Porous ceramic material, porous ceramic-based silicon-carbon negative electrode material and preparation method of porous ceramic-based silicon-carbon negative electrode material

Abstract

The invention relates to a porous ceramic material, a porous ceramic-based silicon-carbon negative electrode material and a preparation method. The porous ceramic material comprises a porous silicon-oxygen-carbon ceramic matrix and free carbon, the chemical general formula of the porous silicon-oxygen-carbon ceramic matrix is S < iO < 2 > (1-x) Cx, wherein x is greater than or equal to 0 and less than or equal to 1; the mass fraction of free carbon in the porous ceramic material is 0.1%-45%; the mass fraction z% of free carbon is equal to z0% * z1%, and z0% is the total content of carbon in the porous ceramic material; z1% is the percentage of free carbon sp2 carbon with binding energy within the range of 284.8 + / -0.3 eV in the total content of carbon in a C1s fine spectrogram measured by XPS; the porous ceramic-based silicon-carbon negative electrode material comprises a porous ceramic material, a silicon nano material deposited on pores and the surface of the porous ceramic material, and a carbon coating layer, when the porous ceramic-based silicon-carbon negative electrode material is applied to the lithium ion battery, the cycle performance of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and in particular to a porous ceramic material, a porous ceramic-based silicon-carbon negative electrode material and a preparation method thereof. Background Art

[0002] Amidst the global energy transition, lithium batteries, as key energy storage devices, are increasingly being used in new energy vehicles, consumer electronics, and energy storage systems, leading to continued market expansion. As battery performance requirements continue to rise across various sectors, high energy density, long cycle life, and rapid charge and discharge have become key areas of lithium battery research and development.

[0003] The theoretical specific capacity of graphite anode materials is 372mAh / g, but actual product specific capacity has reached 360mAh / g, approaching the theoretical limit. Increasing energy density is becoming increasingly difficult, making it difficult to meet the market's urgent demand for high-performance batteries. Silicon-based anode materials, with their theoretical specific capacity of up to 4200mAh / g, over 10 times that of traditional graphite anodes, are considered the ideal next-generation anode material and are the focus of research and development by major companies and research institutions in the industry.

[0004] However, silicon-based anodes undergo significant volume changes during charge and discharge, with a volume expansion rate as high as 300%, far exceeding the 10%-12% of graphite anodes. This can lead to particle pulverization, electrode structure destruction, and separation of the active material from the current collector, significantly reducing the battery's cycle life and coulombic efficiency.

[0005] The current development of new silicon-carbon materials often uses porous carbon as a carrier. Controlling temperature during the silicon deposition process is crucial. Because high temperatures cause the porous carbon to react with the deposited nanosilicon to form silicon carbide, which deactivates the material, excessively high temperatures must be avoided during deposition. This limits the deposition quality and electrochemical performance of new silicon-carbon materials, significantly restricting production efficiency and increasing costs.

[0006] The coating process of silicon-carbon negative electrodes also faces the challenge of temperature limitations. Generally speaking, high-temperature coating can make the coating layer denser, with better crystallinity and conductivity, so that the silicon-carbon negative electrode material and battery have a higher rate. However, when coating under high temperature conditions, the active silicon reacts with carbon, and the coating temperature has to be lowered. This results in limited selection of coating raw materials, low crystallinity and poor conductivity of the coating layer, low coating efficiency, and increased production costs.

[0007] The porous carbon currently used has low strength. During the battery preparation process, the silicon-carbon negative electrode will be broken after rolling, resulting in the exposure of active silicon and reducing the initial efficiency of the battery. During the cycle process, the negative electrode continues to shrink and expand, resulting in a short cycle life of the silicon-carbon negative electrode with porous carbon as the carrier, which does not meet application requirements.

[0008] In the prior art, porous ceramic materials are used as matrix materials to replace porous carbon. Although the above-mentioned problems of porous carbon-based silicon-carbon negative electrodes can be improved to a certain extent, the improvement is limited. Silicon oxygen carbon ceramics (SiOC) are a type of amorphous or partially crystalline polymer-derived ceramics (PDCs) composed of silicon, oxygen, and carbon. Their unique structure and preparation process give them many advantages over traditional oxide ceramics (such as alumina, zirconia) or non-oxide ceramics (such as silicon carbide, silicon nitride), such as flexible process, flexible composition adjustment, high temperature stability, oxidation resistance, chemical inertness, high toughness, and low density, and they are widely concerned. However, traditional SiOC ceramics have a relatively small specific surface area and a wide pore size distribution, which is not conducive to the deposition and particle size control of new nano-silicon, and pure SiOC ceramics have low electrical conductivity, which is limited in their application in the field of battery material technology. Summary of the Invention

[0009] The purpose of the present invention is to address the defects of the prior art and to propose a porous ceramic material, a porous ceramic-based silicon-carbon negative electrode material and a preparation method.

[0010] To achieve the above objectives, in a first aspect, an embodiment of the present invention provides a porous ceramic material, the porous ceramic material comprising: a porous silicon oxycarbon ceramic matrix and free carbon;

[0011] The chemical formula of the porous silicon oxygen carbon ceramic matrix is SiO 2(1-x) C x , where 0≤x≤1;

[0012] The mass fraction of free carbon in the porous ceramic material is z%, where 0.1≤z≤45;

[0013] The mass fraction of free carbon is calculated as follows: z%=z0%×z1%; wherein z0% in the formula is the total carbon content in the porous ceramic material; and z1% is the percentage of free carbon sp2 carbon in the total carbon content obtained by peak fitting of the C1 s fine spectrum of the porous ceramic material measured by X-ray photoelectron spectroscopy and the binding energy in the range of 284.8±0.3 eV.

[0014] Preferably, the average pore size of the porous ceramic material is 1.5 nm to 5.0 nm; the pore volume of the porous ceramic material is 0.5 ml / g to 1.5 ml / g; the specific surface area of the porous ceramic material is 1300 m 2 / g~3000m 2 / g;

[0015] The mass of the porous silicon oxygen carbon ceramic matrix accounts for 55% to 99.9% of the total mass of the porous ceramic material.

[0016] In a second aspect, an embodiment of the present invention provides a method for preparing the porous ceramic material according to the first aspect, the method comprising:

[0017] Step S1, at room temperature, adding raw material A, raw material B, and raw material C in sequence to solvent D, continuously stirring and mixing until uniform, then adding a catalyst and continuing stirring to obtain a precursor solution; wherein the raw material A is an alkyl hydrogen siloxane, the raw material B is an alkyl vinyl siloxane, the raw material C is a silicate, and the catalyst is a chloroplatinic acid-bisvinyltetramethyldisiloxane complex;

[0018] Step S2, placing the precursor solution in an oven for staged heating treatment to cause the precursor solution to react and generate a cross-linked silicone resin and nano-silicon dioxide uniformly dispersed in the cross-linked silicone resin, thereby obtaining a ceramic precursor;

[0019] Step S3, placing the ceramic precursor in a pyrolysis furnace for staged pyrolysis, so that the cross-linked organic silicone resin is cracked to generate silicon oxide carbon and free carbon, and a portion of the free carbon is etched to generate nanopores, thereby obtaining a porous ceramic precursor containing nano-silicon oxide;

[0020] Step S4, acid-washing and purifying the porous ceramic precursor, etching away the nano-silicon oxide, and obtaining a porous ceramic material; wherein the porous ceramic material comprises: a porous silicon-oxygen-carbon ceramic matrix and free carbon; the chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 2(1-x) C x , 0≤x≤1; the mass fraction of free carbon in the porous ceramic material is z%, 0.1≤z≤45.

[0021] Preferably, in step S1: the chemical formula of the alkyl hydrogen siloxane is (R1R2R3SiO)-(R4SiHO) n -(SiR5R6R7); the chemical formula of the alkyl vinyl siloxane is (R7R8SiOCH=CH2)-(R9SiHO) m -(SiCH=CH2R 10 R 11 ); where 3≤n≤6, 4≤m≤8, R1~R 11 are the same or different alkyl groups;

[0022] The chemical formula of the silicate is Si(OR 12 )4, where R 12 Including at least one of CH3, C2H5, C3H7;

[0023] The solvent D comprises at least one of toluene, xylene, isopropyl alcohol, and butyl acetate;

[0024] The molar ratio of the raw material A to the raw material B is 1:1; the ratio of the mass of the raw material C to the sum of the masses of the raw material A and the raw material B is r1, and the ratio of the mass of the catalyst to the mass of A and B is r2, wherein 0.1≤r1≤1, 0.1%≤r2≤1.0%.

[0025] Preferably, step S2 includes: placing the precursor liquid in a stainless steel tray and placing it in an oven, performing staged heating treatment for cross-linking and curing, causing the silicate to undergo a hydrolysis reaction to generate nano-silicon dioxide, and cross-linking and curing the raw materials A and B under the action of a catalyst to obtain a cross-linked silicone resin, wherein the nano-silicon dioxide is dispersed in the cross-linked silicone resin to obtain a ceramic precursor; wherein the staged heating treatment includes: heating the oven to T1°C under a nitrogen atmosphere, keeping the temperature for t1 hours, and then heating to T2°C, keeping the temperature for t2 hours, wherein 50≤T1≤80, 2≤t1≤10, 100≤T2≤160, and 2≤t2≤10.

[0026] Preferably, in step S3, the staged pyrolysis comprises: first heating the temperature to T3°C at a rate of d1°C / min under an inert atmosphere, then switching the atmosphere to an inert atmosphere plus a first active atmosphere, and keeping the temperature at T3°C for t3 hours; then switching the atmosphere to an inert atmosphere, heating the temperature to T4°C at a rate of d2°C / min, and keeping the temperature at T4°C for t4 hours; then cooling the temperature to T5°C at a rate of d3°C / min, and switching the atmosphere to an inert atmosphere plus a second active atmosphere. atmosphere, keep warm at T5℃ for t5 hours; then switch the atmosphere to inert atmosphere, cool to T6℃ at a rate of d4℃ / min, and then cool naturally to room temperature; where, 2≤d1≤6, 600≤T3≤900, 2≤t3≤10, 1≤d2≤5, 1100≤T4≤1500, 4≤t4≤8, 1≤d3≤3, 800≤T5≤1000, 0.5≤t5≤10, 3≤d4≤6, T6=500;

[0027] The gas of the inert atmosphere includes nitrogen and / or argon;

[0028] The gas of the first active atmosphere includes water vapor;

[0029] The gas of the second active atmosphere includes carbon dioxide or water vapor;

[0030] The total air flow of the atmosphere is set to 10 L / min to 50 L / min. When the atmosphere contains an active atmosphere, the volume ratio of the first active atmosphere or the second active atmosphere to the inert atmosphere is 1:20 to 2:3.

[0031] Preferably, in step S4, the pickling purification specifically includes: soaking the porous ceramic precursor containing nano-silicon oxide in a hydrofluoric acid solution with a mass fraction of 5% to 20%, the soaking temperature is 50°C to 80°C, and the soaking time is 5 hours to 48 hours. After soaking, the acid solution is removed by filter press, and then washed with deionized water until neutral, and then baked in an oven at 80°C to 120°C for 4 hours to 12 hours to obtain a porous ceramic material.

[0032] In a third aspect, an embodiment of the present invention provides a porous ceramic-based silicon-carbon negative electrode material, which includes: the porous ceramic material described in the first aspect, silicon nanomaterials deposited in the pores and on the surface of the porous ceramic material, and a carbon coating layer.

[0033] Preferably, the porous ceramic-based silicon-carbon negative electrode material has a total carbon content of 50 wt% to 90 wt% and a total silicon content of 15 wt% to 50 wt%;

[0034] The thickness of the carbon coating layer is 1 nm to 20 nm; the mass of the carbon coating layer accounts for 1% to 25% of the total mass of the porous ceramic-based silicon-carbon negative electrode material;

[0035] The specific surface area of the porous ceramic-based silicon-carbon negative electrode material is 0.3 m 2 / g~20m 2 / g; the particle size Dv50 of the porous ceramic-based silicon-carbon negative electrode material is between 2μm and 30μm.

[0036] In a fourth aspect, an embodiment of the present invention provides a method for preparing the porous ceramic-based silicon-carbon negative electrode material according to the third aspect, the preparation method comprising:

[0037] The porous ceramic material described in the first aspect is subjected to silicon deposition, and silicon nanomaterials are deposited and grown in the pores and on the surface of the porous ceramic material to obtain a semi-finished material; the semi-finished material is then subjected to carbon coating treatment to obtain a porous ceramic-based silicon-carbon negative electrode material.

[0038] Preferably, the silicon deposition specifically includes: placing the porous ceramic material in a vapor deposition furnace, introducing a protective gas for protection, then heating to 500°C to 700°C at a rate of 1°C / min to 5°C / min, introducing a mixed gas of a silicon source gas and the protective gas in a volume ratio of 1:20 to 1.5:1, and keeping the temperature for 0.5 to 12 hours, so that the silicon element decomposed by the silicon source gas is deposited in the pores and on the surface of the porous ceramic material and grows into nanometers, and stopping the introduction of the silicon source gas to obtain a semi-finished material;

[0039] The carbon coating process is a vapor-phase carbon coating process, specifically comprising: adjusting the temperature of the vapor deposition furnace to 500° C. to 600° C. under a protective gas environment, then introducing a mixture of a carbon source gas and the protective gas at a volume ratio of 1:10 to 1:1, and maintaining the mixture for 3 to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the outer surface of the semi-finished material to form a carbon coating layer, thereby finally obtaining a porous ceramic-based silicon-carbon negative electrode material;

[0040] Wherein, the protective gas includes nitrogen and / or argon; the flow rate of the protective gas is 5L / min to 30L / min;

[0041] The silicon source gas includes one or more gases selected from monosilane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorodisilane; the flow rate of the silicon source gas is 5 L / min to 50 L / min;

[0042] The carbon source gas includes one or more of methane, acetylene, ethylene or propylene; the flow rate of the carbon source gas is 5L / min to 50L / min.

[0043] In a fifth aspect, an embodiment of the present invention provides a lithium-ion battery, which includes the porous ceramic-based silicon-carbon negative electrode material described in the third aspect, or the porous ceramic-based silicon-carbon negative electrode material prepared by the preparation method described in the fourth aspect.

[0044] The embodiments of the present invention provide a porous ceramic material, a porous ceramic-based silicon-carbon negative electrode material, and a preparation method thereof, which have the following technical effects.

[0045] (1) The present invention provides a porous ceramic material and a preparation method thereof. First, alkyl hydrogen siloxane, alkyl vinyl siloxane, and silicate are added with a catalyst to prepare a precursor solution. Then, the precursor solution is subjected to a staged heating treatment to cause the silicate to undergo a hydrolysis reaction to generate a pore-forming hard template nano-SiO2, and the silicon-hydrogen bond (Si-H) in the alkyl hydrogen siloxane and the carbon-carbon double bond (C=C) of the alkyl vinyl siloxane undergo a silicon-hydrogen addition reaction under the action of the catalyst, and cross-linked and cured to obtain a cross-linked silicone resin. Nano-SiO2 is dispersed in the cross-linked silicone resin to obtain a ceramic precursor; the ceramic precursor is subjected to segmented pyrolysis to cause the cross-linked silicone resin to crack to generate silicon-oxygen-carbon (SiOC) and free carbon (C), and part of the free carbon is etched by water vapor to form nanopores to obtain a porous ceramic precursor. Then, the porous ceramic precursor is subjected to acid washing and purification to etch away the nano-silicon oxide in the porous ceramic precursor to obtain a porous ceramic material. A porous ceramic material with a silicon-oxygen-carbon ceramic matrix and free carbon; the preparation method of the porous ceramic material provided by the present invention can control the free carbon content in the porous ceramic material by regulating the carbon chain length of the groups in the raw materials, the amount of raw materials, the conditions for staged heating treatment and cross-linking and curing, and the conditions for staged pyrolysis, thereby balancing the mechanical properties and electrical properties of the porous silicon-oxygen-carbon ceramic matrix, so that the porous ceramic material has the advantages of high strength, high temperature resistance, and chemical stability. Compared with traditional SiOC ceramics, the porous ceramic material of the present invention has a large specific surface area and a narrow pore size distribution, which is conducive to the deposition and particle size control of new nano-silicon, and by controlling the free carbon content, the electrical conductivity of the material is controlled, which is conducive to the adjustment and improvement of the rate performance; in addition, by regulating the preparation conditions, the specific surface area and pore volume of the porous ceramic material are controlled, thereby improving the effect of the porous ceramic material in subsequent silicon deposition, and improving the performance of the final porous ceramic-based silicon-carbon negative electrode material.

[0046] (2) The present invention provides a porous ceramic-based silicon-carbon negative electrode material and a preparation method thereof. The porous ceramic material prepared by the present invention is used as a matrix material to carry out silicon deposition, and silicon nanomaterials are deposited and grown in the pores and on the surface of the porous ceramic material. Then, a carbon coating treatment is carried out to form an outermost carbon coating layer, and finally a porous ceramic-based silicon-carbon negative electrode material is obtained. The porous ceramic-based silicon-carbon negative electrode material prepared by the preparation method provided by the present invention has the advantages of high pressure-resistant mechanical properties and high cycle life. The porous ceramic-based silicon-carbon negative electrode material adopts a porous silicon-oxygen-carbon ceramic matrix (SiO 2(1-x) C x0≤x≤1) and free carbon porous ceramic materials serve as carriers, enabling silicon deposition and coating at high temperatures. Because the porous silicon-oxygen-carbon ceramic carrier does not react with nano-silicon, it can inhibit the formation of silicon carbide, reduce the loss of active nano-silicon, and increase the capacity of the negative electrode material and battery. High-temperature coating provides a wider range of coating raw materials, resulting in a highly crystalline, denser, and more conductive coating layer, which can improve the material's first-cycle coulombic efficiency, rate performance, and cycle life. Furthermore, high-temperature deposition and coating improves deposition and coating efficiency, reducing costs.

[0047] (3) The porous ceramic-based silicon-carbon negative electrode material provided by the present invention is used as a negative electrode active material to prepare a negative electrode plate and assembled into a lithium-ion battery. Due to the high mechanical properties, high cycle life and high rate performance of the porous ceramic-based silicon-carbon negative electrode material, the safety and cycle performance of the lithium-ion battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Flowchart of the preparation method of the porous ceramic-based silicon-carbon negative electrode material provided in an embodiment of the present invention.

[0049] Figure 2 This is a C1s fine spectrum of the porous ceramic material prepared in Example 1 of the present invention measured by X-ray photoelectron spectroscopy (XPS).

[0050] Figure 3 This is a scanning electron microscope (SEM) image of the porous ceramic material provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0052] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0053] The embodiment of the present invention provides a porous ceramic material, comprising: a porous silicon oxygen carbon ceramic matrix and free carbon. The chemical formula of the porous silicon oxygen carbon ceramic matrix is SiO 2(1-x) C x , where 0≤x≤1.

[0054] The mass fraction of free carbon in the porous ceramic material is z%, where 0.1≤z≤45; the value of z% can be any value in the range of 0.1% to 45%, for example: 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0055] The calculation formula for the mass fraction of free carbon in porous ceramic materials is: z% = z0% × z1%; where z0% in the formula is the total carbon content in the porous ceramic material; z1% is the percentage of free carbon sp2 carbon in the total carbon content obtained by peak fitting of the C1 s fine spectrum of the porous ceramic material measured by X-ray photoelectron spectroscopy (XPS) to obtain the binding energy in the range of 284.8±0.3 eV.

[0056] The method for testing the total carbon content of porous ceramic materials to 0% is to use a carbon-sulfur analyzer (model: CS-2800) to measure the carbon content of the material. The testing principle is to oxidize the carbon in the sample into gases such as CO and CO2 at high temperature. These gases are then detected and analyzed using infrared spectroscopy to calculate the carbon and sulfur content of the sample. In addition, samples with a carbon content of not less than 6% and samples with a carbon content of less than 6% are defined as high-carbon samples and low-carbon samples, respectively. The test requires taking samples of different masses: 50mg and 100mg of the high-carbon and low-carbon samples, respectively, are sampled with 2.5g and 2.1g of a special rare earth co-solvent, respectively. The crucible is then placed in the carbon-sulfur analyzer for testing.

[0057] The average pore size of the porous ceramic material is 1.5nm to 5.0nm, and can be any value within this range, for example: 1.5nm, 2.0nm, 2.5nm, 3.0nm, 3.5nm, 4.0nm, 4.5nm, 5.0nm, etc., but is not limited to the listed values. Other values not listed within this range are also applicable.

[0058] The pore volume of the porous ceramic material is 0.5 ml / g to 1.5 ml / g, and can be any value within this range, for example: 0.5 ml / g, 0.6 ml / g, 0.7 ml / g, 0.8 ml / g, 0.9 ml / g, 1 ml / g, 1.1 ml / g, 1.2 ml / g, 1.3 ml / g, 1.4 ml / g, 1.5 ml / g, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0059] The specific surface area of porous ceramic materials is 1300m 2 / g~3000m 2 / g, can be any value within this range, for example: 1300m 2 / g、1500m 2 / g、1800m 2 / g、2000m 2 / g、2300m 2 / g、2500m 2 / g、2800m 2 / g、3000m 2 / g, etc., but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0060] In the present invention, the specific surface area, average pore size, and pore volume are measured using a specific surface area analyzer (Model: Micromeritics ASAP2460). The sample to be tested is first sieved using a 200-mesh sieve. Then, it is degassed, typically by placing the sample in a vacuum and heating it at 200°C for several hours (6 hours). Then, under a constant low temperature (-196°C) environment, nitrogen is introduced and the nitrogen pressure is controlled. The sample is adsorbed and desorbed at different pressures to obtain isothermal adsorption-desorption curves. Based on the isothermal adsorption-desorption curves, the specific surface area of the sample is calculated using BET fitting, and the average pore size and pore volume are calculated using t-plot fitting.

[0061] The mass of the porous silicon oxycarbon ceramic matrix accounts for 55% to 99.9% of the total mass of the porous ceramic material, and can be any value within this range, for example: 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99.9%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0062] The present invention provides a method for preparing the porous ceramic material. Figure 1 As shown, the preparation method specifically comprises the following steps:

[0063] Step S1: adding raw material A, raw material B, and raw material C to solvent D in sequence at room temperature, stirring continuously to mix evenly, then adding a catalyst, and continuing stirring to obtain a precursor solution;

[0064] Among them, raw material A is alkyl hydrogen siloxane, raw material B is alkyl vinyl siloxane, raw material C is silicate, and the catalyst is chloroplatinic acid-bisvinyltetramethyldisiloxane complex;

[0065] Specifically, the chemical formula of alkyl hydrogen siloxane is (R1R2R3SiO)-(R4SiHO) n-(SiR5R6R7); the general chemical formula of alkyl vinyl siloxane is (R7R8SiOCH=CH2)-(R9SiHO) m -(SiCH=CH2R 10 R 11 ); where 3≤n≤6, 4≤m≤8, R1~R 11 are the same or different alkyl groups;

[0066] The general chemical formula of silicate is Si(OR 12 )4, where R 12 Including at least one of CH3, C2H5, C3H7;

[0067] Solvent D includes at least one of toluene, xylene, isopropyl alcohol, and butyl acetate;

[0068] The molar ratio of raw material A to raw material B is 1:1; the ratio of the mass of raw material C to the sum of the masses of raw material A and raw material B is r1, and the ratio of the mass of the catalyst to the mass of A and B is r2, wherein 0.1≤r1≤1, 0.1%≤r2≤1.0%.

[0069] Step S2, placing the precursor solution in an oven for staged heating treatment to cause the precursor solution to react and generate a cross-linked silicone resin and nano-silicon dioxide uniformly dispersed in the cross-linked silicone resin, thereby obtaining a ceramic precursor;

[0070] Specifically, the precursor solution is placed in a stainless steel tray and placed in an oven for staged heating treatment for cross-linking and curing, so that the silicate undergoes a hydrolysis reaction to generate nano-silicon dioxide. Raw materials A and B are cross-linked and cured under the action of a catalyst to obtain a cross-linked silicone resin. The nano-silicon dioxide is dispersed in the cross-linked silicone resin to obtain a ceramic precursor.

[0071] Among them, the staged heating treatment includes: heating the oven to T1°C under a nitrogen atmosphere, keeping it warm for t1 hours, then heating it to T2°C, and keeping it warm for t2 hours, wherein 50≤T1≤80, 2≤t1≤10, 100≤T2≤160, 2≤t2≤10.

[0072] Step S3, placing the ceramic precursor in a pyrolysis furnace for staged pyrolysis, cracking the cross-linked organic silicone resin to generate silicon oxide carbon and free carbon, and etching part of the free carbon to generate nanopores, thereby obtaining a porous ceramic precursor containing nano-silicon oxide;

[0073] Among them, the staged pyrolysis includes: the first stage pyrolysis, the atmosphere is an inert atmosphere, first heated to T3 ° C at a rate of d1 ° C / min, then the atmosphere is switched to an inert atmosphere plus the first active atmosphere, and kept at T3 ° C for t3 hours; the second stage pyrolysis, the atmosphere is switched to an inert atmosphere, heated to T4 ° C at a rate of d2 ° C / min, and kept at T4 ° C for t4 hours; the third stage pyrolysis, then cooled to T5 ° C at a rate of d3 ° C / min, and the atmosphere is switched to an inert atmosphere plus the first active atmosphere. 2. Active atmosphere, keep warm at T5℃ for t5 hours; then switch to inert atmosphere, cool to T6℃ at a rate of d4℃ / min, and then cool naturally to room temperature; where 2≤d1≤6, 600≤T3≤900, 2≤t3≤10, 1≤d2≤5, 1100≤T4≤1500, 4≤t4≤8, 1≤d3≤3, 800≤T5≤1000, 0.5≤t5≤10, 3≤d4≤6, T6=500;

[0074] The inert atmosphere includes nitrogen and / or argon;

[0075] The gas of the first reactive atmosphere includes water vapor;

[0076] The gas of the second active atmosphere includes carbon dioxide or water vapor;

[0077] In the present invention, carbon is etched away to form pores through an active atmosphere. In the low temperature range, water vapor is used as the first active atmosphere, which has stronger reaction activity and more obvious etching effect of water vapor on carbon. When the temperature rises, carbon dioxide can also be used as the active atmosphere, but water vapor is still preferred.

[0078] The total air flow of the atmosphere is set to 10 L / min to 50 L / min. When the atmosphere contains an active atmosphere, the volume ratio of the first active atmosphere or the second active atmosphere to the inert atmosphere is 1:20 to 2:3.

[0079] Step S4, acid-washing and purifying the porous ceramic precursor, etching away the nano-silicon oxide, and obtaining a porous ceramic material;

[0080] Among them, the pickling purification specifically includes: placing the porous ceramic precursor containing nano-silicon oxide in a hydrofluoric acid solution with a mass fraction of 5% to 30% for immersion, the immersion temperature is 50°C to 80°C, and the immersion time is 5 hours to 48 hours. After the immersion is completed, the acid solution is removed by filter press, and then washed with deionized water until neutral, and then baked in an oven at 80°C to 120°C for 4 hours to 12 hours to obtain a porous ceramic material.

[0081] In the present invention, the mechanism for preparing porous ceramic materials is specifically as follows: when the precursor solution is subjected to a staged heating treatment, the silicon-hydrogen bond (Si-H) in the alkyl hydrogen siloxane and the carbon-carbon double bond (C=C) in the alkyl vinyl siloxane undergo a silylation reaction under the action of a catalyst, so that the organic silicone resin is cross-linked and cured, and the introduced silicate is hydrolyzed to form nano-SiO2, which serves as a pore-forming template and forms a ceramic precursor after curing; in the staged pyrolysis process, as the temperature rises, the molecular structure of the organic silicone resin gradually disintegrates, undergoes a series of complex thermochemical reactions, and is cracked to form a complex structure of silicon oxygen carbon (SiOC), free carbon (C) and nano-SiO2. The introduction of water vapor can etch away free carbon to form nanopores; further increasing the temperature, SiOC will precipitate some C and nano-SiO2; when the temperature is lowered and water vapor is introduced again, the water vapor continues to react with the precipitated carbon, further reducing the content of free carbon and creating more nanopores; after HF etches away SiO2 in the pyrolysis product, the thermal product has rich pores and is mainly composed of SiOC ceramic phase, with a small amount of free carbon; the introduction of silicate to form nano-SiO2, which serves as a pore-forming template in the ceramic precursor, can promote the regulation of free carbon content and help to regulate the pores and specific surface area of porous ceramics.

[0082] When the present invention prepares the porous ceramic material containing a porous silicon oxygen carbon ceramic matrix and free carbon:

[0083] The staged heating process allows raw materials A and B to crosslink and cure under the action of a catalyst. Different conditions will result in different microscopic crosslinking structures in the silicone resin. After determining raw materials A and B (primarily determining the functional groups), the main factors affecting the microscopic crosslinking structure include temperature and time. Increasing the temperature generally accelerates the curing rate and shortens the time required to achieve full cure. However, exceeding a specific temperature range may trigger side reactions, leading to deterioration of material properties. In addition, uneven temperature distribution may lead to premature curing and formation of a hard shell on the surface, hindering internal reactions and causing an uneven structure. At a constant temperature, extending the curing time can increase the crosslink density until the reaction approaches equilibrium, but excessive curing time may lead to excessive crosslinking or side reactions. Increasing the temperature and time can both increase the crosslink density, forming a denser three-dimensional network, and enhancing heat resistance, mechanical strength, and chemical stability. However, excessive crosslinking may reduce flexibility and reduce carbonization and activation reactivity. Excessive temperature may lead to excessively rapid local crosslinking, resulting in an uneven microstructure due to differences in heat conduction. Excessive temperature or short curing time may result in insufficient and uneven crosslinking, leading to low carbonization yields and uneven activation activity.

[0084] Segmented pyrolysis process: Different microscopic cross-linked structures will produce free carbon and SiOC with different activities during the high-temperature pyrolysis stage. Adjusting the pyrolysis conditions can control the free carbon content and regulate the size of carbon and ceramic microparticles.

[0085] Activation stage: Free carbon of different activities has different reactivity with the activation atmosphere, and the ease with which the free carbon is etched varies. Therefore, the free carbon content, pores, specific surface area, and pore volume in the porous ceramic matrix can be adjusted.

[0086] Porous ceramic materials are composed of a porous silicon-oxygen-carbon ceramic matrix and free carbon. Controlling the free carbon content, i.e., the SiOC ceramic content, also regulates the pore size, specific surface area, and pore volume of the porous matrix. Therefore, the free carbon content affects the strength, conductivity, specific surface area, pore volume, and other properties of the porous ceramic matrix, further influencing the specific capacity, lifespan, and rate performance of the porous ceramic-based silicon-carbon anode material.

[0087] An embodiment of the present invention further provides a porous ceramic-based silicon-carbon negative electrode material, comprising: the above-mentioned porous ceramic material, silicon nanomaterials deposited in the pores and on the surface of the porous ceramic material, and a carbon coating layer.

[0088] Silicon nanomaterials include, but are not limited to, nano-silicon particles, nano-silicon island-shaped materials formed by closely arranged nano-silicon particles, or silicon nanowire-shaped materials formed by closely arranged nano-silicon particles.

[0089] The specific surface area of the porous ceramic-based silicon-carbon negative electrode material provided in the embodiment of the present invention is 0.3m 2 / g~20m 2 / g, can be any value within this range, for example: 0.3m 2 / g, 0.5m 2 / g、1m 2 / g, 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g、15m 2 / g、16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g, 20m 2 / g, etc., but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0090] The particle size Dv50 of the porous ceramic-based silicon-carbon negative electrode material is between 2μm and 30μm, and can be any value within this range, for example: 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0091] In the present invention, the particle size Dv50 refers to the volume median particle size of the material, which indicates the particle size corresponding to 50% of the volume distribution of the material, which is a well-known meaning in the art. The particle size Dv50 of the porous ceramic-based silicon-carbon negative electrode material provided in the embodiment of the present invention can be measured by instruments and conventional methods well-known in the art. Specifically, 1g of porous silicon-oxygen-carbon ceramic powder sample is weighed and added to 20ml of deionized water, and then 50ul of a 1% mass concentration of ethylphenyl polyethylene glycol dispersant aqueous solution is added, ultrasonicated for 5 minutes, and then the dispersion is added to the Mastersizer 3000 laser particle size analyzer of Malvern Instrument Co., Ltd. for particle size measurement, and then the Dv50 value is read.

[0092] In the porous ceramic-based silicon-carbon negative electrode material, the total carbon content is 50wt% to 90wt%, and the total silicon content is 15wt% to 50wt%.

[0093] The thickness of the carbon coating layer of the porous ceramic-based silicon-carbon negative electrode material is 1nm to 20nm, and can be any value within this range, for example: 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable; the mass of the carbon coating layer accounts for 1% to 25% of the total mass of the porous ceramic-based silicon-carbon negative electrode material.

[0094] The present invention provides a method for preparing the porous ceramic-based silicon-carbon negative electrode material, which specifically includes:

[0095] Depositing silicon on the porous ceramic material, depositing and growing silicon nanomaterials in the pores and on the surface of the porous ceramic material to obtain a semi-finished material; then subjecting the semi-finished material to carbon coating to obtain a porous ceramic-based silicon-carbon negative electrode material;

[0096] The silicon deposition specifically includes: placing the porous ceramic material in a vapor deposition furnace, introducing a protective gas for protection, then heating the material to 500°C to 700°C at a rate of 1°C / min to 5°C / min, introducing a mixture of a silicon source gas and a protective gas at a volume ratio of 1:20 to 1.5:1, and maintaining the temperature for 0.5 to 12 hours, so that silicon elements decomposed by the silicon source gas are deposited in the pores and on the surface of the porous ceramic material to grow into silicon nanomaterials, and then stopping the introduction of the silicon source gas to obtain a semi-finished material;

[0097] The carbon coating process is a vapor-phase carbon coating process, specifically comprising: adjusting the temperature of a vapor deposition furnace to 500°C to 600°C under a protective gas environment, then introducing a mixture of a carbon source gas and a protective gas at a volume ratio of 1:10 to 1:1, and maintaining the mixture for 3 to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the outer surface of the semi-finished material to form a carbon coating layer, and finally obtaining a porous ceramic-based silicon-carbon negative electrode material;

[0098] The protective gas includes nitrogen and / or argon; the flow rate of the protective gas is 5L / min to 30L / min;

[0099] The silicon source gas includes one or more gases selected from monosilane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorodisilane; the flow rate of the silicon source gas is 5 L / min to 50 L / min;

[0100] The carbon source gas includes one or more of methane, acetylene, ethylene or propylene; the flow rate of the carbon source gas is 5L / min to 50L / min.

[0101] The porous ceramic-based silicon-carbon negative electrode material prepared by the above-mentioned preparation method provided in the embodiment of the present invention can be used as a negative electrode active material to prepare a negative electrode plate, and the negative electrode plate can be used to assemble a lithium-ion battery.

[0102] In order to better understand the technical solutions provided by the present invention, the preparation process and characteristics of the porous ceramic material and the porous ceramic-based silicon-carbon negative electrode material of the present invention are respectively described below with multiple specific examples.

[0103] Example 1

[0104] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0105] (1) At room temperature, 4.5 kg of polymethylhydrogen siloxane (raw material A), 5.7 kg of polymethylvinylsiloxane (raw material B) and 1.2 kg of methyl orthosilicate (raw material C) were added to 50 kg of toluene (solvent D) in sequence and stirred for 1 hour to mix them evenly; then, 20 g of chloroplatinic acid-bisvinyltetramethyldisiloxane complex was added and stirred for 1 hour to obtain a precursor solution; wherein the chemical formula of polymethylhydrogen siloxane is (CH3)3SiO)-(CH3SiHO) 3-6 -(Si(CH3)3, the chemical formula of polymethylvinylsiloxane is (CH3)2SiOCH=CH2)-(CH3SiHO) 4-8 -(SiCH=CH2(CH3)2.

[0106] (2) The precursor solution is placed in a stainless steel tray and placed in an oven for staged heating treatment. The temperature is first raised to 50°C (T1°C) under a nitrogen atmosphere and kept at 50°C for 2 hours (t1 hour); then the temperature is raised to 100°C (T1°C) and kept at 100°C for 10 hours (t2 hours). During the staged heating treatment, the precursor solution reacts, ethyl silicate undergoes hydrolysis to generate nano-silica, polymethylhydrogensiloxane and polymethylvinylsiloxane are cross-linked and cured to generate a cross-linked silicone resin, and the nano-silica is uniformly dispersed in the cross-linked silicone resin to obtain a ceramic precursor.

[0107] (3) The ceramic precursor is placed in a pyrolysis furnace for staged pyrolysis, firstly heated to 600°C (T3°C) at a rate of 2°C / min (d1°C / min), and the atmosphere is an inert nitrogen atmosphere; then the atmosphere is switched to a nitrogen atmosphere with water vapor, and kept at 600°C for 8 hours (t3 hours); then the atmosphere is switched to a nitrogen atmosphere only, heated to 1100°C (T4°C) at a rate of 2°C / min (d2°C / min), and kept at 1000°C for 4 hours (t4 hours); then the temperature is lowered to 1000°C (T5°C) at a rate of 1°C / min (d3°C / min), and the atmosphere is switched to a nitrogen atmosphere with water vapor, and kept at 10 The reaction mixture was kept at 00℃ for 2 hours (t5 hours); then the atmosphere was switched to nitrogen atmosphere, and the temperature was lowered to 500℃ (T6℃) at a rate of 3℃ / min (d4℃ / min), and then naturally cooled to room temperature; the total air flow into the pyrolysis furnace was set to 30L / min, and when the active atmosphere water vapor was added, the ratio of nitrogen atmosphere to water vapor was 3:2, that is, the air flow sizes of nitrogen atmosphere and water vapor were set to 18L / min and 12L / min, respectively. The segmented pyrolysis process caused the cross-linked silicone resin to crack to generate silicon oxide carbon and free carbon, and part of the free carbon was etched to produce nanopores, thereby obtaining a porous ceramic precursor containing nano-silicon oxide.

[0108] (4) The porous ceramic precursor is soaked in a 20wt% hydrofluoric acid solution for acid washing and purification at a soaking temperature of 80°C for 48 hours. After soaking, the acid solution is removed by filter press, and then washed with deionized water until neutral. Then, it is baked in an oven at 100°C for 12 hours to etch away the nano-silicon oxide to obtain a porous ceramic material containing a porous silicon-oxygen-carbon ceramic matrix and free carbon. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 0.98 C 0.51 The SEM image of the porous ceramic material prepared in this step is as follows: Figure 3 shown.

[0109] (5) The porous ceramic material is placed in a vapor deposition furnace, and nitrogen is introduced into the vapor deposition furnace at a gas flow rate of 10 L / min for protection. The vapor deposition furnace is heated to 560°C at a heating rate of 3°C / min and kept warm for 30 minutes. Then, monosilane and nitrogen are introduced into the vapor deposition furnace at a flow rate ratio of 20 L / min:20 L / min. The temperature is kept warm for 5 hours to deposit silicon, so that the silicon element decomposed by monosilane is deposited in the pores and on the surface of the porous ceramic material to grow into silicon nanomaterials. The introduction of monosilane is stopped to obtain a semi-finished material; then the gas is switched to nitrogen at a flow rate of 12 L / min and maintained for 1 hour. Then the temperature is raised to 580°C, and a mixed gas of nitrogen and acetylene is introduced at a flow rate ratio of 15 L / min:15 L / min. The temperature is kept warm for 8 hours, so that the carbon element decomposed by acetylene is deposited on the outer surface of the semi-finished material to form a carbon coating layer, thereby obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0110] The mass fraction z% of free carbon in the porous ceramic material prepared in step (4) of this embodiment was tested. The testing method was as described above: the carbon content z0% of the porous ceramic material was tested using a carbon-sulfur analyzer (model: CS-2800, manufactured by Gangyan Nano), and was 10.31%; the C1s fine spectrum of the porous ceramic material was measured by X-ray photoelectron spectroscopy (XPS), and the percentage of free carbon sp2 carbon in the total carbon content with a binding energy range of 284.8±0.3eV obtained by peak fitting was obtained, and z1% was 49.63%. The C1s fine spectrum of the porous ceramic material measured by XPS was as follows: Figure 2 As shown; finally, the mass fraction of free carbon is calculated by the formula z% = 10.31% × 49.63%, and the test data is shown in Table 1.

[0111] The specific surface area and pore volume of the porous ceramic material prepared in this example were tested using a specific surface area analyzer (model: Micromeritics ASAP2460) using the same testing method as described above. The test data of the specific surface area and pore volume are detailed in Table 1.

[0112] The porous ceramic-based silicon-carbon negative electrode material prepared in this example was used to prepare electrode pieces and assembled into button-type batteries for testing. The specific process was as follows:

[0113] Preparation of pole pieces: The negative electrode material prepared in this embodiment, the conductive agent SuperP and the binder sodium carboxymethyl cellulose (CMC) are taken in a mortar in a mass ratio of 8:1:1 and initially ground, and then deionized water is added and transferred to a beater and stirred to form a slurry; then, the obtained slurry is coated on a copper foil current collector; after that, it is dried in a vacuum oven at 80°C for 12 hours, and after drying, it is rolled once at a pressure of 14 MPa, and then the rolled pole piece is cut into a disc with a diameter of 14 mm as the pole piece of the button half-cell.

[0114] Assembling a button half-cell: The electrodes are assembled into a button half-cell using conventional methods in an argon-filled glove box. The button half-cell uses a non-aqueous electrolyte with 1 mol / L lithium hexafluorophosphate (LiPF6) as the lithium salt. The solvents are ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), with the volume ratio of EC, DEC, and DMC being 1:1:1. The counter electrode is a lithium sheet.

[0115] The assembled button batteries were tested on a blue battery test system with a test temperature of 25°C and a test voltage window of 0.005V-2V. Step discharge was adopted, first discharging to 0.005V at a rate of 0.2C, standing for 5 minutes, and then discharging to 0.005V at a rate of 0.1C. After standing for 5 minutes, after standing for 5 minutes, discharging to 0.005V at a rate of 0.05C, standing for 5 minutes, and then discharging to 0.005V at a rate of 0.02C, standing for 5 minutes, and then discharging to 0.005V at a rate of 0.01C. Then, constant current charging was used for charging, the charging rate was 0.1C, and the number of cycles was set to 100.

[0116] Cycle capacity retention rate: The ratio of the charge capacity after 100 cycles to the charge capacity in the first cycle is the capacity retention rate. For detailed test data, please see Table 1.

[0117] Example 2

[0118] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0119] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0120] (2) The staged heating treatment is different from that in Example 1: T1=60, t1=6, T2=120, t2=6.

[0121] (3) The staged pyrolysis is different from Example 1: t3=6, T4=1200, t4=6, and other conditions are the same.

[0122] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.02 C 0.49 .

[0123] (5) The holding time during silicon deposition was 5.4 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0124] Example 3

[0125] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0126] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0127] (2) The staged heating treatment is different from that in Example 1: T1=70, t1=4, T2=140, t2=4.

[0128] (3) The staged pyrolysis is different from that in Example 1: t3=5, T4=1300, t4=5, and other conditions are the same.

[0129] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.12 C 0.44 ,.

[0130] (5) The holding time during silicon deposition was 6.1 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0131] Example 4

[0132] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0133] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0134] (2) The staged heating treatment is different from that in Example 1: T1=80, t1=2, T2=160, t2=2.

[0135] (3) The staged pyrolysis is different from that in Example 1: t3=3, T4=1400, t4=4, and other conditions are the same.

[0136] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.28 C 0.36 .

[0137] (5) The holding time during silicon deposition was 4.8 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0138] Example 5

[0139] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0140] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0141] (2) The step-by-step heating treatment is the same as in Example 1.

[0142] (3) The staged pyrolysis is different from that in Example 1: T4=1200, t4=6, t5=3, and other conditions are the same.

[0143] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.1 C 0.45 .

[0144] (5) The holding time during silicon deposition was 5.9 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0145] Example 6

[0146] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0147] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0148] (2) The staged heating treatment is different from that in Example 1: T1=60, t1=6, T2=120, t2=6.

[0149] (3) The staged pyrolysis is different from that in Example 1: t3=6, T4=1200, t4=6, T5=950, t5=3, and other conditions are the same.

[0150] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.08 C 0.46 .

[0151] (5) The holding time during silicon deposition was 5.5 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0152] Example 7

[0153] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0154] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0155] (2) The staged heating treatment is different from that in Example 1: T1=70, t1=4, T2=140, t2=4.

[0156] (3) The staged pyrolysis is different from that in Example 1: t3=5, T4=1200, t4=6, T5=900, t5=3, and other conditions are the same.

[0157] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.06 C 0.47 .

[0158] (5) The holding time during silicon deposition was 4.9 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0159] Example 8

[0160] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0161] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0162] (2) The staged heating treatment is different from that in Example 1: T1=80, t1=2, T2=160, t2=2.

[0163] (3) The staged pyrolysis is different from that in Example 1: t3=3, T4=1200, t4=6, T5=850, t5=3, and other conditions are the same.

[0164] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.04 C 0.48 .

[0165] (5) The holding time during silicon deposition was 4.4 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0166] Example 9

[0167] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0168] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0169] (2) The step-by-step heating treatment is the same as in Example 1.

[0170] (3) The staged pyrolysis is different from that in Example 1: T3=700, t4=6, and other conditions are the same.

[0171] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon oxygen carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon oxygen carbon ceramic matrix is SiOC 0.5 .

[0172] (5) The holding time during silicon deposition was 5.1 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0173] Example 10

[0174] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0175] (1) The preparation process of the precursor solution is the same as that in Example 1.

[0176] (2) The step-by-step heating treatment is the same as in Example 1.

[0177] (3) The staged pyrolysis is different from that in Example 1: T3=800, t4=6, and other conditions are the same.

[0178] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.02 C 0.49 .

[0179] (5) The holding time during silicon deposition was 5.2 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0180] Example 11

[0181] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0182] (1) The preparation of the precursor solution is different from that in Example 1: the raw material C is 3.5 kg of methyl orthosilicate.

[0183] (2) The staged heating treatment is different from that in Example 1: T1=60, t1=6, T2=120, t2=6.

[0184] (3) The staged pyrolysis is different from that in Example 1: t3=6, t4=6, and other conditions are the same.

[0185] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.06 C 0.47 .

[0186] (5) The holding time during silicon deposition was 6.6 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0187] Example 12

[0188] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0189] (1) The preparation of the precursor solution is different from that in Example 1: the raw material C is 7.0 kg of methyl orthosilicate.

[0190] (2) The staged heating treatment is different from that in Example 1: T1=70, t1=4, T2=140, t2=4.

[0191] (3) The staged pyrolysis is different from that in Example 1: t3=5, t4=6, and other conditions are the same.

[0192] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.06 C 0.47 .

[0193] (5) The holding time during silicon deposition was 7.1 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0194] Example 13

[0195] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0196] (1) The preparation of the precursor solution is different from that in Example 1: the raw material C is 10 kg of methyl orthosilicate.

[0197] (2) The staged heating treatment is different from that in Example 1: T1=80, t1=2, T2=160, t2=2.

[0198] (3) The staged pyrolysis is different from that in Example 1: t3=3, t4=6, and other conditions are the same.

[0199] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.06 C 0.47 .

[0200] (5) The holding time during silicon deposition was 7.9 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0201] Example 14

[0202] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0203] (1) The preparation of the precursor solution is different from that in Example 1 in that: raw material A is 4.7 kg of ((CH3CH2)3SiO)-(CH3SiHO)3-6-(Si(CH3CH2)3), raw material B is 5.4 kg of ((CH3CH2)2SiOCH=CH2)-(CH3SiHO)4-8-(SiCH=CH2(CH3CH2)2), raw material C is 10 kg of ethyl orthosilicate, solvent D is xylene, and the other preparation processes are the same.

[0204] (2) The staged heating treatment is different from that of Example 1 in that: T1=60, t1=6, T2=120, t2=5.

[0205] (3) The staged pyrolysis is different from that in Example 1: T3=700, t3=7, T4=1200, t4=7, T5=950, t5=5, and other conditions are the same.

[0206] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.24 C 0.38 .

[0207] (5) The holding time during silicon deposition was 8.2 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0208] Example 15

[0209] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0210] (1) The preparation of the precursor solution is different from that in Example 1 in that: raw material A is 5.0 kg of ((CH3CH2CH2)3SiO)-(CH3SiHO)3-6-(Si(CH3CH2CH2)3), raw material B is 5.5 kg of ((CH3CH2CH2)2SiOCH=CH2)-(CH3SiHO)4-8-(SiCH=CH2(CH3CH2CH2)2), raw material C is 10 kg of ethyl orthosilicate, solvent D is xylene, and the other preparation processes are the same.

[0211] (2) The staged heating treatment is different from that in Example 1: T1=70, t1=4, T2=140, t2=3.

[0212] (3) The staged pyrolysis is different from that in Example 1: T3=700, t3=6, T4=1200, t4=6, T5=950, t5=6, and other conditions are the same.

[0213] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.42 C 0.29 .

[0214] (5) The holding time during silicon deposition was 9.6 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0215] Example 16

[0216] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0217] (1) The preparation of the precursor solution is different from that in Example 1 in that: raw material A is 4.7 kg of ((CH3CH2CH2)3SiO)-(CH3CH2SiHO)3-6-(Si(CH3CH2CH2)3, raw material B is 5.3 kg of ((CH3CH2CH2)2SiOCH=CH2)-(CH3CH2SiHO)4-8-(SiCH=CH2(CH3CH2CH2)2), raw material C is 10 kg of ethyl orthosilicate, solvent D is xylene, and the other preparation processes are the same.

[0218] (2) The staged heating treatment is different from that in Example 1: T1=80, t1=3, T2=120, t2=4.

[0219] (3) The staged pyrolysis is different from that in Example 1: T3=800, t3=6, T4=1300, t4=4, t5=3, and other conditions are the same.

[0220] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.58 C 0.21 .

[0221] (5) The holding time during silicon deposition was 10.1 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0222] Example 17

[0223] This embodiment provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0224] (1) The preparation of the precursor solution is different from that in Example 1 in that: raw material A is 4.9 kg of ((CH3CH2CH2CH2)3SiO)-(CH3CH2SiHO)3-6-(Si(CH3CH2CH2CH2)3), raw material B is 5.4 kg of ((CH3CH2CH2CH2)2SiOCH=CH2)-(CH3CH2SiHO)4-8-(SiCH=CH2(CH3CH2CH2CH2)2), raw material C is 10 kg of ethyl orthosilicate, solvent D is xylene, and the other preparation processes are the same.

[0225] (2) The staged heating treatment is different from that in Example 1: T1=60, t1=5, T2=140, t2=4.

[0226] (3) The staged pyrolysis is different from that in Example 1: T3=800, t3=5, T4=1400, t4=5, t5=4, and other conditions are the same.

[0227] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.724 C 0.14 .

[0228] (5) The holding time during silicon deposition was 5.1 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0229] In order to better illustrate the effects of the embodiments of the present invention, a comparative example is compared with the above embodiments.

[0230] Comparative Example 1

[0231] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0232] (1) The process of preparing the precursor solution is different from that of Example 1 in that the raw material C, methyl orthosilicate, is not added.

[0233] (2) The preparation process is the same as that in Example 1.

[0234] (3) The staged pyrolysis is the same as in Example 1.

[0235] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon oxygen carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon oxygen carbon ceramic matrix is SiOC 0.5 .

[0236] (5) The holding time during silicon deposition was 3.3 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0237] Comparative Example 2

[0238] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0239] (1) The preparation of the precursor solution is different from that in Example 1 in that the raw material C is 10 kg of methyl orthosilicate, and the other preparation processes are the same.

[0240] (2) The preparation process is the same as that in Example 1.

[0241] (3) The staged pyrolysis is different from Example 1 in that: t5=0, and other conditions are the same.

[0242] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 0.98 C 0.51 .

[0243] (5) The holding time during silicon deposition was 9.5 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0244] Comparative Example 3

[0245] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0246] (1) The preparation of the precursor solution is different from that in Example 1 in that the raw material C is 12 kg of methyl orthosilicate, and the other preparation processes are the same.

[0247] (2) The preparation process is the same as that in Example 1.

[0248] (3) The staged pyrolysis differs from Example 1 in that: T3=500, T4=1100, and other conditions are the same.

[0249] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 0.88 C 0.56 .

[0250] (5) The holding time during silicon deposition was 10.3 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0251] Comparative Example 4

[0252] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0253] (1) The preparation of the precursor solution is different from that in Example 1 in that the raw material C is 10 kg of methyl orthosilicate, and the other preparation processes are the same.

[0254] (2) The preparation process is the same as that in Example 1.

[0255] (3) The staged pyrolysis is different from Example 1 in that: T3=500, and other conditions are the same.

[0256] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.02C 0.49 .

[0257] (5) The holding time during silicon deposition was 4.5 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0258] Comparative Example 5

[0259] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0260] (1) The preparation of the precursor solution is different from that in Example 1 in that the raw material C is 10 kg of methyl orthosilicate, and the other preparation processes are the same.

[0261] (2) The preparation process is the same as that in Example 1.

[0262] (3) The staged pyrolysis differs from Example 1 in that: T3 = 500, T4 = 1600, and other conditions are the same.

[0263] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.34 C 0.33 .

[0264] (5) The holding time during silicon deposition was 3.0 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0265] Comparative Example 6

[0266] This comparative example provides a preparation process and performance test of a porous ceramic material and a porous ceramic-based silicon-carbon negative electrode material, as detailed below.

[0267] (1) The preparation of the precursor solution is different from that in Example 1 in that the raw material C is 10 kg of methyl orthosilicate, and the other preparation processes are the same.

[0268] (2) The preparation process is the same as that in Example 1.

[0269] (3) The staged pyrolysis differs from Example 1 in that: T3 = 1000, and other conditions are the same.

[0270] (4) The acid washing and purification process is the same as in Example 1, and a porous ceramic material comprising a porous silicon-oxygen-carbon ceramic matrix and free carbon is obtained. The chemical formula of the porous silicon-oxygen-carbon ceramic matrix is SiO 1.04 C 0.48 .

[0271] (5) The holding time during silicon deposition was 3.8 hours, and other preparation conditions were the same as those in Example 1, ultimately obtaining a porous ceramic-based silicon-carbon negative electrode material.

[0272] Comparative Example 7

[0273] This comparative example uses a commercial porous carbon matrix as the matrix material to prepare a porous carbon-based silicon-carbon negative electrode material. Specifically, the porous carbon matrix is placed in a vapor deposition furnace for silicon deposition and carbon coating treatment. The preparation conditions and process are the same as step (5) of Example 1.

[0274] Comparative Example 8

[0275] In this comparative example, commercial silicon-oxygen-carbon ceramics are used as the matrix material to prepare porous silicon-oxygen-carbon ceramic-based silicon-carbon negative electrode materials. Specifically, the silicon-oxygen-carbon ceramics are placed in a vapor deposition furnace for silicon deposition and carbon coating treatment. The preparation conditions and process are the same as step (5) of Example 1.

[0276] The mass fraction z% of free carbon in the porous ceramic materials prepared in Test Examples 2-17 and Comparative Examples 1-8; the specific surface area and pore volume of the porous ceramic materials prepared in Test Examples 2-17 and Comparative Examples 1-8 were the same as in Example 1. The test data are detailed in Table 1.

[0277] The porous ceramic-based silicon-carbon negative electrode materials prepared in Test Examples 2-17 and Comparative Examples 1-8 were used to prepare electrode pieces and assembled into button-type batteries for testing. The button-type battery assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0278] Table 1 summarizes the test data of button batteries assembled in Examples 1-17 and Comparative Examples 1-8:

[0279]

[0280]

[0281] Table 1

[0282] From the test data in Table 1, it can be seen that, by comparing Comparative Example 1 with Example 1, the addition of hard template nano-silicon oxide in Example 1 can significantly improve the specific surface area and pore volume of the porous ceramic material, leaving more space for depositing nano-silicon, and thus obtaining a higher specific capacity while having excellent cycle life performance; by comparing Comparative Example 2 with Example 1, it can be seen that, after carbon etching, the porous ceramic material in Example 1 has a larger specific surface area and pore volume, while Comparative Example 2 also obtains a larger pore volume by adding more hard templates, but without carbon etching, the specific surface area is smaller, and the pores of the porous ceramic are blocked by excess free carbon, which is not conducive to the deposition of nano-silicon and does not meet the requirements of high capacity.

[0283] Since Comparative Example 3 adds more hard templates compared to Example 1, and the first and second pyrolysis temperatures are both too low, although the pore volume is large, the specific surface area is too small, which easily leads to uneven nano-silicon deposition, resulting in low cycle capacity retention and poor battery life.

[0284] Compared with Example 1, the first-stage pyrolysis temperature of Comparative Example 4 is too low, resulting in lower specific surface area and pore volume, which does not meet the requirement of high specific capacity.

[0285] Compared with Example 1, the second-stage pyrolysis temperature of Comparative Example 5 is too high, resulting in lower specific surface area and pore volume, which does not meet the requirements of high specific capacity, that is, the nano-silicon loading is low, so the specific capacity is low, but the capacity retention rate is still high.

[0286] Compared with Example 1, the first-stage pyrolysis temperature of Comparative Example 6 is too high, resulting in a high free carbon content, low specific surface area and pore volume, low capacity retention rate, and poor battery life.

[0287] Compared with Example 1, Comparative Example 7 shows that since commercial porous carbon is mainly composed of carbon and has insufficient strength, the porous carbon skeleton is broken due to large volume changes during the battery cycle, resulting in poor cycle life.

[0288] From Comparative Example 8 relative to Example 1, although the conventional porous silicon oxygen carbon ceramic has high strength, it has a small specific surface area and a small pore volume, which easily leads to uneven deposition of silicon, further resulting in poor cycle performance and cannot meet the high specific capacity requirements of the silicon carbon negative electrode.

[0289] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A porous ceramic material, characterized in that The porous ceramic material comprises: a porous silicon oxygen carbon ceramic matrix and free carbon; The general chemical formula of the porous silicon oxycarbon ceramic matrix is SiO 2(1-x) C x , where 0≤x≤1; The mass fraction of free carbon in the porous ceramic material is z%, where 0.1≤z≤45; The calculation formula for the mass fraction of the free carbon is: z%=z0%×z1%; wherein z0% in the formula is the total carbon content in the porous ceramic material; z1% is the percentage of the total carbon content of free carbon sp2 carbon with a binding energy in the range of 284.8±0.3eV obtained by peak fitting of the C1s fine spectrum of the porous ceramic material measured by X-ray photoelectron spectroscopy.

2. The porous ceramic material according to claim 1, characterized in that The average pore size of the porous ceramic material is 1.5 nm to 5.0 nm; the pore volume of the porous ceramic material is 0.5 ml / g to 1.5 ml / g; the specific surface area of the porous ceramic material is 1300 m 2 / g~3000m 2 / g; The mass of the porous silicon oxygen carbon ceramic matrix accounts for 55% to 99.9% of the total mass of the porous ceramic material.

3. A method for preparing the porous ceramic material according to any one of claims 1 to 2, characterized in that: The preparation method comprises: Step S1, at room temperature, adding raw material A, raw material B, and raw material C in sequence to solvent D, continuously stirring and mixing until uniform, then adding a catalyst and continuing stirring to obtain a precursor solution; wherein the raw material A is an alkyl hydrogen siloxane, the raw material B is an alkyl vinyl siloxane, the raw material C is a silicate, and the catalyst is a chloroplatinic acid-bisvinyltetramethyldisiloxane complex; Step S2, placing the precursor solution in an oven for staged heating treatment to cause the precursor solution to react and generate a cross-linked silicone resin and nano-silicon dioxide uniformly dispersed in the cross-linked silicone resin, thereby obtaining a ceramic precursor; Step S3, placing the ceramic precursor in a pyrolysis furnace for staged pyrolysis, so that the cross-linked organic silicone resin is cracked to generate silicon oxide carbon and free carbon, and a portion of the free carbon is etched to generate nanopores, thereby obtaining a porous ceramic precursor containing nano-silicon oxide; Step S4, acid-washing and purifying the porous ceramic precursor, etching away the nano-silicon oxide, and obtaining a porous ceramic material; wherein the porous ceramic material comprises: a porous silicon-oxygen-carbon ceramic matrix and free carbon; the chemical formula of the porous silicon-oxygen-carbon ceramic matrix is Si O 2(1-x) C x , 0≤x≤1; the mass fraction of free carbon in the porous ceramic material is z%, 0.1≤z≤45.

4. The preparation method according to claim 3, characterized in that In step S1: the chemical formula of the alkyl hydrogen siloxane is (R1R2R3SiO)-(R4SiHO) n -(Si R5R6R7); the general chemical formula of the alkyl vinyl siloxane is (R7R8SiOCH=CH2)-(R9Si HO) m -(SiCH=CH2R 10 R 11 ); Among them, 3≤n≤6, 4≤m≤8, R1~R 11 are the same or different alkyl groups; The chemical formula of the silicate is Si(OR 12 )4, where R 12 Including at least one of CH3, C2H5, C3H7; The solvent D comprises at least one of toluene, xylene, isopropyl alcohol, and butyl acetate; The molar ratio of the raw material A to the raw material B is 1:1; the ratio of the mass of the raw material C to the sum of the masses of the raw material A and the raw material B is r1, and the ratio of the mass of the catalyst to the mass of A and B is r2, wherein 0.1≤r1≤1, 0.1%≤r2≤1.0%.

5. The preparation method according to claim 3, characterized in that The step S2 includes: placing the precursor liquid in a stainless steel tray and placing it in an oven, performing a staged heating treatment for cross-linking and curing, causing the silicate to undergo a hydrolysis reaction to generate nano-silicon dioxide, cross-linking and curing the raw materials A and B under the action of a catalyst to obtain a cross-linked silicone resin, and dispersing the nano-silicon dioxide in the cross-linked silicone resin to obtain a ceramic precursor; wherein the staged heating treatment includes: heating the oven to T1°C under a nitrogen atmosphere, maintaining the temperature for t1 hours, and then heating to T2°C and maintaining the temperature for t2 hours, wherein 50≤T1≤80, 2≤t1≤10, 100≤T2≤160, and 2≤t2≤10.

6. The preparation method according to claim 3, characterized in that In step S3, the staged pyrolysis includes: first heating the temperature to T3°C at a rate of d1°C / min under an inert atmosphere, then switching the atmosphere to an inert atmosphere plus a first active atmosphere, and keeping the temperature at T3°C for t3 hours; then switching the atmosphere to an inert atmosphere, heating the temperature to T4°C at a rate of d2°C / min, and keeping the temperature at T4°C for t4 hours; then cooling the temperature to T5°C at a rate of d3°C / min, and switching the atmosphere to an inert atmosphere plus a second active atmosphere. , keep warm at T5℃ for t5 hours; then switch the atmosphere to an inert atmosphere, cool to T6℃ at a rate of d4℃ / min, and then cool naturally to room temperature; where, 2≤d1≤6, 600≤T3≤900, 2≤t3≤10, 1≤d2≤5, 1100≤T4≤1500, 4≤t4≤8, 1≤d3≤3, 800≤T5≤1000, 0.5≤t5≤10, 3≤d4≤6, T6=500; The gas of the inert atmosphere includes nitrogen and / or argon; The gas of the first active atmosphere includes water vapor; The gas of the second active atmosphere includes carbon dioxide or water vapor; The total air flow of the atmosphere is set to 10 L / min to 50 L / min. When the atmosphere contains an active atmosphere, the volume ratio of the first active atmosphere or the second active atmosphere to the inert atmosphere is 1:20 to 2:

3.

7. The preparation method according to claim 3, characterized in that In step S4, the pickling purification specifically includes: soaking the porous ceramic precursor containing nano-silicon oxide in a hydrofluoric acid solution with a mass fraction of 5% to 30%, the soaking temperature is 50°C to 80°C, and the soaking time is 5 hours to 48 hours. After soaking, the acid solution is removed by filter press, and then washed with deionized water until neutral, and then baked in an oven at 80°C to 120°C for 4 hours to 12 hours to obtain a porous ceramic material.

8. A porous ceramic-based silicon-carbon negative electrode material, characterized in that: The porous ceramic-based silicon-carbon negative electrode material comprises: the porous ceramic material according to any one of claims 1-2, silicon nanomaterials deposited in the pores and on the surface of the porous ceramic material, and a carbon coating layer.

9. The porous ceramic-based silicon-carbon negative electrode material according to claim 8, characterized in that: The porous ceramic-based silicon-carbon negative electrode material has a total carbon content of 50 wt% to 90 wt% and a total silicon content of 15 wt% to 50 wt%; The thickness of the carbon coating layer is 1 nm to 20 nm; the mass of the carbon coating layer accounts for 1% to 25% of the total mass of the porous ceramic-based silicon-carbon negative electrode material; The specific surface area of the porous ceramic-based silicon-carbon negative electrode material is 0.3 m 2 / g~20m 2 / g; the particle size Dv50 of the porous ceramic-based silicon-carbon negative electrode material is between 2μm and 30μm.

10. A method for preparing the porous ceramic-based silicon-carbon negative electrode material according to any one of claims 8 to 9, characterized in that: The preparation method comprises: The porous ceramic material according to any one of claims 1-2 is subjected to silicon deposition, and silicon nanomaterials are deposited and grown in the pores and on the surface of the porous ceramic material to obtain a semi-finished material; the semi-finished material is then subjected to carbon coating treatment to obtain a porous ceramic-based silicon-carbon negative electrode material.

11. The preparation method according to claim 10, characterized in that: The silicon deposition specifically includes: placing the porous ceramic material in a vapor deposition furnace, introducing a protective gas for protection, then heating the material to 500° C. to 700° C. at a rate of 1° C. / min to 5° C. / min, introducing a mixed gas of a silicon source gas and the protective gas at a volume ratio of 1:20 to 1.5:1, and maintaining the temperature for 0.5 to 12 hours, so that silicon elements decomposed by the silicon source gas are deposited in the pores and on the surface of the porous ceramic material and grow into nanometers, and stopping the introduction of the silicon source gas to obtain a semi-finished material; The carbon coating process is a vapor-phase carbon coating process, specifically comprising: adjusting the temperature of the vapor deposition furnace to 500° C. to 600° C. under a protective gas environment, then introducing a mixture of a carbon source gas and the protective gas at a volume ratio of 1:10 to 1:1, and maintaining the mixture for 3 to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the outer surface of the semi-finished material to form a carbon coating layer, thereby finally obtaining a porous ceramic-based silicon-carbon negative electrode material; Wherein, the protective gas includes nitrogen and / or argon; the flow rate of the protective gas is 5L / min to 30L / min; The silicon source gas includes one or more gases selected from monosilane, disilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorodisilane; the flow rate of the silicon source gas is 5 L / min to 50 L / min; The carbon source gas includes one or more of methane, acetylene, ethylene or propylene; the flow rate of the carbon source gas is 5L / min to 50L / min.

12. A lithium ion battery, characterized in that: The lithium-ion battery comprises the porous ceramic-based silicon-carbon negative electrode material according to any one of claims 8-9, or the porous ceramic-based silicon-carbon negative electrode material prepared by the preparation method according to any one of claims 10-11.

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