Ether solvent-based electrolyte composition and lithium metal battery comprising same

Abstract

Provided, in one embodiment of the present invention, is an electrolyte composition for a lithium metal battery, comprising: an electrolyte including a lithium salt, a non-aqueous ether-based organic solvent, and an organic co-solvent; an SEI-forming agent including LiNO3; and a dissociation-inducing additive, wherein the dissociation-inducing additive is an ionic additive having a fluorine group represented by the following chemical formula 1, and the cation (An+) of the dissociation-inducing additive has a stronger binding affinity for NO3 - than lithium ions (Li+) has for NO3 -. [Chemical formula 1] AFn, wherein A includes any one of Cu, Au, Ag, Pt, and Zn.

Description

Ether solvent-based electrolyte composition 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. 10-2024-0084471, filed June 27, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention discloses an ether solvent-based electrolyte composition and a lithium metal battery comprising the same.

[0004] Recently, with the rapid spread of electronic devices that use batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries are attracting attention as a power source for portable devices due to their light weight and high energy density. Accordingly, active research and development efforts are being conducted to improve the performance of lithium secondary batteries. In particular, lithium has the highest theoretical specific capacity (3860 mAh g) -1 ) and has the lowest reduction potential (-3.04 V vs. SHE), it is attracting attention as a next-generation cathode that can overcome the energy density limit of existing lithium-ion batteries when used as a cathode.

[0005] However, lithium anodes have a tendency to deposit lithium in a dendrite-like manner during charge / discharge. This can lead to separator penetration and dead lithium generation, posing a safety risk to the battery. A primary cause of dendrite growth is the unstable organic film that naturally forms at the lithium-electrolyte interface, which is known to accelerate uneven lithium desorption / deposition.

[0006] Accordingly, various attempts are being made to solve the problems of the lithium metal battery, such as forming a protective layer on the surface of the lithium metal layer or developing a new electrolyte that can suppress the electrolyte decomposition reaction on the surface of the lithium metal layer.

[0007] As one of these multifaceted attempts, so-called localized high-concentration electrolytes (LHCEs) have been recently proposed, which increase the concentration of lithium salt in the electrolyte while adding a non-solvent with relatively low solubility in the lithium salt (Chem Vol. 4, Issue 8, August 9, 2018, p. 1877-1892). These localized high-concentration salt electrolytes are expected to form high-concentration areas of lithium salts, thereby improving the output characteristics of lithium metal batteries. In addition, since the non-solvent surrounds the high-concentration areas of lithium salts, they are expected to suppress side reactions between the lithium metal layer and the electrolyte and improve the lifespan characteristics of lithium metal batteries.

[0008] In addition, many previous studies have reported that one approach to solving this problem is to form a solid electrolyte interphase (SEI) on the lithium electrode, which is composed of LiF, Li3N, etc., which are evaluated to have excellent physical properties while increasing the mobility of lithium ions on the lithium surface, and that this can significantly improve the battery life by suppressing the dendrite phase.

[0009] Meanwhile, LiNO3, which is well known to form a SEI of Li3N component on the lithium surface, can improve the lifespan by stabilizing the electrode interface when dissolved as an electrolyte additive, but due to its own solubility limitations, it is currently limited to use in low-concentration ether-based electrolytes.

[0010] Accordingly, the inventors of the present invention seek to overcome the solubility limitations of LiNO3 additives by applying an ionic dissociation-inducing additive to a lithium metal battery system. Furthermore, they aim to significantly improve battery life by suppressing dendrite formation.

[0011] In one embodiment of the present invention, an electrolyte comprising a lithium salt, a non-aqueous ether organic solvent, and an organic non-solvent; an SEI forming agent comprising LiNO3; and a dissociation-inducing additive; wherein the dissociation-inducing additive is an ionic additive having a fluorine group represented by the following chemical formula 1, and the cation (A) of the dissociation-inducing additive n+ ) NO3 - The binding force for lithium ions (Li + ) NO3 - Provided is an electrolyte composition for a lithium metal battery having a greater bonding strength than that of a lithium metal battery.

[0012] [Chemical Formula 1]

[0013] AF n

[0014] Here, A includes any one of Cu, Au, Ag, Pt, and Zn.

[0015] In one embodiment, the lithium salt may be dissolved in the electrolyte to have a concentration range of 2 to 5 M.

[0016] In one embodiment, the ether organic solvent may include one or more of dimethoxyethane (DME), 1,2-diethoxyethane (EGDEE), dimethyl ether, dibutyl ether, tetraglyme, and diglyme.

[0017] In one embodiment, the organic non-solvent may exhibit a solubility for the lithium salt that is at least 10 times lower than that of the non-aqueous organic solvent.

[0018] In one embodiment, the organic non-solvent may include at least one selected from the group consisting of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethylene glycol bis(1,1,2,2-tetrafluoroethyl) ether (TFEE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE), and ethoxynonafluorobutane (EOFB).

[0019] In one embodiment, the SEI forming agent may be included in an amount ranging from 0.5 to 1.5 wt% based on the total weight of the electrolyte for a lithium secondary battery.

[0020] In one embodiment, the dissociation-inducing additive may be included in an amount ranging from 0.3 to 1.0 wt% based on the total weight of the electrolyte for a lithium secondary battery.

[0021] In one embodiment, the dissociation-inducing additive may be included in an amount ranging from 0.4 to 0.6 wt% based on the total weight of the electrolyte for a lithium secondary battery.

[0022] In one embodiment, the SEI forming agent may be included in an amount of 0.5 to 1.5 wt%, and the dissociation inducing additive may be included in an amount of 0.5 to 1.0 wt%, based on the total weight of the electrolyte for a lithium secondary battery.

[0023] In another embodiment of the present invention, a lithium metal battery is provided, comprising: the electrolyte composition for the lithium metal battery described above; a lithium metal electrode; and an SEI layer formed on the lithium metal electrode; wherein the SEI layer includes LiF and Li3N.

[0024] As described above, the electrolyte composition for a lithium metal battery according to an embodiment of the present invention can overcome the solubility limitations of LiNO3 additives in a lithium metal battery system by applying an ionic dissociation-inducing additive. In particular, by adding a specific amount of an SEI forming agent and a dissociation-inducing additive, the composition promotes the dissolution of a heterogeneous SEI forming additive in a high-concentration salt ether electrolyte, and by itself participating in SEI formation, it can stabilize the lithium interface, thereby improving the battery life.

[0025] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0026] Figure 1 compares the cycle life performance (discharge capacity) of lithium metal batteries according to the presence or absence of an additive in the high-concentration salt ether electrolyte of Example 1 and Comparative Example 1 according to the present invention.

[0027] Figure 2 compares the cycle life performance (capacity retention rate compared to the initial cycle) of a lithium metal battery according to the effect of an additive for each electrolyte of Example 1 and Comparative Examples 2-3 according to the present invention.

[0028] Hereinafter, an electrolyte composition for a lithium metal battery according to a specific embodiment of the invention will be described.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036]

[0037] Electrolyte composition for lithium metal batteries

[0038] In one embodiment of the present invention, an electrolyte comprising a lithium salt, a non-aqueous ether organic solvent, and an organic non-solvent; an SEI forming agent comprising LiNO3; and a dissociation-inducing additive; wherein the dissociation-inducing additive is an ionic additive having a fluorine group represented by the following chemical formula 1, and the cation (A) of the dissociation-inducing additive n+ ) NO3 - The binding force for lithium ions (Li + ) NO3 - Provided is an electrolyte composition for a lithium metal battery having a greater bonding strength than that of a lithium metal battery.

[0039] [Chemical Formula 1]

[0040] AF n

[0041] Here, A includes any one of Cu, Au, Ag, Pt, and Zn.

[0042] The electrolyte of this embodiment may fall into the category of localized high-concentration electrolytes (LHCE), and may exhibit a high-concentration region in which a lithium salt is dissolved in a non-aqueous organic solvent at a high concentration during charging and discharging of a battery, and a form in which the organic non-solvent is distributed around the high-concentration region. Accordingly, when the electrolyte is used, the output characteristics of the battery may be improved due to the high-concentration distribution of the lithium salt. In addition, depending on the organic non-solvent distribution region, side reactions between the lithium metal layer and the electrolyte may be suppressed, and the life characteristics of a lithium metal secondary battery may be improved.

[0043] Specifically, the cation (A) of the ionic additive having a fluorine group n+ ) NO3 - The binding force for lithium ions (Li + ) and NO3 - When two ionic substances are added together, the sea cation is NO3 - It is coordinated by ions, and thus can promote the dissolution of LiNO3.

[0044] Therefore, the electrolyte composition according to an embodiment of the present invention may be significant in that it can function regardless of the concentration of the electrolyte, overcoming the existing limitation that it was applicable only to low-concentration ether electrolytes.

[0045] The lithium salt included in the above electrolyte is used as a medium for transferring ions in a lithium secondary battery, and a lithium salt that is generally widely used in electrolytes can be used. The lithium salt may be, for example, Li as a cation. + Including, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 -, PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - It may contain anions selected from the group consisting of: LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (C2F5SO2)2NLi, (SO2F)2NLi (i.e., LiFSI), (CF3SO2)2NLi (i.e., LiTFSI), (CF3SO2)3CLi, lithium chloroborane, lithium lower aliphatic carboxylic acid having 4 or fewer carbon atoms, lithium 4-phenylborate, and lithium imide, but are not limited thereto. The lithium salt is dissolved in a non-aqueous ether solvent and acts as a source of lithium ions to enable the basic operation of a lithium metal battery, and can play a role in promoting the movement of lithium ions between the positive electrode and the negative electrode.

[0046] In addition, in an exemplary embodiment, the non-aqueous ether-based organic solvent has high solubility in lithium salts, and may include, for example, one or more solvents selected from the group consisting of dimethoxyethane (DME), 1,2-diethoxyethane (EGDEE), dimethyl ether, dibutyl ether, tetraglyme, and diglyme. Meanwhile, carbonate-based solvents, which are widely used as electrolyte solvents, have a higher reduction potential than the non-aqueous ether-based solvents, and are thus easily reduced at the lithium metal negative electrode. Therefore, in the electrolyte composition for a lithium metal battery, the use of a non-aqueous ether-based solvent may be advantageous compared to a carbonate-based solvent.

[0047] Meanwhile, the electrolyte of the exemplary embodiment may include, in addition to the lithium salt and the non-aqueous ether organic solvent described above, an organic non-solvent that exhibits a solubility in the lithium salt that is 10 times or more, or 10 to 30 times less than that of the non-aqueous ether organic solvent, and thus does not substantially dissolve the lithium salt. Such an organic non-solvent may be defined as exhibiting substantially no solubility in the lithium salt, and being capable of dissolving the lithium salt only in a concentration of, for example, 0.1 M or less, or 0 to 0.1 M, or 0 to 0.05 M. In addition, the organic non-solvent may be an organic solvent that exhibits low solubility in the lithium salt and is miscible with the non-aqueous organic solvent.

[0048] In an exemplary embodiment, the organic non-solvent may include at least one selected from the group consisting of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethylene glycol bis(1,1,2,2-tetrafluoroethyl) ether (TFEE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE), and ethoxynonafluorobutane (EOFB).

[0049] These organic solvents can be selected by considering miscibility with the non-aqueous ether organic solvent and solubility according to the type / concentration of the lithium salt. For example, when dimethoxyethane (DME) is used as the non-aqueous ether organic solvent, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) can be appropriately used.

[0050] The electrolyte of an exemplary embodiment further including the organic non-solvent may include, as described above, a region in which a high concentration of lithium salt is locally present within a non-aqueous ether-based organic solvent, and an organic non-solvent distribution region in which a lithium salt is substantially absent. In this way, since a high concentration of lithium salt is locally present in a solvated form within the electrolyte, the output characteristics of a lithium secondary battery can be further improved, while an increase in viscosity and a decrease in fluidity of the electrolyte due to the organic non-solvent distribution region can be reduced.

[0051] The amount of the organic non-solvent used can be adjusted depending on the type of the non-aqueous ether-based organic solvent and the lithium salt, or the overall concentration of the lithium salt, and for example, the organic non-solvent: the non-aqueous ether-based organic solvent can be included in the electrolyte in a molar ratio of 1:0.4 to 1:1, or 1:0.4 to 1:0.67.

[0052] In an exemplary embodiment, the lithium salt may be dissolved in the electrolyte phase to have a concentration range of 2 to 5 M. For example, the concentration range may be 2.5 M or more, 3.0 M or more, 3.5 M or more, or 4.5 M or less, 4.0 M or less, or 3.5 M or less. Unlike conventional electrolyte compositions, the electrolyte composition according to an embodiment of the present invention can sufficiently dissolve the SEI forming agent even at a high salt concentration composition such as the above range, thereby stabilizing the electrode interface and improving the lifespan.

[0053] In an exemplary embodiment, the SEI forming agent may be included in an amount ranging from 0.5 to 1.5 wt% based on the total weight of the electrolyte for a lithium secondary battery. Within this range, an excellent battery life improvement effect may be achieved.

[0054] In an exemplary embodiment, the dissociation-inducing additive may be included in an amount of 0.3 to 1.0 wt% based on the total weight of the electrolyte for a lithium secondary battery. Specifically, it may be 0.4 wt% or more, 0.5 wt% or more, 0.4 wt% or more, or 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, or 0.6 wt% or less. For example, the dissociation-inducing additive may be included in an amount of more than 0.4 to 0.6 wt% based on the total weight of the electrolyte for a lithium secondary battery. When the dissociation-inducing additive is included in the above range, the solubility of the SEI forming agent may be improved. In particular, when the amount is added in an insufficient amount, the effect of improving the lifespan characteristics may be reduced, and when added in an excessive amount, there may be a problem with the solubility.

[0055] Meanwhile, in an exemplary embodiment, the SEI forming agent may be included in an amount of 0.5 to 1.5 wt%, and the dissociation-inducing additive may be included in an amount of 0.5 to 1.0 wt%, based on the total weight of the electrolyte for a lithium secondary battery. In this case, the SEI forming agent may have an excellent battery life-span improvement effect by improving the solubility of the SEI forming agent. However, if included in an excessive amount, the SEI forming agent may not dissolve and may precipitate.

[0056]

[0057] lithium metal battery

[0058] In another embodiment of the present invention, a lithium metal battery is provided, comprising: the electrolyte composition for the lithium metal battery described above; a lithium metal electrode; and an SEI layer formed on the lithium metal electrode; wherein the SEI layer includes LiF and Li3N.

[0059] In an exemplary embodiment, the lithium metal electrode may be a negative electrode including a lithium metal thin film or a lithium metal thin film formed on a negative electrode current collector, and may not have a structural difference from a generally known lithium metal negative electrode.

[0060] Specifically, the lithium metal negative electrode may be composed solely of a copper current collector having a thickness of 1 to 20 um, or may include a lithium metal layer coated on both sides or one side of the copper current collector to a thickness of 1 to 100 um, for example, 1 to 50 um.

[0061] In addition, the lithium metal battery according to the above exemplary embodiment may further include a positive electrode, wherein the positive electrode may not have a structural difference from a positive electrode of a lithium metal battery generally known in the art, and specifically may be a positive electrode including a positive electrode active material layer formed on a positive electrode current collector and including a lithium metal oxide.

[0062] Here, lithium metal oxide is generally known as a cathode active material, such as LiFePO4, LiCoO2, LiMn2O4, LiNiO2, LiNi 1-x Co x O2(0 <x<1), LiMnO2 등의 복합금속 산화물들을 사용할 수 있다.

[0063] Alternatively, the lithium metal oxide represented by the following chemical formula 1 may be used:

[0064] [Chemical Formula 1]

[0065] Li x MeM1 d O2

[0066] In the above chemical formula 1, M1 is Zr, Mg, Al, Ni, Mn, Zn, Fe, Cr, Mo, or W, and Me is represented by the following chemical formula 2,

[0067] [Chemical Formula 2]

[0068] Ni a Co b Mn c

[0069] In the above chemical formulas 1 and 2, 0.97≤x≤1.03, 0.50≤a≤0.90, 0 <b≤0.3, 0<c≤0.3, 0≤d<0.01이고, a+b+c+d = 1이다.

[0070] The lithium metal oxide represented by the above chemical formula 1 is a cathode active material known as NCM, which has a layered structure in its crystal structure, and is similar to LiCoO2, LiMn2O4, LiNiO2, and LiNi listed above. 1-x Co x O2(0 <x<1), LiMnO2 등의 복합금속 산화물들에 대비하여 에너지 밀도가 높은 것일 수 있다.

[0071] More specifically, in the above chemical formula 2, the higher the value of a within the above range, the more it can contribute to improving the output of the battery, but the exemplary implementation examples are not limited thereto.

[0072] Regardless of the composition of the lithium metal oxide, one having a coating layer on its surface may be used, or a compound having the lithium metal oxide and a coating layer may be mixed and used. The coating layer may include, as a coating element compound, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compounds forming these coating layers may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as it can coat the compound with these elements without adversely affecting the properties of the positive electrode active material (for example, spray coating, dipping, etc.), and since this is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0073] The positive electrode active material layer of the above exemplary embodiment may further include an irreversible compensating positive electrode material. The irreversible compensating additive may supply lithium ions onto a single layer of the negative electrode current collector by desorbing lithium ions during the initial charge of the lithium secondary battery, and the irreversible compensating additive from which lithium ions are desorbed may be converted into an irreversible phase so as not to absorb lithium ions. Here, the irreversible compensating additive may be at least one selected from the group including the generally known Li2NiO2, Li2CuO2, Li6CoO4, Li5FeO4, Li6MnO4, Li2MoO3, Li3N, Li2O, LiOH, and Li2CO3. The irreversible compensating additive may be included in a range of 1 to 50 wt% of the total weight of the positive electrode active material, but the present invention is not limited thereto.

[0074] The positive active material layer of the above exemplary embodiment may further include a binder, a conductive material, a filler, etc., as the case may be.

[0075] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0076] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0077] The lithium metal battery according to the above exemplary embodiment may further include a separator formed between the negative electrode and the positive electrode.

[0078] For example, the electrolyte composition for the lithium metal battery described above may be impregnated into the separator, which may mean, for example, that the electrolyte is positioned in pores within the separator.

[0079] In an exemplary embodiment, the electrolyte composition may be impregnated into a porous separator positioned between the negative electrode and the positive electrode. Here, the porous separator may be any separator typically used in lithium batteries, as long as it separates the negative electrode and the positive electrode and provides a passage for lithium ions. Specifically, any porous separator with low resistance to ion movement and excellent electrolyte retention capacity may be used.

[0080] For example, it may be 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, in lithium-ion batteries, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used, and a separator containing or coated with a ceramic component or polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0081] In an exemplary embodiment, a solid electrolyte interface film (SEI layer) may be formed on the lithium metal electrode, and the solid electrolyte interface film may be formed by a reaction on the surface of the negative electrode active material through the initial charging process of the solid electrolyte battery, thereby preventing degradation of the negative electrode and thereby improving the life characteristics of the battery.

[0082] Specifically, the solid electrolyte interfacial film may have a thickness range of 10 nm to 1 μm. The thickness of the solid electrolyte interfacial film may vary depending on the content of the SEI forming agent and the dissociation-inducing additive in the electrolyte composition for a lithium metal battery. When applying the electrolyte composition according to an embodiment of the present invention, the solid electrolyte interfacial film may be formed on the lithium metal electrode in an optimal thickness range, for example, a thickness range of 10 to 30 nm or a thickness range of 15 to 25 nm, thereby realizing excellent battery life characteristics, etc.

[0083] In an exemplary embodiment, the SEI layer may include LiF and Li3N. In particular, the anion (F) of the dissociation-inducing additive - ) can react with a lithium negative electrode after dissociation to form an SEI layer rich in Li3N and LiF. The SEI layer contains components of LiF and Li3N, and has superior mechanical properties compared to the existing native SEI, can be maintained uniformly, induces uniform lithium deposition, and is chemically stable, reducing reduction of byproducts in the reduction voltage range (<3.0), thereby protecting the lithium negative electrode.

[0084]

[0085] Example

[0086] 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.

[0087]

[0088] Comparative Example 1

[0089] A high-concentration lithium salt ether electrolyte was prepared so that the molar ratio was LiFSI: DME: TTE = 1 mol: 2.4 mol: 2.4 mol. That is, the LiFSI salt was dissolved in the DME / TTE solvent at 4.62 m.

[0090]

[0091] Comparative Example 2

[0092] LiPF6 was dissolved in a 1 M concentration in a 1:1 (v:v) solvent mixture of EC:DEC. 1 wt% VC and 10 wt% FEC were added as additives, 1 wt% LiNO3 as an SEI forming agent, and 0.2 wt% CuF2 as a dissociation inducing additive, and the mixture was sufficiently stirred to prepare an electrolyte composition.

[0093]

[0094] Comparative Example 3

[0095] In the ether-based electrolyte of Comparative Example 1, 1 wt% LiNO3 as an SEI forming agent and 0.2 wt% CuF2 as a dissociation-inducing additive were added, and the mixture was sufficiently stirred to prepare an electrolyte composition.

[0096]

[0097] Example 1

[0098] An electrolyte composition was prepared in the same manner as in Comparative Example 1, except that 1 wt% LiNO3 was added as an SEI forming agent and 0.5 wt% CuF2 was added as a dissociation-inducing additive.

[0099]

[0100] Experimental Example 1: Battery Life Characteristics

[0101] 1) Coin cells (2032 standard) using the electrolyte compositions of Comparative Example 1 and Example 1 were manufactured, and charge / discharge tests were performed. Specifically, LFP (purchased from LG Energy Solution) was positioned as a working electrode, and lithium with a thickness of 45 μm was positioned as a counter electrode so that they faced each other, and a polyethylene (PE) separator was interposed between the two electrodes. Then, 60 μL of the electrolyte compositions of Comparative Example 1 and Example 1 were each injected and sealed to manufacture 2032 coin-type LFP|Li full cell samples. For the manufactured cells, the first two cycles were pre-activated under 0.1C / 0.1C conditions, and thereafter, 0.5C charge and 0.5C discharge cycles were repeated, and the discharge capacity according to time (cycle) was measured, and the results are shown in Fig. 1.

[0102] Referring to Fig. 1, in the case of a high-concentration lithium salt ether electrolyte, it can be confirmed that in Example 1, in which an SEI forming agent (LiNO3) and a dissociation-inducing additive (CuF2) were added, a stable SEI of LiF and Li3N components that are advantageous to the lithium negative electrode was formed, thereby reducing side reactions with the electrolyte and suppressing dendritic lithium deposition, resulting in better life characteristics.

[0103] 2) In addition, when an SEI forming agent (LiNO3) and a dissociation-inducing additive (CuF2) were added, the retention rate was measured in charge / discharge cycles under the same conditions according to the salt concentration and the amount of additive, and the results were shown in Fig. 2.

[0104] Referring to Fig. 2, in the case of Comparative Example 2, which applied a low-concentration salt carbonate electrolyte with the solvent and additive composition (1.0 wt% LiNO3, 0.2 wt% CuF2) of the preceding research conditions, the capacity retention rate decreased rapidly within 100 cycles. In the case of Comparative Example 3, which applied the same additive composition to a high-concentration lithium salt ether electrolyte, it was confirmed that the capacity retention rate also decreased within 300 cycles. On the other hand, in Example 1, a high-concentration lithium salt ether electrolyte in which the dissociation-inducing additive was increased to 0.5 wt%, it was confirmed that the cell life was improved by showing a capacity retention rate of 70% or more within about 400 cycles.

[0105]

[0106] 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. An electrolyte comprising a lithium salt, a non-aqueous ether-based organic solvent, and an organic non-solvent; SEI forming agent including LiNO3; and Contains Harry Inducing Additives; The above dissociation-inducing additive is an ionic additive having a fluorine group represented by the following chemical formula 1, and the cation (A) of the dissociation-inducing additive n+ ) NO3 - The binding force for lithium ions (Li + ) NO3 - An electrolyte composition for a lithium metal battery having a greater bonding strength than that of a lithium metal battery. [Chemical Formula 1] OF n Here, A includes any one of Cu, Au, Ag, Pt, and Zn.

2. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the lithium salt is dissolved in the electrolyte and has a concentration range of 2 to 5 M.

3. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the ether-based organic solvent comprises at least one solvent selected from the group consisting of dimethoxyethane (DME), 1,2-diethoxyethane (EGDEE), dimethyl ether, dibutyl ether, tetraglyme, and diglyme.

4. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the organic non-solvent exhibits a solubility in a lithium salt that is at least 10 times lower than that of the non-aqueous organic solvent.

5. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the organic non-solvent comprises at least one selected from the group consisting of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethylene glycol bis(1,1,2,2-tetrafluoroethyl) ether (TFEE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE), and ethoxynonafluorobutane (EOFB).

6. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the SEI forming agent is included in an amount of 0.5 to 1.5 wt% based on the total weight of the electrolyte for a lithium secondary battery.

7. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the above-mentioned dissociation-inducing additive is included in an amount of 0.3 to 1.0 wt% based on the total weight of the electrolyte for a lithium secondary battery.

8. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the above-mentioned dissociation-inducing additive is included in an amount ranging from 0.4 to 0.6 wt% based on the total weight of the electrolyte for a lithium secondary battery.

9. In paragraph 1, An electrolyte composition for a lithium metal battery, wherein the SEI forming agent is included in an amount of 0.5 to 1.5 wt% and the dissociation inducing additive is included in an amount of 0.5 to 1.0 wt%, based on the total weight of the electrolyte for a lithium secondary battery.

10. An electrolyte composition for a lithium metal battery according to any one of claims 1 to 9; lithium metal electrode; and It includes an SEI layer formed on the lithium metal electrode; A lithium metal battery, wherein the SEI layer comprises LiF and Li3N.

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