A method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material

Abstract

The application relates to the technical field of lithium ion battery manufacturing, and discloses a preparation method of a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material, which comprises the following steps: grafting phytic acid on the surface of silicon-containing silicon oxide to construct protonated acid sites, mixing modified silicon-containing silicon oxide, phenolic resin and artificial graphite and keeping constant temperature, using phytic acid to catalyze the interface resin to preferentially generate pre-polycondensation and form a gel layer, quickly removing a solvent to obtain a precursor, and high-temperature carbonization to form a composite negative electrode material with a phosphorus-doped carbon coating layer; the application utilizes a kinetic competition mechanism to establish interface chemical anchoring before solvent volatilization, solves the peeling problem of resin and active particles caused by solvent volatilization in a traditional process, and improves the structural stability and conductive continuity of the material in the battery cycle process.

Description

Technical Field

[0001] This invention relates to a method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material, belonging to the field of lithium-ion battery manufacturing technology. Background Technology

[0002] Currently, silicon-containing silicon oxide has a theoretical specific capacity higher than that of commercial graphite anodes, making it a core material for high-energy-density lithium-ion batteries. In industrial applications, to alleviate the volume expansion effect and poor conductivity issues associated with lithium insertion / extraction in silicon-containing silicon oxide, it is typically composited with structurally stable artificial graphite. Phenolic resin is introduced as a carbon source precursor for liquid-phase coating, and an amorphous carbon conductive network is constructed on the surface of the carbonized particles through high-temperature pyrolysis. This composite strategy utilizes the carbon coating layer to buffer the volume changes of the active particles and leverages the artificial graphite framework to maintain the overall structural stability of the electrode. The engineering preparation process of these multiphase composite materials is constrained by both differences in interfacial chemical properties and process kinetics. The surface of silicon dioxide is rich in polar silanol groups, while the surface of artificial graphite has highly crystalline, hydrophobic, and inert characteristics. The difference in surface energy between the two makes it difficult to achieve uniform wetting and continuous spreading of the two matrices in the phenolic resin precursor slurry. Conventional liquid-phase mixing and drying solvent removal processes suffer from a kinetic mismatch between the physical evaporation rate of the solvent and the chemical reaction rate at the resin interface. During the heating and drying stage, the rapid removal of the solvent causes the solid content and viscosity of the system to increase exponentially. Before the resin molecular chains adjust their posture and undergo chemical condensation with the active sites on the surface of silicon dioxide, they lose fluidity, physically freeze, or undergo phase separation and migration driven by capillary forces at the gas-liquid interface.

[0003] Furthermore, relying solely on the physical shearing action of conventional mechanical dispersion equipment is insufficient to overcome the aforementioned microscopic interface energy barrier. Existing technologies have turned to improving the bonding state between components through specific process assembly and bonding control methods. For example, Chinese invention patent application CN115483376A discloses a method for preparing graphite composite anode materials, attempting to mix single-particle artificial graphite, biomass pyrolysis hard carbon materials, and binders such as asphalt or rubber plasticizers to prepare secondary particles, followed by carbonization treatment. The adhesive properties of the binder are used to physically bond different carbon materials to form a coating. However, due to the weak bonding force between the carbon coating layer and the active particles caused by the physical stacking and non-chemical bonding interface, it is difficult to resist the mechanical stress generated by repeated charge-discharge cycles of silicon oxide particles. Increasing the amount of resin or introducing conventional physical dispersants only improves the macroscopic dispersion state and cannot solve the problem of missing chemical bonds at the microscopic interface. As a result, the anode material is prone to carbon layer peeling, active material pulverization and shedding, and conductive network interruption during long-term cycling.

[0004] Therefore, constructing a forced interfacial chemical reaction mechanism in the liquid phase before solvent removal to achieve in-situ chemical anchoring and uniform spreading of carbon precursor silicon-containing silicon oxide and artificial graphite is the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material, the preparation method comprising the following steps:

[0006] Step S100, surface protonation pre-anchoring: Silica-containing powder with a particle size of 3 to 5 micrometers is dispersed in anhydrous ethanol solvent. The silica-containing powder is silica suboxide powder. Phytic acid aqueous solution is added, with the amount of phytic acid aqueous solution being 2.0% of the mass of silica-containing powder. The concentration of the phytic acid aqueous solution is 50 wt%. The dispersion is carried out at a shear rate of 3000 to 4000 rpm, so that the phosphate groups of phytic acid undergo a condensation reaction with the silanol groups on the surface of silica-containing powder and are grafted onto the surface of silica-containing powder in the form of covalent bonds.

[0007] Step S200, interfacial catalytic locking and assembly: Phenolic resin and artificial graphite are added to the system obtained in step S100. The system temperature is adjusted to 45°C to 55°C and kept at a constant temperature for 3 to 4 hours with a stirring rate of 300 to 500 rpm. The phytic acid grafted onto the surface of the silica-containing powder catalyzes the preferential pre-condensation of the phenolic resin adsorbed on the interface and grows a pre-crosslinked gel layer in situ on the surface of the silica-containing powder. The system temperature is raised to above 85°C at a rate of 5°C per minute and a negative pressure of -0.08 MPa to -0.09 MPa is applied to remove the anhydrous ethanol solvent to obtain the composite precursor.

[0008] Step S300, chemical bonding carbonization, the composite precursor is heated to 180 degrees Celsius at a rate of 2 degrees Celsius per minute under an inert atmosphere and held at that temperature for 2 hours for curing, and then heated to 900 degrees Celsius to 1000 degrees Celsius for carbonization. Phosphorus doping is achieved at the interface using the thermal decomposition products of phytic acid, and a composite anode material with a phosphorus-doped carbon coating layer is formed.

[0009] Preferably, in step S100, the solid content of the silicon oxide powder in anhydrous ethanol solvent is 25% to 35% by weight; the dispersion treatment time is 45 minutes to 60 minutes; the phytic acid is an aqueous solution with a concentration of 50% by weight; the dispersion treatment constructs monolayer-level surface protonated acidic sites on the surface of the silicon oxide powder.

[0010] Preferably, in step S200, the phenolic resin is a thermoplastic phenolic resin or a high ortho-position thermosetting phenolic resin, and the amount of phenolic resin added is 8% to 12% by weight of the total mass of silicon dioxide powder and artificial graphite; the artificial graphite is isotropic coke or needle coke obtained by graphitization treatment of particles, and the stirring rate is 300 rpm to 500 rpm.

[0011] Preferably, in step S200, the temperature range of 45°C to 55°C is set to be below the boiling point of anhydrous ethanol solvent and above the activation energy threshold of the acid-catalyzed polycondensation reaction of phenolic resin; the isothermal holding process makes the polycondensation reaction rate constant of phenolic resin on the surface of silicon-containing silica powder greater than its dissolution-diffusion rate constant in anhydrous ethanol solvent, thereby inhibiting the capillary-driven phase separation of phenolic resin during the removal of anhydrous ethanol solvent.

[0012] Preferably, in step S100, the mass M of phytic acid added is... PA M is determined according to the following formula: PA =k S BET M Si S BET M represents the specific surface area of ​​silicon dioxide powder, expressed in square meters per gram; Si The total mass of silicon dioxide powder is expressed in grams; k is the surface acidity site density coefficient, which ranges from 0.002 g / m² to 0.005 g / m². The surface acidity site density coefficient is used to limit the minimum effective amount of acid per unit surface area that can initiate the pre-condensation reaction of phenolic resin.

[0013] Preferably, in step S200, the process of removing anhydrous ethanol solvent includes maintaining the stirring rate until the system is in powder form; the process of rapidly removing the solvent precipitates the bulk phenolic resin that has not participated in the interfacial reaction onto the surface of the artificial graphite particles and the outside of the pre-crosslinked gel layer, forming a gradient coating structure.

[0014] Preferably, in step S300, the inert atmosphere is nitrogen or argon, and the flow rate is 2 to 5 liters per minute; the curing process causes the hydroxymethyl groups in the phenolic resin to undergo complete cross-linking to form a three-dimensional network structure; the carbonization process takes 3 to 5 hours, during which phytic acid undergoes in-situ thermal decomposition and releases phosphorus atoms, which diffuse in-situ into the generated amorphous carbon lattice.

[0015] Preferably, the composite anode material comprises a silicon oxide core, an amorphous carbon interlayer doped with phosphorus coated on the surface of the silicon oxide core, and artificial graphite particles distributed on the surface of the amorphous carbon interlayer; the amorphous carbon interlayer is connected to the silicon oxide core through a Si-OPC covalent bond network; the intensity ratio of the D peak to the G peak in the Raman spectrum of the composite anode material is I. D / I G It ranges from 0.8 to 1.2.

[0016] Preferably, the preparation method further includes step S400, after step S300, the obtained composite negative electrode material is subjected to sieving treatment; the sieving treatment uses a 300-mesh to 400-mesh sieve to remove agglomerates formed during carbonization; the particle size distribution D50 of the obtained final product is 10 micrometers to 20 micrometers, and the carbon layer retention rate is greater than 98% after ultrasonic power of 300 watts for 30 minutes.

[0017] Preferably, the preparation method establishes a chemical anchor between the silicon-containing silicon oxide powder and the phenolic resin prior to physical drying through kinetic control in step S200; the chemical anchor evolves into a continuous interfacial bonding network during the high-temperature treatment in step S300, and the interfacial bonding network is used to suppress carbon layer delamination caused by the volume expansion of the silicon-containing silicon oxide powder during battery cycling.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. In silicon oxide phenolic resin, a proton donor environment of organophosphate compounds grafted on the surface of silicon oxide is constructed in the liquid phase system. Combined with a specific temperature window below the solvent boiling point and satisfying the activation energy of the polycondensation reaction, the phenolic resin at the contact interface preferentially undergoes acid-catalyzed pre-polycondensation. Before the system loses fluidity due to the removal of a large amount of solvent, a covalent bond-anchored pre-crosslinked gel layer is generated in situ on the surface of silicon oxide. This transforms the traditional physical adsorption interface into a chemical bond strength structure anchoring interface. The chemical bonds form a continuous network to resist the mechanical stress generated by the volume effect of the lithium intercalation and deintercalation process of silicon oxide, and maintain the integrity of the long-term cycle structure of the conductive network.

[0020] 2. By utilizing the in-situ thermal decomposition characteristics of organophosphate compounds as interface binders during high-temperature carbonization, phosphorus atoms are gradient-doped at the interface between silicon-containing silicon oxide and amorphous carbon layers. The entry of phosphorus atoms into the carbon lattice causes adjustment of the electronic band structure, increasing the carrier density near the Fermi level. This constructs a low-contact-resistance electron transport channel between the semiconductor silicon-containing silicon oxide and the external carbon conductive network. Interface band engineering eliminates the local polarization phenomenon inside the multiphase composite material, improving the charge transfer efficiency and rate response capability of the electrode material during charging and discharging.

[0021] 3. Utilizing the amphiphilic molecular structure of organophosphates, a molecular-level bridging induction layer is established between the phosphate group end and the defect site or edge of the graphite surface through hydrogen bonding, and the organic framework end is compatible with phenolic resin. This induction layer overcomes the anti-wetting tendency of the resin melt graphite surface, driving the formation of a uniform and continuous spread morphology on the carbon source precursor graphite matrix. After carbonization treatment, a dense and complete coating structure is formed on the surface of the composite material, avoiding local exposure that could lead to side reactions in the electrolyte, thus establishing the basis for the formation of a stable solid electrolyte interface film structure. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the surface protonation pre-anchoring and chemical bonding preparation process of the silicon-containing silicon oxide composite anode material of the present invention.

[0023] Figure 2 These are the viscosity evolution kinetics and gelation rheological characteristics curves of the system under different thermodynamic environments according to the present invention;

[0024] Figure 3 This is a schematic diagram illustrating the interaction between the industrial control bus architecture and execution unit of the model-driven manufacturing process of this invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of protection of the present invention.

[0026] This invention provides a method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite anode material. Based on a kinetic time-series reconstruction interfacial chemical anchoring mechanism, the traditional physical mixing and drying process is transformed into a process flow comprising three consecutive stages: surface protonation pre-anchoring, interfacial acid catalytic induced directional assembly, and chemical bonding carbonization. By establishing chemical bonds between the silicon-containing silicon oxide and the phenolic resin before solvent removal, the problem of carbon layer peeling caused by the mismatch between solvent evaporation rate and interfacial reaction rate is solved. The final product is a composite anode material with a phosphorus-doped carbon coating layer and an interface connected by a Si-OPC covalent network. Addressing the engineering challenges of uneven precursor coating and weak bonding caused by the difference in surface polarity between silicon-containing silicon oxide and the surface inertness of artificial graphite, this preparation method performs surface protonation pre-anchoring, [further details needed]. In the pre-anchoring process, silicon-containing silica powder with a particle size D50 of 3.0 μm to 5.0 μm is dispersed in anhydrous ethanol solvent. The silicon-containing silica powder is silica suboxide powder, and the solid content of the system is controlled at 25 wt% to 35 wt%. A phytic acid aqueous solution with a mass fraction of 2.0% of the silicon-containing silica powder (50 wt%) is added. A high-shear dispersion device is started, and the shear rate is set to 3000 rpm to 4000 rpm. The dispersion time is maintained for 45 to 60 minutes. The energy provided by the high shear force overcomes the solid-liquid interfacial tension, causing the phosphate groups in the phytic acid molecules to undergo a dehydration condensation reaction with the silanol groups on the surface of the silicon-containing silica. This results in the formation of a monolayer-level structure rich in active protons (H) on the surface of the silicon-containing silica particles. + The organic phosphoric acid molecular layer forms a protonated interface with a specific surface acidic site density for subsequent resin directional adsorption and catalytic curing.

[0027] To address the technical drawbacks of traditional drying processes, such as the physical freezing of resin molecular chains and the formation of coffee rings due to rapid solvent evaporation, this method involves adding phenolic resin and artificial graphite to the aforementioned system and then executing a rigorous interfacial acid-catalyzed directional assembly procedure. The amount of phenolic resin added is controlled to be 8% to 12% of the total mass of silicon dioxide and artificial graphite. The mixture is then transferred to a thermostatically controlled stirred tank with precise temperature control, and the temperature inside the tank is adjusted and locked within a specific process window of 45°C to 55°C. Simultaneously, an anchor-type impeller is activated, and the stirring speed is set to a low-shear range of 300 rpm to 500 rpm. A stirring speed of 300 rpm to 500 rpm corresponds to an impeller linear velocity of 2.0 m / s to 4.0 m / s in a standard 5L planetary mixer. The shear field strength is determined through rheological testing and is set to be lower than the yield stress of the pre-crosslinked gel layer structure. During the stirring process, the shear stress value is maintained at the system's storage modulus G. ' The nonlinear descent begins in the critical stress range of 60% to 80%, maintaining the integrity of the gel network. During the stage of removing anhydrous ethanol solvent by heating, the system is placed in a sealed container equipped with a closed-loop nitrogen circulation and condensation recovery module. The nitrogen flow rate is controlled to maintain a slightly positive pressure environment inside the container. Ethanol vapors are introduced into the condenser for recovery, avoiding the risk of gas-phase flashover and achieving solvent recycling. This temperature is maintained at a constant temperature for 3 to 4 hours. This temperature range is designed to be below the boiling point of anhydrous ethanol solvent to maintain the liquid-phase diffusion ability of resin molecules, while being above the acid-catalyzed phenolic resin... The activation energy threshold of the resin polycondensation reaction is determined by utilizing the high-concentration proton environment provided by the phytic acid layer grafted onto the silicon-containing silica surface. This specifically catalyzes the preferential pre-polycondensation reaction of phenolic resin molecules adsorbed at the interface, thereby growing a pre-crosslinked gel layer in situ on the silicon-containing silica surface that is insoluble in ethanol. The system temperature is rapidly increased to 85°C to 90°C at a rate of 5°C / min, and a negative pressure of -0.08MPa to -0.09MPa is applied for flash drying. The formed chemical anchoring interface is used to resist the capillary force generated by solvent evaporation.

[0028] After the precursor assembly is completed, this method performs a chemical bonding carbonization process. The dried composite precursor powder is placed in a high-temperature heat treatment device such as a tube furnace or rotary kiln, and nitrogen or argon gas with a flow rate of 2 L / min to 5 L / min is introduced as a protective atmosphere. The temperature is raised to 180°C at a heating rate of 2°C / min and held for 2 hours, so that the hydroxymethyl groups in the phenolic resin undergo complete dehydration condensation to form a three-dimensional network solidification structure. The temperature is then raised to 900°C to 1000°C and held for 3 to 5 hours for high-temperature carbonization. During this process, phytic acid, which acts as an interface linker, undergoes in-situ thermal decomposition and releases phosphorus atoms. The generated phosphorus atoms diffuse in-situ and dop into the generated amorphous carbon lattice, causing an increase in the carrier density near the Fermi level of the carbon material. Finally, a composite structure with a Si-OPC covalent bond network connecting the silicon oxide core and the outer amorphous carbon layer is formed. This structure suppresses carbon layer peeling caused by volume expansion during battery cycling and reduces the interfacial contact resistance between the semiconductor silicon oxide and the conductive carbon layer.

[0029] For the precise determination of the amount of phytic acid added in the above process, this method uses a quantitative calculation procedure based on the specific surface area of ​​silicon dioxide powder, where the mass of phytic acid added is M. PA Follow formula M PA =k S BET M Si S BET The specific surface area of ​​silicon oxide powder containing silicon was measured using the nitrogen adsorption-desorption method, in m². 2 / g, M Si The total mass of the silicon-containing silica powder is expressed in grams, and k is the surface acid site density coefficient, with a value range set to [value range missing]. to This coefficient defines the minimum amount of acid required per unit surface area to initiate an effective pre-condensation reaction of phenolic resin, ensuring that phytic acid forms a monolayer covering on the silicon-containing silica surface without excessive free acid residue. This avoids excessive acid causing over-etching of the carbon layer or uncontrollable increase in porosity during subsequent high-temperature processing. The variable M in the calculation model... PA The molecular weight of phytic acid, i.e., 100% pure phytic acid, refers to the actual mass M of the solution added when using a 50wt% phytic acid aqueous solution as the raw material. solution Press M solution =M PA The surface acidic site density coefficient k, calculated using a 0.5 conversion, is based on the theoretical distribution density of silanol groups on silicon-containing silicon oxide surfaces and a monolayer adsorption model, and is 0.002 g / m³. 2 The lowest threshold for non-continuous island adsorption is 0.005 g / m³. 2This corresponds to achieving the steric saturation limit of a single-layer coverage. Regarding particle size control and impurity removal in the final composite anode material product, the preparation method also includes a sieving process after carbonization. A standard sieve of 300 to 400 mesh is used to classify the carbonized powder, removing agglomerates that may form during high-temperature processing. This controls the particle size distribution D50 of the final product within the range of 10 μm to 20 μm, and ensures that the intensity ratio I of the D peak to G peak in Raman spectroscopy is within a certain range. D / I G The ratio, ranging from 0.8 to 1.2, indicates that the carbon coating has a suitable degree of graphitization and defect density, which not only ensures the diffusion channels of lithium ions but also provides excellent electronic conductivity, thereby meeting the dual requirements of high-energy-density lithium-ion batteries for the structural stability and rate performance of the anode material.

[0030] Example 1: In the industrial setting of high-energy-density lithium-ion battery anode material preparation, the production line faces the severe challenge of physical separation between silicon-containing silicon oxide (SiOx) and phenolic resin precursor due to rapid solvent evaporation, leading to large-area peeling of the carbon coating layer and pulverization of active particles during subsequent high-temperature carbonization. To address these challenges, this example employs the preparation process detailed in the specific implementation steps. Through a series of precise chemical and kinetic control steps, the composite anode material is constructed. A surface protonation pre-anchoring process is performed, dispersing silicon-containing silicon oxide powder with a particle size D50 of 4.0 μm in anhydrous ethyl acetate. A suspension with a solid content of 30 wt% was prepared in alcohol, and a 50 wt% phytic acid aqueous solution containing 2.0% silicon dioxide was added. The mixture was then treated in a high-shear disperser at a rate of 3500 rpm for 50 minutes. The condensation reaction between the phosphate groups and silanol groups in the phytic acid molecules was utilized to graft monolayer protonated active sites onto the surface of the silicon dioxide. An interfacial acid catalytic induced directional assembly process was then performed. Phenolic resin and artificial graphite, accounting for 10% of the total mass, were added to the system. The temperature of the reactor was locked at 50°C and maintained at a constant temperature for 3.5 hours under low-shear stirring at 400 rpm.

[0031] In this crucial stage, the high-concentration proton environment on the silicon oxide surface specifically catalyzes the pre-condensation reaction of the phenolic resin adsorbed at the interface, generating an in-situ pre-crosslinked gel layer insoluble in ethanol. The resin molecules are firmly anchored to the silicon oxide surface through chemical bonds. Then, the system temperature is rapidly raised to 85°C and a negative pressure of -0.085 MPa is applied for flash drying. The formed chemical anchoring interface effectively resists the capillary force generated by solvent evaporation, preventing phase separation of the resin. Finally, a chemical bonding carbonization process is performed. The precursor is cured at 180°C for 2 hours under nitrogen protection, and then heated to 950°C for 4 hours for carbonization. During this process, phytic acid undergoes in-situ thermal decomposition, and the released phosphorus atoms are in-situ doped into the amorphous carbon lattice, ultimately forming a composite structure with a Si-OPC covalent bond network connecting the silicon oxide core and the outer carbon layer.

[0032] Example 2: This example aims to systematically verify and quantify the technical effects of the preparation method in suppressing carbon layer stripping, improving conductivity, and enhancing battery cycle stability by constructing a comparative experimental system with multi-dimensional parameter gradients. This experiment establishes a standardized platform simulating industrial battery electrode preparation and cycle testing, including: a 5L dual planetary mixer equipped with temperature control and vacuum systems to simulate the actual homogenization process; a high-precision coating machine for electrode preparation; and a 5V / 10mA multi-channel battery testing system for electrochemical performance evaluation in a constant temperature chamber. All experimental operations are conducted at a dew point below -40°C. The experiment was completed in a drying room to eliminate the interference of ambient moisture on the performance of silicon-containing materials. The following decision-making logic was followed for setting key process parameters in the experiment: For the core variable of interface assembly temperature, considering the competition between the rate constant of acid-catalyzed polycondensation reaction and the solvent evaporation rate constant, this experiment set temperature gradients (30℃, 50℃, 70℃) covering the reaction kinetics deficiency region, the preferred process window region, and the solvent evaporation-dominant region to verify the criticality of the temperature range defined by the present invention. For the amount of phytic acid added, a mass fraction gradient from 0% to 3.0% was set to explore the nonlinear relationship between phosphorus doping amount and conductivity and interface stability.

[0033] The experimental grouping and preparation process are as follows: Sample group of this invention: strictly following the specific implementation method, using 2.0 wt% phytic acid, interface assembly was performed at 50℃. Control group 1 (no chemical bonding): no phytic acid was added; only physical mixing and drying carbonization were performed, with other conditions the same as above, aiming to verify the contribution of chemical bonding to interface stability. Control group 2 (low-temperature assembly): using... Phytic acid was used, but interfacial assembly was performed at 30℃ to verify the effect of insufficient reaction kinetics at low temperatures on the integrity of the coating. Control group 3 (high-temperature assembly): 2.0 wt% phytic acid was used, but interfacial assembly was performed at 70℃ to verify the phase separation effect caused by rapid solvent evaporation at high temperatures. To quantify the structural stability of the materials under extreme conditions, this experiment introduced a high-strength ultrasonic exfoliation test. The specific steps were as follows: 1.0 g of each group of sample powder was weighed, dispersed in 50 mL of anhydrous ethanol, and placed in a 300 W power, frequency of [missing information]. In an ultrasonic cleaner, the particles were continuously vibrated at 25°C for 30 minutes. This process simulated the destructive effect of a high shear force field on the particle interface. After the vibration ended, the particles were filtered through a 0.2μm microporous membrane, dried, and weighed. The retention rate of the carbon coating was calculated. At the same time, the conductivity of each group of powders under 10MPa pressure was tested using the four-probe method. Finally, each group of materials was prepared into a half-cell, and the coulombic efficiency of the first cycle was tested at 0.1C rate, and a 100-cycle test was conducted at 0.5C rate. The key performance data of each test group are shown in Table 1.

[0034] Table 1: Comparison of Key Performance Indicators of Each Experimental Group under Different Process Conditions

[0035]

[0036] A detailed analysis of the data in Table 1 reveals the intrinsic mechanism of the technical solution of this invention: Comparing the sample group of this invention with control group 1, when phytic acid and its constructed chemical bonding network are missing, the carbon layer retention rate drops sharply from 98.5% to 65.2%, and the conductivity is only 1.8 S / cm. This confirms that the Si-OPC covalent bond is the decisive factor in resisting mechanical peeling and maintaining interface integrity. At the same time, phosphorus doping plays a key role in improving the conductivity of the carbon layer. This dual advantage of structure and conductivity makes the cycle capacity retention rate of the sample group of this invention as high as 92.1%, which is far better than the 70.3% of control group 1. Comparing the sample group of this invention with control groups 2 and 3, the nonlinear effect of interface assembly temperature on performance is shown. When the temperature is too low (30℃), although some phytic acid is retained, due to insufficient reaction activation energy, a dense pre-crosslinked gel layer is not formed, resulting in a decrease in carbon layer retention rate and cycle stability. When the temperature is too high (70℃), the rapid volatilization of ethanol dominates the process, and the resin agglomerates and separates before effective chemical bonding occurs, resulting in poor uniformity of the coating layer and deterioration of performance.

[0037] Example 3: This example combines Figures 1 to 3 The preparation method of a silicon-containing silicon oxide-phenolic resin-artificial graphite composite anode material is described, such as... Figure 1As shown, the process flow for preparing the silicon-containing silicon oxide phenolic resin-artificial graphite composite anode material begins with the input of silicon-containing silicon oxide, phytic acid, and anhydrous ethanol. Guided by the parameters of the phytic acid quantitative calculation model, the raw materials are precisely proportioned based on the specific surface area and acidic site density coefficient, and then proceed to step S100, the surface protonation pre-anchoring stage. Through high-shear dispersion treatment at 3000-4000 rpm, monomolecular-level protonation sites are grafted onto the surface of the silicon-containing silicon oxide to form Si-OP chemical bonds. The phenolic resin and artificial graphite raw materials are then introduced into step S200, the interface catalytic locking and assembly stage. Under a constant temperature of 45-55℃, phytic acid is used for preferential pre-condensation and in-situ growth. The pre-crosslinked gel layer is followed by rapid solvent removal. The composite precursor is obtained by flash drying under a negative pressure of -0.08 MPa and raising the temperature to above 85°C to suppress capillary-driven phase separation. Then, the precursor enters the chemical bonding and carbonization stage in step S300. During the gradient temperature increase process of curing at 180°C and carbonization at 1000°C, phosphorus atoms are released by the thermal decomposition of phytic acid to construct a Si-OPC covalent network. Finally, the precursor undergoes sieving in step S400, where high-temperature agglomerates are removed by grading with a 300-400 mesh sieve and the particle size D50 is controlled at 10-20 μm. The final product is a composite anode material with a phosphorus-doped carbon coating layer, high structural stability, and continuous conductivity.

[0038] like Figure 2 As shown, the horizontal axis represents time in hours, and the vertical axis represents viscosity in Pa·s. The figure contains three evolution curves under different temperature conditions, corresponding to interfacial assembly environments of 30℃, 50℃, and 70℃, respectively. It displays the differential regulatory effect of different thermodynamic environments on the resin polycondensation reaction rate and the viscosity growth trend of the system within a time span of 0 to 4 hours. Figure 3 As shown, the industrial control and data bus architecture consists of a top-level model, a middle-level bus, and a bottom-level execution unit. The top-level model includes a phytic acid precision batching model that automatically calculates the optimal addition amount based on specific surface area and acidity site coefficient; an interfacial reaction kinetics center that monitors the activation energy threshold of the polycondensation reaction and dynamically matches the solvent evaporation rate; and a curing and carbonization program set that controls the gradient heating curve and manages the inert atmosphere flow. These modules transmit speed settings, temperature control commands, and heating programs downward through the industrial control and data bus, respectively driving a high-shear dispersion unit that performs 3000-4000 RPM shearing and is in a surface protonation pre-anchoring state; a constant-temperature interfacial assembly unit that performs 45-55°C constant-temperature and negative-pressure flash evaporation and is in a state of acid-catalyzed pre-polycondensation; and an atmosphere-protected heat treatment unit that performs 900-1000°C high-temperature carbonization and is in a state of chemical bonding network construction.

[0039] Example 4: To systematically eliminate potential issues in the original document regarding the grafting density of phytic acid on silicon-containing silicon oxide surfaces and the interfacial reaction kinetics, this example constructs a standardized calibration procedure for the surface acidic site density coefficient k. Through a three-level verification system of gradient grafting, surface titration, and reaction kinetic testing, the optimal dosage range of phytic acid is transformed from empirical selection to precise anchoring based on surface stoichiometry. Gradient grafting experiments are performed in the surface protonation pre-anchoring process, selecting a specific surface area S. BET for Using silicon-containing silica powder as the reference material, a gradient of phytic acid addition was established so that the corresponding surface acid site density coefficients k were respectively... , , , and After treatment at a shear rate of 3500 rpm for 50 minutes in the specific implementation method, each group of samples was washed and dried to remove unreacted free phytic acid. The effective surface acid content of each group of samples was quantitatively determined by acid-base back titration. The test results showed that when the k value increased from... Increase to When the effective acid content on the surface increases linearly, it indicates that phytic acid molecules undergo effective monolayer chemisorption at the hydroxyl sites on the silicon-containing silica surface. When the k value is within a certain range... to Within the range, the growth rate of effective surface acid gradually slows down and tends to saturate. This corresponds to the state where phytic acid molecules achieve monolayer saturation coverage on the particle surface. At this point, the bonding between the phosphate groups and silanol groups of phytic acid is close to the geometric and steric hindrance limits. When the k value further increases to... At that time, the effective acid content on the surface no longer increased, and a large amount of residual phytic acid was detected in the cleaning solution, confirming that the excessive phytic acid failed to participate in chemical grafting and existed only in the form of physical adsorption, which was easy to fall off or agglomerate in subsequent treatment.

[0040] To verify the catalytic efficiency of surface acidic environments corresponding to different k values ​​on the precondensation reaction of phenolic resin, isothermal differential scanning calorimetry (DSC) kinetic tests were performed. The modified silica-containing silicon oxides of the above groups were mixed with phenolic resin and subjected to [a process at 50°C]. Record the exothermic reaction curve under constant temperature C, when When the reaction induction period is long and the exothermic peak is broad and low, it indicates that the surface acidic sites are insufficient to effectively initiate the rapid condensation reaction at the interface, making it difficult to form a continuous gel layer. to Within this range, the reaction induction period shortens, and the exothermic rate constant reaches its maximum and remains stable, confirming that the acidic site density in this range provides optimal catalytic activity, allowing the resin to preferentially crosslink at the interface. Although the reaction rate did not decrease significantly, the excess free acid caused significant mass loss and microporous structure collapse during carbonization, ultimately leading to a decrease in carbon layer density. Based on the combined results of surface chemical titration and reaction kinetics testing, this embodiment confirms the surface acidic site density coefficient. Preferred range to It was not a random choice, but rather an intrinsic physicochemical boundary where phytic acid achieves saturated monolayer coverage on silicon-containing silica surfaces and provides optimal interfacial catalytic activity.

[0041] Example 5: To ensure the stability of the preparation method of the present invention in the face of fluctuations in industrial raw materials, this example establishes a set of offline calibration and data filling procedures based on adsorption isotherm analysis. Through standardized experimental measurements, a method for preparing specific silicon-containing silica raw materials is constructed. Using a value correction factor lookup table, a representative set of silicon-containing silicon oxide raw material samples was selected, whose specific surface area S BET cover to In a typical industrial setting, under the preferred process conditions of a specific implementation method, gradient phytic acid grafting experiments were conducted on each sample. The effective surface acidity at different phytic acid addition amounts was determined by acid-base back titration, and adsorption isotherms of phytic acid addition amount versus effective surface acidity were plotted. By identifying the inflection point on the isotherm corresponding to monolayer saturation coverage, the optimal surface acidity site density coefficient k for each sample was determined. opt S of each sample BET The value and its corresponding k opt The values ​​are fitted, and a correction factor lookup table is established. In actual production, it is only necessary to measure the S of the new batch of raw materials. BET The value can be found in the table to obtain the corrected value. Value, and substitute into formula M PA =k S BET M Si This allows for the precise calculation of the optimal amount of phytic acid to be added.

[0042] To address the impact of potential temperature and humidity fluctuations or equipment differences on reaction kinetics in actual production environments, this embodiment also establishes a pre-deployment calibration procedure. This procedure requires the collection of reaction rheological fingerprints to calibrate process parameters before formal production commences. Specifically, a small amount of the batch of silica-containing silicon dioxide and resin mixture is taken and subjected to low-shear stirring at a predetermined preferred temperature, such as 50°C. The viscosity of the system over time is monitored in real-time using a rheometer, and the time t at which the viscosity abrupt change point (i.e., the gelation point) occurs is recorded. gel And compare it with the reference time t under standard process. ref Compare the values; if the absolute value of the deviation is... If the temperature exceeds 10%, the isothermal time during the interface assembly stage will be fine-tuned according to the preset temperature-time compensation model. For example, at t gel If there is a lag, the isothermal time should be extended appropriately until the overlap between the measured viscosity curve and the reference curve reaches more than 95%, so as to ensure that the pre-condensation degree of the resin on the silicon-containing silica surface is always in the optimal process window.

[0043] Example 6: To address the potential process adaptability risks arising from inherent fluctuations in surface hydroxyl density, particle size distribution, and impurity content among different industrial batches of silicon-containing silica raw materials, a standardized on-site deployment pre-calibration and model building procedure was established. For each batch of newly arrived raw materials, a feature fingerprint acquisition step was performed, and its specific surface area S was obtained through nitrogen adsorption-desorption testing. BET The pore size distribution data were used to determine the surface hydroxyl content using thermogravimetric analysis. These physicochemical parameters were then input into a pre-built adaptive process parameter model, which was trained based on the correlation between a large number of different raw material properties and optimal process parameters in a historical database. This model can output a recommended process parameter window for the current batch of raw materials.

[0044] In addition, small-scale trials and parameter fine-tuning steps were carried out. In a small reactor with a capacity of 1L, a single trial was conducted using the process parameters recommended by the model. The viscosity change curve during the interface assembly stage was monitored. If the deviation between the measured viscosity abrupt change point (gelation time) and the model prediction value was less than 5%, the set of parameters was directly locked as the execution standard for production line scale-up. If the deviation exceeded 5%, the temperature or phytic acid dosage was fine-tuned according to the direction of the deviation (too fast or too slow reaction) until it reached the predetermined deviation range.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material, characterized in that, The preparation method includes the following steps: Step S100, surface protonation pre-anchoring: Silica-containing powder with a particle size of 3 to 5 micrometers is dispersed in anhydrous ethanol solvent. The silica-containing powder is silicon suboxide powder. Phytic acid aqueous solution is added, with the amount of phytic acid aqueous solution being 2.0% of the mass of the silica-containing powder and the concentration of the phytic acid aqueous solution being 50 wt%. The dispersion is carried out at a shear rate of 3000 to 4000 rpm, so that the phosphate groups of phytic acid undergo a condensation reaction with the silanol groups on the surface of the silica-containing powder and are grafted onto the surface of the silica-containing powder in the form of covalent bonds. Step S200, interfacial catalytic locking and assembly: Phenolic resin and artificial graphite are added to the system obtained in step S100. The system temperature is adjusted to 45°C to 55°C and kept at a constant temperature for 3 to 4 hours with a stirring rate of 300 to 500 rpm. The phytic acid grafted onto the surface of the silica-containing powder catalyzes the preferential pre-condensation of the phenolic resin adsorbed on the interface and grows a pre-crosslinked gel layer in situ on the surface of the silica-containing powder. The system temperature is raised to above 85°C at a rate of 5°C per minute and a negative pressure of -0.09 MPa to -0.08 MPa is applied to remove the anhydrous ethanol solvent to obtain the composite precursor. Step S300, chemical bonding carbonization, the composite precursor is heated to 180 degrees Celsius at a rate of 2 degrees Celsius per minute under an inert atmosphere and held at that temperature for 2 hours for curing, and then heated to 900 degrees Celsius to 1000 degrees Celsius for carbonization. Phosphorus doping is achieved at the interface using the thermal decomposition products of phytic acid, and a composite anode material with a phosphorus-doped carbon coating layer is formed. Furthermore, the composite anode material includes a silicon oxide core, an amorphous carbon interlayer doped with phosphorus coated on the surface of the silicon oxide core, and artificial graphite particles coated on the surface of the amorphous carbon interlayer; the amorphous carbon interlayer is connected to the silicon oxide core through a Si-OPC covalent bond network; the intensity ratio of the D peak to the G peak in the Raman spectrum of the composite anode material is I. D / I G It ranges from 0.8 to 1.

2.

2. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, In step S100, the solid content of the silicon-containing silicon oxide powder in anhydrous ethanol solvent is 25% to 35% by weight; the dispersion treatment time is 45 minutes to 60 minutes; and the phytic acid is an aqueous solution with a concentration of 50% by weight.

3. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, In step S200, the phenolic resin is a thermoplastic phenolic resin or a high ortho-position thermosetting phenolic resin, and the amount of phenolic resin added is 8% to 12% by weight of the total mass of silicon dioxide powder and artificial graphite; the artificial graphite is particles obtained by graphitization treatment of isotropic coke or needle coke.

4. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, In step S100, the mass M of phytic acid added is... PA M is determined according to the following formula: PA =k S BET M Si S BET M represents the specific surface area of ​​silicon dioxide powder, expressed in square meters per gram; Si The total mass of silicon dioxide powder is expressed in grams; k is the surface acidity site density coefficient, which ranges from 0.002 g / m² to 0.005 g / m². The surface acidity site density coefficient is used to limit the minimum effective amount of acid per unit surface area that can initiate the pre-condensation reaction of phenolic resin.

5. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, In step S200, the process of removing anhydrous ethanol solvent includes maintaining the stirring rate until the system is in powder form; the process of rapidly removing solvent precipitates the bulk phenolic resin that has not participated in the interfacial reaction onto the surface of the artificial graphite particles and the outside of the pre-crosslinked gel layer, forming a gradient coating structure.

6. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, In step S300, the inert atmosphere is nitrogen or argon, with a flow rate of 2 to 5 liters per minute; the curing process causes the hydroxymethyl groups in the phenolic resin to undergo complete cross-linking to form a three-dimensional network structure; the carbonization process takes 3 to 5 hours, during which phytic acid undergoes in-situ thermal decomposition and releases phosphorus atoms, which diffuse in-situ into the generated amorphous carbon lattice.

7. The method for preparing a silicon-containing silicon oxide-phenolic resin-artificial graphite composite negative electrode material according to claim 1, characterized in that, The preparation method also includes step S400, after step S300, the obtained composite negative electrode material is subjected to sieving treatment; the sieving treatment uses a 300-mesh to 400-mesh sieve to remove agglomerates formed during carbonization; the particle size distribution D50 of the obtained final product is 10 micrometers to 20 micrometers, and the carbon layer retention rate is greater than 98% after ultrasonic power of 300 watts for 30 minutes.

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