A phenolic resin-based composite porous carbon material, its preparation method and application

Abstract

This invention relates to a phenolic resin-based composite porous carbon material, its preparation method, and its application, comprising the following steps: (1) hydrolyzing a silicon source in an acidic aqueous solution to obtain a silicon-based hydrolysate, and then mixing the silicon-based hydrolysate with a transition metal source to obtain a mixture containing silicon and a transition metal; (2) mixing the mixture obtained in step (1) with phenolic resin, and then performing dehydration treatment to obtain a phenolic resin containing silicon and a transition metal; (3) curing the phenolic resin containing silicon and a transition metal obtained in step (2) to prepare a resin precursor, and then performing carbonization and activation treatment to obtain the phenolic resin-based composite porous carbon material. This composite porous carbon material has a multi-level pore structure, generates a functional reinforcing phase in situ, and has a strong interfacial bonding ability with subsequent CVD-deposited silicon.

Description

Technical Field

[0001] This invention relates to the field of porous carbon technology, specifically to a phenolic resin-based composite porous carbon material, its preparation method, and its application. Background Technology

[0002] Porous carbon materials are widely used in the field of electrochemical energy storage materials due to their high specific surface area, tunable pore structure, good chemical stability, and ability to serve as conductive and load-bearing frameworks. In particular, porous carbon materials prepared using phenolic resin as a precursor have advantages such as high carbon yield, good molding and processability, and designable pore structure, thus becoming one of the important technical routes for constructing porous carbon frameworks.

[0003] However, existing phenolic resin-based porous carbon materials still face several key bottlenecks in practical applications: First, the graphitization degree of phenolic resin-derived carbon is limited, and the electron transport channels are insufficiently continuous, leading to increased polarization and internal resistance in electrodes under high rate or high load conditions. Second, during carbonization / activation and subsequent cycling, porous structures may experience structural instability phenomena such as pore wall ablation, pore collapse, or uncontrollable evolution of pore size distribution, weakening the mechanical integrity and stability of the framework. Third, in silicon-carbon composite systems, repeated volume changes in the silicon phase continuously transfer cyclic stress to the pore walls and coating layer. If there is a lack of sufficient interfacial bonding and anchoring mechanisms between the framework and functional components, it can easily lead to silicon / carbon interface debonding, conductive contact degradation, pore blockage, and even electrode pulverization, ultimately resulting in increased interfacial impedance and rapid capacity decay. Therefore, improving the conductivity, mechanical properties, and pore structure stability of the porous carbon framework from the perspective of the material itself, while simultaneously enhancing its interfacial bonding ability with the silicon phase, is a key fundamental issue for improving the overall performance of current silicon-carbon anode materials.

[0004] To address these needs, existing technologies attempt to use porous carbon materials as supports for functional components (such as active phases, reinforcing phases, or catalytic / conductive phases), such as introducing ceramic phases like TiC and SiC or metal silicides, in order to improve conductivity and structural strength. However, many solutions use mechanical blending and other methods to introduce external powders, which easily leads to problems such as particle agglomeration, uneven dispersion, and insufficient interfacial bonding with the carbon matrix. Furthermore, some reinforcing phases have limited electrochemical activity, making it difficult to simultaneously achieve structural strengthening and improved electrochemical performance.

[0005] Therefore, how to achieve uniform introduction and effective anchoring of the reinforcing phase in phenolic resin-based porous carbon skeletons, so as to form a stable and low-resistivity interface bond with the carbon skeleton, while taking into account good electrical conductivity, structural stability and electrochemical performance, remains a technical problem that urgently needs to be solved in this field.

[0006] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] The purpose of this invention is to provide a phenolic resin-based composite porous carbon material, its preparation method, and its application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a phenolic resin-based composite porous carbon material, comprising the following steps: (1) A silicon source is hydrolyzed in an acidic aqueous solution to obtain a silicon-based hydrolysate. The silicon-based hydrolysate is then mixed with a transition metal source to obtain a mixture containing silicon and a transition metal. The silicon source is selected from one or more of silicate esters and silane coupling agents. The transition metal source is selected from one or more of group IVB, group VB, group VIB transition metal alkoxides (metal alkoxy compounds formed by direct bonding between metal and alkoxy groups) and transition metal inorganic salts. (2) The mixture obtained in step (1) is mixed with phenolic resin and then dehydrated to obtain phenolic resin containing silicon and transition metals. (3) The phenolic resin containing silicon and transition metal obtained in step (2) is cured and molded to prepare a resin precursor. After carbonization and activation treatment, the phenolic resin-based composite porous carbon material is obtained.

[0009] This invention pre-constructs a silicon-transition metal composite sol by hydrolyzing a silicon source under acidic conditions to generate a silicon-based hydrolysate rich in active silanol groups (Si-OH), which is then mixed with a transition metal source to form a bonded structure characterized by Si-OM (M being a transition metal). By mixing the silicon-transition metal composite sol with phenolic resin, multiple interactions, including coordination complexation and hydrogen bonding, occur between the Si-OH and M-OH groups on the surface of the composite sol and the phenolic hydroxyl groups (-OH) and ether oxygen groups (COC) of the phenolic resin. This results in uniform dispersion of the silicon and metal components within the resin matrix, significantly suppressing agglomeration, delamination, and the resulting interface defects.

[0010] The subsequent dehydration process removes small molecules (water, alcohol) generated during hydrolysis and condensation reactions (dehydration condensation between silanol groups, between transition metal hydroxyl groups (M–OH), and between silanol groups and transition metal hydroxyl groups, forming Si–O–Si, M–O–M, and Si–O–M covalent bonds). The dispersed state is fixed by molding and solidification, and then carbonization is carried out to transform the organic components into a carbon skeleton. At the same time, the uniformly distributed Si and metal sites are used to generate a functional reinforcing phase mainly composed of metal silicides in situ (a small amount of silicon-based derivative phase may also be formed under certain conditions), thereby improving the structural stability and conductivity of the matrix. Finally, the activation treatment and etching form rich micropores and mesopores, ultimately forming a composite porous carbon matrix with a multi-level porous structure and in-situ generation of functional reinforcing phases. If silicon is subsequently deposited by CVD to form a silicon-carbon composite material, it will have good interfacial bonding ability and compatibility.

[0011] In some embodiments, the silicate ester is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, and propyl orthosilicate.

[0012] In some embodiments, the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0013] In some embodiments, the transition metal source is selected from one or more of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, titanium chloride, tetrabutyl zirconate, tetraethyl zirconate, zirconium chloride, tetrabutyl niobate, niobium chloride, tetrabutyl vanadate, and vanadium chloride.

[0014] In some embodiments, in step (1), the molar ratio of silicon in the silicon source to transition metal in the transition metal source is (1.5~4):1, preferably (1.8~3.6):1, such as: 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1.

[0015] In some embodiments, the mass ratio of the silicon source to the phenolic resin is (0.1~0.5):1, preferably (0.1~0.3:1), and more preferably (0.2~0.3):1.

[0016] In some embodiments, the mass ratio of the transition metal source to the phenolic resin is (0.05~0.3):1, preferably (0.1~0.2):1.

[0017] In some embodiments, the phenolic resin is a thermosetting phenolic resin (alkali-catalyzed methyl phenolic resin).

[0018] Furthermore, when the phenolic resin is a thermosetting phenolic resin, the curing process includes first holding at 60℃~80℃ for 2h~4h, then raising the temperature to 110℃~140℃ and holding for 3h~8h. Preferably, the curing process includes first holding at 60℃~70℃ for 2h~3h, then raising the temperature to 110℃~120℃ and holding for 5h~8h. This step-by-step curing process utilizes the self-curing properties of phenolic resin to crosslink and form a three-dimensional network structure. No external curing agent is added, avoiding impurity residue or damage to the pore structure, and firmly locking transition metals and Si elements within the resin network, achieving molecular-level confinement.

[0019] In some embodiments, the phenolic resin is an acid-catalyzed thermoplastic phenolic resin.

[0020] Furthermore, when the phenolic resin is an acid-catalyzed thermoplastic phenolic resin, the curing includes pre-curing at 80℃~120℃ for 1h~3h, followed by adding a curing agent and heating to 150℃~180℃ for 2h~5h to complete cross-linking curing.

[0021] Furthermore, the curing agent is preferably hexamethylenetetramine.

[0022] In some embodiments, the acid in the acidic aqueous solution is selected from one or more of hydrochloric acid, nitric acid, formic acid, or acetic acid, preferably hydrochloric acid or nitric acid. The amount of the acidic aqueous solution is not specifically limited, as long as it ensures complete hydrolysis of the silicon source and maintains system stability.

[0023] In some specific embodiments, the silicon source is mixed with water, and then acid and / or an aqueous solution thereof are added to adjust the pH of the system. Preferably, the mass-to-volume ratio of the silicon source to the water is 1 g:(0.2~0.6); the pH of the system is adjusted to 3~4.

[0024] In some embodiments, the pH of the hydrolysis reaction is 3-4, the reaction temperature is 30°C-40°C, and the reaction time is 20-30 min.

[0025] In some embodiments, the mixing temperature of the silicon-based hydrolysate and the transition metal source is controlled to be 30°C to 40°C and the mixing time is 20 min to 30 min.

[0026] In some embodiments, the carbonization includes heating to 500°C to 800°C at a heating rate of 2°C / min to 5°C / min and holding at that temperature for 1 hour to 3 hours. Preferably, the carbonization includes heating to 600°C to 700°C at a heating rate of 4°C / min to 5°C / min and holding at that temperature for 1 hour to 2 hours.

[0027] Furthermore, the carbonization is carried out under an inert atmosphere. The inert atmosphere is a conventional inert atmosphere in the art, including but not limited to a nitrogen atmosphere and an argon atmosphere.

[0028] In some embodiments, the activation includes heating to 800°C to 1200°C at a heating rate of 2°C / min to 5°C / min, adding an activating agent, and activating for 0.5h to 4h. Preferably, the activation includes heating to 800°C to 900°C at a heating rate of 4°C / min to 5°C / min, adding an activating agent, and activating for 0.5h to 1h.

[0029] Further, the activator is selected from one or more of gas-phase activators and solid-phase activators. The gas-phase activator includes carbon dioxide, water vapor, ammonia, and oxygen-containing mixed gases (such as air, low-concentration oxygen / inert gas mixtures). The solid-phase activator includes one or more of potassium hydroxide, sodium hydroxide, and potassium carbonate. When a solid-phase activator is used, it is pre-added to the carbonization product and mixed evenly before activation treatment, followed by heating and activation. When a gas-phase activator is used, it is introduced into the reactor during the activation heating and / or holding phases for gas-phase activation. After activation, the introduction of the gas-phase activator is stopped. Cooling is performed under an inert gas atmosphere.

[0030] In some embodiments, the dehydration process includes vacuum devolatilization at 65°C to 70°C.

[0031] In this invention, "reduced pressure devolatilization" refers to a process of removing volatile components from a substance by reducing system pressure. Specifically, in this invention, water and alcoholic volatile components in the system are volatilized and released through reduced pressure devolatilization (which can be recovered by condensation) until distillation essentially stops or the material mass becomes constant, yielding a phenolic resin prepolymer containing silicon and transition metals. As an example, the reduced pressure devolatilization can be achieved using one or more of the following methods: in-reactor reduced pressure devolatilization (with condensation recovery), thin-film / scraped film evaporation, or vacuum drying (such as vacuum disc, vacuum belt, etc.).

[0032] In some embodiments, the preparation method further includes the steps of acid washing, filtration, water washing and drying of the phenolic resin-based composite porous carbon material obtained in step (3) in sequence, so as to remove soluble inorganic by-products and some surface residual impurities on the composite porous carbon material, reduce interfacial impedance and improve the electrochemical stability of the material.

[0033] Furthermore, the drying temperature is 70℃~120℃ and the time is 4h~6h.

[0034] A second aspect of the present invention is to provide a phenolic resin-based composite porous carbon material prepared by the preparation method described above.

[0035] A third aspect of the present invention is to provide the application of a phenolic resin-based composite porous carbon material prepared by the preparation method described above in the preparation of the negative electrode of an energy storage device.

[0036] In some embodiments, the energy storage device is a secondary battery or a supercapacitor.

[0037] In some embodiments, the negative electrode comprises a silicon-carbon composite material, and the phenolic resin-based composite porous carbon material serves as the carbon matrix or conductive framework in the silicon-carbon composite material.

[0038] A fourth aspect of the present invention is to provide a silicon-carbon anode material, the silicon-carbon anode material comprising: a phenolic resin-based composite porous carbon material prepared by the preparation method described above.

[0039] In some embodiments, the phenolic resin-based composite porous carbon material has silicon deposited in its internal pores, and a carbon layer is also coated on the surface of the material after silicon deposition.

[0040] Further, the silicon and the carbon layer are deposited separately using chemical vapor deposition (CVD). The CVD can refer to conventional processes already existing in the art. As an example, in the silicon deposition stage, a fluidized bed reactor can be used, controlling the deposition temperature at 450℃~650℃, introducing a mixture of silane (1%~10% by volume) and argon as the carrier gas, and the deposition time is 0.2h~1h, thereby confining the nano-silicon within the porous carbon channels. After silicon deposition is completed, the silane supply is stopped, and the reactor is purged with an inert gas to remove residual silane and / or silicon-containing active gases. Subsequently, a carbon coating stage is performed in the same fluidized bed reactor: the temperature is raised to 500℃~900℃, and a mixture of acetylene (5%~30% by volume) and argon as the carrier gas is introduced, utilizing acetylene pyrolysis to form an amorphous carbon layer on the surface of the silicon deposited particles.

[0041] In some implementations, amorphous carbon layers of varying thicknesses (e.g., 2 nm to 5 nm) can be obtained by adjusting the acetylene volume fraction and / or deposition time.

[0042] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention obtains a silicon-transition metal composite sol by hydrolyzing a silicon source in an acidic aqueous solution to pre-construct a silicon-based hydrolysate rich in active silanol groups, and further reacting it with a transition metal source to form a bonded structure characterized by Si-OM. The composite sol is then combined with phenolic resin, and after dehydration, curing, carbonization, and activation treatment, a composite porous carbon matrix is ​​finally formed that has a multi-level porous structure, generates an in-situ functional enhancement phase, and has a strong interfacial bonding ability with the subsequently CVD-deposited silicon. Detailed Implementation

[0043] As mentioned in the background section above, there are many problems with mixing external powders with phenolic resin precursors using mechanical blending.

[0044] This invention first catalytically hydrolyzes a silicon source under acidic conditions to generate a silicon-based hydrolysate containing a large number of active silanol groups (Si-OH). In this hydrolysate, silicon exists in a nanoscale aggregate state or as short-chain oligomers, exhibiting extremely high surface reactivity. Subsequently, a transition metal source is added, and the Si-OH reacts with metal ions (M... n+ Coordination complexation and condensation reactions occur, forming a bonded structure characterized by Si-OM, thus obtaining a uniform silicon-transition metal composite sol. In this composite sol, both silicon and transition metal components are uniformly dispersed at the molecular or nanoscale, without macroscopic agglomeration. When mixed with phenolic resin, the abundant Si-OH and M-OH active groups on the surface of the composite sol generate multiple non-covalent interactions, including hydrogen bonding and coordination complexation, with the phenolic hydroxyl groups (-OH) and ether oxygen groups (COC) on the phenolic resin molecular chains. These synergistic effects result in a uniform nanoscale distribution of silicon and transition metal components within the resin matrix, significantly reducing the agglomeration, delamination, and interface defects that are prone to occur in traditional mechanical blending methods.

[0045] Furthermore, during the high-temperature carbonization process, some silicon and metal components in the resin matrix react in situ with the carbon framework to transform into functional phases such as metal silicides. These functional phases form a tighter interfacial bond with the carbon matrix, significantly enhancing the mechanical strength and interfacial stability of the matrix, and to some extent buffering the volume change stress caused by silicon components during electrochemical charging and discharging. These functionally enhanced phases are not introduced externally, but are generated in situ from pre-dispersed precursor components. Therefore, they form atomic-scale chemical bonds and lattice matching with the carbon matrix, resulting in an interfacial bonding strength far exceeding that of physically mixed systems. Simultaneously, the in-situ generation process avoids the increased interfacial resistance that might result from the introduction of an inert second phase.

[0046] Furthermore, considering the inevitable generation of small molecule byproducts such as water and alcohol during silicon source hydrolysis and sol formation, directly introducing these small molecules into the subsequent high-temperature carbonization process would result in uncontrollable macroporous defects in the carbon framework due to their rapid vaporization and escape. This would not only reduce the mechanical strength of the material but also disrupt the uniformity of the pore structure, affecting the uniformity of silicon deposition. This invention introduces a dehydration treatment before the curing step, specifically by heating and / or reducing pressure to fully remove small molecule water and alcohols from the system. This treatment ensures that only the decomposition gases from the resin itself are generated during the subsequent carbonization process, effectively avoiding the formation of macroporous defects, improving the uniformity of the pore structure, and providing better matrix conditions for the uniform deposition and interface stability of subsequent CVD-deposited silicon.

[0047] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0048] In this invention, unless the context explicitly requires otherwise, the numerical range referred to as "numerical value A to numerical value B" refers to the range including the endpoints A and B. The numerical range referred to as "above" or "below" refers to the numerical range including the stated number. "Optional" or "optional" indicates that certain substances, components, execution steps, application conditions, etc., may or may not be used, and there is no limitation on the manner of use.

[0049] Unless otherwise specified, the reagents used in the following examples and comparative examples are all commercially available products, or can be prepared with reference to existing technologies.

[0050] Example 1: Mix 200g of tetraethyl orthosilicate with 80mL of deionized water, then add 0.1mol / L dilute hydrochloric acid solution to adjust the pH of the system to 3.5. Perform pre-hydrolysis by stirring in a water bath at 35℃ for 25min to obtain a silicon-based hydrolysate. Separately, slowly add 130g of tetrabutyl titanate to the above silicon-based hydrolysate and stir continuously at 35℃ for 25min to obtain a homogeneous Ti-Si sol.

[0051] The Ti-Si sol was slowly added to 800g of phenolic resin (type 2130 phenolic resin, purchased from Greenlink (Jining) Chemical Technology Co., Ltd.), heated to 70℃, and removed volatile components (including water and alcohols, etc.) under reduced pressure for 40min until no obvious condensate was produced, thus obtaining Ti-Si hybridized phenolic resin.

[0052] The above-mentioned Ti-Si hybrid phenolic resin was molded by spray drying, with the atomization pressure controlled at 0.4 MPa and the inlet air temperature at 190℃, to obtain a microspherical resin precursor with a particle size of 5~20 μm. The precursor was held at 75℃ for 2.5 h, and then heated to 120℃ and held for 6 h. The cured resin precursor was then heated to 650℃ at 5℃ / min under a nitrogen atmosphere and held for 1.5 h to complete the reduction-silicification reaction, and then heated to 850℃ at 5℃ / min and activated with steam for 45 min. After naturally cooling to room temperature under a nitrogen atmosphere, the product was removed, acid-washed with dilute hydrochloric acid (0.1~1.0 mol / L), filtered, washed with water until neutral, and finally dried at 100℃ for 5 h to obtain a titanium silicide / phenolic resin-based porous carbon composite material.

[0053] Example 2: This embodiment is basically the same as Embodiment 1, except that 200g of tetraethyl orthosilicate is replaced with 190g of γ-glycidoxypropyltrimethoxysilane, and 130g of tetrabutyl titanate is replaced with 91.5g of isopropyl titanate.

[0054] Example 3: This embodiment is basically the same as Embodiment 1, except that 200g of tetraethyl orthosilicate is replaced with 210g of propyl orthosilicate, and 130g of tetrabutyl titanate is replaced with 84g of anhydrous zirconium chloride.

[0055] Example 4: This embodiment is basically the same as Example 1, except that the amount of tetrabutyl titanate used is different. In this embodiment, the amount of tetrabutyl titanate used is 93g.

[0056] Comparative Example 1: This comparative example is basically the same as Example 1, except that: Ti-Si sol is not prepared, nor is the Ti-Si sol-hybridization process in phenolic resin carried out. Instead, titanium silicon powder is directly added to phenolic resin to form a physical mixing system.

[0057] The specific steps are as follows: titanium silicide powder (titanium disilicide) is added to 800g of phenolic resin instead of Ti-Si sol. The amount of titanium silicide powder added is calculated based on the equivalent amount of Ti element introduced by the titanium source (tetrabutyl titanate) in Example 1. Here, 40g of titanium disilicide is added. The mixture is mechanically stirred at 300rpm for 30min to obtain a physically mixed system. Then, following the subsequent molding, curing, washing, and drying processes of Example 1, a titanium silicide / phenolic resin-based porous carbon composite material is prepared.

[0058] Comparative Example 2: This comparative example is basically the same as Example 1, except that: instead of preparing Ti-Si sol, 800g of phenolic resin is directly used to prepare phenolic resin-based porous carbon material by referring to the subsequent molding, curing, washing and drying processes of Example 1.

[0059] Comparative Example 3: This comparative example is essentially the same as Example 1, except that the preparation method of the Ti-Si sol is different; that is, the titanium source is pre-hydrolyzed before the silicon source is added. Because tetrabutyl titanate is prone to rapid hydrolysis and condensation when in localized, high-concentration contact with the aqueous phase, leading to flocculation or precipitation, to ensure the comparability of the comparative examples, this comparative example uses a method of dropwise addition of dilute acid aqueous solution and constant-temperature stirring to control the pre-hydrolysis rate. Details are as follows: In this comparative example, 130g of tetrabutyl titanate was taken and pre-hydrolyzed by adding a 0.1mol / L dilute hydrochloric acid aqueous solution dropwise under stirring at 35℃ until the pH of the system was adjusted to 3.5. After the addition was completed, stirring was continued for 25 minutes to obtain a titanium-based hydrolysate. Separately, 200g of tetraethyl orthosilicate was slowly added dropwise to the above titanium-based hydrolysate, and stirring was continued at 35℃ for 25 minutes to obtain a Ti-Si mixture.

[0060] Performance testing: 1. Physicochemical properties: (1) Average pore size: The pore size distribution is calculated using the DFT micropore model based on the nitrogen adsorption-desorption isotherm, and the average pore size is obtained by the weighted average of the total pore volume, which is automatically output by the test software.

[0061] (2) Specific surface area: The specific surface area of ​​the sample was calculated using the nitrogen adsorption method based on the Brown-Norweg-Emmett-Taylor (BET) theory.

[0062] (3) Total pore volume: The total pore volume was calculated by single-point method using the nitrogen adsorption isotherm under the condition of relative pressure P / P0 ≈ 0.99 (P is the actual pressure of nitrogen in the system during the test; P0 is the pressure when nitrogen is liquefied at the test temperature).

[0063] The pore structure parameters of the phenolic resin-based porous carbon composite materials obtained in each embodiment and comparative example are shown in Table 1.

[0064] Table 1 2. Electrochemical performance: Using porous carbon materials prepared in each embodiment and comparative example as the matrix, silicon-carbon composites were fabricated using chemical vapor deposition (CVD): First, a silane / argon mixture (SiH4 volume percentage 5%, argon as carrier gas) was introduced at 550°C to deposit silicon within the porous carbon channels; then, an acetylene / argon mixture (C2H2 volume percentage 8%) was introduced at 600°C to deposit a carbon layer coating the silicon. The total deposition time for both silicon and carbon layers was 1–2 hours. After deposition, the materials were naturally cooled to room temperature (25 ± 5°C) under an inert atmosphere (such as argon). Phenolic resin-based porous carbon CVD silicon-carbon composite materials were obtained.

[0065] A lithium metal sheet was used as the counter electrode, acetylene black as the conductive agent, and polyacrylic acid (PAA) as the binder. The electrolyte was a 1 mol / L LiPF6 EC / DMC / EMC mixture (volume ratio 1:1:1). The electrode preparation method is as follows: The silicon-carbon composite material (as the active material) prepared in the above examples and comparative examples was mixed with acetylene black and PAA at a mass ratio of 90:5:5 to form a slurry, which was then coated onto copper foil, dried, and cut into pieces.

[0066] All samples were assembled into CR2032 coin cells in a glove box, followed by electrochemical testing.

[0067] (1) Initial discharge specific capacity: Initial discharge specific capacity = initial discharge capacity (mAh) / active material mass (g). The test method for initial discharge capacity is as follows: after standing for 12 hours at 25℃±2℃, the battery under test is discharged to 0.01V with a constant current of 0.1C, and the capacity discharged during this process (unit: mAh) is recorded, which is the initial discharge capacity.

[0068] (2) Initial Coulombic Efficiency: Initial Coulombic Efficiency (%) = (Initial Charge Capacity / Initial Discharge Capacity) × 100%. The test method for the initial charge and discharge capacity is as follows: After standing for 12 hours at 25℃±2℃, the battery under test is discharged to 0.01V with a constant current of 0.1C, and then left to stand for 3 minutes. Then, it is charged to 1.5V with the same constant current, and the charge and discharge capacity (unit: mAh) during this process is recorded.

[0069] (3) Capacity retention after 200 cycles at 1C: After standing for 12 hours at 25℃±2℃, the battery under test was discharged to 0.01V at a constant current of 0.1C, stood for 3 minutes, and then charged to 1.5V at the same constant current. After standing for 3 minutes, the above steps were repeated to complete 10 cycles. Then, the battery under test was discharged to 0.01V at a constant current of 0.5C, stood for 3 minutes, and then charged to 1.5V at the same constant current. After standing for 3 minutes, the steps were repeated to complete 10 cycles. Finally, the battery under test was discharged to 0.01V at a constant current of 1C, stood for 3 minutes, and then charged to 1.5V at the same constant current. After standing for 3 minutes, the 1C charge and discharge steps were repeated to complete 200 cycles. The discharge capacity Q1 of the first cycle and the discharge capacity Q of the 200th cycle were recorded. 200 The capacity retention rate is calculated using the following formula: Capacity retention rate %) = (Q 200 / Q1)×100%.

[0070] The test results are shown in Table 2.

[0071] Table 2 Note: All data in the table above are the average of three parallel experiments, with a test error of ≤±2%.

[0072] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a phenolic resin-based composite porous carbon material, characterized in that, Includes the following steps: (1) A silicon source is hydrolyzed in an acidic aqueous solution to obtain a silicon-based hydrolysate. The silicon-based hydrolysate is then mixed with a transition metal source to obtain a mixture containing silicon and a transition metal. The silicon source is selected from one or more of silicate esters and silane coupling agents. The transition metal source is selected from one or more of group IVB, group VB, group VIB transition metal alkoxides and transition metal inorganic salts. (2) The mixture obtained in step (1) is mixed with phenolic resin and then dehydrated to obtain phenolic resin containing silicon and transition metals. (3) The phenolic resin containing silicon and transition metal obtained in step (2) is cured and molded to prepare a resin precursor. The resin precursor is then carbonized and activated to obtain the phenolic resin-based composite porous carbon material.

2. The method for preparing phenolic resin-based composite porous carbon material according to claim 1, characterized in that, The silicate ester is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, and propyl orthosilicate; and / or, The silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; and / or The transition metal source is selected from one or more of tetrabutyl titanate, tetraethyl titanate, isopropyl titanate, titanium chloride, tetrabutyl zirconate, tetraethyl zirconate, zirconium chloride, tetrabutyl niobate, niobium chloride, tetrabutyl vanadate, and vanadium chloride.

3. The method for preparing phenolic resin-based composite porous carbon material according to claim 1 or 2, characterized in that, In step (1), the molar ratio of silicon in the silicon source to transition metal in the transition metal source is (1.5~4):

1.

4. The method for preparing phenolic resin-based composite porous carbon material according to claim 1, characterized in that, The mass ratio of the silicon source to the phenolic resin is (0.1~0.5):1; and / or, The mass ratio of the transition metal source to the phenolic resin is (0.05~0.3):

1.

5. The method for preparing phenolic resin-based composite porous carbon material according to claim 1, characterized in that, The acid in the acidic aqueous solution is selected from one or more of hydrochloric acid, nitric acid, formic acid, or acetic acid; and / or, The hydrolysis reaction is carried out at a pH of 3-4, a reaction temperature of 30℃-40℃, and a reaction time of 20-30 min; and / or, The mixing temperature of the silicon-based hydrolysate and the transition metal source is controlled at 30℃~40℃ and the mixing time is controlled at 20min~30min.

6. The method for preparing phenolic resin-based composite porous carbon material according to claim 1, characterized in that, The phenolic resin is a thermosetting phenolic resin, and the curing includes first holding at 60℃~80℃ for 2h~4h, then raising the temperature to 110℃~140℃ and holding for 3h~8h; and / or, The carbonization includes heating to 500℃~800℃ at a heating rate of 2℃ / min~5℃ / min, and holding at that temperature for 1h~3h; and / or, The activation process involves heating the temperature to 800℃~1200℃ at a rate of 2℃ / min~5℃ / min, adding an activating agent, and activating for 0.5h~4h.

7. The method for preparing phenolic resin-based composite porous carbon material according to claim 6, characterized in that, The activator is selected from one or more of gas-phase activators and solid-phase activators. The gas-phase activator includes carbon dioxide, water vapor, ammonia, and a mixture of gases containing oxygen. The solid-phase activator includes potassium hydroxide, sodium hydroxide, and potassium carbonate.

8. The method for preparing phenolic resin-based composite porous carbon material according to claim 1, characterized in that, The dehydration process includes vacuum volatilization at 65°C to 70°C.

9. The phenolic resin-based composite porous carbon material prepared by any one of claims 1 to 8.

10. The application of the phenolic resin-based composite porous carbon material prepared by any one of claims 1 to 8 in the preparation of the negative electrode of an energy storage device.

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