CN105186004B - A kind of used as negative electrode of Li-ion battery copper current collector and its preparation method and application - Google Patents

Abstract

The invention belongs to technical field of lithium ion, and in particular to a kind of used as negative electrode of Li-ion battery copper current collector and its preparation method and application.The present invention is pre-processed especially by copper foil, made annealing treatment, the formation of graphene layer, vacuum evaporation metal film, Quenching Treatment step are obtained in copper foil surface successively grapheme modified layer and metal nano-particle layer.Used as negative electrode of Li-ion battery copper current collector of the present invention, with good electric conductivity, can alleviate the erosion of electrolyte, strong with coating layer of active substance adhesion.

Description

A kind of copper current collector for negative electrode of lithium ion battery and its preparation method and application

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a copper current collector for negative electrodes of lithium ion batteries, a preparation method and application thereof.

Background technique

Lithium-ion batteries are considered to be one of the most green and clean energy sources, and are now widely used in portable electronic products, and are considered to be a promising power source for hybrid electric vehicles and pure electric vehicles. Lithium-ion batteries are mainly composed of active materials, battery cases, current collectors, diaphragms, electrolytes and other components. Among them, the current collector is one of the important components of the lithium-ion battery. The surface carries the active material and is in contact with the electrolyte. At the same time, the electrons generated by the positive and negative active materials are collected to the external circuit through it to form a current.

Copper has sufficient mechanical strength, good electrical conductivity, and is not easy to alloy with lithium, etc., and is often used as a current collector for the negative electrode of lithium-ion batteries. The current commercial Li-ion battery anode Cu current collector mainly uses electrolytic Cu foil, which is divided into several types such as double-sided light, double-sided wool, single-sided wool, double-sided roughening, and high elongation. However, an oxide film is easily formed on the surface of the Cu current collector, and the oxide film is a semiconductor, which will affect the conductivity of the current collector; the Cu current collector is easy to react and dissolve with the solvent and impurities of the electrolyte during the charging and discharging process of the battery, making Cu unstable. At the same time, oxides on the surface of Cu are prone to deintercalation reactions with lithium ions, resulting in volume expansion and contraction, which makes the active material coating on the surface of Cu fall off; Great changes, resulting in the separation of electrode materials and Cu current collectors.

Contents of the invention

In order to overcome the above-mentioned defects, one of the objects of the present invention is to provide a copper current collector for the negative electrode of lithium-ion batteries, which has good electrical conductivity, can alleviate the erosion of the electrolyte, and has a strong binding force with the active material coating.

The second object of the present invention is also to provide a method for preparing a copper current collector for negative electrodes of lithium ion batteries.

The third object of the present invention is also to provide an application of a copper current collector in a lithium-ion battery.

To achieve the above object, the present invention adopts the following technical solutions:

A copper current collector for negative electrodes of lithium-ion batteries, in which a graphene layer and a metal nanoparticle layer are sequentially modified on the surface of the copper current collector.

According to the above-mentioned copper current collector for negative electrodes of lithium-ion batteries, the metal is one or an alloy of Cu, Au, and Ag.

According to the above-mentioned copper current collector for negative electrodes of lithium ion batteries, the thickness of the graphene layer is 0.5-2 nm.

According to the above-mentioned copper current collector for negative electrodes of lithium-ion batteries, the average particle diameter of the metal nanoparticles is 10-100 nm.

A kind of preparation method of above-mentioned lithium ion battery negative electrode copper current collector, comprises the steps:

(1) Polish or pickle the Cu foil, and vacuum dry it at 40-60 °C for 30-60 min to obtain a dried Cu foil;

(2) Put the dried Cu foil in step (1) into a CVD tube furnace and calcinate it at 950-1060 °C for 20-70 min under a reducing atmosphere;

(3) Put the Cu foil calcined in step (2) into an oxygen-free reactor, heat it to 950-1060 °C, fill the reactor with carbon source, keep the temperature constant for 5-60 min, and cool it down to At room temperature, a graphene-modified Cu foil is obtained, and the thickness of the graphene layer is 0.5-2 nm;

(4) Vacuum-evaporate a metal film on the surface of the graphene layer with a thickness of 4-20 nm;

(5) Under reducing atmosphere, 250-350 ℃ quenching treatment step (4) metal film for 20-50 min, so that a metal nanoparticle layer is formed on the surface of the graphene layer, and the product copper current collector is obtained.

According to the above-mentioned preparation method of copper current collector for negative electrode of lithium ion battery, the pickling method described in step (1) is: ultrasonic treatment of acid solution for 5-15 minutes, the acid solution is acetic acid or oxalic acid solution, the concentration is 0.5- 2 mol·L ^-1 .

According to the above method for preparing a copper current collector for negative electrodes of lithium-ion batteries, the reducing atmosphere described in step (2) or step (5) is _H2 or a mixed gas of Ar and _H2 , and the reducing atmosphere described in step (3) The neutral atmosphere is H ₂ .

According to the above method for preparing a copper current collector for negative electrodes of lithium-ion batteries, the carbon source described in step (3) is a gaseous carbon source, a liquid carbon source or a solid carbon source.

According to the above method for preparing a copper current collector for negative electrodes of lithium ion batteries, the gaseous carbon source is methane, acetylene or ethylene.

According to the above method for preparing a copper current collector for negative electrodes of lithium ion batteries, the liquid carbon source is ethanol or benzene.

According to the above method for preparing a copper current collector for negative electrodes of lithium ion batteries, the solid carbon source is naphthalene or polystyrene.

An application of the copper current collector prepared above in a lithium ion battery.

Positive beneficial effect of the present invention:

1. The present invention grows a graphene layer with high conductivity on a Cu substrate by chemical vapor deposition (CVD method), and then vapor-deposits a metal film with good conductivity on the graphene layer. After quenching, the metal film is due to the surface The presence of tension ruptures and shrinks to form a layer of metal nanoparticles. Graphene, metal nanoparticles with good conductivity and Cu substrate can form a good conductive network.

The graphene layer grown by CVD can well cover the surface of the Cu substrate, which can alleviate the erosion of the electrolyte on the Cu current collector, and graphene is a kind of carbon atoms arranged according to sp ² hybridization, and mutually Connected into a honeycomb network structure, it has excellent properties such as high transmittance, high conductivity, high mechanical strength and large specific surface area, which can improve the conductivity of Cu current collectors; metal nanoparticles can increase the specific surface area of Cu current collectors And the degree of roughness, which can enhance the contact area and adhesion between the active material and the current collector, thereby improving the reversible specific capacity and cycle performance of the lithium-ion battery.

2. During the growth process of graphene, a reducing gas is introduced to reduce the surface oxide of the Cu substrate to Cu simple substance, thereby reducing the resistance of the Cu substrate. The Cu foil with this structure is used as a collector for the negative electrode of the lithium-ion battery. The fluid can reduce the charge transfer resistance at the interface between the active material and the current collector, which is beneficial to the electrochemical performance of the lithium-ion battery.

3. The preparation method of the copper current collector for the negative electrode of the lithium ion battery is simple, significantly improves the electrochemical performance of the lithium ion battery, and can be widely used in lithium ion batteries.

Description of drawings

Fig. 1 is the structural representation of copper current collector for negative electrode of lithium ion battery of the present invention;

Fig. 2 is the first charge and discharge curve diagram of embodiment 1 lithium-ion battery under 2 A · g ^-1 electric current;

Fig. 3 is the cycle performance figure of embodiment 1 lithium-ion battery under 2 A · g ^-1 electric current;

Fig. 4 is the cycle performance diagram of the lithium-ion battery of Example 1 at 4 A g ^-1 and 6 A g ^-1 current;

Fig. 5 is the cross-sectional SEM figure of embodiment 1 lithium-ion battery negative pole sheet;

Fig. 6 is the cross-sectional SEM figure of contrast lithium-ion battery negative pole piece;

Fig. 7 is the SEM figure of embodiment 2 copper current collector;

Fig. 8 is the SEM image of the copper current collector of Example 2 after ultrasonic treatment for 15 min;

Fig. 9 is the cross-sectional SEM diagram of the negative pole piece after the lithium-ion battery of embodiment 2 cycles 200 times under 1 C electric current;

Figure 10 is a cross-sectional SEM image of the negative electrode sheet of the control lithium-ion battery after 200 cycles at a current of 1 C;

Figure 11 is a graph of the cycle performance of the lithium-ion battery prepared in Example 3 at a current of 0.5 A g ^-1 .

detailed description

The present invention will be further described below in conjunction with some specific embodiments.

Example 1

Referring to Figures 1 to 6, a copper current collector for the negative electrode of a lithium-ion battery is sequentially decorated with a graphene layer and an Au nanoparticle layer on the surface of the copper foil. The thickness of the graphene layer is 1 nm, and the average particle size of the Au nanoparticles is 27 nm. .

The preparation method of the above-mentioned copper current collector for negative electrode of lithium ion battery comprises the following steps:

(1) The copper foil was ultrasonically treated with 1 mol L ^-1 acetic acid solution for 10 min, then rinsed with water and ethanol, and dried in vacuum at 50 °C for 30 min to obtain a dried Cu foil;

(2) The Cu foil dried in step (1) was placed in a CVD tube furnace and calcined at 1045 °C for 60 min under _H2 flow, and the _H2 flow rate was 10 sccm;

(3) Using CH ₄ as carbon source, feed CH ₄ and H ₂ at 1045 ℃, CH ₄ flow rate is 1 sccm, H ₂

The flow rate is 2 sccm, the temperature is kept for 15 min, cooled to room temperature under _H2 atmosphere, and the _H2 flow rate is 10 sccm to obtain a graphene layer-modified Cu foil with a graphene layer thickness of 1 nm;

(4) Vacuum-deposit Au film on the surface of the graphene layer, and the thickness of the Au film is 8 nm;

(5) The Au film was quenched at 300 ℃ for 30 min under the protection of H ₂ and Ar gas to form an Au nanoparticle layer on the surface of the graphene layer. The H ₂ flow rate was 600 sccm and the Ar flow rate was 600 sccm to obtain the product Cu current collector.

A button half-cell was used to detect the influence of the Cu current collector of the present invention on battery performance. The Cu foil prepared in Example 1 was used as the current collector for the lithium-ion battery, and lithium zinc titanate (Li ₂ ZnTi ₃ O ₈ , LZTO) was used as the active material. Li-ion batteries are marked as Cu-G-Au-LZTO.

As a control lithium-ion battery, Cu foil not modified with graphene and Au nanoparticles was used as the current collector, lithium zinc titanate (Li ₂ ZnTi ₃ O ₈ , LZTO) was used as the active material, and the lithium-ion battery was marked as Cu-LZTO.

Figure 2 is the first charge-discharge curve of the lithium-ion battery of this embodiment at a current of 2 A g ^-1 , and the discharge specific capacities of Cu-LZTO and Cu-G-Au-LZTO lithium-ion batteries are 212.2 and 242.1 mAh· g ^-1 , it can be seen that the Cu current collector co-modified with graphene and Au nanoparticles in the present invention significantly improves the discharge specific capacity of the battery.

Figure 3 is the cycle performance diagram of the lithium-ion battery of this embodiment at a current of 2 A g ^-1 , and the specific capacities of the Cu-LZTO and Cu-G-Au-LZTO lithium-ion batteries in the second discharge are 160.0 and 219.4 respectively mAh·g ^-1 , the specific capacity after 200 cycles is 136.1 and 204.9 mAh·g ^-1 respectively, and the capacity retention rate relative to the second time is 85.1% and 93.4%, respectively. The present invention uses graphene and Au nanoparticles The co-modified Cu current collector significantly improves the cycle performance of the battery.

Figure 4 is the cycle performance diagram of the lithium-ion battery of this example under the current of 4 A g ^-1 and 6 A g ^-1 . After 100 cycles, the discharge specific capacity of the battery is 172.2 and 130.0 mAh g ^-1 respectively, The lithium ion battery of the invention exhibits good high-current charging and discharging performance.

Figure 5 is a cross-sectional SEM image of the Cu-G-Au-LZTO lithium-ion battery negative pole piece prepared in this example. It can be seen from the figure that the gap between the active material coating and the current collector is very small, indicating that both There is good adhesion between them; Figure 6 is a cross-sectional SEM image of the negative pole piece of the Cu-LZTO lithium-ion battery. It can be seen from the figure that the gap between the active material coating and the current collector is relatively large, indicating that both The adhesion between them is poor.

Example 2

Referring to Fig. 1, Figs. 7-10, a copper current collector for negative electrodes of lithium-ion batteries, a graphene layer and an alloy nanoparticle layer are sequentially modified on the surface of copper foil, the thickness of the graphene layer is 1 nm, and the alloy is Au and Ag alloy, the mass ratio of the two is 1:1, and the average particle size of alloy nanoparticles is 50 nm.

The preparation method of the above-mentioned copper current collector for negative electrode of lithium ion battery comprises the following steps:

(1) Ultrasonic treatment of Cu foil with 1 mol L ^-1 oxalic acid solution for 15 min, followed by rinsing with water and ethanol, and vacuum drying at 60 °C for 40 min to obtain dried Cu foil;

(2) The dried Cu foil was calcined in a CVD tube furnace at 1050 °C for 20 min under _H2 flow, and the _H2 flow rate was 10 sccm;

(3) Using CH ₄ as the carbon source, feed CH ₄ and H ₂ at 1060 °C, the flow rate of CH ₄ is 1 sccm, the flow rate of H ₂ is 2 sccm, keep the temperature for 10 min, and drop to room temperature under the protection of H ₂ , the flow rate of H ₂ Be 10 sccm, obtain the Cu foil of graphene layer modification, the thickness of graphene layer is 1 nm;

(4) Vacuum evaporation of Au and Ag alloy film on the surface of the graphene layer, the thickness of the alloy film is 12 nm;

(5) The Au and Ag alloy film was quenched at 250 ℃ for 50 min under the protection of H ₂ gas to form an alloy nanoparticle layer on the surface of the graphene layer. The H ₂ flow rate was 700 sccm to obtain the product Cu current collector.

The influence of Cu current collector on battery performance was detected by button half-cell. Lithium-ion battery uses Cu foil prepared in Example 2 as current collector, lithium titanate (Li ₄ Ti ₅ O ₁₂ , LTO) as active material, lithium-ion battery Labeled as Cu-G-Au/Ag-LTO.

As a control lithium-ion battery, Cu foil not modified with graphene and Au/Ag alloy nanoparticles is used as the current collector, lithium titanate (Li ₄ Ti ₅ O ₁₂ , LTO) is used as the active material, and the lithium-ion battery is marked as Cu-LTO .

Figure 7 is the SEM image of the Cu current collector prepared in this example, and Figure 8 is the SEM image of the Cu current collector prepared in this example after ultrasonic treatment for 15 min. It can be seen from Figures 7 and 8 that the graphite after ultrasonic treatment Graphene and alloy nanoparticles did not fall off, indicating that the modified layer of graphene and alloy nanoparticles prepared by the present invention has good binding force with Cu.

Figure 9 is a cross-sectional SEM image of the negative electrode sheet of the Cu-G-Au/Ag-LTO lithium-ion battery of this example after 200 cycles at 1 C current, and Figure 10 is a contrast Cu-LTO lithium-ion battery at 1 C current After 200 cycles, the SEM image of the cross-section of the negative electrode sheet, compared with the Cu-LTO lithium ion battery, the negative electrode active material coating is seriously separated from the current collector, and the negative electrode active material of the Cu-G-Au/Ag-LTO lithium ion battery of the present invention There is good adhesion between the coating and the current collector, and there is no obvious separation between the two after 100 cycles.

Example 3

Referring to Figures 1 and 11, a copper current collector for the negative electrode of a lithium-ion battery, the graphene layer and the Ag nanoparticle layer are sequentially modified on the surface of the copper foil, the thickness of the graphene layer is 2 nm, and the average particle size of the Ag nanoparticles is 22 nm .

The preparation method of the above-mentioned copper current collector for negative electrode of lithium ion battery comprises the following steps:

(1) Polishing with a mechanical polishing machine and drying in vacuum at 40 °C for 30 min to obtain a dried Cu foil;

(2) The dried Cu foil was calcined in a CVD tube furnace at 1060 °C for 70 min under the flow of Ar and _H2 , the flow rate of Ar was 200 sccm, and the flow rate of _H2 was 20 sccm;

(3) Using polystyrene as the carbon source, H ₂ was introduced at 950 ℃, the flow rate of H ₂ was 2 sccm, and the temperature was kept constant for 30 minutes, and then it was lowered to room temperature under the protection of H ₂ , and the flow rate of H ₂ was 15 sccm to obtain graphene layer modification Cu foil with a graphene layer thickness of 2 nm;

(4) Vacuum-deposit Ag film on the surface of the graphene layer with a thickness of 4 nm;

(5) The Ag metal film was quenched at 350 ℃ for 20 min under the protection of H ₂ and Ar gas to form an Ag nanoparticle layer on the surface of the graphene layer. The H ₂ flow rate was 500 sccm, and the Ar flow rate was 500 sccm to obtain the product Cu current collector .

A button half-cell was used to detect the influence of Cu current collector on the performance of the battery. The Cu foil prepared in Example 3 was used as the current collector for the lithium-ion battery, graphite was used as the active material, and the lithium-ion battery was marked as Cu-G-Ag-graphite.

As a control lithium-ion battery, Cu not modified with graphene and Ag nanoparticles was used as the current collector, graphite was used as the active material, and the lithium-ion battery was marked as Cu-graphite.

Using a four-probe tester to test the resistance of the blank Cu and the modified Cu prepared in this example were 50 and 27 mΩ, respectively. It can be seen that the present invention uses graphene and Ag nanoparticles to modify the Cu foil to significantly improve the conductivity of the Cu current collector.

Figure 11 is the cycle performance diagram of the Cu-G-Ag-graphite lithium-ion battery in this embodiment at a current of 0.5 A g ^-1 , and the Cu-G-Ag-graphite lithium-ion battery has a larger specificity in the whole cycle. It can be seen that the Cu current collector co-modified by graphene and Ag nanoparticles can significantly improve the reversible specific capacity of the battery.

Claims (8)

1. a kind of used as negative electrode of Li-ion battery copper current collector, it is characterised in that in copper foil surface successively grapheme modified layer and gold Metal nano-particle layer, the metal is Au and/or Ag, and the average grain diameter of the metal nanoparticle is 10~100 nm.

2. used as negative electrode of Li-ion battery copper current collector according to claim 1, it is characterised in that the graphene layer thickness For 0.5~2 nm.

3. the preparation method of the used as negative electrode of Li-ion battery copper current collector described in a kind of claim 1, it is characterised in that including such as Lower step：

（1）Polishing or pickling Cu paper tinsels, 40~60 DEG C of 30~60 min of vacuum drying, obtain drying Cu paper tinsels；

（2）By step（1）Cu paper tinsels are dried, are placed in CVD tube furnaces, under reducing atmosphere, 950~1060 DEG C of calcinings 20~70 min；

（3）By step（2）Cu paper tinsels after calcining are put into anoxic reactor, are heated to 950~1060 DEG C, are filled into reactor Enter carbon source, the min of constant temperature 5~60 is cooled to room temperature under reducing atmosphere, obtain the Cu paper tinsels of graphene layer modification, graphene layer Thickness is 0.5~2 nm；

（4）In graphene layer surface vacuum deposited metal film, thickness is 4~20 nm；

（5）Under reducing atmosphere, 250~350 DEG C of Quenching Treatment steps（4）The min of metal film 20~50, makes graphene layer surface Metal nano-particle layer is formed, product copper current collector is obtained.

4. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 3, it is characterised in that step （1）Described acid washing method is：Ultrasonically treated 5~15 min of acid solution, the acid solution is acetic acid or oxalic acid solution, concentration For 0.5~2 molL^-1。

5. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 3, it is characterised in that step （2）Or step（5）Described in reducing atmosphere be H₂Or Ar and H₂Gaseous mixture, step（3）Described reducing atmosphere is H₂。

6. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 3, it is characterised in that step （3）Described in carbon source be gaseous carbon sources, liquid carbon source or solid carbon source.

7. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 6, it is characterised in that described Gaseous carbon sources are methane, acetylene or ethene, and described liquid carbon source is ethanol or benzene, described solid carbon source for naphthalene or Polystyrene.

8. a kind of application of the copper current collector prepared by any one of claim 3~7 in lithium ion battery.