Silicon-containing negative electrode active material, negative electrode sheet containing the same, secondary battery, and power consumption device

Abstract

The present application provides a silicon-containing negative electrode active material, and a negative electrode sheet, a secondary battery, and a power consumption device containing the same. The silicon-containing negative electrode active material includes a silicon-based material and a conductive layer located on the surface of the silicon-based material, and the conductive layer includes a polymer and a one-dimensional conductive material, where the polymer includes a polar functional group including one or more of a carboxyl group, a hydroxyl group, an amide group, an amino group, a carbonyl group, and a nitro group, the mass percentage of the polar functional group in the polymer is A1, the mass percentage of silicon element in the silicon-based material is A2, and the silicon-containing negative electrode active material satisfies A2 is 5% to 100% and A2 / A1 is 0.2 to 8. The silicon-containing negative electrode active material of the present application can simultaneously achieve good electronic conductivity, a small volume expansion effect, and high reversible capacity and initial coulombic efficiency, and can maintain good electronic conductivity even after being made into a negative electrode sheet.

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and more particularly to a silicon-containing negative electrode active material, and a negative electrode sheet, secondary battery, and power consuming device containing the same. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As secondary batteries become more widely used, their energy density has attracted increasing attention. Graphite is the most common negative electrode active material for secondary batteries, but its theoretical capacity per gram is only 372 mAh / g, leaving very little room for improvement in its energy density. Silicon-based materials, with a theoretical capacity per gram of up to 4200 mAh / g, are the negative electrode active material with the greatest potential for development. However, silicon-based materials suffer from defects such as high volume expansion and low electronic conductivity, which severely hinder their large-scale commercial application. Summary of the Invention

[0003] The present application aims to provide a silicon-containing negative electrode active material, and a negative electrode sheet, secondary battery, and power consumption device each containing the same. The silicon-containing negative electrode active material of the present application can simultaneously achieve good electronic conductivity, a small volume expansion effect, high reversible capacity, and initial coulombic efficiency, and can maintain good electronic conductivity even after being fabricated into a negative electrode sheet.

[0004] A first aspect of the present application is a silicon-containing negative electrode active material, a silicon-based material; a conductive layer located on a surface of the silicon-based material, the conductive layer including a polymer and a one-dimensional conductive material; wherein the polymer contains polar functional groups including one or more of a carboxyl group, a hydroxyl group, an amide group, an amino group, a carbonyl group, and a nitro group; The present invention provides a silicon-containing negative electrode active material, wherein the mass percentage of the polar functional group in the polymer is A1, the mass percentage of silicon element in the silicon-based material is A2, and the silicon-containing negative electrode active material satisfies A2 being 5% to 100% and A2 / A1 being 0.2 to 8.

[0005] The polymer in the conductive layer contains polar functional groups. The inventors discovered through research that by adjusting the relationship between the mass percentage A1 of the polar functional groups in the polymer and the mass percentage A2 of silicon in the silicon-based material, A2 / A1 can be controlled between 0.2 and 8, ensuring 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 ensures that the one-dimensional conductive material is effectively fixed to the surface of the silicon-based material and that the conductive layer does not fall off completely during the stirring and dispersion process of the slurry. Furthermore, when A2 / A1 is controlled between 0.2 and 8, the polymer and the one-dimensional conductive material can be cross-linked and entangled with each other, resulting in a flexible conductive layer that tightly coats the surface of the silicon-based material, similar to a fishing net. Therefore, the silicon-containing negative electrode active material of the present application has good electronic conductivity and can maintain good electronic conductivity even after being applied to a negative electrode sheet.

[0006] In some embodiments of the present application, A2 is 10% to 80% and A2 / A1 is 0.6 to 2.5, and the silicon-containing negative electrode active material of the present application can have better electronic conductivity, higher reversible capacity and initial coulombic efficiency, and lower volume expansion effect.

[0007] In any embodiment of the present application, A1 is 5% to 90%, and optionally 10% to 75%. When the content of the polar functional groups in the polymer is within an appropriate range, it can ensure 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, thereby effectively fixing the one-dimensional conductive material to the surface of the silicon-based material, further improving the electronic conductivity of the silicon-containing negative electrode active material, reducing side reactions between the silicon-containing negative electrode active material and the electrolyte, and mitigating the volume expansion of the silicon-containing negative electrode active material.

[0008] In any embodiment of the present application, the weight average molecular weight of the polymer is B1, and B1 is 100,000 or more, optionally 200,000 to 1,000,000.

[0009] In any embodiment of the present application, the aspect ratio of the one-dimensional conductive material is B2, and B2 is 100 to 20000, optionally 2000 to 20000. When the aspect ratio of the one-dimensional conductive material is within a suitable range, it can be intertwined with each other on the surface of the silicon-based material to form a good covering effect, which on the one hand can provide long-distance conductivity on the surface of the silicon-based material, and on the other hand can help the conductive layer form a fishnet-like bridged network structure, which can better improve the electronic conductivity and volume expansion of the surface of the silicon-based material.

[0010] In any embodiment of the present application, B1 / B2 is 5 to 200, and optionally 5 to 50. When B1 / B2 is within the appropriate range, the silicon-containing negative electrode active material can have higher electronic conductivity and lower volume expansion.

[0011] In any embodiment of the present application, the diameter of the one-dimensional conductive material is 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 be better cross-linked and entangled with each other, and the conductive layer can form a fishnet-like cross-linked network structure and help cover the surface of the silicon-based material. Therefore, the silicon-containing negative electrode active material can have better electronic conductivity and lower volume expansion.

[0012] In any embodiment of the present application, the length of the one-dimensional conductive material is 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 be better cross-linked and entangled with each other, and the conductive layer can form a fishnet-like cross-linked network structure and help cover the surface of the silicon-based material. Therefore, the silicon-containing negative electrode active material can have better electronic conductivity and lower volume expansion.

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

[0014] In any embodiment of the present application, the crystallinity of the polymer is 80% or less, optionally 10% to 70%.

[0015] When the polymer has an appropriate glass transition temperature and crystallinity, the polymer and the one-dimensional conductive material can be better cross-linked and entangled, and the conductive layer can tightly coat the surface of the silicon-based material like a fishing net, which can better improve the electronic conductivity and volume expansion of the surface of the silicon-based material.

[0016] In any embodiment of the present application, the polymer may comprise one or more of the following: homopolymers or copolymers of (meth)acrylic acid and its salts, homopolymers or copolymers of hydroxymethylcellulose and its salts, homopolymers or copolymers of alginic acid and its salts, polyacetamide homopolymers or copolymers, acrylamide homopolymers or copolymers, and vinyl alcohol homopolymers or copolymers. These polymers can be better cross-linked and entangled with the one-dimensional conductive material. In this case, the conductive layer can tightly coat the surface of the silicon-based material like a fishing net, and can better improve the electronic conductivity and volume expansion of the surface of the silicon-based material.

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

[0018] Optionally, the carbon content of the carbon nanotubes is 90% or more. The higher the carbon content of the carbon nanotubes, the lower the impurity content and the better the electronic conductivity, so that the silicon-containing negative electrode active material can have better electronic conductivity.

[0019] Optionally, I of the carbon nanotube g / I d is greater than 40, I g is 1500 cm in the Raman spectrum of the carbon nanotube. -1 ~1650cm -1 The peak intensity is in the range of I d is 100 cm in the Raman spectrum of the carbon nanotube -1 ~200cm -1 The peak intensity of carbon nanotubes is in the range of g / I d When the thickness is within an appropriate range, the carbon nanotubes themselves have few defects and high tensile strength, so that the formed conductive layer can simultaneously achieve good flexibility and high tensile strength, thereby effectively mitigating the volume expansion of the silicon-based material.

[0020] Optionally, the specific surface area of ​​the carbon nanotubes is 500 m 2 When the specific surface area of ​​the carbon nanotubes is within the appropriate range, the contact area between the carbon nanotubes and the polymer is large, and more hydrogen bonds can be formed, which helps the carbon nanotubes to disperse with the polymer and form a more uniform and stable conductive layer.

[0021] In any embodiment of the present application, the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon carbon compound, silicon alloy, and optionally is further doped with one or two of lithium and magnesium.

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

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

[0024] In any embodiment of the present application, the conductive layer has a thickness of 1 nm to 2 μm.

[0025] In any embodiment of the present application, the powder resistivity of the silicon-containing negative electrode active material is 0.70 Ω·cm to 0.89 Ω·cm.

[0026] In any embodiment of the present application, the silicon-containing negative electrode active material has an average particle size Dv50 of 2 μm to 10 μm.

[0027] In any embodiment of the present application, the specific surface area of ​​the silicon-containing negative electrode active material is 0.8 m 2 / g~5m 2 / g.

[0028] In any embodiment of the present application, I of the silicon-containing negative electrode active material g / I d is 0.1 to 200, and I g is 1500 cm in the Raman spectrum of the silicon-containing negative electrode active material. -1 ~1650cm -1 The peak intensity is in the range of I d is 100 cm in the Raman spectrum of the silicon-containing negative electrode active material. -1 ~200cm-1 The peak intensities located in the range are shown.

[0029] A second aspect of the present application provides a negative electrode sheet including 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 includes the silicon-containing negative electrode active material of the first aspect of the present application, a conductive agent, and an adhesive.

[0030] The silicon-containing negative electrode active material of the present invention can simultaneously achieve good electronic conductivity, a small volume expansion effect, a high reversible capacity, and an initial coulombic efficiency, and can maintain good electronic conductivity even after being fabricated into a negative electrode sheet. Therefore, the negative electrode sheet of the present invention can simultaneously achieve good electronic conductivity, a high capacity, an initial coulombic efficiency, and a small volume expansion.

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

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

[0033] A fourth aspect of the present application provides a power consuming device including the secondary battery of the third aspect of the present application.

[0034] The secondary battery of the present application can simultaneously achieve high energy density and good cycle and storage performance. The power consumption device of the present application includes the secondary battery of the present application, and therefore has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0035] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings necessary for the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can further derive other drawings based on the drawings without any creative effort. In the drawings, the drawings are not necessarily drawn to actual scale. Here, the reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate. [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. [Figure 3] 1 is a schematic diagram of an embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of an embodiment of a power consuming device that includes a secondary battery of the present application as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the silicon-containing negative electrode active material specifically disclosed herein, as well as a negative electrode sheet, a secondary battery, and a power consumption device including the same, will be described in detail with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of actual identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0037] The "ranges" disclosed herein are defined in the form of lower and upper limits, where a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits specifically define the boundaries of the range. Ranges defined in this manner may or may not include the endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a single range. For example, reciting ranges of 60 to 120 and 80 to 110 for a particular parameter is understood to also contemplate ranges of 60 to 110 and 80 to 120. Furthermore, reciting minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 contemplates ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. Unless otherwise specified, the numerical range "a to b" herein refers to a contraction of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification indicates all real numbers between "0 and 5," and "0 to 5" is a contraction of combinations of these numerical values. Furthermore, when a parameter is expressed as an integer ≧2, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0039] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0040] Unless otherwise specified, all steps herein can be performed in sequence, randomly, and preferably in sequence. For example, when a method includes steps (a) and (b), it means that the method can include steps (a) and (b) performed in sequence, or can include steps (b) and (a) performed in sequence. For example, when a method can further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can include steps (a), (c), and (b), or can further include steps (c), (a), and (b), etc.

[0041] Unless otherwise specified, the terms "having," "comprising," and "including" referred to in this application may be open-ended or closed-ended. For example, the terms "having," "comprising," and "comprising" indicate that the term may further comprise, include, or contain other components not listed, or may only comprise or contain the listed components.

[0042] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": 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 A and B are both true (or exist).

[0043] Currently, when silicon-based materials are applied to secondary batteries, they generally need to be uniformly stirred and dispersed with graphite, adhesive, conductive agent, etc. before being applied to the surface of the negative electrode current collector. However, the inventors of the present application discovered during their research that most of the conductive agent aggregates on the graphite surface during the stirring and dispersion process, with a small amount of conductive agent located on the surface of the silicon-based material, resulting in poor electronic conductivity on the surface of the silicon-based material in the negative electrode sheet, and preventing effective improvement of the energy density of the secondary battery.

[0044] In view of this, it is necessary to adopt effective technical means to improve the electronic conductivity of the surface of the silicon-based material in the negative electrode sheet.

[0045] The first aspect according to the embodiment of the present application provides a silicon-containing negative electrode active material, which itself has good electronic conductivity and can maintain good electronic conductivity even after being applied to the negative electrode sheet. Specifically, the silicon-containing negative electrode active material according to the first aspect of the embodiment of the present application includes a silicon-based material and a conductive layer located on the surface of the silicon-based material, and the conductive layer includes a polymer and a one-dimensional conductive material. Here, the polymer includes a polar functional group containing one or more of a carboxyl group, a hydroxyl group, an amide group, an amino group, a carbonyl group, and a nitro group. The mass percentage of the polar functional group in the polymer is A1, and the mass percentage of the silicon element in the silicon-based material is A2. The silicon-containing negative electrode active material satisfies that A2 is 5% to 100% and A2 / A1 is 0.2 to 8.

[0046] The silicon-based material includes, but is not limited to, one or more of elemental silicon, silicon oxide (for example, SiOx, 0 < x ≤ 2), silicon carbon compound (for example, coating type structure, embedded type structure), and silicon alloy. In some embodiments, the silicon-based material can be further doped with one or two elements of lithium and magnesium. In the present application, the method of doping lithium and magnesium into the silicon-based material is not particularly limited, and for example, an electrochemical deposition method can be adopted.

[0047] The mass percentage of the silicon element in the silicon-based material is A2, and A2 is 5% to 100%. Optionally, A2 is 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 an appropriate range, the silicon-based material can simultaneously achieve a high capacity per gram and a low volume expansion effect.

[0048] The polymer in the conductive layer contains polar functional groups. The inventors discovered through research that by adjusting the relationship between the mass percentage A1 of the polar functional groups in the polymer and the mass percentage A2 of silicon in the silicon-based material, A2 / A1 can be controlled between 0.2 and 8, ensuring 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 ensures that the one-dimensional conductive material is effectively fixed to the surface of the silicon-based material and that the conductive layer does not fall off completely during the stirring and dispersion process of the slurry. Furthermore, when A2 / A1 is controlled between 0.2 and 8, the polymer and the one-dimensional conductive material can crosslink and intertwine with each other, resulting in a flexible conductive layer that tightly coats the surface of the silicon-based material, similar to a fishing net. Therefore, the silicon-containing negative electrode active material of the present application has good electronic conductivity and can maintain good electronic conductivity even after being applied to a negative electrode sheet.

[0049] 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 and the content of silicon element in the silicon-based material is relatively low. At this time, most of the polar functional groups in the polymer form hydrogen bonds with the functional groups on the surface of the one-dimensional conductive material, causing cross-linking or entanglement, while the few polar functional groups form hydrogen bonds with the functional groups on the surface of the silicon-based material, resulting in a situation where the conductive layer is easily detached during the stirring and dispersion process of the slurry and cannot be tightly bonded to the silicon-based material. Therefore, when A2 / A1 is less than 0.2, the electronic conductivity of the silicon-containing negative electrode active material in the prepared negative electrode sheet is still poor.

[0050] Further research by the inventors revealed that when A2 / A1 is greater than 8, the polymer contains relatively few polar functional groups, while the silicon content in the silicon-based material is relatively high. At this time, most of the polar functional groups in the polymer preferentially form hydrogen bonds with the functional groups on the surface of the silicon-based material, while a small number of polar functional groups form hydrogen bonds with the functional groups on the surface of the one-dimensional conductive material, resulting in a conductive layer that cannot form a fishnet-like cross-linked network structure. Therefore, when A2 / A1 is greater than 8, the polymer cannot effectively cover the silicon-containing negative electrode active material in the horizontal direction, and can only bond with the silicon-containing material via hydrogen bonds in the vertical direction. At this time, the one-dimensional conductive material cannot be effectively fixed to the surface of the silicon-based material, and the electronic conductivity of the silicon-containing negative electrode active material in the resulting negative electrode sheet remains poor.

[0051] Silicon-based materials also have a large volume expansion effect. Conventional adhesives cannot effectively mitigate or suppress the volume expansion of silicon-based materials, and silicon-based materials can be powdered in the process of constantly desorbing or inserting ions. Furthermore, silicon-based materials can undergo side reactions with electrolytes after long-term cycling, thereby affecting the cycle performance of secondary batteries.

[0052] The conductive layer of the present invention has a flexible structure and is firmly coated on the surface of the silicon-based material like a fishing net, which on the one hand effectively fixes the one-dimensional conductive material to the surface of the silicon-based material, thereby improving the electronic conductivity of the silicon-containing negative electrode active material, and on the other hand reduces the continuous side reaction between the silicon-based material and the electrolyte and the irreversible loss of active ions. In addition, the conductive layer of the present invention has a flexible structure, which further mitigates the volume expansion effect caused by stress concentration on the silicon-based material and reduces the probability of the silicon-based material being pulverized.

[0053] Therefore, the silicon-containing negative electrode active material of the present invention can simultaneously achieve good electronic conductivity, small volume expansion effect, high reversible capacity, and initial coulombic efficiency, thereby allowing a secondary battery using the same to simultaneously achieve high energy density, good cycle performance, and good storage performance.

[0054] In some embodiments, A2 / A1 may 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 negative electrode active material has higher electronic conductivity, a smaller volume expansion effect, and higher reversible capacity and initial coulombic efficiency.

[0055] In some embodiments, A2 is 10% to 80% and A2 / A1 is 0.6 to 2.5, and the silicon-containing negative electrode active material of the present invention can have better electronic conductivity, higher reversible capacity and first coulombic efficiency, and lower volume expansion effect.

[0056] 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 an appropriate range, it can ensure that an appropriate amount of hydrogen bonds are formed between the polar functional groups of the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups of 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 negative electrode active material, reducing side reactions between the silicon-containing negative electrode active material and the electrolyte, and mitigating the volume expansion of the silicon-containing negative electrode active material.

[0057] If the content of polar functional groups in the polymer is low, the polymer cannot form an adequate amount of hydrogen bonds with the functional groups on the surface of the silicon-based material in the longitudinal direction of the silicon-containing negative electrode active material, which may result in the conductive layer falling off. At the same time, the polymer cannot form an adequate 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 negative electrode active material, which may result in the one-dimensional conductive material not being effectively fixed to the surface of the silicon-based material.

[0058] When the content of polar functional groups in the polymer is high, the polymer is prone to self-crosslinking, which deteriorates the mutual dispersion effect between the one-dimensional conductive material in the lateral direction of the silicon-containing negative electrode active material, making it difficult to form a uniform and stable conductive layer, and regions of stress concentration and poor electronic conductivity are likely to exist in the conductive layer. Therefore, when the content of polar functional groups in the polymer is high, the improvement effect on the volume expansion of the silicon-based material is not obvious, and at the same time, the electronic conductivity of the surface region of the silicon-based material is poor, resulting in the inconspicuous improvement of the reversible capacity and initial coulombic efficiency of the silicon-containing negative electrode active material.

[0059] In some embodiments, the weight average molecular weight (dimensionless quantity) of the polymer is B1, and B1 is 100,000 or more. Optionally, B1 is 200,000 to 1,000,000.

[0060] In some embodiments, the one-dimensional conductive material has an aspect ratio B2, where B2 is 100-20,000. Optionally, B2 is 200 to 20,000, 500 to 20,000, 1000 to 20,000, 1500 to 20,000, 2000 to 20,000, 3000 to 20,000, 4000 to 20,000, 200 to 15,000, 500 to 15,000, 1000 to 15,000, 1500 to 15,000, 2000 to 15,000, 3000 to 15,000, 4000 to 15,000, 200 to 10,000, 500 to 10,000, 1000 to 10,000, 1500 to 10,000, 2000 to 10,000, 3000 to 10,000 or 4000 to 10,000.

[0061] When the aspect ratio of the one-dimensional conductive material is within an appropriate range, it will intertwine with each other on the surface of the silicon-based material to form a good coating effect, which on the one hand can provide long-distance conductivity on the surface of the silicon-based material, and on the other hand can help the conductive layer form a fishing net-style bridged network structure, which can better improve the electronic conductivity and volume expansion of the surface of the silicon-based material.

[0062] When the aspect ratio of the one-dimensional conductive material is small, its long-range conductivity is poor and it is difficult for it to intertwine with itself and to form a good coating effect with the polymer, which may result in an incompletely structured conductive layer being formed on the surface of the silicon-based material, and the effect of improving the electronic conductivity and volume expansion of the surface of the silicon-based material may not be obvious.When the aspect ratio of the one-dimensional conductive material is large, the one-dimensional conductive material is more likely to intertwine with itself and the effect of mutual dispersion between it and the polymer is poor, which may result in an inability to form a uniform and stable conductive layer, and the conductive layer is likely to have stress concentration areas and areas with poor electronic conductivity, which may result in an inconspicuous effect of improving the electronic conductivity and volume expansion of the surface of the silicon-based material.

[0063] In some embodiments, the weight average molecular weight B1 of the polymer and the aspect ratio B2 of the one-dimensional conductive material satisfy B1 / B2 in a range 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.

[0064] When B1 / B2 is within a suitable range, the polymer and the one-dimensional conductive material can be more dispersed with each other and form a uniform and stable conductive layer. When B1 / B2 is within a suitable range, the polymer and the one-dimensional conductive material can be cross-linked and entangled with each other, thereby forming a fishnet-like cross-linked network structure in the conductive layer and helping to cover the surface of the silicon-based material. When B1 / B2 is within a suitable range, an appropriate number of hydrogen bonds are formed between the polar functional groups of the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups of the polymer and the functional groups on the surface of the silicon-based material, thereby helping to effectively fix the one-dimensional conductive material to the surface of the silicon-based material. Therefore, when B1 / B2 is within a suitable range, the silicon-containing negative electrode active material can have better electronic conductivity and lower volume expansion.

[0065] 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.

[0066] When the diameter of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can be better cross-linked and entangled with each other, which helps the conductive layer form a fishnet-like cross-linked network structure and coat the surface of the silicon-based material, so that the silicon-containing negative electrode active material can have better electronic conductivity and lower volume expansion.

[0067] When the diameter of the one-dimensional conductive material is small, its surface energy is generally large, and self-aggregation is easily generated, which makes it difficult to maintain a one-dimensional linear shape in the conductive layer. At this time, the mutual dispersion effect between it and the polymer is poor, making it difficult to form a uniform and stable conductive layer, and the conductive layer is likely to have stress concentration areas and areas with poor electronic conductivity, which may result in inconspicuous improvement effects on the electronic conductivity and volume expansion of the silicon-based material surface. When the diameter of the one-dimensional conductive material is large, the one-dimensional conductive material has many surface defects, and at the same time, its flexibility is poor, making it difficult to form a strong conductive layer, which may result in inconspicuous improvement effects on the electronic conductivity and volume expansion of the silicon-based material surface.

[0068] In some embodiments, the length of the one-dimensional conductive material is between 0.5 μm and 20 μm. Alternatively, the length of the one-dimensional conductive material is between 1 μm and 20 μm, between 1 μm and 18 μm, between 1 μm and 16 μm, between 1 μm and 14 μm, between 1 μm and 12 μm, between 1 μm and 10 μm, between 1 μm and 8 μm, between 2 μm and 20 μm, between 2 μm and 18 μm, between 2 μm and 16 μm, between 2 μm and 14 μm, between 2 μm and 12 μm, between 2 μm and 10 μm, or between 2 μm and 8 μm.

[0069] When the length of the one-dimensional conductive material is within a suitable range, the polymer and the one-dimensional conductive material can be better cross-linked and entangled with each other, which helps the conductive layer form a fishnet-like cross-linked network structure and coat the surface of the silicon-based material, so that the silicon-containing negative electrode active material can have better electronic conductivity and lower volume expansion.

[0070] When the length of the one-dimensional conductive material is small, it is difficult for the one-dimensional conductive material to intertwine with the polymer to form a good covering effect, so the one-dimensional conductive material cannot be effectively fixed to the surface of the silicon-based material, and therefore the effect of improving the electronic conductivity and volume expansion of the surface of the silicon-based material may not be obvious.When the length of the one-dimensional conductive material is large, it is easy for it to self-aggregate, and it is difficult to maintain a one-dimensional linear shape in the conductive layer, which will result in poor mutual dispersion effect between it and the polymer, making it difficult to form a uniform and stable conductive layer, and it is easy for stress concentration areas and areas with poor electronic conductivity to appear in the conductive layer, so that the effect of improving the electronic conductivity and volume expansion of the surface of the silicon-based material may not be obvious.

[0071] In some embodiments, the glass transition temperature (Tg) of the polymer is 150°C or less, and optionally, the glass transition temperature of the polymer is 10°C to 120°C. In some embodiments, the crystallinity of the polymer is 80% or less, and optionally, the crystallinity of the polymer is 10% to 70%. When the polymer has an appropriate glass transition temperature and crystallinity, the polymer and the one-dimensional conductive material can be better cross-linked and entangled. In this case, the conductive layer is firmly coated on the surface of the silicon-based material like a fishing net, and the electronic conductivity and volume expansion of the surface of the silicon-based material can be better improved.

[0072] In some embodiments, the polymer may include, but is not limited to, one or more of the following: homopolymers or copolymers of (meth)acrylic acid and its salts, homopolymers or copolymers of hydroxymethylcellulose and its salts, homopolymers or copolymers of alginic acid and its salts, polyacetamide homopolymers or copolymers, acrylamide homopolymers or copolymers, and vinyl alcohol homopolymers or copolymers. In this application, the term "copolymer" refers to any of random copolymers, alternating copolymers, block copolymers, and graft copolymers. The copolymer may be a copolymer of the above-mentioned monomers or may be a copolymer with other monomers, particularly vinyl monomers. Vinyl monomers include, but are not limited to, one or more of acrylic acid, acrylamide, acrylic acid esters, ethylene, propylene, butylene, butadiene, isoprene, styrene, and vinyl acetate.

[0073] Optionally, the polymer comprises one or more of poly(meth)acrylic acid, sodium poly(meth)acrylate, potassium poly(meth)acrylate, magnesium poly(meth)acrylate, hydroxymethylcellulose, sodium carboxymethylcellulose, potassium hydroxymethylcellulose, lithium hydroxymethylcellulose, alginic acid, 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-acrylic acid ester copolymer, ethylene-vinyl alcohol copolymer.

[0074] These polymers can better cross-link and entangle with the one-dimensional conductive material. At this time, the conductive layer is tightly coated on the surface of the silicon-based material like a fishing net, which can better improve the electronic conductivity and volume expansion of the surface of the silicon-based material. At the same time, if these polymers have an appropriate content of polar functional groups, they can form an appropriate amount of hydrogen bonds with the functional groups or defects on the surface of the one-dimensional conductive material. This allows the conductive layer to simultaneously achieve both flexibility and toughness, and further reduce the volume expansion of the silicon-based material.

[0075] In some embodiments, the one-dimensional conductive material comprises one or more of carbon nanotubes, metal fibers, carbon fibers, hollow carbon fibers, etc. Optionally, the one-dimensional conductive material comprises carbon nanotubes, including, for example, single-walled carbon nanotubes, multi-walled carbon nanotubes, or combinations thereof.

[0076] Optionally, the carbon content of the carbon nanotubes is 90% or more. The higher the carbon content of the carbon nanotubes, the lower the impurity content and the better the electronic conductivity, so that the silicon-containing negative electrode active material can have better electronic conductivity.

[0077] Optionally, I of the carbon nanotube g / I d is greater than 40, I g is the Raman spectrum of the carbon nanotube at 1500 cm -1 ~1650cm -1 The peak intensity is in the range of I d is 100 cm in the Raman spectrum of the carbon nanotube -1 ~200cm -1 The peak intensity of carbon nanotubes is in the range of g / I dWhen the thickness is within an appropriate range, the carbon nanotubes themselves have few defects and high tensile strength, so that the formed conductive layer can simultaneously achieve good flexibility and high tensile strength, thereby effectively mitigating the volume expansion of the silicon-based material.

[0078] Optionally, the specific surface area of ​​the carbon nanotubes is 500 m 2 When the specific surface area of ​​the carbon nanotubes is within an appropriate range, the contact area with the polymer is large and more hydrogen bonds can be formed, which helps the carbon nanotubes to disperse with the polymer and form a more uniform and stable conductive layer.

[0079] In some embodiments, based on the total mass of the silicon-containing negative electrode active material, the mass percentage of the silicon-based material is W1, and W1 is 90% to 98%.

[0080] In some embodiments, the weight percentage of the polymer is W2, which is 1% to 9% based on the total weight of the silicon-containing negative electrode active material. When the polymer content is within an appropriate range, it can ensure that the one-dimensional conductive material is sufficiently coated on the surface of the silicon-based material, and can ensure that most of the surface of the silicon-based material (e.g., 70% or more, 80% or more, 90% or more, 95% or more) is open and completely coated. This can improve the electronic conductivity and volume expansion of the surface of the silicon-based material, reduce contact between the silicon-based material and the electrolyte, reduce the decomposition and rupture of the SEI film, and reduce the probability of the silicon-containing negative electrode active material being powdered.

[0081] In some embodiments, the mass percentage of the one-dimensional conductive material is W3, which is 0.1% to 1%, based on the total mass of the silicon-containing negative active material. When the content of the one-dimensional conductive material is within an appropriate range, it can ensure that the surface of the silicon-containing negative active material has good electronic conductivity and also ensure that a fishing 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.

[0082] In some embodiments, the mass ratio W2 / W3 between the polymer and the one-dimensional conductive material is 7-20. Alternatively, W2 / W3 is 7-20, 7-18, 7-16, 7-14, 9-20, 9-18, 9-16, or 9-14.

[0083] When W2 / W3 is within a suitable range, it can ensure that an appropriate amount of hydrogen bonds are formed between the polar functional groups of the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups of the polymer and the functional groups on the surface of the silicon-based material, so that the one-dimensional conductive material can be effectively fixed on the surface of the silicon-based material, and the electronic conductivity and volume expansion of the surface of the silicon-based material can be better improved.

[0084] When the mass ratio of the polymer to the one-dimensional conductive material is large, many hydrogen bonds exist between the polymer and the silicon-based material in the longitudinal direction of the silicon-containing negative electrode active material, but many hydrogen bonds cannot be formed between the polymer and the one-dimensional conductive material in the transverse direction of the silicon-containing negative electrode active material to achieve effective cross-linking and entanglement, and furthermore, the strength of the conductive layer may be affected, and the improvement in the electronic conductivity and volume expansion of the surface of the silicon-based material may not be obvious.

[0085] If the mass ratio of the polymer to the one-dimensional conductive material is small, the hydrogen bonds formed between the polymer and the silicon-based material in the longitudinal direction of the silicon-containing negative electrode active material will decrease, affecting the affinity between the conductive layer and the silicon-based material, which may cause the conductive layer to fall off during the stirring and dispersion process of the slurry.

[0086] In some embodiments, the thickness of the conductive layer is 1 nm to 2 μm. If the thickness of the conductive layer is small, the silicon-based material may not be able to absorb the volume expansion. If the thickness of the conductive layer is large, the resistance to desorption or insertion of active ions may increase, and a concentration difference may easily form between the inside and outside of the conductive layer, which may affect the reversible capacity per gram and the initial coulombic efficiency of the silicon-based material.

[0087] In some embodiments, the powder resistivity of the silicon-containing negative electrode active material is 0.70 Ω cm to 0.89 Ω cm, or 0.70 Ω cm to 0.85 Ω cm, 0.70 Ω cm to 0.82 Ω cm, or 0.70 Ω cm to 0.80 Ω cm.

[0088] In some embodiments, the silicon-containing negative electrode active material has a specific surface area of ​​0.8 m 2 / g~5m 2 When the specific surface area of ​​the silicon-containing negative electrode active material is within an appropriate range, it can simultaneously have a higher capacity and a higher initial coulombic efficiency.

[0089] In some embodiments, the silicon-containing negative electrode active material has an average particle size Dv50 of 2 μm to 10 μm. When the average particle size Dv50 of the silicon-containing negative electrode active material is within an appropriate range, it helps to simultaneously improve the transport performance of active ions and electrons.

[0090] In some embodiments, the silicon-containing negative electrode active material I g / I d is 0.1 to 200, and I g is 1500 cm in the Raman spectrum of the silicon-containing negative electrode active material. -1 ~1650cm -1 The peak intensity is in the range of I d is 100 cm in the Raman spectrum of the silicon-containing negative electrode active material. -1 ~200cm -1 The peak intensities located in the range are shown.

[0091] In this application, the content of an element in a material (e.g., the mass percentage of silicon in a silicon-based material, the carbon content in a carbon nanotube, etc.) is defined as being within the meaning known in the art and can be measured using an apparatus and method known in the art, for example, by X-ray photoelectron spectroscopy (XPS).

[0092] In the present application, the mass percentage of the polar functional groups of the polymer has a meaning known in the art and can be measured using an apparatus and method known in the art, such as titration (e.g., acid-base titration, oxidation-reduction titration, precipitation titration), moisture measurement, gas measurement, colorimetry, infrared spectroscopy, or nuclear magnetic resonance spectroscopy.

[0093] In this application, the weight average molecular weight of a polymer has a meaning known in the art and can be measured using an apparatus and method known in the art. For example, it can be measured using gel permeation chromatography (GPC). The test can be performed using an Agilent 1290 Infinity II GPC system.

[0094] In this application, the glass transition temperature of a polymer has a meaning known in the art and can be measured using known devices and methods in the art. For example, it can be measured with reference to the Chinese standard GB / T29611-2013 Differential Scanning Calorimetry (DSC) for Glass Transition Temperature of Raw Rubber. The test can be performed using a Mettler-Toledo DSC-3 type differential scanning calorimeter.

[0095] In this application, the crystallinity of a polymer has the meaning known in the art and can be measured using devices and methods known in the art, for example, differential scanning calorimetry (DSC).

[0096] In this application, the powder resistivity of a material has the meaning known in the art and can be measured using known devices and methods in the art. For example, it can be measured using a four-probe method in accordance with the Chinese standard GB / T30835-2014. The mass of the sample can be 0.6 g to 0.7 g, and the test pressure can be 16 MPa.

[0097] In this application, the average particle size Dv50 of a material has the meaning known in the art, and refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%, and can be measured using devices and methods known in the art, such as the Chinese standard GB / T19077-2016 Laser Diffraction Method for Particle Size Distribution, and can be easily measured using a laser particle size analyzer, such as the Mastersizer2000E laser particle size analyzer from Malvern, UK.

[0098] In this application, the specific surface area of ​​a material has a meaning known in the art and can be measured using known devices and methods. For example, it can be measured using the gas adsorption specific surface area analysis test method in accordance with the Chinese standard GB / T19587-2017, and calculated using the Brunauer Emmett Teller (BET) method. Here, the gas adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area and pore distribution analyzer manufactured by Micromeritics, Inc., USA. [Production method]

[0099] The first aspect according to the present embodiment further provides a method for producing a silicon-containing negative electrode active material, which can produce the silicon-containing negative electrode active material according to any of the examples of the first aspect according to the present embodiment.

[0100] The method for preparing the silicon-containing negative electrode active material of the present application includes the steps of: (1) providing a first slurry containing a polymer and a one-dimensional conductive material; and (2) slowly adding a silicon-based material to the first slurry and uniformly stirring and dispersing the material to obtain a second slurry, and then drying the second slurry to obtain the silicon-containing negative electrode active material.

[0101] Optionally, the solid content of the first slurry in step (1) is 0.8% to 30%.

[0102] Optionally, the second slurry in step (2) has a solid content of 3% to 50% and a viscosity of 50 cps to 1500 cps at room temperature. If the solid content and viscosity of the second slurry are low, the second slurry may settle, which may result in insufficient coating of the surface of the silicon-based material. If the solid content and viscosity of the second slurry are high, the second slurry may gel, which may result in insufficient drying.

[0103] Optionally, the rotation speed of the stirring and dispersion in step (2) is 400 rpm to 800 rpm, and the stirring and dispersion time is 1 hour to 3 hours.

[0104] Optionally, the drying method in step (2) is spray drying, but the present application is not limited thereto. Furthermore, the spray drying temperature may be 120°C to 300°C. When the spray drying temperature is within an appropriate range, hydrogen bonds are formed between the polymers and between the polymer and the one-dimensional conductive material to form a fishnet-like cross-linked network structure, which is helpful in improving the electronic conductivity of the silicon-based material, reducing persistent side reactions between the silicon-based material and the electrolyte, and mitigating the volume expansion of the silicon-based material.

[0105] If the spray drying temperature is lower than 120°C, the coverage area of ​​the conductive layer on the silicon-based material surface will be small, which may result in increased side reactions between the silicon-based material and the electrolyte.If the spray drying temperature is higher than 300°C, the polymer will easily undergo dehydration condensation reactions, which will result in changes in the structure of the conductive layer.

[0106] In step (1), the polymer and the one-dimensional conductive material may be added to deionized water simultaneously to obtain the first slurry, or the polymer and the one-dimensional conductive material may be added separately to obtain the first slurry. For example, in some embodiments, the method for preparing the first slurry includes step (11) of adding the one-dimensional conductive material to deionized water and stirring to uniformly disperse it to obtain a conductive slurry, and step (12) of slowly adding the polymer to the conductive slurry obtained in step (11) and stirring to uniformly disperse it to obtain the first slurry.

[0107] Optionally, the solid content of the conductive slurry obtained in step (11) is 0.8% to 10%.

[0108] Optionally, the rotation speed of the stirring and dispersion in step (11) is 200 rpm to 600 rpm, and the dispersion time is 20 min to 60 min.

[0109] Optionally, the rotation speed of the stirring and dispersion in step (12) is 200 rpm to 600 rpm, and the dispersion time is 20 min to 60 min. Negative electrode sheet

[0110] A second aspect of the present embodiment provides a negative electrode sheet including the silicon-containing negative electrode active material of the first aspect of the present embodiment.

[0111] The silicon-containing negative electrode active material of the first aspect according to the present embodiment can simultaneously achieve good electronic conductivity, a small volume expansion effect, and high reversible capacity and initial coulombic efficiency. Furthermore, since the silicon-containing negative electrode active material can maintain good electronic conductivity even after being fabricated into a negative electrode sheet, the negative electrode sheet of the present invention can simultaneously achieve good electronic conductivity, high capacity, initial coulombic efficiency, and small volume expansion.

[0112] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector. Here, the negative electrode film layer includes the silicon-containing negative electrode active material according to the first aspect of the present invention, a conductive agent, and an adhesive. For example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode film layer is provided on one or both of the two facing surfaces of the negative electrode current collector.

[0113] In some embodiments, based on the total mass of the negative electrode film layer, the mass percentage of the silicon-containing negative electrode active material may be 5% to 40%, and optionally 5% to 25%.

[0114] In some embodiments, the negative electrode film layer may further include at least one of other negative electrode active materials known in the art, such as graphite (natural graphite, artificial graphite, or a mixture thereof), soft carbon, hard carbon, and lithium titanate, in addition to the silicon-containing negative electrode active material. Optionally, the other negative electrode active material includes graphite. In some embodiments, the mass percentage of the graphite may be 55% to 90%, and optionally 70% to 90%, based on the total mass of the negative electrode film layer.

[0115] The type of conductive agent in the negative electrode sheet of the present application is not particularly limited. For 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, the mass percentage of the conductive agent is 5% or less, and optionally 0.1% to 5%, based on the total mass of the negative electrode film layer.

[0116] The negative electrode sheet of the present application is not particularly limited by the type of adhesive. For example, the adhesive may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (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 adhesive is 5% or less, and optionally 0.1% to 5%, based on the total mass of the negative electrode membrane layer.

[0117] In some embodiments, the negative electrode membrane layer may further optionally contain other additives. For example, the other additives may include a thickener, such as carboxymethylcellulose sodium (CMC-Na), a PTC thermistor material, etc. In some embodiments, the mass percentage of the other additives is 2% or less, and optionally 0.1% to 2%, based on the total mass of the negative electrode membrane layer.

[0118] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is copper foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may be at least one selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0119] The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a conductive agent, an adhesive, and other optional auxiliary agents in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0120] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present 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 some other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer. secondary battery

[0121] A third aspect of the present invention provides a secondary battery including the silicon-containing negative electrode active material of the first aspect of the present invention or the negative electrode sheet of the second aspect of the present invention, thereby enabling the secondary battery to simultaneously achieve high energy density and good cycle performance and storage performance.

[0122] A secondary battery, also known as a rechargeable battery or storage battery, refers to a battery that can be used continuously after discharge by activating the active material through charging. Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is located between the positive electrode sheet and the negative electrode sheet and primarily serves to prevent short-circuiting between the positive and negative electrodes while allowing active ions to pass through. The electrolyte serves to conduct active ions between the positive electrode sheet and the negative electrode sheet. [Negative electrode sheet]

[0123] The negative electrode sheet used in the secondary battery of the present application is the negative electrode sheet described in any of the Examples of the second aspect of the present application. [Positive electrode sheet]

[0124] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces facing each other in the thickness direction of the positive electrode current collector. The positive electrode film layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0125] The positive electrode film layer contains a positive electrode active material, and the positive electrode active material can adopt a positive electrode active material used in a secondary battery known in the art. For example, the positive electrode active material can include at least one of lithium transition metal oxides, lithium-containing phosphates having an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides can 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 having an olivine structure can include at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. The present application is not limited to these materials, and other conventionally known materials used as secondary battery positive electrode active materials can be used. These positive electrode active materials can be used alone only one type, or two or more types can be used in combination.

[0126] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material can include one or more of the lithium transition metal oxides and their modified compounds represented by Formula 1.

[0127] Li a Ni b Co c M d O e A f Formula 1

[0128] 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 one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0129] In the present application, the modifying compound for each of the positive electrode active materials may be doped to the positive electrode active material, surface-coated, or both doped and surface-coated.

[0130] In some embodiments, the positive electrode film layer may further include a conductive agent. The present application does not particularly limit the type of the conductive agent. For 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, the mass percentage of the conductive agent is 5% or less, and optionally 0.1% to 5%, based on the total mass of the positive electrode film layer.

[0131] In some embodiments, the positive electrode membrane layer may further optionally include an adhesive. The present application does not particularly limit the type of adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. In some embodiments, the mass percentage of the adhesive is 5% or less, and optionally 0.1% to 5%, based on the total mass of the positive electrode membrane layer.

[0132] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is aluminum foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may be at least one selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0133] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). [Electrolytes]

[0134] The present application does not specifically limit the type of the electrolyte, and it can be selected according to needs. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

[0135] In some embodiments, the electrolyte employs an electrolyte solution including an electrolyte salt and a solvent.

[0136] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, for example, the electrolyte salt can include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium disoxalate borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0137] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, by way of 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), butylene 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).

[0138] In some embodiments, the electrolyte solution may further optionally include additives, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance of the battery, or an additive for improving the low-temperature power performance of the battery. [Separator]

[0139] Liquid electrolyte secondary batteries and some solid electrolyte secondary batteries further include a separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet and primarily serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. The present application does not particularly limit the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0140] In some embodiments, the separator may be made of at least one of 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.

[0141] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be fabricated into an electrode assembly by a winding process or a stacking process.

[0142] In some embodiments, the secondary battery may include an exterior packaging, which may be used to seal the electrode assembly and electrolyte.

[0143] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0144] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, rectangular, or any other shape. Figure 1 shows a secondary battery 5 having a rectangular structure as an example.

[0145] In some embodiments, as shown in FIG. 2 , the exterior may include a case 51 and a cover plate 53. Here, the case 51 includes a bottom plate and a side plate connected to the bottom plate, which together form a housing cavity. The case 51 has an opening communicating with the housing cavity, and the cover plate 53 covers the opening to close the housing cavity. The positive electrode sheet, the negative electrode sheet, and the separator are wound or stacked to form an electrode assembly 52. ​​The electrode assembly 52 is sealed in the housing cavity. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be adjusted as needed.

[0146] Methods for fabricating the secondary battery of the present application are well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet are wound or stacked to form an electrode assembly, which is then placed in a housing and dried. After that, an electrolyte is injected, and the secondary battery is obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0147] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the battery module can include multiple secondary batteries, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0148] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the length of the battery module 4. Of course, they may be arranged in any other manner. The plurality of secondary batteries 5 may further be fixed by fasteners.

[0149] Optionally, the battery module 4 further includes a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0150] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0151] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 and is used to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged arbitrarily within the battery box. power consumption equipment

[0152] A fourth aspect of the present embodiment provides a power consuming device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0153] The power consumption device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0154] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, which may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0155] Other examples of power consuming devices may include mobile phones, tablet computers, laptop computers, etc. Such power consuming devices are typically required to be thin and may employ secondary batteries as their power source. Example

[0156] The following examples will more specifically illustrate the contents of the present disclosure. These examples are merely used for illustrative purposes, and various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass. In addition, all reagents used in the examples can be purchased or synthesized according to conventional methods and can be used directly without further treatment. In addition, all devices used in the examples can be purchased. Example 1 Preparation of silicon-containing negative electrode active material

[0157] Carbon nanotubes (CNTs, one-dimensional conductive material) with a diameter of 3 nm, a length of 10 μm, and an aspect ratio of 3333 were added to deionized water and stirred and dispersed at 300 rpm for 30 minutes 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 (carboxyl group in Example 1) content of 25% was slowly added to the conductive slurry and stirred and dispersed at 300 rpm for 30 minutes to obtain a first slurry. Silicon oxide (silicon-based material) with a silicon content of 48% was slowly added to the first slurry and stirred and dispersed at 500 rpm for 1 hour to obtain a second slurry. The second slurry was then spray-dried at 180°C to obtain a silicon-containing negative electrode active material. In the silicon-containing negative electrode active material, the mass ratio of silicon oxide, polymer, and one-dimensional conductive material was 96.6:3.0:0.4. Preparation of negative electrode sheet

[0158] The silicon-containing negative electrode active material, graphite, styrene butadiene rubber (SBR), carboxymethyl cellulose sodium (CMC-Na), and carbon black (Super P) were mixed in a mass ratio of 81.3:14.3:2:1.2:1.2 with an appropriate amount of deionized water as a solvent, and stirred thoroughly to form a uniform negative electrode slurry. The negative electrode slurry was then uniformly applied to the surface of copper foil as a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet. Preparation of positive electrode sheet

[0159] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), and adhesive polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1:2 with sufficient stirring in an appropriate amount of NMP solvent to form a uniform cathode slurry. The cathode slurry is then evenly applied to the surface of aluminum foil, which serves as the cathode current collector, and after drying and cold pressing, a cathode sheet is obtained. Preparation of electrolyte

[0160] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then thoroughly dried LiPF6 is dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Preparation of separator

[0161] The separator is a porous polyethylene film. Fabrication of secondary batteries

[0162] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order and wound up to obtain an electrode assembly. The electrode assembly is placed in a housing, dried, and then an electrolyte is injected. After vacuum sealing, leaving it to stand, chemical formation, and shaping, a secondary battery is obtained. Examples 2 to 38, Comparative Examples 1 to 4

[0163] The method for producing the secondary battery was similar to that in Example 1, except for the production parameters for the silicon-containing negative electrode active material. See Table 1 for details.

[0164] [Table 1] JPEG0007787189000002.jpg213125JPEG0007787189000003.jpg212118JPEG0007787189000004.jpg21156 Testing process (1) Powder resistivity test of silicon-containing negative electrode active material

[0165] The powder resistivity of the silicon-containing negative electrode active material prepared above was measured using an FT-341A four-probe powder resistivity tester in accordance with the Chinese standard GB / T30835-2014. The sample mass was 0.6g to 0.7g, and the test pressure was 16MPa. (2) Initial reversible capacity per gram and initial coulombic efficiency tests

[0166] The negative electrode sheet was punched into small wafers and assembled into a CR2430 button cell battery in an argon-protected glove box using a lithium metal sheet as the counter electrode and a polyethylene (PE) film as the separator. The resulting button cell was then allowed to stand for 12 hours, then discharged at 25°C at a constant current of 0.05 C to 0.005 V. After 10 minutes of standing, it was discharged at a constant current of 50 μA to 0.005 V. After another 10 minutes of standing, it was discharged at a constant current of 10 μA to 0.005 V. The total capacity of the three discharges was recorded and used as the initial discharge capacity of the button cell. The button cell was then charged at a constant current of 0.1 C to 2 V, and the initial charge capacity of the button cell was recorded.

[0167] Initial reversible capacity per gram of negative electrode sheet (mAh / g) = Initial charge capacity of button battery / (mass of silicon-containing negative electrode active material + mass of graphite)

[0168] Initial coulombic efficiency of negative electrode sheet = (initial charge capacity of button battery / initial discharge capacity of button battery) x 100% (3) Volume expansion performance test

[0169] At 25°C, the secondary battery was discharged to 2.5V at a constant current of 1C, then charged to 4.25V at a constant current of 0.5C, at which point the secondary battery was at 100% SOC. After disassembling the secondary battery, the thickness of the negative electrode sheet at this time was measured and designated H1. The initial thickness of the negative electrode sheet was designated H0. The negative electrode sheet thickness increase rate (%) = (H1 / H0-1) × 100%.

[0170] The thickness increase rate of the negative electrode sheet indicates the volume expansion of the negative electrode sheet and the secondary battery. Here, the smaller the thickness increase rate of the negative electrode sheet, the smaller the volume expansion of the negative electrode sheet and the secondary battery.

[0171] The test results for Examples 1 to 38 and Comparative Examples 1 to 4 are shown in Table 2.

[0172] [Table 2] JPEG0007787189000006.jpg81125

[0173] As can be seen from the test results in Table 2, compared with Comparative Example 1, the silicon-containing negative electrode active material provided herein has lower powder resistivity, and the negative electrode sheet simultaneously exhibits high reversible capacity per gram, high initial coulombic efficiency, and low volume expansion. This is likely due to the formation of an appropriate amount of hydrogen bonds between the polar functional groups of the polymer and the functional groups on the surface of the one-dimensional conductive material, and between the polar functional groups of the polymer and the functional groups on the surface of the silicon-based material, thereby effectively anchoring the one-dimensional conductive material to the surface of the silicon-based material. Furthermore, the polymer and the one-dimensional conductive material can be crosslinked and entangled with each other, resulting in a flexible conductive layer that tightly coats the surface of the silicon-based material, similar to a fishing net. Therefore, the silicon-containing negative electrode active material of the present invention simultaneously exhibits good electronic conductivity, low volume expansion, high reversible capacity per gram, and high initial coulombic efficiency, and maintains good electronic conductivity even after application to the negative electrode sheet.

[0174] In Comparative Example 2, when preparing the silicon-containing negative electrode active material, the carbon nanotube dispersion liquid and silicon oxide were mixed and then dried, and the bond between the carbon nanotubes and the silicon oxide was not strong. During the slurry stirring and dispersion process, the carbon nanotubes were easily detached, resulting in no significant improvement in the electronic conductivity, reversible capacity per gram, and initial coulombic efficiency of the silicon-containing negative electrode active material, and its volume expansion was still high.

[0175] As can be seen from the test results of Examples 1 to 11, Comparative Examples 3, 12 to 14, and Comparative Example 4, when A2 / A1 is controlled within an appropriate range (between 0.2 and 8), the silicon-containing negative electrode active material has low powder resistivity, and the negative electrode sheet simultaneously has high reversible capacity per gram, high initial coulombic efficiency, and small volume expansion. In Comparative Example 3, when A2 / A1 is greater than 8, the polymer can only bond to the silicon-based material via hydrogen bonding in the longitudinal direction of the silicon-containing negative electrode active material, and does not form a good coating effect in the lateral direction of the silicon-containing negative electrode active material. Therefore, the bond between the carbon nanotubes and silicon oxide is not strong, and the carbon nanotubes are easily detached during the stirring and dispersion process of the slurry. As a result, the reversible capacity per gram and initial coulombic efficiency of the negative electrode sheet are not significantly improved, and the volume expansion remains high. In Comparative Example 4, when A2 / A1 is less than 0.2, most of the polar functional groups in the polymer form hydrogen bonds with the functional groups on the surface of the carbon nanotubes to cause cross-linking or entanglement, and a few polar functional groups form hydrogen bonds with the functional groups on the surface of the silicon carbon compound. Therefore, the bond between the carbon nanotubes and the silicon carbon compound is not strong, and the carbon nanotubes are easily detached during the stirring and dispersion process of the slurry. As a result, the reversible capacity per gram and initial coulombic efficiency of the negative electrode sheet are not significantly improved, and its volume expansion is still high.

[0176] As can be seen from the test results of Examples 1 to 11, when the content of polar functional groups in the polymer is within an appropriate range, the reversible capacity per gram and initial coulombic efficiency of the negative electrode sheet are higher, and at the same time, its volume expansion is also smaller.

[0177] As can be seen from the test results of Examples 15 to 24, when the aspect ratio of the carbon nanotubes and / or the ratio of the weight-average molecular weight of the polymer to the aspect ratio of the carbon nanotubes are within an appropriate range, the reversible capacity per gram and initial coulombic efficiency of the negative electrode sheet are higher, and at the same time, its volume expansion is also smaller.

[0178] As can be seen from the test results of Examples 25 to 31, when the mass ratio of polymer to carbon nanotubes is within an appropriate range, the reversible capacity per gram and initial coulombic efficiency of the negative electrode sheet are higher, and at the same time, its volume expansion is also smaller.

[0179] The present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea within the scope of the technical solution of the present application and achieves similar effects is included in the technical scope of the present application. Furthermore, within the scope of the present application, various modifications conceivable by those skilled in the art to the embodiments and other embodiments constructed by combining some of the components of the embodiments are also included in the scope of the present application.

Claims

1. A silicon-containing negative electrode active material, a silicon-based material; a conductive layer located on a surface of the silicon-based material, the conductive layer including a polymer and a one-dimensional conductive material; wherein the polymer is a copolymer containing polar functional groups including one or more of a carboxyl group, a hydroxyl group, an amide group, an amino group, a carbonyl group, and a nitro group; the mass percentage of the polar functional group in the polymer is A1, the mass percentage of silicon element in the silicon-based material is A2, and the silicon-containing negative electrode active material satisfies the conditions that A2 is 5% to 100% and A2 / A1 is 0.2 to 8; The silicon-containing negative electrode active material has an aspect ratio B2, and B2 is 100 to 20,000.

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

5.

3. 3. The silicon-containing negative electrode active material according to claim 1, wherein A1 is 5% to 90%.

4. 4. The silicon-containing negative electrode active material according to claim 1, wherein the polymer has a weight average molecular weight of B1, and B1 is 100,000 or more.

5. 5. The silicon-containing negative electrode active material according to claim 4, wherein B1 / B2 is 5 to 200.

6. the diameter of the one-dimensional conductive material is between 1 nm and 30 nm; and / or 2. The silicon-containing negative electrode active material according to claim 1, wherein the length of the one-dimensional conductive material is 0.5 μm to 20 μm.

7. the glass transition temperature of the polymer is 150°C or less, and / or 7. The silicon-containing negative electrode active material according to claim 1, wherein the polymer has a crystallinity of 80% or less.

8. 8. The silicon-containing negative electrode active material according to claim 7, wherein the polymer comprises one or more of a copolymer of (meth)acrylic acid and a salt thereof, a copolymer of hydroxymethylcellulose and a salt thereof, a copolymer of alginic acid and a salt thereof, a polyacetamide copolymer, an acrylamide copolymer, and a vinyl alcohol copolymer.

9. The one-dimensional conductive material includes carbon nanotubes, and the carbon nanotubes satisfy at least one of the following conditions (1) to (3). (1) The carbon content of the carbon nanotubes is 90% or more; (2) I of the carbon nanotube ｇ / I ｄ is 40 or more, and I ｇ is 1500 cm in the Raman spectrum of the carbon nanotube －１ ~1650cm －１ and the peak intensity is in the range of I ｄ is 100 cm in the Raman spectrum of the carbon nanotube －１ ~200cm －１ and the peak intensity is in the range of (3) The specific surface area of ​​the carbon nanotubes is 500 m ２ The silicon-containing negative electrode active material according to any one of claims 1 to 8, wherein the silicon-containing negative electrode active material has a SiO2 content of 0.1g or more.

10. The silicon-containing negative electrode active material according to any one of claims 1 to 9, wherein the silicon-based material comprises one or more of elemental silicon, silicon oxide, silicon carbon compound, and silicon alloy, and the silicon-based material is further doped with one or two elements selected from the group consisting of lithium and magnesium.

11. Based on the total mass of the silicon-containing negative electrode active material, The mass percentage of the silicon-based material is W1, and W1 is 90% to 98%; the weight percentage of the polymer is W2, W2 being 1% to 9%; The silicon-containing negative electrode active material according to any one of claims 1 to 10, wherein the mass percentage of the one-dimensional conductive material is W3, and W3 is 0.1% to 1%.

12. 12. The silicon-containing negative electrode active material according to claim 1, wherein the conductive layer has a thickness of 1 nm to 2 μm.

13. The powder resistivity of the silicon-containing negative electrode active material is 0.70 Ω cm to 0.89 Ω cm, and / or The silicon-containing negative electrode active material has an average particle size Dv50 of 2 μm to 10 μm, and / or The specific surface area of ​​the silicon-containing negative electrode active material is 0.8 m ２ / g to 5m ２ / g, and / or I of the silicon-containing negative electrode active material ｇ / I ｄ is 0.1 to 200, and I ｇ is 1500 cm in the Raman spectrum of the silicon-containing negative electrode active material. －１ ~1650cm －１ and the peak intensity is in the range of I ｄ is 100 cm in the Raman spectrum of the silicon-containing negative electrode active material. －１ ~200cm －１ The silicon-containing negative electrode active material according to any one of claims 1 to 12, wherein the silicon-containing negative electrode active material exhibits a peak intensity in the range of

14. A negative electrode sheet including 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 the silicon-containing negative electrode active material according to any one of claims 1 to 13, a conductive agent, and an adhesive; The negative electrode sheet, wherein the negative electrode film layer further contains graphite.

15. A secondary battery comprising the silicon-containing negative electrode active material according to any one of claims 1 to 13 or the negative electrode sheet according to claim 14.

16. A power consuming device comprising the secondary battery of claim 15.

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