Non-aqueous electrolyte solution and lithium secondary battery comprising same

Abstract

Embodiments of the present disclosure provide a non-aqueous electrolyte solution and a lithium secondary battery comprising same. The non-aqueous electrolyte solution includes a non-aqueous organic solvent, a lithium salt, and an additive including a sulfonyl-based compound including a sulfonyl group and two phosphorus atoms in one molecule.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] The disclosure of the present application relates to a non-aqueous electrolyte and a lithium secondary battery including the same.

[0002] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as electric and hybrid vehicles.

[0003] Among the above secondary batteries, lithium secondary batteries are being actively researched and developed due to their high operating voltage and energy density per unit weight, and their advantages in charging speed and weight reduction.

[0004] A lithium secondary battery may include an electrode assembly including a positive electrode and a negative electrode, and an electrolyte that impregnates the electrode assembly. The lithium secondary battery may further include an outer case that accommodates the electrode assembly and the electrolyte.

[0005] Lithium metal oxide can be used as an active material for the positive electrode of a lithium secondary battery. An example of the lithium metal oxide is a nickel-based lithium metal oxide.

[0006] As the application scope of lithium secondary batteries expands, demands for longer life, higher capacity, and more stable operation are increasing. Consequently, lithium secondary batteries that provide consistent output and capacity even during repeated charge and discharge cycles are needed.

[0007] However, the life characteristics may be deteriorated depending on the side reactions of the positive electrode active material and electrolyte.

[0008] According to one embodiment of the present disclosure, a non-aqueous electrolyte having improved mechanical and chemical stability can be provided.

[0009] According to one embodiment of the present disclosure, a lithium secondary battery having improved operational stability and electrical characteristics can be provided.

[0010] In exemplary embodiments, the non-aqueous electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an additive comprising a sulfonyl compound having a sulfonyl group and two phosphorus atoms in one molecule.

[0011] In some embodiments, the sulfonyl compound may include at least one selected from the group consisting of compounds represented by the following chemical formula 1.

[0012] [Chemical Formula 1]

[0013]

[0014] In chemical formula 1, R 1 , R 2 , R 5 and R 6 are each independently C6-C 12 aryl group, C6-C 12 Heteroaryl group, phenoxy group, heterophenoxy group, C1-C6 alkyl group, C1-C6 heteroalkyl group, C1-C6 alkoxy group, C1-C6 heteroalkoxy group, C5-C 12 Cycloalkyl group, C5-C 12 A cycloalkenyl group, a 5 to 7 membered heterocycloalkyl group, or a 5 to 7 membered heterocycloalkenyl group, R 3 and R 4Each may independently include a C1-C6 alkyl group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group.

[0015] In some embodiments, the sulfonyl compound may include a compound represented by the following chemical formula 2.

[0016] [Chemical Formula 2]

[0017]

[0018] In some embodiments, the sulfonyl compound may include a compound represented by the following chemical formula 3.

[0019] [Chemical Formula 3]

[0020]

[0021] In some embodiments, the content of the additive relative to the total weight of the non-aqueous electrolyte may be 0.1 wt% to 5.0 wt%.

[0022] In some embodiments, the content of the additive relative to the total weight of the non-aqueous electrolyte may be 0.3 wt% to 0.8 wt%.

[0023] In some embodiments, an auxiliary additive comprising an alkyl sultone compound may be further included.

[0024] In some embodiments, the content of the auxiliary additive relative to the total weight of the non-aqueous electrolyte may be 2 wt% to 4 wt%.

[0025] In some embodiments, the non-aqueous organic solvent may include at least one selected from the group consisting of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.

[0026] In some embodiments, the lithium salt may include at least one selected from the group consisting of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0027] A lithium secondary battery according to exemplary embodiments includes a positive electrode, a negative electrode opposite to the positive electrode, and the non-aqueous electrolyte described above.

[0028] According to one embodiment of the present disclosure, the initial capacity characteristics of a secondary battery including a non-aqueous electrolyte can be improved.

[0029] According to one embodiment of the present disclosure, the thermal stability of a secondary battery can be improved.

[0030] According to one embodiment of the present disclosure, the high-temperature storage characteristics and lifespan characteristics of a secondary battery can be improved.

[0031] The non-aqueous electrolyte of the present disclosure and the lithium secondary battery containing it can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-based solar and wind power generation. The non-aqueous electrolyte of the present disclosure and the lithium secondary battery containing it can be used in eco-friendly electric vehicles, hybrid vehicles, and the like, which prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0032] FIG. 1 and FIG. 2 are schematic plan views and cross-sectional views, respectively, showing lithium secondary batteries according to exemplary embodiments.

[0033] Embodiments of the present disclosure provide a non-aqueous electrolyte comprising an organic solvent, a lithium salt, and an additive. A lithium secondary battery comprising the non-aqueous electrolyte is also provided.

[0034] In exemplary embodiments, the non-aqueous electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an additive.

[0035] For example, the non-aqueous organic solvent provides sufficient solubility for lithium salts and additives, and may include organic compounds that are not reactive with the lithium secondary battery.

[0036] In exemplary embodiments, the non-aqueous organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, etc. These may be used alone or in combination of two or more.

[0037] For example, the carbonate solvent may include at least one selected from the group consisting of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), and butylene carbonate.

[0038] For example, the ester solvent may include at least one selected from the group consisting of methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), gamma-butyrolactone (GBL), decanolide, valerolactone, mevalonolactone, and caprolactone.

[0039] For example, the ether solvent may include at least one selected from the group consisting of dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0040] For example, the ketone solvent may include cyclohexanone, etc.

[0041] For example, the alcohol solvent may include at least one selected from the group consisting of ethyl alcohol and isopropyl alcohol.

[0042] For example, the aprotic solvent may include at least one selected from the group consisting of nitrile solvents, amide solvents (e.g., dimethylformamide), dioxolane solvents (e.g., 1,3-dioxolane), and sulfolane solvents.

[0043] In some embodiments, the carbonate solvent may include at least one selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0044] In exemplary embodiments, a lithium salt may be provided as the electrolyte. For example, the lithium salt may be Li + X - can be expressed as

[0045] For example, the anion of the lithium salt (X - ) is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , SbF6 - , AsF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3- , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - or PO2F2 - - These may be provided singly or in combination of two or more as anions of lithium salts.

[0046] In some embodiments, the lithium salt may include at least one selected from the group consisting of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In this case, a film with improved thermal stability may be formed on the electrode surface. Accordingly, the ionic conductivity and electrode protection characteristics of the non-aqueous electrolyte may be improved.

[0047] In one embodiment, the lithium salt may be included in the non-aqueous organic solvent at a concentration of about 0.01 M to 5 M, or about 0.01 M to 2 M. In this range, the transfer of lithium ions and / or electrons during charging and discharging of a lithium secondary battery may be promoted, thereby improving capacity characteristics.

[0048] In exemplary embodiments, the additive comprises a sulfonyl compound containing a sulfonyl group and two phosphorus (P) atoms within one molecule. Accordingly, the initial performance, high-temperature storage characteristics, and high-temperature lifespan characteristics of a lithium secondary battery including a non-aqueous electrolyte can be improved.

[0049] For example, lithium secondary batteries may experience swelling during high-temperature storage or high-temperature charge / discharge cycles, which can increase their thickness. This can degrade the durability and stability of the lithium secondary battery.

[0050] According to exemplary embodiments of the present disclosure, the sulfonyl compound can promote the movement of lithium ions and / or electrons, thereby reducing resistance and improving initial capacity characteristics. Furthermore, the sulfonyl compound can suppress side reactions between the non-aqueous organic solvent and the negative electrode, thereby improving storage characteristics and cycle life at high temperatures.

[0051] In some embodiments, the sulfonyl compound may include at least one selected from the group consisting of compounds represented by the following chemical formula 1.

[0052] [Chemical Formula 1]

[0053]

[0054] In chemical formula 1, R 1 , R 2 , R 5 and R 6 are each independently C6-C 12 aryl group, C6-C 12 Heteroaryl group, phenoxy group, heterophenoxy group, C1-C6 alkyl group, C1-C6 heteroalkyl group, C1-C6 alkoxy group, C1-C6 heteroalkoxy group, C5-C 12 Cycloalkyl group, C5-C 12 It may include a cycloalkenyl group, a 5 to 7 membered heterocycloalkyl group, or a 5 to 7 membered heterocycloalkenyl group.

[0055] In chemical formula 1, R 3 and R 4Each may independently include a C1-C6 alkyl group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group.

[0056] For example, the above R 1 Inland R 6 Each may be substituted or unsubstituted.

[0057] For example, the above R 1 Inland R 6 The substituents included are halogen, C1-C6 alkyl group, C3-C6 cycloalkyl group, C1-C6 alkoxy group, 3-7 membered heterocycloalkyl group, C6-C 12 Aryl group, 5-7 membered heteroaryl group, hydroxyl group (-OH), -NR 5 R 6 (R 5 and R 6 Each independently may include at least one selected from the group consisting of hydrogen or a C1-C6 alkyl group), a nitro group (-NO2), and a cyano group (-CN).

[0058] For example, the sulfonyl compound may include one sulfonyl group and two phosphorus atoms, as in the chemical formula 1. Accordingly, the initial performance and high-temperature lifespan of a lithium secondary battery may be improved.

[0059] According to one embodiment, the sulfonyl compound may include a compound represented by the following chemical formula 2.

[0060] [Chemical Formula 2]

[0061]

[0062] According to one embodiment, the sulfonyl compound may include a compound represented by the following chemical formula 3.

[0063] [Chemical Formula 3]

[0064]

[0065] In some embodiments, the additive may include a compound represented by the above chemical formula 2 and a compound represented by the above chemical formula 3. Accordingly, the initial performance and high-temperature lifespan of the lithium secondary battery may be further improved.

[0066] In some embodiments, the content of the additive relative to the total weight of the non-aqueous electrolyte may be 0.1 wt% to 5.0 wt%, and in one embodiment, 0.3 wt% to 0.8 wt%. Within this range, side reactions of the electrolyte may be sufficiently suppressed while reducing the resistance of the lithium secondary battery.

[0067] In some embodiments, the non-aqueous electrolyte may further comprise an auxiliary additive comprising an alkyl sultone compound.

[0068] For example, the alkyl sultone compound may include at least one of 1,3-propane sultone (PS) and 1,4-butane sultone.

[0069] For example, auxiliary additives may further include anhydride compounds such as succinic anhydride, maleic anhydride, etc., nitrile compounds such as glutarnitrile, succinic nitrile, adiponitrile, etc. These may be added alone or in combination of two or more in addition to the above-described sultone compounds.

[0070] In some embodiments, the auxiliary additive may further include at least one selected from the group consisting of fluoroethylene carbonate (FEC), ethylene sulfate (ESA), polyethylene sulfide (PES), vinylene carbonate (VC), and vinylethylene carbonate (VEC).

[0071] In some embodiments, the content of the auxiliary additive relative to the total weight of the non-aqueous electrolyte may be 2 wt% to 4 wt%. Within this range, the high-temperature storage characteristics and high-temperature lifespan characteristics can be sufficiently improved through the additive while suppressing an increase in resistance of the lithium secondary battery.

[0072] FIG. 1 and FIG. 2 are schematic plan views and cross-sectional views, respectively, illustrating a lithium secondary battery according to exemplary embodiments. For example, FIG. 2 is a cross-sectional view taken along line II' of FIG. 1.

[0073] The structures illustrated in FIGS. 1 and 2 are examples for convenience of explanation, and the structure of the lithium secondary battery according to embodiments of the present disclosure is not limited thereto.

[0074] Referring to FIGS. 1 and 2, a lithium secondary battery may include an electrode assembly including a positive electrode (100) and a negative electrode (130) opposite to the positive electrode, wherein the electrode assembly may be contained and impregnated with the non-aqueous electrolyte described above within a case (160).

[0075] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode active material layer (110) formed on at least one surface of the positive electrode current collector (105).

[0076] The positive electrode current collector (105) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector (105) may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. For example, the thickness of the positive electrode current collector (105) may be 10 μm to 50 μm.

[0077] The positive electrode active material layer (110) may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0078] According to exemplary embodiments, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0079] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1.

[0080] [Chemical Formula 1]

[0081] Li x Ni a M b O 2+z

[0082] In Chemical Formula 1, 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b≤0.5, -0.5≤z≤0.1 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0083] The chemical structure represented by Chemical Formula 1 represents the bonding relationship included in the layered structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can serve as the main active element of the positive electrode active material together with Ni. Chemical Formula 1 is provided to express the bonding relationship of the above main active elements and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0084] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated into the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 1.

[0085] The auxiliary element may include at least one selected from the group consisting of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary element may also function as an auxiliary active element that contributes to the capacity / output activity of the positive electrode active material together with Co or Mn, for example, Al.

[0086] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1-1.

[0087] [Chemical Formula 1-1]

[0088] Li x Ni a M1 b1 M2 b2 O 2+z

[0089] In Chemical Formula 1-1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 1-1, 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b1+b2≤0.5, -0.5≤z≤0.1 may be satisfied.

[0090] The above-described positive electrode active material may further include a coating element or doping element. For example, elements substantially identical to or similar to the above-described auxiliary elements may be used as the coating element or doping element. For example, the above-described elements may be used singly or in combination of two or more.

[0091] The above coating element or doping element may be present on the surface of the lithium-nickel metal oxide particle, or may penetrate through the surface of the lithium-nickel metal composite oxide particle and be included in the bonding structure represented by the above chemical formula 1 or chemical formula 1-1.

[0092] The above positive electrode active material may include a nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0093] Ni can be provided as a transition metal associated with the output and capacity of a lithium secondary battery. Therefore, by employing a high-content (High-Ni) composition as described above in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0094] However, as the Ni content increases, the long-term storage stability and lifespan stability of the cathode or secondary battery may relatively deteriorate, and side reactions with the electrolyte may also increase. However, according to exemplary embodiments, the inclusion of Co can maintain electrical conductivity, while improving lifespan stability and capacity retention characteristics through Mn.

[0095] The content of Ni (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) in the NCM-based lithium oxide may be 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0096] In some embodiments, the positive electrode active material may include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0097] In some embodiments, the positive electrode active material may include, for example, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide) active material, a Mn-rich active material, a Co-less active material, etc. having a chemical structure or crystal structure represented by Chemical Formula 2. These may be used alone or in combination of two or more.

[0098] [Chemical Formula 2]

[0099] p[Li2MnO3]·(1-p)[Li q JO2]

[0100] In chemical formula 2, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg 및 B 중 적어도 하나의 원소를 포함할 수 있다.

[0101] The positive electrode active material can be mixed in a solvent to prepare a positive electrode slurry. The positive electrode slurry can be coated on at least one surface of a positive electrode current collector (105), and then dried and rolled to prepare a positive electrode active material layer (110). The coating can include methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting. The positive electrode active material layer (110) can further include a binder and optionally can further include a conductive material and / or a thickener.

[0102] As the above solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. can be used.

[0103] The above binder may include polyvinylidenefluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. These may be used alone or in combination of two or more.

[0104] In one embodiment, a PVDF-based binder may be used as the positive electrode binder. In this case, the amount of binder used to form the positive electrode active material layer (110) may be reduced, while the amount of positive electrode active material may be relatively increased. Accordingly, the output characteristics and capacity characteristics of the secondary battery may be improved.

[0105] The conductive material may be added to enhance the conductivity and / or mobility of lithium ions or electrons of the positive electrode active material layer (110). For example, the conductive material may include a carbon-based conductive material such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc., and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc. These may be used alone or in combination of two or more.

[0106] The positive electrode slurry may further include a thickener and / or a dispersant. In one embodiment, the positive electrode slurry may include a thickener such as carboxymethyl cellulose (CMC).

[0107] The negative electrode (130) may include a negative electrode current collector (125) and a negative electrode active material layer (120) formed on at least one surface of the negative electrode current collector (125).

[0108] For example, the negative electrode current collector (125) may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. These may be used alone or in combination of two or more. For example, the thickness of the negative electrode current collector (125) may be 10 μm to 50 μm.

[0109] The negative electrode active material layer (120) may include a negative electrode active material. A material capable of adsorbing and desorbing lithium ions may be used as the negative electrode active material. For example, the negative electrode active material may be a carbon-based material such as crystalline carbon, amorphous carbon, a carbon composite, or carbon fiber; lithium metal; a lithium alloy; a silicon (Si)-containing material, or a tin (Sn)-containing material. These may be used alone or in combination of two or more.

[0110] The above amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0111] The above crystalline carbon may include graphitic carbon such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0112] The above lithium metal may include pure lithium metal and / or lithium metal having a protective layer formed thereon for suppressing dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on a negative electrode current collector (125) may be used as the negative electrode active material layer (120). In one embodiment, a lithium thin film layer may also be used as the negative electrode active material layer (120).

[0113] Elements included in the above lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc. These may be used alone or in combination of two or more.

[0114] The above silicon-containing material can provide increased capacity characteristics. The above silicon-containing material is Si, SiO x (0 <x<2), 금속 도핑된 SiO x (0 <x<2), 실리콘-탄소 복합체 등을 포함할 수 있다.

[0115] The above metal may include lithium and / or magnesium, and the metal-doped SiO x (0 <x<2)는 금속 실리케이트를 포함할 수 있다.

[0116] The above negative electrode active material can be mixed in a solvent to prepare a negative electrode slurry. After coating / depositing the negative electrode slurry on a negative electrode current collector (125), drying and rolling can be performed to prepare a negative electrode active material layer (120). The coating can include methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting. The negative electrode active material layer (120) can further include a binder and optionally can further include a conductive agent, a thickener, etc.

[0117] The solvent included in the cathode slurry may include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, etc. These may be used alone or in combination of two or more.

[0118] The above-described materials that can be used in manufacturing the positive electrode (100) as the binder, conductive agent and thickener can be used.

[0119] In some embodiments, a styrene-butadiene rubber (SBR)-based binder, a carboxymethyl cellulose (CMC)-based binder, a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene, PEDOT)-based binder, or the like may be used as the negative electrode binder. These may be used alone or in combination of two or more.

[0120] In exemplary embodiments, a separator (140) may be interposed between the anode (100) and the cathode (130). The separator (140) may be configured to prevent electrical short-circuiting between the anode (100) and the cathode (130) and to allow ion flow. For example, the thickness of the separator may be 10 μm to 20 μm.

[0121] For example, the separator (140) may include a porous polymer film or a porous nonwoven fabric.

[0122] The above porous polymer film may include a polyolefin polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer. These may be used alone or in combination of two or more.

[0123] The above porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0124] The separator (140) may include a ceramic material. For example, inorganic particles may be coated on the polymer film or dispersed within the polymer film to improve heat resistance.

[0125] The separator (140) may have a single-layer or multi-layer structure including the above-described polymer film and / or non-woven fabric.

[0126] According to exemplary embodiments, an electrode cell is defined by an anode (100), a cathode (130), and a separator (140), and a plurality of electrode cells may be stacked to form an electrode assembly (150) in the form of, for example, a jelly roll. For example, the electrode assembly (150) may be formed through winding, stacking, z-folding, stack-folding, etc. of the separator (140).

[0127] A lithium secondary battery can be defined by housing the electrode assembly (150) together with the non-aqueous electrolyte described above in the case (160).

[0128] As illustrated in FIGS. 1 and 2, electrode tabs (positive electrode tabs and negative electrode tabs) may protrude from the positive electrode collector (105) and negative electrode collector (125) belonging to each electrode cell and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the case (160) to form electrode leads (positive electrode leads (107) and negative electrode leads (127)) that extend or are exposed to the outside of the case (160).

[0129] The above lithium secondary battery can be manufactured in a cylindrical, square, pouch or coin shape using, for example, a can.

[0130] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and technical idea of ​​the present disclosure, and it is also natural that such changes and modifications fall within the scope of the appended claims.

[0131] Synthesis Example 1: Tetraphenyl[sulfonylbis(ethane-2,1-diyl)]bis(phosphonate) (compound represented by chemical formula 2)

[0132] Divinyl sulfone (3.0 g, 25 mmol), diphenyl phosphite (12 g, 51 mmol), and toluene (33 mL) were added to a round-bottomed flask, and then cooled to 0°C. 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU, 0.77 g, 5 mmol) was added dropwise to the round-bottomed flask while maintaining the temperature at 0°C for 1 hour, and then stirred for 2 hours while maintaining the temperature at 0°C. After the stirring was stopped due to the excessive production of solid, acetone (50 mL) was added to the solid to reslurry. The white solid formed by the reslurry was filtered, washed with methanol, and dried at high temperature to obtain 5.6 g of the product in the form of a solid (compound represented by the chemical formula 2). 1 The H-NMR results are as follows.

[0133] 1 H-NMR (CDCl3, 500 MHz): 7.38-7.31 (m, 8H), 7.25-7.20 (m, 4H), 7.20-7.15 (m, 8H), 3.47-3.41 (m, 4H), 2.66-2.58 (m, 4H)

[0134] Synthesis Example 2: [Sulfonylbis(ethane-2,1-diyl)]bis(diphenylphosphine oxide) (compound represented by chemical formula 3)

[0135] Divinyl sulfone (3.0 g, 25 mmol), diphenylphosphine oxide (10.4 g, 51 mmol), and toluene (20 mL) were added to a round-bottomed flask, heated to 130°C, and stirred. After maintaining 130°C and stirring for more than 12 hours, the temperature was lowered to room temperature, and stirring was stopped as the product solidified while absorbing the solvent. After stirring was stopped, acetone (50 mL) was added to perform reslurrying. The white solid produced by the reslurrying was filtered, washed with methanol, and dried at high temperature to obtain 11.4 g of the product in solid form (compound represented by the chemical formula 3). 1 The H-NMR results are as follows.

[0136] 1 H-NMR (CDCl3, 500 MHz): 7.75-7.71 (m, 8H), 7.52-7.51 (m, 4H), 7.51-7.48 (m, 8H), 3.28-3.12 (m, 4H), 2.79-2.66 (m, 4H)

[0137] Example 1

[0138] (1) Preparation of non-aqueous electrolyte

[0139] A 1.0 M LiPF6 solution was prepared using a mixed solvent of EC / EMC (25:75; volume ratio). The compound represented by the above chemical formula 2 was added and mixed as an additive to the solution so as to be 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0140] A non-aqueous electrolyte was prepared by adding and mixing 1.0 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of 1,3-propane sultone (PS), and 0.5 wt% of ethylene sulfate (ESA) (total 2.0 wt%) as auxiliary additives relative to the total weight of the non-aqueous electrolyte to the above solution.

[0141] (2) Manufacturing of lithium secondary batteries

[0142] Li[Ni as a cathode active material 0.8 Co 0.1 Mn 0.1 ]O 2, A slurry was prepared by mixing carbon black as a conductive material and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 92:5:3. The slurry was uniformly applied to a 15 μm thick aluminum foil and vacuum-dried at 130°C to prepare a positive electrode for a lithium secondary battery.

[0143] An anode slurry containing 95 wt% natural graphite as an anode active material, 1 wt% Super-P as a conductive agent, 2 wt% styrene-butadiene rubber (SBR) as a binder, and 2 wt% carboxymethyl cellulose (CMC) as a thickener was prepared. The anode slurry was uniformly coated on a 15 μm thick copper foil, dried, and pressed to prepare an anode.

[0144] The positive electrode and the negative electrode were each cut to a predetermined size and laminated, and a separator (polyethylene, 20 ㎛ thick) was interposed between the positive electrode and the negative electrode to form an electrode cell, and the tab portions of the positive electrode and the negative electrode were each welded. The welded positive electrode / separator / negative electrode assembly was placed in a pouch and sealed on three sides except for the electrolyte injection portion. At this time, the part with the electrode tab was included in the sealing portion. The non-aqueous electrolyte prepared in (1) was injected through the electrolyte injection portion, and the electrolyte injection portion was also sealed, followed by impregnation for 12 hours or more to manufacture a lithium secondary battery.

[0145] Examples 2 to 17

[0146] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of the compound represented by Chemical Formula 2 or Chemical Formula 3 and the content of auxiliary additives relative to the total weight of the non-aqueous electrolyte were adjusted as shown in Table 1 below.

[0147] Comparative Example 1

[0148] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that no additives were added.

[0149] Comparative Example 2

[0150] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that instead of the compound represented by the above chemical formula 2 as an additive, the raw materials divinyl sulfone and diphenyl phosphite were added in an amount of 0.5 wt% each based on the total weight of the non-aqueous electrolyte and simply mixed.

[0151] Comparative Example 3

[0152] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that instead of the compound represented by the above chemical formula 2 as an additive, the raw materials divinyl sulfone and diphenylphosphine oxide were added in an amount of 0.5 wt% each based on the total weight of the non-aqueous electrolyte and simply mixed.

[0153] The types and contents of additives used in the examples and comparative examples, and the contents of auxiliary additives are shown in Table 1 below.

[0154] Classification Additive (wt%) Auxiliary Additive (wt%) Type Content FECPSESA Total Example 1 Chemical formula 20.5 1.0 0.5 0.5 2.0 Example 2 Chemical formula 20.3 1.0 0.5 0.5 2.0 Example 3 Chemical formula 21.5 1.0 0.5 0.5 2.0 Example 4 Chemical formula 23.2 1.0 0.5 0.5 2.0 Example 5 Chemical formula 24.8 1.0 0.5 0.5 2.0 Example 6 Chemical formula 20.0 8 1.0 0.5 0.5 2.0 Example 7 Chemical formula 25.1 1.0 0.5 0.5 2.0 Example 8 Chemical formula 20.3 1.0 0.7 0.5 2.2 Example 9 Chemical formula 20.51.00.50.31.8 Example 10 Chemical Formula 20.52.51.00.64.1 Example 11 Chemical Formula 30.51.00.50.52.0 Example 12 Chemical Formula 30.31.00.50.52.0 Example 13 Chemical Formula 31.51.00.50.52.0 Example 14 Chemical Formula 33.21.00.50.52.0 Example 15 Chemical Formula 34.81.00.50.52.0 Example 16 Chemical Formula 30.081.00.50.52.0 Example 17 Chemical Formula 35.11.00.50.52.0 Comparative Example 1--1.00.50.52.0 Comparative Example 2 Divinyl Sulfone + Diphenyl Phosphite 1.01.00.50.52.0 Comparative Example 3 Divinyl Sulfone + Diphenyl Phosphine Oxide 1.01.00.50.52.0

[0155] Experimental example

[0156] (1) Initial performance evaluation

[0157] 1) Initial discharge capacity evaluation

[0158] For the lithium secondary batteries according to the above-described examples and comparative examples, charging (CC / CV 1 / 3C 4.2V 0.05C CUT-OFF) and discharging (CC 1 / 3C 2.5V CUT-OFF) were performed once each, and the initial discharge capacity was measured.

[0159] 2) Discharge DCIR (Direct Current Internal Resistance) Evaluation

[0160] At the point where the SOC (State of Charge) of the lithium secondary battery according to the above-described examples and comparative examples was set to 60%, the C-rate was sequentially increased to 0.2C, 0.5C, 1.0C, 1.5C, 2.0C, 2.5C, and 3.0C. The terminal points of the voltage when charging and discharging were performed for 10 seconds at each C-rate were constructed as a straight-line equation, and the slope was adopted as the DCIR (direct current internal resistance).

[0161] (2) Evaluation of high-temperature storage characteristics (60 ℃)

[0162] After the lithium secondary batteries according to the above-described examples and comparative examples were left in a 60°C chamber for 11 weeks, the following evaluations were conducted.

[0163] 1) Capacity retention rate evaluation (60 ℃)

[0164] The discharge capacity was measured by discharging the lithium secondary battery (CC 1 / 3C 2.5V CUT-OFF). The discharge capacity was divided by the initial discharge capacity measured in Experimental Example (1)1) and calculated as a percentage.

[0165] Discharge capacity measurement was performed using the same method as in Experimental Example (1)1).

[0166] 2) Discharge DCIR evaluation

[0167] The discharge DCIR was measured using the same method as in Experimental Example (1)2).

[0168] 3) ACIR (Alternative Current Internal Resistance) measurement

[0169] ACIR was measured by contacting the terminal of a battery tester (BT3562A, HIOKI) to each of the positive and negative tabs of the lithium secondary batteries according to the above-described examples and comparative examples.

[0170] (3) Evaluation of high temperature life characteristics (45 ℃)

[0171] The lithium secondary batteries according to the above-described examples and comparative examples were repeatedly charged (CC / CV 1 / 3C 4.2V 0.05C CUT-OFF) and discharged (CC 1 / 3C 2.5V CUT-OFF) 500 times in a 45°C chamber, and then the following evaluations were performed.

[0172] 1) Capacity retention rate and discharge capacity evaluation (45 ℃)

[0173] The discharge capacity was measured at the 500th discharge.

[0174] The capacity retention rate of the lithium secondary battery was evaluated by dividing the discharge capacity measured at the 500th discharge by the initial discharge capacity measured in the above experimental example (1)1) and multiplying by 100 to obtain the capacity retention rate.

[0175] 2) Discharge DCIR evaluation

[0176] The discharge DCIR was measured using the same method as in Experimental Example (1)2).

[0177] The evaluation results according to the experimental examples described above are shown in Tables 2 and 3 below.

[0178] Initial performance evaluation High temperature storage characteristics evaluation (60 ℃), 11 weeks Initial discharge capacity (mAh) DCIR (mΩ) Capacity retention rate (%) DCIR (mΩ) ACIR (mΩ) Example 1 185941.88742.819.3 Example 2 185542.28643.219.4 Example 3 186341.58842.219.2 Example 4 186840.88942.019.1 Example 5 187539.79041.818.9 Example 6 179045.88346.219.5 Example 7 176438.28346.420.1 Example 8 187139.88744.719.3 Example 9183345.18446.119.7 Example 10187238.58443.519.9 Example 11186541.78644.319.2 Example 12187742.08442.719.5 Example 13187941.48842.519.1 Example 14188540.58942.318.9 Example 15189439.69142.118.8 Example 16175645.28346.519.9 Example 17172047.58247.221.2 Comparative Example 1184240.17554.123.8 Comparative Example 2184943.37749.822.5 Comparative example 3185943.67848.722.2

[0179] ClassificationHigh-temperature life cycle characteristics evaluation (45 ℃, 500cyc)Discharge capacity (mAh)Capacity retention rate (%)DCIR (mΩ)Example 116178728.96Example 216328830.31Example 316378928.58Example 416459028.23Example 516589227.50Example 615908531.14Example 715778632.05Example 816098630.66Example 915818531.47Example 1015948532.03Example 1116598929.19Example 1216148628.25Example 1316658928.11 Example 1416729028.01 Example 1516809227.68 Example 1615838531.01 Example 1715748732.72 Comparative Example 115477835.02 Comparative Example 215538034.20 Comparative Example 315808134.61

[0180] Referring to Tables 2 and 3, in the examples in which a sulfonyl compound containing a sulfonyl group and two phosphorus atoms was added as an additive, the initial performance, high-temperature storage characteristics, and high-temperature life characteristics were improved overall compared to the comparative examples.

[0181] In Examples 6, 7, 16 and 17, where the additive content was outside of 0.1 wt% to 5 wt% of the total weight of the non-aqueous electrolyte, the discharge capacity and capacity retention rate were relatively reduced and the resistance was increased compared to the other examples.

[0182] In Examples 9 and 10, where the content of auxiliary additives was outside of 2 wt% to 4 wt% of the total weight of the non-aqueous electrolyte, the discharge capacity and capacity retention rate were relatively reduced and the resistance increased compared to the other examples.

Claims

1. Non-aqueous organic solvent; lithium salts; and A non-aqueous electrolyte comprising an additive comprising a sulfonyl compound containing a sulfonyl group and two phosphorus atoms in one molecule.

2. In claim 1, the non-aqueous electrolyte comprises at least one selected from the group consisting of compounds represented by the following chemical formula 1: [Chemical Formula 1] (In chemical formula 1, R 1 , R 2 , R 5 and R 6 are each independently C6-C 12 aryl group, C6-C 12 Heteroaryl group, phenoxy group, heterophenoxy group, C1-C6 alkyl group, C1-C6 heteroalkyl group, C1-C6 alkoxy group, C1-C6 heteroalkoxy group, C5-C 12 Cycloalkyl group, C5-C 12 Contains a cycloalkenyl group, a 5 to 7 membered heterocycloalkyl group, or a 5 to 7 membered heterocycloalkenyl group, R 3 and R 4 Each independently includes a C1-C6 alkyl group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group.

3. In claim 2, the sulfonyl compound is a non-aqueous electrolyte comprising a compound represented by the following chemical formula 2: [Chemical Formula 2] .

4. In claim 2, the sulfonyl compound is a non-aqueous electrolyte comprising a compound represented by the following chemical formula 3: [Chemical Formula 3] .

5. A non-aqueous electrolyte according to claim 1, wherein the content of the additive is 0.1 wt% to 5.0 wt% relative to the total weight of the non-aqueous electrolyte.

6. A non-aqueous electrolyte according to claim 1, wherein the content of the additive is 0.3 wt% to 0.8 wt% relative to the total weight of the non-aqueous electrolyte.

7. A non-aqueous electrolyte according to claim 1, further comprising an auxiliary additive comprising an alkyl sultone compound.

8. A non-aqueous electrolyte according to claim 7, wherein the content of the auxiliary additive is 2 wt% to 4 wt% based on the total weight of the non-aqueous electrolyte.

9. A non-aqueous electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises at least one selected from the group consisting of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.

10. A non-aqueous electrolyte according to claim 1, wherein the lithium salt comprises at least one selected from the group consisting of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

11. Bipolar; a cathode opposite to the anode; and A lithium secondary battery comprising the non-aqueous electrolyte of claim 1.

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