Multi-element solid solution strengthened lithium alloy negative electrode material as well as preparation method and application thereof

Abstract

The invention relates to a multi-element solid solution strengthened lithium alloy negative electrode material as well as a preparation method and application thereof. The preparation method of the lithium alloy negative electrode material comprises the following steps: putting lithium and at least one auxiliary element of Mg, Al and Zn into a copper crucible according to a mass ratio of 5-30%, carrying out suspension smelting for 2-10min under vacuum of less than or equal to 1Pa and argon protection at the induction power of 5-20kW, carrying out natural or speed-controlled cooling, transferring into an argon glove box with oxygen / water of less than or equal to 0.01 ppm to remove an oxidation layer, and packaging to obtain the single-phase solid solution lithium alloy. The lithium alloy negative electrode material can be rolled into a wafer with the thickness of 0.5 mm and the diameter of 10 mm, and is used for a lithium copper half battery, a symmetrical battery and a lithium iron phosphate total battery. According to the lithium alloy negative electrode material, the yield strength and the interface stability are remarkably improved, the lithium nucleation overpotential is reduced, dendritic crystal growth is inhibited, the high-rate cycle life of a battery is prolonged, and the lithium alloy negative electrode material is suitable for a high-specific-energy energy storage system.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage, and in particular to a multi-element solid solution strengthened lithium alloy anode material, its preparation method, and its application. Background Technology

[0002] The continuous pursuit of higher energy density in applications such as electric transportation, portable electronics, and large-scale energy storage has pushed traditional lithium-ion batteries with graphite anodes close to their theoretical limits. Even with the combination of high-nickel ternary cathodes and Si-C composite anodes, the specific energy of individual cells still largely hovers around 300 Wh·kg⁻¹. - Around 1, it's difficult to reach 500Wh·kg. - The medium- to long-term goal is 1. In comparison, lithium metal has the advantages of 3860mAh / g. - It boasts an ultra-high theoretical specific capacitance of 1, a minimum potential of -3.04V (vs SHE), and lightweight properties (density 0.534 g·cm³). -3 It is considered a core negative electrode candidate for breaking through the energy bottleneck.

[0003] However, lithium metal has extremely high surface chemical activity. In conventional carbonate or ether-based electrolytes, lithium continuously consumes the solvent and forms a solid electrolyte interphase (SEI) film during the deposition-stripping process. This film is mechanically fragile and prone to repeated rupture, and the exposed fresh metal continues to undergo side reactions, forming a closed loop and accelerating electrolyte depletion. The superposition of local ion concentration gradients and electric field tip effects causes lithium to preferentially grow at high curvature locations, ultimately resulting in dendrites penetrating the membrane, deactivated "dead lithium," and a sharp drop in capacity.

[0004] From a mechanical perspective, pure lithium has an elastic modulus of only about 4.9 GPa and a yield strength of less than 1.2 MPa, and it undergoes significant creep at room temperature. While its excellent ductility (elongation at break can reach 50–100%) facilitates forming, it is accompanied by volume changes of up to about 300% during repeated charge-discharge cycles, leading to electrode pulverization, repeated SEI tearing, and internal stress concentration. Low strength, high ductility, creep sensitivity, and anisotropy collectively constitute the root causes of dendrite growth, interface failure, and short-circuit risks.

[0005] To address the aforementioned failure mechanisms, researchers have attempted improvements through electrolyte optimization, interfacial film construction, three-dimensional current collectors, solid / gel electrolytes, and alloying strengthening. These approaches have achieved some success in suppressing side reactions, dispersing current density, or enhancing mechanical strength. However, under conditions of high areal capacity, high rate capability, and wide temperature window, it remains difficult to simultaneously meet the comprehensive requirements of energy density, cycle life, and manufacturing practicality. Problems such as dendrite recurrence, interfacial fracture, and increased polarization remain prominent.

[0006] Therefore, a new alloying approach and corresponding preparation method are still needed to improve the mechanical properties of lithium metal while maintaining its chemical stability and ensuring high compatibility with battery manufacturing processes; furthermore, the development of anodes based on this material and battery systems thereof is needed to fundamentally improve the key bottlenecks of pure lithium anodes in terms of structure, cycle life and safety. Summary of the Invention

[0007] This invention provides a multi-element solid solution strengthened lithium alloy anode material, its preparation method, and its application, aiming to solve the problems of low mechanical strength, easy dendrite growth, and poor interface stability in existing lithium metal anodes, which lead to capacity decay and safety hazards.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides a method for preparing a multi-element solid solution strengthened lithium alloy anode material, comprising:

[0010] a) Lithium metal is mixed with one or more metallic auxiliary elements by mass percentage, wherein the auxiliary elements account for 5%–30% of the mass of lithium metal, and after mixing, the mixture is placed into a copper crucible under an inert atmosphere.

[0011] b) Place the copper crucible in the center of the induction coil of the suspension melting device, evacuate to a vacuum level not exceeding 1 Pa and fill with inert gas for protection, and perform suspension melting for 1 min–10 min at an induction power of 5 kW–20 kW.

[0012] c) After melting, allow it to cool naturally or at 1°C / min. - 1–20℃min - 1. Control the cooling rate to room temperature;

[0013] d) The obtained alloy was transferred to an argon glove box with oxygen and water content both less than 0.01 ppm, the surface oxide layer was mechanically removed and the alloy was encapsulated to obtain a multi-element solid solution strengthened lithium alloy anode material.

[0014] Furthermore, the metal auxiliary element is selected from one or more of magnesium, aluminum, and zinc, and the resulting alloy is a Li-Mg, Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn, or Li-Mg-Al-Zn alloy.

[0015] Furthermore, the mass percentage of the auxiliary element in the alloy is:

[0016] Li-Mg alloy: Mg is 5%–30%, with the balance being lithium;

[0017] Li-Al alloy: Al is 5%–30%, with the balance being lithium;

[0018] Li-Zn alloy: Zn is 5%–30%, with the balance being lithium;

[0019] Li-Mg-Al alloy: Mg 10%–25%, Al 5%–20%, balance lithium;

[0020] Li-Mg-Zn alloy: Mg 10%–25%, Zn 5%–20%, balance lithium;

[0021] Li-Mg-Al-Zn alloy: Mg 5%–20%, Al 2%–5%, Zn 2%–5%, balance lithium.

[0022] Further, after step d), the resulting lithium alloy is subjected to incremental multi-pass rolling with a thickness of 0.1–5 mm, and stress-relief annealing is performed at 20–100°C between each rolling pass.

[0023] Furthermore, the cooling method in step c) is quenching, in which the crucible and the molten alloy are immersed in a cooling medium of -80°C to -196°C.

[0024] Furthermore, after step b) ends the heating, continue to hold at 650–750℃ for 1–3 minutes.

[0025] Secondly, the present invention provides a multi-element solid solution strengthened lithium alloy anode material, which is obtained by the above preparation method.

[0026] Thirdly, this invention provides the application of a multi-element solid solution reinforced lithium alloy anode material in a copper foil half-cell, the copper foil half-cell comprising:

[0027] a) The lithium alloy negative electrode material is rolled to a thickness of 1.0-3.0 mm and punched into a circular sheet with a diameter of 8-15 mm as the working electrode;

[0028] b) Using copper foil as the counter electrode and current collector;

[0029] c) Celgard 2400 polypropylene porous membrane is used as the separator, and LBC0045I(G) is used as the electrolyte;

[0030] d) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm and encapsulate them under a pressure of 350-500psi.

[0031] Fourthly, the present invention provides an application of a multi-element solid solution-reinforced lithium alloy anode material in a symmetrical battery, the symmetrical battery comprising:

[0032] a) The lithium alloy negative electrode material is rolled to a thickness of 1.0-3.0 mm and punched into circular pieces with a diameter of 8-15 mm, which are then used as the positive and negative electrodes respectively;

[0033] b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte;

[0034] c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm;

[0035] d) Encapsulate under a pressure of 350-500 psi.

[0036] Fifthly, the present invention provides an application of a multi-element solid solution-reinforced lithium alloy anode material in a lithium iron phosphate full battery, wherein the lithium iron phosphate full battery comprises:

[0037] a) The lithium alloy anode material is rolled to a thickness of 1.0-3.0 mm and punched into circular sheets with a diameter of 8-15 mm to serve as the anode. The cathode has an active material surface density of 3-4 mg / cm³. - 2. A LiFePO4 electrode with a LiFePO4:PVDF:SuperP mass ratio of 8:1:1;

[0038] b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte;

[0039] c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm;

[0040] d) Encapsulate under a pressure of 350-500 psi.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The method of this invention employs a process of suspension melting, vacuum cooling, and inert encapsulation, avoiding the segregation and intermetallic compounds easily generated by traditional crucible melting. This enables the mass production of single-phase solid solutions, which can be directly rolled into sheets and are compatible with existing coin cell and laminated battery production lines. The alloy anode of this invention achieves synergistic improvements in mechanical, interfacial, and electrochemical aspects: its multi-element solid solution significantly improves the yield strength of lithium metal, resulting in a smooth, uniform, and crack-free surface on the rolled foil, fundamentally reducing repeated SEI rupture induced by volume expansion. At the electrochemical level, the nucleation overpotential of the Li-Mg-Al-Zn anode is only 35mV, and the deposition overpotential is approximately 35mV, far lower than that of pure lithium and binary alloys, while the interfacial impedance drops to 3.396Ω, indicating the formation of a denser SEI film with higher ionic conductivity, significantly improving electrode / electrolyte contact. Therefore, the average coulombic efficiency of the copper foil half-cell remains stable at 98%, and the symmetric cell achieves a high efficiency of 1 mA / cm². - After two cycles of over 650 hours, it still maintained a low hysteresis of 18mV and could reach 10mAcm.- The battery maintained a polarization voltage of 25mV for over 250 hours continuously. When paired with a lithium iron phosphate cathode, the full cell retained 85% of its capacity after 800 cycles at 1C, and maintained a specific capacity of 96.7 mAhg at a high rate of 10C. -1 The material exhibits minimal polarization and an efficiency approaching 99%. These results demonstrate that the material of this invention effectively suppresses dendrite growth, reduces polarization, and extends cycle life, while also possessing high safety and high rate performance. It can provide a reliable anode solution for the large-scale application of high-energy-density lithium metal batteries.

[0043] Of course, implementing the various technical solutions of this invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0045] Figure 1 The following are XRD characterization diagrams of the alloy components in Examples 1-5 of this invention;

[0046] Figure 2 The images are SEM images of the alloy components in Examples 1-5 of this invention at different magnifications; where (a,b) Li-Al alloy; (c,d) Li-Zn alloy; (e,f) Li-Mg-Al alloy; (g,h) Li-Mg-Zn alloy; (i,j) Li-Mg-Al-Zn alloy;

[0047] Figure 3 The X-ray energy dispersive spectroscopy (EDS) diagrams of each alloy component in Examples 1-5 of the present invention are shown below; where (a) is Li-Al alloy; (b) is Li-Zn alloy; (c) is Li-Mg-Zn alloy; (d) is Li-Mg-Al alloy; and (e) is Li-Mg-Al-Zn alloy.

[0048] Figure 4 The following is a diagram showing the elemental content of each alloy in Examples 1-5 of the present invention; wherein, (a) Li-Al alloy; (b) Li-Zn alloy; (c) Li-Mg-Al alloy; (d) Li-Mg-Zn alloy; (e) Li-Mg-Al-Zn alloy;

[0049] Figure 5The charge-discharge curves of lithium deposition in Li-Al||Cu, Li-Zn||Cu, Li-Mg-Al||Cu, Li-Mg-Zn||Cu, and Li-Mg-Al-Zn||Cu half-cells in Example 6 of this invention are shown.

[0050] Figure 6 The coulombic efficiency diagrams of the Li||Cu, Li-Al||Cu, Li-Zn||Cu, Li-Mg-Al||Cu, Li-Mg-Zn||Cu, and Li-Mg-Al-Zn||Cu half-cells in Example 6 of this invention are shown.

[0051] Figure 7 This refers to the battery cycle performance of different component electrodes in Example 7 of the present invention; wherein, (a) the different component electrodes at 1 mA cm -2 Current density, 1 mAh cm⁻¹ -2 (a) Symmetrical battery cycle performance at areal capacity; (b) 2mAcm -2 Current density, 2mAhcm -2 Cycle performance of symmetrical cells at areal capacity; (c) 5mAcm -2 Current density, 5mAhcm -2 Symmetrical battery cycle performance at areal capacity; (d) 10 mA cm -2 Current density, 10 mAh cm⁻¹ -2 Cycle performance of symmetrical batteries under areal capacity;

[0052] Figure 8 The symmetrical cell impedance spectra of lithium sheet, Li-Mg-Zn, and Li-Mg-Al-Zn electrodes in Example 7 of this invention;

[0053] Figure 9 The full-cell performance of Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, and Li-Mg-Al-Zn||LFP in Example 8 of this invention is shown, including (a) long-cycle performance at 1C and (b) long-cycle performance at 5C.

[0054] Figure 10 The charge-discharge curves of the full cells of each component in Example 8 of the present invention are shown below; (a) the charge-discharge curve of each component at the 50th cycle; (bf) the charge-discharge curves of each component at different cycle numbers.

[0055] Figure 11The following are rate performance diagrams of the Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, and Li-Mg-Al-Zn||LFP full cells in Example 8 of the present invention; wherein, (a) the rate performance of each component; and (bf) the charge-discharge curves of each component at different rates. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0057] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0058] Example 1:

[0059] This embodiment provides a method for preparing a Li-Al solid solution reinforced lithium alloy anode material, including the following steps:

[0060] Step a) Under an inert atmosphere (argon), first zero the clean and dry balance; then weigh 1000 mg of lithium foil (purity ≥ 99.9%, weighing to be completed within 30 seconds after opening the vacuum seal), and then weigh 300 mg of aluminum ingot (purity ≥ 99.9%). Quickly put the two metals into a pre-dried copper crucible and immediately cover the crucible with the lid, ensuring that the entire weighing and loading process is completed within a local argon flow hood.

[0061] Step b) Place the charging crucible at the center of the induction coil of the levitation melting device:

[0062] Close the smelting chamber door and start the vacuum pump, evacuating to 1 Pa;

[0063] High-purity argon gas (99.999%) was introduced to a concentration of 5 × 10⁻⁶. 3 Pa, maintaining static pressure;

[0064] Set the induction power supply to 10kW and maintain continuous power output for 5 minutes. During this period, the crucible is completely lifted away from the support point by the electromagnetic force to achieve non-contact melting. After observing that the metal is completely melted and the surface is bright, the heating is stopped.

[0065] Step c) Turn off the power, keep the furnace cavity still, and let it cool naturally to room temperature (about 25°C) for about 30 minutes.

[0066] Step d) Open the furnace door and transfer the alloy ingot to an argon glove box with O2 / H2O both <0.01ppm; use #800 sandpaper to lightly sweep away the surface oxide scale until the metal color is exposed; after removing the debris with a clean cotton swab, immediately pack it into an aluminum-plastic composite bag and connect it to a vacuum sealing machine for sealing to obtain Li-Al multi-element solid solution strengthened lithium alloy anode material.

[0067] Example 2:

[0068] This embodiment provides a method for preparing a Li-Zn solid solution reinforced lithium alloy anode material, including the following steps:

[0069] Step a) Under argon protection, zero the balance and weigh 1000 mg of lithium foil (purity ≥ 99.9%, weighing to be completed within 30 seconds after opening the vacuum seal) and 300 mg of zinc foil (purity 99.995%). Quickly place the two metals into a pre-dried copper crucible and cover it. The entire process is completed within a local argon flow hood.

[0070] Step b) Place the charging crucible at the center of the induction coil of the levitation melting device:

[0071] Close the smelting chamber door and start the vacuum pump to evacuate to 1 Pa;

[0072] High-purity argon gas (99.999%) was introduced to a concentration of 5 × 10⁻⁶. 3 static pressure (Pa);

[0073] Set the induction power supply to 12kW for continuous output for 6 minutes, during which the crucible is suspended and melted under the action of electromagnetic force; stop heating after confirming that the metal is completely melted and the surface is bright.

[0074] Step c) Turn off the power and let the furnace cavity stand still and cool naturally to room temperature (≈25℃), about 30 minutes.

[0075] Step d) Open the furnace door and transfer the alloy ingot to an argon glove box with O2 / H2O < 0.01ppm; lightly brush off the oxide scale with #800 sandpaper to reveal the metal's original color; remove the shavings with a cotton swab and immediately place it in an aluminum-plastic composite bag, vacuum seal it, and obtain Li-Zn multi-element solid solution strengthened lithium alloy anode material.

[0076] Example 3:

[0077] This embodiment provides a method for preparing a Li-Mg-Al solid solution reinforced lithium alloy anode material, including the following steps:

[0078] Step a) Weigh 1000mg of lithium foil, 150mg of magnesium granules (purity ≥99.95%), and 150mg of aluminum ingot (purity ≥99.9%), and place them into a copper crucible under argon protection and immediately seal it.

[0079] Step b) Place the charging crucible at the center of the induction coil of the levitation melting device:

[0080] Close the smelting chamber door and start the vacuum pump to evacuate to 1 Pa;

[0081] High-purity argon gas (99.999%) was introduced to a concentration of 5 × 10⁻⁶. 3 static pressure (Pa);

[0082] Set the induction power supply to 15kW for continuous output for 7 minutes, during which the crucible is suspended and melted under the action of electromagnetic force; stop heating after confirming that the metal is completely melted and the surface is bright.

[0083] Step c) Stop heating and allow to cool naturally to room temperature.

[0084] Step d) Transfer the alloy ingot to an argon glove box with O2 / H2O both <0.01ppm; use #800 sandpaper to lightly sweep away the surface oxide scale until the metal color is exposed; after removing the debris with a clean cotton swab, immediately pack it into an aluminum-plastic composite bag and connect it to a vacuum sealing machine for sealing to obtain Li-Mg-Al solid solution strengthened lithium alloy anode material.

[0085] Example 4:

[0086] This embodiment provides a method for preparing a Li-Mg-Zn solid solution reinforced lithium alloy anode material, including the following steps:

[0087] Step a) Weigh 1000 mg of lithium foil, 150 mg of magnesium granules, and 150 mg of zinc foil; place them in a copper crucible under an inert atmosphere and cover it.

[0088] Step b) Place the charging crucible at the center of the induction coil of the levitation melting device:

[0089] Close the smelting chamber door and start the vacuum pump to evacuate to 1 Pa;

[0090] High-purity argon gas (99.999%) was introduced to a concentration of 5 × 10⁻⁶. 3 static pressure (Pa);

[0091] Set the induction power supply to 18kW for continuous output for 8 minutes, during which the crucible is suspended and melted under the action of electromagnetic force; stop heating after confirming that the metal is completely melted and the surface is bright.

[0092] Step c) Turn off the power and allow it to cool naturally to room temperature for about 30 minutes.

[0093] Step d) Transfer the alloy ingot to an argon glove box with O2 / H2O both <0.01ppm; use #800 sandpaper to lightly sweep away the surface oxide scale until the metal color is exposed; after removing the debris with a clean cotton swab, immediately pack it into an aluminum-plastic composite bag and connect it to a vacuum sealing machine for sealing to obtain Li-Mg-Zn solid solution strengthened lithium alloy anode material.

[0094] Example 5:

[0095] This embodiment provides a method for preparing a Li-Mg-Al-Zn solid solution reinforced lithium alloy anode material, including the following steps:

[0096] Step a) Weigh 1000mg of lithium foil, 100mg of magnesium granules, 100mg of aluminum ingot, and 100mg of zinc foil, and quickly put them into a copper crucible and cover it.

[0097] Step b) Place the charging crucible at the center of the induction coil of the levitation melting device:

[0098] Close the smelting chamber door and start the vacuum pump to evacuate to 1 Pa;

[0099] High-purity argon gas (99.999%) was introduced to a concentration of 5 × 10⁻⁶. 3 static pressure (Pa);

[0100] Set the induction power supply to 20kW for continuous output for 8 minutes, during which the crucible is suspended and melted under the action of electromagnetic force; stop heating after confirming that the metal is completely melted and the surface is bright.

[0101] Step c) Turn off the power and allow it to cool naturally to room temperature for about 30 minutes.

[0102] Step d) Transfer the alloy ingot to an argon glove box with O2 / H2O both <0.01ppm; use #800 sandpaper to lightly sweep away the surface oxide scale until the metal color is exposed; after removing the debris with a clean cotton swab, immediately pack it into an aluminum-plastic composite bag and connect it to a vacuum sealing machine for sealing to obtain Li-Mg-Al-Zn solid solution strengthened lithium alloy anode material.

[0103] The alloy compositions and proportions of Examples 1-5 are listed in Table 1 below:

[0104] Table 1 Alloy composition and proportioning scheme of Examples 1-5

[0105]

[0106] The following tests were conducted on the relevant parameters of the solid solution-strengthened lithium alloy anode materials prepared in Examples 1-5:

[0107] First, the structures of each alloy component prepared in Examples 1-5 were characterized. Figure 1 The XRD patterns of the above alloy components and pristine Li are shown, with diffraction angles ranging from 5° to 80°. The results show that three strong Li peaks are clearly visible in each alloy component, corresponding to the Li standard card (PDF#01-1131). The diffraction peaks of pure lithium correspond to the body-centered cubic (BCC) structure of lithium. Using its peak position as a benchmark, the peaks of pure lithium are simpler compared to other alloys, indicating a single-phase structure. Characteristic peaks of intermetallic compounds appear in the spectra of Li-Al and Li-Zn alloys. For example, Li-Al exhibits the characteristic peak of Al4Li9 in the 15–30° range, and Li-Zn also exhibits characteristic peaks of LiZn at 25° and 41°, indicating that the addition of Al and Zn successfully introduced new phases. In the diffraction patterns of ternary and quaternary alloys, in addition to the characteristic peaks of Al4Li9 and LiZn, the addition of Mg may cause lattice distortion in the lithium matrix, leading to peak shifts. Li-Mg-Al-Zn may combine the combined effects of LiMgAl2 and Li3Al2 solid solutions, resulting in more diffraction peaks or changes in peak intensity, indicating the presence of multiphase or other intermetallic compounds.

[0108] To obtain the microstructure characteristics of the alloys prepared in Examples 1-5, the obtained materials were characterized by SEM to confirm the uniform distribution of each alloy phase and Li. Figure 2 At low magnification, the obvious differences between lithium and other metal elements can be clearly distinguished. Due to the difference in conductivity of the materials, Li appears dark in the image, while other metal elements are distributed more evenly, and there is no obvious agglomeration between alloy elements. The particle size in the alloy composition is between 100-200 nm, and it can be observed that the surface of the prepared alloy foil is relatively smooth after rolling, without obvious cracks and holes, which is beneficial to improving the electrochemical performance of the alloy electrode.

[0109] These uniformly dispersed alloy particles effectively reduce the overpotential of initial lithium metal nucleation and mitigate battery failure caused by SEI film rupture during subsequent cycling. However, the uniformity between alloy components cannot be determined when observing ternary and quaternary alloys; therefore, element mapping is necessary to determine whether the elements are uniformly dispersed. Figure 3 X-ray energy dispersive spectroscopy (EDS) was performed on each alloy component, combined with... Figure 3The distribution of elements in (ae) clearly shows the morphological distribution of Mg, Al, and Zn, and then compared with... Figure 4 The mapping spectra of the alloy components in the sample prove the presence and uniform distribution of the three alloying elements.

[0110] The solid solution-strengthened lithium alloy anode materials prepared in Examples 1-5 were applied to copper foil half-cells, symmetric cells, and lithium iron phosphate full cells, respectively, to form Examples 6-8.

[0111] Example 6:

[0112] The above-mentioned multi-element solid solution reinforced lithium alloy anode material is applied to a copper foil half-cell, which includes:

[0113] a) The working electrodes are made by rolling Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn and Li-Mg-Al-Zn anode materials to a thickness of 0.5 mm and punching them into circular pieces with a diameter of 10 mm.

[0114] b) Using copper foil as the counter electrode and current collector;

[0115] c) Celgard 2400 polypropylene porous membrane is used as the separator, and LBC0045I(G) is used as the electrolyte;

[0116] d) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm, and encapsulate them under a pressure of 350-500psi to form copper foil half cells, denoted as: Li-Al||Cu, Li-Zn||Cu, Li-Mg-Al||Cu, Li-Mg-Zn||Cu, Li-Mg-Al-Zn||Cu.

[0117] The electrochemical performance of the copper foil half-cell prepared in Example 6 above was tested:

[0118] Testing the lithiophilicity of lithium alloy anodes, their nucleation and deposition overpotentials are important performance indicators, such as... Figure 5 Shown are Li-Al||Cu, Li-Zn||Cu, Li-Mg-Al||Cu, Li-Mg-Zn||Cu, Li-Mg-Al-Zn||Cu in 1mAcm -2Time-voltage curves for lithium deposition were presented. The sharp drop in voltage at the beginning of the deposition curve was considered the lithium nucleation potential, and the difference between the nucleation potential and the stabilized deposition potential was considered the lithium deposition overpotential. The results showed that the lithium nucleation overpotentials for Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn, and Li-Mg-Al-Zn electrodes were 148 mV, 217 mV, 175 mV, 110 mV, and 120 mV, respectively, while the deposition overpotentials were 101 mV, 162 mV, 120 mV, 39 mV, and 35 mV. This indicates that the addition of different elements not only improved mechanical properties but also significantly reduced the nucleation overpotential and optimized the lithium affinity of the electrode material. The absence of a significant voltage peak during the initial deposition process leads to smoother SEI film growth and more stable battery operation in subsequent deposition processes.

[0119] Coulombic efficiency (CE) is an important indicator for evaluating the reversibility of lithium metal anode deposition / stripping. The coulombic efficiency of a lithium metal battery is defined as the amount of lithium stripped during cycling divided by the amount of lithium deposited. Figure 6 The figures shown are the coulombic efficiencies and time-voltage curves of Li||Cu, Li-Al||Cu, Li-Zn||Cu, Li-Mg-Al||Cu, Li-Mg-Zn||Cu, and Li-Mg-Al-Zn||Cu half-cells at different current densities. (1 mA cm⁻¹) -2 Current density, 1 mAh cm⁻¹ -2 Charge-discharge tests were conducted at the areal capacity. Except for the Li-Al electrode, all other alloy electrodes remained stable within 300 cycles, with an average coulombic efficiency of 98%, indicating that the half-cells of the foil electrodes of each component have good cycle stability.

[0120] Example 7:

[0121] The above-mentioned multi-element solid solution-strengthened lithium alloy anode material is applied to a symmetrical battery, which includes:

[0122] a) The Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn and Li-Mg-Al-Zn anode materials are rolled to a thickness of 1.0 mm and punched into 10 mm diameter discs, which are then used as positive and negative electrodes, respectively.

[0123] b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte;

[0124] c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm;

[0125] d) Encapsulate under a pressure of 350-500 psi.

[0126] The electrochemical performance of the symmetric cell prepared in Example 7 above was tested:

[0127] A symmetrical battery was fabricated by matching two identical electrodes. The inventors tested the current density of Example 7 at 1 mA / cm². -2 2mAcm -2 5mAcm -2 and 10mAcm -2 Below, the surface capacity is 1mAh cm -2 2mAhcm -2 5mAhcm -2 and 10mAhcm -2 The test results for the following loop performance are as follows: Figure 7 As shown, at 1 mAh cm⁻² and a current density of 1 mA cm⁻², -2 Under these conditions, Li-Mg-Al-Zn symmetric cells can cycle stably for over 600 hours with relatively low hysteresis voltage, such as... Figure 7 (a) The hysteresis voltage was approximately 45 mV in the initial stage of cycling, subsequently stabilizing at around 18 mV. Similarly, the Li-Mg-Zn symmetric cell also maintained a relatively low hysteresis voltage of 20 mV for over 300 hours of cycling. However, the Li-Mg-Al cell exhibited a larger hysteresis voltage after 300 hours of cycling, resulting in unsatisfactory performance at a low current density of 1 mA. Furthermore, the hysteresis voltage of both the Li-Al and Li-Zn cells began to increase continuously in subsequent cycles, failing to meet the performance requirements of the battery at low current densities and even posing a risk of battery failure. Further increasing the current density to 2 mA / cm² is necessary. -2 Surface capacity 2mAh cm -2 Below, such as Figure 7 (b) It can be seen that there are significant differences in the hysteresis voltage of each component. First, the Li-Mg-Al-Zn component still has the lowest hysteresis voltage and is the most stable in operation. Second, the Li-Mg-Zn component maintains a hysteresis voltage of 30mV after more than 350h of cycling. The cycling conditions of the Li-Al and Li-Zn components are not stable, showing large voltage fluctuations. Further increasing the current density to 5mAcm -2 Current density and 5mAhcm -2 areal capacity test, such as Figure 7(c) It is evident that most alloy components exhibit very large nucleation overpotentials at the beginning of cycling, and the hysteresis voltage even increases to 100mV in subsequent cycles. This has a significant impact on the battery's lifespan and safety in practical applications. In contrast, Li-Mg-Al-Zn can still maintain stable operation at 23mV for over 300 hours at the current current density, while at 10mAcm -2 10mAhcm -2 Under the test conditions, such as Figure 7 (d) All battery components exhibited significant nucleation potentials during the initial nucleation stage. However, the Li-Al, Li-Zn, and Li-Mg-Al components showed short-circuit phenomena during subsequent cycles, failing to cycle at high current densities and ultimately leading to battery failure. In contrast, the Li-Mg-Al-Zn component maintained a stable hysteresis voltage of 25mV for over 200 hours under high current density and high areal capacity testing conditions, demonstrating outstanding performance advantages. This is attributed to the uniform dispersion of alloy components within the composition. Li-Mg provides nucleation sites and reduces nucleation overpotential, while Al and Zn improve the mechanical strength of lithium metal, making it less prone to cracking under high current density cycling and slowing dendrite growth, thus resulting in a more stable and reliable battery.

[0128] To demonstrate the interfacial stability of the alloy electrode, the impedance of the electrode interface was measured using electrochemical impedance spectroscopy (EIS). Figure 8 Impedance spectra of pure lithium foil, Li-Mg-Zn, and Li-Mg-Al-Zn electrodes are shown in Table 2. The pure lithium foil exhibits the highest interfacial impedance (5.091 Ω), indicating high charge transfer resistance and poor interfacial stability at the electrode / electrolyte interface. This is because pure lithium foil is prone to violent reactions in the electrolyte, forming an unstable solid electrolyte interfacial (SEI) film, resulting in low ion transport efficiency. The Li-Mg-Zn alloy shows a significantly lower interfacial impedance of 3.517 Ω compared to the lithium foil, indicating that Mg and Zn help improve interfacial characteristics and may participate in the formation of the SEI film, making the film structure more compact. The Li-Mg-Al-Zn alloy further reduces its interfacial impedance to 3.396 Ω, demonstrating optimal interfacial stability and forming a more uniform, dense, and ionicly conductive SEI film, helping the battery maintain low hysteresis voltage and excellent full-cell rate performance during subsequent long-term cycling.

[0129] Table 2. Impedance data of symmetrical cells with lithium foil, Li-Mg-Zn, and Li-Mg-Al-Zn electrodes.

[0130]

[0131] Example 8:

[0132] The above-mentioned multi-element solid solution-strengthened lithium alloy anode material is applied to a lithium iron phosphate full battery, which comprises:

[0133] a) Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn, and Li-Mg-Al-Zn anode materials are rolled to a thickness of 2.0 mm and punched into 10 mm diameter discs to serve as anodes. The cathode material has an active material surface density of 3–4 mg / cm³. -2 The LiFePO4 electrode has a mass ratio of 8:1:1 for LiFePO4:PVDF:SuperP.

[0134] b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte;

[0135] c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm;

[0136] d) Encapsulate under a pressure of 350-500psi to form a lithium iron phosphate full cell, denoted as: Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, Li-Mg-Al-Zn||LFP.

[0137] The electrochemical performance of the lithium iron phosphate full battery prepared in Example 8 above was tested:

[0138] like Figure 9 The figure shows the full-cell performance of Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, and Li-Mg-Al-Zn||LFP in this embodiment. Figure 9 (a) It can be seen that at a current density of 1C, Li-Mg-Zn||LFP has the highest initial capacity, which is 138 mAh g. -1 Secondly, the Li-Al component has a capacity of 137.56 mAh g. -1 The initial capacity of the Li-Mg-Al-Zn||LFP component was 120.72 mAh g. -1However, after 500 cycles, the capacity of Li-Al||LFP began to decline sharply, eventually approaching zero, and the coulombic efficiency also decreased rapidly. Li-Mg-Zn||LFP's capacity began to decline at 300 cycles, and after 600 cycles, the capacity decayed significantly, while the coulombic efficiency also failed to hold. In contrast, although the initial capacity of the Li-Mg-Al-Zn||LFP component was lower than the former two, its capacity remained at 103 mAh g⁻¹ after nearly 800 cycles. -1 The capacity retention rate was 85%, and the coulombic efficiency remained close to 99%, demonstrating optimal long-cycle performance, with capacity only beginning to decline significantly after 830 cycles. From... Figure 9 (b) shows that during the long-term cycling at 5C, the Li-Mg-Al||LFP, Li-Al||LFP, and Li-Zn||LFP components not only exhibited significant capacity decay during long-term cycling, but also showed large fluctuations in coulombic efficiency and very large voltage hysteresis, indicating that the polarization phenomenon was very obvious after 100 cycles and the battery began to fail. In contrast, the Li-Mg-Zn||LFP and Li-Mg-Al-Zn||LFP components maintained relatively high specific capacity.

[0139] Figure 10 This is represented by the charge-discharge curves of the full cells for each component in this embodiment: Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, and Li-Mg-Al-Zn||LFP. From... Figure 10 As shown in (a), after 300 cycles at a current density of 1C, the Li-Mg-Zn||LFP and Li-Mg-Al-Zn||LFP components maintained high capacity levels, while other components showed significant degradation. Figure 10 As can be seen in (bf), the charge-discharge curves of each component at different cycle numbers show that although the Li-Mg-Zn||LFP component maintains a high specific capacity at the beginning of the cycle, its capacity decreases significantly in subsequent cycles. In contrast, the Li-Mg-Al-Zn component maintains a fairly stable capacity change and has less voltage hysteresis, which demonstrates the superiority of these two full cell groups.

[0140] Figure 11 The figure shows the rate performance of the Li-Al||LFP, Li-Zn||LFP, Li-Mg-Al||LFP, Li-Mg-Zn||LFP, and Li-Mg-Al-Zn||LFP full cells in this embodiment. From... Figure 11As shown in (a), the Li-Mg-Al-Zn||LFP composition exhibits the highest specific capacity at different discharge rates, and its advantage becomes more pronounced with increasing discharge rate. At 5C, the specific capacity of the Li-Mg-Al-Zn||LFP composition is 121.5 mAh g⁻¹. -1 It still retains 96.7 mAh g at 10C. -1 In contrast, the Li-Mg-Zn||LFP component has only 90 mAh g at 10C. -1 The capacity decrease of other components was even more pronounced, with a capacity of less than 40 mAh g. -1 The capacity. Figure 11 As shown in (bf), the charge-discharge curves of different components at different rates are as follows: the Li-Mg-Al-Zn||LFP component not only exhibits smaller polarization, but also has better cycle performance and rate performance than other components, especially at high rates, indicating that it has better application prospects in terms of high rate performance and cycle stability.

[0141] In summary, the embodiments of this invention prepared lithium alloy electrodes with five components—Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn, and Li-Mg-Al-Zn—through suspension melting. The preparation process of the entire alloy composition and its corresponding morphological characteristics were revealed, the dispersion of each alloy component in lithium metal was investigated, and the electrochemical performance of the materials was tested. Copper foil half-cells, symmetrical cells, and matched lithium iron phosphate full cells were assembled to study their cycle performance, leading to the following conclusions:

[0142] This invention systematically evaluated the stability and interfacial kinetics of alloy electrodes by assembling copper foil half-cells, symmetrical cells, and lithium iron phosphate (LFP) full-cell systems. The results show that the lithium alloy anode with the Li-Mg-Al-Zn alloy composition exhibits the best overall performance: the Li-Mg-Al-Zn||Cu half-cell performs optimally at 1 mA cm⁻¹. -2 It exhibits high coulombic efficiency (~98%) at current densities of [value missing], and also possesses low nucleation overpotential (120 mV) and the lowest deposition overpotential (35 mV). Symmetric cells at 1 mA cm⁻¹ [value missing] -2 Cycling at current density for over 650 hours, maintaining a hysteresis voltage of 18mV, and at 10mAcm -2 Even at high current densities, it can still cycle stably for over 250 hours with a hysteresis voltage of 25 mV. In a full-cell system matched with lithium iron phosphate (LFP), the Li-Mg-Al-Zn||LFP battery exhibits good cycle stability, maintaining stable cycling for over 800 hours at a 1C current density while retaining a capacity of 102 mAh / cm³. -2 The capacity retention rate is 85%.

[0143] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for preparing multi-element solid solution strengthened lithium alloy anode materials, characterized in that, include: a) Lithium metal is mixed with one or more metallic auxiliary elements by mass percentage, wherein the auxiliary elements account for 5%–30% of the mass of lithium metal, and after mixing, the mixture is placed into a copper crucible under an inert atmosphere. b) Place the copper crucible in the center of the induction coil of the suspension melting device, evacuate to a vacuum level not exceeding 1 Pa and fill with inert gas for protection, and perform suspension melting for 2 min–10 min at an induction power of 5 kW–20 kW. c) After melting, allow it to cool naturally or at a temperature of 1°C / min. -1 -20℃min -1 Cool to room temperature at a controlled rate; d) The obtained alloy was transferred to an argon glove box with oxygen and water content both less than 0.01 ppm, the surface oxide layer was mechanically removed and the alloy was encapsulated to obtain a multi-element solid solution strengthened lithium alloy anode material.

2. The method for preparing the multi-element solid solution strengthened lithium alloy anode material according to claim 1, characterized in that, The auxiliary metal element is selected from one or more of magnesium, aluminum, and zinc, and the resulting alloy is a Li-Mg, Li-Al, Li-Zn, Li-Mg-Al, Li-Mg-Zn, or Li-Mg-Al-Zn alloy.

3. The method for preparing the multi-element solid solution strengthened lithium alloy anode material according to claim 2, characterized in that, The mass percentage of the auxiliary element in the alloy is: Li-Mg alloy: Mg is 5%–30%, with the balance being lithium; Li-Al alloy: Al is 5%–30%, with the balance being lithium; Li-Zn alloy: Zn is 5%–30%, with the balance being lithium; Li-Mg-Al alloy: Mg 10%–25%, Al 5%–20%, balance lithium; Li-Mg-Zn alloy: Mg 10%–25%, Zn 5%–20%, balance lithium; Li-Mg-Al-Zn alloy: Mg 5%–20%, Al 2%–5%, Zn 2%–5%, balance lithium.

4. The method for preparing the multi-element solid solution strengthened lithium alloy anode material according to any one of claims 1-3, characterized in that, After step d), the resulting lithium alloy is subjected to incremental multi-pass rolling with a thickness of 0.1–5 mm, and stress-relief annealing is performed at 20–100 °C between each rolling pass.

5. The method for preparing the multi-element solid solution strengthened lithium alloy anode material according to any one of claims 1-3, characterized in that, The cooling method in step c) is quenching, in which the crucible and the molten alloy are immersed in a cooling medium of -80°C to -196°C.

6. The method for preparing the multi-element solid solution strengthened lithium alloy anode material according to any one of claims 1-3, characterized in that, After step b) ends the heating, continue to keep warm at 600–800℃ for 1–10 minutes.

7. A multi-element solid solution strengthened lithium alloy anode material, characterized in that, Obtained by the preparation method according to any one of claims 1–6.

8. The application of the multi-element solid solution reinforced lithium alloy anode material according to claim 7 in copper foil half-cells, characterized in that, The copper foil half-cell comprises: a) The lithium alloy negative electrode material is rolled to a thickness of 0.1-3.0 mm and punched into a circular sheet with a diameter of 8-15 mm as the working electrode; b) Using copper foil as the counter electrode and current collector; c) Celgard 2400 polypropylene porous membrane is used as the separator, and LBC0045I(G) is used as the electrolyte; d) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm and encapsulate them under a pressure of 350-500psi.

9. The application of the multi-element solid solution reinforced lithium alloy anode material according to claim 7 in a symmetrical battery, characterized in that, The symmetrical battery includes: a) The lithium alloy negative electrode material is rolled to a thickness of 0.1-3.0 mm and punched into circular pieces with a diameter of 8-15 mm, which are then used as the positive and negative electrodes respectively; b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte; c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm; d) Encapsulate under a pressure of 350-500 psi.

10. The application of the multi-element solid solution reinforced lithium alloy anode material according to claim 7 in lithium iron phosphate full batteries, characterized in that, The lithium iron phosphate full battery includes: a) The lithium alloy anode material is rolled to a thickness of 0.1-3.0 mm and punched into circular sheets with a diameter of 8-15 mm to serve as the anode. The cathode has an active material surface density of 3-4 mg / cm³. -2 The LiFePO4 electrode has a mass ratio of 8:1:1 for LiFePO4:PVDF:SuperP. b) Celgard 2400 polypropylene porous membrane was used as the separator, and LBC0045I(G) was used as the electrolyte; c) Assemble CR2032 button cells in an argon glove box with H2O / O2 both below 0.1ppm; d) Encapsulate under a pressure of 350-500 psi.

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