Electrolyte for lithium secondary battery and lithium secondary battery including same

Abstract

An electrolyte for a lithium secondary battery and a lithium secondary battery including the same are provided. The electrolyte can include a lithium salt, an organic solvent, and an additive forming a catholyte interfacial film to protect the surface of the positive electrode (e.g., sulfolane, cyclic phosphate, cyclic phosphite). The use of the additive can improve cycle life characteristics and suppress or reduce an increase in resistance during high temperature storage of the lithium secondary battery.

Description

Technical Field

[0001] One or more embodiments relate to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. Background Art

[0002] The energy density per unit weight of a lithium secondary battery is three or more times higher than that of existing lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries, and can be charged at a high rate. Summary of the invention

[0003] Technical issues

[0004] However, when an organic electrolyte is used as an electrolyte for a lithium secondary battery, the life and high temperature stability of the lithium secondary battery may be deteriorated due to the side reaction between the positive electrode / negative electrode and the electrolyte. In order to compensate for this, additives are used in the electrolyte for lithium secondary batteries. However, the additives used so far do not provide sufficient life and high temperature stability of the battery at high temperatures. Therefore, there is still a need for an electrolyte for a lithium battery that can provide sufficient life and high temperature stability of the battery at high temperatures, and a lithium battery including the same.

[0005] Technical Solution

[0006] One or more embodiments include an electrolyte for a lithium secondary battery including a novel electrolyte additive.

[0007] One or more embodiments include a lithium secondary battery including an electrolyte.

[0008] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0009] According to one aspect, an electrolyte for a lithium secondary battery is provided, which includes a lithium salt, an organic solvent, and an additive represented by Formula 1 or Formula 2 below.

[0010] [Formula 1]

[0011]

[0012] In Formula 1, A may be -[C(R 5 )(R 6 )]m-,R 1 ~R 6They may each independently be hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n may be an integer of 1 or 2, and m may be an integer of 1-3.

[0013] [Formula 2]

[0014]

[0015] In Formula 2, A may be -[C(R 5 )(R 6 )]m-,R 1 ~R 6 They may each independently be hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n may be an integer of 1 or 2, and m may be an integer of 1-3.

[0016] According to another aspect, a lithium secondary battery is provided, which includes: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte disposed between the positive electrode and the negative electrode.

[0017] Advantageous Effects of the Invention

[0018] The electrolyte for a lithium secondary battery according to one or more embodiments is oxidatively decomposed during formation to form a cathode electrolyte interface (CEI) film on the positive electrode, thereby protecting the positive electrode and suppressing the increase in battery voltage to suppress or reduce electrolyte decomposition. Therefore, if (for example, when) such an electrolyte is used, the positive electrode can be protected to provide a lithium secondary battery with improved safety, improved life characteristics at high temperatures, and improved safety during high temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0020] Figure 1 is a schematic diagram of a lithium secondary battery according to one embodiment; and

[0021] Figure 2A The figure shows the change in the rate of increase of the direct current internal resistance (DC-IR) in the lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Example 1;

[0022] Figure 2B The change of the DC-IR increase rate in the lithium secondary batteries manufactured according to Manufacturing Example 3, Comparative Manufacturing Example 2 and Comparative Manufacturing Example 3 is shown;

[0023] Figure 3A The change in discharge capacity according to the number of cycles in the lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Example 1 is shown;

[0024] Figure 3B The change in discharge capacity according to the number of cycles in the lithium secondary batteries manufactured according to Manufacturing Example 3 and Comparative Manufacturing Example 2 and Comparative Manufacturing Example 3 is shown;

[0025] Figure 4A The high temperature life characteristics of the lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Example 1 are shown; and

[0026] Figure 4B The high temperature life characteristics of the lithium secondary batteries manufactured according to Manufacturing Example 3 and Comparative Manufacturing Examples 2 and 3 are shown. DETAILED DESCRIPTION

[0027] The embodiment will now be explained in more detail in the accompanying drawings with reference to its examples, wherein the same reference numerals refer to the same elements throughout the text, and a repeated description thereof may not be provided. In this regard, the present embodiment may have different forms and should not be construed as being limited to the description stated herein. Accordingly, the embodiment is described only by reference to the accompanying drawings to explain the aspects of the present description. As used herein, the term "and / or" includes any and all combinations of one or more related enumerated items. Expressions such as "at least one of ...", "one of ..." and "selected from ..." modify the entire list of elements if (for example, when) before / after the list of elements, without modifying the individual elements of the list. For example, the expression "at least one of a-c", "at least one of a, b or c" and "at least one of a, b and / or c" may indicate only a, only b, only c, both a and b (for example, at the same time), both a and c (for example, at the same time), both b and c (for example, at the same time), all a, b and c, or variations thereof.

[0028] The terms used in this article are only used to describe the embodiments and are not intended to limit the present disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. It will be understood that although the terms first, second, etc. can be used in this article to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teachings of the present disclosure, the first element may be referred to as the second element. Similarly, the second element may be referred to as the first element.

[0029] Unless otherwise defined, all chemical terms, technical terms and scientific terms used in this article have the same meaning as those generally understood by ordinary technicians in the field. In the event of a conflict, the present specification (including definitions) shall prevail.

[0030] For ease of description, spatially relative terms such as "below," "beneath," "below," "above," "up," "bottom," "top," etc. may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the accompanying drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the accompanying drawings. For example, if (e.g., when) the device in the accompanying drawings is turned over, an element described as being "below" or "beneath" other elements or features will then be oriented "above" or "on" the other elements or features. Thus, the term "below" may encompass both orientations of above and below. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0031] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, suitable methods and materials are described herein. A singular form may include a plural form if (e.g., when) there is no obvious contrary meaning in the context.

[0032] As used herein, it should be understood that terms such as “includes, including, include,” “having, has, have,” and / or “comprises, comprising, comprise,” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, ingredients, materials, or combinations thereof disclosed in the specification, and are not intended to exclude the possibility that one or more other features, numbers, steps, actions, components, parts, ingredients, materials, or combinations thereof may exist or may be added.

[0033] It will be understood that the term "combination thereof" as used herein refers to a mixture or combination of two or more components.

[0034] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, the term "or" refers to the term "and / or". As used herein, the expressions "at least one", "at least one" or "one or more" before / after an element refer to the entire list of elements that the expression can supplement, rather than the individual elements mentioned above.

[0035] In the accompanying drawings, for the sake of clarity, the thickness of layers, films, panels, areas, etc. is magnified. The same reference numerals represent the same elements throughout, and the specification may not provide a repeated description thereof. It will be understood that if (for example, when) an element (such as a layer, film, area, or substrate) is referred to as "on" another element (when), it may be directly on other elements, or there may also be an intermediate element. It will be understood that although the terms "first", "second", and "third" may be used in this article to describe one or more appropriate elements, the element should not be limited by these terms. These terms are only used to distinguish one element from another element. As used in this article, singular forms such as "one (a)", "one (an)", and "said" are intended to also include plural forms, unless the context clearly indicates otherwise.

[0036] As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

[0037] The term "may" will be understood to refer to "one or more embodiments of the present disclosure," some of which include the described elements, while others exclude the elements and / or include alternative elements. Similarly, optional language such as "or" refers to "one or more embodiments of the present disclosure," each including the corresponding enumerated items.

[0038] In this context, "consisting essentially of" means that any additional components will not significantly affect the chemical, physical, optical, or electrical properties of the semiconductor film.

[0039] Further, in this specification, the phrase "on a plane" or "plan view" means observing a target portion from the top, and the phrase "in cross section" means observing a cross section formed by vertically cutting the target portion from the side.

[0040] In the drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity, and the same reference numerals are always used to mark the same elements, and repeated descriptions thereof may not be provided in the specification. It will be understood that if (for example, when) an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on the other element or there may also be intervening elements. In contrast, if (for example, when) an element is referred to as being "directly on" another element, there are no intervening elements.

[0041] In some embodiments, "layer" as used herein includes not only a shape formed on the entire surface but also a shape formed on a partial surface if (for example, when) viewed from a plan view.

[0042] In some embodiments, the terms "about" and "substantially" used throughout this specification refer to the referenced values ​​with the inherent manufacturing error and material tolerance if (e.g., when) they occur, and are used in the sense of being close to or approximately the value. They are used to help understand the present disclosure and to prevent or reduce dishonest infringers from unfairly using the present disclosure when referring to precise values ​​or absolute values.

[0043] As used herein, if (for example, when) no limitation is otherwise provided, "substituted" means that the hydrogen of the compound is replaced by a substituent selected from deuterium, halogen, hydroxyl, amino, substituted or unsubstituted C1-C30 amine, nitro, substituted or unsubstituted C1-C40 silyl, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C20 alkoxy, C1-C10 fluoroalkyl, cyano and / or combinations thereof.

[0044] As used herein, if (for example, when) no limitation is otherwise provided, "substituted" refers to the replacement of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C10 fluoroalkyl or cyano. In some embodiments, in specific examples of the present disclosure, "substituted" refers to the replacement of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C20 alkyl, C6-C30 aryl, C1-C10 fluoroalkyl or cyano. In some embodiments, in specific examples of the present disclosure, "substituted" refers to the replacement of at least one hydrogen of a substituent or compound by deuterium, halogen, C1-C5 alkyl, C6-C18 aryl, C1-C5 fluoroalkyl or cyano. In some embodiments, in specific examples of the present disclosure, "substituted" means that at least one hydrogen of a substituent or compound is replaced by deuterium, cyano, halogen, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl or naphthyl.

[0045] Expressions such as C1-C30 mean that the number of carbon atoms is 1-30.

[0046] Hereinafter, the electrolyte for lithium secondary battery and the lithium secondary battery including the same will be described in more detail with reference to the embodiments and drawings of the present disclosure. It should be understood by those skilled in the art that these embodiments are provided only for more specific explanation of the present disclosure and should not be construed as limiting the scope of the present disclosure.

[0047] Electrolyte

[0048] If (for example, when) a lithium transition metal oxide (including nickel and at least one transition metal other than nickel, and wherein the content (for example, amount) of nickel relative to the total molar number of transition metals is, for example, about 80 mol% or more) is used as a positive electrode active material, it is possible to manufacture a lithium secondary battery with high power and high capacity. However, because the lithium transition metal oxide with a high nickel content (for example, amount) has an unstable surface structure, during the charge / discharge process of the battery, the amount of gas generated increases due to side reactions, and the dissolution of transition metals such as nickel may be further enhanced. Accordingly, in a lithium secondary battery using a lithium transition metal oxide with a high nickel content (for example, amount) as a positive electrode active material, the life characteristics may deteriorate, and the resistance increases at high temperatures. Therefore, it is desirable (or necessary) to improve the stability at high temperatures.

[0049] An electrolyte for a lithium secondary battery according to one embodiment may include a lithium salt, an organic solvent, and an additive represented by Formula 1 or Formula 2.

[0050] Formula 1

[0051]

[0052] In Formula 1, A may be -[C(R 5 )(R 6 )]m-,R 1 ~R 6 They may each independently be hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n may be an integer of 1 or 2, and m may be an integer of 1-3.

[0053] Formula 2

[0054]

[0055] In Formula 2, A may be -[C(R 5 )(R 6 )]m-,R 1 ~R 6 They may each independently be hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n may be an integer of 1 or 2, and m may be an integer of 1-3.

[0056] The additive represented by Formula 1 may include a sulfolane group and a cyclic phosphite group. The additive represented by Formula 2 may include a sulfolane group and a cyclic phosphate group. The additive is oxidatively decomposed during formation to form a cathode electrolyte interface (CEI) film on the surface of the positive electrode and protect the surface of the positive electrode, thereby contributing to the structural stability of the positive electrode. More specifically, the phosphite of Formula 1 or the phosphate of Formula 2 may be oxidatively decomposed to form a film having a polymerized form, thereby protecting the positive electrode and contributing to the structural stability of the positive electrode. In addition, since the additives of Formulas 1 and 2 include a sulfolane group having excellent thermal stability, the thermal stability of the CEI film itself can be improved, thereby improving high temperature characteristics.

[0057] In Formula 1 and Formula 2, when the sulfolane ring is a 6-membered ring, the phosphite substituent or phosphate substituent may be bonded to the para or meta position of the sulfolane ring. When the sulfolane ring is a 5-membered ring, the phosphite substituent or phosphate substituent may be bonded to the meta position of the sulfolane ring. When the phosphite substituent or phosphate substituent connected to the sulfolane ring is bonded to the above position, the excellent effect of reducing the resistance increase rate and gas generation during high temperature storage and increasing high temperature life can be obtained. When the phosphite substituent or phosphate substituent connected to the sulfolane ring is bonded to a position other than the above position, it is chemically very unstable, so it is not easy to synthesize it itself.

[0058] The additive represented by Formula 1 or Formula 2 may include both sulfolane and phosphite structures or may include both sulfolane and phosphate structures. When using a mixture of sulfolane and phosphite or a mixture of sulfolane and phosphate, sulfolane may be electrochemically inactive due to oxidation reaction or reduction reaction not being well performed under the usual driving voltage. Therefore, it may be difficult to add a mixture of sulfolane and phosphite or a mixture of sulfolane and phosphate to the positive electrode as a membrane component.

[0059] However, in an electrolyte according to an embodiment, the additive represented by Formula 1 or Formula 2 described above can form a composite film having a form in which sulfolane capable of improving thermal stability is bonded to a membrane component formed when a phosphite or a phosphate is decomposed. As a result, a CEI film having improved thermal stability can be formed on the positive electrode compared to the case in which a mixture of sulfolane and phosphite or a mixture of sulfolane and phosphate is used. Because the electrolyte for a lithium secondary battery according to an embodiment includes an additive represented by Formula 1, a CEI film can be formed on the positive electrode to form an excellent high heat-resistant film on the surface of the positive electrode, thereby preventing side reactions such as electrolyte decomposition. Accordingly, in a lithium secondary battery including such an electrolyte, the amount of gas generated due to the decomposition reaction of the electrolyte inside the lithium secondary battery during high-temperature storage can be reduced, and the increase in resistance can be suppressed, thereby improving life characteristics.

[0060] The additive represented by Formula 1 or Formula 2 may be, for example, an additive represented by Formula 3, Formula 3-1, Formula 3-2, Formula 3-3, Formula 4, Formula 4-1, Formula 4-2, or Formula 4-3.

[0061] Formula 3

[0062]

[0063] In formula 3, R 1 ~R 4Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0064] Formula 3-1

[0065]

[0066] In formula 3-1, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0067] Formula 3-2

[0068]

[0069] In formula 3-2, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0070] Formula 3-3

[0071]

[0072] In formula 3-3, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0073] Formula 4

[0074]

[0075] In formula 4, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0076] Formula 4-1

[0077]

[0078] In formula 4-1, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0079] Formula 4-2

[0080]

[0081] In formula 4-2, R 1 ~R 4 Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0082] Formula 4-3

[0083]

[0084] In formula 4-3, R 1 ~R 4Each may independently be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

[0085] In the above formula, R 1 ~R 4 For example, all of them may be hydrogen.

[0086] The additive represented by Formula 1 may be, for example, at least one selected from Compound A to Compound H.

[0087]

[0088]

[0089] The content of the additive represented by Formula 1 or Formula 2 may be in the range of about 0.1 wt% to about 10 wt%, about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 5 wt%, or about 0.1 wt% to about 2 wt%, relative to about 100 wt% of the total weight of the electrolyte. When the content of the additive is within the above range, the positive electrode may be protected under high temperature environment to increase the life of the positive electrode, and the gas generation and resistance increase rate during high temperature storage may be reduced.

[0090] According to one embodiment, the lithium salt may include a selected from LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiCF 3 SO 3 、Li(CF 3 SO 2 ) 2 N、Li(FSO 2 ) 2 N、LiC 4 F 9 SO 3 、LiAlO 2 、LiAlCl 4 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2)(where 2≤x≤20 and 2≤y≤20), LiCl, LiI, lithium bis(oxalato)borate (LiBOB), LiPO 2 F 2 and at least one of compounds represented by the following Formula 5 to Formula 8, but one or more embodiments are not limited thereto. Any material usable as a lithium salt in the art may be used.

[0091] Formula 5

[0092]

[0093] Formula 6

[0094]

[0095] Formula 7

[0096]

[0097] Formula 8

[0098]

[0099] The concentration of the lithium salt in the electrolyte may be in the range of about 0.1 M to about 5.0 M, for example, in the range of about 0.1 M to about 3.0 M or about 0.1 M to about 2.0 M. When the concentration of the lithium salt is within the above range, further improved characteristics of the lithium secondary battery may be obtained.

[0100] The organic solvent may be at least one selected from carbonate solvents, ester solvents, ether solvents and ketone solvents.

[0101] The carbonate solvents may include ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), etc.

[0102] Ester solvents may include methyl propionate, ethyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, gamma butyrolactone, decanolactone, gamma valerolactone, mevalonolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Nitrile solvents may include acetonitrile (AN), succinonitrile (SN), adiponitrile, etc.

[0103] Other solvents included in the electrolyte may include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, tetrahydrofuran, etc., but one or more embodiments are not limited thereto. Any material that can be used as an organic solvent in the art can be used. For example, the organic solvent may include 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 (for example, a mixed solvent of about 70 vol% to about 95 vol% of a linear carbonate and about 5 wt% to about 30 vol% of a cyclic carbonate). For example, the organic solvent may be a mixed solvent of three or more organic solvents.

[0104] According to one embodiment, the organic solvent may include at least one selected from EMC, MPC, EPC, DMC, DEC, DPC, PC, 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 and tetrahydrofuran, but one or more embodiments are not limited thereto. Any material that can be used as an organic solvent in the art can be used.

[0105] The electrolyte according to one embodiment may be in a liquid state or a gel state. The electrolyte may be prepared by adding a lithium salt and the above-mentioned additives to an organic solvent.

[0106] A lithium secondary battery according to another embodiment may include: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the above-mentioned electrolyte disposed between the positive electrode and the negative electrode.

[0107] In a lithium secondary battery, by using an electrolyte including the above-described additive for an electrolyte, an increase in initial resistance of the lithium secondary battery can be suppressed, gas generation due to a side reaction can be suppressed, and life characteristics can be improved.

[0108] The positive electrode active material may include a lithium transition metal oxide containing nickel and a transition metal other than nickel. The content of nickel in the lithium transition metal oxide containing nickel and a transition metal other than nickel may be about 60 mol% or more (e.g., about 75 mol% or more, for example, about 80 mol% or more, for example, about 85 mol% or more, or for example, or about 90 mol% or more) relative to the total molar number of the transition metal.

[0109] For example, the lithium transition metal oxide may be a compound represented by the following Formula 9:

[0110] Formula 9

[0111] Li a Ni x Coy M z O 2-b A b。

[0112] In Formula 9, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.6 ≤ x < 1, 0 ≤ y ≤ 0.3, 0 < z ≤ 0.3,

[0113] x + y + z = 1, M can be at least one selected from manganese (Mn), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), and boron (B), and A can be F, S, Cl, Br, or a combination thereof.

[0114] In Formula 9, for example, 0.7 ≤ x < 1, 0 < y ≤ 0.3, 0 < z ≤ 0.3; 0.8 ≤ x < 1, 0 < y ≤ 0.3 and 0 < z ≤ 0.3; 0.8 ≤ x < 1, 0 < y ≤ 0.2 and 0 < z ≤ 0.2; 0.83 ≤ x < 0.97, 0 < y ≤ 0.15 and 0 < z ≤ 0.15; or 0.85 ≤ x < 0.95, 0 < y ≤ 0.1 and 0 < z ≤ 0.1.

[0115] For example, the lithium transition metal oxide can be at least one selected from the compounds represented by the following Formula 10 and Formula 11.

[0116] Formula 10

[0117] LiNi x Co y Mn z O 2

[0118] In Formula 10, 0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2 and 0 < z ≤ 0.1. For example, 0.7 ≤ x ≤ 0.95, 0 < y ≤ 0.3 and 0 < z ≤ 0.3.

[0119] Formula 11

[0120] LiNi x Co y Al z O 2

[0121] In Formula 11, 0.6 ≤ x ≤ 0.95, 0 < y ≤ 0.2 and 0 < z ≤ 0.1. For example, 0.7 ≤ x ≤ 0.95, 0 < y ≤ 0.3 and 0 < z ≤ 0.3. For example, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.3 and 0 < z ≤ 0.3. For example, 0.82 ≤ x ≤ 0.95, 0 < y ≤ 0.15 and 0 < z ≤ 0.15. For example, 0.85 ≤ x ≤ 0.95, 0 < y ≤ 0.1 and 0 < z ≤ 0.1.

[0122] For example, the lithium transition metal oxide may be LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.88 Co 0.08 Mn 0.04 O 2 , LiNi 0.8 Co 0.15 Mn 0.05 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.88 Co 0.1 Mn 0.02 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNi 0.8 Co 0.1 Mn 0.2 O 2 or LiNi 0.88 Co 0.1 Al 0.02 O 2 .

[0123] According to another embodiment, the positive electrode active material may include at least one active material selected from Li-Ni-Co-Al (NCA), Li-Ni-Co-Mn (NCM), lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide (LiMnO 2 ), lithium nickel oxide (LiNiO 2 ) and lithium iron phosphate (LiFePO 4 ).

[0124] The negative electrode active material may include at least one selected from silicon-based compounds, carbon-based materials, composites of silicon-based compounds and carbon-based compounds, and silicon oxides (SiO x)(where 0 < x < 2). The silicon-based compound may include silicon particles, silicon alloy particles, etc.

[0125] The size of the silicon-based compound may be less than about 200 nm, for example, in the range of about 10 nm to about 150 nm. When the silicon-based compound is spherical, the term "size" may refer to the average particle diameter, and when the silicon-based compound is non-spherical, the term "size" may refer to the average major axis length.

[0126] When the size of the silicon-based compound is within the above range, the life characteristics are excellent. Therefore, when using the electrolyte according to one embodiment, the life of the lithium secondary battery can be further improved.

[0127] The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite (such as natural graphite or artificial graphite) in an amorphous, plate-like, flake-like, spherical, or fibrous form. The amorphous carbon may be soft carbon (low-temperature fired carbon), hard carbon, mesophase pitch carbide, or fired coke.

[0128] The composite of the silicon-based compound and the carbon-based compound may be: a composite having a structure in which silicon particles are arranged on the carbon-based compound, a composite having a structure in which silicon particles are included on the surface of the carbon-based compound and inside the carbon-based compound, or a composite in which silicon particles are coated with the carbon-based compound and included inside the carbon-based compound. In the composite of the silicon-based compound and the carbon-based compound, the carbon-based compound may be graphite, graphene, graphene oxide, or a combination thereof.

[0129] The composite of the silicon-based compound and the carbon-based compound may be: an active material obtained by dispersing silicon nanoparticles with an average particle diameter of about 200 nm or less on carbon compound particles and then coating the silicon nanoparticles with carbon, or an active material in which silicon (Si) particles are present on and inside graphite. The composite of the silicon-based compound and the carbon-based compound may have an average secondary particle size of about 5 μm to about 20 μm. The average particle diameter of the silicon nanoparticles may be about 5 nm or more (for example, about 10 nm or more, for example, about 20 nm or more, for example, about 50 nm or more, or for example, about 70 nm or more). The average particle diameter of the silicon nanoparticles may be 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. For example, the average particle diameter of the silicon nanoparticles may be in the range of about 100 nm to about 150 nm.

[0130] The composite of the silicon-based compound and the carbon-based compound may have an average secondary particle diameter of about 5 μm to about 18 μm (for example, about 7 μm to about 15 μm, or for example, about 10 μm to about 13 μm).

[0131] As another example of a composite of a silicon compound and a carbon compound, a porous silicon composite aggregate disclosed in Korean Patent Application Publication No. 10-2018-0031585 and a porous silicon composite aggregate structure disclosed in Korean Patent Application Publication No. 10-2018-0056395 may be used. Korean Patent Application Publication No. 10-2018-0031585 and Korean Patent Application Publication No. 10-2018-0056395 are incorporated herein by reference.

[0132] According to one embodiment, the silicon-carbon compound composite may be a porous silicon composite aggregate, which includes a porous core containing porous silicon composite secondary particles and a shell containing a second graphene disposed on the core, wherein the porous silicon composite secondary particles include an aggregate of two or more silicon composite primary particles, and the silicon composite primary particles include silicon, silicon oxide (SiO x )(where 0 < x < 2) disposed on the silicon, and a first graphene disposed on the silicon oxide.

[0133] According to another embodiment, the silicon-carbon compound composite may be a porous silicon composite aggregate structure including a porous silicon composite aggregate and a carbonaceous coating film. The porous silicon composite aggregate includes porous silicon composite secondary particles and a second carbon sheet on at least one surface of the porous silicon composite secondary particles. The carbonaceous coating film includes amorphous carbon disposed on the porous silicon composite aggregate, wherein the porous silicon composite secondary particles include an aggregate of two or more silicon composite primary particles. The silicon composite primary particles include silicon, silicon oxide (SiO x )(where 0 < x < 2) on at least one surface of the silicon, and a first carbon sheet on at least one surface of the silicon oxide, and the silicon oxide exists in a state of a film, a matrix, or a combination thereof.

[0134] The first carbon sheet and the second carbon sheet may each exist in a state of a film, particles, a matrix, or a combination thereof. The first carbon sheet and the second carbon sheet may each be graphene, graphite, carbon fiber, graphene oxide, etc.

[0135] The composite of the above-mentioned silicon compound and carbon compound may be: a composite having a structure in which silicon particles are disposed on the carbon compound, a composite having a structure in which silicon particles are included on the surface of the carbon compound and included inside the carbon compound, or a composite in which silicon particles are coated with the carbon compound and included inside 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.

[0136] The shape of the lithium secondary battery is not particularly limited, and the lithium secondary battery may include a lithium ion battery, a lithium ion polymer battery, a lithium sulfur battery, etc.

[0137] The lithium secondary battery can be manufactured by the following method.

[0138] First, a positive electrode is prepared.

[0139] For example, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to prepare a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on the metal current collector to prepare a positive electrode plate. The positive electrode is not limited to the forms listed above, and may have other forms other than the above forms.

[0140] As the positive electrode active material, any material commonly used as a lithium-containing metal oxide in the art may be used without limitation. For example, at least one composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and a combination thereof may be used. Specific examples of the positive electrode active material may include a compound represented by any one of the following: Li a A 1-b B 1 b D 1 2 (where 0.90≤a≤1.8, and 0≤b≤0.5), Li a E 1-b B 1 b O 2-c D 1 c (where 0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05), LiE 2-b B 1 b O 4-c D 1 c (where 0≤b≤0.5, and 0≤c≤0.05), 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), 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), Li a Ni 1-b-c Co 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), Li a Ni 1-b-c Mn b B 1 c D α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2), 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), 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), Li a Ni b E c G d O 2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1), Li a Ni b Co c Mn d GeO 2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0.001≤e≤0.1), Li a NeG b O 2 (where 0.90≤a≤1.8, and 0.001≤b≤0.1), Li a CoG b O 2(where 0.90≤a≤1.8, and 0.001≤b≤0.1), Li a MnG b O 2 (where 0.90≤a≤1.8, and 0.001≤b≤0.1), Li a Mn 2 G b O 4 (where 0.90≤a≤1.8, and 0.001≤b≤0.1), QO 2 ;QS 2 ;LiQS 2 ; V 2 O 5 ;LiV 2 O 5 ;LiIO 2 ;LiNiVO 4 ;Li (3-f) J 2 (PO 4 ) 3 (where 0≤f≤2), Li (3-f) Fe 2 (PO 4 ) 3 (where 0≤f≤2) and LiFePO 4 .

[0141] In the above chemical formula, A can be Ni, Co, Mn or a combination thereof, B 1 It can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or their combination. 1 can be O, F, S, P or a combination thereof, E can be Co, Mn or a combination thereof, F 1 It can be F, S, P or a combination thereof, G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof, Q can be Ti, Mo, Mn or a combination thereof, I can be Cr, V, Fe, Sc, Y or a combination thereof, and J can be V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0142] For example, LiCoO 2 、LiMn x O 2x (where x = 1 or 2), LiNi 1-x Mn x O 2x (where 0 <x<1)、LiNi 1-x- y Co x Mn y O 2(where 0≤x≤0.5, and 0≤y≤0.5), LiFePO 4 wait.

[0143] In some embodiments, a compound having a coating on its surface may be used, or a mixture of the compound and a compound having a coating may be used. The coating may include a coating element compound of an oxide or hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a basic carbonate of a coating element. The compound constituting the coating may be amorphous or crystalline. The coating elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. In the process of forming the coating, any coating method may be used, as long as the compound can be coated with these elements by a method (e.g., a spraying method or an impregnation method) that does not adversely affect the physical properties of the positive electrode active material. Because the coating method is well known to those skilled in the art, its detailed description will be omitted.

[0144] The conductive material may include carbon black, graphite fine particles, etc., but one or more embodiments are not limited thereto. Any material that can be used as a conductive material in the art may be used.

[0145] The binder may include at least one selected from vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, a mixture thereof, or a styrene butadiene rubber-based polymer, but one or more embodiments are not limited thereto. Any material that can be used as a binder in the art can be used.

[0146] The solvent may include N-methylpyrrolidone, acetone, or water, but one or more embodiments are not limited thereto. Any solvent available in the art may be used.

[0147] The contents of the positive electrode active material, the conductive material, the binder and the solvent are at the levels commonly used in lithium batteries. Depending on the purpose and configuration of the lithium battery, one or more of the conductive material, the binder and the solvent may be omitted.

[0148] Next, a negative electrode was prepared.

[0149] For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a binder and a solvent. The negative electrode active material composition is directly coated on a metal current collector and dried to prepare a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on a metal current collector to prepare a negative electrode plate.

[0150] As the negative electrode active material, any material that is used as a negative electrode active material for a lithium battery in the art can be used. For example, the negative electrode active material may include at least one selected from lithium metal, a metal capable of forming an alloy with lithium, a transition metal oxide, a non-transition metal oxide, and a carbonaceous material.

[0151] For example, the metal capable of forming an alloy with lithium may be Si, Sn, Al, Ge, Pb, Bi, Sb, a Si-Y alloy (where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof and is not Si), or a Sn-Y alloy (where Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof and is 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, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0152] For example, the transition metal oxide may be lithium titanate oxide, vanadium oxide, or lithium vanadium oxide.

[0153] For example, the non-transition metal oxide may be SnO 2 , SiO x (where 0 < x < 2), etc.

[0154] The carbonaceous material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite (such as natural graphite or artificial graphite that is amorphous, plate-like, flaky, spherical, or fibrous). The amorphous carbon may be soft carbon (low-temperature fired carbon) or hard carbon, mesophase pitch carbide, fired coke, etc.

[0155] Non-limiting examples of the binder for the negative electrode may include various types of binder polymers such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, a polymer in which its hydrogen is replaced by Li, Na, or Ca, and various copolymers.

[0156] The negative electrode active material layer may further include a tackifier.

[0157] The viscosity increasing agent may include at least one selected from the group consisting of CMC, carboxyethyl cellulose, starch, regenerated cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and polyvinyl alcohol. For example, CMC may be used.

[0158] The content of the solvent may be in the range of about 100 to about 300 parts by weight relative to about 100 parts by weight of the total weight of the negative electrode active material. When the content of the solvent is within the above range, the operation of forming the negative electrode active material layer is easy.

[0159] When conductivity is ensured, the negative electrode active material layer does not require a conductive material. The negative electrode active material layer may further include a conductive material as needed. As a conductive material, as long as the material has conductivity and does not cause chemical changes in the corresponding battery, the material is not particularly limited. For example, the conductive material may include graphite (such as natural graphite or artificial graphite), carbon black (such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or summer black), conductive fibers (such as carbon fibers or metal fibers), conductive tubes (such as carbon nanotubes), carbon fluoride, metal powders (such as aluminum powder or nickel powder), conductive whiskers (such as zinc oxide or potassium titanate), conductive metal oxides (such as titanium oxide), conductive materials (such as polyphenylene derivatives), etc. The conductive material may be carbon black, and more specifically, may be carbon black having an average particle size of tens of nanometers.

[0160] When the negative electrode active material layer includes a conductive material, the content of the conductive material may be in a range of about 0.01 to about 10 parts by weight, about 0.01 to about 5 parts by weight, or about 0.1 to about 2 parts by weight, relative to about 100 parts by weight of the total weight of the negative electrode active material layer.

[0161] The negative electrode current collector may be generally prepared to have a thickness of about 3 μm to about 500 μm. As the negative electrode current collector, the material is not particularly limited as long as the material has high conductivity and does not cause chemical changes in the corresponding battery. For example, the negative electrode current collector may include: copper; stainless steel; aluminum; nickel; titanium; heat-treated carbon; copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc.; or aluminum-cadmium alloy. In addition, similar to the positive electrode current collector, fine concave-convex may be formed on the surface of the negative electrode current collector to enhance the bonding strength of the negative electrode active material, and the negative electrode current collector may have various forms (such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics).

[0162] Next, a separator to be inserted between the positive electrode and the negative electrode is prepared.

[0163] As the separator, any separator commonly used in lithium batteries can be used. A separator having low resistance to the movement of ions in the electrolyte and excellent electrolyte impregnation ability can be used. For example, the separator may include at least one selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) and combinations thereof, and may be in the form of a nonwoven fabric or a textile. For example, a reelable separator including polyethylene, polypropylene, etc. can be used in a lithium ion battery, and a separator with excellent electrolyte impregnation ability can be used in a lithium ion polymer battery. For example, the separator can be prepared according to the following method.

[0164] A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition can be directly coated on an electrode and dried to form a separator. Alternatively, the separator composition can be cast on a support, and then the separator film peeled off from the support can be laminated on the electrode to form a separator.

[0165] The polymer resin used to prepare the separator is not particularly limited, and any material used for a bonding material of an electrode plate may be used. For example, the polymer resin may include vinylidene fluoride / hexafluoropropylene copolymer, PVDF, polyacrylonitrile, polymethyl methacrylate, or a mixture thereof.

[0166] Next, the above-mentioned electrolyte solution is prepared.

[0167] like Figure 1 As shown in FIG. 1 , the lithium battery 1 may include a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 may be wound or folded and housed in a battery case 5. Subsequently, an electrolyte may be injected into the battery case 5, and the battery case 5 may be sealed with a cap assembly 6 to complete the lithium battery 1. The battery case 5 may have a cylindrical shape, a prismatic shape, a thin film shape, etc. For example, the lithium battery 1 may be a large-sized thin film battery. The lithium battery 1 may be a lithium ion battery.

[0168] The separator 4 may be disposed between the positive electrode 3 and the negative electrode 2 to form a battery structure. The battery structure may be stacked in a double cell structure and then immersed in an organic electrolyte, and the resultant may be contained in a bag and sealed, thereby completing a lithium ion polymer battery.

[0169] In addition, multiple battery structures can be stacked to form a battery pack, and such a battery pack can be used for all devices that require high capacity and high power. For example, the battery pack can be used for laptop computers, smart phones, electric vehicles, etc.

[0170] In a lithium secondary battery according to one embodiment, an increase in direct current internal resistance (DC-IR) may be significantly reduced, thereby exhibiting excellent battery characteristics, compared to a lithium secondary battery using a general nickel-rich lithium nickel composite oxide as a positive electrode active material.

[0171] The operating voltage of a lithium secondary battery using positive electrode 3, negative electrode 2, and electrolyte may have, for example, a lower limit of about 2.5V to about 2.8V and an upper limit of about 4.1V or more, and may be, for example, in the range of about 4.1V to about 4.45V.

[0172] In addition, lithium secondary batteries can be used in, for example, power tools that move by receiving power from an electric motor, electric motor vehicles (such as electric vehicles (EV), hybrid electric vehicles (HEV), or plug-in hybrid electric vehicles (PHEV)), electric two-wheeled vehicles (such as electric bicycles (E-bikes) or electric scooters (E-scooters)), electric golf carts, power storage systems, etc., but one or more embodiments are not limited to this.

[0173] The term "alkyl" may refer to a branched or unbranched aliphatic hydrocarbon group. In an 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, cycloheptyl, etc., but one or more embodiments are not limited thereto. In other embodiments, each of the examples of alkyl groups may be optionally substituted. In other embodiments, the alkyl group may have 1 to 6 carbon atoms. For example, a C1-C6 alkyl group may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, 3-pentyl, hexyl, etc., but one or more embodiments are not limited thereto.

[0174] In some embodiments, at least one hydrogen in the alkyl group may be substituted by a halogen atom, a C1-C20 alkyl group substituted by a halogen atom (e.g., CCF 3 , CHCF 2 , CH 2 F or CCl 3 ), C1-C20 alkoxy, C2-C20 alkoxyalkyl, hydroxy, nitro, cyano, amino, amidino, hydrazine, hydrazone, carboxyl or its salt, sulfonyl, sulfamoyl, sulfonic acid or its salt, phosphoric acid or its salt, C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C6-C20 aryl, C7-C20 aralkyl, C6-C20 heteroaryl, C7-C20 heteroarylalkyl, C6-C20 heteroaryloxy or C6-C20 heteroaryloxyalkyl.

[0175] As used herein, the term "alkenyl" may refer to a C2 to C20 hydrocarbon group having at least one carbon-carbon double bond. Examples of alkenyl groups may include vinyl, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, cyclopropenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, etc., but one or more embodiments are not limited thereto. In other embodiments, alkenyl groups may be substituted or unsubstituted. In other embodiments, alkenyl groups may have 2 to 40 carbon atoms.

[0176] As used herein, the term "alkynyl" may refer to a C2 to C20 hydrocarbon group having at least one carbon-carbon triple bond. Examples of alkynyl groups may include ethynyl, 1-propynyl, 1-butynyl, 2-butynyl, etc., but one or more embodiments are not limited thereto. In other embodiments, the alkynyl group may be substituted or unsubstituted. In other embodiments, the alkynyl group may have 2 to 40 carbon atoms.

[0177] In this specification, a substituent is derived from an unsubstituted parent group in which at least one hydrogen atom is replaced by another atom or functional group. Unless otherwise indicated, when a functional group is considered to be "substituted", it means that the functional group is independently selected from C 1 ~C 20 Base, C 2 ~C 20 Alkenyl, C 2 ~C 20 Alkynyl, C 1 ~C 20 The functional group may be substituted with at least one substituent selected from the group consisting of alkoxy, halogen, CN, hydroxyl and nitro. When a functional group is described as "optionally substituted", the functional group may be substituted with at least one group selected from the substituents described above.

[0178] The term "halogen" may include fluorine, bromine, chlorine, iodine, and the like.

[0179] The term "alkoxy" may refer to "alkyl-O-", and the alkyl group may be defined above. Non-limiting examples of alkoxy groups may include methoxy, ethoxy, 2-propoxy, butoxy, tert-butoxy, pentyloxy, hexyloxy, and the like. At least one hydrogen atom in the alkoxy group may be substituted with the same substituents as the substituents of the alkyl group described above.

[0180] The term "heteroaryl" may refer to a monocyclic or bicyclic organic group including at least one heteroatom selected from N, O, P and S, wherein the remaining ring atoms are all carbon. The heteroaryl group may include, for example, 1 to 5 heteroatoms, and in some embodiments, may include a 5 to 10-membered ring. S or N may be oxidized to have various oxidation states.

[0181] Examples of heteroaryl groups may include thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol-2-yl, oxazol-4-yl, oxazol-5-yl, isoxazol-3-yl, isoxazol-4-yl, isoxazol-5-yl, 1,2,4-triazol-3-yl, 1,2,4-triazol-5-yl, 1,2,3-triazol-4-yl, 1,2,3-triazol-5-yl, tetrazolyl, pyridin-2-yl, pyridin-3-yl, 2-pyrazin-2-yl, pyrazin-4-yl, pyrazin-5-yl, 2-pyrimidin-2-yl, 4-pyrimidin-2-yl or 5-pyrimidin-2-yl.

[0182] The term "heteroaryl" may include a case where a heteroaromatic ring is selectively fused to at least one of an aryl group, an alicyclic group or a heterocyclic group.

[0183] The term "carbocycle" may refer to a saturated or partially unsaturated non-aromatic monocyclic, bicyclic or tricyclic hydrocarbon group.

[0184] Examples of monocyclic hydrocarbons may include cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, and the like.

[0185] Examples of bicyclic hydrocarbons may include bornyl, decalinyl, bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.1]heptenyl, or bicyclo[2.2.2]octyl.

[0186] Examples of the tricyclic hydrocarbon may include adamantyl and the like.

[0187] At least one hydrogen atom in the carbon ring may be substituted with a substituent similar to the substituent of the alkyl group described above.

[0188] Hereinafter, the present disclosure will be described in more detail through the following examples and comparative examples. However, the following examples and comparative examples are only presented to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto.

[0189] Example

[0190] Preparation of additives for electrolytes

[0191] Preparation Example 1: Synthesis of Compound A

[0192]

[0193] 5 g (42.2 mmol) of 3-cyclobutene sulfone and 2.6 g (46.6 mmol) of potassium hydroxide were dissolved in 8 ml of distilled water, heated and stirred at 40° C. for about 5 hours. After the reaction mixture was cooled to room temperature, the solution was neutralized with a 35 wt % to 37 wt % concentrated hydrochloric acid aqueous solution (pH 6 to pH 7).

[0194] The mixture obtained according to this process was poured into cold acetone to filter and remove the precipitated potassium chloride salt and concentrate the filtrate. The crude product obtained by this process was dissolved in a small amount of acetone, passed through silica gel using ethyl acetate as a developing solution, and then concentrated to obtain Compound 1 as a white solid.

[0195] Synthesis of Compound A

[0196] 3 g (7.34 mmol) of Compound 1 was dissolved in 100 ml of dichloromethane, and 2.45 g of triethylamine was added and stirred.

[0197] 2.84 g of 2-chloro-2-oxo-1,3,2-dioxaphospholane was slowly added dropwise to the solution, and the reaction was carried out for about 5 hours, and the generated precipitate was filtered and the filtrate was concentrated. The concentrated liquid was recrystallized to obtain Compound 2 (Compound A) as a white solid.

[0198] Preparation Example 2: Synthesis of Compound E

[0199]

[0200] Synthesis of compound 1

[0201] 5g (42.2mmol) of 3-cyclobutene sulfone and 2.6g (46.6mmol) of potassium hydroxide were dissolved in 8ml of distilled water, heated and stirred at a temperature of 40°C for about 5 hours. After the reaction mixture was cooled to room temperature, the solution (pH 6 to pH 7) was neutralized with a concentrated hydrochloric acid aqueous solution of 35wt% to 37wt%. The mixture was poured into cold acetone, and the potassium chloride salt of the precipitate was filtered and removed, and the filtrate was concentrated. The crude product obtained was dissolved in a small amount of acetone, and ethyl acetate was used as a developing solution to pass through silica gel, and then concentrated to obtain compound 1 in a white solid state.

[0202] 3 g (7.34 mmol) of Compound 1 was dissolved in 100 ml of dichloromethane, and 2.45 g of triethylamine was added, followed by stirring.

[0203] 3.20 g of 2-chloro-2-oxo-1,3,2-dioxaphospholane was slowly added dropwise to the solution, and the reaction was carried out for about 5 hours, and the generated precipitate was filtered and the filtrate was concentrated. The concentrated liquid was recrystallized to obtain Compound 2 (Compound E) as a white solid.

[0204] Preparation of electrolyte

[0205] Comparative Example 1

[0206] 1.5M LiPF 6 It was added to a mixed solvent of EC, EMC, and DMC having a volume ratio of 20:10:70 to prepare an electrolyte.

[0207] Comparative Example 2

[0208] With respect to 100 wt % of the total weight of the electrolyte of Comparative Example 1, 1 wt % of the following Compound 1 was added as an additive.

[0209]

[0210] Comparative Example 3

[0211] With respect to 100 wt % of the total weight of the electrolyte of Comparative Example 1, 1 wt % of the following compound J was added as an additive.

[0212]

[0213] Example 1

[0214] With respect to 100 wt % of the total weight of the electrolyte of Comparative Example 1, 0.2 wt % of Compound A was added as an additive to prepare an electrolyte.

[0215]

[0216] Example 2 and Example 3

[0217] Electrolytes were prepared in the same manner as in Example 1, except that the contents of Compound A as an additive were changed to 0.5 wt % and 1.0 wt %, respectively.

[0218] Example 4

[0219] With respect to 100 wt % of the total weight of the electrolyte of Comparative Example 1, 0.2 wt % of Compound E was added as an additive to prepare an electrolyte.

[0220]

[0221] Example 5 and Example 6

[0222] Electrolytes were prepared in the same manner as in Example 4, except that the contents of Compound E as an additive were changed to 0.5 wt % and 1.0 wt %, respectively.

[0223] (Manufacturing of lithium secondary batteries (pouch-type battery cells))

[0224] Production Example 1

[0225] 98wt% of graphite particles, 1wt% of CMC and 1wt% of SBR aqueous dispersion binder were mixed, placed in distilled water, and then stirred for 60 minutes using a mechanical stirrer to prepare a slurry of negative active material. The slurry was coated on a copper current collector with a thickness of 10μm using a scraper to a thickness of about 60μm, dried in a hot air dryer at a temperature of 100°C for 0.5 hours, dried for another 4 hours under vacuum and a temperature of 120°C, and then rolled to prepare a negative electrode. The mixed density (E / D) of the negative electrode was 1.55g / cc, and the loading level (L / L) of the negative electrode was 14.36mg / cm 2 .

[0226] In addition, a positive electrode was prepared according to the following process.

[0227] 94wt% LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622 manufactured by Münster Electrochemical Energy Technology), 3.0wt% of a conductive material (Denka black) and 3.0wt% of a binder (PVDF) were mixed, placed in an N-methyl-2-pyrrolidone solvent, and then stirred for 30 minutes using a mechanical stirrer to prepare a slurry of a positive electrode active material. The slurry was coated on an aluminum current collector with a thickness of 20μm using a scraper to a thickness of about 60μm, dried in a hot air dryer at a temperature of 100°C for 0.5 hours, dried for another 4 hours under vacuum and a temperature of 120°C, and then rolled to prepare a positive electrode. The mixed density (E / D) of the positive electrode was 3.15g / cc, and the loading level (L / L) of the positive electrode was 27.05mg / cm 2 .

[0228] A polyethylene separator (thickness of 16 μm) was used as a separator, and the electrolyte solution of Example 3 was used as an electrolyte solution to manufacture a lithium secondary battery (a pouch-type battery cell having a capacity of about 40 mAh).

[0229] Production Examples 2 to 6

[0230] A lithium secondary battery (pouch-type battery cell) was manufactured in the same manner as in Manufacturing Example 1, except that the electrolytes prepared in Examples 4 to 9 were used instead of the electrolyte prepared in Example 3.

[0231] Comparative Manufacturing Examples 1 to 3

[0232] A lithium secondary battery (pouch-type battery cell) was manufactured in the same manner as in Manufacturing Example 1, except that the electrolytes prepared in Comparative Examples 1 to 3 were used instead of the electrolyte prepared in Example 3.

[0233] Evaluation Example 1: Gas Generation after High-Temperature Storage

[0234] The lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Example 1 were fully charged at 25°C (state of charge (SOC) 100), stored in an oven at a temperature of 60°C for 10 days, 20 days or 30 days, and then fully discharged again (SOC 0). Then, for the lithium secondary batteries, the gas generation amount and the gas reduction rate were measured using a refinery gas analyzer (RGA). The results are shown in Table 1 below. Here, SOC 100 is a state in which the battery is charged to have a charge capacity of 100% when the total charge capacity of the battery is 100%, and this state means a state in which the discharge is 0% when observed in a discharged state.

[0235] Description of charging / discharging conditions: At a temperature of 25°C, the lithium secondary battery was charged to 4.2V under constant current (CC) conditions at 0.33C cutoff and charged under constant voltage (CV) conditions at 0.05C cutoff for CC / CV charging. Then, it was discharged to 2.5V at 0.33C cutoff.

[0236] Equation 1

[0237] Gas reduction rate (%) = {(gas generation amount of comparative manufacturing example 1 - gas generation amount of sample) / (gas generation amount of comparative manufacturing example 1)} × 100

[0238] [Table 1]

[0239]

[0240] As shown in Table 1, it can be seen that the amount of gas generated in the lithium secondary batteries of Manufacturing Examples 1 to 6 is reduced compared to the case of Comparative Manufacturing Example 1.

[0241] Production Example 3 and Comparative Production Examples 1 to 3

[0242] The gas generation amount after high-temperature storage of the lithium secondary batteries manufactured according to Manufacturing Example 3 and Comparative Manufacturing Examples 1 to 3 was evaluated under the same evaluation conditions as the gas generation amount after high-temperature storage of the lithium secondary batteries manufactured according to Manufacturing Example 1 and Comparative Manufacturing Example 1. The results are shown in Table 2 below.

[0243] [Table 2]

[0244]

[0245] Referring to Table 2, it can be seen that the gas reduction rate of the lithium secondary battery of Manufacturing Example 3 is increased compared with the cases of Comparative Manufacturing Examples 2 and 3.

[0246] Evaluation Example 2: Resistance increase rate after high-temperature storage

[0247] At a temperature of 25°C, each of the lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Examples 1 to 3 was charged to 4.2 V at 0.33C cutoff under CC conditions, charged at 0.05C cutoff under CV conditions, and then discharged at 0.33C cutoff to 2.5 V. In this case, under the condition where the SOC is set to SOC100 (i.e., a state in which the battery is charged to have a charge capacity of 100% when the total charge capacity of the battery is 100%, and refers to a state in which the battery is not discharged at all in terms of the discharge state), the voltage drop (V) occurring when the current flows at 1C for 10 seconds is measured to calculate (DC-IR).

[0248] Each of the lithium secondary batteries was left at a temperature of 60°C for 10 days, 20 days and 30 days at SOC (=100%), and then the resistance increase rate when left at high temperature (60°C) was evaluated according to the following formula 2. The results are shown in Tables 2 and Figure 2A and Figure 2B Here, the resistance increase rate (%) is the percentage of DC-IR after 30 days relative to the initial DC-IR.

[0249] [Table 3]

[0250]

[0251] In Table 2, 0d, 10d, 20d and 30d represent 0 day, 10 days, 20 days and 30 days, respectively.

[0252] As shown in Table 2 and Figure 2A It is shown that the lithium secondary batteries of Examples 1 to 6 using Compound A or Compound E as an electrolyte additive have a small resistance increase rate during high-temperature storage, compared with Comparative Example 1 in which no electrolyte additive is used, and thus high-temperature storage characteristics are improved.

[0253] In addition, if Figure 2B It is shown that, compared with Comparative Manufacturing Examples 2 and 3, the lithium secondary battery of Manufacturing Example 3 has a reduced resistance increase rate during high-temperature storage.

[0254] Evaluation Example 3: High temperature (45°C) life characteristics

[0255] In the lithium secondary batteries manufactured according to Manufacturing Examples 1 to 6 and Comparative Manufacturing Examples 1 to 3, the lithium secondary batteries undergoing formation operation were charged at a CC rate of 0.33C at a temperature of 45°C until the voltage reached 4.2V (relative to Li), and then, in CV mode, while maintaining 4.2V, the charging was cut off at a current rate of 0.05C. Subsequently, the lithium secondary batteries were discharged at a CC rate of 1.0C during discharge until the voltage reached 2.5V (relative to Li). This charge / discharge cycle was repeated 300 times.

[0256] After each charge / discharge cycle, the lithium battery was left to rest for 10 minutes. Figure 3A , Figure 3B , Figure 4B and Figure 4B Here, the capacity retention rate at the 300th cycle is defined by the following Equation 2. Figure 3A and Figure 3B shows the change in discharge capacity of each lithium secondary battery according to the number of cycles, and Figure 4A and Figure 4B Changes in the capacity retention rate of each lithium secondary battery according to the number of cycles are shown.

[0257] Equation 2

[0258] Capacity retention rate (%) = [discharge capacity at the 300th cycle / discharge capacity at the first cycle] × 100

[0259] like Figure 3A and Figure 4A As shown in the figure, it can be seen that the high temperature life characteristics are improved in the lithium secondary batteries of Manufacturing Examples 1 to Manufacturing Examples 6 using the electrolyte solutions including the additives for the electrolyte solutions of Examples 1 to 6, compared with the case of Comparative Manufacturing Example 1 using the electrolyte solution not including the additive for the electrolyte solution.

[0260] In some embodiments, Figure 3B and Figure 4B As shown in FIG. 2 , it can be seen that the high temperature characteristics are improved in the lithium secondary battery of Manufacturing Example 3 compared with the lithium secondary batteries of Comparative Manufacturing Examples 2 and 3.

[0261] The electrolyte for a lithium secondary battery according to one or more embodiments is oxidatively decomposed during formation to form a CEI film on the positive electrode, thereby protecting the positive electrode and suppressing the increase in battery voltage to suppress electrolyte decomposition. Therefore, when using such an electrolyte, the positive electrode can be protected to provide a lithium secondary battery with improved safety, improved life characteristics at high temperatures, and improved safety during high temperature stability.

[0262] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for limiting purposes. The description of the features or aspects in each embodiment should generally be considered to be applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it will be understood by those of ordinary skill in the art that one or more appropriate changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the claims and their equivalents.

[0263] Terms such as "substantially", "about" and "approximately" are used as relative terms, not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. They may include the stated value and a range of acceptable deviations determined by one of ordinary skill in the art taking into account the limitations and errors associated with a certain amount of measurement. For example, "about" may refer to one or more standard deviations, or ±30%, ±20%, ±10%, ±5% of the stated value.

[0264] The numerical ranges disclosed herein include and are intended to disclose all subranges of the same numerical precision. For example, a range of "1.0 to 10.0" includes all subranges (such as, for example, 2.4 to 7.6) having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0. Therefore, the applicant reserves the right to amend this specification (including the claims) to explicitly set forth any subrange within the range explicitly set forth herein.

[0265] Although one or more embodiments have been described with reference to the accompanying drawings and examples, the description is only illustrative, and those skilled in the art will appreciate that various modifications and other equivalent embodiments may be made therefrom. Therefore, the scope of protection of the present disclosure should be defined by the claims.

Claims

1. An electrolyte for a lithium secondary battery, the electrolyte include: Lithium salts; Organic solvents; and An additive represented by Formula 1 or Formula 2: Formula 1 Wherein, in Formula 1, A is -[C(R 5 )(R 6 )]m-,R 1 ~R 6 are each independently hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n is an integer of 1 or 2, and m is an integer of 1 to 3, and Formula 2 Wherein, in Formula 2, A is -[C(R 5 )(R 6 )]m-,R 1 ~R 6 Each is independently hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, n is an integer of 1 or 2, and m is an integer of 1-3.

2. The electrolyte according to claim 1, wherein the additive represented by Formula 1 or Formula 2 is an additive represented by Formula 3, Formula 3-1, Formula 3-2, Formula 3-3, Formula 4, Formula 4-1, Formula 4-2 or Formula 4-3: Formula 3 in, In formula 3, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 3-1 Among them, in formula 3-1, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 3-2 Among them, in formula 3-2, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 3-3 Among them, in formula 3-3, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 4 Among them, in formula 4, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 4-1 Among them, in formula 4-1, R 1 ~R 4 each independently represents hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl, Formula 4-2 Among them, in formula 4-2, R 1 ~R 4 are each independently hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl, or substituted or unsubstituted C6-C50 heteroaryl, and Formula 4-3 Among them, in formula 4-3, R 1 ~R 4 Each is independently hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C3-C10 alkynyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C6-C50 aryl, substituted or unsubstituted C7-C50 alkaryl or substituted or unsubstituted C6-C50 heteroaryl.

3. The electrolyte according to claim 1, wherein the additive is at least one selected from Compound A to Compound H: 4 . The electrolyte according to claim 1 , wherein the amount of the additive is in the range of about 0.1 wt % to about 10 wt % relative to the total weight of the electrolyte. 5 . The electrolyte according to claim 1 , wherein the concentration of the lithium salt is about 0.1 M to about 5.0 M.

6. The electrolyte according to claim 1, wherein the lithium salt comprises a salt selected from LiPF 6 , LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiCF 3 SO 3 、Li(CF 3 SO 2 ) 2 N、Li(FSO 2 ) 2 N、LiC 4 F 9 SO 3 、LiAlO 2 、LiAlCl 4 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )、LiCl、LiI、LiBOB、LiPO 2 F 2 and at least one of the compounds represented by Formula 5 to Formula 8, wherein 2≤x≤20 and 2≤y≤20: Formula 5 Formula 6 Formula 7 Formula 8.

7. The electrolyte according to claim 1, wherein the organic solvent comprises at least one selected from the group consisting 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 and tetrahydrofuran.

8. A lithium secondary battery, include: a positive electrode, including a positive electrode active material; a negative electrode, including a negative electrode active material; and The electrolyte according to any one of claims 1 to 7 is between the positive electrode and the negative electrode.

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