Sodium ion battery negative electrode material and preparation method thereof

Abstract

The invention discloses a sodium ion battery negative electrode material and a preparation method thereof, and belongs to the technical field of battery materials. The preparation method of the sodium-ion battery negative electrode material comprises the following steps: pre-sintering crushed biomass, fully mixing the pre-sintered biomass with sodium acetate, and carbonizing the mixture in an oxygen-free environment to obtain the sodium-ion battery negative electrode material. According to the invention, sodium acetate is utilized to carry out surface functionalization on the pre-sintered biomass powder, so that the microstructure and surface chemical properties of the prepared sodium ion battery negative electrode material are effectively improved. Compared with an existing method, the performance of a sodium-ion battery negative electrode prepared from the sodium-ion battery negative electrode material is effectively improved, the sodium-ion battery negative electrode material prepared through the method can optimize formation of a solid electrolyte interface film, and the rate capability of an assembled sodium-ion battery is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a negative electrode material for a sodium ion battery and a preparation method thereof. Background Art

[0002] With the rapid development of renewable energy and the growth of energy demand, sodium-ion batteries (SIBs) have attracted much attention as a promising energy storage technology. Hard carbon anodes are considered to be the most promising SIB anodes due to their low sodium storage potential, high capacity, wide range of raw materials and environmental friendliness. However, the rate performance and initial coulombic efficiency of hard carbon hinder the further commercialization of hard carbon. These challenges are closely related to the microstructure and sodium storage mechanism of hard carbon anodes. Among them, the microstructure includes many factors such as surface defects, pore structure, interlayer spacing and surface functional groups of hard carbon materials. How to improve the microstructure of hard carbon materials to improve their rate performance and initial coulombic efficiency is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0003] The purpose of the present invention is to provide a sodium ion battery negative electrode material and a preparation method thereof. From the perspective of improving the microstructure of the surface of the hard carbon material, the present invention performs surface functionalization of the pre-sintered biomass powder with sodium acetate to improve the microstructure and surface chemical properties of the hard carbon material, thereby optimizing the formation of a solid electrolyte interface film to achieve a hard carbon anode with high first coulombic efficiency and high rate performance.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention is to provide a method for preparing a negative electrode material for a sodium ion battery, comprising the following steps:

[0006] The crushed biomass is pre-sintered, then fully mixed with sodium acetate, and then carbonized in an oxygen-free environment to obtain the sodium ion battery negative electrode material.

[0007] Preferably, the pre-sintering temperature is 100-400° C., the heating rate is 1-10° C., and the holding time is 1-15 h.

[0008] The sintering environment of the pre-sintering is not limited, and the sintering environment may selectively include: air, oxygen, argon, nitrogen, argon mixed with hydrogen, nitrogen mixed with hydrogen atmosphere or vacuum sintering.

[0009] Preferably, the sodium acetate comprises solid sodium acetate or a sodium acetate solution.

[0010] Solid sodium acetate can be selected from anhydrous sodium acetate, sodium acetate trihydrate and the like.

[0011] More preferably, the method of fully mixing comprises grinding, mechanically crushing, ball milling or high-energy ball milling solid sodium acetate and pre-sintered biomass powder together; or immersing the pre-sintered biomass powder in a sodium acetate solution and then evaporating the solvent.

[0012] Further preferably, the grinding, mechanical crushing, ball milling or high-energy ball milling is performed to a degree that the particle size of the material is processed to not more than 100 μm.

[0013] Preferably, the carbonization temperature is 800-1600°C, and the heating rate is 1-5°C·min -1 , the insulation time is 1 to 3 hours.

[0014] The carbonization environment may be oxygen-free, and the carbonization environment may optionally include: argon, nitrogen, argon mixed with hydrogen, nitrogen mixed with hydrogen atmosphere or vacuum sintering.

[0015] The second technical solution of the present invention is to provide a sodium ion battery negative electrode material prepared according to the above-mentioned method for preparing the sodium ion battery negative electrode material.

[0016] The third technical solution of the present invention is to provide an application of the above-mentioned sodium ion battery negative electrode material in the preparation of a sodium ion battery negative electrode.

[0017] Technical solution four of the present invention: provides an application of the above-mentioned sodium ion battery negative electrode material in the preparation of a sodium ion battery.

[0018] The beneficial technical effects of the present invention are as follows:

[0019] The present invention provides a sodium ion battery negative electrode material and a preparation method thereof. The present invention uses sodium acetate to perform surface functionalization on pre-sintered biomass powder, effectively improving the microstructure and surface chemical properties of the prepared sodium ion battery negative electrode material. Compared with the existing method, the performance of the sodium ion battery negative electrode prepared by the sodium ion battery negative electrode material is effectively improved. The sodium ion battery negative electrode material prepared by the present invention can optimize the formation of a solid electrolyte interface film and greatly improve the rate performance of the assembled sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The XRD patterns of the negative electrode materials for sodium ion batteries prepared in Examples 1 to 3 and Comparative Example 1 are shown.

[0021] Figure 2 This is the Raman spectrum of the sodium ion battery negative electrode material prepared in Examples 1 to 3 and Comparative Example 1.

[0022] Figure 3 FTIR spectra of the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1.

[0023] Figure 4This is the FTIR enlarged spectrum of the sodium ion battery negative electrode material prepared in Examples 1 to 3 and Comparative Example 1.

[0024] Figure 5 The charge and discharge curves of button cells assembled with the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1 at 0.1C.

[0025] Figure 6 This is a rate diagram of button cells assembled with the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1. DETAILED DESCRIPTION

[0026] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0027] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0029] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0030] Unless otherwise specified, "room temperature" in the present invention refers to a temperature of 20±10°C.

[0031] The steps for preparing the walnut shell precursor used in the examples and comparative examples of the present invention are as follows:

[0032] The dried walnut shell was crushed to less than 0.3 mm, washed with water and dried, and then heated to 300° C. at a heating rate of 5° C. in a muffle furnace and kept warm for 6 hours in an air sintering atmosphere to complete pre-sintering and obtain a walnut shell precursor.

[0033] Example 1

[0034] Preparation of negative electrode materials for sodium ion batteries:

[0035] The walnut shell precursor and anhydrous sodium acetate were mixed in a mass ratio of 4:1 and ball-milled to a particle size of no more than 100 μm. The mixture was then transferred to an atmosphere furnace and heated at 5 °C min under an argon atmosphere. -1 The heating rate was increased to 1400°C and kept warm for 2 hours to obtain the sodium ion battery negative electrode material, which was recorded as WHC@Ac-4.

[0036] Example 2

[0037] Preparation of negative electrode materials for sodium ion batteries:

[0038] The walnut shell precursor and anhydrous sodium acetate were mixed in a mass ratio of 5:1 and ball-milled to a particle size of no more than 100 μm. The mixture was then transferred to an atmosphere furnace and heated at 5 °C·min under an argon atmosphere. -1 The heating rate was increased to 1400°C and kept warm for 2 hours to obtain the sodium ion battery negative electrode material, which was recorded as WHC@Ac-5.

[0039] Example 3

[0040] Preparation of negative electrode materials for sodium ion batteries:

[0041] The walnut shell precursor and anhydrous sodium acetate were mixed in a mass ratio of 10:1 and ball-milled to a particle size of no more than 100 μm. The mixture was then transferred to an atmosphere furnace and heated at 5 °C·min under an argon atmosphere. -1 The heating rate was increased to 1400°C and kept warm for 2 hours to obtain the sodium ion battery negative electrode material, which was recorded as WHC@Ac-10.

[0042] Comparative Example 1

[0043] Preparation of negative electrode materials for sodium ion batteries:

[0044] The walnut shell precursor was ball-milled to a particle size of no more than 100 μm; then transferred to an atmosphere furnace and heated at 5 °C min under an argon atmosphere. -1 The heating rate was raised to 1400°C and kept warm for 2 hours to obtain the sodium ion battery negative electrode material, which was recorded as WHC.

[0045] The sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1 were characterized and their performances were tested.

[0046] XRD test method:

[0047] CuK α X-ray was used to test the sample. The test step length was 0.02° and the test scanning speed was 5°min. -1 .

[0048] Raman test method:

[0049] The laser wavelength was 532 nm and the scanning range was set from 100 to 1000 cm -1 , resolution 1cm -1 All tests were performed at room temperature.

[0050] FTIR test method:

[0051] The samples were tested by conventional powder tableting, with the test wave number ranging from 400 to 4000 cm -1 , resolution 4cm -1 .

[0052] Electrochemical performance test plan:

[0053] The sodium ion battery negative electrode material, carbon black, and sodium alginate were weighed in a mass ratio of 8:1:1 and mixed with deionized water, and then dried in a vacuum drying oven at 80°C for 12 hours. Sodium metal was used as the counter electrode, 1M sodium hexafluorophosphate solution in diethylene glycol dimethyl ether was used as the electrolyte, and the diaphragm was a glass fiber diaphragm, and button batteries were assembled in a glove box.

[0054] The XRD patterns of the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1 are shown in Figure 1 , Raman spectrum see Figure 2 , FTIR spectrum see Figure 3 , FTIR enlarged spectrum see Figure 4 .

[0055] from Figure 1 to Figure 4 It can be seen that compared with the comparative example 1 group, the 002 peak near 23° in the XRD test of the sodium ion battery negative electrode material in the embodiment 1 group is shifted to a higher angle, the Raman spectrum peak intensity has no obvious change, the C=O peak in the FTIR test and the enlarged figure is significantly enhanced, and the C=C peak is relatively smooth. The strength of the absorption peak reflects the content of the functional group of the sample to a certain extent; there is no obvious shift in the XRD test of the sodium ion battery negative electrode material in the embodiment 2 group, the Raman spectrum peak intensity is significantly weakened, and the C=O and C=C peaks in the FTIR test and the enlarged figure are significantly enhanced, indicating that the C=O and C=C bonds of the sample are increased after treatment; there is no obvious shift in the XRD test of the sodium ion battery negative electrode material in the embodiment 3 group, the Raman spectrum peak intensity has no obvious change, the C=O and C=C peaks in the FTIR test and the enlarged figure are both enhanced, and the content of the functional groups to which they belong is increased.

[0056] The capacity of the button cell assembled with the sodium ion battery negative electrode material in Example 1 at 1C is 310.44 mAh·g -1 , the capacity at 5C is 244.0mAh·g -1 The capacity of the button cell assembled with the sodium ion battery negative electrode material in Example 2 at 1C is 345.92 mAh g-1 , the capacity at 5C is 266.8 mAh g -1 The capacity of the button cell assembled with the sodium ion battery negative electrode material in Example 3 at 1C is 304.29 mAh g -1 , the capacity at 5C is 248.3mAh·g -1 ; Comparative Example 1: The capacity of the button cell assembled with the sodium ion battery negative electrode material at 1C is 288.14 mAh g -1 , the capacity at 5C is 193.4 mAh g -1 .

[0057] The charge and discharge curves of the button cells assembled with the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1 at 0.1C are shown in Figure 5 .

[0058] from Figure 5 It can be seen that the specific capacity of the treated samples increased, among which Example 2 (WHC@Ac-5) had the highest specific capacity.

[0059] The rate diagram of the button cells assembled with the sodium ion battery negative electrode materials prepared in Examples 1 to 3 and Comparative Example 1 is shown in Figure 6 .

[0060] from Figure 6 It can be seen that the specific capacity of the treated sample materials at high current density is greatly improved, and in particular, the sample of Example 2 (WHC@Ac-5) is higher than the other three materials at each current density.

[0061] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a negative electrode material for a sodium ion battery, characterized in that: The following steps are involved: The crushed biomass is pre-sintered, then fully mixed with sodium acetate, and then carbonized in an oxygen-free environment to obtain the sodium ion battery negative electrode material.

2. The method for preparing a negative electrode material for a sodium ion battery according to claim 1, characterized in that: The pre-sintering temperature is 100-400° C., the heating rate is 1-10° C., and the heat preservation time is 1-15 hours.

3. The method for preparing a negative electrode material for a sodium ion battery according to claim 1, characterized in that: The sodium acetate includes solid sodium acetate or sodium acetate solution.

4. The method for preparing a negative electrode material for a sodium ion battery according to claim 3, characterized in that: The method for fully mixing comprises grinding, mechanically crushing, ball milling or high-energy ball milling solid sodium acetate and pre-sintered biomass powder together; or immersing the pre-sintered biomass powder in a sodium acetate solution and then evaporating the solvent.

5. The method for preparing a negative electrode material for a sodium ion battery according to claim 4, characterized in that: The degree of the grinding, mechanical crushing, ball milling or high-energy ball milling is to process the material particle size to no more than 100 μm.

6. The method for preparing a negative electrode material for a sodium ion battery according to claim 1, characterized in that: The carbonization temperature is 800-1600°C, and the heating rate is 1-5°C·min -1 , the insulation time is 1 to 3 hours.

7. A sodium ion battery negative electrode material obtained by the method for preparing a sodium ion battery negative electrode material according to any one of claims 1 to 6.

8. Use of the sodium ion battery negative electrode material according to claim 7 in preparing a sodium ion battery negative electrode.

9. Use of the sodium ion battery negative electrode material according to claim 7 in the preparation of sodium ion batteries.

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