Artificial graphite coating modification device and method thereof

Abstract

The invention discloses an artificial graphite coating modification device and a method thereof, relates to the technical field of lithium batteries, and aims to solve the problems that asphalt volatile components cannot be effectively discharged and volatilized and asphalt coating is not uniform. The asphalt powder is slowly melted to uniformly wrap the coke powder, the asphalt is gradually and comprehensively discharged, methane which is not fully combusted in the natural gas is controlled to react with the asphalt powder, the viscosity and the density of the asphalt are reduced, and finally, the artificial graphite has carbon atom sequential arrangement; after the product is coated and modified, an amorphous carbon layer is formed on the surface of crystalline artificial graphite particles, the active end face of the graphite material is reduced, so that the side reaction with an electrolyte is reduced, the compatibility of graphite and the electrolyte is improved, the specific surface area of the negative electrode material can be reduced by a coating modification process, and the service life of the negative electrode material is prolonged. And the first charge reversible capacity and the cycle stability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to an artificial graphite coating modification device and a method thereof. Background Art

[0002] Artificial graphite anode materials are a key battery material in the lithium battery industry. Made primarily from petroleum coke and needle coke, they undergo multiple processes, including crushing, granulation, graphitization, and screening. High-temperature graphitization transforms the carbon atoms into a regular graphite structure. The product boasts a uniform structure, controllable particle size distribution, excellent cycle performance, high initial charge and discharge efficiency, and improved adaptability to the insertion and deintercalation of lithium ions during the charge and discharge process. Widely used in new energy vehicles, mobile electronic devices, energy storage systems, and other fields, it meets the battery performance requirements of diverse application scenarios.

[0003] However, in the lithium battery industry, the traditional graphitization purification process of artificial graphite negative electrode materials is as follows: the artificial graphite negative electrode material is purified at high temperature in a graphitization furnace. Since the artificial graphite negative electrode material powder is mixed with some asphalt, the asphalt volatiles contained in it cannot be effectively discharged and the asphalt coating is uneven, resulting in the shortcomings of low loading capacity of the negative electrode material in the graphitization furnace, high asphalt volatiles and easy furnace spraying.

[0004] Therefore, there is a need for an artificial graphite coating modification device and method. Summary of the Invention

[0005] In order to solve all or part of the above problems, the present invention aims to provide an artificial graphite coating modification device and method thereof, so as to solve the problems of ineffective discharge of asphalt volatiles and uneven asphalt coating.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: an artificial graphite coating and modification device, comprising a box body and an inner liner installed inside the box body, a natural gas heating component installed on the outer side of the box body, an air conveying component installed on the outer side of the box body on one side of the natural gas heating component, an output end of the air conveying component being connected to the output end of the natural gas heating component, a temperature sensor and a gas sensor installed on the inner side of the box body, a controller installed on the outer side of the box body, the temperature sensor and the gas sensor being electrically connected to the controller, and a crucible provided on the inner side of the inner liner;

[0007] The controller includes:

[0008] Temperature monitoring module: receives the temperature data around the crucible collected in real time by the temperature sensor, and converts it into an electrical signal and transmits it to the logic judgment and control module;

[0009] Time recording module: Starts the timing function when the crucible is placed inside the liner and begins to heat, records the time consumed in the heating process, and feeds the time information back to the logic judgment and control module;

[0010] Logic judgment and control module: used to receive data feedback from the temperature monitoring module and the time recording module, and perform logic judgment based on the preset temperature rise program and the oxygen-deficient combustion control strategy. After the judgment is completed, it sends an instruction to adjust the natural gas supply to the natural gas flow control module, and at the same time sends an instruction to proportionally adjust the air supply to the air flow control module;

[0011] Natural gas flow control module: receives instructions from the logic judgment and control module, adjusts the opening of the natural gas regulating valve, and thus controls the supply flow of natural gas.

[0012] Furthermore, the natural gas heating component includes a natural gas main line and a natural gas regulating valve installed at the output end of the natural gas main line, a natural gas branch line is installed at the output end of the natural gas regulating valve, a natural gas heater is installed at the output end of the natural gas branch line, and the output end of the natural gas heater is located inside the liner;

[0013] The air delivery component includes an air main line and an air regulating valve installed at the output end of the air main line. The output end of the air regulating valve is installed with an air branch line, and the output end of the air branch line is connected to the natural gas heater.

[0014] Furthermore, the logical judgment is as follows: the expected temperature is synchronously calculated through the expected temperature algorithm formula, and the expected temperature is compared with the actual temperature fed back by the temperature sensor. If the temperature is lower than the temperature value corresponding to the expected heating rate, the natural gas supply is increased; if the temperature is higher than the temperature value corresponding to the expected heating rate, the natural gas supply is reduced.

[0015] Furthermore, the expected temperature algorithm formula is as follows: Assuming the starting temperature is , heating time is , the heating rate is , then the expected temperature , by comparing the actual temperature feedback from the temperature sensor and to control.

[0016] Furthermore, the natural gas flow control module controls the natural gas regulating valve through a valve opening algorithm. If the temperature is higher than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve is reduced to reduce the natural gas supply; if the temperature is lower than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve is increased to increase the natural gas supply.

[0017] Furthermore, the valve opening algorithm formula is as follows:

[0018]

[0019] is the difference between the expected temperature and the actual temperature, is the opening control signal of the natural gas regulating valve, where is the proportional gain, is the integral gain, is the differential gain.

[0020] Furthermore, the controller also includes an air flow control module: working in conjunction with the natural gas flow control module, adjusting the opening of the air control valve according to the logic judgment and control module instructions, and adjusting the air flow in real time according to the set air-fuel ratio and the change of natural gas flow to ensure that the combustion process is always in an oxygen-deficient combustion state.

[0021] Furthermore, the controller also includes a gas monitoring module: receiving the methane gas content around the crucible collected in real time by the gas sensor, converting the detected methane content data into an electrical signal in real time and transmitting it to the logic judgment and control module, which pre-sets the reasonable range of methane content as - , when receiving the methane content from the gas monitoring module Afterwards, if > , reduce the natural gas supply to reduce the methane production, send a command to the natural gas flow control module to reduce the natural gas supply, and reduce the air supply proportionally; if < , it is necessary to increase the natural gas supply to promote methane generation, send an instruction to increase the natural gas supply to the natural gas flow control module, and increase the air supply accordingly.

[0022] Another technical solution proposed by the present invention is to provide a method for coating and modifying artificial graphite, comprising the following steps:

[0023] S1: Needle-shaped petroleum coke is dried, crushed and ground into 200-300 mesh powder to form coke powder. At the same time, petroleum asphalt is condensed, crushed and ground into 200-300 mesh powder to form asphalt powder.

[0024] S2: 75-80% coke powder, 10-15% asphalt powder, and the remainder pure graphite powder are stirred and mixed to form a mixture;

[0025] S3: Load the mixed material into a high temperature resistant crucible and cover the crucible;

[0026] S4: The crucible containing the mixture is placed in the box. The natural gas heating component and the air delivery component work together to heat it, slowly raising the temperature to 300-400°C over 4-6 hours. The controller controls the natural gas supply in real time to control the temperature. At the same time, the air regulating valve is controlled to control the air-fuel ratio to ensure that it is always in an oxygen-deficient combustion state, allowing the asphalt powder to slowly melt and evenly wrap the coke powder.

[0027] S5: After the temperature is raised, the controller continues to control the natural gas supply in real time to control the temperature, ensuring that the mixture is kept at a constant temperature of 400°C in the box for 1-2 hours, and part of the asphalt volatiles are discharged;

[0028] S6: After the constant temperature is completed, the controller continues to control the natural gas supply in real time to control the temperature. It takes 3-4 hours to raise the temperature to 800-900℃, and then the temperature is maintained at 900℃ for another 5-8 hours. Most of the asphalt volatiles are discharged and participate in combustion;

[0029] S7: After cooling, it becomes artificial graphite coating material, which is directly converted into negative electrode material product after high-temperature purification in a graphitization furnace.

[0030] Furthermore, the specific steps of controlling the temperature by controlling the natural gas supply in real time through the controller are as follows:

[0031] S41: The time recording module is used to measure time in real time, and the temperature monitoring module is used to collect temperature data in real time;

[0032] S42: At regular intervals, the logic judgment and control module obtains the current time and temperature information. If the current time and temperature are within the set time range and the temperature has not reached the temperature value corresponding to the target heating rate, the logic judgment and control module issues a command to increase the natural gas supply to the natural gas flow control module, and simultaneously issues a command to proportionally increase the air supply to the air flow control module.

[0033] If the temperature monitoring module reports that the temperature is too high within the set time range, the logic judgment and control module will issue instructions to reduce the natural gas supply and the air supply to the natural gas flow control module and the air flow control module respectively;

[0034] S43: The above judgment and control process is continuously cycled until the time reaches the set time range and the temperature is stable within the set temperature range.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention proposes an artificial graphite coating and modification device and method, which controls the stable rise or constancy of temperature in different time periods and ensures the stability of the air-fuel ratio through a controller, allowing the asphalt powder to slowly melt and evenly wrap the coke powder, and gradually and comprehensively discharge the asphalt. At the same time, the unburned methane in the natural gas is controlled to react with the asphalt powder, reducing the viscosity and density of the asphalt, increasing the volatility of the asphalt, and promoting the release of active substances therein, so that it has better coating properties, and ultimately achieving the goal of artificial graphite with a sequential arrangement of carbon atoms. After the product is coated and modified, an amorphous carbon layer is formed on the surface of the crystalline artificial graphite particles, reducing the active end faces of the graphite material, thereby reducing side reactions with the electrolyte and improving the compatibility of the graphite with the electrolyte. The coating and modification process will reduce the specific surface area of ​​the negative electrode material, and the first-charge reversible capacity and cycle stability will be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the overall planar structure of the artificial graphite coating and modification device of the present invention;

[0038] Figure 2 This is a controller module diagram of the artificial graphite coating and modification device of the present invention;

[0039] Figure 3 This is a flow chart of the artificial graphite coating modification method of the present invention;

[0040] Figure 4 This is a flow chart of the internal temperature control of the modification device of the artificial graphite coating modification method of the present invention.

[0041] In the picture:

[0042] 1. Box; 2. Lining; 3. Natural gas main line; 4. Natural gas regulating valve; 5. Natural gas branch line; 6. Air main line; 7. Air regulating valve; 8. Air branch line; 9. Natural gas heater; 10. Temperature sensor; 11. Gas sensor; 12. Crucible; 13. Trolley track; 14. Loading trolley; 15. Controller. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] like Figure 1-Figure 2As shown, an artificial graphite coating and modification device includes a box body 1 and an inner liner 2 installed on the inner side of the box body 1. A natural gas heating component is installed on the outer side of the box body 1. An air conveying component is also installed on the outer side of the box body 1 on the side of the natural gas heating component. The output end of the air conveying component is connected to the output end of the natural gas heating component.

[0045] The natural gas heating component includes a natural gas main line 3 and a natural gas regulating valve 4 installed at the output end of the natural gas main line 3. A natural gas branch line 5 is installed at the output end of the natural gas branch line 5. A natural gas heater 9 is installed at the output end of the natural gas branch line 5. The output end of the natural gas heater 9 is located on the inner side of the liner 2. The natural gas branch line 5 can be divided into two lines. A natural gas heater 9 is provided at the output end of each line. The output ends of the two natural gas heaters 9 are opposite to each other, and one of them is located at the lower end of the inner side of the liner 2, and the other is located in the middle of the inner side of the liner 2. This design makes the flame inside the liner 2 sufficient and maximized uniformity, thereby improving the modification effect.

[0046] The air delivery components include an air main line 6 and an air regulating valve 7 installed at the output end of the air main line 6. An air branch line 8 is installed at the output end of the air regulating valve 7. The output end of the air branch line 8 is connected to the natural gas heater 9. The air branch line 8 is also divided into two lines to ensure that the two natural gas heaters 9 have air supply.

[0047] A temperature sensor 10 and a gas sensor 11 are installed inside the box 1 , and at least one temperature sensor 10 and gas sensor 11 are provided. A controller 15 is also installed outside the box 1 , and the temperature sensor 10 and the gas sensor 11 are electrically connected to the controller 15 .

[0048] A trolley track 13 is provided at the inner bottom of the box body 1 , a loading trolley 14 is provided on the trolley track 13 , a crucible 12 loaded with mixed materials is placed on the upper end of the loading trolley 14 , and the crucible 12 is located inside the liner 2 .

[0049] The controller 15 includes:

[0050] Temperature monitoring module: receives the temperature data around the crucible 12 collected in real time by the temperature sensor 10, and converts it into an electrical signal and transmits it to the logic judgment and control module.

[0051] Time recording module: Starts the timing function when the crucible 12 is placed inside the liner 2 and starts heating, records the time consumed in the heating process, and feeds the time information back to the logic judgment and control module.

[0052] Gas monitoring module: receives the methane gas content around the crucible 12 collected in real time by the gas sensor 11, converts the detected methane content data into an electrical signal in real time and transmits it to the logic judgment and control module.

[0053] Logic judgment and control module: It is used to receive data feedback from the temperature monitoring module and the time recording module, and perform logic judgment based on the preset temperature rise program and the oxygen-deficient combustion control strategy. After the judgment is completed, it sends an instruction to adjust the natural gas supply to the natural gas flow control module, and at the same time sends an instruction to proportionally adjust the air supply to the air flow control module.

[0054] At the same time, the logic judgment and control module pre-sets the reasonable range of methane content as - , when receiving the methane content from the gas monitoring module Afterwards, if > , reduce the natural gas supply to reduce the methane production, send a command to the natural gas flow control module to reduce the natural gas supply, and reduce the air supply proportionally; if < , it is necessary to increase the natural gas supply to promote methane generation, send an instruction to increase the natural gas supply to the natural gas flow control module, and increase the air supply accordingly.

[0055] The logical judgment synchronously calculates the expected temperature through the expected temperature algorithm formula, and compares the expected temperature with the actual temperature fed back by the temperature sensor 10. If the temperature is lower than the temperature value corresponding to the expected heating rate, the natural gas supply is increased; if the temperature is higher than the temperature value corresponding to the expected heating rate, the natural gas supply is reduced.

[0056] The specific expected temperature algorithm formula is as follows: Assuming the starting temperature is , heating time is , the target temperature is , the heating rate is , then the expected temperature , by comparing the actual temperature feedback from the temperature sensor 10 and To control, when the target temperature With actual temperature At the same time, proceed to the next control.

[0057] In order to improve the accuracy of temperature control, thermal inertia compensation coefficient and environmental interference correction factor are introduced to improve the expected temperature algorithm. Assuming that the thermal inertia coefficient of the material is , the environmental interference correction factor is , then the new expected temperature algorithm formula is:

[0058]

[0059] in: is the starting temperature, is the target temperature, Real-time heating time and It is the preset total heating time.

[0060] Natural gas flow control module: receives instructions from the logic judgment and control module, adjusts the opening of the natural gas regulating valve 4, and thus controls the supply flow of natural gas.

[0061] Specifically, the natural gas flow control module controls the natural gas regulating valve 4 through a valve opening algorithm. If the temperature is higher than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve 4 is reduced to reduce the natural gas supply; if the temperature is lower than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve 4 is increased to increase the natural gas supply.

[0062] The specific valve opening algorithm formula is as follows:

[0063]

[0064] is the difference between the expected temperature and the actual temperature, is the opening control signal of the natural gas regulating valve, where is the proportional gain, is the integral gain, is the differential gain, The integral term of the time error, Differential of the error.

[0065] In the valve opening algorithm of the natural gas flow control module, thermal inertia and environmental factors are further taken into consideration. The modified valve opening algorithm formula is:

[0066]

[0067] in:

[0068] is the opening control signal of the optimized natural gas regulating valve;

[0069] 、 In order to add compensation gain coefficients for thermal inertia and environmental interference, they also need to be determined through experimental optimization.

[0070] Air flow control module: works in conjunction with the natural gas flow control module to adjust the opening of the air control valve 7 according to the logic judgment and control module instructions. According to the set air-fuel ratio, the air flow is adjusted in real time according to the changes in the natural gas flow to ensure that the combustion process is always in an oxygen-deficient combustion state.

[0071] When supplementation is needed, when the temperature and methane content adjustment requirements are met at the same time, in order to avoid adjustment conflicts, a priority strategy can be adopted. If the temperature deviation exceeds the safe range, the temperature is adjusted first, and the methane content adjustment is suspended. The methane content adjustment is performed after the temperature stabilizes. If the temperature is within a reasonable range, the methane content adjustment is mainly carried out, while taking into account the temperature fine-tuning to ensure the stability and reliability of the overall process.

[0072] like Figure 2-Figure 4 As shown, another technical solution proposed by the present invention is to provide a method for coating and modifying artificial graphite, comprising the following steps:

[0073] Step 1: Needle-shaped petroleum coke is dried, crushed and ground into 200-300 mesh powder to become coke powder. At the same time, petroleum asphalt is condensed, crushed and ground into 200-300 mesh powder to become asphalt powder.

[0074] Step 2: Mix 75-80% coke powder, 10-15% asphalt powder, and the rest pure graphite powder to form a mixture;

[0075] Step 3: Load the mixed material into the high temperature resistant crucible 12 and cover the crucible with a lid;

[0076] Step 4: Place the crucible 12 loaded with the mixture into the box 1 and heat it with the natural gas heating component and the air delivery component. It takes 4-6 hours to slowly raise the temperature to 300-400°C. The controller 15 controls the natural gas supply in real time to control the temperature. At the same time, it is necessary to control the air-fuel ratio by controlling the air regulating valve 7 to keep it in an oxygen-deficient combustion state. This allows the asphalt powder to slowly melt and evenly wrap the coke powder. At the same time, the unburned methane in the natural gas reacts with the asphalt powder, reducing the viscosity and density of the asphalt, increasing the volatility of the asphalt, and promoting the release of active substances therein, so that it has better wrapping properties.

[0077] Step 5: After the temperature is raised, the controller 15 continues to control the natural gas supply in real time to control the temperature, ensuring that the mixture is kept at a constant temperature of 400°C in the box 1 for 1-2 hours, and part of the asphalt volatiles are discharged;

[0078] Step 6: After the constant temperature is completed, the controller 15 continues to control the temperature by controlling the natural gas supply in real time. It takes 3-4 hours to heat up to 800-900°C, and then maintains the temperature at 900°C for another 5-8 hours. Most of the asphalt volatiles are discharged and participate in combustion.

[0079] Furthermore, in steps 4-6, the controller 15 controls the natural gas supply in real time to control the temperature through the cooperation of the temperature monitoring module, the time recording module, the gas monitoring module, the logic judgment and control module, the natural gas flow control module, and the air flow control module in the controller 15. Specifically, the time recording module performs real-time timing, and the temperature monitoring module collects temperature data in real time. At regular intervals, for example, one minute or ten minutes, the logic judgment and control module obtains the current time and temperature information. If the time is within the set time range and the temperature does not reach the temperature value corresponding to the target heating rate, the logic judgment and control module issues an instruction to increase the natural gas supply to the natural gas flow control module, and simultaneously issues an instruction to proportionally increase the air supply to the air flow control module. If the temperature monitoring module reports that the temperature is too high within the set time range, the logic judgment and control module issues instructions to reduce the natural gas supply and the air supply to the air flow control module, respectively. The above judgment and control process is continuously cycled until the time reaches the set time range and the temperature stabilizes within the set temperature range.

[0080] It should be noted that, in the description of this application, it should be understood that the terms "length", "thickness", "inside", "outside", "axial", "radial", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0081] Furthermore, relational terms such as first and second, etc., are used solely to distinguish one entity or operation from another entity or operation and do not necessarily require or imply any actual relationship or order between such entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed or that are inherent to such process, method, article, or apparatus.

[0082] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An artificial graphite coating and modification device, characterized in that: The invention comprises a box body (1) and an inner lining (2) installed on the inner side of the box body (1), a natural gas heating component is installed on the outer side of the box body (1), an air conveying component is also installed on the outer side of the box body (1) on the side of the natural gas heating component, the output end of the air conveying component is connected to the output end of the natural gas heating component, a temperature sensor (10) and a gas sensor (11) are installed on the inner side of the box body (1), a controller (15) is also installed on the outer side of the box body (1), the temperature sensor (10) and the gas sensor (11) are electrically connected to the controller (15), and a crucible (12) is provided on the inner side of the inner lining (2); The controller (15) comprises: Temperature monitoring module: receiving temperature data around the crucible (12) collected in real time by the temperature sensor (10), and converting the data into an electrical signal and transmitting it to the logic judgment and control module; Time recording module: starting the timing function when the crucible (12) is placed inside the lining (2) and heating begins, recording the time spent in the heating process, and feeding the time information back to the logic judgment and control module; Logic judgment and control module: used to receive data feedback from the temperature monitoring module and the time recording module, and perform logic judgment based on the preset temperature rise program and the oxygen-deficient combustion control strategy. After the judgment is completed, it sends an instruction to adjust the natural gas supply to the natural gas flow control module, and at the same time sends an instruction to proportionally adjust the air supply to the air flow control module; Natural gas flow control module: receives instructions from the logic judgment and control module, adjusts the opening of the natural gas regulating valve (4), and thus controls the supply flow of natural gas.

2. The artificial graphite coating and modification device according to claim 1, characterized in that: The natural gas heating component comprises a natural gas main line (3) and a natural gas regulating valve (4) installed at the output end of the natural gas main line (3); a natural gas branch line (5) is installed at the output end of the natural gas regulating valve (4); a natural gas heater (9) is installed at the output end of the natural gas branch line (5); and the output end of the natural gas heater (9) is located inside the liner (2); The air delivery component includes an air main line (6) and an air regulating valve (7) installed at the output end of the air main line (6). An air branch line (8) is installed at the output end of the air regulating valve (7). The output end of the air branch line (8) is connected to a natural gas heater (9).

3. The artificial graphite coating and modification device according to claim 1, characterized in that: The logic judgment is as follows: the expected temperature is calculated synchronously by the expected temperature algorithm formula, and the expected temperature is compared with the actual temperature fed back by the temperature sensor (10). If the temperature is lower than the temperature value corresponding to the expected heating rate, the natural gas supply is increased; if the temperature is higher than the temperature value corresponding to the expected heating rate, the natural gas supply is reduced.

4. The artificial graphite coating and modification device according to claim 2, characterized in that: The expected temperature algorithm formula is as follows: Assuming the starting temperature is , heating time is , the heating rate is , then the expected temperature , by comparing the actual temperature feedback from the temperature sensor (10) and to control.

5. The artificial graphite coating and modification device according to claim 1, characterized in that: The natural gas flow control module controls the natural gas regulating valve (4) through a valve opening algorithm. If the temperature is higher than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve (4) is reduced to reduce the natural gas supply; if the temperature is lower than the temperature corresponding to the expected heating rate, the opening of the natural gas regulating valve (4) is increased to increase the natural gas supply.

6. The artificial graphite coating and modification device according to claim 1, characterized in that: described The valve opening algorithm formula is as follows: , is the difference between the expected temperature and the actual temperature, is the opening control signal of the natural gas regulating valve, where is the proportional gain, is the integral gain, is the differential gain.

7. The artificial graphite coating and modification device according to claim 1, characterized in that: The controller (15) further comprises an air flow control module, which cooperates with the natural gas flow control module to adjust the opening of the air regulating valve (7) according to the logic judgment and the control module instruction, and adjusts the air flow in real time according to the set air-fuel ratio and the change of the natural gas flow, so as to ensure that the combustion process is always in an oxygen-deficient combustion state.

8. The artificial graphite coating and modification device according to claim 1, characterized in that: The controller (15) further comprises a gas monitoring module: receiving the methane gas content around the crucible (12) collected in real time by the gas sensor (11), converting the detected methane content data into an electrical signal in real time and transmitting the signal to the logic judgment and control module, which pre-sets a reasonable range of methane content as - , when receiving the methane content from the gas monitoring module Afterwards, if > , reduce the natural gas supply to reduce the methane production, send a command to the natural gas flow control module to reduce the natural gas supply, and reduce the air supply proportionally; if < , it is necessary to increase the natural gas supply to promote methane generation, send an instruction to increase the natural gas supply to the natural gas flow control module, and increase the air supply accordingly.

9. A method for coating and modifying artificial graphite, implemented by means of an artificial graphite coating and modifying device according to any one of claims 1 to 7, characterized in that: The steps include: S1: Needle-shaped petroleum coke is dried, crushed and ground into 200-300 mesh powder to form coke powder. At the same time, petroleum asphalt is condensed, crushed and ground into 200-300 mesh powder to form asphalt powder. S2: 75-80% coke powder, 10-15% asphalt powder, and the remainder pure graphite powder are stirred and mixed to form a mixture; S3: Load the mixed material into a high temperature resistant crucible (12) and cover the crucible with a lid; S4: The crucible (12) loaded with the mixture is placed in the box (1), and the mixture is heated by the natural gas heating component and the air conveying component. The temperature is slowly raised to 300-400°C in 4-6 hours. The temperature is controlled by controlling the natural gas supply in real time through the controller (15). At the same time, the air regulating valve (7) is controlled to control the air-fuel ratio so that the mixture is always in an oxygen-deficient combustion state, so that the asphalt powder slowly melts and evenly wraps the coke powder. S5: After the temperature is raised, the controller (15) continues to control the natural gas supply in real time to control the temperature, ensuring that the mixture is kept at a constant temperature of 400°C in the box (1) for 1-2 hours, and part of the asphalt volatiles are discharged; S6: After the constant temperature is completed, the controller (15) continues to control the temperature by real-time control of the natural gas supply. It takes 3-4 hours to raise the temperature to 800-900°C, and then the temperature is kept constant at 900°C for another 5-8 hours. Most of the asphalt volatiles are discharged and participate in combustion; S7: After cooling, it becomes artificial graphite coating material, which is directly converted into negative electrode material product after high-temperature purification in a graphitization furnace.

10. The method for coating and modifying artificial graphite according to claim 8, wherein: The specific steps of controlling the temperature by controlling the natural gas supply in real time through the controller (15) are as follows: S41: The time recording module is used to measure time in real time, and the temperature monitoring module is used to collect temperature data in real time; S42: At regular intervals, the logic judgment and control module obtains the current time and temperature information. If the current time and temperature are within the set time range and the temperature has not reached the temperature value corresponding to the target heating rate, the logic judgment and control module issues a command to increase the natural gas supply to the natural gas flow control module, and simultaneously issues a command to proportionally increase the air supply to the air flow control module. If the temperature monitoring module reports that the temperature is too high within the set time range, the logic judgment and control module will issue instructions to reduce the natural gas supply and the air supply to the natural gas flow control module and the air flow control module respectively; S43: The above judgment and control process is continuously cycled until the time reaches the set time range and the temperature is stable within the set temperature range.

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