Preparation method and application of high-strength biomass porous carbon material

Abstract

The application provides a preparation method of high-strength biomass porous carbon material, which is prepared by mixing biomass as raw material, carbonizing and primary crushing the biomass, and hot-melt carbon source uniformly through a preparation method which is high in efficiency, low in cost and strong in controllability, and then carbonizing and activating the mixture to obtain the high-strength biomass porous carbon material. The material is low in cost and high in structural compressive strength. When the material is used as a gas-phase silicon-carbon porous carbon base material, the structural compressive strength and conductivity of the gas-phase silicon-carbon porous carbon base material can be significantly improved, the electrochemical performance of the battery is significantly improved, the application difficulty of the biomass-based gas-phase silicon-carbon is reduced, and the practical application requirement is met. Meanwhile, the application also provides an application of the high-strength biomass porous carbon material, which is applied to a gas-phase silicon-carbon composite material or a lithium ion battery.

Description

Technical Field

[0001] This invention relates to the technical field of porous carbon materials, and in particular to a method for preparing and applying a high-strength biomass porous carbon material. Background Technology

[0002] Silicon-carbon anode materials, with their advantages of high energy density, fast charging capability, high safety, and environmental friendliness, have shown great potential in the field of lithium-ion batteries and are expected to be more widely used in the future. Among the many methods for preparing silicon-carbon anode materials, those prepared by CVD have attracted widespread attention due to their advantages such as high charge-discharge efficiency, good cycle stability, lower equipment requirements, and suitability for industrial production.

[0003] Biomass porous carbon-based CVD vapor-phase silicon-carbon anode materials are widely used due to their advantages such as wide availability, low cost, and environmental friendliness. However, they still have significant drawbacks. The natural heterogeneity of biomass raw materials leads to uneven product structure. For example, differences in lignin and cellulose composition result in uneven pore distribution, with a large number of submicron or even micron-sized pores. The proportion of these pores is negatively correlated with mechanical strength, and structural collapse is particularly prone to occur in electrode applications, leading to a decrease in initial efficiency, rate capability, and cycle life.

[0004] In view of this, the inventors have proposed a method for preparing high-strength biomass porous carbon materials and their applications, which leads to this invention. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for preparing high-strength biomass porous carbon materials. Using biomass as raw material, the biomass is carbonized, initially crushed, and then mixed uniformly with a hot-melt carbon source using an efficient, low-cost, and highly controllable preparation method. The mixture is then subjected to carbonization, activation, and other processes to prepare the high-strength biomass porous carbon material. This material is low-cost and has high structural compressive strength. When used as a fumed silicon-carbon porous carbon substrate, it can significantly improve the structural compressive strength and conductivity, thereby significantly improving the electrochemical performance of batteries, reducing the difficulty of applying biomass-based fumed silicon-carbon materials, and meeting practical application needs.

[0006] This invention also proposes an application of a high-strength biomass porous carbon material, which is then applied to fumed silicon-carbon composite materials or lithium-ion batteries.

[0007] A method for preparing a high-strength biomass porous carbon material according to the present invention includes the following steps: Step (1) Carbonize the biomass carbon source at high temperature in an inert atmosphere to obtain carbonized material A; Step (2) The carbonized material A is initially crushed to obtain the initially crushed material B; Step (3) Mix the initial crushed material B with the hot-melt carbon source in a certain proportion to obtain the mixture C; Step (4) Carbonize the mixture C at high temperature to obtain carbonized material D; Step (5) Crush the carbonized material D to obtain crushed material E; Step (6) Activate and create pores in the crushed material E to obtain activated material F; Step (7) After acid washing and water washing of the activated material F, it is crushed and classified to obtain high-strength biomass porous carbon material.

[0008] The present invention discloses a method for preparing high-strength biomass porous carbon materials. This method involves using a hot-melt carbon source to plug the pores of biomass porous carbon containing numerous submicron or even micron-sized pores, thereby obtaining high-strength biomass porous carbon. This significantly improves the strength of the biomass porous carbon, reduces the difficulty of subsequent applications, and ensures the performance of the silicon-carbon composite materials and batteries prepared from it. Furthermore, the preparation process is simple, and it exhibits good electrochemical performance, including high initial efficiency and reversible specific capacity.

[0009] In some embodiments of the present invention, in step (1), the inert atmosphere is an oxygen-free atmosphere, such as a nitrogen atmosphere or an argon atmosphere.

[0010] In some embodiments of the present invention, in step (1), the high-temperature carbonization temperature is above 500°C, preferably 500-2000°C.

[0011] In some embodiments of the present invention, in step (2), the particle size of the initial crushed material B is 50-50000 micrometers, preferably 50-500 micrometers.

[0012] In some embodiments of the present invention, in step (3), the initial crushed material B is mixed with the hot-melt carbon source in a certain ratio of 99:1 to 50:50.

[0013] In some embodiments of the present invention, the hot-melt carbon source is one or a combination of two or more of sugars, petroleum coke, and resins.

[0014] In some embodiments of the present invention, in step (3), the mixing method is any one of hot melting, impregnation, mixing, and spraying, and the mixing equipment is any one of isostatic pressing equipment, extruder, kneader, impregnation machine, and spraying machine.

[0015] In some embodiments of the present invention, in step (4), the high-temperature carbonization temperature of the mixture C is above 500°C, preferably 500-1500°C.

[0016] In some embodiments of the present invention, in step (5), the particle size of the crushed material E after crushing is 1-50 mm.

[0017] In some embodiments of the present invention, in step (6), the crushed material E is activated by any one or a combination of chemical and physical methods for a period of 0.5-12 hours.

[0018] In some embodiments of the present invention, in step (7), after crushing and grading, the particle size of the high-strength biomass porous carbon material obtained is 1-50 μm.

[0019] The present invention provides an application of a high-strength biomass porous carbon material, which is prepared by a method for preparing high-strength biomass porous carbon material and is used in fumed silicon-carbon composite materials or in lithium-ion batteries.

[0020] In some embodiments of the present invention, the method for preparing the fumed silicon-carbon composite material includes a method for preparing a high-strength biomass porous carbon material, and further includes the following preparation steps: Step (8) The high-strength biomass porous carbon material is subjected to chemical vapor deposition to obtain deposit G; Step (9) Coating the deposited material G using a certain method to obtain a gaseous silicon-carbon composite material.

[0021] In some embodiments of the present invention, in step (8), high-strength biomass porous carbon material is subjected to silicon deposition to obtain deposit G, wherein the silicon deposition is performed using a fluidized bed or rotary furnace, and the silicon deposition ratio is 30-70%.

[0022] In some embodiments of the present invention, in step (9), the method is to coat carbon or other oxides. Attached Figure Description

[0023] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0024] in: Figure 1 SEM image of the high-strength biomass porous carbon prepared in Example 1; Figure 2 SEM image of the high-strength biomass porous carbon prepared in Example 2; Figure 3 SEM image of the high-strength biomass porous carbon prepared in Example 3; Figure 4 SEM image of the high-strength biomass porous carbon prepared in Example 4; Figure 5 SEM image of the high-strength biomass porous carbon prepared in Example 5; Figure 6 SEM image of the high-strength biomass porous carbon prepared in Example 6; Figure 7 SEM image of the high-strength biomass porous carbon prepared in Comparative Example 1. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the embodiments. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially. Example 1

[0026] This embodiment provides a method for preparing high-strength biomass porous carbon materials, their applications, and fumed silicon-carbon composite materials, including the following steps: Step (1) Carbonize coconut shell at 800℃ for 10h in a nitrogen atmosphere to obtain carbonized material A; Step (2) The carbonized material A is initially crushed to obtain the initially crushed material B with a particle size of 1-10 mm; Step (3) Mix the primary crushed material B and petroleum coke at a ratio of 3:1 using a kneader at 200°C for 2 hours to obtain mixture C; Step (4) Carbonize the mixture C at 800℃ for 5 hours under nitrogen atmosphere to obtain carbonized material D; Step (5) The carbonized material is crushed to obtain crushed material E with a particle size of 1-10 mm; Step (6) The crushed material E is activated at 800℃ for 8 hours using the steam activation method to create pores, resulting in activated material F; Step (7) After acid washing and water washing, the activated material is crushed and classified to obtain high-strength biomass porous carbon material with a particle size of 1-30μm; Step (8) High-strength biomass porous carbon material is subjected to silicon deposition in a fluidized bed at 550°C using silane to obtain deposit material G with a silicon deposition rate of 50% of the total mass; Step (9) The deposit G is carbon coated with acetylene in a rotary kiln to obtain a gaseous silicon-carbon composite material. Example 2

[0027] The difference between this embodiment and embodiment 1 is that the hot-melt carbon source in step (3) of this embodiment is phenolic resin, while the rest is the same as in embodiment 1. Example 3

[0028] The difference between this embodiment and embodiment 1 is that the hot-melt carbon source in step (3) of this embodiment is starch, and the ratio of the initial crushed material to starch is 3:2. The rest is the same as in embodiment 1. Example 4

[0029] The difference between this embodiment and embodiment 1 is that the equipment used in step (3) of this embodiment is an extruder, and the extrusion is carried out at 250°C. The rest is the same as that of embodiment 1. Example 5

[0030] The difference between this embodiment and embodiment 1 is that the ratio of primary crushed material to petroleum coke in step (3) of this embodiment is 3:2, while the rest is the same as in embodiment 1. Example 6

[0031] In this embodiment, the ratio of primary crushed material to petroleum coke in step (3) is 3:0.5, and the rest is the same as in embodiment 1.

[0032] Comparative Example 1

[0033] This comparative example uses step (3) of the present invention without adding a hot-melt carbon source, and is otherwise consistent with Example 1. Related tests were conducted on Examples 1-6 and the comparative examples described above:

[0034] I. Preparation of Button Cells Electrode fabrication: The fumed silicon-carbon composite materials prepared in the above examples and comparative examples were respectively mixed with conductive agent SP, conductive agent SWCNT, binder CMC, binder SBR, and deionized water in a certain proportion to form a homogeneous slurry. The mass ratio of silicon-carbon anode material: conductive agent SP: conductive agent SWCNT: binder CMC: binder SBR was 94.55:1.0:0.05:1.4:3. The homogenization equipment used was a vacuum degassing machine with a speed of 2000 rpm and a time of 10 min. The prepared slurry was evenly coated on copper foil and then dried in a 100℃ forced-air drying oven. The baked electrode sheets were cut and pressed into circular electrodes of a certain size. After being accurately weighed (accurate to 0.0001g), they were placed in a vacuum drying oven and baked at 120℃ for 8 hours under vacuum conditions to obtain button electrode sheets. The electrode sheets were then assembled into batteries under an inert atmosphere. The counter electrode of the battery was a lithium sheet, and the FEC content in the electrolyte was 10%. A fumed silicon-carbon composite battery containing high-strength biomass porous carbon material was obtained.

[0035] II. Performance Testing

[0036] Performance testing based on high-strength biomass porous carbon materials and their prepared fumed silicon-carbon composites.

[0037] The pore volume and pore size of the high-strength biomass porous carbon materials prepared in Examples 1-6 and the carbon materials prepared in the comparative examples were measured, and the results are shown in Table 1.

[0038] Table 1 Pore Volume and Pore Size Distribution

[0039] As can be seen from Table 1 above, the pore size distribution of the high-strength biomass porous carbon materials prepared in Examples 1-6 and the comparative examples is significantly reduced in the examples after treatment by the present invention compared with the comparative examples, and the proportion of large pores above 50 nm is negatively correlated with mechanical strength. The data in the table can indirectly demonstrate the excellent performance of the present invention.

[0040] The compressive strength of the high-strength biomass porous carbon materials prepared in the above embodiments and comparative examples was tested, and the results are shown in Table 2.

[0041] Table 2 Compressive Strength

[0042] As can be seen from Table 2 above, the compressive strength of the high-strength biomass porous carbon materials prepared in the above embodiments and comparative examples is significantly increased compared with that of the comparative examples after treatment by the present invention, which indicates that the high-strength porous carbon prepared by the present invention has better compressive strength.

[0043] SEM tests were performed on the high-strength biomass porous carbon materials prepared in the above embodiments and comparative examples, and the results are as follows: Figures 1 to 7 As shown.

[0044] Please refer to details. Figures 1 to 7 As can be seen from the SEM images of the high-strength biomass porous carbon materials prepared in Examples 1, 2, 3, 4, 5, and 6, the submicron and micron-sized macropores on the surface of the material particles in the examples are significantly fewer than those in the comparative examples.

[0045] Performance testing of button electrodes The first-effect specific capacity of the gas-phase silicon-carbon composite material prepared from the high-strength biomass porous carbon material prepared in the above examples and comparative examples was tested. The test process was as follows: 0.1C discharge to 5mV, 0.02C discharge to 5mV; stand for 5 min, 0.1C charge to 1.5V; the results are shown in Table 3.

[0046] Table 3. Initial Efficiency and Capacitance of Button Charge

[0047] As can be seen from Table 3 above, the specific capacity data of the batteries prepared in the above examples and comparative examples show that the specific capacity of Examples 1, 2, 3, 4, 5, and 6 is significantly higher than that of Comparative Example 1. This indicates that under the same battery manufacturing process, Examples 1, 2, 3, 4, 5, and 6 have fewer side reactions and exhibit better electrochemical stability.

[0048] In summary, the method for preparing high-strength biomass porous carbon materials of the present invention uses biomass porous carbon containing a large number of submicron or even micron-sized pores to block the pores with a thermally melted carbon source, thereby obtaining high-strength biomass porous carbon materials. This significantly improves the strength of biomass porous carbon, reduces the difficulty of subsequent applications, and ensures the performance of the fumed silicon-carbon composite materials and batteries prepared from it. Moreover, the preparation process is simple and exhibits good electrochemical performance.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a high-strength biomass porous carbon material, characterized in that, Includes the following steps: Step (1) The biomass carbon source is carbonized at high temperature in an inert atmosphere to obtain carbonized material A; Step (2) The carbonized material A is initially crushed to obtain the initially crushed material B; Step (3) Mix the initial crushed material B with the hot-melt carbon source in a certain proportion to obtain the mixture C; Step (4) Carbonize the mixture C at high temperature to obtain carbonized material D; Step (5) Crush the carbonized material D to obtain crushed material E; Step (6) Activate and create pores in the crushed material E to obtain activated material F; Step (7) After acid washing and water washing of the activated material F, it is crushed and classified to obtain high-strength biomass porous carbon material.

2. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (1), the inert atmosphere is an oxygen-free atmosphere; the high-temperature carbonization temperature is above 500°C.

3. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (2), the particle size of the initial crushed material B is 50-50000 micrometers.

4. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (3), the initial crushed material B is mixed with the hot-melt carbon source in a certain ratio of 99:1 to 50:

50.

5. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (4), the high-temperature carbonization temperature of the mixture C is above 500°C.

6. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (5), the particle size of the crushed material E after crushing is 1-50mm.

7. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (6), the crushed material E is activated by any one or a combination of chemical and physical methods for a period of 0.5-12 hours.

8. The method for preparing a high-strength biomass porous carbon material according to claim 1, characterized in that, In step (7), after crushing and grading, the particle size of the high-strength biomass porous carbon material is 1-50 μm.

9. An application of a high-strength biomass porous carbon material, characterized in that, The application of the high-strength biomass porous carbon material prepared by the preparation method of any one of claims 1-8 in fumed silicon-carbon composite materials or in lithium-ion batteries.

10. The application of a high-strength biomass porous carbon material according to claim 9, characterized in that, The method for preparing the fumed silicon-carbon composite material includes any one of the methods for preparing a high-strength biomass porous carbon material as described in 1-8, and further includes the following preparation steps: Step (8) The high-strength biomass porous carbon material is subjected to chemical vapor deposition to obtain deposit G; Step (9) Coating the deposited material G using a certain method to obtain a gaseous silicon-carbon composite material.

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