KR20230132381A - Electrolyte additives for secondary battery, non-aqueous electrolyte for secondary battery comprising same and secondary battery - Google Patents

Abstract

The present invention relates to an electrolyte additive for lithium secondary batteries, a non-aqueous electrolyte for lithium secondary batteries containing the same, and a lithium secondary battery. Specifically, the electrolyte additive for a lithium secondary battery may include a compound represented by Chemical Formula 1.

Description

Electrolyte additive for secondary batteries, non-aqueous electrolyte for lithium secondary batteries containing the same, and lithium secondary batteries

The present invention relates to an electrolyte additive for secondary batteries, a non-aqueous electrolyte for lithium secondary batteries containing the same, and a lithium secondary battery. More specifically, an electrolyte additive for secondary batteries that is excellent in removing decomposition products generated from lithium salts and a lithium secondary battery containing the same. It relates to non-aqueous electrolytes and lithium secondary batteries.

As dependence on electrical energy increases in modern society, renewable energy generation that can increase production without causing environmental problems is emerging as a next-generation power generation system.

In the case of such renewable energy, it shows intermittent power generation characteristics, so a large-capacity power storage device is essential to stably supply power. Among these power storage devices, lithium-ion batteries are currently in the spotlight as devices with the highest energy density that are commercially available.

The lithium ion battery consists of a positive electrode made of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte solution containing a non-aqueous organic solvent containing lithium salt, and a separator.

Meanwhile, lithium ion batteries mainly use LiPF ₆ as a representative lithium salt in order to realize suitable characteristics of the battery. However, since LiPF ₆ is very vulnerable to heat, when the battery is exposed to high temperature, it thermally decomposes and generates Lewis acid such as PF ₅ .

Lewis acid substances not only cause the decomposition reaction of non-aqueous organic solvents such as ethylene carbonate, but also deteriorate the passivation ability of the solid electrolyte interphase (SEI) formed on the electrode surface, leading to further electrolyte decomposition, increased resistance, and damage from the anode. This results in the elution of transition metals. In addition, the eluted transition metal ions may re-deposit on the anode, causing an increase in the resistance of the anode, or conversely, they may move to the cathode through the electrolyte and then be electrodeposited on the cathode, causing self-discharge of the cathode. It causes destruction and regeneration of the solid electrolyte interphase (SEI) film, which causes additional consumption of lithium ions, causing increased resistance and deterioration of lifespan.

Therefore, in order to suppress the deterioration behavior of the battery when the battery is exposed to high temperatures, a method is used to reduce the SEI attack caused by by-products such as HF and PF ₅ generated by thermal decomposition of lithium salts, thereby suppressing further electrolyte decomposition reaction. This is being demanded.

Korean Patent Publication No. 2020-0089638

The present invention is intended to solve the above problems, and seeks to provide an electrolyte additive for secondary batteries that can remove decomposition products generated from lithium salts and at the same time form a strong passive film on the surfaces of the anode and cathode.

In addition, the present invention seeks to provide a non-aqueous electrolyte for lithium secondary batteries that can achieve excellent high-temperature stability and high-temperature cycle characteristics by including the electrolyte solution additive for secondary batteries, and a lithium secondary battery containing the same.

According to one embodiment, the present invention provides an electrolyte solution additive for secondary batteries containing a compound represented by the following formula (1).

[Formula 1]

In Formula 1,

R ₁ and R ₂ are each independently a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,

R ₃ is an alkyl group having 1 to 5 carbon atoms,

L is a direct bond, -O-, -COO-, -RO-, or -R'COO-,

R and R' are each independently an alkylene group having 1 to 10 carbon atoms,

n is an integer from 1 to 10.

According to another embodiment, the present invention provides a non-aqueous electrolyte solution for lithium secondary batteries containing the electrolyte solution additive for secondary batteries.

According to another embodiment, the present invention

A positive electrode containing a positive electrode active material;

A negative electrode containing a negative electrode active material;

a separator interposed between the cathode and the anode; and

The present invention provides a lithium secondary battery containing a non-aqueous electrolyte for a lithium secondary battery.

The compound represented by Formula 1 included as a non-aqueous electrolyte solution additive of the present invention contains a nitrogen atom in the cationic portion that can act as a Lewis base in its molecular structure, effectively scavenging Lewis acids generated as decomposition products of lithium salts. can do. In addition, the compound represented by Formula 1 contains a propargyl group (-CH ₂ C≡CH-) in its molecular structure, so it can form a stable film on the surface of the anode or cathode.

Therefore, the non-aqueous electrolyte solution for a lithium secondary battery of the present invention containing the compound represented by Formula 1 forms a stable film on the surface of the positive and negative electrodes, effectively suppressing the elution of transition metals from the positive electrode, and at the same time, thermal decomposition of the lithium salt. Since SEI film deterioration can be reduced by removing by-products generated as a result, a lithium secondary battery with improved high-temperature durability such as high-temperature storage characteristics and high-temperature cycling characteristics can be implemented.

First, before describing the present invention, the terms and words used in the specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor should explain his/her invention in the best way possible. It must be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that the concept of the term can be appropriately defined.

Meanwhile, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as “comprise,” “comprise,” or “have” are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, and are intended to indicate the presence of one or more other features or It should be understood that this does not exclude in advance the possibility of the presence or addition of numbers, steps, components, or combinations thereof.

In this specification, “%” means weight percent unless explicitly stated otherwise.

Before explaining the present invention, in the description of “carbon numbers a to b” in the specification, “a” and “b” refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms.

In addition, in this specification, unless otherwise defined, “substitution” means that at least one hydrogen bonded to carbon is replaced with an element other than hydrogen, for example, an alkyl group having 1 to 5 carbon atoms or a fluorine element. It means replaced with .

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

In general, lithium secondary batteries can secure high-temperature storage characteristics by forming a film with passivation ability on the surfaces of the anode and cathode as the non-aqueous electrolyte solution decomposes during initial charging and discharging. However, the film may be deteriorated by Lewis acid substances such as HF and PF ₅ generated by thermal decomposition of lithium salts (LiPF ₆ , etc.) widely used in lithium ion batteries. In other words, when elution of transition metal ions from the anode occurs due to attack by a Lewis acid material, the surface resistance of the electrode increases due to a change in the structure of the surface, and the theoretical capacity decreases as the metal ions that are redox centers disappear, resulting in Capacity may decrease. In addition, the transition metal ions eluted in this way are electrodeposited on the cathode reacting in the strong reduction potential zone, not only consuming electrons, but also destroying the film when electrodeposited, exposing the cathode surface, causing additional non-aqueous electrolyte decomposition reaction. As a result, there is a problem in which cell capacity continues to decrease as cathode resistance and irreversible capacity increase.

Accordingly, the present invention seeks to provide an electrolyte additive for lithium secondary batteries that has the effect of removing decomposition products generated from lithium salts and can form a strong passive film on the surfaces of the anode and cathode, a non-aqueous electrolyte for lithium secondary batteries containing the same, and a lithium secondary battery. .

Electrolyte additive for secondary batteries

The present invention provides an electrolyte solution additive for secondary batteries containing a compound represented by the following formula (1).

[Formula 1]

In Formula 1,

R ₁ and R ₂ are each independently a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,

R ₃ is an alkyl group having 1 to 5 carbon atoms,

L is a direct bond, -O-, -COO-, -RO-, or -R'COO-,

R and R' are each independently an alkylene group having 1 to 10 carbon atoms,

n is an integer from 1 to 10.

In addition, in Formula 1, R ₁ is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ₂ is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, and R ₃ is an alkyl group having 1 to 3 carbon atoms. , and L is -O-, -COO-, or -R'COO-, where R' is an alkylene group having 1 to 5 carbon atoms, and n may be an integer of 1 to 5.

Specifically, the compound represented by Formula 1 may be a compound represented by Formula 1A below.

[Formula 1A]

In Formula 1A,

R ₂ is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,

R ₃ is an alkyl group having 1 to 5 carbon atoms,

n is an integer from 1 to 10.

Preferably, the compound represented by Formula 1 may be a compound represented by Formula 1A-1 below.

[Formula 1A-1]

In the case of the compound represented by Formula 1, the nitrogen element having a lone pair contained in the molecular structure acts as a Lewis base, forming a high binding energy with the Lewis acid material generated as a decomposition product of the lithium salt, and forming the lithium salt. Decomposition products, etc. can be easily scavenged. Furthermore, nitrogen (N) atom-based materials, such as the compound represented by Formula 1, are electrochemically reduced and decomposed, forming a nitrogen (N) atom-based material that can be maintained without being easily decomposed when the battery is exposed to high temperatures on the cathode surface. A film (SEI) can be formed. In addition, in the case of the compound represented by Formula 1, since it contains a propargyl group and a sulfonate group that are easily reduced to terminal groups in the molecular structure, it can form a highly durable film while being reductively decomposed on the surface of the cathode.

non-aqueous electrolyte

Additionally, the non-aqueous electrolyte solution according to an embodiment of the present invention includes the electrolyte solution additive for secondary batteries.

Additionally, the non-aqueous electrolyte solution may further include lithium salt, organic solvent, and optionally other additives.

(1) Electrolyte additive for secondary batteries

The non-aqueous electrolyte solution of the present invention may include an electrolyte solution additive for secondary batteries containing the compound represented by Formula 1, and since the description of the compound overlaps with the above-mentioned content, the description thereof is omitted.

Meanwhile, the content of the electrolyte additive for secondary batteries may be 0.05% by weight to 5.0% by weight based on the total weight of the non-aqueous electrolyte solution, considering the effect of forming a stable film on the electrode surface and the effect of removing thermal decomposition products of lithium salt.

When the electrolyte additive for secondary batteries is contained within the above content range, disadvantages such as side reactions, capacity reduction, and resistance increase caused by the additive are suppressed as much as possible, while forming a strong film on the positive electrode surface, effectively suppressing the elution of transition metals from the positive electrode active material at high temperatures. It is possible to effectively remove thermal decomposition products of lithium salt and achieve excellent high-temperature durability.

That is, if the content of the electrolyte additive for secondary batteries is 0.05% by weight or more, the effect of removing thermal decomposition products of lithium salt can be maintained even if the operating time increases, and the effect of suppressing transition metal elution can be further improved by forming a stable film on the electrode surface. You can. In addition, if the content of the electrolyte solution additive for secondary batteries is 5.0% by weight or less, side reactions caused by a relatively large amount of additives can be prevented.

Specifically, the electrolyte additive for secondary batteries is 0.05% by weight to 5.0% by weight, specifically 0.05% by weight to 4.0% by weight, 0.1% by weight to 3.0% by weight, more specifically 0.3% by weight to 3.0% by weight, based on the total weight of the non-aqueous electrolyte solution. It may be included in weight percent.

As described above, the non-aqueous electrolyte solution of the present invention contains an electrolyte solution additive for secondary batteries containing the compound represented by Formula 1, thereby forming a more robust passive film at the interface between the electrode and the electrolyte, thereby reducing additional transition metals due to SEI decomposition. The cathode reduction reaction can be controlled and the transition metal eluted during high temperature storage can be prevented from being electrodeposited on the cathode. Therefore, when using a high-content nickel positive electrode active material, it is possible to manufacture a lithium secondary battery with improved initial performance, high-temperature durability, and long-term lifespan by suppressing side reactions.

(2) Lithium salt

The lithium salt may be those commonly used in electrolytes for lithium secondary batteries without limitation, and for example, includes Li ⁺ as a cation, and F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , as an anion. N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , B ₁₀ Cl ₁₀ ^- , AlCl ₄ ^- , AlO ₂ ^- , 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 ₂ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiN(SO ₂ F) ₂ (Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO ₂ CF ₂ CF ₃ ) ₂ (lithium bis(pentafluoroethane sulfonyl) imide, LiBETI) and LiN (SO ₂ CF ₃ ) ₂ (lithium bis(trifluoromethane sulfonyl) imide, LiTFSI) may contain a single substance or a mixture of two or more types. In addition to these, lithium salts commonly used in electrolytes of lithium secondary batteries can be used without limitation.

The lithium salt can be appropriately changed within the range commonly used, but in order to obtain the optimal effect of forming an anti-corrosion film on the electrode surface, it should be included in the electrolyte solution at a concentration of 0.8 M to 4.0 M, specifically at a concentration of 1.0 M to 3.0 M. You can.

When the lithium salt satisfies the above concentration range, the mobility of lithium ions can be improved to improve low-temperature output characteristics and cycle characteristics when stored at high temperatures, and the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation. .

(3) Non-aqueous organic solvent

Additionally, a description of the non-aqueous organic solvent is as follows.

As the non-aqueous organic solvent, various organic solvents commonly used in non-aqueous electrolytes can be used without limitation. Decomposition due to oxidation reactions, etc. during the charging and discharging process of secondary batteries can be minimized, and the desired characteristics can be achieved together with additives. There is no limit to the types of things that can be performed.

Specifically, the non-aqueous organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof.

The cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and easily dissociates lithium salts in a non-aqueous electrolyte solution. Specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2, It may contain at least one non-aqueous organic solvent selected from the group consisting of 3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and among these, ethylene carbonate. can do.

The linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and specific examples include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and ethylmethyl carbonate (EMC). , may include at least one non-aqueous organic solvent selected from the group consisting of methylpropyl carbonate and ethylpropyl carbonate, and may specifically include ethylmethyl carbonate (EMC).

The non-aqueous organic solvent of the present invention can be used by mixing the cyclic carbonate non-aqueous organic solvent and the linear carbonate non-aqueous organic solvent. In this case, the cyclic carbonate non-aqueous organic solvent:linear carbonate non-aqueous organic solvent is 10:90 to 50. :50 volume ratio, specifically 20:80 to 30:70 volume ratio.

In addition, the non-aqueous organic solvent may further include a linear ester-based non-aqueous organic solvent and/or a cyclic ester-based non-aqueous organic solvent with a low melting point and high stability at high temperatures in order to prepare an electrolyte solution with high ionic conductivity. It may be possible.

Representative examples of the linear ester-based non-aqueous organic solvent include at least one non-aqueous solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. Organic solvents can be mentioned.

In addition, the cyclic ester-based non-aqueous organic solvent is at least one non-aqueous solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. Organic solvents can be mentioned.

Meanwhile, in the non-aqueous electrolyte of the present invention, all components other than the non-aqueous organic solvent, such as the electrolyte solution additive for secondary batteries of the present invention, lithium salt, and other additives, are all non-aqueous organic solvents unless otherwise specified. You can.

(4) Other additives

In addition, the non-aqueous electrolyte solution for lithium secondary batteries of the present invention may additionally contain the compound represented by Formula 1 and other additives to form a more stable film on the surfaces of the positive and negative electrodes through a synergistic effect.

The other additives include carbonate-based compounds, sultone-based compounds, sulfate-based compounds, phosphate-based or phosphite-based compounds, borate-based compounds, nitrile-based compounds, amine-based compounds, silane-based compounds, and lithium salt-based compounds substituted or unsubstituted with halogen. It may include at least one selected from the group consisting of, and more specifically, a carbonate-based compound substituted or unsubstituted with halogen.

Representative examples of the carbonate-based compound substituted or unsubstituted with halogen include vinylene carbonate (VC), vinylethylene carbonate, or fluoroethylene carbonate (FEC).

The sultone-based compound may be at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethenesultone, and 1,3-propene sultone (PRS).

The sulfate-based compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

The phosphate-based or phosphite-based compounds include lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl) phosphite, and tris(2,2,2-trifluoroethyl). It may be one or more compounds selected from the group consisting of phosphate.

The borate-based compound may be tetraphenyl borate, lithium oxalyldifluoroborate (LiODFB), or lithium bisoxalate borate (LiB(C ₂ O ₄ ) ₂ ; LiBOB).

The nitrile-based compounds include, for example, succinonitrile, adiponitrile, 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. It may be at least one compound selected.

The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte solution and may include LiPO ₂ F ₂ or LiBF ₄ .

The other additives may be used in combination with two or more types of compounds, and may be included in an amount of 0.01 to 10% by weight, specifically 0.05 to 7% by weight, and preferably 0.1 to 5% by weight, based on the total weight of the non-aqueous electrolyte solution. may be included.

When the other additives are included in the above content range, the low-temperature output characteristics, high-temperature storage characteristics, and high-temperature lifespan characteristics of the secondary battery can be improved, and side reactions of the battery due to excessive amounts of additives can be prevented. In addition, the other additives cannot be sufficiently decomposed at high temperatures, thereby preventing unreacted substances from being generated or existing as precipitates in the electrolyte solution at room temperature.

Lithium secondary battery

Next, the 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 solution. In this case, the non-aqueous electrolyte solution may include the non-aqueous electrolyte solution according to the present invention. Since the non-aqueous electrolyte solution has been described above, its description 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 containing 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 electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and is specifically composed of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and aluminum (Al). It may include a lithium composite metal oxide represented by the following formula (2) containing lithium and at least one metal such as cobalt, manganese, nickel, or aluminum containing lithium and at least one metal selected from the group.

[Formula 2]

Li _1+a Ni _x Co _y M ¹ _z M ² _w O ₂

In Formula 1,

M ¹ is Mn, Al or a combination thereof,

M ² is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca and Sr, 0≤a≤0.5, 0<x≤0.6, 0<y≤0.4, 0<z≤0.4, 0 ≤w≤0.1.

The 1+a represents the atomic fraction of lithium in the lithium transition metal oxide, and may be 0≤a≤0.5, preferably 0≤a≤0.2, and more preferably 0≤a≤0.1.

The x represents the atomic fraction of nickel among all transition metal elements in lithium transition metal oxide, 0<x≤0.6, specifically 0.55<x<1.0, more specifically 0.6≤x≤0.98, and even more specifically 0.6. It may be ≤x≤0.95.

The y represents the atomic fraction of cobalt among all transition metal elements in the lithium transition metal oxide, and may be 0<y≤0.4, specifically 0<y≤0.3, and more specifically 0.05≤y≤0.3.

The z represents the atomic fraction of the M ¹ element among all transition metal elements in the lithium transition metal oxide, and may be 0<z≤0.4, preferably 0<z≤0.3, and more preferably 0.01≤z≤0.3.

The w represents the atomic fraction of the M ² element among all transition metal elements in the lithium transition metal oxide, and is 0<w≤0.1, preferably 0<w≤0.05, and more preferably 0<w≤0.02.

Specifically, in order to implement a high-capacity battery, the positive electrode active material is Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ with a Ni content of 0.55 atm% or more, Li(Ni _0.7 Mn _0.2 Co _0.1 )O ₂ , Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ , Li(Ni _0.86 Mn _0.07 Co _0.05 Al _0.02 )O ₂ or It is preferable to include a lithium complex transition metal oxide such as Li(Ni _0.90 Mn _0.05 Co _0.05 )O ₂ .

However, in the case of the high-content Ni-lithium composite metal oxide, after charging and discharging or when exposed to high temperatures, transition metal ions are eluted due to structural collapse of the anode, causing side reactions.

For example, nickel ions (Ni ²⁺ ) contained in high-content Ni-lithium composite metal oxide exist in the form of stable nickel ions before charging and discharging, but after charging and discharging, as the oxidation number increases, they become Ni ³⁺ ions. Or it changes to Ni ⁴⁺ ion. Unlike stable Ni ²⁺ ions, Ni ³⁺ ions or Ni ⁴⁺ ions can be reduced to Ni ²⁺ as rapid oxygen desorption occurs due to instability. At this time, the desorbed oxygen reacts with the electrolyte solution and changes the surface properties of the electrode or increases the charge transfer impedance of the surface, causing a decrease in capacity or high rate characteristics, thereby lowering the energy density. This phenomenon is further exacerbated on the anode surface containing high Ni content.

In addition, when the structure of the anode collapses due to exposure to high temperature, etc., Ni ²⁺ cations are eluted from the anode into the electrolyte solution, and the eluted Ni ²⁺ cations react with the passivation film (SEI) of the cathode to decompose the SEI film. As a result, some of the negative electrode active material is exposed to the electrolyte, which may cause a decrease in capacity and lifespan characteristics and an increase in resistance due to side reactions. This problem can be accelerated when a large amount of HF, etc., exists in the electrolyte.

Therefore, in order to solve these various problems, it is very important to form a strong film on the surface of the high Ni-containing anode that can prevent side reactions with the electrolyte and stabilize the surface.

In the present invention, by employing a non-aqueous electrolyte solution containing the compound represented by Formula 1 as an additive, film stabilization is achieved on the surface of the anode containing a high content Ni lithium composite metal oxide, thereby preventing desorbed oxygen or Ni ⁴⁺ ions. By preventing contact with the electrolyte solution, side reactions can be reduced, and elution of transition metals from the anode can be effectively suppressed.

Meanwhile, in the present invention, the positive electrode active material includes lithium-manganese-based oxides (e.g., LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxides (e.g., LiCoO _2, etc.), lithium-nickel-based oxide (for example, LiNiO ₂ , etc.), lithium-nickel-manganese-based oxide (for example, LiNi _1-Y Mn _Y O ₂ (0<Y<1), LiMn _{2 -z} Ni _z O ₄ (0＜Z＜2), lithium-nickel-cobalt-based oxide (for example, LiNi _1-Y1 Co _Y1 O ₂ (0<Y1<1), lithium-manganese-cobalt-based oxide ( For example, LiCo _1-Y2 Mn _Y2 O ₂ (0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (0<Z1<2), or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (0 ＜p1＜2, 0＜q1＜2, 0＜r2＜2, p1+q1+r2=2), etc. may be additionally included.

The positive electrode active material may be included in an amount of 80 to 98% by weight, more specifically, 85 to 98% by weight, based on the total weight of the positive electrode active material layer. When the positive electrode active material is contained within the above range, excellent capacity characteristics can be exhibited.

Next, the conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. Specific examples include carbon powders such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black; Graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; Conductive fibers such as carbon fiber and metal fiber; Conductive powders such as fluorinated carbon powder, aluminum powder, or 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, and one type of these may be used alone or a mixture of two or more types may be used.

The conductive material may be included in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the positive electrode active material layer.

Next, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive active material and the current collector.

Examples of such binders include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); Rubber-based binders including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethyl cellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; A polyalcohol-based binder containing polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binder; polyester-based binder; And one type alone or a mixture of two or more types of silane-based binders may be used.

The binder may be included in an amount of 0.1 to 15% by weight, preferably 0.1 to 10% by weight, based on the total weight of the positive electrode active material layer.

The positive electrode of the present invention can be manufactured according to a positive electrode manufacturing method known in the art. For example, the positive electrode is prepared by dissolving or dispersing the positive electrode active material, binder, and/or conductive material in a solvent, applying a positive electrode slurry onto the positive electrode current collector, followed by drying and rolling to form an active material layer, or It can be manufactured by casting the positive electrode active material layer on a separate support and then laminating the film obtained by peeling off the support on the positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , surface treated with silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive electrode material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. and the like, and one type of these may be used alone or a mixture of two or more types may be used. The amount of the solvent used can be adjusted so that the positive electrode mixture has an appropriate viscosity in consideration of the application thickness, manufacturing yield, workability, etc. of the positive electrode mixture, and is not particularly limited.

(2) cathode

Next, the cathode will be explained.

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

The negative electrode active material may be various types of negative electrode active materials used in the art, such as carbon-based negative electrode active materials, silicon-based negative electrode active materials, or mixtures thereof.

According to one embodiment, the negative electrode active material may include a carbon-based negative electrode active material, and the carbon-based negative electrode active material may include various carbon-based negative electrode active materials used in the industry, such as natural graphite, artificial graphite, and kishimen. Graphite-based materials such as graphite (Kish graphite); Pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes. High-temperature calcined carbon, soft carbon, hard carbon, etc. may be used. The shape of the carbon-based negative active material is not particularly limited, and materials of various shapes such as amorphous, plate-shaped, flaky, spherical, or fibrous may be used.

Preferably, the carbon-based negative active material may include at least one of natural graphite and artificial graphite. More preferably, the carbon-based negative active material may include natural graphite and artificial graphite. When natural graphite and artificial graphite are used together, the adhesion to the current collector increases and active material detachment can be suppressed.

According to another embodiment, the negative electrode active material may include a carbon-based negative electrode active material and a silicon-based negative electrode active material.

Specific examples of the carbon-based negative electrode active material are the same as described above.

The silicon-based _negative electrode active material is, for example, metallic silicon (Si), silicon oxide (SiO It is an element selected from the group consisting of elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, but may include one or more types selected from the group consisting of Si. The element Y includes 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.

Since the silicon-based negative electrode active material exhibits higher capacity characteristics than the carbon-based negative electrode active material, better capacity characteristics can be obtained when the silicon-based negative electrode active material is additionally included. However, in the case of an anode containing a silicon-based anode active material, the SEI film contains more oxygen (O)-rich components than a graphite anode, and the SEI film containing O-rich components is electrolyte solution. If a Lewis acid such as HF or PF ₅ is present, it tends to decompose more easily. Therefore, in the case of a negative electrode containing a silicon-based negative electrode active material, it is necessary to suppress the generation of Lewis acids such as HF and PF ₅ in the electrolyte solution or to remove (or scavenge) the generated Lewis acids in order to maintain a stable SEI film. Since the non-aqueous electrolyte solution according to the present invention contains an electrolyte additive capable of forming a stable film on the positive and negative electrodes, it can effectively suppress SEI film decomposition when using a negative electrode containing a silicon-based active material.

Meanwhile, the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 3:97 to 99:1, preferably 5:95 to 15:85, in weight ratio. When the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material satisfies the above range, capacity characteristics are improved and volume expansion of the silicon-based negative electrode active material is suppressed, thereby ensuring excellent cycle performance.

The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent capacity characteristics and electrochemical properties can be obtained.

Next, the conductive material is an ingredient to further improve the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. These conductive materials are not particularly limited as long as they are conductive without causing chemical changes in the battery. For example, carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or carbon powder such as thermal black; Graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; Conductive fibers such as carbon fiber and metal fiber; Conductive powders such as fluorinated carbon powder, aluminum powder, 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 usually added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of binders include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); Rubber-based binders including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethyl cellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; A polyalcohol-based binder containing polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binder; polyester-based binder; and silane-based binders.

The binder may be included in an amount of 0.1 to 15% by weight, preferably 0.1 to 10% by weight, based on the total weight of the negative electrode active material layer.

The cathode can be manufactured according to a cathode manufacturing method known in the art. For example, the negative electrode may be prepared by applying a negative electrode slurry prepared by dissolving or dispersing the negative electrode active material and optionally a binder and a conductive material in a solvent onto the negative electrode current collector, followed by rolling and drying to form an active material layer, or using the negative electrode active material. It can be manufactured by casting the layer on a separate support and then peeling off the support and lamination of the obtained film onto the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, it may be used on the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector may typically have a thickness of 3㎛ to 500㎛, and like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. and the like, and one type of these may be used alone or a mixture of two or more types may be used. The amount of the solvent used can be adjusted so that the anode slurry has an appropriate viscosity in consideration of the application thickness of the anode mixture, manufacturing yield, workability, etc., and is not particularly limited.

(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 negative electrode from the positive electrode and provides a passage for lithium ions to move. It can be used without particular restrictions as long as it is normally used as a separator in lithium secondary batteries. In particular, it has low resistance to ion movement of lithium salts and moisturizes the electrolyte. It is desirable to have excellent abilities.

Specifically, a porous polymer film as a separator, for example, a porous polymer film made of polyolefin polymers 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, conventional porous non-woven fabrics, for example, non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., may be used. Additionally, a coated separator containing a ceramic component or polymer material may be used to ensure heat resistance or mechanical strength, 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, laptop computers, and digital cameras, and in the field of electric vehicles such as hybrid electric vehicles (HEV).

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; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it can be used as a power source for any one or more mid- to large-sized devices among power storage systems.

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 square shape, a pouch shape, or a coin shape.

The lithium secondary battery according to the present invention can not only be used in battery cells used as a power source for small devices, but can also be preferably used as a unit cell in medium to large-sized battery modules containing a plurality of battery cells.

Hereinafter, the present invention will be described in detail through specific examples.

Example

Example 1.

(Production of non-aqueous electrolyte solution)

LiPF ₆ was dissolved to 1.2M in a non-aqueous organic solvent mixed with ethylene carbonate (EC):dimethyl carbonate (DMC) at a volume ratio of 30:70, then 0.3% by weight of the compound represented by Chemical Formula 1A-1 and other additives. A non-aqueous electrolyte solution was prepared by adding 2.0% by weight of vinylene carbonate and 1.0% by weight of 1,3-propane sultone (see Table 1 below).

(Anode manufacturing)

Positive electrode active material particles (Li(Ni _0.8 Co _0.1 Mn _0.1 )O ₂ ), carbon black as a conductive material, polyvinylidene fluoride (PVDF) as a binder, and N-methyl-2 as a solvent at a weight ratio of 97.5:1:1.5. -A positive electrode active material slurry (solid content: 48% by weight) was prepared by adding pyrrolidone (NMP). The positive electrode active material slurry was applied and dried on a positive electrode current collector (Al thin film) with a thickness of 15㎛, and then roll pressed to prepare a positive electrode.

(cathode manufacturing)

Negative active material (natural graphite:SiO=96:4 weight ratio), PVDF as a binder, and carbon black as a conductive material were added to the solvent NMP at a weight ratio of 95:3.5:1.5 to create a negative electrode active material slurry (solid content: 70% by weight). Manufactured. The negative electrode active material slurry was applied and dried on a negative electrode current collector (Cu thin film) with a thickness of 6㎛, and then roll pressed to prepare a negative electrode.

(Secondary battery manufacturing)

An electrode assembly was manufactured by a conventional method of sequentially stacking the positive and negative electrodes prepared by the above-mentioned method together with a polyethylene porous film, and then stored in a cylindrical secondary battery case, and the non-aqueous electrolyte solution prepared above was injected to lithium. A secondary battery was manufactured.

Example 2.

Except that the non-aqueous electrolyte solution was prepared by adding 1.0 wt% of the compound represented by Chemical Formula 1A-1 and 2.0 wt% of vinylene carbonate and 1.0 wt% of 1,3-propane sultone as other additives to a non-aqueous organic solvent. Then, a lithium secondary battery was manufactured in the same manner as Example 1.

Example 3.

1.0% by weight of the compound represented by Chemical Formula 1A-1 and 2.0% by weight of vinylene carbonate, 1.0% by weight of 1,3-propane sultone, and 1.0% by weight of ethylene sulfonate as other additives are added to the non-aqueous organic solvent to form a non-aqueous solvent. A lithium secondary battery was manufactured in the same manner as Example 1, except that the electrolyte solution was prepared.

Example 4.

Except that the non-aqueous electrolyte solution was prepared by adding 2.0 wt% of the compound represented by Chemical Formula 1A-1 and 2.0 wt% of vinylene carbonate and 1.0 wt% of 1,3-propane sultone as other additives to a non-aqueous organic solvent. manufactured a lithium secondary battery in the same manner as Example 1 above.

Example 5.

Except for the fact that the non-aqueous electrolyte solution was prepared by adding 0.1% by weight of the compound represented by Chemical Formula 1A-1 and 2.0% by weight of vinylene carbonate and 1.0% by weight of 1,3-propane sultone as other additives to a non-aqueous organic solvent. Then, a lithium secondary battery was manufactured in the same manner as Example 1.

Example 6.

Except for the fact that the non-aqueous electrolyte solution was prepared by adding 5.0% by weight of the compound represented by Chemical Formula 1A-1 and 2.0% by weight of vinylene carbonate and 1.0% by weight of 1,3-propane sultone as other additives to a non-aqueous organic solvent. Then, a lithium secondary battery was manufactured in the same manner as Example 1.

Comparative Example 1.

(Production of non-aqueous electrolyte solution)

LiPF ₆ was dissolved to 1.2M in a non-aqueous organic solvent mixed with ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 30:70, then 2.0% by weight of vinylene carbonate and 1.0% by weight of 1,3-propane sultone were added. A non-aqueous electrolyte solution was prepared by adding % (see Table 1 below).

(Secondary battery manufacturing)

A lithium secondary battery was manufactured in the same manner as Example 1, except that the prepared non-aqueous electrolyte solution was injected instead of the non-aqueous electrolyte solution of Example 1.

Comparative Example 2.

(Production of non-aqueous electrolyte solution)

LiPF ₆ was dissolved to 1.2M in a non-aqueous organic solvent mixed with ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 30:70, then 2.0% by weight of vinylene carbonate and 1.0% by weight of 1,3-propane sultone were added. % and 1.0 wt% of ethylene sulfonate were added to prepare a non-aqueous electrolyte solution (see Table 1 below).

(Secondary battery manufacturing)

A lithium secondary battery was manufactured in the same manner as Example 1, except that the prepared non-aqueous electrolyte solution was injected instead of the non-aqueous electrolyte solution of Example 1.

Comparative Example 3.

A lithium secondary battery was manufactured in the same manner as Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound represented by Formula 3 below instead of the compound represented by Formula 1A-1.

[Formula 3]

The zwitterionic compound of the imidazole structure represented by Formula 3 above has a phenyl group bonded to a nitrogen element, forming nitrophenyl-based SEI. Since nitrophenyl-based SEI has a higher binding energy with lithium ions than sulfonate-based SEI, lithium ion transfer characteristics may be poor, initial resistance may increase, and capacity retention may be relatively reduced.

Comparative Example 4.

A lithium secondary battery was manufactured in the same manner as Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound represented by Formula 4 below instead of the compound represented by Formula 1A-1.

[Formula 4]

Comparative Example 5.

A lithium secondary battery was manufactured in the same manner as Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound represented by Formula 5 below instead of the compound represented by Formula 1A-1.

[Formula 5]

The compound represented by Formula 5 contains a propargyl group and a sulfonate group in the structure, so it has a low LUMO value and is easy to reduce. However, since it does not contain a functional group that can act as a Lewis base, it is prone to forming Lewis acids such as HF. The inhibitory effect is low. For this reason, the Lewis acid may deteriorate the film, increase resistance, or reduce high-temperature durability.

Electrolyte additive of the present invention Other additives chemical formula Content (% by weight) type Content (% by weight) Example 1 1A-1 0.3 VC 2.0 P.S. 1.0 Example 2 1A-1 1.0 VC 2.0 P.S. 1.0 Example 3 1A-1 1.0 VC 2.0 P.S. 1.0 ESa 1.0 Example 4 1A-1 2.0 VC 2.0 P.S. 1.0 Example 5 1A-1 0.1 VC 2.0 P.S. 1.0 Example 6 1A-1 5.0 VC 2.0 P.S. 1.0 Comparative Example 1 - - VC 2.0 P.S. 1.0 Comparative Example 2 - - VC 2.0 P.S. 1.0 ESa 1.0 Comparative Example 3 3 0.3 VC 2.0 P.S. 1.0 Comparative Example 4 4 0.3 VC 2.0 P.S. 1.0 Comparative Example 5 5 0.3 VC 2.0 P.S. 1.0

In Table 1, the abbreviated names of the compounds are as follows.

VC: vinylene carbonate

PS: 1,3-propane sultone

Esa: ethylene sulfonate

Experiment example

Experimental Example 1: Evaluation of capacity retention rate after high temperature storage (1)

The lithium secondary batteries manufactured in Examples 1 to 6 and the lithium secondary batteries manufactured in Comparative Examples 1 to 5 were respectively fully charged to 4.25V and 0.05C cut off under constant current/constant voltage conditions at a 0.5C rate at room temperature (25°C). (SOC 100%) and discharged to 2.5V under constant current conditions at a 0.5C rate, then the discharge capacity before high temperature storage was measured using a PNE-0506 charger/discharger (manufacturer: PNE solution).

Then, after storing at 55°C for 2 months, the capacity after high-temperature storage for each lithium secondary battery was measured, and then the high-temperature capacity retention rate (%) was calculated using the following [Equation 1]. The results are shown in Table 2 below.

[Equation 3]

Capacity maintenance rate (%) = (discharge capacity after high temperature storage for 2 months/discharge capacity before high temperature storage) × 100

Experimental Example 2. Evaluation of resistance increase rate after high temperature storage (2)

The lithium secondary batteries manufactured in Examples 1 to 6 and the lithium secondary batteries manufactured in Comparative Examples 1 to 5 were each charged to 4.25V under constant current/constant voltage conditions at a 0.5C rate at room temperature (25°C), and then charged to DOD (depth) of discharge) was discharged to 50% to set the SOC to 50%, then discharged for 10 seconds at a 0.5C rate, and the initial resistance was measured using a PNE-0506 charger/discharger (manufacturer: PNE solution).

Then, after storage at 55°C for 2 months, the resistance value of each lithium secondary battery was measured, and the resistance increase rate (%) was calculated using the following [Equation 2]. The results are shown in Table 2 below.

[Equation 2]

Resistance increase rate (%) = {(resistance value after high-temperature storage for 2 months - resistance value before high-temperature storage)/resistance value before high-temperature storage}×100

Experimental Example 3. Evaluation of gas generation after high temperature storage (3)

The lithium secondary batteries manufactured in Examples 1 to 6 and the lithium secondary batteries manufactured in Comparative Examples 1 to 5 were each fully charged to 4.25V SOC 100% under constant current/constant voltage conditions at room temperature (25°C) at a 0.5C rate.

Then, after storage at 72°C for 2 months, the gas generation amount (%) after high temperature storage for each lithium secondary battery was measured, and the results are listed in Table 2 below.

After high temperature storage
Capacity maintenance rate (%) After high temperature storage
Resistance increase rate (%) After high temperature storage
Gas generation amount (%) Example 1 88.7 14.2 93.0 Example 2 91.7 11.7 89.5 Example 3 93.5 10.0 86.1 Example 4 95.4 6.3 77.2 Example 5 88.1 15.8 94.0 Example 6 88.3 20.4 95.5 Comparative Example 1 85.2 31.4 100.0 Comparative Example 2 87.9 30.8 96.7 Comparative Example 3 86.1 30.4 97.5 Comparative Example 4 87.0 29.7 96.1 Comparative Example 5 85.5 31.2 98.1

Looking at Table 2, it can be seen that the capacity retention rate (%) of the secondary batteries of Examples 1 to 6 of the present invention after storage at high temperature was improved compared to the secondary batteries of Comparative Examples 1 to 5.

In addition, it can be seen that the secondary batteries of Examples 1 to 6 of the present invention have improved resistance increase rate (%) and gas generation amount (%) after high temperature storage compared to the secondary batteries of Comparative Examples 1 to 5.

Experimental Example 4. Evaluation after high temperature cycle (1)

The lithium secondary batteries manufactured in Examples 1 to 6 and the lithium secondary batteries manufactured in Comparative Examples 1 to 5 were each charged to 4.25V at 40°C at a 0.3C rate under constant current/constant voltage conditions, and then charged under constant current conditions at a 0.5C rate. Discharging to 2.85V was considered one cycle, and 250 cycles of charge and discharge were performed. Then, the resistance increase rate (%) was calculated using [Equation 3] below, and the results are shown in Table 3 below.

[Equation 3]

Resistance increase rate (%) = {(Resistance after 250 cycles of charge/discharge - Resistance after 1 cycle of charge/discharge) / Resistance after 1 cycle of charge/discharge}×100

Resistance increase (%) after 250 cycles Example 1 17.4 Example 2 16.4 Example 3 15.1 Example 4 10.9 Example 5 18.1 Example 6 19.1 Comparative Example 1 21.5 Comparative Example 2 20.6 Comparative Example 3 22.4 Comparative Example 4 20.9 Comparative Example 5 21.9

Looking at Table 3, it can be seen that the resistance increase rate (%) of the secondary batteries of Examples 1 to 6 of the present invention was improved compared to the secondary batteries of Comparative Examples 1 to 5 after 250 cycles.

Experimental Example 5. Hot box evaluation

The lithium secondary batteries manufactured in Examples 1 to 6 and the lithium secondary batteries manufactured in Comparative Examples 1, 2, and 4 were each heated to 130°C at a temperature increase rate of 5°C/min in a fully charged state with SOC of 100%, and then, A hot box evaluation experiment was conducted to check whether ignition occurred by leaving each device for 30 minutes.

The results are listed in Table 4 below. If the battery ignites, it is marked as PASS, and if the battery does not ignite, it is marked as FAIL.

Resistance increase (%) after 250 cycles Example 1 PASS Example 2 PASS Example 3 PASS Example 4 PASS Example 5 PASS Example 6 PASS Comparative Example 1 Fail Comparative Example 2 Fail Comparative Example 4 PASS

Through the results in Table 4, it can be seen that the secondary batteries of Examples 1 to 6 of the present invention are superior to the secondary batteries of Comparative Examples 1 and 2 in terms of thermal safety during high temperature cycling.

Meanwhile, in the case of the secondary battery of Comparative Example 4 equipped with a non-aqueous electrolyte containing the compound of Chemical Formula 4 containing a propargyl group, heat similar to that of the secondary batteries of Examples 1 to 6 due to the film formation effect by the propargyl group It can be seen that it is stable.

Claims (10)

Electrolyte solution additive for secondary batteries containing a compound represented by the following formula (1):
[Formula 1]

In Formula 1,
R ₁ and R ₂ are each independently a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,
R ₃ is an alkyl group having 1 to 5 carbon atoms,
L is a direct bond, -O-, -COO-, -RO-, or -R'COO-,
R and R' are each independently an alkylene group having 1 to 10 carbon atoms,
n is an integer from 1 to 10.
In claim 1,
Wherein R ₁ is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms,
R ₂ is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms,
R ₃ is an alkyl group having 1 to 3 carbon atoms,
Wherein L is -O-, -COO-, or -R'COO-, where R' is an alkylene group having 1 to 5 carbon atoms, and n is an integer of 1 to 5. An electrolyte solution additive for a secondary battery.
In claim 1,
The compound represented by Formula 1 is an electrolyte additive for a secondary battery comprising a compound represented by the following Formula 1A:
[Formula 1A]

In Formula 1A,
R ₂ is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms,
R ₃ is an alkyl group having 1 to 5 carbon atoms,
n is an integer from 1 to 10.
In claim 1,
The compound represented by Formula 1 is an electrolyte additive for a secondary battery, wherein the compound is represented by the following Formula 1A-1:
[Formula 1A-1]
.
A non-aqueous electrolyte solution for a lithium secondary battery containing the electrolyte solution additive for a secondary battery of claim 1.
In claim 5,
The electrolyte solution additive for a lithium secondary battery is a non-aqueous electrolyte solution for a lithium secondary battery that is contained in an amount of 0.05% to 5.0% by weight based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.
In claim 5,
The electrolyte solution additive for a lithium secondary battery is a non-aqueous electrolyte solution for a lithium secondary battery that is contained in an amount of 0.05% to 4.0% by weight based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.
In claim 5,
The non-aqueous electrolyte solution for a lithium secondary battery further includes a lithium salt and a non-aqueous organic solvent.
In claim 5,
The non-aqueous electrolyte for lithium secondary batteries includes carbonate-based compounds substituted or unsubstituted with halogen, sultone-based compounds, sulfate-based compounds, phosphate-based or phosphite-based compounds, borate-based compounds, nitrile-based compounds, amine-based compounds, and silane-based compounds. and at least one other additive selected from the group consisting of lithium salt compounds.
A positive electrode containing a positive electrode active material;
A negative electrode containing a negative electrode active material;
a separator interposed between the cathode and the anode; and
A lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery of claim 5.