Method for manufacturing all-solid-state lithium battery

Abstract

A preparation method of a lithium foil anode of an all-solid-state lithium battery, comprising the following steps: (a) dispersing nanocarbon materials in water to obtain a dispersion liquid; (b) mixing dopamine with the dispersion liquid, and allowing the dopamine to perform a polymerization reaction in the dispersion liquid to obtain nanocarbon materials surface-modified by polydopamine; (c) forming a regular concave-convex texture structure on a lithium foil; and (d) mixing the nanocarbon materials surface-modified by polydopamine and a lithium-ion-containing polymer, and then coating on the lithium foil on which the regular concave-convex texture structure is formed. The all-solid-state lithium battery of the lithium foil anode prepared by the preparation method has a small polarization potential difference, a body impedance value after charge / discharge cycles, an interface charge transfer impedance value after cycles, and a high discharge gram capacity maintenance rate, and has excellent long-term charge / discharge cycle stability.

Description

Technical Field

[0001] This invention relates to a method for preparing an anode, and more particularly to a method for preparing a lithium foil anode for an all-solid-state lithium battery. Background Technology

[0002] Existing all-solid-state lithium batteries (ASSLB) that use lithium metal as the anode have a very high theoretical energy density, making them suitable as an energy source for portable electronic devices and electric vehicles.

[0003] However, during battery charge / discharge cycles, the formation of needle-shaped lithium dendrites is a major factor leading to problems such as short circuits and thermal runaway, which limits the large-scale commercialization of all-solid-state lithium batteries. Furthermore, the thick solid electrolyte interphase (SEI) layer formed by the grown lithium dendrites and dead lithium can result in insufficient contact between the solid electrolyte membrane and the electrodes, leading to high interfacial resistance. This can cause severe battery capacity degradation and affect the battery's cycle life. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing lithium foil anodes for all-solid-state lithium batteries, which can overcome the shortcomings of the above-mentioned background technology.

[0005] The method for preparing the lithium foil anode of the all-solid-state lithium battery of the present invention comprises the following steps: (a) dispersing nano-carbon material in water to obtain a dispersion; (b) mixing dopamine with the dispersion and allowing dopamine to undergo a polymerization reaction in the dispersion to obtain nano-carbon material modified with polydopamine; (c) forming a regular uneven texture structure on a lithium foil, the regular uneven texture structure being at the submillimeter scale; and (d) mixing the polydopamine-modified nano-carbon material with a lithium-ion-containing polymer and coating it onto the lithium foil having the regular uneven texture structure to obtain the lithium foil anode of the all-solid-state lithium battery.

[0006] The beneficial effects of the present invention are as follows: the all-solid-state lithium battery with lithium foil anode prepared by the method of the present invention has a small polarization potential difference, a low bulk impedance value after cycling, a low interfacial charge transfer impedance value after cycling, and a high discharge capacity retention rate, and has excellent long-term charge / discharge cycle stability.

[0007] The following will provide a detailed description of the invention:

[0008] Preferably, step (c) involves cold pressing a metal mesh template with a regular structure onto the lithium foil to form the regular textured structure. More preferably, in step (c), the metal mesh template is selected from copper mesh, nickel mesh, titanium mesh, platinum mesh, or stainless steel mesh. In a specific embodiment of the present invention, the metal mesh template is a copper mesh.

[0009] More preferably, the regular textured structure includes a plurality of spaced-apart and regularly arranged longitudinal grooves and a plurality of spaced-apart and regularly arranged transverse grooves. The longitudinal grooves extend along a first direction, and the transverse grooves extend along a second direction different from the first direction. The longitudinal grooves and the transverse grooves are located at the same horizontal position. Each longitudinal groove has a plurality of discontinuous longitudinal groove segments, and each transverse groove has a plurality of discontinuous transverse groove segments. In a specific embodiment of the invention, the first direction is perpendicular to the second direction. More preferably, each longitudinal groove segment and each transverse groove segment are spindle-shaped structures with a length in the range of 450-650 μm.

[0010] More preferably, the cold pressing process is performed at a pressure of 25-150 psi. In a specific embodiment of the invention, the cold pressing process is performed at a pressure of 50-100 psi.

[0011] Preferably, in step (a), the carbon nanomaterial is selected from carbon fiber, carbon nanotubes, graphene, graphene oxide, carbon black, or a combination thereof. In a specific embodiment of the present invention, the carbon nanomaterial is vapor-grown carbon fiber.

[0012] Preferably, step (b) includes adding a tris(hydroxymethyl)aminomethane buffer to the dispersion to allow dopamine to polymerize in the dispersion. More preferably, in step (b), the dopamine polymerizes in the dispersion at a pH range of 8.0-9.0. In a specific embodiment of the invention, in step (b), the dopamine polymerizes in the dispersion at a pH range of about 8.5.

[0013] Preferably, in step (d), the weight ratio of the polydopamine-modified carbon nanomaterial to the lithium-ion-containing polymer ranges from 1:2 to 1:20. In a specific embodiment of the present invention, the weight ratio of the polydopamine-modified carbon nanomaterial to the lithium-ion-containing polymer is 1:10.

[0014] Preferably, in step (d), the lithium-ion-containing polymer is lithium-ion-containing Nafion (Li-Nafion). Alternatively, the source of the lithium ions may be selected from lithium hydroxide, lithium nitrate, lithium acetate, lithium chloride, lithium hydrogen phosphate, lithium phosphate, lithium carbonate, or combinations thereof. In a specific embodiment of the invention, the source of the lithium ions is lithium hydroxide monohydrate. Attached Figure Description

[0015] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, wherein:

[0016] Figure 1 Optical microscope images of lithium foil anodes of all-solid-state lithium batteries according to embodiments and comparative examples of the present invention are shown, wherein A is an embodiment of the present invention, B is comparative example 1, C is comparative example 2, and D is comparative example 3;

[0017] Figure 2 This refers to the all-solid-state symmetric battery SC of Application Example 1 and Comparative Application Examples 1-3 of the present invention. E and SC CE1 -SC CE3 Time-cell potential relationship during deposition / stripping polarization cycle testing;

[0018] Figure 3 This refers to the all-solid-state symmetric battery SC of Application Example 1 and Comparative Application Examples 1-3 of the present invention. E and SC CE1 -SC CE3 At 0.1 mA·cm -2 Below is the AC impedance spectrum after 100 hours of charge / discharge cycles;

[0019] Figure 4 This refers to the all-solid-state lithium battery LB used in Application Example 2 and Comparative Application Examples 4-6 of this invention. E and LB CE1 -LB CE3 A graph showing the relationship between specific capacity and battery potential after activation (charge / discharge 3 times at a rate of 0.1C);

[0020] Figure 5 This refers to the all-solid-state lithium battery LB used in Application Example 2 and Comparative Application Examples 4-6 of this invention. E and LB CE1 -LB CE3 AC impedance spectrum after activation (charge / discharge 3 times at a rate of 0.1C);

[0021] Figure 6 This refers to the all-solid-state lithium battery LB used in Application Example 2 and Comparative Application Examples 4-6 of this invention. E and LB CE1 -LB CE3The relationship between the number of charge / discharge cycles and the discharge capacity after 100 charge / discharge cycles at a rate of 0.2C; and

[0022] Figure 7 This refers to the all-solid-state lithium battery LB used in Application Example 2 and Comparative Application Examples 4-6 of this invention. E and LB CE1 -LB CE3 AC impedance spectrum after 100 charge / discharge cycles at a rate of 0.2C. Detailed Implementation

[0023] The present invention will be further described with reference to the following embodiments, but it should be understood that the embodiments are for illustrative purposes only and should not be construed as limiting the implementation of the present invention.

[0024] <Example> Lithium foil electrode E of all-solid-state lithium battery and its preparation method

[0025] An embodiment of the method for preparing the lithium foil anode of the all-solid-state lithium battery of the present invention includes the following steps:

[0026] (a) 100 mg of one-dimensional vapor-grown carbon fiber (VGCF, purchased from Xin Yong Yu Applied Technology Materials Co., Ltd., model GS013010) nanocarbon material powder was dispersed in 100 mL of deionized water and subjected to vibration dispersion treatment for 75 min using a probe-type sonicator (purchased from QSONICA, model Q700) (operating power 2-3 W, amplitude 10 mV, frequency 20 kHz, pulse ON for 20 min, pulse OFF for 5 min) to avoid aggregation and obtain a uniform dispersion.

[0027] (b) Subsequently, 100 mg of dopamine was added to the dispersion obtained in step (a) above under stirring, and the pH was adjusted to about 8.5 by adding tris(hydroxymethyl)aminomethane-hydrochloric acid buffer (Tris-HCl, 99%, purchased from Polyhe International Co., Ltd.). The mixture was stirred at 25°C for 24 h to allow the dopamine to polymerize in the dispersion. The mixture was then centrifuged at 6000 rpm for 30 min and the solid was collected. The solid was washed with deionized water and dried in an oven at 80°C for 12 h to obtain vapor-grown carbon fibers with a one-dimensional structure modified with polydopamine.

[0028] (c) A copper mesh with a regular structure (as a metal mesh template with a thickness of 100-300 μm) is cold-pressed onto a smooth circular lithium foil (radius of 0.75 cm and thickness of 200 μm) with a pressure of 50-100 psi to form a regular textured structure with a sub-millimeter scale.

[0029] (d) 25.2 mg of lithium hydroxide monohydrate (LiOH·H2O, purchased from Sigma-Aldrich) was mixed with 10 mL of Nafion solution (5 wt%, solvent being an aliphatic alcohol and water, purchased from Sigma-Aldrich), stirred at 60 °C for 2 h, and then vacuum dried at 80 °C for 12 h to obtain lithium-ion-containing Nafion (Li-Nafion). The Li-Nafion was then dispersed in N-methylpyrrolidone (NMP) to obtain an NMP dispersion of Li-Nafion, and stirred continuously at 80 °C for 6 h. The polydopamine-modified vapor-grown carbon fiber with a one-dimensional structure obtained in step (b) above was mixed with Li-Nafion at a weight ratio of 1:10. The mixture was then coated onto the lithium foil with a regular textured structure formed in step (c) above using a polyethylene terephthalate (PET) film. Finally, the mixture was dried in an argon atmosphere at 25°C and then vacuum dried at 80°C for 2 hours to obtain the lithium foil electrode E of the all-solid-state lithium battery of this embodiment.

[0030] Furthermore, by measuring the thickness of the lithium foil before and after step (d) using a digital thickness gauge, the thickness of the polydopamine-modified vapor-grown carbon fiber and Li-Nafion coated on the lithium foil can be found to be 5-7 μm.

[0031] <Comparative Example 1> Lithium foil electrode CE1 of an all-solid-state lithium battery

[0032] The lithium foil electrode CE1 of the all-solid-state lithium battery in Comparative Example 1 is a smooth circular lithium foil (radius 0.75 cm, thickness 200 μm).

[0033] <Comparative Example 2> Lithium foil electrode CE2 for all-solid-state lithium batteries and its preparation method

[0034] The preparation method of the lithium foil electrode CE2 of the all-solid-state lithium battery in Comparative Example 2 is similar to that of the above-described embodiments. The difference is that step (d) is not performed in the preparation method of Comparative Example 2. That is, the lithium foil electrode CE2 of the all-solid-state lithium battery in Comparative Example 2 is a lithium foil with a regular concave-convex texture structure formed in step (c) above.

[0035] <Comparative Example 3> Lithium foil electrode CE3 for all-solid-state lithium batteries and its preparation method

[0036] The preparation method of the lithium foil electrode CE3 of the all-solid-state lithium battery in Comparative Example 3 is similar to that of the above-described embodiments. The difference is that step (c) is not performed in the preparation method of Comparative Example 3, and step (d) is to mix the polydopamine-modified vapor-grown carbon fiber obtained in step (b) with Li-Nafion and then coat it onto a smooth circular lithium foil (radius of 0.75 cm and thickness of 200 μm) to obtain the lithium foil electrode CE3 of the all-solid-state lithium battery in Comparative Example 3.

[0037] [Observation under an optical microscope]

[0038] The lithium foil electrodes E and CE1-CE3 of the all-solid-state lithium batteries of the above-described examples and Comparative Examples 1-3 were observed using an optical microscope, and the results are as follows: Figure 1 As shown in AD.

[0039] Depend on Figure 1 A and Figure 1 As can be seen from step (c), the lithium foil electrodes E and CE2 obtained after the cold pressing process described above have a regular, sub-millimeter-scale textured structure on their surfaces. This regular textured structure includes multiple longitudinal grooves spaced apart and regularly arranged, and multiple transverse grooves spaced apart and regularly arranged. The longitudinal grooves extend along the longitudinal direction, and the transverse grooves extend in a transverse direction perpendicular to the longitudinal direction. The longitudinal and transverse grooves are located at the same horizontal level. Each longitudinal groove has multiple discontinuous longitudinal groove segments, and each transverse groove has multiple discontinuous transverse groove segments. Each longitudinal groove segment and each transverse groove segment are spindle-shaped structures with a length of approximately 590 μm, a width of approximately 135 μm, and a depth of 30-60 μm. Figure 1 B and Figure 1 As can be seen from D, the lithium foil electrodes CE1 and CE3 obtained without performing the above step (c) have a flat surface and do not form a regular uneven texture structure.

[0040] <Application Example 1> All-solid-state symmetric battery SC E

[0041] Two identical lithium foil electrodes E from the above-described all-solid-state lithium batteries were used as the positive (cathode) and negative (anode) electrodes of the all-solid-state symmetric battery, respectively. A single aluminum-doped lithium lanthanum zirconium oxide (Li₂O₃) electrode was also used. 6.25 Al 0.25 La3Zr2O 12A sandwich structure of PVDF-HFP / PVDF-HFP@Al-LLZO / PVDF-HFP, composed of Al-LLZO and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), is used as a composite polymer electrolyte membrane (CPE membrane, 240 μm thick) for an all-solid-state symmetric battery, forming the all-solid-state (lithium foil-lithium foil) symmetric battery SC in Application Example 1. E .

[0042] <Comparative Application Examples 1-3> All-Solid-State Symmetrical Battery SC CE1 -SC CE3

[0043] Comparative Application Examples 1-3: All-Solid-State Symmetric Cells (SC) CE1 -SC CE3 Similar to Application Example 1, the difference lies in that Comparative Application Examples 1-3 use the lithium foil electrodes CE1-CE3 of two identical all-solid-state lithium batteries from Comparative Examples 1-3 as the positive and negative electrodes of the all-solid-state symmetric battery, respectively, to form the all-solid-state (lithium foil-lithium foil) symmetric battery SC of Comparative Application Examples 1-3. CE1 -SC CE3 .

[0044] [Measurement of the electrical properties of all-solid-state symmetric batteries]

[0045] Using battery testing equipment (purchased from Chia-Yu Technology Co., Ltd., model BAT-750B), the all-solid-state (lithium foil-lithium foil) symmetric batteries SC of Application Example 1 and Comparative Application Examples 1-3 were tested. E and SC CE1 -SC CE3 Deposition / stripping polarization cycling tests were performed (current density 0.1 mA·cm). -2 The area capacitance is 0.1 mAh·cm². -2 The polarization potential difference was measured using AC impedance spectroscopy, and the polarization potential difference was measured in the all-solid-state (lithium foil-to-lithium foil) symmetric cells of Application Example 1 and Comparative Application Examples 1-3, respectively. E and SC CE1 -SC CE3 The volume impedance value R b (at 0.1 mA·cm) -2 (After 100 hours of charge / discharge cycles) and the interface charge transfer impedance value R ct (at 0.1 mA·cm) -2 After 100 hours of charge / discharge cycles, the results are as follows: Figures 2-3 As shown in Table 1 below.

[0046] Table 1

[0047]

[0048] As can be seen from Table 1, the all-solid-state (lithium foil-lithium foil) symmetric battery SC of Application Example 1... E Polarization potential difference, volume impedance R after charge / discharge cycles b and the interfacial charge transfer impedance R after cycling ct All three are significantly smaller than the all-solid-state (lithium foil-lithium foil) symmetric batteries SC in comparative applications 1-3. CE1 -SC CE3 The results show that the all-solid-state (lithium foil-lithium foil) symmetric battery SC applied in Example 1 E It exhibits excellent long-term charge / discharge cycle stability.

[0049] <Application Example 2> All-solid-state lithium battery LB E

[0050] Using one lithium foil electrode E from the all-solid-state lithium battery described in the above embodiment as the negative electrode (anode) of the all-solid-state lithium battery, and using one LiNi... 0.8 Co 0.1 Mn 0.1 O2 (NCM811, 40 μm thick) is used as the positive electrode (cathode) of the all-solid-state lithium battery, and a sandwich structure of PVDF-HFP / PVDF-HFP@Al-LLZO / PVDF-HFP is used as the composite polymer electrolyte membrane of the all-solid-state lithium battery to form the all-solid-state lithium battery LB of Application Example 2. E .

[0051] <Comparative Application Examples 4-6> All-Solid-State Lithium-ion Battery LB CE1 -LB CE3

[0052] Comparative Application Examples 4-6: All-Solid-State Lithium-ion Battery LB CE1 -LB CE3 Similar to Application Example 2, the difference in Comparative Application Examples 4-6 is that the lithium foil electrodes CE1-CE3 of the aforementioned all-solid-state lithium batteries from Comparative Examples 1-3 are used as the negative electrodes of the all-solid-state lithium batteries to form the all-solid-state lithium batteries LB of Comparative Application Examples 4-6 respectively. CE1 -LB CE3 .

[0053] [Measurement of the electrical properties of all-solid-state lithium batteries]

[0054] The all-solid-state lithium batteries (LB) in Application Example 2 and Comparative Application Examples 4-6 were measured using battery testing equipment (purchased from Chia-Yu Technology Co., Ltd., model BAT-750B). E and LBCE1 -LB CE3 The initial specific capacity (activated at room temperature, 3 charge / discharge cycles at 0.1C) and capacity retention (CR) (100 charge / discharge cycles at room temperature at 0.2C) of the all-solid-state lithium batteries in Application Example 2 and Comparative Application Examples 4-6 were measured using AC impedance spectroscopy. E and LB CE1 -LB CE3 The volume impedance value R b (Activation was performed at room temperature, followed by 3 charge / discharge cycles at 0.1C; and 100 charge / discharge cycles at room temperature at 0.2C) and the interfacial charge transfer resistance value R. ct (Activation was performed at room temperature, followed by 3 charge / discharge cycles at 0.1C; and 100 charge / discharge cycles at room temperature at 0.2C). The results are as follows: Figures 4-5 Table 2 below (activation at room temperature, 3 charge / discharge cycles at 0.1C) and Figures 6-7 The results are shown in Table 3 below (after 100 charge / discharge cycles at 0.2C at room temperature).

[0055] Table 2

[0056]

[0057] Table 3

[0058]

[0059] As can be seen from Tables 2 and 3, the all-solid-state lithium battery LB in Application Example 2... E The initial discharge capacity is compared with that of the all-solid-state lithium battery LB in Application Examples 4-6. CE1 -LB CE3 All are similar, but the all-solid-state lithium battery LB used in Example 2 is different. E The capacity retention rate after cycling is higher than that of the all-solid-state lithium battery LB in comparison applications 4-6. CE1 -LB CE3 Among them, the all-solid-state lithium battery LB in Comparative Application Example 4 CE1 The capacity retention rate of the lithium battery in Application Example 2 declined significantly to 7.30%; E The volume impedance value R after activation and cycling b And the interfacial charge transfer impedance R after activation and cycling ct All are significantly smaller than the LB of the all-solid-state lithium batteries in comparative applications 4-6. CE1 -LB CE3 The application example 2 shows the all-solid-state lithium battery LB. EIt exhibits excellent long-term charge / discharge cycle stability.

[0060] In summary, the lithium foil anode prepared by the method of the present invention for preparing the all-solid-state lithium battery helps to enable the all-solid-state lithium battery to have a smaller polarization potential difference, a smaller bulk impedance value after charge / discharge cycles, a smaller interfacial charge transfer impedance value after cycles, and a higher discharge capacity retention rate, thus exhibiting excellent long-term charge / discharge cycle stability. Therefore, it can indeed achieve the purpose of the present invention.

[0061] The above description is merely an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an all-solid-state lithium battery, characterized in that: The preparation method includes the following steps: (a) Disperse the carbon nanomaterials in water to obtain a dispersion; (b) Dopamine is mixed with the dispersion and the dopamine is polymerized in the dispersion to obtain polydopamine-modified carbon nanomaterials. (c) A regular textured structure is formed on a lithium foil, the regular textured structure being sub-millimeter scale; (d) The polydopamine-modified carbon nanomaterial and the lithium-ion-containing polymer are mixed and coated onto a lithium foil with the regular textured structure to obtain a lithium foil anode; and (e) The lithium foil anode, cathode and composite polymer electrolyte membrane are used to assemble the all-solid-state lithium battery.

2. The method for preparing an all-solid-state lithium battery according to claim 1, characterized in that: Step (c) involves cold pressing a metal mesh template with a regular structure onto the lithium foil to form the regular textured structure.

3. The method for preparing an all-solid-state lithium battery according to claim 2, characterized in that: The regular embossed texture structure includes multiple longitudinal grooves spaced apart and regularly arranged and multiple transverse grooves spaced apart and regularly arranged. The longitudinal grooves extend along a first direction, and the transverse grooves extend along a second direction different from the first direction. The longitudinal grooves and the transverse grooves are located at the same horizontal position. Each longitudinal groove has multiple discontinuous longitudinal groove segments, and each transverse groove has multiple discontinuous transverse groove segments.

4. The method for preparing an all-solid-state lithium battery according to claim 2, characterized in that: The cold pressing process is carried out at a pressure of 25-150 psi.

5. The method for preparing an all-solid-state lithium battery according to claim 1, characterized in that: In step (a), the carbon nanomaterial is selected from carbon fiber, carbon nanotube, graphene, graphene oxide, carbon black, or a combination thereof.

6. The method for preparing an all-solid-state lithium battery according to claim 1, characterized in that: Step (b) involves adding a tris(hydroxymethyl)aminomethane buffer to the dispersion to allow dopamine to polymerize in the dispersion.

7. The method for preparing an all-solid-state lithium battery according to claim 6, characterized in that: In step (b), dopamine is polymerized in the dispersion at a pH range of 8.0-9.

0.

8. The method for preparing an all-solid-state lithium battery according to claim 1, characterized in that: In step (d), the weight ratio of the polydopamine-modified carbon nanomaterial to the lithium-ion-containing polymer ranges from 1:2 to 1:

20.

9. The method for preparing an all-solid-state lithium battery according to claim 2, characterized in that: In step (c), the metal mesh template is selected from copper mesh, nickel mesh, titanium mesh, platinum mesh or stainless steel mesh.

10. The method for preparing an all-solid-state lithium battery according to claim 3, characterized in that: Each longitudinal groove segment and each transverse groove segment have a spindle-shaped structure with a length ranging from 450 to 650 μm.

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