Preparation method of integrated silicon-carbon negative electrode material

Abstract

The invention discloses a preparation method of an integrated silicon-carbon negative electrode material, and relates to the technical field of silicon-carbon negative electrode materials. The preparation method comprises the following steps: sequentially adding a modified material, a silicon material and a carbon source material into an organic solvent, and stirring for a preset time under a preset temperature condition to prepare a precursor solution; performing electrostatic spinning treatment on the precursor solution to obtain an electrostatic spinning sample; carrying out solvent removal treatment, pre-oxidation and heat treatment on the electrostatic spinning sample in sequence to prepare the integrated silicon-carbon negative electrode material; wherein the modified material is any one of molybdenum phosphate or copper acetate, the mass ratio of the carbon source material to the modified material to the silicon material is any one of (10-14): (1-4): 4, and the heating rate of heat treatment is any one of 1 DEG C * min <-1 > to 10 DEG C * min <-1 >. By adding the modified material, the silicon material and the carbon source material and combining the electrostatic spinning process, the integrated silicon-carbon negative electrode material with excellent electrical properties is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-carbon negative electrode materials, and in particular to a method for preparing an integrated silicon-carbon negative electrode material. Background Art

[0002] Lithium-ion batteries, widely used energy storage devices in consumer electronics, electric vehicles, and energy storage systems, rely heavily on the development of high-performance electrode materials. Silicon, with its theoretical specific capacity of approximately 4200 mAh / g, is considered a promising next-generation anode material. However, silicon experiences significant volume expansion (up to 300% or more) during the lithium insertion / delithiation process, which can cause electrode pulverization, conductive network fracture, and repeated rupture of the solid electrolyte interface membrane, severely impacting its cycle life and rate performance.

[0003] In the prior art, silicon-carbon composite fibers are prepared through electrospinning, combining silicon particles with carbon materials to improve their cycling stability. However, the prior art lacks an integrated structural design when preparing silicon-carbon composite anodes. Most methods employ coating and electrode slurry application, resulting in a wide variety of materials and increased costs during the material addition phase. Furthermore, the poor conductivity of the carbon fiber materials prevents them from forming high-performance electrode materials. Furthermore, the pre-oxidation and carbonization process utilizes a chemical vapor deposition furnace as pre-oxidation equipment, increasing the cost of electrode material preparation and preventing mass production.

[0004] Therefore, there is an urgent need for a preparation process that utilizes electrospinning technology, combines functional modifiers and optimizes heat treatment conditions to construct an integrated silicon-carbon negative electrode material with stable structure, high electrical conductivity and excellent cycle life. Summary of the Invention

[0005] One object of the present invention is to provide a method for preparing an integrated silicon-carbon negative electrode material, so as to solve the technical problems in the prior art that the raw materials for preparing silicon-carbon negative electrode materials are complex and silicon easily expands in volume, resulting in a decrease in the electrical performance of the negative electrode material.

[0006] Another purpose of the present invention is to further achieve precise control of the morphology, conductivity and structural stability of electrode materials.

[0007] According to the purpose of the present invention, the present invention provides a method for preparing an integrated silicon-carbon negative electrode material, comprising:

[0008] Adding the modified material and the silicon material into an organic solvent, and preparing a first precursor solution after ultrasonic treatment;

[0009] Adding a carbon source material to the first precursor solution and stirring the solution at a preset temperature for a preset time to prepare a second precursor solution;

[0010] preparing an electrospinning sample by electrospinning the second precursor solution;

[0011] The electrospinning sample is subjected to solvent removal treatment, pre-oxidation and heat treatment in sequence to prepare an integrated silicon-carbon negative electrode material; wherein,

[0012] The modified material is any one of molybdenum phosphate or copper acetate, the mass ratio of the carbon source material, the modified material and the silicon material is any value of (10-14):(1-4):4, the pre-oxidation is carried out in a blast drying oven, and the heating rate of the heat treatment is 1°C·min -1 -10℃·min -1 Any value in .

[0013] Optionally, the pre-oxidation temperature is any value between 200°C and 300°C, the pre-oxidation time is any value between 2h and 5h, the heat treatment temperature is any value between 700°C and 900°C, and the heat treatment time is any value between 0.5h and 2h.

[0014] Optionally, the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide.

[0015] Optionally, the particle size of the silicon particles in the silicon material is any value between 20 nm and 40 nm.

[0016] Optionally, the carbon source material is any one of polyacrylonitrile, polyvinyl pyrrolidone, polymethyl methacrylate, polyacrylic acid or polydopamine.

[0017] Optionally, the preset temperature is any value between 60° C. and 80° C., and the preset time is any value between 10 hours and 12 hours.

[0018] Optionally, the ultrasonic treatment time is any value between 0.5h and 1.5h.

[0019] Optionally, the voltage of the electrospinning treatment is any value between 15kV and 30kV, the distance between the needle and the collecting roller is any value between 10cm and 20cm, and the liquid pushing speed is any value between 0.5mL / h and 2mL / h.

[0020] Optionally, the rotation speed of the electrospinning drum is any value between 10 rpm and 90 rpm, and the moving speed of the slide is any value between 10 mm / s and 20 mm / s.

[0021] Optionally, the electrospinning time of the electrospinning treatment is any value between 6.5h and 10h.

[0022] The present invention, by first introducing modifier and silicon material in the first precursor solution, realizes in-situ coating and uniform dispersion of modifier to silicon surface, and then synergizes with the carbon source material added subsequently, i.e., makes the second precursor solution build the silicon-carbon composite fiber network with stable structure in electrostatic spinning process, thus constructs efficient electron transmission channel, simultaneously realizes flexible coating and stress buffering to silicon particles, can significantly alleviate the structural damage caused by volume expansion, and then improves the cycle stability and rate performance of silicon negative pole. Meanwhile, electrostatic spinning process combines the pre-oxidation of electrostatic spinning sample with air drying oven, not only can batch process, improve production efficiency, can also rely on its cavity space large, air circulation strong, oxygen content sufficient advantage, ensure that electrostatic spinning sample is heated evenly in the whole heating process, oxidation fully, avoid the problems such as local carbonization, structural damage or pre-oxidation incomplete caused by insufficient oxygen or uneven heat distribution, thus promote the structural consistency, mechanical stability and electrochemical performance reproducibility of electrode material after thermal treatment.

[0023] Furthermore, the present invention can flexibly select the optimal heat treatment combination according to actual needs, taking into account the integrity and carbonization degree of the carbon nanofiber structure, thereby achieving precise control of the electrode material morphology, conductivity and structural stability by setting, including but not limited to, the pre-oxidation temperature at any value between 200°C and 300°C, the heat treatment temperature at any value between 700°C and 900°C, the pre-oxidation time at any value between 2h and 5h, and the heat treatment time at any value between 0.5h and 2h.

[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 with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0026] Figure 1 is a schematic flow chart of a method for preparing an integrated silicon-carbon negative electrode material according to one embodiment of the present invention;

[0027] Figure 2 According to the MoC in Example 1 1-x -Schematic preparation flow chart of Si@CNFs composites;

[0028] Figure 3 is a scanning electron microscope image of the negative electrode material prepared according to Example 1 and Comparative Example 1 of the present invention;

[0029] Figure 4 Element distribution imaging spectrum and scanning electron microscope image of the negative electrode material prepared according to Example 1 of the present invention;

[0030] Figure 5 is a transmission electron microscope image of the negative electrode material prepared according to Example 1 of the present invention;

[0031] Figure 6 is a line scan image of the negative electrode material prepared according to Example 1 of the present invention;

[0032] Figure 7 This is a line scan of the negative electrode material prepared according to Comparative Example 1 of the present invention;

[0033] Figure 8 The negative electrode material prepared according to Example 1, Example 2 and Comparative Example 1 is 1A·g -1 Long cycle performance diagram tested under current density;

[0034] Figure 9 The negative electrode material prepared in Comparative Example 1 according to the present invention is -1 And the negative electrode material prepared in Example 1 is 4A·g -1 and 10A·g -1 Long cycle performance diagram under current density;

[0035] Figure 10 1 is a rate performance diagram of the negative electrode materials prepared according to Example 1, Example 2 and Comparative Example 1 of the present invention;

[0036] Figure 11 This is a physical picture of the negative electrode material prepared according to Example 1 of the present invention;

[0037] Figure 12 is a scanning electron microscope image of the negative electrode material prepared according to Example 3 of the present invention and Comparative Example 2;

[0038] Figure 13 Element distribution imaging spectrum and scanning electron microscope image of the negative electrode material prepared according to Example 3 of the present invention;

[0039] Figure 14 is a transmission electron microscope image of the negative electrode material prepared according to Example 3 of the present invention;

[0040] Figure 15 is a line scan image of the negative electrode material prepared according to Example 3 of the present invention;

[0041] Figure 16 The negative electrode material prepared according to Example 3 and Comparative Example 2 is 1.0A·g -1 A long cycle test diagram was performed below;

[0042] Figure 17 This is a rate performance diagram of the negative electrode material prepared according to Example 3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0043] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0044] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. It will be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some, rather than all, structures related to the present application are shown in the accompanying drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] As used herein, the terms "comprise," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0046] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0047] Figure 1 is a schematic flow chart of a method for preparing an integrated silicon-carbon negative electrode material according to one embodiment of the present invention. Figure 2 According to the MoC in Example 1 1-x -Schematic preparation flow chart of Si@CNFs composites.

[0048] like Figure 1 As shown, the present invention provides a method for preparing an integrated silicon-carbon negative electrode material, comprising:

[0049] Step S100: adding the modified material and the silicon material into an organic solvent, and preparing a first precursor solution after ultrasonic treatment;

[0050] Step S200: adding a carbon source material to the first precursor solution, stirring the solution at a preset temperature for a preset time, and preparing a second precursor solution;

[0051] Step S300: preparing an electrospinning sample by subjecting the second precursor solution to electrospinning;

[0052] Step S400: The electrospinning sample is sequentially subjected to solvent removal treatment, pre-oxidation and heat treatment to prepare an integrated silicon-carbon negative electrode material; wherein the modified material is any one of molybdenum phosphate or copper acetate, and the mass ratio of the carbon source material, the modified material and the silicon material is any value in (10-14):(1-4):4, that is, the mass ratio of the modified material, the silicon material and the carbon source material can be 10:3:4, 11:3:4, 12:3:4, 13:3:4, 14:3:4, 12:1.5:4, 13:1.5:4 or 14:4:4, or any other value in (10-14):(1-4):4, the pre-oxidation is carried out in a blast drying oven, and the heating rate of the heat treatment is 1°C min -1 -10℃·min -1 Any value, that is, the heating rate can be 1℃·min -1 , 2℃·min -1 、3℃·min -1 、4℃·min -1 、5℃·min -1 、6℃·min -1 、7℃·min -1 、8℃·min -1 、9℃·min -1 or 10℃·min -1 , or 1℃·min -1 -10℃·min -1 Any other value in .

[0053] like Figure 2 As shown, in this embodiment, in the preparation method of the integrated silicon-carbon negative electrode material, the modified material and the silicon material are first added to the organic solvent, and a first precursor solution is prepared after ultrasonic treatment. Then, the carbon source material is added to the first precursor solution, and the mixture is stirred for a preset time under preset temperature conditions to prepare a second precursor solution, so that the mass ratio of the carbon source material, the modified material and the silicon material in the second precursor solution is (10-14): (1-4): 4. Any value, then the second precursor solution is prepared by electrospinning to obtain an electrospun sample, and finally the electrospun sample is subjected to solvent removal treatment, pre-oxidation and heat treatment in sequence, and the heating rate of the heat treatment is controlled to be 1°C min -1 -10℃·min -1The solvent removal and pre-oxidation treatment were both carried out in a blast drying oven, and the heat treatment was carried out in a tube furnace.

[0054] In the present embodiment, by first introducing a modifier and a silicon material into the first precursor solution, the in-situ coating and uniform dispersion of the modifier on the silicon surface are achieved, and then synergistically with the subsequently added carbon source material, the second precursor solution is constructed to form a structurally stable silicon-carbon composite fiber network during the electrospinning process, thereby constructing an efficient electron transmission channel, and simultaneously realizing flexible coating and stress buffering of silicon particles, which can significantly alleviate the structural damage caused by volume expansion, thereby improving the cycle stability and rate performance of the silicon negative electrode. At the same time, the electrospinning process is combined with a blast drying oven to carry out pre-oxidation of the electrospinning sample, which can not only batch process and improve production efficiency, but also rely on its large cavity space, strong air circulation and sufficient oxygen content to ensure that the electrospinning sample is heated evenly and oxidized fully during the whole heating process, avoiding problems such as local carbonization, structural damage or incomplete pre-oxidation caused by insufficient oxygen or uneven heat distribution, thereby improving the structural consistency, mechanical stability and electrochemical performance reproducibility of the electrode material after heat treatment.

[0055] In this embodiment, the integrated silicon-carbon electrode prepared by the above-mentioned preparation method does not require a binder and a current collector. On the one hand, it reduces the content of inactive substances and improves the energy density. On the other hand, the integrated electrode prepared by the above-mentioned preparation method forms a three-dimensional conductive network, which reduces the risk of active substances peeling off the current collector during the coating process and reduces the volume effect. Compared with the technical solutions in the prior art that require a current collector to achieve a certain degree of flexibility, the integrated electrode prepared by the preparation method of this embodiment does not require a current collector as a carrier or as a flexible substrate, which also means that there is no risk of active substances peeling off the current collector.

[0056] In a preferred embodiment, the heating rate of the heat treatment is 7°C·min -1 -10℃·min -1 Any value, that is, the heating rate can be 7℃·min -1 、7.5℃·min -1 、8℃·min -1 、8.5℃·min -1 、9℃·min -1 、9.5℃·min -1 or 10℃·min -1 , or 7℃·min -1 -10℃·min -1Any other value in the . Due to the use of a blast drying oven for pre-oxidation of the electrospinning sample, its oxygen supply is sufficient and the heat distribution is uniform, so that the pre-oxidation reaction of the electrospinning sample is sufficient and consistent, thereby improving the structural stability of the pre-oxidation product, and the carbonization heating rate in the subsequent heat treatment process can be increased to 7 ° C min -1 -10℃·min -1 Any value in the carbonization temperature rise rate is significantly higher than the carbonization heating rate commonly used in the existing technology, which not only effectively shortens the process cycle, but also reduces energy consumption, and achieves high-efficiency carbonization treatment without damaging the fiber structure, which helps to realize the industrialization and large-scale preparation of materials and batch processing of electrospinning samples.

[0057] In this embodiment, the removal of the organic solvent can effectively remove the low-boiling-point solvent remaining in the electrospinning sample, avoiding the fiber structure rupture or uneven carbonization caused by solvent vaporization during the subsequent pre-oxidation and heat treatment process, thereby improving the structural integrity and purity of the carbon nanofibers, and is conducive to the formation of a dense and uniform integrated silicon-carbon negative electrode material, thereby improving the mechanical strength, electrical conductivity and cycle stability of the material.

[0058] In this embodiment, in the preparation method of the integrated silicon-carbon negative electrode material, only by adding modifying materials, silicon materials and carbon source materials, not only the interface discontinuity problem caused by the mixing of multiple components in traditional slurry preparation is avoided, and the overall structural integrity and electron transmission efficiency of the electrode are improved, but the modifier can also be converted into a conductive or buffer phase during the carbonization process, thereby enhancing the mechanical stability and cycle stability of the electrode.

[0059] In this embodiment, when the modified material is molybdenum phosphate, molybdenum phosphate is mixed with the electrospinning precursor solution as the modified material, that is, mixed with silicon material, organic solvent and carbon source material, and subjected to electrospinning treatment, organic solvent removal, pre-oxidation and heat treatment to prepare molybdenum carbide modified carbon nanofiber coated silicon (MoC 1-x -Si@CNFs) composite material, that is, an integrated silicon-carbon negative electrode material. Due to the cross-linked structure of carbon fibers and the modification of molybdenum carbide, the MoC 1-x The electrochemical performance of the Si@CNFs composite material is enhanced by the molybdenum carbide, which enhances the mechanical strength and corrosion resistance of the nanofiber coating, thereby resisting fluoride ion damage and improving electrode integrity, thereby increasing capacity retention. Furthermore, molybdenum phosphate is fully soluble in organic solvents. As the solvent evaporates and the drying process proceeds, the molybdenum oxide crystals are evenly distributed. Subsequent heat treatment converts them into molybdenum carbide crystals, where their uniform distribution enhances their corrosion resistance.

[0060] In this embodiment, when the modifying material is copper acetate, copper acetate is mixed with a silicon material, a carbon source material, and an organic solvent as a modifying material, and is pre-oxidized and heat-treated to prepare a copper-modified silicon-carbon nanofiber (Cu-Si@CNFs) composite material. Since copper particles can effectively increase the degree of graphitization of the Cu-Si@CNFs composite material, the carbon layer not only prevents direct contact between the silicon nanoparticles and the electrolyte, but also buffers volume expansion and contraction, improves interfacial compatibility, reduces side reactions and solid electrolyte interface components, and enhances lithium storage while ensuring that the fiber remains stable and does not collapse under the impact of continuous high current. In addition, the excellent electrical conductivity of copper accelerates lithium ion transport, significantly enhancing the electrochemical performance of the electrode.

[0061] In this example, after adding copper acetate to the electrospinning solution, the inorganic salt decomposes into copper metal during heat treatment, and the silicon nanoparticles are encapsulated by carbon fibers. This effectively relieves the stress caused by the volume change of the silicon particles, thereby maintaining the structural integrity and flexibility of the integrated silicon-carbon anode material. Furthermore, the high specific surface area and porosity of the Cu-Si@CNFs composite material can reduce volume changes, promote ion transport, promote internal activation of the electrolyte, and enhance the electrochemical performance of the electrode.

[0062] In this embodiment, ultrasonic treatment can be carried out in an ultrasonic cleaner or ultrasonic cell disruptor, which can efficiently disperse the precursor solution in batches, and the instrument is inexpensive, which reduces costs. The pre-oxidation process uses a blast drying oven to achieve batch processing of electrospun nanofiber membranes, and more than 10 electrospun samples prepared by electrospinning can be pre-oxidized at a time, with low preparation costs. The subsequent heat treatment process uses a tubular furnace to reduce preparation costs, and can also use a rapid heating rate of 10°C / min, which greatly shortens the carbonization time of the material.

[0063] In a further embodiment, the pre-oxidation temperature is any value between 200°C and 300°C, the pre-oxidation time can be any value between 2h and 5h, the heat treatment temperature is any value between 700°C and 900°C, and the heat treatment time is any value between 0.5h and 2h, that is, the pre-oxidation temperature can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C, or 200 ℃-300℃, the pre-oxidation time can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, or any other value between 2h-5h, the heat treatment temperature can be 700℃, 750℃, 800℃, 850℃ or 900℃, or any other value between 700℃-900℃, the heat treatment time can be 0.5h, 1h, 1.5h or 2h, or any other value between 0.5h-2h. In this embodiment, by setting including but not limited to the pre-oxidation temperature being any value between 200℃-300℃, the heat treatment temperature being any value between 700℃-900℃, the pre-oxidation time being any value between 2h-5h, and the heat treatment time being any value between 0.5h-2h, the optimal heat treatment combination can be flexibly selected according to actual needs, taking into account the integrity and carbonization degree of the carbon nanofiber structure, thereby achieving precise control of the morphology, conductivity and structural stability of the electrode material. This heat treatment scheme not only improves the adaptability and controllability of the preparation process, but also enhances the cycle stability, electrochemical performance repeatability and large-scale preparation capability of the resulting integrated silicon-carbon negative electrode material.

[0064] In a further embodiment, the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide. By selecting N,N-dimethylformamide or dimethyl sulfoxide as the organic solvent, the carbon source material can be effectively dissolved and the modified material and the silicon particles in the silicon material can be uniformly dispersed to obtain a precursor liquid system with uniform structure and suitable viscosity. N,N-dimethylformamide or dimethyl sulfoxide as a polar solvent can also significantly improve the fiber forming stability and the coating consistency of the silicon particles during the electrospinning process, thereby improving the structural integrity and electrochemical performance of the prepared integrated silicon-carbon negative electrode material. In this embodiment, the material of the organic solvent includes but is not limited to N,N-dimethylformamide and dimethyl sulfoxide.

[0065] In a further embodiment, the particle size of the silicon particles in the silicon material is any value between 20nm and 40nm, that is, the particle size of the silicon particles in the silicon material can be 20nm, 25nm, 30nm, 35nm or 40nm, or any other value between 20nm and 40nm. In this embodiment, by selecting a silicon material with a silicon particle size between 20nm and 40nm, since the nano-silicon particles can maintain good structural integrity during the lithiation / delithiation process, the stress caused by their volume expansion is smaller, and they are not easy to crack and pulverize, thereby significantly extending the electrode life and improving the cycle stability. Moreover, during the electrospinning forming process, smaller particle sizes can be more effectively uniformly coated or embedded in the fiber structure by the carbon source fibers, forming a dense and stable integrated carbon coating structure to prevent the silicon particles from falling off. In addition, nano-silicon has a higher specific surface area, can provide more active sites, is conducive to improving the specific capacity of the electrode, is conducive to forming a stable solid electrolyte interface, and improves the first-cycle coulomb efficiency.

[0066] In a further embodiment, the carbon source material is any one of polyacrylonitrile, polyvinylpyrrolidone, polymethyl methacrylate, polyacrylic acid, or polydopamine. In this embodiment, the above-mentioned different carbon sources can form a carbon material with good conductivity and structural stability during the subsequent heat treatment process, achieving effective coating, connection, and buffering of silicon particles. That is, by selecting and optimizing different carbon sources, the electrochemical properties, mechanical flexibility, and structural integrity of the composite material can be further controlled, the cycle stability and rate performance of the electrode can be improved, and the applicability and scalability of the material system can be enhanced. Here, polyacrylonitrile is used as a carbon source material, which has strong thermal stability, high carbon yield and forms a dense conductive carbon layer after carbonization, and can construct a high-strength coating structure. Polyvinylpyrrolidone is used as a carbon source material, which has good film-forming and spinnability. It forms a flexible carbon layer after carbonization, which can improve the mechanical flexibility of the material and the uniformity of the finished product. Polymethyl methacrylate is easily decomposed to produce pores during the carbonization process, which helps to form a porous carbon structure and improve the electrolyte permeability and ion transfer efficiency. Polyacrylic acid contains carboxyl groups, which can form hydrogen bonds or chemical anchoring effects with the silicon surface to improve the coating stability. The nitrogen-containing carbon material formed by polydopamine after carbonization can improve surface wettability and conductivity, and also has a certain interface regulation ability.

[0067] In a further embodiment, the preset temperature is any value in 60 ℃-80 ℃, and the preset time is any value in 10h-12h, that is, when preparing the second precursor solution, the heating temperature of the heated stirring can be 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃, or any other value in 60 ℃-80 ℃, and the stirring time of the heated stirring can be 10h, 10.5h, 11h, 11.5h or 12h, or any other value in 10h-12h. In the present embodiment, a heating temperature of 60 ℃-80 ℃ and a stirring time of 10h-12h are used in the process of preparing the second precursor solution, which contributes to the full dissolution of the carbon source material and the uniform dispersion of the modified material and the silicon material, thereby improving the stability and uniformity of the second precursor solution. At the same time, the above-mentioned heated stirring step can regulate the rheological properties of the system, optimize the electrostatic spinning film-forming performance, and avoid degradation of the carbon source or modified material due to overheating, thereby improving the density, continuity and electrochemical properties of the resulting fiber structure.

[0068] In a further embodiment, the ultrasonic treatment time is any value in the range of 0.5h-1.5h, that is, the ultrasonic treatment time can be 0.5h, 1.0h or 1.5h, or any other value in the range of 0.5h-1.5h. In this embodiment, by setting the ultrasonic treatment time to 0.5h-1.5h, it is helpful to break up the agglomerated structure of the modified material and the silicon particles, improve their dispersion uniformity and stability in the organic solvent, thereby obtaining a first precursor solution with uniform composition, that is, ultrasonic treatment of the first precursor solution can promote the effective compounding of the modifier and the silicon particles, avoid particle sedimentation and clogging problems during the spinning process, and further improve the consistency of the electrospinning film and the structural integrity of the electrode material.

[0069] In a further embodiment, the voltage of the electrospinning treatment is any value between 15kV and 30kV, the distance between the needle and the collecting roller is any value between 10cm and 20cm, and the liquid pushing speed is any value between 0.5mL / h and 2mL / h, that is, the electrospinning voltage can be 15kV, 20kV, 25kV or 30kV, or any other value between 15kV and 30kV, the distance between the needle and the collecting roller can be 10cm, 12cm, 14cm, 16cm, 18cm or 20cm, or any other value between 10cm and 20cm, and the liquid pushing rate of electrospinning can be 0.5mL / h, 1.0mL / h, 1.5mL / h or 2.0mL / h, or any other value between 0.5mL / h and 2mL / h. In this embodiment, the above parameter settings can ensure the stability of the spinning process and the continuity of the fiber, adapt to different precursor liquid systems, and achieve effective regulation of the fiber diameter, structural uniformity and coating morphology under different conditions, thereby improving the structural density, conductivity path connectivity and cycle stability of the prepared integrated silicon-carbon negative electrode material.

[0070] In a further embodiment, the rotation speed of the drum for electrospinning is any value in the range of 10rpm-90rpm, and the sliding table movement speed is any value in the range of 10mm / s-20mm / s, that is, the rotation speed of the drum during the electrospinning process can be 10rpm, 20rpm, 30rpm, 40rpm, 50rpm, 60rpm, 70rpm, 80rpm or 90rpm, or any other value in the range of 10rpm-90rpm, and the sliding table movement speed can be 10mm / s, 12mm / s, 14mm / s, 16mm / s, 18mm / s or 20mm / s, or any value in the range of 10mm / s-20mm / s. In this embodiment, the above parameter range helps to regulate the arrangement morphology and stacking density of the fibers on the surface of the collector, achieve orderly deposition and uniform distribution of carbon nanofibers, thereby improving the structural density, electrical conductivity connectivity and mechanical stability of the prepared electrode film layer, and further improving the cycle life and rate performance of the electrode material during the charge and discharge process.

[0071] In a further embodiment, the electrospinning time of the electrospinning treatment is any value between 6.5h and 10h, that is, the electrospinning time can be 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, or any value between 6.5h and 10h, which effectively regulates the fiber stacking thickness, ensures the structural integrity and thickness uniformity of the electrode film layer, and enables the silicon particles to be fully coated with carbon nanofibers to form a dense and stable three-dimensional conductive network structure, thereby improving the silicon loading, cycle life and structural stability of the prepared integrated silicon-carbon electrode.

[0072] The present application will be further described in detail below with reference to specific embodiments.

[0073] In some embodiments, in the preparation method of the integrated silicon-carbon negative electrode material, the modified material and the silicon material are first added to an organic solvent, the modified material is molybdenum phosphate or copper acetate, the particle size of the silicon particles in the silicon material is any value between 20nm and 40nm, and the first precursor solution is prepared after ultrasonic treatment for 0.5h-1.5h, and then the carbon source material is added to the first precursor solution, and stirred at a temperature of 60℃-80℃ for 10h-12h to prepare a second precursor solution. The mass ratio of the carbon source material, the modified material and the silicon material in the second precursor solution is (10-14): (1 -4):4, then the second precursor solution is prepared by electrospinning to obtain an electrospinning sample, and finally the electrospinning sample is sequentially subjected to solvent removal treatment, pre-oxidation and heat treatment, the solvent removal and pre-oxidation treatments are both carried out in a blast drying oven, the pre-oxidation temperature is any value between 200°C and 300°C, the pre-oxidation time is any value between 2h and 5h, the heat treatment is carried out in a tube furnace, the heat treatment temperature is any value between 700°C and 900°C, the heat treatment time is any value between 0.5h and 2h, and the heating rate of the heat treatment is controlled to be 1°C min -1 -10℃·min -1 By using any value in the range , an integrated silicon-carbon negative electrode material without current collector or binder can be prepared.

[0074] Example 1

[0075] First, 0.3 g of molybdenum phosphate and 0.4 g of silicon material with a particle size of 30 nm were added to N, N-dimethylformamide, and ultrasonically treated for 1 h to prepare a first precursor solution. Then, 1.2 g of polyacrylonitrile was added to the first precursor solution and stirred at 70 ° C for 10 h to prepare a second precursor solution. The second precursor solution was then subjected to electrospinning to prepare an electrospinning sample. Finally, the electrospinning sample was subjected to solvent removal treatment, pre-oxidation and heat treatment in sequence. The solvent removal and pre-oxidation treatments were both carried out in a blast drying oven. The pre-oxidation temperature was 250 ° C and the pre-oxidation time was 5 h. The heat treatment was carried out in a tube furnace at a heat treatment temperature of 700 ° C and a heat treatment time of 2 h, and the heating rate of the heat treatment was controlled to be 10 ° C min -1 , to prepare an integrated silicon-carbon negative electrode material without current collector and binder, namely MoC 1-x -Si@CNFs-1.

[0076] Example 2

[0077] The only difference between Example 2 and Example 1 is that the mass of molybdenum phosphate is 0.15 g, that is, MoC 1-x -Si@CNFs-2.

[0078] Example 3

[0079] The only difference between Example 3 and Example 1 is that the modified material is copper acetate, that is, Cu-Si@CNFs are prepared.

[0080] Comparative Example 1

[0081] The only difference between Comparative Example 1 and Example 1 is that the amount of molybdenum phosphate added is 0 g, and Si@CNFs are prepared.

[0082] Comparative Example 2

[0083] The only difference between Comparative Example 2 and Example 3 is that the amount of copper acetate added is 0 g, and Si@CNFs are prepared.

[0084] Figure 3 is a scanning electron microscope image of the negative electrode material prepared according to Example 1 and Comparative Example 1 of the present invention, Figure 4 This is an element distribution image spectrum and a scanning electron microscope image of the negative electrode material prepared according to Example 1 of the present invention. Figure 5 This is a transmission electron microscope image of the negative electrode material prepared according to Example 1 of the present invention. Figure 6 This is a line scan of the negative electrode material prepared according to Example 1 of the present invention. Figure 7 It is a line scan image of the negative electrode material prepared according to Comparative Example 1 of the present invention.

[0085] The integrated silicon-carbon negative electrode materials prepared in Example 1 and Comparative Example 1 were sequentially subjected to scanning electron microscopy, element distribution characterization, transmission electron microscopy, and line scanning diagrams to obtain the following: Figures 3 to 7 Characterization results shown.

[0086] like Figure 3 As shown, (a) and (b) are MoC at different magnifications. 1-x -Scanning electron microscope images of Si@CNFs composite materials, (c) and (d) are scanning electron microscope images of Si@CNFs composite materials at different magnifications. It can be seen from Figures (a) and (b) that bulges of varying degrees appear on the fiber surface. These bulges are caused by the silicon particles coated with the fibers. At the same time, the scanning electron microscope images show a cross-linked carbon fiber grid, which can effectively enhance the ductility and conductivity of the composite, thereby buffering the stress generated during the cycle and promoting dynamic transmission, ultimately extending the battery failure time. Among them, the surface of the cross-linked carbon fiber grid is relatively rough, mainly because silicon of uneven shape is attached to or embedded in the carbon fiber. Similarly, Figures (c) and (d) show similar structural morphologies, indicating that molybdenum phosphate modification does not have a significant effect on the morphology of the composite material.

[0087] like Figure 4 As shown, (a) is the MoC prepared in Example 1 1-x-Si@CNFs-1 composite material scanning electron microscopy images, (b) and (c) are MoC 1-x -Element distribution image of Si@CNFs-1 composite material. In the image of C element, large continuous and high-intensity signal areas intuitively show the existence and distribution of carbon fiber. After comparing it with the outline of the image of Si element, it can be seen that the Si element is not randomly distributed, but is relatively evenly embedded in the carbon fiber structure or attached to the surface of the carbon fiber. From the image information of Mo element, it can be seen that molybdenum carbide can be evenly distributed on the carbon fiber. The reason is that during the preparation process, molybdenum phosphate can be fully dissolved in N,N-dimethylformamide solvent. As the solvent evaporates and the drying process proceeds, the molybdenum oxide crystals are evenly distributed and are subsequently converted into molybdenum carbide crystals after heat treatment. This uniform distribution can better exert its anti-corrosion effect, making MoC 1-x -Si@CNFs-1 composite materials have stronger resistance to external corrosion factors, thereby effectively improving the overall stability and service life of the material.

[0088] like Figure 5 As shown, (a) is MoC 1-x -The transmission electron microscopy image of Si@CNFs-1 clearly shows the distribution of silicon nanoparticles in the carbon fibers. In the lower right corner of the image is the molybdenum element reflection image. The bright pixels correspond to the black particles in the nanofibers, proving that molybdenum carbide (MoC 1-x ) exists. (b) and (c) are partial enlarged views of the transmission electron microscope images. From Figure (b), it can be seen that there is a thin layer of pyrolytic carbon on the silicon surface. From the partial enlarged view of the transmission electron microscope image in Figure (c), it can be seen that the interplanar spacing of 0.214nm corresponds to the MoC 1-x (200) crystal plane, the interplanar spacing of 0.312nm corresponds to the (111) crystal plane of Si, which indirectly proves that MoC 1-x The existence of MoC, that is, the carbon layer on the surface of the silicon particles has an obvious graphitized structure, and the carbon layer on the surface can not only prevent the direct contact between the silicon particles and the electrolyte, but also alleviate the volume expansion effect of the silicon particles. Figure (d) shows MoC 1-x -Element distribution diagram of Si@CNFs-1 composite material. From the figure, it can be observed that C, O, Si, P and Mo elements are evenly dispersed in the carbon fibers.

[0089] like Figure 6 and Figure 7 As shown, the silicon content peak is obvious, and the contents of carbon, oxygen, and molybdenum elements can also be observed. Comparing the silicon and carbon curves, it can be found that the peak of the silicon curve and the trough of the carbon curve appear at the same position. Similarly, the trough of the silicon curve and the peak of the carbon curve also appear at the same position. Figure 5 The distribution of silicon and carbon elements in the energy spectrum of (d) shows that the silicon particles are surrounded by a carbon shell, forming a silicon / carbon core-shell structure.

[0090] Figure 8 The negative electrode material prepared according to Example 1, Example 2 and Comparative Example 1 is 1A·g -1 Long cycle performance diagram tested under current density, Figure 9 The negative electrode material prepared in Comparative Example 1 according to the present invention is -1 And the negative electrode material prepared in Example 1 is 4A·g -1 and 10A·g -1 Long cycle performance diagram under current density, Figure 10 1 is a rate performance diagram of the negative electrode materials prepared according to Example 1, Example 2 and Comparative Example 1 of the present invention.

[0091] Then the electrical properties of the negative electrode materials prepared in Example 1, Example 2 and Comparative Example 1 were tested, and the results were as follows: Figures 8 to 10 The test results are shown.

[0092] like Figure 8 As shown, the first charge / discharge specific capacities of the negative electrode materials prepared in Example 1, Example 2, and Comparative Example 1 are 2169.5 mAh·g -1 / 3099.2mAh·g -1 、2342.6mAh·g -1 / 3318.1mAh·g -1 and 2229.8mAh·g -1 / 3189.9mAh·g -1 , the corresponding first coulombic efficiencies are 70.0%, 70.6% and 69.9% respectively. -1 At the same current density, after 500 cycles, the charge / discharge specific capacities of the three are 1178.4 mAh g -1 / 1181.1mAh·g -1 、840.5mAh·g -1 / 842.1mAh·g -1 and 422.6mAh·g -1 / 422.8mAh·g -1 , the specific capacity retention rates are 62.6%, 42.4% and 19.0% respectively. -1 After 500 cycles at the same current density, the capacity retention rate can be increased by 43.6%. It can be seen that the more phosphomolybdic acid is added, the better the electrochemical performance of the electrode material is, which is attributed to the MoC 1-xThe modified electrodes have more nanopores, larger specific surface area and better conductivity.

[0093] like Figure 9 As shown, after activation, 4.0A·g -1 The specific capacity of the first cycle charge / discharge at a current density of 2371.8 mAh g -1 / 3224.3mAh·g -1 , after 1000 cycles, MoC 1-x -Si@CNFs-1 still showed 550.6 mAh g -1 The reversible specific capacity of the electrode is 51.1%, and the coulombic efficiency is maintained at above 99.9%. -1 After 1000 cycles, the battery still maintained 360.7 mAh g -1 The reversible capacity is comparable to the theoretical specific capacity of graphite (372 mAh g -1 The capacity retention rate is 42.5% relative to the first cycle after activation, and the Coulomb efficiency is maintained above 99.5%, indicating that this embodiment has excellent long-term cycle performance under high current density, and the silicon surface is coated with MoC 1-x After the coating of MoC and cracked carbon, the cycling performance of the composite material is greatly improved, that is, due to the 1-x Modification, which not only enhances the electrical conductivity and helps alleviate the polarization problem during continuous cycling, but also improves the interfacial compatibility and structural stability.

[0094] like Figure 10 As shown, at 0.1A·g -1 The specific capacity at current density is still MoC 1-x -Si@CNFs-1 is the best, while at a higher current density (4 A·g -1 ), MoC 1-x -Si@CNFs-1 electrode showed more excellent stability. -1 , 0.2A·g -1 , 0.5A·g -1 , 1.0A·g -1 , 2.0A·g -1 , 4.0A·g -1 When, MoC 1-x -Si@CNFs-1 electrode has the highest charge capacity at the corresponding current density. -1 When the current density is 1-x -Si@CNFs-1、MoC 1-x-Si@CNFs-2 and Si@CNFs have a capacity recovery rate of 91%, 86.9% and 82.1%, respectively. 1-x -Si@CNFs-1 has a much better effect. At high magnification, it is necessary to maintain structural stability and high conductivity, while MoC 1-x The modification greatly enhances the conductivity of the material.

[0095] Figure 11 This is a physical picture of the negative electrode material prepared according to Example 1 of the present invention.

[0096] like Figure 11 As shown in the figure, the left image shows the sample after organic solvent removal, pre-oxidation, and heat treatment, respectively. The right image shows the negative electrode material in a flat state and a folded state, respectively. It can be seen from the figure that the composite material's dimensions remain essentially unchanged after pre-oxidation and carbonization. The prepared composite material also exhibits excellent flexibility and can be folded without cracking or deformation.

[0097] Figure 12 is a scanning electron microscope image of the negative electrode material prepared according to Example 3 and Comparative Example 2 of the present invention, Figure 13 This is an element distribution image spectrum and a scanning electron microscope image of the negative electrode material prepared according to Example 3 of the present invention. Figure 14 This is a transmission electron microscope image of the negative electrode material prepared according to Example 3 of the present invention. Figure 15 This is a line scan image of the negative electrode material prepared according to Example 3 of the present invention.

[0098] The negative electrode materials prepared in Example 3 and Comparative Example 2 were characterized by scanning electron microscopy, element distribution, transmission electron microscopy and line scanning, and the following results were obtained: Figures 12 to 15 The test results are shown.

[0099] like Figure 12 As shown, (a) and (b) are Cu-Si@CNFs composites at different magnifications, and (c) and (d) are Si@CNFs composites at different magnifications, respectively. The nanofibers are randomly entangled and interlaced, which helps enhance the composite's ductility and conductivity, reduce stress during cycling, and promote dynamic transmission, ultimately extending the battery's life. The fiber width ranges from tens to hundreds of nanometers, which helps more effectively encapsulate silicon nanoparticles. Because the silicon particles are attached to or embedded in the carbon fibers, the surface of the cross-linked carbon fiber mesh is relatively rough. That is, at different magnifications, the Cu-Si@CNFs composite and the Si@CNFs composite exhibit similar structural morphologies, indicating that the addition of copper modification has no significant effect on the composite's morphology.

[0100] like Figure 13 As shown in the figure, silicon is relatively evenly embedded in the carbon fiber structure or attached to the surface of the carbon fiber. From the Cu element image, it can be seen that copper is also evenly distributed on the carbon fiber, indicating that copper acetate is dissolved in the solvent during the preparation process and then evenly distributed in the spinning solution, allowing the copper element generated after subsequent heat treatment to be evenly distributed in the carbon nanofibers.

[0101] like Figure 14 As shown, (a) is a transmission scanning electron micrograph of the negative electrode material prepared in Example 3, showing a clear image of the nanofiber-wrapped silicon particles in the Cu-Si@CNFs composite material. (b) and (c) are partial enlarged views of the transmission scanning electron micrograph. As can be seen from Figure (b), the silicon nanoparticles are wrapped by carbon fibers. In Figures (b) and (c), a clear carbon layer can be observed on the surface of the silicon particles. The carbon layer not only prevents direct contact between the silicon nanoparticles and the electrolyte, but also buffers volume expansion and contraction, improves interfacial compatibility, and reduces side reactions and solid electrolyte interface components. (d) is an element distribution diagram of the Cu-Si@CNFs composite material, showing that the C, O, Si, and Cu elements are evenly distributed in the nanofibers.

[0102] like Figure 15 As shown, by comparing the silicon and carbon curves, it can be found that the peak of the silicon curve and the trough of the carbon curve appear at the same position, and similarly, the trough of the silicon curve and the peak of the carbon curve also appear at the same position. Figure 14 The distribution of silicon and carbon elements in the image indicates that the silicon particles are surrounded by a carbon shell, forming a silicon / carbon core-shell structure. Furthermore, observing the silicon and copper curves reveals that the presence of a large amount of copper surrounding the silicon particles significantly improves the conductivity of the Cu-Si@CNFs composite.

[0103] Figure 16 The negative electrode material prepared according to Example 3 and Comparative Example 2 is 1.0A·g -1 A long cycle test diagram was performed below. Figure 17 This is a rate performance diagram of the negative electrode material prepared according to Example 3 of the present invention and Comparative Example 1.

[0104] The electrical properties of the negative electrode materials prepared in Example 3 and Comparative Example 2 were tested, and the following results were obtained: Figure 16 and Figure 17 The test results are shown.

[0105] like Figure 16 As shown in the figure, Cu-Si@CNFs anode material and Si@CNFs anode material have the best performance at 1.0A·g -1 After 300 cycles at the same current density, the charge / discharge specific capacities of the two were 1137.3 mAh g-1 / 1176.4mAh·g -1 and 728.0mAh·g -1 / 731.2mAh·g -1 , the specific capacity retention rates were 61.4% and 37.0% respectively. The Cu-Si@CNFs negative electrode material of this embodiment was -1 The capacity retention rate after 300 cycles at the current density can be improved by 24.4%, indicating that the Cu-Si@CNFs prepared in Example 3 have excellent electrical properties.

[0106] like Figure 17 As shown in the figure, the specific capacity of Cu-Si@CNFs composite material is better than that of Si@CNFs at different current densities. -1 At the current density of 1.5 wt %, the specific capacity recovery rates of Cu-Si@CNFs composite material and Si@CNFs composite material were 96.4% and 94.0%, respectively, indicating that Cu-Si@CNFs composite material has better kinetic properties.

[0107] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0108] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing an integrated silicon-carbon negative electrode material, characterized in that: include: Adding the modified material and the silicon material into an organic solvent, and preparing a first precursor solution after ultrasonic treatment; Adding a carbon source material to the first precursor solution and stirring the solution at a preset temperature for a preset time to prepare a second precursor solution; preparing an electrospinning sample by electrospinning the second precursor solution; The electrospinning sample is subjected to solvent removal treatment, pre-oxidation and heat treatment in sequence to prepare an integrated silicon-carbon negative electrode material; wherein, The modified material is any one of molybdenum phosphate or copper acetate, the mass ratio of the carbon source material, the modified material and the silicon material is any value of (10-14):(1-4):4, the pre-oxidation is carried out in a blast drying oven, and the heating rate of the heat treatment is 1°C·min -1 -10℃·min -1 Any value in .

2. The preparation method according to claim 1, characterized in that The pre-oxidation temperature is any value between 200°C and 300°C, the pre-oxidation time is any value between 2h and 5h, the heat treatment temperature is any value between 700°C and 900°C, and the heat treatment time is any value between 0.5h and 2h.

3. The preparation method according to claim 2, characterized in that The organic solvent is N,N-dimethylformamide or dimethyl sulfoxide.

4. The preparation method according to claim 3, characterized in that The particle size of the silicon particles in the silicon material is any value between 20nm and 40nm.

5. The preparation method according to claim 4, characterized in that The carbon source material is any one of polyacrylonitrile, polyvinyl pyrrolidone, polymethyl methacrylate, polyacrylic acid or polydopamine.

6. The preparation method according to claim 5, characterized in that The preset temperature is any value between 60° C. and 80° C., and the preset time is any value between 10 hours and 12 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that The ultrasonic treatment time is any value between 0.5h and 1.5h.

8. The preparation method according to claim 7, characterized in that The voltage of the electrospinning process is any value between 15kV and 30kV, the distance between the needle and the collecting roller is any value between 10cm and 20cm, and the liquid pushing speed is any value between 0.5mL / h and 2mL / h.

9. The preparation method according to claim 8, characterized in that The rotation speed of the electrospinning drum is any value between 10 rpm and 90 rpm, and the moving speed of the slide is any value between 10 mm / s and 20 mm / s.

10. The preparation method according to claim 9, characterized in that The electrospinning time of the electrospinning treatment is any value between 6.5h and 10h.

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