KR20220136783A - Additives for non-aqueous electrolyte, non-aqueous electrolyte comprising the same and lithium secondary battery - Google Patents

Abstract

The present invention relates to an additive for a non-aqueous electrolyte including a sultone-based compound represented by chemical formula 1 capable of improving the lifespan of a lithium secondary battery by forming an electrode-electrolyte interface that is stable even at high temperatures and has low resistance, a non-aqueous electrolyte including the same, and a lithium secondary battery.

Description

Additive for non-aqueous electrolyte, non-aqueous electrolyte and lithium secondary battery containing same

The present invention relates to an additive for a non-aqueous electrolyte containing a sultone-based compound, a non-aqueous electrolyte for a lithium secondary battery comprising the same, and a lithium secondary battery.

Recently, as personal IT devices and computer networks are developed due to the development of the information society, and the overall society's dependence on electric energy increases accordingly, the development of battery technology for efficiently storing and utilizing electric energy is required.

In particular, as interest in solving environmental problems and realization of a sustainable circulating society has emerged, research on power storage devices such as lithium ion batteries and electric double layer capacitors has been extensively conducted.

In particular, lithium ion batteries are in the spotlight as a battery system with the highest theoretical energy density among battery technologies.

The lithium ion battery is largely composed of a positive electrode composed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte serving as a medium for transferring lithium ions, and a separator, and the dual electrolyte is the stability of the battery. , safety), etc., as it is known as a component that has a great influence on it, many studies are being conducted on it.

On the other hand, in a lithium secondary battery, as the charging and discharging proceeds, the positive electrode active material structurally collapses due to the decomposition products of lithium salts contained in the electrolyte, and the positive electrode performance may be deteriorated. This can be eluted. The eluted transition metal ions are electro-deposited on the anode or cathode, increasing the anode resistance, degrading the cathode, and destroying the solid electrolyte interphase (SEI), resulting in additional electrolyte decomposition and battery resistance. increase and deterioration of service life.

This deterioration of battery performance tends to be accelerated when the potential of the positive electrode increases or the battery is exposed to high temperatures.

Accordingly, there is an urgent need to study an electrolyte capable of forming a stable SEI film on the electrode surface in order to suppress the elution of transition metal ions from the anode or to prevent deterioration of the cathode.

Japanese Laid-Open Patent Publication No. 2016-0066481 Korean Patent Publication No. 2020-0090223

An object of the present invention is to provide an additive for a non-aqueous electrolyte including a sultone-based additive capable of forming a film that is stable even at high temperatures and has low resistance on the electrode surface.

In addition, the present invention is to provide a non-aqueous electrolyte for a lithium secondary battery comprising the additive for a non-aqueous electrolyte.

In addition, the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte for the lithium secondary battery.

In order to achieve the above object, the present invention

There is provided an additive for a non-aqueous electrolyte comprising a compound represented by the following formula (1).

[Formula 1]

In Formula 1,

Ak ₁ is a direct bond or an alkylene group having 1 to 10 carbon atoms,

Ak ₂ is -R1-OC(=O)-O-R2 (wherein R1 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R2 is an alkyl group having 1 to 5 carbon atoms) or -(R3) _o - R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R4 is a cyclic carbonate group having 2 to 10 carbon atoms, and o is an integer of 0 or 1).

In addition, the present invention provides a non-aqueous electrolyte for a lithium secondary battery comprising the additive for a non-aqueous electrolyte.

In addition, the present invention provides a lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery.

Since the compound represented by Formula 1 of the present invention includes a carbonate group such as a carbonate-based organic solvent used as an electrolyte solvent as a terminal group, a stable and low resistance increase rate can be formed on the electrode surface. Therefore, the non-aqueous electrolyte containing the same can form a stable SEI film on the surface of the anode and at the same time form an electrode-electrolyte interface with low resistance, and form a stable film on the surface of the anode to effectively control the elution of transition metals from the anode. As a result, a lithium secondary battery capable of reducing battery swelling while having excellent high-temperature storage characteristics and high-temperature cycle characteristics can be implemented. The non-aqueous electrolyte of the present invention may be particularly usefully used in a high-output battery used together with a high-capacity active material such as a high-nickel-based positive electrode active material.

Hereinafter, the present invention will be described in more detail.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

In addition, the terminology used herein is used only to describe exemplary embodiments, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

Prior to describing the present invention, in this specification, terms such as "comprises", "comprises" or "have" are not intended to designate the existence of embodied features, numbers, steps, components, or combinations thereof. , it should be understood that it does not preclude the possibility of addition or existence of one or more other features or numbers, steps, elements, or combinations thereof.

Meanwhile, in the description of "carbon number a to b" in the present specification, "a" and "b" mean the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms. For example, an "alkylene group having 1 to 5 carbon atoms" is an alkylene group containing 1 to 5 carbon atoms, that is, -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, - CH ₂ (CH ₃ )CH—, —CH(CH ₃ )CH ₂ — and —CH(CH ₃ )CH ₂ CH ₂ — and the like.

The term "alkylene group" refers to a branched or unbranched divalent unsaturated hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a tert-butylene group, a pentylene group, a 3-pentylene group, and the like.

In addition, in the present specification, unless otherwise defined, "substitution" means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, for example, an alkyl group having 1 to 6 carbon atoms or fluorine. means replaced.

Additives for non-aqueous electrolytes

The additive for a non-aqueous electrolyte according to an embodiment of the present invention includes a compound represented by the following formula (1).

When the compound represented by the following Chemical Formula 1 is used as an additive for a non-aqueous electrolyte, a strong SEI layer having low resistance is formed, thereby providing a lithium secondary battery having excellent high-temperature capacity characteristics and cycle characteristics.

[Formula 1]

In Formula 1,

Ak ₁ is a direct bond or an alkylene group having 1 to 10 carbon atoms,

Ak ₂ is -R1-OC(=O)-O-R2 (wherein R1 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R2 is an alkyl group having 1 to 5 carbon atoms) or -(R3) _o - R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R4 is a cyclic carbonate group having 2 to 10 carbon atoms, and o is an integer of 0 or 1), n and m are each 1 or It is an integer of 2.

In Formula 1, Ak ₁ is an alkylene group having 1 to 7 carbon atoms, Ak ₂ is -R1-OC(=O)-O-R2 (R1 is a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R2 is an alkyl group having 1 to 4 carbon atoms) or -(R3) _o -R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R4 is a cyclic carbonate group having 2 to 8 carbon atoms, o is It is an integer of 1).

Specifically, in Formula 1, Ak ₁ is an alkylene group having 1 to 4 carbon atoms, Ak ₂ is -R1-OC(=O)-O-R2 (R1 is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms) and R2 is an alkyl group having 1 to 3 carbon atoms) or -(R3) _o -R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, R4 is a cyclic carbonate group having 2 to 6 carbon atoms, and , o is an integer of 1).

More specifically, the compound represented by Formula 1 may include at least one of compounds represented by Formulas 1-1 to 1-19 below.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

[Formula 1-10]

[Formula 1-11]

[Formula 1-12]

[Formula 1-13]

[Formula 1-14]

[Formula 1-15]

[Formula 1-16]

[Formula 1-17]

[Formula 1-18]

[Formula 1-19]

According to an embodiment of the present invention, the compound represented by Formula 1 has at least one sulfate group or a sulfite group in the molecule and is reduced faster than the organic solvent, which is the main component of the electrolyte, so that a solid SEI is formed before side reactions occur. can do. In addition, the compound represented by Chemical Formula 1 includes a carbonate group in the terminal group (Ak2) structure, so that it coordinates with lithium ions like carbonate-based materials used as electrolyte solvents to help form actually movable soluble ions. In addition, it is possible to form a film having low resistance and stable at high temperature on the surface of the anode and the cathode. Therefore, since the increase in interfacial resistance is minimized and the electrode surface is prevented from being exposed, side reactions between the electrode and the electrolyte can be suppressed, so that the generation of gases such as O ₂ and the elution of transition metals from the anode can be effectively controlled. As a result, it is possible to implement a lithium secondary battery having improved high-temperature storage characteristics and high-temperature cycle characteristics.

In particular, in the case of 1,3-propane sultone (PS), which is a conventional commercial additive, its use is limited due to toxicity, whereas the additive of the present invention is non-toxic, unlike 1,3-propane sultone, and is easy to synthesize, and By including a carbonate substituent in the short term, it is possible to form a film having a strong lithium salt conductivity and a high conductivity on the surface of the positive electrode and the negative electrode.

On the other hand, the reduction stability of the compound of the present invention is evaluated by the following method using the Gaussian 09 program package (Gaussian 09 Revision C.01, Gaussian Inc., Wallingford, CT, 2009) to which the DFT calculation method is applied. After calculating the stable structural energy of the compound in the state before reduction (E _neut ) and the stable structural energy of the compound in the reduced state (E _red ), E _neut - E _red -1.45 eV is defined as reduction stability. At this time, the structural stabilization calculation is performed in the state that the PCM (Polarizable Continuum Model) method is applied.

Non-aqueous electrolyte for lithium secondary battery

In addition, the non-aqueous electrolyte according to an embodiment of the present invention includes an additive for a non-aqueous electrolyte including the compound represented by Formula 1 above.

The non-aqueous electrolyte may further include a lithium salt, an organic solvent, and other electrolyte additives.

(1) Additives for non-aqueous electrolytes

Since the description of the compound represented by Formula 1 overlaps with the above description, the description thereof will be omitted.

Meanwhile, according to an embodiment of the present invention, the additive for the non-aqueous electrolyte may be included in an amount of 0.01 wt % to 10 wt %, more specifically 0.1 wt % to 10 wt %, based on the total weight of the non-aqueous electrolyte.

When the content of the additive for non-aqueous electrolyte satisfies the above range, a stable film can be formed to effectively suppress metal elution of the positive electrode active material at a high temperature, and excellent high temperature durability can be realized. That is, when the additive for the non-aqueous electrolyte is included in the non-aqueous electrolyte in an amount of 0.01 wt % or more, the film formation effect is improved and a stable SEI film is formed even when stored at a high temperature. can be improved In addition, when the additive for the non-aqueous electrolyte is included in an amount of 10 wt % or less, an excessively thick film is prevented from being formed during initial charging to prevent an increase in resistance, thereby preventing a decrease in initial capacity and output characteristics of the secondary battery.

(2) lithium salt

The lithium salt may be used without limitation those commonly used in electrolytes for lithium secondary batteries, for example, including Li ⁺ as a cation, F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , B ₁₀ Cl ₁₀ ^- , AlCl ₄ ^- , AlO ₄ ^- , PF ₆ ^- , CF ₃ SO ₃ ^- , CH ₃ CO ₂ ^- , CF ₃ CO ₂ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , BF ₂ C ₂ O ₄ ^- , BC ₄ O ₈ ^- , PF ₄ C ₂ O ₄ ^- , PF ₂ C ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- and SCN ^- may be at least one selected from the group consisting of.

Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO ₂ F) ₂ ), LiBETI (lithium bis(pentafluoroethanesulfonyl) imide, LiN(SO ₂ CF ₂ CF ₃ ) ₂ and LiTFSI (lithium) It may include a single substance or a mixture of two or more selected from the group consisting of bis(trifluoromethanesulfonyl) imide, LiN(SO ₂ CF ₃ ) ₂ ) In addition to these, lithium salts commonly used in electrolytes of lithium secondary batteries can be used without limitation. can

The lithium salt may be appropriately changed within the range that can be used in general, but to be included in the electrolyte at a concentration of 0.8 M to 3.0 M, specifically, at a concentration of 1.0M to 3.0M, in order to obtain an optimal effect of forming a film for preventing corrosion of the electrode surface. can

When the concentration of the lithium salt is less than 0.8 M, the mobility of lithium ions may decrease, and thus capacity characteristics may be deteriorated. When the concentration of the lithium salt exceeds the concentration of 3.0 M, the viscosity of the non-aqueous electrolyte may excessively increase, so that the electrolyte impregnation property may be deteriorated, and the film formation effect may be reduced.

(3) organic solvents

As the organic solvent, various organic solvents commonly used in lithium electrolytes can be used without limitation, and specifically, decomposition by oxidation reaction during the charging and discharging process of secondary batteries can be minimized, and desired properties can be exhibited together with additives. As long as it is possible, there is no limit to its type.

For example, the organic solvent may use a high-viscosity cyclic carbonate-based organic solvent that easily dissociates lithium salts in the electrolyte due to its high dielectric constant. In addition, the organic solvent may be used by mixing a linear carbonate-based organic solvent in an appropriate ratio with the environmental carbonate-based organic solvent in order to prepare an electrolyte having a higher electrical conductivity.

The cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can well dissociate lithium salts in the electrolyte, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene. At least one organic solvent selected from the group consisting of carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, among them, ethylene carbonate may include.

In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and representative examples thereof include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate ( EMC), at least one organic solvent selected from the group consisting of methyl propyl carbonate and ethyl propyl carbonate may be used, and specifically, ethyl methyl carbonate (EMC) may be included.

The organic solvent may be used by mixing the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent, wherein the cyclic carbonate-based organic solvent: the linear carbonate-based organic solvent is 10:90 to 70:30 by volume, specifically 50:50 It can be used by mixing in a volume ratio of 70:30.

In addition, the organic solvent may further include a linear ester-based organic solvent and/or a cyclic ester-based organic solvent in the cyclic carbonate-based organic solvent and/or the linear carbonate-based organic solvent in order to prepare an electrolyte having high ionic conductivity. may be

Specific examples of the linear ester-based organic solvent include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate. can be heard

In addition, the cyclic ester-based organic solvent is a specific example of at least one compound selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone Can be used.

Meanwhile, the remainder of the non-aqueous electrolyte of the present invention except for the organic solvent, for example, additives for non-aqueous electrolytes, lithium salts and other additives may be all organic solvents unless otherwise stated.

(4) other additives

On the other hand, the non-aqueous electrolyte according to an embodiment of the present invention is used together with the additive for the non-aqueous electrolyte to form a stable film on the surface of the anode and the anode without significantly increasing the initial resistance along with the effect expressed by the additive, It may further include other additives capable of inhibiting the decomposition of the solvent in the non-aqueous electrolyte and serving as a complement to improve the mobility of lithium ions.

These other additives are not particularly limited as long as they are additives capable of forming a stable film on the surfaces of the positive and negative electrodes.

Specifically, the other additives may include at least one additive selected from the group consisting of a halogen-substituted carbonate-based compound, a nitrile-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a lithium salt-based compound as a representative example thereof. have.

Specifically, the halogen-substituted carbonate-based compound may include fluoroethylene carbonate (FEC), and may be included in an amount of 5 wt% or less based on the total weight of the non-aqueous electrolyte. When the content of the halogen-substituted carbonate-based compound exceeds 5% by weight, cell swelling performance may be deteriorated.

In addition, the nitrile-based compound is succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, From the group consisting of 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile at least one or more compounds selected.

In this case, when the nitrile-based compound is used together with the above-described mixed additive, effects such as improvement of high temperature characteristics can be expected by stabilizing the anode/cathode film. That is, it can serve as a complement in forming the anode SEI film, inhibit the decomposition of the solvent in the electrolyte, and serve to improve the mobility of lithium ions. The nitrile-based compound may be included in an amount of 8 wt% or less based on the total weight of the non-aqueous electrolyte. When the total content of the nitrile-based compound in the non-aqueous electrolyte exceeds 8 wt %, resistance increases due to an increase in a film formed on the surface of the electrode, and battery performance may deteriorate.

The cyclic carbonate-based compound forms a stable SEI film mainly on the surface of the anode when the battery is activated, thereby improving the durability of the battery. The cyclic carbonate-based compound may include vinylene carbonate (VC) or vinylethylene carbonate, and may be included in an amount of 3 wt% or less based on the total weight of the non-aqueous electrolyte. When the content of the cyclic carbonate-based compound in the non-aqueous electrolyte exceeds 3% by weight, cell swelling inhibition performance and initial resistance may deteriorate.

In addition, since the phosphate-based compound stabilizes PF ₆ anions in the electrolyte and helps to form positive and negative electrode films, durability of the battery may be improved. These phosphate-based compounds include lithium difluoro (bisoxalato) phosphate (LiDFOP), LiDFP (LiPO ₂ F ₂ ), tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, tris(2,2,2). and at least one compound selected from the group consisting of -trifluoroethyl) phosphate and tris(trifluoroethyl) phosphite, and may be included in an amount of 3 wt% or less based on the total weight of the non-aqueous electrolyte.

The borate compound promotes ion pair separation of lithium salts, can improve the mobility of lithium ions, can reduce the interfacial resistance of the SEI film, and materials such as LiF that are generated during battery reaction and are not easily separated By dissociating, problems such as generation of hydrofluoric acid gas can be solved. The borate-based compound may include lithium dioxalyl borate (LiBOB, LiB(C ₂ O ₄ ) ₂ ), lithium oxalyldifluoroborate, or tetramethyl trimethylsilylborate (TMSB), based on the total weight of the non-aqueous electrolyte. It may be included in an amount of 3% by weight or less.

In addition, the lithium salt-based compound is a compound different from the lithium salt included in the non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiODFB and LiBF ₄ , and 3% by weight or less based on the total weight of the non-aqueous electrolyte. may include

The other additives may be used in a mixture of two or more, and may be included in an amount of 10% by weight or less, specifically 0.01% to 10% by weight, preferably 0.1 to 5.0% by weight based on the total amount of the electrolyte.

When the content of the other additives is less than 0.01% by weight, the high temperature storage characteristics and gas reduction effect to be realized from the additives are insignificant, and when the content of the other additives exceeds 10% by weight, side reactions in the electrolyte during charging and discharging of the battery are excessive is likely to occur. In particular, when the other additives are added in excess, they may not be sufficiently decomposed and may exist as unreacted or precipitated substances in the electrolyte at room temperature. Accordingly, resistance may be increased, and thus lifespan characteristics of the secondary battery may be deteriorated.

lithium secondary battery

Next, a lithium secondary battery according to the present invention will be described.

The lithium secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to the present invention. Since the non-aqueous electrolyte has been described above, a description thereof will be omitted, and other components will be described below.

(1) Anode

The positive electrode according to the present invention may include a positive electrode active material layer including a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive material and/or a binder.

The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide including lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. have. More specifically, the lithium composite metal oxide may include a lithium-nickel-manganese-cobalt-based oxide represented by the following Chemical Formula 2 in that it can increase the capacity characteristics and stability of the battery.

[Formula 2]

Li(Ni _x Co _y Mn _z )O ₂

(In Formula 2, 0<x<1, 0<y<1, 0<z<1, x+y+z=1)

Specifically, the lithium composite metal oxide may be a lithium composite transition metal oxide having a nickel content of 50 atm% or more, preferably 70 atm% or more in the transition metal, a representative example of which is Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.2 Co _0.3 )O ₂ , Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ .

In addition to the lithium-nickel-manganese-cobalt-based oxide, the cathode active material includes a lithium-manganese-based oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), a lithium-cobalt-based oxide (eg, LiCoO ₂ , etc.), Lithium-nickel-based oxide (eg, LiNiO ₂ , etc.), lithium-nickel-manganese oxide (eg, LiNi _1-Y Mn _Y O ₂ (where 0<Y<1), LiMn _2-z Ni _z O ₄ (here, 0<Z<2), etc.), lithium-nickel-cobalt-based oxide (for example, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), Lithium-manganese-cobalt oxide (for example, LiCo _1-Y2 Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (here, 0<Z1<2), etc.) ), or lithium-nickel-cobalt-transition metal (M) oxide (eg, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ , where M is Al, Fe, V, Cr, Ti, Ta , Mg and Mo, p2, q2, r3 and s2 are each independent atomic fractions of elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s 2 < 1, p2+q2+r3+s2=1)) and the like, and any one or two or more compounds of these may be included.

Such a positive active material may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , or lithium nickel cobalt aluminum oxide (eg, Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ , etc.).

The positive active material may be included in an amount of 90 wt% to 99 wt%, specifically 93 wt% to 98 wt%, based on the total weight of the solid content in the cathode active material layer.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black. carbon powder; Graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode active material layer.

The binder is a component serving to improve adhesion between the positive active material particles and adhesion between the positive active material and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive active material layer. Examples of the binder include a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); Styrene-butadiene rubber (styrene butadiene rubber, SBR), acrylonitrile-butadiene rubber, styrene-rubber-based binder including isoprene rubber; Cellulose binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester binder; and silane-based binders.

The positive electrode of the present invention as described above may be manufactured according to a method for manufacturing a positive electrode known in the art. For example, in the positive electrode, a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder and/or a conductive material in a solvent is applied on a positive electrode current collector, followed by drying and rolling to form a positive electrode active material layer; Alternatively, the positive electrode active material layer may be cast on a separate support, and then a film obtained by peeling the support may be prepared by laminating on a positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver or the like surface-treated may be used.

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount having a desirable viscosity when the positive active material and optionally a binder and a conductive material are included. For example, it may be included so that the solid content concentration in the active material slurry including the positive active material and, optionally, the binder and the conductive material is 10 wt% to 70 wt%, preferably 20 wt% to 60 wt%.

(2) cathode

Next, the cathode will be described.

The negative electrode according to the present invention includes an anode active material layer including an anode active material, and the anode active material layer may further include a conductive material and/or a binder, if necessary.

The negative active material is lithium metal, a carbon material capable of reversibly intercalating/deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium; and at least one selected from the group consisting of transition metal oxides and transition metal oxides.

As a carbon material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based negative active material generally used in lithium ion secondary batteries may be used without particular limitation, and representative examples thereof include crystalline carbon, Amorphous carbon or these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low temperature calcined carbon). or hard carbon, mesophase pitch carbide, and calcined coke.

Examples of the above metals or alloys of these metals and lithium include Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al. And a metal selected from the group consisting of Sn or an alloy of these metals and lithium may be used.

Examples of the metal composite oxide include PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ . , Bi ₂ O ₅ , Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), and Sn _x Me _1-x Me′ _y O _z (Me: Mn, Fe , Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3; 1≤z≤8) One selected from the group may be used.

Examples of the material capable of doping and dedoping lithium include Si, SiO _x (0<x≤2), Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, An element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth) It is an element selected from the group consisting of elements and combinations thereof, and is not Sn) and the like. Also, at least one of these and SiO ₂ may be mixed and used. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh , Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi , S, Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

The anode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the solid content in the anode active material layer.

The conductive material is a component for further improving the conductivity of the anode active material, and may be added in an amount of 1 to 20 wt% based on the total weight of the solid content in the anode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the negative active material layer. Examples of the binder include a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); Styrene-butadiene rubber (styrene butadiene rubber, SBR), acrylonitrile-butadiene rubber, styrene-rubber-based binder including isoprene rubber; Cellulose binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester binder; and silane-based binders.

The negative electrode may be manufactured according to a method for manufacturing a negative electrode known in the art. For example, the negative electrode is a method of forming a negative electrode active material layer by applying a negative electrode active material slurry prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent on the negative electrode current collector, rolling and drying the negative electrode active material layer, or It can be prepared by casting the anode active material layer on a separate support and then laminating a film obtained by peeling the support on the anode current collector.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. The surface treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

The solvent may include water or an organic solvent such as NMP, alcohol, or the like, and may be used in an amount to achieve a desirable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, it may be included so that the concentration of solids in the active material slurry including the negative active material and, optionally, the binder and the conductive material is 50 wt% to 75 wt%, preferably 50 wt% to 65 wt%.

(3) separator

The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

The separator separates the anode and the cathode and provides a passage for lithium ions to move, and can be used without any particular limitation as long as it is normally used as a separator in a lithium secondary battery. It is preferable that this is excellent.

Specifically, as a separator, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. Alternatively, a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

The lithium secondary battery according to the present invention as described above can be usefully used in portable devices such as mobile phones, notebook computers, digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack is a power tool (Power Tool); electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a system for power storage.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source for a small device, but can also be preferably used as a unit cell in a medium or large battery module including a plurality of battery cells.

Hereinafter, the present invention will be described in detail by way of Examples.

At this time, the embodiment according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiment described in detail below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example

Synthesis Example 1. Synthesis of a compound represented by Formula 1-2

After placing the round bottom flask in an ice bath, dimethyl carbonate (manufactured by Aldrich) 33 g, thionyl chloride (manufactured by Aldrich) 8.3 g, pyridine (manufactured by Aldrich) 6.0 g, 5-(hydroxyl) 10.0 g of methyl)-1,2-oxathiolane-2,2-dioxide (5-(hydroxymethyl)-1,2-oxathiolane-2,2-dioxide was sequentially added dropwise, followed by stirring at room temperature for 1 hour. .

Then, 6.6 g of 2-hydroxyethyl methyl carbonate (manufactured by Aldrich) and 6.0 g of pyridine (manufactured by Aldrich) were slowly added dropwise, followed by stirring at room temperature for 1 hour.

The reaction solution was extracted using water and dimethyl carbonate, and then the organic layer was distilled under reduced pressure to obtain 13 g of the compound represented by Chemical Formula 1-2 (yield: 63%). In order to confirm the synthesis result of the compound represented by Formula 1-2, the mass was measured using an MS analyzer, and then the measured value is shown below.

The MS analyzer used Thermo's LTZ mass spectrometry, the ionization mode was APCI positive, and the Capcellpak C18 column was maintained at a temperature of 45° C., and a mixed solvent of acetonitrile and water was used as a developing solution.

MS (m/z): [M+H] ⁺ = 319

Synthesis Example 2. Synthesis of the compound represented by Formula 1-1

After placing the round bottom flask in an ice bath, 16.0 g of the compound of Formula 1-2 obtained in Synthesis Example 1, water and acetonitrile in a 1:1 weight ratio were mixed in a round bottom flask in a mixed solvent 200 g, sodium periodate (manufactured by Aldrich) 18.0 g and ruthenium (III) chloride (manufactured by Aldrich) 0.15 g were added, followed by stirring in an ice bath for 1 hour.

Then, the obtained compound was purified by column to obtain 9.2 g of 2,2-dioxido-1,2-oxathiolan-5-yl)methyl (2,2,2-trifluroethyl) sulfate represented by Formula 1-1 (yield: 42%) got

In order to confirm the synthesis result of the compound represented by Formula 1-1, the mass was measured using an MS analyzer, and then the measured value is shown below.

MS (m/z): [M+H] ⁺ = 335

Synthesis Example 3. Synthesis of a compound represented by Formula 1-4

In Synthesis Example 1, 14 g of a compound represented by Formula 1-4 (yield: 67%) was obtained in the same manner as in Synthesis Example 1, except that 2-hydroxyethyl propyl carbonate was added instead of 2-hydroxyethyl methyl carbonate. In order to confirm the synthesis result of the compound represented by Formula 1-4, the mass was measured using an MS analyzer, and then the measured value is shown below.

MS (m/z): [M+H] ⁺ = 333

Synthesis Example 4. Synthesis of a compound represented by Formula 1-5

In the same manner as in Synthesis Example 2, except that the compound represented by Formula 1-4 obtained in Synthesis Example 3 was added instead of the compound of Formula 1-2 obtained in Synthesis Example 1, the compound represented by Formula 1-5 Compound 9.2g (yield: 39%) was obtained.

In order to confirm the synthesis result of the compound represented by Formula 1-5, the mass was measured using an MS analyzer, and then the measured value is shown below.

MS (m/z): [M+H] ⁺ = 363

Synthesis Example 5. Synthesis of the compound represented by Formula 1-14

In Synthesis Example 1, in the same manner as in Synthesis Example 1, except that 4-(hydroxymethyl)-5-methyl-1,3-dioxolan-2-one was added instead of 4-hydroxyethyl methyl carbonate, the formula 1-14 was 11.5 g of the indicated compound (yield: 53%) was obtained. In order to confirm the synthesis result of the compound represented by Formula 1-14, the mass was measured using an MS analyzer, and then the measured value is shown below.

MS (m/z): [M+H] ⁺ = 331

Synthesis Example 6. Synthesis of the compound represented by Formula 1-11

In Synthesis Example 1, it was synthesized in the same manner as in Synthesis Example 1, except that 4-(hydroxyethyl)-5-methyl-1,3-dioxolan-2-one was added instead of 2-hydroxyethyl methyl carbonate. The oxidation reaction was carried out in the manner of Example 2 to obtain 10.2 g (yield: 47%) of the compound represented by Formula 1-11.

In order to confirm the synthesis result of the compound represented by Formula 1-11, the mass was measured using an MS analyzer, and then the measured value is shown below.

MS (m/z): [M+H] ⁺ 333

Example

Example 1.

(Manufacture of non-aqueous electrolyte)

Ethylene carbonate (EC): ethyl methyl carbonate (EMC) was dissolved in 99 g of a non-aqueous organic solvent mixed in a volume ratio of 30:70 so that LiPF ₆ was 1.0M, and 1.0 g of the compound represented by Formula 1-1 was added as an additive. to prepare a non-aqueous electrolyte (see Table 1 below).

(anode manufacturing)

The positive active material (Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ ), the conductive material (carbon black), and the binder (polyvinylidene fluoride) are mixed with a solvent in a weight ratio of 97.5:1:1.5 by weight of N-methyl-2-pyrroly It was added to Don (NMP) to prepare a positive electrode active material slurry (solid content concentration of 60% by weight). The positive electrode active material slurry was applied and dried on a positive electrode current collector (Al thin film) having a thickness of 15 μm, and then a roll press was performed to prepare a positive electrode.

(cathode manufacturing)

A negative active material slurry (solids concentration of 50% by weight) was prepared by adding a negative active material (graphite), a conductive material (carbon black), and a binder (polyvinylidene fluoride) to distilled water in a weight ratio of 96:0.5:3.5. The negative electrode active material slurry was applied and dried on a negative electrode current collector (Cu thin film) having a thickness of 8 μm, and then a roll press was performed to prepare a negative electrode.

(Secondary battery manufacturing)

The positive electrode and the negative electrode prepared by the above method were laminated together with a polyethylene porous film as a separator to prepare an electrode assembly, and then put it in a battery case, inject the non-aqueous electrolyte, and seal the pouch-type lithium secondary battery (battery capacity 6.24 mAh). ) was prepared.

Example 2.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 99 g of a non-aqueous organic solvent to 1.0 M, and then adding 1.0 g of a compound represented by Formula 1-5 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Example 3.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 97 g of a non-aqueous organic solvent so as to become 1.0 M, and then adding 3.0 g of the compound represented by Formula 1-1 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Example 4.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 97 g of a non-aqueous organic solvent so that it becomes 1.0 M, and then adding 3.0 g of a compound represented by Formula 1-11 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Example 5.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 99 g of a non-aqueous organic solvent so as to become 1.0 M, and then adding 1.0 g of a compound represented by Formula 1-2 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Example 6.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 99 g of a non-aqueous organic solvent so as to become 1.0 M, and then adding 1.0 g of a compound represented by Formula 1-4 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Example 7.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 99 g of a non-aqueous organic solvent so as to become 1.0 M, and then adding 1.0 g of a compound represented by Formula 1-14 as an additive (see Table 1 below), the above Example A pouch-type lithium secondary battery was manufactured in the same manner as in 1 .

Comparative Example 1.

A lithium secondary battery was prepared in the same manner as in Example 1, except that LiPF ₆ was dissolved in 100 g of a non-aqueous organic solvent so as to become 1.0 M, and a non-aqueous electrolyte was prepared without adding an additive (see Table 1 below). did.

Comparative Example 2.

Except for preparing a non-aqueous electrolyte by dissolving LiPF ₆ in 99 g of a non-aqueous organic solvent so as to become 1.0 M and adding 1.0 g of 1,3-propane sultone as an additive (see Table 1 below), Example 1 and A lithium secondary battery was manufactured in the same manner.

organic solvent additive composition Addition (g) type Added amount (g) Example 1 0.1M LiPF ₆ EC:EMC= 30:70 99 Formula 1-1 One Example 2 99 Formula 1-5 One Example 3 97 Formula 1-1 3 Example 4 97 Formula 1-11 3 Example 5 99 Formula 1-2 One Example 6 99 Formula 1-4 One Example 7 99 Formula 1-14 One Comparative Example 1 100 - - Comparative Example 2 99 PS One

[Experimental example]

Experimental Example 1. Evaluation of resistance increase rate after storage at high temperature (60° C.)

The secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 and 2 were each activated at 0.1C CC. Then, using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA) at 25°C, it was charged at 0.33C CC up to 4.2V under constant current-constant voltage (CC-CV) charging conditions, followed by a 0.05 C Current cut was performed, and discharged at 0.33 C up to 2.5 V under CC conditions. The charging and discharging were performed as 1 cycle, and 2 cycles were performed. Then, it was fully charged with 0.33 C/4.2V constant current-constant voltage, discharged at SOC 50% at 2.5C for 10 seconds, and the initial resistance was calculated through the voltage difference between the voltage before discharging for 10 seconds and the voltage after discharging for 10 seconds.

Then, it was discharged with a constant current of 0.33 C until it became 2.5V. Then, degassing, charging to 4.2 V, respectively, storing (SOC (state of charge) 100%) at 60°C for 4 weeks, and then discharging again at SOC 50% to 2.5C for 10 seconds, resistance after high-temperature storage was measured.

The resistance increase rate (%) was calculated by substituting the initial resistance value measured as described above and the resistance value after high temperature storage into Equation (2) below, and the results are shown in Table 2 below.

[Equation 2]

Resistance increase rate (%) = {(resistance value after high temperature storage for 4 weeks - initial resistance value)/(initial resistance value)}×100

Resistance increase rate (%) after 4 weeks high temperature storage Example 1 6 Example 2 10 Example 3 15 Example 4 19 Example 5 17 Example 6 13 Example 7 18 Comparative Example 1 45 Comparative Example 2 40

As shown in Table 2, it can be seen that the resistance increase rate of the secondary batteries prepared in Examples 1 to 7 is reduced compared to the secondary batteries prepared in Comparative Examples 1 and 2. This characteristic seems to be due to the use of the compound represented by Chemical Formula 1 as an additive for electrolytes, the SEI film having high stability and low resistance is efficiently formed, and the stability of the secondary batteries of Examples 1 to 7 is increased.

Accordingly, when the non-aqueous electrolyte including the compound represented by Formula 1 according to an embodiment of the present invention is used, a lithium secondary battery having excellent high-temperature storage characteristics can be provided.

Experimental Example 2. Evaluation of cycle characteristics at 45°C (1)

The secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 and 2 were each activated at 0.1C CC. Then, using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA) at 25°C, it was charged at 0.33C CC up to 4.2V under constant current-constant voltage (CC-CV) charging conditions, followed by a 0.05 C Current cut was performed, and discharged at 0.33 C up to 2.5 V under CC conditions. The charging and discharging were performed as 1 cycle, and 2 cycles were performed.

Then, it was discharged with a constant current of 0.33 C until it became 2.5V. Then, degas is performed, and each is charged at a constant current of 0.33 C under a voltage driving range of 2.5 V to 4.2 V at 45 ° C. Charging was terminated. Then, after leaving it for 20 minutes, it was discharged with a constant current of 0.33C until it became 2.5 V. 100 cycles of charging and discharging were performed by making the said charging/discharging cycle 1 cycle.

At this time, the capacity after the first cycle and the capacity after the 100th cycle are measured using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA), and the capacity retention rate is measured by substituting the capacity into the following formula (3) did. The results are shown in Table 3 below.

[Equation 3]

Capacity retention rate (%) = (capacity after 100 cycles/1 cycle capacity)×100

Experimental Example 3. Evaluation of cycle characteristics at 45°C (2)

The secondary batteries prepared in Examples 1 to 7 and the secondary batteries prepared in Comparative Examples 1 and 2 were each activated at 0.1C CC. Then, using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA) at 25°C, it was charged at 0.33C CC up to 4.2V under constant current-constant voltage (CC-CV) charging conditions, followed by a 0.05 C Current cut was performed, and discharged at 0.33 C up to 2.5 V under CC conditions. The charging and discharging were performed as 1 cycle, and 2 cycles were performed. Then, it was fully charged with 0.33 C/4.2V constant current-constant voltage, discharged at SOC 50% at 2.5C for 10 seconds, and the initial resistance was calculated through the voltage difference between the voltage before discharging for 10 seconds and the voltage after discharging for 10 seconds.

Then, it was discharged with a constant current of 0.33 C until it became 2.5V. Then, degas is performed, and each is charged at a constant current of 0.33 C under a voltage driving range of 2.5 V to 4.2 V at 45 ° C. Charging was terminated. Then, after leaving it for 20 minutes, it was discharged with a constant current of 0.33C until it became 2.5 V. 100 cycles of charging and discharging were performed by making the said charging/discharging cycle 1 cycle.

Then, after 100 cycles, the SOC was discharged at 50% at 2.5 C for 10 seconds to calculate the resistance after 100 cycles through the voltage difference between the voltage before discharging for 10 seconds and the voltage after discharging for 10 seconds.

The resistance increase rate was measured by substituting the initial resistance value measured as described above and the resistance value after 100 cycles into Equation (4) below. The results are shown in Table 3 below.

[Equation 4]

Resistance increase rate (%)={(resistance value after 100 cycles - initial resistance value)/initial resistance value}×100

Capacity retention after 100 cycles (%) Resistance increase rate (%) after 100 cycles Example 1 91 10 Example 2 95 15 Example 3 90 12 Example 4 88 9 Example 5 87 11 Example 6 90 9 Example 7 85 15 Comparative Example 1 78 40 Comparative Example 2 85 24

As shown in Table 3, looking at the cycle characteristic evaluation results, it can be seen that the capacity retention rate and/or resistance increase rate of the secondary batteries prepared in Examples 1 to 7 are mostly improved compared to the secondary batteries manufactured in Comparative Examples 1 and 2 . This characteristic seems to be due to the use of the compound represented by Chemical Formula 1 as an additive for electrolytes, the SEI film having high stability and low resistance is efficiently formed, and the stability of the secondary batteries of Examples 1 to 7 is increased.

Accordingly, when the non-aqueous electrolyte including the compound represented by Formula 1 according to an embodiment of the present invention is used, a lithium secondary battery having excellent high-temperature cycle characteristics can be provided.

Claims (10)

An additive for a non-aqueous electrolyte comprising a sultone-based compound represented by the following formula (1):
[Formula 1]

In Formula 1,
Ak ₁ is a direct bond or an alkylene group having 1 to 10 carbon atoms,
Ak ₂ is -R1-OC(=O)-O-R2 (wherein R1 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R2 is an alkyl group having 1 to 5 carbon atoms) or -(R3) _o - R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, R4 is a cyclic carbonate group having 2 to 10 carbon atoms, and o is an integer of 0 or 1), n and m are each 1 or It is an integer of 2.
The method according to claim 1,
In Formula 1, Ak ₁ is an alkylene group having 1 to 7 carbon atoms,
Ak ₂ is -R1-OC(=O)-O-R2 (R1 is a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R2 is an alkyl group having 1 to 4 carbon atoms) or -(R3) _o -R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R4 is a cyclic carbonate group having 2 to 8 carbon atoms, and o is an integer of 1).
The method according to claim 1,
In Formula 1, Ak ₁ is an alkylene group having 1 to 4 carbon atoms,
Ak ₂ is -R1-OC(=O)-O-R2 (R1 is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, R2 is an alkyl group having 1 to 3 carbon atoms) or -(R3) _o -R4 (wherein R3 is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, R4 is a cyclic carbonate group having 2 to 6 carbon atoms, and o is an integer of 1).
The method according to claim 1,
The compound represented by Formula 1 is at least one of the compounds represented by Formulas 1-1 to 1-19 below.
[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

[Formula 1-10]

[Formula 1-11]

[Formula 1-12]

[Formula 1-13]

[Formula 1-14]

[Formula 1-15]

[Formula 1-16]

[Formula 1-17]

[Formula 1-18]

[Formula 1-19]

A non-aqueous electrolyte for a lithium secondary battery comprising the additive for a non-aqueous electrolyte of claim 1.
6. The method of claim 5,
The additive for a non-aqueous electrolyte is a non-aqueous electrolyte for a lithium secondary battery that is included in an amount of 0.01 wt % to 10 wt % based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.
6. The method of claim 5,
The additive for a non-aqueous electrolyte is a non-aqueous electrolyte for a lithium secondary battery that is included in an amount of 0.1 wt % to 10 wt % based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.
6. The method of claim 5,
The non-aqueous electrolyte for a lithium secondary battery further comprises a lithium salt and an organic solvent.
6. The method of claim 5,
The non-aqueous electrolyte for a lithium secondary battery further comprises at least one other additive selected from the group consisting of a halogen-substituted carbonate-based compound, a nitrile-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a lithium salt-based compound Non-aqueous electrolyte for phosphorus lithium secondary batteries.
anode; cathode; a separator interposed between the negative electrode and the positive electrode; and
A lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery of claim 5.