Silicon-carbon composite material, negative electrode sheet, battery cell, and electric device

Abstract

The application relates to a silicon-carbon composite material, a negative electrode sheet, a battery monomer and an electric device, wherein the silicon-carbon composite material comprises a carbon-containing material and a silicon-containing material; the carbon-containing material comprises a carbon-based substance and a first group arranged on the surface of the carbon-based substance; the silicon-containing material comprises a silicon-based substance and an organic compound coated on at least part of the surface of the silicon-based substance; the electric property of the organic compound is opposite to that of the first group; and the organic compound and the first group are combined through electrostatic action.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon-carbon composite material, a negative electrode sheet, a battery cell and a power utilization device. BACKGROUND

[0002] Battery cells have characteristics of high capacity and long service life, and are thus widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools, etc. Due to great progress in battery cells, higher requirements are put forward for the performance of battery cells. In order to improve the performance of battery cells, the materials in the battery cells, such as negative electrode active materials, are usually optimized and improved. As carriers of metal ions and electrons in battery cells, negative electrode active materials play a role in energy storage and release, and have a non-negligible influence on the performance of battery cells.

[0003] However, the cycle life and use reliability of the battery cell are still poor when the improved negative electrode active material is applied to the battery cell. SUMMARY

[0004] The present application provides a silicon-carbon composite material, a negative electrode sheet, a battery cell and a power utilization device. The cycle performance and storage performance of the battery cell described in the present application can be improved.

[0005] In a first aspect, the embodiments of the present application provide a silicon-carbon composite material, which comprises a carbon-containing material and a silicon-containing material. The carbon-containing material comprises a carbon-based substance and a first group arranged on the surface of the carbon-based substance. The silicon-containing material comprises a silicon-based substance and an organic compound coated on at least part of the surface of the silicon-based substance. The electric property of the organic compound is opposite to that of the first group, and the organic compound and the first group are combined by electrostatic interaction.

[0006] Thus, in the embodiments of the present application, the silicon-containing material can improve the active ion storage capacity, the organic compound on the surface of the silicon-containing material can enhance the physical crosslinking with the carbon-containing material, and the structural strength of the silicon-carbon composite material formed by the combination of the two is improved. The carbon-containing material can buffer the volume change of the silicon-containing material, improve the electronic conductivity of the silicon-carbon composite material, reduce the volume change of the silicon-containing material, and reduce the risk of fracture and reformation of the SEI film, thereby improving the cycle life and use reliability of the battery cell.

[0007] In some embodiments, the first group is at least one of a hydroxyl group (-OH), an amino group (-NH2), an alkyl group (-R1), an acyloxy group (-OCOR2) and an alkoxy group (-OR3). Such arrangement enables the carbon-containing material and the silicon-containing material to be combined by electrostatic interaction.

[0008] In some embodiments, the organic compound comprises a positive group; optionally, the organic compound comprises at least one of polydiallyldimethylammonium chloride (PDDA), polyacrylamide (PAM), and polydimethyl diallyl ammonium chloride (PDMDAAC). Such arrangement enables the carbon-containing material and the silicon-containing material to be combined through electrostatic interaction.

[0009] In some embodiments, the carbon-based substance comprises at least one of natural graphite, artificial graphite, graphene, carbon nanotube, and carbon fiber; and / or the silicon-based substance comprises at least one of silicon element and silicon oxide; optionally, the silicon element comprises at least one of silicon nano-element and silicon micro-element; further optionally, the silicon nano-element comprises at least one of silicon nanoparticle, silicon nanowire, and silicon nanosheet. The above-mentioned silicon-based substance can be combined with the carbon-based substance in an electrostatic manner, which is conducive to improving the potential of the silicon-carbon composite material for embedding active ions and improving the use reliability of the battery cell.

[0010] In some embodiments, the carbon-based substance comprises at least one of carbon nanotube and carbon fiber; optionally, the carbon nanotube comprises at least one of single-walled carbon nanotube and multi-walled nanotube; and the silicon-based substance comprises silicon nano-element; optionally, the silicon-based substance comprises silicon nanowire.

[0011] Thus, in the embodiments of the present application, the carbon-based substance and the silicon-based substance are both low-dimensional materials, the carbon-containing material formed after the carbon-based substance and the first group are combined is also a low-dimensional material, and the silicon-containing material formed after the silicon-based substance and the organic compound are combined is also a low-dimensional material. When the carbon-containing material and the silicon-containing material are combined, they can be crosslinked to form a two-dimensional material. Since the silicon-carbon composite material has a stable crosslinked structure, the carbon-containing material and the silicon-containing material can be understood as a structure in which they are intertwined with each other, thereby facilitating the carbon-containing material to intertwine reversely to reduce the stress generated by the silicon-containing material, reducing the degree of volume expansion of the silicon-containing material, and improving the stability of the overall structure of the silicon-carbon composite material.

[0012] In some embodiments, the ratio of the mass content of the carbon-containing material to the mass content of the silicon-containing material based on the total mass of the silicon-carbon composite material is (3 to 5): 1; optionally, the mass content of the carbon-containing material is 75% to 85%; and / or the mass content of the silicon-containing material is 15% to 25%.

[0013] Thus, when the ratio of the mass content of the carbon-containing material to the mass content of the silicon-containing material is within the above range in the embodiments of the present application, the carbon-containing material can significantly improve the volume expansion effect of the silicon-containing material, and the structural stability of the silicon-carbon composite material can be improved, and the electrical conductivity of the silicon-carbon composite material can be improved.

[0014] In some embodiments, the ratio of the mass content of the organic compound and the mass content of the silicon-based substance is (1 to 5): 20, based on the total mass of the silicon-carbon composite material; optionally, the mass content of the organic compound is 1% to 5%; and / or the mass content of the silicon-based substance is 15% to 20%.

[0015] Therefore, when the ratio of the mass content of the organic compound and the mass content of the silicon-based substance is within the above range in the embodiments of the present application, the organic compound can provide relatively more second groups for the silicon-based substance, which is conducive to the uniform distribution of the silicon-containing material and the carbon-containing material, and is conducive to the cross-linking of the silicon-containing material and the carbon-containing material, so as to form a silicon-carbon composite material with stable structure.

[0016] In some embodiments, the silicon-carbon composite material satisfies at least one of conditions (1) to (3):

[0017] (1) the volume average particle size Dv50 of the silicon-carbon composite material is 1 μm to 5 μm;

[0018] (2) the BET specific surface area of the silicon-carbon composite material is 200 m 2 / g to 400 m 2 / g;

[0019] (3) the electrical conductivity of the silicon-carbon composite material is 120 S / cm to 3000 S / cm; optionally, 300 S / cm to 3000 S / cm.

[0020] Therefore, when the silicon-carbon composite material of the embodiments of the present application satisfies the above conditions, the cycle life and use reliability of the battery cell can be further improved.

[0021] In a second aspect, the present application provides a method for preparing a silicon-carbon composite material, comprising: providing a carbon-based substance; performing group treatment on the carbon-based substance to make the surface of the carbon-based substance have a first group and form a carbon-containing material; providing a silicon-based substance; providing an organic compound to the silicon-based substance to perform group treatment, so that the silicon-based substance is at least partially coated with the organic compound and forms a silicon-containing material, wherein the electric property of the organic compound and the first group is opposite; and mixing the carbon-containing material and the silicon-containing material to obtain a silicon-carbon composite material, wherein the first group and the organic compound are combined by electrostatic action.

[0022] In a third aspect, the present application provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises the silicon-carbon composite material according to any one of the embodiments of the first aspect of the present application, or the silicon-carbon composite material according to any one of the embodiments of the second aspect of the present application.

[0023] In some embodiments, the adhesion of the negative electrode tab is 15 N / m to 20 N / m; optionally 17 N / m to 20 N / m; and / or the negative electrode tab has an elongation of 1.5% to 2.5% under a force of 1 x 10 4 Kg (10T) is 1.5% to 2.5%; optionally 1.8% to 2.5%.

[0024] In a fourth aspect, the present application provides a battery cell comprising the negative electrode tab according to any one of the embodiments of the third aspect of the present application.

[0025] In a fifth aspect, the present application also provides an electric device comprising the battery cell according to any one of the embodiments of the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0027] Figure 1 is a schematic diagram of an embodiment of the battery cell of the present application.

[0028] Figure 2 is a schematic diagram of an embodiment of the battery cell of Figure 1 .

[0029] Figure 3 is a schematic diagram of an embodiment of the battery module of the present application.

[0030] Figure 4 is a schematic diagram of an embodiment of the battery pack of the present application.

[0031] Figure 5 is a schematic diagram of an embodiment of the battery pack of Figure 4 .

[0032] Figure 6 is a schematic diagram of an embodiment of the electric device comprising the battery cell of the present application as a power supply.

[0033] Figure 7 is a schematic diagram of the preparation of the silicon-carbon composite material in Embodiment 1 of the present application.

[0034] Figure 8 is an infrared spectrum of the single-walled carbon nanotube MWCTN after acid treatment in Embodiment 1 of the present application.

[0035] Figure 9is a zeta potential test chart of the MWCNTs after acid treatment and the PDDA-treated silicon nanowires PDDA-Si in Example 1 of the present application.

[0036] The accompanying drawings are not necessarily drawn to scale.

[0037] The reference signs are explained as follows:

[0038] 1: battery pack; 2: upper case; 3: lower case; 4: battery module

[0039] 5: battery cell; 51: case; 52: electrode assembly

[0040] 53: cover plate

[0041] 6: power consuming device DETAILED DESCRIPTION

[0042] Hereinafter, specific embodiments of the silicon-carbon composite material, the negative electrode sheet, the battery cell, the battery, and the power consuming device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are already well known, and repeated description of actually identical structures, are omitted. This is in order to avoid the following description becoming unnecessarily lengthy, and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided in order for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0043] The ranges disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0044] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions if there is no special description.

[0045] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions if there is no special description.

[0046] All steps of the present application can be performed in sequence or randomly, and preferably in sequence if there is no special description. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c) as mentioned, which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0047] With the popularization of the application range of the battery monomer, the requirement for the performance of the battery monomer, such as the energy density, is gradually improved. The negative electrode film layer has a significant influence on the performance of the battery monomer. Carbon and silicon are commonly used materials for the negative electrode film layer, and have been widely studied.

[0048] The theoretical specific capacity of carbon is low, and the lithium intercalation potential of carbon is low, which can easily cause lithium precipitation and trigger reliability problems. The theoretical specific capacity of silicon is high, up to 4200 mAh / g, and the lithium intercalation potential of silicon is slightly higher than that of graphite, which can reduce the risk of lithium precipitation. However, the many shortcomings of silicon hinder the application of silicon. First, in terms of electron transport, the electrical conductivity of silicon is only 10 -3 S / cm, and the lithium ion diffusion coefficient is 10 -12 cm -2 / s, the charge transfer kinetics is poor during charging and discharging, which limits the rate performance of silicon. The volume change of silicon during the deintercalation reaction process can be greater than 300%, and the volume change is large. The silicon particles with changing volume can easily cause the rupture and regeneration of the solid electrolyte interface film (SEI film) on the surface of the active material. The repeated growth of the SEI film not only consumes lithium and electrolyte, but also limits the transport of lithium ions, reduces the electrical contact of the active material, and increases the impedance. In addition, micron-sized silicon materials also have the phenomenon of rupture and pulverization, and the fresh silicon surface is continuously exposed after rupture and pulverization, forming a new SEI film and increasing the thickness of the SEI film, which prolongs the transport path of lithium ions and shortens the cycle life of the battery monomer.

[0049] In view of the advantages and disadvantages of carbon and silicon, in the related art, it is considered to composite the carbon-containing material and the silicon-containing material, but a simple composite operation cannot effectively improve the structural stability of the negative electrode film layer, and cannot improve the cycle life and use reliability of the battery cell.

[0050] The embodiment of the present application composites the carbon-containing material and the silicon-containing material through electrostatic action. The introduction of the carbon-containing material can improve the electrical conductivity of the silicon-carbon composite material and improve the electronic conductivity. The introduction of the silicon-containing material can improve the specific capacity of the silicon-carbon composite material and reduce the risk of active metal precipitation during the cycle process, thereby improving the use reliability of the battery cell. Moreover, since the carbon-containing material and the silicon-containing material are combined through electrostatic action, the uniformity of the distribution of the carbon-containing material and the silicon-containing material is improved. The silicon-containing material is surrounded by the carbon-containing material. The carbon-containing material acts as a buffer layer for silicon expansion, which can reduce the risk of silicon expansion, thereby reducing the risk of pulverization of the silicon-containing material, improving the structural stability of the silicon-carbon composite material as a whole, and enhancing the physical cross-linking between the organic compound on the surface of the silicon-containing material and the carbon-containing material. The structural strength of the silicon-carbon composite material formed by the composite of the two is further improved, thereby improving the cycle life of the battery cell. Next, the technical solution of the present application will be described in detail.

[0051] Silicon-carbon composite material

[0052] In a first aspect, the present application provides a silicon-carbon composite material. The silicon-carbon composite material is applied as a negative active material in a negative electrode film layer. The silicon-carbon composite material includes a carbon-containing material and a silicon-containing material. The carbon-containing material includes a carbon-based substance and a first group provided on the surface of the carbon-based substance. The silicon-containing material includes a silicon-based substance and an organic compound coated on at least part of the surface of the silicon-based substance. The electric property of the organic compound is opposite to that of the first group. The organic compound and the first group are combined through electrostatic action.

[0053] The carbon-containing material includes a first group, and the silicon-containing material includes an organic compound. The electric property of the first group is opposite to that of the organic compound. It can be understood that the organic compound includes a second group with an electric property opposite to that of the first group. It can be understood that the first group shows negative electric property relative to the second group. Correspondingly, the second group shows positive electric property relative to the first group. Alternatively, the first group shows positive electric property relative to the second group. Correspondingly, the second group shows negative electric property relative to the first group. Since the electric property of the first group is opposite to that of the second group, the two groups can be combined through electrostatic action. The carbon-based substance and the silicon-based substance are combined through Coulomb interaction, i.e., combined in an electrostatic manner. The distribution of the carbon-containing material and the silicon-containing material is relatively uniform, i.e., the uniformity of the distribution is improved. Since the electric potential of the active ion embedded in the silicon-containing material is relatively high, the risk of active metal precipitation is reduced, and the use reliability of the battery cell is improved.

[0054] Since the surface of the silicon-containing material has the organic compound, the organic compound can be combined with the silicon-based substance in the form of a covalent bond, the organic compound can attract the first group, and it can be understood that the periphery of the silicon-containing material is distributed with the carbon-containing material, the introduction of the carbon-containing material can improve the rate of electron conduction to the silicon-containing material, thereby improving the overall conductivity of the silicon-carbon composite material; in addition, the carbon-containing material can act as a buffer layer for silicon expansion, which can buffer the expansion degree of the silicon-containing material, thereby reducing the risk of pulverization of the silicon-containing material and improving the structural stability of the silicon-carbon composite material as a whole, thereby being able to improve the cycle life of the battery cell.

[0055] In addition, since the silicon-based surface is coated with an organic compound, the organic compound provides a charged group for the silicon-containing material on one hand, which is conducive to the combination of the silicon-containing material and the carbon-containing material through electrostatic action; on the other hand, the setting of the organic compound can provide more active sites on the surface of the silicon-containing material to load more charged groups, so that the combination of the silicon-containing material and the carbon-containing material is more compact, and the organic compound on the surface of the silicon-based substance is equivalent to the effect of grafting a branched chain on the surface of the silicon-based substance, which can enhance the physical crosslinking between the silicon-containing material and the carbon-containing material and improve the structural strength of the silicon-carbon composite material; on the other hand, the organic compound is coated on the silicon-based substance, which can provide a certain volume buffer effect for the silicon-based substance, reduce the risk of excessive expansion of the silicon-containing material, and further improve the structural stability of the silicon-carbon composite material as a whole, thereby being able to improve the cycle life of the battery cell. Due to the crosslinked structure of the silicon-carbon composite material, it has good flexibility and structural stability, and when it is added to the negative electrode sheet as a negative electrode active material, it can improve the flexibility of the negative electrode film layer, and the negative electrode film layer is not prone to cracking, and the structural stability of the negative electrode sheet is high.

[0056] Therefore, in the embodiments of the present application, the silicon-containing material can improve the active ion storage capacity, the organic compound on the surface of the silicon-containing material can enhance the physical crosslinking with the carbon-containing material, and the structural strength of the silicon-carbon composite material formed by the combination of the two is improved; the carbon-containing material can buffer the volume change of the silicon-containing material, improve the electronic conductivity of the silicon-carbon composite material, and reduce the volume change of the silicon-containing material, and reduce the risk of fracture and reformation of the SEI film, thereby improving the cycle life and use reliability of the battery cell.

[0057] In some embodiments, the first group can be a negative electric group; correspondingly, the second group in the organic compound can be a positive electric group. Such a setting enables the carbon-containing material and the silicon-containing material to be combined through electrostatic action.

[0058] Exemplarily, the first group includes at least one of a hydroxyl group (-OH), an amino group (-NH2), an alkyl group (-R1), an acyloxy group (-OCOR2), and an alkoxy group (-OR3). Optionally, the first group can include a hydroxyl group. Among them, the alkyl group -R1 can be a substituted or unsubstituted C1 to C10 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, etc.; the acyloxy group can be a formyloxy group, an acetyloxy group, a propionyloxy group, a butyryloxy group, a valeryloxy group, a hexanoyloxy group, etc.; the alkoxy group can be a substituted or unsubstituted C1 to C10 alkoxy group, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a hexyloxy group, etc.; the carbon chain of the above-mentioned groups is relatively short, and the steric hindrance effect is relatively small, which is conducive to the combination of the carbon-containing material and the silicon-containing material. When the above-mentioned groups are substituted, the substituent groups can include halogen atoms, such as fluorine atoms, chlorine atoms, etc.

[0059] Specifically, the positively charged organic compound can include at least one of polydiallyldimethylammonium chloride PDDA, polyacrylamide PAM, and polydimethyl diallyl ammonium chloride PDMDAAC.

[0060] The above-mentioned organic compound has good chemical stability and excellent deformation ability. During the active ion extraction and / or intercalation of the silicon-based substance, the organic compound can shrink or stretch synchronously with the silicon-based substance, so that the silicon-based substance can adapt to a larger volume change, and the structural stability of the overall silicon-carbon composite material is improved.

[0061] In some embodiments, the carbon-based substance includes at least one of natural graphite, artificial graphite, graphene, carbon nanotubes CNTs, and carbon nanofibers CNFs. The above-mentioned carbon-based substance can be combined with the silicon-based substance in an electrostatic manner, which is conducive to improving the conductivity of the silicon-carbon composite material and improving the rate performance. Moreover, the carbon-based substance can also relieve the internal stress generated during the charging and discharging process and buffer the volume change of the silicon-containing material.

[0062] Optionally, the carbon-based substance includes at least one of carbon nanotubes CNTs and carbon nanofibers CNFs; further optionally, the carbon-based substance includes at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes. The above-mentioned carbon-based substance is a low-dimensional carbon material (such as one-dimensional), which can effectively construct a conductive network, promote the effective transmission of electrons and the rapid transfer of electrons, and relieve the stress caused by the expansion of the silicon-containing material, reduce the risk of the silicon-containing material powdering, and improve the stability of the overall structure of the silicon-carbon composite material.

[0063] In some embodiments, the silicon-based substance includes at least one of elemental silicon and silicon oxide. The above-mentioned silicon-based substance can be combined with the carbon-based substance in an electrostatic manner, which is conducive to improving the potential of the silicon-carbon composite material for intercalating active ions and improving the use reliability of the battery cell.

[0064] Optionally, the silicon-based substance can be a nanomaterial, for example, the silicon oxide can be a nanosilicon oxide, and the silicon element can be a silicon nanoelement. The nanoscale silicon-based substance can significantly reduce its own volume expansion effect. Of course, the silicon-based substance can be a micromaterial, for example, the silicon oxide can be a micromaterial silicon oxide, and the silicon element can be a silicon micromaterial element.

[0065] Optionally, the silicon nanoelement can include at least one of a silicon nanoparticle, a silicon nanowire, and a silicon nanosheet. The nanoscale silicon-based substance can significantly reduce its own volume expansion effect, help improve its own structural stability; and can reduce the repeated formation of the SEI film on the surface of the silicon-containing material during the cycle process, improve the cycle performance and use reliability of the battery cell.

[0066] Illustratively, the silicon nanoparticle can include a silicon quantum dot, etc. The silicon quantum dot can be understood as a silicon nanoparticle with a size of less than 100 nm in three dimensions, similar to a point-like object. Of course, the silicon nanoparticle can also include a silicon nanoparticle with a size of greater than or equal to 100 nm in at least one dimension.

[0067] Illustratively, the silicon-based substance can include a silicon nanowire. The silicon nanowire has a relatively low dimension, which is conducive to the compounding of the silicon nanowire and the carbon-containing material.

[0068] In some embodiments, the carbon-based substance can include at least one of a carbon nanotube and a carbon fiber tube; the carbon nanotube can include at least one of a single-walled carbon nanotube and a multi-walled nanotube; and the silicon-based substance can include a silicon nanowire. Both the carbon-based substance and the silicon-based substance are low-dimensional materials, for example, both are one-dimensional materials. The carbon-containing material formed after the combination of the carbon-based substance and the first group is also a low-dimensional material, and the silicon-containing material formed after the combination of the silicon-based substance and the organic compound is also a low-dimensional material. When the carbon-containing material and the silicon-containing material are compounded, the two can be crosslinked to form a two-dimensional material. Since the silicon-carbon composite material has a stable crosslinked structure, the carbon-containing material and the silicon-containing material can be understood as a structure in which they are intertwined with each other, thereby facilitating the carbon-containing material to be wound in the opposite direction to reduce the stress generated by the silicon-containing material, reducing the degree of volume expansion of the silicon-containing material, and improving the stability of the overall structure of the silicon-carbon composite material. Moreover, since the silicon-carbon composite material has a stable crosslinked structure, the viscosity of the negative electrode slurry can be increased, the amount of binder can be reduced, and the amount of negative electrode film layer can be increased to improve the energy density of the battery cell; and the stability of the negative electrode film layer formed by the negative electrode slurry can also be improved.

[0069] Illustratively, the silicon-based substance includes a carbon nanotube; and the silicon-based substance includes a silicon nanowire.

[0070] Optionally, the carbon nanotube has a tube diameter of 5 nm to 20 nm, and / or the carbon nanotube has a length of 1 μm to 5 μm. When the size of the carbon nanotube is within the above range, it is conducive to crosslinking with the low-dimensional silicon-containing material.

[0071] For example, the carbon nanotube can have a tube diameter of 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, 15 nm, 15.5 nm, 16 nm, 16.5 nm, 17 nm, 17.5 nm, 18 nm, 18.5 nm, 19 nm, 19.5 nm, 20 nm, or a range defined by any two of the above values.

[0072] For example, the carbon nanotube can have a length of 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range defined by any two of the above values.

[0073] Optionally, the silicon nanowire has a tube diameter of 50 nm to 100 nm, and / or a length of 1 μm to 10 μm. When the carbon nanotube has a size within the above range, the carbon nanotube is beneficial for cross-linking with the low-dimensional carbon-containing material.

[0074] For example, the silicon nanowire can have a tube diameter of 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range defined by any two of the above values.

[0075] For example, the silicon nanowire can have a length of 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range defined by any two of the above values.

[0076] In the embodiments, the tube diameter of the carbon nanotube and the silicon nanowire has the meaning known in the art, and can be detected by using the equipment and method commonly used in the art, for example, can be characterized by using a scanning electron microscope SEM (e.g., ZEISS Sigma 300).

[0077] In some embodiments, the ratio of the mass content of the carbon-containing material to the mass content of the silicon-containing material is (3 to 5): 1, based on the total mass of the silicon-carbon composite material. When the ratio of the mass content of the carbon-containing material to the mass content of the silicon-containing material is within the above range, the carbon-containing material can significantly improve the volume expansion effect of the silicon-containing material, improve the structural stability of the silicon-carbon composite material, and the electrical conductivity of the silicon-carbon composite material can be improved.

[0078] Exemplarily, the mass content of the carbon-containing material is 75% to 85%. When the mass content of the carbon-containing material is in the above range, the structural stability of the silicon-carbon composite material can be significantly improved.

[0079] For example, the mass content of the carbon-containing material can be 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or a range composed of any two of the above values.

[0080] Exemplarily, the mass content of the silicon-containing material is 15% to 25%. When the mass content of the silicon-containing material is in the above range, the structural stability of the silicon-carbon composite material can be significantly improved.

[0081] For example, the mass content of the silicon-containing material can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range composed of any two of the above values.

[0082] In some embodiments, the ratio of the mass content of the organic compound to the mass content of the silicon-based substance is (1 to 5):20, based on the total mass of the silicon-carbon composite material. When the ratio of the mass content of the organic compound to the mass content of the silicon-based substance is in the above range, the organic compound can provide relatively more second groups for the silicon-based substance, which is conducive to the uniform distribution of the silicon-containing material and the carbon-containing material, and the cross-linking of the silicon-containing material and the carbon-containing material, forming a silicon-carbon composite material with stable structure, and without forming a too thick coating layer for the silicon-based substance, affecting the transmission of active ions such as lithium ions.

[0083] Exemplarily, the mass content of the organic compound is 1% to 5%.

[0084] For example, the mass content of the organic compound can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above values.

[0085] Exemplarily, the mass content of the silicon-based substance is 15% to 20%.

[0086] For example, the mass content of the silicon-based substance can be 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or a range composed of any two of the above values.

[0087] In order to further improve the cycle life and use reliability of the battery cell, the physical and chemical parameters of the silicon-carbon composite material can be further selected in the embodiments of the present application.

[0088] In some embodiments, the silicon-carbon composite material has a volume average particle size Dv50 of 1 μm to 5 μm.

[0089] For example, the silicon-carbon composite material has a volume average particle size Dv50 of 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range defined by any two of the above values.

[0090] In the embodiments of the present application, the volume average particle size Dv50 of the material has the meaning known in the art, for example, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, which can be detected by using the equipment and method commonly used in the art, for example, taking the silicon-carbon composite material as a sample, and testing the volume average particle size Dv50 by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0091] In some embodiments, the silicon-carbon composite material has a BET specific surface area of 200 m 2 / g to 400 m 2 / g.

[0092] For example, the silicon-carbon composite material has a BET specific surface area of 200 m 2 / g, 210 m 2 / g, 220 m 2 / g, 230 m 2 / g, 240 m 2 / g, 250 m 2 / g, 260 m 2 / g, 270 m 2 / g, 280 m 2 / g, 290 m 2 / g, 300 m 2 / g, 310 m 2 / g, 320 m 2 / g, 330 m 2 / g, 340 m 2 / g, 350 m 2 / g, 360 m 2 / g, 370 m 2 / g, 380 m 2 / g, 390 m 2 / g, 400 m 2 / g, or a range defined by any two of the above values.

[0093] In the embodiments of the present application, the BET specific surface area of the silicon-carbon composite material is the meaning known in the art, which can be detected by using the commonly used equipment and methods in the art, for example, taking the silicon-carbon composite material as a sample, calculating according to the BET (Brunauer Emmett Teller) method according to the test standard GB / T 19587-2017, and specifically, the specific surface area can be tested by using a Tri-Star 3020 type specific surface area and pore size analysis tester of the Micromeritics company in the United States.

[0094] In some embodiments, the electrical conductivity of the silicon-carbon composite material is 120 S / cm to 3000 S / cm; optionally 300 S / cm to 3000 S / cm. Exemplarily, the electrical conductivity of the silicon-carbon composite material can be 120 S / cm, 150 S / cm, 200 S / cm, 300 S / cm, 400 S / cm, 500 S / cm, 600 S / cm, 700 S / cm, 800 S / cm, 900 S / cm, 1000 S / cm, 1200 S / cm, 1300 S / cm, 1500 S / cm, 1600 S / cm, 1700 S / cm, 1800 S / cm, 1900 S / cm, 2000 S / cm, 2100 S / cm, 2200 S / cm, 2300 S / cm, 2400 S / cm, 2500 S / cm, 2600 S / cm, 2700 S / cm, 2800 S / cm, 2900 S / cm, or a range composed of any two of the above values.

[0095] Since the carbon-containing material is added to the silicon-carbon composite material, the electrical conductivity of the silicon-carbon composite material can be significantly improved, for example, by adding single-walled carbon nanotubes, multi-walled carbon nanotubes, etc. to improve the electrical conductivity of the whole material. And when the silicon-carbon composite material forms a cross-linked structure, the cross-linked network helps to form a conductive network, thereby improving the electrical conductivity.

[0096] In the embodiments of the present application, the electrical conductivity of the silicon-carbon composite material is the meaning known in the art, which can be detected by using the commonly used equipment and methods in the art, for example, taking the silicon-carbon composite material as a sample, and testing by using a powder resistance instrument.

[0097] Method for preparing silicon-carbon composite material

[0098] In a second aspect, the present application further provides a method for preparing a silicon-carbon composite material.

[0099] The method comprises:

[0100] Step S100, providing a carbon-based substance;

[0101] Step S200, performing a group treatment on the carbon-based substance to make the surface of the carbon-based substance have a first group, and form a carbon-containing material;

[0102] Step S300, providing a silicon-based substance;

[0103] Step S400, providing an organic compound to the silicon-based substance for a group treatment, so that the silicon-based substance is at least partially coated with the organic compound on the surface, and form a silicon-containing material, wherein the organic compound and the first group are opposite in electrical property;

[0104] Step S500, mixing the carbon-containing material and the silicon-containing material to obtain a silicon-carbon composite material, wherein the first group and the organic compound are combined through electrostatic interaction.

[0105] The silicon-carbon composite material prepared by the method according to the embodiments of the present application has excellent cycle life and use reliability when applied to a battery cell.

[0106] In some embodiments, the carbon-based substance can include at least one of natural graphite, artificial graphite, graphene, carbon nanotubes CNTs, and carbon nanofibers CNFs.

[0107] In some embodiments, the silicon-based substance includes at least one of elemental silicon and silicon oxide.

[0108] In some embodiments, in step S200, a compound containing the first group can be used to treat the carbon-based substance, for example,

[0109] The compound containing a hydroxyl group includes at least one of methanol, ethanol, ethylene glycol, sulfuric acid, and nitric acid;

[0110] The compound containing an amino group includes at least one of amine, amide, or amino acid;

[0111] The compound containing an alkyl group includes at least one of methane, dimethyl sulfate, or iodomethane;

[0112] The compound containing an alkoxy group includes at least one of diethyl ether, acetaldehyde, or methylamine;

[0113] The compound containing an acyloxy group includes at least one of acryloyloxy propionic acid or 4-acetoxy styrene.

[0114] In some embodiments, step S200 can include: acid treating the carbon-based substance to make the surface of the carbon-based substance have first groups, the first groups being negative electric groups. The acid treatment can reduce the dangling bonds and carbon-oxygen bonds on the surface of the carbon-based substance to obtain the carbon-based substance with negative electric group modification on the surface. The acid treatment can make the carbon-based substance carry negative electric groups, which is conducive to the combination with the carbon-containing material through electrostatic action.

[0115] Specifically, the carbon-based substance and the mixed acid can be mixed and ultrasonically treated for 2.5 to 3 hours, filtered by using a polytetrafluoroethylene filter membrane, and washed with deionized water for 3 to 5 times until the pH of the filtrate is 6±0.5. After filtration, the carbon-based substance is dried in a freeze-drying box at -50°C for 12 hours and then stored.

[0116] Optionally, the mixed acid includes at least two of concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid. Optionally, the mass ratio of each acid in the mixed acid can be 1:1.

[0117] Optionally, the ratio of the mass content of the carbon-based substance to the mass content of the mixed acid, based on the total mass of the carbon-based substance and the mixed acid, is (1 to 2):200.

[0118] In some embodiments, step S400 can include:

[0119] The ammonia water, the hydrogen peroxide, and the silicon-based substance are mixed and ultrasonically treated for 35 to 45 minutes to obtain a mixed intermediate. The ammonia water and the hydrogen peroxide activate the surface of the silicon-based substance, which is conducive to the combination of the silicon-based substance and the organic compound through a covalent bond.

[0120] The organic compound and the mixed intermediate are mixed and ultrasonically treated for 1.0 to 1.5 hours to obtain a silicon-containing material.

[0121] Optionally, the ratio of the mass content of the ammonia water, the mass content of the hydrogen peroxide, and the mass content of the silicon-based substance, based on the total mass of the mixed intermediate, is 100:100:(1 to 2).

[0122] In some embodiments, step S500 can include:

[0123] The nitrogen-containing material and the silicon-containing material are ultrasonically mixed for 2 to 3 hours, filtered by using a polytetrafluoroethylene aluminum membrane, and washed with deionized water for 3 to 5 times until the pH of the filtrate is 8±0.5. Finally, the silicon-carbon composite material is obtained after drying in a drying box at -50°C for 12 hours.

[0124] In the above embodiments, ultrasonic mixing can promote the degree of uniform mixing.

[0125] Negative electrode sheet

[0126] In a third aspect, the application further provides a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer comprises a negative electrode active material, which can comprise the silicon-carbon composite material of any one of the embodiments of the first aspect of the application or the silicon-carbon composite material prepared by the method of any one of the embodiments of the second aspect of the application. The embodiments of the application add the silicon-carbon composite material to the negative electrode film layer, which is beneficial to improving the cycle life and use reliability of the battery cell.

[0127] In some embodiments, the mass content of the silicon-carbon composite material of the embodiments of the application is 60% to 100% based on the total mass of the negative electrode film layer. Specifically, the mass content can be 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 100% or a range formed by any two of the above values. When the mass content of the silicon-carbon composite material is 100%, it means that the negative electrode film layer is entirely composed of the silicon-carbon composite material. The silicon-carbon composite material has a certain flexibility due to its cross-linked structure, which improves the toughness of the negative electrode film layer, improves the brittleness and strength of the negative electrode sheet, and when the negative electrode sheet is subjected to the brittleness test by folding and rolling the creases for multiple times, it is found that the crease part of the negative electrode sheet after folding is not transparent and does not fall off powder, the brittleness of the negative electrode sheet is obviously improved, and the bonding force between the negative electrode film layer and the negative electrode current collector is strong.

[0128] In some embodiments, the elongation rate of the negative electrode sheet is 1.5% to 2.5% when the negative electrode sheet is rolled under the action of a force of 10 tons (10T), which can be 1.8% to 2.5%, and the negative electrode sheet does not break. The setting of the silicon-carbon composite material significantly improves the flexibility of the negative electrode sheet. Especially when the silicon-carbon composite material has a cross-linked structure, it can further improve the elongation rate.

[0129] For example, the elongation rate of the negative electrode sheet can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or a range formed by any two of the above values.

[0130] In the embodiments of the application, the elongation rate of the negative electrode sheet refers to the percentage of the length deformation amount of the negative electrode sheet under the action of the force to the original length.

[0131] In some embodiments, the negative electrode film layer can further include a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material can include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a second silicon-based material, a tin-based material, and lithium titanate. The second silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0132] In some embodiments, the negative electrode film layer can not include a negative electrode binder, and the silicon-carbon composite material has a certain flexibility and adsorption force due to its cross-linked structure, and can be combined with the negative electrode current collector by itself. The adhesion of the tested negative electrode tab is 15 N / m to 20 N / m; and optionally 17 N / m to 20 N / m. The negative electrode film layer has strong adhesion, and has strong combination ability with the negative electrode current collector, and the two are not easy to separate, so that the overall structural stability of the negative electrode tab is good.

[0133] Illustratively, the adhesion of the negative electrode tab can be 15 N / m, 18 N / m, 20 N / m, 22 N / m, 25 N / m, 26 N / m, 28 N / m, 30 N / m, 32 N / m, 35 N / m, 38 N / m, 40 N / m, 42 N / m, 45 N / m, 48 N / m, 50 N / m, 52 N / m, 55 N / m, 58 N / m, 60 N / m, 62 N / m, 65 N / m, 70 N / m, 75 N / m, 80 N / m, 85 N / m, 90 N / m, or a range formed by any two of the above values.

[0134] In the embodiments of the present application, the adhesion of the negative electrode tab is the meaning known in the art, which can be tested by using devices and methods known in the art, for example, a high-iron tensile testing machine. The negative electrode tab is cut into a test sample with a size of 20*100 mm 2 The size of the test sample is 20*100 mm, and the negative electrode film layer is adhered to the test sample with double-sided tape, and the double-sided tape is pressed flat with a roller to make the double-sided tape fully adhere to the test sample. The other side of the double-sided tape of the test sample is adhered to the surface of stainless steel, and one end of the test sample is bent in the opposite direction with an angle of 180°. A high-iron tensile testing machine is used for testing, and one end of the stainless steel is fixed to the lower clamp of the tensile testing machine, and the bent end of the test sample is fixed to the upper clamp. The angle of the test sample is adjusted to ensure that the upper and lower ends are in a vertical position, and then the test sample is stretched at a speed of 50 mm / min until the test sample is completely peeled off from the stainless steel. The displacement and force during the process are recorded, and the force at the time of force balance is generally considered as the adhesion of the negative electrode film layer. The adhesion mainly refers to the adhesion of the side provided with the negative electrode film layer.

[0135] In some embodiments, the negative electrode film layer has a compacted density of 1.8 g×cc -1 to 2.1 g×cc.-1 When the compaction density of the negative electrode film layer is in the above range, the coating weight of the negative electrode film layer is relatively high, which is beneficial to improve the energy density of the battery cell.

[0136] For example, the compaction density of the negative electrode film layer can be 1.8 g x cc -1 , 1.9 g x cc -1 , 2.0 g x cc -1 , 2.1 g x cc -1 or a range composed of any two of the above values.

[0137] In the embodiments of the present application, the compaction density of the negative electrode film layer is a meaning known in the art and can be tested by a method known in the art. For example, a double-roller vertical cold press. A single-side coated and cold-pressed negative electrode sheet (if a double-side coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first) is taken, the thickness of the negative electrode film layer is tested, and then the areal density of the negative electrode film layer is tested according to the following method: the compaction density of the negative electrode film layer = the areal density of the negative electrode film layer / the thickness of the negative electrode film layer.

[0138] The areal density of the negative electrode film layer is a meaning known in the art and can be tested by a method known in the art. For example, a single-side coated and cold-pressed negative electrode sheet (if a double-side coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first) is punched into a small disc with an area of S1, weighed, and recorded as M1. Then the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative electrode current collector is weighed, and recorded as M0, and the areal density of the negative electrode film layer = (the weight of the negative electrode sheet M1-the weight of the negative electrode current collector M0) / S1.

[0139] In some embodiments, the negative electrode film layer can further optionally comprise a negative electrode binder. The embodiments of the present application do not have special limitations on the type of the negative electrode binder. For example, the negative electrode binder can comprise at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative electrode binder is ≤5% based on the total mass of the negative electrode film layer.

[0140] In some embodiments, the negative electrode film layer can optionally further include a negative electrode conductive agent. The negative electrode conductive agent is not particularly limited in the embodiments of the present application, and can include, for example, at least one of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is ≤5% based on the total mass of the negative electrode film layer.

[0141] In some embodiments, the negative electrode film layer can optionally further include other auxiliary agents. For example, the other auxiliary agents can include a thickening agent, such as sodium carboxymethyl cellulose (CMC-Na), a PTC thermistor material, and the like. In some embodiments, the mass percentage of the other auxiliary agents is ≤2% based on the total mass of the negative electrode film layer.

[0142] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0143] The negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector. The relevant parameters mentioned in the embodiments of the present application, such as the mass content of the metal salt in the negative electrode film layer, refer to the mass content of the metal salt in the negative electrode film layer on one side of the negative electrode current collector.

[0144] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing the negative electrode film layer, a metal salt, an optional conductive agent, an optional binder, and other optional auxiliary agents in a negative electrode solvent and stirring uniformly. The negative electrode solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0145] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab described in the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode tab described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0146] Battery cell

[0147] In a fourth aspect, the present application provides a battery cell including a negative electrode tab. The negative electrode tab can be any of the negative electrode tabs according to the embodiments of the third aspect of the present application. The use of the negative electrode tab can prolong the cycle life of the battery cell and improve the use reliability.

[0148] [Positive electrode tab]

[0149] In some embodiments, the battery cell further includes a positive electrode tab.

[0150] The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material.

[0151] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode active material layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0152] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0153] In some embodiments, the positive electrode active material can be any of the positive electrode active materials known in the art for use in battery cells. As an example, the positive electrode active material can include at least one of the following materials: a layered structure positive electrode active material (such as a material of ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium / sodium-rich layered, and rock salt phase layered, etc.), an olivine-type phosphate active material, a spinel structure positive electrode active material (such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate, etc.).

[0154] As an example, the general formula of the layered structure positive electrode active material is Li x A y Ni a Co b Mn c M (1-a-b-c) Y zwherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A comprises one or more of Na, K, Mg; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y comprises one or more of O, F. Specifically, the layered structure positive electrode active material can comprise one or more of lithium cobaltate LCO, lithium nickelate LNO, lithium manganate LMO, etc.

[0155] Optionally, the layered structure positive electrode active material is a ternary material, for example, 0 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), and LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523).

[0156] Specifically, the general formula of the olivine-type phosphate active material is Li x A y Me a M b P 1-c X c Y z wherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or more of Na, K, Mg; Me comprises one or more of Mn, Fe, Co, Ni; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X comprises one or more of S, Si, Cl, B, C, N; Y comprises one or more of O, F. Specifically, the olivine-type phosphate active material comprises one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0157] Specifically, the general formula of the spinel structure positive electrode active material is Li x Ay Mn a M 2-a Y z wherein 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A comprises one or more of Na, K, Mg; M comprises one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y comprises one or more of O, F. Specifically, the positive electrode active material of spinel structure comprises one or more of LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4, and Li 1.5 Mn2O4.

[0158] The battery cell will be accompanied by the de-embedding and consumption of active ions such as Li during the charging and discharging process, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the positive electrode active material in the embodiments of the application, the molar content of Li is the initial state of the material, i.e., the state before feeding, and the positive electrode active material is applied to the battery system, and after charging and discharging cycles, the molar content of Li may change.

[0159] In the enumeration of the positive electrode active material in the embodiments of the application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate.

[0160] In some embodiments, the positive electrode active material layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0161] In some embodiments, the positive electrode active material layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0162] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0163] Electrolyte

[0164] In some implementations, the battery cell also includes an electrolyte.

[0165] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates, while the electrolyte acts as a conductor for these active ions. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0166] The electrolyte comprises an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0167] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0168] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester 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).

[0169] In some embodiments, the electrolyte can further include an additive. For example, the additive can include a film-forming additive such as a cathode film-forming additive, etc., and can also include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0170] [Separator]

[0171] In some embodiments, the battery cell further includes a separator.

[0172] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0173] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0174] In some embodiments, the cathode electrode sheet, the separator, and the anode electrode sheet can be made into an electrode assembly through a rolling process and / or a stacking process.

[0175] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0176] In some embodiments, the outer package of the battery cell can be a hard shell such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package such as a pouch-type soft package. The material of the soft package can be plastic such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0177] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 is a battery cell 5 in a square structure as an example.

[0178] In some embodiments, as Figure 2As shown, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to requirements.

[0179] The method for preparing the battery cell of the present application is known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and the processes of vacuum packaging, standing, formation, shaping, etc. are performed to obtain the battery cell.

[0180] In some embodiments of the present application, the battery cell according to the present application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0181] Figure 3 is a schematic view of a battery module 4 as an example. As shown, Figure 3 In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0182] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0183] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0184] Figure 4 and Figure 5 is a schematic view of a battery pack 1 as an example. As shown, Figure 4 and Figure 5 In the battery pack 1, a battery box and a plurality of battery modules 4 arranged in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, the upper box body 2 is used to cover the lower box body 3 and forms a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0185] The battery of the embodiments of the present application can include one battery cell or a plurality of battery cells, and in the case of including a plurality of battery cells, the battery can include a battery module or a battery pack.

[0186] Electric device

[0187] The fifth aspect of the embodiments of the present application provides a power consuming device including at least one of the battery cell, the battery module or the battery pack of the present application. The battery cell, the battery module or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can be, but is not limited to, a mobile device (e.g., a mobile phone, a notebook computer, 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 and a satellite, an energy storage system, etc.

[0188] The power consuming device can select the battery cell, the battery module or the battery pack according to its use requirement.

[0189] Figure 6 is a schematic diagram of a power consuming device 6 as an example. The power consuming device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the power consuming device 6, a battery pack or a battery module can be used.

[0190] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device usually requires thin and light, and a battery cell can be used as a power source.

[0191] Embodiment

[0192] The embodiments described below more specifically describe the disclosure of the present application, and these embodiments are only used for illustrative explanation, because various modifications and changes within the scope of the disclosure of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments used in the embodiments are commercially available.

[0193] Preparation of silicon-carbon composite material

[0194] Step 1, after mixing the carbon-based substance and mixed acid, ultrasonic treatment for 3h, filter with polytetrafluoroethylene membrane and rinse with deionized water for 5 times until the pH of the filtrate is 6±0.5, after filtration, dry in a freeze-drying box at-50℃ for 12 hours to obtain the carbon-containing material; wherein the mass content ratio of the carbon-based substance and the mixed acid is (1 to 2):200; the mixed acid includes concentrated sulfuric acid and concentrated nitric acid, and the mass ratio is 1:1;

[0195] Step 2, after mixing ammonia, hydrogen peroxide and silicon-based substance, ultrasonic treatment for 40min; wherein the mass content ratio of ammonia, hydrogen peroxide and silicon-based substance is 100:100:(1 to 2);

[0196] Step 3, mix 20% organic compound aqueous solution with the product of step 2, continue ultrasonic treatment for 1.5h to obtain silicon-containing material; wherein the mass content ratio of organic compound and silicon-based substance is (1 to 5):1;

[0197] Step 4, add the product of step 1 to the reactor of step 3, continue ultrasonic mixing for 2.5h, filter with polytetrafluoroethylene aluminum membrane and rinse with deionized water for 4 times until the pH of the filtrate is 8±0.5, and finally dry in a drying box at-50℃ for 12 hours to obtain silicon-carbon composite material.

[0198] Preparation of lithium ion battery

[0199] 1、 Preparation of positive electrode sheet

[0200] An aluminum foil with a thickness of 12μm is used as the positive current collector.

[0201] The positive active material LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), a conductive agent, conductive carbon black, and a binder, polyvinylidene fluoride (PVDF), are mixed in a mass ratio of 85:10:5 in an appropriate amount of solvent N-methyl pyrrolidone (NMP) to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive current collector aluminum foil, and through processes such as drying, cold pressing, slitting, and cutting, a positive electrode sheet is obtained.

[0202] 2. Preparation of negative electrode sheet

[0203] A copper foil with a thickness of 8μm is used as the negative current collector.

[0204] The silicon-carbon composite material as the negative active material, the conductive agent conductive carbon black, polyacrylic acid (PAA) and the binder sodium carboxymethyl cellulose (CMC-Na) are mixed uniformly in deionized water according to a mass ratio of 92:2:3:3 to prepare a negative electrode slurry. The negative electrode slurry is coated on a current collector copper foil and dried at 85 DEG C, and then cold-pressed to obtain a negative electrode sheet containing a negative electrode film layer.

[0205] 3. Preparation of electrolyte

[0206] In an environment with a water content of less than 10 ppm, organic solvent ethylene carbonate EC and diethyl carbonate DEC are mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, and then lithium salt lithium hexafluorophosphate is added to the mixed solvent, stirred uniformly, and configured into an electrolyte with a lithium salt concentration of 1 mol / L.

[0207] 4. Preparation of lithium ion battery

[0208] The positive electrode sheet, the polyethylene PE separator film and the negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with an electrolyte, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain a lithium ion battery.

[0209] Example 1

[0210] In the silicon-carbon composite material, the carbon-based substance is single-walled carbon nanotubes, and the silicon-based substance is silicon nanowires.

[0211] The mass content ratio of the carbon-based substance to the mixed acid is 1:200.

[0212] The mass content ratio of the ammonia, hydrogen peroxide and silicon-based substance is 100:100:1.5.

[0213] The mass content ratio of the organic compound PDDA and the silicon-based substance is 2:1.

[0214] The mass content ratio of the carbon-containing material and the silicon-containing material is 5:1.

[0215] Examples 2-1 to 2-5

[0216] Different from Example 1, in the silicon-carbon composite material of Examples 2-1 to 2-5, the type of at least one of the carbon-based substance and the silicon-based substance is adjusted.

[0217] Examples 3-1 and 3-2

[0218] Different from Example 1, in the silicon-carbon composite material of Examples 3-1 and 3-2, the type of the group on the surface of the carbon-based substance is adjusted.

[0219] Examples 4-1 and 4-2

[0220] Different from Example 1, in the silicon-carbon composite materials of Example 4-1 and Example 4-2, the type of the organic compound on the surface of the silicon-based substance is adjusted.

[0221] Example 5-1 and Example 5-2

[0222] Different from Example 1, in the silicon-carbon composite materials of Example 5-1 and Example 5-2, the mass ratio of the carbon-based substance and the mixed acid is adjusted, so as to adjust the number of negative groups on the surface of the carbon-based substance.

[0223] In Example 5-1, the mass ratio of the carbon-based substance and the mixed acid is 1:100, and the number of negative groups in Example 5-1 is less than that in Example 1.

[0224] In Example 5-2, the mass ratio of the carbon-based substance and the mixed acid is 1:150, and the number of negative groups in Example 5-2 is less than that in Example 1, but more than that in Example 5-1.

[0225] Example 6-1 and Example 6-2

[0226] Different from Example 1, in the silicon-carbon composite materials of Example 6-1 and Example 6-2, the mass ratio of the silicon-based substance and PDDA (or ammonia, hydrogen peroxide and the silicon-based substance) is adjusted, so as to adjust the number of positive groups on the surface of the silicon-based substance.

[0227] Example 6-1

[0228] The mass content ratio of ammonia, hydrogen peroxide and the silicon-based substance is 100:100:1.

[0229] The mass content ratio of the organic compound PDDA and the silicon-based substance is 1:1; and the number of positive groups in Example 6-1 is less than that in Example 1.

[0230] Example 6-2

[0231] The mass content ratio of ammonia, hydrogen peroxide and the silicon-based substance is 100:100:2.

[0232] The mass content ratio of the organic compound PDDA and the silicon-based substance is 5:1; and the number of positive groups in Example 6-2 is more than that in Example 1.

[0233] Example 7-1 to Example 7-3

[0234] Different from Example 1, in the silicon-carbon composite materials of Example 7-1 to Example 7-3, the mass content ratio of the carbon-containing material and the silicon-containing material is adjusted.

[0235] Comparative Example 1

[0236] Unlike Example 1, the silicon-carbon composite material of Comparative Example 1 was prepared by the following steps:

[0237] The carbon-based substance and the carbon-based substance were mixed in NMP at a mass ratio of 5:1 and ultrasonically mixed for 2.5 h, and finally dried in a drying box at -50°C for 12 hours to obtain a silicon-carbon composite material.

[0238] Comparative Example 2

[0239] Unlike Example 1, the silicon-carbon composite material of Comparative Example 2 was prepared by the following steps:

[0240] Step 1, the carbon-based substance and the mixed acid were mixed and ultrasonically treated for 3 h, filtered using a polytetrafluoroethylene filter and washed with deionized water for 5 times until the pH of the filtrate was 6±0.5, and after filtration, dried in a freeze-drying box at -50°C for 12 hours to obtain a carbon-containing material; wherein the mass content ratio of the carbon-based substance and the mixed acid was 1:200; the mixed acid included concentrated sulfuric acid and concentrated nitric acid, and the mass ratio was 1:1;

[0241] Step 2, the silicon-based substance was added to the product of Step 1, and ultrasonically mixed for 2.5 h, filtered using a polytetrafluoroethylene aluminum membrane and washed with deionized water for 4 times until the pH of the filtrate was 8±0.5, and finally dried in a drying box at -50°C for 12 hours to obtain a silicon-carbon composite material.

[0242] Comparative Example 3

[0243] Unlike Example 1, the silicon-carbon composite material of Comparative Example 3 was prepared by the following steps:

[0244] Step 1, ammonia water, hydrogen peroxide and silicon-based substance were mixed and ultrasonically treated for 40 min for standby use; wherein the mass content ratio of ammonia water, hydrogen peroxide and silicon-based substance was 100:100:1.5;

[0245] Step 2, a 20% PDDA aqueous solution was mixed with the product of Step 1, and ultrasonically treated for 1.5 h to obtain a silicon-containing material; wherein the mass content ratio of PDDA and silicon-based substance was 2:1;

[0246] Step 3, the carbon-based substance was added to the reactor of Step 3, and ultrasonically mixed for 2.5 h, filtered using a polytetrafluoroethylene aluminum membrane and washed with deionized water for 4 times until the pH of the filtrate was 8±0.5, and finally dried in a drying box at -50°C for 12 hours to obtain a silicon-carbon composite material.

[0247] The relevant parameters of the examples and comparative examples are shown in Table 1.

[0248] Test section

[0249] 1. Cycle performance test of lithium ion battery

[0250] The lithium ion batteries prepared from the examples and comparative examples were charged to 4.0V at 0.33C, discharged to 2.0V at 0.33C, and full charge and full discharge cycle test was carried out at 25℃. When the capacity of the lithium ion battery was attenuated to 80% of the initial capacity, the cycle number was recorded.

[0251] 2. Kinetics performance test of lithium ion battery

[0252] The lithium ion batteries prepared from the examples and comparative examples were charged to 4.0V at 0.33C, discharged to 2.0V at 0.33C, and full charge and full discharge cycle test was carried out at 25℃. When the capacity of the lithium ion battery was attenuated to 80% of the initial capacity, the cycle number was recorded.

[0253] Test result

[0254] The test results are shown in Table 1

[0255] Table 1

[0256]

[0257] As can be seen from Table 1, the single-walled carbon nanotubes and silicon nanowires in Comparative Example 1 are physically mixed, the binding effect of the single-walled carbon nanotubes on the silicon nanowires is weak, and the volume expansion effect of the silicon nanowires cannot be well alleviated, which may lead to deterioration of the performance of the lithium ion battery.

[0258] Compared with Comparative Example 1, Comparative Example 2 modifies a negative electric group on the surface of the single-walled carbon nanotubes, and the binding effect of the single-walled carbon nanotubes on the silicon nanowires is still weak due to the weak force between the negative electric group and the silicon nanowires, and the volume expansion effect of the silicon nanowires cannot be well alleviated. Compared with Comparative Example 1, Comparative Example 3 modifies a positive electric group on the surface of the silicon nanowires, and the binding effect of the single-walled carbon nanotubes on the silicon nanowires is still weak due to the weak force between the positive electric group of the single-walled carbon nanotubes and the silicon nanowires, and the volume expansion effect of the silicon nanowires cannot be well alleviated.

[0259] The silicon-carbon composite material prepared by the method has the advantages that the carbon material and the silicon material are combined by electrostatic action through modification of negative electric groups on the surface of the single-walled carbon nanotubes and modification of positive electric groups on the surface of the silicon nanowires, the silicon material is surrounded by the carbon material, the carbon material acts as a buffer layer for expansion of the silicon, the risk of expansion of the silicon is reduced, the risk of pulverization of the silicon material is reduced, the structural stability of the silicon-carbon composite material as a whole is improved, the organic compounds on the surface of the silicon material can enhance physical cross-linking with the carbon material, the structural strength of the silicon-carbon composite material formed by the combination of the two is further improved, and the cycle life of the battery cell is improved.

[0260] Figure 7 The preparation process of the silicon-carbon composite material of Example 1 is described in Example 1. Figure 8 is an infrared spectrum of the single-walled carbon nanotubes MWCTN after acid treatment in Example 1, and a strong phenolic -OH stretching vibration peak is found near 3442 cm -1 and an alcohol hydroxyl carbon oxygen (C-O) stretching vibration peak appears near 1100 cm -1 The infrared results show that a large number of hydroxyl groups appear on the surface of the MWCTN after acid treatment. Figure 9 is the zeta potential test result of the MWCNT and the PDDA-treated silicon nanowires PDDA-Si after acid treatment, and the results show that the MWCNT after acid treatment exhibits negative charge, and the PDDA-Si surface exhibits positive charge.

[0261] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A silicon-carbon composite material, comprising: a carbon-containing material including a carbon-based substance and a first group provided on a surface of the carbon-based substance; and a silicon-containing material including a silicon-based substance and an organic compound coated on at least a part of a surface of the silicon-based substance, the organic compound and the first group being opposite in electric property, and the organic compound and the first group being combined by electrostatic interaction. The first group is a negative group.

2. The silicon-carbon composite material of claim 1, wherein, The first group includes at least one of a hydroxyl group, an amino group, an alkyl group, an acyloxy group, and an alkoxy group.

3. The silicon-carbon composite material of claim 1, wherein, The organic compound includes at least one of polydiallyldimethylammonium chloride, polyacrylamide, and polydimethyl diallyl ammonium chloride.

4. The silicon-carbon composite material of claim 1 or 2, wherein, The carbon-based substance includes at least one of natural graphite, artificial graphite, graphene, carbon nanotube, and carbon fiber; and / or 5. The silicon-carbon composite material of claim 1, wherein, The silicon-based substance includes at least one of silicon element and silicon oxide. The silicon element includes at least one of silicon nano-element and silicon micro-element.

6. The silicon-carbon composite material of claim 5, wherein, The silicon nano-element includes at least one of silicon nanoparticle, silicon nanowire, and silicon nanosheet.

7. The silicon-carbon composite of claim 6, wherein, The carbon-based substance includes at least one of carbon nanotube and carbon fiber.

8. The silicon-carbon composite material of claim 5, wherein, The silicon-based substance includes silicon nano-element. The carbon nanotube includes at least one of single-walled carbon nanotube and multi-walled nanotube.

9. The silicon-carbon composite material of claim 8, wherein, The silicon-based substance includes silicon nanowire.

10. The silicon-carbon composite material of claim 8, wherein, A ratio of a mass content of the carbon-containing material to a mass content of the silicon-containing material is (3 to 5): 1, based on a total mass of the silicon-carbon composite material.

11. The silicon-carbon composite material of claim 1, wherein, The mass content of the carbon-containing material is 75% to 85%; and / or 12. The silicon-carbon composite material of claim 11, wherein, The mass content of the silicon-containing material is 15% to 25%. 13.The silicon-carbon composite material according to claim 1, wherein A ratio of a mass content of the organic compound to a mass content of the silicon-based substance is (1 to 5): 20, based on a total mass of the silicon-carbon composite material. The mass content of the organic compound is 1% to 5%; and / or the mass content of the silicon-based substance is 15% to 20%.

14. The silicon-carbon composite of claim 13, wherein, The silicon-carbon composite material satisfies at least one of conditions (1) to (3):

15. The silicon-carbon composite of claim 1, wherein, (1) a volume average particle diameter Dv50 of the silicon-carbon composite material is 1 μm to 5 μm; (3) an electrical conductivity of the silicon-carbon composite material is 120 S / cm to 3000 S / cm. (2) the silicon-carbon composite material has a BET specific surface area of 200 m 2 / g to 400 m 2 / g; The electrical conductivity of the silicon-carbon composite material is 300 S / cm to 3000 S / cm.

16. The silicon-carbon composite of claim 15, wherein, 17.A method of manufacturing a silicon-carbon composite material, comprising: providing a carbon-based substance; subjecting the carbon-based substance to a group treatment to have a first group on a surface of the carbon-based substance and form a carbon-containing material; providing a silicon-based substance; providing an organic compound to the silicon-based substance to have the organic compound coated on at least a part of a surface of the silicon-based substance and form a silicon-containing material, wherein the organic compound and the first group are opposite in electric property; mixing the carbon-containing material and the silicon-containing material to obtain a silicon-carbon composite material, wherein the first group and the organic compound are combined by electrostatic interaction. ​ 18. A negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising the silicon-carbon composite material of any one of claims 1 to 16, or the silicon-carbon composite material prepared by the method of claim 17.

19. The negative electrode sheet according to claim 18, wherein the adhesion of the negative electrode sheet is 15 N / m to 20 N / m; and / or The negative electrode sheet has an elongation of 1.5% to 2.5% under a force of 1 x 10 4 Kg (10T).

20. The negative electrode sheet according to claim 19, wherein the adhesion of the negative electrode sheet is 17 N / m to 20 N / m.

21. The negative electrode sheet according to claim 19, wherein The negative electrode sheet has an elongation of 1.8% to 2.5% under a force of 1 x 10 4 Kg (10T).

22. A battery cell comprising the negative electrode sheet of any one of claims 18 to 21.

23. An electric device comprising the battery cell of claim 22.

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