Non-aqueous electrolyte for lithium battery and lithium battery containing the same

Abstract

The present invention relates to an electrolyte for a lithium metal battery. When the electrolyte of the present invention is applied to a battery containing lithium metal as a negative electrode active material, it has few side effects, excellent stability, and can improve various performances of the battery.

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte for a lithium metal battery that is applied to a lithium metal battery containing lithium metal as a negative electrode active material and can improve various battery performances, and a lithium metal battery containing the same.

Background Art

[0002] With the rapid development of the electronics, communication, and computer industries, the application fields of energy storage technologies have expanded from camcorders, mobile phones, notebook computers, personal computers, and even to electric vehicles. Accordingly, the development of high-performance secondary batteries that are lightweight, long-lasting, and highly reliable has been carried out. Among the secondary batteries currently in use, the lithium secondary battery developed in the early 1990s has a higher operating voltage and much higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and lead-sulfate batteries using an aqueous electrolyte, and thus has been adopted as a power source for many portable devices.

[0003] As the negative electrode active material of such a lithium secondary battery, lithium metal, carbon-based materials, silicon, etc. are used. Among them, lithium metal has the advantage of obtaining the highest energy density, and continuous research has been carried out. A lithium electrode using lithium metal as an active material is usually manufactured by using a flat copper or nickel foil as a current collector and attaching a lithium foil thereon. Alternatively, the lithium foil itself is used as a lithium electrode without a separate current collector, or a battery is assembled using only the current collector without a lithium foil. After that, methods such as a method (Anodeless method) of forming a lithium metal layer by charging and discharging the battery and using it as a negative electrode are known. However, a lithium secondary battery containing a lithium metal electrode has a problem that a stable interface between the electrolyte and the lithium metal is not formed due to the high reactivity of the lithium metal and the surface non-uniformity phenomenon generated during the process of electrodeposition and peeling of the lithium metal on the electrode during battery charge and discharge, and a continuous decomposition reaction of the electrolyte occurs. The products of the decomposition reaction of such an electrolytic solution act as a resistance layer that hinders the desorption and electrodeposition of lithium, not only rapidly increasing the battery resistance but also depleting the electrolytic solution and soluble lithium in the battery, causing degradation of the battery life.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an attempt to solve the above problems, an object of the present invention is to provide a non-aqueous electrolytic solution that is excellent in stability with respect to lithium metal. Another object of the present invention is to provide a non-aqueous electrolytic solution that is excellent in stability also for a battery containing a negative electrode active material other than lithium metal. Another object of the present invention is to provide a lithium battery containing the non-aqueous electrolytic solution. The objects of the present invention are not limited to those mentioned above, and other objects and advantages of the present invention not mentioned can be understood from the following description and will be more clearly understood from the examples of the present invention. Also, it should be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof shown in the claims.

Means for Solving the Problems

[0005] To solve the above-described technical problems, the present invention provides a compound represented by the following Chemical Formula 1.

Chem.

[0006] [Chemical Formula] In one embodiment of the present invention, the lithium salt contained in the non-aqueous electrolyte may be lithium bis(fluorosulfonyl)imide (LiFSI). In one embodiment of the present invention, the concentration of the lithium salt contained in the non-aqueous electrolyte may be from 0.5 M to 4.0 M (mol / L). In one embodiment of the present invention, the solvent of Chemical Formula 1 may be contained in an amount of 50% by volume to 100% by volume based on 100% by volume of the total non-aqueous solvents. In order to solve the technical problems of the present invention, the present invention provides a lithium secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator interposed between the negative electrode and the positive electrode, and the non-aqueous electrolyte for a lithium battery.

[0007] In one embodiment of the present invention, the negative electrode active material may be lithium metal. In one embodiment of the present invention, the negative electrode active material may be a silicon-based negative electrode active material. In one embodiment of the present invention, the positive electrode active material may be one or more selected from the group consisting of composite oxides of lithium with metals such as cobalt, manganese, nickel, aluminum, iron, or combinations thereof. The means for solving the above problems does not enumerate all the features of the present invention. The various features, advantages, and results of the present invention should be understood in more detail with reference to the following specific examples.

Effects of the Invention

[0008] The effects of the non-aqueous electrolyte of the present invention are as follows. The non-aqueous electrolyte of the present invention is excellent in stability against lithium metal and can suppress the decomposition reaction of the electrolyte. Therefore, when applied to a lithium metal battery, it can improve the life characteristics and high-rate charging performance of the battery. In addition, the non-aqueous electrolyte of the present invention is excellent in stability not only against lithium metal but also against batteries containing other negative electrode active materials, and can improve the life characteristics and high-rate performance of the battery. The specific effects of the present invention, together with the above-described effects, will be described together with reference to the content of the following embodiments for carrying out the invention.

Brief Description of the Drawings

[0009]

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[0010] Hereinafter, the principles of the preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the drawings shown below and the description hereinafter relate to the preferred implementation methods among various methods for effectively explaining the features of the present invention, and the present invention is not limited only to the following drawings and description. On the other hand, terms such as first or second can be used to describe multiple components, but such terms should be interpreted only for the purpose of distinguishing one component from another. For example, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "including" or "having" are used to specify the presence of the described features, numbers, steps, operations, components, parts, or combinations thereof, and should not be construed as precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Unless defined otherwise, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the relevant technical field. Terms defined in commonly used dictionaries shall be interpreted to have a meaning consistent with the meaning in the context of the relevant art, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0011] Hereinafter, the present invention will be described in more detail. First, in the present invention, the "lithium metal battery" means a battery including lithium metal as a negative electrode. The present invention relates to an electrolyte for a lithium metal battery including a solvent represented by the following Chemical Formula 1.

Chemical Formula

[0012] The inventors of the present invention have conducted extensive research on solvents for non-aqueous electrolytes suitable for use in lithium metal batteries including lithium metal as a negative electrode active material. As a result, when applying the solvent of Chemical Formula 1, which has a modified backbone structure of the conventionally widely used DME (1,2-dimethoxyethane) solvent, to a lithium metal battery, it exhibits significantly improved stability compared to conventional electrolytes. As a result, the inventors have confirmed that various electrochemical performances including the lifespan of the lithium metal battery are greatly improved (see Figure 1), and thus completed the present invention. In one embodiment of the present invention, the solvent represented by the above [Chemical Formula 1] may be 1,1,1-trifluoro-2,3-dimethoxypropane (TFDMP) represented by the following Chemical Formula 1a.

Chem.

[0013] The lithium metal used in a lithium metal battery has a low reduction voltage (-3.4V vs. SHE), a high theoretical capacity (3860 mAh g -1 ), and a low density (0.544 g cm -3 ). Therefore, it is a very effective negative electrode material for improving the energy density of a lithium-based battery. In particular, when a lithium metal battery is used with a high-voltage positive electrode material, there is an advantage that the energy density of the battery can be dramatically improved. However, lithium metal batteries have a problem that the battery life is reduced due to the formation of lithium dendrites generated during the charging process and the consumption of the electrolyte due to the side reaction between the electrolyte and the lithium metal.

[0014] Therefore, in order to solve the above problems and achieve a high energy density, an electrolyte that is electrochemically stable, can suppress side reactions with lithium metal, and thus has excellent oxidation stability for use with a high-voltage positive electrode material is required. The compound of Chemical Formula 1 used as the solvent of the non-aqueous electrolyte of the present invention contains a halogen-containing group (-CX3) and an ether-containing group in one molecule. In a specific embodiment, the compound represented by Chemical Formula 1a contains a fluorine-containing group (-CF3) and an ether-containing group in one molecule.

[0015] Generally, if a fluorine-containing group is contained in a molecule, due to the high electronegativity of fluorine, the HOMO (highest occupied molecular orbital) energy level of the molecule becomes low, and the lowered HOMO energy level can improve the oxidation stability of the molecule. In particular, among the examples of the present invention, the compound represented by Chemical Formula 1a, which is one of the examples, has only one fluorine-containing group, thereby minimizing side effects (such as a decrease in solvation degree and a decrease in salt solubility) in the case of having a large number of fluorine-containing groups. As a result, by including a fluorine-containing group (-CF3) in the molecule, it is considered that the oxidation stability of the electrolyte can be improved when used as a solvent for a non-aqueous electrolyte, which was confirmed by the LSV evaluation experiment described later.

[0016] If the oxidation stability of the electrolyte used in a lithium metal battery is ensured, the energy density can be dramatically improved when the lithium metal battery is used with a high-voltage cathode material, for example, a high-nickel cathode material or a high-manganese (High-manganese or Over-lithiated Oxide) cathode material. In addition, from the perspective of molecular design, the solvent used in the electrolyte of the present invention does not directly bond the carbon (-CX3) where the halogen-containing group is located to an oxygen atom, thereby providing a binding site for lithium ions, which has the effect of improving the solvation power of lithium ions. Conventionally, there has been a phenomenon that the solvation degree decreases while directly bonding the carbon where the fluorine-containing group is located to an oxygen atom in the solvent containing a fluorine-containing group used in a lithium metal battery. However, the solvent used in the electrolyte of the present invention has the above-described molecular structure, so it can improve the solvation degree of lithium ions, and thereby it is considered that excellent electrochemical performance can be achieved.

[0017] In one embodiment of the present invention, the electrolyte for a lithium metal battery contains lithium bis(fluorosulfonyl)imide (LiFSI) as a lithium salt. Examples of lithium salts that can be included in addition to LiFSI are LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiC4BO8, LiCF3CO2, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC4F9SO3, LiC(CF3SO2)3, (CF3SO2)2NLi, lithium chloroborate, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, etc. are possible.

[0018] At this time, the total concentration of LiFSI and other lithium salts in the electrolyte is 0.5 M (mol / L) to 4.0 M, preferably 1.0 M to 3.0 M. Such a high salt concentration can suppress the side reaction between the lithium metal and the electrolyte, and can ensure the effect of preventing the corrosion of the positive electrode current collector and the elution of the transition metal of the positive electrode active material. If the concentration of the lithium salt is too high, there may be problems such as performance deterioration due to low ionic conductivity and a decrease in the impregnability of the electrolyte due to high viscosity, so it can be appropriately adjusted within the above range.

[0019] On the other hand, the solvent of the chemical formula 1 may be contained in an amount of 50% to 100% by volume based on the total 100% by volume of the non-aqueous solvent, and the remaining volume may contain a carbonate-based solvent, an ester-based solvent, etc. to be described later. On the other hand, the electrolyte of the present invention may contain a cyclic fluorinated carbonate-based solvent together with the solvent of the chemical formula 1. The cyclic fluorinated carbonate-based solvent is not particularly limited as long as it is a compound in which at least two hydrogens in the cyclic carbonate-based solvent usually used as the solvent of the electrolyte are replaced by fluorine. Specifically, the cyclic fluorinated carbonate-based solvent may be one or more selected from the group consisting of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethyl ethylene carbonate, and may preferably be fluoroethylene carbonate.

[0020] On the other hand, in addition to the cyclic fluorinated carbonate-based solvent, the electrolyte of the present invention may contain one or more solvents (hereinafter referred to as chain solvents) selected from the group consisting of chain carbonates, chain esters, and chain ether solvents as non-aqueous solvents. The chain-like solvent can be used without limitation as the chain-like solvent usually used in the electrolyte for a lithium secondary battery.

[0021] Specifically, the chain-like carbonate can be one or more selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl pyropropyl carbonate. The chain-like ester can be one or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. The chain-like ether can be one or more selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl pyropropyl ether. Preferably, the one or more solvents selected from the group consisting of the chain-like carbonate, chain-like ester, and chain-like ether solvents can be one or more selected from the group consisting of dimethyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, dimethyl ether, and diethyl ether.

[0022] On the other hand, the electrolyte of the present invention may further contain an additive for forming an SEI film in order to improve various battery performances as needed. Examples of the additive for forming an SEI film that can be used in the present invention include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorobis(oxalato)phosphate (WCA), lithium bis(pentafluoroethylsulfonyl)amide (LiBETI), lithium malonate oxalate borate (LiMOB), LiPF2C4O8, LiSO3CF3, LiPF4(C2O4), LiP(C2O4)3, LiC(SO2CF3)3, LiBF3(CF3CF2), LiPF3(CF3CF2)3, Li2B 12 F12 , 1,3 - propane sultone, 1,3 - propene sultone, biphenyl, cyclohexylbenzene, 4 - fluorotoluene, succinic anhydride, ethylene sulfate anhydride, tris(trimethylsilyl) borate, cyclic sulfuric acid, saturated sultone, unsaturated sultone, acyclic sulfone, etc. can be used alone or in combination of two or more thereof, and the present invention is not limited thereto. The additive for forming the SEI film can be contained in an amount of 0.5 wt% to 10 wt% based on the total weight of the electrolyte in order to form an excellent film.

[0023] Lithium metal battery According to one embodiment of the present invention, a lithium metal battery including the above-described asymmetric electrolyte is provided. Specifically, the lithium metal battery includes a positive electrode, a negative electrode containing lithium metal as an active material, a separator, and includes the electrolyte of the present invention as an electrolyte.

[0024] (1) Positive electrode The positive electrode includes a positive electrode active material layer coated on a positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a binder, and optionally a conductive material. The positive electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the corresponding battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. At this time, the positive electrode current collector can use various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc. having fine irregularities formed on the surface so as to increase the adhesion to the positive electrode active material.

[0025] The positive electrode active material is a compound capable of reversible Lithiation and De-Lithiation of lithium, and specifically may include a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo; p2, q2, r3, and s2 are the atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc. may be mentioned, and any one or two or more of these compounds may be included.

[0026] Among them, since the capacity characteristics and stability of the battery can be improved, the lithium composite metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), etc.

[0027] On the other hand, as another example, the positive electrode active material is sulfur atoms (Elemental sulfur, S8); disulfide compounds such as Li2Sn(n = 1), 2,5 - dimercapto - 1,3,4 - thiadiazole, 1,3,5 - trithiocyanuric acid, organic sulfur compounds, or one or more selected from the group consisting of sulfur - containing compounds such as carbon - sulfur polymers ((C2Sx)n: x = 2.5 to 50, n ≥ 2). The positive electrode active material may be contained at 80% by weight to 99% by weight based on the total weight of the solid content in the positive electrode slurry. At this time, if the content of the positive electrode active material is 80% by weight or less, the energy density may be low and the capacity may be reduced.

[0028] The binder is used for binding the electrode active material and the conductive material and for binding to the current collector. Non-limiting examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA), polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluorine rubber, various copolymers thereof, and the like.

[0029] The conductive material is used to further improve the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the corresponding battery. For example, graphite-based materials such as natural graphite and artificial graphite; carbon blacks such as Super-P, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, etc. can be used.

[0030] (2) Negative electrode The negative electrode of the present invention is a lithium metal negative electrode having lithium metal as the metal active material. The lithium metal negative electrode used when assembling a lithium metal battery can consist of only a current collector, or can be in a form in which the current collector is coated with lithium metal, or can consist of only lithium metal.

[0031] The negative electrode current collector is not particularly limited as long as it has conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Also, its form can be various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc. with or without fine unevenness formed on the surface. As an example, a copper foil can be used as the negative electrode current collector, but it is not limited to this.

[0032] The thickness of the current collector is not particularly limited, but a thickness of 5 to 100 μm is preferred, and a thickness of 5 to 50 μm is more preferred. If the thickness of the current collector is less than 5 μm, it may be difficult to handle in the process, and if it exceeds 100 μm, it may affect the performance of the battery, such as unnecessarily increasing the thickness and weight of the battery and decreasing the energy density. Therefore, the above range is preferred.

[0033] When assembling the battery, if an electrode consisting only of the current collector is used as the negative electrode, lithium ions that have moved from the positive electrode during the initial charge and discharge will be irreversibly plated on the negative electrode current collector to form a lithium metal layer after the battery is assembled. Next, the lithium metal layer can act as the negative electrode active material layer. At this time, if an electrode consisting only of the current collector is used as the negative electrode, the current collector may contain metal and metal oxide particles to uniformly induce plating.

[0034] Alternatively, a negative electrode containing lithium metal as the active material may be used from the time of assembling the battery. At this time, the method of coating the lithium metal on the negative electrode current collector is not particularly limited. As an example, a method of laminating a thin film of lithium metal on the current collector and then rolling it, a method of electrolytically or electrolessly plating lithium metal on the current collector, etc. can be used. At this time, the thickness of the lithium metal layer of the negative electrode is not particularly limited, but it can be 10 μm or more or 20 μm or more, while being 50 μm or less or 40 μm or less. In the case of a lithium metal negative electrode consisting only of lithium metal, its thickness is not particularly limited, but it can be 10 μm or more or 20 μm or more, while being 50 μm or less or 40 μm or less.

[0035] On the other hand, according to another embodiment of the present invention, the above-described non-aqueous electrolyte can be applied to other negative electrodes in addition to lithium metal.

[0036] Specifically, the solvent of the present invention can also be applied to an electrode in which a silicon-based active material, for example, Si or SiOx, is used as the negative electrode active material. In this case, the negative electrode is manufactured by applying a mixture of a negative electrode active material, a conductive agent, and a binder onto a negative electrode current collector, followed by drying and pressing.

[0037] (3) Separator The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions, and any separator that is normally used in a lithium battery can be used. That is, a separator having a low resistance to the ion migration of the electrolyte and excellent impregnation ability of the electrolyte can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of a non-woven fabric or a woven fabric. For example, a polyolefin-based polymer separator such as polyethylene or polypropylene, or a separator including a coating layer containing a ceramic component or a polymer substance for heat resistance or mechanical strength may be used, and such a separator may be used in a single-layer or multi-layer structure. In one embodiment, as the separator, a separator manufactured by coating a ceramic coating material containing ceramic particles and an ionic binder polymer on both surfaces of a polyolefin-based polymer substrate can be used. According to one embodiment of the present invention, there is provided a lithium metal battery including the above-described positive electrode, negative electrode, separator, and electrolyte of the present invention. At this time, the shape of the lithium metal is not particularly limited, and it can be in various shapes such as a cylindrical shape, a pouch shape, or a coin shape.

[0038] Hereinafter, preferred embodiments will be presented to facilitate the understanding of the present invention. However, the following embodiments are merely illustrative of the invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the invention and the scope of the technical idea. It is natural that such variations and modifications belong to the appended claims. Hereinafter, embodiments and comparative examples of the present invention will be described. Such following embodiments are merely one embodiment of the present invention, and the present invention is not limited to the following embodiments.

[0039] [Embodiment] Production Example 1 (Production of TFDMP) 600 mL of dry THF and 1 mol (24 g) of NaH were charged into a 1 L round-bottom flask and stirred at 0 °C for 20 minutes under an argon atmosphere. Next, 0.4 mol (54 g) of 1,1,1-trifluoro-2,3-propanediol was gradually added using a syringe pump. After adding 1,1,1-trifluoro-2,3-propanediol, the mixture was further stirred at 0 °C for 1 hour to produce a mixture. Then, 1 mol (62.4 mL) of iodomethane was added dropwise to the mixture under the condition of 0 °C. The mixture was stirred at room temperature for 2 hours and refluxed overnight while gradually heating. Next, the liquid phase portion of the mixture was fractionally distilled using a 60 cm fractionating column, and this distillation process was performed 3 times to obtain the final product (TFDMP).

[0040] (1) Preparation of non-aqueous electrolyte Electrolytes of the examples and comparative examples were prepared with the compositions shown in Table 1 below. In the following table, DMF means 1,2-dimethoxyethane, DMP means 1,2-dimethoxypropane, EC means ethylene carbonate, DEC means diethyl carbonate, and FEC means fluoroethyl carbonate. The concentration (M) of the lithium salt is the number of moles (mol) of the lithium salt per 1 L of the total solvent contained in the electrolyte. All electrolytes were prepared in a glove box filled with an inert gas.

[0041]

Table 1

[0042] (2) Fabrication of the positive electrode Using NCM 811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) as the positive electrode active material, Super-P as the conductive material, polyvinylidene fluoride (PVdF) as the binder, and N-methylpyrrolidone as the solvent, a positive electrode active material slurry with a weight ratio of active material:conductive material:binder of 8:1:1 was prepared. Next, the positive electrode active material slurry was coated on one side of an aluminum foil, rolled and dried to produce a positive electrode with a loading of 5.0 mg / cm 2 .

[0043] (3) Fabrication of the negative electrode Lithium metal electrode A lithium metal foil with a thickness of 20 μm (manufactured by China Energy Lithium) was used as the negative electrode. Silicon electrode A negative electrode was fabricated using Micro Si as the negative electrode active material. Specifically, using Micro Si as the negative electrode active material, carboxymethyl cellulose (CMC) as the binder, Super-P as the conductive material, and distilled water, a negative electrode active material slurry with a weight ratio of active material:conductive material:binder of 92:4:4 was prepared. Next, the negative electrode active material slurry was coated on one side of a copper foil, rolled and dried to produce a negative electrode with a loading of 5.0 mg / cm 2 .

[0044] (4) Fabrication of the full-cell A separator and the lithium metal foil of (3) were laminated on the negative electrode of (2), and a Swagelok type cell or a 2032 type coin cell laminated in the order of negative electrode / separator / positive electrode was fabricated in a glove box. As the separator, a product of Celgard 2400 made of polyethylene (manufactured by Celgard) was used, the N / P Ratio was set to 2.5, and 40 μl of the electrolytes of Example 1, Comparative Example 1, and 2 were injected to fabricate the full-cell. A separator and the Micro Si electrode of (3) were laminated on the negative electrode of (2), and a swage lock type battery or a 2032 type coin cell laminated in the order of negative electrode / separator / positive electrode was fabricated in a glove box. As the separator, a product of Celgard 2400 made of polyethylene (manufactured by Celgard) was used, the N / P Ratio was set to 2.5, and 40 μl of the electrolytes of Example 2 and Comparative Example 3 were injected to fabricate a full cell.

[0045] Evaluation Example 1. Evaluation of oxidation stability An oxidation stability evaluation experiment of the electrolytes of Example 1 and Comparative Examples 1 and 2 was conducted. The oxidation stability was evaluated by performing Linear Sweep Voltammetry (LSV) analysis. Specifically, a Li / Al half cell was fabricated, and after injecting the electrolytes of Example 1 and Comparative Examples 1 and 2, LSV analysis was performed at an open circuit voltage (OCV) of 5.0 V (vs. Li / Li + ) up to a scan rate of 0.5 mVs -1 . The evaluation results are shown in Figure 2.

[0046] Referring to Figure 2, the electrolyte of Example 1 (TFDMP) does not show a large oxidation current up to about 4.8 V (vs. Li / Li + ), while the electrolyte of Comparative Example 1 (DME) shows an oxidation current rapidly at 4.0 V (vs. Li / Li + ), and the electrolyte of Comparative Example 2 (DMP) shows an oxidation current rapidly near 4.4 V (vs. Li / Li + ). From this result, it can be confirmed that the electrolyte containing the solvent of the present invention is excellent in oxidation stability.

[0047] Evaluation Example 2. Evaluation of Coulombic efficiency The coulombic efficiency was evaluated to confirm the reversibility when the electrolytes of Example 1 and Comparative Examples 1 and 2 were used in a lithium metal battery. Specifically, a Li / Cu half cell was fabricated, and after injecting the electrolytes of Example 1 and Comparative Examples 1 and 2, 1 mA cm -2The Coulombic efficiency was evaluated while applying a current of Referring to FIG. 3, it can be confirmed that the half-cells containing the electrolytes of Comparative Examples 1 and 2 have extremely drastic fluctuations in Coulombic efficiency in the entire cycle region, which is judged to be due to the formation of an unstable SEI and irreversible lithium ion plating. On the other hand, it can be confirmed that the half-cell containing the electrolyte of Example 1 shows a relatively stable Coulombic efficiency in the entire cycle region.

[0048] Evaluation Example 3. Evaluation of aluminum corrosion In order to evaluate the oxidation stability of the electrolytes of Example 1 and Comparative Examples 1 and 2, aluminum corrosion evaluation was performed. Although an aluminum foil is used as a current collector of the positive electrode, if corrosion occurs on the surface of the aluminum due to the reaction between the aluminum and the electrolyte under the participating conditions, it may adversely affect the performance of the positive electrode due to an increase in surface resistance or the like. Specifically, after fabricating a Li / Al half-cell and charging the electrolytes of Example 1 and Comparative Examples 1 and 2, 5.0 V (vs. Li / Li + ) was applied for 24 hours (Constant voltage experiment). Next, after disassembling the half-cell, FE-SEM (field emission scanning electron microscopy; Tescan Mira3 LM FE) was used to observe the surface of the aluminum to confirm the corrosion of the aluminum (FIG. 4).

[0049] FIG. 4 is a diagram showing the surface of the aluminum of the half-cells using the electrolytes of Example 1 and Comparative Examples 1 and 2. It can be confirmed that the half-cells using the electrolytes of Comparative Examples 1 and 2 show very severe corrosion (for example, cracks, flakes) on the aluminum surface, while the aluminum of the half-cell using the electrolyte of Example 1 shows a very smooth surface without cracks.

[0050] Evaluation Example 4. Performance evaluation of full battery Full cells containing the electrolytes of Example 1 and Comparative Examples 1 and 2 were fabricated, and after applying a current of 1.0 C-rate (1.6 mA cm -2 ) to perform charge and discharge, the life performance of the full cells was evaluated, and the results are shown in Fig. 5. The cell containing the electrolyte of Example 1 showed 100% retention up to 450 cycles and excellent stability. On the contrary, it was confirmed that the cell containing the electrolyte of Comparative Example 1 had deterioration of life performance within 60 cycles, and it was confirmed that the cell containing the electrolyte of Comparative Example 2 had deterioration of life performance within 157 cycles. On the other hand, in order to observe the high-rate life performance of the cell containing the electrolyte of the present invention, while applying a current of 3.0 C-rate (4.8 mA cm -2 ) to the full cell (NP ratio = 2.5) containing the electrolyte of Example 1, the life performance of the full cell was evaluated, and the results are shown in Fig. 6. The cell containing the electrolyte of the present invention showed 93% retention at 550 cycles even under high current charge and discharge conditions such as 3.0 C-rate (4.8 mA cm -2 ), and it was confirmed that it showed excellent performance.

[0051] Also, while applying a current of 0.5 C-rate (2 mA cm -2 ) and 1.0 C-rate (4.0 mA cm -2 ) to the full cell (NP ratio = 1) containing the electrolyte of Example 1, the life performance of the full cell was evaluated, and the results are shown in Fig. 7. The cell containing the electrolyte of the present invention showed 81% retention at 200 cycles under the current application condition of 0.5 C-rate (2 mA cm -2 ), and also showed 88% retention at 145 cycles under the current application condition of 1.0 C-rate (4.0 mA cm -2 ). Full cells containing the electrolytes of Example 2 and Comparative Example 3 were fabricated, and the initial Coulomb efficiency and high-rate charge performance were observed, and the results are shown in Figs. 8 and 9.

[0052] The battery containing the electrolyte of Example 2 showed an initial Coulombic efficiency of about 85.2%, and it was confirmed that the battery containing Comparative Example 3 with a general electrolyte composition showed an initial Coulombic efficiency of about 83.5% (Figure 8). On the other hand, the battery containing the electrolyte of Example 2 showed a retention of about 75% even at a high rate of 5.0 C-rate and also showed stable Coulombic efficiency throughout the cycles. In contrast, the battery containing Comparative Example 3 with a general electrolyte composition showed a retention of about 67%, and it was confirmed that low Coulombic efficiency was observed in terms of efficiency (Figure 9).

[0053] From such results, it was confirmed that the electrolyte containing the solvent of the present invention can improve the electrochemical performance of a lithium metal battery or a battery containing silicon as a negative electrode active material. It should be understood that all the above-described embodiments are illustrative and not restrictive in all respects. The scope of the present invention is shown by the claims described later rather than the detailed description of the invention, and it should be interpreted that all changes and modified forms derived from the meaning and scope of the claims for patent registration and all equivalent concepts are included in the scope of the present invention.

Claims

1. A compound represented by the following Chemical Formula 1. 【Chemical 1】 In Chemical Formula 1, R １ , R ２ , and R ３ are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, R １ , R ２ , and R ３ is an alkyl group having 1 to 5 carbon atoms, X is F, Cl, Br, or I, n is an integer from 1 to 5, m, o, and p are integers from 0 to 3.

2. A non-aqueous electrolyte for a lithium battery, comprising a solvent represented by the following Chemical Formula 1 and a lithium salt. 【Chemical 2】 In Chemical Formula 1, R １ 、 R ２ 、 and R ３ are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, R １ 、 R ２ 、 and R ３ is an alkyl group having 1 to 5 carbon atoms, X is F, Cl, Br, or I, n is an integer from 1 to 5, m, o, and p are integers from 0 to 3.

3. The non-aqueous electrolyte for a lithium battery according to Claim 2, wherein the Chemical Formula 1 is represented by the following Chemical 1a. 【Chemical Formula 3】

4. The lithium salt is lithium bis(fluorosulfonyl)imide, The non-aqueous electrolyte for a lithium battery according to Claim 2.

5. The non-aqueous electrolyte for a lithium battery according to Claim 4, wherein the concentration of the lithium salt is 0.5 M to 4.0 M (mol / L).

6. The non-aqueous electrolyte for a lithium battery according to Claim 2, wherein the solvent of the Chemical Formula 1 is contained in an amount of 50% by volume to 100% by volume based on the total 100% by volume of the non-aqueous solvent.

7. A positive electrode containing a positive electrode active material, A negative electrode containing a negative electrode active material, A separator interposed between the negative electrode and the positive electrode, A lithium battery, comprising the non-aqueous electrolyte for a lithium metal battery according to Claim 2.

8. The negative electrode active material is lithium metal, The lithium battery according to Claim 7.

9. The lithium battery according to Claim 7, wherein the negative electrode active material contains a silicon-based active material.

10. The lithium battery according to Claim 7, wherein the positive electrode active material is selected from the group consisting of composite oxides of lithium and one or more metals selected from cobalt, manganese, nickel, aluminum, iron, or combinations thereof.

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