Non-aqueous electrolyte solution for lithium secondary battery comprising novel electrolyte solution additive, and lithium secondary battery comprising same

Abstract

The present invention relates to a non-aqueous electrolyte for a lithium secondary battery comprising a novel electrolyte additive, and a lithium secondary battery comprising the same. More specifically, the present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery comprising an additive capable of forming a stable coating film on the surface of an electrode. The present invention also relates to a lithium secondary battery having excellent high-temperature storage performance by improving high-temperature life performance of the lithium secondary battery by including such a non-aqueous electrolyte solution and suppressing thickness expansion of the battery during high-temperature storage of the secondary battery.

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing a novel electrolyte additive and a lithium secondary battery containing the electrolyte. More specifically, the present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing an additive capable of forming a stable coating on an electrode surface. And the present invention aims to provide a lithium secondary battery with improved battery performance by including such a non-aqueous electrolyte, increasing the high temperature life of the lithium secondary battery, suppressing the increase in thickness of the secondary battery during high temperature storage, etc. Background Art

[0002] Lithium secondary batteries are not only used as portable power sources for mobile phones and laptops, but also for medium and large power sources for electric bicycles, electric vehicles (EVs), etc. With the expansion of such application areas, there is a need for lithium secondary batteries that can maintain excellent performance not only under normal temperature conditions but also in more demanding external environments such as high or low temperature environments.

[0003] At present, widely used lithium secondary batteries are usually composed of a carbon-based negative electrode that can embed and deintercalate lithium ions, a lithium-containing transition metal oxide-based positive electrode, a non-aqueous electrolyte in which lithium salts are dissolved in a mixed carbonate organic solvent, and a diaphragm for preventing contact between the positive and negative electrodes. When charging a lithium secondary battery, as the lithium atoms at the positive electrode are ionized and generate lithium ions and electrons, the electrons move to the negative electrode through an external circuit, and the lithium ions move to the negative electrode through the non-aqueous electrolyte and the diaphragm, and are intercalated in the carbon negative electrode. When discharging, the electrons move to the positive electrode through the external circuit. At the same time, the lithium ions also deintercalate from the carbon negative electrode and move to the positive electrode through the non-aqueous electrolyte and the diaphragm, thereby, the lithium ions and electrons meet at the positive electrode and become lithium atoms in a stable state. Lithium secondary batteries generate and consume electrical energy while repeating this charging and discharging.

[0004] During the charge and discharge process of lithium secondary batteries, as the positive electrode active material breaks in structure, metal ions will also dissolve from the positive electrode surface. The metal ions dissolved from the positive electrode will also be electrodeposited on the negative electrode, causing the negative electrode to deteriorate. When the secondary battery is exposed to high temperatures, this deterioration of the negative electrode tends to be further accelerated.

[0005] In order to solve this problem, a method of adding a compound that can form a coating (solid electrolyte interphase (SEI)) on the surface of the negative electrode to the non-aqueous electrolyte is proposed. However, these electrolyte additives will produce other side effects, such as: the life performance and high temperature stability of the secondary battery will deteriorate, thereby causing other problems such as the overall performance of the lithium secondary battery to decrease.

[0006] LiPF6 is mainly used as the lithium salt of lithium secondary batteries to achieve the appropriate characteristics of secondary batteries. - The heat resistance of anions is poor. When the secondary battery is exposed to high temperature, thermal decomposition will occur, thereby generating Lewis acids such as PF5. The PF5 generated in this way will not only cause the decomposition reaction of organic solvents such as ethylene carbonate, but also generate hydrofluoric acid (HF), thereby accelerating the dissolution of transition metals in the positive electrode active material. The transition metals dissolved in this way will be electrodeposited on the positive electrode and become the cause of increasing the resistance of the positive electrode; or electrodeposited on the negative electrode, causing self-discharge of the negative electrode; or destroying the solid electrolyte interface film (SEI) on the negative electrode, thereby causing further decomposition of the electrolyte and the resulting increase in resistance and life degradation of the secondary battery. This decomposition reaction of the electrolyte will also cause gas to be generated inside the secondary battery.

[0007] For these reasons, if lithium secondary batteries are stored at high temperatures in a fully charged state, the solid electrolyte interface (SEI) gradually breaks down over time. This rupture of the solid electrolyte interface exposes the surface of the negative electrode. The exposed negative electrode surface decomposes while reacting with the carbonate solvent in the electrolyte, causing a continuous side reaction. This side reaction continuously generates gas.

[0008] The gas generated in this way, regardless of its type, will increase the internal pressure of the lithium secondary battery and become a resistance factor to the movement of lithium, causing the volume (thickness) of the secondary battery to expand, and also causing a huge problem in the lightweight of the secondary battery and deteriorating the performance of the secondary battery.

[0009] Recently, as the application fields of lithium secondary batteries are expanding, demands for stability and long life characteristics in high temperature environments have emerged. Such performance depends largely on the electrode film formed by the initial reaction of the electrode and the electrolyte.

[0010] [Prior art literature]

[0011] [Patent Document]

[0012] (Patent Document 1) Japanese Patent Publication No. P2015-225713A Summary of the invention

[0013] Problems to be solved by the invention

[0014] It is necessary to continuously develop non-aqueous electrolytes containing additives that can improve the performance and safety of secondary batteries while minimizing these side effects. In order to solve the above problems, the present invention provides a non-aqueous electrolyte for lithium secondary batteries, which contains an additive that can form a stable coating (SEI) on the surface of an electrode, in particular, on the surface of a negative electrode.

[0015] In order to solve the above problems, the present invention provides an electrolyte additive for secondary batteries, which can form a strong coating (SEI) on the surface of electrodes, especially on the surface of negative electrodes, and has an excellent effect of removing decomposition products generated by lithium salts.

[0016] In addition, in order to solve the problems of the prior art as described above, the present invention provides a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery, which can improve the high temperature life and high temperature storage stability of the lithium secondary battery.

[0017] Solutions for solving problems

[0018] A non-aqueous electrolyte for a lithium secondary battery according to one embodiment of the present invention includes:

[0019] Compounds containing pyridyl and sulfonyl groups;

[0020] lithium salts; and

[0021] Non-aqueous organic solvents.

[0022] A non-aqueous electrolyte for a lithium secondary battery according to one embodiment of the present invention includes:

[0023] A compound represented by the following chemical formula 1 and containing a pyridyl group and a sulfonyl group;

[0024] lithium salts; and

[0025] Non-aqueous organic solvents.

[0026] Chemical formula 1:

[0027]

[0028] A non-aqueous electrolyte for a lithium secondary battery according to one embodiment of the present invention includes:

[0029] Compounds containing pyridyl and sulfonyl groups;

[0030] Additional additives;

[0031] lithium salts; and

[0032] Non-aqueous organic solvents.

[0033] A non-aqueous electrolyte for a lithium secondary battery according to one embodiment of the present invention includes:

[0034] A compound represented by the above chemical formula 1 and containing a pyridyl group and a sulfonyl group;

[0035] Additional additives;

[0036] lithium salts; and

[0037] Non-aqueous organic solvents.

[0038] One embodiment of the present invention provides a lithium secondary battery, which includes the non-aqueous electrolyte for lithium secondary batteries of the present invention, a positive electrode, a negative electrode, and a separator.

[0039] The negative electrode may include a carbon-based negative electrode active material and a silicon-based negative electrode active material.

[0040] The negative electrode may include a carbon-based negative electrode active material and a silicon-based negative electrode active material in a weight ratio of 97:3 to 50:50.

[0041] The negative electrode may include a carbon-based negative electrode active material and a silicon-based negative electrode active material in a weight ratio of 90:10 to 60:40.

[0042] Effects of the Invention

[0043] The lithium secondary battery using the lithium secondary battery electrolyte of the present invention improves the life performance at high temperature, and can realize a lithium secondary battery with excellent performance of suppressing the volume expansion of the secondary battery during high temperature storage. In addition, the compound represented by Chemical Formula 1 of the present invention can form a stable coating on the electrode surface through the sulfonyl group (SO2).

[0044] The non-aqueous electrolyte for lithium secondary batteries of the present invention includes a compound containing a pyridine group and a sulfonyl group as an additive, especially a compound represented by the following chemical formula 1, so as to form a stable coating on the electrode surface, especially on the negative electrode surface, which can effectively inhibit the dissolution of metal ions from the positive electrode and reduce the degradation of the SEI film by removing the byproducts generated by the thermal decomposition of the lithium salt. Therefore, the non-aqueous electrolyte for lithium secondary batteries of the present invention can realize a lithium secondary battery with improved life performance at high temperature and excellent high temperature storage stability. DETAILED DESCRIPTION

[0045] The present invention is described in more detail below by way of examples. These examples are only used to illustrate the present invention, and therefore, these examples should not be interpreted as limiting the scope of the present invention.

[0046] The terms “including”, “having” and the like used in this specification should be understood as open-ended terms covering the possibility of including other components unless otherwise mentioned in a sentence or article including the expression.

[0047] In this specification, "%" means weight percentage unless otherwise clearly indicated.

[0048] Hereinafter, the nonaqueous electrolyte for lithium secondary batteries and the lithium secondary batteries including the nonaqueous electrolyte of the present invention will be described in detail.

[0049] <Electrolyte Additives for Lithium Secondary Batteries>

[0050] The present invention provides a compound as an additive for an electrolyte for a lithium secondary battery, which contains a pyridyl group and a sulfonyl group, and particularly contains a pyridyl group and a sulfonyl group represented by the following Chemical Formula 1.

[0051] Chemical formula 1:

[0052]

[0053] <Electrolyte for lithium secondary batteries>

[0054] The present invention provides an electrolyte for a lithium secondary battery, comprising:

[0055] Compounds containing pyridyl and sulfonyl groups;

[0056] lithium salts; and

[0057] Non-aqueous organic solvents.

[0058] The present invention provides an electrolyte for a lithium secondary battery, comprising:

[0059] * A compound containing a pyridyl group and a sulfonyl group represented by the above chemical formula 1;

[0060] lithium salts; and

[0061] Non-aqueous organic solvents.

[0062] The present invention provides an electrolyte for a lithium secondary battery, comprising:

[0063] Compounds containing pyridyl and sulfonyl groups;

[0064] Additional additives;

[0065] lithium salts; and

[0066] Non-aqueous organic solvents.

[0067] The present invention provides an electrolyte for a lithium secondary battery, comprising:

[0068] A compound represented by the above chemical formula 1 and containing a pyridyl group and a sulfonyl group;

[0069] Additional additives;

[0070] lithium salts; and

[0071] Non-aqueous organic solvents.

[0072] The electrolyte for lithium secondary batteries may contain the compound containing a pyridyl group and a sulfonyl group in an amount of 0.05 weight percent to 20 weight percent relative to the total weight of the electrolyte.

[0073] Preferably, the electrolyte for lithium secondary batteries may contain 0.05 weight percent to 10 weight percent of the compound containing a pyridyl group and a sulfonyl group, relative to the total weight of the electrolyte.

[0074] More preferably, the electrolyte for lithium secondary batteries may contain 0.05 to 5 weight percent, 0.05 to 3 weight percent, or 0.05 to 2 weight percent of the compound containing a pyridyl group and a sulfonyl group, relative to the total weight of the electrolyte.

[0075] The electrolyte for lithium secondary batteries may contain the compound containing a pyridyl group and a sulfonyl group in an amount of 0.1 to 20 weight percent relative to the total weight of the electrolyte.

[0076] Preferably, the electrolyte for lithium secondary batteries may contain 0.1 to 10 weight percent of the compound containing a pyridyl group and a sulfonyl group, relative to the total weight of the electrolyte.

[0077] More preferably, the electrolyte for lithium secondary batteries may contain 0.1 to 5 weight percent, 0.1 to 3 weight percent, or 0.1 to 2 weight percent of the compound containing a pyridyl group and a sulfonyl group, relative to the total weight of the electrolyte.

[0078] In a case where the above-mentioned compound containing a pyridine group and a sulfonyl group is contained in an amount of less than 0.05 weight percent relative to the total weight of the above-mentioned electrolyte for lithium secondary batteries, the volume expansion prevention effect and the internal resistance reduction effect of the lithium secondary battery are insufficient. On the contrary, in a case where the above-mentioned compound containing a pyridine group and a sulfonyl group is contained in an amount of more than 20 weight percent relative to the total weight of the above-mentioned electrolyte for lithium secondary batteries, there will be problems of reduced high-temperature life characteristics and reduced high-temperature storage characteristics caused by increased internal resistance and reduced capacity of the secondary battery.

[0079] The above-mentioned electrolyte for lithium secondary batteries may further contain at least one additional additive selected from the group consisting of halogen-substituted or unsubstituted carbonate compounds, nitrile compounds, borate compounds, lithium salt compounds, phosphate compounds, sulfite compounds, sulfone compounds, sulfate compounds, and sultone compounds.

[0080] Representative examples of the additional additives include lithium difluorophosphate, lithium tetrafluoro(oxalate)phosphate, lithium bis(fluorosulfonyl)imide, 1,3-propane sultone, 1,3-propane sultone, fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, and vinyl sulfate.

[0081] The electrolyte for lithium secondary batteries may contain the additional additive in an amount of 0.05 weight percent to 20 weight percent relative to the total weight of the electrolyte.

[0082] Preferably, the electrolyte for lithium secondary batteries may contain the additional additive in an amount of 0.05 weight percent to 10 weight percent relative to the total weight of the electrolyte.

[0083] More preferably, relative to the total weight of the electrolyte for lithium secondary batteries, the additional additive may be included in an amount of 0.05 to 5 weight percent, specifically 0.05 to 3 weight percent.

[0084] When the above-mentioned additional additives are contained in an amount of less than 0.05 weight percent relative to the total weight of the above-mentioned electrolyte for lithium secondary batteries, the coating formation effect of the electrode is very small, and the side reaction inhibition effect of the electrode and the electrolyte will be reduced; and when the above-mentioned additional additives are contained in an amount of more than 20 weight percent relative to the total weight of the above-mentioned electrolyte for lithium secondary batteries, an excessively thick coating will be formed on the electrode surface, and the interface resistance will increase, thereby reducing the capacity.

[0085] In addition, the above-mentioned lithium salt may include at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiBF6, LiSbF6, LiAlO4, LiAlCl4, LiClO4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiF2NO4S2 and LiB(C2O4)2.

[0086] The above lithium salt has a large degree of dissociation of lattice energy, and therefore, preferably a lithium salt having excellent ion conductivity, thermal stability and oxidation resistance is used. The above lithium salt serves as a migration channel for lithium ions in the secondary battery, thereby enabling the basic operation of the lithium secondary battery.

[0087] The concentration of the lithium salt may be 0.1 M (mol / L) to 2.5 M (mol / L) relative to the total amount of the electrolyte for lithium secondary batteries.

[0088] Considering the performance related to conductivity and the viscosity related to the mobility of lithium ions, preferably, the concentration of the lithium salt may be 0.3M (mol / L) to 2.5M (mol / L) relative to the total amount of the electrolyte for the lithium secondary battery.

[0089] Considering the performance related to conductivity and the viscosity related to the mobility of lithium ions, more preferably, the concentration of the lithium salt may be 0.7M (mol / L) to 1.6M (mol / L) relative to the total amount of the electrolyte for lithium secondary batteries.

[0090] If the concentration of the above-mentioned lithium salt is less than 0.1M, the conductivity of the electrolyte for the above-mentioned lithium secondary battery will decrease, thereby resulting in a decrease in the performance of the non-aqueous electrolyte that quickly transfers ions between the positive and negative electrodes of the lithium secondary battery; if the concentration of the above-mentioned lithium salt is greater than 2.5M, the viscosity of the electrolyte for the above-mentioned lithium secondary battery will increase, resulting in a decrease in the mobility of lithium ions and a decrease in the performance of the secondary battery under low temperature conditions.

[0091] The non-aqueous organic solvent may be a linear carbonate solvent, a cyclic carbonate solvent or a mixed solvent thereof.

[0092] The linear carbonate solvent may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylpropyl carbonate (EPC), ethyl methyl carbonate (EMC), and methylpropyl carbonate (MPC).

[0093] In addition, the cyclic carbonate-based solvent may include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC).

[0094] Preferably, a ring-shaped carbonate organic solvent with a high dielectric constant and a linear carbonate organic solvent with a low viscosity are mixed for use. The above-mentioned ring-shaped carbonate organic solvent with a high dielectric constant has a high ionic conductivity that can improve the charge and discharge performance of the secondary battery, and the above-mentioned linear carbonate organic solvent with a low viscosity can appropriately adjust the viscosity of the above-mentioned carbonate organic solvent with a high dielectric constant.

[0095] Specifically, a carbonate organic solvent with a high dielectric constant and a carbonate organic solvent with a low viscosity can be mixed and used, the above-mentioned carbonate organic solvent with a high dielectric constant is used as the above-mentioned cyclic carbonate solvent, which is selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC) and a mixture thereof; the above-mentioned low-viscosity carbonate organic solvent is used as the above-mentioned linear carbonate solvent, which is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and a mixture thereof.

[0096] The above-mentioned cyclic carbonate solvent has a large polarity and can therefore fully dissociate lithium ions. However, due to its high viscosity, it has the disadvantage of low ion conductivity. Therefore, by mixing a linear carbonate solvent with a small polarity and low viscosity with the above-mentioned cyclic carbonate solvent, the characteristics of the lithium secondary battery can be optimized.

[0097] Therefore, it is preferred that at least one solvent selected from the above-mentioned cyclic carbonate solvents and at least one solvent selected from the above-mentioned linear carbonate solvents be mixed and used as the above-mentioned non-aqueous organic solvent.

[0098] As for the mixed solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent, the linear carbonate-based solvent and the cyclic carbonate-based solvent may be mixed in a volume ratio of 9:1 to 1:9.

[0099] For the mixed solvent of the linear carbonate solvent and the cyclic carbonate solvent, it is more preferred that the linear carbonate solvent and the cyclic carbonate solvent be mixed in a volume ratio of 2:8 to 8:2 in consideration of the life and storage characteristics of the secondary battery.

[0100] The non-aqueous organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0101] The non-aqueous organic solvent may include: 5 to 40 weight percent of the ethylene carbonate (EC), 5 to 20 weight percent of the propylene carbonate (PC), 10 to 70 weight percent of the ethyl methyl carbonate (EMC), and 10 to 60 weight percent of the diethyl carbonate (DEC).

[0102] Specifically, among the above-mentioned cyclic carbonate solvents, ethylene carbonate (EC) or propylene carbonate (PC) with a high dielectric constant can be used, however, when artificial graphite is used as the negative electrode active material, it is preferred to use the above-mentioned ethylene carbonate (EC), and among the above-mentioned linear carbonate solvents, it is preferred to use dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) or diethyl carbonate (DEC) with a low viscosity.

[0103] The non-aqueous organic solvent may be contained in an amount of 5% to 80% of the total amount of the electrolyte for lithium secondary batteries. The non-aqueous organic solvent may be contained in an amount of 5% to 70% of the total amount of the electrolyte for lithium secondary batteries.

[0104] <Lithium Secondary Battery>

[0105] The lithium secondary battery containing the non-aqueous electrolyte has improved life characteristics at high temperatures and is excellent in suppressing the expansion of the battery thickness when stored at high temperatures.

[0106] Hereinafter, the lithium secondary battery of the present invention will be described in detail.

[0107] The lithium secondary battery of the present invention comprises:

[0108] positive electrode;

[0109] negative electrode;

[0110] Diaphragms; and

[0111] Non-aqueous electrolyte.

[0112] The positive electrode may include a material selected from LiCoO2, LiFePO4, LiMnO2, LiMn2O4, LiNiO2 or LiNi 1-x-y Co x M y At least one positive electrode active material selected from the group consisting of lithium metal oxides such as O2 (0≤x≤1, 0≤y≤1, 0≤x+y≤1, M is Al, Sr, Mg, Mn or La).

[0113] The negative electrode may include at least one negative electrode active material selected from the group consisting of silicon, silicon compounds, tin, tin compounds, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, natural graphite, and a mixture of artificial graphite and natural graphite.

[0114] The above-mentioned diaphragm can be composed of a porous polymer film alone or a laminate thereof, wherein the porous polymer film is prepared from at least one polyolefin polymer selected from ethylene polymer, propylene polymer, ethylene / butene copolymer and ethylene / hexane copolymer. The above-mentioned diaphragm can include a coating film coated with ceramic or polymer material.

[0115] The non-aqueous electrolyte may include: a compound containing a pyridyl group and a sulfonyl group, in particular, a compound containing a pyridyl group and a sulfonyl group represented by the following Chemical Formula 1;

[0116] Additional additives;

[0117] lithium salts; and

[0118] Non-aqueous organic solvents.

[0119] Chemical formula 1:

[0120]

[0121] Examples of the lithium secondary battery include, but are not limited to, lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, lithium ion polymer secondary batteries, and the like.

[0122] In more detail, the positive electrode active material is preferably selected from one or more substances selected from cobalt, manganese, nickel and a composite metal oxide with lithium. The solid solubility ratio between the cobalt, manganese and nickel metals of the composite metal oxide can be varied, and in addition to these cobalt, manganese and nickel metals, it can also contain an element selected from the group consisting of Mg, Al, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Cr, Fe, Sr, V and rare earth elements.

[0123] Specifically, LiCoO2, LiFePO4, LiMnO2, LiMn2O4, LiNiO2 or LiNi can be used as the positive electrode active material. 1-x-y Co x M y Lithium metal oxides such as lithium sulfide O2 (0≤x≤1, 0≤y≤1, 0≤x+y≤1, M is Al, Sr, Mg, Mn or La) or lithium intercalation compounds such as lithium chalcogenide compounds, but are not limited thereto, and any material that can be used as a positive electrode active material in a secondary battery can be used.

[0124] The positive electrode comprises: a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may comprise a positive electrode active material capable of absorbing and releasing lithium, a binder, a conductive material, and the like.

[0125] The negative electrode includes: a current collector, and a negative electrode active material layer formed on the current collector. The negative electrode active material layer may include a negative electrode active material capable of inserting and extracting lithium, a binder, a conductive material, etc. As the negative electrode active material, crystalline carbon, amorphous carbon, a carbon composite, carbon fiber, lithium metal, lithium alloy or carbon-silicon composite can be used, but it is not limited thereto, and any material that can be used as a negative electrode active material in a secondary battery can be used.

[0126] The positive electrode and / or negative electrode can be prepared by dispersing an electrode slurry composition in a solvent by using an electrode active material, a binder and a conductive material, and if necessary, a thickener, and then applying the slurry composition to an electrode current collector. The positive electrode current collector can usually be made of aluminum or an aluminum alloy, and the negative electrode current collector can usually be made of copper or a copper alloy.

[0127] The positive electrode current collector and the negative electrode current collector may be in a shape of, for example, foil or mesh.

[0128] The above-mentioned binder is a material that plays a role in the gelatinization of the active material, the mutual adhesion of the active material, the adhesion to the current collector, the buffering effect on the expansion and contraction of the active material, etc., as long as it is a binder that can be used by ordinary technicians. For example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyhexafluoropropylene-polyvinylidene fluoride copolymer (PVdF / HFP), polyvinyl acetate, alkylated polyethylene oxide, polyvinyl ether, polymethyl methacrylate, polyethyl acrylate, polyacrylonitrile, polyvinyl pyridine, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, epoxy resin, nylon, etc. can be used, but it is not limited to this.

[0129] The above-mentioned conductive material is used to impart conductivity to the electrode. Therefore, for the constructed battery, any conductive material that does not cause chemical changes can be used. The above-mentioned conductive material can use at least one selected from the group consisting of graphite conductive materials, carbon black conductive materials, metal or metal compound conductive materials. Examples of the above-mentioned graphite conductive materials include: artificial graphite, natural graphite, etc.; examples of the above-mentioned carbon black conductive materials include: acetylene black (acethylene black), Ketjen black (ketjen black), acetylene carbon black (denka black), thermal black (thermal black), channel black (channel black), etc.; examples of the above-mentioned metal or metal compound conductive materials include: tin, tin oxide, tin phosphate (SnPO4), titanium oxide, potassium titanate, such as LaSrCoO3, LaSrMnO3 and other perovskite substances. However, it is not limited to the above-mentioned conductive materials.

[0130] The thickener is not particularly limited as long as it can adjust the viscosity of the active material slurry. For example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. can be used.

[0131] As the solvent for dispersing the electrode active material, binder, conductive material, etc., a non-aqueous solvent or an aqueous solvent can be used. Examples of the non-aqueous solvent may include: N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethyl-1,3-diaminopropane, ethylene oxide or tetrahydrofuran, etc. Examples of the aqueous solvent may include: water, etc.

[0132] The lithium secondary battery may include a separator disposed between the positive electrode and the negative electrode to prevent short circuit and provide a path for the movement of lithium ions. As the separator, polyolefin polymer films such as polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, polypropylene / polyethylene / polypropylene or their multilayer films, microporous films, fabrics and non-woven fabrics may be used. In addition, as the separator, a film in which a porous polyolefin film is coated with a resin having excellent stability may also be used.

[0133] In addition, the lithium secondary battery can be prepared into various shapes such as rectangular, cylindrical, soft-pack or coin shape.

[0134] Embodiments of the invention

[0135] The present invention is described in more detail below by way of examples, but the scope of the invention should not be construed as being limited to these examples.

[0136] <Preparation of an electrolyte solution for a lithium secondary battery containing a compound containing a pyridyl group and a sulfonyl group>

[0137] [Example 1]

[0138] After dissolving LiPF6 and LiFSI in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio EC / EMC = 3 / 7) to concentrations of 0.7 M and 0.3 M respectively, 1.0 wt% of fluoroethylene carbonate (FEC), 1.0 wt% of lithium difluorophosphate (LiPO2F2), 1.0 wt% of vinylene carbonate (VC), 0.5 wt% of ethylene sulfate (Esa), 0.5 wt% of 1,3 - propanesultone (PRS), and 0.5 wt% of the compound represented by Chemical Formula 1 above, 2 - Pyridinesulfonyl Fluoride (produced by Tokyo Chemical Industry Co., Ltd. (TCI)), were added to the above - mentioned mixed solution, thereby preparing an electrolyte for a lithium secondary battery containing the compound having a pyridyl group and a sulfonyl group of Example 1.

[0139] <Preparing a lithium secondary battery comprising an electrolyte, wherein the electrolyte comprises a compound containing a pyridyl group and a sulfonyl group >

[0140] 94 wt% of a NCM - type positive electrode active material containing Li[Ni x Co 1-x-y Mn y O2 (0 < x < 0.5, 0 < y < 0.5), 3 wt% of a conductive material (Super - P), and 3 wt% of a binder (PVdF) were added to an organic solvent N - methyl - 2 - pyrrolidinone (NMP), thereby preparing a positive electrode active material slurry. The above - mentioned positive electrode active material slurry was coated on an aluminum foil as a current collector and dried, thereby preparing a positive electrode, and then the positive electrode was prepared by rolling with a rolling press. In addition, 96 wt% of a graphite - type negative electrode active material containing silicon oxide (SiOx), 1 wt% of a conductive material (Super - P), 1.5 wt% of a binder styrene - butadiene rubber (SBR), and 1.5 wt% of carboxymethyl cellulose (CMC) were mixed, thereby preparing a negative electrode active material slurry. The above - mentioned negative electrode active material slurry was coated on a copper foil as a negative electrode current collector and dried, thereby preparing a negative electrode.

[0141] A positive electrode and a negative electrode prepared as described above are prepared, and a separator is sandwiched between the two electrodes. Then, an electrolyte for a lithium secondary battery containing the compound containing a pyridyl group and a sulfonyl group of Example 1 is injected between the two electrodes sandwiched with the separator, thereby preparing an Al-Pouch type lithium secondary battery containing an electrolyte, wherein the electrolyte includes a compound containing a pyridyl group and a sulfonyl group.

[0142] [Comparative Example]

[0143] <Preparation of an electrolyte for a lithium secondary battery containing 1,3-propane sultone (PS) additive>

[0144] The non-aqueous electrolyte for lithium secondary batteries may contain sultone compounds as needed to prevent the decomposition of the non-aqueous electrolyte, thereby improving the high temperature stability and the effect of inhibiting battery expansion at high temperatures. The sultone compounds may be selected from at least one compound in the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone (BS), ethylene sultone, 1,3-propene sultone, 1,4-butene sultone and 1-methyl-1,3-propene sultone. In the following comparative examples, 1,3-propane sultone, which is called a battery gas (gas) inhibitor, is used.

[0145] [Comparative Example 1]

[0146] LiPF6 and LiFSI were dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio: EC / EMC=3 / 7) to make the concentrations of LiPF6 and LiFSI 0.7M and 0.3M, respectively. Then, 1.0 weight percent of fluoroethylene carbonate (FEC), 1.0 weight percent of lithium difluorophosphate (LiPO2F2), 1.0 weight percent of vinylene carbonate (VC), 0.5 weight percent of vinyl sulfate (Esa), 0.5 weight percent of 1,3-propylene sultone (PRS) and 0.5 weight percent of propane sultone (PS) were added to the mixed solution to prepare an electrolyte for a lithium secondary battery of Comparative Example 1.

[0147] <Preparing a lithium secondary battery comprising an electrolyte, wherein the electrolyte comprises 1,3-propane sultone (PS) Additives>

[0148] As the electrolyte, the lithium secondary battery electrolyte of the above-mentioned Comparative Example 1 containing 1.3-propane sultone (PS) was used instead of adding the 2-pyridinesulfonyl fluoride compound represented by the compound of the above-mentioned Chemical Formula 1. Except for this, a lithium secondary battery containing no compound of Chemical Formula 1 but 1,3-propane sultone (PS) electrolyte was prepared by the same method as the preparation of the lithium secondary battery of the above-mentioned embodiment.

[0149] The compositions of the electrolyte solutions for lithium secondary batteries in the above-described Examples and Comparative Examples are shown in Table 1 below.

[0150] [Table 1]

[0151] <Components of electrolyte for lithium secondary battery>

[0152]

[0153] [Experimental example]

[0154] [Experimental Example 1]

[0155] <Determination of high temperature (45°C) life capacity retention rate>

[0156] Under high temperature (45°C), the soft-pack lithium secondary battery prepared using the lithium secondary battery electrolyte of the above embodiment and comparative example was charged to 4.2V at 1C-rate, rested for 10 minutes, and discharged to 2.7V at 1C-rate, and rested for 10 minutes again. The discharge capacity (mAh) and life capacity retention rate (retention, %) of the battery were determined by repeating the above process 400 times, and the discharge capacity and life capacity retention rate of the measured batteries were compared, and the results are shown in Table 2.

[0157] [Table 2]

[0158] Discharge capacity per time (mAh) 400 times discharge capacity (mAh) Lifetime capacity retention rate (%) Example 886.3 711.5 80.1 Comparative Example 893.1 706.2 79.1

[0159] As shown in Table 2 above, the life evaluation results at high temperature show that the lithium secondary battery of the embodiment shows improved results compared to the lithium secondary battery of the comparative example using 1,3-propane sultone. That is, it is confirmed that the life performance at high temperature of the electrolyte containing the compound containing a pyridyl group and a sulfonyl group is improved compared to the electrolyte containing 1,3-propane sultone.

[0160] It can be confirmed that by including a compound containing a pyridine group and a sulfonyl group, especially an electrolyte including a compound containing a pyridine group and a sulfonyl group represented by the above Chemical Formula 1, the life performance of the lithium secondary battery of the above embodiment at high temperature is improved compared with the lithium secondary battery of the above comparative example.

[0161] [Experimental Example 2]

[0162] <Measurement of high temperature (60°C) storage characteristics>

[0163] The volume increase rate of the soft-pack lithium secondary battery prepared using the lithium secondary battery electrolyte of the above-mentioned embodiment and comparative example was measured after being stored at high temperature (60°C) for 6 weeks. The following Table 3 shows the volume increase rate of the lithium secondary battery after being stored at high temperature (60°C) for 6 weeks.

[0164] [Table 3]

[0165] Volume increase rate after storage at 60℃ for 6 weeks (%) Example 4.33 Comparative Example 4.72

[0166] As shown in Table 3 above, in order to compare the high temperature storage performance, the lithium secondary battery of the embodiment and the lithium secondary battery of the comparative example were placed at high temperature (60°C) for 6 weeks, and the volume increase rate of the secondary battery was measured. Observing the measurement results, the volume increase rate of the battery of Example 1 using a compound containing pyridine and sulfonyl groups is reduced relative to the comparative example containing 1,3-propane sultone (PS). It can be confirmed that the volume increase rate performance of the lithium secondary battery of the embodiment is better when the battery is stored at high temperature than the lithium secondary battery of the comparative example.

[0167] By comparing the experimental results of the above embodiment and the comparative example, it can be seen that compared with the lithium secondary battery of the comparative example containing 1,3-propane sultone (PS), the lithium secondary battery of the embodiment including a compound containing a pyridyl group and a sulfonyl group, especially a compound containing a pyridyl group and a sulfonyl group represented by the above chemical formula 1 to replace 1,3-propane sultone (PS), has improved high temperature life performance and excellent battery volume increase rate performance during high temperature storage.

Claims

1. A non-aqueous electrolyte for a lithium secondary battery, wherein: A non-aqueous electrolyte for a lithium secondary battery comprising: a lithium salt; a non-aqueous organic solvent; and an additive; The additive contains a compound containing a pyridyl group and a sulfonyl group.

2. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein The additive is a compound of the following chemical formula 1: Chemical formula 1:

3. The non-aqueous electrolyte for lithium secondary battery according to claim 1 or 2, wherein Based on the total weight of the non-aqueous electrolyte for lithium secondary batteries, the additive is contained in an amount of 0.05 weight percent to 20 weight percent.

4. The non-aqueous electrolyte for lithium secondary battery according to claim 1 or 2, wherein The invention further comprises additional additives, wherein the additional additives are at least one compound selected from the group consisting of halogen-substituted or unsubstituted carbonate compounds, nitrile compounds, borate compounds, lithium salt compounds, phosphate compounds, sulfite compounds, sulfone compounds, sulfate compounds, and sultone compounds.

5. A lithium secondary battery, wherein: include: A non-aqueous electrolyte for a lithium secondary battery, a positive electrode, a negative electrode, and a separator as claimed in claim 1 or claim 2.

6. The lithium secondary battery according to claim 1 or 2, wherein: The negative electrode comprises a carbon-based negative electrode active material, a silicon-based negative electrode active material and a mixture thereof.

7. The lithium secondary battery according to claim 6, wherein: The weight ratio of the carbon-based negative electrode active material to the silicon-based negative electrode active material is 97:3 to 50:

50.

8. The lithium secondary battery according to claim 7, wherein: The weight ratio of the carbon-based negative electrode active material to the silicon-based negative electrode active material is 90:10 to 60:40.

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