Nonaqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention comprises a lithium salt, an organic solvent and an additive, wherein the additive includes a first additive and a second additive so that an organic film having excellent ion conductivity and high-temperature safety and an inorganic film having excellent mechanical durability can be formed. Therefore, the present invention can provide a lithium secondary battery having improved high-temperature performance and safety.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0193408 filed on December 20, 2024 and Korean Patent Application No. 10-2025-0204072 filed on December 18, 2025, and all contents disclosed in said Korean patent application documents are incorporated herein as part of the specification.

[0003] Technology field

[0004] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same.

[0005]

[0006] Lithium secondary batteries are used in a wide range of fields, including small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and E-bikes, as well as large products requiring high output such as electric vehicles and hybrid vehicles, and power storage devices and backup power storage devices that store surplus power or renewable energy.

[0007] Such lithium secondary batteries are generally manufactured by injecting or impregnating a non-aqueous electrolyte into an electrode assembly consisting of a positive electrode, a negative electrode, and a separator, and said positive and negative electrodes include an active material capable of lithium ion intercalation and deintercalation.

[0008] Carbon-based active materials are used as negative electrode active materials in lithium-ion batteries, and for example, natural graphite and artificial graphite can be used. In this case, natural graphite has the advantage of exhibiting a higher capacity than artificial graphite. However, natural graphite has a higher specific surface area compared to artificial graphite and a greater change in expansion rate during charging and discharging, which leads to adverse reactions with the electrolyte and can consequently impair the performance of the lithium-ion battery.

[0009] Therefore, there is a need for technology that can improve the performance of lithium secondary batteries using natural graphite.

[0010]

[0011] The present invention aims to solve the above-mentioned problems and can provide a non-aqueous electrolyte capable of forming an organic film with excellent ion conductivity and an inorganic film with excellent durability.

[0012] In addition, the present invention can provide a lithium secondary battery with improved high-temperature durability and lifespan performance by including the above-mentioned non-aqueous electrolyte.

[0013]

[0014] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the additive comprises a first compound represented by the following chemical formula 1 and a second compound represented by the following chemical formula 2.

[0015] [Chemical Formula 1]

[0016]

[0017] In the above chemical formula 1,

[0018] R 11 , R 12 , R 13 , R 21 , R 22 and R 23 is independently selected from hydrogen, fluorine (F), and alkyl groups having 1 to 10 carbon atoms substituted with one or more fluorines, and R 11, R 12 and R 13 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and R 21 , R 22 and R 23 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and

[0019] [Chemical Formula 2]

[0020]

[0021] In the above chemical formula 2, R3 is fluorine (F) or a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, R4 is hydrogen, fluorine, or a carbon-1 to carbon-10 alkyl group, and L is an ether group (*-O-*), a carbon-1 to carbon-5 alkylene group, or a combination thereof.

[0022] [2] The present invention is, in [1] above, wherein R in the first compound represented by the formula 1 above 11 and R 21 α is independently a fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorines, and R 12 , R 13 , R 22 and R 23 This may provide a non-aqueous electrolyte in which R3 in the second compound represented by the above chemical formula 2 is fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorines.

[0023] [3] The present invention may provide a non-aqueous electrolyte comprising, in [1] and / or [2], at least one selected from the group consisting of a compound represented by the following formula 1-1 and a compound represented by the following formula 1-2.

[0024] [Chemical Formula 1-1]

[0025]

[0026] [Chemical Formula 1-2]

[0027]

[0028] [4] The present invention may provide a non-aqueous electrolyte comprising, in at least one of [1] to [3], at least one of the second compound selected from the group consisting of a compound represented by the following formula 2-A and a compound represented by the following formula 2-B.

[0029] [Chemical Formula 2-A]

[0030]

[0031] [Chemical Formula 2-B]

[0032]

[0033] In the above chemical formulas 2-A and 2-B, R3 and L are as defined in the above chemical formula 2.

[0034] [5] The present invention may provide a non-aqueous electrolyte comprising, in at least one of [1] to [4], at least one of the second compound selected from the group consisting of a compound represented by the following chemical formula 2-1 and a compound represented by the following chemical formula 2-2.

[0035] [Chemical Formula 2-1]

[0036]

[0037] [Chemical Formula 2-2]

[0038]

[0039] [6] The present invention may provide a non-aqueous electrolyte in which, in at least one of [1] to [5], the first compound is included in the non-aqueous electrolyte in an amount of 0.01% to 10% by weight.

[0040] [7] The present invention may provide a non-aqueous electrolyte in which, in at least one of [1] to [6], the second compound is included in the non-aqueous electrolyte in an amount of 0.01% to 5% by weight.

[0041] [8] The present invention may provide a non-aqueous electrolyte comprising at least one organic solvent selected from the group consisting of linear carbonate compounds and cyclic carbonate compounds, in at least one of [1] to [7].

[0042] [9] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte according to at least one of [1] to [8].

[0043]

[0010] The present invention may provide a lithium secondary battery according to [9], wherein the negative electrode comprises a negative electrode active material and the negative electrode active material comprises a carbon-based active material.

[0044]

[0011] The present invention can provide a lithium secondary battery comprising at least one carbon-based active material selected from the group consisting of artificial graphite, natural graphite, softened carbon and hardened carbon, in the

[0010] above.

[0045]

[0012] The present invention can provide a lithium secondary battery in which the carbon-based active material comprises natural graphite, in the

[0010] above.

[0046]

[0047] The non-aqueous electrolyte of the present invention comprises a first compound and a second compound as additives. The first compound can be ring-opened by an electrochemical reaction to form an electrode film with excellent ion conductivity and mechanical durability, and the second compound can promote the ring-opening reaction of the first compound while simultaneously improving the high-temperature stability of the electrode film.

[0048] Specifically, the first compound can form a highly flexible organic-based film, and the second compound can form an inorganic-based film, thereby ultimately enabling the formation of an organic / inorganic composite film. Since this organic / inorganic composite film possesses excellent mechanical durability and stability, it can be applied to electrodes containing active materials that undergo significant volume expansion during the charging / discharging process, thereby improving the performance of the secondary battery.

[0049] According to the present invention, by using the first compound and the second compound in combination, an electrode film having the characteristics described above can be easily formed in the initial stage of the activation process, and as a result, the internal resistance of the lithium secondary battery can be reduced and high-temperature safety improved, while simultaneously improving the overall performance of the secondary battery.

[0050]

[0051] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0052] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0053] In this specification, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0054] In this specification, “a” and “b” of “carbon number a to b” refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms.

[0055] In this specification, terms such as "first" and "second" may be used simply to distinguish one component from another and do not limit the components in other aspects (e.g., importance or stacking order).

[0056] In this specification, “substitution” means that at least one hydrogen bonded to carbon is substituted with another element, such as fluorine, unless otherwise defined.

[0057] In this specification, “*” refers to a bonding site in a chemical formula unless otherwise defined.

[0058] In this specification, "single particle type" refers to a particle formed by the aggregation of 30 or fewer sub-particles. The sub-particle unit constituting the single particle type is referred to as a nodule. The single particle type includes a single particle consisting of one nodule and a pseudo-single particle which is a composite of 2 to 30 nodules.

[0059] In this specification, the “nodule” is a sub-particle unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline material that does not appear to have grain boundaries when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0060] In this specification, "secondary particle" refers to a particle formed by the aggregation of more than 30 sub-particles. To distinguish it from the sub-particles constituting a single-particle type particle, the sub-particles constituting the secondary particle are referred to as "primary particles."

[0061] In this specification, “particle” is a concept including any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0062] In this specification, “D min ”, “D 50 ” and “D max ” is a particle size value based on the volume-based particle size distribution of the powder to be measured using the laser diffraction method. Specifically, the above D 50 ☐ may refer to the particle size at the point where the cumulative volume ratio reaches 50% in the volumetric cumulative particle size distribution of the powder under measurement. D min and D max represents the minimum and maximum particle sizes observed, respectively, in the volume-based particle size distribution detectable by the laser diffraction particle size measuring device. The particle size value of the volume-cumulative particle size distribution can be measured, for example, by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtic MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, and obtaining a volume-cumulative particle size distribution graph.

[0063] In this specification, “BET specific surface area” is measured by the BET method and can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using, for example, BEL Japan’s BELSORP-mino II.

[0064]

[0065] The present invention will be described in detail below.

[0066] The non-aqueous electrolyte and / or lithium secondary battery according to the present invention comprises at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0067]

[0068] Non-aqueous electrolytes

[0069] The present invention relates to a non-aqueous electrolyte, specifically a non-aqueous electrolyte for a lithium secondary battery.

[0070] The non-aqueous electrolyte according to the present invention comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a first compound and a second compound. The first compound can form a carbonyl-based organic film with excellent ion conductivity by ring opening, and simultaneously form an inorganic film with excellent durability by including fluorine. Furthermore, the present invention can form an electrode film with improved resistance and high-temperature safety by using a second compound, which includes a sulfonyl group and has excellent high-temperature safety, in combination with the first compound while promoting the ring opening of the first compound.

[0071] Electrode films formed by conventional non-aqueous electrolytes are susceptible to damage during the repeated charging and discharging processes of lithium secondary batteries, leading to a problem of degraded battery performance. For example, when a lithium secondary battery includes natural graphite as the negative electrode active material, which has a higher specific surface area and expansion rate compared to artificial graphite, the electrode film can be easily damaged due to volume changes in the active material during charging and discharging. Such film damage induces the continuous decomposition of the electrolyte, causing additional film to form on the electrode surface; consequently, the film thickness increases, and various side reactions may occur.

[0072] By-products, such as gases generated by these side reactions, can degrade the high-temperature stability of the battery, and thickened electrode films can impede ion conductivity, acting as a factor that increases electrode resistance. Furthermore, these issues can act as factors that generally impair the high-temperature performance and safety of lithium-ion batteries.

[0073] Accordingly, the present invention provides a non-aqueous electrolyte capable of forming an electrode film with excellent ion conductivity, improved durability, and high-temperature safety by applying an additive comprising a first compound and a second compound to the non-aqueous electrolyte. Furthermore, by applying the non-aqueous electrolyte to a lithium secondary battery, the electrochemical performance and high-temperature performance of the lithium secondary battery can be effectively improved.

[0074]

[0075] (1) Additive

[0076] The additive according to the present invention comprises a first compound represented by the following chemical formula 1 and a second compound represented by the following chemical formula 2.

[0077] [Chemical Formula 1]

[0078]

[0079] In the above chemical formula 1, R 11 , R 12 , R13 , R 21 , R 22 and R 23 is independently selected from hydrogen, fluorine (F), and alkyl groups having 1 to 10 carbon atoms substituted with one or more fluorines. In this case, R 11 , R 12 and R 13 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and R 21 , R 22 and R 23 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines.

[0080] [Chemical Formula 2]

[0081]

[0082] In the above chemical formula 2, R3 is fluorine (F) or a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, R4 is hydrogen, fluorine, or a carbon-1 to carbon-10 alkyl group, and L is an ether group (*-O-*), a carbon-1 to carbon-5 alkylene group, or a combination thereof.

[0083] The first compound is a compound containing cyclic carbonate and fluorine, wherein the cyclic carbonate can be opened to form a carbonyl group-based organic film. The organic film is derived from the oxygen-rich cyclic carbonate of the first compound, and the oxygen in the carbonyl group can improve the mobility of lithium cations, thereby enhancing the ionic conductivity of the electrode film. Additionally, since the fluorine (F) included in the first compound can form an inorganic film of LiF to improve the durability of the electrode film, both an organic film and an inorganic film can be formed by the first compound.

[0084] However, since the first compound contains two or more cyclic carbonate structures in a single compound, there is a problem that the reaction participation rate is low due to its steric hindrance. Therefore, when the first compound is used alone, it may be difficult to form an electrode film with desired properties due to the low reaction participation rate.

[0085] Accordingly, by using the first additive and the second additive, which is a coumarin-based compound, in combination, the radical generated during the reduction reaction of the second additive promotes the ring opening of the first additive, thereby improving the reaction participation rate of the first additive. As a result, the present invention can easily form an electrode film with excellent ion conductivity and durability at the beginning of the activation process.

[0086] In addition, the second compound comprises a sulfonyl group and fluorine. The sulfonyl-based film has low reactivity in high-temperature environments, thereby reducing the reactivity of the organic film in high-temperature environments and improving the high-temperature safety of the organic film, while the fluorine enables the realization of an inorganic film with excellent mechanical durability. Accordingly, by including the first and second compounds as additives, the present invention can form an organic film with excellent ion conductivity and high-temperature safety, and an inorganic film with excellent mechanical durability.

[0087] According to the present invention, in the first compound represented by the formula 1, the R 11 and R 21α and β may independently be fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorine atoms, preferably fluorine (F) or an alkyl group having 1 to 3 carbon atoms substituted with one or more fluorine atoms, and in the second compound represented by Formula 2, R3 may be fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorine atoms, preferably fluorine (F) or an alkyl group having 1 to 3 carbon atoms substituted with one or more fluorine atoms. In this case, R 12 , R 13 , R 22 and R 23 ≠ hydrogen. The fluorine of each of the first compound and the second compound is intended to form an inorganic film of LiF, and the inorganic film can improve the mechanical durability of the electrode film. In addition, when the first compound and the second compound satisfy the structure described above, the number of carbon atoms in the alkyl group is reduced, thereby minimizing the increase in resistance and improving the output performance of the lithium secondary battery.

[0088] In addition, the first compound represented by the above chemical formula 1 includes a cyclic carbonate having oxygen in the middle that can improve the mobility of lithium ions, which can further improve the ion conductivity of the organic film and lower the resistance, thereby improving the performance of the lithium secondary battery.

[0089] The first compound above may include at least one selected from the group consisting of a compound represented by the following chemical formula 1-1 and a compound represented by the following chemical formula 1-2.

[0090] [Chemical Formula 1-1]

[0091]

[0092] [Chemical Formula 1-2]

[0093]

[0094] The second compound above may include at least one selected from the group consisting of a compound represented by the following chemical formula 2-A and a compound represented by the following chemical formula 2-B.

[0095] [Chemical Formula 2-A]

[0096]

[0097] [Chemical Formula 2-B]

[0098]

[0099] In the above chemical formulas 2-A and 2-B, R3 and L are as defined in the above chemical formula 2. When a sulfonyl group is bonded to the positions shown in the above chemical formulas 2-A and 2-B of a coumarin compound, the synthesis of the second additive is easy, and furthermore, in the case of the compound represented by chemical formula 2-A, radical formation is easy, resulting in high reactivity and making it easier to form a film.

[0100] The second compound according to the present invention may include at least one selected from the group consisting of compounds represented by the following chemical formula 2-1 and the following chemical formula 2-2.

[0101] [Chemical Formula 2-1]

[0102]

[0103] [Chemical Formula 2-2]

[0104]

[0105] The first compound may be included in the non-aqueous electrolyte in an amount of 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.5 wt% or more, or 1.0 wt% or more, based on the total weight of the non-aqueous electrolyte. The first compound may be included in the non-aqueous electrolyte in an amount of 10 wt% or less, 8 wt% or less, 5 wt% or less, 3 wt% or less, or 2 wt% or less, based on the total weight of the non-aqueous electrolyte.

[0106] More specifically, the first compound may be included in the non-aqueous electrolyte in an amount of 0.01 wt% to 10 wt%, specifically 0.05 wt% to 8 wt%, more specifically 0.1 wt% to 5 wt%, even more specifically 0.5 wt% to 3 wt%, and even more specifically 1.0 wt% to 2.0 wt%. When the content of the first compound satisfies the above range, an electrode film with excellent ion conductivity and durability as described above can be realized, thereby improving the lifespan performance effect of the lithium secondary battery while preventing side reactions caused by the excessive use of additives, which can prevent an increase in resistance.

[0107] The second compound may be included in the non-aqueous electrolyte in an amount of 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.5 wt% or more, or 1.0 wt% or more, based on the total weight of the non-aqueous electrolyte. The second compound may be included in the non-aqueous electrolyte in an amount of 10 wt% or less, 8 wt% or less, 5 wt% or less, 3 wt% or less, or 2 wt% or less, based on the total weight of the non-aqueous electrolyte.

[0108] More specifically, the second compound may be included in the non-aqueous electrolyte in an amount of 0.01 wt% to 5 wt%, specifically 0.05 wt% to 3 wt%, more specifically 0.1 wt% to 2 wt%, and even more specifically 0.5 wt% to 1 wt%. When the content of the second compound satisfies the above range, it is desirable in that it can realize an electrode film with excellent high-temperature safety and mechanical durability as described above, thereby improving the high-temperature performance of the lithium secondary battery while preventing side reactions caused by the excessive use of additives and thus preventing an increase in resistance.

[0109]

[0110] (2) Organic solvent

[0111] The organic solvent according to the present invention can be used without special limitations as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0112] For example, the organic solvent according to the present invention may include one or more selected from the group consisting of linear carbonate compounds and cyclic carbonate compounds. By including the linear carbonate compounds and / or cyclic carbonate compounds, the organic solvent can improve the solubility, viscosity, and fluidity of the lithium salt in a non-aqueous electrolyte.

[0113] The above linear carbonate-based compound may include one or more selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, and ethylpropyl carbonate.

[0114] The above linear carbonate-based compound may be included in the organic solvent in an amount of 35 volume% to 85 volume%, specifically in an amount of 35 volume% or more, 40 volume% or more, 45 volume% or more, 47 volume% or more, 50 volume% or more, 53 volume% or more, 55 volume% or more, or 60 volume% or more. Additionally, the above linear carbonate-based compound may be included in the organic solvent in an amount of 85 volume% or less, 80 volume% or less, 78 volume% or less, 75 volume% or less, 73 volume% or less, or 70 volume% or less. The above numerical ranges may be combined without limitation. When the content of the above linear carbonate-based compound satisfies the above range, the viscosity does not rise excessively while preventing a decrease in the degree of dissociation of the lithium salt in the organic solvent, thereby improving the ionic conductivity of the non-aqueous electrolyte.

[0115] The above cyclic carbonate compound may include at least one selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0116] The above cyclic carbonate-based compound may be included in the organic solvent in an amount of 10 volume% to 30 volume%, specifically in an amount of 10 volume% or more, 13 volume% or more, or 15 volume% or more. Additionally, the above cyclic carbonate-based compound may be included in the organic solvent in an amount of 30 volume% or less, 28 volume% or less, 25 volume% or less, or 20 volume% or less. The above numerical ranges may be combined without limitation. When the content of the above cyclic carbonate-based compound satisfies the above range, the degree of dissociation of the lithium salt can be increased while maintaining the viscosity of the organic solvent at an appropriate level, thereby improving the electrochemical stability of the non-aqueous electrolyte.

[0117] The above organic solvent may include a linear carbonate compound and a cyclic carbonate compound. In this case, the ratio of the volume of the cyclic carbonate compound to the volume of the linear carbonate compound may be 0.10 or more, 0.12 or more, 0.15 or more, or 0.20 or more. Additionally, the ratio of the volume of the cyclic carbonate compound to the volume of the linear carbonate compound may be 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, or 0.30 or less. It may be 0.10 or more, 0.12 or more, or 0.15 or more. It may be up to 0.50, specifically 0.15 to 0.40, and more specifically 0.15 to 0.25. The above numerical ranges may be combined with one another without limitation. When the above organic solvent satisfies the above range, the viscosity of the organic solvent is appropriately controlled, and the dissociation, movement, and transfer of the lithium salt can be carried out smoothly.

[0118] The above organic solvent may further include at least one selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents.

[0119] The above linear ester-based organic solvent may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0120] The above-mentioned cyclic ester-based organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0121]

[0122] (3) Lithium salt

[0123] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt is Li as a cation. + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO2 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from a group consisting of

[0124] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO2, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 It may include at least one selected from the group consisting of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2). More specifically, the lithium salt may include LiPF6, in which case the effect of the combined use of ethylene carbonate and the compound represented by Formula 1 may be expressed at a desirable level.

[0125] The above lithium salt may be included in the above non-aqueous electrolyte at a concentration of 0.5M to 5M, specifically 0.8M to 4M, and more specifically 0.8M to 2.0M. When the concentration of the lithium salt satisfies the above range, the lithium ion yield (Li + The transference number and the degree of dissociation of lithium ions are improved, which can enhance the output characteristics of the battery.

[0126]

[0127] Meanwhile, in addition to the above components, the above-mentioned non-aqueous electrolyte may additionally include auxiliary additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery. For example, the above-mentioned non-aqueous electrolyte may include at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphite compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0128] The above auxiliary additive may be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 5 weight%, based on the total weight of the above non-aqueous electrolyte.

[0129]

[0130] lithium secondary battery

[0131] Next, a lithium secondary battery according to the present invention will be described.

[0132] A lithium secondary battery according to the present invention comprises a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and the above-described non-aqueous electrolyte. At this time, since the above-described non-aqueous electrolyte is identical to the non-aqueous electrolyte according to the present invention, a detailed description is omitted, and the remaining components excluding the non-aqueous electrolyte will be described below.

[0133]

[0134] (1) positive electrode

[0135] The anode according to the present invention may include an anode active material.

[0136] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium metal oxide is 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.), or a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2Examples include )O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are each atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc., and any one or more of these compounds may be included.

[0137] The above positive active material may include a lithium transition metal oxide comprising one or more selected from the group consisting of nickel, cobalt, and manganese. Specifically, the above positive active material may include a lithium transition metal oxide comprising nickel, cobalt, and manganese.

[0138] Specifically, the above positive active material may include a lithium transition metal oxide represented by the following [Chemical Formula 3].

[0139] [Chemical Formula 3]

[0140] Li x Ni a Co b M 1 c M 2 d O2

[0141] In the above chemical formula 3, the M 1 It is one or more selected from Mn and Al, and specifically may be Mn or a combination of Mn and Al.

[0142] The above M 2 It may be one or more selected from the group consisting of Zr, Y, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S.

[0143] The above x represents the atomic fraction of lithium in the lithium transition metal oxide, and may be 0.90≤x≤1.1, preferably 0.95≤x≤1.08, and more preferably 1.0≤x≤1.08.

[0144] The above a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, and may be 0.5≤a<1.0, 0.5≤a≤0.8, 0.5≤a≤0.7, 0.55≤a≤0.7, or 0.6≤a≤0.7. When the nickel content satisfies the above range, high voltage performance and capacitance characteristics may be excellent.

[0145] The above b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, where 0 <b<0.5, 0<b<0.4, 또는 0.01≤b≤0.3일 수 있다.

[0146] The above c is M among the metal elements excluding lithium in the lithium transition metal oxide. 1 Representing the atomic fraction of, 0 <c<0.5, 0<c<0.4, 또는 0.01≤c≤0.3일 수 있다.

[0147] The above d is M among the metal elements excluding lithium in the lithium transition metal oxide. 2 It represents the atomic fraction of , which can be 0≤d≤0.1 or 0≤d≤0.05.

[0148] The above-mentioned positive electrode active material may include single-particle particles. The single-particle particles may be in the form of a single particle consisting of one nodule and / or a pseudo-single particle which is a complex of 30 or fewer nodules. When the above-mentioned positive electrode active material includes single-particle particles, particle breakage during the rolling process is reduced compared to secondary particle-based positive electrode active materials, and structural stability can be improved under high temperature and / or high voltage conditions. As a result, the positive electrode containing single-particle particles can minimize degradation under high temperature / high voltage conditions, and the generation of fine particles during the manufacturing process is reduced, thereby reducing gas generation due to side reactions with the electrolyte. Therefore, by including single-particle particles in the above-mentioned positive electrode active material, a secondary battery with excellent cycle characteristics can be realized.

[0149] Average particle size (D of the above positive active material)50 The particle size may be 0.1㎛ to 10㎛, specifically 0.5㎛ to 8㎛, and more specifically 1㎛ to 4㎛. In this case, particle breakage is minimized during electrode manufacturing, and the increase in resistance can be suppressed more effectively.

[0150] Minimum particle size (D) of the above positive active material min ) can be 0.01㎛ to 5.0㎛, specifically 0.1㎛ to 1.0㎛, more specifically 0.2㎛ to 0.8㎛. In this case, particle breakage is minimized during the rolling process, and thermal safety can be ensured.

[0151] Maximum particle size (D) of the above positive active material max ) may be 5㎛ to 15㎛, specifically 6㎛ to 10㎛, more specifically 7㎛ to 10㎛. The maximum particle size (D) of the positive electrode active material may be 5㎛ to 15㎛, specifically 6㎛ to 10㎛, and more specifically 7㎛ to 10㎛. max When the above range is satisfied, the resistance and capacitance characteristics may be even better.

[0152] The BET specific surface area of ​​the above positive active material is 0.05 m² 2 / g to 3m 2 / g, specifically 0.05m 2 / g to 1.5m 2 / g, specifically 0.1m 2 / g to 1.2m 2 / g, more specifically 0.15m 2 / g to 1m 2 It can be / g. In this case, lithium migration beneath the anode surface proceeds smoothly, and high-temperature durability can be improved by suppressing side reactions.

[0153]

[0154] The above positive electrode may include a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0155] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used.

[0156] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0157] The above positive active material layer may be disposed on one or both sides of the positive current collector.

[0158] The above positive active material layer may include the aforementioned positive active material. The positive active material may be included in an amount of 60 to 99 weight%, preferably 70 to 99 weight%, and more preferably 80 to 98 weight% based on the total weight of the positive active material layer.

[0159] The above-described positive active material layer may optionally further include a binder and / or a conductive material together with the positive active material described above.

[0160] The above binder is a component that assists in the bonding of the positive active material and the conductive material, and in the bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0161] The above binder may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, and more preferably 1% to 10% by weight, based on the total weight of the positive active material layer.

[0162] The above conductive material is a component for further improving the conductivity of the positive electrode active material, and is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0163] The above conductive material may be included in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, more preferably 1% to 10% by weight, based on the total weight of the positive active material layer.

[0164] The above positive active material layer may be manufactured by applying and drying a positive slurry composition prepared by dissolving or dispersing a positive active material, and optionally a binder and a conductive material, in a positive slurry solvent on a positive current collector, or by casting the above positive slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto a positive current collector.

[0165] The above anode slurry solvent may include organic solvents such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), and acetone, and may be used in an amount that results in a desirable viscosity when including the anode active material, anode binder, and anode conductive material. For example, the concentration of the solid component including the anode active material, and optionally the anode binder and anode conductive material, may be 50 to 95 weight%, preferably 70 to 95 weight%, and more preferably 70 to 90 weight%.

[0166]

[0167] (2) Negative electrode

[0168] The cathode according to the present invention may include a cathode active material.

[0169] The above-mentioned negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, for example, carbon materials such as artificial graphite, natural graphite, Kish graphite, pyrolytic carbon, meso-carbon microbeads, mesophase pitches, petroleum or coal tar pitch-derived cokes, mesophase pitch-based carbon fiber, graphitized carbon fiber, amorphous carbon, softened carbon, or hardened carbon; (semi)metallic materials capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; SiO b(0 <b≤2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 (준)금속 산화물 재료; Si-C 복합체 또는 Sn-C 복합체과 같은 이종 복합 재료; 또는 금속 리튬 박막 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.

[0170] The above-mentioned negative electrode active material may include at least one selected from the group consisting of carbon-based active materials and silicon-based active materials. The above-mentioned carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, softened carbon, and hardened carbon. The above-mentioned silicon-based active material is silicon (Si) and silicon oxide (SiO₂). x , 0 <x<2) 및 실리콘-탄소 복합체(Si / C composite)로 이루어진 군에서 선택된 적어도 1종을 포함할 수 있으며, 보다 구체적으로 실리콘-탄소 복합체를 포함할 수 있다.

[0171] In addition, the above-mentioned negative electrode active material may be a mixed active material comprising two or more of the above-mentioned materials.

[0172] The above cathode may include a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector.

[0173] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used.

[0174] The above-mentioned negative electrode current collector can typically have a thickness of 3 μm to 500 μm, and preferably can have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. Fine irregularities may be formed on the surface of the current collector to strengthen the bonding force with the negative electrode active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0175] The above cathode active material layer may be disposed on one or both sides of the cathode current collector.

[0176] The above-mentioned cathode active material layer may include the aforementioned cathode active material.

[0177] The above-mentioned negative electrode active material may be included in an amount of 60% to 99% by weight based on the total weight of the negative electrode active material layer, specifically in an amount of 70% or more, 80% or more, 85% or more, or 90% or more by weight, and may also be included in an amount of 98% or less, 97% or less by weight, or 95% or less by weight.

[0178] The above-described cathode active material layer may optionally further include a binder and / or a conductive material together with the cathode active material described above.

[0179] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight based on the total weight of the negative active material layer, and can be included in an amount of 0.2% or more, 0.3% or more, or 0.5% or more by weight, and can also be included in an amount of 8.0% or less, or 5.0% or less by weight. Examples of such binders may include one or more selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, and polyvinyl alcohol. Among these, it may include one or more selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylfluran, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. Preferably, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, or a mixture thereof may be used as a binder.

[0180] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less based on the total weight of the negative electrode active material layer, and may also be included in an amount of 0.01% by weight or more, 0.05% by weight or more, 0.08% by weight or more, 0.1% by weight or more, or 0.3% by weight or more.

[0181] Such conductive materials are not particularly limited as long as they possess conductivity without causing chemical changes in the battery, and for example, graphite such as natural graphite or synthetic graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0182] The above-mentioned cathode active material layer may be manufactured by applying a cathode slurry composition, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a cathode slurry solvent, onto a cathode current collector and drying it, or by casting the cathode slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0183] The above cathode slurry solvent may include at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0184]

[0185] (3) Separator

[0186] The above separator separates the negative and positive electrodes and provides a pathway for the movement of lithium ions; it can be used without any special restrictions as long as it is commonly used as a separator in a lithium secondary battery.

[0187] Specifically, the above-mentioned separator may be a conventional porous polymer film used as a separator, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or in a laminate thereof, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., may be used, but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0188]

[0189] A lithium secondary battery according to the present invention as described above can be used to manufacture a battery pack. The battery pack comprises an assembly of lithium secondary batteries electrically connected according to the present invention and a pack housing that accommodates the same, wherein the pack housing may include a busbar for electrically connecting the lithium secondary batteries, a cooling unit, an external terminal, etc. The battery pack may be mounted in a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheeled vehicle or a two-wheeled vehicle. In particular, the lithium secondary battery according to the present invention has high energy density and excellent rapid charging performance, so it can be usefully used as a battery for an electric vehicle.

[0190]

[0191] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are intended only to aid in understanding the present invention, and the scope of the present invention is not limited to these embodiments.

[0192]

[0193] Example 1

[0194] (Preparation of non-aqueous electrolytes)

[0195] As an organic solvent, a mixture of ethylene carbonate (EC), ethylene methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10 was used. LiPF6 was dissolved in the organic solvent to a concentration of 1.2 M, and then a non-aqueous electrolyte was prepared by adding the first compound represented by Chemical Formula 1-1 and the second compound represented by Chemical Formula 2-1 as additives in amounts of 1% by weight and 3% by weight, respectively.

[0196] (Manufacturing of lithium secondary batteries)

[0197] Li[Ni as positive electrode active material 0.6 Co 0.1 Mn 0.3 A single-particle cathode active material having the composition of ]O2 was prepared. The cathode active material has a specific surface area (BET) of 1.0 m² 2 / g, and average particle size (D 50 ) is 4.0㎛, minimum particle size (D min ) is 0.2㎛, maximum particle size (D max The thickness is 15.0 μm. Subsequently, the anode active material, conductive material (carbon nanotube), and binder (polyvinylidene fluoride, PVDF) were mixed in N-methylpyrrolidone in a weight ratio of 97.74:0.70:1.56 to prepare an anode slurry. The anode slurry was applied to one surface of an aluminum (Al) current collector with a thickness of 15 μm and dried, and then a roll press was performed to produce an anode.

[0198] A cathode slurry was prepared by mixing a cathode active material (a mixture of natural graphite and a silicon-carbon composite in a weight ratio of 85:15), a conductive material (carbon black), and a binder (styrene-butadiene rubber (SBR)-carboxymethylcellulose (CMC)) in water in a weight ratio of 70:20.3:9.7. The cathode slurry was applied to one surface of a copper (Cu) current collector with a thickness of 15 μm and dried, and then a roll press was performed to manufacture a cathode.

[0199] An electrode assembly was manufactured by interposing a polyethylene separator between the positive electrode and the negative electrode manufactured by the above-described method, and then the assembly was placed inside a battery case, and an electrolyte was injected into the battery case to manufacture a lithium secondary battery.

[0200]

[0201] Example 2

[0202] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the first compound was added to the non-aqueous electrolyte at a content of 0.01% by weight relative to the total weight of the non-aqueous electrolyte.

[0203]

[0204] Example 3

[0205] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the first compound was added to the non-aqueous electrolyte at a content of 5% by weight relative to the total weight of the non-aqueous electrolyte.

[0206]

[0207] Example 4

[0208] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the second compound was added to the non-aqueous electrolyte at a content of 0.01% by weight relative to the total weight of the non-aqueous electrolyte.

[0209]

[0210] Example 5

[0211] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the second compound was added to the non-aqueous electrolyte at a content of 5% by weight relative to the total weight of the non-aqueous electrolyte.

[0212]

[0213] Example 6

[0214] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a first compound represented by the following chemical formula 1-2 was added to the non-aqueous electrolyte at 1% by weight relative to the total weight of the non-aqueous electrolyte instead of the first compound represented by chemical formula 1-1 above.

[0215] [Chemical Formula 1-2]

[0216]

[0217]

[0218] Example 7

[0219] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a second compound represented by the following chemical formula 2-2 was added to the non-aqueous electrolyte at 3% by weight relative to the total weight of the non-aqueous electrolyte instead of the second compound represented by chemical formula 2-1 above.

[0220] [Chemical Formula 2-2]

[0221]

[0222]

[0223] Comparative Example 1

[0224] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the first and second compounds were not added as additives.

[0225]

[0226] Comparative Example 2

[0227] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the first compound was not added as an additive.

[0228]

[0229] Comparative Example 3

[0230] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the second compound was not added as an additive.

[0231]

[0232] Comparative Example 4

[0233] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula 2a was added to the non-aqueous electrolyte instead of the second compound represented by chemical formula 2-1.

[0234] [Chemical Formula 2a]

[0235]

[0236]

[0237] Comparative Example 5

[0238] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula 2b was added to the non-aqueous electrolyte instead of the second compound represented by chemical formula 2-1.

[0239] [Chemical Formula 2b]

[0240]

[0241]

[0242] Comparative Example 6

[0243] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula 1a was added to the non-aqueous electrolyte instead of the first compound represented by chemical formula 1-1.

[0244] [Chemical Formula 1a]

[0245]

[0246]

[0247] Comparative Example 7

[0248] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula 1b was added to the non-aqueous electrolyte instead of the first compound represented by chemical formula 1-1.

[0249] [Chemical Formula 1b]

[0250]

[0251]

[0252] Compound 1 Compound 2 Example 1 Chemical Formula 1-1 Chemical Formula 2-1 Example 2 Chemical Formula 1-1 Chemical Formula 2-1 Example 3 Chemical Formula 1-1 Chemical Formula 2-1 Example 4 Chemical Formula 1-1 Chemical Formula 2-1 Example 5 Chemical Formula 1-1 Chemical Formula 2-1 Example 6 Chemical Formula 1-2 Chemical Formula 2-1 Example 7 Chemical Formula 1-1 Chemical Formula 2-2 Comparative Example 1--Comparative Example 2--Chemical Formula 2-1 Comparative Example 3 Chemical Formula 1-1-Comparative Example 4 Chemical Formula 1-1 Chemical Formula 2a Comparative Example 5 Chemical Formula 1-1 Chemical Formula 2b Comparative Example 6 Chemical Formula 1a Chemical Formula 2-1 Comparative Example 7 Chemical Formula 1b Chemical Formula 2-1

[0253]

[0254] Experimental Example 1: Evaluation of High-Temperature Cycle Characteristics

[0255] (1) Capacity retention rate

[0256] The lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 7 prepared above were charged to 4.35V and 0.05C at 45℃ under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and then discharged to 3.0V under CC and 0.33C conditions, with 200 charge-discharge cycles performed as one cycle. Afterwards, the capacity retention rate was calculated using the following formula, and the results are shown in Table 2 below.

[0257] Capacity Retention Rate (%) = (Discharge Capacity after 200 Cycles / Discharge Capacity after 1 Cycle) × 100

[0258] (2) Resistance increase rate

[0259] After performing one cycle of charging and discharging as described above, the initial resistance was measured by the difference in voltage drop when the SOC was 50% based on the discharge capacity at room temperature and discharged for 10 seconds at a current of 2.5C, and the resistance after 200 cycles was measured at 45℃ using the same method as the initial resistance measurement method. Subsequently, the resistance increase rate was calculated using the following formula, and the results are shown in Table 2 below.

[0260] Resistance increase rate (%) = {(Resistance after 200 cycles - Initial resistance) / Initial resistance} × 100

[0261] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 1989 Example 29512 Example 39313 Example 49311 Example 59412 Example 68814 Example 78616 Comparative Example 15562 Comparative Example 25766 Comparative Example 35563 Comparative Example 45864 Comparative Example 55666 Comparative Example 65467 Comparative Example 75663

[0262]

[0263] Referring to Table 2 above, it can be seen that Examples 1 to 7 exhibit significantly superior high-temperature cycle characteristics compared to Comparative Examples 1 to 3, which do not include one or more of the first and second compounds as additives. This is believed to be because when the first compound is used alone as an additive, ring opening is not easy and high-temperature cycle characteristics are degraded due to the absence of sulfonyl groups capable of improving high-temperature performance, or when the second compound is used alone, a durable organic / inorganic composite film is not sufficiently formed.

[0264] In addition, it can be confirmed that Examples 1 to 7 have significantly superior high-temperature cycle performance compared to Comparative Examples 4 and 5. This is believed to be due to the fact that the second compound included in Comparative Examples 4 and 5 lacks a sulfonyl group and contains little to no fluorine, resulting in low high-temperature safety and mechanical durability of the film.

[0265] In addition, it can be confirmed that Examples 1 to 7 exhibit superior high-temperature cycle characteristics compared to Comparative Example 6 and Comparative Example 7. This is believed to be because, in the case of the compound of Formula 1a used in Comparative Example 6, the absence of fluorine (F) in the ethylene carbonate structure prevented sufficient thermal stability of the film formed under high-temperature conditions. Furthermore, the compound of Formula 1b used in Comparative Example 7 is a compound containing ethylene sulfate instead of ethylene carbonate as its core structure; as a result, the film formed by a large amount of sulfate groups has relatively low lithium ion conductivity and forms a film primarily composed of inorganic materials. Consequently, it is believed that the effect of forming an organic / inorganic composite film is reduced, and the internal resistance of the battery increases during repeated charging and discharging processes, leading to a decrease in high-temperature cycle performance.

[0266]

[0267] Experimental Example 2: Evaluation of High-Temperature Storage Characteristics

[0268] The lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 7 prepared above were charged to 4.35V and 0.05C under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and discharged to 3.0V under CC and 0.33C conditions to perform initial charge and discharge. Afterward, they were charged to 4.35V and 0.05C under CC / CV and 0.33C conditions at 25℃, and then stored at 60℃ for 8 weeks.

[0269] (1) Capacity retention rate

[0270] After 8 weeks of storage, the lithium secondary battery was charged to 4.35V and 0.05C at 25℃ under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and discharged to 3.0V at CC and 0.33C to measure the discharge capacity after 8 weeks of storage. Subsequently, the capacity retention rate was evaluated according to the following formula, and the results are shown in Table 3 below.

[0271] Capacity Retention Rate (%) = (Discharge Capacity after 8 weeks of storage / Initial Discharge Capacity) × 100

[0272] (2) Resistance increase rate

[0273] After performing the above initial charge and discharge of the lithium secondary battery, the capacity was checked at room temperature, and the battery was charged to SOC 50% based on the discharge capacity. The battery was then discharged for 10 seconds with a current of 2.5C, and the initial resistance was measured based on the difference in voltage drop. After storing the battery at 60°C for 8 weeks, the resistance was measured after 8 weeks of high-temperature storage using the same method. Subsequently, the resistance increase rate was calculated using the following formula, and the results are shown in Table 3 below.

[0274] Resistance increase rate (%) = {(Resistance after 8 weeks of high-temperature storage - Initial resistance) / Initial resistance} × 100

[0275] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 1957 Example 29110 Example 39212 Example 49011 Example 59113 Example 68513 Example 78315 Comparative Example 15361 Comparative Example 25363 Comparative Example 35664 Comparative Example 45761 Comparative Example 55562 Comparative Example 65167 Comparative Example 75464

[0276]

[0277] Referring to Table 3 above, it can be seen that Examples 1 to 7 exhibit significantly superior high-temperature cycle characteristics compared to Comparative Examples 1 to 3, which do not include one or more of the first and second compounds as additives. This is believed to be because when the first compound is used alone as an additive, ring opening is not easy and high-temperature cycle characteristics are degraded due to the absence of sulfonyl groups capable of improving high-temperature performance, or when the second compound is used alone, a durable organic / inorganic composite film is not sufficiently formed.

[0278] In addition, it can be confirmed that Examples 1 to 7 have significantly superior capacity retention and resistance compared to Comparative Examples 4 and 5. This is believed to be due to the fact that the second compound included in Comparative Examples 4 and 5 lacks a sulfonyl group and contains little to no fluorine, resulting in low high-temperature stability and mechanical durability of the film.

[0279] In addition, it can be confirmed that Examples 1 to 7 exhibit superior high-temperature storage characteristics compared to Comparative Examples 6 and 7. This is believed to be because the high-temperature safety of the film was not sufficiently improved in the case of the compound of Formula 1a used in Comparative Example 6, as fluorine was absent in the ethylene carbonate. Furthermore, the compound of Formula 1b used in Comparative Example 7 is a compound containing ethylene sulfate instead of ethylene carbonate in the center; the film formed due to the large amount of sulfate groups has low ionic conductivity and forms a film primarily composed of inorganic materials, thereby reducing the effectiveness of the organic / inorganic composite film and resulting in low performance due to increased resistance of the battery during charging and discharging.

[0280] In addition, it can be confirmed that Examples 1 to 7 exhibit superior high-temperature storage characteristics compared to Comparative Examples 6 and 7. It is determined that the compound of Formula 1a used in Comparative Example 6, which does not contain fluorine in its ethylene carbonate structure, failed to sufficiently form a stable and durable electrode film under high-temperature storage conditions. Meanwhile, the compound of Formula 1b used in Comparative Example 7, which contains an ethylene sulfate structure, forms a film containing an excessive amount of sulfate-based inorganic components. Consequently, the ionic conductivity of the film is reduced, and the balance of the organic / inorganic composite film is disrupted. As a result, it is determined that the high-temperature durability of the electrode film is reduced under high-temperature storage conditions, leading to a decrease in battery performance.

Claims

1. Contains a lithium salt, an organic solvent, and additives, The above additive is a non-aqueous electrolyte comprising a first compound represented by the following chemical formula 1 and a second compound represented by the following chemical formula 2: [Chemical Formula 1] In the above chemical formula 1, R 11 , R 12 , R 13 , R 21 , R 22 and R 23 The groups are independently selected from hydrogen, fluorine (F), and alkyl groups having 1 to 10 carbon atoms substituted with one or more fluorines, and R 11 , R 12 and R 13 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and R 21 , R 22 and R 23 At least one of them is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and [Chemical Formula 2] In the above chemical formula 2, R3 is fluorine (F) or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and L is an ether group (*-O-*), an alkylene group having 1 to 5 carbon atoms, or a combination thereof.

2. In Claim 1, In the first compound represented by the above chemical formula 1, the R 11 and R 21 is independently a fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorines, and R 12 , R 13 , R 22 and R 23 is hydrogen, and A non-aqueous electrolyte in which R3 in the second compound represented by the above chemical formula 2 is fluorine (F) or an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorines.

3. In Claim 1, The above first compound is a non-aqueous electrolyte comprising at least one selected from the group consisting of a compound represented by the following chemical formula 1-1 and a compound represented by the following chemical formula 1-2: [Chemical Formula 1-1] [Chemical Formula 1-2] .

4. In Claim 1, The second compound is a non-aqueous electrolyte comprising at least one selected from the group consisting of a compound represented by the following chemical formula 2-A and a compound represented by the following chemical formula 2-B: [Chemical Formula 2-A] [Chemical Formula 2-B] In the above chemical formulas 2-A and 2-B, R3 and L are as defined in Chemical Formula 2 above.

5. In Claim 1, The second compound is a non-aqueous electrolyte comprising at least one selected from the group consisting of a compound represented by the following chemical formula 2-1 and a compound represented by the following chemical formula 2-2: [Chemical Formula 2-1] [Chemical Formula 2-2] .

6. In Claim 1, The first compound is a non-aqueous electrolyte included in the non-aqueous electrolyte in an amount of 0.01% to 10% by weight.

7. In Claim 1, The second compound above is a non-aqueous electrolyte included in the non-aqueous electrolyte at a concentration of 0.01% to 5% by weight.

8. In Claim 1, The above organic solvent is a non-aqueous electrolyte comprising one or more selected from the group consisting of linear carbonate compounds and cyclic carbonate compounds.

9. Anode; A cathode opposite to the anode above; A separator interposed between the anode and the cathode; and A lithium secondary battery comprising a non-aqueous electrolyte according to claim 1.

10. In Claim 9, The above cathode includes a cathode active material, and The above negative electrode active material is a lithium secondary battery comprising a carbon-based active material.

11. In Claim 10, A lithium secondary battery comprising at least one carbon-based active material selected from the group consisting of artificial graphite, natural graphite, softened carbon, and hardened carbon.

12. In Claim 10, The above carbon-based active material is a lithium secondary battery containing natural graphite.

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