A thermal battery sulfide cathode material and its preparation method

Abstract

This solution discloses a sulfide cathode material for thermal batteries in the field of chemical power source thermal battery technology. The components of the cathode material include a conductive agent and a sulfide. The conductive agent is a nickel-containing composite conductive agent. The nickel-containing composite conductive agent includes a first-class conductor and a second-class conductor of ternary perchloride. And the metal elements contained in the nickel-containing composite conductive agent and their molar ratios are Ni:K:Li = m:58.8:41.2, where m = 1 - 5. Applying the cathode material to a long-duration high-current thermal battery at the end has a high no-load voltage and a strong load capacity in the later stage.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal batteries for chemical power sources, and particularly relates to a sulfide cathode material for a thermal battery and a preparation method thereof. Background Art

[0002] A thermal battery is a special chemical power source, and is widely used in the aerospace field due to its excellent power output performance and long storage life. Common thermal battery cathode materials (such as sulfides) have a large interfacial resistance at high temperatures. Therefore, an ion conductive agent and an electron conductive agent need to be added to improve the interfacial resistance of the cathode. With the development of remote equipment, higher requirements are put forward for the performance of thermal batteries in the industry, such as a small initial discharge current, a relatively high voltage provided by the cathode material at the initial stage, no-load in the middle stage, and relatively high ion conductivity and electron conductivity of the cathode material at the later stage. Therefore, a cathode material with high conductivity and high thermal shock resistance has become one of the important development directions of thermal batteries.

[0003] The main active substance in the current thermal battery cathode materials is sulfide. In current research, due to the high mobility and high ionic conductivity of alkali metal ions, which are very suitable for high-power thermal batteries, the form of compounding the active substance with an alkali metal halide molten salt is mainly used to construct the thermal battery cathode material. For example, CN201910205114.2 reports a high-potential and high-power thermal battery cathode material composed of a fluoride and eutectic salts of LiF-NaF-LiCl and LiF-KF-LiCl. CN201910304122.2 reports a composite cathode material composed of a sulfide and a potassium-containing electrolyte to reduce the degree of self-discharge; CN201110067556.9 reports a cathode material composed of a nickel chloride cathode and an alkali metal halide eutectic salt; CN201910411142.x reports a cathode material composed of tungsten molybdenum sulfide and an alkali metal molten salt ion conductive agent.

[0004] Since sulfide will decompose to produce sulfur vapor at high temperatures, resulting in loss of cathode capacity or exothermic side reactions, and seriously causing thermal runaway of the battery in severe cases, adding a certain amount of alkali metal halide molten salt to the cathode material containing sulfide can reduce the interfacial resistance and prevent the electrolyte in the separator from diffusing and migrating to the cathode. The alkali metal halide molten salt can effectively reduce the decomposition of sulfide through thermal buffering, extend the working time of the battery, and at the same time, a thermal battery with a large terminal current load for a long time also has the characteristics of a small initial discharge current and a large load current at the later stage.

[0005] In current hot battery cathode materials, due to the use of alkali metal molten salts as ionic conductors, in long-term hot batteries, as the depth of discharge progresses and the heat of the hot battery is lost, the cathode discharge by-products and the cathode process will increase the internal resistance of the battery, resulting in a low voltage, making it impossible to meet the requirements of high-current loads in the later stage of battery discharge, and the comprehensive performance of long-term hot batteries needs to be improved. Therefore, providing a technology that can boost the voltage at the initial stage of discharge, extend the battery working time, increase the actual capacity output of sulfides, and reduce the internal resistance of the battery in the later stage to meet the requirements of high-current loads in the later stage of battery discharge is a technical problem that needs to be focused on in the field of hot battery technology. Summary of the Invention

[0006] The present invention aims to provide a sulfide cathode material for hot batteries to address the problems existing in the prior art.

[0007] A sulfide cathode material for a hot battery in this solution, the components of the cathode material include a conductor and a sulfide, the conductor is a nickel-containing composite conductor, the nickel-containing composite conductor includes a first type of conductor and a second type of conductor with ternary perchloride, and the metal elements contained in the nickel-containing composite conductor and their molar ratios are at least Ni:Li:K = m:58.8:41.2, where m = 1 - 5.

[0008] The working principle and beneficial technical effects of this solution are as follows:

[0009] Long-term end high-current load hot batteries have the characteristics of small current at the initial stage of discharge and large load current in the later stage. The present invention develops a sulfide cathode material for hot batteries in view of the characteristics of high heat, easy decomposition of the cathode, low initial voltage, and large resistance in the later stage of long-term end high-current load hot batteries.

[0010] The nickel-containing composite conductor of the present invention contains at least metal elements and their molar ratio (Ni:Li:K) is Ni:Li:K = m:58.8:41.2, m = 1 - 5. When the proportion of nickel element m < 1, the difference in properties from alkali metal halide electrolytes is small, and the impact on the high-current load capacity of the battery in the later stage is small. When the proportion of nickel element m > 5, the viscosity will increase. When the proportion of nickel element is too large, a muddy melt will form. When adding a carbonaceous conductor, the metallic nickel generated by rapid reduction during the preparation of the composite conductor may stratify and settle, making the composite conductor uneven.

[0011] 1. By introducing the heavy metal element nickel into the molten salt system with fast ion migration speed, the melting point of the molten salt is increased, the thermal shock impact of the initial heating material on the cathode material is reduced, and the decomposition of the sulfide of the cathode active material is reduced; secondly, by introducing the heavy metal element nickel, the viscosity of the material is changed, the high-temperature fluidity of the ionic conductor is reduced, and the bonding force at the interface with the active material is enhanced.

[0012] 2. Particularly importantly, by utilizing the second type of conductor with ternary perchloride, where the chloride ions have a high-temperature solvation effect on heavy metal nickel ions, the uniform distribution of metal nickel ions is achieved, and a nickel-containing solvation conjugate with a monomer voltage regulation function is constructed. Therefore, in addition to having high ionic conductivity, this cathode material can also provide a corrected voltage during the initial small current or no-load operation, and generate highly conductive metal nickel through weak electrochemical action or self-discharge effect, providing a highly active electron conductor for the later electrochemical process of the battery and realizing the output of a large battery load in the later stage.

[0013] 3. The nickel-containing composite conductor in the present invention has a monomer voltage boosting function. Since the conductor in this solution contains metal nickel ions, the metal nickel ions are more likely to accept electrons. Therefore, at the initial stage of battery discharge, the nickel-containing composite conductor has a voltage boosting function, increasing the monomer voltage of the sulfide from about 2V to 2.1 - 2.6V. At the same time, since the metal nickel ions undergo an electrochemical reaction at the cathode, they can provide metal nickel with high electronic conductivity for the later stage of the battery to carry a larger current density.

[0014] Further, the sulfide is selected from FeS2; CoS2; NiS2; Fe x Co y S2, where x + y = 1; Fe x Co y Ni z S2, where x + y + z = 1; WS2; MoS2, or any combination of one or more of them.

[0015] Further, the mass ratio of the sulfide is 50% - 95%. Preferably 70% - 90%. The remaining components are composite conductors, and metal conductors and carbonaceous conductors can also be added additionally. As a preferred solution, when the mass ratio of the active substance is greater than 95%, the material has poor formability, low ionic conductivity, a large internal resistance of the battery, and poor mass consistency. When the mass ratio is less than 50%, the capacity of the cathode material is low, and nickel ions will interfere with the voltage for a long time, which is not suitable for a hot battery with a large current load at the end for a long time.

[0016] Further, the first type of conductor is an electron conductor, including a metal conductor and a non-metallic carbonaceous conductor.

[0017] Further, the contents of the non-metallic carbonaceous and Ni are both 0.01% - 5% of the total mass of the nickel-containing composite conductor. Among them, the content of the non-metallic carbonaceous is preferably 1% - 3%. The specific content of metal nickel can be determined by adding carbonaceous conductor and reduction time.

[0018] Further, the content of the non-metallic carbonaceous is 1% - 3% of the total mass of the nickel-containing composite conductor.

[0019] Furthermore, the metal conductive agent is selected from one or a combination of at least two of gold, silver, platinum, manganese, iron, cobalt, nickel, copper, zinc, lead, tin, indium, antimony, and bismuth. Iron, cobalt, nickel, copper, zinc, gold, and silver are preferred. The metal conductor primarily utilizes a highly conductive metal. The metal can be physically added, or a carbonaceous conductive agent can be used to partially reduce the nickel ions in the composite conductive agent. For example, during the preparation process, a certain amount of carbon material is added to the molten salt, and at high temperature, the carbon reduces the nickel ions to produce metallic nickel.

[0020] Furthermore, the non-metallic carbon material includes any one or more combinations of carbon nanotubes, carbon nanofibers, graphene, carbon nanowires, Ketjen black, conductive carbon black Super P, porous carbon, fullerene or conductive graphite.

[0021] In order to further improve the comprehensive performance of the positive electrode material, the present application also provides a method for preparing a sulfide positive electrode material for a thermal battery, comprising the following steps:

[0022] S1. Sulfide pretreatment

[0023] The active substance sulfide is subjected to a high-temperature heat treatment in stages under an inert atmosphere, cooled, and sieved through 80-200 mesh for later use;

[0024] S2. Preparation of composite conductive agent

[0025] (1) Pretreatment: Ni 2+ , Li + , K + Cations and Cl - The raw materials of anions are dried under high temperature and vacuum, transferred into a dry atmosphere, and the corresponding raw materials are weighed according to the proportion of cations for later use;

[0026] (2) Melt calcination: The raw materials without Ni are mixed evenly, transferred into a crucible, and the raw materials containing Ni are added thereon. The mixture is transferred into a high-temperature furnace and calcined at a temperature of 375-500°C for 2-8 hours to form a uniform and transparent melt.

[0027] (3) Composite carbon material: add 0.01-5% by mass of non-metallic carbonaceous conductive agent to the melt at high temperature, mix well to form a suspension, and keep warm for 1 minute to 1 hour;

[0028] (4) Rapid cooling: Pour the obtained high-temperature melt suspension into a special condensation container and spread it out. After cooling, the cooled block material is crushed and refined, and sieved through 80-200 mesh to obtain a composite conductive agent;

[0029] S3. High-temperature roasting: The active substance sulfide and the composite conductive agent are proportionally powdered and mixed. The mixing method can be any one or a combination of at least two of mechanical mixing, point, line, surface, or volume contact or coating after high-temperature melting.

[0030] S4. Post-treatment: The mixed material in S3 is crushed and sieved through 80 - 200 meshes to obtain the sulfide cathode material.

[0031] Furthermore, the process of segmented high-temperature heat treatment in S1 is roasting at 80 - 200 °C for 4 - 8 h under the condition of replacing the internal atmosphere by circulating dry inert gas, and then heating up to 375 - 500 °C for high-temperature roasting for 2 - 8 h.

[0032] Furthermore, the vacuum drying temperature in the pretreatment process is 60 - 300 °C, and the drying time is 1 - 24 h.

[0033] Furthermore, the special refrigerating container is a container with a heat exchange function at the bottom. The heat exchange medium includes any one or a combination of water with a temperature not higher than 10 °C, chilled brine, chilled ethylene glycol, and low-temperature antifreeze containing ethylene glycol.

[0034] Furthermore, in S3, the active substance sulfide and the composite conductive agent are ball-milled and mixed by a powder mixer at a speed of 200 - 1000 r / min. After being mixed evenly, they are sent into a high-temperature furnace protected by inert gas for high-temperature roasting and cooled with the furnace.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The method for preparing the sulfide cathode material of the thermal battery in the present invention utilizes the high-temperature solvation effect of Cl ions on heavy metal Ni ions to achieve the uniform distribution of metal nickel ions. At the same time, rapid cooling with liquefied gas is combined to achieve rapid shaping of high-temperature molten salt, forming a uniform nickel ion-containing conductive agent. The prepared nickel ion-containing conductive agent has uniform composition and high mass reliability.

[0037] 2) Since the thermal battery works at high temperature, both physical mixing or high-temperature melting treatment can make the cathode and the composite conductive agent form a tight combination during the operation of the thermal battery. The point, line, surface, or volume contact or coating after high-temperature melting treatment can accelerate battery activation and shorten the activation time.

[0038] 3) The method for preparing the sulfide cathode material of the thermal battery in the present invention does not require matching high-precision and sophisticated equipment, has a simple process flow, high efficiency, low cost, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a process flow chart of a method for preparing a sulfide cathode material of a thermal battery of the present invention.

[0040] Figure 2 Schematic diagram of a sulfide cathode material for a thermal battery of the present invention;

[0041] Figure 3 Discharge curve of a sulfide cathode material for a thermal battery in Example 1. Detailed implementation manners

[0042] The following is a further detailed description through specific implementation manners. The preparation method is combined with Figure 1 shown as follows:

[0043] Example 1

[0044] 1. A preparation method of a sulfide cathode material for a thermal battery, the method comprising the following steps:

[0045] S1. Pretreatment of sulfide

[0046] The active material CoS2 is subjected to segmented high-temperature heat treatment under the protection of an argon atmosphere. The segmented high-temperature treatment process is to calcine at 180°C for 4 h under the condition of using dry argon to circulate and replace the internal atmosphere, then raise the temperature to 450°C for high-temperature calcination for 8 h, and cool and screen through a 200-mesh sieve for later use.

[0047] S2. Preparation of composite conductive agent

[0048] (1) Pretreatment: The raw materials with chemical compositions of Li2NiCl4, LiCl, and KCl are subjected to high-temperature vacuum drying at 180°C for 8 h, transferred into a dry atmosphere, and weighed according to the cation ratio. The molar ratio of metal cations (Ni 2+ : Li + : K + ) is 2.5:58.8:41.2 (that is, the molar ratio of Li2NiCl4, LiCl, and KCl raw materials is 2.5:53.8:41.2, and the mass ratio is approximately 536:2281:3074).

[0049] (2) Melting and calcination: The raw materials without Ni (LiCl and KCl) are mixed evenly, transferred into a crucible, and the raw materials containing Ni (Li2NiCl4) are added on it, then transferred into a high-temperature furnace and calcined at 450°C for 8 h to form a uniform and transparent melt.

[0050] (3) Composite carbon material: 0.1% by mass of carbon nanotubes of the raw materials are added to the melt at high temperature, stirred and mixed evenly for 30 min, and then 1% by mass of carbon nanotubes of the raw materials are added again and quickly stirred to form a suspension.

[0051] (4) Rapid cooling: The obtained high-temperature suspension is poured into a special container of a stainless steel plate within 30 seconds and spread out. The bottom of the stainless steel plate is equipped with a water circulation cooling heat exchanger with a temperature less than 10°C, which can quickly cool the high-temperature suspension melt spread out in the stainless steel plate. The cooled block material is crushed and refined, and then sieved through 200 mesh to obtain a composite conductive agent.

[0052] S3. High-temperature calcination: The active material sulfide and the composite conductive agent are powdered in a ratio of 80:20, and ball-milled at a speed of 300 r / min using a powder mixer. After uniform mixing, the mixture is sent into a high-temperature furnace protected by inert gas for high-temperature calcination at a temperature of 400°C and a calcination time of 4 hours, and then cooled in the furnace.

[0053] S4, post-processing: The calcined and cooled material is crushed and sieved through 200 mesh to obtain a sulfide positive electrode material.

[0054] The positive electrode material is made of 80% cobalt disulfide active material and 20% nickel-containing composite conductive agent through high temperature melting. The nickel-containing composite conductive agent is composed of the first type of conductor carbon nanotubes and reduced nickel powder electronic conductive agent and the second type of conductor ternary (Ni-K-Li) full chloride ion conductive agent (schematic diagram) Figure 2 ), and the molar ratio of metal elements in the composite conductive agent (Ni:K:Li) is 2.5:58.8:41.2, the proportion of carbon nanotubes is about 1%, and the metal nickel produced by reduction is about 1%. The positive electrode material is used in a long-term high-current thermal battery with a no-load voltage of 2.32V. Figure 3 shown.

[0055] The present invention also provides the following implementation methods, which achieve substantially the same effects as Example 1.

[0056] Example 2

[0057] A method for preparing a sulfide positive electrode material for a thermal battery, the method comprising the following steps:

[0058] S1. Sulfide pretreatment

[0059] The active material FeS2 was subjected to a staged high-temperature heat treatment under argon atmosphere protection. The staged high-temperature treatment process was to calcine at 180°C for 4 hours while circulating dry argon to replace the internal atmosphere, then heat it to 450°C for 8 hours. After cooling, it was sieved through 200 mesh and set aside.

[0060] S2. Preparation of composite conductive agent

[0061] (1) Pretreatment: The raw materials with chemical composition of NiCl2, LiCl, and KCl were vacuum dried at 180℃ for 8h, transferred into dry atmosphere, and weighed according to the cation ratio. The molar ratio of metal cations (Ni 2+ :Li+ : K + ) is 2.5:58.8:41.2 (i.e., the molar ratio of NiCl2, LiCl, and KCl raw materials is 2.5:58.8:41.2, and the mass ratio is approximately 324:2493:3074).

[0062] (2) Melting roasting: Mix the raw materials without Ni (LiCl and KCl) evenly, transfer them into a crucible, add the raw material containing Ni (NiCl2) on it, transfer it into a high-temperature furnace, and roast it at 450 °C for 8 h to form a homogeneous and transparent melt.

[0063] (3) Composite carbon material: Add carbon nanotubes with a mass ratio of 1% to the melt at high temperature, mix evenly to form a suspension, and keep it warm for 5 min.

[0064] (4) Rapid cooling: Immediately pour the obtained high-temperature melt suspension into a special container of a stainless-steel tray. The bottom of the stainless-steel tray is equipped with a heat exchanger with a coolant circulation for cooling mainly composed of water and ethylene glycol, which can rapidly cool the high-temperature suspension melt spread in the stainless-steel tray. Crush and refine the cooled block material, and obtain the composite conductive agent after sieving through 200 meshes.

[0065] S3. High-temperature roasting: Powder the active substance sulfide and the composite conductive agent in a ratio of 80:20, use a powder mixer to perform ball milling and mixing at a speed of 300 r / min, send it into a high-temperature furnace protected by inert gas for high-temperature roasting after mixing evenly, and cool it with the furnace.

[0066] S4. Post-treatment: Crush the roasted and cooled material, sieve it through 200 meshes to obtain the sulfide cathode material.

[0067] Example 3

[0068] 1. A method for preparing a sulfide cathode material for a thermal battery, the method comprising the following steps:

[0069] S1. Pretreatment of sulfide

[0070] Perform segmented high-temperature heat treatment on the active substances FeS2 and CoS2 respectively under the protection of an argon atmosphere. The segmented high-temperature treatment process is to roast at 180 °C for 5 h under the condition of using dry argon to circulate and replace the internal atmosphere, and then raise the temperature to 440 °C for high-temperature roasting for 12 h. Cool and sieve through 200 meshes for standby.

[0071] S2. Preparation of composite conductive agent

[0072] (1) Pretreatment: Perform high-temperature vacuum drying on the raw materials with chemical components of NiCl2, LiCl, and KCl-LiCl eutectic at 180 °C for 8 h, transfer them into a dry atmosphere, weigh according to the cation ratio, and the molar ratio of metal cations (Ni2+ :Li + :K + ) is 2.5:58.8:41.2 (i.e., the molar ratio of NiCl2, LiCl, and LiCl-KCl eutectic raw materials is 2.5:17.6:41.2, and the mass ratio is approximately 324:746:4820).

[0073] (2) Melt calcination: The raw materials without Ni (LiCl and LiCl-KCl eutectic) are mixed evenly and transferred into a crucible. The raw materials containing Ni (NiCl2) are added on top. The mixture is transferred into a high-temperature furnace and calcined at 480°C for 8 hours to form a uniform and transparent melt.

[0074] (3) Composite carbon material: 1% by mass of carbon nanotubes was added to the melt at high temperature, mixed evenly to form a suspension, and kept warm for 2 minutes.

[0075] (4) Rapid cooling: The obtained high-temperature melt suspension is immediately poured into a special container made of stainless steel tray. The bottom of the stainless steel tray is equipped with a heat exchanger with -5°C chilled brine circulation cooling, which can quickly cool the high-temperature suspension melt spread in the stainless steel tray. The cooled block material is crushed and refined, and then sieved through 200 mesh to obtain a composite conductive agent.

[0076] S3. High-temperature calcination: The active materials FeS2, CoS2 and the composite conductive agent are powdered in a ratio of 40:40:20, and are ball-milled at a speed of 300 r / min using a powder mixer. After uniform mixing, they are sent into a high-temperature furnace protected by inert gas for high-temperature calcination and cooled with the furnace.

[0077] S4, post-processing: crush the calcined and cooled material, and sieve through 200 mesh to obtain a sulfide positive electrode material.

[0078] The cathode material of this scheme is made by high-temperature fusion bonding of 40% cobalt disulfide (cobalt disulfide), 40% iron disulfide (iron disulfide), and 20% nickel-containing composite conductive agent. The nickel-containing composite conductive agent is composed of a first-class conductive carbon nanotube, a reduced nickel powder electronic conductive agent, and a second-class conductive ternary (Ni-K-Li) full chloride ion conductive agent. The molar ratio of the metal elements in the composite conductive agent (Ni:K:Li) is 3:58.8:41.2. The carbon nanotubes account for approximately 1%, and the reduced nickel metal accounts for approximately 1%. The cathode material was used in a long-term, high-current thermal battery, achieving a no-load voltage of 2.34V.

[0079] Example 4

[0080] The difference between this solution and Example 1 is that the positive electrode material in this solution is formed by high-temperature melting and combination of 75% nickel disulfide as the active material, 18% nickel-containing composite conductive agent, 2% silver powder, and 5% graphite powder. The nickel-containing composite conductive agent is composed of a first-class conductor carbon nanotube, a reduced nickel powder electronic conductive agent, and a second-class conductor ternary (Ni-K-Li) all-chloride ion conductive agent. And the molar ratio of metal elements (Ni:K:Li) in the composite conductive agent is 2.5:58.8:41.2, the proportion of carbon nanotubes is about 1%, and the reduced metallic nickel is about 1%. Applying the positive electrode material to a long-time end large-current thermal battery, the no-load voltage is 2.30V.

[0081] Example 5

[0082] The difference between this solution and Example 1 is that the positive electrode material in this solution is formed by high-temperature melting and combination of 78% iron disulfide as the active material, 20% nickel-containing composite conductive agent, and 2% silver powder. The nickel-containing composite conductive agent is composed of a first-class conductor carbon nanotube, a reduced nickel powder electronic conductive agent, and a second-class conductor ternary (Ni-K-Li) all-chloride ion conductive agent. And the molar ratio of metal elements (Ni:K:Li) in the composite conductive agent is 4:58.8:41.2, the proportion of carbon nanotubes is about 1%, and the reduced metallic nickel is about 2%. Applying the positive electrode material to a long-time end large-current thermal battery, the no-load voltage is 2.36V.

Claims

1. A preparation method of a sulfide cathode material for a thermal battery, wherein the components of the cathode material include a conductive agent and a sulfide, and it is characterized in that: The conductive agent is a nickel-containing composite conductive agent, which includes a first type conductor and a second type conductor of ternary perchlorine, the first type conductor is an electronic conductor, including a metal conductive agent and a non-metallic carbonaceous conductive agent, and the nickel-containing composite conductive agent contains at least one metal element and a molar ratio of Ni:Li:K=m:58.8:41.2, wherein m=1-5; The preparation method comprises the following steps: S1. Sulfide pretreatment The active substance sulfide is subjected to a high-temperature heat treatment in stages under an inert atmosphere, cooled, and sieved through 80-200 mesh for later use; S2. Preparation of composite conductive agent (1)Pretreatment: The raw materials containing Ni 2+ , Li + , K + cations and Cl - anions are dried under high temperature and vacuum, transferred into a dry atmosphere, and the corresponding raw materials are weighed according to the cation ratio for standby; (2) Melt roasting: Mix the raw materials without Ni evenly, transfer them into a crucible, add the raw materials containing Ni on top, transfer them into a high-temperature furnace, and roast them at a temperature of 375~500℃ for 2~8h to form a uniform and transparent melt; (3) Composite carbon material: Add 1% to 3% of the total mass of the nickel-containing composite conductive agent to the melt at high temperature, mix evenly to form a suspension, and keep warm for 1 minute to 1 hour; (4) Rapid cooling: The obtained high-temperature melt suspension is poured into a special condensation container and spread out. After cooling, the cooled block material is crushed and refined, and sieved through 80-200 mesh to obtain a composite conductive agent; the special condensation container is a container with a heat exchange function at the bottom of the container, and the heat exchange medium includes any one or more combinations of water with a temperature not greater than 10°C, frozen brine, frozen methanol, frozen ethanol, frozen ethylene glycol, and a low-temperature antifreeze containing ethylene glycol; S3, powder preparation and mixing: the active material sulfide and the composite conductive agent are powdered and mixed in proportion, and the mixing method is any one of mechanical mixing, point, line, surface, body contact or coating after high temperature melting, or a combination of at least two; S4, post-processing: the mixed materials in S3 are crushed and sieved through 80-200 mesh to obtain sulfide positive electrode materials.

2. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, wherein: The sulfide is selected from FeS2; CoS2; NiS2; Fe x Co y S2, where x + y = 1; Fe x Co y Ni z S 2， where x + y + z = 1; any one or a combination of more than one of WS2; MoS2.

3. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, characterized in that: The mass percentage of the sulfide in the positive electrode material is 50% to 95%.

4. The preparation method of a sulfide cathode material for a thermal battery according to claim 3, characterized in that: The content of Ni is 0.01% to 5% of the total mass of the nickel-containing composite conductive agent.

5. The preparation method of a sulfide cathode material for a thermal battery according to claim 4, characterized in that: The metal conductive agent is selected from one or a combination of at least two of gold, silver, platinum, manganese, iron, cobalt, nickel, copper, zinc, lead, tin, indium, antimony, bismuth, etc.

6. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, wherein: The non-metallic carbon material includes any one or more combinations of carbon nanotubes, carbon nanofibers, graphene, carbon nanowires, Ketjen black, conductive carbon black Super P, porous carbon, fullerene or conductive graphite.

7. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, characterized in that: The process of the staged high-temperature heat treatment in S1 is to calcine at 80-200° C. for 4-8 hours while replacing the internal atmosphere with a dry inert gas circulation, and then raise the temperature to 375-500° C. and calcine at high temperature for 2-8 hours.

8. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, characterized in that: During the pretreatment process, the vacuum drying temperature is 60-300° C., and the drying time is 1-24 hours.

9. The preparation method of a sulfide cathode material for a thermal battery according to claim 1, characterized in that: The active material sulfide in S3 and the composite conductive agent are mixed by ball milling at a speed of 200-1000 r / min using a powder mixer. After being mixed evenly, they are sent into a high-temperature furnace protected by inert gas for high-temperature roasting and cooled along with the furnace.

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