Modified resin-based nitrogen-containing hard carbon material, and preparation method and application thereof

Abstract

The application belongs to the technical field of carbon materials and new energy materials, and particularly relates to a modified resin-based nitrogen-containing hard carbon material and a preparation method and application thereof. Melamine is introduced into a phenol formaldehyde resin system to synthesize a phenol-melamine-formaldehyde resin, a trinitrogen heterocyclic covalent polymer resin molecule is formed, an organic pore forming agent is simultaneously used to adjust the pore structure of the material, and after high-temperature carbonization, a hard carbon negative electrode material for sodium ion batteries with high nitrogen doping, rich closed pore structure and disordered microstructure is prepared. After melamine participates in the reaction, a stable trinitrogen heterocyclic ring is introduced into the resin molecular structure, and after carbonization, a nitrogen-doped hard carbon material is formed. Nitrogen elements are uniformly distributed in the inside and surface of the carbon material, providing rich active sites, which is beneficial to improving the reversible capacity of sodium ion storage.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials and new energy materials technology, and particularly relates to a modified resin-based nitrogen-containing hard carbon material, its preparation method and application. Background Technology

[0002] Among various energy storage technologies that can replace lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have been extensively studied due to their low cost, uniform distribution of sodium resources, relatively high energy density, and similar working principle to LIBs. They have become promising candidate technologies for partially replacing LIBs, especially in large-scale energy storage and slow-speed transportation. For large-scale batteries, cost, while a simple evaluation metric, is crucial. Energy density and power density are equally important for such devices. Therefore, the key to the development of SIBs is to minimize costs while maintaining excellent electrochemical performance. Thus, developing novel, low-cost, and high-performance commercial materials for sodium-ion batteries is particularly important.

[0003] Among the materials reported to date for use in sodium-ion batteries (SIBs), hard carbon stands out as one of the most promising anode materials due to its high performance, sustainability, and structural stability. Notably, the precursors for hard carbon, which have been extensively studied, can be broadly categorized into two types: organic polymers and biomass materials. Among the numerous hard carbon precursors, phenolic resins hold promise for commercialization due to their low cost, mature preparation processes, and high carbon residue. Furthermore, the physicochemical properties of phenolic resins can be controlled through artificial synthesis, thereby modulating the electrochemical performance of hard carbon materials and facilitating research into the energy storage mechanism of hard carbon.

[0004] However, although recent research reports have shown that phenolic resin-based hard carbon anodes have reached 410 mAh g⁻¹, -1 While phenolic resin exhibits reversible specific capacity, its unstable cycling performance and poor rate capability indicate that it cannot yet serve as a high-quality hard carbon precursor, a common limitation of phenolic resin-based hard carbon materials. It is worth noting that resin materials are easily cured, and the resulting tightly cross-linked network structure contributes to the formation of hard carbon materials with low specific surface area, high structural stability, and abundant nanopores. These three structural characteristics lead to excellent electrochemical performance. Therefore, finding a new resin-based hard carbon precursor is crucial for the commercialization of sodium-ion batteries. It is well known that by altering the subcategories of phenolic and aldehyde monomers in the synthetic raw materials or introducing other reagents for modification or mixing, phenolic resins with different properties and structures can be prepared, ultimately yielding hard carbon anode materials with distinct characteristics to adjust their electrochemical performance. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to prepare a modified resin-based nitrogen-containing hard carbon anode material. This is achieved by introducing melamine into a phenolic resin system to synthesize a phenol-melamine-formaldehyde resin, forming resin molecules with triaza-heterocyclic covalent polymerization. Simultaneously, an organic pore-forming agent is used to adjust the pore structure of the material. After high-temperature carbonization, a hard carbon anode material for sodium-ion batteries with high nitrogen doping, abundant closed-pore structure, and disordered microstructure is prepared.

[0006] The technical solution of the present invention is as follows:

[0007] The first objective of this invention is to protect a method for preparing a modified resin-based nitrogen-containing hard carbon material, which involves introducing melamine into the polymerization reaction of phenol and formaldehyde to form a triaza-heterocyclic covalently polymerized resin.

[0008] This invention introduces melamine into the polymerization reaction of phenol and formaldehyde to form a structurally stable triaza-heterocyclic covalently polymerized resin molecule; simultaneously, an organic pore-forming agent forms a rich microporous structure in the polymer matrix.

[0009] In some embodiments, the polymerization reaction further includes a catalyst, said catalyst including at least one of asparagine, ethylenediamine, dimethylamine, trimethylamine, 1,6-hexanediamine, diethylenetriamine, lysine, glutamic acid, and aspartic acid.

[0010] In some preferred embodiments, the polymerization reaction further includes a pore-forming agent, which includes at least one of tetrapropylammonium hydroxide, polyvinyl alcohol, polyethylene glycol, and hexadecyltrimethylammonium bromide.

[0011] In some embodiments, the molar ratio of phenol to catalyst is 10 to 20:1;

[0012] And / or, the molar ratio of phenol to pore-forming agent is 20–50:1;

[0013] And / or, the molar ratio of phenol to melamine is 0.5 to 3:1;

[0014] And / or, the molar ratio of phenol to formaldehyde is 0.5 to 2:1.

[0015] In some preferred embodiments, the polymerization reaction conditions include: a temperature of 60–120°C and a time of 1–6 hours.

[0016] More specifically, the preparation method of the modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0017] (1) Phenol is heated and melted, a certain amount of catalyst is added, and the mixture is stirred evenly to obtain mixture A;

[0018] (2) A certain amount of formaldehyde monomer is dispersed in an aqueous solution, heated to 60°C, and then a certain amount of melamine and organic pore-forming agent are added in sequence. After stirring evenly, a mixture B is obtained.

[0019] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C;

[0020] (4) Add the mixture C prepared in step (3) into the reactor and carry out the polymerization reaction at a certain temperature for a period of time;

[0021] (5) After the reaction in step (4) is completed, the carbon is dried and crushed, and then pre-carbonized at low temperature and carbonized at high temperature to obtain the modified resin-based hard carbon.

[0022] In some embodiments, carbonization is further included after the polymerization reaction is completed; preferably, the carbonization includes low-temperature pre-carbonization and high-temperature carbonization.

[0023] The aforementioned low-temperature pre-carbonization conditions include: temperature 500–1000℃, time 1–4 hours;

[0024] And / or, high-temperature carbonization, with conditions including: temperature 1200–1800℃, time 2–8h.

[0025] In some embodiments, the carbonization atmosphere for low-temperature pre-carbonization and / or high-temperature carbonization includes an inert gas.

[0026] Another object of the present invention is to protect the modified resin-based nitrogen-containing hard carbon material prepared by the above preparation method.

[0027] The final objective of this invention is to protect the application of the above-mentioned modified resin-based nitrogen-containing hard carbon material in sodium-ion batteries.

[0028] Preferably, it is used as a negative electrode material for sodium-ion batteries.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] 1. Unlike traditional phenolic resins, the introduction of melamine participates in the co-condensation reaction of phenol and formaldehyde. On the one hand, it lowers the curing temperature of the phenolic resin, accelerates the reaction rate, and shortens the reaction time. On the other hand, it reduces the content of toxic substances such as free phenol and free aldehyde, improving the resin's environmental performance. Furthermore, after participating in the reaction, melamine introduces structurally stable triaza rings into the resin molecular structure. After carbonization, this forms nitrogen-doped hard carbon materials. The nitrogen element is uniformly distributed inside and on the surface of the carbon material, providing abundant active sites, which is beneficial for improving the reversible capacity of sodium ion storage.

[0031] 2. Organic pore-forming agents are linear molecular compounds. On the one hand, they have good toughness and elasticity, which is beneficial to improving the strength of carbon materials. On the other hand, they form micro micelles in the polymer and form a rich pore structure after carbonization. By adjusting the proportion of pore-forming agents and the carbonization temperature, the closed-pore structure can be finely controlled, thereby adjusting the sodium storage performance of hard carbon materials.

[0032] 3. Unlike traditional NaOH or ammonia catalysts, this invention uses amines or amino acids as catalysts, which promote the polymerization reaction while ensuring a gentle and uniform process. This is beneficial for the formation of uniformly pore structures in the phenolic resin carbon, resulting in a more uniform microstructure. Furthermore, this type of organic catalyst does not leave any ash residue during the carbonization process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the polymerization mechanism of phenol-melamine-formaldehyde resin according to the present invention;

[0034] Figure 2 This is a scanning electron microscope (SEM) image of the modified resin-based hard carbon material prepared in Example 1 of this invention;

[0035] Figure 3 The modified resin-based nitrogen-containing hard carbon material of Example 1 of this invention is shown as the first two charge-discharge curves of a sodium-ion battery at 0.1C. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0037] Example 1

[0038] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0039] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it evenly with 0.1 mol of asparagine to obtain a mixture A.

[0040] (2) Take 2 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 0.5 mol of melamine and 0.05 mol of tetrapropylammonium hydroxide in sequence, stir to dissolve, and stir evenly to obtain mixture B.

[0041] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0042] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 90°C for 3 hours.

[0043] (5) After drying the sample prepared in step (4), heat it to 600°C in an argon atmosphere at a heating rate of 5°C / min and hold it for 2 hours. After grinding the prepared sample, heat it to 600°C in an argon atmosphere at a heating rate of 10°C / min, and then heat it to 1400°C at a heating rate of 2°C / min and hold it for 4 hours.

[0044] Example 2

[0045] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0046] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it evenly with 0.05 mol of ethylenediamine to obtain a mixture A.

[0047] (2) Take 1 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 1 mol of melamine and 0.02 mol of polyvinyl alcohol in sequence, stir to dissolve, and stir evenly to obtain mixture B.

[0048] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0049] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 60°C for 6 hours.

[0050] (5) After drying the sample prepared in step (4), heat it to 500°C at a heating rate of 5°C / min in an argon atmosphere and hold it for 4 hours. After grinding the prepared sample, heat it to 500°C at a heating rate of 10°C / min in an argon atmosphere, and then heat it to 1200°C at a heating rate of 2°C / min and hold it for 8 hours.

[0051] Example 3

[0052] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0053] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it with 0.08 mol of 1,6-hexanediamine to obtain a mixture A.

[0054] (2) Disperse 0.5 mol of formaldehyde in 20 mol of water, heat to 60°C, then add 2 mol of melamine and 0.03 mol of cetyltrimethylammonium bromide in sequence, stir to dissolve, and stir evenly to obtain mixture B.

[0055] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0056] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 120°C for 1 hour.

[0057] (5) After drying the sample prepared in step (4), heat it to 1000℃ at a heating rate of 5℃ / min in an argon atmosphere and hold it for 1h. After grinding the prepared sample, heat it to 1000℃ at a heating rate of 10℃ / min in an argon atmosphere, and then heat it to 1800℃ at a heating rate of 2℃ / min and hold it for 2h.

[0058] Example 4

[0059] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0060] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it with 0.06 mol of glutamic acid to obtain a mixture A.

[0061] (2) Take 1.5 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 0.3 mol of melamine and 0.04 mol of polyethylene glycol in sequence, stir to dissolve, and stir evenly to obtain mixture B.

[0062] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0063] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 100°C for 2 hours.

[0064] (5) After drying the sample prepared in step (4), heat it to 800°C at a heating rate of 5°C / min in an argon atmosphere and hold it for 2 hours. After grinding the prepared sample, heat it to 800°C at a heating rate of 10°C / min in an argon atmosphere, and then heat it to 1300°C at a heating rate of 2°C / min and hold it for 6 hours.

[0065] Comparative Example 1

[0066] A method for preparing a resin-based hard carbon material includes the following steps:

[0067] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it evenly with 0.1 mol of asparagine to obtain a mixture A.

[0068] (2) Take 2 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 0.05 mol of tetrapropylammonium hydroxide, stir to dissolve, and stir evenly to obtain mixture B.

[0069] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0070] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 120°C for 6 hours.

[0071] (5) After drying the sample prepared in step (4), heat it to 600°C in an argon atmosphere at a heating rate of 5°C / min and hold it for 2 hours. After grinding the prepared sample, heat it to 600°C in an argon atmosphere at a heating rate of 10°C / min, and then heat it to 1400°C at a heating rate of 2°C / min and hold it for 4 hours.

[0072] Comparative Example 2

[0073] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0074] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it evenly with 0.1 mol of asparagine to obtain a mixture A.

[0075] (2) Take 2 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 0.5 mol of melamine, stir to dissolve, and stir evenly to obtain mixture B.

[0076] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0077] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 90°C for 3 hours.

[0078] (5) After drying the sample prepared in step (4), heat it to 600°C in an argon atmosphere at a heating rate of 5°C / min and hold it for 2 hours. After grinding the prepared sample, heat it to 600°C in an argon atmosphere at a heating rate of 10°C / min, and then heat it to 1400°C at a heating rate of 2°C / min and hold it for 4 hours.

[0079] Comparative Example 3

[0080] A method for preparing a modified resin-based nitrogen-containing hard carbon material includes the following steps:

[0081] (1) Heat 1 mol of phenol to 60°C to melt it into a liquid state, and stir it evenly with 0.05 mol of NaOH aqueous solution to obtain a mixture A.

[0082] (2) Take 2 mol of formaldehyde and disperse it in 20 mol of water, heat it to 60°C, then add 0.5 mol of melamine and 0.05 mol of tetrapropylammonium hydroxide in sequence, stir to dissolve, and stir evenly to obtain mixture B.

[0083] (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C.

[0084] (4) Transfer the mixture C prepared in step (3) to the reactor and treat it at 120°C for 6 hours.

[0085] (5) After drying the sample prepared in step (4), heat it to 600°C in an argon atmosphere at a heating rate of 5°C / min and hold it for 2 hours. After grinding the prepared sample, heat it to 600°C in an argon atmosphere at a heating rate of 10°C / min, and then heat it to 1400°C at a heating rate of 2°C / min and hold it for 4 hours.

[0086] Table 1: Test results of the hard carbon anode materials prepared in Examples 1-4 and Comparative Examples 1-3

[0087]

[0088] The above description is merely a basic explanation of the concept of this invention, and any equivalent modifications made based on the technical solution of this invention shall fall within the protection scope of this invention.

Claims

1. A method for preparing a modified resin-based nitrogen-containing hard carbon material, characterized in that, By introducing melamine into the polymerization reaction of phenol and formaldehyde, a resin of triazacyclic covalent polymerization is formed; The polymerization reaction also includes a catalyst, which includes asparagine, ethylenediamine, dimethylamine, trimethylamine, and 1,6-dimethylamine. At least one of hexamethylenediamine, diethylenetriamine, lysine, glutamic acid, and aspartic acid; The polymerization reaction also includes a pore-forming agent, which includes at least one of tetrapropylammonium hydroxide, polyvinyl alcohol, polyethylene glycol, and hexadecyltrimethylammonium bromide. Specifically, the following steps are included: (1) Phenol is heated and melted, a certain amount of catalyst is added, and the mixture is stirred evenly to obtain mixture A; (2) A certain amount of formaldehyde monomer is dispersed in an aqueous solution, heated to 60°C, and then a certain amount of melamine and pore-forming agent are added in sequence. After stirring evenly, a mixture B is obtained. (3) Add the mixture B prepared in step (2) to the mixture A obtained in step (1), keep heating and stir evenly to obtain mixture C; (4) Add the mixture C prepared in step (3) into the reactor and carry out the polymerization reaction at a certain temperature for a period of time; (5) After the reaction in step (4) is completed, the material is dried and crushed, and then pre-carbonized at low temperature and carbonized at high temperature to obtain the modified resin-based nitrogen-containing hard carbon material. The molar ratio of phenol to catalyst is 10–20:1; The molar ratio of phenol to pore-forming agent is 20–50:1; The molar ratio of phenol to melamine is 0.5–3:1; The molar ratio of phenol to formaldehyde is 0.5 to 2:

1.

2. The preparation method according to claim 1, characterized in that, The conditions for the polymerization reaction include: temperature 60–120℃ and time 1–6 h.

3. The preparation method according to claim 1, characterized in that, The aforementioned low-temperature pre-carbonization conditions include: temperature 500–1000℃, time 1–4 hours; And / or, high-temperature carbonization, with conditions including: temperature 1200–1800℃, time 2–8h.

4. The preparation method according to claim 3, characterized in that, The carbonization atmosphere for low-temperature pre-carbonization and / or high-temperature carbonization includes an inert gas.

5. Modified resin-based nitrogen-containing hard carbon material prepared by any of the preparation methods described in claims 1-4.

6. The application of the modified resin-based nitrogen-containing hard carbon material according to claim 5 in sodium-ion batteries.

7. The application according to claim 6, characterized in that, Applications as a negative electrode material for sodium-ion batteries.

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