Nonaqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to a nonaqueous electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the organic solvent includes a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a sulfonamide-based compound represented by chemical formula 1, the additive includes a cyclic sulfate-based compound represented by chemical formula 2, and the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by chemical formula 1 is 1 to 4. The definition of the compound represented by chemical formula 1 is the same as that described in the description of the invention.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same.

[0002] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for high-capacity, high-output, and high-stability secondary batteries.

[0003] The above lithium secondary battery generally consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, an electrolyte serving as a medium for transporting lithium ions, and a separator. In this case, carbon-based active materials, silicon-based active materials, etc., may be used as the negative active material. Additionally, lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel-cobalt-manganese composite oxide may be used as the positive active material.

[0004] In particular, high capacity, high output, and long lifespan characteristics are becoming increasingly important for lithium secondary batteries used in automobiles. To increase the capacity of lithium secondary batteries, it may be considered to use high-energy-density nickel-content cathode active materials or to operate the lithium secondary batteries at high voltages, while it may be considered to use high-capacity silicon-based active materials as anode active materials.

[0005] However, when operating a lithium secondary battery under the above conditions, transition metal ions may leach from the positive electrode surface due to the degradation of the electrolyte, the film formed on the positive / negative electrode surface, or the degradation of the electrode surface structure. As such, the leached transition metal ions are electrodeposited on the negative electrode, thereby reducing the passivation ability of the SEI (Solid Electrolyte Interface) film on the negative electrode, which leads to the problem of negative electrode degradation. Furthermore, the intensification of side reactions in the electrolyte caused by such leaching of transition metals and the destruction of the SEI film on the negative electrode leads to excessive gas generation within the battery, which causes problems such as capacity degradation and increased resistance.

[0006] One objective of the present invention is to solve the above-mentioned problems by providing a non-aqueous electrolyte that reduces side reactions between the anode / cathode and the electrolyte, thereby simultaneously exhibiting effects of improving battery life performance, suppressing gas generation, and suppressing resistance increase.

[0007] In addition, another objective of the present invention is to provide a lithium secondary battery comprising the aforementioned non-aqueous electrolyte.

[0008] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt; an organic solvent; and an additive, wherein the organic solvent comprises a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a compound represented by the following chemical formula 1, and the additive comprises a compound represented by the following chemical formula 2, and the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by the chemical formula 1 is 1 to 4.

[0009] [Chemical Formula 1]

[0010]

[0011] In the above chemical formula 1, R1 is *-F, *-CF3 or *-OCF3, R2 is a directly bonded or alkylene group having 1 to 5 carbon atoms, and R3 and R4 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms.

[0012] [Chemical Formula 2]

[0013] A-L1-B

[0014] The above A and B are substituents represented by the following chemical formula 2-a independently of each other, and

[0015] L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, a sulfate group, a sulfonate group, an ether group, an ester group, a carbonate group, or a combination of two or more of these.

[0016] [Chemical Formula 2-a]

[0017]

[0018] In the above chemical formula 2-a, X1 is *-C(R X11 )(R X12 )-* or oxygen(*-O-*) and R5, R X11 and R X12 Each is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, n is an integer selected from 0 to 3, and if n is an integer of 2 or more, each R5 is the same or different from each other.

[0019] [2] The present invention provides a non-aqueous electrolyte comprising at least one compound selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-4, wherein the compound represented by chemical formula 1 is the compound represented by chemical formula 1.

[0020] [Chemical Formula 1-1]

[0021]

[0022] [Chemical Formula 1-2]

[0023]

[0024] [Chemical Formula 1-3]

[0025]

[0026] [Chemical Formula 1-4]

[0027]

[0028] [3] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] and [2], the substituent represented by Formula 2-a comprises at least one selected from the group consisting of substituents represented by Formulas 2-a-1 to 2-a-3.

[0029] [Chemical Formula 2-a-1]

[0030]

[0031] [Chemical Formula 2-a-2]

[0032]

[0033] [Chemical Formula 2-a-3]

[0034]

[0035] [4] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [3], a compound represented by Formula 2, selected from the group consisting of compounds represented by Formulas 2-1 to 2-5.

[0036] [Chemical Formula 2-1]

[0037]

[0038] [Chemical Formula 2-2]

[0039]

[0040] [Chemical Formula 2-3]

[0041]

[0042] [Chemical Formula 2-4]

[0043]

[0044] [Chemical Formula 2-5]

[0045]

[0046] [5] The present invention provides a non-aqueous electrolyte in at least one of [1] to [4], wherein the cyclic carbonate-based solvent is included in the organic solvent at 10 volume% to 40 volume%, the linear carbonate-based solvent is included in the organic solvent at 50 volume% to 80 volume%, and the compound represented by Formula 1 is included in the organic solvent at 10 volume% to 30 volume%.

[0047] [6] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [5], the weight ratio of the compound represented by Formula 2 to the weight of the compound represented by Formula 1 is 0.01 to 0.2.

[0048] [7] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [6], the compound represented by Formula 2 is included in the non-aqueous electrolyte in an amount of 0.01% to 10% by weight.

[0049] [8] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [7], at least one additive selected from the group consisting of cyclic carbonate compounds, sulfate compounds, sulfone compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds.

[0050] [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 negative electrode and the positive electrode; and a non-aqueous electrolyte according to at least one of [1] to [8].

[0051]

[0010] The present invention provides a lithium secondary battery according to [9], wherein the negative electrode comprises at least one selected from carbon-based active material and silicon-based active material.

[0052] The non-aqueous electrolyte according to the present invention comprises, as organic solvents, a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a sulfonamide-based solvent represented by Formula 1, and as an additive, a cyclic sulfur oxide-based compound represented by Formula 2, wherein the volume ratio of the cyclic carbonate-based solvent, the linear carbonate-based solvent, and the sulfonamide-based solvent represented by Formula 1 is controlled to a specific range. A lithium secondary battery to which the non-aqueous electrolyte is applied can suppress the generation of oxidizing gas from the positive electrode and the generation of reducing gas from the negative electrode to a significant level through the combination of the above-described components, and can significantly improve overall performance, such as the battery's lifespan and resistance performance.

[0053] The terms and words used in this specification and claims are used merely to describe exemplary embodiments and should not be interpreted as being limited to their ordinary or dictionary meanings, and 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.

[0054] For example, in this specification, terms such as “comprising,” “having,” 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.

[0055] In addition, in the description of "a to b carbon atoms" within this specification, "a" and "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. For example, "alkylene group having 1 to 5 carbon atoms" refers to an alkylene group containing 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH2)CH-, -CH2CH2CH2CH2CH2-, and -CH(CH2)CH2CH2-, etc.

[0056] Additionally, in this specification, the term "alkylene group" refers to a branched or unbranched aliphatic hydrocarbon group or a functional group in which one hydrogen atom is removed from each carbon atom located at both ends of the aliphatic hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, methylene groups, ethylene groups, propylene groups, isopropylene groups, butylene groups, isobutylene groups, tert-butylene groups, pentylene groups, 3-pentylene groups, etc., and each of these may be optionally substituted in other embodiments.

[0057] Additionally, in this specification, "substitution" means that at least one hydrogen bonded to carbon is substituted with another element, such as fluorine, unless otherwise defined.

[0058] In addition, in the present invention, "*" refers to a bonding site in a chemical formula unless otherwise defined.

[0059]

[0060] The present invention will be described in more detail below.

[0061]

[0062] Non-aqueous electrolytes

[0063] The present invention relates to a non-aqueous electrolyte, and more specifically, to a non-aqueous electrolyte for a lithium secondary battery.

[0064] Specifically, the non-aqueous electrolyte of the present invention comprises a lithium salt; an organic solvent; and an additive; wherein the organic solvent comprises a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a compound represented by the following chemical formula 1, and the additive comprises a compound represented by the following chemical formula 2, and the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by the chemical formula 1 is 1 to 4.

[0065] [Chemical Formula 1]

[0066]

[0067] In the above chemical formula 1, R1 is *-F, *-CF3 or *-OCF3, R2 is a directly bonded or alkylene group having 1 to 5 carbon atoms, and R3 and R4 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms.

[0068] [Chemical Formula 2]

[0069] A-L1-B

[0070] The above A and B are substituents represented by the following chemical formula 2-a independently of each other, and L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, a sulfate group, a sulfonate group, an ether group, an ester group, a carbonate group, or a combination of two or more of these.

[0071] [Chemical Formula 2-a]

[0072]

[0073] In the above chemical formula 2-a, X1 is *-C(R X11 )(R X12 )-* or oxygen(*-O-*) and R5, R X11 and R X12 Each is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, n is an integer selected from 0 to 3, and if n is an integer of 2 or more, each R5 is the same or different from each other.

[0074] The non-aqueous electrolyte according to the present invention comprises, as organic solvents, a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a sulfonamide-based solvent represented by Formula 1, and as an additive, a cyclic sulfur oxide-based compound represented by Formula 2, wherein the volume ratio of the cyclic carbonate-based solvent, the linear carbonate-based solvent, and the sulfonamide-based solvent represented by Formula 1 is controlled to a specific range. A lithium secondary battery to which the non-aqueous electrolyte is applied can suppress the generation of oxidizing gas from the positive electrode and the generation of reducing gas from the negative electrode to a significant level through the combination of the above-described components, and can significantly improve overall performance, such as the battery's lifespan and resistance performance.

[0075]

[0076] 1) Lithium salt

[0077] 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 - , 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

[0078] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, 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).

[0079] The above lithium salt may be included in the above-mentioned 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 above-mentioned 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.

[0080] Alternatively, the above lithium salt may be included in the non-aqueous electrolyte in the remainder excluding, for example, the organic solvent and additives described below.

[0081]

[0082] 2) Organic solvent

[0083] The above organic solvent may be included in the non-aqueous electrolyte in the remainder excluding lithium salts and additives, for example.

[0084] The above organic solvent may include a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a compound represented by the following chemical formula 1.

[0085] [Chemical Formula 1]

[0086]

[0087] In the above chemical formula 1, R1 is *-F, *-CF3 or *-OCF3, R2 is a directly bonded or alkylene group having 1 to 5 carbon atoms, and R3 and R4 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms.

[0088]

[0089] The above-mentioned cyclic carbonate-based solvent is a high-viscosity organic solvent with a high dielectric constant capable of effectively dissociating lithium salts within an electrolyte. Specifically, it may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. More specifically, it may include at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC), and even more specifically, it may include ethylene carbonate (EC). The above-mentioned ethylene carbonate is preferably used for the dissociation of lithium salts and for improving mobility. Furthermore, the above-mentioned ethylene carbonate can prevent decomposition according to the compound represented by Chemical Formula 1, thereby further improving the mobility characteristics of lithium. Meanwhile, the above ethylene carbonate is also desirable in that it does not impede the effect of preventing CH4, CO2 gas generation resulting from the application of the compound represented by Chemical Formula 1. More specifically, the above cyclic carbonate-based solvent may be composed of ethylene carbonate.

[0090] If cyclic carbonates other than ethylene carbonates, specifically fluorine-substituted ethylene carbonates (such as fluoroethylene carbonates), are used, the reduction of CO2 may be inhibited due to their higher reducing power compared to CO2. In this regard, it may be desirable that fluorine-substituted ethylene carbonates, such as fluoroethylene carbonates, are not included in the non-aqueous electrolyte, or at least be added in small amounts (e.g., 5% by weight or less of the non-aqueous electrolyte).

[0091] The organic solvent may contain the cyclic carbonate-based solvent in an amount of 10 volume% or more, 12 volume% or more, 15 volume% or more, 18 volume% or more, 20 volume% or more, 22 volume% or more, or 24 volume% or more. The organic solvent may contain the cyclic carbonate-based organic solvent in an amount of 50 volume% or less, 48 ​​volume% or less, 45 volume% or less, 42 volume% or less, 40 volume% or less, 38 volume% or less, 35 volume% or less, or 30 volume% or less. The above numerical ranges may be combined with one another without limitation. Specifically, the organic solvent may contain the cyclic carbonate-based organic solvent in an amount of 10 to 50 volume%, specifically 10 to 40 volume%, specifically 15 to 35 volume%, more specifically 20 to 30 volume%, and even more specifically 22 to 28 volume%. When within this range, the viscosity of the organic solvent is appropriately controlled, and the dissociation, movement, and delivery of the lithium salt can be carried out smoothly. When within this range, not only is it possible to improve the degree of dissociation of the lithium salt and conductivity, but the oxidizing gas reduction effect of the anode by the compound represented by Chemical Formula 1 and the reducing gas reduction effect of the cathode by the compound represented by Chemical Formula 2 can also be harmoniously expressed.

[0092] In addition, the linear carbonate-based solvent is an organic solvent having low viscosity and low dielectric constant, and specifically may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC); more specifically, may include at least one selected from the group consisting of ethylmethyl carbonate and diethyl carbonate; and even more specifically, may include ethylmethyl carbonate.

[0093] The above linear carbonate-based solvent may be included in the above organic solvent in an amount of 50 to 80 volume%, specifically 55 to 70 volume%, more specifically 55 to 65 volume%, and even more specifically 58 to 63 volume%. When within the above range, not only is it possible to achieve an appropriate viscosity of the electrolyte, but the oxidizing gas reduction effect of the anode by the compound represented by Chemical Formula 1 and the reducing gas reduction effect of the cathode by the compound represented by Chemical Formula 2 can also be harmoniously expressed.

[0094] In the above cyclic carbonate-based solvent and the above linear carbonate-based solvent, the cyclic carbonate-based solvent may be contained in smaller amounts in terms of volume or weight compared to the above linear carbonate-based solvent. Specifically, the volume ratio of the cyclic carbonate-based solvent and the above linear carbonate-based solvent may be 12:88 to 48:52, specifically 15:85 to 45:55, and more specifically 20:80 to 30:70.

[0095] In addition, the above-mentioned non-aqueous electrolyte comprises, together with the above-mentioned cyclic carbonate-based solvent and the above-mentioned linear carbonate-based solvent, a compound represented by the following chemical formula 1.

[0096] [Chemical Formula 1]

[0097]

[0098] In the above chemical formula 1, R1 is *-F, *-CF3 or *-OCF3, R2 is a directly bonded or alkylene group having 1 to 5 carbon atoms, and R3 and R4 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms.

[0099] The compound represented by the above chemical formula 1 has a structure in which a fluorine or fluorine-containing functional group (R1) and N (R3) (R4) are combined via a sulfonate group (-SO2-). In particular, the sulfonate group is different from the carbonate functional group, which is the cause of gas generation, and is therefore particularly desirable for gas reduction effects.

[0100] In addition, the compound represented by Chemical Formula 1 above possesses structural stability of its own, and at the same time, has the characteristic of being less affinity for the lithium cation of the lithium salt but more affinity for the corresponding anion. This promotes the formation of a solvation structure between the lithium cation and ethylene carbonate, which can further enhance oxidation stability.

[0101] Meanwhile, the compound represented by Chemical Formula 1 has high structural stability, so decomposition reactions during initial activation or battery operation are minimized, but a very small amount may decompose during the initial activation process to form an SEI film. At this time, the SEI film derived from the compound represented by Chemical Formula 1 contains a Li2SO4-based compound, so it has excellent durability and can prevent rapid decomposition of the additive during initial activation, thereby preventing an increase in the resistance of the negative electrode film.

[0102] The compound represented by Chemical Formula 1 above is a sulfonamide-based compound that can secure the oxidative stability of a non-aqueous electrolyte, has minimal decomposition reactions, and can suppress battery degradation caused by gas generation during charging and discharging, thereby suppressing the generation of oxidizing gas due to electrolyte side reactions at the anode interface. However, simply using the compound represented by Chemical Formula 1 alone cannot achieve the effect of reducing gas generated at the cathode and is difficult to improve the overall performance of the battery; therefore, in order to achieve the effect intended by the present invention, it is absolutely necessary to use in combination with a volume ratio of a cyclic carbonate-based solvent and a linear carbonate-based solvent; and a compound represented by Chemical Formula 2, as described below.

[0103] The above R1 can be selected from *-F, *-CF3 and *-OCF3, and specifically can be *-F.

[0104] The above R2 may be selected from direct bonding and alkylene groups having 1 to 5 carbon atoms, specifically selected from direct bonding and alkylene groups having 1 to 3 carbon atoms, more specifically selected from direct bonding, methylene groups (*-CH2-*) and ethylene groups (*-CH2CH2-*), and even more specifically selected from direct bonding.

[0105] The above R3 and R4 may be independently selected from hydrogen and alkyl groups having 1 to 5 carbon atoms, specifically independently selected from hydrogen and alkyl groups having 1 to 3 carbon atoms, more specifically independently selected from hydrogen, methyl groups (*-CH3) and ethyl groups (*-CH2CH3), and even more specifically, each may be a methyl group.

[0106] The compound represented by the above chemical formula 1 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-4, and more specifically, may include the compound represented by the following chemical formula 1-1.

[0107] [Chemical Formula 1-1]

[0108]

[0109] [Chemical Formula 1-2]

[0110]

[0111] [Chemical Formula 1-3]

[0112]

[0113] [Chemical Formula 1-4]

[0114]

[0115] The compound represented by Chemical Formula 1 above may be included in the organic solvent in an amount of 10 volume% to 30 volume%. Within this range, it is desirable in that it is possible to achieve the desired viscosity of the non-aqueous electrolyte, improve ionic conductivity, and enhance wetting properties while sufficiently exhibiting the effects of reducing oxidation and reduction gases described above. Specifically, the compound represented by Chemical Formula 1 above may be included in the organic solvent in an amount of 10 volume% or more, 12 volume% or more, 15 volume% or more, 18 volume% or more, or 20 volume% or more. Additionally, the compound represented by Chemical Formula 1 above 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.

[0116]

[0117] In the present invention, the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Formula 1 may be 1 to 4. If the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Formula 1 is less than 1, the viscosity of the non-aqueous electrolyte may become excessively high, which may reduce the wetting performance of the battery. If the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Formula 1 exceeds 4, the dielectric constant of the non-aqueous electrolyte becomes excessively low, which may cause a decrease in ionic conductivity and a problem in that the aforementioned reduction effect of oxidation / reduction gases cannot be achieved. Meanwhile, the effect according to the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Chemical Formula 1 can be manifested when combined with the compound represented by Chemical Formula 2, which will be described later. Accordingly, the effect of preventing side reactions of the electrolyte in the anode / cathode and suppressing gas generation is significantly improved, and the overall performance of the battery, such as the improvement of battery life performance and the prevention of resistance increase, is not impaired.

[0118] Specifically, the ratio of the volume of the linear carbonate solvent to the sum of the volumes of the cyclic carbonate solvent and the compound represented by Chemical Formula 1 may be 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, or 1.4 or more. Additionally, the ratio of the volume of the linear carbonate solvent to the sum of the volumes of the cyclic carbonate solvent and the compound represented by Chemical Formula 1 may be 4 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, 1.8 or less, or 1.6 or less.

[0119] In addition, the volume content of each of the cyclic carbonate-based solvent, the compound represented by Formula 1, and the linear carbonate-based solvent described in this specification can be controlled within a range in which the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Formula 1 is satisfied.

[0120]

[0121] The above organic solvent may further include at least one of an ester-based organic solvent, an ether-based organic solvent, a glycine-based solvent, and a nitrile-based organic solvent together with the above components.

[0122] The above ester-based organic solvent may include at least one selected from linear ester-based organic solvents and cyclic ester-based organic solvents. Specifically, the above linear ester-based organic solvent may 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. Additionally, the above 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.

[0123] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0124] The above-mentioned glyme solvent has a high dielectric constant and low surface tension compared to linear carbonate solvents and is a solvent with low reactivity with metal, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0125] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0126]

[0127] 3) Additives

[0128] The above additive includes a compound represented by the following chemical formula 2.

[0129] [Chemical Formula 2]

[0130] A-L1-B

[0131] The above A and B are substituents represented by the following chemical formula 2-a independently of each other, and L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, a sulfate group, a sulfonate group, an ether group, an ester group, a carbonate group, or a combination of two or more of these.

[0132] [Chemical Formula 2-a]

[0133]

[0134] In the above chemical formula 2-a, X1 is *-C(R X11 )(R X12 )-* or oxygen(*-O-*) and R5, R X11 and R X12Each is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, n is an integer selected from 0 to 3, and if n is an integer of 2 or more, each R5 is the same or different from each other.

[0135] The compound represented by Chemical Formula 2 above has a structure in which two cyclic sulfur oxide groups are joined by a linker group (*-L1-*), which is effective in forming a solid electrolyte interface film (SEI film) on the cathode from the initial stage of battery operation or the activation stage. The robust formation of such a cathode SEI film is desirable in that it can effectively prevent adverse reactions with the electrolyte. For example, in the case of a compound containing only one cyclic sulfur oxide within its structure, it is difficult to sufficiently form a film component at the anode / cathode interface, which is undesirable as it results in reduced durability at high voltage and high temperature.

[0136] In particular, the effect of the compound represented by Chemical Formula 2 can be manifested only when the following conditions are satisfied: the simultaneous use of the aforementioned cyclic carbonate-based solvent, linear carbonate-based solvent, and the compound represented by Chemical Formula 1; and the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Chemical Formula 1 is controlled to a desirable level. That is, simply using the compound represented by Chemical Formula 2 without considering the characteristics of the aforementioned organic solvents makes it difficult to prevent the degradation of the oxidation stability of the non-aqueous electrolyte, and also fails to prevent the destruction of the SEI film of the transition metal leached from the anode; thus, the lifespan performance of the battery, the increase in resistance, and the increase in gas generation may be accelerated.

[0137] In the above chemical formula 2, L1 may be a direct bond, an alkylene group having 1 to 10 carbon atoms, a sulfate group (*-OS(=O)2-O-*), a sulfonate group (*-OS(=O)2-*), an ether group (*-O-*)), an ester group (*-C(=O)-O-*), a carbonate group (*-OC(=O)-O-*), or a combination of two or more of these, and more specifically, may be a direct bond.

[0138] In the above chemical formula 2, A and B are substituents represented by the following chemical formula 2-a independently of each other.

[0139] [Chemical Formula 2-a]

[0140]

[0141] The above X1 is *-C(R X11 )(R X12 It can be )-* or oxygen(*-O-*). In this case, *-C(R X11 )(R X12 In the case of )-*, R X11 and R X12 Each can be independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and specifically, each can be hydrogen.

[0142] In the above chemical formula 2-a, the bonding site (*-) with R5 can be arbitrarily bonded to a carbon position within the ring of the cyclic sulfate (the 3rd and 4th carbon positions according to IUPAC standards), and the position is not specifically limited in the above chemical formula 2-a.

[0143] In the above chemical formula 2-a, R5 may be hydrogen or an alkyl group having 1 to 5 carbon atoms, specifically hydrogen or an alkyl group having 1 to 3 carbon atoms, more specifically hydrogen, a methyl group, or an ethyl group, and even more specifically hydrogen. n may be an integer selected from 0 to 3. In this case, when n is an integer of 2 or more (i.e., when there are 2 or more R5s), each R5 may be the same or different from each other.

[0144] The substituent represented by the above chemical formula 2-a may include at least one selected from the group consisting of substituents represented by the following chemical formulas 2-a-1 to 2-a-3, and more specifically, may be the substituent represented by the following chemical formula 2-a-1.

[0145] [Chemical Formula 2-a-1]

[0146]

[0147] [Chemical Formula 2-a-2]

[0148]

[0149] [Chemical Formula 2-a-3]

[0150]

[0151] Specifically, the compound represented by the above chemical formula 2 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1 to 2-5.

[0152] [Chemical Formula 2-1]

[0153]

[0154] [Chemical Formula 2-2]

[0155]

[0156] [Chemical Formula 2-3]

[0157]

[0158] [Chemical Formula 2-4]

[0159]

[0160] [Chemical Formula 2-5]

[0161]

[0162] The compound represented by Chemical Formula 2 above may be included in the non-aqueous electrolyte in an amount of 0.01% to 10% by weight. Specifically, the compound represented by Chemical Formula 2 above may be present in the non-aqueous electrolyte in an amount of 0.01% or more, 0.05% or more, 0.1% or more, 0.2% or more, 0.5% or more, or 0.7% or more. Additionally, the compound represented by Chemical Formula 2 above may be present in the non-aqueous electrolyte in an amount of 10% or less by weight, 9% or less by weight, 8% or less by weight, 7% or less by weight, 5% or less by weight, 3% or less by weight, 2% or less by weight, 1.5% or less by weight, or 1.2% or less by weight.

[0163]

[0164] In the present invention, the weight ratio of the compound represented by Formula 2 to the weight of the compound represented by Formula 1 may be 0.01 to 0.2, specifically 0.02 to 0.15, more specifically 0.025 to 0.1, and even more specifically 0.03 to 0.05. When within the above range, side reactions of the electrolyte at the anode and cathode are effectively prevented simultaneously, thereby effectively improving the lifespan performance, storage performance, and resistance increase of the lithium secondary battery. The weight of the compound represented by Formula 1 can be determined through the volume and density information of the compound represented by Formula 1.

[0165]

[0166] The above additive may additionally include other additives in the electrolyte as needed to prevent the decomposition of the electrolyte in a high-power environment from causing cathode collapse, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures. If other additives are additionally included in the above non-aqueous electrolyte, the compound represented by Chemical Formula 2 may be named the first additive, and the other additive may be named the second additive.

[0167] The above other additives may include at least one selected from the group consisting of cyclic carbonate compounds, sulfate compounds, sulfone compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds.

[0168] The above cyclic carbonate compound may be at least one selected from vinylene carbonate (VC) and vinylethylene carbonate (VEC).

[0169] The above sulfate-based compound may be at least one selected from ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0170] The above sulfone-based compound may be at least one selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0171] The above benzene-based compound may be fluorobenzene. The above amine-based compound may be at least one selected from triethanolamine and ethylenediamine. The above silane-based compound may be at least one selected from tetravinylsilane, tris(trimethylsilyl)phosphate (TMSPa), and tris(trimethylsilyl)phosphite (TMSPi). The above lithium salt-based additive may be at least one selected from lithium bis-(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiODFB), and lithium difluorophosphate (LiDFP).

[0172] The above nitrile compound may be at least one selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0173] Meanwhile, the above other additives may be used in a mixture of two or more types, and may be included in an amount of less than 10% by weight based on the total weight of the non-aqueous electrolyte, specifically 0.01% by weight or more and less than 8.0% by weight, and preferably 0.05% by weight to 5.0% by weight.

[0174]

[0175] lithium secondary battery

[0176] In addition, the present invention provides a lithium secondary battery comprising the aforementioned non-aqueous electrolyte.

[0177] Specifically, a lithium secondary battery according to the present invention may comprise a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte. The non-aqueous electrolyte may be the non-aqueous electrolyte described above.

[0178] The above lithium secondary battery can be manufactured by housing an electrode assembly comprising the above positive electrode; a negative electrode facing the above positive electrode; and a separator interposed between the above positive electrode and the above negative electrode in a battery case, and then injecting the aforementioned non-aqueous electrolyte.

[0179]

[0180] As the non-aqueous electrolyte has been described above, the cathode, anode, and separator will be described below.

[0181]

[0182] (1) positive electrode

[0183] The above anode may include an anode active material.

[0184] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a cathode active material used in the field; specifically, it may include a lithium metal composite oxide. More specifically, the lithium metal composite oxide is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium iron phosphate such as LiFePO4; and a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, *-Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxides represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, *-Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of *-Fe, Co, Ni, Cu and Zn); etc., but are not limited to these. The anode may also be a Li-metal anode.

[0185] More specifically, the lithium metal composite oxide may include at least one selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium nickel-cobalt-manganese oxide, lithium-manganese-rich oxide, and lithium iron phosphate.

[0186] The above lithium nickel-cobalt-manganese oxide may be at least one of the compounds represented by the following chemical formulas P-1 and P-2.

[0187] [Chemical Formula P-1]

[0188] Li 1+x (Ni a Co b Mn c M d )O2

[0189] In the above chemical formula P-1, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 1+x, a, b, c, and d are each atomic fractions of independent elements, where 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.25, 0<c≤0.25, 0≤d≤0.1, a+b+c+d=1이다. 바람직하게는, 상기 a, b, c 및 d는 각각 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, 0≤d≤0.03일 수 있다.

[0190] [Chemical Formula P-2]

[0191] Li 1+y [Ni e Co f Mn g M 1 h ]O2+w

[0192] In the above chemical formula P-2, 0≤y≤0.5, e+f+g+h = 1, 0.5≤e≤0.7, 0≤f≤0.15, g=1-efh, 0≤h≤0.1, 0≤f / e≤0.2, 1≤g / e≤3, 0≤w≤1, and M 1 It is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0193] In the above chemical formula P-2, y may be 0 ≤ y ≤ 0.5, specifically 0 ≤ y ≤ 0.2. In the above chemical formula P-2, 0.5 ≤ e ≤ 0.7, specifically 0.55 ≤ e ≤ 0.65. In the above chemical formula P-2, 0 ≤ f ≤ 0.15, specifically 0 ≤ f ≤ 0.1. In the above chemical formula P-2, 0 ≤ f / e ≤ 0.2, specifically 0.05 ≤ f / e ≤ 0.2. In the above chemical formula P-2, g = 1 - efh. Also, 1 ≤ g / e ≤ 3, specifically 1.5 ≤ g / e ≤ 2.5. In the above chemical formula P-2, M 1 It can be understood as an element doped into a lithium transition metal oxide, and specifically, it may be one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. In this case, h may be 0≤h≤0.1, specifically 0≤h≤0.05.

[0194] The above-mentioned lithium manganese-rich oxide may include a compound represented by the following chemical formula P-3.

[0195] [Chemical Formula P-3]

[0196] Li 1+s [Ni t Co u Mn v M 2 w ]O2+z

[0197] In the above chemical formula P-3, M 2 ... is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.3, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1. Preferably, in the above formula P-3, 0.05≤s≤1.0, 0.1≤t≤0.5, 0≤u≤0.1, 0.5≤v<1.0, 0≤w≤0.2, and 0≤z≤1. More preferably, in the above formula P-3, 0.10≤s≤0.50, 0.1≤t≤0.5, 0≤u≤0.1, 0.6≤v<1.0, 0≤w≤0.1, and 0≤z≤0.50.

[0198] The above lithium iron phosphate may include a compound represented by the following chemical formula P-4.

[0199] [Chemical Formula P-4]

[0200] Li 1+z Fe 1-m M 2 m (PO 4-n )X n

[0201] In the above chemical formula P-4, M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti, and V, X is F, S, or N, and 0≤m≤0.5; -0.5≤z≤+0.5; 0≤n≤0.1. The above chemical formula P-4 can be specifically represented as LiFePO4 (z=0, m=0, and n=0).

[0202]

[0203] The above positive active material may be in the form of particles. Specifically, the average particle size (D) of the above positive active material 50 ) can be 1㎛ to 30㎛.

[0204] The above positive active material may be included in the positive active material layer in an amount of 70% to 99% by weight, specifically 80% to 98% by weight, for capacity enhancement.

[0205]

[0206] 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. In this case, the positive active material layer may include the aforementioned positive active material.

[0207] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0208] The above positive current collector may form fine irregularities on its surface to strengthen the bonding force of the positive active material. For example, the above positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0209] The positive active material layer is disposed on at least one surface of the positive current collector. Specifically, the positive active material layer may be disposed on one or both surfaces of the positive current collector.

[0210] The above positive active material may be included in the positive active material layer in an amount of 80% to 99% by weight, taking into account the sufficient capacity exertion of the positive active material.

[0211] The above positive active material layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0212] The above binder is a component that assists in the binding of active materials and conductive materials, and in binding to current collectors, and specifically may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene ter polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride.

[0213] The above binder may be included in the positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently secure binding strength between components such as the positive active material.

[0214] The above conductive material can be used to assist and enhance conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above cathode conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably may include carbon nanotubes for the purpose of enhancing conductivity.

[0215] The above conductive material may be included in the above positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently ensure electrical conductivity.

[0216] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0217] The above anode can be manufactured by coating an anode slurry comprising an anode active material and optionally a binder, a conductive material, and a solvent for forming an anode slurry onto the above anode current collector, and then drying and rolling.

[0218]

[0219] (2) Cathode

[0220] Next, the cathode is explained.

[0221] The above cathode may include a cathode active material.

[0222] The above-mentioned negative electrode active material may be any material used as a negative electrode active material in the field without limitation. Specifically, the above-mentioned negative electrode active material may include at least one selected from silicon-based active materials and carbon-based active materials.

[0223] The above silicon-based active material is silicon (Si) and silicon oxide (SiO₂). x It may include at least one core particle selected from , 0 < x < 2) and silicon-carbon composite.

[0224] Average particle size (D) of the above silicon-based active material 50 ) can be 1㎛ to 20㎛.

[0225] The carbon-based active material may include at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include graphite. The graphite may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0226] Average particle size (D of the above carbon-based active material) 50) can be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in terms of ensuring structural stability during charging and discharging and reducing adverse reactions with the electrolyte.

[0227] In addition, the cathode of the present invention may use a mixture of the carbon-based active material and the silicon-based active material as needed.

[0228] At this time, the weight ratio of the silicon-based active material and the carbon-based active material may be 1:99 to 30:70, specifically 3:97 to 15:85. When the mixing ratio of the silicon-based active material and the carbon-based active material satisfies the above range, excellent cycle performance can be secured by suppressing the volume expansion of the silicon-based active material while improving capacity characteristics.

[0229]

[0230] 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. In this case, the cathode active material may be included in the cathode active material layer.

[0231] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0232] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0233] The above-mentioned negative current collector may form fine irregularities on its surface to strengthen the bonding force of the negative active material. For example, the above-mentioned negative current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0234] The above-mentioned negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0235] The above negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight to minimize the effect of volume expansion / contraction on the battery while sufficiently expressing capacity in the secondary battery.

[0236] The above negative electrode active material layer may further include a conductive material and / or a binder together with the silicon-based active material.

[0237] The above binder can be used to improve the adhesion between the above negative electrode active material layer and the negative electrode current collector to be described later, or to improve the bonding strength between silicon-based active materials.

[0238] Specifically, the binder may include at least one selected from the group consisting of styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), and polyacryl amide (PAM), in order to further improve electrode adhesion and provide sufficient resistance to volume expansion / contraction of the silicone-based active material.

[0239] The binder may be included in the cathode active material layer in an amount of 1% to 30% by weight. When within this range, the cathode active material can be better bound to minimize the volume expansion problem of the active material, and at the same time, the binder can be easily dispersed during the preparation of a slurry for forming the cathode active material layer, and the coating properties and phase stability of the slurry can be improved.

[0240] The above conductive material may be used to assist and improve conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fiber such as carbon fiber or metal fiber; conductive tube such as carbon nanotube; metal powder such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives.

[0241] The above conductive material may be included in the above cathode active material layer in an amount of 1% to 20% by weight, and when in this range, it is desirable in that it can form an excellent conductive network while mitigating the increase in resistance caused by the binder.

[0242] The thickness of the above negative electrode active material layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0243] The above cathode can be manufactured by coating a cathode slurry comprising a cathode active material and optionally a binder, a conductive material, and a solvent for forming a cathode slurry onto the above cathode current collector, and then drying and rolling.

[0244] The solvent for forming the above cathode slurry may include, for example, at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0245]

[0246] (3) Separator

[0247] 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 specific restrictions as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of ions of a non-aqueous electrolyte and excellent moisture retention capacity for the non-aqueous electrolyte.

[0248] Specifically, as a separator, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, 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.

[0249]

[0250] Meanwhile, the external shape of the lithium secondary battery of the present invention is not particularly limited and can be cylindrical, prismatic, pouch-type, or coin-type.

[0251] In addition, the lithium secondary battery of the present invention can be usefully applied in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0252]

[0253] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0254]

[0255] Examples and Comparative Examples

[0256] Example 1

[0257] (Preparation of non-aqueous electrolytes)

[0258] A non-aqueous electrolyte was prepared by dissolving LiPF6 as a lithium salt to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by Chemical Formula 1-1 in a volume ratio of 20:60:20, and then adding vinylene carbonate (VC), 1,3-propane sulfone (PS), LiDFP, LiODFB, LiBOB, and a compound represented by Chemical Formula 2-1 as additives.

[0259] In the above-mentioned non-aqueous electrolyte, vinylene carbonate (VC), 1,3-propane sulfone (PS), LiDFP, LiODFB, LiBOB, and the compound represented by the above-mentioned formula 2-1 were each included in amounts of 0.5 wt%, 0.5 wt%, 1 wt%, 0.5 wt%, 0.2 wt%, and 1 wt%, respectively.

[0260]

[0261] (Anode manufacturing)

[0262] Cathode active material (Li[Ni 0.6 Co 0.1 Mn 0.3 A positive electrode active material slurry (solid content 72 wt%) was prepared by adding a conductive material (carbon nanotube) and a binder (polyvinylidene fluoride) to the solvent N-methyl-2-pyrrolidone (NMP) in a weight ratio of 97.0:1.2:1.8. The positive electrode active material slurry was coated onto a positive electrode current collector (Al thin film) with a thickness of 15 μm, dried, and rolled to produce a positive electrode.

[0263]

[0264] (Cathode manufacturing)

[0265] A cathode active material slurry (solid content: 53 wt%) was prepared by adding a cathode active material (graphite), a conductive material (carbon black), and a binder (styrene-butadiene rubber and carboxymethylcellulose) to water, which is a solvent, in a weight ratio of 97.4:0.5:2.1. The cathode active material slurry was coated onto a cathode current collector (Cu thin film) with a thickness of 15 μm, dried, and then rolled to produce a cathode.

[0266]

[0267] (Secondary battery manufacturing)

[0268] An electrode assembly was manufactured by sequentially laminating the positive and negative electrodes prepared by the aforementioned method together with a polyethylene porous film using a conventional method, and then the assembly was housed in a pouch-type secondary battery case, and the lithium secondary battery electrolyte prepared above was injected to manufacture a lithium secondary battery.

[0269]

[0270] Example 2

[0271] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 20:70:10.

[0272]

[0273] Example 3

[0274] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 20:50:30.

[0275]

[0276] Example 4

[0277] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 25:55:30.

[0278]

[0279] Example 5

[0280] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 30:50:20.

[0281]

[0282] Example 6

[0283] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2-1 above was added at 0.5 wt% instead of 1 wt%.

[0284]

[0285] Example 7

[0286] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by the above chemical formula 2-1 was added at 1.5 wt% instead of 1 wt%.

[0287]

[0288] Comparative Example 1

[0289] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a mixture of ethylene carbonate and ethylmethyl carbonate in a volume ratio of 20:80 was used as the organic solvent, and the compound represented by Chemical Formula 2-1 was not included in the additives.

[0290]

[0291] Comparative Example 2

[0292] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2-1 above was not included in the additive.

[0293]

[0294] Comparative Example 3

[0295] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a mixture of ethylene carbonate and ethylmethyl carbonate in a volume ratio of 20:80 was used as the organic solvent.

[0296]

[0297] Comparative Example 4

[0298] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 10:85:5.

[0299]

[0300] Comparative Example 5

[0301] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that an organic solvent was used in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and a compound represented by the chemical formula 1-1 were mixed in a volume ratio of 40:40:20.

[0302]

[0303] Organic Solvent Additive - Chemical Formula 2 Weight Ratio of Compound Represented by Chemical Formula 2 / Compound Represented by Chemical Formula 1-1 EC (Volume%) EMC (Volume%) Chemical Formula 1-1 (Volume%) EMC Volume / (EC Volume + Chemical Formula 1-1 Volume) Type Weight % Example 1 20 60 20 1.5 Chemical Formula 2-1 10.05 Example 2 20 70 10 approx. 2.3 Chemical Formula 2-1 110.1 Example 3 20 50 30 1 Chemical Formula 2-11 approx. 0.03 Example 4 25 55 20 approx. 1.2 Chemical Formula 2-1 110.05 Example 5 30 50 20 1 Chemical Formula 2-1 110.05 Example 6 20 60 20 1.5 Chemical Formula 2-10.5 0.025 Example 7 20 60 20 1.5 Chemical Formula 2-11.5 0.075 Comparative Example 1 2080-4--- Comparative Example 2 2060201.5--0 Comparative Example 3 2080-4--- Comparative Example 4 10855 approx. 5.7 Chemical Formula 2-110.2 Comparative Example 5 404020 approx. 0.7 Chemical Formula 2-110.05

[0304]

[0305] Experimental Example

[0306] Experimental Example 1: Evaluation of Initial Activation

[0307] For the lithium secondary batteries according to the above examples and comparative examples, an initial activation process was performed by charging to SOC 60% at a C-rate of 0.2C.

[0308] The amount of gas generated from the activated battery was measured using a buoyancy measurement method at room temperature (25℃). When the amount of gas generated in Comparative Example 1 was set to 100% by volume, the relative amounts of gas generated in each example and comparative example were calculated and shown in Table 2 below.

[0309]

[0310] Gas generation amount (%, based on 100 volume% of the gas generation amount of Comparative Example 1) Example 1 35.5 Example 2 38.2 Example 3 33.7 Example 4 41.1 Example 5 46.6 Example 6 38.7 Example 7 34.9 Comparative Example 1 100 Comparative Example 2 88.2 Comparative Example 3 53.7 Comparative Example 452.9 Comparative Example 5 66.5

[0311]

[0312] Referring to Table 2 above, it can be seen that in the case of the lithium secondary battery according to the embodiment, the amount of gas generated immediately after activation is significantly reduced compared to the comparative examples.

[0313]

[0314] Experimental Example 2: High-temperature cycle performance

[0315] The lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 5 prepared above were charged to 4.4V and 1 / 20C at 45℃ under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and then discharged to 2.5V under CC and 0.33C conditions, with 300 charge / discharge cycles performed as one cycle.

[0316] Subsequently, the amount of gas generated in the batteries of the examples and comparative examples was measured using a buoyancy measurement method at room temperature (25°C). When the amount of gas generated in Comparative Example 1 was set to 100% by volume, the relative amounts of gas generated in each example and comparative example were calculated and shown in Table 3 below.

[0317]

[0318] Gas generation amount (%, based on 100 volume% of gas generation amount of Comparative Example 1) Example 1 64.6 Example 2 72.3 Example 3 65.5 Example 4 62.7 Example 5 61.5 Example 6 68.6 Example 7 64.3 Comparative Example 1 100 Comparative Example 2 75.5 Comparative Example 3 81.8 Comparative Example 494.4 Comparative Example 5 77.3

[0319]

[0320] Referring to Table 3 above, it can be seen that in the case of the lithium secondary battery according to the embodiment, the amount of gas generated during high-temperature cycle charging and discharging is significantly reduced compared to the comparative examples.

[0321]

[0322] Experimental Example 3: Evaluation of High-Temperature Storage Performance

[0323] The lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 5 prepared above were charged to 4.4V and 1 / 20C at 25℃ under CC / CV and 0.33C conditions, and discharged to 2.5V at 0.33C to perform initial charge and discharge, and then charged to 4.4V and 1 / 20C at 25℃ under CC / CV and 0.33C conditions, and then stored at 60℃ for 16 weeks.

[0324] Subsequently, the amount of gas generated in the batteries of the examples and comparative examples was measured using a buoyancy measurement method at room temperature (25°C). When the amount of gas generated in Comparative Example 1 was set to 100% by volume, the relative amounts of gas generated in each example and comparative example were calculated and shown in Table 4 below.

[0325]

[0326] Gas generation amount (%, based on 100 volume% of gas generation amount of Comparative Example 1) Example 1 46.6 Example 2 55.3 Example 3 39.8 Example 4 52.7 Example 5 60.1 Example 6 51.3 Example 7 44.2 Comparative Example 1 100 Comparative Example 2 65.5 Comparative Example 3 74.7 Comparative Example 4 70.1 Comparative Example 5 92.5

[0327]

[0328] Referring to Table 4 above, it can be seen that in the case of the lithium secondary battery according to the embodiment, the amount of gas generated during high-temperature storage is significantly reduced compared to the comparative examples.

Claims

1. Contains a lithium salt; an organic solvent; and an additive; and The above organic solvent comprises a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a compound represented by the following chemical formula 1, and The above additive comprises a compound represented by the following chemical formula 2, and A non-aqueous electrolyte in which the ratio of the volume of the linear carbonate-based solvent to the sum of the volumes of the cyclic carbonate-based solvent and the compound represented by Chemical Formula 1 is 1 to 4: [Chemical Formula 1] In the above chemical formula 1, R1 is *-F, *-CF3 or *-OCF3, R2 is a directly bonded or alkylene group having 1 to 5 carbon atoms, and R3 and R4 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms. [Chemical Formula 2] A-L1-B The above A and B are substituents represented by the following chemical formula 2-a independently of each other, and L1 is a direct bond, an alkylene group having 1 to 10 carbon atoms, a sulfate group, a sulfonate group, an ether group, an ester group, a carbonate group, or a combination of two or more of these. [Chemical Formula 2-a] In the above chemical formula 2-a, X1 is *-C(R X11 )(R X12 )-* or oxygen(*-O-*) and R5, R X11 and R X12 Each is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, n is an integer selected from 0 to 3, and if n is an integer of 2 or more, each R5 is the same or different from each other.

2. In Claim 1, A non-aqueous electrolyte comprising at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-4, wherein the compound represented by the above chemical formula 1: [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] .

3. In Claim 1, A non-aqueous electrolyte comprising at least one substituent selected from the group consisting of the substituents represented by the following chemical formulas 2-a-1 to 2-a-3, wherein the substituent represented by the above chemical formula 2-a is: [Chemical Formula 2-a-1] [Chemical Formula 2-a-2] [Chemical Formula 2-a-3] .

4. In Claim 1, A non-aqueous electrolyte comprising at least one selected from the group consisting of compounds represented by the following chemical formulas 2-1 to 2-5, wherein the compound represented by the above chemical formula 2: [Chemical Formula 2-1] [Chemical Formula 2-2] [Chemical Formula 2-3] [Chemical Formula 2-4] [Chemical Formula 2-5] .

5. In Claim 1, The above-mentioned cyclic carbonate-based solvent is included in the above-mentioned organic solvent in an amount of 10 to 40 volume%, and The above linear carbonate-based solvent is included in the above organic solvent in an amount of 50 volume% to 80 volume%, and The compound represented by the above chemical formula 1 is a non-aqueous electrolyte contained in the above organic solvent in an amount of 10 volume% to 30 volume%.

6. In Claim 1, A non-aqueous electrolyte in which the weight ratio of the compound represented by Chemical Formula 2 to the weight of the compound represented by Chemical Formula 1 is 0.01 to 0.

2.

7. In Claim 1, The compound represented by the above chemical formula 2 is a non-aqueous electrolyte included in the above non-aqueous electrolyte in an amount of 0.01% to 10% by weight.

8. In Claim 1, The above additive further comprises at least one selected from the group consisting of cyclic carbonate compounds, sulfate compounds, sulfone compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds, in a non-aqueous electrolyte.

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

10. In Claim 9, The above negative electrode comprises at least one type selected from carbon-based active material and silicon-based active material, forming a lithium secondary battery.

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