Negative electrode material, manufacturing method thereof, and lithium ion battery

Abstract

A negative electrode material, a method for producing the same, and a lithium-ion battery are provided. The negative electrode material includes a core and a coating layer formed on at least a portion of the surface of the core, the core including a silicon-based material, and the negative electrode material has a pore structure. The pore structure differentiation ratio ΔΦ of the negative electrode material calculated by the following formula (I) is 1×10 -3 ~0.5. TIFF2025537608000008.tif12170 (In formula (I), ΔS is the area of ​​the hysteresis loop in the adsorption / desorption isotherm of the negative electrode material; s is the specific surface area of ​​the negative electrode material; ΔP is the interval difference of the relative pressure P / P0 corresponding to the hysteresis loop; Q max is the maximum isothermal adsorption amount of the negative electrode material.) The method for producing the anode material includes performing a CVD vapor deposition process on a silicon-based material core to obtain an anode material with a pore structure, which creates a pore structure with a certain degree of complexity in the anode material, thereby improving the rate capability and cycle performance of the material.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This disclosure claims priority to a Chinese patent application, application number CN202310809643X, entitled "Negative electrode material and manufacturing method thereof, and lithium ion battery," filed with the China Patent Office on June 30, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to the field of lithium battery technology, and more particularly to a negative electrode material and a method for producing the same, and a lithium ion battery. [Background technology]

[0003] Currently, graphite-based materials are commonly used as battery anode materials in mature commercial lithium-ion batteries. However, the theoretical lithium storage capacity of graphite-based materials is low and cannot meet the demand for high-energy density batteries. Silicon-based anode materials have a high theoretical capacity of approximately 4200 mAh / g, which is much higher than that of commercial graphite. Therefore, silicon-based anode materials have wide application potential in energy storage and are one of the most important materials for high-energy density lithium-ion batteries.

[0004] However, conventional silicon-based anode materials have problems such as large expansion and poor rate characteristics, which seriously affect the widespread application of silicon-based anode materials in lithium batteries. Therefore, suppressing expansion and improving the cycle performance and rate characteristics of silicon-based anode materials are prerequisites for their widespread application. Therefore, at present, there is an urgent need to develop anode materials that can mitigate expansion and improve rate and cycle performance by designing the particle structure of silicon-based anode materials. Summary of the Invention [Means for solving the problem]

[0005] The present disclosure provides a negative electrode material including a core and a coating layer formed on at least a portion of a surface of the core, the core comprises a silicon-based material; The negative electrode material has a pore structure, The pore structure differentiation ratio ΔΦ calculated by the following formula (I) is 1 × 10 -3 0.5〜0.5。

number

[0006] Preferably, the silicon-based material comprises at least one of elemental silicon, silicon oxide, silicon carbide, silicon nitride, silicon phosphide, silicon sulfide, and silicon alloy.

[0007] Preferably, the coating layer includes at least one of a carbon-containing material and a ceramic-based material.

[0008] Preferably, the mass of the coating layer is 0.5% to 10% of the total mass of the negative electrode material.

[0009] Preferably, the thickness of the coating layer is 20 nm to 700 nm.

[0010] Preferably, the core further comprises a carbon-based material.

[0011] Preferably, the core further comprises a doping metal element.

[0012] Preferably, the pore structure differentiation ratio ΔΦ is 5×10 -3 ~0.5.

[0013] Preferably, the area ΔS of the hysteresis loop is 4.5×10 -4 ≦ΔS≦3.0×10 -2 Preferably, the area ΔS of the hysteresis loop satisfies 4.5×10 -4 ≦ΔS≦2.5×10 -2 Meet the following.

[0014] Preferably, the specific surface area s of the negative electrode material is 0.5 m 2 / g~15m 2 / g.

[0015] Preferably, the maximum isothermal adsorption amount Q of the negative electrode material max is less than 1.35 mmol / g.

[0016] Preferably, the negative electrode material has a BJH average pore diameter of 5 nm to 20 nm and a BJH pore volume of 1.0 × 10 -4 cm 3 / g≦V BJH ≦0.1cm 3 / g is met.

[0017] Preferably, the pH of the negative electrode material is 6.0 to 12.0.

[0018] Preferably, the carbon-containing material includes at least one of graphite, hard carbon, soft carbon, diamond-like carbon, carbon fiber, carbide, pitch, and resin-based high molecular weight polymer.

[0019] Preferably, the ceramic-based material includes at least one of a phosphate, a silicate, a nitride, and a metal oxide.

[0020] Preferably, the carbon-based material includes at least one of soft carbon, hard carbon, graphite, graphene, carbon nanotubes, carbon fibers, and diamond-like carbon.

[0021] Preferably, the doping metal element comprises at least one of Li, Mg, Al, Ti, Na, K, Ca, Be, La, Ce, V, Ba.

[0022] Preferably, the mass percentage of the doping metal element in the negative electrode material is 2% to 15%.

[0023] Preferably, the coating layer has the pore structure.

[0024] Preferably, the pore structure comprises micropores, mesopores and macropores.

[0025] The present disclosure provides: A method for producing a silicon-based negative electrode material, comprising: performing a CVD vapor deposition coating process on a silicon-based material core to be coated, to obtain a negative electrode material having a micropore structure; The gas for the vapor phase deposition contains an auxiliary gas and a carbon source gas, and in the gas, the volume ratio of the carbon source gas is 30% to 95%, and the volume ratio of the auxiliary gas is 5% to 70%.

[0026] Preferably, the manufacturing method further includes pretreating the silicon-based material core to be coated before carrying out the CVD vapor phase deposition process.

[0027] Preferably, the temperature of the vapor deposition treatment is 400° C. to 1200° C., and the time is 1 hour to 12 hours.

[0028] Preferably, the manufacturing method further includes placing the silicon-based material core to be coated in a deposition chamber of a deposition furnace when performing the CVD vapor deposition process, wherein the rotation speed of the deposition chamber is 0.1 r / min to 10 r / min, and the air pressure inside the deposition furnace is 0.1 MPa to 10 MPa.

[0029] Preferably, the carbon source gas comprises at least one of methane, ethane, ethylene, acetylene, propane, formaldehyde, acetaldehyde, and methanol.

[0030] Preferably, the auxiliary gas comprises at least one of H2, SO2, NH3, and Ar.

[0031] Preferably, the pretreatment comprises sequentially performing sieving, classification, washing and drying.

[0032] Preferably, the particle size D of the silicon-based material core to be coated obtained after the pretreatment 50 is 2.5μm to 9.0μm.

[0033] Preferably, the specific surface area of ​​the silicon-based material core to be coated obtained after the pretreatment is 0.5 m 2 / g~7.5m 2 / g.

[0034] Preferably, the cleaning comprises first washing with water and then rinsing with an organic solvent.

[0035] Preferably, the drying step includes air-drying the washed material using an inert gas, and then vacuum-drying the material in an environment of 60° C. to 150° C. and 1000 Pa or less.

[0036] Preferably, the production method further comprises, after the vapor deposition process, classifying and drying the product obtained by the vapor deposition process.

[0037] The present disclosure further provides a lithium ion battery including the above-described negative electrode material or a negative electrode material produced by the above-described production method. [Brief explanation of the drawings]

[0038] In order to more clearly explain the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings necessary for the embodiments. Obviously, the following drawings only illustrate some embodiments of the present disclosure, and therefore should not be considered as limiting the scope of the present disclosure. [Figure 1] 1 shows the adsorption and desorption isotherms of the negative electrode material produced in Example 1. [Figure 2] 1 shows the adsorption and desorption isotherms of the negative electrode material produced in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0039] The terms used in this specification are explained below.

[0040] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, product, or device that comprises recited elements is not necessarily limited to those elements, but may include other elements not expressly recited or inherent to the composition, step, method, product, or device. The conjunction "consisting of" excludes any element, step, or ingredient not recited.

[0041] When an equivalent amount, concentration, or other value or parameter is expressed as a range, a selectable range, or a range limited by a series of selectable upper and lower limits, this should be understood to specifically disclose all ranges formed by any combination of any range upper limit or selectable upper limit with any range lower limit or selectable upper limit, regardless of whether a specific range is disclosed alone. For example, if a range of "1 to 5" is disclosed, this range should be interpreted to include ranges such as "1 to 4," "1 to 3," "1 to 2," "1 to 2 and 4 to 5," "1 to 3 and 5," etc. When a range of numerical values ​​is described herein, unless otherwise specified, the range is intended to include the endpoints and all integers and fractions within the range.

[0042] In the examples, unless otherwise specified, the terms "parts" and "percentages" used mean "parts by mass" and "% by mass", respectively.

[0043] "Parts by mass" refers to a basic unit of measurement that expresses the mass proportion relationship of multiple components, and 1 part can represent any unit mass, such as 1 g or 2.689 g. If the parts by mass of component A are a parts and the parts by mass of component B are b parts, this indicates that the ratio of the mass of component A to the mass of component B is a:b, or that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number that indicates a multiplicative factor). It should not be misunderstood that, unlike parts by mass, the total value of the parts by mass of all components is not limited to 100 parts.

[0044] "And / or" indicates that either or both of the stated circumstances can occur; for example, "A and / or B" includes "A and B" and "A or B."

[0045] Silicon-based negative electrode materials have high energy density, but they can experience excessive volume expansion during charge and discharge, which can lead to problems such as deterioration of cycle performance and rate characteristics. In response to this, the inventors of the present disclosure investigated the particle structure of negative electrode materials to improve the performance of the materials and discovered that the pore structure of silicon-based negative electrode materials plays an important role.

[0046] Most studies have only limited the specific surface area and pore size ranges of negative electrode materials to some extent, without thoroughly examining the relationship between the pore size, pore shape, pore structure, etc. and the electrochemical properties, preventing further improvements. The pores on the surface of negative electrode materials serve as high-speed transmission paths (conduction paths) for lithium transport, space for inner core expansion, and skeletal space for SEI deposition. These pores are advantageous for mitigating inner core expansion, improving cycle performance and rate characteristics when the negative electrode material is used as a battery material, stabilizing the SEI-active component interface, improving cycle coulombic efficiency when the negative electrode material is used as a battery material, and reducing the loss of active silicon and lithium. In light of this, the inventors of the present disclosure have conducted extensive research into silicon-based negative electrode materials, particularly the pore structure of the coating layer.

[0047] Of course, different pore structures have different effects on the cycle performance and rate characteristics of negative electrode materials. However, the pores present in negative electrode materials tend to have relatively small diameters and a large number of pores, which, combined with the complex specific pore structures, makes it very difficult to clearly describe the pore structure in practice. Negative electrode materials exhibit different adsorption / desorption isotherms because the pore size, pore distribution, and / or specific surface area of ​​the material affect the adsorption performance of the material. The inventors of the present disclosure have found through their research into negative electrode materials that differences in pore structure can be reflected by comprehensively analyzing the correlation parameters between the adsorption / desorption isotherms and the specific surface area. In light of this, the inventors of the present disclosure have further improved negative electrode materials to obtain negative electrode materials with unique pore structures.

[0048] The appropriate pore distribution and pore structure of silicon-based negative electrode materials are favorable for rapid infiltration of the electrolyte. Such rapid infiltration improves the rapid transport (conduction) of lithium ions, shortens the lithium ion transport path, and improves the lithium ion transport efficiency (conductivity), thereby improving the rate performance of silicon-based negative electrode materials. In addition, the coating layer in the silicon-based negative electrode material can effectively block the co-intercalation of organic small molecules in the electrolyte, reducing the loss of core material and improving cycle performance.

[0049] The present disclosure provides a negative electrode material, a manufacturing method thereof, and a lithium-ion battery. The negative electrode material has a special pore structure that can block unnecessary exposure of the silicon-based material core, reduce the loss of active material and lithium, and improve cycle performance. Meanwhile, the pore structure contributes to rapid infiltration of the electrolyte and improved lithium ion transport efficiency, thereby improving the rate capability of the material.

[0050] One embodiment of the present disclosure comprises: A negative electrode material including a core and a coating layer formed on at least a portion of a surface of the core, the core comprises a silicon-based material; The negative electrode material has a pore structure.

[0051] Here, the pore structure differentiation ratio ΔΦ calculated by the following formula (I) is 1 × 10 -3 ~0.5.

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[0052] Specifically, ΔS means the area of ​​the hysteresis loop in the adsorption / desorption isotherm of the negative electrode material, and is the size of the area of ​​the hysteresis loop calculated using the integration method. s is the specific surface area of ​​the negative electrode material, and the value of s is expressed in units of m 2 ΔP is the difference in the relative pressure P / P0 corresponding to the hysteresis loop, and is 0<ΔP≦1. For example, when the relative pressure P / P0 corresponding to the hysteresis loop in the adsorption / desorption isotherm is in the range of 0.6 to 0.9, ΔP=0.9-0.6=0.3, or when the relative pressure P / P0 corresponding to the hysteresis loop is in the range of 0.53 to 0.76, ΔP=0.76-0.53=0.23. Q max is the maximum isothermal adsorption amount of the negative electrode material, and this value is a specific value corresponding to the unit mmol / g.

[0053] This disclosure uses mercury porosimetry and gas adsorption methods to measure anode materials in accordance with GB / T 21650.3-2011. An accurately weighed sample of the anode material to be measured is placed in a sample tube and evacuated. The entire system is then vacuum-degassed to the desired vacuum level. The sample tube is then submerged in a liquid nitrogen bath and filled with a known amount of gas (nitrogen gas). The sample adsorbs the gas, causing a pressure drop. After adsorption equilibrium is reached, the equilibrium pressure of the gas is measured, and the amount of adsorption is calculated based on the change in system pressure before and after adsorption. The adsorption / desorption isotherm is measured by repeatedly increasing the amount of adsorbate gas in the system and changing the pressure. The specific surface area, pore volume, and pore size distribution of the sample are then equivalently calculated using a theoretical model. The area of ​​the hysteresis loop is primarily determined by integrating the adsorption and desorption curves in the adsorption / desorption isotherm and subtracting the resulting data.

[0054] By studying the regularity of adsorption curves, the inventors of the present disclosure discovered that the data curve characteristics of the hysteresis loop in the adsorption / desorption isotherm of a negative electrode material are significantly correlated with its electrochemical properties. By comprehensively considering data such as the area of ​​the hysteresis loop and the corresponding relative pressure interval difference, the specific surface area of ​​the negative electrode material, and the maximum isothermal adsorption capacity, and combining these data into a calculation formula, they obtained the pore structure differentiation ratio ΔΦ, which represents the pore structure of the negative electrode material. By converting the contribution of the pore structure into an equivalent ratio and expressing it in a more intuitive form, they confirmed the efficiency of mass transfer and charge transfer at the solid-liquid interface, thereby demonstrating the impact of the pore structure of the negative electrode material, particularly the coating layer, on its electrochemical properties.

[0055] Generally, pores have pore diameters and distribution states of different sizes. In the present application, ΔΦ represents the complexity of the pore structure in the negative electrode material. The smaller ΔΦ is, the closer the pore structure is to being single, with the same pore diameter size, uniform distribution, and less intersection between different pores. The larger ΔΦ is, the greater the difference in the sizes of different pore diameters, with a staggered distribution of pores and a higher degree of disorder. In the present application, when ΔΦ is smaller than 1×10 -3 When it is smaller, the difference between pores is small and the pore structure is simple. That is, the size and shape of the pores are single, and there are few combinations between different pore structures. Therefore, under the same specific surface area conditions, a negative electrode material with such a pore structure has low expansion relaxation efficiency, low stability of the SEI interface, and low cycle performance, especially low cycle Coulomb efficiency. On the other hand, when ΔΦ is larger than 0.5, the degree of complexity of the pore structure is high, the combination of pore channels with different pore diameter sizes is excessively large, the mass transfer resistance is strong, the mass transfer efficiency is low, the rate performance is poor, and at the same time, it means deteriorating the concentration polarization in the electrochemical reaction process. Therefore, being within the range of 1×10 -3 ≦ΔΦ≦0.5 means that the pore structure of the negative electrode material has appropriate pore diameters and staggered distributions, so it can ensure that rapid mass charge transfer occurs in the negative electrode material, and there are also sufficient pores to buffer the expansion of the core and stabilize the SEI interface, thereby improving the Coulomb efficiency.

[0056] According to a first aspect, in one preferred embodiment, the silicon-based material in the negative electrode material of the present disclosure includes at least one of elemental silicon, silicon oxide, silicon carbide, silicon nitride, silicon phosphide, silicon sulfide, and silicon alloy. Preferably, the silicon oxide may be a silicon-oxygen composite that can be represented by the general formula SiOx (0 < x ≦ 2). Preferably, in the silicon oxide, the molar ratio of oxygen atoms to silicon atoms is (0.5~2):1.

[0057] In addition to the silicon material, the core may contain at least one of a carbon-based material and a doping (dopant) metal element. If a doping metal element is present in the silicon-based material core, preferably at least a portion of the doping metal element is present in the form of a silicate.

[0058] For example, doped negative electrode materials, such as those in which a doping metal element is combined with elemental silicon to form a core, or those in which a silicate is combined with a silicon oxide to form a core, when they have the pore structure characteristics of the present application, will have ΔΦ closer to the center value of the range, effectively improving electrochemical rate performance and improving cycle capacity retention.

[0059] Preferably, the carbon-based material includes at least one of soft carbon, hard carbon, graphite, graphene, carbon nanotubes, carbon fibers, and diamond-like carbon.

[0060] Preferably, the doping metal element comprises at least one of Li, Mg, Al, Ti, Na, K, Ca, Be, La, Ce, V, Ba.

[0061] Preferably, the doping mass percentage of the doping metal element in the negative electrode material is 2% to 15%, and may be, for example, 3% to 14%, 4% to 12%, or 5% to 10%, specifically, for example, 2%, 3%, 5%, 8%, 10%, 12%, 15%, or any value between 2% and 15%, or any range between two values.

[0062] In one preferred embodiment, the coating layer in the negative electrode material of the present disclosure includes at least one of a carbon-containing material and a ceramic-based material.

[0063] Preferably, the carbon-containing material includes at least one of graphite, hard carbon, soft carbon, diamond-like carbon, carbon fiber, carbide, pitch, and resin-based high molecular weight polymer.

[0064] Preferably, the ceramic-based material comprises at least one of a phosphate, a silicate, a nitride, and a metal oxide.

[0065] In one preferred embodiment, the mass of the coating layer is 0.5% to 10% of the total mass of the negative electrode material, and may be, for example, 1% to 9%, 2% to 8%, or 3% to 7%, specifically, for example, 0.5%, 1%, 3%, 5%, 7%, 10%, or any value between 0.5% and 10%, or any range between two values. Preferably, the mass of the coating layer is 2.5% to 8% of the total mass of the negative electrode material.

[0066] In one preferred embodiment, the thickness of the coating layer is 20 nm to 700 nm, for example, 50 nm to 600 nm, 90 nm to 550 nm, or 150 nm to 400 nm, specifically, for example, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 500 nm, 700 nm, or any value between 20 nm and 700 nm, or any range between two values.

[0067] In one preferred embodiment, the pore structure differentiation ratio ΔΦ of the negative electrode material is 5×10 -3 ≦ΔΦ≦0.5.

[0068] In one preferred embodiment, a hysteresis loop exists in the adsorption / desorption isotherm of the negative electrode material, and the area ΔS of the hysteresis loop is 4.5×10 -4 ≦ΔS≦3.0×10 -2 and ΔS is, for example, 4.5 × 10 -4 ~2.7×10 -2 , 4.5×10 -4 ~2.5×10 -2 , 4.5×10 -3 ~1.5×10 -2 Specifically, ΔS may be, for example, 0.00045, 0.0005, 0.001, 0.005, 0.01, 0.02, 0.025, 0.027, 0.03, or any value between 0.00045 and 0.025, or a range between two arbitrary values. Preferably, ΔS is 4.5×10 -4≦ΔS≦1.0×10 -2 Meet the following.

[0069] In one preferred embodiment, the specific surface area s of the negative electrode material is 0.5 m 2 / g~15m 2 / g, for example, 1.0m 2 / g~12m 2 / g, 2.5m 2 / g~10m 2 / g, or 5.0m 2 / g~7m 2 / g, and specifically, for example, 0.5m 2 / g, 1m 2 / g, 3m 2 / g, 5m 2 / g, 8m 2 / g, 10m 2 / g, 12m 2 / g, 15m 2 / g, or 0.5m 2 / g~15m 2 / g, or a range between any two values. Preferably, s is 0.5m 2 / g~10m 2 / g.

[0070] In one preferred embodiment, the maximum isothermal adsorption capacity Q of the negative electrode material max is 1.35 mmol / g or less, and may be, for example, 1.0 mmol / g or less, 0.45 mmol / g or less, or 0.35 mmol / g or less, and specifically, for example, 0.1 mmol / g, 0.3 mmol / g, 0.5 mmol / g, 0.8 mmol / g, 1.0 mmol / g, 1.2 mmol / g, or 1.35 mmol / g.

[0071] In one preferred embodiment, the negative electrode material has a BJH average pore diameter of 5 nm to 20 nm, and may be, for example, 7 nm to 18 nm, 9 nm to 16 nm, or 10 nm to 14 nm, specifically, for example, 5 nm, 10 nm, 15 nm, 20 nm, or any value between 5 nm and 20 nm, or any range between two values.

[0072] BJH pore volume V of the negative electrode material BJH is also called the BJH adsorption cumulative volume of pores, and is 1.0 × 10 -4 cm 3 / g≦V BJH ≦0.1cm 3 / g, V BJH For example, 5.0 x 10 -4 cm 3 / g~0.05cm 3 / g, 8 × 10 -4 cm 3 / g~0.01cm 3 / g, or 0.008 cm 3 / g~0.05cm 3 / g, and specifically, for example, 0.0001 cm 3 / g, 0.0005cm 3 / g, 0.001cm 3 / g, 0.005cm 3 / g, 0.01cm 3 / g, 0.05cm 3 / g, 0.1cm 3 / g, or 1.0 x 10 -4 cm 3 / g~0.1cm 3 / g, or may be a range between any two values.

[0073] In one preferred embodiment, the pH of the negative electrode material is 6.0 to 12.0, and may be, for example, 7.0 to 11.0, 7.5 to 10.0, or 8.0 to 9.0, specifically, for example, 6.0, 6.5, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, or any value between 6.0 and 12.0, or any range between two values.

[0074] In one preferred embodiment, the negative electrode material has micropores, mesopores, and macropores. Preferably, the pore structure is predominantly mesopores. Preferably, the ratio of the pore volume of mesopores to the total pore volume is in the range of 65 to 90%. Preferably, the ratio of the pore volume of macropores to the total pore volume is in the range of 5 to 20%. Preferably, the ratio of the pore volume of micropores to the total pore volume is in the range of 0.05 to 10%. When the negative electrode material satisfies the above ranges, a balance can be achieved between the lithium ion diffusion interface, diffusion paths, and decomposition of the electrolyte in the negative electrode material during electrochemical charge and discharge in a battery containing the negative electrode material, thereby exhibiting good electrochemical rate characteristics, reducing electrolyte consumption, reducing excessive deposition of SEI, suppressing electrode sheet (electrode piece) expansion, and improving cycle performance.

[0075] One embodiment of the present disclosure further provides a method for producing an anode material, which includes performing a CVD vapor deposition process on a silicon-based material core to be coated to obtain an anode material having a pore structure, wherein the gas used in the vapor deposition process includes a mixed gas containing an auxiliary gas and a carbon source gas, and in the mixed gas, the volumetric percentage of the carbon source gas is 30% to 95% and the volumetric percentage of the auxiliary gas is 5% to 70%.

[0076] In one preferred embodiment, the manufacturing method further comprises pretreating the silicon-based material core to be coated before carrying out the CVD vapor phase deposition process.

[0077] Preferably, the pre-treatment comprises sequentially sieving, classifying, washing and drying.

[0078] Here, cleaning includes first washing with water and then rinsing with an organic solvent, and drying includes air-drying the washed material using an inert gas, followed by vacuum drying in an environment of 60°C to 150°C and 1000 Pa or less.

[0079] Preferably, the silicon-based material core to be coated is vibrated and sieved, and the particle size is appropriately determined by classification (D 50The particle size is adjusted to fall within the selectable range of 2.5 μm to 9.0 μm, then washed with deionized water for 30 minutes, then washed with ethanol for 30 minutes, and finally dried by purging with argon gas. The purged and dried material is further vacuum-dried at a drying temperature between 60°C and 150°C for 3 to 48 hours in a vacuum environment maintained at 1000 Pa or less.

[0080] In addition, by adjusting the particle size of the silicon-based material core to be coated in the pretreatment, the specific surface area of ​​the silicon-based material core raw material can be effectively increased (within the selectable range of 0.5m2). 2 / g~7.5m 2 / g), it has a certain control effect on the formation of pore structure after deposition.

[0081] In addition, cleaning methods such as water washing and alcohol washing can remove adsorbed materials from the core surface, reducing the impact of the adsorbed materials on the deposition, allowing the coating layer to form a tight chemical bond with the core, which is beneficial for rapid charge transfer and improved material conductivity. Furthermore, surface adsorbed materials can have a certain effect on the deposition structure of the coating layer, increasing uncertainty in the formation of the negative electrode material and affecting material performance.

[0082] In one preferred embodiment, the temperature of the CVD vapor deposition process is 400°C to 1200°C, and may be, for example, 500°C to 1100°C, 600°C to 1000°C, or 700°C to 900°C, specifically, for example, 400°C, 600°C, 800°C, 1000°C, 1200°C, or any value between 400°C and 1200°C. Preferably, the time of the CVD vapor deposition process is 1 hour to 12 hours, and may be, for example, 2 hours to 11 hours, 3 hours to 10 hours, or 4 hours to 9 hours, specifically, for example, 1 hour, 3 hours, 5 hours, 7 hours, 10 hours, 12 hours, or any value between 1 hour and 12 hours, or a range between two arbitrary values.

[0083] In one preferred embodiment, when performing the CVD vapor deposition process, the silicon-based material core to be coated is placed in a deposition chamber of a deposition furnace, wherein the rotation speed of the deposition chamber is 0.1 r / min to 10 r / min, and the pressure in the deposition furnace is 0.1 MPa to 10 MPa.

[0084] The temperature of the CVD vapor deposition can control the deposition efficiency, the pressure inside the furnace can control the density of the coating layer, the deposition time can control the thickness of the coating layer, and the rotation of the deposition chamber can improve the uniformity of the deposition coating between particles.

[0085] In one preferred embodiment, the carbon source gas used in the CVD vapor deposition process comprises at least one of methane, ethane, ethylene, acetylene, propane, formaldehyde, acetaldehyde, and methanol.

[0086] Preferably, the CVD vapor deposition process is performed using at least two different carbon source gases, because the different carbon source gases have different dissociation temperatures and dissociation efficiencies, which can result in differentiated deposition, and by utilizing the differentiated deposition of different gas sources, a coating layer having a complex combination of pore structures can be deposited.

[0087] In one preferred embodiment, the auxiliary gas used in the CVD vapor deposition process comprises at least one of H2, CO2, NH3, and Ar.

[0088] Preferably, in the mixed gas, the volumetric ratio of the carbon source gas is 30% to 95% and the volumetric ratio of the auxiliary gas is 5% to 70%. For example, the volumetric ratio of the carbon source gas is 30% and the volumetric ratio of the auxiliary gas is 70%, or the volumetric ratio of the carbon source gas is 50% and the volumetric ratio of the auxiliary gas is 50%, or the volumetric ratio of the carbon source gas is 80% and the volumetric ratio of the auxiliary gas is 20%, or the volumetric ratio of the carbon source gas is 95% and the volumetric ratio of the auxiliary gas is 5%.

[0089] Furthermore, by introducing different proportions of carbon source gas and auxiliary gas, the coating layer can have more amorphous irregular branched chains locally, and the uniformity between the organic (high hydrogen content carbon) and the coating layer part (single carbon part, such as graphite, diamond, graphene, etc.) in the coating layer can be improved, which further increases the complexity of the pore structure in the negative electrode material and changes the pore structure, thereby changing the differentiation ratio of the pore structure and changing the electrochemical properties.

[0090] In one preferred embodiment, after CVD vapor deposition, the resulting product is classified, dried, and then sealed to form the finished negative electrode material.

[0091] In one preferred embodiment, the negative electrode material of the present disclosure can be obtained by liquid-phase coating or solid-phase coating of the silicon-based material core to be coated.

[0092] Preferably, the liquid-phase coating includes dissolving a coating raw material in a solvent, mixing it with the silicon-based material core to be coated to obtain a precursor solution, evaporating the precursor solution, and subjecting it to a first heat treatment in an inert gas to obtain the anode material.

[0093] Here, when the coating layer is made of a ceramic material, the coating raw material used in the liquid phase coating contains at least one of soluble silicates, phosphates, and metal salts, and the solvent used is water.

[0094] If the coating layer is a carbon-containing material, the coating raw material used in the liquid phase coating contains at least one of pitch and a resin-based polymer organic compound, and the solvent used contains at least one of n-hexane, benzene, and toluene.

[0095] Furthermore, when multiple types of pitch, polymer monomers, and other materials are dissolved in an organic solvent, their complex cross-linking polymerization and differential deposition are advantageous for the formation of complex pore structures. By adding soluble mixed organic monomers to a polar solvent, polymer formation can be achieved under certain pH conditions, followed by precursor generation and deposition.

[0096] In one preferred embodiment of the liquid-phase coating, the mass of the coating raw material is 0.5% to 10% of the total mass of the coating raw material and the silicon-based material core to be coated, and may be, for example, 1% to 9%, 2% to 7%, or 3% to 6%, specifically, for example, 0.5%, 1%, 3%, 5%, 8%, 10%, or any value between 0.5% and 10%, or any range between two values, to ensure that the coating raw material can be uniformly deposited on the surface of the silicon-based material core.

[0097] Preferably, the ratio of the mass of the solvent to the mass of the silicon-based material core to be coated is (3-7.5):1, such as 3:1, 4:1, 5:1, 6:1, 7:1, 7.5:1, or any value in between (3-7.5):1, or a range between any two values.

[0098] When evaporating the precursor solution, the precursor solution is placed in a water bath or oil bath and heated to evaporate while stirring the precursor solution at a speed of 10 r / min to 500 r / min. The temperature of the water bath or oil bath is 10°C to 20°C lower than the boiling point of the solvent. For example, when the solvent is water, the temperature of the water bath is set to a range of 80°C to 90°C. Stirring is continued until the particles are completely dried and become powdery again.

[0099] After the evaporated material is put into an inert gas and subjected to a first heat treatment, the precursor undergoes a solid-state reaction to form a silicate, and some of the carbon-containing material is carbonized to form a coating layer, which can improve the conductivity of the negative electrode material. Preferably, the precursor can form a ceramic coating layer through a solid-state reaction, and the precursor material can be uniformly deposited on the surface of the active core through coprecipitation and sol-gel methods, allowing various components to be uniformly mixed, reducing the reaction temperature and improving the reaction efficiency and the molding efficiency of the ceramic body.

[0100] In one preferred embodiment of the liquid-phase coating, the temperature for the first heat treatment is 500°C to 1200°C, and may be, for example, 600°C to 1100°C, 700°C to 1000°C, or 800°C to 900°C. Specifically, the temperature may be, for example, 500°C, 600°C, 800°C, 1000°C, 1200°C, or any value between 500°C and 1200°C, or any range between two values. Preferably, the time for the first heat treatment is 3 hours to 24 hours, and may be, for example, 5 hours to 20 hours, 8 hours to 18 hours, or 10 hours to 15 hours, and may be, for example, 3 hours, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, or any value between 3 hours and 24 hours, or any range between two values. The inert gas used includes at least one of argon gas, nitrogen gas, and helium gas.

[0101] In one preferred embodiment, when a solid-state coating process is used, the process preferably includes solid-state mixing of a solid coating material with a silicon-based material core to be coated to obtain a solid-state precursor, and then placing the solid-state precursor in an inert gas to perform a second heat treatment to obtain a negative electrode material.

[0102] The solid coating material includes at least one of solid pitch, soft carbon, hard carbon, and ceramic precursor material. Because these coating materials have different carbon structures, after uniform mixing by ball milling, the phases are sufficiently bonded and can be uniformly deposited on the surface of the silicon-based material core. This allows the reaction temperature to be lowered, which is advantageous for the internal pore structure combination of each phase and the formation of a good internal structure during the later sintering process. Preferably, the ball milling time is 6 to 72 hours.

[0103] In one preferred embodiment of the solid phase coating, the temperature of the second heat treatment is 500°C to 1200°C, and may be, for example, 600°C to 1100°C, 700°C to 1000°C, or 800°C to 900°C, specifically, for example, 500°C, 600°C, 800°C, 1000°C, 1200°C, or any value between 500°C and 1200°C, or a range between two such values. Preferably, the time of the second heat treatment is 3 hours to 24 hours, and may be, for example, 5 hours to 20 hours, 8 hours to 18 hours, or 10 hours to 15 hours, specifically, for example, 3 hours, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, or any value between 3 hours and 24 hours.

[0104] After the liquid-phase coating or solid-phase coating is completed, the resulting product may be subjected to etching and water washing treatment. Preferably, after acid-alkali etching, water washing, and suction filtration, the product is purged with argon gas to dry, and then the product purged and dried with argon gas is classified and vacuum dried to remove moisture, and then vacuum sealed to form a finished negative electrode material.

[0105] In addition, by subjecting the product produced after liquid-phase coating or solid-phase coating to acid-alkali etching, water washing, and classification, unreacted soluble precursors in the product can be removed and the pore structure in the product can be further improved. Here, by subjecting the product washed with water and purged and dried to classification, powder agglomerations can be broken down and the particle size of the classified negative electrode material can be further controlled to be within an optimized range. Furthermore, because negative electrode materials with a porous structure are very susceptible to moisture adsorption, further removal of moisture by vacuum drying can improve the electrochemical properties of the negative electrode material.

[0106] The present disclosure provides a method for adjusting the coating layer to control the pores of the negative electrode material, particularly the coating layer with a specially characterized pore structure, thereby effectively mitigating the expansion of the negative electrode core, balancing the stability of the SEI growth interface, improving the cycle coulomb efficiency, and ensuring the performance of the negative electrode material.

[0107] The present disclosure provides a negative electrode material having a coating layer and a pore structure. Through investigation, it was discovered that the pore structure has a significant effect on the electrochemical properties of the negative electrode material, and therefore the pore structure of the negative electrode material was investigated in detail. By examining the rules of adsorption defects, it was discovered that the data curve characteristics of the hysteresis loop in the adsorption / desorption isotherm of the negative electrode material are highly correlated with the electrochemical properties, and that there exists a selectable mathematical relationship range (pore structure differentiation ratio ΔΦ). 1×10 -3 ≦ΔΦ≦0.5 means that the pore structure of the negative electrode material has an appropriate pore size and alternating distribution, which can ensure that the mass-charge transfer occurs quickly in the negative electrode material, and there are also enough pores to buffer the expansion of the core and stabilize the SEI interface, thereby improving the Coulomb efficiency. -3If ΔΦ is smaller, the pore differentiation is small and the pore structure is simple, i.e., the pore size and shape are uniform and there are few combinations of different pore structures. Therefore, under the same specific surface area, a negative electrode material with such a pore structure will have low expansion relaxation efficiency, low SEI interface stability, and low cycle performance, especially cycle Coulomb efficiency. On the other hand, if ΔΦ is greater than 0.5, the pore structure will be highly complex and there will be an excessive number of combinations of pore channels with different pore sizes. This will result in high mass transfer resistance, low mass transfer efficiency, poor rate performance, and worse concentration polarization during the electrochemical reaction process.

[0108] The present disclosure provides a method for producing an anode material by CVD vapor deposition to produce an anode material with a micropore structure, where the pore structure in the coating layer and the pore structure between the coating layer and the core can be adjusted and controlled by introducing an auxiliary gas into the carbon source gas, thereby further improving the complexity of the pore channel structure in the coating layer, and by changing the pore structure, the differentiation ratio of the pore structure can be changed, thereby changing the electrochemical properties of the anode material.

[0109] In the lithium-ion battery provided by the present disclosure, by using the above-mentioned negative electrode material and utilizing the appropriate pore structure in the coating layer, mass-charge transfer can occur quickly in the negative electrode material, and the pores in the coating layer can buffer the expansion of the negative electrode material and stabilize the SEI interface, thereby significantly reducing the deposition thickness of the SEI layer, thereby significantly improving the diffusion coefficient of lithium in the negative electrode material core and improving the coulombic efficiency and rate capability of the battery. [Example]

[0110] Hereinafter, embodiments of the present disclosure will be described in detail with reference to specific examples. However, those skilled in the art should understand that the following examples are merely for the purpose of illustrating the present disclosure and do not limit the scope of the present disclosure. Specific conditions not specified in the examples were general conditions or conditions provided by the manufacturer. Unless specified by manufacturer, the reagents or equipment used were conventional products that can be purchased commercially.

[0111] Example 1 This example provides a negative electrode material, and a method for manufacturing the negative electrode material includes the following steps: (1) Weigh out 1000 g of lithium-doped silicon monoxide, which has a lithium mass ratio of 10% and a silicon to oxygen atomic ratio of 1:0.9-1.1, wash with deionized water for 30 minutes, then wash with ethanol for 30 minutes. After that, purge with dry Ar until no visible liquid remains and no adhesion or aggregation between particles is observed. Then, place the silicon monoxide in a vacuum drying box. When the pressure inside the box drops to 500 Pa, heat drying begins. The drying temperature is 100°C, and the drying time is 24 hours. (2) The treated sample was placed in a vapor deposition furnace and coated. A mixed gas of methane, acetylene, and ethylene in a volume ratio of 1:1:1 was selected as the coating gas, and NH3 was introduced as the auxiliary atmosphere, with the volume ratio of the carbon source gas to the auxiliary gas being 1:1. The deposition temperature was 900°C, the deposition time was 5 hours, and the rotation speed of the deposition chamber was 5 r / min. The pressure in the deposition chamber was controlled with a pressure valve, and the pressure was maintained at 0.5 MPa, thereby controlling the mass ratio of the resulting coating layer to (5±0.5)%. (3) The vapor-deposited sample was classified, and the material was sieved to the target particle size. After vacuum drying at 100°C for 24 hours, the finished negative electrode material was formed.

[0112] Example 2 This example provides a negative electrode material, and a method for manufacturing the negative electrode material includes the following steps: (1) Weigh out 1000 g of lithium-doped silicon monoxide, which has a lithium mass ratio of 10% and a silicon to oxygen atomic ratio of 1:0.9-1.1, wash with deionized water for 30 minutes, then wash with ethanol for 30 minutes, then purge with dry Ar until no visible liquid remains and no adhesion or aggregation is observed between particles. Then, place the silicon monoxide in a vacuum drying box. When the pressure inside the box drops to 500 Pa, heat drying begins. The drying temperature is 100°C, and the drying time is 24 hours. (2) The treated sample was placed in a vapor deposition furnace and coated. A methane / acetylene mixture with a volume ratio of 1:1 was selected as the coating gas, and Ar was introduced as the auxiliary atmosphere, with a volume ratio of carbon source gas to auxiliary gas of 1:1. The deposition temperature was 900°C, the deposition time was 5 hours, and the rotation speed of the deposition chamber was 5 r / min. The pressure in the deposition chamber was controlled with a pressure valve, and the pressure was maintained at 0.3 MPa, thereby controlling the mass ratio of the resulting coating layer to (5±0.5)%. (3) The vapor-deposited sample was classified, and the material was sieved to the target particle size. After vacuum drying at 100°C for 24 hours, the finished negative electrode material was formed.

[0113] Example 3 This example provides a negative electrode material, and the manufacturing method of the negative electrode material is similar to that of Example 1, with the following differences: In step (1), 1000 g of silicon monoxide having an atomic ratio of silicon to oxygen of 1:0.9 to 1.1 was weighed out.

[0114] Example 4 This example provides a negative electrode material, and the manufacturing method of the negative electrode material is similar to that of Example 1, except that the ratio of carbon source gas to auxiliary gas is 1:3.

[0115] Example 5 This example provides a negative electrode material, and the manufacturing method of the negative electrode material is similar to that of Example 1, except that the ratio of carbon source gas to auxiliary gas is 1:4.

[0116] Example 6 This example provides a negative electrode material, and the manufacturing method of the negative electrode material is similar to that of Example 1, with the following differences: In step (1), 1000 g of magnesium aluminum-doped silicon monoxide was weighed out, the mass ratio of magnesium being 5%, the mass ratio of aluminum being 5%, and the atomic ratio of silicon to oxygen being 1:0.9-1.1.

[0117] Example 7 This example provides a negative electrode material, and a method for manufacturing the negative electrode material includes the following steps: (1) 1000 g of silicon monoxide with an oxygen-to-silicon atomic ratio of 1:0.9-1.1 was weighed. After washing with deionized water for 30 minutes and then with ethanol for another 30 minutes, the sample was purged with dry Ar until no visible liquid remained and no adhesion or aggregation was observed between particles. The sample was then placed in a vacuum drying box. When the pressure inside the box had dropped to 500 Pa, heating and drying began. The drying temperature was 100°C and the drying time was 24 hours. (2) The treated sample was placed in a vapor deposition furnace and coated. Methane gas was selected as the coating gas, and H2 and SO2 were introduced as auxiliary atmospheres in a volume ratio of 1:1. The ratio of carbon source gas to auxiliary gas was 1:2. The deposition temperature was 900°C, the deposition time was 7 hours, and the rotation speed of the deposition chamber was 5 r / min. The pressure in the deposition chamber was controlled with a pressure valve and maintained at 1 MPa, thereby controlling the mass ratio of the resulting coating layer to (5±0.5)%. (3) The vapor-deposited sample was classified, and the material was sieved to the target particle size. After vacuum drying at 100°C for 24 hours, the finished negative electrode material was formed.

[0118] Comparative Example 1 This comparative example provides a negative electrode material, and the manufacturing method of the negative electrode material includes the following steps. (1) 100 g of silicon monoxide having an atomic ratio of silicon to oxygen of 1:0.9-1.1 was added to an organic solvent in which 100 g of N-methylpyrrolidone and 20 g of polyimide had been mixed and dissolved, and the mixture was stirred for 30 minutes. After that, the mixture was vacuum dried at 100°C for 48 hours to remove the solvent. (2) The mixed precursors were transferred to a high-pressure reactor, heated to 900°C at a rate of 10°C / min under an argon atmosphere, and then reacted for 12 hours. (3) After vapor deposition, the sample was classified and sieved to the target particle size. The heat-treated material was immersed in a hydrochloric acid solution of pH 2 for 30 minutes, washed with deionized water, and then placed in a lithium hydroxide solution of pH 11 for 30 minutes. After that, it was washed with deionized water for 30 minutes and then washed with ethanol for another 30 minutes. After suction filtration, the sample was purged with dry argon gas until no obvious sticky liquid or agglomerated particles remained. It was then placed in a vacuum drying box and vacuum dried at 100°C for 24 hours to form the finished negative electrode material.

[0119] Comparative Example 2 This comparative example provides a negative electrode material, and the manufacturing method of the negative electrode material includes the following steps. (1) 100 g of lithium-doped silicon monoxide, with a lithium mass ratio of 10% and a silicon to oxygen atomic ratio of 1:0.9-1.1, was weighed out, washed with deionized water for 30 minutes, and then washed with ethanol for 30 minutes. After that, the silicon monoxide was purged with dry Ar until no visible liquid remained and no adhesion or aggregation was observed between the particles. The silicon monoxide was then placed in a vacuum drying box. When the pressure inside the box had dropped to 500 Pa, heating and drying began. The drying temperature was 100°C, and the drying time was 24 hours. (2) The processed sample was placed in a vapor deposition furnace and coated. Pure acetylene was selected as the coating gas for carbon source deposition, and acetylene decomposition deposition was performed using plasma. The deposition time was 48 hours, and the plasma source was generated using an electron sputtering radio frequency (RF) gun with a graphite target. A bias voltage of -400 V was set on the material stage in the deposition chamber to ensure carbon source deposition. After the plasma stabilized, the pressure in the chamber was controlled with a vacuum valve and maintained at 100 Pa. (3) After vapor deposition, the sample was classified, and the material was sieved to the target particle size. It was then placed in a vacuum drying box and vacuum dried at 100°C for 24 hours to form the finished negative electrode material.

[0120] Comparative Example 3 This comparative example provides a negative electrode material, and the manufacturing method of the negative electrode material includes the following steps. (1) 100 g of magnesium-doped silicon monoxide, with a magnesium mass fraction of 8.5% and a silicon to oxygen atomic ratio of 1:0.9-1.1, was weighed out, washed with deionized water for 30 minutes, and then washed with ethanol for 30 minutes. After that, the sample was purged with dry Ar until no visible liquid remained and no adhesion or aggregation was observed between the particles. The sample was then placed in a vacuum drying box, and when the pressure inside the box dropped to 500 Pa, heating and drying began. The drying temperature was 100°C, and the drying time was 24 hours. (2) The processed sample was placed in a vapor deposition furnace and coated. Pure acetylene was selected as the coating gas for carbon source deposition, and plasma was used for decomposition deposition of acetylene. The deposition time was 48 hours, and the plasma source was generated using an electron sputtering radio frequency (RF) gun with graphite as the target material. A bias voltage of -400 V was set on the material stage in the deposition chamber to ensure carbon source deposition. After the plasma stabilized, the pressure in the chamber was controlled with a vacuum valve and maintained at 100 Pa. (3) After vapor deposition, the sample was classified, and the material was sieved to the target particle size. It was then placed in a vacuum drying box and vacuum dried at 100°C for 24 hours to form the finished negative electrode material.

[0121] The performance of the negative electrode materials in Examples 1 to 7 and Comparative Examples 1 to 3 was measured, and the results are shown in Table 1. The adsorption and desorption isotherms of the negative electrode materials produced in Example 1 and Comparative Example 1 are also shown in Figures 1 and 2, respectively.

[0122] The adsorption and desorption isotherms were obtained based on the results of measuring the pore size distribution and porosity of the negative electrode material by mercury intrusion porosimetry and gas adsorption method in accordance with GB / T 21650.3-2011 standard.

[0123] Particle size measurement: Particle size measurement was performed according to the Chinese national standard GB / T 24533-2019, and the particle size measurement was performed using Malvern's Mastersizer 3000 as the device to obtain the D50 data.

[0124] Tap density: The data was obtained by measuring according to the method specified in the Chinese national standard GB / T 24533-2019.

[0125] Measurement of the mass fraction of the coating layer: Measured according to the method specified in the Chinese national standard GB / T 20123-2006. For carbon-coated anode materials, samples were burned in a high-temperature furnace with oxygen, generating and emitting CO2 gas. This method was used to separate C element from metal elements and their compounds, and the CO2 content was measured and converted into the carbon content of the sample. For ceramic coating layers, the mass fraction of the ceramic coating layer was calculated based on the mass ratio of the ceramic raw materials used in the synthesis process and the mass of the final ceramic produced after firing. For example, ceramic precursors A and B were reacted at high temperature to produce the target ceramic D and by-product gas E. The reaction equation is A + B = D + E, and the mass of D, m, was calculated from the masses of added A and B. D The mass of the silicon-based raw material is m Si and the formula m D / (m Si +m D ) to obtain the mass proportion of the ceramic coating layer.

[0126] The content of lithium, a doping metal element, ICP (ppm): The negative electrode material was baked in a muffle furnace to remove carbon, and then decomposed with hydrofluoric acid to decompose silicon. The material was then heated and further decomposed with aqua regia. The data was then measured according to the method specified in the Chinese national standard GB / T 24533-2019.

[0127] Table 1: Measurement results of negative electrode materials in Examples 1 to 7 and Comparative Examples 1 to 3 [Table 1]

[0128] The electrochemical properties of the negative electrode materials in Examples 1 to 7 and Comparative Examples 1 to 3 were also measured. Table 2 shows the specific measurement results.

[0129] The battery sample manufacturing process is as follows. To determine the specific capacity of the negative electrode material and the initial charge / discharge coulombic efficiency, a button battery was assembled in accordance with the equipment and methods specified in BTRTC / ZY / 01-020 "Button Battery Method Operation Manual." The counter electrode was a metallic lithium sheet, the separator was a 19.2 mm diameter PP-PE-PP composite membrane, the electrolyte composition was EC / EMC / DMC=1:1:1, and the lithium salt (LiPF6) concentration was 1.05 mol / L.

[0130] Electrochemical property measurements: Material capacity measurement: Using a button battery charge / discharge device, the battery was discharged to 10 mV at a constant current of 0.1 C, then discharged to 5 mV at a constant current of 0.02 C, and charged to 1.5 V at a constant current of 0.1 C. 50-cycle measurement of half-cell: Using a button battery charge / discharge device, in the first cycle, discharge to 0.01V at 0.1C, gradually discharge to 0.01V at 0.01C, discharge to 0.005V at 0.01C, and charge to 1.5V at 0.1C; in the second cycle, discharge to 0.01V at 0.2C, gradually discharge to 0.01V at 0.02C, discharge to 0.005V at 0.02C, and charge to 1.5V at 0.2C; in the third cycle, discharge to 0.01V at 0.5C. Discharge to 0.01V, then discharge at 0.05C in increments to 0.01V, discharge at 0.05C increments to 0.005V, and charge at 0.5C increments to 1.5V; from the 4th to 50th cycles, discharge at 1C increments to 0.01V, discharge at 0.1C increments to 0.01V, discharge at 0.1C increments to 0.005V, and charge at 1C increments to 1.5V; from the 51st cycle, discharge at 0.1C increments to 0.01V, discharge at 0.01C increments to 0.01V, and charge at 0.01C increments to 0.005V. Whole battery performance measurement: Graphite was mixed into the negative electrode material to set the capacity to the standard 450mAh / g, and the capacity retention rate (2.75V to 4.2V) of 0.2C charge / discharge was measured at high temperature (60°C) for 7 consecutive days.

[0131] Table 2: Measurement results of electrochemical properties of negative electrode materials of Examples 1 to 7 and Comparative Examples 1 to 3 [Table 2]

[0132] The adsorption equilibrium curve and the area of ​​the hysteresis loop are numerical representations of the distribution of surface pore structure, which can affect the electrochemical properties of the material. Specific manufacturing techniques can fine-tune the pore structure, thereby improving the material's performance, and different cores also have a certain effect on the material.

[0133] As can be seen from Table 2, Comparative Example 1 used a single carbon source for material coating, resulting in a relatively uniform (homogeneous) pore structure. Therefore, the hysteresis loop area was relatively small and outside the optimal range. While the simple pore structure favors electrolyte infiltration, uncontrolled surface side reactions resulted in significant electrode expansion. In Example 7, the addition of an auxiliary gas to the carbon source gas allowed for tailoring of the pore structure in the carbon layer and the pore structure between the carbon layers during the carbon deposition process. This resulted in the formation of different pore structures and pore distributions within the coating layer, improving the hysteresis loop area and mitigating the expansion of the silicon-based material core and stabilizing the SEI growth interface. Compared to Comparative Example 1, the expansion rate of the button battery electrode sheet in Example 6 was significantly lower, and the corresponding cycle capacity retention rate also showed a difference. The measurement results for Comparative Example 1 and Example 7 in Table 1 show that the pore structure differentiation ratio ΔΦ can indicate electrochemical changes due to the pore structure of the anode material. When ΔΦ is within an appropriate range, the complex pore structure can improve electrolyte infiltration and enhance the migration of active lithium in the electrolyte in the anode material, thereby improving rate performance. The complex pore structure provides a weak polarization transmission barrier to the thermal conduction of lithium ions, thereby limiting decomposition reactions at high temperatures and improving high-temperature storage capacity retention.

[0134] The negative electrode materials of Example 1 and Comparative Example 2 were manufactured using the same lithiated core, but different coating processes were used to control the pore structure of the surface coating layer, resulting in different pore structure differentiation ratios ΔΦ of the manufactured negative electrode materials. The hysteresis loop area ΔS of Comparative Example 2 was within the selectable range, but the calculated pore structure differentiation ratio ΔΦ was 0.568, outside the selectable range. The electrochemical property measurement results in Table 2 reveal the following: The pore structure of the coating layer of the negative electrode material manufactured in Comparative Example 2 was very complex. During charging and discharging, a large amount of electrolyte decomposition by-product (SEI) was present in the pore channels of the surface coating layer of the negative electrode material. This caused the lithiated silicon-based core to expand in volume, destroying the pore channel structure filled with electrolyte and ultimately tearing the coating layer on the surface of the negative electrode material. This resulted in uncontrollable electrolyte decomposition, resulting in an increased expansion rate of the negative electrode sheet and a decrease in rate performance. In Table 2, the rate charge performance of Comparative Example 2 at three rates of 1C / 0.5C, 2C / 0.5C, and 3C / 0.5C was lower than that of Example 1 by 3.49%, 5.67%, and 5.75%, respectively.

[0135] It should be noted that the above embodiments are only for illustrating the technical solutions of the present disclosure and are not intended to be limiting. Although the present disclosure has been described in detail with reference to the above embodiments, those skilled in the art may still modify the technical solutions described in the above embodiments or make equivalent substitutions for some or all of the technical features therein, but it should be understood that these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present disclosure.

[0136] Furthermore, those skilled in the art will understand that although some embodiments herein include some features included in other embodiments and do not include other features, a combination of features from different embodiments constitutes a different embodiment within the scope of the present disclosure. For example, any of the embodiments to be protected above may be used in any combination. The information disclosed in the Background section is intended merely to enhance understanding of the overall background of the present disclosure, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. [Industrial Applicability]

[0137] The present disclosure provides a negative electrode material, a manufacturing method thereof, and a lithium-ion battery, and by providing a coating layer with a special pore structure on the negative electrode material, the lithium diffusion coefficient of the negative electrode material core is significantly improved, and the rate characteristics and cycle performance of the battery are improved, resulting in excellent practical performance.

Claims

1. A negative electrode material including a core and a coating layer formed on at least a portion of a surface of the core, the core comprises a silicon-based material; The negative electrode material has a pore structure, The pore structure differentiation ratio ΔΦ calculated by the following formula (I) is 1 × 10 －３ A negative electrode material characterized in that the value is 0.5 or less. [Equation 1] (In formula (I), ΔS is the area of ​​the hysteresis loop in the adsorption / desorption isotherm of the negative electrode material; s is the specific surface area of ​​the negative electrode material; and ΔP is the relative pressure P / P corresponding to the hysteresis loop. ０ is the interval difference between the ｍａｘ is the maximum isothermal adsorption amount of the negative electrode material.)

2. The negative electrode material according to claim 1 , which satisfies at least one of the following conditions: a. The silicon-based material comprises at least one of elemental silicon, silicon oxide, silicon carbide, silicon nitride, silicon phosphide, silicon sulfide, and silicon alloy. b) The core further comprises a carbon-based material. c) The core further comprises a doping metal element.

3. The negative electrode material according to claim 1 , which satisfies at least one of the following conditions: a. The coating layer includes at least one of a carbon-containing material and a ceramic-based material. b) The mass of the coating layer is 0.5% to 10% of the total mass of the negative electrode material. c) The thickness of the coating layer is between 20 nm and 700 nm.

4. The pore structure differentiation ratio ΔΦ is 5 × 10 －３ The negative electrode material according to claim 1, wherein the ρ is 0.5 or less.

5. The area ΔS of the hysteresis loop is 4.5 × 10 －４ ~3.0 x 10 －２ The negative electrode material according to claim 1 ,

6. The maximum isothermal adsorption amount Q of the negative electrode material ｍａｘ The negative electrode material according to claim 1 , wherein the Cr content is 1.35 mmol / g or less.

7. The negative electrode material has a BJH average pore diameter of 5 nm to 20 nm and a BJH pore volume V ＢＪＨ is 1.0 x 10 －４ cm ３ / g to 0.1 cm ３ The negative electrode material according to claim 1, wherein the Cr content is 1 / g.

8. The negative electrode material according to claim 3 , further satisfying at least one of the following conditions: The carbon-containing material includes at least one of graphite, hard carbon, soft carbon, amorphous carbon, diamond-like carbon, carbon fiber, carbide, pitch, and a resin-based high molecular weight polymer. b) the ceramic-based material comprises at least one of a phosphate, a silicate, a nitride, and a metal oxide;

9. The negative electrode material according to claim 1 , wherein the coating layer has the pore structure.

10. The negative electrode material according to any one of claims 1 to 9, wherein the pore structure includes micropores, mesopores, and macropores.

11. A method for producing an anode material, comprising: performing a coating process on a silicon-based material core to be coated by CVD vapor deposition to obtain an anode material having a micropore structure; The vapor deposition gas includes an auxiliary gas and a carbon source gas, and in the gas, the volume ratio of the carbon source gas is 30% to 95% and the volume ratio of the auxiliary gas is 5% to 70%; In the negative electrode material, the pore structure differentiation ratio ΔΦ calculated by the following formula (I) is 1×10 －３ A manufacturing method characterized in that the value is 0.5 or less. [Equation 2] (In formula (I), ΔS is the area of ​​the hysteresis loop in the adsorption / desorption isotherm of the negative electrode material; s is the specific surface area of ​​the negative electrode material; and ΔP is the relative pressure P / P corresponding to the hysteresis loop. ０ is the interval difference between the ｍａｘ is the maximum isothermal adsorption amount of the negative electrode material.)

12. The method of claim 11 , wherein at least one of the following conditions is satisfied: A. The auxiliary gas is H ２ , S.O. ２ , N.H. ３ , and Ar. B. In the mixed gas, the volume ratio of the carbon source gas is 30% to 95%, and the volume ratio of the auxiliary gas is 5% to 70%.

13. The method of claim 11 further comprising pre-treating the silicon-based material core to be coated before performing the CVD vapor deposition.

14. The method of claim 13, wherein at least one of the following conditions is satisfied: C. The pretreatment includes sequentially screening, classifying, washing, and drying the silicon-based material cores to be coated. D. The particle size D of the silicon-based material core to be coated obtained after the pretreatment ５０ is 2.5 μm to 9.0 μm. E. The specific surface area of ​​the silicon-based material core to be coated obtained after the pretreatment is 0.5 m ２ / g to 7.5m ２ / g.

15. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 10, or the negative electrode material produced by the production method according to any one of claims 11 to 14.

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