A porous long-cycle silicon-carbon negative electrode material and its preparation method

Abstract

The present invention belongs to the technical field of electrode material preparation and provides a porous long-cycle silicon-carbon negative electrode material and a preparation method thereof. SiO2 microspheres are prepared by a sol-gel reaction, and silicon dioxide particles are generated by hydrolysis and polycondensation to form a SiO2@MgO composite structure, which is then subjected to a high-temperature reduction reaction with magnesium powder and chemical etching to form a porous silicon matrix; PANI material is prepared, a LATP layer is formed using a precursor sol to improve the ionic conductivity of the binder, and active functional groups are introduced on the PANI@LATP surface, followed by a photo-initiated polymerization reaction to form a functionalized binder; a Li3PS4 solid electrolyte is prepared, and a conductive protective layer is coated with polydopamine to enhance the bonding between the electrolyte and the silicon negative electrode; the porous silicon-carbon composite material is dispersed with Li3PS4@PDA and PANI@LATP binders to prepare a porous long-cycle silicon-carbon negative electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode material preparation, and relates to a porous long-cycle silicon-carbon negative electrode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and lightweight properties. As these sectors place increasingly higher demands on the performance of lithium-ion batteries, the graphite anode materials currently used in commercial batteries, while offering excellent cycle stability and low lithium insertion potential, struggle to meet the demands of next-generation high-energy-density batteries. This is especially true under high-rate charge-discharge and long-term cycling conditions. Due to their low specific capacity and limited electrochemical performance, graphite anodes are unable to meet the growing market demand for high-performance batteries, and the cycling performance of traditional graphite anode materials is no longer sufficient. Therefore, the development of anode materials with improved cycling performance has become a core area of ​​current research.

[0003] As a novel anode material, silicon has become an important candidate for future lithium-ion battery anode materials due to its extremely high theoretical specific capacity and abundant reserves. However, the practical application of silicon materials still faces multiple challenges. During the charge and discharge process, silicon undergoes significant volume expansion due to the insertion and extraction of lithium ions, leading to particle fragmentation, electrode structure failure, and rapid capacity decay. In addition, the silicon surface easily undergoes side reactions with the electrolyte, forming an unstable solid electrolyte interface (SEI), which further accelerates performance decay. These problems severely limit the application of silicon materials in practical lithium-ion batteries. To alleviate the volume expansion problem of silicon materials and improve their electrochemical performance, silicon-carbon composites have been widely studied. By combining silicon particles with carbon materials, the conductivity and mechanical flexibility of the carbon materials can be utilized to provide a buffer space for silicon, reducing the impact of volume expansion and improving conductivity. However, traditional silicon-carbon composites still suffer from insufficient cycling performance in practical applications. Therefore, the development of a porous, long-cycle silicon-carbon anode material is of great significance. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a porous long-cycle silicon-carbon negative electrode material and a preparation method thereof. By preparing a porous silicon matrix to buffer volume expansion, using a carbon coating to improve conductivity and interface protection, introducing a Li3PS4@PDA composite material to enhance lithium ion conduction and interface stability, and designing a PANI@LATP binder to provide electronic conductivity and mechanical support, thereby meeting the needs of actual production.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a porous long-cycle silicon-carbon negative electrode material, the preparation method comprising:

[0007] A1, tetraethyl orthosilicate is added to an ethanol aqueous solution, ammonia water is added, and the temperature is raised to a first temperature with stirring for reaction, and SiO2 microspheres are obtained after centrifugal washing. The SiO2 microspheres are immersed in a magnesium nitrate ethanol solution, ultrasonically dispersed, and dried at a second temperature. The microspheres are transferred to a muffle furnace and calcined at a third temperature to obtain SiO2@MgO. SiO2@MgO and Pluronic F-127 are then added to anhydrous ethanol, stirred at room temperature, and rotary evaporated to obtain a template material. The template material is mixed with magnesium powder, placed in a tube furnace, and heated to a fourth temperature under an Ar / H2 atmosphere for insulation. After natural cooling, the microspheres are sequentially etched with hydrochloric acid and hydrofluoric acid, and washed with deionized water and dried to obtain a porous silicon substrate.

[0008] S1, after mixing aniline and concentrated sulfuric acid, add ammonium persulfate and continue stirring, place in a water bath at the first temperature and continue stirring, filter, wash, dry and transfer to a tube furnace, heat to the fifth temperature and keep warm to obtain PANI nanomaterial, immerse the PANI nanomaterial in a precursor sol and increase the temperature gradually, then immerse it in a CTAB solution, apply a DC electric field and stir, and then calcine in stages to obtain PANI@LATP; immerse PANI@LATP in a toluene solution of 3-aminopropyltriethoxysilane, reflux at 80°C, add glycidyl methacrylate and CuBr, adjust the temperature to 60°C and reflux, adjust the temperature to 50°C and add lipoic acid to obtain a pre-product, disperse the pre-product and four-arm polyethylene glycol lipoic acid in N,N-dimethylformamide, add a photoinitiator and irradiate with ultraviolet light, and freeze-dry to obtain a PANI@LATP binder;

[0009] S2, dispersing phosphorus pentasulfide and lithium carbonate in anhydrous acetonitrile, reacting under reflux at a second temperature, adding polydopamine microspheres, adjusting the temperature to a sixth temperature, reacting, washing, and drying to obtain Li3PS4@PDA;

[0010] S3, heating the porous silicon substrate to the fourth temperature under an argon atmosphere and then introducing acetylene, keeping the temperature and then naturally cooling it to obtain a silicon-carbon composite material, dispersing the silicon-carbon composite material and Li3PS4@PDA in N-methylpyrrolidone, adding PANI@LATP binder after uniform dispersion, and stirring evenly to obtain a porous long-cycle silicon-carbon negative electrode material.

[0011] Tetraethyl orthosilicate (TES) is a common silicon source. In a mixture of water and alcoholic solvents, it undergoes hydrolysis and polycondensation via a sol-gel process to produce silica. Ammonia plays a crucial role in this process, acting as an alkaline catalyst. Its alkaline environment accelerates the cleavage of siloxane bonds within the TES molecules, promoting their rapid hydrolysis to silicic acid. Subsequently, as the reaction proceeds, the silicic acid molecules undergo dehydration or dealcoholization through polycondensation, gradually forming Si-O-Si bonds and building a three-dimensional silica network. After sufficient reaction time, SiO2 microspheres with uniform morphology and good dispersion are produced. The SiO2 microspheres possess numerous hydroxyl groups on their surfaces, providing active sites for subsequent chemical functionalization. When the SiO2 microspheres are immersed in an ethanolic magnesium nitrate solution, the magnesium ions in the solution undergo electrostatic adsorption or coordination with the hydroxyl groups on the SiO2 microspheres, resulting in uniform adsorption onto the microsphere surfaces. During the drying process, the ethanol evaporates, and the magnesium ions gradually deposit on the microsphere surfaces, forming a uniformly distributed magnesium precursor layer. During the subsequent calcination process, magnesium nitrate decomposes to form magnesium oxide, which is then uniformly coated on the surface of the SiO2 microspheres, forming a SiO2@MgO composite structure. At high temperatures, SiO2@MgO undergoes a strong reduction reaction with magnesium powder (Mg), reducing SiO2 to silicon and generating magnesium oxide. In this process, the MgO coating plays an important synergistic role. The calcined MgO layer is tightly bonded to the SiO2, ensuring that its surface is evenly distributed at every location on the particle, thereby improving the contact conditions between the magnesium powder and the SiO2. This uniform interfacial contact improves the efficiency of the reduction reaction and avoids reaction inhomogeneity. In addition, due to the high thermal conductivity of MgO, it can help evenly distribute heat during the high-temperature reduction process, preventing local overheating or overly intense reactions, thereby enhancing the controllability of the reaction. More importantly, the MgO coating can effectively inhibit the agglomeration of SiO2 particles at high temperatures. SiO2 is easily sintered or agglomerated at high temperatures due to the surface energy of the particles, while the MgO coating forms a physical barrier between the particles, reducing the possibility of direct contact between the particles, thereby maintaining the dispersion and initial morphology of the particles. In addition, MgO itself has a high melting point and excellent thermal stability, and will not undergo phase changes or decomposition within the experimental temperature range. This stability enables MgO to act as a protective layer throughout the high-temperature preparation process, preventing the SiO2 particles from undergoing morphological destruction during the reduction reaction. After the reduction reaction is completed, MgO is partially transformed from the initial coating layer into a by-product of the reduction reaction (newly generated MgO), which is distributed on the surface and pores of the silicon particles. Hydrochloric acid is subsequently used to acid-etch the product to remove excess MgO.The corrosion of hydrochloric acid not only removes MgO but also leaves a porous structure in the silicon matrix. The presence of these pores greatly increases the specific surface area of ​​the porous silicon and regulates its pore size distribution, thereby providing ample reaction interfaces and lithium ion diffusion channels for the electrochemical reactions of lithium-ion batteries. The MgO coating not only protects the SiO2 microspheres from sintering and agglomeration during the high-temperature reduction process, but also lays the foundation for the formation of the porous silicon matrix through post-reaction removal. Its role covers the uniformity of the reaction, the maintenance of particle morphology, and the regulation of pore structure. It is a key step in achieving the preparation of high-performance porous silicon matrices. The resulting porous silicon matrix not only has a high specific surface area and abundant pores, but also improves the cycle performance and rate performance of lithium-ion battery negative electrode materials through its structural characteristics.

[0012] Silicon, as a lithium-ion battery anode material, undergoes volume expansion and contraction during charge and discharge. However, the mechanical stress caused by this volume change can lead to pulverization of silicon particles and compromise the structural integrity of the electrode, resulting in reduced interfacial stability of the anode material, ultimately leading to rapid capacity decay and poor cycling performance. Therefore, to improve the service life and electrochemical performance of silicon-based anode materials, it is necessary to incorporate structures or components that can mitigate volume expansion stress into the material design to optimize its mechanical and chemical stability. In the preparation of silicon-carbon anodes, silicon reduction is a key process. Using magnesium metal as a reducing agent, silicon dioxide is reduced to elemental silicon at high temperatures. This process not only converts SiO2 into high-purity silicon but also modulates the structure of the silicon matrix. During the reduction process, the generated MgO fills or occupies part of the volume of the original SiO2 particles, promoting the formation of pores between the silicon particles. Subsequent etching with hydrochloric and hydrofluoric acids removes residual MgO and incompletely reacted SiO2 templates. These treatments further expand the pores, forming a porous silicon matrix with a high specific surface area and abundant pores. This porous structure not only alleviates the volume expansion of silicon during the charge and discharge process, but also provides abundant channels for the transmission and storage of lithium ions. It is worth noting that the reduction reaction is carried out in an inert atmosphere (Ar / H2). The weak reducing property of H2 further reduces the risk of silicon particles being oxidized at high temperatures, thereby generating high-purity elemental silicon. The generation of high-purity silicon improves the electronic conductivity of the material, which is crucial for the electrochemical performance of the negative electrode material. Silicon has a high theoretical specific capacity, and its capacity advantage is significant compared to traditional graphite negative electrode materials. The silicon generated in the reduction reaction can form an alloy with lithium ions through a lithiation reaction. This process provides active sites for the storage of lithium ions, significantly improving the specific capacity of the negative electrode material. In addition, due to the porous structure generated by the reduction reaction, the pore network of the porous silicon matrix provides abundant channels for the diffusion of lithium ions. This structure significantly reduces the diffusion resistance of lithium ions, allowing lithium ions to quickly pass through the electrode material, thereby improving the rate performance of the material. The porous structure also allows the electrolyte to fully penetrate the entire silicon matrix, increasing the contact area between the electrode and the electrolyte, further promoting the efficient transfer of lithium ions. The resulting pore distribution and optimized structural stability enable the porous silicon matrix to maintain a high capacity over long charge and discharge cycles, demonstrating excellent cycling stability.

[0013] In addition to the contribution of the pore structure, MgO itself also plays an important role in porous silicon negative electrode materials. MgO is a material with high hardness and high melting point and has good mechanical stability. After the reduction reaction, although most of the MgO is corroded and removed, there are still a small amount of residual MgO particles distributed inside or on the surface of the porous silicon matrix. These residual MgO particles act as a structural support, forming a "hard-soft" composite structure, in which the hard MgO and the relatively soft porous silicon together form a composite material. Such a composite structure can absorb part of the stress when the silicon particles expand due to lithiation, preventing direct extrusion and crushing between the silicon particles. Specifically, the residual MgO particles play the following roles in the material: (1) Buffering volume expansion: The residual MgO particles act as mechanical supports and can effectively disperse the stress generated by silicon expansion, reducing the damage to the overall structure of the material caused by expansion; (2) Enhancing mechanical strength: The residual MgO fills the interior or surface of the porous silicon matrix, providing additional mechanical strength to the composite material, thereby reducing the phenomenon of silicon particles breaking due to expansion and contraction during charge and discharge; (3) Maintaining the integrity of the pore structure: The presence of MgO stabilizes the framework structure of porous silicon to a certain extent, and the pore network can still maintain its integrity even after multiple charge and discharge cycles. Maintaining the integrity of the pore structure is particularly important for the long-term cycle performance of the material. The pores not only provide a path for the diffusion of lithium ions, but also provide a buffer space for the volume expansion of silicon. If the pores collapse during the cycle, it will lead to an increase in electrode density, a decrease in electrolyte permeability, and a decrease in lithium ion transmission efficiency, resulting in a rapid decay of electrochemical performance. Therefore, the composite structure composed of residual MgO and porous silicon is of great significance in improving the cycle performance of the material. The porous silicon matrix prepared by the reduction reaction of silicon exhibits multiple advantages in structure and performance. The generation of high-purity silicon provides the material with excellent conductivity and high specific capacity; the porous structure provides abundant channels for the transmission and storage of lithium ions and buffers the volume expansion of silicon; the residual MgO particles further enhance the stability of the material through mechanical support.

[0014] Polyaniline (PANI) is prepared via chemical oxidative polymerization, a common method for preparing conductive polymers. Its core mechanism involves the chemical polymerization of aniline monomers in an acidic solution under the action of an oxidant. In this experiment, sulfuric acid provides an acidic environment, enabling the protonation of aniline molecules to form cationic aniline. Protonated aniline cations are more stable in acidic media. During the reaction, ammonium persulfate, a strong oxidant, oxidizes the aniline monomers to form aniline radical cations. These aniline radical cations are highly reactive intermediates that combine through coupling reactions to form conjugated chains composed of imine and amine units, ultimately forming polyaniline. After preparation, PANI requires further heat treatment to enhance its properties. During the heat-insulating calcination process, PANI undergoes partial carbonization. The primary function of carbonization is to remove low-molecular-weight organic components, such as aniline monomers or oligoanilines that were not fully polymerized during the reaction. This process not only reduces defects in the material but also further enhances the order of the PANI molecular chain by introducing a conjugated structure within some carbon bonds, significantly enhancing the material's electron transport capacity. Calcination also improves the thermal stability and oxidation resistance of PANI, imparting improved stability under high-temperature and electrochemical operating conditions. The carbonized PANI material exhibits high conductivity and can serve as part of an electronically conductive network, compensating for the insufficient conductivity of silicon-carbon anodes. Its oxidation resistance and thermal stability also extend the lifespan of the anode material. After carbonization, the PANI nanomaterial is immersed in a precursor sol and further coated with a LATP coating via a sol-gel method. LATP is a solid-state electrolyte with excellent lithium-ion conductivity and chemical stability. The LATP coating is prepared via a sol-gel method using tetraisopropyl titanate as the titanium source, aluminum nitrate nonahydrate as the aluminum source, and lithium dihydrogen phosphate as the lithium source. In this system, tetraisopropyl titanate first undergoes hydrolysis to form a titanium oxide intermediate. Subsequently, the aluminum and lithium sources interact with this intermediate to form a mixed metal oxide precursor sol. After the PANI material is immersed in the precursor sol, the sol is evenly covered on the surface of the PANI particles due to the surface tension of the liquid. In order to form a stable LATP coating, the sol system is subjected to a gradient temperature treatment to form a continuous and dense coating that firmly adheres to the PANI surface. The LATP coating plays an important role in the silicon-carbon negative electrode: (1) Improving lithium ion conductivity: LATP provides a fast migration channel for lithium ions, improving the ion transport capacity of the negative electrode material; (2) Isolating silicon particles from the electrolyte: The LATP coating can effectively block the direct contact between silicon particles and the electrolyte, reducing the decomposition reaction of the electrolyte and the disordered growth of the solid electrolyte interface (SEI) film on the silicon surface, thereby improving the cycle life of the electrode; (3) Improving chemical stability: LATP has good chemical stability within the electrochemical working potential range.

[0015] To further improve the uniformity and adhesion of the LATP coating, the PANI@LATP material was immersed in a CTAB solution and an electric field was applied. CTAB is a cationic surfactant that interacts with the surface of LATP particles through electrostatic adsorption, thereby improving the uniformity of the coating. When an electric field is applied, the ion migration rate in the LATP coating is accelerated, further promoting the densification of the coating. Furthermore, the electric field induces charge interactions between the PANI surface and the LATP layer, enhancing the bonding strength between the two. This process allows the LATP coating to be more tightly and densely coated on the PANI surface, providing excellent conductivity, ion transport capability, and chemical stability for subsequent electrochemical applications. PANI prepared by chemical oxidation polymerization has high conductivity and thermal stability after initial carbonization, and can provide a reliable electronic conductive network for the silicon-carbon negative electrode. Subsequently, LATP coating is deposited on the PANI surface by the sol-gel method. The presence of LATP significantly improves the lithium ion conductivity of the negative electrode, while isolating the direct contact between silicon particles and the electrolyte, reducing side reactions and improving the cycle life. The uniformity and adhesion of the LATP coating are further optimized using CTAB and electric field-assisted modification, enabling the material to exhibit excellent performance in an electrochemical environment.

[0016] PANI@LATP was immersed in a toluene solution of 3-aminopropyltriethoxysilane and heated under reflux for a reaction. The silyl groups in the 3-aminopropyltriethoxysilane molecules hydrolyzed in the reaction system to form silanols. These highly active silanols reacted with hydroxyl groups on the surface of the LATP or PANI material through a condensation reaction, removing water molecules to form silanol-silicon bonds. The silanols in the 3-aminopropyltriethoxysilane molecules covalently bonded to the hydroxyl groups on the surface, forming stable silanol-silicon bonds. This reaction not only firmly attached the 3-aminopropyltriethoxysilane to the LATP or PANI surface but also introduced amino groups on the surface. These amino groups did not participate in the condensation reaction but remained on the surface, serving as active sites for subsequent chemical reactions and providing a chemical basis for epoxy group binding and polymerization. After the silanization modification was completed, glycidyl methacrylate and lipoic acid were added to the system to introduce epoxy groups and disulfide bonds, respectively, and the reactions occurred under appropriate temperature conditions. The epoxy groups in the glycidyl methacrylate molecule are highly chemically active and can undergo nucleophilic ring-opening reactions with the amino groups introduced by the silanized surface. The carbon atoms in the epoxy groups are susceptible to attack by nucleophiles. The amino groups, acting as nucleophiles, react with the epoxy groups to form stable hydroxyl-amine covalent bonds. Through this reaction, the epoxy groups in GMA are firmly bound to the PANI@LATP surface, providing active sites for subsequent cross-linking polymerization. Simultaneously, the carboxyl groups in the lipoic acid molecule undergo esterification with the hydroxyl groups present on the surface, forming ester bonds through dehydration. This process firmly binds the lipoic acid molecules to the surface. Furthermore, the disulfide bonds in the lipoic acid molecule impart critical flexibility and antioxidant properties to the material. In silicon-based anode applications, the disulfide bonds provide mechanical flexibility, buffering stress during the dramatic volume expansion of silicon particles during charge and discharge, while the antioxidant properties enhance the material's stability during electrochemical cycling. The resulting pre-product is then polymerized with four-arm polyethylene glycol lipoic acid and a photoinitiator to construct a highly cross-linked polymer network. These free radicals can trigger polymerization reactions between the active end groups in the four-arm polyethylene glycol lipoic acid molecules and epoxy groups or other reactive sites on the material surface, forming a highly cross-linked three-dimensional polymer network. This polymer network provides flexibility through the polyethylene glycol molecular segments, while the cross-linked structure enhances the mechanical strength and bonding ability of the material. In addition, the formation of the cross-linked network can effectively prevent the silicon particles from shedding due to volume changes during multiple charge and discharge processes, thereby significantly improving the cycling stability of the electrode.Through light-induced free radical polymerization, a highly cross-linked polymer network is formed on the surface of the material. This network not only acts as a binder, improving the bonding strength of the internal components of the material, but also significantly enhances the flexibility and electrochemical stability of the material through flexible molecular chains and antioxidant structures, thereby enabling it to better adapt to the complex mechanical and chemical environment generated by the silicon-based negative electrode during the charging and discharging process.

[0017] Phosphorus pentasulfide is a strongly electrophilic compound, its chemical properties primarily derived from the phosphorus-sulfur bonds within the molecule, which are highly reactive. After dispersion in anhydrous acetonitrile, the phosphorus pentasulfide molecules partially dissolve, and the phosphorus-sulfur bonds are activated by the polar environment of the solvent molecules, making the phosphorus atoms in the phosphorus pentasulfide highly electrophilic. In this state, the phosphorus atoms in the phosphorus pentasulfide are susceptible to attack by nucleophiles, triggering a chemical reaction. In the reaction system, lithium carbonate acts as a lithium source and participates in the reaction along with the phosphorus pentasulfide. Upon heating, the lithium carbonate dissociates to form lithium ions and carbonate ions. The carbonate ion is a strong nucleophile, actively attacking the electrophilic phosphorus atoms in the phosphorus pentasulfide molecule. Specifically, the carbonate ion, using its oxygen atom as a nucleophilic center, undergoes a nucleophilic substitution reaction with the phosphorus atoms in the phosphorus pentasulfide molecule, gradually releasing carbon dioxide gas and simultaneously triggering the fragmentation and reformation of the phosphorus pentasulfide molecular structure. During the reaction, the phosphorus and sulfur atoms in phosphorus pentasulfide combine with lithium ions in the solution, ultimately forming lithium sulfide phosphate (Li3PS4). Li3PS4 is an important solid-state electrolyte whose crystal structure contains abundant lithium ion migration channels. These channels are formed by the arrangement of sulfide ions and phosphate ions in the structure, allowing lithium ions to migrate rapidly in the crystal lattice with low activation energy, exhibiting excellent ion conductivity.

[0018] After the preparation of Li3PS4 is completed, in order to further improve its stability and inter-particle bonding performance, polydopamine (PDA) microspheres are introduced for surface modification. Polydopamine is a biomimetic polymer material that is prepared by the self-oxidation-self-polymerization reaction of dopamine. The PDA molecular chain is rich in a variety of active functional groups, including phenolic hydroxyl groups, amine groups, and amide structures. These functional groups have extremely high chemical reactivity and adhesion properties, enabling PDA to undergo physical adsorption and chemical bonding with the surfaces of various materials. Under high temperature conditions, PDA microspheres are introduced into the reaction system and composited with Li3PS4. The phenolic hydroxyl groups and amine groups on the PDA surface can form stable interactions with the sulfur or phosphorus atoms exposed on the surface of the Li3PS4 particles through hydrogen bonding or weak chemical bonding. Specifically, the phenolic hydroxyl groups can form hydrogen bonds with the sulfur atoms in the sulfide on the surface of Li3PS4, while the amine groups can bind to the phosphorus atoms on the surface of Li3PS4 through electrostatic interactions or weak chemical bonds. Through this combined process of physical adsorption and chemical bonding, PDA gradually and evenly deposits on the surface of Li3PS4 particles, ultimately forming Li3PS4@PDA. Li3PS4 is a material susceptible to environmental influences, particularly moisture and oxygen, which are highly destructive to its performance. When exposed to moisture, Li3PS4 decomposes, producing byproducts such as hydrogen sulfide, significantly reducing the material's ionic conductivity. By coating the Li3PS4 surface with a layer of PDA, it effectively isolates the intrusion of moisture and oxygen, significantly improving the environmental stability of Li3PS4. Furthermore, the PDA coating reduces the likelihood of side reactions between Li3PS4 and oxygen in the air, extending the material's service life. In addition to its protective properties, PDA exhibits excellent adhesion and mechanical flexibility. Its rich surface functional groups enhance the interaction between Li3PS4 particles and reduce the resistance at the particle interface. This effect helps improve the material's overall ionic conductivity and, by strengthening the close contact between particles, enhances the composite's performance in electrodes.

[0019] Under high-temperature conditions (650-680°C), the surface structure of the porous silicon substrate undergoes a certain degree of activation. The high-temperature thermal energy partially breaks or rearranges chemical bonds (such as silicon-oxygen bonds or silicon-hydrogen bonds) on the silicon surface, exposing more unsaturated bonds or active sites. These active sites significantly enhance the silicon substrate's surface adsorption capacity for foreign molecules (such as acetylene) and provide ideal reaction sites for subsequent chemical vapor deposition reactions. This surface activation not only increases the contact area with the reaction gas but also creates more favorable conditions for the deposition of carbon atoms. When acetylene gas is introduced into the reaction system, its molecules undergo thermal decomposition at high temperatures, generating activated carbon atoms and hydrogen. During this process, the triple bond (C≡C) in the acetylene molecule breaks due to the input of high-temperature energy, producing single carbon atoms. These carbon atoms are extremely chemically active and can rapidly undergo physical adsorption and chemical bonding with the silicon substrate surface, gradually depositing on the surface of the silicon particles through chemical vapor deposition. As the reaction time increases, these carbon atoms accumulate in layers on the silicon surface, eventually forming a uniform carbon coating that completely covers the surface of the silicon particles. The introduction of this carbon coating is crucial for the electrochemical performance of silicon-based electrode materials. Silicon, as a negative electrode material, has attracted considerable attention due to its extremely high specific capacity during the charge and discharge processes of lithium-ion batteries. However, silicon undergoes significant volume expansion during the lithium insertion reaction. This expansion can cause cracking and pulverization of the silicon particles, disrupting the electrode structure and reducing the battery's cycle life. The introduction of a carbon coating provides a buffering effect, absorbing the mechanical stress caused by this volume expansion and preventing pulverization of the silicon particles. Furthermore, the carbon coating maintains the integrity of the silicon particles to a certain extent, thereby maintaining the structural stability of the electrode. Furthermore, the carbon material's excellent electronic conductivity not only provides a fast electron transfer pathway but also reduces the overall impedance, improving the battery's rate capability. Furthermore, the carbon coating also acts as an isolating and protective barrier, effectively isolating the silicon particles from direct contact with the electrolyte. When silicon comes into contact with the electrolyte, it easily induces side reactions, leading to the unstable growth of the solid electrolyte interface (SEI). These unstable SEI layers consume electrolyte and lithium ions, causing capacity decay. The presence of carbon coating can mitigate these adverse reactions, thereby improving the cycling stability and long-term service life of the electrode.

[0020] Polyaniline (PANI) is an important conductive polymer. Its unique molecular structure enables it to provide excellent electronic conductivity through doping and dedoping. In electrode materials, PANI not only serves as part of the conductive network, reducing the electrode's electronic impedance, but also buffers the volume expansion effect of the silicon-carbon composite through its flexible molecular chains. This flexibility enables PANI to adapt to the expansion and contraction of silicon particles during the electrode's charge and discharge processes, thereby avoiding the accumulation of mechanical stress in the material and extending the electrode's cycle life. Lithium aluminum titanium phosphate (LATP) is a high-performance solid-state electrolyte with excellent lithium ion conductivity. In electrode materials, LATP not only improves the electrode's overall ionic conductivity but also enhances the efficiency of lithium ion migration within the electrode, thereby improving the battery's rate capability. Furthermore, the phosphate ions in the LATP crystal structure form weak chemical bonds with the surface of the silicon-carbon composite particles. This bond further enhances the composite's structural stability and prevents separation and shedding of particles. Overall, the introduction of the PANI@LATP binder achieves synergistic optimization of electronic and ionic conduction. PANI provides an efficient electronic conductive network, while LATP builds a fast lithium ion migration channel. The two work together to significantly improve the electrochemical performance of the silicon-carbon composite electrode. At the same time, the chemical bonding between LATP and silicon-carbon particles and the flexible adhesion of PANI enhance the structural integrity and cycling stability of the electrode.

[0021] As a preferred technical solution of the present invention, in step A1, the volume ratio of tetraethyl orthosilicate to ethanol aqueous solution is 1:5.

[0022] In some optional embodiments, the mass fraction of the ethanol aqueous solution is 9-11 wt.%, for example, it can be 9.0 wt.%, 9.2 wt.%, 9.4 wt.%, 9.6 wt.%, 9.8 wt.%, 10.0 wt.%, 10.2 wt.%, 10.4 wt.%, 10.6 wt.%, 10.8 wt.% or 11.0 wt.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0023] In some optional embodiments, the mass fraction of the ammonia water is 20-25wt.%, for example, it can be 20.0wt.%, 20.5wt.%, 21.0wt.%, 21.5wt.%, 22.0wt.%, 22.5wt.%, 23.0wt.%, 23.5wt.%, 24.0wt.%, 24.5wt.% or 25.0wt.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] In some optional embodiments, the volume ratio of tetraethyl orthosilicate to ammonia water is 12:5.

[0025] In some optional embodiments, the first temperature is 40-50°C, for example, it can be 40.0°C, 41.0°C, 42.0°C, 43.0°C, 44.0°C, 45.0°C, 46.0°C, 47.0°C, 48.0°C, 49.0°C or 50.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional embodiments, the first temperature stirring reaction time is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional embodiments, the mass fraction of the magnesium nitrate ethanol solution is 13 wt.%.

[0028] In some optional embodiments, the ultrasonic dispersion time is 30-40 min, for example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional embodiments, the second temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] In some optional embodiments, the third temperature is 500-600°C, for example, it can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] In some optional embodiments, the calcination time is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] In some optional embodiments, the mass ratio of SiO2@MgO to Pluronic F-127 is 5:3.

[0033] In some optional embodiments, the mass volume ratio of the SiO2@MgO to anhydrous ethanol is 1 g:40 mL.

[0034] In some optional embodiments, the stirring time at room temperature is 12-13h, for example, it can be 12.0h, 12.1h, 12.2h, 12.3h, 12.4h, 12.5h, 12.6h, 12.7h, 12.8h, 12.9h or 13.0h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0035] In some optional embodiments, the mass ratio of SiO2@MgO to magnesium powder is 1:16.

[0036] In some optional embodiments, the volume ratio of Ar to H2 is 95:5.

[0037] In some optional embodiments, the fourth temperature is 650-680°C, for example, it can be 650°C, 653°C, 656°C, 659°C, 662°C, 665°C, 668°C, 671°C, 674°C, 677°C or 680°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0038] In some optional embodiments, the fourth temperature holding time is 5-6h, for example, it can be 5.0h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional embodiments, the concentration of the hydrochloric acid is 1M.

[0040] In some optional embodiments, the mass fraction of the hydrofluoric acid is 5 wt.%.

[0041] As a preferred technical solution of the present invention, in step S1, the mass volume ratio of aniline to concentrated sulfuric acid is 1 g:5 mL.

[0042] In some optional embodiments, the mass ratio of aniline to ammonium persulfate is 2:1.

[0043] In some optional embodiments, the continuous stirring time under the water bath conditions is 12-13h, for example, it can be 12.0h, 12.1h, 12.2h, 12.3h, 12.4h, 12.5h, 12.6h, 12.7h, 12.8h, 12.9h or 13.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional embodiments, the fifth temperature is 200-220°C, for example, it can be 200°C, 202°C, 204°C, 206°C, 208°C, 210°C, 212°C, 214°C, 216°C, 218°C or 220°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In some optional embodiments, the fifth temperature holding time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In some optional embodiments, the solute in the precursor sol is tetraisopropyl titanate, aluminum nitrate nonahydrate and lithium dihydrogen phosphate, with a volume mass ratio of 25 mL:8 g:12 g, the solvent is a mixture of ethanol / acetyl and acetone, with a volume ratio of 4:1, and the volume ratio of tetraisopropyl titanate to the solvent is 25:130.

[0047] In some optional embodiments, the gradient temperature increase is sequentially 50° C. for 2 h, 80° C. for 1 h, and 120° C. for 30 min.

[0048] The concentration of the CTAB solution is 0.01M.

[0049] In some optional embodiments, the voltage of the DC electric field is 30V.

[0050] In some optional embodiments, the staged calcination is sequentially calcined at 300° C. for 2 h with a heating rate of 1° C. / min, and calcined at 550° C. for 3 h with a heating rate of 2° C. / min.

[0051] In some optional embodiments, the mass volume ratio of PANI@LATP to 3-aminopropyltriethoxysilane is 2 g:5 mL.

[0052] In some optional embodiments, the volume ratio of 3-aminopropyltriethoxysilane to toluene in the toluene solution of 3-aminopropyltriethoxysilane is 1:7.

[0053] In some optional embodiments, the 80°C reflux reaction time is 12-13h, for example, it can be 12.0h, 12.1h, 12.2h, 12.3h, 12.4h, 12.5h, 12.6h, 12.7h, 12.8h, 12.9h or 13.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In some optional embodiments, the volume ratio of the toluene solution of 3-aminopropyltriethoxysilane to glycidyl methacrylate is 20:1.

[0055] In some optional embodiments, the volume mass ratio of glycidyl methacrylate to CuBr is 10 mL:0.5 g.

[0056] In some optional embodiments, the 60°C reflux reaction time is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In some optional embodiments, the mass ratio of lipoic acid to PANI@LATP is 1:2.

[0058] In some optional embodiments, the reaction time of adding lipoic acid is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In some optional embodiments, the mass ratio of the four-arm polyethylene glycol lipoic acid to PANI@LATP is 1:5.

[0060] In some optional embodiments, the mass volume ratio of the four-arm polyethylene glycol lipoic acid to N,N-dimethylformamide is 1 g:50 mL.

[0061] In some optional embodiments, the photoinitiator is Irgacure 2959, and the mass ratio of the photoinitiator to PANI@LATP is 1:100.

[0062] In some optional embodiments, the ultraviolet irradiation time is 30-40 min, for example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] As a preferred technical solution of the present invention, in step S2, the mass ratio of phosphorus pentasulfide to lithium carbonate is 8:5.

[0064] In some optional embodiments, the mass volume ratio of the lithium carbonate to anhydrous acetonitrile is 1 g:40 mL.

[0065] In some optional embodiments, the second temperature reflux reaction time is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] In some optional embodiments, the mass ratio of phosphorus pentasulfide to polydopamine microspheres is 4:1.

[0067] In some optional embodiments, the sixth temperature is 180-190°C, for example, it can be 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C or 190°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] In some optional embodiments, the sixth temperature reaction time is 12-13h, for example, it can be 12.0h, 12.1h, 12.2h, 12.3h, 12.4h, 12.5h, 12.6h, 12.7h, 12.8h, 12.9h or 13.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] As a preferred technical solution of the present invention, in step S3, the gas flow rate of the argon gas is 100 sccm, and the gas flow rate of the acetylene gas is 20 sccm.

[0070] In some optional embodiments, the mass ratio of the silicon-carbon composite material, Li3PS4@PDA and PANI@LATP binder is 100:3:3.

[0071] In some optional embodiments, the mass-to-volume ratio of the silicon-carbon composite material to N-methylpyrrolidone is 1 g:4 mL.

[0072] In a second aspect, the present invention provides a porous long-cycle silicon-carbon negative electrode material prepared by the preparation method described in the first aspect.

[0073] Compared with the prior art, the present invention has the following beneficial effects: (1) a porous silicon matrix is ​​prepared by a template method to form a porous structure, which alleviates the volume expansion of silicon during the charge and discharge process, reduces the risk of stress concentration and particle pulverization, and enhances the mechanical stability of the electrode. MgO can effectively disperse the stress generated by silicon expansion, reduce the damage to the overall structure of the material caused by expansion, provide additional mechanical strength for the composite material, and maintain its integrity. (2) PANI is a conductive polymer whose flexible molecular chain can buffer the volume expansion of silicon particles while providing an efficient electron conduction channel and reducing the impedance of the electrode. The introduction of LATP into the binder can not only improve the ionic conductivity of the electrode, but also enhance the structural stability of the composite material through the combination of its phosphate ions with the surface of the silicon-carbon composite material. (3) Li3PS4 is a solid electrolyte with high lithium ion conductivity. The polydopamine coating on the surface of Li3PS4 further enhances the interfacial stability of the material. The PDA coating not only protects Li3PS4 from moisture and oxygen corrosion, but also forms stable physical adsorption or weak chemical bonding with the silicon-carbon composite material through its rich functional groups (such as phenolic hydroxyl groups and amino groups) on the surface, thereby improving the overall interfacial stability of the composite material; (4) Through the chemical vapor deposition method, a carbon coating is uniformly introduced on the surface of porous silicon. This carbon coating not only has good electronic conductivity and can provide a fast electron transmission channel for silicon particles, reducing the overall impedance of the electrode, but also can isolate the direct contact between silicon and the electrolyte, inhibit the excessive growth of the SEI layer, and reduce irreversible capacity loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 TEM image of the porous silicon substrate prepared in Example 1 of the present invention (scale: 200 nm);

[0075] Figure 2 TEM image of the porous silicon substrate prepared in Example 1 of the present invention (scale: 50 nm);

[0076] Figure 3 This is the SEM image of the PANI@LATP adhesive prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0077] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0078] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been subjected to any further purification treatment.

[0079] Example 1

[0080] This embodiment provides a method for preparing a porous long-cycle silicon-carbon negative electrode material, which specifically includes the following steps:

[0081] A1, 60 mL of tetraethyl orthosilicate was added to 300 mL of 9.3 wt.% ethanol aqueous solution, 25 mL of 22 wt.% ammonia was added, and the mixture was heated to 44°C with stirring for 6.4 h. After centrifugation and washing, SiO2 microspheres were obtained. The SiO2 microspheres were immersed in 200 mL of 13 wt.% magnesium nitrate ethanol solution, ultrasonically dispersed for 31 min, and dried at 87°C. The microspheres were transferred to a muffle furnace and calcined at 520°C for 3.2 h to obtain SiO2@MgO. 5 g of SiO2@MgO and 3 g of Pluronic F-127 were added to anhydrous ethanol, stirred at room temperature for 12.2 h, and then rotary evaporated to obtain a template material. The template material was mixed with 80 g of magnesium powder, placed in a tube furnace, heated to 660°C under an Ar / H2 atmosphere, and kept warm for 5.2 h. After natural cooling, the microspheres were etched with 1 M hydrochloric acid and 5 wt.% hydrofluoric acid, washed with deionized water, and dried to obtain a porous silicon substrate;

[0082] S1, after mixing 10g aniline with 50mL concentrated sulfuric acid, add 5g ammonium persulfate and continue stirring, place it in a 44℃ water bath and continue stirring for 12.1h, filter, wash, dry and transfer it to a tube furnace, heat it to 205℃ and keep it for 2.4h to obtain PANI nanomaterials, immerse the PANI nanomaterials in the precursor sol and heat it gradually, keep it at 50℃ for 2h, 80℃ for 1h, and 120℃ for 30min, then immerse it in 0.01MCTAB solution, apply a 30V DC electric field and stir, and then calcine it in stages, calcining at 300℃ for 2h at a heating rate of 1℃ / min, calcining at 550℃ for 3h at a heating rate of 2℃ / min to obtain PANI@LATP; 10g PANI@LATP is immersed in 200mL A toluene solution of 3-aminopropyltriethoxysilane was refluxed at 80°C for 12.2 h, 10 mL of glycidyl methacrylate and 0.5 g of CuBr were added, the temperature was adjusted to 60°C and refluxed for 6.3 h, the temperature was adjusted to 50°C and 5 g of lipoic acid was added and reacted for 3.3 h to obtain a pre-product. The pre-product and 2 g of four-arm polyethylene glycol lipoic acid were dispersed in 100 mL of N,N-dimethylformamide, 0.1 g of Irgacure 2959 was added, and the mixture was UV-irradiated for 33 min. The PANI@LATP binder was freeze-dried.

[0083] S2, 8 g of phosphorus pentasulfide and 5 g of lithium carbonate were dispersed in 200 mL of anhydrous acetonitrile, refluxed at 82 °C for 6.9 h, and then 2 g of polydopamine microspheres were added. The temperature was adjusted to 188 °C for 12.2 h, and then washed and dried to obtain Li3PS4@PDA;

[0084] S3, the porous silicon substrate was heated to 650 ° C under an argon atmosphere and then acetylene was introduced. After keeping warm for 3 hours, the temperature was naturally cooled to obtain a silicon-carbon composite material. 10g of the silicon-carbon composite material and 0.3g of Li3PS4@PDA were dispersed in 40mL of N-methylpyrrolidone. After uniform dispersion, 0.3g of PANI@LATP binder was added and stirred evenly to obtain a porous long-cycle silicon-carbon negative electrode material.

[0085] Figure 1 This is a TEM image of the porous silicon substrate prepared in this example, showing a very obvious pore structure. Figure 2 TEM image of the porous silicon substrate prepared in this example; Figure 3 This is the SEM image of the PANI@LATP adhesive prepared in this example.

[0086] Example 2

[0087] This embodiment provides a method for preparing a porous long-cycle silicon-carbon negative electrode material, which specifically includes the following steps:

[0088] A1, 60 mL of tetraethyl orthosilicate was added to 300 mL of 10.8 wt.% ethanol aqueous solution, 25 mL of 25 wt.% ammonia was added, and the mixture was heated to 41°C with stirring for 6.8 h. After centrifugation and washing, SiO2 microspheres were obtained. The SiO2 microspheres were immersed in 200 mL of 13 wt.% magnesium nitrate ethanol solution, ultrasonically dispersed for 38 min, and dried at 81°C. The microspheres were transferred to a muffle furnace and calcined at 580°C for 3.9 h to obtain SiO2@MgO. 5 g of SiO2@MgO and 3 g of Pluronic F-127 were added to anhydrous ethanol, stirred at room temperature for 12.9 h, and then rotary evaporated to obtain a template material. The template material was mixed with 80 g of magnesium powder, placed in a tube furnace, heated to 670°C under an Ar / H2 atmosphere, and kept warm for 5.9 h. After natural cooling, the microspheres were etched with 1 M hydrochloric acid and 5 wt.% hydrofluoric acid, washed with deionized water, and dried to obtain a porous silicon substrate;

[0089] S1, after mixing 10g aniline with 50mL concentrated sulfuric acid, add 5g ammonium persulfate and continue stirring, place it in a 48℃ water bath and continue stirring for 12.8h, filter, wash, dry and transfer it to a tube furnace, heat it to 210℃ and keep it for 2.1h to obtain PANI nanomaterials, immerse the PANI nanomaterials in the precursor sol and heat it gradually, keep it at 50℃ for 2h, 80℃ for 1h, and 120℃ for 30min, then immerse it in 0.01MCTAB solution, apply a 30V DC electric field and stir, and then calcine it in stages, calcining at 300℃ for 2h at a heating rate of 1℃ / min, calcining at 550℃ for 3h at a heating rate of 2℃ / min to obtain PANI@LATP; 10g PANI@LATP is immersed in 200mL A toluene solution of 3-aminopropyltriethoxysilane was refluxed at 80°C for 12.8 h, 10 mL of glycidyl methacrylate and 0.5 g of CuBr were added, the temperature was adjusted to 60°C and refluxed for 6.1 h, the temperature was adjusted to 50°C and 5 g of lipoic acid was added and reacted for 3.7 h to obtain a pre-product. The pre-product and 2 g of four-arm polyethylene glycol lipoic acid were dispersed in 100 mL of N,N-dimethylformamide, 0.1 g of Irgacure 2959 was added, and the mixture was UV-irradiated for 38 min. The PANI@LATP binder was freeze-dried.

[0090] S2, 8 g of phosphorus pentasulfide and 5 g of lithium carbonate were dispersed in 200 mL of anhydrous acetonitrile, refluxed at 89 °C for 6.2 h, and then 2 g of polydopamine microspheres were added. The temperature was adjusted to 182 °C for 12.8 h, and then washed and dried to obtain Li3PS4@PDA;

[0091] S3, the porous silicon substrate was heated to 680 ° C under an argon atmosphere and then acetylene was introduced. After keeping warm for 3 hours, the temperature was naturally cooled to obtain a silicon-carbon composite material. 10g of the silicon-carbon composite material and 0.3g of Li3PS4@PDA were dispersed in 40mL of N-methylpyrrolidone. After uniform dispersion, 0.3g of PANI@LATP binder was added and stirred evenly to obtain a porous long-cycle silicon-carbon negative electrode material.

[0092] Example 3

[0093] This embodiment provides a method for preparing a porous long-cycle silicon-carbon negative electrode material, which specifically includes the following steps:

[0094] A1, 60 mL of tetraethyl orthosilicate was added to 300 mL of 10.2 wt.% ethanol aqueous solution, 25 mL of 20 wt.% ammonia was added, and the mixture was heated to 49°C with stirring for 6.1 h. After centrifugation and washing, SiO2 microspheres were obtained. The SiO2 microspheres were immersed in 200 mL of 13 wt.% magnesium nitrate ethanol solution, ultrasonically dispersed for 36 min, and dried at 89°C. The microspheres were transferred to a muffle furnace and calcined at 550°C for 3.6 h to obtain SiO2@MgO. 5 g of SiO2@MgO and 3 g of Pluronic F-127 were added to anhydrous ethanol, stirred at room temperature for 12.4 h, and then rotary evaporated to obtain a template material. The template material was mixed with 80 g of magnesium powder, placed in a tube furnace, heated to 650°C under an Ar / H2 atmosphere, and kept warm for 5.7 h. After natural cooling, the microspheres were etched with 1 M hydrochloric acid and 5 wt.% hydrofluoric acid, washed with deionized water, and dried to obtain a porous silicon substrate;

[0095] S1, after mixing 10g aniline with 50mL concentrated sulfuric acid, add 5g ammonium persulfate and continue stirring, place in a 41℃ water bath and continue stirring for 12.5h, filter, wash, dry and transfer to a tube furnace, heat to 220℃ and keep warm for 2.8h to obtain PANI nanomaterials, immerse the PANI nanomaterials in the precursor sol and heat them gradually, keep them at 50℃ for 2h, 80℃ for 1h, and 120℃ for 30min, then immerse them in 0.01MCTAB solution, apply a 30V DC electric field and stir, and then calcine them in stages, calcining at 300℃ for 2h at a heating rate of 1℃ / min, calcining at 550℃ for 3h at a heating rate of 2℃ / min to obtain PANI@LATP; 10g PANI@LATP is immersed in 200mL A toluene solution of 3-aminopropyltriethoxysilane was refluxed at 80°C for 12.4 h, 10 mL of glycidyl methacrylate and 0.5 g of CuBr were added, the temperature was adjusted to 60°C and refluxed for 6.9 h, the temperature was adjusted to 50°C and 5 g of lipoic acid was added and reacted for 3.1 h to obtain a pre-product. The pre-product and 2 g of four-arm polyethylene glycol lipoic acid were dispersed in 100 mL of N,N-dimethylformamide, 0.1 g of Irgacure 2959 was added, and the mixture was UV-irradiated for 31 min. The PANI@LATP binder was freeze-dried.

[0096] S2, 8 g of phosphorus pentasulfide and 5 g of lithium carbonate were dispersed in 200 mL of anhydrous acetonitrile, refluxed at 81 °C for 6.1 h, and then 2 g of polydopamine microspheres were added. The temperature was adjusted to 183 °C for 12.4 h, and then washed and dried to obtain Li3PS4@PDA;

[0097] S3, the porous silicon substrate was heated to 660 ° C under an argon atmosphere and then acetylene was introduced. After keeping warm for 3 hours, the temperature was naturally cooled to obtain a silicon-carbon composite material. 10g of the silicon-carbon composite material and 0.3g of Li3PS4@PDA were dispersed in 40mL of N-methylpyrrolidone. After uniform dispersion, 0.3g of PANI@LATP binder was added and stirred evenly to obtain a porous long-cycle silicon-carbon negative electrode material.

[0098] Example 4

[0099] This embodiment provides a method for preparing a porous long-cycle silicon-carbon negative electrode material, which specifically includes the following steps:

[0100] A1, 60 mL of tetraethyl orthosilicate was added to 300 mL of 9.9 wt.% ethanol aqueous solution, 25 mL of 24 wt.% ammonia was added, and the mixture was heated to 46°C with stirring for 6.5 h. After centrifugation and washing, SiO2 microspheres were obtained. The SiO2 microspheres were immersed in 200 mL of 13 wt.% magnesium nitrate ethanol solution, ultrasonically dispersed for 33 min, and dried at 83°C. The microspheres were transferred to a muffle furnace and calcined at 560°C for 3.1 h to obtain SiO2@MgO. 5 g of SiO2@MgO and 3 g of Pluronic F-127 were added to anhydrous ethanol, stirred at room temperature for 12.7 h, and then rotary evaporated to obtain a template material. The template material was mixed with 80 g of magnesium powder, placed in a tube furnace, heated to 680°C under an Ar / H2 atmosphere, and kept warm for 5.2 h. After natural cooling, the microspheres were etched with 1 M hydrochloric acid and 5 wt.% hydrofluoric acid, washed with deionized water, and dried to obtain a porous silicon substrate;

[0101] S1, after mixing 10g aniline with 50mL concentrated sulfuric acid, add 5g ammonium persulfate and continue stirring, place it in a 45℃ water bath and continue stirring for 12.7h, filter, wash, dry and transfer it to a tube furnace, heat it to 215℃ and keep it for 2.6h to obtain PANI nanomaterials, immerse the PANI nanomaterials in the precursor sol and heat it gradually, keep it at 50℃ for 2h, 80℃ for 1h, and 120℃ for 30min, then immerse it in 0.01MCTAB solution, apply a 30V DC electric field and stir, and then calcine it in stages, calcining at 300℃ for 2h at a heating rate of 1℃ / min, calcining at 550℃ for 3h at a heating rate of 2℃ / min to obtain PANI@LATP; 10g PANI@LATP is immersed in 200mL A toluene solution of 3-aminopropyltriethoxysilane was refluxed at 80°C for 12.7 h, 10 mL of glycidyl methacrylate and 0.5 g of CuBr were added, the temperature was adjusted to 60°C and refluxed for 6.5 h, the temperature was adjusted to 50°C and 5 g of lipoic acid was added and reacted for 3.5 h to obtain a pre-product. The pre-product and 2 g of four-arm polyethylene glycol lipoic acid were dispersed in 100 mL of N,N-dimethylformamide, 0.1 g of Irgacure 2959 was added, and the mixture was UV-irradiated for 37 min. The PANI@LATP binder was freeze-dried.

[0102] S2, 8 g of phosphorus pentasulfide and 5 g of lithium carbonate were dispersed in 200 mL of anhydrous acetonitrile, refluxed at 85 °C for 6.6 h, and then 2 g of polydopamine microspheres were added. The temperature was adjusted to 186 °C for 12.7 h, and then washed and dried to obtain Li3PS4@PDA;

[0103] S3, the porous silicon substrate was heated to 670 ° C under an argon atmosphere and then acetylene was introduced. After keeping warm for 3 hours, the temperature was naturally cooled to obtain a silicon-carbon composite material. 10g of the silicon-carbon composite material and 0.3g of Li3PS4@PDA were dispersed in 40mL of N-methylpyrrolidone. After uniform dispersion, 0.3g of PANI@LATP binder was added and stirred evenly to obtain a porous long-cycle silicon-carbon negative electrode material.

[0104] Comparative Example 1

[0105] This comparative example provides a method for preparing a porous long-cycle silicon-carbon negative electrode material. The difference between it and Example 1 is that the mass of lipoic acid in S1 is 1g, which is 4g less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing a porous long-cycle silicon-carbon negative electrode material. The difference between it and Example 1 is that the mass of lipoic acid in S1 is 10g, which is 5g more than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0108] Comparative Example 3

[0109] This comparative example provides a method for preparing a porous long-cycle silicon-carbon negative electrode material. The difference between it and Example 1 is that the mass of phosphorus pentasulfide in S1 is 2g, which is 6g less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0110] Comparative Example 4

[0111] This comparative example provides a method for preparing a porous long-cycle silicon-carbon negative electrode material. The difference between it and Example 1 is that the mass of phosphorus pentasulfide in S1 is 13g, which is 5g more than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0112] Testing method: After the prepared silicon-carbon anode material was stirred evenly, it was evenly coated onto a copper foil current collector using a coating device. The material was then baked in a vacuum drying oven at 80°C for 12 hours. The material was then pressed evenly using a roller press, and finally formed into circular electrode sheets with a diameter of 14 mm using a punching machine. A lithium metal sheet was then used as the counter electrode, a polypropylene film as the separator, and the electrolyte was a mixture of 1 mol / L lithium hexafluorophosphate and equal volumes of ethylene carbonate and dimethyl carbonate. 2025 button-shaped cells were assembled in a vacuum glove box filled with high-purity nitrogen for electrochemical performance testing. Charge and discharge cycles were performed at a 0.1C rate over a voltage range of 0 to 1.5 V for 100 and 300 cycles. After 100 cycles, the cells were disassembled to measure the volume expansion of the electrode sheets. The test results are shown in Table 1.

[0113] Table 1 Test results of porous long cycle silicon-carbon negative electrode materials of Examples 1-4 and Comparative Examples 1-4

[0114]

[0115] As shown in Table 1, compared to Example 1, the first cycle reversible capacity and cycle capacity retention rate of comparative example 1 are reduced, and 100 cycle volume expansion rates increase; The first cycle reversible capacity and cycle capacity retention rate of comparative example 2 are reduced, and 100 cycle volume expansion rates increase. This is due to the fact that the disulfide bond in the thioctic acid molecule participates in cross-linking to form a chemical bond in the reaction, and the mechanical strength and the flexibility of the binder can be enhanced, the volume expansion adaptability to silicon particles is improved, and thioctic acid can enhance its binding force to silicon-carbon composite material by the chemical action on the surface with PANI@LATP, reduce the shedding and interface failure between particles, thioctic acid is not used enough in comparative example 1, and the cross-linking density of the binder can be caused to reduce and the interface bonding force is not enough, in the first cycle, silicon particles are subjected to larger mechanical stress due to volume expansion, and some silicon particles may be caused to lose contact with the conductive network, causing irreversible capacity loss to increase, thereby reducing the first cycle reversible capacity, while the stress caused by the repeated expansion of silicon particles during the cycle cannot be effectively buffered, causing silicon particles to gradually pulverize or fall off, and the electrode structure is seriously damaged, and capacity decays, and volume expansion rate increases. In Comparative Example 2, excessive use of lipoic acid results in an excessively high degree of cross-linking of the binder, which increases the rigidity of the binder. The binder with greater rigidity is difficult to adapt to the volume changes of the silicon particles during the cycle, which may lead to poor connection between the silicon particles and the conductive network, reducing the reversible capacity of the first cycle, and may also cause the binder to become overly dense in structure, affecting the conduction path of ions and electrons, resulting in a decrease in cycle performance.

[0116] As shown in Table 1, compared with Example 1, the first cycle reversible capacity and cycle capacity retention rate of Comparative Example 3 are reduced, and the volume expansion rate after 100 cycles is increased; the first cycle reversible capacity and cycle capacity retention rate of Comparative Example 4 are reduced, and the volume expansion rate after 100 cycles is increased. Phosphorus pentasulfide reacts with lithium carbonate to form lithium phosphorus sulfide, which plays a role in improving the ionic conductivity of the composite material. In Comparative Example 3, the amount of phosphorus pentasulfide used is too small, and the amount of Li3PS4 generated by the reaction is insufficient, resulting in low lithium ion conductivity in the composite material. During the first cycle of the battery, the lithium ion transmission efficiency is reduced, the first cycle reversible capacity is reduced, the overall ion conduction efficiency of the electrode is low, the lithium ion transmission is limited during the cycle, and the cycle capacity retention rate is reduced. In Comparative Example 4, the amount of phosphorus pentasulfide used is too large, forming a thicker covering layer, which may reduce the conductivity inside the electrode and increase the impedance of the lithium ion transmission path, resulting in a decrease in the cycle capacity retention rate.

[0117] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a porous long-cycle silicon-carbon negative electrode material, characterized in that: The preparation method comprises: S1, after mixing aniline with concentrated sulfuric acid, adding ammonium persulfate and transferring to a tube furnace to obtain PANI nanomaterials, immersing the PANI nanomaterials in a precursor sol and gradually increasing the temperature, then immersing them in a CTAB solution, applying a DC electric field and calcining them in stages to obtain PANI@LATP, immersing the PANI@LATP in a toluene solution of 3-aminopropyltriethoxysilane, adding glycidyl methacrylate, CuBr, and lipoic acid to react to obtain a preproduct, mixing the preproduct, four-arm polyethylene glycol lipoic acid, and a photoinitiator and irradiating them with ultraviolet light to obtain a PANI@LATP binder; S2, dispersing phosphorus pentasulfide and lithium carbonate in anhydrous acetonitrile, adding polydopamine microspheres after the reaction, and reacting to obtain Li3PS4@PDA; S3, heating the porous silicon substrate under an argon atmosphere and then introducing acetylene to obtain a silicon-carbon composite material, dispersing the silicon-carbon composite material and Li3PS4@PDA in N-methylpyrrolidone, and then adding PANI@LATP binder to obtain a porous long-cycle silicon-carbon negative electrode material; The preparation method of the porous silicon substrate comprises: adding tetraethyl orthosilicate to an ethanol aqueous solution, adding ammonia water to react to obtain SiO2 microspheres, immersing the SiO2 microspheres in a magnesium nitrate ethanol solution, ultrasonically dispersing and calcining to obtain SiO2@MgO, then adding SiO2@MgO and Pluronic F-127 to anhydrous ethanol, rotary evaporating to obtain a template material, mixing the template material with magnesium powder, placing the mixture in a tube furnace, keeping the mixture warm under an Ar and H2 atmosphere, naturally cooling, corroding the mixture with hydrochloric acid and hydrofluoric acid in sequence, washing with deionized water, and drying the mixture to obtain the porous silicon substrate; The solutes in the precursor sol are tetraisopropyl titanate, aluminum nitrate nonahydrate and lithium dihydrogen phosphate, with a volume mass ratio of 25 mL:8 g:12 g; the solvent is a mixture of ethanol / acetyl and acetone, with a volume ratio of 4:1; and the volume ratio of tetraisopropyl titanate to the solvent is 25:

130.

2. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S1: The mass ratio of the aniline to ammonium persulfate is 2:

1.

3. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S1: The gradient temperature increase is 50°C for 2 hours, 80°C for 1 hour, and 120°C for 30 minutes. The staged calcination is carried out as follows: calcination at 300°C for 2 hours with a heating rate of 1°C / min, and calcination at 550°C for 3 hours with a heating rate of 2°C / min; The mass volume ratio of the PANI@LATP to 3-aminopropyltriethoxysilane is 2 g:5 mL.

4. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S1: The mass ratio of lipoic acid to PANI@LATP is 1:2; The mass ratio of the four-arm polyethylene glycol lipoic acid to PANI@LATP is 1:

5.

5. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S2: The mass ratio of phosphorus pentasulfide to lithium carbonate is 8:5; The mass ratio of phosphorus pentasulfide to polydopamine microspheres is 4:

1.

6. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S3: The mass ratio of the silicon-carbon composite material, Li3PS4@PDA and PANI@LATP binder is 100:3:3; The mass volume ratio of the silicon-carbon composite material to N-methylpyrrolidone is 1 g:4 mL.

7. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S1: The volume ratio of tetraethyl orthosilicate to ethanol aqueous solution is 1:5; The volume ratio of tetraethyl orthosilicate to ammonia water is 12:5; The mass fraction of the magnesium nitrate ethanol solution is 13 wt.%.

8. The method for preparing a porous long-cycle silicon-carbon negative electrode material according to claim 1, characterized in that: In S1: When SiO2@MgO and Pluronic F-127 are added to anhydrous ethanol, the mass ratio of SiO2@MgO to Pluronic F-127 is 5:3; The mass ratio of SiO2@MgO to magnesium powder is 1:16; The volume ratio of Ar to H2 is 95:

5.

9. A porous long-cycle silicon-carbon negative electrode material is obtained according to the preparation method according to any one of claims 1 to 8.

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