Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

According to exemplary embodiments of the present invention, an electrolyte for a lithium secondary battery comprises a compound represented by chemical formula 1, a vinylene carbonate-based compound, and an auxiliary additive, and thus can improve high-temperature performance of the lithium secondary battery.

Description

Electrolyte for lithium secondary batteries and lithium secondary batteries including the same

[0001] The present invention relates to 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 an electrolyte for a lithium secondary battery that can improve the high-temperature performance of the lithium secondary battery.

[0007] One objective of the present invention is to provide a lithium secondary battery with improved high-temperature performance.

[0008] The lithium secondary battery electrolyte according to the present invention comprises: a compound represented by Chemical Formula 1; a vinylene carbonate-based compound; and an auxiliary additive comprising one or more compounds selected from the group consisting of 1,3-propane sulfone, ethylene sulfate, succinonitrile, 1,3,6-hexanetricarbonitrile, propanephosphonic acid anhydride, and butylphosphonic acid anhydride.

[0009] [Chemical Formula 1]

[0010]

[0011] In Chemical Formula 1, 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.

[0012] 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; a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd may be hydrogen.

[0013] 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.

[0014] In one embodiment, the electrolyte for the lithium secondary battery may further include a lithium salt.

[0015] 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.

[0016] In one embodiment, the electrolyte for the lithium secondary battery may further include a non-aqueous organic solvent.

[0017] 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.

[0018] 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.

[0019] In one embodiment, the lithium salt and a non-aqueous organic solvent are further included, 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.

[0020] In one embodiment, the content of the compound represented by Formula 1 may be 0.01% to 10% by weight of the total weight of the electrolyte for the lithium secondary battery.

[0021] In one embodiment, 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.

[0022] In one embodiment, the content of the auxiliary additive may be 0.01% to 10% by weight of the total weight of the electrolyte for the lithium secondary battery.

[0023] In one embodiment, the ratio of the content of the auxiliary additive to the content of the compound represented by Chemical Formula 1 may be 0.1 to 10.

[0024] A lithium secondary battery according to exemplary embodiments may include 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.

[0025] The electrolyte for a lithium secondary battery according to exemplary embodiments can improve the high-temperature performance of the lithium secondary battery by including a compound represented by Formula 1; a vinylene carbonate-based compound; and an auxiliary additive.

[0026] 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.

[0027] Figure 3 is a graph of the storage capacity at 70°C for one week measured for the lithium secondary batteries of Example 6 and Comparative Example 3.

[0028] Figure 4 is a graph of the recovery capacity measured for the lithium secondary batteries of Example 6 and Comparative Example 3 after 1 week of storage at 70°C.

[0029] According to the present invention, an electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same are provided, comprising: a compound represented by Formula 1; a vinylene carbonate-based compound; and an auxiliary additive comprising one or more compounds selected from the group consisting of 1,3-propane sulfone, ethylene sulfate, succinonitrile, 1,3,6-hexanetricarbonitrile, propanephosphonic acid anhydride and butylphosphonic acid anhydride.

[0030] The above electrolyte for a lithium secondary battery suppresses gas generation, and when using a positive electrode containing a lithium metal oxide, the film generated by an auxiliary additive is modified by a compound represented by Chemical Formula 1, thereby simultaneously improving the high-temperature performance and resistance characteristics of the lithium secondary battery.

[0031] In this specification, "X-type compound" may mean a compound containing an X unit in a parent group, a side group, or a substituent.

[0032] 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."

[0033] In one embodiment, the electrolyte for a lithium secondary battery may include a compound represented by the following chemical formula 1.

[0034] [Chemical Formula 1]

[0035]

[0036] In Chemical Formula 1, 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] In one embodiment, at least one of R2 to R5 may be a halogen (e.g., F, Cl, Br, or I).

[0041] In one embodiment, at least one of R2 to R5 may be F.

[0042] In one embodiment, R2 to R5 may all be halogens.

[0043] In some embodiments, R2 to R5 may all be F.

[0044] In one embodiment, M may be Li, Na, or K.

[0045] In one embodiment, Y + It may be an alkali metal ion; an ammonium ion; or a primary to quaternary ammonium ion.

[0046] In some embodiments, Y + is N + RaRbRcRd or ReRfN + = It could be RgRh.

[0047] 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.

[0048] 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.

[0049] In some embodiments, Y + is N + RaRbRcRd, wherein Ra to Rd are independently hydrogen; a substituted or unsubstituted C1-C6 alkyl group; a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd may be hydrogen.

[0050] 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.

[0051] According to exemplary embodiments, a compound of Formula 1 can be prepared by reacting a sulfonate-based salt or a sulfate-based salt with a phosphate-based alkali metal salt.

[0052] In one embodiment, the sulfonate-based salt or sulfate-based salt may be represented by the following chemical formula 2.

[0053] [Chemical Formula 2]

[0054]

[0055] In Chemical Formula 2, Y + It can be a cationic substance.

[0056] In one embodiment, Y + It may be an alkali metal ion; an ammonium ion; or a primary to quaternary ammonium ion.

[0057] In some embodiments, Y + is N + RaRbRcRd or ReRfN + = It could be RgRh.

[0058] 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.

[0059] 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.

[0060] In some embodiments, Y + is N +RaRbRcRd, 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.

[0061] In one embodiment, Ra may be a substituted or unsubstituted C1-C6 alkyl group; or a substituted or unsubstituted C2-C6 alkenyl group.

[0062] In some embodiments, Ra may be a substituted or unsubstituted C2-C6 alkenyl group. In some embodiments, Ra may be an unsubstituted C2-C6 alkenyl group.

[0063] In one embodiment, the phosphate-based alkali metal salt can be represented by the following chemical formula 3.

[0064] [Chemical Formula 3]

[0065]

[0066] 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.

[0067] 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.

[0068] In one embodiment, R2 and R3 may both be halogens. In some embodiments, R2 and R3 may both be F.

[0069] In one embodiment, a crystal produced by reacting the sulfonate-based salt or sulfate-based salt and the phosphate-based alkali metal salt can be filtered and dried to obtain a compound represented by the chemical formula 1.

[0070] In one embodiment, the reaction temperature may be 10°C to 50°C.

[0071] In one embodiment, the molar ratio of the mixture of the sulfonate-based salt or sulfate-based salt and the phosphate-based alkali metal salt may be 1:0.9 to 1:1.1.

[0072] In one embodiment, the electrolyte for the lithium secondary battery may include a vinylene carbonate-based compound.

[0073] In one embodiment, the vinylene carbonate-based compound may be vinylene carbonate.

[0074] In one embodiment, the compound represented by Chemical Formula 1 and the vinylene carbonate-based compound may be provided as additives to the electrolyte for the lithium secondary battery.

[0075] In one embodiment, the electrolyte for the lithium secondary battery may include an auxiliary additive comprising one or more compounds selected from the group consisting of 1,3-propane sulfone, ethylene sulfate, succinonitrile, 1,3,6-hexanetricarbonitrile, propanephosphonic acid anhydride, and butylphosphonic acid anhydride.

[0076] In one embodiment, the electrolyte for the lithium secondary battery may further include a lithium salt.

[0077] For example, the above lithium salt is Li + X - It can be expressed as.

[0078] 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.

[0079] The above lithium salt may be a compound other than the lithium salt form of the compound represented by Chemical Formula 1.

[0080] 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.

[0081] For example, the above lithium salt may be LiPF6.

[0082] In one embodiment, the electrolyte for the lithium secondary battery may further include a non-aqueous organic solvent.

[0083] 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.

[0084] 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.

[0085] The above-mentioned cyclic carbonate-based solvent may include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, etc.

[0086] 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.

[0087] 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.

[0088] For example, the above linear ester-based solvent may include methyl propionate, ethyl propionate, propyl acetate, butyl acetate, ethyl acetate, etc.

[0089] For example, the above-mentioned cyclic ester solvent may include butyrolactone, caprolactone, valerolactone, etc.

[0090] 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.

[0091] 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.

[0092] For example, the above ketone-based solvent may include cyclohexanone, etc.

[0093] For example, the above alcohol-based solvent may include at least one of ethyl alcohol and isopropyl alcohol.

[0094] 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.

[0095] 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.

[0096] In one embodiment, the non-aqueous organic solvent may include ethylene carbonate, methylene carbonate, and dimethyl carbonate.

[0097] 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.

[0098] 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.

[0099] In one embodiment, the content of the compound represented by Formula 1 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.

[0100] For example, the compound represented by Chemical Formula 1 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.

[0101] [Chemical Formula 4]

[0102]

[0103] In Chemical Formula 4, the definitions of the substituents may be applied to the description of the substituents in Chemical Formula 1 mentioned above.

[0104] 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.

[0105] In one embodiment, the content of the auxiliary additive 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 auxiliary additive may be 0.1% to 7.5% by weight or 0.3% to 5% by weight. Within the above range, the high-temperature storage characteristics of the lithium secondary battery, etc., may be further improved.

[0106] 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.

[0107] According to exemplary embodiments of the present invention, a lithium secondary battery comprising the electrolyte for the lithium secondary battery is provided.

[0108] 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.

[0109] 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).

[0110] 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).

[0111] For example, the positive active material layer (110) may include a positive active material, a positive binder and a conductive material as needed.

[0112] 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).

[0113] For example, the positive current collector (105) may include stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof.

[0114] For example, the positive electrode active material may include lithium metal oxide particles capable of reversible insertion and extraction of lithium ions.

[0115] In one embodiment, the lithium metal oxide particles may contain nickel, cobalt, manganese, aluminum, etc.

[0116] 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.

[0117] In some embodiments, the lithium metal oxide particles may be represented by LiNiO2, LiCoO2, LiMnO2, LiMn2O4, or the following chemical formula 5.

[0118] [Chemical Formula 5]

[0119] Li x Ni (1-a-b) Co a M b O y

[0120] 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.

[0121] 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.

[0122] 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).

[0123] 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.

[0124] The cathode (130) may include a cathode current collector (125) and a cathode active material layer (120) on the cathode current collector (125).

[0125] 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.

[0126] 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).

[0127] 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.

[0128] 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.

[0129] For example, the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0130] For example, the carbon-based active material may include crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.

[0131] 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.

[0132] 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.

[0133] 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).

[0134] In one embodiment, a separator (140) may be interposed between the anode (100) and the cathode (130).

[0135] 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.

[0136] 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.

[0137] For example, an electrode cell may be formed including an anode (100), a cathode (130), and a separator (140).

[0138] 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).

[0139] For example, an electrode assembly (150) can be formed by winding, lamination, zigzag-folding, etc. of a separator (140).

[0140] 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).

[0141] 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.

[0142] 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).

[0143] 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).

[0144] 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).

[0145] 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.

[0146] 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).

[0147] 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.

[0148] The above lithium secondary battery can be manufactured in, for example, cylindrical, prismatic, pouch, or coin types.

[0149] 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.

[0150]

[0151] Preparation Example

[0152] 1,000 g of a solvent mixed with ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7 and 50 g of lithium difluorophosphate (LiPO2F2) were added to a reactor and stirred, and 97 g of triethylammonium propenesulfonate was added.

[0153] The mixture in the reactor was stirred at room temperature for about 7 hours to carry out the reaction. After the reaction was finished, the resulting crystals were filtered, washed with DMC, and vacuum dried to obtain a white compound represented by the chemical formula 1-A (yield about 90%).

[0154] [Chemical Formula 1-A]

[0155]

[0156]

[0157] Examples and Comparative Examples

[0158] (1) Preparation of electrolyte

[0159] 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).

[0160] 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.

[0161] (2) Manufacturing of lithium secondary batteries

[0162] 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.

[0163] 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.

[0164] A cathode slurry was prepared by dispersing crystalline artificial graphite, acetylene black, and PVDF in NMP in a weight ratio of 92:1:7.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] (3) Mars charging and discharging

[0169] 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) and 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). Afterwards, a 1C CC / CV charge (4.2V CUT-OFF) was performed.

[0170]

[0171] Classification Additive Composition and Content Example 1 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% + 1,3-Propane Sultone 0.5 wt% Example 2 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% + Ethylene Sulfate 0.5 wt% Example 3 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% + Succino Nitrile 0.5 wt% Example 4 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% + 1,3,6-Hexanetricarbonitrile 0.5 wt% Example 5 Preparation Example: Compound 0.5 wt% + Vinylene Carbonate 1 wt% + Propanephosphonic acid anhydride 0.5 wt% Example 6 Preparation Example Compound 0.5 wt% + Vinylene carbonate 1 wt% + n-Butylphosphonic acid anhydride 0.5 wt% Comparative Example 1 Lithium bis(phosphorodifluoridate) triethylammonium ethenesulfonate 0.5 wt% Comparative Example 2 Preparation Example Compound 0.5 wt% Comparative Example 3 Preparation Example Compound 0.5 wt% + Vinylene carbonate 1 wt%

[0172] Evaluation method

[0173] (1) Initial discharge capacity measurement

[0174] The lithium secondary batteries of the examples and comparative examples were charged at 1C CC / CV (4.2V CUT-OFF) and discharged at 1C CC (3V CUT-OFF) to measure the initial discharge capacity.

[0175] (2) Measurement of capacity retention rate and capacity recovery rate after high-temperature storage (70℃, 1 week)

[0176] After charging the lithium secondary batteries of the examples and comparative examples to 4.2V with 1C and discharging them to SOC 50 with a constant current of 2C, the initial capacity was measured by discharging at charge-discharge rates (C-rate) of 0.5C, 1C, 2C, and 4C for 10 seconds each.

[0177] After charging at 1C to 4.2V and storing at a high temperature (70℃) for 7 days, the retention capacity was measured after charging at 1C to 4.2V twice and discharging at 1C twice and storing at 70℃ for 7 days. The recovery capacity (discharge capacity) was measured by charging and discharging in the same way as when the initial capacity was measured, and the capacity retention rate and capacity recovery rate were calculated as a percentage relative to the initial capacity.

[0178] The retention capacity of the lithium secondary batteries according to Example 6 and Comparative Example 3 is shown in the graph of FIG. 3.

[0179] In addition, the recovery capacity for the lithium secondary batteries according to Example 6 and Comparative Example 3 is shown in the graph of Figure 4.

[0180] (3) Measure the rate of increase in thickness after high-temperature storage (70℃, 1 week).

[0181] After charging the lithium secondary batteries of the examples and comparative examples 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 the examples and comparative examples exposed to air at 70°C for one week (using a constant temperature device), the battery thickness T2 was measured.

[0182] 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.

[0183] Battery thickness increase rate (%) = {(T2-T1) / T1 + 1} * 100

[0184] (4) Resistance characteristics after high-temperature storage (70℃, 1 week)

[0185] After charging the lithium secondary batteries of the examples and comparative examples at 1C CC / CV (4.2V CUT-OFF), they were stored at a high temperature (70℃) for one week and then discharged at 2C CC up to 440 mA. Afterwards, the C-rate was varied to 0.5C, 1C, 2C, and 4C, and the discharge and recharge were each for 10 seconds, and the DCIR measurements were taken and listed in Table 2 below.

[0186] Thickness Increase Rate (%) Initial Capacity (mAh) Capacity Retention Rate (%) Capacity Recovery Rate (%) Resistance Characteristics (mΩ) Example 1 8.28 47.5 98 9.7 29 5.4 46 1.13 Example 2 10.8 848.7 19 0.7 29 6.7 66 3.12 Example 3 11.7 847.9 18 9.6 89 6.5 46 3.11 Example 4 11.0 849.2 88 9.8 49 6.0 16 2.90 Example 5 5.5 848.9 89 2.5 89 8.5 56 2.74 Example 6 6.1 849.8 99 3.3 199 3.3 36 1.76 Comparative Example 1 40.9 843.9 47 2.2 57 7.2 69 4.28 Comparative Example 235.4843.1175.3879.8790.38 Comparative Example 315.5845.7683.8190.1174.61

[0187] Referring to Tables 1 and 2 above, it was confirmed that Comparative Example 2, which applied the compound of the above preparation example, had a lower thickness increase rate compared to Comparative Example 1, which applied "lithium bis(phosphorodifluoridate) triethylammonium ethynesulfonate" alone, which reduced gas generation at high temperatures and reduced resistance characteristics, and improved capacity retention rate and capacity recovery rate.

[0188] It was confirmed that Comparative Example 3, which applied the compound of the above preparation example and vinylene carbonate, had a lower thickness increase rate compared to Comparative Example 2, which reduced gas generation at high temperatures and reduced resistance characteristics, and improved capacity retention rate and capacity recovery rate.

[0189] On the other hand, Examples 1 to 6, which applied the above-mentioned electrolyte for lithium secondary batteries, showed a very low increase in thickness compared to Comparative Example 3, which was confirmed to further reduce gas generation at high temperatures, and it was confirmed that high-temperature characteristics such as a decrease in resistance, capacity retention rate, and capacity recovery rate were generally improved.

Claims

1. Compounds represented by Chemical Formula 1; vinylene carbonate-based compounds; and Electrolyte for a lithium secondary battery comprising: an auxiliary additive comprising one or more compounds selected from the group consisting of 1,3-propane sulfone, ethylene sulfate, succinonitrile, 1,3,6-hexanetricarbonitrile, propanephosphonic acid anhydride, and butylphosphonic acid anhydride; [Chemical Formula 1] (In Chemical Formula 1, 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, 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; a substituted or unsubstituted C2-C6 alkenyl group, and at least one of Ra to Rd is hydrogen.

3. 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.

4. The electrolyte for a lithium secondary battery according to claim 1, further comprising a lithium salt.

5. An electrolyte for a lithium secondary battery according to claim 4, 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.

6. An electrolyte for a lithium secondary battery according to claim 1, further comprising a non-aqueous organic solvent.

7. An electrolyte for a lithium secondary battery according to claim 6, 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.

8. An electrolyte for a lithium secondary battery according to claim 6, wherein the non-aqueous organic solvent is one or more selected from the group consisting of ethylene carbonate, methylene carbonate, and dimethyl carbonate.

9. An electrolyte for a lithium secondary battery according to claim 1, further comprising a lithium salt and a non-aqueous organic solvent, wherein the lithium salt is included at a concentration of 0.1 M to 2 M with respect to the non-aqueous organic solvent.

10. An electrolyte for a lithium secondary battery according to claim 1, wherein the content of the compound represented by Chemical Formula 1 is 0.01% to 10% by weight of the total weight of the electrolyte for a lithium secondary battery.

11. An electrolyte for a lithium secondary battery according to claim 1, wherein the content of the vinylene carbonate-based compound is 0.01% to 10% 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 1, wherein the content of the auxiliary additive is 0.01% to 10% by weight of the total weight of the electrolyte for a lithium secondary battery.

13. An electrolyte for a lithium secondary battery according to claim 1, wherein the ratio of the content of the auxiliary additive to the content of the compound represented by Chemical Formula 1 is 0.1 to 10.

14. 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 1.

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