Preparation method of porous carbon material for preparing silicon-carbon negative electrode

Abstract

The invention discloses a preparation method of a porous carbon material for preparing a silicon-carbon negative electrode, which comprises the following steps: dry mixing, heat treatment, wet mixing, preparation of a porous carbon composite material and vacuum high-temperature purification. A porous carbon precursor prepared through a salt template method is controllable in pore volume and pore diameter and good in consistency, vapor deposition is carried out in the step (4), so that the surface of porous carbon is coated with carbon nanotubes generated by carbon source gas, the conductivity of the subsequently prepared silicon carbon material is greatly improved, and the conductivity of the silicon carbon material is greatly improved through vacuum high-temperature purification in the step (5). The morphology and crystal form of the porous carbon material can be maintained, and the strength of the porous carbon material is effectively enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of porous carbon, and in particular to a preparation method of a porous carbon material for preparing a silicon-carbon negative electrode. Background Art

[0002] With the development of consumer electronics, new energy vehicles and electric aircraft, the demand for high energy density materials is becoming increasingly urgent. The theoretical specific capacity of graphite negative electrode materials is 72 mAh / g, which can no longer meet the growing material requirements. Researchers have found that the theoretical specific capacity of silicon materials is as high as 4200 mAh / g. Therefore, applying silicon materials to the negative electrode of the battery is beneficial to significantly improve the energy density of the battery.

[0003] The new silicon-carbon material is applied to high energy density lithium-ion batteries due to its advantages such as low full-charge expansion, high specific capacity, and high first efficiency. Its preparation method is to pyrolyze silane to generate nano-silicon deposited in porous carbon. The strength, pore size, and pore volume of the porous carbon determine the performance, cost, and consistency of the material, and the conductive uniformity of the porous carbon also determines the performance of the silicon-carbon material. However, the pore size and pore volume of the porous carbon material prepared by the current salt template method can be controlled, but the strength is weak. Therefore, it is necessary to propose a new solution to solve the above problems. Summary of the Invention

[0004] In view of this, in view of the deficiencies of the existing technology, the main purpose of the present invention is to provide a preparation method of a porous carbon material for preparing a silicon-carbon negative electrode, which can effectively solve the problem of weak strength of the existing porous carbon material.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A preparation method of a porous carbon material for preparing a silicon-carbon negative electrode, which includes the following steps:

[0007] (1) Mix phenol formaldehyde resin and sodium chloride evenly, and the mass ratio of phenol formaldehyde resin to sodium chloride is 100:(1 - 6) to obtain a mixture;

[0008] (2) Place the mixture obtained in step (1) in a tube furnace, heat it to 1100 °C, and keep it warm for 5 h to obtain a porous carbon precursor;

[0009] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution, and freeze-dry to obtain a reaction material;

[0010] (4) Place the reaction materials obtained in step (3) in a tubular furnace, heat to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 10 - 30 min to obtain a composite material;

[0011] (5) Place the composite material obtained in step (4) in a vacuum furnace, heat to 1300 - 1500 °C under vacuum conditions, hold for 5 h, and then cool naturally to obtain a porous carbon material.

[0012] As a preferred embodiment, the mass ratio of the phenolic resin to sodium chloride in step (1) is 100:(3 - 4).

[0013] As a preferred embodiment, the iron oxalate solution in step (3) is a saturated iron oxalate solution, wherein the mass ratio of the porous carbon precursor to iron oxalate is 100:(1 - 5).

[0014] As a preferred embodiment, the mass ratio of the porous carbon precursor to iron oxalate is 100:(2 - 3).

[0015] As a preferred embodiment, the carbon source gas in step (4) is one or a mixture of ethylene and acetylene.

[0016] As a preferred embodiment, the introduction time in step (4) is 15 - 20 min.

[0017] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solutions:

[0018] The porous carbon precursor prepared by the salt template method has controllable pore volume and pore diameter, and good consistency. Coupled with chemical vapor deposition in step (4), the carbon nanotubes generated by the carbon source gas are coated on the surface of the porous carbon, greatly improving the conductivity of the subsequent prepared silicon-carbon material. In addition, the vacuum high-temperature purification in step (5) is beneficial to maintaining the morphology and crystal form of the porous carbon material and effectively enhancing the strength of the porous carbon material.

[0019] To more clearly illustrate the structural features and functions of the present invention, the present invention will be described in detail below with specific embodiments. Detailed Embodiments

[0020] The present invention discloses a method for preparing a porous carbon material for a silicon-carbon negative electrode, which includes the following steps:

[0021] (1) Mix the phenolic resin and sodium chloride evenly. The mass ratio of the phenolic resin to sodium chloride is 100:(1 - 6) to obtain a mixture. Preferably, the mass ratio of the phenolic resin to sodium chloride is 100:(3 - 4).

[0022] (2) Place the mixture obtained in step (1) in a tubular furnace, heat it to 1100 °C, and keep it at this temperature for 5 h to obtain a porous carbon precursor.

[0023] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry it to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:(1 - 5). Preferably, the mass ratio of the porous carbon precursor to iron oxalate is 100:(2 - 3).

[0024] (4) Place the reaction material obtained in step (3) in a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 10 - 30 min to obtain a composite material; wherein, the carbon source gas is one or a mixture of ethylene and acetylene, and the introduction time is preferably 15 - 20 min.

[0025] (5) Place the composite material obtained in step (4) in a vacuum furnace, heat it to 1300 - 1500 °C under vacuum conditions, keep it at this temperature for 5 h, and then cool it naturally to obtain a porous carbon material.

[0026] The following is a detailed description in combination with multiple embodiments.

[0027] Example 1

[0028] (1) Mix phenol formaldehyde resin and sodium chloride evenly, with the mass ratio of phenol formaldehyde resin to sodium chloride being 100:1, to obtain a mixture.

[0029] (2) Place the mixture obtained in step (1) in a tubular furnace, heat it to 1100 °C, and keep it at this temperature for 5 h to obtain a porous carbon precursor.

[0030] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry it to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:5.

[0031] (4) Place the reaction material obtained in step (3) in a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 20 min to obtain a composite material; wherein, the carbon source gas is ethylene.

[0032] (5) Place the composite material obtained in step (4) in a vacuum furnace, heat it to 1400 °C under vacuum conditions, keep it at this temperature for 5 h, and then cool it naturally to obtain a porous carbon material.

[0033] Example 2

[0034] (1) Mix phenol formaldehyde resin and sodium chloride evenly. The mass ratio of phenol formaldehyde resin to sodium chloride is 100:6 to obtain a mixture.

[0035] (2) Place the mixture obtained in step (1) into a tubular furnace, and heat it to 1100 °C and keep it warm for 5 h to obtain a porous carbon precursor.

[0036] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:1.

[0037] (4) Place the reaction material obtained in step (3) into a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 10 min to obtain a composite material; wherein, the carbon source gas is acetylene.

[0038] (5) Place the composite material obtained in step (4) into a vacuum furnace, heat it to 1400 °C under vacuum conditions, keep it warm for 5 h, and after natural cooling, obtain a porous carbon material.

[0039] Example 3

[0040] (1) Mix phenol formaldehyde resin and sodium chloride evenly. The mass ratio of phenol formaldehyde resin to sodium chloride is 100:3 to obtain a mixture.

[0041] (2) Place the mixture obtained in step (1) into a tubular furnace, and heat it to 1100 °C and keep it warm for 5 h to obtain a porous carbon precursor.

[0042] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:3.

[0043] (4) Place the reaction material obtained in step (3) into a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 15 min to obtain a composite material; wherein, the carbon source gas is ethylene.

[0044] (5) Place the composite material obtained in step (4) into a vacuum furnace, heat it to 1400 °C under vacuum conditions, keep it warm for 5 h, and after natural cooling, obtain a porous carbon material.

[0045] Example 4

[0046] (1) Mix the phenolic resin and sodium chloride evenly. The mass ratio of the phenolic resin to sodium chloride is 100:4 to obtain a mixture.

[0047] (2) Place the mixture obtained in step (1) into a tubular furnace, and heat it to 1100 °C and keep it warm for 5 h to obtain a porous carbon precursor.

[0048] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:2.

[0049] (4) Place the reaction material obtained in step (3) into a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 20 min to obtain a composite material; wherein, the carbon source gas is ethylene.

[0050] (5) Place the composite material obtained in step (4) into a vacuum furnace, heat it to 1300 °C under vacuum conditions, keep it warm for 5 h, and after natural cooling, obtain a porous carbon material.

[0051] Example 5

[0052] (1) Mix the phenolic resin and sodium chloride evenly. The mass ratio of the phenolic resin to sodium chloride is 100:5 to obtain a mixture.

[0053] (2) Place the mixture obtained in step (1) into a tubular furnace, and heat it to 1100 °C and keep it warm for 5 h to obtain a porous carbon precursor.

[0054] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and freeze-dry to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:5.

[0055] (4) Place the reaction material obtained in step (3) into a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 30 min to obtain a composite material; wherein, the carbon source gas is ethylene.

[0056] (5) Place the composite material obtained in step (4) into a vacuum furnace, heat it to 1500 °C under vacuum conditions, keep it warm for 5 h, and after natural cooling, obtain a porous carbon material.

[0057] Example 6

[0058] (1) Mix the phenolic resin and sodium chloride evenly. The mass ratio of the phenolic resin to sodium chloride is 100:2 to obtain a mixture.

[0059] (2) Place the mixture obtained in step (1) in a tubular furnace, heat it to 1100 °C, and keep it at this temperature for 5 h to obtain a porous carbon precursor.

[0060] (3) Mix the porous carbon precursor obtained in step (2) with an iron oxalate solution and perform freeze-drying to obtain a reaction material; wherein, the iron oxalate solution is a saturated iron oxalate solution, and the mass ratio of the porous carbon precursor to iron oxalate is 100:4.

[0061] (4) Place the reaction material obtained in step (3) in a tubular furnace, heat it to 850 °C under an inert gas atmosphere, and then introduce a carbon source gas for chemical vapor deposition. The flow rate of the carbon source gas is 100 ml / min, and the introduction time is 5 min to obtain a composite material; wherein, the carbon source gas is ethylene.

[0062] (5) Place the composite material obtained in step (4) in a vacuum furnace, heat it to 1400 °C under vacuum conditions, keep it at this temperature for 5 h, and then cool it naturally to obtain a porous carbon material.

[0063] Performance tests were carried out on the above-mentioned multiple embodiments, and the test results are shown in Table 1.

[0064]

[0065]

[0066] Table 1

[0067] As can be seen from the above test results, the specific surface area, total mesopore volume, and average pore diameter of the porous carbon prepared by the preparation method of the present invention are all relatively large, and the mesopore ratio is high. The mesopore ratios of the six embodiments are concentrated in the range of 86.5 - 90.1%, making the prepared porous carbon materials have consistency.

[0068] The above is only a preferred embodiment of the present invention, and does not impose any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a porous carbon material for preparing a silicon-carbon negative electrode, characterized in that: The following steps are included: (1) mixing phenolic resin and sodium chloride uniformly, wherein the mass ratio of phenolic resin to sodium chloride is 100:(1-6), to obtain a mixture; (2) placing the mixture obtained in step (1) in a tube furnace, heating it to 1100° C., and keeping it at this temperature for 5 h to obtain a porous carbon precursor; (3) mixing the porous carbon precursor obtained in step (2) with the ferric oxalate solution, and freeze-drying the mixture to obtain a reaction material; (4) placing the reaction material obtained in step (3) in a tube furnace, heating to 850° C. under an inert gas atmosphere, and then introducing a carbon source gas for vapor deposition, wherein the flow rate of the carbon source gas is 100 ml / min and the introduction time is 10-30 min to obtain a composite material; (5) placing the composite material obtained in step (4) in a vacuum furnace, heating it to 1300-1500° C. under vacuum conditions, keeping the temperature for 5 hours, and naturally cooling it to obtain a porous carbon material.

2. The method for preparing a porous carbon material for preparing a silicon-carbon negative electrode according to claim 1, characterized in that: The mass ratio of the phenolic resin to sodium chloride in the step (1) is 100:(3-4).

3. The method for preparing a porous carbon material for preparing a silicon-carbon negative electrode according to claim 1, characterized in that: The ferric oxalate solution in step (3) is a saturated ferric oxalate solution, wherein the mass ratio of the porous carbon precursor to the ferric oxalate is 100:(1-5).

4. The method for preparing a porous carbon material for preparing a silicon-carbon negative electrode according to claim 3, characterized in that: The mass ratio of the porous carbon precursor to ferric oxalate is 100:(2-3).

5. The method for preparing a porous carbon material for preparing a silicon-carbon negative electrode according to claim 1, characterized in that: The carbon source gas in step (4) is ethylene, acetylene or a mixture of the two.

6. The method for preparing a porous carbon material for preparing a silicon-carbon negative electrode according to claim 1, characterized in that: The introduction time in step (4) is 15-20 min.

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