Phthalonitrile resin modified silicon-carbon negative electrode coating material and preparation method thereof

Abstract

The application relates to a phthalonitrile resin modified silicon-carbon negative electrode coating material and a preparation method thereof, and comprises the following steps: (1) by utilizing the cyano activity of phthalonitrile monomers, a modified phthalonitrile resin coating material with high conductivity is prepared by introducing a high-conductivity conjugated structure; (2) the coating material is dissolved in an organic solvent, silicon monoxide powder and a crosslinking agent are added to perform liquid phase coating, solidification and heat treatment are performed after removing the solvent, and after crushing and sieving, a surface-modified silicon monoxide-carbon negative electrode material is obtained. The prepared coating material has high conductivity, a high coking value, and good mechanical strength; the silicon-carbon negative electrode material after coating has a first reversible specific capacity of greater than 1420 mAh / g, a first coulombic efficiency of 85%, and a specific capacity retention rate of up to 95% after 50 cycles. The synthesis process is simple and controllable, the preparation cost is low, and the process is easy to realize large-scale production.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon anode coating materials for lithium-ion batteries, and particularly to a phthalonitrile resin-modified silicon-carbon anode coating material and its preparation method. Background Technology

[0002] In recent years, graphite anodes have become a widely used commercial material for lithium-ion batteries, with their capacity essentially reaching the theoretical capacity. However, with the rapid development of emerging industries such as new energy vehicles and large-scale energy storage stations, society is placing higher demands on battery capacity, making the search for next-generation lithium-ion battery anode materials a current research hotspot. Silicon-based materials are considered the most promising alternative to graphite anodes due to their advantages such as lower operating voltage, higher theoretical specific capacity, and environmental friendliness. However, silicon materials experience significant volume expansion during lithium insertion / extraction and exhibit low conductivity, which greatly limits their commercial application.

[0003] As a silicon-based material, silicon suboxide (SiO) has attracted widespread attention due to its high theoretical specific capacity, low cost, and abundant reserves. During the first lithium insertion / extraction cycle, SiO forms Li₂SiO₄ and Li₂O, which alleviates its volume expansion during cycling to some extent and improves cycle stability. However, the relatively large volume expansion and poor conductivity of SiO still limit its commercial applications.

[0004] Carbon materials possess excellent electrical conductivity and buffering capacity, making their combination with SiO an effective method to solve this problem. The addition of carbon materials improves the conductivity of silicon materials, prevents direct contact between silicon and the electrolyte, and its buffering capacity effectively suppresses silicon expansion. Common carbon-coated materials can be broadly classified into inorganic and organic carbon sources. Commonly used inorganic carbon sources include acetylene black, carbon gel, carbon nanotubes, graphene, and carbon quantum dots, offering a variety of options for modifying silicon-carbon composites; however, their properties are often limited, and they are relatively expensive. Commonly used organic carbon sources include polymers, aromatics, sugars, and organic acids. Polymers include polyaniline, polyphenylene glycol, and polystyrene; aromatics include resorcinol, phenolic resins, and polycyclic aromatic hydrocarbons; sugars include sucrose, glucose, and cellulose; and organic acids include tartaric acid, ascorbic acid, and citric acid. Among them, aromatic carbon contains at least one benzene ring structure, and after being modified by effective methods, it has relatively good thermal stability and coating effect.

[0005] Phthalonil resin, as an aromatic organic carbon source, is environmentally friendly and widely used. It is a good heat-resistant thermosetting resin material with a low melting point and good solubility, making it easy to prepare various composite materials. After curing at a certain temperature, it will obtain a cyano-terminated conjugated phthalocyanine ring or triazine ring structure, and the carbon residue after carbonization reaches 60-70%. These characteristics provide a very favorable foundation for its use as an excellent carbon coating material.

[0006] Patent document CN113241426B discloses a method for preparing carbon-coated silicon suboxide material for lithium-ion batteries. This invention involves vapor-phase coating of silicon suboxide using CVD, followed by mixing with pitch and boric acid, and then carbonizing and sintering. The pitch is carbonized and coated onto the surface of the vapor-phase coated silicon suboxide to form a solid-phase coated carbon layer, resulting in a solid-phase coated silicon suboxide precursor, which is then used as a negative electrode material. This method can reduce the CVD coating time, lower energy consumption, and improve the stability of the composite material. However, this method is relatively cumbersome and complex, requires high costs, and the pitch and boric acid, as coating materials, do not effectively contribute to the structure and electrochemical performance of the composite material. The prepared composite material has a low initial reversible specific capacity, making it difficult to scale up production.

[0007] Patent document CN104022257B discloses a method for preparing a silicon suboxide composite material for lithium-ion batteries. The silicon suboxide composite material consists of silicon suboxide powder and a conductive carbon layer uniformly coated on its surface. The conductive carbon layer is either a single-layer carbon layer formed by the cracking of an organic carbon source or a double-layer carbon layer formed by the cracking of an organic carbon source and carbon nanomaterials. The prepared composite material retains the original composition of the SiO material system. Simultaneously, by employing processes such as kneading, rolling, and pressing, a coated structure was successfully obtained, improving the cycle performance and conductivity of the silicon suboxide anode material. However, the composite material has poor dispersibility, large particles, and a high silicon oxide content. During electrochemical testing, the initial discharge (lithium insertion) specific capacity is difficult to effectively convert into the initial charge (lithium removal) specific capacity, resulting in a low initial coulombic efficiency of the composite material.

[0008] Therefore, finding a simpler and more efficient method to prepare silicon suboxide-carbon composite materials, and finding suitable carbon coating materials to give the composite materials an ideal structure, good dispersibility and low volume effect, effectively suppressing the volume expansion during lithium insertion and extraction, and exhibiting high conductivity, high specific capacity, good coulombic efficiency and cycle performance, has become a research hotspot and an urgent problem to be solved. Summary of the Invention

[0009] The purpose of this invention is to provide a phthalonitrile resin-modified silicon-carbon anode coating material and its preparation method, which solves the problems of poor conductivity and high expansion rate of silicon suboxide as a negative electrode material in lithium-ion batteries. The prepared silicon-carbon anode coating material has a phthalocyanine or triazine-like coating structure with silicon suboxide as the core and phthalonitrile resin-modified coating material as the shell. It has high conductivity and coking value, large tap density and compaction density, good silicon dispersion, high initial reversible specific capacity and initial coulombic efficiency, and good cycle stability.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] Phthalonil resin-modified silicon-carbon anode coating material has a phthalocyanine or triazine-like coating structure with silicon suboxide as the core and phthallonil resin-modified coating material as the shell, providing sufficient active sites for electrochemical reactions, and is an electrochemical anode material with excellent performance.

[0012] The phthalonitrile resin modified coating material utilizes the cyano group activity of the phthalonitrile monomer to introduce conjugated groups. The nitrogen content in the phthalonitrile resin modified coating material accounts for 10wt% to 25wt% of the total, of which pyrrole N accounts for 20 to 35wt% of the total nitrogen, pyridine N accounts for 30 to 45wt% of the total nitrogen, and graphite N accounts for 25 to 40wt% of the total nitrogen.

[0013] By utilizing the cyano group activity of phthalonitrile monomers, conjugated groups are introduced. This results in high conductivity, coking value, and mechanical strength, while also providing favorable morphology and structure, thus offering a solid foundation for the subsequent preparation of silicon-carbon anode coating materials.

[0014] The coking value of the modified phthalonitrile resin-coated material is 50%–70%; the char residue of the modified phthalonitrile resin-coated material is 50%–65%; the modified phthalonitrile resin-coated material has high conductivity and coking value, and also has a good nitrogen distribution morphology, providing favorable basic conditions for the subsequent preparation of silicon-carbon composite coating materials.

[0015] Modified phthalonitrile resin coating materials can reduce the resistance of silicon-carbon composite coating materials, provide sufficient active sites for electrochemical reactions, and improve their electrochemical performance such as initial reversible specific capacity and initial coulombic efficiency.

[0016] The median particle size of the silicon-carbon anode coating material is below 45 μm; the electrical conductivity is greater than 2 S / cm, and the tap density is 0.8–1.2 g / cm³. 3 The compacted density is 1.2–1.4 g / cm³. 3 .

[0017] A method for preparing phthalonitrile resin-modified silicon-carbon anode coating material, the method comprising the following steps:

[0018] 1) Utilizing the cyano activity of phthalonitrile monomers, an encapsulating agent with a conjugated molecular structure is introduced into an organic solvent, and a catalyst is added to carry out the reaction, thereby preparing a modified phthalonitrile resin coating material with high conductivity and high coking value.

[0019] 2) Add the modified phthalonitrile resin coating material to a reaction vessel containing organic solvent, and stir at room temperature until the modified phthalonitrile resin coating material is completely dissolved to form a homogeneous solution;

[0020] 3) Add the silica powder to the homogeneous solution in step 2), and stir and disperse it to obtain a uniform silica suspension.

[0021] 4) Add crosslinking agent to the suspension in step 3), slowly heat to 60-210℃, keep the temperature constant for 2-8 hours, carry out liquid phase coating in the reactor, crosslinking reaction occurs, forming a coating structure with silica as the core and modified phthalonitrile resin coating material as the shell, remove the solvent and collect the product.

[0022] 5) The product obtained in step 4) is cured at a temperature of 200-350℃ for 1-7 hours and a heating rate of 1-5℃ / min to form a phthalocyanine ring or triazine ring core-shell coated structure. The product is then collected.

[0023] 6) Heat-treat the product obtained in step 5) in a tube furnace under nitrogen or inert gas atmosphere, heat to 500-1000℃ at a heating rate of 1-6℃ / min, hold at the temperature for 1-5 hours, and then remove it after cooling to room temperature.

[0024] 7) The product after heat treatment in step 6) is sieved to obtain a silicon-carbon anode coating material modified with phthalonitrile resin for lithium-ion batteries with controllable particle size.

[0025] In step 1) above, the organic solvent is one of N-methylpyrrolidone, N,N-dimethylacetamide, or dimethyl sulfoxide; the encapsulating agent is 4-(4-aminophenoxy)phthalonitrile or 4-(2-aminophenoxy)phthalonitrile; the catalyst is a complex of triethylamine and acetic anhydride, or dicyclohexylcarbodiimide; the reaction temperature is 15–30°C, and the reaction time is 8–18 h.

[0026] In step 2) above, the organic solvent is one of ethanol, N,N-dimethylformamide or N-methylpyrrolidone; the modified phthalonitrile resin coating material accounts for 15% to 30% of the organic solvent mass.

[0027] In step 3) above, the molecular formula of the silicon suboxide powder is SiOx, 0.5≤x≤1.5, the median particle size is 3~7μm, and the specific surface area is ≤5m². 2 / g; the silica powder accounts for 50% to 250% of the mass of the modified phthalonitrile resin coating material; the stirring speed of the silica powder added to the homogeneous solution is 800 to 1500 rpm.

[0028] In step 4) above, the crosslinking agent is 1,8-diazabicyclo[5.4.0]undec-7-ene or acrylic acid; the crosslinking agent accounts for 20% to 90% of the mass of the modified phthalonitrile resin coating material; the reaction temperature is 70 to 200℃, and the constant temperature time is 3 to 7h; the liquid phase coating method improves the dispersibility and coating uniformity of silicon suboxide and avoids the agglomeration of silicon particles; the addition of the crosslinking agent can promote the liquid phase coating of silicon suboxide and modified phthalonitrile resin coating material in organic solvent. This method is simple and efficient and easy to scale up.

[0029] In step 5) above, the curing temperature is 220-330℃, the curing time is 2-6h, and the heating rate is 2-5℃ / min; in step 6) above, the inert gas is argon, the heating rate of the heat treatment is 2-5℃ / min, the temperature is 600-900℃, and the holding time is 2-5h.

[0030] The prepared silicon-carbon anode coating material can be used in multiple energy storage fields such as lithium-ion batteries and supercapacitors. In particular, as a lithium-ion battery anode material, it has high initial reversible specific capacity and initial coulombic efficiency, and good cycle performance, showing excellent electrochemical performance.

[0031] Compared with existing technologies, the beneficial effects of this invention are:

[0032] The coating material prepared by this invention has high electrical conductivity, high coking value, and good mechanical strength. Its electrical conductivity is greater than 0.5 S / cm, coking value is 50%–70%, and compaction density is 0.8–1.0 g / cm³. 3 The coated silicon-carbon anode material exhibits a conductivity greater than 2 S / cm and a compaction density of 1.2–1.4 g / cm³. 3 The first reversible specific capacity is greater than 1420 mAh / g, the first coulombic efficiency reaches 85%, and the specific capacity retention rate after 50 cycles is as high as 95%. The synthesis process of this invention is simple and controllable, the preparation cost is low, and it is easy to achieve large-scale production. Attached Figure Description

[0033] Figure 1 This is the X-ray diffraction pattern of the silicon suboxide-carbon composite material of Example 1.

[0034] Figure 2This is the Fourier transform infrared spectrum of the silicon suboxide-carbon composite material of Example 1.

[0035] Figure 3 This is the X-ray photoelectron spectrum of the silicon suboxide-carbon composite material of Example 1.

[0036] Figure 4 This is the first charge-discharge curve of the silicon suboxide-carbon composite anode material in Example 1.

[0037] Figure 5 This is a particle size distribution diagram of the silicon suboxide-carbon composite material in Example 2.

[0038] Figure 6 This is the conductivity diagram of the silicon suboxide-carbon composite material in Example 2.

[0039] Figure 7 This is the first charge-discharge curve of the silicon suboxide-carbon composite anode material in Example 2. Detailed Implementation

[0040] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods, and the equipment used is conventional equipment and commercially available products.

[0041] Example 1:

[0042] This embodiment provides a phthalonitrile resin-modified silicon-carbon anode coating material, its preparation method, and its energy storage application. The specific preparation process is as follows:

[0043] (1) Utilizing the cyano activity of phthalonitrile monomer, 4-(4-aminophenoxy)phthalonitrile was introduced into N-methylpyrrolidone, and a complex of triethylamine and acetic anhydride was added. The mixture was reacted at 25°C for 12 h, filtered and washed with water until neutral, and then vacuum dried to prepare a modified phthalonitrile resin coating material with an N content of 15 wt%.

[0044] (2) Add 30g of modified phthalonitrile resin powder with a median particle size of 0.075mm to an organic reactor containing 105g of N,N-dimethylformamide, and stir at room temperature until the modified phthalonitrile resin powder is fully dissolved to form a homogeneous solution.

[0045] (3) Add 18g of silica powder with a median particle size of 5μm to the homogeneous solution in (2) and stir and disperse it at a speed of 900rpm to obtain a uniform silica suspension.

[0046] (4) Add 10g of 1,8-diazabicyclo[5.4.0]undec-7-ene to the suspension of (3), slowly heat to 150℃, and react at a constant temperature for 5h. In the reaction vessel, liquid phase coating is carried out, cross-linking reaction occurs, and a coating structure with silicon suboxide as the core and modified phthalonitrile resin as the shell is formed. Collect the product.

[0047] (5) The product obtained in (4) is cured and heated to 250°C in an oven at a heating rate of 2°C / min. The temperature is then maintained for 4 hours. After cooling to room temperature, the product is taken out to form a phthalocyanine ring-shaped coating structure and the product is collected.

[0048] (6) The product obtained in (5) is subjected to heat treatment. The product is heated to 800°C in a tube furnace under a nitrogen atmosphere at a heating rate of 2°C / min, and then kept at the temperature for 2 hours. After cooling to room temperature, the product is taken out.

[0049] (7) The product after heat treatment in (6) is ground and sieved through a 325-mesh screen to obtain a silicon suboxide-carbon composite material for lithium-ion batteries with controllable particle size.

[0050] Figure 1 The X-ray diffraction pattern of the silicon suboxide-carbon composite material prepared in Example 1 is shown. The broadband indicates the amorphous morphology of the composite material. The broad peak centered at 22° belongs to the amorphous carbon layer. The diffraction peaks centered at 28° and 47° correspond to the (111) and (220) crystal planes of elemental silicon, respectively, which proves the successful synthesis of the silicon suboxide-carbon composite material.

[0051] Figure 2 This is the Fourier transform infrared spectrum of the silicon suboxide-carbon composite material prepared in Example 1. The composite material is at 2228 cm⁻¹. -1 and 1587cm -1 The characteristic peaks at 1641 cm⁻¹ represent the stretching vibrations of C≡N and C=N, respectively; -1 1473cm -1 and 999cm -1 The peak at 1090 cm⁻¹ is a characteristic peak of the phthalocyanine ring, indicating that the composite material has formed a phthalocyanine ring structure; the composite material at 1090 cm⁻¹... -1 and 780cm -1 The peak at this point is the standard characteristic peak of SiO; the above characterizations all demonstrate the successful synthesis of silicon suboxide-carbon composite materials.

[0052] Figure 3 The image shows the X-ray photoelectron spectrum of the silicon suboxide-carbon composite material prepared in Example 1. The image clearly shows the O values ​​at 532.1 eV, 400.1 eV, 284.1 eV, and 284.1 eV, respectively. 1s N 1s C 1s and Si2p The uniform distribution of characteristic peaks proves the presence of the four elements O, N, C, and Si and the successful synthesis of the silicon suboxide-carbon composite material.

[0053] Figure 4 The first charge-discharge curves of the silicon suboxide-carbon composite material prepared in Example 1 are shown. The first discharge (lithium insertion) specific capacity of the composite material is 1859.3 mAh / g, the first charge (lithium removal) specific capacity is 1633.8 mAh / g, the first coulombic efficiency reaches 87.9%, and the capacity retention rate after 50 cycles is 95.8%. The specific capacity is higher than that of silicon suboxide-carbon anode materials reported in most literature and patents. The first coulombic efficiency and cycle performance are better than those of undoped graphite silicon suboxide composite anode materials reported in most literature and patents. This proves that the introduction of modified phthalonitrile resin coating material and crosslinking agent, as well as the liquid phase coating method, play a key role in the electrochemical performance of the composite material.

[0054] Comparative Example 1:

[0055] Without adding the crosslinking agent 1,8-diazabicyclo[5.4.0]undec-7-ene, and with all other raw materials unchanged, silicon suboxide-carbon composite material was prepared in the same manner as in Example 1, and lithium-ion batteries were fabricated and tested in the same manner as in Example 1.

[0056] As shown in Table 1, the lithium-ion battery prepared from the composite material in Comparative Example 1 has an initial discharge (lithium insertion) specific capacity of 1166.7 mAh / g, an initial charge (lithium removal) specific capacity of 913.5 mAh / g, an initial coulombic efficiency of 78.3%, and a capacity retention rate of 88.2% after 50 cycles. All electrochemical performance characteristics are worse than those of the composite material prepared in Example 1, demonstrating that the addition of the crosslinking agent has a significant promoting effect on the electrochemical performance of the composite material.

[0057] Example 2:

[0058] This embodiment provides a phthalonitrile resin-modified silicon-carbon anode coating material, its preparation method, and its energy storage application. The specific preparation process is as follows:

[0059] (1) Utilizing the cyano activity of phthalonitrile monomer, 4-(2-aminophenoxy)phthalonitrile was introduced into N,N-dimethylacetamide, and a complex of triethylamine and acetic anhydride was added. The mixture was reacted at 20°C for 15 h, filtered and washed with water until neutral, and then vacuum dried to prepare a modified phthalonitrile resin coating material with an N content of 20 wt%.

[0060] (2) Add 30g of modified phthalonitrile resin powder with a median particle size of 0.075mm to an organic reactor containing 140g of ethanol, and stir at room temperature until the modified phthalonitrile resin powder is fully dissolved to form a homogeneous solution.

[0061] (3) Add 30g of silica powder with a median particle size of 6μm to the homogeneous solution in step one, and stir and disperse it at a speed of 1100rpm to obtain a uniform silica suspension.

[0062] (4) Add 17g of 1,8-diazabicyclo[5.4.0]undec-7-ene to the suspension of (3), slowly heat to 80℃, and react at a constant temperature for 4h. Liquid phase coating is carried out in the reaction vessel, and cross-linking reaction occurs to form a coating structure with silicon suboxide as the core and modified phthalonitrile resin as the shell. Collect the product.

[0063] (5) The product obtained in (4) is cured and heated to 280°C in an oven at a heating rate of 4°C / min. The temperature is then maintained for 3 hours. After cooling to room temperature, the product is taken out to form a phthalocyanine ring-shaped coating structure and the product is collected.

[0064] (6) The product obtained in (5) was subjected to heat treatment. The product was heated to 900°C in a tube furnace under a nitrogen atmosphere at a heating rate of 3°C / min, and then kept at the temperature for 4 hours. After cooling to room temperature, the product was taken out.

[0065] (7) The product after heat treatment in (6) is ground and sieved through a 325-mesh screen to obtain a silicon suboxide-carbon composite anode material for lithium-ion batteries with controllable particle size.

[0066] Figure 5 This is a particle size distribution diagram of the silicon suboxide-carbon composite material prepared in Example 2. The diagram shows that the composite material has a good particle size distribution. The particle size of commercial silicon-carbon anode materials has a Dv(10) value of 2–9 μm, a Dv(50) value of 10–18 μm, and a Dv(90) value of 22–32 μm. The material prepared in Example 2 has a Dv(10) value of 2.8 μm, a Dv(50) value of 11.9 μm, and a Dv(90) value of 30.1 μm, all within the standard range of particle size for commercial silicon-carbon anode materials, demonstrating its good particle size characteristics.

[0067] Figure 6 The conductivity of the silicon suboxide-carbon composite material prepared in Example 2 is shown. Compared to SiO raw material, the conductivity of the prepared composite material is increased by 12 orders of magnitude, i.e., from 10... -12 The increase in S / cm to 2.5S / cm demonstrates the excellent electrical conductivity of the composite material.

[0068] Figure 7The first charge-discharge curve of the silicon suboxide composite anode material prepared in Example 2 is shown. The first discharge (lithium insertion) specific capacity of the composite material is 1803.2 mAh / g, the first charge (lithium removal) specific capacity is 1558.5 mAh / g, the first coulombic efficiency reaches 86.4%, and the capacity retention rate after 50 cycles is 95.5%.

[0069] Comparative Example 2:

[0070] The modified phthalonitrile resin material prepared in step (1) of Example 2 was replaced with unmodified ordinary phthalonitrile resin as the carbon source, while other raw materials remained unchanged. The silicon suboxide-carbon composite material was prepared in the same way as in Example 2, and a lithium-ion battery was made and tested in the same way as in Example 2.

[0071] As shown in Table 1, the lithium-ion battery prepared from the composite material in Comparative Example 2 has an initial discharge (lithium insertion) specific capacity of 1132.7 mAh / g, an initial charge (lithium removal) specific capacity of 858.6 mAh / g, an initial coulombic efficiency of 75.8%, and a capacity retention rate of 85.5% after 50 cycles. All electrochemical performance characteristics are worse than those of the composite material prepared in Example 2, demonstrating that the addition of the modified phthalonitrile resin coating material can significantly improve the electrochemical performance of the silicon suboxide-carbon composite material.

[0072] Example 3:

[0073] This embodiment provides a phthalonitrile resin-modified silicon-carbon anode coating material, its preparation method, and its energy storage application. The specific preparation process is as follows:

[0074] (1) Utilizing the cyano activity of phthalonitrile monomer, 4-(4-aminophenoxy)phthalonitrile was introduced into dimethyl sulfoxide, and dicyclohexylcarbodiimide was added. The mixture was reacted at 30°C for 10 h, filtered and washed with water until neutral, and then vacuum dried to prepare a modified phthalonitrile resin coating material with an N content of 23 wt%.

[0075] (2) Add 30g of modified phthalonitrile resin powder with a median particle size of 0.075mm to an organic reactor containing 165g of N-methylpyrrolidone, and stir at room temperature until the modified phthalonitrile resin powder is fully dissolved to form a homogeneous solution.

[0076] (3) Add 30g of silica powder with a median particle size of 6μm to the homogeneous solution in step one, and stir and disperse it at a speed of 1400rpm to obtain a uniform silica suspension.

[0077] (4) Add 23g of acrylic acid to the suspension of (3), slowly raise the temperature to 200℃, and react at a constant temperature for 6h. In the reaction vessel, liquid phase coating is carried out, cross-linking reaction occurs, and a coating structure with silicon suboxide as the core and modified phthalonitrile resin as the shell is formed. Collect the product.

[0078] (5) The product obtained in (4) was cured and heated to 300°C in an oven at a heating rate of 3°C / min. The temperature was kept constant for 5 hours and then cooled to room temperature. The product was then collected to form a triazine ring-shaped coating structure.

[0079] (6) The product obtained in (5) is subjected to heat treatment. The product is heated to 700°C in a tube furnace under an argon atmosphere at a heating rate of 5°C / min, and then kept at the temperature for 5 hours. After cooling to room temperature, the product is taken out.

[0080] (7) The product after heat treatment in (6) is ground and sieved through a 325-mesh screen to obtain a silicon suboxide-carbon composite anode material for lithium-ion batteries with controllable particle size.

[0081] The lithium-ion battery prepared using the composite material of Example 3 has a discharge (lithium insertion) specific capacity of 1666.7 mAh / g, a charge (lithium removal) specific capacity of 1421.7 mAh / g, an initial coulombic efficiency of 85.3%, and a capacity retention of 95.2% after 50 cycles.

[0082] The electrochemical properties, electrical conductivity, tap density, and compaction density of the silicon suboxide-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0083] Table 1

[0084]

[0085] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phthalonitrile resin-modified silicon-carbon anode coating material, characterized in that, The silicon-carbon anode coating material has a phthalocyanine or triazine-like coating structure with silicon suboxide as the core and modified phthalonitrile resin as the shell. The modified phthalonitrile resin coating material utilizes the cyano group activity of the phthalonitrile monomer to introduce conjugated groups. The nitrogen content in the modified phthalonitrile resin coating material is 10wt%–25wt% of the total nitrogen, of which pyrrole N accounts for 20–35wt% of the total nitrogen, pyridine N accounts for 30–45wt% of the total nitrogen, and graphite N accounts for 25–40wt% of the total nitrogen. A method for preparing phthalonitrile resin-modified silicon-carbon anode coating material, the method comprising the following steps: 1) Utilizing the cyano activity of phthalonitrile monomers, an encapsulating agent with a conjugated molecular structure is introduced into an organic solvent, and a catalyst is added to carry out the reaction, thereby preparing a modified phthalonitrile resin coating material; 2) Add the modified phthalonitrile resin coating material to a reaction vessel containing organic solvent, and stir at room temperature until the modified phthalonitrile resin coating material is completely dissolved to form a homogeneous solution; 3) Add the silica powder to the homogeneous solution in step 2), and stir and disperse it to obtain a uniform silica suspension; 4) Add a crosslinking agent to the suspension in step 3), heat to 60-210℃, keep the temperature constant for 2-8 h, carry out liquid phase coating in the reactor, and a crosslinking reaction occurs to form a coating structure with silica as the core and modified phthalonitrile resin coating material as the shell. Remove the solvent and collect the product. 5) The product obtained in step 4) is cured at a temperature of 200-350℃ for 1-7 h and a heating rate of 1-5℃ / min to form a phthalocyanine ring or triazine ring core-shell coated structure. The product is then collected. 6) Heat the product obtained in step 5) under nitrogen or inert gas atmosphere, heat to 500-1000℃ at a heating rate of 1-6℃ / min, hold at the temperature for 1-5 h, and then remove it after cooling to room temperature.

2. The phthalonitrile resin-modified silicon-carbon anode coating material according to claim 1, characterized in that, The coking value of the modified phthalonitrile resin-coated material is 50%–70%; the residual carbon content of the modified phthalonitrile resin-coated material is 50%–65%.

3. The phthalonitrile resin-modified silicon-carbon anode coating material according to claim 1, characterized in that, The median particle size of the silicon-carbon anode coating material is below 45 μm; the electrical conductivity is greater than 2 S / cm; and the tap density is 0.8–1.2 g / cm³. 3 The compacted density is 1.2–1.4 g / cm³. 3 .

4. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: 1) Utilizing the cyano activity of phthalonitrile monomers, an encapsulating agent with a conjugated molecular structure is introduced into an organic solvent, and a catalyst is added to carry out the reaction, thereby preparing a modified phthalonitrile resin coating material; 2) Add the modified phthalonitrile resin coating material to a reaction vessel containing organic solvent, and stir at room temperature until the modified phthalonitrile resin coating material is completely dissolved to form a homogeneous solution; 3) Add the silica powder to the homogeneous solution in step 2), and stir and disperse it to obtain a uniform silica suspension; 4) Add a crosslinking agent to the suspension in step 3), heat to 60-210℃, keep the temperature constant for 2-8 h, carry out liquid phase coating in the reactor, and a crosslinking reaction occurs to form a coating structure with silica as the core and modified phthalonitrile resin coating material as the shell. Remove the solvent and collect the product. 5) The product obtained in step 4) is cured at a temperature of 200-350℃ for 1-7 h and a heating rate of 1-5℃ / min to form a phthalocyanine ring or triazine ring core-shell coated structure. The product is then collected. 6) Heat the product obtained in step 5) under nitrogen or inert gas atmosphere, heat to 500-1000℃ at a heating rate of 1-6℃ / min, hold at the temperature for 1-5 h, and then remove it after cooling to room temperature.

5. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to claim 4, characterized in that, In step 1) above, the organic solvent is one of N-methylpyrrolidone, N,N-dimethylacetamide, or dimethyl sulfoxide; the encapsulating agent is 4-(4-aminophenoxy)phthalonitrile or 4-(2-aminophenoxy)phthalonitrile; the catalyst is a complex of triethylamine and acetic anhydride, or dicyclohexylcarbodiimide; the reaction temperature is 15–30°C, and the reaction time is 8–18 h.

6. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to claim 4, characterized in that, In step 2) above, the organic solvent is one of ethanol, N,N-dimethylformamide or N-methylpyrrolidone; the modified phthalonitrile resin coating material accounts for 15% to 30% of the mass of the organic solvent.

7. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to claim 4, characterized in that, In step 3) above, the molecular formula of the silicon suboxide powder is SiOx, 0.5 ≤ x ≤ 1.5, the median particle size is 3~7μm, and the specific surface area is ≤5m². 2 / g; the silica powder accounts for 50% to 250% of the mass of the modified phthalonitrile resin coating material; the stirring speed of the silica powder added to the homogeneous solution is 800 to 1500 rpm.

8. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to claim 4, characterized in that, In step 4) above, the crosslinking agent is 1,8-diazabicyclo[5.4.0]undec-7-ene or acrylic acid; the crosslinking agent accounts for 20% to 90% of the mass of the modified phthalonitrile resin coating material; the reaction temperature is 70 to 200℃, and the constant temperature time is 3 to 7h.

9. The method for preparing the phthalonitrile resin-modified silicon-carbon anode coating material according to claim 4, characterized in that, In step 5) above, the curing temperature is 220-330℃, the curing time is 2-6 h, and the heating rate is 2-5℃ / min; in step 6) above, the inert gas is argon, the heating rate of the heat treatment is 2-5℃ / min, the temperature is 600-900℃, and the holding time is 2-5 h.

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