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

Abstract

The present invention discloses an amorphous nanocrystalline composite lithium metal negative electrode, a preparation method, and an application thereof, and belongs to the field of lithium battery technology. 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, using a mixed target as a sputtering source, placing the sheet in a magnetron sputtering device, and coating the sheet by physical vapor deposition until the thickness reaches 100 nm, thereby obtaining a lithium sheet containing an amorphous alloy layer. The reverse side of the lithium sheet is repeatedly coated with an amorphous alloy layer in the same manner to obtain an amorphous modified lithium metal negative electrode sheet; (2) removing the amorphous modified lithium metal negative electrode sheet, and crystallizing the amorphous alloy layer by nanosecond laser to obtain an amorphous nanocrystalline composite lithium metal negative electrode. The amorphous nanocrystalline composite lithium metal negative electrode prepared by the present invention can significantly improve the cycle performance of a lithium metal battery when used in a lithium metal battery.

Description

Technical Field

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

[0002] Since the mid-20th century, lithium metal batteries have attracted widespread 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 applications requiring 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 number of challenges. During the charge-discharge cycle, the electrolyte is reduced by the lithium metal, forming a solid electrolyte interface (SEI). While this interface protects the lithium metal from further corrosion, it also creates new problems. In particular, during the charging process, lithium deposition (i.e., "lithium plating") is often uneven, leading to increased mechanical instability of the SEI and prone to cracking, which continuously exposes new lithium metal surfaces. This exposure not only accelerates electrolyte consumption and reduces the battery's Coulombic efficiency, but also causes the SEI thickness to increase, thereby increasing the battery's internal resistance. More seriously, the cracked SEI provides new sites for uneven lithium deposition, 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. This means that at high current dendrites, the formation rate accelerates, seriously threatening the battery's safety and cycle life. Traditional technologies can use protective coatings or solid-state electrolytes to improve the lithium dendrite problem, but this often leads to reduced cycling performance of the lithium battery. Summary of the Invention

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

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode comprises the following steps:

[0007] (1) A lithium sheet was polished in a drying room, and a mixed target was used as a sputtering source. The sheet was placed in a magnetron sputtering device and coated by physical vapor deposition until the thickness reached 100 nm. A lithium sheet containing an amorphous alloy layer was obtained. The reverse side of the lithium sheet was repeatedly coated with an amorphous alloy layer in the same manner to obtain an amorphous modified lithium metal negative electrode sheet.

[0008] (2) Take out the amorphous modified lithium metal negative electrode sheet and use nanosecond laser to crystallize the amorphous alloy layer to obtain an amorphous nanocrystalline composite lithium metal negative electrode.

[0009] Furthermore, in step (1), the magnetron sputtering is carried out under the protection of an argon atmosphere, the gas pressure is 3mT-10mT, and the sputtering power of the magnetron sputtering is 80-1000W.

[0010] Furthermore, in step (1), the atomic percentage of the amorphous alloy layer is expressed as D a E b Cu c , wherein D is any three or four of Fe, Al, Zr, Ag, Ti, Mg, V, Y, Co, Ni, and Nb, and the sum of the atomic percentages of the elements is a; E is any one or two of Si, B, C, and N, and the sum of the atomic percentages of the elements is b; a, b, and c are all atomic percentages, and the value range is 71≤a≤90, 0≤b≤19, 1≤c≤10, and a+b+c=100.

[0011] Furthermore, in step (2), the nanosecond laser energy density is 110-500 mJ / cm 2 .

[0012] In the second aspect, an amorphous nanocrystalline composite lithium metal negative electrode has an inner layer of flexible metallic lithium, a middle layer of an amorphous alloy layer, and an outer layer of a nanocrystalline layer.

[0013] The amorphous-nanocrystalline composite negative electrode 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. Nanocrystals can provide more sites for lithium deposition and promote the uniform deposition of lithium ions.

[0014] The third aspect is the application of amorphous nanocrystalline composite lithium metal negative electrode in lithium metal batteries.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention prepares an amorphous nanocrystalline composite lithium metal negative electrode by using 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. The amorphous alloy also has good corrosion resistance, which can effectively inhibit electrolyte corrosion, thereby further improving the cycling performance of lithium metal batteries.

[0017] 2. In-situ formation of nanocrystals on amorphous alloys can increase specific surface area and conductivity. By adjusting the electric field and ion concentration field at the interface, lithium can be induced to nucleate and deposit uniformly on the nanocrystals in a directional manner. This directional deposition helps reduce the formation of lithium dendrites, thereby extending the battery life and improving the cycle performance of lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a morphology diagram of the amorphous nanocrystalline composite lithium metal negative electrode in Example 1;

[0020] Figure 2 This is a morphology diagram of the amorphous lithium metal negative electrode in Comparative Example 2. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Example 1

[0023] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0024] (1) In a drying room, high-purity Fe target, high-purity Si target, high-purity B target, high-purity Nb target, and high-purity Cu target are placed in a magnetron sputtering device. The lithium sheet is polished and placed in the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 3mT, and the sputtering power of the magnetron sputtering is 80W. After the magnetron sputtering equipment is turned off and cooled, Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal negative electrode sheet.

[0025] (2) Removal of Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal negative electrode, the amorphous alloy layer is crystallized by nanosecond laser with a nanosecond laser energy density of 500mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0026] Example 2

[0027] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0028] (1) In a drying room, high-purity AlY target, high-purity Ni target, high-purity Zr target, and high-purity Cu target are loaded into the magnetron sputtering equipment, and the lithium sheet is polished and loaded into the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to the program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 5mT, and the sputtering power of the magnetron sputtering is 900W. After the magnetron sputtering equipment is turned off and cooled, Al 84 Ni8Zr3Cu3Y2 amorphous modified lithium metal negative electrode.

[0029] (2) Remove Al 84 The amorphous Ni8Zr3Cu3Y2 modified lithium metal negative electrode is crystallized by nanosecond laser with an energy density of 320mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0030] Example 3

[0031] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0032] (1) In a drying room, high-purity AlY target, high-purity Ni target, high-purity Nb target, and high-purity Cu target are loaded into the magnetron sputtering equipment, and the lithium sheet is polished and loaded into the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to the program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 10mT, and the sputtering power of the magnetron sputtering is 1000W. After the magnetron sputtering equipment is turned off and cooled, Al 52 Ni 25 Nb 15 Cu3Y2 amorphous modified lithium metal anode sheet.

[0033] (2) Remove Al 52 Ni 25 Nb 15 Cu3Y2 amorphous modified lithium metal negative electrode sheet, the amorphous alloy layer is crystallized by nanosecond laser, and the nanosecond laser energy density is 110mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0034] Example 4

[0035] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0036] (1) In a drying room, high-purity Ti target, high-purity Ni target, high-purity Nb target, high-purity Cu target, and high-purity Zr target are loaded into the magnetron sputtering equipment, and the lithium sheet is polished and loaded into the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly controlled according to the program to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 6mT, and the sputtering power of the magnetron sputtering is 85W. After the magnetron sputtering equipment is turned off and cooled, Ti is obtained. 50 Ni 30 Zr 10 Nb5Cu5 amorphous modified lithium metal anode sheet.

[0037] (2) Remove Ti 50 Ni 30 Zr 10 Nb5Cu5 amorphous modified lithium metal negative electrode sheet, the amorphous alloy layer is crystallized by nanosecond laser, and the nanosecond laser energy density is 430mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0038] Example 5

[0039] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0040] (1) In a drying room, high-purity ZrN target, high-purity Nb target, high-purity B target, and high-purity Cu target are loaded into the magnetron sputtering equipment, and the lithium sheet is polished and loaded into the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to the program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 7mT, and the sputtering power of the magnetron sputtering is 90W. After the magnetron sputtering equipment is turned off and cooled, Zr 75 N5N 10 B5Cu5 amorphous modified lithium metal negative electrode sheet.

[0041] (2) Remove Zr 75 N5N 10 The B5Cu5 amorphous modified lithium metal negative electrode sheet is crystallized by nanosecond laser with an energy density of 130mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0042] Example 6

[0043] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0044] (1) In a drying room, high-purity Zr target, high-purity Al target, high-purity Ni target, and high-purity Cu target are loaded into the magnetron sputtering equipment, and the lithium sheet is polished and loaded into the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to the program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 10mT, and the sputtering power of the magnetron sputtering is 590W. After the magnetron sputtering equipment is turned off and cooled, Zr 60 Al 20 Cu 10 Ni 10 Amorphous modified lithium metal anode sheet.

[0045] (2) Remove Zr 60 Al 20 Cu 10 Ni 10 Amorphous modified lithium metal negative electrode, the amorphous alloy layer is crystallized by nanosecond laser, the nanosecond laser energy density is 450mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0046] Example 7

[0047] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0048] (1) In a drying room, high-purity Ti target, high-purity Nb target, high-purity Fe target, high-purity Zr target, and high-purity Cu target are placed in a magnetron sputtering device. The lithium sheet is polished and placed in the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 8mT, and the sputtering power of the magnetron sputtering is 80W. After the magnetron sputtering equipment is turned off and cooled, Ti is obtained. 60 Nb 18 Fe 10 Zr5Cu7 amorphous modified lithium metal negative electrode sheet.

[0049] (2) Remove Ti 60 Nb 18 Fe 10 Zr5Cu7 amorphous modified lithium metal negative electrode, the amorphous alloy layer is crystallized by nanosecond laser, the nanosecond laser energy density is 500mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0050] Example 8

[0051] This embodiment provides a method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, comprising the following steps:

[0052] (1) In a drying room, 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 are placed in a magnetron sputtering device. The lithium sheet is polished and placed in the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 7mT, and the sputtering power of the magnetron sputtering is 490W. After the magnetron sputtering equipment is turned off and cooled, Ag is obtained. 60 Al 10 Nb 15 Zr5C5Cu5 amorphous modified lithium metal negative electrode sheet.

[0053] (2) Remove Ag 60 Al 10 Nb 15 The Zr5C5Cu5 amorphous modified lithium metal negative electrode is crystallized by nanosecond laser with an energy density of 355mJ / cm 2 , obtaining an amorphous nanocrystalline composite lithium metal negative electrode.

[0054] Comparative Example 1

[0055] This comparative example uses a 100 um pure lithium sheet.

[0056] Comparative Example 2

[0057] This comparative example provides a method for preparing an amorphous modified lithium metal negative electrode, comprising the following steps:

[0058] In the drying room, high-purity Fe target, high-purity Si target, high-purity B target, high-purity Nb target, and high-purity Cu target are loaded into the magnetron sputtering equipment, the lithium sheet is polished, and loaded into the magnetron sputtering cabin. By adjusting the power of different target materials, the corresponding alloy is deposited. According to the program control, the coating is repeatedly performed to achieve the target thickness of 100nm, and this step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 3mT, and the sputtering power of the magnetron sputtering is 80W. After the magnetron sputtering equipment is turned off and cooled, Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal anode.

[0059] Comparative Example 3

[0060] This comparative example provides a method for preparing a nanocrystal-modified lithium metal negative electrode, comprising the following steps:

[0061] (1) In a drying room, high-purity Fe target, high-purity Si target, high-purity B target, high-purity Nb target, and high-purity Cu target are placed in a magnetron sputtering device. The lithium sheet is polished and placed in the magnetron sputtering chamber. The corresponding alloy is deposited by adjusting the power of different target materials. The coating is repeatedly performed according to program control to achieve the target thickness of 100nm. This step is repeated on the reverse side of the lithium sheet. Among them, the magnetron sputtering is carried out under the protection of argon atmosphere, the gas pressure is 3mT, and the sputtering power of the magnetron sputtering is 80W. After the magnetron sputtering equipment is turned off and cooled, Fe 77 Si 10 B9Nb3Cu1 amorphous modified lithium metal negative electrode sheet.

[0062] (2) Removal of Fe 77 Si 10 The amorphous B9Nb3Cu1 modified lithium metal negative electrode was crystallized by nanosecond laser with an energy density of 520mJ / cm 2 , and a nanocrystal-modified lithium metal anode was obtained.

[0063] The amorphous nanocrystalline composite lithium metal negative electrodes prepared in Examples 1 to 8, the pure lithium sheet of Comparative Example 1, the amorphous modified lithium metal negative electrode prepared in Comparative Example 2, and the nanocrystalline modified lithium metal negative electrode prepared in Comparative Example 3 were subjected to performance tests. The test items are as follows:

[0064] 1. Battery Performance Test: The samples prepared in Examples 1 to 8 and Comparative Examples 1 to 3 were cut into 55 The 81 mm negative electrode sheet was used in a soft-pack battery. In an ester electrolyte, it was equipped with a Celgard 2325 separator and NCM811 to assemble a 3.5 Ah soft-pack battery for testing. The test results are shown in Table 1.

[0065] 2. Scanning probe test: The amorphous nanocrystalline composite lithium metal negative electrode and the amorphous modified lithium metal negative electrode prepared in Example 1 and Comparative Example 2 were observed by scanning probe microscopy. The results are as follows: Figure 1 、 Figure 2 shown.

[0066] Table 1

[0067]

[0068] As can be seen from Table 1, the batteries prepared using the amorphous-nanocrystalline composite lithium metal negative electrode in Examples 1 to 8 exhibit significant advantages in terms of cycle number and Young's modulus. Compared with the batteries prepared using the pure lithium negative electrode in Comparative Example 1, the amorphous-modified lithium metal negative electrode in Comparative Example 2, and the nanocrystalline-modified lithium metal negative electrode prepared in Comparative Example 3, the batteries prepared in the Examples achieve a maximum cycle number of over 200 cycles.

[0069] The above results show that amorphous alloys have good corrosion resistance, can effectively inhibit electrolyte corrosion, and promote the cycle performance of lithium metal batteries. After the amorphous alloy is nanocrystallized, nanocrystals are formed in situ 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, lithium can be induced to nucleate and deposit uniformly on the nanocrystals. This directional deposition helps to reduce the formation of lithium dendrites, thereby extending the service life of the battery and improving the cycle performance of lithium metal batteries. However, complete nanocrystallization will lead to the deterioration of the mechanical properties of the surface of the negative electrode material. Nanocrystals can uniformly adjust the electric field concentration, but cannot inhibit the side reactions between lithium metal and the electrolyte and the growth of lithium dendrites, resulting in a decrease in the cycle life of the battery. In summary, the amorphous alloy nanocrystal composite material can better inhibit the growth of lithium dendrites, adjust the electric field and ion concentration field at the interface, and thus improve the cycle performance of lithium metal batteries.

[0070] from Figure 1 and Figure 2 It can be seen that the surface of the amorphous nanocrystalline composite lithium metal negative electrode prepared in Example 1 is rough, and the black fine grains are about 10nm, which provides 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 cycle performance of the battery; the surface of the amorphous lithium metal negative electrode prepared in Comparative Example 2 is smooth, without obvious morphological fluctuations and obvious grains, and cannot 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 higher Young's modulus to inhibit dendrite growth and electrode volume expansion, but without the increase of sites, lithium cannot be uniformly deposited, so the cycle performance of the battery is worse than that of the amorphous nanocrystalline modified electrode, but better than the pure lithium modified layer.

[0071] It should be noted that, in this document, relational terms such as first and second, etc., are used only 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 terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0072] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an amorphous nanocrystalline composite lithium metal negative electrode, characterized in that: The following steps are involved: (1) A lithium sheet was polished in a drying room, and a mixed target was used as a sputtering source. The sheet was placed in a magnetron sputtering device and coated by physical vapor deposition until the thickness reached 100 nm. A lithium sheet containing an amorphous alloy layer was obtained. The reverse side of the lithium sheet was repeatedly coated with an amorphous alloy layer in the same manner to obtain an amorphous modified lithium metal negative electrode sheet. (2) Taking out the amorphous modified lithium metal negative electrode sheet, using nanosecond laser to crystallize the amorphous alloy layer to obtain an amorphous nanocrystalline composite lithium metal negative electrode; In step (1), the atomic percentage expression of the amorphous alloy layer is Fe 77 Si 10 B9Nb3Cu1、Al 84 Ni8Zr3Cu3Y2、Ti 50 Ni 30 Zr 10 Nb5Cu5、Zr 75 N5N 10 B5Cu5、Zr 60 Al 20 Cu 10 Ni 10 、Ti 60 Nb 18 Fe 10 Zr5Cu7、Ag 60 Al 10 Nb 15 Any one of Zr5C5Cu5.

2. The method for preparing an amorphous nanocrystalline composite lithium metal negative electrode according to claim 1, characterized in that: In step (1), magnetron sputtering is carried out under the protection of an argon atmosphere with a pressure of 3mT-10mT.

3. The method for preparing an amorphous nanocrystalline composite lithium metal negative electrode according to claim 1, characterized in that: In step (1), the sputtering power of magnetron sputtering is 80-1000W.

4. The method for preparing an amorphous nanocrystalline composite lithium metal negative electrode according to claim 1, characterized in that: In step (2), the nanosecond laser energy density is 110-500mJ / cm 2 .

5. The amorphous nanocrystalline composite lithium metal negative electrode prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The inner layer is flexible metallic lithium, the middle layer is an amorphous alloy layer, and the outer layer is a nanocrystalline layer.

6. Use of the amorphous nanocrystalline composite lithium metal negative electrode according to claim 5 in a lithium metal battery.

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