A carbon-coated core-shell material and its preparation method, anode material and battery

Abstract

This invention relates to the technical field of carbon-coated core-shell material preparation methods, and particularly to a carbon-coated core-shell material and its preparation method, a negative electrode material, and a battery. The method of this invention includes preparing a pre-precursor solution from a titanium source, a lithium source, a carbon source coating agent, and a solvent; atomizing the pre-precursor solution into droplets; during droplet heating, the titanium and lithium sources in the droplets react first to obtain lithium titanate particles and a first exhaust gas; the lithium titanate particles deposit on the droplet surface to form a shell layer; after the lithium source reaction is complete, the titanium source decomposes into titanium dioxide particles and a second exhaust gas; the titanium dioxide particles deposit inside the droplet to form a core layer, obtaining a composite material powder; sintering the composite material powder in an inert atmosphere; and carbonizing the carbon source coating agent to form a coating layer that coats the shell and core layers to obtain a carbon-coated core-shell material. This method solves the problem of discontinuous or uneven carbon layer distribution in traditional coating methods.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a carbon-coated core-shell material and its preparation method, a negative electrode material, and a battery. Background Technology

[0002] Titanium-based anode materials are a class of lithium-ion battery anode materials that use titanium oxides as the main active material. Existing titanium-based materials exhibit a wide variety of structures. In particular, the emerging carbon composite / coating structures, by introducing a layer of carbon onto the surface of the titanium-based material, greatly improve the electron conductivity between particles. However, traditional coating methods often result in discontinuous or uneven carbon layer distribution, severely affecting the material's conductivity and structural stability. Summary of the Invention

[0003] To address the problem that traditional coating methods often result in discontinuous carbon layer distribution or uneven thickness, this invention provides a carbon-coated core-shell material, its preparation method, a negative electrode material, and a battery.

[0004] To address the problem that traditional coating methods often result in discontinuous carbon layer distribution or uneven thickness, this invention provides the following technical solution: a method for preparing a carbon-coated core-shell material, comprising: providing a titanium source, a lithium source, a carbon source coating agent, and a solvent; preparing a pre-precursor solution from the titanium source, lithium source, carbon source coating agent, and solvent; and atomizing the pre-precursor solution into droplets under an inert atmosphere, wherein during the droplet heating process, the titanium source and lithium source in the droplets first react to obtain lithium titanate particles and a first emission gas, wherein the first emission gas... The lithium titanate particles are deposited on the surface of the droplet to form a shell layer. After the lithium source reaction is completed, the titanium source decomposes into titanium dioxide particles and a second emission gas. The second emission gas is discharged to the outside of the droplet, and the titanium dioxide particles are deposited inside the droplet to form a core layer. Voids are formed between the lithium titanate particles and / or between the titanium dioxide particles. The carbon source coating agent is dispersed in the voids to obtain a composite material powder. The composite material powder is then sintered in an inert atmosphere, and the carbon source coating agent is carbonized to form a coating layer that coats the shell layer and the core layer to obtain a carbon-coated core-shell material.

[0005] Preferably, a titanium source, a lithium source, a carbon source coating agent, an alcohol solvent, and deionized water are provided. The alcohol solvent and deionized water are mixed to obtain a first solvent. A first precursor solution is obtained by mixing the titanium source, lithium source, carbon source coating agent, and the first solvent at a first rotational speed for a first stirring time, wherein the molar concentration of the titanium source is 1.5~5 mol / L, the mass ratio of the alcohol solvent to deionized water is 1:1.2~1:1.5, the molar ratio of the lithium source to the titanium source is 1:1.1~1:10, and the mass ratio of the carbon source coating agent to the titanium source is 1:50~1:100. A dispersant is provided as a second solvent, and the dispersant is any one or more combinations of CMC, PVDF, and PVP. The dispersant and the first precursor solution are mixed... After mixing the bulk solutions, the mixture is first heated in a water bath from room temperature to a first temperature, and then ultrasonically dispersed at a first ultrasonic dispersion power for a first ultrasonic dispersion time to obtain a second precursor solution, wherein the mass ratio of dispersant to titanium source is 1:40~1:60; and an alcohol solvent and citric acid water are provided, and the alcohol solvent and citric acid water are mixed to obtain a third solvent. The third solvent and the second precursor solution are stirred at a second stirring speed for a second stirring time, and the pH of the mixed solution is adjusted to 4~6 to obtain a pre-prepared precursor solution, wherein the volume ratio of alcohol solvent to citric acid aqueous solution is 1:1~1:2, the solubility of citric acid aqueous solution is 5~10 g / L, and the mass ratio of third solvent to titanium source is 1:30~1:60.

[0006] Preferably, the atomization process includes: providing an atomization device, introducing the pre-prepared precursor solution into the atomization device under an inert atmosphere, wherein the power of the atomization device is 1000~2000W, the frequency is 1.2~1.5MHz, the gas flow rate during atomization is 3~5L / min, and the droplet size after atomization is 1~5μm.

[0007] Preferably, the heating process includes: providing a tubular reaction device and connecting the output ends of the tubular reaction device and the atomizing device; heating the tubular reaction device from room temperature to 300~450°C, and then passing the atomized droplets into the tubular reaction device for heating; and depositing lithium titanate particles as a shell layer on the surface of the heated droplets, and then depositing carbon dioxide particles as a core layer inside the droplets, with unreacted carbon source coating agents dispersed on the shell and core layers, forming voids between the lithium titanate particles and / or between the titanium dioxide particles, with the carbon source coating agents dispersed in the voids, and finally depositing the composite material powder on the wall of the tubular reaction device.

[0008] Preferably, the sintering process includes: providing a carbonization device, heating the carbonization device from room temperature to 200-300°C and then placing the composite material powder inside the carbonization device; removing the composite material powder from the wall of the tubular reaction device and placing it inside the carbonization device, sintering the composite material powder inside the carbonization device in an inert atmosphere for 1-2 hours; and removing the sintered product and cooling it to room temperature to obtain a carbon-coated core-shell material.

[0009] Preferably, the titanium source is any one or more combinations of calcium titanate, titanium sulfate, and tetrabutyl titanate; the lithium source is any one or more combinations of lithium carbonate, lithium hydroxide, and lithium acetate; and the carbon source coating agent is any one or more combinations of tannic acid, glucose, and sucrose.

[0010] Preferably, the shell layer has a thickness ranging from 1 to 5 μm, the core layer has a diameter ranging from 0.8 to 7.8 μm, the outer coating layer has a thickness ranging from 100 to 200 nm, and the core and shell materials have a diameter ranging from 1.9 to 13 μm.

[0011] Preferably, the first rotational speed is 40~120 rpm / min, the first stirring time is 5~30 min; the first temperature is 50~100℃, the first ultrasonic dispersion power is 100~200W, and the first ultrasonic dispersion time is 30~80 min; the second stirring speed is 150~200 rpm / min, and the second stirring time is 5~20 min.

[0012] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a carbon-coated core-shell material, prepared by the above-mentioned method for preparing carbon-coated core-shell materials, the core-shell material comprising a shell layer, a core layer, an outer coating layer, and an inner coating layer, wherein the shell layer encapsulates the core layer, the shell layer is lithium titanate particles, and the core layer is titanium dioxide particles; the outer coating layer and the inner coating layer are carbon, the outer coating layer encapsulates the shell layer, and the inner coating layer encapsulates the lithium titanate particles and titanium dioxide particles.

[0013] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a negative electrode material, comprising a current collector stacked in layers and the carbon-coated core-shell material.

[0014] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a battery, the battery comprising a positive electrode material, an electrolyte and the above-mentioned negative electrode material.

[0015] Compared with the prior art, the carbon-coated core-shell material, its preparation method, negative electrode material, and battery provided by the present invention have the following beneficial effects:

[0016] 1. A method for preparing a carbon-coated core-shell material provided in this embodiment of the invention, the method comprising: providing a titanium source, a lithium source, a carbon source coating agent, and a solvent; preparing a pre-prepared precursor solution from the titanium source, lithium source, carbon source coating agent, and solvent; and atomizing the pre-prepared precursor solution into droplets under an inert atmosphere, wherein during the droplet heating treatment, the titanium source and lithium source in the droplets react first to obtain lithium titanate particles and a first emission gas, the first emission gas being emitted to the outside of the droplets, and the lithium titanate particles being released into the droplets. A shell layer is formed by mutual deposition on the surfaces of the lithium source. After the lithium source reaction is completed, the titanium source decomposes into titanium dioxide particles and a second emission gas. The second emission gas is emitted to the outside of the droplet. The titanium dioxide particles are deposited inside the droplet to form a core layer. Voids are formed between the lithium titanate particles and / or between the titanium dioxide particles. The carbon source coating agent is dispersed in the voids to obtain a composite material powder. The composite material powder is then sintered in an inert atmosphere, and the carbon source coating agent is carbonized to form a coating layer that coats the shell and core layers to obtain a carbon-coated core-shell material. This embodiment overcomes the problems of uneven coating, low specific capacity, poor cycle performance, and poor composition controllability in the prior art. It combines the cycle stability of lithium titanate materials with the high specific capacity of titanium dioxide. Through core-shell structure design and uniform amorphous carbon coating, the cycle stability and overall conductivity of the composite material are improved.

[0017] 2. The atomization process defined in this invention includes: providing an atomization device, introducing a pre-prepared precursor solution into the atomization device under an inert atmosphere, wherein the power of the atomization device is 1000~2000W, the frequency is 1.2~1.5MHz, the gas flow rate during atomization is 3~5L / min, and the droplet size after atomization is 1~5μm. Atomization transforms the liquid into small droplets, creating conditions for the subsequent formation of core-shell materials.

[0018] 3. The heating process defined in this invention includes: providing a tubular reaction apparatus and connecting the output ends of the tubular reaction apparatus and an atomizing apparatus; heating the tubular reaction apparatus from room temperature to 300-450°C, and then passing the atomized droplets into the tubular reaction apparatus for heating; and depositing lithium titanate particles as a shell layer on the surface of the heated droplets, followed by the deposition of carbon dioxide particles as a core layer inside the droplets. Unreacted carbon source coating agents are dispersed on the shell and core layers, and voids are formed between the lithium titanate particles and / or between the titanium dioxide particles. The carbon source coating agents are dispersed in the voids, and the final composite material powder is deposited on the wall of the tubular reaction apparatus. The heating process causes the droplets to first form a shell layer. The initial formation of the shell layer provides a physical constraint on the still liquid internal region, and then the core layer is formed, resulting in a lithium titanate-coated titanium dioxide structure.

[0019] 4. The sintering process defined in this invention includes: providing a carbonization device, heating the carbonization device from room temperature to 200-300°C before placing the composite material powder inside the carbonization device; removing the composite material powder from the wall of a tubular reaction device and placing it inside the carbonization device, sintering the composite material powder inside the carbonization device in an inert atmosphere for 1-2 hours; and removing the sintered product and cooling it to room temperature to obtain a carbon-coated core-shell material. In this embodiment, the sintering temperature of the carbonization device is controlled at 200-300°C, far lower than the temperature used for traditional anode material carbonization. This ensures that the shell and core layers already formed in the composite material powder are well preserved, completely avoiding the problems of decreased specific surface area and prolonged lithium-ion diffusion paths caused by particle sintering, growth, and agglomeration under high-temperature conditions.

[0020] 5. This embodiment of the invention also provides a carbon-coated core-shell material. In this embodiment, the core-shell material adopts a layered structure design, with the innermost core layer composed of titanium dioxide particles. Titanium dioxide, as a lithium-ion battery anode material with a high theoretical specific capacity, primarily functions to provide considerable lithium storage capacity for the entire composite material, which is crucial for improving the material's energy density. However, titanium dioxide undergoes certain volume changes during cycling, and its intrinsic electronic conductivity is low. The core layer is tightly wrapped by a shell layer composed of lithium titanate particles. Lithium titanate exhibits minimal crystal volume change during lithium-ion insertion and extraction. This enveloping shell layer plays a vital role in mechanical constraint and stabilization.

[0021] 6. This embodiment of the invention also provides a negative electrode material. The uniform and continuous amorphous outer coating layer on the outside of the core-shell material in this negative electrode material plays a crucial role in the electrode fabrication process. This outer coating layer greatly improves the electrical contact between the active material particles, forming a highly efficient electronic conductive network that runs through the entire electrode coating. This allows electrons collected from the current collector to be transported extremely smoothly to each active particle, significantly reducing the internal impedance and polarization voltage of the electrode.

[0022] 7. The present invention also provides a battery that has the same beneficial effects as the negative electrode material provided in the above embodiments, and therefore will not be described in detail here. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1This is a schematic flowchart of a method for preparing a carbon-coated core-shell material provided in the first embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of droplet atomization forming in a method for preparing a carbon-coated core-shell material according to the first embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the shell forming process in a method for preparing a carbon-coated core-shell material according to the first embodiment of the present invention.

[0027] Figure 4 A schematic diagram of the core layer forming process in a method for preparing a carbon-coated core-shell material according to the first embodiment of the present invention.

[0028] Figure 5 A schematic diagram of the core-shell material forming process provided in the first embodiment of the present invention is shown.

[0029] Figure 6 A schematic diagram of the structure of a carbon-coated core-shell material provided in the second embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] In the embodiments provided by this invention, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0032] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Those skilled in the art should also recognize that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily essential to the invention.

[0033] In various embodiments of the present invention, it should be understood that the sequence number of each process does not necessarily imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process defined by the present invention.

[0034] The flowcharts and block diagrams in the accompanying drawings illustrate methods and possible architectures, functions, and operations according to various embodiments of this application. In this regard, each block in the flowchart or block diagram may represent part of a step. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved.

[0035] Titanium-based anode materials are a class of lithium-ion battery anode materials that use titanium oxides as the main active material. Existing titanium-based materials exhibit a wide variety of structures. In particular, the emerging carbon composite / coating structures, by introducing a layer of carbon onto the surface of the titanium-based material, greatly improve the electron conductivity between particles. However, traditional coating methods often result in discontinuous or uneven carbon layer distribution, severely affecting the material's conductivity and structural stability.

[0036] Traditional coating methods include the following:

[0037] Mechanical mixing method: This method typically involves physically mixing pre-prepared titanium-based materials with a carbon source in a ball mill or high-speed mixer. The impact and rolling of the grinding balls in the mill jar cause the carbon material and titanium-based particles to rub and compress against each other, thus achieving carbon particle adhesion to the surface of the titanium-based material. However, the carbon particles mainly adhere to the surface of the host material through physical adsorption, resulting in weak bonding. If mechanical mixing is used to fabricate battery materials, the particles are prone to detachment during subsequent processing or battery charging and discharging. It only achieves point-to-point contact and cannot form a continuous and complete carbon layer, leading to an imperfect electron conduction network.

[0038] Wet coating method: This method utilizes a solution system to achieve more uniform mixing. First, a soluble carbon source is dissolved in water or an organic solvent to form a homogeneous solution. Then, titanium-based material powder is dispersed into this solution. Through continuous stirring and solvent evaporation, carbon source molecules are uniformly adsorbed onto the surface of the titanium-based particles. After the solvent evaporates, a composite material coated with the carbon source precursor is obtained, which is then subjected to heat treatment for carbonization. In the wet coating method, during solvent evaporation, particles are easily "bridged" together by the carbon source precursor, resulting in severe agglomeration and the formation of large secondary particles, which affects the material properties.

[0039] Furthermore, traditional coating materials typically use carbon to encapsulate silicon-based materials. While silicon possesses a high theoretical specific capacity, it undergoes significant volume expansion during charge and discharge, leading to structural fragmentation. Existing technologies are prone to problems such as uneven material coating, low specific capacity, poor cycle performance, limited composition control, and low energy efficiency. These issues all reduce the material's cycle stability and overall conductivity.

[0040] Please see Figure 1 To address issues such as uneven coating, low specific capacity, poor cycle performance, controllability of composition, and energy efficiency, the first embodiment of this invention provides a method for preparing a carbon-coated core-shell material. The method includes:

[0041] S1. Provide titanium source, lithium source, carbon source coating agent and solvent, and prepare titanium source, lithium source, carbon source coating agent and solvent into a pre-prepared precursor solution;

[0042] S2. The pre-prepared precursor solution is atomized into droplets under an inert atmosphere. During the droplet heating process, the titanium and lithium sources in the droplets react first to obtain lithium titanate particles and a first emission gas. The first emission gas is emitted to the outside of the droplets, and the lithium titanate particles deposit on the droplet surface to form a shell layer. After the lithium source reaction is complete, the titanium source decomposes into titanium dioxide particles and a second emission gas. The second emission gas is emitted to the outside of the droplets, and the titanium dioxide particles deposit inside the droplets to form a core layer. Voids are formed between the lithium titanate particles and / or between the titanium dioxide particles, and the carbon source coating agent is dispersed in the voids to obtain composite material powder; and

[0043] S3. The composite material powder is sintered in an inert atmosphere, and the carbon source coating agent is carbonized to form a coating layer that coats the shell and core layers to obtain a carbon-coated core-shell material.

[0044] Understandably, in step S1, a highly dispersed pre-precursor solution is formed by uniformly mixing the titanium source, lithium source, carbon source coating agent, and solvent in a liquid phase environment. This solution-based mixing method effectively avoids the problems of component segregation, agglomeration, and uneven coating that are prone to occur in traditional mechanical mixing or solid-state sintering. It should be noted that uneven dispersion in the pre-precursor solution directly affects the material morphology during atomization, thus affecting the performance of the final core-shell material. Specifically, the full dispersion of each component in the pre-precursor solution ensures that the reactants can fully contact each other and undergo the expected reaction during subsequent atomization and heat treatment, significantly improving the consistency of the final product's composition and the integrity of its structure.

[0045] Further, in step S2, the precursor solution is atomized under an inert atmosphere to form uniform microdroplets. Each droplet acts as an independent microreactor. During heating, the titanium and lithium sources within the droplets first react to generate lithium titanate (LTO) particles, releasing the first emission gas. The gas release creates micropores and voids inside the droplets, while the lithium titanate particles migrate to the droplet surface due to surface energy effects and deposit to form a shell layer. As the lithium source is consumed, the remaining titanium source further decomposes to generate titanium dioxide (TiO2) particles and releases a second emission gas. The titanium dioxide particles are confined inside the droplets and deposit to form a core. This spontaneously formed "titanium dioxide core-lithium titanate shell" structure fully leverages the volumetric stability advantage of lithium titanate. The shell structure encapsulating it effectively constrains and buffers the volume changes of the internal titanium dioxide during lithium ion insertion / extraction, thereby greatly suppressing the overall cyclic expansion of the material and improving structural stability and cycle life. Meanwhile, the internal voids created by the gas ejected during the reaction provide additional channels for ion migration, facilitating electrolyte wetting and lithium-ion transport. The carbon source coating agent is uniformly dispersed within these voids and between particles, preparing for the subsequent carbonization process to form a continuous carbon-coated structure.

[0046] Furthermore, in step S3, the composite material powder undergoes sintering, and the carbon source coating agent is carbonized to form a coating layer. This coating layer is a two-layer carbon coating structure, comprising an inner coating layer and an outer coating layer. The outer coating layer completely covers the outer surface of the shell, constructing a highly efficient electronic conductivity pathway throughout the entire material particle. The inner coating layer fills the gaps between the core and shell, as well as the pores within the particle, further enhancing the electronic contact between the core and shell, and providing a strong encapsulation and connection for the lithium titanate and titanium dioxide particles. It should be noted that the inner and outer coating layers are not fundamentally different in structure and composition. However, this synergistic carbon coating structure significantly improves the overall conductivity of the composite material, effectively overcoming the bottleneck problem of low intrinsic conductivity in titanium-based materials, enabling the material to maintain excellent electrochemical performance even under high-rate charge-discharge conditions.

[0047] It should be understood that this embodiment overcomes the problems of uneven coating, low specific capacity, poor cycle performance, controllability of composition and energy consumption efficiency in the prior art. It combines the advantages of the cycle stability of lithium titanate material and the high specific capacity of titanium dioxide. Through core-shell structure design and uniform amorphous carbon coating, the cycle stability and comprehensive conductivity of the composite material are improved.

[0048] Further, in step S1 above, preparing the pre-prepared precursor solution includes:

[0049] Provides a titanium source, a lithium source, a carbon source coating agent, an alcohol solvent, and deionized water; mixes the alcohol solvent and deionized water to obtain a first solvent; and

[0050] A first precursor solution is obtained by mixing a titanium source, a lithium source, a carbon source coating agent, and a first solvent at a first rotational speed for a first stirring time, wherein the molar concentration of the titanium source is 1.5~5 mol / L, the mass ratio of the alcohol solvent to deionized water is 1:1.2~1:1.5, the molar ratio of the lithium source to the titanium source is 1:1.1~1:10, and the mass ratio of the carbon source coating agent to the titanium source is 1:50~1:100; and

[0051] A dispersant is provided as a second solvent, wherein the dispersant is any one or more combinations of CMC, PVDF, and PVP. The dispersant and the first precursor solution are mixed and then subjected to water bath heating from room temperature to a first temperature, followed by ultrasonic dispersion at a first ultrasonic dispersion power for a first ultrasonic dispersion time to obtain a second precursor solution. The mass ratio of the dispersant to the titanium source is 1:40 to 1:60.

[0052] An alcohol solvent and citric acid solution are provided. The alcohol solvent and citric acid solution are mixed to obtain a third solvent. The third solvent and the second precursor solution are stirred at a second stirring speed for a second stirring time, and the pH of the mixed solution is adjusted to 4~6 to obtain a pre-prepared precursor solution. The volume ratio of the alcohol solvent to the citric acid aqueous solution is 1:1~1:2, the solubility of the citric acid aqueous solution is 5~10g / L, and the mass ratio of the third solvent to the titanium source is 1:30~1:60.

[0053] The first rotation speed is 40~120 rpm / min, the first stirring time is 5~30 min; the first temperature is 50~100℃, the first ultrasonic dispersion power is 100~200W, and the first ultrasonic dispersion time is 30~80 min; the second stirring speed is 150~200 rpm / min, and the second stirring time is 5~20 min.

[0054] It should be understood that a distribution-dispersion method was used in the preparation of the pre-prepared precursor solution:

[0055] First, an alcohol solvent and deionized water are mixed in a specific mass ratio to form a first solvent. This first solvent is used to dissolve the titanium source, lithium source, and carbon source coating agent. This specific mass ratio effectively balances the solubility of the titanium source in organic solvents with the solubility of the lithium source in inorganic solvents, avoiding the limitations of a single solvent and providing a uniform reaction environment for all reactants. This prevents excessively high local concentrations or component segregation from the outset. It should be noted that in this embodiment, the alcohol solvent can be one or more combinations of ethanol, methanol, or propanol; further details are omitted here.

[0056] Furthermore, the titanium source, lithium source, and carbon source coating agent are mixed with the first solvent under specific low-speed stirring conditions. The purpose is not for high-speed shearing, but to promote the full dissolution and initial dispersion of the solute while avoiding the introduction of excessive air bubbles or excessive solvent evaporation. Strict control over the molar concentration of the titanium source, the lithium-titanium molar ratio, and the mass ratio of the carbon source coating agent to the titanium source ensures precise control over the concentration of each reactant in the precursor solution. The homogeneous mixing of the components at the molecular level in the solution provides a uniform reactant distribution for the subsequent chemical reactions, forming the structural basis for obtaining the ultimately homogeneous composite material.

[0057] It should be noted that the titanium source, lithium source, carbon source coating agent and the first solvent can also be stirred at a speed of 40~80rpm / min, 60~110rpm / min or 50~60rpm / min, and the stirring time can also be 5~10min, 15~20min or 20~30min.

[0058] The mass ratio of alcohol solvent to deionized water is 1:1.2 to 1:1.5, which balances the polarity and properties of the two solvents. As an organic solvent, the alcohol effectively dissolves both the organic titanium source and the carbon source coating agent; while deionized water efficiently dissolves the inorganic lithium source. If the water ratio is too high, for example, if the specific gravity of water is much greater than 1.5, the organic titanium source will undergo severe hydrolysis due to excessive local water content, forming a white titanium dioxide precipitate, leading to reaction failure and disrupting the homogeneity of the precursor solution. If the alcohol solvent ratio is too high, for example, if the specific gravity of the alcohol solvent is much less than 1.2, the inorganic lithium source may not dissolve sufficiently, also resulting in uneven composition. Optionally, the mass ratio of alcohol solvent to deionized water can also be 1:1.3 to 1:1.35. This range ensures that both the organic titanium source and the inorganic lithium source reach a near-saturated dissolution state while maximally suppressing the hydrolysis tendency of the titanium source.

[0059] The molar ratio of lithium source to titanium source, ranging from 1:1.1 to 1:10, directly determines the chemical composition and microstructure of the final product. When the molar ratio is close to 1:1.1, a slight excess of lithium ensures that the titanium source reacts completely to form pure-phase lithium titanate. This slight excess of lithium compensates for lithium volatilization loss during high-temperature processing, guaranteeing the electrochemical performance of the final product. When the ratio reaches 1:10, meaning a significant excess of titanium, the final product will be predominantly titanium dioxide, containing only a small amount of LTO for structural stabilization or conductivity enhancement. Within this range, the thickness of the core and shell layers in the core-shell structure can be precisely controlled. This allows for the achievement of a suitable lithium titanate shell thickness, fully utilizing the coating and stabilizing effect of lithium titanate while retaining sufficient high-capacity titanium dioxide. Optionally, the molar ratio of lithium source to titanium source can also be 1:2 to 1:4. This ratio design provides a sufficient amount of high-capacity titanium dioxide as a core layer to improve the overall specific capacity, and generates a sufficient amount of lithium titanate as a shell layer to encapsulate titanium dioxide.

[0060] The mass ratio of carbon source coating agent to titanium source is 1:50 to 1:100, precisely controlling the thickness and continuity of the carbon coating layer in the final material. If the mass ratio is too low, such as much as less than 1:100, the carbon source content is too low, and a continuous and complete carbon coating layer cannot be formed after subsequent carbonization. This will result in exposed parts of the material surface, limited improvement in electronic conductivity, and inability to effectively suppress side reactions during charging and discharging. If the mass ratio is too high, such as much as greater than 1:50, the excessive carbon source will produce an excessively thick carbon layer. An excessively thick carbon layer will hinder lithium-ion diffusion, leading to a decrease in the material's rate performance; it will also reduce the overall compaction density and volumetric energy density of the material. Optionally, the mass ratio of carbon source coating agent to titanium source can also be 1:60 to 1:80. The carbon content in the carbon source coating agent is sufficient to form a complete and continuous outer coating layer on the outside of the composite material particles through the carbonization process, significantly improving the electronic conduction efficiency between particles. At the same time, an appropriate amount of carbon source can also effectively penetrate into the pores inside the core-shell structure to form an inner coating layer, which tightly connects the lithium titanate shell and the titanium dioxide core, further reducing the interfacial impedance.

[0061] Furthermore, by providing a dispersant as a second solvent, the second solvent and the first precursor solution are mixed and then subjected to heating and ultrasonic dispersion to achieve ultra-uniform dispersion. The dispersant adsorbs onto the surface of the titanium or lithium source, effectively preventing the aggregation of the titanium or lithium source. By heating to 50~100℃ in a water bath and supplementing with 100~200W of ultrasonic energy, the molecular thermal motion is intensified, resulting in more uniform dispersion. Furthermore, the high-temperature and high-pressure microjets generated during ultrasonic dispersion can effectively break up potential nano-agglomerates in the solution, enabling the lithium, titanium, and carbon source coating agent molecules or primary particles to achieve a near-molecular-level dispersion state, forming an extremely stable and uniform second precursor solution. This solves the problems of particle aggregation and uneven distribution that are difficult to avoid with traditional mechanical mixing or ordinary stirring, ensuring a high degree of consistency in the chemical composition of each subsequent atomized droplet.

[0062] It should be noted that the water bath heating temperature can also be 50~80℃, 70~90℃ or 60~100℃, the ultrasonic dispersion power can also be 100~150W, 130~150W or 160~200W, and the ultrasonic dispersion time can also be 30~50min, 40~60min or 70~80min.

[0063] In this process, the mass ratio of dispersant to titanium source is 1:40 to 1:60. The dispersant is a high-molecular-weight polymer whose molecular chains can adsorb onto the surface of nanoparticles or molecular clusters such as titanium and lithium sources. When the mass ratio of dispersant to titanium source is 1:40 to 1:60, the number of dispersant molecules is sufficient to form a dense adsorption layer on the surface of each fine particle. These adsorbed long polymer chains extend into the solvent, effectively preventing particles from approaching, colliding, and agglomerating due to van der Waals forces. If the amount of dispersant is too low, the coating will be incomplete, and agglomeration cannot be effectively suppressed; if the amount of dispersant is too high, the polymer chains may become entangled, causing bridging flocculation or changing the rheological properties of the solution, which is not conducive to subsequent atomization. Optionally, the mass ratio of dispersant to titanium source is 1:45 to 1:55. This mass ratio ensures that the dispersant concentration is significantly higher than the critical minimum effective concentration, providing ample stability for the entire dispersion process. At the same time, this mass ratio is far from the high concentration region that may cause supersaturation, flocculation, or excessive cost, achieving the best balance between effectiveness and cost.

[0064] Furthermore, a third solvent, composed of an alcohol solvent and a citric acid solution, is added, and the pH of the solution is adjusted to a weakly acidic range under a specific stirring speed. Citric acid, as a weak acid, precisely regulates the pH of the solution, ensuring the entire mixture is in its most stable state. This significantly reduces the tendency for the solute to hydrolyze, precipitate, or aggregate due to pH changes during subsequent processing. Additionally, citric acid adjusts the pH, making it more suitable for subsequent ultrasonic atomization processes, producing uniformly sized and stable microdroplets. It should be noted that when the pH of the solution is greater than 6, the concentration of hydroxide ions is extremely high, which will drastically accelerate the hydrolysis reaction of the titanium source, preventing the pre-prepared precursor solution from atomizing. When the pH of the solution is less than 3, the high concentration of hydrogen ions may promote acid-catalyzed dehydration or coking reactions in the carbon source coating agent, affecting the quality of the final carbon coating layer.

[0065] It should be noted that the alcohol solvent is mixed with citric acid water to obtain the third solvent. The third solvent and the second precursor solution can also be stirred at a stirring speed of 150~160 rpm / min, 170~200 rpm / min or 160~180 rpm / min, and the stirring time can also be 5~10 min, 8~15 min or 10~20 min.

[0066] The volume ratio of alcohol solvent to citric acid aqueous solution is 1:1 to 1:2, ensuring sufficient water in the mixed solvent to dissolve and ionize citric acid, allowing it to act as a buffer, while also providing enough alcohol solvent to maintain the polarity balance of the entire solution system, preventing the precipitation of titanium or carbon source coating agents due to the addition of aqueous solution. The citric acid concentration is 5-10 g / L, providing sufficient buffer capacity to regulate and stabilize the pH of large-scale solutions. Optionally, the volume ratio of alcohol solvent to citric acid aqueous solution can also be 1:1.2 to 1:1.5, ensuring more complete dissolution and ionization of citric acid. This also ensures that the alcohol solvent effectively maintains the compatibility of the entire solution system. The mass ratio of the third solvent to the titanium source is 1:30 to 1:60, ensuring that the amount of citric acid added is accurately measured based on the titanium source, avoiding excessive dilution of the pre-prepared precursor solution.

[0067] It should be understood that this embodiment employs a distribution-dispersion method, using a designed solvent system to mix titanium, lithium, and carbon source coating agents, successfully preparing a pre-prepared precursor solution with highly uniform composition and excellent stability. This solution ensures the chemical consistency of each microdroplet during subsequent reactions, serving as a prerequisite for obtaining core-shell materials with uniform coating, precise and controllable composition, and distinct core-shell structure.

[0068] Furthermore, please refer to the following: Figure 2 Atomization processing includes:

[0069] Atomization equipment is provided, in which the pre-prepared precursor solution is introduced into the atomization equipment under an inert atmosphere. The power of the atomization equipment is 1000~2000W, the frequency is 1.2~1.5MHz, the gas flow rate during atomization is 3~5L / min, and the droplet size after atomization is 1~5μm.

[0070] Understandably, the power of the atomizing device is in the range of 1000~2000W. The purpose is to provide a sufficiently high energy density to overcome the surface tension and viscosity of the solution, thereby violently breaking the liquid into micron-sized droplets. If the power is too low, the liquid cannot be effectively broken up, potentially producing droplets with excessively large and uneven distribution, or even forming a continuous liquid flow, leading to incomplete subsequent reactions and product agglomeration. If the power is too high, excessive thermal effects may occur or secondary splashing of droplets may occur, similarly disrupting particle size uniformity and potentially triggering localized pyrolysis of organic matter in the precursor. This power range ensures that ultrasonic energy can be used efficiently and controllably for droplet formation, rather than producing unnecessary side effects. The power of the atomizing device can also be in the range of 1000~1500W, 1300~1800W, or 1500~1600W. The frequency parameter is in the high-frequency range of 1.2~1.5MHz. Higher frequencies can generate more and finer energy points, thus producing smaller and more concentrated droplets. This frequency range, matched with a power of 1000~2000W, ensures that while obtaining fine droplets, each droplet is stably transported in the gas flow and uniformly distributed within the reactor. Simultaneously, high-frequency vibration helps maintain droplet stability, preventing collisions and coalescence during mixing and transport with the gas. Frequency parameters can also be 1.2~1.4MHz, 1.3~1.5MHz, or 1.2~1.3MHz. Furthermore, the gas flow rate is controlled within the range of 3~5L / min. The primary function of the gas flow is to act as a carrier, smoothly and continuously transporting the atomized droplets to the tubular furnace reaction zone. If the flow rate is too low, the carrier gas will lack sufficient power, potentially causing droplets to stagnate, settle, or even re-coalesce into larger droplets in the atomization chamber, compromising the atomization effect. If the flow rate is too high, the gas velocity will be too fast, shortening the droplet residence time in the high-temperature reaction zone, potentially leading to incomplete internal reactions, and excessive shear force may also impact droplet integrity. This flow rate range, in conjunction with the aforementioned power and frequency, ensures that droplets can be efficiently delivered to the reaction zone in the form of diffuse, monodisperse aerosols.

[0071] Specifically, through the synergistic control of the aforementioned multiple parameters, the droplet size was successfully and precisely controlled within a narrow distribution range of 1–5 μm. The extremely small size endows each droplet with a huge specific surface area, allowing it to be heated instantaneously and uniformly during subsequent spray pyrolysis. This enables rapid evaporation of internal moisture and organic solvents, and rapid decomposition and recombination of reactants, significantly improving reaction efficiency and rate. More importantly, each uniformly sized droplet is an independent "microreactor" with completely identical composition. Because the pre-prepared precursor solution has been processed into a highly homogeneous system in the previous steps, each droplet carries the exact same molar proportions of titanium, lithium, and carbon sources. The resulting particles possess a highly regular and structurally uniform core layer of titanium dioxide, a shell layer of lithium titanate, and a carbon-coated core-shell structure.

[0072] It should be noted that the inert atmosphere in this embodiment is an argon or nitrogen atmosphere. The inert gas environment completely isolates oxygen and water vapor, effectively preventing the titanium and carbon sources in the pre-prepared precursor solution from coming into contact with oxygen and undergoing oxidation or metathesis reactions during atomization. This ensures the purity and stability of the chemical composition during the phase transition from solution to droplets, and avoids the deterioration of the final product performance due to the introduction of impurities.

[0073] Furthermore, please combine them together. Figure 3 and Figure 4 The heating process includes:

[0074] Provides tubular reaction equipment, connecting the output ends of the tubular reaction equipment and the atomizing equipment; and

[0075] The tubular reaction apparatus is heated from room temperature to 300-450°C, and then atomized droplets are passed into the tubular reaction apparatus for heating; and

[0076] After heating, lithium titanate particles are first deposited on the surface of the droplet to form a shell layer, and carbon dioxide particles are then deposited inside the droplet to form a core layer. Unreacted carbon source coating agents are dispersed on the shell and core layers. Voids are formed between the lithium titanate particles and / or between the titanium dioxide particles, and the carbon source coating agents are dispersed in the voids. Finally, the composite material powder is deposited on the wall of the tubular reaction device.

[0077] Understandably, directly connecting the tubular reaction equipment to the output of the atomization equipment creates a closed, continuous production system. This ensures that the precursor droplets are immediately introduced into the reaction environment after generation, avoiding aggregation, sedimentation, or compositional changes during droplet transfer. This guarantees the continuity and stability of the liquid-to-solid phase transition, laying the foundation for large-scale continuous production. Preheating the tubular reaction equipment ensures that the atomized droplets react immediately upon entering the equipment. Controlling the maximum reaction temperature within the lower range of 300-450℃ effectively suppresses excessive growth and sintering agglomeration of lithium titanate and titanium dioxide particles. Traditional solid-state methods typically require temperatures above 700℃, which leads to particle coarsening, reducing specific surface area and ion migration rate. The reaction time of the atomized droplets in the tubular equipment is an extremely short and crucial process. The specific residence time depends on the length of the reaction zone in the tubular equipment; at a carrier gas flow rate of 3-5 L / min, the heating time can be 20-60 seconds.

[0078] Specifically, a sequential deposition process that determines the final structure occurs inside the droplet. As the solvent rapidly evaporates, the solute concentration on the droplet surface first reaches supersaturation. The dissolved lithium and titanium sources react preferentially here, generating fine lithium titanate particles that deposit on the outer periphery of the droplet and interconnect to form a porous shell. The initial formation of this shell provides a physical constraint on the still liquid interior. Subsequently, the remaining titanium source inside the droplet continues to thermally decompose, generating titanium dioxide particles. Since the shell has a pre-defined boundary, these newly generated titanium dioxide particles are confined to the interior of the droplet, gradually forming the core. At the same time, the first and second emission gases, such as water vapor, alcohol solvents, and carbon dioxide, generated during the entire reaction process, naturally leave abundant nanoscale voids and channels between the aforementioned lithium titanate and titanium dioxide particles. The voids between titanium dioxide particles in the core layer, between lithium titanate particles in the shell layer, or between the core and shell layers serve as a space for the carbon source coating agent. For example, tetrabutyl titanate and lithium salt have the lowest solubility in droplets. During the tube furnace drying process, they preferentially precipitate on the surface of the droplets to form lithium titanate, while titanium dioxide is formed in the inner layer of the droplets due to insufficient lithium salt content.

[0079] Specifically, since the tubular reaction equipment is preheated, there is no limitation on its specific heating rate. Preferably, the tubular reaction equipment is heated from room temperature to 300-450°C at a rate of 5-10°C / min. This heating rate ensures the service life of the tubular reaction equipment. The temperature at which the tubular reaction equipment is heated from room temperature can also be 300-400°C, 350-420°C, or 380-400°C.

[0080] Specifically, the titanium source is any one or more combinations of calcium titanate, titanium sulfate, and tetrabutyl titanate; the lithium source is any one or more combinations of lithium carbonate, lithium hydroxide, and lithium acetate; and the carbon source coating agent is any one or more combinations of tannic acid, glucose, and sucrose.

[0081] It should be understood that the lithium source in the droplet will first react with the titanium source during the heating process. During the reaction, the lithium source undergoes a solid-state reaction. Taking lithium acetate (LiCH3COO) and tetrabutyl titanate (C16H36O4Ti) as an example:

[0082] First, the lithium and titanium sources undergo thermal decomposition, generating active Li₂O, TiO₂ intermediates, CO₂, and H₂O. CO₂ and H₂O are emitted as the first emission gases. Subsequently, the active Li₂O and TiO₂ undergo a solid-state reaction during heating to generate the final product.

[0083] 2 Li₂O + 5 TiO₂ → Li₄T₅O₁₂; After the lithium source is consumed, the remaining titanium source in the solution will continue to undergo thermal decomposition. Taking tetrabutyl titanate as an example, its thermal decomposition reaction under an inert atmosphere can be simplified as: C₁₆H₃₆O₄Ti → TiO₂ + 8 C₂H₄↑ + 2 H₂O↑.

[0084] C2H4 and H2O will be emitted as the second emission gas. It should be noted that when the titanium source is any one or more combinations of calcium titanate, titanium sulfate, and tetrabutyl titanate; and the lithium source is any one or more combinations of lithium carbonate, lithium hydroxide, and lithium acetate, the solid product of the reaction between the titanium and lithium sources will be lithium titanate (Li4T5O12), only the first emission gas will differ. However, regardless of the lithium source used, the solid product of thermal decomposition is titanium dioxide (TiO2), only the second emission gas will differ, which will not be elaborated further.

[0085] Furthermore, please refer to the following: Figure 5 The sintering process includes:

[0086] Provide carbonization equipment, which heats the composite material powder from room temperature to 200-300°C before placing it inside; and

[0087] The composite material powder was removed from the wall of the tubular reactor and placed inside the carbonization equipment. The composite material powder inside the carbonization equipment was sintered in an inert atmosphere for 1-2 hours.

[0088] After removing the sintered product and cooling it to room temperature, carbon-coated core-shell material is obtained.

[0089] Understandably, during the sintering process, the carbon source coating agent, originally in the voids, carbonizes and gradually fills the voids to form an inner coating layer. After filling the voids, it gradually wraps around the entire outer surface of the shell to form an outer coating layer. The carbonization temperature of traditional anode materials is typically above 500℃. In this embodiment, the sintering temperature of the carbonization equipment is controlled at 200~300℃, far lower than the temperature used for traditional anode material carbonization. This ensures that the shell and core layers already formed in the composite material powder are well preserved, completely avoiding the problems of decreased specific surface area and prolonged lithium-ion diffusion paths caused by particle sintering, growth, and agglomeration under high-temperature conditions. 200~300℃ is the ideal window for organic carbon sources, such as sucrose and glucose, to undergo carbonization reactions to generate amorphous carbon. If the temperature is too low, the carbonization reaction is incomplete, and the residual hydrocarbons have poor conductivity; if the temperature is too high, the amorphous carbon may transform into localized graphitization or cause structural shrinkage, disrupting the continuity of the coating layer. Sintering under an inert atmosphere for 1-2 hours provides ample reaction time for the low-temperature carbonization process. This ensures that the carbon source coating agent dispersed in the voids within the core-shell structure and on the particle surface is fully and thoroughly carbonized, thereby transforming the pre-dispersed carbon precursor from the previous steps into a robust outer coating layer that firmly encapsulates the entire particle and an inner coating layer that fills the internal pores and bridges the lithium titanate and titanium dioxide particles. Furthermore, the sintering process eliminates defects such as closed-cell defects, grain growth defects, and orientation defects in the core-shell material.

[0090] Specifically, since the carbonization equipment is preheated, there is no limitation on its specific heating rate. Preferably, the carbonization equipment is heated from room temperature to 200-300°C at a rate of 5-10°C / min. This heating rate ensures the service life of the carbonization equipment. The temperature at which the carbonization equipment is heated from room temperature can also be 200-150°C, 250-300°C, or 260-270°C.

[0091] Specifically, obtaining the first precursor solution includes:

[0092] Specifically, the shell thickness ranges from 1 to 5 μm. It should be understood that in this embodiment, a shell thickness of 1 to 5 μm can construct a stable framework with sufficient mechanical strength. Its thickness is sufficient to effectively constrain and buffer the volume changes of the internal titanium dioxide particles during charge and discharge, limiting the expansion of the active material to a localized area, thereby greatly suppressing the overall macroscopic expansion of the electrode and improving the cycle life and structural integrity of the battery. Simultaneously, this thickness avoids excessively thick shells that would lead to excessively long ion diffusion paths and a reduced mass ratio of the active material, thus ensuring good rate performance and volumetric energy density. If the shell thickness is less than 1 μm, its mechanical strength is insufficient to effectively constrain the volume expansion of the titanium dioxide particles, easily leading to structural damage and rapid capacity decay during cycling. If the shell thickness is greater than 5 μm, it will excessively encroach on the space of the high-capacity internal titanium dioxide particles, reducing the overall reversible capacity of the material. At the same time, an excessively thick and dense shell will significantly prolong the lithium-ion solid-phase diffusion path, impairing the rate performance of the material.

[0093] Specifically, the diameter of the core layer ranges from 0.8 to 7.8 μm. In this embodiment, the 0.8–7.8 μm core layer ensures a sufficient proportion of high-capacity titanium dioxide particles in the core-shell material, providing the material with a high theoretical reversible capacity. Its size matches the outer shell layer, allowing it to be perfectly encapsulated, thus creating a stable lithium titanate interface between the core layer and the electrolyte, reducing the occurrence of side reactions. If the core layer size is less than 0.8 μm, the proportion of high-capacity titanium dioxide is too low, failing to demonstrate the capacity-enhancing advantages of the composite material. If the core layer size is greater than 7.8 μm, the path for lithium ions to diffuse from the surface to the center within a single particle is too long. Even with carbon coating, the ion migration rate becomes a bottleneck, leading to a decrease in high-rate performance. Furthermore, the excessively large core volume change places more stringent demands on the mechanical properties of the shell layer.

[0094] Specifically, the thickness of the outer coating layer ranges from 100 to 200 nm. In this embodiment, the 100-200 nm outer coating layer forms a continuous, dense, and mechanically strong conductive layer that completely covers the particle surface, significantly reducing inter-particle contact resistance, constructing a highly efficient electron conduction network, and greatly improving the rate performance of the electrode. Simultaneously, this ultra-thin thickness hardly hinders the migration of lithium ions from the electrolyte to the interior of the active material, perfectly balancing electron conduction and ion migration. If the outer coating layer thickness is less than 100 nm, it may be discontinuous or prone to breakage during cycling, failing to form a complete conductive network, and some active material cannot be effectively utilized, resulting in poor conductivity improvement. If the outer coating layer thickness is greater than 200 nm, the excessively thick carbon layer becomes a significant obstacle to ion migration, increasing ion diffusion resistance, leading to poor rate performance, and simultaneously reducing the electrode's compaction density and volumetric energy density.

[0095] Specifically, the diameter of the core-shell material ranges from 1.9 to 13 μm. It should be understood that the particle size of the core-shell material directly affects the actual performance of the lithium-ion battery anode material, influencing the electrode slurry coating, compaction density, ion migration rate, and contact area with the electrolyte. In this embodiment, the diameter of the core-shell material is controlled to be greater than 1.9 μm, effectively avoiding the generation of excessive nanoscale ultrafine powder. Excessively fine powder particles will adsorb a large amount of solvent and binder during electrode slurry preparation, leading to poor slurry rheology and difficulty in uniform coating. A diameter less than 13 μm ensures that the diffusion path of lithium ions within the solid particles is not too long. If the particle size is much larger than 13 μm, the time required for ions to migrate from the particle surface to the core will increase significantly. During high-rate charge and discharge, the interior of the particle cannot be fully utilized, leading to a sharp decrease in capacity and increased polarization.

[0096] It should be noted that existing technologies typically involve first coating titanium dioxide with carbon thermal treatment, and then reacting the lithium source solution with the titanium dioxide through the carbon layer to form lithium titanate. This thermal treatment method is a surface hydrothermal method, which suffers from poor growth uniformity and results in a thin lithium titanate layer and carbon coating layer, leading to poor cycle performance of the final electrode product. The method used in this embodiment precipitates lithium titanate particles as a shell through droplet reaction, allowing for a shell thickness range of 1~5μm, ultimately producing a negative electrode material with better cycle performance.

[0097] Please combine Figure 1 and Figure 6 The second embodiment of the present invention also provides a carbon-coated core-shell material, which is prepared by the above-described method for preparing carbon-coated core-shell materials. The core-shell material includes a shell layer, a core layer, an outer coating layer, and an inner coating layer. The shell layer wraps the core layer. The shell layer is lithium titanate particles, and the core layer is titanium dioxide particles. The outer coating layer and the inner coating layer are carbon. The outer coating layer wraps the shell layer, and the inner coating layer wraps the lithium titanate particles and titanium dioxide particles.

[0098] Understandably, the core-shell material in this embodiment adopts a layered structure design, with the innermost core layer composed of titanium dioxide particles. Titanium dioxide, as a lithium-ion battery anode material with a high theoretical specific capacity, primarily functions to provide considerable lithium storage capacity for the entire composite material, which is crucial for improving the material's energy density. However, titanium dioxide undergoes certain volume changes during cycling, and its intrinsic electronic conductivity is low. The core layer is tightly encased by a shell layer composed of lithium titanate particles. Lithium titanate exhibits minimal crystal volume change during lithium-ion insertion and extraction. This encasing shell layer plays a vital role in mechanical constraint and stabilization. Like a robust framework, it firmly confines the internal titanium dioxide core, effectively suppressing the volume expansion and contraction of titanium dioxide during charge-discharge cycles. This significantly alleviates the overall macroscopic deformation of the material, solving problems such as structural pulverization, contact failure, and detachment from the current collector caused by repeated volume changes in the electrode material, thus providing the battery with an ultra-long cycle life and high safety. This embodiment also includes a carbon coating layer. The inner coating, in the form of amorphous carbon, precisely fills the spaces between lithium titanate and titanium dioxide particles, as well as the tiny voids they themselves create. The inner coating tightly connects the internal titanium dioxide particles to the external lithium titanate particles, significantly reducing the impedance of ion and electron transport within the material. The outer coating, as a continuous, dense thin layer, completely encapsulates the outermost lithium titanate shell, constructing an efficient electron conduction pathway between particles and greatly improving its rate performance as an electrode. Simultaneously, the outer coating also reduces direct contact between the active material and the electrolyte to some extent, contributing to the formation of a more stable electrode-electrolyte interface film, suppressing side reactions, and further enhancing the material's initial coulombic efficiency and cycle stability. It should be understood that the multilayer structure of this embodiment achieves complementary advantages and synergistic effects of a high-capacity core layer, a high-stability shell layer, and a high-conductivity coating layer. It successfully solves the technical problem that traditional single titanium-based materials cannot simultaneously achieve high specific capacity, long cycle life, and high rate performance, making it an advanced lithium-ion battery anode material with extremely excellent comprehensive performance.

[0099] To demonstrate the performance of the core-shell material in this embodiment, the following experimental comparisons are conducted:

[0100] Example 1

[0101] Step 1: Based on the required lithium-titanium molar ratio in the materials, tetrabutyl titanate, lithium acetate, and sucrose are added to a certain amount of a mixture of alcohol solvent and deionized water to prepare the first precursor solution. The molar concentration of the titanium source is 2.5 mol / L, the mass ratio of alcohol solvent to deionized water is 1:1.3, the molar ratio of lithium source to titanium source is 1:3, and the mass ratio of carbon source coating agent to titanium source is 1:75. The first precursor solution is poured into a magnetic stirrer and stirred for 15 minutes at a speed of 60 rpm / min.

[0102] Step 2: Pour the first precursor solution into an ultrasonic disperser, add polyvinylidene fluoride as a dispersant, heat to 70°C in a water bath and then perform ultrasonic dispersion at a heating rate of 2°C / min, with an ultrasonic dispersion power of 150W and a dispersion time of 40min to obtain the second precursor solution.

[0103] Step 3: Add a mixed solution of alcohol solvent and citric acid aqueous solution to the above second precursor solution, wherein the mass ratio of the mixed solution to titanium source is 1:45, the volume ratio of alcohol solvent to citric acid aqueous solution is 1:13, the solubility of citric acid aqueous solution is 6g / L, and continue to stir with a magnetic stirrer for 15min at a stirring speed of 200rpm / min to obtain the pre-prepared precursor solution.

[0104] Step 4: Pour the pre-prepared precursor solution into an atomizing flask, and atomize the solution into small droplets using an ultrasonic atomizer. The droplets are then introduced into a tube furnace with gas to react and deposit the composite material powder. The ultrasonic atomizer has a power of 1200W, the carrier gas is argon, the gas flow rate is 3.5L / min, and the tube furnace is preheated to 330℃ at a rate of 5℃ / min.

[0105] Step 5: Place the above composite material powder into a carbonization furnace, introduce a protective atmosphere, and perform sintering treatment; the protective atmosphere is nitrogen, the carbonization furnace is heated to 230°C in advance at a rate of 5°C / min, and the sintering time is 1 hour to obtain the core-shell material.

[0106] Step 6: Mix the core and shell material with polyvinylidene fluoride, carbon black, and N-methylpyrrolidone solution (NMP) in a mass ratio of 8:1:1 to form a slurry. Coat the slurry onto the copper foil current collector and finally fabricate a CR2032 coin cell for testing. The test voltage window is 0-3V.

[0107] Example 2: Adjust the ratio of lithium source to titanium source in step 1 of Example 1 to 1:1.8 to obtain a lithium titanate & titanium dioxide composite material with a lithium titanate content of approximately 52%, while keeping the other steps unchanged.

[0108] Example 3: Adjust the ratio of lithium source to titanium source in step 1 of Example 1 to 1:1.1 to obtain lithium titanate material with a purity of over 98%, while keeping the other steps unchanged.

[0109] Specifically, specific capacity refers to the amount of electricity that a unit mass of electrode material can release or store at a specific charge-discharge rate, and is measured in milliampere-hours per gram (mAh / g). A higher specific capacity indicates a stronger ability to store lithium ions and a higher energy density.

[0110] Cycling performance refers to a battery's ability to retain its capacity after multiple charge-discharge cycles. It is usually expressed as the capacity retention rate after a specific number of cycles. This experiment tests the battery's capacity as a percentage of its initial capacity after 500 cycles at a 1C charge-discharge rate. A higher retention rate indicates better cycle stability and a longer lifespan for the material.

[0111] Rate performance refers to a battery's ability to retain its capacity when charged and discharged at different currents, essentially measuring its ability to "charge and discharge quickly." This experiment tests the ratio of the actual discharge capacity at a 3C high-rate discharge to the discharge capacity at a low rate, expressed as a percentage. A higher discharge ratio indicates better material performance at high power output, with less polarization and lower internal resistance.

[0112] The battery thickness expansion ratio refers to the percentage increase in the physical thickness of a battery after long-term cycling. This experiment requires testing the percentage increase in battery thickness after 500 charge-discharge cycles. A lower expansion ratio indicates a more stable material structure, making it less prone to pulverization and detachment, which is beneficial for maintaining electrode integrity.

[0113] The CR2032 button cells obtained in Examples 1, 2, and 3 were placed in a battery testing system for testing. The battery testing system can accurately control the charging and discharging current and voltage of the battery, and record data such as capacity and time in real time. It can also directly obtain data on specific capacity, cycle performance, and rate performance.

[0114] The CR2032 coin cells obtained in Examples 1, 2, and 3 are placed in an in-situ expansion analyzer for testing, and the data of the cell thickness expansion ratio can be obtained.

[0115] Table 1. Performance Test Table for Core-Shell Materials

[0116]

[0117] As shown in Table 1, the proportion of lithium titanate in Example 1 is about 30%, and the specific capacity of its composite material reaches 282.5 mAh / g, which greatly improves the specific capacity of the material. The 500-cycle retention rate, rate performance discharge ratio, and battery thickness expansion ratio of Example 1 and Example 2 are all better than those of Example 3.

[0118] The third embodiment of the present invention also provides a negative electrode material, including a current collector stacked in layers and the above-mentioned carbon-coated core-shell material.

[0119] In this embodiment, the uniform and continuous amorphous outer coating layer of the core-shell material plays a crucial role in the electrode fabrication process. This outer coating layer significantly improves the electrical contact between active material particles, forming a highly efficient electronic conductive network that runs through the entire electrode coating. This allows electrons collected from the current collector to be transported extremely smoothly to each active particle, significantly reducing the internal impedance and polarization voltage of the electrode. Therefore, the prepared negative electrode exhibits excellent high-current charge-discharge capability, and the battery maintains a high capacity and voltage plateau even at high power output. Secondly, the excellent structural stability of the core-shell material itself, through its stacked arrangement, directly translates into a long cycle life for the electrode and even the entire battery. The effective constraint of the shell layer on the core layer ensures that the volume change of the composite material is minimal during long-term cycling. This means that after repeated charge-discharge cycles, the electrode can maintain its structural integrity, and the active material and current collector maintain good mechanical contact and electrical connection, effectively avoiding the sharp capacity decay caused by the pulverization, shedding, or detachment of the active material from the current collector. This allows the battery containing this negative electrode to withstand thousands of cycles while still maintaining a high capacity retention rate. Finally, the high-capacity core layer in the core-shell material ensures that the negative electrode has a high specific capacity.

[0120] The fourth embodiment of the present invention also provides a battery, which includes a positive electrode material, an electrolyte, and the aforementioned negative electrode material. The battery provided in this embodiment has the same beneficial effects as the negative electrode material provided in the above embodiments, and therefore will not be described in detail here.

[0121] The foregoing has provided a detailed description of a carbon-coated core-shell material, its preparation method, anode material, and battery disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of preparing a carbon-coated core-shell material, characterized by: The preparation method of the carbon-coated core-shell material comprises: providing a titanium source, a lithium source, a carbon source coating agent, an alcohol solvent, and deionized water, mixing the titanium source, the lithium source, the carbon source coating agent, and the first solvent at 40-120 rpm / min for 5-30 min to obtain a first precursor solution, wherein the molar concentration of the titanium source is 1.5-5 mol / L, the mass ratio of the alcohol solvent to the deionized water is 1:1.2-1:1.5, the molar ratio of the lithium source to the titanium source is 1:1.1-1:10, and the mass ratio of the carbon source coating agent to the titanium source is 1:50-1:100; providing a dispersant as a second solvent, wherein the dispersant is any one or a combination of multiple of CMC, PVDF, and PVP, mixing the dispersant and the first precursor solution, and then performing water bath heating from room temperature to 50-100°C, and then performing ultrasonic dispersion at 100-200 W for 30-80 min to obtain a second precursor solution, wherein the mass ratio of the dispersant to the titanium source is 1:40-1:60; providing an alcohol solvent and a citric acid solution, mixing the alcohol solvent and the citric acid solution to obtain a third solvent, stirring the third solvent and the second precursor solution at 150-200 rpm / min for 5-20 min, and adjusting the pH value of the mixed solution to 4-6 to obtain a pre-prepared precursor solution, wherein the volume ratio of the alcohol solvent to the citric acid solution is 1:1-1:2, the solubility of the citric acid solution is 5-10 g / L, and the mass ratio of the third solvent to the titanium source is 1:30-1:60; and providing an atomization device, and passing the pre-prepared precursor solution into the atomization device under an inert atmosphere, wherein the power of the atomization device is 1000-2000 W, the frequency is 1.2-1.5 MHz, the gas flow rate during atomization is 3-5 L / min, the temperature of the droplets is raised to 300-450°C, the titanium source and the lithium source in the droplets react first to obtain lithium titanate particles and first exhaust gas, the first exhaust gas is discharged to the outside of the droplets, the lithium titanate particles deposit on the surface of the droplets to form a shell layer, the titanium source decomposes into titanium dioxide particles and second exhaust gas when the lithium source reaction is completed, the second exhaust gas is discharged to the outside of the droplets, the titanium dioxide particles deposit in the interior of the droplets to form a core layer, and the lithium titanate particles and / or the titanium dioxide particles form voids between each other, and the carbon source coating agent is dispersed in the voids to obtain a composite material powder; and sintering the composite material powder under an inert atmosphere at 200-300°C for 1-2 h, and carbonizing the carbon source coating agent to form a coating layer to coat the shell layer and the core layer to obtain a carbon-coated core-shell material.

2. The method of claim 1, wherein: The particle size of the atomized droplets is 1-5 μm.

3. The method of claim 1, wherein: The temperature raising process comprises: providing a tubular reaction device, and connecting the output ends of the tubular reaction device and the atomization device; and raising the temperature of the tubular reaction device from room temperature to 300-450°C, and then passing the atomized droplets into the tubular reaction device for heating; and The heated droplet first deposits lithium titanate particles as a shell layer on the surface of the droplet, then deposits titanium dioxide particles as a core layer inside the droplet, and the unreacted carbon source coating agent is dispersed on the shell layer and the core layer, and the lithium titanate particles form gaps between each other and / or between the titanium dioxide particles, and the carbon source coating agent is dispersed in the gaps, and the finally formed composite material powder is deposited on the wall surface of the tubular reaction device.

4. The method of claim 1, wherein: The sintering process includes: providing a carbonization device, the carbonization device is heated from room temperature to 200-300℃, and then the composite material powder is placed in the carbonization device; and The composite material powder is taken off from the wall surface of the tubular reaction device and placed in the carbonization device, and the composite material powder in the carbonization device is sintered for 1-2h under an inert atmosphere; and After the sintered product is taken out and cooled to room temperature, a carbon-coated core-shell material is obtained.

5. The method of claim 1, wherein: The titanium source is any one or a combination of more than one of calcium titanate, titanium sulfate, and tetrabutyl titanate; The lithium source is any one or a combination of more than one of lithium carbonate, lithium hydroxide, and lithium acetate; The carbon source coating agent is any one or a combination of more than one of tannic acid, glucose, and sucrose; The thickness of the shell layer ranges from 1 to 5μm, the diameter of the core layer ranges from 0.8 to 7.8μm, the thickness of the outer coating layer ranges from 100 to 200nm, and the diameter of the core-shell material ranges from 1.9 to 13μm.

6. A carbon-coated core-shell material, characterized by: The carbon-coated core-shell material prepared by the preparation method of any one of claims 1-5, the core-shell material includes a shell layer, a core layer, an outer coating layer, and an inner coating layer, the shell layer wraps the core layer, the shell layer is lithium titanate particles, and the core layer is titanium dioxide particles; the outer coating layer and the inner coating layer are carbon, the outer coating layer wraps the shell layer, and the inner coating layer coats the lithium titanate particles and the titanium dioxide particles.

7. A negative electrode material, characterized by: The battery includes a positive electrode material, an electrolyte, and a negative electrode material as claimed in claim 7.

8. A battery, characterized by: The battery includes a positive electrode material, an electrolyte, and a negative electrode material as claimed in claim 7.

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