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 a core and a first coating layer covering the surface of the core, the core comprises a first core and a second core, the first core comprises a first conductive material, the first conductive material comprises a flexible conductive material, and the second core comprises a silicon-based material coated with a second coating layer, and the second coating layer comprises a second conductive material. The silicon composite material has the characteristics of 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] 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 vehicles, 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, cycle performance, and safety performance.

[0003] Silicon-based materials have attracted attention due to their significantly higher capacity compared to carbon-based materials, as higher capacity translates to higher energy density. However, silicon-based materials undergo enormous volume changes (>300%) during charge and discharge, which can cause particle breakage and collapse of the electrode conductive network, affecting the battery's cycle performance and fast-charging performance. Summary of the Invention

[0004] 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.

[0005] A first aspect of this application provides a silicon composite material, including a core and a first coating layer covering the surface of the core. The core includes a first core and a second core. The first core includes a first conductive material, which includes a flexible conductive material. The second core includes a silicon-based material with a second coating layer covering its surface. The second coating layer contains a second conductive material.

[0006] The aforementioned silicon composite material possesses both excellent expansion inhibition and conductivity, thereby effectively improving cycle performance and fast charging performance.

[0007] In some embodiments, the silicon-based material is a nanoscale or microscale silicon-based material;

[0008] Optionally, the Dv50 of the silicon-based material is 10 nm to 5 μm;

[0009] Optionally, the silicon-based material includes one or both of pure silicon and silicon suboxide;

[0010] Further optionally, the Dv50 of the pure silicon is 10nm to 150nm; even more optionally, the Dv50 of the pure silicon is 50nm to 100nm.

[0011] Further optionally, the Dv50 of the silicon suboxide is 2μm to 5μm; even more optionally, the Dv50 of the silicon suboxide is 2.5μm to 3.5μm.

[0012] In some embodiments, the flexible conductive material comprises one or both of soft carbon or graphite; optionally, the flexible conductive material comprises graphite.

[0013] In some embodiments, the graphite includes one or two of the following characteristics:

[0014] (1) The graphite has a Dv50 of 1 μm to 5 μm; optionally, the graphite has a Dv50 of 1 μm to 3.5 μm.

[0015] (2) The graphite includes one or both of natural graphite and artificial graphite.

[0016] In some embodiments, the second conductive material comprises a conductive carbon material; optionally, the conductive carbon material comprises one or more of graphene, single-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0017] In some embodiments, the thickness of the second coating layer is 0.3 nm to 3 nm; alternatively, the thickness of the second coating layer is 1.2 nm to 3 nm.

[0018] In some embodiments, the mass percentage of the first conductive material to the silicon-based material with the second coating layer is (10% to 90%):(90% to 10%); alternatively, the mass percentage of the first conductive material to the silicon-based material with the second coating layer is (40% to 90%):(60% to 10%).

[0019] In some embodiments, the first coating layer comprises a carbon coating layer; optionally, the carbon coating layer comprises one or two of the following features:

[0020] (1) The thickness is 5nm to 60nm; optionally, the thickness is 20nm to 60nm.

[0021] (2) The carbon coating layer includes amorphous carbon.

[0022] In some embodiments, the silicon composite material includes one or more of the following features:

[0023] (1) The tap density is 0.9 g / cm³. 3 ~1.3g / cm 3 ;

[0024] (2) Specific surface area is 0.6 m² 2 / g~1.4m2 / g;

[0025] (3) The Dv50 of the silicon composite material is 3μm to 30μm;

[0026] Optionally, the silicon-based material includes pure silicon, and the Dv50 of the silicon composite material is 3μm to 15μm;

[0027] Optionally, the silicon-based material includes silicon suboxide, and the Dv50 of the silicon composite material is 8μm to 30μm.

[0028] A second aspect of this application provides a method for preparing a silicon composite material, comprising the following steps:

[0029] A dispersion is prepared by mixing a first conductive material, a silicon-based material with a second coating layer on its surface, and water; the second coating layer contains a second conductive material, and the first conductive material includes a flexible conductive material.

[0030] The dispersion was dried to prepare a precursor;

[0031] The precursor is coated to form a first coating layer, which is coated on the surface of the core. The core includes a first core and a second core. The first core includes a first conductive material, and the second core includes a silicon-based material whose surface is coated with the second coating layer.

[0032] The above preparation method is simple and easy to promote and apply in industrial applications.

[0033] In some embodiments, the method for preparing the silicon-based material with the second coating layer on its surface includes one or both of gas-phase reaction method or liquid-phase coating method, and the second coating layer contains graphene.

[0034] Optionally, the preparation of the silicon-based material with the second coating layer on its surface by gas-phase reaction includes the following steps:

[0035] The silicon-based material is vapor-deposited in a mixture of a second carbon source gas and carbon dioxide to form the second coating layer, thereby preparing the silicon-based material with the second coating layer on its surface.

[0036] Further optionally, the temperature of the vapor deposition is 600℃~800℃;

[0037] Further optionally, the second carbon source gas includes a hydrocarbon gas; even further optionally, the second carbon source gas includes one or both of CH4 and C2H4;

[0038] Optionally, the preparation of the silicon-based material with the second coating layer on its surface by liquid phase coating method includes the following steps:

[0039] The silicon-based material is mixed with a second dispersant, water, and graphene oxide to prepare a mixture.

[0040] The mixture is dried and calcined to prepare the silicon-based material with a second coating layer on its surface;

[0041] Further optionally, the second dispersant comprises one or more of polyvinylpyrrolidone, polyethylene glycol, or sodium carboxymethyl cellulose;

[0042] Further optionally, the drying conditions include a temperature of 60°C to 80°C;

[0043] Further optionally, the calcination conditions include: heating to 600℃~800℃ at a heating rate of 2℃ / min~5℃ / min under a reducing atmosphere, and calcining for 1h~3h.

[0044] In some embodiments, the solid content of the dispersion is 1% to 40%.

[0045] In some embodiments, the preparation of the dispersion also includes the step of adding a first dispersant;

[0046] Optionally, the first dispersant comprises one or more of polyvinylpyrrolidone, polyethylene glycol, or sodium carboxymethyl cellulose;

[0047] Optionally, the percentage of the mass of the first dispersant to the total mass of the first conductive material and the silicon-based material with the second coating layer is (70% to 95%):(30% to 5%); more preferably, the percentage of the mass of the first dispersant to the total mass of the first conductive material and the silicon-based material with the second coating layer is (20% to 5%):(80% to 95%).

[0048] In some embodiments, the drying includes spray drying; optionally, the spray drying includes one or both of the following conditions:

[0049] (1) The temperature is 150℃~200℃;

[0050] (2) Air volume is 0.08m³ 3 / min~0.2m 3 / min.

[0051] In some embodiments, the first coating layer includes a carbon coating layer, and the step of forming the first coating layer includes: placing the precursor in a reaction vessel, introducing a first carbon source gas for vapor deposition, and forming the first coating layer.

[0052] Optionally, the conditions for vapor-phase deposition by introducing the first carbon source gas include one or two of the following:

[0053] (1) The first carbon source gas includes one or both of CH4 or C2H2;

[0054] (2) First, heat the temperature to 600-800℃ at a heating rate of 2℃ / min to 10℃ / min, keep it at that temperature for 1h to 4h, and then introduce the first carbon source gas for 15min to 30min.

[0055] 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.

[0056] A fourth aspect of this application provides a secondary battery, including the negative electrode sheet described in the third aspect.

[0057] 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.

[0058] 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

[0059] 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:

[0060] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0061] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0062] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0063] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0064] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0065] 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.

[0066] Explanation of reference numerals in the attached figures:

[0067] 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

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Some examples of this application provide a silicon composite material including a core and a first coating layer covering the surface of the core. The core includes a first core and a second core. The first core includes a first conductive material, which includes a flexible conductive material. The second core includes a silicon-based material with a second coating layer covering its surface. The second coating layer contains a second conductive material.

[0077] The aforementioned silicon composite material comprehensively improves its expansion resistance and conductive network through two aspects: First, a second coating layer containing a second conductive material is applied to the surface of the silicon-based material. The presence of the second conductive material improves the conductivity of the silicon-based material and also allows for uniform dispersion of the silicon-based material, especially small-particle-size silicon, and facilitates its encapsulation by the first coating layer. Second, a first conductive material containing a flexible conductive material is mixed with the silicon-based material coated with the second coating layer to form a core. The presence of the flexible conductive material buffers the expansion of the silicon-based material and provides good conductivity. Thus, the aforementioned silicon composite material possesses both excellent expansion suppression and conductivity, thereby effectively improving cycle performance and fast-charging performance.

[0078] In addition, the presence of the coating layer can protect the internal particles and effectively isolate the material from the erosion caused by the electrolyte during cycling.

[0079] Understandably, the silicon-based material may be pre-lithiated or non-lithiated.

[0080] In some of these examples, the silicon-based material is a nanoscale or microscale silicon-based material. Using silicon-based materials with small particle sizes can further reduce expansion. Understandably, "nanoscale" means that the Dv50 of the silicon-based material satisfies 1 nm ≤ Dv50 < 100 nm, and "microscale" means that the Dv50 of the silicon-based material satisfies 1 μm ≤ Dv50 < 10 μm.

[0081] In some examples, the Dv50 of the silicon-based material is 10nm to 5μm. Reasonably controlling the particle size of the silicon-based material is beneficial for improving fast-charging performance and cycle life. It also facilitates particle formation and dispersion. Specifically, the Dv50 of the silicon-based material includes, but is not limited to: 10nm, 20nm, 30nm, 40nm, 50nm, 70nm, 80nm, 90nm, 100nm, 110nm, 115nm, 120nm, 150nm, 200nm, 400nm, 600nm, 800nm, 1μm, 2μm, 3μm, 4μm, 5μm, or any range between the foregoing.

[0082] In some of these examples, the silicon-based material includes one or both of pure silicon or silicon suboxide (SiOx, 0 < x < 2).

[0083] Further, the Dv50 of the pure silicon is 10nm to 150nm. Specifically, the Dv50 of the pure silicon includes, but is not limited to: 10nm, 20nm, 30nm, 40nm, 50nm, 70nm, 80nm, 90nm, 100nm, 110nm, 115nm, 120nm, 150nm, or any range between the foregoing. Even further, the Dv50 of the pure silicon is 50nm to 100nm.

[0084] Further, the Dv50 of the silicon suboxide is 2μm to 5μm. Specifically, the Dv50 of the silicon suboxide includes, but is not limited to: 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, or any range between the foregoing. Even further, the Dv50 of the silicon suboxide is 2.5μm to 3.5μm.

[0085] In some examples, the flexible conductive material comprises one or both of soft carbon and graphite. Further, the flexible conductive material comprises graphite. Using graphite as the flexible conductive material provides better buffering against the expansion of silicon-based materials and exhibits good conductivity. Furthermore, the morphology of graphite is not limited and can be spherical, granular, flake-like, or a combination of the aforementioned morphologies.

[0086] In some examples, the Dv50 of the graphite is 1μm to 5μm. Reasonably controlling the Dv50 of the graphite is beneficial for improving fast-charging performance and cycle life. Specifically, the Dv50 of the graphite includes, but is not limited to: 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or any range between the foregoing. Further, the Dv50 of the graphite is 1μm to 3.5μm.

[0087] In some of these examples, the graphite comprises one or both of natural and synthetic graphite. Further, the graphite includes synthetic graphite. This is beneficial for improving cycle life.

[0088] In some examples, the second conductive material comprises a conductive carbon material. Further, the conductive carbon material comprises one or more of graphene, single-walled carbon nanotubes, or multi-walled carbon nanotubes. Even further, the conductive carbon material comprises graphene. Using graphene as the second conductive material to coat silicon-based materials results in a better coating effect and improves conductivity.

[0089] In some examples, the thickness of the second coating layer is 0.3 nm to 3 nm. Reasonably controlling the thickness of the graphene layer makes the material more flexible, facilitating complete coating of silicon-based materials and improving cycle life. Specifically, the thickness of the second coating layer includes, but is not limited to: 0.3 nm, 0.8 nm, 1 nm, 1.2 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, or any combination thereof. Further, the thickness of the second coating layer is 1.2 nm to 3 nm.

[0090] In some examples, the mass percentage of the first conductive material to the silicon-based material with the second coating layer is (10%–90%):(90%–10%). This helps reduce material expansion and also allows the material to have a higher capacity, further improving fast-charging and cycle performance. A higher proportion of silicon-based material can increase the material's capacity; however, in conventional methods, when the proportion of silicon-based material reaches 90%, material expansion is significant, with anode full-charge rebound reaching over 300%. The solution of this application effectively improves material expansion, maintaining a low anode full-charge rebound within the mass percentage range of (10%–90%):(90%–10%).

[0091] Specifically, the mass percentage 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 percentage of the first conductive material to the silicon-based material with the second coating layer on its surface is (40%–90%):(60%–10%).

[0092] In some examples, the first coating layer includes a carbon coating layer. Coating the core with a carbon coating layer can further buffer the expansion of the silicon-based material and also improve the conductivity between particles.

[0093] In some examples, the thickness of the carbon coating layer is 5 nm to 60 nm. This effectively isolates the material from electrolyte erosion during cycling, improving cycling performance and conductivity. Specifically, the thickness of the carbon coating layer includes, but is not limited to, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, or any combination thereof. Further, the thickness of the carbon coating layer is 20 nm to 60 nm.

[0094] Without limitation, the carbon coating layer includes amorphous carbon.

[0095] In some of these examples, the tap density of the silicon composite material is 0.9 g / cm³. 3 ~1.3g / cm 3 .

[0096] In some of these examples, the specific surface area of ​​the silicon composite material is 0.6 m². 2 / g~1.4m 2 / g;

[0097] In some of these examples, the Dv50 of the silicon composite material is 3 μm to 30 μm.

[0098] Furthermore, the silicon-based material comprises pure silicon, and the Dv50 of the silicon composite material is 3μm to 15μm;

[0099] Furthermore, the silicon-based material includes silicon suboxide, and the Dv50 of the silicon composite material is 8μm to 30μm.

[0100] Other examples of this application provide a method for preparing a silicon composite material, comprising the following steps:

[0101] A dispersion is prepared by mixing a first conductive material, a silicon-based material with a second coating layer on its surface, and water; the second coating layer contains a second conductive material, and the first conductive material includes a flexible conductive material.

[0102] The dispersion was dried to prepare a precursor;

[0103] The precursor is coated to form a first coating layer, which is coated on the surface of the core. The core includes a first core and a second core. The first core includes a first conductive material, and the second core includes a silicon-based material whose surface is coated with the second coating layer.

[0104] The above preparation method is simple and easy to promote and apply in industrial applications.

[0105] Understandably, the silicon composite material prepared by the above method has the same or similar scheme and effect as the aforementioned silicon composite material, and will not be repeated here.

[0106] In some examples, the preparation method of the silicon-based material with the second coating layer includes one or both of gas-phase reaction and liquid-phase coating methods. Without limitation, the equipment for the gas-phase reaction method can be any of the following methods: gas condensation, hydrogen arc plasma, sputtering, vacuum deposition, hybrid plasma, gas phase decomposition, plasma-heated physical vapor phase synthesis, wire electric explosion, laser-induction hybrid heating, or laser-induced chemical vapor deposition.

[0107] Furthermore, the second coating layer comprises graphene, and the preparation of the silicon-based material with the second coating layer on its surface by gas-phase reaction includes the following steps:

[0108] The silicon-based material is vapor-deposited in a mixture of a second carbon source gas and carbon dioxide to form the second coating layer, thereby preparing the silicon-based material with the second coating layer on its surface.

[0109] In some of these examples, the temperature of the vapor deposition is 600°C to 800°C;

[0110] In some examples, the second carbon source gas includes hydrocarbon gases. Without limitation, the second carbon source gas includes one or both of CH4 and C2H4.

[0111] Furthermore, the second coating layer comprises graphene, and the preparation of the silicon-based material with the second coating layer on its surface by liquid-phase coating method includes the following steps:

[0112] The silicon-based material is mixed with a second dispersant, water, and graphene oxide to prepare a mixture.

[0113] The mixture is dried and calcined to prepare the silicon-based material with a second coating layer on its surface.

[0114] In some of these examples, the second dispersant comprises one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, or sodium carboxymethyl cellulose (CMC).

[0115] In some of these examples, the drying conditions include a temperature of 60°C to 80°C.

[0116] In some examples, the calcination conditions include: heating to 600°C–800°C at a heating rate of 2°C / min–5°C / min under a reducing atmosphere, and calcining for 1–3 hours. Without limitation, the inert gas includes argon and hydrogen, with a volume ratio of argon to hydrogen of (90–98):(10–2). Understandably, the calcination process includes a cooling step, such as natural cooling to room temperature.

[0117] In addition, in some of these examples, the solid content of the dispersion is 1% to 40%.

[0118] In some examples, the preparation of the dispersion also includes the step of adding a first dispersant. Introducing the first dispersant enables the first conductive material to be uniformly dispersed with the silicon-based material whose surface is coated with a second layer, thereby improving cycle performance and fast-charging performance.

[0119] In some of these examples, the first dispersant comprises one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, or sodium carboxymethyl cellulose (CMC).

[0120] In some examples, the percentage between the mass of the first dispersant and the total mass of the first conductive material and the silicon-based material with the second coating layer is (30%–5%):(70%–95%). Specifically, this percentage includes, but is not limited to: 30%:70%, 25%:75%, 20%:80%, 15%:85%, 10%:90%, 5%:95%, or any range between the foregoing. Further, the percentage is (20%–5%):(80%–95%).

[0121] In some of these examples, the drying process includes spray drying.

[0122] In some of these examples, the spray drying temperature is 150°C to 200°C.

[0123] In some of these examples, the airflow rate for the spray dryer is 0.08 m³ / h. 3 / min~0.2m 3 / min.

[0124] In some of these examples, the first coating layer includes a carbon coating layer, and the step of forming the first coating layer includes: placing the precursor in a reaction vessel, introducing a first carbon source gas for vapor deposition, and forming the first coating layer.

[0125] In some of these examples, during the vapor deposition process, the first carbon source gas includes one or both of CH4 or C2H2.

[0126] In some examples, during the vapor deposition process of introducing the first carbon source gas, the temperature is first raised to 600-800°C at a heating rate of 2°C / min to 10°C / min, held for 1-4 hours, and then the first carbon source gas is introduced for 15-30 minutes.

[0127] 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.

[0128] Other examples of this application provide a secondary battery including the negative electrode as described above.

[0129] 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.

[0130] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0131] 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.

[0132] Positive electrode sheet

[0133] 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.

[0134] 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.

[0135] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0136] 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.

[0137] 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).

[0138] 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 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 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.15 Al 0.05 O2.

[0139] 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.

[0140] 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.

[0141] 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. 2 The 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 .

[0142] Negative electrode sheet

[0143] The negative electrode is as described above.

[0144] 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.

[0145] 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).

[0146] 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.

[0147] 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).

[0148] 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.

[0149] 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)).

[0150] 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 .

[0151] electrolytes

[0152] 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.

[0153] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0154] 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).

[0155] 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.

[0156] 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.

[0157] 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.

[0158] Separating membrane

[0159] 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.

[0160] 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.

[0161] In some embodiments, the thickness of the separator is 6–40 μm, and optionally 12–20 μm.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] The secondary battery can be either battery module 4 or battery pack 1.

[0170] 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.

[0171] 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.

[0172] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0173] 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.

[0174] Figure 4 and Figure 5This 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.

[0175] 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.

[0176] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0177] 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.

[0178] 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.

[0179] Example

[0180] 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.

[0181] Example 1

[0182] 1) Preparation of positive electrode sheet

[0183] 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 .

[0184] 2) Preparation of negative electrode sheet

[0185] 2.1 Preparation of negative electrode active materials

[0186] Preparation of silicon-based materials with a graphene-coated surface:

[0187] Si nanoparticles (Dv50 = 80 nm) and a second dispersant, PVP, were uniformly dispersed in deionized water at a ratio of 1:2 to form a solution with a Si nanoparticle content of 5 wt%. Graphene oxide powder was added at 10% of the Si nanoparticle weight and mixed thoroughly. The solution was then dried at 80 °C. The solution was transferred to a tube furnace, and the air inside the tube was evacuated using a vacuum pump. Argon-hydrogen gas (argon:hydrogen = 95:5) was then slowly introduced as a protective gas, and the temperature was raised to 700 °C at a heating rate of 3 °C / min. After high-temperature calcination for 2 hours, the solution was allowed to cool naturally to obtain a pure silicon material (graphene@silicon-based material) with a graphene layer coated on its surface. The thickness of the graphene layer was 1 nm.

[0188] Preparation of silicon composite precursors:

[0189] The main material and the first dispersant, PVP, were added to deionized water at a weight ratio of 80%:20% and stirred until evenly dispersed to obtain a spare suspension. The main material includes natural graphite particles and silicon-based materials coated with a graphene layer, wherein the weight ratio of natural graphite particles to silicon-based materials coated with a graphene layer is 50%:50%, and the solid content of the spare suspension is 20%. The spare suspension was spray-dried using a spray dryer at a temperature of 180°C and a drying airflow of 0.15 m³ / h. 3 / min, to obtain the spherical precursor of the composite silicon material;

[0190] Preparation of carbon coating layer: The precursor is placed in a clean ceramic boat, and then the ceramic boat is placed in a tube furnace with Ar gas as protective gas. The temperature is raised to 700°C at a heating rate of 5°C and held for 2 hours. Then the Ar gas is replaced with CH4 gas and held for 20 minutes. Then the temperature is cooled to room temperature to prepare a carbon coating layer with a thickness of 25 nm. The core of the carbon coating layer includes natural graphite and silicon-based materials with a graphene layer on the surface, thus obtaining a silicon composite material.

[0191] 2.2 The negative electrode active material prepared in step 2.1, the thickener sodium carboxymethyl cellulose, the binder styrene-butadiene rubber, and the conductive agent acetylene black are mixed in a mass ratio of 97:1:1:1. Deionized water is added, and the mixture is stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto both sides of a copper foil. After the copper foil is dried at room temperature, it is transferred to a 120℃ oven for drying for 1 hour. Then, it is 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 .

[0192] 3) Separating membrane

[0193] A 12μm thick polypropylene separator membrane was selected.

[0194] 4) Preparation of electrolyte

[0195] 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.

[0196] 5) Battery manufacturing

[0197] 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.

[0198] The secondary batteries in Examples 2 to 30 are prepared in a similar manner to those in Example 1, with the main difference being the types and proportions of materials, as shown in Table 1 below.

[0199] The secondary battery of Comparative Example 1 is prepared in a similar manner to the secondary battery of Example 1, the main difference being that no graphene layer is coated on the surface of the silicon-based material.

[0200] The secondary battery of Comparative Example 2 is prepared in a similar manner to the secondary battery of Example 1, the main difference being that natural graphite was not used in the main material.

[0201] Table 1

[0202]

[0203]

[0204] In addition, the tap density, specific surface area, and Dv50 of the silicon composite materials prepared in Examples 1-30 and Comparative Examples 1-2 are summarized in Table 2 below:

[0205] Table 2

[0206]

[0207]

[0208] Test example:

[0209] Test method:

[0210] (1) Anode full charge rebound:

[0211] The thickness H1 of the negative electrode sheet obtained by cold pressing and cutting is measured with a micrometer. Then the cell is fully charged and disassembled. The thickness H2 of the negative electrode sheet is measured with a micrometer again. The negative electrode full charge rebound = (H2 / H1-1)*100%.

[0212] (2) DC internal resistance:

[0213] Adjust the battery cell to 50% SoC and record the DC internal resistance value after 30 seconds of 4C discharge.

[0214] (3) Fast charging performance:

[0215] 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.

[0216] (4) Cyclic performance:

[0217] 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.

[0218] The test results are shown in Table 3 below:

[0219] Table 3

[0220]

[0221] As can be seen from the comparison between Examples 1-30 and Comparative Examples 1-2, this application improves the expansion properties and conductive network of silicon composite materials by coating the surface of silicon-based materials with a conductive graphene layer and combining the conductive natural graphene with the silicon-based materials coated with the conductive graphene layer. This effectively enhances the cycle performance and fast charging performance.

[0222] A comparison between Examples 1 to 5 shows that properly controlling the Dv50 of the graphite is beneficial to further improving fast charging performance and cycle life.

[0223] A comparison between Example 1 and Example 4 shows that using artificial graphite can further optimize cycle life.

[0224] A comparison between Examples 1 and Examples 5-8 shows that reasonably controlling the mass percentage of the first conductive material to the silicon-based material with the second coating layer on its surface can further improve fast charging performance and cycle performance. Furthermore, a comparison between Examples 1 and Examples 5-8 also shows that when the mass percentage of graphite to graphene@silicon-based material varies within the range of (10%–90%):(90%–10%), the anode full-charge rebound remains at a low level.

[0225] A comparison between Examples 1 and Examples 9-17 shows that properly controlling the particle size of silicon-based materials is beneficial to improving fast charging performance and cycle life.

[0226] A comparison between Example 1 and Examples 18-20 shows that properly controlling the thickness of the graphene layer is beneficial to improving cycle life.

[0227] A comparison between Example 1 and Examples 21-24 shows that properly controlling the thickness of the carbon coating can improve fast charging performance and cycle life.

[0228] A comparison between Example 1 and Examples 25-30 shows that properly controlling the amount of the first dispersant can improve cycle performance and fast charging performance.

[0229] 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.

[0230] 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 one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features:

2. The silicon composite of claim 1, wherein (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

3. The silicon composite of claim 1, wherein The silicon composite material comprises one or more of the following features:

4. The silicon composite of claim 3, wherein (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

5. The silicon composite of claim 1, wherein The silicon composite material comprises one or more of the following features:

6. The silicon composite of claim 5, wherein, (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

7. The silicon composite of claim 1, wherein The silicon composite material comprises one or more of the following features:

8. The silicon composite of claim 7, wherein, (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

9. The silicon composite of claim 1, wherein, The silicon composite material comprises one or more of the following features:

10. The silicon composite of claim 9, wherein, (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

11. The silicon composite of claim 1, wherein, The silicon composite material comprises one or more of the following features:

12. The silicon composite of claim 11, wherein, (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

13. The silicon composite of claim 12, wherein, The silicon composite material comprises one or more of the following features:

14. The silicon composite of any one of claims 1-13, wherein, (3) The Dv50 of the silicon composite material is 8 μm-30 μm. (1) a tap density of 0.9 g / cm3 3 1.3 g / cm3 3 ; (2) the specific surface area is 0.6 m 2 / g ~ 1.4 m 2 / g; The silicon composite material comprises one or more of the following features:

15. A method of making a silicon composite material, characterized by, (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features:

16. The method of claim 15, wherein the silicon composite is prepared by a process comprising: (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

17. The method of claim 16, wherein the silicon composite is prepared by a process comprising: The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm.

18. The method of claim 17, wherein the silicon composite is prepared by a process comprising: The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The Dv50 of the silicon composite material is 8 μm-30 μm. The silicon composite material comprises one or more of the following features: (3) The D (2) The second carbon source gas comprises a hydrocarbon gas.

19. The method of claim 18, wherein the silicon composite is prepared by a process comprising: The second carbon source gas comprises one or both of CH4 or C2H4.

20. The method of claim 16, wherein the silicon composite is prepared by a process comprising: The method for preparing the silicon-based material coated with the second coating layer by liquid phase coating comprises the following steps: Mixing the silicon-based material with a second dispersant, water and graphene oxide to prepare a mixed solution; Drying and calcining the mixed solution to prepare the silicon-based material coated with the second coating layer.

21. The method of claim 20, wherein the silicon composite is prepared by a process comprising: One or more of the following features are included: (1) The second dispersant comprises one or more of polyvinylpyrrolidone, polyethylene glycol or sodium carboxymethyl cellulose; (2) The drying conditions comprise a temperature of 60-80°C; (3) The calcining conditions comprise heating to 600-800°C at a heating rate of 2-5°C / min under a reducing atmosphere and calcining for 1-3h.

22. The method for preparing the silicon composite material according to any one of claims 15 to 21, characterized in that, The solid content of the dispersion is 1-40%.

23. The method for preparing the silicon composite material according to any one of claims 15 to 21, characterized in that, The process for preparing the dispersion further comprises a step of adding a first dispersant; The first dispersant comprises one or more of the following features: (1) The first dispersant comprises one or more of polyvinylpyrrolidone, polyethylene glycol or sodium carboxymethyl cellulose; (2) The percentage of the mass of the first dispersant to the total mass of the first conductive material and the silicon-based material coated with the second coating layer is (70-95):(30-5).

24. The method of claim 23, wherein the silicon composite is prepared by a process comprising: The percentage of the mass of the first dispersant to the total mass of the first conductive material and the silicon-based material coated with the second coating layer is (20-5):(80-95).

25. The method for preparing the silicon composite material according to any one of claims 15 to 21, characterized in that, The drying comprises spray drying, and the spray drying comprises one or both of the following conditions: (1) The temperature is 150-200°C; (2) the air volume is 0.08m 3 / min~0.2m 3 / min.

26. The method for preparing the silicon composite material according to any one of claims 15 to 21, characterized in that, The first coating layer comprises a carbon coating layer, and the step of forming the first coating layer comprises placing the precursor in a reaction vessel and introducing a first carbon source gas for vapor deposition to form the first coating layer.

27. The method of claim 26, wherein the silicon composite is prepared by a process comprising: The conditions for introducing the first carbon source gas for vapor deposition comprise one or both of the following conditions: (1) The first carbon source gas comprises one or both of CH4 or C2H2; (2) First heat to 600-800°C at a heating rate of 2-10°C / min, hold for 1-4h, then introduce the first carbon source gas for 15-30min.

28. A negative electrode sheet characterized by comprising: 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 of any one of claims 1-14 or the silicon composite material prepared by the method of any one of claims 15-27.

29. A secondary battery, characterized by comprising: The negative electrode sheet of claim 28.

30. An electrical device, comprising: One or more of the negative electrode sheet of claim 28 or the secondary battery of claim 29.

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