A lithium-aluminum alloy negative electrode material for a lithium metal battery, a preparation method thereof, and an application thereof

Abstract

A lithium-aluminum alloy negative electrode material for a lithium metal battery, its preparation method and application, wherein the method includes: weighing lithium metal and aluminum metal according to an atomic ratio of 93:7 - 81:19 and mixing them as raw materials; putting the weighed and mixed raw materials into the chamber of a melting and spinning equipment, under an argon protection atmosphere, melting the raw materials by heating to form a liquid alloy, then spray-casting the liquid alloy, and collecting the material by a copper roller at a linear speed of 20 - 45 m / sec; rolling the product collected on the copper roller into a thin sheet with a thickness of 100 - 300 um, and obtaining the lithium-aluminum alloy negative electrode material after cutting. The present invention adopts the melting and spinning method, and its controllable process conditions and rapid cooling after melting contribute to the precise control of the lithium alloy preparation process. By performing melting and spinning under a protection atmosphere, it is possible to better manage the composition and structure of the lithium alloy, not only overcoming problems such as lithium metal shedding, but also providing a more customized solution for specific application scenarios of the lithium alloy.

Description

Technical Field

[0001] The present invention relates to the field of lithium metal batteries, and particularly to a lithium-aluminum alloy negative electrode material for lithium metal batteries, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium metal anodes are considered the best choice for next-generation lithium-ion batteries due to their high theoretical specific capacity (3860 mAh g -1 ) and low redox potential (-3.04 V vs standard hydrogen electrode). Among them, lithium-aluminum alloys have the characteristics of low density, high specific strength, high elastic modulus, low fatigue crack growth rate, good low-temperature performance, good corrosion resistance, and excellent superplastic formability. Due to the abundant reserves of aluminum metal, lithium-aluminum alloys are regarded as potential lithium alloy negative electrode materials. However, there is a problem with lithium-aluminum alloys during cycling, that is, they are prone to falling off from the current collector, resulting in the loss of electrochemical activity and thus reducing battery performance. To solve this problem, researchers have been committed to exploring the preparation of lithium-aluminum alloys and the regulation of the mass ratio. Considering the extremely high activity of lithium and its extreme sensitivity during the preparation process, the preparation of nano-lithium powder faces a series of severe challenges. This high activity causes lithium to react rapidly with oxygen in the air to form oxides such as lithium oxide. This reaction not only causes the surface of the nano-lithium powder to be wrapped by oxides, reducing its electrochemical performance, but also may cause additional safety hazards. The extreme sensitivity of lithium metal to moisture and other pollutants further exacerbates the complexity of nano-lithium powder preparation. Tiny moisture or trace pollutants are sufficient to trigger reactions, forming compounds or surface oxides, thereby damaging the purity and stability of nano-lithium powder. At the nanoscale, this sensitivity is more significant, requiring extremely clean conditions to be maintained throughout the preparation process. Due to the extreme activity of lithium metal, the processed and stored nano-lithium powder needs to be carried out in an anhydrous and anoxic environment, which not only increases the strict requirements for equipment and operating environment, but also improves the complexity and cost of the preparation process.

[0003] Generally speaking, the reactivity and extreme sensitivity of lithium bring multiple challenges to the preparation of nano-lithium powder. Comprehensive measures need to be taken in various aspects to ensure the quality, stability, and safety of nano-lithium powder, which is still the focus of current research. Summary of the Invention

[0004] Based on this, the present invention provides a lithium-aluminum alloy negative electrode material for lithium metal batteries, a preparation method thereof, and an application thereof. At present, no one has used a melting and spinning equipment to prepare a lithium alloy negative electrode material, and the introduction of the melting and spinning method fills the blank in this field. This innovative method provides a new way for the preparation of lithium alloy negative electrode materials and brings new possibilities to its application fields.

[0005] To achieve the above object, the present invention provides a method for preparing a lithium-aluminum alloy negative electrode material for a lithium metal battery, which includes the following steps:

[0006] (1) Weigh lithium metal and aluminum metal according to an atomic ratio of 93:7 - 81:19 and mix them as raw materials;

[0007] (2) Select a melting and spinning equipment with a sealed chamber, put the weighed and mixed raw materials into the chamber of the melting and spinning equipment, and under an argon protection atmosphere, heat and melt the raw materials to form a liquid alloy, then spray-cast the liquid alloy, and collect the material with a copper roller at a linear speed of 20 - 50 m / sec;

[0008] (3) Roll the product collected on the copper roller in step (2) into a thin sheet with a thickness of 100 - 300 μm, and after cutting, obtain the lithium-aluminum alloy negative electrode material.

[0009] As a further preferred technical solution of the present invention, in step (2), the raw materials are contained in a crucible with a stainless steel inner lining and put into the chamber of the melting and spinning equipment.

[0010] As a further preferred technical solution of the present invention, in step (2), after putting the raw materials into the chamber and before heating for melting, the vacuum degree of the chamber of the melting and spinning equipment is pumped to below 6×10 -2 Pa, and then argon gas is filled into the chamber to achieve an argon atmosphere.

[0011] As a further preferred technical solution of the present invention, the copper roller is a single copper-made runner with a thickness of 50 mm and a diameter of 300 mm. During the melting process and before spray-casting, the copper roller rotates at a speed of 1500 rpm; during spray-casting and material collection, the rotation speed of the copper roller is 3500 rpm.

[0012] As a further preferred technical solution of the present invention, in step (2), the spray-casting pressure is 0.2 Mpa.

[0013] According to another aspect of the present invention, the present invention also provides a lithium-aluminum alloy negative electrode material prepared by the above method.

[0014] According to another aspect of the present invention, the present invention also provides the application of the above lithium-aluminum alloy negative electrode material in a lithium metal battery.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0016] The present invention adopts the method of melting and spinning, and its controllable process conditions and rapid cooling after melting contribute to the precise regulation of the lithium alloy preparation process. By carrying out melting and spinning under a protective atmosphere, the composition and structure of the lithium alloy can be better managed, not only overcoming problems such as lithium metal shedding, but also providing a more customized solution for specific application scenarios of the lithium alloy.

[0017] The present invention adopts the method of melting and spinning, and the prepared lithium-aluminum alloy negative electrode material has a micro-nano structure. When applied to a lithium metal battery, its electrochemical performance and cycle life can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0019] Figure 1 SEM photographs of (a-c) lithium-aluminum alloy (Li-Al at% = 93:7) for Example 1.

[0020] Figure 2 SEM photographs of (a-c) lithium-aluminum alloy (Li-Al at% = 86:14) for Example 2.

[0021] Figure 3 SEM photographs of (a-c) lithium-aluminum alloy (Li-Al at% = 81:19) for Example 3.

[0022] Figure 4 XRD spectra of lithium-aluminum alloys with different atomic ratios.

[0023] Figure 5 Coulomb efficiency curves of Li-Al alloy||Cu half-cells assembled with lithium-aluminum alloys with different atomic ratios.

[0024] Figure 6 EIS curves of symmetric cells assembled with Li-Al alloys with different atomic ratios.

[0025] Figure 7 Critical current density (CCD) curves of symmetric cells assembled with lithium-aluminum alloys with different atomic ratios.

[0026] Figure 8 For symmetric cells assembled with lithium-aluminum alloys with different atomic ratios at 1 mA cm -2 , 1 mAh cm -2 when the cycle performance curve.

[0027] Figure 9 SEM photographs of the sample of (a-c) lithium-aluminum alloy (Li-Al at% = 93:7) for Example 4 at a rotational speed of 5000 rpm.

[0028] Figure 10 The cyclic performance curve of the symmetric cell assembled with the sample of the lithium-aluminum alloy (Li-Al at% = 93:7) in Example 4 at a rotational speed of 5000 rpm at 1 mA cm -2 , 1 mAh cm -2 .

[0029] The realization of the purpose, functional features and advantages of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0030] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0031] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0032] Example 1

[0033] The lithium-aluminum alloy negative electrode material for a lithium metal battery and its preparation method in this embodiment include the following steps:

[0034] First, weigh lithium metal and aluminum metal as raw materials with an atomic ratio of 93:7 using an electronic balance.

[0035] Second, select a melting and spinning equipment with a sealed cabin, put the weighed raw materials into the cabin in advance, start the melting and spinning system, wait until the vacuum degree reaches below 6*10 -2 Pa, fill the cabin with argon gas, and the subsequent melting and spinning process is carried out under argon protection. Install the raw materials in a crucible with a stainless steel inner lining and install the crucible at the designated position. Start to increase the power to heat and melt the raw materials, and at the same time start the copper roller to rotate at a speed of 1500 rpm; after the power reaches 1.2 kw (about 600 - 800 °C), the raw materials melt to form a liquid alloy. Adjust the speed of the copper roller to 3500 rpm (linear speed is 35 m / sec), lower the crucible for spray casting, and the spray casting pressure is 0.2 Mpa. After the cabin cools down, collect the strip samples on the copper roller. Among them, the copper roller is a single copper-made runner, the copper coating thickness is 50 mm, and the copper roller diameter is 300 mm.

[0036] Fourth, use a roller press to roll the above-prepared sample into a thin sheet with a thickness of about 200 um, and then cut it into a disc with a diameter of 10 mm.

[0037] The SEM image of the lithium-aluminum alloy negative electrode material prepared in this embodiment under a scanning electron microscope is asFigure 1 The X-ray diffraction results are shown in Figure 4 shown.

[0038] Example 2

[0039] Compared with Example 1, the difference of this example is that the atomic ratio of lithium metal to aluminum metal is 86:14. The SEM image of the lithium aluminum alloy negative electrode material prepared in this example under a scanning electron microscope is as follows: Figure 2 The X-ray diffraction results are shown in Figure 4 shown.

[0040] Example 3

[0041] Compared with Example 1, the difference of this example is that the atomic ratio of lithium metal to aluminum metal is 81:19. The SEM image of the lithium aluminum alloy negative electrode material prepared in this example under a scanning electron microscope is as follows: Figure 3 The X-ray diffraction results are shown in Figure 4 shown.

[0042] See also Figures 1-3 It can be seen that when the lithium-aluminum atomic ratio is 93:7, the sample is in the form of nanoparticles ( Figure 1 ), when the ratio of Al atoms increases to 86:14, the particle size increases and is obviously in two different phases ( Figure 2 ), and the two-phase structure becomes more obvious when it further increases to 81:19 ( Figure 3 ).

[0043] See also Figure 4 The XRD results show that the alloy negative electrode materials of Examples 1-3 are all composed of Li single substance, Al single substance and Al4Li9. Therefore, the lithium-aluminum alloy negative electrode material is successfully prepared by the melting and stripping method.

[0044] The lithium aluminum alloy negative electrode materials prepared in Examples 1 and 2 were used to assemble Li-Al alloy||Cu half-cells (2325 was used as the separator, and the electrolyte was 1.0M LiPF6 in EC:DEC=1:1Vol%with 5.0%FEC). The strip sample prepared in step (2) was rolled into a 200 μm thick sheet, which was cut into 10 mm diameter circles using a sheet cutter. A 10 mm diameter copper foil was used as the negative electrode to assemble a 2025 battery to test the electrochemical performance. The results are as follows: Figure 5 As shown, when the atomic ratio of lithium to aluminum is 86:14, it can be cycled 72 times with an average coulombic efficiency of 92.12%, and when the atomic ratio of lithium to aluminum is 93:7, it can be cycled 85 times with an average coulombic efficiency of 93.33%.

[0045] The lithium-aluminum alloy anode materials prepared in Examples 1 and 2 were respectively used to assemble symmetric cells (the separator was 2325, and the electrolyte was 1.0 M LiPF6 in EC:DEC = 1:1 Vol% with 5.0% FEC). The strip-shaped samples prepared in step (2) were rolled into thin sheets with a thickness of 200 μm, and were cut into circles with a diameter of 10 mm using a cutter, and assembled into 2025 cells to test the electrochemical performance. The results are as Figure 6 、 7 and shown in Figure 8. Impedance spectroscopy tests showed that the sample with a lithium-to-aluminum atomic ratio of 93:7 had a smaller charge transfer resistance ( Figure 6 ), and its critical current density (CCD) reached 13 mA cm -2 ( Figure 7 ). The CCD value of the symmetric cell assembled with the lithium-aluminum alloy anode material with an atomic ratio of 86:14 was 11 mA cm -2 . The symmetric cell assembled with the lithium-aluminum alloy with an atomic ratio of 86:14 could stably cycle for 400 h at 1 mA cm -2 and 1 mAh cm -2 . The sample with an atomic ratio of 93:7 could cycle for 600 h ( Figure 8 ).

[0046] Example 4

[0047] This example is different from Example 1 in that the rotational speed of the copper roller in the melt spinning process was changed, and the linear speed was increased from 35 m / sec to 50 m / sec.

[0048] In this example, under the condition of a linear speed of 50 m / sec, the lithium-aluminum alloy (atomic ratio of 93:7) was subjected to strip quenching treatment. Figure 9 Figure is the sample image observed by scanning electron microscopy. It can be clearly seen from the figure that compared with the lithium-aluminum alloy with an atomic ratio of 93:7 and a linear speed of 35 m / sec in Example 1, the two-phase structure of the sample is more obvious, but the electrochemical performance is slightly weakened, as Figure 10 shows that for the symmetric cell assembled with the lithium-aluminum alloy (Li-Al at% = 93:7) at a rotational speed of 5000 rpm, at 1 mA cm -2 and 1 mAh cm -2 , it can cycle for about 500 h.

[0049] Furthermore, on the basis of Example 4, through a large number of experimental comparisons, it can be known that if the rotational speed of the copper roller is further increased, that is, the rapid quenching speed is increased (>5000 rpm), the two-phase structure of the sample will be more obvious, and the electrochemical performance will be further weakened. It is confirmed that the cooling rate has an important influence on the phase composition of the Li-Al alloy and affects its electrochemical performance in applications.

[0050] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The protection scope of the present invention is only defined by the appended claims.

Claims

1. A preparation method of a lithium-aluminum alloy negative electrode material for a lithium metal battery, characterized in that, It includes the following steps: (1) Weigh lithium metal and aluminum metal according to an atomic ratio of 93:7 - 81:19 and mix them as raw materials; (2) Select a melting and spinning equipment with a sealed chamber. Put the weighed and mixed raw materials into the chamber of the melting and spinning equipment. Under an argon protective atmosphere, heat and melt the raw materials to form a liquid alloy through melting, then spray-cast the liquid alloy, and collect the material with a copper roller at a linear speed of 20 - 50 m / sec; (3) Roll the product collected on the copper roller in step (2) into a thin sheet with a thickness of 100 - 300 μm, and obtain the lithium-aluminum alloy negative electrode material after cutting; The temperature of heating and melting in step (2) is 600 - 800 °C.

2. The preparation method of the lithium-aluminum alloy negative electrode material for a lithium metal battery according to claim 1, wherein, In step (2), the raw materials are contained in a crucible with a stainless steel inner lining and put into the chamber of the melting and spinning equipment.

3. The preparation method of the lithium-aluminum alloy negative electrode material for a lithium metal battery according to claim 1, wherein In step (2), after putting the raw materials into the chamber and before heating for melting, the vacuum degree of the chamber of the melting spin casting equipment is pumped to the following, and then argon gas is filled into the chamber to achieve an argon gas atmosphere.

4. The preparation method of the lithium-aluminum alloy negative electrode material for a lithium metal battery according to claim 1, characterized in that, The copper roller is a single copper-made runner with a thickness of 50 mm and a diameter of 300 mm.

5. The preparation method of the lithium-aluminum alloy negative electrode material for a lithium metal battery according to claim 4, wherein, During the melting process and before spray-casting, the copper roller rotates at a speed of 1500 rpm; during spray-casting and material collection, the rotation speed of the copper roller is 3500 rpm.

6. The preparation method of the lithium-aluminum alloy negative electrode material for a lithium metal battery according to claim 1, wherein In step (2), the spray-casting pressure is 0.2 Mpa.

7. A lithium-aluminum alloy negative electrode material, characterized in that, It is prepared by using the method described in any one of claims 1 - 6.

8. Application of the lithium-aluminum alloy negative electrode material described in claim 7 in a lithium metal battery.

Images