Electrolyte additive for lithium secondary battery, and electrolyte for lithium secondary battery and lithium secondary battery each comprising same

Abstract

The purpose of the present invention is to provide an electrolyte additive, for a lithium secondary battery, represented by chemical formula 1, and an electrolyte for a lithium secondary battery and a lithium secondary battery each comprising same. [Chemical formula 1] In chemical formula 1, R1 to <sb / >R4 each independently represent hydrogen, deuterium, a C1-C6 alkyl group, or a C3-C6 cycloalkyl group, and n represents an integer of 0 to 2. The electrolyte additive for a lithium secondary battery according to the present invention can enhance the high-temperature lifespan of the lithium secondary battery and improve the capacity recovery rate, thickness increase rate, and resistance increase rate during high-temperature storage.

Description

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

[0001] The present invention provides an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery.

[0002] [Chemical Formula 1]

[0003]

[0004] (In the above chemical formula 1, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

[0005] The electrolyte additive for a lithium secondary battery according to the present invention can improve the high-temperature life of a lithium secondary battery and improve the capacity recovery rate, thickness increase rate, and resistance increase rate during high-temperature storage.

[0006]

[0007] Batteries are used as power sources for portable electronic devices such as video cameras, cell phones, and laptop computers. Rechargeable lithium secondary batteries offer more than three times the energy density per unit weight of conventional lead-acid, nickel-cadmium, nickel-metal hydride, and nickel-zinc batteries, and are capable of rapid charging.

[0008] The demand for these lithium secondary batteries is rapidly increasing, and accordingly, much research has been conducted on lithium secondary batteries with high energy density and discharge voltage, and they have been commercialized and widely used.

[0009] Lithium secondary batteries offer several advantages over other batteries, including light weight, small volume, high operating voltage, high energy density, high output power, high charging efficiency, no memory effect, and long lifespan. Therefore, they are widely used in digital products such as mobile phones and laptops, and are considered a prime choice for electric vehicles and large-scale energy storage devices.

[0010] Recently, as the development of medium- to large-sized lithium secondary batteries for electric vehicles progresses, various studies are being conducted to implement high-voltage and high-capacity lithium secondary batteries. In particular, there is a need for suitable additives that can improve high-temperature lifespan and implement excellent characteristics even during high-temperature storage.

[0011] Meanwhile, there is the following prior art document regarding an electrolyte additive for lithium secondary batteries.

[0012] Prior art document 1. Republic of Korea Patent Publication No. 10-2179846

[0013] Prior art document 2. Republic of Korea Patent Publication No. 10-2440653

[0014] Prior art document 3. Republic of Korea Patent Publication No. 10-2440657

[0015] Prior art document 4. Republic of Korea Patent Publication No. 10-2440658

[0016]

[0017] The present inventors have made extensive efforts to improve the high-temperature lifespan characteristics of lithium secondary batteries and the capacity recovery rate, thickness increase rate, and resistance increase rate during high-temperature storage, and as a result, have confirmed that the electrolyte additive of the present invention can exhibit a capacity retention rate of 80% or more after 300 cycles at 45°C, a capacity recovery rate of 90% or more after 4 weeks at 60°C, a thickness increase rate of 5% or less, and / or a resistance increase rate of 30% or less (see Examples 1 to 6), and thus have completed the present invention.

[0018] Accordingly, the present invention aims to provide an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1, and more preferably, an electrolyte additive represented by the following chemical formula 2.

[0019] [Chemical Formula 1]

[0020]

[0021] (In the above chemical formula 1, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

[0022] [Chemical Formula 2]

[0023]

[0024] In addition, the present invention aims to provide an electrolyte for a lithium secondary battery comprising an electrolyte additive for a lithium secondary battery represented by the above chemical formula 1, more preferably, an electrolyte additive represented by the above chemical formula 2.

[0025] In addition, the present invention aims to provide a lithium secondary battery comprising an electrolyte additive represented by the chemical formula 1, more preferably, an electrolyte additive represented by the chemical formula 2.

[0026] The purposes of the present invention are not limited to the purposes mentioned above, and other purposes and advantages of the present invention that are not mentioned can be understood by the following description and will be more clearly understood by the embodiments of the present invention.

[0027] In addition, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0028]

[0029] The present invention discloses an electrolyte additive for a lithium secondary battery, an electrolyte for a lithium secondary battery, and a lithium secondary battery.

[0030] According to the first embodiment, an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1 is disclosed.

[0031] [Chemical Formula 1]

[0032]

[0033] (In the above chemical formula 1, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

[0034] In the present invention, the electrolyte additive for a lithium secondary battery can be represented by the following chemical formula 2.

[0035] [Chemical Formula 2]

[0036]

[0037]

[0038] According to a second embodiment, an electrolyte for a lithium secondary battery is disclosed, which comprises an organic solvent, a lithium salt, and an additive according to the chemical formula 1 or 2.

[0039] In the present invention, the additive may be included in an amount of 0.005 to 10 wt% based on the weight of the electrolyte.

[0040] In the present invention, the organic solvent may include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or a combination thereof.

[0041] In the present invention, the lithium salt may include LiPF6, LiFSI, LiDFOB, LiBF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2C2F3)2, LiN(SO2F3)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3 or a combination thereof.

[0042] In the present invention, the additive may further include 0.5 to 3 wt% of vinylene carbonate (VC) based on the weight of the electrolyte.

[0043] In the present invention, the additive may further include 0.5 to 3 wt% of vinylene carbonate (VC), 0.5 to 3 wt% of propane sultone (PS), and 0.1 to 1.5 wt% of ethylene sulfate (ESA) based on the weight of the electrolyte. In addition, the additive may further include 100 to 10,000 ppm of triphenyl phosphite (TPPI) based on the weight of the electrolyte.

[0044]

[0045] According to a third embodiment, a lithium secondary battery is disclosed, which includes an electrolyte including an additive according to the chemical formula 1 or 2; a positive electrode; and a negative electrode.

[0046]

[0047] The electrolyte additive for a lithium secondary battery according to the present invention can improve the high-temperature life of a lithium secondary battery and improve the capacity recovery rate, thickness increase rate, and resistance increase rate during high-temperature storage.

[0048]

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0050] Additionally, throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless specifically stated otherwise.

[0051]

[0052] 1. Electrolyte additive for lithium secondary batteries

[0053] The present invention provides an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1.

[0054] [Chemical Formula 1]

[0055]

[0056] (In the above chemical formula 1, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

[0057] In the electrolyte additive for a lithium secondary battery according to the present invention, the additive can be represented by the following chemical formula 2.

[0058] [Chemical Formula 2]

[0059]

[0060]

[0061] 2. Electrolyte for lithium secondary batteries

[0062] The present invention

[0063] organic solvent,

[0064] lithium salts, and

[0065] A lithium secondary battery electrolyte comprising an electrolyte additive represented by the following chemical formula 1 is provided.

[0066] [Chemical Formula 1]

[0067]

[0068] (In the above chemical formula 1, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

[0069] As a non-limiting example of the present invention, more preferably, the organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, or a combination thereof.

[0070] For example, the carbonate solvent may include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, diethyl carbonate (DEC), dipropyl carbonate, propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), or butylene carbonate. The above ester solvent may include methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), gamma-butyrolactone (γGBL), decanolide, valerolactone, mevalonolactone, or caprolactone.

[0071] For example, the ether-based organic solvent may include dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxy ethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The ketone-based solvent may include cyclohexanone.

[0072] For example, the alcohol-based solvent may include ethyl alcohol and isopropyl alcohol.

[0073] For example, the aprotic solvent may include a nitrile solvent, an amide solvent, a dioxolane solvent such as 1,3-dioxolane, or a sulfolane solvent.

[0074] As a non-limiting example of the present invention, more preferably, the lithium salt may include LiPF6, LiFSI, LiDFOB, LiBF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2C2F3)2, LiN(SO2F3)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3 or a combination thereof.

[0075] As a non-limiting example of the present invention, more preferably, the lithium salt may be included in the solvent at a concentration of 0.01 to 5 M, preferably 0.1 to 2 M. Within the above range, the transfer of lithium ions and / or electrons during charging and discharging of a lithium secondary battery is promoted, thereby securing improved capacity.

[0076] In the electrolyte for a lithium secondary battery according to the present invention, the additive may be represented by the following chemical formula 2.

[0077] [Chemical Formula 2]

[0078]

[0079]

[0080] In the electrolyte for a lithium secondary battery according to the present invention, the additive may be included in an amount of 0.005 wt% or more, 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, 0.8 wt% or more, 1.0 wt% or more, 10 wt% or less, 5 wt% or less, 3 wt% or less, or 2 wt% or less, based on the weight of the electrolyte. Within the above range, improved capacity retention rate after 300 repetitions at 45°C and improved capacity recovery rate, thickness increase rate, and resistance increase rate after 4 weeks at 60°C may be exhibited.

[0081] In the electrolyte for a lithium secondary battery according to the present invention, the additive may further include vinylene carbonate (VC), propanesultone (PS), ethylene sulfate (ESA), triphenyl phosphite (TPPI), or a combination thereof as an additional additive. In this case, the total content of the additional additive or the combination thereof other than the additive represented by the chemical formula 1 may be included in an amount of 0.5 wt% or more, 1.0 wt% or more, 5 wt% or less, 3 wt% or less, or 2 wt% or less, based on the weight of the electrolyte.

[0082] In one exemplary embodiment, the electrolyte for a lithium secondary battery according to the present invention may further include vinylene carbonate (VC) in addition to the additive represented by the chemical formula 1. At this time, the vinylene carbonate (VC) may be included in an amount of 0.5 to 3 wt%, preferably 1.0 to 1.5 wt%, based on the weight of the electrolyte. In addition, in this case, the weight ratio of the additive represented by the chemical formula 1 to vinylene carbonate (VC) may be 0.1:1 to 10:1, preferably 0.5:1 to 5:1.

[0083] In one exemplary embodiment, the electrolyte for a lithium secondary battery according to the present invention may include, in addition to the additive represented by the above chemical formula 1, vinylene carbonate (VC), propane sultone (PS), and ethylene sulfate (ESA). At this time, the vinylene carbonate (VC) may be included in an amount of 0.5 to 3 wt%, preferably 1.0 to 1.5 wt%, based on the weight of the electrolyte, the propane sultone (PS) may be included in an amount of 0.5 to 3 wt%, preferably 1.0 to 1.5 wt%, based on the weight of the electrolyte, and the ethylene sulfate (ESA) may be included in an amount of 0.1 to 1.5 wt%, preferably 0.5 to 1.0 wt%, based on the weight of the electrolyte. In addition, in this case, the weight ratio of the additive represented by chemical formula 1 and vinylene carbonate (VC) may be 0.1:1 to 10:1, preferably 0.5:1 to 5:1, the weight ratio of the additive represented by chemical formula 1 and propane sultone (PS) may be 0.1:1 to 5:1, preferably 0.5:1 to 5:1, and the weight ratio of the additive represented by chemical formula 1 and ethylene sulfate (ESA) may be 0.1:0.5 to 15:1, preferably 0.5:1 to 10:1.

[0084] In one exemplary embodiment, the electrolyte for a lithium secondary battery according to the present invention may include, in addition to the additive represented by the chemical formula 1, vinylene carbonate (VC), propane sultone (PS), ethylene sulfate (ESA), and triphenyl phosphite (TPPI). At this time, the vinylene carbonate (VC) may be included in an amount of 0.5 to 3 wt%, preferably 1.0 to 1.5 wt%, based on the weight of the electrolyte, the propane sultone (PS) may be included in an amount of 0.5 to 3 wt%, preferably 1.0 to 1.5 wt%, based on the weight of the electrolyte, the ethylene sulfate (ESA) may be included in an amount of 0.1 to 1.5 wt%, preferably 0.5 to 1.0 wt%, based on the weight of the electrolyte, and the triphenyl phosphite (TPPI) may be included in an amount of 100 to 10,000 ppm, preferably 300 to 1,000 ppm, based on the weight of the electrolyte. In addition, in this case, the weight ratio of the additive represented by chemical formula 1 and vinylene carbonate (VC) may be 0.1:1 to 10:1, preferably 0.5:1 to 5:1, the weight ratio of the additive represented by chemical formula 1 and propane sultone (PS) may be 0.1:1 to 5:1, preferably 0.5:1 to 5:1, the weight ratio of the additive represented by chemical formula 1 and ethylene sulfate (ESA) may be 0.1:0.5 to 15:1, preferably 0.5:1 to 10:1, and the weight ratio of the additive represented by chemical formula 1 and triphenyl phosphite (TPPI) may be 1:0.01 to 1:0.5.

[0085]

[0086] 3. Lithium secondary battery

[0087] The present invention

[0088] The electrolyte for the lithium secondary battery described above;

[0089] Bipolar; and

[0090] cathode;

[0091] It is intended to provide a lithium secondary battery including:

[0092] In the lithium secondary battery according to the present invention, the positive electrode may include a current collector and a positive electrode active material layer formed on the current collector. Aluminum may be used as the current collector, but is not limited thereto. The positive electrode active material layer may include a positive electrode active material, a binder, and optionally a conductive material. The binder may be selected from, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof. The conductive material is used to impart conductivity to the electrode, and any material that does not cause chemical changes in the battery and is electronically conductive can be used. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powders such as copper, nickel, aluminum, and silver, metal fibers, polyphenylene derivatives, or combinations thereof. In one exemplary embodiment, the positive electrode active material can be represented by the following chemical formula 1.

[0093] [Chemical Formula 3]

[0094] LiNi a Co b Mn c M d O2

[0095] 0.1≤a≤0.98, 0.01≤b≤0.9, 0.01≤c≤0.9, 0.0≤d≤0.05, and a+b+c+d=1,

[0096] The above M may be selected from Al, Mg, Fe, Cu, Zn, Cr, Ag, Ca, Na, K, In, Ga, Ge, V, Mo, Nb, Si, Ti, or a combination thereof. In the above chemical formula 1, the a is preferably 0.5 to 0.98, most preferably 0.6 to 0.98; the b is preferably 0.01 to 0.3, most preferably 0.05 to 0.1; the c is preferably 0.01 to 0.3, most preferably 0.05 to 0.1; and the d may be preferably 0 to 0.1 or less.)

[0097] In the lithium secondary battery according to the present invention, the negative electrode may include a current collector and a negative electrode active material layer formed on the current collector. The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, or a combination thereof. The negative electrode active material layer may include a negative electrode active material, a binder composition, and / or a conductive material. The negative electrode active material may include 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.

[0098] In the lithium secondary battery according to the present invention, the lithium secondary battery may further include a separator that prevents short circuits between the positive and negative electrodes and provides a passage for lithium ions. The separator may be a polyolefin-based polymer film such as polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, polypropylene / polyethylene / polypropylene, or a multi-film thereof, a microporous film, a woven fabric, or a non-woven fabric. In addition, a film coated with a resin having excellent stability on a porous polyolefin film may be used, but is not limited thereto.

[0099] In the lithium secondary battery according to the present invention, the shape of the lithium secondary battery may include a square shape, a cylindrical shape, or a pouch shape.

[0100] In the lithium secondary battery according to the present invention, the lithium secondary battery can exhibit a capacity retention rate of 80% or more after 300 repetitions at 45°C, a capacity recovery rate of 90% or more after 4 weeks at 60°C, a thickness increase rate of 5% or less, and / or a resistance increase rate of 30% or less.

[0101]

[0102] Hereinafter, the present invention will be described in detail through examples, but the following examples and experimental examples are merely illustrative of one form of the present invention, and the scope of the present invention is not limited by the following examples and experimental examples.

[0103]

[0104] Preparation of electrolyte additive of chemical formula 2 of the present invention

[0105] [Scheme 1]

[0106]

[0107]

[0108] An electrolyte additive of chemical formula 2 according to the present invention was prepared according to the above Scheme 1.

[0109] 1 stStep: After adding 16.04 g of Catechol and 80.18 g (5 vol) of Isopropyl ether (IPE) to a 250 mL 3-neck jacket reactor, cooling and stirring were performed (below -10℃), and phosphorous trichloride was added dropwise while maintaining the internal temperature (no exotherm, dropwise addition for about 10 minutes). Then, the mixture was warmed to room temperature and reacted for 48 hours (GC analysis was performed to confirm the completion of the reaction), and the reactant was transferred to a 250 mL 1-neck flask using a membrane filter (to remove unreacted substances and by-products), and the solid was removed and dried using a nitrogen filter, and the solvent and HCl gas, a reaction by-product, were removed under reduced pressure to obtain a pale yellow liquid (yield of about 40%).

[0110] 2 nd Step: 50g of 1,3,2-Benzodioxaphosphole, 2-chloro and 100g (5 vol.) of isopropyl ether were added to a 500ml 3-necked flask and mixed, and then 10.41g (0.4eq) of antimony trifluoride was additionally added at room temperature. The mixture was reacted at room temperature for 2 hours, membrane filtered, and transferred to a 250ml flask. 5% NaHCO3 (350ml) and DIW (50ml) were added to the mixture, and work-up was performed once each, and the organic layer was separated. The organic layer was treated with MgSO4 to remove a trace of moisture, and the filtrate was concentrated under reduced pressure to remove the solvent, obtaining a white solid with a yield of 90% (GC Purity 98.5%).

[0111] Preparation of electrolyte

[0112] [Manufacturing Example 1]

[0113] A basic electrolyte was prepared by dissolving LiPF6 to 1 M in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC=25:75 v / v%).

[0114]

[0115] [Manufacturing Example 2]

[0116] An electrolyte was prepared by adding 1.0 wt% of vinylene carbonate (VC) to the basic electrolyte of the above manufacturing example 1.

[0117]

[0118] [Manufacturing Example 3]

[0119] An electrolyte was prepared by adding 0.01 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0120]

[0121] [Manufacturing Example 4]

[0122] An electrolyte was prepared by adding 0.05 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0123]

[0124] [Manufacturing Example 5]

[0125] An electrolyte was prepared by adding 0.1 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0126]

[0127] [Manufacturing Example 6]

[0128] An electrolyte was prepared by adding 0.2 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0129]

[0130] [Manufacturing Example 7]

[0131] An electrolyte was prepared by adding 0.3 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0132]

[0133] [Manufacturing Example 8]

[0134] An electrolyte was prepared by adding 0.5 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0135]

[0136] [Manufacturing Example 9]

[0137] An electrolyte was prepared by adding 1.0 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0138]

[0139] [Manufacturing Example 10]

[0140] An electrolyte was prepared by adding 2.0 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0141]

[0142] [Manufacturing Example 11]

[0143] An electrolyte was prepared by adding 5.0 wt% of the electrolyte additive of chemical formula 2 of the present invention to the electrolyte of the above manufacturing example 2.

[0144]

[0145] [Manufacturing Example 12]

[0146] An electrolyte was prepared by adding 1.0 wt% of the electrolyte additive of chemical formula 2 of the present invention, 1.0 wt% of PS, and 0.5 wt% of ESA to the electrolyte of the above manufacturing example 2.

[0147]

[0148] [Manufacturing Example 13]

[0149] An electrolyte was prepared by adding 1.0 wt% of the electrolyte additive of Chemical Formula 2 of the present invention, 1.0 wt% of PS, 0.5 wt% of ESA, and 500 ppm of TPPI to the electrolyte of the above-mentioned Manufacturing Example 2.

[0150]

[0151] Manufacturing of lithium secondary batteries

[0152] Li[Ni 0.9 Co 0.05 Mn 0.05]O2, 96 wt% of NCM-based cathode active material, 2 wt% of carbon black as a conductive agent, and 2 wt% of polyvinylidene fluoride (PVdF) as a binder were added to NMP (N-methyl 2-pyrrolidinone) solvent to prepare a cathode active material slurry. The cathode active material slurry was applied to an aluminum thin film as a current collector and dried to prepare a cathode, and then rolled using a roll press to prepare a cathode.

[0153] A slurry of negative active material was prepared by adding graphite as a negative active material, CMC and SBR as binders, and carbon black as a conductive agent in amounts of 97.1 wt%, 1 wt%, 1 wt%, and 0.9 wt%, respectively, to a solvent, H2O. The negative electrode mixture was applied to a copper thin film, which is a negative electrode current collector, and dried to prepare a negative electrode.

[0154] In addition, the positive and negative electrodes manufactured as described above were prepared, and a PE separator was positioned between them. The standard capacity was 730 mAh, and the deviation of the initial capacity for each battery may show a difference of ±20 mAh. Here, the electrolyte according to the manufacturing example was injected into each, and an aluminum pouch type (Al-Pouch type) lithium secondary battery was manufactured.

[0155]

[0156] Characteristic evaluation

[0157] 1. Capacity retention rate at 45℃: After charging to 4.2V at 1C-rate at 45℃, resting for 10 minutes, discharging to 2.7V at 1C-rate, and resting for 10 minutes again, this process was repeated 300 times as one cycle to measure the capacity retention rate (%).

[0158] 2. Capacity recovery rate after 4 weeks at 60℃: After charging for 3 hours at 4.2V, 0.33C CC-CV 0.05C at room temperature, the battery was left at 60℃ for 4 weeks, discharged at 0.33C to 2.8V, and the usable capacity (%) compared to the initial capacity was measured.

[0159] 3. Thickness increase rate after 4 weeks at 60℃: When the thickness of the battery after charging for 3 hours at 4.2V, 0.33C CC-CV 0.05C at room temperature is A, and the thickness of the battery left in a constant temperature device at atmospheric pressure and 60℃ for 4 weeks is B, the thickness increase rate was calculated by the formula (BA) / A * 100.

[0160] 4. Resistance increase rate after 4 weeks at 60℃: After charging at 4.2V, 0.33C CC-CV 0.05C for 3 hours at room temperature, discharged at 0.33C to SOC50%, and discharged at 2 C-rate for 30 seconds, the resistance value at the point of discharge is C, and after leaving it in a constant temperature device at atmospheric pressure 60℃ for 4 weeks, discharged at 0.33C to SOC50%, and discharged at 2 C-rate for 30 seconds, the resistance value at the point of discharge is D. The resistance increase rate was calculated by the formula (CD) / C * 100.

[0161]

[0162] No.45 ℃60 ℃ 4 weeks after capacity retention @300 times capacity recovery rate Thickness increase rate Resistance increase rate Manufacturing example 1 37% 37% 30% 257% Manufacturing example 2 61% 73% 13% 127% Manufacturing example 3 67% 74% 13% 88% Manufacturing example 4 76% 77% 12% 75% Manufacturing example 5 81% 79% 11% 60% Manufacturing example 6 85% 83% 9% 46% Manufacturing example 7 86% 86% 7% 33% Manufacturing example 8 89% 90% 4% 19% Manufacturing example 9 93% 95% 1% 10% Manufacturing example 10 91% 94% 2% 15% Manufacturing example 11 90% 93% 3% 22% Manufacturing example 12 94% 96% 1% 11% Manufacturing example 13 96% 97% 0% 8%

[0163]

[0164] When the electrolyte additive of the above chemical formula 2 was added, compared to the case where it was not added, the capacity retention rate increased after 300 repetitions at 45°C, the capacity recovery rate after 4 weeks at 60°C also increased, and the thickness increase rate and resistance increase rate were found to be significantly reduced.

[0165]

[0166] While specific aspects of the present invention have been described in detail above, it should be apparent to those skilled in the art that these specific descriptions are merely preferred implementation examples and are not intended to limit the scope of the present invention. Therefore, the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An electrolyte additive for a lithium secondary battery, represented by the following chemical formula 1: [Chemical Formula 1] In the chemical formula 1 above, R1 to R4 each independently represents hydrogen, deuterium, a C1-C6 alkyl group, or a C3-C6 cycloalkyl group, and n represents an integer from 0 to 2.

2. In paragraph 1, An electrolyte additive for a lithium secondary battery, represented by the following chemical formula 2: [Chemical formula 2] .

3. Organic solvent; lithium salt; and An electrolyte for a lithium secondary battery, comprising an additive according to Article 1.

4. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the additive is contained in an amount of 0.005 to 10 wt% based on the weight of the electrolyte.

5. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the organic solvent comprises ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or a combination thereof.

6. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the lithium salt comprises LiPF6, LiFSI, LiDFOB, LiBF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2C2F3)2, LiN(SO2F3)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3 or a combination thereof.

7. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the additive further comprises vinylene carbonate (VC), propanesultone (PS), ethylene sulfate (ESA), triphenyl phosphite (TPPI), or a combination thereof as an additional additive.

8. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the additive further comprises 0.5 to 3 wt% of vinylene carbonate (VC) based on the weight of the electrolyte.

9. In paragraph 3, An electrolyte for a lithium secondary battery, wherein the additive further comprises 0.5 to 3 wt% of vinylene carbonate (VC), 0.5 to 3 wt% of propane sultone (PS), and 0.1 to 1.5 wt% of ethylene sulfate (ESA), based on the weight of the electrolyte.

10. In paragraph 9, An electrolyte for a lithium secondary battery, wherein the additive further comprises 100 to 10,000 ppm of triphenyl phosphite (TPPI) based on the weight of the electrolyte.

11. Electrolyte for lithium secondary battery according to Article 3; Bipolar; and A lithium secondary battery including a cathode.

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