Silicon-containing anode active materials, and anode sheets containing them, secondary batteries and electrical devices.

Abstract

This application provides a silicon-containing anode active material, as well as an anode sheet, a secondary battery, and an electrical device comprising the same. The silicon-containing anode active material includes a silicon-based material and a conductive layer on the surface of the silicon-based material. The conductive layer comprises a polymer and a one-dimensional conductive material. The polymer includes polar functional groups, which include one or more of carboxylic acid groups, hydroxyl groups, amide groups, amino groups, carbonyl groups, and nitro groups. The mass percentage of polar functional groups in the polymer is A1, and the mass percentage of silicon in the silicon-based material is A2. The silicon-containing anode active material satisfies the following conditions: A2 is 5% to 100%, and A2 / A1 is 0.2 to 8. The silicon-containing anode active material of this application can simultaneously achieve good electronic conductivity, small volume expansion effect, and high reversible capacity and first coulombic efficiency, and it can still maintain good electronic conductivity after being prepared into an anode sheet.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a silicon-containing negative electrode active material, as well as a negative electrode sheet containing the same, a secondary battery, and an electrical device. Background Technology

[0002] In recent years, rechargeable batteries 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. With the application and promotion of rechargeable batteries, their energy density has received increasing attention. Graphite is the most commonly used negative electrode active material in rechargeable batteries, but its theoretical specific capacity is only 372 mAh / g, leaving very limited room for improvement in energy density. Silicon-based materials have a theoretical specific capacity as high as 4200 mAh / g, making them the most promising negative electrode active materials. However, silicon-based materials suffer from high volume expansion and poor electronic conductivity, which seriously affects their large-scale commercial application. Summary of the Invention

[0003] The purpose of this application is to provide a silicon-containing anode active material, as well as an anode sheet containing the same, a secondary battery, and an electrical device. The silicon-containing anode active material of this application can simultaneously achieve good electronic conductivity, small volume expansion effect, high reversible capacity, and high first coulombic efficiency, and it can still maintain good electronic conductivity after being prepared into an anode sheet.

[0004] The first aspect of this application provides a silicon-containing anode active material, comprising a silicon-based material and a conductive layer located on the surface of the silicon-based material. The conductive layer comprises a polymer and a one-dimensional conductive material, wherein the polymer comprises polar functional groups, including one or more of carboxylic acid groups, hydroxyl groups, amide groups, amino groups, carbonyl groups, and nitro groups; the mass percentage of polar functional groups in the polymer is A1, the mass percentage of silicon element in the silicon-based material is A2, and the silicon-containing anode active material satisfies that: A2 is 5% to 100% and A2 / A1 is 0.2 to 8.

[0005] The polymer in the conductive layer contains polar functional groups. The inventors discovered that by adjusting the mass percentage of polar functional groups (A1) in the polymer and the mass percentage of silicon in the silicon-based material (A2), when A2 / A1 is controlled between 0.2 and 8, it ensures that appropriate amounts of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material to the surface of the silicon-based material and prevents the conductive layer from completely detaching during slurry mixing and dispersion. Furthermore, when A2 / A1 is controlled between 0.2 and 8, the polymer and the one-dimensional conductive material can also cross-link and intertwine, making the conductive layer flexible and able to firmly cover the surface of the silicon-based material like a fishing net. Therefore, the silicon-containing anode active material of this application possesses excellent electronic conductivity, and it maintains good electronic conductivity even after being applied to the anode sheet.

[0006] In any embodiment of this application, A2 is 10% to 80% and A2 / A1 is 0.6 to 2.5. In this case, the silicon-containing anode active material of this application can exhibit better electronic conductivity, higher reversible capacity and initial coulombic efficiency, and lower volume expansion effect.

[0007] In any embodiment of this application, A1 is 5% to 90%, optionally 10% to 75%. When the content of polar functional groups in the polymer is within a suitable range, it can ensure that appropriate amounts of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material on the surface of the silicon-based material, further improving the electronic conductivity of the silicon-containing anode active material, reducing side reactions between the silicon-containing anode active material and the electrolyte, and alleviating the volume expansion of the silicon-containing anode active material.

[0008] In any embodiment of this application, the weight-average molecular weight of the polymer is B1, which is above 100,000, and optionally between 200,000 and 1,000,000.

[0009] In any embodiment of this application, the aspect ratio of the one-dimensional conductive material is B2, which is from 100 to 20000, optionally from 2000 to 20000. When the aspect ratio of the one-dimensional conductive material is within a suitable range, it can intertwine with each other on the surface of the silicon-based material to form a good coating effect. On the one hand, it can provide long-range conductivity to the surface of the silicon-based material; on the other hand, it is beneficial for the conductive layer to form a net-like cross-linked network structure, thereby better improving the electronic conductivity and volume expansion of the silicon-based material surface.

[0010] In any embodiment of this application, B1 / B2 is 5 to 200, optionally 5 to 50. When B1 / B2 is within a suitable range, the silicon-containing anode active material can have better electronic conductivity and lower volume expansion.

[0011] In any embodiment of this application, the diameter of the one-dimensional conductive material is from 1 nm to 30 nm. When the diameter of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can better cross-link and entangle with each other, which is conducive to the formation of a fishing net-like cross-linked network structure of the conductive layer and its covering on the surface of the silicon-based material. Therefore, the silicon-containing anode active material can have better electronic conductivity and lower volume expansion.

[0012] In any embodiment of this application, the length of the one-dimensional conductive material is from 0.5 μm to 20 μm. When the length of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can better cross-link and entangle with each other, which is conducive to the formation of a fishing net-like cross-linked network structure of the conductive layer and its covering of the silicon-based material surface. Therefore, the silicon-containing anode active material can have better electronic conductivity and lower volume expansion.

[0013] In any embodiment of this application, the glass transition temperature of the polymer is below 150°C, optionally between -10°C and 120°C.

[0014] In any embodiment of this application, the crystallinity of the polymer is below 80%, optionally from 10% to 70%.

[0015] When a polymer has a suitable glass transition temperature and crystallinity, it can better cross-link and entangle with a one-dimensional conductive material. At this time, the conductive layer can firmly cover the surface of the silicon-based material like a fishing net, which can better improve the electronic conductivity and volume expansion of the silicon-based material surface.

[0016] In any embodiment of this application, the polymer includes one or more of the following: (meth)acrylic acid and its salt homopolymers or copolymers, hydroxymethyl cellulose and its salt homopolymers or copolymers, alginate and its salt homopolymers or copolymers, polyacetamide homopolymers or copolymers, acrylamide homopolymers or copolymers, and vinyl alcohol homopolymers or copolymers. These polymers can better crosslink and entangle with one-dimensional conductive materials, allowing the conductive layer to firmly cover the surface of the silicon-based material like a fishing net, thus better improving the electronic conductivity and volume expansion of the silicon-based material surface.

[0017] In any embodiment of this application, the one-dimensional conductive material includes carbon nanotubes.

[0018] Optionally, the carbon nanotubes have a carbon content of over 90%. The higher the carbon content of the carbon nanotubes, the lower the impurity content and the better the electronic conductivity, thus allowing the silicon-containing anode active material to have better electronic conductivity.

[0019] Optionally, the carbon nanotube's I g / I d Above 40, I g This indicates that the Raman spectrum of the carbon nanotube is located at 1500 cm⁻¹. -1 Up to 1650cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the carbon nanotube is located at 100 cm⁻¹. -1 Up to 200cm -1 Peak intensity within the range. Io of carbon nanotubes. g / I d Within a suitable range, carbon nanotubes have fewer defects and higher tensile strength, so the resulting conductive layer can simultaneously achieve good flexibility and high tensile strength, thereby effectively mitigating the volume expansion of silicon-based materials.

[0020] Optionally, the specific surface area of ​​the carbon nanotubes is 500 m². 2 / g or more. When the specific surface area of ​​carbon nanotubes is within a suitable range, their contact area with the polymer is large, which can form more hydrogen bonds, thus facilitating mutual dispersion with the polymer and enabling the formation of a uniform and stable conductive layer.

[0021] In any embodiment of this application, the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon carbide, and silicon alloy. Optionally, the silicon-based material is also doped with one or two elements of lithium and magnesium.

[0022] In any embodiment of this application, based on the total mass of the silicon-containing anode active material, the mass percentage of the silicon-based material is W1, where W1 is 90% to 98%; the mass percentage of the polymer is W2, where W2 is 1% to 9%; and the mass percentage of the one-dimensional conductive material is W3, where W3 is 0.1% to 1%.

[0023] In any embodiment of this application, W2 / W3 is 7 to 20. When W2 / W3 is within a suitable range, it ensures that an appropriate amount of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material on the surface of the silicon-based material, thereby better improving the electronic conductivity and volume expansion of the silicon-based material surface.

[0024] In any embodiment of this application, the thickness of the conductive layer is 1 nm to 2 μm.

[0025] In any embodiment of this application, the resistivity of the silicon-containing anode active material powder is from 0.70 Ω-cm to 0.89 Ω-cm.

[0026] In any embodiment of this application, the average particle size Dv50 of the silicon-containing anode active material is 2 μm to 10 μm.

[0027] In any embodiment of this application, the specific surface area of ​​the silicon-containing anode active material is 0.8 m². 2 / g to 5m 2 / g.

[0028] In any embodiment of this application, the silicon-containing anode active material I g / I d From 0.1 to 200, I g This indicates that the Raman spectrum of the silicon-containing anode active material is located at 1500 cm⁻¹. -1 Up to 1650cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the silicon-containing anode active material is located at 100 cm⁻¹. -1 Up to 200cm -1 Peak intensity within the range.

[0029] A second aspect of this application provides a negative electrode sheet, comprising a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, wherein the negative electrode film layer comprises a silicon-containing negative electrode active material, a conductive agent, and a binder as described in the first aspect of this application.

[0030] The silicon-containing anode active material of this application can simultaneously achieve good electronic conductivity, small volume expansion effect, high reversible capacity and first coulombic efficiency, and it can still maintain good electronic conductivity after being prepared into anode sheet. Therefore, the anode sheet of this application can simultaneously achieve good electronic conductivity, high capacity and first coulombic efficiency and small volume expansion.

[0031] In any embodiment of this application, the negative electrode film layer further includes graphite.

[0032] A third aspect of this application provides a secondary battery, including the silicon-containing negative electrode active material of the first aspect of this application, or the negative electrode sheet of the second aspect of this application.

[0033] The fourth aspect of this application provides an electrical device, including the secondary battery of the third aspect of this application.

[0034] The secondary battery of this application can simultaneously achieve high energy density, good cycle performance, and storage performance. The power device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of one embodiment of the secondary battery of this application.

[0037] Figure 2 yes Figure 1 An exploded view of the implementation method of the secondary battery.

[0038] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0039] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0040] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0041] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0042] The accompanying drawings are not necessarily drawn to scale. The reference numerals are as follows: 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0043] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the silicon-containing anode active material, anode sheet comprising the same, secondary battery, and power-consuming device of this application. However, unnecessary detailed descriptions 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 for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0044] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0049] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] Currently, when silicon-based materials are used in secondary batteries, they are typically mixed and dispersed with graphite, binders, and conductive agents before being coated onto the surface of the negative electrode current collector. However, the inventors of this application discovered during their research that during the mixing and dispersion process, most of the conductive agent agglomerates on the graphite surface, while a smaller amount remains on the surface of the silicon-based material. This results in poor electronic conductivity on the surface of the silicon-based material in the negative electrode, and the energy density of the secondary battery cannot be effectively improved.

[0051] Therefore, effective technical means are needed to improve the electronic conductivity of the silicon-based material surface in the negative electrode.

[0052] The first aspect of this application provides a silicon-containing anode active material, which possesses good electronic conductivity and maintains good electronic conductivity even after being applied to a cathode electrode. Specifically, the silicon-containing anode active material of the first aspect of this application includes a silicon-based material and a conductive layer located on the surface of the silicon-based material. The conductive layer includes a polymer and a one-dimensional conductive material. The polymer includes polar functional groups, which include one or more of carboxylic acid groups, hydroxyl groups, amide groups, amino groups, carbonyl groups, and nitro groups. The mass percentage of polar functional groups in the polymer is A1, and the mass percentage of silicon in the silicon-based material is A2. The silicon-containing anode active material satisfies the following conditions: A2 is 5% to 100% and A2 / A1 is 0.2 to 8.

[0053] Silicon-based materials include, but are not limited to, one or more of elemental silicon, silicon oxides (e.g., SiOx, 0 < x ≤ 2), silicon-carbon compounds (e.g., coated structures, embedded structures), and silicon alloys. In some embodiments, the silicon-based material may also be doped with one or more of lithium and magnesium. This application does not impose any particular limitation on the method of doping lithium and magnesium into silicon-based materials; for example, electrochemical deposition can be used.

[0054] The silicon-based material contains silicon as a mass percentage (A2), ranging from 5% to 100%. Optionally, A2 can be 5% to 95%, 10% to 90%, 10% to 85%, 10% to 80%, 15% to 85%, 20% to 80%, 25% to 75%, 30% to 70%, 35% to 65%, or 40% to 60%. When A2 is within a suitable range, the silicon-based material can simultaneously achieve high specific capacity and low volume expansion effect.

[0055] The polymer in the conductive layer contains polar functional groups. The inventors discovered that by adjusting the mass percentage of polar functional groups (A1) in the polymer and the mass percentage of silicon in the silicon-based material (A2), when A2 / A1 is controlled between 0.2 and 8, it ensures that appropriate amounts of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material to the surface of the silicon-based material and prevents the conductive layer from completely detaching during slurry mixing and dispersion. Furthermore, when A2 / A1 is controlled between 0.2 and 8, the polymer and the one-dimensional conductive material can also cross-link and intertwine, making the conductive layer flexible and able to firmly cover the surface of the silicon-based material like a fishing net. Therefore, the silicon-containing anode active material of this application possesses excellent electronic conductivity, and it maintains good electronic conductivity even after being applied to the anode sheet.

[0056] The inventors further discovered that when A2 / A1 is less than 0.2, the content of polar functional groups in the polymer is relatively high, while the content of silicon in the silicon-based material is relatively low. In this case, most of the polar functional groups in the polymer will form hydrogen bonds with the functional groups on the surface of the one-dimensional conductive material, resulting in cross-linking or entanglement. Consequently, fewer polar functional groups form hydrogen bonds with the functional groups on the surface of the silicon-based material, causing the conductive layer to easily detach during the slurry stirring and dispersion process, failing to bond tightly with the silicon-based material. Therefore, when A2 / A1 is less than 0.2, the electronic conductivity of the silicon-containing anode active material in the prepared anode sheet remains poor.

[0057] The inventors further discovered that when A2 / A1 is greater than 8, the content of polar functional groups in the polymer is relatively low, while the content of silicon in the silicon-based material is relatively high. In this case, most of the polar functional groups in the polymer preferentially form hydrogen bonds with functional groups on the surface of the silicon-based material, while only a small portion of the polar functional groups form hydrogen bonds with functional groups on the surface of the one-dimensional conductive material. Therefore, the conductive layer cannot form a net-like cross-linked network structure. Consequently, when A2 / A1 is greater than 8, the polymer can only bond with the silicon-based material through hydrogen bonds in the longitudinal direction of the silicon-containing anode active material, and cannot form a good coating effect in the transverse direction. At this time, the one-dimensional conductive material cannot be effectively fixed to the surface of the silicon-based material, resulting in poor electronic conductivity of the silicon-containing anode active material in the prepared anode sheet.

[0058] Furthermore, silicon-based materials exhibit significant volume expansion, which existing binders cannot effectively mitigate or suppress. Additionally, silicon-based materials undergo pulverization during continuous ion insertion / extraction. Moreover, after long-term cycling, silicon-based materials can react with the electrolyte, further impacting the cycle performance of the secondary battery.

[0059] The conductive layer of this application has a flexible structure and can firmly cover the surface of silicon-based materials like a fishing net. On the one hand, it can effectively fix the one-dimensional conductive material to the surface of silicon-based materials, improving the electronic conductivity of silicon-containing anode active materials. On the other hand, it can also reduce the continuous side reactions between silicon-based materials and electrolytes and reduce the irreversible consumption of active ions. In addition, the conductive layer of this application has a flexible structure, which can also alleviate the volume expansion effect of silicon-based materials caused by stress concentration and reduce the probability of silicon-based materials pulverizing.

[0060] Therefore, the silicon-containing anode active material of this application can simultaneously achieve good electronic conductivity, small volume expansion effect, and high reversible capacity and first coulombic efficiency, so that the secondary battery using it can simultaneously achieve high energy density and good cycle performance and storage performance.

[0061] In some embodiments, A2 / A1 can be 0.2 to 7, 0.3 to 6, 0.4 to 5, 0.5 to 4, 0.6 to 2.5, or 0.6 to 2. In this case, the silicon-containing anode active material has higher electronic conductivity, smaller volume expansion effect, and higher reversible capacity and first coulombic efficiency.

[0062] In some embodiments, A2 is 10% to 80% and A2 / A1 is 0.6 to 2.5. In this case, the silicon-containing anode active material of this application can have better electronic conductivity, higher reversible capacity and first coulombic efficiency, and lower volume expansion effect.

[0063] In some embodiments, A1 is 5% to 90%. Optionally, A1 is 10% to 90%, 20% to 90%, 30% to 90%, 40% to 90%, 10% to 75%, 20% to 75%, 30% to 75%, or 40% to 75%. When the content of polar functional groups in the polymer is within a suitable range, it ensures that an appropriate amount of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material to the surface of the silicon-based material, further improving the electronic conductivity of the silicon-containing anode active material, reducing side reactions between the silicon-containing anode active material and the electrolyte, and mitigating the volume expansion of the silicon-containing anode active material.

[0064] When the content of polar functional groups in the polymer is low, the polymer may not be able to form an appropriate amount of hydrogen bonds with the functional groups on the surface of the silicon-based material in the longitudinal direction of the silicon-containing anode active material, which may cause the conductive layer to fall off; at the same time, the polymer may also not be able to form an appropriate amount of hydrogen bonds with the functional groups on the surface of the one-dimensional conductive material in the transverse direction of the silicon-containing anode active material, which may cause the one-dimensional conductive material to be unable to be effectively fixed on the surface of the silicon-based material.

[0065] When the content of polar functional groups in a polymer is high, the polymer is prone to self-crosslinking. This can lead to a decrease in the dispersion effect between the polymer and the one-dimensional conductive material in the lateral direction of the silicon-based anode active material, making it difficult to form a uniform and stable conductive layer. Furthermore, stress concentration regions and areas with poor electronic conductivity are more likely to appear within the conductive layer. Therefore, a high content of polar functional groups in the polymer may not significantly improve the volume expansion of the silicon-based material. Simultaneously, due to the potentially poor electronic conductivity in some areas of the silicon-based material surface, the improvement in the reversible capacity and initial coulombic efficiency of the silicon-based anode active material may also be minimal.

[0066] In some embodiments, the polymer has a weight-average molecular weight (dimensionless) of B1, where B1 is above 100,000. Optionally, B1 is between 200,000 and 1,000,000.

[0067] In some embodiments, the aspect ratio of the one-dimensional conductive material is B2, where B2 is between 100 and 20000. Optionally, B2 can be 200 to 20000, 500 to 20000, 1000 to 20000, 1500 to 20000, 2000 to 20000, 3000 to 20000, 4000 to 20000, 200 to 15000, 500 to 15000, 1000 to 15000, 1500 to 15000, 2000 to 15000, 3000 to 15000, 4000 to 15000, 200 to 10000, 500 to 10000, 1000 to 10000, 1500 to 10000, 2000 to 10000, 3000 to 10000, or 4000 to 10000.

[0068] When the aspect ratio of one-dimensional conductive materials is within a suitable range, they can intertwine with each other on the surface of silicon-based materials to form a good coating effect. On the one hand, this can provide long-range conductivity to the surface of silicon-based materials, and on the other hand, it is conducive to the formation of a net-like cross-linked network structure of the conductive layer, which can better improve the electronic conductivity and volume expansion of the surface of silicon-based materials.

[0069] When the aspect ratio of a one-dimensional conductive material is small, its long-range conductivity is poor, and it is not easy for it to entangle itself or form a good coating effect with the polymer. Therefore, it may not form a structurally complete conductive layer on the silicon-based material surface, and its effect on improving the electronic conductivity and volume expansion of the silicon-based material surface may be insignificant. When the aspect ratio of a one-dimensional conductive material is large, it is more likely to entangle itself, and its dispersion effect with the polymer may deteriorate. This makes it difficult to form a uniform and stable conductive layer, and stress concentration areas and areas with poor electronic conductivity may easily appear in the conductive layer. Therefore, its effect on improving the electronic conductivity and volume expansion of the silicon-based material surface may also be insignificant.

[0070] In some embodiments, the weight-average molecular weight B1 of the polymer and the aspect ratio B2 of the one-dimensional conductive material satisfy a B1 / B2 ratio of 5 to 200. Optionally, B1 / B2 is 5 to 150, 5 to 100, 5 to 90, 5 to 80, 5 to 70, 5 to 60, 5 to 50, 10 to 90, 10 to 80, 10 to 70, 10 to 60, 10 to 50, 15 to 90, 15 to 80, 15 to 70, 15 to 60, or 15 to 50.

[0071] When B1 / B2 is within a suitable range, the polymer and the one-dimensional conductive material can be better dispersed to form a uniform and stable conductive layer. Within this range, the polymer and the one-dimensional conductive material can also cross-link and entangle with each other, which facilitates the formation of a net-like cross-linked network structure that covers the surface of the silicon-based material. Furthermore, within this range, appropriate amounts of hydrogen bonds can form between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, as well as between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material to the surface of the silicon-based material. Therefore, when B1 / B2 is within a suitable range, silicon-containing anode active materials can exhibit better electronic conductivity and lower volume expansion.

[0072] In some embodiments, the diameter of the one-dimensional conductive material is 1 nm to 30 nm. Optionally, the diameter of the one-dimensional conductive material is 2 nm to 30 nm, 2 nm to 25 nm, 2 nm to 20 nm, 2 nm to 15 nm, 2 nm to 10 nm, 5 nm to 30 nm, 5 nm to 25 nm, 5 nm to 20 nm, 5 nm to 15 nm, or 5 nm to 10 nm.

[0073] When the diameter of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can cross-link and entangle with each other better, which is conducive to the formation of a fishing net-like cross-linked network structure of the conductive layer and its covering on the surface of the silicon-based material. Therefore, the silicon-containing anode active material can have better electronic conductivity and lower volume expansion.

[0074] When the diameter of a one-dimensional conductive material is small, its surface energy is usually large, making it prone to self-aggregation. It may be difficult to maintain a one-dimensional linear morphology within the conductive layer, resulting in poor dispersion between the material and the polymer, thus hindering the formation of a uniform and stable conductive layer. Furthermore, stress concentration regions and areas with poor electronic conductivity are likely to appear within the conductive layer, potentially diminishing its effectiveness in improving the electronic conductivity and volume expansion of silicon-based materials. Conversely, when the diameter of a one-dimensional conductive material is large, its surface defects may be more numerous, and its flexibility may decrease, making it difficult to form a strong and tough conductive layer. Therefore, its effectiveness in improving the electronic conductivity and volume expansion of silicon-based materials may also be limited.

[0075] In some embodiments, the length of the one-dimensional conductive material is 0.5 μm to 20 μm. Optionally, the length of the one-dimensional conductive material is 1 μm to 20 μm, 1 μm to 18 μm, 1 μm to 16 μm, 1 μm to 14 μm, 1 μm to 12 μm, 1 μm to 10 μm, 1 μm to 8 μm, 2 μm to 20 μm, 2 μm to 18 μm, 2 μm to 16 μm, 2 μm to 14 μm, 2 μm to 12 μm, 2 μm to 10 μm, or 2 μm to 8 μm.

[0076] When the length of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can cross-link and entangle with each other better, which is conducive to the formation of a fishing net-like cross-linked network structure of the conductive layer and its covering on the surface of the silicon-based material. Therefore, the silicon-containing anode active material can have better electronic conductivity and lower volume expansion.

[0077] When the length of a one-dimensional conductive material is small, it is difficult for it to intertwine with the polymer to form a good coating effect. Therefore, the one-dimensional conductive material may not be effectively fixed on the surface of the silicon-based material, and its effect on improving the electronic conductivity and volume expansion of the silicon-based material surface may not be significant. When the length of a one-dimensional conductive material is large, it is prone to self-aggregation, and it may be difficult for it to maintain a one-dimensional linear morphology in the conductive layer. In this case, the mutual dispersion effect between it and the polymer may become poor, making it difficult to form a uniform and stable conductive layer. Furthermore, stress concentration areas and areas with poor electronic conductivity are likely to appear in the conductive layer, so the effect on improving the electronic conductivity and volume expansion of the silicon-based material surface may not be significant.

[0078] In some embodiments, the glass transition temperature (Tg) of the polymer is below 150°C; optionally, the glass transition temperature of the polymer is between -10°C and 120°C. In some embodiments, the crystallinity of the polymer is below 80%; optionally, the crystallinity of the polymer is between 10% and 70%. When the polymer has a suitable glass transition temperature and crystallinity, it can better crosslink and entangle with the one-dimensional conductive material. At this time, the conductive layer can firmly cover the surface of the silicon-based material like a fishing net, thereby better improving the electronic conductivity and volume expansion of the silicon-based material surface.

[0079] In some embodiments, the polymer includes, but is not limited to, one or more of (meth)acrylic acid and its salt homopolymers or copolymers, hydroxymethyl cellulose and its salt homopolymers or copolymers, alginate and its salt homopolymers or copolymers, polyacetamide homopolymers or copolymers, acrylamide homopolymers or copolymers, and vinyl alcohol homopolymers or copolymers. In this application, "copolymer" means any one of random copolymers, alternating copolymers, block copolymers, and graft copolymers. A copolymer can be a copolymer of the aforementioned monomers or a copolymer of other monomers, particularly vinyl monomers. Vinyl monomers include, but are not limited to, one or more of acrylic acid, acrylamide, acrylates, ethylene, propylene, butene, butadiene, isoprene, styrene, and vinyl acetate.

[0080] Optionally, the polymer includes one or more of the following: poly(meth)acrylic acid, sodium poly(meth)acrylic acid, potassium poly(meth)acrylic acid, magnesium poly(meth)acrylic acid, hydroxymethyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, lithium hydroxymethyl cellulose, alginate, sodium alginate, potassium alginate, lithium alginate, magnesium alginate, aluminum alginate, polyacetamide, polyvinyl alcohol, polyacrylamide, (meth)acrylic acid-acrylamide copolymer, (meth)acrylic acid-acrylamide-ethylene copolymer, ethylene-(meth)acrylic acid copolymer, (meth)acrylic acid-vinyl acetate copolymer resin, (meth)acrylic acid-ethylene-vinyl acetate copolymer, (meth)acrylic acid-acrylate copolymer, and ethylene-vinyl alcohol copolymer.

[0081] These polymers can better cross-link and entangle with one-dimensional conductive materials. In this case, the conductive layer can firmly cover the surface of the silicon-based material like a fishing net, thus improving the electronic conductivity and volume expansion of the silicon-based material surface. Simultaneously, when these polymers have an appropriate amount of polar functional groups, they can form suitable hydrogen bonds with functional groups or defects on the surface of the one-dimensional conductive material. This allows the conductive layer to simultaneously possess flexibility and toughness, further mitigating the volume expansion of the silicon-based material.

[0082] In some embodiments, the one-dimensional conductive material includes one or more of carbon nanotubes, metal fibers, carbon fibers, and hollow carbon fibers. Optionally, the one-dimensional conductive material includes carbon nanotubes, such as single-walled carbon nanotubes, multi-walled carbon nanotubes, or combinations thereof.

[0083] Optionally, the carbon nanotubes have a carbon content of over 90%. The higher the carbon content of the carbon nanotubes, the lower the impurity content and the better the electronic conductivity, thus allowing the silicon-containing anode active material to have better electronic conductivity.

[0084] Optionally, the carbon nanotube's I g / I d Above 40, I g This indicates that the Raman spectrum of the carbon nanotube is located at 1500 cm⁻¹. -1 Up to 1650cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the carbon nanotube is located at 100 cm⁻¹. -1 Up to 200cm -1 Peak intensity within the range. Io of carbon nanotubes. g / I d Within a suitable range, carbon nanotubes have fewer defects and higher tensile strength, so the resulting conductive layer can simultaneously achieve good flexibility and high tensile strength, thereby effectively mitigating the volume expansion of silicon-based materials.

[0085] Optionally, the specific surface area of ​​the carbon nanotubes is 500 m². 2 / g or more. When the specific surface area of ​​carbon nanotubes is within a suitable range, their contact area with the polymer is large, which can form more hydrogen bonds, thus facilitating mutual dispersion with the polymer and enabling the formation of a uniform and stable conductive layer.

[0086] In some embodiments, the mass percentage of the silicon-based material is W1, which is 90% to 98%, based on the total mass of the silicon-containing anode active material.

[0087] In some embodiments, based on the total mass of the silicon-containing anode active material, the mass percentage of the polymer is W2, where W2 is 1% to 9%. When the polymer content is within a suitable range, it ensures that the one-dimensional conductive material fully covers the surface of the silicon-based material, ensuring that most (e.g., more than 70%, 80%, 90%, or 95%) or even all of the surface of the silicon-based material is covered. This can better improve the electronic conductivity and volume expansion of the silicon-based material surface, reduce the contact between the silicon-based material and the electrolyte, reduce the decomposition and rupture of the SEI film, and reduce the probability of pulverization of the silicon-containing anode active material.

[0088] In some embodiments, based on the total mass of the silicon-containing anode active material, the mass percentage of the one-dimensional conductive material is W3, where W3 is 0.1% to 1%. When the content of the one-dimensional conductive material is within a suitable range, it can ensure that the surface of the silicon-containing anode active material has good electronic conductivity, while ensuring that a net-like coating structure is formed on the surface of the silicon-based material, thereby reducing electronic polarization and better mitigating the volume expansion of the silicon-based material.

[0089] In some embodiments, the mass ratio of the polymer to the one-dimensional conductive material, W2 / W3, is 7 to 20. Optionally, W2 / W3 is 7 to 20, 7 to 18, 7 to 16, 7 to 14, 9 to 20, 9 to 18, 9 to 16, or 9 to 14.

[0090] When W2 / W3 is within a suitable range, it can ensure that appropriate amounts of hydrogen bonds are formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, as well as between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material on the surface of the silicon-based material, thereby better improving the electronic conductivity and volume expansion of the silicon-based material surface.

[0091] When the mass ratio of the polymer to the one-dimensional conductive material is large, there are more hydrogen bonds between the polymer and the silicon-based material in the longitudinal direction of the silicon-containing anode active material. However, in the transverse direction of the silicon-containing anode active material, the polymer may not be able to form more hydrogen bonds with the one-dimensional conductive material and achieve effective cross-linking and entanglement. Consequently, the strength of the conductive layer may be affected, and the improvement on the electronic conductivity and volume expansion of the silicon-based material surface may not be significant.

[0092] When the mass ratio of the polymer to the one-dimensional conductive material is small, the number of hydrogen bonds formed between the polymer and the silicon-based material in the longitudinal direction of the silicon-containing anode active material decreases. This may affect the affinity between the conductive layer and the silicon-based material, and the conductive layer may detach during the slurry stirring and dispersion process.

[0093] In some embodiments, the thickness of the conductive layer is 1 nm to 2 μm. When the thickness of the conductive layer is small, its mitigation of the volume expansion of the silicon-based material may be insignificant. When the thickness of the conductive layer is large, the resistance to the insertion and extraction of active ions may increase, and a concentration gradient may easily form between the inside and outside of the conductive layer, which may affect the reversible specific capacity and initial coulombic efficiency of the silicon-based material.

[0094] In some embodiments, the resistivity of the silicon-containing anode active material powder is from 0.70 Ω-cm to 0.89 Ω-cm. Optionally, the resistivity of the silicon-containing anode active material powder is from 0.70 Ω-cm to 0.85 Ω-cm, from 0.70 Ω-cm to 0.82 Ω-cm, or from 0.70 Ω-cm to 0.80 Ω-cm.

[0095] In some embodiments, the specific surface area of ​​the silicon-containing anode active material is 0.8 m². 2 / g to 5m 2 / g. When the specific surface area of ​​silicon-containing anode active materials is within a suitable range, they can simultaneously possess higher capacity and higher initial coulombic efficiency.

[0096] In some embodiments, the average particle size Dv50 of the silicon-containing anode active material is between 2 μm and 10 μm. When the average particle size Dv50 of the silicon-containing anode active material is within a suitable range, it is beneficial to simultaneously improve the transport performance of active ions and electrons.

[0097] In some embodiments, the silicon-containing anode active material I g / I d From 0.1 to 200, I g This indicates that the Raman spectrum of the silicon-containing anode active material is located at 1500 cm⁻¹. -1 Up to 1650cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the silicon-containing anode active material is located at 100 cm⁻¹. -1 Up to 200cm -1 Peak intensity within the range.

[0098] In this application, the content of elements in the material (e.g., the mass percentage of silicon in silicon-based materials, the carbon content in carbon nanotubes, etc.) has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using X-ray photoelectron spectroscopy (XPS).

[0099] In this application, the mass percentage of polar functional groups in the polymer has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined by titration (e.g., acid-base titration, redox titration, precipitation titration), moisture determination, gas determination, colorimetric analysis, infrared spectroscopy, and nuclear magnetic resonance spectroscopy.

[0100] In this application, the weight-average molecular weight of the polymer has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined by gel permeation chromatography (GPC) using an Agilent 1290 Infinity II GPC system.

[0101] In this application, the glass transition temperature of the polymer has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined by differential scanning calorimetry (DSC) for the determination of the glass transition temperature of raw rubber, as specified in GB / T 29611-2013. The test can be performed using a Mettler-Toledo DSC-3 differential scanning calorimeter.

[0102] In this application, the crystallinity of the polymer has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using differential scanning calorimetry (DSC).

[0103] In this application, the powder resistivity of the material has a meaning known in the art and can be measured using instruments and methods known in the art, such as the four-probe method as described in GB / T 30835-2014. The mass of the test sample can be 0.6 g to 0.7 g, and the test pressure can be 16 MPa.

[0104] In this application, the average particle size Dv50 of the material has a well-known meaning in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 50%, which can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0105] In this application, the specific surface area of ​​the material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., USA.

[0106] [Preparation Method]

[0107] The first aspect of this application also provides a method for preparing a silicon-containing anode active material, which can prepare the silicon-containing anode active material in any embodiment of the first aspect of this application.

[0108] The preparation method of the silicon-containing anode active material of this application includes the following steps: Step (1), providing a first slurry containing a polymer and a one-dimensional conductive material; Step (2), slowly adding the silicon-based material into the first slurry and stirring to disperse it evenly to obtain a second slurry, and then drying the second slurry to obtain the silicon-containing anode active material.

[0109] Optionally, the solid content of the first slurry in step (1) is 0.8% to 30%.

[0110] Optionally, the solid content of the second slurry in step (2) is 3% to 50%, and the viscosity at room temperature is 50 cps to 1500 cps. When the solid content and viscosity of the second slurry are low, the second slurry may settle and thus fail to coat the surface of the silicon-based material well. When the solid content and viscosity of the second slurry are high, the second slurry may gel, making drying impossible.

[0111] Optionally, in step (2), the stirring and dispersing speed is 400 rpm to 800 rpm, and the stirring and dispersing time is 1 h to 3 h.

[0112] Optionally, the drying method in step (2) is spray drying, but this application is not limited to this. Further, the spray drying temperature can be from 120°C to 300°C. When the spray drying temperature is within a suitable range, it is beneficial for hydrogen bonding between polymers and between polymers and one-dimensional conductive materials to form a net-like cross-linked network structure, thereby improving the electronic conductivity of silicon-based materials, reducing continuous side reactions between silicon-based materials and electrolytes, and alleviating the volume expansion of silicon-based materials.

[0113] When the spray drying temperature is below 120℃, the coverage area of ​​the conductive layer on the surface of the silicon-based material is small, which may lead to more side reactions between the silicon-based material and the electrolyte. When the spray drying temperature is above 300℃, the polymer is prone to dehydration condensation reaction, which causes changes in the structure of the conductive layer.

[0114] In step (1), the polymer and the one-dimensional conductive material can be added to deionized water simultaneously to obtain the first slurry, or the polymer and the one-dimensional conductive material can be added separately to obtain the first slurry. For example, in some embodiments, the method for preparing the first slurry includes the following steps: step (11), adding the one-dimensional conductive material to deionized water and stirring to disperse it evenly to obtain a conductive slurry; step (12), slowly adding the polymer to the conductive slurry obtained in step (11) and stirring to disperse it evenly to obtain the first slurry.

[0115] Optionally, the solid content of the conductive paste obtained in step (11) is 0.8% to 10%.

[0116] Optionally, in step (11), the stirring speed is 200 rpm to 600 rpm and the dispersion time is 20 min to 60 min.

[0117] Optionally, in step (12), the stirring speed is 200 rpm to 600 rpm and the dispersion time is 20 min to 60 min.

[0118] Negative electrode sheet

[0119] The second aspect of this application provides a negative electrode sheet, which includes the silicon-containing negative electrode active material of the first aspect of this application.

[0120] The silicon-containing anode active material of the first aspect of the embodiments of this application can simultaneously achieve good electronic conductivity, small volume expansion effect, high reversible capacity and first coulombic efficiency, and can still maintain good electronic conductivity after being prepared into anode sheet. Therefore, the anode sheet of this application can simultaneously achieve good electronic conductivity, high capacity and first coulombic efficiency and small volume expansion.

[0121] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, wherein the negative electrode film layer includes a silicon-containing negative electrode active material, a conductive agent, and a binder according to the first aspect of the present application. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0122] In some embodiments, the mass percentage of the silicon-containing anode active material can be from 5% to 40%, and optionally from 5% to 25%, based on the total mass of the anode film.

[0123] In some embodiments, the negative electrode film layer may, in addition to the silicon-containing negative electrode active material described above, also contain other negative electrode active materials known in the art for use in secondary batteries, such as at least one of graphite (natural graphite, artificial graphite, or a mixture thereof), soft carbon, hard carbon, and lithium titanate. Optionally, the other negative electrode active material includes graphite. In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of graphite may be 55% to 90%, optionally 70% to 90%.

[0124] The negative electrode sheet of this application does not have any particular limitation on the type of conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total mass of the negative electrode film, the mass percentage content of the conductive agent is less than 5%, optionally from 0.1% to 5%.

[0125] The negative electrode sheet of this application does not have any particular limitation on the type of binder. As an example, the binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the binder is less than 5% based on the total mass of the negative electrode film, optionally from 0.1% to 5%.

[0126] In some embodiments, the negative electrode film layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is less than 2% based on the total mass of the negative electrode film layer, optionally from 0.1% to 2%.

[0127] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, the metal material may be selected from at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0128] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing negative electrode active materials, conductive agents, binders, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0129] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0130] Secondary batteries

[0131] The third aspect of this application provides a secondary battery, which includes a silicon-containing negative electrode active material of the first aspect of this application or a negative electrode sheet of the second aspect of this application, so that the secondary battery of this application can simultaneously achieve high energy density and good cycle performance and storage performance.

[0132] A secondary battery, also known as a rechargeable battery or accumulator, is a battery that can be recharged after discharge to reactivate its active materials and continue to be used. Typically, a secondary battery consists of an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is positioned between the positive and negative electrodes, primarily preventing short circuits while allowing active ions to pass through. The electrolyte, located between the positive and negative electrodes, conducts the active ions.

[0133] [Negative electrode plate]

[0134] The negative electrode used in the secondary battery of this application is the negative electrode described in any embodiment of the second aspect of the embodiments of this application.

[0135] [Positive electrode plate]

[0136] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0137] The positive electrode film layer includes a positive electrode active material, which may be a positive electrode active material known in the art for use in secondary batteries. For example, the positive electrode active material may include at least one of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides may include at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of lithium-containing phosphates with an olivine structure may include at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds. This application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0138] In some embodiments, to further improve the energy density of the secondary battery, the positive electrode active material may include one or more of the lithium transition metal oxides and their modified compounds represented by Formula 1.

[0139] Li a Ni b Co c M d O e A f Formula 1,

[0140] In Formula 1, 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S and Cl.

[0141] In this application, the modified compounds of the above-mentioned positive electrode active materials can be those that modify the positive electrode active materials by doping, surface coating, or both doping and surface coating.

[0142] In some embodiments, the positive electrode film layer may optionally include a conductive agent. This application does not impose any particular limitation on the type of conductive agent; as an example, the conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content of the conductive agent is less than 5%, optionally from 0.1% to 5%.

[0143] In some embodiments, the positive electrode film layer may optionally include a binder. This application does not impose any particular limitation on the type of binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the binder is less than 5%, optionally from 0.1% to 5%.

[0144] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be selected from at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0145] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this.

[0146] [Electrolytes]

[0147] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0148] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0149] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include at least one 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0150] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0151] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0152] [Isolation membrane]

[0153] Secondary batteries using electrolytes, as well as some secondary batteries using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. 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.

[0154] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0155] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0156] 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.

[0157] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0158] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 1 This is an example of a square-structured secondary battery 5.

[0159] In some embodiments, such as Figure 2 As shown, 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 is used to cover the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted according to requirements.

[0160] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is then placed in an outer packaging, dried, and injected with an electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0161] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0162] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple secondary batteries 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 secondary batteries 5 can be fixed in place using fasteners.

[0163] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0164] 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 adjusted according to the application and capacity of the battery pack.

[0165] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, 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. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0166] Electrical appliances

[0167] A fourth aspect of this application provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack described in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0168] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0169] Figure 6 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0170] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0171] Example

[0172] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0173] Example 1

[0174] Preparation of silicon-containing anode active materials

[0175] Carbon nanotubes (CNTs, one-dimensional conductive materials) with a diameter of 3 nm, a length of 10 μm, and an aspect ratio of 3333 were added to deionized water and dispersed by stirring at 300 rpm for 30 min to obtain a conductive slurry. An ethylene-acrylic acid copolymer (polymer) with a weight-average molecular weight of 300,000 and a polar functional group content (carboxylic acid group in Example 1) of 25% was slowly added to the conductive slurry and dispersed by stirring at 300 rpm for 30 min to obtain a first slurry. Silicon oxide (silicon-based material) with a silicon element content of 48% was slowly added to the first slurry and dispersed by stirring at 500 rpm for 1 h to obtain a second slurry. The second slurry was then spray-dried at 180°C to obtain the silicon-containing anode active material. In the silicon-containing anode active material, the mass ratio of silicon oxide, polymer, and one-dimensional conductive material was 96.6:3.0:0.4.

[0176] Preparation of negative electrode sheet

[0177] The above-mentioned silicon-containing anode active material, graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), and carbon black (Super P) are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 81.3:14.3:2:1.2:1.2 to form a uniform anode slurry. The anode slurry is then uniformly coated onto the surface of the copper foil of the anode current collector. After drying and cold pressing, the anode sheet is obtained.

[0178] Preparation of positive electrode sheet

[0179] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1O2 (NCM811), conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed thoroughly in an appropriate amount of solvent NMP at a mass ratio of 97:1:2 to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0180] Preparation of electrolyte

[0181] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0182] Preparation of the separating membrane

[0183] Porous polyethylene film is used as the separator.

[0184] Preparation of secondary batteries

[0185] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0186] Examples 2 to 38 and Comparative Examples 1 to 4

[0187] The preparation method of the secondary battery is similar to that in Example 1, except that the preparation parameters of the silicon-containing anode active material are different, as detailed in Table 1.

[0188]

[0189]

[0190] Test section

[0191] (1) Powder resistivity test of silicon-containing anode active materials

[0192] The powder resistivity of the silicon-containing anode active material prepared above was determined using an FT-341A four-probe powder resistivity tester, in accordance with GB / T 30835-2014. The sample mass was 0.6 g to 0.7 g, and the test pressure was 16 MPa.

[0193] (2) First reversible capacity and first coulombic efficiency test

[0194] The prepared negative electrode sheet was punched into small discs, and then assembled into CR2430 coin cells using a lithium metal sheet as the counter electrode and a polyethylene (PE) film as the separator in an argon-protected glove box. After the coin cells were left to stand for 12 hours, they were discharged at 25°C with a constant current of 0.05C to 0.005V. After standing for 10 minutes, they were discharged again with a constant current of 50μA to 0.005V. After standing for another 10 minutes, they were discharged again with a constant current of 10μA to 0.005V. The total capacity of the three discharges was recorded, which is the first discharge capacity of the coin cell. The coin cell was then charged at a constant current of 0.1C to 2V, and the first charge capacity was recorded.

[0195] The initial reversible specific capacity (mAh / g) of the negative electrode sheet = the initial charging capacity of the coin cell / (mass of silicon-containing negative electrode active material + mass of graphite).

[0196] The initial coulombic efficiency of the negative electrode is equal to (the initial charge capacity of the coin cell / the initial discharge capacity of the coin cell) × 100%.

[0197] (3) Volume expansion performance test

[0198] At 25℃, the secondary battery was discharged at a constant current of 1C to 2.5V, and then charged at a constant current of 0.5C to 4.25V. At this point, the secondary battery was at 100% SOC. After disassembling the secondary battery, the thickness of the negative electrode was measured and recorded as H1. The initial thickness of the negative electrode was recorded as H0. The thickness growth rate (%) of the negative electrode is calculated as (H1 / H0-1)×100%.

[0199] The thickness growth rate of the negative electrode sheet can characterize the volume expansion of the negative electrode sheet and the secondary battery. The smaller the thickness growth rate of the negative electrode sheet, the smaller the volume expansion of the negative electrode sheet and the secondary battery.

[0200] Table 2 presents the test results for Examples 1 to 38 and Comparative Examples 1 to 4.

[0201] Table 2

[0202]

[0203]

[0204] As can be seen from the test results in Table 2, compared with Comparative Example 1, the silicon-containing anode active material provided in this application has a lower powder resistivity, and the anode sheet simultaneously exhibits higher reversible specific capacity, higher initial coulombic efficiency, and smaller volume expansion. This may be because appropriate amounts of hydrogen bonds can be formed between the polar functional groups in the polymer and the functional groups on the surface of the one-dimensional conductive material, as well as between the polar functional groups in the polymer and the functional groups on the surface of the silicon-based material. This effectively fixes the one-dimensional conductive material onto the surface of the silicon-based material. Furthermore, the polymer and the one-dimensional conductive material can cross-link and intertwine, making the conductive layer flexible and able to firmly cover the surface of the silicon-based material like a fishing net. Therefore, the silicon-containing anode active material of this application can simultaneously achieve good electronic conductivity, smaller volume expansion, and higher reversible specific capacity and initial coulombic efficiency, and it maintains good electronic conductivity even after being applied to the anode sheet.

[0205] In Comparative Example 2, when preparing silicon-containing anode active materials, carbon nanotube dispersion was mixed with silicon oxide and then dried. At this time, the bond between carbon nanotubes and silicon oxide was not strong. During the stirring and dispersion of the slurry, carbon nanotubes were easy to fall off, resulting in no significant improvement in the electronic conductivity, reversible specific capacity and first coulombic efficiency of the silicon-containing anode active material. At the same time, its volume expansion was still relatively high.

[0206] The test results from Examples 1 to 11 and Comparative Example 3, and Examples 12 to 14 and Comparative Example 4 show that when A2 / A1 is controlled within a suitable range (between 0.2 and 8), the silicon-containing anode active material has a low powder resistivity, and the anode sheet simultaneously exhibits high reversible specific capacity, initial coulombic efficiency, and small volume expansion. In Comparative Example 3, A2 / A1 is greater than 8. At this time, the polymer can only bond with the silicon-based material through hydrogen bonds in the longitudinal direction of the silicon-containing anode active material, but cannot form a good coating effect in the transverse direction of the silicon-containing anode active material. Therefore, the bonding between carbon nanotubes and silicon oxide is not strong, and carbon nanotubes are easily detached during slurry stirring and dispersion, resulting in a lack of significant improvement in the reversible specific capacity and initial coulombic efficiency of the anode sheet, while its volume expansion remains high. In Comparative Example 4, A2 / A1 is less than 0.2. At this ratio, most of the polar functional groups in the polymer form hydrogen bonds with the functional groups on the surface of the carbon nanotubes, resulting in cross-linking or entanglement. Fewer polar functional groups form hydrogen bonds with the functional groups on the surface of the silicon carbide compound. Therefore, the bond between the carbon nanotubes and the silicon carbide compound is not strong, and the carbon nanotubes are prone to detachment during slurry stirring and dispersion. This leads to a lack of significant improvement in the reversible specific capacity and initial coulombic efficiency of the negative electrode, while its volume expansion remains high.

[0207] The test results from Examples 1 to 11 also show that when the content of polar functional groups in the polymer is within a suitable range, the reversible specific capacity and initial coulombic efficiency of the negative electrode are higher, while its volume expansion is also smaller.

[0208] The test results from Examples 15 to 24 show that when the ratio of the aspect ratio of carbon nanotubes and / or the weight-average molecular weight of the polymer to the aspect ratio of carbon nanotubes is within a suitable range, the reversible specific capacity and initial coulombic efficiency of the negative electrode are higher, while its volume expansion is also smaller.

[0209] The test results from Examples 25 to 31 show that when the mass ratio of polymer to carbon nanotubes is within a suitable range, the reversible specific capacity and initial coulombic efficiency of the negative electrode are higher, while its volume expansion is also smaller.

[0210] 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-containing anode active material, comprising a silicon-based material and a conductive layer located on the surface of the silicon-based material, wherein the conductive layer comprises a polymer and a one-dimensional conductive material. in, The polymer includes polar functional groups, which include one or more of carboxylic acid groups, hydroxyl groups, amide groups, amino groups, carbonyl groups, and nitro groups. The polymer has a mass percentage of polar functional groups of A1, the silicon-based material has a mass percentage of silicon of A2, and the silicon-containing anode active material satisfies the following: A2 is 5% to 100% and A2 / A1 is 0.2 to 8; the one-dimensional conductive material has an aspect ratio of B2, where B2 is 100 to 20000.

2. The silicon-containing anode active material according to claim 1, wherein, A2 is 10% to 80% and A2 / A1 is 0.6 to 2.

5.

3. The silicon-containing anode active material according to claim 2, wherein, A1 ranges from 5% to 90%.

4. The silicon-containing anode active material according to claim 3, wherein, A1 ranges from 10% to 75%.

5. The silicon-containing anode active material according to any one of claims 1-4, wherein, The polymer has a weight-average molecular weight of B1, which is above 100,000.

6. The silicon-containing anode active material according to claim 5, wherein, The polymer has a weight-average molecular weight of B1, which is between 200,000 and 1,000,000.

7. The silicon-containing anode active material according to claim 6, wherein, The aspect ratio of the one-dimensional conductive material is B2, where B2 is between 2000 and 20000.

8. The silicon-containing anode active material according to claim 7, wherein, B1 / B2 ranges from 5 to 200.

9. The silicon-containing anode active material according to claim 8, wherein, The B1 / B2 ratio is 5 to 50.

10. The silicon-containing anode active material according to any one of claims 1-4, wherein, The diameter of the one-dimensional conductive material is 1 nm to 30 nm; and / or, The length of the one-dimensional conductive material is from 0.5 μm to 20 μm.

11. The silicon-containing anode active material according to any one of claims 1-4, wherein, The glass transition temperature of the polymer is below 150°C; and / or, The polymer has a crystallinity of 10% to 70%.

12. The silicon-containing anode active material according to claim 11, wherein, The polymer has a glass transition temperature of -10°C to 120°C; and / or, The polymer has a crystallinity of 10% to 70%.

13. The silicon-containing anode active material according to claim 11, wherein, The polymer includes one or more of the following: (meth)acrylic acid and its salt homopolymers or copolymers, hydroxymethyl cellulose and its salt homopolymers or copolymers, alginate and its salt homopolymers or copolymers, polyacetamide homopolymers or copolymers, acrylamide homopolymers or copolymers, and vinyl alcohol homopolymers or copolymers.

14. The silicon-containing anode active material according to any one of claims 1-4, wherein, The one-dimensional conductive material includes carbon nanotubes.

15. The silicon-containing anode active material according to claim 14, wherein, The carbon nanotubes satisfy at least one of the following conditions (1) to (3): (1) The carbon content of the carbon nanotubes is above 90%; (2) The I of the carbon nanotube g / I d Above 40, I g This indicates that the Raman spectrum of the carbon nanotube is located at 1500 cm⁻¹. -1 Up to 1650 cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the carbon nanotube is located at 100 cm⁻¹. -1 Up to 200 cm -1 Peak intensity within the range; (3) The specific surface area of ​​the carbon nanotubes is 500 m². 2 / g or more.

16. The silicon-containing anode active material according to any one of claims 1-4, wherein, The silicon-based material includes one or more of elemental silicon, silicon oxide, silicon carbide, and silicon alloy.

17. The silicon-containing anode active material according to claim 16, wherein, The silicon-based material is also doped with one or two elements, namely lithium and magnesium.

18. The silicon-containing anode active material according to any one of claims 1-4, wherein, Based on the total mass of the silicon-containing anode active material. The silicon-based material has a mass percentage content of W1, where W1 is 90% to 98%. The polymer has a mass percentage content of W2, where W2 is 1% to 9%; The mass percentage of the one-dimensional conductive material is W3, which is 0.1% to 1%.

19. The silicon-containing anode active material according to claim 18, wherein, W2 / W3 ratio is 7 to 20.

20. The silicon-containing anode active material according to any one of claims 1-4, wherein, The thickness of the conductive layer is 1 nm to 2 μm.

21. The silicon-containing anode active material according to any one of claims 1-4, wherein, The resistivity of the silicon-containing anode active material powder is from 0.70 Ω-cm to 0.89 Ω-cm; and / or, The average particle size Dv50 of the silicon-containing anode active material is 2 μm to 10 μm; and / or, The specific surface area of ​​the silicon-containing anode active material is 0.8 m². 2 / g to 5m 2 / g; and / or, The silicon-containing anode active material I g / I d From 0.1 to 200, I g This indicates that the Raman spectrum of the silicon-containing anode active material is located at 1500 cm⁻¹. -1 Up to 1650 cm -1 Peak intensity of the range, I d This indicates that the Raman spectrum of the silicon-containing anode active material is located at 100 cm⁻¹. -1 Up to 200 cm -1 Peak intensity within the range.

22. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, wherein, The negative electrode film layer comprises a silicon-containing negative electrode active material, a conductive agent, and a binder according to any one of claims 1-21.

23. The negative electrode sheet according to claim 22, wherein, The negative electrode film layer also includes graphite.

24. A secondary battery comprising a silicon-containing negative electrode active material according to any one of claims 1-21, or a negative electrode sheet according to claim 22 or 23.

25. An electrical device comprising a secondary battery according to claim 24.

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