Preparation method and application of multilayer shell-shaped bismuth oxide / bismuth / carbon composite material

Abstract

The application relates to a preparation method and application of a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material and belongs to the technical field of lithium ion batteries. Bismuth nitrate pentahydrate and ethylene glycol are added into an ethanol solvent and uniformly ultrasonically mixed, then are placed in a solvent thermal reaction at a temperature of 180-200 DEG C for 150-180 min, are cooled to room temperature, are subjected to solid-liquid separation, and the solid is sequentially washed by deionized water and ethanol and is dried to obtain multilayer shell-shaped bismuth oxide; glucose and the multilayer shell-shaped bismuth oxide are added into deionized water and uniformly ultrasonically mixed, then are placed in a hydrothermal reaction at a temperature of 180-200 DEG C for 120-180 min, are subjected to solid-liquid separation, and the solid is sequentially washed by deionized water and ethanol and is dried to obtain a precursor; the precursor is uniformly heated to a temperature of 400-600 DEG C under an argon atmosphere and is calcined at a constant temperature for 1-2 h to obtain the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material. The multilayer shell-shaped bismuth oxide / bismuth / carbon composite material has a high specific surface area, and as a lithium ion battery negative electrode, can relieve the huge volume expansion of a lithium ion battery in a lithiumation process.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material, belonging to the field of lithium-ion battery technology. Background Technology

[0002] While graphite offers stable cycle performance as a commercial lithium-ion battery anode material, its low theoretical capacity limits the further development of high-performance lithium-ion batteries. To fabricate high-capacity lithium-ion batteries, researchers have been dedicated to developing novel anode materials. Among the many anode materials available, transition metal oxides have attracted attention due to their high theoretical capacity, especially bismuth oxide, which boasts an excellent volumetric capacity (3800 mAh / cm³). -3 This has attracted the attention of researchers, but it causes huge volume expansion during the lithium-ion lithiation process, affecting the stability of the battery and thus its lifespan; secondly, bismuth oxide has poor conductivity, which also affects the electrochemical performance of the battery.

[0003] Therefore, it is necessary to prepare a composite negative electrode for lithium-ion batteries that has both good stability and conductivity. Summary of the Invention

[0004] To address the issue of significant volume expansion of the negative electrode during lithium-ion lithiation, which affects battery stability and consequently lifespan, this invention proposes a method for preparing and applying a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material. The method involves preparing multilayer shell bismuth oxide via a solvothermal reaction using bismuth salt, partially carbonizing it through secondary hydrothermal treatment with added glucose, and finally preparing the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material through calcination. As a composite negative electrode for lithium-ion batteries, this multilayer shell-shaped bismuth oxide / bismuth / carbon composite material can alleviate the significant volume expansion during lithiation, while the reduced bismuth increases the conductivity of the composite material, and the remaining carbon layers enhance the battery's stable cycle performance.

[0005] A method for preparing a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material, the specific steps of which are as follows:

[0006] (1) Add bismuth nitrate pentahydrate and ethylene glycol to ethanol solvent and mix by ultrasonication. Then place it at a temperature of 180-200℃ for a solvothermal reaction for 150-180 min. Cool to room temperature, separate the solid and liquid, wash the solid with deionized water and ethanol in sequence, and dry to obtain multilayer shell bismuth oxide.

[0007] (2) Add glucose and multi-layer shell bismuth oxide to deionized water and mix by ultrasonication. Then place it in a hydrothermal reaction at a temperature of 180-200℃ for 120-180 min. Separate the solid and liquid. Wash the solid with deionized water and ethanol in sequence and dry it to obtain the precursor.

[0008] (3) Under an argon atmosphere, the precursor is heated at a constant rate to a temperature of 400-600℃ and calcined at a constant temperature for 1-2 hours to obtain a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material.

[0009] In step (1), the solid-liquid ratio of bismuth nitrate pentahydrate to ethanol solvent (g:mL) is 0.97–1.455:75, and the volume ratio of ethylene glycol to ethanol solvent (ml:mL) is 5–10:75.

[0010] In step (2), the mass ratio of multilayer shell bismuth oxide to glucose is 10-15:1.

[0011] The uniform heating rate in step (3) is 4-8℃ / min.

[0012] The beneficial effects of this invention are:

[0013] (1) This invention uses bismuth nitrate pentahydrate as raw material and ethylene glycol as an inducer to prepare multi-shell structured bismuth oxide by solvothermal method, then adds glucose to achieve partial carbonization by secondary hydrothermal method, and finally prepares multi-shell bismuth oxide / bismuth / carbon composite material by calcination, which has a high specific surface area.

[0014] (2) The multi-layer shell-shaped bismuth oxide / bismuth / carbon composite material of the present invention, as a composite negative electrode of lithium-ion battery, greatly alleviates the volume expansion caused by lithium-ion battery in the lithiation process, enhances the conductivity and cycle stability of lithium-ion battery composite negative electrode, and extends the service life of bismuth oxide composite material as lithium-ion battery. Attached Figure Description

[0015] Figure 1 Here is a SEM image of the multilayer shell-like bismuth oxide from Example 1;

[0016] Figure 2 The image shows the XRD pattern of multilayer shell-like bismuth oxide from Example 1.

[0017] Figure 3 This is a SEM image of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material from Example 1.

[0018] Figure 4 SEM and EDS images of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in Example 2;

[0019] Figure 5 The image shows the XRD pattern of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in Example 3.

[0020] Figure 6 SEM and EDS images of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in Example 3;

[0021] Figure 7EIS images of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite negative electrodes in Examples 1-3;

[0022] Figure 8 The graph shows the cycle stability test results of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite anode in Example 1 after 160 cycles at a current density of 0.1 A / g.

[0023] Figure 9 The graph shows the cycle stability test results of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite negative electrode in Example 2 after 100 cycles at a current density of 0.1 A / g.

[0024] Figure 10 The graph shows the cycle stability test results of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite anode in Example 3 after 500 cycles at a current density of 0.1 A / g. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0026] Example 1: A method for preparing a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material, the specific steps of which are as follows:

[0027] (1) Add 1.455g of bismuth nitrate pentahydrate and 5ml of ethylene glycol to 75ml of ethanol solvent and sonicate for 30min. Then place it at 180℃ for solvothermal reaction for 180min. Cool to room temperature, separate solid and liquid. Wash the solid three times with deionized water and then three times with ethanol. Dry to obtain multilayer shell bismuth oxide.

[0028] (2) Add glucose and multi-layer shell bismuth oxide to 80 ml of deionized water and mix by ultrasonication. Then place it at 180℃ for hydrothermal reaction for 120 min. Separate the solid and liquid. Wash the solid with deionized water and ethanol in sequence and dry it to obtain the precursor. The mass ratio of the multi-layer shell bismuth oxide to glucose is 10:1.

[0029] (3) Under an argon atmosphere, the precursor was heated to 400℃ at a constant heating rate of 4℃ / min and calcined at a constant temperature for 1h to obtain a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material.

[0030] The SEM image of the multilayer shell-like bismuth oxide in this embodiment is shown below. Figure 1 ,from Figure 1 It can be seen that the product as a whole exhibits a multi-layered shell morphology.

[0031] The XRD pattern of the multilayer shell-like bismuth oxide in this embodiment is shown below. Figure 2 ,from Figure 2It can be seen that the main diffraction peaks and relative intensities of the product are consistent with the JCPDS (Powder Diffraction Standards Committee) card (PDF#27-0052), proving that the generated product is Bi2O3. Figure 1 It is known that multilayer shell-shaped bismuth oxide materials have been successfully prepared.

[0032] The SEM image of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in this embodiment is shown below. Figure 3 ,from Figure 3 It can be seen that the product has a multi-layered shell-like morphology.

[0033] Example 2: A method for preparing a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material, the specific steps of which are as follows:

[0034] (1) Add 0.97g of bismuth nitrate pentahydrate and 10ml of ethylene glycol to 75ml of ethanol solvent and sonicate for 25min. Then place it at 200℃ for solvothermal reaction for 150min. Cool to room temperature, separate solid and liquid. Wash the solid 3 times with deionized water and then 4 times with ethanol. Dry to obtain multilayer shell bismuth oxide.

[0035] (2) Add glucose and multi-layer shell bismuth oxide to 80 ml of deionized water and mix by ultrasonication. Then place it at 200℃ for hydrothermal reaction for 120 min. Separate the solid and liquid. Wash the solid with deionized water and ethanol in sequence and dry it to obtain the precursor. The mass ratio of the multi-layer shell bismuth oxide to glucose is 15:1.

[0036] (3) Under an argon atmosphere, the precursor was heated to 600℃ at a constant heating rate of 8℃ / min and calcined at a constant temperature for 2h to obtain a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material.

[0037] The SEM and EDS images of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in this embodiment are shown below. Figure 4 ,from Figure 4 It can be seen that the prepared composite material exhibits a multi-layered shell morphology, and the O, Bi, and C elements are evenly distributed on each shell in the EDS diagram.

[0038] Example 3: A method for preparing a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material, the specific steps of which are as follows:

[0039] (1) Add 1.455g of bismuth nitrate pentahydrate and 8ml of ethylene glycol to 75ml of ethanol solvent and sonicate for 35min. Then place it at 190℃ for solvothermal reaction for 160min. Cool to room temperature, separate solid and liquid. Wash the solid 4 times with deionized water and then 3 times with ethanol. Dry to obtain multilayer shell bismuth oxide.

[0040] (2) Add glucose and multi-layer shell bismuth oxide to 80 ml of deionized water and mix by ultrasonication. Then place it at 190 °C for hydrothermal reaction for 160 min. Separate the solid and liquid. Wash the solid with deionized water and ethanol in sequence and dry it to obtain the precursor. The mass ratio of the multi-layer shell bismuth oxide to glucose is 12:1.

[0041] (3) Under an argon atmosphere, the precursor was heated to 500°C at a constant heating rate of 6°C / min and calcined at a constant temperature for 2 hours to obtain a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material.

[0042] The XRD pattern of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in this embodiment is shown below. Figure 5 ,from Figure 5 It can be seen that the main diffraction peaks and relative intensities of the product are consistent with the JCPDS (Powder Diffraction Standards Committee) cards (PDF#78-1793, PDF#85-1329), proving that the generated product is mainly a Bi2O3 / Bi composite material.

[0043] The SEM and EDS images of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material in this embodiment are shown below. Figure 6 ,from Figure 6 It can be seen that the O, Bi, and C elements are uniformly distributed in the prepared composite material; combined with Figure 5 XRD analysis showed that multilayer shell-shaped bismuth oxide / bismuth / carbon composite materials have been successfully prepared.

[0044] The multilayer shell-shaped bismuth oxide / bismuth / carbon composite materials of Examples 1-3 were ground and mixed with acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1. Using N-methylpyrrolidone (NMP) as a solvent, the mixture was stirred into a homogeneous slurry. This slurry was then uniformly coated onto copper foil, vacuum dried, and punched into a circular sheet, which became the working electrode. The active material loading on the electrode was approximately 1.0 mg / cm³. -2 Lithium foil was used as the counter electrode and reference electrode, and glass fiber was used as the separator. 1M LiPF6 was dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC) (1:1, v / v) as the electrolyte. The cells were then assembled into 2025 type button half cells in a glove box filled with argon gas and with water and oxygen content of less than 0.1ppm. The cells were left to stand for 24 hours to ensure that the electrolyte and electrodes were in full contact before electrochemical testing was performed.

[0045] Finally, the battery was tested for charge-discharge performance and cycle stability at a current density of 0.1 A / g using a battery tester. The AC impedance was tested using a Donghua DH 7006 electrochemical workstation. The AC voltage amplitude was 10 mV and the frequency range was 0.01-105 Hz.

[0046] Electrochemical impedance spectroscopy (EIS) diagrams of multilayer shell-shaped bismuth oxide / bismuth / carbon composite negative electrodes in Examples 1-3 are shown below. Figure 7 As shown in the figure, Example 1 has the lowest impedance and Example 2 has the highest impedance. This indicates that during secondary hydrothermal treatment, as the glucose content decreases, the carbon source also decreases during calcination, the amount of bismuth reduced also decreases, and the conductivity of the composite material decreases accordingly, resulting in increased impedance.

[0047] The cycle stability test results of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite anodes in Examples 1-3 after 160, 100, and 500 cycles at a current density of 0.1 A / g are shown in the figure. Figure 8 , Figure 9 and Figure 10 As shown in the figure, the batteries in all three embodiments exhibit stable cycle performance, demonstrating excellent initial capacity and cycle stability. The coulombic efficiency is essentially 100%, especially in embodiment 3, which, after 500 cycles at a current density of 0.1 A / g, still retains 150 mAh / g. -1 The capacity (commercial LiFePO4 capacity is 150mAh g) -1 The coulomb efficiency is basically 100%, so multilayer shell-shaped bismuth oxide / bismuth / carbon composite materials have good application prospects.

[0048] 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 skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a multilayer shell-like bismuth oxide / bismuth / carbon composite material, characterized in that, The specific steps are as follows: (1) Add bismuth nitrate pentahydrate and ethylene glycol to ethanol solvent and mix by ultrasonication. Then place it at 180~200℃ for solvothermal reaction for 150~180min. Cool to room temperature, separate solid and liquid, wash the solid with deionized water and ethanol in sequence, and dry to obtain multilayer shell bismuth oxide. (2) Add glucose and multi-layer shell bismuth oxide to deionized water and mix by ultrasonication. Then place it in a hydrothermal reaction at a temperature of 180~200℃ for 120~180 min. Separate the solid and liquid. Wash the solid with deionized water and ethanol in sequence and dry it to obtain the precursor. (3) Under an argon atmosphere, the precursor is heated at a constant rate to a temperature of 400~600℃ and calcined at a constant temperature for 1~2h to obtain a multilayer shell-shaped bismuth oxide / bismuth / carbon composite material.

2. The method for preparing the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material according to claim 1, characterized in that: Step (1) The solid-liquid ratio of bismuth pentahydrate to ethanol solvent (g:mL) is 0.97~1.455:75, and the volume ratio of ethylene glycol to ethanol solvent (ml:mL) is 5~10:

75.

3. The method for preparing the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material according to claim 1, characterized in that: Step (2) The mass ratio of multi-layered shell bismuth oxide to glucose is 10~15:

1.

4. The method for preparing the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material according to claim 1, characterized in that: Step (3) The uniform heating rate is 4~8℃ / min.

5. The application of the multilayer shell-shaped bismuth oxide / bismuth / carbon composite material prepared by the method according to any one of claims 1 to 4 in the preparation of composite anodes for lithium-ion batteries.

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