CN108574083A - Lithium sheet capable of effectively inhibiting uncontrolled growth of dendritic crystal of lithium metal battery, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a lithium sheet that can effectively inhibit the uncontrollable growth of dendrites in a lithium metal battery, a preparation method and an application thereof, and belongs to the technical field of batteries. The invention provides a lithium sheet with a novel structure, the lithium sheet has a concave structure, such as a pit structure and/or a groove structure, especially a pit and/or groove of a micro-nano structure. By using the lithium sheet with this specific structure as the negative electrode, the uncontrollable growth of dendrites in the lithium metal battery can be effectively suppressed, the phenomenon of piercing the battery separator is avoided, and the performance of the lithium battery is improved. The present invention adopts nano-imprinting technology, especially the roll-to-roll nano-imprinting lithium metal battery negative electrode, which can realize large-scale industrial mass production; the micro-nano processing technology adopted in the present invention has a mature and stable process, and can realize precise control of pattern size, Patterns from nanoscale to micron scale can be fabricated.

Description

A lithium sheet that effectively inhibits the uncontrollable growth of dendrites in lithium metal batteries, and its preparation method Law and purpose

technical field

The invention belongs to the technical field of batteries, and relates to a lithium sheet that can effectively inhibit the uncontrollable growth of dendrites in lithium metal batteries, a preparation method and an application thereof.

Background technique

At present, improving the energy density of lithium-ion batteries is an important pursuit direction for the long-term development of the commercial lithium battery industry. However, the theoretical capacity of the current commercialized graphite negative electrode is only 372mA h/g, which limits the application of batteries. According to the latest According to the investigation of scientific research results, there are many anode materials such as silicon, tin, and transition metal oxides that can be used to replace the current commercial graphite anode.

In addition to the above materials, lithium metal is a very promising high-energy-density anode material based on lithium batteries because of its theoretical capacity of up to 3860mA h/g and a very low redox potential (compared to standard hydrogen electrodes -3.04V), so lithium metal plays a key role in meeting the demand for high-energy-density batteries for increasingly new applications in electric vehicles and advanced electronics. However, the formation of lithium dendrites accompanied by low Coulombic efficiency during the charge-discharge cycle of lithium metal batteries hinders the practical application of lithium metal anodes for rechargeable lithium batteries. In particular, the generation of lithium dendrites and the dead lithium it produces may lead to safety issues such as thermal runaway and even combustion, or explosion.

According to research in recent years, by coating a layer of LiF on lithium metal, or adding polysulfide, LiNO ₃ , Cs ⁺ , ionic liquid, etc. to the electrolyte, using a 3D collector combined with a polymer electrolyte, biomimetic The method can improve the SEI (solid electrolyte interphase) film on the surface of lithium metal, etc.

The above-mentioned technologies have limited improvement on uncontrollable lithium dendrite growth, and they cannot be applied to high-throughput industrial production on a large scale.

In conclusion, the uncontrollable lithium dendrite problem is an urgent problem to be solved in the development of rechargeable lithium batteries based on lithium metal anodes. In the prior art, there is no method that can be applied to high-throughput industrial production on a large scale to solve this problem, which severely limits the development and application of lithium batteries.

Contents of the invention

In view of the above-mentioned problems in the prior art, the object of the present invention is to provide a lithium sheet that can effectively inhibit the uncontrollable growth of dendrites in lithium metal batteries, its preparation method and use. The uncontrollable growth of dendrites in lithium metal batteries can be effectively suppressed by using a lithium sheet with a specific structure as the negative electrode.

For reaching above-mentioned purpose, the present invention adopts following technical scheme:

In a first aspect, the present invention provides a lithium sheet, and the lithium sheet is a lithium sheet with a concave structure.

Preferably, the concave structure includes a pit structure and/or a groove structure. The "pit and/or groove" refers to: it can be a pit structure, a groove structure, or a combination of a pit structure and a groove structure.

The concave structure of the present invention includes but not limited to pit structure and/or groove structure, and other regular or irregular concave structures are also suitable for the present invention, and the groove can be a straight groove or a curved groove, The pit can be a pit with a square horizontal section (abbreviated as a square pit), a pit with a circular horizontal section (abbreviated as a circular pit) or a pit with an elliptical horizontal section (abbreviated as an elliptical pit). pits), etc.

Preferably, the pit structure and/or groove structure is a micro-nano structure pattern. By making the lithium flakes form micro-nano patterns, the effect of inhibiting the growth of lithium dendrites can be better achieved.

Preferably, the micro-nano structure pattern is a regular periodic pattern. For example, it can be a periodic pattern formed by individual micro-nano structure pits, each pit is regularly arranged, and has a certain spacing; it can also be a periodic pattern formed by individual micro-nano structure grooves, each groove is regular Arranged with a certain interval; it can also be a regular pattern formed by the combination of micro-nano structure pits and micro-nano structure grooves.

Preferably, the lithium sheet has a thickness of 0.5 mm to 1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.85 mm, 0.9 mm or 1 mm.

Preferably, the pits and/or grooves have a depth of 50nm to 100μm, such as 50nm, 75nm, 80nm, 100nm, 115nm, 130nm, 160nm, 200nm, 235nm, 270nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 6.5μm, 7μm, 8μm, 10μm, 15μm, 20μm, 35μm, 50μm, 60μm, 70μm, 80μm , 90 μm or 100 μm, etc., preferably 5 μm to 15 μm, within the range of 5 μm to 15 μm, the space for the pits and/or grooves to accommodate lithium is more suitable.

Preferably, the depth of the pits and/or grooves is 1/10 to 1 times the minimum line width, such as 1/10, 1/9, 1/8, 1/7.5, 1/7, 1/6 , 1/5, 1/4, 1/3, 1/2 or 1, etc., within this range, the pit and/or groove structure is less difficult to manufacture, and lithium is easier to deposit in a tightly packed form.

The "minimum line width" mentioned in the present invention refers to: the minimum distance between two points passing through the center of the plane on the plane perpendicular to the depth of the pit and/or groove. For example, for a strip-shaped groove, the minimum line width refers to the distance in the width direction of the strip; for a rectangular pit, the minimum line width refers to the distance between the wide sides; for a square pit, the minimum line width refers to The distance of the side length; for an elliptical dimple, the minimum line width refers to the distance of the short side of the ellipse.

In a second aspect, the present invention provides the use of the lithium sheet as described in the first aspect, and the lithium sheet is used as a negative electrode.

In a third aspect, the present invention provides a method for preparing a lithium sheet as described in the first aspect, the method comprising: using a metal template to perform roll-to-roll embossing or plate-to-plate embossing on a lithium sheet, preferably roll-to-roll nanometer printing. Either embossing or plate-to-plate nanoimprinting.

The invention transfers the micro-nano structure of the metal template to the negative electrode lithium sheet through roll-to-roll embossing or plate-to-plate embossing, thereby forming a negative electrode lithium sheet with a micro-nano structure, which can effectively suppress lithium dendrites in lithium metal batteries The growth and piercing of the battery separator improves the performance of lithium batteries.

As a preferred technical solution of the method of the present invention, the method includes:

(1) prepare metal template;

The hardness of the metal template is greater than that of the lithium sheet;

The metal template is a pattern with a raised structure, and the surface of the lithium sheet is formed with a concave structure after embossing the lithium sheet;

(2) Li flakes are patterned by roll-to-roll imprinting or plate-to-plate imprinting in an anhydrous and oxygen-free environment to make the Li flakes have a concave structure.

Preferably, pits and/or grooves are formed on the lithium sheet.

Preferably, the pits and/or grooves are micro-nano structured patterns.

Preferably, the micro-nano structure pattern is a regular periodic pattern.

Preferably, the metal template in step (1) is a nickel template.

Preferably, the preparation method of the nickel template is:

(A) Coating photoresist on the silicon wafer, using the pattern on the mask plate to expose, and finally developing the micro-nano pattern;

(B) removing the photoresist, and then forming a nickel seed layer of 50nm to 100nm;

(C) Electroplating is thickened, and the nickel template is obtained by demolding.

In this preferred technical solution, the thickness of the nickel seed layer in step (B) is 50nm-100nm, such as 50nm, 60nm, 70nm, 80nm, 85nm, 90nm or 100nm.

Preferably, the silicon wafer in step (A) is a cleaned silicon wafer.

Preferably, the coating method in step (A) is spin coating.

Preferably, the method for forming the nickel seed layer in step (B) is magnetron sputtering or electron beam evaporation.

As a further preferred technical solution of the method of the present invention, the method includes: transferring the micro-nano structure of the nickel template to the negative lithium sheet by plate-to-plate imprinting. More specifically, including:

First, spin-coat photoresist on a clean silicon wafer, and use the pattern on the mask to form a micro-nano pattern;

ICP dry etching to remove photoresist;

Then use magnetron sputtering or electron beam evaporation to deposit a layer of 50-100nm nickel as a seed layer, then thicken it by electroplating, and finally demould to make a nickel template;

The prepared nickel template is patterned on the lithium sheet by plate-to-plate nanoimprinting in an anhydrous and oxygen-free environment, so as to obtain a lithium sheet with micro-nano patterns.

As another preferred technical solution of the method of the present invention, only plate-to-plate nanoimprinting is replaced by roll-to-roll nanoimprinting, and the other methods are the same as the above-mentioned further preferred technical solutions. A simple schematic diagram of roll-to-roll nanoimprinting is shown in Fig. 3.

In a third aspect, the present invention provides a lithium metal battery comprising the lithium sheet described in the first aspect as a negative electrode.

The present invention provides a lithium metal battery. The negative pole of the battery is the negative pole described in the first aspect, and also includes components such as a positive pole, a separator, an electrolyte, and a battery case.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention can effectively control the free growth of lithium metal battery dendrites by making the lithium sheet into a specific uneven surface with a concave structure (such as a structure such as pits or grooves).

During the charging and discharging process of the battery, lithium is preferentially deposited on the depressions of the uneven surface, such as pits (such as micro-nano structure pits) and/or grooves, which provide space for the growth of lithium dendrites, thereby effectively inhibiting The growth of lithium dendrites in lithium metal batteries is avoided, the phenomenon of piercing the battery separator is avoided, and the performance of lithium batteries is improved.

(2) The present invention adopts nanoimprint technology, especially the roll-to-roll nanoimprint lithium metal battery negative electrode, which can realize large-scale industrial mass production, and the pattern is stable and regular, the specific surface area of the pattern is large, and the pattern is not easy to generate defects.

(3) The micro-nano processing technology adopted in the present invention has a mature and stable process, and can realize precise control of pattern size, and patterns from nanometer to micrometer levels can be produced.

Description of drawings

Fig. 1 is a process flow chart of preparing a lithium sheet with a micro-nano structure by using a plate-to-plate imprinting process in Example 1.

Fig. 2 is a finished effect diagram of a lithium sheet with a micro-nano structure prepared by a plate-to-plate imprinting process in Example 1.

FIG. 3 is a simplified schematic diagram of the roll-to-roll embossing process used in Embodiment 4. FIG.

FIG. 4 is an SEM image of the lithium sheet with a micro-nano structure in Example 1.

Fig. 5a and Fig. 5b are SEM images of the negative electrode lithium sheet with a micro-nano structure in Example 1 after lithium deposition, wherein Fig. 5b is an enlarged view of the dotted frame area in Fig. 5a.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

Example 1

This embodiment provides a method for preparing a lithium sheet with a micro-nano structure, comprising: transferring the micro-nano structure of a nickel template to a negative lithium sheet by plate-to-plate imprinting. More specifically, it includes (see Figure 1 for the process flow):

First, spin-coat photoresist on a clean silicon wafer, and use the pattern on the mask to form a micro-nano pattern;

ICP dry etching to remove photoresist;

Then use magnetron sputtering or electron beam evaporation to deposit a layer of 100nm nickel seed layer, then thicken it by electroplating, and finally demould to make a nickel template;

The prepared nickel template was patterned on the lithium sheet by plate-to-plate nanoimprinting in an anhydrous and oxygen-free environment, so as to obtain a lithium sheet with micro-nano patterns (see Figure 2 for the finished lithium sheet rendering).

Example 2

Except that the thickness of the nickel seed layer is 50nm, other methods and conditions are the same as in Example 1.

Example 3

Except that the thickness of the nickel seed layer is 75nm, other methods and conditions are the same as in Example 1.

Example 4

This embodiment provides a method for preparing a lithium sheet with a micro-nano structure, comprising: transferring the micro-nano structure of a nickel template to a lithium negative electrode sheet by roll-to-roll embossing. More specifically, including:

First, spin-coat photoresist on a clean silicon wafer, and use the pattern on the mask to form a micro-nano pattern;

ICP dry etching to remove photoresist;

Then use magnetron sputtering or electron beam evaporation to deposit a layer of 100nm nickel seed layer, then thicken it by electroplating, and finally demould to make a nickel template;

The prepared nickel template was patterned on the lithium sheet by roll-to-roll nanoimprinting in an anhydrous and oxygen-free environment, so as to obtain a lithium sheet with micro-nano patterns.

Refer to FIG. 3 for a simplified schematic diagram of the roll-to-roll embossing process in Embodiment 4.

Fig. 4 is the SEM image of the lithium sheet with micro-nano structure of embodiment 1, as can be seen from the figure, the lithium sheet after micro-nano processing has appeared the square groove pattern that is evenly distributed, and the square side length of square groove About 5μm, the depth is about 50nm, and there is a certain distance between the grooves.

Fig. 5a and Fig. 5b are the SEM images after the negative electrode lithium sheet with the micro-nano structure of Example 1 is packed into the battery after a certain number of cycles, wherein Fig. 5b is an enlarged view of the dotted frame area in Fig. 5a, from Fig. 5a and Fig. 5b, it can be seen that lithium is preferentially deposited on the bottom of the square pattern and the groove wall, and adheres in the form of small particles, and does not produce any dendrite lithium. After the battery cycle, almost all lithium metal is deposited in the pattern groove, indicating that the micro-nano-processed lithium sheet can effectively suppress the problem of lithium dendrites breaking through the SEI film caused by excessive local current density, which is a new generation of lithium metal battery application. provides a possibility.

The applicant declares that the present invention illustrates the detailed methods of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed methods, that is, it does not mean that the present invention must rely on the above-mentioned detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A lithium sheet, characterized in that, the lithium sheet is a lithium sheet with a recessed structure. 2. The lithium sheet according to claim 1, wherein the recessed structure comprises a pit structure and/or a groove structure; Preferably, the pit structure and/or groove structure is a micro-nano structure pattern; Preferably, the micro-nano structure pattern is a regular periodic pattern. 3. The lithium sheet according to claim 1 or 2, wherein the thickness of the lithium sheet is 0.5 mm to 1 mm; Preferably, the pits and/or grooves have a depth of 50 nm to 100 μm, preferably 5 μm to 15 μm; Preferably, the depth of the pits and/or grooves is 1/10 to 1 time of the minimum line width. 4. The use of the lithium sheet according to any one of claims 1-3, wherein the lithium sheet is used as a negative electrode. 5. The method for preparing a lithium sheet according to any one of claims 1-3, wherein the method comprises: using a metal template to carry out roll-to-roll embossing or plate-to-plate embossing on the lithium sheet, the The imprinting is preferably nanoimprinting. 6. The method according to claim 5, characterized in that the method comprises: (1) prepare metal template; The hardness of the metal template is greater than that of the lithium sheet; The metal template is a pattern with a raised structure, and the lithium sheet forms a concave structure after embossing the lithium sheet; (2) Li flakes are patterned by roll-to-roll imprinting or plate-to-plate imprinting in an anhydrous and oxygen-free environment to make the Li flakes have a concave structure. 7. The method according to claim 6, wherein the recessed structure comprises pits and/or grooves; Preferably, the pits and/or grooves are micro-nano structured patterns; Preferably, the micro-nano structure pattern is a regular periodic pattern. 8. according to the described method of claim 6 or 7, it is characterized in that, the metal template described in step (1) is a nickel template; Preferably, the preparation method of the nickel template is: (A) Coating photoresist on the silicon wafer, using the pattern on the mask plate to expose, and finally developing the micro-nano pattern; (B) removing the photoresist, and then forming a nickel seed layer of 50nm to 100nm; (C) Electroplating is thickened, and the nickel template is obtained by demolding. 9. The method according to claim 8, characterized in that the silicon wafer in step (A) is a cleaned silicon wafer; Preferably, the coating method described in step (A) is spin coating; Preferably, the method for forming the nickel seed layer in step (B) is magnetron sputtering or electron beam evaporation. 10. A lithium metal battery, characterized in that the lithium metal battery comprises the lithium sheet according to any one of claims 1-3 as a negative electrode.