阅读说明：本技术 一种形貌可控的高性能锂离子电池负极材料及其制备方法 (Morphology-controllable high-performance lithium ion battery negative electrode material and preparation method thereof ) 是由 刘薇 姚建涛 张贵泉 陈君 陈甜甜 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种形貌可控的高性能锂离子电池负极材料及其制备方法,所述的负极材料由氧化铜和石墨烯复合而成。本发明采用三水合硝酸铜作为前驱体,以聚乙烯吡咯烷酮为形貌保护剂,加入尿素作为碱源,通过动态成核结晶的方式在密封溶剂热条件下控制反应的热力和动力学因素,得到不同形貌的氧化铜微球。以石墨烯为基底,通过静置处理最终得氧化铜/石墨烯复合材料,作为各项物理性质测试及电化学电极、电池性能等测试使用。本发明通过简单的操作步骤,温和的反应条件便可得到高稳定性的锂离子电池负极材料,在溶剂热条件控制下可制备不同形貌的氧化铜,有助于提高负极的充电放电效率以及改善循环性能。(The invention discloses a shape-controllable high-performance lithium ion battery cathode material and a preparation method thereof. The method adopts copper nitrate trihydrate as a precursor, polyvinylpyrrolidone as a morphology protective agent, urea as an alkali source and controls the thermal and kinetic factors of the reaction under the condition of sealed solvothermal by a dynamic nucleation crystallization mode to obtain the copper oxide microspheres with different morphologies. The copper oxide/graphene composite material is finally obtained by taking graphene as a substrate through standing treatment and is used for various physical property tests and tests of electrochemical electrodes, battery performance and the like. According to the invention, the high-stability lithium ion battery cathode material can be obtained through simple operation steps and mild reaction conditions, copper oxide with different morphologies can be prepared under the control of solvothermal conditions, and the method is beneficial to improving the charge and discharge efficiency of the cathode and improving the cycle performance.)

1. The shape-controllable high-performance lithium ion battery cathode material is characterized by comprising graphene and transition metal oxide copper oxide attached to the surface of the graphene, wherein the graphene is of a three-dimensional grid hierarchical structure and serves as a supporting framework of a copper oxide active component, the copper oxide grows on the surface of the graphene through a solvothermal method, a three-dimensional hierarchical porous microsphere structure is constructed by compact micro-nano sheets of the copper oxide and is in a flower shape or sea urchin shape, and shape control is achieved by utilizing regulation and control of solvothermal reaction conditions.

2. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material disclosed by claim 1 is characterized by comprising the following steps of:

the method comprises the following steps: adding copper nitrate trihydrate and urea into distilled water under low-speed stirring, adding polyvinylpyrrolidone, and mixing;

step two: fully stirring the mixed solution obtained in the step one to fully dissolve the mixed solution, transferring the solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, and then putting the kettle into a constant-temperature electric heating oven to perform solvothermal reaction;

step three: after the solvothermal reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven; and repeatedly centrifuging the solid-liquid mixture after reaction, repeatedly washing the solid-liquid mixture with distilled water and ethanol for many times to obtain black powder solid, and fully drying the black powder solid in a vacuum drying oven in a constant temperature environment to obtain copper oxide solid powder.

Step four: carrying out ultrasonic treatment on a graphene solution to obtain uniform layered graphene, dispersing copper oxide solid powder in a sodium chloride aqueous solution, uniformly stirring, adding the obtained mixed solution into graphene, stirring, standing, centrifuging the precipitate, washing with distilled water and ethanol for several times, drying in a vacuum drying oven, and finally preparing the copper oxide/graphene composite material, namely the morphology-controllable high-performance lithium ion battery cathode material.

3. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material according to claim 2, wherein the ratio of the copper nitrate trihydrate, urea and distilled water added in the step one is (1.0-1.4) g, (0.3-0.9) g, (260-300) mL.

4. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material as claimed in claim 2, wherein the ratio of the polyvinylpyrrolidone and the copper nitrate trihydrate to the distilled water in the first step is (1:10) g:50 mL.

5. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material as claimed in claim 2, wherein the mixed solution in the second step is stirred for 30-90 min, then solvent heat treatment is carried out, the solution is transferred to a polytetrafluoroethylene hydrothermal synthesis kettle, and the reaction is carried out for 12-16 h in a constant-temperature electric heating oven at 160-180 ℃.

6. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material as claimed in claim 2, wherein in the third step, the rotation speed of the centrifugation is above 6000rpm, the centrifugation time is 20-40 min, and the solid-phase precipitate obtained by the centrifugation is dried in vacuum at 60-70 ℃ for more than 10h to obtain the copper oxide solid powder.

7. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material according to claim 2, wherein the time for the graphene solution to be subjected to ultrasonic treatment in the fourth step is 30-60 min, and the concentration of the graphene solution is 2 mg/mL.

8. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material according to claim 2, characterized in that in the fourth step, the concentration of the sodium chloride aqueous solution is 0.5-1.5M, and the copper oxide solid powder is dispersed in the sodium chloride aqueous solution and uniformly stirred for 1-2 h.

9. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material according to claim 2, wherein the mass ratio of graphene to copper oxide in the copper oxide/graphene composite material in the step four is 1: 1.0-1.5.

10. The preparation method of the morphology-controllable high-performance lithium ion battery negative electrode material according to claim 2, characterized in that the mixed solution in the fourth step is dissolved in a graphene solution, uniformly stirred for 1-3 hours and then subjected to standing treatment; and (3) centrifuging at the rotating speed of more than 6000rpm for 20-40 min, and vacuum drying the solid-phase precipitate obtained by centrifuging at the temperature of 60-70 ℃ for more than 10h to prepare the copper oxide/graphene composite material.

Technical Field

The invention belongs to the technical field of preparation of lithium ion battery electrode materials, and particularly relates to a transition metal oxide/graphene morphology-controllable lithium ion battery anode material and a preparation method thereof.

Background

In order to meet the increasing energy demand of human beings, especially the electric automobile market which is developed vigorously in recent years, it is important to develop new generation Lithium Ion Batteries (LIBs) having excellent performance. At present, commercial lithium ion batteries mainly adopt carbon materials such as artificial graphite and the like as a negative electrode, but due to low theoretical capacity (372mAh/g), the limitations of the traditional electrode materials in the aspects of specific capacity, cycle life and safety are increasingly prominent, and the further development of the lithium ion batteries is restricted.

In recent years, transition metal oxide materials have been developed into a novel lithium ion battery negative electrode material due to their high specific capacity, high energy density and unique phase transition lithium storage mechanism, and have received extensive attention from researchers. Among them, copper oxide (CuO) has a high theoretical specific capacity, a suitable operating voltage, and is considered as one of the most potential negative electrode materials. However, the lithium storage mechanism of copper oxide is derived from the conversion reaction mechanism of self-lithium-releasing and-inserting of transition metal oxides, the inserting process is the conversion from crystalline state to amorphous state, and the volume expansion exists to a large extent in the charging and discharging process, so that CuO active components are pulverized, the electrical contact among the active components is lost, and the stability of the lithium ion battery in the charging and discharging process is influenced.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a morphology-controllable high-performance lithium ion battery cathode material and a preparation method thereof. The copper oxide microspheres with the hierarchical structure are assembled by nanosheet units through a simple and easily-scaled solvent thermal synthesis method, and the copper oxide microspheres with the hierarchical structure are grown by using graphene as a substrate through combination of a solution ionic strength engineering method, so that double optimization of the electrochemical performance of the copper oxide electrode material is realized.

In order to achieve the purpose, the invention adopts the technical scheme that:

the shape-controllable high-performance lithium ion battery cathode material comprises graphene and transition metal oxide copper oxide attached to the surface of the graphene, wherein the graphene is of a three-dimensional grid hierarchical structure and serves as a supporting framework of a copper oxide active component, the copper oxide grows on the surface of the graphene through a solvothermal method, a three-dimensional hierarchical porous microsphere structure is constructed by compact micro-nano sheets of the copper oxide, the copper oxide presents a flower shape or a sea urchin shape, and the shape control is realized by utilizing the regulation and control of solvothermal reaction conditions.

The preparation method of the morphology-controllable high-performance lithium ion battery cathode material comprises the following steps:

the method comprises the following steps: adding copper nitrate trihydrate and urea into distilled water under low-speed stirring, adding polyvinylpyrrolidone, and mixing;

step two: fully stirring the mixed solution obtained in the step one to fully dissolve the mixed solution, transferring the solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, and then putting the kettle into a constant-temperature electric heating oven to perform solvothermal reaction;

step three: after the solvothermal reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven; and repeatedly centrifuging the solid-liquid mixture after reaction, repeatedly washing the solid-liquid mixture with distilled water and ethanol for many times to obtain black powder solid, and fully drying the black powder solid in a vacuum drying oven in a constant temperature environment to obtain copper oxide solid powder.

Step four: carrying out ultrasonic treatment on a graphene solution to obtain uniform layered graphene, dispersing copper oxide solid powder in a sodium chloride aqueous solution, uniformly stirring, adding the obtained mixed solution into graphene, stirring, standing, centrifuging the precipitate, washing with distilled water and ethanol for several times, drying in a vacuum drying oven, and finally preparing the copper oxide/graphene composite material, namely the morphology-controllable high-performance lithium ion battery cathode material.

In the first step, copper nitrate trihydrate, urea and distilled water are added in a ratio of (1.0-1.4) g to (0.3-0.9) g to (260-300) mL.

The ratio of polyvinylpyrrolidone and copper nitrate trihydrate to distilled water in step one is (1:10) g:50 mL.

And stirring the mixed solution in the second step for 30-90 min, carrying out solvent heat treatment, transferring the solution into a polytetrafluoroethylene hydrothermal synthesis kettle, and reacting for 12-16 h in a constant-temperature electric heating oven at 160-180 ℃.

And in the third step, the rotating speed of the centrifugation is more than 6000rpm, the time of the centrifugation is 20-40 min, and the solid-phase precipitate obtained by the centrifugation is dried for more than 10 hours in vacuum at the temperature of 60-70 ℃ to prepare the copper oxide solid powder.

And in the fourth step, the time for carrying out ultrasonic treatment on the graphene solution is 30-60 min, and the concentration of the graphene solution is 2 mg/mL.

In the fourth step, the concentration of the sodium chloride aqueous solution is 0.5-1.5M, and the copper oxide solid powder is dispersed in the sodium chloride aqueous solution and uniformly stirred for 1-2 h.

In the fourth step, the mass ratio of the graphene to the copper oxide in the copper oxide/graphene composite material is 1: 1.0-1.5.

Dissolving the mixed solution in the graphene solution in the step four, uniformly stirring for 1-3 h, and then standing;

and in the fourth step, the rotating speed of the centrifugation is more than 6000rpm, the time of the centrifugation is 20-40 min, and the solid-phase precipitate obtained by the centrifugation is dried in vacuum at the temperature of 60-70 ℃ for more than 10h to prepare the copper oxide/graphene composite material.

Compared with the prior art, the invention has the following advantages:

1. the graphene in the battery cathode material is used as a supporting framework of the copper oxide active component, has better electron and ion transmission channels, is favorable for accelerating the charge and discharge rate, can shorten the electron transmission path between the cathode and the electrolyte after being compounded with the copper oxide, and promotes the effective permeation of the electrolyte, thereby improving the charge and discharge efficiency. The three-dimensional grid of the graphene becomes the attachment point of the copper oxide microsphere with the hierarchical structure, so that the volume change of the copper oxide in the lithium storage process is greatly inhibited, the surface contact area between the electrode and the electrolyte is increased, the lithium ion diffusion distance is shortened, and the migration speed of electrons in the active substance is accelerated. Meanwhile, the three-dimensional structure nano copper oxide microspheres are prepared under the alkaline condition so as to improve the contact area with electrolyte, increase the reaction contact surface and improve the charge-discharge reversibility, thereby obtaining higher capacitance. The copper oxide microspheres and the graphene surface generate a synergistic effect, so that the agglomeration phenomenon of electrode materials is reduced, and the electrochemical performance of the composite material is obviously improved.

2. The invention adopts urea as an alkali source, can better control the appearance, and the urea as a reactant can slowly react in the solution due to the action of heat and hydration, and slowly releases CO after the initial hydrolysis of the urea₃ ^2-With OH^-Same as Cu in solution²⁺Simple alkali precipitation is formed, and finally obtained crystals have various shapes in the further hydrolysis process of urea. While the common alkali source NaOH can generate OH as strong alkali^-In case of too high a concentration, even Cu (OH)₂The generation of the precipitate is not beneficial to the diversification of the appearance of the copper oxide.

3. The copper oxide active material obtained by controlling the preparation conditions by adopting the solvothermal method shows that a three-dimensional hierarchical porous microsphere structure is constructed by compact micro-nano sheets, is sea urchin-shaped, has the advantages of stable structure, difficulty in agglomeration, large specific surface area, good processing performance and the like, can obviously improve the contact area of a negative electrode material and an electrolyte, increase the electrode reaction site, increase the transmission rate of lithium ions, and improve the coulomb efficiency and the multiplying power performance of the negative electrode material.

4. Adding polyvinylpyrrolidone as morphology protecting agent, depositing on the surface of graphene sheet layer and modifying, and reducing the surface energy of graphene to obtain uniformDispersed graphene solution. At the same time, when polyvinylpyrrolidone is mixed with Cu²⁺Uniformly dispersed Cu during graphene mixing²⁺And the copper oxide can be weakly coordinated and/or electrostatically interacted with amide carbonyl of polyvinylpyrrolidone, epoxy group of graphene and hydroxyl, so that the copper oxide is firmly attached to the surface of graphene.

5. The copper oxide/graphene material prepared by the invention is used as a lithium ion battery cathode material, and under the current density of 0.1A/g, after 100 cycles, the average specific discharge capacity can reach 689.1mAh/g, and the capacity retention rate is 86.0%. The composite material exerts the advantages of multiple components, utilizes the synergistic effect among the components, shows excellent cycle stability and rate capability and excellent cycle life, and has good application prospect in the field of lithium ion battery cathode materials.

Drawings

Fig. 1 is a scanning electron microscope image of the flower-like copper oxide/graphene material prepared in example 1 of the present invention.

Fig. 2 is a scanning electron microscope image of the echinoid copper oxide/graphene material prepared in example 2 of the present invention.

Fig. 3 is a graph of the cycle performance of the echinoid copper oxide/graphene material prepared in example 2 of the present invention at a current density of 0.1A/g.

Fig. 4 is a graph of rate performance of the echinoid copper oxide/graphene material prepared in example 2 of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

The lithium ion battery negative electrode materials of embodiments 1 to 6 of the present invention include graphene and active component copper oxide microspheres attached to the surface of the graphene, where the graphene has a three-dimensional network structure, and the copper oxide in a hierarchical structure is attached to the surface of the graphene and has a flower-like or sea urchin-like structure.

Example 1

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.3g of copper nitrate trihydrate and 0.8g of urea, 0.13g of PVP, were dissolved in 6.5mL of distilled water under low-speed stirring, and the two solutions were mixed.

Step two: and fully stirring the mixed solution for 60min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, keeping the temperature in an electric heating oven, and reacting for 16h at 160 ℃ in the constant-temperature electric heating oven.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 7000rpm for 20min, repeatedly washing with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying in a vacuum drying oven at constant temperature of 65 ℃ for 12h to obtain the copper oxide microspheres.

Step four: and (3) carrying out ultrasonic treatment on 10mL of graphene aqueous solution for 45min to obtain the uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Dispersing copper oxide microspheres in 20mL of sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1, the concentration of the sodium chloride solution is 1M, uniformly stirring for 1.5h, dissolving the obtained solution in graphene, uniformly stirring for 2h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of 7000rpm for 20min, and vacuum-drying in a vacuum drying oven at 65 ℃ for 12h to finally prepare the flower-shaped copper oxide/graphene composite material.

Fig. 1 is a scanning electron microscope image of the flower-like copper oxide/graphene material prepared in the embodiment. It can be seen that the whole flower-shaped structure is in cluster structure and three-dimensional arrangement formed by a plurality of micro-nano sheets.

Example 2

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.2g of copper nitrate trihydrate and 0.6g of urea are added to 280mL of distilled water with low-speed stirring, and the two solutions are mixed after 0.12g of PVP is dissolved in 6mL of distilled water.

Step two: and fully stirring the mixed solution for 60min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, keeping the temperature in an electric heating oven, and reacting for 14h in the constant-temperature electric heating oven at the temperature of 170 ℃.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 7000rpm for 30min, repeatedly washing with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying in a vacuum drying oven at the constant temperature of 60 ℃ for 12h to obtain the copper oxide microspheres.

Step four: and (3) carrying out ultrasonic treatment on 10mL of graphene solution for 45min to obtain the uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Respectively dispersing copper oxide microspheres in a sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1.3, the concentration of the sodium chloride solution is 1M, uniformly stirring for 1.5h, dissolving the obtained solution in graphene, uniformly stirring for 2h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of 7000rpm for 30min, and vacuum-drying in a vacuum drying oven at the temperature of 60 ℃ for 12h to finally prepare the sea urchin spherical copper oxide/graphene composite material.

Fig. 2 is a scanning electron microscope image of the echinoid copper oxide/graphene material prepared in this example. It can be seen that the whole sea urchin structure is composed of compact copper oxide micro-nano sheets, and a hierarchical porous structure is constructed.

Fig. 3 is a graph of the cycle performance of the echinoid copper oxide/graphene material prepared in this example at a current density of 0.1A/g. As can be seen from fig. 3, the first charge-discharge capacity of the sea urchin-shaped copper oxide/graphene negative electrode material prepared in the embodiment can reach 785.6 and 1190.8mAh/g respectively at a current density of 0.1A/g, the average specific capacity can reach 689.1mAh/g after 100 cycles, and the capacity retention rate is 86.0%. The sea urchin-shaped copper oxide/graphene negative electrode material prepared by the embodiment shows good long-cycle stability.

Fig. 4 is a graph showing rate performance of the echinoid copper oxide/graphene material prepared in this example. The current density is sequentially cycled for 10 circles under different current densities, the current density returns to 0.2 and 0.1A/g after 0.1, 0.2, 0.5, 1, 2 and 5A/g, and the cycle reversibility of the material is tested, as can be seen from a figure 4, the sea urchin-shaped copper oxide/graphene material shows excellent rate performance, particularly, the sea urchin-shaped copper oxide/graphene material is restored to low-current charge and discharge after high-current charge and discharge, the negative electrode material can basically restore to the initial charge and discharge capacity, and the good cycle reversibility of the sea urchin-shaped copper oxide/graphene material is shown.

Example 3

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.4g of copper nitrate trihydrate and 0.9g of urea are added to 300mL of distilled water with low-speed stirring, and the two solutions are mixed after 0.14g of PVP is dissolved in 7mL of distilled water.

Step two: and fully stirring the mixed solution for 90min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, keeping the temperature in an electric heating oven, and reacting for 14h in the constant-temperature electric heating oven at the temperature of 170 ℃.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 6000rpm for 30min, repeatedly washing the mixture with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying the black powder solid in a vacuum drying oven at the constant temperature of 70 ℃ for 10h to obtain the copper oxide microspheres.

Step four: and (3) carrying out ultrasonic treatment on 10mL of graphene aqueous solution for 60min to obtain the uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Respectively dispersing copper oxide microspheres in a sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1.5, the concentration of the sodium chloride solution is 1.5M, uniformly stirring for 1h, dissolving the obtained solution in graphene, uniformly stirring for 3h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of 6000rpm for 30min, and vacuum drying in a vacuum drying oven at the temperature of 70 ℃ for 10h to finally prepare the copper oxide/graphene composite material.

Example 4

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.0g of copper nitrate trihydrate and 0.3g of urea were added to 260mL of distilled water with low-speed stirring, and the two solutions were mixed after 0.1g of PVP was dissolved in 5mL of distilled water.

Step two: and fully stirring the mixed solution for 90min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the solution, keeping the temperature of the solution constant in an electric heating oven, and reacting the solution in the constant-temperature electric heating oven at 180 ℃ for 12 h.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 7000rpm for 20min, repeatedly washing with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying in a vacuum drying oven at 70 ℃ for 10h in a constant temperature environment to obtain the copper oxide microspheres.

Step four: and (3) carrying out ultrasonic treatment on 10mL of graphene aqueous solution for 30min to obtain the uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Respectively dispersing copper oxide microspheres in a sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1.2, the concentration of the sodium chloride solution is 0.5M, uniformly stirring for 1h, dissolving the obtained solution in graphene, uniformly stirring for 3h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of 7000rpm for 20min, and vacuum-drying in a vacuum drying oven at the temperature of 70 ℃ for 10h to finally prepare the copper oxide/graphene composite material.

Example 5

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.2g of copper nitrate trihydrate and 0.6g of urea are added to 260mL of distilled water with low-speed stirring, and the two solutions are mixed after 0.12g of PVP is dissolved in 6mL of distilled water.

Step two: and fully stirring the mixed solution for 30min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, keeping the temperature in an electric heating oven, and reacting for 16h at 160 ℃ in the constant-temperature electric heating oven.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 6000rpm for 40min, repeatedly washing the mixture with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying the black powder solid in a vacuum drying oven at the constant temperature of 60 ℃ for 12h to obtain the copper oxide microspheres.

Step four: carrying out ultrasonic treatment on 10mL of graphene water solution for 1h to obtain uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Respectively dispersing copper oxide microspheres in a sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1.4, the concentration of the sodium chloride solution is 1.5M, uniformly stirring for 2h, dissolving the obtained solution in graphene, uniformly stirring for 1h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of 6000rpm for 40min, and vacuum drying in a vacuum drying oven at the temperature of 60 ℃ for 12h to finally prepare the copper oxide/graphene composite material.

Example 6

The preparation method of the lithium ion battery negative electrode material comprises the following steps:

the method comprises the following steps: 1.3g of copper nitrate trihydrate and 0.8g of urea, 0.13g of PVP, were dissolved in 6.5mL of distilled water under low-speed stirring, and the two solutions were mixed.

Step two: and fully stirring the mixed solution for 30min by a magnetic stirrer to fully dissolve the mixed solution, transferring the mixed solution into a polytetrafluoroethylene hydrothermal synthesis kettle, screwing and sealing the kettle, keeping the temperature in an electric heating oven, and reacting for 14h in the constant-temperature electric heating oven at the temperature of 170 ℃.

Step three: after the reaction time is reached, the hydrothermal synthesis kettle is naturally cooled to room temperature along with the electric heating oven. And repeatedly centrifuging the reacted solid-liquid mixture at 7000rpm for 20min, repeatedly washing with distilled water and ethanol for multiple times to obtain black powder solid, and vacuum drying in a vacuum drying oven at constant temperature of 65 ℃ for 12h to obtain the copper oxide microspheres.

Step four: carrying out ultrasonic treatment on 10mL of graphene water solution for 1h to obtain uniform layered graphene, wherein the concentration of the graphene solution is 2 mg/mL. Respectively dispersing copper oxide microspheres in a sodium chloride aqueous solution, wherein the mass ratio of graphene to copper oxide is 1:1.2, the concentration of the sodium chloride solution is 0.5M, uniformly stirring for 1h, dissolving the obtained solution in graphene, uniformly stirring for 3h, standing, centrifuging the precipitate, washing with water and ethanol for several times, centrifuging at the rotating speed of above 7000rpm for 20min, and vacuum-drying in a vacuum drying oven at 65 ℃ for 12h to finally prepare the copper oxide/graphene composite material.