A method for selective leaching and recovery of lithium from spent lithium iron phosphate batteries

Abstract

The application discloses a kind of selective leaching and recovery method of lithium in waste lithium iron phosphate battery;The specific steps of the method are as follows: after being disassembled, discharged, broken and sorted, the positive and negative mixture (black powder) obtained from waste lithium iron phosphate battery is uniformly mixed with aqueous solution of chlorine dioxide and reacts, to obtain lithium-containing leaching solution and filter residue;Lithium-containing leaching solution can be used to prepare lithium carbonate, and the filter residue can be directly used to prepare lithium iron phosphate positive material after impurity removal and drying.Based on this, the application provides a kind of selective short-range recovery method of lithium in waste lithium iron phosphate battery, the iron in the form of iron phosphate is recovered by solid-liquid separation in the method, which avoids the shortcomings of the prior art that the leaching solution needs to be separated and purified, realizes the efficient selective recovery and closed-loop recycling of lithium in the black powder of waste lithium iron phosphate battery, has the advantages of short process, high lithium extraction efficiency, no secondary pollution, etc., and has excellent industrialization application and popularization prospect.

Description

Technical Field

[0001] This invention relates to the field of recycling technology for retired power batteries, specifically to a method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries. Background Technology

[0002] With increasing public awareness of environmental protection, new energy vehicles using environmentally friendly energy sources are becoming more and more common. Among them, lithium-ion batteries are widely used in the electric vehicle sector due to their high energy storage potential and environmental friendliness. However, the rapid increase in the number of new energy vehicles has also brought a series of problems. The most direct issue is that when these lithium-ion batteries reach the end of their lifespan, these discarded batteries will cause significant environmental pollution. Furthermore, the surge in demand for lithium-ion batteries has also led to a significant increase in the demand for related metal resources, which has greatly driven up the price of related metals, especially lithium. Therefore, recycling lithium from discarded lithium-ion batteries has become a highly attractive option.

[0003] Currently, the main cathode materials for lithium-ion batteries on the market include lithium iron phosphate (LFP), lithium cobalt oxide (LCO), and ternary lithium (NCM). Among them, lithium iron phosphate is widely used in electric vehicles and other transportation vehicles due to its low cost, high chemical stability, high safety, and long lifespan. Lithium iron phosphate batteries have a lifespan of 7-8 years, and are currently facing a large-scale retirement trend. Their lithium content is far higher than that of primary lithium ore resources, giving them high recycling value.

[0004] Currently, the main recycling processes for waste lithium iron phosphate batteries include pyrometallurgical, biological, and hydrometallurgical methods. Pyrometallurgical methods involve recovering metals through a series of physicochemical processes under high-temperature conditions, generally including direct regeneration and carbothermal reduction. For lithium iron phosphate, direct regeneration has a short process but requires high purity of raw materials; while with carbothermal reduction, lithium remains in the slag and is difficult to recover. Biological methods utilize the metabolic processes of microorganisms to extract the target metals from the raw materials into a solution, which is then separated and recovered using hydrometallurgical techniques. The advantages of biological methods are lower cost compared to traditional methods and no large amounts of wastewater or waste gas generated; the disadvantage is the long cultivation period for microorganisms. Hydrometallurgical methods involve contacting the raw materials with water or other liquids, causing a chemical reaction that transfers the metals from the raw materials into the liquid phase, and then separating the metals in the liquid phase to recover the metal components. The advantages of hydrometallurgical methods are complete recovery of the metals from the raw materials and relatively convenient operation, but they generate a high intensity of wastewater and slag.

[0005] Existing hydrometallurgical technologies generally use strong acids or alkalis as leaching agents to leach all valuable metals from the lithium iron phosphate powder. Lithium is then recovered by adding precipitants and adjusting the pH. For example, Chinese patent CN115504446A describes a method where waste lithium iron phosphate powder is acid-leached with an organic acid solution. After solid-liquid separation to obtain an acidic leachate, an oxidant is added, and an alkaline solution is added dropwise to adjust the pH. After the reaction, solid-liquid separation yields iron phosphate precipitate and a lithium-containing filtrate. The purified lithium-containing filtrate is then boiled, and a carbonate solution is added until saturated. Boiling continues, and solid-liquid separation yields lithium carbonate precipitate and an acidic filtrate. Finally, the acid is recovered from the acidic filtrate. This method is cumbersome, costly, and the waste lithium iron phosphate powder used can easily introduce impurities such as aluminum and copper, affecting product quality. Chinese patent CN109554545A describes a process where lithium iron phosphate waste is slurried with water, then acid is added, and the mixture is heated to 40–100°C. The pH of the system is adjusted to 2–4, and this temperature and pH range are maintained for 1–10 hours. The resulting slurry is then filtered to separate lithium solution and iron phosphate slag. This method is lengthy and prone to causing secondary pollution to the environment.

[0006] In summary, existing technologies generally suffer from drawbacks such as long processes, complex operations, high separation and purification costs, and low lithium recovery rates. There is an urgent need to develop new processes for selectively and efficiently extracting lithium from waste lithium iron phosphate batteries and thereby achieving short-range regeneration. Summary of the Invention

[0007] To address the aforementioned problems, the main objective of this invention is to provide a selective leaching and recovery method for lithium from waste lithium iron phosphate batteries. This invention relates to a selective short-range recovery method for lithium from waste lithium iron phosphate batteries. This method recovers iron as iron phosphate through solid-liquid separation, avoiding the drawbacks of existing technologies that require complex separation and purification of the leachate. It achieves efficient selective recovery and closed-loop recycling of lithium from waste lithium iron phosphate battery black powder, offering advantages such as a short process, high lithium extraction efficiency, and no secondary pollution, thus possessing excellent prospects for industrial application and promotion.

[0008] The present invention solves the above-mentioned technical problems through the following technical solution:

[0009] A method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries, comprising the following steps:

[0010] (1) Disassemble waste lithium iron phosphate batteries into individual cells, and obtain black powder rich in positive electrode active materials after discharge, crushing and sorting.

[0011] (2) The black powder obtained in step (1) is added to a 0.1 wt.% to 0.5 wt.% chlorine dioxide aqueous solution for reaction. After the reaction is completed, the reaction system is separated into solid and liquid to obtain lithium-containing leachate and filter residue.

[0012] (3) Add saturated sodium carbonate solution to the lithium-containing leachate obtained in step (2) to precipitate lithium carbonate. After washing and drying multiple times, battery-grade lithium carbonate with a purity of over 99.5% is obtained.

[0013] (4) The filter residue obtained in step (2) is washed and dried with pure water. The main component of the powder obtained is iron phosphate. The cathode material precursor is prepared by flotation after removing impurities and purifying the graphite by means of easy flotation.

[0014] (5) The battery-grade lithium carbonate obtained in step (3) is mixed with the cathode material precursor obtained in step (4) and calcined at high temperature to prepare lithium iron phosphate cathode material, thereby realizing closed-loop recycling.

[0015] In this invention, in step (2), the mass ratio of battery black powder to chlorine dioxide is 1:0.5 to 1:10, the reaction temperature is 20℃ to 60℃, the leaching time is 5 to 180 min, and the pH value of the solution during the leaching process is 1 to 7.

[0016] In this invention, in step (2), the mass ratio of battery black powder to chlorine dioxide is 1:1 to 1:5, the reaction temperature is 20℃ to 60℃, the leaching time is 5 to 30 min, and the pH value of the solution during the leaching process is 1 to 3.

[0017] In this invention, in step (3), the sodium carbonate precipitation time is 60-180 min, and water at a temperature of 60-80℃ is used when washing lithium carbonate.

[0018] In this invention, the drying temperature in step (4) is 80-105℃.

[0019] In this invention, in step (5), the calcination temperature is 500-750℃ and the calcination time is 1-5h.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The present invention provides a method for selective leaching and recycling of lithium in waste lithium iron phosphate batteries. The method uses chlorine dioxide aqueous solution as a leaching agent to selectively leach lithium in waste lithium iron phosphate batteries. Under optimal conditions, the leaching rate of lithium is as high as 99.76%, while the leaching rate of iron is only 4.56%. The main component of the filter residue is iron phosphate. The precursor of lithium iron phosphate cathode material is prepared by separation, purification and impurity removal. The impurity removal method is mainly flotation. The graphite and iron phosphate are separated by taking advantage of the characteristic that graphite can easily float on water. This realizes the selective leaching of lithium in waste lithium iron phosphate batteries and the closed-loop recycling of cathode materials.

[0022] (2) The present invention provides a selective leaching and recovery method for lithium in waste lithium iron phosphate batteries. After leaching, no additional reagents are required to separate lithium and iron, which solves the problem of short-range and efficient reuse of black powder. It has the advantages of low reagent consumption, short process, low cost and high lithium recovery rate.

[0023] (3) The present invention provides a selective leaching and recovery method for lithium in waste lithium iron phosphate batteries. Starting from the physicochemical characteristics of waste lithium iron phosphate battery black powder, the whole recycling process is clean and free from secondary pollution. It can effectively improve the recycling rate of battery cathode materials, reduce material recycling costs, and has broad prospects for industrial application. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the selective leaching and recovery of lithium from waste lithium iron phosphate batteries according to the present invention.

[0025] Figure 2 The image shows the XRD pattern of the filter residue obtained in Example 1.

[0026] Figure 3 The image shows the XRD pattern of the product after calcination in Example 1. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a process flow diagram of selective leaching and recovery of lithium from waste lithium iron phosphate battery black powder according to the present invention. The specific steps of the process for selective leaching and recovery of lithium from waste lithium iron phosphate battery black powder provided by the present invention are as follows:

[0029] (1) Disassemble waste lithium iron phosphate batteries into individual cells, and obtain black powder rich in positive electrode active materials after discharge, crushing and sorting.

[0030] (2) Add chlorine dioxide aqueous solution to the black powder obtained in step (1), and obtain leachate after reaction;

[0031] (3) Filter the leachate obtained in step (2) and perform solid-liquid separation to obtain lithium-containing filtrate and filter residue;

[0032] (4) Add sodium carbonate to the lithium-containing leachate obtained in step (2) to precipitate lithium carbonate. After washing and drying several times, battery-grade lithium carbonate with a purity of more than 99.5% is obtained.

[0033] (5) The filter residue obtained in step (3) is washed and dried with pure water. The powder obtained is purified by flotation and can be used to prepare cathode material precursors.

[0034] (6) The lithium salt obtained in step (4) and the cathode material precursor obtained in step (5) are sintered to prepare lithium iron phosphate cathode material.

[0035] In step (2), the mass ratio of battery black powder to chlorine dioxide in the leaching process is 1:(0.5-10).

[0036] The leaching time in step (2) is 5 to 180 minutes.

[0037] The reaction temperature in step (2) is 20–60 °C.

[0038] In step (2), the pH value of the solution during the leaching process is 1 to 7.

[0039] In step (4), the precipitation time for sodium carbonate is 60-180 min, and the water temperature for washing lithium carbonate is 60-80℃.

[0040] The filter residue obtained in step (5) is mainly composed of iron phosphate.

[0041] In step (5), the temperature for drying the filter residue is 80-105℃.

[0042] The roasting temperature in step (6) is 500-750℃ and the roasting time is 1-5h.

[0043] Example 1

[0044] The specific steps of a selective leaching and recovery method for lithium in waste lithium iron phosphate battery black powder are as follows:

[0045] (1) Determination of metal content in the sample

[0046] A 0.1g sample of dried waste lithium iron phosphate battery black powder was placed in a digestion vessel, followed by the addition of 6mL concentrated hydrochloric acid, 2mL concentrated nitric acid, and 2mL deionized water. The digestion vessel was then placed in a microwave digestion apparatus. After digestion, the volume was brought to 100mL, and the solution was diluted 10-fold and 100-fold, respectively. The content of metal components was then quantitatively determined using an ICP-OES (ICAP700) instrument manufactured by Thermo Fisher Scientific. The results are shown in Table 1.

[0047] Table 1 Main Components of Black Powder from Waste Lithium Iron Phosphate Batteries

[0048] Content (wt.%) 4.18 39.46

[0049] (2) Selective leaching of lithium using chlorine dioxide system

[0050] Take 1g of black powder and place it in a beaker. Add 0.5wt.% chlorine dioxide aqueous solution and stir until homogeneous. Control the mass ratio of black powder to chlorine dioxide to be 1:5, the reaction temperature to be 20℃, and the pH value during the leaching process to be 2. After the beaker containing the mixed sample has stood for 30 minutes, separate the lithium-containing filtrate and filter residue using a vacuum filtration device. Wash the filter residue with ultrapure water, add the washing liquid to the filtrate, and measure the metal ion content in the filtrate using ICP-OES. Dry the washed filter residue in an oven at 105℃ for 24 hours, weigh it, and then use XRD to detect the phase composition of the filter residue. Take 0.1g of the digestion solution and determine the metal ion content in the digestion solution using ICP-OES. Calculate the leaching rates of lithium and iron using the following formula.

[0051]

[0052]

[0053] In the formula, LE M The leaching rate (%) of metal M;

[0054] C L The concentration of metal in the leachate (measured by ICP, g / L);

[0055] V L The volume of the leachate (L);

[0056] m Z The mass of the filter residue (weighed after drying at 105℃ for 24 hours, in g);

[0057] W represents the mass fraction (%) of metal in the filter residue;

[0058] C Z The concentration of metals in the digestion solution (measured by ICP, g / L);

[0059] M represents the weight (g) of the filter residue.

[0060] The leaching rate of lithium using chlorine dioxide as the leaching agent reached 99.76%, while the leaching rate of iron was 4.56%. The results were then analyzed using XRD (Bruker D8 ADVANCE) from Bruker GmbH, Germany. (See attached figure.) Figure 2 It can be seen that the main phase of the filter residue is iron phosphate. This achieves efficient and selective leaching of lithium from waste lithium iron phosphate battery black powder.

[0061] (3) Lithium carbonate recovery

[0062] The lithium-containing filtrate and washing liquid obtained after leaching are collected, sodium carbonate is added to precipitate lithium carbonate, which is then filtered, washed, and dried to obtain lithium carbonate. The filter residue obtained after leaching is washed with pure water and dried. Then, taking advantage of the fact that graphite easily floats on water, impurities are removed by flotation to obtain the cathode material precursor.

[0063] (4) Synthesis of lithium iron phosphate

[0064] A certain amount of lithium carbonate and cathode material precursor were taken, ensuring that the molar ratio of lithium to iron was 1:1. The two were then mixed and calcined under a nitrogen atmosphere at a temperature of 650℃ for 3 hours. After calcination, lithium iron phosphate was obtained. Figure 3 The image shows the XRD pattern of the product after calcination in Example 1.

[0065] Example 2

[0066] The selective leaching and recovery method for lithium in waste lithium iron phosphate battery black powder in this embodiment is the same as that in Example 1, except that the mass ratio of battery black powder to chlorine dioxide in step (2) is 1:3, and the reaction temperature is 40℃. The leaching rate of lithium in the chlorine dioxide system was measured to be 96.13%, while the leaching rate of iron was 3.57%, thus achieving efficient and selective leaching of lithium in waste lithium iron phosphate battery black powder.

[0067] Example 3

[0068] The selective leaching and recovery method for lithium from waste lithium iron phosphate battery black powder in this embodiment is otherwise the same as in Example 1, except that: in step (2), the mass ratio of battery black powder to chlorine dioxide in the leaching experiment is 1:1, and the reaction temperature is 60℃. The leaching rate of lithium in the chlorine dioxide system was measured to be 95.07%, while the leaching rate of iron was 5.36%, thus achieving efficient and selective leaching of lithium from waste lithium iron phosphate battery black powder.

[0069] Example 4

[0070] The selective leaching and recovery method of lithium from waste lithium iron phosphate battery black powder in this embodiment is the same as that in Example 1, except that the leaching reaction time in step (2) is 10 min. The leaching rate of lithium in the chlorine dioxide system was measured to be 88.19%, while the leaching rate of iron was 3.65%, thus achieving efficient and selective leaching of lithium from waste lithium iron phosphate battery black powder.

[0071] Comparative Example 1

[0072] The selective leaching and recovery method of lithium from waste lithium iron phosphate battery black powder in this comparative example is the same as that in Example 1, except that:

[0073] In step (2), hydrogen peroxide aqueous solution was used instead of chlorine dioxide aqueous solution, and the pH value during the leaching process was 7. The leaching rate of lithium was measured to be 44.09%, and the leaching rate of iron was 0.06%. At this time, efficient leaching of lithium could not be achieved. Therefore, the key to this invention is the use of chlorine dioxide as the leaching agent in the leaching process.

[0074] Comparative Example 2

[0075] The selective leaching and recovery method of lithium from waste lithium iron phosphate battery black powder in this comparative example is the same as that in Example 1, except that the mass ratio of battery black powder to chlorine dioxide in step (2) is 1:0.25. The leaching rate of lithium was measured to be 62.64%, while the leaching rate of iron was 0.04%. At this time, efficient lithium leaching cannot be achieved. Therefore, the appropriate mass ratio between battery black powder and chlorine dioxide during the leaching process is an important factor affecting the selective leaching of lithium.

[0076] Comparative Example 3

[0077] The selective leaching and recovery method of lithium in waste lithium iron phosphate battery black powder in this comparative example is the same as that in Example 1, except that the pH value of the leaching experiment in step (2) is 8. The leaching rate of lithium was measured to be 43.37%, while the leaching rate of iron was 7.89%. At this time, efficient leaching of lithium cannot be achieved. Therefore, the appropriate pH value during the leaching process is an important factor affecting the selective leaching of lithium.

[0078] Table 2 summarizes the leaching rate data of lithium and iron in Examples 1 to 4.

[0079] Table 2. Leaching rates of lithium and iron in different embodiments

[0080] lithium 99.76 96.13 95.07 88.19 iron 4.56 3.57 5.36 3.65

[0081] As shown in the table above, using chlorine dioxide aqueous solution as the leaching agent for waste lithium iron phosphate battery black powder can effectively achieve selective leaching of lithium without introducing other impurity ions into the leachate. This effectively solves the problem of requiring additional lithium-iron separation in the leachate after leaching under previous technical conditions, achieving highly efficient and selective leaching of lithium from waste lithium iron phosphate battery black powder.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries, characterized in that, The method includes the following steps: (1) Disassemble waste lithium iron phosphate batteries into individual cells, and obtain black powder rich in positive electrode active materials after discharge, crushing and sorting. (2) The black powder obtained in step (1) is added to a 0.1wt.%~0.5wt.% chlorine dioxide aqueous solution for reaction. After the reaction is completed, the reaction system is separated into solid and liquid to obtain lithium-containing leachate and filter residue. (3) Add saturated sodium carbonate solution to the lithium-containing leachate obtained in step (2) to precipitate lithium carbonate. After washing and drying several times, battery-grade lithium carbonate with a purity of more than 99.5% is obtained. (4) The filter residue obtained in step (2) is washed and dried with pure water. The main component of the powder obtained is iron phosphate. The cathode material precursor is prepared by flotation after removing impurities and purifying the graphite by means of easy flotation. (5) The battery-grade lithium carbonate obtained in step (3) is mixed with the cathode material precursor obtained in step (4) and calcined at high temperature to prepare lithium iron phosphate cathode material, thereby achieving closed-loop recycling; wherein: In step (2), the mass ratio of battery black powder to chlorine dioxide is 1:0.5~1:10, the reaction temperature is 20℃~60℃, the leaching time is 5~180min, and the pH value of the solution during the leaching process is 1~7; In step (3), sodium carbonate is added and the precipitation time is 60~180 min, and water at a temperature of 60~80℃ is used when washing lithium carbonate.

2. The method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries according to claim 1, characterized in that: In step (2), the mass ratio of battery black powder to chlorine dioxide is 1:1 to 1:5, the reaction temperature is 20℃ to 60℃, the leaching time is 5 to 30 min, and the pH value of the solution during the leaching process is 1 to 3.

3. The method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries according to claim 1, characterized in that: In step (4), the drying temperature is 80~105℃.

4. The method for selective leaching and recovery of lithium from waste lithium iron phosphate batteries according to claim 1, characterized in that: In step (5), the roasting temperature is 500~750℃ and the roasting time is 1~5h.

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