only about 13.3g / L, that is, at least 75.2 tons of water are required to wash 1 ton of lithium carbonate. Using an efficient MVR evaporator to evaporate 75.2 tons of water, the electricity cost is about 3,760 yuan at an electricity cost of 50 yuan per ton of water. The wet + pyrometallurgical process consumes a lot of energy and increases the cost of lithium recovery.

[0004] 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 urgently addressed in order to achieve efficient, energy-saving and low-cost recycling of ternary batteries, promote the healthy and sustainable development of my country's new energy industry, reduce dependence on external resources, and protect the health and stability of the battery industry chain. Summary of the invention

[0005] In view of this, the present application provides a method for recovering lithium elements in ternary black powder, which can reduce the recycling cost and improve the recycling rate of lithium elements by optimizing the fixed form of lithium elements recovered in ternary black powder.

[0006] The present application provides a method for recovering lithium from ternary black powder, comprising the following steps:

[0007] Step S1: washing 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 the acid-washed black powder;

[0008] 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;

[0009] Step S3: washing the roasted black powder with water under a second protective atmosphere, so that the lithium oxide in the roasted black powder is converted into lithium hydroxide and dissolved in water, and filtering to obtain a filtrate b and a washed precipitate.

[0010] 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 the lithium element. At the same time, this method has fewer impurity metal elements in the filtrate a and filtrate b for fixing the lithium element, thereby improving the recovery rate of the lithium element.

[0011] 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.

[0012] In some embodiments, the pickling conditions include: the pickling time is 0.2 to 2 hours, the mass ratio of the ternary black powder to the acid solution is 1:0.1 to 5, and the stirring speed is 50 to 2000 r / min.

[0013] In some embodiments, step S1 comprises: mixing ternary black powder with acid solution, pickling for 0.2 to 2 hours under stirring conditions, controlling the pH of the solution to 4 to 6.5 by dripping acid solution during the pickling process, and filtering to obtain filtrate a and pickled black powder. Adding acid solution in steps can stably control the pH of the system during the pickling process, achieve efficient washing out of lithium carbonate, and reduce the washing out of other impurities.

[0014] In some embodiments, the method further includes step S11: performing a first ion exchange resin on the filtrate a to remove impurities to obtain a lithium-containing washing solution a; and then performing a first evaporation crystallization treatment to obtain a lithium salt.

[0015] In some embodiments, the step S2 further includes: before the roasting, washing and drying the acid-washed black powder in sequence, so that the moisture content of the acid-washed black powder is less than or equal to 20 ppm.

[0016] 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.

[0017] 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.

[0018] In some embodiments, in step S3, the second protective atmosphere is nitrogen and / or argon.

[0019] In some embodiments, 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.

[0020] 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

[0021] 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

[0022] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0023] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the implementation or examples are included in at least one implementation or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more implementations or examples in a suitable manner.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0025] As mentioned in the background technology above, discarded ternary lithium batteries contain rich valuable metal resources, and recycling can effectively save resources and protect the environment. The lithium recovery rate in the hydrometallurgical process is low, and the purity of the front-end products nickel sulfate / cobalt / manganese sulfate is reduced; the hydrometallurgical + pyrometallurgical process consumes a lot of energy and increases the cost of lithium recovery.

[0026] Based on this, the inventors considered that the main reason for the high cost of recovering lithium elements in the related art 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.

[0027] Table 1

[0028] temperature LiCl <![CDATA[Li2CO3]]> LiOH <![CDATA[Li2S04]]> 0℃ 11.33 0.29 3.68 4.56 10℃ 12.20 0.27 3.68 4.48 20℃ 13.67 0.25 3.71 4.40 30℃ 14.11 0.24 3.74 4.32 40℃ 14.70 0.22 3.77 4.26 50℃ / 0.20 3.86 / 60℃ 16.11 0.19 4.00 4.12 80℃ 18.34 0.16 4.44 3.97 90℃ 19.81 / / 3.90 100℃ 20.96 0.14 5.07 /

[0029] Table 2 shows the theoretical water consumption for washing lithium by pre-extraction of 1 ton of lithium to generate different lithium compound products, and the electricity cost required for evaporation and crystallization using an MVR evaporator (the electricity cost for evaporation of 1 ton is set to be 50 yuan). Under the temperature condition of 20°C, when the product is lithium hydroxide, the electricity cost for evaporation and crystallization is 1 / 14.84 of that for lithium carbonate, and when the product is lithium chloride, the electricity cost for evaporation and crystallization is 1 / 54.84 of that for lithium carbonate. Converting the pre-extraction product from low-water-soluble lithium carbonate to highly-water-soluble lithium chloride and lithium hydroxide can greatly reduce energy consumption and production costs.

[0030] Table 2

[0031]

[0032]

[0033] Therefore, the inventor provides a method for recovering lithium from ternary black powder, which fixes the lithium in the ternary black powder in the form of lithium chloride, lithium sulfate, and lithium hydroxide, which have higher solubility, thereby reducing the amount of washing water and further reducing the cost of recovering lithium. The embodiments provided in this application are described in detail below.

[0034] The present application provides a method for recovering lithium from ternary black powder, comprising the following steps:

[0035] Step S1: washing 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 the acid-washed black powder;

[0036] 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;

[0037] Step S3: washing the roasted black powder with water under the second protective atmosphere, so that the lithium oxide in the roasted black powder is converted into lithium hydroxide and dissolved in water, and filtering to obtain a filtrate b and a washed precipitate.

[0038] 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 relatively low.

[0039] 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. The high-valent non-lithium active metal element is reduced to a low-valent non-lithium active metal element by using carbon and / or carbon monoxide as a reducing agent in a protective atmosphere to reduce the metal oxide. In the roasted black powder, the lithium element exists in the form of lithium oxide. As an example, with carbon monoxide as a reducing agent, the main equation of the roasting process is shown in formula (1):

[0040] 2LiNi x Co y Mn 1-x-y O2+(1+2x+2y)CO=Li2O+2xNi+2yCo+2(1-xy)MnO+

[0041] (1+2x+2y)CO2 formula (1)

[0042] Here, x, y and 1-xy represent the molar ratios of various elements.

[0043] It should be noted that if there is water during the roasting process, Li2O will react as shown in formula (2) and (3) during the roasting process. The Li2O generated by the ternary black powder reacts with H2O to generate LiOH, and the generated LiOH reacts with CO2 to generate lithium carbonate. H2O acts as a catalyst in the whole process. A small amount of water can produce a large amount of lithium carbonate, that is, in the relevant technology, the roasting 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 generate 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, so that the lithium element can be mainly present in the form of lithium oxide.

[0044] Li2O+H2O=2LiOH (2)

[0045] 2LiOH+CO2=Li2CO3+H2O (3)

[0046] 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.

[0047] Therefore, the present application can fix the lithium element (lithium element in the negative electrode and the positive electrode) in the ternary black powder 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 lithium elements. At the same time, this method has fewer impurity metal elements in the filtrate a and filtrate b for fixing the lithium element, thereby improving the recovery rate of the lithium element.

[0048] 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, and its main components are the positive electrode active materials and negative electrode active materials derived from the waste ternary lithium batteries.

[0049] 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.

[0050] 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; at the same time, the pH of the solution during the pickling process is controlled to be 4 to 6.5, at which time the dissolution of ternary materials in the ternary black powder can be reduced, thereby further reducing the content of impurity elements in the filtrate a and improving the purity of the target product. As an 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 the composition described by any of the above values.

[0051] In some embodiments, the pickling conditions include: pickling time of 0.2 to 2 hours, a mass ratio of ternary black powder to acid solution of 1:0.1 to 5, and a stirring speed of 50 to 2000 r / min.

[0052] In some of the above embodiments, lithium carbonate may fully react with the acid solution to be converted into a soluble lithium salt fixed in the filtrate a. At this time, the recovery rate of lithium element in the ternary black powder can be further improved, while the purity of other metal elements in the ternary black powder can be improved.

[0053] In some embodiments, 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 dripping acid solution, and filtrate a and pickled black powder are obtained by filtration.

[0054] 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 element in the ternary black powder.

[0055] In some embodiments, the method further includes step S11: performing a first ion exchange resin on the filtrate a to remove impurities to obtain a lithium-containing washing solution a; and then performing a first evaporation crystallization treatment to obtain a lithium salt.

[0056] In some of the above embodiments, since some impurity ions, such as magnesium ions, calcium ions, etc., 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, which is beneficial for further processing and utilization.

[0057] In some embodiments, step S2 further includes: before roasting, washing and drying the pickled black powder in sequence, so that the moisture content of the pickled black powder is less than or equal to 20 ppm.

[0058] In some of the above embodiments, washing the pickled black powder with water can remove the acid on the surface of the pickled black powder, and then drying it to a moisture content of less than or equal to 20 ppm and then roasting it, which can further reduce the effect of moisture in the pickled black powder on the reduction process and reduce the generation of lithium carbonate, thereby further reducing the cost of recovering lithium elements.

[0059] In some embodiments, the pickling black powder is washed with water in countercurrent, which can save washing water. The water after washing the pickling black powder can be recycled to reconfigure the acid solution, which can further save costs.

[0060] 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.

[0061] 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 10ppm. 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.

[0062] In this process, in order to roast the lithium element in the pickled black powder 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 pickled black powder is controlled to be less than or equal to 20 ppm, and the roasting is required to be in a protective atmosphere with a moisture content of less than or equal to 10 ppm. + It reacts catalytically with CO2 in an aqueous environment to generate Li2CO3.

[0063] 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.

[0064] 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 pickled 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.

[0065] In some embodiments, in step S3, the second protective atmosphere is nitrogen and / or argon.

[0066] In some of the above embodiments, the second protective atmosphere not only inhibits the re-oxidation of low-price 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.

[0067] In some embodiments, 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.

[0068] In some of the above embodiments, since some impurity ions, such as magnesium ions, calcium ions, etc., 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, which is beneficial for further processing and utilization.

[0069] 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 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.

[0070] 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.

[0071] 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.

[0072] The scheme of the present application is described below in conjunction with 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.

[0073] Ternary black powder is obtained by disassembling, crushing, roasting and screening waste electrolytic black powder, and the roasting temperature is 300-400℃.

[0074] Example 1

[0075] Process flow chart Figure 1 As shown, 200 g of ternary black powder was taken and the lithium content thereof was 6.21% or 12.6 g by inductively coupled plasma spectroscopy (ICP).

[0076] 200g of ternary black powder was added to 350g of hydrochloric acid solution, the pH value of the hydrochloric acid solution was 5.3, and 24.5g of 30% hydrochloric acid was added dropwise at a speed of 100r / min. The pH value of the solution was controlled to be in the range of 4 to 6.5 during the addition process. After the addition was completed, stirring was performed for 30 minutes. After the acid washing was completed, the acid washed black powder and filtrate a were obtained by filtration. The filtrate a was filtered and then filtered. The high-valent metal ion impurities were removed from CH-93 resin to obtain lithium-containing washing solution a, and the lithium-containing washing solution a was evaporated and crystallized at 280° C. to obtain 8.18 g of lithium chloride with a purity of 99.42%.

[0077] The acid washed black powder was countercurrent washed five times with deionized water, and then dried at 320°C for 5 hours to remove the moisture. After drying, the water content was tested to be 13ppm. The dried black powder was roasted at 700°C for 3 hours using CO gas as a reducing agent under a nitrogen protective atmosphere. The mass of CO introduced during the roasting process was 25% of the mass of the ternary black powder. The moisture in the roasting atmosphere was controlled to be between 7-10ppm during the roasting process. After the roasting was completed, 400g of deionized water was used for washing and filtering under a nitrogen protective atmosphere 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 entered the subsequent wet recovery process. Filtrate b was passed through The high-valent metal ion impurities are removed from CH-93 resin to obtain lithium-containing washing solution b, and the lithium-containing washing solution b is evaporated and crystallized at 280° C. to obtain 36.35 g of lithium hydroxide with a purity of 99.67%.

[0078] 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 773.6 g, of which the amount of water used for deionized water washing of lithium hydroxide is 400 g. The purity of lithium chloride obtained is 99.42%, and the purity of lithium hydroxide obtained is 99.67%.

[0079] Example 2

[0080] 300 g of ternary black powder was taken and tested by inductively coupled plasma spectroscopy (ICP), which showed that the lithium content was 4.90%, that is, the lithium content was 14.7 g.

[0081] 300g of ternary black powder was added to 450g of hydrochloric acid solution, the pH value of the hydrochloric acid solution was 4.7, and 25g of 30% hydrochloric acid was added at a speed of 100r / min. The pH of the solution was controlled to be between 4 and 6.5 during the addition process. After the addition was completed, stirring was performed for 30 minutes. After the pickling was completed, the pickled black powder and filtrate a were obtained by filtration. The filtrate a was filtered and then filtered. The high-valent metal ion impurities were removed from CH-93 resin to obtain lithium-containing washing solution a, and the lithium-containing washing solution a was evaporated and crystallized at 280° C. to obtain 8.37 g of lithium chloride with a purity of 99.59%.

[0082] The acid washed black powder was countercurrent washed five times with deionized water, and then dried at 320°C for 5 hours to remove the moisture. After drying, the water content was tested to be 16ppm. The dried black powder was roasted at 700°C for 3 hours using CO gas as a reducing agent under a nitrogen protective atmosphere. The mass of CO introduced during the roasting process was 30% of the mass of the ternary black powder. The moisture in the roasting atmosphere was controlled to be between 7-10ppm during the roasting process. After the roasting was completed, 600g of deionized water was used to wash the powder under a nitrogen protective atmosphere 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 entered the subsequent wet recovery process. Filtrate b was passed through The high-valent metal ion impurities are removed from CH-93 resin to obtain lithium-containing washing solution b, and the lithium-containing washing solution b is evaporated and crystallized at 280° C. to obtain 44.24 g of lithium hydroxide with a purity of 99.62%.

[0083] 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%.

[0084] Example 3

[0085] Take 200g of the homologous ternary black powder of Example 1 and use inductively coupled plasma spectroscopy (ICP) to test that the lithium content is 6.21%, that is, the lithium content is 12.6g.

[0086] 200g of ternary black powder was added to 350g of hydrochloric acid solution, the pH value of the hydrochloric acid solution was 5.3, and 24.5g of 30% hydrochloric acid was added dropwise at a speed of 100r / min. The pH value of the solution was controlled to be in the range of 4 to 6.5 during the addition process. After the addition was completed, stirring was performed for 30 minutes. After the acid washing was completed, the acid washed black powder and filtrate a were obtained by filtration. The filtrate a was filtered and then filtered. The high-valent metal ion impurities were removed from CH-93 resin to obtain lithium-containing washing solution a, and the lithium-containing washing solution a was evaporated and crystallized at 280° C. to obtain 8.17 g of lithium chloride with a purity of 99.39%.

[0087] The acid washed black powder was countercurrent washed five times with deionized water, and then dried at 320°C for 5 hours to remove the moisture. After drying, the water content was tested to be 12ppm. The dried black powder was roasted at 700°C for 3 hours using CO gas as a reducing agent under a nitrogen protective atmosphere. The mass of CO introduced during the roasting process was 25% of the mass of the ternary black powder. The moisture in the roasting atmosphere was controlled to be between 11-13ppm during the roasting process. After the roasting was completed, 1500g of deionized water was used for washing under a nitrogen protective atmosphere to obtain low-valent metal compounds such as nickel, cobalt, and manganese and filtrate b. The low-valent metal compounds such as nickel, cobalt, and manganese entered the subsequent wet recovery process. Filtrate b was passed through CH-93 resin is used to remove high-valent metal ion impurities to obtain lithium-containing washing solution b, and the lithium-containing washing solution b is evaporated and crystallized at 280°C to obtain 36.99g of lithium hydroxide with a purity of 95.13%. The content of lithium carbonate doped in the obtained lithium hydroxide is 1.6g.

[0088] The comprehensive recovery rate of lithium in the entire pre-lithium extraction process is 95.17%. The amount of water used for acid washing of lithium chloride and deionized water washing of lithium hydroxide 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%, and the product is doped with lithium carbonate, and the product purity is relatively low.

[0089] This indicates that, under the same other conditions, 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.

[0090] Comparative Example 1

[0091] 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.

[0092] 200g of ternary black powder was roasted at 700°C for 3h in a nitrogen atmosphere using a CO / H2 mixed gas (water gas) as a reducing agent. The mass of the CO / H2 mixed gas introduced during the roasting process was 25% of the mass of the ternary black powder. After the roasting, 8600g of deionized water was used for washing. After washing, high-valent metal compounds such as nickel, cobalt, and manganese and washing liquid were obtained. High-valent metal compounds such as nickel, cobalt, and manganese entered the subsequent wet recovery process. 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%.

[0093] 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 that of Example 1, that is, the evaporation power consumption and evaporation electricity fee are also about 11.17 times that of Example 1.

[0094] It is explained that the method for recovering lithium in ternary black powder provided in the present application can effectively improve the recovery rate of lithium and effectively reduce costs.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope 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: washing 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 the acid-washed black powder; 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; The non-lithium active metal elements include nickel, cobalt and manganese; Step S3: washing the roasted black powder with water under a second protective atmosphere, so that the lithium oxide in the roasted black powder is converted into lithium hydroxide and 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 to 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 to 2 hours, a mass ratio of the ternary black powder to the acid solution of 1:0.1 to 5, and a stirring speed of 50 to 2000 r / min.

4. The method according to claim 1, characterized in that: 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 dripping acid solution, and filtrate a and pickled black powder are obtained by filtration.

5. The method according to claim 1, characterized in that The method further comprises step S11: performing a first ion exchange resin on the filtrate a to remove impurities 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 The step S2 further includes: before the roasting, washing the acid-washed black powder with water and drying it in sequence, so that the moisture content of the acid-washed black powder is less than or equal to 20 ppm.

7. The method according to claim 1 or 6, characterized in that: In step S2, the first protective atmosphere is at least one of nitrogen, argon and carbon dioxide, and the moisture in the first protective atmosphere is less than or equal to 10 ppm.

8. The method according to claim 1 or 6, characterized in that: In the 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.

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

10. The method according to claim 5, characterized in that The method further comprises 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 and crystallization treatment to obtain lithium hydroxide.

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