Preparation method and application of phosphorus-doped porous carbon

Abstract

The invention belongs to the field of carbon materials, and discloses a preparation method of phosphorus-doped porous carbon. The preparation method comprises the following steps: mixing biomass pyrolytic carbon, PC13 and water; and putting the mixture into an acid-corrosion-resistant rotary reaction furnace, introducing inert gas, then carrying out segmented heating treatment, finally raising the temperature to sublimate the generated chloride to be discharged along with the inert gas, and cooling the furnace body to obtain the phosphorus-doped high-purity porous carbon, the sectional heating treatment is three-section heating treatment: firstly raising the temperature to 40-80 DEG C for first-section heat preservation, then raising the temperature to 180-320 DEG C for second-section heat preservation, and finally raising the temperature to 500-600 DEG C for third-section heat preservation. According to the preparation method of the phosphorus-doped high-purity porous carbon, phosphorous acid and hydrochloric acid are formed through special reaction of PCl3 and water, phosphoric acid and hydrogen phosphide are generated through disproportionation reaction of phosphorous acid, and finally preparation, phosphorus doping and purification treatment of the porous carbon are achieved through decomposition of hydrogen phosphide.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon materials, and particularly relates to a preparation method and application of phosphorus-doped porous carbon. Background Art

[0002] Porous carbon materials are carbon materials with a high specific surface area and a rich pore structure, having excellent electrical conductivity, physical and chemical stability. Their pore diameters can be divided into micropores (<2 nm), mesopores (2 - 50 nm), and macropores (>50 nm). Due to their high electrical conductivity, good stability, and excellent electrochemical properties, such materials have extensive applications in the fields of energy storage, catalysis, adsorption, etc.

[0003] Lithium-ion batteries have the characteristic of high energy density and have attracted wide attention in an increasingly electrified society. Carbon materials are commonly used anode materials for lithium-ion batteries. However, the theoretical capacity of currently commercial graphite has approached its theoretical limit, and it is difficult to further improve its performance. Therefore, it is crucial to find a new generation of electrode materials for lithium-ion batteries.

[0004] Porous carbon has become an excellent precursor material because it can be used to prepare silicon-carbon anode materials for lithium-ion batteries with excellent performance. The multi-dimensional and complex pore structure provides an effective diffusion channel and a short lithium-ion diffusion distance for lithium ions; defects such as vacancies and heteroatom doping can serve as lithium storage sites; during the lithium deintercalation / insertion process, the mechanical stress of volume expansion / shrinkage is small, and the cycle stability is good. Therefore, as an excellent precursor material for silicon-carbon anodes of lithium-ion batteries, its preparation process is crucial for the research and development of silicon-carbon anode materials.

[0005] The patent document with the publication number CN118515257A proposes a preparation method and application of nitrogen, phosphorus, and sulfur co-doped porous carbon. In this invention, chitosan is used as a carbon source, and thiocyanuric acid and potassium hypophosphite are used as dopants to dope nitrogen, phosphorus, and sulfur elements into the porous carbon, which can increase the specific surface area of the porous carbon to 1318 m 2 / g. However, the porous carbon prepared by this method cannot achieve uniform doping of heteroatoms, and the specific surface area fails to reach more than 2000 m 2 / g, and its lithium storage capacity for lithium ions is relatively low and needs to be further improved.

[0006] A preparation method of a nano red phosphorus-porous carbon composite material was proposed in the patent document with the publication number CN117699752A. Chlorella was used as the carbon source, calcium, potassium, and sodium salts were used as pore-forming agents, and red phosphorus was used as a doping agent. The nano red phosphorus-porous carbon composite material was prepared by liquid-phase mixing and then carbonization. This material can achieve an initial discharge specific capacity of 1673 mAh / g in a coin cell. However, the stability of the material is relatively poor, and the phosphorus element is mainly distributed on the surface of the material, making it difficult to enter the interior of the porous carbon material, and it is impossible to achieve a significant increase in capacity.

[0007] A preparation method of a nitrogen, phosphorus, and oxygen in-situ co-doped porous carbon material was published in the patent document with the publication number CN117877893A. This invention uses coal and heavy petroleum-based organic substances as carbon sources, phospho-threonine and phospho-guanylurea as doping agents, and alkali as a pore-forming agent, and prepares the nitrogen, phosphorus, and oxygen co-doped porous carbon material by solution mixing and heating. However, the porous carbon material prepared by this invention has a relatively low capacity in the battery, and the specific surface area does not reach more than 2000 m 2 / g.

[0008] A patent document with the publication number CN114388799A published a CoFe 2 O 4 / phosphorus-containing porous carbon lithium-ion battery anode material and its preparation method. This method uses triphosphine and acrylonitrile as raw materials, adds tetrahydrofuran and dimethyl sulfoxide, and heats at low temperature in a reaction kettle, and then carbonizes at high temperature to prepare phosphorus-containing porous carbon. The phosphorus-containing porous carbon material prepared by this invention has a relatively high specific surface area, but its charging specific capacity at a current density of 50 mA / g is only 826.3 mAh / g, which is relatively low in the lithium-ion battery system. This is mainly because only a small amount of phosphorus is doped on the surface of the material by this method, and obvious phosphorus doping is not achieved inside.

[0009] A preparation method of a phosphoric acid-crosslinked starch porous carbon material was disclosed in the patent document with the publication number CN117049512A. Starch was used as the raw material, phosphoric acid was used as the activator, and the starch-based porous carbon material was prepared by hydrothermal treatment at 200 °C to promote starch crosslinking. The specific surface area of the porous carbon prepared by this method is only 1866 m 2 / g, which is relatively low in the phosphorus-doped porous carbon system. This may be because using only phosphoric acid solution to activate biomass can only form pores on the surface of the material and cannot treat the internal pores of the material.

[0010] In the article "Preparation and Characterization of Bamboo Sawdust Activated Carbon by Phosphoric Acid Method" by Zhou Jinlong et al., a method for preparing bamboo sawdust activated carbon by the phosphoric acid method is disclosed. However, in this method, an aqueous phosphoric acid solution is sprayed on the surface of bamboo sawdust, and the bamboo sawdust material is stirred while spraying, so that the phosphoric acid solution is evenly sprayed on the surface of the bamboo sawdust, and then a multi-stage calcination method is used to prepare bamboo sawdust-based activated carbon. However, the specific surface area of the bamboo sawdust-based porous carbon prepared by this method is only 1651 m 2 / g, which is relatively low in the phosphoric acid-activated porous carbon system.

[0011] To sum up, the porous carbon produced in the current industry mainly has problems such as too small specific surface area, complex preparation process, and relatively low specific capacity. Moreover, in the current porous carbon doping technology, only surface doping can be basically achieved, and doping of the internal structure of porous carbon cannot be achieved. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background technology, and provide a preparation method and application of phosphorus-doped porous carbon.

[0013] To solve the above technical problem, the technical solution proposed by the present invention is as follows: A preparation method of phosphorus-doped porous carbon, comprising the following steps: (1) Mix biomass pyrolysis carbon, PCl 3 , and water; (2) Place the mixture after step (1) in an acid-resistant rotary reaction furnace, introduce an inert gas, and then perform segmented heating treatment. Finally, raise the temperature to sublime the generated chloride and discharge it with the inert gas, and cool the furnace body to obtain phosphorus-doped high-purity porous carbon. Among them, the segmented heating treatment is a three-stage heating treatment: first, raise the temperature to 40-80 °C for the first-stage heat preservation to make PCl 3 fully react with water to form phosphorous acid and hydrochloric acid, then raise the temperature to 180-320 °C for the second-stage heat preservation to make phosphorous acid start to disproportionate to produce PH 3 , and make hydrochloric acid vaporize to form HCl, and react with the impurity components in the pyrolysis carbon to form chlorides. Finally, raise the temperature to 500-600 °C for the third-stage heat preservation to make PH 3 decompose into P and H 2 , the generated H 2 reacts with the oxygen atoms in the pyrolysis carbon to form H 2 O, and the P gas gradually penetrates into the interior of the pyrolysis carbon.

[0014] In the above preparation method, preferably, in step (2), the time for the first-stage heat preservation is 0.5-4 h.

[0015] In the above preparation method, preferably, in step (2), the time for the second-stage heat preservation is 0.5-3 h.

[0016] In the above preparation method, preferably, in step (2), the holding time in the third stage is 0.5 - 2 h.

[0017] In the above preparation method, preferably, in step (1), the mass ratio of the bio - pyrolytic carbon to PCl 3 is 6:1 - 1:2. If the amount of PCl 3 is too much, the produced carbon material will be over - corroded, and the intercalation of lithium ions cannot be effectively achieved. If the amount of PCl 3 is too little, the etching effect is small, and it is difficult to effectively prepare high - capacity phosphorus - doped porous carbon.

[0018] In the above preparation method, preferably, in step (1), the volume ratio of PCl 3 to ultrapure water is 1:3. Controlling the ratio of PCl 3 to water can promote the full reaction of PCl 3 with water to form phosphorous acid and hydrochloric acid, reduce the water content inside the furnace body at high temperature, and thus avoid obvious harm to the furnace body.

[0019] In the above preparation method, preferably, in step (1), the biomass pyrolytic carbon includes one of coconut shell pyrolytic carbon, bamboo pyrolytic carbon, and walnut shell pyrolytic carbon, with a specific surface area of 350 - 450 m 2 / g and an oxygen content of 1.2 - 1.7%.

[0020] In the above preparation method, preferably, in step (2), the inert gas is one or more of nitrogen, helium, argon, and neon; the flow rate of the inert gas introduced is 0.1 L / min - 0.5 L / min. The flow rate of the inert gas needs to be controlled within this range. Otherwise, if it is lower than this gas flow rate, on the one hand, the exhaust process will cause incomplete exhaustion of air, resulting in the contact of the material with oxygen during the sintering process and being oxidized. On the other hand, too low gas flow rate will cause the generated chloride to not be discharged at the sublimation temperature, thus affecting the purity of the material; if it is higher than this gas flow rate, the P generated during the sintering process will be quickly discharged, and efficient doping cannot be achieved.

[0021] In the above preparation method, preferably, after the segmented heating treatment, continue to raise the temperature to make the generated chloride sublime and be discharged with the inert gas, then cool the furnace body. During the cooling process, P changes from gaseous to solid state and is distributed in each part of the pyrolytic carbon. Finally, the phosphorus - doped high - purity porous carbon is taken out by tilting the furnace tube.

[0022] In the above preparation method, preferably, after the segmented heating treatment, continue to raise the temperature to 700 - 750 °C and hold for 0.5 - 2 h.

[0023] In the above preparation method, preferably, the main reaction equations involved in the above steps are: PCl 3 + 3H 2 O = H 3 PO 3 + 3HCl; 4H 3 PO 3 = 3H 3 PO 4 + PH 3 ; 2HCl + FeO = FeCl 2 + H 2 O; 2PH 3 = 2P + 3H 2 ; H 2 + O 2 = H 2 O。

[0024] Based on a general inventive concept, the present invention also provides an application of the phosphorus-doped porous carbon prepared by the above preparation method in the anode material of a lithium-ion battery.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the preparation method of the phosphorus-doped high-purity porous carbon of the present invention, by adopting the special reaction of PCl 3 with water to form phosphorous acid and hydrochloric acid, and using the disproportionation reaction of phosphorous acid itself to generate phosphoric acid and phosphine, finally, the preparation, phosphorus doping and purification treatment of porous carbon are realized by the decomposition of phosphine.

[0026] (2) The phosphoric acid generated by the disproportionation of phosphorous acid itself activates the pyrolytic carbon at a relatively high temperature. During the activation stage, phosphoric acid etches the carbon structure to form more micropores with a size of less than 2 nm, thereby providing a larger specific surface area and effectively transforming the pyrolytic carbon into porous carbon. In different heating stages, various phosphorus-containing substances etch the pyrolytic carbon, and multi-stage etching fully realizes the formation of pores, which is more conducive to the preparation of porous carbon with a higher specific surface area. Moreover, the subsequent purification of HCl and H 2 further promotes the formation of internal pores in the carbon.

[0027] (3) In the preparation process of the present invention, the generation of PH 3 provides a good doping source for P doping. PH 3 decomposes into P and H 2, where P exists in gaseous form at this temperature. Promoted by thermal motion, gaseous P atoms will enter into the porous carbon. The P atoms that enter the interlayer of the porous carbon will continuously move between the carbon layers and cannot escape outside the carbon because they lose sufficient kinetic energy and their atomic radius is larger than that of carbon. Finally, as the furnace cools down, gaseous P gradually solidifies into solid P atoms, ultimately achieving uniform doping of P.

[0028] (4) During the preparation process of the present invention, the generated HCl reacts with impurities (mainly ferrous oxide) in the porous carbon at a relatively high temperature to form ferrous chloride after sufficient contact. At a subsequent high temperature, ferrous chloride starts to sublime and finally is discharged from the furnace body with the introduction of inert gas, thereby achieving the removal of impurities inside the porous carbon; while PH 3 decomposes to generate H 2 , which will react with oxygen atoms in the carbon material at high temperature to form H 2 O. The formed H 2 O will also be discharged from the furnace body with the introduction of inert gas, further increasing the fixed carbon content of the porous carbon and achieving secondary purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, the following described drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is the SEM picture of the phosphorus-doped porous carbon prepared in Example 1 of the present invention; Figure 2 is the TEM picture of the phosphorus-doped porous carbon prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and meticulously in combination with the specification drawings and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all the professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0033] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0034] The biomass pyrolysis carbon used in the following examples and comparative examples is coconut shell pyrolysis carbon, with a specific surface area of 425.3 m 2 / g and an oxygen content of 1.4%.

[0035] Example 1: A preparation method of phosphorus-doped porous carbon of the present invention includes the following steps: Mix 600 g of biomass pyrolysis carbon, 150 mL of PCl 3 and 450 mL of ultrapure water evenly, and place them in an acid-resistant rotary reaction furnace. Argon is introduced into the furnace at a rate of 0.3 L / min. After 6 hours of gas injection, the temperature is raised to 60 °C and kept warm for 1 hour, then the temperature is continuously raised to 230 °C and kept warm for 2 hours, and then the temperature is raised to 540 °C and kept warm for 1.5 hours. After the three-stage temperature rise is completed, the temperature in the furnace is raised to 730 °C and kept warm for 1 hour. The generated chloride sublimes and is discharged with the inert gas. After the heat preservation is completed, the furnace body starts to cool down. After cooling, the phosphorus-doped porous carbon is taken out by tilting the furnace body.

[0036] SEM photograph of the doped porous carbon prepared in this example Figure 1 , and the TEM photograph is Figure 2 . Figure 1 Under SEM, obvious pores are shown, indicating that the porous carbon material with rich pores is successfully prepared in this example. Figure 2 Under TEM, the material shows evenly distributed black particles, and the black particles are the P elements incorporated into the interior of the porous carbon, indicating that the P elements are successfully distributed inside the porous carbon.

[0037] The specific surface area of the phosphorus-doped porous carbon prepared in this example is detected by the static volumetric method to be 2356.52 m 2 / g, the average pore diameter of the material is 1.2 nm; the P content is tested by the method of spectrophotometer to be 5.7%, the oxygen content is tested by oxygen analyzer to be 0.2%, and the content of other impurities is 0.06%.

[0038] The phosphorus-doped porous carbon, conductive agent, and PVDF prepared in this example are mixed and homogenized and coated in a ratio of 8:1:1. After making the electrode sheet, a lithium-ion button half-cell is prepared by the button cell assembly method, and the performance is tested at a current density of 20 mA / g. The initial discharge specific capacity is 1786 mAh / g.

[0039] Example 2: A preparation method of phosphorus-doped porous carbon of the present invention includes the following steps: Mix 600 g of biomass pyrolysis carbon, 100 mL of PCl 3Mix it evenly with 300 mL of ultrapure water and place it in a rotary reaction furnace resistant to acid corrosion. Introduce argon into the furnace at a rate of 0.3 L / min. After 6 hours of gas introduction, start heating to 60 °C and keep it warm for 1 hour. After completion, continue heating to 230 °C and keep it warm for 2 hours. After the second-stage heating is completed, heat it up to 540 °C again and keep it warm for 1.5 hours. After the third-stage heating is completed, heat it up to 730 °C and keep it warm for 1 hour. The generated chloride sublimes and is discharged with the inert gas. After the heat preservation is completed, start cooling the furnace body. After cooling, take out the phosphorus-doped high-purity porous carbon by tilting the furnace body.

[0040] The specific surface area of the phosphorus-doped porous carbon prepared in this example was detected by the static volumetric method to be 2031.13 m 2 / g. The average pore diameter of the material is 1.6 nm. The P content was tested by the method of spectrophotometer to be 3.9%. The oxygen content was tested by an oxygen analyzer to be 0.5%. The content of other impurities is 0.111%.

[0041] After making the phosphorus-doped porous carbon of this example into a pole piece according to the method of Example 1, a lithium-ion button half-cell was prepared by the button cell assembly method. The performance was tested at a current density of 20 mA / g, and the initial discharge specific capacity was 1618 mAh / g.

[0042] Example 3: A preparation method of the phosphorus-doped porous carbon of the present invention includes the following steps: Mix 600 g of biomass pyrolysis carbon, 150 ml of PCl 3 and 450 mL of ultrapure water evenly and place it in a rotary reaction furnace resistant to acid corrosion. Introduce argon into the furnace at a rate of 0.5 L / min. After 6 hours of gas introduction, start heating to 60 °C and keep it warm for 1 hour. After completion, continue heating to 230 °C and keep it warm for 2 hours. After the second-stage heating is completed, heat it up to 540 °C again and keep it warm for 1.5 hours. Finally, heat it up to 730 °C and keep it warm for 1 hour. The generated chloride sublimes and is discharged with the inert gas. After the heat preservation is completed, start cooling the furnace body. After cooling, take out the phosphorus-doped high-purity porous carbon by tilting the furnace body.

[0043] The specific surface area of the phosphorus-doped porous carbon prepared in this example was detected by the static volumetric method to be 2276.96 m 2 / g. The average pore diameter of the material is 1.3 nm. The P content was tested by the method of spectrophotometer to be 5.2%. The oxygen content was tested by an oxygen analyzer to be 0.3%. The content of other impurities is 0.09%.

[0044] After making the phosphorus-doped porous carbon of this example into a pole piece according to the method of Example 1, a lithium-ion button half-cell was prepared by the button cell assembly method. The performance was tested at a current density of 20 mA / g, and the initial discharge specific capacity was 1705 mAh / g.

[0045] Comparative Example 1: The preparation method of the phosphorus-doped porous carbon in this comparative example includes the following steps: Mix 600 g of biomass pyrolysis carbon with 150 ml of H 3 PO 4 uniformly, and place it in an acid-resistant rotary reaction furnace. Argon is introduced into the furnace at a rate of 0.3 L / min. After 6 h of ventilation, the temperature is raised to 60 °C and held for 1 h. After completion, the temperature is continued to be raised to 230 °C and held for 2 h. After the two-stage temperature rise is completed, the temperature is raised to 540 °C again and held for 1.5 h. After the three-stage temperature rise is completed, the temperature in the furnace is raised to 730 °C and held for 1 h. After the heat preservation is completed, the furnace body starts to be cooled, and after cooling, the phosphorus-doped high-purity porous carbon is taken out by tilting.

[0046] The specific surface area of the porous carbon in this comparative example was detected by the static volumetric method to be 1267.52 m 2 / g, the average pore diameter of the material is 2.7 nm, the P content is tested by the spectrophotometer method to be 0.8%, the oxygen content is tested by the oxygen analyzer to be 1.3%, and the content of other impurities is 0.27%.

[0047] The phosphorus-doped porous carbon in this comparative example was made into a pole piece according to the method of Example 1, and then a lithium-ion button half-cell was prepared by the button cell assembly method. The performance was tested at a current density of 20 mA / g, and the initial discharge specific capacity was 964 mAh / g.

[0048] Comparative Example 2: The preparation method of the phosphorus-doped porous carbon in this comparative example includes the following steps: Mix 600 g of biomass pyrolysis carbon, 150 mL of H 3 PO 4 and 450 mL of HCl uniformly, and place it in an acid-resistant rotary reaction furnace. Argon is introduced into the furnace at a rate of 0.3 L / min. After 6 h of ventilation, the temperature is raised to 60 °C and held for 1 h. After completion, the temperature is continued to be raised to 230 °C and held for 2 h. After the two-stage temperature rise is completed, the temperature is raised to 540 °C again and held for 1.5 h. After the three-stage temperature rise is completed, the temperature is raised to 730 °C and held for 1 h. After the heat preservation is completed, the furnace body starts to be cooled, and after cooling, the phosphorus-doped high-purity porous carbon is taken out by tilting.

[0049] The specific surface area of the porous carbon in this comparative example was detected by the static volumetric method to be 1336.52 m 2 / g, the average pore diameter of the material is 2.3 nm, the P content is tested by the spectrophotometer method to be 0.9%, the oxygen content is tested by the oxygen analyzer to be 1.2%, and the content of other impurities is 0.21%.

[0050] The phosphorus-doped porous carbon of this comparative example was made into an electrode sheet according to the method of Example 1, and then a lithium-ion button half-cell was prepared by a button cell assembly method. The performance was tested at a current density of 20 mA / g, and the initial discharge specific capacity was 1031 mAh / g.

[0051] Comparative Example 3: In this comparative example, the multi-stage heating method was not used to prepare phosphorus-doped porous carbon, which specifically included the following steps: 600 g of biomass pyrolysis carbon, 150 mL of PCl 3 and 450 mL of ultrapure water were mixed evenly and placed in an acid-resistant rotary reaction furnace. Argon was introduced into the furnace at a rate of 0.3 L / min. After 6 h of gas introduction, the temperature was raised to 730 °C and kept warm for 5.5 h. The generated chloride sublimated and was discharged with the inert gas. After the heat preservation was completed, the furnace body began to cool down. After cooling, the phosphorus-doped porous carbon was taken out by tilting the furnace body.

[0052] The specific surface area of the phosphorus-doped porous carbon of this comparative example was detected by the static volumetric method to be 1463.52 m 2 / g, the average pore diameter of the material was 2.1 nμm, the P content was tested by the method of spectrophotometer to be 1.8%, the oxygen content was tested by an oxygen analyzer to be 0.8%, and the content of other impurities was 0.15%.

[0053] The phosphorus-doped porous carbon of this comparative example was made into an electrode sheet according to the method of Example 1, and then a lithium-ion button half-cell was prepared by a button cell assembly method. The performance was tested at a current density of 20 mA / g, and the initial discharge specific capacity was 1216 mAh / g.

[0054] Table 1 Physicochemical properties of porous carbon prepared in each example and comparative example

[0055] From the comparison of the above examples and comparative examples, it can be seen that using PCl 3 as a pore-forming dopant can effectively increase the micropore pores with a pore diameter <2 nm, thereby increasing the specific surface area and specific capacity of the porous carbon. PCl 3 has a smaller molecular volume compared to the mixture of H 3 PO 3 and HCl, and is more likely to enter the internal structure of the material. PCl 3 reacts with water after entering the material structure to generate H 3 PO 3 and HCl can directly act from the inside of the material, achieving a better purification effect while creating pores inside the material. And directly using H 3 PO 3The mixture with HCl is relatively difficult to enter into the interior of the material and mostly acts on the surface contact area of the material, resulting in poor effects.

Claims

1. A method for preparing phosphorus-doped porous carbon, characterized in that: The following steps are involved: (1) Mixing biomass pyrolysis carbon, PCl3 and water; (2) placing the mixture after step (1) in an acid corrosion resistant rotary reaction furnace, introducing an inert gas, and then performing a staged heating treatment, and finally raising the temperature to allow the generated chloride to sublime and be discharged along with the inert gas, and cooling the furnace body to obtain phosphorus-doped porous carbon, wherein the staged heating treatment is a three-stage heating treatment: firstly raising the temperature to 40-80°C for the first stage of heat preservation, then raising the temperature to 180-320°C for the second stage of heat preservation, and finally raising the temperature to 500-600°C for the third stage of heat preservation.

2. The preparation method according to claim 1, characterized in that In step (2), the first insulation period is 0.5-4 hours.

3. The preparation method according to claim 1, characterized in that: In step (2), the second insulation period is 0.5-3h.

4. The preparation method according to claim 1, characterized in that: In step (2), the third insulation period is 0.5-2h.

5. The preparation method according to any one of claims 1 to 4, characterized in that In step (1), the solid-liquid ratio of the bio-pyrolysis carbon to PCl3 is 6:1-1:2, and the ratio unit is g / mL.

6. The preparation method according to any one of claims 1 to 4, characterized in that In step (1), the volume ratio of PCl3 to water is 1:

3.

7. The preparation method according to any one of claims 1 to 4, characterized in that In step (2), the inert gas is one or more of nitrogen, helium, argon, and neon; and the flow rate of the inert gas is 0.1 L / min-0.5 L / min.

8. The preparation method according to any one of claims 1 to 4, characterized in that: After the staged heating treatment, the temperature is continued to rise to 700-750°C and kept at this temperature for 0.5-2h to allow the generated chloride to sublime and be discharged along with the inert gas.

9. Use of phosphorus-doped porous carbon prepared by the preparation method according to any one of claims 1 to 8 in negative electrode materials for lithium-ion batteries.

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