A porous ceramic-based composite material with high electrochemical performance and a preparation method thereof

Abstract

The present application relates to a kind of high electrochemical performance porous ceramic matrix composite and its preparation method, porous ceramic matrix composite includes: porous ceramic composite, carbon coating layer is coated in the outer surface of porous ceramic composite;Porous ceramic composite: porous ceramic matrix, dispersing carbon layer is dispersedly distributed on the outer surface and pore wall of porous ceramic matrix, and silicon nanolayer is deposited on dispersing carbon layer;Silicon nanolayer is made of closely arranged nanometer silicon crystal grain;The average particle size of nanometer silicon crystal grain is between 1nm and 5nm;Silicon element in porous ceramic matrix composite accounts for 20wt% to 70wt%;The thickness of dispersing carbon layer is between 1nm and 20nm;The porous ceramic matrix composite of the present application is used to prepare negative pole piece and is applied in lithium ion battery, can improve the first cycle coulomb efficiency and safety performance of lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a porous ceramic matrix composite material with high electrochemical performance and its preparation method. Background Technology

[0002] With the ever-increasing demand for energy, improving the performance of energy storage materials has become a research hotspot. Taking lithium-ion batteries as an example, the rapid development of portable electronic devices, electric vehicles, and other fields has placed higher demands on battery energy density, cycle life, and rate performance. Silicon-based materials, due to their high theoretical specific capacity, have become one of the most promising next-generation lithium-ion battery anode materials.

[0003] However, silicon undergoes enormous volume changes (up to 400% or more) during charging and discharging, which leads to the destruction of the material structure, resulting in rapid capacity decay and poor cycle stability. Furthermore, silicon's inherently poor conductivity limits its application under high-rate charge-discharge conditions.

[0004] To address these issues, existing technologies typically employ nano-sizing and composite methods, such as preparing silicon nanoparticles, silicon-based composite materials, and silicon-carbon composite materials. However, these methods still have many shortcomings, such as complex preparation processes, high costs, and poor structural stability of composite materials, making it difficult to meet the needs of large-scale industrial production and practical applications. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a porous ceramic matrix composite material with high electrochemical performance and its preparation method. First, a dispersed carbon layer is pre-deposited on a porous ceramic matrix. Then, a silicon nanolayer is deposited on the surface of the dispersed carbon layer. Finally, a carbon coating treatment is performed to form a carbon coating layer, resulting in a porous ceramic matrix composite material with high electrochemical performance. This porous ceramic matrix composite material uses porous ceramic as the matrix, which improves the matrix strength compared to a porous carbon matrix. It can maintain excellent electrochemical performance while suppressing the volume expansion of silicon. The dispersed deposition of the carbon layer in the pores of the porous ceramic improves the conductivity of the material. Using the porous ceramic matrix composite material provided in this invention to prepare negative electrode sheets for assembly into lithium-ion batteries improves both the first-cycle coulombic efficiency and safety performance. Lithium-ion batteries using negative electrode sheets containing the porous ceramic matrix composite material have higher impact resistance.

[0006] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a porous ceramic matrix composite material with high electrochemical performance, the porous ceramic matrix composite material comprising: a porous ceramic composite material, and a carbon coating layer covering the outer surface of the porous ceramic composite material;

[0007] The porous ceramic composite material comprises: a porous ceramic matrix, a dispersed carbon layer dispersed on the outer surface and pore walls of the porous ceramic matrix, and a silicon nanolayer deposited on the dispersed carbon layer.

[0008] Preferably, the porous ceramic matrix comprises at least one of porous alumina, porous zirconium oxide, porous silicon carbide, porous silicon nitride, and porous boron nitride;

[0009] The porous ceramic matrix has pore sizes ranging from 0.5 nm to 100 nm, a porosity of 60% to 90%, and a specific surface area of ​​300 m². 2 / g~2000m 2 / g;

[0010] The silicon nanolayer is composed of closely packed silicon nanocrystals; the average particle size of the silicon nanocrystals is between 1 nm and 5 nm; the silicon content in the porous ceramic matrix composite material is between 20 wt% and 70 wt%.

[0011] Preferably, the thickness of the carbon coating layer is between 5 nm and 50 nm; the thickness of the dispersed carbon layer is between 1 nm and 20 nm.

[0012] Secondly, embodiments of the present invention provide a method for preparing the porous ceramic matrix composite material described in the first aspect above, the method comprising:

[0013] Step S1: Weigh the porous ceramic matrix, or prepare the porous ceramic matrix;

[0014] Step S2, depositing a dispersed carbon layer on the outer surface and pore walls of the porous ceramic matrix, includes: placing the porous ceramic matrix in a reaction device, setting the pressure of the reaction device, heating to the decomposition temperature of the carbon source gas in a protective gas environment, introducing the carbon source gas, and maintaining the temperature so that the carbon elements decomposed by the carbon source gas are dispersed on the outer surface and pore walls of the porous ceramic matrix to form a dispersed carbon layer, thereby obtaining a precursor material;

[0015] Step S3: Adjust the temperature of the reaction equipment to the silicon source gas decomposition temperature under a protective gas environment, introduce silicon source gas, and keep it at a constant temperature so that the silicon element decomposed by the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material.

[0016] Step S4: The porous ceramic composite material is subjected to carbon coating treatment to form a carbon coating layer on the surface of the porous ceramic composite material. After cooling and discharging, a porous ceramic matrix composite material is obtained.

[0017] Preferably, in step S1, the porous ceramic matrix includes at least one of porous alumina, porous zirconium oxide, porous silicon carbide, porous silicon nitride, and porous boron nitride.

[0018] The porous ceramic matrix has pore sizes ranging from 0.5 nm / μm to 100 nm, a porosity of 60% to 90%, and a specific surface area of ​​300 m². 2 / g~2000m 2 / g;

[0019] The method for preparing porous ceramic substrates includes one or more of the following: template method, sol-gel method, and hydrothermal method.

[0020] Preferably, in step S2, the reaction equipment includes any one of a chemical vapor deposition furnace, a tube furnace, and a box furnace;

[0021] The protective gas in the protective gas environment includes at least one of nitrogen, argon, or helium; the flow rate of the protective gas is 1 L / min to 50 L / min.

[0022] The process of setting the pressure of the reaction equipment, heating it to the decomposition temperature of the carbon source gas under a protective gas environment, introducing the carbon source gas, and holding it at that temperature specifically includes: setting the pressure of the reaction equipment to 10 Pa to 100 Pa, heating it to 400°C to 800°C at a heating rate of 1°C / min to 5°C / min under a protective gas environment, introducing the carbon source gas, and holding it at that temperature for 2 to 5 hours.

[0023] The carbon source gas includes one or more of methane, propane, acetylene, ethylene, or propylene; the flow rate of the carbon source gas is 1 L / min to 50 L / min.

[0024] The volume ratio of the protective gas to the carbon source gas is 5:40 to 40:5;

[0025] The thickness of the dispersed carbon layer is 1 nm to 20 nm.

[0026] Preferably, in step S3, the temperature of the reaction equipment is adjusted to the decomposition temperature of the silicon source gas under a protective gas environment, and the silicon source gas is introduced and kept at the temperature. Specifically, this includes: adjusting the temperature to 400℃ to 700℃ under a pressure of 10pa to 100pa, introducing the silicon source gas, and keeping at the temperature for 1 hour to 3 hours.

[0027] The silicon source gas includes one or more gases selected from silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 80 L / min.

[0028] The volume ratio of the protective gas to the silicon source gas is 10:40 to 40:10.

[0029] Preferably, in step S4, the carbon coating process includes either gas-phase carbon coating or liquid-phase carbon coating.

[0030] Thirdly, embodiments of the present invention provide an application of the porous ceramic matrix composite material with high electrochemical performance described in the first aspect above, wherein the porous ceramic matrix composite material is used as a negative electrode active material to prepare a negative electrode sheet.

[0031] Fourthly, embodiments of the present invention provide a lithium-ion battery, the lithium-ion battery comprising the negative electrode sheet described in the third aspect above.

[0032] The present invention provides a porous ceramic matrix composite material with high electrochemical performance and its preparation method, which has the following technical effects:

[0033] (1) The present invention provides a method for preparing a porous ceramic matrix composite material with high electrochemical performance. A dispersed carbon layer is pre-deposited on a porous ceramic matrix, and then a silicon nanolayer is deposited on the surface of the dispersed carbon layer. Finally, a carbon coating treatment is performed to form a carbon coating layer, thereby obtaining a porous ceramic matrix composite material with high electrochemical performance. The preparation method is simple and easy to operate, low in cost, and suitable for large-scale production.

[0034] (2) The porous ceramic matrix composite material prepared by the method of the present invention has improved the mechanical strength of the matrix compared with the porous carbon matrix because it is based on porous ceramic. It can maintain excellent electrochemical performance while suppressing the volume expansion of silicon. In addition, the carbon layer is dispersed and deposited in the pores of the porous ceramic to improve the conductivity of the material.

[0035] (3) The porous ceramic matrix composite material provided in the embodiments of the present invention is used to prepare negative electrode sheets for assembly into lithium-ion batteries. While improving the first-cycle coulombic efficiency, it can also improve the pressure resistance of lithium-ion batteries, that is, improve the safety performance of lithium-ion batteries. The lithium-ion batteries using negative electrode sheets containing porous ceramic matrix composite materials have higher impact resistance. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the preparation method of porous ceramic matrix composite materials provided in an embodiment of the present invention.

[0037] Figure 2 This is a scanning electron microscope (SEM) image of the porous ceramic matrix composite material provided in Embodiment 2 of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0039] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0040] This invention provides a porous ceramic matrix composite material with high electrochemical performance, comprising: a porous ceramic composite material, and a carbon coating layer covering the outer surface of the porous ceramic composite material; wherein, the porous ceramic composite material comprises: a porous ceramic matrix, a dispersed carbon layer dispersed on the outer surface and pore walls of the porous ceramic matrix, and a silicon nanolayer deposited on the dispersed carbon layer.

[0041] Specifically, the silicon nanolayer is composed of closely packed silicon nanocrystals; the average particle size of the silicon nanocrystals is between 1 nm and 5 nm, and can be any value within this range, such as 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] The silicon content in porous ceramic matrix composites is 20wt% to 70wt%, and can be any value within this range, such as 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] The thickness of the dispersed carbon layer is between 1 nm and 20 nm, and can be any value within this range, such as 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The dispersed carbon layer can improve the buffering effect of the material and assist the porous ceramic matrix in suppressing the volume expansion of nano-silicon grains. The preferred thickness of the dispersed carbon layer is 5 nm to 20 nm. If the thickness of the dispersed carbon layer is too small, the deposited nano-silicon grains will directly contact the porous ceramic matrix, and the improvement in conductivity will not be significant.

[0044] The porous ceramic matrix includes at least one of porous alumina, porous zirconia, porous silicon carbide, porous silicon nitride, and porous boron nitride.

[0045] The pore size of the porous ceramic matrix is ​​between 0.5 nm and 100 nm, and can be any value within this range, such as: 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 100 nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] The porosity of the porous ceramic matrix is ​​60% to 90%, and can be any value within this range, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] The specific surface area of ​​the porous ceramic matrix is ​​300 m². 2 / g~2000m 2 / g can be any value within this range, for example: 300m 2 / g、400m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g、1700m 2 / g、1800m 2 / g、1900m 2 / g、2000m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0048] The thickness of the carbon coating layer is between 5nm and 50nm, and can be any value within this range, such as: 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 14nm, 16nm, 18nm, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, 42nm, 44nm, 46nm, 48nm, 50nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] This invention provides a method for preparing the above-mentioned porous ceramic matrix composite material, such as... Figure 1 As shown, the preparation method includes:

[0050] Step S1: Weigh the porous ceramic matrix, or prepare a porous ceramic matrix;

[0051] The present invention can use commercially available porous ceramic matrix, or can prepare porous ceramic matrix;

[0052] Porous ceramic matrices include at least one of porous alumina, porous zirconia, porous silicon carbide, porous silicon nitride, and porous boron nitride;

[0053] The porous ceramic matrix has pore sizes ranging from 0.5 nm / μm to 100 nm, a porosity of 60% to 90%, and a specific surface area of ​​300 m². 2 / g~2000m 2 / g;

[0054] The methods for preparing porous ceramic matrices are conventional methods, including one or more of the following: template method, sol-gel method, and hydrothermal method.

[0055] Step S2: Depositing a dispersed carbon layer on the outer surface and pore walls of the porous ceramic matrix;

[0056] Specifically, the process includes: placing a porous ceramic matrix in a reaction device, setting the pressure of the reaction device, heating it to the decomposition temperature of the carbon source gas under a protective gas environment, introducing the carbon source gas, and maintaining the temperature so that the carbon elements decomposed by the carbon source gas are dispersed on the outer surface and pore walls of the porous ceramic matrix to form a dispersed carbon layer with a thickness of 1nm to 20nm, thereby obtaining a precursor material.

[0057] The reaction equipment includes, but is not limited to, any one of: chemical vapor deposition furnace, tube furnace, and box furnace;

[0058] The protective gas in the protective gas environment includes at least one of nitrogen, argon, or helium; the flow rate of the protective gas is 1 L / min to 50 L / min; the carbon source gas includes one or more of methane, propane, acetylene, ethylene, or propylene; the flow rate of the carbon source gas is 1 L / min to 50 L / min; and the volume ratio of the protective gas to the carbon source gas is 5:40 to 40:5.

[0059] The pressure of the above-mentioned reaction equipment is set to be increased to the decomposition temperature of the carbon source gas under a protective gas environment. The carbon source gas is then introduced and the temperature is maintained. Specifically, the pressure of the reaction equipment is set to be 0.1 kPa to 20 kPa. The temperature is increased to 400°C to 800°C at a heating rate of 1°C / min to 5°C / min under a protective gas environment. The carbon source gas is then introduced and the temperature is maintained for 2 to 5 hours.

[0060] In this step, the decomposition temperature of the carbon source gas is 400℃~800℃, and it can be any temperature value within this range, such as: 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, 800℃, etc., but it is not limited to the listed temperature values. Other unlisted temperatures within this temperature range are also applicable.

[0061] Step S3: Adjust the temperature of the reaction equipment to the decomposition temperature of the silicon source gas under a protective gas environment, introduce the silicon source gas, and keep it at a constant temperature so that the silicon element decomposed by the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material.

[0062] Specifically, the reaction equipment is heated to the decomposition temperature of the silicon source gas under a protective gas environment, and silicon source gas is introduced and kept at that temperature. This includes adjusting the temperature to 400℃ to 800℃ under a pressure of 0.1Kpa to 20Kpa, introducing silicon source gas, and keeping at that temperature for 1 hour to 3 hours.

[0063] The decomposition temperature of the silicon source gas in this step is 400℃~800℃, and it can be any temperature value within this range, such as: 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 800℃, etc., but it is not limited to the listed temperature values. Other unlisted temperatures within this temperature range are also applicable.

[0064] The silicon source gas includes one or more of the following: silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 80 L / min;

[0065] The protective gas includes at least one of nitrogen, argon, or helium; the flow rate of the protective gas is 1 L / min to 50 L / min.

[0066] The volume ratio of protective gas to silicon source gas is 10:40 to 40:10.

[0067] Step S4: The porous ceramic composite material is subjected to carbon coating treatment to form a carbon coating layer on the surface of the porous ceramic composite material. After cooling and discharging, a porous ceramic matrix composite material is obtained.

[0068] The carbon coating treatment includes either gas-phase carbon coating or liquid-phase carbon coating.

[0069] This invention provides an application of a porous ceramic matrix composite material with high electrochemical performance. The porous ceramic matrix composite material can be used as a negative electrode active material to prepare a negative electrode sheet, and the negative electrode sheet containing the porous ceramic matrix composite material can be assembled into a lithium-ion battery.

[0070] The lithium-ion battery using the porous ceramic matrix composite material provided in the embodiments of the present invention can improve the first-cycle coulombic efficiency and also improve the pressure resistance, that is, improve the safety performance of the lithium-ion battery. The lithium-ion battery using the negative electrode sheet containing the porous ceramic matrix composite material of the present invention has higher impact resistance.

[0071] To better understand the technical solution provided by the present invention, the preparation process and characteristics of the porous ceramic matrix composite material of the present invention are illustrated below with several specific examples.

[0072] Example 1

[0073] This embodiment provides a preparation process and performance testing method for porous ceramic matrix composite materials, and the specific process is as follows.

[0074] Step (1) involves preparing porous alumina using a template method. Specifically, aluminum isopropoxide is dissolved in nitric acid solution and hydrolyzed at 80°C to generate Al(OH)3 sol. Polyethylene glycol (PEG, molecular weight 2000) is added and stirred. The mixture is then heated at 120°C to form a gel, followed by calcination at 600°C for 4 hours to remove the PEG, yielding 3.02 kg of porous alumina with an average pore size of 5 nm. This includes 13.5 kg of aluminum isopropoxide, 1.2 L of nitric acid solution (65 wt%), and 1 kg of polyethylene glycol.

[0075] Step (2) The porous alumina is placed in a chemical vapor deposition furnace. The pressure of the chemical vapor deposition furnace is set to 10 kPa. The temperature is raised to 600°C at a heating rate of 5°C / min in a nitrogen atmosphere. Methane is introduced at a flow rate of 10 L / min and kept at this temperature for 2 hours. The carbon elements decomposed by methane are dispersed on the outer surface and pore walls of the porous alumina to form a dispersed carbon layer with a thickness of 10 nm, thus obtaining the precursor material.

[0076] Step (3) The chemical vapor deposition furnace is heated to 800°C in a nitrogen atmosphere at a heating rate of 5°C / min. Silane with a flow rate of 20L / min is introduced and kept at this temperature for 2.5 hours, so that the silicon element decomposed from the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material.

[0077] Step (4) involves gas-phase carbon coating of the porous ceramic composite material. Specifically, the temperature of the chemical vapor deposition furnace is adjusted to 600℃, ethylene with a flow rate of 10L / min is introduced, and the temperature is maintained for 1 hour to form a carbon coating layer with a thickness of 5nm on the surface of the porous ceramic composite material. After cooling and discharging, the porous ceramic matrix composite material is obtained.

[0078] Example 2

[0079] This embodiment provides a preparation process and performance testing method for porous ceramic matrix composite materials, and the specific process is as follows.

[0080] Step (1) involves preparing porous silicon nitride using a combination of sol-gel and spray drying methods. Specifically, tetraethoxysilane (TEOS), urea, and ethanol are mixed, and nitric acid is added for catalytic hydrolysis to form a Si-ON sol. Then, 10 wt% polyethylene glycol (PEG, molecular weight 2000) is added to the sol, ultrasonically dispersed, and spray-dried in a spray dryer to obtain microspheres. The microspheres are then pre-calcined in a tube furnace at 500°C for 2 hours to remove organic matter. Finally, they are calcined at 1300°C for 4 hours under an ammonia atmosphere to obtain porous silicon nitride with an average pore size of 10 nm, totaling 3 kg. The composition includes 16.7 kg of TEOS, 7.7 kg of urea, 20 L of ethanol (65 wt%), 1 L of nitric acid solution (65 wt%), and 9.5 kg of polyethylene glycol. The inlet temperature of the spray dryer is 180°C, and the outlet temperature is 80°C.

[0081] Step (2) The porous silicon nitride is placed in a chemical vapor deposition furnace. The pressure of the chemical vapor deposition furnace is set to 50 Pa. The temperature is raised to 500 °C at a heating rate of 5 °C / min in a nitrogen atmosphere. Acetylene is introduced at a flow rate of 10 L / min and kept at the temperature for 2 hours. This allows the carbon elements from the decomposition of methane to be dispersed on the outer surface and pore walls of the porous silicon nitride, forming a dispersed carbon layer with a thickness of 10 nm, thus obtaining the precursor material.

[0082] Step (3) The chemical vapor deposition furnace is heated to 800°C in a nitrogen atmosphere at a heating rate of 5°C / min. Silane with a flow rate of 20L / min is introduced and kept at this temperature for 2.5 hours, so that the silicon element decomposed from the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material.

[0083] Step (4) involves gas-phase carbon coating of the porous ceramic composite material. Specifically, the temperature of the chemical vapor deposition furnace is adjusted to 600℃, ethylene with a flow rate of 10L / min is introduced, and the temperature is maintained for 1 hour to form a carbon coating layer with a thickness of 5nm on the surface of the porous ceramic composite material. After cooling and discharging, the porous ceramic matrix composite material is obtained.

[0084] SEM image of the porous ceramic matrix composite material prepared in Example 2, as shown below. Figure 2 As shown.

[0085] Example 3

[0086] This embodiment provides a preparation process and performance testing method for porous ceramic matrix composite materials, and the specific process is as follows.

[0087] Step (1) involves preparing porous boron nitride using a combination of template method and hydrothermal method. Specifically, urea and sodium borohydride are mixed, and glucose is added as an organic template for further mixing. The mixture is then subjected to a hydrothermal reaction at 180°C for 12 hours, followed by calcination at 1200°C for 6 hours in an ammonia atmosphere to obtain porous boron nitride with an average pore size of 10 nm, totaling 3 kg. The composition includes 5.7 kg of sodium borohydride, 18.2 kg of urea, and 6 kg of glucose.

[0088] Step (2) The porous boron nitride is placed in a chemical vapor deposition furnace. The pressure of the chemical vapor deposition furnace is set to 50 Pa. The temperature is raised to 500 °C at a heating rate of 5 °C / min in a nitrogen atmosphere. Propylene is introduced at a flow rate of 10 L / min and kept at the temperature for 2 hours. This allows the carbon elements from the decomposition of methane to be dispersed on the outer surface and pore walls of the porous boron nitride, forming a dispersed carbon layer with a thickness of 10 nm, thus obtaining the precursor material.

[0089] Step (3) The chemical vapor deposition furnace is heated to 800°C in a nitrogen atmosphere at a heating rate of 5°C / min. Silane with a flow rate of 20L / min is introduced and kept at this temperature for 2.5 hours, so that the silicon element decomposed from the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material.

[0090] Step (4) involves gas-phase carbon coating of the porous ceramic composite material. Specifically, the temperature of the chemical vapor deposition furnace is adjusted to 700℃, methane with a flow rate of 10L / min is introduced, and the temperature is maintained for 1 hour to form a carbon coating layer with a thickness of 5nm on the surface of the porous ceramic composite material. After cooling and discharging, the porous ceramic matrix composite material is obtained.

[0091] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0092] Comparative Example 1

[0093] This comparative example provides a preparation process for a porous silicon-carbon composite material. Unlike Example 1, step (1) is omitted. Steps (2) to (4) are identical to those in Example 1. Comparative Example 1 uses conventional porous carbon material as the matrix material, wherein the pore volume of the porous carbon material is 0.7 cm³. 3 / g, with an average pore size of 1.5nm and a specific surface area of ​​1650m². 2 / g, a dispersed carbon layer is first deposited in the pores and on the surface of the porous carbon material, then a silicon nanolayer is deposited on the dispersed carbon layer, and finally carbon coating treatment is performed to obtain a silicon-carbon composite material.

[0094] Comparative Example 2

[0095] The present invention provides a porous ceramic composite material, which differs from Example 1 in that step (2) is not performed, that is, a dispersed carbon layer is not formed, and silicon deposition is performed directly. The other steps are the same as those in Example 1, and finally a porous ceramic composite material is obtained.

[0096] Comparative Example 3

[0097] The present invention provides a preparation process for a porous silicon-carbon composite material. The difference from Example 1 is that steps (1) and (2) are not performed. Steps (3) to (4) are the same as in Example 1. Comparative Example 1 uses porous carbon material as the matrix material, and silicon nanolayers are directly deposited in the pores of the porous carbon material. Finally, carbon coating treatment is performed to obtain a silicon-carbon composite material.

[0098] The resistivity of the powders prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The specific method included: using a four-probe resistivity meter to test the resistivity of the powder at 100 MPa. Specifically, 2 g of sample was weighed, placed in the sample cell, and pressurized to 100 MPa. The resistivity was recorded. The test data are shown in Table 1.

[0099] The materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as negative electrode active materials to prepare lithium-ion battery electrodes, which were then assembled into coin half-cells for electrochemical testing, as detailed below:

[0100] Preparation of electrode sheets: The materials prepared in Examples 1-3 and Comparative Examples 1-3 were mixed with conductive carbon black and binder in a mass ratio of 90:5:5, respectively. The binder was sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:0.8. The mixture was slurried at room temperature to prepare a negative electrode slurry. The negative electrode slurry was coated on copper foil to a thickness of 220 μm and dried in a forced-air drying oven at 55°C for 2 hours. The coated electrode sheets were then cut into circular electrode sheets with a diameter of 14 mm and dried in a vacuum drying oven at 100°C for 8 hours. The dried electrode sheets were then transferred to a glove box for use in battery assembly.

[0101] In addition, the dried electrode sheets were subjected to a 50 MPa press for 5 minutes and then randomly transferred into a casing for use in battery assembly.

[0102] The assembly of the button half-cell was carried out in a glove box containing a high-purity Ar atmosphere. Lithium metal was used as the counter electrode, and the electrolyte was LiPF6 with a molar concentration of 1 mol / L. The electrolyte solvent was ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1. The separator was made of polyethylene (PE) membrane, and the cells were assembled into a battery.

[0103] Testing of coin cell half-cells: Constant current charge-discharge mode tests were conducted using the Blue Battery Testing System (CT2001A). The discharge cutoff voltage was 0.005V, and the charge cutoff voltage was 2V. The conventional charge-discharge tests were conducted at a current density of C / 10. The first-cycle discharge specific capacity (referred to as pre-charge capacity) and first-cycle coulombic efficiency (referred to as pre-charge efficiency) of coin cell half-cells without rolled electrode assembly were tested, and the first-cycle discharge specific capacity (referred to as post-charge capacity) and first-cycle coulombic efficiency (referred to as post-charge efficiency) of coin cell half-cells with rolled electrode assembly were tested. The test data are shown in Table 1.

[0104] The expansion test of the button cell (referred to as the coin cell expansion rate): The ratio of the thickness difference of the electrode before and after discharge to the thickness of the electrode before discharge is measured using a micrometer and recorded as A1; after the first discharge of the button cell, the cell is disassembled and the thickness of the electrode is measured as A2; the expansion rate is calculated using the formula: (A2-A1) / A1×100%, and the test data are shown in Table 1.

[0105] Table 1 summarizes the test data of the button cells assembled in Examples 1-3 and Comparative Examples 1-3:

[0106]

[0107] Table 1

[0108] The test data in Table 1 show that:

[0109] The post-pressure capacity, post-pressure first-efficiency, and expansion rate of Examples 1-3 are all greater than those of Comparative Example 1. This is because the composite materials obtained by using porous ceramics as the matrix in Examples 1-3 have excellent pressure resistance and lower expansion rate. This is due to the mechanical strength of porous ceramics, which maintains the integrity of the structure under high pressure, preventing particle breakage and silicon exposure in the electrolyte, while also limiting the electrochemical expansion of silicon and mitigating volume changes during battery charging and discharging. The electrode expansion rate of Comparative Example 2 is much smaller than that of Comparative Example 1 and Comparative Example 3. This is also because Comparative Example 2 uses a porous ceramic matrix with higher mechanical strength, which gives the battery of Comparative Example 2 higher pressure resistance.

[0110] The post-compression capacity, post-compression first effect, and expansion rate of Examples 1-3 are all greater than those of Comparative Example 2. This is because the efficient electron transport network constructed by the dispersed carbon layer deposited in the pores and on the surface of the porous ceramic matrix effectively improves the conductivity of the material and reduces the resistivity, enabling the material to respond quickly to changes in charge and discharge current.

[0111] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A porous ceramic matrix composite material with high electrochemical performance, characterized in that, The porous ceramic matrix composite material includes: a porous ceramic composite material, and a carbon coating layer covering the outer surface of the porous ceramic composite material; The porous ceramic composite material comprises: a porous ceramic matrix, a dispersed carbon layer dispersed on the outer surface and pore walls of the porous ceramic matrix, and a silicon nanolayer deposited on the dispersed carbon layer; The porous ceramic matrix includes at least one of porous alumina, porous zirconium oxide, porous silicon carbide, porous silicon nitride, and porous boron nitride. The silicon nanolayer is composed of closely packed silicon nanocrystals; the average particle size of the silicon nanocrystals is between 1 nm and 5 nm. The thickness of the dispersed carbon layer is between 1 nm and 20 nm.

2. The porous ceramic matrix composite material according to claim 1, characterized in that, The porous ceramic matrix has pore sizes ranging from 0.5 nm to 100 nm, a porosity of 60% to 90%, and a specific surface area of ​​300 m². 2 / g~2000m 2 / g; The silicon content in the porous ceramic matrix composite material is 20wt% to 70wt%.

3. The porous ceramic matrix composite material according to claim 1, characterized in that, The thickness of the carbon coating layer is between 5 nm and 50 nm.

4. A method for preparing a porous ceramic matrix composite material according to any one of claims 1-3, characterized in that, The preparation method includes: Step S1: Weigh the porous ceramic matrix, or prepare the porous ceramic matrix; Step S2, depositing a dispersed carbon layer on the outer surface and pore walls of the porous ceramic matrix, includes: placing the porous ceramic matrix in a reaction device, setting the pressure of the reaction device, heating to the carbon source gas decomposition temperature under a protective gas environment, introducing the carbon source gas, and maintaining the temperature, so that the carbon elements decomposed by the carbon source gas are dispersed on the outer surface and pore walls of the porous ceramic matrix to form a dispersed carbon layer, thereby obtaining a precursor material; Step S3: Adjust the temperature of the reaction equipment to the silicon source gas decomposition temperature under a protective gas environment, introduce silicon source gas, and keep it at the temperature so that the silicon element decomposed by the silicon source gas is deposited on the surface of the dispersed carbon layer to obtain a porous ceramic composite material. Step S4: The porous ceramic composite material is subjected to carbon coating treatment to form a carbon coating layer on the surface of the porous ceramic composite material. After cooling and discharging, a porous ceramic matrix composite material is obtained.

5. The preparation method according to claim 4, characterized in that, In step S1, the porous ceramic matrix includes at least one of porous alumina, porous zirconium oxide, porous silicon carbide, porous silicon nitride, and porous boron nitride. The porous ceramic matrix has pore sizes ranging from 0.5 nm / μm to 100 nm, a porosity of 60% to 90%, and a specific surface area of ​​300 m². 2 / g~2000m 2 / g; The method for preparing porous ceramic substrates includes one or more of the following: template method, sol-gel method, and hydrothermal method.

6. The preparation method according to claim 4, characterized in that, In step S2, the reaction equipment includes any one of a chemical vapor deposition furnace, a tube furnace, and a box furnace. The protective gas in the protective gas environment includes at least one of nitrogen, argon, or helium; the flow rate of the protective gas is 1 L / min to 50 L / min. The process of setting the pressure of the reaction equipment, heating it to the decomposition temperature of the carbon source gas under a protective gas environment, introducing the carbon source gas, and holding it at that temperature specifically includes: setting the pressure of the reaction equipment to 0.1 kPa to 20 kPa, heating it to 400°C to 800°C at a heating rate of 1°C to 5°C to 5°C under a protective gas environment, introducing the carbon source gas, and holding it at that temperature for 2 to 5 hours. The carbon source gas includes one or more of methane, propane, acetylene, ethylene, or propylene; the flow rate of the carbon source gas is 1 L / min to 50 L / min. The volume ratio of the protective gas to the carbon source gas is 5:40 to 40:5; The thickness of the dispersed carbon layer is 1 nm to 20 nm.

7. The preparation method according to claim 4, characterized in that, In step S3, the temperature of the reaction equipment is adjusted to the decomposition temperature of the silicon source gas under a protective gas environment, and the silicon source gas is introduced and kept at the temperature. Specifically, this includes: adjusting the temperature to 400℃ to 800℃ under a pressure of 0.1Kpa to 20Kpa, introducing the silicon source gas, and keeping at the temperature for 1 hour to 3 hours. The silicon source gas includes one or more gases selected from silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 80 L / min. The volume ratio of the protective gas to the silicon source gas is 10:40 to 40:

10.

8. The preparation method according to claim 4, characterized in that, In step S4, the carbon coating process includes either gas-phase carbon coating or liquid-phase carbon coating.

9. The application of a porous ceramic matrix composite material with high electrochemical performance as described in any one of claims 1-3, characterized in that, The porous ceramic matrix composite material is used as the negative electrode active material to prepare the negative electrode sheet.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet as described in claim 9.

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