Lithium secondary battery

Abstract

The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein: the positive electrode comprises a positive electrode active material; the positive electrode active material comprises a lithium nickel-cobalt-manganese oxide containing nickel (Ni) in an amount of 55 mol% to 70 mol% based on the total transition metal elements excluding lithium; the lithium nickel-cobalt-manganese oxide is in the form of single particles or quasi-single particles; the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive; the additive comprises a first additive and a second additive; the first additive is a compound represented by chemical formula 1; and the second additive is a compound represented by chemical formula 2.

Description

lithium secondary battery

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196374 filed December 24, 2024 and Korean Patent Application No. 10-2025-0202479 filed December 17, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a lithium secondary battery with improved high-temperature cycle life performance and high-temperature storage performance.

[0006] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for high-capacity, high-output, and high-stability secondary batteries.

[0007] The above lithium secondary battery is largely composed of a positive electrode made of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte that serves as a medium for transmitting lithium ions, and a separator. For the above lithium secondary battery, carbon materials, lithium metal, sulfur compounds, silicon compounds, tin compounds, etc. are being considered as the main components of the negative electrode active material, and lithium-containing cobalt oxide (LiCoO2) or lithium nickel-cobalt-manganese oxide is mainly used as the positive electrode active material.

[0008] Meanwhile, conventional lithium nickel-cobalt-manganese oxide was generally in the form of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. However, in the case of lithium nickel-cobalt-manganese oxide in the form of secondary particles with many primary particles aggregated in this way, there is a problem in that particle breakage occurs, where primary particles detach during the rolling process for cathode manufacturing, and cracks occur inside the particles during the charging and discharging process. If particle breakage or cracking occurs in the cathode active material, the contact area with the electrolyte increases, leading to increased gas generation and active material degradation due to side reactions with the electrolyte, which in turn reduces lifespan characteristics.

[0009] Furthermore, as the demand for high-output, high-capacity batteries has recently increased, there is a trend of gradually increasing the nickel content in cathode active materials. However, while increasing the nickel content improves initial capacity characteristics, repeated charging and discharging leads to structural breakdown of the cathode active material. This accelerates the degradation rate of the material, resulting in reduced lifespan characteristics and decreased battery safety.

[0010] To solve these problems, a technology has been proposed to manufacture a cathode active material in the form of a single particle rather than a secondary particle by increasing the calcination temperature during the production of lithium nickel-cobalt-manganese oxide. In the case of a cathode active material in the form of a single particle, the particle strength is superior compared to conventional cathode active materials in the form of secondary particles, resulting in less particle breakage during electrode manufacturing. Therefore, when a cathode active material in the form of a single particle is applied, there is an advantage in that it has excellent gas generation and lifespan characteristics.

[0011] However, in the case of a single-particle cathode active material, there are fewer interfaces between primary particles that serve as pathways for lithium ions within the particles, resulting in poorer rolling performance compared to a secondary-particle cathode active material, lower lithium mobility, and inferior electrochemical performance, as well as lower high-temperature durability and stability.

[0012] Therefore, when manufacturing lithium secondary batteries using single-particle cathode active materials, there is a need to develop methods to enhance lithium mobility and secure excellent electrochemical performance.

[0013] One objective of the present invention is to provide a lithium secondary battery with improved high-temperature durability and safety by combining a positive electrode comprising a positive electrode active material in the form of a single particle or a quasi-single particle and a non-aqueous electrolyte capable of forming a robust passivation film capable of improving lithium mobility on the surface of the positive electrode.

[0014] [1] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; wherein the positive electrode comprises a positive electrode active material, the positive electrode active material comprises a lithium nickel-cobalt-manganese oxide comprising 55 mol% to 70 mol% of nickel (Ni) among all transition metal elements excluding lithium, the lithium nickel-cobalt-manganese oxide is in the form of a single particle or a pseudo-single particle, and the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a first additive and a second additive, the first additive is a compound represented by the following chemical formula 1, and the second additive is a compound represented by the following chemical formula 2.

[0015] [Chemical Formula 1]

[0016]

[0017] In the above chemical formula 1,

[0018] R1 and R2 are independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms, and at least one of R1 and R2 is an alkynyl group having 2 to 5 carbon atoms.

[0019] [Chemical Formula 2]

[0020]

[0021] In the above chemical formula 2,

[0022] R3 to R5 are independently alkyl groups having 1 to 10 carbon atoms or alkenyl groups having 2 to 10 carbon atoms, and at least one of R3 to R5 is an alkenyl group having 2 to 10 carbon atoms.

[0023] [2] The present invention provides a lithium secondary battery according to [1], wherein the lithium nickel-cobalt-manganese oxide comprises a compound represented by the following chemical formula P-1.

[0024] [Chemical Formula P-1]

[0025] Li 1+a Ni x Co y M 1 z M 2 w O2

[0026] In the above chemical formula P-1,

[0027] M 1 is Mn, Al, or a combination thereof, and

[0028] M 2 is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca, and Sr, where 0≤a≤0.5, 0.55≤x≤0.70, 0 <y≤0.4, 0<z≤0.4, 0≤w≤0.1 이고, x+y+z+w는 이다.

[0029] [3] In the present invention, in [1] or [2], the lithium nickel cobalt manganese oxide is Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, Li(Ni) 0.6 Co 0.1 Mn 0.3 )O 2, Li(Ni) 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.7 Mn 0.2 Co 0.1 A lithium secondary battery is provided that is selected from the group consisting of )O2.

[0030] [4] The present invention, in at least one of [1] to [3], wherein the average particle size (D) of the lithium nickel-cobalt-manganese oxide is 50 ) provides a lithium secondary battery with a diameter of 3.0 μm or more.

[0031] [5] The present invention, in at least one of [1] to [4], wherein the average particle size (D) of the lithium nickel-cobalt-manganese oxide is 50 ) provides a lithium secondary battery with a thickness of 5.0㎛ to 9.0㎛.

[0032] [6] The present invention provides a lithium secondary battery in which, in at least one of [1] to [5], in Formula 1, R1 is hydrogen or an alkyl group having 1 to 5 carbon atoms, and R2 is an alkynyl group having 2 to 5 carbon atoms.

[0033] [7] The present invention provides a lithium secondary battery in which, in at least one of [1] to [6], in Formula 1, R1 is an alkynyl group having 2 to 5 carbon atoms and R2 is hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0034] [8] The present invention provides a lithium secondary battery in which, in at least one of [1] to [7], the compound represented by Formula 1 is a compound represented by Formula 1A or Formula 1B.

[0035] [Chemical Formula 1A]

[0036]

[0037] [Chemical Formula 1B]

[0038]

[0039] [9] The present invention provides a lithium secondary battery in which, in at least one of [1] to [3], the compound represented by Formula 1 is included in an amount of 0.2% to 2.0% by weight based on the total weight of the non-aqueous electrolyte.

[0040]

[0010] The present invention provides a lithium secondary battery in which, in at least one of [1] to [9], in the formula 2, R3 to R5 are independently an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and at least one of R3 to R5 is an alkenyl group having 2 to 5 carbon atoms.

[0041]

[0011] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0010] , in the formula 2, R3 to R5 are independently alkyl groups having 1 to 5 carbon atoms or alkenyl groups having 2 to 5 carbon atoms, and at least two of R3 to R5 are alkenyl groups having 2 to 10 carbon atoms.

[0042]

[0012] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0011] , the compound represented by Formula 2 is selected from the group consisting of at least one compound represented by Formulas 2A to 2C below.

[0043] [Chemical Formula 2A]

[0044]

[0045] [Chemical Formula 2B]

[0046]

[0047] [Chemical Formula 2C]

[0048]

[0049]

[0013] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0012] , the compound represented by Formula 2 is included in an amount of 0.5% to 7.0% by weight based on the total weight of the non-aqueous electrolyte.

[0050]

[0014] The present invention provides a lithium secondary battery comprising, in at least one of [1] to

[0013] , at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds.

[0051] The lithium secondary battery according to the present invention comprises a cathode containing a cathode active material in the form of a single particle or a pseudo-single particle, thereby suppressing the induction of fine particles during subsequent pressing and rolling processes and effectively suppressing gas generation. In addition, the lithium secondary battery according to the present invention comprises a non-aqueous electrolyte containing two types of additives, such as a coumarin-based compound and a borate-based compound, thereby forming a robust passivation film capable of improving lithium mobility on the surface of the cathode containing the cathode active material in the form of a single particle or a pseudo-single particle. Accordingly, the lithium secondary battery of the present invention can maximize high-temperature durability and high-temperature stability effects.

[0052] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0053] In this specification, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0054] Meanwhile, prior to describing the present invention, unless otherwise specifically mentioned in the present invention, “*” refers to a connected portion (bonding site) between identical or different atoms or terminal portions of a chemical formula.

[0055] In addition, in the description of “carbon number a to b” within this specification, “a” and “b” refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms. For example, “alkyl group having 1 to 5 carbon atoms” refers to an alkyl group containing carbon atoms having 1 to 5 carbon atoms, namely CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0056] In addition, in this specification, alkyl groups or aryl groups may all be substituted or unsubstituted. Unless otherwise defined, the term “substitution” above means that at least one hydrogen bonded to a carbon is substituted with an element other than hydrogen, for example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a 6 to 20 carbon atoms It means that it is substituted with a haloaryl group, etc., and preferably means an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or a halogen atom.

[0057] In addition, in the present invention, “single particle (monolith or single crystal)” refers to a single particle that exists independently of secondary particles and does not have grain boundaries on the surface.

[0058] In addition, in this specification, “pseudo-single particle” means a particle in which a single particle composed of primary particles is aggregated into 10 or fewer particles.

[0059] In the present invention, “D min ”, “D 50 ” and “D max ” is the particle size value of the volume cumulative distribution of the cathode active material powder measured using the laser diffraction method. Specifically, D min is the minimum particle size appearing in the volume cumulative distribution, and D 50 is the particle size when the volume accumulation is 50% of the total particle volume percentage, and Dmax is the maximum particle size appearing in the volume cumulative distribution. The particle size value of the volume cumulative distribution can be measured, for example, by dispersing the positive electrode active material powder in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, and obtaining a volume cumulative particle size distribution graph.

[0060]

[0061] The present invention will be described in more detail below.

[0062] A lithium secondary battery according to the present invention comprises at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0063] lithium secondary battery

[0064] The present invention relates to a lithium secondary battery.

[0065] Specifically, the lithium secondary battery according to the present invention may include a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte.

[0066] The above-mentioned positive electrode may include a positive electrode active material, and such positive electrode active material may include lithium nickel-cobalt-manganese oxide containing 55 mol% to 70 mol% of nickel (Ni) among all transition metal elements excluding lithium.

[0067] The above lithium nickel-cobalt-manganese oxide may be in the form of a single particle or a pseudo-single particle.

[0068] The above-mentioned non-aqueous electrolyte may include a lithium salt, an organic solvent, and an additive.

[0069] The above additive may include a first additive and a second additive.

[0070] The above first additive may include a compound represented by the following chemical formula 1.

[0071] The above second additive may include a compound represented by the following chemical formula 2.

[0072] [Chemical Formula 1]

[0073]

[0074] In the above chemical formula 1,

[0075] R1 and R2 are independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms, and at least one of R1 and R2 is an alkynyl group having 2 to 5 carbon atoms.

[0076] [Chemical Formula 2]

[0077]

[0078] In the above chemical formula 2,

[0079] R3 to R5 are independently alkyl groups having 1 to 10 carbon atoms or alkenyl groups having 2 to 10 carbon atoms, and at least one of R3 to R5 is an alkenyl group having 2 to 10 carbon atoms.

[0080] The lithium secondary battery according to the present invention includes a cathode comprising a cathode active material in the form of a single particle or a quasi-single particle, thereby suppressing the induction of fine particles during subsequent compression and rolling processes and effectively suppressing gas generation.

[0081] In addition, the lithium secondary battery according to the present invention can form a robust passivation film capable of improving lithium mobility on the surface of a positive electrode containing a positive electrode active material in the form of a single particle or a similar-single particle by using a non-aqueous electrolyte containing two types of additives, such as a coumarin-based compound and a borate-based compound, so that the lithium secondary battery can obtain the effect of improving high-temperature durability and high-temperature stability.

[0082]

[0083] The lithium secondary battery of the present invention can be manufactured according to conventional methods known in the art. For example, a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode can be sequentially stacked to form an electrode assembly, the electrode assembly can be inserted into a battery case, and a non-aqueous electrolyte according to the present invention can be injected to manufacture the battery.

[0084] (1) positive electrode

[0085] The anode according to the present invention includes an anode active material.

[0086] The above-mentioned positive electrode active material may be a lithium nickel-cobalt-manganese composite oxide containing nickel, specifically, a lithium nickel-cobalt-manganese composite oxide in which the nickel (Ni) content among the total transition metal elements excluding lithium is 55 mol% or more, specifically 60 mol% or more, and also 70 mol% or less.

[0087] Specifically, the lithium nickel-cobalt-manganese composite oxide may be represented by the following chemical formula P-1.

[0088] [Chemical Formula P-1]

[0089] Li 1+a Ni x Co y M 1 z M 2 w O2

[0090] In the above chemical formula P-1,

[0091] M 1 is Mn, Al, or a combination thereof, and

[0092] M 2 is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca, and Sr, where 0≤a≤0.5, 0.55≤x≤0.70, 0 <y≤0.4, 0<z≤0.4, 0≤w≤0.1 이고, x+y+z+w는 1일 수 있다.

[0093] In the above chemical formula P-1, 1+a represents the molar ratio of lithium in the lithium nickel-cobalt-manganese composite oxide, and may be 0≤a≤0.5, preferably 0≤a≤0.2, and more preferably 0≤a≤0.1. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-cobalt-manganese oxide can be stably formed.

[0094] In the above chemical formula P-1, x represents the molar ratio of nickel among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese composite oxide, and may be 0.55 ≤ x ≤ 0.70, specifically 0.60 ≤ x ≤ 0.70, and more specifically 0.65 ≤ x ≤ 0.70. When the molar ratio of nickel satisfies the above range, high energy density is exhibited, making it possible to realize high capacity.

[0095] In the above chemical formula P-1, y represents the molar ratio of cobalt among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese composite oxide, where 0 <y≤0.4, 구체적으로 0<y≤0.3, 더욱 구체적으로는 0.05≤y≤0.3일 수 있다.

[0096] In the above chemical formula P-1, z is M among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese composite oxide. 1 Representing the molar ratio of elements, 0 <z≤0.4, 바람직하게는 0<z≤0.3, 더 바람직하게는 0.01≤z≤0.3일 수 있다.

[0097] In the above chemical formula P-1, w is M among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese composite oxide. 2 Representing the molar ratio of elements, 0 <w≤0.1, 바람직하게는 0<w≤0.05, 더 바람직하게는 0<w≤0.02이다.

[0098] The above lithium nickel-cobalt-manganese oxide is Li(Ni) with a nickel (Ni) content of 55 mol% to 70 mol%. 0.6 Co 0.2 Mn0.2 )O2, Li(Ni) 0.6 Co 0.1 Mn 0.3 )O 2, Li(Ni) 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.7 Mn 0.2 Co 0.1 It could be O2.

[0099] Meanwhile, if the Ni content in the lithium nickel-cobalt-manganese composite oxide exceeds 70 mol%, the structural instability of Ni increases due to high voltage. Therefore, when mixed with a non-aqueous electrolyte containing highly reactive electrolyte additives, such as the coumarin compound or boron-containing compound described later, the reactivity between the cathode active material and the additive accelerates, leading to increased side reactions. Consequently, film formation may not occur, resistance may increase due to increased film thickness, or electrolyte decomposition reactions may continuously occur on the electrode surface, causing a degradation in cell performance. Accordingly, it is preferable that the cathode of the present invention has a molar ratio of nickel among the total transition metals excluding lithium in the lithium nickel-cobalt-manganese composite oxide of less than 70 mol%.

[0100] In addition, the lithium nickel-cobalt-manganese composite oxide may consist of single particles (monolith or single crystal), pseudo-monolith particles, or a combination thereof.

[0101] Conventionally, as a positive electrode active material for lithium secondary batteries, the average particle size (D 50Bimodal cathode active materials have been widely used, comprising primary particles with a diameter of approximately 5.0 μm and secondary particles formed by the aggregation of tens to hundreds of these primary particles, with an average particle size of 15 μm or more. However, cathode active materials in the form of secondary particles formed by the aggregation of such primary particles have problems, such as particle breakage where primary particles detach during the rolling process in cathode manufacturing and internal cracks occurring during the charge-discharge process. If particle breakage or internal cracks occur in the cathode active material, the contact area with the non-aqueous electrolyte increases, leading to adverse reactions with the electrolyte and increased gas generation; consequently, the risk of ignition and / or explosion of the battery increases. Furthermore, as the average particle size of the cathode active material increases, the lithium migration path lengthens, causing a significant increase in resistance, which can lead to problems such as a degradation of capacity and output characteristics.

[0102] On the other hand, a cathode active material in the form of a single particle consisting of one particle that does not have visible grain boundaries independently of secondary particles, or a pseudo-single particle consisting of primary particles aggregated in groups of 10 or fewer, has a higher particle strength compared to conventional cathode active materials in the form of secondary particles aggregated in groups of tens to hundreds of primary particles, so particle breakage hardly occurs during rolling.

[0103] In addition, since the number of primary particles constituting the particles is small, the change due to volume expansion and contraction of the primary particles during charging and discharging is small, and accordingly, the occurrence of cracks inside the particles can be significantly reduced.

[0104] In the present invention, by applying lithium nickel-cobalt-manganese oxide in the form of single particles or pseudo-single particles, the amount of gas generated due to particle breakage and internal cracking is significantly reduced, thereby minimizing the increase in resistance inside the battery.

[0105] At this time, since the single particle has a reduced specific surface area compared to the existing secondary particle, it has the advantage of reducing side reactions under the electrode surface, but it also has the disadvantage that the film formation reaction is reduced, making it difficult to form a stable film on the anode surface. Accordingly, in the present invention, by using a non-aqueous electrolyte containing a coumarin-based compound of a specific structure with excellent reactivity described below, the effect of forming a stable film on the anode surface can be further improved.

[0106] Meanwhile, the average particle size (D) of the lithium nickel-cobalt-manganese oxide mentioned above 50 ) may be 3.0㎛ or more, or 5.0㎛ or more, or 5.5㎛ or more. In addition, the average particle size (D) of the lithium nickel-cobalt-manganese oxide is 50 ) may be 10.0 μm or less, or 9.0 μm or less.

[0107] D of the above lithium nickel-cobalt-manganese oxide 50 By controlling it within the above range, not only are problems occurring when applying conventional secondary particle-type cathode active materials minimized, but the increase in resistance and energy density can also be suppressed by minimizing the lithium ion diffusion distance within the cathode active material particles. That is, the average particle size (D) of the lithium composite transition metal oxide 50 When ) is 3.0 μm or greater, process productivity (coating speed, slurry gelation) and high rolling density can be achieved. In addition, the average particle size (D) of the lithium composite transition metal oxide 50 When ) is 10.0 μm or less or 9.0 μm or less, the diffusion path of lithium ions is shortened compared to the cathode active material in the form of secondary particles, thereby increasing lithium mobility and thus obtaining an effect of reducing initial resistance. Accordingly, in the present invention, the average particle size (D) of the lithium composite transition metal oxide 50By adjusting ) to the above range, the lithium ion diffusion distance inside the positive electrode active material particles can be minimized, side reactions during firing can be suppressed, and the increase in resistance can be improved.

[0108] In addition, D of the above lithium nickel-cobalt-manganese oxide min ... may be 0.9 μm or larger, or 1.0 μm or larger, or 1.3 μm or larger. In addition, D of the lithium nickel-cobalt-manganese oxide min The µm may be 3.0 µm or less, or 2.5 µm, or 2.0 µm or less. D of the lithium nickel-cobalt-manganese oxide above min When the above range is satisfied, fine particles are reduced, improving adhesion and conductivity, and excellent thermal stability can be secured by lowering the specific surface area.

[0109] In addition, D of the above lithium nickel-cobalt-manganese oxide max The value may be 12㎛ to 20㎛, preferably 12㎛ to 16㎛, and more preferably 12㎛ to 15㎛. The above D max If the above range is satisfied, excellent resistance and capacitance characteristics can be secured. That is, D of the lithium nickel-cobalt-manganese oxide max If becomes too large, the lithium movement path within the particle lengthens, reducing lithium mobility, which may lead to increased resistance. Additionally, D of the lithium nickel-cobalt-manganese oxide max If it is too small, the electrode density of the anode decreases, which can lead to a decrease in energy density.

[0110] The above anode may include an anode current collector; and an anode composite layer disposed on at least one surface of the anode current collector. In this case, the anode composite layer may include the aforementioned anode active material.

[0111] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0112] The above positive current collector may form fine irregularities on its surface to strengthen the bonding force of the positive active material. For example, the above positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0113] The anode composite layer is disposed on at least one surface of the anode current collector. Specifically, the anode composite layer may be disposed on one or both surfaces of the anode current collector.

[0114] The above-mentioned positive active material may be included in the positive composite layer in an amount of 70% to 99% by weight, specifically 80% to 98% by weight, taking into consideration the sufficient capacity exertion of the positive active material.

[0115] The above-mentioned positive composite layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0116] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Examples of such binders include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. One type of silane binder alone or a mixture of two or more types may be used.

[0117] The above binder may be included in an amount of 0.1 to 15.0 weight%, preferably 0.1 to 10.0 weight%, based on the total weight of the anode composite layer.

[0118] Next, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon black such as 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 crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, etc., and one of these alone or a mixture of two or more may be used.

[0119] The above conductive material may be included in an amount of 0.1 to 10.0 weight%, preferably 0.1 to 5.0 weight%, based on the total weight of the anode composite layer.

[0120] The thickness of the anode composite layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0121] The anode may be manufactured by coating an anode slurry comprising an anode active material and optionally a binder, a conductive material, and a solvent for forming an anode slurry onto the anode current collector, and then drying and rolling. Alternatively, the anode may be manufactured by mixing an anode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto an anode current collector.

[0122] The solvent for forming the anode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably N-methylpyrrolidone, in order to facilitate the dispersion of the anode active material, binder, and / or conductive material. The amount of the solvent used is not particularly limited, provided that it is sufficient to allow the anode composite to have an appropriate viscosity, taking into account the coating thickness, manufacturing yield, workability, etc. of the anode composite.

[0123]

[0124] (2) Cathode

[0125] Next, the cathode is explained.

[0126] The above cathode may include a cathode active material.

[0127] The above-mentioned negative electrode active material may include a carbon-based active material.

[0128] The above carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0129] Average particle size (D of the above carbon-based active material) 50 ) can be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in terms of ensuring structural stability during charging and discharging and reducing side reactions with the electrolyte.

[0130] In addition, the above-mentioned negative electrode active material may further include a silicon-based active material.

[0131] The above silicon-based active material has the advantage of having a higher capacity and higher energy density compared to carbon-based active materials such as graphite.

[0132] The above silicon-based active material is metallic silicon (Si) and silicon oxide (SiO₂). x, where 0≤x<2) may include one or more selected from the group consisting of silicon carbide (SiC) and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si). The element Y may be selected from the group consisting of 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.

[0133] Specifically, the silicon-based active material is silicon oxide (SiO₂). x , here 0 <x<2)일 수 있으며, 이때 SiO2의 경우 리튬 이온과 반응하지 않아 리튬을 저장할 수 없으므로, x는 상기 범위 내인 것이 바람직하다. 구체적으로, 상기 실리콘계 활물질은 Si 및 SiO x It may be at least one type selected from a group consisting of (0.7≤x≤1.2, specifically x=1).

[0134] Average particle size (D) of the above silicon-based active material 50 ) can be 1㎛ to 30㎛, preferably 2㎛ to 15㎛, in terms of reducing side reactions with the electrolyte while ensuring structural stability during charging and discharging.

[0135] The above silicon-based active material exhibits higher capacity characteristics compared to carbon-based active materials. Therefore, if a silicon-based active material is additionally included as the negative electrode active material, superior capacity characteristics can be obtained.

[0136] When a carbon-based active material and a silicon-based active material are used in combination as the above-mentioned cathode active material, the weight ratio of the carbon-based active material and the silicon-based active material may be 70:30 to 99:1, preferably 85:15 to 97:3, and more preferably 90:10 to 97:3. When the mixing ratio of the silicon-based active material and the carbon-based active material satisfies the above range, excellent cycle performance can be secured by suppressing the volume expansion of the silicon-based active material while improving capacity characteristics.

[0137] Meanwhile, the above cathode may include a cathode current collector; and a cathode composite layer disposed on at least one surface of the cathode current collector. In this case, the cathode active material may be included in the cathode composite layer.

[0138] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0139] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0140] The above-mentioned negative current collector may form fine irregularities on its surface to strengthen the bonding force of the negative active material. For example, the above-mentioned negative current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0141] The above cathode composite layer is disposed on at least one surface of the cathode current collector. Specifically, the cathode composite layer may be disposed on one or both surfaces of the cathode current collector.

[0142] The above negative electrode active material may be included in the above negative electrode composite layer in an amount of 60% to 99% by weight in order to sufficiently express capacity in the secondary battery while minimizing the effect of volume expansion / contraction on the battery.

[0143] The above cathode composite layer may further include a conductive material and / or a binder together with the cathode active material.

[0144] The above conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 10.0% by weight or less, preferably 5.0% by weight or less, specifically 0.1% to 5.0% by weight, based on the total weight of the negative electrode composite layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, carbon black such as 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 crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as carbon fluoride powder, aluminum powder, nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, etc. may be used.

[0145] The above binder is a component that assists in the bonding between a conductive material, an active material, and a current collector, and specific examples include a fluoropolymer-based binder comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber-based binder comprising styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; a cellulose-based binder comprising carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, or regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; a polyolefin-based binder comprising polyethylene or polypropylene; a polyimide-based binder; a polyester-based binder; and a silane-based binder.

[0146] The above binder may be included in an amount of 0.1 to 15.0 weight%, preferably 0.1 to 10.0 weight%, based on the total weight of the cathode composite layer.

[0147] The thickness of the above cathode composite layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0148] The above cathode may be manufactured by coating a cathode slurry comprising a cathode active material and optionally a binder, a conductive material, and a solvent for forming a cathode slurry onto the cathode current collector, and then drying and rolling. Alternatively, the cathode may be manufactured by mixing a cathode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto a cathode current collector.

[0149] The solvent for forming the above cathode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0150]

[0151] (3) Separator

[0152] The above separator separates the negative and positive electrodes and provides a pathway for the movement of lithium ions. It can be used without any specific restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of ions of a non-aqueous electrolyte and excellent moisture retention capacity for the non-aqueous electrolyte.

[0153] Specifically, as a separator, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0154]

[0155] (4) Non-aqueous electrolyte

[0156] The non-aqueous electrolyte of the present invention may include a lithium salt, an organic solvent, a first additive, and a second additive.

[0157] (4-1) Lithium salt

[0158] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt is Li as a cation. + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO2 - , AlCl4- , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from a group consisting of

[0159] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO2, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10It may include at least one selected from the group consisting of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0160] The above lithium salt may be included in the above-mentioned non-aqueous electrolyte at a concentration of 0.5M to 5M, specifically 0.8M to 4M, and more specifically 0.8M to 2.5M. When the concentration of the above-mentioned lithium salt satisfies the above range, the lithium ion yield (Li + The transference number and the degree of dissociation of lithium ions are improved, which can enhance the output characteristics of the battery.

[0161] Alternatively, the above lithium salt may be included in the non-aqueous electrolyte in the remainder excluding, for example, the organic solvent and additives described below.

[0162]

[0163] (4-2) Organic solvents

[0164] The above organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it minimizes decomposition due to oxidation reactions, etc., during the charging and discharging process of the secondary battery.

[0165] The above organic solvent may be included in the non-aqueous electrolyte in the remainder excluding lithium salts and additives, for example.

[0166] Specifically, the organic solvent may include a carbonate-based organic solvent. Specifically, the carbonate-based organic solvent may include at least one selected from a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent, and more specifically, may include a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0167] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can effectively dissociate lithium salts in the electrolyte. Specifically, it may include at least one organic solvent 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, and more specifically, it may include ethylene carbonate (EC).

[0168] The above linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and specifically may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC); more specifically, may include at least one selected from the group consisting of ethylmethyl carbonate and diethyl carbonate; and even more specifically, may include ethylmethyl carbonate.

[0169] When the above carbonate-based organic solvent includes a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent, the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent may be included in a volume ratio of 10:90 to 50:50, specifically 15:85 to 45:55, more specifically 20:80 to 40:60.

[0170] The above organic solvent may further include at least one of an ester-based organic solvent, an ether-based organic solvent, a glycine-based solvent, and a nitrile-based organic solvent together with the above carbonate-based organic solvent.

[0171] The above ester-based organic solvent may include at least one selected from linear ester-based organic solvents and cyclic ester-based organic solvents. Specifically, the above linear ester-based organic solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. Additionally, the above cyclic ester-based organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0172] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0173] The above-mentioned glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents and is a solvent with low reactivity with metals. It may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0174] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0175] The above organic solvent may consist solely of the carbonate-based organic solvent. Even if only the carbonate-based organic solvent is used as the organic solvent, it is preferable in that it facilitates the dissolution of non-aqueous electrolyte components, such as the additives described later, and enables the realization of appropriate mobility of the lithium salt and viscosity of the non-aqueous electrolyte.

[0176]

[0177] (4-3) 1st additive

[0178] The above first additive may include a compound represented by the following chemical formula 1.

[0179] [Chemical Formula 1]

[0180]

[0181] In the above chemical formula 1,

[0182] R1 and R2 are independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms, and at least one of R1 and R2 is an alkynyl group having 2 to 5 carbon atoms.

[0183] The coumarin-based compound included as the first additive contains at least one alkynyl group having 2 to 5 carbon atoms in its structure and has strong reducing properties; therefore, during the initial activation of a lithium secondary battery, the ring structure opens faster than that of a general carbonate compound, making it possible to form a polyethylene oxide-based polymeric solid electrolyte interface layer. This polymeric solid electrolyte interface layer has the advantage of excellent flexibility and durability. In addition, the compound represented by Chemical Formula 1, which is the first additive of the present invention, has a substituent at the 3rd and / or 7th positions of the ring structure (according to IUPAC nomenclature). Compared to cases where a substituent is present at other positions, such as the 4th, 5th, 6th, and 8th positions, the aromatic ring can be maintained even after the ring-opening reaction, and because the toughness of the film formed as a result is high, an excellent improvement in high-temperature durability due to the stable film formation can be secured. In addition, the compound represented by Chemical Formula 1 above has increased reactivity through a rapid ring-opening reaction, and when mixed with a cathode containing a single particle having a smaller specific surface area compared to existing secondary particles and thus low reactivity, it can achieve the effect of forming a stable film on the surface of the cathode. Furthermore, the coumarin-based compound forms radicals through the ring-opening reaction, which increases the reactivity of the second additive described later, thereby enabling the formation of a more stable solid electrolyte interface layer on the surface of the anode. Additionally, since the aromatic ring remains within the structure of the coumarin-based compound even after the ring-opening reaction, electrons can be evenly distributed, which enables the formation of a film with improved lithium ion mobility characteristics. Simultaneously, due to the increased toughness of the film, the high-temperature durability of the secondary battery can be further improved.

[0184] However, even if an alkynyl group is substituted at position 3 or 7 of the ring structure of the compound represented by Chemical Formula 1, which is the first additive, if additional substituents such as alkyl groups are bonded at positions 4, 5, 6, and 8, the aromatic ring structure may collapse after the ring-opening reaction. As a result, the electron distribution of the formed film may be reduced, which may lower the lithium ion transfer characteristics and simultaneously lower the toughness of the film. In this specification, the position numbers of the ring structure may be as defined in IUPAC.

[0185] As such, the compound represented by Formula 1, which is the first additive of the present invention, has a substituent attached at a specific position, so it is more smoothly reduced at the cathode surface, which is more advantageous for forming a solid electrolyte interface layer, and also forms a robust film on the anode surface, thereby having an excellent effect of inhibiting transition metal leaching.

[0186] In the above formula 1, R1 may be hydrogen or an alkyl group having 1 to 5 carbon atoms, and R2 may be an alkynyl group having 2 to 5 carbon atoms. Or in the above formula 1, R1 may be an alkynyl group having 2 to 5 carbon atoms, and R2 may be hydrogen or an alkyl group having 1 to 5 carbon atoms. Or, in the above formula 1, R1 may be hydrogen or an alkyl group having 1 to 3 carbon atoms, and R2 may be an alkynyl group having 2 to 4 carbon atoms. Or in the above formula 1, R1 may be an alkynyl group having 2 to 4 carbon atoms, and R2 may be hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0187] Specifically, the compound represented by the above chemical formula 1 may be a compound represented by the following chemical formula 1A or chemical formula 1B.

[0188] [Chemical Formula 1A]

[0189]

[0190] [Chemical Formula 1B]

[0191]

[0192] The compound represented by Chemical Formula 1 above may be included in an amount of 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, or 0.8 wt% or more, based on the total weight of the non-aqueous electrolyte. Additionally, the compound represented by Chemical Formula 1 above may be included in an amount of 2.0 wt% or less, 1.8 wt% or less, 1.6 wt% or less, 1.5 wt% or less, 1.4 wt% or less, 1.2 wt% or less, or 1.0 wt% or less, based on the total weight of the non-aqueous electrolyte.

[0193] The above numerical ranges may be combined with each other without limitation and, specifically, may be included in 0.1% to 2.0% by weight, 0.2% to 1.8% by weight, 0.3% to 1.5% by weight, or 0.5% to 1.2% by weight.

[0194] When the content of the compound represented by Chemical Formula 1 satisfies the above range, it is desirable in that it sufficiently imparts flexibility and recovery to the SEI film while preventing an increase in resistance of the lithium secondary battery due to excessive addition and the consequent degradation of lifespan performance. In particular, when using a cathode containing a cathode active material in the form of a single particle or a pseudo-single particle, if the content of the compound represented by Chemical Formula 1 in the non-aqueous electrolyte is 2% by weight or less, the participation of the second additive described later in film formation can be increased through radical reactions based on the stable coumarin-based film formation. Furthermore, this is more desirable in that it allows for the formation of a film with improved coverage characteristics, thereby further improving high-temperature durability. Meanwhile, in the case of the solid electrolyte interface layer derived from the compound represented by Chemical Formula 1, which is the first additive, there is a problem that the resistance is somewhat high, causing a slight increase in the initial resistance of the cell. Accordingly, in order to further reduce initial resistance and improve lithium mobility, the present invention may include the second additive described later together with the first additive.

[0195]

[0196] (4-4) Second additive

[0197] In the present invention, the second additive may include a compound represented by the following chemical formula 2.

[0198] [Chemical Formula 2]

[0199]

[0200] In the above chemical formula 2,

[0201] R3 to R5 are independently alkyl groups having 1 to 10 carbon atoms or alkenyl groups having 2 to 10 carbon atoms, and at least one of R3 to R5 is an alkenyl group having 2 to 10 carbon atoms.

[0202] The boron-based compound included as the second additive possesses negative characteristics because it contains a large number of oxygen (O) elements within its structure. Therefore, since the second additive exhibits high film participation through stable adsorption to the anode surface, it can rapidly form a more stable, low-resistance anode electrolyte interface (CEI) layer with a high oxygen content on the anode surface, thereby significantly improving lithium ion mobility. In particular, the second additive allows for the formation of a uniform film on the anode surface containing a single-particle or pseudo-single-particle type anode active material with a small specific surface area. Consequently, by preventing electrolyte consumption due to side reactions during battery operation and increasing resistance due to increased electrode film thickness, the performance of the lithium secondary battery, such as high-temperature durability and high-temperature stability, can be improved.

[0203] Meanwhile, when the compound represented by Chemical Formula 2 is used in combination with a cathode containing a lithium nickel-cobalt-manganese composite oxide having a Ni content of 70 mol% or less, it can form a more uniform film with excellent coverage characteristics. For example, in the case of a cathode containing a lithium nickel-cobalt-manganese composite oxide having a Ni content exceeding 70 mol%, the structural instability of Ni due to high voltage is high, and positive charges from transition metals are not evenly distributed on the electrode surface. Consequently, the compound represented by Chemical Formula 2 may be adsorbed unevenly, forming a film with reduced coverage characteristics, which may lead to poor cell performance over the long term.

[0204] Meanwhile, the compound represented by Chemical Formula 1, which is the first additive mentioned above, tends to actively participate in the film (CEI / SEI) formation reaction by forming a highly reactive propargyl-based radical intermediate in an electrolyte environment, but this radical-based film has the disadvantage of causing relatively high resistance due to its structurally low density.

[0205] The borate-based compound, which is the second additive mentioned above, exhibits excellent interaction with lithium ions due to its bulky stereochemical structure and numerous oxygen (O) ligands. Consequently, it can form a film with excellent Li+ mobility characteristics, but it has a structural limitation in that the participation rate of the film reaction on the electrode surface is restricted due to the steric hindrance of the borate element.

[0206] Accordingly, in the present invention, by using the first additive and the second additive in combination, radical species derived from the proparzil-based additive promote the initial film reaction of the borate-based additive, thereby effectively increasing the film participation rate, which was low when the borate compound was used alone. As a result, the effect of stably forming a low-resistance, dense composite film formed by radical reaction on the electrode surface while maintaining the Li+ conductivity characteristics of the borate-based film can be obtained.

[0207] Meanwhile, in the above formula 2, R3 to R5 are independently alkyl groups having 1 to 5 carbon atoms or alkenyl groups having 2 to 5 carbon atoms, and at least one of R3 to R5 may be an alkenyl group having 2 to 5 carbon atoms. Specifically, in the above formula 2, R3 to R5 are independently alkyl groups having 1 to 5 carbon atoms or alkenyl groups having 2 to 5 carbon atoms, and at least two of R3 to R5 may be alkenyl groups having 2 to 5 carbon atoms.

[0208] More specifically, the compound represented by the above chemical formula 2 may be at least one selected from the group consisting of compounds represented by the following chemical formulas 2A to 2D.

[0209] [Chemical Formula 2A]

[0210]

[0211] [Chemical Formula 2B]

[0212]

[0213] [Chemical Formula 2C]

[0214]

[0215]

[0216] In particular, when the compound represented by Chemical Formula 2 is substituted with a vinyl group at the terminals compared to when an alkyl group is substituted, the reactivity (adsorption) with the anode surface is higher, making it possible to form a more robust film. Therefore, it is more preferable for the compound represented by Chemical Formula 2 to include the compound represented by Chemical Formula 2A, in which all terminal groups are substituted with vinyl groups.

[0217] Meanwhile, as described above, borate compounds have a low reaction participation rate on the electrode surface due to their bulky structure. However, there is a disadvantage that this tendency is further exacerbated in compounds that do not contain vinyl groups in their structure, such as compounds represented by the following chemical formulas VII to IX, which contain only alkyl groups as terminal groups, or compounds containing halogen groups (F) or halogen-substituted alkyl groups. That is, since the alkyl groups included as terminal groups are chemically stable and have non-polar characteristics, reactions or bonding do not occur well on the electrode surface. Additionally, because the halogen groups (F) have strong bonds and do not easily decompose in the electrolyte, they can suppress reactions that contribute to film formation.

[0218] [Chemical Formula VII]

[0219]

[0220] [Chemical Formula VIII]

[0221]

[0222] [Chemical Formula IX]

[0223]

[0224] The compound represented by Chemical Formula 2 above may be included in an amount of 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1.0 wt% or more, 1.1 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, or 1.5 wt% or more, based on the total weight of the non-aqueous electrolyte. Additionally, the compound represented by Chemical Formula 2 above may be included in an amount of 7.0 wt% or less, 6.0 wt% or less, 5.0 wt% or less, 4.0 wt% or less, or 3.0 wt% or less, based on the total weight of the non-aqueous electrolyte.

[0225] The above numerical ranges can be combined with one another without limitation. Specifically, the compound represented by Chemical Formula 2 may be included in an amount of 0.5% to 7.0%, 0.5% to 5.0%, 0.7% to 5.0%, or 0.8% to 5.0% based on the total weight of the non-aqueous electrolyte.

[0226] When the content of the compound represented by Chemical Formula 2 satisfies the above range, it is desirable in that it can increase lithium ion mobility by forming an oxygen-containing film while providing sufficient flexibility and recovery to the SEI film. In particular, when using a cathode containing a cathode active material in the form of a single particle or a pseudo-single particle, if the content of the compound represented by Chemical Formula 2 in the non-aqueous electrolyte satisfies 0.5% to 7.0% by weight, a more uniform film with excellent coverage characteristics can be formed.

[0227]

[0228] (4-5) Auxiliary additives

[0229] The lithium secondary battery of the present invention may additionally include auxiliary additives as additives in the non-aqueous electrolyte as needed to prevent the decomposition of the electrolyte in a high-power environment from causing cathode collapse, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures. When auxiliary additives are further included in the non-aqueous electrolyte, the compound represented by Chemical Formula 1 may be named the first additive, the compound represented by Chemical Formula 2 may be named the second additive, and the auxiliary additive may be named the third additive.

[0230] The above auxiliary additive may include at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0231] Examples of the above-mentioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0232] Examples of the above halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0233] The above sulfone-based compound may include at least one compound selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0234] Examples of the above sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0235] The above phosphate-based compounds may include 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.

[0236] Examples of the above borate compounds include tetraphenylborate and lithium oxalyl difluoroborate, excluding the compound represented by Chemical Formula 2.

[0237] The above nitrile-based compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0238] Examples of the above benzene-based compounds include fluorobenzene, and examples of the above amine-based compounds include triethanolamine or ethylenediamine.

[0239] Tetravinylsilane can be cited as the above silane compound.

[0240] The above lithium salt-based compound is a compound different from the lithium salt included in the electrolyte, and may include one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate toborate (LiB(C2O4)2)) and LiBF4.

[0241] Meanwhile, the above auxiliary additives may be used in a mixture of two or more types, and may be included in an amount of less than 10% by weight based on the total weight of the non-aqueous electrolyte, specifically 0.01% by weight or more and less than 8.0% by weight, and preferably 0.05% by weight to 5.0% by weight.

[0242] Meanwhile, the external shape of the lithium secondary battery of the present invention is not particularly limited and can be cylindrical, prismatic, pouch-type, or coin-type.

[0243] In addition, the lithium secondary battery of the present invention can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs) and energy storage systems (ESS).

[0244]

[0245] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are merely examples to aid in understanding the invention and do not limit the scope of the invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of this description, and it is natural that such variations and modifications fall within the scope of the appended claims.

[0246] Examples

[0247] Example 1.

[0248] (Preparation of non-aqueous electrolytes)

[0249] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0250] (Anode manufacturing)

[0251] Anode active material in the form of single particles (Li(Ni) in N-methyl-2-pyrrolidone (NMP), a solvent) 0.6 Co 0.1 Mn 0.3 )O2, average particle size (D 50 An anode slurry (solid content 60 wt%) was prepared by adding a conductive material (carbon black) and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6 (Dmin: 0.97 μm, Dmax: 13.1 μm). The anode slurry was applied to an anode current collector (Al thin film) with a thickness of 13.5 μm and dried, after which a roll press was performed to manufacture an anode.

[0252] (Cathode manufacturing)

[0253] A cathode slurry (solid content: 60 wt%) was prepared by adding a cathode active material (graphite), a binder (SBR-CMC), and a conductive material (carbon black) to water, a solvent, in a weight ratio of 97.6:0.8:1.6. The cathode slurry was applied to a 6 μm thick copper (Cu) thin film serving as a cathode current collector, dried, and then subjected to a roll press to manufacture the cathode.

[0254] (Secondary battery manufacturing)

[0255] An electrode assembly was manufactured by sequentially laminating the positive and negative electrodes prepared by the aforementioned method together with a polyethylene porous film using a conventional method, then housing them in a battery case, and injecting the above-mentioned non-aqueous electrolyte to manufacture a lithium secondary battery.

[0256]

[0257] Example 2.

[0258] (Preparation of non-aqueous electrolytes)

[0259] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1B and a compound represented by Formula 2A. The compound represented by Formula 1B and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0260] (Secondary battery manufacturing)

[0261] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0262]

[0263] Example 3.

[0264] (Preparation of non-aqueous electrolytes)

[0265] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2B. The compound represented by Formula 1A and the compound represented by Formula 2B may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0266] (Secondary battery manufacturing)

[0267] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0268]

[0269] Example 4.

[0270] (Preparation of non-aqueous electrolytes)

[0271] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2C. The compound represented by Formula 1A and the compound represented by Formula 2C may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0272] (Secondary battery manufacturing)

[0273] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0274]

[0275] Example 5.

[0276] (Preparation of non-aqueous electrolytes)

[0277] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in an amount of 1.0 wt% and 2.0 wt% of the non-aqueous electrolyte, respectively (see Table 1 below).

[0278] (Secondary battery manufacturing)

[0279] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0280]

[0281] Example 6.

[0282] (Preparation of non-aqueous electrolytes)

[0283] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at 2.0 wt% and 1.0 wt%, respectively (see Table 1 below).

[0284] (Secondary battery manufacturing)

[0285] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0286]

[0287] Example 7.

[0288] (Preparation of non-aqueous electrolytes)

[0289] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2B. The compound represented by Formula 1A and the compound represented by Formula 2B may be included in amounts of 2.0 wt% and 1.0 wt%, respectively, of the non-aqueous electrolyte (see Table 1 below).

[0290] (Secondary battery manufacturing)

[0291] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0292]

[0293] Example 8.

[0294] (Preparation of non-aqueous electrolytes)

[0295] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2C. The compound represented by Formula 1A and the compound represented by Formula 2C may be included in an amount of 2.0 wt% and 1.0 wt% of the non-aqueous electrolyte, respectively (see Table 1 below).

[0296] (Secondary battery manufacturing)

[0297] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0298]

[0299] Example 9.

[0300] (Preparation of non-aqueous electrolytes)

[0301] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in amounts of 0.2 wt% and 5.0 wt% of the non-aqueous electrolyte, respectively (see Table 1 below).

[0302] (Secondary battery manufacturing)

[0303] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0304]

[0305] Example 10.

[0306] (Preparation of non-aqueous electrolytes)

[0307] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 2.0 wt% and 1.5 wt%, respectively (see Table 1 below).

[0308] (Secondary battery manufacturing)

[0309] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0310]

[0311] Example 11.

[0312] (Preparation of non-aqueous electrolytes)

[0313] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in an amount of 3.0 wt% and 2.0 wt% of the non-aqueous electrolyte, respectively (see Table 1 below).

[0314] (Secondary battery manufacturing)

[0315] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0316]

[0317] Example 12.

[0318] (Preparation of non-aqueous electrolytes)

[0319] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in amounts of 0.1 wt% and 2.0 wt% of the non-aqueous electrolyte, respectively (see Table 1 below).

[0320] (Secondary battery manufacturing)

[0321] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0322]

[0323] Example 13.

[0324] (Preparation of non-aqueous electrolytes)

[0325] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 0.2 wt%, respectively (see Table 1 below).

[0326] (Secondary battery manufacturing)

[0327] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0328]

[0329] Comparative Example 1.

[0330] (Preparation of non-aqueous electrolytes)

[0331] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0332] (Anode manufacturing)

[0333] Anode active material in the form of secondary particles formed by the aggregation of primary particles in the solvent N-methyl-2-pyrrolidone (NMP) (Li(Ni 0.6 Co 0.1 Mn 0.3 )O2, average particle size (D 50 An anode slurry (solid content 60 wt%) was prepared by adding a conductive material (carbon black) and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6 (Dmin: 3.3 μm, Dmax: 0.57 μm, Dmax: 11.0 μm). The anode slurry was applied to an anode current collector (Al thin film) with a thickness of 13.5 μm and dried, after which a roll press was performed to manufacture an anode.

[0334] (Secondary battery manufacturing)

[0335] Except for using the positive electrode prepared by the method described above, an electrode assembly was prepared in the same manner as in Example 1, placed in a battery case, and the prepared non-aqueous electrolyte was injected to produce a lithium secondary battery.

[0336]

[0337] Comparative Example 2.

[0338] (Preparation of non-aqueous electrolytes)

[0339] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula 2A. The compound represented by Formula 1A and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0340] (Anode manufacturing)

[0341] Anode active material in the form of single particles (Li(Ni) in N-methyl-2-pyrrolidone (NMP), a solvent) 0.8 Co 0.1 Mn 0.1 )O2, average particle size (D 50 An anode slurry (solid content 60 wt%) was prepared by adding a conductive material (carbon black) and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6 (Dmin: 0.81, Dmax: 15.56). The anode slurry was applied to an anode current collector (Al thin film) with a thickness of 13.5 μm and dried, after which a roll press was performed to manufacture an anode.

[0342] (Secondary battery manufacturing)

[0343] Except for using the positive electrode prepared by the method described above, an electrode assembly was prepared in the same manner as in Example 1, placed in a battery case, and the prepared non-aqueous electrolyte was injected to produce a lithium secondary battery.

[0344]

[0345] Comparative Example 3.

[0346] (Preparation of non-aqueous electrolytes)

[0347] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula I and a compound represented by Formula 2A. The compound represented by Formula I and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0348] [Chemical Formula I]

[0349]

[0350] (Secondary battery manufacturing)

[0351] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0352]

[0353] Comparative Example 4.

[0354] (Preparation of non-aqueous electrolytes)

[0355] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula II and a compound represented by Formula 2A. The compound represented by Formula II and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0356] [Chemical Formula II]

[0357]

[0358] (Secondary battery manufacturing)

[0359] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0360]

[0361] Comparative Example 5.

[0362] (Preparation of non-aqueous electrolytes)

[0363] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula III and a compound represented by Formula 2A. The compound represented by Formula III and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0364] [Chemical Formula III]

[0365]

[0366] (Secondary battery manufacturing)

[0367] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0368]

[0369] Comparative Example 6.

[0370] (Preparation of non-aqueous electrolytes)

[0371] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula IV and a compound represented by Formula 2A. The compound represented by Formula IV and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0372] [Chemical Formula IV]

[0373]

[0374] (Secondary battery manufacturing)

[0375] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0376]

[0377] Comparative Example 7.

[0378] (Preparation of non-aqueous electrolytes)

[0379] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula V and a compound represented by Formula 2A. The compound represented by Formula V and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0380] [Chemical Formula V]

[0381]

[0382] (Secondary battery manufacturing)

[0383] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0384]

[0385] Comparative Example 8.

[0386] (Preparation of non-aqueous electrolytes)

[0387] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula VI and a compound represented by Formula 2A. The compound represented by Formula VI and the compound represented by Formula 2A may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0388] [Chemical Formula VI]

[0389]

[0390] (Secondary battery manufacturing)

[0391] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0392]

[0393] Comparative Example 9.

[0394] (Preparation of non-aqueous electrolytes)

[0395] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula VII. The compound represented by Formula 1A and the compound represented by Formula VII may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0396] [Chemical Formula VII]

[0397]

[0398] (Secondary battery manufacturing)

[0399] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0400]

[0401] Comparative Example 10.

[0402] (Preparation of non-aqueous electrolytes)

[0403] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula VIII. The compound represented by Formula 1A and the compound represented by Formula VIII may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0404] [Chemical Formula VIII]

[0405]

[0406] (Secondary battery manufacturing)

[0407] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0408]

[0409] Comparative Example 11.

[0410] (Preparation of non-aqueous electrolytes)

[0411] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10, and then adding a compound represented by Formula 1A and a compound represented by Formula IX. The compound represented by Formula 1A and the compound represented by Formula IX may be included in the non-aqueous electrolyte at concentrations of 1.0 wt% and 3.0 wt%, respectively (see Table 1 below).

[0412] [Chemical Formula IX]

[0413]

[0414] (Secondary battery manufacturing)

[0415] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0416]

[0417] Comparative Example 12.

[0418] (Anode manufacturing)

[0419] Anode active material in the form of single particles (Li(Ni) in N-methyl-2-pyrrolidone (NMP), a solvent) 0.5 Co 0.3 Mn 0.2 )O2, average particle size (D 50 A positive electrode slurry (solid content 60 wt%) was prepared by adding a conductive material (carbon black) and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6 (Dmin: 0.85 μm, Dmax: 12.1 μm). The positive electrode slurry was applied to a positive electrode current collector (Al thin film) with a thickness of 13.5 μm and dried, then subjected to a roll press to produce a positive electrode (see Table 1 below).

[0420] (Secondary battery manufacturing)

[0421] Except for using the positive electrode manufactured by the method described above, an electrode assembly was manufactured in the same manner as in Example 1, and then housed in a battery case to manufacture a lithium secondary battery.

[0422]

[0423]

[0424] Experimental Example

[0425] Experimental Example 1: Evaluation of Capacity Retention Rate After High-Temperature Cycling

[0426] Each lithium secondary battery prepared in the examples and comparative examples was charged to 4.4V at 25°C under CC / CV and 0.33C conditions using an electrochemical charge / discharger, discharged to 2.5V under CC and 0.33C conditions, and then charged to 50% SOC to adjust the SOC, and the discharge capacity after the initial 1 cycle was calculated.

[0427] Next, charging to 4.4V under CC / CV, 0.33C conditions at 45℃ and discharging to 2.5V under CC, 0.33C conditions constitutes one cycle, and 200 th After performing charge and discharge cycles, the discharge capacity was calculated after 200 cycles.

[0428] The capacity retention rate was calculated using Equation 1 below, and the results are shown in Table 2 below.

[0429] [Equation 1]

[0430] Capacity Retention Rate (%) = (Discharge Capacity after 200 Cycles / Discharge Capacity after 1 Cycle) × 100

[0431]

[0432] Experimental Example 2: Evaluation of Resistance Increase Rate After High-Temperature Cycling

[0433] Each lithium secondary battery prepared in the examples and comparative examples was charged to 4.4V at 25°C under CC / CV and 0.33C conditions using an electrochemical charge / discharger, discharged to 2.5V under CC and 0.33C conditions, then charged to 50% SOC to adjust the SOC, applied a 2.5C pulse for 10 seconds, and calculated the initial resistance through the difference between the voltage before the pulse factor and the voltage after the pulse factor.

[0434] Next, each lithium secondary battery is charged to 4.4V at 45℃ under CC / CV, 0.33C conditions, and discharged to 2.5V under CC, 0.33C conditions, with this constituting one cycle, 200 th After performing charge and discharge cycles, the final resistance was measured.

[0435] The resistance increase rate was calculated using Equation 2 below, and the results are shown in Table 2 below.

[0436] [Equation 2]

[0437] Resistance Increase Rate (%) = {(Final Resistance - Initial Resistance) / (Initial Resistance)} × 100

[0438] Capacitance retention rate (%) after high-temperature cycle Resistance increase rate (%) after high-temperature cycle Example 19 1 19 Example 29 0 18 Example 38 7 20 Example 48 8 19 Example 59 0 21 Example 68 5 23 Example 78 7 24 Example 88 8 23 Example 98 7 23 Example 108 7 21 Example 118 6 23 Example 128 7 20 Example 138 5 22 Comparative Example 16 0 48 Comparative Example 26 2 50 Comparative Example 36 0 55 Comparative Example 45 9 53 Comparative Example 55 8 54 Comparative Example 66 2 57 Comparative Example 76 1 52 Comparative Example 86 4 55 Comparative Example 9 7 0 38 Comparative Example 10 7 3 36 Comparative Example 11 7 2 40 Comparative Example 126044

[0439]

[0440] Referring to Table 2 above, it can be seen that the lithium secondary batteries of Examples 1 to 13 have improved performance after high-temperature cycling compared to the lithium secondary batteries of Comparative Examples 1 to 12.

[0441]

[0442] Experimental Example 3: Evaluation of Capacity Retention Rate After High-Temperature Storage

[0443] Each lithium secondary battery prepared in the examples and comparative examples was charged to 4.4 V under 0.33 C constant current / constant voltage (CC / CV) conditions at room temperature (±25℃), and discharged to 2.5 V under 0.33 C constant current (CC) conditions to perform initial charge and discharge, after which the initial discharge capacity was calculated.

[0444] Next, each lithium secondary battery was stored at 60°C for 8 weeks, then cooled to (±25°C), charged to 4.4V under 0.33C constant current / constant voltage (CC / CV) conditions, discharged to 2.5V under 0.33C constant current (CC) conditions, and the discharge capacity was calculated after 8 weeks of storage.

[0445] The capacity retention rate after high-temperature storage was calculated using Equation 3 below, and the results are shown in Table 3 below.

[0446] [Equation 3]

[0447] Capacity Retention Rate (%) = (Discharge Capacity after 8 weeks of storage / Initial Discharge Capacity) × 100

[0448]

[0449] Experimental Example 4: Evaluation of Resistance Increase Rate After High-Temperature Storage

[0450] Each lithium secondary battery prepared in the examples and comparative examples was charged to 4.4V under 0.33C constant current / constant voltage (CC / CV) conditions at room temperature (±25℃), discharged to 2.5V under 0.33C constant current (CC) conditions, then charged to 50% to adjust the SOC, applied a 2.5C pulse for 10 seconds, and calculated the initial resistance through the difference between the voltage before the pulse factor and the voltage after the pulse factor.

[0451] Next, each lithium secondary battery was stored at 60°C for 8 weeks, then cooled to (±25°C), charged to 4.4V under 0.33C constant current / constant voltage (CC / CV) conditions, discharged to 2.5V under 0.33C constant current (CC) conditions, and the final resistance was calculated after 8 weeks of storage.

[0452] The resistance increase rate was calculated using Equation 4 below, and the results are shown in Table 3 below.

[0453] [Equation 4]

[0454] Resistance Increase Rate (%) = {(Final Resistance - Initial Resistance) / (Initial Resistance)} × 100

[0455] Capacity retention rate (%) after high-temperature storage Resistance increase rate (%) Example 18617 Example 28420 Example 38319 Example 48320 Example 58220 Example 68321 Example 78422 Example 88221 Example 98322 Example 108320 Example 118024 Example 128323 Example 138121 Comparative Example 15350 Comparative Example 25844 Comparative Example 35042 Comparative Example 45144 Comparative Example 55548 Comparative Example 64847 Comparative Example 75040 Comparative Example 85745 Comparative Example 97040 Comparative Example 106839 Comparative Example 116543 Comparative Example 126738

[0456]

[0457] Referring to Table 2, it can be seen that the lithium secondary batteries of Examples 1 to 13 have improved high-temperature storage performance compared to the lithium secondary batteries of Comparative Examples 1 to 12.

Claims

1. A positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; comprising, The above-mentioned positive electrode includes a positive electrode active material, and The above-mentioned positive electrode active material comprises lithium nickel-cobalt-manganese oxide containing 55 mol% to 70 mol% of nickel (Ni) among the total transition metal elements excluding lithium, and The above lithium nickel-cobalt-manganese oxide is in the form of single particles or pseudo-single particles, and The above-mentioned non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, and The above additive includes a first additive and a second additive, and The above first additive is a compound represented by the following chemical formula 1, and The above second additive is a lithium secondary battery that is a compound represented by the following chemical formula 2: [Chemical Formula 1] In the above chemical formula 1, R1 and R2 are independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms, and at least one of R1 and R2 is an alkynyl group having 2 to 5 carbon atoms. [Chemical Formula 2] In the above chemical formula 2, R3 to R5 are independently alkyl groups having 1 to 10 carbon atoms or alkenyl groups having 2 to 10 carbon atoms, and At least one of R3 to R5 is an alkenyl group having 2 to 10 carbon atoms.

2. In Paragraph 1, The above lithium nickel-cobalt-manganese oxide is a lithium secondary battery comprising a compound represented by the following chemical formula P-1: [Chemical Formula P-1] Li 1+a Ni x Co y M 1 z M 2 w O2 In the above chemical formula P-1, M 1 is Mn, Al, or a combination thereof, and M 2 is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca, and Sr, where 0≤a≤0.5, 0.55≤x≤0.70, 0 <y≤0.4, 0<z≤0.4, 0≤w≤0.1 이고, x+y+z+w는 이다.

3. In Paragraph 1, The above lithium nickel-cobalt-manganese oxide is Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, Li(Ni) 0.6 Co 0.1 Mn 0.3 )O 2, Li(Ni) 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.7 Mn 0.2 Co 0.1 A lithium secondary battery selected from the group consisting of )O2.

4. In Paragraph 1, Average particle size (D) of the above lithium nickel-cobalt-manganese oxide 50 ) is a lithium secondary battery with a thickness of 3.0 μm or more.

5. In Paragraph 4, Average particle size (D) of the above lithium nickel-cobalt-manganese oxide 50 ) is a lithium secondary battery with a thickness of 5.0㎛ to 9.0㎛.

6. In Paragraph 1, A lithium secondary battery in which, in the above chemical formula 1, R1 is hydrogen or an alkyl group having 1 to 5 carbon atoms, and R2 is an alkynyl group having 2 to 5 carbon atoms.

7. In Paragraph 6, A lithium secondary battery in which, in the above chemical formula 1, R1 is an alkynyl group having 2 to 5 carbon atoms, and R2 is hydrogen or an alkyl group having 1 to 5 carbon atoms.

8. In Paragraph 1, A lithium secondary battery in which the compound represented by the above chemical formula 1 is a compound represented by the following chemical formula 1A or chemical formula 1B. [Chemical Formula 1A] [Chemical Formula 1B] 9. In Paragraph 1, A lithium secondary battery comprising a compound represented by the above chemical formula 1 in an amount of 0.2% to 2.0% by weight based on the total weight of the non-aqueous electrolyte.

10. In Paragraph 1, A lithium secondary battery in which, in the above chemical formula 2, R3 to R5 are independently alkyl groups having 1 to 5 carbon atoms or alkenyl groups having 2 to 5 carbon atoms, and at least one of R3 to R5 is an alkenyl group having 2 to 5 carbon atoms.

11. In Paragraph 1, A lithium secondary battery in which, in the above chemical formula 2, R3 to R5 are independently alkyl groups having 1 to 5 carbon atoms or alkenyl groups having 2 to 5 carbon atoms, and at least two of R3 to R5 are alkenyl groups having 2 to 5 carbon atoms.

12. In Paragraph 1, A lithium secondary battery in which the compound represented by the above chemical formula 2 is at least one selected from the group consisting of compounds represented by the following chemical formulas 2A to 2C. [Chemical Formula 2A] [Chemical Formula 2B] [Chemical Formula 2C] 13. In Paragraph 1, A lithium secondary battery comprising a compound represented by the above chemical formula 2 in an amount of 0.5% to 7.0% by weight based on the total weight of the non-aqueous electrolyte.

14. In Paragraph 1, A lithium secondary battery comprising at least one auxiliary additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

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