Electrolyte solution comprising metal element salt for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present invention provides an electrolyte solution for a lithium secondary battery comprising a metal element salt and a lithium secondary battery comprising the same, the electrolyte solution comprising a metal element salt as an additive. The electrolyte solution includes a solvent, a lithium salt, and an additive including a metal element including at least one selected from the group consisting of silver, gold, platinum, and combinations thereof.

Description

Technical Field

[0001] The present invention relates to an electrolyte solution containing a metal element salt as an additive for a lithium secondary battery and a lithium secondary battery containing the electrolyte solution. Background Art

[0002] Anode-free lithium secondary batteries are next-generation batteries that do not require anode materials (such as graphite) that occupy a large volume and weight in traditional batteries.

[0003] In an anode-free lithium secondary battery, only an anode current collector made of copper is included in the anode, and lithium ions (Li + ) passes through the separator via the electrolyte solution and is stored in the anode current collector in the form of lithium metal.

[0004] Although the energy density per volume of anode-free lithium secondary batteries has increased by at least 60% compared to conventional batteries, they are difficult to commercialize due to problems such as rapid capacity degradation and short life. In particular, since the electrodeposition of lithium ions on the anode current collector made of copper is not efficient, overvoltage is generated, which may cause side reactions between the anode current collector and the electrolyte solution.

[0005] The information disclosed in this background section of the present invention is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] Various aspects of the present invention are directed to providing an electrolyte solution for a lithium secondary battery and a lithium secondary battery including the electrolyte solution, the electrolyte solution being capable of suppressing a side reaction between a lithium metal single substance and the electrolyte solution.

[0007] Another object of the present invention is to provide an electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the electrolyte solution, which can improve the reversibility of lithium ions.

[0008] The object of the present invention is not limited to the above-mentioned object. The object of the present invention can be clearly understood through the following description, and can be achieved by the means described in the claims and their combination.

[0009] An exemplary embodiment of the present invention provides an electrolyte solution for a lithium secondary battery, the electrolyte solution comprising a solvent, a lithium salt and an additive, the additive comprising a metal element, wherein the metal element may include at least one selected from silver (Ag), gold (Au), platinum (Pt) and a combination thereof.

[0010] The solvent may include dimethylsulfamoyl fluoride.

[0011] The lithium salt may include a salt selected from lithium bis(fluorosulfonyl)imide ((SO 2 F) 2 NLi, LiFSI), lithium bis(trifluoromethanesulfonyl)imide ((CF 3 SO 2 ) 2 NLi, LiTFSI), LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 、LiPF 6 、LiCF 3 SO 3 、LiCF 3 CO 2 ,LiC 4 BO 8 、LiAsF 6 、LiSbF 6 、LiAlCl 4 and at least one of a combination thereof.

[0012] The additive may include at least one selected from the group consisting of nitrates of metal elements, halogen salts of metal elements, and combinations thereof.

[0013] The additive may include AgNO 3 、AuBr 3 、Pt(NO 3 ) 4 and at least one of a combination thereof.

[0014] The electrolyte solution may include 0.05 wt % to 0.1 wt % of the additive.

[0015] Another exemplary embodiment of the present invention provides a lithium secondary battery, which includes an anode current collector, a separator arranged on the anode current collector, a cathode active material layer arranged on the separator, a cathode current collector arranged on the cathode active material layer, and an electrolyte solution, wherein the electrolyte solution is immersed in at least one of the anode current collector, the separator, the cathode active material layer and the cathode current collector, wherein the electrolyte solution may include a solvent, a lithium salt and an additive, the additive including a metal element, and the work function of the metal element may be higher than the work function of the anode current collector.

[0016] The anode current collector may include a substrate including copper (Cu) and a covering layer applied on a surface of the substrate and including an alloy of copper (Cu) and a metal element.

[0017] The work function of the metal element may be greater than 4.7 eV and less than or equal to 6 eV.

[0018] The lithium secondary battery may further include a solid electrolyte interface layer located at least one of a position between the cathode active material layer and the separator and a position between the anode current collector and the separator, wherein the solid electrolyte interface layer may not contain an organic material.

[0019] The solid electrolyte interface layer may include a 2 CO 3 , LiO and at least one of a combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are given below by way of illustration only and therefore do not limit the present invention, wherein:

[0021] Figure 1 A lithium secondary battery according to an exemplary embodiment of the present invention is shown;

[0022] Figure 2 shows a charged lithium secondary battery according to an exemplary embodiment of the present invention;

[0023] Figure 3 shows a lithium secondary battery according to another exemplary embodiment of the present invention;

[0024] Figure 4 An anode current collector according to an exemplary embodiment of the present invention is shown;

[0025] Figure 5A , Figure 5B , Figure 5C and Figure 5D shows the change over time when lithium is stored in 1,2-dimethoxyethane for 1 week, Figure 5A The results for day 1 are shown. Figure 5B The results for day 3 are shown. Figure 5C The results for day 5 are shown, and Figure 5D Results for day 7 are shown;

[0026] Fig. 6A , Figure 6B , Figure 6C and Fig.6D shows the change over time when lithium is stored in dimethylsulfamoyl fluoride for 1 week, Fig. 6A The results for day 1 are shown. Figure 6B The results for day 3 are shown. Figure 6C The results for day 5 are shown, and Fig.6D Results for day 7 are shown;

[0027] Fig. 7A , Figure 7B and Figure 7C The results of analyzing the surface of lithium metal by X-ray photoelectron spectroscopy (XPS) after lithium metal was stored in 1,2-dimethoxyethane and dimethylsulfamoyl fluoride for one week are shown. Fig. 7A The results for the F1s peak are shown. Figure 7B The results for the C1s peak are shown, and Figure 7C Results for the O1s peak are shown;

[0028] Figure 8 shows the results of X-ray diffraction (XRD) of the anode current collector of each battery in Test Example 2;

[0029] Fig. 9A , Fig. 9B , Fig. 9C and Fig.9D The results of X-ray photoelectron spectroscopy (XPS) of the anode current collector of each battery in Test Example 2 are shown, Fig. 9A The results for the Ag 3d peak are shown. Fig. 9B The results for the Ag 3d peak are shown. Fig. 9C The results for the Au 4f peak are shown, and Fig.9D Results for the Pt 4f peak are shown;

[0030] Fig. 10A The initial efficiency of each battery in Test Example 3 is shown;

[0031] Fig. 10B Shows Fig. 10A A magnified image of

[0032] Fig.11 shows the results of visual observation of electrodeposited lithium for each battery in Test Example 3;

[0033] Fig. 12A The results of analyzing the surface of the electrodeposited lithium of the battery containing no additive in Test Example 3 using a scanning electron microscope are shown;

[0034] Fig. 12B The results of SEM analysis of the test sample 3 containing 0.05 wt% AgNO 3 The result of electrodeposition of lithium on the surface of the battery;

[0035] Fig. 12C The results of SEM analysis of the test sample 3 containing 0.1 wt% AgNO 3 The result of electrodeposition of lithium on the surface of the battery;

[0036] Fig.12DThe results show that the sample containing 0.05 wt% AuBr in Test Example 3 was analyzed using scanning electron microscopy. 3 The result of electrodeposition of lithium on the surface of the battery;

[0037] Fig.12E The SEM analysis of Example 3 showed that the Pt(NO 3 ) 3 The result of electrodeposition of lithium on the surface of the battery;

[0038] Fig.12F shows the results of analyzing the cross section of the electrodeposited lithium of the battery containing no additive in Test Example 3 using a scanning electron microscope;

[0039] Figure 12G The results of SEM analysis of the test sample 3 containing 0.05 wt% AgNO 3 The results of the cross section of the battery with electrodeposited lithium;

[0040] Fig.12H The results of SEM analysis of the test sample 3 containing 0.1 wt% AgNO 3 The results of the cross section of the battery with electrodeposited lithium;

[0041] Fig.12I The results show that the sample containing 0.05 wt% AuBr in Test Example 3 was analyzed using scanning electron microscopy. 3 The results of the cross section of the battery with electrodeposited lithium;

[0042] Fig.12J The SEM analysis of Example 3 showed that the Pt(NO 3 ) 3 The results of the cross section of the battery with electrodeposited lithium;

[0043] Fig.13 The evaluation results of the life of each battery in Test Example 4 are shown;

[0044] Fig.14A shows the charge / discharge of the formation process of each battery in Test Example 5;

[0045] Fig. 14B The cycle discharge capacity of each battery in Test Example 5 is shown;

[0046] Fig. 14C The coulombic efficiency of each battery in Test Example 5 is shown;

[0047] Fig.15Ashows a C1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0048] Fig. 15B shows an F1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0049] Fig. 15C shows an O1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0050] Fig.15D shows the N1s spectrum of the surface of the anode current collector of each battery in Test Example 6 by X-ray photoelectron spectroscopy (XPS);

[0051] Fig.15E shows an S2p spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0052] Fig.16A shows the Ag 3d spectrum of the surface of the anode current collector of each battery in Test Example 6 by X-ray photoelectron spectroscopy (XPS);

[0053] Fig. 16B shows the Au 4f spectrum of X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0054] Fig. 16C shows a Pt 4f spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery in Test Example 6;

[0055] Fig.17A shows a C1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6;

[0056] Fig. 17B shows an F1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6;

[0057] Fig. 17C shows an O1s spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6;

[0058] Fig.17D shows the N1s spectrum of the surface of the cathode active material layer of each battery in Test Example 6 by X-ray photoelectron spectroscopy (XPS);

[0059] Fig.17Eshows an S2p spectrum of an X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6;

[0060] Fig.18A shows the Ag 3d spectrum of the surface of the cathode active material layer of each battery in Test Example 6 by X-ray photoelectron spectroscopy (XPS);

[0061] Fig.18B shows an Au 4f spectrum of X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6; and

[0062] Fig.18C A Pt 4f spectrum of X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery in Test Example 6 is shown.

[0063] It is to be understood that the accompanying drawings are not necessarily drawn to scale, and they show various features that illustrate the basic principles of the invention in a somewhat simplified manner. The specific design features of the present invention disclosed herein (including, for example, specific dimensions, directions, locations, and shapes) will be determined in part by the specific intended application and use environment.

[0064] In the drawings, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0065] Reference will now be made in detail to various embodiments of the present invention, examples of which are shown in the accompanying drawings and described below. Although the present invention will be described in conjunction with exemplary embodiments of the present invention, it should be understood that this specification is not intended to limit the present invention to these exemplary embodiments. On the contrary, the present invention is intended to cover not only the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments that may be included in the spirit and scope of the present invention as defined by the appended claims.

[0066] The present invention will be more clearly understood by the following exemplary embodiments presented. However, the present invention is not limited to the embodiments disclosed herein and can be modified into different forms. These embodiments are provided to thoroughly explain the present invention and fully convey the spirit of the present invention to those skilled in the art.

[0067] Throughout the accompanying drawings, the same reference numerals will refer to the same or similar components. For the sake of clarity of the present invention, the size of the structure is depicted as larger than its actual size. It should be understood that although terms such as "first" and "second" can be used herein to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another component. For example, without departing from the scope of the present invention, the "first" component discussed below may be referred to as the "second" component. Similarly, the "second" component may also be referred to as the "first" component. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form.

[0068] It will also be understood that the terms "comprises," "includes," "having," and the like when used in this specification indicate the presence of the described features, values, steps, operations, elements, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, or combinations thereof. In addition, it will be understood that when a component (e.g., a layer, film, region, or sheet) is referred to as being "on" another component, it can be directly on the other component, or there can be intervening components between them. Similarly, when a component (e.g., a layer, film, region, or sheet) is referred to as being "under" another component, it can be directly under the other component, or there can be intervening components between them.

[0069] Unless otherwise stated, all numbers, values ​​and / or expressions used herein to represent the amount of components, reaction conditions, polymer compositions and mixtures should be considered as approximate values ​​containing various uncertainties (especially inherent in obtaining these values, which will affect the measured values), and should therefore be understood to be modified by the term "about" in all cases. In addition, when a numerical range is disclosed in this specification, unless otherwise stated, the range is continuous and includes all values ​​from the minimum value of the range to its maximum value. In addition, when such a range involves integer values, all integers including the minimum value to the maximum value are included unless otherwise stated.

[0070] Figure 1 A lithium secondary battery 100 according to an exemplary embodiment of the present invention is shown. The lithium secondary battery 100 may include an anode current collector 10, a separator 20 disposed on the anode current collector 10, a cathode active material layer 30 disposed on the separator 20, and a cathode current collector 40 disposed on the cathode active material layer 30.

[0071] The lithium secondary battery 100 may include an electrolyte solution (not shown) in which at least one selected from the anode current collector 10 , the separator 20 , the cathode active material layer 30 , and the cathode current collector 40 is impregnated.

[0072] Figure 2 1 shows a charged lithium secondary battery 100. The charged lithium secondary battery 100 may further include a lithium metal single substance layer 50 between the anode current collector 10 and the separator 20. When the lithium secondary battery 100 is charged, lithium ions (Li + ) passes through the separator via the electrolyte solution and moves toward the anode current collector 10. Lithium ions (Li + ) meets the electrons on the anode current collector 10, is precipitated and stored in the form of lithium metal single substance, thereby forming a lithium metal single substance layer 50.

[0073] In the present invention, an electrolyte solution having a specific composition is used, which does not react with the lithium metal element precipitated and stored as described above, and allows lithium ions (Li + ) can be effectively electrodeposited on the surface of the anode current collector 10.

[0074] The electrolyte solution may include a solvent, a lithium salt, and an additive.

[0075] The solvent may include dimethylsulfamoyl fluoride represented by the following Chemical Formula 1. Since the solvent does not react with the lithium metal element, a side reaction between the electrolyte solution and the lithium metal element layer 50 may be effectively suppressed.

[0076] [Chemical formula 1]

[0077]

[0078] Meanwhile, when the lithium secondary battery 100 is repeatedly charged and discharged, a solid electrolyte interface layer 60 may be formed between the cathode active material layer 30 and the separator 20 and / or between the anode current collector 10 and the separator 20, such as Figure 3 When dimethylsulfamoyl fluoride is used as a solvent, the solid electrolyte interface layer 60 is composed of an inorganic material rather than an organic material, so the side reaction between the electrolyte solution and the lithium metal element can be effectively suppressed. If the solid electrolyte interface layer 60 contains an organic material, the electronic conductivity increases, so when lithium ions (Li + ) is electrodeposited on the anode current collector 10, the side reaction between the electrolyte solution and the lithium metal element cannot be suppressed. Therefore, since a specific solvent is used in the present invention, the solid electrolyte interface layer 60 is formed of an inorganic material with low electronic conductivity, thereby preventing the side reaction between the electrolyte solution and the lithium metal element.

[0079] The solid electrolyte interface layer 60 may include a material selected from LiF, Li 2 CO 3 , LiO and at least one of a combination thereof.

[0080] The lithium salt may include a salt selected from lithium bis(fluorosulfonyl)imide ((SO 2 F) 2 NLi, LiFSI), lithium bis(trifluoromethanesulfonyl)imide ((CF 3 SO 2 ) 2 NLi, LiTFSI), LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 、LiPF 6 、LiCF 3 SO 3 、LiCF 3 CO 2 ,LiC 4 BO 8 、LiAsF 6 、LiSbF 6 、LiAlCl 4 and at least one of a combination thereof.

[0081] The concentration of the lithium salt is not particularly limited, but the electrolyte solution may include about 0.5M to 5M or about 0.5M to 3M of the lithium salt.

[0082] The additive may include a metal element. The work function of the metal element may be higher than the work function of the anode current collector 10. Here, the work function of the anode current collector 10 may refer to the work function of elements constituting the anode current collector 10 (particularly, the base material 11 included in the anode current collector 10).

[0083] The work function represents the energy difference required when one electron moves between the highest occupied energy level (Fermi level) of electrons within a material and the potential outside the material, and 1 eV is the work or energy required for an electron to move through a potential difference of 1 V. The work function can be obtained by electronic structure calculation based on density functional theory.

[0084] Since the metal element has a high work function, the metal element receives electrons from the element constituting the anode current collector 10 (particularly the substrate 11), thereby forming an alloy of the metal element and the element constituting the substrate 11 on the surface of the anode current collector 10. The alloy allows lithium ions (Li +) can be effectively electrodeposited on the anode current collector 10, thereby preventing the generation of overvoltage in the lithium secondary battery 100 and ultimately suppressing the side reaction between the lithium metal element and the electrolyte solution.

[0085] Figure 4 There is shown an anode current collector 10. The anode current collector 10 includes a substrate 11 including copper (Cu) and a covering layer 12 applied on a surface of the substrate 11 and including an alloy of copper (Cu) and a metal element.

[0086] Since the work function of copper (Cu) constituting the substrate 11 is about 4.7 eV, the work function of the metal element may be 6 eV or less, but greater than 4.7 eV.

[0087] The metal element may include at least one selected from silver (Ag), gold (Au), platinum (Pt) and a combination thereof. The work function of silver (Ag) is about 4.73 eV, the work function of gold (Au) is about 5.1 eV, and the work function of platinum (Pt) is about 5.65 eV. When an additive containing them is used, the cover layer 12 may be formed.

[0088] The cover layer may include at least one selected from an alloy of copper (Cu) and silver (Ag), an alloy of copper (Cu) and gold (Au), an alloy of copper (Cu) and platinum (Pt), and combinations thereof.

[0089] The additive may include at least one selected from nitrates of metal elements, halogen salts of metal elements, and combinations thereof. Specifically, the additive may include AgNO 3 、AuBr 3 、Pt(NO 3 ) 4 and at least one of a combination thereof.

[0090] The electrolyte solution may include 0.05 wt % to 0.1 wt % of the additive. If the amount of the additive is less than 0.05 wt %, it may be difficult to form the cover layer 12 .

[0091] The separator 20 may be used to separate the anode current collector 10 and the cathode active material layer 30 from each other, and may provide a passage for lithium ions to move. Generally, any material used as a separator in a lithium secondary battery may be used without particular limitation, and in particular, may include a material that has low resistance to ion movement of an electrolyte solution, can be highly impregnated with an electrolyte solution, and is highly safe.

[0092] The separator 20 may include a porous polymer film (eg, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer) or a laminated structure of two or more layers thereof.

[0093] Furthermore, the separator 20 may include a porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like.

[0094] In addition, the separator 20 may be coated with a ceramic component or a polymer material to obtain heat resistance or mechanical strength.

[0095] The cathode active material layer 30 may include a cathode active material, a binder, a conductive material, and the like.

[0096] The cathode active material may include at least one selected from 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 any cathode active material available in the art may be used.

[0097] The binder is a component that helps to bind the cathode active material and the conductive material and to the collector, and may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, and the like.

[0098] There is no particular limitation on the conductive material as long as it has conductivity and does not cause chemical changes in the battery, and examples thereof may include graphite (e.g., natural graphite or artificial graphite), carbon-based materials (e.g., carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, etc.), conductive fibers (e.g., carbon fibers or metal element fibers), metal element powders (e.g., carbon fluoride, aluminum, nickel powder, etc.), conductive whiskers (e.g., zinc oxide, potassium titanate, etc.), conductive metal element oxides (e.g., titanium oxide, etc.), and conductive materials such as polyphenylene derivatives.

[0099] The cathode current collector 40 may be a plate-shaped substrate having conductivity. The cathode current collector 40 may include aluminum foil.

[0100] A better understanding of the present invention can be obtained through the following examples. These examples are set forth only to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0101] Preparation Example 1

[0102] The electrolyte solution was prepared using the components in the amounts shown in Table 1 below. Specifically, the solution was prepared by dissociating 3M LiFSI in dimethylsulfamoyl fluoride (FSA) as a solvent. 1 wt % or more of calcium hydride (CaH 2 ) is placed in a container, the container is added to the solution, and the solution is dehydrated by removing the container after about 30 minutes. AgNO is added as an additive to the obtained solution. 3 , to provide an electrolyte solution. The amount of the additive is adjusted to about 0.05 wt % based on the total weight of the electrolyte solution.

[0103] Preparation Example 2

[0104] The electrolyte solution was prepared in the same manner as in Example 1, except that AgNO 3 The amount was increased to 0.1 wt%.

[0105] Preparation Example 3

[0106] The electrolyte solution was prepared in the same manner as in Example 1, except that AuBr 3 As an additive.

[0107] Preparation Example 4

[0108] The electrolyte solution was prepared in the same manner as in Example 1, except that Pt(NO 3 ) 4 As an additive.

[0109] Comparative Preparation Example 1

[0110] An electrolyte solution was prepared in the same manner as in Preparation Example 1, except that 1,2-dimethoxyethane (DME) was used as a solvent, and no additive was added.

[0111] Comparative Preparation Example 2

[0112] An electrolyte solution was prepared in the same manner as in Preparation Example 1, except that no additive was added.

[0113] [Table 1]

[0114]

[0115] Test Example 1: Evaluation of the Stability of Solvents to Lithium Metal

[0116] 15 pi (15 mm in diameter) of lithium was stored in 2 g of a solvent for 1 week, and changes over time were observed, followed by X-ray photoelectron spectroscopy (XPS) and FT-IR analyses.

[0117] Solvent 1: 1,2-dimethoxyethane (DME)

[0118] Solvent 2: dimethylsulfamoyl fluoride (FSA).

[0119] Figure 5A , Figure 5B , Figure 5C and Figure 5D shows the change over time when lithium is stored in 1,2-dimethoxyethane for 1 week, Figure 5A The results for day 1 are shown. Figure 5B The results for day 3 are shown. Figure 5C The results for day 5 are shown, and Figure 5D Results from day 7 are shown.

[0120] Fig. 6A , Figure 6B , Figure 6C and Fig.6D shows the change over time when lithium is stored in dimethylsulfamoyl fluoride for 1 week, Fig. 6A The results for day 1 are shown. Figure 6B The results for day 3 are shown. Figure 6C The results for day 5 are shown, and Fig.6D Results from day 7 are shown.

[0121] refer to Figure 5A , Figure 5B , Figure 5C and Figure 5D as well as FIG. 6A to FIG. 6D , when lithium metal is stored in 1,2-dimethoxyethane or dimethylaminosulfonyl fluoride, the surface of lithium metal does not change.

[0122] Fig. 7A , Figure 7B and Figure 7C The results of analyzing the surface of lithium metal element by X-ray photoelectron spectroscopy (XPS) after the lithium metal element was stored in each solvent for 1 week are shown. Fig. 7A The results for the F1s peak are shown. Figure 7B The results for the C1s peak are shown, and Figure 7C The results of the O1s peak are shown. Based on the analysis results, unlike 1,2-dimethoxyethane, which forms a solid electrolyte interface layer made of organic materials, dimethylsulfamoyl fluoride is able to form a solid electrolyte interface layer made of inorganic materials (such as LiF, Li 2 CO 3 or LiO) solid electrolyte interface layer.

[0123] Specifically, compared with 1,2-dimethoxyethane, dimethylsulfamoyl fluoride is considered to be a solvent having very high stability for lithium metal since a solid electrolyte interface layer made of an inorganic material is formed and no byproduct is dissolved in the electrolyte solution.

[0124] Test Example 2: Evaluation of alloy formation

[0125] A battery was manufactured as follows, and the electrolyte solution of each of Preparation Examples 1 to 4 and Comparative Preparation Example 2 was injected into the battery.

[0126] Battery type: Cu / W-SCOPE diaphragm (16pi) / NCM811 cathode, 1.5T gasket, button cell (2032)

[0127] Amount of electrolyte solution injected: 15 μl.

[0128] The battery injected with the electrolyte solution was aged at room temperature for about 5 hours, and then X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed on the surface of the anode current collector.

[0129] Figure 8 The results of X-ray diffraction (XRD) of the anode current collector of each battery are shown. Unlike the comparative preparation example 2 (FSA) without additive, 0.05% AgNO 3 (Preparation Example 1) and 0.1% AgNO 3 (Preparation Example 2) shows a Ag(111) peak, and 0.05% AuBr 3 (Preparation Example 3) shows the Au(111) peak. Therefore, when AgNO is introduced 3 AuBr 3 It was found that Ag or Au having a work function higher than that of Cu formed an alloy by receiving electrons from Cu within a 5-hour standing time.

[0130] Fig. 9A , Fig. 9B , Fig. 9C and Fig.9D The results of X-ray photoelectron spectroscopy (XPS) of the anode current collector of each battery are shown. Fig. 9A The results for the Ag 3d peak are shown. Fig. 9B The results for the Ag 3d peak are shown. Fig. 9C The results for the Au 4f peak are shown, and Fig.9D The results of Pt 4f peak are shown. Here, Ag peak and Pt peak appear in 0.1% AgNO 3 (Preparation Example 2) and 0.05% Pt(NO 3 ) 4(Preparation Example 4).

[0131] Therefore, it can be found that when the electrolyte solutions according to Preparation Examples 1 to 4 were injected, alloys between the metal elements of the additives and the components constituting the anode current collector were formed on the anode current collector.

[0132] Test Example 3: Evaluation of initial efficiency of battery

[0133] A battery was manufactured as follows, and the electrolyte solution of each of Preparation Examples 1 to 4 and Comparative Preparation Example 2 was injected into the battery.

[0134] Cell type: 20μm Li / W-SCOPE separator (19pi) / Cu, 1.0T gasket, button cell (2032)

[0135] Amount of electrolyte solution injected: 15 μl

[0136] Test conditions: aging for 1 hour at room temperature, the charge / discharge current density (0.2 mA cm -2 ).

[0137] Fig. 10A The initial efficiency of each cell is shown. Fig. 10B Shows Fig. 10A Compared with 3M FSA without additives, when AgNO 3 、AuBr 3 or Pt(NO 3 ) 4 When AgNO is introduced, it can form an alloy with copper (Cu), resulting in a low initial reversible efficiency. 3 、AuBr 3 or Pt(NO 3 ) 4 The electrodeposition overvoltage was significantly reduced when 0.05% AgNO 3 The electrodeposition overvoltage of 0.1% AgNO was 26.1 mV. 3 The electrodeposition overvoltage of 0.05% AuBr was 19.4 mV. 3 The electrodeposition overvoltage was 25.7 mV, and 0.05% Pt(NO 3 ) 4 The electrodeposition overvoltage was 19.9 mV, indicating that the electrodeposition overvoltage was significantly reduced. The above results are summarized in Table 2 below.

[0138] [Table 2]

[0139]

[0140] Fig.11 The results of visual observation of electrodeposited lithium for each battery are shown. Fig.11 In the figure, FSA shows observation of the surface of the anode current collector, and FSA-Separator shows observation of the surface of the separator. In the case of 3M FSA, since the electrodeposition of lithium on the anode current collector cannot be effectively performed, the electrodeposited lithium adheres to the separator. This is an inherent problem of the anode current collector made of copper, and the electrodeposition of lithium ions cannot be effectively performed, so the electrodeposition may become difficult, and due to the overvoltage during the electrodeposition process, a side reaction with the electrolyte solution may occur.

[0141] FIG. 12A to FIG. 12J Results of analyzing the surface and cross-section of the electrodeposited lithium of each battery using a scanning electron microscope are shown. FIG. 12A to FIG. 12E The surface results of electrodeposited lithium are shown, and FIG. 12F to FIG. 12J Cross-sectional results of electrodeposited lithium are shown. FIG. 12A to FIG. 12J The projects are summarized below.

[0142] A) 3M FSA, B) 0.05% AgNO 3 , C) 0.1% AgNO 3 , D) 0.05% AuBr 3 、E) 0.05% Pt(NO 3 ) 4

[0143] F) 3M FSA, G) 0.05% AgNO 3 , H) 0.1% AgNO 3 , I) 0.05% AuBr 3 、J) 0.05% Pt(NO 3 ) 4

[0144] The thickness of the electrodeposited lithium is summarized in Table 3 below.

[0145] [Table 3]

[0146]

[0147] In the case of 3M FSA, voids are formed on the surface of the electrodeposited lithium. When voids exist on the surface of lithium, the electrolyte solution penetrates into the voids, resulting in a side reaction between lithium and the electrolyte solution, which is undesirable. On the other hand, when AgNO is introduced 3 、AuBr 3 or Pt(NO 3 ) 4When the electrodeposition of lithium is uniform, it is determined that there are no voids on the surface of the electrodeposited lithium. The morphological differences of the electrodeposited lithium significantly affect the thickness of the electrodeposited lithium. Specifically, it can be found that the electrolyte solution containing the additive can inhibit the formation of voids, thereby preventing the side reaction between the electrolyte solution and the lithium metal element, thereby enabling the lithium electrodeposition to be small in thickness.

[0148] Test Example 4: Evaluation of Battery Life

[0149] A battery was manufactured as follows, and the electrolyte solution of each of Preparation Examples 1 to 4 and Comparative Preparation Example 2 was injected into the battery.

[0150] Cell type: 20μm Li / W-SCOPE separator (19pi) / Cu, 1.5T gasket, button cell (2032)

[0151] Amount of electrolyte solution injected: 15 μl

[0152] Test conditions: aging for 1 hour at room temperature, the charge / discharge current density (0.2 mA cm -2 ), cycle charge / discharge current density (0.6667mAcm -2 )

[0153] Coulombic efficiency (%): (cycle discharge capacity / cycle charge capacity)×100.

[0154] Fig.13 The results of the evaluation of the life of each battery are shown. The 3M FSA shorted at the 57th cycle, and its Coulombic efficiency was less than 100% throughout the entire cycle. However, the 0.05% AgNO 3 , 0.1% AgNO 3 , 0.05% AuBr 3 and 0.05% Pt(NO 3 ) 4 They exhibited 61 cycles, 74 cycles, 73 cycles, and 72 cycles, respectively, resulting in an extended lifespan, and their initial cycle Coulombic efficiency was 100% or more.

[0155] When AgNO is introduced 3 、AuBr 3 or Pt(NO 3 ) 4 When the alloy is formed on the anode current collector made of copper, the coulombic efficiency in the initial cycle is 100% or more. In addition, since the alloy reduces the overvoltage during lithium electrodeposition, the introduction of AgNO 3 、AuBr 3 or Pt(NO 3 )4 The electrolyte solution exhibited an extended lifespan.

[0156] Test Example 5: Evaluation of battery life without anode

[0157] A battery was manufactured as follows, and the electrolyte solution of each of Preparation Examples 1 to 4 and Comparative Preparation Example 2 was injected into the battery.

[0158] Battery type: Cu / W-SCOPE diaphragm (16pi) / NCM811 cathode, 1.5T gasket, button cell (2032)

[0159] Amount of electrolyte solution injected: 15 μl

[0160] Test conditions: aging at room temperature for 5 hours, charge / discharge twice during formation (0.1C, 4.25V / -0.1C, 3.0V), cycle (1 / 3C, 4.25V / CV: 4.25V, 0.05C / -1 / 3C, 3.0V / standstill 30min), 1C = 188.24mAhg -1

[0161] Coulombic efficiency (%): (cycle discharge capacity / cycle charge capacity)×100.

[0162] Fig.14A The charge / discharge of each battery formation process is shown. Fig. 14B The cycle discharge capacity of each battery is shown. Fig. 14C The coulombic efficiency of each cell is shown. The results are summarized in Table 4 below.

[0163] Refer to Table 4 and Fig. 14C , the Coulombic efficiency of 3M FSA continuously decreases during the cycling process. In particular, after the 11th cycle, the Coulombic efficiency decreases rapidly, which affects the reduction of discharge capacity and thus shortens the life. Compared with 3M FSA, the AgNO 3 、AuBr 3 or Pt(NO 3 ) 4 The electrolyte solution shows a lower initial reversible efficiency due to the formation of alloys, but its cyclic Coulombic efficiency remains constant and the lifetime is extended.

[0164] [Table 4]

[0165]

[0166] Test Example 6: Evaluation of the electrode interface of anode-free battery

[0167] A battery was manufactured as follows, and the electrolyte solution of each of Preparation Examples 1 to 4 and Comparative Preparation Example 2 was injected into the battery.

[0168] Battery type: Cu / W-SCOPE diaphragm (16pi) / NCM811 cathode, 1.5T gasket, button cell (2032)

[0169] Amount of electrolyte solution injected: 15 μl

[0170] Test conditions: aging at room temperature for 5 hours, charging / discharging once during the formation process (0.1C, 4.25V / -0.1C, 3.0V).

[0171] FIG. 15A to FIG. 15E The results of X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery are shown. Fig.15A , with AgNO 3 AuBr 3 Compared with the electrolyte solution of 3M FSA and 0.05% Pt(NO 3 ) 4 shows a high intensity CC peak. Since CC-based organic films have high electronic conductivity, additional side reactions caused by the efficient movement of electrons have attracted great attention. Fig. 15B It can be seen that 3M FSA forms a high-strength LiF and SF-based solid electrolyte interphase layer. However, the high-strength N and sulfur-based films show that the films are formed due to the side reaction of LiFSI lithium salt during lithium electrodeposition rather than due to FSA decomposition.

[0172] On the other hand, reference FIG. 15D to FIG. 15E , containing AgNO 3 、AuBr 3 or Pt(NO 3 ) 4 The electrolyte solution effectively inhibits the decomposition of LiFSI lithium salt, thereby forming a low-strength N and sulfur-based film. However, due to the decomposition of FSA during lithium electrodeposition, a LiF-based film is formed. Therefore, the film made of inorganic materials (such as LiF) makes it difficult for electrons to move due to low electronic conductivity, thereby effectively inhibiting the side reaction between the electrodeposited lithium and the electrolyte solution.

[0173] FIG. 16A to FIG. 16C The results of X-ray photoelectron spectroscopy (XPS) of the surface of the anode current collector of each battery are shown. FIG. 16A to FIG. 16C , Ag, Au or Pt base peaks appear on the surface of the anode collector. 3 、AuBr 3 or Pt(NO 3 )4 The electrolyte solution is able to form an alloy on the surface of the anode collector due to its high work function during the standing process, thereby reducing the lithium electrodeposition overvoltage, improving the reversibility of lithium ions, and allowing the alloy to remain in film form even after the formation process.

[0174] FIG. 17A to FIG. 17E The results of X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery are shown. Fig.15A , due to the decomposition of LiFSI lithium salt and FSA, 3M FSA forms a high-strength N and sulfur-based solid electrolyte interface layer. Fig. 17C , since 3M FSA cannot suppress the side reaction between lithium salt and solvent, a thick byproduct solid electrolyte interface layer is formed, resulting in a low-intensity MO peak. The thick solid electrolyte interface layer hinders the movement of lithium ions, resulting in overvoltage and deteriorating battery performance. On the other hand, as Fig.17D and Fig.17E As shown, after the introduction of AgNO 3 、AuBr 3 or Pt(NO 3 ) 4 Afterwards, even if used in small amounts, the decomposition of LiFSI lithium salt and FSA can be suppressed, thereby forming a low-strength N and sulfur-based solid electrolyte interface layer, and a thin solid electrolyte interface layer is formed through a high-intensity MO peak.

[0175] 18A to 18C The results of X-ray photoelectron spectroscopy (XPS) of the surface of the cathode active material layer of each battery are shown. 18A to 18C , no Ag, Au or Pt base peaks appeared on the surface of the cathode active material layer. Therefore, it was found that AgNO 3 、AuBr 3 or Pt(NO 3 ) 4 The alloy is formed on the anode current collector made of copper during the standing process without affecting the cathode active material layer.

[0176] As is apparent from the above description, according to the exemplary embodiment of the present invention, a lithium secondary battery capable of suppressing a side reaction between a lithium metal simple substance and an electrolyte solution can be obtained.

[0177] According to the exemplary embodiment of the present invention, a lithium secondary battery having excellent lithium ion reversibility may be obtained.

[0178] According to the exemplary embodiment of the present invention, a lithium secondary battery can be obtained in which the specific capacity of the cathode is high and exhibits good reversibility of lithium ions, no side reaction, and an extended life even when the amount of injected electrolyte solution is small.

[0179] The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the description of the present invention.

[0180] The above description of specific exemplary embodiments of the present invention is shown for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present invention to the precise form disclosed, and it is obvious that many modifications and variations can be made in accordance with the above teachings. The exemplary embodiments are selected and described in order to explain certain principles of the present invention and their practical application, so that those skilled in the art can realize and utilize various exemplary embodiments of the present invention and various alternative forms and modified forms thereof. The scope of the present invention is intended to be limited by the appended claims and their equivalent forms.

Claims

1. An electrolyte solution for a lithium secondary battery, the electrolyte solution comprising: Solvents; lithium salts; and an additive, the additive comprising a metal element, in, The metal element includes at least one selected from silver, gold, platinum and combinations thereof.

2. The electrolyte solution for a lithium secondary battery according to claim 1, wherein The solvent includes dimethylsulfamoyl fluoride.

3. The electrolyte solution for a lithium secondary battery according to claim 1, wherein The lithium salt includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4 and at least one of their combinations.

4. The electrolyte solution for a lithium secondary battery according to claim 1, wherein The additive includes at least one selected from nitrates of metal elements, halogen salts of metal elements and combinations thereof.

5. The electrolyte solution for a lithium secondary battery according to claim 1, wherein The additive includes at least one selected from AgNO3, AuBr3, Pt(NO3)4 and a combination thereof.

6. The electrolyte solution for a lithium secondary battery according to claim 1, wherein The electrolyte solution includes 0.05 wt % to 0.1 wt % of the additive.

7. A lithium secondary battery comprising: Anode current collector; a separator disposed on the anode current collector; a cathode active material layer disposed on the separator; a cathode current collector disposed on the cathode active material layer; as well as an electrolyte solution, the electrolyte solution being impregnated into at least one of the anode current collector, the separator, the cathode active material layer, and the cathode current collector, The electrolyte solution comprises a solvent, a lithium salt and an additive, wherein the additive comprises a metal element, and the work function of the metal element is higher than the work function of the anode current collector.

8. The lithium secondary battery according to claim 7, wherein: The anode current collector comprises: a substrate comprising copper; and A covering layer is applied on the surface of the substrate and contains an alloy of copper and a metal element.

9. The lithium secondary battery according to claim 7, wherein: The solvent includes dimethylsulfamoyl fluoride.

10. The lithium secondary battery according to claim 7, wherein: The lithium salt includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4 and at least one of their combinations.

11. The lithium secondary battery according to claim 7, wherein: The work function of the metal element is greater than 4.7 eV and less than or equal to 6 eV.

12. The lithium secondary battery according to claim 7, wherein: The metal element includes at least one selected from silver, gold, platinum and combinations thereof.

13. The lithium secondary battery according to claim 7, wherein: The anode current collector includes a covering layer on a surface thereof, the covering layer comprising at least one selected from the group consisting of an alloy of copper and silver, an alloy of copper and gold, an alloy of copper and platinum, and combinations thereof.

14. The lithium secondary battery according to claim 7, wherein: The additive includes at least one selected from nitrates of metal elements, halogen salts of metal elements and combinations thereof.

15. The lithium secondary battery according to claim 7, wherein: The additive includes at least one selected from AgNO3, AuBr3, Pt(NO3)4 and a combination thereof.

16. The lithium secondary battery according to claim 7, wherein: The electrolyte solution includes 0.05 wt % to 0.1 wt % of the additive.

17. The lithium secondary battery according to claim 7, further comprising a solid electrolyte interface layer, the solid electrolyte interface layer being located at least one of a position between the cathode active material layer and the separator and a position between the anode current collector and the separator, wherein: The solid electrolyte interface layer does not contain organic materials.

18. The lithium secondary battery according to claim 7, further comprising a solid electrolyte interface layer, the solid electrolyte interface layer being located at least one of a position between the cathode active material layer and the separator and a position between the anode current collector and the separator, wherein: The solid electrolyte interface layer comprises at least one selected from LiF, Li2CO3, LiO and a combination thereof.

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