A method for one-step chlorination recovery and lithium extraction of waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue.

Abstract

This invention relates to a one-step chlorination method for recovering lithium from waste lithium iron phosphate battery black powder and removing copper and aluminum from the lithium extraction residue, belonging to the field of waste battery recycling technology. Specifically, the method involves mixing waste lithium iron phosphate battery black powder with an acidic deionized water solution in a closed reactor, introducing chlorine gas, and selectively extracting lithium and removing copper and aluminum impurities through a one-step chlorination reaction by controlling the initial temperature, maximum temperature rise, reaction pressure, and reaction time. Lithium enters the liquid phase as LiCl through the chlorination reaction, while iron and phosphorus remain in the solid phase as FePO4. Copper and aluminum are removed in the acidic environment and Fe... 3+ After dissolving under the action, it enters the liquid phase. Therefore, this invention has the advantages of high yield, short process and low cost, and solves the problems of large lithium loss and difficult impurity removal in the prior art.

Description

Technical Field

[0001] This application belongs to the field of waste battery recycling technology, specifically relating to a method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction slag. Background Technology

[0002] Lithium iron phosphate (LFP) batteries have been widely used in pure electric vehicles, electrochemical energy storage, and other fields due to their high safety, long cycle life, and low cost. With the widespread use of LFP batteries, an increasing number of end-of-life batteries are also being produced. Retired LFP batteries typically undergo discharge, disassembly, crushing, and sorting processes to produce battery black powder. This black powder is then processed to recover elements such as lithium, phosphorus, and iron.

[0003] Currently, the recycling and processing of lithium iron phosphate battery black powder mostly adopts a wet process, which involves leaching lithium through an acid-hydrogen peroxide reaction. This leads to the dissolution and leaching of iron and phosphorus, and fundamentally alters the structure, morphology, particle size, and specific surface area of ​​the iron phosphate. On the one hand, although most of the lithium is leached and enriched in the lithium leaching solution, large amounts of iron, phosphorus, copper, aluminum, etc., also enter the lithium leaching solution. This not only results in high acid consumption and energy consumption, but also in significant lithium loss due to the impurity removal process, further increasing costs and making it technically uneconomical.

[0004] For example, patent publication number CN118651832B discloses a method and its application for recovering battery-grade iron phosphate and lithium salt from lithium iron phosphate waste, including the following steps: S100, dissolving lithium iron phosphate waste with phosphoric acid solution, filtering to obtain waste dissolution solution; S200, adding acid solution and oxidant to waste dissolution solution to obtain crystallization stock solution; S300, diluting the crystallization stock solution with water to a pH value of 1.0 to 1.5, crystallizing at high temperature to obtain hydrated iron phosphate and lithium-containing filtrate; S400, calcining hydrated iron phosphate to obtain battery-grade iron phosphate; S500, removing water from lithium-containing filtrate to obtain solution a, recycling solution a to dissolve lithium iron phosphate waste, concentrating to obtain lithium salt. The above method uses phosphoric acid solution as the leaching solvent, which can achieve efficient recovery of all elements, including Li, Fe, and P. However, this method is a multi-step cyclic process, and phosphoric acid does not participate in the main reaction. Therefore, the reaction requires the addition of oxidants such as acid and hydrogen peroxide. At the same time, copper and aluminum impurities may remain in the solid or liquid phase, requiring further processing.

[0005] In recent years, a novel process technology has been developed for the gas-solid chlorination of retired lithium iron phosphate batteries, prioritizing lithium extraction and then recycling the lithium extraction slag after impurity removal. This technology has the advantages of relatively simple process, low impurity content in lithium-containing brine, high lithium yield, and low lithium extraction cost. Furthermore, the lithium extraction slag retains the characteristic of preserving the olivine structure of iron phosphate, possessing the potential for low-cost direct recycling. However, the gas-solid chlorination reaction is fast, making it prone to localized overreactions leading to side reactions; simultaneously, the mixing of copper and aluminum with the iron phosphate in the slag phase presents challenges for subsequent iron phosphate impurity removal.

[0006] Therefore, there is an urgent need to develop a high-yield, short-process, and low-cost waste lithium iron phosphate battery black powder recycling technology to achieve high-value recycling and reuse of lithium and iron phosphate. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a one-step chlorination recovery and lithium extraction method for waste lithium iron phosphate battery black powder and a method for removing copper and aluminum from lithium extraction residue. The core of this invention is to remove copper and aluminum impurities while efficiently extracting lithium, and it features high yield, short process, and low cost.

[0008] The basic principle of this invention is as follows:

[0009] In a closed reactor, M kg of waste lithium iron phosphate battery black powder is mixed with V L of aqueous solution, and V L of chlorine gas is continuously introduced while maintaining a positive pressure P in the reactor. The aqueous solution is an acidic deionized water solution. The initial temperature of the mixture after mixing the waste lithium iron phosphate battery black powder with the deionized water solution is T_st. The maximum allowable temperature rise in the reactor during the reaction is ΔT, and the total reaction time is t. At this point, a selective chlorination lithium extraction reaction will occur, and its chemical reaction mechanism is as follows:

[0010] ;

[0011] This method enables the extraction of lithium from waste lithium iron phosphate battery black powder. The generated LiCl is easily soluble in water and thus enters the liquid phase, while the generated FePO4 is poorly soluble in water and thus remains in the solid phase.

[0012] Simultaneously, chlorine dissolves in water, and a chemical reaction occurs between chlorine and water. The chemical reaction mechanism is as follows:

[0013] ;

[0014] Chlorine dissolves in water and reacts with water, as shown in reaction (2), making the aqueous solution acidic. At 20°C, the pH value of the saturated aqueous solution is about 1.5.

[0015] For impurity aluminum, the following two reactions occur, and their reaction mechanisms are as follows:

[0016] ;

[0017] ;

[0018] The above reaction formulas (3) and (4) cause the aluminum impurities to be leached from the solid lithium extraction slag and enter the liquid phase, thereby achieving the removal of aluminum impurities from the lithium extraction slag.

[0019] For impurity copper, the following reaction occurs, and the reaction mechanism is as follows:

[0020] ;

[0021] The above reaction formula (5) causes the copper impurities to be leached from the solid lithium extraction slag and enter the liquid phase, thereby achieving the removal of copper impurities from the lithium extraction slag.

[0022] Fe generated by reactions (4) and (5) 2+ In aqueous solution, it is oxidized again to trivalent form upon contact with chlorine gas. The reaction mechanism is as follows:

[0023] ;

[0024] The presence of the above reaction formula (6) results in Fe in the aqueous solution 3+ It can always remain in existence, thereby promoting the progress of reaction (4) and reaction (5);

[0025] Among them, the initial Fe in the aqueous solution 3+ The presence of FePO4 comes from the trace dissolution of FePO4 in acidic aqueous solution. Alternatively, a small amount of water-soluble divalent or trivalent iron salts, such as FeCl3 or FeCl2, can be added first.

[0026] The lithium chloride extraction reaction (reaction formula (1)) is an exothermic reaction, and side reactions that are detrimental to selective lithium extraction will occur under excessively high temperatures. Therefore, it is necessary to limit the maximum allowable temperature rise ΔT during the reaction. At the same time, the initial temperature T_st affects the rate of the lithium chloride extraction reaction. If the temperature is too low, the lithium chloride extraction reaction will take too long. In summary, the initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction satisfy the following conditions: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT≤80℃.

[0027] The volume of the aqueous solution, V_H2O, is limited by the maximum temperature rise ΔT, i.e. Where Q is the total heat released by the reaction, in kJ; M is the mass of waste lithium iron phosphate battery black powder, in kg; that is, the minimum amount of aqueous solution added must meet the requirements of the lithium chloride extraction reaction formula (1) to prevent overheating; on the other hand, in order to reduce water consumption, reduce cost input, and ensure good fluidity and low viscosity of the slurry, the liquid-solid ratio should be controlled to be less than 10 and greater than 3, that is .

[0028] The amount of chlorine introduced depends on four factors: first, the lithium chlorination reaction (1); second, the aluminum removal reaction (4); third, the copper removal reaction (5); and fourth, the solubility of chlorine in water. Therefore, theoretically, the total amount of chlorine required, V_Cl2, is... Considering both ensuring a complete reaction and cost savings, the excess chlorine coefficient is 1.2, therefore satisfying: , where R Li It is the percentage of lithium by mass in the black powder from waste lithium iron phosphate batteries; R Al It is the percentage by mass of aluminum in the black powder from waste lithium iron phosphate batteries; R Cu It is the percentage of copper by mass in the black powder from waste lithium iron phosphate batteries.

[0029] The total reaction time t satisfies the condition: 30 minutes ≤ t ≤ 72 hours, in order to achieve efficient lithium extraction and full dissolution of copper and aluminum impurities, while also taking into account production efficiency.

[0030] The reactor pressure is positive pressure P and satisfies: 10Pa≤P≤10kPa. If the pressure is too low, it will not be conducive to the full dissolution of chlorine in water and its reaction with the black powder from waste lithium iron phosphate batteries. If the pressure is too high, it will not be conducive to the sealing of the equipment and the prevention of chlorine leakage.

[0031] The pH value of acidic deionized water solution should meet the following requirements: 0.3 ≤ pH ≤ 1.5. If the pH value is too high, the acidity will decrease, which is not conducive to the dissolution reaction of copper and aluminum. If the pH value is too low, the solubility of FePO4 will increase.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] (1) High yield: In traditional wet process, the loss of iron and phosphoric acid is mainly in two aspects. First, some iron and phosphorus will enter the lithium leaching solution and be removed as impurities in the subsequent purification process. Second, the liquid phase impurity removal process after all the lithium residue is dissolved in acid will also inevitably lead to the loss of iron and phosphorus. The yield of traditional wet process iron phosphate is generally 90%. However, this invention selectively extracts lithium through gas-liquid-solid three-phase chlorination. On the one hand, it can achieve the chlorination leaching of more than 99% of lithium in lithium iron phosphate. At the same time, iron and phosphorus do not participate in the chlorination reaction. More than 85% of phosphorus and iron are still retained in the form of olivine structure FePO4. After the phosphorus and iron in the leaching solution are separated by impurity removal, they are then recovered by recrystallization in the form of FePO4•2H2O. The yield of regenerated iron phosphate can reach 98%. Moreover, the removal of copper and aluminum impurities is also one of the core objectives and is achieved simultaneously in the main reaction step. The acidic environment generated by chlorine and the Fe generated by the reaction are utilized. 3+ Through the substitution reaction (Al / Cu + Fe) 3+ → Al 3+ / Cu 2+ + Fe 2+ This allows copper and aluminum ions to enter the liquid phase and separate from the solid-phase iron phosphate; therefore, this invention utilizes the endogenous Fe in the system to efficiently leach lithium through a one-step chlorination reaction. 3+ The acidic environment allows most of the copper and aluminum to dissolve from the solid phase into the liquid phase, thus separating impurities at the source and reducing the burden of impurity removal in the subsequent deep processing of iron phosphate products.

[0034] (2) Short process: Since the present invention omits the lengthy and complicated processes of dissolving all the iron phosphate in acid, removing impurities, recrystallizing, and dehydrating in the traditional method, in the present invention, more than 85% of the phosphorus and iron are retained and recovered in the form of FePO4 with olivine structure; lithium is directly leached into the aqueous solution through one-step selective chlorination of gas, liquid and solid phases; copper and aluminum impurities also enter the liquid phase from the solid phase during the chlorination reaction. The brine contains more than 99% of the lithium, more than 99% of the copper, and more than 95% of the aluminum in the battery black powder; at the same time, the main process of the present invention has only three steps, while the traditional method has more than ten steps. Therefore, the process of the present invention is shortened by about 70%.

[0035] (3) Low cost: Compared with the traditional wet process, the present invention has a significant low cost advantage. The cost of recovering one ton of iron phosphate is only about 30% of that of the traditional wet process. The present invention prioritizes the recovery of lithium and directly achieves lithium chlorination leaching in one step. The lithium concentration in the lithium-containing brine is high and the iron scale dissolution rate is low. The cost per ton of lithium recovery to prepare battery-grade lithium carbonate is reduced by about 20% compared with the traditional wet process. At the same time, the process of the present invention is short, which leads to a significant reduction in fixed asset investment and depreciation. The high yield of iron phosphate further reduces the cost per ton. Moreover, the present invention also abandons the process route of acid dissolution and recrystallization of all iron phosphate in the lithium extraction slag. Instead, it adopts a gas-liquid-solid three-phase one-step selective chlorination process for lithium extraction, aluminum removal and copper removal and a pyrometallurgical-based defluorination-decarbonization-crystallization combined process, which achieves direct repair and regeneration of iron phosphate with extremely low acid consumption and energy consumption.

[0036] (4) High controllability: In the prior art 1, the process control parameters (such as concentration, temperature, time, solid-liquid ratio) are mainly based on empirical ranges, and the reaction control is relatively macroscopic, which may lead to the risk of local concentration or temperature unevenness. However, the present invention introduces a quantitative control model based on reactants and thermodynamics. The key parameters (volume of aqueous solution V_H2O, chlorine gas flow rate V_Cl2) are related and constrained by mathematical formulas with the content of lithium, copper and aluminum (RLi, RCu, RAl) in the raw materials and the heat of reaction (Q). Through strict quantitative material relationship and temperature and pressure window control, the uniform and full reaction of chlorine gas with materials is ensured, which effectively suppresses side reactions such as unconventional dissolution of iron and phosphorus caused by local over-reaction, and improves the selectivity of the main reaction and process stability. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart of a method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction slag, as described in this invention. Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0040] Example 1

[0041] A method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue is described in the attached process flow chart. Figure 1 As shown, the specific process steps are as follows:

[0042] ① One-step chlorination: In a closed reactor, 100 kg of waste lithium iron phosphate battery black powder (M) is mixed with 400 L of deionized water (V_H2O) with a pH of 0.5. Chlorine gas (V_Cl2) is continuously introduced, and the reactor pressure is maintained at a positive pressure P = 10 Pa. The initial temperature of the waste lithium iron phosphate battery black powder mixed with the deionized water in the reactor is T_st = 5℃. The maximum allowable temperature rise in the reactor during the reaction is ΔT = 50℃, and the total reaction time is t = 30 minutes. The lithium content in the waste lithium iron phosphate battery black powder is R. Li =2.68%, copper content is R Cu =0.30%, aluminum content is R Al =0.50%, iron content is 21.55%, and phosphorus content is 12.00%.

[0043] In this chlorination process, a selective chlorination reaction for lithium extraction will occur (i.e., reaction formula (1)). This reaction formula (1) is an exothermic reaction with a heat of reaction of Q = 21072 KJ. At the same time, the process also involves the simultaneous removal of impurities from aluminum and copper (i.e., reaction formula (4) and reaction formula (5)).

[0044] Therefore, the above process conditions for this step satisfy the following:

[0045] and ;

[0046] ;

[0047] The initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction process satisfy: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT=55℃≤80℃;

[0048] The total reaction time t satisfies 30 minutes ≤ t ≤ 72 hours;

[0049] The reactor pressure is positive, P, which satisfies 10 Pa ≤ P ≤ 10 kPa;

[0050] The pH value of the acidic deionized aqueous solution meets the requirement of 0.3 ≤ pH ≤ 1.5;

[0051] ② Filtration: The solid-liquid mixture after the one-step chlorination reaction is filtered and washed to obtain lithium extraction residue and filtrate brine. After testing and analysis, the chlorination leaching rate of lithium is 99.6%, the leaching rate of aluminum is 94.5%, and the leaching rate of copper is 99.2%.

[0052] ③ Preparation of regenerated iron phosphate: The lithium extraction residue is dried and then subjected to defluorination-decarbonization-crystallization process to prepare regenerated iron phosphate. After testing and calculation analysis, the yield of regenerated iron phosphate is 87.3%.

[0053] ④ Lithium carbonate preparation and recrystallized iron phosphate preparation: The brine is purified to obtain lithium purified solution. Soda ash is added to the lithium purified solution to precipitate lithium and prepare lithium carbonate. During the brine purification process, iron and phosphorus are separated and recrystallized according to the traditional recrystallization process to obtain recrystallized iron phosphate. After detection and calculation analysis, the yield of recrystallized iron phosphate is 11.6%. Therefore, the total yield of iron phosphate in this embodiment is 98.9%.

[0054] Example 2

[0055] A method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue is described in the attached process flow chart. Figure 1 As shown, the specific process steps are as follows:

[0056] ① One-step chlorination: In a closed reactor, 100 kg of waste lithium iron phosphate battery black powder (M) is mixed with 500 L of deionized water (V_H2O) with a pH of 1.0. Chlorine gas (V_Cl2) is continuously introduced, and the reactor pressure is maintained at a positive pressure P = 5 kPa. The initial temperature of the waste lithium iron phosphate battery black powder mixed with the deionized water in the reactor is T_st = 30℃. The maximum allowable temperature rise in the reactor during the reaction is ΔT = 30℃. The total reaction time is t = 48 hours. The lithium content in the waste lithium iron phosphate battery black powder is R. Li =2.68%, copper content is R Cu =0.30%, aluminum content is R Al =0.50%, iron content is 21.55%, and phosphorus content is 12.00%.

[0057] In this chlorination step, a selective chlorination reaction for lithium extraction will occur (i.e., reaction formula (1)). This reaction formula (1) is an exothermic reaction with a heat of reaction of Q = 21072 KJ. At the same time, the process also involves the simultaneous removal of impurities from aluminum and copper (i.e., reaction formulas (4) and (5)).

[0058] Therefore, the above process conditions for this step satisfy the following:

[0059] and ;

[0060] ;

[0061] The initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction process satisfy: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT=60℃≤80℃;

[0062] The total reaction time t satisfies 30 minutes ≤ t ≤ 72 hours;

[0063] The reactor pressure is positive, P, which satisfies 10 Pa ≤ P ≤ 10 kPa;

[0064] The pH value of the deionized aqueous solution meets the following requirement: 0.3 ≤ pH ≤ 1.5;

[0065] ② Filtration: The solid-liquid mixture after the one-step chlorination reaction is filtered and washed to obtain lithium extraction residue and filtrate brine. After testing and analysis, the chlorination leaching rate of lithium is 99.7%, the leaching rate of aluminum is 95.8%, and the leaching rate of copper is 99.5%.

[0066] ③ Preparation of regenerated iron phosphate: The lithium extraction residue is dried and then subjected to defluorination-decarbonization-crystallization process to prepare regenerated iron phosphate. After testing and calculation analysis, the yield of regenerated iron phosphate is 91.4%.

[0067] ④ Lithium carbonate preparation and recrystallized iron phosphate preparation: The brine is purified to obtain lithium purified solution. Soda ash is added to the lithium purified solution to precipitate lithium and prepare lithium carbonate. During the brine purification process, iron and phosphorus are separated and recrystallized according to the traditional recrystallization process to obtain recrystallized iron phosphate. After testing and calculation analysis, the yield of recrystallized iron phosphate is 7.2%; therefore, the total yield of iron phosphate in this embodiment is 98.6%.

[0068] Example 3

[0069] A method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue is described in the attached process flow chart. Figure 1 As shown, the specific process steps are as follows:

[0070] ① One-step chlorination: In a closed reactor, 100 kg of waste lithium iron phosphate battery black powder (M) is mixed with 600 L of deionized water (V_H2O) with a pH of 1.5. Chlorine gas (V_Cl2) is continuously introduced, and the reactor pressure is maintained at a positive pressure P = 10 kPa. The initial temperature of the waste lithium iron phosphate battery black powder mixed with deionized water in the reactor is T_st = 65℃. The maximum allowable temperature rise in the reactor during the reaction is ΔT = 15℃, and the total reaction time is t = 72 hours. The lithium content in the waste lithium iron phosphate battery black powder is R. Li =2.68%, copper content is R Cu =0.30%, aluminum content is R Al=0.50%, iron content is 21.55%, and phosphorus content is 12.00%.

[0071] In this step of the chlorination process, a selective chlorination reaction for lithium extraction will occur (i.e., reaction formula (1)). This reaction formula (1) is an exothermic reaction with a heat of reaction of Q = 21072 KJ. At the same time, the process also involves the simultaneous removal of impurities from aluminum and copper (i.e., reaction formula (4) and reaction formula (5)).

[0072] Therefore, the above process conditions for this step satisfy the following:

[0073] and ;

[0074] ;

[0075] The initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction process satisfy: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT=80℃≤80℃;

[0076] The total reaction time t satisfies: 30 minutes ≤ t ≤ 72 hours;

[0077] The reactor pressure is positive, P, which satisfies: 10Pa≤P≤10kPa;

[0078] The pH value of the deionized aqueous solution must satisfy: 0.3 ≤ pH ≤ 1.5.

[0079] ② Filtration: The solid-liquid mixture after the one-step chlorination reaction is filtered and washed to obtain lithium extraction residue and filtrate brine. After testing and analysis, the chlorination leaching rate of lithium is 99.5%, the leaching rate of aluminum is 96.1%, and the leaching rate of copper is 99.4%.

[0080] ③ Preparation of regenerated iron phosphate: The lithium extraction residue is dried and then subjected to defluorination-decarbonization-crystallization process to prepare regenerated iron phosphate. After testing and calculation analysis, the yield of raw iron phosphate is 93.7%.

[0081] ④ Lithium carbonate preparation and recrystallized ferric phosphate preparation: The brine was purified to obtain a lithium-purified solution. Soda ash was added to the lithium-purified solution to precipitate lithium, thus preparing lithium carbonate. During the brine purification process, iron and phosphorus were separated and recrystallized using a traditional process to obtain recrystallized ferric phosphate. Analysis showed that the yield of recrystallized ferric phosphate was 4.6%; therefore, the total yield of ferric phosphate in this embodiment was 98.3%.

[0082] Example 4

[0083] A method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue is described in the attached process flow chart. Figure 1 As shown, the specific process steps are as follows:

[0084] ① One-step chlorination: In a closed reactor, 100 kg of waste lithium iron phosphate battery black powder (M) is mixed with 800 L of deionized water (V_H2O) with a pH of 0.3. Chlorine gas (V_Cl2) is continuously introduced, and the reactor pressure is maintained at a positive pressure P = 4 kPa. The initial temperature of the waste lithium iron phosphate battery black powder mixed with deionized water in the reactor is T_st = 60℃. The maximum allowable temperature rise in the reactor during the reaction is ΔT = 15℃. The total reaction time is t = 36 hours. The lithium content in the waste lithium iron phosphate battery black powder is R. Li =2.68%, copper content is R Cu =0.30%, aluminum content is R Al =0.50%, iron content is 21.55%, and phosphorus content is 12.00%;

[0085] In this step of the chlorination process, a selective chlorination reaction for lithium extraction will occur (i.e., reaction formula (1)). This reaction formula (1) is an exothermic reaction with a heat of reaction of Q = 21072 KJ. At the same time, the process also involves the simultaneous removal of impurities from aluminum and copper (i.e., reaction formula (4) and reaction formula (5)).

[0086] Therefore, the above process conditions for this step satisfy the following:

[0087] and ;

[0088] ;

[0089] The initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction process satisfy: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT=75℃≤80℃;

[0090] The total reaction time t satisfies: 30 minutes ≤ t ≤ 72 hours;

[0091] The reactor pressure is positive, P, which satisfies: 10Pa≤P≤10kPa;

[0092] The pH value of the acidic aqueous solution must satisfy: 0.3 ≤ pH ≤ 1.5.

[0093] ② Filtration: The solid-liquid mixture after the one-step chlorination reaction is filtered and washed to obtain lithium extraction residue and filtrate brine. After testing and analysis, the chlorination leaching rate of lithium is 99.7%, the leaching rate of aluminum is 97.2%, and the leaching rate of copper is 99.6%.

[0094] ③ Preparation of regenerated iron phosphate: The lithium extraction residue was dried and subjected to a defluorination-decarburization-crystallization process to prepare regenerated iron phosphate. After testing and analysis, the yield of regenerated iron phosphate was 73.9%.

[0095] ④ Lithium carbonate preparation and recrystallized iron phosphate preparation: The brine is purified to obtain lithium purified solution. Soda ash is added to the lithium purified solution to precipitate lithium and prepare lithium carbonate. During the brine purification process, iron and phosphorus are separated and recrystallized according to the traditional recrystallization process to obtain recrystallized iron phosphate. After testing and calculation analysis, the yield of recrystallized iron phosphate is 24.7%; therefore, the total yield of iron phosphate in this embodiment is 98.6%.

[0096] Based on the descriptions of Examples 1, 2, 3, and 4 above, the yields of lithium, aluminum, copper, and iron phosphate in the four examples are shown in Table 1.

[0097] Table 1. Yields of lithium, aluminum, copper, and iron phosphate in Examples 1-4

[0098] Lithium yield (%) Aluminum yield (%) Copper yield (%) Total yield of ferric phosphate (%) Example 1 99.6 94.5 99.2 98.9 Example 2 99.7 95.8 99.5 98.6 Example 3 99.5 96.1 99.4 98.3 Example 4 99.7 97.2 99.6 98.6

[0099] As shown in Table 1, the lithium yield in Examples 1, 2, 3, and 4 all reached over 99.5%, the aluminum yield reached 94.5%, and even as high as 97.2%, the copper yield reached over 99%, and the total iron phosphate yield reached 98%. Therefore, the method for one-step chlorination recovery of lithium from spent lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction slag provided by this invention can effectively recover lithium, copper, aluminum, and iron phosphate.

[0100] The foregoing provides a detailed description of a one-step chlorination recovery and lithium extraction method for waste lithium iron phosphate battery black powder, and a method for removing copper and aluminum from the lithium extraction slag. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are merely for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for one-step chlorination recovery of lithium from waste lithium iron phosphate battery black powder and removal of copper and aluminum from lithium extraction residue, characterized in that, The method includes: In a closed reactor, M kg of waste lithium iron phosphate battery black powder is mixed with V L of aqueous solution, and V L of chlorine gas is continuously introduced to carry out a one-step chlorination reaction, while maintaining a positive pressure P in the reactor. The aqueous solution is an acidic deionized water solution. The initial temperature of the waste lithium iron phosphate battery black powder mixed with the deionized water solution in the reactor is T_st. The maximum allowable temperature rise in the reactor during the reaction is ΔT, and the total reaction time is t. In the one-step chlorination reaction, the acidic environment generated by the reaction of chlorine gas and water, and the Fe generated in the reaction system are utilized. 3+ To achieve selective chlorination leaching of lithium and simultaneous dissolution of copper and aluminum impurities in waste lithium iron phosphate battery black powder; and to satisfy: In the formula, Q is the total heat released in the reaction, in kJ; R Li It is the percentage of lithium by mass in the black powder from waste lithium iron phosphate batteries; R Al It is the percentage by mass of aluminum in the black powder from waste lithium iron phosphate batteries; R Cu It is the percentage of copper by mass in the black powder from waste lithium iron phosphate batteries.

2. The method for one-step chlorination recovery and lithium extraction from waste lithium iron phosphate battery black powder and the method for removing copper and aluminum from lithium extraction slag according to claim 1, characterized in that, The initial temperature T_st and the maximum allowable temperature rise ΔT in the reactor during the reaction process satisfy the following conditions: 5℃≤T_st≤80℃ and 5℃≤T_st+ΔT≤80℃.

3. The method for one-step chlorination recovery and lithium extraction from waste lithium iron phosphate battery black powder and the method for removing copper and aluminum from lithium extraction residue according to claim 1, characterized in that, The total reaction time t in the reactor satisfies: 30 minutes ≤ t ≤ 72 hours.

4. The method for one-step chlorination recovery and lithium extraction from waste lithium iron phosphate battery black powder and the method for removing copper and aluminum from lithium extraction residue according to claim 3, characterized in that, The positive pressure P inside the reactor satisfies: 10Pa≤P≤10kPa.

5. The method for one-step chlorination recovery and lithium extraction from waste lithium iron phosphate battery black powder and the method for removing copper and aluminum from lithium extraction residue according to any one of claims 1-4, characterized in that, The pH value of the acidic deionized aqueous solution satisfies: 0.3 ≤ pH ≤ 1.5.

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