An electronic structure regulated carbon-based composite current collector material and a preparation method and application thereof

Abstract

The application provides a carbon-based composite current collector material with electronic structure regulation and a preparation method and application thereof. The carbon-based composite current collector material comprises a carbon-based skeleton and a metal doping component; the carbon-based skeleton has a porous structure and a hollow structure; the metal doping component is distributed in the carbon-based skeleton; and the metal doping component is selected from at least one of Co, Ni, Fe and Zn. The carbon-based composite current collector material is prepared by coaxial electrospinning combined with a pyrolysis technology, has a gradient distribution of the metal doping component in the carbon-based skeleton, and thus forms a continuous work function gradient. The carbon-based composite current collector material significantly improves the metal deposition reversibility, coulombic efficiency and cycle stability of a metal battery without a negative electrode.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy materials and secondary battery technology, specifically relating to a carbon-based anode-free current collector with an electronically modulated structure, its preparation method, and its application. This current collector, by constructing an electronically modulated interface with a work function gradient distributed radially or axially, can be used in anode-free batteries to achieve directional deposition of metal ions, improved growth stability, and suppression of interfacial side reactions. Background Technology

[0002] With the increasing demands for energy density in energy storage systems from electric vehicles, smart grids, and portable electronic devices, anode-free metal batteries have become a research focus for next-generation high-energy battery systems due to their ability to maximize the utilization of active materials, simplify battery manufacturing processes, and significantly improve energy density. In this system, during the first charge, metal ions in the electrolyte (such as Li)... + Na + Metal negative electrodes are formed by in-situ deposition on the surface of the current collector. Therefore, the properties of the current collector directly determine the morphology, reversibility, and overall performance of the metal deposition.

[0003] However, existing negative electrode-less batteries generally face the following key technical challenges: (1) Uneven metal deposition and dendrite growth: The uneven electric field distribution on the surface of traditional planar current collectors (such as copper foil) results in limited nucleation sites for metal and random growth, which easily leads to dendrite formation, causing internal short circuits and rapid capacity decay.

[0004] (2) Severe interfacial side reactions: The newly deposited metal has high activity and reacts continuously with the electrolyte to form an unstable and thick solid electrolyte interphase (SEI) film, resulting in irreversible consumption of active materials and electrolyte and low coulombic efficiency.

[0005] (3) Existing control strategies have limitations: Current research mainly improves deposition behavior by constructing three-dimensional porous structures or applying surface coatings. However, these methods mainly make passive adjustments from the perspective of geometric morphology or chemical affinity, and it is difficult to achieve active and precise guidance of ion deposition paths from the atomic scale of electronic structure.

[0006] (4) Insufficient electronic structure regulation of carbon-based current collectors: Although carbon materials have advantages such as light weight, high conductivity and strong structural designability, their intrinsic work function distribution is uniform and cannot spontaneously form an electronic potential gradient to guide the directional migration of ions.

[0007] Currently, three-dimensional metallic frameworks (such as porous Cu, Al, and Ni) can alleviate polarization and reduce local current density, while the reversibility of metal deposition can be further improved through heteroatom doping or surface metal affinity modulation. However, metallic framework structures generally suffer from large mass and low volume utilization, thus contributing limitedly to improving overall energy density.

[0008] In contrast, carbon-based current collectors, with their advantages of light weight, large specific surface area, and high structural designability, are considered candidate materials with the potential to both suppress dendrites and optimize energy density. However, carbon-based current collectors generally have short cycle lives in anode-free systems and still face problems such as interfacial instability and rapid capacity decay.

[0009] To address the aforementioned issues, there is an urgent need to develop carbon-based current collectors that combine interfacial electronic regulation and structural regulation capabilities in order to achieve highly reversible metal deposition behavior and extend the cycle life of electrodeless metal batteries. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention provides the following technical solution: A carbon-based composite current collector material, the carbon-based composite current collector material comprising a carbon-based framework and a metal doping component; The carbon-based framework has a porous and hollow structure; the metal doping component is distributed within the carbon-based framework. The metal doping component is selected from at least one of Co, Ni, Fe, and Zn.

[0011] According to an embodiment of the present invention, the metal dopant component is preferably distributed on the surface, within the porous structure and / or hollow structure of the carbon-based framework, and more preferably within the hollow structure. Preferably, the concentration of the metal dopant component is gradient-distributed, preferably on the inner surface, within the porous structure and / or hollow structure of the carbon-based framework, forming corresponding electron density gradients and work function gradients. Further, the concentration of the metal dopant component is gradient-distributed along the hollow structure of the carbon-based framework.

[0012] In this invention, the electron density gradient refers to the spatial difference in electron concentration, which, like a concentration gradient, drives electrons to diffuse from high-concentration regions to low-concentration regions. The work function gradient refers to the spatial fluctuations in the energy cost required for electrons to escape from the material. It forms a tilted band structure within the material, equivalent to a built-in quasi-electric field, driving the directional drift of electrons. According to semiconductor physics theory, changes in the electron density gradient in space directly lead to the relative displacement of the Fermi level in the material; and the work function is defined as the energy difference between the vacuum level and the Fermi level. Therefore, the movement of the Fermi level inevitably induces the formation of the work function gradient. This invention induces the work function gradient by constructing a spatially continuous electron density gradient, thereby generating a built-in quasi-electric field and achieving a synergistic drive for the directional migration of charge carriers.

[0013] According to an embodiment of the present invention, the carbon-based framework is selected from carbon nanofibers with a hollow structure, wherein the hollow structure is longitudinally continuous, and the carbon wall of the hollow structure comprises a porous structure of micropores and / or mesopores. Preferably, the inner diameter of the hollow structure is 30-500 nm (preferably 30-300 nm), and the wall thickness of the hollow structure is 10-150 nm (preferably 10-100 nm). Preferably, the pore size of the micropores is 0.1-1 nm, for example, 0.9 nm. Preferably, the pore size of the mesopores is 1.5-10 nm, for example, 4 nm.

[0014] According to an embodiment of the present invention, the metal doping component is distributed in the carbon-based framework in the form of at least one of single atoms, nanoclusters, and nanoparticles.

[0015] According to an embodiment of the present invention, the total content of the metal dopant component in the carbon-based composite current collector is 1-10 wt%, for example, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%.

[0016] According to an embodiment of the present invention, along a certain dimension (such as the radial direction of carbon nanofibers) of the carbon-based composite current collector, the concentration gradient of the metal dopant component ranges from 20% to 80%, for example, 30%, 40%, 50%, 60%, and 70%.

[0017] According to a preferred embodiment of the present invention, in the carbon-based composite current collector, the metal dopant is cobalt, and the carbon-based framework is carbon nanofibers with a hollow structure.

[0018] The inventors discovered that by introducing metal dopant components into a carbon-based framework, these components can exhibit a concentration gradient along the radial direction of the carbon nanofibers, thereby constructing a continuous electron density gradient within the carbon nanofibers. This gradient distribution of the metal dopant components creates a built-in electric field at the interface. When used as a current collector, during electrochemical deposition, it actively guides metal ions such as sodium and lithium ions in the battery to migrate directionally to low work function regions (such as the inner surface of a hollow structure) and preferentially nucleate. Simultaneously, the hollow and porous structure of the carbon-based framework provides a physically confined space for metal ion deposition on the current collector, not only restricting the deposition process within the fiber to suppress dendrite epitaxial growth but also effectively buffering volume changes during deposition / exfoliation, which is beneficial for forming a stable and dense SEI film. Through the synergistic effect of "gradient electron guidance" and "spatial confinement," uniform and dense deposition of metal ions on the current collector is ensured.

[0019] This invention also provides a method for preparing the above-mentioned carbon-based composite current collector, the method comprising the following steps: (1) Provide metal-doped precursors; (2) Prepare inner spinning solution and outer spinning solution respectively; wherein, the outer spinning solution includes carbon source polymer and solvent I; the inner spinning solution includes sacrificial template polymer, metal doped precursor and solvent II; (3) The inner spinning solution of step (2) is used as the raw material for the core structure and the outer spinning solution is used as the raw material for the shell structure. A composite fiber precursor with a core-shell structure is prepared by coaxial electrospinning. (4) The composite fiber precursor obtained in step (3) is subjected to pre-oxidation treatment and high-temperature carbonization treatment in sequence to obtain the carbon-based composite current collector material.

[0020] According to an embodiment of the present invention, in step (1), the metal-doped precursor is selected from metal-organic framework nanoparticles or metal salts. Preferably, the metal-doped precursor contains at least one of Co, Ni, Fe, and Zn.

[0021] Preferably, the metal-organic framework nanoparticles are selected, for example, from ZIF-67 nanoparticles and Co1Zn nanoparticles. 50 - One or a combination or modification of two or more of the following: ZIF nanoparticles, ZIF-8 nanoparticles, ZIF-L nanoparticles, ZIF-67 / ZIF-8 core-shell structured nanoparticles, MOF-5, HKUST-1, MIL series (such as MIL-101, MIL-88, MIL-53), and UIO series (such as UIO-66, UIO-67).

[0022] Preferably, the metal salt is selected from Co salts, Ni salts, Fe salts, Zn salts, such as nitrates of Co, Ni, Fe or Zn, or cobalt nitrate hexahydrate and / or zinc nitrate hexahydrate.

[0023] According to an embodiment of the present invention, in step (1), solvent I and solvent II may be the same or different, and are independently selected from at least one, two or more of alcohol solvents, amide solvents, ketone solvents, alkane solvents, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and deionized water. Preferably, the alcohol solvent is selected from at least one of isopropanol, n-butanol, ethylene glycol, and glycerol. Preferably, the amide solvent is selected from at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP). Preferably, the ketone solvent is selected from acetone or butanone. Preferably, the alkane solvent is selected from dichloromethane (DCM) and chloroform.

[0024] Preferably, solvent I and solvent II may be the same or different, and are selected from any mixture of two or more of the above-mentioned solvents, such as a mixture of ethanol and N,N-dimethylformamide (DMF), a mixture of methanol and dichloromethane, or a mixture of water and ethanol. Further, the ratio of different solvents in the mixture can be selected from a range known in the art, and the present invention does not impose a specific limitation.

[0025] According to an embodiment of the present invention, in step (1), the mass percentage of the carbon source polymer in the outer spinning solution is 5-20%, for example, 10%.

[0026] According to an embodiment of the present invention, in step (1), the mass percentage of the sacrificial template polymer in the inner spinning solution is 20-50%, for example 30%; and the mass percentage of the metal-doped precursor is 1-5%, for example 3%.

[0027] According to an embodiment of the present invention, in step (1), the mass ratio of the sacrificial template polymer and the metal-doped precursor in the inner spinning solution is 20-50:1-5, for example, 10:1.

[0028] The inventors discovered that the mass percentage of the metal-doped precursor in the inner spinning solution determines the distribution of the metal-doped components in the carbon-based framework, which affects the charge transfer density, interfacial dipole strength, and filling density, and thus directly affects the energy electron density and work function gradient from the inner wall to the outer wall (radial) or along the tube length direction (axial) of the hollow carbon tube in the carbon-based framework.

[0029] According to an embodiment of the present invention, in step (2), the carbon source polymer is selected from at least one of polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and polyamic acid (PAA).

[0030] According to an embodiment of the present invention, the sacrificial template polymer is selected from at least one of polymethyl methacrylate (PMMA), polystyrene (PS), and polyvinyl alcohol (PVA).

[0031] According to an embodiment of the present invention, in step (3), the process parameters for coaxial electrospinning are: outer layer spinning solution feed rate 0.3-1.5 mL·h. -1 The propulsion rate of the inner spinning solution is 0.05-0.8 mL·h. -1 Spinning voltage 10-25 kV, receiving distance 10-18 cm.

[0032] Preferably, the ratio of the advance rate of the outer spinning solution to that of the inner spinning solution is 0.3-1.5:0.05-0.8, for example, 1:0.45.

[0033] According to an embodiment of the present invention, in step (4), the pre-oxidation treatment is carried out in an air atmosphere, the pre-oxidation temperature is 180-300℃ (e.g., 200℃, 250℃), and the pre-oxidation time is 0.5-6 h (e.g., 1 h, 2 h, 3 h, 4 h, 5 h).

[0034] According to an embodiment of the present invention, in step (4), the high-temperature carbonization treatment is carried out in an inert atmosphere at a temperature of 600-1000°C for a time of 0.5-6 h. Preferably, the inert atmosphere can be a gas known in the art, such as nitrogen, helium, or argon.

[0035] According to an embodiment of the present invention, in step (4), the shell structure is subjected to high-temperature carbonization to obtain a carbon-based skeleton, and the core structure is subjected to high-temperature carbonization to obtain a metal doped component, which is distributed in the carbon-based skeleton to form the carbon-based composite current collector material.

[0036] The inventors discovered that by adjusting the raw material composition, spinning flow rate ratio, and high-temperature carbonization process conditions in the outer and inner spinning solutions, the direction (increasing or decreasing from the outside to the inside) and intensity of the metal doping gradient can be precisely controlled.

[0037] The present invention also provides the application of the above-mentioned carbon-based composite current collector material in energy storage devices.

[0038] Preferably, the energy storage device is selected from a negative electrode-free metal battery. Further, the negative electrode-free metal battery is selected from one of a negative electrode-free lithium metal battery, a negative electrode-free sodium metal battery, a sodium-sulfur battery, and a lithium-sulfur battery.

[0039] Beneficial effects: The carbon-based composite current collector material provided by this invention achieves a synergistic effect of "gradient electron guidance" and "spatial confinement" through a unique composition and structural design, effectively improving the uniformity and reversibility of metal deposition. It can be used in various high-energy-density electrodeless batteries, such as sodium batteries and lithium batteries. Specifically: (1) The carbon-based composite current collector material of the present invention is prepared by coaxial electrospinning combined with pyrolysis technology. Its carbon-based framework has a gradient distribution of metal doped components, thereby forming a continuous work function gradient. Through the built-in electric field, the directional migration and uniform nucleation of metal ions are actively guided from the electronic structure level. The porous / hollow structure provides a physical confinement space to suppress dendrites and buffer volume changes, fundamentally improving the deposition uniformity and effectively suppressing dendrite growth. The carbon-based composite current collector material of the present invention significantly improves the metal deposition reversibility, coulombic efficiency and cycle stability of anode-free metal batteries.

[0040] (2) The hollow porous structure of the carbon-based framework provides an internal confined space for metal deposition, which not only suppresses the risk of dendrite puncture, but also buffers the volume change during cycling, thereby improving the structural stability and interface (SEI) stability of the electrode.

[0041] (3) The electrodeless battery based on this material exhibits excellent electrochemical performance, including high coulombic efficiency (e.g., ≥99.9%), long cycle life and good rate performance.

[0042] (4) The preparation method of the present invention adopts coaxial electrospinning and gradient pyrolysis technology. The preparation method of the present invention is simple and controllable, the process is highly controllable, the conditions are mild, the raw materials used are readily available, and it has good potential for large-scale production.

[0043] Therefore, this invention achieves precise regulation of metal deposition behavior by combining "coaxial spinning to construct a hollow structure", "work function gradient" and "induced electronic structure regulation", enabling negative electrode-free metal batteries to obtain significantly enhanced safety, lifespan and rate performance, and has significant technical advantages and industrial application value. Attached Figure Description

[0044] Figure 1 This is an optical photograph of the composite fiber precursor prepared in Example 1.

[0045] Figure 2 The X-ray diffraction (XRD) patterns of the products obtained in Examples 1, 2 and Comparative Example 1 are shown.

[0046] Figure 3 This is a scanning electron microscope (SEM) image of the carbon-based composite current collector material (Co-HCNF) with electronic structure regulated in Example 1.

[0047] Figure 4 This is a scanning electron microscope (SEM) image of the carbon-based composite current collector material (CoSA-HCNF) with electronic structure regulated in Example 2.

[0048] Figure 5 This is a scanning electron microscope (SEM) image of the metal-free hollow carbon nanofiber material (HCNF) in Comparative Example 1.

[0049] Figure 6 This is a transmission electron microscope (TEM) image of a single carbon nanofiber in the electronically structured carbon-based composite current collector material (Co-HCNF) of Example 1.

[0050] Figure 7 Sodium metal half-cells assembled using materials from Example 1 (Co-HCNF) and Comparative Example 1 (HCNF) were tested at 4 mAcm. -2Comparison of coulombic efficiency cyclic curves at current density.

[0051] Figure 8 The graph shows the cycle performance of the electrodeless sodium metal full cell assembled using the material of Example 1 (Co-HCNF) at different rates.

[0052] Figure 9 The pore size distribution diagrams are for the materials of Example 1 (Co-HCNF) and Comparative Example 1 (HCNF).

[0053] Figure 10 This is a transmission electron microscope (TEM) image of the carbon-based composite current collector material (Co-HCNF) with electronic structure regulated in Example 1. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0055] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0056] Example 1 The preparation of cobalt nanoparticle-doped carbon-based composite current collector (Co-HCNF) is as follows: (1) Synthesis of ZIF-67 nanoparticles: Cobalt nitrate hexahydrate (2.94 g) and polyvinylpyrrolidone (2.5 g) were dissolved in 250 mL of methanol, denoted as solution A. 2-Methylimidazole (3.313 g) and triethylamine (0.2 mL) were dissolved in another 250 mL of methanol, denoted as solution B. Solution B was poured into solution A with stirring, and the mixture was allowed to react at room temperature for 24 h. The product was collected by centrifugation, washed three times with methanol, and dried under vacuum at 80 °C for 24 h to obtain ZIF-67 nanoparticles.

[0057] (2) Preparation of spinning solution: Outer spinning solution: Polyacrylonitrile (PAN, 0.48 g) was dissolved in N,N-dimethylformamide (DMF, 4 g) and stirred at 60 °C for 12 h.

[0058] Inner spinning solution: ZIF-67 nanoparticles (0.048 g) were dispersed in DMF (1.2 g), sonicated for 30 min, and then polymethyl methacrylate (PMMA, 0.48 g) was added and stirred at 60 °C for 12 h.

[0059] (3) Coaxial electrospinning: The above spinning solution was loaded into the outer and inner injectors of the coaxial electrospinning apparatus, respectively. The spinning voltage was set to 20 kV, and the outer liquid feed rate was set to 1.0 mL / h. -1 The inner layer fluid propulsion rate is 0.45 mL / h. -1 The receiving distance was 15 cm, and the composite fiber precursor was collected, such as... Figure 1 As shown, it is a membrane material with a uniform purple surface.

[0060] (4) Heat treatment: The composite fiber precursor was placed in a muffle furnace and heated to 5°C in air atmosphere. -1 The temperature was raised to 250℃ and held for 2 hours for pre-oxidation. Subsequently, the sample was transferred to a tube furnace and oxidized at 2℃ for 2 minutes under an argon atmosphere. -1 The material was carbonized by heating to 1000℃ and holding for 3 hours, and then naturally cooled to obtain Co-HCNF material.

[0061] Depend on Figure 2 The XRD pattern of the Co-HCNF material in Example 1 shows that cobalt nanoparticles are present in the material. Figure 3 The material obtained in this embodiment has a uniform fibrous morphology and a hollow structure with an inner diameter of 300 nm and a wall thickness of 60 nm. Figure 6 The image shown is a TEM image of the material obtained in this embodiment, which clearly shows its hollow structure and the gradient distribution of the metal within the wall. Figure 10 For the TEM elemental analysis of this embodiment, the cobalt nanoparticles are distributed on the inner surface of the carbon nanofibers.

[0062] Example 2 The preparation of the cobalt single-atom gradient-doped carbon-based composite current collector (CoSA-HCNF) in this embodiment is basically the same as in Example 1, except that the metal precursor in step (1) is replaced with Co1Zn. 50 -ZIF. Details are as follows: (1) Co1Zn 50 Synthesis of -ZIF: 2-Methylimidazole (6.70 g) was dissolved in 204 mL of methanol (solution A). Cobalt nitrate hexahydrate (0.058 g) and zinc nitrate hexahydrate (2.97 g) were dissolved in another 204 mL of methanol (solution B). Solution A was slowly poured into solution B, and the mixture was stirred at room temperature for 24 h. After centrifugation, washing, and drying, Co1Zn was obtained. 50 -ZIF nanoparticles.

[0063] (2) The spinning solution was prepared in the same way as in Example 1, except that the ZIF-67 nanoparticles in the inner spinning solution were replaced with an equal mass of Co1Zn. 50 -ZIF nanoparticles.

[0064] (3) The outer spinning solution and the inner spinning solution of this embodiment are coaxially electrospun to obtain a composite fiber precursor. The coaxial electrospinning conditions are the same as in Example 1. (4) The composite fiber precursor from step (2) above is subjected to heat treatment under the same conditions as step (4) of Example 1.

[0065] This embodiment yields a cobalt single-atom gradient-doped carbon-based composite current collector material, CoSA-HCNF, with the following morphology: Figure 4 As shown, it is a uniform fibrous hollow structure with an inner diameter of 300 nm and a wall thickness of 100 nm. Figure 2 In this embodiment, no obvious cobalt crystal diffraction peaks were observed in the XRD pattern of CoSA-HCNF, indicating that cobalt may exist in a highly dispersed single-atom form.

[0066] Comparative Example 1 The preparation of metal-free hollow carbon nanofiber (HCNF) materials is as follows: (1) Preparation of spinning solution: The outer spinning solution is the same as in Example 1; The inner spinning solution was prepared according to Example 1, except that PMMA (0.48 g) was dissolved in DMF (1.2 g), stirred at 60°C for 12 h, and ZIF-67 nanoparticles were not added.

[0067] (2) The outer spinning solution and the inner spinning solution of this comparative example are coaxially electrospun to obtain a composite fiber precursor, under the same conditions as step (3) of Example 1. (3) The composite fiber precursor from step (2) above is subjected to heat treatment under the same conditions as step (4) of Example 1.

[0068] The product obtained in this comparative example is denoted as HCNF, and its morphology is as follows: Figure 5 As shown, it is a hollow carbon fiber material without metal doping and has almost no micropores or mesopores (see [reference]). Figure 9 (Comparison of data 1).

[0069] Test Example 1 Electrochemical performance testing (1) Half-cell coulombic efficiency test: A sodium metal half-cell was assembled using the Co-HCNF from Example 1 and the HCNF from Comparative Example 1 as working electrodes, and a sodium sheet as the counter / reference electrode. The half-cell was operated at 4 mA cm⁻¹. -2 At current density, 2 mAh cm⁻¹ is deposited per revolution.-2 After sodium removal, the battery was charged to a voltage of 1 V, and the coulombic efficiency was tested.

[0070] like Figure 7 As shown, the Co-HCNF-based cells exhibit extremely high and stable coulombic efficiency, averaging over 99.9%. In contrast, HCNF-based cells show lower efficiency and faster degradation. This indicates that gradient metal doping-induced uniform deposition significantly reduces irreversible losses.

[0071] (2) Full battery performance test: Using Co-HCNF from Example 1 and HCNF from Comparative Example 1 as negative electrode current collectors and sodium vanadium phosphate (Na3V2(PO4)3) as positive electrode, a full cell without a negative electrode was assembled. The cells were cycled 8 times at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 10 C, 15 C, 20 C, 30 C, and 40 C respectively to perform rate cycling tests and calculate the capacity retention rate.

[0072] like Figure 8 As shown, the electrodeless full cell prepared using Co-HCNF in Example 1 exhibits stable cycling performance and high capacity retention over a wide rate range from 0.2 C to 40 C. This demonstrates that the carbon-based composite current collector material obtained in this invention possesses excellent ion transport kinetics and structural stability when used as a current collector.

[0073] Comparing Examples 1-2 with Comparative Example 1, it can be seen that the present invention successfully achieves electronic-level control over metal deposition behavior by constructing a gradient-distributed metal doped layer within the hollow structure of a carbon-based framework. The synergistic effect of the hollow structure and gradient electronic effect of the carbon-based composite current collector material is key to obtaining a cathode-free battery with high coulombic efficiency and long cycle life.

[0074] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon-based composite current collector, characterized in that, The carbon-based composite current collector material includes a carbon-based framework and metal-doped components; The carbon-based framework has a porous and hollow structure; the metal doping component is distributed within the carbon-based framework. The metal doping component is selected from at least one of Co, Ni, Fe, and Zn.

2. The carbon-based composite current collector according to claim 1, characterized in that, The metal doping components are distributed on the surface of the carbon-based framework, within the porous structure and / or hollow structure; The carbon-based framework is selected from carbon nanofibers with hollow structures. The hollow structures are longitudinally continuous, and the carbon walls of the hollow structures contain micropores and / or mesopores in a porous structure. The inner diameter of the hollow structures is 30-500 nm, and the wall thickness of the hollow structures is 10-150 nm. The metal dopant is distributed within the carbon-based framework in at least one of the following forms: single atoms, nanoclusters, and nanoparticles.

3. The carbon-based composite current collector according to claim 1 or 2, characterized in that, The total content of the metal doping component in the carbon-based composite current collector is 1-10 wt%; Along a certain dimension of the carbon-based composite current collector, the concentration gradient of the metal dopant component ranges from 20% to 80%.

4. The method for preparing the carbon-based composite current collector according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Provide metal-doped precursors; (2) Prepare inner spinning solution and outer spinning solution respectively; wherein, the outer spinning solution includes carbon source polymer and solvent I; the inner spinning solution includes sacrificial template polymer, metal doped precursor and solvent II; (3) The inner spinning solution of step (2) is used as the raw material for the core structure and the outer spinning solution is used as the raw material for the shell structure. A composite fiber precursor with a core-shell structure is prepared by coaxial electrospinning. (4) The composite fiber precursor obtained in step (3) is subjected to pre-oxidation treatment and high-temperature carbonization treatment in sequence to obtain the carbon-based composite current collector material.

5. The preparation method according to claim 4, characterized in that, In step (1), the metal-doped precursor is selected from metal-organic framework nanoparticles or metal salts; the metal-doped precursor contains at least one of Co, Ni, Fe, and Zn; In step (1), solvent I and solvent II may be the same or different, and are independently selected from at least one, two or more of alcohol solvents, amide solvents, ketone solvents, alkane solvents, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and deionized water.

6. The preparation method according to claim 4 or 5, characterized in that, In step (1), the mass percentage of the carbon source polymer in the outer spinning solution is 5-20%; In step (1), the mass percentage of the sacrificial template polymer in the inner spinning solution is 20-50%; the mass percentage of the metal-doped precursor is 1-5%. According to an embodiment of the present invention, in step (1), the mass ratio of the sacrificial template polymer to the metal-doped precursor in the inner spinning solution is 20-50:1-5.

7. The preparation method according to any one of claims 4-6, characterized in that, In step (2), the carbon source polymer is selected from at least one of polyacrylonitrile, polyvinylpyrrolidone, and polyamic acid; The sacrificial template polymer is selected from at least one of polymethyl methacrylate, polystyrene, and polyvinyl alcohol.

8. The preparation method according to any one of claims 4-7, characterized in that, In step (3), the process parameters for coaxial electrospinning are: outer layer spinning solution feed rate 0.3-1.5 mL·h. -1 The propulsion rate of the inner spinning solution is 0.05-0.8 mL·h. -1 Spinning voltage 10-25 kV, receiving distance 10-18 cm; The ratio of the propulsion rate of the outer spinning solution to that of the inner spinning solution is 0.3-1.5:0.05-0.

8.

9. The preparation method according to any one of claims 4-8, characterized in that, In step (4), the pre-oxidation treatment is carried out in an air atmosphere, the pre-oxidation temperature is 180-300℃, and the pre-oxidation time is 0.5-6 h; In step (4), the high-temperature carbonization treatment is carried out in an inert atmosphere at a temperature of 600-1000℃ for 0.5-6h. In step (4), the shell structure is subjected to high-temperature carbonization to obtain a carbon-based skeleton, and the core structure is subjected to high-temperature carbonization to obtain a metal doped component, which is distributed in the carbon-based skeleton to form the carbon-based composite current collector material.

10. The application of the carbon-based composite current collector material according to any one of claims 1-3 in energy storage devices.

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