Hydroxyl group-containing carbohydrate-based negative electrode material, negative electrode, battery, and production method
By pre-oxidizing and carbonizing hydroxyl-containing carbohydrates to form hard carbon powder with a three-dimensional network structure, the problems of coulombic efficiency and capacity of hard carbon materials are solved, and the electrochemical performance of sodium-ion batteries is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN UNIVERSITY
- Filing Date
- 2026-03-12
- Publication Date
- 2026-06-09
AI Technical Summary
When existing hard carbon materials are used as anode materials for sodium-ion batteries, the initial coulombic efficiency is generally low, and the rate performance needs to be improved, making it difficult to simultaneously achieve high first-cycle coulombic efficiency and plateau capacity.
Hydroxyl-containing carbohydrates are pre-oxidized and carbonized to form hard carbon powder with a three-dimensional network structure. Closed pores are generated during carbonization through the esterification reaction of hydroxyl and carboxyl groups, which improves the first-cycle coulombic efficiency and reversible capacity of the material.
High first-cycle coulombic efficiency and ultra-high plateau capacity of hard carbon materials were achieved, improving the electrochemical performance of sodium-ion batteries.
Smart Images
Figure CN122177826A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a negative electrode material based on hydroxyl-containing carbohydrates, a negative electrode, a battery, and a method for preparing the same. Background Technology
[0002] Sodium-ion batteries stand out among many alternative systems due to their abundant sodium reserves, greater environmental friendliness, and compatibility with lithium systems, making them suitable for large-scale energy storage and power grid applications.
[0003] Developing sodium-ion batteries requires research into high-performance battery materials. The anode material is one of the core components determining the performance of sodium-ion batteries. Among numerous anode material candidates, hard carbon materials are widely recognized as the most commercially promising anode material for sodium-ion batteries due to their unique disordered carbon layer structure, abundant nanopores, high specific capacity, low sodium-ion insertion / extraction potential, and small volumetric strain during charge and discharge.
[0004] However, the practical application of hard carbon materials faces challenges. First, when used as a negative electrode material in sodium-ion batteries, hard carbon materials generally exhibit low initial coulombic efficiency. This is mainly due to the abundant defects on the hard carbon surface and the irreversible side reactions between oxygen-containing functional groups and the electrolyte during the first charge-discharge cycle, as well as the difficulty of sodium ions diffusing internally, resulting in the formation of "dead sodium" within the closed pores. Second, its rate performance needs improvement, which is closely related to the diffusion kinetics of sodium ions in the complex carbon layer structure.
[0005] Therefore, current technologies improve the performance of hard carbon by altering the surface functional groups and internal structure. However, these processes often suffer from trade-offs. For example, in hard carbon materials, elemental doping can introduce more active sites to increase capacity, but this often comes at the cost of a decrease in first-cycle coulombic efficiency; while optimizing first-cycle coulombic efficiency by reducing defects and porosity usually requires sacrificing some capacity in the plateau region.
[0006] In summary, existing modified hard carbon materials obtained through elemental doping cannot produce batteries that simultaneously possess high first-cycle coulombic efficiency and plateau capacity. Summary of the Invention
[0007] To address the shortcomings of the existing technologies, this invention provides a negative electrode material based on hydroxyl-containing carbohydrates, a negative electrode, a battery, and a method for preparing the same, which solves the technical problem that existing modified hard carbon materials cannot produce batteries with both high first-cycle coulombic efficiency and reversible capacity.
[0008] This invention is achieved by adopting the following technical solution: A negative electrode material based on hydroxyl-containing carbohydrates is obtained by pre-oxidation of carbohydrates containing only hydroxyl groups at 250~350℃ for 3h~4h, grinding, and carbonization in an inert atmosphere; the negative electrode material based on hydroxyl-containing carbohydrates exhibits a three-dimensional network structure with closed pores.
[0009] The method for preparing the anode material based on hydroxyl-containing carbohydrates specifically includes the following steps: pre-oxidizing hydroxyl-containing carbohydrates at 250℃~350℃ for 3h~4h to obtain oxidized carbohydrates; the hydroxyl-containing carbohydrates include at least one of microcrystalline cellulose, glucose, and β-cyclodextrin; grinding the oxidized carbohydrates to obtain carbohydrate powder; carbonizing the carbohydrate powder under an inert atmosphere at a temperature of 1200℃~1600℃, a holding time of 2h~6h, and a heating rate of 2℃ / min~5℃ / min to obtain hard carbon powder, which is the anode material based on hydroxyl-containing carbohydrates.
[0010] Furthermore, the pre-oxidation temperature is 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃.
[0011] Furthermore, the pre-oxidation time is 3h, 3.5h, or 4h.
[0012] Furthermore, the carbonization temperature is 1200℃, 1300℃, 1400℃, 1500℃ or 1600℃.
[0013] Furthermore, the heat preservation time is 2h, 3h, 4h, 5h or 6h.
[0014] Furthermore, the heating rate is 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min.
[0015] Furthermore, the grinding steps are as follows: the oxidized carbohydrates are agitated at a frequency of 40Hz~45Hz (specifically 40Hz, 42Hz or 45Hz) for 60s~80s (specifically 60s, 70s or 80s), and then left to stand for 3 minutes; the above steps are repeated 4 to 5 times to obtain carbohydrate powder; after pre-oxidation, it will expand and become larger, so grinding is required.
[0016] Examples of the above-mentioned pre-oxidation temperature, pre-oxidation time, carbonization temperature, numerical ranges or specific values, as well as the negative electrode materials based on hydroxyl-containing carbohydrates prepared in Examples 1 to 12 of this invention, can all produce batteries with both high first-cycle coulombic efficiency and reversible capacity.
[0017] Furthermore, the inert atmosphere includes nitrogen.
[0018] A sodium-ion battery negative electrode includes a current collector and an active material layer attached to the current collector. The active material layer is made of a negative electrode material based on a hydroxyl-containing carbohydrate, a conductive agent, and a binder in a mass ratio of 9:0.5:0.5. The mass of the active material in each electrode is 1.8 mg to 2.2 mg.
[0019] Furthermore, the conductive agent is conductive carbon, and the binder is polyvinylidene fluoride.
[0020] Furthermore, the current collector is made of aluminum.
[0021] A sodium-ion battery includes a positive electrode, the aforementioned negative electrode, a separator, and an electrolyte.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a negative electrode material based on hydroxyl-containing carbohydrates, which is hard carbon powder obtained by pre-oxidation, grinding and carbonization of carbohydrates containing only hydroxyl groups; the pre-oxidation crosslinking will form a three-dimensional network structure, which will form some closed pores inside, thereby making the material exhibit high first-cycle coulombic efficiency and ultra-high plateau capacity.
[0023] 2. The present invention provides a method for preparing a negative electrode material based on hydroxyl-containing carbohydrates. Through pre-oxidation, oxygen is introduced, and some of the hydroxyl groups in glucose, cyclodextrin and microcrystalline cellulose are oxidized to form carboxyl groups. After being kept at a suitable temperature for a period of time, the hydroxyl and carboxyl groups undergo esterification reaction and cross-link together. This results in more closed pores during the later carbonization process, without causing "dead sodium", thus improving the first-cycle coulombic efficiency and the capacity of the plateau region. Attached Figure Description
[0024] Figure 1 This is a SEM image of the negative electrode material based on hydroxyl-containing carbohydrates, which is shown in Comparative Example 1.
[0025] Figure 2 This is a SEM image of the hydroxyl-containing carbohydrate-based anode material from Example 1.
[0026] Figure 3 The constant current charge-discharge curves of the batteries prepared based on hydroxyl-containing carbohydrate anode materials in Examples 1 to 3 are shown.
[0027] Figure 4 Long-cycle performance curves of batteries prepared using hydroxyl-containing carbohydrate-based anode materials in Examples 1 and 3. Detailed Implementation
[0028] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods. Specific explanations are needed as follows:
[0029] β-Cyclodextrin particles are from Titan Technology Exploration Platform; glucose is from Sinopharm Chemical Reagent Co., Ltd.; microcrystalline cellulose is from Huzhou Linghu Xinwang Chemical Co., Ltd.; PVDF represents polyvinylidene fluoride, from Kelude; the current collector is made of aluminum.
[0030] Example 1 A method for preparing a negative electrode material based on hydroxyl-containing carbohydrates specifically includes the following steps: S1. Weigh 5g of β-cyclodextrin granules and place them in a ceramic boat. Then, pre-oxidize them in an air atmosphere in a muffle furnace for 3 hours at a pre-oxidation temperature of 300℃.
[0031] S2. Place the pre-oxidized sample in a multi-tissue grinder and vibrate at 40Hz for 80 seconds. Let it stand for 3 minutes. Repeat this process 5 times to make the particles more compact.
[0032] S3. Place the precursor powder obtained in the above steps into a nitrogen atmosphere tube furnace, where the carbonization temperature is 1600℃, the holding time is 2h, and the heating rate is 2℃ / min to obtain hard carbon powder, which is the negative electrode material based on hydroxyl-containing carbohydrates; labeled as β-300-1600.
[0033] Example 2 The pre-oxidation temperature in Example 1 was changed to 250°C and the pre-oxidation time was changed to 3.5h. The other steps were the same as those above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as β-250-1600.
[0034] Example 3 The pre-oxidation temperature in Example 1 was changed to 350°C, the oscillation condition was changed to 45Hz oscillation for 60s, and the repetition was changed from 5 times to 4 times. Other steps were the same as the above steps. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as β-350-1600.
[0035] Example 4 The carbonization temperature in Example 1 was changed to 1200℃, the heating rate was 5℃ / min, and the other steps were the same as those above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as β-300-1200.
[0036] Example 5 The carbonization temperature in Example 1 was changed to 1400℃, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as β-300-1400.
[0037] Example 6 The carbonization treatment holding time in Example 1 was changed to 4 hours, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as β-300-1600-4h.
[0038] Example 7 The carbonization treatment holding time in Example 1 was changed to 6 hours, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates, labeled as β-300-1600-6h.
[0039] Example 8 The β-cyclodextrin particles in Example 1 were replaced with glucose, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as glucose-300-1600.
[0040] Example 9 The pre-oxidation temperature in Example 8 was changed to 250°C, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as glucose-250-1600.
[0041] Example 10 The pre-oxidation temperature in Example 8 was changed to 350°C, and the other steps were the same as those described above. The resulting hard carbon powder is a negative electrode material based on hydroxyl-containing carbohydrates and is labeled as glucose-350-1600.
[0042] Example 11 The β-cyclodextrin particles in Example 5 were replaced with microcrystalline cellulose, and the other steps were the same as those described above. The resulting hard carbon powder was labeled as microcrystalline cellulose-300-1400.
[0043] Example 12 Based on Example 1, the pre-oxidation time was extended to 4 hours, while the rest remained unchanged, to obtain a negative electrode material based on hydroxyl-containing carbohydrates, labeled as β-300-4h-1600.
[0044] Comparative Example 1 A method for preparing a negative electrode material based on hydroxyl-containing carbohydrates specifically includes the following steps: S1. Weigh 5g of β-cyclodextrin particles and place them in a multi-tissue grinder. Shake at 40Hz for 60s. Repeat 5 times to make the particles more compact.
[0045] S2. The precursor powder obtained in the above steps is placed in a nitrogen atmosphere tube furnace, where the carbonization temperature is 1600℃, the holding time is 2h, and the heating rate is 2℃ / min to obtain hard carbon powder, which is the comparative example of the anode material based on hydroxyl-containing carbohydrates; labeled as β-1600.
[0046] Comparative Example 2 Based on Comparative Example 1, β-cyclodextrin particles were replaced with glucose, while the rest remained unchanged, to obtain hard carbon powder, which is the negative electrode material based on hydroxyl-containing carbohydrates in the comparative example, labeled as glucose-1600.
[0047] Application Example 1 A method for preparing a sodium-ion battery specifically includes the following steps: The hard carbon powder obtained in Example 1 was mixed with conductive carbon and PVDF in a mass ratio of 9:0.5:0.5 to form a slurry, which was then coated onto an aluminum foil current collector to form an active material layer attached to the current collector. The slurry was dried overnight in a vacuum oven at 80°C to produce a negative electrode sheet. The active material on the negative electrode sheet was 1.8 mg.
[0048] A CR2025 button cell was fabricated in an argon-filled glove box using a positive electrode shell, a negative electrode shell, a PP separator, a sodium sheet, and an electrolyte. The electrolyte was prepared from 1M NaPF6 and diethylene glycol dimethyl ether.
[0049] Application Example 2 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 2, the active material on the negative electrode was 2.2 mg, and everything else remained the same, resulting in a battery using the hard carbon powder of Example 2.
[0050] Application Example 3 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 3, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 3.
[0051] Application Example 4 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 4, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 4.
[0052] Application Example 5 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 5, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 5.
[0053] Application Example 6 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 6, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 6.
[0054] Application Example 7 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 7, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 7.
[0055] Application Example 8 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 8, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 8.
[0056] Application Example 9 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 9, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 9.
[0057] Application Example 10 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 10, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 10.
[0058] Application Example 11 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 11, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Example 11.
[0059] Application Example 12 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Example 12, while other aspects remained unchanged, to obtain a battery using the hard carbon powder of Example 12.
[0060] Comparative Application Example 1 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Comparative Example 1, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Comparative Example 1.
[0061] Comparative Application Example 2 Based on Application Example 1, the hard carbon powder obtained in Example 1 was replaced with the hard carbon powder obtained in Comparative Example 2, while other aspects remained unchanged, resulting in a battery using the hard carbon powder of Comparative Example 2.
[0062] Experiment 1: Observation of the structure of hard carbon powder using scanning electron microscopy The hard carbon powder prepared in Comparative Example 1 was observed using scanning electron microscopy (SEM). Figure 1 As shown, carbon materials formed at high temperatures without pre-oxidation have a sheet-like structure, and there are almost no pores or interlayers inside the material that can store sodium.
[0063] The hard carbon powder prepared in Example 1 was observed using scanning electron microscopy (SEM). Figure 2 As shown, the hard carbon material formed after pre-oxidation becomes a granular structure with stacked carbon layers and a closed-cell three-dimensional network structure inside. This demonstrates that pre-oxidation crosslinking leads to the formation of a three-dimensional network structure and closed pores inside, resulting in high first-cycle coulombic efficiency and ultra-high plateau capacity.
[0064] Experiment 2: First Charge-Discharge Experiment Batteries obtained from Application Examples 1 to 7, Comparative Application Example 1, and Application Example 12 were left to stand for 10 hours and then subjected to charge-discharge tests at a constant temperature of 28°C in a Newway test cabinet. The results are shown in Table 1. The sodium-ion battery prepared using the hard carbon powder of Comparative Example 1 had lower first-cycle coulombic efficiency, reversible capacity, and plateau capacity than the sodium-ion batteries prepared using the pre-oxidized hard carbon material of Examples 1 to 7.
[0065] Table 1 Electrochemical performance of sodium-ion batteries prepared with β-cyclodextrin Charging curve, such as Figure 3 As shown in the figure, 250-1600, 300-1600, and 350-1600 represent the increased pre-oxidation temperature of the hard carbon powder in Examples 2, 1, and 3, respectively, which further promotes the cross-linking of β-cyclodextrin and strengthens the degree of cross-linking. Additionally, the increased capacity in the plateau region below 0.1V indicates the formation of more closed pores.
[0066] Experiment 2: Second Charge-Discharge Experiment The sodium-ion batteries obtained from Application Examples 8 to 11 and Comparative Application Example 2 were left to stand for 10 hours before being subjected to charge-discharge tests at a constant temperature of 28°C in a Newway test chamber. The results are shown in Table 2. The performance of the sodium-ion batteries prepared using pre-oxidized glucose and pre-oxidized microcrystalline cellulose was significantly improved.
[0067] Table 2 Electrochemical performance of sodium-ion batteries prepared from glucose and microcrystalline cellulose Long-cycle performance testing, such as Figure 4As shown in the figure, 300-1600 and 350-1600 represent the hard carbon powders of Examples 1 and 3, respectively. The capacity and first-cycle coulombic efficiency of the batteries prepared by the hard carbon powder with the higher pre-oxidation temperature are slightly higher than those with the lower temperature. However, in terms of long-term cycle stability, the batteries prepared by the hard carbon powder with the lower pre-oxidation temperature are more stable, but both are better than the sodium-ion batteries prepared by the hard carbon material without pre-oxidation.
[0068] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A negative electrode material based on hydroxyl-containing carbohydrates, characterized in that, The anode material is obtained by pre-oxidation of carbohydrates containing only hydroxyl groups at 250℃~350℃ for 3h~4h, grinding, and carbonization in an inert atmosphere; the anode material based on hydroxyl-containing carbohydrates exhibits a three-dimensional network structure with closed pores.
2. The method for preparing the negative electrode material based on hydroxyl-containing carbohydrates according to claim 1, characterized in that, Specifically, the following steps are included: Oxidized carbohydrates are obtained by pre-oxidizing carbohydrates containing only hydroxyl groups; the carbohydrates containing only hydroxyl groups include at least one of microcrystalline cellulose, glucose and β-cyclodextrin. Oxidized carbohydrates are ground to obtain carbohydrate powder; Carbohydrate powder is carbonized in an inert atmosphere at a temperature of 1200℃~1600℃ for 2h~6h and a heating rate of 2℃ / min~5℃ / min to obtain hard carbon powder, which is the anode material based on hydroxyl-containing carbohydrates.
3. The method for preparing the negative electrode material based on hydroxyl-containing carbohydrates according to claim 2, characterized in that, The grinding steps are as follows: The oxidized carbohydrates were agitated at a frequency of 40Hz~45Hz for 60s~80s and then left to stand for 3min. Repeat the above steps 4 to 5 times to obtain carbohydrate powder.
4. The method for preparing the negative electrode material based on hydroxyl-containing carbohydrates according to claim 2, characterized in that, The inert atmosphere includes nitrogen.
5. A sodium-ion battery negative electrode, characterized in that, It includes a current collector and an active material layer attached to the current collector, the active material layer being made of the negative electrode material based on a hydroxyl-containing carbohydrate as described in claim 1, a conductive agent and a binder in a mass ratio of 9:0.5:0.
5.
6. The sodium-ion battery negative electrode according to claim 5, characterized in that, The conductive agent is conductive carbon, and the binder is polyvinylidene fluoride.
7. The sodium-ion battery negative electrode according to claim 5, characterized in that, The current collector is made of aluminum.
8. A sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode is the sodium-ion battery negative electrode according to claim 5.