Silicon-carbon negative electrode material and preparation method thereof

Abstract

The present invention belongs to the technical field of lithium battery negative electrode materials, and in particular relates to a silicon-carbon negative electrode material and a preparation method thereof. The present invention provides a silicon-carbon negative electrode material, the raw material composition of which includes a coating material, a nano-silicon material, carbon black, and a negative electrode material, wherein the coating material is any one or a mixture of asphalt and resin, and the negative electrode material is any one or a mixture of natural graphite, artificial graphite and hard carbon. The present invention also provides a preparation method for the above-mentioned silicon-carbon negative electrode material, the steps of which include in sequence: coating nano-silicon material, coating negative electrode material, carbonization, and screening. The preparation method mainly includes two coating operations, and does not use the CVD method, and can eventually prepare a silicon-carbon negative electrode material with a large capacity and a high first efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery negative electrode materials, and in particular relates to a silicon-carbon negative electrode material and a preparation method thereof. Background Art

[0002] Generally, the common lithium battery negative electrode materials currently available mainly include natural graphite, artificial graphite, hard carbon, and soft carbon. Compared to traditional graphite negative electrode materials, the relatively recent silicon-carbon negative electrode materials have advantages including high energy density, abundant silicon reserves, and environmental friendliness. However, their disadvantages include large volume expansion, low initial efficiency, poor cycle stability, easy breakage and pulverization, and consumption of large amounts of active lithium. Ultimately, directly mixing silicon-carbon negative electrode materials using conventional methods can severely impact the battery's cycle stability and rate performance.

[0003] Therefore, various solutions have emerged to address the above-mentioned defects of silicon-carbon anode materials, the most common of which is porous core-shell technology. Silicon-carbon anode materials with porous core-shell structures have the following advantages over conventional silicon-carbon anode materials:

[0004] 1. The porous structure can buffer the volume expansion of silicon during the lithium ion insertion and extraction process;

[0005] 2. Reduce the degree of direct contact between the silicon surface and the electrolyte, and reduce the amount of active lithium consumed by silicon.

[0006] Ultimately, the porous core-shell structured silicon-carbon negative electrode material was able to significantly improve the battery's cycle stability and rate performance.

[0007] For example, a Chinese invention patent with patent publication number CN115483385A and publication date 2022.12.16 discloses a method for preparing a three-dimensional composite silicon-carbon negative electrode material, including the following steps: S1. Activating carbon black to obtain porous carbon black; S2. Adding 1-10 parts of expanded graphite to 1-300 parts of deionized water and dispersing for 1-5 hours to obtain a suspension; S3. Adding 1-40 parts of porous carbon black to the suspension and dispersing for 0.2-1 hours to obtain a dispersion, and then drying the dispersion to obtain a composite structure carbon; S4. Decomposing and depositing a silicon source on the composite structure carbon by CVD to obtain a three-dimensional porous silicon carbon; S5. Mixing the three-dimensional porous silicon carbon and amorphous carbon, and then carbonizing them to obtain a three-dimensional composite silicon-carbon negative electrode material.

[0008] The three-dimensional composite silicon-carbon negative electrode material in this invention patent ensures the material's high lithium storage capacity and long-cycle stability by depositing an ultra-thin nano-silicon layer inside porous carbon black and graphene nanosheets and using the space in the porous carbon material to alleviate the volume expansion caused by silicon.

[0009] However, in the actual process of this preparation method, there are at least the following two shortcomings, which are also the technical problems to be solved by the present invention:

[0010] First, this method includes one compounding step and two coating steps, which is relatively complicated;

[0011] Second, this method uses chemical vapor deposition (CVD). The CVD process is relatively complicated, requires a high level of technology, and is also relatively expensive.

[0012] So to sum up, there is an urgent need for a new preparation method that does not use chemical vapor deposition and has relatively simple overall operation, so as to produce silicon-carbon negative electrode materials with basically the same overall performance. Summary of the Invention

[0013] The present invention provides a silicon-carbon negative electrode material, the raw materials of which include a coating material, a nano-silicon material, carbon black, and a negative electrode material, wherein the coating material is any one or a mixture of asphalt and resin, and the negative electrode material is any one or a mixture of natural graphite, artificial graphite and hard carbon.

[0014] The present invention also provides a method for preparing the aforementioned silicon-carbon anode material, comprising the following steps: coating with a nano-silicon material, coating with an anode material, carbonization, and screening. This method primarily includes two coating operations and, without the use of CVD, ultimately produces a silicon-carbon anode material with a large capacity and high initial efficiency.

[0015] The technical solution adopted by the present invention to solve the above problems is: silicon-carbon negative electrode material, the raw material composition includes coating material, nano-silicon material, carbon black, and negative electrode material, wherein the coating material is any one or a mixture of asphalt and resin, and the negative electrode material is any one or a mixture of natural graphite, artificial graphite and hard carbon.

[0016] The preparation method of silicon-carbon negative electrode material comprises the following steps in sequence:

[0017] S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material;

[0018] S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material;

[0019] S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material;

[0020] S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product.

[0021] A further preferred technical solution is that: in S1, the weight ratio of the coating material to the nano-silicon material is 1:(2-7).

[0022] A further preferred technical solution is that in S1, the amount of carbon black added accounts for 1-3% of the total weight of the coating material, nano-silicon material and carbon black.

[0023] A further preferred technical solution is that in S1, the temperature of the drying operation is 80-150°C and the time is 12-24 hours.

[0024] A further preferred technical solution is that in S2, the weight ratio of the silicon coating material to the negative electrode material is 1:(3-9).

[0025] A further preferred technical solution is that in S3, the maximum temperature of the carbonization treatment is 1100-1300°C, and the temperature is maintained at the maximum temperature for at least 4 hours.

[0026] A further preferred technical solution is that in S4, the mesh size of the sieve used in the screening process is ≥500 meshes.

[0027] In the present invention, the silicon-carbon negative electrode material and its preparation method have the following four beneficial effects compared with the prior art.

[0028] First, the structural shape of the silicon-carbon negative electrode material is a porous core-shell structure, in which the "core" is the negative electrode material and the "shell" is the coating material, nano-silicon material and carbon black. The resin-based coating material greatly reduces the contact between silicon and the electrolyte, reduces the amount of active lithium consumed by silicon, alleviates the harmful decomposition of the electrolyte, and ultimately improves the cycle performance of the electrode.

[0029] Second, the "pores" in the porous core-shell structure are effectively formed by carbonization, and the sintered layer formed by the resin-based coating material ensures that the volume expansion problem of the silicon-carbon negative electrode material can be fully alleviated.

[0030] Third, the "shell" or coating layer has a relatively large structural strength. A large number of "holes" are opened on it, and it is not easily crushed or collapsed by the rolling action during the electrode manufacturing process.

[0031] Fourth, the entire preparation method mainly includes two coating operations and does not use the CVD method. Therefore, the method is simple as a whole, has high preparation efficiency and relatively low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the microstructure of the silicon coating material in the present invention.

[0033] Figure 2 Schematic diagram of the microstructure of the negative electrode material in the present invention.

[0034] Figure 3 Schematic diagram of the microstructure of the negative electrode coating material in the present invention.

[0035] Figure 4 Schematic diagram of the microstructure of the carbonized material in the present invention.

[0036] From the attached Figure 4 It can be seen that the final carbonized material has a more uniform size and a more suitable particle size range as a silicon-carbon negative electrode material compared to the silicon coating material, negative electrode material, and negative electrode coating material. DETAILED DESCRIPTION

[0037] The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

[0038] Example 1

[0039] A silicon-carbon negative electrode material, the raw materials of which include coating material, nano-silicon material, carbon black, and negative electrode material.

[0040] Wherein, the coating material is petroleum asphalt-based resin, and the negative electrode material is artificial graphite.

[0041] A method for preparing the silicon-carbon negative electrode material comprises the following steps in sequence:

[0042] S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material;

[0043] S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material;

[0044] S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material;

[0045] S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product.

[0046] In S1, the weight ratio of the coating material to the nano-silicon material is 1:3.

[0047] In S1, the added amount of the carbon black accounts for 1% of the total weight of the coating material, nano-silicon material and carbon black.

[0048] In S1, the drying operation is performed at a temperature of 120° C. for 20 hours.

[0049] In S2, the weight ratio of the silicon coating material to the negative electrode material is 1:3.

[0050] In S3, the maximum temperature of the carbonization treatment is 1100° C., and the temperature is maintained at the maximum temperature for 6 hours.

[0051] In S4, the mesh size of the sieve used in the sieving process is 500 meshes.

[0052] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0053] Example 2

[0054] A silicon-carbon negative electrode material, the raw materials of which include coating material, nano-silicon material, carbon black, and negative electrode material.

[0055] Wherein, the coating material is medium-temperature coal tar, and the negative electrode material is natural graphite.

[0056] A method for preparing the silicon-carbon negative electrode material comprises the following steps in sequence:

[0057] S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material;

[0058] S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material;

[0059] S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material;

[0060] S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product.

[0061] In S1, the weight ratio of the coating material to the nano-silicon material is 1:4.

[0062] In S1, the added amount of the carbon black accounts for 3% of the total weight of the coating material, nano-silicon material and carbon black.

[0063] In S1, the drying operation is performed at a temperature of 105° C. for 15 hours.

[0064] In S2, the weight ratio of the silicon coating material to the negative electrode material is 1:4.

[0065] In S3, the maximum temperature of the carbonization treatment is 1200° C., and the temperature is maintained at the maximum temperature for 5 hours.

[0066] In S4, the mesh size of the sieve used in the sieving process is 500 meshes.

[0067] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0068] Example 3

[0069] A silicon-carbon negative electrode material, the raw materials of which include coating material, nano-silicon material, carbon black, and negative electrode material.

[0070] Wherein, the coating material is phenolic resin, and the negative electrode material is hard carbon.

[0071] A method for preparing the silicon-carbon negative electrode material comprises the following steps in sequence:

[0072] S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material;

[0073] S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material;

[0074] S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material;

[0075] S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product.

[0076] In S1, the weight ratio of the coating material to the nano-silicon material is 1:6.

[0077] In S1, the added amount of the carbon black accounts for 2% of the total weight of the coating material, nano-silicon material and carbon black.

[0078] In S1, the drying operation is performed at a temperature of 90° C. for 24 hours.

[0079] In S2, the weight ratio of the silicon coating material to the negative electrode material is 1:5.

[0080] In S3, the maximum temperature of the carbonization treatment is 1300° C., and the temperature is maintained at the maximum temperature for 4 hours.

[0081] In S4, the mesh size of the sieve used in the sieving process is 500 meshes.

[0082] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0083] Example 4

[0084] A silicon-carbon negative electrode material, the raw materials of which include coating material, nano-silicon material, carbon black, and negative electrode material.

[0085] Wherein, the coating material is high-temperature coal tar, and the negative electrode material is hard carbon.

[0086] A method for preparing the silicon-carbon negative electrode material comprises the following steps in sequence:

[0087] S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material;

[0088] S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material;

[0089] S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material;

[0090] S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product.

[0091] In S1, the weight ratio of the coating material to the nano-silicon material is 1:7.

[0092] In S1, the added amount of the carbon black accounts for 2% of the total weight of the coating material, nano-silicon material and carbon black.

[0093] In S1, the drying operation is performed at a temperature of 130° C. for 12 hours.

[0094] In S2, the weight ratio of the silicon coating material to the negative electrode material is 1:6.

[0095] In S3, the maximum temperature of the carbonization treatment is 1300° C., and the temperature is maintained at the maximum temperature for 4 hours.

[0096] In S4, the mesh size of the sieve used in the sieving process is 500 meshes.

[0097] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0098] Comparative Example 1

[0099] The silicon-carbon negative electrode material in this comparative example has only one difference from Example 2 in terms of raw material composition and preparation method:

[0100] S1: In the step of coating the nano-silicon material, no carbon black is added.

[0101] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0102] Comparative Example 2

[0103] The silicon-carbon negative electrode material in this comparative example has only one difference from Example 2 in terms of raw material composition and preparation method:

[0104] In step S3, carbonization, the maximum temperature of the carbonization treatment is 650°C.

[0105] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0106] Comparative Example 3

[0107] The silicon-carbon negative electrode material in this comparative example has only one difference from Example 2 in terms of raw material composition and preparation method:

[0108] Replace the original S1 and S2 with the following steps:

[0109] First, the coating material, nano-silicon material, carbon black and negative electrode material are mixed, and then added into a dry coating machine for coating treatment to obtain the negative electrode coating material.

[0110] That is, the silicon-carbon negative electrode material in this comparative example is directly made by the "one-step coating method".

[0111] Finally, the silicon-carbon negative electrode material in this embodiment was tested for its performance parameters of capacity and first efficiency using existing electrode production, battery assembly, and battery testing methods. The results are shown in Table 1 below.

[0112] Table 1 Performance test results of silicon-carbon negative electrode materials

[0113]

[0114] Analysis Summary

[0115] The silicon-carbon negative electrode materials in the first and fourth embodiments can achieve excellent performance of capacity > 500 mAh / g and first efficiency > 80% after only two coatings and without using the CVD method. This is unexpected and has great promotion value.

[0116] Second, the three comparative examples all changed Example 2 of the optimal solution by means of a single variable, so that at least one of the two parameters of capacity and first effect did not meet the standards, which also proves the importance of the above variables in the examples.

[0117] Third, in Comparative Example 3, the original double coating is changed to single coating, which has the greatest impact on the two properties of capacity and first efficiency.

[0118] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the aforementioned embodiments. Various modifications are possible within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. These modifications are non-inventive and are protected by patent law as long as they fall within the scope of the claims of the present invention.

Claims

1. Silicon-carbon negative electrode material, characterized by: The raw material composition includes coating material, nano-silicon material, carbon black, and negative electrode material, wherein the coating material is any one of asphalt and resin or a mixture of several thereof, and the negative electrode material is any one of natural graphite, artificial graphite and hard carbon or a mixture of several thereof. The method for preparing the silicon-carbon negative electrode material comprises the following steps in sequence: S1. Coating nano-silicon material: first mix the coating material, nano-silicon material and carbon black, then add solvent, then stir, and then dry to obtain a silicon coating material; S2. Coating the negative electrode material: first mix the silicon coating material and the negative electrode material, and then add them to a dry coating machine or a melt coating machine for coating to obtain a negative electrode coating material; S3, carbonization: the negative electrode coating material is carbonized in a carbonization furnace under an inert gas atmosphere to obtain a carbonized material; S4, screening: the carbonized material is screened to obtain the final silicon-carbon negative electrode material product. The structure of the silicon-carbon negative electrode material is a porous core-shell structure, wherein the core is the negative electrode material and the shell is the coating material, nano-silicon material and carbon black.

2. The silicon-carbon negative electrode material according to claim 1, characterized in that: In S1, the weight ratio of the coating material to the nano-silicon material is 1:(2-7).

3. The silicon-carbon negative electrode material according to claim 1, characterized in that: In S1, the added amount of the carbon black accounts for 1-3% of the total weight of the coating material, nano-silicon material and carbon black.

4. The silicon-carbon negative electrode material according to claim 1, wherein: In S1, the drying operation is performed at a temperature of 80-150° C. for 12-24 hours.

5. The silicon-carbon negative electrode material according to claim 1, characterized in that: In S2, the weight ratio of the silicon coating material to the negative electrode material is 1:(3-9).

6. The silicon-carbon negative electrode material according to claim 1, characterized in that: In S3, the maximum temperature of the carbonization treatment is 1100-1300°C, and the temperature is maintained at the maximum temperature for at least 4 hours.

7. The silicon-carbon negative electrode material according to claim 1, characterized in that: In S4, the mesh number of the sieve used in the sieving process is ≥500 meshes.

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