CN108832114A - A kind of preparation method of graphene-coated CuFeO2 composite negative electrode material - Google Patents

Abstract

The invention discloses a preparation method of a graphene-coated _CuFeO2 composite negative electrode material. The steps are as follows: (1) Add a certain amount of copper salt and iron salt into deionized water and stir to form a solution A, and configure a certain concentration of hydrogen Sodium oxide solution is slowly added to solution A, while reducing agent and graphene as a conductive agent are added to form solution B; (2) solution B is transferred to a reactor for hydrothermal reaction, and the product is centrifuged and washed with ethanol and Washed several times with ion water and dried to obtain graphene-coated CuFeO ₂ composite anode material CuFeO ₂ @G. The present invention adopts hydrothermal method to prepare nano-scale CuFeO ₂ material, has larger surface area, increases the contact area with electrolyte, utilizes graphene to improve the electrical conductivity of material again, so this composite material is used in lithium ion battery , with higher specific capacity, charge and discharge rate and longer cycle life.

Description

A kind of preparation method of graphene-coated CuFeO2 composite negative electrode material

technical field

The invention relates to a preparation method of a battery negative electrode material, in particular to a preparation method of a graphene-coated _CuFeO2 composite negative electrode material.

Background technique

With the aggravation of global energy crisis and environmental pollution, the development and application of new energy is imperative. Lithium-ion batteries have developed rapidly since their commercialization in the 1990s. Compared with traditional chemical batteries, it has the advantages of light weight, small size, high voltage, high specific energy, wide operating temperature range, high specific power, stable discharge, long storage time, no memory effect, and no pollution. At present, lithium-ion batteries have been widely used in portable electronic products such as mobile phones, digital cameras, and notebook computers, and have shown broad application prospects in electric vehicles (EV), hybrid electric vehicles (HEV) and grid energy storage systems.

Nowadays, various commercial lithium-ion battery negative electrode materials are mainly carbon materials. Carbon materials are widely used lithium-ion battery negative electrode materials. Carbon negative electrode materials have low lithium intercalation potential, good conductivity, and abundant natural reserves. , no pollution, simple preparation process, the volume expansion in the process of intercalating and removing lithium is basically below 9%, showing high Coulombic efficiency and excellent cycle stability. However, with the continuous improvement of the performance requirements of lithium batteries, the shortcomings of graphite as a negative electrode material have gradually emerged, such as low gram capacity (372 mAh·g ^-1 ), and the layered structure is easy to peel off when the number of cycles is high. It has further improved the specific energy and performance of lithium batteries.

CuFeO ₂ is a copper-iron mineral with good stability, abundant reserves in the earth's crust, etc., and has the properties of a p-type semiconductor. It has a good application prospect in the field of lithium-ion batteries and photoelectric catalysis. CuFeO ₂ as the negative electrode material of lithium-ion batteries has a synthetic voltage platform (1.0V (Vs.Li ⁺ /Li)) and a high theoretical specific capacity (708 mAh g ^-1 ), which is very suitable for the current requirements of high safety, high capacity lithium-ion battery anode materials. However, the low electrical conductivity of _CuFeO2 material leads to its fast capacity fading and poor performance at high rates. At the same time, CuFeO ₂ particle size and electrolyte contact area are also important factors affecting its high rate performance.

Graphene is a planar two-dimensional structure composed of a single layer of carbon atoms. Similar to graphite, 3 of the 4 valence electrons of carbon atoms form a planar regular hexagon with the nearest three carbon atoms in the form of ^sp2 hybridization. In the connected honeycomb structure, another σz orbital electron perpendicular to the plane of carbon atoms forms highly patrolling large π bonds on both sides of the lattice plane like a benzene ring. This binary electronic valence bond structure determines the unique and rich properties of graphene: the sp ² bond has high strength and stability, and the large π bond electrons that are highly patrolling on both sides of the lattice plane make it have a zero band gap. Semiconductor and Dirac carrier characteristics, showing good conductivity, high electron mobility (2.5×105 cm ² •V ^-1 ·s ^-1 ). These excellent properties make graphene have potential applications in many fields such as solar cells, high-performance batteries, supercapacitors and composite materials.

Most of the methods for synthesizing _CuFeO2 are high-temperature solid-phase method and sol-gel method followed by high-temperature calcination. These methods require higher temperature and high energy consumption. High calcination temperature and long calcination time make the prepared _CuFeO Therefore, the length of the migration path of lithium ions in it, the difficulty of intercalation and extraction, affect its electrochemical performance. How to synthesize nano-scale CuFeO ₂ materials while solving the conductivity of the materials is an important issue for the development of the CuFeO ₂ material industry.

Contents of the invention

The purpose of the present invention is to overcome the defects in the prior art, provide a preparation method of graphene-coated _CuFeO2 composite negative electrode material, and solve the problems of low electrical conductivity and particle size of _CuFeO2 material.

In order to achieve the above object, the technical scheme adopted in the present invention is: a kind of graphene-coated CuFeO2 _The preparation method of composite negative electrode material, the steps are as follows:

(1) Add a certain amount of copper salt and iron salt into deionized water and stir to form solution A, configure a certain concentration of sodium hydroxide solution, slowly add it to solution A, and add reducing agent and graphene as a conductive agent at the same time , forming solution B;

(2) The solution B was transferred to the reactor for hydrothermal reaction, the product was centrifuged and washed several times with ethanol and deionized water, and dried to obtain the graphene-coated CuFeO ₂ composite anode material CuFeO ₂ @G.

Further, in the step (1), the copper salt is one or more of copper nitrate, copper sulfate, and copper chloride; the iron salt is one or more of ferric nitrate, ferric sulfate, and ferric chloride. Several kinds; and the roots of copper salts and iron salts correspond.

Further, in the step (1), the amount-to-mass ratio of copper salt, iron salt and graphene is 1:1:0.01-0.05.

Further, in the step (1), the reducing agent is one or more of propionaldehyde, ascorbic acid, and glucose.

Further, in the step (2), the hydrothermal reaction temperature is 160-240° C., and the hydrothermal time is 16-36 hours.

The beneficial technical effect of the present invention is: adopt hydrothermal method to prepare nano-scale CuFeO ₂ material, have larger surface area, increase the contact area with electrolyte, utilize graphene to improve the electrical conductivity of material again, so this composite material When used in lithium-ion batteries, it has high specific capacity, charge and discharge rate and long cycle life.

Description of drawings

The present invention will be further elaborated below in conjunction with the accompanying drawings and implementation examples.

Fig. 1 is CuFeO in the embodiment of the present invention ₁ The discharge curve figure of material under 0.2C rate;

Fig. 2 is a comparison diagram of the cycle performance of a half-cell assembled from CuFeO ₂ material and CuFeO ₂ @G composite material in Example 1 of the present invention and cycled at 1C rate at room temperature for 500 cycles;

Fig. 3 is a cycle performance diagram of a half cell assembled from the CuFeO ₂ @G composite material in Example 1 of the present invention at room temperature at a rate of 1C for 500 cycles.

Detailed ways

Example 1

Dissolve 0.00625 mol of copper nitrate and 0.00625 mol of ferric nitrate in 30 ml of deionized water under magnetic stirring. Next, 0.125 mol of sodium hydroxide was dissolved in 20 ml of deionized water under stirring until completely dissolved, and then slowly added into the prepared mixed nitrate solution under stirring and stirred for 90 minutes. Add 0.01 g of graphene through ultrasonic dispersion and 0.625 ml of reducing agent propionaldehyde into the above mixed solution.

The above mixed solution was transferred into an autoclave (70 ml) and heated at 180 °C for 16 h, after natural cooling to room temperature, the product was centrifuged and washed several times with alcohol and deionized water, and then dried at 80 °C to obtain _CuFeO2 composites.

Adding an appropriate amount of graphene can improve the conductivity of the composite material, thereby improving its electrochemical performance. The low content of graphene is not enough to improve the conductivity of the composite material. If the content is too large, it will affect the specific capacity of the composite material. Therefore, copper The quantity and mass ratio of salt, iron salt and graphene is 1:1:0.01~0.05. Appropriate hydrothermal temperature and time make the synthesized _CuFeO2 material have the advantages of uniform particle size distribution, good crystal form and no agglomeration.

As shown in Figure 1, the _CuFeO2 material obtained in this embodiment is assembled into a half cell, and the discharge curve at 0.2C rate at room temperature;

Figure 2. CuFeO ₂ material and CuFeO ₂ @G composite material were assembled into a half-cell, and the cycle performance diagram was cycled at room temperature for 200 cycles at a rate of 1C. a refers to CuFeO ₂ material, and b refers to CuFeO ₂ @G composite material;

Figure 3. The CuFeO ₂ @G composite material is assembled into a half-cell, and the cycle performance diagram of 500 cycles at a rate of 1C at room temperature, a refers to the charge-discharge efficiency, and b refers to the discharge specific capacity.

The electrochemical performance diagram of CuFeO ₂ material and CuFeO ₂ @G composite material in this example, as can be seen from Figure 1, CuFeO ₂ material has a suitable voltage platform and the first discharge specific capacity; and from Figure 2, it can be seen that CuFeO ₂ After the material is coated with graphene, the electrochemical performance is significantly improved, and it has a long cycle performance; as can be seen from Figure 3, the cycle performance diagram of the CuFeO ₂ @G composite material after 500 long cycles shows that the composite material It has good cycle performance and charge and discharge efficiency.

Example 2

Dissolve 0.00625 mol of copper sulfate and 0.00625 mol of ferric sulfate in 30 ml of deionized water under magnetic stirring. Next, 0.125 mol of sodium hydroxide was dissolved in 20 ml of deionized water with stirring until completely dissolved, and then slowly added to the prepared mixed sulfate solution with stirring and stirred for 90 minutes. Add 0.02g of graphene through ultrasonic dispersion and 0.625ml of reducing agent ascorbic acid into the above mixed solution.

The above mixed solution was transferred into an autoclave (70 ml) and heated at 200 °C for 18 h, after natural cooling to room temperature, the product was centrifuged and washed several times with alcohol and deionized water, then dried at 80 °C to obtain _CuFeO2 composites.

Example 3

Dissolve 0.00625 mol of copper chloride and 0.00625 mol of ferric chloride in 30 ml of deionized water under magnetic stirring. Next, 0.125 mol of sodium hydroxide was dissolved in 20 ml of deionized water under stirring until completely dissolved, and then slowly added into the prepared mixed chloride salt solution under stirring and stirred for 90 minutes. Add 0.03g of graphene through ultrasonic dispersion and 0.625ml of reducing agent glucose into the above mixed solution.

The above mixed solution was transferred into an autoclave (70 ml) and heated at 220 °C for 24 h, after natural cooling to room temperature, the product was centrifuged and washed several times with alcohol and deionized water, then dried at 80 °C to obtain _CuFeO2 composites.

Example 4

Dissolve 0.00625 mol of copper nitrate and 0.00625 mol of ferric nitrate in 30 ml of deionized water under magnetic stirring. Next, 0.125 mol of sodium hydroxide was dissolved in 20 ml of deionized water under stirring until completely dissolved, and then slowly added into the prepared mixed nitrate solution under stirring and stirred for 90 minutes. Add 0.01 g of graphene through ultrasonic dispersion and 0.625 ml of reducing agent propionaldehyde into the above mixed solution.

The above mixed solution was transferred into an autoclave (70 ml) and heated at 230 °C for 24 h, after natural cooling to room temperature, the product was centrifuged and washed several times with alcohol and deionized water, then dried at 80 °C to obtain _CuFeO2 composites.

comparative example

Dissolve 0.00625 mol of copper nitrate and 0.00625 mol of ferric nitrate in 30 ml of deionized water under magnetic stirring. Next, 0.125 mol of sodium hydroxide was dissolved in 20 ml of deionized water under stirring until completely dissolved, and then slowly added into the prepared mixed nitrate solution under stirring and stirred for 90 minutes. 0.625 ml of reducing agent ascorbic acid was added to the above mixed solution.

The above mixed solution was transferred into an autoclave (70 ml) and heated at 200 °C for 24 h, after natural cooling to room temperature, the product was centrifuged and washed several times with alcohol and deionized water, then dried at 80 °C to obtain _CuFeO2 composites.

Table 1 Cycling data of the half-cell at room temperature after 500 cycles

Discharge specific capacity at 1C rate (mAh/g) Capacity retention rate after 500 cycles Example 1 455 93% Example 2 440 91% Example 3 450 92% Example 4 465 94% comparative example 160 90%

Verify the effect

Part of Table 1 shows the specific discharge capacity of the assembled half-battery in the embodiment and the comparative example at a rate of 1C at room temperature and the capacity retention rate after 500 cycles.

It is not difficult to see by comparison that in Examples 1-4, the discharge specific capacity of the _CuFeO2 composite material formed by adding graphene and reducing agent is much higher than that of the comparative example, and the capacity retention rate is higher than that of the comparative example.

It can be seen that the present invention adopts the hydrothermal method to prepare nano-scale CuFeO ₂ material, which has a larger surface area, increases the contact area with the electrolyte, and utilizes graphene to improve the conductivity of the material. Therefore, the composite material is used in lithium When used as an ion battery, it has a high specific capacity, charge and discharge rate and a long cycle life.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (5)

1. a kind of graphene coated CuFeO₂The preparation method of composite negative pole material, which is characterized in that steps are as follows：

（1）A certain amount of mantoquita and molysite are add to deionized water stirring, solution A is formed, configures certain density hydrogen-oxygen Change sodium solution, be slowly added into solution A, while reducing agent and the graphene as conductive agent is added, forms solution B；

（2）Solution B is transferred in reaction kettle and carries out hydro-thermal reaction, product is centrifuged and washs number with ethyl alcohol and deionized water It is secondary, it is dry, obtain graphene coated CuFeO₂Composite negative pole material CuFeO₂@G。

2. graphene coated CuFeO according to claim 1₂The preparation method of composite negative pole material, it is characterised in that：Institute State step（1）In, mantoquita is one or more of copper nitrate, copper sulphate, copper chloride；The molysite be ferric nitrate, ferric sulfate, One or more of iron chloride；And the root of mantoquita and molysite is corresponding.

3. graphene coated CuFeO according to claim 1₂The preparation method of composite negative pole material, it is characterised in that：Institute State step（1）In, the amount and mass ratio of the substance of mantoquita, molysite and graphene are 1：1：0.01~0.05.

4. graphene coated CuFeO according to claim 1₂The preparation method of composite negative pole material, it is characterised in that：Institute State step（1）In, reducing agent is one or more of propionic aldehyde, ascorbic acid, glucose.

5. graphene coated CuFeO according to claim 1₂The preparation method of composite negative pole material, it is characterised in that：Institute State step（2）In, the hydrothermal temperature is 160 ~ 240 DEG C, and the hydro-thermal time is 16 ~ 36h.