CN-122000343-A - Silicon-carbon negative electrode material and preparation method thereof

CN122000343ACN 122000343 ACN122000343 ACN 122000343ACN-122000343-A

Abstract

The invention provides a silicon-carbon negative electrode material and a preparation method thereof, and relates to the technical field of battery manufacturing. The silicon-carbon negative electrode material comprises porous carbon, nano silicon and a nano carbon layer, at least part of nano silicon is distributed in pores of the porous carbon, at least part of the surface of the porous carbon is covered by the nano carbon layer, and the half-peak width FWHM of a diffraction peak of the porous carbon at 16-26 degrees in an X-ray diffraction spectrum is less than 12. The invention uses the high-crystallinity porous carbon carrier with FWHM less than 12, obviously enhances the mechanical strength of the skeleton, can effectively restrict the volume expansion of nano silicon and maintain the structural integrity, and reduces the expansion rate of the pole piece by matching with the coating of the carbon layer, thereby greatly prolonging the cycle life of the battery.

Inventors

ZHONG HUI
HONG JING
ZHANG YI

Assignees

佛山市格瑞芬新能源有限公司
广东道氏硅碳材料科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260409

Claims (10)

1. A silicon-carbon negative electrode material, which is characterized by comprising porous carbon, nano silicon and a nano carbon layer; at least part of the nano silicon is distributed in the pores of the porous carbon, and at least part of the surface of the porous carbon is covered by the nano carbon layer; The half-width FWHM of diffraction peaks of the porous carbon at 16-26 degrees in an X-ray diffraction spectrum is less than 12.
2. The silicon-carbon negative electrode material according to claim 1, wherein the porous carbon has a full width at half maximum FWHM of 16-26 degrees diffraction peak in an X-ray diffraction pattern of 6-9, and/or, The average pore diameter of the porous carbon is 2 nm-15 nm, and/or, The porous carbon has a pore volume of 0.30cm 3 /g~0.9cm 3 /g, and/or, The silicon-carbon anode material is in a block shape, the average grain diameter is 3-12 mu m, and/or, The weight ratio of the nano silicon in the silicon-carbon anode material is 30% -60%, and/or, The specific surface area of the silicon-carbon anode material is less than 5m 2 /g, and/or, The powder compaction density of the silicon carbon anode material under the pressure of 10 tons is 1.70g/cm 3 ~1.80g/cm 3 .
3. The silicon-carbon negative electrode material according to claim 2, wherein the silicon-carbon negative electrode material has a specific surface area <3m 2 /g.
4. A method for producing a silicon-carbon anode material as claimed in any one of claims 1 to 3, comprising: Mixing phenolic raw materials, aldehyde raw materials and pore-forming agents in a liquid phase system and carrying out polymerization reaction to obtain a precursor material; Carbonizing the precursor material to obtain a porous carbon material, wherein strong corrosive activation pore forming which damages the carbon crystal structure is not performed in the carbonization process; And (3) vapor depositing silicon in the pores of the porous carbon material, and vapor depositing a carbon layer on the surface of the material after depositing the silicon to obtain the silicon-carbon anode material.
5. The method for producing a silicon-carbon negative electrode material according to claim 4, wherein the phenolic raw material comprises at least one of phenol, hydroquinone, resorcinol, and/or, The aldehyde raw material comprises at least one of formaldehyde, acetaldehyde and furfural, and/or, The pore-forming agent comprises an amphiphilic block copolymer, and/or, The carbonization treatment temperature is 900-1400 ℃, and/or, The step of mixing and carrying out polymerization reaction comprises the steps of pre-polymerizing the phenolic raw material and the aldehyde raw material under the condition that the pH value is 4-8, adding the pore-forming agent for continuous reaction, and/or, The temperature of the vapor deposition silicon is 400-550 ℃, the gas source comprises mixed gas of silane and inert gas, the volume ratio of the silane to the inert gas is 1 (0.5-10), the deposition duration is 5-50 h, and/or, The temperature of the vapor deposition carbon layer is 500-650 ℃, the gas source comprises a mixed gas of acetylene and inert gas, the volume ratio of the acetylene to the inert gas is 1 (1-5), and the deposition duration time is 2-20 h.
6. The porous carbon material is characterized in that the half-width FWHM of diffraction peaks of 16-26 degrees in an X-ray diffraction spectrum of the porous carbon material is less than 12.
7. The porous carbon material according to claim 6, wherein the porous carbon material has a full width at half maximum FWHM of 16 to 26 diffraction peaks in an X-ray diffraction pattern of 6 to 9, and/or, The average pore diameter of the porous carbon material is 2 nm-15 nm, and/or, The pore volume of the porous carbon material is 0.30cm 3 /g~0.9cm 3 /g.
8. A negative electrode sheet, comprising the silicon-carbon negative electrode material according to any one of claims 1 to 3, or the silicon-carbon negative electrode material produced by the production method according to claim 4 or 5.
9. A battery comprising the negative electrode sheet according to claim 8.
10. An electrical device comprising the battery of claim 9.

Description

Silicon-carbon negative electrode material and preparation method thereof Technical Field The invention relates to the technical field of battery manufacturing, in particular to a silicon-carbon anode material and a preparation method thereof. Background The lithium ion battery has become one of the most widely used energy storage devices at present by virtue of the remarkable advantages of high energy density, long cycle life, no memory effect and the like. Along with the continuous expansion and upgrading of application scenes such as mobile communication terminals, electric automobiles, large-scale energy storage power stations and the like, the market brings forward more stringent requirements on the energy density of lithium ion batteries. In order to break through the energy bottleneck of the existing battery system, the development of electrode materials with higher specific capacity has become a common knowledge of research hotspots and industry in the current electrochemical energy storage field. Among the numerous negative electrode materials, silicon-based negative electrodes are considered as one of the key materials for improving the energy density of lithium ion batteries because of their extremely high theoretical specific capacities (much higher than those of conventional graphite negative electrodes). However, the silicon material undergoes great volume expansion and shrinkage during the lithium intercalation/deintercalation process, and the great volume change easily causes pulverization and falling of active particles, thereby damaging the conductive network of the electrode. In order to alleviate the problem, the prior art generally adopts porous carbon as a carrier, nano silicon is filled into a pore structure of the porous carbon by a vapor deposition method and the like, and the volume expansion of the silicon is buffered by utilizing the binding action of a carbon skeleton and a reserved space, so that the silicon-carbon composite anode material is prepared. However, existing silicon carbon negative electrode carriers, i.e., porous carbon materials, generally rely on an activation process for their preparation. The activation process is essentially an etching reaction aimed at creating a rich pore structure inside the carbon material by physical or chemical means. Although this method can effectively increase the pore volume to load more silicon, the etching reaction may severely damage the crystal structure of the carbon material, resulting in a great reduction in the graphitization degree or crystallinity of the carbon material. This low crystallinity structural feature directly results in a significant decrease in the mechanical strength of the porous carbon matrix, rendering its skeletal structure weaker. In summary, since the existing porous carbon carrier has insufficient matrix strength due to activation and pore-forming, the fragile carbon skeleton is difficult to play an effective mechanical binding and supporting role in the face of high expansion stress generated by silicon charge and discharge, and structural collapse or rupture is very easy to occur in the circulation process. The method can not effectively inhibit the volume effect of silicon, can also cause the overall instability of the cathode plate structure, and finally is characterized in that the cycle life of the lithium ion battery is difficult to meet the long-period use requirement. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide a silicon-carbon negative electrode material and a preparation method thereof, wherein the silicon-carbon negative electrode material is prepared by adopting a high-crystallinity high-strength porous carbon carrier to restrict nano silicon expansion, so that the expansion rate of a pole piece is remarkably reduced, and the cycle life of a battery is greatly prolonged. In order to achieve the above object of the present invention, the following technical solutions are specifically adopted: In a first aspect, the present invention provides a silicon-carbon negative electrode material comprising a porous carbon, a nano-silicon and a nano-carbon layer; at least part of the nano silicon is distributed in the pores of the porous carbon, and at least part of the surface of the porous carbon is covered by the nano carbon layer; The half-width FWHM of diffraction peaks of the porous carbon at 16-26 degrees in an X-ray diffraction spectrum is less than 12. In an alternative embodiment, the half-width FWHM of the diffraction peak of the porous carbon at 16-26 degrees in the X-ray diffraction pattern is 6-9, and/or, The average pore diameter of the porous carbon is 2 nm-15 nm, and/or, The porous carbon has a pore volume of 0.30cm 3/g~0.9cm3/g, and/or, The silicon-carbon anode material is in a block shape, the average grain diameter is 3-12 mu m, and/or, The weight ratio of the nano silicon in the silicon-carbon anode material is 30% -60