A composite cathode material, its preparation method and application

Abstract

This invention belongs to the field of cathode material technology, and specifically relates to a composite cathode material, its preparation method, and its application. The composite cathode material of this invention comprises a fluorine-doped carbon framework and iron-based active species dispersed within the fluorine-doped carbon framework. This invention constructs an iron- and fluorine-containing precursor using iron salts and fluorine-containing organic ligands, and then forms iron-based active species and a fluorine-doped carbon framework in situ through heat treatment. The iron-based active species can promote the reversible decomposition and regeneration of LiF, reduce charge-discharge polarization, and improve reaction reversibility; the fluorine-doped carbon framework can improve electron transport capability, improve interfacial reaction uniformity, and enhance the dispersion of active sites. The synergistic effect of both improves the battery's recharge capacity, cycle stability, and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, and specifically relates to a composite cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-fluorinated carbon (Li-CFCC) batteries, using metallic lithium as the negative electrode and fluorinated carbon as the positive electrode, possess high theoretical specific energy, good storage stability, and a wide operating temperature range, making them valuable for applications in spacecraft power supplies, deep space exploration, emergency power supplies, and special equipment. With the development of high-energy-density, long-life, and rechargeable energy storage devices, the demand for expanding the Li-CFCC system from primary to secondary batteries is becoming increasingly prominent.

[0003] However, Li / CF x Achieving reversible charge-discharge remains a significant bottleneck. During discharge, LiF, which possesses strong electrical insulation and is thermodynamically stable, is readily generated. The continuous accumulation of LiF on the positive electrode surface and within the pores hinders the co-transport of electrons and ions, leading to increased interfacial impedance, increased charging polarization, and deteriorated reaction kinetics. During charging, the reverse decomposition of LiF often requires a high energy barrier and is prone to side reactions, thus limiting recharge capacity and cycle life.

[0004] Existing modification methods mainly focus on strategies such as adding conductive agents, constructing composite networks, surface coating, or precursor-derived carbonization. While these approaches can improve electron transport and interfacial contact to some extent, their improvement on the core issue of LiF reversibility remains limited. Especially when the material system lacks catalytic active centers that can promote LiF decomposition and regeneration, simply relying on improvements to the conductive network is insufficient to meet the requirements of secondary lithium-carbon fluoride batteries for low polarization, high reversibility, and long-cycle stability.

[0005] Therefore, it is of great significance to provide a composite cathode material that can enhance electron transport capability and reversible kinetics of LiF-related reactions, thereby improving the recharge performance and cycle stability of secondary lithium-carbon fluoride batteries. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial alternative. Specifically, the present invention provides a composite cathode material that can reduce charge-discharge polarization, improve electron transport capability and the reversible kinetics of LiF-related reactions, so that the prepared secondary lithium-carbon fluoride battery has good cycle stability and rate performance.

[0007] The inventive concept of this invention: The composite cathode material of this invention includes a fluorine-doped carbon framework and iron-based active species dispersed in the fluorine-doped carbon framework.

[0008] The iron-based active species of this invention can promote the reversible decomposition and regeneration of LiF, reduce charge-discharge polarization, and improve reaction reversibility; the fluorine-doped carbon framework can improve electron transport capability, improve the uniformity of interfacial reaction, and improve the dispersion of active sites. Through the synergistic construction of iron-based active species and fluorine-doped carbon framework, the recharge capacity, cycle stability, and rate performance of the battery are improved.

[0009] Therefore, a first aspect of the present invention provides a composite cathode material.

[0010] Specifically, the composite cathode material includes a fluorine-doped carbon framework and iron-based active species dispersed in the fluorine-doped carbon framework.

[0011] Preferably, the iron-based active species includes at least one of Fe, iron oxide, and iron fluoride.

[0012] Specifically, the iron-based active species are derived from the in-situ transformation of an iron-containing fluorine-containing precursor formed by iron salts and fluorine-containing organic ligands through heat treatment. This in-situ transformation disperses the iron-based active species within the fluorine-doped carbon framework, forming a synergistic interface. This in-situ transformation pathway facilitates both the uniform dispersion of iron within the carbon framework and the formation of iron-based active sites in a fluorine-containing environment during heat treatment, thus ensuring, in principle, the synergistic construction of the active species and the fluorine-doped carbon framework.

[0013] Preferably, the iron oxide includes at least one of FeO, Fe2O3, and Fe3O4.

[0014] Preferably, the ferrofluoride includes at least one of FeF2 and FeF3.

[0015] Preferably, the iron-based active species account for 10-60% of the mass of the fluorine-doped carbon framework; for example, 10%, 20%, 30%, 40%, 50%, 60%, etc.

[0016] Preferably, the composite cathode material is composed of micron-sized particles.

[0017] Preferably, the average particle size of the composite cathode material is 0.5-2 μm.

[0018] Preferably, the micron-sized particles have a polyhedral or polyhedral morphology.

[0019] A second aspect of the present invention provides a method for preparing the composite cathode material described in the first aspect of the present invention.

[0020] Specifically, the preparation method of the composite cathode material includes the following steps: Iron salts and fluorine-containing organic ligands are mixed in a solvent and coordinated to obtain an iron-containing fluorine precursor; then, heat treatment is performed to obtain the final product.

[0021] This invention discovers that by constructing an iron-containing and fluorine-containing precursor with iron salts and fluorine-containing organic ligands, and then forming iron-based active species and fluorine-doped carbon framework in situ during subsequent heat treatment, the reaction kinetics related to the reversible transformation of LiF can be significantly improved, thereby enhancing the recharge capacity, cycle stability, and rate performance of secondary lithium-fluoride carbon batteries.

[0022] Preferably, the iron salt includes at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric acetylacetone; more preferably, the iron salt is ferric chloride hydrate; even more preferably, the iron salt is ferric chloride hexahydrate (FeCl3·6H2O).

[0023] Preferably, the fluorinated organic ligand comprises at least one of 2-fluoroterephthalic acid, 2,5-difluoroterephthalic acid, 2-fluoroisophthalic acid, 2-fluorophthalic acid, and tetrafluoroterephthalic acid; more preferably, the fluorinated organic ligand is 2-fluoroterephthalic acid (2F-H2BDC).

[0024] Preferably, the solvent includes at least one of a polar organic solvent and water; more preferably, the solvent includes at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), ethanol, and water; even more preferably, the solvent is N,N-dimethylformamide.

[0025] Preferably, the mass ratio of the iron salt to the fluorinated organic ligand is 1:(0.4-1.2); more preferably, the mass ratio of the iron salt to the fluorinated organic ligand is 1:(0.6-0.9). Preferably, the ratio of the amount of solvent to iron salt is (30-90) mL:1g; more preferably, the ratio of the amount of solvent to iron salt is (50-70) mL:1g.

[0026] Preferably, the coordination assembly temperature is room temperature - 160°C, and the coordination assembly time is 2-24 hours; more preferably, the coordination assembly temperature is 80-140°C, and the coordination assembly time is 6-16 hours; even more preferably, the coordination assembly temperature is 100-140°C, and the coordination assembly time is 10-16 hours.

[0027] Preferably, the coordination assembly yields an iron- and fluorine-containing precursor suspension, which is then separated, washed, and dried to obtain the iron- and fluorine-containing precursor.

[0028] Preferably, the drying temperature is 50-80°C; more preferably, the drying temperature is 70-80°C.

[0029] Preferably, the drying time is 6-14 hours, and more preferably, the drying time is 8-12 hours.

[0030] Preferably, the drying method is oven drying; more preferably, the drying method is vacuum drying.

[0031] Preferably, the heat treatment includes a pretreatment stage and a carbonization stage.

[0032] Preferably, the temperature of the pretreatment stage is 250-450℃, and the time of the pretreatment stage is 0.5-4h.

[0033] Preferably, the temperature of the carbonization stage is 600-1000℃, and the carbonization stage lasts for 1-10 hours; more preferably, the temperature of the carbonization stage is 700-900℃, and the carbonization stage lasts for 4-7 hours.

[0034] Preferably, the heat treatment is performed under a protective atmosphere.

[0035] Preferably, the protective atmosphere includes at least one of nitrogen and argon.

[0036] Specifically, after heat treatment, the precursor is transformed in situ into an iron-based fluorinated carbon composite cathode material containing iron-based active species and a fluorine-doped carbon framework. Iron exists in the form of Fe, FeO, Fe2O3, Fe3O4, FeF2, and FeF3, and works synergistically with the fluorine-doped carbon framework to promote the reversible transformation of LiF and improve electrode reaction kinetics.

[0037] A third aspect of the present invention provides a positive electrode sheet.

[0038] Specifically, the positive electrode includes a current collector and an active layer disposed on the surface of the current collector, wherein the active layer comprises the composite positive electrode material described in the first aspect of the present invention.

[0039] Preferably, the current collector includes at least one of foamed copper, copper foil, double-sided carbon-containing aluminum foil, carbon paper, and foamed nickel; more preferably, the current collector is double-sided carbon-containing aluminum foil.

[0040] Specifically, this invention does not have any particular limitations on double-sided carbon-containing aluminum foil; conventional double-sided carbon-containing aluminum foil current collectors available on the market can be used to realize this invention.

[0041] Preferably, the active layer further comprises a conductive agent, a binder, and a solvent.

[0042] Preferably, the adhesive comprises at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0043] Preferably, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon powder, and graphene; more preferably, the conductive agent is conductive carbon black.

[0044] Preferably, the solvent includes at least one of N-methylpyrrolidone and deionized water; more preferably, the solvent is N-methylpyrrolidone.

[0045] Preferably, the method for preparing the positive electrode includes the following steps: A conductive paste is prepared by mixing a composite positive electrode material, a conductive agent, a binder, and a solvent; the conductive paste is then applied to the current collector to obtain the positive electrode sheet.

[0046] Preferably, the composite positive electrode material, conductive agent and binder are first mixed and ground, and then a solvent is added for further mixing.

[0047] Preferably, the grinding time is 20-40 minutes.

[0048] Preferably, the conductive paste is dried after being applied to the current collector.

[0049] Preferably, the drying method includes drying in an oven at 40-80°C for 4-16 hours, followed by vacuum drying for 12-18 hours; more preferably, drying in an oven at 40-60°C for 5-6 hours, followed by vacuum drying for 10-14 hours.

[0050] A fourth aspect of the present invention provides a battery.

[0051] Specifically, the battery includes the positive electrode sheet described in the third aspect of the present invention.

[0052] Preferably, the battery comprises a lithium-carbon fluoride battery.

[0053] Preferably, the lithium-carbon fluoride battery is a secondary lithium-carbon fluoride battery.

[0054] Specifically, by using the iron-based fluorinated carbon composite cathode material and cathode sheet provided by this invention, the rechargeability of lithium-fluorinated carbon batteries can be achieved, with a long cycle life and a high specific capacity.

[0055] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: This invention constructs an iron- and fluorine-containing precursor using iron salts and fluorine-containing organic ligands, and then forms iron-based active species and a fluorine-doped carbon framework in situ through heat treatment, thus preparing an iron-based fluorine-carbon composite cathode material suitable for secondary lithium-fluorine-carbon batteries. The iron-based active species promote the reversible decomposition and regeneration of LiF, reduce charge-discharge polarization, and improve reaction reversibility; the fluorine-doped carbon framework enhances electron transport capacity, improves interfacial reaction uniformity and active site dispersion, thereby improving the battery's recharge capacity, cycle stability, and rate performance.

[0056] Compared with existing technologies that improve performance solely through conductive network compositing or precursor carbonization, this invention combines the synergistic advantages of catalytic active centers and conductive frameworks, making it more suitable as a cathode material for secondary lithium-carbon fluoride batteries. Attached Figure Description

[0057] Figure 1 This is an X-ray diffraction pattern of the iron- and fluorine-containing precursor powder and the composite cathode material of Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the iron- and fluorine-containing precursor powder and the composite cathode material of Example 1 of the present invention; Figure 3 The constant current charge-discharge curve of the battery prepared by the composite cathode material in Example 1 of the present invention at 0.1C; Figure 4 The cycle performance and coulombic efficiency of the battery prepared by the composite cathode material in Example 1 of the present invention at 0.1C are shown in the figure. Figure 5 The graph shows the cycle performance and coulombic efficiency of the battery prepared with the cathode material of Comparative Example 1 of this invention at 0.1C. Figure 6 The graph shows the cycle performance and coulombic efficiency of the battery prepared with the cathode material of Comparative Example 2 of this invention at 0.1C. Detailed Implementation

[0058] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0059] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0060] Example 1 This embodiment provides a method for preparing a composite cathode material, the specific steps of which are as follows: Weigh 0.703 g of FeCl3·6H2O ferric chloride hexahydrate and 0.479 g of 2-fluoroterephthalic acid (2F-H2BDC) and add them to 50 mL of DMF. Stir at room temperature for 60 min to mix them evenly. Then transfer the resulting mixed solution to a lidded reaction vessel and carry out a coordination assembly reaction at 120 °C for 12 h to obtain an iron- and fluorine-containing precursor suspension. The obtained iron- and fluorine-containing precursor suspension was centrifuged and washed twice with ethanol and deionized water, respectively. It was then vacuum dried at 80°C for 12 hours to obtain iron- and fluorine-containing precursor powder. Iron-containing and fluorine-containing precursor powders were placed in a tube furnace and subjected to two-step heat treatment under a nitrogen atmosphere: first, the temperature was increased to 350℃ at 2℃ / min and held for 1h to stabilize and preliminarily carbonize the precursor; then, the temperature was increased to 800℃ at 5℃ / min and held for 5h, and then naturally cooled to room temperature to obtain iron-based fluorinated carbon composite cathode material, i.e., composite cathode material.

[0061] This embodiment provides a method for preparing a positive electrode sheet, the specific steps of which are as follows: Weigh 100 mg of the above-mentioned iron-based fluorinated carbon composite positive electrode material, 12.5 mg of conductive carbon black, and 12.5 mg of polyvinylidene fluoride, mix and grind them in an agate mortar for 35 min; then add 500 μL of N-methylpyrrolidone and continue grinding until a uniform slurry is formed; uniformly coat the obtained slurry onto the surface of a double-sided carbon-containing aluminum foil current collector, dry it in an oven at 50 °C for 6 h, and then dry it in a vacuum drying oven at 60 °C for 12 h to obtain a positive electrode sheet; cut the positive electrode sheet into round pieces with a diameter of 10 mm for later use.

[0062] Example 2 The difference between Example 2 and Example 1 is that: the iron salt used is iron nitrate nonahydrate, the fluorine-containing organic ligand is 2,5-difluoroterephthalic acid; the coordination assembly temperature is 110℃ and the time is 10h; the heat treatment carbonization temperature is 750℃ and the holding time is 6h, the protective atmosphere is argon, and the resulting sample can also form a composite cathode material containing iron-based active species and fluorine-doped carbon framework, and other aspects are the same as in Example 1.

[0063] Example 3 The difference between Example 3 and Example 1 is as follows: the iron salt used is iron acetylacetonate, the fluorinated organic ligand is tetrafluoroterephthalic acid; the solvent used is a mixed solvent of N,N-dimethylformamide and ethanol (volume ratio of 1:1); the coordination assembly temperature is 130℃ and the time is 12h; the heat treatment carbonization temperature is 850℃ and the holding time is 4h, the protective atmosphere is nitrogen. The resulting sample can also form a composite cathode material containing iron-based active species and fluorine-doped carbon framework, and other aspects are the same as in Example 1.

[0064] Comparative Example 1 Comparative Example 1 uses an iron-free system to prepare cathode materials, that is, only the fluorine-containing organic ligands are carbonized under the same heat treatment conditions to obtain fluorine-doped carbon materials without iron-based active species, and the rest is the same as in Example 1.

[0065] Comparative Example 2 Comparative Example 2 uses porous carbon and commercial iron fluoride (ferric fluoride) to mechanically mix to prepare the cathode material, i.e., without undergoing an in-situ precursor conversion process, otherwise the same as in Example 1. This comparative example is used to illustrate the difference between the in-situ formed iron-based active species / fluorine-doped carbon framework synergistic structure and the simple physical mixing system.

[0066] Performance testing 1. X-ray diffraction analysis X-ray diffraction (XRD) analysis was performed on the iron- and fluorine-containing precursor powder and composite cathode material of Example 1. The X-ray diffraction patterns are shown below. Figure 1 As shown. Figure 1 In the diagram, the precursor represents iron- and fluorine-containing precursor powder, the fluorinated carbon material represents the composite cathode material, the horizontal axis 2θ (degree) represents the diffraction angle, and the vertical axis intensity (au) represents the diffraction intensity.

[0067] Depend on Figure 1 The X-ray diffraction pattern reveals that the precursor sample exhibits certain coordinated ordered characteristics. After heat treatment, the diffraction peaks are significantly enhanced, indicating the formation of iron-based active species (Fe2O3) with crystalline phase characteristics in the material. These iron-based active species, together with the carbon framework, constitute a composite structure, which helps promote the reversible transformation of LiF. During the heat treatment process, the precursor, after coordination assembly, is transformed in situ into a composite material of iron-based active species and fluorine-doped carbon framework. In this process, the precursor formed by iron salt and fluorine-containing organic ligands is transformed into iron-based active species (Fe2O3) under suitable heat treatment conditions, and synergistically interacts with the carbon framework to form a stable composite cathode material.

[0068] 2. Scanning electron microscopy observation Scanning electron microscopy (SEM) was performed on the iron- and fluorine-containing precursor powder and composite cathode material of Example 1. The SEM images are shown below. Figure 2 As shown. Among them, Figure 2 The term "precursor" refers to iron- and fluorine-containing precursor powders, while "fluorinated carbon material" refers to composite cathode materials.

[0069] Depend on Figure 2 It can be seen that the precursor has a relatively regular micron-sized particle morphology; after heat treatment, the overall outline of the sample is basically preserved, but the surface is rougher, which is conducive to increasing the electrolyte contact area and exposing more iron-based active sites, thereby promoting LiF-related interface reactions.

[0070] 3. Battery performance testing Using the positive electrode sheets prepared in Example 1 and Comparative Examples 1-2 as positive electrodes, and a 15.6 mm diameter lithium metal sheet as the negative electrode, the electrolyte was a 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution (solvent being ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a 1:1 volume ratio), with LiNO3 as an additive, accounting for 1% of the total electrolyte mass. A 19 mm PP membrane was used as the separator. The cells, along with gaskets and spring sheets, were assembled into 2032 button cells in a glove box. The assembled cells were then subjected to constant current charge-discharge and cycle performance tests.

[0071] Example 1: The battery at 0.1C (1C = 500mAh g) -1 The constant current charge-discharge curves under these conditions (test temperature 30℃, voltage test range 1.6-2.8V) are shown below. Figure 3 As shown. Among them, Figure 3 In the numbers 1st, 2nd, 3rd, 10th, 20th, 30th, 50th, and 70th, they represent the 1st, 2nd, 3rd, 10th, 20th, 30th, 50th, and 70th laps, respectively.

[0072] Depend on Figure 3 It can be seen that the battery exhibits a relatively stable charge-discharge plateau at different cycle numbers, indicating that the synergistic effect of the iron-based active sites and the fluorine-doped carbon framework is beneficial to reducing polarization and improving reaction reversibility. The cycling curves are generally similar, indicating that the reaction process tends to be stable after initial activation of the electrode, with small polarization, and the material can maintain good structural stability and reaction reversibility during cycling.

[0073] Example 1: The battery prepared using the composite cathode material was tested at 0.1C (1C = 500 mAh g). -1 The cycle performance and efficiency graphs are shown below (test temperature: 30℃, voltage test range: 1.6-2.8V, positive electrode active material mass: 1.8mg). Figure 4 As shown. Here, 1.8mg refers to the mass of the positive electrode material after the composite positive electrode material is coated and cut into sheets, used as a button cell, with a diameter of 10mm and a positive electrode active material mass of 1.8mg.

[0074] Depend on Figure 4 It can be seen that during approximately 70 cycles, the battery's charge specific capacity and discharge specific capacity remained relatively stable, consistently maintaining a high level, and even in the later stages, it still possessed approximately 350mAh g. -1 The discharge specific capacity exhibits good capacity retention. Meanwhile, the battery efficiency remains close to 100%, indicating that the iron-based fluorinated carbon composite cathode material can effectively promote the reversible transformation of LiF and suppress side reactions, thereby improving the cycle stability of the secondary lithium-fluorinated carbon battery.

[0075] The cycle performance and coulombic efficiency of the battery prepared with the cathode material of Comparative Example 1 at 0.1C are shown in the figure below. Figure 5 As shown, the test conditions are the same as above. (From...) Figure 5 It is evident that in the absence of iron-based active species, the battery's charge-discharge capacity decay is more pronounced, and its capacity retention during cycling is weaker. This indicates that while relying solely on the carbonization of fluorine-containing organic ligands to form a fluorine-doped carbon skeleton can improve conductivity to some extent, it is difficult to effectively promote the reversible decomposition and regeneration of LiF, thus making it difficult to balance high recharge capacity and long-term cycle stability.

[0076] The cycle performance and coulombic efficiency of the battery prepared with the cathode material in Comparative Example 2 at 0.1C are shown in the figure below. Figure 6 As shown, the test conditions are the same as above. (From...) Figure 6 It is evident that the cathode material obtained by mechanically mixing porous carbon with commercial iron fluoride exhibits inferior cycle performance and coulombic efficiency compared to Example 1. This result indicates that although simple physical mixing introduces iron-containing and conductive carbon components, the lack of an in-situ synergistic interface formed during precursor thermal conversion hinders the uniform dispersion of iron-based active species within the carbon framework and the formation of stable and effective reaction sites, thus limiting its promoting effect on the reversible transformation of LiF.

[0077] comprehensive Figures 1 to 6 It can be seen that the iron-based active species / fluorine-doped carbon framework synergistic structure constructed in Example 1 of the present invention is superior to Comparative Example 1 and Comparative Example 2 in terms of cycle capacity retention and reaction reversibility. The above results demonstrate that the composite cathode material obtained by in-situ thermal conversion of iron- and fluorine-containing precursors can simultaneously exert the catalytic effect of the iron-based active center and the conductive support effect of the fluorine-doped carbon framework, thereby more effectively reducing polarization, suppressing side reactions, and improving the overall electrochemical performance of secondary lithium-carbon fluoride batteries.

[0078] The same methods were used to conduct the above-mentioned tests on the batteries of Examples 2-3. The batteries of Examples 2-3 have performance comparable to that of the battery of Example 1 in terms of cycle stability, coulombic efficiency, and reaction reversibility.

[0079] In summary, this invention constructs an iron- and fluorine-containing precursor by combining iron salts and fluorine-containing organic ligands, and then forms an iron-based active species and a fluorine-doped carbon framework in situ through heat treatment. The two work synergistically to simultaneously exert the catalytic effect of the iron-based active center and the conductive support effect of the fluorine-doped carbon framework, thereby more effectively reducing polarization, suppressing side reactions, and improving the battery's recharge capacity, cycle stability, and rate performance. It is suitable as a cathode material for secondary lithium-carbon fluoride batteries.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite cathode material, characterized in that, The composite cathode material includes a fluorine-doped carbon framework and iron-based active species dispersed in the fluorine-doped carbon framework.

2. The composite cathode material according to claim 1, characterized in that, The iron-based active species includes at least one of Fe, iron oxide, and iron fluoride; and / or, the iron-based active species accounts for 10-60% of the mass of the fluorine-doped carbon framework.

3. The composite cathode material according to claim 2, characterized in that, The iron oxide includes at least one of FeO, Fe2O3, and Fe3O4; and / or, the iron fluoride includes at least one of FeF2 and FeF3.

4. The method for preparing the composite cathode material according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: Iron salts and fluorine-containing organic ligands are mixed in a solvent and coordinated to obtain an iron-containing fluorine precursor; then, heat treatment is performed to obtain the final product.

5. The preparation method according to claim 4, characterized in that, The iron salt includes at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric acetylacetone; And / or, the fluorinated organic ligand includes at least one of 2-fluoroterephthalic acid, 2,5-difluoroterephthalic acid, 2-fluoroisophthalic acid, 2-fluorophthalic acid, and tetrafluoroterephthalic acid; And / or, the solvent includes at least one of a polar organic solvent and water.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the iron salt to the fluorinated organic ligand is 1:(0.4-1.2); and / or the amount of the solvent to the iron salt is (30-90) mL:1 g.

7. The preparation method according to claim 4, characterized in that, The coordination assembly temperature is room temperature - 160℃, and the coordination assembly time is 2-24h; And / or, the heat treatment includes a pretreatment stage and a carbonization stage; And / or, the heat treatment is performed under a protective atmosphere.

8. The preparation method according to claim 7, characterized in that, The temperature of the pretreatment stage is 250-450℃, and the time of the pretreatment stage is 0.5-4h; And / or, the temperature of the carbonization stage is 600-1000℃, and the time of the carbonization stage is 1-10h.

9. A positive electrode plate, characterized in that, The positive electrode includes a current collector and an active layer disposed on the surface of the current collector, wherein the active layer comprises the composite positive electrode material as described in any one of claims 1-3.

10. A battery, characterized in that, The battery includes the positive electrode as described in claim 9.

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