Preparation method and application of sodium ion battery hard carbon negative electrode material with confinement structure
By constructing a metal inorganic shell on the surface of the hard carbon precursor ball and adjusting the pore structure, a hard carbon anode material with a limited domain structure is formed, which solves the problem of insufficient rate performance and cycle stability of the existing hard carbon anode material, and achieves high specific capacity and stable electrochemical performance.
Patent Information
- Application Number
- CN202510249427.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-04
- Publication Date
- 2025-05-23
AI Technical Summary
The existing hard carbon anode materials have shortcomings in rate performance and cycle stability, and it is difficult to satisfy the specific capacity and cycle performance under high current density.
The domain-limited structure design is adopted to form a hard carbon negative electrode material by constructing a metal inorganic shell on the surface of the hard carbon precursor sphere, and adjusting the pore structure and graphitization degree during the carbonization process.
It improves the specific capacity and circulation performance of hard carbon negative electrode materials, significantly improves the rate performance and stability, and is suitable for efficient energy storage applications of sodium ion batteries.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a preparation method and application of a hard carbon negative electrode material for a sodium ion battery with a confined structure. Background Art
[0002] Lithium-ion batteries dominate the global new energy battery market with their high energy density, high voltage, long cycle stability and mature technology. However, due to the limited reserves of lithium resources in the earth's crust, the continuous consumption of lithium-ion batteries has led to an increasing shortage of lithium resources, so the development of new energy storage batteries has become particularly important. Sodium-ion batteries are considered to be an effective supplement to lithium-ion batteries due to their abundant sodium resources, low cost and similar working principles to lithium-ion batteries, and are expected to become a new energy storage carrier.
[0003] In sodium-ion batteries, electrode materials are the most important factor in determining the performance indicators of sodium-ion batteries. Carbon-based materials are generally considered to be the most ideal negative electrode materials for sodium-ion batteries due to their wide sources and low costs. In particular, hard carbon materials, with their unique microscopic morphology and stable electrochemical properties, are expected to dominate the negative electrode materials of industrial sodium-ion batteries. However, hard carbon negative electrode materials currently still have problems in terms of rate performance and cycle stability. To address these problems, common optimization methods mainly focus on ion doping, pore structure design, and surface coating. For example, Hu et al. used ethanol as a pore-forming agent to solidify liquid phenolic resin by a solvothermal method. Ethanol was used as a steam generator to induce the formation of pores between the cross-linked matrix, and then constructed a pore with a capacity of 284 mAh g after high-temperature carbonization. -1 Closed-pore-rich hard carbon anode with high platform capacity (Meng, QS; Lu, YX; Ding, Fx; Zhang, QQ; Chen, Li.Q.; Hu, Y.Sh. ACS. Energy. Lett. 2019, 4, 11.). Xiong et al. introduced steric hindrance groups containing aromatic rings into the phenolic resin precursor to promote the formation of closed pores in the final HC anode. The prepared HC anode can show 340.3 mAh g -1 The enhanced capacity of hard carbon can be achieved by using surface coating strategies to construct a new interface layer to reduce the irreversible decomposition of the electrolyte. For example, Ma et al. precisely designed a HC negative electrode with rich closed pores and a nanoscale soft carbon coating by cross-linking asphalt with phenolic resin, with a capacity of 359.8 mAh g-1 (Sun, D.; Zhao, L.; Sun, PL; Zhao, K.; Sun, YK; Zhang, Q; Li, Z. Ch.; Ma, ZH; Zheng, F. Zh.; Yang Y.; Lu, Ch. B.; Peng, Ch.; Xu, Ch. M.; Xiao, Zh. H.; Ma, XLAdv. Funct. Mater. 2024, 34, 40). Although these optimization methods have achieved excellent results, these methods can often only improve a single property of the hard carbon negative electrode. For example, the closed-pore structure design can promote the improvement of sodium storage capacity and first coulomb efficiency, but the introduction of closed pores is complicated and environmentally polluting; the construction of coating structure can alleviate the decomposition of electrolyte and optimize the electrode-electrolyte interface, but due to the poor conductivity and electrochemical activity of the deposited coating layer, the rate performance and cycle performance of the battery are still not ideal. In general, the effects that these modification methods can achieve are often relatively simple, and at high current density, the modified hard carbon is still not satisfactory in terms of specific capacity and cycle performance.
[0004] Therefore, it is necessary to develop new strategies to simultaneously promote the improvement of hard carbon rate performance and cycle performance. Summary of the invention
[0005] The purpose of the present invention is to provide a method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery, so as to simultaneously solve the problems of poor rate performance and unstable cycle of the hard carbon negative electrode in the prior art.
[0006] In order to achieve the purpose, the present invention adopts the following technical scheme:
[0007] A method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery comprises the following steps:
[0008] Step 1, mixing ammonia water, anhydrous ethanol and deionized water and stirring evenly to obtain a mixture A; adding a carbon source to the mixture A, stirring and dispersing evenly to obtain a mixture B; mixing a cationic surfactant and deionized water and stirring evenly to obtain a mixture C;
[0009] Step 2, adding mixture C to mixture B and stirring evenly to obtain mixture D; then adding a coating agent to mixture D and stirring to obtain mixture E; centrifuging and washing mixture E, obtaining a solid phase and vacuum drying to obtain a hard carbon precursor;
[0010] Step 3: Carbonizing the hard carbon precursor under the protection of an inert atmosphere to obtain a hard carbon negative electrode material for a confined structure sodium ion battery.
[0011] Preferably, the carbon source is selected from at least one of phenolic resin balls and small molecule sugar hydrothermal carbon balls, and the most preferred is phenolic resin balls. The abundant hydroxyl functional groups on the surface of phenolic resin balls and small molecule sugar hydrothermal carbon balls can be effectively combined with surfactants.
[0012] Preferably, in step 1, the cationic surfactant is at least one of quaternary ammonium salt cationic surfactants. The surfactant is used to improve the electrical properties of the surface of the phenolic resin sphere or the small molecule sugar hydrothermal carbon sphere, which can promote its combination with the coating agent.
[0013] Preferably, in step 2, the coating agent is at least one of tetraethyl orthosilicate, tetraisopropyl titanate and aluminum isopropoxide. The coating agent selected in the present invention is hydrolyzed in the system to form a coating layer on the surface of the carbon source as a confined structure.
[0014] Preferably, the volume ratio of ammonia water, anhydrous ethanol and deionized water in the mixture A is 1:40-120:160-220, the concentration of the carbon source in the mixture B is 2g / 200-340mL; the concentration of the cationic surfactant in the mixture C is 1.0-1.5g / 40-50mL. The mass ratio of the carbon source to the cationic surfactant in the mixture D is 2:1.0-1.5. The mass ratio of the coating agent to the carbon source in the mixture E is 0.6-1.9:1.
[0015] Preferably, in step 3, the conditions for the carbonization treatment are: temperature of 900-1300°C, holding time of 1-3h, gas flow rate of 150-200mL / min, and heating rate of 1-5°C / min.
[0016] The present invention further provides a sodium ion battery, which comprises a negative electrode made from the above-mentioned hard carbon negative electrode material.
[0017] The beneficial effects of the present invention are embodied in:
[0018] The present invention uses phenolic resin balls or small molecule sugar hydrothermal carbon balls as a carbon source, constructs a metal inorganic shell on its surface to form a confined structure design, and carbonizes under the protection of an inert atmosphere to obtain a confined structure hard carbon negative electrode material. The confined structure design provided in the present invention improves the specific capacity of the hard carbon negative electrode material by adjusting the pore structure and graphitization degree of the hard carbon precursor during the carbonization process. In addition, the shell layer used as the confined structure design not only serves as a buffer structure to improve the stability of the hard carbon structure, but also promotes the decomposition of the electrolyte into an electrolyte interface layer rich in inorganic substances, thereby improving the cycle performance of the hard carbon negative electrode material. The hard carbon negative electrode material of the present invention has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1This is a SEM image of the hard carbon precursor obtained in Example 1 of the present invention.
[0020] Figure 2 This is a TEM image of the confined structure hard carbon material obtained in Example 1 of the present invention.
[0021] Figure 3 The confined structure hard carbon material (CRF-SiO 2 ) is a comparison chart of the pore size distribution of the hard carbon material (CRF) obtained in Example 3.
[0022] Figure 4 The confined structure hard carbon material (CRF-SiO 2 ) and Raman comparison of the hard carbon material (CRF) obtained in Comparative Example 3.
[0023] Figure 5 The confined structure hard carbon material (CRF-SiO 2 ) and the hard carbon material (CRF) obtained in Comparative Example 3 at 0.5Ag -1 Charge and discharge cycle diagram at different rates.
[0024] Figure 6 The confined structure hard carbon material (CRF-SiO 2 ) and the rate performance diagram of the hard carbon material (CRF) obtained in comparative example 3.
[0025] Figure 7 This is a TEM image of the solid electrolyte interface layer formed after activation of the confined structure hard carbon material obtained in Example 1 of the present invention. DETAILED DESCRIPTION
[0026] The present invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the embodiments of the present invention are not limited thereto.
[0027] Example 1
[0028] Step 1. Add 1.2 mL of ammonia water (mass concentration of 28%), 96 mL of anhydrous ethanol, and 240 mL of deionized water into a beaker, stir evenly to obtain a mixture A; then add 2 g of phenolic resin balls (solid, particle size of 700-800 nm) to the mixture A, stir and disperse at 30° C. for 24 h to obtain a mixture B; add 1.44 g of hexadecyltrimethylammonium bromide and 45 mL of deionized water into another beaker, stir for 30 min, and obtain a mixture C.
[0029] Step 2: Add mixture C to mixture B and stir for 30 minutes to obtain mixture D; then add 2.5 g of tetraethyl orthosilicate to mixture D and stir for 16 hours to obtain mixture E; wash mixture E with deionized water and ethanol three times by centrifugation respectively, obtain the solid phase and vacuum dry it at 100°C for 12 hours to obtain a hard carbon precursor.
[0030] Step 3: Pour the dried powder into a crucible and transfer it to a tube furnace. In an argon inert atmosphere, the gas flow rate is 200 mL / min, and the temperature is increased to 1100°C at a rate of 2°C / min for 2 h of carbonization. When the tube furnace is cooled to room temperature, a confined hard carbon anode material (denoted as CRF-SiO) is obtained after carbonization. 2 ).
[0031] Example 2
[0032] Step 1. Add 1.2 mL of ammonia water (mass concentration of 28%), 96 mL of anhydrous ethanol, and 240 mL of deionized water into a beaker, stir evenly to obtain a mixture A; then add 2 g of phenolic resin balls (solid, particle size of 700-800 nm) to the mixture A, stir and disperse at 30° C. for 24 h to obtain a mixture B; add 1.44 g of hexadecyltrimethylammonium bromide and 45 mL of deionized water into another beaker, stir for 30 min, and obtain a mixture C.
[0033] Step 2: Add mixture C to mixture B and stir for 30 minutes to obtain mixture D; then add 2.5 g of tetraisopropyl titanate to mixture D and stir for 16 hours to obtain mixture E; wash mixture E with deionized water and ethanol three times by centrifugation respectively, obtain the solid phase and vacuum dry it at 100°C for 12 hours to obtain a hard carbon precursor.
[0034] Step 3: Pour the dried powder into a crucible and transfer it to a tubular furnace. In an argon inert atmosphere, the gas flow rate is 200 mL / min, and the temperature is heated to 1100°C at a heating rate of 2°C / min and carbonized for 2 hours. When the tubular furnace is cooled to room temperature, a confined structure hard carbon negative electrode material is obtained after the carbonization is completed.
[0035] Example 3
[0036] Step 1. Add 1.2 mL of ammonia water (mass concentration of 28%), 96 mL of anhydrous ethanol, and 240 mL of deionized water into a beaker, stir evenly to obtain a mixture A; then add 2 g of phenolic resin balls (solid, particle size of 700-800 nm) to the mixture A, stir and disperse at 30° C. for 24 h to obtain a mixture B; add 1.44 g of hexadecyltrimethylammonium bromide and 45 mL of deionized water into another beaker, stir for 30 min, and obtain a mixture C.
[0037] Step 2: Add mixture C to mixture B and stir for 30 minutes to obtain mixture D; then add 2.5 g of aluminum isopropoxide to mixture D and stir for 16 hours to obtain mixture E; wash mixture E with deionized water and ethanol three times by centrifugation respectively, obtain the solid phase and vacuum dry it at 100°C for 12 hours to obtain a hard carbon precursor.
[0038] Step 3: Pour the dried powder into a crucible and transfer it to a tubular furnace. In an argon inert atmosphere, the gas flow rate is 200 mL / min, and the temperature is heated to 1100°C at a heating rate of 2°C / min and carbonized for 2 hours. When the tubular furnace is cooled to room temperature, a confined structure hard carbon negative electrode material is obtained after the carbonization is completed.
[0039] Comparative Example 1
[0040] Compared with Example 1, the "96 mL of anhydrous ethanol, 240 mL of deionized water" in step 1 is adjusted to "48 mL of anhydrous ethanol, 288 mL of deionized water", and the "addition of 2.5 g of tetraethyl orthosilicate" in step 2 is adjusted to "addition of 1.25 g of tetraethyl orthosilicate. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a confined structure hard carbon negative electrode material is obtained.
[0041] Comparative Example 2
[0042] Compared with Example 1, the "96 mL of anhydrous ethanol, 240 mL of deionized water" in step 1 is adjusted to "144 mL of anhydrous ethanol, 192 mL of deionized water", and the "addition of 2.5 g of tetraethyl orthosilicate" in step 2 is adjusted to "addition of 3.75 g of tetraethyl orthosilicate. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a confined structure hard carbon negative electrode material is obtained.
[0043] Comparative Example 3
[0044] Pour phenolic resin balls (solid, particle size 700-800nm) directly into the crucible, transfer to a tubular furnace, and heat to 1100℃ at a heating rate of 2℃ / min under an argon inert atmosphere with a gas flow rate of 200mL / min for carbonization for 2h. Wait until the tubular furnace cools to room temperature and the hard carbon negative electrode material (denoted as CRF) is obtained after the carbonization is completed.
[0045] Figure 1 This is the SEM image of the hard carbon precursor obtained in step 2 of Example 1. Figure 2 This is a TEM image of the confined structure hard carbon material obtained in step 3 of Example 1. From the image, it can be seen that the prepared hard carbon precursor has good dispersion and uniformity, and can still maintain a complete confined structure after high-temperature carbonization.
[0046] Figure 3 The confined structure hard carbon material (CRF-SiO2 ) and the pore size distribution comparison of the hard carbon material (CRF) obtained in comparative example 3. It can be seen that the pore size distribution of the confined structure hard carbon material is richer.
[0047] Figure 4 The confined structure hard carbon material (CRF-SiO 2 ) and the Raman comparison diagram of the hard carbon material (CRF) obtained in Example 3, it can be seen that the ratio of the D2 peak to the G peak of the confined pyrolysis hard carbon material is larger, indicating that the confined structure hard carbon material has more defect structures.
[0048] The negative electrode materials obtained in the above-mentioned embodiments and comparative examples are mixed with carbon black and polyvinylidene fluoride in a ratio of (8:1:1) to form a slurry, coated on a carbon-coated aluminum foil current collector, dried at 80°C for 24 hours, cut into pieces to obtain electrode sheets, and used as working electrodes. In a glove box under an argon atmosphere, a sodium sheet is used as a counter electrode, and a CR2025 button battery is assembled in the order of "negative electrode shell, sodium sheet, glass fiber diaphragm, electrolyte, working electrode, steel sheet, shrapnel, positive electrode shell". The electrolyte used is 1MNaPF 6 DME. After the assembled battery was left to stand for 24 hours, constant current charge and discharge test and rate performance test were performed, with the voltage range of 0.01-2.5V. The electrochemical performance test results are as follows:
[0049] Figure 5 The confined structure hard carbon material (CRF-SiO 2 ) and the hard carbon material (CRF) obtained in Comparative Example 3 at 0.5Ag -1 Charge and discharge cycle diagram at different rates. Figure 6 The confined structure hard carbon material (CRF-SiO 2 ) and the rate performance diagram of the hard carbon material (CRF) obtained in Comparative Example 3. Figure 5 , Figure 6 It can be seen that the confined structure material has excellent cycle stability and rate performance.
[0050] Figure 7 The battery assembled with the confined hard carbon material obtained in Example 1 was -1 TEM image of the solid electrolyte interface layer on the working electrode surface after one cycle of activation at a high rate. It can be seen that the solid electrolyte interface layer of the confined structure material contains a large amount of inorganic components, and the surface confined shell promotes the decomposition of the electrolyte into an inorganic-rich structure, which can improve the cycle performance of the hard carbon negative electrode material.
[0051] The test results of the battery performance assembled in each embodiment and comparative example are shown in Table 1.
[0052] Table 1
[0053]
[0054]
[0055] From the electrochemical performance test results of three different confined structure hard carbon negative electrode materials prepared in Examples 1-3, it can be seen that the confined structure sodium ion battery hard carbon negative electrode material prepared by the present invention has good rate performance and stable cycle performance. This is because the present invention introduces a metal shell on the surface of the hard carbon precursor sphere as a confined space structure design, and during the carbonization process, adjusts the pore structure and graphitization degree of the hard carbon precursor to improve the specific capacity of the hard carbon negative electrode material. On the other hand, compared with Examples 2-3, the material retention rate data in Example 1 is better. This is because the introduced inorganic silicon shell can effectively improve the decomposition of the electrolyte on the hard carbon surface, promote the formation of an inorganic substance-rich electrolyte interface layer, and improve the cycle performance of the hard carbon negative electrode. Comparing the data of Comparative Examples 1-2, it can be found that although regulating the thickness of the silicon shell reduces the rate performance, it still has a good capacity retention rate.
[0056] The discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.
[0057] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery, characterized in that: The following steps are involved: Step 1, mixing ammonia water, anhydrous ethanol and deionized water and stirring evenly to obtain a mixture A; adding a carbon source to the mixture A, stirring and dispersing evenly to obtain a mixture B; mixing a cationic surfactant and deionized water and stirring evenly to obtain a mixture C; Step 2, adding mixture C to mixture B and stirring evenly to obtain mixture D; then adding a coating agent to mixture D and stirring to obtain mixture E; centrifuging and washing mixture E, obtaining a solid phase and vacuum drying to obtain a hard carbon precursor; Step 3: Carbonizing the hard carbon precursor under the protection of an inert atmosphere to obtain a hard carbon negative electrode material for a confined structure sodium ion battery.
2. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: In step 1, the carbon source is selected from at least one of phenolic resin balls and small molecule sugar hydrothermal carbon balls.
3. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: In step 1, the cationic surfactant is at least one of quaternary ammonium salt cationic surfactants.
4. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: In step 2, the coating agent is at least one of tetraethyl orthosilicate, tetraisopropyl titanate and aluminum isopropoxide.
5. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: The volume ratio of ammonia water, anhydrous ethanol and deionized water in the mixture A is 1:40-120:160-220, the concentration of the carbon source in the mixture B is 2g / 200-340mL; the concentration of the cationic surfactant in the mixture C is 1.0-1.5g / 40-50mL.
6. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1 or 5, characterized in that: The mass ratio of the carbon source to the cationic surfactant in the mixture D is 2:1.0-1.
5.
7. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: The mass ratio of the coating agent to the carbon source in the mixture E is 0.6-1.9:
1.
8. The method for preparing a hard carbon negative electrode material for a confined structure sodium ion battery according to claim 1, characterized in that: In step 3, the conditions of the carbonization treatment are: temperature of 900-1300° C., holding time of 1-3 h, gas flow rate of 150-200 mL / min, and heating rate of 1-5° C. / min.
9. A hard carbon negative electrode material for a sodium ion battery with a confined structure obtained by the preparation method described in any one of claims 1 to 8.
10. A sodium ion battery comprising a negative electrode made from the hard carbon negative electrode material according to claim 9.