Method for preparing electrolyte additive for lithium secondary battery, electrolyte for lithium secondary battery, and lithium secondary battery comprising same

Abstract

According to exemplary embodiments of the present invention, a method for preparing an electrolyte additive for a lithium secondary battery can reduce manufacturing costs, shorten process time, and provide an additive in high yield, thereby improving economic efficiency. A lithium secondary battery according to exemplary embodiments of the present invention exhibits improved high-temperature performance and storage characteristics.

Description

Method for manufacturing an electrolyte additive for a lithium secondary battery, an electrolyte for a lithium secondary battery, and a lithium secondary battery including the same

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

[0002] Lithium-ion batteries offer high operating voltage, energy density, and charging speed, as well as advantages in terms of weight reduction. Accordingly, lithium-ion batteries are being applied as a power source for electric vehicles as well as small electronic devices.

[0003] Lithium secondary batteries used as a power source for electric vehicles must have a low amount of gas generated within the battery to achieve stable capacity, because if gas is generated, the resistance within the battery increases, leading to a decrease in the battery's capacity.

[0004] A lithium secondary battery may include a negative electrode comprising a negative electrode active material (graphite, silicon), a positive electrode comprising a positive electrode active material (lithium metal oxide), a lithium salt, and a non-aqueous electrolyte comprising an organic solvent.

[0005] By varying the composition of the non-aqueous electrolyte, gas generation within the lithium secondary battery can be suppressed and high-temperature performance and resistance characteristics can be improved. For example, removing moisture from the non-aqueous electrolyte suppresses gas generation, and firmly forming a solid electrolyte interface (SEI; solid electrolyte interface, CEI; cathode electrolyte interface) on the negative and positive electrodes of the lithium secondary battery prevents the decomposition of organic solvents, thereby improving the retention and recovery capacity at high temperatures. Additionally, the resistance characteristics of the lithium secondary battery can be enhanced by improving lithium ion conductivity.

[0006] One objective of the present invention is to provide a method for manufacturing an electrolyte additive for a lithium secondary battery that reduces costs, shortens process time, and improves economic efficiency by obtaining a high yield of the additive.

[0007] One objective of the present invention is to provide an electrolyte for a lithium secondary battery that can improve the high-temperature performance and storage characteristics of the lithium secondary battery.

[0008] One objective of the present invention is to provide a lithium secondary battery with improved high-temperature performance and storage characteristics.

[0009] A method for manufacturing a lithium secondary battery electrolyte additive according to the present invention comprises the steps of: preparing a compound represented by Chemical Formula 1; and reacting the compound represented by Chemical Formula 1 with a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2.

[0010] [Chemical Formula 1]

[0011]

[0012] In Chemical Formula 1, Z is an ammonium ion, and

[0013] [Chemical Formula 2]

[0014]

[0015] In Chemical Formula 2,

[0016] R2 to R5 are independently a halogen; or a substituted or unsubstituted C1-C6 alkyl group, M is an alkali metal, and Y + is a cationic substance.

[0017] In one embodiment, Z + is N + RaRbRcRd, and Ra to Rd may independently be hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

[0018] In one embodiment, the step of preparing a compound represented by the chemical formula 1 may include the step of reacting an alkali metal salt of an allylsulfonate with an alkylamine compound.

[0019] In one embodiment, the alkylamine compound is NRaRbRc, and Ra to Rc may independently be a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

[0020] In one embodiment, the phosphate-based alkali metal salt can be represented by the following chemical formula 3.

[0021] [Chemical Formula 3]

[0022]

[0023] In Chemical Formula 3, R2 and R3 are independently a halogen; or a substituted or unsubstituted C1-C6 alkyl group, and M + It is an alkali metal ion.

[0024] In one embodiment, at least one of R2 to R5 is a halogen, M is Li, Na, or K, and Y + is N + RaRbRcRd, wherein Ra to Rd are independently hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd may be hydrogen.

[0025] In one embodiment, R2 to R5 are all halogens, M is Li, and Y + is N + RaRbRcRd, where Ra is hydrogen, and Rb to Rd can be C1-C3 alkyl groups independently of each other.

[0026] In one embodiment, the step of reacting the alkali metal salt of the allylsulfonate and the alkylamine compound in the step of preparing the compound represented by Chemical Formula 1 can be carried out at 10°C to 50°C and 1 atm for 1 hour to 5 hours.

[0027] In one embodiment, the step of reacting the compound represented by Chemical Formula 1 and a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 below can be carried out at 10°C to 50°C and 1 atm for 5 to 10 hours.

[0028] The electrolyte for a lithium secondary battery according to the present invention comprises a compound represented by the chemical formula 2, prepared by the method for preparing an electrolyte additive for a lithium secondary battery; a lithium salt; and a non-aqueous organic solvent.

[0029] In one embodiment, the compound represented by Formula 2 may be in an amount of 0.01% to 3% by weight of the total weight of the electrolyte for the lithium secondary battery.

[0030] In one embodiment, the lithium salt may be one or more selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(C2F2SO2)2, CF3SO3Li, and LiC(CF3SO2)3.

[0031] In one embodiment, the non-aqueous organic solvent may be one or more selected from the group consisting of linear carbonate-based solvents, cyclic carbonate-based solvents, linear ester-based solvents, and cyclic ester-based solvents.

[0032] In one embodiment, the electrolyte for the lithium secondary battery may further include an auxiliary additive comprising at least one of a fluorine-containing cyclic carbonate-based compound, an unsaturated group-containing cyclic carbonate-based compound, a sulfate-based compound, a sulfone-based compound, a lithium borate-based compound, and a lactone-based compound.

[0033] A lithium secondary battery according to the present invention comprises a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte for the lithium secondary battery.

[0034] The method for manufacturing an electrolyte additive for a lithium secondary battery according to exemplary embodiments reduces costs, shortens process time, and enables the production of a high-yield additive, thereby improving economic efficiency.

[0035] The electrolyte for a lithium secondary battery according to exemplary embodiments has improved high-temperature life and storage characteristics.

[0036] FIGS. 1 and FIGS. 2 are a planar perspective view and a cross-sectional view, respectively, schematically illustrating a lithium secondary battery according to exemplary embodiments.

[0037] According to the present invention, the step of preparing a compound represented by Formula 1; and

[0038] A method for manufacturing an electrolyte additive for a lithium secondary battery is provided, comprising the step of reacting a compound represented by Chemical Formula 1 above with a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 below.

[0039] The method for manufacturing triethylammonium vinylsulfonate may result in increased manufacturing costs and reduced economic efficiency and processability due to the use of high-cost vinylsulfonic acid.

[0040] In addition, the above triethylammonium vinylsulfonate can be prepared by reacting a vinylsulfonate-based salt with an amine compound under acidic conditions, but the yield of triethylammonium vinylsulfonate may be reduced and by-products may be generated during the reaction process.

[0041] However, the method for manufacturing an electrolyte additive for a lithium secondary battery according to the present specification can reduce manufacturing costs and improve economic efficiency and processability by using low-cost allylsulfonic acid. Compared to the aforementioned method for manufacturing a lithium secondary battery electrolyte additive, the purity, storage stability, production volume, and / or yield of the product can be improved.

[0042] In addition, when an additive prepared by the method for preparing an electrolyte additive for a lithium secondary battery according to the present specification is applied to a lithium secondary battery, gas generation in the lithium secondary battery can be suppressed under high temperature conditions and the capacity retention rate can be improved. In one embodiment, the additive prepared by the method for preparing an electrolyte additive for a lithium secondary battery may be a compound represented by Chemical Formula 2.

[0043] Specifically, when the additive prepared by the method for preparing the electrolyte additive for the lithium secondary battery is applied to a lithium secondary battery, the LiPO2F2 ring and sulfonyl group included in the additive are adsorbed onto the surface of the anode through electrostatic attraction and then oxidatively decomposed to form an internal CEI (Cathode-Electrolyte Interphase) in the form of sulfonate and LiPO2F2 ring. A Solid Electrolyte Interphase (SEI) is formed by the reduction of the sulfonyl group included in the compound represented by Chemical Formula 2 on the surface of the cathode. Since the compound represented by Chemical Formula 2 can form a film with excellent thermal stability through the reaction between the sulfonyl group and the triethylamine group, changes in the anode structure can be prevented and the leaching of transition metals can be suppressed, thereby improving the retention capacity and recovery capacity at high temperatures and suppressing gas generation.

[0044] In this specification, "X-type compound" may mean a compound containing an X unit in a parent group, a side group, or a substituent.

[0045] In this specification, "Ca-Cb" may mean "a to b number of carbon atoms." Additionally, "a 5-7 ring" may mean "a ring having 5 to 7 atoms."

[0046] In one embodiment, a method for manufacturing an electrolyte additive for a lithium secondary battery may include the step of preparing a compound represented by Chemical Formula 1.

[0047] [Chemical Formula 1]

[0048]

[0049] In Chemical Formula 1, Z can be an ammonium ion.

[0050] In one embodiment, Z + is N + RaRbRcRd, and Ra to Rd may independently be hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

[0051] In one embodiment, Ra to Rd may independently be hydrogen; or a substituted or unsubstituted C1-C6 alkyl group.

[0052] In one embodiment, Ra to Rd may independently be hydrogen; or a substituted or unsubstituted C1-C5 alkyl group.

[0053] In one embodiment, Ra to Rd may independently be hydrogen; or a substituted or unsubstituted C1-C4 alkyl group.

[0054] In one embodiment, Ra to Rd may independently be hydrogen; or a substituted or unsubstituted C1-C3 alkyl group.

[0055] In one embodiment, Ra to Rd may be independently substituted or unsubstituted ethyl groups.

[0056] In one embodiment, Ra to Rd may be ethyl groups independently of each other.

[0057] In one embodiment, the step of preparing a compound represented by the chemical formula 1 may include the step of reacting an alkali metal salt of an allylsulfonate with an alkylamine compound.

[0058] In one embodiment, the alkali metal of the alkali metal salt of the allylsulfonate may be Na or K.

[0059] In one embodiment, the alkali metal of the alkali metal salt of the allylsulfonate may be Na.

[0060] In one embodiment, the alkylamine compound is NRaRbRc, and Ra to Rc may independently be a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

[0061] In one embodiment, Ra to Rd may be independently substituted or unsubstituted C1-C4 alkyl groups.

[0062] In one embodiment, Ra to Rd may be independently substituted or unsubstituted C1-C3 alkyl groups.

[0063] In one embodiment, Ra to Rd may be independently substituted or unsubstituted ethyl groups.

[0064] In one embodiment, the method for manufacturing the electrolyte additive for the lithium secondary battery may include the step of reacting a compound represented by Chemical Formula 1 with a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 below.

[0065] [Chemical Formula 2]

[0066]

[0067] In Chemical Formula 2, R2 to R5 may independently be a halogen; or a substituted or unsubstituted C1-C6 alkyl group, M is an alkali metal, and Y + It can be a cationic substance.

[0068] For example, the bond between phosphorus (P) and oxygen (O); and the bond between sulfur (S) and oxygen (O) " may indicate that some electrons are delocalized.

[0069] For example, the meaning of "substituted" may imply that a hydrogen atom is replaced by an arbitrary substituent, and that an arbitrary substituent is further bonded to that substituent.

[0070] For example, any of the above substituents may be a halogen, a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a C1-C6 alkoxy group, a nitro group, a cyano group, etc. In some embodiments, any of the above substituents may be a halogen or a C1-C6 alkyl group.

[0071] In one embodiment, at least one of R2 to R5 may be a halogen (e.g., F, Cl, Br, or I).

[0072] In one embodiment, at least one of R2 to R5 may be F.

[0073] In one embodiment, R2 to R5 may all be halogens.

[0074] In some embodiments, R2 to R5 may all be F.

[0075] In one embodiment, M may be Li, Na, or K.

[0076] In one embodiment, Y + It may be an alkali metal ion; an ammonium ion; or a primary to quaternary ammonium ion.

[0077] In some embodiments, Y + is N +RaRbRcRd or ReRfN + = It could be RgRh.

[0078] In some embodiments, Ra to Rd may independently be hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group. Additionally, at least two of Ra to Rd may be bonded to each other to form a 5-7-membered heterocyclic ring.

[0079] In some embodiments, Re to Rh may independently be hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group. Additionally, at least two of Re to Rh may be bonded to each other to form a 5-7-membered heterocyclic ring.

[0080] In some embodiments, Y + is N + RaRbRcRd, wherein Ra to Rd are independently hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd may be hydrogen. In some embodiments, Y + is N + RaRbRcRd, where Ra is hydrogen, and Rb to Rd can be C1-C3 alkyl groups independently of each other.

[0081] In one embodiment, the phosphate-based alkali metal salt can be represented by the following chemical formula 3.

[0082] [Chemical Formula 3]

[0083]

[0084] In Chemical Formula 3, R2 and R3 may independently be a halogen (e.g., F, Cl, Br, or I); or a substituted or unsubstituted C1-C6 alkyl group, and M + It can be an alkali metal ion.

[0085] In one embodiment, at least one of R2 and R3 may be a halogen. In some embodiments, at least one of R2 and R3 may be F.

[0086] In one embodiment, R2 and R3 may both be halogens. In some embodiments, R2 and R3 may both be F.

[0087] In some embodiments, a crystal produced by reacting a compound represented by Formula 1 with a phosphate-based alkali metal salt can be filtered and dried to obtain a compound represented by Formula 2.

[0088] In one embodiment, the step of reacting the alkali metal salt of the allylsulfonate and the alkylamine compound in the step of preparing the compound represented by Formula 1 can be carried out at 10°C to 50°C for 1 hour to 5 hours.

[0089] In some embodiments, the reaction temperature of the step of reacting the alkali metal salt of the allyl sulfonate and the alkylamine compound included in the step of preparing the compound represented by Formula 1 may be 10°C to 40°C, 10°C to 30°C, or 120°C to 30°C. The compound represented by Formula 2 can be obtained in high purity within the above reaction temperature range.

[0090] In some embodiments, the reaction time of the step of reacting the alkali metal salt of the allyl sulfonate and the alkylamine compound included in the step of preparing the compound represented by Formula 1 may be 2 to 4 hours. Within the above reaction time range, the compound represented by Formula 2 can be obtained in high purity.

[0091] In one embodiment, the step of reacting the compound represented by Chemical Formula 1 and a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 below can be carried out at 10°C to 50°C and 1 atm for 5 to 10 hours.

[0092] In some embodiments, the reaction temperature of the step of reacting the compound represented by Formula 1 with a phosphate-based alkali metal salt to produce the compound represented by Formula 2 below may be 10°C to 40°C, 10°C to 30°C, or 120°C to 30°C. The compound represented by Formula 2 can be obtained in high purity within the above reaction temperature range.

[0093] In some embodiments, the reaction time of the step of reacting the compound represented by Formula 1 with a phosphate-based alkali metal salt to produce the compound represented by Formula 2 below may be 6 to 8 hours. Within the above reaction time range, the compound represented by Formula 2 can be obtained with high purity.

[0094] In one embodiment, the molar ratio of the compound represented by Chemical Formula 1 and the phosphate-based alkali metal salt may be 1:0.1 to 1:1.1.

[0095] A compound represented by Chemical Formula 2 can be obtained in high purity within the above range of mixed molar ratios.

[0096] One embodiment provides an electrolyte for a lithium secondary battery comprising: a compound represented by Formula 2 prepared by the method for preparing an electrolyte additive for a lithium secondary battery; a lithium salt; and a non-aqueous organic solvent.

[0097] In one embodiment, the compound represented by Formula 2 may be 0.01% to 3% by weight of the total weight of the electrolyte for the lithium secondary battery. For example, the compound represented by Formula 2 may be 0.01% to 2% by weight or 0.01% to 1% by weight of the total weight of the electrolyte for the lithium secondary battery.

[0098] For example, the above lithium salt is Li + X - It can be expressed as.

[0099] In one embodiment, the anion (X) of the lithium salt - ) is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It could be the back.

[0100] The above lithium salt may be a compound other than the lithium salt form of the compound represented by Chemical Formula 2.

[0101] For example, the lithium salt may be one or more selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(C2F2SO2)2, CF3SO3Li, and LiC(CF3SO2)3.

[0102] For example, the above lithium salt may be LiPF6.

[0103] In one embodiment, the non-aqueous organic solvent may be one or more selected from the group consisting of linear carbonate-based solvents, cyclic carbonate-based solvents, linear ester-based solvents, and cyclic ester-based solvents.

[0104] The above linear carbonate-based solvent may include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, etc.

[0105] The above-mentioned cyclic carbonate-based solvent may include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, etc.

[0106] In some embodiments, the non-aqueous organic solvent may contain more of the linear carbonate-based solvent than the cyclic carbonate-based solvent based on the total volume of the non-aqueous organic solvent.

[0107] For example, among the organic solvents, the volume ratio of the cyclic carbonate-based solvent to the linear carbonate-based solvent may be 1:1 to 9:1, preferably 1.5:1 to 4:1.

[0108] For example, the above linear ester-based solvent may include methyl propionate, ethyl propionate, propyl acetate, butyl acetate, ethyl acetate, etc.

[0109] For example, the above-mentioned cyclic ester solvent may include butyrolactone, caprolactone, valerolactone, etc.

[0110] In one embodiment, the organic solvent may further include an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, etc.

[0111] For example, the above ether-based solvent may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0112] For example, the above ketone-based solvent may include cyclohexanone, etc.

[0113] For example, the above alcohol-based solvent may include at least one of ethyl alcohol and isopropyl alcohol.

[0114] For example, the aprotic solvent may include at least one of a nitrile-based solvent, an amide-based solvent (e.g., dimethylformamide), a dioxolane-based solvent (e.g., 1,3-dioxolane), and a sulfolane-based solvent.

[0115] In one embodiment, the non-aqueous organic solvent may be one or more selected from the group consisting of ethylene carbonate, methylene carbonate, and dimethyl carbonate.

[0116] In one embodiment, the non-aqueous organic solvent may include ethylene carbonate, methylene carbonate, and dimethyl carbonate.

[0117] In one embodiment, the electrolyte for the lithium secondary battery further comprises a lithium salt and a non-aqueous organic solvent, and the lithium salt may be included at a concentration of 0.1 M to 2 M with respect to the non-aqueous organic solvent.

[0118] In one embodiment, the lithium salt may be 0.5 M to 1.5 M, 0.7 M to 1.3 M, or 0.9 M to 1.1 M with respect to the non-aqueous organic solvent. Within the concentration range, lithium ions and / or electrons can be smoothly moved during the charging and discharging of the battery.

[0119] In one embodiment, the electrolyte for the lithium secondary battery may further include an auxiliary additive comprising at least one of a fluorine-containing cyclic carbonate-based compound, an unsaturated group-containing cyclic carbonate-based compound, a sulfate-based compound, a sulfone-based compound, a lithium borate-based compound, and a lactone-based compound.

[0120] The above auxiliary additive can further improve the lifespan and output characteristics of the lithium secondary battery, or further improve high-temperature storage characteristics.

[0121] For example, the above fluorine-containing cyclic carbonate compound may have a 5- to 7-membered cyclic structure. For example, the above fluorine-containing cyclic carbonate compound may have a fluorine atom directly bonded to the ring, or a fluorine-substituted alkyl group (e.g., -CF3, etc.) bonded to the ring.

[0122] In some embodiments, the fluorine-containing cyclic carbonate compound may include fluoroethylene carbonate (FEC), etc.

[0123] In some embodiments, the unsaturated group-containing cyclic carbonate compound may include vinyl ethylene carbonate (VEC), vinylene carbonate (VC), etc.

[0124] In some embodiments, the sulfate compound may include a cyclic sulfate compound or a linear sulfate compound.

[0125] For example, the cyclic sulfate compound may have a 5- to 7-membered cyclic structure. In some embodiments, the cyclic sulfate compound may include ethylene sulfate (ESA), trimethylene sulfate (TMS), methyltrimethylene sulfate (MTMS), 1,3-propanediol cyclic sulfate, etc.

[0126] For example, linear sulfate compounds may include 2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane 3,3,9,9-tetraoxide, 4,4'-bi(1,3,2-dioxathiolan)] 2,2,2',2'-tetraoxide, etc.

[0127] For example, the sulfonate compound may have a cyclic structure of 5 to 7 members. In some embodiments, the sulfonate compound may include at least one of an alkyl sulfonate compound and an alkenyl sulfonate compound. For example, the alkyl sulfonate compound may have only saturated bonds within the ring, and the alkenyl sulfonate compound may include double bonds within the ring.

[0128] In some embodiments, the alkyl sulfone compound may include 1,3-propane sulfone (PS), 1,4-butane sulfone, etc. Additionally, the alkenyl sulfone compound may include ethene sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, etc.

[0129] In some embodiments, the lithium borate-based compound may include lithium tetraphenylborate, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), etc.

[0130] In some embodiments, the lactone compound may include at least one of a linear lactone compound and a lactone compound containing a double bond within a ring. In some embodiments, the lactone compound may include a muconic lactone, etc.

[0131] In some embodiments, the content of the auxiliary additive may be 0.01% to 10% by weight, 0.1% to 7.5% by weight, or 0.3% to 5% by weight of the total weight of the electrolyte. Within this range, the high-temperature storage characteristics of the lithium secondary battery, etc., may be further improved.

[0132] In one embodiment, the auxiliary additive may include a vinylene carbonate-based compound.

[0133] In one embodiment, the vinylene carbonate-based compound may be vinylene carbonate.

[0134] In some embodiments, the content of the vinylene carbonate-based compound may be 0.01% to 10% by weight of the total weight of the electrolyte for the lithium secondary battery. For example, the content of the vinylene carbonate-based compound may be 0.1% to 7.5% by weight or 0.3% to 5% by weight. Within this range, the high-temperature characteristics of the lithium secondary battery may be further improved.

[0135] In one embodiment, the compound represented by Chemical Formula 2 and the vinylene carbonate-based compound may be provided as additives to the electrolyte for the lithium secondary battery.

[0136] In one embodiment, the content of the compound represented by Formula 2 may be 0.01% to 10% by weight, for example, 0.1% to 7.5% by weight, or 0.3% to 5% by weight of the total weight of the electrolyte for the lithium secondary battery. Within this range, the high-temperature characteristics of the lithium secondary battery may be further improved.

[0137] For example, the compound represented by Chemical Formula 2 above may exist as a single unit in the electrolyte, or may exist in the form of a dimer (e.g., see Chemical Formula 4 below, description of substituents omitted), a trimer, a tetramer or more, or a polymer.

[0138] [Chemical Formula 4]

[0139]

[0140] In Chemical Formula 4, the definitions of the substituents may be applied to the description of the substituents in Chemical Formula 1 mentioned above.

[0141] In one embodiment, the ratio of the content of the auxiliary additive to the content of the compound represented by Formula 1 in the total weight of the electrolyte for the lithium secondary battery may be 0.1 to 10, preferably 0.1 to 7, more preferably 0.5 to 5.

[0142] According to exemplary embodiments of the present invention, a lithium secondary battery comprising the electrolyte for the lithium secondary battery is provided.

[0143] Hereinafter, a lithium secondary battery according to exemplary embodiments will be described in more detail with reference to the drawings. FIGS. 1 and 2 are a schematic plan perspective view and a cross-sectional view, respectively, showing a lithium secondary battery according to exemplary embodiments.

[0144] Referring to FIGS. 1 and 2, a lithium secondary battery may include a positive electrode (100) and a negative electrode (130) facing the positive electrode (100).

[0145] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode active material layer (110) on the positive electrode current collector (105).

[0146] For example, the positive active material layer (110) may include a positive active material, a positive binder and a conductive material as needed.

[0147] For example, the anode (100) can be manufactured by mixing and stirring an anode active material, an anode binder, a conductive material, a dispersion medium, etc. to produce an anode slurry, and then applying, drying, and rolling the anode slurry onto an anode current collector (105).

[0148] For example, the positive current collector (105) may include stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof.

[0149] For example, the positive electrode active material may include lithium metal oxide particles capable of reversible insertion and extraction of lithium ions.

[0150] In one embodiment, the lithium metal oxide particles may contain nickel, cobalt, manganese, aluminum, etc.

[0151] In some embodiments, the lithium metal oxide particles contain nickel, and the nickel content in the lithium metal oxide particles may be 80 mol% or more of the total elements excluding lithium and oxygen.

[0152] In some embodiments, the lithium metal oxide particles may be represented by LiNiO2, LiCoO2, LiMnO2, LiMn2O4, or the following chemical formula 5.

[0153] [Chemical Formula 5]

[0154] Li x Ni (1-a-b) Co a M b O y

[0155] In Chemical Formula 5, M is at least one of Al, Zr, Ti, Cr, B, Mg, Mn, Ba, Si, Y, W, and Sr, and 0.9≤x≤1.2, 1.9≤y≤2.1, and 0≤a+b≤0.5.

[0156] In some embodiments, in Formula 5, a and b are 0 <a+b≤0.4, 0<a+b≤0.3, 0<a+b≤0.2 또는 0<a+b≤0.1을 만족할 수 있다.

[0157] For example, the anode binder may include organic binders such as polyvinylidenefluoride (PVDF), vinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyacrylonitrile, and polymethylmethacrylate; and water-based binders such as styrene-butadiene rubber (SBR). Additionally, for example, the anode binder may be used together with a thickener such as carboxymethyl cellulose (CMC).

[0158] For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, graphene, and carbon nanotubes; and metal-based conductive materials such as perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0159] The cathode (130) may include a cathode current collector (125) and a cathode active material layer (120) on the cathode current collector (125).

[0160] For example, the negative electrode active material layer (120) may include a negative electrode active material, a negative electrode binder and a conductive material as needed.

[0161] For example, the cathode (130) can be manufactured by mixing and stirring a cathode active material, a cathode binder, a conductive material, a solvent, etc. to produce a cathode slurry, and then applying, drying, and rolling the cathode slurry onto a cathode current collector (125).

[0162] For example, the negative current collector (125) may include gold, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof, and preferably may include copper or a copper alloy.

[0163] For example, the above-mentioned negative electrode active material may be a material capable of absorbing and extracting lithium ions. For example, the above-mentioned negative electrode active material may include a lithium alloy, a carbon-based active material, a silicon-based active material, etc.

[0164] For example, the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0165] For example, the carbon-based active material may include crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.

[0166] For example, the amorphous carbon may include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500°C or lower, mesophase pitch-based carbon fiber (MPCF), etc. For example, the crystalline carbon may include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0167] In one embodiment, the negative electrode active material may include a silicon-based active material. For example, the silicon-based active material may be Si, SiO x (0 <x<2), Si / C, SiO / C, Si-Metal 등을 포함할 수 있다.

[0168] The above-described cathode binder and conductive material may be materials substantially identical or similar to the anode binder and conductive material described above. For example, the cathode binder may be a water-based binder such as styrene-butadiene rubber (SBR). Additionally, for example, the cathode binder may be used together with a thickener such as carboxymethyl cellulose (CMC).

[0169] In one embodiment, a separator (140) may be interposed between the anode (100) and the cathode (130).

[0170] In some embodiments, the area of ​​the negative electrode (130) may be larger than the area of ​​the positive electrode (100). In this case, lithium ions generated from the positive electrode (100) can move smoothly to the negative electrode (130) without precipitating in the middle.

[0171] For example, the separator (140) may include a porous polymer film made of a polyolefin-based polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc. Additionally, for example, the separator (140) may include a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0172] For example, an electrode cell may be formed including an anode (100), a cathode (130), and a separator (140).

[0173] For example, a plurality of electrode cells may be stacked to form an electrode assembly (150) (however, for convenience, only one electrode cell is shown in FIG. 2).

[0174] For example, an electrode assembly (150) can be formed by winding, lamination, zigzag-folding, etc. of a separator (140).

[0175] A lithium secondary battery according to exemplary embodiments may include a positive electrode lead (107) connected to a positive electrode (100) and protruding outside of a case (160); and a negative electrode lead (127) connected to a negative electrode (130) and protruding outside of a case (160).

[0176] For example, the positive electrode (100) and the positive electrode lead (107) may be electrically connected. Likewise, the negative electrode (130) and the negative electrode lead (127) may be electrically connected.

[0177] For example, the positive lead (107) can be electrically connected to the positive current collector (105). Additionally, the negative lead (130) can be electrically connected to the negative current collector (125).

[0178] For example, the positive current collector (105) may include a protrusion (positive tab, 106) on one side. A positive active material layer (110) may not be formed on the positive tab (106). The positive tab (106) may be integral with the positive current collector (105) or connected by welding or the like. The positive current collector (105) and the positive lead (107) may be electrically connected through the positive tab (106).

[0179] Likewise, the negative current collector (125) may include a protrusion (negative tab, 126) on one side. A negative active material layer (120) may not be formed on the negative tab. The negative tab (126) may be integral with the negative current collector (125) or connected by welding or the like. The negative current collector (125) and the negative lead (127) may be electrically connected through the negative tab (126).

[0180] In one embodiment, the electrode assembly (150) may include a plurality of positive electrodes and a plurality of negative electrodes. For example, the plurality of positive electrodes and the plurality of negative electrodes may be arranged alternately with respect to each other, and a separator may be interposed between the positive electrodes and the negative electrodes. Accordingly, a lithium secondary battery according to one embodiment of the present invention may include a plurality of positive electrode tabs and a plurality of negative electrode tabs protruding from each of the plurality of positive electrodes and the plurality of negative electrodes.

[0181] In one embodiment, the positive tabs (or negative tabs) may be laminated, pressed, and welded to form a positive tab laminate (or negative tab laminate). The positive tab laminate may be electrically connected to a positive lead (107). Additionally, the negative tab laminate may be electrically connected to a negative lead (127).

[0182] For example, the electrode assembly (150) and the above-described electrolyte can be housed together in a case (160) to form a lithium secondary battery.

[0183] The above lithium secondary battery can be manufactured in, for example, cylindrical, prismatic, pouch, or coin types.

[0184]

[0185] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0186]

[0187] Preparation Example

[0188] (1) Preparation of triethylammonium allylsulfonate

[0189] 200 g of H2O / MeOH = 1 / 3 (wt%) was added to a one-neck round flask. Subsequently, 17 g (0.17 mol) of sulfonic acid (97%) and 42.9 g (0.42 mol) of triethylamine were added dropwise. After the addition was complete, the mixture was stirred for 30 minutes at 25°C and 1 atm. Afterward, 51.5 g (0.34 mol) of sodium allylsulfonate (94%) was added, and the mixture was stirred for 3 hours at 25°C and 1 atm. After stirring was completed, the resulting reaction byproduct, NaHSO4 salt, was removed by vacuum filtration. The obtained filtrate was heated at a pressure of 20 torr and a temperature of 60°C for 1 hour to remove water. Triethylammonium allylsulfonate was obtained by repeating the processes of methanol (MeOH) addition and filtration, and dichloromethane (MC) addition and filtration to completely remove the reaction byproduct NaHSO4. (Yield 92%)

[0190]

[0191] (2) Preparation of lithium trifluorophosphate triethylamine salt of propylene sulfonate

[0192] 300 g of EC / DMC = 1 / 3 (v / v) was added to a one-neck round flask. Subsequently, 38.3 g (0.35 mol) of lithium difluorophosphate and 40 g (0.18 mol) of triethylammonium allylsulfonate were added sequentially, followed by stirring for 7 hours. After the reaction was complete, the resulting crystals were filtered, washed with DMC, and vacuum dried to obtain a white target product (compound represented by Chemical Formula 1-A). (Yield 86%)

[0193] [Chemical Formula 1-A]

[0194]

[0195]

[0196] Comparative Manufacturing Example

[0197] (1) Preparation of triethylammonium ethenesulfonate

[0198] 17 g (0.17 mol) of sulfonic acid (97%) and 43 g (0.42 mol) of triethylamine were sequentially added to a one-neck round flask. After stirring for 30 minutes at 25°C and 1 atm, 177 g (0.34 mol) of sodium vinylsulfonate (25%) was added, followed by stirring for 12 hours at 25°C and 1 atm. After stirring was complete, water was removed by heating for 1 hour at a pressure of 20 torr and a temperature of 60°C. Subsequently, to completely remove the reaction byproduct NaHSO4, the processes of adding methanol (MeOH) and filtration, and adding dichloromethane (MC) and filtration were repeated to obtain triethylammonium ethenesulfonate. (Yield 87%)

[0199]

[0200] (2) Preparation of lithium trifluorophosphate triethylamine salt of ethene sulfonate

[0201] 300 g of EC / DMC = 3 / 7 (v / v) was added to a one-neck round flask. Subsequently, 38.3 g (0.35 mol) of lithium difluorophosphate and 40 g (0.18 mol) of triethylammonium ethenesulfonate were added sequentially, followed by stirring for 7 hours. After the reaction was complete, the resulting crystals were filtered, washed with DMC, and vacuum dried to obtain a white target product. (Yield 90%)

[0202]

[0203] Examples and Comparative Examples

[0204] (1) Preparation of electrolyte

[0205] A 1.0 M LiPF6 solution was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed in a ratio of 2:4:4 (v / v).

[0206] The electrolytes of the examples and comparative examples were prepared by adding each additive to the above LiPF6 solution according to the type and content (weight% of the total weight of the electrolyte for lithium secondary batteries) as shown in Table 1 below.

[0207] (2) Manufacturing of lithium secondary batteries

[0208] Li(Ni) 0.8 Co 0.1 Mn 0.1 An anode slurry was prepared by dispersing O2, polyvinylidene fluoride (PVdF), and carbon black in N-methyl-2-pyrrolidone (NMP) in a weight ratio of 92:4:4.

[0209] The above anode slurry was applied onto an aluminum foil (thickness: 20 μm) having a protrusion on one side (hereinafter, anode tab) (excluding the protrusion portion), and an anode was manufactured by drying and rolling.

[0210] A cathode slurry was prepared by dispersing crystalline artificial graphite, acetylene black, and PVDF in NMP in a weight ratio of 92:1:7.

[0211] The above cathode slurry was applied onto a copper foil (thickness: 15 μm) having a protrusion on one side (hereinafter, cathode tab) (excluding the protrusion portion), and the cathode was manufactured by drying and rolling.

[0212] A cell was formed by interposing a polyethylene separator (thickness: 20 μm) between the anode and the cathode. An anode lead and a cathode lead were welded and connected to the anode tab and the cathode tab, respectively.

[0213] The cell was housed inside a pouch such that a portion of the positive lead and the negative lead were exposed to the outside. An electrolyte was injected into the pouch, and the pouch was sealed to manufacture a lithium secondary battery.

[0214] (3) Mars charging and discharging

[0215] The lithium secondary batteries of the examples and comparative examples were subjected to a phosphating charge / discharge (charge / discharge conditions: charged in 0.2C CC / CV mode (4.2V, 0.05C cut-off) and then discharged in 0.2C CC mode (2.5V cut-off), and a standard charge / discharge (charge / discharge conditions: charged in 0.5C CC / CV mode (4.2V, 0.05C cut-off), then discharged in 0.5C CC mode (2.5V cut-off), and then charged in 0.5C CC / CV mode (4.2V, 0.05C cut-off). After that, 1C CC / CV charging (4.2V CUT-OFF) was performed.

[0216] Classification Additive Composition and Content Example 1 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% Comparative Example 1 Comparative Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt%

[0217] Evaluation method

[0218] (1) Measurement of capacity retention rate after 500 repeated charge-discharge cycles

[0219] The lithium secondary batteries of Example 1 and Comparative Example 1 were charged at 1C CC / CV (4.2V CUT-OFF) and discharged at 1C CC (3V CUT-OFF) to measure the initial discharge capacity C1.

[0220] For the lithium secondary batteries of Example 1 and Comparative Example 1, the charge and discharge process was repeated 500 times, and the 500th discharge capacity C2 was measured.

[0221] The dosage retention rate was calculated as a percentage of C2 relative to C1, as follows.

[0222] The initial discharge capacity and capacity retention rate are listed in Table 2.

[0223] Dose Retention Rate (%) = C2 / C1 × 100(%)

[0224] (2) Measure the rate of increase in thickness after high-temperature storage (70℃, 1 week).

[0225] After charging the lithium secondary batteries of Example 1 and Comparative Example 1 at 25°C with 1°C CC / CV (4.2V CUT-OFF), the battery thickness T1 was measured. After leaving the charged lithium secondary batteries of Example 1 and Comparative Example 1 for one week under exposure to 70°C air conditions (using a constant temperature device), the battery thickness T2 was measured.

[0226] The battery thickness was measured using a flat plate thickness measuring device (Mitutoyo, 543-490B). The battery thickness increase rate was calculated as follows, and the results are listed in Table 2 below.

[0227] Battery thickness increase rate (%) = {(T2-T1) / T1 + 1} * 100

[0228] (3) Measure capacity recovery rate after high-temperature storage (70℃, 1 week).

[0229] The lithium secondary batteries of Example 1 and Comparative Example 1 were charged to 4.2V using 1C CC / CV, stored at a high temperature (70℃) for one week, and then discharged using 1C CC (3V CUT-OFF) to measure the initial discharge capacity C1. The recovery capacity (discharge capacity) C3 was measured by charging and discharging in the same manner as when the initial capacity was measured, and the capacity recovery rate was calculated as a percentage relative to the initial capacity.

[0230] Dose recovery rate (%) = C3 / C1 * 100

[0231] (4) Evaluation of initial resistance and resistance characteristics after high-temperature storage (70℃, 1 week)

[0232] After charging the lithium secondary batteries of Example 1 and Comparative Example 1 at 1C CC / CV (4.2V CUT-OFF), they were discharged at 2C CC up to 440 mA. Subsequently, the C-rate was varied to 0.5C, 1C, 2C, and 4C, and discharged and recharged for 10 seconds each, respectively, and the DCIR was measured and recorded in the "Initial Resistance" column of Table 2 below.

[0233] The lithium secondary batteries of Example 1 and Comparative Example 1 were charged to 4.2V using 1C CC / CV, stored at a high temperature (70℃) for one week, and then discharged at 2C CC to 440 mA. Afterward, the C-rate was varied to 0.5C, 1C, 2C, and 4C, and discharged and recharged for 10 seconds each, and the DCIR was measured and recorded in the "Resistance after high-temperature storage" column of Table 2 below.

[0234] (5) Evaluation of life characteristics at 25℃ and 45℃

[0235] The lifespan characteristics of the lithium secondary batteries of Example 1 and Comparative Example 1 were evaluated as a capacity retention rate (%) by comparing the initial capacity (discharge capacity value measured during one standard charge / discharge cycle) with the discharge capacity after 500 charge / discharge cycles under conditions of 25°C and 45°C, and this is listed in Table 2 below.

[0236] Thickness Increase Rate (%) Capacitance Retention Rate (%) Capacitance Recovery Rate (%) Initial Resistance (mΩ) Resistance After High-Temperature Storage (mΩ) Lifespan at 25℃ (%) Lifespan at 45℃ (%) Example 14.229 1.799 8.03 14.40 26.759 9.89 9.7 Comparative Example 18.218 9.379 6.27 14.633 42.899 9.899.5

[0237] Referring to Tables 1 and 2 above, it can be seen that Example 1, to which the compound of the manufacturing example was applied, suppresses gas generation at high temperatures and improves capacity retention and recovery rates compared to Comparative Example 1, to which the compound of the comparative manufacturing example was applied.

Claims

1. A step of preparing a compound represented by Chemical Formula 1; and A method for manufacturing an electrolyte additive for a lithium secondary battery, comprising the step of reacting a compound represented by Chemical Formula 1 above with a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 below: [Chemical Formula 1] (In Chemical Formula 1, Z is an ammonium ion) [Chemical Formula 2] (In Chemical Formula 2, R2 to R5 are independently a halogen; or a substituted or unsubstituted C1-C6 alkyl group, and M is an alkali metal, and Y + is a cationic substance).

2. In Claim 1, Z + is N + A method for preparing an electrolyte additive for a lithium secondary battery, wherein RaRbRcRd, and Ra to Rd are independently hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

3. A method for preparing an electrolyte additive for a lithium secondary battery, wherein the step of preparing a compound represented by Chemical Formula 1 according to Claim 1 comprises the step of reacting an alkali metal salt of an allyl sulfonate with an alkylamine compound.

4. A method for preparing an electrolyte additive for a lithium secondary battery, wherein the alkylamine compound of claim 3 is NRaRbRc, and Ra to Rc are independently a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

5. A method for manufacturing an electrolyte additive for a lithium secondary battery, wherein the phosphate-based alkali metal salt of Claim 1 is represented by the following chemical formula 3: [Chemical Formula 3] (In Formula 3, R2 and R3 are independently a halogen; or a substituted or unsubstituted C1-C6 alkyl group, and M + (It is an alkali metal ion).

6. In Claim 1, At least one of R2 to R5 is a halogen, and M is Li, Na, or K, and Y + is N + An electrolyte for a lithium secondary battery, wherein RaRbRcRd, and Ra to Rd are independently hydrogen; a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd is hydrogen.

7. In Claim 1, R2 to R5 are all halogens, and M is Li, and Y + is N + An electrolyte for a lithium secondary battery, wherein RaRbRcRd, Ra is hydrogen, and Rb to Rd are independently C1-C3 alkyl groups.

8. A method for preparing an electrolyte additive for a lithium secondary battery according to claim 3, wherein the step of reacting an alkali metal salt of an allyl sulfonate and an alkylamine compound in the step of preparing a compound represented by Chemical Formula 1 is performed at 10°C to 50°C and 1 atm for 1 hour to 5 hours.

9. A method for manufacturing an electrolyte additive for a lithium secondary battery, wherein the step of reacting a compound represented by Chemical Formula 1 and a phosphate-based alkali metal salt to produce a compound represented by Chemical Formula 2 is carried out by reacting at 10°C to 50°C and 1 atm for 5 to 10 hours.

10. An electrolyte for a lithium secondary battery comprising: a compound represented by Chemical Formula 2 prepared by the method for preparing an electrolyte additive for a lithium secondary battery according to Claim 1; a lithium salt; and a non-aqueous organic solvent.

11. An electrolyte for a lithium secondary battery according to claim 10, wherein the compound represented by Chemical Formula 2 is 0.01% to 3% by weight of the total weight of the electrolyte for a lithium secondary battery.

12. An electrolyte for a lithium secondary battery according to claim 10, wherein the lithium salt is one or more selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(C2F2SO2)2, CF3SO3Li, and LiC(CF3SO2)3.

13. An electrolyte for a lithium secondary battery according to claim 10, wherein the non-aqueous organic solvent is one or more selected from the group consisting of linear carbonate-based solvents, cyclic carbonate-based solvents, linear ester-based solvents, and cyclic ester-based solvents.

14. An electrolyte for a lithium secondary battery according to claim 10, further comprising an auxiliary additive comprising at least one of a fluorine-containing cyclic carbonate-based compound, an unsaturated group-containing cyclic carbonate-based compound, a sulfate-based compound, a sulfone-based compound, a lithium borate-based compound, and a lactone-based compound.

15. Anode; A negative electrode facing the above positive electrode; A separator interposed between the anode and the cathode; and A lithium secondary battery comprising an electrolyte for a lithium secondary battery according to claim 10.

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