CN118183803A - A method for recovering lithium from waste lithium iron manganese phosphate positive electrode material - Google Patents

Abstract

The invention discloses a method for recycling lithium elements in a waste lithium manganese iron phosphate anode material, and belongs to the field of recycling valuable metal elements in a waste new energy lithium ion battery anode material; the method is realized by the following steps that firstly, after the waste lithium manganese iron phosphate battery is discharged, positive electrode powder is obtained after disassembly, sorting and crushing; then 8.0-15.0mol/L nitric acid is used for acidizing the waste lithium manganese iron phosphate battery anode powder to obtain a nitrified material, and the liquid-solid ratio is 2-5:1, carrying out ultrasonic acidification at 25-80 ℃ in an acidification process; then drying and grinding the obtained nitrified material, and roasting for 1-4 hours at a low temperature of 150-300 ℃ to obtain a nitrified roasting material; then leaching the nitrified roasting material in water at 25-80 ℃ and selectively leaching lithium to obtain a lithium-rich solution and ferromanganese slag; finally adding sodium carbonate into the lithium-rich solution to prepare lithium carbonate; according to the invention, the lithium can be effectively extracted by acidifying and roasting the lithium iron manganese phosphate anode powder, the process is simple, the cost is low, the energy consumption is low, the leaching rate of lithium is high, and the sustainable development of the lithium ion battery can be realized.

Description

A method for recovering lithium from waste lithium iron manganese phosphate positive electrode material

Technical Field

The invention relates to a method for recovering lithium elements, and in particular to a method for recovering lithium elements in waste lithium iron manganese phosphate positive electrode materials, belonging to the field of resource recovery of valuable metal elements in waste new energy lithium ion battery positive electrode materials.

Background technique

Nowadays, the new energy vehicle industry is booming driven by environmental protection, and the annual shipments and retirements of lithium-ion batteries have increased significantly. Although the theoretical specific capacity of lithium iron phosphate batteries is lower than that of ternary batteries, lithium iron phosphate batteries have outstanding advantages such as high safety, long cycle life, good structural stability and cycle performance, environmental friendliness, and low cost. Therefore, lithium iron phosphate batteries are growing rapidly, and their market share has gradually surpassed ternary batteries. However, due to the two major disadvantages of this material: low electronic conductivity and small lithium ion diffusion coefficient, many cathode material manufacturers have conducted doping research on lithium iron phosphate materials to overcome the shortcomings of traditional lithium iron phosphate batteries. Mn is one of the commonly used elements. Its redox potential (Mn ²⁺ /Mn ³⁺ ) is higher than that of Fe ²⁺ /Fe ³⁺ , and the raw material price is low, which is conducive to reducing corporate production costs and improving commercial value.

Lithium iron manganese phosphate is a product of lithium iron phosphate and lithium manganese phosphate. It has the same structure as lithium iron phosphate, and both are orderly and regular olivine structures. Lithium iron manganese phosphate and lithium iron phosphate have the same advantages of low cost, high safety performance, high thermal stability, no spontaneous combustion during needle puncture and overcharging, long life, and safety without explosion risk. It can be said that it has the advantages of both lithium iron phosphate and lithium manganese phosphate, and can also make up for the shortcoming of low energy density of lithium iron phosphate. Therefore, it is also known as the "upgraded version of lithium iron phosphate."

Lithium manganese iron phosphate has both the high energy density of lithium manganese phosphate and the good cycle performance of lithium iron phosphate. It is a very promising lithium-ion battery cathode material. It is not difficult to see that lithium manganese iron phosphate is likely to enter large-scale production and is expected to be used in electric vehicles on a large scale. It is even expected to replace lithium iron phosphate batteries in the future. Therefore, taking the lead in recycling and utilizing waste lithium manganese iron phosphate can not only provide preliminary guidance for the recycling of retired batteries in the later stage, but also reduce the production costs of enterprises, and form a closed-loop application of manufacturing and recycling. Therefore, recycling and reusing lithium manganese iron phosphate is essential.

The applicant of this application has proposed a process for selective lithium extraction and recovery of lithium iron phosphate batteries in the invention patent application with application number _{CN202311494333.X} and patent name "Selective Lithium Extraction Process for Lithium Iron Phosphate Batteries". The process is to acidify the obtained waste lithium iron phosphate battery positive electrode powder with _H2SO4 with sulfuric acid, crush the acidified material after the reaction is completed, and then oxidize and roast it. After the material is roasted, it is washed with water to obtain a lithium-rich solution. The lithium-rich solution uses LiOH solution as a precipitant to adjust the pH of the lithium-rich solution, remove metal impurities in the solution, and then supplement S to the purified solution after impurities are removed. Finally, the S-supplemented solution is evaporated and _crystallized to obtain _Li2SO4 . Although this process can achieve the selective extraction of lithium from the positive electrode material of waste lithium iron phosphate batteries, and the lithium leaching rate is also high, its process is relatively complicated, and the process requirements for selective lithium extraction are relatively high.

Summary of the invention

1. Technical issues to be resolved

The technical problems to be solved by the present invention are:

1. Propose an improved method for recovering valuable metal lithium from waste lithium manganese iron phosphate;

2. Improve the problem that the recovery process of valuable metal lithium in waste lithium manganese iron phosphate is too complicated and has high requirements;

3. Optimize the problem of low lithium recovery rate in waste lithium manganese iron phosphate.

(II) Technical solution

In order to solve the above technical problems, the present invention provides a method for recovering lithium elements in waste lithium iron manganese phosphate positive electrode materials, which comprises the following steps:

Step S1, obtaining raw materials: discharging the waste lithium iron manganese phosphate battery, and then disassembling, sorting and crushing the waste lithium iron manganese phosphate battery to obtain the positive electrode powder;

Step S2, acidification: the waste manganese iron phosphate lithium battery positive electrode powder is acidified with nitric acid to obtain a nitrated material, and ultrasonic acidification is performed during the acidification process;

Step S3, roasting: drying and grinding the obtained nitrified material and then roasting it at low temperature to obtain a nitrified roasted material;

Step S4, water leaching: the nitrated roasted material is water-leached, and lithium is selectively leached during the water leaching process to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

As an improvement of the above technical solution, it can be further limited that in step S2, the nitric acid is selected from nitric acid with a concentration of 8.0-15.0 mol/L, such as nitric acid with a concentration of 8.0 mol/L, 9.0 mol/L, 10 mol/L, 11 mol/L, 12 mol/L, 13 mol/L, 14 mol/L or 15 mol/L.

As an improvement of the above technical solution, the acidification liquid-solid ratio in step S2 can be further limited to 2-5:1. More specifically, the liquid-solid ratio can be 2:1, 2.2:1, 3:1, 4:1 or 5:1.

As an improvement of the above technical solution, the acidification process in step S2 can be further limited to ultrasonic acidification at 25-80°C, such as 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C and 80°C.

As an improvement of the above technical solution, it can be further defined that in step S3, the obtained nitrating material is dried and ground and then low-temperature roasted at 150-300°C. More specifically, the low-temperature roasting temperature can be 150°C, 160°C, 180°C, 190°C, 200°C, 210°C, 230°C, 240°C, 250°C, 280°C and 300°C.

As an improvement of the above technical solution, in step S3, the low-temperature roasting time can be further limited to 1-4 hours, and then the nitration roasting material is obtained. More specifically, the low-temperature roasting time can be 1.0h, 1.5h, 2.0h, 2.4h, 2.6h, 2.8h, 3.0h, 3.3h, 3.5h, 3.8h and 4.0h.

As an improvement of the above technical solution, in step S4, the water immersion temperature of the nitrating roasting material can be further limited to 25-80°C. More specifically, the water immersion temperature of the nitrating roasting material can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C and 80°C.

As an improvement of the above technical solution, it can be further defined that in step S5, the lithium-rich solution is removed from impurities and then sodium carbonate is added to prepare lithium carbonate.

(III) Beneficial effects

The above technical solution of the present invention has the following advantages:

1. Improve the method of recovering valuable metal lithium in waste lithium iron manganese phosphate batteries; use nitric acid acidification, roasting, and water leaching system to extract the lithium element that can be selectively leached from the positive electrode powder of waste lithium iron manganese phosphate batteries, so as to achieve the purpose of resource recovery.

2. The method for recovering valuable metallic lithium in waste lithium manganese iron phosphate provided by the present invention further simplifies the process and reduces the process requirements; waste lithium manganese iron phosphate batteries are selectively extracted by water immersion without adding acid, and the roasting temperature is low, which can reduce the recovery cost of enterprises.

3. The method for recovering lithium from waste lithium iron manganese phosphate positive electrode materials provided by the present invention enables the recovery rate of lithium from waste lithium iron manganese phosphate to reach a lithium leaching rate of more than 97.2%, has considerable economic benefits, and is conducive to promoting the recycling of waste lithium iron manganese phosphate batteries.

In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted, and the advantages brought about by the technical features of these technical solutions described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of a process block diagram of the present invention.

FIG. 2 is a schematic diagram of a block diagram of the steps of the recovery method of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

As shown in Figures 1 and 2: The method for recovering lithium from waste lithium iron manganese phosphate positive electrode materials provided in the present application comprises the following steps:

Step S1, obtaining raw materials: discharging the waste lithium iron manganese phosphate battery, disassembling, sorting and crushing to obtain the waste lithium iron manganese phosphate battery positive electrode powder. Here, a more specific method for obtaining the waste lithium iron manganese phosphate battery positive electrode powder is proposed, which is as follows:

(1) First, the waste lithium iron manganese phosphate battery is discharged, and then the discharged waste lithium iron manganese phosphate battery is crushed under nitrogen protection. The crushed material is in the shape of 30-40 mm large pieces; the crushing process is carried out under nitrogen atmosphere, and the electrolyte volatilized in the crusher is collected and sent to the pyrolysis gas combustion chamber for treatment;

(2) The crushed materials are sent to the pyrolysis furnace for high-temperature carbon reduction pyrolysis, with the temperature controlled at 550°C for 1 hour. The high-temperature pyrolysis is carried out in a nitrogen atmosphere. After the electrolyte, diaphragm and adhesive are decomposed, the waste gas is discharged to the pyrolysis gas combustion chamber for disposal;

(3) After carbon reduction and high-temperature pyrolysis, the mixed material is cooled and passed through a strong magnetic separator under a strong induction magnetic field strength of 15,000 Gauss to separate weakly magnetic materials and non-magnetic materials. Weakly magnetic materials include positive electrode sheets, positive electrode powder, magnetic shells and pile heads; non-magnetic materials include negative electrode sheets, negative electrode powder, non-magnetic shells and pile heads;

(4) The magnetic mixture after magnetic separation includes positive electrode sheets, positive electrode powder, magnetic shells and piles. The magnetic mixture is first passed through a hydrodynamic separator to separate the heavy magnetic shells and piles and the light positive electrode sheets and positive electrode powder mixture. The mixture is then passed through a wet stripping machine to strip the positive electrode powder from the surface of the positive electrode sheets. The mixture is then sieved and separated. The wet positive electrode powder obtained after separation is dehydrated and dried to obtain product positive electrode powder and aluminum foil. The recovery rate of the positive electrode powder can reach 98.3%.

Step S2, acidifying the positive electrode powder: the waste lithium manganese iron phosphate battery positive electrode powder is acidified with nitric acid to obtain a nitrated material, and ultrasonic acidification is performed during the acidification process;

Step S3, roasting the nitrified material: drying, grinding and low-temperature roasting the obtained nitrified material to obtain a nitrified roasted material;

Step S4, water leaching the nitration roasting material: the nitration roasting material is water-leached, and lithium is selectively leached during the water leaching process to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

More specifically, in the above-mentioned method for recovering lithium elements from waste manganese iron lithium phosphate positive electrode materials, in step S2, the nitric acid is selected to be acidified with a concentration of 8.0-15.0 mol/L; the acidification liquid-solid ratio is 2-5:1; and the acidification process is ultrasonically acidified at 25-80°C. In step S3, the obtained nitrated material is dried and ground and then low-temperature roasted at 150-300°C; the low-temperature roasting time is 1-4h, and then the nitrated roasted material is obtained. In step S4, the water immersion temperature of the nitrated roasted material is 25-80°C. In step S5, the lithium-rich solution is decontaminated and sodium carbonate is added to prepare lithium carbonate.

In order to more clearly illustrate the method for recovering lithium elements in waste lithium iron manganese phosphate positive electrode materials provided by the present application, the following embodiments of the present application are specially proposed.

Example 1

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 8.0 mol/L nitric acid for 7 hours to obtain a nitrated material, the acidification liquid-to-solid ratio is 2:1, and the acidification process is performed by ultrasonic acidification at 25°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 150° C. for 1 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water immersion at 25° C., the water immersion pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 97.2%.

Example 2

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2:1, and the acidification process is performed by ultrasonic acidification at 25°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 150° C. for 1 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water immersion at 25° C., the water immersion pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 97.6%.

Example 3

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2.2:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 150° C. for 1 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water immersion at 25° C., the water immersion pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 97.9%.

Example 4

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 3.5:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 150° C. for 1 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water immersion at 25° C., the water immersion pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 97.7%.

Example 5

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2.2:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 150° C. for 2 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water leaching at 25° C., the water leaching pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 98.1%.

Example 6

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2.2:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 200° C. for 2 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water immersion at 25° C., the water immersion pH is 7, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the operation was repeated twice, and the lithium recovery rates were 98.2% and 98.3%, respectively.

Example 7

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2.2:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 200° C. for 2 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water leaching at 40° C., the water leaching pH is 6.5, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 98.5%.

Example 8

A method for recovering lithium elements from waste lithium iron manganese phosphate positive electrode materials, comprising:

Step S1, discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing it to obtain positive electrode powder;

Step S2, the waste manganese iron phosphate lithium battery positive electrode powder is acidified with 11.0 mol/L nitric acid for 7.5 hours to obtain a nitration material, with a liquid-to-solid ratio of 2.2:1, and the acidification process is performed by ultrasonic acidification at 40°C;

Step S3, drying and grinding the obtained nitrified material, and then calcining at 200° C. for 2 h to obtain a nitrified calcined material;

Step S4, the nitrated roasted material is subjected to water leaching at 56° C., the water leaching pH is 6.5, and lithium is selectively leached to obtain a lithium-rich solution and ferromanganese slag;

Step S5, adding sodium carbonate to the lithium-rich solution to prepare lithium carbonate.

In this example, the recovery rate of lithium was 98.9%.

Comparative Example 1

Step S1, dismantling, crushing and sorting the used lithium manganese iron phosphate batteries after discharge to obtain their positive electrode powder;

Step S2, acidifying the positive electrode powder in step S1 with 18 mol/L H ₂ SO ₄ with sulfuric acid, with a liquid-to-solid ratio of 2:1, wherein n(Li ⁺ :H ⁺ )=1:1, i.e., sulfuric acid and positive electrode powder are mixed in a molar ratio of n(Li ⁺ :H ⁺ )=1:1, the reaction temperature is 130°C, the reaction time is 5 hours, and after the reaction is completed, the acidified material is crushed;

Step S3, the acidified material is crushed and then oxidized and roasted at a temperature of 600° C. for 6 hours;

Step S4, the material is washed with water after roasting, with a liquid-to-solid ratio of 6:1, and washed at room temperature for 2 hours to obtain a lithium-rich solution;

Step S5, the Li-rich solution uses 8% LiOH solution as a precipitant, adjusts the pH of the lithium-rich solution to 8, removes metal impurities in the solution, and then uses H ₂ SO ₄ solution as a S replenisher to replenish S to the purified solution until n(Li:S)=2:1;

Step S6, the S-supplemented solution is evaporated and crystallized at 100°C to obtain Li ₂ SO ₄ .

In this example, the recovery rate of lithium was 97%.

The present invention provides a method for recovering lithium elements in waste lithium iron phosphate battery positive electrode materials by acidification low temperature roasting water leaching lithium extraction process. The detailed process flow is to acidify waste lithium iron phosphate positive electrode powder with nitric acid, dry and grind it, roast it to obtain the nitrated roasted material of lithium iron phosphate, use aqueous solution to selectively extract lithium elements, obtain lithium-containing solution, remove impurities from the lithium solution, obtain pure lithium nitrate solution, and finally add sodium carbonate to prepare lithium carbonate. The embodiment of this application partially explores the effects of acidification liquid-solid ratio, acidification temperature, acidification concentration, acidification time, roasting temperature, roasting time, water leaching liquid-solid ratio, water leaching temperature, and water leaching pH on lithium leaching rate. XRD and SEM characterization can also be performed on the prepared lithium carbonate. The present invention application realizes the efficient recovery of lithium elements in waste lithium iron phosphate positive electrode materials, and provides a new idea for the recovery of valuable elements in lithium iron phosphate positive electrode powder.

In addition, in the description of the invention, unless otherwise specified, the terms "multiple", "multiple roots", "multiple groups" are used to mean two or more than two, and "several", "several roots", "several groups" are used to mean one or more than one. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims (8)

1. The method for recycling the lithium element in the waste lithium iron manganese phosphate anode material is characterized by comprising the following steps of:

Step S1, raw materials are obtained: discharging the waste lithium manganese iron phosphate battery, and then disassembling, sorting and crushing to obtain waste lithium manganese iron phosphate battery anode powder;

Step S2, acidizing: acidifying the waste lithium manganese iron phosphate battery anode powder with nitric acid to obtain a nitrified material, and performing ultrasonic acidification in the acidification process;

step S3, roasting: drying and grinding the obtained nitrified material, and roasting at a low temperature to obtain nitrified roasting material;

step S4, soaking in water: leaching the nitrified roasting material by water, and selectively leaching lithium in the water leaching process to obtain a lithium-rich solution and ferromanganese slag;

and S5, adding sodium carbonate into the lithium-rich solution to prepare lithium carbonate.

2. The method for recovering lithium element in the waste lithium manganese iron phosphate anode material according to claim 1, which is characterized in that: in the step S2, nitric acid with the concentration of 8.0-15.0mol/L is selected for acidification.

3. The method for recovering lithium element from waste lithium manganese iron phosphate anode material according to claim 2, which is characterized in that: in the step S2, the acidification liquid-solid ratio is 2-5:1.

4. The method for recovering lithium element from waste lithium manganese iron phosphate anode material according to claim 3, wherein the method is characterized by comprising the following steps: in step S2, the acidification process is carried out ultrasonic acidification at 25-80 ℃.

5. The method for recovering lithium element in the waste lithium manganese iron phosphate anode material according to claim 1 or 4, which is characterized in that: in the step S3, the obtained nitrified material is baked and grinded at a low temperature of 150-300 ℃.

6. The method for recovering lithium element from the waste lithium manganese iron phosphate anode material according to claim 5, which is characterized in that: in the step S3, the low-temperature roasting time is 1-4 hours, and then the nitrified roasting material is obtained.

7. The method for recovering lithium element from waste lithium manganese iron phosphate anode material according to claim 6, which is characterized in that: in the step S4, the water immersion temperature of the nitrifying roasting material is 25-80 ℃.

8. The method for recovering lithium element from waste lithium manganese iron phosphate anode material according to claim 7, wherein the method is characterized in that: in the step S5, the lithium-rich solution is subjected to impurity removal and then sodium carbonate is added to prepare lithium carbonate.