Lithium-ion rechargeable battery

Abstract

The present invention provides a lithium secondary battery having improved high-temperature storage characteristics and high-temperature cycle characteristics. The lithium secondary battery according to the present invention includes a positive electrode, a negative electrode including a silicon-based negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte including a lithium salt, an organic solvent, and an additive, and the additive may include a compound represented by Chemical Formula 1.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2022 - 0033019 filed on March 16, 2022 and Korean Patent Application No. 10 - 2023 - 0031448 filed on March 9, 2023, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification. The present invention relates to a lithium secondary battery with improved high - temperature storage characteristics and high - temperature cycle characteristics.

Background Art

[0002] As the dependence on electric energy in modern society gradually increases, an increase in the production of electric energy is required, and the development of a large - capacity power storage device capable of stably supplying electric power is being carried out.

[0003] Lithium - ion batteries have been in the spotlight as devices showing the highest energy density among commercialized power storage devices.

[0004] A lithium - ion battery is composed of a positive electrode made of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte containing an organic solvent containing a lithium salt, and a separator.

[0005] Among these, the positive electrode stores energy through the redox reaction of the transition metal, which ultimately results in the fact that the transition metal must be necessarily included in the positive electrode material.

[0006] However, repeated charging and discharging can cause the collapse of certain positive electrode structures, leading to the dissolution of the transition metals. Alternatively, under high operating potentials, the transition metals may dissolve due to acids formed by side reactions in the electrolyte or hydrolysis / thermal decomposition of lithium salts. The dissolved transition metals are known to not only increase the resistance of the positive electrode by being re-deposited, but also to increase the interfacial resistance of the negative electrode by being electrodeposited to the negative electrode via the electrolyte, causing self-discharge of the negative electrode, and destroying the SEI (Solid Electrolyte Interphase) film on the negative electrode surface, thereby promoting additional electrolyte decomposition reactions.

[0007] Furthermore, when a silicon-based negative electrode active material is used as the negative electrode component of the lithium-ion battery, the SEI layer may be lost due to electrode expansion as the cycle progresses, leading to increased resistance and increased electrolyte side reactions. Such problems can also cause damage to the electrode structure.

[0008] Therefore, there is a need for research on methods to prevent the degradation of secondary batteries by forming a robust passive film on the electrode surface. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention aims to provide a lithium secondary battery with improved high-temperature storage characteristics and high-temperature cycling characteristics by including a non-aqueous electrolyte containing an additive that can form a solid film on the electrode surface. [Means for solving the problem]

[0010] In one embodiment of the present invention for achieving the above objective, positive electrode, A negative electrode containing silicon-based negative electrode active material, A separator interposed between the positive electrode and the negative electrode, and It comprises a non-aqueous electrolyte containing a lithium salt, an organic solvent, and additives. The additive provides a lithium secondary battery containing a compound represented by the following Chemical Formula 1. [Chemical Formula] In Chemical Formula 1, R1 to R3 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms.

[0011] On the other hand, the silicon-based negative electrode active material may be at least one selected from the group consisting of silicon, silicon chloride, silicon oxide (SiO x (0 < x < 2)), and silicon-carbon composite (SiC). Specifically, the silicon-based negative electrode active material may be silicon oxide.

[0012] On the other hand, the negative electrode may further contain a carbon-based negative electrode active material. In this case, the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 1:99 to 20:80, specifically 1:99 to 10:90, by weight ratio.

[0013] On the other hand, the positive electrode may contain a positive electrode active material containing at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al) and lithium.

[0014] On the other hand, in Chemical Formula 1, R1 to R3 may each independently be an alkyl group having 1 to 8 carbon atoms. Specifically, in Chemical Formula 1, R1 may be an alkyl group having 1 to 5 carbon atoms, and R2 to R3 may each independently be an alkyl group having 2 to 6 carbon atoms. More specifically, in Chemical Formula 1, R1 may be an alkyl group having 1 to 3 carbon atoms, and R2 to R3 may each independently be an alkyl group having 2 to 5 carbon atoms.

[0015] On the other hand, the compound represented by Chemical Formula 1 may be contained in an amount of 0.1% to 5.0% by weight based on the total weight of the non-aqueous electrolyte. [Advantages of the Invention]

[0016] To solve the aforementioned problems, the present invention provides a lithium secondary battery that uses a combination of a negative electrode containing a silicon-based negative electrode active material and a non-aqueous electrolyte containing a compound with a phosphonate (-PO(OR)2) functional group in its structure as an additive. This allows for the formation of a robust inorganic film on the surface of the negative electrode containing the silicon-based negative electrode active material, thereby preventing battery degradation and achieving excellent cycle characteristics and high-temperature storage stability. [Modes for carrying out the invention]

[0017] The present invention will be described in more detail below. The terms and words used herein and in the claims are used solely to describe exemplary embodiments and are not intended to limit the invention.

[0018] For example, in this specification, terms such as “includes,” “equip,” or “have” are used to specify the existence of implemented features, figures, stages, components, or combinations thereof, and other parts may be added unless “only” is used.

[0019] Furthermore, in this specification, "%" means weight percent unless otherwise explicitly indicated.

[0020] In this specification, unless otherwise defined, "substitution" means that at least one hydrogen atom bonded to a carbon atom is substituted with an element other than hydrogen, for example, with an alkyl group having 1 to 5 carbon atoms or with a fluorine element.

[0021] Normally, the passivation performance of the SEI film formed on the negative electrode surface by electrolyte decomposition and the CEI film formed on the positive electrode surface under high potential conditions are factors that greatly influence the improvement of the storage performance of secondary batteries. On the other hand, Lewis acid substances generated by the thermal decomposition of lithium salts (LiPF6) widely used in lithium-ion batteries are known to degrade such negative electrode films (SEI) and positive electrode films (CEI). That is, when the positive electrode surface is degraded by the attack of the Lewis acid substances, a side reaction with the electrolyte is triggered, resulting in the dissolution of transition metals and a change in the local structure of the positive electrode surface, which can increase the surface resistance of the electrode and decrease the expressed capacity. In addition, structural changes of the positive electrode due to repeated charging and discharging cause transition metal ions to dissolve from the positive electrode. These dissolved transition metal ions then move to the negative electrode via the electrolyte and are electrodeposited onto the negative electrode, causing self-discharge of the negative electrode and destroying the film (SEI), thereby promoting additional electrolyte decomposition reactions and increasing the interfacial resistance of the negative and positive electrodes.

[0022] The present invention provides a lithium secondary battery that exhibits excellent cycle characteristics and high-temperature storage stability by using a negative electrode containing a silicon-based negative electrode active material and a non-aqueous electrolyte containing an additive that forms a robust film on the negative electrode surface and the positive electrode surface, thereby suppressing degradation of the positive and negative electrodes during rapid charging.

[0023] Lithium-ion rechargeable battery According to one embodiment of the present invention, the lithium secondary battery of the present invention is positive electrode, A negative electrode containing silicon-based negative electrode active material, A separator interposed between the positive electrode and the negative electrode, and It comprises a non-aqueous electrolyte containing a lithium salt, an organic solvent, and additives. The aforementioned additive may contain a compound represented by the following chemical formula 1. [ka] In the aforementioned chemical formula 1, R1 to R3 are each independently either hydrogen or an alkyl group having 1 to 10 carbon atoms.

[0024] Hereinafter, the configuration of the lithium secondary battery of the present invention will be specifically described. (1) Positive electrode The positive electrode according to the present invention may contain a positive electrode active material, and may further contain a conductive material and / or a binder as required.

[0025] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, it may contain at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al), and a lithium transition metal oxide represented by the following Chemical Formula 2 containing lithium. [Chemical Formula 2] Li 1+a Ni x Co y M 1 z M 2 w O2 In the Chemical Formula 2, M 1 is Mn, Al, or a combination thereof, M 2 is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca, and Sr, and 0≦a≦0.5, 0.55<x<1.0 , 0<y≦0.4, 0<z≦0.4, 0≦w≦0.1.

[0026] The 1 + a represents the atomic fraction of lithium in the lithium transition metal oxide, and 0≦a≦0.5, preferably 0≦a≦0.2, more preferably 0≦a≦0.1. When the atomic fraction of lithium satisfies the above range, the crystal structure of the lithium transition metal oxide can be stably formed.

[0027] The x represents the atomic fraction of nickel among all the transition metal elements in the lithium transition metal oxide 、0 .55<x<1.0<Overall, 0.6 ≦ x ≦ 0.98, and more specifically, 0.6 ≦ x ≦ 0.95 may be satisfied. When the atomic fraction of nickel satisfies the above range, a high energy density is exhibited, so that a high capacity can be realized.

[0028] Said y represents the atomic fraction of cobalt among all transition metal elements in the lithium transition metal oxide, and 0 < y ≦ 0.4, specifically 0 < y ≦ 0.3, and more specifically 0.05 ≦ y ≦ 0.3 may be satisfied. When the atomic fraction of cobalt satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0029] [[ID=‎7]] Said z represents the atomic fraction of element M among all transition metal elements in the lithium transition metal oxide 1 and 0 < z ≦ 0.4, preferably 0 < z ≦ 0.3, and more preferably 0.01 ≦ z ≦ 0.3 may be satisfied. When the atomic fraction of element M 1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0030] Said w represents the atomic fraction of element M among all transition metal elements in the lithium transition metal oxide 2 and 0 < w ≦ 0.1, preferably 0 < w ≦ 0.05, and more preferably 0 < w ≦ 0.02.

[0031] Specifically, in order to realize a high-capacity battery, the positive electrode active material has a Li(Ni 0.6 Mn 0.2 Co 0.2 )O2 with a Ni content of 0.55 atm% or more, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, Li(Ni 0.7 Mn 0.2 Co 0.1 )O2, Li(Ni [[ID=‎41]] 0.8 Mn 0.1 Co 0.1 )O2, Li(Ni 0.8 Co 0.15 Al 0.05 [[ID=5‎2]]O2, Li(Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 )O2, or Li(Ni0.90 Mn 0.05 Co 0.05 It may contain a lithium composite transition metal oxide such as )O2.

[0032] In addition, the positive electrode active material may be used in combination with a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2(0 < Y < 1), LiMn 2-z Ni z O4(0 < Z < 2), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2(0 < Y1 < 1), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2(0 < Y2 < 1), LiMn 2-z1 Co<00​​​​​​​​​​Next, the conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity in the battery without causing a chemical change. Specific examples include carbon powder such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. One of these may be used alone or in mixtures of two or more.

[0034] Next, the binder plays a role in improving adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector.

[0035] Examples of such binders include fluoropolymer binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders, which may be used individually or in mixtures of two or more.

[0036] On the other hand, the positive electrode of the present invention may be manufactured by a method for manufacturing a positive electrode known in the art. For example, the positive electrode may be manufactured by a method in which a positive electrode slurry, prepared by dissolving or dispersing a positive electrode active material, a binder, and / or a conductive material in a solvent, is applied to a positive electrode current collector, and then dried and rolled; or by a method in which the positive electrode slurry is cast onto a separate support to form a film, and then the film obtained by peeling off the support is laminated onto the positive electrode current collector.

[0037] The positive electrode active material may be included in an amount of 80% to 98% by weight, more specifically 85% to 98% by weight, based on the total weight of the positive electrode slurry. When the positive electrode active material is included in this range, excellent capacity characteristics can be observed.

[0038] The conductive material may be present in an amount of 0.1% to 10% by weight, preferably 0.1% to 5% by weight, based on the total weight of the positive electrode slurry, and the binder may be present in an amount of 0.1% to 15% by weight, preferably 0.1% to 10% by weight, based on the total weight of the positive electrode active material layer.

[0039] The positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes to the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., may be used. The positive electrode current collector may also have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0040] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, etc. One of these alone or a mixture of two or more may be used. The amount of the solvent used may be adjusted so that the positive electrode composite material has an appropriate viscosity, considering the coating thickness of the positive electrode composite material, production yield, workability, etc., and is not particularly limited.

[0041] (2) Negative electrode The negative electrode according to the present invention contains a negative electrode active material, and may further contain a conductive material and / or a binder as necessary.

[0042] As the negative electrode active material, a silicon-based negative electrode active material used in the industry may be used, and a carbon-based negative electrode active material may be mixed and used together with the silicon-based negative electrode active material.

[0043] The silicon (Si)-based negative electrode active material includes, for example, silicon (Si), silicon carbide (SiC), silicon chloride, and silicon oxide (SiO x , where 0 < x < 2), Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), and may include one or more selected from the group consisting of. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof may be selected.

[0044] Specifically, the negative electrode active material may contain silicon dioxide (SiO2) and amorphous silicon in a 1:1 weight ratio mixture.

[0045] *On the other hand, the silicon-based anode active material can obtain higher capacity characteristics compared to the carbon-based anode active material. However, in the case of anodes containing silicon-based anode active material, during initial charging and discharging, a SEI film containing more oxygen (O)-rich components is formed on the surface due to reaction with the non-aqueous electrolyte compared to graphite anodes. Such an SEI film is easily decomposed if Lewis acids such as HF or PF5 are present in the electrolyte, which may cause side reactions of the electrolyte or induce electrolyte consumption. Therefore, when using silicon-based anode active material as a negative electrode component, it is important to form a robust SEI film containing inorganic components in order to suppress Si decomposition by HF. In other words, when using anodes containing silicon-based anode active material, the non-aqueous electrolyte used in combination is required to contain additives that can suppress the generation of Lewis acids such as HF and PF5 in the electrolyte, or remove (scavenge) the generated Lewis acids, while simultaneously forming an inorganic film, in order to stably maintain the SEI film.

[0046] Furthermore, as carbon-based anode active materials that can be used in combination with the silicon-based anode active material, a variety of carbon-based anode active materials used in the industry may be used, such as graphite-based materials like natural graphite, artificial graphite, and Kish graphite; high-temperature calcined carbon such as pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch-derived cokes, as well as soft carbon and hard carbon. The shape of the carbon-based anode active material is not particularly limited, and materials of various shapes such as amorphous, plate-like, flake-like, spherical, or fibrous may be used.

[0047] On the other hand, the silicon-based anode active material and the carbon-based anode active material may be mixed and used in a weight ratio of 1:99 to 20:80. When the aforementioned mixing ratio of the silicon-based anode active material and the carbon-based anode active material is satisfied, the volume expansion of the silicon-based anode active material is suppressed while improving capacity characteristics, ensuring excellent cycle performance of the battery and enabling the realization of high capacity. If the mixing ratio of the silicon-based anode active material is less than 1 by weight, it becomes difficult to increase the energy density, making it difficult to increase the capacity of the battery, and if it exceeds 20 by weight, the degree of volume expansion of the anode may increase. Specifically, the mixing ratio of the silicon-based anode active material and the carbon-based anode active material may be 1:99 to 10:90 by weight, more specifically 3:97 to 5:95, and more specifically 5:95 to 3:9.

[0048] Next, the conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, as a component for further improving the conductivity of the negative electrode active material. Specifically, the conductive material may be carbon powder such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives, and may be the same as or different from the conductive material applied to the positive electrode.

[0049] The binder is a component that assists in the adhesion between the conductive material, the active material, and the current collector. Typical examples include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders. The binder used may be the same as or different from the binder used for the positive electrode.

[0050] The negative electrode may be manufactured by a method for manufacturing negative electrodes known in the art. For example, the negative electrode may be manufactured by applying a negative electrode slurry, which is prepared by dissolving or dispersing a negative electrode active material, a binder, and a conductive material selectively in a solvent, onto a negative electrode current collector, and then drying and rolling it; or by casting the negative electrode slurry onto a separate support to form a film, peeling off the support, and then laminating the resulting film onto the negative electrode current collector.

[0051] The negative electrode active material may be present in an amount of 80% to 99% by weight based on the total weight of the negative electrode slurry. When the content of the negative electrode active material satisfies the above range, excellent capacitance characteristics and electrochemical properties can be obtained.

[0052] The conductive material may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode slurry, and the binder may be included in an amount of 0.1 to 15% by weight, preferably 0.1 to 10% by weight, based on the total weight of the negative electrode slurry.

[0053] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treatment with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0054] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used individually or in mixtures of two or more. The amount of solvent used is not particularly limited, and should be adjusted so that the negative electrode slurry has an appropriate viscosity, taking into consideration the coating thickness of the negative electrode mixture, manufacturing yield, workability, etc.

[0055] (3) Separator The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations, and one that has low resistance to lithium salt ion movement while having excellent electrolyte moisture retention capacity is particularly preferred.

[0056] Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or porous polymer films made from polyolefin polymers, or laminated structures of two or more layers thereof, may be used as separators. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and may be selectively used as single-layer or multi-layer structures.

[0057] (4) Non-aqueous electrolyte The lithium secondary battery according to the present invention comprises a non-aqueous electrolyte containing a lithium salt, an organic solvent, and an additive.

[0058] (4-1) Lithium salt First, in the non-aqueous electrolyte of the present invention, the lithium salt may be any lithium salt that is commonly used in non-aqueous electrolytes for lithium secondary batteries, for example, Li as a cation. + It includes F as an anion. - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - ClO4 - B 10 Cl 10 - AlCl4 - AlO4 - PF6 - CF3SO3 - CH3CO2 - CF3CO2 - AsF6 - SbF6 - CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - , C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2) 2CH - CF3(CF2)7SO3 - and SCN - At least one of the following groups can be selected.

[0059] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl10 It may contain a single substance or a mixture of two or more selected from the group consisting of LiAlCl4, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (lithium bis(pentafluoroethanesulfonyl)imide, LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI). In addition, lithium salts commonly used in the electrolyte of lithium secondary batteries may be used without limitation.

[0060] The lithium salt may be appropriately changed within the range of normal use. However, in order to obtain the effect of forming an optimal coating for preventing corrosion of the electrode surface, it may be contained in the electrolyte at a concentration of 0.8M to 4.0M, specifically 1.0M to 3.0M.

[0061] When the concentration of the lithium salt is within the above range, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation properties, and by improving the mobility of lithium ions, the effects of improving the capacity characteristics and cycle characteristics of the lithium secondary battery can be obtained.

[0062] (4-2) Organic Solvent Also, the description of the organic solvent is as follows. As the non-aqueous organic solvent, various organic solvents commonly used in non-aqueous electrolytes may be used without limitation, and decomposition due to oxidation reactions or the like during the charge and discharge process of the secondary battery can be minimized, and as long as it can exhibit the intended characteristics together with additives, there is no limitation on its type.

[0063] Specifically, the non-aqueous organic solvent may include (i) cyclic carbonate-based organic solvents, (ii) linear carbonate-based organic solvents, or (iii) mixed organic solvents thereof.

[0064] The (i) cyclic carbonate-based organic solvent is a high-viscosity organic solvent with a high dielectric constant that readily dissociates lithium salts in a non-aqueous electrolyte. Specific examples of such organic solvents include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. Among these, at least one of ethylene carbonate and propylene carbonate may be included.

[0065] The (ii) linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and specific examples therein may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and specifically may include one of dimethyl carbonate and ethyl methyl carbonate.

[0066] Furthermore, in order to ensure high ionic conductivity, the (i) cyclic carbonate organic solvent and (ii) linear carbonate organic solvent may be mixed and used in a volume ratio of 10:90 to 50:50, specifically 20:80 to 40:60.

[0067] Furthermore, the non-aqueous electrolyte according to the present invention further contains at least one organic solvent, which has a lower melting point and higher stability at high temperatures compared to the cyclic carbonate organic solvent and / or linear carbonate organic solvent, comprising (iv) a linear ester organic solvent and (v) a cyclic ester organic solvent, thereby further improving the ionic conductivity of the non-aqueous electrolyte according to the present invention.

[0068] The (iv) linear ester organic solvent mentioned above includes, as a typical example, at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, and specifically may include at least one of ethyl propionate and propyl propionate.

[0069] The (iv) cyclic ester organic solvent may contain at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0070] On the other hand, the organic solvent may be used with additional organic solvents commonly used in electrolytes for lithium secondary batteries, without limitation, as needed. For example, it may further contain at least one organic solvent from among ether-based organic solvents, amide-based organic solvents, and nitrile-based organic solvents.

[0071] On the other hand, the remainder of the non-aqueous electrolyte of the present invention, excluding the lithium salt, additives, and other additives, may all be organic solvents unless otherwise specified.

[0072] (4-3) Additives On the other hand, the additive may include a compound represented by the following chemical formula 1.

[0073] [ka]

[0074] In the aforementioned chemical formula 1, R1 to R3 are each independently either hydrogen or an alkyl group having 1 to 10 carbon atoms.

[0075] As mentioned above, in the case of a negative electrode containing silicon-based negative electrode active material, the reaction with the electrolyte results in an SEI film on the negative electrode surface containing a large amount of oxygen (O)-rich components. Therefore, in order to stably maintain such an SEI film, it is necessary to use an additive that can suppress the generation of Lewis acids such as HF or PF5 in the electrolyte, or remove (or scavenge) the generated Lewis acids.

[0076] The compound represented by chemical formula 1 contains a phosphonate (-PO(OR)2) group in its structure, which allows it to form an inorganic film on the negative electrode surface containing a silicon-based negative electrode active material. This prevents Si decomposition by HF and the resulting capacity loss, and mitigates electrolyte depletion and film thickness increase due to SEI film decomposition and regeneration. Furthermore, the compound represented by chemical formula 1 contains an unsubstituted alkoxy group to fluorine as a terminal group, which prevents the terminal group from being removed under high temperature and high potential conditions, thereby suppressing side reactions caused by the removed substituent, such as gas generation. Moreover, the compound represented by chemical formula 1 contains a cyanide (-CN) functional group in its structure, which allows it to form a ligand with transition metals and create a stable CEI film on the positive electrode surface. This prevents side reactions between the positive electrode and electrolytes during high-temperature storage and suppresses metal elution.

[0077] Therefore, by employing a non-aqueous electrolyte containing the compound represented by chemical formula 1 as a non-aqueous electrolyte additive, it is possible to manufacture a lithium secondary battery that exhibits excellent cycle characteristics and high-temperature storage stability.

[0078] On the other hand, if R1 to R3 in Chemical Formula 1 are each independently alkyl groups having more than 10 carbon atoms, the solubility in organic solvents may increase due to the increase in the molecular structure and molecular weight of the compound, which may increase the electrolyte viscosity and decrease the electrolyte impregnation ability. Furthermore, if R1 to R3 in Chemical Formula 1 are each independently alkyl groups having more than 10 carbon atoms, the amount of gas generated may increase during the additive decomposition reaction in which oxygen-phosphorus bonds, oxygen-carbon bonds, or carbon-carbon bonds are broken during charging and discharging.

[0079] Specifically, in the above chemical formula 1, R1 to R3 may each be an alkyl group having 1 to 8 carbon atoms independently. Furthermore, R1 may be an alkyl group having 1 to 5 carbon atoms, and R2 to R3 may each be an alkyl group having 2 to 6 carbon atoms independently. Furthermore, R1 may be an alkyl group having 1 to 3 carbon atoms, and R2 to R3 may each be an alkyl group having 2 to 5 carbon atoms independently.

[0080] More specifically, the compound represented by chemical formula 1 may include the compound represented by the following chemical formula 1a.

[0081] [ka]

[0082] On the other hand, the compound of chemical formula 1 may be included in an amount of 0.1% to 5.0% by weight based on the total weight of the non-aqueous electrolyte.

[0083] When the compound represented by chemical formula 1 is included within the specified range, a secondary battery with improved performance can be manufactured by forming a robust film on the negative and positive electrodes while preventing side reactions caused by additives, thereby effectively preventing deterioration of the negative electrode during rapid charging and discharging. Specifically, if the content of the compound represented by chemical formula 1 is 0.1% by weight or more, the effect of removing thermal decomposition products of lithium salts such as HF or PF5 and the film formation effect on the surfaces of the negative and positive electrodes can be maintained more stably during the battery operating time. Furthermore, if the content of the compound represented by chemical formula 1 is 5.0% by weight or less, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation, effectively suppressing the increase in battery resistance due to the decomposition of additives, and preventing a decrease in the ionic conductivity of the electrolyte, thus preventing a decrease in rate characteristics and low-temperature life characteristics.

[0084] More specifically, the compound represented by chemical formula 1 may be present in an amount of 0.1% to 3.0% by weight, more preferably 0.3% to 1.0% by weight.

[0085] (4-4) Other additives On the other hand, the non-aqueous electrolyte may contain other additives as needed to prevent the non-aqueous electrolyte from decomposing in a high-power environment, thereby inducing the collapse of the negative electrode, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery swelling at high temperatures.

[0086] Such other additives may include, as typical examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0087] Examples of the cyclic carbonate compound include vinylene carbonate (VC) or vinylethylene carbonate.

[0088] Examples of the halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0089] The sultone compounds include at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, and 1-methyl-1,3-propensultone.

[0090] Examples of the aforementioned sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyltrimethylene sulfate (MTMS).

[0091] The phosphate compound mentioned above includes one or more compounds selected from the group consisting of lithium difluoro(bisoxalato) phosphate, lithium difluorophosphate, tris(trimethylsilyl) phosphate, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphate.

[0092] Examples of the borate compounds include tetraphenylborate and lithium oxalyl difluoroborate.

[0093] The nitrile compounds mentioned above include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0094] Examples of the benzene-based compound include fluorobenzene, examples of the amine-based compound include triethanolamine or ethylenediamine, and examples of the silane-based compound include tetravinylsilane.

[0095] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and includes one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2), and LiBF4).

[0096] When other additives such as vinylene carbonate, vinylethylene carbonate, or succinonitrile are included, a more robust SEI film can be formed on the negative electrode surface during the initial activation process of the secondary battery.

[0097] The aforementioned other additives may be used in a mixture of two or more types, and may be included in an amount of 50% by weight or less, specifically 0.01% to 10% by weight, and preferably 0.05% to 5.0% by weight, based on the total weight of the non-aqueous electrolyte. If the content of the aforementioned other additives is less than 0.01% by weight, the effect of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery will be slight, and if the content of the aforementioned other additives exceeds 50% by weight, excessive side reactions may occur in the electrolyte during charging and discharging of the battery. In particular, when an excessive amount of the SEI film-forming additive is added, it may not decompose sufficiently at high temperatures and may remain unreacted or precipitated in the electrolyte at room temperature. This may cause side reactions that reduce the life or resistance characteristics of the secondary battery.

[0098] On the other hand, the lithium secondary battery of the present invention may be manufactured by conventional methods known in the art, specifically by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are sequentially stacked, housing it in a battery case, and then pouring in the non-aqueous electrolyte.

[0099] The external shape of the lithium secondary battery according to the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-type, or coin-type, using a can.

[0100] Furthermore, the lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also preferably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells. Specifically, the lithium secondary battery according to the present invention can be usefully used in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the electric vehicle field such as hybrid electric vehicles (HEVs).

[0101] The present invention will be described in detail below with reference to examples. However, the examples of the present invention may be modified into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0102] Examples Example 1. (Manufacturing of non-aqueous electrolytes) A non-aqueous electrolyte was prepared by dissolving LiPF6 in an organic solvent mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M. Then, a compound represented by chemical formula 1a was added in an amount of 0.1% by weight, vinylene carbonate (VC) in an amount of 1.0% by weight, and 1,3-propanesultone (PS) in an amount of 0.5% by weight (see Table 1 below).

[0103] (Manufacturing of secondary batteries) Lithium nickel-cobalt-manganese oxide (Li(Ni)) is used as the positive electrode active material particle. 0.8 Co 0.1 Mn 0.1A positive electrode slurry (solid content 85.0% by weight) was prepared by adding carbon black as a conductive material and polyvinylidene fluoride as a binder in a weight ratio of 97.5:1:1.5 to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode slurry was applied to a positive electrode current collector (Al thin film) with a thickness of 15 μm, dried, and roll-pressed to produce a positive electrode.

[0104] A negative electrode slurry (solid content: 60% by weight) was prepared by adding a negative electrode active material (graphite and SiO=95:5 by weight), a binder (SBR-CMC), and a conductive material (carbon black) to water, the solvent, in a weight ratio of 95:3.5:1.5. The negative electrode slurry was applied to a 6 μm thick copper (Cu) thin film, which was a negative electrode current collector, and dried, after which a negative electrode was manufactured by roll pressing.

[0105] After manufacturing an electrode assembly by interposing a porous polypropylene separator between the manufactured positive electrode and negative electrode, the assembly was placed in a battery case, and the manufactured non-aqueous electrolyte was poured in to produce a lithium secondary battery.

[0106] Example 2. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then a non-aqueous electrolyte was prepared by adding 0.5% by weight of the compound represented by chemical formula 1a, 1.0% by weight of vinylene carbonate (VC), and 0.5% by weight of 1,3-propanesultone (PS) (see Table 1 below).

[0107] Example 3. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then a non-aqueous electrolyte was prepared by adding 1.0% by weight of the compound represented by chemical formula 1a, 1.0% by weight of vinylene carbonate (VC), and 0.5% by weight of 1,3-propanesultone (PS) (see Table 1 below).

[0108] Example 4. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then a non-aqueous electrolyte was prepared by adding 5.0% by weight of the compound represented by chemical formula 1a, 1.0% by weight of vinylene carbonate (VC), and 0.5% by weight of 1,3-propanesultone (PS) (see Table 1 below).

[0109] Example 5. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then a non-aqueous electrolyte was prepared by adding 6.0% by weight of the compound represented by chemical formula 1a, 1.0% by weight of vinylene carbonate (VC), and 0.5% by weight of 1,3-propanesultone (PS) (see Table 1 below).

[0110] Comparative Example 1. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then vinylene carbonate (VC) was added as an additive in an amount of 1.0 wt% and 1,3-propanesultone (PS) in an amount of 0.5 wt% to prepare a non-aqueous electrolyte (see Table 1 below).

[0111] Comparative Example 2. A lithium secondary battery was manufactured in the same manner as in Example 2, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then 0.5% by weight of the compound represented by Chemical Formula 3 was added as an additive instead of the compound of Chemical Formula 1a to produce a non-aqueous electrolyte (see Table 1 below).

[0112] [ka]

[0113] Comparative Example 3. A lithium secondary battery was manufactured in the same manner as in Example 3, except that LiPF6 was dissolved in a non-aqueous organic solvent to a concentration of 1.0 M, and then 1.0% by weight of the compound represented by Chemical Formula 3 was added as an additive instead of the compound of Chemical Formula 1a to produce a non-aqueous electrolyte (see Table 1 below).

[0114] Comparative Example 4. (Manufacturing of lithium-ion batteries) Lithium nickel-cobalt-manganese oxide (Li(Ni)) is used as the positive electrode active material particle. 0.8 Co 0.1 Mn 0.1 A positive electrode slurry (solid content 85.0% by weight) was prepared by adding carbon black as a conductive material and polyvinylidene fluoride as a binder in a weight ratio of 97.5:1:1.5 to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode slurry was applied to a positive electrode current collector (Al thin film) with a thickness of 15 μm, dried, and roll-pressed to produce a positive electrode.

[0115] A negative electrode slurry (solid content: 60% by weight) was prepared by adding a negative electrode active material (graphite), a binder (SBR-CMC), and a conductive material (carbon black) to water, the solvent, in a weight ratio of 95:3.5:1.5. The negative electrode slurry was applied to a 6 μm thick copper (Cu) thin film, which was a negative electrode current collector, and dried. After that, a negative electrode was manufactured by performing a roll press.

[0116] After manufacturing the electrode assembly by interposing a porous polypropylene separator between the manufactured positive and negative electrodes, it was placed in a battery case. Subsequently, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte produced in Example 3 was injected.

[0117] [Table 1]

[0118] On the other hand, the abbreviations for the compounds in Table 1 above mean the following: EC: Ethylene carbonate EMC: Ethyl methyl carbonate VC: Vinylen carbonate PS: 1,3-propanethultone

[0119] Experimental example Experimental Example 1. Performance evaluation after high-temperature storage. The lithium secondary batteries of Examples 1-5 and Comparative Examples 1-4 were each charged to 4.2V at 0.2C in CC-CV mode, and then stored in a 60°C chamber for 30 days. The OCV was measured before storage, and then measured again after 30 days of storage, with the change expressed as dOCV. Subsequently, each secondary battery was discharged to 2.5V at 0.2C in CC mode, and the gas was extracted. The total amount of gas generated after high-temperature storage is recorded as the gas generation amount in Table 2 below. [Table 2]

[0120] Upon examining Table 2, it can be confirmed that in the case of secondary batteries of Examples 1 to 5, which used a non-aqueous electrolyte containing the compound of chemical formula 1a, the dOCV and gas generation amount decreased compared to the secondary battery of Comparative Example 1.

[0121] Furthermore, when comparing the secondary batteries of Examples 2 and 3, which contain the same amount of additive, with the secondary batteries of Comparative Examples 2 and 3, it can be confirmed that in the case of the secondary batteries of Examples 2 and 3, which use a non-aqueous electrolyte containing the compound of chemical formula 1a of the present invention, the dOCV and gas generation amount were reduced compared to the secondary batteries of Comparative Examples 2 and 3.

[0122] Considering these results, it can be confirmed that the compound of chemical formula 1a of the present invention forms a stable film on the surfaces of the negative and positive electrodes, thereby suppressing side reactions of the electrolyte during high-temperature storage, and thus reducing dOCV and gas generation.

[0123] Furthermore, comparing the secondary battery of Example 3, which has a non-aqueous electrolyte containing the same amount of additive, with the secondary battery of Comparative Example 4, it can be confirmed that in the case of the secondary battery of Example 3 of the present invention, which uses a negative electrode containing a silicon-based negative electrode active material, the dOCV is reduced compared to the secondary battery of Comparative Example 4, and the effect of suppressing gas generation is further improved.

[0124] Experimental Example 2. Performance Evaluation After Rapid Charging and Discharging The lithium secondary batteries of Examples 1-5 and Comparative Examples 1-4 were charged to 4.2V at 3C in CC-CV mode and discharged to 2.5V at 0.2C in CC mode, with each cycle being defined as 100 rapid charge-discharge cycles. After these cycles, the capacity retention rate (%) and resistance increase rate (%) were calculated, and the results are shown in Table 3 below.

[0125] [Table 3]

[0126] Upon examining Table 3, it can be confirmed that, in the case of secondary batteries of Examples 1 to 4, which use a non-aqueous electrolyte containing the compound of chemical formula 1a, a better capacity retention rate can be secured after rapid charging and discharging compared to the secondary battery of Comparative Example 1, and the resistance increase rate has decreased.

[0127] On the other hand, in the case of the secondary battery of Example 5, which has a non-aqueous electrolyte containing a slightly larger amount of additives, it can be confirmed that the capacity retention rate is slightly reduced and the resistance increase rate is slightly increased compared to the secondary batteries of Examples 1 to 4 due to the side reactions of the additives.

[0128] On the other hand, when comparing the secondary batteries of Examples 2 and 3, which contain the same amount of additive, with the secondary batteries of Comparative Examples 2 and 3, it can be confirmed that in the case of the secondary batteries of Examples 2 and 3, which use a non-aqueous electrolyte containing the compound of chemical formula 1a of the present invention, the capacity retention rate after rapid charging and discharging is higher and the resistance increase rate is lower compared to the secondary batteries of Comparative Examples 2 and 3.

[0129] Furthermore, comparing the secondary battery of Example 3, which has a non-aqueous electrolyte containing the same amount of additive, with the secondary battery of Comparative Example 4, it can be confirmed that in the case of the secondary battery of Example 3 of the present invention, which uses a negative electrode containing a silicon-based negative electrode active material, the capacity retention rate after rapid charge and discharge is higher and the resistance increase rate is lower compared to the secondary battery of Comparative Example 4.

Claims

1. Positive electrode and, A negative electrode containing a silicon-based negative electrode active material and a carbon-based negative electrode active material, A separator interposed between the positive electrode and the negative electrode, A non-aqueous electrolyte containing a lithium salt, an organic solvent, and an additive, The aforementioned additive contains a compound represented by the following chemical formula 1, The mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material is 1:99 to 20:80 by weight, for lithium secondary batteries: 【Chemistry 1】 In the aforementioned chemical formula 1, The aforementioned R1 is an alkyl group having 1 to 3 carbon atoms. Each of the R2 to R3 is independently an alkyl group having 2 to 5 carbon atoms.

2. The silicon-based negative electrode active material is silicon, silicon chloride, silicon oxide (SiO₂ ｘ The lithium secondary battery according to claim 1, wherein the lithium secondary battery is at least one selected from the group consisting of (0 < x < 2) and silicon-carbon composite (SiC).

3. The lithium secondary battery according to claim 2, wherein the silicon-based negative electrode active material is silicon oxide (SiO).

4. The aforementioned silicon dioxide (SiO) is silicon dioxide (SiO ２ The lithium secondary battery according to claim 3, wherein ) and amorphous silicon are contained in a 1:1 weight ratio.

5. The lithium secondary battery according to claim 1, wherein the mixing ratio of the silicon-based anode active material and the carbon-based anode active material is 1:99 to 10:90 by weight.

6. The lithium secondary battery according to claim 1, wherein the positive electrode comprises a positive electrode active material containing lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

7. The lithium secondary battery according to claim 1, wherein the compound represented by the chemical formula 1 is the compound represented by the chemical formula 1a below. 【Chemistry 2】

8. The lithium secondary battery according to any one of claims 1 to 7, wherein the compound represented by chemical formula 1 is included in an amount of 0.1% to 5.0% by weight based on the total weight of the non-aqueous electrolyte.

9. The lithium secondary battery according to claim 1, wherein the non-aqueous electrolyte further comprises at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, amine compounds, silane compounds, and lithium salt compounds.

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