Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery, which has an advantage that the lithium secondary battery is excellent not only in high-rate discharge at room temperature but also in discharge efficiency at low temperatures by providing a coating layer containing specific amounts of lithium, sulfur and nitrogen elements on a positive electrode composite layer containing a positive electrode active material.

Description

[Technical Field]

[0001] The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery that includes a coating layer containing specific amounts of lithium (Li), sulfur (S), and nitrogen (N) on a positive electrode composite layer containing a positive electrode active material, and that has excellent high-rate discharge and low-temperature discharge performance.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0033398, filed March 17, 2022, and Korean Patent Application No. 10-2023-00011695, filed January 30, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference. [Background technology]

[0003] BACKGROUND ART In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices but also in medium to large devices such as battery packs for hybrid cars and electric cars or power storage devices.

[0004] Such secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, and lithium secondary batteries. Among these, research is focused on lithium secondary batteries, which not only have a discharge voltage more than twice as high as existing batteries that use alkaline aqueous solutions, but also have a high energy density per unit weight and are capable of rapid charging.

[0005] Lithium metal oxide is used as the positive electrode active material in lithium secondary batteries, and lithium metal, lithium alloy, crystalline or amorphous carbon, or carbon composites are used as the negative electrode active material. Secondary batteries are manufactured by applying a composition containing the electrode active material to a current collector in a suitable thickness and length, and drying it, or by forming the electrode active material itself into a film to form a positive electrode and a negative electrode, which are then wound or stacked together with an insulating separator between them to form an electrode assembly, which is then placed in a can or similar container and filled with an electrolyte.

[0006] Lithium secondary batteries fabricated in this way are charged and discharged by repeatedly intercalating and deintercalating lithium ions from the positive electrode active material (e.g., lithium metal oxide) into the negative electrode active material (e.g., graphite). Theoretically, the lithium intercalation and deintercalation reactions within the positive electrode active material layer are completely reversible. However, in practice, more lithium than the theoretical capacity of the positive electrode active material is consumed, and only a portion of that is recovered during discharge. Therefore, after the second cycle, fewer lithium ions are deintercalated during charge, but most of the deintercalated lithium ions are intercalated during discharge.

[0007] The difference in capacity that occurs between the first charge and discharge reactions is called irreversible capacity loss, and most of this irreversible capacity loss is caused by electrolyte decomposition reactions on the surface of the electrode active material layer. At this time, the electrochemical reaction caused by electrolyte decomposition results in the formation of a CEI (Cathode Electrolyte Interface) film (positive electrode electrolyte film) and an SEI (Solid Electrolyte Interface) film (solid electrolyte film) on the surface of the positive and negative electrode active material layers, respectively.

[0008] Once formed during the initial charge, each electrolyte film on the surface of the positive and negative electrodes prevents reactions between lithium ions and the carbon anode or other materials during subsequent repeated charge and discharge cycles, acting as an ion tunnel and allowing only lithium ions to pass through. Here, the ion tunnel solvates lithium ions and prevents them from being co-intercalated into the carbon anode with the organic solvent of the electrolyte, which has a large molecular weight, and thus destroying the structure of the carbon anode.

[0009] Previously, efforts to improve the performance of secondary batteries have focused on the additives used to form the electrolyte membrane formed on the electrode surface, as well as the thickness and / or uniformity of the resulting electrolyte membrane, because these factors have different effects on the battery. However, despite these efforts, there have been limitations in that it is difficult to improve battery performance through the electrolyte membrane, particularly the electrolyte membrane located on the positive electrode surface. Specifically, even if an electrolyte membrane is formed on the surfaces of the positive and negative electrodes using additives, if the additives are not appropriate, the uniformity of the electrolyte membrane formed on the positive electrode surface may be reduced, resulting in little improvement in low-temperature output characteristics. Furthermore, if the additive amount is not properly adjusted, high temperatures induced during high-rate charge / discharge can cause decomposition of the positive electrode surface or oxidation of the electrolyte, ultimately resulting in a decrease in output characteristics.

[0010] Therefore, there is a need for technological development of a new approach that can improve the high rate characteristics and low temperature characteristics of lithium secondary batteries by using an electrolyte film formed on the surface of the positive electrode. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-2018-0106973 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a lithium secondary battery having improved battery performance, particularly high rate characteristics and low temperature characteristics, using an electrolyte membrane formed on the surface of a positive electrode, and a method for manufacturing the same. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, in one embodiment, the present invention provides a lithium secondary battery including: an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and an electrolyte composition including a non-aqueous organic solvent, a lithium salt, and an electrolyte additive, wherein the positive electrode includes a coating layer on a positive electrode mixture layer including a positive electrode active material, and the coating layer contains 5 atomic % to 15 atomic % of lithium (Li), 1.0 atomic % to 4.0 atomic % of sulfur (S), and 0.5 atomic % to 3.0 atomic % of nitrogen (N).

[0014] In this case, the coating layer provided on the positive electrode composite layer is a layer formed during activation of the lithium secondary battery, and may be formed by electrochemical reaction of part and / or all of the electrolyte additives in the electrolyte composition, and may have a thickness of 5 nm to 100 nm.

[0015] In addition, the electrolyte additive included in the electrolyte composition may include a compound represented by the following Chemical Formula 1:

[0016] [ka]

[0017] In the above chemical formula 1, R1 is hydrogen or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 10 carbon atoms, an alkyleneoxy group having 1 to 10 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, and

[0018] [ka]

[0019] and R3 is a fluoro group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or

[0020] [ka]

[0021] and the alkyl group, alkoxy group, and

[0022] [ka]

[0023] may be substituted with a fluorine atom; X is an oxygen atom (O) or -NR4; R4 is hydrogen or an alkyl group having 1 to 4 carbon atoms; M includes at least one selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, and tetraalkylphosphonium having 1 to 4 carbon atoms; l is an integer of 1 to 6; and m and n are each an integer of 2 to 20.

[0024] Specifically, in the above chemical formula 1, R1 is hydrogen or a methyl group, and R2 is a methylene group, an ethylene group, a propylene group, a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group,

[0025] [ka]

[0026] and

[0027] [ka]

[0028] R3 is a fluoro group, a methyl group, an ethyl group, a propyl group, a methoxy group, an ethoxy group,

[0029] [ka]

[0030] or

[0031] [ka]

[0032] wherein X is an oxygen atom (O), —NH, or —NCH 3 , M is lithium, l is an integer of 1 or 2, and m and n can each be an integer of 2 to 10.

[0033] The electrolyte additive may be contained in an amount of 0.01% by weight to 5% by weight based on the total weight of the electrolyte composition.

[0034] The positive electrode mixture layer may contain one or more positive electrode active materials selected from lithium metal oxides represented by the following chemical formulas 2 and 3.

[0035] [Chemical formula 2] Li x [Ni y Co z Mn w M 1 v ]O2

[0036] [Chemical formula 3] LiM 2 p Mn (2-p) O4

[0037] In the above chemical formula 2 and chemical formula 3, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and x, y, z, w, and v are 1.0≦x≦1.30, 0.5≦y<1, 0 <z≦0.3、0<w≦0.3、0≦v≦0.1であり、y+z+w+v=1であり、M 2 is Ni, Co or Fe, and p is in the range of 0.05≦p≦0.6.

[0038] As an example, the positive electrode active material is LiNi 0.8 Co 0.1 Mn0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O2, LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2, LiNi 0.7 Mn 1.3 O4, LiNi 0.5 Mn 1.5 O4, and LiNi 0.3 Mn 1.7 O4.

[0039] The negative electrode may include a negative electrode mixture layer containing a negative electrode active material on a negative electrode current collector, and the negative electrode active material may include one or more carbon materials selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitizable carbon, carbon black, acetylene black, and ketjen black.

[0040] The negative electrode active material may contain silicon (Si), silicon carbide (SiC), and silicon oxide (SiO q The negative electrode active material may further contain one or more silicon materials selected from the group consisting of silicon carbide, ...

[0041] Furthermore, in one embodiment, the present invention provides a method for manufacturing a lithium secondary battery, the method comprising the steps of assembling a secondary battery by injecting an electrolyte composition into a battery case into which an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode is inserted, and charging the assembled secondary battery to an SOC of 40% to 70% to form a coating layer on a positive electrode mixture layer including a positive electrode active material, wherein the electrolyte composition includes a non-aqueous organic solvent, a lithium salt, and an electrolyte additive, and the coating layer contains 5 atomic % to 15 atomic % of lithium (Li), 1.0 atomic % to 4.0 atomic % of sulfur (S), and 0.5 atomic % to 3.0 atomic % of nitrogen (N).

[0042] At this time, the charging can be performed at a temperature of 25°C to 70°C and a C-rate of 0.1C to 2.0C. [Effects of the Invention]

[0043] The lithium secondary battery according to the present invention has an advantage that it not only has excellent high-rate discharge performance at room temperature but also has excellent discharge efficiency at low temperatures, by providing a coating layer containing specific amounts of lithium, sulfur, and nitrogen on a positive electrode composite layer containing a positive electrode active material. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a graph showing the analysis results of a linear sweep voltammetry method for three-electrode batteries containing the electrolyte compositions (compositions of Preparation Example 1 and Comparative Preparation Example 1) used in Example 1 and Comparative Example 1 according to the present invention, respectively. [Figure 2] 1 is a graph showing the analysis results of differential capacity curves for half cells containing the electrolyte compositions (compositions of Preparation Example 1 and Comparative Preparation Example 1) used in Example 1 and Comparative Example 1 according to the present invention, respectively. [Figure 3] 1 is a graph showing the high-rate discharge capacities of lithium secondary batteries prepared in Example 1 and Comparative Example 1. [Figure 4]1 is a graph showing the low-temperature discharge capacities of lithium secondary batteries prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0045] Because the present invention is susceptible to various modifications and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0046] However, this is not intended to limit the invention to any particular embodiment, but should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0047] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0048] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion therebetween. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion therebetween. Furthermore, in this application, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0049] Additionally, in the present invention, "comprising as a main component" may mean that the defined component is contained in an amount of 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, 90 wt % or more, or 95 wt % or more relative to the total weight of the negative electrode active material. For example, "comprising graphite as a main component as a negative electrode active material" may mean that the negative electrode active material contains 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, 90 wt % or more, or 95 wt % or more of graphite relative to the total weight of the negative electrode active material. In some cases, it may mean that the entire negative electrode active material is composed of graphite and contains 100 wt % graphite.

[0050] The present invention will now be described in more detail.

[0051] <Lithium secondary battery> In one embodiment, the present invention provides a lithium secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and an electrolyte composition including a non-aqueous organic solvent, a lithium salt, and an electrolyte additive, wherein the positive electrode comprises a coating layer on a positive electrode mixture layer including a positive electrode active material, and the coating layer contains specific amounts of lithium (Li), sulfur (S), and nitrogen (N).

[0052] The lithium secondary battery according to the present invention includes an electrode assembly in which a positive electrode, a separator, and a negative electrode are sequentially disposed, and an electrolyte composition in which a lithium salt and an electrolyte additive are dissolved in a non-aqueous organic solvent. The positive electrode included in the electrode assembly includes a coating layer on a surface of a positive electrode mixture layer including a positive electrode active material.

[0053] Here, the coating layer is a layer formed during initial charging, i.e., activation, of the lithium secondary battery, and may be the same as the cathode electrolyte interface (CEI), or in some cases, may be a layer added to the cathode electrolyte interface.

[0054] The coating layer also contains specific amounts of lithium (Li), sulfur (S), and nitrogen (N). Specifically, the coating layer may contain lithium (Li) at 5 atomic % to 15 atomic %, more specifically, 7 atomic % to 13 atomic %, or 8 atomic % to 13 atomic %. The coating layer may contain sulfur (S) at 1 atomic % to 4 atomic %, more specifically, 1.5 atomic % to 3.2 atomic %, 1.7 atomic % to 2.6 atomic %, or 2.0 atomic % to 2.6 atomic %. The coating layer may contain nitrogen (N) at 0.5 atomic % to 3 atomic %, more specifically, 0.7 atomic % to 2.2 atomic %, 0.7 atomic % to 1.6 atomic %, or 1.2 atomic % to 2.1 atomic %.

[0055] As an example, the coating layer may contain lithium (Li), sulfur (S), and nitrogen (N) at 9.0 atomic % to 11.5 atomic %, 1.8 atomic % to 2.6 atomic %, and 1.2 atomic % to 2.0 atomic %, respectively.

[0056] The present invention adjusts the contents of lithium (Li), sulfur (S), and nitrogen (N) contained in the coating layer formed on the surface of the positive electrode within the above ranges, thereby enabling the formation of a robust coating layer with excellent physical properties such as acid resistance and high-temperature durability, thereby improving the high-rate performance and low-temperature output performance of the lithium secondary battery.

[0057] The coating layer may be formed on the surface of the positive electrode by an electrochemical reaction caused by decomposition of the electrolyte composition during activation of a lithium secondary battery, similar to the cathode electrolyte interface (CEI) formed during activation. Therefore, the lithium (Li), sulfur (S), and nitrogen (N) contents of the coating layer may be affected by the components constituting the electrolyte composition.

[0058] Specifically, the coating layer may be formed by decomposition of a lithium salt, an electrolyte additive, etc. dissolved and / or dispersed in a non-aqueous organic solvent, and the coating layer thus formed may contain sulfur (S) and nitrogen (N) derived from the electrolyte additive. To this end, the electrolyte additive may include a compound containing sulfur (S) and nitrogen (N), more specifically, an ionic compound represented by Chemical Formula 1 below, having a mother nucleus in which a (meth)acrylate group or a (meth)acrylamide group is bonded to one side of a sulfonylimide group at the center via a functional group having a saturated hydrocarbon chain or a structure in which an oxygen atom is introduced into the saturated hydrocarbon chain.

[0059] [ka]

[0060] In the above chemical formula 1, R1 is hydrogen or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 10 carbon atoms, an alkyleneoxy group having 1 to 10 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, and

[0061] [ka]

[0062] and R3 is a fluoro group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or

[0063] [ka]

[0064] and the alkyl group, alkoxy group, and

[0065] [ka]

[0066] may be substituted with a fluorine atom; X is an oxygen atom (O) or -NR4; R4 is hydrogen or an alkyl group having 1 to 4 carbon atoms; M includes at least one selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, and tetraalkylphosphonium having 1 to 4 carbon atoms; l is an integer of 1 to 6; and m and n are each an integer of 2 to 20.

[0067] Specifically, R1 is hydrogen or a methyl group, and R2 is a methylene group, an ethylene group, a propylene group, a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group,

[0068] [ka]

[0069] and

[0070] [ka]

[0071] R3 is a fluoro group, a methyl group, an ethyl group, a propyl group, a methoxy group, an ethoxy group,

[0072] [ka]

[0073] or

[0074] [ka]

[0075] wherein X is an oxygen atom (O), —NH, or —NCH 3 , M is lithium, l is an integer of 1 or 2, and m can be an integer from 2 to 10.

[0076] As an example, the compound represented by Chemical Formula 1 above may be one or more of the compounds of <Structural Formula 1> to <Structural Formula 120> below.

[0077] [ka]

[0078] [ka]

[0079] [ka]

[0080] [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] The electrolyte additive has a structure represented by Chemical Formula 1, and thus can uniformly form an organic / inorganic coating layer on the surface of the positive electrode as well as the negative electrode upon activation of a secondary battery containing the electrolyte additive. The coating layer thus formed can contain lithium (Li), sulfur (S), and nitrogen (N) within specific content ranges according to the present invention.

[0088] Specifically, the compound represented by Formula 1 has a core structure in which a sulfonylimide group is attached to one side of the core, via a functional group containing a saturated hydrocarbon chain or a saturated hydrocarbon chain with an oxygen atom introduced therein, to which a (meth)acrylate group or a (meth)acrylamide group is attached. Due to these structural characteristics, the electrolyte additive has an oxidation potential of 3.9 V or higher, enabling it to form an organic / inorganic coating layer on the surface of the positive electrode during the activation process of a secondary battery. In contrast, when an electrolyte additive is used that contains a mixture of compounds containing the functional groups, i.e., a sulfonylimide group, a saturated hydrocarbon chain or a hydrocarbon chain with an oxygen atom introduced therein, and a (meth)acrylate group or a (meth)acrylamide group, the oxidation potential of the electrolyte additive does not exceed 3.9 V, making it difficult to form an organic / inorganic coating layer on the surface of the positive electrode during the activation process of a secondary battery containing the electrolyte additive.

[0089] The organic / inorganic coating layer formed on the surface of the positive electrode using the electrolyte additive can improve the room temperature high rate discharge performance and low temperature discharge efficiency of the lithium secondary battery. Moreover, when the lithium secondary battery is exposed to high temperatures, it can suppress the decomposition of the electrolyte and the generation of gas, and it can improve the OCV drop and capacity decrease that occur at the positive electrode, thereby further improving the battery's performance and high temperature safety.

[0090] In addition, the coating layer formed on the positive electrode surface may have a decreasing concentration of metal elements and a increasing concentration of non-metallic elements such as carbon (C), sulfur (S), and nitrogen (N) from the surface in contact with the positive electrode to the surface in contact with the separator. For example, the coating layer may have a concentration gradient in which the concentration of lithium (Li) gradually decreases from the surface in contact with the positive electrode to the surface in contact with the separator.

[0091] The coating layer may have a certain average thickness. Specifically, the coating layer may have an average thickness of 5 nm to 100 nm, more specifically, an average thickness of 5 nm to 80 nm, 10 nm to 50 nm, or 10 nm to 30 nm. By controlling the average thickness of the coating layer within the above range, the present invention can prevent a large amount of electrolyte loss due to excessive coating layer formation, and at the same time, prevent a side reaction between the positive electrode and the electrolyte composition from being insufficiently suppressed due to an extremely thin thickness during charging and discharging of the lithium secondary battery.

[0092] Meanwhile, the positive electrode includes a positive electrode composite layer produced by applying a slurry containing a positive electrode active material onto a positive electrode current collector, drying the slurry, and pressing the slurry, and may optionally further include a conductive material, a binder, other additives, and the like, as needed.

[0093] Here, the positive electrode active material is a material that can undergo an electrochemical reaction on a positive electrode current collector and may include one or more lithium metal oxides represented by the following Chemical Formula 2 and Chemical Formula 3, which are capable of reversibly intercalating and deintercalating lithium ions.

[0094] [Chemical formula 2] Li x [Ni y Co z Mn w M 1 v ]O2

[0095] [Chemical formula 3] LiM 2 p Mn (2-p) O4

[0096] In the above chemical formula 2 and chemical formula 3, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and x, y, z, w, and v are 1.0≦x≦1.30, 0.5≦y<1, 0 <z≦0.3、0<w≦0.3、0≦v≦0.1であり、y+z+w+v=1であり、M 2 is Ni, Co or Fe, and p is in the range of 0.05≦p≦0.6.

[0097] The lithium metal oxides represented by Chemical Formula 2 and Chemical Formula 3 are materials containing high contents of nickel (Ni) and manganese (Mn), respectively, and when used as positive electrode active materials, they have the advantage of being able to stably supply high-capacity and / or high-voltage electricity. Furthermore, a charge potential of 4.0 V or higher is required to form a film on the surface of the positive electrode and / or negative electrode during activation of a secondary battery. Unlike conventional positive electrode active materials such as iron phosphate compounds, which have a charge potential of less than about 4.0 V, the lithium metal oxides have a high charge potential of about 4.0 V or higher, making it easy to form a film on the electrode.

[0098] In this case, the lithium metal oxide represented by the above chemical formula 2 is LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O2, LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2, etc., and the lithium metal oxide represented by the above chemical formula 3 is LiNi 0.7 Mn 1.3 O4, LiNi 0.5 Mn 1.5 O4, LiNi 0.3 Mn 1.7 O4, etc., which may be used alone or in combination.

[0099] The positive electrode may use a current collector having high conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used. In the case of aluminum or stainless steel, it may also be surface-treated with carbon, nickel, titanium, silver, etc. The average thickness of the current collector may be preferably 3 μm to 500 μm, taking into account the conductivity and total thickness of the positive electrode to be manufactured.

[0100] Similarly to the positive electrode, the negative electrode includes a negative electrode mixture layer produced by applying a negative electrode active material onto a negative electrode current collector, drying the applied material, and pressing the material, and may further include, as necessary, a conductive material, a binder, other additives, and the like.

[0101] The negative electrode active material may include a carbon material. Specifically, the carbon material refers to a material containing carbon atoms as a main component, and the carbon material may include at least one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitizable carbon, carbon black, acetylene black, and ketjen black.

[0102] The negative electrode active material may further include a silicon material together with the carbon material. The silicon material refers to a material containing silicon atoms as a main component, and such silicon material may include silicon (Si), silicon carbide (SiC), silicon monoxide (SiO), or silicon dioxide (SiO2) alone or in combination. When silicon monoxide (SiO2) and silicon dioxide (SiO2) are uniformly mixed or composited as the silicon (Si)-containing material and contained in the negative electrode composite layer, they are referred to as silicon oxide (SiO q , where 0.8≦q≦2.5).

[0103] The silicon material may be included in an amount of 1 wt% to 20 wt% of the total weight of the negative electrode active material, specifically 3 wt% to 10 wt%, 8 wt% to 15 wt%, 13 wt% to 18 wt%, or 2 wt% to 8 wt%. By adjusting the content of the silicon material within the above range, the present invention can maximize the energy density of the battery.

[0104] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery, and may be made of, for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. In the case of copper or stainless steel, it may also be surface-treated with carbon, nickel, titanium, silver, etc. The average thickness of the negative electrode current collector is preferably 1 μm to 500 μm, taking into account the conductivity and total thickness of the negative electrode to be manufactured.

[0105] Meanwhile, the separator interposed between the positive and negative electrodes of each unit cell is an insulating thin film having high ion permeability and mechanical strength. It may be any insulating thin film commonly used in the art, including at least one polymer selected from the group consisting of chemically resistant and hydrophobic polypropylene, polyethylene, and polyethylene-propylene copolymer. The separator may be in the form of a porous polymer substrate, such as a sheet or nonwoven fabric containing the above-mentioned polymer. In some cases, it may be in the form of a composite separator, in which organic or inorganic particles are coated on the porous polymer substrate with an organic binder. The separator may have an average pore diameter of 0.01 μm to 10 μm and an average thickness of 5 μm to 300 μm.

[0106] Additionally, the electrolyte composition includes a non-aqueous organic solvent and a lithium salt along with the electrolyte additives described above.

[0107] Here, the lithium salt may be any lithium salt used in the art for non-aqueous electrolytes without any particular limitation. Specifically, the lithium salt may be LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, and (FSO2)2NLi.

[0108] The concentrations of these lithium salts are not particularly limited, but a preferred lower limit of the concentration range is 0.5 mol / L or more, specifically 0.7 mol / L or more, more specifically 0.9 mol / L or more, and a preferred upper limit of the concentration range is 2.5 mol / L or less, specifically 2.0 mol / L or less, more specifically 1.5 mol / L or less. If the lithium salt concentration is below 0.5 mol / L, the ionic conductivity decreases, which may result in a decrease in the cycle characteristics and output characteristics of the nonaqueous electrolyte battery. If the lithium salt concentration exceeds 2.5 mol / L, the viscosity of the electrolyte for the nonaqueous electrolyte battery increases, which may also decrease the ionic conductivity, which may result in a decrease in the cycle characteristics and output characteristics of the nonaqueous electrolyte battery.

[0109] Furthermore, when a large amount of lithium salt is dissolved in a non-aqueous organic solvent at once, the liquid temperature may rise due to the heat of dissolution of the lithium salt. If the temperature of the non-aqueous organic solvent rises significantly due to the heat of dissolution of the lithium salt, decomposition of the fluorine-containing lithium salt may be accelerated, resulting in the production of hydrogen fluoride (HF). Hydrogen fluoride (HF) is undesirable because it can cause deterioration of battery performance. Therefore, the temperature at which the lithium salt is dissolved in the non-aqueous organic solvent is not particularly limited, but may be adjusted to −20° C. to 80° C., specifically 0° C. to 60° C.

[0110] In addition, the non-aqueous organic solvent used in the electrolyte composition may be any organic solvent used in non-aqueous electrolytes in the art without any particular limitations. Specifically, examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, ethylene carbonate (EC), propylene carbonate, butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), gamma-butyrolactone, 1,2-dimethoxyethane (DME), tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0111] The non-aqueous organic solvent used in the present invention may be one type alone or two or more types mixed in any combination and ratio depending on the application. Among these, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate are particularly preferred from the viewpoints of their electrochemical stability against oxidation-reduction and chemical stability against heat and reactions with solutes.

[0112] The electrolyte additive may be included in the electrolyte composition in a specific content. Specifically, the electrolyte additive including the compound represented by Formula 1 may be included in an amount of 0.01 wt % to 5 wt % of the total weight of the electrolyte composition, more specifically, 0.05 wt % to 3 wt % or 1.0 wt % to 2.5 wt % of the total weight of the electrolyte composition. The present invention prevents excessive amounts of the electrolyte additive outside the above range from increasing the viscosity of the electrolyte composition and reducing its wettability to the electrodes and separator, while also preventing reduced ionic conductivity of the electrolyte composition and reduced battery performance. The present invention also prevents small amounts of the electrolyte additive outside the above range from not fully achieving the effects of the additive.

[0113] Meanwhile, the electrolyte composition may further contain additives in addition to the basic components described above. Additives commonly used in the nonaqueous electrolyte of the present invention may be added in any proportion, provided the gist of the present invention is not impaired. Specific examples include compounds that have overcharge prevention effects, anode film formation effects, and cathode protection effects, such as cyclohexylbenzene, biphenyl, t-butylbenzene, vinylene carbonate, vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate, propane sultone, succinonitrile, and dimethylvinylene carbonate. Furthermore, similar to the use in nonaqueous electrolyte batteries known as lithium polymer batteries, the electrolyte for nonaqueous electrolyte batteries can be solidified using a gelling agent or crosslinked polymer.

[0114] Furthermore, the lithium secondary battery according to the present invention may be applied in various shapes, such as a cylindrical shape, a square shape, a pouch shape, or a coin shape, depending on the intended use, without being particularly limited thereto. The lithium secondary battery according to an embodiment of the present invention may be a pouch-type secondary battery.

[0115] <Method of manufacturing lithium secondary batteries> Furthermore, in one embodiment, the present invention provides a method for manufacturing the above-described lithium secondary battery according to the present invention.

[0116] The method for manufacturing a lithium secondary battery according to the present invention may be performed by assembling a secondary battery by injecting an electrolyte composition into a battery case having an electrode assembly inserted therein, and then initially charging, i.e., activating, the assembled secondary battery to form a coating layer on a surface of a positive electrode included in the electrode assembly.

[0117] Specifically, the method for manufacturing the lithium secondary battery includes assembling a secondary battery by injecting an electrolyte composition into a battery case in which an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode is inserted; and charging the assembled secondary battery to an SOC of 40% to 70% to form a coating layer on a positive electrode composite layer including a positive electrode active material.

[0118] Here, the step of assembling the secondary battery includes all of the processes of manufacturing an electrode assembly, inserting the manufactured electrode assembly into a battery case, and injecting an electrolyte composition, and may be performed in a manner commonly used in the art.

[0119] In addition, the electrolyte composition injected into the battery case may have a configuration including an electrolyte additive along with the non-aqueous organic solvent and the lithium salt, as described above, and the electrolyte additive may include a compound represented by the following Chemical Formula 1:

[0120] [ka]

[0121] In the above chemical formula 1, R1 is hydrogen or an alkyl group having 1 to 4 carbon atoms, R2 is an alkylene group having 1 to 10 carbon atoms, an alkyleneoxy group having 1 to 10 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, and

[0122] [ka]

[0123] and R3 is a fluoro group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or

[0124] [ka]

[0125] and the alkyl group, alkoxy group, and

[0126] [ka]

[0127] may be substituted with a fluorine atom; X is an oxygen atom (O) or -NR4; R4 is hydrogen or an alkyl group having 1 to 4 carbon atoms; M includes at least one selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, and tetraalkylphosphonium having 1 to 4 carbon atoms; l is an integer of 1 to 6; and m and n are each an integer of 2 to 20.

[0128] The present invention includes a compound represented by Formula 1 as an electrolyte additive, which allows a uniform organic / inorganic coating layer to be formed on the surface of both the positive and negative electrodes during activation of a secondary battery. The coating layer thus formed may contain lithium (Li), sulfur (S), and nitrogen (N) within a specific content range according to the present invention, thereby improving the room-temperature high-rate discharge performance and low-temperature discharge efficiency of the lithium secondary battery. Furthermore, the coating layer can suppress gas generation due to electrolyte decomposition when the lithium secondary battery is exposed to high temperatures, and can improve the OCV drop and capacity loss that occur at the positive electrode, thereby further improving battery performance and high-temperature safety.

[0129] In addition, the step of forming a coating layer on the positive electrode composite layer involves initially charging the assembled secondary battery to induce an electrochemical reaction of the electrolyte composition on the composite layer, thereby forming coating layers on the positive and negative electrodes, respectively. The initial charging may be performed at an SOC of 40% to 70%, more specifically, at an SOC of 45% to 65%, to uniformly form an organic / inorganic coating layer on the electrode surface.

[0130] The initial charge may be performed under any conditions, but may be performed at 25°C to 70°C, a charge cut-off voltage of 3.0V to 4.2V, and a C-rate of 0.1C to 2.0C, so that the electrode assembly is sufficiently wetted and the volume is maximized to form each coating layer. Specifically, the initial charge may be performed at 45°C to 60°C and a C-rate of 0.5C to 1.5C, 0.8C to 1.2C, 1.0C to 1.5C, 0.5C to 1.0C, 0.5C to 0.9C, or 0.7C to 1.3C.

[0131] By controlling the charging conditions during the initial charge of a lithium secondary battery as described above, the present invention can uniformly form coating layers on the surfaces of the positive electrode and negative electrode. In particular, the contents of lithium (Li), sulfur (S), and nitrogen (N) in the coating layer formed on the surface of the positive electrode composite layer of the positive electrode can be easily adjusted to 5 atomic % to 15 atomic %, 1.0 atomic % to 4.0 atomic %, and 0.5 atomic % to 3.0 atomic %, respectively.

[0132] The method for manufacturing a lithium secondary battery according to the present invention, which has the above-described configuration, can uniformly form an organic / inorganic coating layer on the surface of an electrode, and simultaneously control the lithium (Li), sulfur (S), and nitrogen (N) contents of the coating layer formed on the surface of the positive electrode within specific ranges. The lithium secondary battery manufactured in this way can achieve high-rate discharge performance and low-temperature discharge efficiency, suppress gas generation due to decomposition of the electrolyte when the lithium secondary battery is exposed to high temperatures, and improve the OCV drop and capacity decrease that occur in the positive electrode, thereby further improving battery performance and high-temperature safety.

[0133] The present invention will be described in more detail below with reference to examples and experimental examples.

[0134] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0135] <Production Examples 1 to 6 and Comparative Production Examples 1 to 7. Production of Electrolyte Compositions for Lithium Secondary Batteries> A lithium salt, LiPF, was dissolved at a concentration of 1M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70. Electrolyte additives were weighed based on the total weight of the electrolyte as shown in Table 1 below and dissolved to prepare a nonaqueous electrolyte composition for a lithium secondary battery.

[0136] [Table 1]

[0137] Comparative Preparation Example 8: Preparation of electrolyte composition for lithium secondary battery A nonaqueous electrolyte composition for a lithium secondary battery was prepared in the same manner as in Preparation Example 1, except that an oligomer (weight average molecular weight: 2,500 to 5,000) obtained by polymerizing the compound represented by Structural Formula 61 was used as the electrolyte additive instead of the compound represented by Structural Formula 61.

[0138] <Examples 1 to 8 and Comparative Examples 1 to 10. Production of Lithium Secondary Batteries> The positive electrode active material is LiNi with a particle size of 5 μm. 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 was prepared and mixed with polyvinylidene fluoride as a carbon-based conductive agent and binder in N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 to form a slurry, which was then cast onto an aluminum sheet, dried in a vacuum oven at 120°C, and rolled to produce a positive electrode.

[0139] Separately, a negative electrode active material was prepared by mixing natural graphite and artificial graphite in a 1:1 weight ratio. 97 parts by weight of the negative electrode active material and 3 parts by weight of styrene butadiene rubber (SBR) were mixed with water to form a slurry, which was then cast onto a copper sheet, dried in a vacuum oven at 130°C, and rolled to produce a negative electrode.

[0140] The obtained positive and negative electrodes were inserted into a case with an 18 μm polypropylene separator therebetween, and then the electrolyte compositions prepared in the above Preparation Examples and Comparative Preparation Examples as shown in Table 2 below were injected to assemble a 2.1 Ah lithium secondary battery.

[0141] Each assembled lithium secondary battery was initially charged. Specifically, the lithium secondary battery was initially charged under the conditions shown in Table 2 below at 55±2°C to a cut-off voltage of 4.2 V to produce an activated lithium secondary battery.

[0142] [Table 2]

[0143] <Experimental Example 1> In order to confirm whether or not a coating layer was formed on the surfaces of the positive and negative electrodes of the lithium secondary battery according to the present invention, secondary batteries were fabricated using the electrolyte compositions used in Example 1, Comparative Example 1, and Comparative Example 8, and the following experiment was carried out on each of the fabricated secondary batteries.

[0144] a) Linear sweep voltammetry evaluation of three-electrode batteries First, to confirm whether a coating layer was formed on the positive electrode surface, three-electrode batteries were fabricated by injecting the electrolyte compositions (Preparation Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 8) used in Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 8 into batteries containing a platinum electrode, a platinum electrode, and a lithium metal electrode as three electrodes, and linear sweep voltammetry (LSV) analysis was performed on each of the fabricated batteries. LSV analysis was performed at 60°C, with an observation range of 3.0 V to 6.0 V (lithium reference), and a measurement rate of 10 mV / s.

[0145] As a result, as shown in Figure 1, the electrolyte composition of the example containing the electrolyte additive represented by Formula 1 according to the present invention increases current at around 3.9±0.05 V compared to lithium. This means that an oxidation reaction occurs on the surface of lithium metal at around 3.9±0.05 V, and indicates that the electrolyte additive of the electrolyte composition used in Example 1 forms a film due to an oxidation reaction on the surface of the positive electrode when the voltage is 3.9±0.05 V or higher compared to lithium.

[0146] In addition, it was confirmed that the electrolyte compositions used in Comparative Examples 1 and 8 experienced oxidative decomposition of the electrolyte at approximately 5.5±0.05 V relative to lithium, while the electrolyte composition used in Example 1 experienced oxidative decomposition of the electrolyte at approximately 5.7±0.05 V relative to lithium. This means that the electrolyte additive represented by Formula 1 contained in the electrolyte composition is involved in the formation of a coating layer, thereby widening the oxidation potential window by approximately 0.2 V compared to when the additive is not present.

[0147] It is also shown that the oxidation reaction is induced at a lower potential on the carbon electrode or the positive electrode than on the platinum electrode surface due to the catalytic properties of the carbon or transition metal.

[0148] These results show that in the lithium secondary battery according to the present invention, an oxidation reaction is induced on the surface of the positive electrode during the activation process, resulting in the formation of an organic / inorganic coating layer.

[0149] b) Differential capacity curve analysis of half-cell Next, to confirm whether a coating layer was formed on the anode surface, half-cells were fabricated using lithium metal and graphite (artificial graphite:natural graphite mixed at a weight ratio of 9:1). The electrolyte compositions (Preparation Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 8) used in Example 1, Comparative Example 1, and Comparative Example 8 were injected into the half-cells. The cells were then charged at 25°C from 3.5±0.5 V to 0.05 V at a rate of 0.005 C, and the potential (V) and capacity (mAh) were measured. The reduction potential was determined by differentiating the capacity (dQ / dV) from the potential. The results are shown in Figure 2 below.

[0150] 1, it was confirmed that the electrolyte composition of the example containing the electrolyte additive represented by Chemical Formula 1 according to the present invention exhibited a downward peak at a voltage of approximately 1.32 V relative to lithium, unlike the electrolyte composition of the comparative example not containing an electrolyte additive. This downward peak indicates that a reduction reaction occurred on the surface of the graphite anode, and that the electrolyte additive represented by Chemical Formula 1 contained in the electrolyte composition was converted into a coating material by a reduction reaction on the surface of the anode at approximately 1.32 V relative to lithium.

[0151] These results show that in the lithium secondary battery according to the present invention, a reduction reaction is induced on the surface of the negative electrode during the activation process, resulting in the formation of an organic / inorganic coating layer.

[0152] <Experimental Example 2> The following experiments were carried out to analyze the film formed on the electrode surface during activation of the lithium secondary battery according to the present invention and to evaluate the high rate performance and low temperature performance of the lithium secondary battery.

[0153] a) Analysis of electrode surface film For each secondary battery manufactured in the examples and comparative examples, X-ray photoelectron spectroscopy (XPS) was performed on the coating layer formed on the surface of the positive electrode to obtain a spectrum, and the type and content of elements contained in the coating layer were analyzed from the obtained spectrum.

[0154] The XPS analysis was performed using a Thermo Fisher Scientific ESCALAB250 (accelerating voltage: 15 kV, 150 W, energy resolution: 1.0 eV, analysis area: diameter 500 micrometers, sputter rate: 0.1 nm / sec). Table 3 shows the contents of lithium (Li), sulfur (S), and nitrogen (N) among the analyzed elements.

[0155] b) Evaluation of high-rate discharge capacity The high-rate discharge capacity at room temperature was measured for each of the secondary batteries manufactured in the examples and comparative examples.

[0156] Specifically, each activated lithium secondary battery was first charged at 25°C under CC-CV conditions at a rate of 0.33 C to 4.2 V, and then discharged under CC conditions at a rate of 0.33 C to 2.5 V. The above charge / discharge cycle constituted one cycle, and three charge / discharge cycles were performed.

[0157] Thereafter, the battery was fully charged under CC-CV conditions at a rate of 0.33C at 25°C to 4.2V, and then discharged under CC conditions at a rate of 2.5C to 2.5V, and the high-rate discharge capacity at room temperature was measured. The results are shown in Table 3 below and Figure 3.

[0158] C) Evaluation of low-temperature discharge capacity The discharge capacity at low temperature was measured for each of the secondary batteries manufactured in the examples and comparative examples.

[0159] Specifically, each activated lithium secondary battery was first charged at 25°C under CC-CV conditions at a rate of 0.33 C to 4.2 V, and then discharged under CC conditions at a rate of 0.33 C to 2.5 V. The above charge / discharge cycle constituted one cycle, and three charge / discharge cycles were performed.

[0160] Thereafter, the battery was charged under CC-CV conditions at a rate of 0.33C at 25°C to 4.2V, and discharged under CC conditions to 2.5V to maintain the capacity at an SOC of 10%. After that, the battery was discharged under CC conditions at a rate of 0.04C to 2.5V at -10°C to measure the discharge capacity at low temperature. The results are shown in Table 3 below and Figure 4.

[0161] [Table 3]

[0162] As shown in Table 3 above, the lithium secondary battery according to the present invention contains specific amounts of lithium (Li), sulfur (S), and nitrogen (N) on the surface of the positive electrode, which results in excellent high-rate performance and low-temperature performance.

[0163] Specifically, the lithium secondary batteries manufactured in the examples all had a coating layer formed on the surface of the positive electrode composite layer of the positive electrode, containing lithium (Li), sulfur (S), and nitrogen (N) in amounts of 7 atomic % to 15 atomic %, 0.6 atomic % to 1.1 atomic %, and 1.8 atomic % to 3.1 atomic %, respectively. Furthermore, the lithium secondary batteries of the examples including such a coating layer were confirmed to have excellent room-temperature high-rate discharge capacities of 670 mAh or more and low-temperature discharge capacities of 93 mAh or more.

[0164] These results show that the lithium secondary battery according to the present invention has a coating layer containing specific amounts of lithium (Li), sulfur (S), and nitrogen (N) on the surface of the positive electrode composite layer of the positive electrode, and has excellent room temperature high-rate discharge performance and low temperature discharge performance.

[0165] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art or those with ordinary knowledge in the art that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the present invention as set forth in the claims below.

[0166] Therefore, the technical scope of the present invention should not be limited to the content described in the Summary of the Invention of the specification, but should be defined by the claims.

Claims

1. an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; an electrolyte composition including a non-aqueous organic solvent, a lithium salt, and an electrolyte additive; the positive electrode includes a coating layer on a positive electrode mixture layer containing a positive electrode active material, the coating layer contains 5 atomic % to 15 atomic % of lithium (Li), 1.0 atomic % to 4.0 atomic % of sulfur (S), and 0.5 atomic % to 3.0 atomic % of nitrogen (N); The electrolyte additive has an oxidation potential of 3.9 V or more.

2. 2. The lithium secondary battery according to claim 1, wherein the coating layer has an average thickness of 5 nm to 100 nm.

3. The electrolyte additive includes a compound represented by the following Chemical Formula 1: 【Chemical 1】 In the above Chemical Formula 1, R １ is hydrogen or an alkyl group having 1 to 4 carbon atoms, R ２ represents an alkylene group having 1 to 10 carbon atoms, an alkyleneoxy group having 1 to 10 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, and 【Chemistry 2】 Contains one or more of the following: R ３ represents a fluoro group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or 【Chemistry 3】 wherein the alkyl group, the alkoxy group, and 【Chemistry 4】 One or more of the hydrogen atoms contained in may be substituted with a fluorine atom, X is an oxygen atom (O) or —NR ４ and R ４ is hydrogen or an alkyl group having 1 to 4 carbon atoms, M includes at least one selected from the group consisting of lithium, sodium, potassium, tetraalkylammonium having 1 to 4 carbon atoms, and tetraalkylphosphonium having 1 to 4 carbon atoms; l is an integer from 1 to 6, 3. The lithium secondary battery according to claim 1, wherein m and n are each an integer of 2 to 20.

4. R １ is hydrogen or a methyl group, R ２ is a methylene group, an ethylene group, a propylene group, a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, 【Chemistry 5】 and 【Chemistry 6】 Contains one or more of the following: R ３ is a fluoro group, a methyl group, an ethyl group, a propyl group, a methoxy group, an ethoxy group, 【Chemistry 7】 or 【Chemistry 8】 and X is an oxygen atom (O), —NH, or —NCH ３ and M is lithium; l is an integer of 1 or 2; 4. The lithium secondary battery according to claim 3, wherein m and n are each an integer of 2 to 10.

5. 2. The lithium secondary battery according to claim 1, wherein the electrolyte additive is contained in an amount of 0.01% by weight to 5% by weight based on the weight of the entire electrolyte composition.

6. The positive electrode composite layer includes one or more positive electrode active materials selected from lithium metal oxides represented by the following Chemical Formula 2 and Chemical Formula 3: [Chemical formula 2] Li ｘ [Ni ｙ Co ｚ Mn ｗ M １ ｖ ]O ２ [Chemical formula 3] LiM ２ ｐ Mn （２－ｐ） O ４ In the above Chemical Formula 2 and Chemical Formula 3, M １ は、W、Cu、Fe、V、Cr、Ti、Zr、Zn、Al、In、Ta、Y、La , Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo; x, y, z, w, and v are each in the ranges of 1.0≦x≦1.30, 0.5≦y<1, 0<z≦0.3, 0<w≦0.3, and 0≦v≦0.1, and y+z+w+v=1; M ２ is Ni, Co or Fe, 2. The lithium secondary battery according to claim 1, wherein p satisfies the condition 0.05≦p≦0.

6.

7. The positive electrode active material is LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．９ Co ０．０５ Mn ０．０５ O ２ , LiNi ０．６ Co ０．２ Mn ０．１ Al ０．１ O ２ , LiNi ０．６ Co ０．２ Mn ０．１５ Al ０．０５ O ２ , LiNi ０．７ Co ０．１ Mn ０．１ Al ０．１ O ２ , LiNi ０．７ Mn １．３ O ４ , LiNi ０．５ Mn １．５ O ４ , and LiNi ０．３ Mn １．７ O ４ The lithium secondary battery according to claim 6, comprising one or more selected from the group consisting of:

8. the negative electrode includes a negative electrode mixture layer containing a negative electrode active material on a negative electrode current collector, 2. The lithium secondary battery according to claim 1, wherein the negative electrode active material comprises one or more carbon materials selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitizable carbon, carbon black, acetylene black, and ketjen black.

9. The negative electrode active material is silicon (Si), silicon carbide (SiC), and silicon oxide (SiO ｑ 9. The lithium secondary battery according to claim 8, further comprising one or more silicon materials selected from the group consisting of q and q, where 0.8≦q≦2.

5.

10. The lithium secondary battery according to claim 9, wherein the silicon material is contained in an amount of 1 wt % to 20 wt % based on the total weight of the negative electrode active material.

11. assembling a secondary battery by injecting an electrolyte composition into a battery case in which an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode is inserted; Charging the assembled secondary battery to an SOC of 40% to 70% to form a coating layer on a positive electrode composite layer containing a positive electrode active material, The electrolyte composition includes a non-aqueous organic solvent, a lithium salt, and an electrolyte additive; the coating layer contains 5 atomic % to 15 atomic % of lithium (Li), 1.0 atomic % to 4.0 atomic % of sulfur (S), and 0.5 atomic % to 3.0 atomic % of nitrogen (N); The electrolyte additive has an oxidation potential of 3.9 V or more.

12. The method for producing a lithium secondary battery according to claim 11, wherein charging is performed at a C rate of 0.1 C to 2.0 C at 25° C. to 70° C.

Images