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

Abstract

The present invention relates to an electrolyte additive, an electrolyte containing the same, and a secondary battery, and according to the present invention, the effect of providing a secondary battery in which a stable coating film is formed on a positive electrode and a negative electrode of a plurality of lithium secondary batteries such as a high-nickel, Si negative electrode, an LFP battery, an LMR (lithium manganese rich) battery, a cobalt-free battery, or the like, thereby suppressing side reactions inside the battery, and improving the reliability of the battery. The present invention relates to a lithium-ion secondary battery which has a low charge / discharge resistance and thus can improve charging efficiency and power, can suppress an increase in resistance of the battery even if stored under high-temperature conditions for a long period of time, and also can significantly suppress the generation of gas due to the decomposition of electrolyte components, thereby having excellent long-term life and high-temperature capacity retention rate. In addition, hydrofluoric acid in a side reaction product caused by instability of the high-nickel positive electrode is effectively inhibited, so that the acidity increase of the electrolyte and the elution of transition metal ions of the positive electrode are inhibited, and the battery has excellent battery characteristics and service life.

Description

Technical Field

[0001] The present invention relates to an electrolyte additive, an electrolyte for a battery containing the additive, and a secondary battery containing the electrolyte. More specifically, the present invention relates to an electrolyte additive that can provide a secondary battery in which stable coatings are formed on the positive and negative electrodes of various lithium secondary batteries such as high-nickel, Si negative electrode, LFP (lithium iron phosphate), LMR (lithium-rich manganese), or cobalt-free batteries, thereby suppressing side reactions inside the battery and having low charge and discharge resistance. Therefore, the charging efficiency and power can be improved, and even when stored at high temperatures for a long time, an increase in the battery resistance and the generation of gas can be suppressed, resulting in excellent long-term life and high-temperature capacity retention. In addition, by effectively scavenging hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel positive electrode, an increase in the acidity of the electrolyte and the dissolution of transition metal ions in the positive electrode can be suppressed, thereby having excellent battery characteristics and life. Background Art

[0002] In a lithium secondary battery, by placing an electrolyte between the positive and negative electrodes, lithium ions can migrate smoothly, and through redox reactions generated by insertion and extraction between the positive and negative electrodes, electricity can be generated or consumed, making the utilization of electrical energy easier.

[0003] On the other hand, in recent years, with the increasing attention to the environment, such as the strengthening of global environmental regulations, the attention to eco-friendly vehicles that can replace fossil fuel vehicles, which are one of the main causes of air pollution, has also been increasing. As a result, the domestic and international battery industries are actively developing batteries for vehicles.

[0004] In order to use a battery in a vehicle, it is necessary not only to significantly improve the power and capacity of the battery but also to solve problems such as power improvement and resistance increase under high and low temperature conditions to adapt to the use environment such as weather changes. In particular, for electric vehicles, in relation to the situation of emphasizing power and cruising range performance, research is being conducted to reduce the internal resistance of the battery and increase the remaining capacity. In view of this, in particular, it is necessary to develop a battery that can suppress internal side reactions of the battery and ensure low resistance and long-life performance even when stored at high temperatures for a long time.

[0005] In addition, it is necessary to develop a battery that can form a stable coating film on the positive and negative electrodes of various lithium secondary batteries such as high-nickel, Si negative electrode, LFP, LMR (lithium-rich manganese) battery, or cobalt-free battery, thereby suppressing side reactions inside the battery and having a low charge-discharge resistance, and thus improving the charging efficiency and power. That is, it is necessary to develop a battery that suppresses the increase in the acidity of the electrolyte and the dissolution of transition metal ions in the positive electrode by effectively scavenging hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel positive electrode, thereby having excellent battery characteristics and lifespan.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: US Patent No. 11394057 Summary of the invention

[0009] Problems to be solved by the invention

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

[0011] In addition, an object of the present invention is to provide a secondary battery that can suppress side reactions inside the battery and reduce the charging resistance, thereby improving the power of the battery, increasing the recovery capacity under high-temperature conditions, enabling long-term storage, and having excellent lifespan retention rate under high-temperature conditions.

[0012] The above objects and other objects of the present invention can be achieved by the present invention described below.

[0013] Means for solving the problems

[0014] In order to achieve the above object, the present invention provides an electrolyte additive, characterized in that the electrolyte additive is a compound represented by the following Chemical Formula 1.

[0015] [Chemical Formula 1]

[0016]

[0017] (In Chemical Formula 1, the lines represent bonds. When no individual element is specified, the point where the bonds intersect is carbon. X is carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S). R1 is F, Cl, Br, I, an alkyl group with 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl. R2 and R3 are independently H, F, Cl, Br, I, an alkyl group with 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl.)

[0018] The compound represented by Chemical Formula 1 can be a compound represented by the following Chemical Formulas 1 - 1 to 1 - 7.

[0019] [Chemical Formula 1 - 1]

[0020]

[0021] [Chemical Formula 1 - 2]

[0022]

[0023] [Chemical Formula 1 - 3]

[0024]

[0025] [Chemical Formula 1 - 4]

[0026]

[0027] [Chemical Formula 1 - 5]

[0028]

[0029] [Chemical Formula 1 - 6]

[0030]

[0031] [Chemical Formula 1 - 7]

[0032]

[0033] In addition, the present invention provides an electrolyte additive, characterized in that the electrolyte additive comprises: a compound represented by the following Chemical Formula 1; and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, 1 - propene - 1,3 - sultone, 1,3 - propane sultone, ethylene sulfate, adiponitrile, and succinonitrile.)

[0034] [Chemical Formula 1]

[0035]

[0036] (In Chemical Formula 1, the lines represent bonds. When no individual element is specified, the intersection points of the bonds are carbon. X is carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S). R1 is F, Cl, Br, I, an alkyl group of C1-C3, vinyl, allyl, propargyl, phenyl, or carboxyl. R2 and R3 are independently H, F, Cl, Br, I, an alkyl group of C1-C3, vinyl, allyl, propargyl, phenyl, or carboxyl.)

[0037] As an example, in 100% by weight of the components constituting the electrolyte additive, the compound represented by Chemical Formula 1 may be contained in an amount of 0.1% to 10% by weight, preferably 0.1% to 5% by weight, more preferably 0.1% to 2.0% by weight, further preferably 0.1% to 1.0% by weight, and most preferably 0.2% to 1.0% by weight.

[0038] As an example, in 100% by weight of the components constituting the electrolyte additive, one or more compounds selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate, lithium difluorophosphate, 1,3 - propanesultone, 1 - propene - 1,3 - sultone, ethylene sulfate, adiponitrile, and succinonitrile may be contained in an amount of 0.1% to 20% by weight. As a specific example, it may be contained in an amount of 0.2% to 10% by weight, and as a preferred example, it may be contained in an amount of 0.5% to 5% by weight.

[0039] As an example, the weight ratio of the compound represented by Chemical Formula 1 to one or more compounds selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate, lithium difluorophosphate, 1,3 - propanesultone, 1 - propene - 1,3 - sultone, ethylene sulfate, adiponitrile, and succinonitrile may be 1:0.5 to 1:3, or 1:0.5 to 1:1.5, or 1:0.7 to 1:1.2.

[0040] In addition, the present invention provides an electrolyte additive, characterized in that it contains a compound represented by the following Chemical Formula 1 - 1; and one or more compounds selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate, lithium difluorophosphate, 1,3 - propanesultone, 1 - propene - 1,3 - sultone, ethylene sulfate, adiponitrile, and succinonitrile.

[0041] [Chemical Formula 1 - 1]

[0042]

[0043] (In Chemical Formula 1, the lines represent bonds. When no individual element is specified, the intersection points of the bonds are carbon.)

[0044] As an example, in 100% by weight of the components constituting the electrolyte additive, the compound represented by the chemical formula 1-1 may be contained in an amount of 0.1% to 10% by weight. As a specific example, it may be contained in an amount of 0.1% to 5% by weight. As a preferred example, it may be contained in an amount of 0.5% to 2% by weight.

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

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

[0047] In addition, the present invention provides an electrolyte, which includes an organic solvent, a lithium salt, and an electrolyte additive, and is characterized in that it includes the aforementioned electrolyte additive.

[0048] The organic solvent may include one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0049] The lithium salt may include one selected from LiPF 6 , LiF 4 , LiCl, LiBr, LiI, LiClO 4 , LiBF4, LiB 10 Cl 10 , LiSbF6, LiAsF 6 , LiN(SO 2 C 2 F 5 ) 2 , LiCF 3 SO 3 , LiCF 3 CO 2 , Li(CF 3 SO 2 ) 2 , LiN(SO3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N、LiC 4 F 9 SO 3 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiN(CxF 2x +1SO 2 )(C y F 2y +1SO 2 )(wherein, x and y are natural numbers, such as integers from 1 to 20), LiAsF 6 、LiSbF 6 、LiAlCl 4 、LiB(C 2 O 4 ) 2 (lithium bis(oxalato)borate: LiBOB), CH 3 SO 3 Li, CF 3 SO 3 Li and (CF 3 SO 2 ) 2 NLi, or more than one of the group consisting of them.

[0050] Based on the total amount of the electrolyte being 100% by weight, the electrolyte additive may include 0.1% to 10% by weight, 1% to 10% by weight, 3% to 10% by weight, 1% to 8% by weight, or 1% to 6% by weight.

[0051] In addition, the present invention provides a secondary battery, which includes a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte. The secondary battery is characterized in that the electrolyte in the secondary battery is the aforementioned electrolyte.

[0052] The secondary battery may be an automotive battery.

[0053] The automotive battery may be a high-nickel full cell, an LFP (lithium iron phosphate) battery, an LMR (lithium-rich manganese) battery, or a cobalt-free battery.

[0054] In the high-nickel full cell, as the positive electrode material, it contains a lithium composite metal oxide with a nickel content of 80% or more, and the basic capacity may be 0.1 Ah to 100 Ah.

[0055] The basic capacity of the LFP (lithium iron phosphate) battery can be 0.1 Ah to 100 Ah.

[0056] The basic capacity of the LMR (lithium-rich manganese) battery can be 0.1 Ah to 100 Ah.

[0057] The basic capacity of the cobalt-free battery can be 0.1 Ah to 100 Ah.

[0058] Under the temperature condition of 60 °C, the recovery capacity retention rate of the secondary battery can be 86% or more, 86.3% or more, 86% to 95%, or 86% to 90%.

[0059] Under the temperature condition of 60 °C, the life efficiency of the secondary battery can be 89% or more, 89.3% or more, 89% to 99%, or 89% to 95%.

[0060] Under the temperature condition of 60 °C, the thickness increase rate of the secondary battery can be 6% or less, 5% or less, 1% to 5%, or 3% to 5%.

[0061] When the secondary battery is a high-nickel full cell, under the temperature condition of 60 °C, the resistance increase rate can be 20% or less, 18% or less, 1% to 20%, or 3% to 17%.

[0062] When the secondary battery is a lithium iron phosphate battery, under the temperature condition of 60 °C, the resistance increase rate can be 100% or less, 90% or less, 1% to 90%, or 3% to 90%.

[0063] Advantages of the Invention

[0064] A secondary battery including an electrolyte containing an electrolyte additive according to the present invention can form a stable coating film on the positive and negative electrodes of various lithium secondary batteries such as high-nickel, Si negative electrode, LFP battery, LMR (lithium-rich manganese) battery, or cobalt-free battery, thereby suppressing side reactions inside the battery and having a low charge-discharge resistance. Therefore, the charging efficiency and power can be improved.

[0065] In addition, a secondary battery including an electrolyte containing an electrolyte additive according to the present invention has the effect of providing a secondary battery with excellent long-term life and high-temperature capacity retention rate by suppressing an increase in the resistance of the battery even when stored at a high temperature for a long time, and by effectively suppressing hydrofluoric acid in side reaction products generated due to the instability of the high-nickel positive electrode, thereby suppressing an increase in the acidity of the electrolyte and the dissolution of transition metal ions in the positive electrode. Therefore, the battery characteristics and life are excellent. Detailed Embodiments

[0066] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0067] In order to manufacture a battery that can be used as an automotive battery, the present inventors, in the process of researching a secondary battery that can improve power by suppressing side reactions inside the battery and can suppress an increase in the resistance of the battery even when stored at high temperature for a long time, found that the above objects can be achieved when an additive having a specific structure is added to the electrolyte of the secondary battery, and based on this, the present invention was completed.

[0068] The electrolyte additive contained in the electrolyte of an embodiment of the present invention is characterized in that the electrolyte additive is a compound represented by the following Chemical Formula 1. In this case, the following effects are obtained: suppressing side reactions inside the battery, and since the charge resistance of the secondary battery is low, the charging efficiency and power can be improved. Even when stored at high temperature for a long time, an increase in the resistance of the battery can be suppressed, so that the long-term life and high-temperature capacity retention rate are excellent. And by effectively suppressing hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel cathode, an increase in the acidity of the electrolyte and the dissolution of transition metal ions in the cathode are suppressed, so that the battery characteristics and life are excellent.

[0069] [Chemical Formula 1]

[0070]

[0071] (In Chemical Formula 1, the lines are bonds. When no separate element is described, the point where the bonds intersect is carbon. X is carbon (C), phosphorus (P), nitrogen (N), oxygen (O), or sulfur (S). R1 is F, Cl, Br, I, an alkyl group having 1 to 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl. R2 and R3 are independently H, F, Cl, Br, I, an alkyl group having 1 to 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl.)

[0072] Specifically, the results of density functional theory (DFT) calculations of this compound show that, compared with ethylene carbonate (EC) with a HOMO of -12.72 eV and a LUMO of 1.74 eV, the HOMO is measured to be -10.77 eV and the LUMO is measured to be 0.85 eV. Judging from the high HOMO value and low LUMO value, it is predicted that this compound can also act on the positive electrode and the negative electrode. Actually, it reacts with the initial LiF series of inorganic coating components and forms a sulfonyl-based coating after the middle stage of the reaction, thereby stabilizing the interface between the electrode and the electrolyte. Specifically, Li 2 SO 3 known as a low-resistance component is effectively generated, so it has the effects of electrode stabilization and resistance reduction.

[0073] Preferably, C, S, or N, which has a large electronegativity difference from O and N, is used as X to provide the aforementioned effects.

[0074] When the electrolyte additive represented by Chemical Formula 1 is added to the electrolyte of a battery, due to the electronegativity difference between the O element and the N element directly connected to the S element and the X element (such as the C element, the S element, or the N element), electrons tend to concentrate on the C element, the S element, or the N element. Furthermore, due to the asymmetric structure of the entire chemical formula, the S element is in an electron-deficient (e-poor, δ+) state. Therefore, an oxidation reaction is induced in the electrolyte containing lithium ions, thereby forming a stable coating film on the electrode. As a specific example, a stable coating film is formed on the cathode.

[0075] Due to the stability of the coating film, the decomposition of the electrolyte can be prevented, thereby improving the cycle characteristics. In particular, since it does not decompose under high-temperature conditions, compared with the case where the existing electrode coating film decomposes under high-temperature conditions, resulting in a decrease in high-temperature storage performance, it has an excellent effect of significantly improving high-temperature storage performance. In addition, since the increase in resistance is prevented, there is an effect of improving the charge-discharge efficiency and power, and the generation of gas due to chemical reactions inside the battery can also be suppressed, thereby improving the stability of the battery. In addition, it has the following effects: under high-temperature conditions, by preventing the collapse of the structures of the electrode active materials of the cathode and the anode, the capacity retention rate is improved, thereby not only extending the life but also effectively suppressing hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel cathode, thereby suppressing the increase in the acidity of the electrolyte and the dissolution of transition metal ions in the cathode. Therefore, the battery characteristics and life are excellent.

[0076] Preferably, R1 is an alkyl group having 1 to 3 carbon atoms, which can provide a secondary battery that improves power by suppressing side reactions inside the battery and can suppress an increase in the resistance of the battery even when stored at high temperature for a long time, thereby having excellent high-temperature recovery capacity and life characteristics.

[0077] As a reference, when R1 is hydrogen, the HOMO energy level increases, which can lead to a decrease in the possibility of the additive forming an electrode coating film and an increase in the possibility of decomposition of the main solvent of the electrolyte. Thus, when stored at high temperature, the thickness of the battery can increase, the resistance can increase, and the recovery capacity may decrease.

[0078] Preferably, R2 and R3 are hydrogen, F, Cl, Br, or I, which can provide a secondary battery that improves power by suppressing side reactions inside the battery and can suppress an increase in the resistance of the battery even when stored at high temperature for a long time, thereby having excellent high-temperature recovery capacity and life characteristics.

[0079] As a specific example, the electrolyte additive represented by the chemical formula 1 is optionally selected from the compounds represented by the following chemical formulas 1-1 to 1-7.

[0080] [Chemical formula 1-1]

[0081]

[0082] [Chemical formula 1-2]

[0083]

[0084] [Chemical formula 1-3]

[0085]

[0086] [Chemical formula 1-4]

[0087]

[0088] [Chemical formula 1-5]

[0089]

[0090] [Chemical formula 1-6]

[0091]

[0092] [Chemical formula 1-7]

[0093]

[0094] Based on the total amount of the electrolyte of 100% by weight, the compound represented by the chemical formula 1 may be contained in an amount of 0.1% to 10% by weight, preferably, may be contained in an amount of 0.1% to 5% by weight, more preferably, 0.1% to 2.0% by weight, further preferably, 0.1% to 1.0% by weight, and most preferably, 0.2% to 1.0% by weight. Within this range, the charging efficiency of the battery and the improvement effect of the high-temperature life are the most excellent.

[0095] Preferably, the compound represented by the chemical formula 1 is put together with one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1-propene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, adiponitrile, and succinonitrile, which will not have an adverse effect on the components constituting the battery and can provide a predetermined improvement effect.

[0096] Based on a total electrolyte amount of 100% by weight, the total amount of one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1 - propene - 1,3 - sultone, 1,3 - propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be included in an amount of 0.1% to 20% by weight, preferably 0.1% to 10% by weight, more preferably 0.5% to 8.0% by weight, further preferably 1% to 4.0% by weight, and most preferably 1.0% to 3.5% by weight. When the content of the compound satisfies the above range, it is preferable in terms of the improvement effect of the high - temperature characteristics and cycle characteristics of the battery.

[0097] The compound represented by the Chemical Formula 1; and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorophosphate, 1 - propene - 1,3 - sultone, 1,3 - propane sultone, ethylene sulfate, adiponitrile, and succinonitrile may be used in a weight ratio of 1:0.5 to 1:3, or 1:0.5 to 1:1.5, or 1:0.7 to 1:1.2. Within the above range, the charging efficiency and the improvement effect of high - temperature life of the battery are the most excellent.

[0098] As an example, in addition to the above - mentioned electrolyte additives, the electrolyte of the present invention may further contain additives that can generally be used in electrolytes, for inhibiting side reactions inside the battery, improving the life characteristics of the battery, inhibiting the reduction of battery capacity, and improving the discharge capacity of the battery, etc.

[0099] As a preferred specific example, the additive component may be one or more selected from the group consisting of ethyl propionate (EP), propyl propionate (PP), succinic anhydride, tetravinylsilane, 1,1,2,2 - tetrafluoroethyl 2,2,2 - trifluoroethyl ether, 1,2 - bis((difluorophosphoryl)phenyl)oxy)ethane, 1,3,6 - hexanetricarbonitrile, succinonitrile, 1 - ethyl - 3 - methylimidazolium dicyanamide, trimethoxyboroxine, lithium bis(oxalate)borate, lithium difluoro(oxalate)borate, tris(trimethylsilyl)borate, lithium tetrafluoroborate, triisopropyl borate, lithium tetrafluoro(oxalate)phosphate, lithium difluoro(bis(oxalate))phosphate, diethyl (difluoromethyl)phosphonate, tris(trimethylsilyl)phosphite, tri - propargyl phosphate, 2,4,8,10 - tetraoxa - 3,9 - dithiaspiro[5.5]undecane 3,3,9,9 - tetraoxide, dimethyl sulfate, dimethyl ethyl sulfonate, methylene methanedisulfonate, lithium bis(fluorosulfonyl)imide, 3 - fluoro - 1,3 - propane sultone, ethylene sulfate, 1,3 - propylene sulfate, 1,4 - butane sultone, sulfolene, biphenyl, cyclohexylbenzene, 4 - fluorotoluene, triphenyl phosphate, fluorobenzene, and 2 - fluorobiphenyl.

[0100] Among the foregoing types, as a specific example, the metal phosphate compound is selected from one or more of the group consisting of lithium difluoro(bisoxalato)phosphate, lithium tetrafluorooxalate phosphate, and lithium trioxalate phosphate. The compound is an additive component added to improve the performance of lithium secondary batteries, lithium ion capacitors, etc., suppress side reactions inside the battery, and improve resistance and lifespan. As an example, it can be included in the electrolyte solution at 0.3 wt% to 2.5 wt%, preferably 0.5 wt% to 1.5 wt%. When the content of the foregoing electrolyte additive satisfies the above range, it is preferable in terms of the improvement effect on the high-temperature characteristics and cycle characteristics of the battery.

[0101] As an example, the electrolyte additive (including the total content of the components used) can be included in the foregoing electrolyte solution at 0.1 wt% to 10.1 wt%, 0.1 wt% to 8.0 wt%, 0.1 wt% to 7 wt%, 0.3 wt% to 7 wt%, 0.5 wt% to 6 wt%, or 0.5 wt% to 5 wt%. When the content of the electrolyte additive satisfies the above range, it is preferable in terms of the improvement effect on the high-temperature characteristics and cycle characteristics of the battery.

[0102] The foregoing additive component needs to be additionally included in the compound represented by the foregoing Chemical Formula 1. When only other additive components are injected alone without including the compound represented by the Chemical Formula 1, it can be confirmed through the comparative examples described later that the improvement effect on long-term lifespan and low resistance is not good.

[0103] In addition, the present invention provides an electrolyte solution containing the electrolyte additive of the present invention. The electrolyte solution is an electrolyte solution for a non-aqueous lithium secondary battery, which contains the electrolyte additive, an organic solvent, and a lithium salt.

[0104] As an example, the organic solvent can be a carbonate-based organic solvent. Specifically, the organic solvent can be an organic solvent containing one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0105] As an example, the organic solvent can be a mixed solvent of one or two or more. Preferably, in order to improve the charge and discharge performance of the battery, a high dielectric constant organic solvent with high ionic conductivity can be mixed with a low viscosity organic solvent that can adjust the viscosity of the solvent to be suitable for the application battery, and it can be used as a mixed solvent.

[0106] As an example, the high-dielectric constant organic solvent can be EC, PC, etc. As an example, the low-viscosity organic solvent can be EMC, DMC, DEC, etc. Preferably, the high-dielectric constant organic solvent and the low-viscosity organic solvent are mixed and used at a volume ratio of 2:8 to 8:2. More specifically, it can be a ternary mixed solvent of one of EC and PC, and EMC and DEC. As an example, the ratio of EC or PC, EMC, and DEC can be 1:0.1 to 1:2 to 5, or 1:0.2 to 0.5:3 to 5, or 1:0.2 to 0.3:3 to 4.

[0107] When the organic solvent contains moisture, since lithium ions in the electrolyte can be hydrolyzed, the moisture in the organic solvent is preferably controlled below 150 ppm, and preferably below 100 ppm.

[0108] The lithium salt can be used without particular limitation as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the lithium salt can include those selected from the group consisting of LiPF 6 , LiBF 4 , LiCl, LiBr, LiI, LiClO 4 , LiB 10 Cl 10 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 , Li and (CF 3 SO 2 ) 2 NLi. Preferably, it can be LiPF 6 .

[0109] When the lithium salt is dissolved in the electrolyte, the lithium salt can be used as a source of lithium ions in a lithium secondary battery and can promote the migration of lithium ions between the positive electrode and the negative electrode. Thus, preferably, in the electrolyte, the concentration of the lithium salt is about 0.6 mol% to 2 mol%. When the concentration of the lithium salt is lower than 0.6 mol%, the conductivity of the electrolyte decreases, which may lead to a reduction in electrolyte performance. When it exceeds 2 mol%, the viscosity of the electrolyte increases, which may lead to a reduction in the mobility of lithium ions. Considering the conductivity of the electrolyte and the mobility of lithium ions as described above, preferably, in the electrolyte, the content of the lithium salt can be 0.7 mol% to 1.6 mol%, and more preferably, 0.8 mol% to 1.5 mol%.

[0110] As an example, the electrolyte additive can be included in the electrolyte in an amount of 0.1 wt% to 10.1 wt%, 0.1 wt% to 8.0 wt%, 0.1 wt% to 7 wt%, 0.3 wt% to 7 wt%, 0.5 wt% to 6 wt% or 0.5 wt% to 5 wt%. When the content of the aforementioned electrolyte additive satisfies the above range, it is preferable in terms of the improvement effect of the high-temperature characteristics and cycle characteristics of the battery.

[0111] 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.

[0112] As an example, the positive electrode is prepared by mixing a positive electrode active material, a binder, and an optional conductive agent to form a composition for forming a positive electrode active material layer, and then the composition can be coated on a positive electrode current collector (such as aluminum foil) for preparation.

[0113] The positive electrode active material can use a compound (lithiated insertion compound) capable of reversibly inserting and extracting lithium.

[0114] The positive electrode active material can use a conventional NCM (lithium nickel manganese cobalt oxide, LiNiMnCoO 2 ) positive electrode active material used in lithium secondary batteries. As an example, the positive electrode active material can be a lithium composite metal oxide of the chemical formula Li[Ni x Co y M z O 2 (where M is Mn and / or Al, 0 < x < 98, 0 < y < 35, 0 < z < 35, however, x + y + z = 100), but not limited thereto.

[0115] As an example, the chemical formula of the lithium composite metal oxide is Li[Ni x Co y M z O 2The parameters x, y, and z can be such that 0.0001 < x < 98, 0.0001 < y < 35, and 0.0001 < z < 35. Specifically, they can be 1 ≤ x ≤ 93, 1 ≤ y ≤ 30, and 1 ≤ z ≤ 30. More preferably, they can be 5 ≤ x ≤ 91, 3 ≤ y ≤ 25, and 3 ≤ z ≤ 25. Preferably, they can be 80 ≤ x ≤ 91, 3 ≤ y ≤ 25, and 3 ≤ z ≤ 25. At this time, x + y + z satisfies 100.

[0116] As another example, the lithium composite metal oxide can be selected from the group consisting of LiCoO 2 , LiMnO 2 , LiMn 2 O 4 , LiNiO 2 , LiNi x Mn (1-x) O 2 (However, 0 < x < 1) and LiM1 x M2 y O 2 (However, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, and M1 and M2 are each independently selected from any one of the group consisting of Al, Sr, Mg, and La), and one or more of the group. In this case, the capacity characteristics and stability of the battery can be improved.

[0117] Compounds having a coating layer on the surface of the compound can also be used, or the compound and the compound having a coating layer can also be used in combination. The coating layer can include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming these coating layers can be amorphous or crystalline.

[0118] The coating elements contained in the coating layer can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. As long as the physical properties of the positive electrode active material are not adversely affected by using these elements in the compound (for example, spraying, dipping method, etc.) for coating, any coating method can be used for the coating layer formation process. Since it is well-known in the art, its detailed description is omitted.

[0119] As an example, the content of the positive electrode active material can be 90% by weight or more, or 90% to 98% by weight, based on the total weight of the positive electrode active material layer.

[0120] In an implementation example of the present invention, the positive electrode active material layer may include a binder and a conductive material. At this time, relative to the total weight of the positive electrode active material layer, the contents of the binder and the conductive material may be 1% by weight or more, or 1% to 5% by weight, respectively.

[0121] The function of the binder is to make the positive electrode active material particles adhere well to each other. In addition, the positive electrode active material is well adhered to the current collector. As an example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used.

[0122] The conductive material is used to provide conductivity to the electrode. In the formed battery, any electron conductive material that does not cause a chemical change can be used. As an example, a conductive material can be used. The conductive material includes: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based substances such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as poly(phenylene) derivatives; or mixtures thereof.

[0123] Al can be used as the current collector, but is not limited thereto.

[0124] As an example, the negative electrode is prepared by mixing a negative electrode active material, a binder, and an optional conductive agent to form a composition for forming a negative electrode active material layer, and then the composition can be coated on a negative electrode current collector (such as a copper foil) for preparation.

[0125] The surface of the negative electrode may further include a solid electrolyte interface (SEI) film.

[0126] The negative electrode active material includes a material capable of reversibly inserting / extracting lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping or dedoping with respect to lithium, or a transition metal oxide.

[0127] The material capable of reversibly inserting / extracting the lithium ions is a carbon material, and any material can be used as the carbon-based negative electrode active material commonly used in lithium ion secondary batteries.

[0128] As a specific example, the negative electrode active material may be a carbonaceous material such as artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, etc. In addition, in addition to the carbonaceous material, a metal compound capable of alloying with lithium, or a composite containing a metal compound and a carbonaceous material can also be used as the negative electrode active material. As an example, it can be graphite.

[0129] In addition, as the negative electrode active material, a thin film of metallic lithium can also be used. Since the negative electrode active material has high stability, one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal, and an alloy containing lithium can be used.

[0130] As an example, the metal capable of alloying with lithium can be at least one selected from Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy.

[0131] The material capable of doping or dedoping with lithium may include Si, Si-C composite, SiOx (0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Si), Sn, SnO 2 and Sn-R (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and not Sn), etc. In addition, it can also be used by mixing at least one of them and SiO 2 for use.

[0132] The elements Q and R can be elements 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.

[0133] The transition metal oxide may include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide, etc.

[0134] In the negative electrode active material layer, as an example, relative to the total weight of the negative electrode active material layer, the content of the negative electrode active material can be 95% by weight or more, or 95% to 99% by weight.

[0135] In the negative electrode active material layer, as an example, relative to the total weight of the negative electrode active material layer, the content of the binder can be 1% by weight or more, or 1% to 5% by weight.

[0136] In the case of containing a conductive material, 90% to 98% by weight of negative electrode active material, 1% to 5% by weight of binder, and 1% to 5% by weight of conductive material can be used.

[0137] The function of the binder is to make the negative electrode active material particles adhere well to each other. In addition, the negative electrode active material is well adhered to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof can be used.

[0138] The water-insoluble binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0139] The water-soluble binder may include a rubber-based binder or a polymer resin binder.

[0140] The rubber-based binder can be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), nitrile rubber, acrylic rubber, butyl rubber, fluororubber, and a combination thereof.

[0141] The polymer resin binder can be selected from polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene terpolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and a combination thereof.

[0142] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may also be included.

[0143] As an example, the cellulose-based compound can be used by mixing one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts.

[0144] The alkali metal can be Na, K, or Li. As an example, the usage content of such a thickener can be 0.1 parts by weight to 5 parts by weight or 0.1 parts by weight to 3 parts by weight relative to 100 parts by weight of the negative electrode active material.

[0145] The conductive material is used to provide conductivity to the electrode. In the formed battery, any electron conductive material that does not cause a chemical change can be used. As an example, a conductive material can be used, and the conductive material includes: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber; metal-based substances such as metal powders or metal fibers of copper, nickel, aluminum, silver; conductive polymers such as polybenzene derivatives; or a mixture thereof.

[0146] The current collector can be made of a material selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0147] Depending on the type of the lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. Such a separator can be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. Of course, a mixed multilayer film can also be used, such as a two-layer separator of polyethylene / polypropylene, a three-layer separator of polyethylene / polypropylene / polyethylene, a three-layer separator of polypropylene / polyethylene / polypropylene, etc.

[0148] In the secondary battery of the present invention, in addition to the conventional compounds added to the electrolyte for improving the performance of existing batteries, an electrolyte additive represented by the above Chemical Formula 1 is also added together. Compared with the case where only the existing electrolyte additive is added, by effectively suppressing hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel positive electrode, an increase in the acidity of the electrolyte and the dissolution of transition metal ions of the positive electrode are suppressed. As a result, the improvement effects of the battery charging resistance, power characteristics, and battery characteristics (such as capacity recovery characteristics and life characteristics) when stored for a long time (more than 60 days) under high-temperature conditions of 60 °C or higher, measured by the Hybrid Pulse Power Characterization (HPPC) method, are further improved.

[0149] Specifically, the HPPC discharge resistance value of the secondary battery of the present invention measured after being stored at a temperature of 60 °C for 60 days can be 60 mΩ or less, preferably 55 mΩ or less, and the increase rate does not exceed 93% compared with the initial resistance.

[0150] In the description of the present specification, the HPPC charge (discharge) resistance value can be measured by the method specified in the "Battery test manual for plug-in hybrid electric vehicles" (2010, Idaho National Laboratory for the U.S. Department of Energy.), which is an important index showing battery characteristics (such as battery power). In addition, the charge (discharge) resistance refers to the resistance value measured when the battery is charged (discharged). The lower the charge (discharge) resistance, the lower the energy loss. Therefore, the charging speed can be increased and the power of the battery can be improved. The HPPC discharge resistance value of the secondary battery of the present invention as described above is low, and the charging speed and power are excellent. Therefore, it is suitable for use as an automotive battery, for example.

[0151] The recovery capacity retention rate measured after storing the secondary battery for 60 days under a temperature condition of 60°C is 86% or more, 86.3% or more, 86% to 95%, or 86% to 90%.

[0152] In the description of this specification, the recovery capacity represents the capacity retention characteristic of the battery after long-term storage. It is measured by separately measuring the discharge capacity when the battery stored for a long time is discharged to the discharge cut-off voltage, and the discharge capacity when the discharged battery is recharged and then discharged again to the discharge cut-off voltage, and comparing the two capacity values. The higher the recovery capacity, the less the natural discharge amount generated by battery storage (storage). Therefore, it means that the battery can be stored for a long time. In particular, the higher the storage temperature of the battery, the faster the natural discharge speed. Therefore, the recovery capacity under high-temperature conditions is a very important characteristic for automotive batteries. When the electrolyte additive of the present invention is added to the electrolyte, compared with only using the existing additive, the recovery capacity is increased by up to 11%, for example, increased by 9% to 11%. Thus, it has the effect of enabling longer-term storage with a single charge.

[0153] The life efficiency measured after storing the secondary battery for 60 days under a temperature condition of 60°C can be 89% or more, 89.3% or more, 89% to 99%, or 89% to 95%.

[0154] The thickness increase rate of the secondary battery under a temperature condition of 60°C can be 6% or less, 5% or less, 1% to 5%, or 3% to 5%.

[0155] When the secondary battery is a high-nickel full cell, the resistance increase rate under a temperature condition of 60°C can be 20% or less, 18% or less, 1% to 20%, or 3% to 17%.

[0156] When the secondary battery is an LFP battery, the resistance increase rate under a temperature condition of 60°C can be 100% or less, 90% or less, 1% to 90%, or 3% to 90%.

[0157] Therefore, when the battery of the present invention is used as an automotive battery, not only can power improvement (which becomes important according to the size of the vehicle) and performance at low and high temperatures (problems caused by climate change and the characteristic that the vehicle is mostly directly exposed to sunlight during driving or parking) be achieved, but also when applying a high-content nickel cathode material suitable for high-capacity expression, the hydrofluoric acid in the side reaction products generated due to the instability of the high-nickel cathode can be effectively inhibited, thereby suppressing the increase in the acidity of the electrolyte and the dissolution of transition metal ions in the cathode, ensuring stability, and exhibiting excellent performance as an automotive battery.

[0158] Hereinafter, for the purpose of facilitating the understanding of the present invention, preferred embodiments are given. However, the following embodiments are only used to illustrate the present invention, and various changes and modifications can be made within the scope and technical concept of the present invention, which will be obvious to those skilled in the art. Of course, such variations and modifications fall within the scope of the appended claims.

[0159] Example 1

[0160] A carbonate mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 is used as the organic solvent. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-1 is added to a solution containing LiPF at a concentration of 1.15 M, thereby preparing an electrolyte for a battery. 6

[0161] Example 2

[0162] A carbonate mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 is used as the organic solvent. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-1 and 0.5 wt% of fluoroethylene carbonate (FEC) are added to a solution containing LiPF at a concentration of 1.15 M, thereby preparing an electrolyte for a battery. 6

[0163] Example 3

[0164] A carbonate mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 is used as the organic solvent. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-1 and 1.0 wt% of lithium difluorophosphate (LDFP) are added to a solution containing LiPF at a concentration of 1.15 M, thereby preparing an electrolyte for a battery. 6

[0165] Example 4

[0166] A carbonate mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40 is used as the organic solvent. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-1 and 1.0 wt% of ethylene carbonate (VC) are added to a solution containing LiPF at a concentration of 1.15 M, thereby preparing an electrolyte for a battery. 6

[0167] Example 5

[0168] The organic solvent used is a carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-2 was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared. 6 and 0.5 wt% of the compound represented by Chemical Formula 1-2 was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared.

[0169] Example 6

[0170] The organic solvent used is a carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 1-2 and 0.5 wt% of fluoroethylene carbonate (FEC) were added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared. 6 and 0.5 wt% of the compound represented by Chemical Formula 1-2 and 0.5 wt% of fluoroethylene carbonate (FEC) were added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared.

[0171] Comparative Example 1

[0172] The organic solvent used is a carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40. As the lithium salt, 0.5 wt% of the compound represented by the following Chemical Formula 2 was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared. 6 and 0.5 wt% of the compound represented by Chemical Formula 2 was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared.

[0173] [Chemical Formula 2]

[0174]

[0175] Comparative Example 2

[0176] The organic solvent used is a carbonate-based mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40. As the lithium salt, 0.5 wt% of fluoroethylene carbonate (FEC) was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared. 6 and 0.5 wt% of fluoroethylene carbonate (FEC) was added to a solution containing LiPF6 at a concentration of 1.15 M, and an electrolyte for a battery was thus prepared.

[0177] Comparative Example 3

[0178] The organic solvent used is a carbonate-based mixed solvent with a volume ratio of EC:EMC:DMC = 20:5:75. As the lithium salt, a solution containing LiPF6 at a concentration of 1.15 M was used to prepare an electrolyte for a battery. For reference, Comparative Example 3 corresponds to an experiment in which no electrolyte additive was used at all. 6 and a solution containing LiPF6 at a concentration of 1.15 M was used to prepare an electrolyte for a battery. For reference, Comparative Example 3 corresponds to an experiment in which no electrolyte additive was used at all.

[0179] Comparative Example 4

[0180] The organic solvent used is a carbonate mixed solvent with a volume ratio of EC:EMC:DEC = 20:40:40. As a lithium salt, 0.5 wt% of lithium difluorophosphate is added to a solution containing LiPF 6 at a concentration of 1.15 M, thereby preparing an electrolyte for a battery.

[0181] Preparation of NCM Battery

[0182] 92 wt% of Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 , which is used as the positive electrode active material, 4 wt% of carbon black as the conductive agent, and 4 wt% of polyvinylidene fluoride (PVdF) as the binder are added to N-methyl-2-pyrrolidone (NMP) as the solvent, and a positive electrode mixture slurry is prepared. The positive electrode mixture slurry is coated on an aluminum (Al) film with a thickness of about 20 μm as the positive electrode current collector, and the positive electrode is prepared by drying, and then roll press is performed to prepare the positive electrode.

[0183] 96 wt% of carbon powder as the negative electrode active material, 3 wt% of PVdF as the binder, and 1 wt% of carbon black as the conductive agent are added to NMP as the solvent to prepare a negative electrode mixture slurry. The negative electrode mixture slurry is coated on a copper (Cu) film with a thickness of 10 μm as the negative electrode current collector, and the negative electrode is prepared by drying, and then roll press is performed to prepare the negative electrode.

[0184] The positive electrode, negative electrode prepared in the above-described manner, and a separator formed of a three-layer of polypropylene / polyethylene / polypropylene (PP / PE / PP) are made into a pouch cell by a conventional method, and then each electrolyte prepared in Examples 1 to 6 and Comparative Examples 1 to 4 is injected, thereby completing the preparation of the lithium secondary battery.

[0185] Test Examples 1 to 9

[0186] To evaluate the performance of each of the secondary batteries prepared above, their performance was evaluated by the following method, and the results were summarized and shown in Table 1 below.

[0187] [HPPC Charge (Discharge) Resistance Evaluation]

[0188] It is measured in the manner specified in the document "Battery test manual for plug-in hybrid electric vehicles" (2010, Idaho National Laboratory for the U.S. Department of Energy).

[0189] After storing for 60 days at a temperature of 60 °C, the voltage value, the charge and discharge current values corresponding to the charge and discharge rate (C-rate), the current change amount (ΔI), the discharge voltage change amount (ΔV), the charge voltage change amount (ΔV), the charge resistance, and the discharge resistance are measured. And for each charge and discharge rate (C-rate), the charge and discharge current is allowed to flow briefly for a certain period of time, and the resistance increase rate is calculated from the slope values obtained from the current change amount and the voltage change amount.

[0190] [Evaluation of DC-IR and restored capacity after high-temperature storage]

[0191] The charging condition is to charge at a constant current of 0.5C and a voltage of 4.2V until the charging current reaches 1 / 10C. The discharging condition is to discharge at a constant current of 0.5C until the voltage reaches 3.0V. After charging and discharging in this manner, the discharge capacity is measured.

[0192] After charging under the same charge and discharge conditions and storing at a temperature of 60 °C for 60 days, then discharging under the same conditions until the discharge voltage reaches 3V, the change in the remaining capacity is measured and shown in Table 1 below in terms of the DC-IR increase rate after high-temperature storage, the restored capacity retention rate, and the thickness retention rate.

[0193] [High-temperature life evaluation]

[0194] The secondary battery is charged at a constant current of 1 C-rate at a temperature of 60 °C until the voltage reaches 4.20V (vs. Li), then in the constant voltage mode, it is maintained at 4.20V and cut off at a current of 0.1 C-rate. Then, it is discharged at a constant current of 1 C-rate until the voltage during discharge reaches 3.0V (vs. Li) (the 1st cycle). After repeating 300 cycles as described above, the changes in capacity and retention rate are measured.

[0195] Table 1

[0196]

[0197] As shown in Table 1 above, for Test Examples 1 to 6 using the electrolyte additive of the present invention in Examples 1 to 6, compared with Comparative Example 1 in which an electrolyte additive component similar in structure to the chemical formula 1-1 was used to replace the electrolyte additive, Comparative Example 2 in which a conventionally used carbonate component was used to replace it, and Test Examples 7 to 9 of Comparative Example 3 in which the electrolyte additive was not used, the results that could be confirmed were that the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency of the NCM battery were all improved.

[0198] In particular, there was a significant difference in the resistance increase rate of the battery before and after high-temperature storage. It was confirmed that, compared with 23.2% to 55.0% calculated in Test Examples 7 to 9 using Comparative Examples 1 to 3, Test Examples 1 to 6 using Examples 1 to 6 of the present invention were significantly improved, being 8.5% to 16.5%.

[0199] Furthermore, as a result of measuring the change in battery thickness before and after high-temperature storage, it could be confirmed that the electrolyte additive of the present invention significantly inhibited the oxidation / reduction decomposition of the electrolyte, and thus also had the effect of reducing the amount of gas generated. In fact, as shown in Table 1 above, at a temperature of 60 °C, the electrolyte additive of the present invention provided a thickness increase rate of 5% or less.

[0200] Preparation of LFP Battery

[0201] 92% by weight of Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 as the positive electrode active material, 4% by weight of carbon black as the conductive agent, and 4% by weight of polyvinylidene fluoride (PVdF) as the binder were added to N-methyl-2-pyrrolidone (NMP) as the solvent, and a positive electrode mixture slurry was prepared. The positive electrode mixture slurry was coated on an aluminum (Al) thin film (the film thickness was about 20 μm) as the positive electrode current collector, and the positive electrode was prepared by drying, and then roll-pressed to prepare the positive electrode.

[0202] 96% by weight of carbon powder as the negative electrode active material, 3% by weight of PVdF as the binder, and 1% by weight of carbon black as the conductive agent were added to NMP as the solvent to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was coated on a copper (Cu) thin film (the film thickness was 10 μm) as the negative electrode current collector, and the negative electrode was prepared by drying, and then roll-pressed to prepare the negative electrode.

[0203] The positive electrode, negative electrode prepared in the manner described above, together with a separator formed of polypropylene / polyethylene / polypropylene (PP / PE / PP) three layers, were prepared into a pouch cell by a conventional method, and then each electrolyte prepared in Example 1, Comparative Example 1, and Comparative Example 4 was injected, thus completing the preparation of the lithium secondary battery.

[0204] Test Examples 10 to 12

[0205] To evaluate the performance of each of the secondary batteries prepared above, their performance was evaluated by the following methods, and the results were summarized and shown in Table 2 below.

[0206] [HPPC Charge (Discharge) Resistance Evaluation]

[0207] The measurement was carried out in the manner specified in the document "Battery test manual for plug-in hybrid electric vehicles" (2010, Idaho National Laboratory for the U.S. Department of Energy).

[0208] After storing for 60 days at a temperature of 60 °C, the voltage value, charge and discharge current values corresponding to the charge and discharge rate (C-rate), current change amount (△I), discharge voltage change amount (△V), charge voltage change amount (△V), charge resistance, and discharge resistance were measured, and the charge and discharge current was allowed to flow for a certain time at each charge and discharge rate (C-rate) briefly. The resistance increase rate was calculated from the slope values obtained from the current change amount and voltage change amount.

[0209] [Evaluation of High-Temperature Recovery Capacity]

[0210] The charging conditions were to charge at a constant current of 0.5C and a voltage of 4.2V until the charging current reached 1 / 10C. The discharging conditions were to discharge at a constant current of 0.5C until 3.0V. After charging and discharging in this manner, the discharge capacity was measured.

[0211] After charging under the same charging and discharging conditions and storing at a temperature of 60 °C for 60 days, then discharging under the same conditions until the discharge voltage reached 3V, the remaining capacity change was measured and shown as the high-temperature recovery capacity in Table 1 below.

[0212] [Evaluation of High-Temperature Life]

[0213] The secondary battery was subjected to constant current charging at a current of 1C rate under a temperature condition of 60 °C until the voltage reached 4.20 V (vs. Li). Then, in the constant voltage mode, 4.20 V was maintained and cut-off was performed at a current of 0.1C rate. Subsequently, it was discharged at a constant current of 1C rate until the voltage during discharge reached 3.0 V (vs. Li) (the first cycle). After repeating 300 cycles as described above and storing for 60 days, the changes in capacity and retention rate were measured.

[0214] Table 2

[0215]

[0216]

[0217] As shown in Table 2 above, for Test Example 10 using the electrolyte additive of the present invention of Example 1, compared with Test Examples 11 and 12 using Comparative Example 1 (replacing the electrolyte additive with an electrolyte additive component similar in structure to the chemical formula 1-1) and Comparative Example 4 (replacing with the conventionally used lithium difluorophosphate (LDFP) component), the confirmed results are that at least one physical property among the initial discharge resistance, resistance increase rate, high-temperature recovery capacity, thickness increase rate, and high-temperature life capacity efficiency is equivalent or improved.

[0218] In particular, there is a significant difference in the resistance increase rate of the battery before and after high-temperature storage. It was confirmed that, compared with 109.6% to 120.1% calculated in Test Examples 11 to 12 using Comparative Example 1 and Comparative Example 4, Test Example 10 of Example 1 of the present invention was significantly improved to 86.9%.

[0219] In addition, the high-temperature recovery capacity was improved. In the case of having the structure of the electrolyte additive used in the present invention, compared with the experiment of replacing with a similar structure of Comparative Example 1 or the experiment of using a different structure of Comparative Example 4, it was confirmed that not only an effective protective film was formed on the positive and negative electrodes, but also due to the side reaction inhibition effect between the electrolyte and the electrode, it had excellent recovery capacity and capacity retention rate characteristics.

[0220] For reference, it is known that the recovery capacity is related to the reversibility of Li ions. If the irreversible Li ions increase (such as causing the dissolution of transition metals in the positive electrode, the deposition of dissolved metal ions on the surface of the negative electrode, or causing side reactions at the interface between the positive and negative electrodes, etc.), the capacity will decrease.

[0221] As shown in Table 2 above, at a temperature of 60 °C, the recovery capacity retention rate of the electrolyte additive of the present invention was 89.0%, which was significantly improved compared with 84.2% to 96.9% in Comparative Example 1 or Comparative Example 4.

[0222] Furthermore, from the results of measuring the life efficiency, it was confirmed that Example 1 of the present invention was significantly improved to 89.3% compared with 85.1% to 87.5% calculated in Comparative Example 1 or Comparative Example 4.

[0223] Finally, for the secondary batteries in Example 1 and Example 5 that use only the electrolyte additive of the present invention, and Example 1, Example 2, Example 3, Example 4 and Example 6 that use the electrolyte additive in appropriate combination with the existing electrolyte additive, compared with Comparative Example 1 that uses only a component with a structure similar to that of the electrolyte additive, or Comparative Example 2 and Comparative Example 4 that use only the existing electrolyte additive, and Comparative Example 3 that does not use the electrolyte additive and the existing electrolyte additive at all, it can be seen that the discharge efficiency is excellent in terms of the power and life performance of the finally completed composition.

[0224] Therefore, it can be confirmed that when using the electrolyte additive of the examples of the present invention and the electrolyte containing the additive in a secondary battery, not only can the gas generation amount be reduced by suppressing side reactions inside the battery, but also the charge resistance, discharge resistance, power, recovery capacity and life efficiency can be improved even when stored at high temperature for a long time. Therefore, it is suitable for use in automotive secondary batteries, especially for high-nickel full batteries with a basic capacity of 0.1 Ah to 100 Ah, LFP batteries with a basic capacity of 0.1 Ah to 100 Ah, LMR (lithium-rich manganese) batteries with a basic capacity of 0.1 Ah to 100 Ah, or cobalt-free batteries with a basic capacity of 0.1 Ah to 100 Ah, etc.

Claims

1. An electrolyte additive, characterized in that, the electrolyte additive is a compound represented by the following Chemical Formula 1, [Chemical Formula 1] In Chemical Formula 1, the lines are bonds. When no individual element is specified, the point where the bonds intersect is carbon. X is carbon, phosphorus, nitrogen, oxygen, or sulfur. R1 is F, Cl, Br, I, an alkyl group having 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl. R2 and R3 are independently H, F, Cl, Br, I, an alkyl group having 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl.

2. The electrolyte additive according to claim 1, characterized in that, the compound represented by Chemical Formula 1 is a compound represented by the following Chemical Formulas 1 - 1 to 1 - 7, [Chemical Formula 1 - 1] [Chemical Formula 1 - 2] [Chemical Formula 1 - 3] [Chemical Formula 1 - 4] [Chemical Formula 1 - 5] [Chemical Formula 1 - 6] [Chemical Formula 1 - 7] 3. An electrolyte additive, characterized in that, it comprises: a compound represented by the following Chemical Formula 1; and one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, 1 - propene - 1,3 - sultone, 1,3 - propane sultone, ethylene sulfate, adiponitrile, and succinonitrile, [Chemical Formula 1] In Chemical Formula 1, the lines are bonds. When no individual element is specified, the point where the bonds intersect is carbon. X is carbon, phosphorus, nitrogen, oxygen, or sulfur. R1 is F, Cl, Br, I, an alkyl group having 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl. R2 and R3 are independently H, F, Cl, Br, I, an alkyl group having 1 - 3 carbon atoms, vinyl, allyl, propargyl, phenyl, or carboxyl.

4. The electrolyte additive according to claim 3, characterized in that, the weight ratio of the compound represented by Chemical Formula 1 to one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, 1 - propene - 1,3 - sultone, 1,3 - propane sultone, ethylene sulfate, adiponitrile, and succinonitrile is 1:0.2 to 1:

3.

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

6. The electrolyte according to claim 5, characterized in that, the organic solvent includes one or more selected from the group consisting of ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, propylene carbonate, dipropyl carbonate, butylene carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

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

8. A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, characterized in that, the electrolyte in the secondary battery is the electrolyte according to claim 5.

9. The secondary battery according to claim 8, characterized in that, After the secondary battery is stored for 60 days under the temperature condition of 60 °C, the recovery capacity retention rate of the secondary battery is 86% or more.

10. The secondary battery according to claim 8, wherein, After the secondary battery is stored for 60 days under the temperature condition of 60 °C, the life efficiency of the secondary battery is 89% or more.

11. The secondary battery according to claim 8, wherein, After the secondary battery is stored for 60 days under the temperature condition of 60 °C, the thickness increase rate of the secondary battery is 6% or less.

12. The secondary battery according to claim 8, wherein, The secondary battery is a battery for automobiles.

13. The secondary battery according to claim 8, wherein, When the secondary battery is a high-nickel full cell, the resistance increase rate is 20% or less under the temperature condition of 60 °C.

14. The secondary battery according to claim 8, wherein, When the secondary battery is a lithium iron phosphate battery, the resistance increase rate is 100% or less under the temperature condition of 60 °C.

Images