Silicon carbon material and preparation method thereof, lithium ion battery and electronic product

Abstract

The embodiment of the invention provides a silicon carbon material and a preparation method thereof, a lithium ion battery and an electronic product. The preparation method of the silicon-carbon material comprises the following steps: dissolving a carbon source material in a solvent to obtain a carbon source solution; the preparation method comprises the following steps: dissolving a surfactant in a dipolar aprotic solvent to obtain a surfactant solution, and adding carbon nanotube powder into the surfactant solution to obtain a carbon nanotube dispersion liquid; mixing the carbon source solution with the carbon nanotube dispersion liquid, drying to obtain a solid mixture, and mixing the solid mixture with alkali metal hydroxide to form a precursor material; mixing the precursor material and phosphorus pentanitride, putting the mixture into a tubular furnace, and sintering at high temperature to obtain a nitrogen and phosphorus doped porous carbon material; and carrying out silicon deposition treatment and carbon coating treatment on the nitrogen and phosphorus doped porous carbon material to finally obtain the nitrogen and phosphorus doped silicon carbon material.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of lithium-ion battery materials. More specifically, the embodiments of the present application relate to a silicon-carbon material and a preparation method thereof, a lithium-ion battery, and an electronic product. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, large-scale energy storage and high-power electronic devices, the demand for negative electrode materials with high energy density, long cycle life and high safety has become increasingly urgent. Silicon (Si)-based negative electrode materials have become ideal candidates for lithium-ion battery negative electrodes due to their theoretical specific capacity of up to 4200mAh / g. However, the huge volume change (up to 300% or more) caused by the insertion / deinsertion of lithium ions during the charge and discharge process of silicon leads to the destruction of the electrode structure, the pulverization of active materials and the continuous rupture and regeneration of the solid electrolyte interface film (SEI), which in turn leads to problems such as low coulombic efficiency, short cycle life and poor safety.

[0003] Among them, porous design and element doping have been proven to be effective in buffering volume expansion. At present, the methods for improving the specific capacity of porous carbon are showing a diversified trend. For example, doping or coating phosphorus, tin, sulfur and other elements or compounds have become the mainstream modification methods. By introducing these active substances, the active sites of the material can be effectively increased, and the lithium storage specific capacity of the material can be significantly improved. In the specific preparation process, a gas phase mixing reaction is often used to generate a phosphorus-doped porous silicon-carbon precursor, and then a sulfur vapor passivation technology is used to form an intermediate layer, and finally an amorphous carbon outer layer is coated on the surface by vapor deposition technology. However, this preparation process requires the use of hazardous gases such as phosphine and sulfur vapor, which not only poses significant environmental and safety risks, but also the phosphorus sulfide intermediate layer formed by sulfur vapor passivation is prone to side reactions with the electrolyte during the battery cycle, further affecting the cycle life and safety of the battery.

[0004] In view of this, it is necessary to provide a new technical solution to solve the above technical problems. Summary of the Invention

[0005] The purpose of this application is to provide a new technology solution for silicon-carbon materials and preparation methods thereof, lithium-ion batteries and electronic products.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a silicon-carbon material. The preparation method comprises:

[0007] S1: dissolving the carbon source material in a solvent to obtain a carbon source solution;

[0008] S2: dissolving a surfactant in a dipolar aprotic solvent to obtain a surfactant solution, and adding carbon nanotube powder to the surfactant solution to obtain a carbon nanotube dispersion;

[0009] S3: mixing the carbon source solution with the carbon nanotube dispersion liquid and drying to obtain a solid mixture, mixing the solid mixture with an alkali metal hydroxide to form a precursor material;

[0010] S4: mixing the precursor material and triphosphorus pentanitride and placing in a tube furnace, high-temperature sintering to obtain a nitrogen-phosphorus-doped porous carbon material;

[0011] S5: performing silicon deposition treatment and carbon coating treatment on the nitrogen-phosphorus-doped porous carbon material to finally obtain a nitrogen-phosphorus-doped silicon-carbon material.

[0012] Optionally, in step S4, the adding proportion of the precursor material and triphosphorus pentanitride is in the range of 10:1 to 10:2.

[0013] Optionally, the nitrogen doping amount in the nitrogen-phosphorus-doped porous carbon material is 2% to 10%, and the phosphorus doping amount is 1% to 3%.

[0014] Optionally, in step S4, the high-temperature sintering temperature is 600°C to 1000°C, and the sintering time is 60min to 240min.

[0015] Optionally, in step S5, the silicon content in the nitrogen-phosphorus-doped silicon-carbon material is 45% to 55% of the mass of the silicon-carbon material.

[0016] Optionally, in step S3, the mass ratio of the precursor material to the alkali metal hydroxide is in the range of 5:1 to 15:1.

[0017] Optionally, the mass ratio of the carbon source material to the carbon nanotube powder is 10:1 to 150:1.

[0018] Optionally, in step S5, the silicon deposition treatment and carbon coating treatment on the nitrogen-phosphorus-doped porous carbon material include:

[0019] placing the nitrogen-phosphorus-doped porous carbon material washed with clean water and dried in a fluidized bed, increasing the reaction temperature to a temperature range of 600°C to 800°C under an inert gas atmosphere, then introducing a silicon source gas into the fluidized bed to perform silicon deposition treatment; after the silicon deposition treatment process is completed, switching to introduce a carbon source gas to perform carbon coating treatment on the material surface, and finally obtaining a nitrogen-phosphorus-doped silicon-carbon material.

[0020] Optionally, in step S1, the carbon source material is one or more of pitch, phenolic resin, epoxy resin, polyacrylonitrile, lignin polyimide, polyaniline, petroleum coke, and coal tar.

[0021] Optionally, in step S2, the surfactant is one or more of sodium lauryl sulfate, bile salt, cetyltrimethylammonium bromide, tetrabutylammonium hydroxide, polyvinylpyrrolidone, sodium polystyrene sulfonate, poloxamer, polyoxyethylene sorbitan monooleate, and lignin sulfonate.

[0022] In a second aspect, embodiments of the present application further provide a silicon-carbon material, wherein the silicon-carbon material is prepared using the method for preparing the silicon-carbon material as described in any one of the first aspects.

[0023] In a third aspect, embodiments of the present application further provide a lithium-ion battery comprising the silicon-carbon material as described in the second aspect.

[0024] In a fourth aspect, an embodiment of the present application further provides an electronic product comprising the lithium-ion battery as described in the third aspect.

[0025] One of the technical effects of this application is:

[0026] The silicon-carbon material provided in the embodiment of the present application specifically uses phosphorus pentane as the doping material of the intermediate layer to prepare a nitrogen-phosphorus doped porous carbon structure. Then, by implementing silicon deposition and carbon coating processes on the nitrogen-phosphorus doped porous carbon, a nitrogen-phosphorus doped silicon-carbon material is finally obtained. This silicon-carbon material is applied to batteries. On the one hand, this silicon-carbon material can ensure that the battery has excellent electrochemical cycle performance, providing a strong guarantee for the stable and long-lasting operation of the battery; on the other hand, in the high-temperature preparation process, phosphorus pentane is used to achieve nitrogen-phosphorus doping, which effectively avoids the risk of leakage of toxic or flammable gases and greatly improves the safety of the production process. In addition, the material can also avoid side reactions in the electrolyte, help extend the service life of the battery, reduce the risk of performance degradation of the battery during use, and provide strong support for the high-quality development of battery technology.

[0027] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0029] Figure 1 Shown is a flow chart of the method for preparing silicon-carbon material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0031] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0032] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0033] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0034] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0035] The present invention provides a silicon-carbon material, specifically a silicon-carbon anode material. The silicon-carbon material provided in the present invention utilizes phosphorus pentanitride as the dopant in the intermediate layer to form a nitrogen-phosphorus-doped porous carbon structure. Silicon deposition and carbon coating are then performed on the nitrogen-phosphorus-doped porous carbon to ultimately produce the nitrogen-phosphorus-doped silicon-carbon material.

[0036] Applying this silicon-carbon material to batteries, on the one hand, ensures excellent electrochemical cycle performance, providing strong support for stable and long-lasting battery operation. On the other hand, the use of phosphorus pentanitride to achieve nitrogen and phosphorus doping during the high-temperature preparation process effectively avoids the risk of toxic or flammable gas leakage, greatly improving the safety of the production process. Furthermore, this material can prevent side reactions in the electrolyte, helping to extend the battery's service life and reduce the risk of performance degradation during use, providing strong support for the high-quality development of battery technology.

[0037] Reference Figure 1 , the preparation method of silicon-carbon material comprises the following steps:

[0038] S1: dissolving the carbon source material in a solvent to obtain a carbon source solution;

[0039] S2: dissolving a surfactant in a dipolar aprotic solvent to obtain a surfactant solution, and adding carbon nanotube powder to the surfactant solution to obtain a carbon nanotube dispersion;

[0040] S3: mixing the carbon source solution and the carbon nanotube dispersion and drying them to obtain a solid mixture, and mixing the solid mixture with an alkali metal hydroxide to form a precursor material;

[0041] S4: mixing the precursor material and phosphorus pentane nitride, placing the mixture in a tube furnace, and sintering at a high temperature to obtain a nitrogen-phosphorus doped porous carbon material;

[0042] S5: performing silicon deposition treatment and carbon coating treatment on the nitrogen and phosphorus doped porous carbon material to finally obtain a nitrogen and phosphorus doped silicon-carbon material.

[0043] In the embodiment of the present application, in step S1, the carbon source material is slowly added to a suitable solvent, and the carbon source material is fully dissolved by stirring, ultrasound, etc., so as to obtain a uniform carbon source solution.

[0044] In this step, the carbon source material builds the basic carbon skeleton structure. In subsequent high-temperature sintering and other processes, the carbon source material will undergo a series of physical and chemical changes, such as thermal decomposition and carbonization, gradually forming the main structure of the carbon material.

[0045] Furthermore, the carbon source material in this step and the carbon nanotubes in step S2 synergistically form a carbon skeleton in step S3, which acts as a conductive pathway within the silicon-carbon material. In battery applications, electrons need to be transported through the material to achieve electrochemical reactions. Silicon itself has relatively poor conductivity, but the presence of the carbon skeleton can effectively improve the overall conductivity of the silicon-carbon material, reducing the material's internal resistance, thereby accelerating electron transmission and improving the material's charge and discharge efficiency.

[0046] Furthermore, the synergistic effect of carbon source materials and carbon nanotube powders can interact with other substances to achieve elemental doping. For example, by selecting a carbon source material containing specific elements or introducing other element sources during the preparation process, the carbon skeleton can be doped with elements such as nitrogen and phosphorus. These doping elements can modify the electronic structure and surface properties of the carbon material, further improving the material's conductivity, stability, and electrochemical activity.

[0047] In this step, a carbon source solution is prepared and mixed with a subsequently prepared carbon nanotube dispersion, followed by drying. This allows the carbon source molecules and carbon nanotubes to be uniformly dispersed at the molecular or nanoscale level through the fluidity and surface tension of the solvent.

[0048] Illustratively, the carbon source material may be one or more of asphalt, phenolic resin, epoxy resin, polyacrylonitrile, lignin polyimide, polyaniline, petroleum coke, and coal tar.

[0049] Exemplary solvents include, but are not limited to, toluene, isopropanol, and terephthalic acid. Different solvents have varying physical and chemical properties, such as polarity, boiling point, and solubility. Selecting an appropriate solvent can effectively promote the dissolution process based on the properties of the carbon source material, ensuring the quality and stability of the carbon source solution, thereby positively impacting the entire silicon-carbon material preparation process.

[0050] In step S2, surfactant is a molecule having a hydrophilic group and a hydrophobic group simultaneously. For example, the solvent can be NMP (N-Methylpyrrolidone). NMP (N-Methylpyrrolidone) is a commonly used organic solvent with good solubility. Surfactant is added to NMP, and the surfactant molecules gradually diffuse and dissolve in NMP. The hydrophilic group tends to interact with the NMP molecules, while the hydrophobic group is toward the outside. The surfactant molecules after dissolution can reduce the interfacial tension between CNT powder and NMP in subsequent processes, making CNT powder more easily dispersed in the solution, playing the role of a dispersing aid.

[0051] In this step, carbon nanotube (CNT) powders, due to their large aspect ratio and high surface energy, tend to aggregate and form agglomerates. When a surfactant solution is added to the CNT powder, the hydrophobic groups of the surfactant molecules adsorb onto the CNT surfaces, while the hydrophilic groups face the solvent, forming an adsorption layer. This adsorption layer lowers the surface energy between the CNTs, reducing their mutual attraction and increasing their compatibility with the solvent, allowing the CNTs to be evenly dispersed in the solution, forming a stable CNT dispersion.

[0052] Illustratively, in step S2, the surfactant is one or more of sodium dodecyl sulfate (SDS), cholate, cetyltrimethylammonium bromide (CTAB), tetrabutylammonium hydroxide (TBAH), polyvinylpyrrolidone (PVP), sodium polystyrene sulfonate (PSS), poloxamer (Pluronic), polyoxyethylene sorbitan monooleate (Tween-80), and lignin sulfonate.

[0053] For example, the dipolar aprotic solvent includes but is not limited to NMP (N-methylpyrrolidone) solvent, and may also be dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0054] For example, the surfactant is added to the dipolar aprotic solvent at a concentration ranging from 1% (mass percentage, the same below) to 5%. By controlling this concentration range, the effect of the surfactant in the solvent system can be effectively adjusted to achieve uniform dispersion and stable existence of the dispersoid in the dispersion.

[0055] Alternatively, the surfactant concentration in the dipolar aprotic solvent is within a range of 3%, and the number of surfactant molecules is moderate, allowing for a relatively complete adsorption layer to form on the CNT surface. This effectively weakens the interactions between most CNTs, allowing the CNTs to be more evenly dispersed in the dipolar aprotic solvent. Furthermore, the surfactant concentration in the dipolar aprotic solvent is within a range of 3%, resulting in a relatively stable dispersion.

[0056] For example, a surfactant solution is added to carbon nanotube powder, and a high-pressure homogenizer is used to process the carbon nanotube dispersion.

[0057] After multiple treatments in a high-pressure homogenizer, the CNT agglomerates are gradually dispersed into single CNTs or smaller CNT bundles, which are evenly dispersed in the surfactant solution, thereby obtaining a stable CNT dispersion.

[0058] Optionally, the amount of surfactant used is generally 1-10 times the mass of the CNTs. Further, the amount of surfactant used is generally 3-6 times the mass of the CNTs.

[0059] Specifically, when dispersing CNTs into a surfactant solution to prepare a dispersion, if the amount of surfactant used is too little, all CNTs may not be completely wrapped, resulting in strong van der Waals forces still existing between some CNTs, making them prone to agglomeration and forming larger particles. When the amount of surfactant used is within the above-mentioned appropriate range, the CNTs can be evenly dispersed in the solvent to form a stable dispersion. When preparing silicon-carbon negative electrode materials, CNTs can be used as conductive additives to improve the conductivity of silicon. When the amount of surfactant used is within the above-mentioned appropriate range, the CNTs are evenly dispersed, forming an efficient conductive network, and improving the charge and discharge efficiency and cycle stability of the battery.

[0060] In the above steps S1 and S2, the mass ratio of the carbon source material to the carbon nanotube powder is 10:1 to 150:1. Optionally, the mass ratio of the carbon source material to the carbon nanotube powder is 100:1 to 150:1.

[0061] Specifically, carbon nanotubes have excellent electrical conductivity, but using them alone makes it difficult to form a continuous, efficient conductive network. The carbon source material, during subsequent processing, forms a carbon matrix within which the carbon nanotubes are dispersed, forming a carbon-based composite material. When the mass ratio is within the above range, the carbon source material provides sufficient support and connection space for the carbon nanotubes, allowing them to form a good conductive network within the carbon matrix.

[0062] In addition, when the mass ratio of the two is limited to the above range, the carbon skeleton and carbon nanotubes work synergistically to buffer the volume change of silicon, maintain the structural integrity of the material, and improve the cyclic stability of the material.

[0063] In step S3, the carbon source solution and the CNT dispersion are mixed. During subsequent processing, the carbon source material forms a carbon matrix, and the CNTs are embedded within it as a reinforcing phase, forming a carbon-based composite material (carbon skeleton). This composite structure can fully utilize the excellent properties of CNTs, such as high strength and high conductivity, to enhance the overall performance of the composite material.

[0064] The addition of CNTs can improve the electrical conductivity, thermal conductivity, and mechanical properties of carbon-based materials. For example, in lithium-ion battery negative electrode materials, CNTs can form a conductive network, increase the electron transfer rate, and enhance the material's charge and discharge performance.

[0065] Specifically, after the carbon source solution and the CNT dispersion are mixed and dried, the carbon source solution loses the solvent during the drying process and exists in a solid form, presenting as amorphous carbon or a low-crystallinity carbon precursor. Amorphous carbon or a low-crystallinity carbon precursor serves as a source of carbon matrix for forming a porous carbon structure in subsequent heat treatment. Carbon nanotubes (one or more of multi-walled, oligo-walled, and single-walled) are uniformly dispersed in the mixed solution and still maintain their tubular structure after drying, but some carbon source molecules can be adsorbed on the surface. Carbon nanotubes act as a conductive skeleton or structural reinforcement to improve the conductivity, mechanical strength, etc. of the composite material.

[0066] In this step, the solid mixture is formed by carbon source molecules adsorbing onto the surface of carbon nanotubes through physical adsorption or weak chemical bonds (such as hydrogen bonds), forming a coating or bridging structure. Furthermore, carbon nanotubes, as one-dimensional nanomaterials, form multi-scale composite structures with zero-dimensional or three-dimensional carbon source precursors, facilitating the construction of porous structures.

[0067] In this step, the carbon source solution and the CNT dispersion can be mixed by ultrasound or the like.

[0068] In this step, vacuum drying or atomization drying can be used to form a solid mixture.

[0069] In this step, alkali metal hydroxides (such as sodium hydroxide and potassium hydroxide) act as activators during the subsequent high-temperature sintering process. At high temperatures, KOH, for example, reacts chemically with the carbon source, etching the carbon skeleton and forming a rich porous structure, thereby increasing the specific surface area and pore volume of the product, improving its application performance in fields such as electrochemical energy storage and adsorption.

[0070] For example, the mass ratio of the carbon source material to the CNT powder can be 1:10-1:20, which helps to form a silicon-carbon composite material with good electrochemical properties.

[0071] In step S3 of the present application, the mass ratio of the precursor material to the alkali metal hydroxide is in a range of 5:1 to 15:1. Optionally, the mass ratio of the precursor material to the alkali metal hydroxide is 8:1, 10:1, or 13:1.

[0072] In this step, alkali metal hydroxides (such as NaOH and KOH) typically act as activators, participating in the structural transformation of the precursor material. A low mass ratio of the precursor material to the alkali metal hydroxide may result in incomplete reaction and reduced performance. A high mass ratio of the precursor material to the alkali metal hydroxide may trigger side reactions, waste raw materials, and increase the difficulty of post-processing.

[0073] In this step, controlling the mass ratio of the precursor material and alkali metal hydroxide can optimize the reaction rate and product morphology. For example, when preparing porous carbon materials, alkali metal hydroxide can promote the etching of the carbon source and the formation of pores, but excessive use can lead to pore structure collapse or excessive ablation.

[0074] In step S4, the precursor material and phosphorus pentane are mixed uniformly to ensure that the phosphorus pentane is evenly dispersed in the precursor material, allowing nitrogen and phosphorus to be uniformly doped into the carbon framework during the subsequent high-temperature sintering process. The high aspect ratio of the CNTs in the precursor material creates long-range electron transport channels, reducing interfacial impedance. Nitrogen and phosphorus doping induces distortion in the electronic structure of the carbon layer, enhancing lithium ion adsorption. This composite structure forms a three-dimensional conductive framework, effectively improving the material's dynamic performance.

[0075] At high temperatures, the precursor material and phosphorus pentane will undergo a series of complex chemical reactions and physical changes. On the one hand, the carbon source material will undergo pyrolysis, polycondensation and other reactions to form the basic skeleton structure of carbon; on the other hand, the nitrogen and phosphorus elements in phosphorus pentane will react with the carbon source material and be doped into the carbon skeleton by substitution, insertion and the like. At the same time, some gases (such as carbon dioxide, nitrogen, etc.) will be produced during the high-temperature sintering process. The escape of these gases will form a large number of pores in the carbon material, thereby obtaining a nitrogen-phosphorus-doped porous carbon material. In addition, in step S3, alkali metal hydroxides (such as NaOH, KOH) react with the carbon source material to etch the carbon skeleton to form abundant pores. The porous structure is conducive to increasing the specific surface area of ​​the material, improving the adsorption performance and electrochemical properties of the material, and nitrogen and phosphorus doping can change the electronic structure and surface properties of the carbon material, further improving the performance of the material.

[0076] In this step, safe and pollution-free solid phosphorus pentanitride is used to avoid the risk of leakage of toxic / flammable gases in high-temperature processes and the risk of side reactions in the electrolyte.

[0077] In an embodiment of the present application, in step S4, the ratio of the added parts of the precursor material and phosphorus pentane is in the range of 10:1 to 10:2.

[0078] This ratio helps the nitrogen and phosphorus elements in phosphorus pentane to be more evenly doped into the precursor material. Adding too little phosphorus pentane can lead to uneven distribution of nitrogen and phosphorus, resulting in insufficient doping in some areas and failing to fully realize their role in improving material properties. Adding too much can cause localized overdoping, triggering unwanted side reactions and affecting the overall performance and stability of the material.

[0079] Furthermore, combined with the etching of the carbon skeleton by the alkali metal hydroxide in step S3 and the gas evolution generated by the reaction of phosphorus pentane with the precursor material in step S4, this ratio range can promote the formation of a richer, more uniform porous structure, that is, it helps to form a suitable pore size and distribution in the carbon skeleton, increasing the specific surface area of ​​the material. This allows lithium ions and electrons to be transmitted more smoothly within the carbon skeleton, reducing the transmission resistance of lithium ions and electrons, and improving the battery's charge and discharge efficiency and rate performance.

[0080] In the embodiment of the present application, in step S4, the nitrogen doping amount in the nitrogen-phosphorus doped porous carbon material is 2% to 10%, and the phosphorus doping amount is 1% to 3%. Alternatively, the nitrogen doping amount in the nitrogen-phosphorus doped porous carbon material is 3% to 8%, and the phosphorus doping amount is 1.5% to 2%.

[0081] In this embodiment, nitrogen and phosphorus doping can increase the charge carrier concentration in the porous carbon, thereby improving the conductivity of the material. Within the above-mentioned doping amount range, the synergistic effect of nitrogen and phosphorus can make the electron transport of the porous carbon smoother, reduce the internal resistance of the battery, and improve the battery's charge and discharge efficiency and rate performance. For example, in lithium-ion batteries, faster electron transmission speed means that the battery can complete the charge and discharge process in a shorter time, meeting the needs of high-power devices.

[0082] In addition, nitrogen and phosphorus doping introduces more active sites on the porous carbon surface. These active sites can interact more strongly with lithium ions, enhancing the material's ability to adsorb lithium ions. By limiting the nitrogen and phosphorus doping levels, the silicon-carbon material's adsorption of lithium ions reaches a relatively ideal level, helping to improve the battery's capacity and cycle stability.

[0083] In the embodiment of the present application, in step S4, the high-temperature sintering temperature is 600° C. to 1000° C., and the sintering time is 60 min to 240 min.

[0084] In this embodiment, the high-temperature sintering temperature and sintering time are limited. The appropriate temperature range and sintering time are conducive to the formation of a rich pore structure. During the sintering process, volatile substances in the precursor material escape, leaving pores in the carbon material. A preliminary pore structure begins to form at 600°C, and as the temperature increases, the size and distribution of the pores are gradually optimized. However, if the temperature is too high, the pore structure will be destroyed, resulting in a decrease in the number of pores or an excessively large pore size, affecting the specific surface area and ion transport performance of the material.

[0085] Furthermore, nitrogen and phosphorus doping can significantly alter the surface chemical properties of carbon materials at appropriate temperatures. Within the 600°C-1000°C range, nitrogen and phosphorus atoms react with functional groups on the carbon surface, introducing more active sites. For example, nitrogen doping can form different nitrogen species on the carbon surface, such as pyridinic and pyrrolic nitrogen. These nitrogen species can enhance the material's ability to adsorb lithium ions, improving the battery's capacity and cycle stability.

[0086] In step S5, the nitrogen and phosphorus doped porous carbon material is subjected to silicon deposition treatment and carbon coating to obtain a nitrogen and phosphorus doped silicon-carbon material.

[0087] Specifically, the nitrogen and phosphorus doped porous carbon material that has been washed with clean water and dried is placed in a fluidized bed, and the reaction temperature is raised to a temperature range of 600°C to 800°C under an inert gas atmosphere. Subsequently, silicon source gas is introduced into the fluidized bed to implement silicon deposition treatment; after the silicon deposition treatment process is completed, the carbon source gas is switched to be introduced, and the surface of the material is carbon-coated to finally obtain a nitrogen and phosphorus doped silicon-carbon material.

[0088] The porous carbon material formed in step S4 inherently possesses good electrical conductivity, and its unique pore structure increases the material's specific surface area, providing abundant attachment sites for subsequent silicon deposition and carbon coating. Nitrogen and phosphorus doping further improves the porous carbon material's electronic structure and chemical properties, enhancing its electrical conductivity and ion adsorption capacity. This facilitates the rapid transport and storage of lithium ions in battery electrode materials.

[0089] In silicon-carbon materials, silicon undergoes significant volume changes during charge and discharge (up to 300% or more), which can easily lead to pulverization and shedding of the electrode material, thereby reducing the battery's cycle life. The pore structure of porous carbon materials can buffer silicon's volume changes and maintain the structural stability of the electrode material.

[0090] In a fluidized bed, an inert atmosphere (such as nitrogen or argon) prevents the nitrogen / phosphorus-doped porous carbon material and the subsequently generated silicon-carbon material from reacting with oxygen and moisture in the air, preventing oxidation or other side reactions, thereby ensuring the performance and quality of the materials. Furthermore, the inert atmosphere provides a stable reaction environment for silicon deposition and carbon coating, which is conducive to the smooth progress of the reaction and the consistency of the product.

[0091] For example, an inert gas (such as nitrogen or argon) is introduced into the fluidized bed, and the gas flow rate is controlled at 100-300 mL / min to exclude air from the fluidized bed.

[0092] Silane (such as monosilane SiH4) undergoes thermal decomposition reaction at temperatures between 600°C and 800°C, generating silicon atoms. These silicon atoms then deposit on the surface and pores of nitrogen-phosphorus-doped porous carbon materials, forming silicon nanoparticles or silicon layers, thereby achieving a composite of silicon and carbon. Silicon has a high theoretical specific capacity (approximately 4200mAh / g), and when combined with carbon, it can significantly increase the energy density of the battery.

[0093] After the silicon deposition process is complete, the silane gas is turned off and replaced with acetylene gas for surface carbon coating. Acetylene undergoes thermal decomposition at high temperatures, generating carbon atoms. These carbon atoms form a carbon coating on the surface of the deposited silicon. This carbon coating prevents direct contact between the silicon and the electrolyte, reduces silicon side reactions, and improves the material's cycling stability and Coulombic efficiency. Furthermore, the carbon coating improves the material's conductivity and facilitates lithium ion transport.

[0094] Illustratively, in this step, the silicon deposition temperature is 500°C to 800°C, and the carbon deposition temperature is 500°C to 600°C.

[0095] In an embodiment of the present application, in step S5, silicon in the nitrogen and phosphorus doped silicon-carbon material accounts for 45% to 55% of the mass of the silicon-carbon material.

[0096] In this embodiment, silicon undergoes a huge volume change during the charge and discharge process. This volume change can easily lead to pulverization and shedding of the electrode material, thereby reducing the cycle life of the battery. When the silicon content is between 45% and 55%, the nitrogen-phosphorus-doped porous carbon material can play a certain buffering role. The pore structure of the porous carbon material can accommodate the volume change of silicon during the charge and discharge process, reduce direct contact between silicon and the electrolyte, and reduce the side reactions of silicon.

[0097] In addition, silicon itself has relatively poor conductivity. When the proportion of silicon in the silicon-carbon material is too high, the conductivity of the entire material will decrease. When the silicon proportion is between 45% and 55%, the nitrogen and phosphorus doped porous carbon material and the surface carbon coating can form a good conductive network, compensating for the defect of silicon's insufficient conductivity.

[0098] The present application also provides a silicon-carbon material, which is prepared using the method for preparing the silicon-carbon material described above.

[0099] In an embodiment of the present application, a silicon-carbon material is provided that utilizes safe and pollution-free solid-state phosphorus pentanitride for nitrogen and phosphorus doping, thereby avoiding the risk of toxic / flammable gas leakage during high-temperature processes and the risk of electrolyte side reactions. Furthermore, the high aspect ratio of CNTs creates long-range electron transport channels, reducing interfacial impedance. Nitrogen and phosphorus doping induces distortion in the electronic structure of the carbon layer, enhancing lithium ion adsorption. The resulting composite structure forms a three-dimensional conductive framework, effectively improving the material's dynamic performance.

[0100] The present application also provides a lithium-ion battery comprising the silicon-carbon material described above.

[0101] In the embodiments of the present application, the lithium-ion battery uses the above-mentioned silicon-carbon material to prepare the electrode negative electrode, and the battery has good electrochemical cycle performance. For example, the battery has a higher first charge and discharge efficiency, 5C capacity retention rate and 100-cycle capacity retention rate, and the battery has a lower expansion rate.

[0102] The present application also provides an electronic product comprising the lithium-ion battery described above.

[0103] In the embodiments of the present application, battery products include but are not limited to headphones, smart watches, etc.

[0104] The following specific examples illustrate that the silicon-carbon material prepared by the silicon-carbon material preparation method provided in the embodiments of the present application is applied to a battery, and the battery has good electrochemical cycle performance.

[0105] Example 1

[0106] S1: 120 g of coal tar pitch was added to 180 g of toluene, and the coal tar pitch was completely dissolved in the toluene by ultrasonication to obtain a coal tar pitch solution;

[0107] S2: 1 g of PVP was added to 198 g of NMP. After the PVP was completely dissolved in the NMP, 1 g of SWCNT powder was added and homogenized at a pressure of 80 MPa to obtain a SWCNT dispersion.

[0108] S3: The coal tar solution and the SWCNT dispersion are mixed, ultrasonically mixed until uniform, and then dried. The mixture is then mixed with 20 g of KOH to obtain a precursor material.

[0109] S4: The precursor material and 42 g of phosphorus pentane were uniformly mixed and placed in a tube furnace for sintering at 800 °C for 120 min under an Ar atmosphere to obtain a nitrogen-phosphorus doped porous carbon material;

[0110] S5: 50g of nitrogen and phosphorus doped porous carbon material was washed and dried with clean water, then placed in a fluidized bed. After the temperature was raised to 650°C under Ar atmosphere, SiH4 was introduced at a rate of 150 sccm. After deposition for 2 hours, silane was turned off, the temperature was lowered to 570°C, and acetylene gas was introduced at a rate of 120 sccm. The deposition was continued for 30 minutes to obtain nitrogen and phosphorus doped silicon-carbon material.

[0111] Example 2

[0112] S1: adding 100 g of phenolic resin to 200 g of isopropyl alcohol, and completely dissolving the phenolic resin in the isopropyl alcohol by ultrasonication to obtain a phenolic resin solution;

[0113] S2: 1 g of PVP was added to 198 g of NMP. After the PVP was completely dissolved in the NMP, 1.5 g of SWCNT powder was added and homogenized at 80 MPa to obtain a SWCNT dispersion.

[0114] S3: The phenolic resin solution and the SWCNT dispersion were mixed, mixed uniformly by ultrasonication, dried, and then mixed with 15 g of KOH to obtain a precursor material;

[0115] S4: The precursor material and 37 g of phosphorus pentane were uniformly mixed and placed in a tube furnace and sintered at 900 °C for 90 min under an Ar atmosphere to obtain a nitrogen-phosphorus doped porous carbon material;

[0116] S5: 50g of nitrogen and phosphorus doped porous carbon material was washed and dried with clean water, then placed in a fluidized bed. After rising to 700℃ under Ar atmosphere, SiH4 was introduced at a rate of 150sccm. After deposition for 2h, silane was turned off, the temperature was lowered to 570℃, acetylene gas was introduced at a rate of 120sccm, and deposition was carried out for 30min to obtain nitrogen and phosphorus doped silicon-carbon material.

[0117] Example 3

[0118] S1: Add 150 g of petroleum coke to 250 g of DMSO, and heat and stir until the petroleum coke is completely dispersed and dissolved to obtain a petroleum coke solution;

[0119] S2: 2 g of bile salt was added to 198 g of NMP. After the bile salt was completely dissolved in the NMP, 1 g of SWCNT powder was added and high-pressure homogenization was applied at 100 MPa to obtain a SWCNT dispersion.

[0120] S3: The petroleum coke solution and the SWCNT dispersion were mixed, ultrasonically mixed, dried, and then mixed with 30 g of NaOH to obtain a precursor material;

[0121] S4: The precursor material and 70 g of phosphorus pentane were uniformly mixed and placed in a tube furnace. The mixture was sintered at 700 °C for 180 min under a nitrogen atmosphere to obtain a nitrogen-phosphorus doped porous carbon material.

[0122] S5: 50g of nitrogen and phosphorus doped porous carbon material was washed and dried with clean water, then placed in a fluidized bed. After heating to 750°C under an Ar atmosphere, SiH4 gas was introduced at a rate of 180 sccm. After deposition for 2.5h, the SiH4 gas was turned off, the temperature was lowered to 580°C, and acetylene gas was introduced at a rate of 140 sccm. Deposition was continued for 40min to obtain nitrogen and phosphorus doped silicon-carbon material.

[0123] Comparative Example 1

[0124] S1: adding 100 g of phenolic resin to 200 g of isopropyl alcohol, and completely dissolving the phenolic resin in the isopropyl alcohol by ultrasonication to obtain a phenolic resin solution;

[0125] S2: Mix the above phenolic resin solution with 15 g of KOH to obtain a precursor material;

[0126] S3: The precursor material and 37 g of phosphorus pentane were uniformly mixed and placed in a tube furnace and sintered at 900 °C for 90 min under Ar atmosphere to obtain a nitrogen-phosphorus doped porous carbon material;

[0127] S4: 50g of nitrogen and phosphorus doped porous carbon material was washed and dried with clean water, then placed in a fluidized bed. After rising to 700℃ under Ar atmosphere, SiH4 was introduced at a rate of 150sccm. After deposition for 2h, silane was turned off, the temperature was lowered to 570℃, acetylene gas was introduced at a rate of 120sccm, and deposition was carried out for 30min to obtain nitrogen and phosphorus doped silicon-carbon material.

[0128] Comparative Example 2

[0129] S1: 120 g of coal tar pitch was added to 180 g of toluene, and the coal tar pitch was completely dissolved in the toluene by ultrasonication to obtain a coal tar pitch solution;

[0130] S2: 1 g of PVP was added to 198 g of NMP. After the PVP was completely dissolved in the NMP, 1 g of SWCNT powder was added and homogenized at 80 MPa to obtain a SWCNT dispersion.

[0131] S3: The coal tar pitch solution and the SWCNT dispersion were mixed, mixed evenly by ultrasonication, dried, and then mixed with 20 g of KOH to obtain a precursor material;

[0132] S4: placing the precursor material in a tube furnace and sintering it at 800 °C for 120 min under an Ar atmosphere to obtain a porous carbon material;

[0133] S5: After washing and drying 50g of porous carbon material with clean water, place it in a fluidized bed, raise the temperature to 650℃ under Ar atmosphere, introduce SiH4 at a rate of 150sccm, deposit for 2h, turn off silane, cool to 570℃, introduce acetylene gas at a rate of 120sccm, and deposit for 30min to obtain silicon-carbon material.

[0134] Comparative Example 3

[0135] S1: 120 g of coal tar pitch was added to 180 g of toluene, and the coal tar pitch was completely dissolved in the toluene by ultrasonication to obtain a coal tar pitch solution;

[0136] S2: 1 g of PVP was added to 198 g of NMP. After the PVP was completely dissolved in the NMP, 1 g of SWCNT powder was added and homogenized at 80 MPa to obtain a SWCNT dispersion.

[0137] S3: The coal tar pitch solution and SWCNT dispersion were mixed, ultrasonically homogenized, dried, and then mixed with 20 g of KOH to obtain a precursor material;

[0138] S4: The precursor material was placed in a tube furnace and sintered at 800° C. for 120 min under an Ar atmosphere, and then taken out and washed to obtain a CNT / porous carbon material.

[0139] S5: Place the CNT / porous carbon material in a tube furnace, heat it to 700°C under Ar atmosphere, turn off Ar, introduce SiH4, PH3, and acetylene gas at 10 sccm, 80 sccm, and 60 sccm, respectively, and maintain for 120 min. Turn off SiH4, PH3, and acetylene gas, introduce Ar, and then cool it to 550°C. Then introduce sulfur vapor at a rate of 60 sccm to obtain phosphorus sulfide-coated silicon-carbon material;

[0140] S6: 50 g of phosphorus sulfide-coated silicon-carbon material was placed in a tube furnace, the temperature was raised to 570° C., acetylene gas was introduced at a rate of 120 sccm, and the deposition was carried out for 30 minutes to obtain a phosphorus-doped silicon-carbon material.

[0141] Performance testing:

[0142] The preparation steps of the button battery include: stirring and mixing the above-mentioned (Example 1-Comparative Example 3) silicon-carbon material, binder LA133, conductive carbon black and deionized water to obtain a negative electrode slurry; wherein, the mass volume ratio of the silicon-carbon composite negative electrode material, conductive carbon black, binder LA132, SBR and deionized water is 3g:0.03148g:0.04722g:0.21g:5.5g; the negative electrode slurry is coated on a copper foil, and after drying and rolling, a negative electrode sheet is obtained; the electrolyte is a solution with LiPF6 and 10% FEC as the electrolyte, with a concentration of 1 mol / L, wherein the solvent is a mixture of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1; the metal lithium sheet is the counter electrode, and the diaphragm is a polypropylene film.

[0143] In an argon glove box, the button cell was assembled on a Sunway CT-4008Tn battery tester and subjected to electrochemical cycling performance testing. The charge and discharge voltage range was 0.01 V to 1.5 V, with an initial charge rate of 1 C and a discharge rate of 0.5 C. Subsequent tests were performed at charge / discharge rates of 5 C / 0.7 C. The test results are shown in Table 1.

[0144] Table 1

[0145]

[0146] It can be seen from the data in Table 1 that the first charge and discharge efficiency, 5C capacity retention rate, and 100-cycle capacity retention rate of the battery prepared using the silicon-carbon material prepared in the present application are significantly better than those of Comparative Examples 1-3, and the expansion rate of the battery prepared using the silicon-carbon material prepared in the present application is significantly lower than that of Comparative Examples 1-3.

[0147] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0148] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above examples may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method for preparing a silicon-carbon material, characterized in that: The preparation method comprises: S1: dissolving the carbon source material in a solvent to obtain a carbon source solution; S2: dissolving a surfactant in a dipolar aprotic solvent to obtain a surfactant solution, and adding carbon nanotube powder to the surfactant solution to obtain a carbon nanotube dispersion; S3: mixing the carbon source solution and the carbon nanotube dispersion and drying them to obtain a solid mixture, and mixing the solid mixture with an alkali metal hydroxide to form a precursor material; S4: mixing the precursor material and phosphorus pentane nitride and placing the mixture in a tube furnace for high-temperature sintering to obtain a nitrogen-phosphorus doped porous carbon material; S5: performing silicon deposition treatment and carbon coating treatment on the nitrogen and phosphorus doped porous carbon material to finally obtain a nitrogen and phosphorus doped silicon-carbon material.

2. The method for preparing the silicon-carbon material according to claim 1, wherein In step S4, the ratio of the precursor material to phosphorus pentanenitride is in the range of 10:1 to 10:

2.

3. The method for preparing the silicon-carbon material according to claim 1 or 2, wherein: The nitrogen doping amount in the nitrogen-phosphorus doped porous carbon material is 2% to 10%, and the phosphorus doping amount is 1% to 3%.

4. The method for preparing the silicon-carbon material according to claim 1, wherein In step S4, the high-temperature sintering temperature is 600° C. to 1000° C., and the sintering time is 60 min to 240 min.

5. The method for preparing the silicon-carbon material according to claim 1, wherein: In step S5, the silicon content in the nitrogen and phosphorus doped silicon-carbon material is 45% to 55% by mass.

6. The method for preparing the silicon-carbon material according to claim 1, wherein: In step S3, the mass ratio of the precursor material to the alkali metal hydroxide is in a range of 5:1 to 15:

1.

7. The method for preparing the silicon-carbon material according to claim 1, wherein: The mass ratio of the carbon source material to the carbon nanotube powder is 10:1 to 150:

1.

8. The method for preparing the silicon-carbon material according to claim 1, wherein: In step S5, performing silicon deposition and carbon coating on the nitrogen and phosphorus doped porous carbon material includes: The nitrogen and phosphorus doped porous carbon material that has been washed with clean water and dried is placed in a fluidized bed, and the reaction temperature is raised to a temperature range of 600°C to 800°C under an inert gas atmosphere. Subsequently, silicon source gas is introduced into the fluidized bed to implement silicon deposition treatment; after the silicon deposition treatment process is completed, the carbon source gas is switched to be introduced and the surface of the material is carbon-coated to finally obtain a nitrogen and phosphorus doped silicon-carbon material.

9. The method for preparing the silicon-carbon material according to claim 1, wherein: In step S1, the carbon source material is one or more of asphalt, phenolic resin, epoxy resin, polyacrylonitrile, lignin polyimide, polyaniline, petroleum coke, and coal tar.

10. The method for preparing the silicon-carbon material according to claim 1, wherein: In step S2, the surfactant is one or more of sodium lauryl sulfate, bile salt, cetyltrimethylammonium bromide, tetrabutylammonium hydroxide, polyvinylpyrrolidone, sodium polystyrene sulfonate, poloxamer, polyoxyethylene sorbitan monooleate, and lignin sulfonate.

11. A silicon-carbon material, characterized in that: The silicon-carbon material is prepared by the method for preparing the silicon-carbon material according to any one of claims 1 to 10.

12. A lithium ion battery, characterized in that: The lithium-ion battery comprises the silicon-carbon material according to claim 11.

13. An electronic product, characterized in that: The electronic product includes the lithium-ion battery according to claim 12.

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