Method for full-chain integrated low-carbon production of positive electrode material

Abstract

The present disclosure provides a method for full-chain integrated low-carbon production of a positive electrode material. The method comprises the following steps: (1) preparing a ternary precursor by means of a coprecipitation method, collecting first waste gas, and carrying out pre-oxidation treatment on the precursor to obtain an oxidized precursor; (2) mixing the oxidized precursor and lithium carbonate for first-stage sintering, collecting second waste gas, and introducing oxygen-containing gas for second-stage sintering to obtain a ternary positive electrode material; and (3) mixing a phosphorus source, an iron source and a lithium source to obtain a lithium iron phosphate precursor, mixing the lithium iron phosphate precursor with a carbon source, introducing the second waste gas, carrying out calcination treatment to obtain a lithium iron phosphate positive electrode material, and absorbing the second waste gas with a solution of the first waste gas to obtain an ammonium carbonate solution. According to the present disclosure, by changing the oxidation mode of a ternary material, the two preparation processes of the ternary material and a lithium iron phosphate material can cooperate with each other, and separation and recycling of two atmospheres are achieved by controlling conditions so as to achieve the objective of energy saving and carbon reduction.

Description

A full-chain integrated low-carbon production method for positive electrode materials Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries and relates to a method for producing positive electrode materials in a full-chain integrated low-carbon manner. Background Art

[0002] With the increasing depletion of fossil energy, the development of new energy sources is imperative. Lithium-ion batteries have attracted widespread attention due to their high density, good stability, and environmental friendliness. Especially in the field of new energy vehicles, the development and research of lithium-ion batteries is extremely important, and the core of this research lies in the research of lithium-ion battery cathode materials.

[0003] Layered nickel-cobalt-manganese ternary positive electrode material combines the advantages of lithium nickelate, lithium cobaltate and lithium manganate. It has a stable structure, high capacity and good cycle stability. It is a positive electrode material with great development prospects.

[0004] CN104393278A discloses a method for preparing a nickel-cobalt-manganese oxide ternary positive electrode material. Nickel-cobalt-manganese hydroxide precipitate is prepared by coprecipitation, and then washed, filtered, and dried to obtain a precursor. The precursor is then mixed with lithium carbonate and sintered in a high-temperature furnace to obtain a nickel-cobalt-manganese ternary positive electrode material.

[0005] CN108128814A discloses a method for preparing a ternary cathode material precursor. By specifically adjusting the addition time, addition amount and reaction conditions of the reactants during the co-precipitation reaction, the prepared ternary cathode material precursor has a more uniform particle size and a narrower particle size distribution.

[0006] In the co-precipitation synthesis process described above, ammonia is typically used as a complexing agent, which results in the emission of ammonia gas. Furthermore, the sintering process, which often uses lithium carbonate as a raw material, produces a large amount of mixed exhaust gas of carbon dioxide and oxygen. This is typically discharged directly after dust removal, making it difficult to utilize. This results in a high carbon footprint for the lithium nickel cobalt manganese oxide production process, hindering the achievement of my country's dual carbon goals.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of the present disclosure is to provide a full-chain integrated low-carbon method for producing positive electrode materials. By changing the oxidation method of the ternary material, the present disclosure can make the two preparation processes of the ternary material and the lithium iron phosphate material cooperate with each other, and realize the separation and reuse of the two atmospheres by controlling the conditions, thereby achieving the purpose of energy saving and carbon reduction.

[0010] To achieve this disclosure purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the embodiments of the present disclosure provide a method for producing cathode materials in a fully integrated low-carbon manner, the method comprising the following steps:

[0012] (1) preparing a ternary precursor by a coprecipitation method, collecting a first exhaust gas, and pre-oxidizing the precursor to obtain an oxidized precursor;

[0013] (2) mixing the oxidation precursor and lithium carbonate to perform a first-stage sintering treatment, collecting the second waste gas, introducing an oxygen-containing gas to perform a second-stage sintering treatment, and obtaining a ternary positive electrode material;

[0014] (3) Wet-mixing a phosphorus source, an iron source, and a lithium source to obtain a lithium iron phosphate precursor, mixing the lithium iron phosphate precursor with a carbon source, introducing a second exhaust gas as a protective gas, and calcining the mixture to obtain a lithium iron phosphate positive electrode material, and absorbing the second exhaust gas after the reaction with a solution of the first exhaust gas to obtain an ammonium carbonate solution.

[0015] The pre-oxidation process described in the embodiment of the present disclosure can reduce the mixing of Li / Ni and improve the cycle stability of the material. If oxygen-free calcination is used, the Ni in the ternary precursor 2+ Still at +2 valence, +2 valence Ni 2+ will interact with the Li + Nickel-lithium mixing occurs, and nickel-lithium mixing is irreversible, which will lead to more defects in the material and poor stability. The embodiment of the present disclosure adds oxygen during the second-stage sintering to reduce the occurrence of lithium-nickel mixing at high temperatures and ensure the performance of the positive electrode material. Lithium nickel cobalt manganese oxide is synthesized by sintering in two stages with different atmospheres. The first stage of sintering is vacuum sintering, and pure carbon dioxide can be collected. If oxygen is introduced into the second stage of sintering, the resulting tail gas is also relatively pure oxygen, which can be directly reused in the second stage sintering process, saving costs. Carbon dioxide is reused in the synthesis of lithium iron phosphate, so that other inert gases do not need to be added during the synthesis of lithium iron phosphate, reducing costs. The ammonia produced in the ternary generation process is utilized to absorb carbon dioxide, reducing carbon emissions.

[0016] In one embodiment, the first waste gas in step (1) includes ammonia.

[0017] In one embodiment, the pre-oxidation treatment in step (1) includes mixing a ternary precursor and a strong oxide.

[0018] In one embodiment, the strong oxidizing agent includes ozone and / or lithium perchlorate.

[0019] In one embodiment, the strong oxidant is ozone, which is introduced into the reaction vessel to control the mass of ozone in the reaction vessel to account for 5-10% of the total gas mass, for example, 5%, 6%, 7%, 8%, 9% or 10%.

[0020] The reaction equation of ozone and the ternary precursor is as follows: M(OH)2+O3→MOOH+H2O+O2.

[0021] In one embodiment, the strong oxide is lithium perchlorate, and lithium perchlorate is mixed with a ternary precursor, and the total molar ratio of lithium perchlorate to the metal elements in the ternary precursor is 0.5 to 0.6:1, for example: 0.5:1, 0.52:1, 0.55:1, 0.58:1 or 0.6:1.

[0022] The reaction equation of lithium perchlorate and ternary precursor is as follows: 2M(OH)2+ClO4 - →2MOOH+ClO3 - +H2O.

[0023] In one embodiment, the temperature of the pre-oxidation treatment in step (1) is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C.

[0024] In one embodiment, the pre-oxidation treatment time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0025] The pre-oxidation process described in the embodiment of the present disclosure oxidizes the ternary positive electrode precursor, reduces the use of oxygen during sintering, reduces costs and the difficulty of separating carbon dioxide, is more conducive to collecting pure carbon dioxide and oxygen, and is conducive to the reuse of oxygen.

[0026] In one embodiment, the molar ratio of the oxidation precursor to lithium carbonate in step (2) is 1.01 to 1.05:1, for example, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1.

[0027] The reaction equation of the oxidation precursor and lithium carbonate is as follows: 2MOOH+Li2CO3→2LiMO2+H2O+CO2↑.

[0028] In one embodiment, the one-stage sintering includes one-step sintering and two-step sintering.

[0029] In one embodiment, the temperature of the one-step sintering is 400-500°C, for example, 400°C, 420°C, 450°C, 480°C or 500°C.

[0030] In one embodiment, the one-step sintering time is 2 to 5 hours, for example, 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours.

[0031] In one embodiment, the temperature of the two-step sintering is 800-1100° C., for example, 800° C., 850° C., 900° C., 1000° C., or 1100° C.

[0032] In one embodiment, the temperature of the two-step sintering is 2 to 5 hours, for example, 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours.

[0033] In one embodiment, the temperature of the second-stage sintering in step (2) is 800-1100°C, for example, 800°C, 850°C, 900°C, 1000°C or 1100°C.

[0034] In one embodiment, the second-stage sintering time is 3 to 10 hours, for example, 3 hours, 4 hours, 6 hours, 8 hours or 10 hours.

[0035] In one embodiment, the first exhaust gas and the second exhaust gas are collected and dust-removed to obtain ammonia and carbon dioxide, respectively.

[0036] In one embodiment, the oxygen-containing gas comprises oxygen or an oxygen-air mixture.

[0037] In one embodiment, the volume ratio of air to oxygen in the oxygen-air mixture is 1:(1-4), for example, 1:1, 1:2, 1:3 or 1:4.

[0038] In one embodiment, the flow rate of the oxygen-containing gas is 30-50 mL / min, for example, 30 mL / min, 35 mL / min, 40 mL / min, 45 mL / min or 50 mL / min.

[0039] In one embodiment, the phosphorus source in step (3) includes any one of phosphoric acid, dilithium hydrogen phosphate or lithium phosphate, or a combination of at least two thereof.

[0040] In one embodiment, the iron source includes any one of ferric oxide, ferrosoferric oxide, ferrous oxide, ferric hydroxide, ferric phosphate or ferrous oxalate, or a combination of at least two thereof.

[0041] In one embodiment, the lithium source includes any one of lithium phosphate, lithium hydroxide, or lithium dihydrogen phosphate, or a combination of at least two thereof.

[0042] In one embodiment, the carbon source in step (3) comprises any one of glucose, sucrose, citric acid, polyethylene glycol, cyclodextrin, polyvinyl alcohol, phenolic resin, polyacrylonitrile, starch or cellulose, or a combination of at least two thereof.

[0043] In one embodiment, the mass ratio of the carbon source to the lithium iron phosphate precursor is 5 to 15:100, for example, 5:100, 8:100, 10:100, 12:100 or 15:100.

[0044] In one embodiment, the calcination temperature in step (3) is 600-750°C, for example, 600°C, 620°C, 650°C, 700°C or 750°C.

[0045] In one embodiment, the calcination treatment time is 6 to 12 hours, for example: 6 hours, 7 hours, 8 hours, 10 hours or 12 hours.

[0046] Compared with the related art, the present disclosure has the following beneficial effects:

[0047] The present disclosure combines the two processes of ternary positive electrode materials and lithium iron phosphate positive electrode materials. The present disclosure uses processes such as pre-oxidation and tail gas collection to reduce the use of oxygen in the sintering process while reducing the mixed arrangement of nickel and lithium materials, and can reduce the carbon emissions of this part of purchased liquid oxygen. The method described in the present disclosure can directly obtain reusable carbon dioxide, reducing the carbon emissions of the carbon dioxide separation step in the mixed tail gas. In addition, the generated carbon dioxide is directly reused in the lithium iron phosphate production step, reducing the carbon emissions of purchased inert gases in the lithium iron phosphate production process and the carbon emissions generated in the ternary positive electrode material production process. The method described in the present disclosure can realize the separation, recovery and reuse of waste gas generated in the material preparation process without the need to add other protective gases, realizing the integrated recycling and utilization of the entire waste gas chain, meeting the standards for carbon reduction and emission reduction, and achieving the purpose of energy conservation and carbon reduction.

[0048] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0050] FIG1 is a process flow chart of the method described in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0051] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0052] Example 1

[0053] This embodiment provides a method for producing cathode materials in a full-chain integrated low-carbon manner. The process flow chart of the method is shown in FIG1 . The method comprises the following steps:

[0054] (1) preparing a nickel-cobalt-manganese ternary metal sulfate with a concentration of 1 mol / L and a molar ratio of Ni:Co:Mn of 5:2:3, adding liquid alkali and ammonia water to the mixed solution for co-precipitation, controlling the solution pH to 11 and the temperature to 60°C, stirring continuously for 8 hours and then aging for 12 hours, then filtering and washing to obtain a ternary positive electrode material precursor, collecting the tail gas during the reaction, placing the precursor in a rotary kiln, introducing ozone gas at normal pressure, controlling the ozone gas concentration in the rotary kiln to 6%, and drying at 100°C for 1.5 hours to obtain an oxidized precursor;

[0055] (2) The oxidized precursor and lithium carbonate (the molar ratio of lithium carbonate to the total amount of precursor metal elements is 1.02:1) are sintered in a vacuum atmosphere at a heating rate of 3°C / min to 500°C for 3 hours, then heated to 900°C at a heating rate of 1.5°C / min and kept at this temperature for 4 hours, and the exhaust gas is collected. Maintaining the temperature, a mixture of air and oxygen is introduced at a rate of 35 mL / min for a second sintering reaction, with a volume ratio of oxygen to air of 1:1, and a reaction time of 6 hours to obtain a ternary cathode material;

[0056] (3) The waste gas from the co-precipitation of step (1) and the waste gas from the first-stage sintering of step (2) are collected separately and dust removed to obtain ammonia mixed gas and carbon dioxide gas respectively. Lithium hydroxide, ferrous oxalate and ammonium dihydrogen phosphate are wet-mixed in a molar ratio of 1.01:1:1, dried and crushed to obtain a lithium iron phosphate precursor. The lithium iron phosphate precursor is mixed with polyvinyl alcohol in a mass ratio of 100:5, and the obtained carbon dioxide gas is introduced to maintain a carbon dioxide atmosphere in a tubular furnace. The mixture is calcined at 700°C for 8 hours to obtain a lithium iron phosphate positive electrode material. The collected ammonia gas is dissolved in water, and the carbon dioxide after the reaction in the tubular furnace is absorbed to obtain an ammonium carbonate solution.

[0057] Example 2

[0058] This embodiment provides a method for producing cathode materials in a fully integrated low-carbon manner, the method comprising the following steps:

[0059] (1) preparing a nickel-cobalt-manganese ternary metal sulfate with a concentration of 1 mol / L and a molar ratio of Ni:Co:Mn of 5:2:3, adding liquid alkali and ammonia water to the mixed solution for co-precipitation, controlling the solution pH to 11 and the temperature to 60°C, stirring continuously for 8 hours and then aging for 12 hours, then filtering and washing to obtain a ternary positive electrode material precursor, and collecting the tail gas during the reaction, placing the precursor in a rotary kiln, mixing the precursor with lithium perchlorate at a total molar ratio of lithium perchlorate to the metal elements in the precursor of 0.52:1, and placing it in a drying oven at 120°C for 3 hours to obtain an oxidized precursor;

[0060] (2) The oxidized precursor and lithium carbonate (the molar ratio of lithium carbonate to the total amount of the precursor metal element is 1.02:1) are sintered in a vacuum atmosphere, the temperature is raised to 450°C at a heating rate of 3°C / min and sintered for 3 hours, then raised to 950°C at a heating rate of 1.5°C / min and kept at this temperature for 3 hours, the exhaust gas is collected, the temperature is maintained, and oxygen is introduced for a second sintering reaction at an oxygen flow rate of 40 ml / min and a reaction time of 6 hours to obtain a ternary positive electrode material;

[0061] (3) The waste gas from the co-precipitation of step (1) and the waste gas from the first-stage sintering of step (2) are collected separately and dust removed to obtain ammonia mixed gas and carbon dioxide gas respectively; lithium hydroxide, ferrous oxalate and ammonium dihydrogen phosphate are wet-mixed at a molar ratio of 1.02:1:1, dried and crushed to obtain a lithium iron phosphate precursor; the lithium iron phosphate precursor is mixed with glucose at a mass ratio of 100:10; the obtained carbon dioxide gas is introduced to maintain a carbon dioxide atmosphere in a tubular furnace; the mixture is calcined at 600°C for 8h to obtain a lithium iron phosphate positive electrode material; the collected ammonia is dissolved in water, and the carbon dioxide after the reaction in the tubular furnace is absorbed to obtain an ammonium carbonate solution.

[0062] Example 3

[0063] This embodiment provides a method for producing cathode materials in a fully integrated low-carbon manner, the method comprising the following steps:

[0064] (1) preparing a nickel-cobalt-manganese ternary metal sulfate with a concentration of 1 mol / L and a molar ratio of Ni:Co:Mn of 8:1:1, adding liquid alkali and ammonia water to the mixed solution for co-precipitation, controlling the solution pH to 11 and the temperature to 60°C, stirring continuously for 8 hours and then aging for 12 hours, then filtering and washing to obtain a ternary positive electrode material precursor, collecting the tail gas during the reaction, placing the precursor in a rotary kiln, introducing ozone gas at normal pressure, controlling the ozone gas concentration in the rotary kiln to 6%, and drying at 100°C for 1.5 hours to obtain an oxidized precursor;

[0065] (2) The oxidized precursor and lithium carbonate (the molar ratio of lithium carbonate to the total amount of precursor metal elements is 1.02:1) are sintered in a vacuum atmosphere, the temperature is raised to 500°C at a heating rate of 3°C / min and sintered for 3 hours, and then the temperature is raised to 1100°C at a heating rate of 1.5°C / min and kept warm for 2 hours. The exhaust gas is collected and the temperature is maintained. After oxygen is introduced into the reactor to fill it up, a second sintering reaction is carried out. The oxygen introduction rate is 50 mL / min and the reaction time is 8 hours to obtain a ternary positive electrode material.

[0066] (3) Collecting the waste gas from the co-precipitation of step (1) and the waste gas from the first-stage sintering of step (2) respectively, removing dust, and obtaining ammonia mixed gas and carbon dioxide gas respectively; wet-mixing lithium hydroxide, ferrous oxalate, and ammonium dihydrogen phosphate in a molar ratio of 1.03:1:1, drying and crushing them to obtain a lithium iron phosphate precursor; mixing the lithium iron phosphate precursor with citric acid in a mass ratio of 100:15; introducing the obtained carbon dioxide gas to maintain a carbon dioxide atmosphere in a tubular furnace; calcining at 750°C for 8h to obtain a lithium iron phosphate positive electrode material; dissolving the collected ammonia gas in water, absorbing the carbon dioxide after the reaction in the tubular furnace, and obtaining an ammonium carbonate solution.

[0067] Comparative Example 1

[0068] This comparative example provides a method for producing positive electrode materials in a full-chain integrated low-carbon manner, the method comprising the following steps:

[0069] (1) preparing a ternary nickel-cobalt-manganese metal sulfate with a concentration of 1 mol / L and a molar ratio of Ni:Co:Mn of 5:2:3, adding liquid alkali and ammonia water to the mixed solution for co-precipitation, controlling the solution pH to 11 and the temperature to 60°C, stirring continuously for 8 hours and then aging for 12 hours, then filtering, washing, and drying to obtain a ternary cathode material precursor, and collecting the tail gas during the reaction;

[0070] (2) mixing the precursor and lithium carbonate (the molar ratio of lithium carbonate to the total amount of the precursor metal element is 1.02:1) and calcining them in an oxygen atmosphere at an oxygen flow rate of 40 mL / min, collecting the waste gas, and performing dust removal treatment on the gases obtained in step (1) and step (2) to obtain a carbon dioxide oxygen mixed gas and an ammonia mixed gas, respectively, and separating the carbon dioxide oxygen mixed gas to obtain pure carbon dioxide gas;

[0071] (3) Lithium hydroxide, ferrous oxalate, and ammonium dihydrogen phosphate were wet-mixed in a molar ratio of 1.01:1:1, dried, and crushed to obtain a lithium iron phosphate precursor, into which the obtained carbon dioxide gas was introduced to maintain a carbon dioxide atmosphere in a tubular furnace, and calcined at 700°C for 8 hours to obtain a lithium iron phosphate positive electrode material, and the collected ammonia gas was dissolved in water to absorb the carbon dioxide after the reaction in the tubular furnace to obtain an ammonium carbonate solution.

[0072] Comparative Example 2

[0073] The only difference between this comparative example and Example 3 is that no pre-oxidation is performed and oxygen is introduced during one stage of the sintering process.

[0074] From the comparison between Examples 1-3 and Comparative Example 1, it can be seen that the pre-oxidation of the precursor in the present disclosure reduces the steps of separating and removing impurities from carbon dioxide compared to not performing pre-oxidation, thereby significantly reducing costs.

[0075] According to the carbon calculation method of CN114067922A, the carbon emissions per unit product of Example 1 are calculated to be 7.15 kg CO 2e The unit product carbon emission of Example 2 is 7.64 kg CO 2e The unit product carbon emission of Example 3 is 7.48 kgCO 2e The carbon emission per unit product of comparative example 1 is 10.35 kgCO 2e The carbon emission per unit product of comparative example 2 is 10.96 kgCO 2e .

[0076] From the comparison between Examples 1-3 and Comparative Examples 1-2, it can be seen that in the process of generating ternary positive electrode materials, the method disclosed herein can significantly reduce carbon emissions per unit product.

[0077] The present invention adopts two stages of sintering in different atmospheres to synthesize lithium nickel cobalt manganese oxide, and can obtain pure carbon dioxide for subsequent lithium iron phosphate synthesis. There is no need to add protective gas during the preparation of lithium iron phosphate, which reduces costs. All waste gases generated during the reaction can be recycled, achieving carbon reduction and emission reduction.

Claims

1. A method for producing positive electrode materials in a full-chain integrated low-carbon manner, the method comprising the following steps: (1) preparing a ternary precursor by a coprecipitation method, collecting a first exhaust gas, and performing a pre-oxidation treatment on the precursor to obtain an oxidized precursor; (2) mixing the oxidation precursor and lithium carbonate to perform a first-stage sintering treatment, collecting the second exhaust gas, introducing an oxygen-containing gas to perform a second-stage sintering treatment, and obtaining a ternary positive electrode material; (3) Wet-mixing a phosphorus source, an iron source and a lithium source to obtain a lithium iron phosphate precursor, mixing the lithium iron phosphate precursor with a carbon source, introducing a second exhaust gas as a protective gas, and calcining to obtain a lithium iron phosphate positive electrode material, and absorbing the second exhaust gas after the reaction with a solution of the first exhaust gas to obtain an ammonium carbonate solution.

2. The method of claim 1, wherein: In step (1), the first waste gas comprises ammonia.

3. The method according to claim 1 or 2, wherein: The pre-oxidation treatment in step (1) comprises mixing a ternary precursor and a strong oxide; Optionally, the strong oxidizing agent comprises ozone and / or lithium perchlorate.

4. The method of claim 3, wherein: The strong oxidant is ozone, which is introduced into the reaction container, and the mass of ozone in the reaction container is controlled to account for 5-10% of the total gas mass.

5. The method of claim 3, wherein: The strong oxide is lithium perchlorate, and the lithium perchlorate is mixed with a ternary precursor, and the total molar ratio of the lithium perchlorate to the metal elements in the ternary precursor is 0.5-0.6:

1.

6. The method according to any one of claims 1 to 5, wherein: The temperature of the pre-oxidation treatment in step (1) is 80-120° C. Optionally, the pre-oxidation treatment time is 1 to 3 hours.

7. The method according to any one of claims 1 to 6, wherein: The molar ratio of the oxidation precursor to lithium carbonate in step (2) is 1.01 to 1.05:

1.

8. The method according to any one of claims 1 to 7, wherein: The one-stage sintering includes one-step sintering and two-step sintering; Optionally, the one-step sintering temperature is 400-500° C.; Optionally, the one-step sintering time is 2 to 5 hours; Optionally, the temperature of the second-step sintering is 800-1100° C.; Optionally, the two-step sintering time is 2 to 5 hours.

9. The method according to any one of claims 1 to 8, wherein: The oxygen-containing gas includes oxygen or a mixture of oxygen and air; Optionally, the volume ratio of air to oxygen in the oxygen-air mixture is 1:(1-4); Optionally, the flow rate of the oxygen-containing gas is 30 to 50 mL / min.

10. The method according to any one of claims 1 to 9, wherein: The temperature of the second stage sintering in step (2) is 800-1100° C. Optionally, the second-stage sintering time is 3 to 10 hours.

11. The method according to any one of claims 1 to 10, wherein: The first waste gas and the second waste gas are collected and dust-removed to obtain ammonia and carbon dioxide respectively.

12. The method according to any one of claims 1 to 11, wherein: The phosphorus source in step (3) includes any one of phosphoric acid, dilithium hydrogen phosphate or lithium phosphate, or a combination of at least two of them.

13. The method of claim 12, wherein: The iron source includes any one of ferric oxide, ferrosinite, ferrous oxide, ferric hydroxide, ferric phosphate or ferrous oxalate, or a combination of at least two thereof.

14. The method of claim 12, wherein: The lithium source includes any one of lithium phosphate, lithium hydroxide or lithium dihydrogen phosphate, or a combination of at least two of them.

15. The method according to any one of claims 1 to 14, wherein: The carbon source in step (3) comprises any one of glucose, sucrose, citric acid, polyethylene glycol, cyclodextrin, polyvinyl alcohol, phenolic resin, polyacrylonitrile, starch or cellulose, or a combination of at least two thereof; Optionally, the mass ratio of the carbon source to the lithium iron phosphate precursor is 5 to 15:

100.

16. The method according to any one of claims 1 to 15, wherein: The calcination temperature in step (3) is 600-750°C; Optionally, the calcination treatment time is 6 to 12 hours.

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