Preparation method of plant tar-based hard carbon material

Abstract

The invention relates to the technical field of sodium ion batteries, and discloses a preparation method of a plant tar-based hard carbon material, and the preparation process comprises the following steps: (1) mixing plant tar with a modifier; (2) heating and polymerizing; (3) non-melting treatment; and (4) high-temperature carbonization. The plant tar is used as a raw material to prepare a series of hard carbon materials, and the hard carbon materials are applied to sodium ion battery negative electrodes and have excellent sodium storage capacity and good cycle performance. The raw materials used in the invention are low in cost, the production process is simple, a new method is provided for the treatment of the plant tar, and the high value-added application of the plant tar is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and specifically relates to a technical method for preparing hard carbon materials using plant tar as raw material and applying the hard carbon materials to the negative electrode of sodium ion batteries. Background Art

[0002] Hard carbon materials have good sodium ion storage capacity due to their large interlayer spacing and complex pore structure, and are therefore considered to be one of the most promising negative electrode materials for sodium ion batteries. At present, the main raw materials for producing hard carbon materials include biomass, polymer resins and asphalt, but each has its own advantages and disadvantages. Biomass raw materials have attracted attention due to their wide sources and low costs, but their quality is easily affected by natural conditions, and there are problems such as difficulty in collection and unstable quality. Hard carbon materials made from polymer resins have excellent performance, but are expensive. Asphalt is usually used as a soft carbon material, and a complex modification process is required to prepare hard carbon materials with excellent performance.

[0003] Plant tar is a complex organic mixture extracted from biomass, rich in various compounds such as phenols, ketones, alcohols, aldehydes, acids, esters and hydrocarbons, with a high carbon conversion rate, showing great potential as a precursor for carbon materials. The existing technology mainly uses plant tar as a carbon source to prepare activated carbon materials. For example, patent CN 118373402 A discloses an activated carbon material based on wood tar and a preparation method thereof. The method uses wood tar as a carbon source, urea as a nitrogen source, and a small molecule aldehyde compound as a cross-linking agent. The nitrogen element is uniformly doped on the surface of the precursor through cross-linking, and the specific surface area of ​​the material is increased through chemical activation, and finally an activated carbon material suitable for capacitors is prepared. However, the current research on the preparation of hard carbon negative electrode materials for sodium ion batteries using plant tar is still rare. Therefore, the technical development of plant tar-derived hard carbon materials, especially in structural design and preparation process, still needs further exploration and breakthroughs. Summary of the invention

[0004] In view of the shortcomings of the prior art in the utilization of plant tar and the production of hard carbon, the purpose of the present invention is to provide a method for preparing hard carbon negative electrode materials for sodium ion batteries using plant tar as raw material, thereby broadening the high value-added utilization of plant tar.

[0005] The present invention provides a method for preparing a plant tar-based hard carbon material, which is characterized by comprising the following steps:

[0006] Step 1: Plant tar and a modifier are mixed in a certain proportion to obtain a mixed precursor;

[0007] Step 2: heating the mixed precursor under the protection of an inert gas to cause a polymerization reaction to obtain a polymer;

[0008] Step 3: The polymer is subjected to an infusible treatment in an air atmosphere to further stabilize its structure and obtain an infusible material. ;

[0009] Step 4: Carbonize the infusible material at high temperature under the protection of an inert gas to form a hard carbon material with a three-dimensional cross-linked structure.

[0010] The type of the plant tar described in step 1 is at least one of wood tar, bamboo tar, straw tar and fruit shell tar, preferably wood tar and / or bamboo tar.

[0011] The type of the modifier described in step 1 is one or more of glucose, maltose, lactose, fructose, sucrose, starch, and cellulose, preferably glucose, fructose, and sucrose.

[0012] In step 1, the mass ratio of plant tar to modifier is preferably 9:1 to 6:4, and the mixing method can adopt a common mixing method, preferably mechanical stirring.

[0013] The polymerization method in step 2 can be carried out under common polymerization conditions and in a manner, preferably by heating to melt and stirring in a reaction vessel and / or by hydrothermal reaction in an autoclave.

[0014] The temperature of the polymerization treatment in step 2 is preferably 100-300° C., the heating rate is preferably 1-10° C. / min, the polymerization time is preferably 10-120 minutes, and the inert atmosphere is nitrogen or argon.

[0015] The infusible treatment method and conditions described in step 3 adopt the common infusible treatment method. The infusible temperature is preferably 300-600°C, the heating rate is preferably 2-5°C / min, the infusible time is preferably 1-12 hours, and more preferably 2-11 hours. The infusible treatment step should be carried out in an air atmosphere. There is no special limitation on the infusible treatment equipment, and the common infusible treatment equipment can be used, preferably a tubular furnace or a muffle furnace.

[0016] The carbonization method described in step 4 adopts the carbonization method commonly used in the art, the carbonization temperature is preferably 1000-1500°C, the heating rate is preferably 1-5°C / min, the carbonization time is preferably 1-6 hours, and the inert atmosphere is nitrogen or argon. There is no special limitation on the carbonization equipment, and the carbonization equipment commonly used in the art can be used, preferably a rotary furnace or a roller furnace.

[0017] The present invention also provides a plant tar-based hard carbon material obtained by the above preparation method. The hard carbon material generally has a volume average particle size D50 of 10 to 50 microns, a specific surface area of ​​1 to 20 square meters per gram, a tap density of 0.6 to 1.0 grams per cubic centimeter, and an ash mass fraction of less than 0.1%.

[0018] The present invention provides the use of the hard carbon negative electrode material as a negative electrode of a sodium ion secondary battery.

[0019] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to form various preferred embodiments of the present invention. The reagents and raw materials used in the present invention are all commercially available.

[0020] The positive and progressive effects of the present invention are:

[0021] 1. The present invention uses plant tar as raw material, and the plant tar is cross-linked with a modifier to generate a macromolecular polymer with a complex three-dimensional cross-linked structure. This unique structure lays the foundation for the subsequent improvement of the performance of hard carbon materials. 2. The polymer is subjected to a non-melting treatment and further reacted at a medium temperature to form a sufficiently large molecule. The macromolecule will not undergo a liquid phase transition during the high-temperature carbonization process, thereby inhibiting the rearrangement of the carbon layer, thereby significantly improving the electrochemical properties of the hard carbon material formed by carbonization, making it more suitable for the negative electrode material of sodium ion secondary batteries. 3. As a by-product in the process of plant treatment, plant tar has been mostly used in agriculture or biomass fuel production in the past, but these applications have the problems of complex production process, low yield and poor economic benefits. The present invention has opened up a new way for the high-value utilization of plant tar, which not only increases the added value of plant tar, but also has a simple production process, is easy to meet production conditions, has broad prospects for mass production, and provides an economical and efficient method for the production of hard carbon materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 : SEM of the hard carbon material obtained in Example 2;

[0023] Figure 2 : XRD of the hard carbon material obtained in Example 2;

[0024] Figure 3 : The first charge and discharge cycle curve of the hard carbon material obtained in Example 2. DETAILED DESCRIPTION

[0025] The present invention is further illustrated by the following examples, but the present invention is not limited to the scope of these examples. Without departing from the core idea of ​​the present invention, various replacements or changes made according to common technical knowledge and customary means in this field should be included in the scope of the present invention. For experimental methods that do not show specific conditions in the following examples, they can be selected according to conventional methods and instructions. The embodiments not mentioned in the present invention can be implemented according to the conditions described in the specification.

[0026] In the following examples, the half-cell test method is as follows: the negative electrode material samples of each example or comparative example, analytically pure sodium alginate and conductive carbon black are fully mixed and evenly coated on copper foil, and then the coated electrode is placed in a vacuum drying oven at a temperature of 100°C for vacuum drying for 12 hours for use. The electrode is cut into a disc with a diameter of 12 mm, and the half-cell is assembled in the order of negative electrode shell-negative electrode sodium sheet-diaphragm-electrolyte-electrode sheet-gasket-spring-positive electrode shell, and a manual packaging machine is used for pressure packaging. Among them, the electrolyte is 1M NaPF6+EC:DEC:DMC=1∶1∶1 (volume ratio), and the electrochemical performance test is carried out using a LAND battery test system (CT2001A model), the charge and discharge voltage range is 0 to 2.8V, and the charge and discharge rate is 0.1A / g.

[0027] Example 1

[0028] 90g of wood tar and 10g of glucose were put into the reactor for mixing, the stirring speed was set to 200 rpm and the temperature was raised for reaction. In a nitrogen atmosphere, the mixture was reacted at 150°C, the heating rate was 5°C / min, and the nitrogen flow rate was controlled at 100cc / min to obtain a wood tar polymer. Then, in an air environment, the polymer powder was treated at 400°C for 2 hours without melting, the heating rate was 2°C / min, the nitrogen flow rate was 100cc / min, and an infusible material was obtained. Finally, the infusible material was placed in a tubular furnace and carbonized at 1500°C for 3 hours, the heating rate was 2°C / min, the nitrogen flow rate was 100cc / min, and after cooling to room temperature, the hard carbon negative electrode material was taken out.

[0029] Example 2

[0030] The difference from Example 1 is that 80 g of wood tar and 20 g of glucose are put into the reactor.

[0031] Example 3

[0032] The difference from Example 1 is that 70 g of wood tar and 30 g of glucose are put into the reactor.

[0033] Example 4

[0034] The difference from Example 1 is that 80 g of wood tar and 20 g of fructose are put into the reactor.

[0035] Example 5

[0036] The difference from Example 1 is that 80 g of wood tar and 20 g of lactose are put into the reactor.

[0037] Example 6

[0038] The difference from Example 1 is that 80 g of wood tar and 20 g of sucrose are put into the reactor.

[0039] Example 7

[0040] The difference from Example 1 is that 80 g of wood tar and 20 g of maltose are put into the reactor.

[0041] Example 8

[0042] The difference from Example 1 is that 80 g of wood tar and 20 g of starch are put into the reactor.

[0043] Example 9

[0044] The difference from Example 1 is that 80 g of wood tar and 20 g of cellulose are put into the reactor.

[0045] Example 10

[0046] Different from Example 1, 80 g of bamboo tar and 20 g of glucose were added to the reactor.

[0047] Embodiment 11

[0048] The difference from Example 1 is that 80 g of straw tar and 20 g of glucose are put into the reactor.

[0049] Example 12

[0050] The difference from Example 1 is that 80 g of husk tar and 20 g of glucose are put into the reactor.

[0051] Comparative Example 1

[0052] Different from Example 1, no modifier was added into the reactor.

[0053] Comparative Example 2

[0054] Different from Example 10, no modifier was added into the reactor.

[0055] Comparative Example 3

[0056] Different from Example 11, no modifier was added into the reactor.

[0057] Comparative Example 4

[0058] Different from Example 12, no modifier was added into the reactor.

[0059] Performance Testing

[0060] 1. The particle size, true density, tap density, specific surface area and compacted density of the hard carbon negative electrode materials in Examples 1 to 12 and Comparative Examples 1 to 4 were tested respectively, and the results are listed in Table 1. The names and models of the instruments used in the test are as follows: Particle size: Malvern laser particle size analyzer MS2000; Carbon yield: calculated according to the mass ratio before and after carbonization; Tap density: Tap density tester FZS4-4B; Specific surface area: Quanta Specific surface area measuring instrument NOVA2000e; Compacted density: Powder compacted density meter FT-100F; First discharge capacity and first cycle coulomb efficiency: LAND battery test system (CT2001A model). The test results are listed in Table 1.

[0061] 2. The reversible capacity and first discharge efficiency of the hard carbon negative electrode materials in Examples 1 to 12 and Comparative Examples 1 to 4 were tested using a half-cell test method. The test results are listed in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] It can be seen from Table 1 that the carbon yield and electrochemical performance of the hard carbon negative electrode material in the comparative example are significantly lower than those of the hard carbon material of the present invention.

[0066] The results of Examples 1 to 12 and Comparative Examples 1 to 4 show that the addition of the modifier significantly improves the electrochemical properties of the finished hard carbon material. This is because the modifier contains a large number of aldehyde groups and hydroxyl groups, which can change the structure of the tar, and the two interact to form a complex structure. In the subsequent carbonization process, this complex structure inhibits the graphitization transition and the escape of small molecules, thereby increasing the carbon yield and forming a hard carbon material with disordered structure and complex closed pores, which is beneficial to improving its electrochemical performance.

Claims

1. A method for preparing a plant tar-based hard carbon material, characterized in that: The steps include: Step 1: Plant tar and a modifier are mixed in a certain proportion to obtain a mixed precursor; Step 2: heating the mixed precursor under the protection of an inert gas to cause a polymerization reaction to obtain a polymer; Step 3: subjecting the polymer to an infusible treatment in an air atmosphere to obtain an infusible material; Step 4: The infusible material is carbonized at high temperature under the protection of an inert gas to obtain a hard carbon material.

2. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 1, the plant tar includes one or more of wood tar, bamboo tar, straw tar, and fruit shell tar.

3. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 1, the modifier includes one or more of glucose, maltose, lactose, fructose, sucrose, starch, and cellulose.

4. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 1, the mass ratio of the plant tar to the modifier is 9:1 to 6:

4.

5. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 2, the reaction temperature is 100-300° C., the heating rate is 1-10° C. / min, the reaction time is 10-120 minutes, and the inert atmosphere is nitrogen or argon.

6. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 3, the non-melting treatment temperature is 300-600° C., the heating rate is 2-5° C. / min, the calcination time is 1-12 hours, and the atmosphere is air or oxygen.

7. The method for preparing a plant tar-based hard carbon material according to claim 1, characterized in that: In step 4, the carbonization temperature is 1000-1500° C., the heating rate is 2-5° C. / min, the calcination time is 1-6 hours, and the inert atmosphere is nitrogen or argon.

8. A plant tar-derived hard carbon obtained by the preparation method according to any one of claims 1 to 7.

9. The hard carbon material according to claims 1 to 8 has a volume average particle size D50 of 10 to 50 μm, a specific surface area of ​​1 to 20 m2 / g, a tap density of 0.6 to 1.0 g / cm3, and an ash mass fraction of less than 0.1%.

10. The plant tar-derived hard carbon as claimed in claims 1 to 9 is used as a negative electrode material for a sodium ion secondary battery.

Images