Calculation method of CVD (Chemical Vapor Deposition) carbon coating amount of lithium battery silicon-based negative electrode material

Abstract

The invention is applicable to the technical field of energy materials, and relates to a method for calculating CVD (chemical vapor deposition) carbon coating amount of a silicon-based negative electrode material of a lithium battery, which comprises the following steps: (1) calculating cracking carbon amount # imgabs0 # in unit coating time, C being gas source cracking conversion carbon amount per hour; m is the theoretical filling amount of the negative electrode material in the rotary furnace; (2) the carbon coating time # imgabs1 # is calculated, wherein G3 and G1 are the feeding amount and the discharging amount of the rotary furnace at the same time respectively; v is the discharging speed of the rotary furnace, kg / h; (3) calculating the CVD carbon coating amount # imgabs2 # of the negative electrode material in the rotary furnace; wherein when the required carbon coating amount of the negative electrode material is less than 1%, # imgabs3 #; and when the carbon coating amount of the required negative electrode material is greater than or equal to 1%, # imgabs4 is determined. The method has the advantages that the method is used for rapidly solving the CVD carbon coating amount of the silicon-based negative electrode material of the lithium battery, on the contrary, the technological process of different specifications of CVD rotary furnaces is guided through the required CVD carbon coating amount, the calculation result has high accuracy, and the method has guiding significance on CVD carbon coating on the surface of the silicon-based negative electrode material in the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and more specifically, to a method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material. Background Art

[0002] Lithium-ion batteries have been widely used in portable electronic products and electric vehicles due to their advantages such as high operating voltage, long cycle life, no memory effect, low self-discharge, and environmental friendliness. At present, commercial lithium-ion batteries mainly use graphite-based negative electrode materials, but its theoretical specific capacity is only 372mAh / g, which cannot meet the future demand for high energy density of lithium-ion batteries. Although the existing Si has a theoretical capacity of up to 4200mAh / g, its expansion of 300% and poor conductivity affect the cycle performance, resulting in restrictions on market promotion and application. Silicon-based negative electrode materials have poor conductivity and need to be carbon-coated on their surfaces. Most of the mass production equipment for carbon coating on the market is CVD rotary furnace. During the vapor deposition coating process, the gas source (acetylene, methane, natural gas, etc.) is cracked and converted into carbon at a certain temperature to achieve coating on the surface of the silicon-based negative electrode material. Currently, during the coating process, it is impossible to control the carbon content coated on the surface of the silicon-based negative electrode material. The present invention innovatively proposes a theoretical calculation method for the CVD carbon coating amount, which has guiding significance for the industry to perform CVD carbon coating on the surface of silicon-based negative electrode materials, and there is no report on calculating the carbon content coated on the surface of silicon-based negative electrode materials. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for calculating the CVD carbon coating amount of lithium battery silicon-based negative electrode materials, which has high accuracy and wide adaptability.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material, which comprises the following steps: (1) Calculation of cracked carbon content per unit coating time , where C is the amount of carbon converted by gas source cracking per hour; M is the theoretical filling amount of negative electrode material in the rotary kiln; (2) Calculation of carbon coating time , where G3 and G1 are the feed and discharge amounts of the rotary kiln at the same time respectively; v is the discharge speed of the rotary kiln, kg / h; (3) Calculation of the CVD carbon coating amount of negative electrode materials in the rotary kiln ; When the required carbon coating amount of the negative electrode material is less than 1%, ; When the required carbon coating amount of the negative electrode material is ≥1%, , and the required carbon coating amount of the negative electrode material is generally ≤7%.

[0005] Furthermore, in step (1), , where L 气 is the air flow rate of the rotary kiln gas source, m 3 / h;ρ 气 is the density of the gas source, kg / m 3 ;k 气 is the cracking rate of the source gas in the rotary furnace.

[0006] Furthermore, when the rotary kiln is a continuous rotary kiln, the cracking rate of acetylene k 气 The cracking rate of methane is 30-35%. 气 The cracking rate of natural gas is 10-15%. 气 It is 8-14%.

[0007] Furthermore, when the rotary kiln is an intermittent rotary kiln, the cracking rate of acetylene k 气 The cracking rate of methane is 80±15%. 气 is 40±10%, the cracking rate of natural gas k 气 It is 40±10%.

[0008] Furthermore, when the rotary kiln is a continuous rotary kiln, in step (1), ; where V 炉 is the volume of the furnace tube in the rotary furnace, m 3 ρ 负极 is the density of the negative electrode material filled in the rotary kiln, kg / m 3 ; K is the empirical filling ratio of the negative electrode material filled in the rotary kiln, K is 10-15%.

[0009] Furthermore, when the rotary kiln is an intermittent rotary kiln, in step (1), .

[0010] Furthermore, in step (2), ; Where G2 is the discharge of the rotary kiln at time T2, and G1 is the discharge of the rotary kiln at time T1.

[0011] The advantages of the present invention are: 1. The present invention discloses a method for calculating the CVD carbon coating amount of lithium battery silicon-based negative electrode materials, which is used to quickly solve the CVD carbon coating amount of lithium battery silicon-based negative electrode materials. Conversely, the required CVD carbon coating amount is used to guide the process of CVD rotary kilns of different specifications, and it has wide adaptability.

[0012] 2. The present invention discloses a method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material. The calculation result has high accuracy and has guiding significance for the industry to perform CVD carbon coating on the surface of silicon-based negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a scanning electron microscope image of the negative electrode material after carbon coating in Example 4 of the present invention.

[0014] Figure 2 This is a transmission electron microscope image of the negative electrode material after carbon coating in Example 4 of the present invention. DETAILED DESCRIPTION

[0015] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0016] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0017] In the present invention, unless otherwise specified, the directions used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directions are not used to limit the present invention.

[0018] Example 1: Coating the doped silicon-oxygen raw material, wherein acetylene is used as the gas source, and the gas flow rate L entering the rotary kiln gas source is 气 13 m 3 / h,ρ 气 The density of the gas source is 1.17 kg / m 3 , the cracking rate of the source gas in the rotary furnace k 气 is 35%; the equipment adopts volume V 炉 5m 3 Continuous rotary kiln, bulk density of silicon oxide raw material ρ 负极 550kg / m 3 The empirical filling ratio K value of the negative electrode material in the rotary furnace is 10%. During the production operation, the discharge speed v is 35kg / h. The feeding and discharging weights within T is 8h, and the weight of the coated raw materials G3-G1 in the furnace is 275kg. The required carbon coating amount of the negative electrode material is <1%.

[0019] The overall method of Example 2 to Example 6 is basically the same as that of Example 1, and the specific parameters are shown in Table 1.

[0020] Table 1 Specific parameters

[0021] According to the parameters given in Examples 1-6 in Table 1 and the designed carbon coating amount, the corresponding formula is selected to calculate the theoretical value of the carbon coating amount. The specific results are shown in Table 2. At the same time, a carbon-sulfur detector is used to test the carbon coating amount of the carbon-coated negative electrode materials of Examples 1-6 to obtain the actual value of the carbon coating amount. The specific results are shown in Table 2.

[0022] Table 2

[0023] From Table 2, it can be seen that when different gas sources are used for carbon coating in Example 1 and Example 5, when the designed carbon coating amount is less than 1%, the theoretical calculation results are consistent with the actual detection results; at the same time, when the designed carbon coating amount is ≥1%, the theoretical calculation results of Examples 2, 3, 4, and 6 are not much different from the actual detection results. Therefore, the calculation method of the present invention has high accuracy and has guiding significance for industrial CVD carbon coating on the surface of silicon-based negative electrode materials.

[0024] The surface microstructure of the carbon-coated negative electrode material of Example 4 was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2 It can be seen that the presence of an amorphous carbon film on the surface of the silicon-based material can provide higher electronic conductivity and inhibit the volume expansion of particles inside the matrix.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0026] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material, characterized in that: It includes the following steps: (1) Calculation of cracked carbon content per unit coating time , where C is the amount of carbon converted by gas source cracking per hour; M is the theoretical filling amount of negative electrode material in the rotary kiln; (2) Calculation of carbon coating time , where G3 and G1 are the feed and discharge amounts of the rotary kiln at the same time respectively; v is the discharge speed of the rotary kiln, kg / h; (3) Calculation of the CVD carbon coating amount of negative electrode materials in the rotary kiln ; When the required carbon coating amount of the negative electrode material is less than 1%, ; When the required carbon coating amount of the negative electrode material is ≥1%, .

2. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 1, characterized in that: In step (1), , where L 气 is the air flow rate of the rotary kiln gas source, m 3 / h;ρ 气 is the density of the gas source, kg / m 3 ;k 气 is the cracking rate of the source gas in the rotary furnace.

3. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 2, characterized in that: When the rotary kiln is a continuous rotary kiln, the cracking rate of acetylene is k 气 The cracking rate of methane is 30-35%. 气 The cracking rate of natural gas is 10-15%. 气 It is 8-14%.

4. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 2, characterized in that: When the rotary kiln is an intermittent rotary kiln, the cracking rate of acetylene is k 气 The cracking rate of methane is 80±15%. 气 is 40±10%, the cracking rate of natural gas k 气 It is 40±10%.

5. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 1, characterized in that: When the rotary kiln is a continuous rotary kiln, in step (1), ; where V 炉 is the volume of the furnace tube in the rotary furnace, m 3 ρ 负极 is the density of the negative electrode material filled in the rotary kiln, kg / m 3 ; K is the empirical filling ratio of the negative electrode material filled in the rotary kiln, K is 10-15%.

6. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 1, characterized in that: When the rotary kiln is an intermittent rotary kiln, in step (1), .

7. The method for calculating the CVD carbon coating amount of a lithium battery silicon-based negative electrode material according to claim 1, characterized in that: In step (2), ; Where G2 is the discharge of the rotary kiln at time T2, and G1 is the discharge of the rotary kiln at time T1.

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