Functionalized design carbon-coated silicon negative electrode material and preparation method thereof

Abstract

This invention discloses a functionalized carbon-coated silicon anode material and its preparation method, comprising the following steps: S1, selecting metal M as the polishing medium to polish Si and / or SiO. x M-Si / SiOx powder was used to prepare M-Si / SiOx, with some M distributed on its surface to form a metal layer; in M-Si / SiOx x In the middle, Si / SiO x The mass ratio of M to S2 is (100-1000):1; S2, in M-Si / SiO x Adding an organic carbon source and continuing grinding, followed by high-temperature carbonization of the resulting mixture, yields C-M-Si / SiO2. x Anode material; or fluidized bed vapor deposition method, using M-Si / SiO2. x Using the metal layer M as a catalyst and organic gas as a carbon source, radially grown graphene is generated in situ, thus obtaining radially grown graphene-M-Si / SiO. x The negative electrode material has a specific structure. This invention avoids the formation of a protective layer by high-temperature decomposition of nitrogen-containing organic matter, or by employing a fluidized bed vapor deposition method, thus preventing the formation of C-M-Si / SiO₂. x The anode material clumps together, thus avoiding the problem of re-fragmentation and partial breakage of the newly formed carbon coating layer.

Description

Technical Field

[0001] This invention relates to the field of electrode material preparation, specifically to a functionalized carbon-coated silicon anode material and its preparation method. Background Technology

[0002] The significant volume changes during charge and discharge of silicon anodes severely impact their performance, limiting their commercial applications. Traditional methods for improvement involve grinding or gas-jetting silicon or silicon-oxygen particles to a suitable size before carbon coating. However, solid-state silicon anode materials are prone to agglomeration after sintering, requiring re-crushing. This can cause partial breakage of the newly formed carbon coating layer, affecting material consistency. This is a major reason limiting the large-scale production of silicon anode materials using solid-state methods. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies and solve the problem that silicon anode materials easily agglomerate after sintering, requiring re-crushing and causing partial breakage of the newly formed carbon coating layer. Therefore, it is necessary to develop a stable method for preparing carbon-coated silicon anode materials to avoid agglomeration of silicon anode materials after sintering.

[0004] To achieve the above objectives, the present invention provides a method for preparing a functionalized carbon-coated silicon anode material, comprising the following steps:

[0005] S1, Select metal M as the grinding medium to grind Si and / or SiO. x Powder to prepare M-Si / SiO x A portion of M is distributed on its surface to form a metal layer; in the M-Si / SiO x In the middle, Si / SiO x The mass ratio of M to M is (100-1000):1;

[0006] S2, in the M-Si / SiO x An organic carbon source is added and grinding continues. The resulting mixture is then carbonized at high temperature to prepare CM-Si / SiO. x Anode material; wherein the organic carbon source comprises nitrogen-containing organic matter; the organic carbon source and M-Si / SiO x The mass ratio is (0.001~1):1.

[0007] Preferably, the metal M is one of Fe, Co, Ni, or an alloy thereof.

[0008] Preferably, the M-Si / SiO prepared in step S1 x The particle size is 2–5 μm.

[0009] Preferably, in step S2, the organic carbon source is selected as a mixture of asphalt and PVP, wherein the mass ratio of asphalt to PVP is (0.5~2):1; the method of adding the organic carbon source during grinding is as follows: in the M-Si / SiO x First, add PVP and grind thoroughly, then add asphalt and grind thoroughly.

[0010] Preferably, in step S2, the carbonization temperature is 650-1000℃.

[0011] This invention also discloses a functionalized carbon-coated silicon anode material prepared using the above method, wherein the material is CM-Si / SiO. x The anode material, from the outside to the inside, consists of: a surface layer formed by the carbonization of an organic carbon source, a protective layer formed by the decomposition of nitrogen-containing organic matter, and metal M and Si / SiO. x The inner layer that is formed.

[0012] This invention also provides a radially grown graphene-M-Si / SiO x The method for preparing the negative electrode material with the structure includes the following steps:

[0013] S1, Select metal M as the grinding medium to grind Si and / or SiO. x Powder to prepare M-Si / SiO x A portion of M is distributed on its surface to form a metal layer; in the M-Si / SiO x In the middle, Si / SiO x The mass ratio of M to M is (100-1000):1;

[0014] S2', using a fluidized bed vapor deposition method, with the M-Si / SiO x Using the metal layer M as a catalyst and organic gas as a carbon source, radially grown graphene is generated in situ, thus obtaining radially grown graphene-M-Si / SiO. x Negative electrode material of the structure.

[0015] Preferably, in step S2', the organic gas is selected from at least one of methane and ethylene.

[0016] Preferably, in step S2', the pyrolysis temperature is 750-1000℃.

[0017] This invention also discloses radially grown graphene-M-Si / SiO2 prepared using the above method. x Negative electrode material of the structure.

[0018] The beneficial effects of this invention include:

[0019] (1) By grinding and controlling the quality of the grinding media and the grinding time, metal M can be uniformly dispersed in Si / SiO with a suitable particle size. x A catalyst layer is formed on the surface of the particles; then, CM-Si / SiO can be prepared by high-temperature carbonization or fluidized bed vapor deposition. x Anode materials are simple and easy to develop.

[0020] (2) For M-Si / SiO x The particles are processed by sequentially adding PVP and asphalt. During high-temperature carbonization, the PVP undergoes gasification and decomposition, resulting in CM-Si / SiO₂. x The anode material has a loose structure, which allows it to maintain CM-Si / SiO in this state. x Without clumping, a nitrogen-containing carbon coating layer can be formed on the surface of the negative electrode material. The carbon-doped nitrogen structure can improve the conductivity of carbon, resulting in a negative electrode material with excellent electrochemical performance.

[0021] (3) The steps of grinding and high-temperature carbonization of silicon anode, metal, and organic carbon source can be easily achieved for CM-Si / SiO. x Mass production of anode materials.

[0022] (4) For M-Si / SiO x The particles are deposited using a fluidized bed deposition method to catalyze the cracking of methane or ethylene, which not only avoids product agglomeration but also yields radially grown graphene-M-Si / SiO2. x The radially grown graphene structure of the negative electrode material gives the entire negative electrode material superior electrochemical performance and better conductivity. Attached Figure Description

[0023] Figure 1 SEM images of Fe-SiO prepared by S1 in Examples 1 and 2 of the present invention;

[0024] Figure 2 TEM images of Fe-SiO prepared by S1 in Examples 1 and 2 of the present invention;

[0025] Figure 3 The C-Fe-SiO prepared in Example 1 of this invention x High-magnification TEM image;

[0026] Figure 4 The C-Fe-SiO prepared in Example 1 of this invention x Ratio performance diagram;

[0027] Figure 5 The C-Fe-SiO prepared in Example 1 of this invention x Cycle life diagram;

[0028] Figure 6 The radially grown graphene-Fe-SiO2 prepared in Example 2 of this invention x SEM image;

[0029] Figure 7 The radially grown graphene-Fe-SiO2 prepared in Example 2 of this invention x TEM image;

[0030] Figure 8 The radially grown graphene-Fe-SiO2 prepared in Example 2 of this invention x Ratio performance diagram;

[0031] Figure 9 The radially grown graphene-Fe-SiO2 prepared in Example 2 of this invention x Cycle life diagram. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise clearly indicated, each aspect or embodiment defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0034] This invention provides a method for preparing a functionalized carbon-coated silicon anode material, the specific steps of which include:

[0035] S1 uses metal M or an alloy of metal M as the grinding media to grind large particles of Si and / or SiO. x Through high-energy collisions, a small amount of metal M is attached to Si and / or SiO. x The surface of M-Si / SiO is thus prepared. x The grinding time is generally 0.1-5 hours; where M is a metallic element, preferably Fe, Co, or Ni; x is the ratio of oxygen atoms to silicon atoms in silicon oxide, x > 0, and Si and SiO x It can be mixed in any proportion.

[0036] The grinding media is preferably made of Fe, Co, or Ni, or alloys of these metals; the grinding media is spherical, ellipsoidal, cubic, or cylindrical, preferably cylindrical; the grinding media is in contact with Si / SiO.x The mass ratio is (10-1000):1, and the grinding media and Si / SiO are... x Both excessively high and low mass ratios will negatively impact the formation of M-Si / SiO2 during grinding. x The particle size has an impact; the M-Si / SiO formed after grinding x In the middle, Si / SiO x The mass ratio of M to M is (100-1000):1, and the resulting M-Si / SiO is formed by grinding. x The particle size is 2–5 μm.

[0037] S2, M-Si / SiO2 prepared in S1 x Carbonization is performed by adding a carbon source to prepare CM-Si / SiO. x Anode material, CM-Si / SiO x In this process, the mass fraction of carbon is 1%-7%, specifically:

[0038] In M-Si / SiO x Continue grinding with the addition of an organic carbon source or a mixed carbon source, the organic carbon source and M-Si / SiO x The mass ratio is asphalt:PVP:M-Si / SiO. x = (0.5~2):(0.5~2):1000; grinding time is generally 0.1-5h; and CM-Si / SiO is prepared by high-temperature carbonization under an inert atmosphere. x For the anode material, the preferred carbonization temperature is 650-1000℃; the carbonization time is generally 0.5-5 hours; the preferred organic carbon source is a mixture of PVP and asphalt, with PVP added first and then thoroughly ground, followed by asphalt and another thorough grinding. Asphalt, as the main carbon source, is widely available, while PVP, as the nitrogen source, provides better conductivity when coated with nitrogen-doped graphene. Furthermore, PVP decomposes at high temperatures, so it is in a gaseous decomposition state during carbonization. Therefore, adding PVP first allows it to be located inside the asphalt, where its gaseous decomposition forms a protective layer, ensuring the CM-Si / SiO2 structure is optimized. x The anode material has a loose structure, which allows it to maintain CM-Si / SiO in this state. x It will not clump. During the carbonization process, the protective gas is argon or a hydrogen-argon mixture, preferably a hydrogen-argon mixture. This method is relatively simple and suitable for large-scale production.

[0039] Graphene is widely used in silicon anode materials due to its excellent properties. However, powdered graphene is prone to agglomeration, which limits some of its properties. In-situ or radial growth of carbon nanotubes on the surface of silicon anodes is common, but there are few reports of large-scale radial growth of graphene. Radially grown graphene can not only act as a fast electron conductor, but also as a directional electron conductor between particles when the silicon anode expands, preventing the electrons between particles from losing contact and causing silicon anode failure.

[0040] Currently, the conventional method for graphene-coated silicon anodes involves mixing existing graphene (or graphene oxide) powder with silicon anode particles, or using electrostatic adsorption to adsorb graphene oxide onto silicon oxide, followed by chemical reduction to prepare graphene-coated silicon oxide anodes. Graphene is a single-layer graphite. If graphene powder and silicon anodes are simply physically mixed and sintered for coating, graphene, due to its large specific surface area, tends to agglomerate easily, making single-layer coating difficult. Moreover, agglomerated graphene cannot exhibit the excellent electrical and thermal conductivity and large specific surface area properties of single-layer graphene, thus affecting the improvement of the performance of graphene-reinforced composite materials.

[0041] The process of coating silicon-oxygen anodes with graphene oxide technology, followed by chemical reduction to convert the graphene oxide back into graphene, is not only complex but also requires large amounts of toxic reducing agents. Furthermore, the reduced graphene oxide contains numerous defects. Moreover, this method cannot yield radially grown graphene.

[0042] This invention also provides a method for preparing radially grown graphene-coated silicon anode material, the specific steps of which include:

[0043] S1 is the same as S1 in the aforementioned preparation method of functionalized carbon coating silicon anode material;

[0044] S2', with M-Si / SiO x Using methane or ethylene as raw material, radially grown graphene-M-Si / SiO2 can be obtained by fluidized bed vapor deposition with a metal layer (M) as a catalyst to catalyze the cracking of methane or ethylene. x The negative electrode material has a preferred pyrolysis temperature of 750-1000℃ and a pyrolysis time of 0.1-5h. Fluidized bed preparation technology is used to keep the material in a fluidized state throughout the preparation process, so the product will not clump and does not need to be crushed again.

[0045] Graphene is first grown on the catalyst surface, using the catalyst particles as nuclei and growing radially along the silicon surface. Once it completely encapsulates the catalyst particles, the gaps between the catalyst particles, i.e., the Si / SiO₂ ratio, are then filled. xAmorphous carbon grows in areas where there are no catalyst particles on the surface, thus forming a structure of oriented graphene and amorphous carbon coating.

[0046] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0047] Example 1

[0048] S1, using 20kg Fe rods as grinding media, 1kg of commercially available 100-mesh SiO as raw material is subjected to high-energy grinding to obtain Fe-SiO material;

[0049] S2.1, 100g PVP is added to the mixture obtained in step S1 and ground for 30min; then 100g asphalt is added and ground for another 30min.

[0050] S2.2, Take the mixture obtained in step S2.1 and carbonize it in a 10% hydrogen-argon mixture at 950℃ for 2 hours to obtain C-Fe-SiO. x Material.

[0051] like Figure 1 As shown in the SEM image of the Fe-SiO raw material, the particle size of the ground Fe-SiO material is 2-5 μm; Figure 2 As shown in the transmission electron microscope, Fe atoms are uniformly dispersed on the SiO surface.

[0052] like Figure 3 As shown in the high-magnification transmission electron microscope image, the product obtained in Example 1 contains SiO₂. x A uniform layer of amorphous carbon is coated on the surface, forming C-Fe-SiO. x .

[0053] like Figure 4 As shown, the C-Fe-SiO obtained in Example 1... x The discharge capacity at 0.2C, 0.5C, and 1C is not significantly different, indicating that this material has quite good rate performance.

[0054] like Figure 5 As shown, the C-Fe-SiO obtained in Example 1... x After 100 cycles of 0.5C charge-discharge, the capacity retention rate is over 92%, and the gram capacity is still greater than 1000mAh / g, demonstrating good cycle performance.

[0055] Example 2

[0056] S1 is the same as S1 in Example 1;

[0057] S2': Take 500g of Fe-SiO obtained in step S1, and pyrolyze it in a methane fluidized bed vapor deposition apparatus at a controlled temperature of 900℃ for 1 hour to obtain radially grown graphene-Fe-SiO. x Material;

[0058] like Figure 6 As shown in the SEM image of the negative electrode material in Example 2, SiO x The surface is covered with a layer of radially grown graphene sheets, verifying the radially grown graphene-Fe-SiO₂. x The formation of negative electrode materials. For example... Figure 7 As shown, the radially grown graphene-Fe-SiO₂... x TEM images of the anode material show the radial growth state of graphene and SiO₂. x The surface is surrounded by graphene with this special structure. This graphene structure can not only act as a fast electron conductor, but also as an electron bridge to maintain good connection between silicon anode particles. This feature makes the entire anode material have better electrochemical performance and better conductivity.

[0059] like Figure 8 As shown, the radially grown graphene-Fe-SiO2 obtained in Example 2 x The rate performance graph of the anode material shows that it still maintains a discharge capacity of 1050 mAh / g under 8C discharge conditions, demonstrating excellent rate performance. Figure 9 As shown, this negative electrode material retains 85.4% of its capacity after 100 cycles at 2C, exhibiting excellent high-rate charge-discharge lifetime. Its rate performance and cycle life are superior to those of Example 1.

[0060] In summary, by controlling the quality of the grinding media and the grinding time, this invention can achieve uniform dispersion of metal atoms in Si / SiO with a suitable particle size. x A catalyst layer is formed on the surface of the particles; then, CM-Si / SiO can be prepared by high-temperature carbonization or fluidized bed vapor deposition. x Anode materials are simple and easy to develop.

[0061] In the high-temperature carbonization method, PVP is in a state of gasification and decomposition, which makes CM-Si / SiO x The anode material has a loose structure, which allows it to maintain CM-Si / SiO in this state. x Without clumping, a nitrogen-containing carbon coating layer can form on the surface of the anode material. The nitrogen-doped carbon structure can improve the conductivity of carbon, resulting in anode materials with excellent electrochemical performance. Through grinding and high-temperature carbonization of silicon anodes, metals, and organic carbon sources, CM-Si / SiO can be easily achieved.x Mass production of anode materials.

[0062] And for M-Si / SiO x The particles are deposited using a fluidized bed deposition method to catalyze the cracking of methane or ethylene, which not only avoids product agglomeration but also yields radially grown graphene-M-Si / SiO2. x The radially grown graphene structure of the negative electrode material gives the entire negative electrode material superior electrochemical performance and better conductivity.

[0063] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a functionalized carbon-coated silicon anode material, characterized in that, Includes the following steps: S1, selecting a metal M as a grinding medium to grind Si and / or SiO x powder to prepare M-Si / SiO x , part of M is distributed on the surface thereof to form a metal layer; in the M-Si / SiO x , the mass ratio of Si / SiO x to M is (100-1000): 1; S2, in the M-Si / SiO x An organic carbon source is added and grinding continues. The resulting mixture is then carbonized at high temperature to prepare CM-Si / SiO. x Anode material; wherein the organic carbon source comprises nitrogen-containing organic matter; the organic carbon source and M-Si / SiO x The mass ratio is (0.001~1):1; the organic carbon source is a mixture of asphalt and PVP, wherein the mass ratio of asphalt to PVP is (0.5~2):1; the method for adding the organic carbon source during grinding is as follows: in the M-Si / SiO x First, add PVP and grind thoroughly, then add asphalt and grind thoroughly.

2. A method for preparing a functionalized carbon-coated silicon anode material, characterized in that, Includes the following steps: S1, Select metal M as the grinding medium to grind Si and / or SiO. x Powder to prepare M-Si / SiO x A portion of M is distributed on its surface to form a metal layer; in the M-Si / SiO x In the middle, Si / SiO x The mass ratio of M to M is (100-1000):1; S2', using a fluidized bed vapor deposition method, with the M-Si / SiO x Using the metal layer M as a catalyst and organic gas as a carbon source, radially grown graphene is generated in situ, thus obtaining radially grown graphene-M-Si / SiO. x Negative electrode material of the structure.

3. The method for preparing functionalized carbon-coated silicon anode material as described in claim 1 or 2, characterized in that, The metal M is one of Fe, Co, Ni or an alloy thereof.

4. The method for preparing functionalized carbon-coated silicon anode material as described in claim 1 or 2, characterized in that, The M-Si / SiO prepared in step S1 x The particle size is 2~5μm.

5. The method for preparing functionalized carbon-coated silicon anode material as described in claim 1, characterized in that, In step S2, the carbonization temperature is 650-1000℃.

6. The method for preparing functionalized carbon-coated silicon anode material as described in claim 2, characterized in that, In step S2', the organic gas is selected from at least one of methane and ethylene.

7. The method for preparing functionalized carbon-coated silicon anode material as described in claim 2, characterized in that, In step S2', the pyrolysis temperature is 750-1000℃.

8. A functionalized carbon-coated silicon anode material prepared using the method of claim 1, characterized in that, The material is CM-Si / SiO. x The anode material, from the outside to the inside, consists of: a surface layer formed by the carbonization of an organic carbon source, a protective layer formed by the decomposition of nitrogen-containing organic matter, and metal M and Si / SiO. x The inner layer that is formed.

9. A functionalized carbon-coated silicon anode material prepared using the method of claim 2, characterized in that, The material is radially grown graphene-M-Si / SiO. x Negative electrode material of the structure.

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