Electrolyte and lithium secondary battery comprising same

Abstract

The present disclosure relates to an electrolyte and a lithium secondary battery comprising same. The electrolyte according to the present disclosure comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer, wherein the fluoroacrylic monomer contains 7 or more fluorine atoms. The lithium secondary battery may comprise a positive electrode, a negative electrode including a negative electrode current collector, and the electrolyte according to the present disclosure disposed between the positive electrode and the negative electrode.

Description

Electrolyte and lithium secondary battery containing the same

[0001] The present disclosure relates to an electrolyte and a lithium secondary battery comprising the same.

[0002]

[0003] The demand for high-energy-density rechargeable batteries continues to increase due to the expansion of the electric vehicle market and the need for longer-lasting portable electronic devices. Lithium metal batteries (LMBs) are highly attractive candidates as next-generation energy storage devices due to the high theoretical capacity and low electrochemical potential of the lithium metal anode.

[0004] Conventional liquid electrolytes generally consist of flammable organic carbonate-based solvents. This inherent flammability, combined with the high reactivity of lithium metal, poses a serious risk of thermal runaway, particularly in the event of an internal short circuit. While some improved liquid electrolytes have been developed, they often offer only limited improvements in cycle life and do not completely resolve safety concerns.

[0005] Therefore, there is a need for research on advanced electrolyte systems that can enable the formation of a stable, uniform, and protective solid electrolyte interface (SEI) on the cathode to suppress dendrite growth, improve cycling stability and Coulomb efficiency, and enhance the overall safety of anode-free lithium secondary batteries.

[0006] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art.

[0007]

[0008] The problem that the present invention aims to solve is to provide an electrolyte and a lithium secondary battery containing the same to solve the above-mentioned problems.

[0009] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0010]

[0011] According to one embodiment, the electrolyte comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer, and the fluoroacrylic monomer may comprise seven or more fluorine atoms.

[0012] According to one embodiment, a lithium secondary battery comprises a positive electrode; a negative electrode including a negative electrode current collector; and an electrolyte disposed between the positive electrode and the negative electrode, wherein the electrolyte comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer, and the fluoroacrylic monomer may comprise seven or more fluorine atoms.

[0013]

[0014] An electrolyte according to some embodiments of the present disclosure comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer, thereby including ester groups and CF x It acts as an amphiphilic site for lithium cations to promote a uniform lithium-ion flux distribution and effectively prevent localized hotspots and dendrite growth. In addition, it accommodates volume changes during lithium metal deposition and desorption, allowing for denser and more uniform lithium deposition.

[0015] According to some embodiments of the present disclosure, by including a copolymer formed from a fluoroacrylic monomer containing seven or more fluorine atoms as the electrolyte, it is possible to easily realize a lithium secondary battery that controls the initial nucleation process and thereby improves cycling performance. In addition, the abundant CF bonds can easily form a dynamically evolving Li-F-rich solid electrolyte interface (SEI) to protect the lithium metal and prevent excessive electrolyte consumption by enhancing coordination ability. Accordingly, charge transfer resistance can be reduced, the morphology and density of deposited lithium can be improved, and lithium cracking can be suppressed.

[0016] A lithium secondary battery according to some embodiments of the present disclosure may have improved cycling performance and excellent thermal stability.

[0017] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0018]

[0019] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0020] FIG. 1 is a drawing showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0021] Figure 2 is a diagram showing the stacked structure of the lithium secondary battery of Figure 1 after charging.

[0022] FIG. 3 is a drawing showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0023] FIG. 4 is a drawing illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0024] FIG. 5 is a drawing illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0025] FIG. 6 is a drawing illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0026] FIG. 7 is a drawing illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0027] Figure 8 is an image showing the contact angle of the electrolytes of the example and comparative example according to the evaluation example.

[0028] Figure 9 is an image showing the capacity retention rates of the example and comparative example according to the evaluation example.

[0029] Figure 10 is an image of the SEI layer of the lithium secondary battery of the example, comparative example, and reference example taken by cryo-TEM according to the evaluation example.

[0030] Figure 11 is an image of the negative electrode surface of a lithium secondary battery of an example, a comparative example, and a reference example taken with an SEM according to the evaluation example.

[0031] FIG. 12 is an image of the negative electrode surface of the lithium secondary battery of the example, comparative example, and reference example taken with FIB-SEM according to the evaluation example.

[0032]

[0033] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0034] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0035] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0036] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0037] Methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0038] In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof.

[0039] In this specification, the term “and / or” means any combination of one or more items described in relation and all combinations thereof. In this specification, the term “or” means “and / or”.

[0040] In this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is directly above the other part, but also cases where there is another part in between.

[0041] In this specification, terms such as "first," "second," etc., may be used to describe various components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another.

[0042] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state. In this specification, “alloy” means a mixture of two or more metals.

[0043] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation. In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0044] In this specification, "lithiation" and "to lithiate" refer to the process of adding lithium to a specific substance or compound. In this specification, "delithiation" and "to delithiate" refer to the process of removing lithium from a specific substance or compound.

[0045] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery. In this specification, "discharge" and "to discharge" refer to the process of removing electrochemical energy from a battery.

[0046] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process. In this specification, "negative electrode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0047] Exemplary embodiments will be described in more detail below.

[0048] Embodiments of the present invention relate to an electrolyte for use in lithium secondary batteries, particularly anode-free and lithium-metal batteries, and a battery comprising such electrolyte. The electrolyte of the present invention can form a very stable solid electrolyte interface (SEI) on the surface of the anode, and can easily realize a lithium secondary battery with improved cycle stability, Coulomb efficiency, and safety.

[0049] To address the problems of inferior cycle life and thermal instability caused by unstable cathode morphology and parasitic reactions in lithium secondary batteries, embodiments of the present invention provide an electrolyte comprising an in-situ polymer formed from an amphiphilic fluoroacrylic monomer functioning as a surfactant. The polymer can create a localized high-concentration environment within the gel matrix by utilizing the synergistic effect of a network-forming branched acrylic monomer and a fluoroacrylic monomer. This induces an anion-rich solvation structure, and consequently, the anion-derived SEI can significantly promote the reversibility of lithium deposition and stripping, increase cycle life, and improve the thermal stability of the electrolyte.

[0050]

[0051] electrolytes

[0052] In one embodiment, the electrolyte comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer. The fluoroacrylic monomer comprises seven or more fluorine atoms. An electrolyte according to some embodiments of the present disclosure comprises a copolymer of an acrylic monomer and a fluoroacrylic monomer, thereby comprising ester groups and CF xThe giga acts as an amphiphilic site for lithium cations, promoting a uniform lithium-ion flux distribution and effectively preventing localized hotspots and dendrite growth. Furthermore, it accommodates volume changes during lithium metal deposition and desorption, enabling denser and more uniform lithium deposition. Approximately 1640 cm⁻¹ exists in the monomer. - The characteristic C=C bond peak of ¹ is significantly reduced after the heating and gelation process, indicating complete polymerization.

[0053] According to some embodiments of the present disclosure, by including a copolymer formed from a fluoroacrylic monomer containing seven or more fluorine atoms as the electrolyte, it is possible to easily realize a lithium secondary battery that controls the initial nucleation process and thereby improves cycling performance. In addition, the abundant CF bonds can easily form a dynamically evolving Li-F-rich solid electrolyte interface (SEI) to protect the lithium metal and prevent excessive electrolyte consumption by enhancing coordination ability. Accordingly, charge transfer resistance can be reduced, the morphology and density of deposited lithium can be improved, and lithium cracking can be suppressed.

[0054] In one embodiment, the acrylic monomer can act as a cross-linker. The fluoroacrylic monomer can act as a surfactant. The fluoroacrylic monomer may have an amphiphilic structure having a lithium-philic acrylate "head" portion and a lithium-sparing fluorocarbon "tail" portion.

[0055] Acrylic and fluoroacrylic monomers can form copolymers through an in-situ polymerization process. During in-situ polymerization, fluoroacrylic monomers can be incorporated into the gel network via lithium-friendly acrylate head portions, while lithium-friendly tails can aggregate via perfluorocarbon interactions. This configuration can physically separate the liquid electrolyte into multiple nanoscale regions, creating localized high-concentration environments within the gel network. This can form anion-rich solvation structures around lithium ions. These anion-rich solvation structures can facilitate the formation of inorganic lithium compounds, such as LiF and Li2O, within the SEI at the cathode during battery operation. Inorganic-rich SEIs with high Young's modulus are mechanically strong, which can inhibit lithium dendrite growth and facilitate the formation of higher chemical stability and lower Li diffusion barriers.

[0056] In addition to repulsion from the electrolyte, the sodium fluorocarbon tails of fluoroacrylic monomers tend to aggregate, so they have amphiphilic properties. When the fluoroacrylic monomer has fewer than 7 fluorine atoms, such aggregation is not observed.

[0057] After the copolymer of acrylic monomers and fluoroacrylic monomers is gelled, a cross-linked polymer network can be formed. The cross-linked polymer network can have a porous structure and can create a localized high-concentration environment within each nanoscale pore. Accordingly, an anion-rich solvation structure can be easily formed.

[0058] The spectrum of the lithium salt anion can be deconvolved to determine the ratio of free anions (FA), contact ion pairs (CIP), and ion aggregates (AGG). The ratio of AGG anions increases with longer fluorocarbon chains. The polymer of the present invention exhibits an anion-rich solvation structure by having a higher AGG ratio, and when surfactant molecules with long fluorocarbon chains are incorporated into the gel electrolyte, the anions can preferentially coordinate with lithium cations.

[0059] It can be confirmed that the polymer of the present invention exhibits stronger anion-Li interactions in anion-rich solvation environments, as the electron density around the Li nucleus increases due to stronger shielding by coordination anions.

[0060] The anion-derived SEI formed from the electrolyte of the present invention promotes interfacial charge transfer and may have lower charge transfer resistance. Due to the lower charge transfer resistance, the Coulomb efficiency (CE), which measures the reversibility of lithium plating and deplating, can be increased. Long fluorocarbon chains of fluoroacrylic monomers can improve the reversibility of the lithium cathode. Fluorine-rich domains with a size of 50 nm to 100 nm may be abundantly present on the surface of the SEI. Fluorine-rich SEIs can regulate interfacial charge transfer and lead to smoother and denser lithium deposition. Due to the combination of a high LiF content in the SEI, appropriate domain size, and appropriate lithium density, a battery with excellent cycle performance can be easily realized.

[0061] The lithium secondary battery of the present invention may have excellent thermal stability as a higher concentration of fluorine radicals generated during heating acts as a flame retardant.

[0062] In one embodiment, the fluoroacrylic monomer may include 1H,1H,2H,2H-heptadecafluorodecyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-nonafluorohexyl (meth)acrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl (meth)acrylate, or 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henecosafluorododecyl (meth)acrylate. By selecting the type of fluoromonomer as described above, a uniform lithium-ion flux distribution can be promoted and localized hotspots and dendrite growth can be effectively prevented.

[0063] In one embodiment, the weight of the fluoroacrylic monomer may be 0.1 wt% or more and 20 wt% or less of the electrolyte. For example, the weight of the fluoroacrylic monomer may be 0.5 wt% or more and 15 wt% or less of the electrolyte, 1 wt% or more and 10 wt% or less, 1.5 wt% or more and 5 wt% or less, 2.0 wt% or more and 3 wt% or less, 0.1 wt% or more and 2.5 wt% or less, or 2.5 wt% or more and 3.0 wt% or less. By controlling the content of the fluoroacrylic monomer to the aforementioned range, a uniform lithium-ion flux distribution can be promoted, and localized hotspots and dendrite growth can be effectively prevented. The weight of the fluoroacrylic monomer may be 2.0 wt% or more and 3.0 wt% or less of the electrolyte.

[0064] In one embodiment, the acrylic monomer may include PETTA (pentaerythritol tetraacrylate), TMPTMA (trimethylolpropane trimethacrylate), DPHA (dipentaerythritol hexacrylate), or a combination thereof. By selecting the type of acrylic monomer as described above, a copolymer can be easily formed by effectively crosslinking. Accordingly, a lithium secondary battery with excellent Coulomb efficiency, cycle performance, and thermal stability can be easily realized.

[0065] In one embodiment, the weight of the acrylic monomer may be 0.1 wt% or more and 20 wt% or less of the electrolyte. For example, the weight of the acrylic monomer may be 0.5 wt% or more and 15 wt% or less of the electrolyte, 1 wt% or more and 10 wt% or less, 1.5 wt% or more and 5 wt% or less, 2.0 wt% or more and 3 wt% or less, 0.1 wt% or more and 2.5 wt% or less, or 2.5 wt% or more and 3.0 wt% or less. By controlling the content of the acrylic monomer to the aforementioned range, a copolymer can be easily formed by effectively crosslinking. Accordingly, a lithium secondary battery with excellent Coulomb efficiency, cycle performance, and thermal stability can be easily realized. The weight of the acrylic monomer may be 2.0 wt% or more and 3.0 wt% or less of the electrolyte.

[0066] In one embodiment, the weight ratio of the fluoroacrylic monomer and the acrylic monomer may be 3:7 to 7:3. For example, the weight ratio of the fluoroacrylic monomer and the acrylic monomer may be 3.2:6.8 to 6.8:3.2, 3.5:6.5 to 6.5:3.5, 3.7:6.3 to 6.3:3.7, or 4:6 to 6:4. By adjusting the weight ratio of the fluoroacrylic monomer and the acrylic monomer to the aforementioned range, a uniform lithium-ion flux distribution can be promoted, and localized hotspots and dendrite growth can be effectively prevented.

[0067] An electrolyte according to one embodiment of the present disclosure may include a lithium salt and an organic solvent. A gel polymer electrolyte may be formed as the cross-linked polymer is impregnated by the liquid electrolyte.

[0068] The lithium salt may include LiPF6, LiBF4, LiTFSI, LiFSI, LiDFOB, LiBOB, or a combination thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0069] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0070] The electrolyte may include, for example, an organic electrolyte. The organic electrolyte is prepared, for example, by dissolving a lithium salt in an organic solvent. For example, the organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof. In one embodiment, the organic solvent may include a carbonate-based solvent.

[0071] Carbonate-based solvents such as fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) may be used.

[0072] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0073] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0074] Cyclohexanone and the like can be used as ketone-based solvents. Ethyl alcohol and isopropyl alcohol and the like can be used as alcohol-based solvents, and nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group) and amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes and the like can be used as aprotic solvents.

[0075] Or, the organic solvent is, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof.

[0076] Solid electrolytes are, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0077] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge)2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 It is one or more selected from (M = Te, Nb, or Zr, where x is an integer from 1 to 10). Solid electrolytes are produced by sintering methods, etc. For example, oxide-based solid electrolytes include Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a MaO 12 It is a garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0078] Sulfide-based solid electrolytes may comprise, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or combinations thereof. Sulfide-based solid electrolyte particles may comprise Li2S, P2S5, SiS2, GeS2, B2S3, or combinations thereof. Sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles have high lithium ion conductivity compared to other inorganic compounds. For example, sulfide-based solid electrolytes comprise Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte comprises Li2S-P2S5, the mixed molar ratio of Li2S to P2S5 may be, for example, in the range of about 50:50 to about 90:10. Additionally, Li3PO4, halogens, halogen compounds, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x("LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75 An inorganic solid electrolyte prepared by adding S4 ("ThioLISICON"), Li2O-Al2O3-TiO2-P2O5 ("LATP"), etc., to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiX (X = halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다.

[0079] In addition, a calcination process may be performed after the above treatment. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0080] Polymer solid electrolytes are electrolytes that, for example, contain a mixture of a lithium salt and a polymer, or contain a polymer having ion-conducting functional groups. Polymer solid electrolytes are, for example, polymer electrolytes that do not contain a liquid electrolyte.The polymers included in the polymeric solid electrolyte are, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone), SPEEK, sulfonated poly(arylene ether ketone ketone sulfone), SPAEKKS), sulfonated poly(aryl ether ketone, SPAEK), poly[bis(benzimidazobenzisoquinolinones)], SPBIBI), polystyrene sulfonate (PSS), lithium 9,10-diphenylatlasene-2-sulfonate (lithium It may be 9,10-diphenylanthracene-2-sulfonate, DPASLi+) or a combination thereof, but is not limited to these, and any polymer electrolyte used in the relevant technical field is acceptable.Any lithium salt that can be used as a lithium salt in the relevant technical field is acceptable. Examples of lithium salts include LiDFOB, LiTFSI, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C. x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are each 1 to 20), LiCl, LiI, or mixtures thereof, etc.

[0081] A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is an electrolyte that includes, for example, a liquid electrolyte and a polymer, or includes an organic solvent and a polymer having ion-conducting functional groups. The liquid electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt in a liquid state at room temperature or a room temperature molten salt that has a melting point below room temperature and consists solely of ions. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl- , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include one or more compounds selected from those containing one or more anions selected from among. A gel polymer electrolyte may be formed by impregnating the polymer solid electrolyte into the electrolyte in a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0082] Crosslinked polymers can be selected from among the polymers used in solid polymer electrolytes. Crosslinked polymers can act as crosslinking agents. That is, by forming a polymer network with a three-dimensional structure, crosslinked polymers can improve mechanical strength and chemical stability while maintaining the ionic conductivity of the gel electrolyte.

[0083] The cross-linked polymer may have a molecular weight of 5,000 g / mol or less. The cross-linked polymer may include, for example, an acrylic monomer having three or more reactive functional groups, a fluorinated acrylic monomer, or a combination thereof.

[0084] Crosslinked polymers can contain two or more reactive double bonds within a single molecule. The cross-linked polymer is a polymerization product of cross-linkable monomers, and the cross-linkable monomers are dipentaerythritol hexaacrylate (DPHA), trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), diethylene glycol diacrylate (DEGDA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol diacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dianol diacrylate (DDA), and dianol dimethacrylate (DDMA), Ethoxylated trimethylolpropane triacrylate (ETPTA), acrylate-functionalized ethylene oxide, butanediol dimethacrylate, ethoxylated neopentyl glycol diacrylate (NPEOGDA), propoxylated neopentyl glycol diacrylate (NPPOGDA), pentaerythritol triacrylate (PETA), ethoxylated propoxylated trimethylolpropane triacrylate (TMPEOTA) / (TMPPOTA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), pentaerythritol tetraacrylate (PETTA), Dipentaerythritol pentaacrylate (DPEPA),It may include at least one selected from the group consisting of ditrimethylol propane tetraacrylate (DTMPTTA), diglycidyl ester, acrylamide, divinylbenzene, and combinations thereof.

[0085] The weight-average molecular weight of the crosslinkable monomer may be 200 to 2,000, 200 to 1,000, for example, 200 to 500. If the weight-average molecular weight is less than 200, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be excessively high, which may restrict the free movement of the lithium salt, and if it is greater than 2,000, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be excessively low, which may reduce the electrolyte blocking ability.

[0086] A polymer solid electrolyte can form a gel polymer electrolyte by impregnating the electrolyte in a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0087]

[0088] lithium secondary battery

[0089] FIG. 1 is a drawing showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure. FIG. 2 is a drawing showing a stacked structure of the lithium secondary battery of FIG. 1 after charging. FIG. 3 is a drawing showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0090] FIG. 1 is a drawing showing a stacked structure of a lithium secondary battery (100) in which a negative active material layer is absent on a negative current collector (140), and FIG. 2 may correspond to a drawing showing the appearance of lithium metal being deposited on the negative current collector (140) as the lithium secondary battery (100) of FIG. 1 is charged. FIG. 3 may correspond to a drawing showing a lithium secondary battery (300) further including a lithium metal layer (350) disposed between a negative current collector (340) and an electrolyte (360). The thickness of each layer shown in FIG. 1 to FIG. 3 is shown as an arbitrary size and is not necessarily limited thereto.

[0091] Referring to FIGS. 1 to 3, a lithium secondary battery (100, 300) according to one embodiment of the present disclosure may include a positive electrode (130, 330) for a lithium secondary battery, a negative electrode including a negative current collector (140, 340), a separator (not shown) interposed between the positive electrode (130, 330) and the negative electrode, and an electrolyte (160, 360) disposed between the positive electrode (130, 330) and the negative electrode. The positive electrode (130, 330) may include a positive current collector (110, 310) and a positive composite layer (120, 320) disposed on the positive current collector (110, 310). The electrolyte (160, 360) may include a cross-linked polymer and a liquid electrolyte.

[0092] Referring to FIGS. 1 and 2, a lithium secondary battery (100) according to one embodiment of the present disclosure may have a negative active material layer on a negative current collector (140). In a lithium secondary battery (100) according to one embodiment, a lithium metal layer (150) may be formed on the negative current collector (140) after charging. The lithium metal layer (150) may be disposed between the negative current collector (140) and the electrolyte (160). For example, the lithium metal layer (150) may be a lithium electrodeposited layer.

[0093] Referring to FIG. 3, a lithium secondary battery (300) according to one embodiment of the present disclosure may further include a lithium metal layer (350) disposed between a negative electrode current collector (340) and an electrolyte (360). For example, the lithium secondary battery (300) may include a negative electrode current collector (340), a lithium metal layer (350) disposed on the negative electrode current collector (340), a positive electrode (130), and an electrolyte (360) disposed between the positive electrode (130) and the lithium metal layer (350).

[0094] The lithium metal layer (350) may include lithium metal or a lithium alloy. During the discharge process, the lithium metal layer (350) may dissociate into lithium ions and metal cations, thereby reducing the thickness of the lithium metal layer (350). During the charging process, lithium ions may be electrodeposited, thereby increasing the thickness of the lithium metal layer (350).

[0095] Referring to FIGS. 1 to 3, a lithium secondary battery (100, 300) including an electrolyte (160, 360) may further include a protective layer (not shown) disposed between a negative electrode and the electrolyte (160, 360). For example, the protective layer may be formed between a negative electrode current collector (140, 340) and the electrolyte (160, 360). Alternatively, the protective layer may be formed between a lithium metal layer (150, 350) and the electrolyte (360). According to one embodiment, the protective layer of the lithium secondary battery (100, 300) comprises an inorganic oxide, and the electrolyte (160, 360) may be disposed between the protective layer and the positive electrode (130, 330).

[0096] According to one embodiment, one or more stacked structures of the lithium secondary battery (100, 300) as described above may be stacked or wound and accommodated in a case, and the case may be classified into cylindrical, prismatic, thin film, coin, pin type, etc.

[0097] FIGS. 4 to 7 illustrate a lithium secondary battery according to one embodiment, where FIG. 4 is cylindrical, FIG. 5 is prismatic, and FIGS. 6 and 7 are pouch-type batteries. Referring to FIGS. 4 to 7, the lithium secondary battery (1) includes a battery structure (7, electrode assembly) having a separator (4, separator) interposed between a positive electrode (3) and a negative electrode (2), and a case (5) in which the battery structure (7) is housed. The positive electrode (3), the negative electrode (2), and the separator (4) may be impregnated with an electrolyte (not shown). The lithium secondary battery (1) may include an assembly (6, sealing member) that seals the case (5) as in FIG. 4. Additionally, in FIG. 5, the lithium secondary battery (1) may include a positive lead tab (3') and a positive terminal (3"), a negative lead tab (2') and a negative terminal (2"). As shown in FIGS. 6 and 7, the lithium secondary battery (1) may include electrode tabs (70), namely a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical passages for inducing current formed in the battery structure (7) to the outside.

[0098] Referring to FIG. 4, a lithium secondary battery (1) according to one embodiment includes the anode (3), the cathode (2), and the separator (4) described above. The anode (3), the cathode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5) and sealed with a cap assembly (6) to complete the lithium secondary battery (1). The case (5) is cylindrical but is not necessarily limited to this shape and may be, for example, prismatic, thin film, etc.

[0099] Referring to FIG. 5, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound, folded, or stacked to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5), cross-linked, and sealed to complete the lithium secondary battery (1). The case (5) is prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc. A positive lead tab (3') and a positive terminal (3") are electrically connected to the positive electrode (3). A negative lead tab (2') and a negative terminal (2") are electrically connected to the negative electrode (2).

[0100] Referring to FIG. 6, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is housed in a case (5). It may include an electrode tab (70) that serves as an electrical path for inducing the current formed in the battery structure (7) to the outside. An electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0101] Referring to FIG. 7, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2) and a separator (4) as described above. An electrolyte as described above, including a separator (4), is disposed between the positive electrode (3) and the negative electrode (2) to form a battery structure. For example, the battery structure (7) is stacked in a bicell structure and then housed in a case (5). It may include a positive electrode tab (71) and a negative electrode tab (72) that serve as electrical pathways for inducing current formed in the battery structure (7) to the outside. The electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0102] However, the present invention is not limited to this, and the case (5) may be configured in various shapes such as circular or pouch type. For example, the pouch-type lithium secondary battery corresponds to the lithium secondary battery (1) of FIGS. 4 to 7 in which a pouch is used as the case (5). The pouch-type lithium secondary battery includes one or more battery structures (7). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2) to form the battery structure (7). The battery structure (7) is stacked in a bicell structure, then impregnated with an electrolyte, and then housed and sealed in a pouch to complete the pouch-type lithium secondary battery.

[0103] Specifically, the battery structure (7) including the aforementioned positive electrode (3), negative electrode (2), and separator (4) is simply stacked and contained in a pouch, or wound into a jelly roll shape or folded and contained in a pouch. Subsequently, an electrolyte is injected into the pouch and sealed to complete the lithium secondary battery (1).

[0104] The case (5) may be made of metal such as aluminum, aluminum alloy, nickel-plated steel, or a laminate film or plastic that constitutes the pouch.

[0105] Lithium secondary battery (1) has excellent lifespan characteristics and high rate characteristics, so it is used in, for example, electric vehicles (EV). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEV). In addition, it is used in fields where a large amount of power storage is required. For example, it is used in electric bicycles, power tools, etc.

[0106] A plurality of lithium secondary batteries (1) are stacked to form a battery module, and a plurality of battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. A battery module includes, for example, a plurality of batteries and a frame that holds them.

[0107] A battery pack includes, for example, a plurality of battery modules and a bus bar connecting them. The battery modules and / or battery pack may further include a cooling device. A plurality of battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0108]

[0109] Cathode: Cathode current collector

[0110] Referring to FIGS. 1 to 3, the negative current collector (140, 340) may not include a negative active material layer. In the negative current collector (140, 340) that does not include a negative active material layer, lithium metal may be plated onto the negative current collector (140, 340) by charging. The plated metal layer may include plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The lithium metal layer (150) may include non-fibrous lithium, non-needle lithium, plate lithium, or any combination thereof. The lithium alloy contains lithium and a first metal, and the first metal may include indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0111] Referring to FIGS. 1 to 3, the material constituting the negative electrode current collector (140, 340) can be any material that does not react with lithium, that is, a material that does not form an alloy or compound with lithium and has conductivity. The metal substrate is, for example, a metal or an alloy. The metal substrate may be composed of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The electrode current collector may have a shape selected from, for example, a sheet, foil, film, plate, porous body, mesoporous body, through-hole containing body, polygonal ring body, mesh body, foam, and nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0112] The negative current collector (140, 340) includes, for example, a first metal substrate. The first metal substrate includes the first metal as a main component or is made of the first metal. The content of the first metal included in the first metal substrate is, for example, 90 weight% or more, 95 weight% or more, 99 weight% or more, or 99.9 weight% or more with respect to the total weight of the first metal substrate. The first metal substrate may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium.

[0113] The first metal may be, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited to these; any metal used as a current collector in the relevant technical field may be used. The first metal substrate may be composed of, for example, one of the metals described above, or may be composed of an alloy of two or more metals. The first metal substrate is, for example, in the form of a sheet or foil.

[0114] The negative current collector (140, 340) may further include a coating layer (not shown) containing a second metal on a first metal substrate.

[0115] The negative current collector (140, 340) may include, for example, a first metal substrate and a coating layer disposed on the first metal substrate and comprising a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer comprising the second metal is harder than the substrate comprising the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the first metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The coating layer comprises the second metal. The coating layer may, for example, comprise the second metal as a main component or be composed of the second metal. The content of the second metal included in the coating layer is, for example, 90% by weight or more, 95% by weight or more, 99% by weight or more, or 99.9% by weight or more with respect to the total weight of the coating layer. The coating layer may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is excessively low, it may be difficult to suppress the deterioration of the negative electrode current collector. If the Mohs hardness of the second metal is excessively high, processing may not be easy. The second metal is one or more selected from, for example, titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh).The coating layer may be composed of, for example, one of the metals described above, or an alloy of two or more metals. The difference in Mohs hardness between the first metal included in the first metal substrate and the second metal included in the coating layer may be, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. By having such a difference in Mohs hardness between the first metal and the second metal, the deterioration of the negative current collector can be suppressed more effectively. The coating layer may have a single-layer structure or a multilayer structure of two or more layers. The coating layer may have a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may have a three-layer structure including, for example, a first coating layer, a second coating layer, and a third coating layer. The thickness of the coating layer may be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. The coating layer may be deposited on the first metal substrate by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods; any method capable of forming a coating layer in the relevant technical field is possible.

[0116] For example, the negative current collector (140, 340) may have a reduced thickness compared to a conventional negative current collector. Accordingly, the negative according to the present disclosure is distinguished from a conventional electrode comprising a thick film current collector by including, for example, a thin film current collector.

[0117] As a result, the energy density of the lithium metal secondary battery employing such electrodes is increased. The thickness of the negative electrode current collector (140, 340) may be, for example, less than 15 μm, 14.5 μm or less, or 14 μm or less. The thickness of the negative electrode current collector (140, 340) may be, for example, 0.1 μm to 15 μm, 1 μm to 14.5 μm, 2 μm to 14 μm, 3 μm to 14 μm, 5 μm to 14 μm, or 10 μm to 14 μm.

[0118] The negative current collector (140, 340) may have a shape selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a through-hole containing body, a polygonal ring body, a mesh body, a foam, and a nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0119] The negative current collector (140, 340) may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. The negative current collector may have a structure comprising a substrate, wherein the substrate may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. An intermediate layer may be additionally disposed on the metal substrate layer.

[0120] The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. By including a thermoplastic polymer in the base film, the base film may melt upon the occurrence of a short circuit, thereby suppressing a sudden increase in current. The base film may be, for example, an insulator.

[0121] The metal substrate layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The metal substrate layer can act as an electrochemical fuse and cut off upon overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal substrate layer. The metal substrate layer may be plated or deposited on a base film. As the thickness of the metal substrate layer decreases, the limit current and / or maximum current of the negative electrode current collector decreases, thereby improving the stability of the lithium metal secondary battery during a short circuit.

[0122] A lead tab may be added to the metal substrate layer for external connection. The lead tab may be welded to the metal substrate layer or the metal substrate layer / base film laminate by means of ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal substrate layer may melt, thereby electrically connecting the metal substrate layer to the lead tab. To make the weld between the metal substrate layer and the lead tab more robust, a metal chip may be added between the metal substrate layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal substrate layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to the metal chip / metal substrate layer laminate or the metal chip / metal substrate layer / base film laminate by placing the metal chip on the metal substrate layer and then welding it to the lead tab. During welding, the base film, metal layer, and / or metal chip may melt, allowing the metal layer or the metal layer / metal chip laminate to be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal substrate layer. The thickness of the base film may be, for example, 1 μm to 50 μm, 1.5 μm to 50 μm, 1.5 μm to 40 μm, or 1 μm to 30 μm. By having the base film within this thickness range, the weight of the cathode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100°C to 300°C, 100°C to 250°C, or 100°C to 200°C. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. To improve the adhesion between the base film and the metal substrate layer, a surface treatment such as corona treatment may be performed on the base film.The thickness of the metal substrate layer may be, for example, 0.01 μm to 3 μm, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. By having the metal substrate layer within this range of thickness, the stability of the cathode can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 μm to 10 μm, 2 μm to 7 μm, or 4 μm to 6 μm. By having the metal piece within this range of thickness, the connection between the metal layer and the lead tab can be performed more easily. By having the cathode current collector (140, 340) having this structure, the weight of the electrode can be reduced and, consequently, the energy density can be improved.

[0123] Referring to FIG. 1, the negative active material layer may be free on the negative current collector (140) before charging and discharging. Alternatively, before charging and discharging, the ratio of the negative capacitance to the positive capacitance may be less than 1.

[0124] Referring to FIG. 3, a lithium metal layer (350) including a plate-shaped lithium metal thin film may be disposed on a negative electrode current collector (340) before performing charging and discharging. According to one embodiment, the negative electrode may further include an interlayer disposed between the negative electrode current collector (340) and the lithium metal layer (350).

[0125] According to one embodiment, the interlayer may be placed directly on, for example, one or both sides of the negative current collector (340). Thus, no other layer may be placed between the negative current collector (340) and the interlayer. By placing the interlayer directly on one or both sides of the negative current collector (340), the bonding strength between the negative current collector (340) and the lithium metal layer (350) may be further improved.

[0126] The thickness of the intermediate layer (not shown) may be, for example, 30% or less of the thickness of the negative current collector (340). The thickness of the intermediate layer (not shown) is, for example, 0.01% to 30%, 0.1% to 30%, 0.5% to 30%, 1% to 25%, 1% to 20%, 1% to 15%, 1% to 10%, 1% to 5%, or 1% to 3% of the thickness of the negative current collector (340). The thickness of the intermediate layer is, for example, 10 nm to 5 µm, 50 nm to 5 µm, 200 nm to 4 µm, 500 nm to 3 µm, 500 nm to 2 µm, 500 nm to 1.5 µm, or 700 nm to 1.3 µm.

[0127] By having the intermediate layer have a thickness within this range, the bonding strength between the negative current collector (340) and the lithium metal layer (350) is further improved, and the increase in interfacial resistance can be suppressed.

[0128] For example, the intermediate layer may include a binder. By including a binder in the intermediate layer, the bonding strength between the negative current collector (340) and the lithium metal layer (350) can be further improved. The binder included in the intermediate layer is, for example, a conductive binder or a non-conductive binder.

[0129] Conductive binders are, for example, ion-conducting binders and / or electronic-conducting binders. Binders that possess both ion conductivity and electronic conductivity may belong to both ion-conducting binders and electronic-conducting binders.

[0130] Ion-conducting binders are, for example, polystyrene sulfonate (PSS), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), poly(methylmethacrylate) (PMMA), polyethylene oxide (PEO), polyethylene glycol (PEG), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, and polyacetylene, etc. Ion-conducting binders may include polar functional groups. Ion-conducting binders containing polar functional groups are, for example, Nafion, Aquivion, Flemion, These include Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), and lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi+).The electronically conductive binder is, for example, polyacetylene, polythiophene, polypyrrole, poly(p-phenylene), poly(phenylenevinylene), poly(phenylenesulfide), polyaniline, etc. The intermediate layer may be, for example, a conductive layer containing a conductive polymer.

[0131] The binder included in the intermediate layer may be, for example, a fluorine-based binder. The fluorine-based binder included in the intermediate layer may be, for example, polyvinylidene fluoride (PVDF). The intermediate layer may be disposed on the negative current collector (340) in a dry or wet manner, for example. The intermediate layer may be, for example, a binding layer including a binder.

[0132] The intermediate layer may additionally include, for example, a carbon-based conductive material. By including the carbon-based conductive material, the intermediate layer may be, for example, a conductive layer. The intermediate layer may be, for example, a conductive layer including a binder and a carbon-based conductive material.

[0133] The intermediate layer may be disposed on the cathode current collector in a dry manner by deposition, for example, CVD, PVD, etc. The intermediate layer may be disposed on the cathode current collector (340) in a wet manner by, for example, spin coating, dip coating, etc. The intermediate layer may be disposed on the cathode current collector (340) by, for example, depositing a carbon-based conductive material on the cathode current collector (340) by deposition. The dry-coated intermediate layer may be composed of a carbon-based conductive material and may not contain a binder. Alternatively, the intermediate layer may be disposed on the cathode current collector (340) by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent on the surface of the cathode current collector (340) and drying it. The intermediate layer may have a single-layer structure or a multi-layer structure including multiple layers.

[0134]

[0135] Cathode: Lithium metal layer

[0136] Referring to FIGS. 1 to 3, the lithium secondary battery (100, 300) may further include a lithium metal layer (150, 350) disposed between a negative electrode current collector (140, 340) and an electrolyte (160, 360). For example, the lithium metal layer (150, 350) may include lithium metal or a lithium alloy. For example, the lithium metal layer (150, 350) may be a negative electrode active material layer. For example, the lithium metal layer (150, 350) may be a lithium electrodeposited layer.

[0137] For example, the lithium metal layer (150, 350) can be formed by electrodepositing lithium ions contained in the electrolyte (360) onto the negative current collector (140, 340) as the lithium secondary battery is charged. For example, the lithium metal layer (150, 350) may include a lithium alloy and lithium metal. For example, the lithium alloy included in the lithium metal layer (150, 350) weakens the reactivity of the lithium metal, thereby effectively preventing side reactions between the lithium metal layer (150, 350) and the electrolyte (360). Additionally, the lithium metal layer (150, 350) has excellent electrical conductivity, which can reduce the internal resistance of the lithium secondary battery (100, 300) containing it. Accordingly, the lithium secondary battery (100, 300) containing the lithium metal layer (150, 350) can have improved lifespan characteristics as well as charge / discharge efficiency.

[0138] According to one embodiment, the lithium metal layer (150, 350) may include, for example, lithium foil, lithium powder, plated lithium, a carbon-based material, or a combination thereof. For example, the lithium metal layer (150, 350) may include lithium foil. In this case, the lithium metal layer (150, 350) may be a negative electrode active material layer. For example, the lithium metal layer (150, 350) may be introduced by coating a slurry containing lithium powder and a binder, etc., onto a negative electrode current collector. For example, the binder may be a fluorine-based binder such as polyvinylidene fluoride (PVDF).

[0139] According to one embodiment, the lithium metal layer (150, 350) may comprise only electrodeposited lithium metal or lithium alloy. In this case, the lithium metal layer (150, 350) may be a lithium electrodeposited layer.

[0140] According to one embodiment, the lithium metal layer (150, 350) may not include a carbon-based negative electrode active material. Accordingly, the lithium metal layer (150, 350) may be made of a metal-based negative electrode active material.

[0141] For example, the thickness of the lithium metal layer (150, 350) may be, for example, 0.1 μm to 100 μm, 0.1 μm to 80 μm, 1 μm to 80 μm, or 10 μm to 80 μm, but is not necessarily limited to these ranges and can be adjusted according to the shape, capacity, etc. of the required lithium secondary battery (100, 300). If the thickness of the lithium metal layer (150, 350) increases excessively, the structural stability of the lithium secondary battery (100, 300) may decrease, and side reactions may increase. If the thickness of the lithium metal layer (150, 350) is excessively small, the energy density of the lithium metal secondary battery may decrease.

[0142] According to one embodiment, the thickness of the lithium foil included in the lithium metal layer (150, 350) may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, or 10 μm to 30 μm, or 10 μm to 80 μm. By having the lithium foil have a thickness within this range, the lifespan characteristics of the lithium secondary battery (100, 300) can be further improved.

[0143] According to one embodiment, the particle size of the lithium powder included in the lithium metal layer (150, 350) may be, for example, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. By having the lithium powder have a thickness within this range, the lifespan characteristics of the lithium secondary battery (100, 300) can be further improved.

[0144]

[0145] anode

[0146] Referring to FIGS. 1 to 3, an anode composite layer (120, 320) is disposed on an anode current collector (110, 310) to form an anode (130, 330).

[0147]

[0148] Positive: Positive current collector

[0149] Referring to FIGS. 1 to 3, the anode (130, 330) includes an anode current collector (110, 310).

[0150] The positive current collector (110, 310) may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0151] According to one embodiment, the positive current collector (110, 310) may include aluminum (Al). According to one embodiment, the positive current collector (110, 310) may include a base film and a metal layer disposed on one or both sides of the base film, in the same way as the negative current collector (140, 340) described above.

[0152]

[0153] Anode: Anode composite layer

[0154] The positive composite layer (120, 320) may include a positive active material. The positive composite layer (120, 320) may further include a conductive material and / or a binder.

[0155] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used. The composite oxide may be a lithium transition metal composite oxide. Examples include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0156] For example, the cathode active material may include LiMO2 (M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof), LFP, LMFP, LiM2O4 (M is Ti, V, Mn or a combination thereof) or a combination thereof.

[0157] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni 1-b-c Mn b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

[0158] In the chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is Mn, Al, or a combination thereof.

[0159] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in a lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel cathode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0160] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 1.

[0161]

[0162] <Chemical Formula 1>

[0163] Li a Ni x Co y M z O 2-b A b

[0164]

[0165] In Chemical Formula 1, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0≤y≤0.3, 0 <z≤0.3, x+y+z=1이고, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 규소(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다.

[0166] In Chemical Formula 1, for example, 0.7≤x<1, 0 <y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.2, 0<z≤0.2, 0.83≤x<0.97, 0<y≤0.15, 0<z≤0.15, 또는 0.85≤x<0.95, 0<y≤0.1, 0<z≤0.1일 수 있다.

[0167] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulas 2 and 3.

[0168]

[0169] <Chemical Formula 2>

[0170] LiNi x Co y Mn z O2

[0171]

[0172] In Chemical Formula 2, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다.

[0173]

[0174] <Chemical Formula 3>

[0175] LiNi x Co y Al z O2

[0176]

[0177] In Chemical Formula 3, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.8≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.82≤x≤0.95, 0<y≤0.15, 0<z≤0.15이다. 예를 들어, 0.85≤x≤0.95, 0<y≤0.1, 0<z≤0.1이다.

[0178] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co0.08 Mn 0.04O2 , LiNi 0.8 Co 0.15 Mn 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02O2 , LiNi 0.8 Co 0.15 Al 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0179] For example, the positive electrode active material may be one having a coating layer on the surface of a lithium transition metal oxide, or a mixture of a lithium transition metal oxide and a lithium transition metal oxide having a coating layer may be used.

[0180] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0181] For example, the compound forming the coating layer 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. For the coating layer formation process, any coating method may be used as long as the coating can be applied to the lithium transition metal oxide using the coating elements in a manner that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.).

[0182] For example, the anode may additionally include an additive that can serve as a sacrificial anode.

[0183] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive composite layer (120, 320), and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive composite layer (120, 320).

[0184] A binder can serve to effectively bond the positive active material particles to each other and also to effectively bond the positive active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0185] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0186]

[0187] separator

[0188] A lithium secondary battery according to one embodiment may further include a separator (not shown).

[0189] As a separator, polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof may be used, and of course, mixed multilayer films such as polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0190] The separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0191] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0192] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0193] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0194] Organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0195] This will be explained in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and are not limited thereto.

[0196]

[0197] Example 1

[0198] (Electrolyte manufacturing)

[0199] As a liquid electrolyte, 1.0 M LiDFOB and 0.4 M LiBF₄ were added to DEC / FEC (2:1 volume ratio). A precursor solution was prepared by dissolving 2.5 wt% TMPTMA (trimethylolpropane trimethacrylate), 2.5 wt% HFDA (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henecosafluorododecyl (meth)acrylate) and 0.15 wt% AIBN initiator in the liquid electrolyte.

[0200] Subsequently, the electrolyte was prepared by polymerizing the precursor solution at 55°C for 12 hours under a pressure of 0.7 MPa.

[0201] (Prepare the positive electrode)

[0202] Total area capacity is 4.8 mAh / cm² 2 A phosphorus NCA (lithium nickel cobalt aluminum oxide) anode was prepared.

[0203] (Cathode manufacturing)

[0204] A copper (Cu) foil with a thickness of 8 μm was prepared as a cathode current collector.

[0205] (Lithium secondary battery manufacturing)

[0206] A 17 μm PP / PE / PP triple-layer separator was used as the separator.

[0207] An electrode assembly was prepared by sequentially stacking a cathode, a separator, and a positive electrode, and the electrolyte precursor solution described above was injected into the electrode assembly. Then, a lithium secondary battery was prepared by thermal crosslinking at 80 degrees Celsius.

[0208]

[0209] Comparative Example 1

[0210] As indicated in Table 1 below, a lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the acrylic monomer was 5 wt% and the fluoroacrylic monomer was not used.

[0211]

[0212] Comparative Example 2

[0213] As indicated in Table 1 below, a lithium secondary battery was prepared in the same manner as in Example 1, except that TFEA (trifluoroethyl acrylate) was used as the fluoroacrylic monomer.

[0214]

[0215] Comparative Example 3

[0216] A lithium secondary battery was prepared in the same manner as in Example 1, except that HFBA (2,2,3,4,4,4-hexafluorobutyl acrylate) was used as the fluoroacrylic monomer, as indicated in Table 1 below.

[0217]

[0218] Reference Example

[0219] A lithium secondary battery was prepared in the same manner as in Example 1, except that 1.0 M LiDFOB and 0.4 M LiBF₄ were added to DEC / FEC (2:1 volume ratio) as electrolytes, and acrylic monomers and fluoroacrylic monomers were not used as indicated in Table 1 below.

[0220]

[0221] Acrylic Monomers Fluoroacrylic Monomers Type Content (Wet%) Type Content (Wet%) Example 1 TMPTMA 2.5 HFDA 2.5 Comparative Example 1 TMPTMA 5 -- Comparative Example 2 TMPTMA 2.5 TFEA 2.5 Comparative Example 3 TMPTMA 2.5 HFBA 2.5 Reference Example ----

[0222]

[0223] Evaluation Example 1: Contact Angle Measurement

[0224] In the examples and comparative examples, measurements and analyses were performed using a contact angle analyzer (KRUSS DSA100) and a dedicated measurement program (ADVANCE Software). 20 µl of the electrolyte of the reference example was placed in a drop form on the electrolyte of the example or comparative example, and the angle formed between the electrolyte of the reference example and the electrolyte of the example or comparative example was measured at 1-second intervals for 10 seconds without delay. In the same manner, the position was changed, and the angle formed between the electrolyte and the copolymer was measured. Contact angles were measured at a total of 5 locations, and the results were presented as average values. Photographs of the measurements are shown in Fig. 8, and the calculation results are listed in Table 1 above. Meanwhile, for the measurements, the orientation was set to a sessile drop, the measurement method to Ellipse (Tangent-1), and the reference line to a manual reference line.

[0225] Figure 8 is an image showing the contact angles of the electrolytes of the examples and comparative examples according to the evaluation example. Referring to Figure 8, it was found that the contact angle was 58 degrees for Example 1, 19.4 degrees for Comparative Example 1, 23.8 degrees for Comparative Example 2, and 32.4 degrees for Comparative Example 3.

[0226]

[0227] Evaluation Example 2: Impedance Measurement

[0228] In the examples and comparative examples, for the manufactured lithium secondary battery, the charge transfer resistance (R) at the positive electrode / electrolyte and negative electrode / electrolyte interfaces ct The resistance of (cathode charge transport resistance) was measured using electrochemical impedance spectroscopy (EIS). The charge transport resistance (R ct The measurement results (category , cathode charge transport resistance) are shown in Table 2 below.

[0229]

[0230] Evaluation Example 3: Coulomb Efficiency Evaluation

[0231] After leaving the lithium secondary battery prepared according to the examples and comparative examples at a constant temperature of 25°C for 24 hours, the cell formation process was completed by using a lithium secondary battery charger / discharger (Toyo-System Co., LTD, TOSCAT3600) to charge the battery at 45°C under a constant current condition of 0.1 C to 4.5 V, maintaining 4.5 V in a constant voltage mode while charging under a constant voltage condition with a termination current of 0.05 C, and discharging under a constant current condition of 0.1 C to 2.0 V.

[0232] Next, to verify the initial capacity of the battery, it was charged at 0.2 C to 4.5 V with a constant current at 45°C, charged at 0.05 C while maintaining 4.5 V in constant voltage mode with a termination current, and discharged at 0.2 C to 2.0 V with a constant current to verify the initial capacity of the battery. During the capacity verification process, the initial Coulomb efficiency was calculated according to Equation 1 below and is shown in Table 3 below. In the following equation, the cell formation cycle is excluded.

[0233]

[0234] [Equation 1]

[0235] Initial Efficiency (%) = (Discharge Capacity in Initial Capacity Verification Cycle / Charge Capacity in Initial Capacity Verification Cycle) × 100

[0236]

[0237] Initial efficiency can reflect the amount of lithium irreversibly lost during the battery's first charging process. It can also be used as an indicator to evaluate the battery's initial stability.

[0238]

[0239] Evaluation Example 5: Measurement of Dose Retention Rate

[0240] For the lithium secondary battery prepared according to the examples and comparative examples, constant current charging was performed at 25°C at a current rate of 0.1C until the voltage reached 4.5 V (vs. Li), and then cut-off was performed at a current rate of 0.05C while maintaining 4.5 V in constant voltage mode. Subsequently, during discharge, the battery was discharged at a constant current rate of 0.1C until the voltage reached 3 V (vs. Li) (formation stage, 1st cycle).

[0241] The formation process was completed by performing this charge-discharge process once.

[0242] A lithium secondary battery that has undergone the formation stage was charged at 25°C at a constant current of 0.33C within a voltage range of 3 to 4.5 V relative to lithium metal, and then cut off at a current rate of 0.05C while maintaining 4.5 V in constant voltage mode. Subsequently, constant current discharge was performed at 1.0C until a cut-off voltage of 3 V was reached. The aforementioned charge-discharge process was repeated a total of 100 times. In all charge-discharge cycles, a 5-minute pause was observed after each charge / discharge cycle. Here, the capacity retention rate in the Nth cycle is defined by Equation 2 below, and the capacity retention rates for each are shown in Figure 9.

[0243]

[0244] [Equation 2]

[0245] Capacity Retention Rate (%) = (Discharge Capacity at Nth Cycle / Discharge Capacity at 1st Cycle) × 100

[0246]

[0247] Figure 9 is an image showing the capacity retention rates of the example and comparative example according to the evaluation example. Referring to Figure 9, the lithium secondary battery according to Example 1 showed a high capacity retention rate of 88.2% after 200 cycles at 25°C, which was higher than the 81.6% of Comparative Example 1, 80.3% of Comparative Example 2, 80.1% of Comparative Example 3, and 84.6% of the Reference Example. In addition, the lithium secondary battery according to Example 1 achieved a capacity retention rate of 81.8% after 250 cycles and 72.2% after 300 cycles, which was higher than the retention rates of 73.6% after 250 cycles and 65.2% after 300 cycles in the lithium secondary battery according to the Reference Example.

[0248]

[0249] Evaluation Example 6: TEM

[0250] In the lithium secondary batteries prepared according to the examples, comparative examples, and reference examples, the SEI (Solid Electrolyte Interphase) formed on the surface of the negative electrode was photographed by TEM for each example and is shown in Fig. 10.

[0251] FIG. 10 is a cryo-TEM image of the SEI layer of the lithium secondary battery of the Example, Comparative Example, and Reference Example according to the evaluation example. FIG. 10 (a) is a cryo-TEM image of the SEI layer on the lithium metal deposited in the electrolyte of Example 1, FIG. 10 (b) is a cryo-TEM image of the rectangular portion of FIG. 10 (a) enlarged. FIG. 10 (c) is a cryo-TEM image of the SEI layer on the lithium metal deposited in the electrolyte of Reference Example, FIG. 10 (d) is a cryo-TEM image of the rectangular portion of FIG. 10 (c) enlarged. FIG. 10 (e) is a cryo-TEM image of the SEI layer on the lithium metal deposited in the electrolyte of Comparative Example 1, FIG. 10 (f) is a cryo-TEM image of the rectangular portion of FIG. 10 (e) enlarged.

[0252] Referring to FIG. 10, it was confirmed that Example 1 and Reference Example have a thin SEI layer of 8 nm to 10 nm, whereas Comparative Example 1 has a much thicker SEI layer of 20 nm or more.

[0253]

[0254] Evaluation Example 7: SEM

[0255] In lithium secondary batteries prepared according to the examples, comparative examples, and reference examples, the lithium metal deposited on the electrolyte at the end of the cycle charge was photographed by SEM, respectively, and is shown in FIG. 11, and the lithium metal domain size is shown in Table 4. In addition, the same was photographed by FIB-SEM, respectively, and is shown in FIG. 12, and the density of the deposited lithium was calculated and is shown in Table 4.

[0256] Figure 11 is an image of the negative electrode surface of a lithium secondary battery of an example, a comparative example, and a reference example taken with an SEM according to the evaluation example. Figure 11(a) is an SEM image of lithium deposited on the cathode of the Reference Example after the end of the third charging cycle, (b) is an SEM image of lithium deposited on the cathode of Comparative Example 1 after the end of the third charging cycle, (c) is an SEM image of lithium deposited on the cathode of Comparative Example 2 after the end of the third charging cycle, (d) is an SEM image of lithium deposited on the cathode of Comparative Example 3 after the end of the third charging cycle, (e) is an SEM image of lithium deposited on the cathode of Example 1 after the end of the third charging cycle, (f) is an SEM image of lithium deposited on the cathode of the Reference Example after the end of the 50th charging cycle, (g) is an SEM image of lithium deposited on the cathode of Comparative Example 1 after the end of the 50th charging cycle, and (h) is an SEM image of lithium deposited on the cathode of Comparative Example 2 after the end of the 50th charging cycle These are images taken, (i) is an SEM image of lithium deposited on the cathode of Comparative Example 3 after the end of the 50th cycle of charging, and (j) is an SEM image of lithium deposited on the cathode of Example 1 after the end of the 50th cycle of charging.

[0257] FIG. 12 is an image of the negative electrode surface of the lithium secondary battery of the example, comparative example, and reference example taken with FIB-SEM according to the evaluation example. Figure 12(a) is an FIB-SEM image of lithium deposited on the cathode of the Reference Example after the end of the third charging cycle, (b) is an FIB-SEM image of lithium deposited on the cathode of Comparative Example 1 after the end of the third charging cycle, (c) is an FIB-SEM image of lithium deposited on the cathode of Comparative Example 2 after the end of the third charging cycle, (d) is an FIB-SEM image of lithium deposited on the cathode of Comparative Example 3 after the end of the third charging cycle, (e) is an FIB-SEM image of lithium deposited on the cathode of Example 1 after the end of the third charging cycle, (f) is an FIB-SEM image of lithium deposited on the cathode of the Reference Example after the end of the 50th charging cycle, (g) is an FIB-SEM image of lithium deposited on the cathode of Comparative Example 1 after the end of the 50th charging cycle, and (h) is (i) is an image of lithium deposited on the cathode of Comparative Example 2 after the end of the 50th cycle of charging, taken with FIB-SEM, and (j) is an image of lithium deposited on the cathode of Comparative Example 3 after the end of the 50th cycle of charging, taken with FIB-SEM.

[0258]

[0259] Evaluation Example 8: Stability Evaluation

[0260] Lithium secondary batteries prepared according to the example, comparative example, and reference example were ignited with a butane torch, and whether ignition occurred was filmed. As a result of the filming, it was confirmed that Comparative Example 1 and the reference example ignited easily, but Example 1 did not ignite even after continuous exposure.

[0261] A 200 mAh Cu / NCA multilayer pouch cell manufactured using the electrolytes of the Example and Reference Example was subjected to a drilling test in a buffered state, and the center temperature was measured. As a result of the measurements, in Example 1, the center temperature rose only to 60 degrees (Celsius) during drilling, and the cell voltage recovered after removing the drill, confirming the excellent safety of the electrolyte-based pouch cell of the present invention. In the Reference Example, the center temperature exceeded 146 degrees (Celsius) during drilling and exploded, and it was found that the voltage dropped to 0 V after drilling.

[0262]

[0263] Evaluation Example 9: Initial Discharge Capacity Measurement

[0264] The electrolyte in the examples and comparative examples was 2.8 g / Ah, and the NCA loading was 3.1 mAh / cm² 2 A 200 mAh Cu / NCA multilayer pouch cell was manufactured. After forming at 0.02 C, the cell was charged at 0.2 C and discharged at 0.5 C between 3.6 V and 4.3 V, and the initial discharge capacity was measured. As a result of the measurement, it was confirmed that Example 1 reached 152.6 mAh / g (192.1 mAh) and the capacity retention rate after 100 cycles was 92.2%.

[0265]

[0266] R ct (@50 cycle, Ω) Anode / Electrolyte Interface Cathode / Electrolyte Interface Total Example 10.32 2.08 2.40 Comparative Example 10.78 2.8 13.59 Comparative Example 20.58 2.58 3.16 Comparative Example 30.63 2.7 13.34 Reference Example 0.48 2.35 2.83

[0267]

[0268] Coulomb Efficiency (%) Example 199.0 Comparative Example 198.5 Comparative Example 298.4 Comparative Example 398.8 Reference Example 98.7

[0269]

[0270] Lithium metal domain size (㎛) 2 ,@3 cycle)Lithium density (g / cm³ 3,@3 cycle)Lithium density (g / cm³ 3 ,@50 cycle) Example 1 38.80.500.44 Comparative Example 1 25.00.470.40 Comparative Example 2 24.50.480.43 Comparative Example 3 26.00.490.42 Reference Example 29.10.490.41

[0271]

[0272] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. Copolymer of acrylic monomers and fluoroacrylic monomers Includes, The above fluoroacrylic monomer comprises seven or more fluorine atoms, Electrolytes.

2. In Paragraph 1, The above fluoroacrylic monomer is an electrolyte comprising 1H,1H,2H,2H-heptadecafluorodecyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-nonafluorohexyl (meth)acrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl (meth)acrylate, or 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henecosafluorododecyl (meth)acrylate.

3. In Paragraph 1, The weight of the above fluoroacrylic monomer is 0.1 wt% or more and 20 wt% or less of the electrolyte.

4. In Paragraph 1, The weight of the above fluoroacrylic monomer is 2.0 wt% or more and 3.0 wt% or less of the electrolyte.

5. In Paragraph 1, The above acrylic monomer is an electrolyte comprising PETTA (pentaerythritol tetraacrylate), TMPTMA (trimethylolpropane trimethacrylate), DPHA (dipentaerythritol hexacrylate), or a combination thereof.

6. In Paragraph 1, The weight of the above acrylic monomer is 0.1 wt% or more and 20 wt% or less of the above electrolyte.

7. In Paragraph 1, The weight of the above acrylic monomer is 2.0 wt% or more and 3.0 wt% or less of the above electrolyte.

8. In Paragraph 1, The weight ratio of the fluoroacrylic monomer and the acrylic monomer is 3:7 to 7:3, in an electrolyte.

9. In Paragraph 1, The above-mentioned fluoroacrylic monomer and acrylic monomer have a weight ratio of 4:6 to 6:4, in an electrolyte.

10. In Paragraph 1, Electrolyte, further comprising a lithium salt and an organic solvent.

11. In Paragraph 10, The above lithium salt is an electrolyte comprising LiPF6, LiBF4, LiTFSI, LiFSI, LiDFOB, LiBOB, LiClO4, or a combination thereof.

12. In Paragraph 10, The above organic solvent is an electrolyte comprising a carbonate-based solvent.

13. Anode; A cathode comprising a cathode current collector; and It includes an electrolyte disposed between the anode and the cathode, and The above electrolyte is, Copolymer of acrylic monomers and fluoroacrylic monomers Includes, The above fluoroacrylic monomer is a lithium secondary battery containing 7 or more fluorine atoms.

14. In Paragraph 13, A lithium secondary battery comprising the above fluoroacrylic monomer, 1H,1H,2H,2H-heptadecafluorodecyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-nonafluorohexyl (meth)acrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl (meth)acrylate, or 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henecosafluorododecyl (meth)acrylate.

15. In Paragraph 13, The weight of the above fluoroacrylic monomer is 0.1 wt% or more and 20 wt% or less of the electrolyte.

16. In Paragraph 13, The above acrylic monomer is an electrolyte comprising PETTA (pentaerythritol tetraacrylate), TMPTMA (trimethylolpropane trimethacrylate), DPHA (dipentaerythritol hexacrylate), or a combination thereof.

17. In Paragraph 13, The weight of the above acrylic monomer is 0.1 wt% or more and 20 wt% or less of the above electrolyte.

18. In Paragraph 13, The weight ratio of the fluoroacrylic monomer and the acrylic monomer is 3:7 to 7:3, in an electrolyte.

19. In Paragraph 13, A lithium secondary battery in which a negative active material layer is absent (free) on the negative current collector before charging and discharging, or the ratio of the electrical capacity of the negative electrode to the electrical capacity of the positive electrode before charging and discharging is less than 1.

20. In Paragraph 13, A lithium secondary battery further comprising a lithium metal layer disposed between the negative current collector and the electrolyte before charging is performed.

Images