Amorphous nanocrystalline composite lithium metal negative electrode, preparation method and application

Abstract

The invention discloses an amorphous nanocrystalline composite lithium metal negative electrode, a preparation method and application, and belongs to the technical field of lithium batteries. A preparation method of an amorphous nanocrystalline composite lithium metal negative electrode comprises the following steps: (1) polishing a lithium sheet in a drying room, taking a mixed target material as a sputtering source, putting the mixed target material into magnetron sputtering equipment, and coating by using a physical vapor deposition method until the thickness is 100nm to obtain a lithium sheet containing an amorphous alloy layer, repeatedly plating the amorphous alloy layer on the back surface of the lithium sheet in the same way to obtain an amorphous modified lithium metal negative plate; and (2) taking out the amorphous modified lithium metal negative electrode plate, and crystallizing the amorphous alloy layer by using nanosecond laser to obtain the amorphous nanocrystalline composite lithium metal negative electrode. When the prepared amorphous nanocrystalline composite lithium metal negative electrode is applied to a lithium metal battery, the cycle performance of the battery can be remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and particularly relates to an amorphous-nanocrystalline composite lithium metal anode, a preparation method and an application thereof. Background Art

[0002] Since the mid-20th century, lithium metal batteries have received extensive attention from academia and industry due to their ultra-high theoretical specific capacity and low standard reduction potential. These unique electrochemical properties make lithium metal an ideal choice for high-performance battery anode materials, especially in application fields that pursue high energy density, such as electric vehicles, portable electronic devices and energy storage systems.

[0003] However, the practical application of lithium metal batteries faces a series of challenges. During charge and discharge cycles, the electrolyte will be reduced by lithium metal to form a solid electrolyte interface (SEI). While this interface protects the lithium metal from further corrosion, it also brings new problems. Especially during the charging process, the deposition of lithium (i.e., "lithium plating") is often uneven, leading to an increase in the mechanical instability of the SEI and prone to cracking, thus continuously exposing new lithium metal surfaces. This exposure not only accelerates the consumption of the electrolyte, reduces the coulombic efficiency of the battery, but also makes the SEI thickness increase continuously, thereby increasing the internal resistance of the battery. More seriously, the cracked SEI provides new sites for the uneven deposition of lithium, promoting the formation of dead lithium and lithium dendrites. According to the Sand equation, the formation time of lithium dendrites is inversely proportional to the current density, meaning that at high current densities, the formation rate of lithium dendrites will accelerate, seriously threatening the safety and cycle life of the battery. In traditional technologies, protective coatings or solid electrolytes can be used to improve the problem of lithium dendrites, but this usually leads to a reduction in the cycle performance of lithium batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide an amorphous-nanocrystalline composite lithium metal anode, a preparation method and an application thereof, aiming to improve the problem of lithium dendrites while ensuring the cycle performance of lithium batteries.

[0005] The purpose of the present invention can be achieved by the following technical solutions: In the first aspect, a preparation method of an amorphous-nanocrystalline composite lithium metal anode includes the following steps: (1) Polish a lithium sheet in a drying room, use a mixed target as a sputtering source, put it into a magnetron sputtering device, and perform coating by physical vapor deposition until the thickness reaches 100 nm to obtain a lithium sheet containing an amorphous alloy layer. Repeat the coating of the amorphous alloy layer on the reverse side of the lithium sheet in the same way to obtain an amorphous-modified lithium metal anode sheet; (2) Take out the amorphous-modified lithium metal anode sheet and crystallize the amorphous alloy layer by using a nanosecond laser to obtain an amorphous-nanocrystalline composite lithium metal anode.

[0006] Further, in step (1), magnetron sputtering is carried out under the protection of an argon atmosphere, the air pressure is 3 mT - 10 mT, and the sputtering power of magnetron sputtering is 80 - 1000 W.

[0007] Further, in step (1), the atomic percentage expression of the amorphous alloy layer is D a E b Cu c , where D is any 3 or 4 of Fe, Al, Zr, Ag, Ti, Mg, V, Y, Co, Ni, Nb, and the sum of the atomic percentages of each element is a; E is any 1 or 2 of Si, B, C, N, and the sum of the atomic percentages of each element is b; a, b, and c are all atomic percentages, and the value ranges are 71 ≤ a ≤ 90, 0 ≤ b ≤ 19, 1 ≤ c ≤ 10, and a + b + c = 100.

[0008] Further, in step (2), the nanosecond laser energy density is 110 - 500 mJ / cm 2 .

[0009] In a second aspect, an amorphous-nanocrystalline composite lithium metal anode, with a flexible metallic lithium inner layer, an amorphous alloy layer in the middle, and a nanocrystalline layer on the outer layer.

[0010] The amorphous-nanocrystalline composite anode can greatly improve the processability of lithium metal batteries and inhibit the growth of lithium dendrites through the high Young's modulus of the amorphous layer. The nanocrystals can provide more sites for lithium deposition and promote uniform lithium ion deposition.

[0011] In a third aspect, the application of the amorphous-nanocrystalline composite lithium metal anode in a lithium metal battery.

[0012] Advantages of the present invention: 1. The present invention prepares an amorphous-nanocrystalline composite lithium metal anode through an amorphous-nanocrystalline composite lithium sheet. The amorphous layer has a high Young's modulus, which can inhibit the growth of lithium dendrites and promote the cycling performance of lithium metal batteries. Moreover, the amorphous alloy has good corrosion resistance, which can effectively inhibit electrolyte corrosion, and further improve the cycling performance of lithium metal batteries.

[0013] 2. Forming nanocrystals in-situ on the amorphous alloy can increase the specific surface area and conductivity. By adjusting the electric field and ion concentration field at the interface, it is possible to induce directional and uniform nucleation and deposition of lithium on the nanocrystals. This directional deposition helps reduce the formation of lithium dendrites, thereby extending the service life of the battery and improving the cycling performance of lithium metal batteries. Description of the Drawings

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 Morphology diagram of the amorphous-nanocrystalline composite lithium metal anode in Example 1; Figure 2 Morphology diagram of the amorphous lithium metal anode in Comparative Example 2. Specific embodiments

[0016] The following will describe clearly and completely the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] Example 1

[0018] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal anode, including the following steps: (1) In a drying room, load high-purity Fe target, high-purity Si target, high-purity B target, high-purity Nb target, and high-purity Cu target into a magnetron sputtering device. Polish the lithium sheet and load it into the magnetron sputtering chamber. Deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of an argon atmosphere, the air pressure is 3 mT, and the sputtering power of magnetron sputtering is 80 W. After turning off the magnetron sputtering device and cooling it, obtain Fe 77 Si 10 B9Nb3Cu1 amorphous-modified lithium metal anode sheet.

[0019] (2) Take out the Fe 77 Si 10 B9Nb3Cu1 amorphous-modified lithium metal anode sheet, and crystallize the amorphous alloy layer by nanosecond laser. The energy density of the nanosecond laser is 500 mJ / cm 2 , and obtain an amorphous-nanocrystalline composite lithium metal anode.

[0020] Example 2

[0021] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal anode, including the following steps: (1) In a drying room, load high-purity AlY target, high-purity Ni target, high-purity Zr target, and high-purity Cu target into a magnetron sputtering device. Polish the lithium sheet and load it into the magnetron sputtering chamber. Deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of an argon atmosphere, the air pressure is 5 mT, and the sputtering power of magnetron sputtering is 900 W. After turning off the magnetron sputtering device and cooling it, obtain Al 84Ni8Zr3Cu3Y2 amorphous modified lithium metal negative electrode sheet.

[0022] (2) Take out Al 84 Ni8Zr3Cu3Y2 amorphous modified lithium metal negative electrode sheet, crystallize the amorphous alloy layer by nanosecond laser, and the energy density of the nanosecond laser is 320 mJ / cm 2 to obtain an amorphous-nanocrystalline composite lithium metal negative electrode.

[0023] Example 3

[0024] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a dry room, load high-purity AlY target, high-purity Ni target, high-purity Nb target, and high-purity Cu target into the magnetron sputtering equipment, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 10 mT, and the sputtering power of magnetron sputtering is 1000 W. After turning off the magnetron sputtering equipment and cooling, obtain Al 52 Ni 25 Nb 15 Cu3Y2 amorphous modified lithium metal negative electrode sheet.

[0025] (2) Take out Al 52 Ni 25 Nb 15 Cu3Y2 amorphous modified lithium metal negative electrode sheet, crystallize the amorphous alloy layer by nanosecond laser, and the energy density of the nanosecond laser is 110 mJ / cm 2 to obtain an amorphous-nanocrystalline composite lithium metal negative electrode.

[0026] Example 4

[0027] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a dry room, load high-purity Ti target, high-purity Ni target, high-purity Nb target, high-purity Cu target, and high-purity Zr target into the magnetron sputtering equipment, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 6 mT, and the sputtering power of magnetron sputtering is 85 W. After turning off the magnetron sputtering equipment and cooling, obtain Ti 50 Ni 30 Zr 10 Nb5Cu5 amorphous modified lithium metal negative electrode sheet.

[0028] (2) Take out Ti 50 Ni 30 Zr 10 Nb5Cu5 amorphous modified lithium metal negative electrode sheet, crystallize the amorphous alloy layer by nanosecond laser, and the energy density of the nanosecond laser is 430 mJ / cm 2 , to obtain an amorphous-nanocrystalline composite lithium metal negative electrode.

[0029] Example 5

[0030] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a drying room, load high-purity ZrN target, high-purity Nb target, high-purity B target, and high-purity Cu target into a magnetron sputtering device, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 7 mT, and the sputtering power of magnetron sputtering is 90 W. After turning off the magnetron sputtering device and cooling it, Zr 75 N5Nb 10 B5Cu5 amorphous modified lithium metal negative electrode sheet.

[0031] (2) Take out Zr 75 N5Nb 10 B5Cu5 amorphous modified lithium metal negative electrode sheet, crystallize the amorphous alloy layer by nanosecond laser, and the energy density of the nanosecond laser is 130 mJ / cm 2 , to obtain an amorphous-nanocrystalline composite lithium metal negative electrode.

[0032] Example 6

[0033] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a drying room, load high-purity Zr target, high-purity Al target, high-purity Ni target, and high-purity Cu target into a magnetron sputtering device, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, and repeatedly coat according to the program control until the target thickness of 100 nm is reached. Repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 10 mT, and the sputtering power of magnetron sputtering is 590 W. After turning off the magnetron sputtering device and cooling it, Zr 60 Al 20 Cu 10 Ni 10 amorphous modified lithium metal negative electrode sheet.

[0034] (2) Take out Zr 60 Al 20 Cu 10Ni 10 Amorphous-modified lithium metal negative electrode sheet, the amorphous alloy layer is crystallized by nanosecond laser, and the nanosecond laser energy density is 450 mJ / cm 2 , obtaining an amorphous-nanocrystalline composite lithium metal negative electrode.

[0035] Example 7

[0036] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a dry room, load high-purity Ti target, high-purity Nb target, high-purity Fe target, high-purity Zr target, and high-purity Cu target into a magnetron sputtering device, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, repeatedly coat according to the program control, reach the target thickness of 100 nm, and repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 8 mT, and the sputtering power of magnetron sputtering is 80 W. After turning off the magnetron sputtering device and cooling it, obtain Ti 60 Nb 18 Fe 10 Zr5Cu7 amorphous-modified lithium metal negative electrode sheet.

[0037] (2) Take out the Ti 60 Nb 18 Fe 10 Zr5Cu7 amorphous-modified lithium metal negative electrode sheet, crystallize the amorphous alloy layer by nanosecond laser, and the nanosecond laser energy density is 500 mJ / cm 2 , obtaining an amorphous-nanocrystalline composite lithium metal negative electrode.

[0038] Example 8

[0039] This example provides a method for preparing an amorphous-nanocrystalline composite lithium metal negative electrode, including the following steps: (1) In a dry room, load high-purity Ag target, high-purity Nb target, high-purity Al target, high-purity Zr target, high-purity C target, and high-purity Cu target into a magnetron sputtering device, polish the lithium sheet, load it into the magnetron sputtering chamber, deposit the corresponding alloy by adjusting the power of different targets, repeatedly coat according to the program control, reach the target thickness of 100 nm, and repeat this step on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of argon atmosphere, the air pressure is 7 mT, and the sputtering power of magnetron sputtering is 490 W. After turning off the magnetron sputtering device and cooling it, obtain Ag 60 Al 10 Nb 15 Zr5C5Cu5 amorphous-modified lithium metal negative electrode sheet.

[0040] (2) Take out the Ag 60 Al 10 Nb 15Zr5C5Cu5 amorphous modified lithium metal anode sheet, the amorphous alloy layer is crystallized by nanosecond laser, and the energy density of the nanosecond laser is 355 mJ / cm 2 , obtaining an amorphous-nanocrystalline composite lithium metal anode.

[0041] Comparative Example 1

[0042] In this comparative example, a 100-μm pure lithium sheet is used.

[0043] Comparative Example 2

[0044] This comparative example provides a preparation method for an amorphous modified lithium metal anode, including the following steps: In a drying room, a high-purity Fe target, a high-purity Si target, a high-purity B target, a high-purity Nb target, and a high-purity Cu target are loaded into a magnetron sputtering device. The lithium sheet is polished and loaded into the magnetron sputtering chamber. By adjusting the power of different targets, the deposition of the corresponding alloy is carried out. According to the program control, the plating is repeated to reach the target thickness of 100 nm, and this step is repeated on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of an argon atmosphere, the air pressure is 3 mT, and the sputtering power of magnetron sputtering is 80 W. After the magnetron sputtering device is shut down and cooled, Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal anode.

[0045] Comparative Example 3

[0046] This comparative example provides a preparation method for a nanocrystalline modified lithium metal anode, including the following steps: (1) In a drying room, a high-purity Fe target, a high-purity Si target, a high-purity B target, a high-purity Nb target, and a high-purity Cu target are loaded into a magnetron sputtering device. The lithium sheet is polished and loaded into the magnetron sputtering chamber. By adjusting the power of different targets, the deposition of the corresponding alloy is carried out. According to the program control, the plating is repeated to reach the target thickness of 100 nm, and this step is repeated on the reverse side of the lithium sheet. Among them, magnetron sputtering is carried out under the protection of an argon atmosphere, the air pressure is 3 mT, and the sputtering power of magnetron sputtering is 80 W. After the magnetron sputtering device is shut down and cooled, Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal anode sheet.

[0047] (2) Take out the Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal anode sheet, and crystallize the amorphous alloy layer by nanosecond laser. The energy density of the nanosecond laser is 520 mJ / cm 2 , obtaining a nanocrystalline modified lithium metal anode.

[0048] Performance tests were conducted on the amorphous-nanocrystalline composite lithium metal anodes prepared in Examples 1-8, the pure lithium sheet in Comparative Example 1, the amorphous-modified lithium metal anode prepared in Comparative Example 2, and the nanocrystalline-modified lithium metal anode prepared in Comparative Example 3. The test items are as follows: I. Battery performance test: The samples prepared in Examples 1-8 and Comparative Examples 1-3 were cut into negative electrode sheets with a size of 55 × 81 mm. Using a soft-pack battery, in an ester-based electrolyte, with a Celgard 2325 type separator and NCM811, 3.5 Ah soft-pack batteries were assembled for testing. The test results are shown in Table 1.

[0049] II. Scanning probe test: The amorphous-nanocrystalline composite lithium metal anode and the amorphous-modified lithium metal anode prepared in Example 1 and Comparative Example 2 were observed through a scanning probe microscope. The results are as Figure 1 follows Figure 2 and

[0050] Table 1

[0051] As can be seen from Table 1, the batteries prepared with the amorphous-nanocrystalline composite lithium metal anode in Examples 1 to 8 showed significant advantages in terms of the number of cycling times and Young's modulus. Compared with the batteries prepared with the pure lithium anode in Comparative Example 1, the amorphous-modified lithium metal anode in Comparative Example 2, and the nanocrystalline-modified lithium metal anode prepared in Comparative Example 3, the highest number of cycling times of the batteries prepared in the examples reached more than 200 cycles.

[0052] The above results show that the amorphous alloy has good corrosion resistance, can effectively inhibit the corrosion of the electrolyte, and promote the cycling performance of the lithium metal battery. After the amorphous alloy is nanocrystallized, nanocrystals are in-situ formed on the amorphous alloy, which can increase the specific surface area and conductivity. By adjusting the electric field and ion concentration field at the interface, the directional and uniform nucleation and deposition of lithium on the nanocrystals can be induced. This directional deposition helps to reduce the formation of lithium dendrites, thereby extending the service life of the battery and improving the cycling performance of the lithium metal battery. However, complete nanocrystallization will lead to the deterioration of the surface mechanical properties of the negative electrode material. Nanocrystals can uniformly adjust the electric field concentration, but they cannot inhibit the side reaction between lithium metal and the electrolyte and the growth of lithium dendrites, resulting in a reduction in the battery cycle life. In summary, the amorphous alloy nanocrystalline composite material can better inhibit the growth of lithium dendrites, adjust the electric field and ion concentration field at the interface, thereby improving the cycling performance of the lithium metal battery.

[0053] From Figure 1 and Figure 2It can be seen that the surface of the amorphous-nanocrystalline composite lithium metal anode prepared in Example 1 is rough, with fine black grains of about 10 nm, providing a large number of sites for ion deposition. The nanocrystalline layer can effectively distribute the electric field and homogenize the ion flow, inhibiting dendrite growth and electrode volume expansion, thereby improving the cycling performance of the battery. The surface of the amorphous lithium metal anode prepared in Comparative Example 2 is smooth, without obvious morphological fluctuations and no obvious grains, unable to provide a large number of sites for ion deposition. The amorphous alloy layer cannot effectively distribute the electric field and homogenize the ion flow. The amorphous alloy layer has a high Young's modulus to inhibit dendrite growth and electrode volume expansion, but without an increase in sites, lithium cannot be deposited uniformly. Therefore, the cycling performance of the battery is worse than that of the amorphous-nanocrystalline modified electrode, but better than that of the pure lithium modified layer.

[0054] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0055] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of an amorphous and nanocrystalline composite lithium metal anode, characterized in that It includes the following steps: (1) Polish the lithium sheet in a drying room. Using the mixed target as the sputtering source, place it in the magnetron sputtering equipment and perform coating by physical vapor deposition until the thickness reaches 100 nm, obtaining a lithium sheet with an amorphous alloy layer. Repeat the coating of the amorphous alloy layer on the reverse side of the lithium sheet in the same way to obtain an amorphous-modified lithium metal negative electrode sheet; (2) Take out the amorphous-modified lithium metal negative electrode sheet and crystallize the amorphous alloy layer using a nanosecond laser to obtain an amorphous-nanocrystalline composite lithium metal negative electrode.

2. The preparation method of an amorphous nanocrystalline composite lithium metal anode according to claim 1, characterized in that, In step (1), the magnetron sputtering is carried out under the protection of an argon gas atmosphere, and the gas pressure is 3 mT - 10 mT.

3. The preparation method of an amorphous and nanocrystalline composite lithium metal anode according to claim 1, wherein, In step (1), the sputtering power of the magnetron sputtering is 80 - 1000 W.

4. The preparation method of an amorphous and nanocrystalline composite lithium metal anode according to claim 1, wherein, In step (1), the atomic percentage expression of the amorphous alloy layer is D a E b Cu c , where D is any 3 or 4 of Fe, Al, Zr, Ag, Ti, Mg, V, Y, Co, Ni, Nb, and the sum of the atomic percentages of each element is a; E is any 1 or 2 of Si, B, C, N, and the sum of the atomic percentages of each element is b; a, b, and c are all atomic percentages, and the value ranges are 71 ≤ a ≤ 90, 0 ≤ b ≤ 19, 1 ≤ c ≤ 10, and a + b + c = 100.

5. The preparation method of an amorphous and nanocrystalline composite lithium metal negative electrode according to claim 1, wherein In step (2), the nanosecond laser energy density is 110 - 500 mJ / cm 2 .

6. The amorphous nanocrystalline composite lithium metal anode prepared by the preparation method according to any one of claims 1-5, characterized in that, Its inner layer is flexible metallic lithium, the middle layer is an amorphous alloy layer, and the outer layer is a nanocrystalline layer.

7. The application of the amorphous-nanocrystalline composite lithium metal negative electrode according to claim 6 in a lithium metal battery.

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