A preparation method of a carbon-supported bismuth oxycarbonate negative electrode material

Abstract

The present invention relates to a preparation method of a carbon-supported bismuth oxycarbonate negative electrode material, belonging to the technical field of battery negative electrode materials. In the present invention, bismuth nitrate pentahydrate is dissolved in deionized water to obtain a bismuth nitrate solution, sodium alginate is dissolved in deionized water to obtain a sodium alginate gel, and then the sodium alginate gel is added dropwise into the bismuth nitrate solution, and stirred and reacted at a temperature of 70-100 °C for 30-60 min. After filtration, the droplet-shaped gel is freeze-dried, and then carbonized in a protective atmosphere for 2-3 h to obtain a precursor A; the precursor A is dispersed in ultrapure water to obtain a precursor A dispersion, urea and a carbon material are added to the precursor A dispersion, ultrasonically treated for 30-60 min, and then reacted at a temperature of 160-180 °C for 10-12 h. After cooling to room temperature, the supernatant is removed, and after centrifugal washing and drying, the carbon-supported Bi2O2CO3 negative electrode material is obtained. The present invention prepares a carbon-supported Bi2O2CO3 negative electrode material by a hydrothermal method, which has a high discharge specific capacity, rate performance and stable cycle performance.

Description

Technical Field

[0001] The present invention relates to a preparation method of a carbon-supported bismuth oxycarbonate negative electrode material, belonging to the technical field of battery negative electrode materials. Background Art

[0002] With the rapid development of social economy, the extensive use of the three major fossil energy sources such as coal, oil, and natural gas has caused energy shortages and huge environmental pollution problems. In the development of renewable energy, secondary batteries have become one of the hotspots in the current energy field research due to their characteristics of stable voltage, good safety, low price, wide application range, rich raw materials, and high recycling rate, and have been widely used in the fields of electronic devices and energy storage in recent years. As one of the key materials of lithium-ion batteries, the negative electrode material plays a crucial role in the final performance of lithium-ion batteries. The performance optimization of high-energy-density and high-power-density power lithium-ion batteries relies on technological innovation breakthroughs in negative electrode materials. Therefore, high-performance negative electrode materials have become one of the research hotspots of lithium-ion batteries currently.

[0003] Bismuth oxycarbonate-based (Bi2O2CO3) negative electrode materials have attracted much attention from researchers because of their simple preparation process and low preparation cost. At the same time, the Bi2O2CO3 material has a special sillén layered structure. The Bi2O2CO3 layered structure material is composed of positively charged [Bi2O2] 2+ and negatively charged CO3 2- layers alternatingly formed. The plane where CO3 2- is located is perpendicular to the [Bi2O2] 2+ layer. This alternating arrangement of positive charge layers and negative charge layers will form a two-dimensional ion channel in the Bi2O2CO3 crystal structure. The establishment of this two-dimensional ion channel promotes small-radius S 2- to automatically break through the bondage of water molecules in the hydration layer and directly enter the two-dimensional ion channel to reach the surface of the electrode material, reducing the overpotential of the solution reaction on the electrode surface, resulting in good electrochemical performance of the Bi2O2CO3 material. However, bismuth-based negative electrode materials such as Bi2O2CO3 have always had problems of low electrical conductivity and volume expansion during charge and discharge, resulting in serious attenuation of the capacity of the negative electrode material and restricting its wide application. Summary of the Invention

[0004] Aiming at the problems of low conductivity of current bismuth-based anode materials such as Bi2O2CO3 and volume expansion during charge and discharge, the present invention provides a preparation method of a carbon-supported bismuth oxycarbonate anode material, that is, sodium alginate is cross-linked with bismuth nitrate pentahydrate, and then the cross-linked structure is fixed by freeze-drying, and carbonization is carried out to obtain a Bi@C composite structure supported by carbon materials, and then a carbon-supported bismuth oxycarbonate anode material is prepared by hydrothermal reaction to solve the problems of low capacity of existing carbon materials and low battery capacity and rapid capacity decay during charge and discharge of bismuth oxide-based anode materials due to low conductivity and volume expansion problems.

[0005] A preparation method of a carbon-supported bismuth oxycarbonate anode material is as follows:

[0006] (1) Dissolve bismuth nitrate pentahydrate in deionized water to obtain a bismuth nitrate solution, dissolve sodium alginate in deionized water to obtain a sodium alginate gel, then drop the sodium alginate gel into the bismuth nitrate solution drop by drop, and stir and react at a temperature of 70-100°C for 30-60 min. After filtration, the droplet-shaped gel is freeze-dried, and then carbonized in a protective atmosphere for 2-3 h to obtain precursor A;

[0007] (2) Disperse precursor A in ultrapure water to obtain a precursor A dispersion, add urea and carbon materials to the precursor A dispersion, ultrasonically treat for 30-60 min, then react at a temperature of 160-180°C for 10-12 h, cool to room temperature, remove the supernatant, and dry after centrifugal washing to obtain a carbon-supported Bi2O2CO3 anode material.

[0008] In the step (1), the concentration of the bismuth nitrate solution is 20-50 g / L, the concentration of sodium alginate in the sodium alginate gel is 20-60 g / L, and the mass ratio of sodium alginate to bismuth nitrate pentahydrate is 1-2:1.

[0009] In the step (1), the stirring speed is 400-500 rpm.

[0010] In the step (1), the freeze-drying temperature is -10 to -30°C, and the time is 24-36 h.

[0011] The protective atmosphere is a nitrogen atmosphere or an argon atmosphere, and the temperature of the carbonization treatment is 500-600°C.

[0012] In the step (2), the concentration of the precursor A dispersion is 6-10 g / L, the mass ratio of precursor A to urea is 2-5:1, and the mass ratio of carbon materials to precursor A is 1-2:5.

[0013] In the step (2), the carbon materials are graphene, CNT or glucose.

[0014] The present invention crosslinks sodium alginate with bismuth nitrate pentahydrate, and then freeze-dries to fix the crosslinked structure, and carbonizes to obtain a Bi@C composite structure supported by a carbon material. The introduction of the carbon material is beneficial to improving the conductivity. At the same time, the structure fixed by freeze-drying provides space for the expansion of the material during the charge and discharge process, which is beneficial to improving the structural stability and discharge capacity of the composite material; adding urea for hydrothermal reaction promotes the transformation of Bi into Bi2O2CO3 material. The doping of carbon materials (graphene, CNT or glucose) further improves the conductivity of the material and forms a semi-coated structure on the Bi2O2CO3@C material, which is beneficial to the transport of electrons and ions. At the same time, it can alleviate the capacity attenuation caused by volume expansion during the charge and discharge process of the material and improve the cycle stability of the battery.

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

[0016] (1) The present invention crosslinks sodium alginate with bismuth nitrate pentahydrate, which is beneficial to the formation of droplet-shaped gels; freeze-drying is beneficial to the subsequent construction of a three-dimensional carbon-supported structure. Carbonization at high temperature yields carbon-supported Bi@C composite nanopowders. The carbon in the support structure can not only improve the conductivity of the material but also alleviate the volume change during the charge and discharge process of the material;

[0017] (2) By adding urea for hydrothermal reaction in the present invention, it is beneficial to the synthesis of the Bi2O2CO3 negative electrode material and the realization of N element doping in the carbon material, which can further improve the conductivity of the material and is beneficial to improving the battery capacity;

[0018] (3) By adding carbon materials (graphene, CNT or glucose) in the present invention, a structure semi-coated with carbon materials is obtained. The main function is to inhibit the volume expansion of the material during the charge and discharge process, so that the Bi2O2CO3 negative electrode material has relatively stable cycle performance;

[0019] (4) The Bi2O2CO3 nanopowders uniformly coated with carbon materials (graphene, CNT or glucose) in the present invention can improve the electron transport between powders, improve the structural stability, the prepared negative electrode material has stable electrochemical performance, high battery specific capacity, and excellent cycle stability at the same time. Description of the Drawings

[0020] Figure 1 XRD pattern of the carbon-supported Bi2O2CO3 negative electrode material in Example 1;

[0021] Figure 2 SEM image of the carbon-supported Bi2O2CO3 negative electrode material in Example 1 at low magnification;

[0022] Figure 3 SEM image of the carbon-supported Bi2O2CO3 negative electrode material in Example 1 at high magnification;

[0023] Figure 4 TEM image of Bi2O2CO3 in Example 1;

[0024] Figure 5 Cycling performance graph of the carbon-supported Bi2O2CO3 anode material in Example 1;

[0025] Figure 6 Cycling performance graph of the carbon-supported Bi2O2CO3 anode material in Comparative Example 5;

[0026] Figure 7 Cycling performance graph of the carbon-supported Bi2O2CO3 anode material in Comparative Example 6. Detailed implementation manners

[0027] The present invention will be further described in detail below in conjunction with the detailed implementation manners, but the protection scope of the present invention is not limited to the content described.

[0028] Example: A preparation method of a carbon-supported bismuth oxycarbonate anode material, the specific steps are as follows:

[0029] (1) Dissolve bismuth nitrate pentahydrate in deionized water to obtain a bismuth nitrate solution, dissolve sodium alginate in deionized water to obtain a sodium alginate gel, then drop the sodium alginate gel into the bismuth nitrate solution drop by drop, and stir and react at a temperature of 80 °C for 30 min. After filtration, place the droplet-shaped gel at a temperature of -20 °C for freeze-drying for 24 h, and then place it in a nitrogen atmosphere and carbonize it at a temperature of 600 °C for 2 - 3 h to obtain precursor A; wherein the concentration of the bismuth nitrate solution is 20 - 50 g / L, the concentration of sodium alginate in the sodium alginate gel is 20 - 60 g / L, and the mass ratio of sodium alginate to bismuth nitrate pentahydrate is 1 - 2:1;

[0030] (2) Disperse precursor A into ultrapure water to obtain a precursor A dispersion, add urea and a carbon material (graphene, CNT or glucose) to the precursor A dispersion, perform ultrasonic treatment for 30 - 60 min, and then react at a temperature of 160 - 180 °C for 10 - 12 h. Cool to room temperature, remove the supernatant, and dry after centrifugal washing to obtain the carbon-supported Bi2O2CO3 anode material; wherein the concentration of the precursor A dispersion is 6 - 10 g / L, the mass ratio of precursor A to urea is 2 - 5:1, and the mass ratio of the carbon material (graphene, CNT or glucose) to precursor A is 1 - 2:5;

[0031] The process parameters of Examples 1 - 6 are shown in Table 1;

[0032] Table 1 Process parameters of Examples 1 - 6

[0033] ;

[0034] XRD pattern of the carbon-supported bismuth oxycarbonate negative electrode material in Example 1. According to the standard PDF card, the main peaks of the sample match the standard card of Bi2O2CO3, indicating that the main phase is Bi2O2CO3. At the same time, the diffraction peaks of graphene can also be detected, indicating the presence of graphene in the sample;

[0035] SEM images of the carbon-supported Bi2O2CO3 negative electrode material in Example 1 are shown in Figure 2 and 3 . At the micron-level resolution, carbon materials after the carbonization of sodium alginate, flaky graphene, and flower-like Bi2O2CO3 materials can be observed in the powder. At high magnification, the Bi2O2CO3 material is composed of countless flakes;

[0036] TEM images of Bi2O2CO3 in Example 1 are shown in Figure 4 . It can be seen from the figure that Bi2O2CO3 has a structure of overlapping flakes, which is consistent with the microscopic morphology in the scanning electron microscope;

[0037] Set comparative examples, and the process parameters are shown in Table 2;

[0038] Table 2 Process parameters of comparative examples

[0039] ;

[0040] Electrochemical performance characterization:

[0041] The powder materials obtained in Examples 1-6 and Comparative Examples 1-6 were assembled into coin cells, and charge-discharge tests and cycle stability tests were carried out under the condition of a constant current of 0.1 A / g;

[0042] The preparation process of the CR2025 coin cell is as follows: The lithium-ion battery is assembled in a sealed glove box filled with argon, and the water content and oxygen content are controlled below 0.1 ppm. A self-made circular electrode with a diameter of 12 mm (the material of the example or comparative example) is used as the negative electrode, Celgard 2400 with a diameter of 17 mm is used as the separator, and a pure lithium sheet is used as the positive electrode. The electrolyte solute is 1 mol L -1 of LiPF6, and the solvent is a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), where the volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is 1:1:1. The battery is encapsulated using a tablet press. After the assembled battery is left standing for 24 h, electrochemical tests are carried out;

[0043] Taking the Bi2O2CO3 negative electrode materials prepared in Example 1, Comparative Example 5, and Comparative Example 6 as examples, the test results of the first charge-discharge and 15 cycles are as Figures 5 to 7As shown; the first charge-discharge results of Examples 1-6 and Comparative Examples 1-6 and the capacity results after 100 cycles are shown in Table 3;

[0044] Table 3 Battery performance of Examples 1-6 and Comparative Examples 1-6

[0045] ;

[0046] The carbon-supported Bi2O2CO3 anode material. The carbon obtained by carbonizing sodium alginate (chitosan) provides support for the entire anode material, improving the structural stability. The introduced carbon materials (graphene, CNT or glucose) can significantly enhance the conductivity of the material, promote the transport of lithium ions during charge and discharge, improve the lithium storage performance of the material. Freeze-drying can effectively fix the porous carbon structure, and relieve the volume stress of the material to the greatest extent during charge and discharge, thereby enhancing the cycle stability of the material, improving the significant attenuation of the capacity caused by the volume expansion problem during lithium storage, and further enhancing the material capacity and the retention rate of the capacity.

[0047] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

Claims

1. A preparation method of a carbon-supported bismuth oxycarbonate negative electrode material, characterized in that The specific steps are as follows: (1) Dissolve bismuth nitrate pentahydrate in deionized water to obtain a bismuth nitrate solution, dissolve sodium alginate in deionized water to obtain a sodium alginate gel, then drop the sodium alginate gel into the bismuth nitrate solution drop by drop, and stir and react at a temperature of 70-100°C for 30-60 minutes. After filtration, freeze-dry the droplet-shaped gel, and then carbonize it in a protective atmosphere for 2-3 hours to obtain precursor A; (2) Disperse precursor A in ultrapure water to obtain a precursor A dispersion, add urea and carbon material to the precursor A dispersion, perform ultrasonic treatment for 30-60 minutes, then react at a temperature of 160-180°C for 10-12 hours, cool to room temperature, remove the supernatant, and dry after centrifugal washing to obtain the carbon-supported Bi2O2CO3 anode material.

2. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, characterized in that: In step (1), the concentration of the bismuth nitrate solution is 20-40 g / L, the concentration of sodium alginate in the sodium alginate gel is 20-60 g / L, and the mass ratio of sodium alginate to bismuth nitrate pentahydrate is 1-2:

1.

3. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, wherein: In step (1), the stirring speed is 400-500 rpm.

4. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, characterized in that: In step (1), the freeze-drying temperature is -10 to -30°C, and the time is 24-36 hours.

5. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, wherein: The protective atmosphere is a nitrogen atmosphere or an argon atmosphere, and the carbonization temperature is 500-600°C.

6. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, wherein: In step (2), the concentration of the precursor A dispersion is 6-10 g / L, the mass ratio of precursor A to urea is 2-5:1, and the mass ratio of the carbon material to precursor A is 1-2:

5.

7. The preparation method of the carbon-supported bismuth oxycarbonate negative electrode material according to claim 1, characterized in that: In step (2), the carbon material is graphene, CNT or glucose.

Images