Production method of fast-charging graphite semi-calcined material

Abstract

The invention discloses a production method of a fast-charging graphite semi-calcined material, which comprises the following steps: taking a carbon raw material prepared by matching fast-charging graphite as a base material, adopting an external heating type semi-calcined converter with a multi-pipe structure, feeding the raw material into a product channel with the multi-pipe structure from a feeding end of the external heating type semi-calcined converter, and uniformly distributing the raw material in all pipelines of the product channel; micro-negative pressure is kept in the whole process of the product channel, the raw materials move in the pipeline and are slowly heated to a set highest-temperature area from normal temperature, and the micro-negative pressure environment enables dry distillation substances generated by pyrolysis of the raw materials to fully overflow and form regular initial pore structures in the materials; and the materials are dried, pyrolyzed and cured in a product channel of the external heating type semi-calcined converter and then are converted into the fast-charging graphite semi-calcined materials. The fast-charging graphite semi-calcined material prepared by the method is regular in graphite microcrystalline structure, uniform in volatile component removal, stable in product quality and high in consistency, and meets the process requirements of subsequent fast-charging graphite deep processing; and additional fuel supplement is not needed, so that the production cost and the energy consumption are greatly reduced.

Description

Technical Field

[0001] This invention relates to a method for producing fast-charging semi-calcined graphite material, belonging to the field of new material production technology. Background Technology

[0002] Fast-charging graphite is a core material for the negative electrode of lithium-ion batteries. Its key precursor is semi-calcined graphite. The fast-charging performance of fast-charging graphite is closely related to the pore structure of the semi-calcined material. Well-developed and regular initial pores can effectively improve the lithium-ion transport rate, which is a key factor in improving fast-charging performance. Therefore, the semi-calcination process is the core process in the preparation of fast-charging graphite. The semi-calcination process involves heating the carbonaceous raw material to remove volatiles and impurities, causing the carbon elements to form an ordered basic graphite microcrystalline structure, laying the foundation for subsequent graphitization.

[0003] Currently, the production of semi-calcined graphite mainly relies on semi-calcining furnaces and processes. However, existing semi-calcining furnaces and processes are not designed specifically for the production of semi-calcined graphite, and therefore all have problems, such as: The semi-calcining furnaces used generally suffer from four major problems: First, the pyrolysis gas produced by the raw material pyrolysis is discharged from the feed end of the semi-calcining furnace. The feed end temperature is low, and low-boiling-point substances such as tar in the pyrolysis gas easily condense into liquid, mixing with the raw material and causing blockage of the semi-calcining furnace. This requires frequent shutdowns for slag removal, making continuous industrial production impossible. This not only increases production and operating costs but also leads to fluctuations in product quality, making it difficult to meet the high requirements of fast-charging graphite for the regularity of the semi-calcined material's crystal structure. Second, the pyrolysis heat source of the semi-calcining furnace mostly relies on the combustion of external fuels. The pyrolysis gas produced by the raw material pyrolysis is mostly directly incinerated and emitted, without energy recovery and utilization, which increases the risk of pyrolysis. First, it increases fuel costs and energy consumption, and exacerbates exhaust emissions, which is inconsistent with the industry's trend of green production. Second, the existing semi-calcination process does not regulate the pressure inside the furnace, so the dry distillate produced by the pyrolysis of raw materials cannot be fully discharged, making it difficult for the semi-calcined material to form an effective initial pore structure. This results in insufficient lithium-ion transport channels, which limits the fast-charging performance of the subsequently prepared fast-charging graphite and cannot meet the application requirements of high-rate fast charging. Third, the furnace structure design of the existing semi-calcination process is unreasonable, with a large material accumulation thickness inside the furnace and uneven heating. When increasing output, the product consistency problem cannot be solved, and it is impossible to meet the production requirements of high output and high quality at the same time.

[0004] The semi-calcination process used is mostly designed for ordinary semi-calcined materials. It does not optimize process parameters such as heating rate and temperature range in combination with the production requirements of fast-charging graphite semi-calcined materials. This can easily lead to insufficient pyrolysis of raw materials and disordered graphite microcrystalline structure in semi-calcined materials, which further reduces the fast-charging performance and cycle performance of subsequent products.

[0005] Further research on patent literature, such as CN201710186013.6, discloses a method for preparing high-rate fast-charging graphite, including the following steps: (1) raw material crushing and shaping; (2) mixing; (3) graphitization high-temperature treatment: the mixture is graphitized at 2800-3200℃ for 24-48 hours under inert gas protection; (4) mixing; (5) low-temperature heat treatment; (7) mixing and sieving. Its core technical means is: using petroleum coke or pitch coke raw materials with a particle size of 5-10μm to crush and shape, combined with modifier coating and multi-stage heat treatment process (graphitization + low-temperature carbonization), to form core-shell structure microcrystalline graphite, shortening the lithium ion migration path and reducing anisotropy, thereby improving electrochemical performance and stability.

[0006] For example, CN202310507841.0 discloses a fast-charging graphite composite material, its preparation method, and its application. The preparation method includes the following steps: Step S1: Pre-treating graphite to obtain a graphite precursor; Step S2: Etching the graphite precursor in Step S1 using a chemical etching method, followed by annealing in an inert gas atmosphere to obtain porous graphite; Step S3: Coating and filling the surface and pores of the porous graphite with hard carbon. Its core technical means is: constructing a porous graphite structure through chemical etching and annealing to increase the Li⁺ storage space and shorten the diffusion channels; then coating and filling the pores with hard carbon to form a conductive network, reducing impedance and improving rate performance.

[0007] For example, CN202511320052.1 discloses a method for preparing high-rate fast-charging graphite from semi-calcined coke raw materials, including the following steps: S1: crushing and shaping the semi-calcined coke raw material; S2: subjecting the crushed and shaped semi-calcined coke to high-temperature graphitization treatment; S3: coating the graphitized semi-calcined coke with a coating agent; S4: subjecting the coated semi-calcined coke with the coating agent to high-temperature carbonization heat treatment; S5: sieving the high-temperature carbonized petroleum coke semi-calcined coke to obtain high-rate fast-charging graphite from semi-calcined coke raw materials. Its core technology is: employing a multi-step process of crushing and shaping the semi-calcined coke raw material, high-temperature graphitization treatment, coating agent mixing and coating, and high-temperature carbonization heat treatment to control the particle size to 1–10 μm, reducing the specific surface area and optimizing conductivity through a core-shell structure, significantly improving electrochemical performance and processing consistency.

[0008] Technical research reveals that existing technologies primarily focus on improving processes, but fail to provide better solutions. Based on customer market demands and technical research, it has been found that developing a method for producing fast-charging graphite semi-calcined materials that enables continuous production, energy self-sufficiency, consistent product quality, and the construction of initial pore structures to enhance fast-charging performance has become an urgent problem to be solved in the industry. Summary of the Invention

[0009] In view of the above-mentioned problems existing in the prior art, the purpose of this invention is to provide a method for producing fast-charging graphite semi-calcined material in an externally heated semi-calcining converter, so as to realize the industrial continuous production of fast-charging graphite semi-calcined material, achieve the effects of energy self-sufficiency, energy saving and environmental protection, and stable product quality. At the same time, by setting a micro-negative pressure in the product channel, the dry distillate is fully overflowed and forms an initial pore structure, which greatly improves the fast-charging performance of the material. Furthermore, the multi-product channel structure enables the material to be heated uniformly, thereby improving product consistency.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for producing fast-charging graphite semi-calcined material employs an externally heated semi-calcining converter with a multi-material-pipe structure. This structure utilizes hollow metal tubes open at both ends as material pipes, with the length of the converter serving as the length direction of the material pipes. These multiple material pipes are distributed along the circumference of the converter, forming product channels within the furnace body. Using carbonaceous raw materials suitable for fast-charging graphite preparation as the base material, the raw materials are fed into the multiple material pipes from the feed end of the externally heated semi-calcining converter. The material is evenly distributed within each material pipe, significantly reducing the material's thickness within the furnace. The material is heated evenly, improving product consistency. The product channel maintains a slight negative pressure throughout, and the raw material moves in the product channel and is slowly heated from room temperature to the set maximum temperature zone at a set heating rate. The material completes drying, pyrolysis, and solidification in sequence in the product channel. The slight negative pressure environment promotes the full overflow of the dry distillate produced by the pyrolysis of the raw material and forms a regular initial pore structure inside the material. The material solidifies to form a fast-charging graphite semi-calcined material with a regular crystal structure, reasonable pore distribution, and high quality consistency. It is discharged from the discharge end of the externally heated semi-calcining converter and can be directly used in subsequent deep processing of fast-charging graphite.

[0011] Furthermore, the dry distillation gas volatilized from the raw material during the drying, pyrolysis, and solidification stages flows in the same direction as the material, is discharged from the discharge end of the externally heated semi-calcining converter, and is introduced into the incinerator for complete combustion; the high-temperature exhaust gas after combustion is used as the heat source of the externally heated semi-calcining converter, and enters the furnace cavity from the discharge end of the externally heated semi-calcining converter. The high-temperature exhaust gas flows in the furnace cavity in the opposite direction to the material, and fully heats the product channel in the furnace cavity.

[0012] Furthermore, the incineration temperature inside the incinerator is ≥800℃.

[0013] Furthermore, after the product channel inside the high-temperature waste gas heating furnace, the waste gas is discharged into the gas scrubbing tower through the feed end of the externally heated semi-calcined converter. After the dust and acidic impurities in the waste gas are removed by washing, it is discharged into the air by the induced draft fan.

[0014] The carbonaceous raw material is petroleum coke, needle coke, or pitch coke adapted to fast-charging graphite, with a particle size between 0 and 50 mm; preferably, the particle size is between 1 and 10 mm.

[0015] Preferably, the micro-negative pressure is between 0 and -30 Pa.

[0016] Preferably, the heating rate of the raw material during pipeline operation is 5 to 20°C / min.

[0017] Preferably, the highest temperature zone is 600–750°C.

[0018] Preferably, the product channel is kept under a slight negative pressure throughout by adjusting the induced draft fan, which simultaneously handles exhaust gas discharge and maintains the slight negative pressure.

[0019] As an application, the fast-charging graphite semi-calcined material prepared by this method is a dedicated precursor for fast-charging graphite. It has a well-developed and regular initial pore structure, high product quality consistency, and can be directly applied to subsequent graphitization, granulation, coating and other deep processing processes of fast-charging graphite. The fast-charging performance and cycle performance of the product after deep processing are greatly improved.

[0020] The advantages of this invention over the prior art are as follows: 1. The distillation gas and the material are discharged from the discharge end in the same direction. The distillation gas flows from the low temperature section to the high temperature section with the material. Low boiling point substances such as tar will not condense into liquid, which completely avoids the problems of furnace blockage, furnace shutdown and slag removal caused by agglomeration. This enables continuous industrial production and ensures production continuity. At the same time, the raw materials are slowly heated to achieve orderly pyrolysis and solidification. The prepared fast-charging graphite semi-calcined material has a regular graphite microcrystalline structure, uniform volatile matter removal, stable product quality and high consistency, which is suitable for the process requirements of subsequent fast-charging graphite deep processing. 2. The heat energy from the combustion of the dry distillation gas generated by the pyrolysis of raw materials is used as the sole heat source for the semi-calcined converter, eliminating the need for additional fuel. This achieves self-sufficiency in energy by converting raw materials into energy, significantly reducing fuel costs and energy consumption in production. 3. The dry distillation gas is rendered harmless after complete combustion, and the high-temperature waste gas is discharged after being washed by the gas scrubbing tower. There is no additional fuel combustion waste gas emission, which greatly reduces the amount of waste gas emissions during the production process and meets the requirements of green and low-carbon industry development. The induced draft fan takes into account both waste gas emission and micro-negative pressure maintenance, eliminating the need for additional pressurization / depressurization equipment, simplifying the process and reducing equipment investment. 4. The micro-negative pressure environment of the product channel allows the dry distillate produced by the pyrolysis of raw materials to fully overflow, forming a well-developed and regular initial pore structure inside the semi-calcined material. This provides sufficient channels for lithium-ion transport, significantly improving the high-rate fast charging performance and cycle performance of subsequent fast-charging graphite, and solving the industry pain point of insufficient porosity in the semi-calcined material of the existing process. 5. The converter adopts a multi-tube product channel structure, in which the material is evenly distributed in each metal tube, which greatly reduces the thickness of the material accumulation in the furnace and makes the material heat more evenly. The structural design solves the problem of poor product consistency when the output of the existing process is increased, and achieves high output and high quality at the same time. 6. To meet the production needs of fast-charging graphite semi-calcined materials, a multi-pipe external heating converter is adopted, which optimizes key parameters such as raw material particle size, heating rate, and temperature range, and adds micro negative pressure control. The process flow is simple, the equipment is easy to industrialize, and it can be directly used for the technical transformation of existing external heating semi-calcined converters. The transformation cost is low and it is suitable for large-scale promotion. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Example

[0022] This example uses an externally heated semi-calcining converter, transforming a single tube into a multi-tube structure for the production of fast-charging graphite semi-calcined materials.

[0023] Raw material preparation: Select needle coke as carbonaceous raw material, crush and screen it to a particle size of 1mm to 20mm, and use it as the production base material for fast-charging graphite semi-calcined material; Micro-negative pressure adjustment: Start the induced draft fan and adjust the fan frequency to form and maintain a micro-negative pressure of -5Pa in the product channel of the externally heated semi-calcining converter; Semi-calcination: Needle coke raw material is fed into the multi-tube product channel from the feed end of the externally heated semi-calcination converter. The raw material rotates with the converter and moves towards the discharge end, thus being evenly distributed in each metal pipe, reducing the material accumulation thickness. During the process of running in the product channel, the material is slowly heated from room temperature to 600℃ at a heating rate of 5℃ / min. The raw material undergoes drying, pyrolysis, and solidification in sequence in the product channel. The slightly negative pressure environment allows the dry distillate of the pyrolysis of the raw material to fully overflow and forms an initial porous structure in the raw material. After solidification, it forms fast-charging graphite semi-calcined material, which is continuously discharged from the discharge end of the converter. Dry distillation gas treatment: The dry distillation gas generated by the pyrolysis of raw materials is discharged from the converter discharge end in the same direction as the material. The dry distillation gas is introduced into the incinerator and the combustion temperature is controlled at 800℃ to ensure that the dry distillation gas is fully burned and decomposed. Heat source utilization and waste gas treatment: The high-temperature waste gas generated by incineration enters the furnace cavity from the converter discharge end and flows in the opposite direction to the material, providing a heat source for the pyrolysis of raw materials in the product channel. After the high-temperature waste gas heats the product channel, it is discharged from the converter feed end to the gas scrubbing tower. After being washed with water to remove dust and acidic impurities, it is discharged by the induced draft fan. The induced draft fan continuously maintains a slight negative pressure in the product channel.

[0024] The fast-charging graphite semi-calcined material prepared in this embodiment has a volatile matter content of ≤5% and a true density of 1.5~1.65g / cm³. 3 The graphite has a regular microcrystalline structure with a uniform initial pore structure inside, free from defects such as agglomeration and inclusions. The material is heated evenly, resulting in excellent batch consistency. After graphitization, the lithium-ion transmission rate of the product is increased by more than 25%, and it can be directly used for graphitization treatment of high-rate fast-charging graphite. Example

[0025] This embodiment uses an externally heated semi-calcined converter to produce fast-charging graphite semi-calcined material. The specific steps are as follows: Raw material preparation: Petroleum coke and pitch coke are mixed at a mass ratio of 7:3 as carbonaceous raw materials, and crushed and screened to a particle size of 10mm to 20mm as the production base material for fast-charging graphite semi-calcined material; Micro-negative pressure adjustment: Start the induced draft fan and adjust the fan frequency to form and maintain a micro-negative pressure of -15Pa in the product channel of the externally heated semi-calcining converter; Semi-calcination: The mixed carbonaceous raw material is fed into the multi-pipe product channel from the feed end of the externally heated semi-calcination converter. The raw material is evenly distributed in each metal pipe and slowly heated from room temperature to 700℃ at a heating rate of 15℃ / min. The slightly negative pressure environment allows the dry distillate of the pyrolysis of the raw material to fully overflow and form a well-developed initial pore structure. The raw material is dried, pyrolyzed and solidified in the product channel in sequence to form fast-charging graphite semi-calcined material, which is continuously discharged from the discharge end of the converter. Dry distillation gas treatment: The dry distillation gas generated by the pyrolysis of raw materials is discharged from the converter discharge end in the same direction as the material. The dry distillation gas is introduced into the incinerator and the combustion temperature is controlled at 900℃ to ensure that the dry distillation gas is fully burned and decomposed. Heat source utilization and waste gas treatment: The high-temperature waste gas generated by incineration enters the furnace cavity from the converter discharge end and flows in the opposite direction to the material, providing a heat source for the pyrolysis of raw materials in the product channel. After the high-temperature waste gas heats the product channel, it is discharged from the converter feed end to the gas scrubbing tower. After being washed with alkaline solution to remove dust and acidic impurities, it is discharged by the induced draft fan. The induced draft fan continuously maintains a slight negative pressure in the product channel.

[0026] The fast-charging graphite semi-calcined material prepared in this embodiment has a volatile matter content of ≤5% and a true density of 1.5~1.65g / cm³. 3 The carbon element has a high degree of ordering and good initial pore connectivity. The material is heated evenly, resulting in minimal deviations in various performance indicators. As a fast-charging graphite precursor, the 10C rate fast-charging capacity retention rate of subsequent graphitized products is improved by more than 30%. Moreover, no external fuel needs to be added during the production process, and the energy consumption per ton of semi-calcined material is reduced by more than 60% compared with traditional processes. Example

[0027] This embodiment uses an externally heated semi-calcined converter to produce fast-charging graphite semi-calcined material. The specific steps are as follows: Raw material preparation: Petroleum coke is selected as the carbonaceous raw material, and it is crushed and screened to a particle size of 10mm to 30mm as the production base material for fast-charging graphite semi-calcined material; Micro-negative pressure adjustment: Start the induced draft fan and adjust the fan frequency to form and maintain a micro-negative pressure of -20Pa in the product channel of the externally heated semi-calcining converter; Semi-calcination: Petroleum coke raw material is fed into the multi-pipe product channel from the feed end of the externally heated semi-calcination converter. The raw material is evenly distributed in each metal pipe to reduce the material accumulation thickness. It is slowly heated from room temperature to 700℃ at a heating rate of 10℃ / min. The slightly negative pressure environment allows the dry distillate of the raw material to fully overflow and form a regular multi-level initial pore structure. The raw material is dried, pyrolyzed and solidified in the product channel in sequence to form fast-charging graphite semi-calcined material, which is continuously discharged from the converter discharge end. Dry distillation gas treatment: The dry distillation gas generated by the pyrolysis of raw materials is discharged from the converter discharge end in the same direction as the material. The dry distillation gas is introduced into the incinerator and the combustion temperature is controlled at 850℃ to ensure that the dry distillation gas is fully burned and decomposed. Heat source utilization and waste gas treatment: The high-temperature waste gas generated by incineration enters the furnace cavity from the converter discharge end and flows in the opposite direction to the material, providing a heat source for the pyrolysis of raw materials in the product channel. After the high-temperature waste gas heats the product channel, it is discharged from the converter feed end to the gas scrubbing tower. After two-stage washing with water and alkali, it is discharged by the induced draft fan, which continuously maintains a slight negative pressure in the product channel.

[0028] The fast-charging graphite semi-calcined material prepared in this embodiment has uniform quality with batch-to-batch fluctuations of ≤1%, which is suitable for rapid lithium-ion transport. The fast-charging performance and cycle performance of subsequent deep-processed products are greatly improved. The production process achieves continuous operation without furnace blockage or shutdown, and the exhaust emission indicators are far below the national emission standards, meeting the requirements of green production.

[0029] The above embodiments are merely explanations and illustrations of the technical solutions of the present invention and should not be used to limit the scope of protection of the technical solutions of the present invention. All simple modifications based on this solution are within the scope of protection of the present invention.

Claims

1. A method for producing fast-charging graphite semi-calcined material, characterized in that: An externally heated semi-calcined converter is used. The product channel of the externally heated semi-calcined converter has a multi-material tube structure. The carbonaceous raw material adapted to the preparation of fast-charging graphite is used as the base material. The raw material is fed into the multi-material tube from the feed end of the externally heated semi-calcined converter. The product channel is kept under slight negative pressure throughout. The raw material moves in the product channel and is slowly heated from room temperature to the set maximum temperature zone at a set heating rate. The material completes drying, pyrolysis and solidification in sequence in the product channel. The slight negative pressure environment allows the dry distillate produced by the pyrolysis of the raw material to fully overflow and form a regular initial pore structure inside the material. The material solidifies to form fast-charging graphite semi-calcined material with a regular crystal structure and is discharged from the discharge end of the externally heated semi-calcined converter.

2. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The product channel is kept under slight negative pressure throughout by adjusting the induced draft fan, which simultaneously handles exhaust gas discharge and maintains slight negative pressure.

3. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The micro-negative pressure is between 0 and -30 Pa.

4. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The dry distillation gas volatilized during the drying, pyrolysis, and solidification stages of the raw materials flows in the same direction as the materials, exits from the discharge end of the externally heated semi-calcining converter, and is introduced into the incinerator for combustion. The high-temperature exhaust gas after combustion is used as the heat source for the externally heated semi-calcining converter, enters the furnace cavity from the discharge end of the externally heated semi-calcining converter, heats the product channel in the furnace cavity, and is discharged from the feed end of the externally heated semi-calcining converter after heat exchange.

5. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The aforementioned multi-material pipe structure refers to a hollow metal pipe with openings at both ends serving as the material pipe, with the length direction of the furnace body serving as the length direction of the material pipe. Multiple material pipes are distributed along the circumference of the semi-calcined converter inside the furnace body to form a product channel; the material is evenly distributed in each material pipe, reducing the thickness of material accumulation inside the furnace.

6. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The carbonaceous raw material is one or more of petroleum coke, needle coke, and pitch coke, and the particle size range is 0 mm to 50 mm.

7. The method for producing fast-charging graphite semi-calcined material according to claim 4, characterized in that: The pyrolysis gas is fully burned in the incinerator at a temperature of not less than 800°C, which completely decomposes the organic impurities in the pyrolysis gas.

8. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The set heating rate is 5 to 20 °C / min.

9. The method for producing fast-charging graphite semi-calcined material according to claim 1, characterized in that: The maximum temperature range is set at 600–750°C.

10. The fast-charging graphite semi-calcined material produced by the production method of any one of claims 1 to 9 is directly used in the deep processing of fast-charging graphite.