A preferentially oriented lithium metal negative electrode material with high ion diffusion stability and a preparation method thereof

Abstract

The application discloses a preferentially oriented lithium metal negative electrode material with high ion diffusion stability and a preparation method thereof; the lithium metal negative electrode material is prepared by introducing deformation energy into pure lithium metal through plastic deformation and then performing low-temperature annealing and recrystallization; wherein, the lithium metal negative electrode material has a grain refinement effect and the (110) crystal face is preferentially oriented. The preparation method of the lithium metal negative electrode material comprises the following steps: S1, performing plastic deformation treatment on pure lithium metal raw materials to introduce high-density deformation energy, and obtaining a pre-prepared body with refined grains and (200) texture; S2, performing annealing treatment on the pre-prepared body obtained in the step S1 under the temperature condition of 40 DEG C to 120 DEG C for 5-60 minutes, driving recrystallization by using the deformation energy, changing the crystal orientation from (200) texture to (110) preferred texture, and obtaining the lithium metal negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery anode material technology development, specifically, it relates to a preferred-oriented lithium metal anode material with high ion diffusion stability and its preparation method. Background Technology

[0002] The current development of electric aviation, the low-altitude economy, and next-generation high-specific-energy storage systems has created an urgent demand for battery technologies with energy densities ≥450Wh / kg. Lithium metal anodes, due to their ultra-high theoretical specific capacity (3860mAh / g) and the lowest redox potential (-3.04V vs. SHE), are considered one of the ideal choices to overcome the energy density bottleneck of existing lithium-ion batteries. However, the uncontrollable dendrite growth, huge volume expansion, and continuous interfacial side reactions of lithium metal during cycling severely restrict its commercial application.

[0003] Studies have shown that the deposition / stripping behavior of lithium metal is highly dependent on its internal crystal structure. Body-centered cubic (BCC) lithium metal has predominantly (110), (200), and (211) crystal planes, among which the (110) plane exhibits the highest atomic density and the lowest Li+ diffusion barrier, effectively promoting uniform lithium nucleation and deposition while suppressing dendrite growth. Therefore, fabricating lithium metal anodes with a preferred (110) texture is one of the key strategies for addressing the cycle stability problem of lithium metal batteries.

[0004] In existing technologies, to obtain lithium metal with (110) orientation, two main methods are used: "high-temperature long-time annealing" or "melt recrystallization". For example, some studies have obtained single-crystal (110) lithium by isothermal annealing of pre-textured lithium foil at 150~175℃ for 10~30 hours (see CN202511420244.X), or by melt recrystallization at 200℃ (see CN202511610376.9). The above methods generally have the drawbacks of excessively high annealing temperature (≥150℃), excessively long time (several hours to tens of hours), huge energy consumption, and the risk of thermal runaway.

[0005] Severe Plastic Deformation (SPD) technologies (such as Accumulated Rollover (ARB) and Equal Channel Corner Extrusion) can introduce high-density dislocations and stacking faults into metals, storing a large amount of deformation energy. The inventors of this invention discovered that by performing accumulated rollover on lithium metal foil with an initial thickness of about 100 μm in specific passes and reversal angles (e.g., folding it to 200 μm and then cyclically rolling it from 200 to 150 to 100 μm), high-density deformation energy can be pre-introduced at room temperature to form a (200) texture. Subsequently, only annealing at a low temperature of about 60°C for about 20 minutes is required to drive recrystallization using the deformation energy, causing the crystal orientation to rapidly transform into a (110) preferred texture. This process does not require high temperatures close to the melting point of lithium metal, nor does it require long-term heat preservation for several hours, fundamentally solving the technical bottlenecks of high energy consumption, poor safety, and narrow process window in existing technologies. Summary of the Invention

[0006] This invention provides a preferred-oriented lithium metal anode material with high ion diffusion stability for lithium metal battery anodes and its preparation method; aiming to provide a new reference for the design and selection of lithium metal battery anodes.

[0007] This invention is achieved through the following technical solution: First aspect: This invention provides a preferred-oriented lithium metal anode material with high ion diffusion stability. The lithium metal anode material is prepared by introducing deformation energy storage through plastic deformation of lithium metal raw material, followed by low-temperature annealing and recrystallization. The lithium metal anode material has a grain refinement effect inside, and the (110) crystal plane is preferentially oriented.

[0008] The plastic deformation includes one or more of the following: cumulative rolling, equal channel angular extrusion, high-pressure torsion, or reciprocating extrusion.

[0009] The low-temperature annealing temperature is between 40°C and 120°C, and the time is 5 to 60 minutes.

[0010] As one embodiment of the present invention, the plastic deformation treatment is cumulative rolling, specifically including: folding or stacking the lithium metal raw material (such as pure lithium metal strip or pure lithium metal foil) in multiple layers, and then performing multi-pass, reversing rolling; wherein, the cumulative rolling cycle is 3 to 8 times, each cycle includes at least two rolling passes, and the rolling direction is adjusted after each rolling pass, and the thickness of the lithium metal raw material is restored to or close to its initial thickness after a single cycle.

[0011] The second aspect: This invention provides a method for preparing a lithium metal anode material as described in the first aspect, comprising the following steps: S1, Plastic Deformation: The lithium metal raw material (such as pure lithium metal strip or pure lithium metal foil) is subjected to plastic deformation treatment to introduce high-density deformation energy storage and obtain a preform with refined grains and (200) texture; the plastic deformation includes one or more of cumulative rolling, equal channel corner extrusion, high pressure torsion or reciprocating extrusion. S2. Low-temperature annealing and recrystallization: Under a temperature of 40°C to 120°C, the preform obtained in step S1 is annealed for 5 to 60 minutes. The deformation energy storage is used to drive recrystallization, so that the crystal orientation changes from (200) texture to (110) preferred texture, and the lithium metal anode material is obtained.

[0012] The lithium metal anode material of this invention is prepared from lithium metal raw materials (such as pure lithium metal strips or pure lithium metal foils) through a "cumulative rolling-low temperature annealing" process; it can prepare ultrafine-grained lithium metal anodes with a (110) preferred texture over a large area. This method introduces a large amount of uniform deformation energy storage into the lithium strip through repeated turning rolling to obtain a fine-grained preform with a (200) texture; subsequently, short-time annealing is performed at a lower temperature, utilizing deformation energy storage to drive recrystallization, causing the crystal orientation to rapidly transform into a (110) preferred texture. The entire process requires no high temperature, has low energy consumption, and is highly controllable. This method is simple, effective, and suitable for mass production. The prepared lithium metal anode has an orientation distribution with a (110) preferred texture, which helps to reduce the nucleation barrier of lithium deposition and promote uniform deposition. The lithium metal anode is used as a high-energy-density secondary lithium metal battery anode, effectively suppressing dendrite growth and extending battery cycle life. The lithium metal anode material exhibits stable ion diffusion channels and mechanical structural stability during cycling.

[0013] The lithium metal raw material is pure lithium metal strip or pure lithium metal foil.

[0014] In one embodiment of the present invention, the lithium metal raw material is pure lithium metal foil.

[0015] In step S1, the plastic deformation is cumulative rolling, which specifically includes: folding or stacking pure lithium metal foil in multiple layers and then performing multi-pass, reversing rolling; wherein the cumulative rolling cycle is 3 to 8 times, each cycle includes at least two rolling passes, and the rolling direction is adjusted after each rolling pass, and the thickness of the pure lithium metal foil is restored to or close to its initial thickness after a single cycle.

[0016] In step S1, the initial thickness of the pure lithium metal foil is 50~200μm; each cycle includes: rolling the folded lithium metal foil with a thickness of 1.5~3 times the initial thickness in the first pass, reducing the thickness to 1.2~1.8 times the initial thickness; then changing the rolling direction by 60°~120° to perform the second pass rolling, reducing the thickness to the initial thickness, and completing one cycle.

[0017] In one embodiment of the present invention, the initial thickness is 100 μm, and each cycle includes: rolling a lithium metal foil with a folded thickness of 200 μm to 150 μm, and then turning the rolling direction 90° to continue rolling to 100 μm.

[0018] In step S2, the annealing temperature is 40~100℃, and the annealing time is 10~30 minutes. Preferably, annealing is performed at 60℃ for 20 minutes.

[0019] As one implementation, the annealing described in step S2 is carried out in an inert atmosphere, vacuum, or low dew point drying environment.

[0020] Third aspect: A lithium metal electrode sheet, characterized in that it is obtained by cutting, rolling and leveling or surface cleaning of lithium metal anode material prepared by the method described above or as described above.

[0021] The thickness of the lithium metal electrode is 50~100μm.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method provided by the present invention reduces the annealing temperature from 150~300℃ in the prior art to ≤120℃ (preferably 50~100℃) and shortens the annealing time from several hours to tens of hours to 5~60 minutes (preferably 10~30 minutes), which significantly reduces energy consumption and equipment requirements, avoids the melting risk caused by the low melting point of lithium metal (180.5℃), and has the characteristics of wide process window, high safety and good repeatability, laying the foundation for large-scale continuous production.

[0023] (2) The present invention utilizes the high-density deformation energy storage introduced in advance by cumulative rolling as the recrystallization driving force, which can realize the rapid transformation of (200) texture to (110) texture at low temperature without relying on high temperature thermal activation or melting recrystallization, fundamentally solving the dependence of existing technology on high temperature equipment and strict atmosphere protection.

[0024] (3) The ultrafine-grained lithium metal anode with (110) preferred texture prepared by the present invention has the advantages of high grain boundary density of ultrafine grains and low diffusion energy barrier of (110) crystal plane. When used as a lithium metal battery anode, it can effectively promote uniform lithium deposition, suppress dendrite growth, reduce interface impedance, and significantly improve the cycle stability and safety of the battery.

[0025] (4) The method of the present invention is simple and easy to operate. The cumulative rolling is a mature industrial continuous rolling technology, and the low temperature annealing can be integrated with the rolling line to realize continuous production. It has good practical application potential and commercial prospects. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the figures: Figure 1 Characterization of the original lithium metal strip, the preform after cumulative rolling, and the material after low-temperature annealing for 20 min; where A is a SEM image; B is a comparison of X-ray diffraction patterns. Figure 2 A comparison of the tensile stress-strain curves and yield strengths of the original lithium metal strip and the lithium metal strip after cumulative rolling and annealing. Figure 3 X-ray diffraction patterns of different lithium metal anode materials under different annealing times are shown; where A is a comparison of different holding times for ARB-rolled Li; and B is a comparison of different holding times for pure Li. Figure 4 Electrochemical impedance spectroscopy and ionic conductivity after chronoamperometry testing and calculation are shown for different lithium metal anode materials; where A is the impedance spectrum of pure Li before and after testing; B is the chronoamperometry test spectrum of pure Li; C is the impedance spectrum of ARB Li before and after testing; and D is the chronoamperometry test spectrum of ARB Li. Figure 5 The rate performance of the ultrafine-grained lithium metal anode with (110) preferred texture and the control sample at different current densities is shown in the graph. Figure 6 A comparison of the cycle performance of a symmetrical battery assembled with an ultrafine-grained lithium metal anode with a (110) preferred texture and a commercial lithium anode. Detailed Implementation

[0027] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0028] The mechanical property (yield strength) test methods in each embodiment and comparative example are as follows: In a drying room with a dew point below -40°C, the lithium metal foil to be tested was cut into rectangular tensile specimens with dimensions of 900 mm (length) × 20 mm (width). The gauge length was set to 600 mm, and the specimen thickness was the original material thickness of 50 μm. No additional mechanical polishing was performed on the surface to avoid introducing work hardening. The tensile test was conducted on a universal testing machine, and the entire test was completed in a low dew point dry environment. During the test, the two ends of the specimen were clamped in upper and lower clamps respectively, ensuring that the long axis of the specimen was aligned with the tensile direction. The clamping lengths of the upper and lower clamps were 150 mm each. Then, the test was conducted at a constant rate of 10 mm / min until the specimen broke. During the test, the load-displacement curve was recorded in real time, and the strain data within the gauge length was collected by an extensometer.

[0029] Example 1 Lithium metal strips with a purity of 99.9% and an initial thickness of 100 μm were selected as raw materials and cut into 6 cm × 6 cm sheets. In a drying room with a dew point below -40°C, ultrafine-grained lithium metal anode materials with a (110) preferred texture were prepared using the "cumulative rolling-low temperature annealing" process. The specific steps are as follows: (1) Cumulative rolling: The 6cm×6cm×100μm lithium metal strip is folded along the center line to obtain a 6cm×3cm×200μm folded lithium strip; the folded lithium strip is subjected to the first rolling pass, and the thickness is reduced from 200μm to 150μm; then the rolling direction is reversed by 90° for the second rolling pass, and the thickness is reduced from 150μm to 100μm, thus completing one ARB cycle. The above ARB cycle is repeated 5 times. After 5 cumulative rolling passes, the lithium strip thickness is 100μm, and a preform with refined grains and (200) texture is obtained.

[0030] Among them, the ARB cycle refers to a complete process cycle in which lithium metal foil is folded and rolled in multiple passes with reversing direction to restore its thickness to the initial thickness.

[0031] (2) Low-temperature annealing: The preform obtained in step (1) is subjected to low-temperature annealing in a drying room with a dew point below -40°C. The preform is annealed at 60°C for 20 minutes. The deformation energy storage introduced by cumulative rolling is used to drive recrystallization, so that the crystal orientation changes from (200) texture to (110) preferred texture, and the ultrafine crystalline lithium metal anode material with (110) preferred texture is obtained.

[0032] Figure 1Characterization of the original lithium metal strip, the preform after cumulative stacking, and the material after low-temperature annealing for 20 min is shown; where A is a SEM image; B is a comparison of X-ray diffraction patterns. The lithium metal anode material prepared under these conditions has a smooth and bright surface. XRD tests show that the relative diffraction peak intensity of the (200) crystal plane accounts for more than 99%, the texture intensity index of the (110) crystal plane reaches 12.5, and the diffraction peak of the (200) crystal plane almost completely disappears. Figure 1 China B and Figure 3 Mechanical property tests showed that after five cumulative rolling processes, the yield strength of the material was significantly improved compared to the original lithium strip, while maintaining good ductility, confirming a significant grain refinement effect. Figure 2 Electrochemical impedance spectroscopy and chronoamperometry (CA) tests showed that the interfacial impedance of this ultrafine-grained lithium metal anode was significantly reduced compared to the original lithium band, and the ionic conductivity was improved. Figure 4 ).

[0033] This lithium metal anode material is used to assemble Li||Li symmetric cells at a current density of 1 mA·cm⁻¹. -2 The areal capacity density is 1 mAh·cm³. -2 Under these conditions, it can stably cycle for more than 1500 hours ( Figure 6 In rate performance tests at different current densities, the negative electrode performed well in the range of 1–10 mA·cm⁻¹. -2 Maintain low overpotential and stable cycling within the range ( Figure 5 ).

[0034] Example 2 Lithium metal strips with a purity of 99.9% and an initial thickness of 100 μm were selected as raw materials and cut into 6 cm × 6 cm sheets. In a drying room with a dew point below -40°C, ultrafine-grained lithium metal anode materials with a (110) preferred texture were prepared using the "cumulative rolling-low temperature annealing" process. The specific steps are as follows: (1) Cumulative rolling: The 6cm×6cm×100μm lithium metal strip is folded along the center line to obtain a 6cm×3cm×200μm folded lithium strip; the folded lithium strip is subjected to the first rolling pass, and the thickness is reduced from 200μm to 150μm; then the rolling direction is reversed by 90° for the second rolling pass, and the thickness is reduced from 150μm to 100μm, thus completing one ARB cycle. The above ARB cycle is repeated 5 times. After 5 cumulative rolling passes, the lithium strip thickness is 100μm, and a preform with refined grains and (200) texture is obtained.

[0035] (2) Low temperature annealing: The preform obtained in step (1) is annealed at low temperature in a drying room with a dew point below -40°C. It is then annealed at 60°C for 5 minutes. The deformation energy storage introduced by cumulative rolling is used to drive recrystallization, so that the crystal orientation changes from (200) texture to (110) preferred texture.

[0036] Under these conditions, XRD tests show that the relative diffraction peak intensity of the (110) crystal plane accounts for about 60%, while the diffraction peak of the (200) crystal plane is still clearly present. Figure 3 The result indicates that 5 minutes of annealing is insufficient for the pure lithium sample to fully achieve the transformation from (200) texture to (110) texture. This result proves that for the pure lithium system, a 20-minute annealing time is a necessary condition for achieving a complete transformation of the (110) texture.

[0037] Example 3 Lithium metal strips with a purity of 99.9% and an initial thickness of 100 μm were selected as raw materials and cut into 6 cm × 6 cm sheets. In a drying room with a dew point below -40°C, ultrafine-grained lithium metal anode materials with a (110) preferred texture were prepared using the "cumulative rolling-low temperature annealing" process. The specific steps are as follows: (1) Cumulative rolling: The 6cm×6cm×100μm lithium metal strip is folded along the center line to obtain a 6cm×3cm×200μm folded lithium strip; the folded lithium strip is subjected to the first rolling pass, and the thickness is reduced from 200μm to 150μm; then the rolling direction is reversed by 90° for the second rolling pass, and the thickness is reduced from 150μm to 100μm, thus completing one ARB cycle. The above ARB cycle is repeated 5 times. After 5 cumulative rolling passes, the lithium strip thickness is 100μm, and a preform with refined grains and (200) texture is obtained.

[0038] (2) Low temperature annealing: The preform obtained in step (1) is annealed at low temperature in a drying room with a dew point below -40°C. It is then annealed at 60°C for 10 minutes. The deformation energy storage introduced by cumulative rolling is used to drive recrystallization, so that the crystal orientation changes from (200) texture to (110) preferred texture.

[0039] Under these conditions, XRD tests show that the relative diffraction peak intensity of the (110) crystal plane accounts for about 60%, while the diffraction peak of the (200) crystal plane is still clearly present. Figure 3 This indicates that 10 minutes of annealing is insufficient for the pure lithium sample to fully achieve the transformation from (200) texture to (110) texture. This result proves that for the pure lithium system, a 20-minute annealing time is a necessary condition for achieving a complete transformation of the (110) texture.

[0040] Comparative Example 1 The difference from Example 1 is that the low-temperature annealing process in step (2) is omitted, and only the 5 cumulative rolling steps are retained.

[0041] Specifically, a 6cm×6cm×100μm lithium metal strip was subjected to 5 ARB cycles according to step (1) of Example 1, without subsequent low-temperature annealing.

[0042] Under these conditions, XRD tests showed that the material maintained a strong (200) texture, and the (110) diffraction peak was extremely weak, indicating that without low-temperature annealing, the deformation energy introduced by the cumulative rolling was insufficient to drive the transformation of the (200) texture to the (110) texture. Figure 1 This result demonstrates that low-temperature annealing is a necessary step to achieve the transformation of (200) texture to (110) texture and optimize interface dynamics.

[0043] Comparative Example 2 The difference from Example 1 is that the cumulative rolling process in step (1) is omitted, and the original 100μm lithium metal strip is directly annealed at 60°C for 5 minutes.

[0044] Under these conditions, XRD tests showed that the crystal orientation of the material did not change significantly, and it still maintained the original polycrystalline random orientation state. The (110), (200) and (211) diffraction peaks were present simultaneously, and no preferred texture was formed. Figure 3 This result demonstrates that without the introduction of high-density deformation energy storage through cumulative rolling, low-temperature short-time annealing alone cannot achieve the (110) texture transformation.

[0045] Comparative Example 3 The difference from Example 2 is that the cumulative rolling process in step (1) is omitted, and the original 100μm lithium metal strip is directly annealed at 60°C for 10 minutes.

[0046] Under these conditions, XRD tests show that the material retains its original polycrystalline random orientation state, with (110), (200), and (211) diffraction peaks present simultaneously, and no preferred texture formed. Figure 3 This result further demonstrates that the deformation energy storage introduced by cumulative rolling is a prerequisite for achieving the (110) texture transformation during low-temperature annealing.

[0047] Comparative Example 4 The difference from Example 3 is that the cumulative rolling process in step (1) is omitted, and the original 100μm lithium metal strip is directly annealed at 60°C for 20 minutes.

[0048] Under these conditions, XRD tests show that the material retains its original polycrystalline random orientation state, with (110), (200), and (211) diffraction peaks present simultaneously, and no preferred texture formed. Figure 3This result indicates that even with an extended annealing time of 20 minutes, the original lithium strip without deformation energy storage cannot undergo a texture transformation at 60°C.

[0049] Comparative Example 5 The difference from Example 3 is that the cumulative rolling process in step (1) is omitted, and the original 100μm lithium metal strip is directly annealed at 60°C for 40 minutes.

[0050] Under these conditions, XRD tests showed that the crystal orientation of the material remained largely unchanged, with (110), (200), and (211) diffraction peaks present simultaneously, and no (110) preferred texture was formed. Figure 3 This result confirms that even if the original lithium metal strip is annealed at 60°C for 40 minutes, it cannot achieve the transformation from (200) texture to (110) texture due to the lack of deformation energy storage to drive recrystallization, thus demonstrating the key role of cumulative rolling in the method of this invention.

[0051] In summary, this invention discloses an ultrafine-grained lithium metal anode with a preferred texture and its preparation: A large-area ultrafine-grained lithium metal anode with a (110) preferred texture can be prepared using a "cumulative rolling-low-temperature annealing process". This method introduces a large amount of uniform deformation energy storage into the lithium strip through repeated turning rolling, obtaining a fine-grained preform with a (200) texture; subsequently, short-time annealing is performed at a lower temperature, utilizing deformation energy storage to drive recrystallization, causing the crystal orientation to rapidly transform into a (110) preferred texture. The entire process requires no high temperature, has low energy consumption, and is highly controllable. This method is simple, effective, and suitable for mass production. The prepared lithium metal anode has an orientation distribution with a (110) preferred texture, which helps to reduce the nucleation barrier of lithium deposition and promote uniform deposition. The lithium metal anode is used as a high-energy-density secondary lithium metal battery anode, effectively suppressing dendrite growth and extending battery cycle life.

[0052] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that these are merely illustrative examples, and any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A preferred-oriented lithium metal anode material with high ion diffusion stability, characterized in that, The lithium metal anode material is prepared by introducing deformation energy storage through plastic deformation of lithium metal raw materials, followed by low-temperature annealing and recrystallization; wherein, the lithium metal anode material has a grain refinement effect inside, and the (110) crystal plane is preferentially oriented.

2. The lithium metal anode material according to claim 1, characterized in that, The plastic deformation includes one or more of the following: cumulative rolling, equal channel corner extrusion, high pressure torsion, or reciprocating extrusion; And / or, the low-temperature annealing temperature is between 40°C and 120°C, and the time is 5 to 60 minutes.

3. A method for preparing a lithium metal anode material as described in claim 1 or 2, characterized in that, The steps include the following: S1, Plastic Deformation: The lithium metal raw material is subjected to plastic deformation treatment to introduce high-density deformation energy storage and obtain a preform with refined grains and (200) texture; the plastic deformation includes one or more of cumulative rolling, equal channel corner extrusion, high pressure torsion or reciprocating extrusion. S2. Low-temperature annealing and recrystallization: Under a temperature of 40°C to 120°C, the preform obtained in step S1 is annealed for 5 to 60 minutes. The deformation energy storage is used to drive recrystallization, so that the crystal orientation changes from (200) texture to (110) preferred texture, and the lithium metal anode material is obtained.

4. The preparation method according to claim 3, characterized in that, The lithium metal raw material is lithium metal strip or lithium metal foil.

5. The preparation method according to claim 3, characterized in that, In step S1, the plastic deformation is cumulative rolling, which specifically includes: folding or stacking lithium metal material in multiple layers and then performing multi-pass, reversing rolling; wherein the cumulative rolling cycle is 3 to 8 times, each cycle includes at least two rolling passes, and the rolling direction is adjusted after each rolling pass, and the thickness of the lithium metal material is restored to or close to its initial thickness after a single cycle.

6. The preparation method according to claim 5, characterized in that, In step S1, each cycle includes: rolling a folded lithium metal material with a thickness of 1.5 to 3 times the initial thickness in the first pass, reducing the thickness to 1.2 to 1.8 times the initial thickness; then changing the rolling direction by 60° to 120° to perform a second pass of rolling, reducing the thickness to the initial thickness, thus completing one cycle.

7. The method according to claim 5, characterized in that, The initial thickness is 100 μm, and each cycle includes: rolling the folded lithium metal material with a thickness of 200 μm to 150 μm, and then turning the rolling direction 90° to continue rolling to 100 μm.

8. The method according to claim 3, characterized in that, The annealing described in step S2 is carried out in an inert atmosphere, vacuum, or low dew point drying environment.

9. A lithium metal electrode, characterized in that, The lithium metal anode material prepared by the lithium metal anode material according to claim 1 or 2 or by the preparation method according to any one of claims 3-8 is obtained by cutting, rolling and leveling or surface cleaning treatment, and has a thickness of 50~100μm.

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