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 film on the electrode surface. And the present invention aims to provide a lithium secondary battery in which, by containing such a non-aqueous electrolyte, the high-temperature life of the lithium secondary battery is improved, the increase in the thickness of the secondary battery is suppressed during high-temperature storage, etc., and the battery performance is improved. Background Art

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

[0003] Currently, widely used lithium secondary batteries generally consist of a carbon-based negative electrode capable of inserting and extracting lithium ions, a lithium-containing transition metal oxide-based positive electrode, a non-aqueous electrolyte in which a lithium salt is dissolved in a mixed carbonate organic solvent, and a separator for preventing contact between the positive electrode and the negative electrode. When charging a lithium secondary battery, as lithium atoms located in the positive electrode ionize to generate lithium ions and electrons, the electrons move to the negative electrode through an external circuit, the lithium ions pass through the non-aqueous electrolyte and the separator and move to the negative electrode, and are intercalated into 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, pass through the non-aqueous electrolyte and the separator, and move to the positive electrode. Thus, the lithium ions and electrons meet at the positive electrode and become stable lithium atoms. The lithium secondary battery generates and consumes electrical energy while repeating this charging and discharging.

[0004] During the charge and discharge process of a lithium secondary battery, as the positive electrode active material structurally breaks down, metal ions also dissolve out from the positive electrode surface. The metal ions dissolved out from the positive electrode also electrodeposit onto the negative electrode, deteriorating the negative electrode. When the secondary battery is exposed to high temperatures, this deterioration phenomenon of the negative electrode tends to accelerate further.

[0005] To solve this problem, a method of adding a compound capable of forming a coating film (Solid Electrolyte Interphase (SEI)) on the negative electrode surface in a non-aqueous electrolyte has been proposed. However, these electrolyte additives cause other side effects, such as deterioration of the life performance and high-temperature stability of the secondary battery, and thus other problems of a decline in the comprehensive performance of the lithium secondary battery also occur.

[0006] As the lithium salt of the lithium secondary battery, LiPF is mainly used 6 to achieve suitable characteristics of the secondary battery. It is known that the PF 6 of LiPF 6 - has poor heat resistance. When the secondary battery is exposed to high temperature, thermal decomposition occurs, generating Lewis acids such as PF 5 . The generated PF 5 not only causes decomposition reactions of organic solvents such as ethylene carbonate, but also generates hydrofluoric acid (HF), thereby accelerating the dissolution of transition metals in the positive electrode active material. The dissolved transition metals are electroplated on the positive electrode and become the cause of increasing the resistance of the positive electrode; or electroplated on the negative electrode, causing self-discharge of the negative electrode; or destroying the solid electrolyte interphase film (SEI) on the negative electrode, thereby causing further decomposition of the electrolyte and problems such as an increase in the resistance and deterioration of the life of the secondary battery. This decomposition reaction of the electrolyte also causes gas generation inside the secondary battery.

[0007] For these reasons, if the lithium secondary battery is stored at high temperature in a fully charged state, over time, the problem of gradual rupture of the solid electrolyte interphase film (SEI) will occur. The rupture of this solid electrolyte interphase film exposes the surface of the negative electrode. The exposed negative electrode surface decomposes while reacting with carbonate solvents in the electrolyte, causing continuous side reactions. These side reactions continuously generate gas.

[0008] The generated gas, regardless of its type, will increase the internal pressure of the lithium secondary battery and become a resistance factor for lithium movement, causing the volume (thickness) of the secondary battery to expand, and also causing great problems for the weight reduction of the secondary battery, and deteriorating the performance of the secondary battery.

[0009] Recently, as the application fields of lithium secondary batteries are expanding, requirements for their stability and long-life characteristics in high-temperature environments are constantly emerging. This performance largely depends on the above-mentioned solid electrolyte electrode film formed by the initial reaction of the electrode and the electrolyte.

[0010] [Prior Art Documents]

[0011] [Patent Documents]

[0012] (Patent Document 1) PCT International Publication No. WO2019 / 059365A1 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] There is a need to continuously develop a non-aqueous electrolyte containing an additive that can improve the performance and safety of secondary batteries while minimizing these side effects. To solve the above problems, the present invention provides a non-aqueous electrolyte for a lithium secondary battery, which contains an additive capable of forming a stable coating film (SEI) on the surface of the electrode, especially on the surface of the negative electrode.

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

[0016] In addition, to solve the above problems of the prior art, the present invention provides a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery including 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 the Problems

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

[0019] A compound containing a pyridyl group and a silyl group;

[0020] A lithium salt; and

[0021] A non-aqueous organic solvent.

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

[0023] A compound represented by the following Chemical Formula 1 and containing a pyridyl group and a silyl group;

[0024] A lithium salt; and

[0025] A non-aqueous organic solvent.

[0026] Chemical Formula 1:

[0027]

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

[0029] A compound containing a pyridyl group and a silyl group;

[0030] Additional additive;

[0031] Lithium salt; and

[0032] Non-aqueous organic solvent.

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

[0034] A compound represented by the above Chemical Formula 1 and containing a pyridyl group and a silyl group;

[0035] Additional additive;

[0036] Lithium salt; and

[0037] Non-aqueous organic solvent.

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

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

[0040] The above 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 above 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] Advantages of the Invention

[0043] In the lithium secondary battery using the electrolyte for a lithium secondary battery of the present invention, the life performance at high temperature is improved, and a lithium secondary battery with excellent performance of suppressing the volume expansion of the secondary battery during high-temperature storage can be realized. In addition, the compound represented by Chemical Formula 1 of the present invention can form a stable coating film on the electrode surface through the pyridyl group and the silyl group.

[0044] The non-aqueous electrolyte for a lithium secondary battery of the present invention includes, as an additive, a compound containing a pyridyl group and a silyl group, particularly a compound represented by the following Chemical Formula 1, so as to form a stable coating film on the electrode surface, particularly on the surface of the negative electrode, which can effectively inhibit the dissolution of metal ions from the positive electrode and reduce the deterioration of the SEI film by removing by-products generated by the thermal decomposition of the lithium salt. Therefore, the non-aqueous electrolyte for a lithium secondary battery of the present invention can realize a lithium secondary battery with improved life performance at high temperature and excellent high-temperature storage stability. Detailed Embodiments

[0045] Hereinafter, the present invention will be described in more detail by way of examples. These examples are only for illustrating the present invention, and thus, these examples should not be construed as limiting the scope of the rights of the present invention.

[0046] The terms "comprising", "having", etc. used in this specification should be understood as open-ended terms that cover the possibility of including other components, unless otherwise mentioned in the sentence or passage containing such expressions.

[0047] In this specification, unless otherwise clearly marked, "%" represents weight percentage.

[0048] Hereinafter, the non-aqueous electrolyte for a lithium secondary battery and the lithium secondary battery including the non-aqueous electrolyte of the present invention will be specifically described.

[0049] <Additive for Electrolyte of Lithium Secondary Battery>

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

[0051] Chemical Formula 1:

[0052]

[0053] <Electrolyte for Lithium Secondary Battery>

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

[0055] A compound containing a pyridyl group and a silyl group;

[0056] A lithium salt; and

[0057] A non-aqueous organic solvent.

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

[0059] * A compound containing a pyridyl group and a silyl group represented by the above Chemical Formula 1;

[0060] A lithium salt; and

[0061] A non-aqueous organic solvent.

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

[0063] A compound containing a pyridyl group and a silyl group;

[0064] An additional additive;

[0065] A lithium salt; and

[0066] Non-aqueous organic solvent.

[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 silyl group;

[0069] Additional additives;

[0070] A lithium salt; and

[0071] Non-aqueous organic solvent.

[0072] Based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.05 wt% to 20 wt%.

[0073] Preferably, based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.05 wt% to 10 wt%.

[0074] More preferably, based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.05 wt% to 5 wt%, 0.05 wt% to 3 wt%, or 0.05 wt% to 2 wt%.

[0075] Based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.1 wt% to 20 wt%.

[0076] Preferably, based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.1 wt% to 10 wt%.

[0077] More preferably, based on the total weight of the electrolyte for the lithium secondary battery, the compound containing a pyridyl group and a silyl group may be included in an amount of 0.1 wt% to 5 wt%, 0.1 wt% to 3 wt%, or 0.1 wt% to 2 wt%.

[0078] When the compound containing a pyridyl group and a silyl group is included in an amount of less than 0.05 wt% based on the total weight of the electrolyte for the lithium secondary battery, the effect of preventing volume expansion and the effect of reducing internal resistance of the lithium secondary battery are insufficient. On the contrary, when the compound containing a pyridyl group and a silyl group is included in an amount of more than 20 wt% based on the total weight of the electrolyte for the lithium secondary battery, problems such as a decrease in high-temperature life characteristics and a decrease in high-temperature storage characteristics caused by an increase in internal resistance and a decrease in capacity of the secondary battery occur.

[0079] The electrolyte for the above lithium secondary battery 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 ester compounds, sulfite compounds, sulfone compounds, sulfate compounds, and sultone compounds.

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

[0081] Relative to the total weight of the electrolyte for the above lithium secondary battery, the above additional additives may be contained in an amount of 0.05 wt% to 20 wt%.

[0082] Preferably, relative to the total weight of the electrolyte for the above lithium secondary battery, the above additional additives may be contained in an amount of 0.05 wt% to 10 wt%.

[0083] More preferably, relative to the total weight of the electrolyte for the above lithium secondary battery, the above additional additives may be contained in an amount of 0.05 wt% to 5 wt%, and specifically may be contained in an amount of 0.05 wt% to 3 wt%.

[0084] When the above additional additives are contained in an amount less than 0.05 wt% relative to the total weight of the electrolyte for the above lithium secondary battery, the effect of forming a coating film on the electrode is very small, and thus the effect of suppressing side reactions between the electrode and the electrolyte may be reduced; while when the above additional additives are contained in an amount greater than 20 wt% relative to the total weight of the electrolyte for the above lithium secondary battery, an overly thick coating film will be formed on the electrode surface, increasing the interfacial resistance, thereby reducing the capacity.

[0085] In addition, the above lithium salt may include those selected from LiPF 6 、LiClO 4 、LiAsF6 , LiBF 4 , LiBF 6 , LiSbF 6 , LiAlO 4 , LiAlCl 4 , LiClO 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(C 2 F 5 SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , LiF 2 NO 4 S 2 and LiB(C 2 O 4 ) 2 at least one selected from the group consisting of

[0086] The dissociation degree of the lattice energy of the above-mentioned lithium salts is large. Therefore, it is preferable to use lithium salts with excellent ionic conductivity, thermal stability, and antioxidant properties. The above-mentioned lithium salts serve as a mobile channel for lithium ions in the secondary battery, thus enabling the basic operation of the lithium secondary battery.

[0087] Relative to the total amount of the electrolyte for the above-mentioned lithium secondary battery, the concentration of the above-mentioned lithium salt may be from 0.1 M (mol / L) to 2.5 M (mol / L).

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

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

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

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

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

[0093] In addition, the above cyclic carbonate 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 cyclic carbonate organic solvent with a high dielectric constant and a linear carbonate organic solvent with a low viscosity are mixed and used. The above cyclic carbonate organic solvent with a high dielectric constant has a high ionic conductivity that can improve the charge-discharge performance of the secondary battery, and the above linear carbonate organic solvent with a low viscosity can appropriately adjust the viscosity of the above cyclic 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 carbonate organic solvent with a high dielectric constant is used as the above cyclic carbonate solvent and is selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and mixtures thereof; the above carbonate organic solvent with a low viscosity is used as the above linear carbonate solvent and is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and mixtures thereof.

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

[0097] Therefore, preferably, as the above non-aqueous organic solvent, one or more solvents selected from the above cyclic carbonate solvents and one or more solvents selected from the above linear carbonate solvents are mixed and used.

[0098] For the mixed solvent of the above-mentioned linear carbonate solvent and the above-mentioned cyclic carbonate solvent, the above-mentioned linear carbonate solvent and the above-mentioned cyclic carbonate solvent can be mixed and used at a volume ratio of 9:1 to 1:9.

[0099] For the mixed solvent of the above-mentioned linear carbonate solvent and the above-mentioned cyclic carbonate solvent, considering the life characteristics and storage characteristics of the secondary battery, more preferably, the above-mentioned linear carbonate solvent and the above-mentioned cyclic carbonate solvent can be mixed and used at a volume ratio of 2:8 to 8:2.

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

[0101] The above-mentioned non-aqueous organic solvent may contain: 5 wt% to 40 wt% of the above-mentioned ethylene carbonate (EC), 5 wt% to 20 wt% of the above-mentioned propylene carbonate (PC), 10 wt% to 70 wt% of the above-mentioned ethyl methyl carbonate (EMC), and 10 wt% to 60 wt% of the above-mentioned 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, in the case of using artificial graphite as the negative electrode active material, it is preferable to use the above-mentioned ethylene carbonate (EC). Among the above-mentioned linear carbonate solvents, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC) with a low viscosity is preferably used.

[0103] Relative to the total amount of the electrolyte for the above-mentioned lithium secondary battery, 5% to 80% of the above-mentioned non-aqueous organic solvent can be included. Relative to the total amount of the electrolyte for the above-mentioned lithium secondary battery, 5% to 70% of the above-mentioned non-aqueous organic solvent can also be included.

[0104] <Lithium secondary battery>

[0105] The lithium secondary battery containing the above-mentioned non-aqueous electrolyte has improved life characteristics at high temperatures and excellent performance in suppressing battery thickness expansion during high-temperature storage.

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

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

[0108] A positive electrode;

[0109] A negative electrode;

[0110] A separator; and

[0111] Non-aqueous electrolyte

[0112] The above positive electrode may include at least one positive electrode active material selected from the group consisting of lithium metal oxides such as LiCoO 2 , LiFePO 4 , LiMnO 2 , LiMn 2 O 4 , LiNiO 2 or LiNi 1-x-y Co x M y O 2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, and M is Al, Sr, Mg, Mn, or La).

[0113] The above 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 mixtures of artificial graphite and natural graphite.

[0114] The above separator may be composed of a porous polymer membrane alone or may be composed of a laminate thereof. The above porous polymer membrane is prepared from at least one polyolefin polymer selected from the group consisting of ethylene polymers, propylene polymers, ethylene / butene copolymers, and ethylene / hexane copolymers. The above separator may include a coated film coated with a ceramic or polymer substance.

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

[0116] Additional additives;

[0117] Lithium salt; and

[0118] Non-aqueous organic solvent.

[0119] Chemical Formula 1:

[0120]

[0121] Examples of the above lithium secondary battery include: lithium metal secondary battery, lithium ion secondary battery, lithium polymer secondary battery, or lithium ion polymer secondary battery, etc., and are not limited thereto.

[0122] More specifically, the above-mentioned positive electrode active material is preferably one or more substances selected from cobalt, manganese, and nickel and a composite metal oxide with lithium. The solid solubility rate between the cobalt, manganese, and nickel metals of the above composite metal oxide can be various. In addition to these cobalt, manganese, and nickel metals, elements 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 can also be included.

[0123] Specifically, as the above-mentioned positive electrode active material, LiCoO 2 , LiFePO 4 , LiMnO 2 , LiMn 2 O 4 , LiNiO 2 or LiNi 1-x-y Co x M y O 2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, M is Al, Sr, Mg, Mn, or La), etc., lithium metal oxides or lithium intercalation compounds such as lithium chalcogenide compounds, but not limited thereto. Any substance that can be used as a positive electrode active material in a secondary battery can be used.

[0124] The above positive electrode includes: a current collector, and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material capable of adsorbing and releasing lithium, a binder, a conductive material, etc.

[0125] The above 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, carbon composite, carbon fiber, lithium metal, lithium alloy, or carbon-silicon composite, etc., can be used, but not limited thereto. Any substance that can be used as a negative electrode active material in a secondary battery can be used.

[0126] The above positive electrode and / or negative electrode can be prepared in the following manner: an electrode paste composition is prepared by dispersing an electrode active material, a binder, and a conductive material, and if necessary, a thickener in a solvent, and then the above paste composition is coated on an electrode current collector. Aluminum or aluminum alloy, etc., can usually be used as the positive electrode current collector, and copper or copper alloy, etc., can usually be used as the negative electrode current collector.

[0127] The shapes of the above positive electrode current collector and the above negative electrode current collector can be, for example: foil-shaped or mesh-shaped.

[0128] The above-mentioned binder is a substance that plays roles such as gelatinization of the active material, adhesion of the active material to each other, adhesion to the current collector, and buffering effect on the expansion and contraction of the active material. Any binder that can be used by those skilled in the art can be used. For example, the following can be used: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), copolymer of hexafluoropropylene and polyvinylidene fluoride (PVdF / HFP), polyvinyl acetate, alkylated polyethylene oxide, polyethylene ether, polymethyl methacrylate, polyethyl acrylate, polyacrylonitrile, polyvinylpyridine, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, epoxy resin, nylon, etc., but it is not limited thereto.

[0129] The above-mentioned conductive material is used to impart conductivity to the electrode. Therefore, for the battery formed, any conductive material that does not cause chemical changes can be used. The above-mentioned conductive material can be at least one selected from the group consisting of graphite-based conductive materials, carbon black-based conductive materials, and metal or metal compound-based conductive materials. Examples of the above-mentioned graphite-based conductive materials include artificial graphite, natural graphite, etc.; examples of the above-mentioned carbon black-based conductive materials include acetylene black, ketjen black, denka black, thermal black, channel black, etc.; examples of the above-mentioned metal or metal compound-based conductive materials include tin, tin oxide, tin phosphate (SnPO 4 )), titanium oxide, potassium titanate, perovskite substances such as LaSrCoO 3 , LaSrMnO 3 , etc. However, it is not limited to the conductive materials listed above.

[0130] For the above-mentioned thickener, as long as it can play the role of adjusting the viscosity of the active material slurry, there is no special limitation. For example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. can be used.

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

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

[0133] In addition, the above lithium secondary battery can be fabricated into various shapes such as angular, cylindrical, soft - pack, or coin - shaped.

[0134] Embodiments of the Invention

[0135] Hereinafter, the present invention will be described in more detail through examples. The protection scope of the invention should not be construed as being limited to these examples.

[0136] Preparing an electrolyte for a lithium secondary battery containing a compound, wherein the compound contains a pyridyl group and a silyl group

[0137] [Example 1]

[0138] LiPF was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio EC / EMC = 3 / 7) 6 and LiFSI so that their concentrations were 0.7 M and 0.3 M respectively. Then, 1.0 wt% of fluoroethylene carbonate (FEC), 1.0 wt% of lithium difluorophosphate (LiPO 2 F 2 ), 1.0 wt% of vinylene carbonate (VC), 0.5 wt% of ethylene sulfite (Esa), 0.5 wt% of 1,3 - propanesultone (PRS), and 0.5 wt% of the compound 2 - (allyldimethylsilyl)pyridine represented by the above Chemical Formula 1 (produced by Merck & Co., Inc.) were added to the above mixed solution, thereby preparing an electrolyte for a lithium secondary battery containing the pyridyl - and silyl - containing compound of Example 1.

[0139] Preparing a lithium secondary battery containing an electrolyte, wherein the electrolyte includes a compound containing a pyridyl group and a silyl group >

[0140] 94 wt% of the composition containing Li[Ni x Co 1-x-y Mn y O 2NCM-based cathode active material in the range of (0 < x < 0.5, 0 < y < 0.5), 3 wt% of conductive material (Super-P), and 3 wt% of binder (PVdF) were added to the organic solvent N-methyl-2-pyrrolidinone (NMP) to prepare the cathode active material slurry. The above-mentioned cathode active material slurry was coated on an aluminum thin film as the current collector and dried to prepare the cathode, and then the cathode was prepared by rolling with a rolling press. In addition, 96 wt% of graphite-based anode active material containing silicon oxide (SiOx), 1 wt% of conductive material (Super-P), 1.5 wt% of binder styrene-butadiene rubber (SBR), and 1.5 wt% of carboxymethyl cellulose (Carboxyl Methyl Cellulose, CMC) were mixed to prepare the anode active material slurry. The above-mentioned anode active material slurry was coated on a copper thin film as the anode current collector and dried to prepare the anode.

[0141] The cathode and anode prepared as described above were prepared, and a separator was interposed between them. Then, an electrolyte for a lithium secondary battery containing the compound having a pyridyl group and a silyl group of Example 1 was injected between the two electrodes sandwiching the above-mentioned separator to prepare an aluminum soft-pack type (Al-Pouch type) lithium secondary battery containing the electrolyte, and the above-mentioned electrolyte includes a compound having a pyridyl group and a silyl group.

[0142] [Comparative Example]

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

[0144] The non-aqueous electrolyte for a lithium secondary battery may contain a sultone compound as needed to prevent the decomposition of the non-aqueous electrolyte, thereby improving the high-temperature stability and the effect of suppressing battery swelling at high temperatures. The above-mentioned sultone compound may be at least one compound selected from 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 inhibitor additive, was used.

[0145] [Comparative Example 1]

[0146] LiPF was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio: EC / EMC = 3 / 7) 6 and LiFSI such that LiPF 6After the concentrations of [substance name] and LiFSI became 0.7 M and 0.3 M respectively, 1.0 weight percent of fluoroethylene carbonate (FEC), 1.0 weight percent of lithium difluorophosphate (LiPO 2 F 2 )), 1.0 weight percent of vinylene carbonate (VC), 0.5 weight percent of ethylene sulfate (Esa), 0.5 weight percent of 1,3 - propanesultone (PRS), and 0.5 weight percent of propane sultone (PS) were added to the above - mentioned mixed solution, thereby preparing an electrolyte for a lithium secondary battery of Comparative Example 1.

[0147] Preparing a lithium secondary battery containing an electrolyte, wherein the above - mentioned electrolyte contains 1,3 - propane sultone (PS) additive additive

[0148] As the electrolyte, the electrolyte for a lithium secondary battery of Comparative Example 1 containing 1,3 - propanesultone (PS) was used, instead of adding the 2 - (allyldimethylsilyl)pyridine compound represented by the compound of Chemical Formula 1 above. Except for this, a lithium secondary battery containing an electrolyte of 1,3 - propanesultone (PS) instead of the compound of Chemical Formula 1 was prepared by the same method as the preparation of the lithium secondary battery in the above - mentioned Example.

[0149] The components of the electrolytes for lithium secondary batteries in the above - mentioned Examples and Comparative Examples are shown in Table 1 below.

[0150] [Table 1]

[0151] [Components of the electrolyte for a lithium secondary battery]

[0152]

[0153] [Experimental Example]

[0154] [Experimental Example 1]

[0155] Measuring the high - temperature (45 °C) life capacity retention rate

[0156] Under high - temperature (45 °C) conditions, a pouch - type lithium secondary battery prepared using the electrolytes for lithium secondary batteries of the above - mentioned Examples and Comparative Examples was charged to 4.2 V at a 1C - rate, rested for 10 minutes, and then discharged to 2.7 V at a 1C - rate and rested for 10 minutes again. The discharge capacity (mAh) and life capacity retention rate (retention, %) of the battery were measured by repeating the above process 400 times. 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] The first discharge capacity (mAh) The 400th discharge capacity (mAh) Life capacity retention rate (%) Examples 890.9 709.9 79.7 Comparative examples 893.1 706.2 79.1

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

[0160] From this, it can be confirmed that by including a compound containing a pyridyl group and a silyl group, especially an electrolyte including a compound containing a pyridyl group and a silyl group represented by the above Chemical Formula 1, compared with the lithium secondary battery of the above - mentioned comparative example, the lithium secondary battery of the above - mentioned example has improved life performance at high temperature.

[0161] [Experimental Example 2]

[0162] Measuring the high - temperature (60 °C) storage characteristics

[0163] After storing the pouch - type lithium secondary battery prepared with the electrolytes of the above - mentioned examples and comparative examples at a high temperature (60 °C) for 6 weeks, the volume increase rate of the battery was measured. The volume increase rate of the lithium secondary battery after storing for 6 weeks under the condition of high temperature (60 °C) is shown in Table 3 below.

[0164] [Table 3]

[0165] Volume increase rate (%) after storage at 60 °C for 6 weeks Examples 4.35 Comparative examples 4.72

[0166] As shown in Table 3 above, in order to compare the high - temperature storage performance, after placing the lithium secondary battery of the example and the lithium secondary battery of the comparative example at a high temperature (60 °C) for 6 weeks, 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 a pyridyl group and a silyl group was lower than that of the comparative example containing 1,3 - propane sultone. It can be confirmed that, compared with the lithium secondary battery of the comparative example, the lithium secondary battery of the example has more excellent performance in terms of the volume increase rate of the battery during high - temperature storage.

[0167] Comparing the experimental results of the above - mentioned examples and comparative examples, 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 example including a compound containing a pyridyl group and a silyl group, especially the lithium secondary battery of the example using a compound containing a pyridyl group and a silyl group represented by the above Chemical Formula 1 to replace 1,3 - propane sultone (PS), has improved high - temperature life performance and excellent performance in terms of the volume increase rate of the battery during high - temperature storage.

Claims

1. A non-aqueous electrolyte for a lithium secondary battery, wherein, as a non-aqueous electrolyte for a lithium secondary battery, it contains: a lithium salt; a non-aqueous organic solvent; and an additive; the additive contains a compound having a pyridyl group and a silyl group.

2. The non-aqueous electrolyte for a lithium secondary battery 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 a lithium secondary battery according to claim 1 or 2, wherein, based on the total weight of the non-aqueous electrolyte for a lithium secondary battery, it contains 0.05 wt% to 20 wt% of the additive.

4. The non-aqueous electrolyte for a lithium secondary battery according to claim 1 or 2, wherein, it further includes an additional additive, and the additional additive is 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, it includes: the non-aqueous electrolyte for a lithium secondary battery according to claim 1 or claim 2, a positive electrode, a negative electrode, and a separator.

6. The lithium secondary battery according to claim 1 or 2, wherein, the negative electrode contains 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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