CN120809756B

CN120809756B - Preparation method and application of carbon-coated silicon nanowire anode material

Info

Publication number: CN120809756B
Application number: CN202511301966.3A
Authority: CN
Inventors: 梁坤; 王佳磊; 喻雄; 余陶
Original assignee: Ningbo Guangke New Materials Co ltd
Current assignee: Ningbo Guangke New Materials Co ltd
Priority date: 2025-09-12
Filing date: 2025-09-12
Publication date: 2026-01-13
Anticipated expiration: 2045-09-12
Also published as: CN120809756A

Abstract

This invention belongs to the field of lithium battery technology and relates to a method for preparing and applying carbon-coated silicon nanowire anode materials. The preparation method includes the following steps: adding micron-sized silicon powder, an iridium source, and a solvent to a container, dispersing them evenly, then heating and stirring in an oil bath to remove the solvent, followed by further drying; ball milling the resulting mixture, and then passing it through a 100-300 mesh sieve; subjecting the sieved powder to CVD coating, introducing a gaseous carbon source, and coating at 850-1050 °C for 1-3 h, followed by passing the coated powder through a 200-450 mesh sieve to obtain the carbon-coated silicon nanowire anode material. This method efficiently converts low-cost raw materials such as iridium sources and micron-sized silicon into silicon nanowire composite anode materials, reducing costs and simplifying the process. Applying this material to batteries can effectively improve battery performance.

Description

Preparation method and application of carbon-coated silicon nanowire anode material

Technical Field

The invention belongs to the technical field of lithium batteries, and relates to a preparation method and application of a carbon-coated silicon nanowire anode material.

Background

Lithium ion batteries are currently the mainstream energy storage technology, and the performance improvement of the lithium ion batteries is highly dependent on the innovation of electrode materials. In the negative electrode field, it has been difficult for conventional graphite materials to meet the increasing high energy density requirements (e.g., electric vehicles, portable electronic devices). Silicon (Si) is considered as one of the most potential next-generation negative electrode materials due to its extremely high theoretical specific capacity, abundant reserves, and moderate lithium intercalation potential.

However, silicon materials present a serious challenge in charge and discharge processes, namely, lithium ion intercalation/deintercalation is accompanied by a huge volume expansion/contraction (up to 300% or more). This dramatic volumetric effect is extremely prone to pulverization of the electrode material, exfoliation of the active material from the current collector or conductive network, and continuous destruction and reconstruction of the Solid Electrolyte Interface (SEI) film. The results are shown by rapid capacity decay, rapid cycle life shortening and low coulombic efficiency of the battery, which seriously hampers commercial application of silicon-based cathodes.

In order to overcome the volume effect of silicon materials, a great deal of research has been carried out in the industry to develop various nanostructure control strategies including nanoparticles, nanotubes, nanoplatelets, nanowires, etc. Among them, silicon nanowire (SiNWs) structures exhibit significant advantages:

1. the one-dimensional nanowire has good mechanical flexibility in the axial direction, can effectively buffer the stress generated by volume change, and inhibits pulverization;

2. The high-efficiency ion/electron transmission is realized by directly growing or closely contacting the nanowire with the current collector, thereby providing a continuous electron conduction path, along with small radial dimension and shortening the diffusion distance of lithium ions;

3. structural stability the interstices between the nanowires provide containment space for volume expansion, helping to maintain the structural integrity of the electrode.

Therefore, the construction of the silicon-carbon composite anode material containing the silicon nanowires has important significance.

Disclosure of Invention

The invention aims to provide a preparation method and application of a carbon-coated silicon nanowire anode material, and the following technical scheme is adopted to realize the aim of the invention:

the invention provides a preparation method of a carbon-coated silicon nanowire anode material, which comprises the following steps:

(1) Adding micron-sized silicon powder, an iridium source and a solvent into a container, uniformly dispersing, heating in an oil bath, stirring to remove the solvent, and further drying;

(2) Ball milling is carried out on the mixed material obtained in the step (1), the ball milling rotating speed is 300-500 rpm, the ball milling time is 50-100 min, and the mixed material is subjected to 100-300 mesh screen after ball milling;

(3) And (3) coating the powder obtained by sieving through Chemical Vapor Deposition (CVD), introducing a gaseous carbon source, coating for 1-3 hours at 850-1050 ℃, and passing through a 200-450-mesh screen after coating to obtain the carbon-coated silicon nanowire anode material.

Preferably, the grain size of the micron-sized silicon powder is 2-50 μm. More preferably 3 to 20. Mu.m.

Preferably, the iridium source is one or more of iridium nitrate, iridium chloride and iridium acetate. Further preferred is iridium acetate.

Preferably, the solvent is one or more of alcohol solvents and acetone. More preferably, the alcohol solvent is ethanol.

Preferably, the mass ratio of the micron-sized silicon powder to the iridium source is 0.8-1.2:1.

Preferably, the volume ratio of the total mass of the micron-sized silicon powder and the iridium source to the solvent is 1 g:5-15 ml.

Preferably, the micron-sized silicon powder, the iridium source and the solvent are uniformly dispersed by adopting ultrasonic and/or shearing steps.

Further preferably, the ultrasonic frequency is 20-50 kHz, the ultrasonic power density is 0.5-2W/cm ², and the ultrasonic time is 30-60 min.

Further preferably, the shearing step comprises the following parameters of a shearing rate of 3000-10000 rpm and a shearing time of 30-60 min.

Preferably, the heating temperature of the oil bath is 70-90 ℃, and the stirring speed is 200-800 rpm.

Preferably, the drying in the step (1) is vacuum drying or hot air drying, the drying temperature is 70-90 ℃, and the drying time is 4-10 hours.

Placing the mixed material obtained in the step (1) into a ball milling tank, adding ball milling beads, vacuumizing the ball milling tank, introducing inert gas, and then placing into a ball mill for ball milling. Preferably, the ball-milling beads are one or more of zirconia beads, alumina beads, steel balls and the like, and the diameter of the ball-milling beads is 0.2-50 mm. Preferably, the inert gas is argon or nitrogen. Preferably, the mass ratio of the mixed material to the ball-milling beads is 1:7-15.

Preferably, after ball milling, sieving with a 150-250 mesh sieve for 20-30 min.

Preferably, the gaseous carbon source is methane and/or acetylene. The flow rate of methane or acetylene is 20-100 sccm.

Preferably, in the CVD coating process, carrier gas is also introduced, the carrier gas is nitrogen or argon, and the volume ratio of the carrier gas to the gaseous carbon source is 10-20:1.

And (3) after coating, sieving with a 300-400 mesh sieve for 20-30 min.

The silicon nanowire is mainly prepared based on the following principles that 1) an iridium source is heated and decomposed in inert atmosphere, iridium particles generated by decomposition are uniformly dispersed on the surface of micron-sized silicon powder, the iridium particles are contacted with the surface of micron-sized silicon, ir-Si eutectic alloy liquid drops are formed locally, 2) solid silicon is continuously dissolved into the liquid drops from liquid drop/silicon contact interfaces, silicon atoms are diffused from a high temperature side (contact interface) to a low temperature side (top of the liquid drops) in the liquid drops, silicon is separated out from the liquid drops and a gas phase interface, and the liquid drops are pushed to move upwards, so that the silicon nanowire is formed.

The invention also provides a carbon-coated silicon nanowire anode material, which is prepared by the preparation method.

A third aspect of the invention provides a battery comprising the carbon-coated silicon nanowire anode material.

Preferably, the battery is a lithium ion battery or a sodium ion battery, etc.

Preferably, the negative electrode sheet of the battery comprises the carbon-coated silicon nanowire negative electrode material.

Preferably, the negative electrode sheet of the battery is prepared by the following method:

and mixing the carbon-coated silicon nanowire anode material, the conductive agent, the binder and the solvent to obtain slurry, and coating the slurry on a current collector to obtain the anode sheet.

The conductive agent component is not particularly limited, and any conductive agent component commonly used in the art may be used, and may be exemplified by one or more of conductive carbon black, carbon nanotubes, carbon fibers, and graphene. The binder component is not particularly limited, and any binder component commonly used in the art may be used, and may be exemplified by one or more of PVDF, polytetrafluoroethylene, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

Compared with the prior art, the invention has the following beneficial effects:

1. The invention adopts micron-sized silicon powder as the initial raw material, the price of the composite anode material is far lower than that of the traditional silicon-based anode-dependent nanometer silicon powder, and adopts low-cost iridium sources such as iridium nitrate, iridium chloride, iridium acetate and the like as catalysts, so that the composite anode material of the silicon nanowire is efficiently converted from the low-cost raw materials such as the iridium sources and the micron-sized silicon, thereby solving the problems of complex preparation process and high cost of the traditional silicon-carbon anode material and sweeping one of main barriers for large-scale commercial application of the traditional silicon-carbon anode material.

2. The preparation process comprises three core steps of dispersion drying, ball milling sieving and CV coating, does not need complex equipment and multi-step purification, has simple process, high efficiency and low cost, does not generate and discharge three wastes in the whole process, avoids the hidden trouble of environmental pollution in the conventional preparation technology, combines the advantages of low cost of raw materials, simple process and nano structure performance, and has huge industrialization potential.

3. The silicon nanowire structure formed by in-situ growth has one-dimensional characteristics and internal gaps, wherein the nanowires mainly expand and shrink along the axial direction when being charged and discharged, the radial stress is smaller, the integral damage of the electrode structure is reduced, the gaps between the nanowires and the micron silicon particles provide precious buffer space for the volume expansion of silicon during lithium intercalation, electrode pulverization is effectively inhibited, the repeated contact between an active material and electrolyte is reduced by a more stable structure, the continuous growth and rupture of an SEI film are reduced, and the coulomb efficiency and the cycle life are improved.

4. The iridium source not only serves as a catalyst in the reaction to promote the growth of the silicon nanowire, but also the decomposition products (metal Ir or iridium silicide such as IrSi) of the iridium source can be embedded or attached to the surface/matrix of the silicon nanowire in situ, and the high-conductivity iridium/iridium silicide particles construct efficient electron transmission channels between the silicon nanowires and a current collector, so that faster electron conduction is beneficial to improving the quick charge and quick discharge capacity (rate capability) of the battery.

5. The invention directly integrates the silicon nanowire growth process and the carbon cladding process into the silicon-carbon negative electrode growth process in one step, thereby greatly reducing the synthesis process difficulty.

Drawings

FIG. 1 is an SEM image of a carbon-coated silicon nanowire anode material made in example 1;

FIG. 2 is an SEM image of the carbon-coated silicon nanowire anode material of comparative example 1;

FIG. 3 is an SEM image of the carbon-coated silicon nanowire anode material prepared in comparative example 2;

FIG. 4 is an EDAX Mapping graph of the carbon-coated silicon nanowire anode material prepared in example 1;

fig. 5 is an EDAX Mapping spectrum of the carbon-coated silicon nanowire anode material prepared in comparative example 3.

Detailed Description

In the description of the present invention, unless otherwise indicated, the numerical range "a-b" represents an abbreviated representation of any real combination between a and b, and includes a and b. The plurality includes two, three, four, five or more.

The technical solution of the present invention will be further described by means of specific examples and drawings, it being understood that the specific examples described herein are only for aiding in understanding the present invention and are not intended to be limiting. And the drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure. Unless otherwise indicated, all materials used in the examples of the present invention are those commonly used in the art, and all methods used in the examples are those commonly used in the art.

Raw material sources in examples and comparative examples:

micron-sized silica powder 5 micron-sized silica powder of a Xinnai metal material;

nano silicon powder is a metal-resistant material of 50 nano silicon powder.

Example 1

The carbon-coated silicon nanowire anode material of the embodiment is prepared by the following steps:

(1) Adding 2000ml of ethanol into a stainless steel barrel, adding 100g of micron-sized silicon raw material and 100g of iridium acetate (52705-52-9 of Wuhanana pharmaceutical chemical Co., ltd.), carrying out ultrasonic treatment on the slurry in the barrel, wherein the ultrasonic frequency is 30 kHz, the ultrasonic power density is 1W/cm ², the ultrasonic time is 40 min, then carrying out shearing emulsification, the shearing rate is 8000 rpm and the shearing time is 40 min, placing the stainless steel barrel on an oil bath pot with the temperature of 80 ℃ and fully stirring by using a stirrer at the rotating speed of 350 rpm, heating and stirring until the solvent is evaporated by using an oil bath, enabling the solute to be solid, and then placing the mixed material into a vacuum drying box to be dried at the temperature of 80 ℃ for 6 h.

(2) Placing the mixed material obtained in the step (1) into a clean vacuum ball milling tank, placing zirconium beads with the prepared mass into the ball milling tank, wherein the ball milling beads are 1000g of 20mm zirconium beads, 600g of 2mm zirconium beads and 400g of 1mm zirconium beads, vacuumizing the ball milling tank, introducing argon gas, placing into a ball mill for ball milling, wherein the rotating speed of the ball mill is 420rpm, the ball milling time is 60 min, and the ball milled powder passes through a 200-mesh screen for 30 minutes, so as to obtain 175g of undersize powder.

(3) And (3) carrying out CVD coating on the powder of which the meshes are 200 in the step (2), introducing carrier gas nitrogen, wherein the gaseous carbon source is methane and acetylene gas, the flow rate of the nitrogen is 800sccm, the flow rate of the methane is 30sccm, the flow rate of the acetylene is 20sccm, the coating temperature is 950 ℃, the coating time is 2h, and the coated powder is screened by a 325-mesh screen for 30 minutes, so that the carbon-coated silicon nanowire anode material is obtained after the coated powder is subjected to 325-mesh screening.

Example 2

The carbon-coated silicon nanowire anode material of this example was different from example 1 in that example 2 uses iridium chloride instead of iridium acetate of example 1, and the carbon-coated silicon nanowire anode material was prepared in the same manner as in example 1.

Comparative example 1

Comparative example 1 differs from example 1 in that comparative example 1 uses 100g of the nano-sized silicon raw material instead of 100g of the micro-sized silicon raw material in example 1, and the other is the same as comparative example 1.

Fig. 1 and 2 are SEM scanning electron microscope images of the carbon-coated silicon nanowire anode materials prepared in example 1 and comparative example 1, respectively, and it can be seen that the micro-sized silicon powder and the nano-sized silicon powder can grow more silicon nanowires under the induction of iridium acetate.

Comparative example 2

Comparative example 2 differs from example 1 in that comparative example 2 was added with graphite instead of iridium acetate, and the other is the same as example 1.

As shown in fig. 3, the SEM image of the product prepared in comparative example 2 showed only sporadically distributed silicon nanowires.

Comparative example 3

The negative electrode material of comparative example 3 was prepared by the following steps:

(1) Placing 100g of micron-sized silicon raw material and 100g of iridium acetate into a clean vacuum ball milling tank, placing zirconium beads with the prepared mass into the ball milling tank, wherein the ball milling beads are 1000g of 20mm zirconium beads, 600g of 2mm zirconium beads and 400g of 1mm zirconium beads, vacuumizing the ball milling tank, introducing argon gas, placing into a ball mill for ball milling, wherein the rotating speed of the ball mill is 420rpm, the ball milling time is 60min, and the ball milled powder passes through a 200-mesh screen, and the sieving time is 30 minutes, so that 175g of undersize powder is obtained.

(2) And (3) carrying out CVD coating on the powder of which the meshes are 200 in the step (1), introducing carrier gas nitrogen, gaseous carbon sources such as methane and acetylene gas, wherein the flow rate of the nitrogen is 800sccm, the flow rate of the methane is 30sccm, the flow rate of the acetylene is 20sccm, the coating temperature is 950 ℃, the coating time is 2h, and sieving the coated powder with a 325-mesh sieve for 30 minutes to obtain the cathode material after the coated powder is subjected to 325-mesh sieving.

Fig. 4 and 5 are Mapping graphs of carbon-coated silicon nanowire anode materials prepared in example 1 and comparative example 3, respectively, in which the micrometer-sized silicon raw material and iridium acetate were not uniformly dispersed in advance before coating in comparative example 3, and silicon distribution was very non-uniform.

The composite materials prepared in examples 1-2 and comparative examples 1-3, single-walled carbon nanotubes (SWCNTs), polyacrylic acid (PAA) and SBR were added to deionized water in a ratio of 94.55:1:0.15:1.3:3, stirred and mixed to prepare uniform slurry, coated on copper foil, dried in a vacuum drying oven at 110 ℃ for 12 hours, and cut into a negative electrode sheet with a diameter of 14 mm. After a button cell was assembled using a metallic lithium sheet as a counter electrode and PE as a diaphragm, and a 1M LiPF ₆ solution of Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) in a volume ratio of 1:1:1 as an electrolyte, conventional electrochemical performance test and four-probe powder resistance test were performed, and the results are shown in table 1.

Table 1 test results of examples 1 to 2 and comparative examples 1 to 3

It is seen from comparative example 1 and example 2 that the silicon nanowires induced with iridium acetate exhibit better performance than iridium chloride induction. Comparative example 1 and comparative example 1 show that while the use of nano silicon powder in comparative example 1 also induces the formation of a large amount of silicon nanowires, the agglomeration phenomenon of powder produced from nano silicon powder is serious, and the battery performance is weaker than that of example 1. Comparative example 2 using graphite-induced silicon nanowires, only very small amounts of silicon nanowires can be induced to be generated, and the powder resistivity is high, and the battery performance, particularly the cycle performance, is poor. Comparative example 3, in which the micrometer-sized silicon raw material and iridium acetate were not uniformly dispersed in advance before coating, silicon was very unevenly distributed, and the performance of the prepared battery was poor.

In the preparation method of the invention, the sequence of each step is not limited to the listed sequence, and the sequential change of each step is also within the protection scope of the invention without the inventive labor for the person skilled in the art. Furthermore, two or more steps or actions may be performed simultaneously.

Finally, it should be noted that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention's embodiments. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions in a similar manner, and need not and cannot fully practice all of the embodiments. While these obvious variations and modifications, which come within the spirit of the invention, are within the scope of the invention, they are to be construed as being without departing from the spirit of the invention.

Claims

1. The preparation method of the carbon-coated silicon nanowire anode material is characterized by comprising the following steps of:

(3) And (3) carrying out chemical vapor deposition coating on the powder obtained by sieving, introducing a gaseous carbon source, coating for 1-3 hours at 850-1050 ℃, and passing through a 200-450 mesh screen after coating to obtain the carbon-coated silicon nanowire anode material.

2. The method of claim 1, wherein the micron-sized silicon powder has a particle size of 2 to 50 μm.

3. The method according to claim 1, wherein the iridium source is one or more of iridium nitrate, iridium chloride and iridium acetate;

The solvent is one or more of alcohol solvent and acetone.

4. The preparation method of claim 1, wherein the mass ratio of the micron-sized silicon powder to the iridium source is 0.8-1.2:1.

5. The preparation method of the silicon powder, according to claim 1, wherein the volume ratio of the total mass of the micron-sized silicon powder and the iridium source to the solvent is 1 g:5-15 ml.

6. The method of claim 1, wherein the micron-sized silicon powder, the iridium source and the solvent are uniformly dispersed by ultrasonic and/or shearing steps;

The ultrasonic frequency is 20-50 kHz, the ultrasonic power density is 0.5-2W/cm ², and the ultrasonic time is 30-60 min;

the shearing step comprises the following parameters of shearing rate of 3000-10000 rpm and shearing time of 30-60 min.

7. The method according to claim 1, wherein the heating temperature in the oil bath is 70-90 ℃ and the stirring speed is 200-800 rpm.

8. The method of claim 1, wherein the gaseous carbon source is methane and/or acetylene;

The flow rate of methane or acetylene is 20-100 sccm.

9. The carbon-coated silicon nanowire anode material is characterized by being prepared by the preparation method according to any one of claims 1-8.

10. A battery comprising the carbon-coated silicon nanowire anode material of claim 9.