Preparation method and application of pure-phase Fe2SiS4 and Fe2SiS4 / NC

Abstract

The application discloses a preparation method and application of pure-phase Fe2SiS4 and Fe2SiS4 / NC, and adopts a high-temperature solid-phase synthesis method to uniformly physically grind Fe, Si, S and PAN powders according to a certain proportion, moves the powders to a quartz tube to perform vacuum sealing, and then is placed into a muffle furnace to be stepwise heated to 900-1000 DEG C, and is kept at a constant temperature for 12-36 hours, and then is cooled to room temperature, so that pure-phase Fe2SiS4 and Fe2SiS4 / NC can be obtained. The high-temperature solid-phase synthesis method is adopted to realize one-step synthesis of pure-phase Fe2SiS4 and Fe2SiS4 / NC, and the process is simple, and large-scale synthesis can be realized. The pure-phase Fe2SiS4 and Fe2SiS4 / NC can be applied to sodium ion battery negative electrode materials, and stable long cycle performance can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of inorganic material preparation and energy storage, and discloses a preparation method of pure-phase Fe2SiS4 and Fe2SiS4 / NC and application of the pure-phase Fe2SiS4 and Fe2SiS4 / NC prepared by the preparation method in a negative electrode material of a sodium ion battery. BACKGROUND

[0002] For the sustainable development of society, the exploration of clean and sustainable energy is imminent. However, these energies have the problems of discontinuity and instability, so we need to develop large energy storage systems to store these renewable energies. Lithium ion batteries (LIBs) have rapidly dominated the commercial market due to their high energy density and long service life, and have promoted the development of new energy.

[0003] However, the traditional positive electrode material LiCoO2 of LIBs is high in price and not environmentally friendly, lithium resources are scarce, and the actual energy density of LIBs is difficult to reach the theoretical peak value under the current technology, which cannot meet the application requirements of large power grids, electric vehicles and cyclic charging stations. Therefore, developing a new type of sodium ion battery (SIBs) negative electrode material with abundant reserves, low cost and excellent electrochemical performance is a necessary condition for the sustainable development of new generation energy storage systems. However, Na + has a larger radius (-0.102 nm), which leads to slow Na + diffusion, large volume change of the electrode material and easy formation of sodium dendrites, making it difficult for SIBs to simultaneously achieve high rate performance, high specific capacity and long cycle life.

[0004] It is urgent to explore suitable materials to solve the above problems. Fe2SiS4 and Fe2SiS4 / NC have the advantages of significant structural stability, non-toxicity and abundant reserves of raw materials, and are considered to be one of the more promising SIBs negative electrode materials. SUMMARY

[0005] In view of the deficiencies of the prior art, the application provides a preparation method and application of pure-phase Fe2SiS4 and Fe2SiS4 / NC.

[0006] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:

[0007] The application discloses a preparation method of pure-phase Fe2SiS4, comprising:

[0008] (1) Fe, Si and S elemental powders are used as raw materials, put into a mortar and physically ground for 5-15 min to obtain a mixture powder;

[0009] (2) Put the mixture powder into a quartz tube, vacuum seal the tube, and then move to a muffle furnace for calcination to obtain pure phase Fe2SiS4.

[0010] Further, the molar ratio of Fe, Si and S in step (1) is 2:x:4, and 1.1≤x<1.5.

[0011] Further, the calcination condition of the muffle furnace in step (2) is:

[0012] From room temperature 25℃, increase the temperature to 250℃ at a gradient of 0.5-3℃ / min, and keep the temperature for 2-4h;

[0013] Then increase the temperature to 500℃ at a gradient of 0.5-3℃ / min, and keep the temperature for 2-4h;

[0014] Then increase the temperature to 900-1000℃ at a gradient of 0.5-3℃ / min, and keep the temperature for 12-36h, and naturally cool to room temperature.

[0015] The application also discloses pure phase Fe2SiS4 prepared according to any of the above preparation methods.

[0016] The application discloses a preparation method of pure phase Fe2SiS4 / NC, comprising:

[0017] (1) Fe, Si, S and PAN powder are used as raw materials, and are physically ground in a mortar for 5-15min to obtain a mixture powder;

[0018] (2) The mixture powder is put into a quartz tube, vacuum sealing is performed, and then the quartz tube is moved to a muffle furnace for calcination to obtain pure phase Fe2SiS4 / NC.

[0019] Further, the molar ratio of Fe, Si and S in step (1) is 2:x:4, and 1.3<x;

[0020] The mass ratio of Fe2SiS4:NC is y;

[0021] x and y satisfy a linear regression curve y=-11.4x+23.42;

[0022] In the value range of x, y takes a corresponding value in the range, and pure phase Fe2SiS4 / NC can be synthesized.

[0023] Further, the calcination condition of the muffle furnace in step (2) is:

[0024] From room temperature 25℃, increase the temperature to 250℃ at a gradient of 0.5-3℃ / min, and keep the temperature for 2-4h;

[0025] Then increase the temperature to 500℃ at a gradient of 0.5-3℃ / min, and keep the temperature for 2-4h;

[0026] Then, the temperature is increased to 900-1000 DEG C at a gradient of 0.5-3 DEG C / min, and the temperature is kept for 12-36 h, and then the temperature is naturally cooled to room temperature.

[0027] The application further discloses pure-phase Fe2SiS4 / NC prepared according to any of the above preparation methods.

[0028] The application further discloses application of the Fe2SiS4 in preparation of a sodium ion battery negative electrode material.

[0029] The application further discloses application of the Fe2SiS4 / NC in preparation of a sodium ion battery negative electrode material.

[0030] Compared with the prior art, the application has the advantages of:

[0031] 1. The pure-phase Fe2SiS4 and Fe2SiS4 / NC can be synthesized.

[0032] 2. The preparation process is simple, the process condition is not harsh, the yield is high, and large-scale production can be realized.

[0033] 3. The coated carbon is in the form of nanoscale small balls, and the conductivity of the material is improved.

[0034] 4. The raw material is green, environment-friendly, pollution-free, widely sourced, low in price and can be widely applied. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a linear regression curve for synthesizing the pure-phase Fe2SiS4 / NC;

[0036] Figure 2 is XRD of the pure-phase Fe2SiS4 / NC prepared in example 1 of the application;

[0037] Figure 3 is SEM of the pure-phase Fe2SiS4 / NC prepared in example 1 of the application;

[0038] Figure 4 is an electrochemical performance diagram of the pure-phase Fe2SiS4 / NC prepared in example 1 of the application;

[0039] Figure 5 is XRD of the pure-phase Fe2SiS4 / NC prepared in example 2 of the application;

[0040] Figure 6 is SEM of the pure-phase Fe2SiS4 / NC prepared in example 2 of the application;

[0041] Figure 7An electrochemical performance graph of the pure-phase Fe2SiS4 / NC prepared in Embodiment 2 of the present application;

[0042] Figure 8 An XRD of the pure-phase Fe2SiS4 / NC prepared in Embodiment 3 of the present application;

[0043] Figure 9 An SEM of the pure-phase Fe2SiS4 / NC prepared in Embodiment 3 of the present application;

[0044] Figure 10 An electrochemical performance graph of the pure-phase Fe2SiS4 / NC prepared in Embodiment 3 of the present application;

[0045] Figure 11 An XRD of the pure-phase Fe2SiS4 prepared in Embodiment 4 of the present application;

[0046] Figure 12 An SEM of the pure-phase Fe2SiS4 prepared in Embodiment 4 of the present application;

[0047] Figure 13 An electrochemical performance graph of the pure-phase Fe2SiS4 prepared in Embodiment 4 of the present application. DETAILED DESCRIPTION

[0048] In order to better understand the present application, the present application is further described below in conjunction with the embodiments and the accompanying drawings, but the content of the present application is not limited to the scope described in the following embodiments.

[0049] Embodiment 1

[0050] The pure-phase Fe2SiS4 / NC comprises the following synthesis steps:

[0051] (1) The values of Si = 1.5 and Fe2SiS4 / NC = 6.5 are taken on the regression curve, and then Fe: 111.7 mg, Si: 42.2 mg, S: 128.24 mg, and PAN: 43.4 mg are weighed according to Fe: Si: S = 2: 1.5: 4, Fe2SiS4: NC: 6.5: 1, and are physically ground in a mortar for 10 min to obtain a black mixture.

[0052] (2) The black mixture is transferred to a quartz tube, vacuum sealing is performed, and then calcination is performed in a muffle furnace. The calcination specific conditions are as follows: starting from room temperature 25℃, 2℃ / min gradient heating to 250℃ for 2h, then 2℃ / min gradient heating to 500℃ for 2h, then 2℃ / min gradient heating to 950℃ for 24h, and natural cooling to room temperature to obtain a black powder.

[0053] The product prepared in the present embodiment is analyzed by X-ray diffraction, and the results show that (as shown in Figure 2), and compared with the Fe2SiS4 standard card, it can be completely matched, and pure phase Fe2SiS4 / NC is indeed synthesized; by scanning electron microscopy (SEM), as shown in Figure 3 , it can be seen that Fe2SiS4 is in block shape, and PAN is carbonized into nanometer small balls with a diameter of 150-300 nm, attached to the surface of Fe2SiS4 block.

[0054] The pure phase Fe2SiS4 / NC prepared in this example is applied to prepare the negative electrode of the sodium ion battery, which can still reach a specific capacity of 545 mAhg -1 after 90 cycles at a current density of 1 Ag -1 (like Figure 4 ), showing good electrochemical performance.

[0055] Example 2

[0056] The pure phase Fe2SiS4 / NC includes the following synthesis steps:

[0057] (1) On the regression curve, take Si = 1.4 and Fe2SiS4 / NC = 7.5, then according to Fe: Si: S = 2: 1.4: 4, Fe2SiS4: NC = 7.5: 1, weigh Fe: 111.7 mg, Si: 39.34 mg, S: 128.24 mg, PAN: 37.23 mg, and put them into a mortar for physical grinding for 10 min to obtain a black mixture.

[0058] (2) Transfer the black mixture to a quartz tube, vacuum seal, and then move to a muffle furnace for calcination. The specific calcination conditions are as follows: start from room temperature 25℃, 2℃ / min gradient to 250℃, keep for 2h, then 2℃ / min gradient to 500℃, keep for 2h, then 2℃ / min gradient to 950℃, keep for 24h, and naturally cool to room temperature to obtain a black powder.

[0059] The product prepared in this example is analyzed by X-ray diffraction, and the results (as shown in Figure 5 ) show that, compared with the Fe2SiS4 standard card, it can be completely matched, and pure phase Fe2SiS4 / NC is indeed synthesized; by scanning electron microscopy (SEM) (as shown in Figure 6 ), it can be seen that Fe2SiS4 is in block shape, and PAN is carbonized into nanometer small balls with a diameter of 150-300 nm, attached to the surface of Fe2SiS4 block.

[0060] The pure phase Fe2SiS4 / NC prepared in this example is applied to prepare the negative electrode of the sodium ion battery, which can still reach a specific capacity of 595 mAhg -1 after 90 cycles at a current density of 1 Ag -1 (likeFigure 7 ), which exhibits good electrochemical performance.

[0061] Example 3

[0062] Pure-phase Fe2SiS4 / NC, comprising the following synthesis steps:

[0063] (1) On the regression curve, take Si = 1.75 and Fe2SiS4 / NC = 4, then according to Fe: Si: S = 2: 1.75: 4, Fe2SiS4: NC = 4: 1, take Fe: 111.7 mg, Si: 49.2 mg, S: 128.24 mg, PAN: 72.3 mg, and put them into a mortar for physical grinding for 10 min to obtain a black mixture.

[0064] (2) Transfer the black mixture into a quartz tube, vacuum seal the tube, and then transfer it into a muffle furnace for calcination. The specific calcination conditions are as follows: start from room temperature 25℃, increase the temperature to 250℃ at a gradient of 2℃ / min, keep the temperature for 2h, then increase the temperature to 500℃ at a gradient of 2℃ / min, keep the temperature for 2h, then increase the temperature to 950℃ at a gradient of 2℃ / min, keep the temperature for 24h, and naturally cool to room temperature to obtain a black powder.

[0065] The product prepared in this example was analyzed by X-ray diffraction, and the results (as shown in Figure 8 ) show that it can be completely matched with the Fe2SiS4 standard card, indicating that pure-phase Fe2SiS4 / NC is indeed synthesized. Figure 9 The product prepared in this example was analyzed by scanning electron microscopy (as shown in ), which shows that Fe2SiS4 is in block shape, and PAN high-temperature carbonization is in the form of nanoscale spheres with a diameter of 150-300 nm, attached to the surface of Fe2SiS4 blocks.

[0066] Figure 10 The pure-phase Fe2SiS4 / NC prepared in this example was applied to prepare a negative electrode for a sodium ion battery, which can still achieve a specific capacity of 492mAhg -1 after 90 cycles at a current density of 1Ag -1 (as shown in ), which exhibits good electrochemical performance.

[0067] Example 4

[0068] Pure-phase Fe2SiS4, comprising the following synthesis steps:

[0069] (1) In the range of x values, when x is 1.1 (Si: 1.1), then according to Fe: Si: S = 2: 1.1: 4, take Fe: 111.7 mg, Si: 30.9 mg, S: 128.24 mg, and put them into a mortar for physical grinding for 10 min to obtain a black mixture.

[0070] (2) The black mixture was transferred into a quartz tube, vacuum sealed, and then transferred into a muffle furnace for calcination. The specific conditions for calcination were as follows: starting from room temperature 25℃, 2℃ / min gradient heating to 250℃ for 2h, then 2℃ / min gradient heating to 500℃ for 2h, then 2℃ / min gradient heating to 950℃ for 24h, and natural cooling to room temperature, to obtain a black powder.

[0071] The product prepared in this example was analyzed by X-ray diffraction. As shown in Figure 11 , compared with the Fe2SiS4standard card, it can be completely matched, and pure-phase Fe2SiS4was indeed synthesized; as shown in Figure 12 , scanning electron microscopy showed that Fe2SiS4was in a block shape.

[0072] The pure-phase Fe2SiS4prepared in this example was applied to prepare a negative electrode for a sodium-ion battery. After 90 cycles at a current density of 0.2Ag -1 , the specific capacity of the battery was still 820mAhg -1 (as shown in Figure 13 ), showing good electrochemical performance.

[0073] Obviously, the above examples are only examples to make it clear, and are not a limitation on the implementation method. It should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present application, and should be covered in the scope of the claims of the present application.

Claims

1. Application of Fe2SiS4 in the preparation of sodium-ion battery negative electrode material, wherein: The Fe2SiS4 is prepared by the following method: (1) Fe, Si, and S elemental powder is used as raw material, put into a mortar and physically ground for 5-15 min to obtain a mixture powder, the molar ratio of Fe, Si, and S is 2:x:4, and 1.1≤x<1.5; (2) The mixture powder is put into a quartz tube, vacuum sealed, and then moved to a muffle furnace for calcination, the muffle furnace calcination conditions are: starting from room temperature 25℃, increasing the temperature to 250℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 2-4h; then increasing the temperature to 500℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 2-4h; then increasing the temperature to 900-1000℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 12-36h, and naturally cooling to room temperature to obtain pure phase Fe2SiS4.

2. Application of Fe2SiS4 / NC in the preparation of sodium-ion battery negative electrode material, wherein: The Fe2SiS4 / NC is prepared by the following method: (1) Fe, Si, S, and PAN powder is used as raw material, put into a mortar and physically ground for 5-15 min to obtain a mixture powder, the molar ratio of Fe, Si, and S is 2:x:4, and 1.3<x≤1.75; the mass ratio of Fe2SiS4:NC is y; x and y satisfy the linear regression curve y=-11.4x+23.42; (2) The mixture powder is put into a quartz tube, vacuum sealed, and then moved to a muffle furnace for calcination, the muffle furnace calcination conditions are: starting from room temperature 25℃, increasing the temperature to 250℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 2-4h; then increasing the temperature to 500℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 2-4h; then increasing the temperature to 900-1000℃ at a gradient of 0.5-3℃ / min, and keeping the temperature for 12-36h, and naturally cooling to room temperature to obtain pure phase Fe2SiS4 / NC.

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