Composite negative electrode material, preparation method, negative electrode sheet, battery and electrical equipment

Abstract

The present disclosure provides a composite negative electrode material, a preparation method, a negative electrode plate, a battery and an electrical device, wherein the composite negative electrode material comprises a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube; the carbon-tin composite nanowire comprises a tin nanowire and a carbon coating layer, and the carbon coating layer is coated on the surface of the tin nanowire; the carbon nanotube and the carbon-tin composite nanowire are attached to the porous silicon active material, wherein a part of the carbon-tin composite nanowire is attached to the pores of the porous silicon active material, and another part of the carbon-tin composite nanowire is extended and arranged in the outer area of ​​the porous silicon active material. The charge-discharge cycle performance of the silicon active material in the composite negative electrode material having the above structure is significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a composite negative electrode material, a preparation method, a negative electrode sheet, a battery and an electrical device. Background Art

[0002] A battery is a device that can store and release electrical energy. With the rapid development and widespread application of portable electronic devices and electric vehicles, further improving the specific capacity and cycle life of batteries has become an urgent need. Lithium-ion batteries are currently the most widely used battery system in commercial applications. Graphite is often used as the negative electrode material of lithium-ion batteries in traditional technologies. However, the theoretical specific capacity of graphite can only reach 372mAh / g, which limits the further improvement of battery capacity.

[0003] The theoretical specific capacity of silicon can reach 4200mAh / g, making it an ideal candidate for negative electrode materials. However, the volume change of silicon during the charge and discharge process exceeds 300%, which easily causes the silicon material to pulverize and fall off the current collector. Furthermore, the electronic conductivity of silicon materials is poor, and lithium ions are not easy to migrate into silicon materials during the charge and discharge process. The above factors together lead to poor battery cycle performance. Some traditional technologies propose to add carbon materials to silicon materials to improve the problems of silicon material shedding and pulverization and poor electronic conductivity, but the improvement effect is relatively limited, and there is still the problem of poor ion conductivity. Some traditional technologies propose to add carbon nanotubes and tin nanowires to silicon materials to alleviate the volume effect of silicon material lithium insertion and extraction and improve the ionic conductivity and electronic conductivity, but the cycle performance still needs to be further improved. Summary of the invention

[0004] Based on this, it is necessary to provide a composite negative electrode material to address the problems in the above background technology, and the composite negative electrode material can further improve the cycle performance of the silicon active material.

[0005] In a first aspect, the present disclosure provides a composite negative electrode material comprising a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube;

[0006] The carbon-tin composite nanowire comprises a tin nanowire and a carbon coating layer, wherein the carbon coating layer is coated on the surface of the tin nanowire; the carbon nanotube and the carbon-tin composite nanowire are attached to the porous silicon active material, wherein a portion of the carbon-tin composite nanowire is attached to the pores of the porous silicon active material, and another portion of the carbon-tin composite nanowire is extended to the external area of ​​the porous silicon active material.

[0007] In some embodiments of the present disclosure, the porous silicon active material has through holes, wherein:

[0008] One end of the carbon-tin composite nanowire is located in the through hole, and the other end is located in the external area of ​​the porous silicon active material, or the carbon-tin composite nanowire is passed through the through hole and both ends are located in the external area of ​​the porous silicon active material.

[0009] In some embodiments of the present disclosure, the tin nanowires are formed by in-situ growth in the pores of the porous silicon active material.

[0010] In some embodiments of the present disclosure, part of the carbon-tin composite nanowires are wound and attached to the surface of the porous silicon active material.

[0011] In some embodiments of the present disclosure, the diameter of the carbon-tin composite nanowire is ≤100 nm, and the aspect ratio of the carbon-tin composite nanowire is 5-1000.

[0012] In some embodiments of the present disclosure, the particle size of the porous silicon active material is 20 nm to 1000 nm, and the pore size of the pores in the porous silicon active material is 5 nm to 200 nm.

[0013] In some embodiments of the present disclosure, the porous silicon active material includes one or more of silicon element, silicon monoxide and silicon alloy.

[0014] In some embodiments of the present disclosure, the diameter of the carbon nanotube is ≤20 nm, and the aspect ratio of the carbon nanotube is 10-1000.

[0015] In some embodiments of the present disclosure, in the overall structure of the porous silicon active material, the carbon-tin composite nanowires and the carbon nanotubes, the mass proportion of silicon element is 70% to 98%, the mass proportion of tin element is 0.5% to 20%, and the mass proportion of carbon element is 1.5% to 20%.

[0016] In a second aspect, the present disclosure also provides a method for preparing a composite negative electrode material, which comprises the following steps:

[0017] mixing a porous silicon active material, a tin source and carbon nanotubes to obtain a mixed precursor;

[0018] The mixed precursor is placed in a carbon-containing reducing atmosphere for calcination to form the carbon-tin composite nanowire.

[0019] In a third aspect, the present disclosure further provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, wherein the negative electrode active layer includes the composite negative electrode material as described in any of the above embodiments.

[0020] In a fourth aspect, the present disclosure further provides a battery, comprising a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode are arranged opposite to each other, and the negative electrode comprises the negative electrode plate as described in any of the above embodiments.

[0021] In a fifth aspect, the present disclosure further provides an electrical device, wherein the electrical device comprises a functional body and a battery as described in the above embodiment, wherein the battery is used to supply energy to the functional body.

[0022] The composite negative electrode material disclosed in the present invention comprises a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube, and has at least the following beneficial effects.

[0023] The use of carbon nanotubes and carbon-tin composite nanowires can construct a three-dimensional conductive network between the particles of the porous silicon active material, which can promote the conduction of electrons to the surface of the porous silicon active material while alleviating the volume change of the porous silicon active material. Tin nanowires have excellent ion conductivity, and the carbon coating layer can ensure the stability and integrity of the structure of the tin nanowires during the charge and discharge process. The carbon-tin composite nanowires can promote the conduction of ions into the porous silicon active material during the charge and discharge process. On the basis of the above, a part of the carbon-tin composite nanowire is arranged in the pores of the porous silicon active material, which is conducive to promoting the conduction of ions toward the inside of the porous silicon active material, and further increasing the ions that the porous silicon active material can actually receive. In addition, the carbon-tin composite nanowires located in the pores can also support the pore structure of the porous silicon active material, thereby playing a role in buffering the volume change of the porous silicon active material and inhibiting its pulverization. Therefore, the charge and discharge cycle performance of the silicon active material in the composite negative electrode material having the above structure is significantly improved.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic diagram of the partial structure of a composite negative electrode material disclosed in the present invention;

[0027] Figure 2 This is a diagram showing the observation results of the composite negative electrode material prepared in Example 2 observed using a transmission electron microscope;

[0028] Figure 3 This is a diagram showing the observation results of the composite negative electrode material prepared in Comparative Example 2 using a transmission electron microscope. DETAILED DESCRIPTION

[0029] To facilitate understanding of the present invention, a more comprehensive description of the present invention is provided below. The preferred embodiments of the present invention are given herein. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the content of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this document pertains. The terms used herein in the specification of this document are only for describing specific embodiments and are not intended to limit this document.

[0031] It should be understood that when an element or layer is referred to as being "on, "adjacent to, "connected to, or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, "directly adjacent to, "directly connected to, or "directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion.

[0032] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein for ease of description to describe the relationship of one element or feature to other elements or features. It should be understood that the spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be otherwise oriented (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used may be interpreted accordingly.

[0033] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms of "a", "an" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0034] The present disclosure provides a composite negative electrode material, including a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube. The carbon-tin composite nanowire includes a tin nanowire and a carbon coating layer, wherein the carbon coating layer is coated on the surface of the tin nanowire; the carbon nanotube and the carbon-tin composite nanowire are attached to the porous silicon active material, wherein a portion of the carbon-tin composite nanowire is attached to the pores of the porous silicon active material, and another portion of the carbon-tin composite nanowire is extended and arranged in the outer region of the porous silicon active material.

[0035] The composite negative electrode material disclosed in the present invention comprises a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube, and has at least the following beneficial effects.

[0036] The use of carbon nanotubes and carbon-tin composite nanowires can construct a three-dimensional conductive network between the particles of the porous silicon active material, which can promote the conduction of electrons to the surface of the porous silicon active material while alleviating the volume change of the porous silicon active material. Tin nanowires have excellent ion conductivity, the carbon coating layer can ensure the stability and integrity of the structure of the tin nanowires during the charge and discharge process, and the carbon-tin composite nanowires can promote the conduction of ions to the surface of the porous silicon active material during the charge and discharge process. On the basis of the above, a part of the carbon-tin composite nanowire is arranged in the pores of the porous silicon active material, which is conducive to promoting the conduction of ions toward the inside of the porous silicon active material, and further increasing the ions that the porous silicon active material can actually receive. In addition, the carbon-tin composite nanowires located in the pores can also support the pore structure of the porous silicon active material, thereby playing a role in buffering the volume change of the porous silicon active material and inhibiting its pulverization. Therefore, the charge and discharge cycle performance of the silicon active material in the composite negative electrode material having the above structure is significantly improved.

[0037] Figure 1 Schematic diagram of the partial structure of a composite negative electrode material disclosed in the present invention. Figure 1As shown, the composite negative electrode material includes a porous silicon active material, a carbon-tin composite nanowire and a carbon nanotube. The carbon-tin composite nanowire includes a tin nanowire and a carbon coating layer, wherein the carbon coating layer is coated on the surface of the tin nanowire; the carbon nanotube and the carbon-tin composite nanowire are attached to the porous silicon active material, wherein a portion of the carbon-tin composite nanowire is attached to the pores of the porous silicon active material, and another portion of the carbon-tin composite nanowire is extended to the outer region of the porous silicon active material. It can be understood that the carbon-tin composite nanowire is used to promote the conduction of electrons and ions in the outer region of the porous silicon active material toward the pores.

[0038] It can be understood that in this embodiment, the porous silicon active material may include a plurality of porous silicon particles, wherein the porous silicon particles have holes, wherein the porous silicon particles may be purchased from the market, or may be obtained by etching the silicon particles in a chemical etching manner.

[0039] As some examples of this embodiment, the porous silicon particles in the porous silicon active material may be in a spherical shape, a flake shape, or other irregular shapes.

[0040] As some examples of this embodiment, the porous silicon active material may have one or more holes. It is understood that the porous silicon active material with multiple holes can accommodate more carbon-tin composite nanowires, thereby accepting more electrons and ions, thereby enabling the battery to have a higher charge and discharge rate.

[0041] As some examples of this embodiment, the porous silicon active material may be provided with a through hole penetrating the porous silicon active material. One end of the carbon-tin composite nanowire is located in the through hole, and the other end is located in the outer region of the porous silicon active material.

[0042] As some examples of this embodiment, the porous silicon active material may be provided with a through hole penetrating the porous silicon active material. The carbon-tin composite nanowire is penetrated in the through hole and both ends thereof can be located in the outer region of the porous silicon active material.

[0043] As some examples of this embodiment, a blind hole with one end open and one section closed may also be provided in the porous silicon active material. One end of the carbon-tin composite nanowire is located in the blind hole, and the other end is located in the outer area of ​​the porous silicon active material.

[0044] As some examples of this embodiment, multiple carbon-tin composite nanowires may be disposed in the same hole of the porous silicon active material. Further, among the multiple carbon-tin composite nanowires, each carbon-tin composite nanowire may be disposed in a through hole of the porous silicon active material and both ends are located in the external region of the porous silicon active material, and each carbon-tin composite nanowire may also have one end located in the through hole of the porous silicon active material and one end located in the external region of the porous silicon active material.

[0045] As some examples of this embodiment, tin nanowires are grown in situ in the holes of the porous silicon active material. It can be understood that when the tin nanowires are grown in situ, the tin nanowires can contact the pore walls of the holes in the porous silicon active material and fit into the pore walls. This can ensure the stability of the carbon-tin composite nanowires on the one hand, and can further promote the conduction of electrons and ions to the interior of the porous silicon active material on the other hand.

[0046] As some examples of this embodiment, some carbon-tin composite nanowires are wound and attached to the surface of the porous silicon active material, which can increase the contact area between the carbon-tin composite nanowires and the porous silicon active material and also help maintain the structural stability of the porous silicon active material.

[0047] As some examples of this embodiment, nanotubes are wound and attached to the surface of the porous silicon active material.

[0048] As some examples of this embodiment, the diameter of the carbon-tin composite nanowire is ≤100 nm. In some examples, the diameter of the carbon-tin composite nanowire can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or the diameter of the carbon-tin composite nanowire can be between any two of the above diameters.

[0049] As some examples of this embodiment, the aspect ratio of the carbon-tin composite nanowire is 5 to 1000. In some examples, the aspect ratio of the carbon-tin composite nanowire is 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or the aspect ratio of the carbon-tin composite nanowire can also be between any two of the above ratios.

[0050] As some examples of this embodiment, the particle size of the porous silicon active material is 20nm~1000nm. In some examples, the particle size of the porous silicon active material is 20nm, 50nm, 100nm, 200nm, 300nm, 500nm, 700nm, 900nm, 1000nm, or the particle size of the porous silicon active material can also be between any two of the above particle sizes.

[0051] As some examples of this embodiment, the pores in the porous silicon active material have a pore size of 5 nm to 200 nm. In some examples, the pore size of the porous silicon active material is 5 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, or the pore size of the porous silicon active material may also be between any two of the above pore sizes.

[0052] As some examples of this embodiment, the porous silicon active material includes one or more of silicon simple substance, silicon monoxide, and silicon alloy.

[0053] As some examples of this embodiment, the porous silicon active material further includes a modified coating layer, and the material of the modified coating layer is selected from one or more of carbon, oxides and organic matter.

[0054] As some examples of this embodiment, the diameter of the carbon nanotube is ≤20nm. In some examples, the diameter of the carbon nanotube can be 1nm, 2nm, 3nm, 5nm, 8nm, 10nm, 12nm, 15nm, 18nm, 20nm, or the diameter of the carbon nanotube can be between any two of the above diameters.

[0055] As some examples of this embodiment, the aspect ratio of the carbon nanotube is 10 to 1000. In some examples, the aspect ratio of the carbon nanotube is 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or the aspect ratio of the carbon nanotube can also be between any two of the above ratios.

[0056] As some examples of this embodiment, the carbon nanotubes may be selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0057] As some examples of this embodiment, in the whole composed of porous silicon active material, carbon-tin composite nanowires and carbon nanotubes, the mass proportion of silicon element is 70% to 98%. For example, the mass proportion of silicon element is 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, or the mass proportion of silicon element can also be between any two of the above proportions. It can be understood that the silicon element mainly comes from the porous silicon active material.

[0058] As some examples of this embodiment, in the whole composed of porous silicon active material, carbon tin composite nanowires and carbon nanotubes, the mass proportion of tin element is 0.5% to 20%. For example, the mass proportion of tin element is 0.5%, 1%, 2%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, or the mass proportion of tin element can also be between any two of the above proportions. It can be understood that the tin element is mainly located in the tin nanowires.

[0059] As some examples of this embodiment, in the whole composed of porous silicon active material, carbon-tin composite nanowires and carbon nanotubes, the mass proportion of carbon element is 1.5% to 20%. For example, the mass proportion of carbon element is 1.5%, 2%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, or the mass proportion of carbon element can also be between any two of the above proportions. It can be understood that the carbon element is located in the carbon nanotubes and the carbon coating layer.

[0060] It is understood that the active material in the composite negative electrode material may include other active materials in addition to the porous silicon active material. As some examples of this embodiment, the composite negative electrode material may also include one or more of graphite, hard carbon and soft carbon.

[0061] The present disclosure also provides a method for preparing a composite negative electrode material, which comprises the following steps: mixing a porous silicon active material, a tin source and carbon nanotubes to obtain a mixed precursor, and calcining the mixed precursor in a carbon-containing reducing atmosphere to form carbon-tin composite nanowires.

[0062] As some examples of this embodiment, the steps of mixing the porous silicon active material, the tin source and the carbon nanotubes include: dispersing the porous silicon active material and the surfactant in the carbon nanotube solution, filtering and drying after mixing evenly to form a mixture; dispersing the tin source in the solvent, filtering and drying after mixing evenly, and then mixing with the mixture to form a mixed precursor.

[0063] In some examples, the surfactant can include polyvinyl pyrrolidone (PVP).

[0064] In some examples, the tin source can be selected from compounds containing the element tin, such as stannous oxide.

[0065] As some examples of this embodiment, in the step of placing the mixed precursor in a carbon-containing reducing atmosphere for calcining, the calcining temperature may be 650° C. to 900° C.

[0066] In some examples, the calcination temperature is 650° C., 700° C., 750° C., 800° C., 950° C., or 900° C. Alternatively, the calcination temperature may be between any two of the above temperatures.

[0067] In some examples, the carbon-containing reducing atmosphere may include hydrocarbons such as one or more of acetylene and ethylene.

[0068] It can be understood that during the calcination process, the carbon-containing reducing atmosphere reduces the tin source and generates tin atoms. The pore walls of the pores in the porous silicon active material can reduce the difficulty of nucleation, so the tin atoms can begin to grow and extend on the pore wall surface of the pores in the porous silicon active material, and finally form tin nanowires. At the same time, the carbon atoms generated by the decomposition of the carbon-containing gas are in situ attached to the surface of the tin nanowires, and form a carbon coating layer covering the surface of the tin nanowires.

[0069] It can be understood that after the calcination is completed, the composite negative electrode material of the present disclosure can be formed.

[0070] On the other hand, the present disclosure further provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, wherein the negative electrode active layer includes the composite negative electrode material as described in any of the above embodiments.

[0071] As some examples of this embodiment, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. Among them, in the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0072] As some examples of this embodiment, the negative electrode active layer may further include one or more of a conductive agent and a binder.

[0073] In the negative electrode active layer, the conductive agent may be selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon nanofibers.

[0074] In the negative electrode active layer, the binder may be selected from one or more of polyvinyl pyrrolidone, polyvinylidene fluoride, polyethylene oxide, polytetrafluoroethylene, carboxymethyl cellulose and a copolymer of styrene and butadiene.

[0075] On the other hand, the present disclosure further provides a battery, which includes a positive electrode and a negative electrode, the positive electrode and the negative electrode are arranged opposite to each other, and the negative electrode includes a negative electrode plate as described in any of the above embodiments.

[0076] As some examples of this embodiment, the positive electrode may include a positive electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer.

[0077] As some examples of this embodiment, the positive electrode active layer includes a positive electrode active material selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, layered ternary positive electrode materials, spinel lithium nickel manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese phosphate and lithium cobalt phosphate.

[0078] As some examples of this embodiment, the positive electrode active layer may further include one or more of a conductive agent and a binder.

[0079] In the positive electrode active layer, the conductive agent may be selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon nanofibers.

[0080] In the positive electrode active layer, the binder may be selected from one or more of polyvinyl pyrrolidone, polyvinylidene fluoride, polyethylene oxide, polytetrafluoroethylene, carboxymethyl cellulose and a copolymer of styrene and butadiene.

[0081] As some examples of this embodiment, the battery may further include a separator, which is disposed between the positive electrode sheet and the negative electrode sheet.

[0082] As some examples of this embodiment, the battery may further include an electrolyte, the electrolyte infiltrating the isolation membrane, the positive electrode active layer and the negative electrode active layer.

[0083] On the other hand, the present disclosure further provides an electrical device, which includes a functional body and a battery as described in any of the above embodiments, wherein the battery is used to supply energy to the functional body.

[0084] As some examples of this embodiment, the power-consuming device may be a mobile phone, a laptop computer, a smart watch, or an electric car.

[0085] In order to facilitate understanding of the specific implementation methods and beneficial effects of the present disclosure, the present disclosure also provides the following more specific examples and comparative examples. Through the description of the examples and comparative examples, the beneficial effects of the present disclosure will also be more obvious.

[0086] Example 1

[0087] Preparation of composite negative electrode material: Add porous silicon particles with a particle size of 5μm~10μm and polyvinyl pyrrolidone to the carbon nanotube solution and disperse them in a homogenizer. Grind the homogenized suspension in a sand mill, filter, wash and dry to obtain a uniformly dispersed mixture. Disperse stannous oxide in a solvent and disperse them in a homogenizer. Grind the homogenized suspension in a sand mill, filter, wash and dry to obtain uniformly dispersed stannous oxide. Mix the stannous oxide with the mixture and put it into a sintering furnace. Pass a mixed gas of nitrogen and acetylene and heat it to 700℃ for calcination. After calcination, a composite negative electrode material is formed.

[0088] It has been determined that in this composite negative electrode material, by weight percentage, silicon accounts for 82.4% of the composite negative electrode material, tin accounts for 5.6% of the negative electrode material, carbon accounts for 9.9% of the negative electrode material, and other elements account for 2.1% of the negative electrode material.

[0089] Preparation of negative electrode sheet: The composite negative electrode material, Super P and sodium alginate prepared above are dispersed in water at a mass ratio of 80:5:15 and stirred evenly to form a slurry. The slurry is scraped onto the surface of the copper foil and then dried to form a negative electrode sheet.

[0090] Preparation of electrolyte: A mixed solvent of EC, DMC and FEC in a volume ratio of 4.8:4.8:0.4 was used, and lithium hexafluorophosphate with a concentration of 1 mol / L was dissolved therein to form an electrolyte.

[0091] Prepare half-cell: Pair the negative electrode sheet with the lithium sheet, use Celgard2300 as an isolation membrane to separate the negative electrode sheet and the lithium sheet, inject electrolyte, and form a button-type half-cell.

[0092] Example 2

[0093] The only difference between Example 2 and Example 1 is that Example 2 uses a porous silicon sheet material with a thickness of 5nm~100nm and a plane size of 100nm~2000nm to replace the porous silicon particles in Example 1.

[0094] Example 3

[0095] The only difference between Example 3 and Example 1 is that Example 3 uses porous silicon oxide particles with a particle size of 5 μm to 10 μm to replace the porous silicon particles in Example 1.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is only the step of preparing the composite negative electrode material. In Comparative Example 1, tin nanowires are used instead of stannous oxide in Example 1.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 2 is only the step of preparing the composite negative electrode material. In Comparative Example 2, tin nanowires are used instead of stannous oxide in Example 2.

[0100] Comparative Example 3

[0101] The difference between Comparative Example 3 and Example 3 is only the step of preparing the composite negative electrode material. In Comparative Example 3, tin nanowires are used instead of stannous oxide in Example 3.

[0102] Comparative Example 4

[0103] The difference between Comparative Example 4 and Example 1 is only the step of preparing the composite negative electrode material. In Comparative Example 4, only porous silicon particles are used, and carbon nanotubes and stannous oxide are not added.

[0104] Comparative Example 5

[0105] The difference between Comparative Example 5 and Example 1 is only the step of preparing the composite negative electrode material. In Comparative Example 5, silicon particles without pores on the surface are used instead of porous silicon particles.

[0106] Comparative Example 6

[0107] The difference between Comparative Example 6 and Example 1 is only the step of preparing the composite negative electrode material. In Comparative Example 6, the carbon nanotubes are in-situ grown on the surface of the porous silicon particles in the following manner: the loaded iron nanoparticles are deposited on the surface of the porous silicon particles, and then placed in a tube furnace and a mixed gas of acetylene and hydrogen is introduced, and the carbon nanotubes are grown on the surface of the porous silicon particles by chemical vapor deposition. In Comparative Example 6, no stannous oxide or tin nanowires are added.

[0108] Comparative Example 7

[0109] The difference between Comparative Example 7 and Comparative Example 6 is only the step of preparing the composite negative electrode material. In Comparative Example 7, the carbon nanotubes are in-situ grown on the surface of the porous silicon particles, and Comparative Example 7 also uses tin nanowires instead of stannous oxide in Example 1.

[0110] Test 1: The composite negative electrode materials prepared in Example 2 and Comparative Example 2 were observed using a transmission electron microscope. The observation results can be seen in the following figures: Figure 2 and Figure 3 .

[0111] Reference Figure 2 and Figure 3 As shown in the figure, through the contrast comparison in the figure, it can be seen that in the composite negative electrode material prepared in Example 2, part of the carbon-coated tin nanowires are obviously located inside the porous silicon material, which means that the tin nanowires grow based on the pores of the porous silicon material and extend to the outer area of ​​the porous silicon material. Comparative Example 2 directly adds tin nanowires to the raw materials, and the tin nanowires are only wrapped around the surface of the silicon material and cannot extend into the pores of the porous silicon material.

[0112] Test 2: The half-cells of each embodiment and comparative example were charged and discharged at a constant current using a Blue Electric charge and discharge tester. The cut-off voltage was set to 0.005 V ~ 1.0 V, the rate was set to 0.2C, and the charge and discharge cycle was 100 times. The first-week charging capacity, first-week coulomb efficiency, 100th-week cycle charging capacity and cycle capacity retention rate of each battery were tested. The results can be seen in Table 1.

[0113] Table 1

[0114]

[0115] As shown in Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 3 all use stannous oxide as the raw material of tin nanowires, and the tin nanowires are grown in situ based on the porous silicon material during the preparation process. Examples 1, 2, and 3 have significantly higher cycle capacity retention rates, which is mainly due to the fact that the tin nanowires can grow in situ based on the holes of the porous silicon material during the preparation process, which promotes the conduction of electrons and ions to the surface of the porous silicon active material during the charge and discharge process.

[0116] Furthermore, Comparative Example 4 uses porous silicon particles as active materials, and does not introduce carbon nanotubes and tin nanowires. Its cycle capacity retention rate is low, indicating that the charge and discharge performance of the porous silicon particles themselves is poor. Comparative Example 5 uses silicon particles without holes on the surface, and its cycle capacity retention rate is similar to that of Comparative Example 1. That is, the actual performance of growing tin nanowires on the surface of non-porous silicon material is similar to that of directly mixing tin nanowires with porous silicon material, which also shows that growing tin nanowires on the surface of porous silicon material can effectively improve the actual performance of the battery.

[0117] In addition, unlike Example 1, Comparative Example 6 uses porous silicon as a raw material and grows carbon nanotubes on its surface, so that the carbon nanotubes can be grown in situ from the pores of porous silicon. In addition, tin nanowires are not introduced in Comparative Example 6. Referring to the contents shown in Table 1, the first cycle charging capacity of Comparative Example 6 is significantly lower than that of Example 1. This may be because although carbon nanotubes have good electronic conductivity, they basically do not have ion conductivity. Carbon nanotubes are densely distributed on the surface of porous silicon particles, which hinders the further transmission of lithium ions into the porous silicon particles, making it difficult for porous silicon materials to be fully discharged. Although Comparative Example 7 is additionally provided with tin nanowires on the basis of Comparative Example 6, its charge and discharge performance is similar to that of Comparative Example 6. This is mainly because the in-situ grown carbon nanotubes block the contact between the tin nanowires and the porous silicon particles, resulting in the introduction of tin nanowires not being able to further improve the ion conductivity of the composite negative electrode material.

[0118] Please note that the above embodiments are for illustrative purposes only and are not meant to be limiting of this document.

[0119] It should be understood that, unless otherwise specified herein, there is no strict order restriction for the execution of the steps, and the steps may be executed in other orders. Moreover, at least a portion of the steps in the preparation process may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0120] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0121] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A composite negative electrode material, characterized in that: including porous silicon active materials, carbon-tin composite nanowires and carbon nanotubes; The carbon-tin composite nanowire comprises a tin nanowire and a carbon coating layer, wherein the carbon coating layer is coated on the surface of the tin nanowire; the carbon nanotube and the carbon-tin composite nanowire are attached to the porous silicon active material, wherein a portion of the carbon-tin composite nanowire is attached to the pores of the porous silicon active material, and another portion of the carbon-tin composite nanowire is extended to the outer region of the porous silicon active material; The tin nanowires are in-situ grown in the pores of the porous silicon active material. The preparation method of the composite negative electrode material comprises the following steps: The carbon nanotube solution and the porous silicon active material are homogenously dispersed in a homogenizer, stannous oxide is dispersed in a solvent and homogenized in a homogenizer, and then the homogenized stannous oxide, carbon nanotubes and porous silicon active material are mixed to obtain a mixed precursor, wherein the pores in the porous silicon active material have a pore size of 5 nm to 200 nm; The mixed precursor is placed in a carbon-containing reducing atmosphere for calcination to form the carbon-tin composite nanowire.

2. The composite negative electrode material according to claim 1, characterized in that: The porous silicon active material has through holes, wherein: One end of the carbon-tin composite nanowire is located in the through hole, and the other end is located in the external area of ​​the porous silicon active material, or the carbon-tin composite nanowire is passed through the through hole and both ends are located in the external area of ​​the porous silicon active material.

3. The composite negative electrode material according to claim 2, characterized in that: Part of the carbon-tin composite nanowires is wound and attached to the surface of the porous silicon active material.

4. The composite negative electrode material according to any one of claims 1 to 3, characterized in that The diameter of the carbon-tin composite nanowire is ≤100nm, and the aspect ratio of the carbon-tin composite nanowire is 5-1000.

5. The composite negative electrode material according to any one of claims 1 to 3, characterized in that: The particle size of the porous silicon active material is 20nm-1000nm.

6. The composite negative electrode material according to any one of claims 1 to 3, characterized in that: The porous silicon active material includes one or more of silicon simple substance, silicon monoxide and silicon alloy.

7. The composite negative electrode material according to any one of claims 1 to 3, characterized in that: The diameter of the carbon nanotube is ≤20nm, and the aspect ratio of the carbon nanotube is 10-1000.

8. The composite negative electrode material according to any one of claims 1 to 3, characterized in that: In the composition of the porous silicon active material, the carbon-tin composite nanowires and the carbon nanotubes, the mass proportion of silicon is 70% to 98%, the mass proportion of tin is 0.5% to 20%, and the mass proportion of carbon is 1.5% to 20%.

9. A method for preparing a composite negative electrode material according to any one of claims 1 to 8, characterized in that: The steps include: The carbon nanotube solution and the porous silicon active material are homogenously dispersed in a homogenizer, stannous oxide is dispersed in a solvent and homogenized in a homogenizer, and then the homogenized stannous oxide, carbon nanotubes and porous silicon active material are mixed to obtain a mixed precursor, wherein the pores in the porous silicon active material have a pore size of 5 nm to 200 nm; The mixed precursor is placed in a carbon-containing reducing atmosphere for calcination to form the carbon-tin composite nanowire.

10. The method for preparing a composite negative electrode material according to claim 9, characterized in that: In the step of placing the mixed precursor in a carbon-containing reducing atmosphere for calcination, the calcination temperature is 650° C. to 900° C.

11. A negative electrode plate, characterized in that: It comprises a negative electrode current collector and a negative electrode active layer arranged on the negative electrode current collector, wherein the negative electrode active layer comprises the composite negative electrode material according to any one of claims 1 to 8.

12. A battery, characterized in that: It comprises a positive electrode and a negative electrode, the positive electrode and the negative electrode are arranged opposite to each other, and the negative electrode comprises the negative electrode sheet as claimed in claim 11.

13. An electrical equipment, characterized in that: The electric device comprises a functional body and the battery as claimed in claim 12, wherein the battery is used to supply energy to the functional body.

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