Pre-defluorination method for waste lithium battery recovery

Abstract

The invention provides a pre-defluorination method for waste lithium battery recovery. The pre-defluorination method for waste lithium battery recovery comprises the following steps: S100, obtaining waste lithium battery black powder, carrying out reduction roasting on the waste lithium battery black powder in an inert atmosphere to obtain roasted black powder, and then washing and filtering to obtain washed black powder; wherein the waste lithium battery black powder comprises LiF and LiMO2, and M comprises at least one of Ni, Co or Mn; s200, concentrated sulfuric acid is used for passivating the washed black powder, passivated black powder and hydrogen fluoride are obtained, a passivation film is attached to the surface of the passivated black powder, and defluorination treatment is conducted after passivation is completed; and S300, after the defluorination treatment is finished, a passive film on the surface of the passivated black powder is damaged, and the defluorination black powder can be obtained. According to the method, most fluorine elements in the waste lithium battery black powder can be removed in advance, a high-purity recycled product can be obtained, and meanwhile the service life of recycling equipment can be prolonged.

Description

Technical Field

[0001] The present application relates to the field of battery material recycling, and in particular, to a pre-defluorination method for recycling waste lithium batteries. Background Art

[0002] In recent years, with the development of the new energy industry, the production and sales of lithium batteries have risen rapidly, and the amount of waste lithium batteries has continued to grow. Therefore, strengthening the recycling of waste batteries can reduce my country's dependence on imported key raw materials for lithium battery manufacturing on the one hand, and bring economic benefits to recycling companies on the other hand, while playing a positive role in environmental protection.

[0003] The recycling process of waste ternary lithium batteries is usually to discharge the battery, crush, sort, and heat-treat it into waste lithium battery black powder, and then recover the valuable metal elements through acid leaching, impurity removal, extraction, lithium precipitation and other processes. During the heat treatment of waste lithium battery black powder, the battery fragments need to be pyrolyzed at about 300°C in a pyrolysis furnace under a protective atmosphere. During pyrolysis, LiPF6 in the battery electrolyte is decomposed into LiF and PF5, etc. The fluoride produced by the decomposition of the binder PVDF will also react with lithium to form LiF. LiF is a thermally stable compound with a melting point of 848°C. After pyrolysis, some fluoride ion impurities exist in the waste lithium battery black powder in the form of LiF.

[0004] The traditional ternary lithium battery recycling and defluorination process uses an acid solution for acid leaching to obtain an acid-soluble leachate, then uses P204 to extract manganese and P507 to extract nickel and cobalt, leaving fluorine in the raffinate, and then uses a defluorination resin to adsorb and remove fluoride ions in the raffinate. Since fluoride ions are extremely corrosive, this method will accelerate equipment corrosion and shorten equipment life. In addition, some fluoride ions will enter the P204 and P507 extractants, resulting in a decrease in the purity of the extracted nickel / cobalt / manganese products, and the remaining fluoride ions are not conducive to the regeneration of nickel / cobalt / manganese as precursors. Summary of the invention

[0005] The present application provides a pre-defluorination method for recycling waste lithium batteries. Through pre-defluorination, most of the fluorine elements in the black powder of waste lithium batteries can be removed in advance, and a higher purity recycled product can be obtained, while also extending the service life of the recycling equipment.

[0006] The present application provides a pre-defluorination method for recycling waste lithium batteries, which comprises the following steps: S100, obtaining waste lithium battery black powder, reduction roasting the waste lithium battery black powder under an inert atmosphere to obtain roasted black powder, and then washing and filtering to obtain washed black powder; wherein the waste lithium battery black powder comprises LiF and LiMO2, and M comprises at least one of Ni, Co or Mn; S200, passivating the washed black powder with concentrated sulfuric acid to obtain passivated black powder and hydrogen fluoride, wherein a passivation film is attached to the surface of the passivated black powder, and after the passivation is completed, defluorination treatment is performed; S300, after the defluorination treatment is completed, the passivation film on the surface of the passivated black powder is destroyed to obtain defluorinated black powder.

[0007] In the above technical scheme, after the waste lithium battery black powder is treated by the method of the present application, the fluorine element in the waste lithium battery black powder is almost removed from the waste lithium battery black powder in the form of HF, and the fluorine ion concentration in the obtained defluorinated black powder is lower than 0.01g / L, and the fluorine ion removal efficiency in the waste lithium battery black powder can reach 99%, and the recovered products such as nickel / cobalt / manganese with high purity can be obtained, and the service life of the recycling equipment can also be extended. Specifically, in the step S100 of the present application, when the waste battery black powder including LiF and LiMO2 is reduced and roasted in an inert atmosphere, high-valent elements such as Ni, Co and Mn are reduced to low-valent forms (such as metal state or low-valent oxide state), and LiF will not be reduced; therefore, the washed black powder obtained after washing and filtering the roasted black powder will have a large amount of nickel-cobalt alloy and manganese oxide with large particles and part of LiF. In step S200, when concentrated sulfuric acid is used to passivate the washed black powder, a dense metal oxide passivation film will be formed on the surface of the nickel-cobalt alloy, which can prevent the nickel-cobalt alloy from further reacting with concentrated sulfuric acid. At this time, LiF will react with concentrated sulfuric acid to generate hydrogen fluoride, which is easy to volatilize and can be well separated from the passivated black powder. In step S300, the passivation film on the surface of the passivated black powder is removed, and elements such as nickel, cobalt, and manganese can be further recovered. It should be noted that "concentrated sulfuric acid" in this application refers to an aqueous solution of sulfuric acid with a mass fraction of not less than 70%.

[0008] In a possible implementation, in step S100, the reduction roasting satisfies at least one of the following conditions: condition 1, the roasting temperature is 600°C to 800°C; condition 2, the roasting time is 1h to 3h; condition 3, the reducing agent includes at least one of carbon, hydrogen, carbon monoxide or natural gas; condition 4, the inert atmosphere includes at least one of nitrogen or argon.

[0009] In the above technical solution, the reduction roasting efficiency of waste lithium battery black powder is higher and the process is safer.

[0010] In one possible implementation, the reducing agent is carbon, and the mass ratio of the reducing agent to the black powder of waste lithium batteries is 8% to 15%; or the reducing agent is hydrogen, and the mass ratio of the reducing agent to the black powder of waste lithium batteries is 2% to 4%; or the reducing agent is at least one of carbon monoxide and natural gas, and the mass ratio of the reducing agent to the black powder of waste lithium batteries is 45% to 55%.

[0011] In the above technical scheme, the mass ratio of the reducing agent to the waste lithium battery black powder is within a specific range, which can reduce the high-priced nickel and cobalt elements in the waste lithium battery black powder to nickel and cobalt metals, and make the lithium element exist in the form of lithium compounds, which is beneficial to improving the recovery rate of lithium.

[0012] In a possible implementation, in step S100, during washing, the roasted black powder is mixed with a detergent to obtain a washing mixed solution, and the pH value of the washing mixed solution is 5.5-6.8; the detergent includes any one of acid solution and water.

[0013] In the above technical solution, by adjusting the pH during the washing process, other lithium compounds are washed into the liquid phase as much as possible, while LiF remains in the solid phase of the washed black powder, thereby ensuring that fluorine can be efficiently removed in the subsequent process and a large amount of lithium can be efficiently separated from the roasted black powder.

[0014] In a possible implementation, in step S200, when concentrated sulfuric acid is used to passivate the washing black powder, at least one of the following conditions is met: condition a, the passivation temperature is 10°C to 30°C, and the passivation time is 20min to 40min; condition b, the concentration of concentrated sulfuric acid is ≥96wt%; condition c, the mass ratio of washing black powder and concentrated sulfuric acid is 1:0.2 to 0.7, and the mass of concentrated sulfuric acid is measured in terms of the mass of H2SO4.

[0015] In the above technical solution, the washed black powder will be passivated into the passivated black powder more quickly, and the passivation film formed on the surface of the passivated black powder will be denser.

[0016] In a possible implementation, in step S200, the passivation film includes any one of the substances having the chemical formula shown in Formula I;

[0017] M x O y Formula I

[0018] Wherein, M is selected from Ni and / or Co; the value range of x is 1≤x≤3; the value range of y is 1≤y≤4; y>x.

[0019] In a possible implementation, in step S200, the defluorination treatment includes: heating the system after the passivation is completed, and using a solution containing alkaline earth metal elements to spray and absorb the volatilized hydrogen fluoride; preferably, the heating conditions include: heating to 110°C to 160°C, a heating rate of 3°C / min to 7°C / min, and keeping warm for 30min to 90min; preferably, the solution containing alkaline earth metal elements includes at least one of an alkaline earth metal hydroxide solution or an alkaline earth metal chloride solution.

[0020] In the above technical solution, the method of removing hydrogen fluoride in the system by heating is simple and low in cost; using a solution containing alkaline earth metal elements to absorb hydrogen fluoride is beneficial to protecting the environment and ensuring that hydrogen fluoride can be further recycled. Moreover, the preferred heating conditions can increase the volatilization rate of hydrogen fluoride in the system and make the hydrogen fluoride in the system volatilize more thoroughly.

[0021] In a possible implementation, in step S300, destroying the passivation film on the surface of the passivated black powder includes: after defluorination treatment, adding water and a reducing agent to the system to destroy the passivation film; preferably, the reducing agent includes at least one of hydrogen peroxide, sulfur dioxide or hydrazine; preferably, the mass of the added reducing agent is 0.002 times to 0.008 times the mass of the washed black powder in step S100; preferably, the mass of the added water is 0.2 times to 0.75 times the mass of the concentrated sulfuric acid in step S200.

[0022] In the above technical solution, adding water to the system can reduce the concentration of concentrated sulfuric acid, thereby destroying the passivation film in combination with the reducing agent. Preferably, the quality of the water and / or the quality of the reducing agent can effectively and quickly remove most of the fluorine elements in the waste lithium battery black powder.

[0023] In a possible implementation, the pre-defluorination method for recycling waste lithium batteries also includes: S400, adding sulfuric acid to the solution containing defluorination black powder obtained in step S300, performing acid leaching to obtain a defluorination acid leaching solution; removing impurities and extracting the defluorination acid leaching solution to obtain a sulfate product; the sulfate product includes at least one of nickel sulfate, cobalt sulfate, manganese sulfate, and lithium sulfate.

[0024] In a possible implementation, in step S100, after washing and filtering, a lithium-containing solution is obtained.

[0025] Beneficial effects of this application:

[0026] The present application provides a pre-defluorination method for recycling waste lithium batteries. The method provided by the present application can be used to obtain defluorinated black powder, and the fluoride ion concentration in the defluorinated black powder obtained is less than 0.01g / L. Compared with the fluoride ions in the black powder of waste lithium batteries, the removal efficiency in the defluorinated black powder can reach 99%; therefore, the method provided by the present application can not only obtain nickel / cobalt / manganese products with higher purity, but also extend the service life of the recycling equipment.

[0027] In the present application, the LiF in the black powder is first retained in the washed black powder, and then the passivation film is used to prevent the reaction of sulfuric acid with the Ni / Co / Mn elements in the washed black powder, so that sulfuric acid reacts with LiF to generate volatile HF, and the F element is separated and removed from the Ni / Co / Mn element. Specifically:

[0028] The waste batteries are heat-treated to become waste lithium battery black powder (the F element exists in the form of LiF), and the waste lithium battery black powder is subjected to reduction roasting treatment to reduce the high-valent elements Ni / Co / Mn in the waste lithium battery black powder to low-valent elements (in the form of metal or low-valent oxide). After reduction roasting, the nickel-cobalt alloy and manganese oxide form larger particles, and LiF is located on the surface or between these particles. Then, concentrated sulfuric acid is used to form a dense nickel-cobalt metal oxide passivation film on the surface of the nickel-cobalt alloy (or on the surface of the particles) to "protect" the nickel and cobalt elements from further reaction with sulfuric acid, while LiF reacts with concentrated sulfuric acid to generate volatile HF, and the F element is removed by heating and spraying with alkali solution.

[0029] In the present application, after F is removed, concentrated sulfuric acid is diluted by adding water to destroy the passivation film in coordination with the reducing agent. The mass of the effective substance in the reducing agent is 0.002 to 0.008 times the mass of the washing black powder, which can not only effectively activate the metal that is already in a passivated state, but also significantly shorten the time used for subsequent acid leaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A process flow chart of the pre-defluorination method for recycling waste lithium batteries provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0033] The current new energy industry is developing rapidly, so the recycling of waste lithium batteries is particularly important. However, in the existing technology, it is difficult to separate fluoride ions from waste lithium batteries at the beginning of the process when recycling waste lithium batteries; this will not only corrode the recycling equipment, but also reduce the purity of the recovered nickel / cobalt / manganese products. To achieve the above purpose, the present application provides a pre-defluorination method for recycling waste lithium batteries, which includes the following steps:

[0034] Before pre-defluorination of the recycled waste lithium batteries, the present application generally discharges, crushes, sorts, and heat-treats the waste ternary lithium batteries into waste lithium battery black powder, which usually contains LiF and LiMO2, wherein M is selected from any one of Ni, Co, and Mn; and then performs the following operations:

[0035] S100, reducing and roasting the waste lithium battery black powder under an inert atmosphere, and then washing and filtering it.

[0036] In this step, the operation of reduction roasting is generally to add a reducing agent to the waste lithium battery black powder under a protective atmosphere (i.e., an inert atmosphere) for roasting, so that roasted black powder can be obtained, and the roasted black powder usually contains nickel cobalt metal, manganese oxide, lithium compound, and LiF, etc.; then the roasted black powder is washed to obtain a solution containing lithium compounds and washed black powder (containing nickel cobalt metal and manganese oxide, and LiF, etc.), and then filtered, the filtrate is the solution containing lithium compounds, and the obtained solid is washed black powder. This step will preferentially separate the lithium compound before extraction. Compared with the traditional extraction of nickel / cobalt / manganese and then lithium precipitation, this step can reduce the mechanical inclusion loss of lithium in the extraction process and improve the recovery rate of lithium.

[0037] Specifically, in this step, during reduction roasting, the gas used to provide a protective atmosphere is usually at least one of nitrogen or argon, the reducing agent during roasting is C, H2, CO, NG (natural gas) or a mixed component thereof, the roasting temperature is 600-800°C, and the roasting time is 1-3h. For example, the roasting temperature can be 600°C, 650°C, 700°C, 750°C, 800°C, etc., or within a range consisting of any two of the above values; the roasting time can be 1h, 1.5h, 2h, 2.5h, 3h, etc., or within a range consisting of any two of the above values. In this process, the roasting temperature is within the range of 600-800°C, which can fully reduce the black powder of waste lithium batteries, so that the concentrated sulfuric acid added subsequently can fully react with LiF to achieve defluorination.

[0038] Further, in the above step S100, when the reducing agent is C, the ratio of the mass of the reducing agent to the mass of the waste lithium battery black powder is 8% to 15%, specifically 8%, 9%, 10%, 12%, 15%, etc., or in the range of any two of the above values; or when the reducing agent is H2, the ratio of the mass of the reducing agent to the mass of the waste lithium battery black powder is 2% to 4%, specifically 2%, 2.5%, 3%, 3.5%, 4%, etc., or in the range of any two of the above values; or when the reducing agent is CO, NG and a mixture thereof, the ratio of the mass of the reducing agent to the mass of the waste lithium battery black powder is 45% to 55%, specifically 45%, 48%, 50%, 52%, 55%, etc., or in a range consisting of any two of the above values; in this step, controlling the amount of the reducing agent can reduce the high-priced nickel and cobalt elements in the waste lithium battery black powder to nickel and cobalt metals, and make the lithium element exist in the form of a lithium compound (for example, at least one of Li2O, LiOH, Li2CO3, etc.), which can be dissolved in the washing liquid for separation and recovery.

[0039] In addition, in this step, countercurrent washing is usually used for washing, and the number of washing times is 3 to 10 times, specifically 3 times, 5 times, 7 times, 8 times, 10 times, etc., or within a range consisting of any two of the above values; the washing liquid is deionized water or a slightly acidic liquid, and the slightly acidic liquid component is sulfuric acid or hydrochloric acid. When washing with a slightly acidic liquid, the pH of the washing liquid is maintained at 5.5 to 6.8 during the washing process, so that LiF remains in the solid phase, which is convenient for subsequent defluorination treatment.

[0040] S200, using concentrated sulfuric acid to passivate the washing black powder into passivated black powder and hydrogen fluoride, and then performing defluorination treatment.

[0041] In this step, when the washing black powder is passivated with concentrated sulfuric acid, a dense metal oxide passivation film will form on the surface of the nickel-cobalt alloy, preventing the concentrated sulfuric acid and the nickel-cobalt alloy from further reacting; and the fluoride ions in the washing black powder will react with the concentrated sulfuric acid to generate hydrogen fluoride, which is easy to volatilize and can easily escape and separate from the passivation system after heating.

[0042] Specifically, in this step, the ratio of the mass of the washed black powder to the mass of the added concentrated sulfuric acid is 1:0.2-0.7 (based on the weight of the concentrated sulfuric acid itself), the passivation temperature is 10-30°C, the passivation time is 20-40min, and the concentration of the concentrated sulfuric acid used is 96% or more. Specifically, the mass ratio of the concentrated sulfuric acid for washing the black powder can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, etc., or a range consisting of any two of the above, the passivation temperature can be 10°C, 15°C, 20°C, 25°C, 30°C, etc., or a range consisting of any two of the above values, and the passivation time can be 20min, 25min, 30min, 35min, 40min, etc., or a range consisting of any two of the above values.

[0043] In this step, during passivation, the nickel-cobalt metal forms a dense layer of nickel-cobalt metal oxide M on the metal surface under the action of concentrated sulfuric acid. x O y (M is Ni and / or Co, 1≤x≤3, 1≤y≤4, and y>x) passivation film is formed to prevent concentrated sulfuric acid from further reacting with the nickel-cobalt alloy. After the passivation film is formed, concentrated sulfuric acid will react with LiF in the washing black powder to generate HF, rather than reacting with the nickel-cobalt metal and / or its oxides in the washing black powder to generate acid leaching solution. In addition, during the passivation process, manganese oxide in the washing black powder also reacts with concentrated sulfuric acid to generate manganese sulfate, and manganese elements exist in the form of manganese sulfate in the subsequent process.

[0044] In addition, after the passivation is completed, the defluorination treatment in this step is generally to heat the system after the passivation is completed, and at the same time, the alkali solution is sprayed to absorb the hydrogen fluoride volatilized due to the temperature increase to obtain a fluoride residue. During heating, the passivated system is usually heated to 110-160°C for defluorination, the insulation time is 30-90 minutes, and the heating rate is 3-7°C / min. Specifically, the temperature can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, etc. or a range consisting of any two of the above values, the insulation time can be 30min, 50min, 70min, 80min, 90min, etc. or a range consisting of any two of the above values, and the heating rate can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, etc. or a range consisting of any two of the above values.

[0045] In addition, the alkali solution used for spraying and absorbing hydrogen fluoride can be at least one of alkaline earth metal hydroxides and alkaline earth metal chlorides, which reacts with hydrogen fluoride to form a solid phase precipitate.

[0046] S300, destroying the passivation film on the surface of the passivation black powder to obtain the defluorinated black powder.

[0047] In this step, the sulfuric acid in the system is diluted and used in combination with a reducing agent to perform an acid leaching to destroy the passivation film on the surface of the passivation black powder, thereby obtaining the defluorination black powder; after losing the protection of the passivation film, a small amount of defluorination black powder may dissolve. Subsequently, the defluorination black powder is subjected to a secondary acid leaching to dissolve it completely, thereby efficiently recovering the metals in the waste lithium batteries.

[0048] Specifically, this step is usually to add water to the system containing the passivation black powder to reduce the concentration of sulfuric acid in the system, and before adding water, the temperature of the system containing the passivation black powder is reduced to 40-60°C, which can be 40°C, 45°C, 50°C, 55°C, 60°C, etc. or a range consisting of any two of the above values; the initial amount of water added is 0.2-0.75 times the mass of the concentrated sulfuric acid in step S200, which can be 0.2 times, 0.3 times, 0.4 times, 0.5 times, 0.6 times, 0.7 times, 0.75 times or a range consisting of any two of the above values, so that the diluted sulfuric acid solution is highly active and corrosive in this concentration range, and can cooperate with the reducing agent to destroy the passivation film and activate the metal that is already in the passivation state. And at this temperature, the amount of water added can be effectively controlled, and the passivation film is destroyed and the acid leaching is accelerated under the conditions of adding water dilution from 40-60°C to 70-95°C, which can effectively shorten the heating time and reduce energy consumption.

[0049] In addition, in this step, a reducing agent is usually added after the initial water replenishment is completed. The mass of the added reducing agent (i.e., the mass of the reducing substance) is 0.002 to 0.008 times the mass of the washed black powder in step S100, and can be specifically 0.002 times, 0.003 times, 0.004 times, 0.006 times, 0.008 times, or a range consisting of any two of the above values. The reducing agent includes a mixture of one or more of hydrogen peroxide, sulfur dioxide, hydrazine, etc. The added reducing agent can synergistically destroy the passivation film with the diluted acid, and convert the high-valent metal in the passivation film into a divalent metal (NiO, CoO). The amount of reducing agent added is within the above range, which can not only achieve the effect of synergistically destroying the passivation film, but also help to shorten the subsequent acid leaching time, save the amount of reducing agent, and avoid waste. After the reducing agent is supplemented in this step, the temperature is raised, and the whole system is kept at 70-95°C for 10-30 minutes to destroy the passivation film and accelerate the acid leaching; specifically, the temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc. or a range consisting of any two of the above values; the holding time can be 10min, 15min, 20min, 25min, 30min, etc. or a range consisting of any two of the above values.

[0050] The defluorination black powder contains a large amount of nickel, cobalt and manganese. In order to further recover these metal elements, in some embodiments of the present application, the solution containing the defluorination black powder is usually further processed as follows:

[0051] S400, adding sulfuric acid to the solution containing the defluorination black powder, performing secondary acid leaching, and obtaining a defluorination acid leaching solution.

[0052] In this step, dilute sulfuric acid is generally used when performing secondary acid leaching, so that the valuable elements in the defluorination black powder are converted into corresponding salts, such as nickel sulfate, cobalt sulfate, and manganese sulfate, which are convenient for subsequent extraction and recovery. The specific method can be selected by technicians in this field as needed, such as supplementing pure water + concentrated sulfuric acid, or supplementing pure water + dilute sulfuric acid, or directly supplementing dilute sulfuric acid. The method of concentrated sulfuric acid + pure water is specifically introduced below.

[0053] Pure water and concentrated sulfuric acid with a concentration of more than 96% are added for secondary acid leaching. The amount of pure water added for the secondary acid leaching is 4 to 6 times the mass of the washed black powder, and the amount of concentrated sulfuric acid added is 0.35 to 1.1 times the mass of the nickel, cobalt and manganese compounds in the washed black powder. In addition, in this step, the temperature of the secondary acid leaching is 70 to 95°C, the acid leaching time is 12 hours, the pH of the acid leaching solution is 2 to 4 after the acid leaching, and the concentration of nickel, cobalt and manganese metal elements after the acid leaching is about 110g / L.

[0054] The defluorination acid leaching solution obtained in this step will contain a large amount of nickel, cobalt, and manganese. These metal elements are mostly present in the solution in the form of sulfates. The defluorination acid leaching solution can be subsequently subjected to impurity removal and extraction operations to obtain products corresponding to the Ni / Co / Mn elements. The present application uses a combination of pyrometallurgy and wet metallurgy to add concentrated sulfuric acid to the washing black powder at room temperature to generate Mn on the surface of the nickel-cobalt alloy. x O y (M=Ni / Co, x=1~3, y=1~4, and y>x) passivation film, and then heat up to 110℃~160℃ to remove HF volatiles produced by the reaction of LiF and concentrated sulfuric acid by alkali solution spray absorption. After the temperature is increased for defluorination, pure water and reducing agent are added, and diluted sulfuric acid and a small amount of reducing agent are used for an acid leaching operation to destroy the passivation film, and then a second acid leaching is performed to dissolve all the defluorination black powder to obtain a defluorination acid leaching solution. The fluoride ion concentration of the defluorination acid leaching solution obtained by this process is lower than 0.01g / L, and the fluoride ion removal efficiency reaches 99%, realizing the efficient removal of fluoride ions before nickel / cobalt / manganese extraction. The defluorination acid leaching solution is used for subsequent impurity removal / extraction operations to reduce corrosion to subsequent equipment and reduce impurities in subsequent products.

[0055] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0056] The method for obtaining black powder is a conventional technology in the field. A possible method is introduced below, which is of course not limited to this. The specific process conditions in the following method can be selected by those skilled in the art according to actual needs.

[0057] The method for obtaining black powder from NCM811 type waste lithium battery is as follows: the waste battery is discharged, disassembled, and then crushed to obtain positive electrode material layer powder. The positive electrode material layer powder is pre-treated by passing air in a rotary kiln at 300℃~500℃ to remove the residual conductive agent and adhesive therein, and the pre-treatment time is 1~4h, and then the battery black powder is obtained by screening.

[0058] Example 1

[0059] This embodiment provides a pre-defluorination method for recycling waste lithium batteries, which comprises the following steps:

[0060] (1) 1000 g of NCM811 model waste lithium battery black powder was added with 150 g of carbon (the mass of carbon was 15% of the mass of black powder) as a reducing agent under a nitrogen protection atmosphere to perform reduction roasting to obtain roasted black powder. The reduction roasting temperature was 700° C. and the reduction roasting time was 2 h.

[0061] Then, the roasted black powder is counter-currently washed 7 times with a sulfuric acid solution, and the pH value of the solution is maintained between 5.5 and 6.8 during the washing process. After washing, the washed black powder is dried to obtain washed black powder.

[0062] (2) 120 g of washed black powder was taken, and its fluorine content was calculated to be 0.76% by fluorine electrode potential method. 24.5 g of concentrated sulfuric acid with a concentration of 98% was added thereto, and passivation was carried out at 20° C. for 30 min. After the passivation, the temperature was raised to 110° C. at 5° C. / min and kept at this temperature for 80 min to volatilize the generated hydrogen fluoride to remove the fluoride ions therein, and the volatilized hydrogen fluoride was sprayed and absorbed by a spray tower, and the alkali solution used in the spray tower was calcium hydroxide.

[0063] (3) After the defluorination is completed, the passivated mixed system is cooled to 60°C and then 10g of water is added, followed by 3g of 8wt% hydrogen peroxide (the mass of the effective substance H2O2 in the hydrogen peroxide is 0.002 times the mass of the washed black powder). After adding the hydrogen peroxide, the mixture is kept at 95°C for 10 minutes to remove the passivation film.

[0064] (4) After the passivation film is removed, 650 g of pure water is added, and 97 g of 98% concentrated sulfuric acid is supplemented, and the temperature is kept at 95°C for 120 minutes for secondary acid leaching. After the secondary acid leaching, the defluorination acid leaching solution is obtained. The fluoride ion content is 0.008 g / L and the fluoride ion removal efficiency is 99.21% as determined by the fluoride electrode potential method.

[0065] Example 2

[0066] This embodiment provides a pre-defluorination method for recycling waste lithium batteries, which comprises the following steps:

[0067] (1) 1000g of NCM111 model waste lithium battery black powder was reduced and roasted by adding 90g of carbon (the mass of carbon was 9% of the mass of black powder) as a reducing agent under a nitrogen atmosphere, thereby obtaining roasted black powder. The temperature of reduction roasting was 700°C and the roasting time was 2h.

[0068] Then, the roasted black powder is counter-currently washed 7 times with a hydrochloric acid solution, and the pH value of the solution is maintained between 5.5 and 6.8 during the washing process. After washing, the washed black powder is dried to obtain washed black powder.

[0069] (2) 150 g of washed black powder was taken, and its fluorine content was calculated to be 0.59% by fluorine electrode potential method. 100 g of concentrated sulfuric acid with a concentration of 98% was added thereto, and passivation was performed at 20° C. for 30 min. After the passivation, the temperature was raised to 110° C. at 5° C. / min and kept at this temperature for 80 min to volatilize the generated hydrogen fluoride to remove the fluoride ions therein, and the volatilized hydrogen fluoride was sprayed and absorbed by a spray tower, and the alkali solution used in the spray tower was calcium hydroxide.

[0070] (3) After the defluorination is completed, the passivated mixed system is cooled to 60°C and then 66.5g of water is added, followed by 15g of 8% hydrogen peroxide (the mass of the effective substance H2O2 in the hydrogen peroxide is 0.008 times the mass of the washed black powder). After adding the hydrogen peroxide, the mixture is kept at 95°C for 10 minutes to remove the passivation film.

[0071] (4) After the passivation film is removed, 760 g of pure water is added, and 52 g of 98% concentrated sulfuric acid is supplemented, and the acid leaching operation is carried out at 95°C for 120 minutes. After the acid leaching, the defluorination acid leaching solution is obtained. The fluoride ion content is 0.006 g / L and the fluoride ion removal efficiency is 99.24% as determined by the fluoride electrode potential method.

[0072] Example 3

[0073] This embodiment provides a pre-fluorination method for recycling waste lithium batteries. The steps are different from those in Example 1 in that:

[0074] In step (3), 12 g of 8 wt% hydrogen peroxide is added (the mass of the effective substance H2O2 in the hydrogen peroxide is 0.008 times the mass of the washed black powder).

[0075] In this embodiment, a defluorination acid leaching solution was obtained after the acid leaching was completed. The fluoride ion content of the defluorination acid leaching solution was 0.007 g / L as measured by the fluoride electrode potential method, and the fluoride ion removal efficiency was 99.31%.

[0076] Example 4

[0077] This embodiment provides a pre-defluorination method for recycling waste lithium batteries, which comprises the following steps:

[0078] (1) Same as step (1) of Example 1.

[0079] (2) 120 g of the washed black powder in Example 1 was taken, and the fluorine content thereof was calculated to be 0.76% by fluorine electrode potential method. 24.5 g of concentrated sulfuric acid with a concentration of 98% was added thereto, and the mixture was passivated at 20° C. for 30 min. After the passivation, the temperature was raised to 110° C. at a rate of 5° C. / min and kept at that temperature for 80 min to volatilize the generated hydrogen fluoride to remove the fluoride ions therein, and the volatilized hydrogen fluoride was sprayed and absorbed by a spray tower, and the alkali solution used in the spray tower was calcium hydroxide.

[0080] (3) After the defluorination is completed, the passivated mixed system is cooled to 60°C and then 10g of water is added, followed by 2.7g of 8wt% hydrogen peroxide (the mass of the effective substance H2O2 in the hydrogen peroxide is 0.0018 times the mass of the washed black powder). After adding the hydrogen peroxide, the mixture is kept at 95°C for 10 minutes to remove the passivation film.

[0081] (4) After the removal of the passivation film, 650 g of pure water was added, and 97 g of 98% concentrated sulfuric acid was supplemented. The acid leaching operation was carried out at 95°C for 120 min. After the acid leaching was completed, it was found that there were still insoluble residues in the acid leaching solution. After the acid leaching time was extended for 40 min, there was no solid insoluble matter in the acid leaching solution, and the acid leaching was completed.

[0082] After the acid leaching, the defluorination acid leaching solution was obtained. The fluoride ion content was 0.0083 g / L and the fluoride ion removal efficiency was 99.18% as determined by the fluoride electrode potential method.

[0083] Compared with Example 4, the mass of the active substance H2O2 in the hydrogen peroxide added in the process of destroying the passivation film at the end of defluorination is reduced from 0.002 times the mass of the washing black powder to 0.0018 times. Although the defluorination effect is similar, the acid leaching time is increased from 120min to 160min, which greatly prolongs the acid leaching time.

[0084] Example 5

[0085] This embodiment provides a pre-fluorination method for recycling waste lithium batteries, which comprises the following steps:

[0086] (1) Same as step (1) of Example 1.

[0087] (2) Same as step (2) of Example 1.

[0088] (3) After the defluorination is completed, the passivated mixed system is cooled to 60°C and then 10g of water is added, followed by 13.5g of 8wt% hydrogen peroxide (the mass of the effective substance H2O2 in the hydrogen peroxide is 0.009 times the mass of the washed black powder). After adding the hydrogen peroxide, the mixture is kept at 95°C for 10 minutes to remove the passivation film.

[0089] (4) After the removal of the passivation film, 650 g of pure water was added, and 97 g of 98% concentrated sulfuric acid was supplemented. The acid leaching operation was carried out at 95° C. and no solid insoluble matter was observed in the solution at 118 minutes.

[0090] After the acid leaching, the defluorination acid leaching solution was obtained. The fluoride ion content was 0.0082 g / L and the fluoride ion removal efficiency was 99.19% as determined by the fluoride electrode potential method.

[0091] Compared with Example 5, the mass of the active substance H2O2 in the hydrogen peroxide added in the process of destroying the passivation film at the end of defluorination is increased from 0.002 times to 0.009 times of the original mass of the washing black powder, and the defluorination effect is similar. The acid leaching time is reduced from 120min to 118min. The reduction of the acid leaching time is limited, and the increase in the amount of hydrogen peroxide increases the material waste to a certain extent.

[0092] Comparative Example 1

[0093] This comparative example provides a pre-fluorination method for recycling waste lithium batteries, which comprises the following steps:

[0094] 120g of washed black powder in Example 1 was taken, without defluorination treatment, and 660g of pure water and 122g of 98% concentrated sulfuric acid were directly added, and the acid leaching operation was carried out at 95°C for 180min. After the acid leaching, the acid leaching solution was obtained, and the fluoride ion content thereof was measured by fluorine electrode potential method to be 0.61g / L.

[0095] Compared with Comparative Example 1, the fluoride ion concentration in the acid leaching solution of Example 1 was reduced from 0.61 g / L to 0.008 g / L, and the fluoride ion removal effect was obvious.

[0096] The above are only embodiments of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A pre-defluorination method for recycling waste lithium batteries, characterized in that: It includes the following steps: S100, obtaining waste lithium battery black powder, reducing and roasting the waste lithium battery black powder under an inert atmosphere to obtain roasted black powder, and then washing and filtering to obtain washed black powder; Wherein, the waste lithium battery black powder includes LiF and LiMO2, and M includes at least one of Ni, Co or Mn; S200, passivating the washed black powder with concentrated sulfuric acid to obtain passivated black powder and hydrogen fluoride, wherein a passivation film is attached to the surface of the passivated black powder, and after the passivation is completed, defluorination treatment is performed; S300, after the defluorination treatment is completed, the passivation film on the surface of the passivation black powder is destroyed to obtain the defluorinated black powder.

2. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S100, the reduction roasting satisfies at least one of the following conditions: Condition 1: Calcination temperature is 600℃~800℃; Condition 2: calcination time is 1h to 3h; Condition 3: The reducing agent includes at least one of carbon, hydrogen, carbon monoxide or natural gas; Condition 4: The inert atmosphere includes at least one of nitrogen or argon.

3. The pre-defluorination method for recycling waste lithium batteries according to claim 2, characterized in that: The reducing agent is carbon, and the mass ratio of the reducing agent to the waste lithium battery black powder is 8% to 15%; Or, the reducing agent is hydrogen, and the mass ratio of the reducing agent to the waste lithium battery black powder is 2% to 4%; Alternatively, the reducing agent is at least one of carbon monoxide and natural gas, and the mass ratio of the reducing agent to the waste lithium battery black powder is 45% to 55%.

4. The pre-defluorination method for recycling waste lithium batteries according to any one of claims 1 to 3, characterized in that: In step S100, during the washing, the roasted black powder is mixed with a detergent to obtain a washing mixed solution, wherein the pH value of the washing mixed solution is 5.5 to 6.8; The detergent includes any one of acid solution and water.

5. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S200, when the concentrated sulfuric acid is used to passivate the washing black powder, at least one of the following conditions is satisfied: Condition a: passivation temperature is 10℃~30℃, and passivation time is 20min~40min; Condition b: the concentration of the concentrated sulfuric acid is ≥ 96wt%; Condition c: the mass ratio of the washing black powder to the concentrated sulfuric acid is 1:0.2-0.7, and the mass of the concentrated sulfuric acid is calculated as the mass of H2SO4.

6. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S200, the passivation film includes any one of the substances having the chemical formula shown in Formula I; M x O y Formula I Wherein, M is selected from Ni and / or Co; The value range of x is 1≤x≤3; The value range of y is 1≤y≤4; y>x.

7. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S200, the defluorination treatment includes: The passivated system is heated, and a solution containing alkaline earth metal elements is sprayed to absorb the volatilized hydrogen fluoride; Preferably, the heating conditions include: heating to 110°C to 160°C, heating rate of 3°C / min to 7°C / min, and keeping warm for 30min to 90min; Preferably, the solution containing alkaline earth metal elements includes at least one of an alkaline earth metal hydroxide solution or an alkaline earth metal chloride solution.

8. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S300, destroying the passivation film on the surface of the passivation black powder includes: After the defluorination treatment, water and a reducing agent are added to the system containing the passivation black powder to destroy the passivation film. Preferably, the temperature is 70° C. to 95° C. and the time is 10 min to 30 min. Preferably, the reducing agent comprises at least one of hydrogen peroxide, sulfur dioxide or hydrazine; Preferably, the mass of the added reducing agent is 0.002 to 0.008 times the mass of the washed black powder in step S100; Preferably, the mass of the added water is 0.2 to 0.75 times the mass of the concentrated sulfuric acid in step S200.

9. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: Also includes: S400, adding sulfuric acid to the solution containing the defluorination black powder obtained in step S300 to perform acid leaching to obtain a defluorination acid leaching solution; The defluorinated acid leaching solution is subjected to impurity removal and extraction to obtain a sulfate product; The sulfate product includes at least one of nickel sulfate, cobalt sulfate, manganese sulfate and lithium sulfate.

10. The pre-defluorination method for recycling waste lithium batteries according to claim 1, characterized in that: In step S100, after washing and filtering, a lithium-containing solution is obtained.

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