Hard carbon negative electrode material prepared from rice husks and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to a hard carbon negative electrode material prepared from rice husks as well as a preparation method and application of the hard carbon negative electrode material, the rice husks are used as raw materials, and the hard carbon negative electrode material is prepared through the processes of cleaning, drying, grinding, acid cooking, pre-carbonization, high-temperature carbonization and the like. The raw materials are low in cost, the preparation method is simple and environment-friendly, the green sustainable development concept is met, and the prepared hard carbon negative electrode is good in structural stability, low in cost and excellent in electrochemical performance. An effective way is provided for recycling and reusing the rice husks.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a hard carbon negative electrode material prepared from rice husks, and a preparation method and application thereof. Background Art

[0003] Among many new energy storage technologies, lithium-ion batteries occupy an absolute dominant position. Lithium batteries have significant advantages in terms of cycle times, energy density and response speed. However, due to the scarcity of lithium resources and uneven geographical distribution, the cost of lithium-ion batteries continues to rise, and their large-scale application is limited. Sodium-ion batteries are expected to accelerate their penetration in power energy storage with their own advantages. Sodium resources are abundant (the sodium content in the earth's crust is 2.75%, much higher than the 0.065‰ of lithium), evenly distributed, low-cost, with strong sustainability and broad application prospects. The development of sodium-ion batteries is of great strategic significance for reducing my country's dependence on foreign lithium resources. However, the atomic radius of sodium ions is large, and the thermodynamic properties of the interlayer compounds formed are unstable. Conventional materials suitable for lithium ion embedding and de-embedding are difficult to meet the needs of sodium ions. This is also one of the main reasons why lithium-ion batteries have been widely used in commercial applications, while sodium-ion batteries are still in the laboratory stage.

[0004] In order to realize the commercialization of sodium-ion batteries, it is crucial to choose a suitable negative electrode material. Compared with metal alloys and metal oxides with defects such as high volume expansion rate and low conductivity, hard carbon is the most promising industrial-grade negative electrode material for sodium-ion batteries. Among them, biomass-based hard carbon materials with a wide range of sources and unique sodium storage microstructures have become a hot topic in current research. Biomass, such as agricultural and forestry waste, fruit shells, straw, etc., are regarded as ideal precursors due to their wide sources and low costs. However, hard carbon materials prepared from different biomass materials differ in composition and structure, resulting in uneven sodium storage performance. However, the lignin in the precursor will cause the prepared hard carbon to be severely graphitized, which is not conducive to the storage of sodium ions. Therefore, it is necessary to remove part of the lignin before preparing hard carbon, which can improve the electrochemical performance and stability of hard carbon materials.

[0005] Chinese patent document CN118183695A discloses a hard carbon negative electrode material prepared from waste poplar board skin and a preparation method thereof, wherein the waste poplar board skin is crushed, mixed evenly with water, and then alkali and anthraquinone compounds are added to react at a certain temperature. After the reaction is completed, the treated waste poplar board skin is washed and dried to obtain the treated waste poplar board skin; the treated waste poplar board skin is ball-milled to obtain a precursor; the precursor is pre-carbonized in an inert atmosphere and then carbonized to obtain a hard carbon material. However, the precursor preparation process of the patent has the problem of low delignification selectivity, resulting in low delignification efficiency. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a hard carbon negative electrode material prepared using rice husks, and a preparation method and application thereof.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A method for preparing a hard carbon negative electrode using rice husks, wherein the lignin content in a biomass precursor is efficiently regulated by acid pretreatment of the rice husks, and a hard carbon negative electrode material with high performance is prepared. The acid is formic acid, and hydrogen peroxide is used as a cooking aid. By regulating the amount of the acid and the aid added, a hard carbon material with good performance is obtained.

[0009] A method for preparing a hard carbon negative electrode using rice husks comprises the following steps:

[0010] (1) drying rice husk and preparing rice husk powder;

[0011] (2) mixing rice husk powder and water to obtain a mixture;

[0012] (3) adding formic acid and hydrogen peroxide to the mixture of step (2), heating the rice husk powder at a rate of 1 to 3° C. / min to steam the rice husk powder, and then naturally cooling the steamed rice husk powder to room temperature;

[0013] (4) washing the cooked rice husk powder with deionized water until it is neutral, drying it in an oven, and then grinding it into a precursor powder by ball milling;

[0014] (5) Under an inert atmosphere, the precursor powder is first heated to a pre-carbonization temperature at a rate of 3 to 8° C. / min for pre-carbonization, and then heated to a carbonization temperature for carbonization to obtain a hard carbon material.

[0015] The present invention first performs acid cooking on the rice husk powder with the addition of a cooking aid, in order to remove a certain amount of lignin in the rice husk and protect cellulose and hemicellulose. The cooked rice husk is then cleaned and dried, in order to wash away excess acid and soften the rice husk powder, so as to facilitate subsequent ball milling to obtain rice husk powder with richer pores. Finally, carbonization treatment is performed to obtain a high-performance rice husk-based hard carbon negative electrode material.

[0016] Preferably, in step (2), the solid-liquid weight ratio of the rice husk powder to water is 1:3-7.

[0017] Preferably, in step (3), the mass ratio of formic acid to rice husk powder is 5-25%, preferably 5-20%, further preferably 15-20%, and more preferably 20%.

[0018] Preferably, the mass ratio of hydrogen peroxide to rice husk powder in step (3) is 0.3-0.8%. Adding too much hydrogen peroxide will increase the delignification rate during cooking, thereby significantly reducing the lignin content of rice husks, while adding too little hydrogen peroxide will reduce the delignification rate, thereby reducing the amount of rice husk lignin removed during cooking, both of which will affect the performance of the final hard carbon material.

[0019] Preferably, the temperature of the steaming treatment in step (3) is 120° C.-160° C., and the steaming treatment time is 3 to 8 hours.

[0020] Preferably, the inert atmosphere in step (5) is under an atmosphere of nitrogen, argon, etc. The pre-carbonization temperature is 350-500°C, and the pre-carbonization time is 2-4 hours. The carbonization temperature is 1200°C-1400°C, and the carbonization time is 4-6 hours. Pre-carbonization and carbonization are carried out in a tubular furnace.

[0021] The present invention also provides the method for preparing a hard carbon negative electrode using rice husk to prepare a rice husk-based hard carbon negative electrode material.

[0022] The present invention also provides the use of the rice husk-based hard carbon negative electrode material in preparing a negative electrode sheet of an ion-type battery.

[0023] Preferably, the preparation steps of the battery negative electrode sheet include: mixing the rice husk-based hard carbon negative electrode material with conductive carbon black and a binder, and stirring evenly to obtain an electrode slurry; applying the electrode slurry on a current collector, drying it, and then stamping it to obtain a battery negative electrode sheet.

[0024] In the electrode slurry, the mass proportion of rice husk-based hard carbon negative electrode material is 75-85%, the mass proportion of conductive carbon black is 5-15%, the mass proportion of binder is 5-15%, and the rest is solvent. The solvent in the electrode slurry is water. The binder is specifically carboxymethyl cellulose and styrene-butadiene rubber.

[0025] Preferably, the mass ratio of rice husk-based hard carbon negative electrode material to conductive carbon black and binder is 8:1:1.

[0026] Preferably, the coating amount on the current collector is 3.0 mg / cm 2 .

[0027] The beneficial technical effects of the present invention are as follows:

[0028] (1) The present invention uses formic acid and hydrogen peroxide for the first time to regulate the lignin content of rice husks to prepare precursors with different lignin contents, and then obtain precursors with different crystallinity and closed-cell structures, which are then prepared into hard carbon materials through high-temperature carbonization, effectively improving the electrochemical performance of batteries, which will expand the application of biomass materials in the field of sodium ion negative electrode materials. In the precursor prepared using rice husks in the present invention, when the lignin content is 5% to 10wt%, the crystallinity is high and the closed-cell structure is high, and the electrochemical performance of the prepared hard carbon is higher.

[0029] (2) The formic acid cooking pretreatment used in the present invention has a high delignification selectivity and high delignification efficiency. The formic acid in the waste liquid can be recycled after recovery, which has great advantages in energy saving and consumption reduction, COD emission reduction, environmental protection and improving the quality of biomass products. In addition, the rice husk-based hard carbon negative electrode material and battery negative electrode sheet preparation process provided by the present invention are simple, which is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is the X-ray diffraction pattern of the precursor obtained in the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments.

[0032] Examples 1 to 16

[0033] A method for preparing a hard carbon negative electrode using rice husks comprises the following steps:

[0034] (1) Wash the rice husks discarded from the food processing plant with clean water, dry them, grind them into powder and sieve them;

[0035] (2) adding the rice husk powder dried in step (1) and water into a reaction kettle at a solid-to-liquid weight ratio of 1:5;

[0036] (3) Add a certain amount of formic acid to the reactor; then add hydrogen peroxide in an amount of 0.5% of the weight of the rice husk powder, heat the reactor to 120°C-160°C at a rate of 2°C / min, keep the temperature for 5 hours, and then cool naturally to room temperature;

[0037] (4) washing the cooked rice husk powder with clean water until the pH value is 7, drying it in an oven at 60° C. for 12 h, and then grinding it into a precursor powder by ball milling;

[0038] (5) Inert gas is introduced into the tubular furnace, and the precursor powder is placed in the tubular furnace for pre-carbonization at 350°C-500°C for 3 h at a heating rate of 5°C / min, and then carbonized at 1200°C-1400°C for 5 h to obtain a hard carbon material.

[0039] Comparative Example 1 is the rice husk powder obtained in step (1).

[0040] Comparative Example 2

[0041] The difference from Example 12 is that formic acid was not added.

[0042] Comparative Example 3

[0043] The difference from Example 12 is that no hydrogen peroxide was added.

[0044] Comparative Example 4

[0045] The difference from Example 12 is that hydrogen peroxide is replaced by anthraquinone of the same amount.

[0046] Comparative Example 5

[0047] The difference from Example 12 is that hydrogen peroxide is replaced by an equal amount of sodium hydroxide.

[0048] Comparative Example 6

[0049] The difference from Example 12 is that sulfuric acid is replaced by an equal amount of formic acid.

[0050] Comparative Example 7

[0051] The difference from Example 12 is that the cooking conditions set the formic acid: rice husk ratio to 25:100.

[0052] Table 1 shows the powder precursor prepared according to the above steps (1) to (5). The specific conditions are shown in the table below.

[0053]

[0054]

[0055] The precursors obtained in the examples and comparative examples were used to prepare hard carbon negative electrode materials.

[0056] Test method for the electrochemical performance of hard carbon negative electrode materials: Use a charge and discharge tester and follow the sodium ion battery test process in the hard carbon national standard GB / T 43114-2023 at 30 mA g -1 The material was charged and discharged at a current density of .

[0057] Table 2 Electrochemical properties of the hard carbon materials obtained in the present invention

[0058]

[0059]

[0060]

[0061] From the above results, it can be seen that when the mass ratio of formic acid: rice husk is between 15 and 20:100, the obtained lignin content is about 7% to 10%. Within this range, the crystallinity of the precursor is between 35% and 45%, and the pore structure is mainly mesoporous. The crystallinity and pore structure of the obtained precursor are more conducive to battery performance after formic acid cooking pretreatment at 140°C. The crystallinity of the precursor obtained in Example 1 is 37.3%, the crystallinity of the precursor obtained in Example 6 is 39.4%, the crystallinity of the precursor obtained in Example 12 is 43.2%, and the crystallinity of the precursor obtained in Comparative Example 1 is 32.1%. The XRD spectrum is shown in Table 1. The precursor is carbonized to obtain hard carbon, and the number of closed micropores is negatively correlated with the lignin content. For precursors with a lignin content of 7% to 10%, the lower the lignin content, the richer the closed pores, which is more conducive to the sodium ion storage of hard carbon.

Claims

1. A method for preparing a hard carbon negative electrode using rice husk, characterized in that: The following steps are involved: (1) drying rice husk and preparing rice husk powder; (2) mixing rice husk powder and water to obtain a mixture; (3) adding formic acid and hydrogen peroxide to the mixture of step (2), heating the rice husk powder at a rate of 1 to 3° C. / min to steam the rice husk powder, and then naturally cooling the steamed rice husk powder to room temperature; (4) washing the cooked rice husk powder with deionized water until it is neutral, drying it in an oven, and then grinding it into a precursor powder by ball milling; (5) Under an inert atmosphere, the precursor powder is first heated to a pre-carbonization temperature at a rate of 3 to 8° C. / min for pre-carbonization, and then heated to a carbonization temperature for carbonization to obtain a hard carbon material.

2. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: The solid-to-liquid weight ratio of the rice husk powder to water in step (2) is 1:3-7.

3. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: In step (3), the mass ratio of formic acid to rice husk powder is 5-20%.

4. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: In step (3), the ratio of hydrogen peroxide to rice husk powder is 0.3-0.8%.

5. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: The temperature of the steaming treatment in step (3) is 120° C.-160° C., and the steaming treatment time is 3 to 8 hours.

6. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: In step (5), the pre-carbonization temperature is 350°C-500°C, and the pre-carbonization time is 2-4 hours; the carbonization temperature is 1200°C-1400°C, and the pre-carbonization time is 4-6 hours.

7. The method for preparing a hard carbon negative electrode using rice husk according to claim 1, characterized in that: The inert atmosphere in step (5) is a nitrogen or argon atmosphere.

8. A rice husk-based hard carbon negative electrode material prepared by the method according to any one of claims 1 to 7.

9. Use of the rice husk-based hard carbon negative electrode material obtained by the method according to any one of claims 1 to 7 in preparing negative electrode sheets of ionic batteries.

10. The use according to claim 9, characterized in that: The preparation steps of the battery negative electrode sheet include: mixing the rice husk-based hard carbon negative electrode material with conductive carbon black and a binder, and stirring evenly to obtain an electrode slurry; applying the electrode slurry on a current collector, drying it, and then punching it to obtain a battery negative electrode sheet.

Images