A hard carbon negative electrode material prepared from waste poplar board skin and a preparation method thereof

Abstract

The application belongs to the technical field of battery materials, and provides a hard carbon negative material prepared from waste poplar board skin and a preparation method thereof.The hard carbon negative material is prepared from waste poplar board skin through the processes of washing, drying, crushing, alkali cooking, pre-carbonization and high-temperature carbonization.The raw material cost is low, the preparation method is simple and environment-friendly, and the green and sustainable development concept is met.The prepared hard carbon negative material has good structural stability, low cost and excellent electrochemical performance, and provides an effective way for recycling and reusing the waste poplar board skin.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to the field of hard carbon anode materials for batteries, and particularly to a hard carbon anode material prepared using waste poplar veneer and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Currently, the energy structure is accelerating its transition to non-fossil energy, and the increase in the proportion of renewable energy has become a definite trend, leading to an imminent surge in demand for new energy storage technologies. To achieve a cleaner and lower-carbon energy structure, countries are investing heavily in energy storage construction. Among various new energy storage technologies, lithium-ion batteries hold a dominant position, offering significant advantages in cycle life, energy density, and response speed. However, due to the scarcity and uneven geographical distribution of lithium resources, the cost of lithium-ion batteries continues to rise, limiting their further large-scale application. Sodium-ion batteries, on the other hand, are expected to accelerate their penetration in power storage due to their inherent advantages.

[0004] Sodium resources are abundant (containing 2.75% of the Earth's crust, higher than lithium by 0.065‰), evenly distributed, and inexpensive, thus offering strong sustainability and broad application prospects. However, sodium ions have a larger atomic radius than lithium ions, and the interlayer compounds they form are thermodynamically unstable. Conventional materials suitable for lithium ion intercalation and deintercalation struggle to meet the same requirements for effective sodium ion intercalation and deintercalation. This is one of the main reasons why lithium-ion batteries have been widely commercialized, while sodium-ion batteries, which are theoretically similar, remain in the laboratory stage.

[0005] Therefore, selecting a suitable anode material is crucial for the commercialization of sodium-ion batteries. Compared to metal alloys and metal oxides, which suffer from fatal defects such as high volume expansion and low conductivity, hard carbon is the most promising industrial-grade anode for sodium-ion batteries. Among them, biomass, with its wide availability and unique sodium-storage microstructure, is currently a popular choice. However, hard carbon materials prepared from different biomass materials have significant differences in composition and structure, resulting in inconsistent sodium storage performance. Furthermore, existing biomass hard carbon preparation processes are complex, leading to low initial coulombic efficiency, low sodium storage capacity, and poor rate and cycle performance. Therefore, there is an urgent need to develop a biomass hard carbon material that is easy to prepare, has excellent performance, and is stable. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a hard carbon anode material prepared from waste poplar veneer and its preparation method. This invention utilizes an alkaline pretreatment method to efficiently control the lignin content in biomass precursors, thereby preparing a high-performance hard carbon anode material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing hard carbon anode materials using waste poplar veneer, comprising:

[0009] Waste poplar bark is crushed, mixed evenly with water, and then alkali and anthraquinone compounds are added. The mixture is reacted at a certain temperature. After the reaction is completed, it is washed and dried to obtain the treated waste poplar bark.

[0010] The treated waste poplar bark was ball-milled to obtain the precursor;

[0011] The precursor is pre-carbonized in an inert atmosphere and then carbonized to obtain a hard carbon material.

[0012] This invention first involves alkaline cooking of waste poplar bark blocks with the addition of cooking aids to remove a certain amount of lignin and protect cellulose and hemicellulose. Then, the cooked waste poplar bark blocks are washed and dried to remove excess alkali and soften the blocks, facilitating subsequent ball milling to obtain waste poplar bark powder with richer pores. Finally, carbonization is performed to obtain a high-performance waste poplar bark-based hard carbon anode material.

[0013] In some embodiments, the solid-liquid ratio of the waste poplar bark to water is 1:4-6.

[0014] In some embodiments, the alkali is sodium hydroxide or potassium hydroxide, and the amount used is 1%-25% or 5%-15% of the oven-dry weight of waste poplar bark.

[0015] In some embodiments, the anthraquinone compound is selected from at least one of anthraquinone, disodium dihydrodihydroxyanthracene, and quinone.

[0016] In some embodiments, the amount of the anthraquinone compound used is 0.01-0.1% or 0.03-0.06% of the oven-dry weight of waste poplar bark.

[0017] In some embodiments, the reaction is carried out at a temperature of 80-160°C or 120-140°C for a time of 3-6 hours.

[0018] In some implementations, the heating rate is 3-5°C / min.

[0019] In some embodiments, the pre-carbonization temperature is 300-500℃ or 350-450℃, and the holding time is 2-3 hours.

[0020] In some embodiments, the carbonization temperature is 1000-1500℃ or 1200-1400℃, and the holding time is 4-6 hours.

[0021] More specifically, including:

[0022] (1) Wash and dry the poplar bark discarded by the wood processing plant and then break it into small pieces;

[0023] (2) Add the dried waste poplar bark pieces from step (1) and water to the reactor in a certain solid-liquid weight ratio;

[0024] (3) Add a certain amount of sodium hydroxide or potassium hydroxide to the reactor; then add a certain amount of anthraquinone or dihydrodihydroxyanthracene disodium salt or quinone and other cooking aids. Set the reactor to heat up to a certain temperature at a rate of 3℃ / min, keep it at that temperature for 3-6 hours, and then let it cool naturally to room temperature.

[0025] (4) Wash the boiled waste poplar bark pieces with water until pH=7, put them in an oven at 90℃ for 8 hours to dry, and then ball mill them into precursor powder;

[0026] (5) Inert gas (such as helium, argon, etc.) is introduced into a tube furnace, and the precursor powder is placed into the tube furnace at a heating rate of 1-10℃ / min. It is pre-carbonized at a certain temperature for 0.5-3h and then carbonized at a certain temperature for 1-5h to obtain hard carbon material.

[0027] In a second aspect, the present invention provides a hard carbon anode material prepared by the method described above.

[0028] A third aspect of the present invention provides a sodium-ion battery comprising: the aforementioned hard carbon anode material.

[0029] A fourth aspect of the present invention provides the application of the above-mentioned waste poplar bark-based hard carbon anode material in the preparation of anode electrode sheets for ion-ion batteries.

[0030] In some embodiments, the preparation steps of the battery negative electrode sheet include: mixing the waste poplar bark-based hard carbon negative electrode material with conductive carbon black and a binder, stirring evenly to obtain an electrode slurry; coating the electrode slurry onto a current collector, drying it, and then stamping it to obtain the battery negative electrode sheet.

[0031] Beneficial effects of the present invention

[0032] (1) This invention uses waste poplar bark from biological waste as raw material, which is environmentally friendly and low in cost;

[0033] (2) This invention is the first to regulate the lignin content of waste poplar bark to prepare hard carbon with different lignin contents. Compared with other treatment methods, the alkaline treatment can not only regulate the lignin content, but also reduce the degree of polymerization of cellulose components and change the crystal form under certain conditions, resulting in hard carbon materials with different porosities. This effectively improves the electrochemical performance of the battery, especially the charge-discharge performance and cycle performance, which will expand the application of biomass materials in the field of sodium-ion anode materials.

[0034] (3) The preparation process of the waste poplar bark-based hard carbon negative electrode material and battery negative electrode sheet provided by the present invention is simple and conducive to large-scale promotion and application. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0037] Example 1

[0038] The preparation method of waste poplar bark-based hard carbon anode material includes the following steps:

[0039] (1) Wash and dry the poplar bark discarded by the wood processing plant and then break it into small pieces;

[0040] (2) Add the dried waste poplar wood bark pieces from step (1) and water to the reactor at a solid-liquid weight ratio of 1:5;

[0041] (3) Add sodium hydroxide to the reactor according to the dosage in Table 1; then add 0.03% disodium dihydrodihydroxyanthracene, set the reactor to heat up to the preset temperature in Table 1 at a rate of 3℃ / min, keep it at the temperature for 3h, and then let it cool naturally to room temperature.

[0042] (4) Wash the boiled waste poplar bark pieces with water until pH=7, put them in an oven at 90℃ for 8 hours to dry, and then ball mill them into precursor powder;

[0043] (5) Inert gas (such as helium, argon, etc.) is introduced into a tube furnace, and the precursor powder is placed into the tube furnace at a heating rate of 5℃ / min. It is pre-carbonized at 350℃ for 2h and carbonized at 1200℃ for 4h to obtain hard carbon material.

[0044] Examples 2-16

[0045] The preparation method is the same as in Example 1, except that the sodium hydroxide and the temperature of the reaction vessel are adjusted according to Table 1 to obtain precursors with different lignin contents.

[0046] Comparative Example 1

[0047] Commercially available hard carbon.

[0048] Comparative Example 2

[0049] The difference from Example 1 is that no alkali (sodium hydroxide) was added.

[0050] Comparative Example 3

[0051] The difference from Example 1 is that no anthraquinone compound (dihydrodihydroxyanthracene disodium salt) was added.

[0052] Comparative Example 4

[0053] The difference from Example 1 is that sodium hypochlorite is used instead of anthraquinone compounds (disodium dihydrodihydroxyanthracene).

[0054] Table 1

[0055]

[0056] Experimental Example 1

[0057] In Examples 1-6, the two types of examples with the highest and lowest residual lignin content were selected. Only the carbonization process was changed, and their electrochemical performance was tested. The test methods are as follows:

[0058] (1) The prepared hard carbon anode material, conductive carbon black and binder (sodium carboxymethyl cellulose) are mixed evenly in a mass ratio of 93:5:2, and then dispersed in an aqueous solution and stirred evenly to obtain an electrode slurry. The electrode slurry is then coated onto a current collector (copper foil), dried and stamped to obtain a hard carbon electrode sheet.

[0059] (2) Pair the hard carbon electrode from step (1) with the metallic sodium negative electrode, assemble a CR2032 coin cell in an inert atmosphere, and test the electrochemical performance of the hard carbon electrode. The electrolyte is 1M NaPF6-EC / DEC (volume ratio 1:1) + 5% FEC. The coin cell structure includes a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a hard carbon electrode, a sodium sheet, an electrolyte, and a separator (glass fiber).

[0060] The results are shown in Table 2.

[0061] Table 2

[0062]

[0063] A comparison of Example 1 and Comparative Example 1 shows that the waste poplar veneer-based hard carbon anode material prepared by this invention has electrochemical performance almost equivalent to commercially available hard carbon, realizing the high-value utilization of waste poplar veneer. A comparison of Example 1 and Comparative Examples 2 and 3 shows that the combined treatment with alkali and anthraquinone compounds can significantly improve the electrochemical performance of the waste poplar veneer-based hard carbon anode material. A comparison of Example 1 and Comparative Example 4 shows that using anthraquinone compounds as additives can better improve the electrochemical performance of the waste poplar veneer-based hard carbon anode material.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing hard carbon anode materials using waste poplar veneer, characterized in that, include: Waste poplar bark is crushed, mixed evenly with water, and then alkali and anthraquinone compounds are added. The mixture is reacted at a certain temperature. After the reaction is completed, it is washed and dried to obtain the treated waste poplar bark. The treated waste poplar bark was ball-milled to obtain the precursor; The precursor is pre-carbonized in an inert atmosphere and then carbonized to obtain a hard carbon material.

2. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The solid-liquid ratio of the waste poplar bark to water is 1:4-6.

3. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The alkali is sodium hydroxide or potassium hydroxide, and the amount used is 1%-25% or 5%-15% of the oven-dry weight of waste poplar bark.

4. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The anthraquinone compound is selected from at least one of anthraquinone and disodium dihydrodihydroxyanthracene.

5. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The amount of the anthraquinone compound used is 0.01-0.1% or 0.03-0.06% of the oven-dry weight of waste poplar bark.

6. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The reaction is carried out at a temperature of 80-160℃ or 120-140℃ for 3-6 hours. Alternatively, the heating rate is 3-5℃ / min.

7. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The pre-carbonization temperature is 300-500℃ or 350-450℃, and the holding time is 2-3 hours.

8. The method for preparing hard carbon anode material using waste poplar veneer as described in claim 1, characterized in that, The carbonization temperature is 1000-1500℃ or 1200-1400℃, and the holding time is 4-6 hours.

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

10. A sodium-ion battery, characterized in that, include: The hard carbon anode material as described in claim 9.

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