Method for producing single-crystal metal lithium negative electrode
By annealing polycrystalline lithium foil, Li(110) single-crystal lithium metal anodes were prepared, solving the dendrite growth problem, improving the kinetics of the electrode reaction process and the safety of the battery, and realizing the application of highly safe lithium metal batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI JIAOTONG UNIV
- Filing Date
- 2022-08-30
- Publication Date
- 2026-06-26
AI Technical Summary
In the prior art, lithium metal anodes suffer from dendrite growth during charging and discharging, leading to irreversible capacity loss, reduced coulombic efficiency, and battery safety hazards. Furthermore, the difference in self-diffusion barriers of polycrystalline lithium foils limits the electrode process kinetics.
By annealing polycrystalline lithium foil under vacuum or inert atmosphere, Li(110) single-crystal lithium metal anodes are prepared, reducing the surface self-diffusion barrier, achieving uniform deposition, and suppressing dendrite growth.
It improves the kinetics of the electrode reaction process of lithium metal anode, broadens the safety boundary, enhances the cycle stability and safety of the battery, avoids dendrite puncture of the separator, and significantly improves battery assembly efficiency.
Smart Images
Figure CN117673276B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a technology in the field of lithium batteries, specifically a method for preparing a single-crystal lithium metal anode. Background Technology
[0002] With the continuous popularization and development of 5G technology, electric vehicles, and energy storage power stations, people have put forward higher requirements for the energy density and safety of energy storage devices. Lithium-ion batteries, as the main power source for new energy vehicles and various portable electronic devices, are constantly approaching their theoretical limits in terms of energy density. Lithium metal, due to its theoretical specific capacity (3860 mAh / g) being 10 times that of graphite anodes (372 mAh / g) and its lowest electrochemical reduction potential (-3.04 V), is considered the ideal anode for next-generation high-energy-density rechargeable batteries (Nature Nanotechnology 2017, 12, 194). High-energy-density lithium-air batteries and lithium-sulfur batteries using lithium metal as the anode have received widespread attention in recent years.
[0003] However, lithium metal anodes suffer from severe dendrite growth problems during practical use (Chemical Reviews 2017, 117, 10403). During charge-discharge cycles, dendrites break down to form "dead lithium," leading to severe irreversible capacity loss, reduced coulombic efficiency, and electrolyte consumption and decomposition. If lithium dendrites pierce the separator, they can cause internal short circuits and thermal runaway, resulting in serious fires or even explosions (Nature 2001, 414, 359), greatly limiting the practical application and development of lithium metal anodes. To address these issues, researchers have proposed numerous strategies, including anode structural design, electrolyte composition optimization, separator modification, and the use of solid-state electrolytes (Chemical Society Reviews 2020, 49, 5407), but these have not yet effectively solved the problems of lithium dendrite growth and piercing.
[0004] Currently, the lithium metal anodes used in battery assembly and testing are typically polycrystalline lithium containing Li(110), Li(200), and Li(211) crystal planes. The self-diffusion barriers of lithium atoms on different crystal planes vary significantly, greatly limiting the electrode process kinetics of lithium metal anodes (Energy & Environmental Science, 11, 3400). Therefore, how to prepare a single-crystal lithium metal anode that precisely controls the surface self-diffusion barrier to induce uniform lithium deposition, eliminate lithium dendrite growth, and simultaneously improve the electrode process kinetics of lithium deposition is of great significance for the development of practical, high-safety lithium metal anodes. However, due to the high reactivity, low melting point, and demanding processing conditions of lithium metal, the preparation technology for single-crystal lithium metal anodes remains undeveloped. Summary of the Invention
[0005] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by proposing a method for preparing a single-crystal lithium metal anode. By reducing the self-diffusion barrier on the surface of the lithium metal anode, the kinetics of the electrode reaction process are significantly improved, while simultaneously widening its safety boundary, ensuring no dendrite growth within the practical current density range. The prepared single-crystal lithium metal anode can be directly used for battery assembly, achieving a significant improvement in the cycle stability and safety of high-energy-density lithium metal batteries, and promoting the development of practical high-safety lithium metal batteries.
[0006] This invention is achieved through the following technical solution:
[0007] This invention relates to a method for preparing a single-crystal lithium metal anode, which involves annealing a horizontally placed polycrystalline lithium metal foil after heating it in a vacuum or inert atmosphere to obtain a Li(110) single-crystal lithium metal anode with a close-packed surface that can be directly used for battery assembly.
[0008] The polycrystalline lithium foil is preferably a circular sheet structure.
[0009] The inert atmosphere referred to is an argon or helium atmosphere.
[0010] The heating process includes: first raising the temperature to 200-250℃ and heating at a constant temperature for 1-10 minutes; then cooling the temperature down to 178℃ at a cooling rate of 0.5-5℃ / min.
[0011] The annealing process refers to constant-temperature annealing at 178°C followed by furnace cooling to room temperature.
[0012] The purity of the polycrystalline lithium foil is preferably above 98 wt%.
[0013] The thickness of the polycrystalline lithium foil is preferably 10 micrometers or more.
[0014] The heating equipment is a vacuum tube furnace or a muffle furnace.
[0015] The heating rate is 1-20℃ / min.
[0016] The annealing process takes more than 0.5 hours, and generally the thicker the lithium foil, the longer the annealing process.
[0017] The annealing process and battery assembly process are both completed under vacuum or inert atmosphere protection.
[0018] The battery assembly includes rolling a single-crystal lithium metal anode to different thicknesses.
[0019] The batteries mentioned include symmetrical batteries and full batteries.
[0020] Technical effect
[0021] This invention prepares a Li(110) single-crystal lithium metal anode with a close-packed surface by placing high-purity polycrystalline lithium foil horizontally in a vacuum or inert atmosphere and annealing it. This anode exhibits a high exchange current density. Compared with batteries assembled with polycrystalline lithium metal anodes, batteries assembled with single-crystal lithium metal anodes have lower overpotentials and better cycle stability under the same current density and deposition capacity conditions. They also have higher critical current dendrites and wider safety boundary conditions, effectively suppressing the formation and growth of lithium metal dendrites and preventing dendrites from piercing the separator. This effectively improves the battery cycle life and safety, and significantly enhances the efficiency of battery assembly. Attached Figure Description
[0022] Figure 1 XRD patterns of different lithium metal anodes;
[0023] In the figure: a is the XRD of the polycrystalline lithium metal anode before annealing, and b is the XRD of the single-crystal lithium metal anode after annealing.
[0024] Figure 2 A schematic diagram comparing the exchange current density of monocrystalline lithium metal anodes and polycrystalline lithium metal anodes;
[0025] Figure 3 A schematic diagram comparing the cycle performance of symmetrical batteries with monocrystalline lithium metal anodes and polycrystalline lithium metal anodes;
[0026] Figure 4 The results show the critical current density test results for different lithium metal anodes;
[0027] In the figure: a is the critical current density test of single-crystal lithium metal anode, and b is the critical current density test of polycrystalline lithium metal anode.
[0028] Figure 5 The images show the deposition morphology of lithium metal on different anode surfaces, with a deposition current density of 10 mA / cm². -2 The deposition capacity is 5 mAh / cm³. -2 ;
[0029] In the figure: a shows the deposition morphology of lithium metal on the surface of a single-crystal lithium metal anode, and b shows the deposition morphology of lithium metal on the surface of a polycrystalline lithium metal anode.
[0030] Figure 6 A schematic diagram comparing the cycle performance of full cells assembled with monocrystalline lithium metal anodes and polycrystalline lithium metal anodes matched with NCM811 cathodes. Detailed Implementation
[0031] Example 1
[0032] This embodiment illustrates the preparation of a single-crystal lithium metal anode, including:
[0033] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 99 wt%, a thickness of 300 μm, and a diameter of 12 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0034] Step 2) Heat the muffle furnace to 200°C at a heating rate of 20°C / min, and keep it at 200°C for 10 min.
[0035] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 2 hours.
[0036] Step 4) Cool the furnace to room temperature.
[0037] The untreated polycrystalline lithium foil and the annealed lithium foil from Example 1 were characterized by XRD, and the results are as follows: Figure 1 As shown. Figure 1 As shown in (a), the untreated polycrystalline lithium foil mainly includes (110), (200) and (211) diffraction peaks, indicating that the polycrystalline lithium foil contains three crystal planes: (110), (200) and (211); Figure 1 As shown in (b), the lithium metal foil obtained after the annealing treatment in Example 1 has only (110) diffraction peaks at 37 degrees on both sides, indicating that a single crystal of lithium metal with a close-packed Li (110) surface has been formed.
[0038] Example 2
[0039] This embodiment illustrates the preparation of single-crystal lithium metal anodes of different sizes, including:
[0040] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 98 wt%, a thickness of 500 μm, and a diameter of 16 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0041] Step 2) Heat the muffle furnace to 220°C at a heating rate of 20°C / min, and keep it at 220°C for 5 minutes.
[0042] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 5 hours.
[0043] Step 4) Cool to room temperature with the furnace to obtain a single crystal lithium metal anode with a close-packed surface (110).
[0044] XRD was used to characterize the untreated polycrystalline lithium foil and the annealed lithium foil from Example 2. The results are consistent with those shown below. Figure 1 They are basically the same.
[0045] Example 3
[0046] This embodiment illustrates the preparation of single-crystal lithium metal anodes in different devices, including:
[0047] Step 1) Place a high-purity polycrystalline lithium foil with a purity of 99wt%, a thickness of 500μm, and a diameter of 12mm horizontally on a stainless steel substrate and transfer it to a vacuum tube furnace.
[0048] Step 2) Heat the tube furnace to 200°C at a heating rate of 10°C / min, and keep it at 200°C for 7 minutes.
[0049] Step 3) Cool down to 178℃ at a cooling rate of 1.5℃ / min, and anneal at 178℃ for 10 hours.
[0050] Step 4) Cool to room temperature with the furnace to obtain a single-crystal lithium metal anode with a close-packed surface (110).
[0051] XRD was used to characterize the untreated polycrystalline lithium foil and the annealed lithium foil in Example 3. The results are consistent with those shown below. Figure 1 They are basically the same.
[0052] Example 4
[0053] This embodiment illustrates the kinetics of the fast reaction process in a single-crystal lithium metal anode, including:
[0054] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 99 wt%, a thickness of 500 μm, and a diameter of 12 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0055] Step 2) Heat the muffle furnace to 200°C at a heating rate of 20°C / min, and keep it at 200°C for 10 min.
[0056] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 2 hours.
[0057] Step 4) Cool to room temperature with the furnace to obtain a single-crystal lithium metal anode with a close-packed surface (110).
[0058] The exchange current density of the obtained single-crystal lithium metal anode was measured in a 1M LiPF6, 0.02M LiDFOBinFEC / HFE / FEMC electrolyte and compared with that of the polycrystalline lithium metal anode. Figure 2 As shown, compared to polycrystalline lithium metal anodes, monocrystalline lithium metal anodes exhibit higher exchange current density, demonstrating their faster reaction kinetics. Under the same current density and deposition capacity conditions, symmetrical cells assembled with this monocrystalline lithium metal anode can achieve stable cycling for a longer period with lower overpotential, such as... Figure 3 As shown.
[0059] Example 5
[0060] This embodiment illustrates the safety boundary conditions for single-crystal lithium metal anodes, including:
[0061] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 99 wt%, a thickness of 500 μm, and a diameter of 12 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0062] Step 2) Heat the muffle furnace to 200°C at a heating rate of 10°C / min, and keep it at 200°C for 10 min.
[0063] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 2 hours.
[0064] Step 4) Cool to room temperature with the furnace to obtain a single-crystal lithium metal anode with a close-packed surface (110).
[0065] The obtained single-crystal lithium metal anode was used to assemble a symmetrical cell in a 1M LiPF6, 0.02M LiDFOBinFEC / HFE / FEMC electrolyte, and the cell was tested at a 3mAh / cm² temperature. -2 Critical current density was tested under fixed deposition / dissolution capacity and compared with the critical current density of polycrystalline lithium metal anodes. Figure 4As shown, compared with polycrystalline lithium metal anodes, monocrystalline lithium metal anodes have a higher critical current density, indicating that dendrite puncture and battery short circuit will not occur within a wider current density range, thus providing higher safety conditions for use.
[0066] Example 6
[0067] This embodiment illustrates the deposition morphology of a single-crystal lithium metal anode, including:
[0068] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 99 wt%, a thickness of 500 μm, and a diameter of 12 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0069] Step 2) Heat the muffle furnace to 200°C at a heating rate of 10°C / min, and keep it at 200°C for 10 min.
[0070] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 5 hours.
[0071] Step 4) Cool to room temperature with the furnace to obtain a single-crystal lithium metal anode with a close-packed surface (110).
[0072] The prepared single-crystal lithium metal anode was used to assemble a symmetrical cell in a 1M LiPF6, 0.02M LiDFOBinFEC / HFE / FEMC electrolyte, and the cell was tested at 10 mA / cm². -2 10mAhcm -2 Unidirectional deposition was performed under specific conditions, and the deposition morphology of lithium metal on the surfaces of monocrystalline and polycrystalline lithium metal anodes was characterized by SEM. Figure 5 As shown, under the same conditions, lithium metal deposited on the surface of a single-crystal lithium metal anode exhibits a flat, bulk morphology, while on a polycrystalline lithium metal anode it exhibits a dendritic lithium metal dendrite morphology. This further indicates that the single-crystal lithium metal anode has a high-safety "dendritic-free" characteristic within the practical range.
[0073] Example 7
[0074] This embodiment illustrates the feasibility of single-crystal lithium metal anodes in practical full cells, including:
[0075] Step 1) In an argon-filled glove box, a high-purity polycrystalline lithium foil with a purity of 99 wt%, a thickness of 500 μm, and a diameter of 12 mm is placed horizontally on a stainless steel substrate and transferred to a muffle furnace.
[0076] Step 2) Heat the muffle furnace to 200°C at a heating rate of 10°C / min, and keep it at 200°C for 10 min.
[0077] Step 3) Cool down to 178°C at a cooling rate of 1.5°C / min, and anneal at 178°C for 5 hours.
[0078] Step 4) Cool to room temperature with the furnace to obtain a single-crystal lithium metal anode with a close-packed surface (110).
[0079] The prepared single-crystal lithium metal anode was rolled to 50 μm, and a Li||NMC811 full cell was assembled in a 1M LiPF6, 0.02M LiDFOBin FEC / HFE / FEMC electrolyte. The cell was then subjected to constant current charge-discharge cycle testing under practical conditions. Figure 6 As shown, under the same conditions, the Li||NCM811 full cell assembled with a single-crystal lithium metal anode exhibits higher discharge specific capacity and longer cycle life, verifying the feasibility of practical applications of single-crystal lithium metal anodes.
[0080] This invention prepares a single-crystal lithium metal anode with a close-packed Li(110) surface by isothermal annealing of a commercial polycrystalline lithium metal anode. This method is simple and flexible, and the prepared single-crystal lithium metal anode exhibits a lower surface self-diffusion energy barrier, faster reaction kinetics, and a wider safety boundary range, which helps to promote the practical application of high-safety lithium metal anodes.
[0081] Compared with existing technologies, the single-crystal lithium metal anode prepared by this method has faster reaction kinetics and a wider safety boundary range, which significantly improves the cycle stability and practical safety of lithium metal anodes. This provides new ideas for exploring practical high-safety lithium metal anodes and greatly promotes the practical development of high-safety lithium metal anodes and lithium metal batteries.
[0082] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.
Claims
1. A method for preparing a single-crystal lithium metal anode, characterized in that, By annealing a horizontally placed polycrystalline lithium foil under vacuum or inert atmosphere, a Li(110) single-crystal lithium anode with a close-packed surface that can be directly used for battery assembly is obtained. The heating process includes: first raising the temperature to 200-250℃, maintaining the temperature for 1-10 minutes, and then cooling the temperature down to 178℃ at a rate of 0.5-5℃ / min. The annealing process refers to constant-temperature annealing at 178°C followed by furnace cooling to room temperature. The purity of the polycrystalline lithium foil is above 98 wt%. The thickness of the polycrystalline lithium foil is 10 micrometers or more.
2. The method for preparing a single-crystal lithium metal anode according to claim 1, characterized in that, The polycrystalline lithium foil has a circular sheet structure.
3. The method for preparing a single-crystal lithium metal anode according to claim 1, characterized in that, The heating rate is 1-20 °C / min.
4. The method for preparing a single-crystal lithium metal anode according to claim 1, characterized in that, The annealing process described herein takes at least 0.5 hours.
5. The method for preparing a single-crystal lithium metal anode according to claim 1, characterized in that, The annealing process and battery assembly process are both completed under vacuum or inert atmosphere protection.
6. The method for preparing a single-crystal lithium metal anode according to claim 1, characterized in that, The battery assembly includes rolling a single-crystal lithium metal anode to different thicknesses; the battery includes symmetrical cells and full cells.