Low-temperature hard carbon, preparation method thereof and sodium ion battery
Low-temperature hard carbon was prepared by combining phenolic resin with honeycomb briquettes. The addition of block copolymers and nitrogen sources solved the problems of low initial coulombic efficiency and metal salt residue in hard carbon materials, improved the low-temperature and high-temperature performance of sodium-ion batteries, simplified the production process, and reduced costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHUANGDENG GRP CO LTD
- Filing Date
- 2026-01-23
- Publication Date
- 2026-05-12
AI Technical Summary
Existing hard carbon materials in sodium-ion batteries suffer from low initial coulombic efficiency, excessive porosity leading to large irreversible losses, and the tendency to leave residues when modified with metal salts, which can affect battery performance.
Low-temperature hard carbon was prepared by combining phenolic resin with honeycomb briquettes and through cross-linking and carbonization treatment. Block copolymers and nitrogen sources were added to form a stable porous structure, avoid metal ion residue, and improve conductivity and pore structure.
It improves the cycle stability of sodium-ion batteries at low and high temperatures, enhances the ability of sodium ions to insert and extract, improves the kinetic and electrical performance of the batteries, simplifies the manufacturing process, and reduces costs.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion batteries, and more particularly to a low-temperature hard carbon, its preparation method, and a sodium-ion battery. Background Technology
[0002] Winter temperatures are widespread, posing a significant challenge to charging backup batteries in communication base stations located in cold regions. Current methods, such as installing air conditioning in equipment rooms, adding heating equipment, or burying batteries underground, aim to ensure charging. However, these methods still offer poor insulation, greatly reducing battery life and impacting the operation of base stations in cold areas. Therefore, developing batteries with low-temperature charging capabilities is of great importance.
[0003] Compared to lithium-ion batteries, sodium-ion batteries exhibit superior low-temperature performance, capable of charging below 0°C, giving them a competitive edge in low-temperature applications. Hard carbon materials are commonly used for the anodes of sodium-ion batteries. However, conventional hard carbon suffers from low initial coulombic efficiency due to excessive surface defects and porosity. This leads to significant irreversible sodium ion loss during the initial charge-discharge cycle, resulting in reduced battery capacity and energy density. Furthermore, the capacity of hard carbon materials is composed of a plateau region and a ramp region; an imbalance in the capacity ratio between these two regions can also degrade battery kinetics. While some researchers have modified hard carbon by adding metal salts, insufficient or mismatched acid pickling processes can lead to residual metal ions, affecting the formation of the hard carbon material's pore structure and ultimately impacting the battery's electrical performance. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-temperature hard carbon, its preparation method, and a sodium-ion battery.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] The first aspect of this invention is to provide a method for preparing low-temperature hard carbon, comprising the steps of:
[0007] S1. The pretreated honeycomb briquettes and thermosetting phenolic resin powder are mixed and dispersed in ethanol, stirred evenly, and then block copolymers and nitrogen sources are added. After stirring again, the mixture is subjected to filtration, washing and drying in sequence to obtain the composite material.
[0008] S2. The composite material is subjected to crosslinking treatment, carbonization treatment, grinding treatment and cleaning treatment in sequence to obtain the low temperature hard carbon.
[0009] Preferably, in step S1, the pretreatment of the honeycomb briquettes includes: grinding the honeycomb briquettes into powder with a particle size of less than 200 μm, adding them to a compound acid for acid washing for 4-6 hours, adding sodium hydroxide to adjust the pH to neutral, then filtration, washing the product with deionized water and filtration again, washing the product with deionized water three times and filtration again to obtain the filter material, and placing the filter material in an oven to bake for 10-12 hours to obtain the pretreated honeycomb briquettes.
[0010] More preferably, the composite acid includes two of sulfuric acid, hydrochloric acid, hydrofluoric acid, and nitric acid, with a volume ratio of (2:8) to (8:2); the injection rate of the honeycomb briquettes into the composite acid is 30-100 mg / min.
[0011] Preferably, in step S1, the particle size of the thermosetting phenolic resin powder is less than 200 μm.
[0012] Preferably, in step S1, the mass ratio of the honeycomb briquettes to the thermosetting phenolic resin powder is (2:8)-(5:5).
[0013] Preferably, in step S1, the block copolymer comprises: PEO 100 -PPO 65 -PEO 100 PEO 20 -PPO 70 -PEO 20 PEO 141 -PPO 44 -PEO 141 At least one of PMMA-PEO; the nitrogen source includes at least one of polyaniline, ammonium nitrate, urea, and amino acids.
[0014] Preferably, in step S1, the washing process includes: washing with deionized water and ethanol alternately.
[0015] Preferably, in step S2, the crosslinking treatment is carried out at a temperature of 300-400℃ for 3-5 hours; the carbonization treatment includes: heating to 1000-1500℃ at a rate of 5℃ / min for 2-4 hours, and then naturally cooling to room temperature under an argon atmosphere.
[0016] A second aspect of the present invention is to provide a low-temperature hard carbon, which is prepared by the above-described preparation method.
[0017] A third aspect of the present invention is to provide a sodium-ion battery, prepared from low-temperature hard carbon obtained by the above-described preparation method, the steps of which include:
[0018] A1. A negative electrode slurry is prepared by mixing low-temperature hard carbon, conductive agent, binder and solvent in a certain mass ratio. After coating, rolling and punching, a negative electrode sheet is obtained.
[0019] A2. A positive electrode slurry is prepared by mixing layered oxide, conductive agent, binder and solvent in a certain mass ratio. After coating, rolling and punching, a positive electrode sheet is obtained.
[0020] A3. After assembling the positive electrode, separator, and negative electrode, a sodium-ion battery is obtained through liquid injection, formation, capacity testing, and aging.
[0021] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:
[0022] 1. This invention uses a composite of phenolic resin precursor and honeycomb briquette precursor to produce hard carbon. The phenolic resin provides the framework structure, suppressing the dense structure of the hard carbon material obtained from honeycomb briquette. This results in a high-performance hard carbon material with good interlayer spacing and a porous structure, providing more sodium storage sites. The combination of phenolic resin and honeycomb briquette in the preparation of hard carbon material stabilizes the framework structure and controls the porous structure of the hard carbon material through the inherent structures of the two materials. This avoids the method of adding metal ions dispersed in the carbon material structure and then removing the metal ions through acid washing to form a porous structure. This method achieves the effect of controlling the stability of the framework structure and the porous structure of the hard carbon material without using metal ions, effectively reducing the use of additives, simplifying the hard carbon production process, and lowering costs. Simultaneously, the phenolic resin provides oxygen to the hard carbon and the honeycomb briquette provides sulfur, eliminating the need to supplement oxygen and sulfur through additives, thus simplifying the production process as well.
[0023] 2. Adding a nitrogen source to hard carbon materials, along with oxygen from phenolic resin and sulfur from honeycomb briquettes, provides active sites and effectively improves the conductivity of hard carbon materials. Adding block copolymers to hard carbon acts as a template, regulating the pore structure and forming mesopores to increase the specific surface area and defect sites, effectively enhancing the ramp capacity and kinetic performance of the hard carbon material. This significantly improves the sodium ion insertion and extraction capabilities at low temperatures, improving the low-temperature performance of sodium-ion batteries. Simultaneously, the formation of closed pores regulates the plateau capacity, increasing both the ramp and plateau capacities. The closed-pore structure effectively suppresses electrolyte decomposition at high temperatures, improving the high-temperature performance of sodium-ion batteries. Furthermore, its steric hindrance effectively improves the interlayer spacing of hard carbon, promoting sodium ion insertion and extraction, thus also improving the low-temperature performance of sodium-ion batteries. This results in good cycle stability for sodium-ion batteries in both low and high-temperature environments. Compared to other batteries where improving low-temperature performance sacrifices high-temperature performance, this effectively increases the market competitiveness of sodium-ion batteries. Detailed Implementation
[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.
[0026] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.
[0027] Example 1
[0028] This embodiment provides a method for preparing low-temperature hard carbon, the steps of which include:
[0029] S1. The pretreated honeycomb briquettes and thermosetting phenolic resin powder are mixed and dispersed in ethanol at a mass ratio of 5:5, and magnetically stirred for 2 hours before adding PEO. 100 -PPO 65 -PEO 100 The mixture was stirred again for 4 hours and then filtered. After filtration, it was washed with deionized water and ethanol alternately and filtered again to obtain the composite material. The composite material was then baked in an oven for 10 hours to obtain the composite material.
[0030] The pretreatment of the honeycomb briquettes includes: grinding the honeycomb briquettes into powder with a particle size of 100 μm; adding the honeycomb briquette powder to a compound acid (sulfuric acid: nitric acid = 4:6) at an injection rate of 60 mg / min for acid washing; stirring for 6 hours; adding sodium hydroxide to adjust the pH value to neutral; filtration; washing with deionized water; filtration again; washing three times; and obtaining the filter material; baking the filter material in an oven for 12 hours to obtain dried honeycomb briquette powder; the thermosetting phenolic resin powder has a particle size of 100 μm.
[0031] S2. The composite material is heated at 400°C for 3 hours to crosslink the phenolic resin with the honeycomb briquettes. Then, under an argon atmosphere, the temperature is increased to 1200°C at a rate of 5°C / min for 2 hours to carbonize the composite material and then naturally cooled to room temperature. After grinding and sieving, the composite material is acid-washed and then washed with deionized water until neutral to obtain the low-temperature hard carbon.
[0032] Example 2
[0033] This embodiment provides another method for preparing low-temperature hard carbon, the steps of which include:
[0034] S1. The pretreated honeycomb briquettes and thermosetting phenolic resin powder were mixed and dispersed in ethanol at a mass ratio of 5:5. After magnetic stirring for 3 hours, PMMA-PEO and ammonium nitrate were added. After stirring for another 4 hours, the mixture was filtered. After filtration, the mixture was washed with deionized water and ethanol alternately and filtered again to obtain the composite material. The composite material was then baked in an oven for 12 hours.
[0035] The pretreatment of the honeycomb briquettes includes: grinding the honeycomb briquettes into powder with a particle size of 150 μm; adding the honeycomb briquette powder to a compound acid (sulfuric acid: nitric acid = 4:6) at an injection rate of 50 mg / min for acid washing; stirring for 5 h; adding sodium hydroxide to adjust the pH value to neutral; filtration; washing with deionized water; filtration again; washing three times; and obtaining the filter material; baking the filter material in an oven for 10 h to obtain dried honeycomb briquette powder; the thermosetting phenolic resin powder has a particle size of 100 μm.
[0036] S2. The composite material is heated at 300°C for 3 hours to crosslink the phenolic resin with the honeycomb briquettes. Then, under an argon atmosphere, the temperature is increased to 1100°C at a rate of 5°C / min for 3 hours and then naturally cooled to room temperature. After grinding and sieving, the material is acid-washed and then cleaned with deionized water until neutral to obtain the low-temperature hard carbon.
[0037] Comparative Example 1
[0038] This comparative example provides a method for preparing hard carbon, which uses only honeycomb briquettes to make hard carbon, without adding block copolymers or nitrogen sources, and is otherwise the same as in Example 1.
[0039] Comparative Example 2
[0040] This comparative example provides another method for preparing hard carbon, which uses only phenolic resin to make hard carbon without adding block copolymers and nitrogen sources, and is otherwise the same as in Example 2.
[0041] Comparative Example 3
[0042] This comparative example provides a method for preparing hard carbon, which uses honeycomb briquettes and phenolic resin to make hard carbon, adds metal salts, and does not add block copolymers or nitrogen sources. The rest is the same as in Example 2.
[0043] Detection Examples
[0044] Sodium-ion batteries were prepared using hard carbon from Examples 1-2 and Comparative Examples 1-3, respectively, and the performance of the sodium-ion batteries was tested. The results are shown in Table 1.
[0045] Table 1
[0046]
[0047] According to the test data, using Examples 1 and 2 can effectively improve the kinetic performance of sodium-ion batteries. The batteries exhibit good low-temperature performance, and while ensuring low-temperature performance, the room-temperature and high-temperature performance of the batteries are not affected.
[0048] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.
Claims
1. A method for preparing low-temperature hard carbon, characterized in that the steps include... include: S1. The pretreated honeycomb briquettes and thermosetting phenolic resin powder are mixed and dispersed in ethanol, stirred evenly, and then block copolymers and nitrogen sources are added. After stirring again, the mixture is subjected to filtration, washing and drying in sequence to obtain the composite material. S2. The composite material is subjected to crosslinking treatment, carbonization treatment, grinding treatment and cleaning treatment in sequence to obtain the low temperature hard carbon.
2. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment of the honeycomb briquettes includes: grinding the honeycomb briquettes into powder with a particle size of less than 200 μm, adding them to a compound acid for acid washing for 4-6 hours, adding sodium hydroxide to adjust the pH to neutral, and then filtration. The product is then washed with deionized water and filtered again. The product is washed three more times with deionized water and then filtered again to obtain the filter material. The filter material is then placed in an oven and baked for 10-12 hours to obtain the pretreated honeycomb briquettes.
3. The preparation method according to claim 2, characterized in that, The composite acid includes two of sulfuric acid, hydrochloric acid, hydrofluoric acid, and nitric acid, with a volume ratio of (2:8) to (8:2); the injection rate of the honeycomb briquettes into the composite acid is 30-100 mg / min.
4. The preparation method according to claim 1, characterized in that, In step S1, the particle size of the thermosetting phenolic resin powder is less than 200 μm.
5. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the honeycomb briquettes to the thermosetting phenolic resin powder is (2:8)-(5:5).
6. The preparation method according to claim 1, characterized in that, In step S1, the block copolymer comprises: PEO 100 -PPO 65 -PEO 100 PEO 20 -PPO 70 -PEO 20 PEO 141 -PPO 44 -PEO 141 At least one of PMMA-PEO; the nitrogen source includes at least one of polyaniline, ammonium nitrate, urea, and amino acids.
7. The preparation method according to claim 1, characterized in that, In step S1, the washing process includes: washing with deionized water and ethanol alternately.
8. The preparation method according to claim 1, characterized in that, In step S2, the crosslinking treatment is carried out at a temperature of 300-400℃ for 3-5 hours; the carbonization treatment includes: heating to 1000-1500℃ at a rate of 5℃ / min for 2-4 hours, and then naturally cooling to room temperature under an argon atmosphere.
9. A low-temperature hard carbon, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. A sodium-ion battery, characterized in that, The low-temperature hard carbon is prepared by the preparation method according to any one of claims 1-8, the steps of which include: A1. A negative electrode slurry is prepared by mixing low-temperature hard carbon, conductive agent, binder and solvent in a certain mass ratio. After coating, rolling and punching, a negative electrode sheet is obtained. A2. A positive electrode slurry is prepared by mixing layered oxide, conductive agent, binder and solvent in a certain mass ratio. After coating, rolling and punching, a positive electrode sheet is obtained. A3. After assembling the positive electrode, separator, and negative electrode, sodium-ion batteries are produced through liquid injection, formation, capacity testing, and aging.