CN116288088A - Integrated construction method for surface microstructure and internal defect of copper current collector - Google Patents

Abstract

The invention relates to the field of lithium metal batteries, in particular to a copper current collector surface structure and internal defect integrated construction method, which comprises the following steps: (1) Cleaning, polishing, cleaning again and drying the surface of the copper current collector; (2) Integrally constructing a microstructure on the surface of the copper current collector and an internal defect through a mechanical pressing method; (3) heat treatment of copper current collector; and (4) cleaning and drying the treated copper current collector. The method is simple, high in repeatability and good in controllability. The defects in the copper current collector can adjust nucleation sites for depositing metal lithium, the external three-dimensional structure can reconstruct surface electric field distribution, the reaction rate is delayed, uniform nucleation and deposition of the metal lithium are realized through the synergistic effect of the internal defects and the external structure, and the growth of lithium dendrites is effectively inhibited. In addition, the modification method only aims at the copper current collector, does not introduce any foreign matters, and can ensure the advantage of high energy density of the lithium metal negative electrode to the greatest extent.

Description

Integrated Construction Method of Surface Microstructure and Internal Defects of Copper Current Collector

technical field

The invention relates to the field of lithium metal batteries, in particular to a method for integrally constructing the surface structure and internal defects of a copper current collector.

Background technique

The current lithium-ion battery using graphite as the negative electrode material has reached the limit of its theoretical capacity density, which cannot meet the growing demand for high-energy-density batteries for new energy applications. Lithium metal has a very high theoretical capacity (3860mAh/g), which is 10 times that of the current graphite anode (376mAh/g), low density (0.534g/cm ³ ) and low voltage window (-3.04V vs. Standard hydrogen electrode) is considered to be the ideal negative electrode material for the next generation of high specific energy batteries. When lithium metal is used as the negative electrode material in lithium secondary batteries, it can significantly improve the energy density of the battery and is called the "Holy Grail" of the energy storage industry. ".

However, lithium metal as an anode material easily leads to huge volume change and internal stress of the electrode due to the uneven lithium deposition behavior during cycling, resulting in an unstable electrode/electrolyte interface. The unstable interface causes continuous consumption of electrode active materials and electrolyte, resulting in low energy density and coulombic efficiency. In addition, the dendrite growth caused by uneven lithium deposition can also pierce the separator and contact with the positive electrode, causing internal short circuit of the battery, causing safety accidents such as fire or even explosion.

At present, the control of lithium deposition behavior mainly includes three-dimensional current collector design and lithium-philic material deposition. However, on the one hand, the introduction of foreign materials weakens the huge theoretical capacity advantage of metal lithium, which makes the mass specific energy of the prepared lithium metal battery decrease; on the other hand, On the one hand, the continuous loss of lithium-friendly substances during the cycle causes the unsustainable regulation effect.

Therefore, regulating the lithium deposition behavior under the premise of ensuring the energy density of the metal lithium anode can not only save resources and reduce costs, but also help promote the commercial application of lithium metal batteries.

Contents of the invention

The purpose of the present invention is to solve the problems of weak control effect of traditional three-dimensional current collectors and poor long-range effectiveness of lithium-friendly materials, and provide a method for integrating the surface structure and internal defects of copper current collectors. By modifying commercial copper current collectors, Realize the one-step construction of its surface structure and internal defects. The internal defects of the copper current collector can adjust the nucleation sites of metal lithium deposition. Its external three-dimensional structure can reconstruct the surface electric field distribution and delay the reaction rate. Through the internal defects and external structure The synergistic effect of these materials can realize the uniform nucleation and deposition of lithium metal, and effectively inhibit the growth of lithium dendrites.

In order to achieve the purpose of the present invention, the technical solution adopted is: an integrated construction method of the surface microstructure and internal defects of the copper current collector,

Include the following steps:

(1) Cleaning, polishing, cleaning and drying of the copper current collector surface;

(2) Integrated construction of copper current collector surface microstructure and internal defects;

(3) heat treatment of copper current collector;

(4) Cleaning and drying of the treated copper current collector.

further:

Step 1) described cleaning agent is organic solvent, ethanol, acetone and dimethyl carbonate etc.;

And/or, in order to further obtain the roughness that matches with the present application, the polishing described in step 1) is electrochemical polishing, calculated by volume fraction, the composition of polishing liquid comprises mass fraction and is 50-80 parts of 85% phosphoric acid, 60-200 parts of glycerol, 200-400 parts of deionized water. The voltage of the electrochemical polishing is 3-10V, the electrochemical polishing time is 2-5 minutes, and the cleaning after polishing is performed by ultrasonic cleaning in an organic solvent, and the cleaning time is 5-10 minutes;

And/or, the integral construction method described in step 2) is a mechanical indentation method, including but not limited to micro-indentation and nano-indentation.

And/or, the indenter used in the mechanical pressing method described in step 2) is pyramid-shaped, spherical or needle-shaped;

And/or, the load of the mechanical pressing method described in step 2) is 0.1-10N, the loading rate is 5mN/s-1N/s, the number of pressings is 20-100 times, and the pressing distance is 0.1-1mm.

And/or, the temperature range of the heat treatment in step 3) is 200-300° C., and the heat treatment time is 60-600 min. Under the heat treatment conditions, the purpose of eliminating defects can be achieved.

And/or, the cleaning described in step (4) includes flushing and ultrasonic cleaning.

And/or, the cleaning described in step (4) is completed in an organic solvent, including but not limited to ethanol, acetone or dimethyl carbonate (DMC).

And/or, the drying is room temperature drying or nitrogen blowing.

The application of the copper current collector with surface microstructure and internal defects prepared by the above method in lithium batteries, preferably, the lithium batteries include lithium metal batteries, quasi-solid-state batteries, all-solid-state batteries, lithium-sulfur batteries, lithium-oxygen batteries, Anode-free lithium metal batteries.

Compared with the prior art, the present invention has achieved the following beneficial effects:

1) The surface microstructure and internal defects are prepared by mechanical indentation method, which is simple, repeatable, and controllable, and is suitable for large-scale applications;

2) Based on the modification of the copper current collector itself, no foreign substances are introduced, which ensures the theoretical capacity advantage of the lithium metal negative electrode and helps to prepare a lithium metal battery with high specific energy;

3) The three-dimensional structure helps to reduce the current density to slow down the reaction rate, and the internal defects can induce lithium nucleation, and the two synergistically achieve uniform dendrite-free deposition of lithium.

Description of drawings

Fig. 1 is the voltage and capacity graph of the lithium copper half cell prepared by embodiment 1;

Fig. 2 is the voltage and capacity graph of the lithium copper half cell prepared by embodiment 2;

Fig. 3 is the transmission electron microscope picture of copper current collector after embodiment 1 to 3 microns are pressed into;

Figure 4 shows the difference in the deposition morphology of lithium on the surface of the copper current collector after a single indentation after different indentation loads;

Figure 5 shows the difference in the deposition morphology of lithium on the surface of the blank and modified copper current collectors in Example 4, where the indentation distance is 0.6mm.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent requirements of the present invention.

All raw materials in the present invention have no particular limitation on their sources, they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

The invention relates to an integrated construction method of the surface microstructure and internal defects of a copper current collector.

Example 1

An integrated construction method for the surface microstructure and internal defects of a copper current collector, comprising the following steps:

(1) ultrasonically clean the copper current collector in absolute ethanol for 10 minutes, and dry it with nitrogen gas for later use;

(2) Configure 400mL polishing solution, the solution components are 50mL phosphoric acid, 150mL glycerol and 200mL deionized water, the voltage of electrochemical polishing is set to 5V, and the polishing time is 5min;

(3) Use a micron indenter to perform micron indentation on the surface of the copper collector, the shape of the indenter is a square pyramid, the load size is 0.5N, and the loading rate is 0.1N/s;

(4) Carry out heat treatment on the copper current collector after the micron pressing, the temperature is 200° C., and the time is 60 minutes.

A metal lithium secondary battery, the metal lithium secondary battery includes the above-mentioned treated copper current collector, the assembly process of the metal lithium secondary battery is as follows:

The processed copper current collector is assembled into a lithium-copper half-cell according to the order of the positive electrode shell, electrode sheet, separator, lithium metal negative electrode, gasket, shrapnel, and negative electrode shell. The battery model is a button battery 2032.

Electrochemical performance test of lithium copper half-cell:

According to the capacity of 0.1mAh/ ^cm2 and the current density of 0.5mA/ ^cm2 , lithium is deposited on the surface of the modified copper current collector, and the deposition overpotential of lithium on the surface of the blank and the modified copper current collector is compared. Figure 1 shows the prepared lithium copper Half-cell voltage versus capacity graph. The mark in the circle box is the nucleation overpotential. It can be seen from FIG. 1 that the overpotential of the lithium-copper half-cell prepared by the present invention is obviously lower than that of the conventional lithium-copper half-cell.

Example 2

An integrated construction method for the surface microstructure and internal defects of a copper current collector, comprising the following steps:

(1) ultrasonically clean the copper current collector in absolute ethanol for 10 minutes, and dry it with nitrogen gas for later use;

(2) Configure 400mL polishing solution, the solution components are 50mL phosphoric acid, 150mL glycerol and 200mL deionized water, the voltage of electrochemical polishing is set to 5V, and the polishing time is 5min;

(3) Use a micron indenter to perform micron indentation on the surface of the copper collector, the shape of the indenter is a square pyramid, the load size is 1N, and the loading rate is 0.1N/s;

(4) Carry out heat treatment on the copper current collector after the micron pressing, the temperature is 200° C., and the time is 60 minutes.

A metal lithium secondary battery, the metal lithium secondary battery includes the above-mentioned recovered metal lithium negative electrode that has been compressed.

Example 3

An integrated construction method for the surface microstructure and internal defects of a copper current collector, comprising the following steps:

(1) ultrasonically clean the copper current collector in absolute ethanol for 10 minutes, and dry it with nitrogen gas for later use;

(2) Configure 400mL polishing solution, the solution components are 50mL phosphoric acid, 150mL glycerol and 200mL deionized water, the voltage of electrochemical polishing is set to 5V, and the polishing time is 5min;

(3) Use a micron indenter to perform micron indentation on the surface of the copper collector, the shape of the indenter is a square pyramid, the load size is 2N, and the loading rate is 0.2N/s;

(4) Carry out heat treatment on the copper current collector after the micron pressing, the temperature is 200° C., and the time is 60 minutes.

A metal lithium secondary battery, the metal lithium secondary battery includes the above-mentioned recovered metal lithium negative electrode that has undergone compression treatment, and the assembly process of the metal lithium secondary battery is the same as that in Example 1.

Characterization of internal defects in copper current collector:

Fig. 3 is the transmission electron microscope picture of the copper current collector after embodiment 1-3 microns are indented (both embodiments 1 to 3 are single indented), and it can be seen from the figure that the defects inside the copper current collector are under different indentation loads As the indentation load increases, the internal dislocation defects gradually increase. It can be seen that the microstructure of the surface of the copper current collector can also be induced by the mechanical indentation method to induce the initiation of internal defects.

Lithium deposition morphology characterization:

According to the capacity of 0.1mAh/cm ² and the current density of 0.5mA/cm ² , lithium was deposited on the surface of the modified copper current collector of Example 1-3 respectively. It can be seen from the figure that under the low pressure loading (Example 1), the number of internal dislocations is small, and the nucleation of lithium cannot be induced, so the number of lithium nuclei at the indentation is relatively small. few. As the indentation load and the internal defects of the copper current collector increase, the number of lithium nuclei at the indentation gradually increases, but the number of lithium nuclei inside the indentation is still very small (Example 2). When the indentation load increased to 2N, the number of dislocations inside it increased, which induced the nucleation of lithium, resulting in a significant increase in the number of lithium nuclei at the indentation.

Example 4

An integrated construction method for the surface microstructure and internal defects of a copper current collector, comprising the following steps:

(1) ultrasonically clean the copper current collector in absolute ethanol for 10 minutes, and dry it with nitrogen gas for later use;

(2) Configure 400mL polishing solution, the solution components are 50mL phosphoric acid, 150mL glycerol and 200mL deionized water, the voltage of electrochemical polishing is set to 5V, and the polishing time is 5min;

(3) Use a micron indenter to perform micron indentation on the surface of the copper collector. The shape of the indenter is a square pyramid, the load size is 1N, the loading rate is 0.1N/s, the loading interval is 0.6mm, and the number of indentations is 2 times;

(4) Carry out heat treatment on the copper current collector after the micron pressing, the temperature is 200° C., and the time is 60 minutes.

Characterization of lithium deposition morphology (battery assembly method is the same as in Example 1):

Lithium was deposited on the surface of the modified copper current collector with a capacity of 0.1mAh/ ^cm2 and a current density of 0.5mA/ ^cm2 , and the difference in the deposition morphology of lithium on the surface of the blank and the modified copper current collector was compared (as shown in Figure 5) . It can be seen from Figure 5 that the deposition morphology of lithium in different regions of the surface of the modified current collector is significantly different, and the deposition of lithium at the indentation is uniform and dense, and it is spherical ((a) in Figure 5 and (a) in Figure 5 (c)), while in the blank area on the surface of the copper current collector, the deposition of lithium is not uniform, and a large number of dendrites appear. It can be seen that the integrated construction method of the surface microstructure and internal defects of the copper current collector can significantly improve the uniformity of lithium deposition.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Equivalent replacements or changes to the concepts thereof shall fall within the protection scope of the present invention.

Claims (10)

1. An integrated construction method for a copper current collector surface microstructure and internal defects is characterized by comprising the following steps: comprises the following steps:

(1) Cleaning, polishing, cleaning again and drying the surface of the copper current collector;

(2) Integrally constructing a microstructure on the surface of the copper current collector and an internal defect through a mechanical pressing method;

(3) Heat treatment of copper current collector;

(4) And (5) cleaning and drying the treated copper current collector.

2. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the cleaning liquid used for cleaning before polishing in the step (1) is ethanol, acetone or dimethyl carbonate; and/or the polishing in the step (1) is electrochemical polishing, and the polishing solution comprises 50-80 parts of phosphoric acid with the mass fraction of 85%, 60-200 parts of glycerol and 200-400 parts of deionized water according to the volume fraction;

and/or the polishing in the step (1) is electrochemical polishing, wherein the voltage set by a direct current power supply in the electrochemical polishing is 3-10V, and the electrochemical polishing time is 2-5 minutes;

and/or, performing ultrasonic cleaning in an organic solvent after the polishing in the step (1), wherein the cleaning time is 5-10 minutes.

3. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the mechanical pressing method in the step (2) is micro pressing and/or nano pressing.

4. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the pressing head used in the mechanical pressing method in the step (2) is pyramid-shaped, sphere-shaped or needle-shaped.

5. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the load of the mechanical pressing method in the step (2) is 0.1-10N, the loading speed is 5mN/s-1N/s, the pressing times are 20-100 times, and the pressing interval is 0.1-1mm.

6. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the temperature range of the heat treatment in the step (3) is 200-300 ℃, and the time of the heat treatment is 60-600min.

7. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the cleaning in step (4) includes rinsing and ultrasonic cleaning.

8. The integrated construction method for the surface microstructure and internal defects of a copper current collector according to claim 1, wherein: the washing in the step (4) is completed in an organic solvent, wherein the organic solvent is ethanol, acetone or dimethyl carbonate.

9. A copper current collector obtained by the integrated construction method of a copper current collector surface microstructure and internal defects according to any one of claims 1 to 8.

10. Use of the copper current collector according to claim 9 in a lithium battery, characterized in that: lithium batteries include lithium metal batteries, quasi-solid state batteries, all-solid state batteries, lithium sulfur batteries, lithium oxygen batteries, or non-negative lithium metal batteries.

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