Method for synthesizing ferrous sulfide material from pyrite raw material and application

Abstract

The present application relates to the field of lithium-ion battery preparation, and provides a method for synthesizing a ferrous sulfide material from a pyrite raw material and an application. A pyrite raw material is crushed and then physically mixed with iron powder and carbon source powder, and is heated in an inert atmosphere to obtain ferrous sulfide powder; the ferrous sulfide powder is mixed with deionized water and then subjected to wet ball milling and high-speed fine grinding to obtain a ferrous sulfide suspension; then, the ferrous sulfide suspension is spray-dried to obtain a precursor of ferrous sulfide microspheres, and the precursor is annealed to obtain a ferrous sulfide material. In the present application, the ferrous sulfide material is applied to a lithium-ion battery to serve as an active material of a negative electrode. By introducing a reducing agent, the present application can solve the problem in conventional methods that pyrite cannot be directly used to synthesize ferrous sulfide due to the presence of an impurity phase. In addition, the present application involves low costs, a simple process and low energy consumption, and is environmentally friendly and easy to realize large-scale production.

Description

A method for synthesizing ferrous sulfide material using pyrite raw material and its application

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on April 12, 2024, with application number 202410278434.1 and invention name “A method for synthesizing ferrous sulfide materials using pyrite raw materials and its application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to a method for synthesizing ferrous sulfide material based on pyrite raw material and its application, belonging to the field of lithium-ion battery preparation. Background Art

[0003] Transition metal sulfides have a high theoretical specific capacity for lithium storage and are considered to be one of the possible commercial negative electrode materials for lithium-ion batteries. Ferrous sulfide is widely used due to its low cost and high specific capacity (609 mAh g -1 ) and good electrochemical performance have attracted attention.

[0004] Industrial synthesis of ferrous sulfide is mainly achieved through a high-temperature solid-phase reaction between Fe and S, or through a solvent reaction between ferrous sulfate and inorganic / organic sulfur salts. The production process has strict technical requirements and involves toxic or irritating substances and flammable materials. It is not environmentally friendly, has great safety risks, and has high process costs.

[0005] Pyrite, which includes pyrite and marcasite, is the second most abundant iron ore after hematite. Pyrite is primarily composed of FeS2, along with some impurities. Notably, pyrite is easily weathered under surface conditions to form stable limonite (FeOOH·nH2O). Consequently, pyrite often contains a certain amount of iron oxyhydroxide, a composition significantly different from FeS2, making it unsuitable for direct use in battery material preparation.

[0006] In the invention patent application of publication number CN110127773A, in order to solve the problem of low purity of iron disulfide ore, hydrochloric acid solution is added to the ground ore powder, and heating is used to enhance the reaction speed with hydrochloric acid, followed by continuous stirring and washing, and finally filtering and drying to obtain industrial-grade purity iron disulfide. In the invention patent application of publication number CN105355918A, natural iron disulfide is ball-milled and mixed with dilute hydrochloric acid, filtered and washed, and then diluted sulfuric acid is added for stirring, filtering, and washing to eliminate impurities in natural iron disulfide. These purification processes for iron disulfide ores all require pickling, involve hazardous chemicals, are environmentally unfriendly, and present a large safety risk.

[0007] Summary of the Invention

[0008] This application provides a method for synthesizing ferrous sulfide using pyrite as a raw material. By adding a carbon source, the iron oxyhydroxide in the pyrite is reduced to iron, which can be used as an iron source in the reaction to prepare ferrous sulfide. This application is environmentally friendly, with a pollution-free production process throughout, making it environmentally friendly.

[0009] In order to achieve the above objectives, the technical solution adopted in this application is:

[0010] The present application provides a method for synthesizing ferrous sulfide powder using pyrite raw material, the method comprising the following steps:

[0011] S1: The pyrite raw material is crushed into particles with a particle size of 20 mesh or finer.

[0012] S2: The crushed particles are physically mixed with iron powder and carbon source powder, then heated in an inert atmosphere and cooled to obtain ferrous sulfide powder. In this step, the carbon source acts as a reducing agent, reducing the hydroxylated iron to iron powder, which further participates in the FeS2 reaction.

[0013] The ferrous sulfide powder obtained in step S2 can also be subjected to wet ball milling, high-speed fine grinding, spray drying, and annealing treatment in sequence to obtain ferrous sulfide microspheres, as follows:

[0014] S3: The ferrous sulfide powder is mixed with deionized water and then wet ball milled to obtain a turbid ferrous sulfide solution. In this step, the remaining carbon source powder can act as a lubricant during ball milling, and its high specific surface area and strong adsorption can replace the binder.

[0015] S4: Transferring the turbid ferrous sulfide solution to a high-speed ball mill for fine grinding to obtain a ferrous sulfide suspension. In this step, the addition of a carbon source can significantly reduce the wear of the grinding balls during high-speed ball milling and improve the ball milling efficiency.

[0016] S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres.

[0017] S6: placing the precursor of the ferrous sulfide microspheres in an inert atmosphere furnace for annealing to obtain ferrous sulfide microspheres.

[0018] Furthermore, the fine particles in step S1 are particles with a particle size of no greater than 20 mesh; the ferrous sulfide powder obtained in step S2 is irregular particles of 10 to 150 microns. The pyrite in step S1 can be at least one of pyrite and marcasite. The pyrite after crushing in step S1 can have a particle size of either micrometers or nanometers. The iron powder in step S2 has a particle size of either micrometers or nanometers.

[0019] Furthermore, in step S2: the mass ratio of pyrite particles to iron powder is 2:1 to 3:1; the mass ratio of pyrite particles to carbon source powder is 50:1 to 100:1; the carbon source is at least one of coke, carbon black and activated carbon, preferably coke; the temperature of the heating treatment is 600 to 1100°C, and the time is 2 to 20 hours. Furthermore, the temperature of the heating treatment is preferably 750 to 1000°C, and the time is preferably 4 to 10 hours.

[0020] Furthermore, the inert gas in step S2 is at least one of nitrogen or argon. The heating rate of the heating treatment in step S2 is 1 to 8°C per minute. The ferrous sulfide compound FeS in step S2 is generally Fe 1-x S (0≤x≤0.2) solid solution exists, and the specific composition is related to the synthesis process. As the reaction temperature increases, Fe 1-x The sulfur content of S decreases.

[0021] Furthermore, in step S6, the diameter of the ferrous sulfide microspheres is 0.5 to 10 micrometers, and the size of the primary particles in the microspheres is 50 to 200 nanometers.

[0022] Furthermore, in step S3, the solid-liquid mass ratio of ferrous sulfide powder and deionized water is 1:3 to 1:10; the speed of wet ball milling is 100 to 600 rpm, and the time is 3 to 6 hours; and the speed of high-speed ball mill in step S4 is 1500 to 2500 rpm, and the time is 0.3 to 3 hours.

[0023] Furthermore, the inlet air temperature of the spray drying in step S5 is 150-230° C., and the feed rate is 500-1500 ml / h; the temperature of the annealing treatment in step S6 is 300-1000° C., and the annealing treatment time is 0.5-6 hours.

[0024] The present application provides an application of ferrous sulfide powder obtained by the above method, wherein the ferrous sulfide powder obtained by S2 is applied to a lithium-ion battery as an active material for the negative electrode. Specifically, the ferrous sulfide material is used as an active material, mixed with a conductive agent and a binder, and a lithium-ion battery negative electrode material is prepared. The mass ratio of the ferrous sulfide powder, the conductive agent, and the binder is (8-9): (0.5-1): (0.5-1). When the battery charge and discharge voltage range is 1-2.7V and the current density is 400mA·g -1 Under the condition of the first charge capacity can reach 380mAh g -1 Above, the reversible capacity after 50 cycles is 350mAh·g -1 above.

[0025] The present application provides an application of ferrous sulfide microspheres prepared by the above method, wherein the ferrous sulfide microspheres obtained by S6 are applied to lithium-ion batteries as the active material of the negative electrode. Specifically, the ferrous sulfide microspheres are used as the active material, mixed with a conductive agent and a binder, and the negative electrode material of the lithium-ion battery is prepared. The mass ratio of the ferrous sulfide microspheres, the conductive agent, and the binder is (8-9): (0.5-1): (0.5-1). When the battery charge and discharge voltage range is 1-2.7V and the current density is 400mA·g -1 Under the condition of the first charge capacity can reach 415mAh g -1 Above, the reversible capacity after 50 cycles is 405 mAh g -1 above.

[0026] The principles of this application are:

[0027] This application mainly utilizes the reducing property of carbon source (coke) to reduce the main impurity ferric oxyhydroxide in pyrite into iron powder in a high temperature process, which then reacts with the main component FeS2 and S impurity to prepare ferrous sulfide powder, solving the problem that the impurity phase (FeOOH, S) in pyrite cannot be directly used to synthesize ferrous sulfide. The main reaction mechanism is as follows: FeS2+Fe=2FeS (1) 2FeOOH=Fe2O3+H2O (2) 2Fe2O3+3C=4Fe+3CO2 (3) Fe+S=FeS (4)

[0028] The beneficial effects of this application are:

[0029] (1) By using a reducing agent, the problem that the impurity phase (FeOOH, S) in pyrite cannot be directly used to synthesize ferrous sulfide in the traditional method can be solved.

[0030] (2) Low cost, the main raw materials are pyrite, followed by iron powder and coke.

[0031] (3) The process is simple and easy to operate, does not require complex and expensive equipment, and is easy to achieve large-scale production.

[0032] (4) Low energy consumption. Compared with the heating temperature of 2500°C or above for graphite negative electrode, the maximum heating temperature in the synthesis process of this application does not exceed 1100°C.

[0033] (5) Environmentally friendly, the entire production process is pollution-free and green.

[0034] (6) High economic value. Currently, pyrite is mainly used in industry to extract sulfur and prepare sulfuric acid. The preparation process has high energy consumption, high pollution and low economic benefits. This application can make pyrite be used as a negative electrode material for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is an X-ray diffraction (XRD) pattern of the pyrite raw material in Example 1;

[0036] FIG2 is an energy dispersive X-ray spectroscopy (EDS) spectrum of the pyrite raw material in Example 1;

[0037] FIG3 is an XRD image of the ferrous sulfide powder product obtained by calcination in Example 1;

[0038] FIG4 is a scanning electron microscope (SEM) image of the ferrous sulfide powder product obtained by calcination in Example 1;

[0039] FIG5 is a SEM image of porous ferrous sulfide microspheres formed after spray granulation and annealing in Example 1.

[0040] FIG6 is a particle size distribution diagram of porous ferrous sulfide microspheres formed after spray granulation and annealing in Example 1;

[0041] FIG7 is a graph showing the electrochemical performance of ferrous sulfide microspheres in Example 1;

[0042] FIG8 is an XRD pattern of FeS synthesized by calcination in Example 2;

[0043] FIG9 is a graph showing the electrochemical performance of ferrous sulfide microspheres in Example 2;

[0044] FIG10 is a graph showing the electrochemical performance of ferrous sulfide microspheres in Example 3;

[0045] FIG11 is a graph showing the electrochemical performance of ferrous sulfide powder in Example 4;

[0046] FIG12 is a graph showing the electrochemical performance of ferrous sulfide microspheres formed after spray granulation and annealing in Comparative Example 1. DETAILED DESCRIPTION

[0047] The specific preparation process and effects of this application are further described below through examples.

[0048] Example 1:

[0049] S1: 50 g of pyrite raw material was crushed and sieved to select particles with a particle size of 20 mesh or finer to obtain pyrite particles; the particles were characterized by X-ray diffraction (XRD), and the results showed that the main phase of the raw material particles was FeS2, and also contained impurity phases of FeOOH and S (see Figure 1); the energy dispersive X-ray spectroscopy (EDS) test results showed (as shown in Figure 2) that in addition to the main elements Fe and S, the raw material particles also contained impurity elements C, O, Si and Al. The EDS spectrum can confirm the presence of light elements such as C and O, but the quantitative analysis of these light elements is not accurate.

[0050] S2: 50 grams of pyrite particles were mixed with 25 grams of iron powder and 0.5 grams of coke powder by simple physical stirring. The mixture was placed in an alumina crucible and placed in a nitrogen atmosphere tube furnace. The temperature was then raised to 800°C at 4°C per minute and kept at this temperature for 7 hours. The mixture was then cooled to room temperature with the furnace to obtain a ferrous sulfide powder product. XRD test results showed that the product was single-phase FeS (Figure 3), and scanning electron microscopy (SEM) test results showed that the powder product was irregular particles of 10-150 microns (Figure 4). In this step, the coke powder reacted with impurities in the pyrite raw material, ultimately converting it into ferrous sulfide.

[0051] S3: The ferrous sulfide powder was mixed with deionized water in a mass ratio of 1:6, and wet ball milled at a ball milling speed of 350 rpm for 4.5 hours to obtain a ferrous sulfide suspension.

[0052] S4: The ferrous sulfide suspension is transferred to a high-speed ball mill for fine grinding at a ball milling speed of 2000 rpm for 2 hours to obtain a ferrous sulfide suspension.

[0053] S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres, wherein the inlet air temperature is 190° C. and the feed rate is 1000 ml / h.

[0054] S6: The ferrous sulfide microsphere precursor was annealed in a nitrogen atmosphere at 600°C for 3 hours to produce ferrous sulfide microspheres. SEM results (Figure 5) indicate that the spray granulation process formed porous ferrous sulfide microspheres. Particle size distribution analysis (Figure 6) shows that the particle size of the ferrous sulfide microspheres is primarily distributed between 1 and 5 microns.

[0055] Electrochemical performance test:

[0056] The obtained ferrous sulfide microspheres were used as the active material, acetylene black and polyvinylidene fluoride (PVDF) were added in a mass ratio of 8:1:1 and mixed to make a negative electrode slurry. The slurry was evenly coated on aluminum foil and dried in a vacuum oven at 120°C for 6 hours. The negative electrode was punched into a circular negative electrode sheet with a diameter of 12 mm. The lithium metal sheet was used as the counter electrode, 1 mol / LLiPF6 / (EC+DMC) electrolyte (volume ratio 1:1) was used as the electrolyte, and Celgard 2300 was used as the separator. The CR2032 button cell was assembled in an argon-filled glove box and electrochemical tests were carried out at room temperature after removal. The negative electrode was uniformly coated on aluminum foil and dried in a vacuum oven at 120°C for 6 hours ... -1 Under the condition of the first charge capacity is 425mAh g -1 After 50 cycles, the reversible capacity is 419 mAh g -1 (Figure 7).

[0057] Example 2:

[0058] S1: 24 g of pyrite raw material was crushed and screened to obtain particles with a particle size of 20 mesh or finer to obtain pyrite particles.

[0059] S2: 24 grams of pyrite particles were mixed with 8 grams of iron powder and 0.3 grams of carbon black powder by simple physical stirring. The mixture was then placed in an alumina crucible and placed in an argon atmosphere tube furnace. The temperature was raised at 8°C per minute to 1100°C and held for 2 hours. The mixture was then cooled to room temperature to obtain ferrous sulfide powder. XRD characterization results showed single-phase FeS (Figure 8). In this step, the carbon black reacted with impurities in the pyrite raw material, ultimately converting it into ferrous sulfide.

[0060] S3: The ferrous sulfide powder was mixed with deionized water in a mass ratio of 1:10, and wet ball milled at a ball milling speed of 600 rpm for 3 hours to obtain a ferrous sulfide suspension.

[0061] S4: The ferrous sulfide suspension is transferred to a high-speed ball mill for fine grinding at a speed of 2500 rpm for 0.3 hours to obtain a ferrous sulfide suspension.

[0062] S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres, wherein the inlet air temperature is 230° C. and the feed rate is 1500 ml / h.

[0063] S6: annealing the ferrous sulfide microsphere precursor in a nitrogen atmosphere furnace at an annealing temperature of 1000° C. for 0.5 hours to obtain ferrous sulfide microspheres.

[0064] Electrochemical performance test:

[0065] The prepared ferrous sulfide microspheres were used as the active material, and Ketjen black superconducting carbon black and polyacrylic acid (PAA) were added in a mass ratio of 9:0.5:0.5 to form a slurry. The mixture was evenly coated on aluminum foil and vacuum-dried at 120°C for 6 hours before being punched into circular electrode sheets with a diameter of 12 mm. A lithium metal sheet was used as the counter electrode, a 1 mol / L lithium bis(fluorosulfonyl)imide LiFSI / (DIOX+DMC) electrolyte (volume ratio 1:1) was used as the electrolyte, and Celgard 2300 was used as the separator. The CR2032 button cells were assembled in an argon-filled glove box and electrochemical tests were performed at room temperature after removal. The battery charge and discharge voltage range was 1-2.7 V, and the current density was 400 mA g -1 Under the condition of the first charge capacity is 415mAh g -1 After 50 cycles, the reversible capacity is 405 mAh g -1 (Figure 9).

[0066] Example 3:

[0067] S1: 30 g of marcasite raw material was crushed and screened to obtain particles with a particle size of 20 mesh or finer to obtain marcasite particles.

[0068] S2: 30 grams of marcasite particles were briefly physically stirred with 12 grams of iron powder and 0.6 grams of activated carbon powder. The mixture was then placed in an alumina crucible and placed in an argon atmosphere tube furnace. The temperature was raised at 1°C per minute to 600°C and held there for 20 hours. The mixture was then cooled to room temperature to obtain ferrous sulfide powder. In this step, the activated carbon reacted with impurities in the pyrite raw material, ultimately converting it into ferrous sulfide.

[0069] S3: The ferrous sulfide powder was mixed with deionized water in a mass ratio of 1:3, and wet ball milled at a ball milling speed of 100 rpm for 6 hours to obtain a ferrous sulfide suspension.

[0070] S4: The ferrous sulfide suspension was transferred to a high-speed ball mill for fine grinding at a speed of 1500 rpm for 3 hours to obtain a ferrous sulfide suspension.

[0071] S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres, wherein the inlet air temperature is 150° C. and the feed rate is 500 ml / h.

[0072] S6: annealing the ferrous sulfide microsphere precursor in an argon atmosphere at a temperature of 300° C. for 6 hours to obtain ferrous sulfide microspheres.

[0073] Electrochemical performance test:

[0074] The prepared ferrous sulfide microspheres were used as the active material, and activated carbon and polyacrylic acid (PAA) were added in a mass ratio of 8.5:1:0.5 and mixed to form a slurry. The slurry was evenly coated on aluminum foil and then vacuum-dried at 120°C for 6 hours before being punched into circular electrode pieces with a diameter of 12 mm. A lithium metal sheet was used as the counter electrode, a 1 mol / L LiPF6 / (EC+DMC) electrolyte (volume ratio 1:1) was used as the electrolyte, and Celgard 2300 was used as the separator. The CR2032 button cell was assembled in an argon-filled glove box and electrochemically tested at room temperature after removal. The battery charge and discharge voltage range was 1-2.7 V, and the current density was 400 mA g -1 Under the condition of the first charge capacity is 416mAh g -1 After 50 cycles, the reversible capacity is 407 mAh g -1 (Figure 10).

[0075] Example 4:

[0076] S1: 50 g of pyrite raw material was crushed and sieved to obtain particles with a particle size of 20 mesh or finer to obtain pyrite particles.

[0077] S2: 50 grams of pyrite particles were simply physically stirred and mixed with 25 grams of iron powder and 1 gram of coke powder. The mixture was placed in an alumina crucible and placed in a tubular furnace with a nitrogen atmosphere. The temperature was then raised to 800°C at a rate of 4°C per minute and kept at this temperature for 7 hours. The mixture was then cooled to room temperature with the furnace to obtain a ferrous sulfide powder product.

[0078] Electrochemical performance test:

[0079] The ferrous sulfide powder was sieved to obtain a powder of 2000 mesh or finer. The sieved ferrous sulfide powder was used as the active material, and acetylene black and polyvinylidene fluoride (PVDF) were added in a mass ratio of 8:1:1 to form a slurry. The slurry was evenly coated on aluminum foil and vacuum-dried at 120°C for 6 hours. The electrode was punched into a circular electrode with a diameter of 12 mm. A lithium metal sheet was used as the counter electrode, a 1 mol / L LiPF6 / (EC+DMC) electrolyte (volume ratio of 1:1) was used as the electrolyte, and Celgard 2300 was used as the separator. The CR2032 button cell was assembled in an argon-filled glove box and electrochemical testing was performed at room temperature after removal. The battery charge and discharge voltage range was 1-2.7 V and the current density was 400 mA g -1 Under the condition of the first charge capacity is 383mAh g -1 After 50 cycles, the reversible capacity is 358 mAh g -1 (Figure 11).

[0080] It can be seen from the above examples that ferrous sulfide microspheres or powders can be used as negative electrode materials for lithium-ion batteries, and the microspheres have higher specific capacity and cycle stability.

[0081] Comparative Example 1:

[0082] S1: 50 g of pyrite raw material was crushed and screened to obtain particles with a particle size of 20 mesh or finer to obtain pyrite particles.

[0083] S2: 50 grams of pyrite particles and 25 grams of iron powder were simply physically stirred and mixed, then placed in an alumina crucible, and placed in an argon atmosphere tubular furnace. The temperature was raised to 1100°C at 8°C per minute and kept at this temperature for 2 hours. The mixture was then cooled to room temperature to obtain ferrous sulfide powder.

[0084] S3: The ferrous sulfide powder was mixed with deionized water in a mass ratio of 1:6, and wet ball milled at a ball milling speed of 350 rpm for 4.5 hours to obtain a ferrous sulfide suspension.

[0085] S4: The ferrous sulfide suspension is transferred to a high-speed ball mill for fine grinding at a ball milling speed of 2000 rpm for 2 hours to obtain a ferrous sulfide suspension.

[0086] S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres, wherein the inlet air temperature is 190° C. and the feed rate is 1000 ml / h.

[0087] S6: annealing the ferrous sulfide microsphere precursor in an argon atmosphere at a temperature of 500° C. for 6 hours to obtain ferrous sulfide microspheres.

[0088] Electrochemical performance test:

[0089] The prepared ferrous sulfide microspheres were used as the active material, and acetylene black and polyvinylidene fluoride (PVDF) were added in a mass ratio of 8:1:1 to form a negative electrode slurry. The slurry was evenly coated on aluminum foil and vacuum-dried at 120°C for 6 hours. The negative electrode was then punched into a circular negative electrode sheet with a diameter of 12 mm. A lithium metal sheet was used as the counter electrode, a 1 mol / L LiPF6 / (EC+DMC) electrolyte (volume ratio 1:1) was used as the electrolyte, and Celgard 2300 was used as the separator. The CR2032 button cell was assembled in an argon-filled glove box and electrochemically tested at room temperature after removal. The battery charge and discharge voltage range was 1-2.7 V, and the current density was 400 mA g -1 Under the condition of the first charge capacity is 414mAh g -1 After 50 cycles, the reversible capacity is 320 mAh g -1 (Figure 12).

[0090] It can be seen from the above examples and comparative examples that the addition of a carbon source can effectively improve the electrochemical stability of the obtained ferrous sulfide product.

[0091] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for synthesizing ferrous sulfide powder using pyrite raw material, characterized in that: The following steps are involved: S1: crushing the pyrite raw material into fine particles to obtain pyrite particles; S2: physically mixing the pyrite particles with iron powder and carbon source powder, placing the mixture in an inert atmosphere for heating, and cooling the mixture to obtain ferrous sulfide powder.

2. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1, characterized in that: The pyrite raw material in step S1 is at least one of pyrite and marcasite.

3. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1 or 2, characterized in that: The particle size of the pyrite particles in step S1 is no larger than 20 mesh; and the ferrous sulfide powder in step S2 is irregular particles of 10 to 150 microns.

4. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1, characterized in that: In step S2, the mass ratio of pyrite particles to iron powder is 2:1 to 3:1; the mass ratio of pyrite particles to carbon source powder is 50:1 to 100:1; the carbon source is at least one of coke, carbon black and activated carbon; the heating temperature is 600 to 1100° C., and the time is 2 to 20 hours.

5. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1, characterized in that: The heating treatment in step S2 is performed at a temperature of 750 to 1000° C. for 4 to 10 hours.

6. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1 or 4, characterized in that: The particle size of the iron powder in step S2 is micrometer-level or nanometer-level.

7. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1 or 4, characterized in that: The inert atmosphere in step S2 is at least one of a nitrogen atmosphere and an argon atmosphere.

8. The method for synthesizing ferrous sulfide powder using pyrite raw material according to claim 1, 4 or 5, characterized in that: In the step S2, the heating rate to the temperature of the heat treatment is 1-8°C / min.

9. A method for synthesizing ferrous sulfide microspheres using pyrite raw materials, characterized in that: The following steps are involved: synthesizing ferrous sulfide powder according to steps S1 and S2 of the method according to any one of claims 1 to 8; The ferrous sulfide powder is sequentially subjected to wet ball milling, high-speed fine grinding, spray drying, and annealing to obtain ferrous sulfide microspheres, as follows: S3: mixing the ferrous sulfide powder and deionized water and then performing wet ball milling to obtain a turbid ferrous sulfide solution; S4: transferring the ferrous sulfide turbid solution to a high-speed ball mill for fine grinding to obtain a ferrous sulfide suspension; S5: spray drying the ferrous sulfide suspension to obtain a precursor of ferrous sulfide microspheres; S6: placing the precursor of the ferrous sulfide microspheres in an inert atmosphere furnace for annealing to obtain the ferrous sulfide microspheres.

10. The method for synthesizing ferrous sulfide microspheres using pyrite raw materials according to claim 9, characterized in that: In step S3, the solid-liquid mass ratio of the ferrous sulfide powder and deionized water is 1:3 to 1:10; the speed of the wet ball milling is 100 to 600 rpm, and the time is 3 to 6 hours; In step S4, the rotation speed of the high-speed ball mill is 1500 to 2500 rpm, and the time is 0.3 to 3 hours.

11. The method for synthesizing ferrous sulfide microspheres using pyrite raw materials according to claim 9, characterized in that: The inlet air temperature of the spray drying in step S5 is 150-230°C, and the feed rate is 500-1500 ml / h; The temperature of the annealing treatment in step S6 is 300-1000° C., and the time of the annealing treatment is 0.5-6 hours.

12. The method for synthesizing ferrous sulfide microspheres using pyrite raw materials according to claim 9, characterized in that: The diameter of the ferrous sulfide microspheres in step S6 is 0.5 to 10 micrometers, and the size of the primary particles in the microspheres is 50 to 200 nanometers.

13. Use of the ferrous sulfide powder prepared by the method according to any one of claims 1 to 8 or the ferrous sulfide microspheres prepared by the method according to any one of claims 9 to 12 as an active material for a negative electrode in a lithium ion battery.

14. The use according to claim 13, characterized in that The ferrous sulfide powder or ferrous sulfide microspheres are mixed with a conductive agent and a binder to prepare a negative electrode material for a lithium ion battery.

15. The use according to claim 14, characterized in that The mass ratio of the active material, the conductive agent and the binder is (8-9): (0.5-1): (0.5-1).

Images