Three-dimensional vertical porous lithium-tin alloy negative electrode, preparation method and battery

Abstract

The application discloses a kind of three-dimensional vertical porous lithium-tin alloy negative electrode, its preparation method and battery.The negative electrode is provided with periodic three-dimensional vertical hole array on the surface of lithium metal matrix side, and lithium-tin alloy layer is formed on the surface of the lithium metal matrix.The side length of the three-dimensional vertical hole is 50 μm, interval 100 μm, depth 20 μm, and is perpendicular cuboid shape.When preparing, first, three-dimensional vertical porous lithium metal is obtained by hard resin mold imprinting, then tin atoms are deposited on the surface and inner wall of hole by magnetron sputtering technology, and tin and lithium spontaneously react to form alloy layer containing Li-Sn intermetallic compound.The application significantly reduces local current density, guides lithium uniform deposition, inhibits lithium dendrite growth and buffers volume expansion through the synergistic effect of three-dimensional hole structure and lithium-tin alloy layer, thereby greatly improving the cycle stability and rate performance of lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery material technology, specifically relating to a three-dimensional vertical porous lithium-tin alloy anode, its preparation method, and a lithium metal battery containing the anode. Background Technology

[0002] Lithium metal is widely recognized as the ultimate anode material for next-generation high-energy-density batteries (such as lithium-sulfur batteries, lithium-air batteries, and solid-state batteries) due to its extremely high theoretical specific capacity (3860 mAh / g) and the lowest redox potential (-3.04 V vs. SHE). However, the commercial application of lithium metal anodes has long been constrained by two fundamental problems: first, the uneven deposition of lithium ions during charging and discharging leads to the growth of lithium dendrites, which may puncture the separator and cause short circuits and safety accidents; second, the huge volume expansion caused by the "hostless" nature of lithium metal causes the solid electrolyte interface film to repeatedly rupture and regenerate, continuously consuming electrolyte and active lithium, resulting in low coulombic efficiency and rapid capacity decay.

[0003] To suppress lithium dendrite formation and mitigate volume expansion, researchers have proposed various strategies, among which constructing a three-dimensional porous structure is an effective approach. The applicant previously filed a patent for "A Three-Dimensional Vertical Porous Lithium Metal Anode, Preparation Method, and Battery" (2025120270035, hereinafter referred to as "Prior Document 1"). This patent significantly improves the cycle stability of the lithium metal anode by imprinting a periodic array of vertical holes onto the lithium metal surface. However, Prior Document 1 only involves a porous structure of pure lithium metal, and there is still room for improvement in guiding uniform lithium nucleation and further reducing local current density.

[0004] On the other hand, introducing a lithiophilic alloy layer (such as a lithium-tin alloy) onto the lithium metal surface has also been shown to reduce nucleation overpotential and induce uniform deposition. For example, Wuhan University of Technology disclosed a three-dimensional composite lithium metal anode with a multifunctional interface layer (CN114512637B, hereinafter referred to as "Comparative Document 2"), which uses a high-temperature molten lithium method to construct a lithium-tin alloy + lithium fluoride interface layer on a three-dimensional conductive substrate; Sun Yongming's research group at Huazhong University of Science and Technology magnetron sputtered a tin layer on copper foil and generated a Li-Sn alloy interface in situ through electrochemical cycling (Energy Storage Materials, 2020); Ji Xiaobo et al. at Central South University modified a tin layer on a three-dimensional porous brass current collector using a chemical plating method (Energy Storage Materials, 2020). However, these schemes either involve complex processes such as high-temperature melting and wet chemical plating, or the alloy layer is formed on a non-lithium substrate, failing to directly and organically combine the three-dimensional porous structure with the alloy layer of the lithium metal itself.

[0005] Therefore, there is an urgent need for a composite anode structure that can utilize the volume buffering and current density dispersion advantages of a three-dimensional porous structure, as well as the lithium-affinity nucleation and mechanical reinforcement effects of the alloy layer. Furthermore, the preparation process should be simple, environmentally friendly, and easy to scale up. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as high nucleation overpotential and insufficient surface lithiophilicity of pure porous lithium metal anodes, as well as the complex preparation process (high temperature, wet process) of existing composite anodes. This invention provides a three-dimensional vertical porous lithium-tin alloy anode and its preparation method. Through the dual synergistic effect of the three-dimensional vertical pores and the surface lithium-tin alloy layer, the cycle stability, rate performance and safety of lithium metal batteries are significantly improved.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a three-dimensional vertical porous lithium-tin alloy negative electrode, characterized in that a periodic three-dimensional vertical hole array is provided on one side surface of a lithium metal substrate, and a lithium-tin alloy layer is formed on the surface of the lithium metal substrate.

[0008] Preferably, the cross-sectional shape of the three-dimensional vertical hole is square, and the hole shape is a vertical cuboid. More preferably, the side length of the three-dimensional vertical hole is 50 μm, the interval between adjacent holes is 100 μm, and the hole depth is 20 μm.

[0009] Preferably, the lithium-tin alloy layer contains a Li-Sn intermetallic compound (such as Li). 22 Sn5, Li7Sn3, Li 13 Sn5, etc.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned three-dimensional vertical porous lithium-tin alloy anode, comprising the following steps: S1: Provides customized molds with a surface array of protrusions; S2: Align one side of the protrusion array of the mold with the surface of the lithium metal foil; S3: Apply pressure to the mold to press the mold protrusion into the lithium metal foil, forming a three-dimensional vertical hole array on the surface of the lithium metal foil; S4: Separate the formed lithium metal foil from the mold to obtain a three-dimensional vertical porous lithium metal foil; S5: The three-dimensional vertical porous lithium metal foil is placed in a vacuum chamber, and magnetron sputtering technology is used to sputter and deposit tin atoms on the surface and inner wall of the holes of the three-dimensional vertical porous lithium metal foil with a tin target as the sputtering source, so that tin and lithium metal spontaneously react to form a lithium-tin alloy layer, and a three-dimensional vertical porous lithium-tin alloy negative electrode is obtained.

[0011] Preferably, the mold is made of a rigid resin (such as polycarbonate or polymethyl methacrylate). The pressure applied in step S3 is 70-90 N, and the holding time is 20-40 seconds; more preferably, it is 80 N, and the holding time is 30 seconds.

[0012] Preferably, in step S5, magnetron sputtering is performed under an argon atmosphere with a vacuum level of 1×10⁻⁶. -3 The sputtering conditions were: Pa, current 290mA, voltage 350V, power 100W, gas flow rate 10sccm, and sputtering time 180s.

[0013] Preferably, during the magnetron sputtering process, the tin atoms sputtered onto the lithium metal surface undergo a spontaneous alloying reaction with the lithium metal to form a lithium-tin alloy layer containing Li-Sn intermetallic compounds.

[0014] Thirdly, the present invention provides the application of the above-mentioned three-dimensional vertical porous lithium-tin alloy anode in lithium metal batteries.

[0015] Fourthly, the present invention provides a lithium metal battery, comprising a positive electrode, a separator, and an electrolyte, characterized in that the negative electrode of the lithium metal battery is the aforementioned three-dimensional vertical porous lithium-tin alloy negative electrode.

[0016] Beneficial effects Compared with the prior art, the present invention has the following significant advantages: Dual synergistic effects: The three-dimensional vertical aperture array provides a fast ion / electron transport channel, significantly reducing local current density and guiding lithium preferentially to deposit inside the apertures; the surface lithium-tin alloy layer provides a large number of lithiophilic sites, reducing nucleation overpotential, while forming a rigid framework to support and suppress volume expansion. The synergistic effect of these two factors greatly improves cycle stability and rate performance.

[0017] The process is simple and environmentally friendly: it combines imprinting (room temperature, solvent-free) with magnetron sputtering (vacuum dry method), avoiding the oxidation risk and high energy consumption associated with high-temperature molten lithium (>180℃), and also avoiding waste liquid pollution from wet processes such as chemical plating. This process is highly compatible with existing lithium foil production lines and roll-to-roll coating equipment, and is easy to scale up.

[0018] Structural parameter optimization: After systematic screening, the optimal combination of pore parameters—50 μm side length, 100 μm spacing, and 20 μm depth—was determined to achieve the best balance between increased specific surface area, ion transport efficiency, and structural mechanical strength. Combined with an alloy layer formed by 180s magnetron sputtering of tin, optimal electrochemical performance can be achieved.

[0019] Excellent electrochemical performance: Experiments show that the three-dimensional vertical porous lithium-tin alloy anode of this invention (50 μm pores, sputtered for 180 s) retains a specific capacity of 155.55 mAh / g and a capacity retention of 85.12% after 100 cycles at 1C rate; significantly better than pure porous lithium anodes (76.63%) and flat lithium anodes (69.24%). Meanwhile, the symmetrical battery cycle life exceeds 450 hours, and volume expansion is significantly suppressed. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the three-dimensional vertical porous lithium-tin alloy negative electrode in Embodiment 1 of the present invention.

[0021] Figure 2 The image shows the EDS spectrum of the three-dimensional vertical porous lithium-tin alloy anode in Embodiment 1 of the present invention, indicating that the Sn element is uniformly distributed on the surface, at the edge of the pores, and inside the pores.

[0022] Figure 3 The following is a schematic diagram of the preparation method of the present invention: (a) providing a mold and lithium foil; (b) aligning and overlapping; (c) applying pressure to imprint; (d) separating to obtain porous lithium; (e) magnetron sputtering to deposit tin to form an alloy layer.

[0023] Figure 4 SEM image of the Sn deposition thickness on a stainless steel substrate (corresponding to sputtering time 180 s).

[0024] Figure 5 This is a SEM image of the thickness of the Li-Sn alloy layer formed on a lithium substrate.

[0025] Figure 6 This is a comparison chart of the cycling performance of Example 1 (50 μm hole Li@Sn180s), Comparative Example 1 (50 μm hole Li pure porous), and flat lithium foil (Bare Li) at 1C rate.

[0026] Figure 7 This is a comparison of the lithium deposition morphology observed under an in-situ optical microscope between Example 1 and Bare Li foil (0.5 mA / cm² deposition capacity). Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0028] Before providing a further detailed description of the present invention, the nouns and terms used in the embodiments of the present invention will be explained, and the nouns and terms used in the embodiments of the present invention shall be interpreted as follows.

[0029] Example 1: Preparation of a three-dimensional vertical porous lithium-tin alloy anode (50 μm pores, magnetron sputtering for 180 s) Step 1: Mold Preparation The raised array is machined on a rigid polycarbonate (PC) sheet using precision machining technology. Each raised element is a regular square prism with a base side length of 50 μm and a height of 20 μm, and the center-to-center distance between adjacent raised elements is 150 μm (i.e., the interval between raised elements is 100 μm). The mold surface must be smooth and burr-free.

[0030] Step 2: Imprinting to create holes like Figure 3 As shown in (a)-(b), in an argon-protected glove box (water and oxygen content <0.1 ppm), a 450 μm thick, clean commercial lithium metal foil was placed flat on a flat base. The raised side of the mold was aligned with the surface of the lithium foil. Then, as follows... Figure 3 As shown in (c), an imprinting device equipped with a pressure sensor is used to apply a pressure of 80N vertically downward and hold the pressure for 30 seconds, causing the mold protrusion to press into the lithium metal foil to form a three-dimensional vertical hole.

[0031] Step 3: Demolding After the pressure holding period, slowly and vertically lift the mold, using precision tweezers to assist in separation, to obtain the desired result. Figure 3 (d) shows a three-dimensional vertical porous lithium metal foil. This negative electrode has a three-dimensional vertical cubic array of holes with a side length of 50 μm, a depth of 20 μm, and a spacing of 100 μm (its structure is shown in the diagram). Figure 1 As shown, a lithium metal substrate 1 has periodically arranged three-dimensional vertical holes 2 on one side surface. The holes have a square cross-section and a vertical cuboid shape. Under an optical microscope, the holes are observed to be intact and have clear edges.

[0032] Step 4: Magnetron sputtering tin plating like Figure 3 As shown in (e), the aforementioned three-dimensional vertical porous lithium metal foil was placed in a magnetron sputtering vacuum chamber, with high-purity tin (99.99% purity) as the target material. The vacuum was evacuated to 1×10⁻⁶. -3 At Pa, argon gas is introduced (gas flow rate 10 sccm), and the process parameters are adjusted as follows: current 290mA, voltage 350V, power 100W. Sputtering is started, and the sputtering time is 180 seconds. During this process, tin atoms are sputtered and deposited onto the surface of the lithium foil and the inner walls of the pores, immediately undergoing a spontaneous alloying reaction with lithium to form a gray-black lithium-tin alloy layer (e.g., ...). Figure 1 As shown in the middle alloy layer 3), a three-dimensional vertical porous lithium-tin alloy anode (denoted as 50μm hole Li@Sn180s) is obtained.

[0033] Step 5: Characterization The above samples were subjected to SEM and EDS analysis, and the results are as follows: Figure 1 and 2 As shown in the figure. EDS spectra indicate that Sn was successfully introduced into the porous lithium metal anode surface, pore edges, and pore interiors, exhibiting excellent uniformity. SEM images show that the surface morphology of the porous lithium metal anode changed, with Sn undergoing a self-alloying reaction with the surface lithium metal to form Li-Sn intermetallic compounds (such as Li). 22 Sn5, Li7Sn3, Li 13 Sn5, etc. Comparative Example 1 (Pure Three-Dimensional Vertical Porous Lithium Anode) Following the method in Prior Art Document 1 (Application No. 2025120270035), a three-dimensional vertical porous lithium anode with the same pore parameters as in Example 1 (50 μm side length, 100 μm spacing, 20 μm depth) but without magnetron sputtering tin plating was prepared and denoted as 50 μm hole Li (without alloy layer).

[0034] Comparative Example 2 (Smooth lithium foil with tin alloy plating) A flat lithium foil (Bare Li) was plated with tin under the same magnetron sputtering conditions (180 s) as in Example 1 to obtain a negative electrode with only a lithium-tin alloy layer and no three-dimensional pores, denoted as Bare Li-Sn180s.

[0035] Comparative Example 3 (flat lithium foil, untreated) Commercially available flat lithium foil is used directly, denoted as Bare Li.

[0036] Electrochemical performance testing The four types of negative electrodes were assembled into CR2032 coin cells. The positive electrode used a high-nickel ternary material (NMC83), and the electrolyte was 1M LiPF6 in EC / DEC (1:1). Test conditions: room temperature, voltage range 2.7–4.3 V.

[0037] 1C cycle performance: Results are as follows Figure 6 As shown in Table 1, the anode of Example 1 exhibited a specific capacity of 155.55 mAh / g after 100 cycles at 1C, with a capacity retention of 85.12%. Comparative Example 1 (pure porous lithium) showed a specific capacity of 139.7 mAh / g after 100 cycles, with a capacity retention of 76.63%. Comparative Example 2 (planar lithium + alloy layer) showed a specific capacity of 136.0 mAh / g after 100 cycles, with a capacity retention of 71.64%. Comparative Example 3 (planar lithium) showed a specific capacity of 129.9 mAh / g after 100 cycles, with a capacity retention of 69.24%. It is evident that the anode of this invention, possessing both a porous structure and an alloy layer, exhibits optimal performance, significantly exceeding the linear expectation of the sum of the individual structures, thus confirming the synergistic effect of "1+1>2".

[0038] Table 1. Performance comparison of different negative electrodes after 100 cycles at 1C rate. Symmetrical battery cycling: The negative electrodes of Example 1 and Comparative Example 1 were assembled with lithium sheets to form Li||Li symmetric batteries, respectively, at 1 mA / cm². 2 1 mAh / cm 2 Tests were conducted under the specified conditions. The overpotential of Example 1 stabilized at approximately 20 mV and remained stable for over 450 hours of cycling. The overpotential of Comparative Example 1 began to increase after 300 hours of cycling and failed around 400 hours. The overpotential of Comparative Example 2 was initially low but increased rapidly after 300 hours. This indicates that the alloy layer and the pores synergistically stabilized the interface.

[0039] In-situ optical microscopy characterization: such as Figure 7 As shown, Example 1 was performed at 0.5 mA / cm 2 Uniform deposition and a smooth surface are achieved in the lower-permeability lithium foil; however, the smooth lithium foil (Bare Li) exhibits a large number of lithium dendrites, leading to non-uniform deposition. This indicates that the microporous structure provides a host, guiding lithium deposition into the pores, while the Li-Sn alloy layer on the surface reduces the nucleation overpotential, enabling ordered lithium deposition.

[0040] Effect of different sputtering times: Samples with sputtering times of 90 s and 270 s (with the same pore parameters) were prepared additionally. Their performance after 100 cycles at 1C was 144.86 mAh / g (77.36%) and 144.06 mAh / g (79.22%), respectively, both lower than that of the 180 s sample, indicating that 180 s is the optimal sputtering time.

[0041] The above data fully demonstrates that the present invention achieves electrochemical performance significantly superior to that of pure porous lithium anodes or anodes with a single alloy layer through the dual synergy of a three-dimensional vertical porous structure and a lithium-tin alloy layer.

[0042] Example 2: Comparison of different hole sizes Samples with pore side lengths of 15 μm, 50 μm, and 150 μm (interval and depth adjusted proportionally, maintaining interval / side length = 2 and depth / side length = 0.4) were prepared using the same method as in Example 1, and all samples were sputtered for 180 s. 1C cycle performance was tested. The 50 μm sample showed the highest capacity retention (85.12%), while the 15 μm sample, due to its small pore size, was prone to clogging, resulting in a retention rate of approximately 78%. The 150 μm sample, with its larger pore size leading to decreased mechanical strength, had a retention rate of approximately 80%. Therefore, 50 μm is the preferred parameter.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A three-dimensional vertical porous lithium-tin alloy anode, characterized in that, A periodic three-dimensional vertical hole array is provided on one side of the lithium metal substrate, and a lithium-tin alloy layer is formed on the surface of the lithium metal substrate.

2. The three-dimensional vertical porous lithium-tin alloy negative electrode according to claim 1, characterized in that, The cross-sectional shape of the three-dimensional vertical hole is square, and the hole shape is a vertical cuboid.

3. The three-dimensional vertical porous lithium-tin alloy negative electrode according to claim 2, characterized in that, The three-dimensional vertical hole has a side length of 50 μm, a spacing of 100 μm between adjacent holes, and a hole depth of 20 μm.

4. The three-dimensional vertical porous lithium-tin alloy negative electrode according to any one of claims 1 to 3, characterized in that, The lithium-tin alloy layer contains Li-Sn intermetallic compounds.

5. A method for preparing the three-dimensional vertical porous lithium-tin alloy anode according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Provides customized molds with a surface array of protrusions; S2: Align one side of the protrusion array of the mold with the surface of the lithium metal foil; S3: Apply pressure to the mold to press the mold protrusion into the lithium metal foil, forming a three-dimensional vertical hole array on the surface of the lithium metal foil; S4: Separate the formed lithium metal foil from the mold to obtain a three-dimensional vertical porous lithium metal foil; S5: The three-dimensional vertical porous lithium metal foil is placed in a vacuum chamber, and magnetron sputtering technology is used to sputter and deposit tin atoms on the surface and inner wall of the holes of the three-dimensional vertical porous lithium metal foil with a tin target as the sputtering source, so that tin and lithium metal spontaneously react to form a lithium-tin alloy layer, and a three-dimensional vertical porous lithium-tin alloy negative electrode is obtained.

6. The preparation method according to claim 5, characterized in that, The mold is made of hard resin; the pressure applied in step S3 is 80N, and the holding time is 30s.

7. The preparation method according to claim 5, characterized in that, In step S5, the magnetron sputtering is performed under an argon atmosphere with a vacuum level of 1×10⁻⁶. -3 The sputtering conditions were: Pa, current 290mA, voltage 350V, power 100W, gas flow rate 10sccm, and sputtering time 180s.

8. The preparation method according to claim 5, characterized in that, During the magnetron sputtering process, tin atoms sputtered onto the lithium metal surface undergo a spontaneous alloying reaction with the lithium metal to form a lithium-tin alloy layer containing Li-Sn intermetallic compounds.

9. The application of the three-dimensional vertical porous lithium-tin alloy anode according to any one of claims 1 to 4 in lithium metal batteries.

10. A lithium metal battery, comprising a positive electrode, a separator, and an electrolyte, characterized in that, The negative electrode of the lithium metal battery is a three-dimensional vertical porous lithium-tin alloy negative electrode according to any one of claims 1 to 4.

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