Biomass-based hard carbon negative electrode material and preparation method and use thereof

Abstract

The application provides a biomass-based hard carbon negative electrode material and a preparation method and use thereof; a resin and a dianhydride organic matter are sequentially subjected to esterification reaction with hydroxyl groups on cellulose, hemicellulose and lignin in biomass, the resin and the dianhydride organic matter are sequentially grafted (grafted) onto molecular chains in biomass fibers through the esterification reaction, assembly of the resin, the dianhydride organic matter and the biomass raw material is realized at a molecular level, and modified biomass raw material 2 which is uniformly dispersed is obtained. Then, the modified biomass raw material 2 is subjected to heat compaction treatment and carbonization treatment. The biomass-based hard carbon negative electrode material has high capacity and a first coulomb efficiency, and also has excellent cycle performance and rate performance.

Description

Technical Field

[0001] This invention belongs to the technical field of anode materials for sodium-ion batteries, specifically relating to a biomass-based hard carbon anode material, its preparation method, and its applications. Background Technology

[0002] Sodium-ion batteries, as a novel battery technology, offer advantages over lithium-ion batteries, including lower cost, superior high and low temperature performance, and better fast-charging rate performance. Currently, hard carbon is the mainstream anode material for sodium-ion batteries, with biomass materials being the preferred raw material for hard carbon production due to their environmental friendliness, low cost, strong sodium storage capacity, and good high and low temperature performance. However, the low initial coulombic efficiency (<70%) and poor rate performance of commonly used biomass-based hard carbon anode materials hinder their commercial application. Therefore, developing biomass-based hard carbon anode materials with high initial coulombic efficiency and high rate performance is currently a key research focus and hot topic in sodium-ion battery development. Summary of the Invention

[0003] To address the issues of low initial coulombic efficiency and poor rate performance in existing biomass-based hard carbon anode materials, this invention provides a biomass-based hard carbon anode material, its preparation method, and its applications. The biomass-based hard carbon anode material exhibits high capacity and initial coulombic efficiency, as well as excellent cycle performance and rate performance.

[0004] The objective of this invention is achieved through the following technical solution: A method for preparing a biomass-based hard carbon anode material, the method comprising the following steps: (1) Add the resin to the first organic solvent, stir evenly, then add the biomass raw material, soak for a period of time, filter to remove the first organic solvent, and then dry to obtain modified biomass raw material 1; (2) Add the modified biomass raw material 1 from step (1) to the second organic solvent, stir evenly, then add dianhydride organic matter, stir until the second organic solvent is completely evaporated, and then dry to obtain modified biomass raw material 2. (3) The modified biomass raw material 2 from step (2) is subjected to hot pressing and densification, cooled and then crushed to obtain a hard carbon precursor; (4) The hard carbon precursor from step (3) is placed in a high-temperature furnace and carbonized under an inert atmosphere. After cooling to room temperature, it is crushed to obtain the biomass-based hard carbon anode material.

[0005] According to an embodiment of the present invention, in step (1), the resin is selected from at least one of rosin, acrylate resin and polyurethane.

[0006] According to an embodiment of the present invention, in step (1), the first organic solvent is selected from at least one of ethanol, propanol and acetone.

[0007] According to an embodiment of the present invention, in step (1), the mass ratio of the first organic solvent to the resin is 100:1-6, for example, 100:1, 100:2, 100:3, 100:4, 100:5 or 100:6.

[0008] According to an embodiment of the present invention, in step (1), the source of the biomass raw material is not specifically defined, and can be any biomass raw material known in the art; for example, the biomass raw material can be at least one of lychee wood, apple wood, poplar wood, bamboo, fruit shell, straw, coconut shell and corn cob.

[0009] According to an embodiment of the present invention, in step (1), the mass ratio of the biomass raw material to the resin is 100:3-7, for example, 100:3, 100:4, 100:5, 100:6 or 100:7.

[0010] According to an embodiment of the present invention, in step (1), the soaking time is 3-12 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or 12 hours. The soaking temperature is room temperature.

[0011] According to an embodiment of the present invention, in step (1), the drying temperature is 150-180°C, for example, 150°C, 160°C, 170°C, or 180°C. The drying time is 1-12 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 12 hours. The drying is carried out, for example, in an oven.

[0012] According to an embodiment of the present invention, in step (1), during the drying process, the carboxyl groups in the resin undergo an esterification reaction with the hydroxyl groups on cellulose, hemicellulose and lignin in the biomass raw materials. Through the esterification reaction, the resin is grafted (grafted) onto the molecular chains in the biomass fibers (such as cellulose, hemicellulose and lignin) to obtain modified biomass raw material 1, thereby realizing the assembly of resin and biomass raw materials at the molecular level.

[0013] According to an embodiment of the present invention, in step (2), the second organic solvent is selected from at least one of ethanol, propanol and acetone.

[0014] According to an embodiment of the present invention, in step (2), the mass ratio of the modified biomass raw material 1 to the second organic solvent is 1:10-15, for example, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15.

[0015] According to an embodiment of the present invention, in step (2), the dianhydride organic compound is selected from at least one of perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic dianhydride.

[0016] According to an embodiment of the present invention, in step (2), the mass ratio of the modified biomass raw material 1 to the dianhydride organic compound is 100:5-10, for example, 100:5, 100:6, 100:7, 100:8, 100:9 or 100:10.

[0017] According to an embodiment of the present invention, in step (2), the stirring temperature is 50-80°C, for example, 50°C, 60°C, 70°C or 80°C.

[0018] According to an embodiment of the present invention, in step (2), during the stirring process, the anhydride in the dianhydride organic compound undergoes an esterification reaction with the hydroxyl groups on the cellulose, hemicellulose and lignin in the modified biomass raw material 1. Through the esterification reaction, the dianhydride organic compound is grafted onto the molecular chain in the fiber (such as cellulose, hemicellulose and lignin) of the modified biomass raw material 1 to obtain the modified biomass raw material 2, thereby realizing the assembly of the dianhydride organic compound and the modified biomass raw material 1 (resin and biomass raw material) at the molecular level.

[0019] According to an embodiment of the present invention, in step (2), the drying temperature is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C, or 120°C. The drying time is 1-12 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 12 hours. The drying is carried out, for example, in an oven.

[0020] According to an embodiment of the present invention, in step (3), the temperature of the hot pressing densification treatment is 120-150°C, for example, 120°C, 130°C, 140°C, 150°C or 160°C; the pressure of the hot pressing densification treatment is 2-5 MPa, for example, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa or 5 MPa; the time of the hot pressing densification treatment is 8-15 min, for example, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0021] According to an embodiment of the present invention, in step (3), the pulverization method is not specifically defined, as long as a hard carbon precursor with a suitable particle size can be obtained; for example, the average particle size of the hard carbon precursor is 7-10µm.

[0022] According to an embodiment of the present invention, in step (4), the inert atmosphere is, for example, nitrogen, argon or helium.

[0023] According to an embodiment of the present invention, in step (4), the temperature of the carbonization treatment is 1000-1500℃, for example 1000℃, 1100℃, 1200℃, 1300℃, 1400℃ or 1500℃; the time of the carbonization treatment is 1-6 hours, for example 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0024] The present invention also provides a biomass-based hard carbon anode material prepared by the above method.

[0025] The present invention also provides the use of the above-mentioned biomass-based hard carbon anode material for sodium-ion batteries, preferably for preparing anodes for sodium-ion batteries.

[0026] The present invention also provides a negative electrode for sodium-ion batteries, the negative electrode comprising the above-mentioned biomass-based hard carbon negative electrode material.

[0027] The present invention also provides a sodium-ion battery, wherein the sodium-ion battery comprises the above-mentioned biomass-based hard carbon anode material.

[0028] The beneficial effects of this invention are: In this invention, resin and dianhydride organics are sequentially esterified with the hydroxyl groups on cellulose, hemicellulose and lignin in biomass. Through the esterification reaction, resin and dianhydride organics are sequentially grafted (grafted) onto the molecular chains in biomass fibers, thereby achieving the assembly of resin, dianhydride organics and biomass raw materials at the molecular level, and obtaining uniformly dispersed modified biomass raw material 2.

[0029] During the hot-pressing densification process, some hemicellulose in the modified biomass raw material 2 is removed, and cross-linking reactions occur between the lignins in the modified biomass raw material 2. The removal of some hemicellulose and the occurrence of cross-linking reactions between lignins effectively increase the density of the hard carbon precursor. The increased density of the hard carbon precursor makes it easier to form a denser hard carbon structure after high-temperature carbonization, which is beneficial to reducing the specific surface area of ​​the biomass-based hard carbon anode material, resulting in a reduction in solid-liquid interface reactions and an increase in the first coulombic efficiency of the biomass-based hard carbon anode material.

[0030] The increased density of the hard carbon precursor restricts the escape channels of volatile gases generated by resin decomposition during the carbonization process, resulting in a more pronounced compression and reshaping effect on the surrounding pore structure. This leads to the formation of nanopores with a pore size of less than 1 nm in the biomass-based hard carbon anode material. The formation of these nanopores further reduces the specific surface area of ​​the biomass-based hard carbon anode material, resulting in good first-pass coulombic efficiency.

[0031] During the carbonization process of hard carbon precursors, when the carbonization temperature is in the range of 200-600℃, the biomass raw materials in the hard carbon precursors will decompose to form a carbonaceous skeleton (in particular, the esterification and cross-linking structure in the hard carbon precursors is conducive to the formation of a highly cross-linked three-dimensional network carbonaceous skeleton from the biomass raw materials). At around 500℃, the dianhydride organic compounds in the hard carbon precursors will decompose to generate carbon free radicals that can enter the interlayer of the carbonaceous skeleton. When the temperature is higher than 600℃, the dianhydride organic compounds begin to carbonize, and their oxygen-containing groups will release a large amount of gaseous components such as CO2 and CO, which helps to further expand the interlayer of the biomass-based hard carbon anode material, constructing a hard carbon anode material with a large interlayer spacing, so that the obtained biomass-based hard carbon anode material exhibits good rate performance and cycle performance. Detailed Implementation

[0032] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0034] Example 1 (1) Add 5g of rosin to 100g of ethanol and stir evenly. Then add 100g of coconut shell and soak for 6 hours. Filter to remove ethanol and then dry in an oven at 180℃ to obtain modified coconut shell 1. (2) Add 10g of modified coconut shell 1 from step (1) to 100g of acetone, stir evenly, then add 0.5g of perylene tetracarboxylic acid dianhydride, stir until the acetone is completely evaporated, and then dry in an oven at 100℃ to obtain modified coconut shell 2. (3) Place the modified coconut shell 2 from step (2) on a hot press molding machine and perform hot pressing densification treatment (temperature is 140℃, pressure is 3MPa, time is 10min). After cooling, crush it to obtain hard carbon precursor 1. (4) The hard carbon precursor 1 from step (3) is placed in a high-temperature furnace and heated to 1200°C at a heating rate of 5°C / min in a nitrogen atmosphere. After holding at the temperature for 4 hours in a nitrogen atmosphere, it is cooled to room temperature to obtain the hard carbon anode material.

[0035] Example 2 (1) Add 4g of rosin to 100g of ethanol and stir evenly. Then add 100g of straw and soak for 6 hours. After filtering to remove the ethanol, dry in an oven at 170℃ to obtain modified straw 1. (2) Add 10g of modified straw 1 from step (1) to 100g of acetone, stir evenly, then add 0.6g of perylene tetracarboxylic acid dianhydride, stir until the acetone is completely evaporated, and then dry in an oven at 100℃ to obtain modified straw 2. (3) The modified straw 2 from step (2) is placed on a hot press molding machine and subjected to hot pressing densification treatment (temperature is 120℃, pressure is 4MPa, time is 12min). After cooling, it is crushed to obtain hard carbon precursor 1. (4) The hard carbon precursor 1 from step (3) is placed in a high-temperature furnace and heated to 1280°C at a heating rate of 5°C / min in a nitrogen atmosphere. After holding at the temperature for 4 hours in a nitrogen atmosphere, it is cooled to room temperature to obtain the hard carbon anode material.

[0036] Example 3 (1) Add 3g of rosin to 100g of ethanol and stir evenly. Then add 100g of corn cob and soak for 8 hours. After filtering to remove the ethanol, dry in an oven at 160℃ to obtain modified corn cob 1. (2) Add 10g of modified corn cob 1 from step (1) to 100g of acetone, stir evenly, then add 0.8g of perylene tetracarboxylic acid dianhydride, stir until the acetone is completely evaporated, and then dry in an oven at 100℃ to obtain modified corn cob 2. (3) The modified corn cob 2 from step (2) is placed on a hot press molding machine and subjected to hot pressing densification treatment (temperature is 150℃, pressure is 3MPa, time is 8min). After cooling, it is crushed to obtain hard carbon precursor 1. (4) The hard carbon precursor 1 from step (3) is placed in a high-temperature furnace and heated to 1200°C at a heating rate of 5°C / min in a nitrogen atmosphere. After holding at the temperature for 4 hours in a nitrogen atmosphere, it is cooled to room temperature to obtain the hard carbon anode material.

[0037] Comparative Example 1 (1) Add 5g of rosin to 100g of ethanol and stir evenly. Then add 100g of coconut shell and soak for 6 hours. Filter to remove ethanol and then dry in an oven at 180℃ to obtain modified coconut shell 1. (2) Add 10g of modified coconut shell 1 from step (1) to 100g of acetone, stir evenly, then add 0.5g of perylene tetracarboxylic acid dianhydride, stir until the acetone is completely evaporated, and then dry in an oven at 100℃ to obtain modified coconut shell 2. (3) The modified coconut shell 2 from step (2) is placed in a high-temperature furnace and heated to 1200°C at a heating rate of 5°C / min in a nitrogen atmosphere. After being kept at the temperature for 4 hours in a nitrogen atmosphere, it is cooled to room temperature to obtain a hard carbon anode material.

[0038] Electrochemical performance testing The hard carbon anode materials prepared in Examples 1-3 and Comparative Example 1 were used as anode materials for sodium-ion batteries, and their electrochemical performance was tested using the following methods: The above-mentioned hard carbon anode material, conductive agent Super P, binder sodium carboxymethyl cellulose (CMC), and aqueous binder (SBR) were weighed in a mass ratio of 95:2:1.5:1.5. After thorough grinding in an agate mortar, a small amount of deionized water was added to form a uniform black paste. This paste was coated onto a copper foil current collector as a test electrode, and a sodium metal sheet was used as a control electrode to assemble a coin cell. The electrolyte was a 1M sodium hexafluorophosphate solution dissolved in a 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC), with 5 wt.% fluoroethylene carbonate (FEC) added as an additive. A glass fiber separator and a CR2032 stainless steel casing were used to assemble the coin cell. The resulting coin cells were tested for initial discharge capacity and initial coulombic efficiency at a constant rate of 0.1C within a voltage range of 0.01-3.0V.

[0039] Using the hard carbon anode materials prepared in Examples 1-3 and Comparative Example 1 as anodes, sodium nickel iron manganese oxide as cathode, and 1M NaPF6+EC:DEC:DMC (volume ratio 1:1:1) solution as electrolyte, the cells were assembled into full cells in a stacked manner. The cells were tested at room temperature with a 1C rate, and the voltage range was 1.5-3.9V.

[0040] Rate performance testing: Under normal temperature conditions, the prepared batteries were tested on the LAND battery testing system, and the specific capacity of the batteries was tested at current densities of 1A / g, 2A / g, 4A / g, 6A / g, 8A / g, and 10A / g. The test results are shown in Table 1.

[0041] Table 1. Electrochemical performance of hard carbon anode materials in Examples 1-3 and Comparative Example 1

[0042] As can be seen from the test results in Table 1, the hard carbon anode material of the present invention has high initial coulombic efficiency and rate performance, while also maintaining high cycle performance.

[0043] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a biomass-based hard carbon anode material, the method comprising the following steps: (1) Add the resin to the first organic solvent, stir evenly, then add the biomass raw material, soak for a period of time, filter to remove the first organic solvent, and then dry to obtain modified biomass raw material 1; (2) Add the modified biomass raw material 1 from step (1) to the second organic solvent, stir evenly, then add dianhydride organic matter, stir until the second organic solvent is completely evaporated, and then dry to obtain modified biomass raw material 2. (3) The modified biomass raw material 2 from step (2) is subjected to hot pressing and densification, cooled and then crushed to obtain a hard carbon precursor; (4) The hard carbon precursor from step (3) is placed in a high-temperature furnace and carbonized under an inert atmosphere. After cooling to room temperature, it is crushed to obtain the biomass-based hard carbon anode material.

2. The preparation method according to claim 1, wherein, In step (1), the resin is selected from at least one of rosin, acrylate resin and polyurethane; And / or, in step (1), the first organic solvent is selected from at least one of ethanol, propanol and acetone; And / or, in step (1), the mass ratio of the first organic solvent to the resin is 100:1-6; And / or, in step (1), the mass ratio of the biomass raw material to the resin is 100:3-7.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the soaking time is 3-12 hours; the soaking temperature is room temperature; And / or, in step (1), the drying temperature is 150-180°C; the drying time is 1-12 hours.

4. The preparation method according to any one of claims 1-3, wherein, In step (2), the second organic solvent is selected from at least one of ethanol, propanol, and acetone; And / or, in step (2), the mass ratio of the modified biomass raw material 1 to the second organic solvent is 1:10-15; And / or, in step (2), the dianhydride organic compound is selected from at least one of perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic dianhydride; And / or, in step (2), the mass ratio of the modified biomass raw material 1 to the dianhydride organic compound is 100:5-10.

5. The preparation method according to any one of claims 1-4, wherein, In step (2), the stirring temperature is 50-80℃; And / or, in step (2), the drying temperature is 80-120°C; the drying time is 1-12 hours.

6. The preparation method according to any one of claims 1-5, wherein, In step (3), the temperature of the hot pressing densification process is 120-150℃; the pressure of the hot pressing densification process is 2-5MPa; and the time of the hot pressing densification process is 8-15min.

7. The method according to any one of claims 1-6, wherein, In step (4), the inert atmosphere is nitrogen, argon, or helium; And / or, in step (4), the carbonization temperature is 1000-1500℃; the carbonization time is 1-6 hours.

8. The biomass-based hard carbon anode material prepared by the method according to any one of claims 1-7.

9. A negative electrode for a sodium-ion battery, the negative electrode comprising the biomass-based hard carbon negative electrode material as described in claim 8.

10. A sodium-ion battery, the sodium-ion battery comprising the biomass-based hard carbon anode material as described in claim 8.

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