Self-supporting composite lithium negative electrode material with controllable lithium loading capacity and preparation method of self-supporting composite lithium negative electrode material

Abstract

The invention discloses a self-supporting composite lithium negative electrode material with controllable lithium loading capacity and a preparation method of the self-supporting composite lithium negative electrode material, aiming at the problems of lithium dendrite growth, volume shrinkage / expansion in a lithium stripping / deposition process, low lithium metal utilization rate and the like of a lithium metal electrode, a lithium-loving metal oxide is loaded on a flexible carbon nanofiber membrane; and the composite negative electrode with different lithium loading capacities is prepared in a low-temperature melting lithium injection manner. The three-dimensional structure of the flexible carbon fiber membrane plays a self-supporting role, the influence of volume shrinkage / expansion in the lithium stripping / deposition process is relieved, the lithium-loving metal oxide serves as an active site to guide uniform distribution of lithium, growth of lithium dendrites is effectively inhibited, and the electrochemical performance of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite lithium anode materials, and particularly relates to a self-supporting composite lithium anode material with controllable lithium loading and a preparation method thereof. Background Art

[0002] Lithium metal anodes have the highest theoretical specific capacity and the lowest electrochemical potential, and are ideal anode materials for simultaneously achieving high energy density and efficient fast charging requirements.

[0003] Lithium metal anodes have attracted extensive research attention due to their ultra-high theoretical capacity, lowest redox potential and low weight density. However, problems such as lithium dendrite growth and volume change of the lithium anode during the lithium stripping / deposition process lead to low Coulomb efficiency and poor cycle life; secondly, during the lithium stripping process, due to the reduction of lithium thickness, a gap is generated between the separator and the lithium metal, thereby generating separator stress, posing a serious safety hazard; in addition, in traditional lithium metal batteries, due to lithium dendrite growth and uncontrolled reactions with liquid electrolytes, active lithium metal is continuously consumed. Therefore, in order to ensure performance, lithium metal is usually in excess, which greatly reduces the energy density of the battery and increases the cost of the battery, hindering the practical application of lithium metal batteries.

[0004] Currently, there are many designs for the negative electrode current collector. Among them, carbon materials have the advantages of light weight, adjustable physical and chemical properties, high electronic conductivity, low cost, etc., and are considered to be perfect hosts for lithium. The carbon nanofiber membrane prepared by electrospinning has characteristics such as high porosity, large specific surface area, and controllable diameter, which can enhance the wettability of the electrolyte and form a matrix similar to a three-dimensional network storage library for storing active substances, and functional carbon fibers with adjustable properties can be synthesized by reasonably adjusting the composition of the spinning solution. However, the carbon nanofiber membrane has problems such as low strength, poor toughness, and poor lithium affinity, which limit its use as a negative electrode current collector. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-supporting composite lithium anode material with controllable lithium loading and a preparation method thereof to solve one or more of the above-mentioned technical problems. The present invention prepares a flexible carbon fiber membrane by electrospinning using a soluble polymer as a carbon source, uniformly loads metal oxide particles on its surface, and then prepares a composite lithium anode by melt lithium injection. The carbon fiber has a three-dimensional network structure, which alleviates the volume change during lithium stripping / deposition as a self-supporting skeleton. The interaction between the lithiumophilic metal oxide on the surface of the carbon fiber and lithium enables lithium to be uniformly deposited on the surface of the carbon fiber, inhibits the generation of lithium dendrites, and improves the cycle stability of the battery.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a self-supporting composite lithium anode material with controllable lithium loading amount, comprising the following steps: Weigh a soluble polymer, a metal acetate and a pore former with a mass ratio of 1:0.1~0.4:0.1~0.2:10, dissolve them in a dimethylformamide solution for mixing treatment to obtain a precursor solution; Transfer the precursor solution to an electrospinning experimental platform to obtain an organic polymer fiber membrane; Pre-oxidize the organic polymer fiber membrane in a muffle furnace, then put it into a tube furnace and heat it under a nitrogen atmosphere to complete carbonization to obtain a flexible carbon fiber membrane; during this process, the metal acetate thermally decomposes and is reduced to a metal single substance coated inside the carbon fiber; Soak the obtained carbon fiber membrane in a metal salt solution with a concentration of 0.2~1mol / L, dry it and then put it into a tube furnace and heat it under a nitrogen atmosphere. The metal salt thermally decomposes into metal oxide particles attached to the surface of the carbon fiber to obtain a flexible carbon fiber membrane loaded with metal oxide particles; Heat the carbon fiber membrane, and combine different masses of lithium with the flexible carbon fiber membrane loaded with metal oxide particles by the method of molten lithium injection to obtain a self-supporting composite lithium anode material with controllable lithium loading amount.

[0007] A further improvement of the present invention is that the selected soluble polymer is polyacrylonitrile, polyvinylidene fluoride or polystyrene; the selected metal acetate is zinc acetate, copper acetate or aluminum acetate; the selected pore former is urea, ammonium bicarbonate or ferrocene.

[0008] A further improvement of the present invention is that the mass ratio of the soluble polymer to the metal acetate is 3:1~3.

[0009] A further improvement of the present invention is that the selected metal oxide particles are zinc oxide, lead oxide, molybdenum oxide or titanium oxide.

[0010] A further improvement of the present invention is that the voltage of electrospinning is set to 12~17kV.

[0011] A further improvement of the present invention is that the pre-oxidation temperature is 200~300°C and the heat preservation time is more than 2h.

[0012] A further improvement of the present invention is that the carbonization temperature under a nitrogen atmosphere is 600~1000°C and the heat preservation time is more than 2h.

[0013] A further improvement of the present invention is that the heat treatment temperature under a nitrogen atmosphere is 400~600°C and the heat preservation time is more than 3h.

[0014] A further improvement of the present invention is that when injecting lithium into the carbon fiber, the molten lithium temperature is 200~300°C.

[0015] A self-supporting composite lithium anode material with controllable lithium loading, which is prepared by the described preparation method.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. The carbon fiber membrane prepared in the present invention is prepared by an electrospinning process, and has characteristics such as high porosity, large specific surface area, and controllable diameter. It can enhance the wettability of the electrolyte, and the carbon fiber has a three-dimensional network structure to play a self-supporting role, which can effectively avoid volume changes during the lithium deposition and stripping process, and no gap will be generated between the separator and the anode, thereby eliminating the separator stress and effectively improving safety.

[0017] 2. A small amount of metal acetate is added to the carbon fiber membrane prepared in the present invention. During the heat treatment process, the metal acetate decomposes and is reduced to metal nanoparticles coated inside the carbon fiber, making the carbon fiber have good flexibility and still can remain intact after multiple bending and winding.

[0018] 3. A pore-forming agent in a set proportion is added during the preparation process of the metal salt solution of the present invention. The aim is to form a more uniform and suitable pore structure during the subsequent treatment process through the action of the pore-forming agent. These pores not only provide more attachment sites for metal oxide particles, but also ensure that the particles can be evenly and firmly attached to the surface of the carbon fiber membrane. This uniform attachment method greatly increases the contact area between the metal oxide and the carbon fiber membrane, thereby enhancing the interaction force between them. In addition, the use of the pore-forming agent is also beneficial to the diffusion and transmission of lithium ions in the carbon fiber membrane, promoting the effective combination of lithium and the carbon fiber membrane. It provides a better material choice for application fields such as lithium-ion batteries.

[0019] 4. In the present invention, a carbon fiber membrane loaded with metal oxide is obtained by soaking in a lithiophilic metal salt solution and then performing high-temperature heat treatment. The metal oxide can effectively improve the lithiophilicity of the carbon fiber, and at the same time retains the advantage of low density of the carbon fiber. The equipment in the preparation process is simple, avoiding complex process flows, and the raw material cost is low.

[0020] 5. The present invention adopts a low-temperature molten lithium injection method, and lithium injection can be completed at 200 - 300 °C. And a composite anode with different lithium loadings is obtained by controlling the mass of the molten lithium block. Description of the Drawings

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the carbon fiber membrane after multiple folds and windings.

[0023] Figure 2 It is an XRD pattern of the flexible carbon fiber membrane loaded with zinc oxide particles after heat preservation at 500 °C for 4 h.

[0024] Figure 3 It is an SEM image of the flexible carbon fiber membrane composite lithium anode with different lithium loadings.

[0025] Figure 4 It is a comparison chart of the rate performance of the symmetric battery of the flexible carbon fiber membrane composite lithium anode with different lithium loadings.

[0026] Figure 5 It is a comparison chart of the cycle performance of the symmetric battery of the flexible carbon fiber membrane composite lithium anode with different lithium loadings.

[0027] Figure 6 It is a comparison chart of the cycle performance of the lithium iron phosphate battery of the flexible carbon fiber membrane composite lithium anode with different lithium loadings.

[0028] Figure 7 It is the charge-discharge curve after 300 cycles of the lithium iron phosphate battery assembled with the composite lithium anode prepared in Example 4 and Example 5. Specific Embodiments

[0029] In the following, only some exemplary embodiments are briefly described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0030] It should be understood that when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0031] It should also be understood that the terms used in the specification of the present invention are merely for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0032] It should be further understood that the term "and / or" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0033] Schematic diagrams of various structures according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0034] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0035] A preparation method of a self-supporting composite lithium negative electrode material with controllable lithium loading amount in an embodiment of the present invention, wherein the preparation method includes the following steps: I. Preparation of flexible carbon fiber membrane by electrospinning 1. Preparation of precursor solution: Metal acetate and pore-forming agent are added to dimethylformamide solution in a set ratio, and after ultrasonic dispersion and dissolution, a clear and transparent solution is formed; then the solution is transferred to a magnetic stirrer, the rotation speed is set to 300 - 400 rpm, and at the same time, soluble polymer powder is slowly added; when the soluble polymer powder is completely dissolved to obtain a clear solution, the precursor solution can be obtained.

[0036] 2. Preparation of flexible carbon fiber membrane: The spinning dope is transferred to a syringe on an electrospinning experimental platform. After electrospinning is completed, the organic fiber membrane is transferred to a forced-air drying oven to remove the unevaporated dimethylformamide solvent; then it is pre-oxidized by heating to 200 - 300 °C. The pre-oxidized fiber membrane is transferred to a tubular furnace. After exhausting the air in the quartz tube, it is kept at 600 - 1000 °C for 2 - 6 h to complete carbonization, and a flexible carbon fiber membrane is obtained.

[0037] II. Preparation of self-supporting composite lithium negative electrode material with controllable lithium loading amount 1. Flexible carbon fiber composite metal oxide particles: Prepare a zinc acetate solution (or metal salt solutions such as lead nitrate and molybdenum acetate solution) with a concentration of 0.2 - 1 mol / L. Immerse a certain mass of carbon fiber membrane in the above solution, take it out and dry it, then transfer it to a tubular furnace. Pass nitrogen at a rate of 100 - 200 ml / h as a protective atmosphere, heat it to 450 - 600 °C at a rate of 10 °C / min, and keep it for 2 - 6 h. During this process, the metal salt is completely decomposed into metal oxide and evenly distributed on the surface of the carbon fiber.

[0038] 2. Flexible carbon fiber molten lithium injection: The process of melting lithium is carried out in a glove box under an argon atmosphere. Place the lithium block on the carbon fiber membrane maintained at 200 - 300 °C for melting preparation. By controlling the respective masses of the lithium block and the carbon fiber membrane, composite anodes with different lithium loadings are prepared. According to the above operation, a self-supporting composite lithium anode material with controllable lithium loading is prepared.

[0039] Furthermore, the selected soluble polymer is polyacrylonitrile, polyvinylidene fluoride or polystyrene; the selected metal acetate is zinc acetate, copper acetate or aluminum acetate; the selected pore-forming agent is urea, ammonium bicarbonate or ferrocene. The selected metal oxide particles are zinc oxide, lead oxide, molybdenum oxide or titanium oxide.

[0040] Among them, polyacrylonitrile is commonly used to prepare the precursor of carbon fiber and is also used to prepare ultrafiltration membranes and nanofiltration membranes, etc. Polyvinylidene fluoride has excellent chemical corrosion resistance, thermal stability and electrical insulation, and is widely used in fields such as battery separators, microfiltration membranes and nanofiltration membranes. Polystyrene is a commonly used plastic material with good processing performance and transparency, and can be used to prepare foam materials, packaging materials, etc.

[0041] Among metal acetates, metal acetates such as zinc acetate, copper acetate and aluminum acetate are usually used as metal sources and play an important role in the preparation of nanomaterials such as metal oxides and metal sulfides. They can be converted into corresponding metal oxides or sulfides by methods such as thermal decomposition or chemical precipitation.

[0042] Among pore-forming agents, pore-forming agents such as urea, ammonium bicarbonate and ferrocene play a key role in the preparation of porous materials. They can generate gas or volatilize during the material preparation process, thus leaving pores in the material, increasing the specific surface area and porosity of the material. This is of great significance for improving the adsorption performance, catalytic performance, etc. of the material.

[0043] Among metal oxide particles, metal oxide particles such as zinc oxide, lead oxide, molybdenum oxide and titanium oxide have unique physical and chemical properties and are widely used in fields such as photocatalysis, electrocatalysis, sensors and energy storage materials. For example, zinc oxide and titanium oxide are commonly used photocatalysts and can be used to degrade organic pollutants and prepare solar cells, etc.

[0044] Example 1 This example provides a method for preparing a self-supporting composite lithium anode material with controllable lithium loading, and the specific steps are as follows: Weigh 1.28 g of polyacrylonitrile, (2 mmol, 4 mmol, 6 mmol) of copper acetate and urea (the molar ratio of copper acetate to urea is 2:1) respectively. Add copper acetate and urea into 10 g of dimethylformamide solution, and form a clear and transparent solution through ultrasonic dispersion and dissolution. Then transfer the solution to a magnetic stirrer, set the rotation speed to 400 rpm, and slowly add polyacrylonitrile powder at the same time. Wait until the polyacrylonitrile powder is completely dissolved to obtain a blue-green clear solution, marked as #1, #2, #3 samples.

[0045] Transfer the #1, #2, #3 samples to the syringe in the electrospinning experimental platform, and set the solution injection speed to 0.8 mL / h, the distance between the needle tip and the roller to 15 cm, the voltage to 16 kV, and the roller rotation speed to 60 rpm. After the electrospinning is completed, transfer the polyacrylonitrile fiber to a blast drying oven to remove the unevaporated dimethylformamide solvent; then pre-oxidize it by heating to 260 °C. Transfer the pre-oxidized fiber membrane to a tube furnace, evacuate the air in the quartz tube, and keep it at 700 °C for 2 h to complete carbonization, obtaining a flexible carbon fiber membrane.

[0046] Example 2 This example provides a method for preparing a self-supporting composite lithium anode material with controllable lithium loading, and the specific steps are as follows: Prepare a 1 mol / L zinc acetate solution. Take 38 mg of carbon fiber membrane (#1 sample) and soak it in the zinc acetate solution for 30 min. Evaporate water and ethanol at 80 °C, transfer it to a tube furnace, and heat it to 550 °C at a rate of 10 °C / min and keep it for 6 h. Obtain a carbon fiber membrane loaded with zinc oxide particles.

[0047] Cut the above product into small round pieces with a diameter of 1.4 cm and a thickness of 200 μm, place them on a heating table, heat to 280 °C, and place 5 mg of lithium block on the carbon fiber membrane until it is completely absorbed to obtain a composite lithium anode with lithium loading #1.

[0048] Example 3 This example provides a method for preparing a self-supporting composite lithium anode material with controllable lithium loading, and the specific steps are as follows: Prepare a 1 mol / L zinc acetate solution. Take 38 mg of carbon fiber membrane (#1 sample) and soak it in the zinc acetate solution for 30 min. Evaporate water and ethanol at 80 °C, transfer it to a tube furnace, and heat it to 550 °C at a rate of 10 °C / min and keep it for 6 h. Obtain a carbon fiber membrane loaded with zinc oxide particles.

[0049] Cut the above product into small round pieces with a diameter of 1.4 cm and a thickness of 200 μm, place them on a heating table, heat to 280 °C, take 6.5 mg of lithium block and place it on the carbon fiber membrane until it is completely absorbed, obtaining a composite lithium negative electrode with a lithium loading of #1.

[0050] The difference from Example 2 is that the mass of lithium injected into the carbon fiber is changed from 5 mg to 6.5 mg, obtaining a composite lithium negative electrode with a lithium loading of #2; the others are exactly the same as Example 2. Example 4 This example provides a preparation method of a self-supporting composite lithium negative electrode material with controllable lithium loading, and the specific steps are as follows: Prepare a 1 mol / L zinc acetate solution. Take 38 mg of carbon fiber membrane (#1 sample) and soak it in the zinc acetate solution for 30 min. Evaporate water and ethanol at 80 °C, transfer it to a tubular furnace, heat it to 550 °C at a rate of 10 °C / min, and keep it warm for 6 h. Obtain a carbon fiber membrane loaded with zinc oxide particles.

[0051] Cut the above product into small round pieces with a diameter of 1.4 cm and a thickness of 200 μm, place them on a heating table, heat to 280 °C, take 8 mg of lithium block and place it on the carbon fiber membrane until it is completely absorbed, obtaining a composite lithium negative electrode with a lithium loading of #1.

[0052] The difference from Example 2 is that the mass of lithium injected into the carbon fiber is changed from 5 mg to 8 mg, obtaining a composite lithium negative electrode with a lithium loading of #3; the others are exactly the same as Example 2.

[0053] Example 5 This example provides a preparation method of a self-supporting composite lithium negative electrode material with controllable lithium loading, and the specific steps are as follows: Prepare a 1 mol / L zinc acetate solution. Take 38 mg of carbon fiber membrane (#1 sample) and soak it in the zinc acetate solution for 30 min. Evaporate water and ethanol at 80 °C, transfer it to a tubular furnace, heat it to 550 °C at a rate of 10 °C / min, and keep it warm for 6 h. Obtain a carbon fiber membrane loaded with zinc oxide particles.

[0054] Cut the above product into small round pieces with a diameter of 1.4 cm and a thickness of 200 μm, place them on a heating table, heat to 280 °C, take 10 mg of lithium block and place it on the carbon fiber membrane until it is completely absorbed, obtaining a composite lithium negative electrode with a lithium loading of #1.

[0055] The difference from Example 2 is that the mass of lithium injected into the carbon fiber is changed from 5 mg to 10 mg, obtaining a composite lithium negative electrode with a lithium loading of #4; the others are exactly the same as Example 2.

[0056] The present invention provides a method for preparing a self-supporting composite lithium anode material with a controllable lithium loading amount. The prepared composite lithium anode is assembled into a symmetric battery, and its performance is tested. At a current density of 1 A / cm 2 , it has a stable cycle of 400 h, and the battery also has good rate performance. Assemble a lithium iron phosphate battery for cycle performance testing, and still maintain a capacity retention rate of 92% after 400 cycles.

[0057] In summary, the present invention prepares a flexible carbon fiber membrane by electrospinning using a soluble polymer as a carbon source, uniformly loads metal oxide particles on its surface, and then prepares a composite lithium anode by melt lithium injection. The carbon fiber has a three-dimensional network structure, which alleviates the volume change during lithium stripping / deposition as a self-supporting skeleton. The interaction between the lithiumophilic metal oxide on the carbon fiber surface and lithium enables lithium to be uniformly deposited on the carbon fiber surface, inhibits the generation of lithium dendrites, and improves the cycle stability of the battery.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed claims.

[0059] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading, characterized in that: The following steps are involved: Weighing a soluble high molecular polymer, a metal acetate and a pore-forming agent in a mass ratio of 1:0.1-0.4:0.1-0.2:10, dissolving them in a dimethylformamide solution for mixing, and obtaining a precursor solution; The precursor solution is transferred to an electrospinning experimental platform to obtain an organic polymer fiber membrane; The organic polymer fiber membrane is pre-oxidized in a muffle furnace, and then placed in a tubular furnace and heated in a nitrogen atmosphere to complete carbonization to obtain a flexible carbon fiber membrane; during the process, the metal acetate is thermally decomposed and reduced to a metal element that is coated inside the carbon fiber; The obtained carbon fiber membrane is immersed in a metal salt solution with a concentration of 0.2-1 mol / L, and after drying, it is placed in a tube furnace and heated under a nitrogen atmosphere, and the metal salt is thermally decomposed into metal oxide particles attached to the surface of the carbon fiber, thereby obtaining a flexible carbon fiber membrane loaded with metal oxide particles; The carbon fiber membrane is heated, and different masses of lithium are combined with the flexible carbon fiber membrane loaded with metal oxide particles by melt-injection of lithium to obtain a self-supporting composite lithium negative electrode material with controllable lithium loading.

2. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The selected soluble high molecular polymer is polyacrylonitrile, polyvinylidene fluoride or polystyrene; the selected metal acetate is zinc acetate, copper acetate or aluminum acetate; the selected pore-forming agent is urea, ammonium bicarbonate or ferrocene.

3. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The mass ratio of the soluble high molecular polymer to the metal acetate is 3:1~3.

4. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The selected metal oxide particles are zinc oxide, lead oxide, molybdenum oxide or titanium oxide.

5. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The voltage of electrospinning was set at 12–17 kV.

6. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The pre-oxidation temperature is 200 ~ 300℃ and the holding time is more than 2h.

7. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The carbonization temperature under nitrogen atmosphere is 600 ~ 1000℃, and the holding time is more than 2h.

8. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: The heat treatment temperature in nitrogen atmosphere is 400 ~ 600℃, and the holding time is more than 3h.

9. The method for preparing a self-supporting composite lithium negative electrode material with controllable lithium loading according to claim 1, characterized in that: When lithium is injected into carbon fiber, the molten lithium temperature is 200 ~ 300℃.

10. A self-supporting composite lithium negative electrode material with controllable lithium loading, characterized in that: The preparation method is described in any one of claims 1 to 9.

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