Electrolyte additive, battery electrolyte comprising same, and secondary battery comprising same

Abstract

The present invention relates to an electrolyte additive, an electrolyte comprising same, and a secondary battery comprising same. According to the present invention, formation of a stable protective film at the interface between the positive electrode and the negative electrode in various lithium secondary battery systems such as high nickel (NCM, NCA) positive electrodes, silicon (Si) negative electrodes, lithium iron phosphate (LFP) batteries, lithium manganese rich (LMR) batteries, or cobalt-free batteries allows for the suppression of side reactions inside the battery and the reduction of charge resistance, thereby improving charging efficiency and output performance. In addition, even after long-term storage under high-temperature conditions, the increase in internal resistance is suppressed, and gas generation resulting from decomposition of electrolyte components is significantly reduced, thereby achieving excellent long-term lifespan and high-temperature capacity retention. In particular, the electrolyte additive of the present invention forms stable SEI and CEI at the interface between the negative electrode and the positive electrode, respectively, thereby protecting the interface from aggressive decomposition products such as hydrofluoric acid (HF) generated due to structural instability of the high-nickel positive electrode, and suppressing an increase in the acidity of the electrolyte and elution of transition metal ions of the positive electrode. Consequently, the characteristics and lifespan of the battery can be remarkably improved.

Description

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

[0001] The present invention relates to an electrolyte additive, a battery electrolyte containing the same, and a secondary battery containing the same.

[0002] More specifically, the present invention relates to an electrolyte additive that can suppress side reactions inside a battery and improve charging efficiency and output performance by reducing charge / discharge resistance by forming a stable protective film at the interface between the positive and negative electrodes of various lithium secondary batteries, such as nickel-nickel (NCM, NCA), silicon-based (Si) anodes, lithium iron phosphate (LFP), lithium manganese-rich (LMR) batteries, or cobalt-free batteries, particularly a solid electrolyte interface (SEI) at the negative electrode and an interfacial electrolyte interface (CEI) at the positive electrode, and an electrolyte and a secondary battery containing the same.

[0003] In addition, it can effectively suppress the increase in battery resistance and gas generation even when stored for a long time in a high-temperature environment, thereby improving the long-term lifespan and high-temperature capacity retention rate. In particular, the additive of the present invention protects the interface from aggressive impurities such as HF through stable SEI formation at the negative electrode, and suppresses metal dissolution and electrolyte decomposition through CEI formation at the positive electrode, thereby significantly improving battery performance and lifespan. The present invention relates to an electrolyte additive, an electrolyte including the same, and a secondary battery, etc.

[0004] Lithium secondary batteries facilitate the use of electrical energy by allowing the smooth movement of lithium ions by placing an electrolyte between the positive and negative electrodes, and generating or consuming electricity through oxidation-reduction reactions resulting from insertion and deintercalation at the positive and negative electrodes.

[0005] Meanwhile, with environmental regulations strengthening globally and growing concern for the environment, interest in eco-friendly vehicles that can replace fossil fuel-powered vehicles, a major source of air pollution, is also growing. Consequently, the domestic and international battery industries are actively developing automotive batteries.

[0006] In order to use batteries in automobiles, not only must the output and capacity of the battery be significantly increased, but also the problem of improving output and increasing resistance at high and low temperatures must be solved according to the usage environment such as weather changes. In particular, in the case of electric vehicles, since output and driving range performance are important, research is being conducted to lower the internal resistance of the battery and increase the remaining capacity. In particular, it is necessary to develop a battery that suppresses internal side reactions of the battery and secures low resistance and long-life performance even when stored for a long time under high-temperature conditions.

[0007] In addition, there is a need for the development of a battery system that can form a stable film at the interface between the positive and negative electrodes of various lithium secondary batteries, such as high-nickel (NCM, NCA), silicon anode (Si anode), lithium iron phosphate (LFP), lithium manganese-rich (LMR) batteries, or cobalt-free batteries, thereby suppressing side reactions inside the battery and lowering the charge / discharge resistance, thereby improving the charging efficiency and output performance.

[0008] In particular, in order to protect the anode and cathode interfaces from aggressive decomposition products such as hydrofluoric acid (HF) generated under high voltage or high temperature conditions due to the structural instability of the nickel anode, it is necessary to develop a technology that can form a stable solid electrolyte interface (SEI) and interfacial electrolyte interface (CEI) through electrolyte additives, thereby suppressing electrode interface deterioration and electrolyte acidity increase, thereby minimizing transition metal ion dissolution from the electrode and ensuring excellent battery performance and long-term life.

[0009] [Prior Art Literature]

[0010] [Patent Document]

[0011] Korean Patent Publication No. 10-2021-0129241

[0012] In order to solve the problems of the prior art as described above, the present invention aims to provide a novel battery electrolyte additive, a battery electrolyte containing the same, and a secondary battery containing the same.

[0013] In addition, the present invention aims to provide a secondary battery that suppresses internal side reactions of the battery, reduces charging resistance to improve battery output, improves recovery capacity at high temperatures to enable long-term storage, and has excellent lifespan retention at high temperatures.

[0014] The above and other objects of the present invention can all be achieved by the present invention described below.

[0015] In order to achieve the above purpose, the present invention provides an electrolyte additive characterized by being a compound represented by the following chemical formula 1.

[0016] [Chemical Formula 1]

[0017]

[0018] (In the above chemical formula 1, a line is a bond, and when a separate element is not described, the point where a bond meets a bond is carbon, and X' and X" are each independently fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).)

[0019] II) In the above I), the compound represented by the chemical formula 1 may be a compound represented by the following chemical formulas 1-1 to 1-16.

[0020] [Chemical Formulas 1-1 to 1-4]

[0021]

[0022] [Chemical Formulas 1-5 to 1-8]

[0023]

[0024] [Chemical Formulas 1-9 to 1-12]

[0025]

[0026] [Chemical Formula 1-13 to 1-16]

[0027]

[0028] In addition, the present invention provides III) a compound represented by the following chemical formula 1; And an electrolyte additive is provided, characterized in that it comprises at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite (PS), propylene carbonate sulfite (PRS), ethyl sulfate (ESA), vinylethylene carbonate (VEC), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), succinonitrile (SN), and 1,3,6-hexanetricarbonitrile (HTCN).

[0029] [Chemical Formula 1]

[0030]

[0031] (In the above chemical formula 1, a line is a bond, and when a separate element is not described, the point where a bond meets a bond is carbon, and X' and X" are each independently fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).)

[0032] IV) In the above III), the compound represented by the above chemical formula 1 may be included in an amount of 0.1 to 10 wt% among 100 wt% of the components constituting the electrolyte additive.

[0033] V) In the above III) to IV), at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite (PS), propylene carbonate sulfite (PRS), ethyl sulfate (ESA), vinylethylene carbonate (VEC), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), succinonitrile (SN) and 1,3,6-hexanetricarbonitrile (HTCN) is used as an electrolyte. It may be included in an amount of 0.1 to 20 wt% among 100 wt% of the components constituting the additive.

[0034] VI) In the above III) to V), a compound represented by the above chemical formula 1; And at least one compound selected from the group consisting of Vinylene Carbonate, Fluoroethylene Carbonate, Lithium Difluorophosphate, Propylene Sulfite (PS), Propylene Carbonate Sulfite (PRS), Ethyl Sulfate (ESA), Vinylethylene Carbonate (VEC), Lithium Bis(oxalato)borate (LiBOB), Lithium Difluoro(oxalato)borate (LiDFOB), Succinonitrile (SN) and 1,3,6-Hexanetricarbonitrile (HTCN) is mixed in a ratio of 1:0.5 to 1:50. May be included by weight ratio.

[0035]

[0036] In addition, the present invention provides an electrolyte comprising VII) an organic solvent, a lithium salt, and an electrolyte additive, wherein the electrolyte additive comprises the electrolyte additive described above.

[0037] VIII) In the above VII), the organic solvent may include 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, ethyl propyl carbonate, ethyl propionate (EP), propyl propionate (PP), and methyl acetate (MA).

[0038] IX) In the above VII) to VIII), the lithium salt is LiPF6, LiF4, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiSbF6, LiAsF6, LiN(SO2C2F5)2, LiCF3SO3, LiCF3CO2, Li(CF3SO2)2N, LiN(SO2F)2, LiN(SO3C2F5)2, Li(FSO2)2N, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2) (wherein x and y are natural numbers from 1 to 20), LiB(C2O4)2(lithium bisoxalate borate (Lithium Bis(oxalato)borate, LiBOB)), CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, Lithium Difluoro(oxalato)borate (LiDFOB), Lithium Bis(fluorosulfonyl)imide (LiFSI), Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(pentafluoroethanesulfonyl)imide (LiBETI), Lithium Fluoro(oxalato)borate (LiFOB), Lithium Fluorosulfonate (LiFSO3), and modifications of these lithium salts or combinations thereof.

[0039] X) In the above VII) to IX), the electrolyte additive may be included in a range of 0.1 to 10 wt% based on 100 wt% of the total electrolyte.

[0040]

[0041] In addition, the present invention provides a secondary battery comprising XI) a cathode, an anode, a separator interposed between the cathode and the anode, and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0042] XII) In the above XI), the secondary battery may be a battery for an automobile.

[0043] XIII) In the above XI) to XII), the automobile battery may be a high-nickel full-cell battery, a mid-nickel full-cell battery, an LFP (lithium iron phosphate) battery, an LMR (lithium manganese rich) battery, an NMX (nickel-manganese, Co free) battery, an LMR (lithium-manganese-rich) battery, an LMX (lithium-manganese-rich, Co free) battery, an OLO (over lithiated layered oxide) battery, an LCO (lithium cobalt oxide) battery, a DRX (disordered rocksalt) battery, an NCMA (nickel-cobalt-manganese-aluminum oxide) battery, or an LMFP (lithium-manganese-iron-phosphate) battery.

[0044] XIV) In the above XI) to XIII), the high-nickel full-cell battery includes a lithium composite metal oxide having a nickel content of 80% or more as a cathode material, and may have a basic capacity of 0.1 to 100 Ah.

[0045] XV) In the above XI) to XIV), the mid-nickel-based full-cell battery includes a lithium composite metal oxide having a nickel content of 50 to 80% as a cathode material, and may have a basic capacity of 0.1 to 100 Ah.

[0046] XVI) In the above XI) to XV), the LFP (lithium iron phosphate) battery may have a basic capacity of 0.1 to 100 Ah.

[0047] XVII) In the above XI) to XVI), the LMR (lithium manganese rich) battery may have a basic capacity of 0.1 to 100 Ah.

[0048] XVIII) In the above XI) to XVII), the LMFP (Lithium-Manganese-Iron-Phosphate) battery may have a basic capacity of 0.1 to 100 Ah.

[0049] XIX) In the above XI) to XVIII), the NCMA (Nickel-Cobalt-Manganese-Aluminum Oxide) battery may have a basic capacity of 0.1 to 100 Ah.

[0050] XX) In the above XI) to XIX), the NMX (Nickel-Manganese, Co free) battery can have an operating voltage in the range of 2.0 to 4.6 V.

[0051] XXI) In the above XI) to XX), the LMR (Lithium-Manganese-Rich) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0052] XXII) In the above XI) to XXI), the LMX (Lithium-Manganese-Rich, Co free) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0053] XXIII) In the above XI) to XXII), the OLO (Over Lithiated layered Oxide) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0054] XXIV) In the above XI) to XXIII), the LCO (Lithium Cobalt Oxide) battery may have an operating voltage in the range of 2.0 to 4.8 V.

[0055] XXV) In the above XI) to XXIV), the DRX (Disordered Rocksalt) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0056] XXVI) In the above XI) to XXV), the LMFP (Lithium-Manganese-Iron-Phosphate) battery may have an operating voltage in the range of 2.0 to 4.2 V.

[0057] XXVII) In the above XI) to XXVI), the NCMA (Nickel-Cobalt-Manganese-Aluminum Oxide) battery may have an operating voltage in the range of 2.0 to 4.6 V.

[0058] XXVIII) In the above XI) to XXVII), the secondary battery may have a retention capacity of 60% or more after storage for 30 days at 60°C.

[0059] XXIX) In the above XI) to XXVIII), the secondary battery may have a recovery capacity of 70% or more after storage at 60°C for 30 days.

[0060] XXX) In the above XI) to XXIX), the increase rate compared to the initial resistance of the secondary battery after storage at 60°C for 30 days may be 70% or less.

[0061] XXXI) In the above XI) to XXX), the secondary battery may have a capacity retention rate of 70% or more after 300 charge and discharge cycles at 45°C.

[0062] XXXII) In the above XI) to XXXI), the secondary battery may have a rate capability of 90% or more when measured under 2.0C discharge conditions compared to 1.0C discharge.

[0063] XXXIII) In the above XI) to XXXII), the secondary battery may have a rate capability of 80% or more when measured under 3.0C discharge conditions compared to 1.0C discharge.

[0064] XXXIV) In the above XI) to XXXIII), the secondary battery may have a rate capability of 50% or more when measured under 5.0C discharge conditions compared to 1.0C discharge.

[0065] A secondary battery including an electrolyte including an electrolyte additive according to the present invention forms a stable film on a positive and negative electrode of various lithium secondary batteries including a high-nickel, Si negative electrode, LFP battery, LMR (lithium manganese rich) battery, or cobalt-free battery, thereby suppressing side reactions inside the battery and lowering charge / discharge resistance, thereby improving charging efficiency and output.

[0066] In addition, a secondary battery including an electrolyte including an electrolyte additive according to the present invention has an excellent long-term lifespan and high-temperature capacity retention rate because the increase in resistance of the battery is suppressed even when stored for a long time under high-temperature conditions, and a stable solid electrolyte interface (SEI) and interfacial electrolyte interface (CEI) are formed that can protect the interface from aggressive decomposition products such as hydrofluoric acid (HF) generated due to the structural instability of a high-nickel positive electrode, thereby suppressing an increase in the acidity of the electrolyte and preventing the elution of transition metal ions from the positive electrode, thereby having the effect of improving the characteristics and lifespan of the battery.

[0067] The present invention will be described in detail below, but the present invention is not limited thereto.

[0068] The inventors of the present invention were researching a secondary battery that has excellent high-temperature recovery capacity and lifespan characteristics by suppressing internal side reactions of the battery to improve output and suppressing an increase in resistance of the battery even when stored for a long time under high-temperature conditions, in order to manufacture a battery that can be used as an automobile battery. While doing so, they confirmed that when an additive of a specific structure is added to the electrolyte of the secondary battery, all of the above-mentioned objectives can be achieved, and completed the present invention based on this.

[0069] The electrolyte additive included in the electrolyte according to embodiments of the present invention is characterized by being a compound represented by the following chemical formula 1, and when such an additive is included, side reactions inside the battery are effectively suppressed, and the charging resistance of the secondary battery is lowered, so that the charging efficiency and output characteristics can be improved.

[0070] In addition, even if stored for a long time under high temperature conditions, the increase in the resistance of the battery is suppressed, so that the long-term life and high-temperature capacity retention rate are excellent. In particular, since a stable solid electrolyte interface (SEI) and an interfacial electrolyte interface (CEI) are formed at the negative and positive electrode interfaces, respectively, through the additive, the interface is protected from aggressive products such as hydrofluoric acid (HF) generated due to the instability of the high-nickel positive electrode, and the increase in the acidity of the electrolyte and the elution of positive electrode transition metal ions are suppressed, so that the performance and life of the battery are remarkably improved.

[0071] [Chemical Formula 1]

[0072]

[0073] (In the above chemical formula 1, a line is a bond, and when a separate element is not described, the point where a bond meets a bond is carbon, and X' and X" are each independently fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).)

[0074] Specifically, the result of DFT (Density functional theory) calculation for this compound shows that the HOMO is -9.94 eV and the LUMO is 0.43 eV compared to ethylene carbonate (EC) which has a HOMO of -12.72 eV and a LUMO of 1.74 eV. Judging from the high HOMO and low LUMO values, it is predicted to be able to act on both the positive and negative electrodes. In fact, a sulfonyl-based film is formed after the middle of the reaction together with the initial LiF-based inorganic film component, thereby stabilizing the interface between the electrode and the electrolyte. Specifically, it effectively generates Li2SO3, which is known as a low-resistance component, to stabilize the electrode and reduce resistance, and in particular, it suppresses the formation of SEI (Solid Electrolyte Interphase) and CEI (Cathode-Electrolyte Interface) reformation at high temperatures and blocks the penetration of electrolyte thermal decomposition byproducts.

[0075] Furthermore, the electronic stability and planar structure of the phenyl ring ensure a uniform decomposition reaction path by being adsorbed on the electrode surface. In particular, the halogen atom substituted on the phenyl ring acts as an electron withdrawer, lowering the HOMO energy of the additive molecule to induce preferential reduction, thereby enabling the formation of a uniform, low-resistance SEI, so that the internal resistance (DC-IR) of the battery can be significantly reduced in the initial cycle, and since it does not decompose even under high-temperature conditions, it maintains the electrode surface as a protective layer with heat dissipation, electronic insulation, and ion permeability, enabling excellent electrical conductivity and maintenance of output without an increase in resistance even after high-temperature storage.

[0076] The above X' and / or X" is preferably used as fluorine (F) and chlorine (Cl) having a large difference in electronegativity from carbon (C) and sulfur (S), as this suppresses internal side reactions of the battery, thereby improving output, and can suppress an increase in resistance of the battery even when stored for a long time under high-temperature conditions, thereby providing a secondary battery with excellent high-temperature recovery capacity and lifespan characteristics. In particular, it is more preferable to use fluorine (F) that can act as a strong electron withdrawer.

[0077] It is preferable that at least one of the above X' and X" contains fluorine (F), and it is more preferable that both contain fluorine (F).

[0078] When the electrolyte additive (F-Ph-SO₂F) represented by the above chemical formula 1 is added to the electrolyte, the S atom becomes electron deficient (δ) due to the difference in electronegativity and electronic asymmetry between the F group and the phenyl group, which are electron withdrawing groups bonded to the sulfur (S) atom in the molecule. + ) state. This structure induces reduction decomposition at a potential of approximately 2.2 to 2.3 V at the cathode, and during this process, a SEI protective film based on thermally and chemically stable inorganic compositions such as LiF and Li₂SO₃ is formed. The formed SEI reduces the interfacial resistance and can improve the life and efficiency of the battery by suppressing electrolyte decomposition and lithium consumption even at high temperatures or during long-term storage.

[0079] The stability of the above film can prevent decomposition of the electrolyte, thereby extending the lifespan and suppressing interface damage caused by electrolyte decomposition by-products such as PF5 and HF among the side reaction products induced by the instability of the high-nickel anode.

[0080] In particular, the SO₂F functional group of the above chemical formula 1 induces an inorganic-based SEI with high chemical stability, such as Li₂SO₃ and LiF, through a reduction reaction, thereby indirectly suppressing the interfacial reactivity and damage of HF through the formation of a thermally and chemically stable protective film.

[0081] As a result, it suppresses the increase in acidity in the electrolyte and the dissolution and deposition of transition metal ions (Mn, Ni, etc.), which delays the mechanical collapse of the electrode and the interfacial oxidation reaction, thereby contributing to improving the long-term life characteristics and Coulombic efficiency.

[0082] In addition, the inorganic-centered SEI generated through the reduction decomposition of the additive maintains a balance of electronic insulation and ion permeability, and in particular, it can improve the high-rate retention of the battery during high-speed discharge and charge by securing interface stability through the low electronic conductivity of the LiF-rich layer, the effect of improving the density of phenyl ring-based adsorbent molecules, and the inhibition of electrolyte penetration.

[0083] In addition, in a low-temperature environment, electrochemical reactivity generally decreases due to increased electrolyte viscosity and decreased Li diffusion, but a structure such as chemical formula 1 induces the formation of a thin and uniform SEI even at low temperatures, and suppresses the decrease in low-temperature efficiency through a stable inorganic film centered on LiF and Li₂SO₃, and also has a positive effect on improving the initial charge efficiency (ICE) and long-term capacity retention rate.

[0084]

[0085] The electrolyte additive represented by the above chemical formula 1 may be selected from compounds represented by the following chemical formulas 1-1 to 1-16, as specific examples.

[0086] [Chemical Formulas 1-1 to 1-4]

[0087]

[0088] [Chemical Formulas 1-5 to 1-8]

[0089]

[0090] [Chemical Formulas 1-9 to 1-12]

[0091]

[0092] [Chemical Formula 1-13 to 1-16]

[0093]

[0094]

[0095] The compound represented by the above chemical formula 1 may be included in an amount of 0.1 to 10 wt% based on 100 wt% of the total electrolyte, 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 0.15 to 1.0 wt%. Within the above range, the charging efficiency and high-temperature lifespan improvement effects of the battery may be most excellent.

[0096] The compound represented by the above chemical formula 1 is at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite (PS), propylene carbonate sulfite (PRS), ethyl sulfate (ESA), vinylethylene carbonate (VEC), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), succinonitrile (SN) and 1,3,6-hexanetricarbonitrile (HTCN), preferably at least two compounds. It is preferable to introduce compounds, more preferably all three, together, as this can provide a desired synergistic effect without adversely affecting the components that make up the battery.

[0097] At least one compound selected from the group consisting of Vinylene Carbonate, Fluoroethylene Carbonate, Lithium Difluorophosphate, Propylene Sulfite (PS), Propylene Carbonate Sulfite (PRS), Ethyl Sulfate (ESA), Vinylethylene Carbonate (VEC), Lithium Bis(oxalato)borate (LiBOB), Lithium Difluoro(oxalato)borate (LiDFOB), Succinonitrile (SN) and 1,3,6-Hexanetricarbonitrile (HTCN) is present in an amount of 100 wt% based on the total weight of the electrolyte. The compound may be included in an amount of 0.1 to 20 wt%, 0.1 to 20 wt%, specifically 0.2 to 10 wt%, and preferably 0.5 to 5 wt%. When the content of the compound satisfies the above range, it is preferable in terms of the effect of improving the high-temperature characteristics and cycle characteristics of the battery.

[0098] A compound represented by the above chemical formula 1; And at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite (PS), propylene carbonate sulfite (PRS), ethyl sulfate (ESA), vinylethylene carbonate (VEC), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), succinonitrile (SN) and 1,3,6-hexanetricarbonitrile (HTCN) is mixed in a ratio of 1:0.5 to It can be used in a weight ratio of 1:20, or a weight ratio of 1:1 to 1:15, or a weight ratio of 1:1.5 to 1:15. Within the above range, the charging efficiency and high-temperature lifespan improvement effect of the battery can be most excellent.

[0099]

[0100] For example, in addition to the electrolyte additives described above, the electrolyte of the present invention may further include additives that can be generally used in electrolytes for the purposes of suppressing internal side reactions of a battery, improving the life characteristics of a battery, suppressing battery capacity reduction, and improving the discharge capacity of a battery.

[0101] Preferred specific examples of the above additive components include ethyl propionate (EP), propyl propionate (PP), succinic anhydride, tetravinyl silane, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, 1,2-bis((difluorophosphaenyl)oxy)ethane, 1,3,6-hexanetricarbonitrile, succinonitrile, 1-ethyl-3-methylimidazolium dicyanamide, trimethoxyboroxine, tris(trimethylsilyl) borate, lithium tetrafluoroborate, triisopropyl borate, lithium tetrafluoro(oxalato) phosphate, lithium difluoro(bisoxalato) phosphate, diethyl(difluoromethyl) phosphonate, tris(trimethylsilyl) phosphite, tripropargyl. It may be at least one selected from the group consisting of phosphate, 2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane 3,3,9,9-tetraoxide, dimethyl sulfate, ethylene dimethanesulfonate, methylene methyl disulfonate, 3-fluoro-1,3-propanesultone, ethylene sulfate, 1,3-propylene sulfate, 1,4-butanesultone, sulfolene, biphenyl, cyclohexyl benzene, 4-fluorotoluene, triphenyl phosphate, fluorobenzene, 2-fluoro-biphenyl, vinylene ethylene carbonate (VEC), 1,3,2-dioxathiolane-2,2-dioxide (DTD), tris(methylpropyl)phosphate (TMPi), etc.

[0102] Among the aforementioned types, at least one selected from the group consisting of lithium metal compounds, specific examples thereof include lithium difluoro(bisoxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium trioxalato phosphate, and borate compounds such as lithium tetrafluoroborate (LiBF₄), lithium bis(oxalato)borate (LiBOB), and lithium difluoro(oxalato)borate (LiDFOB), is a component added to improve the performance of lithium secondary batteries, lithium ion capacitors, etc., suppress internal side reactions of the batteries, reduce resistance, and improve lifespan characteristics, and may be included in the electrolyte at, for example, 0.3 to 2.5 wt%, preferably 0.5 to 1.5 wt%.

[0103] When the content of the electrolyte additive described above 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 above electrolyte additive may be included in the above-described electrolyte in an amount of, for example, 0.1 to 15 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 5.7 wt%, including the total content of all components used. When the electrolyte additive content satisfies the above range, it is preferable in terms of the effect of improving the high-temperature characteristics and cycle characteristics of the battery.

[0105] The above-mentioned additive component must be additionally included in the compound represented by the above-mentioned chemical formula 1. When only the other additive components are injected without the compound represented by the above-mentioned chemical formula 1, it was confirmed through comparative examples described below that the improvement effect on long-term life and low resistance, etc. is poor.

[0106]

[0107] The present invention also provides an electrolyte comprising the electrolyte additive of the present invention. The electrolyte is an electrolyte for a non-aqueous lithium secondary battery, and comprises the electrolyte additive, an organic solvent, and a lithium salt.

[0108] The organic solvent may be, for example, a carbonate-based organic solvent, and specifically, may be an organic solvent including at least one selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylpropionate (EP), propylpropionate (PP), ethyl acetate (EA), and methyl acetate (MA).

[0109] The organic solvent may be, for example, one type or a mixed solvent of two or more types, and preferably, a high-dielectric constant organic solvent having high ionic conductivity to improve the charge / discharge performance of the battery and a low-viscosity organic solvent whose viscosity can be adjusted to have an appropriate viscosity for application to the battery may be mixed and used as a mixed solvent.

[0110] Examples of the organic solvent with the high dielectric constant may include EC and PC, and examples of the organic solvent with the low viscosity may include EMC, DMC, EP, and DEC. It is preferable to mix and use the organic solvents with the high dielectric constant and low viscosity in a volume ratio of 2:8 to 8:2. More specifically, the organic solvent may be a binary mixed solvent of EC and EMC, a ternary mixed solvent of EC, EMC, and EP, a ternary mixed solvent of EC, EMC, and DEC, or a ternary mixed solvent of EC, EMC, and DMC, but is not limited thereto.

[0111] The ratio of the above binary mixed solvent (EC / EMC) may be, for example, 1:1 to 5, or 1:1.2 to 4, or 1:1.5 to 3.5.

[0112] The ratio of the above ternary mixed solvent may be, for example, 1:0.1 to 4:0.1 to 4, or 1:0.2 to 3.5:0.2 to 3.5. Here, the ratio may be a weight ratio or a volume ratio unless otherwise specified.

[0113] Since lithium ions in the electrolyte may be hydrolyzed when the organic solvent contains moisture, it is preferable that the moisture in the organic solvent be controlled to 150 ppm or less, preferably 100 ppm or less.

[0114] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery, and specifically, may include at least one selected from the group consisting of LiPF6, LiBF₄, LiCl, LiBr, LiI, LiClO₄, LiB₁0Cl₁0, LiCF₃SO₃, LiCF₃CO₂, LiAsF6, LiSbF6, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi (LiTFSI), and LiN(SO₂F)₂ (LiFSI). Preferably, it may be LiPF6 or LiFSI.

[0115] When the lithium salt is dissolved in the electrolyte, the lithium salt can function as a source of lithium ions in the lithium secondary battery and promote the movement of lithium ions between the positive and negative electrodes. Accordingly, the lithium salt is preferably included in the electrolyte at a concentration of approximately 0.6 mol% to 2 mol%. If the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may decrease, thereby deteriorating the electrolyte performance, and if it exceeds 2 mol%, the viscosity of the electrolyte may increase, thereby reducing the mobility of lithium ions. Considering the conductivity of the electrolyte and the mobility of lithium ions, the lithium salt may be included in the electrolyte at a concentration of preferably 0.7 mol% to 1.6 mol%, and more preferably 0.8 mol% to 1.5 mol%.

[0116] The above electrolyte additive may be included in the electrolyte at, 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 5.7 wt%. When the content of the above electrolyte additive satisfies the above range, it is preferable in terms of the effect of improving the high-temperature characteristics and cycle characteristics of the battery.

[0117]

[0118] The secondary battery of the present invention is characterized by including a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and the electrolyte.

[0119] The above positive electrode can be manufactured by, for example, mixing a positive electrode active material, a binder, and optionally a conductive agent 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.

[0120] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used.

[0121] The above cathode active material may be a conventional NCM (lithium nickel manganese cobalt oxide, LiNiMnCoO2) cathode active material used in lithium secondary batteries, and for example, may be a cathode active material having the chemical formula Li[Ni x Co y M z ]O2 (where M is Mn and / or Al, 0 <x<98, 0<y<35, 0<z<35, 단 x+y+z=100이다.) 형태의 리튬 복합금속 산화물일 수 있으나 이에 제한되는 것은 아니다.

[0122] The chemical formula of the above lithium composite metal oxide is Li[NixCoyM z]O2's variables x, y, z are, for example, 0.0001 <x<98, 0.0001<y<35, 0.0001<z<35일 수 있고, 구체적으로는 1≤x≤93, 1≤y≤30, 1≤z≤30일 수 있으며, 보다 바람직하게는 5≤x≤91, 3≤y≤25, 3≤z≤25일 수 있고, 이때 x+y+z는 100을 만족한다.

[0123] The above variables x, y, and z can provide a high-nickel cathode material by satisfying 80≤x≤91, 3≤y≤25, and 1≤z≤25, and can provide a mid-nickel cathode material by satisfying 50≤x≤80, 0.5≤y≤35, and 0.5≤z≤35.

[0124] Unless otherwise specified, the above-mentioned high-nickel cathode material contains Ni in an amount of 80 mol% or more, preferably 80 to 95 mol%, more preferably 80 to 93 mol%, and even more preferably 80 to 91 mol%, based on 100 mol% of the total metals other than Li, and within this range, the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics of the lithium-ion battery are excellent.

[0125] For example, high-nickel batteries with an operating voltage in the range of 2.0 to 4.3 V are applicable, and specific examples include NCM811 (80% nickel, 10% cobalt, 10% manganese) and NCA (more than 80% nickel, 15% cobalt, 5% aluminum), and they have the effect of achieving very high energy density required in high-performance applications such as electric vehicles.

[0126] The above mid-nickel cathode material, unless otherwise specified, contains 50 to 79 mol% of Ni, preferably 50 to 75 mol%, and more preferably 50 to 70 mol%, based on 100 mol% of the total metals excluding Li, and within this range, the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics of the lithium-ion battery are excellent. For example, the mid-nickel battery having an operating voltage in the range of 2.0 to 4.5 V is applicable, and specific examples include NCM523 (nickel 50%, cobalt 20%, manganese 30%), NCM613 (nickel 60%, cobalt 10%, manganese 30%), NCM 622 (nickel 60%, cobalt 20%, manganese 20%), etc., and the like, and the like, have excellent effects such as stability and lifespan, and since the energy density is lower than that of high-nickel, there are also high-voltage NCM products.

[0127] The above lithium ion battery cathode material may be, for example, a high-nickel cathode material, a mid-nickel cathode material, or a lithium iron phosphate cathode material.

[0128] As another example of the above lithium composite metal oxide, a compound having an olivine structure can be used.

[0129] The compound of the above olivine structure may be, for example, a compound represented by the following chemical formula 2, and in this case, it has the advantages of excellent high-temperature stability and lifespan characteristics and excellent economic efficiency.

[0130] [Chemical Formula 2]

[0131]

[0132] (In the above chemical formula 2, M includes at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X includes at least one element selected from the group consisting of F, S, and N, and a, b, and c are -0.5≤a≤0.5, 0≤b≤0.5, and 0≤c≤0.1, respectively.)

[0133] The compound of the above olivine structure may preferably include LiFePO4 of the olivine structure, and as an example, it is applicable to an LFP (lithium iron phosphate) battery or an LMFP battery having an operating voltage in the range of 2.0 to 4.0 V, and as a specific example, in this case, there is an advantage of excellent high-temperature stability and lifespan characteristics and excellent economic efficiency.

[0134] A compound having a coating layer on the surface of the compound may also be used, or a compound having a coating layer may be mixed and used. The coating layer may include at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming the coating layer may be amorphous or crystalline.

[0135] The coating elements included in the above coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as it can coat the compound with these elements using a method that does not adversely affect the properties of the positive electrode active material (e.g., spray coating, dipping, etc.), and since it is well known in the art, a detailed description thereof will be omitted.

[0136]

[0137] A compound having a coating layer on the surface of the compound may also be used, or a compound having a coating layer may be mixed and used. The coating layer may include at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming the coating layer may be amorphous or crystalline.

[0138] The coating elements included in the above coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as it can coat the compound with these elements using a method that does not adversely affect the properties of the positive electrode active material (e.g., spray coating, dipping, etc.), and since it is well known in the art, a detailed description thereof will be omitted.

[0139]

[0140] In addition, the above-mentioned positive electrode active material can be used in an NMX (Nickel-Manganese, Co free) battery having an operating voltage range of 2.0 to 4.6 V, an LMR (Lithium-Manganese-Rich) battery having an operating voltage of 2.0 to 4.8 V, an LMX (Lithium-Manganese-Rich, Co free) battery having an operating voltage of 2.0 to 4.8 V, an OLO (Over Lithiated layered Oxide) battery having an operating voltage of 2.0 to 4.8 V, an LCO (Lithium Cobalt Oxide) battery having an operating voltage of 2.0 to 4.8 V, and a DRX (Disordered Rocksalt) battery having an operating voltage of 2.0 to 4.8 V.

[0141] As a specific example, the NMX (Nickel-Manganese, Co free) battery has the chemical formula Li[NixCoyM] of the lithium composite metal oxide. z ]O2's variables x, y, z, for example 0.001 <x<0.999, y=0, 0.001<z<0.999일 수 있고, 구체적으로는 0.01≤x≤0.97, y=0, 0.03≤z≤0.99일 수 있고 이때 x+z는 1을 만족한다.

[0142] The above LCO (Lithium Cobalt Oxide) battery may have the chemical formula of the lithium composite metal oxide LiCoO2.

[0143] The above LMR (Lithium-Manganese-Rich, OLO) battery has the chemical formula xLi2MnO3*?*(1-x)LiNi of lithium composite metal oxide. a Co b Mn c As variables x, a, b, c of O2, for example 0.1 <x<0.99이고, a+b+c는 1을 만족하는 범위 내에서 a, b, c 값을 가질 수 있다.

[0144] The above LMX (Lithium-Manganese-Rich, Co free) battery has the chemical formula xLi2MnO3*?*(1-x)LiNi of lithium composite metal oxide. a Mn c As variables x, a, c of O2, for example 0.1 <x<0.99, a+c는 1을 만족하는 범위 내에서 a, c 값을 가질 수 있다.

[0145]

[0146] 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.

[0147] In one embodiment of the present invention, the positive electrode active material layer may include a binder and a conductive material. In this case, the content of the binder and the conductive material may be 1 wt% or more, or 1 to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.

[0148] The above binder serves to adhere positive electrode active material particles well to each other and also to adhere positive electrode active material well to a current collector, and examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.

[0149] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. For example, a conductive material including a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; a metal-based material such as a metal powder or metal fiber such as copper, nickel, aluminum, silver, etc.; a conductive polymer such as a polyphenylene derivative; or a mixture thereof can be used.

[0150] Al can be used as a current collector, but is not limited thereto.

[0151]

[0152] The above negative electrode can be manufactured by, for example, mixing a negative electrode active material, a binder, and optionally a conductive agent 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 copper foil.

[0153] The surface of the above cathode may further include a SEI film (solid electrolyte interface).

[0154] The above negative active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0155] The material capable of reversibly intercalating / deintercalating the lithium ions is a carbon material, and any carbon-based negative electrode active material commonly used in lithium ion secondary batteries can be used.

[0156] Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon. In addition to the carbonaceous materials, a metallic compound capable of alloying with lithium, or a composite including a metallic compound and a carbonaceous material, may also be used as the negative electrode active material, and an example thereof may be graphite.

[0157] Additionally, a metallic lithium thin film may be used as the negative electrode active material. As the negative electrode active material, any one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composites, lithium metal, and alloys containing lithium may be used in view of their high stability.

[0158] As a metal that can be alloyed with the lithium, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy can be used, for example.

[0159] The materials capable of doping and dedoping the lithium include Si, Si-C composites, SiOx (0 < x < 2), Si-Q alloys (wherein 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 (wherein 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), and at least one of these may be mixed with SiO2 for use.

[0160] The above elements Q and R may be 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.

[0161] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0162] In the above negative electrode active material layer, the content of the negative electrode active material may be, for example, 95 wt% or more, or 95 to 99 wt%, based on the total weight of the negative electrode active material layer.

[0163] The content of the binder in the above negative electrode active material layer may be, for example, 1 wt% or more, or 1 to 5 wt%, based on the total weight of the negative electrode active material layer.

[0164] In the case of including a conductive material, the negative active material can be used in a range of 90 to 98 wt%, the binder in a range of 1 to 5 wt%, and the conductive material in a range of 1 to 5 wt%.

[0165] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be an insoluble binder, a water-soluble binder, or a combination thereof.

[0166] Examples of the above-described non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0167] Examples of the above water-soluble binder include a rubber-based binder or a polymer resin binder.

[0168] The above rubber binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, and combinations thereof.

[0169] 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, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0170] When a water-soluble binder is used as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0171] The above cellulose series compound may be used by mixing one or more kinds of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof, for example.

[0172] As the alkali metal, Na, K or Li may be used. The amount of such thickener may be, for example, 0.1 to 5 parts by weight or 0.1 to 3 parts by weight per 100 parts by weight of the negative electrode active material.

[0173] The above conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive in the battery to be constructed can be used. For example, a conductive material including a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; a metal-based material such as metal powder or metal fiber such as copper, nickel, aluminum, silver, etc.; a conductive polymer such as a polyphenylene derivative; or a mixture thereof can be used.

[0174] The above-mentioned current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0175]

[0176] Depending on the type of lithium secondary battery, a separator may exist between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Of course, 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 may also be used.

[0177]

[0178] The secondary battery of the present invention additionally includes an electrolyte additive represented by the above chemical formula 1 in addition to a general additive added to an electrolyte to improve conventional battery performance, thereby exhibiting an excellent effect in suppressing side reactions occurring at the interface of high-nickel, mid-nickel, and lithium iron phosphate positive electrodes, compared to when only the conventional additive is applied or when an additive of a similar structure that does not have the structure of chemical formula 1 is applied.

[0179] In particular, the additive of the present invention forms stable CEI and SEI at the positive and negative electrode interfaces, thereby protecting the interface from aggressive decomposition products such as hydrofluoric acid (HF) generated due to the structural instability of a high-nickel positive electrode, and suppressing an increase in the acidity of the electrolyte and the dissolution of transition metal ions (Ni, Mn, etc.), thereby exhibiting a remarkable improvement effect in various battery performance items such as the charge resistance, output characteristics, capacity recovery characteristics after long-term storage at a high temperature of 60°C or higher for more than 60 days, and life characteristics of the battery measured by the HPPC (Hybrid Pulse Power Characterization) method.

[0180] That is, the electrolyte additive of the present invention induces an electronic insulating film based on an inorganic material with excellent conductivity, such as LiF and LiSO, through the -SOF functional group, thereby improving the initial resistance, thereby contributing to improving the electrical performance of the battery.

[0181] In addition, the electrolyte additive of the present invention maintained stable SEI formation even at high temperatures, thereby demonstrating excellent high-temperature durability, and thanks to this characteristic, it is possible to suppress performance degradation after high-temperature storage of the battery.

[0182] In addition, the electrolyte additive of the present invention improves rate capability at 2C, 3C, and 5C by increasing the interfacial passage rate of Li ions and reducing the resistance of the electrode interface, thereby improving performance during high-speed discharge and charge.

[0183] In addition, the electrolyte additive of the present invention suppresses heterogeneous reactions between the electrode and the electrolyte and forms a stable SEI component, thereby increasing the long-term maintenance capacity and recovery capacity, thereby improving the overall performance and efficiency of the battery.

[0184] Specifically, the secondary battery of the present invention may have an HPPC discharge resistance value of 110 mΩ or less, preferably 90 mΩ or less, measured after storage at 60°C for 30 days.

[0185] In this description, the HPPC charge (discharge) resistance value can be measured by 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.), and is an important index indicating the characteristics of the battery, such as battery output. In addition, the charge (discharge) resistance is a resistance value measured when charging (discharging) the battery, and the lower the charge (discharge) resistance, the less energy loss there is, so the charging speed can be faster and the output of the battery can be improved. The secondary battery of the present invention has a low HPPC discharge resistance value as described above, and thus has excellent charging speed and output, and is suitable for use as a battery for automobiles, for example.

[0186] The above secondary battery exhibits a recovery capacity of 75% or more, 77% or more, and 80% or more measured after storage at 60°C for 30 days.

[0187] In this specification, “recovered capacity” is an index for evaluating the capacity preservation characteristics of a battery stored for a long period of time, and is defined based on the electric capacity when a battery stored for a long period of time is discharged to the discharge end voltage, recharged, and then discharged again. More specifically, the recovered capacity is calculated by discharging and recharging a battery stored at high temperature for a long period of time, re-discharging it, and then re-discharging it under the same discharge conditions, measuring each discharge capacity, and comparing the difference between the two discharge capacities. A higher recovered capacity indicates a lower self-discharge amount during storage and fewer deterioration factors such as film damage or electrolyte deterioration, indicating excellent long-term storage stability of the battery. In particular, in applications that may be exposed to high-temperature environments such as automotive batteries, the recovered capacity characteristics under high-temperature storage conditions (e.g., 60°C, 30 days) are a very important factor.

[0188] When the present additive is included in the electrolyte composition of the present invention, the recovery capacity is improved by, for example, up to about 11% compared to the conventional additive composition, and specifically, by about 9% to 11%, thereby exhibiting the effect of enabling stable long-term battery storage even after a single charge.

[0189]

[0190] The secondary battery may have a retention capacity of, for example, 80% or more, preferably 82.5% or more, more preferably 80 to 95%, or 82.5 to 92% after storage at 60°C for 30 days.

[0191] In this specification, “retained capacity” is an indicator of the capacity preservation characteristic of a battery stored for a long period of time, and is defined based on the electric capacity secured when the battery is directly discharged without recharging after storage.

[0192] More specifically, the battery is maintained at a predetermined initial state of charge (SOC 100%), stored under high temperature conditions (e.g., 30 days at 60°C) for a predetermined period of time, and then directly discharged to the end-of-discharge voltage without going through a charging process immediately thereafter to measure the discharge capacity, thereby evaluating the maintenance capacity.

[0193] This reflects how much of the actual available capacity is preserved during storage due to natural discharge, increased internal resistance, film degradation, and electrolyte decomposition. It is an important metric for assessing a battery's practical energy transfer capability in the absence of charge compensation. A higher retention capacity indicates less self-discharge and degradation, even in high-temperature storage environments, indicating superior energy preservation during storage.

[0194] In particular, as the storage temperature of the battery increases, electrolyte deterioration, film damage, and loss of active Li are accelerated, and therefore, the retention capacity characteristics under high-temperature conditions are a very important performance indicator in high-temperature exposure applications such as lithium secondary batteries for automobiles.

[0195] By applying specific additives included in the electrolyte composition of the present invention, the retention capacity of the battery after high-temperature storage was improved compared to the prior art, for example, up to about 11%, and preferably about 9% to 11%. This means that the loss of available capacity can be minimized during long-term storage even after a single charge, and provides excellent technical effects in terms of long-term storage stability and retention of available capacity during actual use.

[0196]

[0197] The secondary battery may have a life efficiency of 80% or more, 83% or more, or 83.1 to 97.4% after 300 charge / discharge cycles at 45°C.

[0198] The secondary battery may have a resistance increase rate of, for example, 55% or more, preferably 55.0% or more, and more preferably 55% to 60%, or 55.0% to 59.9%, compared to the initial resistance after storage at 60°C for 30 days.

[0199] The secondary battery may have an initial internal resistance of, for example, 15 mΩ or more and 65 mΩ or less, preferably 30 mΩ or more and 65 mΩ or less, and more preferably 40 mΩ or more and 60 mΩ or less.

[0200] The secondary battery may have a rate capability of, for example, 90% or more, preferably 95.7% or more, more preferably 90% to 100%, or 93% to 98%, when measured under 2.0C discharge conditions compared to 1.0C discharge.

[0201] The secondary battery may have a rate capability of, for example, 80% or more, preferably 92.1% or more, more preferably 80% to 100%, or 85% to 95%, when measured under 3.0C discharge conditions compared to 1.0C discharge.

[0202] The secondary battery may have a rate capability of, for example, 50% or more, preferably 68.2% or more, more preferably 50% to 70%, or 60% to 68%, when measured under 5.0C discharge conditions compared to 1.0C discharge.

[0203]

[0204] Therefore, when the battery of the present invention is used as an automobile battery, it can exhibit excellent performance as an automobile battery by effectively scavenging hydrofluoric acid among the side reaction products due to the instability of each of the aforementioned cathode materials, thereby suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the cathode, thereby securing stability, and improving output, which becomes important depending on the size of the automobile, and improving performance at low and high temperatures, which are problematic due to climate change and the characteristics of automobiles that are mostly directly exposed to sunlight while driving or parked, even when a high-content nickel cathode material is applied for high-capacity expression.

[0205]

[0206] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0207]

[0208] Example 1

[0209] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC = 25:75 was used, and as a lithium salt, LiPF6 and bis(fluorosulfonyl)imide (LiFSI) were each contained in concentrations of 1.0 M and 0.2 M, respectively. Into a solution containing 0.25 wt% of the compound represented by the above chemical formula 1-1, 1.5 wt% of vinylene carbonate (VC), 1.0 wt% of fluoroethylene carbonate (FEC), and 1.0 wt% of lithium difluorophosphate (LDFP) were added, thereby preparing a battery electrolyte.

[0210]

[0211] Example 2

[0212] A carbonate-based mixed solvent having a volume ratio of EC:EMC = 25:75 was used as an organic solvent, and a lithium salt was LiPF6 and bis(fluorosulfonyl)imide (LiFSI) at concentrations of 1.0 M and 0.2 M, respectively, to which 0.5 wt% of the compound represented by the above chemical formula 1-1, 1.5 wt% of vinylene carbonate (VC), 1.0 wt% of fluoroethylene carbonate (FEC), and 1.0 wt% of lithium difluorophosphate (LDFP) were added to prepare a battery electrolyte.

[0213]

[0214] Comparative Example 1

[0215] A carbonate-based mixed solvent having a volume ratio of EC:EMC = 25:75 was used as an organic solvent, and a lithium salt was LiPF6 and bis(fluorosulfonyl)imide (LiFSI) at concentrations of 1.0 M and 0.2 M, respectively, to which 1.5 wt% of vinylene carbonate (VC), 1.0 wt% of fluoroethylene carbonate (FEC), and 1.0 wt% of lithium difluorophosphate (LDFP) were added to prepare a battery electrolyte.

[0216]

[0217] Comparative Example 2

[0218] A carbonate-based mixed solvent having a volume ratio of EC:EMC = 25:75 was used as an organic solvent, and a solution containing LiPF6 and bis(fluorosulfonyl)imide (LiFSI) as lithium salts at concentrations of 1.0 M and 0.2 M, respectively, was added to prepare a battery electrolyte by adding 1.5 wt% of vinylene carbonate (VC), 1.0 wt% of fluoroethylene carbonate (FEC), 1.0 wt% of lithium difluorophosphate (LDFP), 0.5 wt% of 1,3-propane sultone (PS), and 0.3 wt% of 1,3-propene sultone (PRS).

[0219]

[0220] Comparative Example 3

[0221] A carbonate-based mixed solvent having a volume ratio of EC:EMC = 25:75 was used as an organic solvent, and a lithium salt was LiPF6 and bis(fluorosulfonyl)imide (LiFSI) at concentrations of 1.0 M and 0.2 M, respectively. Into a solution containing the compound represented by the following chemical formula 3, 0.5 wt%, 1.5 wt% of vinylene carbonate (VC), 1.0 wt% of fluoroethylene carbonate (FEC), and 1.0 wt% of lithium difluorophosphate (LDFP) were added to prepare a battery electrolyte.

[0222] [Chemical Formula 3]

[0223]

[0224] Manufacturing of LFP batteries

[0225] A positive electrode mixture slurry was prepared by adding 92 wt% of LiFePO4 as a positive electrode active material, 4 wt% of carbon black as a conductive agent, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode mixture slurry was applied to an aluminum (Al) thin film as a positive electrode current collector with a thickness of about 20 μm, dried, and then roll pressed to prepare a positive electrode.

[0226] A negative electrode mixture slurry was prepared by adding 96 wt%, 3 wt%, and 1 wt% of carbon powder as a negative electrode active material, PVdF as a binder, and carbon black as a conductive agent to NMP as a solvent. The negative electrode mixture slurry was applied to a copper (Cu) thin film as a negative electrode current collector with a thickness of 10 μm, dried, and then roll pressed to prepare a negative electrode.

[0227] After manufacturing a pouch-type battery using the positive and negative electrodes manufactured as described above together with a separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) in a conventional manner (operating voltages of 3.65 V, 3.66 V, and 3.67 V), the respective electrolytes manufactured in Examples 1 to 2 and Comparative Examples 1 to 3 were injected to complete the manufacture of a lithium secondary battery.

[0228]

[0229] Manufacturing of NCM batteries

[0230] Li(Ni) as a cathode active material 0.8 Co 0.1 Mn 0.1 )O292 wt%, carbon black (4 wt% as a conductive agent), and polyvinylidene fluoride (PVdF) (4 wt% as a binder) were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film as a positive electrode current collector with a thickness of about 20 μm, dried, and then roll pressed to prepare a positive electrode.

[0231] A negative electrode mixture slurry was prepared by adding 96 wt%, 3 wt%, and 1 wt% of carbon powder as a negative electrode active material, PVdF as a binder, and carbon black as a conductive agent to NMP as a solvent. The negative electrode mixture slurry was applied to a copper (Cu) thin film as a negative electrode current collector with a thickness of 10 μm, dried, and then roll pressed to prepare a negative electrode.

[0232] After manufacturing a pouch-type battery using the positive and negative electrodes manufactured as described above together with a separator made of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) in a conventional manner, the respective electrolytes manufactured in Examples 1 to 2 and Comparative Examples 1 to 3 were injected to complete the manufacture of a lithium secondary battery.

[0233]

[0234] Exam example

[0235] The performance of each secondary battery manufactured above was measured according to the evaluation method below, and the results are summarized and presented in Table 1 below.

[0236] In Table 1 below, the measurement value of Comparative Example 1 is set as 100%, and the relative increase / decrease rate (%) for this is described for each example and comparative example, and the measurement value of Comparative Example 1 is also listed.

[0237]

[0238] [HPPC Charge (Discharge) Resistance Evaluation]

[0239] Measurements were made according to the method specified in the literature, "Battery test manual for plug-in hybrid electric vehicles," (2010, Idaho National Laboratory for the US Department of Energy.).

[0240] After storing at 60℃ for 30 days, the measured voltage value, charge / discharge current value corresponding to the C-rate, current change (△I), discharge voltage change (△V), charge voltage change (△V), charge resistance, and discharge resistance were measured, and the charge / discharge current was briefly applied for a certain period of time for each C-rate, and the resistance increase rate was calculated using the slope value obtained from the current and voltage changes.

[0241]

[0242] [Initial Resistance Assessment]

[0243] The initial internal resistance evaluation was performed based on the Hybrid Pulse Power Characterization (HPPC) method, and was measured using a charger / discharger at room temperature (25±2℃) immediately after cell manufacturing at a SOC of 50%. The initial internal resistance value of Comparative Example 1 was set as 100% as the comparison standard, and the relative increase / decrease rate (%) for this is summarized and shown in Table 1.

[0244]

[0245]

[0246] [Evaluation of high-temperature storage characteristics]

[0247] The high-temperature storage characteristics evaluation was performed under the following conditions to evaluate the high-temperature heat resistance stability of the battery and the performance retention characteristics during storage.

[0248] The test cells were initially charged, brought to 100% SOC, and then stored in a thermostat at 60±2°C for 30 days. No external current was applied during storage, and cell voltage and appearance were periodically checked for abnormalities. After storage, the cells were returned to room temperature (25±2°C) and evaluated for the following items:

[0249] (1) Retained Capacity

[0250] After storage, the battery was immediately discharged without additional charging, and the discharge capacity was measured. This was compared with the initial discharge capacity to calculate the maintenance capacity. Maintenance capacity reflects energy loss due to self-discharge, interfacial degradation, and electrolyte decomposition during storage, indicating whether the battery is ready for immediate use after storage. The calculation formula is as follows:

[0251]

[0252] (2) Recovered Capacity:

[0253] After storage, the battery was fully charged once and then discharged to the end-of-discharge voltage to measure the discharge capacity.

[0254] The recovery capacity was calculated by comparing the discharge capacity with the initial discharge capacity, and the calculation formula is as follows:

[0255]

[0256] (3) Resistance measurement after storage

[0257] The resistance value of the battery after storage was measured in the same way as the initial resistance measurement after measuring the maintenance capacity and recovery capacity.

[0258]

[0259] [Rate Characteristics Evaluation]

[0260] To verify the battery's output characteristics, rate capability evaluation was performed. Each test cell was fully charged at 0.5 C at room temperature (25±2°C), and then the discharge performance was measured by varying the discharge current to 1.0 C (reference), 2.0 C, 3.0 C, and 5.0 C, respectively.

[0261] Five cycles of repeated discharge were performed under each C-rate condition, and the average discharge capacity of the five cycles was used as the representative value for the corresponding C-rate condition. Each measured discharge capacity was converted into a ratio (%) compared to the reference 1.0C discharge capacity to calculate the rate characteristics. Through this evaluation, the indirect influence of the battery's output maintenance performance and internal resistance characteristics during high-rate discharge was analyzed.

[0262] The rate characteristics were calculated according to the following equation:

[0263]

[0264]

[0265] [High Temperature Life Evaluation]

[0266] The secondary battery was charged at a constant current (CC) of 1C in a 45°C environment until the voltage reached 2.7 to 4.20 V (vs. Li), then switched to constant voltage (CV) mode to maintain 4.20 V and continue charging until the current reached 0.1 C. Thereafter, discharge was performed at a constant current of 1 C until the voltage reached 2.7 V (vs. Li). After repeating this charge / discharge cycle a total of 300 times, the change in capacity according to the repeated cycles was measured to evaluate the high-temperature life characteristics.

[0267]

[0268] The measurement results of a secondary battery manufactured using the above NCM (Ni 80% or more) battery are shown in Table 1 below. Table 1 below corresponds to a performance comparison table compared to Comparative Example 1.

[0269] Electrolyte Lot. Initial DC-IR High Temperature Lifetime Characteristics (1C vs xC) High Temperature Storage Evaluation (45C@300) (%) (%) 2.0C 3.0C 5.0C Retention Capacity Recovery Capacity Resistance After DC-IR (%) (%) (%) Comparative Example 1 (Measured Value) 57.65 (mRhom) 82.34% 93.17% 87.14% 58.24% 72.06% 77.53% 79.64 (mRhom) Comparative Example 1 (Conversion Reference Value) 100100100100100100100100 Comparative Example 2 (Conversion Value) 105.1100100.4100.194.299.810099 Comparative Example 3 (Conversion Value) 999899.498.894.996.297.7106.6 Example 1 (Conversion Value) 98.4104.1101.8103.4101.4100.8101.898.1 Example 2 (Conversion Value) 97.1101.2103.8107.8115.8104.9102.1100.8

[0270] As shown in Table 1 above, when Examples 1 to 2, which are electrolyte additives of the present invention, were used, it was confirmed that the initial resistance, high-temperature durability, high-speed charge / discharge performance, high-temperature maintenance capacity, and high-temperature recovery capacity were all improved in the LFP battery and the NCM battery, respectively, compared to Comparative Example 1 in which the electrolyte additive was not used, Comparative Example 2 in which the electrolyte additive was replaced with a conventional sulfur-based compound, and Comparative Example 3 in which the electrolyte additive was replaced with an electrolyte additive component having a structure similar to Chemical Formula 1-1. Specifically, it was confirmed that in Examples 1 to 2, which are electrolyte additives of the present invention, an electronic insulating film based on an inorganic material with excellent conductivity, such as LiF and LiSO, was induced through the -SOF functional group, thereby improving the initial resistance, thereby contributing to improving the electrical performance of the battery.

[0271] In addition, the electrolyte additives of the present invention, Examples 1 to 2, maintained stable SEI formation even at high temperatures, thereby demonstrating excellent high-temperature durability. It is inferred that this characteristic enabled the suppression of performance degradation after high-temperature storage of the battery.

[0272] In addition, it is inferred that the electrolyte additives of Examples 1 to 2 of the present invention improved the rate capability at 2C, 3C, and 5C by increasing the interfacial passage rate of Li ions and reducing the resistance of the electrode interface, thereby improving the performance during high-speed discharge and charge.

[0273] In addition, it was confirmed that the electrolyte additives of Examples 1 to 2 of the present invention suppressed heterogeneous reactions between the electrode and the electrolyte and formed a stable SEI component, thereby increasing the long-term maintenance capacity and recovery capacity, thereby improving the overall performance and efficiency of the battery.

[0274] In particular, it was confirmed that a remarkable difference was shown from the initial resistance of the battery, and that when the electrolyte additive according to the present invention was included, an electronic insulating film based on highly conductive inorganic materials such as LiF and Li2SO3 was induced through the -SO2F functional group, thereby improving the initial resistance and contributing to the improvement of the electrical performance of the battery. In fact, it was confirmed that a remarkable improvement was observed from 97.1 to 98.4% in Examples 1 to 2 according to the present invention, compared to 99 to 105.1% calculated in Comparative Examples 1 to 3.

[0275] It was confirmed that when the electrolyte additive according to the present invention is included, a stable solid electrolyte layer (SEI) is maintained on the electrode surface even when charge and discharge are repeated more than 300 times under high temperature conditions (45°C), and thus the battery exhibits excellent high temperature durability.

[0276] In particular, the additive of the present invention suppresses the structural stability of SEI and the deterioration of interface resistance characteristics even during high-temperature charge / discharge, thereby providing a significant improvement in life characteristics compared to the prior art.

[0277] In fact, according to Table 1 described above, Examples 1 to 2 of the present invention showed performances of 101.2% to 104.1% in the life evaluation, while Comparative Examples 1 to 3 remained at the level of 98% to 100%, confirming that the life characteristics were significantly improved through the additive of the present invention.

[0278] Furthermore, it was confirmed that the rate characteristics of the battery also showed a significant difference. When the electrolyte additive according to the present invention was included, the interfacial passage rate of Li ions in the electrolyte was improved and the resistance of the electrode interface was reduced, thereby maintaining excellent output performance even under high-rate conditions.

[0279] In fact, Examples 1 to 2 showed yield characteristics of 101.8 to 103.8%, 103.4 to 107.8%, and 101.4 to 115.8%, respectively, at 2.0 C, 3.0 C, and 5.0 C conditions, whereas Comparative Examples 1 to 3 showed yield characteristics of 99.4 to 100.4%, 98.8 to 100.1%, and 94.2 to 100%, respectively, at the same conditions.

[0280] As a result, Examples 1 and 2, which applied the additive of the present invention, showed improved performance in all items including initial resistance, high-temperature durability, rate characteristics, maintenance capacity, and recovery capacity compared to Comparative Example 1, which used only a conventional additive, Comparative Example 2, which used the additive of the present invention in combination with a conventional additive, and Comparative Example 3, which used a similar structural compound alone.

[0281] This result can be said to be proof that the additive of the present invention is effective in simultaneously improving the efficiency, lifespan, and electrical characteristics of a battery in high and low temperature environments.

[0282]

[0283] Therefore, when the electrolyte additive according to embodiments of the present invention and the electrolyte containing the same are applied to a secondary battery, not only is the internal side reaction of the battery suppressed to provide the effect of reducing gas generation, but also the charge resistance, discharge resistance, output, recovery capacity and life efficiency are improved even when stored for a long time at high temperatures, so that it can be seen that it is suitable for use in an automobile secondary battery, particularly a high-nickel full-cell battery having a basic capacity of 0.1 to 100 Ah, an LFP battery having a basic capacity of 0.1 to 100 Ah, an LMR (lithium manganese rich) battery having a basic capacity of 0.1 to 100 Ah, or a cobalt-free battery having 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] (In the above chemical formula 1, a line is a bond, and when a separate element is not described, the point where a bond meets a bond is carbon, and X' and X" are each independently fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).) 2. In paragraph 1, An electrolyte additive characterized in that the compound represented by the above chemical formula 1 is a compound represented by the following chemical formulas 1-1 to 1-16. [Chemical Formulas 1-1 to 1-4] [Chemical Formulas 1-5 to 1-8] [Chemical Formulas 1-9 to 1-12] [Chemical Formula 1-13 to 1-16] 3. An electrolyte additive characterized by comprising a compound represented by the following chemical formula 1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite, propylene carbonate sulfite, ethyl sulfate, vinylethylene carbonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, succinonitrile, and 1,3,6-hexanetricarbonitrile. [Chemical Formula 1] (In the above chemical formula 1, a line is a bond, and when a separate element is not described, the point where a bond meets a bond is carbon, and X' and X" are each independently fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).) 4. In paragraph 3, An electrolyte additive characterized in that the compound represented by the above chemical formula 1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, propylene sulfite, propylene carbonate sulfite, ethyl sulfate, vinylethylene carbonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, succinonitrile, and 1,3,6-hexanetricarbonitrile are included in a weight ratio of 1:0.5 to 1:

20.

5. An electrolyte comprising an organic solvent, a lithium salt, and an electrolyte additive, An electrolyte characterized in that the electrolyte additive comprises the electrolyte additive of claim 1 or 3.

6. In paragraph 5, An electrolyte solution characterized in that the organic solvent comprises at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, propylene carbonate, dipropyl carbonate, butylene carbonate, methylpropyl carbonate, ethyl propyl carbonate, ethyl propionate, propyl propionate, and methyl acetate.

7. In paragraph 5, The above lithium salts are LiPF6, LiF4, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiSbF6, LiAsF6, LiN(SO2C2F5)2, LiCF3SO3, LiCF3CO2, Li(CF3SO2)2N, LiN(SO2F)2, LiN(SO3C2F5)2, Li(FSO2)2N, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x +1SO2)(C y F 2y +1SO2) ) (wherein, x and y are each an integer from 1 to 20), LiAsF6, LiSbF6, LiAlCl4, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), CH3SO3Li, CF3SO3Li, and (CF3SO2)2NLi.

8. A secondary battery comprising a cathode, an anode, a separator interposed between the cathode and the anode, and an electrolyte, A secondary battery characterized in that the electrolyte is the electrolyte of claim 5.

9. In paragraph 8, A secondary battery characterized in that the secondary battery is a battery for automobiles.

10. In paragraph 9, A secondary battery characterized in that the secondary battery is a high-nickel full-cell battery, a mid-nickel full-cell battery, an LFP (lithium iron phosphate) battery, an LMR (lithium manganese rich) battery, an NMX (nickel-manganese, Co free) battery, an LMR (lithium-manganese-rich) battery, an LMX (lithium-manganese-rich, Co free) battery, an OLO (over lithiated layered oxide) battery, an LCO (lithium cobalt oxide) battery, or a DRX (disordered rock salt) battery.

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