CN105186004A - Copper current collector for lithium-ion battery anodes as well as preparation method and application of copper current collector - Google Patents

Abstract

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. In the present invention, the graphene layer and the metal nano particle layer are sequentially modified on the surface of the copper foil, which is specifically obtained through the steps of copper foil pretreatment, annealing treatment, formation of the graphene layer, vacuum evaporation of a metal film, and quenching treatment. The copper current collector for the lithium ion battery negative electrode of the present invention has good electrical conductivity, can alleviate the erosion of the electrolyte, and has strong binding force with the active material coating.

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 lithium ion battery negative electrode, 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 minutes to obtain a dried Cu foil;

(2) Put the dried Cu foil in step (1) into a CVD tube furnace and calcinate at 950-1060°C for 20-70 minutes 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 5-60min, and cool to room temperature under a reducing atmosphere , to obtain a graphene-modified Cu foil, the thickness of the graphene layer is 0.5-2nm;

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

(5) Under a reducing atmosphere, 250-350° C. quenching treatment step (4) metal film for 20-50 minutes, 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 lithium ion battery negative electrode, 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 0.5-2mol ·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 the 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 negative electrodes of lithium ion batteries is simple, significantly improves the electrochemical performance of lithium ion batteries, 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 charging and discharging curve diagram of embodiment 1 lithium-ion battery under 2A g ^-1 electric current;

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

Fig. 4 is the cycle performance figure of embodiment 1 lithium-ion battery under 4A·g ^-1 and 6A·g ^-1 electric 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 figure of embodiment 2 copper current collector after ultrasonic treatment 15min;

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 1C electric current;

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

Fig. 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 ways

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 negative electrodes of lithium-ion batteries 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 1nm, and the average particle size of the Au nanoparticles is 27nm.

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 copper foil with 1mol L ^-1 acetic acid solution for 10 minutes, followed by rinsing with water and ethanol, and vacuum drying at 50°C for 30 minutes to obtain dried Cu foil;

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

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

Flow rate is 2sccm, constant temperature 15min, is cooled to room temperature under _H2 atmosphere, _H2 flow rate is 10sccm, obtains the Cu foil of graphene layer modification, and the thickness of graphene layer is 1nm;

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

(5) The Au film was quenched at 300°C 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.

Fig. 2 is the first charge and discharge curve diagram of the lithium ion battery of this embodiment at a current of 2A g ^-1 , and the discharge specific capacities of Cu-LZTO and Cu-G-Au-LZTO lithium ion batteries are 212.2 and 242.1mAh g respectively ^-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.

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

Fig. 4 is the cycle performance diagram of the lithium ion battery of this embodiment under the current of 4A·g ^-1 and 6A·g ^-1 , the discharge specific capacity of the battery after 100 cycles is 172.2 and 130.0mAh·g ^-1 respectively, the present invention Lithium-ion batteries exhibit good high-current charge-discharge 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, Fig. 7～10, a kind of copper current collector for negative electrode of lithium ion battery, on the surface of copper foil, modify graphene layer and alloy nano particle layer in turn, the thickness of graphene layer is 1nm, described alloy is Au and Ag alloy, the mass ratio of the two is 1:1, and the average particle size of alloy nanoparticles is 50nm.

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

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

(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 minutes, and drop to room temperature under the protection of H ₂ , the flow rate of H ₂ is 10 sccm, Obtain a Cu foil modified by a graphene layer, and the thickness of the graphene layer is 1nm;

(4) Au and Ag alloy films were vacuum evaporated on the surface of the graphene layer, and the thickness of the alloy film was 12nm;

(5) The Au and Ag alloy film was quenched at 250°C for 50 min under the protection of H ₂ gas to form an alloy nanoparticle layer on the surface of the graphene layer, and 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 an SEM image of the Cu current collector prepared in this example, and Figure 8 is an SEM image of the Cu current collector prepared in this example after ultrasonic treatment for 15 minutes, and it can be seen from Figures 7 and 8 that the graphene after ultrasonic treatment and alloy nanoparticles did not fall off, indicating that the graphene and alloy nanoparticle modification layer 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 embodiment after 200 cycles at 1C current, and Figure 10 is a comparison Cu-LTO lithium ion battery cycled at 1C current for 200 times The cross-sectional SEM figure of the negative electrode pole piece after the second time, the negative electrode active material coating is seriously separated from the current collector after the Cu-LTO lithium ion battery is cycled, and the negative electrode active material coating of the Cu-G-Au/Ag-LTO lithium ion battery of the present invention It has good adhesion to 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 a negative electrode of a lithium ion battery is sequentially modified with a graphene layer and an Ag nanoparticle layer on the surface of the copper foil. The thickness of the graphene layer is 2nm, and the average particle size of the Ag nanoparticles is 22nm.

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

(1) Polish with a mechanical polishing machine, and dry at 40°C for 30 minutes in vacuum to obtain a dried Cu foil;

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

(3) Using polystyrene as the carbon source, H _{2 was introduced at 950°C, the H 2 flow} rate was 2 sccm, the temperature was kept constant for 30 minutes, and the H ₂ protection dropped to room temperature, and the H ₂ flow rate was 15 sccm to obtain a graphene layer-modified Cu foil , the graphene layer thickness is 2nm;

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

(5) The Ag metal film was quenched at 350°C 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 of this embodiment at a current of 0.5A g ^-1 , and the Cu-G-Ag-graphite lithium-ion battery has a larger ratio in the whole cycle process 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 (10)

1. a used as negative electrode of Li-ion battery copper current collector, is characterized in that, at copper foil surface successively grapheme modified layer and metal nano-particle layer.

2. used as negative electrode of Li-ion battery copper current collector according to claim 1, is characterized in that, described metal is one or several the alloy in Cu, Au, Ag.

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

4. the used as negative electrode of Li-ion battery copper current collector according to any one of claims 1 to 3, is characterized in that, the average grain diameter of described metal nanoparticle is 10 ~ 100nm.

5. a preparation method for used as negative electrode of Li-ion battery copper current collector according to claim 1, is characterized in that, comprise the steps:

(1) polishing or pickling Cu paper tinsel, 40 ~ 60 DEG C of vacuumize 30 ~ 60min, obtain dry Cu paper tinsel;

(2) by dry for step (1) Cu paper tinsel, CVD tube furnace is placed in, under reducing atmosphere, 950 ~ 1060 DEG C of calcining 20 ~ 70min;

(3) anoxic reactor put into by the Cu paper tinsel after step (2) being calcined, and is heated to 950 ~ 1060 DEG C, in reactor, is filled with carbon source, constant temperature 5 ~ 60min, cool to room temperature under reducing atmosphere, obtain the Cu paper tinsel that graphene layer is modified, graphene layer thickness is 0.5 ~ 2nm;

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

(5) under reducing atmosphere, 250 ~ 350 DEG C of Quenching Treatment step (4) metal film 20 ~ 50min, make graphene layer surface form metal nano-particle layer, obtain product copper current collector.

6. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 5, it is characterized in that, acid washing method described in step (1) is: the ultrasonic process 5 ~ 15min of acid solution, and described acid solution is acetic acid or oxalic acid solution, and concentration is 0.5 ~ 2molL ^-1.

7. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 5, is characterized in that, step (2) or the reducing atmosphere described in step (5) are H ₂or Ar and H ₂gaseous mixture, the reducing atmosphere described in step (3) is H ₂.

8. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 5, is characterized in that, the carbon source described in step (3) is gaseous carbon sources, liquid carbon source or solid carbon source.

9. the preparation method of used as negative electrode of Li-ion battery copper current collector according to claim 5, it is characterized in that, described gaseous carbon sources is methane, acetylene or ethene, and described liquid carbon source is ethanol or benzene, and described solid carbon source is naphthalene or polystyrene.

10. the application of copper current collector in lithium ion battery prepared by an any one of claim 5 ~ 9.