Method for preparing hard carbon negative electrode material from bagasse
By processing sugarcane bagasse and leaves to form a conductive carbon mesh and a hard carbon layer, the problem of low specific capacity of hard carbon anode materials is solved, thereby improving the energy density and cycle performance of sodium-ion batteries.
Patent Information
- Application Number
- CN202511581609.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-02-03
AI Technical Summary
The low specific capacity of existing hard carbon anode materials limits the energy density of sodium-ion batteries, making large-scale application difficult.
After soaking sugarcane bagasse and leaves in organic iron salt solutions, the mixture undergoes carbonization, grinding, and mixing. Soluble starch is then added to form a conductive carbon mesh. The outer starch layer is carbonized to form a hard carbon layer, which improves conductivity and reduces the volume of the SEI film.
It improves the specific capacity of the negative electrode material and the energy density of the battery, enhances conductivity and cycle performance, reduces the formation volume of the SEI film, and improves the first-pass efficiency.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of anode materials, and in particular to a method for preparing hard carbon anode materials using sugarcane bagasse. Background Technology
[0002] With the rapid development of the new energy industry, the market demand for lithium-ion batteries has surged, but global lithium reserves are relatively scarce and will be unable to meet future demand. Sodium-ion batteries work on a similar principle to lithium-ion batteries, and sodium resources have significant advantages in terms of abundant reserves and low cost. Therefore, research and development of sodium-ion batteries has been rapid and has attracted much attention, gaining increasing focus in the field of chemical power sources. However, because sodium ions have a larger atomic radius than lithium, they are difficult to penetrate into the layers of traditional lithium-ion battery anode materials such as graphite. Amorphous carbons such as hard carbon, with larger interlayer spacing than graphite, can store sodium ions, making them ideal anode materials for sodium-ion batteries.
[0003] However, the actual specific capacity of hard carbon is relatively low, generally below 350 mAh·g. -1 This limitation leads to an overall limited energy density in sodium-ion batteries, which has become a core bottleneck restricting their large-scale application. Therefore, it is necessary to propose a new solution to address this problem. Summary of the Invention
[0004] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a method for preparing hard carbon anode materials using sugarcane bagasse. This method can effectively solve the problem that the specific capacity of existing hard carbon anodes is low, which limits the energy density of sodium-ion batteries and hinders their widespread application.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for preparing hard carbon anode materials using sugarcane bagasse includes the following steps:
[0007] (1) Soak sugarcane bagasse and leaves separately in an organic iron salt solution, raise the temperature to 90-100℃ at a heating rate of 2-5℃ / min, react for 12-24h, and dry to obtain sugarcane bagasse and leaves with iron ions introduced.
[0008] (2) The sugarcane bagasse and leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 350-480°C at a heating rate of 3-6°C / min under a protective atmosphere and held for 2 hours. Then the temperature is increased to 650-700°C and a mixed gas containing reducing gas is introduced. The temperature is held for 1-2 hours to obtain sugarcane bagasse and leaves containing FeO.
[0009] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 5-8 times that of leaf powder. During the drying process, after the soluble starch is precipitated, it will adsorb the small-particle leaf powder onto the large-particle bagasse powder.
[0010] (4) Add the sugarcane bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of sugarcane bagasse powder, leaf powder and soluble starch is 10:(2-3):(2-4). After drying, a mixed powder is obtained.
[0011] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 800-1100℃ at a heating rate of 2-4℃ / min under a protective atmosphere. The temperature is held for 4-6 hours to obtain hard carbon anode material.
[0012] As a preferred embodiment, the organic iron salt is ferric citrate.
[0013] As a preferred embodiment, the protective atmosphere in steps (1), (2) and (5) is nitrogen or argon.
[0014] As a preferred embodiment, the reducing gas in the mixed gas in step (2) is hydrogen.
[0015] As a preferred embodiment, the volume percentage of the reducing gas in step (2) is 4-6%.
[0016] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:
[0017] By introducing FeO, the conductivity of the negative electrode material can be improved, the specific capacity of the product can be increased, and the energy density of the battery can be improved. In addition, the particle size of sugarcane bagasse powder is 5-8 times that of leaf powder. The small particle size of leaf powder is more conducive to adsorption on the large particle size of sugarcane bagasse powder. In addition, the coating of soluble starch allows the cellulose inside the material to build a conductive carbon network, which improves conductivity and can also expand in volume. At the same time, the carbonization of the outer starch forms a hard carbon layer, which reduces the specific surface area of the negative electrode material and effectively reduces the formation volume of the SEI film, which is conducive to improving the first efficiency.
[0018] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to several specific embodiments. Detailed Implementation
[0019] This invention discloses a method for preparing hard carbon anode materials using sugarcane bagasse, which includes the following steps:
[0020] (1) Sugarcane bagasse and leaves are soaked in an organic iron salt solution, heated to 90-100℃ at a heating rate of 2-5℃ / min, reacted for 12-24h, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is nitrogen or argon.
[0021] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 350-480°C at a heating rate of 3-6°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 650-700°C and a mixed gas containing a reducing gas is introduced. The mixture is held for 1-2 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is either nitrogen or argon. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4-6%.
[0022] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder and leaf powder is 5-8 times larger.
[0023] (4) Add the sugarcane bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of sugarcane bagasse powder, leaf powder and soluble starch is 10:(2-3):(2-4). After drying, a mixed powder is obtained.
[0024] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 800-1100°C at a heating rate of 2-4°C / min under a protective atmosphere, and held for 4-6 hours to obtain a hard carbon anode material; the protective atmosphere is nitrogen or argon.
[0025] Example 1
[0026] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 90°C at a heating rate of 2°C / min, reacted for 14 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is nitrogen.
[0027] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 380°C at a heating rate of 5°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 650°C and a mixed gas containing reducing gas is introduced. The mixture is held for 1 hour to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is nitrogen. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4%.
[0028] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 6 times that of leaf powder.
[0029] (4) Add the bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of bagasse powder, leaf powder and soluble starch is 10:2:3. After drying, a mixed powder is obtained.
[0030] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 1100°C at a heating rate of 3°C / min under a protective atmosphere and held for 5 hours to obtain a hard carbon anode material; the protective atmosphere is nitrogen.
[0031] Example 2
[0032] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 100°C at a heating rate of 5°C / min, reacted for 18 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is argon.
[0033] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 350°C at a heating rate of 5°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 680°C and a mixed gas containing a reducing gas is introduced. The temperature is held for 1.5 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is argon. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 6%.
[0034] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 7 times that of leaf powder.
[0035] (4) Add the bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of bagasse powder, leaf powder and soluble starch is 10:2.5::4. After drying, a mixed powder is obtained.
[0036] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 900°C at a heating rate of 2.5°C / min under a protective atmosphere. The temperature is held for 5 hours to obtain a hard carbon anode material. The protective atmosphere is nitrogen.
[0037] Example 3
[0038] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 95°C at a heating rate of 3°C / min, reacted for 12 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is nitrogen.
[0039] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 400°C at a heating rate of 3°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 700°C and a mixed gas containing a reducing gas is introduced. The mixture is held for 2 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is argon. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4.6%.
[0040] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 5 times that of leaf powder.
[0041] (4) Add the sugarcane bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of sugarcane bagasse powder, leaf powder and soluble starch is 10:3:2. After drying, a mixed powder is obtained.
[0042] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 880°C at a heating rate of 2.5°C / min under a protective atmosphere, and held for 4.5 h to obtain a hard carbon anode material; the protective atmosphere is argon.
[0043] Example 4
[0044] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 90°C at a heating rate of 4°C / min, reacted for 20 h, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is argon.
[0045] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 480°C at a heating rate of 6°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 680°C and a mixed gas containing reducing gas is introduced. The temperature is held for 1.5 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is nitrogen. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4.6%.
[0046] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 7 times that of leaf powder.
[0047] (4) Add the bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of bagasse powder, leaf powder and soluble starch is 10:2.5:3.5. After drying, a mixed powder is obtained.
[0048] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 800°C at a heating rate of 3.5°C / min under a protective atmosphere. The temperature is held for 6 hours to obtain a hard carbon anode material. The protective atmosphere is nitrogen.
[0049] Example 5
[0050] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 100°C at a heating rate of 4°C / min, reacted for 24 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is argon.
[0051] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 380°C at a heating rate of 4°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 680°C and a mixed gas containing a reducing gas is introduced. The mixture is held for 2 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is argon. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 5.8%.
[0052] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 8 times that of leaf powder.
[0053] (4) Add the bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of bagasse powder, leaf powder and soluble starch is 10:2.5:3.6. After drying, a mixed powder is obtained.
[0054] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 1000°C at a heating rate of 2°C / min under a protective atmosphere and held for 6 hours to obtain a hard carbon anode material; the protective atmosphere is nitrogen.
[0055] Example 6
[0056] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 95°C at a heating rate of 5°C / min, reacted for 12 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is nitrogen.
[0057] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 400°C at a heating rate of 5°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 700°C and a mixed gas containing a reducing gas is introduced. The mixture is held for 2 hours to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is argon. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4.6%.
[0058] (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder is 6.8 times that of leaf powder.
[0059] (4) Add the sugarcane bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of sugarcane bagasse powder, leaf powder and soluble starch is 10:3:2. After drying, a mixed powder is obtained.
[0060] (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 980°C at a heating rate of 4°C / min under a protective atmosphere. The temperature is maintained for 4 hours to obtain a hard carbon anode material. The protective atmosphere is nitrogen.
[0061] Comparative Example 1
[0062] (1) Sugarcane bagasse and leaves were soaked in an organic iron salt solution, heated to 90°C at a heating rate of 2°C / min, reacted for 14 hours, and dried to obtain sugarcane bagasse and leaves with iron ions introduced; wherein the organic iron salt is iron citrate, and the protective atmosphere is nitrogen.
[0063] (2) The bagasse with iron ions introduced in step (1) and the leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 380°C at a heating rate of 5°C / min under a protective atmosphere and held for 2 hours. Then, the temperature is increased to 650°C and a mixed gas containing a reducing gas is introduced. The temperature is held for 1 hour to obtain bagasse with FeO and leaves containing FeO. The protective atmosphere is nitrogen. The reducing gas in the mixed gas is hydrogen, and the volume percentage of the reducing gas is 4%. Then, the temperature is increased to 1100°C at a heating rate of 3°C / min and held for 5 hours to obtain hard carbon anode material.
[0064] Comparative Example 2
[0065] Sugarcane bagasse is placed in a carbonization furnace and heated to 1100°C at a heating rate of 3°C / min under a protective atmosphere, and held at that temperature for 5 hours to obtain a hard carbon anode material; the protective atmosphere is nitrogen.
[0066] The biomass hard carbon anode materials prepared in the above embodiments and comparative examples were used to prepare anode sheets. The preparation method was as follows: the prepared hard carbon anode material, conductive agent SP, binder CMC, SBR and deionized water were mixed and stirred. The mass ratio of carbon anode material, conductive agent SP, binder CMC and SBR was 95%:1.5%:1.5%:2% to obtain anode slurry with a solid content of 30%. The slurry was uniformly coated on copper foil and dehydrated under vacuum at 100°C. The dried anode sheet was punched to obtain the anode sheet. Sodium was selected as the positive electrode, and the electrolyte was 1 mol of NaFP6 dissolved in a mixed solvent of EC, DEC and DMC with a volume ratio of EC, DEC and DMC of 1:1:1. The separator was Celgard 2400. Performance tests were then conducted, and the test results are shown in Table 1.
[0067]
[0068] Table 1
[0069] Analyzing the above data, comparing Comparative Example 1 and Comparative Example 2, Comparative Example 2 showed a significantly higher initial efficiency and a much smaller specific surface area than Comparative Example 1. However, after 200 charge-discharge cycles, its capacity retention was at the same level as Comparative Example 1. This is because Comparative Example 2 directly used bagasse for carbonization without adding other particles, resulting in no other particles adhering to the surface of the carbonized bagasse particles, effectively avoiding an increase in specific surface area. However, its cycle performance was worse than the comparative example. This is because Comparative Example 1 introduced ferrous oxide, which improved the conductivity of the negative electrode material. Furthermore, comparing Example 1 and Comparative Example 1, the difference lies in the fact that Comparative Example 1... The bagasse and leaves containing iron ions were not ball-milled or coated with starch. After introducing ferrous oxide, they were directly carbonized. Although the scheme of Comparative Example 1 can improve its conductivity and effectively improve its cycle performance, so that the capacity retention rate of Comparative Example 1 is at the same level as that of Comparative Example 2 when its specific surface area is much larger than that of Comparative Example 2, the conductivity of Comparative Example 1 is not significantly improved because it cannot construct a conductive carbon network. Moreover, the coulombic efficiency is not significantly improved, and a hard carbon layer cannot be formed, which cannot effectively reduce the formation volume of the SEI film. As a result, its capacity retention rate is significantly lower than that of Example 1.
[0070] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for preparing hard carbon anode materials using sugarcane bagasse, characterized in that: It includes the following steps: (1) Soak sugarcane bagasse and leaves separately in an organic iron salt solution, raise the temperature to 90-100℃ at a heating rate of 2-5℃ / min, react for 12-24h, and dry to obtain sugarcane bagasse and leaves with iron ions introduced. (2) The sugarcane bagasse and leaves with iron ions introduced in step (1) are placed in different carbonization furnaces. Both are heated to 350-480°C at a heating rate of 3-5°C / min under a protective atmosphere and held for 2 hours. Then the temperature is increased to 650-700°C and a mixed gas containing reducing gas is introduced. The temperature is held for 1-2 hours to obtain sugarcane bagasse and leaves containing FeO. (3) The bagasse containing FeO and the leaves containing FeO obtained in step (2) are put into different grinding mills for grinding to obtain bagasse powder and leaf powder. The particle size of bagasse powder and leaf powder is 5-8 times larger. (4) Add the sugarcane bagasse powder, leaf powder and soluble starch obtained in step (3) to deionized water and mix them using a mixing device. The mass ratio of sugarcane bagasse powder, leaf powder and soluble starch is 10:(2-3):(2-4). After drying, a mixed powder is obtained. (5) The mixed powder obtained in step (4) is placed in a carbonization furnace and heated to 800-1100℃ at a heating rate of 2-4℃ / min under a protective atmosphere. The temperature is held for 4-6 hours to obtain hard carbon anode material.
2. The method for preparing hard carbon anode material from sugarcane bagasse according to claim 1, characterized in that: The organic iron salt is ferric citrate.
3. The method for preparing hard carbon anode material from sugarcane bagasse according to claim 1, characterized in that: The protective atmosphere in steps (1), (2) and (5) is either nitrogen or argon.
4. The method for preparing hard carbon anode material from sugarcane bagasse according to claim 1, characterized in that: The reducing gas in the mixed gas in step (2) is hydrogen.
5. The method for preparing hard carbon anode material from sugarcane bagasse according to claim 1, characterized in that: The volume percentage of the reducing gas in step (2) is 4-6%.