Composite material of graphitized carbon-coated tin-based metal heterogeneous phase, and preparation method and application thereof

Abstract

The invention discloses a graphitized carbon-coated tin-based metal heterogeneous phase composite material as well as a preparation method and application thereof, and belongs to the technical field of battery materials. The graphitized carbon coated tin-based metal heterogeneous phase composite material takes nitrogen-doped graphitized carbon as a shell and takes a tin-based metal heterogeneous phase as a core; the tin-based metal heterogeneous phase is defined as SnHE and is composed of elemental tin and an alloy of tin and a first transition metal element, and the first transition metal element is at least one of copper, zinc, manganese, cobalt, nickel, vanadium and iron. The sulfur fixation and catalysis functions of the positive electrode material can be improved.

Description

Technical Field

[0001] The invention relates to a graphitized carbon-coated tin-based metal heterogeneous phase composite material, a preparation method and application thereof, and belongs to the technical field of battery materials. Background Art

[0002] Sulfur cathodes have the advantages of high energy density, good environmental compatibility, high content and low cost. Lithium-sulfur batteries are electrochemical energy storage technologies with great application prospects in the post-lithium-ion era. However, the dissolution of lithium polysulfide intermediates during the charge and discharge cycle of lithium-sulfur batteries has seriously hindered the commercial application of this technology. This is because lithium polysulfide will dissolve into the electrolyte and then be driven by the flowing liquid to shuttle back and forth between the positive and negative electrodes, and deposit a solid Li2S / Li2S2 layer on the electrode surface (shuttle effect), resulting in low capacity and poor utilization efficiency. In recent years, studies have found that constructing a core-shell structure is an effective way to inhibit the shuttling of sulfur cathodes and low energy efficiency. However, how to construct a comprehensive strategy that combines inhibiting shuttling and improving conversion power through reasonable design to synergistically improve the electrochemical sulfur storage performance remains a huge challenge. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a composite material of graphitized carbon coated with a tin-based metal heterogeneous phase, a preparation method and application thereof, which can enhance the sulfur fixation and catalytic functions of the positive electrode material.

[0004] The first aspect of the present invention relates to a composite material of graphitized carbon coated with a tin-based metal heterogeneous phase, wherein the graphitized carbon doped with nitrogen is used as a shell and the tin-based metal heterogeneous phase is used as a core; the tin-based metal heterogeneous phase is defined as Sn HE , consisting of a single substance of tin and an alloy of tin and a first transition series metal element, wherein the first transition series metal element is at least one of copper, zinc, manganese, cobalt, nickel, vanadium and iron; preferably, the ratio of the total number of metal elements in the composite material to the molar number of all elements is 1% to 80%.

[0005] The second aspect of the present invention relates to the use of the above-mentioned graphitized carbon-coated tin-based metal heterogeneous phase composite material in a lithium-sulfur battery. The composite material is used as a sulfur storage material in a lithium-sulfur battery to make a positive electrode of a lithium-sulfur battery, and can be stably charged and discharged for more than 750 cycles at a high current density (for example, 6C).

[0006] The third aspect of the present invention relates to a method for preparing the above-mentioned graphitized carbon-coated tin-based metal heterogeneous phase composite material, comprising the following steps:

[0007] S1, uniformly dispersing tin oxide powder having oxygen defects in an organic solvent, n-hexane, and then adding a chloride solution of a first transition metal element, dispersing the powder uniformly, then performing solid-liquid separation, and drying to obtain a first powder;

[0008] S2, weighing tris(hydroxymethyl)aminomethane) at a ratio of 1 to 200 mg / mL and dissolving it in deionized water, mixing them evenly to obtain a first mixture; weighing the first powder obtained in step S1 and evenly dispersing it in the first mixture to obtain a second mixture, wherein the amount of the first powder added relative to deionized water is 0.01 to 10 mg / mL; weighing dopamine hydrochloride and evenly dispersing it in the second mixture, wherein the amount of dopamine hydrochloride added relative to deionized water is 0.01 to 10 mg / mL; then performing solid-liquid separation and drying to obtain a second powder;

[0009] S3, calcining the second powder, heating to 400-1000°C under a flowing inert atmosphere, keeping the temperature for 1-6 hours and then cooling to obtain a composite material Sn of a tin-based metal heterogeneous phase coated with graphitized carbon HE @NC.

[0010] For some specific implementation schemes, the solid-liquid separation adopts a centrifugal washing or suction filtration method.

[0011] For some specific implementation schemes, the heating rate during heating in step S3 is 1-20° C. / min.

[0012] For some specific implementation schemes, the tin oxide powder with oxygen defects is prepared by the following method: using water and ethanol as a mixed solvent; adding SnCl4 to the mixed solvent at a concentration of 1 to 200 mg / mL to prepare a first mixed solution; then adding NH3·H2O to the first mixed solution at a concentration of 0.1 to 50 mg / mL, mixing evenly, and preparing a second mixed solution; then, adding tetradecylamine (TDA) at a concentration of 1 to 200 mg / mL, mixing evenly, heating to 80 to 200°C and keeping warm for 2 to 50 hours for hydrothermal reaction, then cooling, solid-liquid separation, and finally drying to obtain tin oxide powder; the above concentrations are measured based on the volume of the mixed solvent. The above preparation method can be used to obtain tin oxide powder with initial nano morphology and oxygen defects through hydrothermal reaction under weak alkaline conditions, creating conditions for forming a composite material of graphitized carbon-coated tin-based metal heterogeneous phase.

[0013] Compared with the prior art, the present invention has the following technical effects:

[0014] 1) Step S1 uses tin oxide with oxygen defects to adsorb a certain amount of first transition metal element ions on its surface by a double solvent method, thereby obtaining a first powder; on this basis, step S2 forms a composite material with an original core-shell structure modified with polydopamine by self-polymerization of dopamine on the surface of the first powder, i.e., the second powder; finally, in an inert gas atmosphere, a one-step high-temperature calcination treatment is performed to reduce the Sn with a heterogeneous phase core. HE@NC, in this process, polydopamine is carbonized at high temperature to form a nitrogen-doped graphitized carbon-based shell material, and part of the reduced Sn metal forms an alloy with the first transition metal element under high temperature conditions;

[0015] 2) The heterogeneous core is composed of tin and tin-based alloys, and the sulfur fixation and catalytic functions are improved at the same time; that is, the organic combination of inhibiting shuttle and improving conversion power is achieved, which can not only reduce the loss of intermediate phase lithium sulfide in the electrolyte, but also accelerate the electrocatalytic efficiency in multi-electron conversion, ensuring that the sulfur lithiation reaction is more sufficient, rapid and efficient, and thus can obtain ultra-stable cycle performance at high rates;

[0016] 3) The preparation method has the advantages of low cost, simplicity and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Sn prepared in Example 1 HE @NC’s XRD diffraction pattern;

[0018] Figure 2 Sn prepared in Example 2 HE @NC’s SEM photo;

[0019] Figure 3a Sn prepared in Example 3 HE @NC’s SEM photo;

[0020] Figure 3b Sn prepared in Example 3 HE @NC element spectrum distribution diagram;

[0021] Figure 4 Sn prepared in Example 4 HE TEM photo of @NC;

[0022] Figure 5 This is a comparison chart of the cycle performance of batteries made with MnSn3-Sn@NC / S and Sn@NC / S as sulfur storage positive electrode materials in Example 5;

[0023] Figure 6 This is a comparison chart of the sulfur fixation function (lithium polysulfide adsorption capacity) of V2Sn3-Sn@NC and Sn@NC in Example 6;

[0024] Figure 7 This is a comparison diagram of the electrocatalytic functions of NiSn-Sn@NC / S and Sn@NC / S in Example 7;

[0025] Figure 8 Based on Sn in Example 8 HE @The performance curve of the sulfur storage cathode material prepared by NC in a high current and long cycle;

[0026] Fig. 9 Sn prepared in Example 9 HE @NC’s XRD diffraction pattern;

[0027] Fig.10 Sn prepared in Example 10 HE SEM photo of @NC. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The experimental methods without specific conditions in the examples are carried out according to conventional methods and conditions.

[0029] Example 1

[0030] In this example, Sn HE @NC's process is as follows.

[0031] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 20 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 10 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 5 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 15 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 100 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 150°C for 7 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0032] The first powder preparation step: weigh 500 mg of tin oxide powder and add it to 50 mL of n-hexane, ultrasonically disperse and mix evenly; then add 50 mL of 20 mg / mL CoCl2 aqueous solution, ultrasonically and stir in an ice-water bath, wash to remove surface impurities, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0033] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 150 mg / mL, added to 200 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 0.8 mg / mL, and ultrasonically stirred is continued to be mixed evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 6 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol to remove excess cationic impurities, and dried to obtain a second powder.

[0034] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 700°C under a flowing inert atmosphere, kept warm for 2 hours, and then cooled to room temperature and taken out to obtain a composite material Co3Sn2-Sn@NC of graphitized carbon-coated tin-based metal heterogeneous phase.

[0035] After analysis: the XRD spectrum of the prepared powder sample is as follows Figure 1 As shown, the prepared powder has obvious characteristic peaks of CoSn alloy and Sn single substance, and contains a carbon matrix with a high degree of graphitization without any other metal compound impurities.

[0036] Example 2

[0037] In this example, Sn HE @NC's process is as follows.

[0038] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 30 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 12 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 20 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 63 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 175°C for 3 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0039] The first powder preparation step: weigh 270 mg of tin oxide powder and add it to 30 mL of n-hexane, ultrasonically disperse and mix evenly; then add 30 mL of 50 mg / mL CuCl2 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0040] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 10 mg / mL, added to 60 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 6.5 mg / mL, and ultrasonically stirred is continued to mix evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 0.8 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol, and dried to obtain a second powder.

[0041] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 600°C under a flowing inert atmosphere, kept warm for 2.5 hours, and then cooled to room temperature to obtain a composite material Cu3Sn-Sn@NC with a tin-based metal heterogeneous phase coated with graphitized carbon.

[0042] After analysis: the SEM spectrum of the prepared powder sample is as follows Figure 2 As shown. It can be seen that the prepared powder particles have the morphology of nanospheres observed under SEM. The size of the nanospheres is about 200nm, and the surface is relatively rough and not smooth, indicating that there is a coating phase on the surface of the nanospheres.

[0043] Example 3

[0044] In this example, Sn HE @NC's process is as follows.

[0045] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 22 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 15 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 26 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 30 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 160 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 180°C for 6 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0046] The first powder preparation step: weigh 875 mg of tin oxide powder and add it to 35 mL of n-hexane, ultrasonically disperse it and mix it evenly; then add 30 mL of a 50 mg / mL TiCl4 aqueous solution, ultrasonically mix it in an ice-water bath, stir it, and then centrifuge and wash it three times with a mixture of water and ethanol to remove excess cationic impurities, and dry it to obtain the first powder.

[0047] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane is weighed at a concentration of 100 mg / mL, added to 120 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 1 mg / mL, and ultrasonically stirred is continued to be mixed evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 5 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixed solution of water and ethanol, and dried to obtain a second powder.

[0048] Sn HE @NC synthesis steps: the second powder is transferred to a quartz tube furnace for calcination, heated to 800°C under a flowing inert atmosphere, kept warm for 1.5 hours, and then cooled to room temperature to obtain a composite material Ti2Sn-Sn@NC with a graphitized carbon-coated tin-based metal heterogeneous phase.

[0049] After analysis: The scanning electron microscope image of the powder sample of the prepared composite material is as follows Figure 3a The element distribution diagram is shown in Figure 3b As shown, the size of the prepared powder particles is similar to the size of the nanospheres observed under SEM. The size of the nanospheres is about 200 nm, and the Ti, Sn, C and N elements are evenly distributed in the nanospheres.

[0050] Example 4

[0051] In this example, Sn HE @NC's process is as follows.

[0052] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 56 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 10 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 45 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 60 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 165°C for 12 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0053] The first powder preparation step: weigh 1200 mg of tin oxide powder and add it to 60 mL of n-hexane, ultrasonically disperse and mix evenly; then add 50 mL of 60 mg / mL FeCl3 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0054] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 100 mg / mL, added to 400 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 5.5 mg / mL, and ultrasonically stirred is continued to be mixed evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 6 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol, and dried to obtain a second powder.

[0055] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 700°C under a flowing inert atmosphere, kept warm for 2.5 hours, and then cooled to room temperature to obtain a composite material FeSn3-Sn@NC with a graphitized carbon-coated tin-based metal heterogeneous phase.

[0056] After analysis: The transmission electron microscope image of the prepared composite material is as follows Figure 4 As shown, the prepared powder particles were observed to have FeSn alloy and Sn single-element heterogeneous phases, as well as the core-shell interface of the graphitized carbon layer under high-resolution TEM.

[0057] Example 5

[0058] In this example, Sn HE @NC's process is as follows.

[0059] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 8 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 8 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 10 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 10 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 30 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 155°C for 6 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0060] The first powder preparation step: weigh 1620 mg of tin oxide powder and add it to 45 mL of n-hexane, ultrasonically disperse it and mix it evenly; then add 50 mL of a 60 mg / mL MnCl2 aqueous solution, ultrasonically mix it in an ice-water bath, stir it, and then centrifuge and wash it three times with a mixture of water and ethanol to remove excess cationic impurities, and dry it to obtain the first powder.

[0061] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 100 mg / mL, added to 200 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 6.5 mg / mL, and ultrasonically stirred is continued to be mixed evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 7.5 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixed solution of water and ethanol, and dried to obtain a second powder.

[0062] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 820°C under a flowing inert atmosphere, kept warm for 3 hours, and then cooled to room temperature and taken out to obtain a composite material MnSn3-Sn@NC of graphitized carbon-coated tin-based metal heterogeneous phase.

[0063] MnSn3-Sn@NC and sulfur were fully ground and mixed in a mortar in a mass ratio of 1:3, placed in a reactor, heated to 155°C and kept warm for 12 hours to obtain the positive electrode material MnSn3-Sn@NC / S.

[0064] After analysis: the prepared positive electrode material MnSn3-Sn@NC / S was assembled into a button battery; after testing, the following results were obtained: Figure 5 The cyclic voltammetry curves shown in Figure 2 show that the MnSn3-Sn@NC / S electrode with a heterogeneous core-shell structure has obvious reaction characteristic peaks of long-chain lithium polysulfides and short-chain lithium polysulfides, indicating that its kinetics are faster and the conversion is more complete.

[0065] Example 6

[0066] In this example, Sn HE @NC's process is as follows.

[0067] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 17.5 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 15 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 33 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 30 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 60 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 120°C for 6 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0068] The first powder preparation step: weigh 275 mg of tin oxide powder and add it to 25 mL of n-hexane, ultrasonically disperse it and mix it evenly; then add 30 mL of a 36 mg / mL VCl3 aqueous solution, ultrasonically mix it in an ice-water bath, stir it, and then centrifuge and wash it three times with a mixture of water and ethanol to remove excess cationic impurities, and dry it to obtain the first powder.

[0069] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 70 mg / mL, added to 190 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 0.3 mg / mL, and ultrasonically stirred is continued to mix evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 1 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol, and dried to obtain a second powder.

[0070] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 600°C under a flowing inert atmosphere, kept warm for 3 hours, and then cooled to room temperature and taken out to obtain a composite material V2Sn3-Sn@NC with a graphitized carbon-coated tin-based metal heterogeneous phase.

[0071] After analysis: the prepared composite material was coated on a PP diaphragm and placed in an H-type electrolytic cell. The color changes of lithium polysulfide on both sides were observed at the same time. Figure 6 As shown, it can be clearly seen that compared with the Sn@NC material (b) on the right side of the figure, the V2Sn3-Sn@NC material (a) on the left side of the figure has a stronger adsorption capacity for lithium polysulfide, indicating that the heterogeneous core-shell structure has a better sulfur fixation effect.

[0072] Example 7

[0073] In this example, Sn HE @NC's process is as follows.

[0074] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 15 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 12 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 10 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 10 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 160°C for 8 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0075] The first powder preparation step: weigh 1100 mg of tin oxide powder and add it to 22 mL of n-hexane, ultrasonically disperse and mix evenly; then add 30 mL of 50 mg / mL NiCl2 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0076] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 90 mg / mL, added to 300 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 2.5 mg / mL, and ultrasonically stirred is continued to mix evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 5.5 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixed solution of water and ethanol, and dried to obtain a second powder.

[0077] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 900°C under a flowing inert atmosphere, kept warm for 3.5 hours, and then cooled to room temperature to obtain a composite material NiSn-Sn@NC with a tin-based metal heterogeneous phase coated with graphitized carbon.

[0078] NiSn-Sn@NC and sulfur were fully ground and mixed in a mortar at a mass ratio of 1:3, placed in a reactor, heated to 155°C and kept warm for 12 hours to obtain the positive electrode material NiSn-Sn@NC / S.

[0079] After analysis: the prepared cathode material NiSn-Sn@NC / S was assembled into a button-type battery, and the battery Tafel slope was as follows Figure 7 When the button cell is discharged to 2.05 V, the exchange current density is obtained according to the Tafel slope. The comparison results show that NiSn-Sn@NC / S has a larger exchange current density than Sn@NC / S, indicating that the overpotential of the reaction is lower and the catalytic kinetics is faster.

[0080] Example 8

[0081] In this example, Sn HE @NC's process is as follows.

[0082] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 60 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 7 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 16 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 50 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 190°C for 7 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0083] The first powder preparation step: weigh 2000 mg of tin oxide powder and add it to 100 mL of n-hexane, ultrasonically disperse and mix evenly; then add 90 mL of 40 mg / mL FeCl3 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0084] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 70 mg / mL, added to 150 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 6 mg / mL, and ultrasonically stirred and mixed evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 9 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol, and dried to obtain a second powder.

[0085] Sn HE @NC synthesis steps: The second powder is transferred to a quartz tube furnace for calcination, heated to 800°C under a flowing inert atmosphere, kept warm for 4 hours, and then cooled to room temperature and taken out to obtain a composite material FeSn3-Sn@NC with a graphitized carbon-coated tin-based metal heterogeneous phase.

[0086] FeSn3-Sn@NC and sulfur element were fully ground and mixed in a mortar in a mass ratio of 1:3, placed in a reactor, heated to 155°C and kept warm for 12 hours to obtain the positive electrode material FeSn3-Sn@NC / S.

[0087] After analysis, the prepared molybdenum nitride modified carbon nanotube material was obtained after melt sulfurization at 155°C. The long cycle performance of the assembled button battery is as follows Figure 8As shown. When the current is increased and the cycle period is extended, the FeSn3-Sn@NC / S composite electrode shows a more stable high-rate performance. When the test current density is increased to 6C, the FeSn3-Sn@NC / S composite cathode can still release a first-cycle discharge capacity of 1120mAh / g. After 800 cycles, the reversible capacity is 639mAh / g. In 800 cycles, the capacity retention rate is 60%, and the average capacity decay rate per cycle is only 0.052%.

[0088] Example 9

[0089] In this example, Sn HE @NC's process is as follows.

[0090] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 80 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 12 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 40 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 10 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 50 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 70°C for 10 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0091] The first powder preparation step: weigh 1000 mg of tin oxide powder and add it to 50 mL of n-hexane, ultrasonically disperse and mix evenly; then add 55 mL of 30 mg / mL VCl3 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0092] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 20 mg / mL, added to 230 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 7 mg / mL, and ultrasonically stirred is continued to mix evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 8 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixture of water and ethanol, and dried to obtain a second powder.

[0093] Composite material synthesis steps: transfer the second powder to a quartz tube furnace for calcination, heat to 750° C. under a flowing inert atmosphere, keep warm for 3 hours, cool to room temperature and take out to obtain a composite material.

[0094] After analysis: the XRD pattern of the prepared composite material is as follows Fig. 9 It is found that in addition to the signal of graphitized carbon matrix, many diffraction peaks of oxides appear. It can be seen that when the temperature of hydrothermal synthesis exceeds the range of 80-200℃, the final composite material is a mixture of many heterogeneous phases, rather than Sn HE @NC.

[0095] Example 10

[0096] In this example, Sn HE @NC's process is as follows.

[0097] Preparation steps of tin oxide powder: using water and ethanol as mixed solvents, determining the concentration based on the volume of the mixed solvent, and adding corresponding raw materials; adding SnCl4 at a concentration of 11 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding NH3·H2O at a concentration of 22 mg / mL, using a probe ultrasonic instrument to ultrasonically disperse for 20 minutes, and mixing evenly; then adding tetradecylamine (TDA) at a concentration of 60 mg / mL, slowly stirring at a speed of 450 rpm for 1 hour, and mixing evenly; then transferring to a hydrothermal reactor, performing a hydrothermal reaction, and keeping warm at 150°C for 8 hours; finally, cooling to room temperature, and then centrifugally washing three times with a mixed solution of water and ethanol, and drying to obtain tin oxide powder for standby use.

[0098] The first powder preparation step: weigh 1100 mg of tin oxide powder and add it to 50 mL of n-hexane, ultrasonically disperse and mix evenly; then add 60 mL of 33 mg / mL CuCl2 aqueous solution, ultrasonically mix and stir in an ice-water bath, then centrifuge and wash three times with a mixture of water and ethanol to remove excess cationic impurities, and dry to obtain the first powder.

[0099] The second powder preparation steps are as follows: the concentration is determined based on the volume of deionized water, and the corresponding raw materials are added; tris(hydroxymethyl)aminomethane) is weighed at a concentration of 20 mg / mL, added to 90 mL of deionized water, ultrasonically stirred, and mixed evenly to obtain a first mixture; the prepared first powder is added to the first mixture at a concentration of 6 mg / mL, and ultrasonically stirred is continued to mix evenly to obtain a second mixture; dopamine hydrochloride is weighed at a concentration of 9 mg / mL, added to the second mixture, stirred at room temperature, and mixed evenly; and then centrifuged and washed three times with a mixed solution of water and ethanol, and dried to obtain a second powder.

[0100] Composite material synthesis steps: transfer the second powder to a quartz tube furnace for calcination, heat to 1100° C. under a flowing inert atmosphere, keep warm for 1 hour, cool to room temperature and take out to obtain a composite material.

[0101] After analysis: the SEM image of the prepared composite material is as follows Fig.10 No regular and ordered tin-based compound nanosphere structure was found, and the regular nanosphere skeleton had collapsed as a whole. It can be seen that when the synthesis conditions exceeded the range of (400-1000°C), the prepared composite material was not Sn HE @NC.

[0102] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A composite material of graphitized carbon coated with a tin-based metal heterogeneous phase, characterized in that: The nitrogen-doped graphitized carbon is used as the shell and the tin-based metal heterogeneous phase is used as the core; the tin-based metal heterogeneous phase is defined as Sn HE , consisting of tin alone and an alloy of tin and a first transition series metal element, wherein the first transition series metal element is at least one of copper, zinc, manganese, cobalt, nickel, vanadium and iron.

2. The composite material according to claim 1, characterized in that The ratio of the total metal elements in the composite material to the molar number of all elements is 1% to 80%.

3. A method for preparing the composite material according to claim 1 or 2, characterized in that: The following steps are involved: S1, uniformly dispersing tin oxide powder with oxygen defects in an organic solvent, n-hexane, and then adding a chloride solution of a first transition metal element and uniformly dispersing for a period of time; Then the solid and liquid are separated and dried to obtain the first powder; S2, weighing tris(hydroxymethyl)aminomethane) at a ratio of 1 to 200 mg / mL and dissolving it in deionized water, mixing them evenly to obtain a first mixture; weighing the first powder obtained in step S1 and evenly dispersing it in the first mixture to obtain a second mixture, wherein the amount of the first powder added relative to deionized water is 0.01 to 10 mg / mL; weighing dopamine hydrochloride and evenly dispersing it in the second mixture, wherein the amount of dopamine hydrochloride added relative to deionized water is 0.01 to 10 mg / mL; then performing solid-liquid separation and drying to obtain a second powder; S3, calcining the second powder, heating to 400-1000°C under a flowing inert atmosphere, keeping the temperature for 1-6 hours and then cooling to obtain a composite material Sn of a tin-based metal heterogeneous phase coated with graphitized carbon HE @NC.

4. The preparation method according to claim 3, characterized in that: The solid-liquid separation is carried out by centrifugal washing or suction filtration.

5. The preparation method according to claim 3, characterized in that: The heating rate during heating in step S3 is 1 to 20° C. / min.

6. The preparation method according to claim 3, characterized in that: The tin oxide powder is prepared by the following method: using water and ethanol as a mixed solvent, adding SnCl4 into the mixed solvent at a concentration of 1 to 200 mg / mL to prepare a first mixed solution; then adding NH3·H2O into the first mixed solution at a concentration of 0.1 to 50 mg / mL, mixing evenly, and preparing a second mixed solution; then adding TDA at a concentration of 1 to 200 mg / mL, mixing evenly, heating to 80 to 200°C and keeping the temperature for 2 to 50 hours to perform a hydrothermal reaction, then cooling, performing solid-liquid separation, and finally drying to obtain the tin oxide powder with oxygen defects.

7. Use of the composite material according to claim 1 or 2 in a positive electrode material of a lithium-sulfur battery.

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