New energy automobile lithium battery carbon negative electrode material preparation process optimization method

Abstract

The invention relates to the technical field of data processing, in particular to a new energy automobile lithium battery carbon negative electrode material preparation process optimization method. The method comprises the following steps: installing a preset number of ultrasonic detection devices to collect ultrasonic signals when silicon powder and a carbon source are mixed in benzene; obtaining a sub-signal corresponding to each ultrasonic signal; obtaining a difference value sequence of any sub-signal in one ultrasonic signal, calculating a characteristic factor of each sub-signal, and calculating a variable coefficient of the ultrasonic signal according to the characteristic factors; obtaining a vertical sub-signal sequence, and calculating a variable coefficient of the vertical sub-signal sequence in the vertical sub-signal sequence; calculating to obtain a quality index by using the variable coefficient of each ultrasonic signal and the variable coefficient of the vertical sub-signal sequence; and determining the stirring stopping time of the silicon powder and the carbon source according to the quality indexes. The mixing quality of the silicon powder and the carbon source in the benzene can be improved, and the preparation process of the carbon negative electrode material of the lithium battery of the new energy automobile is optimized.

Description

Technical Field

[0001] The present invention relates to the field of data processing technology, and in particular to a method for optimizing the preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles. Background Art

[0002] Lithium batteries are widely used in various devices due to their high capacity and long cycle life. With the increasing popularity and development of new energy vehicles, there is a demand for batteries with higher capacity, lower manufacturing costs, and greater stability. The performance of lithium-ion batteries depends primarily on the materials used in their positive and negative electrodes. Optimizing the preparation process for these materials plays a significant role in determining their energy density, safety, and manufacturing costs.

[0003] As the energy density of lithium batteries continues to increase, carbon negative electrode materials are approaching their theoretical energy density values. To improve the energy density of lithium batteries, existing silicon-carbon composite structures are closer to current battery design and practical application requirements, and can effectively improve the energy density of lithium batteries using traditional carbon negative electrode materials. Existing methods can effectively improve the energy density of lithium batteries, but when mixing silicon powder and carbon source (graphite) in benzene at a certain ratio, the mixing time is long and the mixing uniformity is unknown. This may affect the production efficiency and the subsequent stability of the performance of carbon-silicon negative electrode materials in large-scale lithium battery production. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for optimizing the preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles. The technical solutions adopted are as follows: One embodiment of the present invention provides a method for optimizing a preparation process of a carbon negative electrode material for a lithium battery of a new energy vehicle, the method comprising: Installing a preset number of ultrasonic detection devices on the stirring device; obtaining ultrasonic signals collected by each ultrasonic detection device when the silicon powder and the carbon source are stirred; Each ultrasonic signal is evenly divided to obtain a sub-signal corresponding to each ultrasonic signal; a difference value of the two sub-signals is obtained according to the amplitude corresponding to each frequency in the spectrum diagram of the two sub-signals of an ultrasonic signal; Obtaining a difference value sequence of each sub-signal according to the difference value of any two sub-signals of an ultrasonic signal; and calculating a characteristic factor of each sub-signal using the difference value sequence of each sub-signal; Calculating the coefficient of variation of an ultrasonic signal based on the characteristic factors of each sub-signal of the ultrasonic signal; selecting the sub-signal with the largest characteristic factor in each ultrasonic signal to form a vertical sub-signal sequence; calculating the characteristic factor of each sub-signal in the vertical sub-signal sequence, and calculating the coefficient of variation of the vertical sub-signal sequence based on the characteristic factor; The coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence are combined into a coefficient of variation sequence; the quality index is calculated using the data in the coefficient of variation sequence; and the time to stop stirring the silicon powder and the carbon source is determined according to the quality index.

[0005] Preferably, a preset number of ultrasonic detection devices are installed on the stirring device, including: An ultrasonic detection device includes an ultrasonic transmitter and an ultrasonic receiver; the ultrasonic transmitter in the ultrasonic detection device is installed on one side of the stirring chamber of the stirring device, and the ultrasonic receiver in the ultrasonic detection device is installed on the other side; the installation positions of the ultrasonic transmitter and the ultrasonic receiver in one ultrasonic detection device are symmetrical to each other and on the same horizontal line.

[0006] Preferably, the calculation formula of the difference value of the two sub-signals is specifically: , in, represents the difference between the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal; and They represent the amplitudes corresponding to the points with frequency s in the spectrum diagrams of the i-th and r-th sub-signals in the a-th ultrasonic signal respectively; Represents the set of all frequency values ​​in the spectrum of the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal.

[0007] Preferably, obtaining a difference value sequence of each sub-signal according to the difference values ​​of any two sub-signals of an ultrasonic signal comprises: The difference value between a sub-signal and other sub-signals in the ultrasonic signal is obtained according to the difference value between any two sub-signals in the ultrasonic signal; the difference value between a sub-signal and other sub-signals constitutes a difference value sequence of the sub-signal.

[0008] Preferably, calculating the characteristic factor of each sub-signal using the difference value sequence of each sub-signal includes: The average value of the data in the difference value sequence of the sub-signal is obtained as the characteristic factor of the sub-signal.

[0009] Preferably, calculating the coefficient of variation of an ultrasonic signal based on the characteristic factors of each sub-signal of the ultrasonic signal includes: The standard deviation and mean of the characteristic factors of each sub-signal of an ultrasonic signal are obtained, and the ratio of the standard deviation to the mean is the coefficient of variation of the ultrasonic signal.

[0010] Preferably, the calculation formula of the quality index is specifically: , in, Indicates quality indicators; represents the mean of the coefficient of variation series; and They represent the maximum and minimum values ​​in the coefficient of variation sequence respectively; e represents a natural constant.

[0011] Preferably, determining the time to stop stirring the silicon powder and the carbon source according to the quality index includes: Set a threshold. If the quality index is greater than or equal to the threshold, send an early warning instruction to remind the staff to stir the mixed liquid in the mixing chamber to reach the set production standard and stop stirring.

[0012] The embodiment of the present invention has at least the following beneficial effects: a preset number of ultrasonic detection devices are installed on the stirring equipment, and the ultrasonic signals collected by each ultrasonic detection device when the silicon powder and the carbon source are stirred are obtained, and the ultrasonic signals are divided into sub-signals, and the difference value of any two sub-signals in each ultrasonic signal is obtained, which can characterize the mixing uniformity of the silicon powder and the carbon source at the horizontal position; further, the characteristic factor of each sub-signal is calculated using the difference value sequence of each sub-signal, and the coefficient of variation of the ultrasonic signal is calculated based on the characteristic factors of each sub-signal of the ultrasonic signal, and the coefficient of variation can characterize the mixing characteristics of the silicon powder and the carbon source at the horizontal position; then the vertical sub-signal sequence is obtained, and the vertical sub-signal sequence is obtained. The coefficient of variation of the vertical sub-signal sequence is calculated from the sub-signal sequence to characterize the mixing characteristics of silicon powder and carbon source in the vertical position; then the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence are combined into a coefficient of variation sequence, and the coefficient of variation sequence is used for comprehensive analysis to obtain the quality index, which characterizes the mixing uniformity of silicon powder and carbon source in the entire stirring chamber, pays attention to the uniformity of each position in the stirring chamber, and improves the accuracy of monitoring; finally, when the quality index of the mixed liquid meets the set production standard, a timely warning is issued, which saves the time for setting up the mixing of the mixed liquid and improves the accuracy and objectivity of the mixing monitoring, thereby improving the efficiency and quality of the subsequent production of carbon-silicon negative electrode composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 A flow chart of a method for optimizing a preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles provided in an embodiment of the present invention.

[0015] Figure 2 A schematic diagram of the layout of an ultrasonic detection device for a method for optimizing a preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail the method for optimizing the preparation process of a carbon negative electrode material for a new energy vehicle lithium battery proposed by the present invention, its specific implementation method, structure, characteristics and effects. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable form.

[0017] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0018] The specific scheme of the method for optimizing the preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles provided by the present invention is described in detail below with reference to the accompanying drawings.

[0019] Example: The main application scenario of the present invention is: the existing preparation method of lithium battery carbon-silicon negative electrode composite material can effectively improve the energy density of lithium batteries, but when silicon powder and graphite are mixed in benzene in a certain proportion, the mixing time is long and the uniformity of the mixing is unknown, which may affect the production efficiency and the subsequent stability of the performance of lithium battery carbon-silicon negative electrode materials during large-scale production of lithium batteries.

[0020] By monitoring the mixing of silicon powder and graphite in benzene at a specific ratio, the present invention avoids problems such as poor mixing quality or excessive mixing time caused by artificially setting the mixing time. This improves the uniformity of the mixed solution in this step and effectively reduces the time required for the mixing process, thereby improving the quality, performance, stability, and production efficiency of the carbon-silicon negative electrode composite material for lithium batteries.

[0021] See also Figure 1 , which shows a method flow chart of a method for optimizing a preparation process of a carbon negative electrode material for a new energy vehicle lithium battery provided by an embodiment of the present invention, the method comprising the following steps: Step S1, installing a preset number of ultrasonic detection devices on a stirring device; obtaining ultrasonic signals collected by each ultrasonic detection device when silicon powder and carbon source are stirred.

[0022] The general process of preparing carbon-silicon negative electrode composite materials for lithium batteries is as follows: 1. First, clean the leftover silicon material in a solvent through ultrasonic cleaning to remove the dirt on the surface, and then dry it to obtain the silicon material; 2. The obtained silicon material is crushed to submicron size, and then the obtained silicon powder and carbon source (graphite) are stirred and dispersed in a solvent (benzene solution) to obtain a uniform turbid liquid; 3. The obtained turbid liquid is carbonized at high temperature in an inert atmosphere to obtain silicon carbide powder; and then ground to obtain a lithium battery silicon-carbon negative electrode composite material.

[0023] After the silicon material is crushed, silicon powder is obtained. The silicon powder needs to be mixed and stirred with a carbon source. During the mixing and stirring, the mixing time may be too long or insufficient, and the uniformity of the mixing is unknown, affecting the stability and performance of the subsequent carbon-silicon negative electrode composite material. Therefore, an ultrasonic detection device is installed on the stirring equipment. One of the ultrasonic detection devices includes an ultrasonic transmitter and an ultrasonic receiver. The ultrasonic data received by the receiver is transmitted to the host for analysis. The uniformity of the mixed liquid in the stirring equipment is monitored. When the mixing standard is reached, an early warning alert is issued through the early warning module to save time during the mixing process and ensure the uniformity of the mixed liquid.

[0024] The specific method of installing an ultrasonic detection device on a stirring device is as follows: an ultrasonic transmitter in the ultrasonic detection device is installed on one side of the stirring chamber of the stirring device, and an ultrasonic receiver in the ultrasonic detection device is installed on the other side; the installation positions of the ultrasonic transmitter and the ultrasonic receiver in one ultrasonic detection device are symmetrical to each other. Figure 2 As shown in the figure, 2, 3, 4, and 5 respectively represent ultrasonic transmitters in the ultrasonic detection device, and 7, 8, 9, and 10 respectively represent ultrasonic receivers in the ultrasonic detection device; wherein 2 and 10, 3 and 9, 4 and 8, and 5 and 7 are respectively an ultrasonic detection device, and the ultrasonic transmitter and ultrasonic receiver in each ultrasonic detection device are located at the same horizontal height and symmetrically with each other when installed, and are located on both sides of the stirring chamber of the stirring device; wherein 1 represents the stirring chamber of the stirring device, and 6 represents the stirring rod in the stirring chamber of the stirring device.

[0025] When the mixer starts operating, an ultrasonic transmitter in an ultrasonic detection device transmits an ultrasonic signal of a certain frequency (3 MHz, adjustable according to actual usage) to a receiver. The ultrasonic receiver collects data in real time, acquiring the ultrasonic signal. The ultrasonic signal received by the ultrasonic receiver is analyzed every t seconds (t is 10, an empirical value that can be adjusted). This means that the data collected every 10 seconds serves as the basis for data analysis. Each ultrasonic receiver in the ultrasonic detection device receives an ultrasonic signal every 10 seconds. This allows us to obtain the ultrasonic signal received by each ultrasonic receiver every t seconds while the silicon powder and carbon source are being stirred.

[0026] Step S2: uniformly divide each ultrasonic signal to obtain a sub-signal corresponding to each ultrasonic signal; and obtain a difference value between the two sub-signals according to the amplitude corresponding to each frequency in the spectrum diagram of the two sub-signals of an ultrasonic signal.

[0027] When the mixed liquid is uniform and stable, the mixed liquid at any position in the stirring device has similar uniformity. Therefore, the ultrasonic signals received by the receivers at different positions have high consistency. When the mixed liquid has uniform and stable mixing quality, the ultrasonic signals received at any position have high stability in terms of timing. This is mainly manifested in that the signal frequency characteristics of the ultrasonic signals received by any receiver at different positions in the timing are also highly consistent, and the probability of change over time is small.

[0028] Therefore, in order to understand the frequency change of the ultrasonic signal received by any receiver at any time, and thus obtain the stability of the signal received by the receiver at that time, the ultrasonic time series signal received by the ultrasonic receiver within the set time range is taken as an example for analysis.

[0029] First, each ultrasonic signal is evenly divided to obtain the sub-signals corresponding to each ultrasonic signal. In the present invention, the ultrasonic signal of t seconds is evenly divided according to the timestamp, and is divided into Each divided signal is a sub-signal, so each ultrasonic signal will have corresponding sub-signals.

[0030] Furthermore, each sub-signal corresponding to the ultrasonic data is transformed using a Fast Fourier Transform (FFT) to obtain the corresponding spectrum data (spectrogram). If the signal is stable in time, the frequency components in the spectrogram of each sub-signal are also relatively stable in time. By analyzing the signal's temporal changes, we can analyze its stability. First, we align the spectrogram corresponding to any sub-signal of the ultrasonic signal with that of any other sub-signal in the same ultrasonic signal.

[0031] Next, the difference between the two sub-signals is obtained according to the amplitude corresponding to each frequency in the spectrum diagram of the two sub-signals of an ultrasonic signal. The specific calculation formula of the difference is: , in, represents the difference between the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal, and can also be called the difference between the i-th sub-signal and the r-th sub-signal in the ultrasonic signal received by the a-th ultrasonic receiver; and They represent the amplitudes corresponding to the points with frequency s in the spectrum diagrams of the i-th and r-th sub-signals in the a-th ultrasonic signal respectively; Represents the set of all frequency values ​​in the spectrum of the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal. It represents the sum of the squares of the differences between the amplitude corresponding to each frequency in the spectrum graph corresponding to the i-th sub-signal in the a-th ultrasonic signal and the amplitude corresponding to each frequency in the spectrum graph corresponding to the r-th sub-signal. This value represents the difference between the two sub-signals.

[0032] It should be noted that when a point with a frequency value of s exists in one spectrum graph but not in another spectrum graph, the value of the existing point is the corresponding amplitude, and the value of the non-existent point is 0. For example, if a point with a frequency value of 20 does not exist in the spectrum graph of the i-th sub-signal, the corresponding amplitude is is 0, and exists in the spectrum of the rth sub-signal, then the corresponding amplitude is its amplitude in the spectrum of the rth sub-signal. On the contrary, if the point with a frequency value of 20 does not exist in the spectrum of the rth sub-signal, then The value is 0. In this way, the difference between any two sub-signals in each ultrasonic signal can be obtained.

[0033] Step S3: obtaining a difference value sequence of each sub-signal according to the difference values ​​of any two sub-signals of an ultrasonic signal; and calculating a characteristic factor of each sub-signal using the difference value sequence of each sub-signal.

[0034] In step S2, the difference value between any two sub-signals in each ultrasonic signal is obtained, thereby obtaining the difference value between a sub-signal and other sub-signals in the ultrasonic signal. The difference value between a sub-signal and other sub-signals constitutes a difference value sequence of the sub-signal.

[0035] Furthermore, the average value of the data in the difference value sequence of the sub-signal is obtained as the characteristic factor of the sub-signal. The specific calculation formula is: , in, represents the characteristic factor of the i-th sub-signal in the a-th ultrasonic signal; Indicates the number of neutron signals in the ultrasonic signal, represents the number of sub-signals other than the i-th sub-signal in a ultrasonic signal; Represents the difference between the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal. It represents the mean of the sum of the difference values ​​between the i-th sub-signal and the remaining sub-signals in the ultrasonic signal received at the a-th position. The larger the value, the greater the difference between the sub-signal and the remaining sub-signals.

[0036] In this way, the characteristic factors of each sub-signal in the ultrasonic signal can be obtained. When the characteristic factors of the sub-signals in the ultrasonic signal are relatively stable, it means that the mixed liquid at the corresponding position of the signal may be relatively stable, and the mixed liquid at this position may be mixed evenly.

[0037] Step S4, calculating the coefficient of variation of an ultrasonic signal based on the characteristic factors of each sub-signal of the ultrasonic signal; selecting the sub-signal with the largest characteristic factor in each ultrasonic signal to form a vertical sub-signal sequence; calculating the characteristic factor of each sub-signal in the vertical sub-signal sequence, and calculating the coefficient of variation of the vertical sub-signal sequence based on the characteristic factor.

[0038] The characteristic factor of any sub-signal in the signal is obtained through the calculation in step S3, and the characteristic factors of all sub-signals of the signal can form a characteristic factor sequence.

[0039] When the ultrasonic signal is stable in time, the corresponding characteristic factors are relatively close. Therefore, the coefficient of variation of the characteristic factors of the ultrasonic signal is further calculated and used as the basis for judging the stability of the signal at that location. The standard deviation and mean of the characteristic factors of each sub-signal in the ultrasonic signal are obtained respectively. The ratio of the standard deviation to the mean is the coefficient of variation, which can be used to obtain the coefficient of variation of each ultrasonic signal.

[0040] At the same time, when silicon powder and carbon source are mixed in benzene liquid, it is necessary to ensure that they are mixed evenly in the vertical and horizontal directions. This means that the liquid is mixed evenly as a whole, without uneven stratification up and down or left and right. Since the coefficient of variation corresponding to the characteristic factor of the sub-signal in the ultrasonic signal received at each position indicates the uniformity of its mixing in the horizontal direction, in order to ensure the uniformity of the vertical mixing of the liquid during mixing, it is necessary to further screen out the sub-signal with the largest characteristic factor in the ultrasonic signal received at each position. Since the sub-signal with the largest characteristic factor corresponds to the data when the mixing is the most uneven in the ultrasonic signal, if the sub-signals corresponding to the largest characteristic factor in each ultrasonic signal are relatively close in the vertical direction, then it means that the mixing in the vertical direction is relatively close, and the stability of the mixing may be relatively stable.

[0041] The sub-signals with the largest characteristic factors in each ultrasonic signal are selected to form a vertical sub-signal sequence. The characteristic factors of each sub-signal in the vertical sub-signal sequence are then calculated. The method for calculating the characteristic factors of each sub-signal in the vertical sub-signal sequence is the same as the method for calculating the characteristic factors of the sub-signals in each ultrasonic signal described above. The coefficient of variation of the vertical sub-signal sequence is then calculated based on the characteristic factors of each sub-signal in the vertical sub-signal sequence. This yields the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence.

[0042] Step S5, combining the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence into a coefficient of variation sequence; using the data in the coefficient of variation sequence to calculate a quality index; and determining the time to stop stirring the silicon powder and carbon source based on the quality index.

[0043] In step S4, the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence are obtained. When the silicon powder and the carbon source are mixed and stirred, the solution in the entire stirring chamber needs to be evenly mixed, so the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence need to be analyzed comprehensively. Therefore, the coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence constitute a coefficient of variation sequence. When the coefficient of variation sequence is overall low and close, it means that the mixed liquid in the stirring chamber may tend to a uniform and stable state at this time.

[0044] Therefore, the quality index of the mixed liquid at this time is obtained based on the above obtained coefficient of variation sequence. The calculation formula of the quality index is specifically as follows: , in, Indicates quality indicators; represents the mean of the coefficient of variation series; and The maximum and minimum values ​​of the coefficient of variation sequence are represented respectively; e represents a natural constant. The mean of the coefficient of variation sequence The smaller it is, the better the stability of the mixed liquid in the stirring chamber is; the difference between the maximum and minimum values ​​of the coefficient sequence The smaller it is, the closer the values ​​in the anomaly coefficient sequence are. At this time, the uniformity of the mixed liquid in the mixing chamber is better and the mixing quality is higher.

[0045] Through the above, the quality index of the mixed liquid at any monitoring time can be obtained, and a threshold value T is set. Here, T is set to 0.8 (the specific value can be determined according to production needs or obtained by mathematical statistics). When W≥T, an early warning instruction is sent to remind the staff that the mixed liquid in the mixing chamber reaches the set production standard and stops stirring, so as to process the mixed liquid in time to avoid long mixing time or uneven mixing, which leads to reduced production efficiency, further improve the efficiency and performance quality of the production of carbon-silicon negative electrode composite materials, and reduce the production cost of lithium batteries.

[0046] It should be noted that the order in which the embodiments of the present invention are described above is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0047] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for optimizing the preparation process of carbon negative electrode materials for lithium batteries of new energy vehicles, characterized in that: The method includes: Installing a preset number of ultrasonic detection devices on the stirring device; obtaining ultrasonic signals collected by each ultrasonic detection device when the silicon powder and the carbon source are stirred; Each ultrasonic signal is evenly divided to obtain a sub-signal corresponding to each ultrasonic signal; a difference value of the two sub-signals is obtained according to the amplitude corresponding to each frequency in the spectrum diagram of the two sub-signals of an ultrasonic signal; Obtaining a difference value sequence of each sub-signal according to the difference value of any two sub-signals of an ultrasonic signal; and calculating a characteristic factor of each sub-signal using the difference value sequence of each sub-signal; Calculating the coefficient of variation of an ultrasonic signal based on the characteristic factors of each sub-signal of the ultrasonic signal; selecting the sub-signal with the largest characteristic factor in each ultrasonic signal to form a vertical sub-signal sequence; calculating the characteristic factor of each sub-signal in the vertical sub-signal sequence, and calculating the coefficient of variation of the vertical sub-signal sequence based on the characteristic factor; The coefficient of variation of each ultrasonic signal and the coefficient of variation of the vertical sub-signal sequence are combined into a coefficient of variation sequence; the quality index is calculated using the data in the coefficient of variation sequence; and the time to stop stirring the silicon powder and the carbon source is determined according to the quality index.

2. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: The method of installing a preset number of ultrasonic detection devices on the stirring device includes: An ultrasonic detection device includes an ultrasonic transmitter and an ultrasonic receiver; the ultrasonic transmitter in the ultrasonic detection device is installed on one side of the stirring chamber of the stirring device, and the ultrasonic receiver in the ultrasonic detection device is installed on the other side; the installation positions of the ultrasonic transmitter and the ultrasonic receiver in one ultrasonic detection device are symmetrical to each other and on the same horizontal line.

3. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: The calculation formula of the difference value of the two sub-signals is specifically: ， in, represents the difference between the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal; and They represent the amplitudes corresponding to the points with frequency s in the spectrum diagrams of the i-th and r-th sub-signals in the a-th ultrasonic signal respectively; Represents the set of all frequency values ​​in the spectrum of the i-th sub-signal and the r-th sub-signal in the a-th ultrasonic signal.

4. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: The step of obtaining a difference value sequence of each sub-signal according to the difference values ​​of any two sub-signals of an ultrasonic signal comprises: The difference value between a sub-signal and other sub-signals in the ultrasonic signal is obtained according to the difference value between any two sub-signals in the ultrasonic signal; the difference value between a sub-signal and other sub-signals constitutes a difference value sequence of the sub-signal.

5. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: The calculating the characteristic factor of each sub-signal by using the difference value sequence of each sub-signal includes: The average value of the data in the difference value sequence of the sub-signal is obtained as the characteristic factor of the sub-signal.

6. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: Calculating the coefficient of variation of an ultrasonic signal based on the characteristic factors of each sub-signal of an ultrasonic signal includes: The standard deviation and mean of the characteristic factors of each sub-signal of an ultrasonic signal are obtained, and the ratio of the standard deviation to the mean is the coefficient of variation of the ultrasonic signal.

7. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: The calculation formula of the quality index is specifically: ， in, Indicates quality indicators; represents the mean of the coefficient of variation series; and They represent the maximum and minimum values ​​in the coefficient of variation sequence respectively; e represents a natural constant.

8. The method for optimizing the preparation process of carbon negative electrode materials for lithium batteries for new energy vehicles according to claim 1, characterized in that: Determining the time to stop stirring the silicon powder and the carbon source according to the quality index includes: Set a threshold. If the quality index is greater than or equal to the threshold, send an early warning instruction to remind the staff to stir the mixed liquid in the mixing chamber to reach the set production standard and stop stirring.

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