Titanium-doped silicon-carbon negative electrode material and preparation method thereof

Abstract

The application discloses a titanium-doped silicon-carbon negative electrode material and a preparation method thereof. The preparation method comprises the following steps: S100, mixing a carbon source, a titanium source and a pore-forming agent in water to obtain a first product containing titanium oxide through freeze-drying; S200, calcining the first product in a reducing gas to obtain Ti4O7-doped porous carbon; and S300, performing gas-phase deposition of a silane gas source and a carbon gas source on the outer surface and pores of the Ti4O7-doped porous carbon in an inert gas to obtain a silicon-carbon negative electrode material. The carbon source, the titanium source and the pore-forming agent are mixed in water to generate titanium oxide, and the titanium oxide is calcined by using a reducing gas, so that the titanium oxide is reduced into Ti4O7 with metallic conductivity and high catalytic activity, and the electron transmission is fast and the structure is stable. The silane gas source and the carbon gas source are gas-phase deposited on the Ti4O7-doped porous carbon to generate silicon-carbon active substances in situ, and the structural stability and the conductivity are improved.

Description

Technical Field

[0001] This application relates to the field of anode materials, and in particular to a titanium-doped silicon-carbon anode material and its preparation method. Background Technology

[0002] Currently, lithium-ion batteries, as high-efficiency energy storage devices, are widely used in electric vehicles, portable electronic devices, and renewable energy storage. To further expand the application range of lithium-ion batteries, continuously improving their energy density is a core research direction in the industry. As a key component of lithium-ion batteries, the anode material directly affects the battery's energy storage capacity, charging speed, lifespan, and safety; therefore, breakthroughs in anode material performance are a major limiting factor.

[0003] The theoretical specific capacity of traditional graphite anodes is nearing its physical limit (approximately 372 mAh / g), making it difficult to meet future demands. In contrast, silicon-based anodes offer advantages such as ultra-high theoretical specific capacity (4200 mAh / g) and suitable low lithium intercalation potential (<0.5 V vs. Li / Li). + With its advantages such as abundant element reserves, it is regarded as an ideal choice for the next generation of anode materials.

[0004] However, the large-scale commercialization of silicon-based anodes faces two major challenges: first, the severe volume effect, where silicon undergoes up to 300% volume expansion and contraction during charging and discharging, i.e., lithium insertion / extraction, which easily leads to the breakage of active particles, pulverization of the electrode structure, and damage to the conductive network; second, severe interfacial instability, where continuous volume changes cause the solid electrolyte interfacial film on the particle surface to repeatedly rupture and regenerate, continuously consuming electrolyte and active lithium, and increasing interfacial impedance, thus triggering severe capacity decay and reduced cycle life. Therefore, to improve the quality and stability of anode materials, it is urgent to optimize a preparation process that can produce anode materials with high stability and long service life. Summary of the Invention

[0005] One objective of this application is to provide a titanium-doped silicon-carbon anode material and its preparation method, which is beneficial to improving the stability and service life of silicon-carbon anode materials, optimizing ion transport paths and reaction kinetics, and further enhancing the intrinsic conductivity of silicon-carbon anode materials.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a method for preparing titanium-doped silicon-carbon anode material, comprising the following steps: S100, mixing a carbon source, a titanium source, and a pore-forming agent in water in a liquid phase, and freeze-drying to obtain a first product containing titanium oxide; S200, calcining the first product in a reducing gas to obtain Ti4O7-doped porous carbon; S300, using a silane gas source and a carbon gas source in an inert gas to perform vapor-phase deposition on the outer surface and pores of the Ti4O7-doped porous carbon to obtain a silicon-carbon anode material.

[0007] In some embodiments, the preparation method satisfies at least one of the following conditions: the carbon source is one or more of phenolic resin, formaldehyde resin, urea-formaldehyde resin, furfural resin, furfural ketone resin, acrylic resin, glucose, sucrose, and citric acid; the titanium source is one or more of tetraisopropyl titanate, tetrabutyl titanate, titanium oxysulfate, titanium tetrachloride, titanium isopropoxide, and titanium ethoxide; and the pore-forming agent is one or more of sodium chloride, potassium chloride, ammonium bicarbonate, urea, polyethylene glycol, and polyacrylic acid.

[0008] In some embodiments, the mass ratio of the carbon source, the titanium source, and the pore-forming agent is 1:(0.01~0.5):(1~10).

[0009] In some embodiments, the reducing gas is hydrogen, or a mixture of hydrogen and a protective gas; in the mixture of hydrogen and a protective gas, the volume fraction of hydrogen is 2% to 10%, and the protective gas is argon and / or nitrogen.

[0010] In some embodiments, the preparation method satisfies at least one of the following conditions: the silane gas source is one or more of methane and silane; the carbon gas source is one or more of methane, ethane, propane, acetylene, and propyne; and the inert gas is one or more of nitrogen, argon, and helium.

[0011] In some embodiments, in step S300, the volume flow rate ratio of the silane gas source to the inert gas is 1:(1~10), and the volume flow rate ratio of the carbon gas source to the inert gas is 1:(1~10); the vapor deposition temperature is 500℃~1000℃, and the deposition time is 1h~12h.

[0012] In some embodiments, step S300 includes the following sub-steps: S310, immersing the Ti4O7-doped porous carbon in deionized water and stirring and washing to obtain a second product, wherein the mass ratio of the Ti4O7-doped porous carbon to deionized water is 1:(30~60), and vacuum drying the second product to obtain a third product, wherein the vacuum drying temperature is 50℃~100℃ and the processing time is 10h~24h; S320, using a silane gas source and a carbon gas source in an inert gas to perform vapor phase deposition on the outer surface and pores of the third product to obtain a silicon-carbon anode material.

[0013] In some embodiments, the freeze-drying process is carried out at a temperature of -30°C to -20°C for 12 hours to 36 hours.

[0014] In some embodiments, the calcination temperature in step S200 is 800℃~1000℃, and the treatment time is 1h~5h.

[0015] To achieve the above objectives, this application also provides a titanium-doped silicon-carbon anode material prepared by the aforementioned preparation method, wherein the mass ratio of silicon to carbon in the silicon-carbon anode material is 1:(0.1~9).

[0016] Compared with the prior art, the beneficial effects of this application are as follows:

[0017] (1) In this application, the carbon source, titanium source, and pore-forming agent are first uniformly mixed in water, which is beneficial to improving the mixing uniformity of each component and generating titanium oxide. The freeze-drying method is beneficial to quickly remove the solvent in the mixture, and the removal of solvent by sublimation treatment can reduce the risk of pore collapse caused by liquid surface tension in the traditional drying process, thereby preserving the complete pore structure. Therefore, this application can not only set the pore size, shape, and distribution in the first product by controlling the freezing rate, the type of pore-forming agent, and the amount of pore-forming agent, but also use a reducing gas for calcination, which is beneficial to reduce the titanium oxide to the Magnéli phase Ti4O7 with high conductivity and high catalytic activity, and form Ti4O7-doped porous carbon with a stable carbon skeleton as support and Ti4O7 nanoparticles as active sites at high temperature. It is worth mentioning that the Ti4O7 nanoparticles generated under high temperature calcination are generated in situ in the carbon skeleton and embedded in it. The two are tightly combined, which is beneficial to realize the rapid electron transport and improve the structural stability. Furthermore, by vapor-depositing silane and carbon gas sources on Ti4O7-doped porous carbon to generate silicon-carbon active materials in situ, not only can the silicon-carbon active materials be uniformly and precisely deposited on the channels and outer surface of Ti4O7-doped porous carbon, but the silicon-carbon active materials and Ti4O7-doped porous carbon are also tightly intercalated. In addition, silicon atoms and carbon atoms form strong chemical bonds with carbon atoms on the surface of Ti4O7-doped porous carbon, achieving strong interfacial bonding, thereby improving the strength and conductivity of the silicon-carbon anode material itself.

[0018] (2) This application generates Ti4O7 nanoparticles with high conductivity and good structural stability by calcining at high temperature. These nanoparticles can act as conductive bridges in the anode material, connecting silicon particles and carbon skeletons in the silicon-carbon active material, thereby reducing the internal resistance and charge transfer impedance of the electrode. Furthermore, when Ti4O7 is uniformly dispersed in the carbon skeleton in the form of nanoparticles, it can form an interpenetrating three-dimensional conductive network with the carbon skeleton, ensuring that even when silicon undergoes volume changes, electrons can still quickly reach the surface of the silicon-carbon active material, thus maintaining a high capacity output at high current densities. On the one hand, Ti4O7 nanoparticles with high mechanical strength and thermal stability are embedded in the carbon skeleton, restraining the silicon when it undergoes volume expansion, thus improving the stability of the silicon-carbon anode material in use and in terms of thermal stability. In addition, Ti4O7 nanoparticles can disperse the stress generated by silicon during lithium insertion / extraction, reducing the risk of particle cracking and pulverization, and maintaining the integrity of the electrode. On the other hand, due to the abundant oxygen vacancies and Ti4O7 on the surface, 3+ / Ti 4+Mixed valence states possess high surface energy, which is beneficial for catalyzing electrolyte decomposition and promoting the formation of a dense, uniform, and stable solid electrolyte interface film. A stable solid electrolyte interface film helps reduce the risk of continued electrolyte decomposition, thereby reducing the consumption of active lithium and suppressing side reactions between the silicon surface and the electrolyte, further improving the initial coulombic efficiency. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the preparation process of a titanium-doped silicon-carbon anode material in this application. Detailed Implementation

[0020] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0021] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements and may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0022] When a quantity, concentration, or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range is disclosed as “1 to 5”, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range includes its endpoints and all integers and fractions within that range.

[0023] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0024] like Figure 1It is understood that this application provides a method for preparing titanium-doped silicon-carbon anode material, including the following steps: S100, mixing carbon source, titanium source and pore-forming agent in water in liquid phase, and freeze-drying to obtain a first product including titanium oxide; S200, calcining the first product in a reducing gas to obtain Ti4O7-doped porous carbon; S300, using silane gas source and carbon gas source in an inert gas to perform vapor phase deposition on the outer surface and pores of Ti4O7-doped porous carbon to obtain silicon-carbon anode material.

[0025] It is worth mentioning that this application first uniformly mixes the carbon source, titanium source, and pore-forming agent in water, which is beneficial to improving the mixing uniformity of each component and generating titanium oxide. The freeze-drying method facilitates the rapid removal of solvent from the mixture, and the sublimation treatment reduces the risk of pore collapse caused by liquid surface tension during conventional drying, thus preserving the complete pore structure. Therefore, this application can not only set the predetermined pore size, shape, and distribution in the first product by controlling the freezing rate, the type of pore-forming agent, and the amount of pore-forming agent, but also, by using a reducing gas for calcination, facilitates the reduction of titanium oxide into the highly conductive and catalytically active Magnéli phase Ti4O7, and forms Ti4O7-doped porous carbon at high temperature with a stable carbon framework as support and Ti4O7 nanoparticles as active sites. It is worth noting that the Ti4O7 nanoparticles generated under high-temperature calcination are formed in situ within the carbon framework, and the two are tightly bound, which is beneficial for rapid electron transport and improves structural stability. Furthermore, by vapor-depositing silane and carbon gas sources on Ti4O7-doped porous carbon to generate silicon-carbon active materials in situ, not only can the silicon-carbon active materials be uniformly and precisely deposited on the channels and outer surface of Ti4O7-doped porous carbon, but the silicon-carbon active materials and Ti4O7-doped porous carbon are also tightly intercalated. In addition, silicon atoms and carbon atoms form strong chemical bonds with carbon atoms on the surface of Ti4O7-doped porous carbon, achieving strong interfacial bonding, thereby improving the strength and conductivity of the silicon-carbon anode material itself.

[0026] It is understandable that by generating Magnéli-phase Ti4O7 nanoparticles with high conductivity and good structural stability through high-temperature calcination, they can act as conductive bridges in anode materials, connecting silicon particles and the carbon skeleton in silicon-carbon active materials, thereby reducing the internal resistance and charge transfer impedance of the electrode. Furthermore, when Ti4O7 is uniformly dispersed in the carbon skeleton as nanoparticles, it can form an interpenetrating three-dimensional conductive network with the carbon skeleton, ensuring that electrons can quickly reach the surface of the silicon-carbon active material even when silicon undergoes volume changes, thus maintaining a high capacity output at high current densities. On one hand, the Ti4O7 nanoparticles, with their high mechanical strength and thermal stability, are embedded in the carbon skeleton, restraining the volume expansion of silicon and improving the stability of the silicon-carbon anode material in use and in terms of thermal stability. Moreover, Ti4O7 nanoparticles can disperse the stress generated in silicon during lithium insertion / extraction, reducing the risk of particle cracking and pulverization, and maintaining the integrity of the electrode. On the other hand, due to the abundant oxygen vacancies and Ti4O7 on the surface... 3+ / Ti 4+ Mixed valence states possess high surface energy, which is beneficial for catalyzing electrolyte decomposition and promoting the formation of a dense, uniform, and stable solid electrolyte interface film. A stable solid electrolyte interface film helps reduce the risk of continued electrolyte decomposition, thereby reducing the consumption of active lithium and suppressing side reactions between the silicon surface and the electrolyte, further improving the initial coulombic efficiency.

[0027] Among them, the Magnéli phase is a metal oxide that combines metallic conductivity and chemical stability, formed by the regular absence of oxygen atoms in a regular crystal structure. The introduction of oxygen vacancies leads to the partial loss of Ti... 4+ Restore to Ti 3+ This is beneficial for constructing ultrafast electron transport networks for silicon-carbon anode materials. Furthermore, its ordered crystal structure and strong Ti-O bonds enable the Magnéli phase material to be stably recycled when used as an electrode framework, and provide mechanical support for silicon-carbon anode materials to buffer the volume expansion of silicon.

[0028] In some embodiments, the carbon source can be one or more selected from phenolic resin, formaldehyde resin, urea-formaldehyde resin, furfural resin, furfuryl ketone resin, acrylic resin, glucose, sucrose, and citric acid. Phenolic resin, furfural resin, and furfuryl ketone resin, upon pyrolysis, form glassy carbon or hard carbon with high mechanical strength, which is beneficial for obtaining a porous framework with high structural stability. Glucose, sucrose, and citric acid have good water solubility, thus achieving uniform mixing with the titanium source, and generating gas during pyrolysis to introduce complex channels into the Ti4O7-doped porous carbon. Acrylic resin and urea-formaldehyde resin, after pyrolysis, can in-situ dope nitrogen, oxygen, and other heteroatoms into the carbon framework, thereby improving the surface wettability of the Ti4O7-doped porous carbon and further enhancing its chemisorption performance for lithium ions.

[0029] In some embodiments, the titanium source can be one or more of tetraisopropyl titanate, tetrabutyl titanate, titanium oxysulfate, titanium tetrachloride, titanium isopropoxide, and titanium ethoxide. It is understood that the uniform distribution of tetraisopropyl titanate and tetrabutyl titanate in the liquid phase is beneficial for obtaining highly dispersed Ti4O7 nanoparticles. Titanium oxysulfate is inexpensive and suitable for industrial production, while titanium tetrachloride exhibits high reactivity and low cost. Titanium isopropoxide and titanium ethoxide undergo hydrolysis-condensation reactions in water to form titanium oxides.

[0030] In some embodiments, the pore-forming agent may be one or more of sodium chloride, potassium chloride, ammonium bicarbonate, urea, polyethylene glycol, and polyacrylic acid. It should be understood that sodium chloride and potassium chloride are beneficial for controlling the size and morphology of the pores, while ammonium bicarbonate, urea, polyethylene glycol, and polyacrylic acid decompose to produce gas during high-temperature calcination, leaving no residue in the product, thus eliminating the need for post-treatment.

[0031] In some embodiments, the mass ratio of carbon source, titanium source, and pore-forming agent is 1:(0.01~0.5):(1~10). It should be understood that the mass ratio of carbon source to titanium source can be 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:4, or 1:5, and the mass ratio of carbon source to pore-forming agent can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0032] In other words, when the carbon source content is too high, the carbon skeleton becomes too thick, causing the pores inside the Ti4O7-doped porous carbon to become blocked or collapsed, thus reducing the Ti4O7 content and consequently lowering the volumetric energy density. Conversely, when the carbon source content is too low, the resulting carbon skeleton is too thin to effectively support the porous structure, thus reducing its stability. When the titanium source content is too high, the excess titanium source is prone to agglomeration, forming large TiO2 nanoparticle aggregation regions, disrupting uniformity. When the titanium source content is too low, the Ti4O7 content decreases, thus lowering the volumetric energy density. When the pore-forming agent content is too high, the excess pore-forming agent comes into contact with each other, forming large, irregular voids after washing or melting, rather than an ideal uniform porous network. The resulting carbon skeleton has thin walls and is prone to collapse. Conversely, when the pore-forming agent content is too low, the porosity of the Ti4O7-doped porous carbon is low, resulting in a low specific surface area and limited internal transport channels.

[0033] In other words, selecting appropriate amounts of carbon source, titanium source, and pore-forming agent is beneficial for obtaining Ti4O7-doped porous carbon with good mechanical strength and stability in use.

[0034] In some embodiments, the reducing gas is hydrogen, or a mixture of hydrogen and a protective gas; in the mixture of hydrogen and a protective gas, the volume fraction of hydrogen is 2% to 10%, specifically, the volume fraction of hydrogen can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. The protective gas is argon and / or nitrogen. It is worth noting that hydrogen, as a highly efficient reducing agent, can combine with oxygen in metal oxides at high temperatures to generate water, providing a low oxygen partial pressure environment for TiO2 nanoparticles, which is beneficial for promoting the transformation of TiO2 to Ti4O7. When the reducing gas is a mixture of hydrogen and a protective gas, since the hydrogen concentration is controllable, the reduction process of TiO2 can be selectively stopped at the Ti4O7 stage, further avoiding over-reduction reactions that could generate lower valence oxides (such as Ti2O3) or carbides (TiC).

[0035] In some embodiments, the preparation method satisfies at least one of the following conditions: the silane gas source is one or more of methane and disilane; the carbon gas source is one or more of methane, ethane, propane, acetylene, and propyne; and the inert gas is one or more of nitrogen, argon, and helium. It should be understood that the silicon-hydrogen bonds (Si-H) in methane and disilane have low bond energies and moderate thermal decomposition temperatures, allowing them to cleave under relatively mild conditions to generate highly active silicon atoms or silicon clusters, which are readily nucleated and grown on the Ti4O7-doped porous carbon surface. Alkanes and alkynes have high deposition rates, which is beneficial for forming uniformly distributed silicon-carbon active materials.

[0036] In some embodiments, in step S300, the volumetric flow rate ratio of silane gas source to inert gas is 1:(1~10), and the volumetric flow rate ratio of carbon gas source to inert gas is 1:(1~10); the vapor deposition temperature is 500℃~1000℃, and the deposition time is 1h~12h. Specifically, the volumetric flow rate ratio of silane gas source to inert gas can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10; the vapor deposition temperature can be 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃; and the deposition time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h. By selecting suitable vapor deposition processing conditions and gas flow rate ratios, it is beneficial to obtain silicon-carbon anode materials with good stability.

[0037] In some embodiments, step S300 includes the following sub-steps: S310, immersing Ti4O7-doped porous carbon in deionized water and stirring and washing to obtain a second product, wherein the mass ratio of Ti4O7-doped porous carbon to deionized water is 1:(30~60), and vacuum drying the second product to obtain a third product, wherein the vacuum drying temperature is 50℃~100℃ and the treatment time is 10h~24h; S320, performing vapor phase deposition on the outer surface and pores of the third product using a silane gas source and a carbon gas source in an inert gas atmosphere to obtain a silicon-carbon anode material. It is understood that a small amount of byproducts or other impurities may be generated during high-temperature calcination. These impurities may volatilize, decompose, or react during subsequent vapor phase deposition, thereby contaminating the deposition chamber and easily introducing defects into the silicon-carbon layer, thus affecting the electrochemical performance and structural compactness of the silicon-carbon anode material. Therefore, washing with water and using appropriate washing conditions effectively removes such impurities to improve the stability of the silicon-carbon anode material in use and structural stability.

[0038] In some embodiments, the freeze-drying temperature is -30℃ to -20℃, specifically, the freeze-drying temperature can be -30℃, -29℃, -28℃, -27℃, -26℃, -25℃, -24℃, -23℃, -22℃, -21℃, or -20℃, and the processing time is 12h to 36h, specifically, the processing time can be 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, or 36h. By selecting suitable freeze-drying conditions, channels of suitable size can be introduced into Ti4O7-doped porous carbon.

[0039] In some embodiments, the calcination temperature in step S200 is 800℃~1000℃, specifically 800℃, 850℃, 900℃, 950℃, or 1000℃, and the treatment time is 1h~5h, specifically 1h, 2h, 3h, 4h, or 5h. By selecting suitable calcination conditions, it is beneficial to obtain silicon-carbon anode materials with good performance stability and structural stability.

[0040] This application also provides a titanium-doped silicon-carbon anode material prepared by the aforementioned method, wherein the mass ratio of silicon to carbon in the silicon-carbon anode material is 1:(0.1~9). Specifically, the mass ratio of silicon to carbon can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. It should be understood that the silicon-carbon anode material prepared by the method provided in this application has good stability and service life, further improving the intrinsic conductivity of the silicon-carbon anode material.

[0041] Example 1

[0042] A method for preparing a titanium-doped silicon-carbon anode material includes the following steps:

[0043] (1) Phenolic resin, tetraisopropyl titanate and sodium chloride were mixed evenly in pure water at a mass ratio of 1:0.1:1.5 and then freeze-dried to obtain the first product. The freeze-drying temperature was -20℃ and the drying time was 24h. The mass of phenolic resin was 25g and the mass of pure water was 500g.

[0044] (2) The first product was placed in a box furnace and a mixture of hydrogen and argon was introduced for high-temperature calcination to obtain Ti4O7 doped porous carbon. The volume fraction of hydrogen was 5%, the high-temperature calcination temperature was 850℃, and the calcination time was 2h.

[0045] (3) After washing Ti4O7-doped porous carbon with water and drying it, it is placed in a fluidized bed and silane is introduced under nitrogen protection. The ratio of silane flow rate to nitrogen flow rate is 1:10, and the deposition temperature is 500℃. After silane deposition is completed, methane is introduced under nitrogen protection. After the gas phase deposition is completed, silicon-carbon anode material is obtained. The ratio of methane flow rate to nitrogen flow rate is 1:10. The mass fraction of silicon in the silicon-carbon anode material is 10wt.% and the mass fraction of carbon is 90wt.% (based on a total silicon-carbon mass content of 100wt.%).

[0046] (4) The silicon-carbon anode material, conductive carbon black, carbon nanotubes and binder LA132 were made into a negative electrode sheet with a mass ratio of 94:1:1:4 and the electrical performance was tested.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that in step (1), phenolic resin is replaced with glucose.

[0049] Example 3

[0050] The difference between Example 3 and Example 1 is that in step (1), phenolic resin is replaced with acrylic resin.

[0051] Example 4

[0052] The difference between Example 4 and Example 1 is that in step (1), tetraisopropyl titanate is replaced with titanium oxysulfate.

[0053] Example 5

[0054] The difference between Example 5 and Example 1 is that in step (1), tetraisopropyl titanate is replaced with titanium isopropoxide.

[0055] Example 6

[0056] The difference between Example 6 and Example 1 is that sodium chloride is replaced with urea in step (1).

[0057] Example 7

[0058] The difference between Example 7 and Example 1 is that sodium chloride is replaced with polyethylene glycol in step (1).

[0059] Example 8

[0060] The difference between Example 8 and Example 1 is that the mass ratio of phenolic resin, tetraisopropyl titanate and sodium chloride in step (1) is 1:0.3:1.5.

[0061] Example 9

[0062] The difference between Example 9 and Example 1 is that the mass ratio of phenolic resin, tetraisopropyl titanate and sodium chloride in step (1) is 1:0.05:1.5.

[0063] Example 10

[0064] The difference between Example 10 and Example 1 is that the mass of phenolic resin in step (1) is 35g.

[0065] Example 11

[0066] The difference between Example 11 and Example 1 is that the mass of phenolic resin in step (1) is 10g.

[0067] Example 12

[0068] The difference between Example 12 and Example 1 is that the mass ratio of phenolic resin, tetraisopropyl titanate and sodium chloride in step (1) is 1:0.05:1.

[0069] Example 13

[0070] The difference between Example 13 and Example 1 is that the mass ratio of phenolic resin, tetraisopropyl titanate and sodium chloride in step (1) is 1:0.05:5.

[0071] Example 14

[0072] The difference between Example 14 and Example 1 is that in step (2), the volume fraction of hydrogen in the mixture of hydrogen and argon is 10%.

[0073] Example 15

[0074] The difference between Example 15 and Example 1 is that in step (2), the volume fraction of hydrogen in the mixture of hydrogen and argon is 2%.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 1 is that in step (2), the mixed gas of hydrogen and argon is replaced with argon, and TiO2-doped porous carbon is formed by high-temperature calcination.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 1 is that tetraisopropyl titanate was not used in step (1), and step (2) was to carbonize the first product in an argon atmosphere at 850°C to obtain a porous carbon material. Then, the porous carbon and Ti4O7 powder were mixed in a solid phase at a mass ratio of 99:1 to obtain Ti4O7-doped porous carbon.

[0079] Comparative Example 3

[0080] The difference between Comparative Example 3 and Example 1 is that step (1) did not use tetraisopropyl titanate, and step (2) was: the first product was placed in a box furnace and argon gas was introduced for high-temperature calcination to produce porous carbon.

[0081] Performance testing

[0082] The silicon-carbon anode plates prepared in Examples 1-15 and Comparative Examples 1-3 were tested using the test methods provided in GB / T 24533-2019, and the performance results are shown in Table 1.

[0083] Table 1: Performance Testing of Silicon-Carbon Anode Sheets

[0084]

[0085] As shown in Table 1, comparing Examples 1-7, various titanium sources, carbon sources, and pore-forming agents can all produce silicon-carbon anode materials with good performance stability and electrical properties. Examples 1 and 8-9 show that when the titanium source content is too high, the excess titanium source easily agglomerates, forming large TiO2 nanoparticle aggregation regions, disrupting uniformity. When the titanium source content is too low, the Ti4O7 content decreases, thereby reducing the volumetric energy density. Examples 1 and 10-11 show that when the carbon source content is too high, the carbon skeleton becomes too thick, causing the pores inside the Ti4O7-doped porous carbon to be blocked or collapsed, thus reducing the Ti4O7 content and consequently reducing the volumetric energy density. Conversely, when the carbon source content is too low, the resulting carbon skeleton is too thin and cannot effectively support the porous structure, thus reducing performance stability. As shown in Examples 1 and 12-13, when the content of the pore-forming agent is too high, the excess pore-forming agent comes into contact with each other, forming large, irregular voids after washing or melting, rather than an ideal uniform porous network. The resulting carbon skeleton has thinner walls and is prone to collapse. Conversely, when the content of the pore-forming agent is too low, the porosity of the Ti4O7-doped porous carbon is low, resulting in a low specific surface area and limited internal transport channels. Comparing Examples 1 and 14-15, when the volume fraction of hydrogen in the hydrogen-argon mixture is too high, the excessively strong reducing atmosphere may further reduce Ti4O7 to lower-valence titanium oxides, such as Ti3O5 and Ti2O3, and may even react with carbon to form titanium carbides. Conversely, when the volume fraction of hydrogen in the hydrogen-argon mixture is too low, the reduction kinetics are insufficient, and TiO2 cannot be completely converted into the target product Ti4O7. By comparing Example 1 and Comparative Examples 1 to 3, it can be seen that selecting appropriate preparation conditions is beneficial to obtaining silicon-carbon anode sheets with good electrical properties and stability in use.

[0086] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a titanium-doped silicon-carbon anode material, characterized in that, Including the following steps: S100. A carbon source, a titanium source, and a pore-forming agent are mixed in water in the liquid phase and then freeze-dried to obtain a first product containing titanium oxide. The mass ratio of the carbon source, the titanium source, and the pore-forming agent is 1:(0.01~0.5):(1~10). The freeze-drying temperature is -30℃~-20℃ and the treatment time is 12h~36h. S200. The first product is calcined in a reducing gas to obtain Ti4O7-doped porous carbon. The calcination temperature is 800℃~1000℃ and the treatment time is 1h~5h. The reducing gas is a mixture of hydrogen and protective gas, and the volume fraction of hydrogen in the mixture is 2%~10%. S300. In an inert atmosphere, a silane gas source and a carbon gas source are used to perform vapor phase deposition on the outer surface and pores of the Ti4O7 doped porous carbon to obtain a silicon-carbon anode material.

2. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The carbon source is one or more of the following: phenolic resin, formaldehyde resin, urea-formaldehyde resin, furfural resin, furfural ketone resin, acrylic resin, glucose, sucrose, and citric acid. The titanium source is one or more of tetraisopropyl titanate, tetrabutyl titanate, titanium oxysulfate, titanium isopropoxide, and titanium ethoxide. The pore-forming agent is one or more of sodium chloride, potassium chloride, ammonium bicarbonate, urea, polyethylene glycol, and polyacrylic acid.

3. The preparation method according to claim 1, characterized in that, The protective gas is argon and / or nitrogen.

4. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The silane gas source is one or more of methane and ethyl silane; The carbon source is one or more of methane, ethane, propane, acetylene, and propyne. The inert atmosphere is one or more of nitrogen, argon, and helium.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step S300, the volume flow rate ratio of the silane gas source to the inert atmosphere is 1:(1~10), and the volume flow rate ratio of the carbon gas source to the inert atmosphere is 1:(1~10); the vapor deposition temperature is 500℃~1000℃, and the deposition time is 1h~12h.

6. The preparation method according to claim 1, characterized in that, Step S300 includes the following sub-steps: S310. The Ti4O7-doped porous carbon is immersed in deionized water and stirred and washed to obtain a second product. The mass ratio of the Ti4O7-doped porous carbon to deionized water is 1:(30~60). The second product is vacuum dried to obtain a third product. The vacuum drying temperature is 50℃~100℃ and the processing time is 10h~24h. S320. In an inert atmosphere, a silane gas source and a carbon gas source are used to perform vapor phase deposition on the outer surface and pores of the third product to obtain a silicon-carbon anode material.

7. A titanium-doped silicon-carbon anode material, characterized in that, The silicon-carbon anode material is prepared by any one of the preparation methods described in claims 1 to 6, wherein the mass ratio of silicon to carbon in the silicon-carbon anode material is 1:(0.1 to 9).

Images