Anode materials and lithium-ion batteries

Abstract

The present application relates to an anode material and a lithium-ion battery, wherein the anode material comprises a porous carbonaceous material having a silicon material distributed therein, and the anode material has a uniformity N, where N satisfies N≧80%. In a backscattered electron image obtained by scanning the anode material with an SEM scanning electron microscope in a BSE automatic brightness and contrast mode, within any 100 μm×100 μm region, the number of particles of the anode material having a first brightness is denoted by C1, the first brightness representing anode material having a grayscale value of 5500 or more in the backscattered electron image, and the number of particles of the anode material having a second brightness representing anode material having a grayscale value of less than 5500 in the backscattered electron image. The uniformity N' of the anode material within the region is N'=C2 / (C2+C1)×100%, and the uniformity N of the anode material is the arithmetic average of at least 10 N's.

Description

[Technical Field]

[0001] The present application is in the technical field of anode materials, and more particularly relates to anode materials and lithium ion batteries. [Background technology]

[0002] Silicon-based anode materials have advantages such as high specific capacity, low voltage platform, environmental friendliness, and abundant resources, making them promising candidates for next-generation high-specific-energy lithium-ion batteries. However, silicon undergoes large volume changes during the absorption and desorption process, which can easily lead to particle pulverization and even detachment from the current collector. Furthermore, the repeated volume changes of silicon materials during electrochemical cycling can also cause the SEI film formed on the silicon material surface to be constantly destroyed and regenerated, resulting in continuous consumption of lithium ions and ultimately rapid capacity decay.

[0003] Typically, silicon anode materials are improved through processes such as nanosizing, carbon coating, and polymer coating, which can suppress the volumetric expansion of silicon to a certain extent. Silicon is usually deposited in porous carbon to suppress the volumetric expansion of silicon, and the current mainstream manufacturing method for porous carbonaceous materials is to produce them using biomass methods. However, porous carbon produced using existing biomass processes generally has uneven activation, resulting in the presence of a number of particles that are non-porous (i.e., unactivated). Because these particles are not activated during the silicon deposition process, they have very few or no pores, which makes it easy for silicon to accumulate on the particle surface, resulting in deterioration of the expansion performance, cycle performance, and rate performance of the anode material.

[0004] Therefore, there is currently an urgent need to provide a silicon negative electrode material that has low expansion, high cycle and high rate performance. Summary of the Invention

[0005] The present application provides a negative electrode material and a lithium ion battery that can improve the expansion performance, cycle performance, and rate performance of the negative electrode material. To achieve the above objectives, the first technical solution of this application is as follows:

[0006] An embodiment of the present application provides a negative electrode material, the negative electrode material comprising a porous carbonaceous material, a silicon material distributed within the porous carbonaceous material, and the negative electrode material has a uniformity N, where N≧80%; In a backscattered electron image obtained by scanning the negative electrode material using an SEM scanning electron microscope in a BSE automatic brightness and contrast mode, within any 100 μm × 100 μm region, the number of particles of the negative electrode material having a first brightness is denoted by C1, the particles of the negative electrode material having the first brightness representing a negative electrode material having a grayscale value of 5500 or more in the backscattered electron image, the number of particles of the negative electrode material having a second brightness is denoted by C2, the particles of the negative electrode material having the second brightness representing a negative electrode material having a grayscale value of less than 5500 in the backscattered electron image, the uniformity of the negative electrode material within the region N' = C2 / (C2 + C1) × 100%, and the uniformity N of the negative electrode material is the arithmetic average of the uniformities N' of at least 10 of the regions.

[0007] The technical solution of the present application has at least the following beneficial effects: The negative electrode material of the present application comprises a porous carbonaceous material and a silicon material, and the negative electrode material has a uniformity N, where N is 80% or more. This indicates that the negative electrode material of the present application is mainly present in the form of particles with a grayscale value of less than 5500 in a backscattered electron image. Particles with a grayscale value of less than 5500 in a backscattered electron image indicate that the silicon material in the negative electrode material particles is mainly distributed within the pores of the porous carbonaceous material, and the distribution is uniform. That is, in the present application, the proportion of the number of particles in which the silicon material is uniformly distributed within the pores of the porous carbonaceous material, relative to the total number of negative electrode material particles being 100%, is 80% or more. This clearly indicates that the porous carbonaceous material of the present application has uniformly distributed activated pores, and the number of activated pores is appropriate, so that the silicon material can be mainly distributed within the pores of the porous carbonaceous material, and has a high silicon deposition amount. The uniformity N of the present application is obtained by measuring the negative electrode material obtained within any 100 μm × 100 μm region, and N≧80% indicates that the number and distribution of activated pores in the porous carbonaceous material of each negative electrode material particle of the present application are highly similar. That is, the negative electrode material of the present application has a porous carbonaceous material with good uniformity. A porous carbonaceous material with good uniformity can improve the dispersion of the silicon material in the negative electrode material, suppress the volume effect caused by the silicon material agglomeration during the lithium absorption / desorption process, and reduce the pulverization of the negative electrode material particles. In addition, the negative electrode material can form an SEI film within the limited space during the lithium absorption / desorption process, forming a stable SEI film and improving the structural stability of the negative electrode material, which is beneficial to improving the expansion performance, cycle performance, and capacity of the negative electrode material. [Brief explanation of the drawings]

[0008] The present application will now be further described with reference to the figures and examples. [Figure 1] 1 is a flowchart for manufacturing the negative electrode material of the present application. [Figure 2] 1 is an SEM image of the negative electrode material prepared in Example 1 of the present application. [Figure 3] 1 is an XRD chart of the negative electrode material produced in Example 1 of the present application. [Figure 4] 1 is an initial charge-discharge curve of the negative electrode material prepared in Example 1 of the present application. [Figure 5] 1 is a cycle performance curve of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to better understand the technical solution of the present application, the following detailed description of the embodiments of the present application will be given with reference to the accompanying drawings.

[0010] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all of the embodiments, and all other embodiments that a person skilled in the art can obtain based on the embodiments of the present application without performing any creative work fall within the scope of protection of the present application.

[0011] The terms used in the examples of this application are used only for the purpose of describing particular examples and are not intended to limit the application. As used in the examples of this application and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms unless the context clearly dictates otherwise.

[0012] It should be understood that the term "and / or" used in this application merely describes the relationship between related objects and indicates that three relationships may exist, for example, A and / or B can indicate three cases: A exists alone, A and B exist simultaneously, and B exists alone. Also, the character " / " in this application generally indicates that the related objects before and after it are in an "or" relationship.

[0013] The production of porous carbonaceous materials using biomass methods is currently the mainstream manufacturing method, but porous carbonaceous materials produced using existing biomass processes generally have non-uniform activation, resulting in the presence of some particles that are non-porous (i.e., unactivated).Since these particles are not activated during the silicon deposition process, they have very few or no pores, resulting in little or no silicon deposition, which leads to deterioration of the performance of the negative electrode material.

[0014] The examples of the present application are An anode material, comprising a porous carbonaceous material, wherein a silicon material is distributed within at least a portion of the porous carbonaceous material, and the anode material has a uniformity N, where N≧80%; The present invention provides a negative electrode material, wherein, in a backscattered electron image obtained by scanning the negative electrode material using a Hitachi S4800 SEM scanning electron microscope in BSE automatic brightness and contrast mode, within any 100 μm × 100 μm region, the number of particles of a negative electrode material having a first brightness is denoted by C1, where the negative electrode material having the first brightness represents a negative electrode material having a grayscale value of 5500 or more in the backscattered electron image, and the number of particles of a negative electrode material having a second brightness is denoted by C2, where the negative electrode material having the second brightness represents a negative electrode material having a grayscale value of less than 5500 in the backscattered electron image, and the uniformity of the negative electrode material within the above region is N' = C2 / (C2 + C1) × 100%, where the uniformity N of the negative electrode material is the arithmetic average of the uniformities N' of at least 10 of the above regions.

[0015] In the above technical solution, the negative electrode material of the present application comprises a porous carbonaceous material and a silicon material, and the negative electrode material has a uniformity N, where N is 80% or more. This indicates that the negative electrode material of the present application is mainly present in the form of particles with a grayscale value of less than 5500 in a backscattered electron image. Particles with a grayscale value of less than 5500 in a backscattered electron image indicate that the silicon material in the negative electrode material particles is mainly distributed within the pores of the porous carbonaceous material and the distribution is uniform. That is, in the present application, the proportion of the number of particles in which the silicon material is uniformly distributed within the pores of the porous carbonaceous material, relative to the total number of negative electrode material particles being 100%, is 80% or more. This indicates that the porous carbonaceous material of the present application has uniformly distributed activated pores and an appropriate number of activated pores, so that the silicon material can be mainly distributed within the pores of the porous carbonaceous material and has a high silicon material deposition amount. The present application was obtained by measuring the anode material obtained within any 100 μm × 100 μm area, and found that the number and distribution of activated pores in the porous carbonaceous material of each anode material particle of the present application are highly similar. That is, the anode material of the present application has a consistent porous carbonaceous material, which can improve the dispersion of the silicon material in the anode material, reduce the volume effect caused by the silicon material agglomeration during the lithium absorption / desorption process, and reduce the pulverization of the anode material particles. In addition, the anode material forms an SEI film within the limited space during the lithium absorption / desorption process, forming a stable SEI film and improving the structural stability of the anode material, which is advantageous for improving the expansion performance, cycle performance, and capacity of a battery manufactured using the anode material.

[0016] Because there is a large difference in electrical conductivity between carbonaceous materials and silicon materials, when a negative electrode material is examined using a scanning electron microscope (SEM) with backscattered electrons (BSE) in automatic brightness and contrast mode, negative electrode material particles with relatively high electrical conductivity are generally darker in color, i.e., particles of porous carbonaceous material in which the amount of silicon deposited on the porous carbonaceous material in the negative electrode material is relatively small or no silicon is deposited are generally dark in color. Negative electrode material particles with low electrical conductivity are generally lighter in color, i.e., particles of negative electrode material in which silicon material is primarily deposited on a porous carbonaceous material with uniformly distributed pores are generally lighter in color, typically exhibiting a bright white color. In this application, a grayscale value of 5500 is used as a criterion for determining whether the color of the material particles is dark or light. A negative electrode material with a grayscale value of 5500 or more indicates that the material surface is relatively dark, i.e., the material particles have a first brightness. Material particles with the first brightness indicate that the silicon material is deposited in a relatively small amount inside the negative electrode material particles, i.e., the amount of silicon material deposited is relatively small. A negative electrode material with a grayscale value of less than 5500 indicates that the material surface is relatively bright, i.e., the material particles have a second brightness. Material particles with the second brightness indicate that the silicon material is mainly deposited on a porous carbonaceous material with uniformly distributed pores and that the amount of silicon material deposited is relatively large, i.e., the silicon material is present in a relatively large amount inside the negative electrode material particles.

[0017] In the present application, the uniformity N is measured and calculated using a Hitachi S4800 SEM scanning electron microscope. Specifically, the scanning electron microscope (SEM) is adjusted to the BSE automatic brightness and contrast mode to scan the negative electrode material particles, the scanned image is converted into a grayscale image, and the grayscale image is calculated using ImageJ image processing software. Specifically, the grayscale image is opened using ImageJ image processing software, and the particle region for which the grayscale value is to be calculated is selected using the "selection frame" tool. The selected region is an arbitrary region of 100 μm × 100 μm. Next, the Ctrl+1 and Ctrl+3 keys are pressed in sequence to obtain the grayscale change curves of all particles. Next, perpendicular lines are drawn from each valley point to the horizontal axis using the line tool (rectangular or rounded rectangular selection) to form multiple different closed shapes under the grayscale change curves. Finally, the magic wand (tracing tool) tool is used to click on the closed shapes in order, excluding the beginning and end, to obtain the total grayscale value for each shape, which is recognized as the grayscale value of the multiple particles within the selected region. The above procedure is repeated to obtain uniformity N' for at least 10 selected regions, and then the arithmetic mean value of the uniformity N' for all selected regions is calculated to obtain uniformity N.

[0018] In some embodiments, N may be, for example, 80%, 86%, 88%, 90%, 93%, 95%, 97%, 99%, or 100%, and may be other values ​​within the above range, without any limitation thereto. Within the above limited range, the porous carbonaceous material has an appropriate number of activated pores with uniform distribution, allowing the silicon material to be distributed mainly within the pores of the porous carbonaceous material. This indicates that the silicon material content in the negative electrode material is relatively high and the negative electrode material is relatively bright in scanning electron microscope (SEM)-backscattered electron (BSE) automatic brightness and contrast mode. However, if N is less than 80%, the distribution of activated pores in the porous carbonaceous material is relatively poor, and there are a certain number of particles with few or no activated pores. As a result, the silicon material is deposited less or almost not at all within the porous carbonaceous material, resulting in poor performance of the resulting negative electrode material. Preferably, the uniformity of the negative electrode material is 86%≦N≦99%.

[0019] In some embodiments, the silicon material is further distributed on at least a portion of the surface of the porous carbonaceous material.

[0020] In some embodiments, the porous carbonaceous material comprises at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, and carbon gel.

[0021] In some embodiments, the porous carbonaceous material comprises micropores, which refer to pores with a pore size of less than 2 nm. The micropores are activated pores, which are advantageous for filling with silicon material. The silicon material filled inside the micropores can ensure the structural integrity of the porous carbonaceous material, thereby preventing structural collapse during the compaction process of the negative electrode material to manufacture the electrode.

[0022] In some embodiments, the percentage of micropores in the porous carbonaceous material is 80% or more, with the total number of pores being 100%, and may be, for example, 80%, 85%, 90%, 92%, 95%, 97%, or 99%, although other values ​​within the above range are also possible, and the present application is not limited thereto. Within the above limited range, the present application indicates the presence of many activated pores, which have an energy storage function, reduce the diffusion resistance of the electrolyte, and improve the capacity and rate performance of the anode material. Preferably, the percentage of micropores in the porous carbonaceous material is 90% or more, more preferably, 92% or more, as measured by nitrogen gas desorption / adsorption. If the number of micropores in the porous carbonaceous material is less than 80%, this indicates a small number of micropores in the porous carbon and a low loading of silicon material, which is detrimental to improving the capacity performance of the anode material.

[0023] In some embodiments, the pores in the porous carbonaceous material include micropores with a pore diameter of less than 2 nm, and the micropore volume ratio is ≥ 80% based on the total pore volume. Specifically, the micropore volume ratio may be other values ​​within the above range, such as 80%, 82%, 85%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, without limitation. It should be understood that the size of the silicon material particles deposited in the pores of the porous carbonaceous material is determined by the size of the pores. The higher the micropore volume ratio, the smaller the average pore diameter of the pores in the porous carbonaceous material and the smaller the particle diameter of the silicon material particles deposited in the pores of the porous carbonaceous material. A small particle diameter of the silicon material particles deposited in the pores of the porous carbonaceous material reduces the volume expansion of the negative electrode material during cycling, which is advantageous for improving the cycling performance of the negative electrode material.

[0024] In some embodiments, the average pore diameter in the porous carbonaceous material is 5 nm or less, and may be, for example, 1 nm, 1.3 nm, 1.8 nm, 2 nm, 3 nm, 4 nm, or 5 nm, and of course, other values within the above range may also be used, and the present application does not limit here. Preferably, the average pore diameter of the pores in the porous carbonaceous material is 2 nm or less, and preferably, the average pore diameter of the pores in the porous carbonaceous material is 1.8 nm or less.

[0025] In some embodiments, the silicon material includes at least one of crystalline silicon, silicon oxide material, amorphous silicon, and silicon alloy, and the silicon oxide material includes silicon oxide SiO x where 0 < x ≤ 2, and the silicon oxide is a silicon-oxygen composite, including oxygen atoms and silicon atoms, and the molar ratio of oxygen atoms to silicon atoms is 0 to 2 and does not include 0. SiO 0.2 SiO 0.5 SiO 0.8 SiO, SiO 1.2 SiO 1.5 SiO 1.8 or a combination of two or more such as SiO2, or a compound with the chemical formula SiO x and of course, other values within the above range may also be used, and the present application does not limit here.

[0026] In some embodiments, the silicon material includes at least one of crystalline silicon, amorphous silicon, and a composite of crystalline silicon and amorphous silicon. Preferably, the silicon material is amorphous silicon, which has a lower expansion compared to other types of silicon and helps to improve the problem of large volume expansion during the lithium release and absorption process of the silicon-carbon negative electrode material.

[0027] In some embodiments, the silicon material includes silicon particles. The morphology of the silicon particles includes at least one of dot-like, spherical, ellipsoidal, and flaky.

[0028] In some embodiments, the mass content of silicon element in the silicon material ≥ 99%.

[0029] In some embodiments, the mass proportion of the silicon material in the negative electrode material is 30% to 80%, i.e., the mass proportion of elemental silicon in the negative electrode material is 30% to 80%, and may be specifically 30%, 40%, 50%, 60%, 70%, 80%, etc., and may of course be other values ​​within the above range, and this application is not limited thereto. Within the above limited range, the mass proportion of the silicon material in the negative electrode material, i.e., the mass proportion of elemental silicon in the negative electrode material, is high, which is advantageous for improving the capacity of the negative electrode material.

[0030] In some embodiments, the average particle size of the silicon material is 0.1 nm to 500 nm, for example, 0.1 nm, 1 nm, 5 nm, 10 nm, 30 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, and may be other values ​​within the above range, without any limitation thereto. Within the above limited range, stress and strain generated in the silicon material during the lithium ion desorption / sorption process are alleviated, which is advantageous for improving the capacity and cycle performance of the negative electrode material. Preferably, the average particle size of the silicon material is 0.1 nm to 10 nm, and more preferably, the average particle size of the silicon material is 0.1 nm to 5 nm.

[0031] In some embodiments, the negative electrode material further includes a coating layer distributed on at least a portion of the surface of the porous carbonaceous material. The coating layer can, on the one hand, prevent the electrolyte from penetrating the inside of the negative electrode material and causing side reactions that result in a decrease in initial efficiency and capacity, and, on the other hand, the coating layer cooperates with the porous carbonaceous material to mitigate the volume expansion of the silicon material, reduce the volume expansion of the entire negative electrode material, and reduce swelling of the electrode sheet.

[0032] In some embodiments, the coating layer is at least one of a carbon layer, a metal oxide layer, and a nitride layer.

[0033] In some embodiments, the material of the carbon layer includes at least one of graphene, soft carbon, hard carbon, and a conductive polymer, and specifically, the conductive polymer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly3-hexylthiophene, poly(p-phenylenevinylene), polypyridine, and polyphenylenevinylene.

[0034] In some embodiments, the metal oxide layer comprises at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide.

[0035] In some embodiments, the nitride layer comprises at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0036] In some embodiments, the thickness of the coating layer is 0.1 nm to 100 nm, and specifically may be 0.1 nm, 1 nm, 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 100 nm, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto. When the thickness of the coating layer is within the above range, it is advantageous to balance electrochemical performance such as capacity and rate performance of the negative electrode material and to improve the cycle performance of the negative electrode material.

[0037] In some embodiments, the pore volume of the porous carbonaceous material is greater than or equal to 0.4 cm 3 / g or more, for example, 0.4 cm 3 / g, 0.5cm 3 / g, 0.7cm 3 / g, 1.0cm 3 / g, 1.5cm 3 / g, 2.0cm 3 / g, 2.5cm 3 / g, 3cm 3 / g, 3.5cm 3 / g or 5.0cm 3 / g, etc., and of course, other values ​​within the above range are also possible, and the present application is not limited thereto. Within the above limited range, the porous carbonaceous material of the present application has a large number of activated pores, which is advantageous for depositing more silicon material in the porous carbonaceous material and improving the capacity performance of the negative electrode material. Preferably, the pore volume of the porous carbonaceous material is 0.5 cm 3 / g or more, and more preferably, the pore volume of the porous carbonaceous material is 0.7 cm 3 / g or more.

[0038] In some embodiments, the porous carbonaceous material is a silicon-free anode material, and the method for producing the same may further include adding 150 mL of a 20% by mass HF acid solution dropwise to 10 g of the anode material while stirring, until SiF and H gases are generated and heat is released. After gas generation stops, the supernatant acid solution is removed by centrifugation, and 150 mL of the 20% by mass HF acid solution is added again to the anode material. After stirring for 12 hours, the supernatant acid solution is removed by centrifugation again. Thereafter, the anode material is washed with pure water until it becomes neutral, and then dried to obtain the silicon-free anode material.

[0039] In some embodiments, the median diameter of the negative electrode material is 10 μm or less, and may be, for example, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, or 10 μm, or may be other values ​​within the above range, and the present application is not limited thereto. Controlling the median diameter of the negative electrode material within the above range is advantageous for improving the cycle performance of a battery manufactured from the negative electrode material.

[0040] In some embodiments, the specific surface area of ​​the negative electrode material is 5 m 2 / g, e.g., 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g or 4.5m 2 / g, etc., and of course, other values ​​within the above range are also acceptable, and the present application does not limit the scope of the present invention. It should be understood that controlling the specific surface area of ​​the negative electrode material within the above range can suppress volume expansion of the negative electrode material, which is advantageous for improving the cycle performance of a battery manufactured from the negative electrode material.

[0041] In some embodiments, the electrical conductivity of the negative electrode material is greater than or equal to 10 -1 S / m or more, e.g., 10 -1 The above-mentioned ranges are advantageous for the internal transmission of electrons within the negative electrode material and for improving the rate performance of a battery manufactured from the negative electrode material during charging and discharging.

[0042] The present application further provides a method for producing the above-mentioned negative electrode material, and as shown in FIG. 1, is a flowchart for producing the negative electrode material of the present application, which includes the following steps S100 to S300.

[0043] In step S100, the carbon-based carbonized material and the first activator are mixed together to perform a first activation process to obtain an activated material.

[0044] In step S200, the activation material and the second activator are mixed to perform a second activation process to obtain a porous carbonaceous material, in which the amount of the first activator is 4 to 10 times the amount of the second activator, and the time of the first activation process is longer than the time of the second activation process.

[0045] In step S300, the porous carbonaceous material and the silicon source are mixed and heat-treated to obtain the negative electrode material.

[0046] In the above technical solution, the present application sequentially activates the carbon-based carbonized material twice. In the first activation treatment, the amount of the first activator is 4 to 10 times the amount of the second activator, and the first activation treatment lasts longer than the second activation treatment. This indicates that the first activation treatment has a stronger activation ability for the carbon-based carbonized material, which is advantageous for forming a larger number of activated pores within the activated material and for the activated pores to have a larger pore size distribution. The second activation treatment has a weaker activation ability, which further activates the unactivated regions of the activated material, forming activated pores with smaller pore sizes and enlarging the pores that are too small after the first activation treatment. As a result, the porous carbonaceous material has a larger number of activated pores with a more uniform distribution. The present application discloses a controlled two-stage activation process to produce a highly consistent porous carbonaceous material. Furthermore, the silicon source is deposited within the porous carbonaceous material, and the silicon material is distributed primarily within the activated pores of the porous carbonaceous material, improving the silicon material's dispersion and deposition amount within the anode material and ensuring a uniformity (N) of the anode material of N≥80%. This suppresses the volume effect caused by agglomeration of the silicon material during lithium absorption and desorption, reducing the particle size of the anode material. Furthermore, the anode material allows a stable SEI film to form within the limited space during the lithium absorption and desorption process, improving the structural stability of the anode material and thereby improving the expansion performance, cycle performance, and capacity of the anode material. The present application discloses a controlled two-stage activation process to produce a highly consistent porous carbonaceous material. This process is simple, allows for large-batch production, and improves the electrochemical performance of batteries manufactured with the anode material.

[0047] The manufacturing method of the present invention will be described in detail below with reference to examples. In step S100, the carbon-based carbonized material and the first activator are subjected to a first mixing to obtain an activated material.

[0048] In some embodiments, the carbon-based carbonized material is obtained by carbonizing a carbon-based feedstock.

[0049] In some embodiments, the carbon-based feedstock comprises at least one of lignin, coconut shells, fruit shells, peanut shells, rice husks, coal-based biomass, and resin.

[0050] In some embodiments, the carbonization temperature is 400°C to 900°C, specifically 400°C, 500°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0051] In some embodiments, the carbonization time is 1 hour to 20 hours, and may be specifically 1 hour, 3 hours, 5 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0052] In some embodiments, the carbonization is carried out in a protective atmosphere, where the protective gas comprises at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0053] In some embodiments, after obtaining the carbon-based carbonized material, the method further comprises pickling the carbon-based carbonized material, wherein the acid used for pickling comprises at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, perchloric acid, acetic acid, and benzoic acid.

[0054] In some embodiments, the concentration of the pickling solution is 1 mol / L to 10 mol / L, such as 1 mol / L, 3 mol / L, 5 mol / L, 8 mol / L, or 10 mol / L, and may be other values ​​within the above range, without limitation. It should be understood that the purpose of pickling is to remove impurities from the material, and after the carbon-based carbonized material is pickled, it is washed with deionized water until the product becomes neutral.

[0055] In some embodiments, the pickling time is 3 hours to 8 hours, and may be, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, or may be any other value within the above range, and is not limited thereto.

[0056] In some embodiments, the first activating agent comprises an alkaline substance.

[0057] In some embodiments, the alkaline substance comprises at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and rubidium hydroxide.

[0058] In some embodiments, the mass ratio of the carbon-based carbonized material to the first activator is 1:(0.5-30), specifically 1:0.5, 1:1, 1:5, 1:10, 1:20, 1:30, etc., and may be other values ​​within the above range, without limitation. Within the above limited range, a large amount of the first activator added results in strong activation ability, and relatively large and uniformly distributed activation pores can be formed in the carbon-based carbonized material, which is advantageous for subsequent filling of the activation pores with silicon material. If the amount of the first activator added is too large, the pore size of the pore structure in the activation material will increase, and the number of pores will increase, resulting in structural collapse of the negative electrode material during the desorption / sorption process and a reduction in the cycle performance of the negative electrode material. If the amount of the first activator added is too small, an appropriate number of uniformly distributed activated holes cannot be formed inside the carbon-based carbonized material, which is unfavorable for the subsequent deposition of the silicon source, and the negative electrode material will have a relatively large volume expansion, resulting in a decrease in the capacity and expansion performance of the negative electrode material.

[0059] In some embodiments, the first activating agent comprises at least one of water vapor, oxygen gas, and air. The gaseous first activating agent activates the carbon-based carbonized material, and the gaseous water vapor, oxygen gas, and air react with carbon at high temperatures to produce hydrogen gas and carbon monoxide, which etches the carbon-based carbonized material and produces activated pores.

[0060] In some embodiments, the concentration of the first activator is 3% to 20%, and may be, for example, 3%, 5%, 7%, 9%, 10%, 12%, 15%, 18%, or 20%, or may be other values ​​within the above range, and this application is not limited thereto. Within the above limited range, the amount of the first activator added is large, the activation ability is strong, and a relatively large number of uniformly distributed activation pores can be formed in the carbon-based carbonized material, which is advantageous for the subsequent filling of the silicon material into the activation pores.

[0061] It should be understood that when the first activating agent is water vapor, the concentration of the water vapor can be considered as the humidity of the water vapor.

[0062] In some embodiments, the duration of the first activation treatment is 5 hours to 20 hours, and may be, for example, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, or 20 hours, and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0063] In some embodiments, the temperature of the first activation treatment is 900°C to 1200°C, and specifically may be 900°C, 930°C, 950°C, 1000°C, 1100°C, 1200°C, etc., and of course may be other values ​​within the above range, and the present application is not limited thereto.

[0064] In step S200, the activation material and the second activator are mixed to perform a second activation process to obtain a porous carbonaceous material, in which the amount of the first activator is 4 to 10 times the amount of the second activator, and the time of the first activation process is longer than the time of the second activation process.

[0065] In the present application, the amount of the first activator added is set to 4 to 10 times the amount of the second activator added, and the time of the first activation treatment is limited to be longer than the time of the second activation treatment, thereby performing two activation treatments on the carbon-based carbonized material, thereby obtaining a porous carbonaceous material with a large number of activated pores that are uniformly distributed.

[0066] In some embodiments, the amount of the first activator added is 4 to 10 times the amount of the second activator added, and may be 4, 5, 6, 7, 8, 9, or 10 times the amount of the second activator added, and may be other values ​​within this range, without limitation. If the amount of the second activator added is too small, the activation ability of the second activation treatment will be poor and the effect of increasing the activated pores will not be exerted, resulting in a small number of activated pores in the porous carbonaceous material and poor distribution uniformity. If the amount of the second activator added is too large, secondary pore size expansion will occur in the activated pores formed in the first activation treatment, making it easier for mesopores or large pores to form, which will be detrimental to the distribution uniformity of the subsequent silicon source deposition and result in poor expansion performance of the produced negative electrode material.

[0067] It should be understood that the first activator and the second activator may be gaseous activators or solid activators, and when the first activator is gaseous, the amount of the added activator can represent the concentration of the gaseous activator introduced, and when the second activator is solid, the amount of the added activator can represent the mass of the solid activator added. When the first activator is gaseous and the second activator is solid, a person skilled in the art can determine the concentration of the gaseous activator and the mass of the solid activator added by empirically knowing the difference in activation between the gaseous activator and the solid activator.

[0068] In some embodiments, the second activating agent comprises an alkaline substance.

[0069] In some embodiments, the alkaline substance comprises at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and rubidium hydroxide.

[0070] In some embodiments, the mass ratio of the carbon-based carbonized material to the second activator is 1:1 (0.1-10), including, for example, 1:0.1, 1:0.5, 1:1.5, 1:3, 1:5, and 1:10. Other values ​​within the above range are also possible and are not limited herein. If too little second activator is added, the activated material produced in step S100 cannot be effectively activated; if too much second activator is added, the pore size after secondary pore expansion becomes too large, affecting the subsequent deposition of silicon material. This results in the silicon material being more likely to aggregate, creating a large volume effect in the negative electrode material, making the negative electrode material more susceptible to cracking or even pulverization during use, which is detrimental to improving the expansion performance of the material. Furthermore, the increased pore size of the porous carbon makes the material more susceptible to collapse and reduces structural stability. Preferably, the mass ratio of the carbon-based carbonized material to the second activator is 1:(0.1-3).

[0071] In some embodiments, the second activating agent comprises at least one of water vapor, oxygen gas, and air.

[0072] In some embodiments, the concentration of the second activator is 0.1% to 5%, specifically 0.1%, 0.3%, 0.8%, 1%, 2%, 3%, 4%, 5%, etc., and may be other values ​​within the above range, and this application is not limited thereto. Within the above limited range, the amount of the second activator added is small, which on the one hand can enlarge the activated pores obtained by the first activation treatment without making the pores too large after the pore enlargement, which is advantageous for subsequent filling with silicon material; on the other hand, the second activator can activate the unactivated regions in the activated material, resulting in activated pores with smaller pore sizes, so that the produced porous carbonaceous material has more activated pores and a relatively uniform distribution of the activated pores. If the concentration of the second activator is less than 0.1%, the activated material produced in step S100 cannot be effectively activated secondary; if the concentration of the second activator is more than 5%, the pore size after secondary pore enlargement will be too large, which will affect the subsequent deposition of silicon material, resulting in the silicon material being more likely to agglomerate, causing a large volume effect in the negative electrode material, making the negative electrode material more likely to crack or even pulverize during use, which is detrimental to improving the expansion performance of the material, and also increasing the inner pore size of the porous carbon, making the produced negative electrode material more likely to collapse and reducing its structural stability.

[0073] In some embodiments, the time for the second activation treatment is 3 hours to 10 hours, and may be, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, etc., and may be other values ​​within the above range, and the present application is not limited thereto. Within the above limited range, the produced porous carbonaceous material has a large number of activated pores with a uniform distribution, which is further advantageous for the subsequent deposition of a silicon material inside the porous carbonaceous material. If the second activation treatment time is too short, the activated material produced in step S100 cannot be effectively activated, resulting in a small amount of silicon material deposited inside the porous carbonaceous material and degraded performance; if the second activation treatment time is too long, the pore size after secondary pore expansion will be too large, which will affect the deposition of silicon material, resulting in a large volumetric effect on the negative electrode material, making it prone to cracking or even pulverization during use, which is detrimental to improving the expansion performance of the material; and because the inner pore size of the porous carbon will be large, the negative electrode material produced will be prone to collapse and have poor structural stability.

[0074] In some embodiments, the temperature of the second activation treatment is 800°C to 1000°C, and may be, for example, 800°C, 830°C, 850°C, 900°C, 950°C, or 1000°C, and may be other values ​​within the above range, and the present application is not limited thereto. In some embodiments, by limiting the temperature of the first activation treatment to be higher than the temperature of the second activation treatment, the activation levels of the two activation treatment processes are different and the difference is large, thereby enabling the production of porous carbonaceous materials with good consistency.

[0075] Based on the above, the present application produces a porous carbonaceous material having an appropriate number of activated pores with a uniform distribution by controlling the amount of activator added, the activation temperature, and the activation time in the two activation treatments.

[0076] In step S300, the porous carbonaceous material and the silicon source are mixed and heat-treated to obtain the negative electrode material.

[0077] In some embodiments, the silicon source comprises at least one of monosilane, disilane, and trisilane.

[0078] In some embodiments, the flow rate of the silicon source is 0.1 L / min to 1000 L / min, and can be specifically 0.1 L / min, 1 L / min, 10 L / min, 100 L / min, 300 L / min, 600 L / min, 1000 L / min, etc., and of course, can be other values ​​within the above range, and the present application is not limited thereto.

[0079] In some embodiments, the temperature of the heat treatment is 300°C to 800°C, specifically, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, etc., and of course, other values ​​within the above range may also be used, and the present application is not limited thereto.

[0080] In some embodiments, the heat treatment time is 2 hours to 25 hours, and may be, for example, 2 hours, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0081] In some embodiments, after mixing the porous carbonaceous material with the silicon source and performing the heat treatment, the method further comprises mixing the material obtained by the heat treatment with a coating material and performing the heat treatment.

[0082] In some embodiments, the coating material comprises one of a carbon source, a metal oxide, and a nitride.

[0083] In some embodiments, the nitride comprises at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0084] In some embodiments, the metal oxide comprises at least one of iron oxide, zinc oxide, tin oxide, copper oxide, and titanium oxide.

[0085] In some embodiments, the carbon source comprises at least one of a gaseous carbon source and a solid carbon source.

[0086] In some embodiments, the gaseous carbon source comprises at least one of acetylene, methane, propylene, benzene, ethanol, methanol, ethylene, propane, and butane.

[0087] In some embodiments, the flow rate of the gaseous carbon source is 0.1 L / min to 1000 L / min, and specifically may be 0.1 L / min, 1 L / min, 10 L / min, 100 L / min, 300 L / min, 600 L / min, 1000 L / min, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0088] In some embodiments, the solid carbon source comprises at least one of sucrose, fructose, glucose, asphalt, phenolic resin, polyimide, citric acid, epoxy resin, amino resin, polystyrene, polyacrylic acid, carboxymethyl cellulose, and cellulose acetate butyrate.

[0089] In some embodiments, the mass ratio of the solid carbon source to the material obtained by the heat treatment is (1 to 100):100, specifically, 1:100, 10:100, 30:100, 50:100, 80:100, 100:100, etc., and of course, other values ​​within the above range may also be used, and the present application is not limited thereto.

[0090] In some embodiments, the heat treatment temperature is 600°C to 1100°C. Specifically, the heat treatment temperature may be, for example, 600°C, 650°C, 700°C, 800°C, 900°C, 1000°C, or 1100°C, and may be other values ​​within the above range, and the present application is not limited thereto. If the heat treatment temperature is less than 600°C, carbonization of the coating material will be incomplete, and a dense coating layer will not be obtained. If the heat treatment temperature is more than 1100°C, crystallization of the silicon material will occur, and the cycle performance and expansion performance of the negative electrode material will deteriorate.

[0091] In some embodiments, the incubation time for the heat treatment is 2 hours to 10 hours. Specifically, the incubation time for the heat treatment may be, for example, 2 hours, 5 hours, 7 hours, 8 hours, 10 hours, etc., and of course, may be other values ​​within the above range, and the present application is not limited thereto.

[0092] In some embodiments, the method further includes a step of sieving and classifying the material obtained after mixing the material obtained by the heat treatment with the coating material and performing the heat treatment.

[0093] According to a third aspect, the present application provides a lithium ion battery including the above-described negative electrode material or a negative electrode material produced by the above-described production method.

[0094] Those skilled in the art should understand that the above-described method for manufacturing a lithium ion battery is merely an example, and other methods commonly used in the art may be adopted without departing from the scope of the present disclosure.

[0095] The following examples of the present application will be further explained in several separate examples. However, the examples of the present application are not limited to the specific examples below. The present application may be modified as appropriate within the scope of the main rights.

[0096] Example 1 (1) 10 g of bamboo charcoal was placed in a carbonization furnace and carbonized at a temperature of 800°C for 7 hours. After carbonization, the bamboo charcoal was pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through it, the steam concentration of which was 9%, the activation time was 18 hours, and the activation temperature was 900°C, and the activated material was obtained. (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration was 2%, the activation time was 3 hours, and the activation temperature was 900°C, and a porous carbonaceous material was obtained. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0097] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0098] According to the scanning electron microscope (SEM) BSE image of the negative electrode material produced in this example, as can be seen from FIG. 2, the negative electrode material produced in this example had a distinguishable structure between typical particles of a first brightness and particles of a second brightness, and the proportion of negative electrode material particles having the second brightness was high in a batch size of the negative electrode material. This indicated that the present application could obtain a negative electrode material in which silicon material was deposited inside a porous carbonaceous material in an appropriate number and with a uniform distribution.

[0099] The XRD chart of the negative electrode material produced in this example is shown in FIG. 3. As can be seen from FIG. 3, the negative electrode material does not have a characteristic peak at a position of 25° to 30°, but has a diffraction hump, which indicates the presence of amorphous silicon in the negative electrode material, i.e., the silicon deposited on the porous carbonaceous material is amorphous silicon, which is advantageous for reducing the volume expansion of the negative electrode material.

[0100] The initial charge-discharge curve of the negative electrode material prepared in this example is shown in FIG. 4. As can be seen from FIG. 4, the initial charge-discharge capacity of the negative electrode material was high, and the initial efficiency was also high.

[0101] The cycle performance curve of the negative electrode material prepared in this example is shown in FIG. 5. As can be seen from FIG. 5, the negative electrode material had excellent cycle performance, with a capacity retention rate of 92.2% after 50 cycles.

[0102] Example 2 (1) 10g of coconut shell was placed in a carbonization furnace and carbonized at a temperature of 800°C for 10 hours. After carbonization, the coconut shell was pickled with a hydrochloric acid concentration of 10mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 3.5%, the activation time was 12 hours, and the activation temperature was 950°C, to obtain the activated material; (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration in the mixture was 0.5%, the activation time was 6 hours, and the activation temperature was 950°C, resulting in a porous carbonaceous material. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0103] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0104] Example 3 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 5.7%, the activation time was 14 hours, and the activation temperature was 950°C, to obtain the activated material; (3) The activated material was subjected to alkaline activation treatment, the alkali was sodium hydroxide, the amount of sodium hydroxide added was 3% of the mass of the fruit shell, the activation time was 9 hours, and the activation temperature was 950°C, and a porous carbonaceous material was obtained. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0105] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0106] Example 4 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 14.5%, the activation time was 8 hours, and the activation temperature was 990°C, to obtain the activated material; (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration in the mixture was 1.5%, the activation time was 5 hours, and the activation temperature was 850°C, resulting in a porous carbonaceous material. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0107] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0108] Example 5 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 20%, the activation time was 5 hours, and the activation temperature was 1050°C, to obtain the activated material; (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration was 5%, the activation time was 3 hours, and the activation temperature was 900°C, and a porous carbonaceous material was obtained. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0109] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0110] Example 6 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) The carbon-based carbonized material was subjected to alkali activation treatment, where the alkali was sodium hydroxide, the amount of sodium hydroxide added was 15% of the mass of the fruit shell, the activation time was 10 hours, and the activation temperature was 950°C, and the activated material was obtained; (3) The activated material was subjected to a secondary alkali activation treatment, in which the alkali was sodium hydroxide, the amount of sodium hydroxide added was 3% of the mass of the fruit shell, the activation time was 5 hours, and the activation temperature was 850°C, resulting in a porous carbonaceous material. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0111] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0112] Example 7 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) The carbon-based carbonized material was subjected to alkali activation treatment, where the alkali was sodium hydroxide, the amount of sodium hydroxide added was 10% of the mass of the fruit shell, the activation time was 12 hours, and the activation temperature was 1000°C, and the activated material was obtained; (3) The activated material was subjected to a secondary alkali activation treatment, in which the alkali was sodium hydroxide, the amount of sodium hydroxide added was 1% of the mass of the fruit shell, the activation time was 3 hours, and the activation temperature was 850°C, resulting in a porous carbonaceous material. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0113] The negative electrode material obtained in this example includes a core and a carbon coating layer laid on the surface of the core. The core includes a porous carbonaceous material and silicon particles distributed inside and on the surface of the porous carbonaceous material. Table 1 shows the uniformity N of the negative electrode material, the median diameter, specific surface area, and electrical conductivity of the negative electrode material produced in this example, as well as the pore volume of the porous carbonaceous material, the proportion of the volume of micropores in the porous carbonaceous material, the average pore diameter, and the mass proportion of silicon particles (elemental silicon) in the negative electrode material.

[0114] Comparative Example 1 (1) 10 g of bamboo charcoal was placed in a carbonization furnace and carbonized at a temperature of 800°C for 7 hours. After carbonization, the bamboo charcoal was pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After placing the carbon-based carbonized material in a CVD reactor, monosilane was passed through the reactor, the monosilane concentration was controlled to 25%, the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (3) The material obtained in step (2) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0115] Comparative Example 2 The difference from Example 1 is as follows: Step (3) was not carried out, and the activated material obtained in Step (2) was directly subjected to Step (4).

[0116] Comparative Example 3 The difference from Example 1 is as follows: Step (2) was not carried out, and the carbon-based carbonized material obtained in Step (1) was directly subjected to Step (3).

[0117] Comparative Example 4 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 9%, the activation time was 18 hours, and the activation temperature was 900°C, to obtain the activated material; (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration was 9%, the activation time was 16 hours, and the activation temperature was 900°C, resulting in a porous carbonaceous material. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0118] Comparative Example 5 (1) 10 g of fruit shells were placed in a carbonization furnace and carbonized at a temperature of 950°C for 5 hours. After carbonization, the fruit shells were pickled with a hydrochloric acid concentration of 10 mol / L for 5 hours to obtain a carbon-based carbonized material. (2) After drying the carbon-based carbonized material, it was subjected to steam activation treatment. A mixture of steam and nitrogen gas was passed through the material, the steam concentration of which was 9%, the activation time was 2 hours, and the activation temperature was 900°C, to obtain the activated material; (3) The activated material was subjected to a secondary steam activation treatment, in which a mixture of steam and nitrogen gas was passed through, the steam concentration in the mixture was 2%, the activation time was 12 hours, and the activation temperature was 900°C, and a porous carbonaceous material was obtained. (4) The porous carbonaceous material was placed in a CVD apparatus, and then monosilane was passed through the CVD apparatus. The monosilane concentration was controlled to 25%, and the temperature was raised to 460°C, and the reaction was carried out for 8 hours. (5) The material obtained in step (4) was placed in a reactor, and methane gas was passed through it. The methane concentration was 12%. Heat treatment was carried out at 720°C, and the temperature was maintained for 2 hours. The obtained sample was then sieved and classified to obtain the negative electrode material.

[0119] Performance Measurement 1. Before measuring the pore volume size of the porous carbonaceous material by the BET pore size distribution method and measuring the porosity, it is necessary to remove the silicon material in the negative electrode material by etching with HF. 2. The number or volume of micropores in the porous carbonaceous material was measured by nitrogen gas desorption / adsorption method. Using the PhysiChem Instruments LTD iPore620 pore size measurement device and the BET pore size distribution measurement method, the nitrogen gas isothermal adsorption characteristic curve was used to obtain the pore size distribution data of the material through DFT simulation analysis, and furthermore, the number of micropores, average pore size, pore volume, and BET specific surface area of ​​the material were obtained.

[0120] 3. Before etching the silicon material in the negative electrode material, the mass M1 of the negative electrode material was measured. After etching the silicon material with HF, the mass M2 of the negative electrode material was measured again, and (M2-M1) / M2 is the mass ratio of the silicon material in the negative electrode material. Alternatively, the sample was calcined in an oxygen atmosphere using a box-type atmosphere furnace (model number: SA2-9-17TP), and the silicon in the sample reacted with silicon suboxide to form silicon dioxide. The carbon was burned and emitted as carbon dioxide, and the weight was measured to calculate the mass content of silicon in the negative electrode material.

[0121] 4. A laser granulometer was used to measure the median diameter of the negative electrode material. Particle size was measured using Mastersizer 3000 laser diffraction technology. Particle size measurement was accomplished by measuring the intensity of scattered light when a laser beam passed through a dispersed particle sample. The data was then used to analyze and calculate the particle size distribution of the particles that formed the scattering spectrum. D50: The particle size corresponding to the cumulative particle size distribution percentage of the sample's volume distribution reaching 50%. Physically, it means that particles larger than this size account for 50% of the total, and particles smaller than this size also account for 50%. D50 is also known as the median size. D90 particle size, D50 particle size, and D10 particle size refer to the equivalent diameter of the largest particle when the cumulative distribution in the volume distribution curve is 90%, 50%, and 10%, respectively.

[0122] 5. After etching the silicon material in the porous carbonaceous material with HF, the average pore diameter of the pores was measured using a Micromeritics ASAP 2460 fully automatic specific surface area and porosity analyzer from the United States, and the gas used during the measurement was CO2 or N2. Etching method: After immersing the anode material in a 1M nitric acid solution for 4 hours, a 20% HF acid solution was added dropwise to the anode material, generating yellow smoke. The addition was continued until the yellow smoke ceased; finally, the residue was decomposed with a 1M nitric acid solution, followed by washing and drying to obtain a silicon-free anode material. The etching method can also be as follows: 150 mL of a 20% HF acid solution was added dropwise to 10 g of anode material while stirring, generating SiF and H gases and releasing heat. After the gas generation ceased, the supernatant acid solution was removed by centrifugation. Another 150 mL of a 20% HF acid solution was added to the anode material, stirred for 12 hours, and then centrifuged again to remove the supernatant acid solution. The anode material was then washed with pure water until neutral and dried to obtain a silicon-free anode material.

[0123] 6.Measuring method of average particle size of silicon material: The diameter of silicon material in the transmission electron microscope image was mathematically statistically analyzed.

[0124] 7. The model number of the scanning electron microscope was Hitachi S4800, and the measurement conditions were: voltage 3 kV, current 10 μA.

[0125] 8. Thickness of the coating layer: The material was cut using a FIB-SEM device and measured with the SEM to obtain the average thickness of the coating layer.

[0126] 9. Electrical conductivity of powder: The volume resistivity of the negative electrode material powder was measured using the four-point probe method with the MCP-PD51 powder resistance measurement system manufactured by Mitsubishi Chemical Corporation of Japan. The device was used to measure the resistance of the powder under five pressure points of 4, 8, 12, 16, and 20 KN, respectively, and then the computer automatically calculated the electrical conductivity and resistivity of the negative electrode material powder.

[0127] 10. Specific surface area: The specific surface area was measured using a TriStar 3000 specific surface area and pore size analyzer from Micromeritics, USA.

[0128] 11. The following method was adopted to measure the electrochemical performance of the negative electrode material: The negative electrode material, conductive agent, and binder were dissolved and mixed in a solvent in a 94:1:5 mass ratio, adjusted to a 50% solids content, and coated onto a copper foil current collector. The resulting negative electrode sheet was then vacuum-dried. Subsequently, a ternary positive electrode sheet manufactured using a conventional, mature process, a 1 mol / L LiPF6 / EC+DMC+EMC (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a case were assembled using a standard production process to fabricate 18650 cylindrical cells. Charge and discharge measurements of the cylindrical cells were performed using a LAND battery measurement system from Wuhan Jinnuo Electronics Co., Ltd., with 0.2 C constant current charging and discharging at room temperature and limited to a charge and discharge voltage of 2.75 to 4.2 V. The measurement results are shown in Tables 1 and 2.

[0129] [Table 1]

[0130] [Table 2]

[0131] As shown in Tables 1 and 2, the negative electrode materials prepared in Examples 1 to 7 of the present application comprise a porous carbonaceous material and a silicon material, and the negative electrode materials have a uniformity N, where N is 80% or more. This indicates that the porous carbonaceous material of the present application has uniformly distributed activated pores and the number of activated pores is appropriate, so that the silicon material is mainly distributed in the pores of the porous carbonaceous material. This is obtained by measuring the negative electrode material obtained within any 100 μm × 100 μm area, and this indicates that the number and distribution of activated pores of the porous carbonaceous material of each negative electrode material particle of the present application are highly similar, i.e. This indicates that the negative electrode material of the present application has a porous carbonaceous material with good consistency. The porous carbonaceous material with good consistency can improve the dispersion of the silicon material in the negative electrode material, suppress the volume effect caused by the agglomeration of the silicon material during the lithium absorption and desorption process, and reduce the powdering of the negative electrode material particles. In addition, the negative electrode material can form an SEI film in the limited space during the lithium absorption and desorption process, forming a stable SEI film on the surface of the negative electrode material, thereby improving the structural stability of the negative electrode material, which is advantageous to improving the expansion performance, cycle performance and capacity of the negative electrode material.

[0132] The carbon-based carbonized material in Comparative Example 1 was not subjected to activation treatment, and the silicon source was deposited as is. Therefore, the amount of silicon material deposited in the negative electrode material was extremely small, and the uniformity N of the negative electrode material was too small. As a result, the batteries manufactured from the negative electrode material had problems such as low capacity, large expansion, and poor cycle performance.

[0133] In Comparative Example 2, only the activation treatment of step (2) was performed on the carbon-based carbonized material, and the activation treatment of step (3) was not performed. Therefore, the distribution uniformity of the activated pores in the porous carbonaceous material was inferior to that in Example 1, and the silicon source was deposited on the porous carbonaceous material. As a result, the distribution uniformity of the silicon material in the porous carbonaceous material was poor, and the uniformity of the negative electrode material was <80%, which did not meet the limited range of the present application, and the expansion and cycle performance of the negative electrode material were poor.

[0134] In Comparative Example 3, only the activation treatment of step (3) was performed on the carbon-based carbonized material, so the number of activated holes in the porous carbonaceous material was small and the distribution uniformity was inferior to that of Example 1 and Comparative Example 2. A silicon source was deposited on the porous carbonaceous material, resulting in poor distribution uniformity of the silicon material in the porous carbonaceous material and a small amount of silicon material deposited in the porous carbonaceous material. The uniformity N of the negative electrode material was <80%, which did not meet the limited range of the present application, and the expansion performance and cycle performance of the negative electrode material were poor.

[0135] In Comparative Example 4, two activation treatments were performed, but the difference in the degree of activation between the two treatments was not significant. As a result, the number of pores in the produced porous carbonaceous material was large and the pore diameters were also large. As a result, the silicon material was prone to agglomeration inside the porous carbonaceous material, and the uniformity of the negative electrode material N was <80%, which did not meet the limited range of the present application, and the expansion performance of the negative electrode material was poor.

[0136] In Comparative Example 5, two activation treatments were performed, and the time of the first activation treatment was much shorter than the time of the second activation treatment. As a result, the pore volume of the produced porous carbonaceous material was small. As a result, the amount of silicon source deposited inside the anode material was small, and the uniformity of the anode material was N<80%, which did not meet the limited range of the present application, and the capacity performance and cycle performance of the anode material were poor.

[0137] The above description is only a preferred embodiment of the present application, and does not limit the present application, and those skilled in the art can make various modifications and variations to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall all be included in the protection scope of the present application.

[0138] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority from a Chinese patent filed with the China Patent Office on November 24, 2023, bearing application number 202311591084.6 and entitled "Negative electrode material and manufacturing method thereof for lithium ion batteries," the entire contents of which are incorporated herein by reference.

Claims

1. A negative electrode material, The negative electrode material includes a porous carbonaceous material, and a silicon material is distributed within the porous carbonaceous material. The negative electrode material has a uniformity N, where N≧80%; a negative electrode material, characterized in that, in a backscattered electron image obtained by scanning the negative electrode material with an SEM scanning electron microscope in a BSE automatic brightness and contrast mode, within any 100 μm × 100 μm region, the number of particles of the negative electrode material having a first brightness is denoted by C1, the particles of the negative electrode material having the first brightness representing a negative electrode material having a grayscale value of 5500 or more in the backscattered electron image, the number of particles of the negative electrode material having a second brightness is denoted by C2, the particles of the negative electrode material having the second brightness representing a negative electrode material having a grayscale value of less than 5500 in the backscattered electron image, the negative electrode material having a uniformity within the region N′=C2 / (C2+C1)×100%, and the uniformity N of the negative electrode material is an arithmetic average of the uniformities N′ of at least 10 of the regions.

2. The negative electrode material according to claim 1, characterized in that the negative electrode material has at least one of the following characteristics (1) to (2): (1) The porous carbonaceous material contains micropores, and the ratio of the number of the micropores to the total number of pores in the porous carbonaceous material is 80% or more, where the total number of pores in the porous carbonaceous material is 100%; (2) The porous carbonaceous material contains micropores, and the ratio of the volume of the micropores to the total volume of the pores in the porous carbonaceous material is 80% or more.

3. 2. The negative electrode material according to claim 1, wherein the average pore size of the pores in the porous carbonaceous material is 5 nm or less.

4. 2. The negative electrode material according to claim 1, wherein the mass ratio of the silicon material in the negative electrode material is 30% to 80%.

5. 2. The negative electrode material according to claim 1, wherein the silicon material is further distributed on at least a portion of the surface of the porous carbonaceous material.

6. 2. The negative electrode material according to claim 1, wherein the porous carbonaceous material comprises at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, and carbon gel.

7. The negative electrode material according to claim 1, characterized in that the negative electrode material has at least one of the following characteristics (1) to (4): (1) The silicon material includes silicon particles, and the shape of the silicon particles includes at least one of dot-like, spherical, oval-spherical, and flake-like; (2) The silicon material includes at least one of crystalline silicon, silicon oxide material, amorphous silicon, and silicon alloy; (3) The average particle size of the silicon material is 0.1 nm to 500 nm; (4) The mass content of silicon element in the silicon material is ≥ 99%.

8. The negative electrode material according to claim 1 , further comprising a coating layer distributed on at least a portion of the surface of the porous carbonaceous material.

9. The negative electrode material according to claim 8, characterized in that the negative electrode material has at least one of the following characteristics (1) to (4): (1) The coating layer includes a carbon layer, and the material of the carbon layer includes at least one of graphene, soft carbon, hard carbon, and a conductive polymer; (2) The coating layer includes a metal oxide layer, and the material of the metal oxide layer includes at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide; (3) The coating layer includes a nitride layer, and the material of the nitride layer includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride; (4) The thickness of the coating layer is 0.1 nm to 100 nm.

10. 2. The negative electrode material according to claim 1, wherein the median diameter of the negative electrode material is 10 μm or less.

11. The specific surface area of ​​the negative electrode material is 5 m ２ 2. The negative electrode material according to claim 1, wherein the Cr content is less than 1 / g.

12. The electrical conductivity of the negative electrode material is 10 －１ 2. The negative electrode material according to claim 1, wherein the negative electrode material has a conductivity of 0.5 S / m or more.

13. The pore volume of the porous carbonaceous material is 0.4 cm ３ 2. The negative electrode material according to claim 1, wherein the Cr content is 1 / g or more.

14. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 13.

Images