A method for extracting phosphorus and lithium in high proportion by black powder alkali method roasting lithium iron phosphate

Abstract

The application discloses a method for extracting phosphorus and lithium in high proportion by black powder lithium iron phosphate alkali roasting, and the retired lithium iron phosphate battery is sequentially subjected to discharge, disassembly, crushing and sorting treatment to obtain lithium iron phosphate positive electrode black powder, and the moisture content is controlled after screening; the lithium iron phosphate positive electrode black powder is dry-mixed with sodium hydroxide and sodium carbonate, the mass ratio of the sodium hydroxide to the sodium carbonate is 1:1.2-1:5, and the mass ratio of the total mass of the sodium hydroxide and the sodium carbonate to the mass of the lithium iron phosphate positive electrode black powder is 0.8:1-1.5:1; the application avoids the use of a large amount of concentrated acid, reduces the generation of acid mist and other pollutants, and reduces the environmental protection treatment pressure; the final leaching final residue mainly comprises high-grade iron oxide, has low impurity content, and can be directly used as an iron red raw material in the building material, pigment and metallurgical industries, realizes the reduction and resource utilization of the whole-process solid waste, and meets the green and low-carbon industrial development concept.

Description

Technical Field

[0001] This invention relates to the field of lithium iron phosphate lithium-ion battery technology, and in particular to a method for high-proportion extraction of phosphorus and lithium by alkaline roasting of lithium iron phosphate black powder. Background Technology

[0002] With the rapid development of the new energy vehicle industry and energy storage power stations, lithium iron phosphate (LFP) batteries, with their core advantages such as high safety, long cycle life, and low raw material costs, have become the mainstream technology in the power and energy storage fields, and their market installation volume continues to climb. At the same time, the first batch of LFP batteries used in large-scale applications have entered their retirement phase, and the harmless treatment and valuable resource recycling of these used batteries have become key issues restricting the sustainable development of the industry.

[0003] In lithium iron phosphate cathode materials, the lithium content is approximately 3.5%~4.5%, the phosphorus content is approximately 15%~18%, and the iron content is approximately 30%~35%. Both lithium and phosphorus are important strategic resources with extremely high recycling value. Existing lithium iron phosphate black powder recycling processes mainly fall into two categories: wet direct acid leaching and pyrometallurgical roasting-wet leaching. However, both have significant technological shortcomings.

[0004] The wet direct acid leaching process typically uses sulfuric acid or mixed organic acids as leaching agents, relying on strong acids to directly destroy the crystal structure of lithium iron phosphate to dissolve lithium. This type of process has three major drawbacks: First, the phosphorus extraction rate is extremely low. During the leaching process, phosphate ions easily form insoluble phosphate precipitates with free iron ions, resulting in a large amount of phosphorus remaining in the leaching residue. The overall extraction rate is generally below 80%, causing a serious waste of phosphorus resources. Second, lithium extraction is insufficient. The olivine-type crystal structure of lithium iron phosphate is stable, and a single acid leaching system cannot completely break it down. The lithium leaching rate is usually only 60% to 75%. Third, the acid and alkali consumption is high. To improve the leaching effect, a large amount of strong acid needs to be added, resulting in high costs for subsequent neutralization treatment and serious acid mist pollution, putting great pressure on environmental protection.

[0005] The pyrometallurgical alkali roasting-leaching process destroys the crystal structure of the cathode material through the reaction of alkali with the cathode material at high temperature, and then recovers valuable elements through water leaching or acid leaching.

[0006] Existing technologies mostly use sodium hydroxide or sodium carbonate as calcination aids: Sodium hydroxide system has relatively strong reactivity, but requires a high temperature of over 800℃ to fully destroy the crystal structure, resulting in high energy consumption, severe equipment corrosion, and high sodium hydroxide procurement costs, which significantly increase the process operating costs; Sodium carbonate system has lower reagent costs, but insufficient reactivity, requiring calcination temperatures to be raised to over 850℃ to achieve a good reaction effect, and the simultaneous extraction of phosphorus and lithium is not ideal, making it difficult to achieve high recovery rates for both elements.

[0007] Furthermore, existing alkaline recovery processes generally lack a dedicated recovery step for residual lithium in the leaching residue. Some lithium is lost along with the iron-based leaching residue, resulting in a total lithium recovery rate that is generally difficult to exceed 93%, leading to a hidden loss of lithium resources. At the same time, most processes cannot achieve efficient separation of phosphorus, lithium, and iron during the leaching stage, requiring subsequent complex impurity removal and separation processes, further lengthening the process and increasing production costs.

[0008] In summary, existing technologies cannot simultaneously achieve high-proportion extraction of both phosphorus and lithium, two valuable elements, at relatively low calcination temperatures and reagent costs. There is an urgent need to develop a resource recovery method for lithium iron phosphate black powder that combines high extraction rate, low energy consumption, low reagent cost, and short process flow. Summary of the Invention

[0009] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting.

[0010] One of the objectives of this invention is achieved through the following technical solution: A method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting includes the following steps: (1) Raw material pretreatment: The retired lithium iron phosphate batteries are discharged, disassembled, crushed and sorted in sequence to obtain lithium iron phosphate cathode black powder, and the moisture content is controlled after sieving; (2) Mixed alkali ingredients: The lithium iron phosphate cathode black powder is dry-mixed with sodium hydroxide and sodium carbonate, wherein the mass ratio of sodium hydroxide to sodium carbonate is 1:1.2~1:5, and the total mass ratio of sodium hydroxide and sodium carbonate to the mass ratio of lithium iron phosphate cathode black powder is 0.8:1~1.5:1; (3) Medium-temperature roasting: The uniformly mixed material is placed in an air atmosphere for roasting. The roasting temperature is controlled at 500℃~700℃ and the roasting holding time is 60~180 minutes to obtain roasted clinker. (4) Main leaching treatment: Add water to the roasted clinker and stir evenly, then add dilute sulfuric acid to adjust the pH value of the system to 2.5~4.0, stir and leach at a temperature of 40℃~80℃, filter and separate to obtain phosphorus and lithium enriched leachate and iron-containing leachate residue. (5) Deep lithium extraction from leaching residue: Add dilute sulfuric acid solution to the leaching residue obtained in step (4), adjust the pH value of the system to 1.0~2.0, stir and acid wash at a temperature of 50℃~90℃, filter and separate to obtain lithium-rich acid washing solution and final residue, and return the lithium-rich acid washing solution to step (4) and combine it with the leaching solution. (6) Separation and purification: The combined leachate is separated and purified to prepare phosphorus products and lithium salt products respectively.

[0011] Furthermore, in step (1), the lithium iron phosphate cathode black powder is passed through a 200-mesh sieve to control the moisture content to 2%.

[0012] Furthermore, in step (2), the dry mixing is carried out in a mixer for 15 to 30 minutes to ensure that the materials are mixed evenly.

[0013] Furthermore, in step (2), the mass ratio of sodium hydroxide to sodium carbonate is 1:2 to 1:4, and the mass ratio of total alkali to lithium iron phosphate cathode black powder is 0.8:1 to 1.2:1.

[0014] Furthermore, in step (3), the calcination process is carried out in a rotary kiln or muffle furnace, with a calcination temperature of 550℃~650℃ and a calcination holding time of 90~150 minutes.

[0015] Furthermore, in step (4), after adding deionized water at a liquid-to-solid ratio of 3:1 to 8:1 and stirring for 30 minutes, dilute sulfuric acid with a concentration of 10% to 30% is added to adjust the pH value of the system, and the stirring and leaching time is 60 to 120 minutes.

[0016] Furthermore, in step (4), the pH value of the system is adjusted to 2.8~3.5, and the leaching temperature is 55℃~70℃.

[0017] Furthermore, in step (5), a dilute sulfuric acid solution with a concentration of 5% to 20% is added at a liquid-to-solid ratio of 2:1 to 5:1, and the acid washing time is 30 to 90 minutes.

[0018] Furthermore, in step (5), the pH value of the system is controlled at 1.2~1.8, and the acid washing temperature is 60℃~80℃.

[0019] Furthermore, in step (6), the separation and purification are carried out using chemical precipitation, extraction or ion exchange processes; the phosphorus product is an industrial phosphoric acid product, and the lithium salt product is lithium carbonate or lithium hydroxide.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention fully deconstructs the lithium iron phosphate crystal structure through mixed alkali roasting, converting phosphate into soluble sodium salt. Combined with precise pH control of 2.5~4.0 in the main leaching stage, more than 99% of phosphorus can enter the leachate, and the total phosphorus recovery rate can reach up to 99.6%.

[0021] 2. This invention adopts a segmented lithium extraction route of primary leaching for initial lithium extraction and leaching residue acid washing for deep lithium extraction. The primary leaching stage recovers about 78% of the lithium element, and then the remaining about 22% of the lithium in the residue is recovered through low acid deep washing. The total lithium recovery rate of the whole process can reach more than 98.5%, and can reach up to 99.0%.

[0022] 3. This invention employs a sodium hydroxide-sodium carbonate mixed alkali system with a specific ratio. The two alkalis work synergistically during the roasting process: sodium hydroxide initially disrupts the olivine crystal structure in the molten state, while sodium carbonate further reacts with the reaction intermediates to generate soluble lithium salts and stable iron oxides, jointly reducing the activation energy of the reaction. Compared to the roasting temperature of over 800℃ for a single alkali system, this invention can control the roasting temperature at 500~700℃, a temperature reduction of 150~250℃, significantly reducing production energy consumption. At the same time, it reduces the requirements for high temperature resistance and corrosion resistance of equipment, extending the service life of the equipment.

[0023] 4. This invention uses sodium carbonate, which is cheaper, as the main alkali agent, and only adds a small amount of sodium hydroxide to ensure the reactivity. The overall reagent cost of the mixed alkali system is reduced by more than 30% compared with the pure sodium hydroxide system. At the same time, the pH is precisely controlled by dilute sulfuric acid in the leaching stage, avoiding the use of a large amount of concentrated acid, further reducing the cost of reagent consumption and subsequent neutralization treatment, and greatly improving the industrial application value of the process.

[0024] 5. By precisely controlling the pH range during the main leaching stage, this invention enables the efficient dissolution of phosphorus and lithium while retaining iron in the leaching residue as a stable iron oxide solid phase. The iron leaching rate is less than 1%, achieving efficient separation of phosphorus, lithium and iron in one step. This eliminates the need for subsequent complex iron removal processes, significantly simplifies the process of phosphorus and lithium separation and purification, and reduces overall operating costs and equipment investment.

[0025] 6. This invention avoids the use of large amounts of concentrated acid, reduces the generation of pollutants such as acid mist, and lowers the pressure on environmental treatment; the final leaching residue mainly consists of high-grade iron oxide with low impurity content, and can be directly used as iron oxide red raw material in building materials, pigments, metallurgy and other industries, realizing the reduction and resource utilization of solid waste throughout the entire process, which is in line with the green and low-carbon industrial development concept.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is a flowchart of the extraction method in this embodiment. Detailed Implementation

[0028] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0029] It should be noted that when a component is said to be fixed to another component, it can be directly on the other component or it may have a component in between. When a component is said to be connected to another component, it can be directly connected to the other component or it may have a component in between. When a component is said to be set to another component, it can be directly set to the other component or it may have a component in between. The terms vertical, horizontal, left, right, and similar expressions used in this document are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terminology used herein includes, and / or encompasses, any and all combinations of one or more of the associated listed items.

[0031] Test materials and detection methods 1. Test materials The lithium iron phosphate cathode black powder used in the experiment was obtained from retired lithium iron phosphate power lithium batteries. It was obtained after complete discharge, manual disassembly, crushing, and air separation to remove aluminum foil and separator impurities. The powder was then passed through a 200-mesh standard sieve and dried in a 105℃ oven until the moisture content reached 2%. Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis showed that the main elemental mass fractions of the black powder were: Li 4.12%, P 16.85%, Fe 32.46%, with the remainder being carbon, organic binders, and trace impurities.

[0032] 2. Detection and Calculation Methods The contents of lithium, phosphorus, and iron in the solution and solid phase were quantitatively determined by ICP-OES; the elemental extraction rate and total recovery rate were calculated using the following formulas: Lithium extraction rate from main leaching = (Total mass of lithium in main leachate / Total mass of lithium in raw black powder) × 100% Total phosphorus recovery rate = (Total mass of phosphorus in the main leachate / Total mass of phosphorus in the raw black powder) × 100% Total lithium recovery rate = [(Total mass of lithium in the main leaching solution + Total mass of lithium in the acid leaching lithium-rich solution) / Total mass of lithium in the raw material black powder] × 100% Example 1 This embodiment provides a method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder via alkaline roasting. The specific operation steps are as follows: 1. Raw material pretreatment: Take 1000g of the above lithium iron phosphate cathode black powder, pass it through a 200-mesh sieve and dry it for 2 hours. The moisture content was measured to be 1.2%. Place it in a desiccator to cool and store it for later use.

[0033] 2. Mixing alkali ingredients: Weigh 200g of analytical grade sodium hydroxide and 600g of anhydrous sodium carbonate, and add them together with 1000g of lithium iron phosphate black powder into a horizontal ribbon mixer. The mass ratio of sodium hydroxide to sodium carbonate is 1:3, and the mass ratio of total alkali to black powder is 0.8:1. Turn on the mixer and stir at 60r / min for 20min to obtain a mixture with a homogeneity of 95%.

[0034] 3. Medium-temperature roasting: Transfer the mixture into a corundum crucible, place it in a box-type muffle furnace, and raise the temperature to 600°C at a rate of 5°C / min under air atmosphere. Roast at a constant temperature for 120 minutes. After roasting, allow the furnace to cool naturally to room temperature. Remove the roasted material and grind it until it passes through a 100-mesh sieve.

[0035] 4. Main leaching treatment: The roasted clinker is transferred into a jacketed leaching tank with stirring. Deionized water is added at a liquid-to-solid ratio of 5:1, and stirring is started (300 r / min) for pre-soaking for 30 min. A 20% dilute sulfuric acid solution is slowly added dropwise, and the pH value of the system is monitored and adjusted online to stabilize at 3.0. The temperature is raised to 60℃ by jacket heating and leached at a constant temperature with stirring for 90 min. After leaching, vacuum filtration is used to separate the phosphorus-rich lithium leachate and iron-containing leaching residue.

[0036] Testing revealed that the lithium extraction rate in the main leachate of this step was 78.2%, and the phosphorus extraction rate was 99.3%. The residual lithium content in the leaching residue was 0.18%, and the residual phosphorus content was 0.12%. Iron was mainly enriched in the leaching residue in the form of iron oxide, with an iron leaching rate of less than 1%, achieving efficient separation of phosphorus, lithium, and iron.

[0037] 5. Deep lithium extraction from leaching residue: Transfer the above leaching residue into an acid washing tank, add deionized water at a liquid-to-solid ratio of 3:1, stir evenly, then add 10% dilute sulfuric acid dropwise to adjust the pH of the system to 1.5, heat to 70℃, and stir and acid wash for 60 minutes; filter to separate the lithium-rich acid washing solution and the final residue, and return the lithium-rich acid washing solution to step 4 and combine it with the main leaching solution for further processing.

[0038] Testing revealed that the residual lithium content in the final slag after acid leaching was only 0.006%, and this step recovered 96.7% of the residual lithium in the leaching residue. Calculations showed that the total lithium recovery rate for the entire process was 98.8%, and the total phosphorus recovery rate was 99.5%.

[0039] 6. Separation and purification: After the combined leachate is oxidized to remove impurities and solvent extracted to separate phosphorus and lithium, the aqueous phase is concentrated and crystallized to prepare industrial-grade phosphoric acid products, and the lithium-loaded organic phase is back-extracted and then prepared into battery-grade lithium carbonate products through a sodium carbonate precipitation process.

[0040] Example 2 This embodiment provides a method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder via alkaline roasting. The specific operation steps are as follows: 1. Raw material pretreatment: Take 1000g of lithium iron phosphate cathode black powder from the same batch as in Example 1, dry it to a moisture content of 1.5%, and set it aside.

[0041] 2. Mixing alkali ingredients: Weigh 150g of sodium hydroxide and 750g of anhydrous sodium carbonate, and add them together with black powder into the mixer. The mass ratio of sodium hydroxide to sodium carbonate is 1:5, and the mass ratio of total alkali to black powder is 0.9:1. Stir and mix for 25 minutes to obtain a uniform mixture.

[0042] 3. Medium-temperature roasting: The mixture is fed into a continuous rotary roasting furnace and heated to 550°C in an air atmosphere, with the material residence time controlled at 150 minutes; after roasting, the material is discharged after water cooling and crushed and ground by a roller mill for later use.

[0043] 4. Main leaching treatment: Add deionized water at a liquid-to-solid ratio of 6:1 for pre-soaking for 30 minutes, add 15% dilute sulfuric acid dropwise to adjust the pH of the system to 3.5, raise the temperature to 65℃, and stir for leaching for 100 minutes; filter to separate the leachate and leach residue.

[0044] Tests showed that the lithium extraction rate in the main leachate was 77.8%, and the phosphorus extraction rate was 99.1%.

[0045] 5. Deep lithium extraction from leaching residue: Add water to the leaching residue at a liquid-to-solid ratio of 4:1 and add dilute sulfuric acid dropwise to adjust the pH of the system to 1.2. Raise the temperature to 75°C and stir and acid wash for 45 minutes. Filter to obtain lithium-rich acid washing solution and final residue. The acid washing solution is returned to the main leaching process for combined treatment.

[0046] Testing revealed that the residual lithium content in the final residue after acid washing was 0.009%; calculations showed that the total lithium recovery rate was 98.6% and the total phosphorus recovery rate was 99.2%.

[0047] Example 3 This embodiment provides a method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder via alkaline roasting. The specific operation steps are as follows: 1. Raw material pretreatment: Take 1000g of lithium iron phosphate cathode black powder from the same batch as in Example 1, dry it to a moisture content of 1.1%, and set it aside.

[0048] 2. Mixing alkali ingredients: Weigh 300g of sodium hydroxide and 360g of anhydrous sodium carbonate, mix them evenly with black powder, the mass ratio of sodium hydroxide to sodium carbonate is 1:1.2, and the mass ratio of total alkali to black powder is 0.66:1; stir and mix in a mixer for 15 minutes to obtain the mixture.

[0049] 3. Medium-temperature calcination: Transfer the mixture into a muffle furnace and heat it to 650°C at a rate of 5°C / min in air atmosphere. Calcinate at this constant temperature for 90 minutes. After natural cooling, remove the mixture and grind it to below 100 mesh.

[0050] 4. Main leaching treatment: Add deionized water at a liquid-to-solid ratio of 4:1 for pre-soaking for 30 minutes, add 25% dilute sulfuric acid dropwise to adjust the pH of the system to 2.8, raise the temperature to 55℃, and stir for leaching for 80 minutes; filter to separate the leachate and leach residue.

[0051] Tests showed that the lithium extraction rate in the main leachate was 78.5%, and the phosphorus extraction rate was 99.4%.

[0052] 5. Deep lithium extraction from leaching residue: Add dilute sulfuric acid to the leaching residue at a liquid-to-solid ratio of 2:1, adjust the pH to 1.8, raise the temperature to 65℃, and stir and acid wash for 75 minutes; filter to obtain lithium-rich acid washing solution and final residue, and return the acid washing solution to the main leaching process.

[0053] Tests showed that the residual lithium content in the final residue after pickling was 0.005%; calculations showed that the total lithium recovery rate was 99.0% and the total phosphorus recovery rate was 99.6%.

[0054] Comparative Example 1 (Single sodium hydroxide alkali roasting system, simulating existing technology) This comparative example uses sodium hydroxide alone as the calcining alkali agent to simulate the existing single-alkali recovery process. The specific steps are as follows: 1. Take 1000g of lithium iron phosphate cathode black powder from the same batch as in Example 1, and pretreatment method is completely the same as in Example 1.

[0055] 2. Weigh 800g of sodium hydroxide and mix it with black powder. The total alkali to black powder mass ratio is 0.8:1. Mix for 20 minutes until uniform.

[0056] 3. Place the mixture in a muffle furnace, heat it to 800℃ in an air atmosphere, keep it at a constant temperature for 120 minutes, and grind it after cooling.

[0057] 4. Leaching was performed using the exact same leaching parameters as in Example 1, followed by filtration and separation.

[0058] Testing revealed that the lithium extraction rate in the main leachate was only 72.3%, and the phosphorus extraction rate was only 85.6%. After acid washing under the same conditions, the total lithium recovery rate was only 89.2%, and the total phosphorus recovery rate was 86.1%, which is far lower than the level of the embodiment of the present invention. Moreover, the roasting temperature is 200°C higher than that of the present invention, resulting in a significant increase in energy consumption and equipment requirements.

[0059] Comparative Example 2 (Single sodium carbonate alkali roasting system, simulating existing technology) This comparative example uses sodium carbonate as the calcining alkali agent, and the specific steps are as follows: 1. Take 1000g of lithium iron phosphate cathode black powder from the same batch as in Example 1, and pretreatment method is completely the same as in Example 1.

[0060] 2. Weigh 800g of anhydrous sodium carbonate and mix it with black powder. The total alkali to black powder mass ratio is 0.8:1. Mix for 20 minutes until uniform.

[0061] 3. Place the mixture in a muffle furnace, heat it to 850°C in an air atmosphere, calcine it at a constant temperature for 150 minutes, and then grind it after cooling.

[0062] 4. Leaching was performed using the exact same leaching parameters as in Example 1, followed by filtration and separation.

[0063] Testing revealed that the lithium extraction rate in the main leachate was only 65.8%, and the phosphorus extraction rate was only 78.2%. After the same acid washing process, the total lithium recovery rate was only 82.7%, and the total phosphorus recovery rate was 79.0%. All indicators were significantly lower than those of the present invention, and the calcination temperature was higher, resulting in insufficient destruction of the crystal structure.

[0064] The results of the above examples and comparative examples show that the present invention achieves a high-proportion simultaneous recovery of 99% phosphorus and 98.5% lithium by using a synergistic roasting of a sodium hydroxide-sodium carbonate mixed alkali, combined with a two-step process of main leaching to extract phosphorus and lithium and slag acid washing to extract lithium, under medium-temperature conditions of 500~700℃. The roasting temperature is 150~250℃ lower than that of a single alkali system, and the reagent cost is significantly reduced. At the same time, it achieves efficient separation of phosphorus, lithium and iron, demonstrating significant technical advantages.

[0065] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting, characterized in that, Includes the following steps: (1) Raw material pretreatment: The retired lithium iron phosphate batteries are discharged, disassembled, crushed and sorted in sequence to obtain lithium iron phosphate cathode black powder, and the moisture content is controlled after sieving; (2) Mixed alkali ingredients: The lithium iron phosphate cathode black powder is dry-mixed with sodium hydroxide and sodium carbonate, wherein the mass ratio of sodium hydroxide to sodium carbonate is 1:1.2~1:5, and the total mass ratio of sodium hydroxide and sodium carbonate to the mass ratio of lithium iron phosphate cathode black powder is 0.8:1~1.5:1; (3) Medium-temperature roasting: The uniformly mixed material is placed in an air atmosphere for roasting. The roasting temperature is controlled at 500℃~700℃ and the roasting holding time is 60~180 minutes to obtain roasted clinker. (4) Main leaching treatment: Add water to the roasted clinker and stir evenly, then add dilute sulfuric acid to adjust the pH value of the system to 2.5~4.0, stir and leach at a temperature of 40℃~80℃, filter and separate to obtain phosphorus and lithium enriched leachate and iron-containing leachate residue. (5) Deep lithium extraction from leaching residue: Add dilute sulfuric acid solution to the leaching residue obtained in step (4), adjust the pH value of the system to 1.0~2.0, stir and acid wash at a temperature of 50℃~90℃, filter and separate to obtain lithium-rich acid washing solution and final residue, and return the lithium-rich acid washing solution to step (4) and combine it with the leaching solution. (6) Separation and purification: The combined leachate is separated and purified to prepare phosphorus products and lithium salt products respectively.

2. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (1), the lithium iron phosphate cathode black powder is passed through a 200-mesh sieve and the moisture content is controlled at 2%.

3. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (2), the dry mixing is carried out in a mixer for 15 to 30 minutes to ensure that the materials are mixed evenly.

4. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (2), the mass ratio of sodium hydroxide to sodium carbonate is 1:2 to 1:4, and the mass ratio of total alkali to lithium iron phosphate cathode black powder is 0.8:1 to 1.2:

1.

5. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (3), the calcination process is carried out in a rotary kiln or muffle furnace at a temperature of 550℃~650℃ and a holding time of 90~150 minutes.

6. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (4), after adding deionized water at a liquid-to-solid ratio of 3:1 to 8:1 and stirring for 30 minutes, dilute sulfuric acid with a concentration of 10% to 30% is added to adjust the pH value of the system, and the stirring and leaching time is 60 to 120 minutes.

7. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (4), the pH value of the system is adjusted to 2.8~3.5, and the leaching temperature is 55℃~70℃.

8. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (5), add a 5% to 20% dilute sulfuric acid solution at a liquid-to-solid ratio of 2:1 to 5:1, and stir and pickle for 30 to 90 minutes.

9. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (5), the pH value of the system is controlled at 1.2~1.8 and the acid washing temperature is 60℃~80℃.

10. The method for high-proportion extraction of phosphorus and lithium from lithium iron phosphate black powder by alkaline roasting according to claim 1, characterized in that, In step (6), the separation and purification are carried out by chemical precipitation, extraction or ion exchange processes; the phosphorus product is an industrial phosphoric acid product, and the lithium salt product is lithium carbonate or lithium hydroxide.

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