Method for recycling lithium, iron and phosphorus from waste lithium iron phosphate battery positive pole powder

Abstract

This application provides a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder, relating to the field of battery recycling. The method includes: mixing waste lithium iron phosphate battery cathode powder, a reducing agent, and a chlorinating agent to obtain a mixture; subjecting the mixture to a first roasting under an inert atmosphere, followed by a second roasting under an oxygen-containing atmosphere, to obtain volatile gases and solid roasted sand; condensing the volatile gases to obtain lithium-containing dust, and subjecting the lithium-containing dust to a first water leaching to obtain a lithium-containing liquid; mixing the solid roasted sand with water, performing a second water leaching and solid-liquid separation to obtain a water-leached liquid and water-leached residue; subjecting the water-leached residue to wet magnetic separation to obtain magnetically separated iron concentrate and non-magnetic phosphorus slag. This method efficiently recovers lithium chloride through volatilization, and the iron powder and phosphorus generated by magnetic separation and reduction are fixed into stable calcium phosphate, avoiding the cross-contamination problems caused by element separation in traditional processes, and achieving the directional migration of the three elements.

Description

Technical Field

[0001] This application relates to the field of battery recycling, and in particular to a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage industries, the amount of waste lithium iron phosphate batteries generated has been increasing year by year. Among these, cathode powder, as the core functional material of the battery, contains abundant valuable elements such as lithium, iron, and phosphorus. If it cannot be effectively recycled, it will not only waste strategic resources such as lithium and phosphorus, but may also cause soil and water pollution due to leakage of heavy metals and electrolytes from the electrode materials, posing a potential threat to the ecological environment. Therefore, developing economical, efficient, and environmentally friendly waste lithium iron phosphate cathode powder recycling technology has become a key issue in the field of resource recycling.

[0003] Currently, the main technologies for recycling waste lithium iron phosphate cathode powder include wet leaching oxidative roasting and chlorination roasting. Wet leaching technology is based on acid leaching, using strong acids (such as sulfuric acid and hydrochloric acid) to dissolve lithium, iron, and phosphorus in the cathode powder, followed by elemental separation through chemical precipitation and solvent extraction. However, existing technologies rely on strong acid leaching, requiring multiple chemical precipitation steps for impurity removal. This process is complex and generates large amounts of acidic wastewater. Lithium recovery is not incorporated into the core process, resulting in limitations in resource utilization.

[0004] Oxidative roasting, as a key pretreatment method for the resource recovery of spent lithium-ion batteries, can achieve crystal transformation and elemental morphology control of electrode materials through high-temperature oxidation, thereby improving the recovery efficiency of target metals. For example, Chinese invention patent (CN109088120B) discloses a method for preparing battery-grade lithium carbonate from spent lithium iron phosphate electrode sheets. This method involves oxidizing and roasting the spent lithium iron phosphate electrode sheets at 700-850°C after releasing their remaining charge, causing the binder and conductive carbon black to burn, resulting in a roasted material containing lithium iron phosphate active material and aluminum foil. Subsequently, lithium is separated and recovered through crushing, sieving, acid dissolution, and alkali dissolution steps, ultimately yielding battery-grade lithium carbonate. However, in this method, the oxidative roasting causes iron to exist in a non-magnetic form, making direct magnetic separation impossible. Acid leaching and other steps are required, making the process lengthy.

[0005] Compared to the high pollution of wet acid leaching and the process limitations of oxidative roasting, chlorination roasting has become an important technological direction in the field of waste lithium iron phosphate cathode powder recycling due to its synergistic conversion ability of multiple elements. Related patent technologies have also been explored in a variety of ways around this idea.

[0006] Chinese invention patent (CN110835683B) discloses a method for selectively extracting lithium from waste lithium-ion battery materials. The method involves oxidizing and roasting cathode materials such as lithium iron phosphate, and then using calcium chloride or lime milk solution to extract lithium, thereby achieving the separation of lithium from iron and phosphorus. However, it has limitations such as the need for additional treatment of iron, low phosphorus utilization, and high requirements for equipment corrosion resistance.

[0007] Chinese invention patent (CN106365180B) discloses a process for extracting high-purity lithium chloride from lithium ore. The process involves chlorinating and roasting a mixture of spodumene powder with ammonium chloride and calcium chloride at 600-800°C, removing impurities, and then obtaining high-purity lithium chloride through extraction or precipitation. However, this method is for lithium ore and only focuses on the recovery of lithium, without involving the recovery and utilization of iron and phosphorus.

[0008] Chinese invention patent (CN107180999B) discloses a method for the comprehensive utilization of waste lithium iron phosphate material. The method involves mixing and calcining the material with chloride, then introducing chlorine gas to react the mixture. The tail gas is then condensed to recover ferric chloride, and the lithium chloride solution and phosphorus-containing filter residue are obtained through leaching and filtration. However, this method requires the introduction of chlorine gas, and the reaction conditions are relatively complex.

[0009] Chinese invention patent (CN114835099B) discloses a method for recycling waste lithium iron phosphate. After crushing and screening, it is extracted with hydrochloric acid using a wet process. Through oxidation, phosphoric acid precipitation and other steps, iron, phosphorus and lithium are recovered and lithium iron phosphate is regenerated. Hydrochloric acid is also recycled. However, this method uses a wet process and requires multiple liquid-solid separations and the participation of chemical reagents.

[0010] Chinese invention patent (CN119191392B) discloses a method for extracting and recovering metal elements from lithium batteries using chlorination. After removing organic matter by roasting, the metal salts are recovered by chlorination in stages using a Joule heating device under a chlorine atmosphere, followed by gas sublimation and precipitation treatment. However, this method relies on a chlorine atmosphere and precise temperature control in multiple stages. Iron is recovered in the form of ferric hydroxide and phosphorus recovery is not involved.

[0011] Existing technologies for recycling waste lithium iron phosphate cathode powder have significant limitations: hydrometallurgy relies on strong acid leaching, which causes lithium, iron, and phosphorus to dissolve simultaneously in the solution to form complexes, resulting in low separation efficiency and the generation of large amounts of acidic wastewater; in pyrometallurgy, oxidative roasting converts iron into non-magnetic oxides, requiring additional treatment; chlorination roasting relies on highly toxic chlorine gas, leading to waste of phosphorus resources or environmental risks, and most technologies only focus on the recovery of a single element, failing to achieve the synergistic separation of lithium, iron, and phosphorus, resulting in lengthy processes and low overall recovery rates.

[0012] Therefore, there is an urgent need to provide a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder to solve the above problems. Summary of the Invention

[0013] The purpose of this application is to provide a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder, so as to solve the above-mentioned problems.

[0014] To achieve the above objectives, this application provides a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder, comprising:

[0015] The waste lithium iron phosphate battery cathode powder, reducing agent and chlorinating agent are mixed to obtain a mixture.

[0016] The mixture is first calcined in an inert atmosphere and then second calcined in an oxygen-containing atmosphere to obtain volatile gases and solid calcined sand.

[0017] The volatile gas is condensed to obtain lithium-containing dust, and the lithium-containing dust is subjected to a first water immersion to obtain lithium-containing liquid;

[0018] The solid-phase roasted sand is mixed with water and subjected to a second water leaching and solid-liquid separation to obtain water leaching liquid and water leaching residue. The water leaching residue is then subjected to wet magnetic separation to obtain magnetically separated iron concentrate and non-magnetic phosphorus slag.

[0019] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0020] (1) The waste lithium iron phosphate battery cathode powder is prepared by dismantling, crushing and screening the waste lithium-ion battery;

[0021] (2) The lithium content in the waste lithium iron phosphate battery cathode powder is 2.5%-5%, the iron content is 20%-30%, and the phosphorus content is 12%-20%.

[0022] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0023] (1) The reducing agent includes a low-reducing component and a high-reducing component;

[0024] The low-reducing components include one or more of graphite powder, coke, and unactivated coconut shell charcoal;

[0025] The high-reducing components include activated carbon and / or waste lithium battery negative electrode powder;

[0026] (2) The mass of the reducing agent accounts for 5%-12% of the mass of the waste lithium iron phosphate battery cathode powder;

[0027] (3) The chlorinating agent includes anhydrous calcium chloride and / or calcium chloride dihydrate;

[0028] (4) The mass of the chlorinating agent accounts for 25%-50% of the mass of the waste lithium iron phosphate battery cathode powder.

[0029] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0030] (1) The mass ratio of the low-reducing component to the high-reducing component is 1-3:1;

[0031] (2) The mass ratio of the anhydrous calcium chloride to the dihydrate calcium chloride is 3-5:1;

[0032] (3) Before the waste lithium battery negative electrode powder is used as the high reducing component, it is also pretreated. The pretreatment temperature is ≥800℃ and the time is 1h-4h.

[0033] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0034] (1) The final temperature of the first roasting is 600℃-1000℃, and the holding time is 1h-3h;

[0035] (2) The final temperature of the second roasting is 1000℃-1300℃, and the holding time is 1h-3h.

[0036] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0037] (1) When the final temperature of the second calcination is 1000℃-1100℃, the holding time is 2.5h-3h, and the mass of the reducing agent accounts for 8%-12% of the mass of the waste lithium iron phosphate battery cathode powder;

[0038] When the final temperature of the second calcination is >1100℃, the mass of the reducing agent accounts for 5%-8% of the mass of the waste lithium iron phosphate battery cathode powder;

[0039] When the final temperature of the second calcination is greater than 1100℃ but less than 1200℃, the holding time is 1.5-2.5h;

[0040] When the final temperature of the second calcination is 1200℃-1300℃, the holding time is 1-1.5h;

[0041] (2) As the final temperature of the second calcination increases, the proportion of the low-activity component in the reducing agent decreases sequentially until the mass ratio of the low-activity component to the high-activity component is 1:1.

[0042] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0043] (1) The condensation temperature is 100℃-200℃;

[0044] (2) The liquid-to-solid ratio of the first water immersion is 2mL-10mL:1g, and the temperature is 10℃-95℃.

[0045] Optionally, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0046] (1) The temperature of the second water immersion is room temperature;

[0047] (2) The liquid-to-solid ratio of the second water immersion is 5mL-10mL:1g.

[0048] Optionally, the wet magnetic separation includes a first magnetic separation and a second magnetic separation performed sequentially;

[0049] The magnetic field strength for the first magnetic separation is 100-200 mT;

[0050] The magnetic field strength for the second magnetic separation is 50-80 mT.

[0051] Optionally, the method for recovering lithium, iron, and phosphorus from the waste lithium iron phosphate battery cathode powder is adopted, wherein the recovery rate of lithium is ≥90%, the recovery rate of iron is ≥78%, and the solidification rate of phosphorus is ≥88%.

[0052] Compared with the prior art, the beneficial effects of this application include:

[0053] The method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder provided in this application involves the efficient volatilization recovery of lithium chloride, and the iron powder and phosphorus generated by magnetic separation and reduction are fixed into stable calcium phosphate. This avoids the problem of cross-contamination caused by element separation in traditional processes and achieves the directional migration of the three elements. By utilizing the differences in water solubility and magnetic properties of the products, the application of complex chemical reagents is not required, avoiding the large amount of acidic phosphorus-containing wastewater generated by traditional acid leaching processes, thus reducing environmental pressure. The entire process is short, has a high recovery rate, and is suitable for industrial applications. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0055] Figure 1This is a schematic diagram of the process for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder provided in Example 1. Detailed Implementation

[0056] First, the solution provided in this application will be explained in more detail as follows:

[0057] This application provides a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder, including:

[0058] The waste lithium iron phosphate battery cathode powder, reducing agent and chlorinating agent are mixed to obtain a mixture.

[0059] It is important to note that the chlorinating agent reacts with lithium iron phosphate, disrupting its stable structure. The reducing agent provides a reducing environment during the roasting process. Its presence inhibits the peroxidation and decomposition of lithium chloride, while simultaneously reducing high-valence iron to metallic iron, facilitating efficient enrichment via subsequent wet magnetic separation. Furthermore, the exothermic combustion of the reducing agent replaces an external heat source, reducing energy consumption.

[0060] The mixture is first calcined under an inert atmosphere and then second calcined under an oxygen-containing atmosphere to obtain volatile gases and solid calcined sand.

[0061] It is important to note that the first roasting aims to isolate oxygen: on the one hand, it selectively volatilizes lithium, as the chlorinating agent reacts with lithium iron phosphate to form lithium chloride, which escapes in gaseous form; on the other hand, it effectively inhibits the oxidation of iron, preserving a low-valence iron source for subsequent reduction reactions. The second roasting aims to regulate the conversion of the reducing agent: the solid carbon-based reducing agent generates gaseous carbon monoxide, transforming the reduction reaction from a solid-solid contact reaction to a gas-solid diffusion reaction, resulting in more advantageous reaction kinetics and significantly accelerating the overall reduction rate and uniformity.

[0062] The volatile gas is condensed to obtain lithium-containing dust, and the lithium-containing dust is subjected to a first water immersion to obtain lithium-containing liquid;

[0063] The solid-phase roasted sand is mixed with water and subjected to a second water leaching and solid-liquid separation to obtain water leaching liquid and water leaching residue. The water leaching residue is then subjected to wet magnetic separation to obtain magnetically separated iron concentrate and non-magnetic phosphorus slag.

[0064] It is important to note that the second water leaching selectively dissolves unreacted chlorides such as sodium chloride, as well as other soluble impurities, while simultaneously reducing the viscosity of the slurry and dispersing the particles. Wet magnetic separation then directionally enriches strongly magnetic substances, while non-magnetic phases, including phosphates and trace amounts of silica and aluminum impurities, are discharged as separate products. Therefore, the second water leaching provides the foundation for magnetic separation by dissolving impurities and dispersing particles, while the magnetic separation itself achieves efficient separation within the optimized system.

[0065] It should also be noted that this method designs a synergistic reaction of lithium volatilization, iron reduction and phosphorus fixation through carbothermal reduction and chlorination roasting, achieving differentiated and efficient separation of lithium, iron and phosphorus. The process is short, has a high recovery rate, and is suitable for industrial applications.

[0066] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0067] (1) The waste lithium iron phosphate battery cathode powder is prepared by dismantling, crushing and screening the waste lithium-ion battery;

[0068] (2) The lithium content in the waste lithium iron phosphate battery cathode powder is 2.5%-5%, the iron content is 20%-30%, and the phosphorus content is 12%-20%.

[0069] Optionally, the lithium content in the waste lithium iron phosphate battery cathode powder can be any value between 2.5%, 3%, 4%, 5% or 2.5%-5%, the iron content can be any value between 20%, 25%, 30% or 20%-30%, and the phosphorus content can be any value between 12%, 14%, 16%, 18%, 20% or 12%-20%.

[0070] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0071] (1) The reducing agent includes a low-reducing component and a high-reducing component;

[0072] The low-reducing components include one or more of graphite powder, coke, and unactivated coconut shell charcoal;

[0073] The high-reducing components include activated carbon and / or waste lithium battery negative electrode powder;

[0074] It is important to note that low-reducing components have stable structures and low activity. Using only low-reducing components may result in an insufficient degree of reaction, insufficient formation of magnetic iron, and consequently, low recovery rate of magnetic iron. High-reducing components, on the other hand, have high activity, and the rapid exothermic reaction during calcination can lead to localized overheating. Therefore, a combination of low-reducing and high-reducing components can be used to achieve deep reduction at different temperature ranges.

[0075] (2) The mass of the reducing agent accounts for 5%-12% of the mass of the waste lithium iron phosphate battery cathode powder;

[0076] Optionally, the mass of the reducing agent can be any value between 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 5%-12% of the mass of the waste lithium iron phosphate battery cathode powder.

[0077] (3) The chlorinating agent includes anhydrous calcium chloride and / or calcium chloride dihydrate;

[0078] It is important to note that calcium chloride dihydrate dehydrates first in the low-temperature range (<300℃), generating water vapor, which makes the material fluffy and increases its porosity, providing a channel for subsequent chlorination; anhydrous calcium chloride continuously provides a chlorination environment during medium and high-temperature calcination, ensuring the continuous generation and volatilization of lithium chloride; with chlorinating agents such as sodium chloride and ammonium chloride, the byproduct of the calcium chloride system is calcium phosphate, which is an inert solid phase and will not contaminate the volatile phase;

[0079] (4) The mass of the chlorinating agent accounts for 25%-50% of the mass of the waste lithium iron phosphate battery cathode powder.

[0080] Optionally, the mass of the chlorinating agent can be any value between 25%, 30%, 35%, 40%, 45%, 50%, or 25%-50% of the mass of the waste lithium iron phosphate battery cathode powder.

[0081] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0082] (1) The mass ratio of the low-reducing component to the high-reducing component is 1-3:1;

[0083] Optionally, the mass ratio of the low-reducing component to the high-reducing component can be any value between 1:1, 2:1, 3:1, or 1-3:1;

[0084] It is important to note that if the mass ratio of low-reducing components to high-reducing components is too high, the low-reducing components will play a dominant role, reducing the overall reduction rate and requiring a longer calcination time, leading to increased energy consumption. If the mass ratio of low-reducing components to high-reducing components is too low, the high-reducing components will be excessive, increasing the cost of reducing agents and causing local overheating. This can lead to sintering or even melting of the solid calcined sand, which will adhere to the kiln wall and cause ring formation in the kiln body. At the same time, excessive high-active carbon will not react completely, resulting in low purity of the calcined sand product.

[0085] (2) The mass ratio of the anhydrous calcium chloride to the dihydrate calcium chloride is 3-5:1;

[0086] Optionally, the mass ratio of anhydrous calcium chloride to calcium chloride dihydrate can be any value between 3:1, 4:1, 5:1, or 3-5:1;

[0087] It is important to note that if the mass ratio of anhydrous calcium chloride to calcium chloride dihydrate is too high, the excessive proportion of anhydrous calcium chloride will cause the material to clump due to its hygroscopic properties, resulting in uneven heating. Insufficient water of crystallization provided by calcium chloride dihydrate will lead to low humidity inside the kiln, causing lithium chloride to easily condense and form scale on the kiln walls after volatilization. Conversely, if the mass ratio of anhydrous calcium chloride to calcium chloride dihydrate is too low, excessive water of crystallization will be released by calcium chloride dihydrate, resulting in kiln humidity >30%. This will cause volatilized lithium chloride and water vapor to form droplets, which will fall into the solid phase with the calcined sand, leading to a decrease in lithium separation rate. Furthermore, the added calcium element will not fully participate in the reaction due to insufficient chloride ions, and some phosphorus will exist in the form of soluble phosphate, resulting in some phosphorus loss.

[0088] (3) Before the waste lithium battery negative electrode powder is used as the high reducing component, it is also pretreated. The pretreatment temperature is ≥800℃ and the time is 1h-4h.

[0089] Optionally, the pretreatment temperature can be any value of 800℃, 900℃, 1000℃, 1100℃, 1200℃ or ≥800℃, and the time can be any value of 1h, 2h, 3h, 4h or 1-4h.

[0090] It is important to note that because waste lithium battery negative electrode powder contains binders, electrolyte residues, and metallic impurities, pretreatment can remove organic impurities and avoid interference during the roasting process. Simultaneously, high-temperature pretreatment can disrupt some of the interlayer structure of the graphite in the negative electrode powder, increasing surface active sites and improving its reduction performance. Furthermore, the reduction performance of pretreated waste negative electrode powder is comparable to that of activated carbon, but at a lower cost. The pretreatment process can be combined with waste heat recovery from the roasting system to reduce additional energy consumption.

[0091] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0092] (1) The final temperature of the first roasting is 600-1000℃, and the holding time is 1-3h;

[0093] Optionally, the final temperature of the first roasting can be any value between 600℃, 700℃, 800℃, 900℃, 1000℃ or 600-1000℃, and the time can be any value between 1h, 2h, 3h or 1-3h.

[0094] It should be noted that the first sintering can remove residual electrolyte and adsorbed water from the material;

[0095] (2) The final temperature of the second roasting is 1000℃-1300℃, and the holding time is 1h-3h.

[0096] Optionally, the final temperature of the second roasting can be any value between 1000℃, 1200℃, 1300℃ or 1000℃-1300℃, and the holding time can be any value between 1h, 2h, 3h or 1-3h.

[0097] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0098] (1) When the final temperature of the second calcination is 1000℃-1100℃, the holding time is 2.5h-3h, and the mass of the reducing agent accounts for 8%-12% of the mass of the waste lithium iron phosphate battery cathode powder;

[0099] Optionally, when the final temperature of the second calcination is any value between 1000℃, 1050℃, 1100℃ or 1000℃-1100℃, the holding time can be any value between 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3h or 2.5-3h, and the mass of the reducing agent can be any value between 8%, 9%, 10%, 11%, 12% or 8%-12% of the mass of the waste lithium iron phosphate battery cathode powder;

[0100] When the final temperature of the second calcination is >1100℃, the mass of the reducing agent accounts for 5%-8% of the mass of the waste lithium iron phosphate battery cathode powder;

[0101] Optionally, when the final temperature of the second calcination is 1110℃, 1150℃, 1200℃, 1250℃, 1300℃ or any value greater than 1110℃, the mass of the reducing agent can be any value between 5%, 6%, 7%, 8% or 5-8% of the mass of the waste lithium iron phosphate battery cathode powder.

[0102] When the final temperature of the second calcination is greater than 1100℃ but less than 1200℃, the holding time is 1.5-2.5h;

[0103] Optionally, when the final temperature of the second roasting can be any value of 1110℃, 1150℃, 1190℃ or greater than 1100℃ and less than 1200℃, the holding time can be any value of 1.5h, 2h, 2.5h or between 1.5 and 2.5h.

[0104] When the final temperature of the second calcination is 1200℃-1300℃, the holding time is 1-1.5h;

[0105] Optionally, when the final temperature of the second roasting can be any value between 1200℃, 1250℃, 1300℃ or 1200℃-1300℃, the holding time can be any value between 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h or 1-1.5h.

[0106] It is important to note the following relationship between the amount of reducing agent, temperature, and time: At 1000-1100℃, the reactivity is low and the reduction kinetics are slow. Sufficient reduction kinetics need to be provided by increasing the amount of reducing agent (8%-12%), while extending the holding time (2.5-3h) to ensure complete reaction. At 1100-1300℃, the reactivity is significantly improved. Excessive reducing agent will lead to over-reduction, and unreacted carbon will form a coating structure with calcium phosphate, resulting in a decrease in the purity of phosphorus slag. Therefore, the amount of reducing agent needs to be reduced (5%-8%), and the holding time should be further shortened as the temperature increases to avoid energy waste.

[0107] (2) As the final temperature of the second calcination increases, the proportion of the low-activity component in the reducing agent decreases sequentially until the mass ratio of the low-activity component to the high-activity component is 1:1.

[0108] In some embodiments, when the second calcination temperature is 1100-1300°C, the mass ratio of the low-activity component to the high-activity component of the reducing agent is 1:1.

[0109] It is important to note that the chlorination-reduction reaction rate is relatively slow at 1000-1100℃, and the highly active component already possesses a certain level of reactivity at this temperature. If the proportion of low-activity component is insufficient, the highly active component is prone to concentrated heat release, causing the local temperature to rise too quickly and resulting in ring formation within the kiln. When the temperature rises to 1100℃, the reaction kinetics significantly intensify, and the reduction reaction's demand for active sites is lower than in the low-temperature range. At this point, reducing the proportion of low-activity component to 1:1 allows for the provision of sufficient active sites through highly active components (such as pretreated negative electrode powder), matching the rapid reaction requirements at high temperatures and ensuring deep reduction is completed within 1-2 hours.

[0110] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0111] (1) The condensation temperature is 100℃-200℃;

[0112] Optionally, the condensation temperature can be any value between 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or 100℃-200℃.

[0113] (2) The liquid-to-solid ratio of the first water immersion is 2mL-10mL:1g, and the temperature is 10℃-95℃.

[0114] Optionally, the liquid-to-solid ratio of the first water immersion can be any value between 2 mL:1 g, 3 mL:1 g, 4 mL:1 g, 5 mL:1 g, 6 mL:1 g, 7 mL:1 g, 8 mL:1 g, 9 mL:1 g, 10 mL:1 g, or 2 mL:10 mL:1 g, and the temperature can be any value between 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 95℃, or 10℃-95℃.

[0115] In some embodiments, the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder satisfies at least one of the following conditions:

[0116] (1) The temperature of the second water immersion is room temperature;

[0117] (2) The liquid-to-solid ratio of the second water immersion is 5mL-10mL:1g.

[0118] Optionally, the liquid-to-solid ratio of the second water immersion can be any value between 5 mL:1g, 6 mL:1g, 7 mL:1g, 8 mL:1g, 9 mL:1g, 10 mL:1g, or 5 mL:10 mL:1g.

[0119] In some embodiments, the wet magnetic separation includes a first magnetic separation and a second magnetic separation performed sequentially;

[0120] The magnetic field strength for the first magnetic separation is 100-200 mT;

[0121] Optionally, the magnetic field strength for the first magnetic separation can be any value between 100mT, 150mT, 200mT, or 100mT-200mT.

[0122] The magnetic field strength for the second magnetic separation is 50-80 mT.

[0123] Optionally, the magnetic field strength for the second magnetic separation can be any value between 50mT, 60mT, 70mT, 80mT, or 50mT-80mT.

[0124] It should be noted that the first magnetic separation is used to collect strongly magnetic products, while the second magnetic separation can be used for secondary recovery of tailings from the first magnetic separation.

[0125] In some embodiments, a method for recovering lithium, iron, and phosphorus using the waste lithium iron phosphate battery cathode powder is described, wherein the lithium recovery rate is ≥90%, the iron recovery rate is ≥78%, and the phosphorus solidification rate is ≥88%.

[0126] Optionally, the lithium recovery rate can be any value of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or ≥90%, the iron recovery rate can be any value of 78%, 80%, 85%, 90% or ≥78%, and the phosphorus solidification rate can be any value of 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or ≥88%.

[0127] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0128] Because the composition of waste lithium iron phosphate battery cathode powder varies greatly, it is prepared by dismantling, crushing, and sieving (through a 150-mesh sieve) the waste lithium-ion batteries to remove metallic impurities such as aluminum foil and copper foil. The method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder of this application is applicable to waste lithium iron phosphate battery cathode powder of various compositions. To illustrate the extraction effect of lithium, iron, and phosphorus, a typical waste lithium iron phosphate battery cathode powder is used for explanation. In addition, to better compare the method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder of this application, the same waste lithium iron phosphate battery cathode powder is used in the following examples and comparative examples. The specific composition is shown in Table 1.

[0129] Table 1 Raw Material List of Waste Lithium Iron Phosphate Battery Cathode Powder / %

[0130]

[0131] Example 1

[0132] This embodiment provides a method for recovering lithium, iron, and phosphorus from waste lithium iron phosphate battery cathode powder. A schematic flowchart is shown below. Figure 1 As shown, the specific steps are as follows:

[0133] S1: Take 10.0 kg of waste lithium iron phosphate battery cathode powder, 0.6 kg of reducing agent (6.0% of the cathode powder mass), and 2.5 kg of chlorinating agent (25.0% of the cathode powder mass) and mix them to obtain a mixture; wherein, the reducing agent includes a low reducing component (graphite powder) and a high reducing component (activated carbon) in a mass ratio of 3:1, and the chlorinating agent is anhydrous calcium chloride and calcium chloride dihydrate in a mass ratio of 5:1;

[0134] S2: Place the mixture in a rotary kiln, introduce inert gas (argon) to replace the air, raise the temperature to 600℃, and hold for 1.0h to complete the first calcination; then stop the introduction of inert gas, raise the temperature to 1100℃, and hold for 3h to complete the second calcination, to obtain volatile gas and solid calcined sand.

[0135] S3: The volatile gas is condensed at 200℃ to obtain lithium-containing dust. The lithium-containing dust is then soaked in water at 95℃ with a liquid-to-solid ratio of 10mL:1g to obtain lithium-containing liquid.

[0136] S4: At room temperature, solid roasted sand and water are mixed and stirred at a solid-liquid ratio of 1g:5mL, filtered to obtain water leaching liquid and water leaching residue. The water leaching residue is separated by wet magnetic separation to obtain magnetically separated iron concentrate and non-magnetic phosphorus slag. The wet magnetic separation includes a first magnetic separation and a second magnetic separation performed sequentially. The magnetic field strength of the first magnetic separation is 200mT. The magnetic field strength of the second magnetic separation is 80mT.

[0137] Example 2

[0138] The difference from Example 1 is that the amount of reducing agent used is 1 kg (accounting for 10% of the mass of the positive electrode powder), and the final temperature during the second calcination is 1000°C, and the holding time is 2.5 h.

[0139] Example 3

[0140] The difference from Example 1 is that the amount of reducing agent used is 1.2 kg (accounting for 12% of the mass of the positive electrode powder), and the final temperature during the second calcination is 1150°C, and the holding time is 1.5 hh.

[0141] Example 4

[0142] The difference from Example 1 is that the amount of reducing agent used is 0.6 kg (accounting for 6% of the mass of the positive electrode powder), and the final temperature during the second calcination is 1200°C, and the holding time is 1.5 hh.

[0143] Example 5

[0144] The difference from Example 1 is that the reducing agent includes a low reducing component (graphite powder, coke and unactivated coconut shell carbon) and a high reducing component (waste lithium battery negative electrode powder) in a mass ratio of 1:1. Before using the waste lithium battery negative electrode powder as the high reducing component, it is also pretreated at a temperature of 800°C for 4 hours.

[0145] Comparative Example 1

[0146] The difference from Example 1 is that no reducing agent is added.

[0147] Comparative Example 2

[0148] The difference from Example 1 is that no chlorinating agent is added.

[0149] Comparative Example 3

[0150] The difference from Example 1 is that only coke (low reducing component) is added as the reducing agent.

[0151] Comparative Example 4

[0152] The difference from Example 1 is that only activated carbon (a high-reducing component) is added as the reducing agent.

[0153] Comparative Example 5

[0154] The difference from Example 1 is that the mass ratio of the low-reducing component to the high-reducing component in the reducing agent is 5:1.

[0155] Comparative Example 6

[0156] The difference from Example 1 is that the mass of the reducing agent accounts for 3% of the mass of the waste lithium iron phosphate battery cathode powder.

[0157] Comparative Example 7

[0158] The difference from Example 1 is that the mass of the chlorinating agent accounts for 15% of the mass of the waste lithium iron phosphate battery cathode powder.

[0159] Comparative Example 8

[0160] The difference from Example 1 is that the first roasting is not performed.

[0161] Comparative Example 9

[0162] The difference from Example 1 is that the first calcination is carried out in air.

[0163] Comparative Example 10

[0164] The difference from Example 1 is that the second calcination is carried out in argon gas.

[0165] Comparative Example 11

[0166] The difference from Example 1 is that the first roasting is carried out in air, while the second roasting is carried out in argon.

[0167] The overall recovery rates of lithium, iron, and phosphorus in the above embodiments and comparative examples are shown in Table 2.

[0168] Table 2 Recovery Rate

[0169]

[0170] analyze:

[0171] As can be seen from the above tests, the recovery rate data of Examples 1-5 and Comparative Examples 1-8 show that the present invention is innovative in that it recovers lithium chloride through efficient volatilization, and the iron powder generated by magnetic separation and reduction is fixed into stable calcium phosphate.

[0172] Among them, without reducing agent (Comparative Example 1): the lithium recovery rate was only 12.3%, indicating that reducing agent is a prerequisite for iron reduction and lithium volatilization;

[0173] Without chlorinating agent (Comparative Example 2): the lithium recovery rate was only 15.7%, indicating that chlorinating agent is a necessary condition for lithium volatilization;

[0174] Without first roasting (Comparative Example 8): Lithium recovery rate was 41.5%, indicating that staged roasting is crucial for reaction stability.

[0175] The compound reducing agent has synergistic advantages. Single low-reducing component (Comparative Example 3): lithium recovery rate 82.4%, iron 80.6%, lower than Example 1 (96.5%, 85.2%), due to insufficient reducing agent activity;

[0176] Single high reducing component (Comparative Example 4): Iron recovery rate 75.3%, lower than Example 1, due to excessively strong reducing agent activity leading to local overheating;

[0177] The compound system (Example 5, 1:1) showed the best results with lithium recovery rate of 97.3%, iron recovery rate of 88.1%, and phosphorus solidification rate of 93.6%.

[0178] Inappropriate parameter settings are detrimental to improving the recovery rates of lithium, iron, and phosphorus. An imbalance in the reducing agent ratio (Comparative Example 5, 5:1): lithium recovery rate 88.6%, iron recovery rate 81.2%, indicating the necessity of a 1-3:1 ratio of low-reducing components and high-reducing components in the reducing agent.

[0179] Insufficient reducing agent / chlorinating agent dosage (Comparative Examples 6-7): Lithium recovery rates were 65.8% and 78.2%, respectively, indicating the rationality of a reducing agent ratio of 5%-12% and a chlorinating agent ratio of 25%-50%.

[0180] Examples 2-4 demonstrate the logic that a larger amount of reducing agent and a longer time are required at low temperatures, while a smaller amount of reducing agent and a shorter time are required at high temperatures, ensuring efficient and low-consumption recovery of lithium, iron, and phosphorus.

[0181] The first roasting was carried out in air (Comparative Example 9): the lithium recovery rate decreased to 45.8% and the iron recovery rate decreased to 77.3%, indicating that the first roasting must be carried out in an inert atmosphere to isolate oxygen in order to ensure the volatilization of LiCl and the reduction and magnetic separation of high-valence iron.

[0182] The second roasting was carried out in an inert gas atmosphere (Comparative Example 10): the inert atmosphere could not achieve the conversion of solid reducing agent to gaseous carbon monoxide, the reduction reaction was limited to solid-solid contact, so the iron recovery rate was low, at 62.8%.

[0183] Meanwhile, the first and second roasting atmospheres were changed. The roasting process used in Comparative Example 11 was: the first roasting was done with air and the second roasting was done with argon, which deviated from the process requirements of this invention. The recovery rates of lithium and iron were significantly reduced, far lower than those in Example 1.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0185] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for recovering lithium, iron and phosphorus from waste old lithium iron phosphate battery positive pole powder, characterized in that, The application relates to a method for preparing lithium phosphate from waste lithium iron phosphate battery positive electrode powder. The waste lithium iron phosphate battery positive electrode powder, a reducing agent and a chlorinating agent are mixed to obtain a mixture; The mixture is subjected to first roasting in an inert atmosphere and second roasting in an oxygen-containing atmosphere to obtain volatile gas and solid-phase roasted sand; The volatile gas is subjected to condensation treatment to obtain lithium-containing fume, and the lithium-containing fume is subjected to first water immersion to obtain lithium-containing liquid; The solid-phase roasted sand is mixed with water, subjected to second water immersion and solid-liquid separation to obtain water immersion liquid and water immersion residue, and the water immersion residue is subjected to wet magnetic separation to obtain magnetic iron concentrate and non-magnetic phosphorus residue; The chlorinating agent comprises anhydrous calcium chloride and / or calcium chloride dihydrate.

2. The method according to claim 1, characterized in that, At least one of the following conditions is met: (1) the waste lithium iron phosphate battery positive electrode powder is prepared by disassembling, crushing and screening waste lithium ion batteries; (2) the mass content of lithium in the waste lithium iron phosphate battery positive electrode powder is 2.5%-5%, the mass content of iron is 20%-30%, and the mass content of phosphorus is 12%-20%.

3. The method according to claim 1, characterized in that, At least one of the following conditions is met: (1) the reducing agent comprises a low-reduction component and a high-reduction component; The low-reduction component comprises one or more of graphite powder, coke and unactivated coconut shell carbon; The high-reduction component comprises activated carbon and / or waste lithium battery negative electrode powder; (2) the mass of the reducing agent accounts for 5%-12% of the mass of the waste lithium iron phosphate battery positive electrode powder; (3) the mass of the chlorinating agent accounts for 25%-50% of the mass of the waste lithium iron phosphate battery positive electrode powder.

4. The method for recovering lithium, iron and phosphorus from the positive pole powder of waste old lithium iron phosphate battery according to claim 3, characterized in that, At least one of the following conditions is met: (1) the mass ratio of the low-reduction component to the high-reduction component is 1-3:1; (2) the mass ratio of the anhydrous calcium chloride to the calcium chloride dihydrate is 3-5:1; (3) the waste lithium battery negative electrode powder is pretreated before being used as the high-reduction component, the temperature of the pretreatment is greater than or equal to 800 DEG C, and the time is 1h-4h.

5. The method for recovering lithium, iron and phosphorus from the positive pole powder of waste old lithium iron phosphate battery according to claim 3, characterized in that, At least one of the following conditions is met: (1) the terminal temperature of the first roasting is 600 DEG C-1000 DEG C, and the holding time is 1h-3h; (2) the terminal temperature of the second roasting is 1000 DEG C-1300 DEG C, and the holding time is 1h-3h.

6. The method for recovering lithium, iron and phosphorus from the positive pole powder of waste old lithium iron phosphate battery according to claim 5, characterized in that, At least one of the following conditions is met: (1) when the terminal temperature of the second roasting is 1000 DEG C-1100 DEG C, the holding time is 2.5h-3h, and the mass of the reducing agent accounts for 8%-12% of the mass of the waste lithium iron phosphate battery positive electrode powder; when the terminal temperature of the second roasting is greater than 1100 DEG C, the mass of the reducing agent accounts for 5%-8% of the mass of the waste lithium iron phosphate battery positive electrode powder; when the terminal temperature of the second roasting is greater than 1100 DEG C and less than 1200 DEG C, the holding time is 1.5-2.5h; when the terminal temperature of the second roasting is 1200 DEG C-1300 DEG C, the holding time is 1-1.5h; (2) with the increase of the terminal temperature of the second roasting, the proportion of the low-activity component in the reducing agent is sequentially reduced until the mass ratio of the low-activity component to the high-activity component is 1:

1.

7. The method according to claim 1, wherein the method is characterized by, At least one of the following conditions is met: (1) the condensation temperature is 100-200 DEG C; (2) the liquid-solid ratio of the first water immersion is 2-10 mL:1 g, and the temperature is 10-95 DEG C.

8. The method for recovering lithium, iron and phosphorus from the positive pole powder of waste old lithium iron phosphate battery according to claim 1, characterized in that, At least one of the following conditions is met: (1) the temperature of the second water immersion is room temperature; (2) the liquid-solid ratio of the second water immersion is 5-10 mL:1 g.

9. The method according to claim 1, wherein the method is characterized by, The wet magnetic separation includes a first magnetic separation and a second magnetic separation performed in sequence; The magnetic field strength of the first magnetic separation is 100-200 mT; The magnetic field strength of the second magnetic separation is 50-80 mT.

10. The method for recovering lithium, iron and phosphorus from the positive pole powder of waste and old lithium iron phosphate battery according to any one of claims 1-9, characterized in that, The method for recovering lithium, iron and phosphorus from the positive electrode powder of the waste lithium iron phosphate battery, wherein the recovery rate of lithium is greater than or equal to 90%, the recovery rate of iron is greater than or equal to 78%, and the solidification rate of phosphorus is greater than or equal to 88%.

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