阅读说明：本技术 用于金属锂带表面非晶化处理的方法及其产品和应用 (Method for non-crystallizing surface of metal lithium strip, product and application thereof ) 是由 孔德钰 郇庆娜 孙兆勇 陈强 牟瀚波 于 2021-06-25 设计创作，主要内容包括：本发明提供用于金属锂带表面非晶化处理的方法及其产品和应用,该方法包括：采用选自热辐照、热传导和热对流中的至少一种以在175℃至1200℃的温度下将金属锂带表面熔融；和以50℃/s至1000℃/s的降温速率对表面熔融的所述金属锂带进行快速冷却至10℃至50℃的温度。所得到的具有表面非晶化层的金属锂带可以用作电池体系的金属锂负极,由于其表面锂原子完全无序排列,使得金属锂沉积时没有趋向性,因此当用于电池体系时,金属锂会均匀沉积,基本上没有锂枝晶产生,进而提高金属锂负极的循环寿命。此外,在本发明的金属锂带表面非晶化处理过程后,锂带表面粗糙度降低,且未引入杂质化学基团和杂原子,使得所得金属锂带的表面物理或化学状态一致性提高。(The invention provides a method for the surface amorphization treatment of a lithium metal strip, a product and application thereof, wherein the method comprises the following steps: melting the surface of the lithium metal strip at a temperature of 175 ℃ to 1200 ℃ using at least one selected from the group consisting of thermal irradiation, thermal conduction, and thermal convection; and rapidly cooling the surface-melted metallic lithium ribbon to a temperature of 10 ℃ to 50 ℃ at a cooling rate of 50 ℃/s to 1000 ℃/s. The obtained metal lithium belt with the surface amorphization layer can be used as a metal lithium negative electrode of a battery system, and because lithium atoms on the surface of the metal lithium belt are completely arranged in a disordered mode, the metal lithium belt has no tendency during deposition of the metal lithium, so that when the metal lithium belt is used for the battery system, the metal lithium can be uniformly deposited, lithium dendrites are basically not generated, and the cycle life of the metal lithium negative electrode is further prolonged. In addition, after the surface of the lithium metal strip is subjected to the non-crystallization treatment process, the surface roughness of the lithium strip is reduced, and impurity chemical groups and heteroatoms are not introduced, so that the consistency of the surface physical or chemical state of the obtained lithium metal strip is improved.)

1. A method for amorphizing a surface of a lithium metal strip, the method comprising:

melting the surface of the lithium metal strip at a temperature of 175 ℃ to 1200 ℃ using at least one selected from the group consisting of thermal irradiation, thermal conduction, and thermal convection; and

rapidly cooling the surface-melted metallic lithium ribbon to a temperature of 10 ℃ to 50 ℃ at a cooling rate of 50 ℃/s to 1000 ℃/s, thereby obtaining a metallic lithium ribbon having a surface amorphization layer.

2. The method of claim 1, wherein the lithium metal strip is pre-treated for cutting and surface cleaning prior to the melting.

3. The method according to claim 1, characterized in that the thermal radiation is carried out using a laser or an infrared emitter; the heat transfer is performed by using a hot roll; the thermal convection is performed by using a flame generator.

4. The method of claim 1, wherein the rapid cooling is performed by using a chill roll, liquid nitrogen, or a combination thereof.

5. A lithium metal strip with a surface amorphization layer obtained by the method of any one of claims 1-4.

6. The lithium metal ribbon according to claim 5, wherein the surface amorphization layer has a thickness of 1 to 50 μm.

7. The lithium metal ribbon of claim 5, wherein the lithium metal ribbon is an ultra-thin lithium metal ribbon having a thickness of 1-100 microns.

8. The lithium metal tape according to claim 5, wherein the lithium metal tape comprises a lithium alloy containing at least one element selected from the group consisting of Y, B, Ag, Al, Au, Ba, Be, Bi, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Zn, Zr, Pb, Pd, Sb and Cu.

9. Use of a lithium metal ribbon according to any of claims 5-8 for a primary or secondary battery system, characterized in that the lithium metal ribbon is used as a lithium metal negative electrode.

10. Use according to claim 9, wherein the primary or secondary battery system is one or more of a lithium-based primary battery, a lithium-ion battery, a quasi-solid-state lithium battery, an all-solid-state lithium-ion battery, a lithium-sulfur battery and a lithium-oxygen battery.

Technical Field

The invention relates to the field of metal surface treatment and batteries, in particular to a method for performing surface amorphization treatment on a metal lithium strip, and a product and application thereof.

Background

Lithium metal is an ideal material for preparing high energy density batteries because of its high specific capacity (3860mAh/g) and low electrode potential (-3.04V vs. hydrogen standard electrode). However, to realize the large-scale application of the metallic lithium, the dendritic growth problem of the metallic lithium still needs to be solved. When used as a negative electrode in a battery system, a large amount of lithium dendrites may be generated on the surface of the metallic lithium negative electrode due to the non-uniform deposition of lithium ions on the surface of the metallic lithium during cycling of the metallic lithium negative electrode. The presence of lithium dendrites not only consumes active lithium and electrolyte to cause a reduction in battery capacity, but also pierces the separator to cause an internal short circuit of the battery as the lithium dendrites grow, resulting in a safety accident.

Currently, in order to inhibit the growth of lithium dendrites, there are generally two methods: (1) the method comprises the following steps of generating a high-elasticity Solid Electrolyte Interface (SEI) on the surface of the lithium metal in situ by adopting a functional additive and a gas phase reaction or a liquid phase reaction, wherein the generated solid electrolyte interface has high mechanical strength and can prevent dendritic crystals from puncturing; such as lithium nitrate, fluorine-containing organics, and the like. However, this method introduces a large number of chemical groups on the surface of the lithium metal, which reduces the consistency of the physical or chemical state of the lithium metal surface. (2) Surface alloying, generating an alloy layer on the surface of the metal lithium by magnetron sputtering and other processes, reducing the surface reactivity of the metal lithium and simultaneously inducing the deposition of the metal lithium. However, in this method, after the alloy is used, the specific capacity of the whole electrode is reduced, the distribution of alloy elements is not controlled, and the consistency of the physical or chemical state of the surface of the metallic lithium is not effectively improved.

Accordingly, there remains a need in the art to develop new methods for inhibiting lithium dendrite growth.

Disclosure of Invention

The invention aims to provide a novel method for the surface amorphization treatment of a metallic lithium strip to inhibit the growth of lithium dendrites, and a product and application obtained by the method.

To this end, in one aspect, the present invention provides a method for surface amorphization of a lithium metal strip, the method comprising: melting the surface of the lithium metal strip at a temperature of 175 ℃ to 1200 ℃ using at least one selected from the group consisting of thermal irradiation, thermal conduction, and thermal convection; and rapidly cooling the surface-melted metallic lithium ribbon to a temperature of 10 ℃ to 50 ℃ at a cooling rate of 50 ℃/s to 1000 ℃/s, thereby obtaining a metallic lithium ribbon having a surface amorphization layer.

In some preferred embodiments, the lithium metal strip is pre-treated for slitting and surface cleaning prior to the melting.

In some preferred embodiments, the thermal radiation is performed using a laser or an infrared emitter; the heat transfer is performed by using a hot roll; the thermal convection is performed by using a flame generator.

In some preferred embodiments, the rapid cooling is performed by using a chill roll, liquid nitrogen, or a combination thereof.

In another aspect, the present invention provides a metallic lithium ribbon with a surface amorphization layer obtained by the above method.

In some preferred embodiments, the surface amorphization layer has a thickness of 1 to 50 μm.

In some preferred embodiments, the lithium metal ribbon is an ultra-thin lithium metal ribbon having a thickness of 1 to 100 microns.

In some preferred embodiments, the metallic lithium ribbon comprises a lithium alloy containing at least one element selected from the group consisting of Y, B, Ag, Al, Au, Ba, Be, Bi, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Zn, Zr, Pb, Pd, Sb, and Cu.

In another aspect, the present invention provides the use of the above-described lithium metal ribbon for a primary or secondary battery system, wherein the lithium metal ribbon having a surface amorphization layer is used as a lithium metal negative electrode.

In some preferred embodiments, the primary or secondary battery system is one or more of a lithium-based primary battery, a lithium ion battery, a quasi-solid state lithium battery, an all solid state lithium ion battery, a lithium sulfur battery, and a lithium oxygen battery.

The invention provides a novel method for carrying out surface amorphization treatment on a lithium metal strip, in particular to an ultrathin lithium metal strip, by melting the surface of the lithium metal strip and then cooling the lithium metal strip at a specific cooling rate. By utilizing the method, the lithium atoms on the surface of the metal lithium band after the surface amorphization treatment are completely arranged in disorder, so that the metal lithium has no tropism during deposition; therefore, when the obtained metallic lithium ribbon with the surface amorphization layer is applied to a battery system as a metallic lithium negative electrode, uniform deposition of metallic lithium occurs, lithium dendrite growth is remarkably inhibited (generation of lithium dendrites is hardly generated), and the cycle life of the metallic lithium negative electrode is further improved.

In addition, when the metal lithium belt with the surface amorphization layer obtained by the method is used as a metal lithium negative electrode in a battery system, the problem of battery capacity reduction caused by consumption of active lithium and electrolyte by lithium dendrites and the problem of safety accidents caused by internal short circuit of the battery caused by growth of the lithium dendrites are avoided because the lithium dendrites are hardly generated.

In addition, in the process of the surface amorphization treatment of the lithium metal strip, impurity chemical groups and heteroatoms are not introduced, so that the consistency of the surface physical or chemical state of the obtained lithium metal strip is improved. Moreover, compared with the existing surface alloying treatment method, the amorphization treatment of the invention does not introduce additional components, so that the composition of the metallic lithium strip itself is not changed, and accordingly, the problems of the decrease of the overall specific capacity and the consistency of the physical or chemical state of the surface of the metallic lithium due to the controlled distribution of the alloying elements are not caused.

Drawings

Fig. 1 is a schematic view of a metallic lithium ribbon with a surface amorphization layer obtained according to the method of the invention.

Fig. 2 is an Atomic Force Microscope (AFM) photograph of a surface of a lithium metal strip (without a surface amorphization layer) before a surface amorphization process according to the present invention.

Fig. 3 is an Atomic Force Microscope (AFM) photograph of a lithium metal surface (having a surface amorphization layer) after a surface amorphization process according to the present invention.

Figure 4 optical microscopy images of lithium metal strips with 10 micron surface amorphized layer were prepared from example 1.

Fig. 5 is a graph showing battery cycle curves when metallic lithium ribbons obtained according to example 1 and comparative example 1, respectively, of the present invention are used as a metallic lithium negative electrode.

Detailed Description

The inventor of the present invention has studied and found that in order to inhibit the growth of lithium dendrites and improve the consistency of the physical or chemical state of the surface of metallic lithium, it is necessary to modify the metallic lithium itself, i.e., modify the consistency of the physical or chemical state of the surface of metallic lithium. In particular, metallic lithium dendrites tend to grow in the <111>, <110> or <211> direction, wherein the <111> direction is preferred, so that the formation of metallic lithium dendrites is inevitable without changing the surface lattice state of the metallic lithium.

In view of the above, the present inventors have conducted intensive and extensive studies and unexpectedly discovered a novel method for surface amorphization of a lithium metal strip, wherein lithium atoms on the surface of the obtained surface amorphized lithium metal strip are completely disordered by melting the surface of the lithium metal strip (especially, an ultra-thin lithium metal strip) and then cooling the surface at a specific cooling rate, so that there is no tendency for the lithium metal to be deposited, and thus when the lithium metal strip is applied to a battery system as a lithium metal negative electrode, uniform deposition of lithium metal occurs, lithium dendrite growth is significantly suppressed (generation of lithium dendrites is hardly generated), and thus the cycle life of the lithium metal negative electrode is improved.

The method for performing surface amorphization treatment on the lithium metal strip provided by the invention comprises the steps of melting the surface of the lithium metal strip, and then rapidly cooling the surface-melted lithium metal strip, thereby obtaining the lithium metal strip with the surface amorphization layer, as shown in fig. 1.

In the present invention, the surface melting of the metallic lithium ribbon may be performed, for example, in a glove box, and preferably may be performed in an inert atmosphere such as an argon atmosphere.

In the present invention, generally, the surface of the metallic lithium ribbon is melted at a temperature of 175 to 1200 deg.c in view of the melting point and vaporization temperature of lithium metal.

In the present invention, the surface melting of the lithium metal strip may be performed using a process of surface melting of lithium metal including at least one of thermal irradiation (e.g., using a laser, an infrared generator, etc.), thermal conduction (using a high-temperature hot roll, etc.), and thermal convection (e.g., a high-temperature flame generator, etc.). Preferably, from the viewpoint of precisely controlling the surface melting region and thickness, etc., the surface melting of the lithium metal strip is preferably performed using a high-energy laser.

In the present invention, the surface-melted metallic lithium ribbon needs to be rapidly cooled at a cooling rate of 50 ℃/s to 1000 ℃/s, for example, 100 ℃/s to 500 ℃/s. The applicant has found that when rapid cooling is carried out at the above-mentioned cooling rate, it is possible to cool the surface-melted lithium metal ribbon at a high temperature to a desired temperature for a proper period of time, thereby maintaining the lithium atoms on the surface of the obtained surface-amorphized lithium metal ribbon in a molten state, i.e., in a completely disordered arrangement, so that there is no tendency for the lithium metal to deposit. In contrast, when the cooling rate is less than 50 ℃/s or more than 1000 ℃/s, lithium atoms in the surface amorphized layer of the obtained metallic lithium ribbon cannot be completely disordered arranged, so that the growth of lithium dendrites cannot be maximally inhibited.

In the present invention, although not particularly limited, the surface-melted metallic lithium ribbon is generally rapidly cooled to a temperature of 10 ℃ to 50 ℃ at the above-mentioned specific cooling rate, and the lithium ribbon in this temperature range can be directly wound without worrying about problems such as local re-melting of the lithium ribbon due to heat aggregation or an increase in surface roughness of the lithium ribbon due to significant creep of metallic lithium, and the like.

In the present invention, preferably, the rapid cooling of the surface-melted lithium metal strip may be performed by using a low-temperature chill roll (e.g., at a temperature of 0 ℃), liquid nitrogen (typically at a temperature of-196.5 ℃), or a combination thereof. More preferably, liquid nitrogen is used for rapid cooling. As is known in the art, rapid cooling can be achieved by purging the molten surface of the lithium metal strip with liquid nitrogen using an air pump, wherein the cooling rate can be easily adjusted, for example, by adjusting the flow rate of the purge gas stream.

In the present invention, the lithium metal strip may be subjected to a pretreatment as needed before surface melting, which includes, but is not limited to, cutting the lithium metal strip into a desired size, and performing surface cleaning using a dust-free paper or a nonwoven fabric, for example, wiping off dust, oil stains, and the like on the surface of the lithium metal strip.

In the present invention, preferably, the lithium metal ribbon used for the surface amorphization process is an ultra-thin lithium metal ribbon, and the thickness thereof may be 1 to 100 micrometers, for example, 50 micrometers.

In the present invention, although not particularly limited, it is preferable that the thickness of the surface amorphization layer of the surface amorphized layer of the lithium metal strip subjected to the surface amorphization treatment is generally 1/5 to 1/20 range of the thickness of the entire lithium metal strip, such as generally in the range of 1 to 50 micrometers, such as 5 micrometers thick.

In the present invention, there is no particular limitation on the composition of the lithium metal ribbon itself, as long as it is suitable for use as a lithium metal negative electrode in a primary or secondary battery system. For example, In some preferred embodiments, metallic lithium ribbons used In the present invention may comprise lithium alloys, e.g., which may contain one or more elements selected from the group consisting of Y, B, Ag, Al, Au, Ba, Be, Bi, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Zn, Zr, Pb, Pd, Sb, and Cu, and the like.

The metallic lithium ribbon with a surface amorphization layer obtained by the present invention can be used as a metallic lithium negative electrode of a primary or secondary battery system. Preferably, the primary or secondary battery system to which the present invention can be applied is one or more of a lithium-based primary battery, a lithium ion battery, a quasi-solid lithium battery, an all-solid lithium ion battery, a lithium sulfur battery, a lithium oxygen battery, and the like.

For a better understanding of the technical features, objects, and advantages of the present invention, reference will now be made to the following drawings and examples, in which the present invention is illustrated in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Preparation of example 1

Commercially available lithium metal tape (available from tianjin lithium industries limited) having a thickness of 40 μm was cut into a lithium tape sheet having a length of 10 cm and a width of 100 mm, and dust, oil stains, and the like on the surface of the lithium tape were wiped off using a dust-free paper. The pretreated lithium metal strip was sampled and the surface morphology of the lithium strip before surface amorphization was observed using an Atomic Force Microscope (AFM) (Bruker, USA, model: Dimension ICON), and the result is shown in FIG. 2.

The surface of the lithium tape sheet was scanned with a high-energy laser (a major group of laser intelligent equipment group, controlling the laser power at 1 ten thousand watts) under a high-purity argon atmosphere to melt the surface of the lithium metal (the specific temperature was 500 ℃).

After the surface melting treatment is finished, the lithium strip can immediately pass through a cooling roller with the temperature of 0 ℃, then is put into liquid nitrogen with the temperature of 196 ℃ below zero.5 ℃ for natural cooling, the liquid nitrogen can also be immediately adopted for carrying out rapid cooling treatment on the molten metal lithium layer, and the molten lithium strip can also pass through a steel rolling laminar flow cooling device with the liquid nitrogen or white oil as a medium, the medium speed is controlled so as to realize the cooling speed of 100 ℃/s until the lithium strip is cooled to the temperature of 35 ℃, thereby obtaining the metal lithium with the non-crystallized surface. The surface-amorphized lithium metal strip was sampled, and the surface morphology of the lithium strip having the surface amorphized layer was observed using an Atomic Force Microscope (AFM) (Bruker, USA, model: Dimension ICON), and the result is shown in FIG. 3. It is to be noted with respect to fig. 2 and 3 that the scale on the right of each of these two figures represents the variation range of the height difference of the corresponding material, the scale in fig. 2 being large to illustrate the surface roughness and the height difference being large; meanwhile, the upper and left scales of the two figures are regions of the sample tested in the AFM test, and as can be seen from fig. 2 and 3, the test regions of the two figures are the same in area.

As is clear from fig. 2 and 3, the surface of the metallic lithium ribbon without surface amorphization treatment is large grains, the grain boundary thereof is distinct and the surface waviness is ± 0.8 micrometer (μm); in contrast, the surface of the metallic lithium ribbon subjected to the surface amorphization treatment is small grains which are completely randomly arranged, the grain boundary is small and not obvious, and the overall surface physical undulation degree is small (about +/-0.6 microns). In addition, the surface height difference shown in fig. 3 is small and the particles are small and dense over the same test area, which reflects that the surface of the test sample does not have the large cells shown in fig. 2. Therefore, the metal lithium strip subjected to the surface amorphization treatment has small surface undulation degree and higher surface physical state consistency. The surface amorphization layer thickness of the metallic lithium ribbon was determined to be 10.83 μm by a Ginzhi digital microscope system (model: VHX-7000), and the results are shown in FIG. 4.

Preparation of example 2

The same procedure as in preparation example 1 was followed to increase the flow rate of liquid nitrogen and allow the liquid nitrogen to carry away the heat from the surface of the lithium strip in a short time to achieve a rapid cooling rate of 500 ℃/s, thereby obtaining a metallic lithium strip having a surface amorphization layer of 10 μm thickness. Similar results as in example 1 were observed via AFM.

Preparation of example 3

The same procedure as in preparation example 1 was followed, and the surface of the lithium ribbon sheet was heat-melted using a hot steel roll having a temperature of 500 c, thereby obtaining a metallic lithium ribbon having a surface amorphization layer of 15 μm thickness. Similar results as in example 1 were observed via AFM.

Performance testing

The lithium metal strip used in example 1 and the surface-amorphized lithium metal strip were prepared into samples having a length and a width of 5mm × 5mm, respectively, and the samples were fixed on a sample stage, and the samples were placed into an atomic force microscope test chamber for testing. The test area was 10 microns by 10 microns.

The interface of the metallic lithium ribbon having the surface amorphized layer prepared in example 1 was observed using a kirschner digital microscope system, and the thickness of the amorphized layer was measured.

The lithium ribbon with the surface amorphization layer obtained in the above example 1 was cut into a circular sheet with a diameter of 15mm, and used as a lithium metal negative electrode to assemble a button cell, and the button cell obtained was subjected to a constant-capacity constant-current charge-discharge test with a cycle current of 10mA and a cycle capacity of 5mAh, and the test results are shown in fig. 5. It is to be noted with respect to fig. 5 that the graph is a cycle curve for a symmetric cell, the cycle test for which is a means for characterizing the performance of the lithium metal anode after processing. Under the ideal condition, namely when the electrode surface appearance is unchanged, the charge-discharge cycle is carried out on the cycle curve by using a constant potential with 0V as a symmetrical line, but under the actual condition, the electrode appearance is changed, which causes the cycle potential to change, after the electrode of the battery is changed at the later stage of the cycle, the internal resistance of the battery is increased, the overpotential is enlarged, and the electrode is opened in a horn shape. As can be seen from fig. 5, after the battery is assembled by using the metallic lithium ribbon subjected to the surface amorphization treatment of the present invention as a negative electrode, the polarization potential of the battery is only slightly increased after 300 hours of cycling, which indicates that the metallic lithium subjected to the surface amorphization treatment of the present invention hardly generates lithium dendrites during cycling, and the cycling stability of the metallic lithium negative electrode is very good.

Comparative example 1

Commercially available metallic lithium tapes (Tianjin Li industries Co., Ltd.) with a thickness of 40 μm mentioned in example 1 were punched out directly after the surface cleaning treatment into disks with a diameter of 15mm (i.e., without the surface amorphization treatment of the present invention) and assembled into cells for performance testing in the same procedure as described above, and the results are shown in FIG. 5. As can be seen from fig. 5, the polarization potential (V) of the battery assembled using the metallic lithium ribbon of comparative example 1, which was not surface-amorphized, started to increase after 40 hours of cycling; and the cycle time does not exceed 100 hours due to failure due to internal short circuit of the lithium metal negative electrode due to the generation of a large amount of lithium metal dendrites.

The invention has been described in detail with reference to specific embodiments thereof, but the invention is not limited thereto. Any modification and improvement of the details within the spirit and principle of the invention should be considered within the scope of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.