Lithiophilic current collector for lithium metal battery and preparation method and application thereof

Abstract

The application discloses a lithium metal battery lithium-philic current collector and a preparation method and application thereof, and relates to the technical field of lithium metal batteries. The lithium-philic current collector comprises a current collector base (a copper foil or a foamed copper), a sheet-shaped silver-coated copper stacking layer loaded on the surface of the current collector base, and spherical particles loaded on the stacking layer by reaction of lithium with silver in the stacking layer. When the lithium-philic current collector is used in a lithium metal battery, the lithium-philic current collector can better homogenize the lithium deposition and effectively inhibit the growth of lithium dendrites.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium metal battery, in particular to a lithium metal battery lithiumophilic current collector and a preparation method and application thereof. BACKGROUND

[0002] The energy density of lithium ion batteries with graphite as the negative electrode has reached the limit, and it is urgent to develop new battery systems to meet the market demand for high energy density energy storage devices. Since the metal lithium negative electrode has a high theoretical specific capacity (3860 mAh g -1 ) and the lowest redox potential (-3.04 V compared with the standard hydrogen electrode), the lithium metal battery formed by matching it with any positive electrode material has higher energy density than the commercial lithium ion battery, so it can better solve the market demand for high energy density.

[0003] However, the uncontrollable growth of lithium dendrites during the deposition process of the lithium metal negative electrode and the resulting safety problems have yet to be solved. In recent years, researchers have developed many strategies to solve the above problems, such as electrolyte component design, solid electrolyte, and current collector modification. By adjusting the ratio of lithium salt and solvent in the electrolyte or adding various electrolyte additives, the strategy of in-situ generating a solid electrolyte interface on the lithium metal negative electrode is simple and effective. However, the mechanical strength of this in-situ generated solid electrolyte interface often cannot withstand the volume expansion of lithium, so the performance of the lithium metal battery cannot be effectively improved for a long time. Solid-state electrolytes can significantly inhibit the volume expansion and dendrite growth of the lithium metal negative electrode due to their high mechanical modulus, but the problems of low intrinsic ionic conductivity and poor mechanical contact caused by solid interfaces still need to be solved. Among these strategies, current collector modification is considered to be a simple and effective, easy-to-scale strategy to achieve long-term protection of the lithium metal negative electrode, as it can alleviate the concentration of local current density and make the lithium insertion / exfoliation behavior uniform. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a lithium metal battery lithiumophilic current collector and a preparation method and application thereof, which aims to improve the electrochemical performance of the lithium metal battery by preparing a current collector that inhibits the growth of lithium dendrites.

[0005] To achieve the purpose, the present application adopts the following technical solutions:

[0006] The present application first provides a lithium metal battery lithiumophilic current collector, which comprises a current collector substrate, a sheet-shaped silver-coated copper stack layer loaded on the surface of the current collector substrate, and spherical particles loaded on the stack layer by the reaction of lithium with silver in the stack layer; wherein the current collector substrate is a copper foil or a foamed copper.

[0007] The present invention also provides a method for preparing the lithium-metal current collector for lithium metal batteries, the specific steps of which are as follows:

[0008] Step 1: Add the flake-shaped silver-coated copper powder to deionized water, ultrasonically disperse it at room temperature for 20-40 minutes, and then magnetically stir it for 20-40 minutes to obtain the silver-coated copper dispersion.

[0009] Step 2: Add the binder to the silver-coated copper dispersion, stir magnetically at room temperature for 2-4 hours, and then sonicate for 20-40 minutes to obtain a uniform mixture;

[0010] Step 3: Load the mixture obtained in step 2 onto the surface of the current collector substrate and dry it in a forced-air dryer at 60-90°C for 2-4 hours to form a sheet-like silver-coated copper stacked layer on the surface of the current collector substrate.

[0011] Step 4: Assemble an electrolytic cell using the current collector substrate treated in Step 3 as the cathode and the lithium sheet as the anode. Use a charge-discharge tester at a current density of 0.4–0.6 mA / cm². -2 Under these conditions, 0.1–0.5 mAh cm⁻¹ is electroplated onto the current collector substrate. -2 Lithium metal is used to load spherical particles onto the stacked layers to obtain a lithium-friendly current collector for lithium metal batteries.

[0012] Furthermore, in step 1, the silver content of the flake-shaped silver-coated copper powder is 1-5%.

[0013] Furthermore, in step 1, the mass ratio of the flake-shaped silver-coated copper powder to deionized water is 1:1 to 3.

[0014] Further, in step 2, the binder is hydroxypropyl methylcellulose with a molecular weight of 80,000 to 120,000, and the mass ratio of the binder to the flake silver-coated copper powder is 1:40 to 60.

[0015] Further, in step 3, the mixture is loaded onto the surface of the current collector substrate using either a doctor blade coating method or a vacuum impregnation method. When copper foil is used as the current collector substrate, the doctor blade coating method is used. The procedure is as follows: the mixture obtained in step 2 is dropped onto the surface of the copper foil, and the surface loading of the copper foil is achieved by adjusting the gap between the doctor blade and the copper foil. When foamed copper is used as the current collector substrate, the vacuum impregnation method is used. The procedure is as follows: the foamed copper is immersed in the mixture obtained in step 2 and a vacuum is drawn. After holding the pressure for 3–7 minutes, it is removed, thus achieving the surface loading of the foamed copper.

[0016] Furthermore, in step 4, the electrolyte added to the electrolytic cell is a mixed solution of DOL and DME with a volume ratio of 1:1 containing 1M LiTFSI, and 1% LiNO3 is added as an additive.

[0017] The present invention also provides a lithium metal battery comprising the aforementioned lithium-philic current collector.

[0018] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0019] 1. This lithium-loving current collector is designed with a lithium-loving layer on copper foil or copper foam. The lithium-loving layer consists of a sheet-like silver-coated copper stack and spherical particles loaded on the stack. The sheet-like stack provides a three-dimensional space for lithium deposition, effectively reducing the local current density. The spherical particles provide a nucleation basis for lithium deposition, enabling lithium to be deposited uniformly. When this current collector is used in lithium metal batteries, it can effectively suppress the growth of lithium dendrites.

[0020] 2. Using hydroxypropyl methylcellulose as a binder avoids the use of organic solvents, effectively alleviating the environmental pressure caused by the use of organic solvents, and at the same time saving production costs to a certain extent.

[0021] 3. Batteries assembled using this lithium-friendly current collector exhibit high coulombic efficiency, which is beneficial to improving the cycle stability and lifespan of lithium metal secondary batteries, thereby effectively promoting the commercialization of lithium metal batteries. Attached Figure Description

[0022] Figure 1 The image shows a scanning electron microscope (SEM) image of the lithiophilic current collector prepared in Example 1.

[0023] Figure 2 The X-ray diffraction pattern of the lithiophilic current collector prepared in Example 1.

[0024] Figure 3 To deposit 3 mAh cm⁻¹ on the surface of the current collector prepared in Example 1 -2 SEM image of the surface after lithium deposition.

[0025] Figure 4 The coulombic efficiency diagrams are shown for the current collectors of Example 1, Comparative Example 1, and Comparative Example 2 after they are assembled into lithium metal batteries.

[0026] Figure 5 The image shows the coulombic efficiency of the current collector in Example 2 after it is assembled into a lithium metal battery.

[0027] Figure 6 To deposit 3 mAh cm⁻¹ on the surface of the current collector prepared in Comparative Example 1 -2 SEM image of the surface after lithium deposition.

[0028] Figure 7 To deposit 3 mAh cm⁻¹ on the surface of the current collector prepared in Comparative Example 2 -2 SEM image of the surface after lithium deposition. Detailed Implementation

[0029] The technical solutions of the present invention are further described and explained below with reference to embodiments, but these embodiments are not intended to limit the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing a lithium-friendly current collector for lithium metal batteries, including the following steps:

[0032] Step 1: Add 1g of commercially available flake silver-coated copper powder with a silver content of 3% to 1g of deionized water, ultrasonically disperse at room temperature for 30min, and then magnetically stir for 30min to obtain a silver-coated copper dispersion.

[0033] Step 2: Take 0.02g of hydroxypropyl methylcellulose powder with a molecular weight of 100,000 and add it to the silver-coated copper dispersion. Stir magnetically at room temperature for 3 hours, and then sonicate for 30 minutes to obtain a uniform mixture.

[0034] Step 3: Drop the uniform mixture obtained in Step 2 onto the surface of the copper foil. By adjusting the gap between the scraper and the copper foil, the surface of the copper foil is loaded. Dry it in a forced-air dryer at 80°C for 3 hours to form a sheet-like silver-coated copper stacked layer on the surface of the current collector substrate.

[0035] Step 4: Using the current collector substrate treated in Step 3 as the cathode, lithium sheet as the anode, and a mixed solution of DOL and DME with a volume ratio of 1:1 containing 1M LiTFSI and 1% LiNO3 (1% by mass) as the electrolyte, assemble the electrolytic cell and test it using a charge-discharge tester at a current density of 0.5 mA / cm². -2 Under these conditions, 0.5 mAh cm⁻¹ is electroplated onto the current collector substrate. -2 The metallic lithium allows for the loading of spherical particles onto the stacked layers, resulting in a lithium-loving current collector.

[0036] Step 5: Preparation of lithium metal batteries

[0037] Under the protection of an argon atmosphere glove box, the obtained lithiophilic current collector was matched and assembled with lithium metal to form a half-cell. The separator used was a polypropylene separator, and the electrolyte composition was a mixed solution of 1M LiTFSI dissolved in DOL / DME (volume ratio 1:1) (with 1% LiNO3 added as an additive), and the electrolyte injection volume was 50μL.

[0038] Figure 1 The image shows a scanning electron microscope (SEM) image of the lithiophilic current collector prepared in Example 1. The results show that a lithiophilic layer consisting of a sheet-like stacked layer and spherical particles on the stacked layer was successfully prepared on the surface of the copper foil substrate. Figure 2The X-ray diffraction pattern of the lithiophilic current collector prepared in Example 1 shows that the sheet-like stacked layers and the spherical particles on the stacked layers on the copper foil substrate are mainly composed of Cu and Ag3Li. 10 It is composed of Li.

[0039] To investigate the effect of this lithiophilic current collector on the lithium deposition morphology. Figure 3 In this embodiment, a 3mAh cm⁻¹ current collector surface deposition is given. -2 SEM image of the surface after lithium deposition (3mAh cm⁻¹) -2 Under the test conditions, a 3mAh cm⁻¹ was deposited onto the current collector of a lithium metal battery. -2 The lithium was removed from the battery and taken out for SEM observation. It was found that the lithium deposition was a dense blocky morphology rather than dendritic lithium, which indicates that the lithium-loving current collector has a good regulating effect on lithium deposition.

[0040] Figure 4 This is a coulombic efficiency diagram of the current collector used in Example 1 after being assembled into a lithium metal battery. It can be seen that at 0.5 mA / cm²... -2 0.5mAh cm -2 Under the test conditions, the lithium metal battery based on this lithiophilic current collector exhibited the best cycle performance, maintaining a high coulombic efficiency (98.2%) even at a long number of cycles (500 cycles). This indicates that the lithiophilic layer composed of the sheet-like stacked layers and the spherical particles on the stacked layers can play a good role in homogenizing lithium deposition and effectively suppressing the growth of lithium dendrites.

[0041] Example 2

[0042] This embodiment provides a method for preparing a lithium-friendly current collector for lithium metal batteries, including the following steps:

[0043] Step 1: Add 0.8g of commercially available flake silver-coated copper powder with a silver content of 3% to 1g of deionized water, ultrasonically disperse at room temperature for 30min, and then magnetically stir for 30min to obtain a silver-coated copper dispersion.

[0044] Step 2: Take 0.016g of hydroxypropyl methylcellulose powder with a molecular weight of 100,000 and add it to the silver-coated copper dispersion. Continue to stir magnetically at room temperature for 3 hours, and then sonicate for 30 minutes to obtain a uniform mixture.

[0045] Step 3: Immerse the copper foam in the homogeneous mixture obtained in Step 2 and evacuate it to a vacuum. After holding the pressure for 5 minutes, remove it to achieve surface loading of the copper foam. Then, dry it in a forced-air dryer at 80°C for 3 hours to form a sheet-like silver-coated copper stacked layer on the surface of the current collector substrate.

[0046] Step 4: Using the current collector substrate treated in Step 3 as the cathode, lithium sheet as the anode, and a mixed solution of DOL and DME with a volume ratio of 1:1 containing 1M LiTFSI and 1% LiNO3 at a mass concentration of 1% as the electrolyte, assemble an electrolytic cell and test it using a charge-discharge tester at a current density of 0.5 mA / cm². -2 Under these conditions, 0.1 mAh cm⁻¹ was electroplated onto the current collector substrate. -2 After adding metallic lithium, spherical particles are loaded onto the stacked layers to obtain a lithium-loving current collector.

[0047] Step 5: Preparation of lithium metal batteries

[0048] Under the protection of an argon atmosphere glove box, the obtained lithiophilic current collector was matched and assembled with lithium metal to form a half-cell. The separator used was a polypropylene separator, and the electrolyte composition was a mixed solution of 1M LiTFSI dissolved in DOL / DME (volume ratio 1:1) (with 1% LiNO3 added as an additive), and the electrolyte injection volume was 50μL.

[0049] Figure 5 The coulombic efficiency diagram of the current collector assembled into a lithium metal battery in Example 2 is presented. It can be seen that at 0.5 mA cm⁻¹... -2 0.5mAh cm -2 Under the test conditions, the lithium metal battery based on this lithium-friendly current collector maintained relatively stable cycle performance, and its coulombic efficiency was still as high as 98.3% after 150 cycles.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that the surface of the copper foil substrate was not modified, and the lithium metal battery was assembled directly using bare copper foil.

[0052] Figure 6 The deposition of 3 mAh cm⁻¹ on the current collector surface in Comparative Example 1 is shown. -2 The scanning electron microscope (SEM) image of the lithium deposit reveals a distinct dendritic morphology. Figure 4 It can be seen that the coulombic efficiency of the lithium metal battery corresponding to Comparative Example 1 is only 79.1% after 100 cycles. This indicates that there is severe lithium dendrite growth and loss of inactive lithium during the cycling process, which leads to the deterioration of the cycling performance of the lithium metal battery.

[0053] Comparative Example 2

[0054] The difference from Example 1 is that in step 1, commercially available silver-free flake copper powder is used, and the resulting current collector is used for the assembly of lithium metal batteries.

[0055] Figure 7The deposition of 3 mAh cm⁻¹ on the current collector surface in Comparative Example 2 is shown. -2 The surface scanning electron microscope (SEM) image after lithium deposition reveals poor uniformity and the continued formation of dendritic lithium deposits. Figure 4 It can be seen that the coulombic efficiency of the lithium metal battery corresponding to Comparative Example 2 is 93.2% after 100 cycles, which is still lower than the coulombic efficiency of Example 1.

[0056] The above embodiments are only used to explain the present invention and are intended to illustrate the technical concept and features of the present invention. They do not constitute any limitation on the present invention. For those skilled in the art, various changes and modifications can be made to the present invention without departing from the principles and spirit of the present invention, and these changes and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a lithiumophilic current collector for a lithium metal battery, characterized by, The lithium metal battery with a liphophilic current collector comprises a current collector substrate, a sheet-shaped silver-coated copper stack layer loaded on the surface of the current collector substrate, and spherical particles loaded on the stack layer by the reaction of lithium with silver in the stack layer; wherein the current collector substrate is a copper foil or a foamed copper; the sheet-shaped silver-coated copper stack layer and the spherical particles on the stack layer are composed of Cu, Ag3Li 10 and Li. The preparation method of the lithium metal battery with the lithiumophilic current collector comprises the following steps: Step 1: add flaky silver-coated copper powder into deionized water, ultrasonically disperse at room temperature for 20-40 min, and then magnetically stir for 20-40 min to obtain a silver-coated copper dispersion liquid; Step 2: add a binder to the silver-coated copper dispersion liquid, magnetically stir at room temperature for 2-4 h, and then ultrasonically treat for 20-40 min to obtain a uniform mixture liquid; Step 3: load the mixture liquid obtained in Step 2 on the surface of a current collector substrate, and dry by blowing air at 60-90 ℃ for 2-4 h to form a flaky silver-coated copper stacked layer on the surface of the current collector substrate; Step 4, an electrolytic cell was assembled with the current collector substrate treated in step 3 as cathode and lithium sheet as anode, and 0.1-0.5 mAh cm -2 of lithium metal was electroplated on the current collector substrate using a charge-discharge tester under the condition of a current density of 0.4-0.6 mA cm -2 , so as to load the spherical particles on the stacked layer, and a lithium-metal battery-lithiophilic current collector was obtained.

2. The method of claim 1, wherein: In Step 1, the silver content of the flaky silver-coated copper powder is 1-5%.

3. The method of claim 1, wherein: In Step 1, the mass ratio of the flaky silver-coated copper powder to deionized water is 1:1-3.

4. The method of claim 1, wherein: In Step 2, the binder is hydroxypropyl methyl cellulose with a molecular weight of 80-120 thousand.

5. The method of claim 1, wherein: In Step 2, the mass ratio of the binder to the flaky silver-coated copper powder is 1:40-60.

6. The method of claim 1, wherein: In Step 3, the method for loading the mixture liquid on the surface of the current collector substrate is a doctor blade coating method or a vacuum impregnation method.

7. The preparation method according to claim 6, characterized in that: when a copper foil is used as the current collector substrate, the doctor blade coating method is used, and the operation steps are as follows: drop the mixture liquid obtained in Step 2 on the surface of the copper foil, and adjust the gap between the doctor blade and the copper foil to load the surface of the copper foil; when a foamed copper is used as the current collector substrate, the vacuum impregnation method is used, and the operation steps are as follows: immerse the foamed copper in the mixture liquid obtained in Step 2 and vacuumize, and then take out after pressure maintaining for 3-7 min to load the surface of the foamed copper.

8. The method of claim 1, wherein: In Step 4, the electrolyte added into the electrolytic cell is a mixed solution of DOL and DME with a volume ratio of 1:1 and containing 1M LiTFSI, and 1% LiNO3 by mass concentration is added as an additive.

9. A lithium metal battery, characterized in that, The lithium metal battery with the lithiumophilic current collector. The lithium metal battery with the lithiumophilic current collector.

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