Silicon composite material and preparation method thereof, negative electrode sheet, secondary battery, and electric device

Abstract

The application relates to a silicon composite material and a preparation method thereof, a negative electrode sheet, a secondary battery and a power utilization device. The silicon composite material comprises one-dimensional conductive material, an inner core and a coating layer, the coating layer is coated on the outer surface of the inner core, the one-dimensional conductive material is arranged on the outer surface of the coating layer, and the inner core comprises a silicon-based material. The above silicon composite material has good cycle performance and fast charging performance.

Description

Technical Field

[0001] This application relates to the field of battery materials technology, and in particular to a silicon composite material and its preparation method, a negative electrode sheet, a secondary battery, and an electrical device. 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] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion battery technology, higher requirements have been placed on its energy density and cycle performance.

[0004] Silicon-based materials have attracted attention due to their significantly higher capacity compared to carbon-based materials, as this higher capacity translates to higher energy density. However, the battery cycle performance and fast-charging performance of silicon-based materials still require further improvement. Summary of the Invention

[0005] This application provides a silicon composite material with good cycle performance and fast charging performance, a method for preparing the same, and a negative electrode sheet, a secondary battery, and an electrical device using the silicon composite material.

[0006] A first aspect of this application provides a silicon composite material, comprising a one-dimensional conductive material, an inner core, and a covering layer, wherein the covering layer covers the outer surface of the inner core, the one-dimensional conductive material is disposed on the outer surface of the covering layer, and the inner core comprises a silicon-based material.

[0007] The aforementioned silicon composite material incorporates the one-dimensional conductive material on the outer surface of the silicon-based material's coating layer, thereby comprehensively improving both cycle performance and fast charging performance.

[0008] In some embodiments, the one-dimensional conductive material extends outward from the outer surface of the coating layer.

[0009] In some embodiments, the outer surface of the coating layer also has catalyst particles, and the one-dimensional conductive material is disposed on the surface of the catalyst particles;

[0010] Optionally, the catalyst particles comprise transition metal nanoparticles;

[0011] Further optionally, the transition metal nanoparticles include one or more of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles;

[0012] Optionally, the coating layer includes a carbon coating layer;

[0013] Alternatively, the carbon coating may comprise amorphous carbon.

[0014] In some embodiments, the catalyst particles account for 0.001% to 0.3% of the mass of the silicon-based material.

[0015] In some embodiments, the one-dimensional conductive material includes carbon nanotubes;

[0016] Optionally, the carbon nanotubes have one or more of the following characteristics:

[0017] (1) The average tube length is 0.5 μm to 10 μm; optionally, the average tube length of the carbon nanotube is 1 μm to 10 μm;

[0018] (2) The average diameter of the tube is 1 nm to 50 nm; optionally, the average diameter of the carbon nanotube is 20 nm to 30 nm.

[0019] In some embodiments, the mass percentage of the one-dimensional conductive material is 0.01% to 5% based on the mass of the silicon-based material; optionally, the mass percentage of the catalyst particles is 0.4% to 5%.

[0020] In some embodiments, the Dv50 of the silicon composite material is 1 μm to 30 μm.

[0021] In some embodiments, the silicon-based material includes one or more of silicon oxides, silicon-carbon composites, elemental silicon, or silicon alloys.

[0022] A second aspect of this application provides a method for preparing a silicon composite material, comprising the following steps:

[0023] A coating layer is prepared on the outer surface of the core, wherein the core comprises a silicon-based material;

[0024] A one-dimensional conductive material is prepared on the outer surface of the coating layer.

[0025] The above preparation method is simple and easy to promote and apply industrially. Furthermore, this method prepares a one-dimensional conductive material on the outer surface of the coating layer, reducing the problems of slurry gelation and agglomeration caused by adding the one-dimensional conductive material to the slurry, thus simplifying the manufacturing process of the negative electrode sheet.

[0026] In some embodiments, preparing a one-dimensional conductive material on the outer surface of the coating layer includes the following steps:

[0027] Catalyst particles are prepared on the outer surface of the coating layer;

[0028] A one-dimensional conductive material is prepared on the surface of the catalyst particles;

[0029] Optionally, the catalyst particles comprise transition metal nanoparticles;

[0030] Further optionally, the transition metal nanoparticles include one or more of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles.

[0031] In some embodiments, preparing catalyst particles on the outer surface of the coating layer includes the following steps:

[0032] Transition metal oxides and / or transition metal hydroxides are prepared on the surface of the coating layer;

[0033] Calcination is carried out under a reducing atmosphere to generate transition metal nanoparticles from the transition metal oxides and / or transition metal hydroxides.

[0034] Optionally, the calcination temperature is 600℃~800℃.

[0035] In some embodiments, the one-dimensional conductive material is grown in situ on the surface of the catalyst particles.

[0036] In some embodiments, the one-dimensional conductive material includes carbon nanotubes, and the preparation of the one-dimensional conductive material on the surface of the catalyst particles includes the following steps:

[0037] Carbon source gas is introduced to grow carbon nanotubes in situ on the surface of the catalyst particles;

[0038] Optionally, the carbon source gas includes hydrocarbon gases; more preferably, the carbon source gas includes one or more of CH4, C2H2, and propylene.

[0039] A third aspect of this application provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises one or more of the silicon composite material described in the first aspect or the silicon composite material prepared by the preparation method described in the second aspect.

[0040] In some embodiments, the negative electrode active material layer further includes a carbon-based material;

[0041] Optionally, the mass ratio of the silicon composite material to the carbon-based material is (10% to 90%):(90% to 10%).

[0042] A fourth aspect of this application provides a secondary battery, including the negative electrode sheet described in the third aspect.

[0043] A fifth aspect of this application provides an electrical device comprising one or more of the negative electrode sheet described in the third aspect or the secondary battery described in the fourth aspect.

[0044] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0045] To better describe and illustrate the embodiments or examples provided in this application, 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 applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0046] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0047] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0048] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0049] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0050] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0051] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0052] Figure 7 This is a surface electron microscope image of a silicon composite material with in-situ grown CNTs prepared according to an embodiment of this application;

[0053] Explanation of reference numerals in the attached figures:

[0054] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device. Detailed Implementation

[0055] The following describes in detail, with appropriate reference to the accompanying drawings, some embodiments of the silicon composite material, its preparation method, negative electrode sheet, secondary battery, and electrical device of this application. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0056] The "range" disclosed in this application can be defined in the form of 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 the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, and they can be combined arbitrarily; 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 also 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 "a–b" 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" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0057] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0058] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0059] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0060] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can 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.

[0061] In this application, open-ended technical features or solutions described using terms such as "containing," "comprising," or "including" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0062] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0063] Silicon-based materials undergo enormous volume changes (>300%) during charging and discharging, far exceeding those of carbon-based materials. Traditional conductive agents and negative electrode active material particles have point contact, while silicon-based materials expand with larger gaps between particles, making it impossible to form an effective conductive network. This results in a significant decrease in their fast charging and cycle performance.

[0064] One approach is to incorporate carbon nanotubes (CNTs) into materials to address this issue. However, due to the scarcity of surface defects and active groups, CNTs exhibit low solubility in various solvents. Furthermore, as carbon nanotubes are composed of layered graphite, the sp2 hybridization of carbon atoms creates highly delocalized electrons, resulting in significant van der Waals attraction between them. Their large specific surface area and aspect ratio also contribute to their tendency to exist as entangled aggregates. Adding CNTs to the slurry layer introduces several problems, such as slurry gelation, agglomeration, and poor dispersion. Moreover, since CNTs are hybridized with carbon-based materials like graphite, after coating the slurry into electrodes, CNTs tend to adhere and aggregate more readily on the surface of carbon-based materials, resulting in fewer CNTs on silicon-based materials. This makes it difficult to improve the conductive network of silicon-based materials and achieve long-range conductivity.

[0065] Another approach involves a composite material that uses carbon material to coat a physical mixture of carbon nanotubes and silicon-based materials. While this disperses the carbon nanotubes within the carbon coating layer, reducing their aggregation, the dispersed carbon nanotubes only serve to connect the silicon-based materials within the negative electrode active material particles. Their contribution to building a conductive network between multiple negative electrode active material particles is minimal. Especially during charging and discharging, as the negative electrode active material particles expand, it becomes difficult to achieve good electrical contact between them to form an effective conductive network. Therefore, this approach offers little improvement to the cycle performance and fast-charging performance of the secondary battery.

[0066] Based on this, some examples of this application provide a silicon composite material, including a one-dimensional conductive material, an inner core, and a covering layer, wherein the covering layer covers the outer surface of the inner core, the one-dimensional conductive material is disposed on the outer surface of the covering layer, and the inner core comprises a silicon-based material.

[0067] In the aforementioned silicon composite material, the one-dimensional conductive material is disposed on the outer surface of the coating layer of the silicon-based material. This reduces the entanglement and agglomeration of the one-dimensional conductive material, thereby mitigating the problems of slurry gelation, agglomeration, and poor dispersion during the preparation of the negative electrode sheet. Furthermore, the one-dimensional conductive material disposed on the outer surface of the coating layer improves the electrical contact between multiple negative electrode active material particles. Even if the negative electrode active material particles at the electrode layer expand during charging and discharging, an effective conductive network can still be constructed between the particles, thus comprehensively improving cycle performance and fast charging performance.

[0068] Understandably, the coating layer preferably covers the outer surface of the silicon-based core continuously and completely, but discontinuous or partial coating on the outer surface of the core is not excluded.

[0069] Understandably, the one-dimensional conductive material and the coating layer may have the same, different, or partially the same material composition, preferably the one-dimensional conductive material and the coating layer have the same material composition.

[0070] Understandably, "the one-dimensional conductive material is disposed on the outer surface of the coating layer" can mean that the one-dimensional conductive material is directly disposed on the outer surface of the coating layer without intermediate connecting units, or it can mean that the one-dimensional conductive material is disposed on the outer surface of the coating layer through intermediate connecting units. In some examples of this application, the intermediate connecting unit can be a catalyst particle.

[0071] In some examples, the one-dimensional conductive material extends outward from the outer surface of the coating layer. The one-dimensional conductive material formed on the surface of the coating layer allows for sufficient outward extension and dispersion, which facilitates the construction of a conductive network between particles, improving cycle performance and fast charging performance.

[0072] Understandably, the coating layer may include a single-layer coating layer or a multi-layer coating layer.

[0073] In some examples, the outer surface of the coating layer also has catalyst particles, and the one-dimensional conductive material is disposed on the surface of the catalyst particles. Without limitation, the presence of catalyst characteristic elements can be characterized by methods such as ICP.

[0074] Furthermore, the catalyst particles comprise transition metal nanoparticles.

[0075] In some examples, the transition metal nanoparticles include one or more of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles. Selecting suitable transition metal nanoparticles is beneficial for improving structural stability, thereby increasing cycle life. Understandably, the iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles are all elemental metallic particles. Further, the transition metal nanoparticles include one or more of cobalt nanoparticles and nickel nanoparticles.

[0076] In some examples, the coating layer comprises a carbon coating layer. Coating the core with a carbon coating layer is beneficial for further improving the conductivity between particles. Without limitation, the carbon coating layer comprises amorphous carbon.

[0077] In some examples, the mass percentage of the catalyst particles, based on the mass of the silicon-based material, is 0.001% to 0.3%. Reasonably controlling the mass percentage of the catalyst particles can regulate the content and distribution of the one-dimensional conductive material, allowing it to extend and disperse more fully, which is beneficial for improving cycle performance and fast-charging performance. Specifically, the mass percentage of the catalyst particles includes, but is not limited to: 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or any range between the foregoing. Further, the mass percentage of the catalyst particles is 0.05% to 0.3%.

[0078] Understandably, the term "one-dimensional conductive material" refers to a one-dimensional material that exhibits electrical conductivity. One-dimensional materials are linear materials, such as whiskers. In one direction, atoms are arranged regularly to the micrometer to centimeter scale, while in the other two directions, only a small number of atoms are arranged at the nanometer scale. Correspondingly, electrons move primarily in a linear motion along a single nanometer-scale direction. One-dimensional materials include nanoribbons, nanotubes, quantum wire materials, etc. Without limitation, examples of one-dimensional conductive materials include carbon nanotubes, metal nanofibers, and one-dimensional conductive polymer nanomaterials.

[0079] In some of these examples, the one-dimensional conductive material includes carbon nanotubes.

[0080] Furthermore, the average length of the carbon nanotubes is 0.5 μm to 10 μm. Reasonably controlling the length of the carbon nanotubes is beneficial for the construction of a conductive network between the negative electrode active material particles, and reduces the possibility of entanglement and aggregation between carbon nanotubes, thereby improving fast-charging performance and cycle performance. Specifically, the average length of the carbon nanotubes includes, but is not limited to: 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, 9.5 μm, 10 μm, or any range between the foregoing. Even more specifically, the average length of the carbon nanotubes is 1 μm to 10 μm.

[0081] Furthermore, the average diameter of the carbon nanotubes is 1 nm to 50 nm. Reasonably controlling the diameter of the carbon nanotubes is beneficial for improving cycle performance. Specifically, the average diameter of the carbon nanotubes includes, but is not limited to: 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any range between the foregoing. Even further, the average diameter of the carbon nanotubes is 20 nm to 30 nm.

[0082] In some examples, the mass percentage of the one-dimensional conductive material, based on the mass of the silicon-based material, is 0.01% to 5%. Reasonably controlling the mass percentage of the one-dimensional conductive material is beneficial for the construction of a conductive network between the negative electrode active material particles, and reduces the possibility of entanglement and aggregation between the one-dimensional conductive materials. Specifically, the mass percentage of the one-dimensional conductive material includes, but is not limited to: 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range between the foregoing. Further, the mass percentage of the one-dimensional conductive material is 0.4% to 5%.

[0083] In some examples, the Dv50 of the silicon composite material is 1 μm to 30 μm. The silicon composite material exhibits good size and dimensional uniformity. A Dv50 within this range is beneficial for improving ion conductivity, reducing internal resistance during discharge, and extending material lifetime. Furthermore, it provides a suitable specific surface area, reducing particle agglomeration during processing and improving storage performance. Specifically, the Dv50 of the silicon composite material includes, but is not limited to, 1 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any combination thereof.

[0084] In addition, without limitation, the silicon-based material includes one or more of silicon oxide compounds (SiOx, 0 < x < 2), silicon-carbon composites, elemental silicon, or silicon alloys.

[0085] Understandably, silicon oxide compounds (SiOx, 0 < x < 2) and silicon-carbon composites have structures that are coated, supported, or dispersed.

[0086] In some examples of this application, the silicon-based material includes a silicon oxide compound with a supported structure, specifically a composite material formed by supporting nano-silicon particles on a silica matrix.

[0087] In some examples of this application, the silicon-based material includes a coated silicon oxide compound, specifically a silicon suboxide outer layer coated with a carbon-based material layer as a protective layer.

[0088] In some examples of this application, the silicon-based material includes a coated silicon-carbon composite, wherein the silicon-carbon compound is a layer of elemental silicon and / or silicon alloy coated with a layer of carbon-based material as a protective layer.

[0089] In some examples of this application, the silicon-based material includes a silicon-carbon composite with a dispersed structure, wherein the silicon-carbon compound is specifically a composite system in which elemental silicon and / or a silicon alloy core and a carbon-based core form physical contact and are homogeneous.

[0090] In other examples of this application, a method for preparing a silicon composite material is provided, comprising the following steps:

[0091] A coating layer is prepared on the outer surface of the core, wherein the core comprises a silicon-based material;

[0092] A one-dimensional conductive material is prepared on the outer surface of the coating layer.

[0093] The above preparation method is simple and easy to promote and apply industrially. Furthermore, this method prepares a one-dimensional conductive material on the outer surface of the coating layer, reducing the problems of slurry gelation and agglomeration caused by adding the one-dimensional conductive material to the slurry, thus simplifying the manufacturing process of the negative electrode sheet.

[0094] It is understood that the silicon composite material in the preparation method has the same or similar technical solutions and effects as the aforementioned silicon composite material, and will not be repeated here.

[0095] In some examples, preparing a one-dimensional conductive material on the outer surface of the coating layer includes the following steps:

[0096] Catalyst particles are prepared on the outer surface of the coating layer;

[0097] A one-dimensional conductive material is prepared on the surface of the catalyst particles.

[0098] In some of these examples, preparing catalyst particles on the outer surface of the coating layer includes the following steps:

[0099] Transition metal oxides and / or transition metal hydroxides are prepared on the surface of the coating layer;

[0100] Calcination is performed under a reducing atmosphere to generate transition metal nanoparticles from the transition metal oxides and / or transition metal hydroxides.

[0101] In some of these examples, the calcination temperature is 600°C to 800°C.

[0102] In some examples, preparing transition metal oxides and / or transition metal hydroxides on the surface of the sub-coating layer includes: mixing an inner core covering the surface of the sub-coating layer with a solution of a transition metal salt to generate transition metal oxides and / or transition metal hydroxides on the surface of the sub-coating layer.

[0103] In some examples, the one-dimensional conductive material is grown in situ on the surface of the catalyst particles. In-situ growth allows for a better uniformity in the distribution of the one-dimensional conductive material, and can even achieve directional alignment.

[0104] In some examples, the one-dimensional conductive material includes carbon nanotubes, and the preparation of the one-dimensional conductive material on the surface of the catalyst particles includes the following steps:

[0105] A carbon source gas is introduced to grow carbon nanotubes in situ on the surface of the catalyst particles.

[0106] Without limitation, the carbon source gas includes hydrocarbon gases. Further, the carbon source gas includes one or more of CH4, C2H2, and propylene.

[0107] Without limitation, the temperature conditions for preparing the one-dimensional conductive material on the surface of the catalyst particles are 500°C to 800°C.

[0108] Without limitation, the flow rate of the carbon source gas is 0.5 to 1.5 L / min, and the reaction time is 0.5 h to 5 h.

[0109] Other examples of this application provide a negative electrode sheet, including 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 including one or more of the silicon composite material as described above or the silicon composite material prepared by the preparation method as described above.

[0110] In some of these examples, the negative electrode active material layer also includes carbon-based materials.

[0111] Without limitation, the mass ratio of the silicon composite material to the carbon-based material is (10%–90%):(90%–10%). Specifically, this mass ratio includes, but is not limited to: 10%:90%, 20%:80%, 30%:70%, 40%:60%, 50%:50%, 60%:40%, 70%:30%, 80%:20%, 90%:10%, or any range between the foregoing. Further, the mass ratio of the silicon composite material to the carbon-based material is (10%–50%):(90%–50%).

[0112] Other examples of this application provide a secondary battery including the negative electrode as described above.

[0113] Other examples of this application provide an electrical device including one or more of the negative electrode sheet as described above or the secondary battery as described above.

[0114] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0115] 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.

[0116] Positive electrode sheet

[0117] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0118] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0119] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0120] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0121] In some embodiments, the positive electrode 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0122] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing 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 positive electrode active materials for batteries 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, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co0.2 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 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.15 Al 0.05 O2.

[0123] In some embodiments, the positive electrode active material layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0124] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0125] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 to 25000 mPa·s. When coating the positive electrode slurry, the areal density per unit area of ​​the coating, based on dry weight (excluding solvent), can be 15–35 mg / cm³. 2The compaction density of the positive electrode sheet can be 3.0–3.6 g / cm³. 3 The concentration can be selected as 3.3–3.5 g / cm³. 3 .

[0126] Negative electrode sheet

[0127] The negative electrode is as described above.

[0128] Additionally, as a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0129] 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0130] In some embodiments, the negative electrode active material layer may further include other negative electrode active materials known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more 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.

[0131] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may include one or more 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).

[0132] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0134] 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 (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 to 10000 mPa·s. When coating the negative electrode slurry, the coating unit areal density (dry weight, minus solvent) can be 75 to 220 g / m². 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~1.8g / cm 3 .

[0135] electrolytes

[0136] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0137] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0138] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0139] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate Fluoroethylene carbonate (FEC), 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.

[0140] 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.

[0141] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0142] Separating membrane

[0143] 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.

[0144] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0145] In some embodiments, the thickness of the separator is 6–40 μm, and optionally 12–20 μm.

[0146] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0147] 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.

[0148] In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0149] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0150] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0151] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0152] In some of these embodiments, reference is made to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0153] The secondary battery can be either battery module 4 or battery pack 1.

[0154] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0155] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0156] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0157] 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. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0158] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0159] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of 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.

[0160] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0161] Figure 6 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0162] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0163] Example

[0164] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0165] Example 1

[0166] 1) Preparation of positive electrode sheet

[0167] The positive electrode active material NCM811, conductive carbon black SP, and binder PVDF were dispersed in NMP solvent at a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, wherein the coating amount per unit area on both sides was 0.27 g / 1540.25 mm². 2 .

[0168] 2) Preparation of negative electrode sheet

[0169] 2.1 Preparation of negative electrode active materials

[0170] Amorphous carbon-coated pure silicon material (commercially available product, with a pure silicon content of 95% by mass) was used as raw material. The material was ultrasonically dispersed in an ethanol-water solution of FeCl3 (volume ratio 1:1). Iron oxides were generated on the surface of the amorphous carbon-coated pure silicon material. The product was then calcined at 700℃ in a reducing atmosphere (argon:hydrogen = 95:5, volume ratio) to generate iron nanoparticles (0.15% by mass of pure silicon). Using the iron nanoparticles as a catalyst, carbon source gas C2H2 was introduced at a flow rate of 1 L / min and reacted at a constant temperature of 700℃ for 3 h, followed by natural cooling to obtain a silicon composite material with in-situ grown CNTs. The particle size Dv50 was 8 μm, with an average tube length of 5 μm and an average tube diameter of 25 nm. The CNTs accounted for 2% by mass of pure silicon. The surface electron microscope image of this in-situ grown CNT silicon composite material is shown below. Figure 7 As shown, CNTs extend outward from the outer surface of the amorphous carbon coating, rather than being tightly attached to the surface of the carbon coating or fused with it.

[0171] 2.2 The negative electrode active material (silicon material (silicon composite material) for in-situ CNT growth prepared in step 2.1 mixed with graphite (carbon-based material) at a mass ratio of 20%:80%), thickener sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black are mixed at a mass ratio of 97:1:1:1. Deionized water is added, and a negative electrode slurry is obtained under vacuum stirring. The negative electrode slurry is uniformly coated on both sides of a copper foil. After the copper foil is dried at room temperature, it is transferred to a 120℃ oven for 1 hour, then cold-pressed and slit to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides is 0.17 g / 1540.25 mm. 2 .

[0172] 3) Separating membrane

[0173] A 12μm thick polypropylene separator membrane was selected.

[0174] 4) Preparation of electrolyte

[0175] The organic solvent was a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC:20:20:60. Thoroughly dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly in an argon-atmosphere glove box with a water content of <10 ppm to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L.

[0176] 5) Battery manufacturing

[0177] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. After being wound into a square bare cell, it is placed in an aluminum-plastic film, baked at 80°C to remove water, and then 10g of the corresponding non-aqueous electrolyte is injected and sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, a finished battery with a capacity of 4000mAh is obtained.

[0178] The secondary batteries in Examples 2-23 are similar to those in Example 1 in terms of preparation method, with the main difference being the different types and proportions of materials, as shown in Table 1 below. The average length and average diameter of the carbon nanotubes can be controlled by adjusting parameters such as temperature, carbon source gas flow rate, and time.

[0179] The secondary batteries in Examples 24-27 are prepared in a similar manner to those in Example 1, with the main difference being that the mass ratio of silicon composite material to carbon-based material is 10%:90%, 90%:10%, 50%:50%, and 65%:35%, respectively.

[0180] The secondary battery of Comparative Example 1 is similar to the secondary battery of Example 1 in terms of preparation method. The main difference is that the in-situ growth of CNT silicon composite material in step 2.1 is not carried out. Instead, in step 2.2, amorphous carbon-coated pure silicon material is directly mixed with graphite at a ratio of 20% to 80% as the negative electrode active material. At the same time, CNTs accounting for 2% of the mass percentage of pure silicon are added to the negative electrode slurry.

[0181] Table 1

[0182]

[0183]

[0184] Test example:

[0185] Test method:

[0186] (1) Fast charging performance:

[0187] At 25℃, a battery with pre-embedded copper wire is charged at a constant current of 0.33C to 4.2V, and then charged at a constant voltage until the current reaches 0.05C. At this point, the battery is fully charged, and the charging capacity is recorded, which is the first charging capacity. After the battery is left to stand for 30 minutes, it is discharged at a constant current of 0.33C to 2.8V. This completes one charge-discharge cycle, and the discharge capacity is recorded, which is the first discharge capacity. Then, lithium plating begins. The charging device is connected to the copper wire and the positive electrode, and charged at a constant current of 20uA for 2 hours. Then, the charging device is connected to the copper wire and the negative electrode, and charged at a constant current of 20uA for 2 hours. The copper wire after lithium plating becomes the reference electrode, and the reference electrode potential is assumed to be 0mV. After lithium plating, the battery is charged at a constant current of 2C, and the potential difference between the anode and the reference electrode is recorded. When the potential difference reaches 0mV, the ratio of the charged capacity to the first charging capacity is recorded. This ratio represents the fast-charging performance of the cell.

[0188] (2) Cyclic performance:

[0189] At 25℃, the battery was charged at a constant current of 0.5C to 4.2V, and then charged at a constant voltage until the current reached 0.05C. At this point, the battery was fully charged, and the charging capacity was recorded, which is the first charge capacity. After letting the battery rest for 30 minutes, it was discharged at a constant current of 1C to 2.8V. This completes one charge-discharge cycle, and the discharge capacity was recorded, which is the first discharge capacity. The battery was subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle was recorded until the battery's discharge capacity decreased to 80% of the first discharge capacity. The number of cycles at this point represents the battery's cycle life.

[0190] (3) Slurry dispersibility: After the processed slurry is left to stand for 24 hours, the slurry is lifted by the stirring rod and the flow characteristics of the slurry are observed. If there is no obvious aggregation or gelation, it is judged as "good".

[0191] The test results are shown in Table 2 below:

[0192] Table 2

[0193]

[0194]

[0195] A comparison between Examples 1-23 and Comparative Example 1 shows that this application, by disposing of a one-dimensional conductive material on the outer surface of the coating layer, can effectively improve the fast-charging and cycle performance of the silicon composite material. Furthermore, in terms of process, the good dispersion of the materials facilitates the fabrication of the negative electrode sheet.

[0196] The comparison between Examples 1 to 7 shows that properly controlling the mass percentage of carbon nanotubes is beneficial to further improving cycle performance and fast charging performance.

[0197] A comparison between Example 1 and Examples 8-9 shows that selecting appropriate transition metal nanoparticles is beneficial to improving the stability of the structure, thereby improving cycle life.

[0198] A comparison between Example 1 and Examples 10-18 shows that properly controlling the length of carbon nanotubes is beneficial to further improving cycle performance and fast charging performance.

[0199] A comparison between Example 1 and Examples 19-23 shows that properly controlling the diameter of carbon nanotubes is beneficial to improving cycle performance.

[0200] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0201] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A silicon composite material, characterized by, The silicon composite material comprises a one-dimensional conductive material, an inner core, and a coating layer, the coating layer is coated on the outer surface of the inner core, the one-dimensional conductive material is arranged on the outer surface of the coating layer, and the inner core comprises a silicon-based material; the one-dimensional conductive material comprises carbon nanotubes, the average tube length is 0.5 μm to 10 μm, and the average tube diameter is 10 nm to 50 nm.

2. The silicon composite of claim 1, wherein, The one-dimensional conductive material extends outward from the outer surface of the coating layer.

3. The silicon composite of claim 1 or 2, wherein The outer surface of the coating layer further has catalyst particles, and the one-dimensional conductive material is arranged on the surface of the catalyst particles.

4. The silicon composite of claim 3, wherein, The catalyst particles comprise transition metal nanoparticles.

5. The silicon composite of claim 4, wherein, The transition metal nanoparticles comprise one or more of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles.

6. The silicon composite of claim 3, wherein The mass percentage of the catalyst particles is 0.001% to 0.3% based on the mass of the silicon-based material.

7. The silicon composite of claim 1 or 2, wherein The coating layer comprises a carbon coating layer.

8. The silicon composite of claim 7, wherein, The carbon coating layer comprises amorphous carbon.

9. The silicon composite of claim 1 or 2, wherein The carbon nanotubes have one or more of the following characteristics: (1) the average tube length of the carbon nanotubes is 1 μm to 10 μm; (2) the average tube diameter of the carbon nanotubes is 20 nm to 30 nm.

10. The silicon composite of claim 1 or 2, wherein The mass percentage of the one-dimensional conductive material is 0.01% to 5% based on the mass of the silicon-based material.

11. The silicon composite of claim 10, wherein, The mass percentage of the one-dimensional conductive material is 0.4% to 5%.

12. The silicon composite of claim 1 or 2, wherein The Dv50 of the silicon composite material is 1 μm to 30 μm.

13. The silicon composite of claim 1 or 2, wherein The silicon-based material comprises one or more of a silicon oxide compound, a silicon-carbon composite, elemental silicon, or a silicon alloy.

14. A method of producing a silicon composite material, characterized by, The method comprises the following steps: preparing a coating layer on the outer surface of an inner core, the inner core comprising a silicon-based material; preparing a one-dimensional conductive material on the outer surface of the coating layer; the one-dimensional conductive material comprises carbon nanotubes, the average tube length is 0.5 μm to 10 μm, and the average tube diameter is 10 nm to 50 nm.

15. The method of claim 14, wherein the silicon composite is prepared by a process comprising: The step of preparing a one-dimensional conductive material on the outer surface of the coating layer comprises the following steps: preparing catalyst particles on the outer surface of the coating layer; preparing a one-dimensional conductive material on the surface of the catalyst particles.

16. The method of claim 15, wherein the silicon composite is prepared by a process comprising: The catalyst particles comprise transition metal nanoparticles.

17. The method of claim 16, wherein the silicon composite is prepared by a process comprising: The transition metal nanoparticles comprise one or more of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles.

18. The method for preparing the silicon composite material according to any one of claims 15 to 17, characterized in that, The step of preparing catalyst particles on the outer surface of the coating layer comprises the following steps: preparing a transition metal oxide and / or a transition metal hydroxide on the surface of the coating layer; carrying out calcination under a reducing atmosphere to generate transition metal nanoparticles from the transition metal oxide and / or the transition metal hydroxide.

19. The method of claim 18, wherein the silicon composite is prepared by a process comprising: The temperature of the calcination is 600°C to 800°C.

20. The method for preparing the silicon composite material according to any one of claims 15 to 17, characterized in that, The one-dimensional conductive material is grown in situ on the surface of the catalyst particles.

21. The method of claim 20, wherein the silicon composite is prepared by a process comprising: The step of preparing a one-dimensional conductive material on the surface of the catalyst particles comprises the following steps: introducing a carbon source gas to grow the carbon nanotubes in situ on the surface of the catalyst particles.

22. The method of claim 21, wherein the silicon composite is prepared by a process comprising: The carbon source gas comprises a hydrocarbon gas.

23. The method of claim 22, wherein the silicon composite is prepared by a process comprising: The carbon source gas comprises one or more of CH4, C2H2, and propylene.

24. A negative electrode sheet characterized by comprising: The negative electrode active material layer further comprises a carbon-based material.

25. The negative electrode sheet according to claim 24, wherein The mass ratio of the silicon composite material to the carbon-based material is (10%~90%):(90%~10%).

26. The negative electrode sheet according to claim 25, wherein The negative electrode active material layer further comprises a carbon-based material.

27. A secondary battery characterized by comprising: The mass ratio of the silicon composite material to the carbon-based material is (10%~90%):(90%~10%).

28. An electrical device, comprising: The negative electrode active material layer further comprises a carbon-based material. The mass ratio of the silicon composite material to the carbon-based material is (10%~90%):(90%~10%).

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