Additive, electrolyte for lithium secondary battery, and lithium secondary battery including the electrolyte

Abstract

An electrolyte additive for a lithium secondary battery, an electrolyte and a lithium secondary battery, the additive comprising a compound represented by the following formula 1: <Formula 1> #imgabs0#

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] Korean Patent Application No. 10-2019-0064727, filed on May 31, 2019 in the Korean Intellectual Property Office and entitled: “Additive, electrolyte for lithium secondary battery, and lithium secondary battery including the same” is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments relate to an additive, an electrolyte for a lithium secondary battery, and a lithium secondary battery including the same. Background Art

[0004] Lithium secondary batteries are used as power sources for driving portable electronic devices such as video cameras, mobile phones, and notebook computers. Rechargeable lithium secondary batteries have an energy density per unit weight that is three times that of lead batteries, nickel-cadmium batteries, nickel-metal batteries, and nickel-zinc batteries, and can be charged at high speed.

[0005] Because lithium secondary batteries operate at high driving voltages, aqueous electrolytes that are highly reactive with lithium cannot be used. Organic electrolytes can be used as electrolytes for lithium secondary batteries. Organic electrolytes can be prepared by dissolving lithium salts in organic solvents. Organic solvents can be stable at high voltages and can have high ionic conductivity, high dielectric constant, and low viscosity. Summary of the invention

[0006] Embodiments may be implemented by providing an electrolyte additive for a lithium secondary battery, the additive including a compound represented by the following Formula 1:

[0007] <Formula 1>

[0008]

[0009] Wherein, in Formula 1, X is O or S, R 1 To R 3 are each independently substituted or unsubstituted C 1 -C 30 Alkyl, substituted or unsubstituted C 2 -C 30 Alkenyl, substituted or unsubstituted C 2 -C 30 Alkynyl or substituted or unsubstituted vinyl, and the substituted C 1 -C 30 Alkyl, substituted C 2 -C 30 Alkenyl, substituted C 2 -C 30 The substituent of the alkynyl or substituted vinyl group is C 1 -C10 Alkyl, C 2 -C 10 Alkenyl, C 2 -C 20 Alkynyl, C 1 -C 10 alkoxy, halogen, cyano, hydroxy or nitro.

[0010] X can be O.

[0011] In formula 1, R 1 To R 3 can each independently be unsubstituted C 1 -C 30 Alkyl or C substituted by methyl, ethyl, propyl, butyl, -F, -Cl, -Br, -I, cyano, hydroxyl or nitro 1 -C 30 alkyl.

[0012] In formula 1, R 1 To R 3 can be each independently unsubstituted C 1 -C 30 alkyl.

[0013] The compound represented by Formula 1 may be the following Compound 1:

[0014] <Compound 1>

[0015]

[0016] The embodiments may be implemented by providing an electrolyte for a lithium secondary battery, the electrolyte including: a lithium salt; a non-aqueous organic solvent; and the additive according to the embodiments.

[0017] The additive may be included in the electrolyte in an amount of about 0.1 wt % to about 10 wt % based on the total weight of the electrolyte.

[0018] The additive may be included in the electrolyte in an amount of about 0.1 wt % to about 5 wt % based on the total weight of the electrolyte.

[0019] The lithium salt may include LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiCF 3 SO 3 、Li(CF 3 SO 2 ) 2 N、LiC 4 F 9SO 3 、LiAlO 2 、LiAlCl 4 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), wherein 2≤x≤20 and 2≤y≤20, LiCl, LiI, lithium bis(oxalato)borate or LiPO 2 F 2 At least one of .

[0020] The non-aqueous organic solvent may include at least one of ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), butylene carbonate, ethyl propionate, ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, γ-valerolactone, γ-butyrolactone or tetrahydrofuran.

[0021] The non-aqueous organic solvent may include a mixed solvent of about 50 vol % to about 95 vol % of the linear carbonate and about 5 vol % to about 50 vol % of the cyclic carbonate.

[0022] The embodiments may be implemented by providing a lithium secondary battery including a cathode, an anode, and an electrolyte according to the embodiments.

[0023] The cathode may include a cathode active material having a layered structure.

[0024] The cathode active material can be represented by Formula 2:

[0025] <Formula 2>

[0026] Li s Ni 1-t M t O 2

[0027] Wherein, in Formula 2, M can be at least one of Co, Mn, Al, Cu, Fe, Mg, Cr, Zn, B or Ga, and satisfies 0.9≤s≤1.2 and 0 <t≤0.99。

[0028] The cathode active material can be represented by Formula 3 or Formula 4:

[0029] <Formula 3>

[0030] Li s' Nit' Co 1-t'-u' Al u' O 2

[0031] <Formula 4>

[0032] Li s' Ni t' Co 1-t'-u' Mn u' O 2

[0033] Among them, in Formula 3 and Formula 4, 0.9 ≤ s' ≤ 1.2, 0.1 < t' ≤ 0.98, 0 < u' ≤ 0.5, and 0 < 1 - t' - u' ≤ 0.5 are satisfied.

[0034] The anode may include an anode active material, and the anode active material includes at least one of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, or a carbon material.

[0035] The anode active material may include at least one of a silicon compound, a carbon compound, a composite of a silicon compound and a carbon compound, or a silicon oxide (SiO a , where 0 < a < 2). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] By describing the exemplary embodiments in detail with reference to the drawings, each feature will be apparent to those skilled in the art, where:

[0037] Figure 1 is a schematic diagram of a lithium secondary battery according to an embodiment;

[0038] Figure 2 is a graph showing the initial EIS of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 under the condition of SOC 50;

[0039] Figure 3 is a graph showing the initial EIS of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 under the condition of SOC 100;

[0040] Figure 4 is a graph showing the change in EIS of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 after high-temperature storage under the condition of SOC 50;

[0041] Figure 5 is a graph showing the change in resistance of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 after high-temperature storage;

[0042] Figure 6 is a graph showing the life characteristics of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 at room temperature;

[0043] Figure 7 A graph showing resistance changes according to cycles of lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 at room temperature (RT) under the condition of SOC 50;

[0044] Figure 8 is a graph showing resistance changes according to cycles of lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 at room temperature (RT) under the condition of SOC 100;

[0045] Fig. 9 is a graph showing the life characteristics of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 at high temperatures; and

[0046] Fig.10 Graphs showing resistance changes of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 according to high temperature cycles under the condition of SOC 50. DETAILED DESCRIPTION

[0047] Example embodiments will now be described more fully below with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary embodiments to those skilled in the art.

[0048] In the accompanying drawings, the dimensions of layers and regions may be exaggerated for clarity. It will also be understood that when a layer or element is referred to as being "on" another layer or element, it can be directly on the other layer or element, or there may be intervening layers or elements. In addition, it will be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there may be one or more intervening layers. The same reference numerals refer to the same elements throughout.

[0049] As used herein, the terms "or" and "and / or" are not exclusive terms, but include any and all combinations of one or more of the associated listed items. Throughout this disclosure, the expression "at least one of a, b, or c" means only a; only b; only c; both a and b; both a and c; both b and c; all of a, b, and c, or variations thereof.

[0050] Hereinafter, an electrolyte additive for a lithium secondary battery, an organic electrolyte including the additive, and a lithium secondary battery using the electrolyte according to an embodiment will be described in more detail.

[0051] As used herein, “C a -C b " " refers to the number of carbon atoms in a particular functional group. That is, a functional group may include from "a" to "b" carbon atoms. Thus, for example, the term "C1 -C 4 "Alkyl" refers to an alkyl group having 1 to 4 carbon atoms, such as CH 3 -、CH 3 CH 2 -、CH 3 CH 2 CH 2 -、(CH 3 ) 2 CH-、CH 3 CH 2 CH 2 CH 2 -、CH 3 CH 2 CH(CH 3 )-or (CH 3 ) 3 C-.

[0052] Depending on the context, certain radical nomenclatures may include either monoradicals or diradicals. For example, when a substituent requires two points of attachment to the rest of the molecule, it is understood that the substituent is a diradical. For example, substituents of an alkyl group that require two points of attachment are considered to include diradicals, such as -CH 2 -、-CH 2 CH 2 -or-CH 2 CH(CH 3 )CH 2 -. Another radical nomenclature clearly indicates that the radical is a diradical such as "alkylene" or "alkenylene".

[0053] As used herein, the term "alkyl" refers to a branched aliphatic hydrocarbon group or an unbranched aliphatic hydrocarbon group. In one embodiment, the alkyl group may be substituted or unsubstituted. Examples of alkyl groups may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl and cycloheptyl. In another embodiment, each of these alkyl groups may be selectively substituted. In another embodiment, the alkyl group may include 1 to 6 carbon atoms. Examples of alkyl groups with 1 to 6 carbon atoms may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, 3-pentyl and hexyl.

[0054] As used herein, the term "alkenyl" is a hydrocarbon group having 2 to 20 carbon atoms (including at least one carbon-carbon double bond), and examples thereof include vinyl, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, cyclopropenyl, cyclopentenyl, cyclohexenyl and cycloheptenyl. In another embodiment, the alkenyl group may be substituted or unsubstituted. In another embodiment, the number of carbon atoms in the alkenyl group may be 2 to 30. As used herein, the term "vinyl" refers to a hydrocarbon group having a "CH 2 =CH-*" (here, * is a bonding site with an adjacent atom).

[0055] As used herein, the term "alkynyl" is a hydrocarbon group having 2 to 20 carbon atoms (including at least one carbon-carbon triple bond), and examples thereof include ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, and 2-butynyl. In another embodiment, the alkynyl group may be substituted or unsubstituted. In another embodiment, the number of carbon atoms in the alkynyl group may be 2 to 30.

[0056] As used herein, a substituent may be derived from an unsubstituted parent group. Here, at least one hydrogen atom may be replaced by another atom or functional group. Unless otherwise specified, when a functional group is considered to be "substituted", it means that the functional group is selected from C 1 -C 20 Alkyl, C 2 -C 20 Alkenyl, C 2 -C 20 Alkynyl, C 1 -C 20 At least one substituent selected from alkoxy, halogen, cyano, hydroxyl and nitro is substituted. When it is described that a functional group is "optionally substituted", the functional group may be substituted with the above substituent.

[0057] The electrolyte additive for a lithium secondary battery according to an embodiment may include, for example, a compound represented by Formula 1 below.

[0058] <Formula 1>

[0059]

[0060] In Formula 1, X may be, for example, O or S.

[0061] R 1 To R 3 may each independently be or include, for example, substituted or unsubstituted C 1 -C 30 Alkyl, substituted or unsubstituted C 2 -C 30alkenyl (e.g., substituted or unsubstituted vinyl) or substituted or unsubstituted C 2 -C 30 Alkynyl.

[0062] In one embodiment, the substituted C 1 -C 30 Alkyl, substituted C 2 -C 30 Alkenyl, substituted C 2 -C 30 The substituents of the alkynyl or substituted vinyl groups may be, for example, C 1 -C 10 Alkyl, C 2 -C 10 Alkenyl, C 2 -C 20 Alkynyl, C 1 -C 10 alkoxy, halogen, cyano, hydroxy or nitro.

[0063] When an additive including the compound of Formula 1 is added to an electrolyte for a lithium secondary battery, lifespan characteristics and high temperature stability of the lithium secondary battery may be improved.

[0064] In one embodiment, in Formula 1, X may be O.

[0065] In one embodiment, in Formula 1, R 1 To R 3 can each independently be, for example, unsubstituted C 1 -C 30 Alkyl, or C substituted by methyl, ethyl, propyl, butyl, -F, -Cl, -Br, -I, cyano, hydroxyl or nitro 1 -C 30 alkyl.

[0066] In one embodiment, in Formula 1, R 1 To R 3 can each independently be, for example, unsubstituted C 1 -C 30 alkyl.

[0067] In one embodiment, the compound of Formula 1 may be, for example, the following Compound 1.

[0068] <Compound 1>

[0069]

[0070] Without being bound by theory, the compound may be added to the electrolyte to help improve the performance of the lithium secondary battery and is described in more detail below.

[0071] The compound represented by Formula 1 above may include a sulfone group (—SO 2 R) and alkoxyamide groups, which have excellent electrical reactivity and chemical reactivity at their ends, and can inhibit the decomposition of organic solvents such as ethylene carbonate (EC) to help reduce gas generation, thereby reducing the rate of increase in resistance.

[0072] LiPF 6 Can be used as a lithium salt included in electrolytes. LiPF 6 The thermal stability may be insufficient and even be easily hydrolyzed by water. When an additive including a compound represented by Formula 1 is added to an electrolyte, water (H 2 O) Molecules and LiPF 6 The PF produced by the decomposition of 5 - The ion can be sulfone (-SO 2 R) and alkoxyamide capture, thereby inhibiting the LiPF 6 As a result, the generation of gas in the lithium secondary battery can be suppressed to help improve the cycle life characteristics. In addition, due to the suppression or reduction of gas generation, the swelling phenomenon of the battery can be prevented or reduced.

[0073] In addition, the sulfone group (-SO 2 R) can be eluted from the metal substrate by reacting with metal ions (e.g., copper ions (Cu 2+ The complexation reaction of )) forms a stable film on the surface of the metal substrate. Due to the formation of this film, the additional elution of the metal from the metal substrate can be suppressed, and the over-discharge of the battery during the storage of the battery can be suppressed to help improve the battery characteristics.

[0074] During the initial charging process of a lithium secondary battery, a decomposition reaction of the electrolyte may occur on the surface of the anode. The reason may be that the reduction potential of the electrolyte may be relatively higher than the reduction potential of lithium. The decomposition reaction of the electrolyte may form a solid electrolyte interface (SEI) on the surface of the electrode to help suppress the movement of electrons required for the reaction between the anode and the electrolyte, thereby preventing additional decomposition of the electrolyte. Therefore, the performance of the battery may depend on the characteristics of the film formed on the surface of the anode. With this in mind, a harder SEI layer may be formed and may have excellent electrical properties by introducing an electrolyte additive, which decomposes before the electrolyte during the charging reaction.

[0075] According to one embodiment, the electrolyte additive for a lithium secondary battery represented by Formula 1 may include a sulfone group (—SO 2R), and the additives can be decomposed before the electrolyte during the charging reaction, thereby forming a hard SEI film on the surface of the anode with excellent electrical characteristics.

[0076] In one embodiment, the electrolyte additive for a lithium secondary battery represented by Formula 1 according to an embodiment may include an alkoxyamide group at the other end thereof, and may form an SEI film having a high alkoxyamide group concentration, thereby forming a chemically stable film having high polarity. In one embodiment, the resistance at the interface between the electrolyte and the anode may be reduced to help improve the conductivity of lithium ions, and there is an effect of increasing the low temperature discharge voltage.

[0077] In one embodiment, the sulfone group (—SO 2 R) may have excellent electrochemical reactivity, a transition metal oxide exposed to the surface of the cathode active material and a donor-acceptor bond may be formed, and a protective layer may be formed in the form of a composite.

[0078] An electrolyte for a lithium secondary battery according to an embodiment may include, for example, a lithium salt; a nonaqueous organic solvent; and an additive.

[0079] In one embodiment, the additive may be included in the electrolyte in an amount of about 0.1 wt % to about 10 wt % based on the total weight of the electrolyte. In one embodiment, its content may be appropriately selected within a range that does not deteriorate battery characteristics. In one embodiment, the additive may be included in the electrolyte in an amount of about 0.1 wt % to about 5 wt % based on the total weight of the electrolyte.

[0080] Maintaining the amount of additives to about 10 wt % or less, based on the total weight of the electrolyte, can help ensure that battery life is not degraded.

[0081] In one embodiment, the lithium salt may include, for example, LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiCF 3 SO 3 、Li(CF 3 SO 2 ) 2 N、LiC 4 F 9 SO 3 、LiAlO 2 、LiAlCl 4 、LiN(C x F 2x+1 SO 2 )(Cy F 2y+1 SO 2 )(2≤x≤20, 2≤y≤20), LiCl, LiI, lithium bis(oxalato)borate (LiBOB) or LiPO 2 F 2 In one embodiment, the lithium salt may include another suitable lithium salt.

[0082] In one embodiment, the concentration of the lithium salt in the electrolyte may be, for example, about 0.01 M to about 2.0 M. An appropriate concentration may be used as required. Within the above concentration range, further improved battery characteristics may be obtained.

[0083] In one embodiment, the non-aqueous organic solvent may include, for example, ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), butylene carbonate, ethyl propionate, ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, gamma-valerolactone, gamma-butyrolactone or at least one of tetrahydrofuran. In one embodiment, other suitable organic solvents may be used.

[0084] In one embodiment, the nonaqueous organic solvent may include, for example, a mixed solvent of about 50 vol % to about 95 vol % of a linear carbonate and about 5 vol % to about 50 vol % of a cyclic carbonate.

[0085] The electrolyte can be in a liquid or gel state. The electrolyte can be prepared by adding lithium salts and additives to an organic solvent.

[0086] A lithium secondary battery according to another embodiment may include, for example, a cathode; an anode; and an electrolyte. In one embodiment, the lithium battery may include a lithium secondary battery such as a lithium ion battery, a lithium ion polymer battery, a lithium sulfur battery, etc., and a lithium primary battery.

[0087] In one embodiment, the operating voltage of the lithium secondary battery may be about 4.2 V or higher, for example, about 4.3 V or higher, for example, about 4.45 V or higher.

[0088] In one embodiment, a lithium secondary battery may be manufactured by the following method.

[0089] First, the cathode can be prepared.

[0090] In one embodiment, for example, a cathode active material composition can be prepared, wherein a cathode active material, a conductive material, a binder and a solvent are mixed. A cathode plate can be prepared by coating a cathode current collector with the cathode active material composition. In one embodiment, a cathode plate can be prepared by casting the cathode active material composition onto a separate support, separating the film from the support, and then laminating the separated film onto a metal current collector.

[0091] The cathode active material as a lithium-containing metal oxide may include a suitable active material. As the lithium-containing metal oxide, for example, a composite oxide of two or more lithium and a metal selected from cobalt, manganese, nickel and a combination thereof may be used. In one embodiment, as the lithium-containing metal oxide, a compound represented by any one of the following formulas may be used: Li a A 1-b B 1 b D 1 2 (where 0.90≤a≤1.8 and 0≤b≤0.5 are satisfied); Li a E 1-b B 1 b O 2-c D 1 c (wherein 0.90≤a≤1.8, 0≤b≤0.5 and 0≤c≤0.05 are satisfied); LiE 2-b B 1 b O 4-c D 1 c (where 0≤b≤0.5 and 0≤c≤0.05 are satisfied); Li a Ni 1-b-c Co b B 1 c D 1 α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α≤2 are satisfied); Li a Ni 1-b- c Co b B 1 c O 2-α F 1 α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2) are satisfied; Li a Ni 1-b- c Co b B1 c O 2-α F 1 2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2) are satisfied; Li a Ni 1-b- c Mn b B 1 c D 1 α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α≤2 are satisfied); Li a Ni 1-b-c Mn b B 1 c O 2-α F 1 α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2) are satisfied; Li a Ni 1-b-c Mn b B 1 c O 2-α F 1 2 (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05 and 0<α<2) are satisfied; Li a Ni b E c G d O 2 (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5 and 0.001≤d≤0.1 are satisfied); Li a Ni b Co c Mn d G e O 2 (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5 and 0.001≤e≤0.1 are satisfied); Li a NeG b O 2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1 are satisfied); Li a CoG b O 2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1 are satisfied); Li a MnGb O 2 (where 0.90≤a≤1.8 and 0.001≤b≤0.1 are satisfied); Li a Mn 2 G b O 4 (where 0.90≤a≤1.8 and 0.001≤b≤0.1 are satisfied); QO 2 ;QS 2 ;LiQS 2 ; V 2 O 5 ;LiV 2 O 5 ;LiI 1 O 2 ;LiNiVO 4 ;Li (3-f) J 2 (PO 4 ) 3 (0≤f≤2);Li (3-f) Fe 2 (PO 4 ) 3 (0≤f≤2) and LiFePO 4 .

[0092] In the above formula, A can be, for example, Ni, Co, Mn or a combination thereof; B 1 It may be, for example, Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D 1 It can be, for example, O, F, S, P or a combination thereof; E can be Co, Mn or a combination thereof; F 1 It can be, for example, F, S, P or a combination thereof; G can be, for example, Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q can be, for example, Ti, Mo, Mn or a combination thereof; I 1 It may be, for example, Cr, V, Fe, Sc, Y, or a combination thereof; and J may be, for example, V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0093] In one embodiment, the lithium-containing metal oxide may be LiCoO 2 、LiMn g O 2g (g = 1 or 2), LiNi 1- g Mn g O 2g (0 <g<1)、LiNi 1-g-k Co g Mn k O2 (0 ≤ g ≤ 0.5, 0 ≤ k ≤ 0.5) or LiFePO 4 .

[0094] In one embodiment, the cathode may include a cathode active material having a layered structure.

[0095] In one embodiment, the cathode active material may be represented by the following Formula 2.

[0096] <Formula 2>

[0097] Li s Ni 1-t M t O 2

[0098] In Formula 2,

[0099] M may be, for example, at least one of Co, Mn, Al, Cu, Fe, Mg, Cr, Zn, B, and Ga, and

[0100] may satisfy 0.9 ≤ s ≤ 1.2 and 0 < t ≤ 0.99.

[0101] In one embodiment, the cathode active material may be represented by, for example, Formula 3 or Formula 4.

[0102] <Formula 3>

[0103] Li s' Ni t' Co 1-t'-u' Al u' O 2

[0104] <Formula 4>

[0105] Li s' Ni t' Co 1-t'-u' Mn u' O 2

[0106] In Formulas 3 and 4, 0.9 ≤ s' ≤ 1.2, 0.1 < t' ≤ 0.98, 0 < u' ≤ 0.5, and 0 < 1 - t' - u' ≤ 0.5 may be satisfied.

[0107] In one embodiment, the cathode active material may be, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 、LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.6 Co 0.2 Al 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 or LiNi 0.8 Co 0.1 Al 0.1 O 2 At least one of .

[0108] In one embodiment, the compound having a coating on the surface of the compound can be used, or a mixture of the above-mentioned compound and the compound having a coating can be used. The coating can include a coating element compound of an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting the coating can be amorphous or crystalline. As the coating element contained in the coating, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof can be used. In the process of forming the coating, an appropriate coating method can be used, as long as the compound can be coated with these elements by a method (e.g., spraying, dipping, etc.) that does not adversely affect the physical properties of the cathode active material.

[0109] In one embodiment, the conductive material may include, for example, carbon black or graphite particles, or other suitable conductive materials.

[0110] In one embodiment, the binder may include, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, and styrene-butadiene rubber-based polymers, or other suitable binders.

[0111] In one embodiment, the solvent may include, for example, N-methylpyrrolidone, acetone, water, etc., or other suitable solvents.

[0112] The content of the cathode active material, the content of the conductive material, the content of the binder and the content of the solvent may be at suitable levels for lithium secondary batteries. In one embodiment, at least one of the conductive material, the binder and the solvent may be omitted depending on the use and configuration of the lithium secondary battery.

[0113] Next, the anode can be prepared.

[0114] In one embodiment, an anode active material composition can be prepared, wherein an anode active material, a conductive material, a binder and a solvent are mixed. Anode plate can be prepared by directly coating an anode current collector with the anode active material composition and drying the anode active material composition. In one embodiment, the anode plate can be prepared by casting the anode active material composition onto a separate support, separating the film from the support, and then laminating the separated film onto a metal current collector.

[0115] In one embodiment, a suitable anode active material may be used. In one embodiment, the anode active material may include, for example, lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, or a carbon material.

[0116] In one embodiment, the anode active material may include, for example, a silicon compound, a carbon compound, or a composite of a silicon compound and a carbon compound. The silicon compound may be, for example, silicon particles, silicon alloy particles, etc. In one embodiment, the silicon compound may be, for example, silicon oxide (SiO a , 0 <a<2)。

[0117] The size of the silicon compound is less than 200 nm, for example, about 10 nm to about 150 nm. The term "size" may refer to an average particle diameter when the silicon compound is spherical, and may refer to a major axis length when the silicon particles are non-spherical.

[0118] When the size of the silicon compound is within the above range, life characteristics may be excellent. Therefore, when the electrolyte according to the embodiment is used, the life of the lithium secondary battery is further improved.

[0119] Carbon material can include, for example, crystalline carbon, amorphous carbon or its mixture.Crystalline carbon can be graphite, such as natural graphite or artificial graphite in amorphous, plate-like, flaky, spherical or fibrous form.Amorphous carbon can be soft carbon (carbon fired at low temperature), hard carbon, mesophase pitch carbide or fired coke.

[0120] The composite of the silicon compound and the carbon compound may be a composite having a structure in which silicon nanoparticles are arranged on the carbon compound, a composite having a structure in which silicon nanoparticles are arranged on the surface of the carbon compound and inside the carbon compound, or a composite having a structure in which silicon nanoparticles are coated with the carbon compound and included in the carbon compound. In the composite of the silicon compound and the carbon compound, the carbon compound may be graphite, graphene, graphene oxide, or a combination thereof.

[0121] The composite of a silicon compound and a carbon compound can be an active material obtained by dispersing silicon nanoparticles with an average particle size of about 200 nm or less on carbon compound particles and carbon-coating the dispersed silicon nanoparticles, or can be an active material in which silicon (Si) particles are present on and in graphite. The average particle size of the secondary particles of the composite of the silicon compound and the carbon compound can be from about 5 μm to about 20 μm. The average particle size of the silicon nanoparticles can be about 5 nm or greater, for example, about 10 nm or greater, about 20 nm or greater, about 50 nm or greater, or about 70 nm or greater. The average particle size of the silicon nanoparticles can be, for example, about 200 nm or less, about 150 nm or less, about 100 nm or less, about 50 nm or less, about 20 nm or less, or about 10 nm or less. In one embodiment, the average particle size of the silicon nanoparticles can be about 100 nm to about 150 nm.

[0122] The average particle size of the secondary particles of the composite of the silicon compound and the carbon compound can be from about 5 μm to about 18 μm, for example, about 7 μm to about 15 μm or about 10 μm to about 13 μm.

[0123] Other examples of the composite of the silicon compound and the carbon compound can include, for example, a porous silicon composite cluster structure and a porous silicon composite cluster structure. Korean Patent Publication Nos. 10-2018-0031585 and 10-2018-0056395 are incorporated herein by reference.

[0124] The composite of the silicon compound and the carbon compound according to an embodiment can be a porous silicon composite cluster that includes a porous core containing porous silicon composite secondary particles and a shell provided on the core and including a second graphene. The porous silicon composite secondary particles can include an aggregate of two or more silicon composite primary particles. The silicon composite primary particles can be a porous silicon composite cluster that includes silicon, silicon oxide (SiO a )(0 < a < 2) on the silicon, and a first graphene on the silicon oxide. The composite of the silicon compound and the carbon compound according to another embodiment can include: a porous silicon composite cluster that includes porous silicon composite secondary particles and a second carbon sheet on at least one surface of the porous silicon composite secondary particles; and a carbon coating film including amorphous carbon and provided on the porous silicon composite cluster. The porous silicon composite secondary particles can include an aggregate of two or more silicon composite primary particles. The silicon composite primary particles can include silicon, silicon oxide (SiO a )(0 < a < 2) on at least one surface of the silicon, and a first carbon sheet on at least one surface of the silicon oxide. The silicon oxide can be a porous silicon composite cluster structure in the form of a film, a matrix, or a combination thereof.

[0125] Each of the first carbon sheet and the second carbon sheet may exist in the form of a film, particles, a matrix, or a combination thereof. Each of the first carbon sheet and the second carbon sheet may be graphene, graphite, carbon fiber, graphene oxide, etc.

[0126] The composite of the above-mentioned silicon compound and carbon compound may be implemented in the following forms.

[0127] In one embodiment, the composite of the silicon compound and the carbon compound may be implemented in the form of an active material obtained by dispersing silicon (Si) particles with an average particle size of about 50 nm to about 150 nm on graphite particles and coating the graphite particles with a carbon-based material.

[0128] In one embodiment, the composite of the silicon compound and the carbon compound may be implemented by forming a plurality of primary particles into secondary particles, and may be further implemented by coating the secondary particles with a carbon-based material, wherein silicon (Si) particles with an average particle size of about 50 nm to about 150 nm are located on graphite in the primary particles.

[0129] In one embodiment, the composite of the silicon compound and the carbon compound may be implemented in the form of a composite of silicon (Si) particles and amorphous carbon without graphite.

[0130] The composite of the silicon compound and the carbon compound may include, for example, porous silicon composite clusters.

[0131] In one embodiment, the metal that can form an alloy with lithium may be Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y' alloy (Y' is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, or a combination thereof, but not Si), or Sn-Y' alloy (Y' is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, or a combination thereof, but not Sn). The element Y' may be 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, or Te.

[0132] In one embodiment, the transition metal oxide may be lithium titanate oxide, vanadium oxide, lithium vanadium oxide, etc.

[0133] In one embodiment, the non-transition metal oxide may be SnO 2 、SiO x (0 < x < 2), etc.

[0134] The conductive material, binder, and solvent in the anode active material composition may be the same as those in the cathode active material composition.

[0135] The content of the anode active material, the content of the conductive material, the content of the binder and the content of the solvent may be at appropriate levels for lithium secondary batteries. Depending on the use and configuration of the lithium secondary battery, at least one of the conductive material, the binder and the solvent may be omitted.

[0136] Next, a separator to be interposed between the anode and the cathode may be prepared.

[0137] As a separator, a suitable separator for lithium batteries can be used. A separator having low resistance to the movement of ions in the electrolyte and superior in terms of electrolyte wettability can be used. In one embodiment, the separator may include, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) or a combination thereof, and may be manufactured in the form of a non-woven or woven fabric. In one embodiment, a windable separator including polyethylene, polypropylene, etc. may be used in a lithium ion battery, and a separator having good electrolyte impregnation ability may be used in a lithium ion polymer battery. For example, the separator may be manufactured by the following method.

[0138] The polymer resin, filler and solvent may be mixed to prepare a separator composition. The separator composition is directly coated on the electrode and dried to form a separator. In one embodiment, the separator composition is cast on a support and dried, the separation membrane is separated from the support, and then the separation membrane can be laminated on the electrode to form a separator.

[0139] The polymer resin used in the manufacture of the separator may include suitable materials for electrode plate binders. In one embodiment, as the polymer resin, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or a mixture thereof may be used.

[0140] Next, the above-mentioned electrolyte for a lithium secondary battery may be prepared.

[0141] like Figure 1 As shown, the lithium secondary battery 1 includes a cathode 3, an anode 2 and a separator 4. The anode 2, the cathode 3 and the separator 4 can be wound (or folded) and contained in a battery case 5. Then, the electrolyte is injected into the battery case 5, and the battery case 5 is sealed with a cap assembly 6 to complete the manufacture of the lithium secondary battery 1. The battery case 5 can have, for example, a cylindrical, rectangular or thin film shape. In one embodiment, the lithium secondary battery 1 can be a large-sized thin film battery. The lithium secondary battery 1 can be a lithium ion battery.

[0142] The separator 4 may be located between the anode 2 and the cathode 3 to form a battery structure. The battery structure may be laminated into a bi-cell structure and then impregnated with an electrolyte, and the resulting product may be contained in a bag and sealed to complete a lithium ion polymer battery.

[0143] In one embodiment, a plurality of battery structures are laminated to form a battery pack, and the battery pack can be used in all devices requiring high capacity and high power. In one embodiment, the battery pack can be used in notebooks, smart phones, electric vehicles, etc.

[0144] In one embodiment, the lithium secondary battery can have excellent life characteristics and high rate characteristics, and it can be used in electric vehicles (EV). In one embodiment, the lithium secondary battery can be used in hybrid vehicles, such as plug-in hybrid vehicles. In one embodiment, the lithium secondary battery can be used in fields requiring a large amount of power storage. In one embodiment, the lithium secondary battery can be used in electric bicycles, power tools, etc.

[0145] The following examples and comparative examples are provided to highlight the features of one or more embodiments, but it should be understood that the examples should not be interpreted as limiting the scope of the embodiments, and the comparative examples should not be interpreted as being outside the scope of the embodiments. In addition, it will be understood that the embodiments are not limited to the specific details described in the examples and comparative examples.

[0146] (Preparation of Electrolyte)

[0147] Preparation Example 1

[0148] LiPF 6 An amount sufficient to prepare a 1 M solution was added to a mixed solvent (in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:7) to prepare a mixed solution.

[0149] 1.0 wt % of the following Compound 1 was added to the mixed solution to prepare an electrolyte for a lithium secondary battery.

[0150] <Compound 1>

[0151]

[0152] Comparative Preparation Example 1

[0153] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that Compound 1 was not added, and vinylene carbonate (VC) was added in an amount of 2.0 wt % based on the mixed solution.

[0154] Comparative Preparation Example 2

[0155] An electrolyte for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that the following Compound A was added in an amount of 1.0 wt % instead of the above Compound 1, and vinylene carbonate (VC) was added in an amount of 2.0 wt % based on the mixed solution.

[0156] <Compound A>

[0157]

[0158] (Manufacturing of lithium secondary batteries)

[0159] Example 1

[0160] 87wt% of graphite, 11wt% of a composite of a silicon compound and a carbon compound, 1wt% of a styrene-butadiene rubber (SBR) binder (ZEON) and 1.0wt% of a carboxymethyl cellulose binder (CMC, manufactured by NIPPON A&L) were mixed, introduced into distilled water, and then stirred for 60 minutes using a mechanical stirrer to prepare an anode active material slurry. The slurry was coated on a copper current collector having a thickness of 10 μm to about 60 μm using a scraper, dried for 0.5 hour at 100°C using a hot air dryer, further dried for 4 hours at 120°C under vacuum, and then rolled to prepare an anode plate.

[0161] (Preparation of cathode)

[0162] 97wt% LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM), 0.5% artificial graphite (SFG6, Timcal) powder, 0.8% carbon black (Ketjen black, ECP), 0.2% modified acrylonitrile rubber (BM-720H, manufactured by Zeon), 1.2% polyvinylidene fluoride (PVDF, S6020, Solvay) and 0.3wt% polyvinylidene fluoride (PVDF, S5130, Solvay) were mixed, introduced into N-methyl-2-pyrrolidone solvent, and then stirred for 30 minutes using a mechanical stirrer to prepare a cathode active material slurry. The slurry was coated on an aluminum current collector having a thickness of 20 μm to about 60 μm using a scraper, dried at 100 ° C for 0.5 hours using a hot air dryer, further dried at 120 ° C under vacuum for 4 hours, and then rolled to prepare a cathode plate.

[0163] A lithium secondary battery was manufactured by using a polyethylene separator having a thickness of 14 μm and coated with ceramic on the anode side, and using the electrolyte prepared in Preparation Example 1.

[0164] Comparative Example 1

[0165] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared in Comparative Preparation Example 1 was used instead of the electrolyte prepared in Preparation Example 1.

[0166] Comparative Example 2

[0167] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte prepared in Comparative Preparation Example 2 was used instead of the electrolyte prepared in Preparation Example 1.

[0168] Evaluation Example 1: Initial Resistance Test

[0169] The electrochemical impedance spectroscopy (EIS) of the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 according to the state of charge (SOC) was measured to measure the degree of resistance formed at the interface of the electrode, and the results are shown in Figure 2 and Figure 3 middle.

[0170] Figure 2 is a graph showing the initial EIS under the condition of SOC 50, and Figure 3 is a graph showing the initial EIS under the condition of SOC 100.

[0171] See also Figure 2 and Figure 3 It can be seen that, compared with the lithium secondary batteries of Comparative Examples 1 and 2, the lithium secondary battery of Example 1 is improved in initial resistance.

[0172] Evaluation Example 2: High-temperature storage characteristics test

[0173] 1) After the lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 were stored at 60°C for four weeks, their EIS according to SOC was measured to measure the degree of resistance formed at the interface of the electrodes, and the results were shown in Figure 4 middle.

[0174] See also Figure 4 , it can be seen that the resistance increase suppression characteristics are improved during high-temperature storage compared with the degree of resistance under the condition of SOC 50.

[0175] 2) The lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 were stored at 60°C for four weeks, and the resistance increase rate of the lithium secondary batteries for four weeks was measured, and the results were shown in Figure 5 middle.

[0176] In this case, the resistance value is a 10-second DC-IR (Direct Current Internal Resistance) value obtained by discharging the lithium secondary battery at a rate of 1 C for 10 seconds under the condition of SOC 50 and then dividing the voltage change by the current.

[0177] See also Figure 5 It can be seen that, compared with the lithium secondary batteries of Comparative Examples 1 and 2, the longer the storage time at high temperature of the lithium secondary battery of Example 1 is, the better the resistance increase suppression characteristic is.

[0178] Evaluation Example 3: Cyclic Characteristics Test

[0179] 1) Each lithium secondary battery of Example 1 and Comparative Examples 1 and 2 was charged at a constant current at a current rate of 0.2C at 25°C until the voltage reached 4.3V, and then the current was cut off at a current rate of 0.05C while maintaining the voltage at 4.3V in a constant voltage mode. Subsequently, each lithium secondary battery was charged at a constant current at a current rate of 0.2C until the voltage reached 2.8V during discharge. Thus, the charge-discharge capacity of each lithium secondary battery was determined.

[0180] Subsequently, each lithium secondary battery is charged with a constant current at a current of 1C rate until the voltage reaches 4.3V, then the current is cut off at a current of 0.05C rate, while maintaining a voltage of 4.3V in a constant voltage mode. Subsequently, each lithium secondary battery is charged with a constant current at a current of 1C rate until the voltage reaches 2.8V (formation step, first cycle). Repeat this charge-discharge cycle for 300 times. In addition, the rated capacity is measured for every 100 cycles.

[0181] In all charge-discharge cycles, a rest time of 10 minutes was set after one charge-discharge cycle.

[0182] The results of the charge-discharge experiments are shown in Figure 6 middle.

[0183] See also Figure 6 It can be seen that the cycle characteristics of Example 1 are better than those of Comparative Examples 1 and 2.

[0184] 2) In 1) above, the EIS of each lithium secondary battery of Example 1 and Comparative Examples 1 and 2 after 300 cycles was measured according to SOC, and the results are shown in Figure 7 and Figure 8 middle.

[0185] See also Figure 7 and Figure 8 It can be seen that, compared with the lifespan and resistance characteristics of the lithium secondary batteries of Comparative Example 2 and Comparative Example 1 after 300 cycles, the lifespan and resistance characteristics of the lithium secondary battery of Example 1 after 300 cycles are improved.

[0186] Evaluation Example 4: High temperature (45°C) cycle characteristics test

[0187] 1) Each lithium secondary battery of Example 1 and Comparative Examples 1 and 2 was charged at a constant current at a current rate of 0.5C at 25°C until the voltage reached 4.3V, and then the current was cut off at a current rate of 0.05C while maintaining the voltage at 4.3V in a constant voltage mode. Subsequently, each lithium secondary battery was charged at a constant current at a current rate of 1C until the voltage reached 2.8V (formation step, first cycle). The charge-discharge cycle was repeated once more.

[0188] Subsequently, this charge-discharge cycle was repeated 200 times at 45° C. In addition, the rated capacity was measured for every 100 cycles.

[0189] In all charge-discharge cycles, a rest time of 10 minutes was set after one charge-discharge cycle.

[0190] The results of the charge-discharge experiments are shown in Fig. 9 middle.

[0191] See also Fig. 9 It can be seen that the high temperature cycle characteristics of Example 1 are better than those of Comparative Examples 1 and 2.

[0192] 2) In 1) above, the EIS of each lithium secondary battery of Example 1 and Comparative Examples 1 and 2 after 200 cycles was measured according to SOC, and the results are shown in Fig.10 middle.

[0193] See also Fig.10 It can be seen that, compared with the lifespan and resistance characteristics of the lithium secondary batteries of Comparative Example 2 and Comparative Example 1 after 200 cycles, the lifespan and resistance characteristics of the lithium secondary battery of Example 1 after 200 cycles are improved.

[0194] By way of summary and review, when an organic electrolyte including a lithium salt is used as an electrolyte for a lithium secondary battery, lifespan characteristics and high temperature stability of the lithium secondary battery may be deteriorated by a side reaction between an anode / cathode and the electrolyte.

[0195] The electrolyte for a lithium secondary battery according to an embodiment may be able to provide a lithium secondary battery having improved lifespan characteristics and high temperature stability.

[0196] According to one or more embodiments, when an electrolyte for a lithium secondary battery is an electrolyte including an additive including a sulfone compound having a structure described herein, lifespan characteristics and high temperature characteristics of the lithium secondary battery may be improved.

[0197] One or more embodiments may provide an electrolyte additive for a lithium secondary battery.

[0198] One or more embodiments may provide an electrolyte for a lithium secondary battery, the electrolyte including an additive.

[0199] One or more embodiments may provide a lithium secondary battery including the above-mentioned electrolyte.

[0200] Example embodiments have been disclosed herein, and although specific terms are employed, they are used and interpreted in a general and descriptive sense only and not for purposes of limitation. In some cases, as will be apparent to one of ordinary skill in the art when filing this application, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise specifically stated. Therefore, it should be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

1. An electrolyte for a lithium secondary battery, the electrolyte comprising: a lithium salt; a non-aqueous organic solvent; and an additive, wherein the additive comprises a compound represented by the following Formula 1: <Formula 1> wherein, in Formula 1, X is S, R1 to R3 are each independently substituted or unsubstituted C1-C 30 Alkyl, substituted or unsubstituted C2-C 30 Alkenyl, substituted or unsubstituted C2-C 30 alkynyl or substituted or unsubstituted vinyl, and The substituted C1-C 30 Alkyl, the substituted C2-C 30 Alkenyl, the substituted C2-C 30 The substituent of the alkynyl or substituted vinyl is C1-C 10 Alkyl, C2-C 10 Alkenyl, C2-C 20 Alkynyl, C1-C 10 alkoxy, halogen, cyano, hydroxy or nitro, and wherein based on the total weight of the electrolyte, the additive is included in the electrolyte in an amount of 0.1 wt% to 5 wt%.

2. The electrolyte according to claim 1, wherein In Formula 1, R1 to R3 are each independently an unsubstituted C1-C 30 Alkyl or C1-C1 substituted by methyl, ethyl, propyl, butyl, -F, -Cl, -Br, -I, cyano, hydroxyl or nitro 30 alkyl.

3. The electrolyte according to claim 1, wherein In Formula 1, R1 to R3 are each independently an unsubstituted C1-C 30 alkyl.

4. The electrolyte according to claim 1, wherein the compound represented by Formula 1 is the following Compound 1: <Compound 1> 5. The electrolyte of claim 1, wherein the lithium salt comprises LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), wherein 2≤x≤20 and 2≤y≤20, at least one of LiCl, LiI, lithium bis(oxalato)borate or LiPO2F2.

6. The electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises at least one of ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, ethylene vinylene carbonate, butylene carbonate, ethyl propionate, ethyl butyrate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, γ-valerolactone, γ-butyrolactone, or tetrahydrofuran.

7. The electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises a mixed solvent of 50 vol% to 95 vol% of a linear carbonate and 5 vol% to 50 vol% of a cyclic carbonate.

8. A lithium secondary battery, comprising: a cathode; an anode; and the electrolyte according to any one of claims 1 to 7.

9. The lithium secondary battery according to claim 8, wherein the cathode comprises a cathode active material having a layered structure.

10. The lithium secondary battery according to claim 9, wherein the cathode active material is represented by Formula 2: <Formula 2> Li s Ni 1-t M t O2 in, In Formula 2, M is Co, Mn, Al, Cu, Fe, Mg, Cr, Zn, B, or Ga, and 0.9 ≤ s ≤ 1.2 and 0 < t ≤ 0.99 are satisfied.

11. The lithium secondary battery according to claim 9, wherein the cathode active material is represented by Formula 3 or Formula 4: <Formula 3> Li s' Ni t' Co 1-t'-u' Al u' O2 <Formula 4> Li s' Ni t' Co 1-t'-u' Mr u' O2 in, In Formulas 3 and 4, 0.9 ≤ s' ≤ 1.2, 0.1 < t' ≤ 0.98, 0 < u' ≤ 0.5, and 0 < 1 - t' - u' ≤ 0.5 are satisfied.

12. The lithium secondary battery according to claim 8, wherein the anode comprises an anode active material, and the anode active material comprises at least one of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, or a carbon material.

13. The lithium secondary battery according to claim 12, wherein the anode active material includes a silicon compound, a carbon compound, a composite of a silicon compound and a carbon compound, or silicon oxide SiO a , and at least one of 0 < a < 2.

Images