Nanostructure-based lithium ion battery negative electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a nano-structure-based lithium ion battery negative electrode material and a preparation method thereof. The preparation method comprises the following steps: S1, mixing ferric salt, cobalt salt, lanthanum salt, a first carbon source and water, and then freeze-drying to obtain a precursor; s2, performing Joule heat shock on the precursor to obtain an intermediate A; s3, carrying out ball milling on the intermediate A and a second carbon source to obtain an intermediate B; and S4, sintering the intermediate B to obtain the lithium ion battery negative electrode material. The lithium ion battery negative electrode material based on the nano structure prepared by the invention can simultaneously realize the effects of high capacity, high first efficiency and long cycle life.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a lithium-ion battery anode material based on a nanostructure and its preparation method. Background Technology

[0002] Lithium-ion batteries, as a core representative of modern electrochemical energy storage technology, have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage since their commercialization in 1991. With increasing societal demands for energy density, cycle life, and safety performance, the research and development of key materials for lithium-ion batteries has received growing attention. Among these, the anode material, as the primary component for lithium-ion insertion / extraction, directly impacts the overall performance of the battery.

[0003] Traditional commercial graphite anode materials, due to their low theoretical specific capacity and general rate performance, are no longer sufficient to meet the needs of high energy density devices. To address this, existing processes have developed various novel anode materials such as silicon-based, tin-based, and transition metal oxides. Among them, iron-based and cobalt-based transition metal oxides have attracted much attention due to their abundant resources, environmental friendliness, and high theoretical capacity. However, these materials have the following problems in practical applications: (1) Transition metal oxides undergo significant volume changes during charge and discharge, which leads to a decrease in the cycle stability of the battery; (2) The above materials are more likely to form a solid electrolyte interphase (SEI) film and irreversible phase transition during the first charge and discharge process, consuming a large amount of lithium ions, which will reduce the actual energy density of the lithium battery. CN113707861A provides a nitrogen-doped carbon layer-coated cobalt oxide nanosheet and its preparation method and energy storage application. It prepares nitrogen-doped carbon layer-coated cobalt oxide nanosheets by solvothermal synthesis, using polyvinylpyrrolidone as a nitrogen source and carbon source, and calcining at high temperature to form a nitrogen-doped carbon layer, thereby improving the conductivity of cobalt oxide and lithium ion active sites. However, its single carbon coating layer is insufficient to buffer the volume change of the material during charging and discharging, resulting in poor structural stability. Furthermore, its conductivity improvement depends entirely on the external carbon layer, and its interface resistance is relatively large, which limits the further improvement of rate performance.

[0004] Therefore, there is an urgent need for a negative electrode material that can simultaneously achieve high capacity, high initial efficiency, and long cycle life. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-ion battery anode material based on a nanostructure and its preparation method. The lithium-ion battery anode material of this invention can simultaneously achieve high capacity, high initial efficiency, and long cycle life.

[0006] The first aspect of this invention provides a method for preparing a lithium-ion battery anode material based on a nanostructure, the method comprising the following steps: S1. Iron salt, cobalt salt, lanthanum salt, first carbon source and water are mixed and then freeze-dried to obtain the precursor; S2. Subject the precursor to Joule thermal shock to obtain intermediate A; S3. Intermediate A and the second carbon source are ball-milled to obtain intermediate B; S4. Sinter intermediate B to obtain lithium-ion battery anode material.

[0007] The lithium-ion battery anode material of this invention exhibits high capacity, high initial efficiency, and excellent cycle stability through the synergistic effect of iron-cobalt-lanthanum multi-element combination, along with "dual carbon" source coating and sulfur-selenium doping. This is presumably because the lanthanum doping and specific Joule thermal shock process in this invention enable the final lithium-ion battery anode material to possess a stable nanoporous framework structure, effectively mitigating volume expansion. Subsequently, the two-step carbon coating in steps S1 and S2 better constructs a continuous conductive network, and finally, sintering increases the material's conductivity, structural stability, and interfacial ion transport efficiency.

[0008] Furthermore, the cobalt salt is selected from at least one of cobalt chloride, cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt acetate tetrahydrate, preferably cobalt sulfate heptahydrate.

[0009] Furthermore, the iron salt is selected from at least one of ferrous sulfate heptahydrate, ferric nitrate nonahydrate, and ferric chloride, preferably ferrous sulfate heptahydrate.

[0010] Furthermore, the lanthanum salt is selected from at least one of lanthanum nitrate hexahydrate, lanthanum sulfate, and lanthanum carbonate, preferably lanthanum nitrate hexahydrate.

[0011] Further, the first carbon source is selected from polyvinylpyrrolidone and / or polyacrylamide, preferably polyvinylpyrrolidone; even further, the average molecular weight of the polyvinylpyrrolidone is 30,000~60,000 g / mol, preferably 40,000 g / mol.

[0012] Further, in step S1, the iron salt is calculated as iron element, the cobalt salt as cobalt element, and the lanthanum salt as lanthanum element, and the molar ratio of the iron salt, cobalt salt, and lanthanum salt is 1:(0.3~0.7):(0.01~0.1), preferably 1:0.5:0.04.

[0013] In this invention, controlling the molar ratio of iron salt, cobalt salt, and lanthanum salt within the aforementioned range achieves a synergistic improvement in high specific capacity, excellent cycle stability, and high initial coulombic efficiency. This is presumably because lanthanum has a large ionic radius and a unique 4f electron layer structure, which can suppress the aggregation and growth of iron-cobalt active particles and structural collapse during cycling, while stabilizing the crystal framework and reducing volume changes during lithium-ion insertion / extraction, thus achieving ultra-high cycle stability while ensuring high capacity. However, research revealed that excessive lanthanum content actually reduces the performance of the anode material, presumably because excessive lanthanum content leads to over-dilution of the active sites.

[0014] Further, in step S1, the mass ratio of the first carbon source to the total mass of the iron salt, cobalt and lanthanum salt is (1~8):1, preferably (4~6):1.

[0015] Further, in step S1, the total mass ratio of the iron salt, cobalt salt, and lanthanum salt to the mass-volume ratio of the water is 1~20 mg / mL, preferably 8~12 mg / mL.

[0016] Furthermore, in step S1, the mixing conditions include stirring at 40~50°C for 2~3 hours.

[0017] Further, in step S1, the freeze-drying conditions include: freezing in liquid nitrogen at -80°C for 18 to 30 hours, then transferring to a freeze dryer, drying at -40°C for 24 to 30 hours under a vacuum of <10 Pa, and then heating to 20 to 40°C and drying for 8 to 15 hours.

[0018] Further, in step S2, the conditions for the Joule thermal shock include: a temperature of 1000~1500℃ and a time of 10~15 seconds. Specifically, the Joule thermal shock can be performed in a Joule thermal shock apparatus, that is, the precursor is loaded into the support of the Joule thermal shock apparatus, and then the support containing the precursor is firmly clamped between two electrode clamps in the reaction chamber, connected to the positive and negative electrodes respectively through wires, vacuum treatment for 10 minutes, the power supply in the Joule heat treatment apparatus is turned on, and a voltage of 30~40V and a current of 300~400A are applied for a duration of 10~15 seconds, and the temperature of the Joule thermal shock treatment is 1000~1500℃.

[0019] Furthermore, the second carbon source is selected from at least one of cellulose, sucrose, and glucose, preferably glucose.

[0020] In this invention, it was found that controlling the first carbon source to be polyvinylpyrrolidone (PVP) and the second carbon source to be glucose can better increase the rate performance and cycle stability of the anode material. This is presumably because the long molecular chain of PPVP acts as an excellent dispersing template in step S1, forming a uniform precursor with the metal salt. After pyrolysis, it generates nitrogen-doped conductive graphitized carbon, which provides the main electron transport channels and structural support. The glucose added in step S3 adheres to the surface of intermediate A and carbonizes to form amorphous carbon. The interaction between the two carbon layers can better improve the carbon matrix density to suppress the aggregation and volume expansion of active materials. The specific functional groups of both also contribute to the formation of a stable solid electrolyte interface film, thereby synergistically improving the rate performance and cycle stability of the material.

[0021] Further, in step S3, the mass ratio of the intermediate to the second carbon source is 1:(0.3~2), preferably 1:(0.85~1.2).

[0022] Further, in step S3, the conditions for ball milling include: a rotation speed of 400~1000 rpm, a ball milling time of 10~30 hours, and a ball-to-material ratio of (10~25):1. Preferably, the rotation speed is 500~800 rpm, the ball milling time is 12~15 hours, and the ball-to-material ratio is (18~22):1.

[0023] Furthermore, in step S4, the sintering conditions include: For the first sintering, the temperature is first increased to 350-400℃ at a rate of 1-3℃ / min and held for 1.5-2 hours; The second sintering is then carried out, followed by heating to 550-600℃ at a rate of 1-3℃ / min and holding for 3-5 hours. The third sintering is carried out, followed by heating to 700-800℃ at a rate of 5-8℃ / min and holding for 1.5-3 hours; The fourth sintering is performed, followed by cooling to 500-550℃ at a rate of 0.3-0.5℃ / min and holding for 1-1.5 hours.

[0024] Furthermore, the first sintering is carried out in a sulfur vapor and nitrogen atmosphere with a volume ratio of (0.2~0.3):1.

[0025] Furthermore, the second sintering is carried out in a selenium vapor and nitrogen atmosphere with a volume ratio of (0.2~0.3):1.

[0026] Furthermore, the third and fourth sintering processes are carried out under a nitrogen atmosphere.

[0027] In this invention, it was found that controlling the sintering conditions within the aforementioned range can better increase the rate performance and cycle stability of the anode material. This is presumably because the first sintering stage, conducted in the presence of sulfur vapor, allows sulfur to preferentially incorporate into the material surface and shallow layers, forming a stable sulfide interface layer, which facilitates the formation of the initial SEI film and improves the first-stage efficiency. The second sintering stage, conducted in the presence of selenium vapor, allows selenium atoms to penetrate deep into the bulk phase, expanding the lattice spacing and promoting lithium-ion transport. Simultaneously, it forms a concentration gradient with the previously sulfur-doped layer. The third sintering stage crystallizes the material, and the fourth sintering stage releases the lattice stress formed in the previous stages, reducing defect concentration. Ultimately, a structurally complete and interface-stable anode material is obtained, resulting in high first-stage efficiency and excellent cycle retention.

[0028] The second aspect of the present invention provides a lithium-ion battery anode material based on a nanostructure, wherein the lithium-ion battery anode material based on a nanostructure is prepared by the preparation method of the lithium-ion battery anode material based on a nanostructure described in the first aspect of the present invention.

[0029] The nanostructure-based lithium-ion battery anode material of this invention can be used to prepare batteries according to any method in the art, and this invention has no special limitations on this.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: The anode material in this invention can simultaneously achieve high capacity, high initial efficiency, and long cycle life. This is presumably because lanthanum doping effectively stabilizes the crystal structure, followed by the formation of a porous nanomatrix using a specific Joule-thermal second-level reaction. Furthermore, the combination of a "dual-carbon" conductive network and staged doping with sulfur and selenium atmospheres optimizes interfacial ion transport. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1 This embodiment provides a method for preparing a lithium-ion battery anode material, which includes the following steps: S1. Ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, lanthanum nitrate hexahydrate, polyvinylpyrrolidone (molecular weight 40000 g / mol) and water were stirred at 45°C for 2.5 hours, then frozen in liquid nitrogen at -80°C for 24 hours. Afterwards, the mixture was transferred to a freeze dryer and dried at -40°C for 28 hours under a vacuum of <10 Pa, and then heated to 25°C and dried for 12 hours to obtain the precursor. The molar ratio of iron in ferrous sulfate heptahydrate, cobalt in cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 1:0.5:0.04, the mass ratio of polyvinylpyrrolidone to the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 5:1, and the mass-volume ratio of the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate to water was 10 mg / mL. S2. The precursor is loaded into the support of the Joule thermal shock apparatus. Then, the support containing the precursor is firmly clamped between the two electrode clamps in the reaction chamber. The precursor is connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule heat treatment apparatus is turned on, and a voltage of 40V and a current of 350A are applied for 12 seconds. The Joule thermal shock treatment temperature is 1100℃ to obtain intermediate A. S3. Intermediate A with a mass ratio of 1:1 and glucose are ball-milled at a speed of 600 rpm for 13 hours with a ball-to-material ratio of 20:1 to obtain intermediate B. S4. Sinter intermediate B to obtain a lithium-ion battery anode material; wherein the sintering conditions include: in a sulfur vapor and nitrogen atmosphere with a volume ratio of 0.25:1, first heating to 380℃ at a rate of 2℃ / min and holding for 2 hours; then heating to 560℃ at a rate of 2℃ / min and holding for 4 hours in a selenium vapor and nitrogen atmosphere with a volume ratio of 0.25:1; then heating to 720℃ at a rate of 6℃ / min and holding for 2 hours in a nitrogen atmosphere; and then cooling to 550℃ at a rate of 0.5℃ / min and holding for 1 hour in a nitrogen atmosphere.

[0033] Example 2 This embodiment provides a method for preparing a lithium-ion battery anode material, which includes the following steps: S1. Ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, lanthanum nitrate hexahydrate, polyvinylpyrrolidone (molecular weight 40000 g / mol) and water were stirred at 50°C for 2 hours, then frozen in liquid nitrogen at -80°C for 24 hours. After that, the mixture was transferred to a freeze dryer and dried at -40°C for 30 hours under a vacuum of <10 Pa, and then heated to 25°C and dried for 12 hours to obtain the precursor. The molar ratio of iron in ferrous sulfate heptahydrate, cobalt in cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 1:0.5:0.04, the mass ratio of polyvinylpyrrolidone to the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 4:1, and the mass-volume ratio of the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate to water was 10 mg / mL. S2. The precursor is loaded into the support of the Joule thermal shock apparatus. The support containing the precursor is then securely clamped between two electrode clamps within the reaction chamber, connected to the positive and negative electrodes respectively via wires. A vacuum is applied for 10 minutes. The power supply in the Joule thermal shock apparatus is then turned on, applying a voltage of 40V and a current of 400A for 10 seconds. The Joule thermal shock temperature is 1200℃, yielding intermediate A. S3. Intermediate A and glucose at a mass ratio of 1:1.2 are ball-milled at a speed of 800 rpm for 12 hours with a ball-to-material ratio of 20:1 to obtain intermediate B. S4. Sinter intermediate B to obtain a lithium-ion battery anode material. The sintering conditions include: in a sulfur vapor and nitrogen atmosphere with a volume ratio of 0.2:1, first heating to 350°C at a rate of 2°C / min and holding for 2 hours; then heating to 550°C at a rate of 2°C / min and holding for 4.5 hours in a selenium vapor and nitrogen atmosphere with a volume ratio of 0.3:1; then heating to 700°C at a rate of 5°C / min and holding for 3 hours in a nitrogen atmosphere; and finally cooling to 550°C at a rate of 0.5°C / min and holding for 1 hour in a nitrogen atmosphere.

[0034] Example 3 This embodiment provides a method for preparing a lithium-ion battery anode material, which includes the following steps: S1. Ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, lanthanum nitrate hexahydrate, polyvinylpyrrolidone (molecular weight 40000 g / mol) and water were stirred at 40°C for 3 hours, then frozen in liquid nitrogen at -80°C for 30 hours. After that, the mixture was transferred to a freeze dryer and dried at -40°C for 24 hours under a vacuum of <10 Pa, and then heated to 25°C and dried for 12 hours to obtain the precursor. The molar ratio of iron in ferrous sulfate heptahydrate, cobalt in cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 1:0.5:0.04, the mass ratio of polyvinylpyrrolidone to the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate was 6:1, and the mass-volume ratio of the total mass of ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, and lanthanum nitrate hexahydrate to water was 12 mg / mL. S2. The precursor is loaded into the support of the Joule thermal shock apparatus. Then, the support containing the precursor is firmly clamped between the two electrode clamps in the reaction chamber. The precursor is connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule heat treatment apparatus is turned on, and a voltage of 30V and a current of 300A are applied for 15 seconds. The Joule thermal shock treatment temperature is 1000℃ to obtain intermediate A. S3. Intermediate A with a mass ratio of 1:0.85 is ball-milled with glucose at a speed of 500 rpm for 15 hours with a ball-to-material ratio of 20:1 to obtain intermediate B. S4. Sinter intermediate B to obtain a lithium-ion battery anode material; wherein the sintering conditions include: in a sulfur vapor and nitrogen atmosphere with a volume ratio of 0.3:1, first heating to 400℃ at a rate of 3℃ / min and holding for 1.5 hours; then heating to 600℃ at a rate of 3℃ / min and holding for 3 hours in a selenium vapor and nitrogen atmosphere with a volume ratio of 0.2:1; then heating to 800℃ at a rate of 8℃ / min and holding for 1.5 hours in a nitrogen atmosphere; and then cooling to 500℃ at a rate of 0.5℃ / min and holding for 1.5 hours in a nitrogen atmosphere.

[0035] Comparative Example 1 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: In step S1, ferrous sulfate heptahydrate, cobalt sulfate heptahydrate, polyvinylpyrrolidone (molecular weight 40000 g / mol) and water were stirred at 40°C for 3 hours, then frozen in liquid nitrogen at -80°C for 30 hours. After that, the mixture was transferred to a freeze dryer and dried at -40°C for 24 hours under a vacuum of <10 Pa, and then heated to 25°C and dried for 12 hours to obtain the precursor. The molar ratio of iron in ferrous sulfate heptahydrate to cobalt in cobalt sulfate heptahydrate was 1:0.504, the mass ratio of polyvinylpyrrolidone to the total mass of ferrous sulfate heptahydrate and cobalt sulfate heptahydrate was 6:1, and the mass-volume ratio of the total mass of ferrous sulfate heptahydrate and cobalt sulfate heptahydrate to water was 12 mg / mL.

[0036] Comparative Example 2 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: The molar ratio of iron in ferrous sulfate heptahydrate, cobalt in cobalt sulfate heptahydrate, and lanthanum in lanthanum nitrate hexahydrate is 1:0.5:0.2.

[0037] Comparative Example 3 This comparative example provides a method for preparing a lithium-ion battery anode material. The preparation method is the same as that in Example 1, except that: in step S1, polyvinylpyrrolidone (molecular weight of 40000 g / mol) is replaced with glucose, and in step S3, glucose is replaced with polyvinylpyrrolidone (molecular weight of 40000 g / mol).

[0038] Comparative Example 4 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: In step S2, the precursor is sintered at 800°C in a nitrogen atmosphere for 2 hours to obtain intermediate A.

[0039] Comparative Example 5 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: Without step S3, intermediate A is directly sintered according to the method in step S4 to obtain the lithium-ion battery anode material.

[0040] Comparative Example 6 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: In step S4, the sintering conditions include: under a selenium vapor and nitrogen atmosphere with a volume ratio of 0.25:1, first heating to 380°C at a rate of 2°C / min and holding for 2 hours; then heating to 560°C at a rate of 2°C / min and holding for 4 hours under a sulfur vapor and nitrogen atmosphere with a volume ratio of 0.25:1; then heating to 720°C at a rate of 6°C / min and holding for 2 hours under a nitrogen atmosphere; and then cooling to 550°C at a rate of 0.5°C / min and holding for 1 hour under a nitrogen atmosphere.

[0041] Comparative Example 7 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: In step S4, the sintering conditions include: under a nitrogen atmosphere, first heating to 380°C at a rate of 2°C / min and holding for 2 hours; then heating to 560°C at a rate of 2°C / min and holding for 4 hours under a nitrogen atmosphere with a selenium vapor and nitrogen atmosphere at a volume ratio of 0.25:1; then heating to 720°C at a rate of 6°C / min and holding for 2 hours under a nitrogen atmosphere; and then cooling to 550°C at a rate of 0.5°C / min and holding for 1 hour under a nitrogen atmosphere.

[0042] Comparative Example 8 This comparative example provides a method for preparing a lithium-ion battery anode material, which is the same as in Example 1, except that: The sintering conditions included: in a sulfur vapor and nitrogen atmosphere with a volume ratio of 0.25:1, the temperature was first raised to 380°C at a rate of 2°C / min and held for 2 hours; then, in a nitrogen atmosphere, the temperature was raised to 560°C at a rate of 2°C / min and held for 4 hours; then, in a nitrogen atmosphere, the temperature was raised to 720°C at a rate of 6°C / min and held for 2 hours; and finally, in a nitrogen atmosphere, the temperature was lowered to 550°C at a rate of 0.5°C / min and held for 1 hour.

[0043] Performance testing Battery assembly: Weigh out lithium-ion battery anode materials (the lithium-ion battery anode materials in Examples 1-3 and Comparative Examples 1-8, respectively), conductive carbon black conductive agent, and polyvinylidene fluoride binder in a mass ratio of 80:10:10. Using N-methylpyrrolidone as a solvent, mix the lithium-ion battery anode materials, conductive carbon black conductive agent, polyvinylidene fluoride binder, and N-methylpyrrolidone evenly to obtain a negative electrode slurry with a solid content of 55wt%. Coat the negative electrode slurry onto copper foil and vacuum dry it at 90°C for 6 hours. Then roll and punch it to obtain small circular electrode sheets with a certain area. In a vacuum glove box, use a lithium metal sheet as the counter electrode, a polypropylene microporous membrane as the separator, and 1mol / L LiPF6 / EC:DMC:DEC (volume ratio 1:1:1) as the electrolyte to assemble a CR2025 coin cell.

[0044] First-cycle discharge specific capacity test: At 25℃ and normal pressure, the coin cell is discharged at a constant current rate of 0.1C to a voltage of 0.005V, and then discharged at a constant current rate of 0.05C to a voltage of 0.005V. The discharge specific capacity at this time is recorded, which is the first discharge specific capacity.

[0045] First Coulomb efficiency and 300-cycle capacity retention test: Under normal temperature and pressure conditions, the coin cell battery was discharged at a constant current rate of 0.1C to a voltage of 0.005V, and then discharged at a constant current rate of 0.05C to a voltage of 0.005V. The discharge specific capacity at this point was recorded, which is the first discharge capacity. Subsequently, it was charged at a constant current rate of 0.1C to a voltage of 2.5V, and the charging specific capacity at this point was recorded, which is the first charging capacity. The coin cell battery was subjected to 300 charge-discharge cycles using the above method, and the discharge specific capacity was recorded for each cycle.

[0046] Initial coulombic efficiency (%) = (first discharge specific capacity / first charge specific capacity) × 100%. 300-cycle capacity retention rate (%) = (300-cycle discharge specific capacity / first-cycle discharge specific capacity) × 100%.

[0047] The electrochemical test results are shown in Table 1.

[0048] Table 1 Electrochemical test results

[0049] As can be seen from the above performance test results, the lithium-ion battery anode materials in Examples 1-3 have excellent electrochemical performance, and the lithium-ion batteries containing the lithium-ion battery anode materials of the present invention have excellent first-cycle discharge specific capacity, first coulombic efficiency and cycle performance.

[0050] The comparative examples, lacking the necessary technical solutions, showed significantly worse performance than the examples in relevant tests. Comparative Example 1 lacked lanthanum salt, while Comparative Example 2 used excessively high amounts of lanthanum salt, resulting in a significant decrease in battery capacity and cycle performance. This is presumably because the absence of lanthanum salt reduces the structural site stability of the lithium-ion battery anode material, while excessive amounts of lanthanum salt can damage the nanostructure of the final anode material, leading to poor performance. In Comparative Example 3, the order of adding polyvinylpyrrolidone and glucose differed from Example 1, ultimately leading to reduced electrochemical performance, indicating that the order of adding polyvinylpyrrolidone and glucose is crucial in this invention. Comparative Example 4 used conventional sintering instead of Joule thermal shock in Example 1, ultimately resulting in reduced electrochemical performance, possibly because Joule thermal shock better forms nanostructures. Comparative Example 5 did not add a second carbon source (glucose), leading to reduced electrochemical performance, presumably because the lack of a second carbon source affects the carbon uniformity and conductivity of the final product. Compared with Example 1 and Comparative Example 6, the order of sulfur and selenium atmospheres was changed, and sulfur vapor was used in Comparative Example 7. The electrochemical performance of the batteries was reduced in both cases. In Comparative Example 8, there was no selenium atmosphere. Although the battery had a higher first-cycle discharge specific capacity, the first coulombic efficiency and cycle performance were severely reduced. The comparison between Example 1 and Comparative Examples 6-8 further illustrates that in this invention, sulfur and selenium doping are carried out simultaneously, and their specific doping order affects the bulk stability of the negative electrode material, leading to a decrease in performance.

[0051] The above experimental results further demonstrate the importance of the technical solution defined in this invention to its technical effect.

[0052] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium-ion battery anode material based on a nanostructure, characterized in that, The preparation includes the following steps: S1. Iron salt, cobalt salt, lanthanum salt, first carbon source and water are mixed and then freeze-dried to obtain the precursor; S2. Subject the precursor to Joule thermal shock to obtain intermediate A; S3. Intermediate A and the second carbon source are ball-milled to obtain intermediate B; S4. Sinter intermediate B to obtain lithium-ion battery anode material.

2. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, The cobalt salt is selected from at least one of cobalt chloride, cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt acetate tetrahydrate; the iron salt is selected from at least one of ferrous sulfate heptahydrate, ferric nitrate nonahydrate, and ferric chloride; the lanthanum salt is selected from at least one of lanthanum nitrate hexahydrate, lanthanum sulfate, and lanthanum carbonate; and the first carbon source is selected from polyvinylpyrrolidone and / or polyacrylamide.

3. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, In step S1: the iron salt is calculated as iron element, the cobalt salt as cobalt element, and the lanthanum salt as lanthanum element; the molar ratio of the iron salt, cobalt salt, and lanthanum salt is 1:(0.3~0.7):(0.01~0.1); the mass ratio of the first carbon source to the total mass of the iron salt, cobalt salt, and lanthanum salt is (1~8):1; and the mass-volume ratio of the total mass of the iron salt, cobalt salt, and lanthanum salt to the mass-volume ratio of the water is 1~20 mg / mL.

4. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, In step S1: the mixing conditions include stirring at 40~50°C for 2~3 hours; the freeze-drying conditions include freezing in liquid nitrogen at -80°C for 18~30 hours, then transferring to a freeze dryer, drying at -40°C for 24~30 hours under a vacuum of <10Pa, and then heating to 20~40°C and drying for 8~15 hours.

5. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, In step S2, the conditions for the Joule thermal shock include: a temperature of 1000~1500℃ and a time of 10~15 seconds.

6. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, The second carbon source is selected from at least one of cellulose, sucrose, and glucose.

7. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 1, characterized in that, In step S3: the mass ratio of the intermediate to the second carbon source is 1:(0.3~2); the ball milling conditions include: a rotation speed of 400~1000 rpm, a ball milling time of 10~30 hours, and a ball-to-material ratio of (10~25):

1.

8. The method for preparing the nanostructure-based lithium-ion battery anode material according to any one of claims 1 to 7, characterized in that, In step S4, the sintering conditions include: For the first sintering, the temperature is first increased to 350-400℃ at a rate of 1-3℃ / min and held for 1.5-2 hours; The second sintering is then carried out, followed by heating to 550-600℃ at a rate of 1-3℃ / min and holding for 3-5 hours. The third sintering is carried out, followed by heating to 700-800℃ at a rate of 5-8℃ / min and holding for 1.5-3 hours; The fourth sintering is performed, followed by cooling to 500-550℃ at a rate of 0.3-0.5℃ / min and holding for 1-1.5 hours.

9. The method for preparing the lithium-ion battery anode material based on nanostructure according to claim 8, characterized in that, The first sintering is carried out in a sulfur vapor and nitrogen atmosphere with a volume ratio of (0.2~0.3):1; the second sintering is carried out in a selenium vapor and nitrogen atmosphere with a volume ratio of (0.2~0.3):1; the third and fourth sintering are carried out in a nitrogen atmosphere.

10. A lithium-ion battery anode material based on a nanostructure, characterized in that, The nanostructure-based lithium-ion battery anode material is prepared by the preparation method of the nanostructure-based lithium-ion battery anode material according to any one of claims 1 to 9.

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