Method for preparing high-capacity sodium ion material based on precursor particle size screening and application

Abstract

The invention discloses a method for preparing a high-capacity sodium ion material based on precursor particle size screening and application, and belongs to the technical field of sodium ion batteries. According to the method, bamboo-based biomass is used as a raw material, and air pre-carbonization and high-temperature refining are performed to prepare the sodium ion material. Before pre-carbonization, crushing and screening are adopted to control the granularity of the bamboo-based biological particles, so that the morphology and the size of the precursor are more uniform, the pore structure of hard carbon is optimized, the energy storage performance of the precursor is improved, meanwhile, the sodium ion negative electrode material prepared by the preparation method is applied to a sodium ion battery, the capacity can reach 384.8 mAh / g, the preparation method is simple, the cost is low, and the method is suitable for industrial production. And the method is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a method for preparing high-capacity sodium ion materials based on precursor particle size screening and application. BACKGROUND

[0002] In the field of energy storage, especially in the research and application of battery technology and supercapacitors, gradually becoming the key to solving the energy problem. Hard carbon material as an ideal energy storage material, because of its good electrochemical performance and high specific surface area, is widely used in lithium ion batteries, sodium ion batteries and supercapacitors and other energy storage devices.

[0003] At present, there are still some technical problems and bottlenecks in the preparation method of bamboo-based hard carbon. In the traditional preparation method of bamboo-based hard carbon, the pretreatment and pyrolysis process of bamboo are not effectively optimized, resulting in unsatisfactory specific surface area, pore structure and electrochemical performance of the hard carbon material. In addition, there is great uncertainty in the parameter control during the activation process, and different activation methods and conditions have a great influence on the performance of the hard carbon. Based on this, the application provides a method for preparing high-capacity sodium ion materials based on precursor particle size screening, which improves the performance of the hard carbon material, reduces the production cost, and realizes more efficient and environmentally friendly production process. SUMMARY

[0004] The technical problem to be solved by the application is to provide a method for preparing high-capacity sodium ion materials based on precursor particle size screening, which controls the particle size range of the biomass precursor by crushing and screening the bamboo-based biomass before pre-carbonization, and selects the appropriate particle size range to optimize the pore structure of the hard carbon and improve its energy storage performance. Another technical problem to be solved by the application is to provide the application of the sodium ion material in sodium ion batteries.

[0005] In order to solve the above technical problems, the technical scheme adopted by the application is as follows:

[0006] A method for preparing high-capacity sodium ion materials based on precursor particle size screening, comprising the following steps:

[0007] 1) The bamboo is dried after two-step cleaning, then crushed, and screened with a 50-300 mesh screen for standby;

[0008] 2) The bamboo powder obtained in step 1) is pre-carbonized to obtain pre-carbonized carbon powder;

[0009] 3) The pre-carbonized carbon powder obtained in step 2) is disc milled, acid washed and dried;

[0010] 4) The pre-carbonized carbon powder dried in step 3) is carbonized to obtain a sodium ion material.

[0011] Further, in the step 1), the two-step cleaning step is: first, using a steel ball to remove the impurities on the surface of the bamboo-based material until the bamboo material is free of dirt; second, immersing the bamboo material free of dirt in deionized water for cleaning.

[0012] Further, in the step 1), the drying temperature is not more than 120 DEG C.

[0013] Further, in the step 2), the pre-carbonization temperature is 400-600 DEG C, the heating rate is 1-10 DEG C / min, and the time is 1-3 h.

[0014] Further, in the step 3), the disc milling time is 3-5 min.

[0015] Further, in the step 3), the acid is HCl, the concentration is 1-3 mol / L, the pickling method is boiling, the pickling time is 10 min, and the drying temperature is not more than 120 DEG C.

[0016] Further, in the step 4), the inert gas in the carbonization treatment is nitrogen or argon, the heating rate is 1-10 DEG C / min, the temperature is 1000-1400 DEG C, and the time is 1-3 h.

[0017] Further, the method for preparing high-capacity sodium ion material based on precursor particle size screening.

[0018] Further, the method for preparing high-capacity sodium ion material based on precursor particle size screening is applied to sodium ion batteries.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] (1) The present application pulverizes and screens the bamboo-based biomass before pre-carbonization, controls the particle size range of the biomass precursor, and selects an appropriate particle size range through screening to optimize the pore structure of the hard carbon and improve its energy storage performance.

[0021] (2) The material prepared by the present application can be widely applied to sodium ion battery negative electrodes, and the capacity can reach 384.8 mAh / g.

[0022] (3) The present application adopts dirt removal and cleaning, the first step uses a steel ball to remove the impurities on the surface of the bamboo-based material until the bamboo material is free of dirt, and the second step immerses the bamboo material free of dirt in deionized water for cleaning. The first step does not involve water, and the water consumption in the second step is also very small, which greatly reduces the water consumption cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The SEM image of the sodium ion material particles prepared in Example 1 of the present application at a low magnification.

[0024] Figure 2 SEM image of the sodium-ion material particles prepared in Example 1 of the present application at high magnification;

[0025] Figure 3 Charge-discharge curve of the sodium-ion battery prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0026] The present application will be further illustrated below in conjunction with specific examples, which are implemented on the premise of the technical solutions of the present application, and should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application.

[0027] Example 1

[0028] A method for preparing high-capacity sodium-ion material based on precursor particle size screening, comprising the following steps:

[0029] (1) First, remove the surface impurities of the bamboo base material using a steel ball until the bamboo material is free of dirt, and second, soak the bamboo material free of dirt in deionized water for cleaning. Dry the cleaned bamboo at 80℃ for 12h, then crush and sieve through a 100-150 mesh screen for later use;

[0030] (2) Transfer the bamboo powder obtained in step (1) to a muffle furnace and perform carbonization treatment under air atmosphere, with a heating rate of 5℃ / min and a carbonization temperature of 400℃, and keep the temperature for 1h to preliminarily carbonize the material to carbon powder;

[0031] (3) Further pan mill the pre-carbonized carbon powder obtained in step (2) for 3min, wash the obtained pre-carbonized carbon powder in boiling 2mol / L HCl aqueous solution for 10min to remove ash, then wash with deionized water until neutral, and finally dry at 80℃ for 12h;

[0032] (4) Transfer the pre-carbonized carbon powder dried in step (3) to a tube furnace and perform carbonization treatment under argon atmosphere, with a heating rate of 5℃ / min and a carbonization temperature of 1200℃, and keep the temperature for 2h after the temperature reaches the carbonization temperature to obtain sodium-ion material.

[0033] (5) The obtained sodium ion material, conductive agent (SUPER P) and binder (polyvinylidene fluoride, PVDF) were mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone (NMP) was added as a dispersant, and uniform stirring was performed to form a slurry. The slurry was uniformly coated on a single-side polished copper foil using a doctor blade coater, and then dried in a forced air drying oven at 80°C for 6 hours, and then transferred to a vacuum drying oven at 80°C for 4 hours to completely remove the residual solvent. The dried electrode sheet was punched into a 14 mm diameter disc by a cutting machine for standby use. Cell assembly and testing: the assembly of button cells (CR2032 type) was completed in an inert argon glove box (H2O / O2<0.1 ppm): the positive electrode shell, hard carbon working electrode, glass fiber separator (Whatman GF / D), sodium metal counter electrode (thickness 0.6 mm) were stacked in sequence, and 1M NaPF6 electrolyte (solvent: ethylene carbonate (EC): dimethyl carbonate (DMC): tetraethyl carbonate (EMC) = 1:1:1, volume ratio) was injected. Then stainless steel gaskets, spring sheets and negative electrode shells were added in sequence, and the electric sealing machine was used for pressure sealing. After sealing, the battery was detected by open circuit voltage, and then placed at room temperature for 12 hours to stabilize the interface, and then subjected to electrochemical test.

[0034] Figure 1 The SEM image of the obtained sodium ion material at low magnification shows that the particles are uniformly dispersed, the overall particle size is small, and the particles have irregular block or sheet structure, which is beneficial to the penetration of electrolyte.

[0035] Figure 2 The SEM image of the obtained sodium ion material at high magnification shows that the particles have obvious layered sheet structure, which is beneficial to charge conduction.

[0036] Figure 3 The galvanostatic charge-discharge test (GCD) of the obtained sodium ion material shows that the electrochemical performance test results: the first discharge specific capacity is 384.8 mAh / g, and the first cycle coulombic efficiency is 85.5%.

[0037] Example 2

[0038] The difference between this example and Example 1 is that in step (3), the pre-carbonization temperature is 600°C, and the rest is the same as Example 1. The electrochemical performance test results: the first discharge specific capacity is 378.7 mAh / g, and the first cycle coulombic efficiency is 82.1%.

[0039] Example 3

[0040] The difference between the present example and Example 1 is that in step (4), the temperature of the carbonization treatment is 1000℃, and the rest is the same as Example 1. The electrochemical performance test results: the first discharge specific capacity is 354.6 mAh / g, and the first cycle coulombic efficiency is 80.2%.

[0041] Example 4

[0042] The difference between the present example and Example 1 is that in step 4, the temperature of the carbonization treatment is 1400℃, and the rest is the same as Example 1. The electrochemical performance test results: the first discharge specific capacity is 370.2 mAh / g, and the first cycle coulombic efficiency is 81.5%.

[0043] Comparative Example 1

[0044] Compared with Example 1, the difference is that blocky bamboo (10x4 cm) is selected, and the crushing and screening treatment of step (1) is not performed, and the other operations and parameters are the same as Example 1. The electrochemical performance test results: the first discharge specific capacity is 361.8 mAh / g, and the first cycle coulombic efficiency is 81.3%.

[0045] Comparative Example 2

[0046] Compared with Example 1, the difference is that one-step carbonization is directly performed in a muffle, and steps (2) and (3) are not performed, and in step (4), the heating device is a muffle furnace and no inert gas is added, and the other operations and parameters are the same as Example 1. The electrochemical performance test results: the first discharge specific capacity is 345 mAh / g, and the first cycle coulombic efficiency is 83.9%.

[0047] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a high-capacity sodium ion material based on precursor particle size screening, characterized in that: The following steps are involved: 1) The bamboo is cleaned in two steps and then dried, then crushed, sieved through a 50-300 mesh sieve and set aside; 2) pre-carbonizing the bamboo powder obtained in step 1) to obtain pre-carbonized carbon powder; 3) grinding the pre-carbonized carbon powder obtained in step 2), pickling, and drying; 4) Carbonizing the pre-carbonized carbon powder obtained after drying in step 3) to obtain a sodium ion material.

2. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In step 1), the two-step cleaning process is as follows: the first step is to use a steel wool to remove impurities on the surface of the bamboo-based material until the bamboo material is free of dirt; the second step is to soak the free of dirt bamboo material in deionized water for cleaning.

3. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In the step 1), the drying temperature does not exceed 120°C.

4. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In the step 2), the pre-carbonization temperature is 400-600° C., the heating rate is 1-10° C. / min, and the time is 1-3 hours.

5. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In the step 3), the disc grinding time is 3-5 minutes.

6. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In the step 3), the acid is HCl with a concentration of 1-3 mol / L, the pickling method is boiling, the pickling time is 10 min, and the drying temperature does not exceed 120°C.

7. The method for preparing a high-capacity sodium ion material based on precursor particle size screening according to claim 1, characterized in that: In the step 4), the inert gas in the carbonization treatment is nitrogen or argon, the heating rate is 1-10°C / min, the temperature is 1000-1400°C, and the time is 1-3 hours.

8. A high-capacity sodium ion material is prepared according to the method for preparing a high-capacity sodium ion material based on precursor particle size screening according to any one of claims 1 to 7.

9. Use of the high-capacity sodium ion material prepared based on precursor particle size screening according to claim 8 in sodium ion batteries.

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