ZnSe (at) MWCNT composite material and application thereof in lithium ion battery

Abstract

The invention discloses a ZnSSe (at) MWCNT composite material and application thereof in a lithium ion battery, the composite material is synthesized by using zinc acetate, thiourea, MWCNT and sodium selenite as raw materials through a hydrothermal method, firstly, the raw materials are placed in an ammonia water solution for ultrasonic treatment, then sodium hydroxide and hydrazine hydrate are added for uniform stirring, and the ZnSSe (at) MWCNT composite material is obtained. And finally, filling the obtained mixed solution into a high-temperature reaction kettle for hydrothermal reaction to obtain the ZnSe-coated MWCNT composite material. The preparation method of the composite material is simple, the reaction condition is mild, the production cost is relatively low, the composite material has relatively large specific capacity when being applied to a lithium ion battery negative electrode material, the conductivity of the composite material is high, the capacity loss in the cycle process is reduced, and the service life of the composite material is prolonged. The material has a good application prospect in a high-performance lithium ion battery negative electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a composite material for improving the performance of lithium-ion batteries. Background Art

[0002] Due to its advantages such as high energy density, long cycle life, and low self-discharge rate, lithium-ion batteries have been widely used in the fields of portable electronic devices, electric vehicles, and large-scale energy storage. As an important component of lithium-ion batteries, the performance of the negative electrode material plays a key role in the overall performance of the battery.

[0003] At present, the most widely commercially used negative electrode material for lithium-ion batteries is graphite-based carbon materials. Graphite has a good layered structure, and lithium ions can reversibly intercalate and deintercalate between the layers, thereby realizing the charge and discharge process of the battery. However, the theoretical specific capacity of graphite materials is relatively low, only 372 mAh g -1 . With the growing demand for high-energy density batteries in the fields of modern electronic devices and electric vehicles, etc., graphite negative electrode materials have been difficult to meet the increasing demand.

[0004] In order to improve the specific capacity of lithium-ion batteries, researchers have tried various new negative electrode materials. For example, silicon-based negative electrode materials have an extremely high theoretical specific capacity, up to 4200 mAh g -1 or more, which is more than ten times that of graphite. However, silicon-based materials will undergo huge volume changes during the charge and discharge process, resulting in the destruction of the material structure and electrode pulverization, and then the rapid attenuation of the battery capacity and the deterioration of the cycle performance. In addition, transition metal oxide negative electrode materials have also received extensive attention. Their theoretical specific capacity is relatively high, and the resources are rich and the cost is low. However, such materials also have volume change problems during the charge and discharge process, and the conductivity is poor, which limits their practical applications.

[0005] In terms of preparation processes, traditional preparation methods for negative electrode materials such as the high-temperature solid-phase method, although the process is simple and easy for large-scale production, require high-temperature sintering during the preparation process, with high energy consumption and it is difficult to precisely control the microstructure and performance of the materials. The sol-gel method can prepare materials with high purity, small particle size and uniform distribution at a relatively low temperature, but this method has a complex process and high raw material costs, which is not conducive to large-scale industrial production.

[0006] In summary, the existing negative electrode materials for lithium-ion batteries have many deficiencies in specific capacity, cycle performance, preparation processes, etc., which seriously restrict the further development of lithium-ion batteries in high-performance fields. Therefore, it is of great practical significance to develop a lithium-ion battery negative electrode material with high specific capacity, good cycle performance, simple preparation process and low cost. Summary of the Invention

[0007] The object of the present invention is to provide a ZnSSe@multi-walled carbon nanotube (denoted as ZnSSe@MWCNT) composite material with high specific capacity, good cycling performance, simple preparation process and low cost.

[0008] For the above object, the ZnSSe@MWCNT composite material provided by the present invention is prepared by the following method:

[0009] Step 1: Zinc acetate, thiourea, multi-walled carbon nanotubes and sodium selenite are added to an aqueous ammonia solution and subjected to ultrasonic treatment, and then hydrazine hydrate and sodium hydroxide are added and stirred and mixed evenly.

[0010] Step 2: The mixed solution obtained in Step 1 is transferred to a high-pressure reaction kettle, and hydrothermal reaction is carried out at 160-200 °C for 8-12 hours. After the reaction is completed, centrifugal separation is carried out, and the precipitate is washed and dried to obtain the ZnSSe@MWCNT composite material.

[0011] In the above Step 1, preferably, the mass ratio of zinc acetate to multi-walled carbon nanotubes is 1:0.2-0.4.

[0012] In the above Step 1, preferably, the molar ratio of zinc acetate, thiourea and sodium selenite is 1:0.3-0.6:0.2-0.5.

[0013] In the above Step 1, preferably, the molar ratio of zinc acetate, aqueous ammonia, hydrazine hydrate and sodium hydroxide is 1:80-120:45-60:2.5-4.

[0014] In the above Step 1, preferably, the power of the ultrasonic treatment is 50-80 W, and the ultrasonic time is 20-40 minutes.

[0015] In the above Step 2, preferably, the hydrothermal reaction is carried out at 180 °C for 10 hours.

[0016] The present invention also provides the application of the above ZnSSe@MWCNT composite material as a negative electrode material in a lithium ion battery.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The present invention composits ZnSSe with multi-walled carbon nanotubes, and the synergistic effect of the two greatly improves the specific capacity of the composite material. Compared with the theoretical specific capacity of the traditional graphite negative electrode material of 372 mAh g -1 , the specific capacity of the composite material of the present invention can be increased to more than 750 mAh g -1 , greatly improving the energy density of the lithium ion battery, meeting the urgent needs of high energy density batteries such as electric vehicles and high-performance drones, enabling the device to store more electric energy under the same volume or weight and extending the use time.

[0019] 2. As the anode material of a lithium-ion battery, the composite material of the present invention has a stable structure of multi-walled carbon nanotubes that effectively buffers the volume change of the material during charge and discharge, greatly reducing structural damage. After testing, after 1000 charge and discharge cycles, the battery capacity retention rate can still reach more than 80%, showing good cycle stability. In contrast, the capacity retention rate of traditional graphite anode materials may be only about 60% under the same number of cycles. This means that during long-term use, the lithium-ion battery equipped with the composite material of the present invention has a slower capacity decay, greatly extending the service life of the battery and reducing the cost of battery replacement and environmental pollution.

[0020] 3. Compared with the high energy consumption caused by high-temperature sintering in the traditional high-temperature solid-phase method, the composite material of the present invention is prepared by a hydrothermal method, with a relatively low reaction temperature, low requirements for equipment, and a significant reduction in overall energy consumption, saving energy costs. Moreover, the raw materials are widely sourced and inexpensive, the process steps are relatively simple, without complex raw material pretreatment and high-cost equipment investment, having a significant cost advantage in large-scale industrial production, effectively reducing the production cost of lithium-ion batteries, improving the market competitiveness of products, promoting the further development of the lithium-ion battery industry, and enabling high-performance batteries to be more widely applied in various fields. Description of the Drawings

[0021] Figure 1 are the X-ray diffraction patterns (a) of ZnSSe and the ZnSSe@MWCNT composite material prepared in Example 1, and the atomic structure schematic diagram (b) of ZnSSe.

[0022] Figure 2 are the scanning electron microscope images and energy spectrum diagrams of the ZnSSe@MWCNT composite material prepared in Example 1.

[0023] Figure 3 are the high-resolution XPS spectra of C, Zn, S, and Se elements in the ZnSSe@MWCNT composite material prepared in Example 1.

[0024] Figure 4 are the charge and discharge cycle diagrams of ZnSSe and the ZnSSe@MWCNT composite material prepared in Example 1 at a current density of 0.1 A g -1 current density.

[0025] Figure 5 are the charge and discharge cycle diagrams of ZnSSe and the ZnSSe@MWCNT composite material prepared in Example 1 at a current density of 1 A g -1 current density. Detailed Embodiments

[0026] The present invention will be further described in detail below in conjunction with the drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0027] Example 1

[0028] Step 1: Add 1.1 g (6 mmol) of zinc acetate, 0.22 g (2.9 mmol) of thiourea, 0.38 g of multi-walled carbon nanotubes, and 0.34 g (2 mmol) of sodium selenite into 100 mL (0.56 mol) of ammonia aqueous solution with a mass concentration of 10%, ultrasonically treat at room temperature for 30 minutes under 60 W, then add 20 mL (0.33 mol) of hydrazine hydrate and 20 mL of 1 mol / L sodium hydroxide aqueous solution, and stir for 30 minutes to make the mixture uniform.

[0029] Step 2: Transfer the mixed solution obtained in Step 1 to a high-pressure reaction kettle, carry out hydrothermal reaction at 180 °C for 10 hours under closed conditions. After the reaction, centrifuge and separate the obtained product. The precipitate is repeatedly washed with absolute ethanol and deionized water, and then dried at 60 °C for 12 hours to obtain ZnSSe@MWCNT composite material.

[0030] The obtained composite material was characterized by X-ray diffractometer, scanning electron microscope, and X-ray photoelectron spectrometer. The results are shown in Figures 1 to 3 . From Figure 1 it can be seen that the XRD diffraction peaks of the obtained composite material and ZnSSe are both between ZnS and ZnSe. In terms of atomic structure, part of S is replaced by Se with a larger radius, and the diffraction peak shifts towards a small angle. From Figure 2 it can be seen that ZnSSe in the obtained composite material is surrounded by MWCNT and has a good composite structure. The four elements of Zn, S, Se, and C are evenly dispersed in the sample. From Figure 3 it can be seen that the peak positions in the X-ray photoelectron spectra of the four elements are consistent with their standard binding energies. The above characterization results prove the successful preparation of ZnSSe@MWCNT composite material.

[0031] Example 2

[0032] Step 1: Add 1 g (5.45 mmol) of zinc acetate, 0.2 g (2.63 mmol) of thiourea, 0.35 g of multi-walled carbon nanotubes, and 0.3 g (1.73 mmol) of sodium selenite into 80 mL (0.45 mol) of ammonia aqueous solution with a mass concentration of 10%, ultrasonically treat at room temperature for 40 minutes under 50 W, then add 16 mL (0.26 mol) of hydrazine hydrate and 16 mL of 1 mol / L sodium hydroxide aqueous solution, and stir for 30 minutes to make the mixture uniform.

[0033] Step 2: Transfer the mixed solution obtained in Step 1 to a high-pressure reactor, and carry out hydrothermal reaction at 160 °C for 12 hours under closed conditions. After the reaction, centrifuge the obtained product, repeatedly wash the precipitate with absolute ethanol and deionized water, and then dry it at 60 °C for 12 hours to obtain the ZnSSe@MWCNT composite material.

[0034] Example 3

[0035] Step 1: Add 0.5 g (2.72 mmol) of zinc acetate, 0.1 g (1.31 mmol) of thiourea, 0.18 g of multi-walled carbon nanotubes, and 0.16 g (0.925 mmol) of sodium selenite to 45 mL (0.25 mol) of an aqueous ammonia solution with a mass concentration of 10%. Ultrasonically treat at room temperature for 20 minutes at 80 W, then add 9 mL (0.15 mol) of hydrazine hydrate and 9 mL of 1 mol / L sodium hydroxide aqueous solution, and stir for 30 minutes to make the mixture uniform.

[0036] Step 2: Transfer the mixed solution obtained in Step 1 to a high-pressure reactor, and carry out hydrothermal reaction at 200 °C for 8 hours under closed conditions. After the reaction, centrifuge the obtained product, repeatedly wash the precipitate with absolute ethanol and deionized water, and then dry it at 60 °C for 12 hours to obtain the ZnSSe@MWCNT composite material.

[0037] Example 4

[0038] Application of the ZnSSe@MWCNT composite material prepared in Example 1 as a negative electrode material in a lithium-ion battery

[0039] Use ZnSSe@MWCNT coated on nickel foam as the anode (with an area of 1 cm 2 , and the loading amount is 1 mg cm -2 ), use a lithium sheet as the counter electrode to assemble a button battery in a glove box to construct a two-electrode half-cell system (ZnSSe@MWCNT||lithium sheet). Then, perform charge-discharge performance testing on the assembled button battery on a Neware battery testing system: control the current density at 100 mA g -1 during the battery cycle test, and the results are shown in Figure 4 . Control the current density at 1 A g -1 during the battery cycle test, and the results are shown in Figure 5 . As can be seen from Figure 4 , after the prepared battery is cycled 100 times, the specific capacity of the battery remains at 700 mAh g -1 , which is much higher than the specific capacity of the commercial graphite anode (372 mAh g -1 ). As can be seen from Figure 5 , the prepared battery also shows excellent performance in the long-term cycle test. At 1 A g -1It still has a specific capacity of 530 mAh / g after 1000 cycles at a certain current density, which can well meet the new requirements of contemporary society for high-performance energy storage devices. -1 ​

Claims

1. A ZnSSe@MWCNT composite material, characterized in that: The composite material is prepared by the following method: Step 1: adding zinc acetate, thiourea, multi-walled carbon nanotubes and sodium selenite to an aqueous ammonia solution and subjecting it to ultrasonic treatment, and then adding hydrazine hydrate and sodium hydroxide and stirring to mix evenly; Step 2: The mixed solution obtained in step 1 is transferred to a high-pressure reactor, and subjected to a hydrothermal reaction at 160-200° C. for 8-12 hours. After the reaction is completed, the mixed solution is centrifuged, and the precipitate is washed and dried to obtain a ZnSSe@MWCNT composite material.

2. The ZnSSe@MWCNT composite material according to claim 1, characterized in that: In step 1, the mass ratio of zinc acetate to multi-walled carbon nanotubes is 1:0.2-0.

4.

3. The ZnSSe@MWCNT composite material according to claim 1, characterized in that: In step 1, the molar ratio of zinc acetate, thiourea and sodium selenite is 1:0.3-0.6:0.2-0.

5.

4. The ZnSSe@MWCNT composite material according to claim 1, characterized in that: In step 1, the molar ratio of zinc acetate, ammonia water, hydrazine hydrate and sodium hydroxide is 1:80-120:45-60:2.5-4.

5. The ZnSSe@MWCNT composite material according to claim 1, characterized in that: In step 1, the power of the ultrasonic treatment is 50 to 80 W, and the ultrasonic time is 20 to 40 minutes.

6. The ZnSSe@MWCNT composite material according to claim 1, characterized in that: In step 2, a hydrothermal reaction is carried out at 180° C. for 10 hours.

7. Use of the ZnSSe@MWCNT composite material according to any one of claims 1 to 6 as a negative electrode material in a lithium-ion battery.

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