Porous-filled hard carbon material and preparation method thereof

Abstract

The invention discloses a porous-filling type hard carbon material and a preparation method thereof, and relates to the field of battery negative electrode material preparation, resin is dissolved in water, metal salt is added, after dissolving and uniform mixing, spray pyrolysis is carried out to obtain mixture powder, then primary carbonization is carried out, then the mixture powder is washed with dilute nitric acid and dried, and porous hard carbon is obtained; dissolving cane sugar in water, adding the porous hard carbon powder, uniformly mixing, carrying out hydrothermal treatment, drying the turbid liquid, and carrying out secondary carbonization so as to fill pores in the outer layer of the porous hard carbon and increase sodium storage sites; according to the porous-filling type hard carbon material and the preparation method thereof, sucrose filled in pores of the porous hard carbon is pyrolyzed and shrunk through secondary carbonization to leave more pore channels for ion transmission, and the porous characteristic of the porous-filling type hard carbon material is enhanced by increasing ion diffusion channels, so that electrolyte permeation is promoted; the contact area of the electrolyte and the hard carbon material is increased, the rate capability of the material is improved, and the initial coulombic efficiency is enhanced.

Description

Technical Field

[0001] The present invention relates to the preparation technology of battery anode materials, and particularly relates to a porous-filled hard carbon material and a preparation method thereof. Background Art

[0002] Since Sony successfully commercialized lithium-ion batteries in the 1990s, the application of lithium-ion batteries in the field of large-scale energy storage in green new energy has been restricted due to problems such as high costs and resource shortages. At the same time, sodium-ion batteries have emerged, with performance comparable to that of lithium-ion batteries. Moreover, sodium resources are rich in reserves and evenly distributed, which can meet the current human demand for energy storage devices and have become a research hotspot.

[0003] Graphite, which is currently widely used as a battery anode material, can accommodate the insertion of lithium ions between graphite carbon layers. However, since the graphite layer spacing is greater than the lithium ion radius (0.102 nm) and less than the sodium ion radius (0.076 nm), it is difficult to use graphite as the anode material for sodium-ion batteries. In addition, graphite anode materials also have defects such as poor cycling performance and low initial charge-discharge efficiency.

[0004] Hard carbon materials are more suitable as anode materials for sodium-ion batteries compared with graphite materials because their layer spacing is larger than that of graphite, which is beneficial to the insertion and extraction of sodium ions, maintaining good stability, the preparation process is simple, the raw materials are cheap and easy to obtain. However, due to the low degree of graphitization and underdeveloped layered structure of existing hard carbon materials, there are problems such as low material capacity and low initial Coulomb efficiency, making it difficult to meet the increasing demand for battery performance. Therefore, it is necessary to change the microscopic morphology structure of hard carbon to improve the performance of hard carbon materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a porous-filled hard carbon material and a preparation method thereof, by filling the pores on the outer layer of porous hard carbon, improving the initial charge-discharge efficiency and capacity of the hard carbon material, so as to solve the deficiencies such as low capacity and low initial Coulomb efficiency of hard carbon materials in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A preparation method of a porous-filled hard carbon material, comprising the following steps:

[0007] S1. Dissolve the resin in deionized water, add metal salts after ultrasonic stirring and dissolving at room temperature, mix evenly by magnetic stirring, and then perform spray pyrolysis with nitrogen as the carrier gas to obtain a mixture powder;

[0008] S2. Place the mixture powder in a carbonization test kettle, perform primary carbonization under a nitrogen atmosphere, add dilute acid and stir, and after the reaction, filter, wash with deionized water and dry to obtain porous hard carbon powder;

[0009] S3. Dissolve the soluble carbon precursor in deionized water, add the porous hard carbon powder, mix evenly at room temperature, transfer it to a hydrothermal autoclave for hydrothermal reaction, then dry the suspension. The drying conditions are the same as those in S2. The obtained product is subjected to secondary carbonization under a nitrogen atmosphere, and after the reaction, it is filtered, washed with deionized water, and dried to obtain a porous-filled hard carbon material.

[0010] Further, the resin in S1 is a water-soluble resin that can be carbonized into hard carbon, including any one of epoxy resin, phenolic resin, modified resin, carbon nanotube-containing resin, or graphene-filled resin; the metal salt in S1 is any one of copper nitrate, sodium sulfate, or zinc acetate.

[0011] Further, the ultrasonic stirring time in S1 is set to 2 - 12 h, and the magnetic stirring time is set to 2 - 12 h.

[0012] Further, the pyrolysis temperature of the spray pyrolysis reaction in S1 is set to 300 - 1000 °C, and the nitrogen flow rate is set to 500 - 10000 ml / min.

[0013] Further, the heating rate of the primary carbonization in S2 is set to 2 °C / min, the reaction temperature is set to 800 - 1600 °C, the holding time is set to 1 - 12 h, and the nitrogen flow rate is set to 20 - 200 ml / min.

[0014] Further, the dilute acid in S2 is dilute nitric acid or dilute hydrochloric acid, the concentration of the dilute acid is set to 0.1 - 10 mol / L, and the stirring time is set to 2 - 24 h.

[0015] Further, the drying temperature in S2 is set to 40 - 150 °C, and the drying time is set to 6 - 24 h.

[0016] Further, the soluble carbon precursor in S3 is any one of sucrose or glucose; the hydrothermal reaction temperature in S3 is set to 100 - 250 °C, the reaction pressure is set to 0.1 - 10 MPa, and the reaction time is set to 2 - 48 h.

[0017] Further, the heating rate of the secondary carbonization in S3 is set to 2 °C / min, the reaction temperature is set to 800 - 1600 °C, the holding time is set to 1 - 12 h, and the nitrogen flow rate is set to 20 - 200 ml / min.

[0018] A porous-filled hard carbon material, the raw materials of which by weight include: 1 - 5 parts of resin, 0.1 - 0.5 parts of metal salt, 1 - 10 parts of porous hard carbon powder, 0.1 - 1 part of soluble carbon precursor, and 10 - 600 parts of deionized water.

[0019] Compared with the prior art, a porous-filled hard carbon material and its preparation method provided by the present invention mix copper nitrate and phenolic resin to obtain porous hard carbon by spray pyrolysis. Through the process of hydrothermal coating with sucrose and then carbonization, sucrose is filled into the pores on the outer layer of the porous hard carbon to obtain the porous-filled hard carbon material. The filled sucrose in the pores leaves pores due to pyrolysis volume shrinkage and is sealed inside by the outer layer of sucrose, thereby increasing the sodium storage sites, facilitating the uniform insertion of sodium, and improving the sodium storage capacity of the porous-filled hard carbon.

[0020] Secondary carbonization causes the sucrose filled in the pores of the porous hard carbon to pyrolyze and shrink, leaving more pores for ion transport. The increase in ion diffusion channels enhances the porous characteristics of the porous-filled hard carbon material, which is beneficial to promoting electrolyte penetration, increasing the contact area between the electrolyte and the hard carbon material, improving the rate capability of the material, and enhancing the initial Coulomb efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0022] Figure 1 Scanning electron microscope images (SEM) of the porous hard carbon powder (a) provided by the embodiment of the present invention and the porous-filled hard carbon materials (b, c, d) with different sucrose addition amounts;

[0023] Figure 2 X-ray crystal diffraction patterns (XRD) of the porous hard carbon powder provided by the embodiment of the present invention and the porous-filled hard carbon materials with different sucrose addition amounts;

[0024] Figure 3 First charge-discharge curves of the porous hard carbon powder provided by the embodiment of the present invention and the porous-filled hard carbon materials with different sucrose addition amounts;

[0025] Figure 4 Rate curves of the porous hard carbon powder provided by the embodiment of the present invention and the porous-filled hard carbon materials with different sucrose addition amounts;

[0026] Figure 5 Schematic flow chart of the preparation method of the porous-filled hard carbon material provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further introduce the present invention in detail in conjunction with the drawings.

[0028] Please refer toFigure 5 , A porous-filled hard carbon material and its preparation method, comprising the following steps:

[0029] S1. Dissolve the resin in water, add a metal salt after ultrasonic stirring and dissolving at room temperature, mix evenly by magnetic stirring, and then perform spray pyrolysis with nitrogen as the carrier gas to obtain a mixture powder; the resin is a resin that is soluble in water and can be carbonized into hard carbon, including any one of epoxy resin, phenolic resin, modified resin, carbon nanotube-containing resin or graphene-filled resin; the metal salt is any one of copper nitrate, sodium sulfate or zinc acetate; the mass ratio of deionized water to resin is 10:0.01 - 0.1; the mass ratio of resin to metal salt is 10:0.1 - 10; the ultrasonic stirring time is set to 2 - 12 h, the magnetic stirring time is set to 2 - 12 h; the pyrolysis temperature of the spray pyrolysis reaction is set to 300 - 1000 °C, and the nitrogen flow rate is set to 500 - 10000 ml / min.

[0030] Specifically, the ultrasonic power for ultrasonic stirring and dissolving phenolic resin includes but is not limited to 30 W, 40 W, 50 W, 60 W, 70 W, 80 W, 90 W, 100 W, and the magnetic stirring speed includes but is not limited to 200 rmp, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1500 rpm.

[0031] S2. Place the mixture powder in a carbonization test kettle, perform primary carbonization under a nitrogen atmosphere, add dilute acid and stir, filter, wash and dry after the reaction to obtain porous hard carbon powder; the heating rate of the primary carbonization is set to 1 - 10 °C / min, the reaction temperature is set to 800 - 1600 °C, the holding time is set to 1 - 12 h, and the nitrogen flow rate is set to 20 - 200 ml / min; the dilute acid is dilute nitric acid or dilute hydrochloric acid, the concentration of the dilute acid is set to 0.1 - 10 mol / L, and the stirring time is set to 2 - 24 h; the drying temperature is set to 40 - 150 °C, and the drying time is set to 6 - 24 h.

[0032] S3. Dissolve the soluble carbon precursor in deionized water, add the porous hard carbon powder, mix evenly at room temperature, then transfer it to a hydrothermal reactor for hydrothermal reaction. After that, dry the suspension. The drying conditions are the same as those in S2. The obtained product is subjected to secondary carbonization under a nitrogen atmosphere. After the reaction, filter, wash, and dry to obtain the porous-filled hard carbon material. The soluble carbon precursor is either sucrose or glucose. The mass ratio of the porous hard carbon powder to the soluble carbon precursor is 10:1 - 10, and the mass ratio of deionized water to the soluble carbon precursor is 10:0.1 - 10. The hydrothermal reaction temperature is set at 100 - 250 °C, the reaction pressure is set at 0.1 - 10 MPa, and the reaction time is set at 2 - 48 h. The heating rate of the secondary carbonization is set at 1 - 10 °C / min, the reaction temperature is set at 800 - 1600 °C, the holding time is set at 1 - 12 h, and the nitrogen flow rate is set at 20 - 200 ml / min.

[0033] Comparative example:

[0034] Please refer to Figure 5 , in this comparative example, porous hard carbon powder SPC is prepared without the steps of mixed sucrose hydrothermal and secondary carbonization. The preparation method includes the following steps:

[0035] (1) Dissolve 20 g of phenolic resin in 3000 ml of deionized water, stir and sonicate alternately for 2 h, then add 2 g of copper nitrate and stir magnetically for 2 h. Then spray pyrolyze the solution at 800 °C and a nitrogen flow rate of 5000 ml / min to obtain a mixture powder.

[0036] (2) Place the mixture powder in a carbonization test reactor, heat it to 1000 °C at a rate of 2 °C / min, hold for 4 h for primary carbonization, then immerse it in 1 mol / L dilute hydrochloric acid and stir for 12 h. Then wash it with deionized water until the pH is close to 7, and place it in an oven to dry at 80 °C for 12 h to obtain the porous hard carbon powder SPC.

[0037] Example 1:

[0038] Please refer to Figure 5 , a preparation method of a porous-filled hard carbon material, the specific steps are as follows:

[0039] (1) Dissolve 20 g of phenolic resin in 3000 ml of deionized water, stir and sonicate alternately for 2 h, then add 2 g of copper nitrate and stir magnetically for 2 h. Then spray pyrolyze the solution at 800 °C and a nitrogen flow rate of 5000 ml / min to obtain a mixture powder.

[0040] (2) Place the mixture powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min, hold for 4 h for the first carbonization, then immerse it in dilute hydrochloric acid with a concentration of 1 mol / L and stir for 12 h, then wash it with deionized water until the pH is close to 7, and place it in an oven to dry at 80 °C for 12 h to obtain porous hard carbon powder SPC.

[0041] (3) Add 5 g of porous hard carbon powder SPC and 1 g of sucrose to 50 ml of deionized water, mix evenly and transfer to a hydrothermal kettle, carry out hydrothermal reaction at 180 °C under a pressure of 5 MPa for 12 h, filter, wash and dry the suspension, place the obtained powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min and hold for 4 h to finally obtain powder SPS-1.

[0042] Example 2:

[0043] Please refer to Figure 5 , the difference between this example and Example 1 lies in the change of the sucrose addition amount in the hydrothermal reaction. The preparation method of the porous-filled hard carbon material SPS-2 includes the following steps:

[0044] (1) Dissolve 20 g of phenolic resin in 3000 ml of deionized water, stir and ultrasonicate alternately for 2 h, then add 2 g of copper nitrate and stir magnetically for 2 h, and then carry out spray pyrolysis of the solution at 800 °C and a nitrogen flow rate of 5000 ml / min to obtain a mixture powder.

[0045] (2) Place the mixture powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min, hold for 4 h for the first carbonization, then immerse it in dilute hydrochloric acid with a concentration of 1 mol / L and stir for 12 h, then wash it with deionized water until the pH is close to 7, and place it in an oven to dry at 80 °C for 12 h to obtain porous hard carbon powder SPC.

[0046] (3) Add 5 g of porous hard carbon powder SPC and 2 g of sucrose to 50 ml of deionized water, mix evenly and transfer to a hydrothermal kettle, carry out hydrothermal reaction at 180 °C under a pressure of 5 MPa for 12 h, filter, wash and dry the suspension, place the obtained powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min and hold for 4 h to finally obtain powder SPS-2.

[0047] Example 3:

[0048] Please refer to Figure 5 , the difference between this example and Example 1 lies in the change of the sucrose addition amount in the hydrothermal reaction. The preparation method of the porous-filled hard carbon material SPS-5 includes the following steps:

[0049] (1) Dissolve 20 g of phenolic resin in 3000 ml of deionized water, stir and sonicate alternately for 2 h, then add 2 g of copper nitrate and stir magnetically for another 2 h. Then spray pyrolyze the solution at 800 °C with a nitrogen flow rate of 5000 ml / min to obtain a mixture powder.

[0050] (2) Place the mixture powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min, keep it warm for 4 h for the first carbonization, then immerse it in 1 mol / L dilute hydrochloric acid and stir for 12 h, then wash it with deionized water until the pH is close to 7, and place it in an oven to dry at 80 °C for 12 h to obtain porous hard carbon powder SPC.

[0051] (3) Add 5 g of porous hard carbon powder SPC and 5 g of sucrose to 50 ml of deionized water, mix evenly and transfer it to a hydrothermal kettle. Carry out hydrothermal reaction at 180 °C for 12 h under a pressure of 5 MPa. Filter, wash and dry the suspension. Place the obtained powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min and keep it warm for 4 h to finally obtain powder SPS-5.

[0052] Example 4:

[0053] Please refer to Figure 5 , this example provides a technical solution on the basis of Example 2: The preparation method of porous-filled hard carbon materials at different hydrothermal temperatures (120 °C, 180 °C, 240 °C) includes the following steps:

[0054] (1) Dissolve 20 g of phenolic resin in 3000 ml of deionized water, stir and sonicate alternately for 2 h, then add 2 g of copper nitrate and stir magnetically for another 2 h. Then spray pyrolyze the solution at 800 °C with a nitrogen flow rate of 5000 ml / min to obtain a mixture powder.

[0055] (2) Place the mixture powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min, keep it warm for 4 h for the first carbonization, then immerse it in 1 mol / L dilute hydrochloric acid and stir for 12 h, then wash it with deionized water until the pH is close to 7, and place it in an oven to dry at 80 °C for 12 h to obtain porous hard carbon powder SPC.

[0056] (3) Add 5 g of porous hard carbon powder SPC and 2 g of sucrose to 50 ml of deionized water, mix evenly and transfer it to a hydrothermal kettle. Carry out hydrothermal reaction at 120 °C, 180 °C, and 240 °C respectively for 12 h under a pressure of 5 MPa. Filter, wash and dry the suspension. Place the obtained powder in a carbonization test kettle, heat it to 1000 °C at a rate of 2 °C / min and keep it warm for 4 h to finally obtain powders SPS-120, SPS-2, and SPS-240.

[0057] Specifically, in the hydrothermal reaction, the high-temperature and high-pressure environment helps to enhance the adhesion degree of sucrose. By controlling the temperature of the hydrothermal treatment, the properties of the porous hard carbon powder SPC can be changed. Sucrose molecules can diffuse better under high temperature and pressure, enabling sucrose to better fill the outer pores of the porous hard carbon powder SPC, reducing the specific surface area of the porous carbon spheres, and thus improving the initial Coulomb efficiency.

[0058] Example 5:

[0059] Please refer to Figures 1 - 4 , and the hard carbon materials prepared in each example and comparative example are assembled into an ionic battery as the negative electrode material for electrochemical performance testing. The specific method is as follows:

[0060] The ionic battery material powder, acetylene black, and PVDF900 are mixed in a ratio of 8:1:1, uniformly ground in an agate mortar, and then deionized water is added for stirring; the obtained slurry is coated on a copper foil and dried at 80 °C for 12 h to obtain an electrode sheet; a button battery is assembled in a glove box filled with argon, with a sodium sheet as the counter electrode, a glass microfiber as the separator, and an electrolyte with NaPF6 as the solute and DIGLYME as the solvent; the assembled battery is subjected to electrochemical performance testing.

[0061] The obtained porous hard carbon powder SPC and porous-filled hard carbon materials SPS-1, SPS-2, and SPS-5 are characterized by a Zeiss Gemini SEM 360 scanning electron microscope, a Rigaku-Miniflex600 rotating X-ray diffractometer of Rigaku Corporation, Japan (rotation range 5 - 90°, scanning speed 7° min-1, emission voltage 45 kV, current 50 mA, sampling interval 0.02°), and a Neware battery test system.

[0062] The results of the scanning electron microscope images (SEM) are shown in the appendix Figure 1As shown, a is the porous hard carbon powder SPC without mixed sucrose hydrothermal and secondary carbonization in the comparative example, and b, c, and d correspond to the porous-filled hard carbon materials SPS-1 with 1 g of sucrose added during the hydrothermal reaction in Example 1, the porous-filled hard carbon material SPS-2 with 2 g of sucrose added during the hydrothermal reaction in Example 2, and the porous-filled hard carbon material SPS-5 with 5 g of sucrose added during the hydrothermal reaction in Example 3, respectively; after adding sucrose to the porous hard carbon powder SPC and performing hydrothermal coating to fill the pores, the morphology of the surface of the porous carbon spheres changes significantly. Its surface changes from a porous and pitted morphology to a round spherical shape. Sucrose fills the pores of the porous hard carbon powder SPC, reducing the specific surface area of the outer layer of the porous-filled hard carbon materials SPS-1, SPS-2, and SPS-5, thereby improving the initial Coulomb efficiency. In addition, after the sucrose filling the pores in the pore channels of the porous hard carbon powder SPC undergoes secondary carbonization pyrolysis, the volume shrinks, increasing the number of pores, which are sealed inside by the outer layer of sucrose, increasing the sodium storage sites and ion diffusion channels, and improving the sodium storage capacity and rate performance of the porous-filled hard carbon.

[0063] The results of the X-ray crystal diffraction pattern (XRD) are as shown in the appendix Figure 2 As shown, curve HC corresponds to the porous hard carbon powder SPC in the comparative example, and curves 1*, 2*, and 3* correspond to the porous-filled hard carbon materials SPS-1 with 1 g of sucrose added during the hydrothermal reaction in Example 1, the porous-filled hard carbon material SPS-2 with 2 g of sucrose added during the hydrothermal reaction in Example 2, and the porous-filled hard carbon material SPS-5 with 5 g of sucrose added during the hydrothermal reaction in Example 3, respectively; the porous hard carbon powder SPC and the porous-filled hard carbon materials SPS-1, SPS-2, and SPS-5 with different sucrose filling amounts all have typical characteristic peaks of hard carbon, indicating that the filling of sucrose does not change the basic structure of the porous hard carbon powder SPC. Compared with the porous hard carbon powder SPC without sucrose filling, the (002) peak of the porous-filled hard carbon materials SPS-1, SPS-2, and SPS-5 after sucrose filling shows a slight shift towards a larger angle direction, and its d002 decreases, providing evidence for the successful filling of sucrose into the pores of the porous hard carbon.

[0064] The first charge-discharge curves of the porous-filled hard carbon materials with different sucrose addition amounts are as shown in the appendix Figure 3As shown, curve HC corresponds to the porous hard carbon powder SPC of the comparative example, and curves 1*, 2*, and 3* respectively correspond to the porous-filled hard carbon material SPS-1 with a sucrose addition amount of 1 g in the hydrothermal reaction of Example 1, the porous-filled hard carbon material SPS-2 with a sucrose addition amount of 2 g in the hydrothermal reaction of Example 2, and the porous-filled hard carbon material SPS-5 with a sucrose addition amount of 5 g in the hydrothermal reaction of Example 3. It can be seen from the figure that the charge-discharge curves of all hard carbon materials have similar trends and are composed of a medium voltage ramp region and a low voltage plateau region. After filling the pores with sucrose, the gap between the first-cycle charge capacity and the first-cycle discharge capacity of the porous hard carbon material decreases, indicating that the reduction of the specific surface area of the outer layer of the porous hard carbon material will lead to an increase in the initial Coulomb efficiency. With the increase of the sucrose addition amount for pore filling, the initial Coulomb efficiency remains basically unchanged, but the reversible capacity increases, and the main increase is in the low voltage plateau region, indicating that the number of closed pores for sodium storage in the low voltage plateau of the hard carbon material after sucrose pore filling treatment increases. The secondary carbonization causes the sucrose filled in the macropores of the porous hard carbon powder to pyrolyze and shrink, generating pores and channels with appropriate sizes and being sealed by the outer sucrose carbon layer, thereby forming closed pores and ion transport channels for the storage and conduction of sodium ions.

[0065] The rate performance curves of porous-filled hard carbon materials with different sucrose addition amounts are shown in the appendix Figure 4 As shown, curve HC corresponds to the porous hard carbon powder SPC of the comparative example, and curves 1*, 2*, and 3* respectively correspond to the porous-filled hard carbon material SPS-1 with a sucrose addition amount of 1 g in the hydrothermal reaction of Example 1, the porous-filled hard carbon material SPS-2 with a sucrose addition amount of 2 g in the hydrothermal reaction of Example 2, and the porous-filled hard carbon material SPS-5 with a sucrose addition amount of 5 g in the hydrothermal reaction of Example 3. It can be seen from the figure that at the rates of 40 mA / g, 80 mA / g, 200 mA / g, 400 mA / g, and 800 mA / g, the capacities of the porous-filled hard carbon materials SPS-1, SPS-2, and SPS-5 after sucrose pore filling treatment are all higher than those of the unfilled porous hard carbon powder SPC. The maximum capacity improvement limit of the porous hard carbon powder SPC at 200 mA / g is increased from 121 mAh / g to 231 mAh / g, which is because the secondary carbonization causes the sucrose filled in the pores of the porous hard carbon to pyrolyze and shrink, leaving more pores for ion transport. For different sucrose addition amounts for filling, too much addition amount will cause excess to be coated on the surface of the porous hard carbon powder due to limited pores, resulting in a decrease in the overall rate performance.

[0066] Considering the rate performance and reversible capacity comprehensively, the performance of the porous-filled hard carbon material SPS-2 with a ratio of 5 g of porous hard carbon powder SPC to 2 g of filled sucrose addition amount is the best.

[0067] Only some exemplary embodiments of the present invention have been described by way of illustration. Undoubtedly, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a porous-filled hard carbon material, characterized in that: The preparation method comprises the following steps: S1, dissolving the resin in water, adding metal salt after dissolving by ultrasonic stirring at room temperature, mixing evenly by magnetic stirring, and then spray pyrolysis using nitrogen as carrier gas to obtain a mixture powder; S2, placing the mixed powder in a carbonization test kettle, carbonizing once under a nitrogen atmosphere, adding dilute acid and stirring, filtering, washing and drying after the reaction to obtain a porous hard carbon powder; S3. Dissolve the soluble carbon precursor in deionized water, add porous hard carbon powder, mix well at room temperature and transfer to a hydrothermal kettle for hydrothermal reaction. Then dry the suspension and perform secondary carbonization on the obtained product under a nitrogen atmosphere. After the reaction, filter, wash and dry to obtain a porous-filled hard carbon material.

2. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The resin in S1 is a resin that is soluble in water and can be carbonized into hard carbon, including any one of epoxy resin, phenolic resin, modified resin, carbon nanotube-containing resin or graphene-filled resin; the metal salt in S1 is any one of copper nitrate, sodium sulfate or zinc acetate.

3. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: In the S1, the ultrasonic stirring time is set to 2-12 h, and the magnetic stirring time is set to 2-12 h.

4. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The pyrolysis temperature of the spray pyrolysis reaction in S1 is set to 300-1000° C., and the nitrogen flow rate is set to 500-10000 ml / min.

5. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The heating rate of the primary carbonization in S2 is set to 1-10°C / min, the reaction temperature is set to 800-1600°C, the insulation time is set to 1-12h, and the nitrogen flow rate is set to 20-200ml / min.

6. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The dilute acid in S2 is dilute nitric acid or dilute hydrochloric acid, the concentration of the dilute acid is set to 0.1-10 mol / L, and the stirring time is set to 2-24 h.

7. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: In S2, the drying temperature is set to 40-150° C., and the drying time is set to 6-24 hours.

8. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The soluble carbon precursor in S3 is sucrose or glucose; the hydrothermal reaction temperature in S3 is set to 100-250° C., the reaction pressure is set to 0.1-10 MPa, and the reaction time is set to 2-48 h.

9. The method for preparing a porous-filled hard carbon material according to claim 1, characterized in that: The heating rate of the secondary carbonization in S3 is set to 1-10°C / min, the reaction temperature is set to 800-1600°C, the insulation time is set to 1-12h, and the nitrogen flow rate is set to 20-200ml / min.

10. A porous-filled hard carbon material, characterized in that: It is applicable to the preparation method of the porous-filled hard carbon material described in any one of claims 1-9, and its raw materials include by weight: 1-5 parts of resin, 0.1-0.5 parts of metal salt, 1-10 parts of porous hard carbon powder, 0.1-1 parts of soluble carbon precursor, and 10-600 parts of deionized water.

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