Electrolyte for lithium secondary battery, and lithium secondary battery including the same

Abstract

An electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same are disclosed. The electrolyte for the lithium secondary battery may comprise a lithium salt; a non-aqueous organic solvent; and a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups.

Description

Technology Field

[0001] The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery containing the same. Background Technology

[0002] Compared to conventional lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries, lithium-ion batteries have an energy density more than three times higher per unit weight and can be fast-charged.

[0003] Lithium secondary batteries must be stable within the operating voltage range of the battery and must maintain safety even beyond the said operating voltage range. However, under overcharging and overvoltage conditions, lithium is excessively released from the positive electrode and excessively inserted into the negative electrode. As a result, both the positive and negative electrodes become unstable.

[0004] Various additives are added to the electrolyte to solve problems under such overcharging and overvoltage environments, but this causes problems that degrade some of the performance of the lithium secondary battery.

[0005] Therefore, there is still a need to improve the overcharge characteristics of lithium secondary batteries to enhance safety while maintaining battery performance such as low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or to minimize the degradation of said battery performance. The problem to be solved

[0006] One aspect is to provide an electrolyte for a lithium secondary battery containing a novel electrolyte additive.

[0007] Another aspect is to provide a lithium secondary battery containing the above-mentioned electrolyte. means of solving the problem

[0008] According to one aspect,

[0009] Lithium salt;

[0010] Non-aqueous organic solvents; and

[0011] An electrolyte for a lithium secondary battery is provided, comprising a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups.

[0012] The above sulfone-based compound additive may be a compound represented by the following chemical formula 1:

[0013] [Chemical Formula 1]

[0014]

[0015] During the meal,

[0016] R1 and R2 are independently substituted or unsubstituted C1-C10 alkyl groups, substituted or unsubstituted C2-C10 alkenyl groups, substituted or unsubstituted C3-C10 alkynyl groups, substituted or unsubstituted C3-C20 cycloalkyl groups, substituted or unsubstituted C6-C50 aryl groups, substituted or unsubstituted C6-C50 alkylaryl groups, or substituted or unsubstituted C6-C50 heteroaryl groups, wherein

[0017] At least one of the above R1 and R2 may be a C6 aryl group substituted or unsubstituted with a halogen element.

[0018] The above sulfone-based compound additive may include a compound represented by the following chemical formula 1-1:

[0019] [Chemical Formula 1-1]

[0020]

[0021] During the meal,

[0022] R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 They are independently hydrogen atoms, halogen atoms, cyano groups, -OR a (R a is a C1-C10 alkyl group or a C6-C20 aryl group), -C(=O)R b , -C(=O)OR b , -OCO(OR b ), -(X) n-NH2(X is a C1-C10 alkyl group or a C1-C10 alkoxy group, and n is an integer from 0 to 10), -C=N(R b ), -SR b , -S(=O)R b , -S(=O)2R b , a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkoxy group, a substituted or unsubstituted C2-C20 alkenyl group, a substituted or unsubstituted C2-C20 alkynyl group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R b is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, but,

[0023] The above R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 At least one of them may be a fluorine atom.

[0024] The above silane compound additive may be a compound represented by the following chemical formula 2:

[0025] [Chemical Formula 2]

[0026]

[0027] During the meal,

[0028] R3, R4, R5, and R6 are independent of each other -OR' a (R' a is a C1-C10 alkyl group or a C6-C20 aryl group), C(=O)R' b , -C(=O)OR' b, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C3-C10 alkynyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C6-C50 aryl group, a substituted or unsubstituted C6-C50 aryloxy group, a substituted or unsubstituted C6-C50 alkylaryl group, or a substituted or unsubstituted C6-C50 heteroaryl group, wherein R' b is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, but,

[0029] At least one of the above R3, R4, R5, and R6 may be a substituted or unsubstituted C6 aryl group.

[0030] The above silane-based compound additive may include a compound represented by the following chemical formula 2-1:

[0031] [Chemical Formula 2-1]

[0032]

[0033] During the meal,

[0034] R' 11 , R' 12 are independently C(=O)R" a , -C(=O)OR" a , a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C3-C10 alkynyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 alkylaryl group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R" a can be hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group.

[0035] The above sulfone-based compound additive may include one or more of the following compounds 1 and 2, and the above silane-based compound additive may include one or more of the following compounds 3 and 4:

[0036]

[0037] Compound 1 Compound 2

[0038]

[0039] Compound 3 Compound 4

[0040] The weight ratio of the above sulfone-based compound additive and the above silane-based compound additive may be 1:7 to 7:1.

[0041] The total content of the above sulfone-based compound additive and the above silane-based compound additive may be 0.1 to 10 parts by weight based on 100 parts by weight of the total electrolyte.

[0042] According to other aspects of work,

[0043] Anode containing a positive electrode active material;

[0044] A cathode comprising a cathode active material; and

[0045] A lithium secondary battery is provided comprising the aforementioned electrolyte disposed between the positive and negative electrodes. Effects of the invention

[0046] An electrolyte for a lithium secondary battery according to one aspect comprises a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups. A lithium secondary battery containing the electrolyte forms a film on the positive electrode to protect the positive electrode under overcharging and overvoltage environments, and suppresses the rise in voltage of the battery to suppress electrolyte decomposition. Accordingly, the lithium secondary battery can improve safety by maintaining the performance of low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or by improving overcharging characteristics while minimizing the degradation of said performances. Brief explanation of the drawing

[0047] FIG. 1 is a schematic diagram of a lithium secondary battery according to one embodiment. Figure 2 shows the results of an overcharge test on lithium secondary batteries prepared according to Examples 8 to 13 and Comparative Example 6. Specific details for implementing the invention

[0048] Hereinafter, an electrolyte for a lithium secondary battery and a lithium secondary battery including the same will be described in detail with reference to the embodiments and drawings of the present invention. These embodiments are presented merely as examples to explain the present invention more specifically, and it will be obvious to those skilled in the art that the scope of the present invention is not limited by these embodiments.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. In the event of a conflict, the present specification, including definitions, shall prevail.

[0050] Methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0051] In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof.

[0052] In this specification, the term “combination of these” means a mixture or combination with one or more of the described components.

[0053] In this specification, the term “and / or” means including any combination and all combinations of one or more items described in relation. In this specification, the term “or” means “and / or.” In this specification, expressions such as “at least one,” “one or more,” or “one or more” preceding components are to supplement the list of all components and do not mean that they are to supplement the individual components described above.

[0054] In the drawings, thicknesses have been enlarged or reduced to clearly represent various layers and regions. Throughout the specification, the same reference numerals have been used for similar parts. Throughout the specification, when a part such as a layer, film, region, or plate is described as being "on" or "above" another part, this includes not only cases where it is directly above another part but also cases where there is another part in between. Throughout the specification, terms such as "first," "second," etc., may be used to describe various components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another.

[0055] Generally, additives that improve overcharge characteristics have a structure containing biphenyl groups. If the above-mentioned additives that improve overcharge characteristics are included in the electrolyte, the lithium secondary battery containing them has a problem in which electrolyte decomposition begins even within a normal operating voltage range, increasing the internal resistance of the cell and degrading performance such as lifespan characteristics.

[0056] An electrolyte for a lithium secondary battery according to one embodiment may comprise a lithium salt; a non-aqueous organic solvent; and a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups.

[0057] An electrolyte for a lithium secondary battery according to one embodiment comprises a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups. The sulfone-based compound additive having one or more phenyl groups forms a film on the positive electrode to protect the positive electrode under overcharge and overvoltage environments. The silane-based compound additive having one or more phenyl groups suppresses the voltage rise of the battery under overcharge and overvoltage environments, thereby preventing electrolyte decomposition. Accordingly, a lithium secondary battery containing the electrolyte can improve safety by improving overcharge characteristics, while simultaneously maintaining performance in low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or minimizing the degradation of said performance.

[0058] For example, the above sulfone compound additive may be a compound represented by the following chemical formula 1:

[0059] [Chemical Formula 1]

[0060]

[0061] During the meal,

[0062] R1 and R2 are independently substituted or unsubstituted C1-C10 alkyl groups, substituted or unsubstituted C2-C10 alkenyl groups, substituted or unsubstituted C3-C10 alkynyl groups, substituted or unsubstituted C3-C20 cycloalkyl groups, substituted or unsubstituted C6-C50 aryl groups, substituted or unsubstituted C6-C50 alkylaryl groups, or substituted or unsubstituted C6-C50 heteroaryl groups, wherein

[0063] At least one of the above R1 and R2 may be a C6 aryl group substituted or unsubstituted with a halogen element.

[0064] For example, the above sulfone-based compound additive may include a compound represented by the following chemical formula 1-1:

[0065] [Chemical Formula 1-1]

[0066]

[0067] During the meal,

[0068] R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 They are independently hydrogen atoms, halogen atoms, cyano groups, -OR a (R a is a C1-C10 alkyl group or a C6-C20 aryl group), -C(=O)R b , -C(=O)OR b , -OCO(OR b ), -(X) n -NH2(X is a C1-C10 alkyl group or a C1-C10 alkoxy group, and n is an integer from 0 to 10), -C=N(R b ), -SR b , -S(=O)R b , -S(=O)2R b , a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkoxy group, a substituted or unsubstituted C2-C20 alkenyl group, a substituted or unsubstituted C2-C20 alkynyl group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R b is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, but,

[0069] The above R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 At least one of them may be a fluorine atom.

[0070] The above sulfone-based compound additive forms a film on the surface of the anode and acts as a protective film that blocks the active sites on the surface of the anode, thereby preventing some of the transition metal from leaching out and precipitating on the cathode during charging and discharging, and suppresses side reactions and gas generation occurring between the electrolyte and the anode, which can improve high-temperature performance and overcharge characteristics.

[0071] For example, the above silane compound additive may include a compound represented by the following chemical formula 2-1:

[0072] [Chemical Formula 2-1]

[0073]

[0074] During the meal,

[0075] R' 11 , R' 12 are independently C(=O)R" a , -C(=O)OR" a , a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C3-C10 alkynyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 alkylaryl group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R" a can be hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group.

[0076] The above silane-based compound additive is partially reduced and decomposed on the cathode during initial charging, thereby forming a protective film of suitable ion conductivity on the cathode surface and preventing electrolyte decomposition by suppressing voltage rise even under an overcharged environment.

[0077] For example, the sulfone compound additive may include one or more of the following compounds 1 and 2, and the silane compound additive may include one or more of the following compounds 3 and 4:

[0078]

[0079] Compound 1 Compound 2

[0080]

[0081] Compound 3 Compound 4

[0082] The weight ratio of the sulfone-based compound additive and the silane-based compound additive may be 1:7 to 7:1. For example, the weight ratio of the sulfone-based compound additive and the silane-based compound additive may be 1:5 to 5:1 or 1:3 to 3:1. Within the above weight ratio range, a lithium secondary battery containing the same can maintain the performance of low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or improve overcharge characteristics while minimizing the degradation of said performance, thereby maximizing safety.

[0083] The total content of the above sulfone-based compound additive and the above silane-based compound additive may be 0.1 to 10 parts by weight based on 100 parts by weight of the total electrolyte. For example, the total content of the above sulfone-based compound additive and the above silane-based compound additive may be 0.1 to 9 parts by weight, 0.1 to 8 parts by weight, 0.1 to 7 parts by weight, 0.1 to 6 parts by weight, 0.1 to 5 parts by weight, 0.1 to 4 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, or 0.1 to 1 part by weight based on 100 parts by weight of the total electrolyte. Within the above content range, a lithium secondary battery containing this can maintain the performance of low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or improve overcharge characteristics while minimizing the degradation of said performances, thereby maximizing safety.

[0084] The above lithium salt consists of a lithium cation and,

[0085] F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N-, CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , PO2F2 - and (CF3CF2SO2)2N - It may include anions selected from. In the electrolyte, the concentration of the lithium salt may be 0.01 to 2.0 M, but is not necessarily limited to this range, and an appropriate concentration may be used as needed. Battery performance may be further improved within the above concentration range.

[0086] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, aprotic solvent, or a combination thereof.

[0087] The non-aqueous organic solvent included in the above-mentioned electrolyte for a lithium secondary battery serves as a medium through which ions involved in the electrochemical reaction of the battery can move, and the non-aqueous organic solvent used in the present invention is not particularly limited as long as it is one commonly used in the industry.

[0088] More specifically, the carbonate-based solvent may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc., and the ester-based solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, propylpropionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, etc. The above ether-based solvents may include dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc., and the above ketone-based solvents may include cyclohexanone, etc.

[0089] In addition, the above alcohol-based solvent may include ethyl alcohol, isopropyl alcohol, etc., and the above aprotic solvent may include nitriles such as R-CN (where R is a hydrocarbon group with a straight, branched, or ring structure having 2 to 20 carbon atoms and may include a double aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, etc.

[0090] The above-mentioned non-aqueous organic solvents may be used alone or in a mixture of two or more types, and when two or more types are mixed, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field.

[0091] In addition, for the above carbonate-based solvent, it is preferable to use a mixture of cyclic carbonates and chain carbonates. In this case, using a mixture of cyclic carbonates and chain carbonates in a volume ratio of 1:1 to 1:9 can result in excellent electrolyte performance.

[0092] The non-aqueous organic solvent of the present invention may further include an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1:1 to 30:1. The above aromatic hydrocarbon-based organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, It may be 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4-trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotoluene, 1,2,3-triiodotoluene, 1,2,4-triiodotoluene, xylene, or a combination thereof.

[0093] For example, the above-mentioned non-aqueous organic solvent may include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, vinyl ethylene carbonate (VEC), butylene carbonate, ethyl propionate (EP), propyl propionate (PP), ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, gamma-valerolactone, gamma-butyrolactone, or tetrahydrofuran. However, it is not limited thereto, and any non-aqueous organic solvent available in the art may be used.

[0094] The above electrolyte may be in a liquid or gel state.

[0095] A lithium secondary battery according to another embodiment may include a positive electrode comprising a positive active material; a negative electrode comprising a negative active material; and the aforementioned electrolyte disposed between the positive electrode and the negative electrode. The form of the lithium secondary battery is not particularly limited and includes lithium secondary batteries such as lithium-ion batteries, lithium-ion polymer batteries, lithium-sulfur batteries, etc.

[0096] The above lithium secondary battery includes the aforementioned electrolyte, and safety can be improved by maintaining the performance of low temperature (-10 ℃) discharge capacity (r), high temperature (60 ℃) storage characteristics, and high temperature (45 ℃) life characteristics, or by improving overcharge characteristics while minimizing the degradation of said performances.

[0097] For example, the above positive active material may be selected from compounds represented by the following chemical formulas. Li a A 1-b D' b E2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5); Li a G 1-b D' b O 2-c Ec (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiG 2-b D' b O 4-c E c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b D' c E α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b D' c O 2-α J α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b D' c O 2-α J2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b D' c E α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b D' c O 2-α J α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b D' c O 2-αJ2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b G c L d O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.2); Li a Ni b G c O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5); Li a Ni b Co c Mn d L e O2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.2); Li a Ni b Co c Mn d O2(wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5); Li a NiL b O2(wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.2); Li a CoL b O2(wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.2); Li a MnL b O2(wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.2); Li a Mn2L b O4(wherein the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.2); Li a Mn2O4 (wherein the above formula, 0.90 ≤ a ≤ 1.8); MO2; MS2; LiMS2; V2O5; LiV2O5; LiQO2; LiNiVO4; Li(3-f) T2(PO4)3(wherein 0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3 (wherein 0 ≤ f ≤ 2); a compound represented by any one of the chemical formulas of LiFePO4 may be used:

[0098] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn and combinations thereof; D' is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; E is selected from the group consisting of O, F, S, P and combinations thereof; G is selected from the group consisting of Co, Mn and combinations thereof; J is selected from the group consisting of F, S, P and combinations thereof; and L is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, Si, Ge, Sn, P, As, Sb, Bi, S, Se, Te, Po, Mn, La, It is a transition metal or lanthanide element selected from the group consisting of Ce and combinations thereof, M is selected from the group consisting of Ti, Mo, Mn and combinations thereof, Q is selected from the group consisting of Cr, V, Fe, Sc, Ti, Y and combinations thereof, and T is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu and combinations thereof. Specifically, the positive electrode active material may be LiCoO2.

[0099] The above-mentioned cathode active material may include a carbon-based material, a silicon-based material, or a silicon-carbon-based composite.

[0100] The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in amorphous, plate-like, flake-like, spherical, or fibrous forms, and the amorphous carbon may be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, or calcined coke.

[0101] The silicon-based material may include silicon particles, silicon alloy particles, or / and silicon nanowires, etc. For example, the silicon-based material may be silicon particles and may have an average particle size of 50 nm to 150 nm.

[0102] The above silicon-carbon composite may be a composite having a structure in which silicon nanoparticles are disposed on top of a carbon-based compound, a composite in which silicon particles are contained on the surface and inside of a carbon-based compound, or a composite in which silicon particles are coated with a carbon-based compound and contained inside a carbon-based compound. In the composite of the silicon-based compound and the carbon-based compound, the carbon-based compound may be graphite, graphene, graphene oxide, or a combination thereof.

[0103] For example, the negative electrode active material may be an active material obtained by dispersing silicon nanoparticles with an average particle size of about 200 nm or less on carbon-based compound particles and then carbon coating, or an active material in which silicon (Si) particles exist on top of and inside graphite. The silicon nanoparticles may have an average particle size of 50 nm to 150 nm. The average particle size of the silicon-carbon-based composite may be, for example, 1 μm to 20 μm. A lithium secondary battery comprising the negative electrode active material may have improved initial efficiency, capacity, and lifespan characteristics.

[0104] The above lithium secondary battery can be manufactured by the following method.

[0105] First, the positive electrode is prepared.

[0106] The anode is manufactured, for example, by the following exemplary method, but is not necessarily limited to this method and is adjusted according to the required conditions.

[0107] First, a positive active material composition is prepared by mixing the aforementioned positive active material, conductive agent, binder, and solvent. The prepared positive active material composition is directly coated and dried onto an aluminum current collector to manufacture a positive electrode plate with a positive active material layer formed thereon. Alternatively, the positive active material composition is cast onto a separate support, and the film obtained by peeling it off from the support is laminated onto the aluminum current collector to manufacture a positive electrode plate with a positive active material layer formed thereon.

[0108] Conductive agents include carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders such as copper, nickel, aluminum, and silver, or metal fibers or metal tubes; conductive polymers such as polyphenylene derivatives, but are not limited to these, and any material used as a conductive agent in the relevant technical field is acceptable.

[0109] As binders, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the aforementioned polymers, styrene butadiene rubber-based polymers, etc. are used, and as solvents, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not necessarily limited to these and any solvent used in the relevant technical field is acceptable.

[0110] It is also possible to form pores inside the electrode plate by adding a plasticizer or a pore-forming agent to the positive electrode active material composition.

[0111] The content of the positive active material, conductive agent, binder, and solvent used in the positive electrode is at a level typically used in lithium secondary batteries. Depending on the application and composition of the lithium secondary battery, one or more of the above conductive agent, binder, and solvent may be omitted. In addition to the aforementioned positive active material, the positive active material may further include the following positive active materials.

[0112] The above-mentioned cathode active material is a lithium-containing metal oxide, and any that is commonly used in the industry may be used without limitation. For example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples thereof include Li a A 1-b B' b D'2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D' c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D' c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B'c O 2-α F'2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O 2-α F'2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG bO2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); compounds represented by any one of the chemical formulas of LiFePO4 may be used:

[0113] In the chemical formula representing the compound described above, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D' is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0114] For example, the above positive active material is LiCoO2, LiMn g O 2g (g=1, or 2), LiNi 1-g-k Co g Al k O2(0 <g<1, 0<k≤0.5), LiNi 1-g-k Co g Mn k It may include O2 (0≤g≤0.5, 0≤k≤0.5), or LiFePO4.

[0115] It is possible to use a compound having a coating layer added to the surface of the compound described above, and it is also possible to use a mixture of the compound described above and the compound having a coating layer added. The coating layer added to the surface of the compound described above includes, for example, a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. The compound forming such a coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method is, for example, spray coating or immersion. Since specific coating methods are well understood by those skilled in the art, a detailed explanation will be omitted.

[0116] Next, the cathode is manufactured as follows. The cathode is manufactured in substantially the same manner as the anode, except that, for example, the aforementioned cathode active material is used instead of the anode active material. In addition, the conductive agent, binder, and solvent in the cathode active material composition may be substantially the same as those used in the anode.

[0117] For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive agent, a binder, and a solvent, and a negative electrode plate is manufactured by directly coating this composition onto a copper current collector. Alternatively, the prepared negative electrode active material composition is cast onto a separate support, and a negative electrode active material film peeled from the support is laminated onto a copper current collector to manufacture a negative electrode plate.

[0118] In addition to the aforementioned negative electrode active material, any material used as a negative electrode active material for a lithium secondary battery in the relevant technical field may be used. For example, it includes one or more selected from lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials.

[0119] The metals that can be alloyed with the above lithium are, for example, Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y' alloys (where Y' is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and is not Si), Sn-Y' alloys (where Y' is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and is not Sn), etc. The element Y' is, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0120] The above transition metal oxides are, for example, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

[0121] The above non-transfer metal oxides are, for example, SnO2, SiO2 x (0 <x<2) 등이다.

[0122] The carbon-based material is, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon is, for example, graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon is, for example, soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0123] The content of the above-mentioned negative electrode active material, conductive agent, binder, and solvent is at a level typically used in lithium secondary batteries. Depending on the application and composition of the lithium secondary battery, one or more of the above-mentioned conductive agent, binder, and solvent may be omitted.

[0124] Next, a separator to be inserted between the anode and cathode is prepared.

[0125] Any separator commonly used in lithium secondary batteries may be used. A separator with low resistance to ion movement of the electrolyte and excellent electrolyte impregnation capability may be used. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a nonwoven or woven fabric. For example, a windable separator such as polyethylene or polypropylene is used for lithium-ion batteries, and a separator with excellent electrolyte impregnation capability may be used for lithium-ion polymer batteries. For example, the above separator may be manufactured according to the following method.

[0126] A separator composition is prepared by mixing a polymer resin, a filler, and a solvent. The separator composition may be directly coated and dried on the electrode to form a separator. Alternatively, the separator composition may be cast and dried on a support, and then a separator film peeled from the support may be laminated onto the electrode to form a separator.

[0127] The polymer resin used in the manufacture of the above separator is not particularly limited, and any material used as a binder for the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

[0128] Next, the aforementioned electrolyte is prepared.

[0129] The electrolyte may further include an organic solid electrolyte or / and an inorganic solid electrolyte in addition to the aforementioned electrolyte.

[0130] For example, the above organic solid electrolyte may be a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, etc.

[0131] For example, the above-mentioned inorganic solid electrolyte is not limited to boron oxide, lithium oxynitride, etc., and any solid electrolyte used in the relevant technical field is acceptable. The above-mentioned inorganic solid electrolyte is formed on the cathode, for example, by a method such as sputtering, or a separate solid electrolyte sheet is laminated on the cathode.

[0132] As shown in FIG. 1, the lithium secondary battery (1) includes a positive electrode (3), a negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded and accommodated in a battery case (5). An electrolyte is injected into the battery case (5) and sealed with a cap assembly (6) to complete the lithium secondary battery (1). The battery case (5) is cylindrical but is not necessarily limited to this shape and may be, for example, prismatic, thin-film, coin-shaped, etc.

[0133] For example, a pouch-type lithium secondary battery comprises one or more battery structures. A separator is placed between the positive and negative electrodes to form the battery structure. The battery structures are stacked in a bicell structure, impregnated with an organic electrolyte, and then housed and sealed in a pouch to complete the pouch-type lithium secondary battery. Multiple battery structures are stacked to form a battery pack, and such battery packs are used in all devices requiring high capacity and high output. For example, they are used in laptops, smartphones, electric vehicles, etc.

[0134] Lithium-ion batteries are used in, for example, electric vehicles (EVs) due to their excellent lifespan and high-rate performance. For instance, they are used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). Additionally, they are used in fields requiring large amounts of power storage, such as electric bicycles and power tools.

[0135] In this specification, a and b of “carbon number a to b” refer to the number of carbon atoms of a specific functional group. That is, the functional group may include carbon atoms from a to b. For example, “alkyl group having 1 to 4 carbon atoms” refers to an alkyl group having 1 to 4 carbons, namely CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, CH3CH2CH(CH3)-, and (CH3)3C-.

[0136] Nomenclature for specific radicals may include monoradicals or diradicals depending on the context. For example, if a substituent requires two linkages to the rest of the molecule, said substituent should be understood as a diradical. For instance, substituents identified as alkyl groups requiring two linkages include diradicals such as -CH2-, -CH2CH2-, -CH2CH(CH3)CH2-, etc. Other radical nomenclatures, such as "alkylene," clearly indicate that said radical is a diradical.

[0137] In this specification, the terms “alkyl group” or “alkylene group” refer to a branched or unbranched aliphatic hydrocarbon group. In one embodiment, the alkyl group may or may not be substituted. The alkyl group includes, but is not necessarily limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, etc., and each of these may or may not be optionally substituted. In one embodiment, the alkyl group may have 1 to 6 carbon atoms. For example, the alkyl group having 1 to 6 carbon atoms may be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, hexyl, etc., but is not necessarily limited to these.

[0138] In this specification, the term "cycloalkyl group" means a fully saturated carbocyclic ring or ring system. For example, it means cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0139] In this specification, the term “alkenyl group” refers to a hydrocarbon group comprising 2 to 20 carbon atoms containing at least one carbon-carbon double bond, including but not limited to an ethenyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 1-butenyl group, 2-butenyl group, cyclopropenyl group, cyclopentenyl group, cyclohexenyl group, cycloheptenyl group, etc. In one embodiment, the alkenyl group may or may not be substituted. In one embodiment, the alkenyl group may have 2 to 40 carbon atoms.

[0140] In this specification, the term “alkynyl group” refers to a hydrocarbon group comprising 2 to 20 carbon atoms containing at least one carbon-carbon triple bond, including but not limited to ethinyl groups, 1-propynyl groups, 1-butynyl groups, 2-butynyl groups, etc. In one embodiment, the alkynyl group may or may not be substituted. In one embodiment, the alkynyl group may have 2 to 40 carbon atoms.

[0141] In this specification, the term "alkoxy group" means an alkyl group bonded with oxygen, and specific examples of the alkoxy group include methoxy, ethoxy, propoxy, etc., and one or more hydrogen atoms of the alkoxy group may or may not be substituted.

[0142] In this specification, the term “aromatic” means a ring or ring system having a conjugated pi-electron system and includes carbon ring aromatics (e.g., phenyl groups) and heterocyclic aromatic groups (e.g., pyridines). The term includes a single ring or a fused polycyclic ring (i.e., a ring sharing adjacent pairs of atoms) if the entire ring system is aromatic.

[0143] In this specification, the term “aryl group” means an aromatic ring or ring system in which the ring skeleton comprises only carbons (i.e., two or more fused rings sharing two adjacent carbon atoms). If the aryl group is a ring system, each ring in the system is aromatic. For example, the aryl group includes, but is not limited to, phenyl groups, biphenyl groups, naphthyl groups, phenanthrenyl groups, naphthacenyl groups, etc. The aryl group may or may not be substituted.

[0144] In this specification, the term “heteroaryl group” means an aromatic ring system having one ring or a plurality of fused rings, wherein one or more ring atoms are not carbon, i.e., heteroatoms. In a fused ring system, one or more heteroatoms may exist in only one ring. For example, heteroatoms include oxygen, sulfur, and nitrogen, but are not necessarily limited to these. For example, a heteroaryl group may be a furanyl group, a thienyl group, an imidazolyl group, a quinazolinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a pyridinyl group, a pyrrolyl group, an oxazolyl group, an indolyl group, etc., but is not limited to these.

[0145] In this specification, the terms “aryl group” and “alkylaryl group” refer to an aryl group connected as a substituent via an alkylene group, such as an aryl group having 7 to 14 carbon atoms, and include, but are not limited to, a benzyl group, a 2-phenylethyl group, a 3-phenylpropyl group, and a naphthylalkyl group. In one embodiment, the alkylene group is a lower alkylene group (i.e., an alkylene group having 1 to 4 carbon atoms).

[0146] In this specification, the term "aryloxy group" refers to an aryl group bonded to oxygen, specific examples of said aryloxy group include phenoxy, and one or more hydrogen atoms of said aryl group may or may not be substituted.

[0147] In this specification, "cycloalkenyl group" is a carbosite ring or ring system having one or more double bonds, and is a ring system without an aromatic ring. For example, it is a cyclohexenyl group.

[0148] In this specification, "heterocyclyl group" is a non-aromatic ring or ring system comprising one or more heteroatoms in a ring backbone.

[0149] In this specification, “halogen” refers to a stable element belonging to Group 17 of the periodic table, such as fluorine, chlorine, bromine, or iodine, and in particular fluorine and / or chlorine.

[0150] In this specification, "cyano group" means "-CN group".

[0151] In this specification, a substituent is derived by exchanging one or more hydrogens from an unsubstituted mother group with another atom or functional group. Unless otherwise stated, when a functional group is considered to be "substituted," it means that the functional group is substituted with one or more substituents selected from an alkyl group having 1 to 40 carbon atoms, an alkenyl group having 2 to 40 carbon atoms, a cycloalkyl group having 3 to 40 carbon atoms, a cycloalkenyl group having 3 to 40 carbon atoms, an alkyl group having 1 to 40 carbon atoms, and an aryl group having 7 to 40 carbon atoms. When a functional group is described as "optionally substituted," it means that the functional group may be substituted with the substituents described above.

[0152] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0153] [Example]

[0154] (Preparation of electrolytes)

[0155] Example 1: 1 part by weight of Compound 1 and 1 part by weight of Compound 3

[0156] 1.3 M LiPF6 was added to a mixed solvent in which the volume ratio of ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), and propyl propionate (PP) was 10:15:30:45. To the above mixed solvent, based on 100 parts by weight of the total electrolyte, 1 part by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 1 part by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to prepare an electrolyte.

[0157]

[0158] Compound 1 Compound 3

[0159] Example 2: 1.5 parts by weight of Compound 1 and 1.5 parts by weight of Compound 3

[0160] An electrolyte was prepared in the same manner as in Example 1, except that 1.5 parts by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 1.5 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0161] Example 3: 0.3 parts by weight of Compound 1 and 0.3 parts by weight of Compound 3

[0162] An electrolyte was prepared in the same manner as in Example 1, except that 0.3 parts by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 0.3 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0163] Example 4: 1 part by weight of Compound 1 and 2 parts by weight of Compound 3

[0164] An electrolyte was prepared in the same manner as in Example 1, except that 1 part by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 2 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0165] Example 5: 1 part by weight of Compound 1 and 3 parts by weight of Compound 3

[0166] An electrolyte was prepared in the same manner as in Example 1, except that 1 part by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 3 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0167] Example 6: 1 part by weight of Compound 1 and 7 parts by weight of Compound 3

[0168] An electrolyte was prepared in the same manner as in Example 1, except that 1 part by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 7 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0169] Example 7: 7 parts by weight of Compound 1 and 1 part by weight of Compound 3

[0170] An electrolyte was prepared in the same manner as in Example 1, except that 7 parts by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 1 part by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0171] Comparative Example 1

[0172] An electrolyte was prepared by adding 1.3 M LiPF6 to a mixed solvent in which the volume ratio of ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), and propyl propionate (PP) was 10:15:30:45.

[0173] Comparative Example 2: Compound 1 2 parts by weight

[0174] An electrolyte was prepared in the same manner as in Example 1, except that 2 parts by weight of bis(4-fluorophenyl)sulfone (bis(4-fluorophenyl)sulfone, manufactured by Sigma Aldrich, 'Compound 1') was added as a sulfone-based compound additive to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0175] Comparative Example 3: 2 parts by weight of Compound 3

[0176] An electrolyte was prepared in the same manner as in Example 1, except that 2 parts by weight of dimethoxy diphenylsilane (dimethoxy diphenyl silane, manufactured by Sigma Aldrich, 'Compound 3') was added as a silane compound additive to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0177] Comparative Example 4: 2 parts by weight of Compound 4

[0178] An electrolyte was prepared in the same manner as in Example 1, except that 2 parts by weight of diethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 4') was added as a silane compound additive to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0179]

[0180] Compound 4

[0181] Comparative Example 5: 8 parts by weight of Compound 1 and 8 parts by weight of Compound 3

[0182] An electrolyte was prepared in the same manner as in Example 1, except that 8 parts by weight of bis(4-fluorophenyl)sulfone (manufactured by Sigma Aldrich, 'Compound 1') as a sulfone-based compound additive and 8 parts by weight of dimethoxy diphenylsilane (manufactured by Sigma Aldrich, 'Compound 3') as a silane-based compound additive were added to the above mixed solvent based on 100 parts by weight of the total electrolyte.

[0183] (Manufacturing of lithium-ion batteries (coin cells))

[0184] Example 8

[0185] A cathode active material slurry was prepared by mixing 98 wt% artificial graphite, 1 wt% styrene-butadiene rubber (SBR), and 1 wt% carboxymethylcellulose (CMC), adding the mixture to distilled water, and stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0186] A cathode active material slurry was prepared by mixing 97 wt% of LiCoO2 (LCO), 0.5 wt% of artificial graphite powder as a conductive material, 0.8 wt% of carbon black (Ketjen black), 0.2 wt% of acrylonitrile rubber, and 1.5 wt% of polyvinylidene fluoride (PVdF), adding the mixture to N-methyl-2-pyrrolidone, and stirring for 30 minutes using a mechanical stirrer. The slurry was applied to a thickness of about 60 μm on a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100 ℃ for 0.5 hours, dried once more under vacuum conditions at 120 ℃ for 4 hours, and then rolled to produce a cathode.

[0187] A lithium secondary battery (coin cell) was manufactured using a 14 μm thick polyethylene separator with a ceramic coating on the positive electrode as the separator and the electrolyte prepared in Example 1 as the electrolyte.

[0188] Examples 9~14

[0189] A lithium secondary battery (coin cell) was manufactured in the same manner as in Example 8, except that the electrolyte prepared according to Examples 2 to 7 was used instead of the electrolyte prepared in Example 1.

[0190] Comparative Examples 6~10

[0191] A lithium secondary battery (coin cell) was manufactured in the same manner as in Example 8, except that the electrolyte prepared according to Comparative Examples 1 to 5 was used instead of the electrolyte prepared in Example 1.

[0192] (Manufacturing of lithium secondary batteries (pouch cells))

[0193] Example 15

[0194] A cathode active material slurry was prepared by mixing 98 wt% graphite particles, 1 wt% carboxymethylcellulose (CMC), and 1 wt% styrene-butadiene rubber (SBR) aqueous dispersion binder, adding the mixture to distilled water, and stirring for 60 minutes using a mechanical stirrer. The slurry was applied to a thickness of approximately 60 μm onto a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, dried again under vacuum at 120°C for 4 hours, and then rolled to produce the cathode. The composite density (E / D) of the cathode was 1.55 g / cc, and the loading level (L / L) was 14.36 mg / cm². 2 am.

[0195] Separately, the anode was manufactured by carrying out the following process.

[0196] LiNi 0.6 Co 0.2 Mn 0.2A cathode active material slurry was prepared by mixing 94 wt% O2 (NCM 622), 3.0 wt% Denka black as a conductive material, and 3.0 wt% PVDF as a binder, adding the mixture to an N-methyl-2-pyrrolidone solvent, and stirring for 30 minutes using a mechanical stirrer. The slurry was applied to a thickness of approximately 60 μm onto a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, dried again under vacuum at 120°C for 4 hours, and then roll-pressed to produce the cathode. The composite density (E / D) of the cathode was 3.15 g / cc, and the loading level (L / L) was 27.05 mg / cm². 2 am.

[0197] A lithium secondary battery (pouch cell of about 40 mAh) was manufactured using a polyethylene separator (thickness: 16 μm) as the separator and the electrolyte of Example 1 as the electrolyte.

[0198] Examples 16~21

[0199] A lithium secondary battery (pouch cell) was prepared in the same manner as in Example 15, except that the electrolyte prepared according to Examples 2 to 7 was used instead of the electrolyte prepared in Example 1.

[0200] Comparative Examples 11~15

[0201] A lithium secondary battery (pouch cell) was prepared in the same manner as in Example 15, except that the electrolyte prepared according to Comparative Examples 1 to 5 was used instead of the electrolyte prepared in Example 1.

[0202] Evaluation Example 1: Overcharge characteristics

[0203] For the lithium secondary batteries prepared according to Examples 8-9 and Comparative Examples 6-10, a formation step was performed, and the lithium secondary batteries that underwent the formation step were charged at 25°C with a current of 0.2 C rate until the voltage reached 6 V (vs. Li), and the time to reach was calculated. The results are shown in Table 1 and Figure 2 below.

[0204] division Time (seconds) until 6V voltage is reached Example 8 7970 Example 9 8390 Comparative Example 6 3579 Comparative Example 7 6756 Comparative Example 8 4300 Comparative Example 9 6415 Comparative Example 10 4576

[0205] As shown in Table 1 and Figure 2, it can be confirmed that the lithium secondary battery prepared according to Examples 8 and 9 (using 1 part by weight and 1.5 parts by weight of additive compound 1 and compound 3, respectively, in the electrolyte) has the slowest voltage rise rate compared to the lithium secondary battery prepared according to Comparative Examples 6 to 10 (using 2 parts by weight of additive compound 1, compound 3, or compound 4 alone in the electrolyte, or using 8 parts by weight of compound 1 and 8 parts by weight of compound 3).

[0206] In addition, for each of the two cells (hereinafter referred to as "first cell" and "second cell") of the lithium secondary batteries prepared according to Examples 15 to 21 and Comparative Examples 11, 12, 13, and 15, a formation step was performed at 25°C, and the state of the lithium secondary batteries that had undergone the formation step was observed while charging the lithium secondary batteries at a constant current of 0.2 C rate for 7 hours and 30 minutes until the voltage reached 10 V (vs. Li). The experimental results were indicated as NG (NOT GOOD) and OK, and the maximum temperature (°C) of the first cell and the second cell and the time of short circuit occurrence of the first cell and the second cell were recorded. The results are shown in Table 2 below.

[0207] division Overcharging result 1st Cell / 2nd Cell Maximum Temperature (°C) First cell / Second cell short circuit occurrence time Example 15 OK 41.2 / 77.1 - Example 16 OK 67.2 / 44.9 - Example 17 OK 71.8 / 83.4 - Example 18 OK 73.6 / 32.5 - Example 19 OK 56.3 / 69.2 - Example 20 OK 74.7 / 79.6 - Example 21 OK 73.8 / 52.9 - Comparative Example 11 NG 452 / 428 2 hours 58 minutes / 2 hours 53 minutes Comparative Example 12 NG 286 / 303 5 hours 12 minutes / 5 hours 24 minutes Comparative Example 13 NG 265 / 242 4 hours 56 minutes / 4 hours 37 minutes Comparative Example 15 OK 78.1 / 67.5 -

[0208] As shown in Table 2, it can be confirmed that the lithium secondary batteries prepared according to Examples 15 to 21 (using additive compound 1 and compound 3 in the electrolyte) showed improved safety during the overcharging stage. Compared to the lithium secondary batteries prepared according to Examples 15 to 21 (using additive compound 1 and compound 3 in the electrolyte), the lithium secondary batteries prepared according to Comparative Examples 11, 12, and 13 (no additive in the electrolyte, or using additive compound 1 or compound 3 in the electrolyte) had lower maximum temperatures during the overcharging stage and no short circuits occurred.

[0209] Evaluation Example 2: Low Temperature (-10 ℃) Discharge Capacity Ratio

[0210] For the lithium secondary batteries prepared according to Examples 15–21 and Comparative Examples 12, 13, 15, and 17, a formation step was performed at 25°C. The lithium secondary batteries that underwent the formation step were charged at a constant current of 1.5 C rate at 25°C until the voltage reached 4.48 V (vs. Li), and then cut-off was performed at a current of 0.02 C rate while maintaining 4.48 V in a constant voltage mode. Subsequently, cells were prepared by storing them at 25°C and -10°C for 2 hours, and then discharging them at a constant current of 0.2 C rate until the voltage reached 3.0 V (vs. Li) during discharge at 25°C and -10°C, respectively. The discharge capacity of the prepared cells at each temperature (25°C, -10°C) was measured. The discharge capacity at each measured temperature (25 ℃, -10 ℃) was substituted into Equation 1 below to calculate the low temperature (-10 ℃) discharge capacity ratio (%). The results are shown in Table 3 below.

[0211] [Equation 1]

[0212] Low temperature (-10℃) discharge capacity ratio (%) = [ x 100]

[0213] division Low temperature (-10 ℃) discharge capacity ratio (%) Example 15 85.1 Example 16 86.7 Example 17 87.9 Example 18 83.5 Example 19 85.3 Example 20 82.4 Example 21 83.6 Comparative Example 11 82.1 Comparative Example 12 83.1 Comparative Example 13 84.9 Comparative Example 15 73.2

[0214] As shown in Table 3, the low temperature (-10 ℃) discharge capacity ratio of the lithium secondary batteries prepared by Examples 15 to 21 was similar to or higher than that of the lithium secondary batteries prepared by Comparative Examples 11, 12, 13, and 15 (no additives used in the electrolyte, 2 parts by weight of compound 1 and 2 parts by weight of compound 3 used in the electrolyte, and 8 parts by weight of compound 1 and 8 parts by weight of compound 3 used).

[0215] Among these, the lithium secondary battery prepared according to Example 17 (using 0.3 parts by weight of additive compound 1 and 0.3 parts by weight of compound 3 in the electrolyte) had the highest low temperature (-10 ℃) discharge capacity ratio.

[0216] Comparative Example 15 contained a sulfone compound having one or more phenyl groups and a silane compound having one or more phenyl groups in a 1:1 ratio, but the low-temperature discharge capacity ratio was the lowest at 16 parts by weight, with the sum of the two compounds being 10 parts by weight or more.

[0217] From this, it can be seen that the lithium secondary batteries prepared according to Examples 15 to 21 can improve safety by improving overcharge characteristics without a decrease in low-temperature (-10 ℃) discharge capacity ratio, even when sulfone-based compound additives and silane-based compound additives are used in the electrolyte.

[0218] Evaluation Example 3: High Temperature (60℃) Storage Characteristics - Thickness Increase Rate

[0219] For the lithium secondary batteries prepared according to Examples 15–21 and Comparative Examples 12, 13, 15, and 17, a formation step was performed at 25°C. The lithium secondary batteries that underwent the formation step were then charged at a constant current of 1.5 C rate at 25°C until the voltage reached 4.48 V (vs. Li), and then cut-off was performed at a current of 0.02 C rate while maintaining 4.48 V in constant voltage mode. Subsequently, the lithium secondary batteries were stored at 60°C for 8 weeks. The battery thickness was measured before storage and after 8 weeks of storage. The thickness increase rate was calculated by substituting the measured battery thickness before storage and the battery thickness after 8 weeks of storage into Equation 2 below. The results are shown in Table 4 below.

[0220] [Equation 2]

[0221] Thickness increase rate (%) = [ x 100]

[0222] division High temperature (60℃) storage thickness increase rate (%) Example 15 9.15 Example 16 9.01 Example 17 8.82 Example 18 9.36 Example 19 9.24 Example 20 9.67 Example 21 9.43 Comparative Example 11 9.75 Comparative Example 12 9.51 Comparative Example 13 9.45 Comparative Example 15 14.8

[0223] As shown in Table 4, the high-temperature storage thickness increase rate of the lithium secondary batteries prepared by Examples 15 to 21 was slightly higher or lower compared to the lithium secondary batteries prepared by Comparative Examples 11, 12, 13, and 15 (no additives used in the electrolyte, 2 parts by weight of compound 1 and 2 parts by weight of compound 3 used in the electrolyte, and 8 parts by weight of compound 1 and 8 parts by weight of compound 3 used).

[0224] Among these, the high-temperature storage thickness increase rate of the lithium secondary battery prepared according to Example 17 (using 0.3 parts by weight of additive compound 1 and 0.3 parts by weight of compound 3 in the electrolyte) was the lowest.

[0225] Comparative Example 15 contains a sulfone compound having one or more phenyl groups and a silane compound having one or more phenyl groups in a 1:1 ratio, but the thickness increase rate was high at 16 parts by weight, which is 10 parts by weight or more of the sum of the two compounds.

[0226] From this, it can be seen that the lithium secondary battery prepared according to Examples 15 to 21 can improve safety by improving overcharge characteristics without increasing the rate of increase in storage thickness at high temperature (60°C), even when sulfone-based compound additives and silane-based compound additives are used in the electrolyte.

[0227] Evaluation Example 4: High Temperature (45℃) Charge / Discharge Characteristics

[0228] For the lithium secondary batteries prepared according to Examples 15–21 and Comparative Examples 11, 12, 13, and 15, a formation step was performed at 25°C, and the lithium secondary batteries that had undergone the formation step were charged at 45°C at a current rate of 1.5 C until the voltage reached 4.48 V (vs. Li), and then cut off at a current rate of 0.05 C while maintaining 4.48 V in a constant voltage mode. Subsequently, during discharge, the batteries were discharged at a constant current rate of 0.5 C until the voltage reached 3.0 V (vs. Li). This charge-discharge cycle was repeated 300 times. In all of the above charge / discharge cycles, a 10-minute pause was taken after each charge / discharge cycle. The results are shown in Table 5 below. 300 th The capacity retention rate in a cycle is defined by the following Equation 3.

[0229] [Equation 3]

[0230] Capacity Retention Rate (%)=[ x 100]

[0231] division High temperature (45℃) capacity retention rate (%) Example 15 92.8 Example 16 92.1 Example 17 93.2 Example 18 91.0 Example 19 92.6 Example 20 89.7 Example 21 88.1 Comparative Example 11 87.4 Comparative Example 12 87.9 Comparative Example 13 86.9 Comparative Example 15 83.2

[0232] As shown in Table 5, the high temperature (45 ℃) capacity retention rate of the lithium secondary batteries prepared by Examples 15 to 21 was similar to or higher than that of the lithium secondary batteries prepared by Comparative Examples 11, 12, 13, and 15 (no additives used in the electrolyte, 2 parts by weight of compound 1 and 2 parts by weight of compound 3 used in the electrolyte, and 8 parts by weight of compound 1 and 8 parts by weight of compound 3 used).

[0233] Among these, the lithium secondary battery prepared according to Example 17 (using 0.3 parts by weight of additive compound 1 and 0.3 parts by weight of compound 3 in the electrolyte) had the highest high temperature (45°C) capacity retention rate.

[0234] From this, it can be seen that the lithium secondary battery prepared according to Examples 15 to 21 can improve safety by improving overcharge characteristics without reducing capacity retention rate at high temperature (45°C) even when sulfone-based compound additives and silane-based compound additives are used in the electrolyte. Explanation of the symbols

[0235] 1: Lithium-ion battery 2: Negative electrode 3: Anode 4: Separator 5: Battery case 6: Cap assembly

Claims

Claim 1 An electrolyte for a lithium secondary battery comprising: a lithium salt; a non-aqueous organic solvent; and a sulfone-based compound additive having one or more phenyl groups and a silane-based compound additive having one or more phenyl groups, wherein the content of each of the sulfone-based compound additive and the silane-based compound additive is 0.3 to 7 parts by weight based on 100 parts by weight of the total electrolyte. Claim 2 In claim 1, the electrolyte for a lithium secondary battery, wherein the sulfone-based compound additive is a compound represented by the following chemical formula 1: [Chemical Formula 1] In the formula, R1 and R2 are independently substituted or unsubstituted C1-C10 alkyl groups, substituted or unsubstituted C2-C10 alkenyl groups, substituted or unsubstituted C3-C10 alkynyl groups, substituted or unsubstituted C3-C20 cycloalkyl groups, substituted or unsubstituted C6-C50 aryl groups, substituted or unsubstituted C6-C50 alkylaryl groups, or substituted or unsubstituted C6-C50 heteroaryl groups, wherein at least one of R1 and R2 is a C6 aryl group substituted or unsubstituted with a halogen element. Claim 3 In claim 1, the electrolyte for a lithium secondary battery comprises a compound represented by the following chemical formula 1-1, wherein the sulfone-based compound additive comprises: [Chemical Formula 1-1] Among the food, R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 They are independently hydrogen atoms, halogen atoms, cyano groups, -OR a (R a is a C1-C10 alkyl group or a C6-C20 aryl group), -C(=O)R b , -C(=O)OR b , -OCO(OR b ), -(X) n -NH2(X is a C1-C10 alkyl group or a C1-C10 alkoxy group, and n is an integer from 0 to 10), -C=N(R b ), -SR b , -S(=O)R b , -S(=O)2R b , a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkoxy group, a substituted or unsubstituted C2-C20 alkenyl group, a substituted or unsubstituted C2-C20 alkynyl group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R b is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, wherein R'1, R'2, R'3, R'4, R'5, R'6, R'7, R'8, R'9, R' 10 At least one of them is a fluorine atom. Claim 4 In claim 1, the electrolyte for a lithium secondary battery, wherein the silane-based compound additive is a compound represented by the following chemical formula 2: [Chemical Formula 2] In the expression, R3, R4, R5, and R6 are independent of each other -OR' a (R' a is a C1-C10 alkyl group or a C6-C20 aryl group), C(=O)R' b , -C(=O)OR' b , a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C3-C10 alkynyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C6-C50 aryl group, a substituted or unsubstituted C6-C50 aryloxy group, a substituted or unsubstituted C6-C50 alkylaryl group, or a substituted or unsubstituted C6-C50 heteroaryl group, wherein R' b is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, wherein at least one of R3, R4, R5, and R6 is a substituted or unsubstituted C6 aryl group. Claim 5 In claim 1, the electrolyte for a lithium secondary battery comprises a compound represented by the following chemical formula 2-1, wherein the silane-based compound additive comprises: [Chemical Formula 2-1] During the meal, R' 11 , R' 12 are independently C(=O)R" a , -C(=O)OR" a , a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C3-C10 alkynyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 alkylaryl group, or a substituted or unsubstituted C6-C30 heteroaryl group, where R" a is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group. Claim 6 An electrolyte for a lithium secondary battery according to claim 1, wherein the sulfone-based compound additive comprises one or more of the following compounds 1 and 2, and the silane-based compound additive comprises one or more of the following compounds 3 and 4: Compound 1 Compound 2 Compound 3 Compound 4 Claim 7 An electrolyte for a lithium secondary battery according to claim 1, wherein the weight ratio of the sulfone-based compound additive to the silane-based compound additive is 1:7 to 7:

1. Claim 8 delete Claim 9 A lithium secondary battery comprising: a positive electrode comprising a positive active material; a negative electrode comprising a negative active material; and an electrolyte according to any one of claims 1 to 7 disposed between the positive electrode and the negative electrode.

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