A negative electrode material for fast-charging lithium-ion batteries and its preparation method

Abstract

This invention discloses a negative electrode material for fast-charging lithium-ion batteries and its preparation method, comprising the following steps: sulfonating iron-composite porous graphite in a reaction vessel, adding nano-silicon and polyacrylic acid, vacuum drying, annealing, then ball milling and centrifuging, collecting the bottom precipitate, and vacuum drying to obtain the negative electrode material for fast-charging lithium-ion batteries. The negative electrode material for fast-charging lithium-ion batteries prepared by this invention improves the conductivity and ion transport capacity of the lithium-ion battery negative electrode by embedding nano-silicon and iron oxide (Fe3O4) in porous graphite; by coating the surface of nano-silicon with a carbon layer formed by polyacrylic acid, the volume expansion of nano-silicon during charging and discharging is reduced; and by generating a precursor of iron oxide in situ on the surface of porous graphite, the iron oxide is generated based on the structure of the precursor, resulting in uniform bonding with porous graphite, a large specific surface area, and good ion transport efficiency, thereby improving the charging speed and charging efficiency of the negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery material technology, specifically relating to a negative electrode material for fast-charging lithium-ion batteries and its preparation method. Background Technology

[0002] With the rapid growth of the global electric vehicle market and the increasing demand for fast-charging battery technology, the development of high-performance lithium-ion batteries with fast-charging capabilities has become an inevitable trend. However, the application of silicon-based anodes in lithium-ion batteries faces key technical obstacles such as volume expansion, capacity degradation during fast charging, and safety hazards.

[0003] Silicon has a band gap, which limits the availability of charge carriers compared to traditional anode materials such as graphite, resulting in lower conductivity. This hinders efficient electron transport during fast charge-discharge cycles. During fast charging, the current is large and needs to pass through the anode material quickly and efficiently. The low conductivity of silicon leads to increased internal resistance, which limits the charging speed of silicon-based anodes.

[0004] Chinese invention patent application CN118198292A discloses a fast-charging negative electrode material, its preparation method, and its application. The material includes porous graphite and a nano-solid electrolyte embedded in the pores of the porous graphite. The conductivity of graphite is improved by using a nano-solid electrolyte slurry with strong conductivity. However, the mixing method of the nano-solid electrolyte slurry and porous graphite in this scheme is only physical vibration mixing. This method is greatly affected by the dispersibility of the nano-solid electrolyte slurry. The nano-sized material is prone to agglomeration, resulting in a small improvement in the conductivity of the obtained negative electrode material.

[0005] Chinese invention patent application CN114538431A discloses a fast-charging graphite anode material for lithium batteries and its preparation method. It uses small-diameter primary single particles to shorten the lithium-ion transport path, and uses resin to make hard carbon to coat the primary single particles, resulting in larger graphitized secondary particles, which increases the carbon layer spacing and is beneficial to lithium-ion transport. However, this scheme uses pure carbon material as the battery anode material, resulting in low energy density of the battery anode material. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of how to improve the conductivity, current transmission speed and energy density of lithium-ion battery anode materials, and to provide a fast-charging lithium-ion battery anode material and its preparation method.

[0007] This invention improves the conductivity and ion transport capacity of lithium-ion battery anode materials by embedding nano-silicon and iron oxide into porous graphite, and reduces the volume expansion of nano-silicon during charging and discharging by coating the surface of nano-silicon with a carbon layer formed by polyacrylic acid, thereby increasing the energy density of the anode material.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for preparing a negative electrode material for fast-charging lithium-ion batteries includes the following steps:

[0010] Step 1: In a reaction vessel, mix iron-composite porous graphite with 65-75 wt% ethanol aqueous solution, dissolve p-toluenesulfonic acid in deionized water and add it to the reaction vessel, stir for 20-24 h, then add nano-silicon, heat to 80-90℃, sonicate for 1-2 h, then add polyacrylic acid, stir for 3-4 h, filter and collect the precipitate, wash the precipitate, and vacuum dry to obtain silicon / iron composite porous graphite.

[0011] Step 2: Place the silicon / iron composite porous graphite in a tube furnace and anneal it at 450-480℃ for 120-150 min at a rate of 5℃ / min in an argon atmosphere to obtain iron oxide / silicon composite porous graphite. Ball mill the iron oxide / silicon composite porous graphite to a particle size of 10-20μm, centrifuge it in an ethanol solution, collect the bottom layer precipitate, and vacuum dry it at 60-70℃ to obtain the negative electrode material for fast-charging lithium-ion batteries.

[0012] Furthermore, in step one, the ratio of iron-composite porous graphite, ethanol aqueous solution, p-toluenesulfonic acid, deionized water, nano-silicon and polyacrylic acid is 10-20g: 500-800mL: 4-6g: 200-400mL: 10-15g: 2-3g.

[0013] Furthermore, the iron-coated porous graphite is prepared by the following steps:

[0014] In a reaction vessel, a porous graphite dispersion and a trimesic acid ethanol solution were mixed. Ferric nitrate nonahydrate was dissolved in an ethanol aqueous solution and added to the reaction vessel for ultrasonic mixing. The mixture was heated to 110-130℃ and reacted in a sealed container for 20-24 hours. After cooling, the precipitate was collected by filtration, washed, and vacuum dried to obtain iron-composite porous graphite. The ethanol aqueous solution had a mass fraction of 65-75%.

[0015] Furthermore, the ratio of porous graphite dispersion, pyromellitic acid ethanol solution, ferric nitrate nonahydrate and ethanol aqueous solution is 500-800mL: 100-150mL: 10-20g: 100-150mL.

[0016] Furthermore, the porous graphite dispersion is prepared by mixing porous graphite with an aqueous ethanol solution at a ratio of 10-20g: 500-800mL; the pyromellitic acid ethanol solution is prepared by mixing pyromellitic acid and anhydrous ethanol at a ratio of 8-10g: 100-150mL.

[0017] Furthermore, porous graphite is prepared by the following steps:

[0018] Sodium chloride, cellulose fibers, and mesophase pitch at 300-350℃ are stirred and mixed in an argon atmosphere for 3-4 hours in a reactor. Then, the reactor is heated to 400-450℃ and reacted at a pressure of 2-2.5MPa for 2-3 hours. After cooling, the mixture is washed with deionized water and dried at 100-120℃ to obtain pitch intermediate foam. The foam is then carbonized at 850-900℃ for 60-70 minutes under nitrogen protection at a rate of 5℃ / min to obtain carbonized foam. Finally, the mixture is graphitized at 2500-2600℃ to obtain porous graphite.

[0019] Furthermore, the mass ratio of sodium chloride, cellulose fiber, and mesophase pitch is 8-10:20-30:350-400.

[0020] Furthermore, both the mesophase pitch and sodium chloride were ground through a 200-mesh sieve.

[0021] Furthermore, the cellulose fibers are wood fibers, with a length of 10-15 μm and a diameter of 1-2 μm.

[0022] The beneficial effects of this invention are:

[0023] (1) The fast-charging lithium-ion battery anode material prepared by the present invention improves the conductivity and ion transport capacity of the lithium-ion battery anode by embedding nano-silicon and iron oxide in porous graphite, reduces the volume expansion of nano-silicon during charging and discharging by coating the surface of nano-silicon with a carbon layer formed by polyacrylic acid, and generates the precursor Fe-MOF of iron oxide in situ on the surface of porous graphite, so that iron oxide is generated on the basis of the Fe-MOF structure, and has a uniform degree of bonding with porous graphite, a large specific surface area, and good ion transport efficiency, thereby improving the charging speed and charging efficiency of the anode material.

[0024] (2) The preparation method of the present invention prepares porous graphite by mixing refined coal tar pitch with sodium chloride and cellulose fiber. The resulting porous graphite has abundant pores and cracks, high specific surface area and strong conductivity. Fe-MOF is generated in situ on the surface of porous graphite, so that Fe-MOF is uniformly combined in the pores and cracks of porous graphite. The modification effect of sulfonic acid groups on porous graphite and Fe-MOF is used to make nano-silicon uniformly attached under the cross-linking effect of sulfonic acid groups, increasing the dispersion of nano-silicon in porous graphite. Finally, polyacrylic acid is used to coat nano-silicon and anneal at high temperature to oxidize Fe-MOF into iron oxide, improve ion transport capacity, and high temperature carbonization is used to carbonize the ligands in polyacrylic acid and Fe-MOF, so that nano-silicon is coated with carbon layer, reducing the volume expansion of nano-silicon and improving the bonding strength of nano-silicon, iron oxide and porous graphite. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: A method for preparing a negative electrode material for fast-charging lithium-ion batteries, comprising the following steps:

[0027] S1. In a reactor, refined coal tar pitch is heated to 400°C under a nitrogen atmosphere and stirred for 5 hours. After purging with nitrogen for 3 hours, it is cooled and ground through a 200-mesh sieve to obtain mesophase pitch. In the reactor, 8g of sodium chloride ground through a 200-mesh sieve, 20g of cellulose fiber, and 350g of 300°C mesophase pitch are stirred and mixed under an argon atmosphere for 3 hours. Then, the reactor is heated to 400°C and reacted under a pressure of 2MPa for 2 hours. After cooling, it is washed with deionized water and dried at 100°C to obtain pitch intermediate foam. Under nitrogen protection, it is heated to 850°C at a rate of 5°C / min and carbonized for 60 minutes to obtain carbonized foam. Finally, it is heated to 2500°C for graphitization to obtain porous graphite.

[0028] S2. In a reaction vessel, 10g of porous graphite was mixed with 500mL of 65wt% ethanol aqueous solution to obtain a porous graphite dispersion. 8g of trimellitic acid was dissolved in 100mL of anhydrous ethanol to obtain a trimellitic acid ethanol solution. 500mL of the porous graphite dispersion and 100mL of the trimellitic acid ethanol solution were added to the reaction vessel and ultrasonically mixed for 20min. Then, 10g of ferric nitrate nonahydrate was dissolved in 100mL of 65wt% ethanol aqueous solution and added to the reaction vessel and ultrasonically mixed for 20min. The mixture was heated to 110℃ and reacted in a sealed container for 20h. After cooling, the precipitate was collected by filtration, washed with ethanol and deionized water, and vacuum dried at 60℃ for 10h to obtain iron-composite porous graphite.

[0029] S3. In a reaction vessel, 10g of iron-composite porous graphite was mixed with 500mL of 65wt% ethanol aqueous solution. 4g of p-toluenesulfonic acid was dissolved in 200mL of deionized water and added to the reaction vessel. The mixture was stirred for 20h. Then, 10g of nano-silicon powder was added, the temperature was raised to 80℃, and the mixture was sonicated for 1h. Then, 2g of polyacrylic acid was added and stirred for 3h. The precipitate was collected by filtration, washed with ethanol and deionized water, and dried under vacuum at 60℃ for 10h to obtain silicon / iron composite porous graphite.

[0030] S4. After crushing the silicon / iron composite porous graphite through a 200-mesh sieve, it is placed in a tube furnace and annealed at 450°C for 120 min at a rate of 5°C / min in an argon atmosphere to obtain iron oxide / silicon composite porous graphite. The iron oxide / silicon composite porous graphite is ball-milled to a particle size of 10 μm, centrifuged in an ethanol solution, and the bottom layer precipitate is collected and vacuum dried at 60°C to obtain the negative electrode material for fast-charging lithium-ion batteries.

[0031] Example 2: A method for preparing a negative electrode material for fast-charging lithium-ion batteries, comprising the following steps:

[0032] S1. In a reactor, refined coal tar pitch is heated to 425°C under a nitrogen atmosphere and stirred for 5.5 hours. After purging with nitrogen for 3.5 hours, it is cooled and ground through a 200-mesh sieve to obtain mesophase pitch. In the reactor, 9g of sodium chloride ground through a 200-mesh sieve, 25g of cellulose fiber, and 375g of 325°C mesophase pitch are stirred and mixed under an argon atmosphere for 3.5 hours. Then, the reactor is heated to 425°C and reacted under a pressure of 2.25MPa for 2.5 hours. After cooling, it is washed with deionized water and dried at 110°C to obtain pitch intermediate foam. Under nitrogen protection, it is heated to 875°C at a rate of 5°C / min and carbonized for 65 minutes to obtain carbonized foam. Finally, it is heated to 2550°C for graphitization to obtain porous graphite.

[0033] S2. In a reaction vessel, 15g of porous graphite was mixed with 650mL of 70wt% ethanol aqueous solution to obtain a porous graphite dispersion. 9g of trimellitic acid was dissolved in 125mL of anhydrous ethanol to obtain a trimellitic acid ethanol solution. 650mL of the porous graphite dispersion and 125mL of the trimellitic acid ethanol solution were added to the reaction vessel and ultrasonically mixed for 25min. Then, 15g of ferric nitrate nonahydrate was dissolved in 125mL of 70wt% ethanol aqueous solution and added to the reaction vessel and ultrasonically mixed for 25min. The mixture was heated to 120℃ and reacted in a sealed container for 22h. After cooling, the precipitate was collected by filtration, washed with ethanol and deionized water, and dried under vacuum at 65℃ for 11h to obtain iron-composite porous graphite.

[0034] S3. In a reaction vessel, 15g of iron-composite porous graphite was mixed with 650mL of 70wt% ethanol aqueous solution. 5g of p-toluenesulfonic acid was dissolved in 300mL of deionized water and added to the reaction vessel. The mixture was stirred for 22h. Then, 12.5g of nano-silicon powder was added, the temperature was raised to 85℃, and the mixture was sonicated for 1.5h. Then, 2.5g of polyacrylic acid was added, and the mixture was stirred for 3.5h. The precipitate was collected by filtration, washed with ethanol and deionized water, and dried under vacuum at 65℃ for 11h to obtain silicon / iron composite porous graphite.

[0035] S4. After crushing the silicon / iron composite porous graphite through a 200-mesh sieve, it is placed in a tube furnace and annealed at 465°C for 135 min at a rate of 5°C / min in an argon atmosphere to obtain iron oxide / silicon composite porous graphite. The iron oxide / silicon composite porous graphite is ball-milled to a particle size of 15 μm, centrifuged in an ethanol solution, and the bottom layer precipitate is collected and vacuum dried at 65°C to obtain the negative electrode material for fast-charging lithium-ion batteries.

[0036] Example 3: A method for preparing a negative electrode material for fast-charging lithium-ion batteries, comprising the following steps:

[0037] S1. In a reactor, refined coal tar pitch is heated to 450°C under a nitrogen atmosphere and stirred for 6 hours. After purging with nitrogen for 4 hours, it is cooled and ground through a 200-mesh sieve to obtain mesophase pitch. In the reactor, 10g of sodium chloride ground through a 200-mesh sieve, 30g of cellulose fiber, and 400g of 350°C mesophase pitch are stirred and mixed under an argon atmosphere for 4 hours. Then, the reactor is heated to 450°C and reacted under a pressure of 2.5MPa for 3 hours. After cooling, it is washed with deionized water and dried at 120°C to obtain pitch intermediate foam. Under nitrogen protection, it is heated to 900°C at a rate of 5°C / min and carbonized for 70 minutes to obtain carbonized foam. Finally, it is heated to 2600°C for graphitization to obtain porous graphite.

[0038] S2. In a reaction vessel, 20g of porous graphite was mixed with 800mL of 75wt% ethanol aqueous solution to obtain a porous graphite dispersion. 10g of trimellitic acid was dissolved in 150mL of anhydrous ethanol to obtain a trimellitic acid ethanol solution. 800mL of the porous graphite dispersion and 150mL of the trimellitic acid ethanol solution were added to the reaction vessel and ultrasonically mixed for 30min. Then, 20g of ferric nitrate nonahydrate was dissolved in 150mL of 75wt% ethanol aqueous solution and added to the reaction vessel and ultrasonically mixed for 30min. The temperature was raised to 130℃ and the reaction was sealed for 24h. After cooling, the precipitate was collected by filtration, washed with ethanol and deionized water, and vacuum dried at 70℃ for 12h to obtain iron composite porous graphite.

[0039] S3. In a reaction vessel, 20g of iron-composite porous graphite was mixed with 800mL of 75wt% ethanol aqueous solution. 6g of p-toluenesulfonic acid was dissolved in 400mL of deionized water and added to the reaction vessel. The mixture was stirred for 24h. Then, 15g of nano-silicon powder was added, the temperature was raised to 90℃, and the mixture was sonicated for 2h. Then, 3g of polyacrylic acid was added, and the mixture was stirred for 4h. The precipitate was collected by filtration, washed with ethanol and deionized water, and dried under vacuum at 70℃ for 12h to obtain silicon / iron composite porous graphite.

[0040] S4. After crushing the silicon / iron composite porous graphite through a 200-mesh sieve, it is placed in a tube furnace and annealed at 480°C for 150 min at a rate of 5°C / min in an argon atmosphere to obtain iron oxide / silicon composite porous graphite. The iron oxide / silicon composite porous graphite is ball-milled to a particle size of 20 μm, centrifuged in an ethanol solution, and the bottom layer precipitate is collected and vacuum dried at 70°C to obtain the negative electrode material for fast-charging lithium-ion batteries.

[0041] Invention Principle: Using pitch mesophase as raw material, sodium chloride as template, and cellulose fibers as porous channels, graphite with a porous structure is prepared. By utilizing the difference in graphitization rate and volume between cellulose and pitch mesophase, the proportion of pores and cracks in the porous graphite is increased, thereby increasing the deposition area of ​​Fe-MOF and nano-silicon. Fe-MOF is generated in situ via hydrothermal treatment on the porous graphite surface, and then uniformly composited with conductive graphite on the surface and in the pores. The Fe-MOF ligands in the iron / graphite composite powder are sulfonated with toluenesulfonic acid, and the porous graphite surface is modified with sulfonic acid. The electrostatic attraction between the sulfonic acid groups and the basic centers of nano-silicon is utilized... Hydrogen bonding is used to uniformly composite nano-silicon onto the surface of iron / graphite composite powder. Then, the grafting effect of polyacrylic acid and sulfonic acid groups is used to coat the porous graphite surface with polyacrylic acid, thus encapsulating the nano-silicon on the porous graphite surface. After high-temperature annealing, Fe-MOF is oxidized into iron(III) oxide. The anode material doped with iron(III) oxide has high specific capacity, cycle stability, and rate capability. The high-temperature annealing process also carbonizes the ligands in Fe-MOF and polyacrylic acid, forming a strong carbon structure that encapsulates the nano-silicon in the porous graphite. This reduces the volume expansion of the nano-silicon during charging and discharging, improves conductivity and ion transport efficiency, and increases the charging speed.

[0042] Cellulose fibers are wood fibers, 10-15 μm in length and 1-2 μm in diameter.

[0043] Comparative Example 1: The difference from Example 1 is that cellulose fibers are not added in S1 to obtain a negative electrode material for fast-charging lithium-ion batteries.

[0044] Comparative Example 2: The difference from Example 1 is that, in S2, 10g of porous graphite was mixed with 500mL of 65wt% ethanol aqueous solution in a reaction vessel, and 8g of nano-iron was added to the reaction vessel and ultrasonically mixed for 20min to obtain iron composite porous graphite, thus preparing a negative electrode material for fast-charging lithium-ion batteries.

[0045] Comparative Example 3: The difference from Example 1 is that p-toluenesulfonic acid is not added in S3, and a negative electrode material for fast-charging lithium-ion batteries is obtained.

[0046] The performance of the fast-charging lithium-ion battery anode materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested. 80 mg of the fast-charging lithium-ion battery anode material was used as the active material, and 10 mg of conductive carbon black and 10 mg of polyvinylidene fluoride were mixed in agate slurry to form a uniform ink. This ink was then coated onto an 18 μm copper foil using a doctor blade and dried at 80°C for 1 hour, followed by vacuum drying for 3 hours. The prepared electrode was then fabricated into a 10 mm diameter disk. The electrolyte used was a silicon-based anode material electrolyte (1 mol / L LiPF6, EC:DEC = 1:1, 10% FEC). The separator was made of PP material, and the lithium foil was used as the counter electrode. A CR2032 type lithium half-cell was assembled. The batteries corresponding to Examples 1-3 and Comparative Examples 1-3 were tested at 0.2 A g. -1 and 1A g -1 Its rate performance was tested at a certain current density, and the discharge capacity was tested after 50 cycles. The capacity decay rate was calculated, and the results are shown in Table 1.

[0047] Table 1

[0048]

[0049] As shown in Table 1, the battery assembled with the fast-charging lithium-ion battery anode material prepared by the present invention has a high specific capacity. Even under high current density charging and discharging, it can still maintain a high battery capacity. After 50 cycles, the capacity decrease rate is low. Even under high current density, the capacity decrease rate is still less than 50%. This indicates that the fast-charging lithium-ion battery anode material prepared by the present invention has high stability, fast current transmission speed, and high discharge capacity.

[0050] Comparative Example 1, due to the absence of cellulose fibers, resulted in a smaller crack content in the porous graphite and a lower degree of Fe-MOF-porous graphite composite, thus its performance was slightly lower than that of Examples 1-3.

[0051] In Comparative Example 2, due to the physical mixing of nano-iron and porous graphite, the nano-iron tends to agglomerate, resulting in a low degree of dispersion on the surface of porous graphite and poor performance of the prepared anode material.

[0052] In Comparative Example 3, due to the absence of p-toluenesulfonic acid, the nano-silicon was prone to agglomeration, resulting in low dispersion in porous graphite. The agglomerated nano-silicon particles exhibited a large volume expansion rate during charging and discharging, leading to damage to the negative electrode material and a significant capacity reduction rate.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a negative electrode material for fast-charging lithium-ion batteries, characterized in that, Includes the following steps: Step 1: Mix iron-composite porous graphite with 65-75 wt% ethanol aqueous solution in a reaction vessel. Dissolve p-toluenesulfonic acid in deionized water and add it to the reaction vessel. Stir for 20-24 h. Then add nano-silicon, heat to 80-90℃, and sonicate for 1-2 h. Then add polyacrylic acid and stir for 3-4 h. Filter and collect the precipitate, wash the precipitate, and vacuum dry to obtain silicon / iron composite porous graphite. Step 2: Place the silicon / iron composite porous graphite in a tube furnace and anneal it at 450-480℃ for 120-150 min at a rate of 5℃ / min in an argon atmosphere to obtain iron oxide / silicon composite porous graphite. Ball mill the iron oxide / silicon composite porous graphite to a particle size of 10-20μm, centrifuge it in an ethanol solution, collect the bottom layer precipitate, and vacuum dry it at 60-70℃ to obtain the negative electrode material for fast-charging lithium-ion batteries. The iron-composite porous graphite is prepared by the following steps: In a reaction vessel, a porous graphite dispersion and a pyromellitic acid ethanol solution were mixed. Ferric nitrate nonahydrate was dissolved in a 65-75 wt% ethanol aqueous solution and added to the reaction vessel for ultrasonic mixing. The mixture was heated to 110-130℃ and reacted in a sealed container for 20-24 hours. After cooling, the precipitate was collected by filtration, washed, and vacuum dried to obtain iron composite porous graphite. The porous graphite dispersion is prepared by mixing porous graphite with an aqueous ethanol solution at a ratio of 10-20g: 500-800mL; the pyromellitic acid ethanol solution is prepared by mixing pyromellitic acid and anhydrous ethanol at a ratio of 8-10g: 100-150mL. The porous graphite is prepared by the following steps: Sodium chloride, cellulose fibers, and mesophase pitch at 300-350℃ are stirred and mixed in an argon atmosphere for 3-4 hours in a reactor. Then, the reactor is heated to 400-450℃ and reacted at a pressure of 2-2.5MPa for 2-3 hours. After cooling, the mixture is washed with deionized water and dried at 100-120℃ to obtain pitch intermediate foam. The foam is then carbonized at 850-900℃ for 60-70 minutes under nitrogen protection at a rate of 5℃ / min to obtain carbonized foam. Finally, the mixture is graphitized at 2500-2600℃ to obtain porous graphite.

2. The method for preparing a negative electrode material for a fast-charging lithium-ion battery according to claim 1, characterized in that, In step one, the ratio of iron-composite porous graphite, ethanol aqueous solution, p-toluenesulfonic acid, deionized water, nano-silicon and polyacrylic acid is 10-20g: 500-800mL: 4-6g: 200-400mL: 10-15g: 2-3g.

3. The method for preparing a negative electrode material for a fast-charging lithium-ion battery according to claim 1, characterized in that, The ratio of the porous graphite dispersion, pyromellitic acid ethanol solution, ferric nitrate nonahydrate, and ethanol aqueous solution is 500-800 mL: 100-150 mL: 10-20 g: 100-150 mL.

4. The method for preparing a negative electrode material for a fast-charging lithium-ion battery according to claim 1, characterized in that, The mass ratio of sodium chloride, cellulose fiber and mesophase pitch is 8-10:20-30:350-400.

5. The method for preparing a negative electrode material for a fast-charging lithium-ion battery according to claim 4, characterized in that, Both the mesophase pitch and sodium chloride were ground through a 200-mesh sieve.

6. The method for preparing a negative electrode material for a fast-charging lithium-ion battery according to claim 4, characterized in that, The cellulose fiber is wood fiber, with a length of 10-15 μm and a diameter of 1-2 μm.

7. A negative electrode material for fast-charging lithium-ion batteries, characterized in that, It is prepared by the method for preparing the negative electrode material for fast-charging lithium-ion batteries according to any one of claims 1-6.

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