Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery comprising: an electrode assembly comprising a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode; an electrolyte; and a battery case accommodating the electrode assembly and the electrolyte, in which the positive electrode contains, as a positive electrode active material, a lithium nickel-based oxide containing 80 mol% or more of nickel in all metals other than lithium, the lithium nickel-based oxide containing single-particle-type particles, secondary particles, or a combination thereof, the negative electrode contains, as a negative electrode active material, at least one type of graphite selected from the group consisting of natural graphite and artificial graphite, and has a TS index (unit: g / m2) of 1.72 or less as defined by Equation 1 below. [Equation 1] The variables in Equation 1 are the same as the variables described in the description.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0188774, filed December 21, 2023, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

[0003] The present application relates to a lithium secondary battery, and more particularly, to a lithium secondary battery exhibiting excellent thermal safety. BACKGROUND

[0004] Lithium secondary batteries provide high energy density and excellent performance, and are widely used in various applications such as portable electronic devices, electric vehicles, and energy storage devices. Therefore, for lithium secondary batteries, high energy density and thermal safety have become important considerations.

[0005] Specifically, a lithium secondary battery can cause a rapid increase in internal temperature due to various factors such as overcharging, overdischarging, external impact, or internal short circuit, and such a temperature increase can accelerate chemical reactions inside the battery, thereby causing thermal runaway. Thermal runaway can cause a series of exothermic reactions inside the battery, thereby causing the battery to catch fire or explode, seriously threatening user safety.

[0006] In addition, a lithium secondary battery with insufficient thermal stability can reduce the life and performance of the battery and significantly reduce the reliability of the product. In particular, in applications such as electric vehicles that use high-capacity batteries, the importance of thermal safety issues is more pronounced.

[0007] Therefore, there is a need to develop a technology that can improve the thermal safety of a lithium secondary battery. SUMMARY

[0008] Technical Problem

[0009] The present application aims to overcome the above limitations, and thus one aspect of the present application provides a lithium secondary battery exhibiting excellent thermal safety.

[0010] Technical Solution

[0011] [1] According to an aspect of the present application, there is provided a lithium secondary battery including: an electrode assembly including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode; an electrolyte; and a battery case accommodating the electrode assembly and the electrolyte, wherein the positive electrode includes a lithium nickel-based oxide containing 80 mol% or more of nickel among all metals except lithium as a positive electrode active material, the lithium nickel-based oxide includes single particle type particles, secondary particles, or a combination thereof, the negative electrode includes at least one selected from the group consisting of natural graphite and artificial graphite as a negative electrode active material, and a TS index (unit: g / m 2 ) defined by the following Equation 1 is 1.72 or less.

[0012] [Equation 1]

[0013]

[0014] In the above Equation 1, P S represents a proportion of the weight of the lithium nickel-based oxide in the form of secondary particles with respect to the total weight of the lithium nickel-based oxide, N G represents a proportion of the weight of the natural graphite with respect to the total weight of the natural graphite and the artificial graphite, S N represents a BET specific surface area (unit: m 2 / g) of the negative electrode active material, and E represents a proportion of the total weight of the electrolyte with respect to the total weight of the lithium secondary battery.

[0015] [2] The present application provides the lithium secondary battery according to the above [1], wherein P S is 0.7 or less.

[0016] [3] The present application provides the lithium secondary battery according to the above [1] or [2], wherein N G is 0.6 or less.

[0017] [4] The present application provides the lithium secondary battery according to at least one of the above [1] to [3], wherein S N is 1.3 m 2 / g to 1.9 m 2 / g.

[0018] [5] The present application provides the lithium secondary battery according to at least one of the above [1] to [4], wherein E is 0.08 to 0.13.

[0019] [6] The present application provides the lithium secondary battery according to at least one of the above [1] to [5], wherein the lithium nickel-based oxide is represented by the following Formula 1.

[0020] [Formula 1]

[0021] Lia1 [Ni x1 Co y1 Mn z1 M 1 w1 ]O2

[0022] In the above Formula 1, M 1 is at least one doping element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0.8≤a1≤1.2, 0.8≤x1<1, 0<y1≤0.2, 0<z1≤0.2, and 0≤w1≤0.1.

[0023] [7] The lithium secondary battery according to at least one of the above [1] to [6] is provided, wherein the battery case is a cylindrical battery case.

[0024] [8] The lithium secondary battery according to at least one of the above [1] to [7] is provided, wherein a ratio (R / H) of a diameter (R) to a height (H) of the lithium secondary battery is 0.4 or more.

[0025] [9] The lithium secondary battery according to at least one of the above [1] to [8] is provided, wherein the lithium secondary battery is a 46110 battery, a 48110 battery, a 4880 battery, or a 4680 battery.

[0026]

[10] The lithium secondary battery according to at least one of the above [1] to [9] is provided, wherein the lithium secondary battery includes uncoated portions on at least a portion of the positive electrode and the negative electrode on which an active material layer is not formed, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are defined as electrode tabs.

[0027]

[11] The lithium secondary battery according to the above

[10] is provided, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are formed at one side end portion of the positive electrode and the negative electrode, respectively, along a winding direction of the electrode assembly, the positive electrode uncoated portion and the negative electrode uncoated portion are each coupled to a current collector plate, and the current collector plate is connected to an electrode terminal.

[0028]

[12] The lithium secondary battery according to the above

[10] or

[11] is provided, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are processed in a form of a plurality of segments that are independently bendable, and at least a portion of the plurality of segments is bent toward a winding center of the electrode assembly.

[0029]

[13] The lithium secondary battery according to the above

[12] is provided, wherein at least a portion of the plurality of bent segments overlaps with upper and lower end portions of the electrode assembly, and the current collector plate is coupled to the plurality of overlapping segments.

[0030]

[14] According to another aspect of the present application, there is provided a battery pack including the lithium secondary battery according to any one of the above [1] to

[13] as a unit cell.

[0031] Advantages

[0032] The lithium secondary battery of the present application contains lithium nickel-based oxide having a high lithium content among metals other than lithium in the positive active material, thereby achieving high capacity characteristics, and by adjusting the weight ratio of lithium nickel-based oxide in the form of secondary particles in the lithium nickel-based oxide, the weight ratio of natural graphite in the negative active material, the BET specific surface area of the negative active material, and the weight ratio of the electrolyte to satisfy a specific relationship, it is possible to quickly discharge heat inside the battery to the outside of the battery, thereby improving thermal safety. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a view showing a stacked state before the electrode assembly of the present application is wound;

[0034] Figure 2 is a cross-sectional view showing an electrode structure of the electrode assembly of one embodiment of the present application.

[0035] Figure 3 is a view describing the structure of the electrode assembly of one embodiment of the present application.

[0036] Figure 4 is a cross-sectional view showing a lithium secondary battery structure of one embodiment of the present application.

[0037] Figure 5 is a cross-sectional view showing a lithium secondary battery structure of another embodiment of the present application.

[0038] Figure 6 is a view describing a battery pack of one embodiment of the present application. DETAILED DESCRIPTION

[0039] Hereinafter, the present application will be described in detail.

[0040] It should be understood that the words or terms used herein and in the claims of the present application should not be construed as being limited to having the meanings defined in commonly used dictionaries. It should also be understood that the words or terms used herein and in the claims of the present application should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the technical idea of the present application, on the principle that the inventor can appropriately define the meaning of the words or terms to best explain the present application.

[0041] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0042] It will be further understood that the terms "comprises" and / or "comprising," or "includes" and / or "including" when used herein, specify the presence of stated features, integers, steps, elements, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, elements, or combinations thereof.

[0043] As used herein, the term "single particle type" refers to a particle formed by aggregation of 30 or less sub-particles. A sub-particle unit constituting a single particle type particle is defined as a nodule. The single particle type particle includes a single particle consisting of 1 nodule and a quasi-single particle which is a complex of 2 to 30 nodules.

[0044] The term "nodule" indicates a secondary particle unit constituting a single particle and a quasi-single particle, and can be a single crystal lacking a crystal boundary or a polycrystal having no crystal boundary when observed at a field of view of 5000x to 20000x using a scanning electron microscope.

[0045] As used herein, the term "secondary particle" refers to a particle formed by aggregation of more than 30 sub-particles. In order to be distinguished from sub-particles forming a single particle, sub-particles forming a secondary particle are referred to as "primary particles".

[0046] As used herein, when describing "particles", any one or all of single particles, quasi-single particles, primary particles, nodules, and secondary particles can be included.

[0047] As used herein, "specific surface area" is measured by the BET method, specifically, BELSORP-mino II of BEL JAPAN Co. can be used to calculate from the amount of nitrogen adsorption at liquid nitrogen temperature (77 K).

[0048] With recent advances in electric vehicle technology, there is an increasing demand for high-capacity batteries. In order to develop a battery having such a high-capacity characteristic, a large cylindrical battery having a larger volume than a conventional small cylindrical battery is being developed. However, for a large cylindrical battery, as the size of the battery increases, heat and gas generated inside the battery also increase, which can cause the battery to catch fire or explode.

[0049] Meanwhile, in order to increase the capacity of a battery, there is an increasing trend of using high-nickel (high-Ni) lithium transition metal oxide having a higher nickel content than a conventional nickel-cobalt-manganese-based lithium transition metal oxide as a positive active material for a lithium secondary battery. However, for the high-nickel lithium transition metal oxide, as the nickel content increases, the amount of residual lithium increases, which can cause a side reaction with an electrolyte during charging and discharging, generating gas, thereby reducing the thermal safety of the battery due to an explosion and / or fire.

[0050] Accordingly, the present inventors have developed a lithium secondary battery having excellent capacity characteristics and excellent thermal safety, and have completed the present application by finding that, by adjusting the ratio of secondary particles of a lithium nickel-based oxide contained in a positive active material according to the positive and negative electrode materials, the ratio of natural graphite in a negative active material, and the ratio of an electrolyte to the weight of a battery, and the BET specific surface area of the negative active material, so as to satisfy a specific relational expression, the capacity characteristics and the thermal safety of the battery can be improved.

[0051] Hereinafter, the present application will be described in detail.

[0052] Lithium secondary battery

[0053] The lithium secondary battery of the present application comprises: an electrode assembly comprising a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode; an electrolyte; and a battery case accommodating the electrode assembly and the electrolyte, wherein the positive electrode comprises a lithium nickel-based oxide containing 80 mol% or more of nickel among all metals except lithium as a positive active material, the lithium nickel-based oxide comprises single-particle type particles, secondary particles, or a combination thereof, the negative electrode comprises at least one selected from the group consisting of natural graphite and artificial graphite as a negative active material, and a TS index (unit: g / m 2 ) is 1.72 or less.

[0054] [Equation 1]

[0055]

[0056] In Equation 1 above, P S represents the ratio of the weight of the lithium nickel-based oxide in the form of secondary particles to the total weight of the lithium nickel-based oxide, N G represents the ratio of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, S N represents the BET specific surface area (unit: m 2 / g) of the negative active material, and E represents the ratio of the weight of the electrolyte to the total weight of the lithium secondary battery.

[0057] Specifically, the TS index defined by Equation 1 above corresponds to a parameter that defines a relationship between the proportion of the weight of the lithium nickel-based oxide in the form of secondary particles to the total weight of the lithium nickel-based oxide, the proportion of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, the BET specific surface area of the negative active material, and the proportion of the weight of the electrolyte to the total weight of the lithium secondary battery, in order to improve the thermal safety of the lithium secondary battery.

[0058] When the proportion of the weight of the lithium nickel-based oxide in the form of secondary particles to the total weight of the lithium nickel-based oxide, the proportion of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, the BET specific surface area of the negative active material, and the proportion of the weight of the electrolyte to the total weight of the lithium secondary battery are each independently too high or too low, the thermal safety of the lithium secondary battery can not be sufficiently improved. Therefore, there is a need to design a relationship such that even if the proportion of the weight of the lithium nickel-based oxide in the form of secondary particles to the total weight of the lithium nickel-based oxide, the proportion of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, the BET specific surface area of the negative active material, and the proportion of the weight of the electrolyte to the total weight of the lithium secondary battery are each too high or too low, they can be complemented with each other, so that the thermal safety can be improved.

[0059] Therefore, the present application can improve the thermal safety of the lithium secondary battery by expressing the relationship between the proportion of the weight of the lithium nickel-based oxide in the form of secondary particles to the total weight of the lithium nickel-based oxide, the proportion of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, the BET specific surface area of the negative active material, and the proportion of the weight of the electrolyte to the total weight of the lithium secondary battery as the TS index defined by Equation 1, and by adjusting the values of each component such that the TS index is 1.72 or less.

[0060] The TS index can be 1.72 or less, preferably 1.60 or less, and more preferably 1.50 or less. When the above range is satisfied, by appropriately adjusting the proportion of the secondary particles of the lithium nickel-based oxide contained in the positive active material, the proportion of the natural graphite in the negative active material, and the proportion of the electrolyte to the total weight of the lithium secondary battery, and the BET specific surface area of the negative active material according to the positive and negative electrode materials, the rate of exothermic reaction occurring in the positive electrode, the negative electrode, and the electrolyte inside the battery at high temperature can be reduced while improving the capacity characteristics. Therefore, the amount of gas generated by high temperature exposure time is reduced, so that the temperature increase due to thermal decomposition reaction can be suppressed, thereby preventing battery explosion and fire due to high temperature gas, thereby improving the thermal safety of the battery.

[0061] P Srepresents the proportion of lithium nickel-based oxide in the form of secondary particles with respect to the total weight of lithium nickel-based oxide. The proportion of lithium nickel-based oxide in the form of secondary particles with respect to the total weight of lithium nickel-based oxide can be measured by observing a cross section of the positive electrode perpendicular to the surface of the positive electrode using a scanning electron microscope (SEM), distinguishing secondary particles and single-particle-type particles by the particle shape of the secondary particles and the single-particle-type particles, then measuring the volume ratio of the secondary particles and the single-particle-type particles therefrom, and calculating the weight ratio of lithium nickel-based oxide in the form of secondary particles to the total weight of the secondary particles and the single-particle-type particles by multiplying the respective densities of the secondary particles and the single-particle-type particles, thereby measuring P S . P S may be 0.7 or less, preferably 0.6 or less, and more preferably 0.5 or less. When the above range is satisfied, excellent thermal safety, output characteristics, and long-term life characteristics can be obtained, and improved processability is achieved.

[0062] N G represents the proportion of the weight of natural graphite to the total weight of natural graphite and artificial graphite. The proportion of the weight of natural graphite to the total weight of natural graphite and artificial graphite can be measured by observing a cross section of the negative electrode perpendicular to the surface of the negative electrode using a scanning electron microscope (SEM), distinguishing artificial graphite and natural graphite by the particle shape of the artificial graphite and the natural graphite, then measuring the volume ratio of the artificial graphite and the natural graphite therefrom, and calculating the proportion of the weight of natural graphite to the total weight of natural graphite and artificial graphite by multiplying the respective densities of the artificial graphite and the natural graphite, thereby measuring N G . N G may be 0.6 or less, preferably 0.1 to 0.6, and more preferably 0.2 to 0.5. When the above range is satisfied, the battery can have excellent rapid charging characteristics, improved thermal safety, and increased adhesion, thereby improving long-term life characteristics.

[0063] S N represents the BET specific surface area (unit: m 2 / g) of the negative electrode active material. The negative electrode containing the negative electrode active material can be scraped into a powder, and then the nitrogen adsorption amount of the powder at liquid nitrogen temperature (77 K) can be measured using a BELSORP-mino II of Japan BEL Co., Ltd., thereby obtaining S N , i.e., the BET specific surface area (unit: m 2 / g) of the negative electrode active material. S N may be 1.3 m 2 / g to 1.9 m 2 / g, preferably 1.4 m 2 / g to 1.8 m 2 / g, and more preferably 1.5 m 2 / g to 1.7 m 2When the above range is satisfied, the specific surface area of the negative electrode material is optimized in the process in which a chain side reaction occurs in a high temperature environment, so that generation of heat and generation of a high temperature gas can be minimized.

[0064] E represents a ratio of the weight of the electrolyte to the total weight of the lithium secondary battery. In this case, the weight of the electrolyte can be the weight of the electrolyte remaining in the lithium secondary battery after the activation treatment, and the total weight of the lithium secondary battery can be the total weight of the lithium secondary battery after the activation treatment, but embodiments of the present application are not limited thereto.

[0065] Activation refers to a process of charging and / or discharging a lithium secondary battery that has been manufactured but has not been charged and discharged to provide electrical characteristics and form a solid electrolyte interphase (SEI) film on an electrode to stabilize the battery so that the battery can be practically used.

[0066] For E, activation can be achieved by charging the lithium secondary battery to a voltage of 4.2 V or more at 70°C and discharging the lithium secondary battery to a voltage of 2.5 V or less at least three times, but embodiments of the present application are not limited thereto.

[0067] Specifically, the weight of the electrolyte can represent the sum of the weight of the electrolyte impregnated in the internal pores of the electrode assembly and the weight of the electrolyte located outside the electrode assembly in the internal space of the battery case.

[0068] For example, the weight of the electrolyte can be measured by (1) measuring the weight (M L ) of the lithium secondary battery after activation, which includes the electrode assembly, the electrolyte, and the battery case, wherein the battery case is sealed, (2) disassembling the lithium secondary battery to remove the electrolyte present in the battery case, (3) immersing the battery case and the electrode assembly in a dimethyl carbonate solvent to remove the electrolyte in the surface of the battery case, the surface of the electrode assembly, and the internal pores, and then drying the battery case and the electrode assembly, and (4) measuring the weight (M C ) of the dried battery case and the weight (M A ) of the dried electrode assembly, and then inputting the measured M L , M C , and M A into Equation A below.

[0069] [Equation A]

[0070] The weight of the electrolyte above = M L -M C -M A

[0071] E can be 0.08 to 0.13, preferably 0.09 to 0.12, and more preferably 0.095 to 0.11. When the above range is satisfied, the voids inside the battery are reduced, and thus, when the amount of gas generated inside the battery reaches a certain level, the opening time of the gas exhaust portion can be reduced, thereby improving the thermal safety of the lithium secondary battery.

[0072] Hereinafter, each component of the lithium secondary battery according to the present application will be described in detail.

[0073] The lithium secondary battery according to the present application includes an electrode assembly including a cathode, an anode, and a separator between the cathode and the anode; an electrolyte; and a battery case accommodating the electrode assembly and the electrolyte.

[0074] (1) Electrode assembly

[0075] The electrode assembly according to the present application includes a cathode, an anode, and a separator between the cathode and the anode.

[0076] The electrode assembly can be an electrode assembly of various forms well known in the art, such as a jelly-roll type, a stack type, a stack-lamination type, or a stack-folding type electrode assembly, and the form thereof is not particularly limited.

[0077] Preferably, the electrode assembly can be a jelly-roll type electrode assembly.

[0078] Figure 1 A stack structure before the electrode assembly according to the present application is wound is shown, Figure 2 A cross-sectional structure of an electrode plate (cathode or anode) of one embodiment of the present application is shown, Figure 3 A structure of the electrode assembly according to one embodiment of the present application is shown.

[0079] Referring to Figure 1 and Figure 2 When the electrode assembly is a jelly-roll type electrode assembly, the electrode assembly A according to the present application can be prepared by winding a stack in one direction X, the stack being formed by sequentially stacking the separator 12, the cathode 10, the separator 12, and the anode 11 at least once.

[0080] Hereinafter, each component of the electrode assembly according to the present application will be described in detail.

[0081] 1) Cathode

[0082] The cathode can be prepared by coating a cathode slurry on one side or both sides of a sheet-shaped cathode current collector, removing the solvent of the cathode slurry through a drying process, and then roll-pressing. Meanwhile, a cathode containing an uncoated portion can be prepared by not coating the cathode slurry on a portion (for example, one end of the cathode current collector) of the cathode current collector when coating the cathode slurry.

[0083] In addition, the positive electrode slurry can be prepared by dispersing the positive electrode material of the present application in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl pyrrolidone (NMP), acetone, or water.

[0084] The positive electrode thus prepared can include a positive electrode active material, and specifically, the positive electrode can include a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer can include a positive electrode active material.

[0085] As the positive electrode current collector, various positive electrode current collectors known in the art can be used. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like can be used as the positive electrode current collector. The thickness of the positive electrode current collector is generally 3 μm to 500 μm, 5 μm to 300 μm, or 7 μm to 200 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance the adhesion of the positive electrode active material. For example, the positive electrode current collector can take various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam, and a nonwoven fabric body.

[0086] The positive electrode active material layer can be located on the positive electrode current collector, and specifically, on one surface or both surfaces of the positive electrode current collector. The positive electrode active material layer can be a single layer structure or a multilayer structure of two or more layers.

[0087] The positive electrode active material layer includes a lithium nickel-based oxide containing 80 mol% or more, 85 mol% or more, 88 mol% or more, 90 mol% or more, or 92 mol% or more of nickel in addition to lithium as a positive electrode active material. When the lithium nickel-based oxide is contained, a lithium secondary battery manufactured with a high nickel content can exhibit excellent capacity.

[0088] The lithium nickel-based oxide can be represented by the following Chemical Formula 1.

[0089] [Formula 1]

[0090] Li a1 [Ni x1 Co y1 Mn z1 M 1 w1 ]O2

[0091] In the above Formula 1, M 1 may be at least one doping element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and can be at least one doping element selected from the group consisting of W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. When M is contained, the lithium nickel-based oxide can exhibit excellent capacity.1 In this case, the lithium-nickel-based oxide can have improved structural stability.

[0092] In addition, in the above Formula 1, the following conditions can be satisfied: 0.8 ≤ a1 ≤ 1.2, 0.8 ≤ x1 < 1, 0 < y1 ≤ 0.2, 0 < z1 ≤ 0.2, and 0 ≤ w1 ≤ 0.1.

[0093] Specifically, a1 can represent a molar ratio of lithium (Li) in the lithium-nickel-based oxide represented by the above Formula 1, and the following conditions can be satisfied: 0.8 ≤ a1 ≤ 1.2, 0.9 ≤ a1 ≤ 1.15, or 1.0 ≤ a1 ≤ 1.1. When the above range is satisfied, a balance can be achieved between a significant improvement in the capacity characteristics of the positive active material resulting from Li content control and sintering performance in the manufacturing process of the positive active material.

[0094] x1 can represent a molar ratio of nickel in the lithium-nickel-based oxide represented by the above Formula 1, and the following conditions can be satisfied: 0.80 ≤ x1 < 1, 0.88 ≤ x1 < 1, 0.90 ≤ x1 < 1, or 0.92 ≤ x1 < 1. By satisfying the above range, it is possible to ensure a sufficient content of nickel in the lithium-nickel-based oxide to facilitate charging and discharging, thereby achieving high capacity.

[0095] y1 can represent a molar ratio of cobalt in the lithium-nickel-based oxide represented by the above Formula 1, and the following conditions can be satisfied: 0 < y1 ≤ 0.2, 0 < y1 ≤ 0.18, or 0.01 ≤ y1 ≤ 0.15. When the above range is satisfied, the lithium transition metal oxide contains a small amount of cobalt, and thus it is possible to save costs and achieve satisfactory resistance characteristics and output characteristics.

[0096] z1 can represent a molar ratio of manganese in the lithium-nickel-based oxide represented by the above Formula 1, and the following conditions can be satisfied: 0 < z1 ≤ 0.2, 0 < z1 ≤ 0.18, or 0.01 ≤ z1 ≤ 0.15. When the above range is satisfied, the lithium-nickel-based oxide can have improved structural stability.

[0097] w1 can represent a molar ratio of M 1 in the lithium-nickel-based oxide represented by the above Formula 1, and the following conditions can be satisfied: 0 ≤ w1 ≤ 0.1, 0 ≤ w1 ≤ 0.08, or 0 ≤ w1 ≤ 0.05. When the above range is satisfied, the lithium-nickel-based oxide can have improved structural stability and energy density.

[0098] The lithium-nickel-based oxide can include single-particle type particles, secondary particles, or a combination thereof,

[0099] When the lithium nickel-based oxide contains only single particle type particles, there can be difficulties in the manufacturing process of the lithium secondary battery due to the generation of roll gap pressure, the specific surface area is small, resulting in a decrease in electrolyte impregnation properties, while the lithium migration path is lengthened, resulting in a decrease in the mobility of lithium ions, and thus the resistance properties, output properties, and long-term life are decreased.

[0100] However, when the lithium nickel-based oxide contains only single particle type particles, there can be difficulties in the manufacturing process of the lithium secondary battery due to the generation of roll gap pressure, the specific surface area is small, resulting in a decrease in electrolyte impregnation properties, while the lithium migration path is lengthened, resulting in a decrease in the mobility of lithium ions, and thus the resistance properties, output properties, and long-term life are decreased.

[0101] Therefore, the lithium secondary battery of the present application includes single particle type particles, secondary particles, or a combination thereof in the lithium nickel-based oxide, and adjusts the N G , S N , and E values constituting the TS index according to the weight ratio of the lithium nickel-based oxide in the form of secondary particles contained in the lithium nickel-based oxide, such that the TS index defined in Equation 1 above is 1.72 or less, thereby enabling excellent thermal safety and life characteristics while improving the resistance properties, output properties, and processability.

[0102] Meanwhile, the average particle diameter (D 50 ) of the secondary particle type lithium nickel-based oxide in the positive electrode active material can be 11 μm to 20 μm, preferably 12 μm to 15 μm, and more preferably 13 μm to 14 μm. The average particle diameter (D 50 ) of the single particle type lithium nickel-based oxide in the positive electrode active material can be 3 μm to 6 μm, preferably 3.5 μm to 5.5 μm, and more preferably 4 μm to 5 μm. When the above ranges are satisfied, the side reaction with the electrolyte can be minimized, while preventing an increase in resistance and a decrease in output properties, and thus the battery can have improved safety and life characteristics.

[0103] The positive electrode active material layer can include 80% to 99.9% by weight, preferably 90% to 99.9% by weight, and more preferably 95% to 99.9% by weight of the positive electrode active material.

[0104] Meanwhile, the positive electrode active material layer can also optionally include at least one of a positive electrode conductive material or a positive electrode binder.

[0105] The positive electrode conductive material is used to impart conductivity to the electrode, and any positive electrode conductive material can be used without particular limitation, as long as it has electronic conductivity without causing chemical changes in the battery. Specific examples thereof can include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal cracking carbon black, carbon fibers, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, any one of which or a mixture of two or more thereof can be used. The content of the positive electrode conductive material can generally be 0.1 to 30% by weight, preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and more preferably 0.7 to 5% by weight, relative to the total weight of the positive electrode active material layer.

[0106] The positive electrode binder is used to improve the binding between the positive electrode material particles and the adhesion between the positive electrode material and the positive electrode current collector, and specific examples of the positive electrode binder can be a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber-based binder including styrene butadiene rubber (SBR), nitrile rubber, and styrene-isoprene rubber; a cellulose-based binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyhydric alcohol-based binder including polyvinyl alcohol; a polyolefin-based binder including polyethylene and polypropylene; a polyimide-based binder; a polyester-based binder; a silane-based binder, any one of which or a mixture of two or more thereof can be used. The content of the positive electrode binder can be 0.1 to 30% by weight, preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and more preferably 0.7 to 5% by weight, relative to the total weight of the positive electrode active material layer.

[0107] 2) Negative electrode

[0108] The negative electrode can be prepared by coating a negative electrode slurry on one side or both sides of a long sheet-shaped negative electrode current collector, removing the solvent of the negative electrode slurry through a drying process, and then roll-pressing. Meanwhile, a negative electrode containing an uncoated portion can be prepared by not coating the negative electrode slurry on a portion (for example, one end of the negative electrode current collector) of the negative electrode current collector when coating the negative electrode slurry.

[0109] The negative electrode slurry can be prepared by dispersing a negative electrode active material in a solvent such as distilled water, ethanol, methanol, or isopropanol.

[0110] Alternatively, the negative electrode can be prepared by casting a separate support with a negative electrode slurry, and then laminating the negative electrode current collector with a film separated from the support.

[0111] The negative electrode can include a negative electrode active material, and specifically can include a negative electrode current collector and a negative electrode active material layer, which can include a negative electrode active material.

[0112] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like, aluminum cadmium alloy, or the like can be used. The thickness of the negative electrode current collector can generally be 3 μm to 500 μm, 5 μm to 300 μm, or 7 μm to 200 μm.

[0113] In addition, similar to the positive electrode current collector, the negative electrode current collector can form fine irregularities on its surface to improve the binding strength of the negative electrode active material. For example, the current collector can take various forms such as a film, a sheet, a foil, a mesh, a porous body, a foamed body, and a nonwoven fabric body.

[0114] The negative electrode active material layer can be located on the negative electrode current collector, and specifically can be located on one surface or both surfaces of the negative electrode current collector. The negative electrode active material layer can be a single layer structure or a multilayer structure of two or more layers.

[0115] The negative electrode active material layer includes at least one selected from the group consisting of natural graphite and artificial graphite as a negative electrode active material. By controlling the material of the negative electrode active material such that the TS index represented by Equation 1 above is 1.72 or less, the manufactured lithium secondary battery can provide cost effectiveness while exhibiting excellent capacity characteristics, life characteristics, and thermal safety.

[0116] The negative electrode active material layer can include 80% by weight to 99.9% by weight, preferably 90% by weight to 99.5% by weight, more preferably 95% by weight to 99.9% by weight, and even more preferably 97% by weight to 99.9% by weight of the negative electrode active material.

[0117] Meanwhile, the negative electrode active material layer can optionally include a negative electrode conductive material and a negative electrode binder in addition to the negative electrode active material.

[0118] The negative electrode conductive material is used to impart conductivity to the electrode, and any negative electrode conductive material can be used without particular limitation, as long as it has electronic conductivity without causing chemical changes in the battery of which it is a constituent. Specific examples thereof can include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal crack carbon black, carbon fibers, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, any one of which or a mixture of two or more thereof can be used. The content of the negative electrode conductive material can generally be 0.1 to 30% by weight, preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and more preferably 0.7 to 5% by weight, relative to the total weight of the negative electrode active material layer.

[0119] The negative electrode binder is used to improve the binding between the negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples thereof can include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene rubber (EPDM rubber), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of these or a mixture of two or more thereof can be used. The content of the negative electrode binder can be 0.1 to 30% by weight, preferably 0.3 to 20% by weight, more preferably 0.5 to 10% by weight, and more preferably 0.7 to 5% by weight, relative to the total weight of the negative electrode active material layer.

[0120] 3) Separator

[0121] Then, a separator is located between the negative electrode and the positive electrode, plays a role of separating the negative electrode and the positive electrode, and provides a passage for the migration of lithium ions, and any separator commonly used in lithium secondary batteries can be used without particular limitation. Specifically, as the separator, a porous polymer film such as a porous polymer film formed of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or having a stacked structure of two or more layers thereof can be used. In addition, a typical porous nonwoven fabric such as a nonwoven fabric formed of high-melting-point glass fibers or polyethylene terephthalate fibers can be used. Furthermore, a coated separator containing a ceramic component or a polymeric material can be used to ensure heat resistance or mechanical strength.

[0122] Meanwhile, the positive electrode 10 and the negative electrode 11 have a structure in which the active material layer 21 is formed on the sheet-shaped current collector 20, and a partial region of the current collector 20 can have an uncoated portion 22 in which the active material layer 21 is not formed.

[0123] As described above, when the positive electrode 10 and the negative electrode 11 containing the uncoated portion 22 are used, a battery having no separate electrode tab structure can be obtained, in which at least a portion of the uncoated portion of the positive electrode 10 and the negative electrode 11 defines an electrode tab.

[0124] Specifically, the uncoated portion 22 can be formed at an end portion of the current collector 20, extending in the winding direction X. The current collecting plate is coupled to the positive electrode uncoated portion and the negative electrode uncoated portion, respectively, and the current collecting plate is connected to the electrode terminal, allowing the uncoated portion 22 to function as an electrode tab.

[0125] For example, a battery in which the uncoated portion of the positive electrode and the uncoated portion of the negative electrode function as an electrode tab can be manufactured by the following method. First, a separator, a positive electrode, a separator, and a negative electrode are sequentially stacked such that the uncoated portion of the positive electrode and the uncoated portion of the negative electrode are located in opposite directions, and then wound in one direction to prepare an electrode assembly. Next, the uncoated portions of the positive electrode and the negative electrode are bent toward the winding center C, and then a current collecting plate is welded and coupled to the uncoated portion of the positive electrode and the uncoated portion of the negative electrode, and then the current collecting plate is connected to the electrode terminal to manufacture a battery. Meanwhile, the current collecting plate has a larger cross-sectional area than the strip-shaped electrode tab, and the resistance is inversely proportional to the cross-sectional area of the current flow path. Therefore, when a secondary battery having the above-described structure is formed, the battery resistance can be significantly reduced.

[0126] Meanwhile, the uncoated portion of the positive electrode and the uncoated portion of the negative electrode can be processed in the form of a plurality of segments that can be independently bent, and at least a portion of the plurality of segments can be bent toward the winding center C of the electrode assembly.

[0127] The current collector of the positive electrode and the negative electrode can be processed to form segments through a metal foil cutting process such as laser grooving, ultrasonic cutting, and stamping.

[0128] When the uncoated portion of the positive electrode and the uncoated portion of the negative electrode are processed in the form of a plurality of segments, the stress acting on the uncoated portion when bent can be reduced to prevent the uncoated portion from being deformed or damaged, thereby improving the welding characteristics with the current collecting plate.

[0129] The current collector and the uncoated portion are generally combined by welding, and in order to enhance the welding characteristics, it is necessary to bend the uncoated portion as uniformly as possible by applying strong pressure to the welding area of the uncoated portion. However, in this bending process, the shape of the uncoated portion can be irregularly twisted and deformed, and the deformed area can come into contact with the electrode of the opposite polarity, thereby causing internal short-circuiting or micro-cracks in the uncoated portion. However, when the uncoated portions of the positive and negative electrodes are processed in the form of a plurality of segments that can be independently bent, the stress acting on the uncoated portion during the bending process can be alleviated, thereby minimizing the deformation and damage of the uncoated portion.

[0130] In addition, when the uncoated portion is processed in the form of segments as described above, the plurality of segments overlap each other during the bending process, thereby increasing the welding strength with the current collector, and when an advanced technique such as laser welding is used, the laser is prevented from penetrating into the electrode assembly to melt and evaporate the separator or the active material. Preferably, at least a portion of the plurality of bent segments can overlap the upper and lower ends of the electrode assembly, and the current collector can be coupled to the plurality of overlapping segments.

[0131] Meanwhile, the electrode assembly of the present application can have a structure in which an insulating layer 24 is further formed on the positive electrode 10 as shown in FIG. 1B. Specifically, the insulating layer 24 can be formed to cover a portion of the positive active material layer and a portion of the uncoated portion in a direction parallel to the winding direction of the electrode assembly. Figure 3

[0132] For a battery having a tab-less structure in which the uncoated portions 22c of the positive electrode 10 and the uncoated portions 22a of the negative electrode 11 serve as electrode tabs, the electrode assembly is formed such that the positive electrode 10 can protrude upward from the separator 12, the negative electrode 11 can protrude downward from the separator 12, the protruding positive electrode 10 and / or the negative electrode 11 are bent, and then coupled to the current collector. However, when the positive electrode 10 or the negative electrode 11 is bent as described above, the current collector of the positive electrode 10 or the negative electrode 11 passes through the separator and is disposed close to the electrode of the opposite polarity, which can cause the positive and negative electrodes to electrically contact each other, thereby causing internal short-circuiting. However, as shown in FIG. 1B, when the insulating layer 24 covering a portion of the positive active material layer and a portion of the uncoated portion is formed, the insulating layer 24 can prevent the positive electrode 10 and the negative electrode 11 from electrically contacting each other, thereby preventing short-circuiting inside the battery. Figure 5

[0133] Preferably, the insulating layer 24 can be disposed on at least one surface of the current collector of the positive electrode 10, and preferably, can be disposed on both surfaces of the positive electrode 10.

[0134] ​​Further, the insulating layer 24 can be formed in a region of the active material layer 21a of the positive electrode 10 that can face the negative electrode 11. For example, on the surface of the uncoated portion 22c of the positive electrode 10 that faces the negative electrode 11 after being bent, the insulating layer 24 can be formed to extend to the end of the uncoated portion 22c. However, with respect to the surface opposite to the surface that faces the negative electrode 11 after being bent, it is desirable that the insulating layer 24 be formed only in a portion of the uncoated portion 22c, for example, up to before the bending point of the uncoated portion 22c. This is because when the insulating layer 24 is formed on the entire region of the uncoated portion on the surface opposite to the surface that faces the negative electrode 11, it cannot be in electrical contact with the current collector plate, and thus the uncoated portion cannot be used as an electrode tab.

[0135] Meanwhile, the material or composition of the insulating layer 24 is not particularly limited as long as it can adhere to the positive electrode while ensuring insulating properties. For example, the insulating layer can be an insulating coating layer or an insulating tape, and the insulating coating layer can include an organic binder and inorganic particles. In this case, the organic binder can be, for example, styrene butadiene rubber (SBR), and the inorganic particles can be alumina, but embodiments of the present application are not limited thereto.

[0136] (2) Battery case

[0137] The battery case serves to accommodate the electrode assembly and the electrolyte, and various battery cases known in the art, such as a cylindrical battery case, a prismatic battery case, and a pouch-type battery case, can be used.

[0138] Preferably, the battery case can be a cylindrical battery case.

[0139] When the battery case is a cylindrical battery case, the ratio (R / H) of the diameter (R) to the height (H) (the ratio of the shape factor) can be 0.4 or more, preferably 0.4 to 0.8, and more preferably 0.5 to 0.7. When the above range is satisfied, in combination with the configuration satisfying the high capacity characteristic and the TS index defined by Equation 1 being 1.72 or less, the effect of further maximizing the improvement in thermal safety of the lithium secondary battery can be maximized.

[0140] Further, the lithium secondary battery of the present application can be, for example, a 46110 battery (diameter: 46 mm, height: 110 mm, shape factor ratio: 0.418), a 4875 battery (diameter: 48 mm, height: 75 mm, shape factor ratio: 0.640), a 48110 battery (diameter: 48 mm, height: 110 mm, shape factor ratio: 0.436), a 4880 battery (diameter: 48 mm, height: 80 mm, shape factor ratio: 0.600), a 4680 battery (diameter: 46 mm, height: 80 mm, shape factor ratio: 0.575), and a 4695 battery (diameter: 46 mm, height: 95 mm, shape factor ratio: 0.484). In the numerical value indicating the shape factor, the first two numbers indicate the diameter (R) of the lithium secondary battery, and the last two or three numbers indicate the height (H) of the lithium secondary battery. When the above range is satisfied, high capacity characteristics can be obtained.

[0141] (3) Electrolyte

[0142] The electrolyte of the present application can include a lithium salt and an organic solvent.

[0143] As the lithium salt, any compound can be used without particular limitation, as long as it is a compound capable of providing lithium ions used in the lithium secondary battery. Specifically, as the lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, LiB(C2O4)2, and the like can also be used. The use concentration of the lithium salt can be 0.1 M to 5.0 M, preferably 0.1 M to 3.0 M. When the concentration of the lithium salt is within the above range, since the electrolyte can have appropriate conductivity and viscosity, excellent electrolyte performance can be obtained, and lithium ions can move efficiently.

[0144] The organic solvent can include at least one of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, or a cyclic ester-based organic solvent.

[0145] As the cyclic carbonate-based organic solvent which is a high viscosity organic solvent, at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylenecarbonate, 2,3-butylenecarbonate, 1,2-pentylenecarbonate, 2,3-pentylenecarbonate, and vinylene carbonate can be generally included.

[0146] In addition, as an organic solvent having low viscosity and low dielectric constant, the linear carbonate-based organic solvent can be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and specifically can include ethyl methyl carbonate (EMC).

[0147] The linear ester-based organic solvent can be, for example, at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0148] The cyclic ester-based organic solvent can be at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-hexalactone, ε-valerolactone, and ε-hexalactone.

[0149] Preferably, the electrolyte of the present application can include ethylene carbonate and dimethyl carbonate as the organic solvent.

[0150] Meanwhile, in addition to the electrolyte components, the electrolyte can further include other additives to improve the life characteristics of the battery, prevent the capacity of the battery from decreasing, and increase the discharge capacity of the battery.

[0151] Typical examples of the other additives can include at least one selected from the group consisting of a cyclic carbonate compound, a halogenated carbonate compound, a sultone compound, a sulfate compound, a borate compound, a nitrile compound, a benzene compound, an amine compound, a silane compound, and a lithium salt compound different from the lithium salt contained in the electrolyte.

[0152] Specifically, the other additive can be one or more compounds selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), 1,4-butane sultone, ethylene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, 1-methyl-1,3-propene sultone, ethylene sulfate (Esa), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, butanedinitrile, hexanedinitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, octanitrile, heptanitrile, cyclopentanitrile, cyclohexanitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetraethenylsilane, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethylsulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiB(C2O4)2 (lithium bis(oxalato)borate, LiBOB), and LiBF4.

[0153] The content of the other additive can be 0.01 to 20% by weight, preferably 0.05 to 5.0% by weight, with respect to the total weight of the electrolyte. When the content of the other additive is less than 0.01% by weight, the effect of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is not significant, and when the content of the other additive is more than 20% by weight, the side reaction of the electrolyte can excessively occur during the charging and discharging of the battery. In particular, when an excessive amount of the SEI layer-forming additive is added, the additive can not be sufficiently decomposed at high temperatures, and thus can remain in the electrolyte in the form of unreacted substances or precipitated substances at room temperature. Therefore, a side reaction that reduces the life or resistance characteristics of the secondary battery can occur.

[0154] Next, a lithium secondary battery according to the present application will be described.

[0155] Figure 4 and Figure 5 Embodiments of the lithium secondary battery according to the present application are disclosed. Hereinafter, the lithium secondary battery according to the present application will be described with reference to Figure 4 and 5 The lithium secondary battery according to the present application is described. However, Figure 4 and 5 Only one embodiment of the present application is illustrated, and the battery structure of the present application is not limited to Figure 4 and 5 the range shown.

[0156] Figure 4 A cross-sectional view of a lithium secondary battery according to an embodiment of the present application having a tabless structure is illustrated.

[0157] Reference Figure 4 The lithium secondary battery 140 of the present invention may include an electrode assembly 141, a battery case 142 that houses the electrode assembly 141 and an electrolyte (not shown), and a sealing body 143 that seals the opening end of the battery case 142.

[0158] In this configuration, the electrode assembly can be a stack of a positive electrode, a separator, and a negative electrode wound in one direction. Furthermore, the positive and negative electrodes of the electrode assembly may include uncoated portions without an active material layer, and they can be stacked and wound such that the uncoated portions of the positive and negative electrodes are located at the upper and lower ends of the electrode assembly, respectively. Since the electrode assembly has been described above, the following description will focus only on components other than the electrode assembly.

[0159] Meanwhile, the battery casing 142 is a can-shaped container with an opening at the top, made of a conductive metal material such as aluminum or steel. The battery casing houses the electrode assembly 141 in its internal space through the upper opening, and together with it, the electrolyte (not shown).

[0160] Meanwhile, the lithium secondary battery 140 of the present invention preferably does not contain a current interruption device (CID).

[0161] However, as Figure 4 As shown, the battery case 142 is electrically connected to the uncoated portion 146b of the negative electrode plate and is in contact with an external power source, serving as a means to deliver current applied by the external power source to the negative terminal of the negative electrode.

[0162] If necessary, a rounded edge 147 and a pressing part 148 can be provided at the upper end of the battery housing 142. The rounded edge 147 can be formed by pressing the outer peripheral surface of the battery housing 142 inward to a distance D1. The rounded edge 147 prevents the electrode assembly 141 housed inside the battery housing 142 from coming out through the top opening of the battery housing 142, and can also serve as a support for placing the sealing body 143.

[0163] The crimping portion 148 may be formed above the circular edge portion 147, and its shape extends and bends to surround a portion of the outer peripheral surface of the cover plate 143a disposed above the circular edge portion 147 and a portion of the top surface of the cover plate 143a.

[0164] Next, the sealing body 143 seals the open end of the battery case 142 and includes a cover plate 143a and a first gasket 143b that provides airtightness and insulation to the space between the cover plate 143a and the battery case 142. It may also include a connecting plate 143c that is electrically and mechanically connected to the cover plate 143a, if necessary. The cover plate 143a can be pressed against the circular edge 147 formed in the battery case 142 and secured by a pressing part 148.

[0165] The cover plate 143a is a member made of a metal material having electrical conductivity and covers the upper opening of the battery case 142. The cover plate 143a is electrically connected to the positive electrode of the electrode assembly 141 and is electrically insulated from the battery case 142 by the first gasket 143b. Accordingly, the cover plate 143a can serve as a positive terminal of the lithium secondary battery. The cover plate 143a can include a protrusion 143d protruding upward from a center portion C thereof. The protrusion 143d contacts an external power source and allows an electric current to be applied from the external power source.

[0166] The first gasket 143b can be interposed between the cover plate 143a and the crimp portion 148 to ensure the air tightness of the battery case 142 and the electrical insulation between the battery case 142 and the cover plate 143a.

[0167] Meanwhile, the lithium secondary battery 140 of the present application can further include current collectors 144 and 145 as needed. The current collectors are coupled to the positive uncoated portion 146a and the negative uncoated portion 146b and connected to the electrode terminals (i.e., the positive terminal and the negative terminal).

[0168] Specifically, the cylindrical battery 140 of the present application can include a first current collector 144 coupled to the upper portion of the electrode assembly 141 and a second current collector 145 coupled to the lower portion of the electrode assembly 141.

[0169] The first current collector 144 and / or the second current collector 145 can be included.

[0170] The first current collector 144 is coupled to the upper portion of the electrode assembly 141. The first current collector 144 can be made of an electrically conductive metal material such as aluminum, copper, or nickel and is electrically connected to the uncoated portion 146a of the positive electrode. The first current collector 144 can be connected to a lead wire 149. The lead wire 149 extends upward from the electrode assembly 141 and can be coupled to the connecting plate 143c or directly to the lower surface of the cover plate 143a. The coupling between the lead wire 149 and other components can be achieved by welding. Preferably, the first current collector 144 can be integrally formed with the lead wire 149. In this case, the lead wire 149 can have a plate shape extending outward from the center portion C of the first current collector 144.

[0171] Meanwhile, the first current collector 144 is coupled to the end of the uncoated portion 146a of the positive electrode. Such coupling can be achieved by laser welding, resistance welding, ultrasonic welding, or brazing, etc.

[0172] The second current collector 145 is connected to the lower part of the electrode assembly 141. The second current collector 145 may be made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode. One surface of the second current collector 145 may be connected to the uncoated portion 146b of the negative electrode, while the other surface may be connected to the inner bottom surface of the battery casing 142. In this case, this connection can be achieved by laser welding, resistance welding, ultrasonic welding, brazing, etc.

[0173] Furthermore, the lithium secondary battery 140 of the present invention may further include an insulator 146 as needed. The insulator 146 may be configured to cover the upper surface of the first current collector 144. The insulator 146 covers the first current collector 144, thereby preventing the first current collector 144 from directly contacting the inner peripheral surface of the battery casing 142.

[0174] The insulator 146 includes a lead hole 151 through which a lead 149 extending upward from the first current collector 144 can be led out. The lead 149 is led out upward through the lead hole 151 and connected to the lower surface of the connecting plate 143c or the lower surface of the cover plate 143a.

[0175] Insulator 146 may be made of polymer resins with insulating properties, such as polyethylene, polypropylene, polyimide or polybutylene terephthalate.

[0176] Furthermore, the lithium secondary battery 140 of the present invention may, as needed, include an venting portion 152 formed on the lower surface of the battery casing 142. The venting portion 152 corresponds to a region on the lower surface of the battery casing 142 that is thinner than the surrounding region. Because the venting portion 152 is thinner, it is structurally more fragile than the surrounding region. Therefore, when the pressure inside the lithium secondary battery 140 rises above a certain level, the venting portion 152 ruptures, and the gas inside the battery casing 152 is released outward, thereby preventing the battery from exploding.

[0177] Figure 5 A cross-sectional view of a lithium secondary battery with a non-connector structure according to another embodiment of the present invention is shown.

[0178] Reference Figure 5 The structure of the battery can and the sealing body of the lithium secondary battery 170 according to another embodiment of the present invention is similar to... Figure 3 The lithium secondary battery 140 shown is different, but the electrode components and electrolytes are basically the same.

[0179] Specifically, the lithium secondary battery 170 includes a battery case 171 through which a rivet terminal 172 passes and is mounted. The rivet terminal 172 is mounted on a partially closed surface (upper surface in the drawing) of the battery case 171, which is partially closed at the end portion of the battery can. The rivet terminal 172 is riveted to a through-hole (first opening of the first end) of the battery case 171 in a state in which the second gasket 173 having insulating properties is inserted. The rivet terminal 172 is outwardly exposed in a direction opposite to the direction of gravity.

[0180] The rivet terminal 172 includes a terminal exposure portion 172a and a terminal insertion portion 172b. The terminal exposure portion 172a is outwardly exposed from the partially closed surface of the battery case 171. The terminal exposure portion 172a can be located at the substantially central portion C of the partially closed surface of the battery case 171. The maximum diameter of the terminal exposure portion 172a can be formed to be greater than the maximum diameter of the through-hole formed in the battery case 171. The terminal insertion portion 172b passes through the substantially central portion of the partially closed surface of the battery case 171 and can be electrically connected to the uncoated portion 146a of the positive electrode. The terminal insertion portion 172b can be riveted to the inner surface of the battery case 171. That is, the end portion of the terminal insertion portion 172b can have a shape bent toward the inner surface of the battery case 171. The maximum diameter of the end portion of the terminal insertion portion 172b can be greater than the maximum diameter of the through-hole of the battery case 171.

[0181] The lower end surface of the terminal insertion portion 172b can be welded to the first current collector plate 144 connected to the uncoated portion 146a of the positive electrode. An insulating cover 174 made of an insulating material can be inserted between the first current collector plate 144 and the inner surface of the battery case 171. The insulating cover 174 covers the upper portion of the first current collector plate 144 and the upper end edge portion of the electrode assembly 141. Thus, short circuiting can be prevented when the uncoated portion B3 of the outer periphery of the electrode assembly 141 comes into contact with the inner surface of the battery case 171 having a different polarity. The terminal insertion portion 172b of the rivet terminal 172 passes through the insulating cover 174 and can be welded to the first current collector plate 144.

[0182] The second gasket 173 is inserted between the battery case 171 and the rivet terminal 172 to prevent electrical contact between the battery case 171 and the rivet terminal 172 having different polarities from each other. Thereby, the upper surface of the battery case 171 having a substantially flat shape can serve as a positive terminal of the lithium secondary battery 170.

[0183] The second gasket 173 includes a gasket exposed portion 173a and a gasket inserted portion 173b. The gasket exposed portion 173a is inserted between the terminal exposed portion 172a of the rivet terminal 172 and the battery case 171. The gasket inserted portion 173b is inserted between the terminal inserted portion 172b of the rivet terminal 172 and the battery case 171. The gasket inserted portion 173b can be deformed together and come into close contact with the inner surface of the battery case 171 when the terminal inserted portion 172b is riveted. The second gasket 173 can be made of, for example, a polymer resin having insulating properties.

[0184] The gasket exposed portion 173a of the second gasket 173 can have a shape extending to cover the outer circumferential surface of the terminal exposed portion 172a of the rivet terminal 172. When the second gasket 173 covers the outer circumferential surface of the rivet terminal 172, it is possible to prevent a short circuit from occurring in the process of coupling an electrically connecting member such as a bus bar to the upper surface of the battery case 171 and / or the rivet terminal 172. Although not shown, the gasket exposed portion 173a can have a shape extending to cover a portion of the upper surface of the terminal exposed portion 172a as well as the outer circumferential surface thereof.

[0185] When the second gasket 173 is made of a polymer resin, the second gasket 173 can be coupled to the battery case 171 and the rivet terminal 172 by heat fusion. In this case, it is possible to reinforce the airtightness of the coupling interface of the second gasket 173 with the rivet terminal 172 and the coupling interface of the second gasket 173 with the battery case 171. On the other hand, when the gasket exposed portion 173a of the second gasket 173 has a shape extending to the upper surface of the terminal exposed portion 172a, the rivet terminal 172 can be integrally coupled with the second gasket 173 by insert injection molding.

[0186] Except for the area occupied by the rivet terminal 172 and the second gasket 173 on the upper surface of the battery case 171, the remaining area 175 corresponds to a negative terminal having a polarity opposite to that of the rivet terminal 172.

[0187] The second current collector plate 176 is coupled to the lower portion of the electrode assembly 141. The second current collector plate 176 can be made of an electrically conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode.

[0188] It is preferable that the second current collector plate 176 be electrically connected to the battery case 171. To this end, at least a portion of the edge portion of the second current collector plate 176 can be inserted and fixed between the inner surface of the battery case 171 and the first gasket 178b. In one example, at least a portion of the edge portion of the second current collector plate 176 can be fixed to the circular rim portion 180 formed at the lower end of the battery case 171 by welding, while being supported by the lower end surface of the circular rim portion 180. In a modified example, at least a portion of the edge portion of the second current collector plate 176 can be directly welded to the inner wall surface of the battery case 171.

[0189] The second current collector 176 can include a plurality of protrusions and recesses (not shown) formed radially on a surface facing the uncoated portion 146b. When the protrusions and recesses are formed, the protrusions and recesses can be press-fitted into the uncoated portion 146b by pressing the second current collector 176.

[0190] Preferably, the second current collector 176 and the end portion of the uncoated portion 146b can be coupled by welding (e.g., laser welding).

[0191] The seal 178 for sealing the lower open end of the battery case 171 includes a cover plate 178a and a first gasket 178b. The first gasket 178b electrically separates the cover plate 178a and the battery case 171. A crimp portion 181 fixes the edge of the cover plate 178a and the first gasket 178b together. An exhaust portion 179 is provided in the cover plate 178a. The exhaust portion 179 has substantially the same configuration as the above-described embodiment.

[0192] Preferably, the cover plate 178a can be made of an electrically conductive metal material. However, since the first gasket 178b is interposed between the cover plate 178a and the battery case 171, the cover plate 178a has no electrode polarity. The seal 178 serves to seal the lower open end of the battery case 171 and to vent gas when the internal pressure of the battery cell 170 rises above a threshold value.

[0193] Preferably, the rivet terminal 172 electrically connected to the uncoated portion 146a of the positive electrode serves as a positive electrode terminal. Also, a portion 175 of the upper surface of the battery case 171 excluding the rivet terminal 172, which is electrically connected to the uncoated portion 146b of the negative electrode through the second current collector 176, serves as a negative electrode terminal. As described above, when both electrode terminals are located at the upper portion of the lithium secondary battery, an electrical connection member such as a busbar can be provided only on one side of the lithium secondary battery 170. This can simplify the structure of the battery pack and increase the energy density. Also, the portion 175 serving as the negative electrode terminal has a substantially flat shape, so that a sufficient bonding area can be ensured when the electrical connection member such as a busbar is bonded. Therefore, in the lithium secondary battery 170, the electrical resistance of the bonding site of the electrical connection assembly can be reduced to a preferred level.

[0194] When the lithium secondary battery is formed in the tab-less structure as described above, the current concentration degree is smaller compared to a conventional battery having electrode tabs, so that the heat generation inside the battery can be effectively reduced. Therefore, the thermal stability of the battery can be improved. Also, when the lithium secondary battery of the present application has the tab-less structure as described above, the configuration in which the TS index defined by Equation 1 above is 1.72 or less can maximize the effect of improving the thermal safety.

[0195] Battery pack

[0196] A battery pack can be manufactured by including the above-described lithium secondary battery of the present application as a unit cell. Figure 6 The configuration of a battery pack of an embodiment of the present application is schematically shown. Referring to Figure 6 , a battery pack 3 of an embodiment of the present application includes an assembly in which lithium secondary batteries 1 are electrically connected; and a pack case 2 that accommodates the same. The lithium secondary batteries 1 are the lithium secondary batteries of the above-described embodiment. In this figure, components such as bus bars for electrically connecting the secondary batteries 1, a cooling unit, and external terminals are omitted for convenience of explanation.

[0197] The battery pack 3 can be mounted on a motor vehicle. The motor vehicle can be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The motor vehicle includes a four-wheeled vehicle or a two-wheeled vehicle.

[0198] Hereinafter, the present application will be described in more detail by specific embodiments.

[0199] Example 1

[0200] <Production of positive electrode>

[0201] A positive electrode active material, a conductive material, and a binder were added to N-methylpyrrolidone at a weight ratio of 97:1:2 to prepare a positive electrode slurry. In this example, single-particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 were used as the positive electrode active material, CNT was used as the conductive material, and PVDF was used as the binder.

[0202] The positive electrode slurry was coated onto an aluminum current collector, dried, and then roll-pressed to prepare a positive electrode.

[0203] <Production of negative electrode>

[0204] A negative electrode active material, a conductive material, a binder, and a thickening agent were added to distilled water at a weight ratio of 98:0.1:1:0.9 to prepare a negative electrode slurry. In this example, natural graphite and artificial graphite were mixed at a weight ratio of 6:4 as the negative electrode active material, SW-CNT was used as the conductive material, SBR was used as the binder, and CMC was used as the thickening agent.

[0205] The negative electrode slurry was coated onto a copper current collector having a thickness of 10 μm, dried, and then roll-pressed to prepare a negative electrode including a negative electrode active material layer. In this example, the BET specific surface area of the negative electrode active material was 1.7 m 2 / g.

[0206] <Production of lithium secondary battery>

[0207] As described above, the separator is placed between the positive electrode and the negative electrode, and stacked in the order of separator / positive electrode / separator / negative electrode, and then wound to prepare a jelly-roll type electrode assembly.

[0208] The electrode assembly is inserted into a cylindrical battery case having a height of 80 mm and a diameter of 46 mm, and an electrolyte is injected to manufacture a lithium secondary battery (4680 battery). In this example, the electrolyte is prepared by adding LiPF6 at a molar concentration of 1.25 M to an organic solvent of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and DMC (dimethyl carbonate) mixed at a weight ratio of 20:20:60.

[0209] In this example, the weight ratio of the electrolyte to the total weight of the lithium secondary battery is 0.098.

[0210] Example 2

[0211] <Manufacture of Positive Electrode>

[0212] The positive electrode is manufactured in the same manner as in Example 1, except that single-particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 are mixed at a weight ratio of 5:5 as the positive electrode active material.

[0213] <Manufacture of Negative Electrode>

[0214] In this example, the negative electrode is manufactured in the same manner as in Example 1, except that natural graphite and artificial graphite are mixed at a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material is 1.5 m 2 / g.

[0215] <Manufacture of Lithium Secondary Battery>

[0216] In this example, the lithium secondary battery is manufactured in the same manner as in Example 1, except that the electrolyte is injected such that the weight ratio of the electrolyte to the total weight of the lithium secondary battery is 0.105.

[0217] Example 3

[0218] <Manufacture of Positive Electrode>

[0219] The positive electrode is manufactured in the same manner as in Example 1, except that single-particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co0.005 Mn 0.025 ]O2 were mixed in a weight ratio of 5:5 as the positive electrode active material.

[0220] <Manufacture of the negative electrode>

[0221] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed in a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0222] <Manufacture of the lithium secondary battery>

[0223] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected such that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.098.

[0224] Example 4

[0225] <Manufacture of the positive electrode>

[0226] The positive electrode was prepared in the same manner as in Example 1, except that single particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed in a weight ratio of 8:2 as the positive electrode active material.

[0227] <Manufacture of the negative electrode>

[0228] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed in a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0229] <Manufacture of the lithium secondary battery>

[0230] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected such that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0231] Example 5

[0232] <Manufacture of the positive electrode>

[0233] The positive electrode was prepared in the same manner as in Example 1, except that single particle type particles Li2[Ni 0.93 Co 0.05Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 4:6 as a positive electrode active material.

[0234] <Manufacture of a negative electrode>

[0235] In this example, a negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 1:9 as a negative electrode active material, and the BET specific surface area of the negative electrode active material was 0.9 m 2 / g.

[0236] <Manufacture of a lithium secondary battery>

[0237] In this example, a lithium secondary battery was manufactured in the same manner as in Example 1, except that an electrolyte was injected such that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.098.

[0238] Comparative Example 1

[0239] <Manufacture of a positive electrode>

[0240] A positive electrode was prepared in the same manner as in Example 1, except that single-particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 2:8 as a positive electrode active material.

[0241] <Manufacture of a negative electrode>

[0242] In this example, a negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 3:7 as a negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.2 m 2 / g.

[0243] <Manufacture of a lithium secondary battery>

[0244] In this example, a lithium secondary battery was manufactured in the same manner as in Example 1, except that an electrolyte was injected such that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0245] Comparative Example 2

[0246] <Manufacture of a positive electrode>

[0247] A positive electrode was prepared in the same manner as in Example 1, except that secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were used as the positive electrode active material.

[0248] <Manufacture of a negative electrode>

[0249] In this example, a negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 6:4 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.7 m 2 / g.

[0250] <Manufacture of a lithium secondary battery>

[0251] In this example, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0252] Comparative Example 3

[0253] <Manufacture of a positive electrode>

[0254] A positive electrode was prepared in the same manner as in Example 1, except that single-particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 2:8 as the positive electrode active material.

[0255] <Manufacture of a negative electrode>

[0256] In this example, a negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0257] <Manufacture of a lithium secondary battery>

[0258] In this example, a lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0259] Comparative Example 4

[0260] <Manufacture of a positive electrode>

[0261] The positive electrode was prepared in the same manner as in Example 1, except that primary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were used as the positive electrode active material.

[0262] <Manufacture of the negative electrode>

[0263] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0264] <Manufacture of the lithium secondary battery>

[0265] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0266] Comparative Example 5

[0267] <Manufacture of the positive electrode>

[0268] The positive electrode was prepared in the same manner as in Example 1, except that primary particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 5:5 as the positive electrode active material.

[0269] <Manufacture of the negative electrode>

[0270] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 5:5 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0271] <Manufacture of the lithium secondary battery>

[0272] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.098.

[0273] Comparative Example 6

[0274] <Manufacture of the positive electrode>

[0275] The positive electrode was prepared in the same manner as in Example 1, except that primary particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 5:5 as the positive electrode active material.

[0276] <Manufacture of the negative electrode>

[0277] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 7:3 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 1.5 m 2 / g.

[0278] <Manufacture of the lithium secondary battery>

[0279] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.105.

[0280] Comparative Example 7

[0281] <Manufacture of the positive electrode>

[0282] The positive electrode was prepared in the same manner as in Example 1, except that primary particle type particles Li2[Ni 0.93 Co 0.05 Mn 0.02 ]O2 and secondary particles Li2[Ni 0.97 Co 0.005 Mn 0.025 ]O2 were mixed at a weight ratio of 6:4 as the positive electrode active material.

[0283] <Manufacture of the negative electrode>

[0284] In this example, the negative electrode was prepared in the same manner as in Example 1, except that natural graphite and artificial graphite were mixed at a weight ratio of 9:1 as the negative electrode active material, and the BET specific surface area of the negative electrode active material was 2.1 m 2 / g.

[0285] <Manufacture of the lithium secondary battery>

[0286] In this example, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrolyte was injected so that the weight ratio of the electrolyte to the total weight of the lithium secondary battery was 0.092.

[0287] Experimental Example 1: Measurement of TS Index

[0288] For the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7, TS index defined by Equation 1 below was calculated and shown in Table 1 below.

[0289] [Equation 1]

[0290]

[0291] In Equation 1 above, P S represents the proportion of the weight of lithium nickel-based oxide in the form of secondary particles with respect to the total weight of lithium nickel-based oxide, N G represents the proportion of the weight of natural graphite with respect to the total weight of natural graphite and artificial graphite, S N represents the BET specific surface area (unit: m 2 / g) of the negative active material, and E represents the proportion of the total weight of the electrolyte with respect to the total weight of the lithium secondary battery.

[0292] 1) Measurement of P S

[0293] The positive electrode cross-section of the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7 was observed perpendicularly to the positive electrode surface using a scanning electron microscope (SEM), secondary particles and single particle type particles were distinguished by the particle shape of the secondary particles and the single particle type particles, and then the volume ratio of the secondary particles and the single particle type particles was measured therefrom, the weight ratio of lithium nickel-based oxide in the form of secondary particles with respect to the total weight of the secondary particles and the single particle type particles was calculated by multiplying the density of each of the secondary particles and the single particle type particles, and thus P S was measured. The results are shown in Table 1 below.

[0294] 2) Measurement of N G

[0295] The negative electrode cross-section of the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7 was observed perpendicularly to the negative electrode surface using a scanning electron microscope (SEM), artificial graphite and natural graphite were distinguished by the particle shape of the artificial graphite and the natural graphite, and then the volume ratio of the artificial graphite and the natural graphite was measured therefrom, and the proportion of the weight of the natural graphite with respect to the total weight of the natural graphite and the artificial graphite was calculated by multiplying the density of each of the artificial graphite and the natural graphite, and thus N G was measured. The results are shown in Table 1 below.

[0296] 3) Measurement of S N

[0297] The negative electrode of the lithium secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 7 was scraped into a powder form, and then the nitrogen gas adsorption amount of the powder at liquid nitrogen temperature (77 K) was measured using a BEL Japan BELSORP-mino II to obtain S​​​N i.e. BET specific surface area (unit: m 2 / g) of the negative active material contained in the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7. The results are shown in Table 1 below.

[0298] 4) Measurement of E

[0299] The lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7 were each stored at 25°C for 24 hours, and then charged to 4.2 V and then discharged to 2.5 V at 25°C during a charge-discharge cycle, which was repeated three times, thereby activating each of the lithium secondary batteries.

[0300] Subsequently, the total weight of each of the activated lithium secondary batteries was measured, and each of the lithium secondary batteries was disassembled to measure the weight of the electrolyte in the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7. Specifically, the weight of the electrolyte was measured by (1) measuring the weight (M L ) of the activated lithium secondary battery before disassembling the activated lithium secondary battery, (2) disassembling the lithium secondary battery to remove the electrolyte present in the battery case, (3) immersing the battery case and the electrode assembly in a dimethyl carbonate solvent to remove the electrolyte in the surface of the battery case, the surface of the electrode assembly, and the internal pores, and then drying the battery case and the electrode assembly, and (4) measuring the weight (M C ) of the dried battery case and the weight (M A ) of the dried electrode assembly, and then inputting the measured M L , M C , and M A into Equation A below.

[0301] [Equation A]

[0302] The weight of the electrolyte above = M L - M C - M A

[0303] [Table 1]

[0304]

[0305] Experimental Example 2: Hot Box Test

[0306] After the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 7 were activated, the activated lithium secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 7 were charged to 4.2 V and 0.05 C at 25℃ under CC / CV and 1 / 3 C conditions until full charge to SOC reached 100%. Each of the fully charged lithium secondary batteries was put into a hot box at room temperature, heated to 130℃ at a temperature increase rate of 5℃ / min for 30 min, and then maintained for 1 hour to measure the temperature change of the battery. When no thermal runaway or fire occurred during the test, it was marked as "Pass", and when thermal runaway and / or fire occurred, it was marked as "Fail". The results are shown in Table 2 below.

[0307] [Table 2]

[0308]

[0309] Referring to Table 2 above, it can be determined that the lithium secondary batteries manufactured in Examples 1 to 5 did not show thermal runaway and / or fire in the hot box test, while the lithium secondary batteries manufactured in Comparative Examples 1 to 7 showed thermal runaway and / or fire in the hot box test. Therefore, it can be seen that the lithium secondary batteries manufactured in Examples 1 to 5 have excellent thermal safety.

[0310] (Explanation of Reference Numerals)

[0311] 1: Lithium secondary battery

[0312] 2: Package outer case

[0313] 3: Battery pack

[0314] 10: Positive electrode

[0315] 11: Negative electrode

[0316] 12: Separator

[0317] 20: Current collector

[0318] 21: Active material layer

[0319] 21a: Negative active material layer

[0320] 22: Uncoated portion

[0321] 22a: Negative uncoated portion

[0322] 22c: Positive uncoated portion

[0323] 24: Insulating layer

[0324] C: Winding center

[0325] 140: Lithium secondary battery

[0326] 141: Electrode assembly

[0327] 142: battery case

[0328] 143: seal body

[0329] 143a: cover plate

[0330] 143b: first gasket

[0331] 143c: connecting plate

[0332] 143d: protrusion

[0333] 144: first current collector plate

[0334] 145: second current collector plate

[0335] 146: insulator

[0336] 146a: positive electrode non-coated portion

[0337] 146b: negative electrode non-coated portion

[0338] 147: round rim portion

[0339] 148: crimp portion

[0340] 149: lead wire

[0341] 151: lead wire hole

[0342] 152: exhaust portion

[0343] 170: lithium secondary battery

[0344] 171: battery case

[0345] 172: rivet terminal

[0346] 172a: terminal exposure portion

[0347] 172b: terminal insertion portion

[0348] 173: second gasket

[0349] 173a: gasket exposure portion

[0350] 173b: gasket insertion portion

[0351] 174: insulating cover

[0352] 176: second current collector plate

[0353] 178: seal body

[0354] 178a: cover plate

[0355] 178b: first gasket

[0356] 179: exhaust portion

[0357] 180: round edge portion

[0358] 181: crimping portion

Claims

1. A lithium secondary battery comprising: an electrode assembly comprising a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode; an electrolyte; and a battery case accommodating the electrode assembly and the electrolyte, wherein the positive electrode comprises a lithium nickel-based oxide containing 80 mol% or more of nickel among all metals except lithium as a positive electrode active material, the lithium nickel-based oxide includes single particle type particles, secondary particles, or a combination thereof, the negative electrode comprises at least one selected from the group consisting of natural graphite and artificial graphite as a negative electrode active material, and The TS index defined by Equation 1 below is 1.72 or less, units: g / m 2 [Equation 1] wherein, in the above Equation 1, P S the proportion of the weight of the lithium nickel-based oxide in the form of secondary particles relative to the total weight of the lithium nickel-based oxide, N G denotes the proportion of the weight of the natural graphite to the total weight of the natural graphite and the artificial graphite, S N S represents the BET specific surface area of the negative electrode active material, in m 2 / g, and E represents a ratio of a total weight of the electrolyte to a total weight of the lithium secondary battery.

2. The lithium secondary battery according to claim 1, wherein P S is 0.7 or less.

3. The lithium secondary battery according to claim 1, wherein N G is 0.6 or less.

4. The lithium secondary battery according to claim 1, wherein S N 1.3 m 2 1.9 m 2 1.9 m.

5. The lithium secondary battery according to claim 1, wherein E is 0.08 to 0.

13.

6. The lithium secondary battery according to claim 1, wherein the lithium nickel-based oxide is represented by the following Formula 1: [Formula 1] Li a1 [Ni x1 Co y1 Mn z1 M 1 w1 ]O2 wherein, in the above Formula 1, M 1 is at least one doping element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0.8≤a1≤1.2, 0.8≤x1<1, 0<y1≤0.2, 0<z1≤0.2, and 0≤w1≤0.

1.

7. The lithium secondary battery according to claim 1, wherein the battery case is a cylindrical battery case.

8. The lithium secondary battery according to claim 1, wherein a ratio R / H of a diameter R to a height H of the lithium secondary battery is 0.4 or more.

9. The lithium secondary battery according to claim 1, wherein, the lithium secondary battery is a 46110 battery, a 48110 battery, a 4880 battery, or a 4680 battery.

10. The lithium secondary battery according to claim 1, wherein the lithium secondary battery includes uncoated portions on at least a portion of the positive electrode and the negative electrode on which an active material layer is not formed, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are defined as electrode tabs.

11. The lithium secondary battery according to claim 10, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are formed at one side end of the positive electrode and the negative electrode in a winding direction of the electrode assembly, respectively, the positive electrode uncoated portion and the negative electrode uncoated portion are each coupled with a current collector plate, and the current collector plate is connected with an electrode terminal.

12. The lithium secondary battery according to claim 10, wherein, the positive electrode uncoated portion and the negative electrode uncoated portion are processed in a form of a plurality of segments that are independently bendable, and at least a portion of the plurality of segments is bent toward a winding center of the electrode assembly.

13. The lithium secondary battery according to claim 12, wherein, at least a portion of the plurality of bent segments overlaps with upper and lower ends of the electrode assembly, and a current collector plate is coupled to the plurality of overlapping segments. 14.A battery pack comprising the lithium secondary battery of any one of claims 1 to 13 as a unit cell.

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