Electrolyte composition for lithium metal battery for fast charging and lithium metal battery comprising same

Abstract

The present specification discloses: an electrolyte composition for a lithium metal battery, enabling uniform electrodeposition of lithium metal under fast charging conditions; and a lithium metal battery comprising same.

Description

Electrolyte composition for lithium metal battery for rapid charging and lithium metal battery comprising the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0091552, filed July 11, 2024, and Korean Patent Application No. 10-2025-0093247, filed July 10, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present specification discloses an electrolyte composition for a lithium metal battery for rapid charging and a lithium metal battery comprising the same.

[0004] Battery technology is rapidly advancing due to the electrification of transportation, and next-generation batteries are being developed for this purpose. Notable examples include thin Li foil and high-nickel LiNi. x Co y Mn z Metal batteries (LMB) composed of O2 are being actively studied, especially Li||LiNi x Co y Mn z O2 battery is 300Wh kg -1 It shows promise, such as achieving energy densities above. Through this development, it is expected to have useful potential in terms of space and driving range when applied to electric vehicles (EVs) compared to conventional lithium-ion batteries. Recent studies on liquid electrolytes for lithium metal anodes, including highly concentrated electrolytes, localized highly concentrated electrolytes, regulating solvents, and additives, have reported improvements in the solid-electrolyte interface (SEI) design and energy density and cycle life of LMB.

[0005] When it comes to improving the convenience of electric vehicles, extending driving range and reducing charging times are key factors. The U.S. Department of Energy's guidelines suggest achieving an 80% state of charge (SoC) within 15 minutes is ideal. However, for high-energy-density LMBs, charging times exceed 30 minutes, demonstrating a significant difference in charging times compared to these guidelines.

[0006] Recently, the energy density is 300Wh kg -1 The LMB of this ideal cell type is charged at about 1 to 2 C-rate (charge current density is about 3 to 6 mA cm -2 ) is reported to have a lifespan of approximately 100 cycles, but to apply it to electric vehicles, a higher charging speed of less than 10 minutes and a longer lifespan are required. In particular, there is a problem that lithium deposition is uneven under fast charging conditions, making it difficult to achieve fast charging speed and lifespan characteristics.

[0007] The electrolyte composition for a lithium metal battery according to the present invention aims to solve the problem that a lithium metal negative electrode exhibits morphological non-uniformity due to uneven lithium deposition under fast charging conditions, and that it is difficult to achieve fast charging speed and life characteristics due to this.

[0008] In one embodiment of the present invention, an electrolyte composition for a lithium metal battery is provided, comprising: a first lithium salt represented by the following chemical formula 1; a second lithium salt different from the first lithium salt; and an organic solvent.

[0009] [Chemical Formula 1]

[0010] LiX

[0011] Here, X can be any one of the anions of AsF6, PF6, FSI, TFSI, CLO4, BF, DFOB, or NO3, RF-substituted alkoxide (ORF), borate anion, or aluminate anion.

[0012] In an exemplary embodiment, the anion of the first lithium salt may have a lower Li-anion binding energy than the anion of the second lithium salt.

[0013] In an exemplary embodiment, the borate anion may include one or more of tetraphenylborate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis(pentafluorophenyl)borate, and hydridotris(pentafluorophenyl)borate.

[0014] In an exemplary embodiment, the RF-substituted alkoxide (ORF) may comprise OC(CF3)3.

[0015] In an exemplary embodiment, the aluminate anion may include one or more of tetrakis(perfluoro-tert-butoxy)aluminate and tetrakis(pentafluorophenoxy)aluminate.

[0016] In an exemplary embodiment, the first lithium salt may comprise LiAsF6, LiPF6, or lithium tetraphenylborate.

[0017] In one embodiment, the anion of the first lithium salt can reduce the partial solubility of an inorganic species on the electrolyte composition.

[0018] In an exemplary embodiment, the second lithium salt may include one or more lithium salts selected from the group consisting of LiTFSI, LiFSI, LiBETI, LiAsF6, LiPF6, LiSbF6, LiDFOB, and LiBOB.

[0019] In an exemplary embodiment, the organic solvent may include one or more of a pyran-based solvent or an ether-based solvent.

[0020] In an exemplary embodiment, the pyran solvent may include dihydropyran (DHP) or tetrahydropyran (THP).

[0021] In addition, the ether solvent may include at least one solvent selected from the group consisting of 1,2-dimethoxyethane (DME), diglyme, tetraglyme, diethylether, dipropylether, furan, tetrahydrofuran, 2-methylfuran, and 1,2-diethoxyethane.

[0022] In one embodiment, the electrolyte composition for a lithium metal battery may further include an additive comprising one or more additives selected from the group consisting of fluoroethylene carbonate (FEC), DFEC, TFEC, TFTFE, TTE, BTFE, OFE, and TFOFE.

[0023] Meanwhile, the additive may act as a nonsolvent in the electrolyte composition. The nonsolvent may exhibit a solubility in the lithium salt that is at least 10 times lower than that of the solvent. In particular, the nonsolvent may exhibit a solubility in the lithium salt that is at least 10 times lower, or 10 to 30 times lower, than that of the solvent, such that the nonsolvent substantially does not dissolve the lithium salt.

[0024] At this time, the electrolyte may fall into the category of localized high-concentration electrolytes (LHCE), and may exhibit a high-concentration region in which lithium salt is dissolved in a solvent at a high concentration as lithium ions during charging and discharging of the battery, and a form in which the non-solvent is distributed around this high-concentration region.

[0025] As a result, even when the electrolyte contains a lithium salt at a higher concentration, for example, a concentration of 3.0 M or more, or 3.0 to 4.0 M, or 3.1 to 3.9 M, or 3.3 to 3.7 M relative to the entire electrolyte, the side reaction between the lithium metal negative electrode and the electrolyte and the resulting decomposition or depletion of the electrolyte can be suppressed, thereby improving the life characteristics of the lithium metal secondary battery.

[0026] In addition, the electrolyte can further improve the life characteristics of the lithium metal secondary battery by including a lithium salt in a higher concentration and controlling the composition ratio of the specific non-solvent, and the output characteristics of the lithium metal secondary battery can be further improved due to the presence of the high-concentration lithium salt.

[0027] In addition, the concentration of the lithium salt may be included at a high concentration of 3.0 M or more, or 3.0 to 4.0 M, or 3.1 to 3.9 M, or 3.3 to 3.7 M, with respect to the entire electrolyte, taking into account the output characteristics of the lithium secondary battery, etc. The concentration of the lithium salt may be defined as a molar concentration considering the total volume of the solvent and nonsolvent.

[0028] In addition, the concentration of the lithium salt may correspond to a concentration of 7.0 to 9.0 M, or 7.2 to 8.8 M, or 7.5 to 8.5 M when converted based on the volume of the solvent contained in the electrolyte. That is, in the electrolyte, the specific non-solvent molecules or ions may be distributed around the region where the lithium salt is dissolved in the solvent at such a high concentration, and the non-solvent may interact with lithium ions derived from the lithium salt, etc., to stabilize the form in which the lithium salt is solvated in the solvent. Accordingly, the high concentration of the lithium salt may further accelerate the solvation / desolvation of lithium ions, thereby further improving the output characteristics of the lithium secondary battery.

[0029] In an exemplary embodiment, the nonsolvent may be 40 to 60 vol%, or 45 to 58 vol%, based on the total content of the solvent and nonsolvent, taking into account the stabilizing effect of the solvated lithium salt in the electrolyte, the appropriate solubility of the entire electrolyte for a high-concentration lithium salt, etc., and may include the remaining solvent. If the content of the nonsolvent is excessively low, the life characteristics of the lithium metal secondary battery may be deteriorated due to an increase in the viscosity of the electrolyte and a decrease in the nonsolvent effect, and conversely, if the content of the nonsolvent is excessively high, the basic electrochemical characteristics such as the capacity and output characteristics of the lithium metal secondary battery may be deteriorated, or the life characteristics may be deteriorated due to a decrease in the concentration of the electrolyte salt.

[0030] In another embodiment of the present invention, a lithium metal battery is provided, comprising: an electrolyte composition for a lithium metal battery as described above; a negative electrode including a lithium metal thin film formed on a negative electrode current collector; a positive electrode including a positive electrode active material layer formed on a positive electrode current collector; and a separator formed between the negative electrode and the positive electrode.

[0031] First, in the lithium metal battery of the other embodiment, the negative electrode may include a lithium metal thin film formed on a negative electrode current collector. This may be manufactured by depositing lithium metal on the metal current collector or by rolling a lithium foil.

[0032] The above metal current collector is a metal having high conductivity and not causing chemical changes in the battery, and can be formed using any metal previously known to be usable as a metal current collector.

[0033] Specific examples thereof include metals such as stainless steel, aluminum, nickel, titanium, or copper, or surfaces of copper, aluminum, or stainless steel treated with carbon, nickel, titanium, silver, etc. These negative electrode current collectors can be formed into various forms such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0034] Additionally, the metal collector may have a thickness of 3 to 100 μm, and the lithium metal layer may have a thickness of, for example, 1 to 300 μm.

[0035] In an exemplary embodiment, the lithium metal thin film further comprises an SEI layer formed on the lithium metal thin film, wherein the SEI may have a crystal size range of 1 to 10 nm. Specifically, the SEI layer may have a crystal size in the D90 range of 2 nm to 9 nm and a D50 range of 1 nm to 7 nm.

[0036] In addition, it includes lithium formed between a lithium metal thin film formed on the negative electrode current collector and an SEI layer, and in the lithium, Li particles may have a projected area diameter of 1 to 4 μm. In addition, the SEI layer may include LiF crystals having a size of 1 to 3 nm.

[0037] Meanwhile, the anode-free lithium metal battery according to an embodiment of the present invention may further include a cathode, and the cathode may include a cathode current collector and a cathode active material layer positioned on the cathode current collector.

[0038] These positive electrodes can be manufactured by mixing an active material and a binder, and in some cases, a conductive material, a filler, etc. in a solvent to prepare a positive electrode slurry composition, and applying the composition to a positive electrode current collector.

[0039] The positive electrode current collector may generally have a thickness of 3 to 500 μm. In addition, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may also form fine unevenness on its surface to increase the adhesiveness of the positive electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric may be used.

[0040] And, in the case of the above positive electrode active material, it may include a lithium metal compound including lithium and one or more metals such as iron, cobalt, manganese, nickel, or aluminum, as a compound capable of reversible intercalation and deintercalation of lithium.

[0041] Specifically, the lithium metal compound is a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (wherein, 0<Z1<2) etc.), lithium (nickel-cobalt-manganese) composite oxide (e.g., Li(Ni p Co q Mnr )O2(wherein, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), or lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (Here, M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, -0.5≤a≤+0.5, 0≤x≤0.5, 0≤b≤0.1), and any one or two or more compounds thereof may be included.

[0042] Among these, the positive electrode active material may include lithium iron phosphate. For reference, the lithium iron phosphate is being considered for expansion of use due to its low unit price, etc., but a lithium metal secondary battery including a positive electrode using the same as an active material exhibits a more pronounced decline in life characteristics and capacity characteristics, especially a decline in initial capacity, etc. However, the lithium metal secondary battery of the other embodiment can solve the decline in capacity and initial discharge capacity, etc. by combining the electrolyte of one embodiment including a high-concentration lithium salt with the positive electrode including the lithium iron phosphate, and can contribute to the application of a lithium metal secondary battery at a lower unit price.

[0043] The above-described positive electrode active material may be included in an amount of 60 to 99 wt%, or 70 to 99 wt%, or 80 to 98 wt% based on the total weight of the positive electrode active material layer.

[0044] Meanwhile, the conductive material included in the positive electrode active material layer is a component for further improving the conductivity of the positive electrode active material. The conductive material is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive nanomaterials such as carbon nanofibers or carbon nanotubes; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used. Among these, the conductive material can further lower the resistance of the lithium metal secondary battery and improve the output characteristics, etc. by including a conductive nanomaterial such as carbon nanotubes or carbon nanofibers.

[0045] Typically, the conductive material may be included in an amount of 1 to 20 wt%, or 1 to 15 wt%, or 1 to 10 wt% based on the total weight of the positive electrode active material layer.

[0046] The binder optionally included in the above-described positive electrode active material layer is a component that assists in the bonding of the positive electrode active material and the conductive material, and in the bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, nitrile rubber, styrene-butadiene rubber, or fluororubber, and a mixture or copolymer of two or more selected from these may also be used.

[0047] Typically, the binder may be included in an amount of 1 to 20 wt%, or 1 to 15 wt%, or 1 to 10 wt% based on the total weight of the positive electrode active material layer.

[0048] Additionally, a filler may be optionally added to the positive electrode as a component that suppresses its expansion. Such filler is not particularly limited as long as it can suppress the expansion of the electrode without causing chemical changes in the battery. Examples of fillers that can be used include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0049] The above-described positive electrode can be manufactured by dispersing and mixing the positive electrode active material, binder, and conductive agent in a dispersion medium (solvent) to make a slurry, applying the slurry on a metal current collector, and then drying and rolling. At this time, the dispersion medium may be NMP (N-methyl-2-pyrrolidone), DMF (Dimethyl formamide), DMSO (Dimethyl sulfoxide), ethanol, isopropanol, water, and mixtures thereof, but is not necessarily limited thereto.

[0050] Meanwhile, the lithium metal secondary battery described above may further include a porous separator interposed between the positive electrode and the negative electrode.

[0051] These porous membranes can be made of olefin polymers such as polyethylene and polypropylene, glass fibers, etc. in the form of sheets, multi-membranes, microporous films, woven fabrics, and non-woven fabrics, but are not necessarily limited thereto. However, it may be preferable to use porous polyethylene or porous glass fiber non-woven fabric (glass filter) as the membrane, and it may be more preferable to use porous glass filter (glass fiber non-woven fabric) as the membrane. The membrane may be an insulating thin film having high ion permeability and mechanical strength, and the pore diameter of the membrane may generally be in the range of 0.01 to 10 ㎛, and the thickness may generally be in the range of 5 to 300 ㎛, but is not limited thereto.

[0052] Meanwhile, the lithium metal secondary battery described above can be manufactured according to a conventional method in the art. For example, the battery can be manufactured by housing an electrode assembly including a positive electrode, a negative electrode, and a separator in a case and injecting and impregnating the electrolyte described above.

[0053] These lithium metal secondary batteries are not only applicable to battery cells used as power sources for small devices, but are also particularly suitable for use as unit batteries of battery modules used as power sources for medium and large devices. In consideration of an appropriate discharge rate for each purpose, the batteries of the above-described embodiment or other embodiments can be selectively used.

[0054] The electrolyte composition for a lithium metal battery according to the present invention comprises a first lithium salt and a second lithium salt different from the first lithium salt, so that additional anions derived therefrom have low binding energy to lithium, thereby suppressing clustering and crystallization of inorganic substances within the SEI.

[0055] Lithium metal batteries using this electrolyte composition can achieve high energy density, enabling efficient use of space and alleviating concerns about driving range when applied to electric vehicles.

[0056] Figures 1a to 1f illustrate the results of fast charging of a lithium negative electrode using the latest electrolyte.

[0057] Figures 2a to 2f illustrate the results of fast charging with a lithium metal negative electrode using an electrolyte according to an embodiment of the present invention with various additional anions added thereto.

[0058] Figures 3a to 3e illustrate the results of correlation analysis using an electrolyte according to an embodiment of the present invention.

[0059] Figures 4a to 4f illustrate the results of molecular dynamics simulations using an electrolyte according to an embodiment of the present invention.

[0060] Figures 5a to 5h illustrate performance analysis results in a pouch cell using an electrolyte according to an embodiment of the present invention.

[0061] Figures 6a to 6d illustrate the results of oxidation stability tests for Li||Al batteries based on double salt electrolyte and LHCE.

[0062] Figures 7a to 7d show XPS analysis results for the SEI layer formed on the lithium deposit in LiDFOB / LiBF4FEC:DEC.

[0063] Figures 8a to 8d show XPS analysis results for the SEI layer formed on the lithium deposit in LiFSI DME:TTE.

[0064] Figures 9a to 9c illustrate the results of molecular dynamics simulations of changes in Li+ coordination structure according to changes in electrode surface charge.

[0065] Figures 10a and 10b show the results of voltage float tests performed on Li||NCM cells using pyran-based electrolytes.

[0066] Figures 11a to 11c show the cycle performance of Li||NCM811 cells at 4C and 6C charges for LiAsF6 / LiTFSI THP:FEC.

[0067] Figure 12 shows an electron diffraction pattern for the SEI layer formed on the Li deposit at 4.0 C in a pyran-based electrolyte.

[0068] Figures 13a to 13c show XPS spectra for the SEI layer formed on Li deposits at 4.0 C in a pyran-based electrolyte.

[0069] Figures 14a and 14b show the change in ionic conductivity of pyran-based electrolytes LiDFOB / LiBF4FEC:DEC, LiFSI DME:TTE, and LiPF6EC:EMC and the characteristic size of lithium deposited at 4C.

[0070] Figure 15 shows the interfacial resistance of pyran-based electrolytes LiDFOB / LiBF4FEC:DEC and LiFSI DME:TTE.

[0071] Figures 16a and 16b show the lithium plating voltage profiles of a pyran-based electrolyte in a Li||Cu battery.

[0072] Figures 17a and 17b show the critical current densities of pyran-based electrolytes LiDFOB / LiBF4FEC:DEC and LiFSI DME:TTE.

[0073] Figures 18a to 18d show the lithium deposition morphology and J at 0.2C charge rate. crit. and Li + It shows the correlation with binding energy.

[0074] Figures 19a to 19e show the Li content in precipitated LiF particles according to the supporting anion. + It represents the coordination number of .

[0075] Figures 20a to 20h show the analysis results of the electrolyte applied with LiPF6 / LiBPh4 lithium salt.

[0076] Figures 21a and 21b show the performance of an ether solvent-based electrolyte (solvent: DME, tetrahydrofuran) under EV applicable conditions.

[0077] Figures 22a to 22e show the battery evaluation results, SEI uniformity, and lithium deposition morphology of electrolytes composed of LiFSI / LiPF6, LiAsF6, and DME:TTE, DEM:PEB, respectively.

[0078] Figures 23a to 23h illustrate the results of measuring D50, D90, and particle size distribution of particles in SEI formed according to the application of each electrolyte according to the present invention.

[0079] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0080] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0081] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0082] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0083] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0084] Furthermore, when we say that a layer, membrane, region, plate, or other part is "on" or "over" another part, this includes not only cases where it is "directly on" the other part, but also cases where there are other parts in between. Conversely, when we say that a part is "directly on" another part, it means that there are no other parts in between. Furthermore, saying that a part is "on" or "over" a reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "over" the direction opposite to gravity.

[0085] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0086] Additionally, throughout the specification, when we say "in plan", we mean when the target portion is viewed from above, and when we say "in cross section", we mean when the target portion is viewed from the side in a cross-section cut vertically.

[0087]

[0088] To understand the lithium deposition behavior during fast charging, 1 M lithium difluoro(oxalato)borate (LiDFOB) / 0.2 M LiBF4 ('LiDFOB / LiBF4FEC:DEC') on fluoroethylene carbonate (FEC):diethyl carbonate (DEC) as a representative double salt electrolyte and 1.5 M lithium bis(fluorosulfonyl)imide (LiFSI) on 1,2-dimethoxyethane (DME):1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a local high-concentration electrolyte (LHCE) were applied and evaluated, respectively.

[0089] In fast charge tests, commercially viable cathode loading (2.1 mAh cm for high-power cell design) was achieved with EV-applicable cycling protocol (4C charge and 1C discharge). -2 ), the electrolyte / capacitance (E / C) ratio of 40 μm Li foil (40 μm) is 6 g Ah -1 was applied.

[0090] Referring to Figure 6, to minimize the impact of cathode-side degradation at high SoC during fast charging, the evaluation was performed under 0% to 70% SoC conditions (4.1 V to 3.0 V). Furthermore, a pre-charge step, frequently used in lithium-ion batteries, was introduced to minimize the adverse effects of local lithium deposition at a 0.3C charge rate within the 0% to 5% SoC range of each cycle.

[0091] As a result, it has a long cycle life under standard charging conditions, unlike 4C (8.4 mA cm -2) showed a rapid decrease in capacity during fast charging in LHCE and dual salt electrolytes. Referring to Fig. 1a, the Li||NCM811 coin cell using LHCE showed a gradual increase in charge overvoltage during the initial cycles, and a severe overcharge in the 5th cycle. Referring to Fig. 1b, when the dual salt electrolyte was used, the cell voltage immediately reached the upper voltage cutoff as soon as the 4C constant current (CC) charge stage began and entered the constant voltage (CV) stage due to the large overvoltage, and the cell capacity gradually decreased after 30 cycles.

[0092] The morphology of the deposited Li was observed using a scanning electron microscope (SEM). Referring to Figure 1c, both the double salt electrolyte and LHCE showed large Li particles at 0.2C charging, but smaller, pulverized Li particles were observed at 4.0C charging. The characteristic size of the deposited Li may be related to the uniformity of the fine SEI structure and the rich inorganic components of the SEI.

[0093] Referring to Fig. 1d, cryogenic transmission electron microscopy (cryo-TEM) analysis revealed that these electrolytes formed a uniform SEI at 0.2C charging, but a non-uniform SEI at 4C charging. In both electrolytes, crystalline domains of approximately 5-8 nm in size were observed scattered throughout the SEI.

[0094] Also referring to Figures 1e and 7, 8, anion-derived inorganic species (e.g., DFOB) are identified in X-ray photoelectron spectroscopy (XPS) analysis. - Fluorine and boron derived from FSI - The content of sulfur and nitrogen (derived from) was found to decrease as the charging speed increased.

[0095] Meanwhile, these electrolytes preferentially contain Li +-It is known to easily form an inorganic SEI component through anion coordination and cathodic decomposition, thereby forming a uniform and amorphous SEI.

[0096] Referring to Fig. 23, the uniformity of SEI according to each electrolyte application can be confirmed. Specifically, the particle distribution of the SEI may have a D90 range of 2 nm to 9 nm, preferably a D90 range of 3.5 nm to 5 nm, or a D90 range of 3.8 nm to 4.5 nm. In addition, it may have a D50 range of 1 nm to 7 nm, preferably a D50 range of 2.5 nm to 3.5 nm, or a D50 range of 2.5 nm to 3.0 nm.

[0097] Referring to Figure 9, however, under fast charging conditions, the anions are Li at the lithium / electrolyte interface due to the strong negative polarization at the negative electrode surface. + can bounce off of.

[0098] Referring to Fig. 1f, since preferential decomposition is difficult, the inorganic SEI component does not easily precipitate but grows into crystals, thereby inducing a heterogeneous SEI rich in organic matter and locally crystallized, and forming a branched Li morphology.

[0099]

[0100] First, we designed an electrolyte based on 1.2 M lithium bis(trifluorosulfonyl)imide (LiTFSI) in tetrahydropyran (THP):FEC (6:4 volume ratio). The reference formulation forms a LiF-rich SEI with the FEC solvent, which is less affected by the charge rate due to its neutral properties. In this formulation, 1) the FEC solvent is expected to be dominantly decomposed, minimizing the effect of anion decomposition on SEI formation, and 2) it is expected to serve as a platform for investigating the role of anions as supporting components.

[0101] Referring to Fig. 2a, it shows superior performance (80% capacity retention at 53 cycles) compared to LHCE under 4C fast charge conditions, which is due to the LiF-rich SEI formed by the FEC solvent, and shows somewhat better performance compared to the double salt electrolyte.

[0102] Referring to Fig. 11, the cycling performance of LiNO3, LiDFOB, and LiClO4 electrolytes was lower than that of LiTFSI electrolyte, while the LiFSI electrolyte showed some improvement, such as maintaining 80% capacity after 71 cycles. Meanwhile, in terms of fast charge performance, LiPF6 and LiAsF6 electrolytes were significantly improved, and in particular, the cycles at 80% capacity retention were 115 cycles for LiPF6 electrolyte and 279 cycles for LiAsF6 electrolyte. The cycle number at 80% capacity retention at 4C charge rate was 115 cycles for AsF6 electrolyte. - ≫ PF6 - ≫ FSI - > TFSI - ≒ ClO4 - > BF4 - ≒ DFOB - > NO3 - It was confirmed in order.

[0103] Referring to Fig. 2b, a 6C (50% SoC in 5 minutes, 70% SoC in 10 minutes) charge rate was also performed, which is faster than the 4C charge rate (50% SoC in 7 minutes, 70% SoC in 11 minutes), similar to Fig. 11, and the cell can be seen to operate for up to 200 cycles.

[0104] The Li deposition morphology during 4C charging was investigated through SEM analysis. Referring to Fig. 2c, the Li morphology of LiTFSI (base electrolyte) showed an inhomogeneous shape with a projected area diameter of Li particles of approximately 1 μm.

[0105] The LiNO3, LiDFOB, LiBF4, and LiClO4 electrolytes exhibited a curved and relatively porous Li morphology. In contrast, the LiAsF6 electrolyte exhibited a flat and densely deposited lithium morphology with a projected area diameter of Li particles of 3 to 5 μm. The LiPF6 electrolyte exhibited a similar flat morphology to the LiAsF6 electrolyte, but the projected area diameter of Li particles was smaller, at 1 to 4 μm.

[0106] Referring to Fig. 2d, it can be confirmed that the Li characteristic size has a similar tendency to the cycling stability.

[0107] Referring to Fig. 2e, cryo-TEM images of SEI for the pyran-based electrolyte sets show that LiTFSI (base electrolyte), LiClO4, LiBF4, LiDFOB, and LiNO3 electrolytes form highly crystalline SEI.

[0108] Referring to FIGS. 2f and 12-13, the selected area electron diffraction (SAED, FIG. 12) pattern and XPS (FIG. 13) confirm the formation of LiF crystals (4-6 nm in size) for LiTFSI, LiBF4, and LiClO4 electrolytes.

[0109] Referring to Fig. 2f, sporadic dark domains and rare large crystallites (> 6 nm) are observed in the SEI of LiDFOB and LiNO3 electrolytes.

[0110] Referring to Figures 2d and 2f, for LiFSI, LiPF6, and LiAsF6 electrolytes, smaller crystals with sizes of 3-4 nm, 2-3 nm, and 1-3 nm are distributed, respectively. The crystal signals in the SAED patterns appear as faint ring-like shapes, indicating a structure with low crystallinity. In addition, the LiF crystal size shows an inverse relationship with the characteristic size of the deposited Li, indicating that the SEI structure significantly influences the Li morphology.

[0111]

[0112] Correlation analysis of electrolyte and interphase properties for pyran-based electrolytes with various salt anions at 4C charging was performed.

[0113] Figures 3a and 3b show the results of Pearson correlation analysis for pyran-based electrolytes.

[0114] 1) Specifically, the characteristic size of lithium at 4C charging shows a correlation coefficient (r) of +0.75 with the interfacial resistance, which means that the interfacial resistance does not necessarily need to be low for uniform lithium deposition.

[0115] 2) For pyran-based electrolytes, Li characteristic size and J crit A strong correlation was found between the two (r = 0.97). This is J crit For electrolytes with higher values, more uniform Li deposition can be achieved at 4C charging. Referring to Fig. 3c, when the correlation was investigated by incorporating LHCE and double salt electrolytes in addition to pyran-based electrolytes, a similar strong correlation was observed. The crystallite size and J crit A strong negative correlation was observed between the values ​​(r = -0.91). In contrast, the Li characteristic magnitude at standard charge conditions (0.2C) was J crit showed a weak correlation with .

[0116] 3) Referring to Figs. 3d and 3f, the crystallite size shows a strong correlation with the Li characteristic size at 4C charge, which is also the case for other state-of-the-art electrolytes (r = 0.92 excluding LHCE and double salt electrolytes, r = 0.93 including them, Fig. 3d). It can also be seen that the Li form has a stronger correlation with the crystallite size of the SEI than with the chemical composition of the SEI (r = -0.52 for F1s, +0.26 for C1s, and +0.36 for O1s).

[0117] 4) Referring to Fig. 3e, in the pyran-based electrolyte, as the SSL ratio increased or the anion binding energy decreased (the number of anions decreased), the crystal size (r = -0.93 and -0.97, respectively) tended to decrease and the characteristic size of the deposited Li (r = +0.97 and +0.85, respectively) tended to increase. This trend was different from the conventional one, in that the characteristic size of the deposited lithium increased as the SSL ratio decreased and the lithium anion binding energy increased.

[0118]

[0119] SSL or Li + - From the strong correlation between the ratio of anion binding energies and the LiF crystal size, the electrolyte design principle that can control the SEI structure during fast charging can be suggested. To understand the precipitation behavior of inorganic species during SEI formation according to additional anions, several factors influencing the nanoscale SEI morphology were considered. The by-products of electrolyte decomposition are precipitated on the electrode surface through clustering and coalescence processes over a short time (several to tens of nanoseconds). However, since multiple Li coordination by anions is required in the liquid electrolyte, this mechanism is not suitable for Li as in the case of pyran-based electrolytes. + - The decrease in the crystal size of the SEI as the anion coordination decreases cannot be explained (Fig. 3e). Referring to Fig. 2e, the main inorganic component, LiF, is actually derived primarily from FEC in the pyran-based electrolyte, diluting the inorganic supply effect through anion decomposition.

[0120] Referring to Figure 4a, Li is added to the electrolyte composed of THP solvent molecules and Li salt molecules. + Wow F - A model structure containing atoms was constructed. THP, Li + , F -The ratio of the number of AsF and anions was 800:280:200:80, which corresponds to approximately 0.5 M Li salt and 1.3 M LiF. As the system reached equilibrium, Li and F atoms precipitated over the simulation time due to the initial supersaturation. During the precipitation process, LiF clusters evolved into more stable clusters, forming larger aggregates. Referring to Fig. 4b, in particular, the degree of clustering evolution varied depending on the anion. The cluster size increased in the following order: AsF6 - < PF6 - ≪ FSI - < TFSI - ≒ ClO4 - < BF4 - ≒ DFOB - ≪ NO3 - This is in the same order as observed by cryo-TEM for the increase in LiF crystal size in the SEI (Figures 2e and 2f).

[0121] The rapid appearance of larger clusters over time in the simulation indicates that a greater number of coalescence events occurred within the same amount of time.

[0122] Figures 4c and 4d show that the coalescence process of clusters consists of four stages: the stage where the clusters become close enough to recognize each other's presence, the formation of the first atomic bond between the clusters (the formation of a 'sintering neck'), the growth of the sintering neck, and the 'spheroidization' of the cluster.

[0123] During this coalescence step, we observed significant differences in the first sintering neck formation and growth rate depending on the type of anion. Referring to Fig. 4c, AsF6 - In the case of , it took 50 ps to form the first sintering neck after the small clusters came into close contact, and 150 ps to form the second sintering neck adjacent to the first sintering neck. In contrast, referring to Fig. 4d, NO3 -In this case, this process occurred within approximately 30 ps. Therefore, these results suggest that the preference for inter-cluster atomic bond formation, i.e., neck formation, may be due to the degree of cluster evolution depending on the anion.

[0124] Referring to Fig. 4e, since neck formation and growth can be initiated by surface atoms with low coordination, such as terrace adsorbates or step adsorbates on the cluster surface, a 'ligand index' was introduced as an index to quantitatively compare the ligand preference of LiF clusters according to anions. The index can be defined as the number of Li atom sites whose coordination number (CN) with neighboring F atoms formed in the simulated LiF cluster is less than 3. The sites calculated by the bonding index (CN <3) are relatively unstable (in the case of a perfect face-centered cubic LiF cluster) than core atoms (CN = 6), terrace sites (CN = 5), step sites (CN = 4), and kink sites (CN = 3), making them more likely to form bonds with other atoms, such as necks.

[0125] Referring to Fig. 4f, Li + - Anions with high anion binding energy have a high binding index (AsF6) with a correlation coefficient r = 0.818 - < PF6 - ≒ FSI - < TFSI - ≒ ClO4 - ≒ BF4 - < DFOB - ≒ NO3 - ) and shows rapid aggregation of LiF clusters in this order. Therefore, the nanoscale uniformity of SEI observed in LiAsF6 and LiPF6 electrolytes is due to low Li + It may be due to binding energy.

[0126] Li + Anions that bind strongly to free Li in the electrolyte + The total concentration of (i.e., Li surrounded by solvent) +), the partial solubility of soluble inorganic species (e.g., LiF, Li2O, and Li2S) can be increased. Increasing the partial solubility of LiF can loosen the coordination of Li and F atoms at the cluster surface, which can induce dissolution at the cluster-liquid electrolyte interface and the formation of abundant low-coordination sites.

[0127] Therefore, Li + The weakly binding AsF6 or PF6 anions may act to reduce the partial solubility of the inorganic species of the decomposition products of pyran-based electrolytes, thereby reducing their preference for forming low coordination sites, inhibiting neck formation between clusters, and inhibiting their aggregation during precipitation.

[0128]

[0129] Referring to Figure 5a, two pouch cells with high-power and high-energy cell designs were tested to demonstrate the performance of the pyran-based electrolyte (LiAsF6 / LiTFSI THP:FEC) under EV-applicable conditions. Referring to Table S1, the energy densities of the high-power and high-energy cell designs were 321 Wh kg, respectively. -1 and 386Wh kg -1 It is expected.

[0130] Li||NMC811(High-power cell)Li||NMC811(High-energy cell)Al current collector (13 μm)3.51 mg cm -2 3.51 mg cm -2 Cu current collector (8 μm)7.12 mg cm -2 7.12 mg cm -2 Lithium metal (20 μm)1.07 mg cm -2 1.07 mg cm -2 NMC811 cathode11.46 mg cm -2 18.75 mg cm -2 PP separator (25 μm)2.28 mg cm -22.28 mg cm -2 ElectrolyteE / C=3.0 g Ah -1 E / C=2.5 g Ah -1 Discharge capacity2.25 mAh cm -2 (4.25 V, SoC 100%)3.76 mAh cm -2 (4.25 V, SoC 100%)Average discharge voltage3.84 V3.78 VTotal stack energy (bi-cell)259.8 mWh426.6 mWhTotal stack weight (bi-cell)0.806 g1.104 gProjected energy density322.1 Wh kg -1 386.3 Wh kg -1

[0131] Referring to Figures 5b and 5c, the rate capacity of the LiAsF6 / LiTFSI THP:FEC electrolyte was investigated over the range of 3.0 to 4.25 V at a fixed charge rate of 0.2 C and at discharge rates from 0.2 C to 4.0 C. At a 1 C charge rate, the high-power cell and the high-energy cell exhibited discharge capacities of 93% and 88%, respectively, of those at 0.2 C, and at a 4 C rate, the discharge capacities were 85% and 61%, respectively, of those at 0.2 C.

[0132] Figures 5d to 5f compare the SoC and charge energy density according to the charging time of high-power and high-energy cells. Referring to Figure 5d, the high-power cell was charged at 4C CC-CV (0.3C current cutoff in the CV stage), and referencing Figure 5e, the high-energy cell was charged at 3C CC-CV (0.3C current cutoff in the CV stage), so the charge current density in the CC stage (8.4 mA cm 2 each) -2 and 9.9mA cm -2) were at similar levels. For the high-power cell, a pre-charge step of 0.3C charge rate was performed at 0-5% SoC, and for the high-energy cell, a 0-10% charge step was performed. Referring to Figures 5d and 5f, the high-power cell was charged at 70% SoC (210 Wh kg) with a 4.1 V voltage cutoff. -1 , 1C discharge) took 12 minutes to charge. Referring to Figures 5e and 5f, the high-energy cell achieved 70% SoC (250 Wh kg) at 4.2 V cut-off voltage condition. -1 , 1C discharge) in 13 minutes and 80% SoC (286Wh kg) -1 , 1C discharge) was charged within 17 minutes. Both cell designs produced up to approximately 200 Wh kg within the same charging time. -1 Almost the same energy density was achieved up to 200 Wh kg. However, -1 Above, high-energy cells (4.2 V and 4.25 V upper voltage cutoff) were able to achieve higher energy density within the same charging time.

[0133] Each cell design was evaluated by operating the high-power cells at 4.1 V voltage cutoff (1 C current cutoff, 70% SoC) for fast charging, and the high-energy cells at 4.2 V voltage cutoff (0.3 C current cutoff, 90% SoC).

[0134] Referring to Figure 5g, the high-power cell showed stable discharge capacity of 82% and 74% after 200 and 300 cycles, respectively, without premature cell degradation or sudden overcharge. The high-power cell operated 350 cycles with a 12-minute charge, showing a high energy density (210 Wh kg) with an energy retention rate of 70%. -1 , 1C discharge) was achieved.

[0135] Also, referring to FIG. 21, the performance of an ether solvent-based electrolyte (solvent: DME, tetrahydrofuran) under EV applicable conditions is shown.

[0136] In conclusion, by elucidating a strong correlation between SEI homogeneity (primarily cluster or crystal size) and the morphology of deposited lithium, we can provide tailored mesophases for fast-charge applications in lithium metal batteries. Furthermore, we highlight the critical role of electrolyte composition, particularly the selection of additional anions, in mitigating clustering or crystallization of inorganic species and, consequently, promoting the formation of a homogeneous mesophase.

[0137]

[0138] electrolyte

[0139] Electrolytes were prepared in an argon-filled glove box. For the preparation of pyran-based electrolytes, THP (anhydrous, 99%), LiAsF6 (98%), LiFSI (99.9%), LiTFSI (99.95%), LiClO4 (99.9%), LiBF4 (99.99%), LiDFOB (99.5%), and LiNO3 (99.99%) were obtained from Sigma-Aldrich. LiPF6 (97%) and FEC (98%) were obtained from TCI.

[0140] 0.2 M LiBF4 (99.99%, Sigma-Aldrich), and 1.5 M LiFSI (99.9%, Sigma-Aldrich) in 1 M LiPF6EC:EMC (1:1 v / v, Phanax), 1 M LiDFOB (99.5%, Sigma-Aldrich) FEC (98%, TCI):DEC (anhydrous, 99%, Sigma-Aldrich) (3:7 by volume) were used as comparative electrolytes along with DME (99.5%, Sigma-Aldrich):TTE (97%, SynQuest Labs.) (22:78 by volume).

[0141]

[0142] Lithium morphology and SEI characterization

[0143] The deposited Li morphology was observed through a field emission scanning electron microscope (Sirion, FEI). Under the set conditions, Li||NCM811 (active material loading 11 mg cm -2) was charged to perform Li plating. The SEI layer formed on the plated Li was compositionally analyzed using in-situ XPS (Axis-Supra, Kratos) with an X-ray source (Al, hν = 1486.7 eV). The sample inlet of the XPS instrument was located in an argon-filled glove box (<0.1 ppm O2 and H2O) to minimize sample contamination due to exposure to the atmosphere. For SEM and XPS measurements, the plated lithium samples were washed with the corresponding solvent for each electrolyte, dried under vacuum, and then transferred to the instrument for measurement.

[0144]

[0145] Cryo-TEM characterization

[0146] The SEI layer formed on the deposited Li was observed using cryo-TEM (Krios, Thermo Fisher). 1.0 mAh cm -2 Current-density Li-plated TEM grids (copper grids supported by lacey carbon, 200-mesh size) were placed in Eppendorf microtubes in an Ar-filled glove box. Immediately after removal from the glove box, the tubes were immersed in liquid nitrogen and then broken to prepare samples. The prepared TEM grid samples were loaded into a cryoautoloader to maintain cryogenic conditions.

[0147]

[0148] Pouch cell manufacturing

[0149] Two types of pouch cells were manufactured by the following methods.

[0150]

[0151] high power cell

[0152] LiNi 0.8 Mn 0.1 Co 0.1 O2 anode (active material / Super P C65 / polyvinylidene fluoride (PVDF) ratio 96:2:2, active material loading 11 mg cm -2) was prepared by coating one side of a 13 μm thick aluminum current collector, and a 20 μm thick Li anode (Honjo Metal) was laminated on a copper current collector (sequentially washed with MTI, hydrochloric acid, acetone, and deionized water) to prepare a negative electrode. A PP separator (25 μm, Celgard) was positioned between the positive and negative electrodes, and each negative electrode, positive electrode, and separator were cut into sizes of 30 mm × 50 mm, 40 mm × 60 mm, and 40 mm × 60 mm, respectively, using a puncher. The negative and positive electrodes were welded to aluminum and nickel tabs, respectively, using an ultrasonic welder (WC-TW-300SJ, Wellcos), and all electrodes and separators were laminated and packaged in aluminum pouches by adding a specified amount of liquid electrolyte.

[0153]

[0154] high energy cell

[0155] Double-sided coated LiNi 0.8 Mn 0.1 Co 0.1 O2 (provided by LG Energy Solution, active material / Super P C65 / polyvinylidene fluoride (PVDF) ratio 96:2:2, active material loading 18 mg cm -2 ) and two 20 μm standalone Li electrodes were stacked on a copper current collector and used as the cathode. A PP separator (25 μm, Celgard) was placed between the cathode and anode, and each cathode, anode, and separator were cut to the sizes of 33 mm × 50 mm, 35 mm × 52 mm, and 37 mm × 54 mm, respectively. The cathode and anode were welded to aluminum and nickel tabs, respectively, using an ultrasonic welder (WC-TW-300SJ, Wellcos), and all electrodes and separators were stacked and packaged in aluminum pouches with the specified amount of liquid electrolyte added.

[0156]

[0157] Energy density calculation

[0158] The expected energy density of each cell was calculated using the weight and energy value of the unit bicell, assuming a stacked cell structure. The areal mass of the bicell was determined by adding the areal weights of the double-sided negative electrode (including the Al current collector), two separator sheets, the double-sided Li anode (including the Cu current collector), and the liquid electrolyte. The specific energy density was calculated by dividing the cell's areal energy by its areal mass. Table S1 shows the areal weights of the cell components and cell design parameters.

[0159]

[0160] electrochemical analysis

[0161] Electrochemical measurements were performed using 2032-type coin cells, each containing 50 μL of electrolyte. Impedance spectroscopy for ionic conductivity (SUS||SUS, PP membrane) and interfacial resistance (Li||Li, PP membrane) was performed using a Biologic VSP potentiostat over the frequency range of 1 MHz to 0.1 Hz with a perturbation amplitude of 10 mV.

[0162] The critical current density and critical overpotential of Li||Li cell are 1 mV s -1 It is defined as the point where an uneven current-voltage signal begins to occur while scanning the voltage at a speed of .

[0163] The fast charge performance evaluation of Li||NCM811 full cells was performed according to the following protocol. The formation was performed as 0.2C charge (4.3 V) - 1.0C discharge for 2 cycles, 0.5C charge (4.25 V) - 1.0C discharge for 2 cycles, 1C charge - 1C discharge for 2 cycles, and 2C charge - 1C discharge for 2 cycles.

[0164] Li||NCM811 pouch cells were tested under pressure using a pressure jig and 5 mm thick silicone foam pads, and galvanostatic cycling was performed using a WBCS3000L battery tester (Wonatech) at 25°C.

[0165]

[0166] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A first lithium salt represented by the following chemical formula 1; A second lithium salt different from the first lithium salt; An electrolyte composition for a lithium metal battery, comprising an organic solvent: [Chemical Formula 1] LiX Here, X is any one of the anions of AsF6, PF6, FSI, TFSI, CLO4, BF, DFOB, or NO3, RF-substituted alkoxide (ORF), borate anion, or aluminate anion.

2. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the anion of the first lithium salt has a lower Li-anion binding energy than the anion of the second lithium salt.

3. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the borate anion comprises at least one of tetraphenylborate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis(pentafluorophenyl)borate, and hydridotris(pentafluorophenyl)borate.

4. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the aluminate-based anion comprises at least one of tetrakis(perfluoro-tert-butoxy)aluminate and tetrakis(pentafluorophenoxy)aluminate.

5. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the first lithium salt represented by the above chemical formula 1 comprises LiAsF6, LiPF6, or lithium tetraphenylborate (LiBPh4).

6. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the anion of the first lithium salt lowers the partial solubility of an inorganic species on the electrolyte composition.

7. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the second lithium salt comprises at least one lithium salt selected from the group consisting of LiTFSI, LiFSI, LiBETI, LiAsF6, LiPF6, LiSbF6, LiDFOB, and LiBOB.

8. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the organic solvent comprises at least one of a pyran-based solvent and an ether-based solvent.

9. In paragraph 8, An electrolyte composition for a lithium metal battery, wherein the pyran-based solvent comprises dihydropyran (DHP) and tetrahydropyran (THP).

10. In paragraph 8, An electrolyte composition for a lithium metal battery, wherein the ether solvent comprises at least one solvent selected from the group consisting of 1,2-dimethoxyethane (DME), diglyme, tetraglyme, diethylether, dipropylether, furan, tetrahydrofuran, 2-methylfuran, and 1,2-diethoxyethane.

11. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the electrolyte composition further comprises an additive comprising at least one additive selected from the group consisting of fluoroethylene carbonate (FEC), DFEC, TFEC, TFTFE, TTE, BTFE, OFE, and TFOFE.

12. An electrolyte composition for a lithium metal battery according to any one of claims 1 to 11; A negative electrode comprising a lithium metal thin film formed on a negative electrode current collector; A cathode including a cathode active material layer formed on a cathode current collector; and A lithium metal battery comprising a separator formed between the cathode and the anode.

13. In paragraph 12, Further comprising an SEI layer formed on the lithium metal thin film, A lithium metal battery, wherein the SEI has a crystal size range of 1 to 10 nm.

14. In paragraph 12, A lithium metal battery, wherein the SEI layer has a crystal size in the D90 range of 2 nm to 9 nm and a D50 range of 1 nm to 7 nm.

15. In paragraph 12, A lithium metal battery comprising lithium formed between a lithium metal thin film formed on the negative electrode current collector and an SEI layer, wherein Li particles in the lithium have a projected area diameter of 1 to 4 μm.

16. In paragraph 12, A lithium metal battery, wherein the SEI layer comprises LiF crystals having a size of 1 to 3 nm.

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