Lithium metal electrode in which dendrite formation is suppressed, method for manufacturing same, and secondary battery comprising same

Abstract

The present invention relates to a lithium metal electrode in which dendrite formation is suppressed, a method for manufacturing same, and a secondary battery comprising same, the lithium metal electrode comprising: a current collector; a metal-organic framework coated on the current collector, the metal-organic framework comprising a lithium-affinity metal ion and an organic linker; and lithium metal plated on the metal-organic framework.

Description

Lithium metal electrode with suppressed dendrite formation, method for manufacturing same, and secondary battery including same

[0001] The present invention relates to a lithium metal electrode in which dendrite formation is suppressed, a method for manufacturing the same, and a secondary battery including the same.

[0002] As demand for portable electronic devices, large-capacity storage devices, and electric vehicles increases, the need for development of high-capacity secondary batteries is increasing.

[0003] Recently, lithium metal electrodes with a theoretical capacity of 3840 mAh / g and a low reduction potential are attracting attention as high-capacity secondary battery anode materials that can replace existing graphite (372 mAh / g), and as next-generation secondary battery anode materials along with lithium-sulfur secondary batteries and lithium-air secondary batteries.

[0004] However, lithium metal electrodes have limitations such as a short lifespan and stability issues such as explosion due to dendrite formation, unstable and thick SEI (Solid Electrolyte Interphase) layer formation, and internal volume expansion of the electrode, so these issues must be addressed in advance.

[0005] In particular, active research is being conducted on optimizing electrode and current collector designs to suppress dendrite formation, and strategies such as utilizing current collectors with high surface areas, improving lithium affinity of electrodes, and uniformizing lithium ion flux are required.

[0006] The present invention aims to provide a lithium metal electrode with suppressed dendrite formation, characterized in that it comprises a current collector; a metal-organic framework including a lithium-affinity metal ion and an organic linker coated on the current collector; and lithium metal plated on the metal-organic framework, in order to simultaneously produce a lithium alloy layer with high lithium affinity and a solid electrolyte interphase (SEI) layer with high lithium ion conductivity while suppressing dendrite formation.

[0007] However, the technical problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0008] The present invention provides a lithium metal electrode with suppressed dendrite formation, characterized by comprising: a current collector; a metal-organic framework comprising a lithium-affinity metal ion and an organic linker coated on the current collector; and lithium metal plated on the metal-organic framework.

[0009] The lithium-affinity metal ion may be an ion selected from the group consisting of silver, gold, magnesium, zinc, and copper.

[0010] The organic linker may comprise one or more thiol group-containing compounds.

[0011] The one or more thiol group-containing compounds may be trithiocyanuric acid (TCA).

[0012] Within the above metal-organic framework, lithium-affinity metal ions and organic linkers can be repeatedly stacked through coordinate covalent bonds.

[0013] The thickness of the above metal-organic framework may be 1 nm to 100 nm.

[0014] The above metal-organic framework may have a contact angle of 30° or less for an electrolyte including lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) and a mixed solvent of 1,3-dioxalane (DOL) and dimethyl ether (DME).

[0015] As one embodiment of the present invention, a method for manufacturing a lithium metal electrode with suppressed dendrite formation is provided, characterized by comprising the steps of: (a) coating a metal-organic framework comprising a lithium-affinity metal ion and an organic linker on a current collector; and (b) plating lithium metal on the coated metal-organic framework.

[0016] In another embodiment of the present invention, a secondary battery is provided, characterized in that it includes a lithium metal electrode in which dendrite formation is suppressed.

[0017] When the secondary battery is operated, the lithium metal electrode can form a solid electrolyte interphase (SEI) layer containing Li2S or Li3N.

[0018] A lithium metal electrode with suppressed dendrite formation according to the present invention is characterized by including: a current collector; a metal-organic framework including lithium-affinity metal ions and an organic linker coated on the current collector; and lithium metal plated on the metal-organic framework. Accordingly, when a secondary battery using the lithium metal electrode with suppressed dendrite formation according to the present invention is operated, there is an advantage in that a lithium alloy layer with high lithium affinity and a solid electrolyte interphase (SEI) layer with high lithium ion conductivity can be simultaneously generated while suppressing dendrite formation.

[0019] Therefore, the present invention can be applied to various high-capacity secondary batteries that require excellent driving stability and power density.

[0020] FIG. 1 is a schematic diagram schematically illustrating a method for manufacturing a dendrite-free lithium metal electrode according to one embodiment of the present invention.

[0021] Figure 2 shows the results of analysis using UV-vis spectroscopy on a metal-organic framework coated on a flat quartz glass.

[0022] Figure 3 shows the results of an analysis using SEM (Scanning Electron Microscopy) of a metal-organic framework coated on a Si wafer in the form of a flat plate.

[0023] Figure 4 shows the results of evaluating the lithium affinity (lithiophilicity) of a metal organic framework coated on a flat Ni collector.

[0024] Figure 5 shows the results of analysis using SEM (Scanning Electron Microscopy) and XRD (X-ray Differaction Analysis) on a metal organic framework coated on a fabric-shaped Ni collector before and after lithium metal plating.

[0025] Figure 6 shows the results of evaluating the lithium affinity (lithiophilicity) of a metal organic framework coated on a fabric-type Ni collector.

[0026] Figure 7 shows the results of analyzing the components of the SEI (Solid Electrolyte Interphase) layer formed when a secondary battery (Half-Cell) using a fabric-type Ni current collector-based lithium metal electrode is operated using XPS (X-ray Photoelectron Spectroscopy).

[0027] Figure 8 shows the performance of a secondary battery (Half-Cell) using a fabric-type Ni current collector-based lithium metal electrode at 1 mA cm. -2 , 1 mA h cm -2 It shows the results evaluated under the conditions.

[0028] Figure 9 shows the performance of a secondary battery (Symmetric Full-Cell) using a fabric-type Ni current collector-based lithium metal electrode at 3 mA cm. -2 , 1 mA h cm -2 It shows the results evaluated under the conditions.

[0029] Accordingly, the inventors of the present invention have been trying to manufacture a lithium metal electrode with suppressed dendrite formation, and have discovered that lithium-friendly metal ions (e.g., Ag) are added to the current collector. + , Au 3+ , Mg 2+ , Zn 2+A metal-organic framework including a metal oxide (MOF) and an organic linker (e.g., trithiocyanuric acid (TCA)) was coated on the electrode, and then lithium metal was plated to manufacture a lithium metal electrode. The present invention was completed by confirming that the manufactured lithium metal electrode simultaneously produces a lithium alloy layer with high lithium affinity and a solid electrolyte interphase (SEI) layer with high lithium ion conductivity while suppressing dendrite formation.

[0030]

[0031] Hereinafter, the present invention will be described in detail.

[0032]

[0033] Lithium metal electrode with suppressed dendrite formation

[0034]

[0035] The present invention provides a lithium metal electrode with suppressed dendrite formation, characterized by comprising: a current collector; a metal-organic framework comprising a lithium-affinity metal ion and an organic linker coated on the current collector; and lithium metal plated on the metal-organic framework.

[0036]

[0037] The term "dendrite" in this specification refers to a needle or branch-shaped precipitate that is formed when lithium crystals are formed on the surface of the negative electrode during the charging and discharging process of lithium metal, and these become nuclei and gradually accumulate.

[0038]

[0039] First, the lithium metal electrode with suppressed dendrite formation according to the present invention includes a current collector.

[0040] The current collector refers to a conductive current collector or support, and may be various known conductive current collectors or supports. For example, it may be a flat-plate type conductive current collector or support, or a fabric-type conductive current collector or support. Accordingly, conductive metal atoms may be present in the current collector. For example, the current collector may be a flat-plate type quartz glass, a Si wafer, or a Ni current collector (Ni 99.9% foil), or a current collector in which Ni is electroplated on a fabric.

[0041]

[0042] Next, the lithium metal electrode according to the present invention, in which dendrite formation is suppressed, includes a metal-organic framework including a lithium-affinity metal ion and an organic linker coated on the current collector.

[0043] The above lithium-affinity metal ion is characterized by having high lithium affinity while forming a coordinate covalent bond with the organic linker.

[0044] Specifically, the lithium-affinity metal ion is silver (Ag + ), gold (Au 3+ , Au + ), magnesium (Mg 2+ ), zinc (Zn 2+ ) and copper (Cu 2+ ) may be an ion selected from the group consisting of, and is preferably a silver ion, but is not limited thereto.

[0045] Among the organic linkers, the organic linker located at the innermost shell can form a coordinate covalent bond with a conductive metal atom in the current collector, and further, the organic linker can form a coordinate covalent bond with the lithium-affinity metal ion, and among the organic linkers, the organic linker located at the outermost shell can bind to a lithium metal described below.

[0046] Specifically, the organic linker may include one or more (preferably two or more, more preferably three or more) thiol group-containing compounds, and the thiol group-containing compounds are preferably, but not limited to, trithiocyanuric acid (TCA).

[0047] Within the above-described coated metal-organic framework, the lithium-affinity metal ion and the organic linker can be repeatedly stacked through coordinate covalent bonds. The number of layers of the lithium-affinity metal ion can be viewed as the number of repetitions. The number of repetitions is for controlling the thickness of the above-described coated metal-organic framework, and can be 1 to 20 times, preferably 3 to 10 times, but is not limited thereto.

[0048] Depending on the number of repetitions, the thickness of the coated metal-organic framework may be from 1 nm to 100 nm, preferably from 10 nm to 100 nm, but is not limited thereto.

[0049] The above-mentioned coated metal-organic framework is effective in lithium affinity, and the contact angle for an electrolyte including lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) and a mixed solvent of 1,3-dioxalane (DOL) and dimethyl ether (DME) may be 30° or less, preferably 10° or less, and more preferably 0°, but is not limited thereto.

[0050]

[0051] Next, the lithium metal electrode with suppressed dendrite formation according to the present invention includes lithium metal plated on the metal organic framework.

[0052] The above-mentioned plated lithium metal can be formed through plating using an electroplating solution using a lithium precursor.

[0053] Depending on the conditions of the above electroplating, the thickness of the plated lithium metal can be 1 μm to 10 μm, and the thickness can be adjusted in various ways while suppressing dendrite formation.

[0054]

[0055] Method for manufacturing a lithium metal electrode with suppressed dendrite formation

[0056]

[0057] The present invention provides a method for manufacturing a lithium metal electrode with suppressed dendrite formation, characterized by comprising the steps of (a) coating a metal-organic framework comprising a lithium-affinity metal ion and an organic linker on a current collector; and (b) plating lithium metal on the coated metal-organic framework.

[0058]

[0059] Figure 1 is a schematic diagram schematically showing a method for manufacturing a dendrite-free lithium metal electrode according to one embodiment of the present invention, wherein a lithium-affinity metal ion (e.g., Ag) is deposited on a current collector. + , Au 3+ , Mg 2+ , Zn 2+ A method for manufacturing a dendrite-free lithium metal electrode by coating a metal-organic framework including a metal linker (e.g., trithiocyanuric acid (TCA)) and an organic linker (e.g., trithiocyanuric acid (TCA)) and then plating lithium metal is schematically shown.

[0060]

[0061] First, the method for manufacturing a lithium metal electrode with suppressed dendrite formation according to the present invention includes a step [step (a)] of coating a metal-organic framework including a lithium-affinity metal ion and an organic linker on a current collector.

[0062] Since the above-mentioned collector, the lithium-affinity metal ion, the organic linker, and the coated metal-organic framework have been described above, a redundant description will be omitted.

[0063] The above coating is performed through a solution process-based layered self-assembly method, and can be performed by first stacking the organic linker on the current collector through a coordinate covalent bond with a conductive metal atom in the current collector, and then repeatedly stacking the organic linker and the lithium-affinity metal ion through a coordinate covalent bond with each other. Meanwhile, the thiol group of the organic linker located at the outermost layer among the organic linkers can form an interface with high lithium affinity by combining with a lithium metal described below. The number of layers of the lithium-affinity metal ion can be regarded as the number of repetitions, and the number of repetitions is for controlling the thickness of the coated metal-organic framework, and can be 1 to 20 times, and is preferably 3 to 10 times, but is not limited thereto.

[0064]

[0065] Next, the method for manufacturing a lithium metal electrode with suppressed dendrite formation according to the present invention includes a step [step (b)] of plating lithium metal on the coated metal organic framework.

[0066] Since the above-mentioned plated lithium metal has been described above, a duplicate explanation will be omitted.

[0067] The above electroplating can be performed using a lithium precursor and an electroplating solution. The conditions for the above electroplating are to control the thickness of the plated lithium metal, and are about 100 mA cm -2 About 500 mA cm -2 It can be performed for about 1 minute to about 60 minutes under the current density condition of about 200 mA cm -2 About 300 mA cm -2 It is preferable to perform the process for about 10 to about 30 minutes under current density conditions, but is not limited thereto.

[0068]

[0069] secondary batteries

[0070]

[0071] The present invention provides a secondary battery characterized by including a lithium metal electrode in which dendrite formation is suppressed.

[0072] Specifically, a secondary battery according to the present invention is configured to include a separator, a positive electrode and a negative electrode positioned with the separator between them, and an electrolyte in contact with the positive electrode and the negative electrode, and a lithium metal electrode in which dendrite formation is suppressed can be applied to the negative electrode.

[0073]

[0074] The above secondary battery can significantly increase the theoretical storage capacity by applying a lithium metal electrode having a theoretical capacity of 3840 mAh / g and a low reduction potential to the negative electrode.

[0075] In particular, when the secondary battery is operated, the lithium metal electrode can form a SEI (Solid Electrolyte Interphase) layer containing Li2S or Li3N, which correspond to materials having high lithium ion conductivity. Accordingly, the secondary battery according to the present invention has the advantage of being able to simultaneously produce a lithium alloy layer having high lithium affinity and a SEI (Solid Electrolyte Interphase) layer having high lithium ion conductivity while suppressing dendrite formation.

[0076] Therefore, the present invention can be applied to various high-capacity secondary batteries that require excellent operating stability and power density, such as portable electronic devices, large-capacity storage devices, and electric vehicles.

[0077]

[0078] Hereinafter, preferred examples are presented to aid in understanding the present invention. However, the following examples are provided solely to facilitate a better understanding of the present invention, and the scope of the present invention is not limited by the following examples.

[0079]

[0080] [Example]

[0081] Example 1: Coating of a metal-organic framework on a flat-shaped collector

[0082] Lithium-affinity metal ions (Ag) on ​​quartz glass, Si wafer, or Ni current collector (Ni 99.9% foil) in the form of a flat plate + , Au 3+ , Mg 2+ , Zn 2+ or Cu 2+ ) as a compound containing 30 mM silver acetate, 30 mM gold chloride trihydrate, 30 mM magnesium acetate, 30 mM zinc acetate, or 30 mM cupper acetate in an aqueous solution and 10 mM trithiocyanuric acid (TCA) in an ethanol solution as an organic linker were repeatedly (n=1 to 10) layered through a dipping process for 10 minutes each to coat the metal-organic framework. At this time, lithium-affinity metal ions were added within the coated metal-organic framework. and TCA form a coordinate covalent bond.

[0083]

[0084] Figure 2 shows the results of analysis using UV-vis spectroscopy on a metal-organic framework coated on a flat quartz glass.

[0085] As shown in Fig. 2, according to the UV-vis spectroscopy analysis results, as the number of repetitions increased from 1 to 10, various lithium-affinity metal ions (Ag + , Au + or Cu 2+ ) and TCA are confirmed to be qualitatively and consistently laminated.

[0086]

[0087] In addition, Fig. 3 shows the results of an analysis using SEM (Scanning Electron Microscopy) of a metal-organic framework coated on a Si wafer in the form of a flat plate.

[0088] As shown in Fig. 3, according to the SEM analysis results, lithium-affinity metal ions (Ag + ) and TCA were confirmed to form a metal-organic framework in the form of nanoparticles bonded to each other, and the thickness of the metal-organic framework was confirmed to increase steadily as the number of repetitions increased (n=1, 3, 5, and 10).

[0089]

[0090] In addition, Fig. 4 shows the results of evaluating the lithium affinity (lithiophilicity) of a metal organic framework coated on a Ni collector in the form of a flat plate.

[0091] Specifically, a 1:1 mixed solvent electrolyte of 1,3-dioxalane (DOL) and dimethyl ether (DME) (LiTFSi in DOL / DME (1:1) electrolyte) containing 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) was dropped onto the surface of a metal-organic framework coated on a flat Ni collector, and the contact angle was measured.

[0092] As shown in Fig. 4, according to the contact angle measurement results, the bare surface of the flat Ni current collector has a contact angle of about 45.2° for the LiTFSi in DOL / DME (1:1) electrolyte, whereas the metal-organic framework surface coated on the flat Ni current collector has a contact angle of about 0° for the LiTFSi in DOL / DME (1:1) electrolyte. In other words, it can be seen that the metal-organic framework coating is effective in improving lithium affinity.

[0093]

[0094] Example 2: Preparation of lithium metal electrode (fabric type)

[0095] A lithium metal electrode was manufactured in the same manner as in Example 1, except that a Ni-electroplated textile was used instead of a Ni-electroplated textile.

[0096]

[0097] Figure 5 shows the results of analysis using SEM (Scanning Electron Microscopy) and XRD (X-ray Differaction Analysis) on a metal organic framework coated on a fabric-shaped Ni collector before and after lithium metal plating.

[0098] As shown in Fig. 5, according to the SEM analysis results, the metal-organic framework coated on the fabric-shaped Ni current collector, like the metal-organic framework coated on the flat-shaped Ni current collector, has a lithium-affinity metal ion (Ag + ) and TCA were confirmed to be in the form of nanoparticles bonded to each other, and subsequent lithium metal plating was also confirmed to be performed evenly without dendrite formation.

[0099] Additionally, according to the XRD analysis results, it was confirmed that the metal-organic framework coated on the fabric-shaped Ni current collector was well formed to have a specific crystal structure.

[0100]

[0101] In addition, Fig. 6 shows the results of evaluating the lithium affinity (lithiophilicity) of a metal organic framework coated on a Ni current collector in the form of a fabric.

[0102] Specifically, the nucleation overpotential was measured using a galvanostatic charge / discharge test method for a metal-organic framework coated on a Ni current collector in the form of a fabric.

[0103] As shown in Fig. 6, the nucleation overvoltage measurement results show that, compared to a fabric-type Ni current collector (bare), the nucleation overvoltage increases steadily as the number of repetitions increases (n = 1, 3, and 5). This suggests that the metal-organic framework coating is effective in improving lithium affinity and that the lithium affinity can be controlled depending on the number of repetitions.

[0104]

[0105] Example 3: Manufacturing of secondary batteries (half-cell and symmetric full-cell) with lithium metal electrodes (in the form of fabric)

[0106] Secondary batteries (Half-Cell and Symmetric Full-Cell) were manufactured using the Ni current collector and lithium metal electrode (n=1, 3, or 5) manufactured in Example 2, respectively.

[0107]

[0108] Figure 7 shows the results of analyzing the components of the SEI (Solid Electrolyte Interphase) layer formed when a secondary battery (Half-Cell) using a fabric-type Ni current collector-based lithium metal electrode is operated using XPS (X-ray Photoelectron Spectroscopy).

[0109] As shown in Fig. 7, a secondary battery (half-cell) using a fabric-type Ni current collector-based lithium metal electrode (n=5) was applied at 1 mA / cm -2 , 6 mAh / cm -2 When driven under the conditions, Li2S and Li3N were identified as components of the formed SEI layer. Each of these has a value of ~ 10 at room temperature. -3 S / cm and ~10 -5 It corresponds to a material with a high lithium ion conductivity of S / cm.

[0110]

[0111] In addition, Fig. 8 shows the performance of a secondary battery (Half-Cell) using a fabric-type Ni current collector-based lithium metal electrode at 1 mA cm -2 , 1 mA h cm -2 It shows the results evaluated under the conditions.

[0112] As shown in Fig. 8, when a lithium metal electrode based on a fabric-type Ni current collector (bare) is applied, unstable cycle stability is observed, whereas when a fabric-type Ni current collector-based lithium metal electrode (n=1, 3, or 5) is applied, it is confirmed that a high stability of about 99% or more is observed even after 400 cycles due to the metal-organic framework coating.

[0113]

[0114] In addition, Fig. 9 shows the performance of a secondary battery (Symmetric Full-Cell) using a fabric-type Ni current collector-based lithium metal electrode at 3 mA cm -2 , 1 mA h cm -2 It shows the results evaluated under the conditions.

[0115] As shown in Fig. 9, when a lithium metal electrode based on a fabric-type Ni current collector (bare) is applied, unstable cycle stability is observed, whereas when a fabric-type Ni current collector-based lithium metal electrode (n=1, 3, or 5) is applied, high stability is observed due to the metal-organic framework coating. In particular, it is confirmed that the stability shows a trend of further improvement as the number of repetitions increases (n=1, 3, and 5).

[0116]

[0117] The foregoing description of the present invention is for illustrative purposes only. Those skilled in the art will readily appreciate that modifications to other specific embodiments can be made without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Whole house; A metal-organic framework comprising a lithium-affinity metal ion and an organic linker coated on the entire body; and A lithium metal electrode with suppressed dendrite formation, characterized in that it comprises lithium metal plated on the metal-organic framework.

2. In paragraph 1, A lithium metal electrode with suppressed dendrite formation, characterized in that the lithium-affinity metal ion is an ion selected from the group consisting of silver, gold, magnesium, zinc, and copper.

3. In paragraph 1, A lithium metal electrode with suppressed dendrite formation, characterized in that the organic linker comprises at least one thiol group-containing compound.

4. In paragraph 3, A lithium metal electrode with suppressed dendrite formation, characterized in that the one or more thiol group-containing compounds is trithiocyanuric acid (TCA).

5. In paragraph 1, A lithium metal electrode with suppressed dendrite formation, characterized in that lithium-affinity metal ions and organic linkers are repeatedly stacked through coordinate covalent bonds within the metal-organic framework.

6. In paragraph 1, A lithium metal electrode with suppressed dendrite formation, characterized in that the thickness of the metal-organic framework is 1 nm to 100 nm.

7. In paragraph 1, A lithium metal electrode with suppressed dendrite formation, characterized in that the metal-organic framework has a contact angle of 30° or less for an electrolyte containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) and a mixed solvent of 1,3-dioxalane (DOL) and dimethyl ether (DME). 8.(a) a step of coating a metal-organic framework comprising a lithium-affinity metal ion and an organic linker on the entire body; and (b) A method for manufacturing a lithium metal electrode with suppressed dendrite formation, characterized by including a step of plating lithium metal on the coated metal-organic framework.

9. A secondary battery characterized by including a lithium metal electrode in which dendrite formation is suppressed according to paragraph 1.

10. In paragraph 9, When the above secondary battery is operated, the lithium metal electrode is Li 2 S or Li 3 A secondary battery characterized by forming a SEI (Solid Electrolyte Interphase) layer containing N.

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