KR20230032500A - Producing method of anode for lithium secondary battery using electroless plating - Google Patents

Abstract

The present invention relates to a method for manufacturing a negative electrode for a lithium secondary battery using electroless plating. The present invention includes the steps of: preparing an electroless plating solution containing metal ions; and forming a plating layer on the lithium metal by providing the electroless plating solution to the lithium metal. According to the present invention, a lithium secondary battery having an extended lifespan can be obtained.

Description

Manufacturing method of negative electrode for lithium secondary battery using electroless plating

The present invention relates to a method for manufacturing a negative electrode for a lithium secondary battery using electroless plating.

A lithium secondary battery is a secondary battery having the highest energy density among currently commercialized secondary batteries and can be used in various fields such as electric vehicles.

A negative electrode of a commercially available lithium secondary battery is a graphite material, and the graphite material has a theoretical capacity of 372 mAh/g, but has limitations in application to electric vehicles and large-capacity energy storage systems requiring high energy density.

With the development of next-generation secondary batteries such as lithium-sulfur batteries and lithium-air batteries, capacity enhancement of commercial anodes is required.

Lithium metal is attracting attention as an anode material that can realize high energy density due to its high theoretical capacity of 3860mAh/g and very low oxidation-reduction potential (-3.04V vs. S.H.E).

However, due to the high reactivity characteristic of alkali metals, side reactions with the liquid electrolyte continuously occur during battery operation.

In addition, there is a risk of internal short circuit due to dendritic growth during the lithium electrodeposition process. An internal short circuit generates a lot of heat and sparks, which can be a major cause of battery fire and explosion.

In order to solve this problem, there has been an attempt to suppress the growth of lithium dendrite by depositing a metal layer friendly to lithium on the lithium metal. However, the deposition method has limitations in that it may cause side reactions and is not suitable for mass production due to high production cost.

An object of the present invention is to provide a method that can conveniently manufacture a negative electrode for a lithium secondary battery without side reactions.

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof set forth in the claims.

A method for manufacturing a negative electrode for a lithium secondary battery according to an embodiment of the present invention includes preparing an electroless plating solution containing metal ions and providing the electroless plating solution to lithium metal to form a plating layer on the lithium metal. Including, the plating layer may include a metal originating from the metal ion.

The metal ion may include at ^least one selected from ^the group consisting of Ag ⁺ , Au ⁺ , Zn ²⁺ , Mg ²⁺ , and combinations thereof.

The metal ion may be derived from a metal salt.

The metal salt is M _x A _y (where M is Ag, Au, Zn or Mg, A is TFSI ^- , FSI ^- , NO ^3- or PF ^6- , and x and y balance the charge of M and A It is a number determined to) may include a compound represented by.

The concentration of the metal salt may be 0.1 mM to 10 M.

The electroless plating solution may include a solvent including at least one selected from the group consisting of ether-based solvents, aldehyde-based solvents, ketone-based solvents, carbonate-based solvents, and combinations thereof.

The solvent may include at least one selected from the group consisting of 1,2-dimethoxyethane, 1,4-dioxane, tetrahydrofuran, and combinations thereof.

The electroless plating solution may include at least one selected from the group consisting of a reducing agent, a complexing agent, a stabilizer, a speed enhancer, and combinations thereof.

The manufacturing method may include forming the plating layer by immersing the lithium metal in the electroless plating solution.

The manufacturing method may include forming a plating layer by applying the electroless plating solution on the lithium metal.

The metal may include at least one selected from the group consisting of Ag, Au, Zn, Mg, and combinations thereof.

According to the present invention, the growth of dendritic lithium is inhibited by the plating layer formed on the lithium metal, and thus a lithium secondary battery having an extended lifespan can be obtained.

According to the present invention, a lithium secondary battery can be manufactured at a low production cost, which can be of great help in securing market competitiveness.

According to the present invention, it is possible to form a plating layer on lithium metal without side reactions.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a cross-sectional view showing a lithium secondary battery according to the present invention.
2 is a visual observation of the negative electrode obtained through Example 1.
3 is a visual observation of the negative electrode obtained through Example 2.
4 is a visual observation of the negative electrode obtained through Example 3.
5 is a visual observation of the negative electrode obtained through the comparative example.
6a is a result of analyzing the surface of the negative electrode according to Example 1 with an electron microscope. 6B is a result of analyzing the surface of the negative electrode according to Example 2 with an electron microscope. 6C is a result of analyzing the surface of the negative electrode according to Example 3 with an electron microscope. Figure 6d is a result of analyzing the surface of the negative electrode according to the comparative example with an electron microscope.
7A is an elemental analysis result of the negative electrode according to Example 1; 7B is an elemental analysis result of the negative electrode according to Example 2. 7c is an elemental analysis result for the negative electrode according to Example 3; 7D is an elemental analysis result of a negative electrode according to a comparative example.
8 is a result of evaluating the lifespan of coin cells made of negative electrodes according to Examples 1 to 3 and Comparative Example.
9a is a result of visual observation of the surface of the negative electrode according to Example 1 after charging. 9B is a result of visual observation of the surface of the negative electrode according to Example 2 after charging. 9C is a result of visual observation of the surface of the negative electrode according to Example 3 after charging. 9D is a result of visually observing the surface of the negative electrode according to the comparative example after charging.
10A is a visual observation of the surface of the negative electrode according to Example 1 after discharging. In addition, the surface of the separator was also observed. 10B is a visual observation of the surface of the negative electrode according to Example 2 after discharging. 10C is a visual observation of the surface of the negative electrode according to Example 3 after discharging. 10D is a visual observation of the surface of a negative electrode according to a comparative example after discharging.
11A is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 1. 11B is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 2. 11C is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 3. 11D is a result of analyzing the shape of lithium during charging of an anode according to a comparative example.
12a is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 1. 12B is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 2. 12c is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 3. 12d is a result of analyzing the shape of lithium during discharging of the negative electrode according to the comparative example.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

Like reference numerals have been used for like elements throughout the description of each figure. In the accompanying drawings, the dimensions of the structures are shown enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where another part is present in the middle. Conversely, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is in the middle.

Unless otherwise specified, all numbers, values and/or expressions expressing quantities of components, reaction conditions, polymer compositions and formulations used herein refer to the number of factors that such numbers arise, among other things, to obtain such values. Since these are approximations that reflect the various uncertainties of the measurement, they should be understood to be qualified by the term "about" in all cases. Also, when numerical ranges are disclosed herein, such ranges are contiguous and include all values from the minimum value of such range to the maximum value inclusive, unless otherwise indicated. Furthermore, where such ranges refer to integers, all integers from the minimum value to the maximum value inclusive are included unless otherwise indicated.

1 is a cross-sectional view showing a lithium secondary battery according to the present invention. Referring to this, the lithium secondary battery may include a positive electrode 10, a negative electrode 20, and a separator 30 positioned between the positive electrode 10 and the negative electrode 20.

The cathode 10 may include a cathode active material, a binder, a conductive material, and the like.

The cathode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof. However, the cathode active material is not limited thereto, and all cathode active materials available in the art may be used.

The binder is a component that assists in the binding of the positive electrode active material and the conductive agent and the binding to the current collector, and includes polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, These may include recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, and the like. can

The conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be included.

The anode 20 may include a lithium metal 21 and a plating layer 22 positioned on the lithium metal.

The lithium metal 21 may be composed only of lithium or a lithium metal alloy.

The lithium metal alloy may include lithium and an alloy of a metal or metalloid capable of alloying with lithium.

The metal or metalloid capable of alloying with lithium may include Si, Sn, Al, Ge, Pb, Bi, Sb, and the like.

Lithium metal has a large electric capacity per unit weight, which is advantageous for realizing a high-capacity battery. However, lithium metal may cause a short circuit between an anode and a cathode due to the growth of a dendritic structure during the process of electrodeposition and dissolution of lithium ions. In addition, lithium metal has high reactivity to the electrolyte, and the lifespan of the battery may be reduced due to side reactions between them.

Accordingly, the present invention forms a lithium-friendly (Lithiophillic) plating layer 22 on the lithium metal 21 to suppress the growth of dendrite lithium.

The plating layer 22 may include a lithium-friendly metal. The metal may include at least one selected from the group consisting of Ag, Au, Zn, Mg, and combinations thereof.

The manufacturing method of the negative electrode 20 according to the present invention may include preparing an electroless plating solution containing metal ions and providing the electroless plating solution to lithium metal to form a plating layer on the lithium metal. there is.

The electroless plating solution may include metal ions, solvents, additives, and the like.

The metal of the plating layer 22 originates from metal ions of the electroless plating solution, and the metal ions are at least ^one selected from the group consisting of Ag ⁺ , Au ⁺ , Zn ²⁺ , Mg ^{2+ and} combinations thereof. can include

The metal ion may be derived from a metal salt. Metal ions may be prepared by dissolving the metal salt in the solvent.

The metal salt may include a compound represented by Chemical Formula 1 below.

[Formula 1]

M _x A _y

Here, M is Ag, Au, Zn or Mg, A is TFSI ^- , FSI ^- , NO ^{3 -} or PF ^{6 -} , and x and y are numbers determined to balance the charge of M and A.

The concentration of the metal salt is not particularly limited, but may be, for example, less than or equal to the saturation concentration for the solvent, or 0.1 mM to 10 M.

The solvent may be one that has no or very little reactivity with lithium metal and can dissolve the metal salt.

The solvent may include at least one selected from the group consisting of ether-based solvents, aldehyde-based solvents, ketone-based solvents, carbonate-based solvents, and combinations thereof, and specifically, the solvent is 1,2-dimethoxyethane, 1,4 It may include at least one selected from the group consisting of -dioxane, tetrahydrofuran, and combinations thereof.

The electroless plating solution may further include additives commonly used in the art to which the present invention pertains. For example, the electroless plating solution may include at least one selected from the group consisting of a reducing agent, a complexing agent, a stabilizer, a speed enhancer, and combinations thereof.

The reducing agent may include formaldehyde, hydrazine, aminoborane (eg, dimethylamine borane), borohydride, hypophosphite, dithionite, and the like.

The complexing agent may include ammonium chloride, tartrate, ethylenediaminetetraacetic acid (EDTA) and salts thereof, tetramethylammonium hydroxide, alkanolamine, and the like.

The stabilizer includes mercaptobenzothiazole, thiourea, sulfur compounds, cyanide or ferrocyanide salts, mercury compounds, molybdenum, tungsten, heterocyclic nitrogen compounds, methylbutinol, propionitrile, molecular oxygen, etc. can do.

The rate enhancer may include ammonium salt, nitrate, chloride, chlorate, perchlorate, tartrate, molybdate, tungstate, and the like.

The plating layer 22 may be formed on the lithium metal 21 by providing the electroless plating solution prepared as described above to the lithium metal 21 .

A method of providing the electroless plating solution is not particularly limited.

For example, the plating layer 22 may be formed by immersing the lithium metal 21 in a container containing the electroless plating solution for a predetermined period of time. At this time, a masking tape or the like may be attached to the other surface and side surface of the lithium metal 21 so that the plating layer 22 may be formed on only one surface of the lithium metal 21 .

As another example, the plating layer 22 may be formed by applying the electroless plating solution to one surface of the lithium metal 21 . The application method is not particularly limited, and may be applied by a method such as spin coating or spraying.

The separator 30 is a porous polymer film commonly used in the art to which the present invention pertains, for example, ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer and ethylene/methacrylate copolymer. A porous polymer film made of a polyolefin-based polymer such as a polymer may be used alone or in a laminated manner. On the other hand, as the separator 30, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto.

The separator 30 may be impregnated with an electrolyte (not shown). The electrolyte may include an electrolyte solution and a lithium salt.

The electrolyte solution is a kind of organic solvent, and is not limited as long as it can be used in a lithium secondary battery. For example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, 1,2-dimethoxy ethane, 1 ,2-diethoxyethane, dimethyl ethylene glycol dimethyl ether, trimethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinonitrile, sulfolane, dimethyl sulfone, ethyl methyl sulfone , diethylsulfone, adiponitrile, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, dimethylacetamide and the like.

The lithium salt is not limited as long as it can be used in a lithium secondary battery, and may include, for example, LiNO ₃ , LiPF ₆ , LiBF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiBr, LiI, and the like.

Hereinafter, the present invention will be described in detail with reference to the following Examples and Comparative Examples. However, the technical spirit of the present invention is not limited or limited thereby.

Example 1

An electroless plating solution was prepared by using 1,2-dimethoxyethane as a solvent and dissolving AgTFSI, a metal salt, to a concentration of 0.5 mM.

Lithium metal was added to the electroless plating solution and immersed for a sufficient time to form a plating layer to obtain a negative electrode. 2 is a visual observation of the negative electrode obtained through Example 1.

Example 2

An anode was prepared in the same manner as in Example 1, except that MgTFSI was used as the metal salt. 3 is a visual observation of the negative electrode obtained through Example 2.

Example 3

An anode was prepared in the same manner as in Example 1, except that ZnTFSI was used as the metal salt. 4 is a visual observation of the negative electrode obtained through Example 3.

comparative example

An anode was prepared in the same manner as in Example 1 except that no metal salt was used. That is, lithium metal was immersed in 1,2-dimethoxyethane as a solvent for the same time as in Example 1. 5 is a visual observation of the negative electrode obtained through the comparative example.

Experimental example 1

The surfaces of the negative electrodes according to Examples 1 to 3 and Comparative Example were analyzed with an electron microscope. 6a is a result of analyzing the surface of the negative electrode according to Example 1 with an electron microscope. 6B is a result of analyzing the surface of the negative electrode according to Example 2 with an electron microscope. 6C is a result of analyzing the surface of the negative electrode according to Example 3 with an electron microscope. Figure 6d is a result of analyzing the surface of the negative electrode according to the comparative example with an electron microscope.

Experimental Example 2

Elemental analysis was performed on the anodes according to Examples 1 to 3 and Comparative Example. 7A is an elemental analysis result of the negative electrode according to Example 1. 7B is an elemental analysis result of the negative electrode according to Example 2. 7C is an elemental analysis result of the negative electrode according to Example 3. 7d is an elemental analysis result of a negative electrode according to a comparative example. Referring to FIGS. 7A to 7C , it can be seen that a plating layer was formed because metals of Ag, Mg, and Zn were detected, respectively.

Experimental example 3

Coin cells were manufactured using negative electrodes according to Examples 1 to 3 and Comparative Example, and lifespan was evaluated. The result is shown in FIG. 8 . Referring to this, it can be seen that the lifespan of the coin cells of Examples 1 to 3 is greatly increased compared to the comparative example.

Experimental Example 4

Coin cells were fabricated using the negative electrodes according to Examples 1 to 3 and Comparative Example, and the surfaces of the negative electrodes were analyzed after initial charging and discharging.

9a is a result of visual observation of the surface of the negative electrode according to Example 1 after charging. 9B is a result of visual observation of the surface of the negative electrode according to Example 2 after charging. 9C is a result of visual observation of the surface of the negative electrode according to Example 3 after charging. 9D is a result of visually observing the surface of the negative electrode according to the comparative example after charging. There was no significant difference between the surface after filling in Examples and Comparative Examples.

10A is a visual observation of the surface of the negative electrode according to Example 1 after discharging. In addition, the surface of the separator was also observed. 10B is a visual observation of the surface of the negative electrode according to Example 2 after discharging. 10C is a visual observation of the surface of the negative electrode according to Example 3 after discharging. 10D is a visual observation of the surface of a negative electrode according to a comparative example after discharging. Referring to this, it can be seen that the negative electrodes according to Examples 1 to 3 have less irreversible lithium remaining in the separator than Comparative Example. As a result, it can be confirmed that the plating layer improves the reversibility of lithium.

Experimental Example 5

Coating cells were fabricated using the negative electrodes according to Examples 1 to 3 and Comparative Example, and the shape of lithium precipitated on the negative electrode during initial charging and discharging was analyzed with a scanning electron microscope.

11A is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 1. 11B is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 2. 11C is a result of analyzing the shape of lithium during charging of the negative electrode according to Example 3. 11D is a result of analyzing the shape of lithium during charging of an anode according to a comparative example. During charging, there was no significant difference between Examples and Comparative Examples.

12a is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 1. 12B is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 2. 12c is a result of analyzing the shape of lithium during discharging of the negative electrode according to Example 3. 12D is a result of analyzing the shape of lithium during discharging of the negative electrode according to the comparative example. Referring to this, it can be seen that lithium was non-uniformly desorbed from the surface of the anode after discharging in Comparative Example, but lithium was uniformly desorbed from the surface of the anode in Examples 1 to 3, especially Example 3. This means that the reversibility of lithium is improved when the anodes according to Examples 1 to 3 are used.

As described above, although the embodiments have been described with limited examples and drawings, those skilled in the art can make various modifications and variations from the above description. For example, even if the described techniques are performed in a different order from the described method, and/or the described components are combined or combined in a different form than the described method, or substituted or replaced by other components or equivalents. Appropriate results can be achieved. Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Reference Numerals 10: anode 20: cathode 21: lithium metal 22: plating layer
30: separator

Claims (11)

preparing an electroless plating solution containing metal ions; and
Forming a plating layer on the lithium metal by providing the electroless plating solution to the lithium metal;
The plating layer is a method of manufacturing a negative electrode for a lithium secondary battery containing a metal derived from the metal ion. According to claim 1,
The method of manufacturing a negative electrode for a lithium secondary battery, wherein the metal ion includes at least one selected from the group consisting of Ag ⁺ , Au ⁺ , Zn ^{2 +} , Mg ^{2 +} and combinations thereof. According to claim 1,
The method of manufacturing a negative electrode for a lithium secondary battery in which the metal ion is derived from a metal salt. According to claim 3,
The metal salt is M _x A _y (where M is Ag, Au, Zn or Mg, A is TFSI ^- , FSI ^- , NO ^3- or PF ^6- , and x and y balance the charge of M and A A method for producing a negative electrode for a lithium secondary battery comprising a compound represented by According to claim 3,
The concentration of the metal salt is a method for producing a negative electrode for a lithium secondary battery of 0.1mM to 10M. According to claim 1,
The electroless plating solution is a method for producing a negative electrode for a lithium secondary battery comprising a solvent containing at least one selected from the group consisting of ether-based solvents, aldehyde-based solvents, ketone-based solvents, carbonate-based solvents, and combinations thereof. According to claim 6,
The method of manufacturing a negative electrode for a lithium secondary battery, wherein the solvent includes at least one selected from the group consisting of 1,2-dimethoxyethane, 1,4-dioxane, tetrahydrofuran, and combinations thereof. According to claim 1,
The electroless plating solution is a method for producing a negative electrode for a lithium secondary battery comprising at least one selected from the group consisting of a reducing agent, a complexing agent, a stabilizer, a rate enhancer, and combinations thereof. According to claim 1,
A method of manufacturing a negative electrode for a lithium secondary battery, wherein the plating layer is formed by immersing the lithium metal in the electroless plating solution. According to claim 1,
A method for producing a negative electrode for a lithium secondary battery, wherein the electroless plating solution is applied on the lithium metal to form a plating layer. According to claim 1,
The method of manufacturing a negative electrode for a lithium secondary battery, wherein the metal includes at least one selected from the group consisting of Ag, Au, Zn, Mg, and combinations thereof.

Images