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

Abstract

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

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0029662 filed on March 8, 2022 and Korean Patent Application No. 10-2023-0028790 filed on March 3, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated by reference into this specification.

[0002] The present invention relates to an electrolyte additive for secondary batteries, and a nonaqueous electrolyte for lithium secondary batteries and a lithium secondary battery containing the same. More specifically, the present invention relates to an electrolyte additive for secondary batteries that is excellent in the effect of removing decomposition products generated from lithium salts, and a nonaqueous electrolyte for lithium secondary batteries and a lithium secondary battery containing the same. [Background technology]

[0003] 2. Description of the Related Art As modern society becomes increasingly dependent on electrical energy, renewable energy power generation, which does not cause environmental problems and can increase production, is emerging as a next-generation power generation system.

[0004] Since renewable energy sources have intermittent power generation characteristics, a large-capacity power storage device is essential to ensure a stable supply of power. Among such power storage devices, lithium-ion batteries are attracting attention as the devices with the highest energy density currently available commercially.

[0005] The lithium ion battery is composed 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 a lithium salt, and a separator.

[0006] On the other hand, in lithium-ion batteries, LiPF6 is mainly used as a representative lithium salt to realize suitable battery characteristics. However, LiPF6 is very sensitive to heat, and when the battery is exposed to high temperatures, it is thermally decomposed, generating Lewis acids such as PF5.

[0007] Lewis acid substances not only cause decomposition reactions of non-aqueous organic solvents such as ethylene carbonate, but also deteriorate the passivation ability of the solid electrolyte interphase (SEI) formed on the surface of the electrode, leading to additional decomposition of the electrolyte, increased resistance, and dissolution of transition metals from the positive electrode. In addition, the dissolved transition metal ions are redeposited on the positive electrode, causing an increase in the resistance of the positive electrode, and conversely, they migrate to the negative electrode via the electrolyte and are deposited on the negative electrode, causing self-discharge of the negative electrode, or cause destruction and regeneration of the solid electrolyte interphase (SEI) film, which consumes additional lithium ions, causing an increase in resistance and a deterioration in life.

[0008] Therefore, in order to suppress the degradation behavior of batteries when exposed to high temperatures, a method is needed that can mitigate the attack on the SEI by by-products such as HF and PF5 generated by the thermal decomposition of lithium salts and suppress additional electrolyte decomposition reactions. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is intended to solve the above problems, and provides an additive for an electrolyte solution for a secondary battery that can remove decomposition products generated from lithium salts and form a robust passivation film on the surfaces of the positive and negative electrodes.

[0010] The present invention also provides a non-aqueous electrolyte for a lithium secondary battery, which can achieve excellent high-temperature stability and high-temperature cycle characteristics by including the electrolyte additive for a secondary battery, and a lithium secondary battery including the same. [Means for solving the problem]

[0011] According to one embodiment, the present invention provides an electrolyte additive for a secondary battery, comprising a compound represented by the following Chemical Formula 1:

[0012] [Chemical formula 1] [ka]

[0013] In the above Chemical Formula 1, R1 and R2 each independently represent a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms; R3 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.

[0014] According to another embodiment, the present invention provides a non-aqueous electrolyte for a lithium secondary battery, comprising the electrolyte additive for a secondary battery.

[0015] According to yet another embodiment, the present invention provides a method for producing a method for manufacturing a semiconductor device comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator interposed between the negative electrode and the positive electrode; The present invention provides a lithium secondary battery comprising the nonaqueous electrolyte solution for lithium secondary batteries of the present invention. Effect of the Invention

[0016] The compound represented by Chemical Formula 1 contained as the non-aqueous electrolyte additive of the present invention contains a nitrogen atom in the cation moiety that can act as a Lewis base in its molecular structure, and therefore can effectively remove (scavenge) Lewis acid generated as a decomposition product of lithium salt. In addition, the compound represented by Chemical Formula 1 contains a propargyl group (-CH2C≡CH-) in its molecular structure, and therefore can form a stable coating on the surface of the positive or negative electrode.

[0017] Therefore, the nonaqueous electrolyte for a lithium secondary battery of the present invention, which contains the compound represented by Chemical Formula 1, can form a stable coating on the surfaces of the positive electrode and negative electrode to effectively suppress the elution of transition metals from the positive electrode, and can also remove by-products generated by thermal decomposition of the lithium salt to reduce deterioration of the SEI coating, thereby achieving a lithium secondary battery with improved high-temperature durability, such as high-temperature storage characteristics and high-temperature cycle characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] First, before describing the present invention, the terms and words used in this specification and claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a manner that is consistent with the technical ideas of the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0019] On the other hand, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly indicated in the context.

[0020] It should be understood that, as used herein, terms such as "comprises," "comprising," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0021] In this specification, "%" means % by weight unless clearly indicated otherwise. Prior to describing the present invention, in the description of "carbon number a to b" in the specification, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group can contain "a" to "b" carbon atoms.

[0022] In addition, in this specification, unless otherwise defined, "substituted" means that at least one hydrogen bonded to a carbon is replaced with an element other than hydrogen, for example, with an alkyl group having 1 to 5 carbon atoms or a fluorine element.

[0023] The present invention will now be described in more detail. In general, in lithium secondary batteries, a non-aqueous electrolyte is decomposed during initial charging and discharging, forming a coating having a passivating ability on the surfaces of the positive and negative electrodes, thereby ensuring high-temperature storage characteristics. However, the coating can be deteriorated by Lewis acid substances such as HF and PF5, which are generated by thermal decomposition of lithium salts (such as LiPF6) widely used in lithium-ion batteries. That is, when transition metal ions are eluted from the positive electrode due to attack by Lewis acid substances, the surface structure changes, increasing the surface resistance of the electrode, and the metal ions, which are redox centers, disappear, reducing the theoretical capacity and the actual capacity. In addition, the eluted transition metal ions are deposited on the negative electrode, which reacts in a strong reduction potential zone, and not only consume electrons, but also destroy the coating during deposition to expose the surface of the negative electrode, which can cause additional decomposition reactions of the non-aqueous electrolyte. As a result, there is a problem that the resistance and irreversible capacity of the negative electrode increase, and the capacity of the cell decreases continuously.

[0024] Therefore, the present invention provides an electrolyte additive for a lithium secondary battery that can remove decomposition products generated from lithium salts and form a robust passivation film on the surfaces of the positive and negative electrodes, as well as a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery containing the same.

[0025] Electrolyte additives for secondary batteries The present invention provides an additive for an electrolyte solution for a secondary battery, comprising a compound represented by the following Chemical Formula 1:

[0026] [Chemical formula 1] [ka]

[0027] In the above Chemical Formula 1, R1 and R2 each independently represent a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms; R3 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.

[0028] In addition, in the above chemical formula 1, R1 is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R2 is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, R3 is an alkyl group having 1 to 3 carbon atoms, L is -O-, -COO-, or -R'COO-, in which case R' is an alkylene group having 1 to 5 carbon atoms, and n may be an integer of 1 to 5.

[0029] Specifically, the compound represented by Chemical Formula 1 may be a compound represented by Chemical Formula 1A below.

[0030] [Chemical formula 1A] [ka]

[0031] In the above Chemical Formula 1A, R2 is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms; R3 is an alkyl group having 1 to 5 carbon atoms, n is an integer from 1 to 10.

[0032] Preferably, the compound represented by Chemical Formula 1 may be a compound represented by Chemical Formula 1A-1 below.

[0033] [Chemical formula 1A-1] [ka]

[0034] In the case of the compound represented by Chemical Formula 1, the nitrogen element having an unshared electron pair contained in the molecular structure acts as a Lewis base and forms a high bond energy with a Lewis acid substance generated as a decomposition product of the lithium salt, thereby easily removing (scavenging) the decomposition products of the lithium salt. Furthermore, a nitrogen (N) atom-based substance such as the compound represented by Chemical Formula 1 can be electrochemically reduced and decomposed to form a nitrogen (N) atom-based coating (SEI) on the surface of the negative electrode that can be maintained without being easily decomposed when the battery is exposed to high temperatures. In addition, the compound represented by Chemical Formula 1 contains a propargyl group and a sulfonate group, which are easily reduced, as terminal groups in the molecular structure, and can be reduced and decomposed on the surface of the negative electrode to form a coating with high durability.

[0035] non-aqueous electrolyte In addition, a non-aqueous electrolyte according to an embodiment of the present invention includes an electrolyte additive for a secondary battery, the electrolyte additive including the compound represented by Chemical Formula 1. The non-aqueous electrolyte may further include a lithium salt, an organic solvent, and optionally other additives.

[0036] (1) Electrolyte additives for secondary batteries The non-aqueous electrolyte of the present invention may contain an electrolyte additive for a secondary battery, which includes a compound represented by Chemical Formula 1. In this case, the description of the compound is the same as that described above, so the description will be omitted.

[0037] Meanwhile, the content of the electrolyte additive for secondary batteries may be 0.05 wt % to 5.0 wt % based on the total weight of the non-aqueous electrolyte, taking into consideration the effect of forming a stable coating on the surface of the electrode and the effect of removing thermal decomposition products of the lithium salt.

[0038] When the secondary battery electrolyte additive is included within the above content range, it is possible to minimize defects such as side reactions, capacity reduction, and resistance increase due to the additive, while forming a strong coating on the surface of the positive electrode, effectively suppressing the elution of transition metals in the positive electrode active material at high temperatures, and effectively removing thermal decomposition products of lithium salt, thereby achieving excellent high temperature durability.

[0039] That is, when the content of the additive in the electrolyte for secondary batteries is 0.05 wt% or more, the effect of removing the thermal decomposition products of the lithium salt can be maintained even if the driving time increases, and a stable coating can be formed on the surface of the electrode to further improve the effect of inhibiting the elution of transition metals, etc. Also, when the content of the additive in the electrolyte for secondary batteries is 5.0 wt% or less, side reactions caused by a relatively large amount of additive can be prevented.

[0040] Specifically, the secondary battery electrolyte additive may be included in an amount of 0.05 wt % to 5.0 wt %, more specifically 0.05 wt % to 4.0 wt %, 0.1 wt % to 3.0 wt %, and more specifically 0.3 wt % to 3.0 wt %, based on the total weight of the nonaqueous electrolyte.

[0041] As described above, the non-aqueous electrolyte of the present invention contains an electrolyte additive for secondary batteries, which contains the compound represented by Chemical Formula 1, and thus forms a stronger passivation film at the interface between the electrode and the electrolyte, thereby controlling the anode reduction reaction of additional transition metals due to SEI decomposition and preventing the deposition of transition metals eluted during high-temperature storage on the anode. Therefore, when using a high-content nickel positive electrode active material, side reactions can be suppressed, and a lithium secondary battery with improved initial performance, high-temperature durability, and long life can be manufactured.

[0042] (2) Lithium salt As the lithium salt, any salt commonly used in electrolytes for lithium secondary batteries can be used without limitation. For example, Li + The anion is F. - , Cl - , Br - , I- , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - , and SCN - At least one selected from the group consisting of:

[0043] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10, LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (lithium bis(pentafluoroethane sulfonyl)imide, LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI). In addition to these, lithium salts commonly used in electrolytes for lithium secondary batteries can be used without any restrictions.

[0044] The lithium salt may be appropriately changed within a range that is normally usable, but in order to obtain an optimal effect of forming a corrosion prevention coating on the electrode surface, the lithium salt may be contained in the electrolyte at a concentration of 0.8 M to 4.0 M, specifically, at a concentration of 1.0 M to 3.0 M.

[0045] 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 during high-temperature storage, and the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation.

[0046] (3) Nonaqueous organic solvent The non-aqueous organic solvent is described as follows. As the non-aqueous organic solvent, various organic solvents commonly used in non-aqueous electrolytes can be used without limitation, and the type is not limited as long as it can minimize decomposition due to oxidation reaction during the charge / discharge process of the secondary battery and can exhibit desired properties together with the additives.

[0047] Specifically, the non-aqueous organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof. The cyclic carbonate organic solvent is a high-viscosity organic solvent that has a high dielectric constant and effectively dissociates the lithium salt in the non-aqueous electrolyte solution. Specific examples of the cyclic carbonate organic solvent include at least one non-aqueous organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and among these, ethylene carbonate may be included.

[0048] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and specific examples thereof may include at least one non-aqueous organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and specifically may include ethyl methyl carbonate (EMC).

[0049] The non-aqueous organic solvent of the present invention may be a mixture of the cyclic carbonate-based non-aqueous organic solvent and the linear carbonate-based non-aqueous organic solvent. In this case, the cyclic carbonate-based non-aqueous organic solvent:linear carbonate-based non-aqueous organic solvent may be mixed in a volume ratio of 10:90 to 50:50, specifically, a volume ratio of 20:80 to 30:70.

[0050] 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 having a low melting point and high stability at high temperatures in order to prepare an electrolyte solution having high ionic conductivity.

[0051] Representative examples of the linear ester-based non-aqueous organic solvent include at least one non-aqueous organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0052] The cyclic ester-based non-aqueous organic solvent may be at least one non-aqueous organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0053] Meanwhile, the other components in the nonaqueous electrolyte of the present invention, excluding the nonaqueous organic solvent, for example, the remainder excluding the electrolyte additive for a secondary battery of the present invention, the lithium salt, and other additives, may all be nonaqueous organic solvents, unless otherwise specified.

[0054] (4) Other additives In addition, the nonaqueous electrolyte for a lithium secondary battery of the present invention may further contain other additives so that a more stable coating can be formed on the surfaces of the positive and negative electrodes through a synergistic effect with the compound represented by Chemical Formula 1.

[0055] The other additives may include at least one selected from the group consisting of halogen-substituted or unsubstituted 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, and more specifically, examples of the other additives include halogen-substituted or unsubstituted carbonate-based compounds.

[0056] Representative examples of the halogen-substituted or unsubstituted carbonate compounds include vinylene carbonate (VC), vinylethylene carbonate, and fluoroethylene carbonate (FEC).

[0057] The sultone compound may be at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, and 1,3-propene sultone (PRS).

[0058] The sulfate compound may be, for example, ethylene sulfate (ESa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0059] The phosphate or phosphite compound may be one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphite, and tris(2,2,2-trifluoroethyl)phosphate.

[0060] The borate-based compound may be tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), or lithium bis(oxalato)borate (LiB(C2O4)2; LiBOB), etc.

[0061] The nitrile compound may be, for example, at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile. The lithium salt compound is a compound different from the lithium salt contained in the nonaqueous electrolyte, and examples of the lithium salt include LiPO2F2 and LiBF4.

[0062] The other additives may be used in combination of two or more compounds, and may be contained in an amount of 0.01 to 10 wt %, specifically 0.05 to 7 wt %, and preferably 0.1 to 5 wt %, based on the total weight of the nonaqueous electrolyte.

[0063] When the other additives are contained within the above content ranges, it is possible to obtain an effect of improving the low-temperature output characteristics, high-temperature storage characteristics, and high-temperature life characteristics of the secondary battery, and to prevent side reactions in the battery caused by excess additives. In addition, it is possible to prevent the other additives from being insufficiently decomposed at high temperatures, resulting in the generation of unreacted substances or their presence in a precipitated state in the electrolyte at room temperature.

[0064] 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, and the non-aqueous electrolyte may include the non-aqueous electrolyte according to the present invention. The non-aqueous electrolyte has been described above, so a description thereof will be omitted, and other components will be described below.

[0065] (1) Positive electrode 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.

[0066] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide represented by the following Chemical Formula 2, which includes at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and aluminum (Al) and lithium, such as one or more metals such as cobalt, manganese, nickel, or aluminum, and lithium.

[0067] [Chemical formula 2] Li1+a Ni x Co y M 1 z M 2 w O2

[0068] In the chemical 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, and 0 ≦ a ≦ 0.5, 0 < x ≦ 0.6, 0 < y ≦ 0.4, 0 < z ≦ 0.4, 0 ≦ w ≦ 0.1.

[0069] The 1 + a represents the atomic fraction of lithium in the lithium transition metal oxide, and 0 ≦ a ≦ 0.5, preferably 0 ≦ a ≦ 0.2, more preferably 0 ≦ a ≦ 0.1 may be used.

[0070] The x represents the atomic fraction of nickel among all the transition metal elements in the lithium transition metal oxide, and 0 < x ≦ 0.6, specifically 0.55 < x < 1.0, more specifically 0.6 ≦ x ≦ 0.98, and even more specifically 0.6 ≦ x ≦ 0.95 may be used.

[0071] The y represents the atomic fraction of cobalt among all the transition metal elements in the lithium transition metal oxide, and 0 < y ≦ 0.4, specifically 0 < y ≦ 0.3, more specifically 0.05 ≦ y ≦ 0.3 may be used.

[0072] The z represents the atomic fraction of the M 1 element among all the transition metal elements in the lithium transition metal oxide, and 0 < z ≦ 0.4, preferably 0 < z ≦ 0.3, more preferably 0.01 ≦ z ≦ 0.3 may be used.

[0073] The w represents the atomic fraction of the M 2 element among all the transition metal elements in the lithium transition metal oxide, and 0 < w ≦ 0.1, preferably 0 < w ≦ 0.05, more preferably 0 < w ≦ 0.02.

[0074] Specifically, the positive electrode active material is Li(Ni) having a Ni content of 0.55 atm % or more in order to realize a high-capacity battery. 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.7 Mn 0.2 Co 0.1 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li(Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 )O2, or Li(Ni 0.90 Mn 0.05 Co 0.05 It is preferable that the lithium composite transition metal oxide includes a lithium composite transition metal oxide such as 02.

[0075] However, in the case of the high-content Ni-lithium composite metal oxide, after charging and discharging, or when exposed to high temperatures, the structure of the positive electrode collapses, causing transition metal ions to dissolve, resulting in side reactions.

[0076] For example, the nickel ions (Ni 2+ ) exists in a stable nickel ion form before charging and discharging, and after charging and discharging, its oxidation number increases to Ni 3+ ion or Ni 4+ It changes to a stable Ni ion. 2+ Unlike the Ni ion, 3+ Ion and Ni 4+ The ions are unstable and undergo rapid oxygen elimination, resulting in Ni 2+ In this case, the released oxygen reacts with the electrolyte to change the surface properties of the electrode or increases the surface charge transfer impedance, causing problems such as capacity loss, reduced high rate characteristics, and reduced energy density. This phenomenon is even more severe on the surface of a positive electrode containing a high Ni content.

[0077] In addition, when the structure of the positive electrode collapses due to exposure to high temperatures or the like, Ni 2+ cations elute into the electrolytic solution, and the eluted Ni 2+ cations react with the passive film (SEI) of the negative electrode to decompose the SEI film. As a result, a part of the negative electrode active material is exposed to the electrolytic solution, which can cause a decrease in capacity and life characteristics due to side reactions and an increase in resistance. Such problems can be accelerated when a large amount of HF or the like is present in the electrolytic solution.

[0078] Therefore, in order to solve such various problems, it is very important to form a firm film on the surface of the high-content Ni-containing positive electrode that can prevent side reactions with the electrolytic solution and bring about surface stabilization.

[0079] The present invention adopts a non-aqueous electrolytic solution containing the compound represented by the above Chemical Formula 1 as an additive, realizes film stabilization on the surface of a positive electrode containing a high-content Ni lithium composite metal oxide, and prevents the desorbed oxygen and Ni 4+ ions from coming into contact with the electrolytic solution to reduce side reactions, and can effectively suppress the elution of transition metals from the positive electrode.

[0080] On the other hand, in the present invention, in addition to the high-content Ni lithium composite metal oxide as described above, the positive electrode active material also includes lithium-manganese-based oxides (for example, LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (for example, LiCoO2, etc.), lithium-nickel-based oxides (for example, LiNiO2, etc.), lithium-nickel-manganese-based oxides (for example, LiNi 1-Y Mn Y O2 (0 < Y < 1), LiMn 2-z Ni z O4 (0 < Z < 2), lithium-nickel-cobalt-based oxides (for example, LiNi 1-Y1 Co Y1 O2 (0 < Y1 < 1), lithium-manganese-cobalt-based oxides (for example, LiCo 1-Y2 Mn Y2 O2 (0 < Y2 < 1), LiMn 2-z1 Co z1O4 (0 < Z1 < 2), or Li(Ni p1 Co q1 Mn r2 )O4 (0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc. may be further included.

[0081] The positive electrode active material may be contained in a content 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.

[0082] Next, the conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without particular limitation as long as it does not cause a chemical change and has electron conductivity. 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 powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Among these, one kind alone or a mixture of two or more kinds may be used. The conductive material may be contained 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.

[0083] Next, the binder serves to improve the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the current collector. Examples of such binders include fluororesin-based binders including 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 carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol-based binders including polyvinyl alcohol; polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binders; and silane-based binders, which may be used alone or in combination of two or more. The binder may be contained 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.

[0084] The positive electrode of the present invention may be manufactured by a method known in the art. For example, the positive electrode may be manufactured by a method of dissolving or dispersing a positive electrode active material, a binder, and / or a conductive material in a solvent to prepare a positive electrode slurry, which is then coated on a positive electrode current collector, followed by drying and rolling to form an active material layer, or a method of casting the positive electrode active material layer on another support, peeling off the support, and laminating the resulting film on the positive electrode current collector.

[0085] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and may be, for example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may generally have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0086] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., and one or more of these may be used alone or in combination. The amount of the solvent used is not particularly limited as long as it can be adjusted to a level that allows the positive electrode mixture to have an appropriate viscosity in consideration of the coating thickness of the positive electrode mixture, production yield, workability, etc.

[0087] (2) Negative electrode Next, the negative electrode will be described. 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 a binder, as necessary.

[0088] The negative electrode active material may be any of various negative electrode active materials used in the art, such as a carbon-based negative electrode active material, a silicon-based negative electrode active material, or a mixture thereof.

[0089] According to an 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 art, such as graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature fired carbon such as petroleum or coal tar pitch derived cokes, soft carbon, hard carbon, etc. The shape of the carbon-based negative electrode active material is not particularly limited, and materials of various shapes such as amorphous, plate-like, flaky, spherical, or fibrous may be used.

[0090] Preferably, the carbon-based negative electrode active material may include at least one of natural graphite and artificial graphite. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite. When both natural graphite and artificial graphite are used, the adhesive strength with the current collector is increased, and detachment of the active material can be suppressed.

[0091] 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 as described above.

[0092] The silicon-based negative electrode active material is, for example, metal silicon (Si), silicon oxide (SiO x, where 0 < x < 2), silicon carbide (SiC), and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si) may be included. As the element Y, it may be selected from the group consisting of 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.

[0093] Since the silicon-based negative electrode active material exhibits higher capacity characteristics than the carbon-based negative electrode active material, when further containing the silicon-based negative electrode active material, even more excellent capacity characteristics can be obtained. However, in the case of a negative electrode containing a silicon-based negative electrode active material, compared with a graphite negative electrode, it contains even more oxygen (O)-rich components in the SEI film, and the SEI film containing oxygen-rich components tends to be further decomposed when Lewis acids such as HF or PF5 are present in the electrolytic solution. Therefore, in the case of a negative electrode containing a silicon-based negative electrode active material, in order to maintain a stable SEI film, it is necessary to suppress the generation of Lewis acids such as HF and PF5 in the electrolytic solution, or remove (or scavenge) the generated Lewis acids. Since the non-aqueous electrolytic solution according to the present invention contains an electrolytic solution additive capable of forming a stable film on the positive electrode and the negative electrode, it is possible to effectively suppress the decomposition of the SEI film when using a negative electrode containing a silicon-based active material.

[0094] On the other hand, the mixing ratio of the silicon-based negative electrode active material:carbon-based negative electrode active material may be 3:97 to 99:1, preferably 5:95 to 15:85 by 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, while improving the capacity characteristics, the volume expansion of the silicon-based negative electrode active material can be suppressed, and excellent cycle performance can be ensured.

[0095] The negative electrode active material may be included in an amount of 80 wt % to 99 wt % based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material is in the above range, excellent capacity characteristics and electrochemical characteristics can be obtained.

[0096] Next, the conductive material is a component for further improving 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. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and examples thereof include carbon powders such as carbon black, acetylene black (or denka black), ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystal structures; conductive fibers such as carbon fibers and metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0097] The binder is a component that aids in bonding between the conductive material, the active material, and the current collector, and is usually added in an amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. Examples of binders include fluororesin-based binders including 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 carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol-based binders including polyvinyl alcohol; polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binders; and silane-based binders. The binder may be contained 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.

[0098] The negative electrode may be manufactured by a method for manufacturing a negative electrode well known in the art. For example, the negative electrode may be manufactured by applying a negative electrode slurry, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, onto a negative electrode current collector, rolling and drying the slurry to form an active material layer, or by casting the negative electrode active material layer onto another support, peeling off the support, and laminating the resulting film onto the negative electrode current collector.

[0099] The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloy. The negative electrode current collector may generally have a thickness of 3 μm to 500 μm, and may have fine irregularities formed on the surface of the current collector to strengthen the binding force of the negative electrode active material, as in the case of the positive electrode current collector. For example, the negative electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0100] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., and one or more of these may be used alone or in combination. The amount of the solvent used is not particularly limited as long as it can be adjusted to an appropriate viscosity for the negative electrode slurry in consideration of the coating thickness of the negative electrode composite, production yield, workability, etc.

[0101] (3) Separator The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

[0102] The separator separates the negative electrode and the positive electrode and provides a path for lithium ion migration. Any separator that is typically used as a separator in a lithium secondary battery can be used without any particular limitation. In particular, it is preferable that the separator has low resistance to ion migration of lithium salts and has excellent electrolyte humidification ability.

[0103] Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof. Also, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high-melting point glass fiber, polyethylene terephthalate fiber, or the like, may be used. Also, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric substance may be used, and may be selectively used as a single layer or multilayer structure.

[0104] The lithium secondary battery according to the present invention can be effectively used in portable devices such as mobile phones, notebook computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs).

[0105] According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same. The battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0106] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0107] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but also preferably as a unit battery for a medium- to large-sized battery module including a plurality of battery cells. The present invention will now be described in more detail with reference to specific examples.

[0108] Working Example Example 1 (Production of non-aqueous electrolyte) LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC): dimethyl carbonate (DMC) was mixed in a volume ratio of 30:70 to a concentration of 1.2 M, and then 0.3 wt % of the compound represented by formula 1A-1 and other additives such as 2.0 wt % vinylene carbonate and 1.0 wt % 1,3-propane sultone were added to prepare a non-aqueous electrolyte (see Table 1 below).

[0109] (Production of positive electrodes) Positive electrode active material particles (Li(Ni 0.8 Co 0.1 Mn 0.1 )O2), carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were added in a weight ratio of 97.5:1:1.5 to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a cathode active material slurry (solid content: 48% by weight). The cathode active material slurry was applied to a cathode current collector (aluminum thin film) with a thickness of 15 μm, dried, and then roll pressed to prepare a cathode.

[0110] (Production of negative electrodes) A negative electrode active material (natural graphite:SiO = 96:4 weight ratio), PVDF as a binder, and carbon black as a conductive material were added in a weight ratio of 95:3.5:1.5 to NMP as a solvent to prepare a negative electrode active material slurry (solid content: 70 wt%). The negative electrode active material slurry was applied to a negative electrode current collector (Cu thin film) with a thickness of 6 μm, dried, and then roll pressed to prepare a negative electrode.

[0111] (Secondary battery manufacturing) The positive and negative electrodes prepared as described above were sequentially laminated together with a polyethylene porous film to prepare an electrode assembly in a conventional manner, which was then placed in a cylindrical secondary battery case and the non-aqueous electrolyte prepared as described above was injected to prepare a lithium secondary battery.

[0112] Example 2 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 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 were added to the non-aqueous organic solvent to prepare a non-aqueous electrolyte solution.

[0113] Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding 1.0 wt % of the compound represented by Chemical Formula 1A-1 and other additives, such as 2.0 wt % vinylene carbonate, 1.0 wt % 1,3-propane sultone, and 1.0 wt % ethylene sulfonate, to a non-aqueous organic solvent.

[0114] Example 4 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a 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.

[0115] Example 5 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 0.1 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 were added to the non-aqueous organic solvent to prepare a non-aqueous electrolyte solution.

[0116] Example 6 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding 5.0 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.

[0117] Comparative Example 1 (Production of non-aqueous electrolyte) LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC): dimethyl carbonate (DMC) was mixed in a volume ratio of 30:70 to a concentration of 1.2 M, and then 2.0 wt % vinylene carbonate and 1.0 wt % 1,3-propane sultone were added to prepare a non-aqueous electrolyte (see Table 1 below).

[0118] (Secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the nonaqueous electrolyte prepared above was poured in place of the nonaqueous electrolyte of Example 1.

[0119] Comparative Example 2 (Production of non-aqueous electrolyte) LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC): dimethyl carbonate (DMC) was mixed in a volume ratio of 30:70 to a concentration of 1.2 M, and then 2.0 wt % vinylene carbonate, 1.0 wt % 1,3-propane sultone, and 1.0 wt % ethylene sulfonate were added to prepare a non-aqueous electrolyte (see Table 1 below).

[0120] (Secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the nonaqueous electrolyte prepared above was poured in place of the nonaqueous electrolyte of Example 1.

[0121] Comparative Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a compound represented by the following Formula 3 was added instead of the compound represented by Formula 1A-1 to prepare a non-aqueous electrolyte solution.

[0122] [Chemical formula 3] [ka]

[0123] The zwitterionic compound having an imidazole structure represented by Chemical Formula 3 has a phenyl group bonded to a nitrogen element to form a nitrophenyl-based SEI. The nitrophenyl-based SEI has a higher binding energy with lithium ions than the sulfonate-based SEI, and therefore the lithium ion transfer characteristics may be deteriorated, the initial resistance may be increased, and the capacity retention rate may be relatively decreased.

[0124] Comparative Example 4 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound represented by the following Formula 4 instead of the compound represented by Formula 1A-1.

[0125] [Chemical formula 4] [ka]

[0126] Comparative Example 5 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte solution was prepared by adding a compound represented by the following Formula 5 instead of the compound represented by Formula 1A-1.

[0127] [Chemical formula 5] [ka]

[0128] The compound represented by the formula 5 has a low LUMO value and is easily reduced because it contains a propargyl group and a sulfonate group in its structure, but does not contain a functional group that can act as a Lewis base, so it has a low effect of suppressing the formation of Lewis acids such as HF, etc. Therefore, the coating may be deteriorated by Lewis acids, increasing resistance or decreasing high temperature durability.

[0129] [Table 1]

[0130] In Table 1, the abbreviations of the compounds are as follows. VC: Vinylene carbonate PS: 1,3-propane sultone ESa: Ethylene sulfate

[0131] Experimental Example Experimental Example 1: Evaluation of capacity retention rate after high temperature storage (1) The lithium secondary batteries prepared in Examples 1 to 6 and the lithium secondary batteries prepared in Comparative Examples 1 to 5 were each fully charged (SOC 100%) to 4.25 V, 0.05 C cut off under constant current / constant voltage conditions at 0.5 C rate at room temperature (25° C.), and discharged to 2.5 V under constant current conditions at 0.5 C rate, and then the discharge capacity before high temperature storage was measured using a PNE-0506 charger / discharger (manufacturer: PNE solution).

[0132] Next, after storing at 55° C. for 2 months, the capacity of each lithium secondary battery after high-temperature storage was measured, and the high-temperature capacity retention rate (%) was calculated using the following [Equation 1]. The results are shown in Table 2 below.

[0133] [Formula 3] Capacity retention rate (%) = (discharge capacity after 2 months of high temperature storage / discharge capacity before high temperature storage) x 100

[0134] Experimental Example 2: Evaluation of resistance increase rate after high temperature storage (2) The lithium secondary batteries prepared in Examples 1 to 6 and the lithium secondary batteries prepared in Comparative Examples 1 to 5 were each charged to 4.25 V at room temperature (25° C.) under constant current / constant voltage conditions at a rate of 0.5 C, and then discharged to a depth of discharge (DOD) of 50% to adjust the SOC to 50%, and then discharged at a rate of 0.5 C for 10 seconds, and the initial resistance was measured using a PNE-0506 charger / discharger (manufacturer: PNE solution).

[0135] Next, after storing the lithium secondary batteries at 55° C. for 2 months, the resistance value of each battery was measured, and the resistance increase rate (%) was calculated using the following [Equation 2]. The results are shown in Table 2 below.

[0136] [Formula 2] Resistance increase rate (%) = {(resistance value after 2 months of high temperature storage - resistance value before high temperature storage) / resistance value before high temperature storage} x 100

[0137] Experimental Example 3: Evaluation of gas generation rate after high temperature storage (3) The lithium secondary batteries produced in Examples 1 to 6 and Comparative Examples 1 to 5 were each fully charged at room temperature (25° C.) under constant current / constant voltage conditions at a rate of 0.5 C to 4.25 V SOC 100%. Next, after storing at 72° C. for 2 months, the amount of gas generated (%) after high-temperature storage for each lithium secondary battery was measured. The results are shown in Table 2 below.

[0138] [Table 2]

[0139] Referring to Table 2, it can be seen that the secondary batteries of Examples 1 to 6 of the present invention have improved capacity retention rates (%) after high-temperature storage compared to the secondary batteries of Comparative Examples 1 to 5. It is also apparent that the secondary batteries of Examples 1-6 of the present invention have improved resistance increase rates (%) and gas generation amounts (%) after high-temperature storage, as compared with the secondary batteries of Comparative Examples 1-5.

[0140] Experimental Example 4: Evaluation after high temperature cycle (1) Each of the lithium secondary batteries produced in Examples 1 to 6 and the lithium secondary batteries produced in Comparative Examples 1 to 5 was charged to 4.25 V at 40° C. under constant current / constant voltage conditions at a rate of 0.3 C, and then discharged to 2.85 V under constant current conditions at a rate of 0.5 C. After 250 cycles of charge and discharge, the resistance increase rate (%) was calculated using the following [Equation 3], and the results are shown in Table 3 below.

[0141] [Formula 3] Resistance increase rate (%) = {(resistance after 250 charge / discharge cycles - resistance after 1 charge / discharge cycle) / resistance after 1 charge / discharge cycle} x 100

[0142] [Table 3]

[0143] Referring to Table 3, it can be seen that the secondary batteries of Examples 1 to 6 of the present invention have improved resistance increase rates (%) after 250 cycles compared to the secondary batteries of Comparative Examples 1 to 5.

[0144] 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 heating rate of 5°C / min in a fully charged state of SOC 100%, and then left for 30 minutes, in a hot box evaluation experiment to check for the presence or absence of ignition. The results are shown in Table 4 below. If the battery ignited, it was indicated as PASS, and if it did not ignite, it was indicated as FAIL.

[0145] [Table 4]

[0146] From the results in Table 4, it can be confirmed 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 cycles.

[0147] On the other hand, in the case of the secondary battery of Comparative Example 4, which is provided with a non-aqueous electrolyte solution containing the compound of Chemical Formula 4 containing a propargyl group, it is found that the secondary battery has the same thermal stability as the secondary batteries of Examples 1 to 6 due to the coating effect of the propargyl group.

Claims

1. An electrolyte additive for a secondary battery, comprising a compound represented by the following chemical formula 1: [Chemical formula 1] 【Chemistry 1】 In the above Chemical Formula 1, R １ and R ２ each independently represents 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.

2. The R １ is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, The R ２ is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, The R ３ is an alkyl group having 1 to 3 carbon atoms, 2. The electrolyte additive for secondary batteries according to claim 1, 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.

3. The compound represented by Chemical Formula 1 includes a compound represented by the following Chemical Formula 1A: [Chemical formula 1A] 【Chemistry 2】 In the above Chemical 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.

4. The compound represented by Chemical Formula 1 is a compound represented by the following Chemical Formula 1A-1: [Chemical formula 1A-1] 【Chemistry 3】

5. A non-aqueous electrolyte for a lithium secondary battery, comprising the electrolyte additive for a secondary battery according to claim 1.

6. The non-aqueous electrolyte for a lithium secondary battery according to claim 5, wherein the secondary battery electrolyte additive is included in an amount of 0.05 wt % to 5.0 wt % based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.

7. The non-aqueous electrolyte for a lithium secondary battery according to claim 5, wherein the secondary battery electrolyte additive is included in an amount of 0.05 to 4.0 wt % based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.

8. The nonaqueous electrolyte for a lithium secondary battery according to claim 5 , further comprising a lithium salt and a nonaqueous organic solvent.

9. 6. The nonaqueous electrolyte solution for a lithium secondary battery according to claim 5, further comprising at least one other additive selected from the group consisting of halogen-substituted or unsubstituted 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.

10. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator interposed between the negative electrode and the positive electrode; The nonaqueous electrolyte for a lithium secondary battery according to claim 5 , A lithium secondary battery comprising:

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