Low-cost high-first-effect long-cycle silicon monoxide carbon composite negative electrode material and large-scale preparation method thereof

Abstract

The invention provides a low-cost high-first-effect long-cycle silicon monoxide carbon composite negative electrode material and a large-scale preparation method thereof, and belongs to the technical field of lithium ion battery negative electrode materials. The preparation method of the silicon monoxide carbon composite negative electrode material comprises the steps of SiOx preparation, water system dispersion pulping, shell enrichment construction, spray granulation forming, high-temperature cracking carbonization and post-treatment and collection, and controllable stoichiometric SiOx is prepared through solid phase mechanical activation-inert atmosphere heat treatment. And an internal and external double-carbon coating structure is constructed by combining aqueous dispersion spray granulation and continuous carbonization, so that large-scale preparation with low cost, high first efficiency and long cycle performance is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of anode materials for lithium-ion batteries, and particularly relates to a low-cost, high first-cycle efficiency, long-cycle-life silicon suboxide-carbon composite anode material and a large-scale preparation method thereof. Background Art

[0002] With the increasing requirements of power batteries and energy storage batteries for energy density and cycle life, the capacity of traditional graphite anodes is limited and it is difficult to meet the demand for higher energy density. Silicon oxide (SiOx, 0 < x < 2) is considered to be one of the important candidate materials for the industrialization of silicon-based anodes because of its relatively high reversible capacity, rich raw material sources, and milder volume effect compared with pure silicon.

[0003] However, there are still obvious deficiencies in the practical application of existing SiOx materials: on the one hand, irreversible phases such as Li2O and lithium silicate are easily formed during the first-cycle lithium intercalation process of SiOx. At the same time, if the specific surface area of the material is too high, it will aggravate the decomposition of the electrolyte and the continuous growth of the SEI film, resulting in a large irreversible capacity loss in the first cycle and a low first-cycle Coulomb efficiency; on the other hand, the stress accumulation caused by repeated lithium intercalation and deintercalation is likely to lead to particle cracking, pulverization, and the destruction of the conductive network. The continuous exposure of fresh surfaces further induces side reactions and impedance increase, resulting in capacity attenuation and insufficient cycle stability.

[0004] In addition, from an engineering perspective, some existing technologies use routes such as vacuum evaporation, vapor deposition, or multiple high-temperature treatments to improve coating or structural stability, which have problems such as large equipment investment, high energy consumption, limited production capacity, or long process chains; although some processes can reduce costs, they often only perform simple mechanical mixing or non-dense carbon coating, resulting in uneven carbon distribution, discontinuous shell layers, and insufficient control of specific surface area, making it difficult to achieve a balance among "high first-cycle efficiency - long cycle - high compaction - low cost and ton-scale scalability".

[0005] Therefore, there is an urgent need for a preparation method of SiOx / carbon composite anode materials with low production cost, ton-scale continuous preparation, and good batch-to-batch consistency, which can achieve high first-cycle efficiency and long-cycle performance by reducing the specific surface area, constructing a stable conductive / toughening structure, and suppressing interfacial side reactions. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a low-cost, high-efficiency, long-cycle silicon suboxide-carbon composite anode material and its large-scale preparation method. This invention uses industrial silicon powder and industrial silica as raw materials, employing solid-phase mechanical activation followed by inert atmosphere heat treatment to prepare stoichiometrically controllable SiOx. Then, it constructs low-specific-surface-area secondary particles through aqueous dispersion and spray granulation, increasing tap density and reducing side reactions. Finally, it employs a "stepwise carbon precursor introduction + shell enrichment - stabilization - carbonization densification" process to construct an inner carbon conductive and tough network and an outer dense carbon shell, inhibiting electrolyte penetration and excessive SEI growth. This achieves high initial efficiency and long-cycle performance while maintaining high reversible capacity, thus reducing production costs and meeting the requirements for ton-scale continuous production.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method, comprising the following steps: Industrial silicon powder and silicon dioxide powder are mechanically activated and mixed to obtain a uniformly mixed powder; The uniformly mixed powder was heat-treated under an inert atmosphere to obtain SiOx powder; The SiOx powder was dispersed in water, and conductive carbon black and a first carbon precursor were added to obtain a uniform slurry. A second carbon precursor is added to the homogeneous slurry and dispersed to obtain a composite slurry, which is then spray-dried and granulated to obtain a secondary particle composite precursor. The secondary particle composite precursor is subjected to pre-oxidation stabilization and inert atmosphere carbonization in sequence to obtain the silicon suboxide carbon composite anode material.

[0008] Furthermore, the mass ratio of industrial silicon powder to silicon dioxide powder is (20-60):(80-40). By adjusting the mass ratio of industrial silicon powder to silicon dioxide powder, x in SiOx powder satisfies 0.8≤x≤1.3. The preferred mass ratio of industrial silicon powder to silicon dioxide powder is (35-50):(50-70).

[0009] Furthermore, the silica powder is selected from silica micropowder (also known as microsilica powder), precipitated silica (composed of silica), or a combination thereof.

[0010] Further, the heat treatment temperature is 850–1200℃, and the holding time is 0.5–6h; preferably, the temperature is 900–1050℃, and the holding time is 1.5–3h.

[0011] Further, the amount of conductive carbon black added is 0.5-5% of the total mass of the SiOx powder, and the solid content of the uniform slurry is 35-55%; preferably, the amount of conductive carbon black added is 1.5-2.5% of the total mass of the SiOx powder, and the solid content of the uniform slurry is 42-48%.

[0012] Furthermore, the first carbon precursor is selected from phenolic resin aqueous solution and / or asphalt emulsion; the second carbon precursor is selected from sugar solution and / or low softening point asphalt emulsion.

[0013] Furthermore, after adding the second carbon precursor, the total carbon content in the composite slurry is 10-35 wt%; preferably, the total carbon content in the composite slurry is 15-30 wt%.

[0014] Furthermore, the D of the secondary particle composite precursor 50 The value is 5–20 μm; preferably, D 50 It is 10–18 μm.

[0015] Further, the pre-oxidation stabilization temperature is 200-300℃ and the time is 0.5-2h; preferably, the temperature is 230-260℃ and the time is 1-1.5h.

[0016] Furthermore, the inert atmosphere carbonization is carried out under N2 or Ar atmosphere at a temperature of 600–1100°C for 1–3 hours; preferably, the inert atmosphere carbonization is carried out under N2 atmosphere at a temperature of 800–950°C for 2–2.5 hours.

[0017] Furthermore, after the inert atmosphere carbonization treatment is completed, the carbonized products are also subjected to airflow classification, iron removal, homogenization and batch mixing, and packaging.

[0018] Technical principle: In the preparation method of this invention, mechanical activation breaks the inert layer on the surface of the raw material particles, increasing the contact area between Si and SiO2 and generating lattice defects, providing kinetic conditions for subsequent solid-state reactions. Simultaneously, it controls the particle size of the mixed powder, reducing the introduction of metal impurities. Inert atmosphere heat treatment under N2 / Ar protection avoids oxidation or reduction of the raw materials. High temperatures of 850–1200℃ promote a solid-state reaction between Si and SiO2 to generate stoichiometrically controllable SiOx (0.8 ≤ x ≤ 1.3), solving the problem of severe volume effects in pure silicon. Furthermore, water is used as the dispersion medium to avoid pollution and high costs associated with organic solvents. Conductive carbon black pre-constructs a preliminary conductive pathway, and the first carbon precursor (phenolic resin aqueous solution / asphalt emulsion) is adsorbed and anchored on the surface of the SiOx particles, forming an internal carbon network. The formation of the network lays the foundation; the introduced second carbon precursor (sugar / low softening point asphalt emulsion) is mobile and accumulates on the surface of the droplets during the solvent evaporation process of spray drying, forming a shell precursor layer; at the same time, the slurry is transformed into secondary particles, which significantly reduces the specific surface area, reduces electrolyte contact and side reactions, and increases the tap density; the pre-oxidation treatment (200-300℃) causes the carbon precursor to be slightly cross-linked, avoiding particle cracking or carbon shell damage during carbonization; carbonization at 600-1100℃ transforms the first carbon precursor into an inner carbon conductive toughness network (buffering volume effect, maintaining conductive pathway), and the second carbon precursor into an outer dense carbon shell (inhibiting electrolyte penetration and reducing excessive growth of SEI film), ultimately forming a composite structure of "SiOx host + inner carbon network + outer carbon shell".

[0019] The present invention also provides a silicon suboxide carbon composite anode material prepared according to the above preparation method, wherein the silicon suboxide carbon composite anode material comprises a SiOx host, an inner carbon conductive toughness network and an outer dense carbon shell, and the total carbon content is 10-35 wt%.

[0020] The present invention also provides an application of the above-mentioned silicon suboxide carbon composite anode material in the preparation of lithium-ion battery anodes.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Low cost and scale-up to ton level: Industrial silicon powder and industrial silica are used as raw materials. The process adopts mature equipment such as continuous ball milling, spray drying and rotary kiln / push plate furnace carbonization, avoiding high investment routes such as vacuum evaporation and CVD, and is suitable for continuous production at the ton level.

[0022] (2) High first-cycle efficiency: Spray granulation forms secondary particles with low specific surface area and forms a continuous and dense outer carbon shell through shell enrichment-stabilization-carbonization, which reduces electrolyte penetration and side reaction area, inhibits excessive SEI growth, and thus significantly improves the first-cycle coulombic efficiency.

[0023] (3) Long-term cycle stability: The inner carbon conductive toughness network maintains electrical contact and buffers volume effect during cycling, while the outer dense carbon shell enhances interface stability and structural integrity, reduces pulverization and contact failure, and significantly improves cycle life.

[0024] (4) Balance between capacity and compaction: By adjusting the SiOx stoichiometry and carbon phase distribution, the balance between capacity, first-efficiency and cycle is achieved; the secondary particle structure improves the tap density and the consistency of electrode compaction, which is conducive to the improvement of energy density. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the preparation process of a silicon suboxide carbon composite anode material according to the present invention; Figure 2 The image shows a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1. Figure 3 This is the first charge-discharge curve of the silicon suboxide carbon composite anode material obtained in Example 1; Figure 4 The graph shows the cycle performance of the silicon suboxide carbon composite anode material obtained in Example 3. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] This invention provides a low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method, comprising the following steps: Industrial silicon powder and silicon dioxide powder are mechanically activated and mixed to obtain a uniformly mixed powder; The uniformly mixed powder was heat-treated under an inert atmosphere (N2 and / or Ar) to obtain SiOx powder; SiOx powder was dispersed in water, and conductive carbon black and a first carbon precursor were added to obtain a uniform slurry. A second carbon precursor was added to a homogeneous slurry and dispersed to obtain a composite slurry, which was then spray-dried and granulated to obtain a secondary particle composite precursor. The secondary particle composite precursor was subjected to pre-oxidation stabilization and inert atmosphere carbonization in sequence to obtain silicon suboxide carbon composite anode material.

[0032] In a preferred embodiment of the present invention, mechanical activation is carried out in a continuous ball mill, stirred mill, or sand mill, preferably controlling the uniform mixing of powder D. 50 The thickness is 2–8 μm, and low-wear lining and abrasive media are used to reduce the introduction of metal impurities such as Fe.

[0033] In a preferred embodiment of the present invention, the mass ratio of industrial silicon powder to silicon dioxide powder is (20-60):(80-40), preferably (30-50):(50-70). By adjusting the mass ratio of industrial silicon powder to silicon dioxide powder, x in SiOx powder satisfies 0.8≤x≤1.3.

[0034] In a preferred embodiment of the present invention, the silica powder is selected from silica micropowder, precipitated silica, or a combination thereof.

[0035] In a preferred embodiment of the present invention, the heat treatment temperature is 850–1200°C, and the holding time is 0.5–6 h (calculated based on the residence time for continuous rotary kilns).

[0036] In a preferred embodiment of the present invention, the amount of conductive carbon black added is 0.5 to 5% of the total mass of SiOx powder, and the solid content of the homogeneous slurry is 35 to 55%.

[0037] In a preferred embodiment of the present invention, the first carbon precursor is selected from phenolic resin aqueous solution and / or asphalt emulsion; the second carbon precursor is selected from sugar solution and / or low softening point asphalt emulsion, wherein the sugar solution includes glucose solution and / or sucrose solution.

[0038] In a preferred embodiment of the present invention, after adding the second carbon precursor, the total carbon content in the composite slurry is 10-35 wt%.

[0039] In a preferred embodiment of the present invention, the D of the secondary particle composite precursor 50 The size ranges from 5 to 20 μm.

[0040] In a preferred embodiment of the present invention, the pre-oxidation stabilization temperature is 200–300°C and the time is 0.5–2 h.

[0041] In a preferred embodiment of the present invention, inert atmosphere carbonization is carried out under N2 or Ar atmosphere at a temperature of 600–1100°C for 1–3 hours.

[0042] In a preferred embodiment of the present invention, after the inert atmosphere carbonization treatment is completed, the carbonization product is further subjected to airflow classification, iron removal, homogenization and batch mixing and packaging.

[0043] More specifically, this invention provides a method for preparing a silicon suboxide carbon composite anode material, including SiOx preparation, aqueous dispersion slurry preparation, shell enrichment construction, spray granulation molding, high-temperature pyrolysis carbonization, and post-processing and collection steps (see flowchart). Figure 1 Specifically, it includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and silica powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silica powder (selected from silica micro powder, precipitated silica or a combination thereof) is (20-60): (80-40), preferably (30-50): (50-70). By adjusting the mass ratio of industrial silicon powder to silica powder, x in SiOx powder satisfies 0.8≤x≤1.3; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous ball mill, stirred mill, or sand mill for mechanical activation mixing to obtain a uniformly mixed powder; preferably, the D of the uniformly mixed powder is controlled. 50 The thickness is 2–8 μm, and low-wear linings and abrasive media are used to reduce the introduction of metal impurities such as Fe. (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2 and / or Ar) at a temperature of 850 to 1200°C, preferably 900 to 1150°C, and the equivalent holding time is 0.5 to 6 h, preferably 1 to 4 h (calculated by residence time in continuous rotary kiln). After the heat treatment, SiOx powder is obtained. X in the SiOx powder must satisfy 0.8 ≤ x ≤ 1.3. Subsequently, air classification / sieving can be performed to obtain the target particle size (1 to 10 μm) distribution. (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and a first carbon precursor to obtain a uniform slurry; wherein, the amount of conductive carbon black is 0.5-5 wt% of SiOx powder, preferably 1-3 wt%; the first carbon precursor is selected from phenolic resin aqueous solution and / or asphalt emulsion, used to adsorb and anchor to the surface of SiOx primary particles before spray granulation and form an internal carbon conductive toughness network after carbonization; the solid content of the finally obtained uniform slurry is 35-55%, preferably 40-50%; (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry. Shear dispersion can keep the second carbon precursor mobile. During the solvent evaporation process of spray drying, the second carbon precursor migrates and enriches to the surface of the droplets to form the shell precursor layer; wherein the second carbon precursor is selected from sugar solution (glucose / sucrose) and / or low softening point asphalt emulsion, and the amount used is such that the total carbon content in the final composite slurry is 10-35 wt%, preferably 15-30 wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor. The D of the secondary particle composite precursor 50 The specific surface area is 5–20 μm, preferably 8–15 μm, in order to reduce the specific surface area and increase the tap density; (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first subjected to pre-oxidation stabilization and then carbonized in an inert atmosphere. The temperature of pre-oxidation stabilization is 200-300℃ and the time is 0.5-2h to improve carbon yield and improve the integrity of the outer carbon shell. The inert atmosphere carbonization is carried out in N2 or Ar atmosphere, the carbonization temperature is 600-1100℃, preferably 700-1000℃, and the time is 1-3h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0044] This invention also provides a silicon suboxide carbon composite anode material prepared according to the above preparation method. The silicon suboxide carbon composite anode material includes a SiOx host, an inner carbon conductive and tough network, and an outer dense carbon shell. The total carbon content is 10-35 wt%, preferably 15-30 wt%, and the BET specific surface area of ​​the material is preferably ≤10 m². 2 / g, tap density preferably ≥0.7g / cm³ 3 The material prepared in the embodiments of the present invention can be further used in the negative electrode of lithium-ion batteries.

[0045] All raw materials used in the embodiments of this invention were purchased commercially.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1 A method for preparing a silicon suboxide carbon composite anode material includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder is 45:55; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous stirred mill for mechanical activation mixing to obtain a uniformly mixed powder; the D of the uniformly mixed powder is controlled. 50 It is 5μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1000℃ and an equivalent holding time of 2h. After heat treatment, SiOx powder is obtained (the mass fractions of oxygen and silicon are measured by O / Si elemental analysis, and the x value is calculated to be approximately 1.0 to 1.1 according to x=n(O) / n(Si)). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2wt% of SiOx powder; the first carbon precursor is a mixture of phenolic resin aqueous solution and asphalt emulsion with a mass ratio of 10wt%, and the final homogeneous slurry has a solid content of 45%; (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the uniform slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a glucose solution, and the amount used is such that the total carbon content in the final composite slurry is 30wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor. The D of the secondary particle composite precursor 50It is 12μm; (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first subjected to pre-oxidation stabilization and then carbonized in an inert atmosphere. The pre-oxidation stabilization temperature is 250°C and the time is 1h. The inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 900°C and the time is 2h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0048] The specific surface area (BET) of the negative electrode material prepared in Example 1 is 7.6 μm. 2 ·g -1 The tap density is 0.78 g·cm³. -3 The total carbon content is approximately 20 wt%.

[0049] The scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 is shown below. Figure 2 As can be seen, the spherical secondary particles obtained after spray drying have relatively uniform particle size and smooth surface, indicating that the specific surface area of ​​the secondary particles is small.

[0050] Example 2 A method for preparing a silicon suboxide carbon composite anode material includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and precipitated silica are used as SiOx precursors, with the mass ratio of industrial silicon powder to precipitated silica being 50:50. (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous ball mill for mechanical activation mixing to obtain a uniformly mixed powder, and the D50 of the uniformly mixed powder is controlled to be 4-6 μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 950℃ and an equivalent holding time of 1.5h. After the heat treatment, SiOx powder is obtained (the x value is 0.85~1.0 after elemental analysis and the test method is the same as above). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a uniform slurry; wherein, the amount of conductive carbon black is 1.5wt% of SiOx powder; the first carbon precursor is an aqueous solution of phenolic resin, and the solid content of the final uniform slurry is 42%. (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a sucrose solution, and the amount used is such that the total carbon content in the final composite slurry is 20 wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 10 μm. (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first pre-oxidized and stabilized, and then carbonized in an inert atmosphere. The temperature of the pre-oxidation stabilization is 280°C and the time is 1h. The inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 850°C and the time is 2h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0051] The specific surface area (BET) of the negative electrode material prepared in Example 2 is 8.3 μm. 2 ·g -1 The tap density is 0.74 g·cm³. -3 The total carbon content is approximately 15 wt%.

[0052] Example 3 A method for preparing a silicon suboxide carbon composite anode material includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder is 35:65; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous ball mill for mechanical activation mixing to obtain a uniformly mixed powder, and the D50 of the uniformly mixed powder is controlled to be 5-7 μm; (3) Preparation of SiOx by heat treatment in an inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1050℃ and an equivalent holding time of 3h. After the heat treatment, SiOx powder is obtained (the x value is 1.15~1.30 after elemental analysis). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2.5 wt% of SiOx powder; the first carbon precursor is asphalt emulsion, and the solid content of the final homogeneous slurry is 48%; (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a glucose solution, and the amount used is such that the total carbon content in the final composite slurry is 35 wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 15 μm. (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first pre-oxidized and stabilized, and then carbonized in an inert atmosphere. The temperature of the pre-oxidation and stabilization is 260°C and the time is 1h. The inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 950°C and the time is 2h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0053] The specific surface area (BET) of the negative electrode material prepared in Example 3 was 5.9 μm. 2 ·g -1 The tap density is 0.83 g·cm³. -3 The total carbon content is approximately 30 wt%.

[0054] Example 4 A method for preparing a silicon suboxide carbon composite anode material includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder is 40:60; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous ball mill for mechanical activation mixing to obtain a uniformly mixed powder, and the D50 of the uniformly mixed powder is controlled to be 3-5 μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1020℃ and an equivalent holding time of 2.5h. After the heat treatment, SiOx powder is obtained (the x value is 1.05~1.20 after elemental analysis). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2wt% of SiOx powder; the first carbon precursor is asphalt emulsion, and the solid content of the final homogeneous slurry is 47%. (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a glucose solution, and the amount used is such that the total carbon content in the final composite slurry is 30 wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 18 μm. (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first subjected to pre-oxidation stabilization and then carbonized in an inert atmosphere. The pre-oxidation stabilization temperature is 250°C and the time is 1.5h. The inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 900°C and the time is 2.5h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0055] The specific surface area (BET) of the negative electrode material prepared in Example 4 is 4.8 μm. 2 ·g -1 The tap density is 0.86 g·cm³. -3 The total carbon content is approximately 23 wt%.

[0056] Example 5 A method for preparing a silicon suboxide carbon composite anode material includes the following steps: (1) Raw material selection and proportioning: Industrial silicon powder and precipitated silica are used as SiOx precursors, with the mass ratio of industrial silicon powder to precipitated silica being 45:55. (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous ball mill for mechanical activation mixing to obtain a uniformly mixed powder, and the D50 of the uniformly mixed powder is controlled to be 5μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 980℃ and an equivalent holding time of 2h. After the heat treatment, SiOx powder is obtained (the x value is 0.95~1.10 after elemental analysis). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2wt% of SiOx powder; the first carbon precursor is a phenolic resin aqueous solution and an asphalt emulsion with a mass ratio of 5wt%, and the solid content of the final homogeneous slurry is 45%; (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a sucrose solution, and the amount used is such that the total carbon content in the final composite slurry is 25 wt%; (6) Spray granulation: The composite slurry obtained in step (5) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 12-14 μm. (7) Stabilization and continuous carbonization (shell densification step): The composite precursor obtained in step (6) is first subjected to pre-oxidation stabilization and then carbonized in an inert atmosphere. The pre-oxidation stabilization temperature is 230°C and the time is 1h. The inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 800°C and the time is 2.5h, so that the first carbon precursor forms an inner carbon network and the second carbon precursor forms a continuous and dense outer carbon shell. (8) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished silicon suboxide carbon composite anode material.

[0057] The negative electrode material prepared in Example 5 has a specific surface area (BET) of 7.2 μm. 2 ·g -1 The tap density is 0.76 g·cm³. -3 The total carbon content is approximately 20 wt%.

[0058] Comparative Example 1 Same as Example 1, except that spray granulation is not performed; instead, the slurry is directly dried, pulverized, and then carbonized to obtain the material. Specifically: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder is 45:55; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous stirred mill for mechanical activation mixing to obtain a uniformly mixed powder; the D50 of the uniformly mixed powder is controlled to be 5 μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1000℃ and an equivalent holding time of 2h. After the heat treatment, SiOx powder is obtained (the x value is 1.0 to 1.1 after elemental analysis). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2wt% of SiOx powder; the first carbon precursor is a phenolic resin aqueous solution and asphalt emulsion with a mass ratio of 10wt%, and the solid content of the final homogeneous slurry is 45%; (5) Shell enrichment construction (outer dense carbon shell precursor layer formation step): The second carbon precursor is added to the homogeneous slurry obtained in step (4) and shear dispersion is continued to obtain a composite slurry; wherein the second carbon precursor is a glucose solution, and the amount used is such that the total carbon content in the final composite slurry is 30 wt%; (6) Stabilization and continuous carbonization (shell densification step): The composite slurry obtained in step (5) is first pre-oxidized and stabilized, and then carbonized in an inert atmosphere. The temperature of the pre-oxidation and stabilization is 250°C and the time is 1h; the inert atmosphere carbonization is carried out in N2 atmosphere, the carbonization temperature is 900°C and the time is 2h. (7) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain composite negative electrode materials.

[0059] The negative electrode material prepared in Comparative Example 1 has a D50 of 6.2 μm and a specific surface area (BET) of 18.5 μm. 2 ·g -1 The tap density is 0.55 g·cm³. -3 The total carbon content is approximately 20 wt%.

[0060] Comparative Example 2 Same as Example 1, except that the shell enrichment construction in step (5) and the stabilization step in step (7) are omitted. Specifically: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder is 45:55; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous stirred mill for mechanical activation mixing to obtain a uniformly mixed powder; the D50 of the uniformly mixed powder is controlled to be 5 μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1000℃ and an equivalent holding time of 2h. After the heat treatment, SiOx powder is obtained (the x value is 1.0 to 1.1 after elemental analysis). (4) Aqueous composite dispersion slurry preparation (internal carbon network formation step): SiOx powder is added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and the first carbon precursor to obtain a homogeneous slurry; wherein, the amount of conductive carbon black is 2wt% of SiOx powder; the first carbon precursor is a phenolic resin aqueous solution and an asphalt emulsion with a mass ratio of 15wt%, and the solid content of the final homogeneous slurry is 45%; (5) Spray granulation: The uniform slurry obtained in step (4) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 12 μm. (6) Continuous carbonization (shell densification step): The composite precursor obtained in step (5) is carbonized in an inert atmosphere, wherein the inert atmosphere carbonization is carried out in a N2 atmosphere, the carbonization temperature is 900℃, and the time is 2h. (7) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished negative electrode material.

[0061] The negative electrode material prepared in Comparative Example 2 has a D50 of 12 μm and a specific surface area (BET) of 11.2 μm. 2 ·g -1 The tap density is 0.72 g·cm³. -3 The total carbon content is approximately 10 wt%.

[0062] Comparative Example 3 Same as Example 1, except that no stabilization is performed, and only sugars are used as carbon precursors in a low amount, resulting in a total carbon content of 9 wt%. Specifically: (1) Raw material selection and proportioning: Industrial silicon powder and silicon dioxide powder are used as SiOx precursors, wherein the mass ratio of industrial silicon powder to silicon dioxide powder (selected from silicon micro powder) is 45:55; (2) Mechanical activation mixing: The raw materials from step (1) are added to a continuous stirred mill for mechanical activation mixing to obtain a uniformly mixed powder; the D50 of the uniformly mixed powder is controlled to be 5 μm; (3) Preparation of SiOx by heat treatment in inert atmosphere: The uniform mixed powder obtained in step (2) is heat treated in an inert atmosphere (N2) at a temperature of 1000℃ and an equivalent holding time of 2h. After the heat treatment, SiOx powder is obtained (the x value is 1.0 to 1.1 after elemental analysis). (4) SiOx powder was added to deionized water for high-shear dispersion, followed by the addition of conductive carbon black and a second carbon precursor to obtain a uniform slurry; wherein the second carbon precursor was a glucose solution, and the amount used was such that the total carbon content in the final composite slurry was 9 wt%; (5) Spray granulation: The uniform slurry obtained in step (4) is spray dried and granulated to obtain a secondary particle composite precursor with a D50 of 12 μm. (6) Continuous carbonization (shell densification step): The composite precursor obtained in step (5) is carbonized in an inert atmosphere; wherein the inert atmosphere carbonization is carried out in a N2 atmosphere, the carbonization temperature is 900℃, and the time is 2h. (7) Post-processing: The carbonized products are subjected to air classification, iron removal, homogenization and batching and packaging to obtain the finished negative electrode material.

[0063] The negative electrode material prepared in Comparative Example 3 has a D50 of 9.8 μm and a specific surface area (BET) of 14.8 μm. 2 ·g-1 The tap density is 0.6 g·cm³. -3 The total carbon content is approximately 9 wt%.

[0064] Performance testing The composite materials obtained in Examples 1-5 and Comparative Examples 1-3 were used as negative electrode active materials, mixed with conductive carbon black and CMC in an 8:1:1 ratio, and coated onto copper foil to form a negative electrode sheet. A coin cell was assembled using lithium metal as the counter electrode. The electrolyte was 1M LiPF6 (EC / EMC=3 / 7) + 10% FEC. Cycles were performed at 0.1C for 2 cycles; followed by 0.5C cycling at 0.01-1.5V. The first-cycle ICE was calculated as the first-cycle discharge capacity / first-cycle charge capacity; capacity retention was calculated as the 300th cycle / 3rd cycle discharge capacity. The first-cycle charge-discharge curve of the silicon suboxide carbon composite negative electrode material obtained in Example 1 is shown below. Figure 3 The cycle performance diagram of the silicon suboxide carbon composite anode material obtained in Example 3 is shown in [Figure Number]. Figure 4 The electrochemical performance test results of each embodiment and comparative example are shown in Table 1.

[0065] Table 1. Electrochemical performance test results of the examples and comparative examples. As shown in Table 1, the first-cycle coulombic efficiencies of Examples 1-5 were 86.4%, 84.8%, 88.2%, 89.0%, and 85.9%, respectively, which were significantly higher than those of Comparative Examples 1-3 (76.0%, 78.1%, and 74.5%). The capacity retention rates of Examples 1-5 in the 300th cycle were 93.0%, 86.0%, 97.0%, 95.0%, and 89.0%, respectively, which were significantly better than those of Comparative Examples 1-3 (70.0%, 76.0%, and 68.0%).

[0066] Based on the aforementioned data, the BET specific surface areas of Examples 1-5 are 7.6, 8.3, 5.9, 4.8, and 7.2 m², respectively. 2 ·g -1 The concentration was significantly lower than that of Comparative Example 1 (18.5 m³) without spray granulation. 2 ·g -1 This indicates that spray granulation can effectively reduce the specific surface area and increase the tap density (reaching 0.86 g·cm³ in Example 4). -3 This reduces interfacial side reactions and improves first-efficiency; while the outer dense carbon shell strategy further inhibits electrolyte penetration and continuous SEI growth, significantly improving cycle retention (reaching 97.0% and 95.0% in Examples 3 and 4, respectively). These results demonstrate that the present invention, through secondary particle construction and synergistic use of inner and outer dual carbon layers, can simultaneously improve first-efficiency and cycle stability.

[0067] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method, characterized in that, Includes the following steps: Industrial silicon powder and silicon dioxide powder are mechanically activated and mixed to obtain a uniformly mixed powder; The uniformly mixed powder was heat-treated under an inert atmosphere to obtain SiOx powder; The SiOx powder was dispersed in water, and conductive carbon black and a first carbon precursor were added to obtain a uniform slurry. A second carbon precursor is added to the homogeneous slurry and dispersed to obtain a composite slurry, which is then spray-dried and granulated to obtain a secondary particle composite precursor. The secondary particle composite precursor is subjected to pre-oxidation stabilization and inert atmosphere carbonization in sequence to obtain the silicon suboxide carbon composite anode material.

2. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The mass ratio of industrial silicon powder to silicon dioxide powder is (20-60): (80-40).

3. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The heat treatment temperature is 850–1200℃, and the holding time is 0.5–6h.

4. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The amount of conductive carbon black added is 0.5-5% of the total mass of the SiOx powder, and the solid content of the uniform slurry is 35-55%.

5. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The first carbon precursor is selected from phenolic resin aqueous solution and / or asphalt emulsion; the second carbon precursor is selected from sugar solution and / or low softening point asphalt emulsion.

6. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, After adding the second carbon precursor, the total carbon content in the composite slurry is 10-35 wt%.

7. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The secondary particle composite precursor D 50 The size ranges from 5 to 20 μm.

8. The low-cost, high-efficiency, long-cycle silicon suboxide carbon composite anode material and its large-scale preparation method according to claim 1, characterized in that, The pre-oxidative stabilization temperature is 200–300°C, and the time is 0.5–2 hours; The inert atmosphere carbonization is carried out under N2 or Ar atmosphere at a temperature of 600–1100℃ for 1–3 hours.

9. A silicon suboxide carbon composite anode material prepared by the preparation method according to any one of claims 1-8.

10. The application of the silicon suboxide carbon composite anode material as described in claim 9 in the preparation of lithium-ion battery anodes.

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