SiOx / C negative electrode material based on fluorine-containing silica gel and preparation method of SiOx / C negative electrode material

Abstract

The invention belongs to the field of new energy materials, and relates to a SiOx / C negative electrode material based on fluorine-containing silica gel and a preparation method thereof.The method comprises the steps that silicon powder and fluorine-containing silica gel are premixed according to a certain proportion; carrying out ball milling on the premixed raw materials and zirconium balls according to a certain proportion under an inert atmosphere condition; a primary product obtained after ball milling is finished is annealed in an inert atmosphere according to a certain temperature, a target SiOx material is formed, and the amorphous / low-crystal SiOx composite negative electrode material is obtained after cooling and sieving; uniformly dispersing the mixture and a certain amount of carbon source in an aqueous solution, uniformly stirring, and carrying out spray drying; the preparation method has the advantages that the raw material cost is low, resources can be recycled, the operability of the processing technology is high, the preparation method is suitable for large-scale production, the problems of complicated flow, poor structure control, fluctuation of electrochemical performance and the like can be solved, and the electrochemical performance is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy materials, and in particular to a SiOx / C negative electrode material based on fluorine-containing silica gel and a preparation method thereof. BACKGROUND

[0002] At present, silicon-based negative electrode materials are widely concerned in the industry due to their high theoretical specific capacity (about 4200 mAh / g). However, the volume expansion of pure silicon during the charging and discharging process leads to poor cycle stability. SiOx materials have become an important research direction due to their composite structure, which combines the advantages of capacity and cycle life.

[0003] Traditional SiOx preparation methods, such as pyrolysis of organosilicon, sol-gel or thermal reduction, have problems such as complex process, high cost, heavy environmental burden, high energy consumption, poor structure control and fluctuation of electrochemical performance.

[0004] At the same time, the industrial waste such as fluorine-containing organosilicon by-products faces resource waste during the treatment process. A large amount of fluorosilicic acid (H2SiF6) is produced as a by-product in the wet-process phosphoric acid processing process. A large amount of fluorine-containing silica gel is produced as a by-product in the production of phosphoric acid and the secondary resource processing and utilization of fluorosilicic acid. The main component is SiO2. According to the phosphorus chemical production capacity, the annual by-product of the phosphorus chemical industry and the fluorosilicon field in Yunnan can reach hundreds of thousands of tons. The silicon resource supply is sufficient, and the annual by-product of fluorine-containing silica gel in the phosphorus chemical industry and the fluorosilicon field in Yunnan reaches more than 100,000 tons. The fluorine-containing SiO2 raw material usually comes from the defluorination purification system or the secondary resource utilization process of the by-product fluorosilicic acid, which is originally a silicon slag waste with low utilization value. How to convert the by-product fluorine-containing silica gel into useful fluorine-containing SiO2 to realize "waste treatment with waste" and solid waste resource utilization is an important research direction.

[0005] High-energy ball milling is a low-cost, scalable mechanical chemical method that can induce solid-phase reactions at room temperature. In recent years, it has attracted attention in the synthesis of amorphous SiOx. Based on this technology, how to effectively apply fluorine-containing silica gel to the preparation of silicon monoxide negative electrode materials is worth studying. SUMMARY

[0006] In order to solve the problems of complex process, high cost, heavy environmental burden, high energy consumption, poor structure control and fluctuation of electrochemical performance, the present application aims to provide a SiOx / C negative electrode material based on fluorine-containing silica gel and a preparation method thereof.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a preparation method of a SiOx / C negative electrode material based on fluorine-containing silica gel, comprising the following steps: Step (1) : Pre-mixing silicon powder and fluorine-containing silica gel according to a certain ratio; Step (2) The premixed raw materials and zirconium balls are ball-milled in an inert atmosphere at a certain ratio to complete the disproportionation reaction; The primary product obtained after ball milling in step (3) is annealed at a certain temperature in an inert atmosphere to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material. Step (4) Cool and sieve the target SiOx material to obtain the amorphous / low-crystal SiOx composite anode material; Step (5) The amorphous / low-crystal SiOx composite anode material and a certain amount of carbon source are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried; then heat-treated at a certain temperature under an inert atmosphere to form a dense carbon coating layer, thus obtaining the SiOx / C anode material.

[0008] This invention utilizes fluorinated silica gel, a byproduct of phosphate chemical enterprises, as the main raw material to achieve high-value recycling and utilization of industrial by-product resources, significantly reducing the preparation cost of SiOx anode materials, while avoiding the high energy consumption and environmental burden associated with high-purity silicon sources or vapor deposition processes. The processing technology is highly operable and suitable for large-scale production.

[0009] Fluorinated silica gel is mixed with silica powder and subjected to a disproportionation reaction through high-energy ball milling to improve cycle performance.

[0010] This invention employs a high-energy ball milling and low-temperature carbonization process, which requires minimal equipment, is easy to operate, and has a simple process, making it suitable for large-scale production. This method is compatible with existing electrode manufacturing processes, providing a high-performance, low-cost anode solution for high-energy-density lithium-ion batteries.

[0011] As a preferred embodiment, in step (1), the fluorine content in the fluorinated silica gel is 0~10%wt, and the molar ratio of silica powder to fluorinated silica gel is 1:1~2:1. The range of the molar ratio determines the number of Si and O atoms in the product, and can determine the main components and structure of the final product.

[0012] Fluorine provides chemical stability and interfacial reinforcement, while carbon coating provides conductivity and stress buffering. The synergistic effect of the two can significantly improve the cycling stability and rate performance of the material.

[0013] As a preferred option, in step (2), the mass ratio of raw material to zirconium balls is 1:5 to 1:10, and the ball milling time is 8 to 48 hours.

[0014] In the ball milling disproportionation reaction, fluorine can form Si–F bonds with silicon, partially replacing Si–O bonds and regulating the local structure of SiOx. During electrochemical cycling, fluorine further reacts with lithium to generate LiF components, promoting the formation of a uniform, stable, and low-impedance SEI film. This structure can significantly improve the initial coulombic efficiency.

[0015] As a preferred option, in step (3), the annealing temperature is 120~300℃. This promotes the stable formation of the Si–O–F structure and adjusts the Si phase distribution to form the target SiOx material.

[0016] As a preferred option, in step (5), the amount of carbon source added is 0~30%wt, the heat treatment temperature is 600~900℃, the treatment time is 30~120min, and the carbon source is glucose, sucrose or maltose.

[0017] The carbon source of the present invention is added after ball milling. The carbon layer generated by carbonization of carbon sources such as glucose is rich in hydroxyl groups, carbonyl groups and C=C structures, which can form Si–O–C bonds with the SiOx surface, enhance the interfacial bonding force between the carbon layer and the matrix, and effectively prevent pulverization and structural collapse.

[0018] As a preferred embodiment, in step (5), the inlet air temperature of the spray dryer is ≤300℃ and the outlet air temperature is ≤230℃. The inlet air temperature is higher than the outlet air temperature, which rapidly evaporates moisture and forms spherical agglomerates, resulting in uniform granulation and the formation of carbon-coated SiOx / C anode materials.

[0019] Secondly, this invention relates to a SiOx / C anode material obtained by the above-described preparation method. The raw material cost is low and resources can be recycled and reused; the processing technology is highly operable and suitable for large-scale production.

[0020] Thirdly, the present invention relates to a SiOx / C anode material, comprising a core and a coating layer located on at least a portion of the surface of the core, the coating layer comprising a carbon material, and the core comprising a carbon matrix and SiOx loaded in the carbon matrix; the SiOx / C anode material has a particle size of 2μm < D50 < 20μm, and a Si to O atomic ratio ≤ 1.5. Based on the control of particle size and atomic ratio, high-capacity products exhibit excellent first-cycle discharge / charge capacity at 0.1C rate, and long-cycle products exhibit excellent first-cycle discharge / charge capacity at 0.1C rate.

[0021] Fourthly, the present invention relates to a battery comprising the aforementioned SiOx / C anode material, which can solve problems such as poor structural control and fluctuations in electrochemical performance, and exhibits excellent electrochemical performance. Attached Figure Description

[0022] Figure 1 The image shows the XRD pattern of the SiOx / C anode material prepared in Example 3. Figure 2 The images shown are SEM images of the SiOx / C anode material prepared in Example 3, where (a) is the SEM image of the high-magnification SiOx / C anode material; and (b) is the SEM image of the low-magnification SiOx / C anode material. Figure 3The images show test results of the SiOx / C anode material assembled battery sample prepared in Example 3, including (a) the capacity-voltage diagram for the first three cycles and (b) the capacity diagram for 100 cycles. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents, instruments, and equipment used, unless otherwise specified, are all conventionally available products that can be purchased.

[0024] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations. Unless otherwise specified in the methods of this invention, all ratios are mass percentages.

[0025] Some hydroxyl groups (Si–OH) on the SiO2 surface are replaced by fluorine to form Si–F, ​​resulting in a stable structure. F substitution can form Si–F–Si or Si–O–F bonds during pyrolysis, regulating the SiOx amorphous network; it also facilitates the formation of metastable SiOxFy structures and improves cycle stability. Fluorine forms a LiF / LixSiFy composition in the first cycle, enhancing interfacial stability and suppressing volume effects.

[0026] To investigate how to effectively apply fluorinated silica gel to the preparation of silicon suboxide anode materials, this invention provides a green, efficient, and scalable method for synthesizing SiOx. Using fluorinated silica gel and silicon powder as raw materials, SiOx is prepared through a solid-state disproportionation reaction induced by high-energy ball milling. High-energy ball milling can induce a solid-state reaction at room temperature. By introducing fluorinated components (such as fluorinated silica gel) into the ball milling process, the Si–O–Si network rearrangement can be further promoted. Introducing structural fluorine (F) elements is expected to regulate the distribution and oxidation degree of active silicon in SiOx, improve its structural stability and electrochemical performance, and offer significant performance improvements and cost advantages.

[0027] In a first aspect, embodiments of the present invention provide a method for preparing a SiOx / C anode material based on fluorinated silica gel, comprising the following steps: Step (1) Premix the silicon powder and fluorinated silica gel in a certain ratio; Step (2) The premixed raw materials and zirconium balls are ball-milled in an inert atmosphere at a certain ratio to complete the disproportionation reaction; The primary product obtained after ball milling in step (3) is annealed at a certain temperature in an inert atmosphere to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material. Step (4) Cool and sieve the target SiOx material to obtain the amorphous / low-crystal SiOx composite anode material; Step (5) The amorphous / low-crystal SiOx composite anode material and a certain amount of carbon source are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried; then heat-treated at a certain temperature under an inert atmosphere to form a dense carbon coating layer, thus obtaining the SiOx / C anode material.

[0028] This invention utilizes fluorinated silica gel, a byproduct of phosphate chemical enterprises, as the main raw material to achieve high-value recycling and utilization of industrial by-product resources, significantly reducing the preparation cost of SiOx anode materials, while avoiding the high energy consumption and environmental burden associated with high-purity silicon sources or vapor deposition processes. The processing technology is highly operable and suitable for large-scale production.

[0029] Fluorinated silica gel is mixed with silica powder and undergoes a disproportionation reaction through high-energy ball milling. The fluorinated silica gel simultaneously acts as an oxygen source, dispersant, and structure regulator. The introduction of fluorine element forms a Si–O–F structure, which stabilizes the interfacial reaction, inhibits initial pulverization and electrolyte side reactions, and improves cycle performance.

[0030] This invention employs a high-energy ball milling and low-temperature carbonization process, which requires minimal equipment, is easy to operate, and has a simple process, making it suitable for large-scale production. This method is compatible with existing electrode manufacturing processes, providing a high-performance, low-cost anode solution for high-energy-density lithium-ion batteries. In the embodiments of this invention, the inert atmosphere can be argon or nitrogen.

[0031] In one embodiment, in step (1), the fluorine content in the fluorinated silica gel is 0~10%wt, and the molar ratio of silica powder to fluorinated silica gel is 1:1~2:1. The range of the molar ratio determines the number of Si and O atoms in the product, and can determine the main components and structure of the final product.

[0032] Fluorine provides chemical stability and interfacial reinforcement, while carbon coating provides conductivity and stress buffering. The synergistic effect of these two elements significantly improves the cycling stability and rate performance of the material. Tests show that the prepared material exhibits optimal capacity retention of nearly 90% after 100 cycles, with a significantly slower increase in electrochemical impedance.

[0033] Due to the presence of fluorine-containing groups and the LiF phase on the surface, the electrode can form a uniform, fluorine-rich SEI film after the first charge and discharge. This film has high ion conductivity and chemical inertness, which can effectively suppress continuous side reactions and keep the electrode interface stable under long-term cycling and high-temperature environments.

[0034] In one embodiment, in step (2), the mass ratio of raw material to zirconium balls is 1:5 to 1:10, and the ball milling time is 8 to 48 hours.

[0035] In the ball milling disproportionation reaction, fluorine can form Si–F bonds with silicon, partially replacing Si–O bonds and regulating the local structure of SiOx. During electrochemical cycling, fluorine further reacts with lithium to generate LiF components, promoting the formation of a uniform, stable, and low-impedance SEI film. This structure can effectively suppress side reactions with the electrolyte and significantly improve the initial coulombic efficiency (≥85% without pre-physicochemical treatment).

[0036] In one implementation method, the annealing temperature in step (3) is 120~300℃. This promotes the stable formation of the Si–O–F structure and adjusts the Si phase distribution to form the target SiOx material.

[0037] In one embodiment, in step (5), the amount of carbon source added is 0~30%wt, the heat treatment temperature is 600~900℃, the treatment time is 30~120min, and the carbon source is glucose, sucrose or maltose.

[0038] In this invention, the carbon source is added after ball milling. The carbon layer generated by carbonization of sources such as glucose is rich in hydroxyl groups, carbonyl groups, and C=C structures, which can form Si–O–C bonds with the SiOx surface, enhancing the interfacial bonding between the carbon layer and the substrate. The resulting carbon coating layer is continuous and dense, providing both electron conduction channels and flexible buffering during charge-discharge volume changes, effectively preventing pulverization and structural collapse. If the carbon source is added simultaneously with ball milling, coating cannot be achieved.

[0039] All heat treatment equipment in the embodiments are tube furnaces, and the heat treatment can be sintering with a heating rate of 5°C / min.

[0040] In one implementation, in step (5), the inlet air temperature of the spray dryer is ≤300℃ and the outlet air temperature is ≤230℃. When the inlet air temperature is higher than the outlet air temperature, a carbon-coated SiOx / C anode material can be formed. If the temperature is too high or the inlet air temperature and the outlet air temperature are about the same, such a structure cannot be formed.

[0041] Secondly, embodiments of the present invention relate to a SiOx / C anode material, obtained by the above-described preparation method. The raw material cost is low and resources can be recycled and reused; the processing technology is highly operable and suitable for large-scale production.

[0042] Thirdly, embodiments of the present invention relate to a SiOx / C anode material, comprising a core and a coating layer located on at least a portion of the surface of the core. The coating layer comprises a carbon material, and the core comprises a carbon matrix and SiOx loaded in the carbon matrix. The SiOx / C anode material has a particle size of 2 μm < D50 < 20 μm and a Si to O atomic ratio ≤ 1.5. Based on the control of particle size and atomic ratio, high-capacity products exhibit excellent first-cycle discharge / charge capacity at 0.1C rate, and long-cycle products exhibit excellent first-cycle discharge / charge capacity at 0.1C rate.

[0043] Fourthly, embodiments of the present invention relate to a battery comprising the aforementioned SiOx / C anode material, which can solve problems such as poor structural control and fluctuations in electrochemical performance, exhibiting excellent electrochemical performance. The initial reversible capacity is ≥1400 mAh / g, and the initial coulombic efficiency is 69-80%.

[0044] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a SiOx / C anode material based on fluorinated silica gel and its preparation method.

[0045] Example 1 This embodiment describes a method for preparing silicon suboxide anode material based on fluorinated silica gel. The fluorinated silica gel in this embodiment is derived from a defluorination and purification system, and its trace components are shown in Table 1 below. Table 1 Trace components of fluorinated silica gel The composition of this fluorinated silica gel is shown in Table 2: Table 2. Components of Fluorinated Silica Gel The silicon powder is nano-silicon powder: the average particle size is ≤1μm, the purity is 99.99%, and it is produced by Xintie Metal Materials Co., Ltd.; the ball mill is Changsha Tianchuang Powder Technology Co., Ltd.'s QXQM-4; the tube furnace for heat treatment is Shenzhen Kejing Zhida Technology Co., Ltd.'s GSL-1800X.

[0046] The method includes the following steps: Step (1) Take silicon powder and fluorinated silica gel and premix them in a molar ratio of 1:1; the fluorine content in the fluorinated silica gel is 1%.

[0047] Step (2) The premixed raw materials and zirconium balls are ball-milled for 8 hours under nitrogen conditions at a ratio of 1:8.

[0048] After ball milling in step (3), the primary product obtained is annealed at 150°C under argon to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material.

[0049] Step (4) Cool and sieve the target SiOx material to obtain the amorphous / low-crystal SiOx composite anode material.

[0050] Step (5) The amorphous / low-crystal SiOx composite anode material and 1% glucose are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried. The inlet air temperature of the spray drying is 300℃ and the outlet air temperature is 230℃. Then, it is sintered at 600℃ in a nitrogen atmosphere for 30 minutes to form a dense carbon coating layer and obtain the SiOx / C anode material.

[0051] Example 2 The method for preparing silicon suboxide anode material based on fluorinated silica gel in this embodiment differs from that in Example 1 in that: Step (1) Take silicon powder and fluorinated silica gel and premix them in a molar ratio of 1.5:1.

[0052] Step (2) The premixed raw materials and zirconium balls are ball-milled at a ratio of 1:8 under nitrogen for 12 hours.

[0053] After ball milling in step (3), the primary product obtained is annealed at 250°C under argon to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material.

[0054] Step (5) The amorphous / low-crystal SiOx composite anode material and 10% glucose are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried. The inlet air temperature of the spray drying is 280℃ and the outlet air temperature is 220℃. Then, it is sintered at 680℃ in a nitrogen atmosphere for 60 minutes to form a dense carbon coating layer and obtain the SiOx / C anode material.

[0055] Example 3 The method for preparing silicon suboxide anode material based on fluorinated silica gel in this embodiment differs from that in Example 1 in that: Step (1) Take silicon powder and fluorinated silica gel and premix them in a molar ratio of 2:1.

[0056] Step (2) The premixed raw materials and zirconium balls are ball-milled at a ratio of 1:8 under nitrogen for 24 hours.

[0057] After ball milling in step (3), the primary product obtained is annealed at 200°C in an inert atmosphere to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material.

[0058] Step (5) The amorphous / low-crystal SiOx composite anode material and 15% glucose are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried. The inlet air temperature of the spray drying is 300℃ and the outlet air temperature is 230℃. Then, it is sintered at 700℃ in a nitrogen atmosphere for 120 minutes to form a dense carbon coating layer and obtain the SiOx / C anode material.

[0059] Example 4 The method for preparing silicon suboxide anode material based on fluorinated silica gel in this embodiment differs from that in Example 1 in that: The composition of this fluorinated silica gel is shown in Table 3: Table 3. Components of Fluorinated Silica Gel Step (1) Take silicon powder and fluorinated silica gel and premix them in a molar ratio of 2:1; the fluorine content in the fluorinated silica gel is 2%.

[0060] Step (2) The premixed raw materials and zirconium balls are ball-milled at a ratio of 1:7 under nitrogen for 24 hours.

[0061] After ball milling in step (3), the primary product obtained is annealed at 200°C in an inert atmosphere to promote the stable formation of the Si–O–F structure and adjust the Si phase distribution to form the target SiOx material.

[0062] Step (5) The amorphous / low-crystal SiOx composite anode material and 18% glucose are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried; then sintered at 700℃ under a nitrogen atmosphere for 120 min to form a dense carbon coating layer, and SiOx / C anode material is obtained.

[0063] Comparative Example 1 In Example 1, step (1) involves premixing silicon powder with normal silicone (Aladdin S433070) in a molar ratio of 1:1. The rest is the same as in Example 1.

[0064] Comparative Example 2 In Example 1, step (1) involves taking silicon powder, the fluorinated silica gel of Example 1 and normal silica gel (Aladdin S433070) and premixing them in a molar ratio of 1:0.5:0.5. The rest is the same as in Example 1.

[0065] Comparative Example 3 In Example 1, step (2) is a ratio of raw material to zirconium ball material of 1:3.

[0066] Comparative Example 4 In Example 1, the carbon source in step (5) is starch.

[0067] Comparative Example 5 In Example 1, the heat treatment temperature in step (5) is 380°C.

[0068] Test Instance Examples 1-4 were subjected to XRD detection and scanning electron microscopy observation. Taking Example 3 as an example, ... Figure 1 As shown, the SiOx / C anode material is granulated to obtain a complete spherical shape, with large and small particles evenly distributed in the sphere.

[0069] like Figure 2 As shown, Figure 2 (a) is a SEM image of the high-rate SiOx / C anode material. It can be seen that in step (5), the primary particles of 30~120nm form porous micron-sized secondary aggregates. Figure 2(b) is a SEM image of the low-rate SiOx / C anode material. It can be seen that in step (5), the secondary particles are 1–36 μm spherical particles.

[0070] The SiOx / C anode materials from the examples and comparative examples were assembled into half-cells, and their electrochemical performance was tested: Half-cell preparation: The SiOx / C composite material, conductive carbon black, and CMC-Na from the examples and comparative examples were placed in a ball mill jar at a mass ratio of 6:3:1. An appropriate amount of deionized water was added, and the mixture was ball-milled for 30 minutes, with a 1-minute pause every 4 minutes during milling, followed by reversal. The slurry was then removed and placed on a carbon-coated copper foil, and then coated evenly with a 15 μm scraper. The coating was then vacuum-dried at 180°C for 12 hours, resulting in a coating thickness of 14 ± 0.1 μm. The coated material was then cut into 14 mm diameter discs for later use. Subsequently, in a glove box, a CR2032 type button half-cell was assembled using the following sequence: negative electrode shell - lithium sheet - separator - electrode plate - stainless steel gasket - spring sheet - positive electrode shell. The cell was filled with 100 μL of electrolyte, containing LiPF6 at a concentration of 1 M, and a mixture of DMC, EC, and EMC in a volume ratio of 1:1:1. The separator was Celgard 2320.

[0071] Electrochemical performance testing was conducted as follows: Connect the coin cell to the electrochemical performance tester using appropriate clamps and place it in a test environment at a specific temperature (around 25°C). Charge it at a set constant current rate (0.5C) to the cutoff voltage (4.2V), then charge it at a constant voltage rate to the set low current threshold (0.05C). Let it stand for 5 minutes, then discharge it at a set constant current rate to the set lower voltage limit (3.0V). Repeat the above charge and discharge steps for multiple cycles to obtain the changes in charge and discharge capacity and coulombic efficiency with the number of cycles. (The negative electrode half-cell is discharged first and then charged). The equipment is a Blue Electric Test Cabinet.

[0072] Taking Example 3 as an example, Figure 3 This is a test image of the battery sample assembled with the SiOx / C anode material prepared in Example 3. Figure 3 (a) illustrates the relationship between capacitance and voltage changes in the first three cycles. A clear voltage ramp / plateau is observed in the 0.8~1.2 V range, with a long plateau near 0.1~0.2 V. The coulombic efficiency (ICE) of the first cycle is relatively low, which is a typical phenomenon for SiOx / C oxygen-containing silicon anodes. The capacitance values ​​per cycle within 100 cycles are as follows: Figure 3 As shown in (b).

[0073] The test results are shown in the table below: Table 4 The negative electrode material of Example 1 was assembled into a half cell. At a 0.1C rate, the first discharge / charge capacity was 2600.3 / 1795.6 mAh·g⁻¹, and the first coulombic efficiency was 69.05%. After 100 cycles at 0.1C, the electrode material still had a high capacity, with a capacity retention rate of 81%.

[0074] After 200 cycles at 0.1C, the electrode material capacity remained high in Examples 2 and 3, with Example 3 reaching 87%, close to 90%.

[0075] Comparative Example 1: The negative electrode material prepared according to the above steps was assembled into a half cell. At a 0.1C rate, the first discharge / charge capacity was 2638.3 / 1747.3, and the first coulombic efficiency was 66.23%. After 200 cycles at 0.1C, the capacity of the electrode material was not as high as that of Example 1, and the capacity retention rate was 74%.

[0076] Comparative Example 2: The negative electrode material prepared according to the above steps was assembled into a half cell. At a 0.1C rate, the first discharge / charge capacity was 2642.1 / 1807.2, and the first coulombic efficiency was 68.4%. After 200 cycles at 0.1C, the capacity of the electrode material was higher than that of Comparative Example 1 but lower than that of Example 1, with a capacity retention rate of 77%, but both were not as good as those of Example 1.

[0077] It is evident that fluorinated silica gel contains fluorine (F), which can artificially construct SEI films. This reduces the repeated formation of SEI films during battery cycling, decreases the likelihood of stage breakage, and improves cycle stability.

[0078] Since the loss of active Li is reduced after artificially constructing the SEI film, the initial coulombic efficiency of the comparative example is also lower than that of the example.

[0079] Furthermore, the electrical performance of SiOx / C anode materials prepared with conventional silicone is not as good as that of fluorinated silicone, and even when conventional silicone and fluorinated silicone are mixed, the effect is still not good.

[0080] Furthermore, the fluorine (F) content is also crucial. If the F content is too high, the proportion of active substances decreases, the capacity drops, and the corrosiveness of the equipment increases. If the F content is too low, the effect of artificially constructing SEI membranes is poor.

[0081] The test results of Example 4 are also better than those of the comparative example. Table 4 shows the results of Examples 1 to 3.

[0082] In Comparative Example 3, the ratio of raw material to zirconium pellets was 1:3, resulting in insufficient energy supply and incomplete reaction. This demonstrates that a suitable ratio is crucial for product quality.

[0083] In Comparative Example 4, the carbon source was starch, which has poor water dispersibility and is prone to sedimentation. This demonstrates that not all carbon sources are suitable, and the choice of carbon source is crucial to the stability of product performance.

[0084] In Comparative Example 5, the heat treatment temperature was 380℃, resulting in incomplete glucose carbonization and poor carbon coating. This demonstrates that the heat treatment temperature is crucial to the final coating effect.

[0085] The electrical performance test results of Comparative Examples 3-5 were unstable, and they could not even complete long-cycle tests, and were far inferior to those of Examples 1-2 and Comparative Examples 1-2.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing SiOx / C anode material based on fluorinated silica gel, characterized in that, Includes the following steps: Step (1) Premix the silicon powder and fluorinated silica gel in a certain ratio; Step (2) The premixed raw materials and zirconium balls are ball-milled in an inert atmosphere at a certain ratio; The primary product obtained after ball milling in step (3) is annealed at a certain temperature in an inert atmosphere to form the target SiOx material. Step (4) Cool and sieve the target SiOx material to obtain the amorphous / low-crystal SiOx composite material; Step (5) The amorphous / low-crystal SiOx composite material and a certain amount of carbon source are uniformly dispersed in an aqueous solution, stirred evenly and spray-dried; then heat-treated at a certain temperature under an inert atmosphere to form a dense carbon coating layer, and SiOx / C anode material is obtained.

2. The method for preparing SiOx / C anode material based on fluorinated silica gel according to claim 1, characterized in that, In step (1), the fluorine content in the fluorinated silica gel is 0~10%wt, and the molar ratio of silica powder to fluorinated silica gel is 1:1~2:

1.

3. The method for preparing SiOx / C anode material based on fluorinated silica gel according to claim 1, characterized in that, In step (2), the mass ratio of raw material to zirconium balls is 1:5 to 1:10, and the ball milling time is 8 to 48 hours.

4. The method for preparing SiOx / C anode material based on fluorinated silica gel according to claim 1, characterized in that, In step (3), the annealing temperature is 120~300℃.

5. The method for preparing SiOx / C anode material based on fluorinated silica gel according to claim 1, characterized in that, In step (5), the amount of carbon source added is 0~30%wt, the heat treatment temperature is 600~900℃, the treatment time is 30~120min, and the carbon source is glucose, sucrose or maltose.

6. The method for preparing SiOx / C anode material based on fluorinated silica gel according to claim 1, characterized in that, In step (5), the inlet air temperature of the spray dryer is ≤300℃ and the outlet air temperature is ≤230℃.

7. A SiOx / C anode material, characterized in that: It is obtained by the preparation method according to any one of claims 1 to 6.

8. A SiOx / C anode material, characterized in that: The material includes a core and a coating layer located on at least a portion of the surface of the core. The coating layer includes a carbon material, and the core includes a carbon matrix and SiOx loaded in the carbon matrix. The SiOx / C anode material has a particle size of 2 μm < D50 < 20 μm and a Si to O atomic ratio ≤ 1.

5.

9. A battery, characterized in that: Includes the SiOx / C anode material as described in claim 7 or 8.

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