Negative active material, method for preparing the same, secondary battery, method for preparing the same, and electric device

Abstract

A negative electrode active material includes a carbon-based material and a silicon-based material, a first functional group is present on a surface of the carbon-based material, a second functional group is present on a surface of the silicon-based material, and the first functional group carries an opposite charge to the second functional group.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, and more specifically to negative electrode active materials and their preparation methods, secondary batteries and their preparation methods, and electrical devices. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] To meet market demand for high-performance power batteries, silicon-based materials with high specific capacity can replace graphite to improve battery energy density. However, silicon-based materials expand much larger in volume after charging than graphite, and their high polarization can worsen anode kinetics. Therefore, to obtain a more balanced anode, it is often necessary to blend silicon-based materials with carbon-based materials to create a hybrid anode material.

[0004] Traditional technologies often employ simple physical mixing to process silicon-based and carbon-based materials. This approach struggles to prevent agglomeration of similar particles, such as silicon-based particles or carbon-based particles. In particular, compared to graphite, silicon particle agglomeration is more likely to lead to large local lithium intercalation concentration gradients at the anode, resulting in excessive cell expansion force, poor kinetics, and safety issues such as lithium plating. The most direct manifestation of this is a decrease in battery rate performance. Summary of the Invention

[0005] According to various embodiments of this application, in a first aspect, a negative electrode active material is provided, comprising a carbon-based material and a silicon-based material, wherein a first functional group is present on the surface of the carbon-based material, and a second functional group is present on the surface of the silicon-based material, wherein the first functional group carries a charge opposite to that of the second functional group.

[0006] This application modifies the surfaces of carbon-based and silicon-based materials with functional groups carrying opposite charges, enabling particles of the same type to repel each other due to the same charge, thus avoiding agglomeration of particles of the same type. Particles of different types carry opposite charges and have a certain electrostatic effect, thereby enabling different types of active materials to be evenly distributed in the entire system. This effectively avoids problems such as reduced rate performance, uneven thickness due to local expansion of the cell, and lithium plating caused by uneven particle distribution in traditional technologies.

[0007] In some implementations, the first functional group carries a positive charge, and the second functional group carries a negative charge. With other conditions remaining constant, since silicon agglomeration has a more severe negative impact on battery performance than carbon agglomeration, when silicon carries a negative charge and carbon carries a positive charge, agglomeration between silicon and the conductive agent can be effectively avoided, thereby further improving the dispersion performance of the entire system and enhancing the battery's rate performance. This silicon-negative, carbon-positive approach is particularly advantageous in systems with high silicon content.

[0008] In some embodiments, the first functional group includes one or more of amino, amide, cyano, and borate groups.

[0009] In some embodiments, the second functional group includes one or more of a carboxyl group, a sulfonic acid group, a hydroxyl group, and a halogen group.

[0010] The appropriate type of functional group can not only prevent particle aggregation and improve the dispersibility of the system, but also will not have an adverse effect on other battery performance.

[0011] In some embodiments, the silicon-based material comprises 1% to 99% by mass in the negative electrode active material; alternatively, the silicon-based material comprises 25% to 85% by mass in the negative electrode active material.

[0012] In some embodiments, the carbon-based material comprises 1% to 99% by mass in the negative electrode active material; alternatively, the carbon-based material comprises 15% to 75% by mass in the negative electrode active material.

[0013] Controlling the proportion of silicon-based and carbon-based materials in the negative electrode active material within a suitable range can balance the contradiction between battery capacity and rate performance, thereby maximizing the overall performance of the battery. At the same time, it can also make the overall electrical properties of the negative electrode active material suitable, thereby further improving the dispersion stability of the slurry during the preparation of the negative electrode slurry.

[0014] In some embodiments, the carbon-based material comprises small-sized particles and large-sized particles, wherein the small-sized particles have a D50 particle size of 0.2 μm to 9.99 μm, and the large-sized particles have a D50 particle size of 10 μm to 100 μm. The carbon-based material, by combining large-sized and small-sized particles within a certain particle size range, can effectively reduce material defects and improve battery capacity without causing excessive deterioration of battery kinetic performance.

[0015] In some embodiments, the small-sized particles constitute 1% to 99% of the negative electrode active material by mass, and the large-sized particles constitute 1% to 99% of the negative electrode active material by mass. Optionally, the small-sized particles constitute 5% to 75% of the negative electrode active material by mass, and the large-sized particles constitute 25% to 95% of the negative electrode active material by mass. Controlling the proportions of large-sized and small-sized particles within a suitable range allows for better blending and further improves the rate performance of the battery.

[0016] In some embodiments, the D50 particle size of the silicon-based material is 0.2 μm to 100 μm; optionally, the D50 particle size of the silicon-based material is 0.2 μm to 30 μm. Controlling the particle size of the silicon-based material within a suitable range can balance battery capacity and kinetic performance, resulting in better overall battery performance.

[0017] In some embodiments, the negative electrode active material satisfies at least one of the following conditions (1) to (2):

[0018] (1) The concentration of the stable aqueous dispersion of the carbon-based material is 0.1 mg / mL to 100 mg / mL;

[0019] (2) The concentration of the stable aqueous dispersion of the silicon-based material is 0.1 mg / mL to 100 mg / mL;

[0020] The stable aqueous dispersion refers to the liquid phase obtained by solid-liquid separation of a dispersion prepared with water as a solvent and left to stand for more than 2 hours without precipitation.

[0021] Controlling the concentration of the stable aqueous dispersion of the material within a suitable range is essential to ensure that the material acquires an appropriate charge, thereby helping to further improve the dispersion stability of the system.

[0022] A second aspect of this application provides a method for preparing the negative electrode active material described in one or more of the foregoing embodiments, comprising the following steps:

[0023] A carbon-based raw material, a first surfactant, and a solvent are mixed to prepare a first dispersion. After standing for more than 2 hours, solid-liquid separation is performed, and the liquid phase is retained to obtain a first stable dispersion. The first stable dispersion is centrifuged to obtain a first precipitate. The first precipitate is washed and dried to obtain the carbon-based material.

[0024] Mix a silicon-based raw material, a second surfactant, and a solvent to prepare a second dispersion liquid. After standing for more than 2 h, perform solid-liquid separation and retain the liquid phase to obtain a second stable dispersion liquid; perform centrifugal separation on the second stable dispersion liquid to obtain a second precipitate; wash and dry the second precipitate to obtain the silicon-based material;

[0025] Mix the carbon-based material and the silicon-based material to prepare the negative electrode active material;

[0026] Wherein, the first surfactant and the second surfactant carry opposite charges in the solvent respectively.

[0027] A suitable preparation method can make the raw materials uniformly carry charges and have a moderate amount of charge, further improving the dispersion performance of the negative electrode active material and reducing aggregation.

[0028] In some embodiments, the preparation method satisfies one or more of the following conditions (1) to (5):

[0029] (1) The carbon-based raw material includes one or more of artificial graphite, natural graphite, soft carbon, and hard carbon;

[0030] (2) The silicon-based raw material includes one or more of Si and SiO x (0 < x < 2);

[0031] (3) The first surfactant and the second surfactant are each independently selected from one or more of the following: dodecylamine, hexadecanamide, dodecanenitrile, bisglycerol ethoxylated borate, sodium cholate, sodium dodecylbenzenesulfonate, decynediol, and cetyl bromide; Surfactants of suitable types can make the surface of the raw materials carry suitable types of functional groups, providing charges and improving the dispersion performance of the materials without causing damage to other battery performances;

[0032] (4) The dosage of the first surfactant is 0.1% to 40% of the mass of the carbon-based raw material; A suitable dosage of the surfactant can make the surface of the obtained carbon-based material uniformly carry a suitable amount of charge;

[0033] (5) The dosage of the second surfactant is 0.1% to 40% of the mass of the silicon-based raw material, and a suitable dosage of the surfactant can make the surface of the obtained silicon-based material uniformly carry a suitable amount of charge.

[0034] In the third aspect of the present application, a secondary battery is provided, including a positive electrode sheet, a negative electrode sheet, and a separator, and the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0035] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes the negative active material described in one of the aforementioned embodiments.

[0036] A fourth aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0037] A positive electrode current collector is provided, and a positive electrode slurry is coated on the surface of the positive electrode current collector. The slurry is then dried and pressed to obtain a positive electrode sheet.

[0038] A negative electrode current collector is provided, and a negative electrode slurry is coated on the surface of the negative electrode current collector. The slurry is then dried and pressed to obtain a negative electrode sheet. The negative electrode slurry includes the negative electrode active material described in one or more of the aforementioned embodiments. Optionally, the solid content of the negative electrode slurry is 30% to 70%. A suitable solid content of the slurry can better match the technical solution of this application, further improve the dispersion stability of various particles in the negative electrode active material, and avoid agglomeration.

[0039] The secondary battery is prepared by stacking or winding the positive electrode, the separator, and the negative electrode.

[0040] A fifth aspect of this application provides an electrical device comprising the aforementioned secondary battery or a secondary battery prepared by the aforementioned method. Attached Figure Description

[0041] To better describe and illustrate embodiments or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the embodiments or examples currently described, or the best mode of these inventions as currently understood.

[0042] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0043] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0044] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1: Secondary battery; 11: Casing; 12: Electrode assembly; 13: Cover plate; 2: Electrical device. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0049] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0054] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0055] Silicon-based materials, due to their high theoretical specific capacity and lower risk of lithium plating, have been increasingly used as anode active materials to meet the growing market demand for high-capacity rechargeable batteries. However, due to their high coefficient of thermal expansion and inherent polarization, silicon-based materials typically need to be mixed with carbon-based materials such as graphite to balance the trade-off between specific capacity and thermal expansion coefficient, thereby improving the overall battery performance. However, when silicon and carbon are mixed, uniform dispersion is often difficult, especially for silicon-based materials. Agglomeration can significantly negatively impact battery performance, easily leading to problems such as localized over-expansion and decreased rate performance.

[0056] Based on the above background, in a first aspect, this application provides a negative electrode active material, including a carbon-based material and a silicon-based material, wherein the surface of the carbon-based material has a first functional group and the surface of the silicon-based material has a second functional group, and the first functional group carries a charge opposite to that of the second functional group.

[0057] This application modifies the surfaces of carbon-based and silicon-based materials with functional groups carrying opposite charges, enabling particles of the same type to repel each other due to the same charge, thus avoiding agglomeration of particles of the same type. Particles of different types carry opposite charges and have a certain electrostatic effect, thereby enabling different types of active materials to be evenly distributed in the entire system. This effectively avoids problems such as reduced rate performance, excessive expansion, and lithium plating caused by uneven particle distribution in traditional technologies.

[0058] In some implementations, the first functional group carries a positive charge, and the second functional group carries a negative charge. With other conditions remaining constant, since silicon agglomeration has a more severe negative impact on battery performance than carbon agglomeration, when silicon carries a negative charge and carbon carries a positive charge, agglomeration between silicon and the conductive agent can be effectively avoided, thereby further improving the dispersion performance of the entire system and enhancing the battery's rate performance. This is particularly advantageous in systems with high silicon content (silicon-based material mass percentage above 20%).

[0059] In some embodiments, the first functional group includes one or more of amino, amide, cyano, and borate groups.

[0060] In some embodiments, the second functional group includes one or more of a carboxyl group, a sulfonic acid group, a hydroxyl group, and a halogen group.

[0061] Suitable functional groups can not only prevent particle aggregation and improve the dispersibility of the system, but also avoid adversely affecting other battery performance characteristics. It is understood that the presence of functional groups is to enable the negative electrode material particles to carry a charge; therefore, the specific substituents present on the material surface are not limited, as long as they contain the aforementioned functional groups and can carry a charge normally. For example, an amino group can be a single amino group, an amino group present in -CH2NH2, or an amino group present in -COOCH2NH2; another example is that a carboxyl group can be a single carboxyl group or -CH2COOH; yet another example is that a halogen group can be a single fluorine atom or a perfluoroalkyl group. In this application, the halogen group includes one or more of -F, -Cl, and -Br.

[0062] In some embodiments, the mass percentage of silicon-based material in the negative electrode active material is 1% to 99%; optionally, the mass percentage of silicon-based material in the negative electrode active material can be, for example, 25% to 85%, or even 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0063] In some embodiments, the mass percentage of carbon-based material in the negative electrode active material is 1% to 99%; optionally, the mass percentage of carbon-based material in the negative electrode active material can be, for example, 15% to 75%, or even 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0064] Controlling the proportion of silicon-based and carbon-based materials in the negative electrode active material within a suitable range can balance the contradiction between battery capacity and rate performance, thereby maximizing the overall performance of the battery. At the same time, it can also make the overall electrical properties of the negative electrode active material suitable, thereby further improving the dispersion stability of the slurry during the preparation of the negative electrode slurry.

[0065] In some embodiments, the carbon-based material includes small-sized particles and large-sized particles, wherein the D50 particle size of the small-sized particles is 0.2 μm to 9.9 μm, and the D50 particle size of the large-sized particles is 10 μm to 100 μm. Optionally, the D50 particle size of the small-sized particles may also be, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, or 9.5 μm. Optionally, the D50 particle size of the large-size particles can also be, for example, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, or 95μm. Using a blend of large-size and small-size particles within a certain particle size range in carbon-based materials can effectively reduce material defects and increase battery capacity without causing excessive degradation of battery kinetic performance.

[0066] In this application, D50 refers to the particle size at which the cumulative distribution of particles reaches 50% in the cumulative particle size distribution curve. Physically, it means that the proportion of particles smaller than (or larger than) this particle size value is 50%. As an example, D50 can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0067] In some embodiments, the mass percentage of small-sized particles in the negative electrode active material is 1% to 99%, and the mass percentage of large-sized particles in the negative electrode active material is 1% to 99%. Optionally, the mass percentage of small-sized particles in the negative electrode active material is 5% to 75%, and the mass percentage of large-sized particles in the negative electrode active material is 25% to 95%. The mass percentage of small-sized particles in the negative electrode active material can also be, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. The mass percentage of large-size particles in the negative electrode active material can be, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. Controlling the proportion of large-size and small-size particles within an appropriate range can improve the blending effect of the two and further enhance the rate performance of the battery.

[0068] In some embodiments, the D50 particle size of the silicon-based material is 0.2 μm to 100 μm; optionally, the D50 particle size of the silicon-based material is 0.2 μm to 30 μm, and the D50 particle size of the silicon-based material can also be, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, or 95 μm. Controlling the particle size of the silicon-based material within a suitable range can balance battery capacity and kinetic performance, resulting in better overall battery performance.

[0069] In some embodiments, the negative electrode active material satisfies at least one of the following conditions (1) to (2):

[0070] (1) The concentration of the stable aqueous dispersion of carbon-based materials is 0.1 mg / mL to 100 mg / mL; the concentration of the stable aqueous dispersion of carbon-based materials can also be, for example, 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL or 90 mg / mL;

[0071] (2) The concentration of the stable aqueous dispersion of silicon-based materials is 0.1 mg / mL to 100 mg / mL; the concentration of the stable aqueous dispersion of silicon-based materials can also be, for example, 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL or 90 mg / mL;

[0072] Among them, the stable aqueous dispersion refers to the liquid phase obtained after solid-liquid separation of a dispersion that uses water as a solvent and does not precipitate after standing for more than 2 hours after preparation.

[0073] Only by controlling the concentration of the stable aqueous dispersion of the material within a suitable range can the material be charged with an appropriate amount of electricity, thereby helping to further improve the dispersion stability of the system.

[0074] In a second aspect of the present application, there is provided a method for preparing the negative electrode active material according to one or more of the foregoing embodiments, including the following steps:

[0075] Mix a carbon-based raw material, a first surfactant, and a solvent to prepare a first dispersion. After standing for more than 2 hours, perform solid-liquid separation, retain the liquid phase, and obtain a first stable dispersion; perform centrifugal separation on the first stable dispersion to obtain a first precipitate; wash and dry the first precipitate to obtain a carbon-based material;

[0076] Mix a silicon-based raw material, a second surfactant, and a solvent to prepare a second dispersion. After standing for more than 2 hours, perform solid-liquid separation, retain the liquid phase, and obtain a second stable dispersion; perform centrifugal separation on the second stable dispersion to obtain a second precipitate; wash and dry the second precipitate to obtain a silicon-based material;

[0077] Mix the carbon-based material and the silicon-based material to prepare the negative electrode active material;

[0078] Among them, the first surfactant and the second surfactant carry opposite charges in the solvent respectively.

[0079] A suitable preparation method can make the raw materials uniformly charged with an appropriate amount of electricity, further improve the dispersion performance of the negative electrode active material, and reduce agglomeration.

[0080] In some embodiments, the preparation method satisfies one or more of the following conditions (1) to (5):

[0081] (1) The carbon-based raw material includes one or more of artificial graphite, natural graphite, soft carbon, and hard carbon;

[0082] (2) The silicon-based raw material includes one or more of Si and SiO x (0 < x < 2);

[0083] (3) The first surfactant and the second surfactant are each independently selected from one or more of the following: dodecylamine, hexadecylamide, dodecylonitrile, ethoxyborate diglyceride, sodium cholate, sodium dodecylbenzenesulfonate, decynediol and hexadecyl bromide; a suitable type of surfactant can give the surface of the raw material a suitable type of functional group, provide charge and improve the dispersion performance of the material without causing damage to other battery performance, but the surfactants that can be used are not limited to the types listed above. The types listed above are only representatives of some readily available and effective surfactants.

[0084] (4) The amount of the first surfactant is 0.1% to 40% of the mass of the carbon-based raw material; the amount of the first surfactant can also be, for example, 5%, 10%, 15%, 20%, 25%, 30% or 35% of the mass of the carbon-based raw material. A suitable amount of surfactant can make the surface of the obtained carbon-based material uniformly carry a suitable amount of charge;

[0085] (5) The amount of the second surfactant is 0.1% to 40% of the mass of the silicon-based raw material; the amount of the second surfactant may also be 5%, 10%, 15%, 20%, 25%, 30% or 35% of the mass of the silicon-based raw material. The appropriate amount of surfactant can make the surface of the obtained silicon-based material uniformly carry an appropriate amount of charge.

[0086] A third aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode.

[0087] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes the negative active material of one of the aforementioned embodiments.

[0088] A fourth aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0089] A positive electrode current collector is provided, a positive electrode slurry is coated on the surface of the positive electrode current collector, and then dried and pressed to obtain a positive electrode sheet;

[0090] A negative electrode current collector is provided, and a negative electrode slurry is coated on the surface of the negative electrode current collector. The coating is then dried and pressed to obtain a negative electrode sheet. The negative electrode slurry includes the negative electrode active material described in one or more of the aforementioned embodiments. Optionally, the solid content of the negative electrode slurry is 30% to 70%. For example, the solid content of the negative electrode slurry can also be 35%, 40%, 45%, 50%, 55%, 60%, or 65%. A suitable solid content in the slurry can better match the technical solution of this application, further improving the dispersion stability of various particles in the negative electrode active material and avoiding agglomeration.

[0091] A secondary battery is prepared by stacking or winding the positive electrode, separator, and negative electrode.

[0092] A fifth aspect of this application provides an electrical device comprising the aforementioned secondary battery or a secondary battery prepared by the aforementioned method.

[0093] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0094] In one embodiment of this application, a secondary battery is provided.

[0095] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0096] Positive electrode sheet

[0097] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0098] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0099] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0100] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0101] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0102] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0104] Negative electrode sheet

[0105] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including the negative electrode active material described in the first aspect of this application.

[0106] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] In some embodiments, in addition to the negative electrode active material described in the first aspect of this application, the negative electrode active material of this application may also include negative electrode active materials known in the art for use in batteries, such as: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0109] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0110] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0112] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0113] electrolytes

[0114] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0115] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0116] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0117] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0118] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0119] Separating membrane

[0120] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0121] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0122] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0123] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0124] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0125] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 1.

[0126] In some implementations, refer to Figure 2 The outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The shell 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0127] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0128] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0129] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0130] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0131] Figure 3 Here is an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0132] Another example device could be a mobile phone, tablet, laptop, etc.

[0133] Example 1

[0134] (1) Preparation of positive electrode sheet

[0135] The positive electrode active material ternary material nickel cobalt manganese (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 97:2:1 and added to the solvent NMP to prepare a positive electrode slurry. The positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, dried at 85°C, cold pressed, and then die-cut and slit to produce a lithium-ion battery positive electrode sheet.

[0136] (2) Preparation of negative electrode sheet

[0137] a. Preparation of negative electrode active materials:

[0138] Artificial graphite (40% by mass percentage of small particles with a D50 diameter of 5 μm and 60% by mass percentage of large particles with a D50 diameter of 25 μm) and dodecylamine were mixed at a mass ratio of 100:20, and water was used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase was separated to obtain a stable aqueous dispersion with a concentration of 50 mg / mL. The stable aqueous dispersion was centrifuged at 10,000 rpm, and the solid phase was separated to obtain a carbon-based material with amino groups on its surface and a positive charge.

[0139] Si (D50 particle size of 5 μm) and sodium cholate were mixed at a mass ratio of 100:20, and water was used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase was separated to obtain a stable aqueous dispersion with a concentration of 50 mg / mL. The stable aqueous dispersion was centrifuged at 10,000 rpm, and the solid phase was separated to obtain a silicon-based material with carboxyl groups on the surface and a negative charge.

[0140] A negative electrode active material is obtained by mixing carbon-based materials with amino groups on their surface and silicon-based materials with carboxyl groups on their surface at a mass ratio of 50:50.

[0141] b. The negative electrode active material, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) obtained in step a are added to solvent water at a mass ratio of 96:2:1:1 and mixed evenly to form a negative electrode slurry with a solid content of 50%. The negative electrode slurry is evenly coated on the negative electrode current collector copper foil, dried at 85°C, and then cold-pressed to form a lithium-ion battery negative electrode sheet.

[0142] (3) Preparation of the separating membrane

[0143] Using polyethylene microporous film as the porous separator film substrate, inorganic alumina powder, polyvinylpyrrolidone, and acetone solvent are mixed evenly in a weight ratio of 3:1.5:5.5 to form a slurry, which is then coated on one side of the substrate and dried to obtain the separator film.

[0144] (4) Preparation of electrolyte

[0145] Lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was 1:2:1) to obtain a lithium-ion battery electrolyte.

[0146] (5) Preparation of lithium-ion batteries

[0147] The positive electrode, negative electrode, and separator are wound together to obtain an electrode assembly. After encapsulation, liquid injection, formation, and degassing, a lithium-ion battery is produced. The battery has an N / P ratio of 1 and a designed rated capacity of 100Ah.

[0148] Example 2

[0149] The process is basically the same as in Example 1, except that in step (2)a, artificial graphite is mixed with sodium cholate to prepare a carbon-based material with carboxyl groups on the surface, which carries a negative charge; and Si is mixed with dodecylamine to prepare a silicon-based material with amino groups on the surface, which carries a positive charge.

[0150] Example 3

[0151] The process is basically the same as in Example 1, except that in step (2)a, carbon-based materials with amino groups on their surface and silicon-based materials with carboxyl groups on their surface are mixed at a mass ratio of 97:3 to obtain the negative electrode active material.

[0152] Example 4

[0153] The process is basically the same as in Example 1, except that in step (2)a, carbon-based materials with amino groups on their surface and silicon-based materials with carboxyl groups on their surface are mixed at a mass ratio of 20:80 to obtain a negative electrode active material.

[0154] Example 5

[0155] The process is basically the same as in Example 1, except that in step (2)a, all artificial graphite particles are small-sized particles with a D50 particle size of 5μm.

[0156] Example 6

[0157] The process is basically the same as in Example 1, except that in step (2)a, all artificial graphite particles are large-sized particles with a D50 particle size of 25μm.

[0158] Example 7

[0159] It is basically the same as Example 1, except that in step (2)a, the D50 particle size of Si is 0.2 μm.

[0160] Example 8

[0161] It is basically the same as Example 1, except that in step (2)a, the D50 particle size of Si is 100 μm.

[0162] Example 9

[0163] The process is basically the same as in Example 1, except that step (2)a is as follows:

[0164] Natural graphite (80% by mass percentage of small particles with a D50 diameter of 1 μm and 20% by mass percentage of large particles with a D50 diameter of 95 μm) and diglyceride ethoxyborate were mixed at a mass ratio of 100:20, and water was used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase was separated to obtain a stable aqueous dispersion with a concentration of 50 mg / mL. The stable aqueous dispersion was centrifuged at 10,000 rpm, and the solid phase was separated to obtain a carbon-based material with boric acid groups on its surface, which carries a positive charge.

[0165] Si (D50 particle size of 30 μm) and sodium dodecylbenzenesulfonate were mixed at a mass ratio of 100:20, and water was used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase was separated to obtain a stable aqueous dispersion with a concentration of 50 mg / mL. The stable aqueous dispersion was centrifuged at 10,000 rpm, and the solid phase was separated to obtain a silicon-based material with sulfonic acid groups on the surface and a negative charge.

[0166] A negative electrode active material is obtained by mixing a carbon-based material with boric acid groups on its surface and a silicon-based material with sulfonic acid groups on its surface at a mass ratio of 5:95.

[0167] Example 10

[0168] The process is basically the same as in Example 1, except that step (2)a is as follows: Hard carbon (50% by mass percentage of small particles with a D50 particle size of 5 μm and 50% by mass percentage of large particles with a D50 particle size of 50 μm) and hexadecamide are mixed at a mass ratio of 100:20, and water is used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase is separated by solid-liquid separation, and the resulting liquid phase has a concentration of 50 mg / mL and is a stable aqueous dispersion. The stable aqueous dispersion is centrifuged at a speed of 10000 rpm, and the solid phase is separated by solid-liquid separation to obtain a carbon-based material with amide groups on the surface, which is positively charged.

[0169] Si (D50 particle size of 50 μm) and hexadecyl bromide were mixed at a mass ratio of 100:20, and water was used as a solvent to prepare a dispersion. After standing for 2 hours, the liquid phase was separated to obtain a stable aqueous dispersion with a concentration of 50 mg / mL. The stable aqueous dispersion was centrifuged at 10,000 rpm, and the solid phase was separated to obtain a silicon-based material with bromine atoms on the surface and a negative charge.

[0170] A negative electrode active material is obtained by mixing carbon-based materials with amide groups on their surface and silicon-based materials with bromine atoms on their surface at a mass ratio of 70:30.

[0171] Comparative Example 1

[0172] The process is basically the same as in Example 1, except that step (2)a is as follows:

[0173] Artificial graphite (40% by mass percentage of small particles with a D50 particle size of 5 μm and 60% by mass percentage of large particles with a D50 particle size of 25 μm) and Si (D50 particle size of 5 μm) are mixed at a mass ratio of 50:50 to obtain the negative electrode active material.

[0174] Characterization test

[0175] The above embodiments and comparative examples were subjected to the following characterization tests:

[0176] (1) Capacity test

[0177] At 25℃, the secondary battery is charged at a constant current rate of 0.33C to 4.3V, then charged at a constant voltage rate to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to 2.5V. The discharge capacity at this point is recorded as the 0.33C discharge capacity.

[0178] (2) Ratio Performance Test

[0179] At 25°C, the secondary batteries of each embodiment and comparative example were charged at a constant current rate of 0.33C to 4.3V, then charged at a constant voltage rate to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 2.5V. The discharge capacity at this point was recorded, which is the 0.33C discharge capacity. After standing for 30 minutes, the secondary batteries were charged at a constant current rate of 1.0C to 4.3V, then charged at a constant voltage rate to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 1C to 2.5V. The discharge capacity at this point was recorded, which is the 1C discharge capacity.

[0180] Battery rate performance: Capacity retention rate = 1C / 0.33C (%) = 1C discharge capacity / 0.33C discharge capacity × 100%.

[0181] Table 1

[0182]

[0183] Table 2

[0184]

[0185]

[0186] Table 3

[0187]

[0188] Analyzing the data in Table 3, compared to Example 1, the negative electrode active materials in Example 2 have opposite electrical properties: silicon-based materials carry a positive charge, and carbon-based materials carry a negative charge. Since silicon agglomeration has a greater negative impact on battery performance than carbon agglomeration, especially in high-silicon systems, when the silicon content in the negative electrode active material is as high as 50%, the silicon-negative, carbon-positive scheme of Example 1 has a greater advantage than the silicon-positive, carbon-negative scheme of Example 2, because the silicon-negative, carbon-positive scheme can effectively improve the agglomeration of silicon and the conductive agent. In Example 3, the silicon content is lower; although the capacity retention rate is improved compared to Example 1, the battery produced under the same conditions has a capacity of 0.3%. The 3C capacity was too low; in Example 4, the silicon content was too high, making dispersion more difficult than in Example 1. Although the 0.33C capacity was improved to some extent, the capacity retention rate was significantly reduced; in Example 5, small-particle carbon materials were used. Due to the numerous defects in small particles, the specific capacity was low, and the 0.33C capacity was also lower than in Example 1; in Example 6, the use of large-particle carbon materials led to deterioration of battery kinetics, and all performance characteristics were lower than in Example 1; in Example 7, the silicon particles were small, agglomeration was aggravated, and the capacity retention rate decreased; in Example 8, the silicon particles were large, which also led to deterioration of kinetics and a decrease in all performance characteristics.

[0189] Examples 9 and 10 demonstrate that the solution of this application is applicable to different types of functional groups.

[0190] In Comparative Example 1, the carbon-based and silicon-based raw materials were not surface-treated, resulting in severe agglomeration after mixing. This led to a significant decrease in capacity retention compared to the other examples, greatly reducing the rate performance of the battery.

[0191] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0192] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A negative electrode active material, comprising a carbon-based material and a silicon-based material, a first functional group being present on a surface of the carbon-based material, a second functional group being present on a surface of the silicon-based material, the first functional group carrying a charge opposite to the second functional group; the carbon-based material comprising small-size particles and large-size particles, the small-size particles having a D50 particle size of 0.2 μm to 9.9 μm, the large-size particles having a D50 particle size of 10 μm to 100 μm.

2. The negative electrode active material according to claim 1, characterized by The first functional group carries a positive charge, and the second functional group carries a negative charge.

3. The negative electrode active material according to claim 1, characterized by The first functional group comprises one or more of an amino group, an amide group, a cyano group, and a boronic acid group.

4. The negative electrode active material according to claim 1, characterized by The second functional group comprises one or more of a carboxyl group, a sulfonic acid group, a hydroxyl group, and a halogen group.

5. The negative electrode active material according to claim 1, characterized by The silicon-based material has a mass percentage content of 1% to 99% in the negative electrode active material.

6. The negative electrode active material according to claim 5, characterized by The silicon-based material has a mass percentage content of 25% to 85% in the negative electrode active material.

7. The negative electrode active material according to claim 1, characterized by The carbon-based material has a mass percentage content of 1% to 99% in the negative electrode active material.

8. The negative electrode active material according to claim 7, characterized by The carbon-based material has a mass percentage content of 15% to 75% in the negative electrode active material.

9. The negative electrode active material according to claim 1, characterized by The small-size particles have a mass percentage content of 1% to 99% in the negative electrode active material, and the large-size particles have a mass percentage content of 1% to 99% in the negative electrode active material.

10. The negative electrode active material according to claim 9, characterized by The small-size particles have a mass percentage content of 5% to 75% in the negative electrode active material, and the large-size particles have a mass percentage content of 25% to 95% in the negative electrode active material.

11. The negative electrode active material according to any one of claims 1 to 10, characterized by, The silicon-based material has a D50 particle size of 0.2 μm to 100 μm.

12. The negative electrode active material according to claim 11, characterized by The silicon-based material has a D50 particle size of 0.2 μm to 30 μm.

13. The negative electrode active material according to any one of claims 1 to 10, characterized by, The negative electrode active material satisfies at least one of the following (1) to (2): (1) the carbon-based material has a stable aqueous dispersion liquid with a concentration of 0.1 mg / mL to 100 mg / mL; (2) the silicon-based material has a stable aqueous dispersion liquid with a concentration of 0.1 mg / mL to 100 mg / mL; The stable aqueous dispersion liquid refers to a liquid phase obtained by subjecting a dispersion liquid prepared by using water as a solvent and standing for 2 hours or more without precipitation to solid-liquid separation. 14.A method for preparing the negative electrode active material according to any one of claims 1 to 13, comprising the following steps: mixing a carbon-based raw material, a first surfactant, and a solvent to prepare a first dispersion liquid, and performing solid-liquid separation after standing for 2 hours or more to retain a liquid phase, thereby obtaining a first stable dispersion liquid; centrifuging the first stable dispersion liquid to obtain a first precipitate; and washing and drying the first precipitate to obtain the carbon-based material; mixing a silicon-based raw material, a second surfactant, and a solvent to prepare a second dispersion liquid, and performing solid-liquid separation after standing for 2 hours or more to retain a liquid phase, thereby obtaining a second stable dispersion liquid; centrifuging the second stable dispersion liquid to obtain a second precipitate; and washing and drying the second precipitate to obtain the silicon-based material. mixing the carbon-based material and the silicon-based material to prepare the negative active material; wherein the first surfactant and the second surfactant carry opposite charges in the solvent, respectively.

15. The method of claim 14, wherein, The preparation method satisfies one or more of the following (1)~(5): (1) the carbon-based raw material includes one or more of artificial graphite, natural graphite, soft carbon, and hard carbon; (2) the silicon-based raw material includes Si and SiO x one or more of Si and SiO (3) the first surfactant and the second surfactant are independently selected from one or more of the following: dodecylamine, hexadecanamide, dodecanenitrile, ethoxyboronic acid diglyceride, sodium cholate, sodium dodecylbenzenesulfonate, decyne glycol, and hexadecyl bromide; (4) the amount of the first surfactant is 0.1%~40% of the mass of the carbon-based raw material; (5) the amount of the second surfactant is 0.1%~40% of the mass of the silicon-based raw material.

16. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator, the separator being disposed between the positive electrode sheet and the negative electrode sheet; wherein the negative electrode sheet comprises a negative electrode current collector and a negative active material layer disposed on at least one surface of the negative electrode current collector, the negative active material layer comprising the negative active material of any one of claims 1~13.

17. A preparation method of a secondary battery, comprising the following steps: providing a positive electrode current collector, coating a positive electrode slurry on the surface of the positive electrode current collector, drying and pressing to obtain a positive electrode sheet; providing a negative electrode current collector, coating a negative electrode slurry on the surface of the negative electrode current collector, drying and pressing to obtain a negative electrode sheet; wherein the negative electrode slurry comprises the negative active material of any one of claims 1~13; stacking or winding the positive electrode sheet, the separator, and the negative electrode sheet to prepare the secondary battery.

18. The method of claim 17, wherein the method further comprises: The solid content of the negative electrode slurry is 30%~70%.

19. An electric device comprising the secondary battery of claim 16 or the secondary battery prepared by the preparation method of any one of claims 17~18.

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