Electrolyte solution for lithium secondary battery, and lithium secondary battery

Abstract

To provide an electrolyte solution for a lithium secondary battery with excellent safety against overcharging and under high temperature, and a lithium secondary battery including the same.SOLUTION: An electrolyte solution for a lithium secondary battery in an embodiment includes a nonaqueous organic solvent, a lithium salt, and an additive. The additive includes a first compound expressed by Chemical Formula 1, and a second compound expressed by Chemical Formula 2. (R1 and R2 independently represent a substituted or non-substituted aryl group with 6 to 30 carbons, and X1 to X3 independently represent a halogen or -O-La-Ra.)SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One embodiment of the present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery containing the same.

Background Art

[0002] In recent years, with the rapid spread of electronic devices using batteries, such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries with high energy density and high capacity has been rapidly increasing. For this reason, research and development for improving the performance of lithium secondary batteries have been actively conducted.

[0003] A lithium secondary battery is a battery including a positive electrode and a negative electrode containing an active material capable of insertion (intercalation) and desorption (deintercalation) of lithium ions, and an electrolyte, and produces electrical energy by oxidation and reduction reactions when lithium ions are inserted / desorbed between the positive electrode and the negative electrode.

[0004] Recently, lithium secondary batteries with high capacity, high energy density, and high safety have been actively studied for use as a driving power source for hybrid vehicles and electric vehicles, or a power storage power source.

[0005] In a lithium secondary battery, the electrolyte plays an important role in transmitting lithium ions, contains an organic solvent and a lithium salt, and exhibits very high ionic conductivity. Such an electrolyte plays an important role in determining the safety and performance of a lithium secondary battery.

[0006] When a lithium secondary battery is in an overcharged state or exposed to high-temperature heat, problems such as the battery rapidly generating heat and gas, leading to cell explosion, have arisen regarding the safety of the battery.

[0007] Therefore, the development of an electrolyte for realizing a battery with excellent safety even under overcharging and high temperatures is required.

Summary of the Invention

Problems to be Solved by the Invention

[0008] One embodiment of the present invention is an electrolyte for a lithium secondary battery that is excellent in overcharge and high-temperature safety.

[0009] Another embodiment of the present invention is a lithium secondary battery including the above electrolyte.

Means for Solving the Problems

[0010] One embodiment of the present invention is an electrolyte for a lithium secondary battery, which includes a non-aqueous organic solvent, a lithium salt, and an additive, and the additive includes a first compound represented by the following Chemical Formula 1 and a second compound represented by the following Chemical Formula 2.

[0011]

Chem.

[0012] In Chemical Formula 1, R 1 and R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and at least one of R 1 and R 2 is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. In Chemical Formula 2, X 1 to X 3 are each independently a halogen or -O-L a -R a and at least one of X 1 to X 3 is -O-L a -R a where L a is a single bond or a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms. R a is a cyano group (-CN), a difluorophosphate group (-OPF 2) is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

[0013] R a When R is an alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkynyl group, or aryl group, at least two carbons may be linked to form a substituted or unsubstituted monocyclic or polycyclic aliphatic heterocycle, or a substituted or unsubstituted monocyclic or polycyclic aromatic heterocycle.

[0014] Another embodiment of the present invention is a lithium secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator located between the positive electrode and the negative electrode, and the above electrolyte.

Advantages of the Invention

[0015] The electrolyte for a lithium secondary battery according to one embodiment of the present invention can realize a battery excellent in overcharge and safety at high temperatures.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example and the present invention is not limited thereby, and the present invention is defined only by the scope of the claims described later.

[0018] Unless otherwise specifically mentioned in this specification, when a part such as a layer, film, region, plate, etc. is “on” another part, this includes not only the case where it is “directly on” another part, but also the case where there are other parts in between.

[0019] Unless otherwise specifically mentioned in this specification, those expressed in the singular can also include the plural. At the same time, unless otherwise specifically mentioned, “A or B” can mean “including A, or including B, or including both A and B”.

[0020] In this specification, “these combinations” can mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0021] Unless otherwise defined herein, the particle size may be the average particle size. Also, the particle size means the average particle size (D50) which is the diameter of the particle with a cumulative volume of 50% in the particle size distribution. The measurement of the average particle size (D50) can be carried out by methods widely known to those skilled in the art. For example, the average particle size (D50) can be measured with a particle size analyzer, or can also be measured using a transmission electron microscope photograph or a scanning electron microscope photograph. In other methods, a measuring device using the dynamic light-scattering method is used, data analysis is performed to count the number of particles for each particle size range, and then the average particle size (D50) can be calculated therefrom. Or it can be measured using the laser diffraction method. When measuring by the laser diffraction method, more specifically, after dispersing the particles to be measured in a dispersion medium, the dispersion liquid is introduced into a commercially available laser diffraction particle size measuring device (for example, MT3000 of Microtrac), irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and then the average particle size (D50) based on the 50% standard of the particle size distribution in the measuring device may be calculated.

[0022] Here, "substitution" means that unless otherwise defined, at least one hydrogen in the substituent or compound is substituted with deuterium, halogen, hydroxy group, amino group, amine group having 1 to 30 carbon atoms, nitro group, silyl group having 1 to 40 carbon atoms, alkyl group having 1 to 30 carbon atoms, alkylsilyl group having 1 to 10 carbon atoms, arylsilyl group having 6 to 30 carbon atoms, cycloalkyl group having 3 to 30 carbon atoms, heterocycloalkyl group having 3 to 30 carbon atoms, aryl group having 6 to 30 carbon atoms, heteroaryl group having 2 to 30 carbon atoms, alkoxy group having 1 to 20 carbon atoms, fluoroalkyl group having 1 to 10 carbon atoms, cyano group, or a combination thereof.

[0023] Specifically, "substituted" can mean that at least one hydrogen in a substituent or a compound is substituted with deuterium, halogen, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, an arylsilyl group having 6 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, a heteroaryl group having 2 to 30 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a cyano group. For example, "substituted" can mean that at least one hydrogen in a substituent or a compound is substituted with deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a cyano group. Or, "substituted" can mean that at least one hydrogen in a substituent or a compound is substituted with deuterium, halogen, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, or a cyano group. As an example, "substituted" can mean that at least one hydrogen in a substituent or a compound is substituted with deuterium, a cyano group, halogen, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a biphenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0024] The electrolyte for a lithium secondary battery according to an embodiment of the present invention includes a non-aqueous organic solvent, a lithium salt, and an additive, and the additive includes a first compound and a second compound. The first compound and the second compound will be described in detail below.

[0025] When the first compound and the second compound are used in combination, both the stability of the battery under overcharge and the safety of the battery at high temperature can be effectively realized.

[0026] 1. First Compound The first compound is a sulfoxide-based compound and plays a role in effectively suppressing the heat generation temperature of the battery under overcharge driving conditions. The first compound is represented by the following Chemical Formula 1.

[0027]

Chemical Formula

[0028] In Chemical Formula 1, R 1 and R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and one or more of R 1 and R 2 is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.

[0029] In one embodiment, Chemical Formula 1 can be represented by the following Chemical Formula 1-1 or Chemical Formula 1-2. As the most specific example, Chemical Formula 1 can be represented by the following Chemical Formula 1-1.

[0030]

Chemical Formula

[0031] In Chemical Formula 1-1, R 1a is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and H a ~H e may each independently be hydrogen, halogen, a hydroxy group, a cyano group, a nitro group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms.

[0032] As a specific example, H a ~H e may each independently be hydrogen, halogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms.

[0033] [ka]

[0034] In chemical formula 1-2, H a ~H j may each independently be a hydrogen atom, a halogen atom, a hydroxy group, a cyano group, a nitro group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms.

[0035] As a specific example, a ~H j may each independently be a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms.

[0036] As an example, the first compound may be one or more compounds selected from the compounds listed in Group 1 below.

[0037] [ka]

[0038] In one embodiment, the first compound may be included in an amount of more than 0.05 wt % or 0.1 wt % or more, and may be included in an amount of less than 6 wt %, or 5 wt % or less, based on the total weight of the electrolyte for a lithium secondary battery.

[0039] As a specific example, the first compound may be included in an amount of more than 0.05 wt % and less than 6 wt % based on the total weight of the electrolyte for a lithium secondary battery, for example, more than 0.05 wt % and less than 5 wt %, 0.1 wt % or more and less than 6 wt %, or 0.1 wt % to 5 wt %.

[0040] When the first compound is contained at 0.05% by weight or less based on the total weight of the electrolyte for a lithium secondary battery, the effect of improving the battery safety during overcharge is low, and when it is contained at 6% by weight or more, there is a problem that the resistance of the battery increases excessively.

[0041] 2. Second compound The second compound plays a role in stabilizing the lithium salt in the electrolyte and suppressing the decomposition of the electrolyte at high temperatures. As a result, the generation of gas inside the battery at high temperatures can be effectively suppressed, and the battery safety and life characteristics at high temperatures can be improved simultaneously.

[0042] The second compound is represented by the following Chemical Formula 2.

[0043]

Chemical formula

[0044] In Chemical Formula 2, X 1 ~X 3 are each independently a halogen or -O-L a -R a and at least one of X 1 ~X 3 is -O-L a -R a and L a is a single bond or a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, and R a is a cyano group (-CN), a difluorophosphate group (-OPF 2 ), a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms. R aWhen it is an alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkynyl group, or aryl group, at least two carbons may be linked to form a substituted or unsubstituted monocyclic or polycyclic aliphatic heterocycle, or a substituted or unsubstituted monocyclic or polycyclic aromatic heterocycle.

[0045] Here, the substituted or unsubstituted monocyclic or polycyclic aliphatic heterocycle may be a heterocycloalkyl group having 1 to 8 carbon atoms containing a heteroatom of N, O, S, P, or Si in the ring, and the substituted or unsubstituted aromatic heterocycle may be a heteroaryl group having 3 to 8 carbon atoms containing a heteroatom of N, O, S, P, or Si in the ring.

[0046] In one embodiment, Chemical Formula 2 can be represented by any one of the following Chemical Formulas 2-1 to 2-3.

[0047]

Chemical Formula

[0048] In Chemical Formula 2-1, m is one of the integers from 1 to 5, and R 10 may be a cyano group (-CN) or a difluorophosphate group (-OPF 2 ).

[0049]

Chemical Formula

[0050] In Chemical Formula 2-2, L a1 ~L a3 are each independently a single bond or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and R a1 ~R a3may each independently be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

[0051] [Chemical formula]

[0052] In Chemical formula 2-3, X 1 is halogen or -O-L a4 -R a4 wherein L a4 is a single bond or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and R a4 is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, and L 1 may be a substituted or unsubstituted alkylene group having 2 to 5 carbon atoms.

[0053] As an example, the second compound may be any one or more selected from the compounds listed in Group 2 below.

[0054] [Chemical formula]

[0055] According to one of the most specific embodiments, the additive contained in the electrolyte for a lithium secondary battery may be a composition containing at least one of the compounds listed in Group 1 as the first compound and at least one of the compounds listed in Group 2 as the second compound.

[0056] As an example, the additive contained in the electrolyte for a lithium secondary battery may be a composition containing Compound 1-a of Group 1 as the first compound and Compound 2-a or Compound 2-d as the second compound.

[0057] In one embodiment, the second compound may be contained in an amount exceeding 0.05% by weight, or 0.1% by weight or more, based on the total weight of the electrolyte for a lithium secondary battery, and may be contained in an amount less than 5% by weight, less than 4% by weight, or 3% by weight or less.

[0058] As a specific example, the second compound may be contained in an amount exceeding 0.05% by weight and less than 4% by weight, or 0.1% by weight to 3% by weight, based on the total weight of the electrolyte for a lithium secondary battery.

[0059] When the second compound is contained in an amount of 0.05% by weight or less based on the total weight of the electrolyte for a lithium secondary battery, the effect of improving the safety of the battery at high temperatures is low, and when it is contained in an amount of 4% by weight or more, there is a problem that the resistance of the battery increases excessively.

[0060] In one embodiment, the first compound and the second compound may be contained in a weight ratio of 0.01:1 to 100:1, for example, a weight ratio of 0.05:1 to 100:1, a weight ratio of 0.01:1 to 40:1, a weight ratio of 0.05:1 to 40:1, a weight ratio of 0.05:1 to 20:1, or a weight ratio of 0.1:1 to 20:1.

[0061] When the weight ratio of the first compound and the second compound satisfies the above numerical range, a battery with excellent safety both in overcharge and at high temperatures can be realized.

[0062] The electrolyte for a lithium secondary battery contains a non-aqueous organic solvent and a lithium salt.

[0063] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0064] The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0065] As the carbonate-based solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used. As the ester-based solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. can be used. As the ether-based solvent, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used. Also, as the ketone-based solvent, cyclohexanone, etc. can be used. As the alcohol-based solvent, ethyl alcohol, isopropyl alcohol, etc. can be used, and as the aprotic solvent, nitriles represented by R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, sulfolane, etc. can be used.

[0066] The non-aqueous organic solvent can be used alone or in admixture of two or more thereof.

[0067] When using a carbonate-based solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed at a volume ratio of 1:1 to 1:9.

[0068] The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery. Representative examples of lithium salts include LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ), 2 , Li(FSO 2 ), 2 N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC 4 F 9 SO 3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), lithium bis(oxalate)borate (LiBOB), and one or more selected therefrom.

[0069] A lithium secondary battery according to another embodiment includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator positioned between the positive electrode and the negative electrode, and the aforementioned electrolytic solution.

[0070] 3. Positive Electrode Active Material As the active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, one or more composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof with lithium can be used.

[0071] The composite oxide may be a lithium transition metal composite oxide. Specific examples include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0072] As an example, a compound represented by any one of the following chemical formulas can be used. Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05), Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2), Li a Ni 1-b-c Mn b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2), Li a Ni b Co c L 1 d G e O 2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1), Li a NiG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a CoG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 1-b G b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 2 G b O 4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 1-g G g PO 4 (0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5), Li (3-f) Fe 2 (PO 4 ) 3 (0 ≤ f ≤ 2), Li a FePO 4 (0.90 ≤ a ≤ 1.8).

[0073] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof, X 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, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, L 1 is Mn, Al, or a combination thereof.

[0074] As an example, the positive electrode active material may be a high-nickel type positive electrode active material in which the content of nickel with respect to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel type positive electrode active material can achieve a high capacity and can be applied to a high-capacity and high-density lithium secondary battery.

[0075] 4. Positive electrode The positive electrode for a lithium secondary battery can include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer contains a positive electrode active material and can further contain a binder and / or a conductive material.

[0076] As an example, the positive electrode can further contain an additive that can serve as a sacrificial positive electrode.

[0077] The content of the positive electrode active material is 90% to 99.5% by weight based on 100% by weight of the positive electrode active material layer, and the contents of the binder and the conductive material can each be 0.5% to 5% by weight based on 100% by weight of the positive electrode active material layer.

[0078] The binder serves to firmly adhere the positive electrode active material particles to each other and also to firmly adhere the positive electrode active material to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0079] The conductive material is used to impart conductivity to the electrode and can be any material as long as it does not cause a chemical change in the battery being formed and is an electron-conductive material. Examples of the conductive material include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc., conductive polymers such as polyphenylene derivatives, or mixtures thereof.

[0080] Al can be used as the current collector, but is not limited thereto.

[0081] 5. Anode active material The anode active material includes substances that can reversibly intercalate / deintercalate lithium ions, lithium metal, alloys of lithium metal, substances that can be doped and undoped with lithium, or transition metal oxides.

[0082] Examples of substances that can reversibly intercalate / deintercalate lithium ions include carbon-based anode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0083] As the alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0084] As the material capable of being doped and undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. As the Sn-based negative electrode active material, Sn, SnO 2 , a Sn-based alloy, or a combination thereof may be used.

[0085] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may have a form in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon is also located between the primary silicon particles. For example, the primary silicon particles are coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0086] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of the core.

[0087] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material.

[0088] 6. Negative Electrode The negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer contains a negative electrode active material and may further contain a binder and / or a conductive material.

[0089] For example, the negative electrode active material layer can contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0% to 5% by weight of the conductive material.

[0090] The binder serves to firmly adhere the negative electrode active material particles to each other and also firmly adhere the negative electrode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0091] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0092] Examples of the aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0093] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity can be further included. As this cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof can be mixed and used. As the alkali metal, Na, K, or Li can be used.

[0094] The dry binder is a polymer substance capable of being fibrillated, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0095] The conductive material is used to impart conductivity to the electrode, and any material can be used as long as it does not cause a chemical change in the battery being constructed and is an electron - conductive material. Specific examples include carbon - based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, metal - based substances in the form of metal powder or metal fiber including copper, nickel, aluminum, silver, etc., conductive polymers such as polyphenylene derivatives, or mixtures thereof.

[0096] As the negative electrode current collector, those selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof can be used.

[0097] 7. Separator Depending on the type of lithium secondary battery, there may be a separator between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and of course, mixed multilayer films such as a two - layer separator of polyethylene / polypropylene, a three - layer separator of polyethylene / polypropylene / polyethylene, and a three - layer separator of polypropylene / polyethylene / polypropylene can be used.

[0098] The separator can include a porous substrate and a coating layer containing an organic substance, an inorganic substance, or a combination thereof located on one or both sides of the porous substrate.

[0099] The porous substrate may be a polymer film formed from any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0100] The organic substance may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0101] The inorganic substance is Al 2 O 3 、SiO 2 、TiO 2 、SnO 2 、CeO 2 、MgO, NiO, CaO, GaO, ZnO, ZrO 2 、Y 2 O 3 、SrTiO 3 、BaTiO 3 、Mg(OH) 2 、boehmite, and inorganic particles selected from combinations thereof, but not limited thereto.

[0102] The organic substance and the inorganic substance may be mixed and present in one coating layer, or may be present in a form in which a coating layer containing the organic substance and a coating layer containing the inorganic substance are laminated.

[0103] 8. Lithium secondary battery Lithium secondary batteries are classified into cylindrical, square, pouch, coin, etc. according to their form. FIGS. 1 to 4 are schematic views showing a lithium secondary battery according to an embodiment. FIG. 1 shows a cylindrical type, FIG. 2 shows a square type, and FIGS. 3 and 4 show a pouch type battery form. Referring to FIGS. 1 to 4, the lithium secondary battery 100 can include an electrode assembly 40 in which a separator 30 is interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is incorporated. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolytic solution (not shown). The lithium secondary battery 100 can include a sealing member 60 that seals the case 50 as shown in FIG. 1. Further, as shown in FIG. 2, the lithium secondary battery 100 can include a positive electrode lead tap 11, a positive electrode terminal 12, a negative electrode lead tap 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 can include electrode taps 70, that is, a positive electrode tap 71 and a negative electrode tap 72, which serve as electrical paths for guiding the current formed by the electrode assembly 40 to the outside.

[0104] The lithium secondary battery according to an embodiment of the present invention can be applied to automobiles, mobile phones, and / or various forms of electrical devices, etc., and the present invention is not limited thereto.

Examples

[0105] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only one example of the present invention, and the present invention is not limited to the following examples.

[0106] Example 1 1.5 M LiPF was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC) were mixed in a volume ratio of 20:10:70 in this order to prepare a basic electrolytic solution. A compound 1-a below was added as a first compound and a compound 2-a below was added as a second compound to the basic electrolytic solution to prepare an electrolytic solution. 6 A lithium salt was dissolved to prepare a basic electrolytic solution. A compound 1-a below was added as a first compound and a compound 2-a below was added as a second compound to the basic electrolytic solution to prepare an electrolytic solution.

[0107] [Chemical]

[0108] At this time, with respect to the entire electrolytic solution, the first compound was contained at 2% by weight and the second compound was contained at 1% by weight.

[0109] As the positive electrode active material, LiNi 0.91 Co 0.07 Al 0.02 O 2 , polyvinylidene fluoride as a binder, and Ketjen black as a conductive material were mixed at a weight ratio of 97:2:1, respectively, and this mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0110] The positive electrode active material slurry was coated on an aluminum foil with a thickness of 14 μm, dried at 110 °C, and then rolled (press) to fabricate a positive electrode.

[0111] As the negative electrode active material, artificial graphite, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener were mixed at a weight ratio of 97:1:2, respectively, and this mixture was dispersed in distilled water to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated on a copper foil current collector with a thickness of 10 μm, dried at 100 °C, and then rolled to fabricate a negative electrode.

[0112] An electrode assembly was fabricated with a separator having a polyethylene-polypropylene multilayer structure with a thickness of 25 μm between the fabricated positive electrode and negative electrode, inserted this into a circular battery case, and then injected the prepared electrolytic solution to fabricate the lithium secondary battery of Example 1.

[0113] Example 2 A lithium secondary battery was fabricated in the same manner as in Example 1, except that compound 2-d below was used as the second compound during the production of the electrolytic solution.

[0114] [Chemical]

[0115] Examples 3 to 6 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the contents of the first compound were 0.05 wt%, 0.1 wt%, 5 wt%, and 6 wt% with respect to the entire electrolyte solution, respectively.

[0116] Examples 7 to 10 A lithium secondary battery was fabricated in the same manner as in Example 2, except that the contents of the first compound were 0.05 wt%, 0.1 wt%, 5 wt%, and 6 wt% with respect to the entire electrolyte solution, respectively.

[0117] Examples 11 to 14 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the contents of the second compound were 0.05 wt%, 0.1 wt%, 3 wt%, and 4 wt% with respect to the entire electrolyte solution, respectively.

[0118] Examples 15 to 18 A lithium secondary battery was fabricated in the same manner as in Example 2, except that the contents of the second compound were 0.05 wt%, 0.1 wt%, 3 wt%, and 4 wt% with respect to the entire electrolyte solution, respectively.

[0119] Comparative Example 1 A lithium secondary battery was fabricated in the same manner as in Example 1, except that neither the first compound nor the second compound was added to the electrolyte solution.

[0120] Comparative Example 2 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the second compound was not added during the production of the electrolyte solution.

[0121] Comparative Example 3 A lithium secondary battery was fabricated in the same manner as in Example 1, except that the first compound was not added during the production of the electrolyte solution.

[0122] Comparative Example 4 A lithium secondary battery was fabricated in the same manner as in Example 2, except that the first compound was not added during the production of the electrolyte solution.

[0123] The types and contents of the first compound and the second compound contained in the electrolyte solutions of Examples 1 to 18 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0124]

Table 1

[0125] Evaluation Example Evaluation Example 1: Overcharge Safety Evaluation An overcharge evaluation was performed on the lithium secondary batteries fabricated in Examples 1 to 18 and Comparative Examples 1 to 4, and the results are shown in Table 2 below and Figure 5.

[0126] A safety protection element was welded to the negative electrode portion of the lithium secondary battery cell, a tap was welded to the positive electrode portion, and a thermocouple was attached to the middle portion of the cell and fixed so that temperature measurement was possible. Thereafter, the cell was charged to 10 V at a charging rate of 2.0C, and the maximum temperature (°C) of the cell during overcharge was measured.

[0127] Referring to Table 2, it can be confirmed that in the cases of Comparative Examples 1, 3, and 4 where the first compound was not added to the electrolyte solution, the maximum temperature of the cell during overcharge was very high.

[0128] Also, referring to Figure 5, in the cases of Examples 1 and 2, the maximum temperature of the cell reached about 70°C before about 10 minutes had elapsed, while in the cases of Comparative Examples 1, 3, and 4, it can be confirmed that the maximum temperature of the cell reached about 88°C or higher after 10 minutes had elapsed.

[0129] Evaluation Example 2: High Temperature Safety Evaluation For the lithium secondary batteries manufactured in Examples 1 to 18 and Comparative Examples 1 to 4, after constant current charging at a charging rate of 0.5C in a 2.8V discharge state and cutoff conditions of 4.2V / 3hr, charging was continued to 0.05C while maintaining a constant voltage of 4.2V. After charging, a high-temperature safety evaluation was performed using cells fully charged at SOC100.

[0130] After placing the lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 4 in a chamber, the temperature was increased from room temperature (25°C) to 139°C, 140°C, 141°C, 142°C, 143°C, and 144°C at a heating rate of 5°C / min, and the changes in the lithium secondary batteries were observed while maintaining the temperature for about 1 hour.

[0131] The experimental results of a total of three runs are shown in Table 2. In Table 2, when thermal runaway did not occur while maintaining the temperature, it is indicated as "P (Pass)", and when rapid thermal runaway occurred, it is indicated as "F (Fail)".

[0132] In addition, the high-temperature safety evaluation results of the lithium secondary batteries prepared in Examples 1 to 2 and Comparative Examples 1 to 4 are shown in FIG. 6. In FIG. 6, the relatively thick line indicates the voltage change over time, and the relatively thin line indicates the temperature change over time.

[0133] Referring to Table 2, it can be confirmed that in the cases of Comparative Examples 1 and 2 where the second compound was not added to the electrolyte, thermal runaway was observed at a temperature of 140°C.

[0134] Referring to FIG. 6, a rapid voltage drop was observed in the lithium secondary batteries of Examples 1 to 2 and Comparative Examples 1 to 4. When the cylindrical battery is suddenly exposed to a high temperature, gas is generated and the internal pressure increases, causing the battery protection circuit (CID) to operate and the voltage to drop rapidly. From the occurrence of the rapid voltage drop, it can be seen that the lithium secondary batteries according to Examples 1 to 2 and Comparative Examples 1 to 4 caused the protection circuit to operate due to gas generation at high temperatures.

[0135] Specifically, in the lithium secondary batteries of Comparative Example 1 and Comparative Example 2, the vent of the battery was completely opened at about 55 minutes, and the voltage reached 0V completely. On the contrary, in the case of the lithium secondary batteries of Examples 1 to 2, which contain all of the first compound and the second compound, and Comparative Examples 3 to 4, the protection circuit (CID) operated, but the vent of the battery was not opened.

[0136] Referring to FIG. 6, it was confirmed that the lithium secondary batteries of Example 1 and Example 2 did not undergo thermal runaway even when exposed to a temperature of 142°C.

[0137] On the contrary, in Comparative Example 1, it was confirmed that a rapid thermal runaway occurred up to about 500°C at about 55 minutes, and in Comparative Example 2, it was confirmed that a rapid thermal runaway occurred above 600°C at about 56 minutes.

[0138] Evaluation Example 3: DC-IR Resistance Evaluation The direct current-internal resistance (DC-IR) of the lithium secondary batteries fabricated in Examples 1 to 18 and Comparative Examples 1 to 4 was measured at a state of charge (SOC, state of charge = 100%), and the results are shown in Table 2 below.

[0139] Referring to Table 2, it can be confirmed that the lithium secondary batteries of Examples 1 to 18 are excellent in overcharge and high-temperature safety as described above, and the direct current-internal resistance is maintained at the same level as that of the comparative examples.

[0140] [Table 2]

[0141] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited thereto, and various modifications can be made and implemented within the scope of the claims, the detailed description of the invention, and the appended drawings, and it is natural that this also belongs to the scope of the present invention.

Explanation of Reference Numerals

[0142] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tap 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead tap 22: Negative electrode terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode tap 71: Positive electrode tap 72: Negative electrode tap

Claims

1. A non-aqueous organic solvent, a lithium salt, and an additive, The additive includes a first compound represented by the following formula 1 and a second compound represented by the following formula 2: 【Chemistry 1】 In the above formula 1, R １ and R ２ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms; R １ and R ２ at least one of the groups is a substituted or unsubstituted aryl group having 6 to 30 carbon atoms; In the above chemical formula 2, X １ ~X ３ Each independently represents a halogen or -OL ａ -R ａ and X １ ~X ３ At least one of -O-L ａ -R ａ and L ａ is a single bond or a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, R ａ is a cyano group (-CN), a difluorophosphate group (-OPF ２ ), a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

2. R ａ wherein, when is the alkyl group, the alkenyl group, the alkynyl group, the cycloalkyl group, the cycloalkenyl group, the cycloalkynyl group, or the aryl group, at least two carbons are linked to form a substituted or unsubstituted monocyclic or polycyclic aliphatic heterocycle, or a substituted or unsubstituted monocyclic or polycyclic aromatic heterocycle.

3. The formula 1 is represented by the following formula 1-1 or 1-2: 【Chemistry 2】 In the above Chemical Formula 1-1, R １ａ is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, H ａ ~H ｅ each independently represents a hydrogen atom, a halogen atom, a hydroxy group, a cyano group, a nitro group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms, 【Chemistry 3】 In the above formula 1-2, H ａ ~H ｊ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms.

4. The electrolyte for a lithium secondary battery according to claim 1 , wherein the first compound is at least one of the compounds listed in Group 1 below: 【Chemistry 4】

5. The formula 2 is represented by any one of the following formulas 2-1 to 2-3: 【Chemistry 5】 In the above Chemical Formula 2-1, m is an integer from 1 to 5; R １０ is a cyano group (-CN) or a difluorophosphate group (-OPF ２ ) and 【Chemistry 6】 In the above Chemical Formula 2-2, L ａ１ ~L ａ３ each independently represents a single bond or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R ａ１ ~R ａ３ each independently represents a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, 【Chemistry 7】 In the above Chemical Formula 2-3, X １ is halogen or -O-L ａ４ -R ａ４ and L ａ４ is a single bond or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R ａ４ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkynyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, L １ The electrolyte for a lithium secondary battery according to claim 1, wherein is a substituted or unsubstituted alkylene group having 2 to 5 carbon atoms.

6. The electrolyte for a lithium secondary battery according to claim 1 , wherein the second compound is at least one of the compounds listed in Group 2 below: 【Chemistry 8】

7. The electrolyte for a lithium secondary battery according to claim 1 , wherein the first compound is contained in an amount of more than 0.05 wt % and less than 6 wt % based on a total weight of the electrolyte for a lithium secondary battery.

8. The electrolyte for a lithium secondary battery according to claim 1 , wherein the second compound is contained in an amount of more than 0.05 wt % and less than 4 wt % based on a total weight of the electrolyte for a lithium secondary battery.

9. 2. The electrolyte for a lithium secondary battery according to claim 1, wherein the first compound and the second compound are contained in a weight ratio of 0.01:1 to 100:

1.

10. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator located between the positive electrode and the negative electrode; and A lithium secondary battery comprising the electrolyte solution for lithium secondary batteries according to any one of claims 1 to 9.

Images