Preparation method and application of high-performance metal sulfide carbon composite positive electrode material

Abstract

The invention belongs to the technical field of thermal battery materials, and particularly relates to a preparation method and application of a high-performance metal sulfide carbon composite positive electrode material. Transition metal-based nitrate and carbon-containing organic matter are evenly mixed in deionized water, the deionized water is removed, powder obtained after sufficient grinding serves as a pyrolysis precursor, and the high-performance metal sulfide carbon composite positive electrode material is obtained. And preparing the composite material of the multi-element transition metal sulfide and the sulfur-doped carbon through a vulcanization process. When the composite material is applied to the thermal battery, on one hand, the multi-metal sulfide has high specific capacity and stability, and the discharge capacity and time of the thermal battery are ensured; meanwhile, the sulfur-doped carbon material can improve the conductivity of the positive electrode material, improve the utilization rate of sulfide and further improve the performance of the thermal battery. The preparation method disclosed by the invention is simple, small in environmental pollution and low in material cost, and has relatively high practical application potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal battery materials, and specifically relates to a preparation method and application of a high-performance metal sulfide carbon composite positive electrode material, and in particular to the preparation of a high-performance metal sulfide / carbon composite positive electrode material and its application as an active material in a thermal battery positive electrode to obtain a high-capacity, long-stability thermal battery. Background Art

[0002] A thermal battery is a primary storage battery that uses an inorganic salt as an electrolyte. It is in an inactive state at room temperature (the electrolyte is non-conductive); when the battery is in an activated state, the electrolyte is heated and presents a molten state with ion conduction characteristics, and the single cell can output a large current. Compared with other energy storage devices, thermal batteries have the advantages of high specific power / specific energy, wide temperature range, high reliability and long storage life. Therefore, it has become one of the most ideal supporting power sources for various devices. With the continuous development and progress of science and technology, higher requirements are placed on the capacity and stability of supporting thermal batteries, and there is an urgent need to explore a positive electrode material with high capacity and long stability.

[0003] At present, the most widely used positive electrode materials for thermal batteries are transition metal sulfides (such as FeS2, CoS2, NiS2, ZnS, CuS, etc.), and each metal sulfide has its own characteristics. For example, FeS2 has the advantages of abundant resources and stable electrical properties, but its thermal stability is poor; CoS2 has excellent thermal stability and chemical stability, but requires artificial synthesis and is costly; the properties of NiS2 are between FeS2 and CoS2, with relatively neutral stability and specific capacity. In order to combine the advantages of various sulfides, a lot of work has been focused on compounding various sulfides to prepare composite positive electrode materials. Literature reports show that multi-metal sulfides can obtain high-performance thermal batteries, but these studies have the disadvantages of difficulty in batch production, high preparation cost, and limited improvement in mechanical mixing performance, which greatly limits the large-scale application of materials.

[0004] Carbon materials, as materials with excellent conductivity and electrochemical stability, are often introduced into positive electrode materials as additives. The introduction of carbon materials can effectively reduce the internal resistance of the electrode sheet and increase the electrochemical performance of the battery. At the same time, by doping sulfur atoms in carbon materials, the conductivity of the positive electrode sheet can be further improved, the adsorption sites of chemical reactions can be increased, and the electrochemical reaction rate inside the thermal battery can be increased and the reaction barrier can be reduced.

[0005] The patent document with publication number CN110336000A discloses a method for preparing and applying a microspherical transition metal sulfide / carbon composite material, which comprises dissolving a transition metal salt and a sulfur source in a solvent and performing a solvothermal reaction; obtaining transition metal sulfide microspheres by centrifugation, washing, and drying; taking transition metal sulfide microspheres and a carbon source, adding them to a solvent and stirring and mixing, obtaining transition metal sulfide microspheres / carbon precursors; and then calcining under a protective atmosphere to obtain microspherical transition metal sulfide / carbon composite materials. However, the sulfide and carbon material composite involved in the preparation process of the metal sulfide / carbon composite material in the patent belongs to a process of first mixing and then pyrolysis, which greatly weakens the synergistic effect between the two, especially for some long-life and harsh battery operation, the contact resistance between the two affects the battery performance. On the other hand, the solvothermal method for preparing sulfides causes great difficulties and high costs for large-scale production of materials. Therefore, it is necessary to explore a preparation process that can conveniently and quickly prepare metal sulfide / carbon composite materials.

[0006] In response to the above problems, in order to combine the advantages of various metal sulfides and sulfur-doped carbon materials, it is necessary to explore a preparation process that can realize multi-metal sulfides and sulfur-doped carbon materials, so as to achieve the application of high-performance and long-stability thermal batteries. Summary of the invention

[0007] In view of the deficiencies of the prior art, the present invention provides a preparation method and application of a high-performance metal sulfide carbon composite positive electrode material.

[0008] This is achieved specifically through the following technical solutions:

[0009] A method for preparing a high-performance metal sulfide / carbon composite positive electrode material comprises the following steps:

[0010] (1) Synthesis of pyrolysis precursor

[0011] Add three or more transition metal-based nitrates to deionized water, with the concentration of each metal ion accounting for no less than 20% of the total metal ion concentration, and stir at room temperature for 2 to 4 hours to form a solution containing a metal ion concentration of 0.1 to 0.5 mmol / mL; then raise the solution temperature to 50 to 80°C, add a carbon material precursor to form an aqueous solution with a concentration of 0.1 to 0.4 mmol / mL, and continue stirring for 1 to 2 hours until the substances in the solution are uniformly mixed; place the mixed solution in a blast drying oven, dry it at 100 to 120°C, take it out after the water is completely evaporated, collect the obtained solid material, and obtain a pyrolysis precursor after sufficient grinding;

[0012] (2) Synthesis of multi-element transition metal sulfides and sulfur-doped carbon composites

[0013] The pyrolysis precursor obtained in step (1) and the sulfur-containing substance are weighed in a mass ratio of 1:1 to 1:3, fully ground and placed in a tubular furnace. Under an inert gas atmosphere, the pyrolysis temperature is 350 to 500° C., the pyrolysis time is 1 to 4 hours, and the heating rate is 2 to 5° C. / min. After the temperature drops to room temperature, a composite material of ternary transition metal sulfide and sulfur-doped carbon is obtained.

[0014] Select any variety of metal-based nitrates and carbon material precursors and mix them evenly in an aqueous solution. Then heat and evaporate the water. The nitrate complex is thermally decomposed. The generated gas turns the carbon precursor into a looser structure. The product obtained by grinding is a carbon precursor rich in metal ions. After the obtained powder is fully mixed with a sulfur source, it is pyrolyzed. On the one hand, the sulfur atoms provided by the sulfur-containing substance combine with metal ions to form metal sulfides; on the other hand, the sulfur atoms can be doped into the carbon precursor as heterogeneous atoms to form sulfur-doped carbon materials, and finally form a composite material of multi-metal sulfide and sulfur-doped carbon. Applying the prepared composite material to the positive electrode of a thermal battery can improve battery performance.

[0015] Furthermore, the transition metal-based nitrate includes but is not limited to iron nitrate, nickel nitrate, zinc nitrate, cobalt nitrate, and copper nitrate.

[0016] Furthermore, the carbon material precursor includes but is not limited to citric acid and glucose.

[0017] Furthermore, the sulfur-containing substances include but are not limited to thioacetamide and sublimated sulfur.

[0018] The application of the above-mentioned high-performance metal sulfide / carbon composite positive electrode material as a positive electrode active material in a thermal battery is to apply the synthesized composite material as an active material to the positive electrode. The specific operation process is as follows:

[0019] Step 1: Prepare the positive electrode

[0020] The prepared composite material, separator and conductive carbon were weighed and ground thoroughly in a mass ratio of 80:18:2, 0.25 g of powder was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 20 to 30 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained;

[0021] Step 2: Prepare the diaphragm

[0022] 0.45 g of the prepared diaphragm powder was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 15 to 25 MPa was applied. After demolding, a hot battery electrolyte sheet used for the monomer test was obtained;

[0023] Step 3: Battery assembly and testing

[0024] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0025] Furthermore, the lithium salt electrolyte described in the first step includes but is not limited to a ternary all-lithium electrolyte for thermal batteries and a low melting point electrolyte.

[0026] Furthermore, the conductive carbon material in the second step includes but is not limited to graphene, carbon nanotubes, and XC-72.

[0027] Beneficial effects:

[0028] The composite material prepared by the present invention is a composite material comprising multi-metal sulfide and sulfur-doped carbon, which is prepared by using transition metal-based nitrates (ferric nitrate, nickel nitrate, zinc nitrate, cobalt nitrate, copper nitrate, etc.) as metal ion sources, citric acid, glucose and other materials as carbon sources, and thioacetamide, sublimated sulfur and the like as sulfur sources. The composite material can combine the advantages of different metal sulfides and has excellent specific capacity and stability; on the other hand, sulfur-doped carbon can further enhance the electron transmission capacity of the composite material, increase the electrochemical reaction rate, and reduce the reaction barrier. Therefore, the composite material can provide a guarantee for the development of high-power, high-stability thermal batteries.

[0029] (1) The composite material has a simple preparation process, low material cost, and little environmental pollution. In addition, the prepared material can significantly improve battery performance and has a good benefit effect.

[0030] (2) The prepared multi-metal sulfide can combine the characteristics of multiple metal sulfides and has the advantages of high specific capacity and stability as the positive electrode material of thermal batteries.

[0031] (3) Sulfur-doped carbon materials can further enhance the electron transport capacity of metal sulfide electrodes, reduce resistance and reaction energy barriers, and promote the electrochemical reaction rate.

[0032] The prepared metal sulfide has a strong bonding force with the carbon material, which can better exert the advantages of the composite material, facilitate long-term storage and resist thermal shock. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM image of the composite material prepared in Example 1;

[0034] Figure 2 This is an element distribution picture of the composite material prepared in Example 1;

[0035] Figure 3 The XRD pattern of the composite material prepared in Example 1;

[0036] Figure 4Thermogravimetric test results of the composite material prepared in Example 1;

[0037] Figure 5 The electrical properties test results of the composite material prepared in Example 1 are shown. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments, and any improvement or substitution based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0039] Example 1

[0040] Step 1: Synthesis of pyrolysis precursor

[0041] Weigh cobalt nitrate, nickel nitrate, and iron nitrate in a molar ratio of 1:1:1 and add them to deionized water. Stir for 0.5h at room temperature to form a solution with a metal ion concentration of 0.3mmol / mL. Then raise the solution temperature to 60°C, add citric acid and continue stirring for 2h until the substances in the solution are evenly mixed, and the concentration of citric acid is 0.3mmol / L. Place the mixed solution in a forced air drying oven and dry it at 100°C until the water evaporates completely. Collect the obtained solid material and grind it thoroughly to obtain a pyrolysis precursor.

[0042] Step 2: Synthesis of ternary transition metal sulfide and sulfur-doped carbon composites

[0043] The pyrolysis precursor and sulfur powder were weighed at a mass ratio of 1:2, fully ground and placed in a tube furnace. In an argon atmosphere, the temperature was raised to 500°C and maintained for 2 hours at a heating rate of 2°C / min. After the temperature dropped to room temperature, a composite material of ternary transition metal sulfide and sulfur-doped carbon was obtained.

[0044] A high-performance metal sulfide / carbon composite cathode material is applied to a thermal battery. The synthesized composite material is used as an active material in the cathode. The specific operation process is as follows:

[0045] Step 1: Prepare the positive electrode

[0046] The prepared composite material, ternary all-lithium electrolyte separator for thermal battery and conductive carbon were weighed and ground thoroughly in a mass ratio of 80:18:2. 0.25 g of powder was placed in a circular mold with a diameter of 20 mm. A molding pressure of 20 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained.

[0047] Step 2: Prepare the diaphragm

[0048] 0.45 g of the configured ternary all-lithium electrolyte diaphragm powder for thermal batteries was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 15 MPa was applied. After demolding, the thermal battery electrolyte sheet used for the monomer test was obtained.

[0049] Step 3: Battery assembly and testing

[0050] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0051] The morphology of the prepared material is Figure 1 As shown, it can be seen that the composite material is a block structure, and there is no obvious structural difference between the various metal sulfides and sulfur-doped carbon materials, indicating that the two-phase structure is evenly combined. A part of the area was selected for element surface distribution test ( Figure 2 The results show that C, S, Fe, Co, and Ni elements are evenly distributed in the sheet structure, further indicating that the various phases in the composite material are closely combined.

[0052] In order to prove the phase composition of the composite, XRD analysis was carried out, such as Figure 3 As shown. After comparison with the standard card, it was found that the composition of the ternary metal sulfide is Co 1～x S and (Ni,Fe)S2 phases. Some diffraction peaks are offset, indicating that there are some atomic substitutions between metal atoms, resulting in lattice distortion. Since the diffraction peak intensity of carbon materials is weak and the carbon in this material is mainly amorphous carbon, the peak position of carbon materials is not obvious, but the carbon diffraction peak can still be observed at a diffraction angle of about 25°.

[0053] Figure 4 The TG and DSC test results of the ternary transition metal sulfide and sulfur-doped carbon composite material show that the material loss is not obvious before 600°C, and this part of the weight loss is attributed to the phase change of impurities and moisture in the material. Between 600°C and 680°C, the material shows obvious weight loss, which is caused by the decomposition of metal sulfides. Before 680°C, the total weight loss rate of the material is 25%, and then it maintains a low weight loss rate. This shows that the introduction of carbon materials reduces the high-temperature weight loss rate of the composite material; at the same time, due to the strong synergistic effect between the three metal sulfides, the thermal stability of the material is improved.

[0054] Figure 5 The electrochemical performance of a single cell. 2 At a current density of , the initial discharge voltage of the battery is 2.0V. When the battery discharge voltage drops to 1.5V, the discharge specific capacity of the battery is 597mAh / g, which has good electrochemical performance.

[0055] Example 2

[0056] Step 1: Synthesis of pyrolysis precursor

[0057] Cobalt nitrate, nickel nitrate, iron nitrate and zinc nitrate were weighed in a molar ratio of 1:1:1:1 and added to deionized water. The mixture was stirred at room temperature for 1 hour to form a solution containing a metal ion concentration of 0.5 mmol / mL. The solution temperature was then raised to 80°C, citric acid was added and stirred for 2 hours until the substances in the solution were evenly mixed, and the concentration of citric acid was 0.4 mmol / L. The mixed solution was placed in a forced air drying oven and taken out after the water was completely evaporated at 120°C. The obtained solid material was collected and fully ground to obtain a pyrolysis precursor.

[0058] Step 2: Synthesis of quaternary transition metal sulfides and sulfur-doped carbon composites

[0059] The pyrolysis precursor and thioacetamide were weighed at a mass ratio of 1:3, fully ground and placed in a tube furnace. In a nitrogen atmosphere, the temperature was raised to 500°C and maintained for 4 hours at a heating rate of 5°C / min. After the temperature dropped to room temperature, a quaternary transition metal sulfide and sulfur-doped carbon composite material was obtained.

[0060] A high-performance metal sulfide / carbon composite cathode material is applied to a thermal battery. The synthesized composite material is used as an active material in the cathode. The specific operation process is as follows:

[0061] Step 1: Prepare the positive electrode

[0062] The prepared composite material, ternary all-lithium electrolyte separator for thermal battery and conductive carbon were weighed and ground thoroughly in a mass ratio of 80:18:2. 0.25 g of powder was placed in a circular mold with a diameter of 20 mm. A molding pressure of 30 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained.

[0063] Step 2: Prepare the diaphragm

[0064] 0.45 g of the configured ternary all-lithium electrolyte diaphragm powder for thermal batteries was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 25 MPa was applied. After demolding, the thermal battery electrolyte sheet used for the monomer test was obtained.

[0065] Step 3: Battery assembly and testing

[0066] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0067] At 0.1A / cm 2At a current density of , the initial discharge voltage of the battery is 2.0V. When the battery discharge voltage drops to 1.5V, the battery's discharge specific capacity is 553mAh / g.

[0068] Example 3

[0069] Step 1: Synthesis of pyrolysis precursor

[0070] Cobalt nitrate, iron nitrate and zinc nitrate were weighed in a molar ratio of 1:2:1 and added to deionized water. The mixture was stirred at room temperature for 0.75 h to form a solution containing a metal ion concentration of 0.1 mmol / mL. The solution temperature was then raised to 50°C, and citric acid was added and stirred for 1 h until the substances in the solution were evenly mixed. The concentration of citric acid was 0.1 mmol / L. The mixed solution was placed in a forced air drying oven and taken out after the water was completely evaporated at 100°C. The obtained solid phase material was collected and fully ground to obtain a pyrolysis precursor.

[0071] Step 2: Synthesis of ternary transition metal sulfide and sulfur-doped carbon composites

[0072] The pyrolysis precursor and sulfur powder were weighed in a mass ratio of 1:1, fully ground and placed in a tube furnace. In a nitrogen atmosphere, the temperature was raised to 350°C and maintained for 1 hour at a heating rate of 2°C / min. After the temperature dropped to room temperature, a ternary transition metal sulfide and sulfur-doped carbon composite material was obtained.

[0073] A high-performance metal sulfide / carbon composite cathode material is applied to a thermal battery. The synthesized composite material is used as an active material in the cathode. The specific operation process is as follows:

[0074] Step 1: Prepare the positive electrode

[0075] The prepared composite material, ternary all-lithium electrolyte separator for thermal battery and XC-72 were weighed and ground thoroughly in a mass ratio of 80:18:2. 0.25 g of powder was placed in a circular mold with a diameter of 20 mm. A molding pressure of 20 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained.

[0076] Step 2: Prepare the diaphragm

[0077] 0.45 g of the configured ternary all-lithium electrolyte diaphragm powder for thermal batteries was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 15 MPa was applied. After demolding, the thermal battery electrolyte sheet used for the monomer test was obtained.

[0078] Step 3: Battery assembly and testing

[0079] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0080] At 0.1A / cm 2 At a current density of , the initial discharge voltage of the battery is 1.9V. When the battery discharge voltage drops to 1.5V, the discharge specific capacity of the battery is 568mAh / g.

[0081] Example 4

[0082] Step 1: Synthesis of pyrolysis precursor

[0083] Weigh cobalt nitrate, nickel nitrate, iron nitrate, zinc nitrate, and copper nitrate in a molar ratio of 1:1:1:1:1 and add them to deionized water. Stir for 0.5 h at room temperature to form a solution containing a metal ion concentration of 0.1 mmol / mL. Then, after the solution temperature is raised to 70°C, add citric acid and continue stirring for 1 h until the substances in the solution are evenly mixed. The concentration of citric acid is 0.2 mmol / L. The mixed solution is placed in a forced air drying oven and taken out after the water is completely evaporated at 110°C. Collect the obtained solid material and grind it thoroughly to obtain a pyrolysis precursor.

[0084] Step 2: Synthesis of five-element transition metal sulfide and sulfur-doped carbon composites

[0085] The pyrolysis precursor and sulfur powder were weighed at a mass ratio of 1:2, fully ground and placed in a tube furnace. In an argon atmosphere, the temperature was raised to 400°C and maintained for 3 hours at a heating rate of 3°C / min. After the temperature dropped to room temperature, a five-element transition metal sulfide and sulfur-doped carbon composite material was obtained.

[0086] A high-performance metal sulfide / carbon composite cathode material is applied to a thermal battery. The synthesized composite material is used as an active material in the cathode. The specific operation process is as follows:

[0087] Step 1: Prepare the positive electrode

[0088] The prepared composite material, low-melting-point electrolyte separator for thermal batteries and graphene were weighed and ground thoroughly in a mass ratio of 80:18:2. 0.25 g of powder was placed in a circular mold with a diameter of 20 mm. A molding pressure of 25 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained.

[0089] Step 2: Prepare the diaphragm

[0090] 0.45 g of the configured ternary all-lithium electrolyte diaphragm powder for thermal batteries was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 20 MPa was applied. After demolding, the thermal battery electrolyte sheet used for the monomer test was obtained.

[0091] Step 3: Battery assembly and testing

[0092] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0093] At 0.1A / cm 2 At a current density of , the initial discharge voltage of the battery is 2.0V. When the battery discharge voltage drops to 1.5V, the discharge specific capacity of the battery is 576mAh / g.

[0094] Example 5

[0095] Step 1: Synthesis of pyrolysis precursor

[0096] Copper nitrate, nickel nitrate and iron nitrate were weighed in a molar ratio of 2:2:1 and added to deionized water. The mixture was stirred at room temperature for 2.5 hours to form a solution containing a metal ion concentration of 0.4 mmol / mL. The solution temperature was then raised to 70°C, and citric acid was added and stirred for 1.5 hours until the substances in the solution were evenly mixed. The concentration of citric acid was 0.2 mmol / L. The mixed solution was placed in a forced air drying oven and dried at 110°C until the water was completely evaporated and then taken out. The obtained solid material was collected and fully ground to obtain a pyrolysis precursor.

[0097] Step 2: Synthesis of ternary transition metal sulfide and sulfur-doped carbon composites

[0098] The pyrolysis precursor and thioacetamide were weighed at a mass ratio of 1:3, fully ground and placed in a tube furnace. In an argon atmosphere, the temperature was raised to 400°C and maintained for 3 hours at a heating rate of 4°C / min. After the temperature dropped to room temperature, a ternary transition metal sulfide and sulfur-doped carbon composite material was obtained.

[0099] A high-performance metal sulfide / carbon composite cathode material is applied to a thermal battery. The synthesized composite material is used as an active material in the cathode. The specific operation process is as follows:

[0100] Step 1: Prepare the positive electrode

[0101] The prepared composite material, ternary all-lithium electrolyte separator for thermal battery and graphene were weighed and ground thoroughly in a mass ratio of 80:18:2. 0.25 g of powder was placed in a circular mold with a diameter of 20 mm. A molding pressure of 25 MPa was applied. After demolding, the thermal battery positive electrode sheet used for the single-cell test was obtained.

[0102] Step 2: Prepare the diaphragm

[0103] 0.45 g of the prepared low-melting-point electrolyte diaphragm powder for thermal batteries was placed in a circular mold with a diameter of 20 mm, and a molding pressure of 15 MPa was applied. After demolding, the thermal battery electrolyte sheet used for the monomer test was obtained.

[0104] Step 3: Battery assembly and testing

[0105] In the glove box, the pressed positive electrode, electrolyte and commercial lithium-boron alloy are placed on the guide bar in order to form a single thermal battery. After being taken out, they are placed on a single tester for testing.

[0106] At 0.1A / cm 2 At a current density of , the initial discharge voltage of the battery is 2.1V. When the battery discharge voltage drops to 1.5V, the discharge specific capacity of the battery is 536mAh / g.

[0107] Although the present invention has selected the preferred embodiments disclosed above, it is not intended to limit the present invention. Any researcher in the field can use the design parameters and contents in the above disclosed embodiments to change and modify the research scheme of the present invention without departing from the spirit and scope of the present invention. Therefore, any simple modification, parameter change and modification made to the above embodiments based on the research essence of the present invention without departing from the content of the present invention, all belong to the protection scope of the present invention.

Claims

1. A method for preparing a high-performance metal sulfide / carbon composite positive electrode material, characterized in that: The following steps are involved: (1) Synthesis of pyrolysis precursor Add three or more transition metal-based nitrates to deionized water, with the concentration of each metal ion accounting for no less than 20% of the total metal ion concentration, and stir at room temperature for 2 to 4 hours to form a solution containing a metal ion concentration of 0.1 to 0.5 mmol / mL; then raise the solution temperature to 50 to 80°C, add a carbon material precursor to form an aqueous solution with a concentration of 0.1 to 0.4 mmol / mL, and continue stirring for 1 to 2 hours until the substances in the solution are uniformly mixed; place the mixed solution in a blast drying oven, dry it at 100 to 120°C, take it out after the water is completely evaporated, collect the obtained solid material, and obtain a pyrolysis precursor after sufficient grinding; (2) Synthesis of multi-element transition metal sulfides and sulfur-doped carbon composites The pyrolysis precursor obtained in step (1) and the sulfur-containing substance are weighed in a mass ratio of 1:1 to 1:3, fully ground and placed in a tubular furnace. Under an inert gas atmosphere, the pyrolysis temperature is 350 to 500° C., the pyrolysis time is 1 to 4 hours, and the heating rate is 2 to 5° C. / min. After the temperature drops to room temperature, a composite material of ternary transition metal sulfide and sulfur-doped carbon is obtained.

2. The method for preparing a high-performance metal sulfide / carbon composite positive electrode material according to claim 1, characterized in that: The transition metal-based nitrates include, but are not limited to, iron nitrate, nickel nitrate, zinc nitrate, cobalt nitrate, and copper nitrate.

3. The method for preparing a high-performance metal sulfide / carbon composite positive electrode material according to claim 1, characterized in that: The carbon material precursor includes but is not limited to citric acid and glucose.

4. The method for preparing a high-performance metal sulfide / carbon composite positive electrode material according to claim 1, characterized in that: The sulfur-containing substances include but are not limited to thioacetamide and sublimed sulfur.

5. A high-performance metal sulfide / carbon composite positive electrode material prepared by the preparation method according to any one of claims 1 to 4.

6. Use of a high-performance metal sulfide / carbon composite positive electrode material as claimed in claim 5 as a positive electrode active material in a thermal battery.

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