Resin-based hard carbon material, method for preparing the same, and battery

Abstract

The application provides a resin-based hard carbon material, a preparation method thereof and a battery. The preparation method comprises the following steps: subjecting a hard carbon precursor material to a first solidification treatment and a second solidification treatment to obtain a solidified resin product; and sequentially performing pre-carbonization and high-temperature carbonization under a protective atmosphere to obtain a resin-based hard carbon material with a closed pore structure; wherein the hard carbon precursor material comprises a phenolic resin and a curing agent. The preparation method provided by the application obtains a resin-based hard carbon material with rich closed pore structure and high capacity, and the preparation method is simple, does not require a complex treatment process, and the raw materials are widely sourced, low in price and stable in property, and is more suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a resin-based hard carbon material, a preparation method thereof and a battery, in particular to a resin-based hard carbon material more suitable for a sodium ion battery, a preparation method thereof and the sodium ion battery. BACKGROUND

[0002] As an important battery material, the hard carbon negative electrode has various significant advantages, has excellent sodium storage capacity, and can store more sodium ions per unit mass of material, thereby improving the energy density and endurance of the battery. From the sodium storage mechanism of the hard carbon negative electrode, different types of pore structures in the hard carbon material have an important influence on the electrochemical performance of the sodium ion battery, and the hard carbon material with a closed pore structure is more conducive to the formation of sodium clusters in the characteristic pores during the sodium storage process, thereby providing high specific capacity and affecting the intercalation and filling process of sodium ions. With the increase of the closed pore structure content, the sodium ion storage sites increase, and the specific surface area of the hard carbon also decreases accordingly. This structural feature can significantly improve the low-voltage platform capacity, initial coulombic efficiency and cycle stability of the hard carbon negative electrode.

[0003] The hard carbon negative electrode on the market today can be divided into biomass-based, resin-based, pitch-based and anthracite-based, among which resin has the advantages of high carbon yield and good product consistency and is widely used in the manufacture of hard carbon. However, the resin-based hard carbon obtained at present is mostly of open pore structure, which is not conducive to the improvement of the reversible sodium storage capacity of the hard carbon material.

[0004] Therefore, how to obtain resin-based hard carbon with rich closed pore structure is a technical problem that needs to be solved at present. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a resin-based hard carbon material, a preparation method thereof and a battery. The preparation method provided by the present application obtains a resin-based hard carbon material with rich closed pore structure and high capacity, and the preparation method is simple, does not require a complex processing process, the raw materials are widely available, the price is low, the properties are stable, and it is more suitable for industrial production.

[0006] To achieve the purpose of the present application, the following technical solutions are adopted:

[0007] In a first aspect, the present application provides a preparation method of a resin-based hard carbon material, which comprises the following steps:

[0008] The hard carbon precursor material is subjected to first and second solidification treatments to obtain a solidified resin product;

[0009] Under a protective atmosphere, pre-carbonization and high-temperature carbonization are sequentially performed to obtain a resin-based hard carbon material with a closed pore structure;

[0010] The hard carbon precursor material comprises a phenolic resin and a curing agent.

[0011] It should be noted that the present application does not specially limit the specific types of phenolic resin, and the types of conventional phenolic resin that can be used for the preparation of hard carbon are all applicable to the present application, such as at least one of phenol-formaldehyde resin, m-diphenol-formaldehyde resin, p-diphenol-formaldehyde resin, or phenol-furfural resin.

[0012] The preparation method, raw materials, preparation process, preparation sequence and reaction atmosphere provided by the present application are synergistically matched, the crosslinking degree of the phenolic resin and the growth process of the microstructure of the microcrystalline transverse length La closely related to the closed pores in the material during the pre-carbonization process are regulated, the formation of the closed pores in the hard carbon material is facilitated, and thus a resin-based hard carbon material with high capacity is obtained; meanwhile, the preparation process does not involve a synthesis reaction and complex equipment, and the raw materials are widely sourced, low in price and stable in properties, and are more suitable for industrial production.

[0013] In the present application, the first curing process realizes the preliminary crosslinking of the curing agent and the phenolic resin, which can effectively avoid the non-uniformity of the pores of each part of the material caused by the large amount of gas escaping during curing, the swelling of the resin block, and the influence on the hardness and density of the material; the second curing process realizes the control of the crosslinking process of the phenolic resin, so that the resin has a high crosslinking degree, which is conducive to the regulation of the microcrystalline transverse length La in the microstructure during the subsequent pre-carbonization process, and avoids the softening and caking of the material during the subsequent pre-carbonization treatment stage, so as to affect the generation of the closed pores, and finally affect the pore size and quantity of the hard carbon product and the electrochemical performance.

[0014] The pre-carbonization treatment in the present application is carried out in a protective atmosphere, which reduces the oxygen content of the obtained product, which promotes the migration and rearrangement of carbon atoms during the subsequent carbonization process; and effectively regulates the growth process of the microstructure of the microcrystalline transverse length La closely related to the closed pores, so that the carbon layer with longer La can better develop into a closed pore structure; long La is conducive to the formation of closed pores in hard carbon, thereby improving the electrochemical performance; different pre-carbonization temperatures can change the intermolecular connection form to reduce the oxygen content, thereby greatly promoting the growth of the microcrystalline transverse length La related to the closed pores during the carbonization process, and accelerating the formation of the closed pore structure.

[0015] In the present application, the raw materials, preparation process, preparation sequence and reaction atmosphere are indispensable and cooperate with each other to achieve the purpose of obtaining the hard carbon material with closed pore structure. If there is no curing agent in the hard carbon precursor material, the non-crosslinked linear molecular structure will cause uncontrollable foaming and swelling of the material during carbonization, which not only affects the performance of the material, but also makes the subsequent processing process unable to control the structure, thereby affecting the physical indicators and electrochemical performance. If other atmosphere is used in the pre-carbonization process, the etching atmosphere will react with the material, increase the specific surface area and destroy the pore structure, so that the hard carbon with suitable closed pore structure cannot be obtained.

[0016] The following is a preferred technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0017] Preferably, the mass ratio of the curing agent in the hard carbon precursor material is 8% to 12%, for example, 8%, 8.5%, 10%, 11.5% or 12%, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0018] In the present application, the mass ratio of the curing agent in the hard carbon precursor material is 8% to 12%, so that the effects of the subsequent first curing treatment and the second curing treatment are better exerted.

[0019] Preferably, the curing agent includes any one or a combination of at least two of hexamethylenetetramine, paraformaldehyde, A-stage thermosetting phenolic or furfuraldehyde, preferably hexamethylenetetramine.

[0020] In the present application, in addition to hexamethylenetetramine, the remaining curing agent types can be selected from curing agent substances generating aldehyde groups or curing agent substances containing aldehyde groups.

[0021] In the present application, hexamethylenetetramine is selected as the curing agent. It decomposes during the first curing treatment to form dimethanolamine and formaldehyde, thereby crosslinking with phenolic resin. This can effectively avoid the non-uniformity of the pores of each part of the material caused by the large amount of gas released during curing, which leads to the swelling of the resin block and affects the hardness and density of the material. During the second curing treatment, mainly di(hydroxybenzyl)amine and tri(hydroxybenzyl)amine are generated, which effectively controls the crosslinking degree of the resin, and a resin hard block with more excellent thermal stability is obtained.

[0022] Preferably, the temperature of the first curing treatment is lower than the temperature of the second curing treatment.

[0023] Preferably, the temperature of the first curing treatment is 100-120℃, such as 100℃, 105℃, 110℃, 115℃ or 120℃, etc., but not limited to the listed values, other values not listed in the range of values are also applicable.

[0024] Preferably, the time of the first curing treatment is 1-5h, such as 1h, 2h, 3h, 4h or 5h, etc., but not limited to the listed values, other values not listed in the range of values are also applicable.

[0025] Preferably, the temperature of the second curing treatment is 120-180℃, such as 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, etc., but not limited to the listed values, other values not listed in the range of values are also applicable.

[0026] In the present application, by regulating the temperature of the first curing treatment to be 100-120℃ and / or the temperature of the second curing treatment to be 120-180℃, the temperature of the first curing treatment can effectively avoid the non-uniformity of the pores of each part of the material caused by the large amount of gas escaping during curing, that is, to avoid the simultaneous crosslinking and defoaming; the temperature of the second curing treatment avoids the excessive decomposition of the curing agent, for example, when the curing agent is hexamethylenetetramine, the temperature greater than 180℃ will react with free phenol, release NH3, form methylene bond, thereby affecting the migration and rearrangement of carbon atoms in the pyrolysis process during the pre-carbonization process.

[0027] Preferably, the time of the second curing treatment is 4-8h, such as 4h, 5h, 6h, 7h or 8h, etc., but not limited to the listed values, other values not listed in the range of values are also applicable.

[0028] Preferably, the product after the second curing treatment is subjected to a crushing treatment, and the mesh number of the crushing treatment is 100-325 mesh, such as 100 mesh, 125 mesh, 150 mesh, 175 mesh, 200 mesh, 225 mesh, 250 mesh, 275 mesh, 300 mesh or 325 mesh, etc., but not limited to the listed values, other values not listed in the range of values are also applicable.

[0029] In the present application, the hard block of the cured resin is subjected to a crushing treatment of 100-325 mesh, which is more conducive to the regulation of the particle size during pre-carbonization, and the smaller the particle size in the pre-carbonization stage, the more complete the carbonization, the better the development of the lateral length La of the microcrystal with a larger lateral length, and the higher the capacity of the hard carbon material after subsequent carbonization.

[0030] Preferably, the product obtained by the pre-carbonization has a crystallite lateral length La of 7-15 nm, such as 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, or 15 nm, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0031] Preferably, the product obtained by the pre-carbonization has an oxygen element mass fraction of 3-10%, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0032] In the present application, the crystallite lateral length La of the product after further pre-carbonization is 7-15 nm and / or the oxygen element mass fraction is 3-10%, which can better promote the formation of closed pores.

[0033] Preferably, the pre-carbonization temperature is 300-800℃, such as 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0034] In the present application, the pre-carbonization process at 300-800℃ under a protective atmosphere can effectively regulate the crystallite lateral length La and the oxygen element mass fraction.

[0035] Preferably, the pre-carbonization time is 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h, or 8h, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0036] Preferably, the high-temperature carbonization temperature is 1100-1600℃, such as 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, or 1600℃, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0037] Preferably, the high-temperature carbonization time is 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h, or 8h, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0038] As a preferred technical solution, the preparation method comprises the following steps:

[0039] The hard carbon precursor material is sequentially subjected to a first solidification treatment at 100-120 DEG C and a second solidification treatment at 120-180 DEG C, the temperature of the first solidification treatment is less than the temperature of the second solidification treatment, the product after the second solidification treatment is subjected to a crushing treatment at 100-325 mesh, and a solidified resin product is obtained;

[0040] The product after the pre-carbonization is subjected to high-temperature carbonization at 1100-1600 DEG C to obtain a resin-based hard carbon material with a closed pore structure.

[0041] The product after the pre-carbonization is subjected to high-temperature carbonization at 1100-1600 DEG C to obtain a resin-based hard carbon material with a closed pore structure.

[0042] The hard carbon precursor material comprises phenolic resin and hexamethylenetetramine, and the mass percentage of the hexamethylenetetramine in the hard carbon precursor material is 8-10%.

[0043] It should be further pointed out that the protective atmosphere in the present application is an atmosphere that only plays a protective role and does not participate in the reaction, for example, it can be a nitrogen atmosphere and / or an inert gas atmosphere, and the inert gas includes argon or helium.

[0044] In a second aspect, the present application provides a resin-based hard carbon material prepared by the preparation method of the first aspect.

[0045] The resin-based hard carbon material has a closed pore structure inside.

[0046] In a third aspect, the present application further provides a battery comprising the resin-based hard carbon material of the second aspect.

[0047] Preferably, the battery comprises a sodium ion battery.

[0048] The resin-based hard carbon material provided by the present application is more suitable for use in a sodium ion battery, and when used as a negative active material, it has a more excellent performance improvement effect on the sodium ion battery. However, in addition to sodium ion batteries, it is also possible that it is used in other types of battery structures, such as lithium ion batteries, and the use of conventional hard carbon materials is applicable in principle.

[0049] In addition, the sodium ion battery provided by the present application has the remaining structure, preparation raw materials and preparation process as defined above, which are conventional technical solutions, and the person skilled in the art can make adaptive selection and adjustment according to the actual needs, and the present application will not be described here.

[0050] Compared with the prior art, the present application has the following beneficial effects:

[0051] The preparation method, raw material, preparation process, preparation sequence and reaction atmosphere are cooperated with each other, the cross-linking degree of the phenolic resin and the growth process of the microstructure of the closed pore closely related transverse length La of the material in the pre-carbonization process are controlled, the formation of the closed pore in the hard carbon material is facilitated, and thus the resin-based hard carbon material with high capacity is obtained; meanwhile, the preparation process does not involve a synthesis reaction and a complex device, and the raw material is widely sourced, low in price and stable in property, and is more suitable for industrial production. DETAILED DESCRIPTION

[0052] The technical solutions of the present application are further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "comprising" and "having," and any variations thereof, are intended to cover not exclusively containing.

[0054] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0055] Embodiment 1

[0056] The present embodiment provides a resin-based hard carbon material with a closed pore structure inside the material, and a preparation method of the resin-based hard carbon material is as follows:

[0057] A commercially available phenolic resin material (containing phenol-formaldehyde resin and a curing agent hexamethylenetetramine, and the mass ratio of the curing agent in the commercially available phenolic resin material is 10%) is subjected to a first curing treatment at 120°C for 5h, and then subjected to a second curing treatment at 180°C for 8h; the resin hard block obtained by the curing treatment is subjected to a crushing treatment at 150 mesh to obtain a cured resin product;

[0058] The cured resin product is subjected to a pre-carbonization treatment at 600°C for 2h under a nitrogen atmosphere to obtain a pre-carbonization product;

[0059] The pre-carbonization product is subjected to a high-temperature carbonization treatment at a carbonization temperature of 1600°C under a nitrogen atmosphere to obtain the resin-based hard carbon material.

[0060] Embodiment 2

[0061] The resin-based hard carbon material with closed pore structure inside the material is prepared by the following method:

[0062] The commercially available phenolic resin material (containing phenol-formaldehyde resin and curing agent hexamethylenetetramine, and the mass ratio of the curing agent in the commercially available phenolic resin material is 8%) is subjected to first curing treatment at 100°C for 1h, and then subjected to second curing treatment at 150°C for 4h; the resin hard block obtained by the curing treatment is subjected to crushing treatment at 300 mesh to obtain a cured resin product;

[0063] The cured resin product is subjected to pre-carbonization treatment at 350°C for 8h under nitrogen atmosphere to obtain a pre-carbonization product;

[0064] The pre-carbonization product is subjected to high-temperature carbonization treatment at a carbonization temperature of 1100°C under nitrogen atmosphere to obtain the resin-based hard carbon material.

[0065] Example 3

[0066] The resin-based hard carbon material with closed pore structure inside the material is prepared by the following method:

[0067] The commercially available phenolic resin material (containing phenol-formaldehyde resin and curing agent hexamethylenetetramine, and the mass ratio of the curing agent in the commercially available phenolic resin material is 12%) is subjected to first curing treatment at 110°C for 5h, and then subjected to second curing treatment at 120°C for 8h; the resin hard block obtained by the curing treatment is subjected to crushing treatment at 150 mesh to obtain a cured resin product;

[0068] The cured resin product is subjected to pre-carbonization treatment at 800°C for 4h under nitrogen atmosphere to obtain a pre-carbonization product;

[0069] The pre-carbonization product is subjected to high-temperature carbonization treatment at a carbonization temperature of 1300°C under nitrogen atmosphere to obtain the resin-based hard carbon material.

[0070] Example 4

[0071] The difference between this example and Example 1 is that the curing agent in this example is paraformaldehyde, and the phenolic resin is m-diphenol-formaldehyde resin.

[0072] The rest of the preparation method and parameters are consistent with those of Example 1.

[0073] Example 5

[0074] The difference between this example and Example 1 is that the mass ratio of the curing agent in the commercially available phenolic resin material in this example is 15%.

[0075] The remaining preparation method and parameters are consistent with Example 1.

[0076] Example 6

[0077] The difference between this example and Example 1 is that the mass ratio of the curing agent in the commercially available phenolic resin material in this example is 5%.

[0078] The remaining preparation method and parameters are consistent with Example 1.

[0079] Example 7

[0080] The difference between this example and Example 1 is that the temperature of the first curing treatment in this example is 80°C.

[0081] The remaining preparation method and parameters are consistent with Example 1.

[0082] Example 8

[0083] The difference between this example and Example 1 is that the temperature of the first curing treatment in this example is 140°C.

[0084] The remaining preparation method and parameters are consistent with Example 1.

[0085] Example 9

[0086] The difference between this example and Example 1 is that the temperature of the second curing treatment in this example is 200°C.

[0087] The remaining preparation method and parameters are consistent with Example 1.

[0088] Example 10

[0089] The difference between this example and Example 1 is that the temperature of the pre-carbonization in this example is 250°C.

[0090] The remaining preparation method and parameters are consistent with Example 1.

[0091] Example 11

[0092] The difference between this example and Example 1 is that the temperature of the pre-carbonization in this example is 850°C.

[0093] The remaining preparation method and parameters are consistent with Example 1.

[0094] Example 12

[0095] The difference between this example and Example 1 is that the cured resin product is obtained by crushing the cured resin block under 40 mesh.

[0096] The remaining preparation method and parameters are consistent with Example 1.

[0097] Comparative Example 1

[0098] The difference between the present comparative example and Example 1 is that the hard carbon precursor material provided in the present comparative example is a commercially available phenol formaldehyde resin without curing agent.

[0099] The rest of the preparation method and parameters are consistent with Example 1.

[0100] Comparative Example 2

[0101] The difference between the present comparative example and Example 1 is that the first curing treatment is not performed in the present comparative example.

[0102] The rest of the preparation method and parameters are consistent with Example 1.

[0103] Comparative Example 3

[0104] The difference between the present comparative example and Example 1 is that the second curing treatment is not performed in the present comparative example.

[0105] The rest of the preparation method and parameters are consistent with Example 1.

[0106] Comparative Example 4

[0107] The difference between the present comparative example and Example 1 is that the pre-carbonization treatment atmosphere in the present comparative example is carbon dioxide atmosphere.

[0108] The rest of the preparation method and parameters are consistent with Example 1.

[0109] Comparative Example 5

[0110] The difference between the present comparative example and Example 1 is that the pre-carbonization treatment process is not performed in the present comparative example.

[0111] The rest of the preparation method and parameters are consistent with Example 1.

[0112] The pre-carbonized products provided in Examples 1-12 and Comparative Examples 1-5 are characterized by the crystallite lateral length Laand the mass percentage of oxygen element, and the specific characterization method is as follows:

[0113] The crystallite lateral length (La) of pseudo-graphitic domains is calculated according to the Scherrer equation from the X-ray diffraction (XRD) test results,

[0114]

[0115] wherein K is a shape factor, usually taken as 0.94, λ is the wavelength of the X-rays used, β is the full width at half maximum of the XRD peak, and θ is the magnitude of the diffraction angle. The XRD test results were measured by a Bruker D2 phase X-ray diffractometer with Cu Kα radiation, and the X-ray photoelectron spectroscopy was obtained by using an XPS spectrum spectrometer (Thermo Scientific K-Alpha, USA) to characterize the content of oxygen element.

[0116] The characterization results are shown in Table 1.

[0117] Table 1

[0118] crystallite lateral length La (nm) mass fraction of oxygen element (%) Example 1 14.8 4.2 Example 2 8.7 9.6 Example 3 13.7 3.5 Example 4 8.9 4.2 Example 5 7.4 2.2 Example 6 6.3 11.9 Example 7 15.8 2.4 Example 8 14.2 5.8 Example 9 10.4 4.8 Example 10 5.8 12.5 Example 11 16.7 12.5 Example 12 13.9 4.5 Comparative Example 1 4.5 11.1 Comparative Example 2 5.9 10.8 Comparative Example 3 16.9 4.9 Comparative Example 4 17.5 5.3 Comparative Example 5 4.4 15.2

[0119] The hard carbon negative electrode materials provided by Examples 1-12 and Comparative Examples 1-5 were tested for pore structure, including pore volume, pore size, and specific surface area, under the following conditions: the pore size distribution and specific surface area were determined by gas adsorption / desorption experiments. Specifically, the hard carbon material was degassed at 150-300°C and a pressure of <10 -6 Bar for 1-6h; then nitrogen / carbon dioxide was introduced at a liquid nitrogen temperature, the pressure was slowly returned to normal pressure, and degassing was performed again for 10 -6 Bar, and the data were recorded to obtain the adsorption / desorption isotherm. The pore size distribution and pore volume data of the hard carbon negative electrode material were calculated according to the density functional theory (DFT) model. The test results are shown in Table 2.

[0120] Table 2

[0121]

[0122]

[0123] The resin-based hard carbon materials provided by Examples 1-12 and Comparative Examples 1-5 were applied to batteries and performance tests were performed.

[0124] I. Battery preparation:

[0125] The hard carbon negative electrode materials provided by the examples and comparative examples were respectively mixed with the conductive agent SuperP, the binder sodium carboxymethyl cellulose, and the butadiene rubber in a mass ratio of 94.5:1.5:1.5:2.5, and a proper amount of water was added to form a slurry, which was then uniformly coated on a copper foil current collector. After drying, the slurry was cut into a circular electrode with a diameter of 18mm. The electrode was dried at 80°C under a blast for about 3 hours, vacuum dried at 80°C for 6h, and rolled to a surface density of 7mg / cm 2Reserved. Then transferred to the glove box for later use. The assembly of the simulated battery was carried out in an Ar atmosphere glove box, using a sodium metal sheet as the counter electrode and 1 mol / L NaPF6 dissolved in ethylene carbonate solution as the electrolyte, to assemble a CR2430 button cell.

[0126] II Performance Testing

[0127] The prepared sodium-ion battery was tested for reversible specific capacity and initial coulombic efficiency: the coin cell was placed in a constant temperature chamber (T-3002A-5V 1mA) at 25℃ and left to stand for 6 hours. The coin cell was then charged and discharged at a constant current of 0.05C, with a voltage range of 0-2V. The discharge specific capacity of the coin cell was recorded as D, and the charge specific capacity as C. The initial coulombic efficiency was calculated using the following formula:

[0128] Initial Coulomb efficiency = C / D × 100%.

[0129] The test results are shown in Table 3.

[0130] Table 3

[0131]

[0132]

[0133] From Tables 1 to 3, we can obtain:

[0134] The curing step in this invention can significantly improve the capacity and first-time efficiency of hard carbon. Specifically, the two-step curing process can prevent the foaming and expansion of phenolic resin while ensuring the degree of cross-linking, which is beneficial for the adjustment of pore structure in subsequent processes. At the same time, it can reduce the specific surface area of ​​the final product and improve the first-time coulombic efficiency of the product.

[0135] Meanwhile, a series of characterizations show that pre-carbonization can reduce oxygen content by changing the connection form between molecules, thereby reducing the resistance to carbon atom migration and rearrangement, which greatly promotes the growth of La related to pore closure during subsequent carbonization. However, low oxygen content can easily lead to excessive growth of La, which is not conducive to increasing the number and volume of pores, although it helps to expand the pore size. Therefore, only pre-carbonization products with appropriate La and oxygen content can yield hard carbon materials with suitable pore size and pore volume, thus enabling the obtained hard carbon materials to have high capacity and first coulombic efficiency.

[0136] In summary, the preparation method, raw materials, preparation process, preparation sequence and reaction atmosphere are cooperated with each other, the cross-linking degree of the phenolic resin and the growth process of the microstructure of the material in the pre-carbonization process are controlled, the closed pores in the hard carbon material are formed, and the resin-based hard carbon material with high capacity is obtained.

[0137] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a resin-based hard carbon material, characterized in that, The preparation method comprises the following steps: The hard carbon precursor material is subjected to a first curing treatment and a second curing treatment to obtain a cured resin product; Under a protective atmosphere, pre-carbonization and high-temperature carbonization are sequentially performed to obtain a resin-based hard carbon material with a closed pore structure; The hard carbon precursor material comprises phenolic resin and a curing agent; The temperature of the first curing treatment is lower than the temperature of the second curing treatment; The temperature of the first curing treatment is 100-120 DEG C, and the temperature of the second curing treatment is 120-180 DEG C; In the product obtained by pre-carbonization, the lateral length La of the microcrystal is 7-15 nm; In the product obtained by pre-carbonization, the mass percentage of oxygen is 3-10%.

2. The production method according to claim 1, characterized by, The mass percentage of the curing agent in the hard carbon precursor material is 8-12%.

3. The production method according to claim 1, characterized by, The curing agent comprises any one or a combination of at least two of hexamethylenetetramine, paraformaldehyde or furfural.

4. The method of claim 1, wherein, The curing agent is hexamethylenetetramine.

5. The preparation method according to claim 1, characterized in that, The time of the first curing treatment is 1-5 h.

6. The method of claim 1, wherein, The time of the second curing treatment is 4-8 h.

7. The preparation method according to claim 1, characterized in that, The product after the second curing treatment is subjected to a crushing treatment, and the mesh number of the crushing treatment is 100-325.

8. The method of claim 1, wherein, The temperature of the pre-carbonization is 300-800 DEG C, and the time of the pre-carbonization is 2-8 h.

9. The method of any one of claims 1-8, wherein, The temperature of the high-temperature carbonization is 1100-1600 DEG C, and the time of the high-temperature carbonization is 2-8 h.

10. The method of claim 1, wherein, The preparation method comprises the following steps: The hard carbon precursor material is sequentially subjected to a first curing treatment at 100-120 DEG C and a second curing treatment at 120-180 DEG C, and the temperature of the first curing treatment is lower than the temperature of the second curing treatment, and the product after the second curing treatment is subjected to a crushing treatment at 100-325 mesh to obtain a cured resin product; Under a protective atmosphere, pre-carbonization is performed at 300-800 DEG C, and in the product after pre-carbonization, the lateral length La of the microcrystal is 7-15 nm, and the mass percentage of oxygen is 3-10%. The product after pre-carbonization is subjected to high-temperature carbonization at 1100-1600 DEG C to obtain a resin-based hard carbon material with a closed pore structure; The hard carbon precursor material comprises phenolic resin and hexamethylenetetramine, and the mass percentage of the hexamethylenetetramine in the hard carbon precursor material is 8-12%.

11. A resin-based hard carbon material, characterized by, The resin-based hard carbon material is prepared by the preparation method of any one of claims 1-10. The resin-based hard carbon material has a closed pore structure inside.

12. A battery, characterized by The battery comprises the resin-based hard carbon material of claim 11.

13. The battery of claim 12, wherein, The battery comprises a sodium ion battery.

Images