A manganese-doped fluoride composite carbon material and its preparation method and application

Abstract

The present invention discloses a manganese-doped fluoride composite carbon material and its preparation method and application. The manganese-doped fluoride composite carbon material comprises: a perovskite-type KFe x Mn 1‑x The material matrix is ​​composed of F3 grains, and the surface of the material matrix is ​​doped with carbon; wherein 0.2≤x≤0.8. The preparation method comprises: S1, using KF, FeF2 and MnF2 as raw materials, mixing and ball milling according to a preset molar ratio to obtain KFe with a cubic perovskite structure x Mn 1‑x F3 material matrix; S2, adding carbon, and the KFe x Mn 1‑x The F3 material matrix is ​​mixed and ball-milled to obtain the manganese-doped fluoride composite carbon material. The manganese-doped fluoride composite carbon material of the present invention can be used as a negative electrode material for lithium-ion batteries or sodium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a manganese-doped fluoride composite carbon material, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid promotion of high-energy-density lithium-ion batteries in smart terminals, electric vehicles, and large-scale energy storage, conversion-type negative electrode materials based on metal fluorides have gradually become a research hotspot for next-generation negative electrode materials due to their advantages such as high theoretical capacity, low voltage platform, and adjustable cycle stability. Among them, perovskite-type KFeF3 materials have attracted widespread attention due to their structural stability and resource availability. However, in existing technologies, KFeF3 materials have problems such as dual limitations in electronic conductivity and ion diffusion rate, insufficient active sites, and instability of the SEI film (Solid Electrolyte Interface) during cycling. These problems result in poor rate performance and low capacity retention, which seriously restricts their application in actual lithium-ion battery systems. Summary of the Invention

[0003] In view of this, the present invention proposes a manganese-doped fluoride composite carbon material for lithium-ion battery negative electrode, and its preparation method and application. Through the synergistic effect of manganese doping and carbon composite, the crystal structure and SEI film composition of the perovskite-type fluoride negative electrode material KFeF3 are regulated, thereby solving the technical problems of low conductivity, short cycle life and poor interface stability of existing fluoride negative electrode materials, and improving the comprehensive electrochemical performance of fluoride battery negative electrode materials.

[0004] According to one aspect of the present invention, a manganese-doped fluoride composite carbon material is provided, comprising: a perovskite-type KFe x Mn 1-x A material matrix composed of F3 grains, the surface of which is doped with carbon; wherein 0.2≤x≤0.8.

[0005] Furthermore, the grains have a cubic crystal structure of space group Pm-3m.

[0006] Furthermore, the size of the grains is 2nm-8nm, and the (110) interplanar spacing, (200) interplanar spacing, and (220) interplanar spacing of the grains are 0.293±0.02 nm, 0.202±0.02 nm, and 0.147±0.02 nm, respectively.

[0007] Furthermore, the c-axis lattice constant of the material is 4.12Å~4.16Å.

[0008] Furthermore, 0.2≤x≤0.5.

[0009] According to another aspect of the present invention, a method for preparing the aforementioned manganese-doped fluoride composite carbon material is provided, comprising the following steps: S1, using KF, FeF2 and MnF2 as raw materials, mixing and ball milling according to a preset molar ratio to obtain KFe with a cubic perovskite structure. x Mn 1-x F3 material matrix; S2, adding carbon, and the KFe x Mn 1-x The F3 material matrix is ​​mixed and ball-milled to obtain the manganese-doped fluoride composite carbon material.

[0010] Furthermore, the preset molar ratio in step S1 is KF:FeF2:MnF2=1~5:2.5~5:2.5~5.

[0011] Furthermore, the mass of the carbon added in step S2 accounts for 10% to 30% of the total mass of KF, FeF2 and MnF2.

[0012] Furthermore, the mixing ball milling in step S1 is carried out at a rotation speed of 500 rpm to 900 rpm, and the ball milling time is 4 to 12 hours; the mixing ball milling in step S2 is carried out at a rotation speed of 200 rpm to 600 rpm, and the ball milling time is 2 to 6 hours.

[0013] According to another aspect of the present invention, the application of the aforementioned manganese-doped fluoride composite carbon material as a negative electrode material for lithium-ion batteries or sodium-ion batteries is also proposed.

[0014] The beneficial effect of the technical solution of the present invention is that the content of Fe in the perovskite KFeF3 material is regulated by doping with Mn to obtain a KFe x Mn 1-x The manganese-doped fluoride composite carbon material with F3 grains achieves dual optimization of crystal structure regulation and electronic structure, achieving synergistic optimization at the material design and interface regulation levels, effectively solving the key bottlenecks of short cycle life and interface instability of existing fluoride negative electrode materials. Compared with the existing KFeF3 material, the manganese-doped fluoride composite carbon material of the present invention has the following technical advantages:

[0015] 1) The manganese-doped fluoride composite carbon material of the present invention forms an in-situ LiF-rich SEI film during the lithiation process, significantly inhibiting side reactions and improving cycle stability;

[0016] 2) After doping with Mn at a preset ratio, the c-axis lattice constant of the resulting manganese-doped fluoride carbon composite material increases, indicating that its interlayer spacing has expanded. This structural change helps improve the diffusion path of lithium ions in the material, thereby improving its rate capability and enhancing its electrochemical performance.

[0017] 3) Good reversibility and electrochemical stability during lithium ion storage;

[0018] 4) After doping with Mn at a preset ratio, the resulting manganese-doped fluoride composite carbon material exhibits a synergistic effect between Mn and carbon, significantly reducing the material impedance and enhancing the electronic conductivity compared to the existing KFeF3 material. This indicates that the appropriate Mn doping strategy effectively reduces the interfacial resistance while improving the migration efficiency of lithium ions within the electrode, thereby enhancing the electrochemical reaction kinetics of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of preparing a manganese-doped fluoride composite carbon material according to an embodiment of the present invention.

[0020] Figure 2 1 is the XRD pattern of multiple samples of the embodiment of the present invention.

[0021] Figure 3 It is the XRD refined pattern of the samples of the examples and comparative examples of the present invention.

[0022] Figure 4 It is the scanning electron microscope spectrum of the sample of the embodiment of the present invention and comparative example.

[0023] Figure 5 This is the sample KFe of the embodiment of the present invention 0.5 Mn 0.5 EDS spectrum of F3@C.

[0024] Figure 6 This is the sample KFe of the embodiment of the present invention 0.5 Mn 0.5 TEM spectrum of F3@C.

[0025] Figure 7-1 、 Figure 7-2 、 Figure 7-3 They are sample 1KFeF3@C, sample 2KFe 0.5 Mn 0.5 F3@C, sample 3KFe 0.25 Mn 0.75 The F3@C electrode was scanned at a rate of 0.1 mVs -1 、The voltage range is 0.01~3.0V (relative to Li / Li + ) conditions.

[0026] Figure 8 It is a magnification diagram of the samples of the embodiments of the present invention and the comparative example.

[0027] Figure 9-1 、 Figure 9-2 、 Figure 9-3 They are sample 1KFeF3@C, sample 2KFe 0.5 Mn0.5 F3@C, sample 3KFe 0.25 Mn 0.75 Charge and discharge diagram of F3@C.

[0028] Figure 10 It is a long cycle life graph of the samples of the embodiment of the present invention and the comparative example.

[0029] Figure 11 1 and 2 are impedance diagrams of samples of the embodiments of the present invention and the comparative example.

[0030] Figure 12 It is the XPS graph of the samples of the examples of the present invention and the comparative examples.

[0031] Figure 13 3 are TOF-SIMS images of samples of the embodiments of the present invention and the comparative examples. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings, specific implementation methods, and examples. The examples are provided for illustration only and are not intended to limit the scope of protection of the present invention.

[0033] The embodiment of the present invention provides a Mn-doped fluoride (such as KFeF3) composite carbon material, which comprises: a perovskite-type KFe x Mn 1-x The material matrix is ​​composed of F3 grains, and the surface of the material matrix is ​​doped with carbon. Therefore, in the embodiment of the present invention, the chemical formula of the material is also recorded as KFe x Mn 1-x F3@C, where "@C" represents carbon (C) doping. Wherein, 0.2≤x≤0.8, preferably, 0.2≤x≤0.5. The grains constituting the matrix of the material have a cubic crystal structure of space group Pm-3m, with a grain size of 2nm-8nm. The (110) interplanar spacing, (200) interplanar spacing, and (220) interplanar spacing of the grains are 0.293±0.02nm, 0.202±0.02nm, and 0.147±0.02nm, respectively. The c-axis lattice constant of the Mn-doped KFeF3 composite carbon material of the embodiment of the present invention is 4.12Å~4.16Å.

[0034] The present invention also provides a method for preparing the aforementioned manganese-doped fluoride composite carbon material, which adopts a secondary ball milling method and specifically includes:

[0035] Step S1: Figure 1 As shown, KF, FeF2 and MnF2 are used as raw materials and mixed and milled according to a preset molar ratio to obtain KFe with a cubic perovskite structure. x Mn 1-xF3 material matrix. Wherein, the preset molar ratio is KF:FeF2:MnF2=1~5:2.5~5:2.5~5.

[0036] Step S2: Add a predetermined proportion of carbon to the KFe x Mn 1-x The F3 material matrix is ​​mixed and ball-milled to obtain the manganese-doped fluoride composite carbon material KFe x Mn 1-x F3@C. The mass of the added carbon accounts for 10% to 30% of the total mass of KF, FeF2 and MnF2, preferably 10%.

[0037] In a specific embodiment of the present invention, three fluoride negative electrode materials with different Mn doping ratios were synthesized by ball milling, as follows:

[0038] Sample 1 (control group / comparative example): reference Figure 1 KF, FeF2, and carbon are used as raw materials, mixed in appropriate proportions and ball-milled to synthesize the benchmark material KFeF3@C. In some specific embodiments, the preparation process of Sample 1 is as follows: KF and FeF2 are first uniformly mixed in a 1:1 molar ratio (for example, 5 mmol KF and 5 mmol FeF2), and then ball-milled at 700 rpm for 8 hours to synthesize the KFeF3 material; then, carbon is added at a ratio of 10% of the total mass of KF and FeF2, and ball-milled with the KFeF3 material at 400 rpm for 4 hours to obtain the carbon-doped KFeF3 material - KFeF3@C.

[0039] Sample 2 (KFe 0.5 Mn 0.5 F3@C doping group): Based on sample 1, MnF2 was introduced as the Mn source, and the mixed ball milling was carried out according to the molar ratio of Fe:Mn=0.5:0.5 to obtain the doping material KFe 0.5 Mn 0.5 F3@C. In some specific embodiments, the preparation process of sample 2 can refer to Figure 1 : First, 5mmol KF, 2.5mmol FeF2 and 2.5mmol MnF2 were uniformly mixed, and then ball milled at 700rpm for 8 hours to synthesize KFe 0.5 Mn 0.5 F3 material; then, add carbon in a ratio of 10% of the total mass of KF and FeF2, and 0.5 Mn 0.5 The F3 material was ball milled at 400 rpm for 4 hours to obtain carbon-doped KFe 0.5 Mn 0.5 F3 material——KFe 0.5Mn 0.5 F3@C.

[0040] Sample 3 (KFe 0.25 Mn 0.75 F3@C doping group): Based on sample 1, MnF2 was introduced as the Mn source, and mixed ball milling was performed according to the molar ratio of Fe:Mn=0.25:0.75 to obtain the doping material KFe 0.25 Mn 0.75 F3@C.

[0041] It should be noted that all three groups of samples were prepared using a two-step ball milling method. The rotation speed during the first ball milling is not limited to the aforementioned 700 rpm, but can be 500 rpm to 900 rpm. The ball milling time is not limited to 8 hours, but can be longer or shorter, for example, 4-12 hours. The rotation speed during the second ball milling is not limited to the aforementioned 400 rpm, but can be 200 rpm to 600 rpm. The ball milling time is not limited to 4 hours, but can be longer or shorter, for example, 2-6 hours.

[0042] The crystal structures of the samples were characterized by X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer with a CuKα radiation source (wavelength λ = 0.15406 nm) at a voltage of 45 kV and a current of 40 mA. The scan range was set between 2θ = 10° and 80° at a scan rate of 10° / min. The XRD patterns of the three samples are shown in Figure 2. Figure 2 As shown in the figure, the left panel (a) represents the material without C doping (i.e., the material obtained after the first ball milling), and the right panel (b) represents the final sample material obtained after the addition of C and secondary ball milling. The results show that all samples have the characteristics of a cubic perovskite structure with a Pm-3m space group, and no impurity phases were detected.

[0043] The detailed crystal structure information of the sample was obtained by Rietveld refinement of the XRD data using GSAS II software. Figure 3 As shown in Figures a, b, and c, respectively, are the KFeF3@C sample and KFe 0.5 Mn 0.5 F3@C sample, KFe 0.25 Mn 0.75 The specific structural parameters of F3@C samples are summarized in Table 1. The refinement results show that after appropriate doping with Mn, KFe 0.5 Mn 0.5 The c-axis lattice constant of the F3@C sample (column 3 in Table 1) increases, indicating that its interlayer spacing has expanded. This structural change helps improve the diffusion path of lithium ions in the material, thereby enhancing its electrochemical performance.

[0044] Table 1. Summary of XRD refinement data

[0045]

[0046] The morphology of the materials was observed by field emission scanning electron microscopy (HITACHI S-4800, SU 8010), and elemental analysis was performed using an energy dispersive spectrometer (EDS, IXRF SYSTEM, 550i). The relevant characterization results are shown in Figure 4 , where a and b are KFeF3@C samples, c and d are KFe 0.5 Mn 0.5 F3@C sample, Figures e and f are KFe 0.25 Mn 0.75 F3@C sample. Scanning electron microscope images show that KFeF3@C and KFe 0.25 Mn 0.75 Compared with F3@C sample, KFe 0.5 Mn 0.5 F3@C shows a more uniform particle distribution. Figure 5 As shown, EDS element mapping further confirmed that K, Mn, Fe, F and C elements are present in KFe 0.5 Mn 0.5 The uniform distribution in the F3@C material indicates that the doping elements have been successfully introduced and well dispersed.

[0047] Transmission electron microscopy (TEM) images were acquired using FEI Tecnai T12 and FEI Tecnai G2 F30 instruments, and the samples were prepared using a focused ion beam system (FIB, Scios, FEI). 0.5 Mn 0.5 High-resolution transmission electron microscopy (HRTEM) images of F3@C samples ( Figure 6 (a, b) show that the (110) interplanar spacing, (200) interplanar spacing, and (220) interplanar spacing of the grains are 0.293 nm, 0.202 nm, and 0.147 nm, respectively. These interplanar spacings are conducive to promoting the growth of Li + Diffusion in the crystal structure. Selected area electron diffraction (SAED) pattern ( Figure 6 Figure c) shows diffraction rings corresponding to the (110) and (200) crystal planes, further confirming that KFe 0.5 Mn 0.5 The F3@C material has a cubic perovskite structure, which is consistent with the XRD results.

[0048] Manganese-doped fluoride composite carbon material KFe according to an embodiment of the present invention x Mn 1-x F3@C materials can be used as negative electrode materials for lithium-ion batteries or sodium-ion batteries.

[0049] The following provides KFe 0.5 Mn 0.5 Specific implementation method of using F3@C material to make lithium-ion battery negative electrode.

[0050] To prepare the electrode slurry, the negative electrode active material, acetylene black, and polyvinylidene fluoride (PVDF, Solef 5130) were dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 7:2:1 and stirred thoroughly to obtain a homogeneous mixture. The resulting slurry was evenly coated on the surface of the aluminum foil current collector, with the active material loading controlled at 1.5-2 mg·cm. -2 Subsequently, the electrodes were dried at 120°C in a vacuum environment for 12 h. The dried electrode sheets were punched into discs with a diameter of 12 mm and transferred to an argon-filled glove box (LABstar, MBRAUN) for battery assembly.

[0051] The cells were assembled using a CR2032 button-type structure, using the synthesized material as the working electrode, metallic lithium as the counter electrode, and Celgard PP2400 as the separator. Each cell was injected with 60 μL of electrolyte: 1.0 mol of LiPF₆ dissolved in a 1:1 v / v mixture of diethyl carbonate and ethylene carbonate (DEC / EC), supplemented with 10% fluoroethylene carbonate (FEC) and 1% vinyl carbonate (VC) to enhance interfacial stability.

[0052] Cyclic voltammetry was performed using a Bio-Logic VMP-300 workstation with a scan rate of 0.1 mVs. -1 , voltage range is 0.01-3.0V (relative to Li / Li + ), the test process is carried out at room temperature. Figure 7-1 、 7-2 and 7-3 respectively show the three sample electrodes at a scan rate of 0.1 mVs -1 、The voltage range is 0.01~3.0V (relative to Li / Li + ) under the conditions of the first five cycles of cyclic voltammetry curves. Figure 7-2 As shown, in the first cycle, KFe 0.5 Mn 0.5The cathodic peaks C1 and C2 of F3@C at 0.9-1.1V and 0.01-0.45V are attributed to the conversion reaction, the formation of solid electrolyte interface (SEI) and the insertion of lithium ions; while the anodic peaks A1 and A2 at 0.4-0.5V and 0.6-0.8V correspond to the decomposition of part of SEI, the deintercalation of lithium ions and the reversible conversion reaction. Figure 7-1 As shown in Figure 2, KFeF3@C also has a similar phenomenon, with anodic peaks A1, A2, A3 and cathodic peaks C1, C2, C3 appearing in the first cycle; Figure 7-3 As shown, KFe 0.25 Mn 0.75 F3@C also has a similar phenomenon, with anodic peaks A1 and A2 and cathodic peaks C1 and C2 appearing in the first cycle. 0.25 Mn 0.75 Compared with F3@C, KFe 0.5 Mn 0.5 The subsequent CV curves of F3@C basically coincide with each other, indicating that KFe 0.5 Mn 0.5 F3@C perovskite-type fluoride exhibits good reversibility and electrochemical stability during lithium-ion storage.

[0053] The electrochemical performance tests of button cells were carried out on a multi-channel battery test system (LAND CT 2001 A) in the voltage range of 0.01–3 V (vs. Li + / Li). Figure 8 and Figure 9-1 、 Figure 9-2 、 Figure 9-3 As shown in Figure 2, when the current density increases from 100 to 1000 mA g -1 When KFe 0.5 Mn 0.5 The reversible capacity of F3@C gradually increased from 368.5 mA g -1 When the current density returned to 10 mA g -1 When the capacity is increased to 365.7mA g -1 , which is almost consistent with the initial value. In all samples, KFe 0.5 Mn 0.5 F3@C compared with KFeF3@C and KFe 0.25 Mn 0.75 F3@C exhibits the best rate performance. -1 Down, KFe 0.5 Mn 0.5 F3@C still maintains 231.44 mAh g after 1700 cycles. -1The capacity of KFeF3@C and KFe 0.25 Mn 0.75 F3@C only retained 54.25mAh g -1 and 74.32mAh g -1 (like Figure 10 KFe 0.5 Mn 0.5 The capacity retention rate of F3@C is 94.65%, which is much higher than that of KFeF3@C and KFe 0.25 Mn 0.75 F3@C (both 45%). This fully demonstrates that KFe 0.5 Mn 0.5 F3@C has excellent cycling stability.

[0054] Electrochemical impedance spectroscopy (EIS) tests were performed on a multi-channel electrochemical workstation (VMP3, Biologic) with a test frequency range of 100 kHz to 10 mHz. Figure 11 As shown, compared with the KFeF3@C material without Mn doping, KFe 0.5 Mn 0.5 The impedance of the F3@C material is significantly reduced, indicating that the appropriate Mn doping strategy effectively reduces the interface resistance while improving the migration efficiency of lithium ions inside the electrode, improving the electrical conductivity, and helping to enhance the electrochemical reaction kinetics of the material.

[0055] In order to further clarify the interfacial chemical characteristics, X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB250, with monochromatic Al Kα excitation source and energy of 1486 eV) was used to analyze the interfacial chemical properties of KFeF3@C, KFe 0.5 Mn 0.5 F3@C and KFe 0.25 Mn 0.75 The surface of the F3@C electrode was characterized after the 500th cycle, and its solid electrolyte interface (SEI) composition was systematically analyzed. Figure 12 The F 1s, C1s, and O1s spectra of the three samples after 500 cycles are shown. The characteristic peak of the F1s spectrum at about 684.5 eV corresponds to LiF, while KFe 0.5 Mn 0.5 The peak intensity of the F3@C sample is significantly enhanced, indicating that its surface is rich in LiF; after further etching, it is almost close to 100%, indicating that Mn doping helps promote the decomposition of FEC (Fluoroethylene Carbonate) and lithium salt to generate LiF, thereby stabilizing the SEI film structure. The intensity of the peak corresponding to Li2CO3 in the C1s spectrum is higher than that of KFe 0.5 Mn 0.5The decrease in F3@C indicates that Mn doping effectively inhibits the reduction and decomposition of EC (Ethylene Carbonate) and the formation of its by-products, which is beneficial to the construction of an inorganic phase-dominated interface film. The O1s spectrum shows that as the etching time increases, KFe 0.5 Mn 0.5 The increasing Li2O content in F3@C indicates that its SEI film gradually enriches with inorganic components during cycling, forming a more uniform and stable structure, thereby improving the cycling stability of the electrode. In summary, Mn doping not only enhances the uniformity of the SEI structure and the content of inorganic components, but also inhibits side reactions, significantly improving the material's cycle life and rate performance.

[0056] Time-of-flight secondary ion mass spectrometry (TOF-SIMS, PHI NanoTOF II) was used to detect the distribution of chemical substances on the electrode surface and inside. Figure 13 KFeF3@C, KFe 0.5 Mn 0.5 F3@C and KFe 0.25 Mn 0.75 The three-dimensional composition distribution reconstruction of F3@C and its corresponding depth distribution information. - POF2 - and PO2 - The signal is related to the inorganic decomposition products, while C2H3O - and C2H - The signal corresponds to the organic decomposition products. It is worth noting that KFeF3@C and KFe 0.25 Mn 0.75 The products generated by the side reactions in the F3@C electrode are widely distributed on the particle surface and penetrate deeply into the interior. 0.5 Mn 0.5 The decomposition behavior of the electrolyte in the F3@C electrode was significantly suppressed, indicating that the accumulation of its decomposition products was significantly reduced. These results together indicate that the optimized manganese doping effectively alleviated the interfacial side reactions, thereby significantly improving the long-term cycling stability of the material.

[0057] Combined with the above results, it can be seen that appropriate amount of Mn doping significantly optimizes the interfacial chemical behavior and electrochemical performance of KFeF3-based fluoride anode materials. Cyclic voltammetry (CV) and rate performance tests show that KFe 0.5 Mn 0.5 F3@C has excellent reversibility and rate performance, and shows good capacity retention and cycle stability at high current density. Electrochemical impedance spectroscopy (EIS) analysis shows that Mn doping effectively reduces the interface impedance and improves the ion migration ability. XPS and TOF -SIMS revealed in depth the SEI composition and its evolution mechanism. Mn doping promoted the formation of a stable LiF-rich SEI film and inhibited the generation and penetration of harmful byproducts within the particles, thereby enhancing interfacial stability and extending battery life. These results demonstrate that Mn element regulation achieves synergistic optimization of material structure and interfacial chemistry, providing an effective strategy for the design of high-performance fluoride anode materials.

[0058] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. Those skilled in the art will recognize that several equivalent substitutions or obvious variations can be made without departing from the scope of the present invention, and that any equivalent performance or application should be considered to fall within the scope of protection of the present invention.

Claims

1. An application of a manganese-doped fluoride composite carbon material, characterized in that: Used as negative electrode material for lithium ion battery or sodium ion battery; wherein the manganese doped fluoride composite carbon material comprises: perovskite type KFe x Mn 1-x A material matrix composed of F3 grains, wherein the surface of the material matrix is ​​doped with carbon, and the carbon doping ratio is 10~30wt%; wherein 0.2≤x≤0.8; the size of the grains is 2nm-8nm, and the (110) crystal plane spacing, (200) crystal plane spacing, and (220) crystal plane spacing of the grains are 0.293±0.02 nm, 0.202±0.02 nm, and 0.147±0.02 nm, respectively; and the c-axis lattice constant of the material is 4.12Å~4.16Å.

2. The use of the manganese-doped fluoride composite carbon material according to claim 1, characterized in that: The crystal grains have a cubic crystal structure of space group Pm-3m.

3. The use of the manganese-doped fluoride composite carbon material according to claim 1, characterized in that: 0.2≤x≤0.5。 4. The use of the manganese-doped fluoride composite carbon material according to claim 1, characterized in that: The manganese-doped fluoride composite carbon material is prepared by the following steps: S1, KF, FeF2 and MnF2 are mixed and milled according to the preset molar ratio to obtain KFe with a cubic perovskite structure. x Mn 1-x F3 material matrix; the preset molar ratio is KF:FeF2:MnF2=1~5:2.5~5:2.5~5; S2, adding carbon, and the KFe x Mn 1-x The F3 material matrix is ​​mixed and ball-milled to obtain the manganese-doped fluoride composite carbon material; wherein the mass of the added carbon accounts for 10% to 30% of the total mass of KF, FeF2 and MnF2.

5. The use of the manganese-doped fluoride composite carbon material according to claim 4, characterized in that: The mixing ball milling in step S1 is carried out at a rotation speed of 500 rpm to 900 rpm, and the ball milling time is 4 to 12 hours; the mixing ball milling in step S2 is carried out at a rotation speed of 200 rpm to 600 rpm, and the ball milling time is 2 to 6 hours.

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