Synthesis of High-Performance Silicon Suboxide Composite Materials from Natural Silicon Minerals: Methods and Applications

Abstract

This invention provides a method and application for synthesizing high-performance silicon suboxide composite materials from natural silicon minerals. The method includes: mixing natural silicon mineral powder and silicon powder in a certain proportion, reacting them fully under vacuum and high temperature to generate a first precursor; then mixing with a lithium source and sintering in an oxygen-free environment to obtain a second precursor; further modifying the precursor to obtain a third precursor; and performing negative pressure chemical vapor deposition carbon coating in a mixed atmosphere of organic carbon source and inert atmosphere to obtain the high-performance silicon suboxide composite material. The silicon suboxide composite material is a complex of silicon suboxide, lithium silicate, silicon, and carbon, and can be used as a negative electrode material in electrode material preparation. This invention successfully synthesizes a high-performance silicon suboxide composite pre-lithiation material, effectively improving the cycle stability and first coulombic efficiency of silicon suboxide as a negative electrode; the coating layer is dense, the technical operation is simple, the raw material cost is low, the preparation process is simple, suitable for large-scale mass production applications, and has commercial prospects.

Description

Technical Field

[0001] This invention relates to the field of new materials technology for energy storage and lithium-ion batteries, specifically to the synthesis of high-performance silica-suboxide composite materials from natural silicon minerals, methods thereof, and applications. Background Technology

[0002] The theoretical specific capacity of silicon suboxide anode materials is as high as 2600 mAh / g, nearly 10 times that of commercial graphite anode materials. Silicon suboxide anode materials are mainly divided into two categories: oxygen-rich silicon suboxide and silicon-rich silicon suboxide. Due to its abundant reserves, low cost, and ease of synthesis, silicon suboxide is considered a mainstream alternative to elemental silicon. Furthermore, compared to elemental silicon, silicon suboxide exhibits smaller volume changes during cycling. During the first lithiation process, the in-situ generated lithium oxide and lithium silicate can buffer the larger volume changes, thereby improving cycle stability. Despite these advantages, silicon oxides also have some drawbacks that hinder their widespread application. First, silicon suboxide is a material with low inherent conductivity, which reduces electrochemical activity. Second, although the volume change problem is not as severe as in elemental silicon, it is not negligible. Third, the initial coulombic efficiency (ICE) of silicon oxides is relatively low, which is related to the irreversible formation of lithium oxide and lithium silicate in the first cycle.

[0003] In practical applications, the performance of silicon suboxide is still unsatisfactory. To address the problems of expansion, failure, and low coulombic efficiency in silicon suboxide anode materials, various anode modification methods have been developed in the industry, including silicon oxidation, nano-sizing, composite processing, porosimetry, alloying, pre-lithiation, and pre-magnesiation. Among these, coating modification of silicon suboxide is a commonly used and effective method. The coating layer can not only improve the conductivity of silicon suboxide materials but also absorb the stress accumulation caused by the volume change of the internal silicon material, thereby improving the cycle stability and initial coulombic efficiency of silicon suboxide as an anode. At the same time, the coating layer can also suppress the severe gas generation problem of silicon-based materials under alkaline conditions and the slurry flocculation problem caused by alkalinity.

[0004] However, conventional coating processes cannot effectively address the alkalinity issue arising after pre-lithiation of silicon-oxygen materials, nor the resulting gas generation problem in alkaline environments. Furthermore, since gas-phase coating is not a completely closed process, the material can slowly absorb moisture, carbon dioxide, and other substances from the air, leading to denaturation. Therefore, researching a method to improve the alkalinity and reactivity of the material before coating is of great significance. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a silicon oxide composite pre-lithiation material with a dense coating layer and a simple preparation process. Another objective of this invention is to provide a method for improving the alkalinity and reactivity of the material before silicon oxide coating.

[0006] To achieve the above objectives, the present invention provides a method for preparing high-performance silica-substrate composite materials synthesized from natural silica minerals, the method comprising:

[0007] Natural silica mineral powder and silica powder are mixed in a certain proportion and reacted fully under vacuum and high temperature to generate the first precursor.

[0008] The first precursor was mixed with a lithium source and sintered in an oxygen-free environment to obtain the second precursor.

[0009] The second precursor was modified to obtain the third precursor;

[0010] The third precursor was carbon-coated by negative pressure chemical vapor deposition in a mixed atmosphere of organic carbon source and inert atmosphere to obtain a high-performance silica-suboxide composite material.

[0011] Optionally, the natural silicon mineral powder has a purity of ≥98% and a particle size of 1–50 μm, and the silicon powder has a purity of ≥98% and a particle size of 1–50 μm.

[0012] Alternatively, the natural silica mineral powder may include one or more of opal, obsidian, diatomaceous earth, and quartz.

[0013] Alternatively, the mass ratio of silicon to natural silicon mineral powder is 1:(1-4).

[0014] Alternatively, the vacuum high-temperature reaction temperature is 900–1600°C, and the reaction time is 0.5–6 h.

[0015] Alternatively, the first precursor is silicon suboxide (SiO2). x Negative electrode material, the SiO x In this context, 0 < x < 2, and the D50 particle size ranges from 1 to 12 μm.

[0016] Optionally, the lithium source accounts for 1% to 30% of the total mass of the first precursor and the lithium source mixture, and the vacuum degree of the reaction environment for sintering the first precursor and the lithium source is not higher than 5 Pa.

[0017] Alternatively, the sintering is performed using a dynamic pre-lithiation device, which includes a feed inlet, a receiving area, a reaction chamber, a vacuum unit, an atmosphere unit, and a stirring structure, with a stirring speed of 1 to 10 rpm.

[0018] Alternatively, the dynamic pre-lithiation device has the ability to maintain a certain atmospheric or vacuum environment.

[0019] Alternatively, the material of the reaction chamber may include one or more of molybdenum alloy, Monel alloy, 314S stainless steel, and 310S stainless steel.

[0020] Alternatively, the second precursor is silicate, silicon, and SiO2. x A complex.

[0021] Alternatively, the modification may include the following steps:

[0022] The second precursor is dispersed in an organic solvent and stirred continuously to obtain a dispersion by uniformly dispersing the material.

[0023] The surface-modifying agent was added to the dispersion and mixed with water as an initiator. After the reaction was complete, the mixture was dried to obtain the modified precursor powder.

[0024] The modified precursor powder was annealed in an inert atmosphere, and the annealed product was ultrasonically vibrated and sieved to obtain the third precursor.

[0025] Alternatively, the organic solvent may include one or more of methanol (CH3OH), ethanol (C2H5OH), dimethyl ether (DME), dimethyl carbonate (DMC), N-methylpyrrolidone (NMP), and ethyl acetate (C4H8O2).

[0026] Alternatively, the modified pharmaceutical product may include one or more of sodium fluoride (NaF), polyvinylidene fluoride (PVDF), N-fluorobis(benzenesulfonamide) (NSFI), ammonium fluoride (NH4F), and ammonium hydrogen fluoride (NH4HF2).

[0027] Alternatively, the mass ratio of the dispersion to the modified drug is 1:(0.01 to 0.5).

[0028] Optionally, the mechanical stirring speed of the mixing process is 500-800 rpm, the mechanical stirring time is 0.5-3 hours, and the heating temperature is 25℃-80℃.

[0029] Alternatively, the annealing temperature is 300℃~900℃, and the holding time is 2~6h.

[0030] Alternatively, the organic carbon source may include one or more of methane, acetylene, ethylene, and propylene.

[0031] Alternatively, the inert atmosphere may include one or more of nitrogen, argon, and helium.

[0032] Alternatively, the volume ratio of the organic carbon source to the inert atmosphere is 1:1 to 6.

[0033] Alternatively, the temperature of the chemical vapor deposition reaction is 700℃~900℃, and the reaction time is 30~120min.

[0034] Alternatively, the negative pressure chemical vapor deposition reaction uses a negative pressure CVD device to carbon-coat the third precursor, the negative pressure CVD device including an inlet, an outlet, a heating unit and a vacuum unit.

[0035] Another aspect of the present invention provides a high-performance silica-suboxide composite material synthesized from natural silicon minerals. The composite material is prepared by the above-described method, and the high-performance silica-suboxide composite material is a complex of silica-suboxide, lithium silicate, silicon, and carbon.

[0036] Optionally, the composite material has a D50 particle size of 1–12 μm, a silicon suboxide mass percentage of 1%–9%, ​​a lithium silicate mass percentage of 1%–79%, a silicon mass percentage of 20%–80%, and a carbon mass percentage of 0%–10%.

[0037] In another aspect, the present invention provides an application of a high-performance silicon suboxide composite material as a negative electrode material in the preparation of electrode materials, wherein the silicon suboxide composite material is the aforementioned composite material.

[0038] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0039] 1) This invention successfully synthesizes high-performance silicon suboxide composite pre-lithiation materials, which effectively improves the cycle stability and first coulombic efficiency of silicon suboxide as a negative electrode.

[0040] 2) The coating layer of this invention is dense, the technical operation is simple, and the coating effect is improved; it solves the common gas generation problem of silicon-based anode materials and the pulping and coating problem caused by excessively high pH.

[0041] 3) The raw materials of this invention are inexpensive, the preparation process is simple, it is suitable for large-scale mass production and has commercial prospects. Attached Figure Description

[0042] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0043] Figure 1 A schematic diagram of the dynamic pre-lithiation device in exemplary embodiment 1 of the present invention is shown.

[0044] Figure 2 A schematic diagram of the negative pressure CVD device in exemplary embodiment 1 of the present invention is shown.

[0045] Figure 3The SEM image of the third precursor prepared in Example 1 of the present invention is shown.

[0046] Figure 4 The SEM image of the silica-suboxide composite material prepared in Example 1 of the present invention is shown.

[0047] Figure 5 The diagram shows the first charge-discharge curve of the silicon suboxide composite material prepared in Example 1 of the present invention.

[0048] Explanation of key figure labels:

[0049] 1-Receiving area; 2-Feed inlet; 3-Reaction chamber; 4-Stirring shaft; 5-Vacuum unit; 6-Atmosphere unit; 7-Discharge outlet; 8-Heating unit; 9-Furnace body; 10-Feed inlet; 11-Vacuum unit. Detailed Implementation

[0050] In the following sections, the method and application of synthesizing high-performance silica-suboxide composite materials from natural silica minerals according to the present invention will be described in detail with reference to exemplary embodiments.

[0051] Exemplary Example 1

[0052] This exemplary embodiment provides a method for preparing high-performance silica-substrate composite materials from natural silica minerals, the method comprising the following steps:

[0053] S10: Natural silica mineral powder and silica powder are mixed in a certain proportion and reacted fully under vacuum and high temperature to generate the first precursor.

[0054] In this embodiment, the purity of the natural silicon mineral powder is ≥98%, such as 98%, 99%, or 99.5%, and the particle size is 1–50 μm, such as 2 μm, 10 μm, 25 μm, 30 μm, or 49 μm; the purity of the silicon powder is ≥98%, such as 98%, 98.9%, or 99.9%, and the particle size is 1–50 μm, such as 2 μm, 10 μm, 25 μm, 30 μm, or 49 μm; the purity of the raw materials affects the consistency and purity of each batch of product. Excessive levels of gold impurities and magnetic foreign matter in raw materials are not permitted for use in battery materials, as subsequent demagnetization is difficult to complete. The national standard for battery anode materials requires gold impurities to be ≤0.1pp. The uniformity of particle size and a certain particle size difference can ensure the homogeneity of the two materials during solid-phase mixing, which is beneficial to improving the product yield of the process. At the same time, the smaller the particle size, the lower the reaction temperature required, the faster the reaction rate, and the less energy consumed. However, if the particle size is too small, serious problems of material slippage and stratification and material loss with exhaust will occur.

[0055] The natural silica mineral powder includes one or more of opal, obsidian, diatomaceous earth, and quartz; the mass ratio of silica to natural silica mineral powder can be 1:(1-4), such as 1:1, 1:2, or 1:4. When the mass ratio of silica to natural silica mineral powder is within a certain range, the specific capacity and coulombic efficiency of the material can be finely controlled by adjusting parameters such as temperature, pressure, and particle size difference. If the ratio is lower or higher than a certain level, the capacity, coulombic efficiency, and cycle performance of the material will become out of control and extremely poor, making adjustment impossible.

[0056] In this embodiment, the temperature at which the natural silicon mineral powder and silicon powder fully react in a vacuum high-temperature environment can be 900–1600°C, for example, 910°C, 1000°C, 1200°C, 1450°C, or 1590°C; the reaction time can be 0.5–6 hours, for example, 0.6 hours, 1 hour, 3 hours, 5 hours, or 5.9 hours; the two materials need to react at a temperature higher than the critical temperature but lower than the upper limit temperature. Below the critical temperature of 900°C, the reaction product has poor performance and the reaction yield is extremely low, and even extending the reaction time cannot improve the yield; above the upper limit temperature of 1600°C, the material sublimation deposition rate becomes faster. On the one hand, the uniformity of the material will be greatly affected, and on the other hand, the increased temperature will change the crystallinity of the product, resulting in a higher oxygen content and extremely severe capacity decay. The reaction is based on the symbiotic phenomenon of multiple materials. If the temperature is too low, the mixture will not sublimate, and if the temperature is too high, the mixture will undergo rapid single-phase sublimation. Therefore, the process needs to control the temperature within a certain range and extend the reaction time to control the silicon-oxygen ratio of the product to meet the requirements.

[0057] In this embodiment, the first precursor is silicon suboxide (SiO2). x Anode material, SiO x In this context, 0 < x < 2, and the D50 particle size can be 1–12 μm, such as 2 μm, 3 μm, 8 μm, or 9 μm. This is because the first precursor needs to be mixed and sintered with the lithium source. Solid-state mixing and sintering is influenced by factors such as temperature, pressure, particle size, and particle size difference (mixing uniformity). Due to the adhesiveness of the lithium source at high temperatures, if the uniformity of material mixing cannot be guaranteed during the solid-state mixing of the precursor, the sintered product will exhibit agglomeration and grain growth problems. Furthermore, the particle size of commercial anode materials is generally controlled between 2 and 15 μm. If the precursor particle size is too large, coupled with subsequent modification and coating treatments, the particle size will not meet commercial standards, making the process unsuitable for commercialization.

[0058] S20: The first precursor is mixed with a lithium source and dynamically sintered in an oxygen-free environment to obtain the second precursor.

[0059] In this embodiment, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium nitride, lithium hydride, lithium oxide, lithium amide, methyl lithium, and hexyl lithium. After the lithium source is mixed with the first precursor, the total lithium source accounts for 1% to 30% of the total mass of the mixture, such as 2%, 6%, 15%, 20%, or 29%. If the lithium source proportion is too low, it will be impossible to improve the material's first-efficiency to ≥85% of the standard coulombic efficiency of commercial batteries. If the lithium source proportion is too high, it will seriously reduce the capacity parameters of the material. Therefore, it is necessary to control the lithium source proportion within a certain balance range to balance the relationship between the capacity and first-efficiency parameters of the modified material. The sintering temperature of the first precursor and the lithium source can be 500℃~900℃, such as 510℃, 600℃, 780℃, 820℃ or 890℃; the holding time can be 2~6h, such as 3h, 4h or 5h. Solid-state sintering is to form a lithium silicate layer on the surface of the first precursor. This reaction requires a certain temperature. Below the critical temperature, the reaction cannot proceed or is insufficient, resulting in obvious residual lithium phenomena in the material, such as heating upon contact with water or open flame, heating upon standing, and exceeding the acidity or alkalinity limit. Above the upper limit temperature, the phase of lithium silicate will change, causing the material's performance to degrade or even be lost. Therefore, this reaction needs to be controlled within a certain temperature range, and the reaction time needs to be extended to improve the fullness and uniformity of surface modification.

[0060] The vacuum level of the reaction environment should not exceed 5 Pa. The vacuum level is achieved by using a vacuum pump. If the vacuum level is too high, it will cause oxidation and failure of the materials and lithium source. Generally, it should not exceed 5 Pa. The upper limit of commercial Roots pumps in China is generally around 2 Pa. There is no lower limit to the vacuum level, the lower the better. At the same time, there is an upper limit to the vacuum pump.

[0061] In this embodiment, the sintering of the first precursor with the lithium source is accomplished using a dynamic pre-lithiation device, such as... Figure 1 As shown, because the lithium source has wettability after heating, dynamic stirring can obtain a uniform product without causing silicon suboxide particles to agglomerate, while also avoiding excessive lithium source residue. The main structure of the device includes a stirring structure, in which the stirring shaft 4 can rotate at 1 to 10 rpm, more preferably 1 to 5 rpm. Dynamic stirring is used to improve the uniformity of the reaction product. In a static state, the lithium source will exhibit local agglomeration as the temperature rises. This phenomenon will lead to the growth of precursor particles and an increase in the silicon-oxygen ratio, which will greatly damage the material's cycle performance. If the rotation speed is too slow, the problem of local lithium agglomeration cannot be solved; if the rotation speed is too fast, centrifugal stratification between the solid phases and a large amount of powder will be lost with the exhaust gas will occur.

[0062] In this embodiment, as Figure 1As shown, the dynamic pre-lithiation device has the ability to maintain a certain atmosphere or vacuum environment, and also has a reaction chamber 3 that is heated to maintain a certain temperature; the device is equipped with a feed inlet 2, a receiving area 1, a vacuum unit 5, and an atmosphere unit 6. The material of the reaction chamber 3 is very critical. Given that traditional ceramic materials cannot withstand rapid temperature rises and falls, and traditional alloy materials cannot withstand the alkaline corrosion problem caused by the lithium source, the material of the reaction chamber 3 can be one or more of the following: molybdenum alloy, Monel alloy, 314S stainless steel, and 310S stainless steel.

[0063] In this embodiment, the second precursor is silicate, silicon, and SiO. x A complex.

[0064] S30: Modify the second precursor to obtain the third precursor.

[0065] In this embodiment, modifying the second precursor includes the following steps:

[0066] S31: The second precursor is dispersed in an organic solvent and stirred continuously to obtain a dispersion by uniformly dispersing the material.

[0067] In this embodiment, the organic solvent may be one or more selected from methanol (CH3OH), ethanol (C2H5OH), dimethyl ether (DME), dimethyl carbonate (DMC), N-methylpyrrolidone (NMP), and ethyl acetate (C4H8O2). Adding the second precursor to the organic solvent requires continuous stirring to ensure uniform dispersion of the material and obtain a dispersion. The second precursor does not react with the organic solvent; the organic solvent serves only as a dispersion system for fluorination modification, and the amount of organic solvent is sufficient to ensure uniform dispersion of the second precursor.

[0068] S32: Add the surface-modifying drug solution to the dispersion and mix and stir. At the same time, add an appropriate amount of water as an initiator and react fully. Then dry to obtain the modified precursor powder.

[0069] In this embodiment, the modified drug can be one or more of sodium fluoride (NaF), polyvinylidene fluoride (PVDF), N-fluorobis(benzenesulfonamide) (NSFI), ammonium fluoride (NH4F), and ammonium hydrogen fluoride (NH4HF2). The mass ratio of the second precursor to the modified drug can be 1:(0.01-0.5), such as 1:0.02, 1:0.08, 1:0.1, 1:0.3, or 1:0.49. The amount of fluoride used in the modification of the second precursor needs to be controlled according to the acidity or alkalinity of the material. If the amount is too small, the acidity or alkalinity of the modified product will be too high, which is not conducive to the subsequent dense carbon coating process. If the amount is too large, the excess fluoride will damage the process equipment, and the excess fluoride will also lead to a decrease in material performance and an increase in gas production problems.

[0070] In this embodiment, the modified drug solution and the second precursor dispersed by the organic solvent are mixed by stirring. The stirring speed can be 500-800 rpm, such as 550 rpm, 600 rpm or 780 rpm, and the stirring time can be 2-6 h, such as 3 h, 4 h or 5 h. The heating temperature during the stirring process can be 25℃-80℃, such as 26℃, 30℃, 50℃, 60℃ or 79℃, to improve the reaction rate and the uniformity of co-precipitation.

[0071] In this embodiment, the modified drug solution can be dissolved and dispersed using an appropriate amount of pure water, or dissolved and decomposed using an appropriate amount of organic solvent. Different solvents are required for different modified drugs. The solvent only serves as a dispersion system and only needs to be able to dissolve the modified drug. The powder reacts with the fluorinating agent in the dispersion system in the form of a suspension.

[0072] In this embodiment, while the modified drug is mixed with the dispersion, an appropriate amount of water is added as an initiator to allow the reaction to proceed fully. After drying, the modified precursor powder can be obtained. The total amount of water can be 1 to 1.5 times the mass of the powder, and the specific amount can be adjusted according to the properties of the modified drug.

[0073] S33: The modified precursor powder is annealed in an inert atmosphere, and the annealed product is ultrasonically vibrated and sieved to obtain the third precursor.

[0074] In this embodiment, the modified precursor powder is annealed in an inert atmosphere. The annealing temperature can be 300℃~900℃, such as 310℃, 380℃, 650℃, 760℃ or 899℃. The annealing holding time can be 2~6h, such as 3h, 4h or 5h. Annealing can improve the density of the coating layer and also improve the crystallinity of the precursor.

[0075] The annealed product is then sieved using ultrasonic vibration to obtain the third precursor. The ultrasonic vibration sieving is determined according to the particle size standards of commercial anode materials. Generally, an ultrasonic vibrating screen with a lower limit of 500 mesh is used for sieving. For irregular ultrafine powders, the screen aperture is generally selected to be twice the particle size of the powder.

[0076] S40: The third precursor is carbon-coated by negative pressure chemical vapor deposition in a mixed atmosphere of organic carbon source and inert atmosphere to obtain a high-performance silicon suboxide composite material.

[0077] In this embodiment, the organic carbon source can be one or more of methane, acetylene, ethylene, and propylene, and the inert atmosphere includes one or more of nitrogen, argon, and helium. The volume ratio of the organic carbon source to the inert atmosphere can be 1:1 to 6, for example, 1:2, 1:3, or 1:5. This volume ratio determines the cracking rate, propulsion rate, and deposition rate of the carbon source gas during the carbon coating process. Excessively fast cracking and deposition rates can lead to longitudinal growth of nano-carbon, which is detrimental to the formation of a dense carbon layer. Conversely, an excessively slow propulsion rate will prevent the downstream material from forming a carbon coating layer. Due to the size of the process equipment, the carbon source gas and the driving gas (i.e., the inert gas) need to be adjusted according to the equipment dimensions.

[0078] In this embodiment, the temperature of the chemical vapor deposition reaction can be 700℃~900℃, such as 710℃, 750℃, 850℃, 860℃ or 899℃, etc., and the reaction time can be 30~120min, such as 31min, 50min, 90min, 100min or 119min, etc. Different carbon source gases require different temperatures for decomposition. Too high a temperature will lead to an excessively rapid decomposition rate of the carbon source gas, resulting in accelerated longitudinal growth of the carbon coating layer and severe carbon deposition. Too low a temperature will result in insufficient decomposition of the carbon source gas, leading to severe gelation problems. Therefore, the temperature needs to be controlled within a certain range, while adjusting the carrier gas volume and decomposition time to achieve the goal of forming a uniform carbon coating layer. The negative pressure chemical vapor deposition reaction uses a negative pressure CVD device to carbon-coat the third precursor, such as... Figure 2 As shown, the negative pressure CVD device includes a feed inlet 10, a discharge outlet 7, a heating unit 8, and a vacuum unit 11.

[0079] In this embodiment, the negative pressure CVD device preferably adopts an intermittent gas-inlet pyrolysis principle. That is, after the material enters the furnace body 9, a vacuum is created inside the furnace body 9, and a certain amount of carbon source and inert gas mixture is simultaneously introduced for pyrolysis. The pressure is controlled at a negative pressure level. After pyrolysis for a period of time, the vacuum is maintained, and this process is repeated. The pyrolysis time is determined by the feed rate, the carbon source ratio of the carrier gas, and the required coating amount. This device reduces the pyrolysis temperature of the carbon source gas, effectively avoiding phase changes in the third precursor; it improves the pyrolysis efficiency of the carbon source gas, while also enhancing the density and stability of the carbon coating layer.

[0080] Meanwhile, the furnace body can be rotated using a variable frequency drive to lift the material, resulting in a more uniform carbon coating. The negative pressure CVD unit has the ability to maintain a stable vacuum, control the gas intake, and maintain the heating temperature. The unit includes a feed inlet, a discharge outlet, a heating unit, and a vacuum unit. The material of the furnace body is also crucial; the inner and outer parts are generally made of the same material to prevent equipment damage and hazards caused by different coefficients of thermal expansion during heating. Traditional alloy materials have a strong ability to accumulate carbon, easily leading to carbon buildup on the tube walls and unstable coating. The furnace body can preferably be made of one or more of the following: molybdenum alloy, Monel alloy, 314S stainless steel, and 310S stainless steel.

[0081] In this embodiment, a high-performance silicon suboxide composite material is obtained by carbon coating via negative pressure chemical vapor deposition. The carbon coating amount can be 1% to 12%, for example, 2%, 5%, 8%, 10%, or 11%. Carbon coating is used to improve the conductivity of the material and suppress the expansion problem during battery cycling, since the theoretical specific capacity of carbon is 372 mAh g / g. -1 The theoretical specific capacity of silicon-oxygen materials is 2600 mAh g. -1 Excessive coating will cause the material to be affected by carbon, resulting in a reduction in capacity. Insufficient coating will prevent the formation of a dense carbon coating layer on the surface to suppress volume expansion and low first-efficiency.

[0082] Exemplary Example 2

[0083] This exemplary embodiment provides a high-performance silica-suboxide composite material, which is prepared by the method described in Exemplary Embodiment 1.

[0084] In this embodiment, the high-performance silica-suboxide composite material is a composite of silica-suboxide, lithium silicate, silicon, and carbon. The composite material has a D50 particle size of 1–12 μm, with silica-suboxide accounting for 1%–9% of the mass, lithium silicate accounting for 1%–79% of the mass, silicon accounting for 20%–80% of the mass, and carbon accounting for 0%–10% of the mass. In this high-performance silica-suboxide composite material, silicon is the main capacity provider. The silica structure in the silica-suboxide and the external lithium silicate layer mainly function to suppress the volume expansion of the silicon material and improve the first-efficiency. The carbon coating layer mainly functions to improve the conductivity of the material and suppress the volume expansion. The higher the silicon content, the higher the capacity, but the cycle performance will decrease sharply. The higher the lithium silicate and carbon content, the better the first-efficiency and cycle performance, but the capacity will decrease significantly. It is necessary to control the proportion of each component in the material to optimize the capacity, first-efficiency, and cycle performance to achieve commercial-grade performance.

[0085] Exemplary Example 3

[0086] This exemplary embodiment provides an application of a high-performance silica suboxide composite material as a negative electrode material in the preparation of electrode materials. The high-performance silica suboxide composite material is the silica suboxide composite material described in Exemplary Embodiment 2.

[0087] To better understand the above exemplary embodiment 1 of the present invention, it will be further described below in conjunction with specific embodiments.

[0088] Example 1

[0089] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0090] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0091] 0.37 g of ammonium fluoride was dissolved and dispersed in 30 mL of pure water to obtain a modifier. Then, 5 g of the second precursor (D50 particle size of 5 μm) was added to 20 mL of ethanol and dispersed. The mixture was stirred and reacted with the modifier at room temperature for 40 min, followed by filtration and drying to obtain the precursor. The precursor was statically sintered at 400 °C for 2 h under argon atmosphere to obtain the third precursor-modified pre-lithium silicon suboxide material. The SEM image of the obtained third precursor is shown below. Figure 3 As shown, the coated particles have a uniform coating layer on their surface.

[0092] The aforementioned third precursor was subjected to CVD carbon coating using an acetylene:nitrogen gas ratio of 1:3. The coating temperature was 750℃, the coating time was 2 hours, and the coating amount was 5%, resulting in a silica-suboxide composite material. Figure 4 The image shows the SEM image of the obtained silicon suboxide. As can be seen from the image, after carbon coating, the original coating surface is composed of obvious film-like coatings and dot-like coatings.

[0093] Figure 5 The above-mentioned silicon suboxide composite material's initial charge-discharge curve is shown in the figure at 0.1 Ag. -1 At current density, the discharge specific capacity of this composite material is 1458 mAh g. -1 The initial Coulomb efficiency was 92.2%.

[0094] Example 2

[0095] 1 kg of silicon and 3 kg of opal powder were mixed evenly, heated in a vacuum furnace at 1300 °C for 6 h, ground and dried, and the first precursor silicon suboxide powder was collected.

[0096] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0097] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0098] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0099] Example 3

[0100] 1 kg of silicon and 3 kg of obsidian powder were mixed evenly, heated in a vacuum furnace at 900 °C for 6 h, ground and dried, and the first precursor silicon suboxide powder was collected.

[0101] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0102] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0103] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0104] Example 4

[0105] 1 kg of silicon and 3 kg of quartz powder were mixed evenly, heated in a vacuum furnace at 1450 °C for 6 h, ground and dried, and the first precursor silicon suboxide powder was collected.

[0106] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0107] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0108] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0109] Example 5

[0110] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0111] Weigh 1 kg of the first precursor and 200 g of lithium hydride, mix them evenly, and react them dynamically at 600 °C for 4 h under argon atmosphere until naturally cooled to obtain the second precursor silicate / silicon / SiO. x A complex.

[0112] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0113] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0114] Example 6

[0115] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0116] Weigh 1 kg of the first precursor and 100 g of lithium amide, mix them evenly, and react them dynamically at 700 °C under vacuum for 6 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0117] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0118] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0119] Example 7

[0120] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0121] Weigh 1 kg of the first precursor and 300 g of lithium oxide, mix them evenly, and react them dynamically at 800 °C under vacuum for 5 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0122] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0123] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0124] Example 8

[0125] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0126] Weigh 1 kg of the first precursor and 150 g of lithium hydroxide, mix them evenly, and react them dynamically at 900 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0127] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0128] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0129] Example 9

[0130] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0131] Weigh 1 kg of the first precursor and 180 g of lithium carbonate, mix them evenly, and react them dynamically at 900 °C under vacuum for 4 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0132] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0133] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0134] Example 10

[0135] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0136] Weigh 1 kg of the first precursor and 250 g of lithium amide, mix them evenly, and react them dynamically at 700 °C for 6 h under argon atmosphere until naturally cooled to obtain the second precursor silicate / silicon / SiO. x A complex.

[0137] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0138] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0139] Example 11

[0140] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0141] Weigh 1 kg of the first precursor and 300 g of lithium oxide, mix them evenly, and react them dynamically at 800 °C for 2 h under argon atmosphere until naturally cooled to obtain the second precursor silicate / silicon / SiO. x A complex.

[0142] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0143] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0144] Example 12

[0145] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0146] Weigh 1 kg of the first precursor and 100 g of lithium hydroxide, mix them thoroughly, and react them dynamically at 850 °C for 2 h under argon atmosphere until naturally cooled to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0147] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0148] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0149] Example 13

[0150] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0151] Weigh 1 kg of the first precursor and 200 g of lithium carbonate, mix them evenly, and react them dynamically at 700 °C for 2 h under argon atmosphere until naturally cooled to obtain the second precursor silicate / silicon / SiO. x A complex.

[0152] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0153] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0154] Example 14

[0155] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0156] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0157] 0.42g of sodium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0158] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0159] Example 15

[0160] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0161] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0162] 0.25g of polyvinylidene fluoride was dissolved and dispersed in 30mL of N-methylpyrrolidone to obtain a modifier; then 5g of the above-mentioned second precursor (D50 particle size of 5μm) was added to the modifier, and polyvinylidene fluoride was fully and uniformly coated on the surface of the second precursor by co-precipitation. The precursor was then filtered and dried to obtain the precursor; after static sintering of the above precursor at 300℃ in an argon atmosphere for 2h, the third precursor modified pre-lithium silicon suboxide material was obtained.

[0163] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0164] Example 16

[0165] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0166] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0167] 0.25g of N-fluorobisbenzenesulfonamide was dissolved and dispersed in 30mL of ethyl acetate to obtain a modifier; then 5g of the above-mentioned second precursor (D50 particle size of 5μm) was added to the modifier, and the N-fluorobisbenzenesulfonamide was fully and uniformly coated on the surface of the second precursor by co-precipitation. The precursor was then filtered and dried to obtain the precursor; after static sintering of the above precursor at 900℃ in an argon atmosphere for 6h, the third precursor modified pre-lithium silicon suboxide material was obtained.

[0168] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0169] Example 17

[0170] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0171] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0172] 0.57g of ammonium bifluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0173] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0174] Example 18

[0175] 1 kg of silicon and 2 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0176] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0177] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0178] The third precursor was subjected to CVD carbon coating using an acetylene:nitrogen ratio of 1:3, with a coating temperature of 750℃, a coating time of 2 hours, and a coating amount of 5%, to obtain a silica-suboxide composite material.

[0179] Example 19

[0180] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0181] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0182] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0183] The third precursor was subjected to CVD carbon coating using a gas source ratio of acetylene:propylene:nitrogen = 0.6:0.4:9. The coating temperature was 750℃, the coating time was 4h, and the coating amount was 10%, resulting in a silica-suboxide composite material.

[0184] Example 20

[0185] 1 kg of silicon and 3 kg of diatomaceous earth powder were mixed evenly, heated in a vacuum furnace at 1400 °C for 4 h, and then ball-milled to obtain the first precursor, silicon suboxide powder.

[0186] Weigh 1 kg of the first precursor and 100 g of lithium oxide, mix them evenly, and react them dynamically at 500 °C under vacuum for 2 h until they cool naturally to obtain the second precursor, silicate / silicon / SiO. x A complex.

[0187] 0.37g of ammonium fluoride was dissolved and dispersed in 30mL of pure water to obtain a modifier; then 5g of the above second precursor (D50 particle size of 5μm) was added to 20mL of ethanol and dispersed. After mixing and stirring with the above modifier at room temperature for 40min, the mixture was filtered and dried to obtain a precursor; after static sintering of the above precursor at 400℃ in an argon atmosphere for 2h, a third precursor modified pre-lithium silicon suboxide material was obtained.

[0188] The third precursor was subjected to CVD carbon coating using a gas source ratio of acetylene:propylene:nitrogen = 0.5:0.5:9. The coating temperature was 750℃, the coating time was 1h, and the coating amount was 3%, resulting in a silica-suboxide composite material.

[0189] Experimental Example

[0190] A. Take 0.16g of silica-substrate composite material, 0.02g of carbon black, and 0.5g of 4%wt. PAA binder to form a slurry and coat it to a thickness of 100µm. Record the coating details. After vacuum drying at 100℃ for 8 hours, cut the cells. Using copper foil as the current collector and lithium foil as the counter electrode, assemble an R2032 half-cell and perform electrochemical performance testing.

[0191] B. Perform constant current charge-discharge tests on the battery. Activate the battery with 0.1 A / g for the first three cycles, then cycle 97 times with 0.5 A / g. The upper limit of the charging voltage is 1.5V. Record the specific capacity and cycle performance.

[0192] C. Take 2g of silica-suboxide composite material, add it to 20ml of pure water, stir and disperse for three minutes, filter and centrifuge, and use a pH meter to measure the pH value of the supernatant.

[0193] D. Take 2g of silica-substrate composite material into a 10ml PE self-sealing bag, add 4g of 5%wt. NaOH solution, vacuum seal the bag using a heat sealer, and place it in a 45℃ constant temperature water bath to observe the daily gas production of the PE bag.

[0194] The test results of the silica-suboxide composite materials obtained in Examples 1-20 above are recorded in Table 1.

[0195] Table 1

[0196]

[0197] The data in Table 1 shows that the raw material ratio, lithium source, and carbon content are closely related to the material's performance. Increasing the silicon content in the raw material can effectively improve material performance, but it will reduce the material's first-efficiency and cycle performance. Using lithium sources such as lithium oxide and lithium hydroxide often results in severe pinholes during coating, a problem caused by alkalinity and silicon exposure. Insufficient carbon content also leads to pinholes, while excessive carbon content causes capacity decay. In subsequent commercialization, it is crucial to rationally control the ratios of these parameters to optimize material performance.

[0198] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing a high-performance silica-substrate composite material synthesized from natural silica minerals, characterized in that, The method includes the following steps: Natural silica mineral powder and silica powder are mixed in a certain proportion and reacted under vacuum and high temperature to generate a first precursor; wherein, the natural silica mineral powder includes one or more of opal, obsidian, diatomaceous earth and quartz; the mass ratio of silica to natural silica mineral powder is 1:(1-4); the first precursor is silicon suboxide SiO x Anode material, SiO x In this context, 0 < x < 2, and the D50 particle size is 1–12 μm; The first precursor is mixed with a lithium source and sintered in an oxygen-free environment to obtain the second precursor; the sintering is completed by a dynamic pre-lithiation device, which includes a stirring structure and is dynamically stirred during the sintering process. The second precursor is modified to obtain a third precursor. The modification includes the following steps: dispersing the second precursor in an organic solvent and stirring continuously to obtain a uniform dispersion; adding a surface-modifying agent to the dispersion and stirring, while adding an appropriate amount of water as an initiator to react fully, and then drying to obtain a modified precursor powder; annealing the modified precursor powder in an inert atmosphere, and ultrasonically vibrating and sieving the annealed product to obtain the third precursor; the modifying agent includes one or more of sodium fluoride (NaF), polyvinylidene fluoride (PVDF), N-fluorobis(benzenesulfonamide) (NSFI), ammonium fluoride (NH4F), and ammonium hydrogen fluoride (NH4HF2); the mass ratio of the dispersion to the modifying agent is 1:(0.01-0.5). The third precursor was carbon-coated by negative pressure chemical vapor deposition in a mixed atmosphere of organic carbon source and inert atmosphere to obtain a high-performance silica-suboxide composite material; the volume ratio of organic carbon source to inert atmosphere was 1:1 to 6.

2. The method according to claim 1, characterized in that, The natural silicon mineral powder has a purity of ≥98% and a particle size of 1-50μm; the silicon powder has a purity of ≥98% and a particle size of 1-50μm. The vacuum high-temperature reaction temperature is 900–1600℃, and the reaction time is 0.5–6 hours.

3. The method according to claim 1, characterized in that, The lithium source accounts for 1% to 30% of the total mass of the first precursor and the lithium source mixture, and the vacuum degree of the reaction environment for sintering the first precursor and the lithium source is not higher than 5 Pa. The dynamic pre-lithiation device includes a feed inlet, a receiving area, a reaction chamber, a vacuum unit, an atmosphere unit, and a stirring structure, with a stirring speed of 1 to 10 rpm. The dynamic pre-lithiation device has the ability to maintain a certain atmospheric or vacuum environment. The material of the reaction chamber includes one or more of molybdenum alloy, Monel alloy, 314S stainless steel and 310S stainless steel; The second precursor is silicate, silicon, and SiO. x A complex.

4. The method according to claim 1, characterized in that, The organic solvent includes one or more of methanol (CH3OH), ethanol (C2H5OH), dimethyl ether (DME), dimethyl carbonate (DMC), N-methylpyrrolidone (NMP), and ethyl acetate (C4H8O2).

5. The method according to claim 1, characterized in that, The mechanical stirring speed for the mixing process is 500-800 rpm, the mechanical stirring time is 0.5-3 hours, and the heating temperature is 25℃-80℃. The annealing temperature is 300℃~900℃, and the holding time is 2~6h.

6. The method according to claim 1, characterized in that, The organic carbon source includes one or more of methane, acetylene, ethylene, and propylene; The inert atmosphere includes one or more of nitrogen, argon and helium; The volume ratio of the organic carbon source to the inert atmosphere is 1:1 to 6; The chemical vapor deposition reaction temperature is 700℃~900℃, and the reaction time is 30~120min; The negative pressure chemical vapor deposition reaction uses a negative pressure CVD device to carbon-coat the third precursor. The negative pressure CVD device includes an inlet, an outlet, a heating unit, and a vacuum unit.

7. A high-performance silica-substrate composite material synthesized from natural silica minerals, characterized in that, The composite material is prepared by the method of any one of claims 1-6, and the high-performance silica-suboxide composite material is a composite of silica-suboxide, lithium silicate, silicon and carbon; The composite material has a D50 particle size of 1–12 μm, a silicon suboxide mass percentage of 1%–9%, ​​a lithium silicate mass percentage of 1%–79%, a silicon mass percentage of 20%–80%, and a carbon mass percentage of 0%–10%.

8. The application of a high-performance silica-suboxide composite material as a negative electrode material in the preparation of electrode materials, characterized in that, The silicon suboxide composite material is the composite material described in claim 7.

Images