An alloy material and a preparation method thereof, a battery negative electrode and a preparation method thereof, and a lithium ion battery

Abstract

This invention provides an alloy material and its preparation method, a battery negative electrode and its preparation method, and a lithium-ion battery. It belongs to the field of lithium metal battery technology. The alloy material, by mass percentage, comprises: 70-90% lithium, 7-29% magnesium, 0.5-3% aluminum, and 0.5%-20% tin. The preparation method involves heating metallic lithium to a molten state to obtain molten lithium; adding a lithium-magnesium alloy and an aluminum-tin master alloy to the molten lithium, stirring to obtain an alloy melt, wherein the mass ratio of Al to Sn in the aluminum-tin master alloy is (0.5-3):1; and cooling the alloy melt to obtain the alloy material. This invention solves the problems of electrode structure collapse, uncontrolled lithium dendrite growth, severe high-density tin segregation, and uneven composition caused by large volume changes during cycling in existing materials.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, specifically to an alloy material and its preparation method, a battery negative electrode containing the alloy material and its preparation method, and a lithium-ion battery containing the battery negative electrode. Background Technology

[0002] With the ever-increasing demand for energy density from portable electronic devices, electric vehicles, and large-scale energy storage systems, traditional graphite anode materials have become a key bottleneck restricting further improvements in lithium-ion battery performance. Lithium metal, due to its extremely high theoretical specific capacity and low electrochemical potential, is considered the most promising next-generation anode material.

[0003] However, lithium metal anodes face severe challenges in practical applications. First, the continuous side reactions between metallic lithium and organic electrolytes form an unstable and ever-thickening solid electrolyte interphase (SEI) film, leading to irreversible consumption of active lithium and electrolyte. Second, the repeated deposition and dissolution of lithium during charge-discharge cycles cause huge volume changes (usually exceeding 300%), resulting in repeated rupture and reconstruction of the SEI film and accelerating performance degradation. More seriously, the uneven deposition of lithium ions on the electrode surface can easily induce the growth of lithium dendrites, which may pierce the separator and cause internal short circuits in the battery, posing serious safety hazards.

[0004] Therefore, there is an urgent need to develop a highly stable anode material that can suppress volume expansion, guide uniform lithium deposition, and possess good cycle stability. Summary of the Invention

[0005] This invention provides a highly stable alloy material and its preparation method, aiming to solve the technical problems of existing lithium alloy anode materials being unstable, prone to electrode structure collapse due to huge volume changes during cycling, uncontrollable growth of lithium dendrites, severe segregation of high-density tin, and uneven composition.

[0006] The specific technical solution of the present invention is as follows: In a first aspect, the present invention provides an alloy material comprising, by mass percentage: 70-90% lithium, 7-29% magnesium, 0.5-3% aluminum, and 0.5-20% tin.

[0007] Optionally, the material contains Li 22 A lithium-magnesium solid solution formed by Sn5 phase, Li9Al4 phase, and Mg dissolved in a Li lattice; the Li 22 The Sn5 phase is distributed in a continuous network, while the Li9Al4 phase is distributed in a nanoscale dispersed manner.

[0008] Optionally, the material is composed of the following components: 70-90% lithium, 7-29% magnesium, 0.5-3% aluminum, and 0.5%-20% tin, with the sum of the mass percentages of each component being 100%.

[0009] Optionally, the material is composed of the following components: 80-90% lithium, 9-18% magnesium, 0.5-1.5% aluminum, and 0.5-1% tin, with the sum of the mass percentages of each component being 100%.

[0010] Optionally, the Li 22 The mass fraction of the Sn5 phase is 0.63%~1.26%, and the mass fraction of the Li9Al4 phase is 0.79%~2.37%.

[0011] Secondly, the present invention also provides a method for preparing the above-mentioned alloy material, comprising the following steps: Molten lithium is obtained by heating metallic lithium to a molten state. A lithium-magnesium alloy and an aluminum-tin master alloy are added to molten lithium and stirred to obtain an alloy melt. The mass ratio of Al to Sn in the aluminum-tin master alloy is (0.5~3):1. The alloy melt is cooled to obtain the alloy material.

[0012] Optionally, in the aluminum-tin master alloy, tin is dispersed in the aluminum matrix at the nanoscale.

[0013] Optionally, the stirring rate is 150-300 r / min, and the stirring time is 1-5 hours.

[0014] Optionally, the cooling rate is not less than 50°C / s.

[0015] Optionally, the cooling rate is 60~80℃ / s.

[0016] Thirdly, the present invention also provides a method for preparing a battery negative electrode, comprising the following steps: Alloy materials were prepared using the above method; The alloy material is heat-treated in a vacuum environment; The heat-treated alloy material is rolled into a thin sheet; The thin material is punched into a battery negative electrode.

[0017] Optionally, the heat treatment temperature is 120–160°C and the time is 10–20 hours.

[0018] Fourthly, the present invention also provides a battery negative electrode, which is prepared by the above-described preparation method.

[0019] Fifthly, the present invention also provides a battery negative electrode comprising the aforementioned alloy material.

[0020] In a sixth aspect, the present invention also provides a lithium-ion battery comprising the above-described negative electrode.

[0021] Compared with the prior art, the advantages of the present invention are as follows: 1. The alloy material provided by this invention, through optimization of element composition and ratio, forms a multiphase composite structure with complementary functions, comprising a continuous network distribution of Li 22 Sn5 phase and nanoscale dispersed Li9Al4 phase, with Mg dissolved in the Li lattice in the material, Li 22 The Sn5 phase, acting as a lithiophilic nucleation and transport framework with high ionic / electronic conductivity, significantly reduces the overpotential of lithium deposition and guides uniform lithium deposition, fundamentally suppressing lithium dendrite growth. Simultaneously, the solid solution network formed by Mg dissolved in the Li lattice provides buffering properties. The nanoscale dispersed Li9Al4 phase ensures good material uniformity, a balance between active lithium sites and mechanical strength, and stable and excellent performance. This multiphase composite structure contributes to the overall stability of the material's performance. Its application in batteries effectively enhances the electrochemical performance of the batteries, demonstrating significant advantages. This solution addresses the problems of electrode structure collapse, uncontrolled lithium dendrite growth, severe high-density tin segregation, and compositional inhomogeneity caused by large volume changes during cycling.

[0022] 2. The method for preparing an alloy material provided by the present invention achieves precise control of each element by adjusting and controlling the ratio of lithium, magnesium, aluminum, and tin, and simultaneously controlling the mass ratio of Al to Sn in the aluminum-tin master alloy, thereby forming a multiphase composite structure with complementary functions in situ in the alloy; in addition, the process synergy of element control, strong mechanical stirring, and rapid cooling greatly reduces the segregation of the high-density component Sn element; thus achieving a high-stability alloy material.

[0023] 3. The present invention has a mature process and a compact flow, and has the potential for large-scale production: Based on the traditional smelting, casting and rolling process, it does not require complex equipment or lengthy processes; through the synergistic effect of three processes—intermediate alloy ratio design, stirring rate control and cooling rate optimization—it solves the core pain point of uniformity control in large-scale production, and the prepared materials have a high yield and are easy to achieve stable and efficient industrial production.

[0024] 4. The method for preparing a battery negative electrode provided by the present invention is simple, the alloy material used has excellent performance, and the prepared negative electrode has stable and excellent performance, and has a wide range of applications.

[0025] 5. The battery negative electrode and the lithium-ion battery provided by this invention have excellent electrochemical performance and broad application prospects. Attached Figure Description

[0026] Figure 1This is the X-ray diffraction pattern of the alloy prepared in Example 1 of this invention.

[0027] Figure 2 Symmetrical cells assembled using the alloy negative electrodes prepared in Examples 1-5 and Comparative Examples 1-9 of this invention are used at 4 mA·cm⁻¹ -2 Comparison of cycle life under current density.

[0028] Figure 3 The images show the in-situ optical microscope surface morphology comparisons of Example 1, Comparative Example 1, Comparative Example 6, and Comparative Example 7 before, after 300 hours of cycling, and after the cycling. (a) is Example 1, (b) is Comparative Example 1, (c, d) are Comparative Example 6, and (e, f) are Comparative Example 7.

[0029] Figure 4 The image shows the TOFSIMS (Time-of-Flight Secondary Ion Mass Spectrometry) single-element distribution and oxide ion cluster distribution of the lithium alloy anode sample in Example 1.

[0030] Figure 5 The image shows the TOFSIMS single-element distribution and oxide ion cluster distribution of the upper sample of the lithium alloy anode in Comparative Example 7.

[0031] Figure 6 This is a TOFSIMS comparison diagram of various metal solid solution clusters and mass spectra of the lithium alloy anode material in Example 1.

[0032] Figure 7 The image shows a comparison of TOF-SIMS and different selected area mass spectrometry of the lithium alloy anode material in Example 1.

[0033] Figure 8 The image shows the EBSD (electron backscattering diffraction) results of the lithium alloy anode material in Example 1. Specific Implementation

[0035] In a first aspect, embodiments of the present invention provide an alloy material comprising, by mass percentage: 70-90% lithium, 7-29% magnesium, 0.5-3% aluminum, and 0.5-20% tin.

[0036] In some embodiments of the present invention, the material contains Li. 22 A lithium-magnesium solid solution formed by Sn5 phase, Li9Al4 phase, and Mg dissolved in a Li lattice; the Li 22 The Sn5 phase is distributed in a continuous network, while the Li9Al4 phase is distributed in a nanoscale dispersed manner.

[0037] In some embodiments of the present invention, the material is composed of the following components: 70-90% lithium, 7-29% magnesium, 0.5-3% aluminum, and 0.5%-20% tin, with the sum of the mass percentages of each component being 100%.

[0038] In some embodiments of the present invention, more preferably, the material is composed of the following components: 80-90% lithium, 9-18% magnesium, 0.5-1.5% aluminum, and 0.5-1% tin, with the sum of the mass percentages of each component being 100%.

[0039] In some embodiments of the present invention, the Li 22 The mass fraction of the Sn5 phase is 0.63%~1.26%, and the mass fraction of the Li9Al4 phase is 0.79%~2.37%.

[0040] It is understood that this invention, through optimizing the elemental composition and ratio, forms a multiphase composite structure with complementary functions, containing a continuous network distribution of Li. 22 Sn5 phase and nanoscale dispersed Li9Al4 phase, wherein Mg is dissolved in the Li lattice in the material, and Li 22 The Sn5 phase, acting as a lithiophilic nucleation and transport framework with high ionic / electronic conductivity, significantly reduces the overpotential of lithium deposition and guides uniform lithium deposition, fundamentally suppressing lithium dendrite growth. Simultaneously, Mg dissolved in the Li lattice forms a solid solution network, providing buffering properties. The nanoscale dispersed Li9Al4 phase ensures good material uniformity, balancing active lithium sites with mechanical strength, resulting in stable and excellent performance. This multiphase composite structure contributes to the overall stability of the material's performance. Its application in batteries effectively enhances electrochemical performance, demonstrating significant advantages. This solution addresses the problems of electrode structure collapse, uncontrolled lithium dendrite growth, severe high-density tin segregation, and compositional inhomogeneity caused by large volume changes during cycling.

[0041] Specifically, this invention optimizes the elemental composition and ratio to ensure that the molar ratio of Li to Sn is conducive to the formation of a sufficient amount of Li with a continuous and uniformly distributed network. 22 The Sn5 lithium-philic conductive framework, coupled with the Mg content, ensures good buffering performance of the lithium-magnesium solid solution. The dispersion strengthening effect of the Li9Al4 phase is gradually improved without excessive occupation of active lithium sites. The Mg and Al content guarantees the formation of an effective buffering and strengthening network without excessive occupation of active lithium sites, thus preventing significant capacity loss. This allows for controllable phase separation during solidification of the alloy, forming a structure containing Li... 22 The multiphase composite structure consists of Sn5 phase, lithium magnesium solid solution and Li9Al4 phase. These phases are intertwined to form a continuous three-dimensional conductive and mechanical support framework network.

[0042] Secondly, embodiments of the present invention also provide a method for preparing an alloy material, comprising the following steps: Molten lithium is obtained by heating metallic lithium to a molten state. A lithium-magnesium alloy and an aluminum-tin master alloy are added to molten lithium and stirred to obtain an alloy melt. The mass ratio of Al to Sn in the aluminum-tin master alloy is (0.5~3):1. The alloy melt is cooled to obtain the alloy material.

[0043] In some embodiments of the present invention, in the aluminum-tin master alloy, tin is dispersed in the aluminum matrix at the nanoscale.

[0044] In some embodiments of the present invention, the stirring rate is 150-300 r / min and the stirring time is 1-5 hours.

[0045] In some embodiments of the present invention, the cooling rate is not less than 50°C / s.

[0046] In some embodiments of the present invention, the cooling rate is 60~80°C / s. Rapid cooling yields an alloy ingot with a fine-grained multiphase structure; if the cooling rate is too slow, the phases in the melt coarsen and segregate, making it impossible to freeze a uniform multiphase structure.

[0047] It is understood that this invention explicitly limits the mass ratio of Al to Sn in the aluminum-tin master alloy. When the mass ratio of Al to Sn in the aluminum-tin master alloy is within this range, uniform Al-Sn micro-droplets can be formed in the melt, which is Li 22 The continuous network growth of the Sn5 phase provides uniform nucleation sites; when the ratio is <0.5:1, excess Sn cannot form stable microdroplets, and Li... 22 Sn5 readily agglomerates into particles; simultaneously, when the ratio is >3:1, excess Al occupies active lithium sites, leading to a significant decrease in battery capacity. Furthermore, by controlling the molar ratio of Li to Sn in the elemental composition, this invention achieves Li… 22 The Sn5 phase can be controlled to change from "isolated particles" to "continuous network," and the framework structure can be altered by adjusting the component ratio.

[0048] Furthermore, by adjusting and controlling the ratio of lithium, magnesium, aluminum, and tin, and simultaneously controlling the mass ratio of Al to Sn in the aluminum-tin master alloy, precise control of each element was achieved, resulting in the formation of a multiphase composite structure with complementary functions in situ within the alloy. In addition, the segregation of the high-density component Sn was greatly reduced through the synergistic process of element control, intense mechanical stirring, and rapid cooling, thus preparing a high-stability alloy material.

[0049] Thirdly, embodiments of the present invention also provide a method for preparing a battery negative electrode, comprising the following steps: Alloy materials were prepared using the above method; The alloy material is heat-treated in a vacuum environment; The heat-treated alloy material is rolled into a thin sheet; The thin material is punched into a battery negative electrode.

[0050] In some embodiments of the present invention, the heat treatment temperature is 120–160°C, and the time is 10–20 hours. The parameters of the heat treatment are controlled to eliminate internal stress and stabilize the intermetallic compound phase.

[0051] It is understood that the method for preparing the battery negative electrode of the present invention is simple, the alloy material used has excellent performance, and the prepared negative electrode has stable and excellent performance, and has a wide range of applications.

[0052] Fourthly, embodiments of the present invention also provide a battery negative electrode, which is prepared by the above-described preparation method.

[0053] Fifthly, embodiments of the present invention also provide a battery negative electrode comprising the aforementioned alloy material.

[0054] Sixthly, embodiments of the present invention also provide a lithium-ion battery comprising the above-described battery negative electrode.

[0055] It is understood that the battery negative electrode and the lithium-ion battery provided by this invention have excellent electrochemical performance and broad application prospects.

[0056] Example 1 Alloy composition (mass percentage): Li 85%, Mg 12.5%, Al 1.5%, Sn 1%; Li to Sn molar ratio is 1453.9:1.

[0057] Preparation steps: In an argon glove box with a dew point ≤ -50℃ and an oxygen content ≤ 1ppm, preheat the melting furnace to 200℃ and hold for 10 min. Add lithium metal blocks and heat to 220℃ to completely melt them. Add the pre-prepared lithium-magnesium alloy (Mg content 14.7wt%) and mechanically stir at 200 r / min for 40 min to form a homogeneous lithium-magnesium melt.

[0058] An aluminum-tin master alloy (Al / Sn mass ratio 1.5:1, Sn content 40wt%) was added, and the melt temperature was controlled at 280℃. Stirring was continued for 3 hours. The melt was poured into a copper mold with circulating cooling water (water temperature 20℃) to achieve rapid cooling (cooling rate >60℃ / s) to obtain an alloy ingot.

[0059] The ingot was placed in a vacuum drying oven and aged at 140°C for 15 hours. In a drying room with a dew point of -50°C and humidity <1%RH, the alloy ingot was rolled into a thin material (strip) with a thickness of 100μm, and then punched into electrode sheets with a diameter of 10mm.

[0060] Using this electrode as the negative electrode, Celgard 2325 as the separator, and 1M LiTFSI in DME / DOL (v / v=1 / 1) as the electrolyte, a CR2025 symmetric cell was assembled for performance testing. The resulting alloy contains Li... 22 The Sn5 phase is a continuous network with a mass fraction of 1.26%, while the Li9Al4 phase is a nanoscale dispersed distribution with a mass fraction of 2.37%.

[0061] Example 2 (Preferred range endpoint values: lower limit for Li, upper limit for Mg, median value for Al, upper limit for Sn) Alloy composition: Li 80%, Mg 18%, Al 1.0%, Sn 1.0%; Li to Sn molar ratio is 1368.1:1. Preparation steps are the same as in Example 1.

[0062] Li in the obtained alloy 22 The Sn5 phase is a continuous network with a mass fraction of 1.257%, while the Li9Al4 phase is a nanoscale dispersed distribution with a mass fraction of 1.58%.

[0063] Example 3 (Preferred range endpoint values: upper limit of Li, lower limit of Mg, lower limit of Al, lower limit of Sn) Alloy composition: Li 90%, Mg 9%, Al 0.5%, Sn 0.5%; Li to Sn molar ratio is 3078:1. Preparation steps are the same as in Example 1.

[0064] Li in the obtained alloy 22 The Sn5 phase is a continuous network with a mass fraction of 0.629%, while the Li9Al4 phase is a nanoscale dispersed distribution with a mass fraction of 0.79%.

[0065] Example 4 (Mg univariate adjustment: 15%) Alloy composition: Li 83%, Mg 15%, Al 1.0%, Sn 1.0%; Li to Sn molar ratio is 1419:1. Preparation steps are the same as in Example 1.

[0066] Li in the obtained alloy 22 The Sn5 phase is a continuous network with a mass fraction of 1.257%, while the Li9Al4 phase is a nanoscale dispersed distribution with a mass fraction of 1.58%.

[0067] Example 5 (Al univariate adjustment: 1.0%, Mg median 9%) Alloy composition: Li 88%, Mg 10%, Al 1.0%, Sn 1.0%; Li to Sn molar ratio is 1505:1. Preparation steps are the same as in Example 1.

[0068] Li in the obtained alloy 22The Sn5 phase is a continuous network with a mass fraction of 1.257%, while the Li9Al4 phase is a nanoscale dispersed distribution with a mass fraction of 1.58%.

[0069] Comparative Example 1 (Pure Lithium Foil) Pure lithium foil (100 μm thick) was used as the negative electrode, and the rest of the battery assembly conditions were exactly the same as in Example 1.

[0070] Comparative Example 2 (components outside the preferred range: Li below the lower limit, Mg above the upper limit, Al above the upper limit, Sn above the upper limit) Alloy composition: Li 70%, Mg 25%, Al 2.5%, Sn 2.5%; Li to Sn molar ratio is 478:1. Preparation steps are the same as in Example 1.

[0071] Li in the obtained alloy 22 The Sn5 phase is in the form of isolated granules with a mass fraction of 3.14%, while the Li9Al4 phase is aggregated with a mass fraction of 3.95%.

[0072] Comparative Example 3 (components outside the preferred range: above the upper limit of Li and below the lower limit of Mg) Alloy composition: Li 95%, Mg 2%, Al 2%, Sn 1%; Li to Sn molar ratio is 1624.7:1. Preparation steps are the same as in Example 1.

[0073] Li in the obtained alloy 22 The Sn5 phase is discontinuous, with a mass fraction of 1.26%, and there is no continuous lithium-magnesium solid solution network.

[0074] Comparative Example 4 (components exceeding the preferred range: Al above the upper limit, Sn above the upper limit) Alloy composition: Li 75%, Mg 10%, Al 5%, Sn 10%; Li to Sn molar ratio is 128.2:1. Preparation steps are the same as in Example 1.

[0075] Li in the obtained alloy 22 Sn5 phase aggregates extensively, with a mass fraction of 12.6%, indicating that Al excessively occupies active lithium sites.

[0076] Comparative Example 5 (Missing process factors: Aluminum-tin master alloy not used, pure Al and pure Sn added directly) Using the same composition as in Example 1 (Li 85%, Mg 12.5%, Al 1.5%, Sn 1%), the aluminum-tin master alloy was removed and replaced with pure Al and pure Sn blocks respectively. The rest of the process (stirring 200 r / min, cooling rate >100℃ / s) remained unchanged.

[0077] Comparative Example 6 (Li / Sn molar ratio < 1368:1, Sn in excess) Alloy composition: Li 80%, Mg 16.5%, Al 1.5%, Sn 2%; Li to Sn molar ratio is 684:1. Preparation steps are the same as in Example 1.

[0078] Li in the obtained alloy 22 The Sn5 phase consists of isolated granules with a mass fraction of 2.5%.

[0079] Comparative Example 7 (Li / Sn molar ratio > 3079:1, Sn insufficient) Alloy composition: Li 80%, Mg 18.3%, Al 1.5%, Sn 0.2%; Li to Sn molar ratio is 6840:1. Preparation steps are the same as in Example 1.

[0080] Li in the obtained alloy 22 The Sn5 phase is discontinuous and island-like, with a mass fraction of 0.25%.

[0081] Comparative Example 8 (Single process factor missing: mechanical stirring rate reduced to 50 r / min) Using the same composition and intermediate alloy as in Example 1, the mechanical stirring rate was reduced to 50 r / min, while the rest of the process remained unchanged.

[0082] Comparative Example 9 (Single process factor missing: rapid cooling rate reduced to 20℃ / s) Using the same composition and intermediate alloy as in Example 1, the rapid cooling rate was reduced to 20°C / s, while the rest of the process remained unchanged.

[0083] Comparative Example 10 Using the same composition as in Example 1, but replacing the intermediate alloy with an equal amount of pure Al / pure Sn, the process was carried out without stirring or natural cooling, and the rest of the process remained unchanged.

[0084] Experimental Example 1 1. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to test the elemental content of the upper, middle, and lower parts of the alloy ingot. The test samples were taken from the longitudinal section of the alloy ingot, which was divided into three equal regions along the height direction. Samples were taken from each region and analyzed. The results are shown in Table 1.

[0085] RD% is the relative deviation of the mass fraction of Sn element in the upper, middle, and lower parts, calculated using the following formula: RD% = (Maximum value - Minimum value) / Average value × 100% 2. The alloy anodes prepared in the examples and comparative examples were assembled into CR2025 type symmetrical cells, and their electrical performance was tested. The results are shown in Table 2.

[0086] The test conditions were: current density 4 mA•cm -2 .

[0087] Cycle life is the cycle time when the battery voltage polarization voltage reaches a set threshold; 200-cycle capacity retention is the ratio of the battery's discharge capacity after 200 charge-discharge cycles to its discharge capacity in the first cycle; rate performance is the ratio of the discharge capacity at 4C current density to its discharge capacity at 1C current density.

[0088] All tests were conducted at room temperature.

[0089] Table 1. Test results of elemental mass content in different regions of the upper, middle, and lower parts of the examples and comparative samples.

[0090]

[0091]

[0092] Table 2. Electrical performance test results of the examples and comparative samples.

[0093]

[0094]

[0095] Results analysis: 1. Structural characterization and structure-property relationship of phase composition-molar ratio

[0096] Figure 1 The X-ray diffraction pattern of the alloy prepared in Example 1 of this invention shows obvious diffraction peaks of the Li (110), (200), and (211) crystal planes, as well as characteristic peaks of Li9Al4 (24°, 39°, 42°, etc.). Mg and Sn do not show independent diffraction peaks, indicating that Mg is dissolved in the Li lattice, while Sn is dispersed at the nanoscale or dissolved in the AlLi phase.

[0097] Figure 4 The images show the TOFSIMS single-element distribution and oxide ion cluster distribution of the lithium alloy anode sample in Example 1. Figure 6 The TOFSIMS comparison diagram of various metal solid solution clusters and mass spectra of the lithium alloy anode material in Example 1 shows that the sample of Example 1 (Li / Sn=1453.7:1) shows significant LiSn alloy clusters and mass spectra signals. Figure 5 The upper sample of Comparative Example 7 showed no LiSn alloy clusters or mass spectrometry signals, directly demonstrating the effect of the Li / Sn molar ratio on Li 22 The decisive influence of the Sn5 phase structure morphology was verified, and the criticality of the molar ratio range of 1368 to 3079:1 was confirmed.

[0098] 2. Relationship between cycle stability and component-molar ratio-univariate analysis

[0099] Figure 2Symmetrical cells assembled using the alloy negative electrodes prepared in Examples 1-5 and Comparative Examples 1-9 of this invention operate at 4 mA•cm. -2 Comparison of cycle life under current density.

[0100] Figure 2 The cycle life data in Table 2 show that at 4 mA•cm -2 At current density, the cycle life of the symmetrical batteries in Examples 1-5 were 2415h, 2250h, 2100h, 2300h, and 2180h, respectively, all exceeding 2100h and far higher than the 256h of the pure lithium foil in Comparative Example 1.

[0101] Furthermore, Examples 2-5 covered the endpoints and univariate adjustment values ​​of the preferred range, all maintaining high cycle life, demonstrating the effectiveness of the preferred range; while Comparative Examples 2-4 (components outside the preferred range) and Comparative Examples 6-7 showed a significant decrease in cycle life due to the Li / Sn molar ratio deviating from (1368-3079):1 (850h, 920h, 780h, 1050h, and 980h, respectively). Among them, Comparative Example 6 experienced a decrease in Li due to excessive Sn. 22 Sn5 particles agglomerate, and the volume effect worsens. In contrast, in Comparative Example 7, insufficient Sn leads to the absence of lithophile nucleation sites, resulting in significant lithium dendrite growth, fully demonstrating the threshold effect of the optimal composition and key molar ratio.

[0102] Meanwhile, performance data from Examples 4 (Mg=15%) and 5 (Al=1.0%) show that when Mg is adjusted by a single variable of 9-18%, the cycle life first increases and then stabilizes, while when Al is adjusted by a single variable of 0.5-1.5%, the cycle life gradually increases. This clarifies the influence of Mg and Al as single variables and proves the refinement of the component design in this invention.

[0103] 3. Relationship between lithium dendrite suppression effect and Li / Sn molar ratio

[0104] Figure 3 The images show the in-situ optical microscope surface morphology comparisons of Example 1, Comparative Example 1, Comparative Example 6, and Comparative Example 7 before, after 300 hours of cycling, and after the cycling. (a) is Example 1, (b) is Comparative Example 1, (c, d) are Comparative Example 6, and (e, f) are Comparative Example 7.

[0105] Figure 3 In-situ optical microscopy images show that the surface of the alloy anode (a) of Example 1 remained flat after 300 hours of cycling and at the end of the cycle, with only a very small number of lithium dendrites. Comparative Example 1, pure lithium foil (b), showed a large number of dendrites under the same conditions; Comparative Example 6 (Sn excess) (c, d) showed local lithium deposition protrusions on the surface; and Comparative Example 7 (Sn deficiency) (e, f) showed obvious dendrites on the surface. This is because when the Li / Sn molar ratio deviated from the preferred range, Li...22 The Sn5 phase loses its continuous network structure and cannot effectively guide the uniform deposition of lithium, directly proving the structure-property relationship between the Li / Sn molar ratio and the dendrite suppression effect.

[0106] 4. The necessity of component uniformity and synergistic effect of three processes

[0107] Figure 4 The image shows the TOFSIMS single-element distribution and oxide ion cluster distribution of the lithium alloy anode sample in Example 1. Figure 7 The image shows a comparison of TOF-SIMS and different selected area mass spectrometry of the lithium alloy anode material in Example 1. Figure 8 The image shows the EBSD results of the lithium alloy anode material in Example 1, the IPF (Inverse Pole Figure) plot used to display crystal orientation, and the PQ, KAM, and GAM plots used to evaluate crystal quality and strain. The IPF plot uses color to visually represent the grain orientation distribution. It does not directly display the sample coordinates, but rather shows which crystal orientation (e.g.,

[001] ,

[101] , etc.) is parallel to a specific direction of the sample.

[0108] IPF X / Y / Z: These three graphs represent which crystal orientation within the grains is parallel to the X, Y, and Z directions of the sample, respectively. In EBSD, sample coordinates are typically defined as follows: X direction corresponds to RD (Rolling Direction), Y direction corresponds to TD (Transverse Direction), and Z direction corresponds to ND (Normal Direction). Application: By comparing the IPF X, Y, and Z graphs, the crystal orientation of the material in three-dimensional space can be comprehensively analyzed to determine the presence of texture. For example, if a large number of grains appear the same color in the IPF Y graph, it indicates that the same crystal orientation of these grains is parallel to the Y-axis, meaning the material has a preferred orientation in the Y direction.

[0109] Crystal quality and strain are parameters used to assess crystal integrity, defect density, and strain by analyzing the quality of the Kikuchi band or the orientation difference between grains. PQ (Pattern Quality) is defined as a measure of the sharpness or clarity of each EBSD Kikuchi pattern. It is calculated by measuring the contrast between the Kikuchi band and the background. Applications: Areas with high PQ values ​​(brighter on the image) represent good crystal integrity and few defects; areas with low PQ values ​​(darker on the image) may correspond to grain boundaries, high-strain regions, or surface contamination. Therefore, PQ plots are often used as a basis for evaluating sample preparation quality.

[0110] KAM (Kernel Average Misorientation). Definition: A method for calculating local orientation difference based on the "core". It calculates the average orientation difference between a pixel and its neighboring pixels within a certain range (called the "core"). Application: KAM values ​​are a powerful tool for characterizing local plastic strain and geometrically required dislocation (GND) density in materials. Regions with high KAM values ​​usually indicate large local plastic deformation.

[0111] GAM (Grain Average Misorientation) definition: A method for calculating local orientation difference based on a "grain". It is the average of the KAM values ​​of all pixels within a grain.

[0112] Applications: If KAM reflects "local" strain, then GAM reflects the "average" strain level of the entire grain. It is often used to distinguish between recrystallized grains (low GAM value) and deformed grains (high GAM value). Note: GAM is different from GOS (Grain Orientation Spread), which calculates the difference between each pixel and the average orientation of the grain.

[0113] Figure 8 The EBSD results showed that the IPF-X, IPF-Y, and IPF-Z inverse pole figures clearly distinguished lithium alloy grains with sizes of tens of micrometers. The grain boundaries between grains were clear, and the grain orientations exhibited diverse color distributions. No obvious strong preferred texture was observed, indicating that the internal grains of this lithium alloy anode do not have a significant rolling orientation preference, and the grain orientations are randomly distributed. The PQ pattern quality map showed high overall signal brightness, with only local dark areas appearing at the grain boundaries, indicating good overall crystal integrity, low overall defect level, and minimal damage introduced during sample preparation, demonstrating reliable EBSD data quality. The KAM and GAM strain mapping maps showed that most grains exhibited low-value blue signals, with only localized high orientation difference signals appearing near some grain boundaries and at the edges of a few grains. The KAM and GAM values ​​within the grain body were generally at a low level. The above results indicate that the lithium alloy anode matrix obtained in this embodiment has a low overall degree of plastic strain, a low overall density of geometrically necessary dislocations, and good crystal integrity of the grains; strain and dislocations are mainly concentrated in the grain boundary region, and the degree of deformation inside the grains is weak.

[0114] Figure 4 and Figure 7 The TOFSIMS results showed that the Mg signal in Example 1 had a consistent intensity within the selected region, proving that the Mg was uniformly distributed. Figure 4The surface scan of Al elements shows that the Al element in Example 1 is relatively uniformly distributed in the alloy. The relatively uniform distribution of Li, Mg, and Al, along with the elemental results, confirms the uniformity of the alloy's elemental distribution.

[0115] and Figure 5 The TOFSIMS single-element distribution and oxide ion cluster distribution of the upper sample of the lithium alloy anode in Comparative Example 7 are shown. As can be seen from the comparison, no obvious LiSn alloy clusters and mass spectrometry signals were found on the surface of the sample in Comparative Example 7, indicating that the Sn element was severely unevenly distributed.

[0116] Combination Figure 1 and Figure 7 The results show that when the Li / Sn molar ratio deviates from the range of 1368–3079:1, a continuous network of Li cannot be formed in the alloy. 22 The presence of the Sn5 phase further demonstrates that the Li / Sn molar ratio has a decisive influence on the alloy's microstructure.

[0117] In Table 1, the relative deviation (RD%) of Sn element in Examples 2-5 is less than 5%, while the RD% of Sn element in Comparative Examples 6-10 is significantly increased. The absence of any single process will lead to increased segregation. This fully demonstrates that the synergistic effect of aluminum-tin master alloy, mechanical stirring, and rapid cooling is the key to suppressing Sn segregation, rather than the effect of a single process, thus verifying the originality of the process design of this invention.

[0118] 5. Relationship between Al / Sn master alloy ratio and skeleton structure

[0119] Example 1 uses an Al / Sn master alloy with a mass ratio of 1.5:1 and Li 22 The Sn5 phase is a continuous network, but when the Al / Sn mass ratio decreases, Al-Sn micro-droplets cannot be formed, and Sn directly precipitates and segregates, while Li... 22 Sn5 phase agglomeration; when the Al / Sn mass ratio is high, excess Al leads to a reduction in active lithium sites and a decrease in capacity, which proves the necessity of the Al / Sn master alloy ratio.

[0120] 6. Overall electrochemical performance

[0121] Table 2 shows that Examples 1-5 of the present invention, while maintaining high cycle life, also exhibit excellent rate performance (4C capacity retention >85%), comprehensively outperforming all comparative examples. Among them, Example 1 achieves optimal performance due to the Li / Sn molar ratio being at the middle of the preferred range and the Mg / Al being the optimal single-variable combination, fully demonstrating the synergistic effect of the components and process design of the present invention.

[0122] The preparation method of a high-stability lithium magnesium aluminum tin alloy anode material provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An alloy material, characterized in that, By weight percentage, it contains: lithium 70-90%, magnesium 7-29%, aluminum 0.5-3%, and tin 0.5-20%.

2. The material according to claim 1, characterized in that, The material contains Li 22 A lithium-magnesium solid solution formed by Sn5 phase, Li9Al4 phase, and Mg dissolved in a Li lattice; the Li 22 The Sn5 phase is distributed in a continuous network, while the Li9Al4 phase is distributed in a nanoscale dispersed manner.

3. The material according to claim 2, characterized in that, The material is composed of the following components: lithium 70-90%, magnesium 7-29%, aluminum 0.5-3%, and tin 0.5-20%, with the sum of the mass percentages of each component being 100%.

4. The material according to claim 2, characterized in that, The material is composed of the following components: 80-90% lithium, 9-18% magnesium, 0.5-1.5% aluminum, and 0.5-1% tin, with the sum of the mass percentages of each component being 100%.

5. The material according to claim 4, characterized in that, The Li 22 The mass fraction of the Sn5 phase is 0.63%~1.26%, and the mass fraction of the Li9Al4 phase is 0.79%~2.37%.

6. A method for preparing an alloy material as described in any one of claims 1-5, characterized in that, Includes the following steps: Molten lithium is obtained by heating metallic lithium to a molten state. A lithium-magnesium alloy and an aluminum-tin master alloy are added to molten lithium and stirred to obtain an alloy melt. The mass ratio of Al to Sn in the aluminum-tin master alloy is (0.5~3):

1. The alloy melt is cooled to obtain the alloy material.

7. The preparation method according to claim 6, characterized in that, In the aluminum-tin master alloy, tin is dispersed in the aluminum matrix at the nanoscale.

8. The preparation method according to claim 6, characterized in that, The stirring rate is 150–300 r / min, and the stirring time is 1–5 hours.

9. The preparation method according to claim 6, characterized in that, The cooling rate is not less than 50°C / s.

10. The preparation method according to claim 6, characterized in that, The cooling rate is 60~80℃ / s.

11. A method for preparing a battery negative electrode, characterized in that, Includes the following steps: Alloy materials are prepared by the method according to any one of claims 6-10; The alloy material is heat-treated in a vacuum environment; The heat-treated alloy material is rolled into a thin sheet; The thin material is punched into a battery negative electrode.

12. The preparation method according to claim 11, characterized in that, The heat treatment is performed at a temperature of 120–160°C for 10–20 hours.

13. A battery negative electrode, characterized in that, It is prepared by the preparation method described in claim 11 or 12.

14. A battery negative electrode, characterized in that, It includes the alloy material described in any one of claims 1 to 5.

15. A lithium-ion battery, characterized in that, It includes the battery negative electrode as described in claim 13 or 14.

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