Producing method of anode for lithium secondary battery using electroless plating

Abstract

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

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a negative electrode for a lithium secondary battery using electroless plating. Background Technology

[0002] Lithium-ion batteries have the highest energy density among currently commercialized secondary batteries and can be used in various fields such as electric vehicles.

[0003] The negative electrode of a commercially available lithium secondary battery is a graphite material, and although the graphite material has a theoretical capacity of 372 mAh / g, it has limitations in being applied to electric vehicles and large-capacity energy storage systems that require high energy density.

[0004] With the advancement of next-generation rechargeable batteries such as lithium-sulfur batteries and lithium-air batteries, there is a demand for increased capacity in commercial anodes.

[0005] Lithium metal is attracting attention as a cathode material capable of realizing high energy density due to its high theoretical capacity of 3860 mAh / g and very low redox potential (-3.04 V vs. SHE).

[0006] However, due to the high reactivity characteristic of alkali metals, side reactions with the liquid electrolyte occur continuously during battery operation.

[0007] In addition, there is a risk of internal short circuits caused by dendritic growth during the lithium electrodeposition process. Internal short circuits generate significant heat and sparks, which can be a major cause of battery fires and explosions.

[0008] To address this, there have been attempts to suppress the growth of lithium dendrites by depositing a lithium-affinity metal layer onto the lithium metal. However, this deposition method has limitations, as it can cause side reactions and results in high production costs, making it unsuitable for mass production. The problem to be solved

[0009] The present invention aims to provide a method for easily manufacturing a negative electrode for a lithium secondary battery without side reactions.

[0010] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become more apparent from the following description and will be realized by the means and combinations thereof described in the claims. means of solving the problem

[0011] A method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present invention comprises the steps of preparing an electroless plating solution containing metal ions and providing the electroless plating solution to a lithium metal to form a plating layer on the lithium metal, wherein the plating layer may include a metal derived from the metal ions.

[0012] The above metal ion is Ag + , Au + , Zn 2 + , Mg 2 + It may include at least one selected from a group consisting of combinations thereof.

[0013] The above metal ions may be derived from metal salts.

[0014] The above metal salt is M x A y (Here, M is Ag, Au, Zn, or Mg, and A is TFSI - , FSI - , NO 3- or PF 6- It may include a compound represented as (where x and y are numbers determined to balance the charges of M and A).

[0015] The concentration of the metal salt may be 0.1 mM to 10 M.

[0016] The above electroless plating solution may include a solvent comprising at least one selected from the group consisting of ether-based solvents, aldehyde-based solvents, ketone-based solvents, carbonate-based solvents, and combinations thereof.

[0017] The above solvent may include at least one selected from the group consisting of 1,2-dimethoxyethane, 1,4-dioxane, tetrahydrofuran, and combinations thereof.

[0018] The above electroless plating solution may include at least one selected from the group consisting of a reducing agent, a complexing agent, a stabilizer, a rate enhancer, and combinations thereof.

[0019] The above manufacturing method may involve immersing the lithium metal in the above electroless plating solution to form the plating layer.

[0020] The above manufacturing method may involve applying the above electroless plating solution onto the lithium metal to form a plating layer.

[0021] The above metal may include at least one selected from the group consisting of Ag, Au, Zn, Mg, and combinations thereof. Effects of the invention

[0022] According to the present invention, the growth of dendritic lithium is suppressed by a plating layer formed on a lithium metal, and thereby a lithium secondary battery with an extended lifespan can be obtained.

[0023] According to the present invention, lithium secondary batteries can be manufactured at a low production cost, which can be of great help in securing market competitiveness.

[0024] According to the present invention, a plating layer can be formed on lithium metal without side reactions.

[0025] The effects of the present invention are not limited to those mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description. Brief explanation of the drawing

[0026] FIG. 1 is a cross-sectional view illustrating a lithium secondary battery according to the present invention. Figure 2 is a visual observation of the cathode obtained through Example 1. Figure 3 is a visual observation of the cathode obtained through Example 2. Figure 4 is a visual observation of the cathode obtained through Example 3. Figure 5 shows the cathode obtained through the comparative example observed with the naked eye. Figure 6a shows the results of analyzing the surface of the cathode according to Example 1 using an electron microscope. Figure 6b shows the results of analyzing the surface of the cathode according to Example 2 using an electron microscope. Figure 6c shows the results of analyzing the surface of the cathode according to Example 3 using an electron microscope. Figure 6d shows the results of analyzing the surface of the cathode according to a comparative example using an electron microscope. Figure 7a shows the elemental analysis results for the cathode according to Example 1. Figure 7b shows the elemental analysis results for the cathode according to Example 2. Figure 7c shows the elemental analysis results for the cathode according to Example 3. Figure 7d shows the elemental analysis results for the cathode according to the Comparative Example. Figure 8 shows the results of evaluating the lifespan of coin cells manufactured with cathodes according to Examples 1 to 3 and Comparative Example. Figure 9a shows the result of visual observation of the surface of the cathode after charging according to Example 1. Figure 9b shows the result of visual observation of the surface of the cathode after charging according to Example 2. Figure 9c shows the result of visual observation of the surface of the cathode after charging according to Example 3. Figure 9d shows the result of visual observation of the surface of the cathode after charging according to the comparative example. FIG. 10a is a visual observation of the surface of the cathode after discharge according to Example 1. The surface of the separator was also observed together. FIG. 10b is a visual observation of the surface of the cathode after discharge according to Example 2. FIG. 10c is a visual observation of the surface of the cathode after discharge according to Example 3. FIG. 10d is a visual observation of the surface of the cathode after discharge according to a comparative example. FIG. 11a is the result of analyzing the shape of lithium during charging of the cathode according to Example 1. FIG. 11b is the result of analyzing the shape of lithium during charging of the cathode according to Example 2. FIG. 11c is the result of analyzing the shape of lithium during charging of the cathode according to Example 3. FIG. 11d is the result of analyzing the shape of lithium during charging of the cathode according to a comparative example. FIG. 12a is the result of analyzing the shape of lithium during the discharge of the cathode according to Example 1. FIG. 12b is the result of analyzing the shape of lithium during the discharge of the cathode according to Example 2. FIG. 12c is the result of analyzing the shape of lithium during the discharge of the cathode according to Example 3. FIG. 12d is the result of analyzing the shape of lithium during the discharge of the cathode according to a comparative example. Specific details for implementing the invention

[0027] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated 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 to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0028] In describing each drawing, similar reference numerals have been used for similar components. In the attached drawings, the dimensions of the structures are depicted enlarged from their actual size for clarity of the invention. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0029] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0030] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0032] FIG. 1 is a cross-sectional view illustrating a lithium secondary battery according to the present invention. Referring thereto, the lithium secondary battery may include a positive electrode (10), a negative electrode (20), and a separator (30) located between the positive electrode (10) and the negative electrode (20).

[0033] The above anode (10) may include an anode active material, a binder, a conductive material, etc.

[0034] The above-mentioned positive electrode active material may include one or more 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 above-mentioned positive electrode active material is not limited to these, and any positive electrode active material available in the relevant technical field may be used.

[0035] The above binder is a component that assists in the bonding of the positive active material and the conductive agent, and the bonding to the current collector, and may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, etc.

[0036] The above conductive agent is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may include, for example, 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, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0037] The above cathode (20) may include a lithium metal (21) and a plating layer (22) located on the lithium metal.

[0038] The above lithium metal (21) may be composed solely of lithium or be a lithium metal alloy.

[0039] The above lithium metal alloy may include lithium and an alloy of a metal or metalloid capable of alloying with lithium.

[0040] The metals or metalloids capable of alloying with the above lithium may include Si, Sn, Al, Ge, Pb, Bi, Sb, etc.

[0041] Lithium metal is advantageous for implementing high-capacity batteries due to its high electrical capacity per unit weight. However, dendritic structures can grow during the deposition and dissolution processes of lithium ions, potentially causing short circuits between the anode and cathode. Additionally, lithium metal has high reactivity with electrolytes, which can reduce battery lifespan due to side reactions between them.

[0042] Accordingly, the present invention inhibits the growth of dendritic lithium by forming a lithium-affinity plating layer (22) on the lithium metal (21).

[0043] 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.

[0044] The method for manufacturing the cathode (20) according to the present invention may include the step of preparing an electroless plating solution containing metal ions and the step of providing the electroless plating solution to lithium metal to form a plating layer on the lithium metal.

[0045] The above electroless plating solution may include metal ions, solvents, additives, etc.

[0046] The metal of the plating layer (22) is derived from the metal ions of the electroless plating solution, and the metal ions are Ag + , Au + , Zn 2 + , Mg 2 + It may include at least one selected from a group consisting of combinations thereof.

[0047] The above metal ions may be derived from a metal salt. Metal ions can be prepared by dissolving the metal salt in the solvent.

[0048] The above metal salt may include a compound represented by the following chemical formula 1.

[0049] [Chemical Formula 1]

[0050] M x A y

[0051] Here, M is Ag, Au, Zn, or Mg, and A is TFSI - , FSI - , NO 3- or PF 6- and x and y are numbers determined to balance the charges of M and A.

[0052] The concentration of the metal salt is not particularly limited, but, for example, may be below the saturation concentration for the solvent, or 0.1 mM to 10 M.

[0053] The above solvent may be one that has little to no reactivity with lithium metal and is capable of dissolving the metal salt.

[0054] The above 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 may include at least one selected from the group consisting of 1,2-dimethoxyethane, 1,4-dioxane, tetrahydrofuran, and combinations thereof.

[0055] The above electroless plating solution may further include additives commonly used in the technical field to which the present invention belongs. For example, the above electroless plating solution may include at least one selected from the group consisting of reducing agents, complexing agents, stabilizers, rate enhancers, and combinations thereof.

[0056] The above reducing agent may include formaldehyde, hydrazine, aminoborane (e.g., dimethylamine borane), borohydride, hypophosphite, dithionite, etc.

[0057] The above complexing agent may include ammonium chloride, tartrate, ethylenediaminetetraacetic acid (EDTA) and its salts, tetramethylammonium hydroxide, alkanolamine, etc.

[0058] The above stabilizer may include mercaptobenzothiazole, thiourea, sulfur compounds, cyanide or ferrocyanide salts, mercury compounds, molybdenum, tungsten, heterocyclic nitrogen compounds, methylbutinol, propionitrile, molecular oxygen, etc.

[0059] The above rate enhancer may include ammonium salts, nitrates, chlorides, chlorates, perchlorates, tartrates, molybdate, tungstates, etc.

[0060] The electroless plating solution prepared as above can be applied to the lithium metal (21) to form a plating layer (22) on the lithium metal (21).

[0061] The method of providing the above electroless plating solution is not particularly limited.

[0062] For example, the lithium metal (21) can be immersed in a container containing the above electroless plating solution for a certain period of time to form a plating layer (22). At this time, masking tape or the like can be attached to the other surface and side of the lithium metal (21) so that the plating layer (22) can be formed only on one surface of the lithium metal (21).

[0063] As another example, the above electroless plating solution can be applied to one surface of the lithium metal (21) to form a plating layer (22). The application method is not particularly limited and can be applied by methods such as spin coating or spraying.

[0064] The above-mentioned separator (30) may be a porous polymer film made of a polyolefin-based polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, which is commonly used in the technical field to which the present invention belongs, used alone or by laminating them. Meanwhile, the above-mentioned separator (30) may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., but is not limited thereto.

[0065] The above separator (30) may be impregnated with an electrolyte (not shown). The electrolyte may include an electrolyte solution and a lithium salt.

[0066] The above electrolyte is a type of organic solvent and is not limited to any solvents that can be used in a lithium secondary battery, and may include, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylene glycol dimethyl ether, trimethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinonitrile, sulforaine, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, dimethylacetamide, etc.

[0067] The above lithium salt is not limited to any type that can be used in a lithium secondary battery and may include, for example, LiNO3, LiPF6, LiBF6, LiClO4, LiCF3SO3, LiBr, LiI, etc.

[0069] The present invention will be described in detail below with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited or restricted by these examples.

[0071] Example 1

[0072] 1,2-dimethoxyethane was used as a solvent, and a metal salt, AgTFSI, was dissolved in it to a concentration of 0.5 mM to prepare an electroless plating solution.

[0073] A lithium metal was introduced into the above electroless plating solution and immersed for a sufficient amount of time to form a plating layer to obtain a cathode. Figure 2 is a visual observation of the cathode obtained through Example 1.

[0075] Example 2

[0076] A cathode was prepared in the same manner as in Example 1, except that MgTFSI was used as the metal salt. Figure 3 is a visual observation of the cathode obtained through Example 2.

[0078] Example 3

[0079] A cathode was prepared in the same manner as in Example 1, except that ZnTFSI was used as the metal salt. Figure 4 is a visual observation of the cathode obtained through Example 3.

[0081] Comparative example

[0082] A cathode was prepared in the same manner as in Example 1 above, except that no metal salt was used. That is, lithium metal was immersed in 1,2-dimethoxyethane, the solvent, for the same amount of time as in Example 1. Figure 5 shows the cathode obtained through the comparative example observed visually.

[0084] Experimental Example 1

[0085] The surfaces of the cathodes according to Examples 1 to 3 and the Comparative Example were analyzed using an electron microscope. Fig. 6a shows the results of analyzing the surface of the cathode according to Example 1 using an electron microscope. Fig. 6b shows the results of analyzing the surface of the cathode according to Example 2 using an electron microscope. Fig. 6c shows the results of analyzing the surface of the cathode according to Example 3 using an electron microscope. Fig. 6d shows the results of analyzing the surface of the cathode according to the Comparative Example using an electron microscope.

[0087] Experimental Example 2

[0088] Elemental analysis was performed on the cathodes according to Examples 1 to 3 and the Comparative Example. Fig. 7a shows the results of the elemental analysis of the cathode according to Example 1. Fig. 7b shows the results of the elemental analysis of the cathode according to Example 2. Fig. 7c shows the results of the elemental analysis of the cathode according to Example 3. Fig. 7d shows the results of the elemental analysis of the cathode according to the Comparative Example. Referring to Figs. 7a to 7c, it can be seen that a plating layer was formed, as metals Ag, Mg, and Zn were detected, respectively.

[0090] Experimental Example 3

[0091] Coin cells were fabricated using the cathodes according to Examples 1 to 3 and Comparative Example, and their lifespan was evaluated. The results are shown in FIG. 8. Referring to this, it can be seen that the lifespan of the coin cells of Examples 1 to 3 was significantly increased compared to the Comparative Example.

[0093] Experimental Example 4

[0094] Coin cells were fabricated using the cathodes according to Examples 1 to 3 and Comparative Example, and the surface of the cathode was analyzed after initial charging and discharging.

[0095] Figure 9a shows the results of visual observation of the surface of the cathode after charging according to Example 1. Figure 9b shows the results of visual observation of the surface of the cathode after charging according to Example 2. Figure 9c shows the results of visual observation of the surface of the cathode after charging according to Example 3. Figure 9d shows the results of visual observation of the surface of the cathode after charging according to the Comparative Example. There was no significant difference in the surface after charging between the Examples and the Comparative Example.

[0096] Figure 10a shows the surface of the cathode after discharge according to Example 1, observed visually. The surface of the separator was also observed at the same time. Figure 10b shows the surface of the cathode after discharge according to Example 2, observed visually. Figure 10c shows the surface of the cathode after discharge according to Example 3, observed visually. Figure 10d shows the surface of the cathode after discharge according to the Comparative Example, observed visually. Referring to these figures, it can be seen that the cathodes according to Examples 1 to 3 have less irreversible lithium remaining in the separator compared to the Comparative Example. Consequently, it can be confirmed that the plating layer improves the reversibility of lithium.

[0098] Experimental Example 5

[0099] Coated cells were fabricated using the cathodes according to Examples 1 to 3 and Comparative Example, and the morphology of lithium deposited on the cathode during initial charging and discharging was analyzed using a scanning electron microscope.

[0100] Figure 11a shows the results of analyzing the shape of lithium during charging of the cathode according to Example 1. Figure 11b shows the results of analyzing the shape of lithium during charging of the cathode according to Example 2. Figure 11c shows the results of analyzing the shape of lithium during charging of the cathode according to Example 3. Figure 11d shows the results of analyzing the shape of lithium during charging of the cathode according to the Comparative Example. There was no significant difference between the Examples and the Comparative Example during charging.

[0101] FIG. 12a shows the results of analyzing the shape of lithium during discharge of the cathode according to Example 1. FIG. 12b shows the results of analyzing the shape of lithium during discharge of the cathode according to Example 2. FIG. 12c shows the results of analyzing the shape of lithium during discharge of the cathode according to Example 3. FIG. 12d shows the results of analyzing the shape of lithium during discharge of the cathode according to the Comparative Example. Referring to this, it can be seen that in the Comparative Example, lithium was unevenly detached from the surface of the cathode after discharge, whereas in Examples 1 to 3, particularly Example 3, lithium was uniformly detached from the surface of the cathode. This means that using the cathode according to Examples 1 to 3 improves the reversibility of lithium.

[0103] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or the described components are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents. Therefore, other implementations, other embodiments, and equivalents to the claims below are also within the scope of the claims. Explanation of the symbols

[0104] 10: Anode 20: Cathode 21: Lithium metal 22: Plating layer 30: Separator

Claims

Claim 1 A method for manufacturing a negative electrode for a lithium secondary battery, comprising: a step of preparing an electroless plating solution containing metal ions; and a step of providing the electroless plating solution to a lithium metal to form a plating layer on the lithium metal, wherein the plating layer comprises a metal derived from the metal ions, the electroless plating solution comprises a solvent comprising at least one selected from the group consisting of an ether-based solvent, an aldehyde-based solvent, a ketone-based solvent, a carbonate-based solvent, and combinations thereof, wherein the solvent is non-reactive with the lithium metal, and the lithium metal is immersed in the electroless plating solution to form the plating layer. Claim 2 In paragraph 1, the metal ion is Ag + , Au + , Zn 2 + , Mg 2 + A method for manufacturing a negative electrode for a lithium secondary battery comprising at least one selected from the group consisting of combinations thereof. Claim 3 A method for manufacturing a negative electrode for a lithium secondary battery according to claim 1, wherein the metal ions are derived from a metal salt. Claim 4 In paragraph 3, the metal salt is M x A y (Here, M is Ag, Au, Zn, or Mg, and A is TFSI - , FSI - , NO 3- or PF 6- A method for manufacturing a negative electrode for a lithium secondary battery comprising a compound represented as (where x and y are numbers determined to balance the charges of M and A). Claim 5 A method for manufacturing a negative electrode for a lithium secondary battery according to claim 3, wherein the concentration of the metal salt is 0.1 mM to 10 M. Claim 6 delete Claim 7 A method for manufacturing a negative electrode for a lithium secondary battery according to claim 1, wherein the solvent comprises at least one selected from the group consisting of 1,2-dimethoxyethane, 1,4-dioxane, tetrahydrofuran, and combinations thereof. Claim 8 A method for manufacturing a negative electrode for a lithium secondary battery according to claim 1, wherein the electroless plating solution comprises at least one selected from the group consisting of a reducing agent, a complexing agent, a stabilizer, a rate enhancer, and combinations thereof. Claim 9 delete Claim 10 delete Claim 11 A method for manufacturing a negative electrode for a lithium secondary battery according to claim 1, wherein the metal comprises at least one selected from the group consisting of Ag, Au, Zn, Mg and combinations thereof.

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