A high-capacity, long-cycle lithium battery anode material and its preparation method

Abstract

This invention discloses a high-capacity, long-cycle lithium-ion battery anode material and its preparation method, belonging to the field of electrode material technology. The anode material is composed of natural flake graphite, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, carbon nanotubes, boron source compounds, urea, an aqueous ethanol solution, hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum nitrate hexahydrate. In the preparation process, natural flake graphite is first subjected to air-jet milling, classification, and initial spheroidization to obtain a precursor. The precursor is then mixed and stirred with the other components, dried, sieved, and sintered to obtain an intermediate. Finally, the intermediate is obtained through further air-jet milling, classification, and secondary spheroidization to obtain the final product. Compared with existing technologies, this invention effectively improves the uniformity and density of the coating layer, reduces interfacial impedance, and significantly enhances the cycle stability and rate performance of the anode material.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a high-capacity, long-cycle lithium battery anode material and its preparation method. Background Technology

[0002] Natural graphite is widely used as a negative electrode material in lithium-ion batteries due to its abundant resources and low cost. However, the anisotropy and volume expansion caused by its layered structure limit its performance in batteries with high energy density and long cycle life. To address this, researchers have modified graphite through strategies such as spheroidization, element doping, and surface coating to improve its conductivity, structural stability, and cycle life.

[0003] Chinese patent CN120545348A discloses a graphite anode material for lithium-ion batteries and its preparation method. This method improves the mechanical strength and cycle performance of the material through multi-element synergistic modification with silicon, titanium, and cerium, and a secondary spheroidization process. However, the difference in hydrolysis rate of the soluble precursor in this patent easily leads to uneven composition of the coating layer, and it does not address further optimization of interfacial conductivity through doping with light elements such as boron and nitrogen. Chinese patent CN120664523A discloses a porous carbon anode material for lithium-ion batteries and its preparation method. This method improves rate performance through multi-element doping and a hierarchical porous structure. However, the template preparation and carbonization processes of this method are complex, and the porous structure increases the specific surface area, easily triggering more side reactions, which is detrimental to long-term cycle stability.

[0004] Therefore, existing technologies still suffer from problems such as the incomplete synergistic effect of modified elements, insufficient uniformity and density of the coating layer, and interface defects caused by gas impact during sintering. There is an urgent need to develop a graphite anode material with controllable process, dense interface structure, high capacity and long cycle life, as well as its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a high-capacity, long-cycle lithium battery anode material and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A high-capacity, long-cycle lithium battery anode material comprises the following raw materials in parts by weight:

[0008] 40-100 parts natural flake graphite, 10-20 parts methyltrimethoxysilane, 20-35 parts tridecafluorooctyltriethoxysilane, 5-15 parts carbon nanotubes, 1-5 parts boron source compound, 1-5 parts urea, 200-400 parts 40-60 wt% aqueous ethanol solution, 40-60 parts hexadecyltrimethylammonium bromide, 10-25 parts tetraisopropyl titanate, and 15-30 parts lanthanum hexahydrate;

[0009] The boron source compound is at least one selected from triethyl borate, boron phosphate, phenylboronic acid, trimethyl borate, tributyl borate, and triisopropyl borate.

[0010] Preferably, the boron source compound is trimethyl borate.

[0011] The preparation method of the high-capacity, long-cycle lithium battery anode material is as follows:

[0012] Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor.

[0013] Step 2: Mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, carbon nanotubes, boron source compound, urea, and 40-60 wt% ethanol aqueous solution, and stir at room temperature for 2-5 hours; then add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum nitrate hexahydrate in sequence, and continue stirring for 4-10 hours; dry the resulting slurry, pass it through an 80-200 mesh sieve, and sinter it at 600-800℃ for 5-20 hours to obtain a graphite anode intermediate;

[0014] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

[0015] Preferably, the preparation method of the high-capacity, long-cycle lithium battery anode material is as follows:

[0016] Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor.

[0017] Step 2: Mix boron phosphate, carbon nanotubes, and a portion of a 40-60 wt% ethanol aqueous solution in a planetary ball mill. Mill the mixture at 200-500 rpm for 1-5 hours using zirconia balls as the milling media, with a ball-to-material ratio of 3-6:1, to obtain a uniformly dispersed pre-dispersed slurry. Then, mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, urea, and the remaining 40-60 wt% ethanol aqueous solution, and stir at room temperature for 0.5-2 hours. Add the pre-dispersed slurry and continue stirring for 1-4 hours. Then, add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum nitrate hexahydrate sequentially, and continue stirring for 4-10 hours. Dry the resulting slurry, pass it through an 80-200 mesh sieve, and sinter it at a controlled temperature to obtain a graphite anode intermediate.

[0018] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

[0019] A further preferred embodiment is the preparation method of the high-capacity, long-cycle lithium battery anode material as follows:

[0020] Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor.

[0021] Step 2: Mix boron phosphate, carbon nanotubes, and a portion of a 40-60 wt% ethanol aqueous solution, place the mixture in a planetary ball mill, and mill at 200-500 rpm for 1-5 hours using zirconia balls as the milling media, with a ball-to-material ratio of 3-6:1, to obtain a uniformly dispersed pre-dispersed slurry; then mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, urea, and the remaining 40-60 wt% ethanol aqueous solution, and stir at room temperature for 0.5-2 hours; then add the above pre-dispersed slurry, and continue stirring for 1-4 hours; then add sequentially... Add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum hexahydrate, and continue stirring for 4-10 hours. Dry the resulting slurry, pass it through an 80-200 mesh sieve, and then perform segmented sintering. In the pre-decomposition stage, raise the temperature to 300-400℃ at a rate of 1-3℃ / min and hold for 1-3 hours. In the pre-crystallization stage, raise the temperature to 500-600℃ at a rate of 4-6℃ / min and hold for 0.5-2 hours. In the densification stage, raise the temperature to 600-800℃ at a rate of 2-4℃ / min and hold for 5-12 hours to obtain a graphite anode intermediate.

[0022] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

[0023] The airflow pulverizing pressure in steps 1 and 3 is independently 0.2-0.5 MPa.

[0024] The grading and sieving in step 1 is carried out until the grading and sieving D50 is 12-18μm.

[0025] The sphericification in step 1 involves processing at a rotation speed of 800-1500 rpm for 30-60 minutes.

[0026] The grading and sieving in step 3 is carried out until the grading and sieving D50 is 10-16μm.

[0027] In step 3, sphericification involves running the machine at a speed of 500-1000 rpm for 10-50 minutes.

[0028] In existing technologies, when graphite is modified using silane coupling agents, the difference in hydrolysis rates of different alkoxy groups (such as ethoxy and methoxy) can lead to segregation of the coating layer composition, affecting interface uniformity. This invention discovers that by using trimethyl borate, which shares the same methoxy system as methyltrimethoxysilane, as the boron source, both exhibit synchronized hydrolysis rates in ethanol-water solutions, forming a dense Si-OBO three-dimensional cross-linked network. Simultaneously, the boron source and urea synergistically decompose to achieve boron-nitrogen co-doping, significantly reducing charge transfer impedance and stabilizing the SEI film, thereby achieving superior cycling performance compared to other soluble boron sources.

[0029] While boron phosphate provides a synergistic effect between boron and phosphorus, it is almost insoluble in aqueous ethanol solutions. When added directly, it exists as micron-sized agglomerates, which become stress concentration points and conductive network blocking points after sintering, resulting in cycling performance even worse than the control group without a boron source. This invention nanoscales boron phosphate using planetary ball milling and leverages the high aspect ratio and surface adsorption properties of carbon nanotubes to form a stable composite dispersion. This allows the nanoscale boron phosphate to uniformly adhere to the conductive network, subsequently undergoing an interfacial solid-state reaction with lanthanum nitrate to generate a composite interfacial layer of LaPO4 crystalline phase or complex and B2O3 glass phase. This achieves ternary synergistic modification of boron, phosphorus, and lanthanum, significantly reducing interfacial impedance and improving cycling stability.

[0030] During the single-stage sintering process at 700℃, organic components such as urea and silane decompose rapidly, generating a large amount of gas. This gas can easily form pores and microcracks in the incompletely cured coating layer, affecting interface integrity and long cycle life. This invention employs a three-stage sintering process: first, a pre-decomposition stage at 350℃ allows for slow gas release of the organic matter, avoiding gas impact; then, a pre-crystallization stage at 550℃ allows boron phosphate to pre-react with lanthanum oxide to form a La-POB mesophase; finally, a densification stage at 700℃ completes the composite sintering of the crystalline phase or composite with the glassy phase. This process yields a defect-free, high-density multi-component composite interface layer, reducing interfacial impedance and achieving a better cycle capacity retention rate.

[0031] Compared with existing technologies, it has the following advantages:

[0032] 1) By selecting a boron source that matches the hydrolysis rate of the silicon source, this invention achieves in-situ co-doping of boron and nitrogen, forming a uniform and dense cross-linked network, which significantly reduces the interfacial charge transfer impedance and improves the cycle stability of the anode material.

[0033] 2) This invention employs a ball milling pre-dispersion and carbon nanotube anchoring strategy for insoluble boron phosphate, which nano-sized particles and uniformly anchors them in a conductive network, achieving ternary synergistic modification of boron, phosphorus and lanthanum, and avoiding damage to the coating layer structure.

[0034] 3) The present invention adopts a segmented sintering process, which enables the organic components to decompose in a gradient and the crystalline phase or composite phase to form with the glass phase in sequence, thereby obtaining a defect-free and highly dense multi-component composite interface layer, further optimizing the interface stability and long cycle life of the material. Detailed Implementation

[0035] Main source of materials:

[0036] Natural flake graphite is selected from high-carbon flake graphite with a fixed carbon content of 94% and a particle size of 200 mesh.

[0037] The carbon nanotubes used are multi-walled carbon nanotubes with a purity of 98%, an outer diameter of 8-15 nm, and a length of 50 μm.

[0038] Methyltrimethoxysilane, CAS number 1185-55-3, is a colorless and transparent liquid with a purity of 98%.

[0039] Tridecafluorooctyltriethoxysilane, CAS No. 51851-37-7, is a fluorinated silane coupling agent with a purity of 95%.

[0040] Hexadecyltrimethylammonium bromide, CAS No. 57-09-0, is a white microcrystalline powder with a purity of 99%.

[0041] Tetraisopropyl titanate, CAS number 546-68-9, is a colorless to pale yellow liquid with a purity of 98%.

[0042] Triethyl borate, CAS number 150-46-9, is a colorless liquid with a purity of 99%.

[0043] Boron phosphate, CAS number 13308-51-5, is a white micron-sized powder with a purity of 99% and a D50 of 5μm.

[0044] Phenylated boric acid, CAS number 98-80-6, is selected as a white needle-like crystal with a purity of 98%.

[0045] Trimethyl borate, CAS number 121-43-7, is a colorless liquid with a purity of 98% and a boiling point of 67-68℃.

[0046] Tributyl borate, CAS number 688-74-4, is a colorless liquid with a purity of 98%.

[0047] Triisopropyl borate, CAS number 5419-55-6, is a colorless liquid with a purity of 98% and a boiling point of 139-141℃.

[0048] Lanthanum nitrate hexahydrate, CAS number 10277-43-7, is selected as a white crystalline powder with a purity of 99%.

[0049] Urea, CAS number 57-13-6, is selected as a white crystalline powder with a purity of 99%.

[0050] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0051] Example 1

[0052] The following is a method for preparing a high-capacity, long-cycle lithium battery anode material, in parts by weight:

[0053] Step 1: 60 parts of natural flake graphite were pulverized by airflow at a pressure of 0.3MPa, graded and sieved to a D50 of 15μm and shaped into particles, and then sent to a spheroidizing device. The particles were processed at a speed of 1100 rpm for 45 minutes to complete the initial spheroidization and obtain the spheroidized precursor.

[0054] Step 2: Mix 45 parts of the spherical precursor prepared in Step 1, 15 parts of methyltrimethoxysilane, 27 parts of tridecafluorooctyltriethoxysilane, 10 parts of carbon nanotubes, 3 parts of boron source compound, 3 parts of urea, and 300 parts of 50wt% ethanol aqueous solution, and stir at room temperature for 3.5 hours; then add 50 parts of hexadecyltrimethylammonium bromide, 16 parts of tetraisopropyl titanate, and 23 parts of lanthanum nitrate hexahydrate in sequence, and continue stirring for 6.5 hours; dry the resulting slurry, pass it through a 100-mesh sieve, and sinter it at 700℃ for 12 hours to obtain a graphite anode intermediate;

[0055] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to 0.3MPa pressure airflow pulverization and classification sieving again to control the product D50 to 13μm. Then, it is put into a spheroidizing device and run at 800 rpm for 30 minutes to achieve secondary spheroidization, and finally obtains high-capacity long-cycle lithium battery anode material.

[0056] The boron source compound is triethyl borate.

[0057] Example 2

[0058] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is boron phosphate.

[0059] Example 3

[0060] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is phenylboronic acid.

[0061] Example 4

[0062] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is trimethyl borate.

[0063] Example 5

[0064] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is tributyl borate.

[0065] Example 6

[0066] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is triisopropyl borate.

[0067] Example 7

[0068] The following is a method for preparing a high-capacity, long-cycle lithium battery anode material, in parts by weight:

[0069] Step 1: 60 parts of natural flake graphite were pulverized by airflow at a pressure of 0.3MPa, graded and sieved to a D50 of 15μm and shaped into particles, and then sent to a spheroidizing device. The particles were processed at a speed of 1100 rpm for 45 minutes to complete the initial spheroidization and obtain the spheroidized precursor.

[0070] Step 2: Mix 3 parts boron phosphate, 10 parts carbon nanotubes, and 100 parts 50wt% ethanol aqueous solution in a planetary ball mill and mill at 300 rpm for 2 hours. Use zirconia balls as the milling media and a ball-to-material ratio of 5:1 to obtain a uniformly dispersed pre-dispersed slurry. Then, mix 45 parts of the spheroidized precursor prepared in Step 1, 15 parts methyltrimethoxysilane, 27 parts tridecafluorooctyltriethoxysilane, 3 parts urea, and the remaining 200 parts 50wt% ethanol aqueous solution and stir at room temperature for 1 hour. Add the above pre-dispersed slurry and continue stirring for 2.5 hours. Then, add 50 parts hexadecyltrimethylammonium bromide, 16 parts tetraisopropyl titanate, and 23 parts lanthanum nitrate hexahydrate in sequence and continue stirring for 6.5 hours. Dry the resulting slurry, pass it through a 100-mesh sieve, and sinter it at 700℃ for 12 hours to obtain a graphite anode intermediate.

[0071] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to 0.3MPa pressure airflow pulverization and classification sieving again to control the product D50 to 13μm. Then, it is put into a spheroidizing device and run at 800 rpm for 30 minutes to achieve secondary spheroidization, and finally obtains high-capacity long-cycle lithium battery anode material.

[0072] Example 8

[0073] The following is a method for preparing a high-capacity, long-cycle lithium battery anode material, in parts by weight:

[0074] Step 1: 60 parts of natural flake graphite were pulverized by airflow at a pressure of 0.3MPa, graded and sieved to a D50 of 15μm and shaped into particles, and then sent to a spheroidizing device. The particles were processed at a speed of 1100 rpm for 45 minutes to complete the initial spheroidization and obtain the spheroidized precursor.

[0075] Step 2: Mix 3 parts boron phosphate, 10 parts carbon nanotubes, and 100 parts 50wt% ethanol aqueous solution, place in a planetary ball mill, and ball mill at 300 rpm for 2 hours. The ball milling media is zirconia balls, and the ball-to-material ratio is 5:1 to obtain a uniformly dispersed pre-dispersed slurry. Then, mix 45 parts of the spheroidized precursor prepared in Step 1, 15 parts methyltrimethoxysilane, 27 parts tridecafluorooctyltriethoxysilane, 3 parts urea, and the remaining 200 parts 50wt% ethanol aqueous solution, and stir at room temperature for 1 hour. Then add the above pre-dispersed slurry and continue stirring. Stir for 2.5 hours; then add 50 parts of hexadecyltrimethylammonium bromide, 16 parts of tetraisopropyl titanate, and 23 parts of lanthanum nitrate hexahydrate sequentially, and continue stirring for 6.5 hours; dry the resulting slurry, pass it through a 100-mesh sieve, and then perform segmented sintering. In the pre-decomposition stage, the temperature is increased to 350°C at a rate of 2°C / min and held for 2 hours; in the pre-crystallization stage, the temperature is increased to 550°C at a rate of 5°C / min and held for 1 hour; in the densification stage, the temperature is increased to 700°C at a rate of 3°C / min and held for 9 hours; thus, a graphite anode intermediate is obtained.

[0076] Step 3: The graphite anode intermediate prepared in Step 2 is subjected to 0.3MPa pressure airflow pulverization and classification sieving again to control the product D50 to 13μm. Then, it is put into a spheroidizing device and run at 800 rpm for 30 minutes to achieve secondary spheroidization, and finally obtains high-capacity long-cycle lithium battery anode material.

[0077] Comparative Example 1

[0078] The preparation method of a high-capacity, long-cycle lithium battery anode material is basically the same as that in Example 1, except that the boron source compound is not added.

[0079] Test Example 1

[0080] Electrochemical performance testing of coin cell half-cells:

[0081] The graphite anode materials prepared in Examples 1-8 and Comparative Example 1 were mixed with conductive carbon black (SuperP) and polyvinylidene fluoride (PVDF) at a mass ratio of 90:5:5, respectively. N-methylpyrrolidone (NMP) was added to form a slurry, which was then uniformly coated onto copper foil. After vacuum drying at 110°C for 12 hours, the slurry was cut into circular electrode sheets with a diameter of 12 mm. Using lithium metal sheets as the counter electrode, and 1 mol / L LiPF6 dissolved in a 1:1:1 volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) as the electrolyte, and Celgard 2400 as the separator, CR2032 coin cells were assembled in an argon-filled glove box (with water and oxygen content both below 0.1 ppm). A Blue Battery testing system was used to perform constant current charge-discharge tests at a rate of 0.1C, with a voltage range of 0.005~2.0V. The initial discharge specific capacity and initial coulombic efficiency were recorded. Cyclic testing was performed at a 0.5C rate for 200 charge-discharge cycles, and the capacity retention rate was calculated as (capacity at the 200th discharge cycle / capacity at the first discharge cycle × 100%). The results are shown in Table 1.

[0082] Table 1

[0083]

[0084] Test Example 2

[0085] Interface impedance test:

[0086] The coin cell assembled according to Test Method 1 (adjusted to 50% state of charge and left to stand for 2 hours after the first charge-discharge cycle) was connected to the electrochemical workstation. Test parameters were set as follows: frequency range 0.01Hz~100kHz, AC excitation voltage amplitude 5mV. The test was conducted at room temperature (25±1℃), and the Nyquist plot was recorded (with the real part of impedance Z' as the x-axis and the imaginary part -Z'' as the y-axis). The spectrum was fitted with an equivalent circuit using ZView or Nova software; the equivalent circuit is R... s (R) sei CPE sei (R) ct CPE ct ), where R s R is the ohmic resistance (resistance between the electrolyte and the electrode contact). sei R is the SEI film resistance. ct This represents the charge transfer resistance. For each embodiment, three parallel cells were tested, and the average value was recorded. sei and R ct The smaller the value, the better the interface stability and lithium-ion transport capability. The test results are shown in Table 2.

[0087] Table 2

[0088]

[0089] Example 4 uses trimethyl borate as the boron source. It belongs to the methoxy system, the same as methyltrimethoxysilane, and their hydrolysis rates in ethanol-water solution are matched, allowing for simultaneous hydrolysis-condensation reactions to form a uniform and dense Si-OBO three-dimensional cross-linked network. This avoids the localized component segregation that might have occurred in Example 1 due to the difference in hydrolysis rates between ethoxy and methoxy groups. Simultaneously, trimethyl borate and urea synergistically decompose during high-temperature sintering, achieving in-situ co-doping of boron and nitrogen: boron atoms, as electron-deficient elements, embed into the graphite interlayer and coating layer, improving the intrinsic electronic conductivity of the material; nitrogen atoms further modulate the interfacial band structure, enhancing the affinity between the coating layer and the electrolyte. The combined effect significantly reduces the interfacial charge transfer impedance, resulting in a more stable and dense SEI film structure. This effectively suppresses the continuous decomposition of the electrolyte and side reactions during cycling, leading to a significantly higher cycle capacity retention rate than Comparative Example 1 without a boron source.

[0090] In Example 2, when boron phosphate was directly added, its extremely low solubility in a 50 wt% ethanol aqueous solution resulted in its mechanical dispersion in the slurry as micron-sized agglomerated particles. These rigid insulating particles disrupted the continuous coating layer formed by the Si-O-Ti-La precursor during drying and sintering, becoming structural defect points and stress concentration sources. During charge-discharge cycles, microcracks formed around the particles due to volume expansion and contraction. Electrolyte penetrated along these cracks, causing repeated rupture and regeneration of the local SEI film. Simultaneously, the insulating particles blocked the carbon nanotube conductive network, significantly increasing charge transfer impedance and accelerating capacity decay. Ultimately, the cycling performance was even worse than that of Comparative Example 1 without a boron source.

[0091] In Example 7, micron-sized boron phosphate was broken down to nanoscale using a planetary ball mill. Simultaneously, utilizing the high aspect ratio and surface adsorption properties of carbon nanotubes, nano-boron phosphate was uniformly adhered to the surface of the carbon nanotubes, forming a stable carbon nanotube and boron phosphate composite dispersion, effectively inhibiting the re-agglomeration of nanoparticles. The nano-sized boron phosphate and lanthanum nitrate hexahydrate were fully contacted during sintering, undergoing an interfacial solid-phase reaction to generate a uniformly distributed crystalline phase or composite layer with the molten B₂O₃ glass phase, achieving synergistic modification of boron, phosphorus, and lanthanum. The crystalline phase or composite provides high mechanical strength and structural stability, while the B₂O₃ glass phase fills the gaps between ceramic particles and promotes lithium-ion conduction. This composite interfacial layer combines high mechanical strength with good ionic and electronic conductivity, thereby significantly reducing interfacial impedance and significantly improving cycle stability.

[0092] In conventional single-stage heating to 700℃, the organic components such as urea and silane added in the early stage decompose rapidly during the heating process, generating a large amount of gas. This can easily lead to the formation of pores and microcracks in the incompletely cured coating layer. Example 8 employs a segmented sintering process. First, in the 350℃ pre-decomposition stage, the organic components such as urea and silane decompose slowly and release gas, avoiding the rapid impact of gas on the coating layer structure. Next, in the 550℃ pre-crystallization stage, boron phosphate reacts with lanthanum oxide produced by the decomposition of lanthanum nitrate hexahydrate to form a La-POB composite intermediate phase, laying the foundation for the subsequent complete reaction. Finally, in the 700℃ densification stage, the crystalline phase or composite is fully composited with the B2O3 glass phase, resulting in a defect-free, high-density boron-phosphorus-lanthanum-silicon-titanium multi-component composite interface layer. This process effectively overcomes the microcracks and porosity problems that may remain in single-stage sintering, minimizing interfacial impedance and achieving the best cycle capacity retention rate in all examples.

Claims

1. A high-capacity, long-cycle lithium battery anode material, characterized in that, Including the following parts by weight of raw materials: 40-100 parts natural flake graphite, 10-20 parts methyltrimethoxysilane, 20-35 parts tridecafluorooctyltriethoxysilane, 5-15 parts carbon nanotubes, 1-5 parts boron source compound, 1-5 parts urea, 200-400 parts 40-60 wt% aqueous ethanol solution, 40-60 parts hexadecyltrimethylammonium bromide, 10-25 parts tetraisopropyl titanate, and 15-30 parts lanthanum hexahydrate; The boron source compound is at least one selected from triethyl borate, boron phosphate, phenylboronic acid, trimethyl borate, tributyl borate, and triisopropyl borate.

2. The high-capacity, long-cycle lithium battery anode material as described in claim 1, characterized in that, The boron source compound is trimethyl borate.

3. A method for preparing the high-capacity, long-cycle lithium battery anode material as described in any one of claims 1-2, characterized in that, The method is as follows: Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor. Step 2: Mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, carbon nanotubes, boron source compound, urea, and 40-60 wt% ethanol aqueous solution, and stir at room temperature for 2-5 hours; then add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum nitrate hexahydrate in sequence, and continue stirring for 4-10 hours; dry the resulting slurry, pass it through an 80-200 mesh sieve, and sinter it at 600-800℃ for 5-20 hours to obtain a graphite anode intermediate; Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

4. The method as described in claim 3, characterized in that, The airflow pulverizing pressure in steps 1 and 3 is independently 0.2-0.5 MPa.

5. The method as described in claim 3, characterized in that, The grading and sieving in step 1 is carried out until the grading and sieving D50 is 12-18μ2.

6. The method as described in claim 3, characterized in that, The sphericification in step 1 involves processing at a rotation speed of 800-1500 rpm for 30-60 minutes.

7. The method as described in claim 3, characterized in that, The grading and sieving in step 3 is carried out until the grading and sieving D50 is 10-16μm.

8. The method as described in claim 3, characterized in that, In step 3, sphericification involves running the machine at a speed of 500-1000 rpm for 10-50 minutes.

9. The method as described in claim 3, characterized in that, The preparation method of the high-capacity, long-cycle lithium battery anode material is as follows: Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor. Step 2: Mix boron phosphate, carbon nanotubes, and a portion of a 40-60 wt% ethanol aqueous solution in a planetary ball mill. Mill the mixture at 200-500 rpm for 1-5 hours using zirconia balls as the milling media, with a ball-to-material ratio of 3-6:1, to obtain a uniformly dispersed pre-dispersed slurry. Then, mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, urea, and the remaining 40-60 wt% ethanol aqueous solution, and stir at room temperature for 0.5-2 hours. Add the pre-dispersed slurry and continue stirring for 1-4 hours. Then, add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum nitrate hexahydrate sequentially, and continue stirring for 4-10 hours. Dry the resulting slurry, pass it through an 80-200 mesh sieve, and sinter it at a controlled temperature to obtain a graphite anode intermediate. Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

10. The method as described in claim 3, characterized in that, The preparation method of the high-capacity, long-cycle lithium battery anode material is as follows: Step 1: After natural flake graphite is subjected to airflow pulverization, classification and sieving, and particle shaping, it is initially spheroidized to obtain a spheroidized precursor. Step 2: Mix boron phosphate, carbon nanotubes, and a portion of a 40-60 wt% ethanol aqueous solution, place the mixture in a planetary ball mill, and mill at 200-500 rpm for 1-5 hours using zirconia balls as the milling media, with a ball-to-material ratio of 3-6:1, to obtain a uniformly dispersed pre-dispersed slurry; then mix the spheroidized precursor prepared in Step 1, methyltrimethoxysilane, tridecafluorooctyltriethoxysilane, urea, and the remaining 40-60 wt% ethanol aqueous solution, and stir at room temperature for 0.5-2 hours; then add the above pre-dispersed slurry, and continue stirring for 1-4 hours; then add sequentially... Add hexadecyltrimethylammonium bromide, tetraisopropyl titanate, and lanthanum hexahydrate, and continue stirring for 4-10 hours. Dry the resulting slurry, pass it through an 80-200 mesh sieve, and then perform segmented sintering. In the pre-decomposition stage, raise the temperature to 300-400℃ at a rate of 1-3℃ / min and hold for 1-3 hours. In the pre-crystallization stage, raise the temperature to 500-600℃ at a rate of 4-6℃ / min and hold for 0.5-2 hours. In the densification stage, raise the temperature to 600-800℃ at a rate of 2-4℃ / min and hold for 5-12 hours to obtain a graphite anode intermediate. Step 3: The graphite anode intermediate prepared in Step 2 is subjected to airflow pulverization and classification sieving again, and then spheroidized a second time to finally obtain a high-capacity, long-cycle lithium battery anode material.

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