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

Abstract

The present invention relates to an electrolyte additive, and an electrolyte and a secondary battery which comprise same. According to the present invention, a stable film is formed on anodes and cathodes of various lithium secondary batteries including high-nickel, Si anode, LFP, lithium manganese rich (LMR), and cobalt-free batteries. As a result, side reactions inside a battery are suppressed, charging efficiency and output can be enhanced due to low charge / discharge resistance, an increase in battery resistance can be suppressed even if stored for a long time under high-temperature conditions, gas generation due to decomposition of electrolyte components can also be remarkably suppressed so as to have excellent long-term lifespan and high-temperature capacity retention ratios, and hydrofluoric acid from among side reaction products caused by instability of a cathode of a battery can be effectively scavenged so as to suppress an increase in acidity of the electrolyte and elution of transition metal ions from the cathode, and thus secondary batteries having excellent battery characteristics and an excellent lifespan can be provided.

Description

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

[0001] The present invention relates to an electrolyte additive, an electrolyte for a battery containing the same, and a secondary battery containing the same, and more particularly, to an electrolyte additive that forms a stable film on the positive and negative electrodes of various lithium secondary batteries, including high-nickel, mid-nickel, Si negative electrodes, LFP (lithium iron phosphate), LMR (lithium manganese rich) batteries, or cobalt-free batteries, thereby suppressing side reactions inside the battery and improving charging efficiency and output by lowering charge and discharge resistance, and that can suppress an increase in battery resistance and gas generation even when stored for a long time under high-temperature conditions, thereby providing a long-term lifespan and excellent high-temperature capacity retention, and that can effectively scavenge hydrofluoric acid, one of the side reaction products caused by the instability of the battery 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 even under high-voltage conditions.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] Furthermore, there is a need to develop a battery that forms a stable film on various lithium secondary battery anodes, including high-nickel, Si anodes, LFP, LMR (lithium manganese rich) batteries, or cobalt-free batteries, thereby suppressing side reactions within the battery and lowering charge / discharge resistance, thereby improving charging efficiency and output. In other words, there is a need to develop a battery with excellent battery characteristics and lifespan by effectively scavenging hydrofluoric acid, one of the side reaction products caused by the instability of the battery anode, thereby suppressing an increase in the acidity of the electrolyte and the dissolution of transition metal ions from the anode.

[0006] [Prior Art Literature]

[0007] [Patent Document]

[0008] Korean Patent Publication No. 10-2023-0168034

[0009] 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.

[0010] 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.

[0011] The above and other objects of the present invention can all be achieved by the present invention described below.

[0012] 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.

[0013] [Chemical Formula 1]

[0014]

[0015] (In the above chemical formula 1, the line is a bond, and when a separate element is not described, the point where the bond and bond meet is carbon, and A1, A2, and A3 are each independently oxygen (O), nitrogen (N), or sulfur (S).)

[0016]

[0017] The compound represented by the above chemical formula 1 may be a compound represented by the following chemical formulas 1-1 to 1-5.

[0018] [Chemical Formulas 1-1 to 1-5]

[0019]

[0020] In addition, the present invention provides an electrolyte additive characterized by including a compound represented by the following chemical formula 1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate.

[0021] [Chemical Formula 1]

[0022]

[0023] (In the above chemical formula 1, the line is a bond, and when a separate element is not described, the point where the bond and bond meet is carbon, and A1, A2, and A3 are each independently oxygen (O), nitrogen (N), or sulfur (S).)

[0024] The compound represented by the above chemical formula 1 may be included in an amount of, for example, 0.1 to 10 wt% among 100 wt% of the components constituting the electrolyte additive, preferably 0.1 to 5 wt%, more preferably 0.1 to 2.0 wt%, still more preferably 0.1 to 1.0 wt%, and most preferably 0.15 to 1.0 wt%.

[0025] At least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate and lithium difluorophosphate may be included in 100 wt% of the components constituting the electrolyte additive, for example, 0.1 to 20 wt%, specifically 0.2 to 10 wt%, and preferably 0.5 to 5 wt%.

[0026] The compound represented by the above chemical formula 1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate may be included in a weight ratio of, for example, 1:0.5 to 1:20, or a weight ratio of 1:1 to 1:15, or a weight ratio of 1:1.5 to 1:15.

[0027]

[0028] In addition, the present invention provides an electrolyte additive characterized by including a compound represented by the following chemical formula 1-1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate.

[0029] [Chemical Formula 1-1]

[0030]

[0031] (In the above chemical formula 1-1, the line is a bond, and if a separate element is not described, the point where the bond and bond meet is carbon.)

[0032] The compound represented by the above chemical formula 1-1 may be included 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 0.15 to 1.0 wt%, among 100 wt% of the components constituting the electrolyte additive.

[0033] At least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate and lithium difluorophosphate may be included in 100 wt% of the components constituting the electrolyte additive, for example, 0.1 to 20 wt%, specifically 0.2 to 10 wt%, and preferably 0.5 to 5 wt%.

[0034] The compound represented by the above chemical formula 1-1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate may be included in a weight ratio of 1:0.5 to 1:20, or a weight ratio of 1:1 to 1:15, or a weight ratio of 1:1.5 to 1:15.

[0035]

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

[0037] The above organic solvent may include 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, and ethylpropyl carbonate.

[0038] 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 natural numbers, for example, integers from 1 to 20), LiAsF6, LiSbF6, LiAlCl4, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), CH3SO3Li, CF3SO3Li, and (CF3SO2)2NLi.

[0039] The electrolyte additive may be included in an amount of 0.1 to 10 wt%, 0.3 to 10 wt%, 0.3 to 8 wt%, 0.5 to 6 wt%, or 0.5 to 5.7 wt% based on 100 wt% of the total electrolyte.

[0040]

[0041] In addition, the present invention provides a secondary battery including a cathode, an anode, a separator interposed between the cathode and the anode, and an electrolyte, wherein the electrolyte is the electrolyte described above.

[0042] The above secondary battery may be a battery for automobiles.

[0043] The above-mentioned automotive 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, or a DRX (disordered rock salt) battery.

[0044] The above 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] The above-mentioned mid-nickel full-cell battery includes a lithium composite metal oxide having a nickel content of 60 to 80% as a cathode material and may have a basic capacity of 0.1 to 100 Ah.

[0046] The above LFP (lithium iron phosphate) battery may have a basic capacity of 0.1 to 100 Ah.

[0047] The above LMR (lithium manganese rich) battery may have a basic capacity of 0.1 to 100 Ah.

[0048] The above NMX (Nickel-Manganese, Co free) battery can have an operating voltage in the range of 2.0 to 4.6 V.

[0049] The above LMR (Lithium-Manganese-Rich) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0050] The above LMX (Lithium-Manganese-Rich, Co free) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0051] The above OLO (Over Lithiated Layered Oxide) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0052] The above LCO (Lithium Cobalt Oxide) battery can have an operating voltage within the range of 2.0 to 4.8 V.

[0053] The above DRX (Disordered Rocksalt) battery can have an operating voltage in the range of 2.0 to 4.8 V.

[0054]

[0055] The secondary battery may have a retention capacity of 86% or more, 86.3% or more, 86 to 95%, or 86 to 99% after storage at 60°C for 30 days.

[0056] The secondary battery may have a recovery capacity of 86% or more, 86.3% or more, 86 to 95%, or 86 to 99% after storage at 60°C for 30 days.

[0057] The secondary battery may have a resistance increase rate of 50% or less, 40% or less, 20 to 40%, or 10 to 40% after storage at 60°C for 30 days.

[0058] The secondary battery may have a rate property of 90% or more, or 85 to 98%, when measured at 2.0 C versus 1.0 C.

[0059] The secondary battery may have a rate characteristic of 80% or more, or 80 to 98%, when measured at 3.0 C versus 1.0 C.

[0060] The secondary battery may have a rate characteristic of 70% or more, or 70 to 95%, when measured at 5.0 C versus 1.0 C.

[0061] 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.

[0062] In addition, a secondary battery including an electrolyte including an electrolyte additive according to the present invention can suppress an increase in battery resistance even when stored for a long time under high-temperature conditions, so that it has excellent long-term lifespan and high-temperature capacity retention, and effectively scavenges hydrofluoric acid among side reaction products caused by instability of the battery positive electrode, thereby suppressing an increase in 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.

[0063]

[0064] The present invention will be described in detail below, but the present invention is not limited thereto.

[0065]

[0066] 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.

[0067]

[0068] 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, in which case the internal side reaction of the battery is suppressed and the charging resistance of the secondary battery is lowered, so that the charging efficiency and output can be improved, and even when stored for a long time under high temperature conditions, the increase in the resistance of the battery can be suppressed, so that the long-term lifespan and the high-temperature capacity retention rate are excellent, and the battery characteristics and lifespan are excellent because the hydrofluoric acid among the side reaction products caused by the instability of the battery positive electrode is effectively scavenged, thereby suppressing the increase in the acidity of the electrolyte and the elution of transition metal ions from the positive electrode.

[0069] [Chemical Formula 1]

[0070]

[0071] (In the above chemical formula 1, the line is a bond, and when a separate element is not described, the point where the bond and bond meet is carbon, and A1, A2, and A3 are each independently oxygen (O), nitrogen (N), or sulfur (S).)

[0072] Specifically, the DFT (Density functional theory) calculation results for this compound show that the HOMO is -9.87 eV and the LUMO is 1.32 eV compared to ethylene carbonate (EC) which has a HOMO of -10.92 eV and a LUMO of 1.41 eV. Judging from the high HOMO and low LUMO values, it is predicted that it can act on both the positive and negative electrodes, and in fact, the interface between the electrode and the electrolyte can be stabilized by forming a P-based inorganic film after the middle of the reaction together with the organic film component of the initial series. Specifically, the acetate ester fraction (functional group) is reduced to form an organic-based film in the form of Li2CO3 and / or ROCO2Li, and the cyclic phosphite fraction (functional group) is oxidized to form a lithium phosphate-based inorganic layer (LixPOyFz, where x is an integer from 1 to 3, y is 1, z is an integer from 2 to 6, and y+z is an integer with a lower limit of 2 and an upper limit of 6). This compound forms an organic-inorganic composite film by forming an SEI (Solid Electrolyte Interphase) and a CEI (Cathode Electrolyte Interphase) on the negative and positive electrodes, thereby stabilizing the electrode, reducing resistance, and stabilizing long-term cycling, and also improving high-voltage stability. In addition, it also has the effects of suppressing metal dissolution and reducing gas generation.

[0073] Furthermore, the electronic stability and planar structure of the ring ensure a uniform decomposition reaction path by being adsorbed on the electrode surface. In particular, the heteroatom contained in the 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 it does not decompose even under high-temperature conditions, so that the electrode surface is maintained 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.

[0074] The above A1, A2 and A3 are preferably used independently of oxygen (O), nitrogen (N) or sulfur (S), which are hetero elements having a large difference in electronegativity from phosphorus (P), so that internal side reactions of the battery are suppressed, thereby improving output, and even when stored for a long time under high temperature conditions, an increase in the resistance of the battery can be suppressed, thereby providing a secondary battery with excellent high temperature recovery capacity and life characteristics. In particular, it is more preferable to use oxygen (O) or nitrogen (N), which can act as a strong electron withdrawer.

[0075] It is preferable that at least one of the above A1, A2 and A3 contains oxygen (O), it is more preferable that two or more contain oxygen (O), and it is most preferable that all three contain oxygen (O).

[0076] When the electrolyte additive represented by the above chemical formula 1 is added to the electrolyte of a battery, electrons are concentrated toward the P element due to the difference in electronegativity between the (P) element and the directly connected hetero element (e.g., oxygen (O) element), and further, due to the overall asymmetric structure of the chemical formula, the P element becomes electron-deficient (e-poor, δ+), and an oxidation reaction is induced in the electrolyte containing lithium ions, thereby forming a stable film on the electrode, specifically, the cathode.

[0077] The stability of the film prevents electrolyte decomposition, thereby improving cycle characteristics. In particular, since it does not decompose at high temperatures, it has the excellent effect of significantly improving high-temperature storability compared to conventional electrode films that decompose at high temperatures and thus have poor high-temperature storability. In addition, since resistance increase is prevented, charge / discharge efficiency and output are improved, and gas generation due to chemical reactions within the battery is also suppressed, thereby enhancing battery safety. In addition, a chemically stable residual film can be maintained even during long-term, repeated charge / discharge cycles. In addition, by preventing the collapse of the electrode active material structure of the positive and negative electrodes at high temperatures, the capacity retention rate is improved, and through this, the lifespan is extended. In addition, the hydrofluoric acid generated by the reaction with residual moisture in the electrolyte, which is a side reaction product due to the instability of the battery positive electrode, is effectively captured or neutralized by the acidity control ability of the phosphite group, thereby suppressing the increase in the acidity of the electrolyte and the dissolution and deposition of transition metal ions (Mn, Ni, etc.) of the positive electrode, thereby delaying the mechanical collapse and interfacial oxidation reaction of the electrode, thereby improving the long-term lifespan characteristics and Coulombic Efficiency.

[0078] In addition, the inorganic SEI formed after decomposition maintains a balance of electronic insulation and ion permeability, and in particular, the LixPOyFz-based inorganic layer acts as an electron insulator and redox inhibitor, thereby stabilizing the interface. This CEI layer blocks the contact between the anode surface and the electrolyte, thereby inhibiting electrolyte decomposition and suppressing the dissolution of transition metals (TM) such as Ni, Mn, and Co. In addition, the oxygen negative charge and Lewis base function of the phosphite structure capture PF5 and HF, thereby suppressing decomposition. The phosphite, which is the central structure, reduces CO2 and O2, which are electrolyte oxidation byproducts, thereby suppressing gas generation. The formation of a highly thermally stable inorganic layer improves high-temperature stability, and the formation of a uniform, thin film can suppress initial and long-term resistance increase.

[0079] Meanwhile, while the viscosity of the electrolyte typically increases in a low-temperature environment and the diffusion of Li ions is restricted, the present invention can provide an effect of not hindering the interfacial passage of Li ions by maintaining a thin and dense inorganic SEI even at low temperatures. In particular, at low temperatures, the reactivity often decreases rapidly during cycling or the efficiency drops due to uneven SEI growth, whereas the present invention can form a film of stable SEI components (Li2CO3, ROCO2Li) that is relatively quickly reduced even at low temperatures to form a uniform film and does not deteriorate electrochemical characteristics even in subsequent cycles, and since it has a structure that ensures decomposition reactivity even at low temperatures, it is advantageous in securing initial charge efficiency (ICE) and can stabilize the capacity retention rate and efficiency in the long term.

[0080]

[0081] The electrolyte additive represented by the above chemical formula 1 may be selected from compounds represented by the following chemical formulas 1-1 to 1-5, as specific examples.

[0082] [Chemical Formulas 1-1 to 1-6]

[0083]

[0084] 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.

[0085]

[0086] The compound represented by the above chemical formula 1 is preferably added together with one or more compounds, preferably two or more compounds, and more preferably all three compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate, as this can provide a predetermined synergistic effect without adversely affecting the components constituting the battery.

[0087] At least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate and lithium difluorophosphate may be included in a total amount of 0.1 to 20 wt% based on 100 wt% of the total electrolyte, and may be included in a total amount of 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.

[0088] The compound represented by the above chemical formula 1; and at least one compound selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate may be used in a weight ratio of 1:0.5 to 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 effects of the battery may be most excellent.

[0089]

[0090] 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.

[0091] 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, lithium bis(oxaleto)borate, lithium difluoro(oxalato)borate, 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, lithium bis(fluorosulfonyl)imide, 3-fluoro-1,3-propanesultone, ethylene sulfate, 1,3-propylene sulfate, 1,4-butanesultone, sulfolene, biphenyl, cyclohexyl benzene, 4-fluorotoluene, triphenyl phosphate, fluorobenzene, and 2-fluoro-biphenyl.

[0092] Among the aforementioned types, at least one selected from the group consisting of metal phosphate compounds, specifically lithium difluoro(bisoxalato) phosphate, lithium tetrafluorooxalato phosphate, and lithium trioxalato phosphate, is a component added to improve the performance of lithium secondary batteries, lithium ion capacitors, etc., suppress internal side reactions of the battery, improve resistance and lifespan, etc., and may be included in the electrolyte at, 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 the effect of improving the high-temperature characteristics and cycle characteristics of the battery.

[0093] The above electrolyte additive may be included in the above-described electrolyte in an amount of, for example, 0.1 to 10.1 wt%, 0.1 to 8.0 wt%, 0.1 to 7 wt%, 0.2 to 7 wt%, or 0.25 to 5.5 wt%, including the total content of all components used. When the electrolyte additive content satisfies the above range, it is preferable in terms of improving the high-temperature characteristics and cycle characteristics of the battery.

[0094] 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.

[0095]

[0096] 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.

[0097] 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, and ethylpropyl carbonate.

[0098] 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.

[0099] 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, 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 DEC, or a ternary mixed solvent of EC, EMC, and DMC, but is not limited thereto.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The above lithium salt can be used without any special restrictions as long as it is a compound that can provide lithium ions used in a lithium secondary battery, and specifically, LiPF6, LiBF4, LiCl, LiBr, LiI, LiClO4, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (FSO2)2NLi and (CF3SO2)2NLi. Preferably, it may be LiPF6 and / or (FSO2)2NLi.

[0104] 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%.

[0105] 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%, 0.2 to 7 wt%, or 0.25 to 5.5 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.

[0106]

[0107] 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.

[0108] 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.

[0109] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] As another example of the above lithium composite metal oxide, a compound having an olivine structure can be used.

[0118] 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.

[0119] [Chemical Formula 2]

[0120]

[0121] (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.)

[0122] The compound of the above olivine structure may preferably include LiFePO4 of the olivine structure, and for example, an LFP (lithium iron phosphate) battery or an LMFP battery having an operating voltage in the range of 2.0 to 4.0 V is applicable, and in this case, as a specific example, there is an advantage of excellent high-temperature stability and lifespan characteristics and excellent economic efficiency.

[0123] 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.

[0124] 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.

[0125]

[0126] 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.

[0127] 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.

[0128]

[0129] 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.

[0130] 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.

[0131] The above LCO (Lithium Cobalt Oxide) battery may have the chemical formula of the lithium composite metal oxide LiCoO2.

[0132] 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.

[0133] 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.

[0134]

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] Al can be used as a current collector, but is not limited thereto.

[0140]

[0141] 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.

[0142] The surface of the above cathode may further include a SEI film (solid electrolyte interface).

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0151] 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.

[0152] 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.

[0153] 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%.

[0154] 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.

[0155] 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.

[0156] Examples of the above water-soluble binder include a rubber-based binder or a polymer resin binder.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] The above cellulose series compound may be used by mixing one or more kinds of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof, for example.

[0161] 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.

[0162] 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.

[0163] 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.

[0164]

[0165] 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.

[0166]

[0167] The secondary battery of the present invention has the effect of significantly improving battery characteristics such as battery charging resistance, output characteristics, capacity recovery characteristics, and lifespan characteristics measured by the HPPC (Hybrid Pulse Power Characterization) method even when long-term storage at a high temperature of 60°C or higher for more than 60 days is performed by adding an electrolyte additive represented by the above chemical formula 1 together with a conventional compound added to an electrolyte, thereby effectively scavenging hydrofluoric acid among side reaction products generated due to the instability of each positive electrode of a high-nickel / mid-nickel / lithium iron phosphate battery, compared to when only the conventional electrolyte additive is added or when an electrolyte additive having a similar structure but not having the structure of chemical formula 1 is added together.

[0168] Specifically, the secondary battery of the present invention may have an HPPC discharge resistance value of 300 mΩ or less, preferably 200 mΩ or less, measured after storage at 60°C for 60 days, and the increase rate compared to the initial resistance may not exceed 95%.

[0169] 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.

[0170] The above secondary battery exhibits a recovery capacity retention rate of 86% or more, 86.3% or more, 86 to 95%, or 86 to 98% measured after storage at 60°C for 60 days.

[0171] In this paper, the recovery capacity represents the capacity preservation characteristic of a battery that has been left for a long time. It measures the discharged electric capacity when a battery that has been left for a long time is discharged to the discharge end voltage, and the discharged electric capacity when the discharged battery is recharged and discharged again to the discharge end voltage, and compares the two capacity values. The higher the recovery capacity, the less the natural discharge due to battery preservation (storage), which means that the battery can be preserved for a long time. In particular, the higher the storage temperature of the battery, the faster the natural discharge rate, so the recovery capacity at high temperatures is a very important characteristic in automotive batteries. When the electrolyte additive of the present invention is added to the electrolyte, the recovery capacity is improved by, for example, up to 11%, specifically, 9 to 11%, compared to when only the conventional additive is used, thereby enabling longer-term storage with a single charge.

[0172] The secondary battery may have a life efficiency of 86% or more, 86.3% or more, 86 to 95%, or 86 to 98% measured after storage at 60°C for 60 days.

[0173] The secondary battery may have a thickness increase rate of 46% or less, 45% or less, 15 to 40%, or 10 to 35% at 60°C.

[0174] When the secondary battery is a high-nickel full-cell battery, the resistance increase rate at 60°C may be 30% or less, 28% or less, 5 to 20%, or 3 to 17%.

[0175] 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%.

[0176]

[0177] 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 the high-nickel anode by suppressing an increase in the acidity of the electrolyte and the elution of transition metal ions from the anode by effectively suppressing an increase in the acidity of the electrolyte and the elution of the ... 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.

[0178]

[0179] 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.

[0180]

[0181] Example 1

[0182] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 20:40:40 was used, and as a lithium salt, 0.5 wt% of the compound represented by the chemical formula 1-1 was added to a solution containing LiPF6 at a concentration of 1.15 M to prepare a battery electrolyte.

[0183]

[0184] Example 2

[0185] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 20:40:40 was used, and as a lithium salt, 0.3 wt% of the compound represented by the chemical formula 1-1 was added to a solution containing LiPF6 at a concentration of 1.15 M to prepare a battery electrolyte.

[0186]

[0187] Example 3

[0188] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 20:40:40 was used, and as a lithium salt, 1.0 wt% of the compound represented by the chemical formula 1-1 was added to a solution containing LiPF6 at a concentration of 1.15 M to prepare a battery electrolyte.

[0189]

[0190] Comparative Example 1

[0191] A carbonate-based mixed solvent having a volume ratio of EC:EMC:DMC = 20:5:75 was used as the organic solvent, and a battery electrolyte was prepared using a solution containing LiPF6 at a concentration of 1.15 M as the lithium salt. For reference, Comparative Example 1 corresponds to an experiment in which no electrolyte additives were used at all.

[0192]

[0193] Comparative Example 2

[0194] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 20:40:40 was used, and as a lithium salt, 0.5 wt% of fluoroethylene carbonate (FEC) was added to a solution containing LiPF6 at a concentration of 1.15 M to prepare a battery electrolyte.

[0195]

[0196] Comparative Example 3

[0197] As an organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:DEC = 20:40:40 was used, and as a lithium salt, 0.5 wt% of a 2-oxido-1,3,2-dioxaphospholan-2-yl acetate compound represented by the following chemical formula 3 was added to a solution containing LiPF6 at a concentration of 1.15 M to prepare a battery electrolyte.

[0198] [Chemical Formula 3]

[0199]

[0200] Manufacturing of NCM batteries

[0201] 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.

[0202] 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.

[0203] 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 3 and Comparative Examples 1 to 3 were injected to complete the manufacture of a lithium secondary battery.

[0204]

[0205] Test Example 1

[0206] In order to evaluate the performance of the NCM secondary battery manufactured above, the performance was evaluated using the following method, and the results are summarized and presented in Table 1 below.

[0207]

[0208] [HPPC Charge (Discharge) Resistance Evaluation]

[0209] 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.).

[0210] After storing at 60℃ for 60 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.

[0211]

[0212] [High-temperature storage DC-IR, recovery capacity evaluation]

[0213] The charging conditions were a constant current of 0.5 C and a voltage of 4.2 V, charging until the charging current became 1 / 10 C. The discharging conditions were a constant current of 0.5 C, charging and discharging until 3.0 V, and then the discharge capacity was measured.

[0214] After charging under the same charge and discharge conditions, the battery was stored at 60°C for 60 days, and then discharged to a discharge voltage of 3 V under the same conditions. The remaining capacity change was measured, and the high-temperature storage DC-IR increase rate, recovery capacity retention rate, and thickness retention rate are shown in Table 1 below.

[0215]

[0216] [High Temperature Life Evaluation]

[0217] The secondary battery was charged at a constant current of 1C at 60°C until the voltage reached 4.20 V (vs. Li), and then cut off at a current of 0.1C while maintaining 4.20 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 1C until the voltage reached 3.0 V (vs. Li) (1st cycle). After repeating the above cycle 300 times, the changes in capacity and retention rate were measured.

[0218] Classification Additive Weeding Machine Discharge DC-IR (mΩ) High Temperature Storage DC-IR Increase Rate (%) High Temperature Storage Recovery Capacity Maintenance Rate (%) Life Efficiency (%) Comparative Example 1 (Measured Value) -107.0mΩ 40.7% 88.6% 89.0% Comparative Example 1 (Conversion Reference Value) -100 100 100 100 Example 1 (Conversion Value) Chemical Formula 1 - 10.5 wt% 98.4 87.3 106.8 104.3 Example 2 (Conversion Value) Chemical Formula 1 - 10.3 wt% 95.8 87.7 104.5 103.1 Example 3 (Conversion Value) Chemical Formula 1 - 11.0 wt% 99.2 86.5 107.6 105.1 Comparative Example 2 (Conversion Value) FEC 0.5wt% 103.399.5102.7102.9 Comparative Example 3 (Conversion Value) Chemical Formula 3 0.5wt% 98.995.2103.1102.4

[0219] (In the above Table 1, the numerical value 100 of Comparative Example 1 is the experimental result of Comparative Example 1 converted to 100, and then the values ​​converted to % values ​​compared to Comparative Example 1 are described in Comparative Examples 2 and 3 and Examples 1, 2, and 3, respectively.)

[0220] As shown in Table 1 above, in the case of Examples 1 to 3, which are electrolyte additives of the present invention, it was confirmed that the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency were all improved in the NCM battery 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 conventionally used carbonate component, 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.

[0221] In particular, a significant difference was shown in the resistance increase rate of the battery before and after high-temperature storage. It was confirmed that in Examples 1 to 3 according to the present invention, there was a 12.3 to 13.5% improvement compared to Comparative Example 1 (reference value), which was a significant improvement compared to 40.7%, which was an actual measurement value of Comparative Example 1. In addition, a significant difference was also shown in the recovery capacity increase rate after high-temperature storage. It was confirmed that in Examples 1 to 3 according to the present invention, there was a 4.5 to 7.6% improvement compared to Comparative Example 1 (reference value), which was a significant improvement compared to 88.6%, which was an actual measurement value of Comparative Example 1.

[0222] A difference was also observed in life efficiency. In Examples 1 to 3 according to the present invention, it was confirmed that the efficiency was significantly improved by 3.1 to 5.1% compared to Comparative Example 1 (reference value), which was 89.0%, the actual measured value of Comparative Example 1.

[0223] Furthermore, the results of measuring the thickness change of the battery before and after high-temperature storage 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. Although not summarized in Table 1, the electrolyte additive of the present invention provided a thickness increase rate of 15% or less at 60°C.

[0224]

[0225] Manufacturing of mid-nickel NCM batteries

[0226] Li(Ni) as a cathode active material 0.6 Co 0.1 Mn 0.3)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.

[0227] 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.

[0228] 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 3 and Comparative Examples 1 to 3 were injected to complete the manufacture of a lithium secondary battery.

[0229]

[0230] Test Example 2

[0231] In order to evaluate the performance of the mid-nickel NCM-based secondary battery manufactured above, the performance was evaluated using the same method as in Test Example 1. The performance evaluation of the mid-nickel NCM-based secondary battery was conducted under high-voltage conditions by increasing the evaluation voltage to 4.4 V.

[0232] Classification Additive Weeding Machine Discharge DC-IR (mΩ) High Temperature Storage DC-IR Increase Rate (%) High Temperature Storage Recovery Capacity Maintenance Rate (%) Life Efficiency (%) Comparative Example 1 (Measured Value) -75.5mΩ 60.7% 69.6% 69.0% Comparative Example 1 (Conversion Reference Value) -100 100 100 100 Example 1 (Conversion Value) Chemical Formula 1 - 10.5 wt% 98.3 8 9.4 108.5 110.0 Example 2 (Conversion Value) Chemical Formula 1 - 10.3 wt% 97.6 94.5 105.4 107.5 Example 3 (Conversion Value) Chemical Formula 1 - 11.0 wt% 98.9 8 6.8 109.6 112.1 Comparative Example 2 (Conversion Value) FEC 0.5 wt% 105.398.5102.5103.2 Comparative Example 3 (Conversion Value) Chemical Formula 30.5 wt% 99.194.6103.1104.4

[0233] (In the above Table 2, the numerical value 100 of Comparative Example 1 is the experimental result of Comparative Example 1 converted to 100, and then the values ​​converted to % values ​​compared to Comparative Example 1 are described in Comparative Examples 2 and 3 and Examples 1, 2, and 3, respectively.)

[0234] As a result, in the case of Examples 1 to 3, which are electrolyte additives of the present invention, as in the above Test Example 1, it was confirmed that the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency were all improved in the mid-nickel NCM battery 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 conventionally used carbonate component, and Comparative Example 3 in which the electrolyte additive was replaced with an electrolyte additive component having a structure similar to the above Chemical Formula 1-1.

[0235] In particular, a significant difference was shown in the resistance increase rate of the battery before and after high-temperature storage. In Examples 1 to 3 according to the present invention, it was confirmed that there was a 5.5 to 13.2% improvement compared to Comparative Example 1 (reference value), which was a significant improvement compared to the actual measurement value of 60.7% in Comparative Example 1. In addition, a significant difference was also shown in the recovery capacity increase rate after high-temperature storage. In Examples 1 to 3 according to the present invention, it was confirmed that there was a 5.4 to 9.6% improvement compared to Comparative Example 1 (reference value), which was a significant improvement compared to the actual measurement value of 69.6% in Comparative Example 1.

[0236] A significant difference was also observed in life efficiency. In Examples 1 to 3 according to the present invention, it was confirmed that the improvement was significantly greater than that of Comparative Example 1 (reference value), which was 7.5 to 12.1%, compared to the actual measurement value of Comparative Example 1, which was 69.0%.

[0237] Furthermore, the results of measuring the thickness change of the battery before and after high-temperature storage 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. Although not summarized in Table 1, the electrolyte additive of the present invention provided a thickness increase rate of 20% or less at 60°C.

[0238]

[0239] Manufacturing of LFP batteries

[0240] 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.

[0241] 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.

[0242] 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 3 and Comparative Examples 1 to 3 were injected to complete the manufacture of a lithium secondary battery.

[0243]

[0244] Test Example 3

[0245] In order to evaluate the performance of the LFP secondary battery manufactured above, the performance was evaluated using the same method as in Test Example 1.

[0246] As a result, in the case of Examples 1 to 3, which are electrolyte additives of the present invention, as in the above Test Example 1, it was confirmed that the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency were all improved in the LFP battery 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 conventionally used carbonate component, and Comparative Example 3 in which the electrolyte additive was replaced with an electrolyte additive component having a structure similar to the above Chemical Formula 1-1.

[0247] In particular, a significant difference was observed in the resistance increase rate of the battery before and after high-temperature storage. It was confirmed that the resistance increase rate was significantly improved from 8.5 to 16.5% in Examples 1 to 3 according to the present invention, compared to 23.2 to 55.0% calculated in Comparative Examples 1 to 3.

[0248] Furthermore, the results of measuring the thickness change of the battery before and after high-temperature storage 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. Although not summarized in Table 1, the electrolyte additive of the present invention provided a thickness increase rate of 5% or less at 60°C.

[0249]

[0250] As a result, in the case of the secondary batteries of Examples 1 to 3 using the electrolyte additive of the present invention, compared to Comparative Example 1 in which the electrolyte additive and the conventional electrolyte additive were not used at all, Comparative Example 2 in which only the conventional electrolyte additive was used, 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, the secondary batteries showed positive performance improvements in initial resistance, high-temperature durability, rate characteristics, maintenance capacity, and recovery capacity. This can be seen as contributing to maximizing the efficiency and lifespan of the battery at high and low temperatures and improving the electrical characteristics.

[0251]

[0252] 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 an 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 automotive secondary battery, particularly a high-nickel full-cell battery having a basic capacity of 0.1 to 100 Ah, a mid-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, the line is a bond, and when a separate element is not described, the point where the bond and bond meet is carbon, and A1, A2, and A3 are each independently oxygen (O), nitrogen (N), or sulfur (S).) 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 1-5. [Chemical Formulas 1-1 to 1-5] 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, and lithium difluorophosphate. [Chemical Formula 1] (In the above chemical formula 1, the line is a bond, and when a separate element is not described, the point where the bond and bond meet is carbon, and A1, A2, and A3 are each independently oxygen (O), nitrogen (N), or sulfur (S).) 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, and lithium difluorophosphate 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 characterized in that the organic solvent comprises 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, and ethylpropyl carbonate.

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.

Images