Preparation method of FePS3 and electrode material

Abstract

The invention discloses a preparation method of FePS3, which comprises the following steps: mechanically mixing pyrite powder, sulfur-containing small molecules and elemental phosphorus, calcining the fully mixed powder in two temperature stages under a protective atmosphere, and cooling to obtain FePS3 nano-powder; wherein in the first temperature stage, the temperature is 200-300 DEG C, and the heat preservation time is 120-240 minutes, and in the second temperature stage, the temperature is 400-600 DEG C, and the heat preservation time is 120-180 minutes; the sulfur-containing small molecules are thiourea, thioacetamide or a mixture of the thiourea and the thioacetamide; the molar ratio of sulfur atoms to phosphorus atoms in FeS2 molecules and sulfur-containing small molecules in the pyrite powder is (1: 3: 5)-(1: 1: 5). According to the method, pyrite is used as an iron source and a sulfur source, sulfur-containing small molecules are used as a second sulfur source, and the FePS3 nano-powder is directly obtained through solid-phase reaction with the simple substance phosphorus without additional purification treatment. The method is low in solid-phase reaction temperature and simple in process, does not need harsh reaction conditions, and is easy for large-scale production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of material synthesis, in particular to a preparation method of FePS3. BACKGROUND

[0002] Transition metal sulfides can be converted with lithium ions to generate metal elements and Li2S to realize the storage of lithium ions, and can be used as negative materials of lithium ion batteries. The content of sulfur in the compound directly determines the theoretical capacity of lithium storage, but the sulfur content of most transition metal sulfides is the highest in disulfide, and part of the transition metal exists in trisulfide and tetrasulfide, but the preparation is difficult and the stability is poor. Compared with the inertness of transition metals to lithium, the fourth / fifth main group elements (such as tin and phosphorus) can alloy with lithium, providing lithium storage capacity. Therefore, in transition metal sulfides, if the cation substitution of the fourth / fifth main group elements or the formation of ternary sulfides with the fourth / fifth main group elements can be realized, the theoretical capacity can be effectively improved.

[0003] Due to the huge difference between the characteristics of transition metal elements and the fourth / fifth main group elements, the amount of cation substitution in transition metal sulfides is very limited. FePS3 in ternary sulfide has high sulfur content and low material cost, which is very attractive, but its synthesis is not easy. At present, FePS3 is mainly synthesized by directly mixing iron, phosphorus and sulfur elements in a vacuum tube and then reacting at a temperature of 700 DEG C or above for 6h to 14h. The reaction process needs to be carried out under strict vacuum conditions, which is harsh and difficult to scale up. Literature also reports a method of using NaCl template and mixing with iron chloride, 5 times excess of elemental phosphorus and 21 times excess of elemental sulfur, and then combining in nitrogen to synthesize FePS3 [1] . After washing with deionized water to remove NaCl, FePS3 nanometer powder is obtained (Salt-Templated Construction of Ultrathin Cobalt Doped Iron Thiophosphite Nanosheets toward Electrochemical Ammonia Synthesis. Small 2019, 15: e1903500.). This method uses a large amount of chloride, which is harmful to the environment and human health, and a large amount of sulfur escapes in the form of sulfur vapor to form SO2 harmful gas in the reaction process, and washing NaCl also wastes a lot of water, so this method is difficult to popularize. SUMMARY

[0004] The present application is proposed in view of the above problems, and a preparation method of FePS3 is designed. The technical means adopted by the present application are as follows: A preparation method of FePS3, characterized in that: pyrite powder, a sulfur-containing small molecule and elemental phosphorus are mechanically mixed, the mixed powder is calcined and cooled in a protective atmosphere in two temperature stages, and FePS3 nano powder is obtained; The first temperature stage is 200-300 DEG C, the holding time is 120-240 minutes, the second temperature stage is 400-600 DEG C, and the holding time is 120-180 minutes; the sulfur-containing small molecule is thiourea, thioacetamide or a mixture of the two; the molar ratio of FeS2 molecules in the pyrite powder, sulfur atoms in the sulfur-containing small molecule and phosphorus atoms is 1:3:5-1:1:5, wherein the excess phosphorus is to prevent the phosphorus element from being insufficient due to gasification of elemental phosphorus during heating.

[0005] The FePS3 obtained in the application is a layered nanomaterial and may be accompanied by a small amount of nanocarbon or graphene.

[0006] Further, the pyrite powder has a particle size range of 500-1200 mesh.

[0007] Further, the pyrite powder has a particle size range of 600-800 mesh.

[0008] Further, the protective atmosphere is nitrogen, argon or a mixture of the two.

[0009] An electrode material comprising the material prepared by the preparation method of FePS3 according to the application.

[0010] Compared with the prior art, the preparation method of FePS3 according to the application has the following advantages: 1. Pyrite (FeS2) is used as the iron source and sulfur source, and a sulfur-containing small molecule is used as the second sulfur source, FePS3 nano powder is directly obtained by solid phase reaction with elemental phosphorus, the raw material sources are abundant, and China has abundant and widely distributed pyrite reserves; 2. The method has low solid phase reaction temperature, simple process, does not require strict reaction conditions, and does not require complex equipment, and is easy to scale up; 3. The sulfur source in the reaction is stable and controllable, and no obvious excess of the sulfur source needs to be added; 4. The impurities are controllable, the possible impurity elements are C, N and H, part of them is discharged in the form of NH3 gas in the reaction, and the remaining part exists in the form of nanocarbon, which can improve the conductivity of the main material and is beneficial to the battery performance, and no additional purification treatment is required. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The X-ray diffraction pattern of the pyrite powder used in Example 1 of the application is compared with the standard pattern of FeS2.

[0012] Figure 2 This is a comparison between the X-ray diffraction pattern of the FePS3 powder synthesized in Example 1 of this invention and the standard FePS3 pattern.

[0013] Figure 3 This is a scanning electron microscope image of the FePS3 powder synthesized in Example 1 of this invention.

[0014] Figure 4 The X-ray diffraction pattern of the FePS3 powder synthesized in Example 2 of this invention is compared with the standard FePS3 pattern.

[0015] Figure 5 This is a scanning electron microscope image of the FePS3 powder synthesized in Example 2 of this invention.

[0016] Figure 6 The X-ray diffraction pattern of the FePS3 powder synthesized in Example 3 of this invention is compared with the standard FePS3 pattern.

[0017] Figure 7 This is a scanning electron microscope image of the FePS3 powder synthesized in Example 3 of this invention.

[0018] Figure 8 This is a comparison of the X-ray diffraction pattern of the sample prepared in Comparative Example 1 of this invention with the standard FeS2 pattern.

[0019] Figure 9 This is a comparison of the X-ray diffraction pattern of the sample prepared in Comparative Example 2 of this invention with the standard patterns of FeS2 and P4S7. Detailed Implementation

[0020] Example 1: Synthesis of FePS3 using thiourea as the second sulfur source In this example, 30 grams of 800-mesh pyrite powder, 57 grams of thiourea, and 38.75 grams of elemental phosphorus (FeS2, with a sulfur to phosphorus molar ratio of 1:3:5 in thiourea) were mechanically mixed using a mixer. The mixed powder was then heated in a nitrogen atmosphere. The heating program was as follows: nitrogen was pre-purged into a tube furnace for 30 minutes, the temperature was increased to 200°C at a rate of 5°C / min and held for 240 minutes, then increased to 600°C at the same rate and held for 180 minutes. The mixture was then cooled with the furnace to obtain a black powder sample. X-ray diffraction (XRD) tests on the pyrite raw material and the synthesized powder showed that the pyrite raw material used had an FeS2 structure (…). Figure 1 The prepared powder has a FePS3 structure ( Figure 2 Scanning electron microscopy (SEM) images show that the prepared powder is a layered nanomaterial encapsulated by an ultrathin carbon film. Figure 3The carbon film is formed because thiourea produces some solid products during its thermal decomposition as a second sulfur source, including carbon, ammonium sulfide, and a small amount of elemental sulfur. The carbon cannot be further thermally decomposed or participate in the reaction, so it coats the surface of the products to form a carbon film.

[0021] Example 2: Synthesis of FePS3 using thioacetamide as the second sulfur source In this example, 30 g of 800-mesh pyrite powder, 18.75 g of thiourea, and 38.7 g of elemental phosphorus (FeS2, the molar ratio of sulfur to phosphorus atoms in thiourea is 1:1:5) were mechanically mixed using a mixer. The mixed powder was then heated in an argon atmosphere. The heating program was as follows: nitrogen gas was pre-purged into the tube furnace for 30 min, the temperature was increased to 300 °C at a rate of 5 °C / min and held for 120 min, then increased to 400 °C at the same rate and held for 120 min, followed by furnace cooling to obtain a black powder sample. XRD characterization of the sample showed that the obtained sample had a FePS3 structure (…). Figure 4 SEM results showed that the prepared powder was a layered nanomaterial, and the ultrathin carbon film in Example 1 was almost invisible. Figure 5 Unlike thiourea, the thermal decomposition of thioacetamide produces no solid products. The carbon elements in the process escape from the reaction system as CH4 gas in an oxygen-free environment with the nitrogen or argon atmosphere and cannot be coated on the product surface. Therefore, no ultrathin carbon film was observed during the characterization process.

[0022] Example 3: Synthesis of FePS3 using a mixture of thiourea and thioacetamide as a second sulfur source. In this example, 30 g of 700-mesh pyrite powder, 19 g of thiourea, 19 g of thioacetamide, and 38.75 g of elemental phosphorus (FeS2, the molar ratio of sulfur atoms to phosphorus atoms in thiourea is 1:2:5) were mechanically mixed using a mixer. The mixed powder was then heated in an argon atmosphere. The heating program was as follows: nitrogen gas was pre-purged into the tube furnace for 30 min, the temperature was increased to 250 °C at a rate of 5 °C / min and held for 180 min, then increased to 500 °C at the same rate and held for 150 min, followed by furnace cooling to obtain a black powder sample. XRD characterization of the sample showed that the obtained sample had a FePS3 structure (…). Figure 6 SEM results showed that the prepared powder was a layered nanomaterial. Figure 7 ), and accompanied by a small amount of ultrathin carbon film.

[0023] Comparative Example 1 used thiourea as the second sulfur source and calcined it only at temperatures above 600 degrees Celsius. In this example, 30 g of 800-mesh pyrite powder, 57 g of thiourea, and 38.75 g of elemental phosphorus (FeS2, with a sulfur to phosphorus molar ratio of 1:3:5 in thiourea) were mechanically mixed using a mixer. The mixed powder was then heated in a nitrogen atmosphere. The heating program was as follows: nitrogen was pre-purged into a tube furnace for 30 min, the temperature was increased to 700 °C at a rate of 5 °C / min and held for 420 min, followed by furnace cooling to obtain a black powder sample. X-ray diffraction (XRD) was performed on the synthesized black powder. The tests showed that the main component of the black powder was FeS2 (… Figure 8 FePS3 was not generated because the excessively high temperature caused elemental phosphorus to vaporize and escape from the reaction system as phosphorus vapor.

[0024] Comparative Example 2 used thiourea as the second sulfur source and calcined it only at temperatures below 310°C. In this example, 30 g of 800-mesh pyrite powder, 57 g of thiourea, and 38.75 g of elemental phosphorus (FeS2, with a sulfur to phosphorus atom molar ratio of 1:3:5 in thiourea) were mechanically mixed using a mixer. The mixed powder was then heated in a nitrogen atmosphere. The heating program was as follows: nitrogen was pre-purged into a tube furnace for 30 min, the temperature was increased to 180 °C at a rate of 5 °C / min and held for 360 min, followed by furnace cooling to obtain a black powder sample. X-ray diffraction (XRD) was performed on the synthesized black powder. The tests showed that the main component of the black powder was a mixture of FeS2 and phosphorus-sulfur compounds. Figure 9 FePS3 was not generated because the temperature was too low, which only caused phosphorus and sulfur to combine and react, and FeS2 did not participate in the reaction.

[0025] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing FePS3, characterized in that: Pyrite powder, sulfur-containing small molecules and elemental phosphorus are mechanically mixed. The well-mixed powder is then calcined and cooled in two temperature stages under a protective atmosphere to obtain FePS3 nanopowder. The first temperature stage is 200℃~300℃, with a holding time of 120 minutes~240 minutes; the second temperature stage is 400℃~600℃, with a holding time of 120 minutes~180 minutes; the sulfur-containing small molecules are thiourea, thioacetamide, or a mixture of both; the molar ratio of FeS2 molecules, sulfur atoms, and phosphorus atoms in the sulfur-containing small molecules in the pyrite powder is 1:3:5~1:1:

5.

2. The method for preparing FePS3 according to claim 1, characterized in that: Pyrite powder, with a particle size range of 500~1200 mesh.

3. The method for preparing FePS3 according to claim 2, characterized in that: Pyrite powder, with a particle size range of 600~800 mesh.

4. The method for preparing FePS3 according to claim 1, characterized in that: The protective atmosphere is nitrogen, argon, or a mixture of both.

5. An electrode material, characterized in that: The material comprises the FePS3 prepared by the preparation method according to any one of claims 1 to 4.

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