Carbon fluoride material and preparation method thereof, electrode plate and battery

Abstract

The invention relates to a carbon fluoride material and a preparation method thereof, an electrode plate and a battery. The preparation method comprises the following steps: S1, carrying out carbonization treatment on a vulcanized polymer precursor in an inert atmosphere to obtain a heteroatom-doped hard carbon material; s2, placing the heteroatom-doped hard carbon material in a mixed atmosphere containing a protective gas and a fluorination reagent, and carrying out fluorination treatment at 300-600 DEG C to obtain a fluorinated material; the volume ratio of the fluorination reagent in the mixed atmosphere is below 40%. According to the invention, the carbon fluoride material with controllable doping, high fluorination degree and stable skeleton structure can be prepared, and as an active material of a positive plate of a lithium carbon fluoride battery, the carbon fluoride material can exert high specific capacity and improve the rate capability of the lithium carbon fluoride battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium / carbon fluoride batteries, in particular to a carbon fluoride material, a preparation method thereof, an electrode sheet and a battery. BACKGROUND

[0002] With the rapid development of high-energy-density energy storage devices, carbon fluoride materials as lithium primary battery anode materials have attracted much attention due to their high theoretical specific capacity (up to 865 mAh / g), stable voltage platform, and low self-discharge rate. Traditional carbon fluoride materials are mainly prepared by direct reaction of different carbon sources and fluorine gas. The carbon material affects the difficulty of fluorination process and the skeleton structure of the final product. Selecting a suitable carbon source has a significant impact on the performance and cost of the carbon fluoride material. Industrialized carbon materials such as fluorinated industrial graphene and fluorinated activated carbon provide higher discharge specific capacity and energy density, but the cost of fluorinated industrial graphene is high, and the voltage platform of fluorinated activated carbon is low and unstable. Biomass carbon such as sorghum, reed, bamboo, and cotton has a unique transport channel due to its natural structure, and can exhibit excellent electrochemical performance as a carbon source for fluorinated carbon. However, the consistency of biomass carbon and the stability of the supply chain are difficult to guarantee, which limits its large-scale development. In order to meet the future market demand for large-scale synthesis and multi-level lithium / carbon fluoride, it is urgent to improve the design and preparation technology of carbon fluoride and further optimize the production process of the material.

[0003] Traditional carbon materials have high fluorination reaction activation energy and easy collapse of interlayer structure, resulting in poor conductivity and limited rate performance. In recent years, researchers have tried to improve the reactivity of carbon matrix by doping with heteroatoms, but conventional doping processes mostly use physical mixing or post-treatment modification, which has the defects of uneven doping and serious element loss, making it difficult to achieve the synergistic optimization of the structure and electrochemical performance of carbon fluoride materials. In addition, existing fluorination processes generally use high-concentration fluorine gas (>50%) at low temperature (<200℃) for a long time, which not only causes serious equipment corrosion and high cost, but also easily leads to structural heterogeneity problems such as over-fluorination on the surface and insufficient fluorination inside the material. Therefore, developing a modified carbon fluoride material preparation method that achieves controllable doping through molecular structure design and has high fluorination degree and stable skeleton structure is key to improving the energy density and rate performance of lithium / carbon fluoride batteries. SUMMARY

[0004] The present application aims to overcome the above technical deficiencies and provide a carbon fluoride material, a preparation method thereof, an electrode sheet and a battery, which solve the technical problems of uneven doping, low fluorination degree and unstable structure of existing carbon fluoride materials, resulting in low energy density and poor rate performance of lithium / carbon fluoride batteries.

[0005] To achieve the above technical purpose, the technical solution provided by the present application is: In a first aspect, the present application provides a preparation method of fluorinated carbon material, comprising the following steps: S1, carbonizing a sulfurized polymer precursor in an inert atmosphere to obtain a hard carbon material doped with heteroatoms; S2, placing the hard carbon material doped with heteroatoms in a mixed atmosphere containing a protective gas and a fluorination reagent, and performing fluorination treatment at 300-600°C to obtain a fluorinated material; the volume ratio of the fluorination reagent in the mixed atmosphere is less than 40%.

[0006] In a second aspect, the present application provides a fluorinated carbon material prepared by the above preparation method.

[0007] In a third aspect, the present application provides an electrode sheet, which comprises an active material layer, and the composition of the active material layer comprises the above fluorinated carbon material.

[0008] In a fourth aspect, the present application provides a fluorinated carbon battery, and the positive electrode of the fluorinated carbon battery is the above electrode sheet.

[0009] Compared with the prior art, the present application has the following beneficial effects: (1) The present application selects a sulfurized polymer precursor as a carbon source, and performs carbonization treatment, so that the sulfur atoms and other heteroatoms are located between the carbon layers, part of the covalent bonds can be converted into semi-ionic bonds or even ionic bonds, the carbon layer spacing is increased, and there are rich defect sites, polar groups and hierarchical micro / mesoporous structures, which are beneficial to the subsequent fluorination reaction, thereby improving the fluorination degree, and the volume ratio of the fluorination reagent in the fluorination treatment is low, and the reaction temperature is high, which is beneficial to fluorination, effectively avoiding the structural heterogeneity defect of over-fluorination on the surface and insufficient fluorination inside; and the high temperature in the carbonization treatment and the fluorination treatment can reduce organic impurities, improve the crystallinity of the carbon skeleton, and increase the stability of the carbon material. Therefore, the present application can prepare a fluorinated carbon material with controllable doping, high fluorination degree and stable skeleton structure; (2) The fluorinated carbon material prepared by the present application can play a high specific capacity as an active material of a lithium fluorinated carbon battery positive electrode sheet, and the heteroatom doping and unique pore structure are beneficial to enhancing the transmission of lithium ions and improving the rate performance of the lithium fluorinated carbon battery. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is a scanning electron microscope (SEM) image of the sulfurized polymer in Example 1 of the present application; Figure 2 It is an SEM image of the sulfurized polymer after carbonization in Example 1 of the present application; Figure 3 It is an SEM image of the fluorinated carbon material in Example 1 of the present application; Figure 4 It is a discharge test curve of the lithium fluorinated carbon battery in Example 1 of the present application at different rates; Figure 5 Discharge test curves of lithium-carbon fluoride batteries in Example 1 of the present application at different rates; Figure 6 Discharge test curves of lithium-carbon fluoride batteries in Examples 2-6 of the present application at 0.1C rate. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0012] In view of the defects of current carbon fluoride material, such as uneven doping, low fluorination degree, unstable structure, low energy density of lithium-carbon fluoride battery and poor rate performance, based on the characteristics of the existing lithium-carbon fluoride battery, the present application designs a kind of heteroatom-doped carbon fluoride material, a preparation method thereof, an electrode sheet and a battery. The heteroatom-doped carbon fluoride material of the present application is obtained by using sulfidized polymer as a precursor, high-temperature carbonization and then fluorination treatment, finally obtaining a carbon fluoride material with high fluorocarbon ratio and high semi-ionic C-F bond, which can realize high capacity of carbon fluoride battery, and the heteroatom doping and unique pore structure are beneficial to enhance the transmission of lithium ions and improve the rate performance of lithium-carbon fluoride battery.

[0013] In the first aspect, the present application provides a preparation method of a carbon fluoride material, comprising the following steps: S1, carbonizing a sulfidized polymer precursor in an inert atmosphere to obtain a hard carbon material doped with heteroatoms; S2, placing the hard carbon material doped with heteroatoms in a mixed atmosphere containing a protective gas and a fluorination reagent, and performing fluorination treatment at 300-600 DEG C to obtain a fluorinated material; the volume ratio of the fluorination reagent in the mixed atmosphere is below 40%.

[0014] In the technical scheme of the present application, the sulfidized polymer precursor is used as a carbon source, and after carbonization treatment, the heteroatoms such as sulfur atoms (or other possible nitrogen atoms) are located between the carbon layers, achieving the purpose of uniform doping; at the same time, the uniformly doped heteroatoms can convert part of the covalent bond into semi-ionic bond or even ionic bond, and also make the carbon layer spacing larger, which is beneficial to the subsequent fluorination reaction, thereby improving the fluorination degree, and the volume ratio of the fluorination reagent in the fluorination treatment is low, and the reaction temperature is high, which is beneficial to fluorination, effectively avoiding the structural heterogeneity defect of over-fluorination on the surface and insufficient fluorination inside; and the high temperature in the carbonization treatment and the fluorination treatment can reduce organic impurities, improve the crystallinity of the carbon skeleton, and increase the stability of the carbon material. Therefore, the present application can realize the preparation of a controllable doped carbon fluoride material with high fluorination degree and stable skeleton structure.

[0015] Meanwhile, the temperature of the fluorination treatment is controlled at 300-600℃, wherein the fluorination reaction is relatively slower at low temperature (300-400℃) than at high temperature (500-600℃), the obtained fluorinated carbon material has stable structure, but the overall energy consumption is slightly increased; the fluorine diffusion capacity is strong at high temperature (500-600℃), high fluorides can be generated and the specific capacity is improved, but the carbon skeleton is prone to collapse if the temperature is too high, so the temperature should not be higher than 600℃.

[0016] Specifically, the temperature of the fluorination treatment includes but is not limited to 300℃, 320℃, 350℃, 380℃, 400℃, 410℃, 430℃, 450℃, 460℃, 480℃, 500℃, 520℃, 525℃, 540℃, 550℃, 560℃, 580℃, 600℃, etc.

[0017] Preferably, in step S1, the sulfurized polymer precursor includes one or more of sulfurized polyacrylonitrile, selenium-doped sulfurized polyacrylonitrile, sulfurized polyaniline, sulfurized polymethyl methacrylate, sulfurized polydimethylsiloxane, sulfurized polyurethane, sulfurized polyamide, sulfurized triallyl isocyanurate, sulfurized triallyl amine, and sulfurized triallyl phosphate.

[0018] Preferably, in step S1, the sulfur content of the sulfurized polymer precursor is 20%-80%. Specifically, the sulfur content includes but is not limited to 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0019] In the technical scheme of the present application, the sulfur content of the sulfurized polymer precursor mainly affects the structure of the hard carbon material after carbonization and the fluorination reaction process. In terms of material structure, when the sulfur content is low, the pore structure of the hard carbon after carbonization is dense and the specific surface area is small; when the content is high, the pores increase and the specific surface area increases, but too high content will lead to carbon skeleton defects and agglomeration. Moderate sulfur content can make sulfur uniformly doped and enhance the structural stability. In the fluorination reaction process, the higher the sulfur content, the more defect sites and doped sites of the material after carbonization, which is beneficial to improving the fluorocarbon ratio of the fluorinated carbon material, but too high content is prone to over-fluorination and produce unstable substances. When the sulfur content is moderate, the fluorination reaction is uniform; too low or too high content will cause insufficient internal fluorination or form "fluorination blind area".

[0020] Preferably, in step S1, the preparation steps of the sulfurized polymer precursor include: S101, dissolving the polymer in an organic solvent to prepare a polymer solution with a mass / volume concentration of 10%-15% (w / v); S102, obtaining a nanofiber membrane by electrospinning the polymer solution; S103, the nanofiber membrane is mixed with sulfur powder at a mass ratio of 1:(1-3) under a protective atmosphere, and is pre-sulfurized at 150-200 DEG C for 2-4 hours, and then is heated to 250-300 DEG C for 4-6 hours to obtain a sulfurized polymer; S104, the sulfurized polymer is post-treated to obtain a sulfurized polymer precursor.

[0021] Further preferably, in step S101, the organic solvent comprises N,N-dimethylformamide (DMF).

[0022] Further preferably, in step S102, the electrospinning conditions comprise a voltage of 10-20 kV, a spinning distance of 10-15 cm, and a flow rate of 0.5-1.5 mL / h. Specifically, the voltage comprises but is not limited to 10 kV, 12 kV, 14 kV, 15 kV, 16 kV, 18 kV, 20 kV, etc.; the spinning distance comprises but is not limited to 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, etc.; and the flow rate comprises but is not limited to 0.5 mL / h, 0.6 mL / h, 0.8 mL / h, 0.9 mL / h, 1.0 mL / h, 1.2 mL / h, 1.5 mL / h, etc.

[0023] Further preferably, in step S103, the protective atmosphere comprises nitrogen.

[0024] Further preferably, in step S104, the post-treatment is that the sulfurized polymer is first soaked in a 0.1-0.5 mol / L sodium sulfide solution at 60-80 DEG C for 1-3 hours, is washed with water until neutral, and then is cleaned with ethanol and vacuum dried to obtain the sulfurized polymer precursor.

[0025] Preferably, in step S1, the carbonization treatment is performed at a temperature of 600-1300 DEG C for 1-4 hours. Specifically, the carbonization treatment temperature comprises but is not limited to 600 DEG C, 650 DEG C, 680 DEG C, 700 DEG C, 720 DEG C, 750 DEG C, 800 DEG C, 850 DEG C, 880 DEG C, 900 DEG C, 920 DEG C, 960 DEG C, 1000 DEG C, 1050 DEG C, 1100 DEG C, 1150 DEG C, 1200 DEG C, 1250 DEG C, 1300 DEG C, etc.; and the time comprises but is not limited to 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc.

[0026] In the technical scheme of the present application, on the one hand, the carbonization treatment promotes rearrangement of the carbon skeleton, generates more micropores and mesopores, increases the specific surface area, and provides abundant active sites for the fluorination reaction; on the other hand, high temperature can reduce organic impurities, improve the crystallinity of the carbon skeleton, increase the stability of the carbon material, and allow the CF xThe layer is more stable, and meanwhile, can make the carbon skeleton produce unsaturated bond and uniform sulfur doping, enhance the reaction activity with fluorinating agent, improve the fluorocarbon ratio of fluorinated carbon, and optimize the material performance.

[0027] It can be understood that the sulfur is easy to volatilize and lose if the carbonization treatment temperature is too high, and therefore, the carbonization treatment temperature is controlled to be not more than 1300 DEG C in the present application, and the high sulfur content precursor can be used to compensate.

[0028] Preferably, in the step S2, the protective gas comprises one or more of nitrogen, argon and helium.

[0029] Preferably, in the step S2, the fluorinating agent comprises one or more of fluorine gas, hydrogen fluoride, nitrogen trifluoride, carbon tetrafluoride, sulfur hexafluoride and xenon difluoride.

[0030] Preferably, in the step S2, the volume ratio of the fluorinating agent in the mixed gas atmosphere is 15% to 40%. Specifically, the volume ratio of the fluorinating agent includes but is not limited to 15%, 20%, 25%, 30%, 35%, 40% and the like.

[0031] Preferably, in the step S2, the fluorination treatment time is 6 to 24 hours. Specifically, the fluorination treatment time includes but is not limited to 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours and the like.

[0032] In the technical scheme of the present application, if the fluorination treatment time is too short, the fluorination is limited to the surface layer, the internal fluorine content is low, and the cycle stability is poor; if the time is too long, although uniform fluorination can be achieved, the side reaction is intensified, and the specific surface area and the rate performance are reduced.

[0033] It should be noted that the fluorination treatment in the present application is carried out at 300 to 600 DEG C for 6 to 24 hours, which can ensure the stability of the structure of the obtained fluorinated carbon material, and realize the controllable synthesis from low fluorinated compound to high fluorinated compound, so that the material has high specific capacity and rate performance.

[0034] In the second aspect, the present application provides a fluorinated carbon material prepared by the above preparation method.

[0035] In the third aspect, the present application provides an electrode sheet, which comprises a current collector and an active material layer, and the active material layer is stacked on the surface of the current collector; the composition of the active material layer comprises the above fluorinated carbon material.

[0036] In the fourth aspect, the present application provides a fluorinated carbon battery, which comprises a positive electrode sheet, a separator, a lithium negative electrode sheet and an electrolyte, and the separator is arranged between the positive electrode sheet and the lithium negative electrode sheet; the positive electrode sheet of the fluorinated carbon battery is the above electrode sheet.

[0037] The present application is further illustrated and described by specific examples. To avoid redundancy, the preparation of the sulfidized polyacrylonitrile precursor, selenium-doped sulfidized polyacrylonitrile precursor and sulfidized polyaniline precursor is described as follows.

[0038] (a) The preparation steps of the sulfidized polyacrylonitrile precursor include: S101, solution preparation: 12% (w / v) polyacrylonitrile (PAN) is dissolved in DMF, stirred at 70°C until transparent, and filtered to remove impurities; S102, electrospinning: spin at a flow rate of 1.0 mL / h under a voltage of 15 kV and a spinning distance of 12 cm, and vacuum dry the collected PAN nanofiber membrane; S103, sulfidization treatment: mix the PAN nanofiber membrane with sulfur powder at a ratio of 1:2, pre-sulfidize at 180°C for 3 hours in nitrogen, and then heat to 260°C for 5 hours to obtain sulfidized polyacrylonitrile; S104, post-treatment: treat the sulfidized polyacrylonitrile with 0.3 mol / L sodium sulfide solution at 70°C for 2 hours, wash with water until neutral, and then wash with ethanol. Vacuum dry the sulfidized polyacrylonitrile to obtain the sulfidized polyacrylonitrile precursor. According to the TG test results, the sulfur content in the sulfidized polymer precursor is 50%.

[0039] Among them, using the above steps, only step S103 at 300°C for 5h to obtain a sulfidized polymer precursor with a sulfur content of 30%; at 200°C for 5h to obtain a sulfidized polymer precursor with a sulfur content of 80%.

[0040] (b) The selenium-doped sulfidized polyacrylonitrile precursor is prepared by first soaking the PAN nanofiber membrane in a 0.05-0.1 mol / L sodium selenide (Na2Se) solution for 90 minutes before the sulfidization treatment in step S103 in (a), and the other steps and conditions are the same as steps S101-S104 in (a).

[0041] (b) Preparation of the sulfidized polyaniline precursor: replace the polyacrylonitrile in step S101 with polyaniline, and the other steps and conditions are the same as steps S101-S104 in (a).

[0042] Example 1 A method for preparing a fluorinated carbon material, comprising the following steps: S1, take the sulfidized polyacrylonitrile precursor with a sulfur content of 50%, place it in a tube furnace, and carbonize it at 1000°C for 2 hours in a nitrogen atmosphere to obtain a sulfur-doped hard carbon material; S2, transfer the hard carbon material to a fluorination reaction furnace, introduce 20% fluorine gas (the rest is argon), and fluorinate at 300°C for 12 hours to obtain a fluorinated carbon material.

[0043] Figure 1 SEM image of sulfurized polyacrylonitrile precursor. By controlling the spinning voltage, solution concentration, feeding rate and other parameters in the electrospinning process, smooth-surfaced polyacrylonitrile fibers can be prepared, and then the polyacrylonitrile can be converted into sulfurized polyacrylonitrile by heat treatment, while the initial surface characteristics of the fibers are maintained. The diameter of the fibers is about 100-300 nm.

[0044] Figure 2 SEM image of sulfurized polyacrylonitrile carbonized. Although it has undergone high-temperature carbonization treatment, the material still maintains the overall morphology of fibers, but the diameter is significantly reduced to about 70-150 nm, which is due to the mass loss and structure densification caused by pyrolysis of polymer chains. At the same time, the fiber surface presents rough and porous characteristics, which may be due to the volatilization of a small amount of sulfur and the escape of gas (such as H2S, CO2) to form holes or cracks on the surface. A small amount of carbon fiber fracture may be due to the increase in brittleness of the material after carbonization. A small amount of sulfur is still retained in the carbon layer structure, together with nitrogen atoms to form a sulfur-nitrogen co-doped hard carbon material with layered structure, certain defects and rich functional groups, and appropriate defects are beneficial to ion transmission in fluorinated carbon, which can improve the poor high-rate discharge performance of fluorinated carbon batteries.

[0045] Figure 3 SEM image of fluorinated carbon material obtained from Example 1. The surface of the fiber after fluorination is relatively rough, with a diameter of 120-180 nm, and the overall morphology of the fiber is mostly retained.

[0046] Example 2 Compared with Example 1, the only difference is that in step S1, the sulfur content of 50% of the sulfurized polyacrylonitrile precursor is replaced by a selenium-doped sulfurized polyacrylonitrile precursor with a sulfur content of 50%; other steps and conditions are the same as in Example 1.

[0047] Example 3 Compared with Example 1, the only difference is that in step S1, the sulfur content of 50% of the sulfurized polyacrylonitrile precursor is replaced by a sulfurized polyaniline precursor with a sulfur content of 50%; other steps and conditions are the same as in Example 1.

[0048] Example 4 Compared with Example 1, the only difference is that step S1 is different (change the sulfur content of the sulfurized polymer precursor and the carbonization treatment conditions); other steps and conditions are the same as in Example 1. The difference is that: S1, take a sulfur content of 30% of the sulfurized polyacrylonitrile precursor, place it in a tube furnace, and carbonize it at 800°C for 3 hours under a nitrogen atmosphere to obtain a sulfur-doped hard carbon material.

[0049] Example 5 Compared with Example 1, the only difference is that step S1 is different (change the sulfur content of the sulfurized polyacrylonitrile precursor and the carbonization treatment conditions); other steps and conditions are the same as Example 1. The difference is that: S1, take the sulfurized polyacrylonitrile precursor with a sulfur content of 80%, place it in a tube furnace, and carbonize it at 1300°C for 1 hour under a nitrogen atmosphere to obtain a sulfur-doped hard carbon material.

[0050] Example 6 Compared with Example 1, the only difference is that in step S2, the fluorination treatment is carried out at 600°C for 6 hours to obtain a fluorinated carbon material; other steps and conditions are the same as Example 1.

[0051] Comparative Example 1 A method for preparing a fluorinated carbon material, comprising the following steps: (1) Take polyacrylonitrile (not sulfurized, sulfur content is 0%) and place it in a nitrogen atmosphere, and carbonize it at 1000°C for 2 hours to obtain a common hard carbon material; (2) The hard carbon material is fluorinated in an atmosphere containing 20% fluorine gas (the rest is argon) at 300°C for 12 hours to obtain a fluorinated carbon material.

[0052] Application Example 1 The fluorinated carbon materials of Examples 1-6 and Comparative Example 1 are respectively mixed with conductive carbon black and polyvinylidene fluoride binder at a mass ratio of 8:1:1 in N-methylpyrrolidone, then coated on the surface of an aluminum foil current collector, and dried to obtain a fluorinated carbon electrode.

[0053] The fluorinated carbon electrode is used as the positive electrode, the negative electrode material is metal lithium, the electrolyte is 1 mol / L lithium perchlorate in propylene carbonate / / glycol dimethyl ether (V:V=1:1), and the separator is a 25μm polyethylene separator. The above materials are assembled into a sandwich structure according to the positive electrode, the separator, and the negative electrode, and then injected with sufficient electrolyte to form a CR2032 button cell. After the battery is placed at room temperature for 12 hours, a constant current discharge test is performed, and the voltage cutoff is discharged to 1.5V.

[0054] Figure 4 and Figure 5 are the rate performance comparison diagrams of the lithium fluorinated carbon batteries in Example 1 and Comparative Example 1 of the present application, respectively. From Figure 4 it can be seen that the lithium fluorinated carbon battery composed of the fluorinated carbon positive electrode prepared from the polyacrylonitrile precursor in Comparative Example 1 has a capacity of 505mAh / g at a discharge rate of 0.1C; but as the discharge rate increases, the battery capacity rapidly decreases, and at a discharge rate of 1C, the capacity is only 308mAh / g. While Figure 5As shown, the lithium fluorocarbon battery composed of the fluorocarbon cathode prepared from the sulfidized polyacrylonitrile precursor according to Example 1 of the present application has a discharge capacity of 684 mAh / g at 0.1C rate and a discharge capacity of 546 mAh / g at 1C rate. The improvement in battery capacity and rate performance can be attributed to the improved reactivity of the semi-ionic C-F bond in fluorocarbon and the synergistic reduction of Li + diffusion barrier.

[0055] Figure 6 A comparison chart of the discharge capacity of the lithium fluorocarbon batteries in Examples 2-6 of the present application at 0.1C is shown in the figure. As can be seen from the figure, through the synergistic effect of precursor design and carbonization-fluorination process, the specific capacity of Examples 2-6 is better than that of Comparative Example 1, and has different degrees of improvement compared with Example 1, among which Example 2 performs best, followed by Example 3, which indicates that the type of sulfidized polymer precursor has a certain influence on the performance of the obtained fluorocarbon material. The present application selects sulfidized polyacrylonitrile precursor with a sulfur content of 30%-80%, which has more sulfur doping sites, developed pores and high defect density after high-temperature carbonization, providing more active centers for fluorination; precise control of the fluorination temperature and time can form gradient C-F bonds, improving the uniformity of fluorination and the fluorocarbon ratio; the stable C-S bond during carbonization inhibits excessive fluorination of carbon, preserving active sites, and comprehensively improving the specific capacity to 690-800 mAh / g, which is better than that of Comparative Example 1.

[0056] The present application carbonizes the sulfidized polymer precursor powder at high temperature to obtain a hard carbon material doped with heteroatoms, and then continuously introduces a mixed gas containing a fluorination reagent and a protective gas, and obtains a fluorocarbon material after fluorination reaction at 300-600°C. The hard carbon material obtained by the preparation method of the present application has abundant defect sites, polar groups and hierarchical micro / mesopore structures as a carbon source, which is beneficial to complete the subsequent fluorination reaction, and the prepared fluorocarbon has a high fluorocarbon ratio and a fast lithium ion transmission channel, so that the lithium fluorocarbon battery exhibits high specific capacity and excellent rate characteristics.

[0057] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made in accordance with the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A method for preparing a fluorinated carbon material, characterized in that: The following steps are involved: S1, carbonizing the sulfide polymer precursor under an inert atmosphere to obtain a heteroatom-doped hard carbon material; S2, placing the heteroatom-doped hard carbon material in a mixed atmosphere containing a protective gas and a fluorination agent, and performing a fluorination treatment at 300-600° C. to obtain a fluorinated material; the volume proportion of the fluorination agent in the mixed atmosphere is less than 40%.

2. The method for preparing a fluorinated carbon material according to claim 1, wherein: In step S1, the sulfurized polymer precursor includes one or more of sulfurized polyacrylonitrile, selenium-doped sulfurized polyacrylonitrile, sulfurized polyaniline, sulfurized polymethyl methacrylate, sulfurized polydimethylsiloxane, sulfurized polyurethane, sulfurized polyamide, sulfurized triallyl isocyanurate, sulfurized triallylamine, and sulfurized triallyl phosphate.

3. The method for preparing a fluorinated carbon material according to claim 1, wherein: In step S1, the steps of preparing the sulfurized polymer precursor include: S101, dissolving the polymer in an organic solvent to prepare a polymer solution with a mass volume concentration of 10% to 15%; S102, electrospinning the polymer solution to obtain a nanofiber membrane; S103, the nanofiber membrane and sulfur powder are mixed in a mass ratio of 1:(1-3), pre-cured at 150-200°C for 2-4 hours under a protective atmosphere, and then heated to 250-300°C and kept at this temperature for 4-6 hours to obtain a vulcanized polymer; S104, the vulcanized polymer is post-treated to obtain a vulcanized polymer precursor.

4. The method for preparing a fluorinated carbon material according to claim 3, wherein: The organic solvent includes N,N-dimethylformamide; and / or, The electrospinning conditions include: voltage 10-20 kV, spinning distance 10-15 cm, flow rate 0.5-1.5 mL / h; and / or, The protective atmosphere comprises nitrogen; and / or, The post-treatment is to soak the sulfide polymer in a 0.1-0.5 mol / L sodium sulfide solution at 60-80° C. for 1-3 hours, wash with water until neutral, then wash with ethanol and vacuum dry to obtain a sulfide polymer precursor.

5. The method for preparing a fluorinated carbon material according to claim 1, wherein: In step S1, the temperature of the carbonization treatment is 600-1300° C., and the time of the carbonization treatment is 1-4 hours.

6. The method for preparing a fluorinated carbon material according to claim 1, wherein: In step S2, the protective gas includes one or more of nitrogen, argon and helium; and / or, The fluorination agent includes one or more of fluorine gas, hydrogen fluoride, nitrogen trifluoride, carbon tetrafluoride, sulfur hexafluoride and xenon difluoride; and / or, The volume proportion of the fluorination agent in the mixed atmosphere is 15% to 40%.

7. The method for preparing a fluorinated carbon material according to claim 1, wherein: In step S2, the fluorination treatment time is 6 to 24 hours.

8. The fluorinated carbon material obtained by the preparation method according to any one of claims 1 to 7.

9. An electrode sheet, characterized in that: The electrode sheet includes an active material layer, and components of the active material layer include the carbon fluoride material according to claim 8.

10. A carbon fluoride battery, characterized in that: The positive electrode sheet of the carbon fluoride battery is the electrode sheet according to claim 9.

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