A carbonization method for porous carbon precursors and its application

Abstract

This invention provides a carbonization method for porous carbon precursors and its application, relating to the field of secondary battery materials technology. The carbonization method includes: reacting low-rank coal sequentially in a first temperature range, a second temperature range, and a third temperature range; the first temperature range satisfies the following conditions: temperature 200–450°C, air atmosphere, and holding time 0.5–5 h; the second temperature range satisfies the following conditions: temperature 350–650°C, nitrogen atmosphere, holding time 0.5–3 h, and heating rate 1–4°C / min; the third temperature range satisfies the following conditions: temperature 650–950°C, nitrogen atmosphere, holding time 1–2 h, and heating rate 1–5°C / min. This carbonization method completes low-temperature oxidation crosslinking and high-temperature carbonization in the same reaction system, improving the retention of the pore structure and the density of the framework of the carbon material, achieving a balance between pore structure and framework performance, and can be used in the field of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of secondary battery materials technology, and in particular to a carbonization method for porous carbon precursors and its application. Background Technology

[0002] Porous carbon precursors are a class of porous carbon materials prepared from coal through carbonization and activation processes. They possess advantages such as wide availability of raw materials, low cost, tunable pore structure, and high chemical stability, and are widely used in lithium-ion battery anode materials, supercapacitor electrodes, gas adsorption, and catalyst supports. Traditional porous carbon precursor preparation processes typically include three steps: pretreatment, carbonization, and activation. The carbonization stage is the key step determining the pore structure and framework stability. Existing technologies mainly focus on improving these processes through two directions: raw material modification and optimization of the carbonization method.

[0003] Currently, conventional carbonization processes mostly employ a single-stage heating mode, which involves heating to 500-1000℃ at a rate of 5-10℃ / min in an inert atmosphere (such as nitrogen or argon) and holding at that temperature for 1-3 hours to release volatiles from the coal and form a primary carbon framework. Although this method is simple, the resulting porous carbon precursor has an unstable pore structure, low specific surface area, low compaction density, and unstable electrical conductivity.

[0004] In existing technologies, to improve the pore structure and properties of porous carbon precursors, attempts have been made to introduce oxidative crosslinking pretreatment, chemical auxiliaries (such as KOH and ZnCl2), or adopt post-activation methods to enhance pore development. However, these improvements mainly focus on the activation stage, while research on the carbonization stage is relatively insufficient. This often results in the sacrifice of compaction density and electrical conductivity while achieving high specific surface area, which is detrimental to improving energy density in electrochemical applications. Summary of the Invention

[0005] In order to overcome the above-mentioned defects and deficiencies in the prior art, one of the objectives of this application is to provide a carbonization method for porous carbon precursors and its application.

[0006] One objective of this invention is to provide a method for carbonizing porous carbon precursors, comprising: Low-rank coal is provided, and the low-rank coal reacts sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 200-450℃, atmosphere is air, holding time is 0.5-5 h, and heating rate is 1-4℃ / min; The second temperature range meets the following process parameters: temperature is 350~650℃, atmosphere is nitrogen, holding time is 0.5~3 h, and heating rate is 1~4℃ / min; The third temperature range meets the following process parameters: temperature is 650-950℃, atmosphere is nitrogen, holding time is 1-2 h, and heating rate is 1-5℃ / min.

[0007] Preferably, the first temperature range meets the following process parameters: temperature is 250-400℃, atmosphere is air, holding time is 1-4 h, and heating rate is 2-4℃ / min.

[0008] Preferably, the first temperature range meets the following process parameters: temperature is 300-350℃, atmosphere is air, holding time is 2-3 h, and heating rate is 2.5-4℃ / min.

[0009] Preferably, the second temperature range satisfies the following process parameters: temperature 400~650℃, nitrogen atmosphere, holding time 1~3 h, heating rate 2~4℃ / min, and / or, The third temperature range meets the following process parameters: temperature is 650~900℃, atmosphere is nitrogen, holding time is 1~2 h, and heating rate is 2~5℃ / min.

[0010] Preferably, the second temperature range satisfies the following process parameters: temperature of 500~600℃, atmosphere of nitrogen, holding time of 2 h, heating rate of 2.5~4℃ / min, and / or, The third temperature range satisfies the following process parameters: temperature 650~800℃, nitrogen atmosphere, holding time 2h, heating rate 2.5~5℃ / min, and / or, After the reaction in the third temperature range is completed, the product obtained from the reaction in the third temperature range is transferred to a cooling chamber for rapid cooling at a rate of 60~150℃ / min, preferably 80~130℃ / min.

[0011] Preferably, the low-rank coal is long-flame coal.

[0012] Preferably, the particle size of the low-rank coal is controlled between 5 and 75 μm.

[0013] A second objective of this invention is to provide a method for preparing porous carbon, including the carbonization method described above.

[0014] A third objective of this invention is to provide a porous carbon prepared by the porous carbon preparation method described above.

[0015] A fourth objective of this invention is to provide an application of porous carbon as described above in lithium-ion batteries.

[0016] The beneficial effects of this invention are: This invention solves the problems of tar deposition, pore wall collapse and unstable conductivity in existing processes by precisely controlling the temperature, time and atmosphere in stages of the carbonization stage, and completing the oxidation and carbonization process in the same reaction system. It achieves oxidation crosslinking and preliminary devolatilization in the low temperature zone, and skeleton formation and pore structure development in the medium and high temperature zone. It achieves synergistic optimization of pore structure preservation and skeleton densification, and improves the problems of unstable pore structure, low specific surface area, low compaction density and unstable conductivity of porous carbon precursors. Detailed Implementation

[0017] The present application will be further described in detail below with reference to embodiments. The specific embodiments described herein are only for explaining the related invention and are not intended to limit the invention. Unless otherwise specified, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to embodiments.

[0018] Existing carbonization processes mostly employ a single-stage heating mode, i.e., heating to 500-1000℃ at a rate of 5-10℃ / min in an inert atmosphere (such as nitrogen or argon) and holding at that temperature for 1-3 hours to release volatiles from the coal and form a primary carbon framework. While this method is simple, the resulting porous carbon precursor exhibits unstable pore structure, low specific surface area, low compaction density, and unstable electrical conductivity. The inventors discovered that the reason for these phenomena is: 1. The carbonization and oxidation stages are separated, resulting in a complex process and high energy consumption; Existing solutions generally adopt a step-by-step process of "pre-oxidation-carbonization-activation", which requires multiple heating and cooling in different equipment. The process results in large energy losses and discontinuous atmosphere control, making it difficult to achieve stable control of the skeleton structure.

[0019] 2. The carbonization stage lacks a precise, phased temperature control mechanism; While existing technologies mention "multi-stage heating" or "step-by-step heat preservation," the temperature zones are coarsely divided and the control methods are simplistic. They fail to dynamically adjust for tar precipitation and volatile matter release characteristics, leading to tar condensation and pore blockage in the low-temperature zone and skeletal collapse in the high-temperature zone, resulting in damage to the continuity of the pore structure and specific surface area. Furthermore, the excessively rapid heating rate of existing technologies causes volatile components in the coal to precipitate quickly, easily generating internal pressure accumulation and causing particle expansion or collapse.

[0020] 3. The carbon skeleton shrinks severely in the high-temperature carbonization section, leading to micropore closure and a decrease in compaction density; When the carbonization temperature exceeds 900 ℃, the carbon layer spacing shrinks, micropores merge into closed pores, the internal void ratio of the powder increases, the compaction density decreases, and the conductivity fluctuates accordingly.

[0021] 4. Uneven emission of tar and volatile matter, and poor controllability of pore structure; Most existing processes involve unidirectional heating in an inert atmosphere with a fixed atmosphere (N2 or Ar), which makes it difficult to coordinate the gas phase flow and tar discharge during the carbonization process, resulting in a decrease in pore volume and a reduction in activation efficiency.

[0022] 5. Multi-system reactions Using stepwise oxidation and single-stage carbonization methods makes it difficult to simultaneously achieve oxidative crosslinking and framework shaping within the same system, and also makes it impossible to achieve real-time control over tar release and pore structure evolution.

[0023] The inventors discovered that by precisely controlling the temperature, time, and atmosphere in stages during the carbonization process, and completing the oxidation and carbonization process within the same reaction system, oxidation crosslinking and preliminary devolatilization are achieved in the low-temperature zone, while framework formation and pore structure development are achieved in the medium- and high-temperature zone. This solves the problems of tar deposition, pore wall collapse, and unstable conductivity in existing processes, and achieves synergistic optimization of pore structure preservation and framework densification. It improves the problems of unstable pore structure, low specific surface area, low compaction density, and unstable conductivity of porous carbon precursors, thus completing this invention.

[0024] According to a first aspect of the present invention, a method for carbonizing a porous carbon precursor is provided, comprising: Low-rank coal is provided, and the low-rank coal reacts sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 200-450℃, atmosphere is air, holding time is 0.5-5 h, and heating rate is 1-4℃ / min; The second temperature range meets the following process parameters: temperature is 350~650℃, atmosphere is nitrogen, holding time is 0.5~3 h, and heating rate is 1~4℃ / min; The third temperature range meets the following process parameters: temperature is 650-950℃, atmosphere is nitrogen, holding time is 1-2 h, and heating rate is 1-5℃ / min.

[0025] The carbonization method described in this invention can be implemented in the same reaction system, simultaneously achieving the oxidation and carbonization processes of low-rank coal through precise three-stage temperature and atmosphere control. The carbonization method achieves oxidative cross-linking and preliminary devolatilization in the low-temperature zone, and framework formation, pore structure development, and framework formation-densification in the medium- and high-temperature zone. Continuous reaction is achieved through atmosphere switching, avoiding multiple heating cycles and energy waste, and yielding a coal precursor more suitable for porous carbon activation.

[0026] Furthermore, this invention employs three heating stages—low, medium, and high—to regulate the heating rate and atmosphere composition according to the volatile matter release patterns within different temperature zones. This multi-stage heating achieves stable volatile matter release, resulting in more controllable pore structure and effectively preventing pore wall collapse and internal pressure buildup. This leads to a more developed open microporous structure in the carbonized product, significantly improving the pore structure retention and framework compactness of the porous carbon precursor. Moreover, the oxidation and carbonization processes are carried out continuously within the same system, allowing the structural units generated by oxidation crosslinking to stably transform into graphitized carbon sheets at subsequent high temperatures, thereby achieving a synergistic improvement in framework strengthening and porosity optimization.

[0027] Furthermore, the oxidation and carbonization processes are continuous, improving process efficiency and simplifying equipment. The integrated design of this invention avoids heat loss caused by stepwise heating and cooling, saving approximately 12-18% energy compared to conventional processes, while also reducing the amount of inert gas used, resulting in better process stability and scale-up.

[0028] The carbonized product obtained after carbonization according to this invention can be used as a high-quality activation precursor.

[0029] This invention employs a three-stage temperature zone (low-temperature oxidation zone, medium-temperature structure formation zone, and high-temperature densification zone), with independent control of the heating rate and holding time at each stage, matching the volatile release characteristics to achieve dynamic controllability of the pore structure, as detailed below: The first temperature range, namely the low-temperature oxidation zone, is set to meet the following process parameters: temperature 200~450℃, atmosphere is air, holding time is 0.5~5, and heating rate is 1~4℃ / min h.

[0030] The exemplary first temperature range is 200°C, 220°C, 240°C, 250°C, 280°C, 310°C, 340°C, 370°C, 400°C, 430°C, or 450°C.

[0031] The exemplary holding time for the first temperature range is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h.

[0032] The exemplary heating rate for the first temperature range is 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, or 4℃ / min.

[0033] In this invention, the first temperature range is 200~450℃, which is the optimal oxidation range obtained from comprehensive analysis of long-flame coal raw materials. Within this temperature range, oxidative crosslinking-dehydration and devolatilization reactions mainly occur. Oxidative crosslinking introduces oxygen-containing functional groups, which can promote aromatization and oxidative crosslinking in coal. The aliphatic chains oxidatively break down to form new COC / CC crosslinking bonds, increasing the molecular weight and transforming the structure from a disordered stacked structure to a network structure. The carbon skeleton network becomes denser, forming a primary skeleton and effectively inhibiting tar formation in subsequent carbonization stages. Achieving oxidative crosslinking in an air atmosphere allows aromatic rings in the coal molecular structure to form a crosslinking network through oxygen bonds or carboxyl groups, improving skeleton stability and reducing tar formation. Furthermore, introducing air at the initial stage of carbonization causes mild oxidative crosslinking of coal molecules, allowing tar to be gasified and decomposed during formation, significantly reducing condensation and pore blockage, inhibiting tar condensation and pore blockage, and significantly improving pore structure retention. The pore volume of the carbonization product is increased by approximately 20% compared to the traditional single-stage process, and the pore walls are more uniform.

[0034] In this invention, if the temperature in the first temperature range is too low and / or the holding time is too short, the oxidation cross-linking will be insufficient, the primary skeleton strength will be inadequate, and softening shrinkage and pore wall collapse will easily occur in the subsequent heating stage, resulting in unstable pore structure and low pore volume. If the temperature in the first temperature range is too high, excessive oxidation or even local burn-off will easily occur, the carbon yield will decrease, the skeleton embrittlement and shrinkage will intensify, the pore wall will be excessively corroded, and defective pore structures that are not conducive to subsequent activation control will be generated.

[0035] In this invention, if low-rank coal remains in the first temperature range of air atmosphere for too long, the oxidation reaction will accumulate and deepen, which will easily lead to over-oxidation and ineffective ablation, manifested as loss of fixed carbon, decreased yield, and relative enrichment of ash. Excessive oxygen-containing groups on the surface will also lead to structural embrittlement and uncontrollable pore structure in subsequent high-temperature treatment, resulting in longer process cycles, increased energy consumption, and poor batch stability. Typical but non-limiting forms of uncontrollable pore structure include: local collapse or excessive enlargement of pore size.

[0036] Furthermore, coal oxidation is an exothermic process, and rapid heating can easily lead to a large temperature difference between the inside and outside of the coal bed, resulting in uneven oxidation, with the outer layer undergoing over-oxidation and the inner layer under-oxidized. Localized exothermic reactions can also create hot spots, leading to runaway oxidation, smoke, or even combustion risks. At the same time, rapid heating can cause volatile matter to combine with the oxidation reaction, resulting in problems such as coking / agglomeration and pore blockage, leading to uneven distribution of subsequent activation reactions and fluctuations in product performance.

[0037] The second temperature range, also known as the medium-temperature structure formation zone, is set to meet the following process parameters: temperature 350–650℃, nitrogen atmosphere, holding time 0.5–3 h, and heating rate 1–4℃ / min. This temperature range primarily sees the formation of the framework and the development of the porous structure, which promotes uniform release of volatiles, controls the tar gasification rate, forms a multi-level porous structure, and prevents pore blockage.

[0038] Examples of the second temperature range are 350°C, 380°C, 410°C, 440°C, 470°C, 500°C, 530°C, 560°C, 590°C, 620°C, or 650°C.

[0039] The exemplary holding time for the second temperature range is 0.5h, 1h, 1.5h, 2h, 2.5h or 3h.

[0040] The exemplary heating rates for the second temperature range are 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, or 4℃ / min.

[0041] In the second temperature range, slow heating and a nitrogen atmosphere can promote the uniform release of volatiles and a mild vaporization reaction, generating a well-developed multi-level pore structure, while suppressing pore wall rupture caused by internal pressure accumulation.

[0042] In this invention, if the temperature in the second temperature range is too low, the heating rate is too slow, and / or the holding time is too short, the skeleton rearrangement and volatile matter release will be insufficient, resulting in inadequate pore structure development and problems such as tar condensation blocking pores and undeveloped micropores. If the temperature in the second temperature range is too high, the heating rate is too fast, and / or the holding time is too long, the violent precipitation of volatile matter will cause a sudden increase in internal gas pressure, which can easily lead to pore wall collapse, macroscopic cracks, and excessive shrinkage, resulting in reduced carbon yield and difficulty in finely controlling the pore structure.

[0043] The third temperature range, also known as the high-temperature densification zone or high-temperature zone, is set to meet the following process parameters: temperature 650–950℃, nitrogen atmosphere, holding time 1–2 h, and heating rate 1–5℃ / min. Within this parameter range, sufficient high-temperature rearrangement and moderate densification of the carbon skeleton can be promoted, providing a stable precursor for subsequent activation.

[0044] The third temperature range primarily involves densification and structural stabilization reactions, resulting in carbon layer rearrangement, improved conductivity, and prevention of excessive shrinkage and pore wall collapse. High-temperature, short-time carbonization avoids excessive shrinkage of the carbon skeleton, enhancing compaction density and conductivity. A strategy of rapid high-temperature heating followed by short-time holding (650~950℃, 1~2h, 1~5℃ / min) induces orderly rearrangement of the carbon layers, forming a conductive network. This prevents excessive shrinkage of the carbon skeleton and micropore closure, suppresses pore-closing caused by graphitization orientation aggregation, and results in denser powder packing and continuous conductive pathways, thereby improving compaction density and conductivity. Compaction density is increased by approximately 10~15% compared to traditional processes, and electrical conductivity is increased by over 20%.

[0045] Examples of third temperature ranges are 650°C, 680°C, 710°C, 740°C, 770°C, 810°C, 840°C, 870°C, 900°C, 930°C, or 950°C.

[0046] The exemplary holding time for the third temperature range is 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2 hours.

[0047] The exemplary heating rates for the third temperature range are 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, or 5℃ / min.

[0048] By introducing air or inert nitrogen gas into different temperature zones, the oxidation intensity and vaporization reaction rate can be controlled, preventing tar condensation and pore blockage, and maintaining the connectivity of the pore structure. Furthermore, by controlling the atmosphere in the three temperature zones, the oxidation, vaporization, and protective reactions can be sequentially linked. Tar decomposes during the oxidation phase, is vaporized and removed during the intermediate temperature phase, and regeneration and deposition are completely suppressed during the high temperature phase, ensuring a stable pore structure.

[0049] In this invention, if the temperature in the third temperature range is too low, the heating rate is too slow, and / or the holding time is insufficient, the high-temperature rearrangement and densification will be inadequate, resulting in a low degree of graphitization and insufficient strength of the skeleton. This can easily lead to skeleton breakage and pore structure collapse during subsequent activation. Conversely, if the temperature in the third temperature range is too high, the heating rate is too fast, and / or the holding time is too long, excessive sintering and shrinkage can easily occur. Some open pores may be blocked by sintering or transformed into closed pores, leading to a decrease in specific surface area and effective pore volume. Furthermore, thermal stress concentration can cause cracks, disrupting pore connectivity and hindering the acquisition of a structurally stable activated precursor.

[0050] In a preferred embodiment of the present invention, the first temperature range satisfies the following process parameters: temperature is 250-400℃, atmosphere is air, holding time is 1-4 h, and heating rate is 2-4℃ / min.

[0051] In a preferred embodiment of the present invention, the first temperature range satisfies the following process parameters: temperature of 300–350°C, atmosphere of air, holding time of 2–3 h, and heating rate of 2.5–4°C / min. Under these preferred conditions, the controlled oxidation degree in the air atmosphere can be maintained within a suitable range, promoting the initial cross-linking and stabilization of the carbonized material skeleton and reducing collapse and cracking in the subsequent heating stage.

[0052] In a preferred embodiment of the present invention, the second temperature range satisfies the following process parameters: temperature is 400~650℃, atmosphere is nitrogen, holding time is 1~3 h, and heating rate is 2~4℃ / min.

[0053] In a preferred embodiment of the present invention, the second temperature range satisfies the following process parameters: temperature is 500~600℃, atmosphere is nitrogen, holding time is 2 h, and heating rate is 2.5~4℃ / min.

[0054] In a preferred embodiment of the present invention, the third temperature range satisfies the following process parameters: temperature is 650~900℃, atmosphere is nitrogen, holding time is 1~2 h, and heating rate is 2~5℃ / min.

[0055] In a preferred embodiment of the present invention, the third temperature range satisfies the following process parameters: temperature is 650~800℃, atmosphere is nitrogen, holding time is 2h, and heating rate is 2.5~5℃ / min.

[0056] In a preferred embodiment of the present invention, after the reaction in the third temperature range is completed, the product obtained from the reaction in the third temperature range is transferred to a cooling chamber for rapid cooling at a rate of 60~150℃ / min, preferably 80~130℃ / min.

[0057] Preferably, the cooling method includes: after the reaction in the third temperature range is completed, the product obtained from the reaction in the third temperature range is transferred to the cooling chamber, liquid nitrogen is introduced into the cooling chamber or cooling circulating water is introduced into the outer wall of the cooling chamber, and the material is rapidly cooled to room temperature at a cooling rate of 60~150℃ / min, preferably 80~130℃ / min.

[0058] The cooling rate is, for example, 60℃ / min, 70℃ / min, 80℃ / min, 90℃ / min, 100℃ / min, 110℃ / min, 120℃ / min, 130℃ / min, 140℃ / min, or 150℃ / min. After the high-temperature reaction in the third temperature range, the carbon atoms are more disordered and the pores are more developed. The rapid cooling method with a high cooling rate can help maintain the reaction products in the third temperature range in this state, prevent the pore collapse caused by the microcrystal ordering during slow cooling, and thus maintain a large amount of short-range ordered graphite microcrystal structure + closed pores generated at high temperature, which is more conducive to the activation of pore formation.

[0059] If the cooling rate is lower than 60℃ / min, it will not achieve the effect of maintaining the microcrystalline structure at a high temperature. If the cooling rate is higher than 150℃ / min, the cost of cooling will be higher, and the actual effect on the crystal lattice will not be significantly improved. Considering the need to maintain the effect and achieve the optimal effect, the cooling rate is preferably 80~130℃ / min.

[0060] In a preferred embodiment of the present invention, the low-rank coal is long-flame coal.

[0061] In a preferred embodiment of the present invention, the D50 particle size of the low-rank coal is controlled between 5 and 75 μm.

[0062] D50, also known as median particle size, represents the characteristic particle size at which the cumulative distribution percentage in a particle group reaches 50%. D50 has a well-known meaning in the art and can be determined using instruments and methods known in the art. For example, it can be determined using laser diffraction, and can be measured using a laser diffraction scattering intensity distribution measuring device.

[0063] Examples of D50 are 10μm, 20μm, 30μm, 40μm, 50μm, 60μm or 70μm.

[0064] In a preferred embodiment of the present invention, the method includes a step of pretreating low-rank coal by uniformly spreading low-rank coal powder in a rotary kiln and drying it to 150-200°C under nitrogen protection at a temperature of 1-4°C / min.

[0065] According to a second aspect of the present invention, a method for preparing porous carbon is provided, comprising the carbonization method described above.

[0066] Typical but non-limiting methods for preparing porous carbon include: (a) The porous carbon precursor is carbonized using the carbonization method described above to obtain the carbonized product; (b) The carbonized product is activated to obtain porous carbon.

[0067] According to a third aspect of the present invention, a porous carbon prepared by the above-described method for preparing porous carbon is provided.

[0068] According to a fourth aspect of the present invention, an application of porous carbon as described above in a lithium-ion battery is provided.

[0069] Example 1 A method for carbonizing a porous carbon precursor includes: Long-flame pulverized coal is evenly spread in a rotary kiln and dried at 180°C at a rate of 2°C / min under nitrogen protection to remove water, so that the free water in the material is fully removed. The dried and dehydrated long-flame coal is made to react sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 220℃, atmosphere is air, holding time is 2h, and heating rate is 2℃ / min. The second temperature range meets the following process parameters: temperature is 350℃, atmosphere is nitrogen, holding time is 1h, and heating rate is 2℃ / min; The third temperature range meets the following process parameters: temperature is 800℃, atmosphere is nitrogen, holding time is 1.5h, and heating rate is 3℃ / min.

[0070] The product obtained from the reaction in the third temperature zone was transferred to a cooling chamber for rapid cooling at a rate of 100°C / min, and then pulverized and sieved to obtain the carbonized product.

[0071] Example 2 Long-flame pulverized coal is evenly spread in a rotary kiln and dried at 180°C at a rate of 2°C / min under nitrogen protection to remove water, so that the free water in the material is fully removed. The dried and dehydrated long-flame coal is made to react sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 200℃, atmosphere is air, holding time is 4h, and heating rate is 1℃ / min. The second temperature range meets the following process parameters: temperature is 350℃, atmosphere is nitrogen, holding time is 1h, and heating rate is 1℃ / min; The third temperature range meets the following process parameters: temperature is 650℃, atmosphere is nitrogen, holding time is 1h, and heating rate is 1℃ / min.

[0072] The product obtained from the reaction in the third temperature zone was transferred to a cooling chamber for rapid cooling at a rate of 100°C / min, and then pulverized and sieved to obtain the carbonized product.

[0073] Example 3 Long-flame pulverized coal is evenly spread in a rotary kiln and dried at 180°C at a rate of 2°C / min under nitrogen protection to remove water, so that the free water in the material is fully removed. The dried and dehydrated long-flame coal is made to react sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 340℃, atmosphere is air, holding time is 1h, and heating rate is 2℃ / min. The second temperature range meets the following process parameters: temperature is 600℃, atmosphere is nitrogen, holding time is 2h, and heating rate is 3℃ / min; The third temperature range meets the following process parameters: temperature is 900℃, atmosphere is nitrogen, holding time is 1.5h, and heating rate is 4℃ / min.

[0074] The product obtained from the reaction in the third temperature zone was transferred to a cooling chamber for rapid cooling at a rate of 100°C / min, and then pulverized and sieved to obtain the carbonized product.

[0075] Example 4 Long-flame pulverized coal is evenly spread in a rotary kiln and dried at 180°C at a rate of 2°C / min under nitrogen protection to remove water, so that the free water in the material is fully removed. The first temperature range meets the following process parameters: temperature is 430℃, atmosphere is air, holding time is 0.5h, and heating rate is 3℃ / min; The second temperature range meets the following process parameters: temperature is 650℃, atmosphere is nitrogen, holding time is 0.5h, and heating rate is 4℃ / min; The third temperature range meets the following process parameters: temperature is 950℃, atmosphere is nitrogen, holding time is 2h, and heating rate is 5℃ / min.

[0076] The product obtained from the reaction in the third temperature zone was transferred to a cooling chamber for rapid cooling at a rate of 100°C / min, and then pulverized and sieved to obtain the carbonized product.

[0077] Example 5 Long-flame pulverized coal is evenly spread in a rotary kiln and dried at 180°C at a rate of 2°C / min under nitrogen protection to remove water, so that the free water in the material is fully removed. The dried and dehydrated long-flame coal is made to react sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 280℃, atmosphere is air, holding time is 3h, and heating rate is 1.5℃ / min. The second temperature range meets the following process parameters: temperature is 500℃, atmosphere is nitrogen, holding time is 3h, and heating rate is 2℃ / min; The third temperature range meets the following process parameters: temperature is 750℃, atmosphere is nitrogen, holding time is 1h, and heating rate is 2.5℃ / min.

[0078] The product obtained from the reaction in the third temperature zone was transferred to a cooling chamber for rapid cooling at a rate of 100°C / min, and then pulverized and sieved to obtain the carbonized product.

[0079] Example 6 The temperature of the first temperature range in Example 1 was changed to 280°C, and the remaining preparation steps and methods were the same as in Example 1.

[0080] Example 7 The temperature of the first temperature range in Example 1 was changed to 320°C, and the remaining preparation steps and methods were the same as in Example 1.

[0081] Example 8 The time in the first temperature range in Example 1 was changed to 1.5 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0082] Example 9 The time in the first temperature range in Example 1 was changed to 2.5 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0083] Example 10 The temperature in the second temperature range in Example 1 was changed to 450°C, and the remaining preparation steps and methods were the same as in Example 1.

[0084] Example 11 The temperature in the second temperature range in Example 1 was changed to 550°C, and the remaining preparation steps and methods were the same as in Example 1.

[0085] Example 12 The time in the second temperature range in Example 1 was changed to 2 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0086] Example 13 The time in the second temperature range in Example 1 was changed to 2.5 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0087] Example 14 The heating rate in the second temperature range of Example 1 was changed to 2.5℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0088] Example 15 The heating rate in the second temperature range of Example 1 was changed to 3℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0089] Example 16 The temperature of the third temperature range in Example 1 was changed to 700°C, and the remaining preparation steps and methods were the same as in Example 1.

[0090] Example 17 The temperature in the third temperature range in Example 1 was changed to 850°C, and the remaining preparation steps and methods were the same as in Example 1.

[0091] Example 18 The heat preservation time in the third temperature range in Example 1 was changed to 2, and the remaining preparation steps and methods were the same as in Example 1.

[0092] Example 19 The heat preservation time in the third temperature range in Example 1 was changed to 1.75 h, and the remaining preparation steps and methods were the same as in Example 1.

[0093] Example 20 The heating rate in the third temperature range of Example 1 was changed to 2℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0094] Example 21 The heating rate in the third temperature range of Example 1 was changed to 5℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0095] Example 22 Compared with Example 1, after the reaction in the third temperature range was completed, the product obtained from the reaction in the third temperature range was cooled to room temperature at a rate of 60°C / min, and then pulverized and sieved to obtain the carbonized product.

[0096] Example 23 Compared with Example 1, after the reaction in the third temperature range was completed, the product obtained from the reaction in the third temperature range was cooled to room temperature at a rate of 150°C / min, and then pulverized and sieved to obtain the carbonized product.

[0097] Example 24 Compared with Example 1, after the reaction in the third temperature range was completed, the product obtained from the reaction in the third temperature range was cooled to room temperature at a rate of 10°C / min, and then pulverized and sieved to obtain the carbonized product.

[0098] Example 25 Compared with Example 1, after the reaction in the third temperature range was completed, the product obtained from the reaction in the third temperature range was cooled to room temperature at a rate of 170°C / min, and then pulverized and sieved to obtain the carbonized product.

[0099] Example 26 Compared with Example 1, after the reaction in the third temperature range was completed, the product obtained from the reaction in the third temperature range was cooled to room temperature at a rate of 1°C / min, and then pulverized and sieved to obtain the carbonized product.

[0100] Example 27 Compared to Example 1, no cooling treatment was performed after the reaction in the third temperature range was completed.

[0101] Comparative Example 1 The temperature of the first temperature range in Example 1 was changed to 180°C, and the remaining preparation steps and methods were the same as in Example 1.

[0102] Comparative Example 2 The temperature of the first temperature range in Example 1 was changed to 500°C, and the remaining preparation steps and methods were the same as in Example 1.

[0103] Comparative Example 3 The heat preservation time in the first temperature range in Example 1 was changed to 0.4h, and the remaining preparation steps and methods were the same as in Example 1.

[0104] Comparative Example 4 The heat preservation time in the first temperature range in Example 1 was changed to 6 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0105] Comparative Example 5 The temperature in the second temperature range in Example 1 was changed to 300°C, and the remaining preparation steps and methods were the same as in Example 1.

[0106] Comparative Example 6 The temperature in the second temperature range in Example 1 was changed to 700°C, and the remaining preparation steps and methods were the same as in Example 1.

[0107] Comparative Example 7 The heat preservation time in the second temperature range in Example 1 was changed to 0.4h, and the remaining preparation steps and methods were the same as in Example 1.

[0108] Comparative Example 8 The heat preservation time in the second temperature range in Example 1 was changed to 4 hours, and the remaining preparation steps and methods were the same as in Example 1.

[0109] Comparative Example 9 The heating rate in the second temperature range of Example 1 was changed to 0.5℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0110] Comparative Example 10 The heating rate in the second temperature range of Example 1 was changed to 5℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0111] Comparative Example 11 The temperature in the third temperature range in Example 1 was changed to 600°C, and the remaining preparation steps and methods were the same as in Example 1.

[0112] Comparative Example 12 The temperature of the third temperature range in Example 1 was changed to 1000℃, and the remaining preparation steps and methods were the same as in Example 1.

[0113] Comparative Example 13 The heat preservation time in the third temperature range in Example 1 was changed to 0.5 h, and the remaining preparation steps and methods were the same as in Example 1.

[0114] Comparative Example 14 The heat preservation time in the third temperature range in Example 1 was changed to 2.5 hours, while the remaining preparation steps and methods were the same as in Example 1.

[0115] Comparative Example 15 The heating rate in the third temperature range of Example 1 was changed to 0.5℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0116] Comparative Example 16 The heating rate in the third temperature range of Example 1 was changed to 6℃ / min, and the remaining preparation steps and methods were the same as in Example 1.

[0117] Comparative Example 17 A method for preparing coal-based activated carbon, comprising: (1) Prepare bituminous coal from Guoneng Heishan Coal Mine in Toksun County as the first coal-based raw material (caking index of 12), and raw coal from Hami Baolijilangde Coal Mine as the second coal-based raw material (ash content of 1.9%, volatile content of 37%, caking index of 11). Mix 70 parts by weight of bituminous coal from Guoneng Heishan Coal Mine in Toksun County, 29 parts by weight of raw coal from Hami Baolijilangde Coal Mine, and 1 part by weight of coal direct liquefaction residue to obtain the material to be processed. The material to be processed is then subjected to briquetting and granulation in sequence. During the briquetting process, the pressure applied to the material to be processed is 28 MPa. The particle size of the coal-based particles obtained after granulation is 8 mm, and the roller strength is greater than 90%. (2) The coal-based particles prepared above were oxidized in an oxygen atmosphere, wherein the oxygen content in the oxygen atmosphere was 21 vol%, the oxidation temperature was 250 °C, and the oxidation product was obtained after 3 h of oxidation treatment. (3) The above-prepared oxidation product is carbonized in an inert atmosphere. Specifically, the oxidation product is heated to 250°C at a heating rate of 10°C / min, and then heated from 250°C to 550°C at a heating rate of 10°C / min for carbonization. The carbonized product is obtained after reacting for 2.5 hours. The roller strength of the carbonized product is greater than 96%.

[0118] (4) The carbonized product obtained above is activated. Specifically, a small activation furnace (Shijiazhuang Hengye Machinery Factory) is used to heat the carbonized product to 920°C at a heating rate of 10°C / min. Distilled water is introduced and activated under test conditions of 120 drops / min for 5.5 hours to obtain coal-based activated carbon.

[0119] Performance testing The performance of the carbonized products obtained in the examples and comparative examples was tested as follows: Oxygen content: JY / T 0580-2020 Volatile matter: GB / T30732-2014 Table 1

[0120] Table 2

[0121] Table 3

[0122] The carbonized products obtained in Examples 1-26 and Comparative Examples 1-17 were mixed with potassium hydroxide at an alkali-to-carbon mass ratio of 2:1 and then transferred to a quartz tube furnace. The mixture was heated to the set activation temperature of 850°C under nitrogen protection. After the furnace temperature stabilized, the mixture was held at this temperature for 4 hours. After activation, the mixture was cooled to room temperature under a nitrogen atmosphere. The sample was washed with dilute hydrochloric acid (5 wt.%) to remove inorganic residues, then rinsed with deionized water until pH 6-7, and dried at 180°C for 6 hours to obtain coal-based porous carbon material.

[0123] The specific surface area and electrical conductivity of the obtained coal-based porous carbon material were tested using the following methods: Specific surface area: GT / T 19587-2017 Resistivity: GB / T 30835-2014 In Table 4, Example 1 refers to the coal-based porous carbon material obtained by activating the porous carbon precursor of Example 1. Other examples and comparative examples are similar.

[0124] Table 4

[0125] Table 5

[0126] Table 6

[0127] Electrochemical performance testing Test Method: The porous carbon precursors obtained in Examples 1-26 and Comparative Examples 1-17 were mixed with potassium hydroxide at an alkali-to-carbon mass ratio of 2:1 and then transferred to a quartz tube furnace. The mixture was heated to the set activation temperature of 850°C under nitrogen protection. After the furnace temperature stabilized, the mixture was held at this temperature for 4 hours. After activation, the mixture was cooled to room temperature under a nitrogen atmosphere. The sample was washed with dilute hydrochloric acid (5 wt.%) to remove inorganic residues, then rinsed with deionized water until pH=6-7, and dried at 180°C for 6 hours to obtain coal-based porous carbon material. This coal-based porous carbon material was used to prepare silicon-carbon composite anode material via CVD silicon deposition, and then its electrochemical performance was tested.

[0128] Table 7

[0129] Table 8

[0130] Table 9

Claims

1. A method for carbonizing a porous carbon precursor, characterized in that, include: Low-rank coal is provided, and the low-rank coal reacts sequentially in the first temperature range, the second temperature range, and the third temperature range. The first temperature range meets the following process parameters: temperature is 200-450℃, atmosphere is air, holding time is 0.5-5 h, and heating rate is 1-4℃ / min; The second temperature range meets the following process parameters: temperature is 350~650℃, atmosphere is nitrogen, holding time is 0.5~3 h, and heating rate is 1~4℃ / min; The third temperature range meets the following process parameters: temperature is 650-950℃, atmosphere is nitrogen, holding time is 1-2 h, and heating rate is 1-5℃ / min.

2. The method as described in claim 1, characterized in that, The first temperature range meets the following process parameters: temperature is 250-400℃, atmosphere is air, holding time is 1-4 h, and heating rate is 2-4℃ / min.

3. The method as described in claim 2, characterized in that, The first temperature range meets the following process parameters: temperature is 300-350℃, atmosphere is air, holding time is 2-3 h, and heating rate is 2.5-4℃ / min.

4. The method according to any one of claims 1-3, characterized in that, The second temperature range satisfies the following process parameters: temperature 400~650℃, nitrogen atmosphere, holding time 1~3 h, heating rate 2~4℃ / min, and / or, The third temperature range meets the following process parameters: temperature is 650~900℃, atmosphere is nitrogen, holding time is 1~2 h, and heating rate is 2~5℃ / min.

5. The method as described in claim 4, characterized in that, The second temperature range satisfies the following process parameters: temperature 500~600℃, nitrogen atmosphere, holding time 2 h, heating rate 2.5~4℃ / min, and / or, The third temperature range satisfies the following process parameters: temperature 650~800℃, nitrogen atmosphere, holding time 2h, heating rate 2.5~5℃ / min, and / or, After the reaction in the third temperature range is completed, the product obtained from the reaction in the third temperature range is transferred to a cooling chamber for rapid cooling at a rate of 60~150℃ / min, preferably 80~130℃ / min.

6. The method according to any one of claims 1-3, characterized in that, The low-rank coal is long-flame coal.

7. The method according to any one of claims 1-3, characterized in that, The particle size of the low-rank coal is controlled between 5 and 75 μm.

8. A method for preparing porous carbon, characterized in that, Including the carbonization method as described in any one of claims 1-7.

9. A porous carbon prepared by the method for preparing porous carbon as described in claim 8.

10. The application of the porous carbon as described in claim 9 in a lithium-ion battery.

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