CN108063220A - A kind of lithium ion battery coats copper oxide nano material and preparation method with polypyrrole - Google Patents

Abstract

The invention provides a polypyrrole-coated copper oxide nanometer material for lithium ion battery negative electrodes and a preparation method thereof. The method is to add the prepared copper oxide nanomaterial into the aqueous solution of the surfactant, stir evenly, and prepare the copper oxide nanomaterial coated with polypyrrole by chemical oxidation polymerization by adding pyrrole, dopant and oxidant. . After the reaction is completed, it is centrifuged, washed with deionized water, ethanol, etc., and vacuum-dried or freeze-dried to prepare CuO@PPy composite materials. Compared with pure CuO as the negative electrode of lithium-ion batteries, the advantage of CuO@PPy composite material as the negative electrode of lithium-ion batteries is that when copper oxide is used as the negative electrode material of lithium-ion batteries, the capacity begins to have a large attenuation after 50 cycles. CuO@PPy composite material, because the polypyrrole shell has a protective effect on CuO, the specific capacity of the material has a good capacity retention rate after multiple cycles.

Description

Polypyrrole-coated copper oxide nanometer material for lithium ion battery and preparation method thereof

technical field

The invention relates to the field of lithium ion batteries, and to the technical field of preparation of inorganic semiconductor nanometer materials. It mainly relates to a polypyrrole-coated copper oxide nanomaterial and its preparation method. The material is mainly used in the negative electrode of lithium-ion batteries. Compared with uncoated copper oxide nanomaterials, it can improve the charge-discharge cycle of the negative electrode of lithium-ion batteries. stability.

Background technique

Lithium-ion batteries have been widely used in mobile electronic devices, backup energy storage and other fields due to their high voltage, high energy, light weight, small size, low internal resistance, low self-discharge, long cycle life, and no memory effect. It is one of the research hotspots of new energy materials at present. The development of lithium-ion batteries depends largely on the improvement of the performance of battery materials. At present, negative electrode materials are also an important factor in improving battery energy and cycle life. Commercial lithium-ion battery anode materials are mainly graphite, coke, and non-graphitizable carbon. However, the theoretical capacity is low, and it is difficult to meet the needs of the power supply. In 2000, the French Tarascon research group published an article in Nature, reporting that nano-sized transition metal oxides MO (M=Co, Ni, Cu, Fe, etc.) can be used as negative electrode materials for lithium-ion secondary batteries, and It exhibits a high specific capacity (>600 mAhg-1), which is about twice the theoretical capacity of carbon materials. And the charge-discharge reaction mechanism of this kind of material is proposed, which is different from the previous intercalation reaction mechanism. During the charge and discharge process, the redox reaction between transition metal oxide and metal lithium brings high specific capacity and good rate charge and discharge performance. It is one of the important directions for the development of lithium ion batteries and has a good development prospect.

Although metal oxide lithium-ion battery anodes have the advantage of large specific capacity, they have the disadvantages of large specific capacity fading and unstable cycle performance in reversible cycles. This is because most metal oxides are semiconductor materials with poor conductivity, and the Li2O generated during the reaction further deteriorates the conductivity of the material, resulting in poor conductivity of the negative electrode. At the same time, after the transition metal oxide particles intercalate lithium for the first time, a large volume expansion often occurs, resulting in a large stress, and the pulverization of the material is very easy to occur, and the particles and between the particles and the current collector will gradually lose Electrical contact; in addition, after a large number of lithium ions are intercalated, the volume expansion increases the chance of contact between adjacent nanoparticles, and the atoms on the surface of the nanoparticles form bonds with each other to gradually fuse the adjacent nanoparticles, thereby triggering the so-called electrochemical agglomeration, Many originally active particles lose their electrochemical activity. Second, during the first discharge, the electrolyte and the CuO surface react to form an SEI layer (solid electrolyte interfacial layer), which leads to a large irreversible charge-discharge capacity. These are urgent issues to be solved in the research of transition metal oxides as anodes for lithium-ion batteries, including CuO nanomaterials. Preparation of metal oxides into composite materials with core-shell structure can improve their reversible specific capacity and cycle performance. This is because the shell structure can prevent stress changes and cracks in the core structure, forming a protective layer on the surface of the core to prevent the reaction between the active material and the electrolyte.

For example, our research group found in the research that when copper oxide is used as the anode material of lithium-ion batteries, after 50 cycles, the anode capacity begins to decline greatly. Therefore, we polymerized the polypyrrole shell on the surface of copper oxide nanomaterials to improve the charge-discharge cycle stability of copper oxide as the anode of lithium-ion batteries. Similar methods have also been reported in the literature. For example, when Wang Zhaoxiang's research group at the Institute of Physics, Chinese Academy of Sciences used NiO as the anode material for lithium-ion batteries, the reversible specific capacity was about 400 mAhg ^-1 . The reversible specific capacity of the material increases to 680 mAh g ^-1 . Dr. Qingdong Zheng and others found that when CuO is used as the negative electrode material of lithium-ion batteries, the reversible specific capacity is about 200 mAh g ^-1 (10 charge-discharge cycles). The reversible specific capacity increases to 600 mAhg ^-1 .

In the research of this patent application, we first used the copper oxide patent sample studied by our research group - copper oxide nanomaterials prepared by calcining octahedral hollow cuprous oxide. Secondly, in order to improve the charge-discharge cycle stability of copper oxide nanomaterials as the negative electrode of lithium-ion batteries, we prepared CuO@PPy composite nanomaterials on the surface of copper oxide nanomaterials by chemical oxidation polymerization. In this preparation process, we researched and improved the polymerization method. For example, when _FeCl3 is used as an oxide, the substance can react with copper oxide, so we choose a persulfate with high oxidizing property as the oxide, but the excessive oxidizing property will lead to the decrease of the electrical conductivity of polypyrrole, which will make the oxidation The electrochemical performance of copper decreases. Here, we found a method to prepare polypyrrole by chemical oxidation polymerization on the surface of copper oxide, and prepared CuO@PPy nanomaterials, and achieved improved charge-discharge cycle stability as the negative electrode of lithium-ion batteries. sexual goals.

Contents of the invention

The object of the present invention is to provide a polypyrrole-coated copper oxide nanometer material for lithium ion battery negative electrode; another object of the present invention is to provide a preparation method of the material.

The technical scheme of the invention is divided into two processes of preparing copper oxide nanometer material and coating polypyrrole on the copper oxide material. The preparation process of copper oxide nanomaterials is as follows:

Under the condition of alkaline solution, the complexing agent ethylenediamine is added to complex with copper ions, so as to realize the good dissolution state of copper ions under alkaline conditions, and through the lamellar structure of ethylenediamine, the copper ions are regulated Hollow or porous structure when reduced to cuprous oxide. Then, add copper ion solution to the solution, stir evenly at 30-100° C., add reducing agent hydrazine, and continue stirring for 10 minutes to 1 hour to prepare cuprous oxide nanomaterials. The prepared cuprous oxide nano material solution is centrifuged, washed with a large amount of deionized water and ethanol to obtain purified cuprous oxide nano material, then dried and calcined at 250-900 DEG C to obtain black copper oxide nano material.

The preparation process of coating polypyrrole on the copper oxide material is as follows:

Add a certain amount of copper oxide material to a solution containing a surfactant (such as sodium benzenesulfonate) and place it at a low temperature, then add pyrrole monomer solution and KCl, mix well, and control the reaction temperature to be constant, ranging from -5 After ℃～50℃, add K ₂ S ₂ O ₈ solution drop by drop, polymerize the monomeric pyrrole on the copper oxide material by chemical oxidation method, and continue stirring for 10 to 72 hours to prepare polypyrrole-coated copper oxide nanoparticles. Material. The prepared material solution was centrifuged, washed with a large amount of deionized water and ethanol, and then vacuum-dried at 60 °C to obtain the CuO@PPy composite material.

In the preparation process of the present invention, the surfactant used mainly includes sodium benzenesulfonate (BSNa), sodium dodecylbenzenesulfonate (DBSNa), sodium dodecylsulfonate (DSNa), β-naphthalenesulfonic acid Sodium (β-NSNa), sodium p-toluenesulfonate (TSNa), etc. The ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl in the reaction system is 1:1-6:1-3:1-10.

Compared with pure CuO as the negative electrode of lithium-ion batteries, the advantage of CuO@PPy composite material as the negative electrode of lithium-ion batteries is that when copper oxide is used as the negative electrode material of lithium-ion batteries, the capacity begins to have a large attenuation after 50 cycles. CuO@PPy composite material, because the polypyrrole shell has a protective effect on CuO, the specific capacity of the material has a good capacity retention rate after multiple cycles.

Description of drawings

Fig. 1 is a scanning electron microscope image of the CuO@PPy composite material obtained in Example 1 of the present invention.

Fig. 2 is an energy spectrum diagram of the CuO@PPy composite material obtained in Example 1 of the present invention.

Fig. 3 is an energy spectrum diagram of the CuO@PPy composite material obtained in Example 2 of the present invention.

4 is a charge-discharge cycle diagram of the CuO@PPy composite material obtained in Example 2 of the present invention as a negative electrode of a lithium-ion battery and a charge-discharge cycle diagram with pure CuO.

5 is a charge-discharge cycle diagram of the CuO@PPy composite material obtained in Example 3 of the present invention as the negative electrode of a lithium-ion battery and a charge-discharge cycle diagram with pure CuO.

Detailed ways

The present invention will be further explained and illustrated below in conjunction with specific embodiments. However, these examples are only used to further illustrate the present invention, and do not limit the protection scope of the present invention in any way.

Example 1:

1. First configure the following solution:

Surfactant solution (such as sodium benzenesulfonate solution): Weigh 0.0447 g of sodium benzenesulfonate and dissolve it in 200 mL of deionized water, and stir at room temperature for 12 hours to fully dissolve the surfactant.

K ₂ S ₂ O ₈ solution: Weigh 0.09747 g of K ₂ S ₂ O ₈ and dissolve in 20 mL of deionized water.

2. Preparation of CuO@PPy composites:

Weighed 0.2 g of black CuO powder and added it to the prepared surfactant solution, and added 0.1076 g of KCl after magnetic stirring for 30 min. Afterwards, the beaker was placed in an ice-water bath, and after 20 min of magnetic stirring, 50 μL of pyrrole monomer was pipetted into the mixture. After continuing to stir for 30 min, the prepared K ₂ S ₂ O ₈ solution was slowly added dropwise to the mixture, stirred magnetically for 12 hours and the reaction system was kept in an ice-water bath to obtain the CuO@PPy composite material.

3. Purification of CuO@PPy composites:

The prepared CuO@PPy composite was centrifuged three times at 8000 revolutions per minute (rpm), 5 minutes each time, and washed alternately with deionized water and absolute ethanol, thus removing unreacted ions and Finally, the CuO@PPy composite was vacuum-dried at 60 °C, or freeze-dried.

As shown in the figure: Figure 1 is a scanning electron microscope image of the CuO@PPy composite material prepared in this example. Figure 2 is the energy spectrum of the CuO@PPy composite material prepared in this example. The presence of the polypyrrole component can be seen from the N element peak and the C element peak in the energy spectrum. It can be seen from the above preparation method that the method is simple, flexible and requires simple production equipment.

In Example 1, the ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl is 1:3:1.5:9.

Example 2:

Weighed 0.2 g of black CuO powder and added it to the prepared surfactant solution, and added 0.01076 g of KCl after magnetic stirring for 30 min. Afterwards, the beaker was placed in an ice-water bath, stirred by magnetic force for 20 min, and 5 μL of pyrrole monomer was pipetted into the mixture. After continuing to stir for 30 min, the prepared K ₂ S ₂ O ₈ solution was slowly added dropwise to the mixture, stirred magnetically for 12 hours and the reaction system was kept in an ice-water bath to obtain the CuO@PPy composite material.

As shown in the figure: Figure 3 is a scanning electron microscope image of the CuO@PPy composite material prepared in this example. Fig. 4 is a charge-discharge cycle diagram of the CuO@PPy composite material prepared in this example as the negative electrode of a lithium-ion battery and a charge-discharge cycle diagram with pure CuO. It can be seen that when the CuO@PPy composite material with a core-shell structure is prepared as the anode of a lithium-ion battery, the cycle stability is significantly improved.

In Example 2, the ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl is 1:0.3:0.15:0.9.

Example 3:

Weighed 0.2 g of black CuO powder and added it to the prepared surfactant solution, and added 0.03228 g of KCl after magnetic stirring for 30 min. Afterwards, the beaker was placed in an ice-water bath, stirred by magnetic force for 20 min, and 15 μL of pyrrole monomer was pipetted into the mixture. After continuing to stir for 30 min, the prepared K ₂ S ₂ O ₈ solution was slowly added dropwise to the mixture, stirred magnetically for 12 hours and the reaction system was kept in an ice-water bath to obtain the CuO@PPy composite material.

As shown in the figure: Figure 5 is the charge-discharge cycle diagram of the CuO@PPy composite material prepared in this example as the negative electrode of the lithium-ion battery and the charge-discharge cycle diagram with pure CuO. It can be seen that when the CuO@PPy composite material with a core-shell structure is prepared as the anode of a lithium-ion battery, the cycle stability is significantly improved.

In Example 3, the ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl is 1:1:0.5:3.

Example 4:

Weighed 0.2 g of black CuO powder and added it to the prepared surfactant solution, and added 0.06456 g of KCl after magnetic stirring for 30 min. Afterwards, the beaker was placed in an ice-water bath, and after 20 min of magnetic stirring, 30 μL of pyrrole monomer was pipetted into the mixture. After continuing to stir for 30 min, the prepared K ₂ S ₂ O ₈ solution was slowly added dropwise to the mixture, stirred magnetically for 12 hours and the reaction system was kept in an ice-water bath to obtain the CuO@PPy composite material.

In Example 4, the ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl is 1:2:1:6.

Example 5:

Weighed 0.2 g of black CuO powder and added it to the prepared surfactant solution, and added 0.1076 g of KCl after magnetic stirring for 30 min. Afterwards, the beaker was placed in an ice-water bath, stirred by magnetic force for 20 min, and 100 μL of pyrrole monomer was pipetted into the mixture. After continuing to stir for 30 min, the prepared K ₂ S ₂ O ₈ solution was slowly added dropwise to the mixture, stirred magnetically for 12 hours and the reaction system was kept in an ice-water bath to obtain the CuO@PPy composite material.

In Example 5, the ratio of surfactant: pyrrole monomer: K ₂ S ₂ O ₈ : KCl is 1:6:3:9.

The above examples illustrate in detail: in this method, in the surfactant solution, by adding pyrrole, dopant, and oxidizing agent, the surface of the copper oxide nanomaterial that has been prepared is prepared by chemical oxidation polymerization to obtain polypyrrole coating copper oxide nanomaterials. The polypyrrole-coated copper oxide nanometer material prepared by the invention has good electrical conductivity, and has good charge-discharge cycle stability when used as a lithium-ion battery negative electrode. The suitable conditions for preparing polypyrrole-coated copper oxide nanomaterials are 1:1-6:1-3:1-10.

Claims (4)

1. a kind of preparation method of polypyrrole cladding copper oxide nano material, it is characterised in that include the following steps：It weighs certain Amount CuO powder is added in prepared surfactant solution, and magnetic agitation adds in a certain amount of KCl after a certain period of time；It Beaker is placed in ice-water bath afterwards, pipetting pyrrole monomer after magnetic agitation is uniform is added in mixed liquor；Continue after stirring evenly K is slowly added dropwise₂S₂O₈Solution, stir and react 10 to 72 it is small when CuO PPy composite materials are prepared.

2. by the preparation method of CuO@PPy composite materials described in claim 1, it is characterised in that：Table in the reaction system Face activating agent：Pyrrole monomer：K₂S₂O₈：The amount ratio of the substance of KCl is：1：1~6：1~3：1~10.

3. by the preparation method of CuO@PPy composite materials described in claim 1, it is characterised in that：Surfactant master used To include benzene sulfonic acid sodium salt (BSNa), neopelex (DBSNa), dodecyl sodium sulfate (DSNa), sodiumβ-naphthalenesulfonate (β-NSNa), paratoluenesulfonic acid sodium salt (TSNa) etc., between range of reaction temperature is -5 DEG C~50 DEG C.

4. the method in claim, the copper oxide nano material for the polypyrrole cladding being prepared.