A gradient sodium-philic carbon material and its application in sodium metal secondary battery negative electrode material

Abstract

This invention discloses a gradient sodium-loving carbon material and its application in the anode material of sodium metal secondary batteries. The preparation method of the gradient sodium-loving carbon material includes the following steps: (1) generation of carbon dots: tartary buckwheat powder is carbonized in an air atmosphere at a carbonization temperature of 200-400℃ for 1-3 hours to obtain a carbon doped carbon precursor; (2) carbonization: the carbon doped carbon precursor is carbonized again in an inert gas atmosphere at a carbonization temperature of 700-1000℃ for 1-3 hours to obtain a carbon doped three-dimensional carbon framework material, which is the gradient sodium-loving carbon material. The gradient sodium-loving carbon material of this invention can provide sufficient space for the deposition of metallic sodium and can effectively inhibit the growth of sodium dendrites.

Description

Technical Field

[0001] This invention belongs to the field of sodium metal secondary battery technology, specifically relating to a gradient sodium-loving carbon material and its application in sodium metal secondary battery anode materials. Background Technology

[0002] As a novel rechargeable battery technology, sodium metal batteries possess advantages such as abundant resources, low cost, high safety, and excellent high and low temperature performance, making them a potential complement or replacement for next-generation high-energy lithium metal batteries. However, sodium metal anodes also face several challenges during cycling, the most serious being the formation of sodium dendrites. Sodium dendrites refer to irregular, branching structures that form during sodium metal deposition under uneven electric field distributions. Sodium dendrites not only penetrate the separator, causing internal short circuits and safety hazards, but also lead to the loss of effective active materials and the destruction of the solid electrolyte intermediate phase, thus reducing cycle performance. Therefore, suppressing or eliminating sodium dendrites is crucial for achieving stable cycling and commercial application of sodium metal anodes.

[0003] Related research indicates that structural design of anode materials can effectively suppress dendrite growth. In sodium metal batteries, the dendrite problem is mainly due to the precipitation and growth of sodium metal on the electrode surface. Therefore, by using conductive substrates, surface modification, and pore structure design to alter the morphology and interface characteristics of the sodium metal anode, the precipitation and growth of sodium metal can be effectively slowed down, thereby suppressing dendrite growth. Carbon materials possess advantages such as abundant resources, low cost, excellent conductivity, and controllable microstructure, showing great potential in stabilizing sodium metal anodes and serving as ideal materials for sodium metal deposition frameworks. Therefore, controlling the structure of carbon materials can provide a new method and approach to solving the dendrite problem in sodium metal batteries. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a gradient sodium-loving carbon material and its application in sodium metal secondary battery anode materials, which can provide sufficient space for sodium metal deposition while effectively suppressing the growth of sodium dendrites.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] This invention discloses a method for preparing gradient sodium-loving carbon materials, comprising the following steps:

[0007] (1) Carbon dot formation: Buckwheat powder is carbonized in air at a temperature of 200-400℃ for 1-3 hours to obtain carbon dot-doped carbon precursor.

[0008] (2) Carbonization: The carbon precursor doped with carbon dots is carbonized again in an inert gas atmosphere. The carbonization temperature is 700-1000℃ and the carbonization time is 1-3h to obtain a three-dimensional carbon framework material doped with carbon dots, which is a gradient sodium-loving carbon material.

[0009] As a preferred technical solution, in step (1), the buckwheat powder is obtained by washing, drying and pulverizing buckwheat.

[0010] As a preferred technical solution, in step (1), the heating rate is 3-10℃ / min. -1 .

[0011] As a preferred technical solution, in step (2), the obtained product is washed with HCl solution and water to remove impurities, and then filtered and dried.

[0012] As a preferred technical solution, in step (2), the heating rate is 3-10℃ / min. -1 .

[0013] The present invention also discloses a gradient sodium-loving carbon material prepared by the above preparation method.

[0014] This invention also discloses the application of gradient sodium-loving carbon materials as anode materials for sodium metal secondary batteries.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. The material of the present invention is composed of highly graphitized carbon dots and highly disordered three-dimensional carbon framework, which combine to form a gradient sodium-loving structure. The three-dimensional porous structure of the carbon material can provide sufficient space for the deposition of metallic sodium and alleviate the volume expansion during the cycling process.

[0017] 2. Due to the presence of carbon dots, the sodium affinity of some sites is reduced. Sodium metal will preferentially deposit on non-carbon dot sites with higher disorder, and then gradually diffuse to the carbon dot region, eventually spreading across the entire electrode. This effectively inhibits the growth of sodium dendrites and significantly improves the cycle stability of sodium metal batteries. Attached Figure Description

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0019] Figure 1 The image shows a field emission scanning electron microscope (FESEM) image of the gradient sodium-loving carbon material prepared in Example 1.

[0020] Figure 2 This is a transmission electron microscope (TEM) image of the gradient sodium-loving carbon material prepared in Example 1.

[0021] Figure 3The images show the Raman spectra of the carbon materials prepared in Example 1 and Comparative Example 1.

[0022] Figure 4 The button cells of Example 1 and Comparative Example 1 were tested at 1 mA cm⁻¹. -2 Coulombic efficiency under 1mAh test conditions.

[0023] Figure 5 The button cell of Example 1 is at 1mA cm -2 Charge-discharge curves under 1mAh test conditions. Detailed Implementation

[0024] The preferred embodiments of the present invention will now be described in detail with reference to the examples. The described embodiments are only a part of the embodiments of the present invention, and not all of them. The scope of the present invention should not be construed as limited to the embodiments described below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing a gradient sodium-loving carbon material includes the following steps:

[0027] Step 1: Pretreatment of reactants: Take an appropriate amount of buckwheat, wash it repeatedly with deionized water, dry it, and then grind it into powder using a grinder.

[0028] Step 2, Carbon point formation: Place the powdered buckwheat obtained in Step 1 into a muffle furnace and heat it at 5°C for 1 minute in an air atmosphere. -1 Heat to 300℃ at a certain heating rate, hold for 2 hours, and then allow to cool naturally to room temperature.

[0029] Step 3, Carbonization: The product obtained in Step 2 is placed in a tube furnace and carbonized at 5°C for 1 minute under an inert gas atmosphere. -1 Heat to 900℃ at a certain heating rate, hold for 2 hours, and then allow to cool naturally to room temperature.

[0030] Step 4: Remove impurities: Take out and grind the product obtained in Step 3, wash and filter it with excess 1M HCl solution and deionized water, and dry it to obtain a gradient sodium-loving carbon material with a three-dimensional carbon framework in situ doped with carbon dots.

[0031] Comparative Example 1

[0032] A method for preparing a carbon material includes the following steps:

[0033] Step 1: Pretreatment of reactants: Take an appropriate amount of buckwheat, wash it repeatedly with deionized water, dry it, and then grind it into powder using a grinder.

[0034] Step 2, Carbonization: The powdered buckwheat obtained in Step 1 is placed in a tube furnace and carbonized at 5°C for 1 minute under an inert gas atmosphere. -1 Heat to 900℃ at a certain heating rate, hold for 2 hours, and then allow to cool naturally to room temperature.

[0035] Step 3: Remove impurities: Take out the product obtained in Step 2, grind it, wash it with excess 1M HCl solution and deionized water, filter it, and dry it to obtain a three-dimensional carbon framework material.

[0036] Figure 1 The image shown is a field emission scanning electron microscope (FESEM) image of the gradient sodium-loving carbon material prepared in Example 1. It can be seen that it has a three-dimensional porous structure, which can provide sufficient space for the deposition of metallic sodium and alleviate the volume expansion and contraction of the electrode material caused by cycling.

[0037] Figure 2 The image shows a transmission electron microscope (TEM) image of the gradient sodium-loving carbon material prepared in Example 1. The highly graphitized carbon dots and the highly disordered three-dimensional carbon skeleton combine to form a gradient sodium-loving structure. This gradient sodium-loving microstructure can induce uniform and orderly deposition of sodium metal, thereby inhibiting dendrite growth.

[0038] Figure 3 The Raman spectra of the carbon materials prepared in Example 1 and Comparative Example 1 show that highly graphitized carbon dots with low defect concentration were successfully introduced into the gradient sodium-loving carbon material prepared in Example 1.

[0039] The carbon materials prepared in Example 1 and Comparative Example 1 were assembled into button cells, and the relevant electrochemical performance of the materials was tested. Carbon materials, acetylene black, and polyvinylidene fluoride (PVDF) prepared in Example 1 and Comparative Example 1 were mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1. The slurry was then ground and dispersed, uniformly coated onto a copper current collector, and dried overnight in a vacuum oven at 120°C to obtain electrode sheets. All cells were assembled into 2032 type button cells in a glove box filled with Ar (water and oxygen content both below 0.01 ppm). The separator was a polypropylene separator, and the electrolyte was sodium trifluoromethanesulfonate electrolyte (1.0 M NaCF3SO3 in DIGLYME = 100 vol%). The current density was 1 mA cm⁻¹. -2 The coin cells were discharged under a constant areal capacity of 1 mAh, with a charging cutoff voltage of 1.0 V. The assembled coin cells were then subjected to electrochemical performance testing on the LAND battery testing system.

[0040] Figure 4 The button cells of Example 1 and Comparative Example 1 were tested at 1 mA cm⁻¹. -2Compared with the coulombic efficiency under the 1mAh test condition, the coulombic efficiency of Comparative Example 1 began to fluctuate after 330 cycles due to sodium dendrite growth. However, the coulombic efficiency of Example 1 remained very stable after 1000 cycles. It can be seen that the cycling stability of the gradient sodium-loving carbon material in Example 1 was significantly improved.

[0041] Figure 5 The button cell of Example 1 is at 1mA cm -2 The charge-discharge curves under 1mAh test conditions show that it has excellent cycle stability.

[0042] The above embodiments are only used to illustrate preferred embodiments of the present invention, and are not intended to limit the concept and scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a gradient sodium-loving carbon material, characterized in that: Includes the following steps: (1) Carbon dot formation: Buckwheat powder is carbonized in air at a temperature of 200-400℃ for 1-3 hours to obtain carbon dot-doped carbon precursor. (2) Carbonization: The carbon precursor doped with carbon dots is carbonized again in an inert gas atmosphere. The carbonization temperature is 700-1000℃ and the carbonization time is 1-3h. The resulting material is composed of highly graphitized carbon dots and a highly disordered three-dimensional carbon skeleton, which is a gradient sodium-loving carbon material.

2. The method for preparing gradient sodium-loving carbon materials as described in claim 1, characterized in that: In step (1), the buckwheat powder is obtained by washing, drying and pulverizing buckwheat.

3. The method for preparing gradient sodium-loving carbon materials as described in claim 1, characterized in that: In step (1), the heating rate is 3–10 °C / min. -1 .

4. The method for preparing gradient sodium-loving carbon materials as described in claim 1, characterized in that: In step (2), the obtained product is washed with HCl solution and water to remove impurities, and then filtered and dried.

5. The method for preparing gradient sodium-loving carbon materials as described in claim 1, characterized in that: In step (2), the heating rate is 3–10 °C / min. -1 .

6. The gradient sodium-loving carbon material prepared by the preparation method according to any one of claims 1-5.

7. The application of the gradient sodium-loving carbon material as described in claim 6 as a negative electrode material for sodium metal secondary batteries.

Images