A short-range, high-value recycling method for spent lithium iron phosphate batteries

Abstract

This application provides a short-range, high-value recycling method for spent lithium iron phosphate (LFP) batteries, relating to the field of solid waste resource utilization technology. The method employs a crystal phase dissociation purification + ordered reconstruction approach to process spent LFP batteries, combining the advantages of deep impurity purification through wet dissociation with short-range recycling for preparing LFP cathode materials. This enables efficient regeneration and high-quality utilization of spent LFP batteries, with strong raw material adaptability. Crystal dissociation and reconstruction can solve problems such as lithium deficiency, crystal uniformity, and surface carbon coating, resulting in stable performance of the synthesized LFP material. The liquid-phase purification and precipitation process offers high purification efficiency and eliminates the need for filtration during precipitation. The original solution is directly used for ball milling and spray drying, achieving molecular-level mixing of Li, Fe, P, and the carbon source, resulting in good mixing and uniform LFP particle size.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource processing, in particular to a short-range high-value recycling method of waste and old lithium iron phosphate batteries. BACKGROUND

[0002] The recycling of retired lithium iron phosphate batteries can be divided into long-range and short-range recycling processes. The long-range wet recycling process takes high-quality lithium salt (lithium carbonate / lithium phosphate) and iron phosphate as products, including wet selective lithium extraction + lithium residue recycling iron phosphate process and wet full immersion + step-by-step preparation of iron phosphate and lithium carbonate process. The long-range wet recycling process contains two main lines. One is the lithium carbonate preparation line, which involves unit operations such as leaching, chemical purification, pH adjustment, resin purification, carbonate precipitation, and carbon separation. The other is the iron phosphate preparation line, which involves unit operations such as leaching, purification, precipitation, aging, drying, and calcination. If lithium iron phosphate is the final product, lithium carbonate and iron phosphate need to be mixed and calcined. The overall process is long and the cost is high. In the current stage of lithium price decline, the profit space is extremely compressed, but the process is mature and the product quality is reliable.

[0003] The short-range recycling process takes lithium iron phosphate material as the product, including solid-phase direct regeneration technology and hydrothermal direct regeneration technology. The common point of these methods is to use external energy to restore the defective iron lithium lattice, and only need to be mixed and then synthesized by hydrothermal method or sintered at high temperature to realize the preparation of lithium iron phosphate material. However, these methods have high purity requirements for waste positive electrode materials, and the pre-purification of waste materials has always been a difficulty.

[0004] The existing technology system faces the dilemma of compatibility between performance improvement and process simplification: high-purity regeneration requires high energy and material consumption, while low-cost routes cannot break through the technical threshold of material structure reconstruction. SUMMARY

[0005] The purpose of the present application is to provide a short-range high-value recycling method of waste and old lithium iron phosphate batteries, aiming to solve the problem of high energy and material consumption required by high-purity regeneration of existing waste positive electrode materials.

[0006] To achieve the above purpose, the present application provides a short-range high-value recycling method of waste and old lithium iron phosphate batteries, comprising:

[0007] The waste and old lithium iron phosphate battery powder is subjected to acid leaching to obtain leaching residue and leaching solution;

[0008] The leaching solution is added with a first adjusting agent to adjust the pH value to 1.8-2.5 for first-stage purification to obtain first-stage purification solution and copper-containing residue;

[0009] The first-stage purification solution is added with a first adjusting agent to adjust the pH value to 2.5-3.5 for second-stage purification to obtain second-stage purification solution and aluminum fluoride residue;

[0010] extracting the two-stage purified solution to obtain a raffinate;

[0011] adding the raffinate to a second regulator to adjust the composition ratio to obtain a solution after ratio adjustment;

[0012] adding the solution after ratio adjustment to ammonia water to adjust the pH value to 10-14 for precipitation to obtain a slurry after precipitation;

[0013] adding the slurry after precipitation to a carbon source and water to adjust the solid content and perform ball milling to obtain a slurry after ball milling;

[0014] spray drying the slurry after ball milling to obtain a precursor;

[0015] sintering the precursor to obtain a lithium iron phosphate material.

[0016] In some embodiments, at least one of the following conditions is met:

[0017] A. The acid used in the acid leaching is phosphoric acid;

[0018] B. The temperature of the acid leaching is 20-80°C, and the time is 1-3 hours;

[0019] C. The liquid-solid ratio of the acid leaching is (3-5) mL:1g;

[0020] D. The molar concentration of phosphoric acid in the leaching solution is 3-5 mol / L.

[0021] In some embodiments, at least one of the following conditions is met:

[0022] A. The first regulator is selected from at least one of iron powder, ammonium phosphate, diammonium hydrogen phosphate;

[0023] B. The temperature of the first-stage purification is 20-50°C, and the time of the first-stage purification is 1-3 hours;

[0024] C. The temperature of the second-stage purification is 20-50°C, and the time of the second-stage purification is 0.5-3 hours.

[0025] In some embodiments, the second regulator is selected from at least one of lithium dihydrogen phosphate, lithium phosphate, lithium hydroxide, iron sesquioxide, phosphoric acid;

[0026] And / or, the molar ratio of Li, Fe, and P in the solution after ratio adjustment is (1-1.04):(0.95-0.98):1.

[0027] In some embodiments, the precipitation time is 5h-10h, and the precipitation temperature is 30℃-60℃.

[0028] In some embodiments, at least one of the following conditions is met:

[0029] A. The molar amount of the carbon source is 10%-20% of the molar amount of Li in the slurry after precipitation;

[0030] B. The solid content is 30%-40%;

[0031] C. The ball milling time is 5h-20h.

[0032] In some embodiments, the inlet air temperature of the spray drying is 100℃-130℃;

[0033] And / or, the particle size of the precursor is 20μm-50μm.

[0034] In some embodiments, the sintering includes one-stage sintering and two-stage sintering, and at least one of the following conditions is met:

[0035] A. The atmosphere of the one-stage sintering and the two-stage sintering is inert atmosphere;

[0036] B. The temperature of the one-stage sintering is 400℃-600℃;

[0037] C. The heating rate of the one-stage sintering is 2℃ / min-5℃ / min;

[0038] D. The holding time of the one-stage sintering is 5h-10h;

[0039] E. The temperature of the two-stage sintering is 650℃-800℃;

[0040] F. The heating rate of the two-stage sintering is 2℃ / min-5℃ / min;

[0041] G. The holding time of the two-stage sintering is 8h-10h.

[0042] In some embodiments, further comprising:

[0043] The leaching residue is washed to obtain washing water and washing residue, the washing water is combined with the leaching liquid, and the washing residue is dried to obtain carbon residue.

[0044] In some embodiments, the liquid-solid ratio of the washing is (5-10)mL:1g.

[0045] Compared with the prior art, the beneficial effects of the present application include:

[0046] The short-range high-value recovery method for waste lithium iron phosphate batteries provided by the application adopts a method of crystal phase dissociation purification + ordered reconstruction to process waste lithium iron phosphate batteries, which takes into account the advantages of wet dissociation impurity deep purification and short-range recovery of lithium iron phosphate cathode materials, and can realize efficient regeneration and high-quality utilization of waste lithium iron phosphate batteries, and has strong raw material adaptability.

[0047] The simple solid-phase regeneration and hydrothermal regeneration processes have high requirements for raw material quality, poor raw material adaptability, and difficulty in deep separation of impurities, which have been the bottleneck of the application of the processes; and the traditional wet recovery technology prepares lithium carbonate and iron phosphate in steps, and the preparation process is relatively long, but it has natural advantages in raw material adaptability and impurity deep purification, and has large operation space.

[0048] The process fully considers the influence of harmful impurities Al, F and Cu in the black powder, and uses displacement, precipitation and extraction to remove impurities; during the leaching, purification and precipitation processes, impurities such as sulfate ions and sodium ions are strictly avoided, so that high-quality lithium iron phosphate can be synthesized by direct sintering.

[0049] Compared with the inconsistent and unstable performance of the product directly repaired without dissociation of the crystal, the crystal dissociation and reconstruction can solve the problems of lithium deficiency, crystal consistency and surface carbon coating, and the synthesized lithium iron phosphate material has stable performance. The liquid phase purification and precipitation of the process has high purification efficiency, and during the precipitation, there is no need for filtration, and the original solution is directly used for ball milling + spray drying operation, so that molecular-level mixing is achieved between Li, Fe, P and the carbon source, the mixing effect is good, and the prepared lithium iron phosphate has uniform particle size. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope of the application.

[0051] Figure 1 The flowchart of the short-range high-value recovery method for waste lithium iron phosphate batteries of the application;

[0052] Figure 2 The operation flowchart of the short-range high-value recovery method for waste lithium iron phosphate batteries of example 1. DETAILED DESCRIPTION

[0053] As used herein:

[0054] "comprising," "having," "including," "containing," "characterized by" or any other variation thereof is intended to cover non-exclusive inclusion, such that a composition, step, method, article, or apparatus that comprises, has, includes, contains, characterizes, or is characterized by a list of elements can include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus. "Consisting essentially of, when

[0055] The conjunctive term "consisting of' excludes any element, step, or ingredient not specified. If used in the claims, this phrase shall

[0056] When expressing a range of values, concentrations, or other values or parameters as a range, a preferred range, or a range in terms of an upper preferred value and a lower preferred value, it is to be understood that the disclosure specifically contemplates all ranges formed from any pair of values between the upper and lower preferred values, whether or not the range is expressly stated. For example, if a range "1-5" is disclosed, then the disclosure is to be interpreted to include ranges such as "1-4," "1-3," "1-2," "1-2 and 4-5," "1-3 and 5," etc. When numerical ranges are disclosed herein, unless stated otherwise, the range is intended to include both the upper and lower values and all intervening values, including all integers and fractions within the range.

[0057] In these embodiments, unless otherwise indicated, the parts and percentages are by mass.

[0058] "Parts by mass" refers to a basic unit of measurement that represents the proportional relationship of the mass of multiple components, 1 part can represent any unit mass, such as 1 g, 2.689 g, etc. If we say that the mass of component A is a parts, and the mass of component B is b parts, it means that the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK, and the mass of component B is bK (K is an arbitrary number, representing a multiple factor). It must not be misunderstood that, unlike parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0059] "and / or" is used to indicate one or both of the stated circumstances can occur, for example, A and / or B includes (A and B) and (A or B).

[0060] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an ordered ranking of the indicated technical features. Thus, features defined with "first", "second" or "third" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0061] The present application provides a short-range high-value recycling method for waste lithium iron phosphate batteries, please refer to Figure 1 , comprising:

[0062] S100: acid leaching of waste lithium iron phosphate battery powder to obtain leaching residue and leaching solution;

[0063] S200: adding the leaching solution to the first adjusting agent to adjust the pH value to 1.8-2.5 to carry out a first purification to obtain a first purification solution and a copper-containing residue;

[0064] S300: adding the first purification solution to the first adjusting agent to adjust the pH value to 2.5-3.5 to carry out a second purification to obtain a second purification solution and an aluminum-fluorine residue;

[0065] S400: extracting the second purification solution to obtain a raffinate;

[0066] S500: adding the raffinate to the second adjusting agent to adjust the composition ratio to obtain a solution after ratio adjustment;

[0067] S600: adding the solution after ratio adjustment to ammonia water to adjust the pH value to 10-14 to carry out precipitation to obtain a slurry after precipitation;

[0068] S700: adding the slurry after precipitation to a carbon source and water to adjust the solid content and carrying out ball milling to obtain a slurry after ball milling;

[0069] S800: spray drying the slurry after ball milling to obtain a precursor;

[0070] S900: sintering the precursor to obtain a lithium iron phosphate material.

[0071] In some embodiments, the waste lithium iron phosphate battery powder in step S100 can be a mixed black powder of lithium iron phosphate batteries, or a positive electrode powder of lithium iron phosphate batteries.

[0072] In some embodiments, the acid used in the acid leaching of step S100 is phosphoric acid, which avoids the introduction of impurities such as sulfate ions and sodium ions. The temperature of the acid leaching of step S100 is 20-80°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any value between 20-80°C. The time of the acid leaching is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, or any value between 1-3h.

[0073] The selection of phosphoric acid as the acid leaching agent for the waste lithium iron phosphate battery embodies the systematicness of the process design. As the leaching medium, phosphoric acid can effectively dissolve the lithium iron phosphate components in the waste material. More importantly, the phosphate ions in the phosphoric acid have the same anion group as the target product lithium iron phosphate, and do not need to be removed by evaporation, meeting the quality requirements of the lithium iron phosphate material prepared by spray drying + calcination.

[0074] In some embodiments, the liquid-solid ratio of the acid leaching of step S100 is (3-5) mL: 1g, for example, it can be 3mL:1g, 4mL:1g, 5mL:1g, or any ratio between 3-5mL:1g.

[0075] In some embodiments, the molar concentration of phosphoric acid in the leaching solution of step S100 is 3-5 mol / L, for example, it can be 3mol / L, 3.5mol / L, 4mol / L, 4.5mol / L, 5mol / L, or any value between 3-5mol / L.

[0076] In some embodiments, the short-range high-value recovery method for the waste lithium iron phosphate battery of the present application further comprises:

[0077] The leaching residue is washed to obtain wash water and washed residue, and the wash water is combined with the leaching solution, and the washed residue is dried to obtain carbon residue.

[0078] The leaching residue is washed with pure water, and the wash water is combined with the leaching solution to enter the next step, thereby achieving the effects of improving the leaching rate, diluting the concentration of the leaching solution, and reducing the acidity of the leaching solution.

[0079] In some embodiments, the liquid-solid ratio of the washing is (5-10) mL:1g, for example, it can be 5mL:1g, 6mL:1g, 7mL:1g, 8mL:1g, 9mL:1g, 10mL:1g, or any ratio between 5-10mL:1g.

[0080] In some embodiments, the first adjusting agent of step S200 and step S300 is selected from at least one of iron powder, ammonium phosphate, diammonium hydrogen phosphate. It should be noted that the first adjusting agent of step S200 and step S300 can be the same substance or different substances.

[0081] The core advantage of selecting the pH adjusting agent lies in that its chemical composition is highly matched with the element system of the target product lithium iron phosphate. These adjusting agents can improve the pH value of the solution while not introducing heterogeneous ions outside the Li-Fe-P system, effectively avoiding the pollution of impurity elements such as sodium, potassium, and calcium, ensuring the systematic maintenance of raw material purity, and realizing the synergistic effect of pH adjustment and raw material supplement.

[0082] In some embodiments, the pH of the first-stage purification of step S200 can be, for example, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or any value between 1.8 and 2.5. The temperature of the first-stage purification can be, for example, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, or any value between 20℃ and 50℃. The time of the first-stage purification can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, or any value between 1h and 3h.

[0083] In some embodiments, the pH of the second-stage purification of step S300 can be, for example, 2.5, 3, 3.5, or any value between 2.5 and 3.5. The temperature of the second-stage purification can be, for example, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, or any value between 20℃ and 50℃. The time of the second-stage purification can be, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or any value between 0.5h and 3h.

[0084] In some embodiments, the extractant used in the extraction of step S400 is composed of 25% TBP + 5% N235 + 70% sulfonated kerosene by volume, and the volume ratio of the organic phase to the aqueous phase is 2:1. The purpose of the extraction is to purify and remove fluorine. The organic phase is regenerated after stripping. It can be understood that the extractant provided in the present application is only an example, and the scheme of the present application can only use this extractant.

[0085] In some embodiments, the second adjusting agent of step S500 is selected from at least one of lithium dihydrogen phosphate, lithium phosphate, lithium hydroxide, diiron trioxide, and phosphoric acid.

[0086] In some embodiments, the molar ratio of Li, Fe, and P in the solution after the ratio adjustment of step S500 is (1-1.04):(0.95-0.98):1.

[0087] In some embodiments, the pH of the precipitation in step S600 can be, for example, 10, 11, 12, 13, 14, or any value between 10 and 14, the precipitation time can be, for example, 5h-10h, such as 5h, 6h, 7h, 8h, 9h, 10h, or any value between 5h and 10h, and the precipitation temperature can be, for example, 30℃-60℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, or any value between 30℃ and 60℃.

[0088] In some embodiments, the molar amount of the carbon source in step S700 can be 10%-20% of the molar amount of Li in the slurry after precipitation, such as 10%, 15%, 20%, or any value between 10% and 20%.

[0089] In some embodiments, the solid content in step S700 can be 30%-40%, such as 30%, 35%, 40%, or any value between 30% and 40%. The ball milling time can be, for example, 5h-20h, such as 5h, 10h, 15h, 20h, or any value between 5h and 20h.

[0090] Ball milling can achieve uniform mixing of Li, Fe, P, and carbon source at the molecular level through high-energy mechanical force, which is far beyond the traditional physical stirring method. During the ball milling process, the repeated impact and shearing action of the grinding balls not only breaks the particles of the raw materials and reduces the particle size to the nanometer level, but more importantly, it activates the surface of the raw materials, increases the active sites, and promotes the subsequent synthesis reaction. At the same time, the mechanochemical effect generated during the ball milling process can partially break the crystal lattice structure of the raw materials, allowing the components to be rearranged at the atomic level, creating an ideal microstructure foundation for the formation of a uniform lithium iron phosphate precursor. This highly uniform mixing state directly determines the consistency of the phase purity and electrochemical performance of the final product.

[0091] In some embodiments, the inlet air temperature of the spray drying in step S800 can be, for example, 100℃-130℃, such as 100℃, 110℃, 120℃, 130℃, or any value between 100℃ and 130℃.

[0092] The slurry after ball milling is sent to the top of the spray drying tower and sprayed into mist droplets through an atomizer. The surface area of the droplets is very large, and the drying process can be completed in a very short time after contact with hot air. Directly using the original solution for ball milling + spray drying operation, Li, Fe, P, and carbon source are mixed at the molecular level, the mixing effect is good, and a uniform lithium iron phosphate particle size is obtained.

[0093] The spray drying technology has unique process advantages and product quality improvement effects in the preparation of lithium iron phosphate. The technology can disperse the slurry after ball milling into micron-sized droplets through a atomizer. These droplets have a large specific surface area, which can achieve rapid and uniform dehydration in a hot air environment of 100-130 ℃, effectively avoiding the segregation and agglomeration of components that may occur in traditional drying methods. The instantaneous dehydration characteristics of spray drying can lock the uniform distribution state of each component in the slurry, preventing the redistribution of Li, Fe, and P ions during the long drying process, thereby maintaining the chemical uniformity of the precursor. In addition, the spherical particles formed by spray drying have good flowability and compactness, providing ideal material properties for subsequent calcination processes.

[0094] In some embodiments, the particle size of the precursor of step S800 is 20-50 μm, for example, it can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value between 20 μm and 50 μm.

[0095] In some embodiments, the sintering of step S900 includes one-stage sintering and two-stage sintering, and the atmosphere of one-stage sintering and two-stage sintering is inert atmosphere.

[0096] In some embodiments, the temperature of one-stage sintering is 400-600 ℃, for example, it can be 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃ or any value between 400 ℃ and 600 ℃. The heating rate of one-stage sintering is 2-5 ℃ / min, for example, it can be 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min or any value between 2 ℃ / min and 5 ℃ / min. The holding time of one-stage sintering is 5-10 h, for example, it can be 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or any value between 5 h and 10 h.

[0097] In some embodiments, the temperature of two-stage sintering is 650-800 ℃, for example, it can be 650 ℃, 700 ℃, 750 ℃, 800 ℃ or any value between 650 ℃ and 800 ℃; the heating rate of two-stage sintering is 2-5 ℃ / min, for example, it can be 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min or any value between 2 ℃ / min and 5 ℃ / min; the holding time of two-stage sintering is 8-10 h, for example, it can be 8 h, 9 h, 10 h or any value between 8 h and 10 h.

[0098] Compared with single-stage calcination, the two-stage calcination process has significant technical advantages in the lithium iron phosphate calcination process. The staged heat treatment strategy can better control the structure evolution and performance optimization of the material.

[0099] One-stage sintering mechanism:

[0100] In this temperature range, the main processes are thermal decomposition of organic precursors, preliminary carbonization of carbon source and pre-reaction of iron phosphate precursor. Slow heating (2-5℃ / min) and long holding time (5-10h) in this stage ensure the complete decomposition and volatilization of organic matter, avoiding local overheating and uneven reaction caused by rapid heating. At the same time, this temperature range is conducive to the formation of uniform carbon-coated layer precursor, laying the foundation for the subsequent carbon-coated structure.

[0101] Mechanism of two-stage sintering:

[0102] At higher temperatures, the crystallization process of lithium iron phosphate is completed, and the olivine-type LiFePO4 crystal structure is fully developed. At this temperature, the carbon source is further graphitized to form a carbon-coated layer with better electrical conductivity. The temperature of two-stage sintering ensures sufficient crystallization and avoids grain coarsening and excessive graphitization of the carbon layer caused by high temperature.

[0103] The embodiments of the present application will be described in detail below with specific examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, they are carried out under conventional conditions or according to the manufacturer's recommendations. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0104] Example 1

[0105] Example 1 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, please refer to Figure 2 , including the following steps:

[0106] Take 100g of waste lithium iron phosphate battery positive electrode powder as raw material, containing Li 4.28%, Fe 32.22%, P 19.67%, Al 0.33%, Cu 0.006%, F 0.68%. The raw material is subjected to acid leaching with phosphoric acid, the leaching temperature is 60℃, the leaching time is 2h, the liquid-solid ratio is 5mL:1g, the molar concentration of the leaching liquid phosphoric acid is 3.5 mol / L, and the leaching liquid and the leaching residue are obtained; The leaching residue is washed with pure water, the amount of pure water is 100ml, the washing liquid-solid ratio is 6.5mL:1g, and after washing, the washing water and the phosphoric acid leaching liquid are combined into the purification section.

[0107] Iron powder is added to the leaching liquid, the pH value is adjusted to 2.5, the purification temperature is 30℃, and the purification time is 3h. After reaction, solid-liquid separation is carried out to obtain a first purification liquid and a copper-containing residue.

[0108] Ammonium phosphate is added to the first-stage purified solution, and the pH value is adjusted to 3, the purification temperature is 50℃, and the purification time is 2h. After the reaction, the second-stage purified solution and aluminum fluoride slag are obtained by precision filtration.

[0109] The second-stage purified solution is extracted, and the extractant is 25% TBP + 5% N235 + 70% sulfonated kerosene by volume. The volume ratio of organic phase to aqueous phase is 2:1, and the raffinate enters the next process.

[0110] 14.28g of lithium dihydrogen phosphate is added to the raffinate as a proportioning regulator, and the molar ratio of Li, Fe and P is adjusted to 1.023:0.974:1 to obtain the proportioning adjusted solution.

[0111] Ammonia is added to the proportioning adjusted solution, and the pH value is adjusted to 12. The precipitation time is 7h, and the precipitation temperature is 60℃ to obtain the slurry after precipitation.

[0112] 15% of Li molar glucose is added to the slurry after precipitation as a carbon source, and pure water is added to adjust the solid content of the slurry to 35%. Then the slurry is added to a ball mill for ball milling, and the ball milling time is 10h.

[0113] The slurry after ball milling is sent to spray drying, and the inlet air temperature is set to 120℃ to obtain the dried precursor powder.

[0114] The obtained precursor powder is subjected to one-stage sintering in a nitrogen atmosphere at a sintering temperature of 450℃, a heating rate of 2℃ / min and a holding time of 8h. After the holding time of one-stage sintering, the temperature is directly increased, and the one-stage sintered powder is subjected to two-stage sintering in a nitrogen atmosphere at a sintering temperature of 700℃, a heating rate of 3℃ / min and a sintering holding time of 8h to obtain the lithium iron phosphate material of Example 1.

[0115] Example 2

[0116] Example 2 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, which includes the following steps:

[0117] The positive electrode powder of the waste lithium iron phosphate battery is used as the raw material, which contains Li 4.28%, Fe 32.22%, P 19.67%, Al 0.33%, Cu 0.006% and F 0.68%. 100g of the raw material is subjected to acid leaching with phosphoric acid at a leaching temperature of 60℃, a leaching time of 2h, a liquid-solid ratio of 5mL:1g, and a phosphoric acid molar concentration of 3.5mol / L to obtain a leaching solution and a leaching residue. The leaching residue is washed with pure water, and the amount of pure water used is 100ml. The liquid-solid ratio of the washing liquid is 6.5mL:1g. After washing, the washing water and the phosphoric acid leaching solution are combined and sent to the purification section.

[0118] Iron powder is added to the leaching solution, the pH value is adjusted to 2.5, the purification temperature is 30℃, the purification time is 3h, after the reaction, solid-liquid separation is performed to obtain a first purification solution and a copper-containing residue.

[0119] Iron powder is added to the first purification solution, the pH value is adjusted to 3.2, the purification temperature is 50℃, the purification time is 3h, after the reaction, precision filtration is performed to obtain a second purification solution and an aluminum-fluorine residue.

[0120] The second purification solution is subjected to extraction, the extractant is 25% TBP+5% N235+70% sulfonated kerosene by volume, the volume ratio of organic phase to aqueous phase is 2:1, and the raffinate enters the next process.

[0121] 18.3g of lithium dihydrogen phosphate and 1.2g of lithium hydroxide are added to the raffinate as a proportioning regulator, the molar ratio of Li, Fe and P is adjusted to 1.033:0.978:1, and a proportioning-regulated solution is obtained.

[0122] Ammonia is added to the proportioning-regulated solution, the pH value is adjusted to 12, the precipitation time is 7h, and the precipitation temperature is 60℃, and a precipitated slurry is obtained.

[0123] 15% of Li molar amount of glucose is added to the precipitated slurry as a carbon source, and pure water is added to adjust the solid content of the slurry to 35%; then the slurry is added to a ball mill for ball milling, and the ball milling time is 10h.

[0124] The ball-milled slurry is sent to a spray dryer, and the inlet air temperature is set to 120℃ to obtain a dried precursor powder.

[0125] The obtained precursor powder is subjected to first sintering in a nitrogen atmosphere at a sintering temperature of 450℃, a heating rate of 2℃ / min, and a holding time of 8h. After the first sintering holding time, the temperature is directly increased, and the first sintered powder is subjected to second sintering in a nitrogen atmosphere at a sintering temperature of 700℃, a heating rate of 3℃ / min, and a sintering holding time of 8h, to obtain the lithium iron phosphate material of Example 2.

[0126] Example 3

[0127] Example 3 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, comprising the following steps:

[0128] The waste old positive electrode powder of lithium iron phosphate battery is used as raw material, containing Li 4.28%, Fe 32.22%, P 19.67%, Al 0.33%, Cu 0.006%, F 0.68%. 100g of the raw material is subjected to acid leaching with phosphoric acid, the leaching temperature is 60℃, the leaching time is 2h, the liquid-solid ratio is 5mL:1g, the molar concentration of the leaching solution is 3.5mol / L, and the leaching solution and the leaching residue are obtained; the leaching residue is washed with pure water, the amount of pure water is 100ml, the washing liquid-solid ratio is 6.5mL:1g, and after washing, the washing water and the phosphoric acid leaching solution are combined into the purification section.

[0129] Iron powder is added to the leaching solution, the pH value is adjusted to 2.5, the purification temperature is 30℃, and the purification time is 3h, after reaction, solid-liquid separation is carried out to obtain a first purification solution and a copper-containing residue.

[0130] Ammonium phosphate is added to the first purification solution, the pH value is adjusted to 3.5, the purification temperature is 50℃, and the purification time is 2h, after reaction, precision filtration is carried out to obtain a second purification solution and an aluminum-fluorine residue.

[0131] The second purification solution is subjected to extraction, the extractant is 25% TBP+5% N235+70% sulfonated kerosene by volume, the volume ratio of organic phase to aqueous phase is 2:1, and the raffinate enters the next process.

[0132] 13.51g of 85% phosphoric acid (mass percentage) and 3.5g of lithium hydroxide are added to the raffinate as a proportioning regulator, the molar ratio of Li, Fe and P is adjusted to 1.035:0.98:1, and a proportioning-regulated solution is obtained.

[0133] Ammonia is added to the proportioning-regulated solution, the pH value is adjusted to 14, the precipitation time is 10h, and the precipitation temperature is 60℃, and a slurry after precipitation is obtained.

[0134] 15% of Li molar amount of glucose is added to the slurry after precipitation as a carbon source, and pure water is added to adjust the solid content of the slurry to 35%; then the above slurry is added to a ball mill for ball milling, and the ball milling time is 10h.

[0135] The slurry after ball milling is sent to spray drying, the inlet air temperature is set to 120℃, and a dry precursor powder is obtained.

[0136] The obtained precursor powder is subjected to one-stage sintering, the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 400℃, the heating rate is 2℃ / min, and the holding time is 8h; after the one-stage sintering holding time ends, the temperature is directly raised, the one-stage sintered powder is subjected to two-stage sintering, the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 700℃, the heating rate is 3℃ / min, and the sintering holding time is 10h, and a lithium iron phosphate material of Example 3 is obtained.

[0137] Comparative Example 1

[0138] Comparative Example 1 does not use a impurity removal step compared to Example 1, and the specific conditions are as follows:

[0139] Comparative Example 1 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, which includes the following steps:

[0140] The positive electrode powder of the waste lithium iron phosphate battery is used as the raw material, containing Li 4.28%, Fe 32.22%, P 19.67%, Al 0.33%, Cu 0.006%, and F 0.68%. 100g of the raw material is subjected to acid leaching with phosphoric acid, the leaching temperature is 60°C, the leaching time is 2h, the liquid-solid ratio is 5mL:1g, and the molar concentration of the leaching solution is 3.5 mol / L, to obtain a leaching solution and a leaching residue; the leaching residue is washed with pure water, the amount of pure water is 100ml, the washing liquid-solid ratio is 6.5mL:1g, and after washing, the washing water and the phosphoric acid leaching solution are combined into the purification section.

[0141] 0.742 g of lithium hydroxide and 3.11 g of ferric sesquioxide are added to the leaching solution as a proportioning regulator, and the molar ratio of Li, Fe and P is adjusted to 1.023:0.974:1, to obtain a proportioning-adjusted solution.

[0142] The subsequent precipitation, ball milling, spray drying, one-stage sintering and two-stage sintering conditions are the same as those of Example 1, to obtain the lithium iron phosphate material of Comparative Example 1.

[0143] Comparative Example 2

[0144] Comparative Example 2 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, which is different from Example 2 only in that the pH value of the first-stage purification is 1.5 and the pH value of the second-stage purification is 1.8. The remaining steps and conditions are the same as those of Example 2, to obtain the lithium iron phosphate material of Comparative Example 2.

[0145] Comparative Example 3

[0146] Comparative Example 3 provides a short-range high-value recycling method for waste lithium iron phosphate batteries, which is different from Example 3 only in that Comparative Example 3 omits the spray drying and one-stage sintering steps, and the specific conditions are as follows:

[0147] The slurry after ball milling is placed in an oven for drying, and the drying temperature is set to 120°C to obtain a dried precursor powder. The obtained precursor powder is sintered, the sintering atmosphere is nitrogen atmosphere, the sintering temperature is 800°C, the heating rate is 2°C / min, and the holding time is 10h. The remaining steps and conditions are the same as those of Example 3, to obtain the lithium iron phosphate material of Comparative Example 3.

[0148] The impurities of the lithium iron phosphate materials obtained in each of the examples and the comparative examples were analyzed by elemental composition analysis, and the lithium iron phosphate materials (LiFePO4 / C) obtained in each of the examples and the comparative examples were mixed with conductive carbon black (SP) and polyvinylidene fluoride (PVDF) to prepare electrode sheets, and the electrode sheets were assembled into 2032 button cells with carbon-coated aluminum foils (carbon coating thickness: 0.6 μm, electrical conductivity: 30 S / cm) as current collectors. The 0.1C initial discharge capacity and the capacity retention rate after 100 cycles were tested in the voltage range of 2.0-3.75 V, and the results are shown in Table 1.

[0149] Table 1 Impurity analysis and electrochemical performance of the lithium iron phosphate materials in each of the examples and the comparative examples

[0150]

[0151] As can be seen from Table 1, the content of F and Al in the lithium iron phosphate product prepared in Comparative Example 1 is high because no purification step is adopted, and the impurities have a great negative effect on the initial discharge capacity; the content of Al in the lithium iron phosphate product prepared in Comparative Example 2 is high because the pH value is not adjusted to a proper value in the step of removing copper and aluminum, and the impurities have a certain negative effect on the initial discharge capacity; the electrochemical performance of the lithium iron phosphate product prepared in Comparative Example 3 is poor because the spray drying and the first sintering step are omitted, and the product has uneven particle size and produces sintering impurity phases.

[0152] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent replacements for some or all of the technical features; and such modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the examples of the present application.

[0153] In addition, those skilled in the art can understand that although some of the embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in the BACKGROUND section is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A short-range high-value recovery method of waste old lithium iron phosphate battery, characterized in that, The application relates to a preparation method of a lithium iron phosphate material. The waste lithium iron phosphate battery powder is subjected to acid leaching to obtain leaching residues and leaching liquor; The leaching liquor is added into a first adjusting agent to adjust the pH value to 1.8-2.5 for one-stage purification to obtain one-stage purified liquor and copper-containing residues; The one-stage purified liquor is added into a first adjusting agent to adjust the pH value to 2.5-3.5 for two-stage purification to obtain two-stage purified liquor and aluminum-fluorine residues; The two-stage purified liquor is subjected to extraction to obtain raffinate; The raffinate is added into a second adjusting agent to adjust the composition ratio to obtain a solution after ratio adjustment; The solution after ratio adjustment is added into ammonia water to adjust the pH value to 10-14 for precipitation to obtain slurry after precipitation; The slurry after precipitation is added into a carbon source and water to adjust the solid content and is subjected to ball milling to obtain slurry after ball milling; The slurry after ball milling is subjected to spray drying to obtain a precursor; The precursor is subjected to sintering to obtain a lithium iron phosphate material; The first adjusting agent is at least one selected from iron powder, ammonium phosphate, diammonium hydrogen phosphate; The second adjusting agent is at least one selected from lithium dihydrogen phosphate, lithium phosphate, lithium hydroxide, diiron trioxide and phosphoric acid.

2. The short run high value recovery process of spent and old lithium iron phosphate battery as claimed in claim 1 wherein, At least one of the following conditions is met: A. The acid used in the acid leaching is phosphoric acid; B. The temperature of the acid leaching is 20-80 DEG C, and the time is 1-3 h; C. The liquid-solid ratio of the acid leaching is (3-5) mL:1 g; D. The molar concentration of phosphoric acid in the leaching liquor is 3-5 mol / L.

3. The method of short run high value recovery of spent lithium ion battery of iron phosphate as claimed in claim 1 wherein, At least one of the following conditions is met: A. The temperature of the one-stage purification is 20-50 DEG C, and the time is 1-3 h; B. The temperature of the two-stage purification is 20-50 DEG C, and the time is 0.5-3 h.

4. The short run high value recovery process of spent and old lithium iron phosphate battery as claimed in claim 1 wherein, The molar ratio of Li, Fe and P in the solution after ratio adjustment is (1-1.04):(0.95-0.98):

1.

5. The short run high value recovery process of spent and old lithium iron phosphate battery as claimed in claim 1 wherein, The precipitation time is 5-10 h, and the precipitation temperature is 30-60 DEG C.

6. The method of short run high value recovery of spent lithium ion battery of iron phosphate of claim 1, wherein, At least one of the following conditions is met: A. The molar amount of the carbon source is 10%-20% of the molar amount of Li in the slurry after precipitation; B. The solid content is 30%-40%; C. The ball milling time is 5-20 h.

7. The method of short run high value recovery of spent lithium ion battery of iron phosphate as claimed in claim 1 wherein, The inlet air temperature of the spray drying is 100-130 DEG C. And / or, the particle size of the precursor is 20-50 mu m.

8. The short run high value recovery process of spent and old lithium iron phosphate battery of claim 1 wherein, The sintering comprises one-stage sintering and two-stage sintering, and at least one of the following conditions is met: A. The atmosphere of the one-stage sintering and the two-stage sintering is inert atmosphere; B. The temperature of the one-stage sintering is 400-600 DEG C; C. The heating rate of the one-stage sintering is 2-5 DEG C / min; D. The holding time of the one-stage sintering is 5-10 h; E. The temperature of the two-stage sintering is 650-800 DEG C; F. The heating rate of the two-stage sintering is 2-5 DEG C / min; G. The holding time of the two-stage sintering is 8-10 h.

9. The short run high value recovery process of spent and old lithium iron phosphate battery of claim 1 wherein, Further comprising: The leaching residues are washed to obtain washing water and washing residues, the washing water is combined with the leaching liquor, and the washing residues are dried to obtain carbon residues.

10. The method of short range high value recovery of spent lithium ion battery of claim 9, wherein, The liquid to solid ratio of the washing is (5-10) mL:1 g. The liquid to solid ratio of the washing is (5-10) mL:1 g.

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