Compound, nonaqueous electrolyte solution containing the same, and lithium secondary battery

Abstract

This invention relates to a compound, and to a compound represented by Formula I as described herein, a non-aqueous electrolyte containing the compound, and a lithium secondary battery. When the compound is contained in a non-aqueous electrolyte, the compound can reduce the flammability of the non-aqueous electrolyte and can improve the battery's lifespan characteristics by forming an electrode-electrolyte interface that is stable at high temperatures and has low resistance.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims the benefit of the following Korean patent applications filed with the Korean Intellectual Property Office: Korean Patent Application No. 10-2021-0037393 filed on March 23, 2021; Korean Patent Application No. 10-2021-0039092 filed on March 25, 2021; Korean Patent Application No. 10-2021-0043329 filed on April 2, 2021; and Korean Patent Application No. 10-2022-0035958 filed on March 23, 2022, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0004] This invention relates to a sulfonyl lactone compound, a non-aqueous electrolyte containing the compound, and a lithium secondary battery. Background Technology

[0005] Recently, as the application of lithium secondary batteries has rapidly expanded to powering electronic devices such as electrical, electronic, communication and computer devices, as well as power storage supply for large-area devices such as automobiles and power storage devices, the demand for high-capacity, high-output and high-stability secondary batteries has been increasing.

[0006] Lithium-ion rechargeable batteries are typically manufactured as follows: A positive electrode and a negative electrode are formed by coating a mixture of a positive electrode active material made of lithium-containing transition metal oxides or the like, or a negative electrode active material made of carbon or silicon capable of absorbing and releasing lithium ions, along with selective binders and conductive materials. These materials are then applied to positive and negative electrode current collectors to create the positive and negative electrodes. The positive and negative electrodes are then stacked on each side of a separator to form an electrode current collector of a predetermined shape. Finally, the electrode current collector and a non-aqueous electrolyte are inserted into the battery casing. To ensure battery performance, formation and aging processes are usually required.

[0007] The formation process is a step in activating a secondary battery after assembly through repeated charge and discharge cycles. During charging, lithium ions released from the lithium-containing transition metal oxide used as the positive electrode are transferred and inserted into the carbon-based negative electrode active material used as the negative electrode. At this point, the highly reactive lithium ions react with the electrolyte to generate compounds such as Li₂CO₃, Li₂O, and LiOH, which form a solid electrolyte interphase (SEI) layer on the electrode surface. Since the SEI layer significantly affects battery life and capacity retention, its formation is a crucial factor.

[0008] Recently, high capacity, high power, and long lifespan characteristics have become increasingly important, particularly for lithium-ion batteries used in vehicles. To achieve high capacity, high-energy-density but low-stability positive electrode active materials are used. Therefore, it is necessary to form an active material-electrolyte interface (SEI) that stabilizes the positive electrode active material by protecting its surface. For the negative electrode, problems such as the decomposition of surface materials in the electrolyte and the induction of side reactions have been reported, necessitating the formation of a low-resistivity and robust SEI layer. Furthermore, since the SEI layer may slowly degrade during high-temperature storage, leading to problems such as electrode exposure, efforts have been made to develop an additive for the electrolyte that helps to create an SEI interface capable of suppressing side reactions during high-temperature storage. On the other hand, 1,3-propanesulfonyl lactone, a known effective additive for forming the SEI layer of the negative electrode, has toxicity issues, and 1,3,2-dioxane-2,2-dioxide and similar additives have problems such as gas generation and chemical stability.

[0009] As mentioned above, with high-temperature drive and long-term life characteristics becoming important for lithium secondary batteries, electrolyte decomposition reactions caused by redox reactions occurring at the interface between the electrolyte and electrodes accumulate during repeated cycles, thereby increasing resistance and thus causing a problem of deterioration in life characteristics. Summary of the Invention

[0010] Technical issues

[0011] One aspect of the present invention provides a compound, a non-aqueous electrolyte containing the compound, and a lithium secondary battery. When the compound is contained in the non-aqueous electrolyte, it can reduce the flammability of the non-aqueous electrolyte and enable the formation of a thin and stable SEI layer, thereby achieving a lithium secondary battery with excellent high-temperature stability and lifespan characteristics.

[0012] Technical solution

[0013] According to one aspect of the present invention, a compound, a non-aqueous electrolyte, and a lithium secondary battery are provided.

[0014] (1) The present invention provides compounds represented by the following formula I.

[0015] [Formula I]

[0016]

[0017] In equation I above, n and m are each independently 1 or 2, and Ak is substituted or unsubstituted C1-C. 10 alkylene, and

[0018] X is a C1-C molecule that has been replaced by one or more halogen elements. 10Alkyl group; -Y1-C≡C-Y2 group; or -Y1-CN group, wherein

[0019] Y1 is a direct bond, or a substituted or unsubstituted C1-C bond. 10 alkylene, and

[0020] Y2 is hydrogen, or a substituted or unsubstituted C1-C. 10 alkyl.

[0021] (2) In (1) above, the present invention provides a compound, wherein the compound represented by the above formula I is the compound represented by the following formula 1.

[0022] [Formula 1]

[0023]

[0024] In Equation 1 above, n and m are each independently 1 or 2, and Ak is substituted or unsubstituted C1-C. 10 Alkylene

[0025] X is a C1-C molecule that has been replaced by one or more halogen elements. 10 Alkyl, -Y1-C≡C-Y2 group, or -Y1-CN group, wherein

[0026] Y1 is a direct bond, or a substituted or unsubstituted C1-C bond. 10 alkylene, and

[0027] Y2 is hydrogen, or a substituted or unsubstituted C1-C. 10 alkyl.

[0028] (3) In (1) or (2) above, the present invention provides a compound wherein Ak is an unsubstituted C1-C6 alkylene group.

[0029] (4) In any of (1) to (3) above, the present invention provides a compound wherein X is a C1-C6 alkyl group substituted with one or more halogen elements.

[0030] (5) In any of (1) to (3) above, the present invention provides a compound wherein X is a -Y1'-C≡C-Y2' group, wherein Y1' is an unsubstituted C1-C6 alkylene group, and Y2' is hydrogen or an unsubstituted C1-C6 alkyl group.

[0031] (6) In any of (1) to (3) above, the present invention provides a compound wherein X is a -Y1'-CN group, wherein Y1' is an unsubstituted C1-C6 alkylene group.

[0032] (7) In any of (1) to (3) above, the present invention provides a compound, wherein the compound represented by the above formula I is any one of the compounds represented by the following formulas a to f.

[0033] [Formula a]

[0034]

[0035] [Formula b]

[0036]

[0037] [Formula c]

[0038]

[0039] [Formula d]

[0040]

[0041] [Form e]

[0042]

[0043] [Form f]

[0044]

[0045] (8) In addition, the present invention provides a non-aqueous electrolyte comprising an organic solvent, a lithium salt and a compound according to any one of (1) to (7) above.

[0046] (9) In (8) above, the present invention provides a non-aqueous electrolyte, wherein the content of the compound is from 0.01% by weight to 10% by weight based on the total weight of the non-aqueous electrolyte.

[0047] (10) In addition, the present invention provides a lithium secondary battery comprising the non-aqueous electrolyte according to (8) or (9) above.

[0048] Beneficial effects

[0049] When the compound represented by Formula I according to the present invention is included in a non-aqueous electrolyte, the flammability of the non-aqueous electrolyte can be reduced, and a thin and stable SEI layer can be formed, thereby providing a lithium secondary battery with excellent high-temperature stability and life characteristics. Detailed Implementation

[0050] The invention will be described in more detail below.

[0051] It should be understood that the terms or words used in this specification and claims should not be construed as having the meanings defined in common dictionaries, but should be interpreted as having meanings and concepts consistent with the technical ideas of the invention, based on the principle that the inventors can appropriately define the concepts of the terms to best interpret the invention.

[0052] The terminology used in this invention is for describing specific embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0053] It should be understood that the terms “comprising” or “having” are intended to specify the presence of the features, figures, steps, operations, elements, parts or combinations thereof described in this disclosure, but do not exclude the presence or addition of more than one other feature, figure, step, operation, element, part or combination thereof.

[0054] In this invention, in "C" a -C b In the description of "C1-C", "a" and "b" refer to the number of carbon atoms. For example, "C1-C 10 "Alkylene" refers to alkylene containing 1 to 10 carbon atoms, such as -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH(CH3)-, -CH(CH3)CH2-, -CH(CH3)CH2-, etc.

[0055] The inventors conducted repeated research to develop lithium secondary batteries with excellent performance at high temperatures, and found that when sulfonyl lactone compounds represented by Formula 1 are used as additives for non-aqueous electrolytes, high-temperature storage characteristics and lifespan characteristics are improved, and thus the present invention was completed.

[0056] Compounds represented by formula I

[0057] This invention provides a compound represented by the following formula I.

[0058] [Formula I]

[0059]

[0060] In equation I above, n and m are each independently 1 or 2, and Ak is substituted or unsubstituted C1-C. 10 alkylene, and

[0061] X is a C1-C molecule that has been replaced by one or more halogen elements. 10 Alkyl, -Y1-C≡C-Y2 group, or -Y1-CN group, wherein

[0062] Y1 is a direct bond, or a substituted or unsubstituted C1-C bond. 10 alkylene, and

[0063] Y2 is hydrogen, or a substituted or unsubstituted C1-C. 10 alkyl.

[0064] In this invention, the substituents in the substituted alkylene or substituted alkyl group may be selected from one or more of the following: deuterium, halogen group, hydroxyl group, amino group, thiol group, nitro group, nitrile group, silyl group and straight-chain or branched C1-C6 alkoxy group.

[0065] 1,3-propanesulfonyl lactone (PS), which is commonly used as an electrolyte additive, is limited in use due to its toxicity. However, the compound of formula I of the present invention is less toxic than 1,3-propanesulfonyl lactone and contains electron-withdrawing functional groups as terminal groups, as well as sulfite groups or sulfate groups. Therefore, a durable film with high lithium salt conductivity can be formed on the surfaces of the positive and negative electrodes.

[0066] The compound represented by Formula I above has an electron-withdrawing group located at the end (position X), thereby lowering the lowest unoccupied molecular orbital (LUMO) energy and increasing reducing power. Therefore, a film (SEI layer) can be more easily formed on the electrode surface.

[0067] Furthermore, the compound represented by Formula I contains sulfonyl lactone groups with high ionic conductivity in its molecule, thereby minimizing the increase in interfacial resistance and forming a stable film that prevents the electrode surface from being exposed, thus preventing side reactions between the electrode and the electrolyte, inhibiting O2 generation, and effectively controlling the dissolution of transition metals from the positive electrode.

[0068] As a result, lithium secondary batteries with improved high-temperature storage and high-temperature cycling characteristics can be realized.

[0069] The sulfonyl lactone compounds of the present invention, represented by Formula I, can be prepared by: sulfonating an olefin compound containing a diol or a halogen compound containing a diol; preparing a hydroxyl-containing sulfonyl lactone compound by condensing an alcohol group of a diol with a sulfonate group; preparing a compound containing a chlorosulfite group by sulfonating a residual hydroxyl group; preparing a compound containing a sulfite group by reacting a compound containing a chlorosulfite group with an alcohol group; and preparing a compound containing a sulfate group by oxidizing the sulfite group. However, the invention is not limited to these methods, and the sulfonyl lactone compounds of the present invention, represented by Formula I, can be prepared by known methods.

[0070] On the other hand, the compound represented by Formula I has a higher reduction potential than that of non-aqueous solvents, which allows it to decompose first under battery-driven conditions to form a robust film. The reduction potential can be measured in the following manner using the Gaussian 09 package (Gaussian 09Revision C.01, Gaussian Corporation, Wallingford, CT, 2009) with DFT calculations applied.

[0071] 1) Calculate the stable structure energy (Eneut) of the compound in its unreduced state and the stable structure energy (Ered) of the compound in its reduced state. 2) Calculate E... neut -E red -1.45 eV is defined as the reduction stability value. At this point, the structural stabilization calculation is performed using the polarizable continuum model (PCM) method.

[0072] According to the present invention, in Formula I above, Ak can be an unsubstituted C1-C6 alkylene group, more specifically, an unsubstituted C1-C5 alkylene group. In this case, it is advantageous for the synthesis of the compound, and when used as an additive for non-aqueous electrolytes, it can prevent an increase in the resistance of the SEI layer, and thus prevent an increase in the resistance of the battery.

[0073] According to the present invention, in Formula I above, X can be a C1-C6 alkyl group substituted with one or more halogen elements, more specifically, it can be a C1-C5 alkyl group substituted with one or more halogen elements. In this case, the electron-withdrawing force is stronger, resulting in high reducing power, making it easier to form an SEI layer on the surface of the electrode. On the other hand, the halogen element can specifically be fluorine.

[0074] According to the present invention, in Formula I above, X can be a -Y1'-C≡C-Y2' group, wherein Y1' can be an unsubstituted C1-C6 alkylene group, and Y2' can be hydrogen or an unsubstituted C1-C6 alkyl group. In this case, the C≡C triple bond in one molecule polymerizes with the C≡C triple bond in another molecule, thereby forming a more robust SEI layer. Specifically, Y1' can be an unsubstituted C1-C5 alkylene group, and Y2' can be hydrogen or an unsubstituted C1-C5 alkyl group.

[0075] According to the present invention, in Formula I above, X can be a -Y1'-CN group, where Y1' can be an unsubstituted C1-C6 alkylene group. Specifically, Y1' can be an unsubstituted C1-C5 alkylene group. In this case, the electron-withdrawing force is stronger, resulting in high reducibility, making it easier to form an SEI layer on the electrode surface.

[0076] According to the present invention, the compound represented by Formula I above can be a compound represented by Formula 1 below.

[0077] [Formula 1]

[0078]

[0079] In Equation 1 above, n and m are each independently 1 or 2, and Ak is substituted or unsubstituted C1-C. 10 alkylene, and

[0080] X is a C1-C molecule that has been replaced by one or more halogen elements. 10 Alkyl, -Y1-C≡C-Y2 group, or -Y1-CN group, wherein

[0081] Y1 is a direct bond, or a substituted or unsubstituted C1-C bond. 10 alkylene, and

[0082] Y2 is hydrogen, or a substituted or unsubstituted C1-C. 10 alkyl.

[0083] When compounds such as 1,3-propanesulfonyl lactone or 1,4-butanesulfonyl lactone are used as electrolyte additives, there are problems with ring-opening reactions and the manifestation of toxicity. However, when compounds such as those shown in Formula 1 above are used, the position adjacent to oxygen in the ring structure is -Ak-O- (S=O). m When compounds with OX groups are used as electrolyte additives, they can prevent ring-opening reactions, thereby preventing them from exhibiting toxicity.

[0084] In Equation 1 above, n, m, Ak, X, Y1, and Y2 can be the same as n, m, Ak, X, Y1, and Y2 in Equation I above.

[0085] In Formula 1 above, Ak can specifically be an unsubstituted C1-C6 alkylene group, X can be a C1-C6 alkylene group substituted with one or more halogen elements; a -Y1'-C≡C-Y2' group (where Y1' is an unsubstituted C1-C6 alkylene group and Y2' is hydrogen; or an unsubstituted C1-C6 alkyl group); or a -Y1'-CN group (where Y1' is an unsubstituted C1-C6 alkylene group).

[0086] According to the present invention, the compound represented by Formula I above can be a compound represented by any one of Formulas a to f below.

[0087] [Formula a]

[0088]

[0089] [Formula b]

[0090]

[0091] [Formula c]

[0092]

[0093] [Formula d]

[0094]

[0095] [Form e]

[0096]

[0097] [Form f]

[0098]

[0099] Non-aqueous electrolyte

[0100] The present invention provides a non-aqueous electrolyte comprising an organic solvent, a lithium salt, and a compound represented by Formula I above.

[0101] (1) Compounds represented by formula I

[0102] The non-aqueous electrolyte according to the present invention contains a compound represented by Formula I above as an additive.

[0103] When a compound represented by Formula I above is included in a non-aqueous electrolyte to reduce toxicity issues, a thin and stable SEI layer can be formed, thereby providing a lithium secondary battery with excellent high-temperature stability and lifespan characteristics.

[0104] According to the present invention, the content of the compound can be from 0.01 wt% to 10 wt% based on the total weight of the non-aqueous electrolyte, specifically from 0.01 wt% to 5 wt%, from 0.01 wt% to 1 wt%, or from 0.1 wt% to 1 wt%. In this case, when the non-aqueous electrolyte is applied to a secondary battery, a robust SEI layer can be formed to help improve long-term life characteristics and reduce gas generation.

[0105] (2) Organic solvents

[0106] The organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries. There are no restrictions on it, as long as it can minimize the decomposition caused by oxidation reactions during the charging and discharging of the secondary battery, and can exhibit the required performance when used with additives.

[0107] The organic solvent may be, for example, linear or cyclic carbonates, linear or cyclic esters, ethers, glycol dimethyl ether, nitriles (acetonitrile, SN, etc.), but is not limited thereto. Carbonate-based electrolyte solvents, including cyclic carbonates, linear carbonates, or mixtures thereof, may be representative examples of such organic solvents.

[0108] On the other hand, specific examples of the cyclic carbonate compounds may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, vinylene carbonate, and fluoroethylene carbonate (FEC).

[0109] Specific examples of the linear carbonate compounds may include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, etc.

[0110] Specific examples of the linear ester compound may include, but are not limited to, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, etc.

[0111] Specific examples of the cyclic ester compounds may include, but are not limited to, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, etc.

[0112] Specific examples of the ether solvent may include, but are not limited to, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), etc.

[0113] The glycol dimethyl ether solvent is a solvent with a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents, and with less reactivity with metals. It may include, but is not limited to, dimethoxyethane (glycol dimethyl ether, DME), diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether (TEGDME), etc.

[0114] Specific examples of the nitrile solvents may include, but are not limited to, acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptanitrile, cyclopentanoic acid, cyclohexanoic acid, 2-fluorobenzyl nitrile, 4-fluorobenzyl nitrile, difluorobenzyl nitrile, trifluorobenzyl nitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, etc.

[0115] On the other hand, ethylene carbonate and propylene carbonate, as cyclic carbonate organic solvents, can preferably be used because they are high-viscosity organic solvents with high dielectric constants, thus enabling good dissociation of lithium salts in the electrolyte. Such cyclic carbonates can be further preferably used in combination with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate in appropriate proportions, because an electrolyte with high conductivity can be prepared. In this case, the cyclic carbonates and linear carbonates can be mixed and used in a volume ratio of 2:8 to 4:6.

[0116] (3) Lithium salts

[0117] The lithium salt is used as an electrolyte salt in lithium secondary batteries and as a medium for ion transfer. Typically, the lithium salt may contain one or more compounds selected from the following: LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiN(C2F5SO2)2, LiN(CF3SO2)2, CF3SO3Li, LiC(CF3SO2)3, LiC4BO8, LiTFSI, LiFSI, and LiClO4. Preferably, LiPF6 may be included, but it is not limited thereto. Alternatively, one of these compounds may be used as the lithium salt, or, if desired, two or more may be used in combination.

[0118] According to the present invention, lithium salt can be included at a concentration of 0.5M to 5M, preferably at a concentration of 0.5M to 4M. When the concentration of lithium salt is within the above range, the concentration of lithium ions in the electrolyte is appropriate, thereby allowing the battery to charge and discharge normally. Furthermore, due to the appropriate viscosity of the electrolyte, the wettability in the battery is excellent, which improves the battery performance.

[0119] (4) Other electrolyte additives

[0120] The non-aqueous electrolyte may also contain other electrolyte additives.

[0121] The other electrolyte additives are electrolyte additives known in the art, which can be additionally added to the non-aqueous electrolyte of the present invention, and may include, for example, vinylene carbonate, vinyl ethylene carbonate, catechol carbonate, α-bromo-γ-butyrolactone, methyl chloroformate, succinimide, N-benzyloxycarbonyloxysuccinimide, N-hydroxysuccinimide, N-chlorosuccinimide, methyl cinnamate, 1,3,5-tricyanobenzene, tetracyanoquinone dimethane, pyrocarbonate, cyclohexylbenzene, propane sulpholactone, succinic acid, etc. Adiponitrile, ethylene sulfate, propylene sulfonyl lactone, fluoroethylene carbonate, LiPO2F2, lithium difluorooxalate borate (LiODFB), lithium bis(oxalate)borate (LiBOB), 3-trimethoxysilyl-propyl-N-aniline (TMSPa), tri(trimethylsilyl)phosphite (TMSPi), 12-crown-4, 15-crown-5, 18-crown-6, azeotropic ethers, boranes, borate esters, boronates, ferrocene and its derivatives, LiBF4, etc.

[0122] The content of the other electrolyte additives can be from 0.01% by weight to 10% by weight, preferably from 0.05% by weight to 7.0% by weight, and more preferably from 0.05% by weight to 5.0% by weight.

[0123] Lithium secondary batteries

[0124] The present invention provides a lithium secondary battery comprising a non-aqueous electrolyte.

[0125] Specifically, the lithium secondary battery contains a positive electrode comprising a positive electrode active material, a negative electrode comprising a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte according to the present invention.

[0126] At this time, the lithium secondary battery of the present invention can be manufactured by a conventional method known in the art. For example, the lithium secondary battery of the present invention can be manufactured as follows: an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode is formed, and then the electrode assembly is inserted into a battery case, and then a non-aqueous electrolyte according to the present invention is injected therein.

[0127] (1) Positive electrode

[0128] The positive electrode can be manufactured by coating a positive electrode paste on a positive electrode current collector, and the positive electrode paste contains a positive electrode active material, a binder, a conductive material, a solvent, etc.

[0129] There is no particular limitation on the positive electrode current collector as long as it has conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used. In addition, in order to improve the binding force of the positive electrode active material, fine irregularities can be formed on the surface of the positive electrode current collector, and the positive electrode current collector can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

[0130] The positive electrode active material is a compound capable of reversibly inserting and extracting lithium. Specifically, it may include a lithium metal oxide, which includes one or more metals such as cobalt, manganese, nickel, and aluminum and lithium. More specifically, the lithium metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2- z Ni z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2O2 (where 0) <Y2<1)、LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2, etc.), lithium-nickel-manganese-cobalt oxides (such as Li(Ni) p Co q Mn r1 O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li (Ni p1 Co q1 Mn r2 O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2, etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni)O4) (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2, etc.), or lithium p2 Co q2 Mn r3 A S2 O2 (where M is selected from the group composed of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r3 and s2 are the atomic fractions of each element, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, p2 + q2 + r3 + s2 = 1, etc.), can contain any one of them or a mixture of two or more of them.

[0131] Among these, the lithium metal oxide can be LiCoO2, LiMnO2, LiNiO2, or lithium-nickel-manganese-cobalt oxide (e.g., Li(NiO2)2) to increase the battery's capacity characteristics and stability. 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Li(Ni) 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2, Li(Ni) 0.8 Mn 0.1 Co 0.1 (O2, etc.) or lithium-nickel-cobalt-aluminum oxides (e.g., Li(Ni) 0.8 Co 0.15 Al 0.05 (O2, etc.). When considering the significant improvement effect of controlling the type and content ratio of the constituent elements forming the lithium metal oxide, the lithium metal oxide can be Li(Ni) 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2, Li(Ni) 0.8 Mn 0.1 Co 0.1 O2, etc., and any one or a mixture of two or more of them can be used.

[0132] Based on the total solid weight of the positive electrode slurry excluding solvent, the content of the positive electrode active material can be from 60% to 99% by weight, preferably from 70% to 99% by weight, and more preferably from 80% to 98% by weight.

[0133] The adhesive is a component used to assist in the bonding of active materials, conductive materials, etc., and in the bonding of current collectors.

[0134] Examples of the adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0135] Typically, based on the total solid weight of the positive electrode slurry excluding solvent, the content of the binder can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0136] The conductive material is a component used to further improve the conductivity of the positive electrode active material.

[0137] There are no particular limitations on the conductive material, as long as it is conductive and will not cause chemical changes in the battery. For example, graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; fluorocarbon powders; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives, etc.

[0138] Typically, based on the total solid weight of the positive electrode slurry excluding solvent, the content of the conductive material can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0139] The solvent may comprise an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and the solvent may be used in an amount that achieves a preferred viscosity when the positive electrode active material and selective binders, conductive materials, etc., are included. For example, the solvent content may be such that the concentration of solids containing the positive electrode active material and selective binders and conductive materials is 50% to 95% by weight, preferably 70% to 95% by weight, and more preferably 70% to 90% by weight.

[0140] (2) Negative electrode

[0141] The negative electrode can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc., onto a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the negative electrode.

[0142] For example, when the negative electrode is manufactured by coating a negative electrode slurry onto a negative electrode current collector, the negative electrode current collector typically has a thickness of 3 μm to 500 μm. There are no particular limitations on the negative electrode current collector, as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., can be used. Furthermore, similar to the case of the positive electrode current collector, to improve the adhesion of the negative electrode active material, fine irregularities can be formed on the surface of the negative electrode current collector. The negative electrode current collector can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0143] Examples of the negative electrode active material may include one or more negative electrode active materials selected from the group consisting of: natural graphite, artificial graphite, carbonaceous materials; metals (Me), such as lithium titanium oxide (LTO), Si, SiO2. x Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of metals (Me); oxides of metals (MeO) x ); and composites of metal (Me) and carbon. Specifically, as the negative electrode active material, silicon (Si), silicon oxide (SiO2) and other materials can be used. x Silicon-based anode active materials, such as silicon alloys, can be used. In this case, a thin and stable SEI layer containing siloxane bonds can be formed, thereby further improving the high-temperature stability and lifespan characteristics of the battery.

[0144] Based on the total solid weight of the negative electrode slurry excluding solvent, the content of the negative electrode active material can be from 60% to 99% by weight, preferably from 70% to 99% by weight, and more preferably from 80% to 98% by weight.

[0145] The adhesive is a component used to facilitate the bonding between conductive materials, active materials, and current collectors. Examples of the adhesive may include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0146] Typically, based on the total solid weight of the negative electrode slurry excluding solvent, the content of the binder can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0147] The conductive material is a component used to further improve the conductivity of the negative electrode active material. There are no particular limitations on the conductive material, as long as it is conductive and does not cause chemical changes in the battery. For example, graphite, such as natural and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; fluorocarbon powders; metal powders, such as aluminum and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxides; or conductive materials, such as polyphenylene derivatives, etc.

[0148] Based on the total solid weight of the negative electrode slurry excluding solvent, the content of the conductive material can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0149] The solvent may include water or an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and the solvent may be used in an amount that achieves a preferred viscosity when the negative electrode active material and selective binders, conductive materials, etc., are included. For example, the solvent content may be such that the solid concentration of the negative electrode active material and selective binders and conductive materials is 50% to 95% by weight, preferably 70% to 90% by weight.

[0150] When the metal itself is used as the negative electrode, the metal film can be used as the negative electrode, or the negative electrode can be manufactured by physically bonding, rolling, or depositing the metal onto the negative electrode current collector. The deposition method can be electrical phase deposition or chemical vapor deposition.

[0151] For example, the metal film itself, or the metal bonded / rolled / deposited on the negative electrode current collector, may be one of the metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two of these metals.

[0152] (3) Diaphragm

[0153] Furthermore, as the diaphragm, ordinary porous polymer membranes commonly used as diaphragms can be used alone, for example, porous polymer membranes made of polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers; or laminates thereof can be used. Alternatively, common porous nonwoven fabrics can be used, such as nonwoven fabrics made of glass fibers or polyethylene terephthalate fibers with high melting points, but the invention is not limited thereto. Additionally, coated diaphragms containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0154] There are no particular limitations on the shape of the lithium secondary battery of the present invention; it can be cylindrical, square, bag-shaped, coin-shaped, etc.

[0155] According to the present invention, a battery module comprising a lithium secondary battery as a unit cell, and a battery pack comprising the battery module can be provided. The battery module and battery pack contain the lithium secondary battery having high capacity, high rate capability, and high cycle performance, and therefore can be used as a power source for medium to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems.

[0156] Modes for implementing inventions

[0157] The invention will be described in more detail below with reference to specific embodiments. However, the following embodiments are for illustrative purposes only to facilitate understanding of the invention and do not limit its scope. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope and spirit of the invention, and such changes and modifications are obviously within the scope of the appended claims.

[0158] Synthesis example

[0159] Synthetic Example 1. Preparation of the compound represented by formula a

[0160] After placing the round-bottom flask in an ice bath, dimethyl carbonate (Aldrich) was introduced into the flask, followed by the sequential addition of 1.1 eq of thionyl chloride (Aldrich), 1.15 eq of pyridine (Aldrich), and 1.0 eq of 5-(hydroxymethyl)-1,2-oxothiacyclopentane-2,2-dioxide (LG Chem). The mixture was then stirred at room temperature for 1 hour. Subsequently, 1.15 eq of 2,2,2-trifluoroethanol (Aldrich) and 1.15 eq of pyridine (Aldrich) were added dropwise in the ice bath. The mixture was then stirred at room temperature for 1 hour, and the residual salt was extracted with water. The organic layer was distilled under reduced pressure to give the intermediate (2,2-dioxido-1,2-oxathiolan-5-yl)methyl(2,2,2-trifluroethyl)sulfite.

[0161] Without performing any additional separation steps, a flask containing the intermediate (2,2-dioxo-1,2-oxothiacyclopentane-5-yl)methyl(2,2,2-trifluoroethyl)sulfite was placed in an ice bath. Then, 1.3 equivalents of sodium periodate (Aldrich) and 0.01 equivalents of ruthenium(III) chloride (Aldrich) were introduced into a mixed solvent in which water and acetonitrile were mixed in a 1:1 weight ratio. The mixture was then stirred in an ice bath for 1 hour.

[0162] Subsequently, tert-butyl ether (Aldrich) was introduced to filter out the precipitated catalyst, and the organic layer was then extracted. The catalyst was further removed using an aqueous solution of sodium metabisulfite (Aldrich). The resulting compound was then column purified after the organic layer was concentrated to give the compound represented by formula a ((2,2-dioxo-1,2-oxothiacyclopentan-5-yl)methyl(2,2,2-trifluoroethyl)sulfate), which was the final compound (yield 27%).

[0163] [Formula a]

[0164]

[0165] pass 1 The synthesis of the compound represented by formula a was confirmed by 1H NMR spectroscopy (Bruker, AVANCE NEO, 500 MHz, acetonitrile-d).

[0166] 1H NMR (acetonitrile-d): δ5.0(m,1H), δ4.9~4.5(m,2H), δ4.8(dd,2H), δ3.5(m,2H), δ2.8(m,1H), δ2.4(m,1H)

[0167] Synthetic Example 2. Preparation of the compound represented by formula b

[0168] The compound represented by formula b ((2,2-dioxo-1,2-oxothiacyclopentan-5-yl)methyl(2,2-difluoroethyl)sulfate) (yield 29%) was obtained by reacting in the same manner as in Synthetic Example 1, except that 2,2-difluoroethanol (Aldrich) was used instead of 2,2,2-trifluoroethanol (Aldrich).

[0169] [Formula b]

[0170]

[0171] pass 1 The synthesis of the compound represented by formula b was confirmed by 1H NMR spectroscopy (Bruker, AVANCE NEO, 500 MHz, acetonitrile-d).

[0172] 1 H NMR (acetonitrile-d): δ6.1(t,1H), δ5.1(m,1H), δ4.9~4.4(m,2H), δ4.7(m,2H), δ3.4(m,2H), δ2.7(m,1H), δ2.3(m,1H)

[0173] Synthetic Example 3. Preparation of the compound represented by formula c

[0174] The compound represented by formula c (but-2-yn-1-yl((2,2-dioxo-1,2-oxothiacyclopentan-5-yl)methyl) sulfate) was obtained by reacting in the same manner as in Synthetic Example 1 (yield 31%), except that 2-butyn-1-ol (Aldrich) was used instead of 2,2,2-trifluoroethanol (Aldrich).

[0175] [Formula c]

[0176]

[0177] pass 1 The synthesis of the compound represented by formula c was confirmed by 1H NMR spectroscopy (Bruker, AVANCE NEO, 500 MHz, acetonitrile-d).

[0178] 1H NMR (acetonitrile-d): δ4.9(m,1H), δ4.6(m,2H), δ4.4~4.1(m,2H), δ3.4(m,2H), δ2.6(m,1H), δ2.4(m,1H), δ1.8(s,3H)

[0179] Synthetic Example 4. Preparation of the compound represented by formula d

[0180] The compound represented by formula c ((2,2-dioxo-1,2-oxothiacyclopentan-5-yl)methylprop-2-yn-1-yl sulfate) (yield 31%) was obtained by reacting in the same manner as in Synthetic Example 1, except that propargyl alcohol (Aldrich) was used instead of 2,2,2-trifluoroethanol (Aldrich).

[0181] [Formula d]

[0182]

[0183] pass 1 The synthesis of the compound represented by formula d was confirmed by 1H NMR spectroscopy (Bruker, AVANCE NEO, 500MHz, DMSO-d6).

[0184] 1 H NMR (DMSO-d6): δ4.9(m,1H), δ4.7(dd,2H), δ4.3~4.1(m,2H), δ3.7(m,1H), δ3.5(m,2H), δ2.6(m,1H), δ2.3(m,1H)

[0185] Synthetic Example 5. Preparation of the compound represented by formula e

[0186] The compound represented by formula e (2-cyanoethyl((2,2-dioxo-1,2-oxothiacyclopentan-5-yl)methyl) sulfate) was obtained by reacting in the same manner as in Synthetic Example 1 (yield 31%), except that 3-hydroxypropionitrile (Aldrich) was used instead of 2,2,2-trifluoroethanol (Aldrich).

[0187] [Form e]

[0188]

[0189] pass 1 1H NMR spectroscopy (Bruker, AVANCE NEO, 500MHz, DMSO-d6) confirmed the synthesis of the compound represented by formula e.

[0190] 1H NMR (DMSO-d6): δ5.1(m,1H), δ4.7~4.5(m,4H), δ3.5(m,2H), δ3.1(m,2H), δ2.9(m,1H), δ2.6(m,1H)

[0191] Synthetic Example 6. Preparation of the compound represented by formula f

[0192] After placing the round-bottom flask in an ice bath, dimethyl carbonate (Aldrich) was introduced into the flask, followed by the sequential introduction of 1.1 equivalents of thionyl chloride (Aldrich), 1.15 equivalents of pyridine (Aldrich), and 1.0 equivalent of 5-(hydroxymethyl)-1,2-oxothiacyclopentane-2,2-dioxide (manufactured by LG Chem). The mixture was then stirred at room temperature for 1 hour. Subsequently, 1.15 equivalents of 3-hydroxypropionitrile and 1.15 equivalents of pyridine (Aldrich) were added dropwise in the ice bath. The mixture was then stirred at room temperature for 1 hour, and the residual salt was extracted with water. The organic layer was distilled under reduced pressure to give the compound represented by formula f (2-cyanoethyl(2,2-dioxo-1,2)-oxothiacyclopentane-5-yl)methyl)sulfite (yield 35%).

[0193] [Form f]

[0194]

[0195] pass 1 The synthesis of the compound represented by formula f was confirmed by 1H NMR spectroscopy (Bruker, AVANCE NEO, 500MHz, DMSO-d6).

[0196] 1 H NMR (DMSO-d6): δ5.0(m,1H), δ4.4~4.2(m,4H), δ3.4(m,2H), δ3.0(m,2H), δ2.8(m,1H), δ2.6(m,1H)

[0197] Examples and Comparative Examples

[0198] Example 1

[0199] (Preparation of non-aqueous electrolytes)

[0200] To prepare a non-aqueous electrolyte, 1 g of the compound represented by formula a was added to 99 g of organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 volume ratio) containing 1 M LiPF6.

[0201] (Manufacturing of secondary batteries)

[0202] The positive electrode active material (LiNi) 0.8 Co 0.1 Mn 0.1 O2): Conductive material (carbon black): Binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) in a weight ratio of 97.5:1:1.5 to prepare a positive electrode slurry (60% by weight solids). This positive electrode slurry was coated onto one surface of a 15 μm thick positive current collector (Al film), followed by drying and rolling to manufacture the positive electrode.

[0203] A negative electrode slurry (50% by weight) was prepared by adding a negative electrode active material (graphite), a conductive material (carbon black), and a binder (polyvinylidene fluoride) to distilled water in a weight ratio of 96:0.5:3.5. This negative electrode slurry was then coated onto one surface of an 8 μm thick negative electrode current collector (Cu film), followed by drying and rolling to fabricate the negative electrode.

[0204] In a drying chamber, a porous polypropylene separator is inserted between the positive and negative electrodes to manufacture an electrode assembly. The electrode assembly is then placed into a battery casing, and a non-aqueous electrolyte is injected. The battery casing is then sealed to manufacture a pouch-type lithium secondary battery (battery capacity: 6.24mAh).

[0205] Example 2

[0206] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, the non-aqueous electrolyte prepared by adding the compound represented by formula b prepared in Synthesis Example 2 instead of the compound represented by formula a prepared in Synthesis Example 1 was used (see Table 1 below).

[0207] Example 3

[0208] The lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte (see Table 1 below) was prepared by adding 0.5 g of the compound represented by Formula a above to 99.5 g of an organic solvent containing 1 M LiPF6 (ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 volume ratio).

[0209] Example 4

[0210] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, the non-aqueous electrolyte prepared by adding the compound represented by formula c prepared in Synthesis Example 3 instead of the compound represented by formula a prepared in Synthesis Example 1 (see Table 1 below).

[0211] Example 5

[0212] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, a non-aqueous electrolyte prepared by adding the compound represented by formula d prepared in Synthesis Example 4 instead of the compound represented by formula a prepared in Synthesis Example 1 was used (see Table 1 below).

[0213] Example 6

[0214] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, the non-aqueous electrolyte prepared by adding the compound represented by formula e prepared in Synthesis Example 5 instead of the compound represented by formula a prepared in Synthesis Example 1 (see Table 1 below).

[0215] Example 7

[0216] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, the non-aqueous electrolyte prepared by adding the compound represented by formula f prepared in Synthesis Example 6 instead of the compound represented by formula a prepared in Synthesis Example 1 (see Table 1 below).

[0217] Comparative Example 1

[0218] The lithium secondary battery was manufactured in the same manner as in Example 1, except that an organic solvent containing 1M LiPF6 (ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 volume ratio) was used instead of the non-aqueous electrolyte in Example 1 (see Table 1 below).

[0219] Comparative Example 2

[0220] The lithium secondary battery was manufactured in the same manner as in Example 1, except that, as the non-aqueous electrolyte, a non-aqueous electrolyte prepared by adding 1 g of 1,3-propanesulfonyl lactone to 99 g of an organic solvent containing 1 M LiPF6 (ethylene carbonate (EC): ethyl carbonate (EMC) = 3:7 volume ratio) was used (see Table 1 below).

[0221] [Table 1]

[0222]

[0223] Experimental Example

[0224] Experimental Example 1: Evaluation of High-Temperature (60℃) Storage Characteristics

[0225] The rate of volume change and the rate of increase in resistivity after high-temperature storage are calculated in the following way.

[0226] (1) Volume change rate (%) after high-temperature storage

[0227] The secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 and 2 were activated using a constant current (CC) of 0.1C. Subsequently, the secondary batteries were charged to 4.2V at a constant current of 0.33C under constant current-constant voltage (CC-CV) charging conditions at 25°C using a PESC05-0.5 charge / discharger (manufacturer: PNE Solution). Then, the current was cut off at 0.05C, and the secondary batteries were discharged to 2.5V at 0.33C under CC conditions. This charge-discharge cycle was defined as one cycle, and two cycles were performed. Next, the secondary batteries were fully charged at a constant current-constant voltage of 0.33C / 4.2V, and then the SOC was adjusted to 50%. The secondary batteries were then discharged at 2.5C for 10 seconds, and the initial resistance was calculated by the difference between the voltage before discharge and the voltage after 10 seconds of discharge. Finally, the secondary batteries were discharged to 2.5V at a constant current of 0.33C. Subsequently, degassing was performed, and the initial volume of the lithium-ion batteries, after initial charge-discharge, was measured by placing them in a bowl filled with water at room temperature using a Two-pls TWD-150DM instrument. The lithium-ion batteries were then fully charged at a constant current-constant voltage of 0.33C / 4.2V and stored at 60°C for 4 weeks (SOC 100%). The volume after high-temperature storage was then measured by placing the lithium-ion batteries in a bowl filled with water at room temperature using a Two-pls TWD-150DM instrument.

[0228] Substitute the initial volume and the volume after high-temperature storage as measured above into the following formula (1) to calculate the volume change rate (%) after high-temperature storage. The results are shown in Table 2 below.

[0229] Equation (1): Volume change rate (%) after high-temperature storage = {(Volume after high-temperature storage - Initial volume) / (Initial volume)} × 100

[0230] (2) Rate of increase in resistivity after high-temperature storage (%)

[0231] The secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 and 2 were activated using a constant current (CC) of 0.1C. Subsequently, the secondary batteries were charged to 4.2V at a constant current of 0.33C under constant current-constant voltage (CC-CV) charging conditions at 25°C using a PESC05-0.5 charge / discharger (manufacturer: PNE Solution). Then, the current was cut off at 0.05C, followed by discharge to 2.5V at 0.33C under CC conditions. This charge-discharge cycle was defined as one cycle, and two cycles were performed. Next, the secondary batteries were fully charged at a constant current-constant voltage of 0.33C / 4.2V, and the SOC was adjusted to 50%. Then, the secondary batteries were discharged at 2.5C for 10 seconds, and the initial resistance was calculated by the difference between the voltage before discharge and the voltage after 10 seconds of discharge. Finally, the secondary batteries were discharged to 2.5V at a constant current of 0.33C. Afterward, the battery was degassed and charged to 4.2V, stored at 60°C (SOC 100%) for 4 weeks, and then discharged again at 2.5C at SOC 50% for 10 seconds to calculate the resistance after high-temperature storage.

[0232] Substitute the initial resistance and the resistance after high-temperature storage as measured above into the following formula (2) to calculate the resistance increase rate (%) after high-temperature storage. The results are shown in Table 2 below.

[0233] Equation (2): Resistance increase rate (%) after high-temperature storage = {(resistance after high-temperature storage - initial resistance) / (initial resistance)} × 100

[0234] [Table 2]

[0235]

[0236] Experiment Example 2: Evaluation of Cyclic Characteristics

[0237] The secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 and 2 were activated using a constant current (CC) of 0.1C. Subsequently, the secondary batteries were charged to 4.2V at a constant current of 0.33C under constant current-constant voltage (CC-CV) charging conditions at 25°C using a PESC05-0.5 charge / discharger (manufacturer: PNE Solution). Then, the current was cut off at 0.05C, and the secondary batteries were discharged to 2.5V at 0.33C under CC conditions. This charge-discharge cycle was defined as one cycle, and two cycles were performed. Next, the secondary batteries were fully charged at a constant current-constant voltage of 0.33C / 4.2V, and the SOC was adjusted to 50%. The secondary batteries were then discharged at 2.5C for 10 seconds, and the initial resistance was calculated by the difference between the voltage before discharge and the voltage after 10 seconds of discharge. Finally, the secondary batteries were discharged to 2.5V at a constant current of 0.33C.

[0238] Afterwards, degassing was performed, and the secondary battery was charged to 4.2V at a constant current of 0.33C under CC-CV charging conditions at 45°C, followed by a 0.05C current cutoff, and then discharged to 2.5V at 0.33C under CC conditions. The above charge-discharge cycle was defined as 1 cycle, and 100 cycles were performed. At this time, the discharge capacity (initial discharge capacity) after the first cycle and the discharge capacity after the 100th cycle were measured using a PESC05-0.5 charge-discharger (manufacturer: PNE solution, 5V, 500mA), and the discharge capacity retention rate after 100 cycles was calculated using the following formula (3). The results are shown in Table 3 below.

[0239] Equation (3): Discharge capacity retention rate (%) after 100 cycles = {(Discharge capacity after 100 cycles) / Initial discharge capacity} × 100

[0240] On the other hand, after 100 cycles, the secondary battery was discharged at 2.5C at 50% SOC for 10 seconds, and the resistance after 100 cycles was calculated by the difference between the voltage before discharge and the voltage after 10 seconds of discharge. The initial resistance calculated as described above and the resistance after 100 cycles were substituted into the following equation (4) to calculate the resistance increase rate (%) after 100 cycles, and the results are shown in Table 3 below.

[0241] Equation (4): Resistance increase rate (%) after 100 cycles = {(resistance after 100 cycles - initial resistance) / (initial resistance)} × 100

[0242] [Table 3]

[0243] Discharge capacity retention rate (%) after 100 cycles Resistance increase rate (%) after 100 cycles Example 1 93 10 Example 2 91 12 Example 3 88 15 Example 4 89 17 Example 5 91 16 Example 6 94 9.5 Example 7 92 14 Comparative Example 1 78 40 Comparative Example 2 85 24

[0244] Referring to Table 2 above, it can be confirmed that the secondary batteries manufactured in Examples 1 to 7 exhibited significantly lower rates of volume change and resistance increase during high-temperature storage compared to the secondary batteries manufactured in Comparative Examples 1 and 2. Furthermore, referring to Table 3, it can be confirmed that the secondary batteries manufactured in Examples 1 to 7 possessed high discharge capacity retention and low resistance increase after 100 cycles, thus exhibiting significantly superior lifetime characteristics compared to the secondary batteries manufactured in Comparative Examples 1 and 2. These performance characteristics are attributed to the effective formation of a highly stable and low-resistance SEI layer by the sulfonyl lactone compounds (represented by Formula I of the present invention) contained in the non-aqueous electrolytes of Examples 1 to 7.

[0245] Therefore, when a compound represented by Formula I is included as an additive in a non-aqueous electrolyte as in this invention, it can be seen that the flammability of the non-aqueous electrolyte can be reduced, and a low-resistance and robust SEI layer can be formed, thereby providing a lithium secondary battery with excellent high-temperature stability and lifespan characteristics.

Claims

1. A compound, The compound is any one of the compounds represented by formulas a to f: [Formula a] [Formula b] [Formula c] [Formula d] [Form e] [Form f] 2. A non-aqueous electrolyte comprising: an organic solvent; a lithium salt; and the compound according to claim 1.

3. The non-aqueous electrolyte according to claim 2, wherein, The content of the compound is from 0.01% to 10% by weight, based on the total weight of the non-aqueous electrolyte.

4. A lithium secondary battery comprising the non-aqueous electrolyte according to claim 2.

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