A starch-based hard carbon material and a preparation method thereof
By coating the starch surface with thermosetting resin and performing high-temperature carbonization, the foaming and expansion problem during starch carbonization was solved. The prepared hard carbon material was used as the negative electrode of sodium-ion batteries, improving the battery performance and production adaptability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAMEN UNIV
- Filing Date
- 2026-04-15
- Publication Date
- 2026-07-14
AI Technical Summary
Starch is prone to foaming and swelling during carbonization. Existing modification methods are time-consuming, energy-intensive, and pose safety hazards, making them unsuitable for large-scale production.
A thermosetting resin was used as a coating agent to coat starch, and a hard carbon material was prepared by high-temperature carbonization. The thermal stability of the resin was used to prevent starch particles from contacting and melting together, thus inhibiting foaming and expansion.
The foaming and expansion during starch carbonization is effectively suppressed, and the prepared hard carbon material has high specific capacity and first coulombic efficiency, making it suitable for large-scale production and application in sodium-ion battery anodes.
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Figure CN122380341A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery materials technology, specifically to a starch-based hard carbon material and its preparation method. Background Technology
[0002] Sodium-ion batteries have unique advantages in large-scale energy storage and other applications due to their abundant raw material resources, relatively low cost, and good performance in high-current charging and discharging and low-temperature environments.
[0003] Among the many candidate anode materials for sodium-ion batteries, hard carbon is considered the most promising. Its large interlayer spacing, abundant closed-cell and defect structures provide more sodium storage sites, making it particularly suitable as an anode material for sodium-ion batteries.
[0004] Starch is one of the most abundant biomass resources in nature, widely available, inexpensive, and easily accessible. Elementally, starch mainly contains carbon, hydrogen, and oxygen, with a high carbon content, allowing it to be converted into amorphous hard carbon materials through a relatively simple heat treatment process. During the carbonization process, the graphite microcrystalline wafers formed in starch are arranged in a disordered and tortuous pattern, resulting in hard carbon with a large interlayer spacing and abundant closed-cell structure. This facilitates the insertion and extraction of sodium ions and provides more sodium storage sites. These characteristics make starch an important precursor material for preparing hard carbon anodes in sodium-ion batteries.
[0005] However, during direct carbonization, starch particles melt and fuse together, generating a large amount of gas and causing severe foaming and swelling. Therefore, unmodified starch is difficult to use directly. Currently, common methods to address starch swelling include esterification, cross-linking, and pre-oxidation. Esterification and cross-linking typically require hydrothermal reactions under high temperature and pressure, placing high demands on equipment. Pre-oxidation requires prolonged air oxidation, which is not only time-consuming and energy-intensive but also suffers from insufficient process stability and safety hazards. These methods all face significant challenges in large-scale production. Therefore, there is an urgent need to develop a new strategy with milder process conditions that can effectively suppress starch swelling. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing starch-based hard carbon materials, thereby solving the problem of easy foaming and expansion of starch during carbonization and improving the electrochemical performance of the resulting materials. The preparation method is simple and operates under mild conditions.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A method for preparing a starch-based hard carbon material includes the following steps: first, coating starch with a coating agent to obtain a hard carbon precursor material; then, subjecting the hard carbon precursor material to high-temperature carbonization treatment under an inert atmosphere to obtain the starch-based hard carbon material. The coating agent is a thermosetting resin.
[0009] The thermosetting resin is one or more of the following: resorcinol-formaldehyde resin, aminophenol-formaldehyde resin, linear phenolic resin, methyl phenolic resin, epoxy resin, and polyurethane resin.
[0010] The coating agent selected in this invention exhibits good thermal stability at carbonization temperatures and maintains its structural integrity at high temperatures. During carbonization, this coating layer effectively prevents direct contact and melting of starch granules, thereby inhibiting foaming and expansion.
[0011] Furthermore, the high-temperature carbonization treatment of the hard carbon precursor material is carried out at a temperature of 1200 ℃~1400 ℃, a holding time of 1~4 h, and a heating rate of 2~6 ℃ / min.
[0012] Furthermore, depending on the type of coating agent, appropriate methods are used to coat the starch:
[0013] Method 1: Starch is coated with resorcinol-formaldehyde resin or aminophenol-formaldehyde resin. The method involves dispersing starch, resorcinol or aminophenol, and formaldehyde in a mixed solution of water and ethanol, adding ammonia, stirring continuously, and then filtering, washing, and drying to obtain the hard carbon precursor material. The volume ratio of water to ethanol in the water-ethanol mixture is 1:0.4 to 1:2, and the ratio of starch, resorcinol or aminophenol, formaldehyde, the water-ethanol mixture, and ammonia is 10g:1-10g:13 mmol-130 mmol:100 mL-1000 mL:8 mmol-32 mmol. The reaction time is 8-36 hours.
[0014] Method 2: Coating starch with a primary phenolic resin or a linear phenolic resin. The method involves mixing starch with a primary phenolic resin or a linear phenolic resin containing 10% hexamethylenetetramine, followed by heating and curing to obtain a hard carbon precursor material. The mixing method includes grinding or ball milling, dispersing in ethanol, and then evaporating one or more solvents. The ratio of starch to primary phenolic resin or linear phenolic resin containing 10% hexamethylenetetramine is 10 g: 0.5–10 g. The curing conditions are heat treatment at 120–180 °C for 1–12 h.
[0015] Method 3: Coating starch with epoxy resin or polyurethane resin. The method involves uniformly mixing starch with epoxy resin or polyurethane main agent, then uniformly mixing with epoxy resin curing agent or polyurethane curing agent, and heating to cure, thereby obtaining a hard carbon precursor material. The ratio of starch, epoxy resin or polyurethane main agent, and epoxy resin or polyurethane curing agent is 10 g: 2–10 g: 2–10 g. The mixing method is thorough stirring or ball milling. The curing conditions are treatment at 80–150 °C for 1–12 h.
[0016] The present invention also provides starch-based hard carbon materials prepared by the above preparation method.
[0017] The present invention also provides a sodium-ion battery negative electrode comprising the above-mentioned starch-based hard carbon material.
[0018] The present invention also provides a sodium-ion battery comprising the above-described negative electrode.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] This invention provides a method for preparing starch-based hard carbon materials. This method involves coating the surface of starch with a thermosetting resin. The thermosetting resin's thermal stability and physical insulating properties during carbonization effectively prevent direct contact and melting between starch particles, thereby suppressing foaming and expansion during carbonization. The preparation method is simple, operates under mild conditions, requires no complex post-processing, and is suitable for large-scale production. Furthermore, the starch-based hard carbon material prepared by this method exhibits high specific capacity and initial coulombic efficiency when applied to the anode of sodium-ion batteries, demonstrating promising application prospects. Attached Figure Description
[0021] Figure 1 Photographs of the hard carbon materials prepared in Comparative Examples 1-3 and Examples 1-8 are shown. a, b, c, d, e, f, g, h, i, j, and k correspond to the hard carbon materials in Comparative Examples 1-3 and Examples 1-8, respectively.
[0022] Figure 2 The first charge-discharge curves of the hard carbon materials prepared in Examples 1-3, Example 6 and Comparative Example 1 in a half-cell are shown, with the test current being 20 mA / g.
[0023] Figure 3 The data represent the rate performance test data of the hard carbon materials prepared in Examples 1-3, Example 6 and Comparative Example 1 at different currents in half-cells. Detailed Implementation
[0024] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.
[0025] The starches described in this invention include corn starch, potato starch, wheat starch, cassava starch, rice starch, mung bean starch, and sweet potato starch, among others. Soluble starches are preferred.
[0026] In the following embodiments, soluble starch (CAS No.: 9005-84-9, melting point 256-258 °C) was specifically used.
[0027] Example 1:
[0028] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0029] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 250 mL of deionized water and stir until homogeneous. Add 1 g of resorcinol and 1.4 mL of a 37% (w / w) formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0030] S2. Add 0.5 mL of 28% ammonia water to the above mixed liquid, stir continuously, react for 24 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0031] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 1.
[0032] Example 2:
[0033] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0034] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 250 mL of deionized water and stir until homogeneous. Add 3 g of resorcinol and 4.2 mL of a 37% (w / w) formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0035] S2. Add 0.5 mL of 28% ammonia water to the above mixed liquid, stir continuously, react for 36 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0036] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 2.
[0037] Example 3:
[0038] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0039] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 250 mL of deionized water and stir until homogeneous. Add 10 g of resorcinol and 14 mL of a 37% (w / w) formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0040] S2. Add 0.5 mL of 28% by mass to the above mixed liquid, stir continuously, react for 18 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0041] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 4 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 3.
[0042] Example 4:
[0043] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0044] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 750 mL of deionized water and stir until homogeneous. Add 3 g of resorcinol and 4.2 mL of a 37% (w / w) formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0045] S2. Add 2 mL of 28% ammonia water to the above mixed liquid, stir continuously, react for 12 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0046] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1200 °C for 4 hours under an argon atmosphere with a heating rate of 2 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 4.
[0047] Example 5:
[0048] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0049] S1. Disperse 10 g of starch in a mixture of 67 mL of ethanol and 33 mL of deionized water and stir until homogeneous. Add 3 g of resorcinol and 4.2 mL of 37% formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0050] S2. Add 0.5 mL of 28% ammonia water to the above mixed liquid, stir continuously, react for 8 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0051] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1400 °C for 1 h in an argon atmosphere with a heating rate of 4 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 5.
[0052] Example 6:
[0053] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0054] S1. Mix 10 g of starch with 1 g of linear phenolic resin containing 10% hexamethylenetetramine and grind for 30 min to make the two evenly mixed and obtain a uniform solid powder.
[0055] S2. The above solid powder is placed in a nitrogen atmosphere and treated at 130 °C for 2 h, then heated to 170 °C and treated for 2 h to obtain hard carbon precursor material.
[0056] S3. The above precursor material was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under a nitrogen atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 6.
[0057] Example 7:
[0058] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0059] S1. Disperse 10 g of starch in 0.5 g of 10% ethanol solution of methyl phenolic resin and stir until homogeneous to obtain a uniform mixed liquid.
[0060] S2. Place the mixed liquid on a 40 ℃ heating plate and stir to evaporate the solvent. Grind to obtain a uniform solid powder.
[0061] S3. Place the above solid powder in an argon atmosphere and treat it at 170 °C for 2 h to obtain hard carbon precursor material.
[0062] S4. The above precursor material was placed in an alumina crucible and carbonized at 1200 °C for 1 h under a nitrogen atmosphere with a heating rate of 6 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 7.
[0063] Example 8:
[0064] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0065] S1. Mix 10 g of starch with 10 g of linear phenolic resin containing 10% hexamethylenetetramine, and ball mill at 200 r / min for 2 h to make the solids uniformly mixed and obtain a homogeneous solid powder.
[0066] S2. The above solid powder is placed in an argon atmosphere and treated at 130 °C for 12 h to obtain hard carbon precursor material.
[0067] S3. The above precursor material was placed in an alumina crucible and carbonized at 1400 °C for 1 h in an argon atmosphere with a heating rate of 3 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 8.
[0068] Example 9:
[0069] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0070] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 250 mL of deionized water and stir until homogeneous. Add 3 g of m-aminophenol and 4.2 mL of 37% formaldehyde aqueous solution and stir until homogeneous milky white liquid is obtained.
[0071] S2. Add 0.5 mL of 28% ammonia water to the above mixed liquid, stir continuously, react for 36 h, filter, wash with deionized water and ethanol, and dry to obtain hard carbon precursor.
[0072] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 9.
[0073] Example 10:
[0074] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0075] S1. Mix 10 g of starch with 3 g of epoxy resin base and stir until homogeneous. Add 3 g of epoxy resin curing agent and stir thoroughly to obtain the final mixture.
[0076] S2. The above mixture is placed in an 80 ℃ oven and cured for 12 h to obtain a hard carbon precursor.
[0077] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 10.
[0078] Example 11:
[0079] This embodiment prepares a hard carbon anode material, and the steps are as follows:
[0080] S1. Mix 10 g of starch with 3 g of polyurethane resin base and stir until homogeneous. Add 3 g of polyurethane resin curing agent and stir thoroughly to obtain the mixture.
[0081] S2. The above mixture is placed in an oven at 120 °C and cured for 10 h to obtain a hard carbon precursor.
[0082] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Example 11.
[0083] Comparative Example 1:
[0084] This comparative example prepares a hard carbon anode material, which differs from Example 1 in that it does not undergo resin coating. The preparation steps are as follows:
[0085] S1. Place 10 g of starch in an alumina crucible and carbonize it at 1300 °C for 2 h under an argon atmosphere with a heating rate of 5 °C / min. Then, allow it to cool naturally to room temperature to obtain the hard carbon material of Comparative Example 1.
[0086] Comparative Example 2:
[0087] This comparative example prepares a hard carbon anode material. The difference from Example 1 is that resorcinol-formaldehyde resin is not added. The preparation steps are as follows:
[0088] S1. Disperse 10 g of starch in a mixture of 250 mL of ethanol and 250 mL of deionized water, and stir until homogeneous. A uniform milky white mixture is obtained.
[0089] S2. The above mixed liquid is continuously stirred for 24 h, filtered, washed with deionized water and ethanol, and dried to obtain the hard carbon precursor.
[0090] S3. The above-mentioned hard carbon precursor was placed in an alumina crucible and carbonized at 1300 °C for 2 hours under an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Comparative Example 2.
[0091] Comparative Example 3:
[0092] This comparative example prepares a hard carbon anode material, which differs from Example 7 in that no resin is added. The preparation steps are as follows:
[0093] S1. Disperse 10 g of starch in 10 g of ethanol solution and stir until homogeneous to obtain a uniform mixed liquid.
[0094] S2. Place the mixed liquid on a 40 ℃ heating plate and stir to evaporate the solvent. Obtain the hard carbon precursor material.
[0095] S3. The above precursor material was placed in an alumina crucible and carbonized at 1300 °C for 2 hours in an argon atmosphere with a heating rate of 5 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Comparative Example 3.
[0096] Comparative Example 4:
[0097] This comparative example prepares a hard carbon anode material, which differs from Example 8 in that no resin is added. The preparation steps are as follows:
[0098] S1. 10 g of starch was ball-milled at 200 r / min for 2 h to obtain hard carbon precursor material.
[0099] S2. The above precursor material was placed in an alumina crucible and carbonized at 1400 °C for 1 h in an argon atmosphere with a heating rate of 3 °C / min. Then it was naturally cooled to room temperature to obtain the hard carbon material of Comparative Example 4.
[0100] Appendix Figure 1 The images show actual photos of the hard carbon materials prepared in Comparative Examples 1-3 and Examples 1-8 after carbonization. The hard carbon materials prepared in Comparative Examples 1-3 all exhibited significant foaming and expansion, while the foaming and expansion problem during starch carbonization was effectively suppressed in Examples 1-8 after resin coating modification.
[0101] The hard carbon materials obtained in Examples 1-3, Example 6, and Comparative Example 1 were used as active materials and mixed with conductive carbon black and sodium carboxymethyl cellulose at a mass ratio of 90:5:5 to form a slurry. The slurry was then uniformly coated onto a copper foil current collector, dried, and cut to obtain a circular negative electrode sheet for a sodium-ion battery. In an argon-filled glove box (with water and oxygen contents both below 0.1 ppm), a half-cell was assembled using the aforementioned negative electrode sheet as the working electrode, a sodium metal sheet as the counter electrode, glass fiber as the separator, and a 1 M NaPF6 ether solution as the electrolyte for sodium storage performance testing.
[0102] Table 1. First-cycle performance test results of half-cells assembled from hard carbon materials.
[0103]
[0104] Figure 2 The first charge-discharge curves of each sample at a current density of 20 mA / g are shown in Table 1. The corresponding charge-discharge specific capacity and first coulombic efficiency are summarized in Table 1. Figure 3 The results show the rate performance test results for each sample. The test data indicate that, compared with Comparative Example 1, the hard carbon materials prepared in Examples 1-3 and Example 6 all exhibit higher specific capacity, higher initial coulombic efficiency, and superior rate performance.
[0105] In summary, the method for preparing starch-based hard carbon materials provided by this invention can effectively solve the foaming and expansion problem in the direct carbonization process of starch under mild conditions. On the other hand, when the hard carbon material prepared by this method is applied to the anode of sodium-ion batteries, it can simultaneously improve the battery's initial coulombic efficiency, specific capacity, and rate performance, showing good application prospects.
[0106] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.
Claims
1. A method for preparing a starch-based hard carbon material, characterized in that, Includes the following steps: Starch is coated with a coating agent to obtain a hard carbon precursor material; the hard carbon precursor material is subjected to high-temperature carbonization treatment under an inert atmosphere to obtain a starch-based hard carbon material, wherein the coating agent is a thermosetting resin.
2. The preparation method according to claim 1, characterized in that, The curing temperature of the thermosetting resin is below 185°C.
3. The preparation method according to claim 1, characterized in that, The thermosetting resin is one or more of the following: resorcinol-formaldehyde resin, aminophenol-formaldehyde resin, linear phenolic resin, methyl phenolic resin, epoxy resin, and polyurethane resin.
4. The preparation method according to claim 1, characterized in that, The high-temperature carbonization treatment is carried out at a temperature of 1200 ℃ to 1400 ℃, with a holding time of 1 to 4 h and a heating rate of 2 to 5 ℃ / min.
5. The preparation method according to claim 3, characterized in that, When the coating agent is resorcinol-formaldehyde resin or aminophenol-formaldehyde resin, the coating method is as follows: starch, resorcinol or aminophenol, and formaldehyde are dispersed in a mixed solution of water and ethanol, ammonia is added, and the mixture is stirred continuously. Then, the mixture is filtered, washed, and dried to obtain a hard carbon precursor material. The volume ratio of water to ethanol in the mixed solution is 1:0.4 to 1:2, and the ratio of starch, resorcinol or aminophenol, formaldehyde, the mixed solution of water and ethanol, and ammonia is 10 g: 1 to 10 g: 13 mmol to 130 mmol: 100 mL to 1000 mL: 8 mmol to 32 mmol. The reaction time is 8 to 36 h.
6. The preparation method according to claim 3, characterized in that, When the coating agent is a methyl phenolic resin or a linear phenolic resin, the coating method is to mix starch with a methyl phenolic resin or a linear phenolic resin containing 10% hexamethylenetetramine, and then heat and cure it to obtain a hard carbon precursor material. The mixing method is to grind or ball mill, disperse in ethanol, and then evaporate one or more of the solvents. The ratio of starch, methyl phenolic resin, or linear phenolic resin containing 10% hexamethylenetetramine is 10 g: 0.5-10 g. The curing conditions are heat treatment at 120-180 °C for 1-12 h.
7. The preparation method according to claim 3, characterized in that, When the coating agent is epoxy resin or polyurethane resin, the method is as follows: starch is mixed evenly with epoxy resin main agent or polyurethane main agent, and then mixed evenly with epoxy resin curing agent or polyurethane curing agent, and heated to cure to obtain hard carbon precursor material. The ratio of starch, epoxy resin main agent or polyurethane main agent, epoxy resin curing agent or polyurethane curing agent is 10 g: 1~10 g: 1~10 g. The mixing method is thorough stirring or ball milling. The curing conditions are treatment at 80~150 ℃ for 1~12 h.
8. The starch-based hard carbon material prepared by the preparation method according to any one of claims 1 to 7.
9. A sodium-ion battery negative electrode, characterized in that, It includes the starch-based hard carbon material as described in claim 8.
10. A sodium-ion battery, characterized in that, It includes the sodium-ion battery negative electrode as described in claim 9.