Electrolyte additive, battery electrolyte containing the same, and secondary battery containing the same

Abstract

The present invention relates to an electrolyte additive, an electrolyte, and a secondary battery containing the same. According to the present invention, a stable coating is formed on the positive and negative electrodes of a wide variety of lithium secondary batteries, including high-nickel, silicon (Si) negative electrodes, LFP (lithium iron phosphate) batteries, LMR (lithium manganese rich) batteries, and cobalt-free batteries, suppressing side reactions inside the battery. This reduces charge / discharge resistance, improving charging efficiency and output, and suppressing increases in battery resistance and gas generation even when stored at high temperatures for long periods of time. Gas generation due to decomposition of electrolyte components is also significantly suppressed, resulting in excellent long-term life and high-temperature capacity retention. Furthermore, the present invention effectively adsorbs and eliminates hydrofluoric acid, a by-product of side reactions caused by the instability of high-nickel positive electrodes, thereby suppressing increases in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, thereby providing a secondary battery with excellent battery characteristics and life.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte additive, a battery electrolyte containing the same, and a secondary battery containing the same. More specifically, the present invention relates to an electrolyte additive that forms a stable coating on the positive and negative electrodes of a wide variety of lithium secondary batteries, including high-nickel, silicon (Si) negative electrodes, LFP (lithium iron phosphate), LMR (lithium manganese rich) batteries, and cobalt-free batteries, thereby suppressing side reactions inside the battery and resulting in low charge / discharge resistance, improving charging efficiency and output, and suppressing an increase in battery resistance and gas generation even when stored at high temperatures for long periods of time, thereby achieving long life and excellent capacity retention at high temperatures. It also relates to an electrolyte additive that effectively adsorbs and scavenges hydrofluoric acid, a by-product of side reactions caused by the instability of high-nickel positive electrodes, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, thereby providing a secondary battery with excellent battery characteristics and life. [Background technology]

[0002] Lithium secondary batteries facilitate the use of electrical energy by sealing an electrolyte between the positive and negative electrodes to allow smooth movement of lithium ions, and generating or consuming electricity through oxidation-reduction reactions caused by insertion into and desorption from the positive and negative electrodes.

[0003] Meanwhile, as environmental regulations have become stricter around the world and environmental concerns have grown, so has interest in eco-friendly vehicles that can replace fossil fuel vehicles, which are one of the main causes of air pollution. As a result, battery manufacturers both in Korea and overseas are actively working on developing automotive batteries.

[0004] In order for batteries to be used in automobiles, not only must the battery output and capacity be significantly increased, but the problem of increased resistance and improved output at high and low temperatures must be solved to adapt to changes in the weather and other operating environments. In particular, in the case of electric vehicles, where output and driving range are important, research efforts are being made to reduce the internal resistance of batteries and increase their remaining capacity. In particular, it is necessary to develop batteries that can suppress internal side reactions even when stored for long periods of time under high-temperature conditions, thereby ensuring low resistance and long life.

[0005] Additionally, it is necessary to develop batteries that can suppress side reactions inside the battery by forming a stable coating on the positive and negative electrodes of a wide variety of lithium secondary batteries, including high-nickel, silicon (Si) negative electrodes, LFP, LMR (lithium manganese rich) batteries, and cobalt-free batteries, thereby reducing charge / discharge resistance and improving charging efficiency and output. In other words, it is necessary to develop batteries that effectively adsorb and scavenge hydrofluoric acid, a by-product of the instability of high-nickel positive electrodes, to suppress an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, thereby providing excellent battery characteristics and lifespan.

[0006]

[0007]

[0008] [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 11394057 Summary of the Invention [Problem to be solved by the invention]

[0010] In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a novel battery electrolyte additive, a battery electrolyte containing the same, and a secondary battery containing the same.

[0011] Another object of the present invention is to provide a secondary battery that suppresses side reactions inside the battery, reduces charging resistance, improves battery output, improves recovery capacity at high temperatures, allows long-term storage, and has an excellent life maintenance rate at high temperatures.

[0012] The above and other objects of the present invention can all be achieved by the present invention described below. [Means for solving the problem]

[0013] In order to achieve the above objects, the present invention provides an electrolyte additive characterized by being a compound represented by the following chemical formula 1:

[0014] [Chemical formula 1]

[0015] [ka]

[0016] (In the above Chemical Formula 1, lines represent bonds, and unless otherwise specified, the point where bonds are connected is carbon; X represents carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S); R1 represents fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group; and R2 and R3 represent, independently of each other, hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group.)

[0017] The compound represented by the above chemical formula 1 can be a compound represented by the following chemical formulas 1-1 to 1-7.

[0018] [Chemical formula 1-1]

[0019] [ka]

[0020] [Chemical Formula 1-2]

[0021]

change

[0022] [Chemical Formulas 1-3]

[0023]

change

[0024] [Chemical Formulas 1-4]

[0025]

change

[0026] [Chemical Formulas 1-5]

[0027]

change

[0028] [Chemical Formulas 1-6]

[0029]

change

[0030] [Chemical Formulas 1-7]

[0031]

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[0032] The present invention also provides an electrolyte additive comprising a compound represented by the following Chemical Formula 1 and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile:

[0033] [Chemical formula 1]

[0034] [ka]

[0035] (In the above Chemical Formula 1, lines represent bonds, and unless otherwise specified, the point where bonds are connected is carbon; X represents carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S); R1 represents fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group; and R2 and R3 represent, independently of each other, hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group.)

[0036] The compound represented by the above chemical formula 1 may be contained in an amount of, for example, 0.1 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 0.1 to 2.0 wt %, even more preferably 0.1 to 1.0 wt %, and most preferably 0.2 to 1.0 wt %, based on 100 wt % of the components constituting the electrolyte additive.

[0037] The one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in an amount of, for example, 0.1 to 20% by weight, specifically 0.2 to 10% by weight, and preferably 0.5 to 5% by weight, relative to 100% by weight of the components constituting the electrolyte additive.

[0038] The compound represented by Chemical Formula 1 above and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in a weight ratio of, for example, 1:0.5 to 1:3, or 1:0.5 to 1:1.5, or 1:0.7 to 1:1.2.

[0039]

[0040] The present invention also provides an electrolyte additive comprising a compound represented by the following Chemical Formula 1-1 and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile.

[0041] [Chemical formula 1-1]

[0042] [ka]

[0043] (In the above chemical formula 1, the lines represent bonds, and unless otherwise specified, the point where the bonds are connected is carbon.)

[0044] The compound represented by the above chemical formula 1-1 can be contained in an amount of, for example, 0.1 to 10 wt %, specifically 0.1 to 5 wt %, and preferably 0.5 to 2 wt %, based on 100 wt % of the components constituting the electrolyte additive.

[0045] The one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in an amount of, for example, 0.1 to 20% by weight, specifically 0.2 to 10% by weight, and preferably 0.5 to 5% by weight, relative to 100% by weight of the components constituting the electrolyte additive.

[0046] The compound represented by Chemical Formula 1-1 and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in a weight ratio of 1:0.5 to 1:3.

[0047]

[0048] The present invention also provides an electrolyte solution comprising an organic solvent, a lithium salt, and an electrolyte additive, wherein the electrolyte additive comprises the above-described electrolyte additive.

[0049] The organic solvent may include one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0050] The lithium salts include LiF4, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiSbF6, LiAsF6, LiN(SO2C2F5)2, LiCF3SO3, LiCF3CO2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x +1SO2)(C y F 2y +1SO2) (where x and y are natural numbers, for example, integers of 1 to 20), LiAsF6, LiSbF6, LiAlCl4, LiB(C2O4)2 (lithium bis(oxalato)borate: LiBOB), CH3SO3Li, CF3SO3Li, and (CF3SO2)2NLi.

[0051] The electrolyte additive may be included in an amount of 0.1 to 10 wt %, 1 to 10 wt %, 3 to 10 wt %, 1 to 8 wt %, or 1 to 6 wt % based on 100 wt % of the total electrolyte.

[0052]

[0053] The present invention also provides a secondary battery including a negative electrode, a positive electrode, a separator sandwiched between the negative electrode and the positive electrode, and an electrolyte solution, wherein the electrolyte solution is the above-described electrolyte solution.

[0054] The secondary battery may be an automobile battery.

[0055] The automotive battery can be a high-nickel full-cell battery, an LFP (lithium iron phosphate) battery, an LMR (lithium manganese rich) battery or a cobalt-free battery.

[0056] The high-nickel full-cell battery includes a lithium composite metal oxide containing 80% or more nickel as a positive electrode material, and may have a basic capacity of 0.1 to 100 Ah.

[0057] The LFP (lithium iron phosphate) battery may have a basic capacity of 0.1 to 100 Ah.

[0058] The LMR (lithium manganese rich) battery may have a basic capacity of 0.1 to 100 Ah.

[0059] The cobalt-free battery may have a basic capacity of 0.1 to 100 Ah.

[0060]

[0061] The secondary battery may have a recovered capacity retention rate at 60°C of 86% or more, 86.3% or more, 86 to 95%, or 86 to 90%.

[0062] The secondary battery may have a life efficiency at 60°C of 89% or more, 89.3% or more, 89 to 99%, or 89 to 95%.

[0063] The secondary battery may have a thickness increase rate at 60°C of 6% or less, 5% or less, 1 to 5%, or 3 to 5%.

[0064] When the secondary battery is a high-nickel full-cell battery, the resistance increase rate at 60°C may be 20% or less, 18% or less, 1 to 20%, or 3 to 17%.

[0065] When the secondary battery is a lithium iron phosphate battery, the resistance increase rate at 60°C may be 100% or less, 90% or less, 1 to 90%, or 3 to 90%. [Effects of the Invention]

[0066] A secondary battery containing an electrolyte containing the electrolyte additive according to the present invention forms a stable coating on the positive and negative electrodes of a wide variety of lithium secondary batteries, including high nickel, silicon (Si) negative electrodes, LFP batteries, LMR (lithium manganese rich) batteries, and cobalt-free batteries, thereby suppressing side reactions inside the battery and reducing charge / discharge resistance, thereby improving charge efficiency and output.

[0067] In addition, a secondary battery containing an electrolyte containing the electrolyte additive according to the present invention can suppress an increase in battery resistance even when stored for a long period of time under high-temperature conditions, thereby providing a long-term lifespan and excellent high-temperature capacity retention. It also effectively adsorbs and eliminates hydrofluoric acid, a by-product of a reaction caused by instability of a high-nickel positive electrode, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, thereby providing a secondary battery with excellent battery characteristics and lifespan. DETAILED DESCRIPTION OF THE INVENTION

[0068]

[0069] The present invention will be described in detail below, but the present invention is not limited thereto.

[0070]

[0071] In order to manufacture a battery that can be used as an automobile battery, the present inventors have been conducting extensive research into a secondary battery that suppresses side reactions inside the battery, improves output, and suppresses an increase in battery resistance even when stored under high-temperature conditions for a long period of time, thereby providing excellent high-temperature recovery capacity and life characteristics.During this research, the present inventors discovered that it is possible to achieve all of the above-mentioned objects by adding an additive with a specific structure to the electrolyte of the secondary battery, and have completed the present invention based on this discovery.

[0072]

[0073] The electrolyte additive contained in the electrolyte according to the embodiment of the present invention is characterized by being a compound represented by the following Chemical Formula 1. In this case, side reactions inside the battery are suppressed, the charging resistance of the secondary battery is low, and charging efficiency and output can be improved. Even when stored for a long time under high temperature conditions, an increase in battery resistance is suppressed, resulting in a long lifespan and excellent high-temperature capacity retention. Furthermore, hydrofluoric acid, which is a by-product of a side reaction caused by instability of the high-nickel positive electrode, is effectively adsorbed and eliminated, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, resulting in excellent battery characteristics and lifespan.

[0074] [Chemical formula 1]

[0075] [ka]

[0076] (In the above Chemical Formula 1, lines represent bonds, and unless otherwise specified, the point where bonds are connected is carbon; X represents carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S); R1 represents fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group; and R2 and R3 represent, independently of each other, hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), a C1-C3 alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group.)

[0077] Specifically, density functional theory (DFT) calculations for this compound revealed a highest occupied molecular orbital (HOMO) of -12.72 eV and a lowest unoccupied molecular orbital (LUMO) of 1.74 eV for ethylene carbonate (EC), with a measured HOMO of -10.77 eV and a LUMO of 0.85 eV. Judging from these high and low HOMO values, this compound is predicted to be functional at both positive and negative electrodes. In fact, a sulfonyl-based coating is formed midway through the reaction, along with the initial lithium fluoride (LiF)-based inorganic coating component, stabilizing the interface between the electrode and electrolyte. Specifically, it effectively produces Li2SO3, a known low-resistance component, which stabilizes the electrode and reduces resistance.

[0078]

[0079] For the above-mentioned X, it is preferable to use carbon (C), sulfur (S) or nitrogen (N), which have a large difference in electronegativity from oxygen (O) and nitrogen (N), in order to achieve the above-mentioned effects.

[0080] When the electrolyte additive represented by Chemical Formula 1 above is added to a battery electrolyte, the electrons are biased toward the C, S, or N element due to the difference in electronegativity between the O and N elements directly bonded to the sulfur (S) element and the X element (e.g., C, S, or N). Furthermore, due to the overall asymmetric structure of the chemical formula, the S element becomes electron-poor (e-poor, δ+), which induces an oxidation reaction in an electrolyte containing lithium ions, forming a stable coating on an electrode, specifically, a cathode.

[0081] The stability of the coating prevents decomposition of the electrolyte, thereby improving cycle characteristics. In particular, since it does not decompose at high temperatures, it offers the outstanding advantage of significantly improving high-temperature storage stability compared to conventional electrode coatings, which decompose at high temperatures. Furthermore, it prevents an increase in resistance, improving charge / discharge efficiency and output, and suppresses gas generation due to chemical reactions inside the battery, thereby improving battery safety. Furthermore, it prevents the structure of the electrode active materials in the positive and negative electrodes from collapsing at high temperatures, improving capacity retention. This not only extends battery life, but also effectively adsorbs and eliminates hydrofluoric acid, a by-product of the instability of the high-nickel positive electrode, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, resulting in excellent battery characteristics and life.

[0082] It is preferable to use a C1-C3 alkyl group as R1, because this can suppress side reactions inside the battery, improve output, and suppress an increase in battery resistance even when stored under high-temperature conditions for a long period of time, thereby providing a secondary battery with excellent high-temperature recovery capacity and life characteristics.

[0083] For reference, when R1 is hydrogen, the HOMO energy level increases, which reduces the possibility of the additive forming a coating on the electrode and increases the possibility of the electrolyte's main solvent decomposing, which increases the battery thickness during high-temperature storage, leading to increased resistance and reduced recovery capacity.

[0084] It is preferable to use hydrogen, fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) as R2 and R3, because side reactions inside the battery are suppressed to improve output, and an increase in battery resistance is suppressed even when stored under high temperature conditions for a long period of time, thereby providing a secondary battery with excellent high-temperature recovery capacity and life characteristics.

[0085] Specific examples of the electrolyte additive represented by the above chemical formula 1 can be selected from compounds represented by the following chemical formulas 1-1 to 1-7.

[0086] [Chemical Formula 1-1]

[0087]

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[0088] [Chemical Formula 1-2]

[0089]

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[0090] [Chemical Formulas 1-3]

[0091]

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[0092] [Chemical Formulas 1-4]

[0093]

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[0094] [Chemical Formulas 1-5]

[0095]

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[0096] [Chemical Formulas 1-6]

[0097]

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[0098] [Chemical Formulas 1-7]

[0099]

change

[0100] The compound represented by Chemical Formula 1 may be contained in an amount of 0.1 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 0.1 to 2.0 wt %, even more preferably 0.1 to 1.0 wt %, and most preferably 0.2 to 1.0 wt %, based on a total of 100 wt % of the electrolyte solution. Within this range, the effects of improving the charging efficiency and high-temperature life of the battery can be most effectively achieved.

[0101]

[0102] The compound represented by Chemical Formula 1 is preferably added together with one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile, since this can produce a predetermined synergistic effect without adversely affecting the components constituting the battery.

[0103] The one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in a total amount of 0.1 to 20 wt%, preferably 0.1 to 10 wt%, more preferably 0.5 to 8.0 wt%, even more preferably 1 to 4.0 wt%, and most preferably 1.0 to 3.5 wt%, based on 100 wt% of the total electrolyte solution. When the content of the compounds satisfies the above range, it is preferable in terms of the effect of improving the high-temperature characteristics and cycle characteristics of the battery.

[0104] The compound represented by Formula 1 and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be used in a weight ratio of 1:0.5 to 1:3, 1:0.5 to 1:1.5, or 1:0.7 to 1:1.2. Within these ranges, the effects of improving the charging efficiency and high-temperature life of the battery can be most effectively achieved.

[0105]

[0106] For example, in addition to the electrolyte additive, the electrolyte of the present invention may further include additives that are commonly used in electrolytes to suppress side reactions within the battery, improve the life characteristics of the battery, suppress a decrease in the battery capacity, improve the discharge capacity of the battery, etc.

[0107] Specific preferred examples of the additive component include ethyl propionate (EP), propyl propionate (PP), succinic anhydride, tetravinylsilane, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, 1,2-bis((difluorosulfanyl)oxy)ethane, 1,3,6-hexanetricarbonitrile, succinonitrile, 1-ethyl-3-methylimidazolium dicyanamide, trimethoxyboroxine, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, tris(trimethylsilyl)borate, lithium tetrafluoroborate, triisopropyl borate, lithium tetrafluoro(oxalato)phosphate, and lithium difluoro(bisoxalato). The fluoroisotope may be one or more selected from the group consisting of 3-fluoro-1,3-propane sultone, ethylene sulfate, 1,3-propylene sulfate, 1,4-butane sultone, sulfolene, biphenyl, cyclohexylbenzene, 4-fluorotoluene, triphenyl phosphate, fluorobenzene, and 2-fluoro-biphenyl.

[0108] Among the above-mentioned types, metal phosphate-based compounds, specifically at least one selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium tetrafluorooxalatophosphate, and lithium trioxalatophosphate, are components added to improve the performance of lithium secondary batteries, lithium ion capacitors, etc., suppress side reactions within the battery, and improve resistance and lifespan, and may be included in the electrolyte in an amount of, for example, 0.3 to 2.5 wt %, preferably 0.5 to 1.5 wt %. When the content of the electrolyte additive satisfies the above range, it is preferable in terms of improving the high-temperature characteristics and cycle characteristics of the battery.

[0109] The electrolyte additive may be contained in the electrolyte in an amount of, for example, 0.1 to 10.1 wt %, 0.1 to 8.0 wt %, 0.1 to 7 wt %, 0.3 to 7 wt %, 0.5 to 6 wt %, or 0.5 to 5 wt % in total, based on the total components used. When the content of the electrolyte additive satisfies the above range, it is preferable in terms of improving the high-temperature characteristics and cycle characteristics of the battery.

[0110] The additive components must be further included in the compound represented by Chemical Formula 1. It has been confirmed through the comparative examples described below that when other additive components are added alone without the compound represented by Chemical Formula 1, the improvement effects on long-term life and low resistance are poor.

[0111]

[0112] The present invention also provides an electrolyte solution containing the electrolyte additive of the present invention, which is an electrolyte solution for a non-aqueous lithium secondary battery, and includes the electrolyte additive, an organic solvent, and a lithium salt.

[0113] The organic solvent may be, for example, a carbonate-based organic solvent, and more specifically, may be an organic solvent including at least one selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0114] For example, the organic solvent may be a single solvent or a mixed solvent of two or more solvents. Preferably, a mixed solvent may be used by mixing a high-dielectric organic solvent having high ionic conductivity to enhance the charge / discharge performance of the battery and a low-viscosity organic solvent whose viscosity can be adjusted to have a suitable viscosity for application to the battery.

[0115] Examples of the high-dielectric-constant organic solvent that can be used include EC and PC, and examples of the low-viscosity organic solvent that can be used include EMC, DMC, and DEC. The high-dielectric-constant and low-viscosity organic solvents are preferably mixed at a volume ratio of 2:8 to 8:2. More specifically, the solvent may be a ternary mixed solvent of EC or PC with EMC and DEC, and the ratio of EC or PC to EMC and DEC may be, for example, 1:0.1 to 1:2-5, or 1:0.2-0.5:3-5, or 1:0.2-0.3:3-4.

[0116] If the organic solvent contains water, there is a possibility that the lithium ions in the electrolyte may be hydrolyzed. Therefore, it is preferable that the water content in the organic solvent is controlled to 150 ppm or less, preferably 100 ppm or less.

[0117] The lithium salt can be any compound that can provide lithium ions used in lithium secondary batteries without any particular limitation. Specifically, LiPF, LiBF, LiCl, LiBr, LiI, LiClO, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, and (CF3SO2)2NLi. Preferably, it is LiPF6.

[0118] When the lithium salt is dissolved in the electrolyte, it functions as a lithium ion supply source in the lithium secondary battery and can promote the migration of lithium ions between the positive electrode and the negative electrode. Therefore, the lithium salt is preferably contained in the electrolyte at a concentration of approximately 0.6 mol% to 2 mol%. If the lithium salt concentration is less than 0.6 mol%, the conductivity of the electrolyte may be reduced, resulting in a decrease in the performance of the electrolyte. If the lithium salt concentration is greater than 2 mol%, the viscosity of the electrolyte may be increased, resulting in a decrease in the mobility of lithium ions. Considering the conductivity of the electrolyte and the mobility of lithium ions, the lithium salt may be contained in the electrolyte at a concentration of preferably 0.7 mol% to 1.6 mol%, more preferably 0.8 mol% to 1.5 mol%.

[0119] The electrolyte additive may be contained in the electrolyte in an amount of, for example, 0.1 to 10.1 wt %, 0.1 to 8.0 wt %, 0.1 to 7 wt %, 0.3 to 7 wt %, 0.5 to 6 wt %, or 0.5 to 5 wt %. When the content of the electrolyte additive satisfies the above range, it is preferable in terms of improving the high-temperature characteristics and cycle characteristics of the battery.

[0120]

[0121] The secondary battery of the present invention is characterized by comprising a negative electrode, a positive electrode, a separator sandwiched between the negative electrode and the positive electrode, and the electrolyte solution.

[0122] For example, the positive electrode may be manufactured by mixing a positive electrode active material, a binder, and optionally a conductive material to prepare a composition for forming a positive electrode active material layer, and then applying the composition to a positive electrode current collector such as aluminum foil.

[0123] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used.

[0124] As the positive electrode active material, a normal NCM (lithium nickel manganese cobalt oxide, LiNiMnCoO2) positive electrode active material used in a lithium secondary battery can be used. As an example, the chemical formula is Li[Ni x Co y M z O2 (where M is Mn and / or Al, 0 < x < 98, 0 < y < 35, 0 < z < 35, provided that x + y + z = 100). It can be a lithium composite metal oxide in this form, but is not limited thereto.

[0125] For the variables x, y, and z in the chemical formula Li[NixCoyM z O₂ of the lithium composite metal oxide, as an example, 0.0001 < x < 98, 0.0001 < y < 35, 0.0001 < z < 35 can be possible. Specifically, 1 ≤ x ≤ 93, 1 ≤ y ≤ 30, 1 ≤ z ≤ 30 can be possible. More preferably, 5 ≤ x ≤ 91, 3 ≤ y ≤ 25, 3 ≤ z ≤ 25 can be possible. Preferably, 80 ≤ x ≤ 91, 3 ≤ y ≤ 25, 3 ≤ z ≤ 25 can be possible. At this time, x + y + z satisfies 100.

[0126] As another example of the lithium composite metal oxide, it can be one or more selected from the group consisting of LiCoO₂, LiMnO₂, LiMn₂O₄, LiNiO₂, LiNi x Mn (1-x) O₂ (where 0 < x < 1), and LiM1 x M2 y O₂ (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, and M1 and M2 are each independently any one selected from the group consisting of Al, Sr, Mg, and La). In this case, the capacity characteristics and stability of the battery can be enhanced.

[0127] The compound may have a coating layer on its surface, or may be used in combination with a compound having a coating layer. The coating layer may contain at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming these coating layers may be amorphous or crystalline.

[0128] The coating element contained in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation process may be performed using any coating method as long as the compound can be coated with these elements using a method (e.g., spray coating, immersion, etc.) that does not adversely affect the physical properties of the positive electrode active material. Since this method is well known in the art, detailed description thereof will be omitted.

[0129] The content of the positive electrode active material may be, for example, 90 wt % or more, or 90 to 98 wt % based on the total weight of the positive electrode active material layer.

[0130] In one embodiment of the present invention, the positive electrode active material layer may include a binder and a conductive material, each of which may be present in an amount of 1 wt % or more, or 1 to 5 wt %, based on the total weight of the positive electrode active material layer.

[0131] The binder serves to effectively adhere positive electrode active material particles to each other and to effectively adhere the positive electrode active material to a current collector. Examples of the binder that can be used include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0132] The conductive material is used to impart conductivity to the electrode, and any electrically conductive material can be used as long as it does not cause a chemical change in the constructed battery. Examples of the conductive material that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and conductive materials containing mixtures thereof.

[0133] The current collector may be made of Al, but the present invention is not limited to this.

[0134]

[0135] For example, the negative electrode may be manufactured by mixing a negative electrode active material, a binder, and optionally a conductive material to prepare a composition for forming a negative electrode active material layer, and then applying the composition to a negative electrode current collector such as a copper foil.

[0136] The surface of the negative electrode may further include a solid-electrolyte interphase (SEI) film.

[0137] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0138] The material capable of reversibly intercalating / deintercalating lithium ions may be any carbonaceous negative electrode active material that is commonly used in lithium ion secondary batteries.

[0139] Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, etc. In addition to the carbonaceous materials, metallic compounds that can be alloyed with lithium or complexes containing metallic compounds and carbonaceous materials can also be used as the negative electrode active material, and one example of such a material is graphite.

[0140] The negative electrode active material may also be a thin film of metallic lithium. In terms of high stability, the negative electrode active material may be at least one selected from the group consisting of crystalline carbon, amorphous carbon, carbon complexes, lithium metal, and lithium alloys.

[0141] As the metal that can be alloyed with lithium, for example, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy can be used.

[0142] Examples of substances that can be doped and undoped with lithium include Si, Si-C complexes, SiOx (0 < x < 2), Si-Q alloys (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-R (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. Also, it is possible to use a mixture of at least one of these and SiO2.

[0143] Examples of the elements Q and R include those selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0144] Examples of the transition metal oxides include vanadium oxides, lithium vanadium oxides, or lithium titanium oxides, etc.

[0145] The content of the negative electrode active material in the negative electrode active material layer can be, for example, 95% by weight or more, or 95 - 99% by weight, based on the total weight of the negative electrode active material layer.

[0146] The content of the binder in the negative electrode active material layer can be, for example, 1% by weight or more, or 1 - 5% by weight, based on the total weight of the negative electrode active material layer.

[0147] When including a conductive material, it is possible to use the negative electrode active material in the range of 90 - 98% by weight, the binder in the range of 1 - 5% by weight, and the conductive material in the range of 1 - 5% by weight.

[0148] The binder serves to effectively adhere the negative electrode active material particles to each other and to the current collector. The binder may be a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0149] Examples of the non-water-soluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0150] The water-soluble binder may be a rubber-based binder or a polymer resin binder.

[0151] The rubber binder may be selected from styrene butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof.

[0152] The polymer resin binder may be selected from polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0153] When a water-soluble binder is used as the negative electrode binder, it may further contain a cellulose-based compound capable of imparting viscosity.

[0154] The cellulose-based compound may be, for example, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof, which may be mixed together.

[0155] The alkali metal may be Na, K, or Li. The amount of the thickener used may be, for example, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight, based on 100 parts by weight of the negative electrode active material.

[0156] The conductive material is used to impart conductivity to the electrode, and any material can be used as long as it does not cause a chemical change in the constructed battery and is electronically conductive. Examples of the conductive material that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and conductive materials containing mixtures thereof.

[0157] The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0158]

[0159] Depending on the type of lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and it goes without saying that mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator can also be used.

[0160]

[0161] The secondary battery of the present invention improves the performance of conventional batteries by adding an electrolyte additive represented by Chemical Formula 1 above in addition to the usual compounds added to the electrolyte. This effectively adsorbs and eliminates hydrofluoric acid, a by-product of the instability of the high-nickel positive electrode, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, compared to when only an electrolyte additive is added. This further improves battery characteristics such as battery charging resistance and output characteristics measured by a Hybrid Pulse Power Characterization (HPPC) method, capacity recovery characteristics and life characteristics even after long-term storage at high temperatures of 60°C or higher for 60 days or more.

[0162] Specifically, the secondary battery of the present invention may have an HPPC discharge resistance value of 60 mΩ or less, preferably 55 mΩ or less, measured after storage at 60°C for 60 days, and the increase rate compared to the initial resistance does not exceed 93%.

[0163] In this description, the HPPC charge (discharge) resistance value can be measured by a method defined in the document "Battery test manual for plug-in hybrid electric vehicles," (2010, Idaho National Laboratory for the US Department of Energy), and is an important indicator of battery characteristics such as battery output. The charge (discharge) resistance is the resistance value measured when charging (discharging) a battery. The lower the charge (discharge) resistance, the less energy loss there is, the faster the charging rate, and the more battery output there is. The secondary battery of the present invention exhibits the above-described low HPPC discharge resistance value and is excellent in charging rate and output, making it suitable for use as, for example, an automotive battery.

[0164] The secondary battery exhibits a recovered capacity retention rate measured after storage at 60° C. for 60 days of 86% or more, 86.3% or more, 86 to 95%, or 86 to 90%.

[0165] In this description, the recovered capacity indicates the capacity retention characteristics of a battery that has been left unused for a long period of time. It is calculated by measuring the discharged electrical capacity when a battery that has been left unused for a long period of time is discharged to the end-of-discharge voltage, and the discharged electrical capacity when the discharged battery is recharged and discharged again to the end-of-discharge voltage, and comparing the two capacity values. The higher the recovered capacity, the smaller the amount of natural discharge during storage of the battery, meaning that the battery can be stored for a long period of time. In particular, the higher the storage temperature of the battery, the faster the natural discharge rate, so the recovered capacity at high temperatures is a very important characteristic for automotive batteries. When the electrolyte additive of the present invention is added to an electrolyte, the recovered capacity is improved by, for example, up to 11%, specifically 9 to 11%, compared to when a conventional additive is used alone, resulting in the effect of enabling longer storage periods on a single charge.

[0166] The secondary battery may have a life efficiency of 89% or more, 89.3% or more, 89 to 99%, or 89 to 95%, measured after storage at 60° C. for 60 days.

[0167] The secondary battery may have a thickness increase rate at 60°C of 6% or less, 5% or less, 1 to 5%, or 3 to 5%.

[0168] When the secondary battery is a high-nickel full-cell battery, the resistance increase rate at 60°C may be 20% or less, 18% or less, 1 to 20%, or 3 to 17%.

[0169] When the secondary battery is an LFP battery, the resistance increase rate at 60°C may be 100% or less, 90% or less, 1 to 90%, or 3 to 90%.

[0170]

[0171] Therefore, when the battery of the present invention is used as an automobile battery, it is possible to improve output, which becomes increasingly important depending on the size of the automobile, and improve performance at low and high temperatures, which are problematic due to changes in climate and the characteristics of automobiles that are exposed to sunlight almost directly while driving or parked.Even if a high-content nickel positive electrode material is used to achieve high capacity, it is possible to effectively adsorb and eliminate hydrofluoric acid, which is a by-product of the instability of the high-nickel positive electrode, and to suppress an increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode, thereby ensuring stability and exhibiting excellent performance as an automobile battery.

[0172]

[0173] Below, preferred examples are presented to deepen understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it should be obvious to those skilled in the art that various changes and modifications can be made within the scope and technical idea of ​​the present invention. It goes without saying that such changes, variations and modifications also fall within the scope of the appended claims.

[0174]

[0175] Example 1

[0176] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by the above chemical formula 1-1 was added to a solution containing LiPF6 at a concentration of 1.15 M as the lithium salt to prepare a battery electrolyte.

[0177]

[0178] Example 2

[0179] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by the above Chemical Formula 1-1 and 0.5 wt % of fluoroethylene carbonate (FEC) were added to a solution containing LiPF6 as the lithium salt at a concentration of 1.15 M to prepare a battery electrolyte.

[0180]

[0181] Example 3

[0182] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by Chemical Formula 1-1 and 1.0 wt % of lithium difluorophosphate (LDFP) were added to a solution containing LiPF6 as the lithium salt at a concentration of 1.15M to prepare a battery electrolyte.

[0183]

[0184] Example 4

[0185] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by the above Chemical Formula 1-1 and 1.0 wt % of vinyl carbonate (VC) were added to a solution containing LiPF6 as the lithium salt at a concentration of 1.15 M to prepare a battery electrolyte.

[0186]

[0187] Example 5

[0188] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by the above chemical formula 1-2 was added to a solution containing LiPF6 at a concentration of 1.15 M as the lithium salt to prepare a battery electrolyte.

[0189]

[0190] Example 6

[0191] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by the above chemical formula 1-2 and 0.5 wt % of fluoroethylene carbonate (FEC) were added to a solution containing LiPF6 as the lithium salt at a concentration of 1.15 M to prepare a battery electrolyte.

[0192]

[0193] Comparative Example 1

[0194] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC=20:40:40 was used as the organic solvent, and 0.5 wt % of the compound represented by Chemical Formula 2 was added to a solution containing LiPF6 as the lithium salt at a concentration of 1.15 M to prepare a battery electrolyte.

[0195] [Chemical formula 2]

[0196] [ka]

[0197] Comparative Example 2

[0198] A carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 was used as the organic solvent, and 0.5 wt% of fluoroethylene carbonate (FEC) was added to a solution containing LiPF6 at a concentration of 1.15M as the lithium salt to prepare a battery electrolyte.

[0199]

[0200] Comparative Example 3

[0201] A carbonate-based mixed solvent with a volume ratio of EC:EMC:DMC=20:5:75 was used as the organic solvent, and a solution containing LiPF6 at a concentration of 1.15 M was used as the lithium salt to prepare a battery electrolyte. For reference, Comparative Example 3 corresponds to an experiment in which no electrolyte additive was used at all.

[0202]

[0203] Comparative Example 4

[0204] A carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 was used as the organic solvent, and 0.5 wt% of lithium difluorophosphate was added to a solution containing LiPF6 at a concentration of 1.15M as the lithium salt to prepare a battery electrolyte.

[0205]

[0206] NCM battery manufacturing

[0207] Li(Ni) as a positive electrode active material 0.8 Co 0.1 Mn 0.1 A positive electrode mixture slurry was prepared by adding 92 wt% of SiO2, 4 wt% of carbon black as a conductive material, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder to a solvent, N-methyl-2-pyrrolidone (NMP). The positive electrode mixture slurry was applied to an aluminum (Al) thin film (positive electrode current collector) with a thickness of approximately 20 μm, dried, and then roll pressed to prepare the positive electrode.

[0208] Anode active material carbon powder, binder polyvinylidene fluoride (PVdF), and conductive material carbon black were mixed at 96 wt%, 3 wt%, and 1 wt%, respectively, and added to solvent N-methylpyrrolidone (NMP) to prepare anode mixture slurry. The anode mixture slurry was applied to a 10 μm-thick copper (Cu) thin film anode current collector, dried, and then roll pressed to prepare the anode.

[0209] The positive and negative electrodes produced as described above were used in combination with a separator consisting of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) to produce a pouch-type battery by a conventional method, and then each of the electrolyte solutions produced in Examples 1 to 6 and Comparative Examples 1 to 4 was injected to complete the production of the lithium secondary battery, thereby completing the lithium secondary battery.

[0210]

[0211] Test Examples 1-9

[0212] In order to evaluate the performance of each secondary battery manufactured above, the performance was evaluated by the following method, and the results are summarized in Table 1 below.

[0213]

[0214] [HPPC charge (discharge) resistance evaluation]

[0215] Measurements were performed using the method specified in the document "Battery test manual for plug-in hybrid electric vehicles," (2010, Idaho National Laboratory for the US Department of Energy.)

[0216] After storing at 60°C for 60 days, the measured voltage value, charge / discharge current value corresponding to C rate, change in current (ΔI), change in discharge voltage (ΔV), change in charge voltage (ΔV), charge resistance, and discharge resistance were measured. For each C rate, charge / discharge current was applied within a short period of time for a certain period of time, and the resistance increase rate was calculated from the gradient value obtained from the change in current and voltage.

[0217]

[0218] [Evaluation of high temperature storage DC-IR (direct current internal resistance) and recovery capacity]

[0219] The charging conditions were a constant current of 0.5 C and a voltage of 4.2 V, with charging until the charging current was reduced to 1 / 10 C. The discharging conditions were a constant current of 0.5 C with discharging down to 3.0 V, and after charging and discharging under these discharging conditions, the discharge capacity was measured.

[0220] After charging under the same charge-discharge conditions, the batteries were stored at 60°C for 60 days, and then discharged to a discharge voltage of 3V under the same conditions. The change in remaining capacity was measured, and the results are shown in Table 1 below in terms of the high-temperature storage DC-IR increase rate, recovered capacity retention rate, and thickness retention rate.

[0221]

[0222] [High temperature life evaluation]

[0223] The secondary battery was charged at a constant current of 1 C at 60°C until the voltage reached 4.20 V (vs. Li), and then cut off at a current of 0.1 C while maintaining 4.20 V in constant voltage mode. It was then discharged at a constant current of 1 C until the voltage reached 3.0 V (vs. Li) during discharge (first cycle). This cycle was repeated 300 times, and the changes in capacity and retention rate were measured.

[0224] [Table 1]

[0225] As shown in Table 1 above, in Test Examples 1 to 6 using Examples 1 to 6, which are the electrolyte additives of the present invention, improvements were confirmed in the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency of the NCM batteries compared to Test Examples 7 to 9, which used Comparative Example 1, in which the electrolyte additive was replaced with an electrolyte additive component having a structure similar to Chemical Formula 1-1 above, Comparative Example 2, in which the electrolyte additive was replaced with a conventionally used carbonate component, and Comparative Example 3, in which the electrolyte additive was not used.

[0226] In particular, there was a significant difference in the resistance increase rate of the battery before and after high-temperature storage. It was 8.5 to 16.5% in Test Examples 1 to 6 using Examples 1 to 6 according to the present invention, and it was confirmed that this was a significant improvement compared to the 23.2 to 55.0% calculated in Test Examples 7 to 9 using Comparative Examples 1 to 3.

[0227] Furthermore, when the change in the thickness of the battery before and after high-temperature storage was measured, it was confirmed that the electrolyte additive of the present invention significantly suppresses the oxidation / reduction decomposition of the electrolyte, thereby reducing the amount of gas generated. In fact, as is clear from Table 1 above, the electrolyte additive of the present invention achieved a thickness increase rate of 5% or less at 60°C.

[0228]

[0229] LFP battery manufacturing

[0230] Li(Ni) as a positive electrode active material 0.8 Co 0.1 Mn 0.1 A positive electrode mixture slurry was prepared by adding 92 wt% of SiO2, 4 wt% of carbon black as a conductive material, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder to a solvent, N-methyl-2-pyrrolidone (NMP). The positive electrode mixture slurry was applied to an aluminum (Al) thin film (positive electrode current collector) with a thickness of approximately 20 μm, dried, and then roll pressed to prepare the positive electrode.

[0231] A negative electrode mixture slurry was prepared by adding carbon powder as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive material at 96 wt%, 3 wt%, and 1 wt%, respectively, to N-methyl-2-pyrrolidone (NMP) as a solvent. The negative electrode mixture slurry was applied to a 10 μm-thick copper (Cu) thin film as a negative electrode current collector and dried to prepare a negative electrode, which was then roll-pressed.

[0232] The positive and negative electrodes produced as described above were used in combination with a separator consisting of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) to produce a pouch-type battery by a conventional method, and then each of the electrolyte solutions produced in Example 1, Comparative Example 1, and Comparative Example 4 was injected to complete the production of the lithium secondary battery, thereby completing the lithium secondary battery.

[0233]

[0234] Test Examples 10-12

[0235] In order to evaluate the performance of each secondary battery manufactured above, the performance was evaluated by the following method, and the results are summarized in Table 2 below.

[0236]

[0237] [HPPC charge (discharge) resistance evaluation]

[0238] Measurements were performed using the method specified in the document "Battery test manual for plug-in hybrid electric vehicles," (2010, Idaho National Laboratory for the US Department of Energy.)

[0239] After storing at 60°C for 60 days, the measured voltage value, charge / discharge current value corresponding to C rate, change in current (ΔI), change in discharge voltage (ΔV), change in charge voltage (ΔV), charge resistance, and discharge resistance were measured. For each C rate, charge / discharge current was applied within a short period of time for a certain period of time, and the resistance increase rate was calculated from the gradient value obtained from the change in current and voltage.

[0240]

[0241] [Evaluation of high temperature recovery capacity]

[0242] The charging conditions were a constant current of 0.5 C and a voltage of 4.2 V, with charging until the charging current was reduced to 1 / 10 C. The discharging conditions were a constant current of 0.5 C with discharging down to 3.0 V, and after charging and discharging under these discharging conditions, the discharge capacity was measured.

[0243] After charging under the same charge / discharge conditions, the batteries were stored at 60°C for 60 days, and then discharged to a discharge voltage of 3V under the same conditions. The change in remaining capacity was measured and shown in Table 1 below as high temperature recovery capacity.

[0244]

[0245] [High temperature life evaluation]

[0246] The secondary battery was charged at a constant current of 1 C at 60°C until the voltage reached 4.20 V (vs. Li), and then cut off at a current of 0.1 C while maintaining 4.20 V in constant voltage mode. It was then discharged at a constant current of 1 C until the voltage reached 3.0 V (vs. Li) during discharge (first cycle). This cycle was repeated 300 times, and the battery was then stored for 60 days, after which the changes in capacity and retention rate were measured.

[0247] [Table 2]

[0248] As shown in Table 2 above, in Test Example 10 using Example 1, which is an electrolyte additive of the present invention, at least one of the physical properties of initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency was confirmed to be equivalent to or improved from Test Examples 11 and 12, which used Comparative Example 1, in which the electrolyte additive was replaced with an electrolyte additive component having a structure similar to Chemical Formula 1-1 above, and Comparative Example 4, in which the electrolyte additive was replaced with a conventionally used lithium difluorophosphate (LDFP) component.

[0249] In particular, there was a significant difference in the resistance increase rate of the battery before and after high-temperature storage. In Test Example 10 using Example 1 according to the present invention, the increase rate was 86.9%, which was confirmed to be a significant improvement over the 109.6 to 120.1% calculated in Test Examples 11 and 12 using Comparative Examples 1 and 4.

[0250]

[0251] In addition, the high-temperature recovery capacity was improved. Compared to experiments using a structure similar to that of Comparative Example 1 or a structure different from that of Comparative Example 4, the electrolyte additive structure used in the present invention not only formed an effective protective film on the positive and negative electrodes, but also suppressed side reactions between the electrolyte and the electrodes, resulting in excellent recovery capacity and capacity retention characteristics.

[0252] For reference, the recovery capacity is related to the reversibility of Li ions, and it is known that if irreversible Li ions increase, such as through the dissolution of transition metals from the positive electrode, the deposition of the dissolved metal ions on the surface of the negative electrode, or side reactions at the interface between the positive and negative electrodes, this will lead to a decrease in capacity.

[0253] As is clear from Table 2 above, the electrolyte additive of the present invention exhibits a recovered capacity retention rate of 89.0% at 60°C, which is a significant improvement over the 84.2 to 96.9% in Comparative Examples 1 and 4.

[0254] Furthermore, when the lifetime efficiency was measured, it was found to be 89.3% in Example 1 according to the present invention, which was a significant improvement over the 85.1 to 87.5% calculated in Comparative Examples 1 and 4.

[0255]

[0256] As a result, it was found that the secondary batteries of Examples 1 and 5, in which the electrolyte additive of the present invention was used alone, and Examples 1, 2, 3, 4, and 6, in which the electrolyte additive was used in appropriate combination with a conventional electrolyte additive, had superior discharge efficiency in terms of output and life performance of the final completed composition compared to Comparative Example 1, in which a structure similar to the electrolyte additive was used alone, or Comparative Examples 2 and 4, in which only a conventional electrolyte additive was used, and Comparative Example 3, in which neither the electrolyte additive nor a conventional electrolyte additive was used at all.

[0257]

[0258] Therefore, when the electrolyte additive according to the embodiment of the present invention and the electrolyte containing the same are applied to a secondary battery, not only can they suppress side reactions inside the battery and reduce the amount of gas generated, but they also improve charge resistance, discharge resistance, output, recovery capacity, and life efficiency even when stored for a long period at high temperatures. This shows that the electrolyte additive according to the embodiment of the present invention is suitable for use in automotive secondary batteries, particularly high-nickel full-cell batteries with a basic capacity of 0.1 to 100 Ah, LFP batteries with a basic capacity of 0.1 to 100 Ah, LMR (lithium manganese rich) batteries with a basic capacity of 0.1 to 100 Ah, and cobalt-free batteries with a basic capacity of 0.1 to 100 Ah.

Claims

1. An electrolyte additive characterized by being a compound represented by the following chemical formula 1: [Chemical formula 1] 【Chemistry 1】 (In the above chemical formula 1, the lines represent bonds, and unless otherwise specified, the point where bonds are connected is carbon, X represents carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S), and R represents fluorine (F), chlorine (Cl), bromine (Br), iodine (I), C １ ~C ３ R2 and R3 are each independently hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), C １ ~C ３ an alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group.

2. The electrolyte additive according to claim 1, wherein the compound represented by Chemical Formula 1 is a compound represented by the following Chemical Formulas 1-1 to 1-7. [Chemical formula 1-1] 【Chemistry 2】 [Chemical formula 1-2] 【Transformation 3】 [Chemical formula 1-3] 【Chemistry 4】 [Chemical formula 1-4] 【Transformation 5】 [Chemical formula 1-5] 【Transformation 6】 [Chemical formula 1-6] 【Transformation 7】 [Chemical formula 1-7] 【Transformation 8】

3. An electrolyte additive comprising a compound represented by the following Chemical Formula 1 and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile: [Chemical formula 1] 【Chemistry 9】 (In the above chemical formula 1, the lines represent bonds, and unless otherwise specified, the point where bonds are connected is carbon, X represents carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S), and R represents fluorine (F), chlorine (Cl), bromine (Br), iodine (I), C １ ~C ３ R2 and R3 are each independently hydrogen (H), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), C １ ~C ３ an alkyl group, a vinyl group, an allyl group, a propargyl group, a phenyl group, or a carboxy group.

4. 4. The electrolyte additive of claim 3, wherein the compound represented by Formula 1 and the at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile are contained in a weight ratio of 1:0.2 to 1:

3.

5. An electrolyte solution comprising an organic solvent, a lithium salt, and an electrolyte additive, 10. An electrolytic solution, comprising the electrolytic solution additive according to claim 1 or 3.

6. 6. The electrolyte solution according to claim 5, wherein the organic solvent comprises at least one selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

7. The lithium salt is LiPF ６ , LiF ４ , LiCl, LiBr, LiI, LiClO ４ , LiB １０ Cl １０ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , C.H. ３ SO ３ Li, CF ３ SO ３ Li and (CF ３ SO ２ ) ２ The electrolyte solution according to claim 5, comprising one or more selected from the group consisting of NLi.

8. A secondary battery comprising a negative electrode, a positive electrode, a separator sandwiched between the negative electrode and the positive electrode, and an electrolyte solution, 6. A secondary battery, wherein the electrolyte solution is the electrolyte solution according to claim 5.

9. 9. The secondary battery according to claim 8, wherein the secondary battery has a recovered capacity retention rate of 86% or more after storage at 60°C for 60 days.

10. 9. The secondary battery according to claim 8, wherein the secondary battery has a life efficiency of 89% or more after being stored at 60° C. for 60 days.

11. 9. The secondary battery according to claim 8, wherein the secondary battery has a thickness increase rate of 6% or less after storage at 60°C for 60 days.

12. 9. The secondary battery according to claim 8, wherein the secondary battery is a battery for an automobile.

13. 9. The secondary battery according to claim 8, wherein the secondary battery is a high-nickel full-cell battery, and the resistance increase rate at 60°C is 20% or less.

14. 9. The secondary battery according to claim 8, wherein the secondary battery is a lithium iron phosphate battery and has a resistance increase rate of 100% or less at 60°C.

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